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Sample records for existing cardiac myocytes

  1. Engineering design of a cardiac myocyte

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    Adams, W. J.; Pong, T.; Geisse, N. A.; Sheehy, S. P.; Diop-Frimpong, B.; Parker, K. K.

    2007-04-01

    We describe a design algorithm to build a cardiac myocyte with specific spatial dimensions and physiological function. Using a computational model of a cardiac muscle cell, we modeled calcium (Ca2+) wave dynamics in a cardiac myocyte with controlled spatial dimensions. The modeled myocyte was replicated in vitro when primary neonate rat ventricular myocytes were cultured on micropatterned substrates. The myocytes remodel to conform to the two dimensional boundary conditions and assume the shape of the printed extracellular matrix island. Mechanical perturbation of the myocyte with an atomic force microscope results in calcium-induced calcium release from intracellular stores and the propagation of a Ca2+ wave, as indicated by high speed video microscopy using fluorescent indicators of intracellular Ca2+. Analysis and comparison of the measured wavefront dynamics with those simulated in the computer model reveal that the engineered myocyte behaves as predicted by the model. These results are important because they represent the use of computer modeling, computer-aided design, and physiological experiments to design and validate the performance of engineered cells. The ability to successfully engineer biological cells and tissues for assays or therapeutic implants will require design algorithms and tools for quality and regulatory assurance.

  2. Signaling Pathways in Cardiac Myocyte Apoptosis

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    Xia, Peng; Liu, Yuening

    2016-01-01

    Cardiovascular diseases, the number 1 cause of death worldwide, are frequently associated with apoptotic death of cardiac myocytes. Since cardiomyocyte apoptosis is a highly regulated process, pharmacological intervention of apoptosis pathways may represent a promising therapeutic strategy for a number of cardiovascular diseases and disorders including myocardial infarction, ischemia/reperfusion injury, chemotherapy cardiotoxicity, and end-stage heart failure. Despite rapid growth of our knowledge in apoptosis signaling pathways, a clinically applicable treatment targeting this cellular process is currently unavailable. To help identify potential innovative directions for future research, it is necessary to have a full understanding of the apoptotic pathways currently known to be functional in cardiac myocytes. Here, we summarize recent progress in the regulation of cardiomyocyte apoptosis by multiple signaling molecules and pathways, with a focus on the involvement of these pathways in the pathogenesis of heart disease. In addition, we provide an update regarding bench to bedside translation of this knowledge and discuss unanswered questions that need further investigation. PMID:28101515

  3. Network Reconstruction and Systems Analysis of Cardiac Myocyte Hypertrophy Signaling*

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    Ryall, Karen A.; Holland, David O.; Delaney, Kyle A.; Kraeutler, Matthew J.; Parker, Audrey J.; Saucerman, Jeffrey J.

    2012-01-01

    Cardiac hypertrophy is managed by a dense web of signaling pathways with many pathways influencing myocyte growth. A quantitative understanding of the contributions of individual pathways and their interactions is needed to better understand hypertrophy signaling and to develop more effective therapies for heart failure. We developed a computational model of the cardiac myocyte hypertrophy signaling network to determine how the components and network topology lead to differential regulation of transcription factors, gene expression, and myocyte size. Our computational model of the hypertrophy signaling network contains 106 species and 193 reactions, integrating 14 established pathways regulating cardiac myocyte growth. 109 of 114 model predictions were validated using published experimental data testing the effects of receptor activation on transcription factors and myocyte phenotypic outputs. Network motif analysis revealed an enrichment of bifan and biparallel cross-talk motifs. Sensitivity analysis was used to inform clustering of the network into modules and to identify species with the greatest effects on cell growth. Many species influenced hypertrophy, but only a few nodes had large positive or negative influences. Ras, a network hub, had the greatest effect on cell area and influenced more species than any other protein in the network. We validated this model prediction in cultured cardiac myocytes. With this integrative computational model, we identified the most influential species in the cardiac hypertrophy signaling network and demonstrate how different levels of network organization affect myocyte size, transcription factors, and gene expression. PMID:23091058

  4. Separation of Beating Cardiac Myocytes from Suspensions of Heart Cells

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    Pretlow, Thomas G.; Glick, Melvin R.; Reddy, William J.

    1972-01-01

    Heart cells were obtained in suspension after incubation with collagenase and hyaluronidase in Saline A. Cardiac myocytes were separated by isopycnic centrifugation in 88.6 to 92.4% purity from other heart cells with different densities, and by velocity or rate-zonal sedimentation, in 92.8 to 97.4% purity from heart cells with different diameters. A previously described computer integration of the differential sedimentation equation was used to determine the centrifugal force, duration of centrifugation and gradient design, which would permit the separation of cardiac myocytes from other heart cells by velocity sedimentation. The myocytes continued to contract rhythmically after being recovered from the density gradients. Velocity sedimentation was superior to isopycnic sedimentation for the separation of cardiac myocytes from heart cell suspensions because it gave the most highly purified myocytes, resulted in recovery of the largest proportion of myocytes in purified fractions from the gradient and required lower centrifugal forces for shorter periods of time. The potential significance of the availability of pure cardiac myocytes is discsused. ImagesFig 2Fig 1 PMID:4336547

  5. Rat cardiac myocyte adenosine transport and metabolism

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    Ford, D.A.; Rovetto, M.J.

    1987-01-01

    Based on the importance of myocardial adenosine and adenine nucleotide metabolism, the adenosine salvage pathway in ventricular myocytes was studied. Accurate estimates of transport rates, separate from metabolic fllux, were determined. Adenosine influx was constant between 3 and 60 s. Adenosine metabolism maintained intracellular adenosine concentrations < 10% of the extracellular adenosine concentrations and thus unidirectional influx could be measured. Myocytes transported adenosine via saturable and nonsaturable processes. A minimum estimate of the V/sub max/ of myocytic adenosine kinase indicated the saturable component of adenosine influx was independent of adenosine kinase activity. Saturable transport was inhibited by nitrobenzylthioinosine and verapamil. Extracellular adenosine taken up myocytes was rapidly phosphorylated to adenine taken up by myocytes was rapidly phosphorylated to adenine nucleotides. Not all extracellular adenosine, though, was phosphorylated on entering myocytes, since free, as opposed to protein-bound, intracellular adenosine was detected after digitonin extraction of cells in the presence of 1 mM ethylene-diaminetetraacetic acid.

  6. Angiopoietin-1 promotes cardiac and skeletal myocyte survival through integrins.

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    Dallabrida, Susan M; Ismail, Nesreen; Oberle, Julianne R; Himes, Blanca E; Rupnick, Maria A

    2005-03-04

    Cardiac myocyte loss, regardless of insult, can trigger compensatory myocardial remodeling leading to heart failure. Identifying mediators of cardiac myocyte survival may advance clinical efforts toward myocardial preservation. Angiopoietin-1 limits ischemia-induced cardiac injury. This benefit is ascribed to angiogenesis because the receptor, tie2, is largely endothelial-specific. We propose that direct, non-tie2 interactions of angiopoietin-1 on cardiac myocytes contribute to this cardioprotection. We found that mouse C2C12 skeletal myocytes lack tie2, yet dose-dependently adhered to angiopoietin-1 and angiopoietin-2 similarly to laminin, fibronectin, vitronectin, and more than to collagen-I, -III, and -IV. Adhesion was divalent cation-mediated (Mn2+, Ca2+, not Mg2+), blocked with EDTA/EGTA, RGD-based peptides, and select integrin subunit antibodies. Similar findings were obtained with human skeletal myocytes (HSMs) and freshly isolated rat neonatal cardiac myocytes (NCMs). Furthermore, angiopoietin-1 conferred significant survival advantage exceeding that of most cell matrices, which was not fully explained by differences in cell adhesion. Angiopoietin-1 promoted survival of serum-starved C2C12, HSM, and NCM (MTT, trypan blue) and prevented taxol-induced apoptosis (caspase-3). Immobilized and soluble angiopoietin-1 phosphorylated Akt(S473) and MAPK(p42/44), (not FAK(Y397)) in C2C12 more than in endothelial cells and more than did angiopoietin-2 or cell matrices. EDTA, RGD-based peptides, and some integrin antibodies blocked these responses. Angiopoietin-1 activated HSM and NCM Akt(S473) and MAPK(p42/44) survival pathways. We propose that this novel function contributes to developmental and cardioprotective actions of angiopoietin-1 presently attributed to vascular effects alone. Angiopoietin-1 may prove therapeutically valuable in cardiac remodeling by supporting myocyte viability and preserving pump function. The full text of this article is available online at

  7. Carvedilol stimulates nitric oxide synthesis in rat cardiac myocytes.

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    Kurosaki, K; Ikeda, U; Maeda, Y; Shimada, K

    2000-02-01

    The purpose of this study was to investigate the effects of the beta-adrenergic blocker carvedilol on nitric oxide (NO) synthesis in cardiac myocytes. We measured the accumulation of nitrite, a stable oxidation product of NO, and the expression of inducible NO synthase (iNOS) protein in cultured neonatal rat cardiac myocytes. Incubation of the cultures with interleukin 1 beta (IL-1 beta; 10 ng/ml) caused a marked increase in nitrite production. Although carvedilol alone showed no effect on nitrite accumulation, it significantly enhanced IL-1 beta-induced nitrite production by cardiac myocytes. The effect of carvedilol was completely abolished in the presence of aminoguanidine or actinomycin D. The nitrite production enhanced by carvedilol was accompanied by increased iNOS protein expression. Unlike carvedilol, other beta-blockers, namely propranolol, atenolol and arotinolol, did not enhance IL-1 beta-induced nitrite production. Addition of isoproterenol significantly increased nitrite production by IL-1 beta-stimulated cardiac myocytes. Atenolol suppressed this isoproterenol-induced nitrite accumulation, while carvedilol further increased the nitrite accumulation. These findings indicate that carvedilol increases NO synthesis in IL-1 beta-stimulated rat cardiac myocytes by a beta-adrenoceptor-independent mechanism. Copyright 2000 Academic Press.

  8. Phosphatidylinositol-bisphosphate regulates intercellular coupling in cardiac myocytes

    DEFF Research Database (Denmark)

    Hofgaard, Johannes P; Banach, Kathrin; Mollerup, Sarah

    2008-01-01

    Changes in the lipid composition of cardiac myocytes have been reported during cardiac hypertrophy, cardiomyopathy, and infarction. Because a recent study indicates a relation between low phosphatidylinositol-bisphosphate (PIP(2)) levels and reduced intercellular coupling, we tested the hypothesis...... in cardiomyocytes grown on microelectrode arrays. Intercellular coupling was reduced by angiotensin II (43.7 +/- 9.3%, N = 11) and noradrenaline (58.0 +/- 10.7%, N = 11). To test if reduced intercellular coupling after agonist stimulation was caused by PIP(2)-depletion, myocytes were stimulated by angiotensin II...... coupling. In beating myocytes, conduction velocity was reduced by angiotensin II stimulation, and recovery after wash out was prevented by inhibition of PIP(2) production. Reductions in PIP(2) inhibit intercellular coupling in cardiomyocytes, and stimulation by physiologically relevant agonists reduces...

  9. Design-based stereological estimation of the total number of cardiac myocytes in histological sections

    DEFF Research Database (Denmark)

    Brüel, Annemarie; Nyengaard, Jens Randel

    2005-01-01

    BACKGROUND: Counting the total number of cardiac myocytes has not previously been possible in ordinary histological sections using light microscopy (LM) due to difficulties in defining the myocyte borders properly. AIM: To describe a method by which the total number of cardiac myocytes is estimated...

  10. Matrix elasticity regulates the optimal cardiac myocyte shape for contractility

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    McCain, Megan L.; Yuan, Hongyan; Pasqualini, Francesco S.; Campbell, Patrick H.

    2014-01-01

    Concentric hypertrophy is characterized by ventricular wall thickening, fibrosis, and decreased myocyte length-to-width aspect ratio. Ventricular thickening is considered compensatory because it reduces wall stress, but the functional consequences of cell shape remodeling in this pathological setting are unknown. We hypothesized that decreases in myocyte aspect ratio allow myocytes to maximize contractility when the extracellular matrix becomes stiffer due to conditions such as fibrosis. To test this, we engineered neonatal rat ventricular myocytes into rectangles mimicking the 2-D profiles of healthy and hypertrophied myocytes on hydrogels with moderate (13 kPa) and high (90 kPa) elastic moduli. Actin alignment was unaffected by matrix elasticity, but sarcomere content was typically higher on stiff gels. Microtubule polymerization was higher on stiff gels, implying increased intracellular elastic modulus. On moderate gels, myocytes with moderate aspect ratios (∼7:1) generated the most peak systolic work compared with other cell shapes. However, on stiffer gels, low aspect ratios (∼2:1) generated the most peak systolic work. To compare the relative contributions of intracellular vs. extracellular elasticity to contractility, we developed an analytical model and used our experimental data to fit unknown parameters. Our model predicted that matrix elasticity dominates over intracellular elasticity, suggesting that the extracellular matrix may potentially be a more effective therapeutic target than microtubules. Our data and model suggest that myocytes with lower aspect ratios have a functional advantage when the elasticity of the extracellular matrix decreases due to conditions such as fibrosis, highlighting the role of the extracellular matrix in cardiac disease. PMID:24682394

  11. Nanomaterials for Cardiac Myocyte Tissue Engineering

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    Rodolfo Amezcua

    2016-07-01

    Full Text Available Since their synthesizing introduction to the research community, nanomaterials have infiltrated almost every corner of science and engineering. Over the last decade, one such field has begun to look at using nanomaterials for beneficial applications in tissue engineering, specifically, cardiac tissue engineering. During a myocardial infarction, part of the cardiac muscle, or myocardium, is deprived of blood. Therefore, the lack of oxygen destroys cardiomyocytes, leaving dead tissue and possibly resulting in the development of arrhythmia, ventricular remodeling, and eventual heart failure. Scarred cardiac muscle results in heart failure for millions of heart attack survivors worldwide. Modern cardiac tissue engineering research has developed nanomaterial applications to combat heart failure, preserve normal heart tissue, and grow healthy myocardium around the infarcted area. This review will discuss the recent progress of nanomaterials for cardiovascular tissue engineering applications through three main nanomaterial approaches: scaffold designs, patches, and injectable materials.

  12. Nanomaterials for Cardiac Myocyte Tissue Engineering.

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    Amezcua, Rodolfo; Shirolkar, Ajay; Fraze, Carolyn; Stout, David A

    2016-07-19

    Since their synthesizing introduction to the research community, nanomaterials have infiltrated almost every corner of science and engineering. Over the last decade, one such field has begun to look at using nanomaterials for beneficial applications in tissue engineering, specifically, cardiac tissue engineering. During a myocardial infarction, part of the cardiac muscle, or myocardium, is deprived of blood. Therefore, the lack of oxygen destroys cardiomyocytes, leaving dead tissue and possibly resulting in the development of arrhythmia, ventricular remodeling, and eventual heart failure. Scarred cardiac muscle results in heart failure for millions of heart attack survivors worldwide. Modern cardiac tissue engineering research has developed nanomaterial applications to combat heart failure, preserve normal heart tissue, and grow healthy myocardium around the infarcted area. This review will discuss the recent progress of nanomaterials for cardiovascular tissue engineering applications through three main nanomaterial approaches: scaffold designs, patches, and injectable materials.

  13. Nuclear morphology and deformation in engineered cardiac myocytes and tissues.

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    Bray, Mark-Anthony P; Adams, William J; Geisse, Nicholas A; Feinberg, Adam W; Sheehy, Sean P; Parker, Kevin K

    2010-07-01

    Cardiac tissue engineering requires finely-tuned manipulation of the extracellular matrix (ECM) microenvironment to optimize internal myocardial organization. The myocyte nucleus is mechanically connected to the cell membrane via cytoskeletal elements, making it a target for the cellular response to perturbation of the ECM. However, the role of ECM spatial configuration and myocyte shape on nuclear location and morphology is unknown. In this study, printed ECM proteins were used to configure the geometry of cultured neonatal rat ventricular myocytes. Engineered one- and two-dimensional tissue constructs and single myocyte islands were assayed using live fluorescence imaging to examine nuclear position, morphology and motion as a function of the imposed ECM geometry during diastolic relaxation and systolic contraction. Image analysis showed that anisotropic tissue constructs cultured on microfabricated ECM lines possessed a high degree of nuclear alignment similar to that found in vivo; nuclei in isotropic tissues were polymorphic in shape with an apparently random orientation. Nuclear eccentricity was also increased for the anisotropic tissues, suggesting that intracellular forces deform the nucleus as the cell is spatially confined. During systole, nuclei experienced increasing spatial confinement in magnitude and direction of displacement as tissue anisotropy increased, yielding anisotropic deformation. Thus, the nature of nuclear displacement and deformation during systole appears to rely on a combination of the passive myofibril spatial organization and the active stress fields induced by contraction. Such findings have implications in understanding the genomic consequences and functional response of cardiac myocytes to their ECM surroundings under conditions of disease. Copyright 2010 Elsevier Ltd. All rights reserved.

  14. Improving cardiac myocytes performance by CNTs platforms

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    Valentina eMartinelli

    2013-09-01

    Full Text Available The application of nanotechnology to the cardiovascular system has increasingly caught scientists’ attention as a potentially powerful tool for the development of new generation devices able to interface, repair or boost the performance of cardiac tissue. Carbon nanotubes (CNTs are considered as promising materials for nanomedicine applications in general and have been recently tested towards excitable cell growth. CNTs are cylindrically shaped structures made up of rolled-up graphene sheets, with unique electrical, thermal and mechanical properties, able to effectively conducting electrical current in electrochemical interfaces. CNTs-based scaffolds have been recently found to support the in vitro growth of cardiac cells: in particular, their ability to improve cardiomyocytes proliferation, maturation and electrical behavior are making CNTs extremely attractive for the development and exploitation of interfaces able to impact on cardiac cells physiology and function.

  15. Simultaneous measurement of contraction and oxygen consumption in cardiac myocytes.

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    Rose, H; Strotmann, K H; Pöpping, S; Fischer, Y; Kulsch, D; Kammermeier, H

    1991-10-01

    A setup has been developed that simultaneously measures the mechanics and the energetics of electrically induced contractions at physiological frequencies of isolated cardiac myocytes. The core of the setup is a self-manufactured stimulation chamber in which most of the myocytes are in suspension while some are attached to a plastic cover slip prepared from culture Petri dishes. The analysis of the contractile behavior of the attached myocytes is based on an image-processing system with digitized frames of a charge-coupled device camera. Thirty-six frames illuminated by a stroboscope are taken at increasing time intervals between stimulus and flash (snap), allowing one to resolve the contraction cycle with a very high time resolution (down to 1 ms). The number of pixels that differ between each of these frames and a "reference" frame of the cells in the relaxed state (slack cell length) are used to quantify the contractions. An oxygen electrode in the chamber registers the drop of oxygen tension resulting from the consumption by the myocytes, which exhibit a strictly aerobic metabolism. The resulting data are also stored and analyzed in an IBM-AT-compatible computer.

  16. Loss of Adult Cardiac Myocyte GSK-3 Leads to Mitotic Catastrophe Resulting in Fatal Dilated Cardiomyopathy

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    Zhou, Jibin; Ahmad, Firdos; Parikh, Shan; Hoffman, Nichole E.; Rajan, Sudarsan; Verma, Vipin K.; Song, Jianliang; Yuan, Ancai; Shanmughapriya, Santhanam; Guo, Yuanjun; Gao, Erhe; Koch, Walter; Woodgett, James R.; Muniswamy, Madesh; Kishore, Raj; Lal, Hind; Force, Thomas

    2016-01-01

    Rationale Cardiac myocyte-specific deletion of either Glycogen Synthase Kinase (GSK)3A or GSK3B leads to cardiac protection following myocardial infarction, suggesting that deletion of both isoforms may provide synergistic protection. This is an important consideration due to the fact that all GSK-3–targeted drugs including the drugs already in clinical trial target both isoforms of GSK-3 and none are isoform specific. Objective To identify the consequences of combined deletion of cardiac myocyte GSK3A and GSK3B in heart function. Methods and Results We generated tamoxifen-inducible cardiac myocyte-specific mice lacking both GSK-3 isoforms (double knockout, DKO). We unexpectedly found that cardiac myocyte GSK-3 is essential for cardiac homeostasis and overall survival. Serial echocardiographic analysis reveals that within 2 weeks of tamoxifen treatment, DKO hearts leads to excessive dilatative remodeling and ventricular dysfunction. Further experimentation with isolated adult cardiac myocytes and fibroblasts from DKO implicated cardiac myocytes intrinsic factors responsible for observed phenotype. Mechanistically, loss of GSK-3 in adult cardiac myocytes resulted in induction of mitotic catastrophe, a previously unreported event in cardiac myocytes. DKO cardiac myocytes showed cell cycle progression resulting in increased DNA content and multi-nucleation. However, increased cell cycle activity was rivaled by marked activation of DNA damage, cell cycle checkpoint activation, and mitotic catastrophe induced apoptotic cell death. Importantly, mitotic catastrophe was also confirmed in isolated adult cardiac myocytes. Conclusion Together, our findings suggest that cardiac myocyte GSK-3 is required to maintain normal cardiac homeostasis and its loss is incompatible with life due to cell cycle dysregulation that ultimately results in a severe fatal dilated cardiomyopathy. PMID:26976650

  17. The Electrophysiological Effects of Qiliqiangxin on Cardiac Ventricular Myocytes of Rats

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    Wei, Yidong; Liu, Xiaoyu; Wei, Haidong; Hou, Lei; Che, Wenliang; The, Erlinda; Li, Gang; Jhummon, Muktanand Vikash; Wei, Wanlin

    2013-01-01

    Qiliqiangxin, a Chinese herb, represents the affection in Ca channel function of cardiac myocytes. It is unknown whether Qiliqiangxin has an effect on Na current and K current because the pharmacological actions of this herb's compound are very complex. We investigated the rational usage of Qiliqiangxin on cardiac ventricular myocytes of rats. Ventricular myocytes were exposed acutely to 1, 10, and 50 mg/L Qiliqiangxin, and whole cell patch-clamp technique was used to study the acute effects of Qiliqiangxin on Sodium current (I Na), outward currents delayed rectifier outward K+ current (I K), slowly activating delayed rectifier outward K+ current (I Ks), transient outward K+ current (I to), and inward rectifier K+ current (I K1). Qiliqiangxin can decrease I Na by 28.53% ± 5.98%, and its IC50 was 9.2 mg/L. 10 and 50 mg/L Qiliqiangxin decreased by 37.2% ± 6.4% and 55.9% ± 5.5% summit current density of I to. 10 and 50 mg/L Qiliqiangxin decreased I Ks by 15.51% ± 4.03% and 21.6% ± 5.6%. Qiliqiangxin represented a multifaceted pharmacological profile. The effects of Qiliqiangxin on Na and K currents of ventricular myocytes were more profitable in antiarrhythmic therapy in the clinic. We concluded that the relative efficacy of Qiliqiangxin was another choice for the existing antiarrhythmic therapy. PMID:24250713

  18. Heterogeneity of ATP-sensitive K+ Channels in Cardiac Myocytes

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    Hong, Miyoun; Bao, Li; Kefaloyianni, Eirini; Agullo-Pascual, Esperanza; Chkourko, Halina; Foster, Monique; Taskin, Eylem; Zhandre, Marine; Reid, Dylan A.; Rothenberg, Eli; Delmar, Mario; Coetzee, William A.

    2012-01-01

    Ventricular ATP-sensitive potassium (KATP) channels link intracellular energy metabolism to membrane excitability and contractility. Our recent proteomics experiments identified plakoglobin and plakophilin-2 (PKP2) as putative KATP channel-associated proteins. We investigated whether the association of KATP channel subunits with junctional proteins translates to heterogeneous subcellular distribution within a cardiac myocyte. Co-immunoprecipitation experiments confirmed physical interaction between KATP channels and PKP2 and plakoglobin in rat heart. Immunolocalization experiments demonstrated that KATP channel subunits (Kir6.2 and SUR2A) are expressed at a higher density at the intercalated disk in mouse and rat hearts, where they co-localized with PKP2 and plakoglobin. Super-resolution microscopy demonstrate that KATP channels are clustered within nanometer distances from junctional proteins. The local KATP channel density, recorded in excised inside-out patches, was larger at the cell end when compared with local currents recorded from the cell center. The KATP channel unitary conductance, block by MgATP and activation by MgADP, did not differ between these two locations. Whole cell KATP channel current density (activated by metabolic inhibition) was ∼40% smaller in myocytes from mice haploinsufficient for PKP2. Experiments with excised patches demonstrated that the regional heterogeneity of KATP channels was absent in the PKP2 deficient mice, but the KATP channel unitary conductance and nucleotide sensitivities remained unaltered. Our data demonstrate heterogeneity of KATP channel distribution within a cardiac myocyte. The higher KATP channel density at the intercalated disk implies a possible role at the intercellular junctions during cardiac ischemia. PMID:23066018

  19. Magnesium homeostasis in cardiac myocytes of Mg-deficient rats.

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    Michiko Tashiro

    Full Text Available To study possible modulation of Mg(2+ transport in low Mg(2+ conditions, we fed either a Mg-deficient diet or a Mg-containing diet (control to Wistar rats for 1-6 weeks. Total Mg concentrations in serum and cardiac ventricular tissues were measured by atomic absorption spectroscopy. Intracellular free Mg(2+ concentration ([Mg(2+]i of ventricular myocytes was measured with the fluorescent indicator furaptra. Mg(2+ transport rates, rates of Mg(2+ influx and Mg(2+ efflux, were estimated from the rates of change in [Mg(2+]i during Mg loading/depletion and recovery procedures. In Mg-deficient rats, the serum total Mg concentration (0.29±0.026 mM was significantly lower than in control rats (0.86±0.072 mM after 4-6 weeks of Mg deficiency. However, neither total Mg concentration in ventricular tissues nor [Mg(2+]i of ventricular myocytes was significantly different between Mg-deficient rats and control rats. The rates of Mg(2+ influx and efflux were not significantly different in both groups. In addition, quantitative RT-PCR revealed that Mg deficiency did not substantially change mRNA expression levels of known Mg(2+ channels/transporters (TRPM6, TRPM7, MagT1, SLC41A1 and ACDP2 in heart and kidney tissues. These results suggest that [Mg(2+]i as well as the total Mg content of cardiac myocytes, was well maintained even under chronic hypomagnesemia without persistent modulation in function and expression of major Mg(2+ channels/transporters in the heart.

  20. ErbB4 localization to cardiac myocyte nuclei, and its role in myocyte DNA damage response

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    Icli, Basak [Department of Medicine, Cardiovascular Division, Brigham and Women' s Hospital, Harvard Medical School, Boston, MA 02115 (United States); Bharti, Ajit [Center of Molecular Stress Response Whitaker Cardiovascular Institute, Department of Medicine, Boston University Medical Center, Boston, MA 02118 (United States); Pentassuglia, Laura; Peng, Xuyang [Department of Medicine, Vanderbilt University Medical Center, Nashville, TN (United States); Sawyer, Douglas B., E-mail: douglas.b.sawyer@vanderbilt.edu [Department of Medicine, Vanderbilt University Medical Center, Nashville, TN (United States)

    2012-02-03

    Highlights: Black-Right-Pointing-Pointer ErbB4 localizes to cardiac myocyte nuclei as a full-length receptor. Black-Right-Pointing-Pointer Cardiac myocytes express predominantly JM-a/CYT-1 ErbB4. Black-Right-Pointing-Pointer Myocyte p53 activation in response to doxorubicin requires ErbB4 activity. -- Abstract: The intracellular domain of ErbB4 receptor tyrosine kinase is known to translocate to the nucleus of cells where it can regulate p53 transcriptional activity. The purpose of this study was to examine whether ErbB4 can localize to the nucleus of adult rat ventricular myocytes (ARVM), and regulate p53 in these cells. We demonstrate that ErbB4 does locate to the nucleus of cardiac myocytes as a full-length protein, although nuclear location occurs as a full-length protein that does not require Protein Kinase C or {gamma}-secretase activity. Consistent with this we found that only the non-cleavable JM-b isoform of ErbB4 is expressed in ARVM. Doxorubicin was used to examine ErbB4 role in regulation of a DNA damage response in ARVM. Doxorubicin induced p53 and p21 was suppressed by treatment with AG1478, an EGFR and ErbB4 kinase inhibitor, or suppression of ErbB4 expression with small interfering RNA. Thus ErbB4 localizes to the nucleus as a full-length protein, and plays a role in the DNA damage response induced by doxorubicin in cardiac myocytes.

  1. Mitochondria-Targeted Antioxidant Prevents Cardiac Dysfunction Induced by Tafazzin Gene Knockdown in Cardiac Myocytes

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    Quan He

    2014-01-01

    Full Text Available Tafazzin, a mitochondrial acyltransferase, plays an important role in cardiolipin side chain remodeling. Previous studies have shown that dysfunction of tafazzin reduces cardiolipin content, impairs mitochondrial function, and causes dilated cardiomyopathy in Barth syndrome. Reactive oxygen species (ROS have been implicated in the development of cardiomyopathy and are also the obligated byproducts of mitochondria. We hypothesized that tafazzin knockdown increases ROS production from mitochondria, and a mitochondria-targeted antioxidant prevents tafazzin knockdown induced mitochondrial and cardiac dysfunction. We employed cardiac myocytes transduced with an adenovirus containing tafazzin shRNA as a model to investigate the effects of the mitochondrial antioxidant, mito-Tempo. Knocking down tafazzin decreased steady state levels of cardiolipin and increased mitochondrial ROS. Treatment of cardiac myocytes with mito-Tempo normalized tafazzin knockdown enhanced mitochondrial ROS production and cellular ATP decline. Mito-Tempo also significantly abrogated tafazzin knockdown induced cardiac hypertrophy, contractile dysfunction, and cell death. We conclude that mitochondria-targeted antioxidant prevents cardiac dysfunction induced by tafazzin gene knockdown in cardiac myocytes and suggest mito-Tempo as a potential therapeutic for Barth syndrome and other dilated cardiomyopathies resulting from mitochondrial oxidative stress.

  2. Parallel acceleration for modeling of calcium dynamics in cardiac myocytes.

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    Liu, Ke; Yao, Guangming; Yu, Zeyun

    2014-01-01

    Spatial-temporal calcium dynamics due to calcium release, buffering, and re-uptaking plays a central role in studying excitation-contraction (E-C) coupling in both healthy and defected cardiac myocytes. In our previous work, partial differential equations (PDEs) had been used to simulate calcium dynamics with realistic geometries extracted from electron microscopic imaging data. However, the computational costs of such simulations are very high on a single processor. To alleviate this problem, we have accelerated the numerical simulations of calcium dynamics by using graphics processing units (GPUs). Computational performance and simulation accuracy are compared with those based on a single CPU and another popular parallel computing technique, OpenMP.

  3. Genetically engineered cardiac pacemaker: Stem cells transfected with HCN2 gene and myocytes-A model

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    Kanani, S. [Institut Genomique Fonctionelle, 141 Rue de la Cardonille, 34396 Montpellier (France); Institut Non Lineaire de Nice, CNRS and Universite de Nice, 1361 route des Lucioles, 06560 Valbonne (France); Pumir, A. [Institut Non Lineaire de Nice, CNRS and Universite de Nice, 1361 route des Lucioles, 06560 Valbonne (France); Laboratoire J.A. Dieudonne, CNRS and Universite de Nice, Parc Valrose, 06108 Nice (France)], E-mail: alain.pumir@unice.fr; Krinsky, V. [Institut Non Lineaire de Nice, CNRS and Universite de Nice, 1361 route des Lucioles, 06560 Valbonne (France)

    2008-01-07

    One of the successfully tested methods to design genetically engineered cardiac pacemaker cells consists in transfecting a human mesenchymal stem cell (hMSC) with a HCN2 gene and connecting it to a myocyte. We develop and study a mathematical model, describing a myocyte connected to a hMSC transfected with a HCN2 gene. The cardiac action potential is described both with the simple Beeler-Reuter model, as well as with the elaborate dynamic Luo-Rudy model. The HCN2 channel is described by fitting electrophysiological records, in the spirit of Hodgkin-Huxley. The model shows that oscillations can occur in a pair myocyte-stem cell, that was not observed in the experiments yet. The model predicted that: (1) HCN pacemaker channels can induce oscillations only if the number of expressed I{sub K1} channels is low enough. At too high an expression level of I{sub K1} channels, oscillations cannot be induced, no matter how many pacemaker channels are expressed. (2) At low expression levels of I{sub K1} channels, a large domain of values in the parameter space (n, N) exists, where oscillations should be observed. We denote N the number of expressed pacemaker channels in the stem cell, and n the number of gap junction channels coupling the stem cell and the myocyte. (3) The expression levels of I{sub K1} channels observed in ventricular myocytes, both in the Beeler-Reuter and in the dynamic Luo-Rudy models are too high to allow to observe oscillations. With expression levels below {approx}1/4 of the original value, oscillations can be observed. The main consequence of this work is that in order to obtain oscillations in an experiment with a myocyte-stem cell pair, increasing the values of n, N is unlikely to be helpful, unless the expression level of I{sub K1} has been reduced enough. The model also allows us to explore levels of gene expression not yet achieved in experiments, and could be useful to plan new experiments, aimed at improving the robustness of the oscillations.

  4. Theory of arrhythmia based on mechano-electric feedback between cardiac myocytes and cardiac fibroblasts

    Directory of Open Access Journals (Sweden)

    Sergey V. Kolmakow

    2016-05-01

    Full Text Available When analyzing the articles submitted to our current issue, we involved into the preparation processing some relevant papers deserving special attention. The papers reveal the mechano-electric mechanism of the feedback between cardiac myocytes and cardiac fibroblasts that is capable of directly initiating cardiac arrhythmia. In the meantime, unfortunately, direct communication with Russian researchers Kamkin A.G., Kiseleva I.S. and Yarygin V.N. was not possible, but nevertheless, we are of the opinion that it is reasonable to review their articles, which discuss this interesting and logically justified mechanism of arrhythmia.

  5. Cardiac-generated prostanoids mediate cardiac myocyte apoptosis after myocardial ischaemia

    Science.gov (United States)

    Qiu, Hong; Liu, Jun-Yan; Wei, Dongguang; Li, Ning; Yamoah, Ebenezer N.; Hammock, Bruce D.; Chiamvimonvat, Nipavan

    2012-01-01

    Aims The objective of the present study is to elucidate the pathogenic role of eicosanoids in myocardial infarction (MI). The accumulation of eicosanoid metabolites in ischaemic myocardium has been demonstrated in animal models and patients with MI, and it occurs in parallel with the development of irreversible cardiac damage. However, the key question that remains unanswered is whether cardiac-generated eicosanoids are the cause or the consequence of cardiac cell damage in MI. Methods and results We used a clinically relevant animal model of MI and metabolic profiling to monitor the eicosanoid profile in ischaemic myocardium. We demonstrate that ischaemia induces the generation of prostanoids mainly through the cyclooxygenase (COX)-1 pathway in the myocardium. Cardiac-generated prostanoids, particularly prostaglandin D2 (PGD2), can directly induce apoptosis in cardiac myocytes. This effect involves the up-regulation of the pro-apoptotic gene, Fas ligand (FasL), in a D-type prostanoid receptor-independent manner. The treatment of the MI mice with low-dose aspirin effectively inhibits the ischaemia-induced prostanoid generation and FasL expression in the myocardium, leading to the reduction in cardiac apoptosis following cardiac ischaemia. Conclusions Cardiac ischaemia results in COX-1-mediated generation of prostanoids, which by inducing cardiac myocyte apoptosis, contribute to the cardiac cell loss following MI. The benefits of low-dose aspirin treatment in MI may be attributable, in part, to the inhibition of cardiac prostanoid generation and attenuation of apoptosis. Further understanding of the mechanisms underlying prostanoid-induced cardiac apoptosis may be of significant value in designing new therapeutic strategies to prevent aberrant cell loss following MI and subsequent progression to heart failure. PMID:22707158

  6. Regulation of cardiac myocyte contractility by phospholemman: Na+/Ca2+ exchange versus Na+ -K+ -ATPase.

    Science.gov (United States)

    Song, Jianliang; Zhang, Xue-Qian; Wang, JuFang; Cheskis, Ellina; Chan, Tung O; Feldman, Arthur M; Tucker, Amy L; Cheung, Joseph Y

    2008-10-01

    Phospholemman (PLM) regulates cardiac Na(+)/Ca(2+) exchanger (NCX1) and Na(+)-K(+)-ATPase in cardiac myocytes. PLM, when phosphorylated at Ser(68), disinhibits Na(+)-K(+)-ATPase but inhibits NCX1. PLM regulates cardiac contractility by modulating Na(+)-K(+)-ATPase and/or NCX1. In this study, we first demonstrated that adult mouse cardiac myocytes cultured for 48 h had normal surface membrane areas, t-tubules, and NCX1 and sarco(endo)plasmic reticulum Ca(2+)-ATPase levels, and retained near normal contractility, but alpha(1)-subunit of Na(+)-K(+)-ATPase was slightly decreased. Differences in contractility between myocytes isolated from wild-type (WT) and PLM knockout (KO) hearts were preserved after 48 h of culture. Infection with adenovirus expressing green fluorescent protein (GFP) did not affect contractility at 48 h. When WT PLM was overexpressed in PLM KO myocytes, contractility and cytosolic Ca(2+) concentration ([Ca(2+)](i)) transients reverted back to those observed in cultured WT myocytes. Both Na(+)-K(+)-ATPase current (I(pump)) and Na(+)/Ca(2+) exchange current (I(NaCa)) in PLM KO myocytes rescued with WT PLM were depressed compared with PLM KO myocytes. Overexpressing the PLMS68E mutant (phosphomimetic) in PLM KO myocytes resulted in the suppression of I(NaCa) but had no effect on I(pump). Contractility, [Ca(2+)](i) transient amplitudes, and sarcoplasmic reticulum Ca(2+) contents in PLM KO myocytes overexpressing the PLMS68E mutant were depressed compared with PLM KO myocytes overexpressing GFP. Overexpressing the PLMS68A mutant (mimicking unphosphorylated PLM) in PLM KO myocytes had no effect on I(NaCa) but decreased I(pump). Contractility, [Ca(2+)](i) transient amplitudes, and sarcoplasmic reticulum Ca(2+) contents in PLM KO myocytes overexpressing the S68A mutant were similar to PLM KO myocytes overexpressing GFP. We conclude that at the single-myocyte level, PLM affects cardiac contractility and [Ca(2+)](i) homeostasis primarily by its direct

  7. VAMP-1, VAMP-2, and syntaxin-4 regulate ANP release from cardiac myocytes.

    Science.gov (United States)

    Ferlito, Marcella; Fulton, William B; Zauher, Mohamed A; Marbán, Eduardo; Steenbergen, Charles; Lowenstein, Charles J

    2010-11-01

    ANP is a peptide released by cardiac myocytes that regulates blood pressure and natriuresis. However, the molecular mechanisms controlling ANP release from cardiac myocytes are not defined. We now identify three components of the exocytic machinery that regulate ANP release from atrial myocytes. We found that cardiac myocytes express N-ethylmaleimide sensitive factor (NSF), soluble NSF attachment protein (α-SNAP), and SNAP receptors (SNAREs). Additionally we found that specific SNARE molecules, VAMP-1 and VAMP-2, both co-sediment and co-localize with ANP. Also, one SNARE molecule, syntaxin-4, partially co-sediments and partially co-localizes with ANP. Furthermore, these three SNAREs, syntaxin-4 and VAMP-1 and VAMP-2, form a SNARE complex inside cardiac myocytes. Finally, knockdown of VAMP-1, VAMP-2, or syntaxin-4 blocks regulated release of ANP. In contrast, silencing of VAMP-3 did not have an effect on ANP release. Our data suggest that three specific SNAREs regulate cardiac myocyte exocytosis of ANP. Pathways that modify the exocytic machinery may influence natriuresis and blood pressure. Copyright © 2010 Elsevier Ltd. All rights reserved.

  8. L-type calcium channel targeting and local signalling in cardiac myocytes.

    Science.gov (United States)

    Shaw, Robin M; Colecraft, Henry M

    2013-05-01

    In the heart, Ca(2+) influx via Ca(V)1.2 L-type calcium channels (LTCCs) is a multi-functional signal that triggers muscle contraction, controls action potential duration, and regulates gene expression. The use of LTCC Ca(2+) as a multi-dimensional signalling molecule in the heart is complicated by several aspects of cardiac physiology. Cytosolic Ca(2+) continuously cycles between ~100 nM and ~1 μM with each heartbeat due to Ca(2+) linked signalling from LTCCs to ryanodine receptors. This rapid cycling raises the question as to how cardiac myocytes distinguish the Ca(2+) fluxes originating through L-type channels that are dedicated to contraction from Ca(2+) fluxes originating from other L-type channels that are used for non-contraction-related signalling. In general, disparate Ca(2+) sources in cardiac myocytes such as current through differently localized LTCCs as well as from IP3 receptors can signal selectively to Ca(2+)-dependent effectors in local microdomains that can be impervious to the cytoplasmic Ca(2+) transients that drive contraction. A particular challenge for diversified signalling via cardiac LTCCs is that they are voltage-gated and, therefore, open and presumably flood their microdomains with Ca(2+) with each action potential. Thus spatial localization of Cav1.2 channels to different types of microdomains of the ventricular cardiomyocyte membrane as well as the existence of particular macromolecular complexes in each Cav1.2 microdomain are important to effect different types of Cav1.2 signalling. In this review we examine aspects of Cav1.2 structure, targeting and signalling in two specialized membrane microdomains--transverse tubules and caveolae.

  9. Hyperoxia Induces Inflammation and Cytotoxicity in Human Adult Cardiac Myocytes.

    Science.gov (United States)

    Hafner, Christina; Wu, Jing; Tiboldi, Akos; Hess, Moritz; Mitulovic, Goran; Kaun, Christoph; Krychtiuk, Konstantin Alexander; Wojta, Johann; Ullrich, Roman; Tretter, Eva Verena; Markstaller, Klaus; Klein, Klaus Ulrich

    2017-04-01

    Supplemental oxygen (O2) is used as adjunct therapy in anesthesia, emergency, and intensive care medicine. We hypothesized that excessive O2 levels (hyperoxia) can directly injure human adult cardiac myocytes (HACMs). HACMs obtained from the explanted hearts of transplantation patients were exposed to constant hyperoxia (95% O2), intermittent hyperoxia (alternating 10 min exposures to 5% and 95% O2), constant normoxia (21% O2), or constant mild hypoxia (5% O2) using a bioreactor. Changes in cell morphology, viability as assessed by lactate dehydrogenase (LDH) release and trypan blue (TB) staining, and secretion of vascular endothelial growth factor (VEGF), macrophage migration inhibitory factor (MIF), and various pro-inflammatory cytokines (interleukin, IL; chemokine C-X-C motif ligand, CXC; granulocyte-colony stimulating factor, G-CSF; intercellular adhesion molecule, ICAM; chemokine C-C motif ligand, CCL) were compared among treatment groups at baseline (0 h) and after 8, 24, and 72 h of treatment. Changes in HACM protein expression were determined by quantitative proteomic analysis after 48 h of exposure. Compared with constant normoxia and mild hypoxia, constant hyperoxia resulted in a higher TB-positive cell count, greater release of LDH, and elevated secretion of VEGF, MIF, IL-1β, IL-6, IL-8, CXCL-1, CXCL-10, G-CSF, ICAM-1, CCL-3, and CCL-5. Cellular inflammation and cytotoxicity gradually increased and was highest after 72 h of constant and intermittent hyperoxia. Quantitative proteomic analysis revealed that hypoxic and hyperoxic O2 exposure differently altered the expression levels of proteins involved in cell-cycle regulation, energy metabolism, and cell signaling. In conclusion, constant and intermittent hyperoxia induced inflammation and cytotoxicity in HACMs. Cell injury occurred earliest and was greatest after constant hyperoxia, but even relatively brief repeating hyperoxic episodes induced a substantial inflammatory response.

  10. Numerical Simulations of Calcium Ions Spiral Wave in Single Cardiac Myocyte

    Science.gov (United States)

    Bai, Yong-Qiang; Zhu, Xing

    2010-04-01

    The calcium ions (Ca2+) spark is an elementary Ca2+ release event in cardiac myocytes. It is believed to buildup cell-wide Ca2+ signals, such as Ca2+ transient and Ca2+ wave, through a Ca2+-induced Ca2+ release (CICR) mechanism. Here the excitability of the Ca2+ wave in a single cardiac myocyte is simulated by employing the fire-diffuse-fire model. By modulating the dynamic parameters of Ca2+ release and re-uptake channels, we find three Ca2+ signaling states in a single cardiac myocyte: no wave, plane wave, and spiral wave. The period of a spiral wave is variable in the different regimes. This study indicates that the spiral wave or the excitability of the system can be controlled through micro-modulation in a living excitable medium.

  11. β-Adrenergic Receptor-Stimulated Cardiac Myocyte Apoptosis: Role of β1 Integrins

    Directory of Open Access Journals (Sweden)

    Parthiv Amin

    2011-01-01

    Full Text Available Increased sympathetic nerve activity to the myocardium is a central feature in patients with heart failure. Accumulation of catecholamines plays an important role in the pathogenesis of heart disease. Acting via β-adrenergic receptors (β-AR, catecholamines (norepinephrine and isoproterenol increase cardiac myocyte apoptosis in vitro and in vivo. Specifically, β1-AR and β2-AR coupled to Gαs exert a proapoptotic action, while β2-AR coupled to Gi exerts an antiapoptotic action. β1 integrin signaling protects cardiac myocytes against β-AR-stimulated apoptosis in vitro and in vivo. Interaction of matrix metalloproteinase-2 (MMP-2 with β1 integrins interferes with the survival signals initiated by β1 integrins. This paper will discuss background information on β-AR and integrin signaling and summarize the role of β1 integrins in β-AR-stimulated cardiac myocyte apoptosis.

  12. Uptake and metabolism of the novel peptide angiotensin-(1-12 by neonatal cardiac myocytes.

    Directory of Open Access Journals (Sweden)

    Sarfaraz Ahmad

    2011-01-01

    Full Text Available Angiotensin-(1-12 [Ang-(1-12] functions as an endogenous substrate for the productions of Ang II and Ang-(1-7 by a non-renin dependent mechanism. This study evaluated whether Ang-(1-12 is incorporated by neonatal cardiac myocytes and the enzymatic pathways of ¹²⁵I-Ang-(1-12 metabolism in the cardiac myocyte medium from WKY and SHR rats.The degradation of ¹²⁵I-Ang-(1-12 (1 nmol/L in the cultured medium of these cardiac myocytes was evaluated in the presence and absence of inhibitors for angiotensin converting enzymes 1 and 2, neprilysin and chymase. In both strains uptake of ¹²⁵I-Ang-(1-12 by myocytes occurred in a time-dependent fashion. Uptake of intact Ang-(1-12 was significantly greater in cardiac myocytes of SHR as compared to WKY. In the absence of renin angiotensin system (RAS enzymes inhibitors the hydrolysis of labeled Ang-(1-12 and the subsequent generation of smaller Ang peptides from Ang-(1-12 was significantly greater in SHR compared to WKY controls. ¹²⁵I-Ang-(1-12 degradation into smaller Ang peptides fragments was significantly inhibited (90% in WKY and 71% in SHR in the presence of all RAS enzymes inhibitors. Further analysis of peptide fractions generated through the incubation of Ang-(1-12 in the myocyte medium demonstrated a predominant hydrolytic effect of angiotensin converting enzyme and neprilysin in WKY and an additional role for chymase in SHR.These studies demonstrate that neonatal myocytes sequester angiotensin-(1-12 and revealed the enzymes involved in the conversion of the dodecapeptide substrate to biologically active angiotensin peptides.

  13. Cell-specific expression of SERCA, the exogenous Ca2+ transport ATPase, in cardiac myocytes.

    Science.gov (United States)

    Ma, Hailun; Sumbilla, Carlota M; Farrance, Iain K G; Klein, Michael G; Inesi, Giuseppe

    2004-03-01

    We evaluated various constructs to obtain cell-specific expression of the sarco(endo)plasmic reticulum Ca2+ -ATPase (SERCA) gene in cardiac myocytes after cDNA transfer by means of transfections or infections with adenovirus vectors. Expression of exogenous enhanced green fluorescent protein (EGFP) and SERCA genes was studied in cultured chicken embryo and neonatal rat cardiac myocytes, skeletal and smooth muscle cells, fibroblasts, and hepatocytes. Whereas the cytomegalovirus (CMV) promoter yielded high levels of protein expression in all cells studied, cardiac troponin T (cTnT) promoter segments demonstrated high specificity for cardiac myocytes. Their efficiency for protein expression was lower than that of the CMV promoter, but higher than that of cardiac myosin light chain or beta-myosin heavy chain promoter segments. A double virus system for Cre-dependent expression under control of the CMV promoter and Cre expression under control of a cardiac-specific promoter yielded high protein levels in cardiac myocytes, but only partial cell specificity due to significant Cre expression in hepatocytes. Specific intracellular targeting of gene products was demonstrated in situ by specific immunostaining of exogenous SERCA1 and endogenous SERCA2 and comparative fluorescence microscopy. The -374 cTnT promoter segment was the most advantageous of the promoters studied, producing cell-specific SERCA expression and a definite increase over endogenous Ca2+ -ATPase activity as well as faster removal of cytosolic calcium after membrane excitation. We conclude that analysis of promoter efficiency and cell specificity is of definite advantage when cell-specific expression of exogenous SERCA is wanted in cardiac myocytes after cDNA delivery to mixed cell populations.

  14. An Experimental Model Using Cultured Cardiac Myocytes for a Study of the Generation of Premature Ventricular Contractions Under Ultrasound Exposure

    Science.gov (United States)

    Kudo, Nobuki; Yamamoto, Masaya

    2011-09-01

    It is known that use of a contrast agents in echocardiography increases the probability of generation of premature ventricular contractions (PVCs). As a basic study to elucidate the mechanisms and to reduce adverse effects, the generation of PVCs was investigated using cultured cardiac myocytes instead of the intact heart in vivo. Cardiac myocytes were isolated from neonatal rats and cultured on a cover slip. The myocyte sample was exposed to pulsed ultrasound with microbubbles adjacent to the myocytes, and generation of PVCs was examined with ultrasound exposure at various delay times after onset of myocyte contraction. The experimental results showed that generation of PVCs had a stable threshold delay time and that PVCs were generated only when myocytes were exposed to ultrasound with delay times longer than the threshold. The results indicate that the model used in this study is useful for revealing the mechanisms by which PVCs are induced by ultrasound exposure.

  15. Microdomain heterogeneity in 3D affects the mechanics of neonatal cardiac myocyte contraction

    Science.gov (United States)

    Curtis, Matthew W.; Budyn, Elisa; Desai, Tejal A.; Samarel, Allen M.

    2012-01-01

    Cardiac muscle cells are known to adapt to their physical surroundings, optimizing intracellular organization and contractile function for a given culture environment. A previously developed in vitro model system has shown that the inclusion of discrete microscale domains (or microrods) in three dimensions (3D) can alter long-term growth responses of neonatal ventricular myocytes. The aim of this work was to understand how cellular contact with such a domain affects various mechanical changes involved in cardiac muscle cell remodeling. Myocytes were maintained in 3D gels over 5 days in the presence or absence of 100 – μm-long microrods, and the effect of this local heterogeneity on cell behavior was analyzed via several imaging techniques. Microrod abutment resulted in approximately twofold increases in the maximum displacement of spontaneously beating myocytes, as based on confocal microscopy scans of the gel xy-plane or the myocyte long axis. In addition, microrods caused significant increases in the proportion of aligned myofibrils (≤20° deviation from long axis) in fixed myocytes. Microrod-related differences in axial contraction could be abrogated by long-term interruption of certain signals of the RhoA-/Rho-associated kinase (ROCK) or protein kinase C (PKC) pathway. Furthermore, microrod-induced increases in myocyte size and protein content were prevented by ROCK inhibition. In all, the data suggest that microdomain heterogeneity in 3D appears to promote the development of axially aligned contractile machinery in muscle cells, an observation that may have relevance to a number of cardiac tissue engineering interventions. PMID:22407215

  16. Measuring single cardiac myocyte contractile force via moving a magnetic bead.

    Science.gov (United States)

    Yin, Shizhuo; Zhang, Xueqian; Zhan, Chun; Wu, Juntao; Xu, Jinchao; Cheung, Joseph

    2005-02-01

    One of the biggest problems of heart failure is the heart's inability to effectively pump blood to meet the body's demands, which may be caused by disease-induced alterations in contraction properties (such as contractile force and Young's modulus). Thus, it is very important to measure contractile properties at single cardiac myocyte level that can lay the foundation for quantitatively understanding the mechanism of heart failure and understanding molecular alterations in diseased heart cells. In this article, we report a novel single cardiac myocyte contractile force measurement technique based on moving a magnetic bead. The measuring system is mainly composed of 1), a high-power inverted microscope with video output and edge detection; and 2), a moving magnetic bead based magnetic force loading module. The main measurement procedures are as follows: 1), record maximal displacement of single cardiac myocyte during contraction; 2), attach a magnetic bead on one end of the myocyte that will move with myocyte during the contraction; 3), repeat step 1 and record contraction processes under different magnitudes of magnetic force loading by adjusting the magnetic field applied on the magnetic bead; and 4), derive the myocyte contractile force base on the maximal displacement of cell contraction and magnetic loading force. The major advantages of this unique approach are: 1), measuring the force without direct connections to the cell specimen (i.e., "remote sensing", a noninvasive/minimally invasive approach); 2), high sensitivity and large dynamic range (force measurement range: from pico Newton to micro Newton); 3), a convenient and cost-effective approach; and 4), more importantly, it can be used to study the contractile properties of heart cells under different levels of external loading forces by adjusting the magnitude of applied magnetic field, which is very important for studying disease induced alterations in contraction properties. Experimental results

  17. Immunolocalization of KATP channel subunits in mouse and rat cardiac myocytes and the coronary vasculature

    Directory of Open Access Journals (Sweden)

    Nakamura Tomoe Y

    2005-01-01

    Full Text Available Abstract Background Electrophysiological data suggest that cardiac KATP channels consist of Kir6.2 and SUR2A subunits, but the distribution of these (and other KATP channel subunits is poorly defined. We examined the localization of each of the KATP channel subunits in the mouse and rat heart. Results Immunohistochemistry of cardiac cryosections demonstrate Kir6.1 protein to be expressed in ventricular myocytes, as well as in the smooth muscle and endothelial cells of coronary resistance vessels. Endothelial capillaries also stained positive for Kir6.1 protein. Kir6.2 protein expression was found predominantly in ventricular myocytes and also in endothelial cells, but not in smooth muscle cells. SUR1 subunits are strongly expressed at the sarcolemmal surface of ventricular myocytes (but not in the coronary vasculature, whereas SUR2 protein was found to be localized predominantly in cardiac myocytes and coronary vessels (mostly in smaller vessels. Immunocytochemistry of isolated ventricular myocytes shows co-localization of Kir6.2 and SUR2 proteins in a striated sarcomeric pattern, suggesting t-tubular expression of these proteins. Both Kir6.1 and SUR1 subunits were found to express strongly at the sarcolemma. The role(s of these subunits in cardiomyocytes remain to be defined and may require a reassessment of the molecular nature of ventricular KATP channels. Conclusions Collectively, our data demonstrate unique cellular and subcellular KATP channel subunit expression patterns in the heart. These results suggest distinct roles for KATP channel subunits in diverse cardiac structures.

  18. Angiotensin II type 1 receptor signalling regulates microRNA differentially in cardiac fibroblasts and myocytes

    DEFF Research Database (Denmark)

    Jeppesen, Pia Lindgren; Christensen, Gitte Lund; Schneider, Mikael

    2011-01-01

    and -independent pathways. MiRNA regulation was verified with quantitative PCR in both HEK293N cells and primary cardiac myocytes and fibroblasts. Key results: Our studies revealed five miRNAs (miR-29b, -129-3p, -132, -132* and -212) that were upregulated by Ang II in HEK293N cells. In contrast, the biased Ang II...... in primary cultures of adult cardiac fibroblasts. Interestingly, Ang II did not regulate miRNA expression in cardiac myocytes, but SII Ang II significantly downregulated miR-129-3p. Conclusions and implications: Five miRNAs were regulated by Ang II through mechanisms depending on Gaq/11 and Erk1/2 activation...

  19. MicroRNA-208a Silencing Attenuates Doxorubicin Induced Myocyte Apoptosis and Cardiac Dysfunction

    Directory of Open Access Journals (Sweden)

    Hasahya Tony

    2015-01-01

    Full Text Available Aims. GATA4 depletion is a distinct mechanism by which doxorubicin leads to cardiomyocyte apoptosis, and preservation of GATA4 mitigates doxorubicin induced myocyte apoptosis and cardiac dysfunction. We investigated a novel approach of attenuating doxorubicin induced cardiac toxicity by silencing miR-208a, a heart specific microRNA known to target GATA4. Methods and Results. Eight-week-old female Balb/C mice were randomly assigned to sham, antagomir, and control groups. Antagomir group were pretreated with miR-208a antagomir 4 days before doxorubicin administration. At day 0, control and antagomir groups received 20 mg/kg of doxorubicin, while sham mice received phosphate buffered solution. Echocardiography was done at day 7, after which animals were sacrificed and hearts harvested and assessed for apoptosis and expression of miR-208a, GATA4, and BCL-2. Doxorubicin significantly upregulated miR-208a, downregulated GATA4, and increased myocyte apoptosis, with resulting decrease in cardiac function. In contrast, therapeutic silencing of miR-208a salvaged GATA4 and BCL-2 and decreased apoptosis, with improvement in cardiac function. Conclusion. Doxorubicin upregulates miR-208a and promotes cardiomyocyte apoptosis, while therapeutic silencing of miR-208a attenuates doxorubicin induced myocyte apoptosis with subsequent improvement in cardiac function. These novel results highlight the therapeutic potential of targeting miR-208a to prevent doxorubicin cardiotoxicity.

  20. Cell contact as an independent factor modulating cardiac myocyte hypertrophy and survival in long-term primary culture

    Science.gov (United States)

    Clark, W. A.; Decker, M. L.; Behnke-Barclay, M.; Janes, D. M.; Decker, R. S.

    1998-01-01

    Cardiac myocytes maintained in cell culture develop hypertrophy both in response to mechanical loading as well as to receptor-mediated signaling mechanisms. However, it has been shown that the hypertrophic response to these stimuli may be modulated through effects of intercellular contact achieved by maintaining cells at different plating densities. In this study, we show that the myocyte plating density affects not only the hypertrophic response and features of the differentiated phenotype of isolated adult myocytes, but also plays a significant role influencing myocyte survival in vitro. The native rod-shaped phenotype of freshly isolated adult myocytes persists in an environment which minimizes myocyte attachment and spreading on the substratum. However, these conditions are not optimal for long-term maintenance of cultured adult cardiac myocytes. Conditions which promote myocyte attachment and spreading on the substratum, on the other hand, also promote the re-establishment of new intercellular contacts between myocytes. These contacts appear to play a significant role in the development of spontaneous activity, which enhances the redevelopment of highly differentiated contractile, junctional, and sarcoplasmic reticulum structures in the cultured adult cardiomyocyte. Although it has previously been shown that adult cardiac myocytes are typically quiescent in culture, the addition of beta-adrenergic agonists stimulates beating and myocyte hypertrophy, and thereby serves to increase the level of intercellular contact as well. However, in densely-plated cultures with intrinsically high levels of intercellular contact, spontaneous contractile activity develops without the addition of beta-adrenergic agonists. In this study, we compare the function, morphology, and natural history of adult feline cardiomyocytes which have been maintained in cultures with different levels of intercellular contact, with and without the addition of beta-adrenergic agonists

  1. Predicting changes in cardiac myocyte contractility during early drug discovery with in vitro assays

    Energy Technology Data Exchange (ETDEWEB)

    Morton, M.J., E-mail: michael.morton@astrazeneca.com [Discovery Sciences, AstraZeneca, Macclesfield, Cheshire SK10 4TG (United Kingdom); Armstrong, D.; Abi Gerges, N. [Drug Safety and Metabolism, AstraZeneca, Macclesfield, Cheshire SK10 4TG (United Kingdom); Bridgland-Taylor, M. [Discovery Sciences, AstraZeneca, Macclesfield, Cheshire SK10 4TG (United Kingdom); Pollard, C.E.; Bowes, J.; Valentin, J.-P. [Drug Safety and Metabolism, AstraZeneca, Macclesfield, Cheshire SK10 4TG (United Kingdom)

    2014-09-01

    Cardiovascular-related adverse drug effects are a major concern for the pharmaceutical industry. Activity of an investigational drug at the L-type calcium channel could manifest in a number of ways, including changes in cardiac contractility. The aim of this study was to define which of the two assay technologies – radioligand-binding or automated electrophysiology – was most predictive of contractility effects in an in vitro myocyte contractility assay. The activity of reference and proprietary compounds at the L-type calcium channel was measured by radioligand-binding assays, conventional patch-clamp, automated electrophysiology, and by measurement of contractility in canine isolated cardiac myocytes. Activity in the radioligand-binding assay at the L-type Ca channel phenylalkylamine binding site was most predictive of an inotropic effect in the canine cardiac myocyte assay. The sensitivity was 73%, specificity 83% and predictivity 78%. The radioligand-binding assay may be run at a single test concentration and potency estimated. The least predictive assay was automated electrophysiology which showed a significant bias when compared with other assay formats. Given the importance of the L-type calcium channel, not just in cardiac function, but also in other organ systems, a screening strategy emerges whereby single concentration ligand-binding can be performed early in the discovery process with sufficient predictivity, throughput and turnaround time to influence chemical design and address a significant safety-related liability, at relatively low cost. - Highlights: • The L-type calcium channel is a significant safety liability during drug discovery. • Radioligand-binding to the L-type calcium channel can be measured in vitro. • The assay can be run at a single test concentration as part of a screening cascade. • This measurement is highly predictive of changes in cardiac myocyte contractility.

  2. Minocycline suppresses oxidative stress and attenuates fetal cardiac myocyte apoptosis triggered by in utero cocaine exposure

    Science.gov (United States)

    Sinha-Hikim, Indrani; Shen, Ruoqing; Nzenwa, Ify; Gelfand, Robert; Mahata, Sushil K.

    2015-01-01

    This study investigates the molecular mechanisms by which minocycline, a second generation tetracycline, prevents cardiac myocyte death induced by in utero cocaine exposure. Timed mated pregnant Sprague-Dawley (SD) rats received one of the following treatments twice daily from embryonic (E) day 15–21 (E15–E21): (i) intraperitoneal (IP) injections of saline (control); (ii) IP injections of cocaine (15 mg/kg BW); and (iii) IP injections of cocaine + oral administration of 25 mg/kg BW of minocycline. Pups were killed on postnatal day 15 (P15). Additional pregnant dams received twice daily IP injections of cocaine (from E15–E21) + oral administration of a relatively higher (37.5 mg/kg BW) dose of minocycline. Minocycline treatment continued from E15 until the pups were sacrificed on P15. In utero cocaine exposure resulted in an increase in oxidative stress and fetal cardiac myocyte apoptosis through activation of c-Jun-NH2-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK)-mediated mitochondria-dependent apoptotic pathway. Continued minocycline treatment from E15 through P15 significantly prevented oxidative stress, kinase activation, perturbation of BAX/BCL-2 ratio, cytochrome c release, caspase activation, and attenuated fetal cardiac myocyte apoptosis after prenatal cocaine exposure. These results demonstrate in vivo cardioprotective effects of minocycline in preventing fetal cardiac myocyte death after prenatal cocaine exposure. Given its proven clinical safety and ability to cross the placental barrier and enter into the fetal circulation, minocycline may be an effective therapy for preventing cardiac consequences of in utero cocaine exposure. PMID:21424555

  3. Optimisation of a Generic Ionic Model of Cardiac Myocyte Electrical Activity

    Science.gov (United States)

    Guo, Tianruo; Al Abed, Amr; Lovell, Nigel H.; Dokos, Socrates

    2013-01-01

    A generic cardiomyocyte ionic model, whose complexity lies between a simple phenomenological formulation and a biophysically detailed ionic membrane current description, is presented. The model provides a user-defined number of ionic currents, employing two-gate Hodgkin-Huxley type kinetics. Its generic nature allows accurate reconstruction of action potential waveforms recorded experimentally from a range of cardiac myocytes. Using a multiobjective optimisation approach, the generic ionic model was optimised to accurately reproduce multiple action potential waveforms recorded from central and peripheral sinoatrial nodes and right atrial and left atrial myocytes from rabbit cardiac tissue preparations, under different electrical stimulus protocols and pharmacological conditions. When fitted simultaneously to multiple datasets, the time course of several physiologically realistic ionic currents could be reconstructed. Model behaviours tend to be well identified when extra experimental information is incorporated into the optimisation. PMID:23710254

  4. Cardiac desmosomal (dys)function and myocyte viability

    NARCIS (Netherlands)

    Remme, Carol Ann; Bezzina, Connie R.

    2010-01-01

    Cardiac desmosomes form intercellular junctions at the boundaries of intercalated discs between neighboring cardiomyocytes and are essential for proper cell-to-cell coupling between cardiomyocytes and for normal mechanical and electrical function of myocardial tissue. Genetic mutations in desmosomal

  5. Paracrine Effects of the Pluripotent Stem Cell-Derived Cardiac Myocytes Salvage the Injured Myocardium.

    Science.gov (United States)

    Tachibana, Atsushi; Santoso, Michelle R; Mahmoudi, Morteza; Shukla, Praveen; Wang, Lei; Bennett, Mihoko; Goldstone, Andrew B; Wang, Mouer; Fukushi, Masahiro; Ebert, Antje D; Woo, Y Joseph; Rulifson, Eric; Yang, Phillip C

    2017-09-01

    Cardiac myocytes derived from pluripotent stem cells have demonstrated the potential to mitigate damage of the infarcted myocardium and improve left ventricular ejection fraction. However, the mechanism underlying the functional benefit is unclear. To evaluate whether the transplantation of cardiac-lineage differentiated derivatives enhance myocardial viability and restore left ventricular ejection fraction more effectively than undifferentiated pluripotent stem cells after a myocardial injury. Herein, we utilize novel multimodality evaluation of human embryonic stem cells (hESCs), hESC-derived cardiac myocytes (hCMs), human induced pluripotent stem cells (iPSCs), and iPSC-derived cardiac myocytes (iCMs) in a murine myocardial injury model. Permanent ligation of the left anterior descending coronary artery was induced in immunosuppressed mice. Intramyocardial injection was performed with (1) hESCs (n=9), (2) iPSCs (n=8), (3) hCMs (n=9), (4) iCMs (n=14), and (5) PBS control (n=10). Left ventricular ejection fraction and myocardial viability, measured by cardiac magnetic resonance imaging and manganese-enhanced magnetic resonance imaging, respectively, was significantly improved in hCM- and iCM-treated mice compared with pluripotent stem cell- or control-treated mice. Bioluminescence imaging revealed limited cell engraftment in all treated groups, suggesting that the cell secretions may underlie the repair mechanism. To determine the paracrine effects of the transplanted cells, cytokines from supernatants from all groups were assessed in vitro. Gene expression and immunohistochemistry analyses of the murine myocardium demonstrated significant upregulation of the promigratory, proangiogenic, and antiapoptotic targets in groups treated with cardiac lineage cells compared with pluripotent stem cell and control groups. This study demonstrates that the cardiac phenotype of hCMs and iCMs salvages the injured myocardium effectively than undifferentiated stem cells through

  6. Hypotonic swelling-induced activation of PKN1 mediates cell survival in cardiac myocytes

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    Kajimoto, Katsuya; Shao, Dan; Takagi, Hiromitsu; Maceri, Gregorio; Zablocki, Daniela; Mukai, Hideyuki; Ono, Yoshitaka

    2011-01-01

    Hypotonic cell swelling in the myocardium is induced by pathological conditions, including ischemia-reperfusion, and affects the activities of ion transporters/channels and gene expression. However, the signaling mechanism activated by hypotonic stress (HS) is not fully understood in cardiac myocytes. A specialized protein kinase cascade, consisting of Pkc1 and MAPKs, is activated by HS in yeast. Here, we demonstrate that protein kinase N1 (PKN1), a serine/threonine protein kinase and a homolog of Pkc1, is activated by HS (67% osmolarity) within 5 min and reaches peak activity at 60 min in cardiac myocytes. Activation of PKN1 by HS was accompanied by Thr774 phosphorylation and concomitant activation of PDK1, a potential upstream regulator of PKN1. HS also activated RhoA, thereby increasing interactions between PKN1 and RhoA. PP1 (10−5 M), a selective Src family tyrosine kinase inhibitor, significantly suppressed HS-induced activation of RhoA and PKN1. Constitutively active PKN1 significantly increased the transcriptional activity of Elk1-GAL4, an effect that was inhibited by dominant negative MEK. Overexpression of PKN1 significantly increased ERK phosphorylation, whereas downregulation of PKN1 inhibited HS-induced ERK phosphorylation. Downregulation of PKN1 and inhibition of ERK by U-0126 both significantly inhibited the survival of cardiac myocytes in the presence of HS. These results suggest that a signaling cascade, consisting of Src, RhoA, PKN1, and ERK, is activated by HS, thereby promoting cardiac myocyte survival. PMID:21037231

  7. Direct, differential effects of tamoxifen, 4-hydroxytamoxifen, and raloxifene on cardiac myocyte contractility and calcium handling.

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    Michelle L Asp

    Full Text Available Tamoxifen (Tam, a selective estrogen receptor modulator, is in wide clinical use for the treatment and prevention of breast cancer. High Tam doses have been used for treatment of gliomas and cancers with multiple drug resistance, but long QT Syndrome is a side effect. Tam is also used experimentally in mice for inducible gene knockout in numerous tissues, including heart; however, the potential direct effects of Tam on cardiac myocyte mechanical function are not known. The goal of this study was to determine the direct, acute effects of Tam, its active metabolite 4-hydroxytamoxifen (4OHT, and related drug raloxifene (Ral on isolated rat cardiac myocyte mechanical function and calcium handling. Tam decreased contraction amplitude, slowed relaxation, and decreased Ca²⁺ transient amplitude. Effects were primarily observed at 5 and 10 μM Tam, which is relevant for high dose Tam treatment in cancer patients as well as Tam-mediated gene excision in mice. Myocytes treated with 4OHT responded similarly to Tam-treated cells with regard to both contractility and calcium handling, suggesting an estrogen-receptor independent mechanism is responsible for the effects. In contrast, Ral increased contraction and Ca²⁺ transient amplitudes. At 10 μM, all drugs had a time-dependent effect to abolish cellular contraction. In conclusion, Tam, 4OHT, and Ral adversely and differentially alter cardiac myocyte contractility and Ca²⁺ handling. These findings have important implications for understanding the Tam-induced cardiomyopathy in gene excision studies and may be important for understanding effects on cardiac performance in patients undergoing high-dose Tam therapy.

  8. Paying for the Tolls: The High Cost of the Innate Immune System for the Cardiac Myocyte.

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    Knowlton, Anne A

    2017-01-01

    The cardiac myocyte differs strikingly from the specialized cells of the immune system, which has two different responses to invading organisms and tissue damage. Adaptive or acquired immunity generates highly specific antibodies in response to threats and is an essential component of immunity; however, adaptive immunity can take 4-7 days to mobilize, and a more primitive response, innate immunity, fills the gap. Innate immunity is expressed in complex and in primitive life forms. Specialized receptors, Toll-like receptors (TLRs), which are widely distributed throughout different tissues recognize danger signals and rapidly respond with the release of noxious substances, such as TNFα. The problem is that many endogenous molecules have been found to act as ligands for specific TLRs, and when these molecules are released into the extracellular environment, they can cause problems by activating innate immunity and an inflammatory response. In cardiac myocytes heat shock protein (HSP)60 can activate TLR4, as can HMGB1, and this type of response can amplify the response to ischemia/reperfusion leading to increased cell and tissue injury. Activation of TLRs can potentially amplify chronic, inflammatory diseases, such as ischemic heart failure. Thus, it is important to understand the regulation of the TLRs and their downstream effects. This chapter will focus on the TLRs and cardiac myocytes.

  9. Formulation and in vitro interaction of rhodamine-B loaded PLGA nanoparticles with cardiac myocytes.

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    Antranik Jonderian

    2016-12-01

    Full Text Available This study aims to characterize rhodamine B (Rh B loaded poly(D,L-lactide-co-glycolide (PLGA nanoparticles (NPs and their interactions with cardiac myocytes. PLGA NPs were formulated using single emulsion solvent evaporation technique. The influence of varying parameters such as the stabilizer concentration, the sonication time, and the organic to aqueous ratio were investigated. The diameter, the dispersity, the encapsulation efficiency and the zeta potential of the optimized nanoparticles were about 184 nm, 0.19, 40% and -21.7 mV respectively. In vitro release showed that 29% of the Rh B was released within the first 8 hours. Scanning electron microscopy (SEM measurements performed on the optimized nanoparticles showed smooth surface and spherical shapes. No significant cytotoxic or apoptotic effects were observed on fetal cardiac myocytes after 24 and 48 hours of exposure with concentrations up to 200 µg/mL. The kinetic of the intracellular uptake was confirmed by confocal microscopy and cells took up PLGA NPs within the first hours. Interestingly, our data show an increase in the nanoparticles’ uptake with time of exposure. Taken together, we demonstrate for the first time that the designed NPs can be used as potential probes for drug delivery in cardiac myocytes.

  10. Modeling calcium wave based on anomalous subdiffusion of calcium sparks in cardiac myocytes.

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    Xi Chen

    Full Text Available Ca(2+ sparks and Ca(2+ waves play important roles in calcium release and calcium propagation during the excitation-contraction (EC coupling process in cardiac myocytes. Although the classical Fick's law is widely used to model Ca(2+ sparks and Ca(2+ waves in cardiac myocytes, it fails to reasonably explain the full-width at half maximum(FWHM paradox. However, the anomalous subdiffusion model successfully reproduces Ca(2+ sparks of experimental results. In this paper, in the light of anomalous subdiffusion of Ca(2+ sparks, we develop a mathematical model of calcium wave in cardiac myocytes by using stochastic Ca(2+ release of Ca(2+ release units (CRUs. Our model successfully reproduces calcium waves with physiological parameters. The results reveal how Ca(2+ concentration waves propagate from an initial firing of one CRU at a corner or in the middle of considered region, answer how large in magnitude of an anomalous Ca(2+ spark can induce a Ca(2+ wave. With physiological Ca(2+ currents (2pA through CRUs, it is shown that an initial firing of four adjacent CRUs can form a Ca(2+ wave. Furthermore, the phenomenon of calcium waves collision is also investigated.

  11. Cardiac mast cells regulate myocyte ANP release via histamine H2 receptor in beating rabbit atria.

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    Li, Dan; Wen, Jin Fu; Jin, Jing Yu; Quan, He Xiu; Cho, Kyung Woo

    2009-06-05

    It has been shown that histamine inhibits atrial natriuretic peptide (ANP) release. Because cardiac mast cells are the principal source of histamine in the heart, we hypothesized that cardiac mast cells are involved in the regulation of atrial ANP release. To test the hypothesis, experiments were performed in perfused beating rabbit atria allowing atrial pacing and measurements of changes in atrial stroke volume, intraatrial pulse pressure and myocyte ANP release. Mast cell degranulation with Compound 48/80 decreased atrial myocyte ANP release, and the response was blocked by a selective histamine H(2) receptor blocker, cimetidine, indicating that histamine was responsible for the decrease in ANP release. Mast cell stabilization with cromolyn blocked the Compound 48/80-induced decrease in ANP release. These data suggest that mast cell-derived histamine is involved in the regulation of cardiac ANP release. Thus, the cardiac mast cell-cardiomyocyte communication via the histamine-ANP pathway may implicate in the cardiac disorder associated with mast cell degranulation such as in acute coronary syndrome or cardiac hypertrophy.

  12. PARM-1 is an endoplasmic reticulum molecule involved in endoplasmic reticulum stress-induced apoptosis in rat cardiac myocytes.

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    Koji Isodono

    Full Text Available To identify novel transmembrane and secretory molecules expressed in cardiac myocytes, signal sequence trap screening was performed in rat neonatal cardiac myocytes. One of the molecules identified was a transmembrane protein, prostatic androgen repressed message-1 (PARM-1. While PARM-1 has been identified as a gene induced in prostate in response to castration, its function is largely unknown. Our expression analysis revealed that PARM-1 was specifically expressed in hearts and skeletal muscles, and in the heart, cardiac myocytes, but not non-myocytes expressed PARM-1. Immunofluorescent staining showed that PARM-1 was predominantly localized in endoplasmic reticulum (ER. In Dahl salt-sensitive rats, high-salt diet resulted in hypertension, cardiac hypertrophy and subsequent heart failure, and significantly stimulated PARM-1 expression in the hearts, with a concomitant increase in ER stress markers such as GRP78 and CHOP. In cultured cardiac myocytes, PARM-1 expression was stimulated by proinflammatory cytokines, but not by hypertrophic stimuli. A marked increase in PARM-1 expression was observed in response to ER stress inducers such as thapsigargin and tunicamycin, which also induced apoptotic cell death. Silencing PARM-1 expression by siRNAs enhanced apoptotic response in cardiac myocytes to ER stresses. PARM-1 silencing also repressed expression of PERK and ATF6, and augmented expression of CHOP without affecting IRE-1 expression and JNK and Caspase-12 activation. Thus, PARM-1 expression is induced by ER stress, which plays a protective role in cardiac myocytes through regulating PERK, ATF6 and CHOP expression. These results suggested that PARM-1 is a novel ER transmembrane molecule involved in cardiac remodeling in hypertensive heart disease.

  13. Clenbuterol induces cardiac myocyte hypertrophy via paracrine signalling and fibroblast-derived IGF-1.

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    Bhavsar, Pankaj K; Brand, Nigel J; Felkin, Leanne E; Luther, Pradeep K; Cullen, Martin E; Yacoub, Magdi H; Barton, Paul J R

    2010-12-01

    The β(2)-selective adrenoreceptor agonist clenbuterol promotes both skeletal and cardiac muscle hypertrophy and is undergoing clinical trials in the treatment of muscle wasting and heart failure. We have previously demonstrated that clenbuterol induces a mild physiological ventricular hypertrophy in vivo with normal contractile function and without induction of α-skeletal muscle actin (αSkA), a marker of pathological hypertrophy. The mechanisms of this response remain poorly defined. In this study, we examine the direct action of clenbuterol on cardiocyte cultures in vitro. Clenbuterol treatment resulted in increased cell size of cardiac myocytes with increased protein accumulation and myofibrillar organisation characteristic of hypertrophic growth. Real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) revealed elevated mRNA expression of ANP and brain natriuretic peptide (BNP) but without change in αSkA, consistent with physiological hypertrophic growth. Clenbuterol-treated cultures also showed elevated insulin-like growth factor I (IGF-1) mRNA and activation of the protein kinase Akt. Addition of either IGF-1 receptor-blocking antibodies or LY294002 in order to inhibit phosphatidylinositol 3-kinase, a downstream effector of the IGF-1 receptor, inhibited the hypertrophic response indicating that IGF-1 signalling is required. IGF-1 expression localised primarily to the minor population of cardiac fibroblasts present in the cardiocyte cultures. Together these data show that clenbuterol acts to induce mild cardiac hypertrophy in cardiac myocytes via paracrine signalling involving fibroblast-derived IGF-1.

  14. The adult heart responds to increased workload with physiologic hypertrophy, cardiac stem cell activation, and new myocyte formation.

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    Waring, Cheryl D; Vicinanza, Carla; Papalamprou, Angela; Smith, Andrew J; Purushothaman, Saranya; Goldspink, David F; Nadal-Ginard, Bernardo; Torella, Daniele; Ellison, Georgina M

    2014-10-14

    It is a dogma of cardiovascular pathophysiology that the increased cardiac mass in response to increased workload is produced by the hypertrophy of the pre-existing myocytes. The role, if any, of adult-resident endogenous cardiac stem/progenitor cells (eCSCs) and new cardiomyocyte formation in physiological cardiac remodelling remains unexplored. In response to regular, intensity-controlled exercise training, adult rats respond with hypertrophy of the pre-existing myocytes. In addition, a significant number (∼7%) of smaller newly formed BrdU-positive cardiomyocytes are produced by the exercised animals. Capillary density significantly increased in exercised animals, balancing cardiomyogenesis with neo-angiogenesis. c-kit(pos) eCSCs increased their number and activated state in exercising vs. sedentary animals. c-kit(pos) eCSCs in exercised hearts showed an increased expression of transcription factors, indicative of their commitment to either the cardiomyocyte (Nkx2.5(pos)) or capillary (Ets-1(pos)) lineages. These adaptations were dependent on exercise duration and intensity. Insulin-like growth factor-1, transforming growth factor-β1, neuregulin-1, bone morphogenetic protein-10, and periostin were significantly up-regulated in cardiomyocytes of exercised vs. sedentary animals. These factors differentially stimulated c-kit(pos) eCSC proliferation and commitment in vitro, pointing to a similar role in vivo. Intensity-controlled exercise training initiates myocardial remodelling through increased cardiomyocyte growth factor expression leading to cardiomyocyte hypertrophy and to activation and ensuing differentiation of c-kit(pos) eCSCs. This leads to the generation of new myocardial cells. These findings highlight the endogenous regenerative capacity of the adult heart, represented by the eCSCs, and the fact that the physiological cardiac adaptation to exercise stress is a combination of cardiomyocyte hypertrophy and hyperplasia (cardiomyocytes and capillaries

  15. GSK-3β/NFAT Signaling Is Involved in Testosterone-Induced Cardiac Myocyte Hypertrophy.

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    Javier Duran

    Full Text Available Testosterone induces cardiac hypertrophy through a mechanism that involves a concerted crosstalk between cytosolic and nuclear signaling pathways. Nuclear factor of activated T-cells (NFAT is associated with the promotion of cardiac hypertrophy, glycogen synthase kinase-3β (GSK-3β is considered to function as a negative regulator, mainly by modulating NFAT activity. However, the role played by calcineurin-NFAT and GSK-3β signaling in testosterone-induced cardiac hypertrophy has remained unknown. Here, we determined that testosterone stimulates cardiac myocyte hypertrophy through NFAT activation and GSK-3β inhibition. Testosterone increased the activity of NFAT-luciferase (NFAT-Luc in a time- and dose-dependent manner, with the activity peaking after 24 h of stimulation with 100 nM testosterone. NFAT-Luc activity induced by testosterone was blocked by the calcineurin inhibitors FK506 and cyclosporine A and by 11R-VIVIT, a specific peptide inhibitor of NFAT. Conversely, testosterone inhibited GSK-3β activity as determined by increased GSK-3β phosphorylation at Ser9 and β-catenin protein accumulation, and also by reduction in β-catenin phosphorylation at residues Ser33, Ser37, and Thr41. GSK-3β inhibition with 1-azakenpaullone or a GSK-3β-targeting siRNA increased NFAT-Luc activity, whereas overexpression of a constitutively active GSK-3β mutant (GSK-3βS9A inhibited NFAT-Luc activation mediated by testosterone. Testosterone-induced cardiac myocyte hypertrophy was established by increased cardiac myocyte size and [3H]-leucine incorporation (as a measurement of cellular protein synthesis. Calcineurin-NFAT inhibition abolished and GSK-3β inhibition promoted the hypertrophy stimulated by testosterone. GSK-3β activation by GSK-3βS9A blocked the increase of hypertrophic markers induced by testosterone. Moreover, inhibition of intracellular androgen receptor prevented testosterone-induced NFAT-Luc activation. Collectively, these results

  16. Stimulation of ICa by basal PKA activity is facilitated by caveolin-3 in cardiac ventricular myocytes.

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    Bryant, Simon; Kimura, Tomomi E; Kong, Cherrie H T; Watson, Judy J; Chase, Anabelle; Suleiman, M Saadeh; James, Andrew F; Orchard, Clive H

    2014-03-01

    L-type Ca channels (LTCC), which play a key role in cardiac excitation-contraction coupling, are located predominantly at the transverse (t-) tubules in ventricular myocytes. Caveolae and the protein caveolin-3 (Cav-3) are also present at the t-tubules and have been implicated in localizing a number of signaling molecules, including protein kinase A (PKA) and β2-adrenoceptors. The present study investigated whether disruption of Cav-3 binding to its endogenous binding partners influenced LTCC activity. Ventricular myocytes were isolated from male Wistar rats and LTCC current (ICa) recorded using the whole-cell patch-clamp technique. Incubation of myocytes with a membrane-permeable peptide representing the scaffolding domain of Cav-3 (C3SD) reduced basal ICa amplitude in intact, but not detubulated, myocytes, and attenuated the stimulatory effects of the β2-adrenergic agonist zinterol on ICa. The PKA inhibitor H-89 also reduced basal ICa; however, the inhibitory effects of C3SD and H-89 on basal ICa amplitude were not summative. Under control conditions, myocytes stained with antibody against phosphorylated LTCC (pLTCC) displayed a striated pattern, presumably reflecting localization at the t-tubules. Both C3SD and H-89 reduced pLTCC staining at the z-lines but did not affect staining of total LTCC or Cav-3. These data are consistent with the idea that the effects of C3SD and H-89 share a common pathway, which involves PKA and is maximally inhibited by H-89, and suggest that Cav-3 plays an important role in mediating stimulation of ICa at the t-tubules via PKA-induced phosphorylation under basal conditions, and in response to β2-adrenoceptor stimulation. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

  17. Myocyte-Derived Hsp90 Modulates Collagen Upregulation via Biphasic Activation of STAT-3 in Fibroblasts during Cardiac Hypertrophy

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    Datta, Ritwik; Bansal, Trisha; Rana, Santanu; Datta, Kaberi; Datta Chaudhuri, Ratul; Chawla-Sarkar, Mamta

    2016-01-01

    ABSTRACT Signal transducer and activator of transcription 3 (STAT-3)-mediated signaling in relation to upregulated collagen expression in fibroblasts during cardiac hypertrophy is well defined. Our recent findings have identified heat shock protein 90 (Hsp90) to be a critical modulator of fibrotic signaling in cardiac fibroblasts in this disease milieu. The present study was therefore intended to analyze the role of Hsp90 in the STAT-3-mediated collagen upregulation process. Our data revealed a significant difference between in vivo and in vitro results, pointing to a possible involvement of myocyte-fibroblast cross talk in this process. Cardiomyocyte-targeted knockdown of Hsp90 in rats (Rattus norvegicus) in which the renal artery was ligated showed downregulated collagen synthesis. Furthermore, the results obtained with cardiac fibroblasts conditioned with Hsp90-inhibited hypertrophied myocyte supernatant pointed toward cardiomyocytes' role in the regulation of collagen expression in fibroblasts during hypertrophy. Our study also revealed a novel signaling mechanism where myocyte-derived Hsp90 orchestrates not only p65-mediated interleukin-6 (IL-6) synthesis but also its release in exosomal vesicles. Such myocyte-derived exosomes and myocyte-secreted IL-6 are responsible in unison for the biphasic activation of STAT-3 signaling in cardiac fibroblasts that culminates in excess collagen synthesis, leading to severely compromised cardiac function during cardiac hypertrophy. PMID:28031326

  18. Speckle based configuration for simultaneous in vitro inspection of mechanical contractions of cardiac myocyte cells

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    Golberg, Mark; Fixler, Dror; Shainberg, Asher; Zlochiver, Sharon; Micó, Vicente; Garcia, Javier; Beiderman, Yevgeny; Zalevsky, Zeev

    2013-04-01

    In this manuscript we propose optical lensless configuration for a remote non-contact measuring of mechanical contractions of vast number of cardiac myocytes. All the myocytes were taken from rats, and the measurements were done in an in vitro mode. The optical method is based on temporal analysis of secondary reflected speckle patterns generated in lensless microscope configuration. The processing involves analyzing the movement and the change in the statistics of the generated secondary speckle patterns that are created on top of the cell culture when it is illuminated by a spot of laser beam. The main advantage of the proposed system is the ability to measure many cells simultaneously (approximately one thousand cells) and to extract the statistical data of their movement at once. The presented experimental results also include investigation the effect of isoproteranol on cells contraction process.

  19. High frequency stimulation of cardiac myocytes: A theoretical and computational study

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    Weinberg, Seth H.

    2014-12-01

    High-frequency stimulation (HFS) has recently been identified as a novel approach for terminating life-threatening cardiac arrhythmias. HFS elevates myocyte membrane potential and blocks electrical conduction for the duration of the stimulus. However, low amplitude HFS can induce rapidly firing action potentials, which may reinitiate an arrhythmia. The cellular level mechanisms underlying HFS-induced electrical activity are not well understood. Using a multiscale method, we show that a minimal myocyte model qualitatively reproduces the influence of HFS on cardiac electrical activity. Theoretical analysis and simulations suggest that persistent activation and de-inactivation of ionic currents, in particular a fast inward window current, underlie HFS-induced action potentials and membrane potential elevation, providing hypotheses for future experiments. We derive analytical expressions to describe how HFS modifies ionic current amplitude and gating dynamics. We show how fast inward current parameters influence the parameter regimes for HFS-induced electrical activity, demonstrating how the efficacy of HFS as a therapy for terminating arrhythmias may depend on the presence of pathological conditions or pharmacological treatments. Finally, we demonstrate that HFS terminates cardiac arrhythmias in a one-dimensional ring of cardiac tissue. In this study, we demonstrate a novel approach to characterize the influence of HFS on ionic current gating dynamics, provide new insight into HFS of the myocardium, and suggest mechanisms underlying HFS-induced electrical activity.

  20. TNFα Modulates Cardiac Conduction by Altering Electrical Coupling between Myocytes

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    Sharon A. George

    2017-05-01

    Full Text Available Background: Tumor Necrosis Factor α (TNFα upregulation during acute inflammatory response has been associated with numerous cardiac effects including modulating Connexin43 and vascular permeability. This may in turn alter cardiac gap junctional (GJ coupling and extracellular volume (ephaptic coupling respectively. We hypothesized that acute exposure to pathophysiological TNFα levels can modulate conduction velocity (CV in the heart by altering electrical coupling: GJ and ephaptic.Methods and Results: Hearts were optically mapped to determine CV from control, TNFα and TNFα + high calcium (2.5 vs. 1.25 mM treated guinea pig hearts over 90 mins. Transmission electron microscopy was performed to measure changes in intercellular separation in the gap junction-adjacent extracellular nanodomain—perinexus (WP. Cx43 expression and phosphorylation were determined by Western blotting and Cx43 distribution by confocal immunofluorescence. At 90 mins, longitudinal and transverse CV (CVL and CVT, respectively increased with control Tyrode perfusion but TNFα slowed CVT alone relative to control and anisotropy of conduction increased, but not significantly. TNFα increased WP relative to control at 90 mins, without significantly changing GJ coupling. Increasing extracellular calcium after 30 mins of just TNFα exposure increased CVT within 15 mins. TNFα + high calcium also restored CVT at 90 mins and reduced WP to control values. Interestingly, TNFα + high calcium also improved GJ coupling at 90 mins, which along with reduced WP may have contributed to increasing CV.Conclusions: Elevating extracellular calcium during acute TNFα exposure reduces perinexal expansion, increases ephaptic, and GJ coupling, improves CV and may be a novel method for preventing inflammation induced CV slowing.

  1. miR-218 suppresses cardiac myxoma proliferation by targeting myocyte enhancer factor 2D.

    Science.gov (United States)

    Cao, Quanxing; Dong, Pingshuan; Wang, Yanyu; Zhang, Junwei; Shi, Xinge; Wang, Yongsheng

    2015-05-01

    Cardiac myxoma is the most common type of human heart tumor, yet the molecular mechanism is still poorly understood. In the present study, we found that the level of myocyte enhancer factor 2D (MEF2D), a key regulatory protein for cardiac development, was elevated in specimens of cardiac myxoma, and was positively associated with the proliferation of myxoma cells. MEF2D suppression reduced the proliferation of myxoma cells and its tumorigenicity. Cell cycle progression was also inhibited by MEF2D suppression. miR-218, which is downregulated in myxoma, suppressed MEF2D expression by targeting its mRNA 3'UTR. Altogether, we found that miR-218/MEF2D may be an effective target for myxoma treatment.

  2. Levosimendan exerts anti-inflammatory effects on cardiac myocytes and endothelial cells in vitro.

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    Krychtiuk, Konstantin A; Watzke, Lukas; Kaun, Christoph; Buchberger, Elisabeth; Hofer-Warbinek, Renate; Demyanets, Svitlana; Pisoni, Julia; Kastl, Stefan P; Rauscher, Sabine; Gröger, Marion; Aliabadi, Arezu; Zuckermann, Andreas; Maurer, Gerald; de Martin, Rainer; Huber, Kurt; Wojta, Johann; Speidl, Walter S

    2015-02-01

    Levosimendan is a positive inotropic drug for the treatment of acute decompensated heart failure (HF). Clinical trials showed that levosimendan was particularly effective in HF due to myocardial infarction. Myocardial necrosis induces a strong inflammatory response, involving chemoattractants guiding polymorphonuclear neutrophils (PMN) into the infarcted myocardial tissue. Our aim was to examine whether levosimendan exhibits anti-inflammatory effects on human adult cardiac myocytes (HACM) and human heart microvascular endothelial cells (HHMEC). Cardiac myocytes and endothelial cells were stimulated with interleukin-1β (IL)-1β (200 U/ml) and treated with levosimendan (0.1-10 µM) for 2-48 hours. IL-1β strongly induced expression of IL-6 and IL-8 in HACM and E-selectin and intercellular adhesion molecule-1 (ICAM-1) in HHMEC and human umbilical vein endothelial cells (HUVEC). Treatment with levosimendan strongly attenuated IL-1β-induced expression of IL-6 and IL-8 in HACM as well as E-selectin and ICAM-1 in ECs. Levosimendan treatment further reduced adhesion of PMN to activated endothelial cells under both static and flow conditions by approximately 50 %. Incubation with 5-hydroxydecanoic acid, a selective blocker of mitochondrial ATP-dependent potassium channels, partly abolished the above seen anti-inflammatory effects. Additionally, levosimendan strongly diminished IL-1β-induced reactive oxygen species and nuclear factor-κB (NF-κB) activity through inhibition of S536 phosphorylation. In conclusion, levosimendan exhibits anti-inflammatory effects on cardiac myocytes and endothelial cells in vitro. These findings could explain, at least in part, the beneficial effects of levosimendan after myocardial infarction.

  3. Hypoxia inducible factor-1 improves the negative functional effects of natriuretic peptide and nitric oxide signaling in hypertrophic cardiac myocytes.

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    Tan, Tao; Scholz, Peter M; Weiss, Harvey R

    2010-07-03

    Both natriuretic peptides and nitric oxide may be protective in cardiac hypertrophy, although their functional effects are diminished in hypertrophy. Hypoxia inducible factor-1 (HIF-1) may also protect in cardiac hypertrophy. We hypothesized that upregulation of HIF-1 would protect the functional effects of cyclic GMP (cGMP) signaling in hypertrophied ventricular myocytes. A cardiac hypertrophy model was created in mice by transverse aorta constriction. HIF-1 was increased by deferoxamine (150 mg/kg for 2 days). HIF-1alpha protein levels were examined. Functional parameters were measured (edge detector) on freshly isolated myocytes at baseline and after BNP (brain natriuretic peptide, 10(-8)-10(-7)M) or CNP (C-type natriuretic peptide, 10(-8)-10(-7)M) or SNAP (S-nitroso-N-acetyl-penicillamine, a nitric oxide donor, 10(-6)-10(-5)M) followed by KT5823 (a cyclic GMP-dependent protein kinase (PKG) inhibitor, 10(-6)M). We also determined PKG expression levels and kinase activity. We found that under control conditions, BNP (-24%), CNP (-22%) and SNAP (-23%) reduced myocyte shortening, while KT5823 partially restored function. Deferoxamine treated control myocytes responded similarly. Baseline function was reduced in the myocytes from hypertrophied heart. BNP, CNP, SNAP and KT5823 also had no significant effects on function in these myocytes. Deferoxamine restored the negative functional effects of BNP (-22%), CNP (-18%) and SNAP (-19%) in hypertrophic cardiac myocytes and KT5823 partially reversed this effect. Additionally, deferoxamine maintained PKG expression levels and activity in hypertrophied heart. Our results indicated that the HIF-1 protected the functional effects of cGMP signaling in cardiac hypertrophy through preservation of PKG. Copyright (c) 2010 Elsevier Inc. All rights reserved.

  4. [Fast 2-dimension scanning and line-scanning of intracellular Ca2+ transients in cardiac myocytes].

    Science.gov (United States)

    Shen, Jian-xin; Wang, Hai-yan; Li, Chao-yan; Xiao, Jian-feng

    2008-11-01

    Fast 2-dimension scanning and line-scanning of confocal imaging were employed for measurement of cardiac Ca2+ transients, and the advantages and disadvantages about these two scannings were discussed. Single adult SD rat cardiac myocytes were made freshly and loaded with fluo4-AM. Intracellular Ca2+ was imaging by the LSMS10 META system. The Ca2+ transients were evoked by electrical field stimulation from an electronic stimulator which was triggered to work synchronically with the confocal imaging system. Fast 2-dimension scanning showed the global Ca2+ signal clearly, which would be more helpful especially in monitoring a cell of Ca2+ overload or in other pathological conditions. And the images could be packaged into a vivid animation, which showed the process of Ca2+ transients and cell contraction visually and virtually. Line-scanning showed the Ca2+ transients in good temporal and spacial resolutions along the long axis of the cell. And the dynamic shortening of the cell length could be used for indicating the contraction of the cell. Data from line-scanning would be helpful for drawing some more exact conclusions. In general, fast 2-dimension scanning and line-scanning could work reciprocally to show a more perfect picture of the intracellular Ca2+ transients in cardiac myocytes.

  5. Maturation status of sarcomere structure and function in human iPSC-derived cardiac myocytes.

    Science.gov (United States)

    Bedada, Fikru B; Wheelwright, Matthew; Metzger, Joseph M

    2016-07-01

    Human heart failure due to myocardial infarction is a major health concern. The paucity of organs for transplantation limits curative approaches for the diseased and failing adult heart. Human induced pluripotent stem cell-derived cardiac myocytes (hiPSC-CMs) have the potential to provide a long-term, viable, regenerative-medicine alternative. Significant progress has been made with regard to efficient cardiac myocyte generation from hiPSCs. However, directing hiPSC-CMs to acquire the physiological structure, gene expression profile and function akin to mature cardiac tissue remains a major obstacle. Thus, hiPSC-CMs have several hurdles to overcome before they find their way into translational medicine. In this review, we address the progress that has been made, the void in knowledge and the challenges that remain. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

  6. Cardiac sodium channel palmitoylation regulates channel availability and myocyte excitability with implications for arrhythmia generation

    Science.gov (United States)

    Pei, Zifan; Xiao, Yucheng; Meng, Jingwei; Hudmon, Andy; Cummins, Theodore R.

    2016-01-01

    Cardiac voltage-gated sodium channels (Nav1.5) play an essential role in regulating cardiac electric activity by initiating and propagating action potentials in the heart. Altered Nav1.5 function is associated with multiple cardiac diseases including long-QT3 and Brugada syndrome. Here, we show that Nav1.5 is subject to palmitoylation, a reversible post-translational lipid modification. Palmitoylation increases channel availability and late sodium current activity, leading to enhanced cardiac excitability and prolonged action potential duration. In contrast, blocking palmitoylation increases closed-state channel inactivation and reduces myocyte excitability. We identify four cysteines as possible Nav1.5 palmitoylation substrates. A mutation of one of these is associated with cardiac arrhythmia (C981F), induces a significant enhancement of channel closed-state inactivation and ablates sensitivity to depalmitoylation. Our data indicate that alterations in palmitoylation can substantially control Nav1.5 function and cardiac excitability and this form of post-translational modification is likely an important contributor to acquired and congenital arrhythmias. PMID:27337590

  7. Dependence of exogenous SERCA gene expression on coxsackie adenovirus receptor levels in neonatal and adult cardiac myocytes.

    Science.gov (United States)

    Sumbilla, Carlota; Ma, Hailun; Seth, Malini; Inesi, Giuseppe

    2003-07-15

    We demonstrate that the efficiency of adenovirus-assisted exogenous Ca(2+) ATPase (SERCA) and reporter (EGFP) gene expression is much higher in primary cultures of myocytes from neonatal rat hearts, than in primary cultures of myocytes from adult rat hearts. In this respect, the neonatal myocytes behave similarly to the established COS-1 cell line. This difference is related to the level of coxsackie adenovirus receptor (CAR) that affects cell penetration and expression level of exogenous genes, and explains variations in the observed consequences of exposure to adenovirus vector carrying SERCA cDNA. Awareness of these differences should be highly advantageous in complementary studies of exogenous gene expression in neonatal and adult myocytes. It should also be advantageous in evaluating conditions yielding optimal ratios of functional benefits over possible toxic effects upon exogenous SERCA gene delivery to cardiac muscle.

  8. Lysosomal integral membrane protein 2 is a novel component of the cardiac intercalated disc and vital for load-induced cardiac myocyte hypertrophy

    NARCIS (Netherlands)

    Schroen, Blanche; Leenders, Joost J.; van Erk, Arie; Bertrand, Anne T.; van Loon, Mirjam; van Leeuwen, Rick E.; Kubben, Nard; Duisters, Rudy F.; Schellings, Mark W.; Janssen, Ben J.; Debets, Jacques J.; Schwake, Michael; Høydal, Morten A.; Heymans, Stephane; Saftig, Paul; Pinto, Yigal M.

    2007-01-01

    The intercalated disc (ID) of cardiac myocytes is emerging as a crucial structure in the heart. Loss of ID proteins like N-cadherin causes lethal cardiac abnormalities, and mutations in ID proteins cause human cardiomyopathy. A comprehensive screen for novel mechanisms in failing hearts demonstrated

  9. Quantifying the Release of Biomarkers of Myocardial Necrosis from Cardiac Myocytes and Intact Myocardium.

    Science.gov (United States)

    Marjot, Jack; Kaier, Thomas E; Martin, Eva D; Reji, Shiney S; Copeland, O'Neal; Iqbal, Mohammed; Goodson, Bob; Hamren, Sarah; Harding, Sian E; Marber, Michael S

    2017-05-01

    Myocardial infarction is diagnosed when biomarkers of cardiac necrosis exceed the 99th centile, although guidelines advocate even lower concentrations for early rule-out. We examined how many myocytes and how much myocardium these concentrations represent. We also examined if dietary troponin can confound the rule-out algorithm. Individual rat cardiac myocytes, rat myocardium, ovine myocardium, or human myocardium were spiked into 400-μL aliquots of human serum. Blood was drawn from a volunteer after ingestion of ovine myocardium. High-sensitivity assays were used to measure cardiac troponin T (cTnT; Roche, Elecsys), cTnI (Abbott, Architect), and cardiac myosin-binding protein C (cMyC; EMD Millipore, Erenna®). The cMyC assay could only detect the human protein. For each rat cardiac myocyte added to 400 μL of human serum, cTnT and cTnI increased by 19.0 ng/L (95% CI, 16.8-21.2) and 18.9 ng/L (95% CI, 14.7-23.1), respectively. Under identical conditions cTnT, cTnI, and cMyC increased by 3.9 ng/L (95% CI, 3.6-4.3), 4.3 ng/L (95% CI, 3.8-4.7), and 41.0 ng/L (95% CI, 38.0-44.0) per μg of human myocardium. There was no detectable change in cTnI or cTnT concentration after ingestion of sufficient ovine myocardium to increase cTnT and cTnI to approximately 1 × 108 times their lower limits of quantification. Based on pragmatic assumptions regarding cTn and cMyC release efficiency, circulating species, and volume of distribution, 99th centile concentrations may be exceeded by necrosis of 40 mg of myocardium. This volume is much too small to detect by noninvasive imaging. © 2017 American Association for Clinical Chemistry.

  10. Stochastic initiation and termination of calcium-mediated triggered activity in cardiac myocytes.

    Science.gov (United States)

    Song, Zhen; Qu, Zhilin; Karma, Alain

    2017-01-17

    Cardiac myocytes normally initiate action potentials in response to a current stimulus that depolarizes the membrane above an excitation threshold. Aberrant excitation can also occur due to spontaneous calcium (Ca2+) release (SCR) from intracellular stores after the end of a preceding action potential. SCR drives the Na+/Ca2+ exchange current inducing a "delayed afterdepolarization" that can in turn trigger an action potential if the excitation threshold is reached. This "triggered activity" is known to cause arrhythmias, but how it is initiated and terminated is not understood. Using computer simulations of a ventricular myocyte model, we show that initiation and termination are inherently random events. We determine the probability of those events from statistical measurements of the number of beats before initiation and before termination, respectively, which follow geometric distributions. Moreover, we elucidate the origin of randomness by a statistical analysis of SCR events, which do not follow a Poisson process observed in other eukaryotic cells. Due to synchronization of Ca2+ releases during the action potential upstroke, waiting times of SCR events after the upstroke are narrowly distributed, whereas SCR amplitudes follow a broad normal distribution with a width determined by fluctuations in the number of independent Ca2+ wave foci. This distribution enables us to compute the probabilities of initiation and termination of bursts of triggered activity that are maintained by a positive feedback between the action potential upstroke and SCR. Our results establish a theoretical framework for interpreting complex and varied manifestations of triggered activity relevant to cardiac arrhythmias.

  11. C-reactive protein inhibits survivin expression via Akt/mTOR pathway downregulation by PTEN expression in cardiac myocytes.

    Directory of Open Access Journals (Sweden)

    Beom Seob Lee

    Full Text Available C-reactive protein (CRP is one of the most important biomarkers for arteriosclerosis and cardiovascular disease. Recent studies have shown that CRP affects cell cycle and inflammatory process in cardiac myocytes. Survivin is also involved in cardiac myocytes replication and apoptosis. Reduction of survivin expression is associated with less favorable cardiac remodeling in animal models. However, the effect of CRP on survivin expression and its cellular mechanism has not yet been studied. We demonstrated that treatment of CRP resulted in a significant decrease of survivin protein expression in a concentration-dependent manner in cardiac myocytes. The upstream signaling proteins of survivin, such as Akt, mTOR and p70S6K, were also downregulated by CRP treatment. In addition, CRP increased the protein and mRNA levels of PTEN. The siRNA transfection or specific inhibitor treatment for PTEN restored the CRP-induced downregulation of Akt/mTOR/p70S6K pathway and survivin protein expression. Moreover, pretreatment with a specific p53 inhibitor decreased the CRP-induced PTEN expression. ERK-specific inhibitor also blocked the p53 phosphorylation and PTEN expression induced by CRP. Our study provides a novel insight into CRP-induced downregulation of survivin protein expression in cardiac myocytes through mechanisms that involved in downregulation of Akt/mTOR/p70S6K pathway by expression of PTEN.

  12. Brief Myocardial Ischemia Produces Cardiac Troponin I Release and Focal Myocyte Apoptosis in the Absence of Pathological Infarction in Swine

    Directory of Open Access Journals (Sweden)

    Brian R. Weil, PhD

    2017-04-01

    Full Text Available Summary: In a porcine model of brief ischemia leading to reversible stunning in the absence of tissue necrosis, we demonstrated delayed release of cardiac troponin I (cTnI that exceeded the 99th percentile for normal animals 60 min after reperfusion and rose to readily detectable levels 24 h later. Although tissue analysis at 60 min showed no evidence of infarction, TUNEL staining demonstrated isolated myocytes undergoing apoptosis, which was absent after 24 h. These results demonstrate that cTnI elevations occur after ischemia of a duration that is insufficient to produce myocyte necrosis and reflect myocyte injury associated with apoptosis in the absence of pathological evidence of infarction. Key Words: cardiac troponin I, cardiomyocyte apoptosis, myocardial ischemia, myocardial stunning

  13. Cardiac myocyte alternans in intact heart: Influence of cell-cell coupling and β-adrenergic stimulation.

    Science.gov (United States)

    Hammer, Karin P; Ljubojevic, Senka; Ripplinger, Crystal M; Pieske, Burkert M; Bers, Donald M

    2015-07-01

    Cardiac alternans are proarrhythmic and mechanistically link cardiac mechanical dysfunction and sudden cardiac death. Beat-to-beat alternans occur when beats with large Ca(2+) transients and long action potential duration (APD) alternate with the converse. APD alternans are typically driven by Ca(2+) alternans and sarcoplasmic reticulum (SR) Ca(2+) release alternans. But the effect of intercellular communication via gap junctions (GJ) on alternans in the intact heart remains unknown. We assessed the effects of cell-to-cell coupling on local alternans in intact Langendorff-perfused mouse hearts, measuring single myocyte [Ca(2+)] alternans synchronization among neighboring cells, and effects of β-adrenergic receptor (β-AR) activation and reduced GJ coupling. Mouse hearts (C57BL/6) were retrogradely perfused and loaded with Fluo8-AM to record cardiac myocyte [Ca(2+)] in situ with confocal microscopy. Single cell resolution allowed analysis of alternans within the intact organ during alternans induction. Carbenoxolone (25 μM), a GJ inhibitor, significantly increased the occurrence and amplitude of alternans in single cells within the intact heart. Alternans were concordant between neighboring cells throughout the field of view, except transiently during onset. β-AR stimulation only reduced Ca(2+) alternans in tissue that had reduced GJ coupling, matching effects seen in isolated myocytes. Ca(2+) alternans among neighboring myocytes is predominantly concordant, likely because of electrical coupling between cells. Consistent with this, partial GJ uncoupling increased propensity and amplitude of Ca(2+) alternans, and made them more sensitive to reversal by β-AR activation, as in isolated myocytes. Electrical coupling between myocytes may thus limit the alternans initiation, but also allow alternans to be more stable once established. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Modeling beta-adrenergic control of cardiac myocyte contractility in silico

    Science.gov (United States)

    Saucerman, Jeffrey J.; Brunton, Laurence L.; Michailova, Anushka P.; McCulloch, Andrew D.; McCullough, A. D. (Principal Investigator)

    2003-01-01

    The beta-adrenergic signaling pathway regulates cardiac myocyte contractility through a combination of feedforward and feedback mechanisms. We used systems analysis to investigate how the components and topology of this signaling network permit neurohormonal control of excitation-contraction coupling in the rat ventricular myocyte. A kinetic model integrating beta-adrenergic signaling with excitation-contraction coupling was formulated, and each subsystem was validated with independent biochemical and physiological measurements. Model analysis was used to investigate quantitatively the effects of specific molecular perturbations. 3-Fold overexpression of adenylyl cyclase in the model allowed an 85% higher rate of cyclic AMP synthesis than an equivalent overexpression of beta 1-adrenergic receptor, and manipulating the affinity of Gs alpha for adenylyl cyclase was a more potent regulator of cyclic AMP production. The model predicted that less than 40% of adenylyl cyclase molecules may be stimulated under maximal receptor activation, and an experimental protocol is suggested for validating this prediction. The model also predicted that the endogenous heat-stable protein kinase inhibitor may enhance basal cyclic AMP buffering by 68% and increasing the apparent Hill coefficient of protein kinase A activation from 1.0 to 2.0. Finally, phosphorylation of the L-type calcium channel and phospholamban were found sufficient to predict the dominant changes in myocyte contractility, including a 2.6x increase in systolic calcium (inotropy) and a 28% decrease in calcium half-relaxation time (lusitropy). By performing systems analysis, the consequences of molecular perturbations in the beta-adrenergic signaling network may be understood within the context of integrative cellular physiology.

  15. Regulation of excitation-contraction coupling in mouse cardiac myocytes: integrative analysis with mathematical modelling

    Science.gov (United States)

    Koivumäki, Jussi T; Korhonen, Topi; Takalo, Jouni; Weckström, Matti; Tavi, Pasi

    2009-01-01

    cellular physiology. We propose that integrative modelling as in the present work is a valuable complement to experiments in understanding the causality within complex biological systems such as cardiac myocytes. PMID:19715618

  16. Regulation of excitation-contraction coupling in mouse cardiac myocytes: integrative analysis with mathematical modelling

    Directory of Open Access Journals (Sweden)

    Weckström Matti

    2009-08-01

    normal and defective cellular physiology. We propose that integrative modelling as in the present work is a valuable complement to experiments in understanding the causality within complex biological systems such as cardiac myocytes.

  17. Fructose-1,6-bisphosphate enhances hypothermic preservation of cardiac myocytes.

    Science.gov (United States)

    Wheeler, Thomas J; Wiegand, Christina B; Chien, Sufan

    2005-09-01

    Previous studies from our project found that fructose-1,6-bisphosphate (FBP) enhanced the functional recovery of animal hearts after hypothermic preservation, and that rat cardiac myocytes take up FBP at 3 degrees C. In this study we tested the effects of FBP, as well as other compounds related to glycolysis and pyruvate oxidation, on the hypothermic preservation of myocytes. Isolated myocytes were incubated in ischemic suspensions at 3 degrees C, and aliquots examined over 72 hours for retention of rod-shaped morphology. In some experiments adenine nucleotide levels were measured by high-performance liquid chromatography (HPLC). FBP at 1 to 10 mmol/liter markedly reduced the death rate (65% reduction at 5 mmol/liter). Glucose at 2 to 10 mmol/liter was less beneficial (20% reduction). Insulin increased the death rate by about 25% when present alone, and it did not enhance the beneficial effects of FBP or glucose. Dichloroacetate (DCA), which stimulates pyruvate dehydrogenase, had little effect at 0.5 to 10 mmol/liter. Glucose and DCA did not increase the beneficial effects of FBP. After 6 to 24 hours of hypothermia, FBP- and glucose-treated cells had 25% to 50% higher ATP levels and 10% to 20% higher ATP:ADP ratios than untreated cells. Effects of FBP on preservation of morphology were much greater than effects on ATP levels. The results suggest that the effects of FBP and glucose were through glycolytic ATP production rather than through sugar oxidation via pyruvate dehydrogenase. The divergence in effects on preservation and effects on ATP suggests a role for a sub-cellular compartment of ATP in preservation.

  18. Slow [Na+]i dynamics impacts arrhythmogenesis and spiral wave reentry in cardiac myocyte ionic model

    Science.gov (United States)

    Krogh-Madsen, Trine; Christini, David J.

    2017-09-01

    Accumulation of intracellular Na+ is gaining recognition as an important regulator of cardiac myocyte electrophysiology. The intracellular Na+ concentration can be an important determinant of the cardiac action potential duration, can modulate the tissue-level conduction of excitation waves, and can alter vulnerability to arrhythmias. Mathematical models of cardiac electrophysiology often incorporate a dynamic intracellular Na+ concentration, which changes much more slowly than the remaining variables. We investigated the dependence of several arrhythmogenesis-related factors on [Na+]i in a mathematical model of the human atrial action potential. In cell simulations, we found that [Na+]i accumulation stabilizes the action potential duration to variations in several conductances and that the slow dynamics of [Na+]i impacts bifurcations to pro-arrhythmic afterdepolarizations, causing intermittency between different rhythms. In long-lasting tissue simulations of spiral wave reentry, [Na+]i becomes spatially heterogeneous with a decreased area around the spiral wave rotation center. This heterogeneous region forms a functional anchor, resulting in diminished meandering of the spiral wave. Our findings suggest that slow, physiological, rate-dependent variations in [Na+]i may play complex roles in cellular and tissue-level cardiac dynamics.

  19. Expression of androgen-binding protein (ABP) in human cardiac myocytes.

    Science.gov (United States)

    Schock, H W; Herbert, Z; Sigusch, H; Figulla, H R; Jirikowski, G F; Lotze, U

    2006-04-01

    Cardiomyocytes are known to be androgen targets. Changing systemic steroid levels are thought to be linked to various cardiac ailments, including dilated cardiomyopathy (DCM). The mode of action of gonadal steroid hormones on the human heart is unknown to date. In the present study, we used high-resolution immunocytochemistry on semithin sections (1 microm thick), IN SITU hybridization, and mass spectrometry to investigate the expression of androgen-binding protein (ABP) in human myocardial biopsies taken from male patients with DCM. We observed distinct cytoplasmic ABP immunoreactivity in a fraction of the myocytes. IN SITU hybridization with synthetic oligonucleotide probes revealed specific hybridization signals in these cells. A portion of the ABP-positive cells contained immunostaining for androgen receptor. With SELDI TOF mass spectrometry of affinity purified tissue extracts of human myocardium, we confirmed the presence of a 50 kDa protein similar to ABP. Our observations provide evidence of an intrinsic expression of ABP in human heart. ABP may be secreted from myocytes in a paracrine manner perhaps to influence the bioavailabity of gonadal steroids in myocardium.

  20. Optical single-channel resolution imaging of the ryanodine receptor distribution in rat cardiac myocytes.

    Science.gov (United States)

    Baddeley, David; Jayasinghe, Isuru D; Lam, Leo; Rossberger, Sabrina; Cannell, Mark B; Soeller, Christian

    2009-12-29

    We have applied an optical super-resolution technique based on single-molecule localization to examine the peripheral distribution of a cardiac signaling protein, the ryanodine receptor (RyR), in rat ventricular myocytes. RyRs form clusters with a mean size of approximately 14 RyRs per cluster, which is almost an order of magnitude smaller than previously estimated. Clusters were typically not circular (as previously assumed) but elongated with an average aspect ratio of 1.9. Edge-to-edge distances between adjacent RyR clusters were often distribution, is compatible with a stochastic cluster assembly process. We suggest that calcium sparks may be the result of the concerted activation of several RyR clusters forming a functional "supercluster" whose gating is controlled by both cytosolic and sarcoplasmic reticulum luminal calcium levels.

  1. Cyclic nucleotide phosphodiesterase PDE1C1 in human cardiac myocytes.

    Science.gov (United States)

    Vandeput, Fabrice; Wolda, Sharon L; Krall, Judith; Hambleton, Ryan; Uher, Lothar; McCaw, Kim N; Radwanski, Przemyslaw B; Florio, Vincent; Movsesian, Matthew A

    2007-11-09

    Isoforms in the PDE1 family of cyclic nucleotide phosphodiesterases were recently found to comprise a significant portion of the cGMP-inhibited cAMP hydrolytic activity in human hearts. We examined the expression of PDE1 isoforms in human myocardium, characterized their catalytic activity, and quantified their contribution to cAMP hydrolytic and cGMP hydrolytic activity in subcellular fractions of this tissue. Western blotting with isoform-selective anti-PDE1 monoclonal antibodies showed PDE1C1 to be the principal isoform expressed in human myocardium. Immunohistochemical analysis showed that PDE1C1 is distributed along the Z-lines and M-lines of cardiac myocytes in a striated pattern that differs from that of the other major dual-specificity cyclic nucleotide phosphodiesterase in human myocardium, PDE3A. Most of the PDE1C1 activity was recovered in soluble fractions of human myocardium. It binds both cAMP and cGMP with K(m) values of approximately 1 microm and hydrolyzes both substrates with similar catalytic rates. PDE1C1 activity in subcellular fractions was quantified using a new PDE1-selective inhibitor, IC295. At substrate concentrations of 0.1 microm, PDE1C1 constitutes the great majority of cAMP hydrolytic and cGMP hydrolytic activity in soluble fractions and the majority of cGMP hydrolytic activity in microsomal fractions, whereas PDE3 constitutes the majority of cAMP hydrolytic activity in microsomal fractions. These results indicate that PDE1C1 is expressed at high levels in human cardiac myocytes with an intracellular distribution distinct from that of PDE3A and that it may have a role in the integration of cGMP-, cAMP- and Ca(2+)-mediated signaling in these cells.

  2. Inhibition of PKR protects against H2O2-induced injury on neonatal cardiac myocytes by attenuating apoptosis and inflammation.

    Science.gov (United States)

    Wang, Yongyi; Men, Min; Xie, Bo; Shan, Jianggui; Wang, Chengxi; Liu, Jidong; Zheng, Hui; Yang, Wengang; Xue, Song; Guo, Changfa

    2016-12-08

    Reactive oxygenation species (ROS) generated from reperfusion results in cardiac injury through apoptosis and inflammation, while PKR has the ability to promote apoptosis and inflammation. The aim of the study was to investigate whether PKR is involved in hydrogen peroxide (H2O2) induced neonatal cardiac myocytes (NCM) injury. In our study, NCM, when exposed to H2O2, resulted in persistent activation of PKR due to NCM endogenous RNA. Inhibition of PKR by 2-aminopurine (2-AP) or siRNA protected against H2O2 induced apoptosis and injury. To elucidate the mechanism, we revealed that inhibition of PKR alleviated H2O2 induced apoptosis companied by decreased caspase3/7 activity, BAX and caspase-3 expression. We also revealed that inhibition of PKR suppressed H2O2 induced NFκB pathway and NLRP3 activation. Finally, we found ADAR1 mRNA and protein expression were both induced after H2O2 treatment through STAT-2 dependent pathway. By gain and loss of ADAR1 expression, we confirmed ADAR1 modulated PKR activity. Therefore, we concluded inhibition of PKR protected against H2O2-induced injury by attenuating apoptosis and inflammation. A self-preservation mechanism existed in NCM that ADAR1 expression is induced by H2O2 to limit PKR activation simultaneously. These findings identify a novel role for PKR/ADAR1 in myocardial reperfusion injury.

  3. Towards an integrative computational model of the guinea pig cardiac myocyte

    Directory of Open Access Journals (Sweden)

    Laura Doyle Gauthier

    2012-07-01

    Full Text Available The local control theory of excitation-contraction (EC coupling asserts that regulation of calcium (Ca2+ release occurs at the nanodomain level, where openings of single L-type Ca2+ channels (LCCs trigger openings of small clusters of ryanodine receptors (RyRs co-localized within the dyad. A consequence of local control is that the whole-cell Ca2+ transient is a smooth continuous function of influx of Ca2+ through LCCs. While this so-called graded release property has been known for some time, it’s functional importance to the integrated behavior of the cardiac ventricular myocyte has not been fully appreciated. We previously formulated a biophysically-based model, in which LCCs and RyRs interact via a coarse-grained representation of the dyadic space. The model captures key features of local control using a low-dimensional system of ordinary differential equations. Voltage-dependent gain and graded Ca2+ release are emergent properties of this model by virtue of the fact that model formulation is closely based on the sub-cellular basis of local control. In this current work, we have incorporated this graded release model into a prior model of guinea pig ventricular myocyte electrophysiology, metabolism, and isometric force production. The resulting integrative model predicts the experimentally-observed causal relationship between action potential (AP shape and timing of Ca2+ and force transients, a relationship that is not explained by models lacking the graded release property. Model results suggest that even relatively subtle changes in AP morphology that may result, for example, from remodeling of membrane transporter expression in disease or spatial variation in cell properties, may have major impact on the temporal waveform of Ca2+ transients, thus influencing tissue-level electro-mechanical function.

  4. Toward an integrative computational model of the Guinea pig cardiac myocyte.

    Science.gov (United States)

    Gauthier, Laura Doyle; Greenstein, Joseph L; Winslow, Raimond L

    2012-01-01

    The local control theory of excitation-contraction (EC) coupling asserts that regulation of calcium (Ca(2+)) release occurs at the nanodomain level, where openings of single L-type Ca(2+) channels (LCCs) trigger openings of small clusters of ryanodine receptors (RyRs) co-localized within the dyad. A consequence of local control is that the whole-cell Ca(2+) transient is a smooth continuous function of influx of Ca(2+) through LCCs. While this so-called graded release property has been known for some time, its functional importance to the integrated behavior of the cardiac ventricular myocyte has not been fully appreciated. We previously formulated a biophysically based model, in which LCCs and RyRs interact via a coarse-grained representation of the dyadic space. The model captures key features of local control using a low-dimensional system of ordinary differential equations. Voltage-dependent gain and graded Ca(2+) release are emergent properties of this model by virtue of the fact that model formulation is closely based on the sub-cellular basis of local control. In this current work, we have incorporated this graded release model into a prior model of guinea pig ventricular myocyte electrophysiology, metabolism, and isometric force production. The resulting integrative model predicts the experimentally observed causal relationship between action potential (AP) shape and timing of Ca(2+) and force transients, a relationship that is not explained by models lacking the graded release property. Model results suggest that even relatively subtle changes in AP morphology that may result, for example, from remodeling of membrane transporter expression in disease or spatial variation in cell properties, may have major impact on the temporal waveform of Ca(2+) transients, thus influencing tissue level electromechanical function.

  5. Infrasound exposure induces apoptosis of rat cardiac myocytes by regulating the expression of apoptosis-related proteins.

    Science.gov (United States)

    Pei, Zhao-Hui; Chen, Bao-Ying; Tie, Ru; Zhang, Hai-Feng; Zhao, Ge; Qu, Ping; Zhu, Xiao-Xing; Zhu, Miao-Zhang; Yu, Jun

    2011-12-01

    It has been reported that exposure to infrasound causes cardiac dysfunction. Allowing for the key role of apoptosis in the pathogenesis of cardiovascular diseases, the objective of this study was to investigate the apoptotic effects of infrasound. Cardiac myocytes cultured from neonatal rats were exposed to infrasound of 5 Hz at 130 dB. The apoptosis was determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling. Also, the expression levels of a series of apoptosis-related proteins were detected. As a result, infrasound induced apoptosis of cultured rat cardiac myocytes in a time-dependant manner. The expression of proapoptotic proteins such as Bax, caspase-3, caspase-8, caspase-9, and FAS was significantly up-regulated, with concomitant down-regulated expression of antiapoptotic proteins such as Bcl-x, and the inhibitory apoptosis proteins family proteins including XIAP, cIAP-1, and cIAP-2. The expression of poly (ADP-ribose) polymerase and β-catenin, which are the substrate proteins of caspase-3, was significantly decreased. In conclusion, infrasound is an apoptotic inducer of cardiac myocytes.

  6. PGC-1{alpha} accelerates cytosolic Ca{sup 2+} clearance without disturbing Ca{sup 2+} homeostasis in cardiac myocytes

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Min, E-mail: chenminyx@gmail.com [Institute of Molecular Medicine, State Key Laboratory of Biomembrane and Membrane Biotechnology, Peking University, Beijing 100871 (China); Yunnan Centers for Diseases Prevention and Control, Kunming 650022 (China); Wang, Yanru [Institute of Molecular Medicine, State Key Laboratory of Biomembrane and Membrane Biotechnology, Peking University, Beijing 100871 (China); Qu, Aijuan [Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 (United States)

    2010-06-11

    Energy metabolism and Ca{sup 2+} handling serve critical roles in cardiac physiology and pathophysiology. Peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1{alpha}) is a multi-functional coactivator that is involved in the regulation of cardiac mitochondrial functional capacity and cellular energy metabolism. However, the regulation of PGC-1{alpha} in cardiac Ca{sup 2+} signaling has not been fully elucidated. To address this issue, we combined confocal line-scan imaging with off-line imaging processing to characterize calcium signaling in cultured adult rat ventricular myocytes expressing PGC-1{alpha} via adenoviral transduction. Our data shows that overexpressing PGC-1{alpha} improved myocyte contractility without increasing the amplitude of Ca{sup 2+} transients, suggesting that myofilament sensitivity to Ca{sup 2+} increased. Interestingly, the decay kinetics of global Ca{sup 2+} transients and Ca{sup 2+} waves accelerated in PGC-1{alpha}-expressing cells, but the decay rate of caffeine-elicited Ca{sup 2+} transients showed no significant change. This suggests that sarcoplasmic reticulum (SR) Ca{sup 2+}-ATPase (SERCA2a), but not Na{sup +}/Ca{sup 2+} exchange (NCX) contribute to PGC-1{alpha}-induced cytosolic Ca{sup 2+} clearance. Furthermore, PGC-1{alpha} induced the expression of SERCA2a in cultured cardiac myocytes. Importantly, overexpressing PGC-1{alpha} did not disturb cardiac Ca{sup 2+} homeostasis, because SR Ca{sup 2+} load and the propensity for Ca{sup 2+} waves remained unchanged. These data suggest that PGC-1{alpha} can ameliorate cardiac Ca{sup 2+} cycling and improve cardiac work output in response to physiological stress. Unraveling the PGC-1{alpha}-calcium handing pathway sheds new light on the role of PGC-1{alpha} in the therapy of cardiac diseases.

  7. High-Resolution Mapping of Chromatin Conformation in Cardiac Myocytes Reveals Structural Remodeling of the Epigenome in Heart Failure.

    Science.gov (United States)

    Rosa-Garrido, Manuel; Chapski, Douglas J; Schmitt, Anthony D; Kimball, Todd H; Karbassi, Elaheh; Monte, Emma; Balderas, Enrique; Pellegrini, Matteo; Shih, Tsai-Ting; Soehalim, Elizabeth; Liem, David; Ping, Peipei; Galjart, Niels J; Ren, Shuxun; Wang, Yibin; Ren, Bing; Vondriska, Thomas M

    2017-10-24

    Cardiovascular disease is associated with epigenomic changes in the heart; however, the endogenous structure of cardiac myocyte chromatin has never been determined. To investigate the mechanisms of epigenomic function in the heart, genome-wide chromatin conformation capture (Hi-C) and DNA sequencing were performed in adult cardiac myocytes following development of pressure overload-induced hypertrophy. Mice with cardiac-specific deletion of CTCF (a ubiquitous chromatin structural protein) were generated to explore the role of this protein in chromatin structure and cardiac phenotype. Transcriptome analyses by RNA-seq were conducted as a functional readout of the epigenomic structural changes. Depletion of CTCF was sufficient to induce heart failure in mice, and human patients with heart failure receiving mechanical unloading via left ventricular assist devices show increased CTCF abundance. Chromatin structural analyses revealed interactions within the cardiac myocyte genome at 5-kb resolution, enabling examination of intra- and interchromosomal events, and providing a resource for future cardiac epigenomic investigations. Pressure overload or CTCF depletion selectively altered boundary strength between topologically associating domains and A/B compartmentalization, measurements of genome accessibility. Heart failure involved decreased stability of chromatin interactions around disease-causing genes. In addition, pressure overload or CTCF depletion remodeled long-range interactions of cardiac enhancers, resulting in a significant decrease in local chromatin interactions around these functional elements. These findings provide a high-resolution chromatin architecture resource for cardiac epigenomic investigations and demonstrate that global structural remodeling of chromatin underpins heart failure. The newly identified principles of endogenous chromatin structure have key implications for epigenetic therapy. © 2017 The Authors.

  8. S100A4 is upregulated in injured myocardium and promotes growth and survival of cardiac myocytes

    DEFF Research Database (Denmark)

    Schneider, Mikael; Kostin, Sawa; Strøm, Claes C

    2007-01-01

    and immunoblotting that S100A4 mRNA and protein is upregulated in hypertrophic rat and human hearts and show by way of confocal microscopy that S100A4 protein, but not mRNA, appears in cardiac myocytes only in the border zone after an acute ischemic event in rat and human hearts. In normal rat and human hearts, S100...... after injury. Promisingly, recombinant S100A4 protein elicited a robust hypertrophic response and increased the number of viable cells in cardiac myocyte cultures by inhibiting apoptosis. We also found that ERK1/2 activation was necessary for both the hypertrophy and survival effects of S100A4 in vitro...

  9. Candesartan abrogates G protein-coupled receptors agonist-induced MAPK activation and cardiac myocyte hypertrophy

    Directory of Open Access Journals (Sweden)

    Djamel Lebeche

    2001-03-01

    Full Text Available The renin-angiotensin-aldosterone system (RAAS has been identified as a major contributor to the development of cardiac hypertrophy and the subsequent transition to heart failure. G protein-coupled receptors agonists such as angiotensin II (Ang II, endothelin-1 (ET-1 and phenylephrine (PE have been implicated in hypertrophic responses in ventricular myocytes through the activation of several families of MAP kinases. In this study we examined the effect of candesartan, an Ang II type 1-(AT1-receptor antagonist, on cardiac hypertrophy by using cultured neonatal rat cardiomyocytes. Stimulation with Ang II (100 nM, ET-1 (100 nM or PE (1 µM induced marked increases in [3H]Leucine incorporation (≥ 50%, compatible with enhanced protein synthesis. The addition of candesartan abrogated the increase in [3H]Leucine incorporation in response not only to Ang II but also to ET-1 and PE. To elucidate the mechanisms involved in this antihypertrophic effect of candesartan, we studied the activation of p38-MAPK, extracellular signal-regulated kinases (ERK1/2 and stress-activated protein kinases (SAPKs. Ang II, ET-1 and PE increased the phosphorylation levels of ERK1/2, p54 SAPK and p46SAPK and p38 in a time-dependent manner. This activation was completely blocked in the case of Ang II by pretreatment with candesartan. ET-1-induced activation of ERKs, SAPKs and p38 was also partially, but significantly, reduced by candesartan. PE-induced activation of SAPKs, but not ERKs and p38, was also reduced by candesartan. These results suggest that the hypertrophic response to ET-1 and PE, along with Ang II, is dependent upon a functioning AT1-receptor and may be mediated by AT 1 activation of the MAP kinases.

  10. Impaired long-chain fatty acid utilization by cardiac myocytes isolated from mice lacking the heart-type fatty acid binding protein gene

    NARCIS (Netherlands)

    Schaap, F. G.; Binas, B.; Danneberg, H.; van der Vusse, G. J.; Glatz, J. F.

    1999-01-01

    Heart-type fatty acid binding protein (H-FABP), abundantly expressed in cardiac myocytes, has been postulated to facilitate the cardiac uptake of long-chain fatty acids (LCFAs) and to promote their intracellular trafficking to sites of metabolic conversion. Mice with a disrupted H-FABP gene were

  11. Tyrosine kinase activation is an immediate and essential step in hypotonic cell swelling-induced ERK activation and c-fos gene expression in cardiac myocytes.

    OpenAIRE

    Sadoshima, J; Qiu, Z; Morgan, J P; Izumo, S

    1996-01-01

    Hypotonic stress causes rapid cell swelling and initiates various cellular adaptive processes. However, it is unknown how cells initially sense low osmolarity and convert it into intracellular signals. We investigated the signal transduction mechanism initiated by hypotonic cell swelling in cardiac myocytes using c-fos expression as a nuclear marker. Treatment of myocytes with hypotonic culture media rapidly induced c-fos expression, whereas hypertonic stress had no effect. Transfection of c-...

  12. Stretch-Induced Regulation of Angiotensinogen Gene Expression in Cardiac Myocytes and Fibroblasts: Opposing Roles of JNK1/2 and p38α MAP Kinases

    OpenAIRE

    Lal, Hind; Verma, Suresh K.; Golden, Honey B.; Foster, Donald M.; Smith, Manuela; Dostal, David E.

    2008-01-01

    The cardiac renin-angiotensin system (RAS) has been implicated in mediating myocyte hypertrophy, remodeling, and fibroblast proliferation in the hemodynamically overloaded heart. However, the intracellular signaling mechanisms responsible for regulation of angiotensinogen (Ao), a substrate of the RAS system, are largely unknown. Here we report the identification of JNK1/2 as a negative, and p38α as a major positive regulator of Ao gene expression. Isolated neonatal rat ventricular myocytes (N...

  13. MicroRNA-451 exacerbates lipotoxicity in cardiac myocytes and high-fat diet-induced cardiac hypertrophy in mice through suppression of the LKB1/AMPK pathway.

    Science.gov (United States)

    Kuwabara, Yasuhide; Horie, Takahiro; Baba, Osamu; Watanabe, Shin; Nishiga, Masataka; Usami, Shunsuke; Izuhara, Masayasu; Nakao, Tetsushi; Nishino, Tomohiro; Otsu, Kinya; Kita, Toru; Kimura, Takeshi; Ono, Koh

    2015-01-16

    In some patients with type 2 diabetes mellitus (DM) without hypertension, cardiac hypertrophy and attenuated cardiac function are observed, and this insult is termed diabetic cardiomyopathy. To date, microRNA (miRNAs or miR) functions in diabetic cardiomyopathy remain to be elucidated. To clarify the functions of miRNAs involved in diabetic cardiomyopathy caused by type 2 DM. C57BL/6 mice were fed a high-fat diet (HFD) for 20 weeks, which induced obesity and type 2 DM. miRNA microarray analyses and real-time polymerase chain reaction revealed that miR-451 levels were significantly increased in the type 2 DM mouse hearts. Because excess supply of saturated fatty acids is a cause of diabetic cardiomyopathy, we stimulated neonatal rat cardiac myocytes with palmitic acid and confirmed that miR-451 expression was increased in a dose- and time-dependent manner. Loss of miR-451 function ameliorated palmitate-induced lipotoxicity in neonatal rat cardiac myocytes. Calcium-binding protein 39 (Cab39) is a scaffold protein of liver kinase B1 (LKB1), an upstream kinase of AMP-activated protein kinase (AMPK). Cab39 was a direct target of miR-451 in neonatal rat cardiac myocytes and Cab39 overexpression rescued the lipotoxicity. To clarify miR-451 functions in vivo, we generated cardiomyocyte-specific miR-451 knockout mice. HFD-induced cardiac hypertrophy and contractile reserves were ameliorated in cardiomyocyte-specific miR-451 knockout mice compared with control mice. Protein levels of Cab39 and phosphorylated AMPK were increased and phosphorylated mammalian target of rapamycin (mTOR) was reduced in cardiomyocyte-specific miR-451 knockout mouse hearts compared with control mouse hearts. Our results demonstrate that miR-451 is involved in diabetic cardiomyopathy through suppression of the LKB1/AMPK pathway. © 2014 American Heart Association, Inc.

  14. Statistical Metamodeling and Sequential Design of Computer Experiments to Model Glyco-Altered Gating of Sodium Channels in Cardiac Myocytes.

    Science.gov (United States)

    Du, Dongping; Yang, Hui; Ednie, Andrew R; Bennett, Eric S

    2016-09-01

    Glycan structures account for up to 35% of the mass of cardiac sodium ( Nav ) channels. To question whether and how reduced sialylation affects Nav activity and cardiac electrical signaling, we conducted a series of in vitro experiments on ventricular apex myocytes under two different glycosylation conditions, reduced protein sialylation (ST3Gal4(-/-)) and full glycosylation (control). Although aberrant electrical signaling is observed in reduced sialylation, realizing a better understanding of mechanistic details of pathological variations in INa and AP is difficult without performing in silico studies. However, computer model of Nav channels and cardiac myocytes involves greater levels of complexity, e.g., high-dimensional parameter space, nonlinear and nonconvex equations. Traditional linear and nonlinear optimization methods have encountered many difficulties for model calibration. This paper presents a new statistical metamodeling approach for efficient computer experiments and optimization of Nav models. First, we utilize a fractional factorial design to identify control variables from the large set of model parameters, thereby reducing the dimensionality of parametric space. Further, we develop the Gaussian process model as a surrogate of expensive and time-consuming computer models and then identify the next best design point that yields the maximal probability of improvement. This process iterates until convergence, and the performance is evaluated and validated with real-world experimental data. Experimental results show the proposed algorithm achieves superior performance in modeling the kinetics of Nav channels under a variety of glycosylation conditions. As a result, in silico models provide a better understanding of glyco-altered mechanistic details in state transitions and distributions of Nav channels. Notably, ST3Gal4(-/-) myocytes are shown to have higher probabilities accumulated in intermediate inactivation during the repolarization and yield a

  15. Urokinase plasminogen activator protects cardiac myocytes from oxidative damage and apoptosis via hOGG1 induction

    OpenAIRE

    Hohensinner, Philipp J.; Takacs, Nikol; Kaun, Christoph; Thaler, Barbara; Krychtiuk, Konstantin A.; Pfaffenberger, Stefan; Aliabadi, Arezu; Zuckermann, Andreas; Huber, Kurt; Wojta, Johann

    2017-01-01

    The role of uPA in tissue remodeling and cell migration is already well established. In addition, uPA was reported to stabilize p53, a key cell cycle control, DNA repair and apoptosis initiation protein. We aimed to determine the role of uPA-uPAR signaling towards cell survival or apoptosis in human adult cardiac myocytes (HACM). HACM were stimulated with uPA and DNA damage was inflicted by incubating cells with 200??M H2O2. To analyze for apoptotic cells we applied TUNEL staining. Oxidative ...

  16. Ca2+/Calmodulin-Dependent Protein Kinase II and Androgen Signaling Pathways Modulate MEF2 Activity in Testosterone-Induced Cardiac Myocyte Hypertrophy

    Directory of Open Access Journals (Sweden)

    Javier Duran

    2017-09-01

    Full Text Available Testosterone is known to induce cardiac hypertrophy through androgen receptor (AR-dependent and -independent pathways, but the molecular underpinnings of the androgen action remain poorly understood. Previous work has shown that Ca2+/calmodulin-dependent protein kinase II (CaMKII and myocyte-enhancer factor 2 (MEF2 play key roles in promoting cardiac myocyte growth. In order to gain mechanistic insights into the action of androgens on the heart, we investigated how testosterone affects CaMKII and MEF2 in cardiac myocyte hypertrophy by performing studies on cultured rat cardiac myocytes and hearts obtained from adult male orchiectomized (ORX rats. In cardiac myocytes, MEF2 activity was monitored using a luciferase reporter plasmid, and the effects of CaMKII and AR signaling pathways on MEF2C were examined by using siRNAs and pharmacological inhibitors targeting these two pathways. In the in vivo studies, ORX rats were randomly assigned to groups that were administered vehicle or testosterone (125 mg⋅kg-1⋅week-1 for 5 weeks, and plasma testosterone concentrations were determined using ELISA. Cardiac hypertrophy was evaluated by measuring well-characterized hypertrophy markers. Moreover, western blotting was used to assess CaMKII and phospholamban (PLN phosphorylation, and MEF2C and AR protein levels in extracts of left-ventricle tissue from control and testosterone-treated ORX rats. Whereas testosterone treatment increased the phosphorylation levels of CaMKII (Thr286 and phospholambam (PLN (Thr17 in cardiac myocytes in a time- and concentration-dependent manner, testosterone-induced MEF2 activity and cardiac myocyte hypertrophy were prevented upon inhibition of CaMKII, MEF2C, and AR signaling pathways. Notably, in the hypertrophied hearts obtained from testosterone-administered ORX rats, both CaMKII and PLN phosphorylation levels and AR and MEF2 protein levels were increased. Thus, this study presents the first evidence indicating that

  17. Image Processing Techniques for Assessing Contractility in Isolated Adult Cardiac Myocytes

    Directory of Open Access Journals (Sweden)

    Carlos Bazan

    2009-01-01

    The physiologic application of the methodology is evaluated by assessing overall contraction in enzymatically dissociated adult rat cardiocytes. Our results demonstrate the effectiveness of the proposed approach in characterizing the true, two-dimensional, “shortening” in the contraction process of adult cardiocytes. We compare the performance of the proposed method to that of a popular edge detection system in the literature. The proposed method not only provides a more comprehensive assessment of the myocyte contraction process but also can potentially eliminate historical concerns and sources of errors caused by myocyte rotation or translation during contraction. Furthermore, the versatility of the image processing techniques makes the method suitable for determining myocyte shortening in cells that usually bend or move during contraction. The proposed method can be utilized to evaluate changes in contractile behavior resulting from drug intervention, disease modeling, transgeneity, or other common applications to mammalian cardiocytes.

  18. Calcium phosphate coprecipitation greatly enhances transduction of cardiac myocytes and vascular smooth muscle cells by lentivirus vectors

    Science.gov (United States)

    Sakoda, Tsuyoshi; Kasahara, Nori; Kedes, Larry; Ohyanagi, Mitsumasa

    2007-01-01

    BACKGROUND Lentivirus vectors provide a delivery system that can both transduce nondividing cells and integrate transgenes into the genome of target cells without cytotoxicity. However, their relatively low transduction efficiency presents a significant obstacle to progress. OBJECTIVES In the present paper, a simple and easy method using calcium phosphate (CaPi) to enhance the efficiency of lentivirus gene transfer in both vascular smooth muscle cells and cardiac myocytes is reported. METHODS AND RESULTS Delivery of lentivirus vectors in the presence of CaPi coprecipitates increased vector-encoded transgene expression up to 13-fold. Of interest, the magnitudes of enhancement of transgene expression by CaPi coprecipitates in 293T cells, vascular smooth muscle cells and cardiac myocytes were greater during brief periods (10 min and 120 min) of virus-cell contact than during long periods (16 h). Moreover, with a short duration of incubation with CaPi coprecipitates (up to 120 min), there was little evidence of direct cell toxicity. CaPi coprecipitates had no effect on host range specificity of ecotropic viruses and thus appears to enhance transduction efficiency physiologically by facilitating physical interaction between virus and cell. CONCLUSIONS These data show that lentivirus with CaPi coprecipitates increases both the efficiency and the speed of gene transfer. These approaches provide an efficient method and an improved tool for research and possibly for therapy of cardiovascular diseases. PMID:18650994

  19. Image Processing Techniques for Assessing Contractility in Isolated Neonatal Cardiac Myocytes

    Directory of Open Access Journals (Sweden)

    Carlos Bazan

    2011-01-01

    employed in determining myocyte contractility almost simultaneously with the acquisition of the Ca2+ transient and other correlates of cell contraction. The proposed methodology can be utilized to evaluate changes in contractile behavior resulting from drug intervention, disease models, transgeneity, or other common applications of neonatal cardiocytes.

  20. Oxidative Stress-Responsive Apoptosis Inducing Protein (ORAIP) Plays a Critical Role in High Glucose-Induced Apoptosis in Rat Cardiac Myocytes and Murine Pancreatic β-Cells.

    Science.gov (United States)

    Yao, Takako; Fujimura, Tsutomu; Murayama, Kimie; Okumura, Ko; Seko, Yoshinori

    2017-10-18

    We previously identified a novel apoptosis-inducing humoral factor in the conditioned medium of hypoxic/reoxygenated-cardiac myocytes. We named this novel post-translationally-modified secreted-form of eukaryotic translation initiation factor 5A Oxidative stress-Responsive Apoptosis-Inducing Protein (ORAIP). We confirmed that myocardial ischemia/reperfusion markedly increased plasma ORAIP levels and rat myocardial ischemia/reperfusion injury was clearly suppressed by neutralizing anti-ORAIP monoclonal antibodies (mAbs) in vivo. In this study, to investigate the mechanism of cell injury of cardiac myocytes and pancreatic β-cells involved in diabetes mellitus (DM), we analyzed plasma ORAIP levels in DM model rats and the role of ORAIP in high glucose-induced apoptosis of cardiac myocytes in vitro. We also examined whether recombinant-ORAIP induces apoptosis in pancreatic β-cells. Plasma ORAIP levels in DM rats during diabetic phase were about 18 times elevated as compared with non-diabetic phase. High glucose induced massive apoptosis in cardiac myocytes (66.2 ± 2.2%), which was 78% suppressed by neutralizing anti-ORAIP mAb in vitro. Furthermore, recombinant-ORAIP clearly induced apoptosis in pancreatic β-cells in vitro. These findings strongly suggested that ORAIP plays a pivotal role in hyperglycemia-induced myocardial injury and pancreatic β-cell injury in DM. ORAIP will be a biomarker and a critical therapeutic target for cardiac injury and progression of DM itself.

  1. KChIP2 regulates the cardiac Ca2+ transient and myocyte contractility by targeting ryanodine receptor activity.

    Directory of Open Access Journals (Sweden)

    Drew M Nassal

    Full Text Available Pathologic electrical remodeling and attenuated cardiac contractility are featured characteristics of heart failure. Coinciding with these remodeling events is a loss of the K+ channel interacting protein, KChIP2. While, KChIP2 enhances the expression and stability of the Kv4 family of potassium channels, leading to a more pronounced transient outward K+ current, Ito,f, the guinea pig myocardium is unique in that Kv4 expression is absent, while KChIP2 expression is preserved, suggesting alternative consequences to KChIP2 loss. Therefore, KChIP2 was acutely silenced in isolated guinea pig myocytes, which led to significant reductions in the Ca2+ transient amplitude and prolongation of the transient duration. This change was reinforced by a decline in sarcomeric shortening. Notably, these results were unexpected when considering previous observations showing enhanced ICa,L and prolonged action potential duration following KChIP2 loss, suggesting a disruption of fundamental Ca2+ handling proteins. Evaluation of SERCA2a, phospholamban, RyR, and sodium calcium exchanger identified no change in protein expression. However, assessment of Ca2+ spark activity showed reduced spark frequency and prolonged Ca2+ decay following KChIP2 loss, suggesting an altered state of RyR activity. These changes were associated with a delocalization of the ryanodine receptor activator, presenilin, away from sarcomeric banding to more diffuse distribution, suggesting that RyR open probability are a target of KChIP2 loss mediated by a dissociation of presenilin. Typically, prolonged action potential duration and enhanced Ca2+ entry would augment cardiac contractility, but here we see KChIP2 fundamentally disrupts Ca2+ release events and compromises myocyte contraction. This novel role targeting presenilin localization and RyR activity reveals a significance for KChIP2 loss that reflects adverse remodeling observed in cardiac disease settings.

  2. Cardiac Myocyte Diversity and a Fibroblast Network in the Junctional Region of the Zebrafish Heart Revealed by Transmission and Serial Block-Face Scanning Electron Microscopy

    KAUST Repository

    Lafontant, Pascal J.

    2013-08-23

    The zebrafish has emerged as an important model of heart development and regeneration. While the structural characteristics of the developing and adult zebrafish ventricle have been previously studied, little attention has been paid to the nature of the interface between the compact and spongy myocardium. Here we describe how these two distinct layers are structurally and functionally integrated. We demonstrate by transmission electron microscopy that this interface is complex and composed primarily of a junctional region occupied by collagen, as well as a population of fibroblasts that form a highly complex network. We also describe a continuum of uniquely flattened transitional cardiac myocytes that form a circumferential plate upon which the radially-oriented luminal trabeculae are anchored. In addition, we have uncovered within the transitional ring a subpopulation of markedly electron dense cardiac myocytes. At discrete intervals the transitional cardiac myocytes form contact bridges across the junctional space that are stabilized through localized desmosomes and fascia adherentes junctions with adjacent compact cardiac myocytes. Finally using serial block-face scanning electron microscopy, segmentation and volume reconstruction, we confirm the three-dimensional nature of the junctional region as well as the presence of the sheet-like fibroblast network. These ultrastructural studies demonstrate the previously unrecognized complexity with which the compact and spongy layers are structurally integrated, and provide a new basis for understanding development and regeneration in the zebrafish heart. © 2013 Lafontant et al.

  3. Interleukin-17-induced expression of monocyte chemoattractant protein-1 in cardiac myocytes requires nuclear factor κB through the phosphorylation of p65.

    Science.gov (United States)

    Shen, Yan; Xie, Xin; Li, Zhuolun; Huang, Yan; Ma, Li; Shen, Xinhe; Liu, Yanyue; Zhao, Yuxia

    2017-07-01

    IL-17 plays a key role in a variety of autoimmune diseases. MCP-1 is involved in the infiltration of mononuclear cells of myocardium in VMC. However, the relationship between IL-17 and MCP-1 in myocardial injury remains unclear. In this study, expression of MCP-1 mRNA and protein in cardiac myocytes was detected with qRT-PCR and ELISA, respectively. It was found that IL-17A induced MCP-1 expression in a dose- and time-dependent manner in cardiac myocytes, which could be blocked by IL-17A and IL-17RA neutralizing antibodies. NF-κB p65 and p-p65 protein expression in cardiac myocytes was studied with western blotting. Rates of p-p65 in whole lysates and in nuclear lysates all increased in the first 15 min. Meanwhile, the amount of NF-κB p65 in whole lysates did not change, but the amount of NF-κB p65 in nuclear lysates increased in the first 15 min. Then the optimal sequence and concentration of NF-κB p65 siRNAs was selected. After transfection of 10 nM siRNA-2 of NF-κB p65 into cardiac myocytes before stimulation by IL-17A, expression of MCP-1 mRNA and protein obviously decreased. In conclusion, expression of MCP-1 induced by IL-17 requires NF-κB through the phosphorylation of p65 in cardiac myocytes, which is meaningful to study the onset of chronic viral myocarditis and will provide a new target for the treatment of viral myocarditis. © 2017 The Societies and John Wiley & Sons Australia, Ltd.

  4. JS-K, a GST-activated nitric oxide donor prodrug, enhances chemo-sensitivity in renal carcinoma cells and prevents cardiac myocytes toxicity induced by Doxorubicin.

    Science.gov (United States)

    Qiu, Mingning; Ke, Longzhi; Zhang, Sai; Zeng, Xin; Fang, Zesong; Liu, Jianjun

    2017-08-01

    Doxorubicin, a highly effective and widely used anthracycline antibiotic in multiple chemotherapy regimens, has been limited by its cardiotoxicity. The aim of this study is to investigate the effect of nitric oxide donor prodrug JS-K on proliferation and apoptosis in renal carcinoma cells and cardiac myocytes toxicity induced by Doxorubicin and to explore possible p53-related mechanism in renal carcinoma cells. The effect of JS-K on anti-cancer activity of Doxorubicin was investigated in renal carcinoma cells via detecting cell proliferation, cytotoxicity, cell death and apoptosis and expressions of apoptotic-related proteins. Effect of p53 on the combination of JS-K and Doxorubicin was determined using p53 inhibitor Pifithrin-α and p53 activator III. Furthermore, the effect of JS-K on cardiac myocytes toxicity of Doxorubicin was investigated in H9c2 (2-1) cardiac myocytes via measuring cell growth, cell death and apoptosis, expressions of proteins involved in apoptosis and intracellular reactive oxygen species. We demonstrated that JS-K could increase Doxorubicin-induced renal carcinoma cell growth suppression and apoptosis and could increase expressions of proteins that are involved in apoptosis. Additionally, Pifithrin-α reversed the promoting effect of JS-K on Doxorubicin-induced renal carcinoma cell apoptosis; conversely, the p53 activator III exacerbated the promoting effect of JS-K on Doxorubicin-induced renal carcinoma cell apoptosis. Furthermore, JS-K protected H9c2 (2-1) cardiac myocytes against Doxorubicin-induced toxicity and decreased Doxorubicin-induced reactive oxygen species production. JS-K enhances the anti-cancer activity of Doxorubicin in renal carcinoma cells by upregulating p53 expression and prevents cardiac myocytes toxicity of Doxorubicin by decreasing oxidative stress.

  5. Ca(2+ release events in cardiac myocytes up close: insights from fast confocal imaging.

    Directory of Open Access Journals (Sweden)

    Vyacheslav M Shkryl

    Full Text Available The spatio-temporal properties of Ca(2+ transients during excitation-contraction coupling and elementary Ca(2+ release events (Ca(2+ sparks were studied in atrial and ventricular myocytes with ultra-fast confocal microscopy using a Zeiss LSM 5 LIVE system that allows sampling rates of up to 60 kHz. Ca(2+ sparks which originated from subsarcolemmal junctional sarcoplasmic reticulum (j-SR release sites in atrial myocytes were anisotropic and elongated in the longitudinal direction of the cell. Ca(2+ sparks in atrial cells originating from non-junctional SR and in ventricular myocytes were symmetrical. Ca(2+ spark recording in line scan mode at 40,000 lines/s uncovered step-like increases of [Ca(2+]i. 2-D imaging of Ca(2+ transients revealed an asynchronous activation of release sites and allowed the sequential recording of Ca(2+ entry through surface membrane Ca(2+ channels and subsequent activation of Ca(2+-induced Ca(2+ release. With a latency of 2.5 ms after application of an electrical stimulus, Ca(2+ entry could be detected that was followed by SR Ca(2+ release after an additional 3 ms delay. Maximum Ca(2+ release was observed 4 ms after the beginning of release. The timing of Ca(2+ entry and release was confirmed by simultaneous [Ca(2+]i and membrane current measurements using the whole cell voltage-clamp technique. In atrial cells activation of discrete individual release sites of the j-SR led to spatially restricted Ca(2+ release events that fused into a peripheral ring of elevated [Ca(2+]i that subsequently propagated in a wave-like fashion towards the center of the cell. In ventricular myocytes asynchronous Ca(2+ release signals from discrete sites with no preferential subcellular location preceded the whole-cell Ca(2+ transient. In summary, ultra-fast confocal imaging allows investigation of Ca(2+ signals with a time resolution similar to patch clamp technique, however in a less invasive fashion.

  6. Ca(2+) release events in cardiac myocytes up close: insights from fast confocal imaging.

    Science.gov (United States)

    Shkryl, Vyacheslav M; Blatter, Lothar A

    2013-01-01

    The spatio-temporal properties of Ca(2+) transients during excitation-contraction coupling and elementary Ca(2+) release events (Ca(2+) sparks) were studied in atrial and ventricular myocytes with ultra-fast confocal microscopy using a Zeiss LSM 5 LIVE system that allows sampling rates of up to 60 kHz. Ca(2+) sparks which originated from subsarcolemmal junctional sarcoplasmic reticulum (j-SR) release sites in atrial myocytes were anisotropic and elongated in the longitudinal direction of the cell. Ca(2+) sparks in atrial cells originating from non-junctional SR and in ventricular myocytes were symmetrical. Ca(2+) spark recording in line scan mode at 40,000 lines/s uncovered step-like increases of [Ca(2+)]i. 2-D imaging of Ca(2+) transients revealed an asynchronous activation of release sites and allowed the sequential recording of Ca(2+) entry through surface membrane Ca(2+) channels and subsequent activation of Ca(2+)-induced Ca(2+) release. With a latency of 2.5 ms after application of an electrical stimulus, Ca(2+) entry could be detected that was followed by SR Ca(2+) release after an additional 3 ms delay. Maximum Ca(2+) release was observed 4 ms after the beginning of release. The timing of Ca(2+) entry and release was confirmed by simultaneous [Ca(2+)]i and membrane current measurements using the whole cell voltage-clamp technique. In atrial cells activation of discrete individual release sites of the j-SR led to spatially restricted Ca(2+) release events that fused into a peripheral ring of elevated [Ca(2+)]i that subsequently propagated in a wave-like fashion towards the center of the cell. In ventricular myocytes asynchronous Ca(2+) release signals from discrete sites with no preferential subcellular location preceded the whole-cell Ca(2+) transient. In summary, ultra-fast confocal imaging allows investigation of Ca(2+) signals with a time resolution similar to patch clamp technique, however in a less invasive fashion.

  7. Temperature dependence of unitary properties of an ATP-dependent potassium channel in cardiac myocytes.

    OpenAIRE

    McLarnon, J G; Hamman, B.N.; Tibbits, G.F.

    1993-01-01

    The temperature dependence of the properties of unitary currents in cultured rat ventricular myocytes has been studied. Currents flowing through an ATP-dependent K+ channel were recorded from inside-out patches with the bath temperature varied from 10 degrees to 30 degrees C. The channel conductance was 56 pS at room temperature (22 degrees C), and the amplitudes of unitary currents and the channel conductance exhibited a relatively weak (Q10 from 1.4 to 1.6) dependence on temperature. The te...

  8. Activation of PPARβ/δ protects cardiac myocytes from oxidative stress-induced apoptosis by suppressing generation of reactive oxygen/nitrogen species and expression of matrix metalloproteinases.

    Science.gov (United States)

    Barlaka, Eleftheria; Görbe, Anikó; Gáspár, Renáta; Pálóczi, János; Ferdinandy, Péter; Lazou, Antigone

    2015-01-01

    Heart failure still remains one of the leading causes of morbidity and mortality worldwide. A major contributing factor is reactive oxygen/nitrogen species (RONS) overproduction which is associated with cardiac remodeling partly through cardiomyocyte apoptosis. Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that belong to the nuclear receptor superfamily and have been implicated in cardioprotection. However, the molecular mechanisms are largely unexplored. In this study we sought to investigate the potential beneficial effects evoked by activation of PPARβ/δ under the setting of oxidative stress induced by H2O2 in adult rat cardiac myocytes. The selective PPARβ/δ agonist GW0742 inhibited the H2O2-induced apoptosis and increased cell viability. In addition, generation of RONS was attenuated in cardiac myocytes in the presence of PPARβ/δ agonist. These effects were abolished in the presence of the PPARβ/δ antagonist indicating that the effect was through PPARβ/δ receptor activation. Treatment with PPARβ/δ agonist was also associated with attenuation of caspase-3 and PARP cleavage, upregulation of anti-apoptotic Bcl-2 and concomitant downregulation of pro-apoptotic Bax. In addition, activation of PPARβ/δ inhibited the oxidative-stress-induced MMP-2 and MMP-9 mRNA upregulation. It is concluded that PPARβ/δ activation exerts a cytoprotective effect in adult rat cardiac myocytes subjected to oxidative stress via inhibition of oxidative stress, MMP expression, and apoptosis. Our data suggest that the novel connection between PPAR signaling and MMP down-regulation in cardiac myocytes might represent a new target for the management of oxidative stress-induced cardiac dysfunction. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Modeling a Complex Biological Network with Temporal Heterogeneity: Cardiac Myocyte Plasticity as a Case Study

    Science.gov (United States)

    Mazloom, Amin R.; Basu, Kalyan; Mandal, Subhrangsu S.; Das, Sajal K.

    Complex biological systems often characterize nonlinear dynamics. Employing traditional deterministic or stochastic approaches to quantify these dynamics either fail to capture their existing deviant effects or lead to combinatorial explosion. In this work we devised a novel approach that projects the biological functions within a pathway to a network of stochastic events that are random in time and space. By applying this approach recursively to the object system we build the event network of the entire system. The dynamics of the system evolves through the execution of the event network by a simulation engine which comprised of a time prioritized event queue. As a case study we utilized the current method and conducted an in-silico experiment on the metabolic plasticity of a cardiac myocyete. We aimed to quantify the down stream effects of insulin signaling that predominantly controls the plasticity in myocardium. Intriguingly, our in-silico results on transcription regulatory effect of insulin showed a good agreement with experimental data. Meanwhile we were able to characterize the flux change across major metabolic pathways over 48 hours of the in-silico experiment. Our simulation performed a remarkable efficiency by conducting 48 hours of simulation-time in less that 2 hours of processor time.

  10. Re-evaluation of the action potential upstroke velocity as a measure of the Na+ current in cardiac myocytes at physiological conditions.

    Directory of Open Access Journals (Sweden)

    Géza Berecki

    Full Text Available BACKGROUND: The SCN5A encoded sodium current (I(Na generates the action potential (AP upstroke and is a major determinant of AP characteristics and AP propagation in cardiac myocytes. Unfortunately, in cardiac myocytes, investigation of kinetic properties of I(Na with near-physiological ion concentrations and temperature is technically challenging due to the large amplitude and rapidly activating nature of I(Na, which may seriously hamper the quality of voltage control over the membrane. We hypothesized that the alternating voltage clamp-current clamp (VC/CC technique might provide an alternative to traditional voltage clamp (VC technique for the determination of I(Na properties under physiological conditions. PRINCIPAL FINDINGS: We studied I(Na under close-to-physiological conditions by VC technique in SCN5A cDNA-transfected HEK cells or by alternating VC/CC technique in both SCN5A cDNA-transfected HEK cells and rabbit left ventricular myocytes. In these experiments, peak I(Na during a depolarizing VC step or maximal upstroke velocity, dV/dt(max, during VC/CC served as an indicator of available I(Na. In HEK cells, biophysical properties of I(Na, including current density, voltage dependent (inactivation, development of inactivation, and recovery from inactivation, were highly similar in VC and VC/CC experiments. As an application of the VC/CC technique we studied I(Na in left ventricular myocytes isolated from control or failing rabbit hearts. CONCLUSIONS: Our results demonstrate that the alternating VC/CC technique is a valuable experimental tool for I(Na measurements under close-to-physiological conditions in cardiac myocytes.

  11. Re-evaluation of the action potential upstroke velocity as a measure of the Na+ current in cardiac myocytes at physiological conditions.

    Science.gov (United States)

    Berecki, Géza; Wilders, Ronald; de Jonge, Berend; van Ginneken, Antoni C G; Verkerk, Arie O

    2010-12-31

    The SCN5A encoded sodium current (I(Na)) generates the action potential (AP) upstroke and is a major determinant of AP characteristics and AP propagation in cardiac myocytes. Unfortunately, in cardiac myocytes, investigation of kinetic properties of I(Na) with near-physiological ion concentrations and temperature is technically challenging due to the large amplitude and rapidly activating nature of I(Na), which may seriously hamper the quality of voltage control over the membrane. We hypothesized that the alternating voltage clamp-current clamp (VC/CC) technique might provide an alternative to traditional voltage clamp (VC) technique for the determination of I(Na) properties under physiological conditions. We studied I(Na) under close-to-physiological conditions by VC technique in SCN5A cDNA-transfected HEK cells or by alternating VC/CC technique in both SCN5A cDNA-transfected HEK cells and rabbit left ventricular myocytes. In these experiments, peak I(Na) during a depolarizing VC step or maximal upstroke velocity, dV/dt(max), during VC/CC served as an indicator of available I(Na). In HEK cells, biophysical properties of I(Na), including current density, voltage dependent (in)activation, development of inactivation, and recovery from inactivation, were highly similar in VC and VC/CC experiments. As an application of the VC/CC technique we studied I(Na) in left ventricular myocytes isolated from control or failing rabbit hearts. Our results demonstrate that the alternating VC/CC technique is a valuable experimental tool for I(Na) measurements under close-to-physiological conditions in cardiac myocytes.

  12. Towards a Tissue-Engineered Contractile Fontan-Conduit: The Fate of Cardiac Myocytes in the Subpulmonary Circulation.

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    Daniel Biermann

    Full Text Available The long-term outcome of patients with single ventricles improved over time, but remains poor compared to other congenital heart lesions with biventricular circulation. Main cause for this unfavourable outcome is the unphysiological hemodynamic of the Fontan circulation, such as subnormal systemic cardiac output and increased systemic-venous pressure. To overcome this limitation, we are developing the concept of a contractile extracardiac Fontan-tunnel. In this study, we evaluated the survival and structural development of a tissue-engineered conduit under in vivo conditions. Engineered heart tissue was generated from ventricular heart cells of neonatal Wistar rats, fibrinogen and thrombin. Engineered heart tissues started beating around day 8 in vitro and remained contractile in vivo throughout the experiment. After culture for 14 days constructs were implanted around the right superior vena cava of Wistar rats (n = 12. Animals were euthanized after 7, 14, 28 and 56 days postoperatively. Hematoxylin and eosin staining showed cardiomyocytes arranged in thick bundles within the engineered heart tissue-conduit. Immunostaining of sarcomeric actin, alpha-actin and connexin 43 revealed a well -developed cardiac myocyte structure. Magnetic resonance imaging (d14, n = 3 revealed no constriction or stenosis of the superior vena cava by the constructs. Engineered heart tissues survive and contract for extended periods after implantation around the superior vena cava of rats. Generation of larger constructs is warranted to evaluate functional benefits of a contractile Fontan-conduit.

  13. P2X4 receptor–eNOS signaling pathway in cardiac myocytes as a novel protective mechanism in heart failure

    Science.gov (United States)

    Yang, Ronghua; Beqiri, Dardan; Shen, Jian-Bing; Redden, John M.; Dodge-Kafka, Kimberly; Jacobson, Kenneth A.; Liang, Bruce T.

    2014-01-01

    We have demonstrated using immunoprecipitation and immunostaining a novel physical association of the P2X4 receptor (P2X4R), a ligand-gated ion channel, with the cardioprotective, calcium-dependent enzyme endothelial nitric oxide synthase (eNOS). Treatment of murine ventricular myocytes with the P2XR agonist 2-methylthioATP (2-meSATP) to induce a current (mainly Na+) increased the formation of nitric oxide (NO), as measured using a fluorescent probe. Possible candidates for downstream effectors mediating eNOS activity include cyclic GMP and PKG or cellular protein nitrosylation. A cardiac-specific P2X4R overexpressing mouse line was protected from heart failure (HF) with improved cardiac function and survival in post-infarct, pressure overload, and calsequestrin (CSQ) overexpression models of HF. Although the role of the P2X4R in other tissues such as the endothelium and monocytes awaits characterization in tissue-specific KO, cardiac-specific activation of eNOS may be more cardioprotective than an increased activity of global systemic eNOS. The intra-myocyte formation of NO may be more advantageous over NO derived externally from a donor. A small molecule drug stimulating this sarcolemmal pathway or gene therapy-mediated overexpression of the P2X4R in cardiac myocytes may represent a new therapy for both ischemic and pressure overloaded HF. PMID:25750695

  14. P2X4 receptor–eNOS signaling pathway in cardiac myocytes as a novel protective mechanism in heart failure

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    Ronghua Yang

    2015-01-01

    Full Text Available We have demonstrated using immunoprecipitation and immunostaining a novel physical association of the P2X4 receptor (P2X4R, a ligand-gated ion channel, with the cardioprotective, calcium-dependent enzyme endothelial nitric oxide synthase (eNOS. Treatment of murine ventricular myocytes with the P2XR agonist 2-methylthioATP (2-meSATP to induce a current (mainly Na+ increased the formation of nitric oxide (NO, as measured using a fluorescent probe. Possible candidates for downstream effectors mediating eNOS activity include cyclic GMP and PKG or cellular protein nitrosylation. A cardiac-specific P2X4R overexpressing mouse line was protected from heart failure (HF with improved cardiac function and survival in post-infarct, pressure overload, and calsequestrin (CSQ overexpression models of HF. Although the role of the P2X4R in other tissues such as the endothelium and monocytes awaits characterization in tissue-specific KO, cardiac-specific activation of eNOS may be more cardioprotective than an increased activity of global systemic eNOS. The intra-myocyte formation of NO may be more advantageous over NO derived externally from a donor. A small molecule drug stimulating this sarcolemmal pathway or gene therapy-mediated overexpression of the P2X4R in cardiac myocytes may represent a new therapy for both ischemic and pressure overloaded HF.

  15. VANADIUM EXPOSURE ALTERS SPONTANEOUS BEAT RATE AND GENE EXPRESSION OF CULTURED CARDIAC MYOCYTES

    Science.gov (United States)

    Ambient air pollution particulate matter (PM) exposure is associated with increased morbidity and mortality. Recent toxicological studies report PM-induced changes in a number of cardiac parameters, including heart rate variability, arrhythmias, repolarization, and internal defib...

  16. Meta-Analysis of Transcriptome Regulation During Induction to Cardiac Myocyte Fate From Mouse and Human Fibroblasts.

    Science.gov (United States)

    Rastegar-Pouyani, Shima; Khazaei, Niusha; Wee, Ping; Yaqubi, Moein; Mohammadnia, Abdulshakour

    2017-08-01

    Ectopic expression of a defined set of transcription factors (TFs) can directly convert fibroblasts into a cardiac myocyte cell fate. Beside inefficiency in generating induced cardiomyocytes (iCMs), the molecular mechanisms that regulate this process remained to be well defined. The main purpose of this study was to provide better insight on the transcriptome regulation and to introduce a new strategy for candidating TFs for the transdifferentiation process. Eight mouse and three human high quality microarray data sets were analyzed to find differentially expressed genes (DEGs), which we integrated with TF-binding sites and protein-protein interactions to construct gene regulatory and protein-protein interaction networks. Topological and biological analyses of constructed gene networks revealed the main regulators and most affected biological processes. The DEGs could be categorized into two distinct groups, first, up-regulated genes that are mainly involved in cardiac-specific processes and second, down-regulated genes that are mainly involved in fibroblast-specific functions. Gata4, Mef2a, Tbx5, Tead4 TFs were identified as main regulators of cardiac-specific gene expression program; and Trp53, E2f1, Myc, Sfpi1, Lmo2, and Meis1 were identified as TFs which mainly regulate the expression of fibroblast-specific genes. Furthermore, we compared gene expression profiles and identified TFs between mouse and human to find the similarities and differences. In summary, our strategy of meta-analyzing the data of high-throughput techniques by computational approaches, besides revealing the mechanisms involved in the regulation of the gene expression program, also suggests a new approach for increasing the efficiency of the direct reprogramming of fibroblasts into iCMs. J. Cell. Physiol. 232: 2053-2062, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  17. A device for rapid and quantitative measurement of cardiac myocyte contractility

    Science.gov (United States)

    Gaitas, Angelo; Malhotra, Ricky; Li, Tao; Herron, Todd; Jalife, José

    2015-03-01

    Cardiac contractility is the hallmark of cardiac function and is a predictor of healthy or diseased cardiac muscle. Despite advancements over the last two decades, the techniques and tools available to cardiovascular scientists are limited in their utility to accurately and reliably measure the amplitude and frequency of cardiomyocyte contractions. Isometric force measurements in the past have entailed cumbersome attachment of isolated and permeabilized cardiomyocytes to a force transducer followed by measurements of sarcomere lengths under conditions of submaximal and maximal Ca2+ activation. These techniques have the inherent disadvantages of being labor intensive and costly. We have engineered a micro-machined cantilever sensor with an embedded deflection-sensing element that, in preliminary experiments, has demonstrated to reliably measure cardiac cell contractions in real-time. Here, we describe this new bioengineering tool with applicability in the cardiovascular research field to effectively and reliably measure cardiac cell contractility in a quantitative manner. We measured contractility in both primary neonatal rat heart cardiomyocyte monolayers that demonstrated a beat frequency of 3 Hz as well as human embryonic stem cell-derived cardiomyocytes with a contractile frequency of about 1 Hz. We also employed the β-adrenergic agonist isoproterenol (100 nmol l-1) and observed that our cantilever demonstrated high sensitivity in detecting subtle changes in both chronotropic and inotropic responses of monolayers. This report describes the utility of our micro-device in both basic cardiovascular research as well as in small molecule drug discovery to monitor cardiac cell contractions.

  18. Variations in Local Calcium Signaling in Adjacent Cardiac Myocytes of the Intact Mouse Heart Detected with Two-Dimensional Confocal Microscopy

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    Karin P Hammer

    2015-01-01

    Full Text Available Dyssynchronous local Ca release within individual cardiac myocytes has been linked to cellular contractile dysfunction. Differences in Ca kinetics in adjacent cells may also provide a substrate for inefficient contraction and arrhythmias. In a new approach we quantify variation in local Ca transients between adjacent myocytes in the whole heart.Langendorff-perfused mouse hearts were loaded with Fluo-8 AM to detect Ca and Di-4-ANEPPS to visualize cell membranes. A spinning disc confocal microscope with a fast camera allowed us to record Ca signals within an area of 465 µm by 315 µm with an acquisition speed of 55 fps. Images from multiple transients recorded at steady state were registered to their time point in the cardiac cycle to restore averaged local Ca transients with a higher temporal resolution. Local Ca transients within and between adjacent myocytes were compared with regard to amplitude, time to peak and decay at steady state stimulation (250 ms cycle length.Image registration from multiple sequential Ca transients allowed reconstruction of high temporal resolution (2.4 ±1.3ms local CaT in 2D image sets (N= 4 hearts, n= 8 regions. During steady state stimulation, spatial Ca gradients were homogeneous within cells in both directions and independent of distance between measured points. Variation in CaT amplitudes was similar across the short and the long side of neighboring cells. Variations in TAU and TTP were similar in both directions. Isoproterenol enhanced the CaT but not the overall pattern of spatial heterogeneities.Here we detected and analyzed local Ca signals in intact mouse hearts with high temporal and spatial resolution, taking into account 2D arrangement of the cells. We observed significant differences in the variation of CaT amplitude along the long and short axis of cardiac myocytes. Variations of Ca signals between neighboring cells may contribute to the substrate of cardiac remodeling.

  19. [Ca2+]i Elevation and Oxidative Stress Induce KCNQ1 Protein Translocation from the Cytosol to the Cell Surface and Increase Slow Delayed Rectifier (IKs) in Cardiac Myocytes*

    Science.gov (United States)

    Wang, Yuhong; Zankov, Dimitar P.; Jiang, Min; Zhang, Mei; Henderson, Scott C.; Tseng, Gea-Ny

    2013-01-01

    Our goals are to simultaneously determine the three-dimensional distribution patterns of KCNQ1 and KCNE1 in cardiac myocytes and to study the mechanism and functional implications for variations in KCNQ1/KCNE1 colocalization in myocytes. We monitored the distribution patterns of KCNQ1, KCNE1, and markers for subcellular compartments/organelles using immunofluorescence/confocal microscopy and confirmed the findings in ventricular myocytes by directly observing fluorescently tagged KCNQ1-GFP and KCNE1-dsRed expressed in these cells. We also monitored the effects of stress on KCNQ1-GFP and endoplasmic reticulum (ER) remodeling during live cell imaging. The data showed that 1) KCNE1 maintained a stable cell surface localization, whereas KCNQ1 exhibited variations in the cytosolic compartment (striations versus vesicles) and the degree of presence on the cell surface; 2) the degree of cell surface KCNQ1/KCNE1 colocalization was positively correlated with slow delayed rectifier (IKs) current density; 3) KCNQ1 and calnexin (an ER marker) shared a cytosolic compartment; and 4) in response to stress ([Ca2+]i elevation, oxidative overload, or AT1R stimulation), KCNQ1 exited the cytosolic compartment and trafficked to the cell periphery in vesicles. This was accompanied by partial ER fragmentation. We conclude that the cellular milieu regulates KCNQ1 distribution in cardiac myocytes and that stressful conditions can increase IKs by inducing KCNQ1 movement to the cell surface. This represents a hitherto unrecognized mechanism by which IKs fulfills its function as a repolarization reserve in ventricular myocytes. PMID:24142691

  20. [Ca2+]i elevation and oxidative stress induce KCNQ1 protein translocation from the cytosol to the cell surface and increase slow delayed rectifier (IKs) in cardiac myocytes.

    Science.gov (United States)

    Wang, Yuhong; Zankov, Dimitar P; Jiang, Min; Zhang, Mei; Henderson, Scott C; Tseng, Gea-Ny

    2013-12-06

    Our goals are to simultaneously determine the three-dimensional distribution patterns of KCNQ1 and KCNE1 in cardiac myocytes and to study the mechanism and functional implications for variations in KCNQ1/KCNE1 colocalization in myocytes. We monitored the distribution patterns of KCNQ1, KCNE1, and markers for subcellular compartments/organelles using immunofluorescence/confocal microscopy and confirmed the findings in ventricular myocytes by directly observing fluorescently tagged KCNQ1-GFP and KCNE1-dsRed expressed in these cells. We also monitored the effects of stress on KCNQ1-GFP and endoplasmic reticulum (ER) remodeling during live cell imaging. The data showed that 1) KCNE1 maintained a stable cell surface localization, whereas KCNQ1 exhibited variations in the cytosolic compartment (striations versus vesicles) and the degree of presence on the cell surface; 2) the degree of cell surface KCNQ1/KCNE1 colocalization was positively correlated with slow delayed rectifier (IKs) current density; 3) KCNQ1 and calnexin (an ER marker) shared a cytosolic compartment; and 4) in response to stress ([Ca(2+)]i elevation, oxidative overload, or AT1R stimulation), KCNQ1 exited the cytosolic compartment and trafficked to the cell periphery in vesicles. This was accompanied by partial ER fragmentation. We conclude that the cellular milieu regulates KCNQ1 distribution in cardiac myocytes and that stressful conditions can increase IKs by inducing KCNQ1 movement to the cell surface. This represents a hitherto unrecognized mechanism by which IKs fulfills its function as a repolarization reserve in ventricular myocytes.

  1. Interleukin-6 deficiency attenuates angiotensin II-induced cardiac pathogenesis with increased myocyte hypertrophy.

    Science.gov (United States)

    Chen, Fan; Chen, Dandan; Zhang, Yubin; Jin, Liang; Zhang, Han; Wan, Miyang; Pan, Tianshu; Wang, Xiaochuan; Su, Yuheng; Xu, Yitao; Ye, Junmei

    2017-12-16

    Interleukin-6 (IL-6) signaling is critical for cardiomyocyte hypertrophy, while the role of IL-6 in the pathogenesis of myocardium hypertrophy remains controversial. To determine the essential role of IL-6 signaling for the cardiac development during AngII-induced hypertension, and to elucidate the mechanisms, wild-type (WT) and IL-6 knockout (IL-6 KO) mice were infused subcutaneously with either vehicle or AngII (1.5 μg/h/mouse) for 1 week. Immunohistological and serum studies revealed that the extents of cardiac fibrosis, inflammation and apoptosis were reduced in IL-6 KO heart during AngII-stimulation, while cardiac hypertrophy was obviously induced. To investigate the underlying mechanisms, by using myocardial tissue and neonatal cardiomyocytes, we observed that IL-6/STAT3 signaling was activated under the stimulation of AngII both in vivo and in vitro. Further investigation suggested that STAT3 activation enhances the inhibitory effect of EndoG on MEF2A and hampers cardiomyocyte hypertrophy. Our study is the first to show the important role of IL-6 in regulating cardiac pathogenesis via inflammation and apoptosis during AngII-induced hypertension. We also provide a novel link between IL-6/STAT3 and EndoG/MEF2A pathway that affects cardiac hypertrophy during AngII stimulation. Copyright © 2017 Elsevier Inc. All rights reserved.

  2. Comparative study of cellular kinetics of reporter probe [{sup 131}I]FIAU in neonatal cardiac myocytes after transfer of HSV1-tk reporter gene with two vectors

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    Lan Xiaoli [Department of Nuclear Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022 (China); Hubei Province Key Laboratory of Molecular Imaging, Wuhan 430022 (China)], E-mail: lxl730724@hotmail.com; Yin Xiaohua; Wang Ruihua; Liu Ying [Department of Nuclear Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022 (China); Hubei Province Key Laboratory of Molecular Imaging, Wuhan 430022 (China); Zhang Yongxue [Department of Nuclear Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022 (China) and Hubei Province Key Laboratory of Molecular Imaging, Wuhan 430022 (China)], E-mail: zhyx1229@163.com

    2009-02-15

    Aim: Reporter gene imaging is a promising approach for noninvasive monitoring of cardiac gene therapy. In this study, HSV1-tk (herpes simplex virus type 1 thymidine kinase) and FIAU (2'-fluoro-2'-deoxy-1-{beta}-D-arabinofuranosyl-5-iodouracil) were used as the reporter gene and probe, respectively. Cellular uptakes of radiolabeled FIAU of neonatal rat cardiac myocytes transferred with HSV1-tk were compared between two vectors, adenovirus and liposome. The aims of this study were to choose the better vector and to provide a theoretical basis for good nuclide images. Methods: Neonatal cardiac myocytes were obtained from rat heart by single collagenase digestion. HSV1-tk inserted into adenovirus vector (recombinant adenovirus type 5, Ad5-tk) and plasmid (pDC316-tk) coated with Lipofectamine 2000 (pDC316-tk/lipoplex) were developed; thus, HSV1-tk could be transferred into neonatal cardiac myocytes. FAU (2'-fluoro-2'-deoxy-1-{beta}-D-arabinofuranosyluracil) was labeled with {sup 131}I, and the product was assessed after purification with reversed-phase Sep-Pak C-18 column. The uptake rates of [{sup 131}I]FIAU in the transferred cardiac myocytes at different times (0.5, 1, 2, 3, 4 and 5 h) were detected. Furthermore, mRNA expression and protein expression of HSV1-tk were detected by semiquantitative reverse-transcriptase polymerase chain reaction and immunocytochemistry. Results: FAU could be labeled with {sup 131}I, and the labeling efficiency and radiochemical purity rates were 53.82{+-}2.05% and 94.85{+-}1.76%, respectively. Time-dependent increase of the accumulation of [{sup 131}I]FIAU was observed in both the Ad5-tk group and the pDC316/lipoplex group, and the highest uptake rate occurred at 5 h, with peak values of 12.55{+-}0.37% and 2.09{+-}0.34%, respectively. Greater uptakes of [{sup 131}I]FIAU in Ad5-tk-infected cells compared with pDC316/lipoplex-transfected ones occurred at all the time points (t=12.978-38.253, P<.01). The exogenous gene

  3. Cardiac myocyte follistatin-like 1 functions to attenuate hypertrophy following pressure overload

    NARCIS (Netherlands)

    Shimano, Masayuki; Ouchi, Noriyuki; Nakamura, Kazuto; van Wijk, Bram; Ohashi, Koji; Asaumi, Yasuhide; Higuchi, Akiko; Pimentel, David R.; Sam, Flora; Murohara, Toyoaki; van den Hoff, Maurice J. B.; Walsh, Kenneth

    2011-01-01

    Factors secreted by the heart, referred to as "cardiokines," have diverse actions in the maintenance of cardiac homeostasis and remodeling. Follistatin-like 1 (Fstl1) is a secreted glycoprotein expressed in the adult heart and is induced in response to injurious conditions that promote myocardial

  4. Impulse Propagation in Synthetic Strands of Neonatal Cardiac Myocytes With Genetically Reduced Levels of Connexin43

    Science.gov (United States)

    Thomas, Stuart P.; Kucera, Jan P.; Bircher-Lehmann, Lilly; Rudy, Yoram; Saffitz, Jeffrey E.; Kléber, André G.

    2007-01-01

    Connexin43 (Cx43) is a major determinant of the electrical properties of the myocardium. Closure of gap junctions causes rapid slowing of propagation velocity (θ), but the precise effect of a reduction in Cx43 levels due to genetic manipulation has only partially been clarified. In this study, morphological and electrical properties of synthetic strands of cultured neonatal ventricular myocytes from Cx43+/+ (wild type, WT) and Cx+/− (heterozygote, HZ) mice were compared. Quantitative immunofluorescence analysis of Cx43 demonstrated a 43% reduction of Cx43 expression in the HZ versus WT mice. Cell dimensions, connectivity, and alignment were independent of genotype. Measurement of electrical properties by microelectrodes and optical mapping showed no differences in action potential amplitude or minimum diastolic potential between WT and HZ. However, maximal upstroke velocity of the transmembrane action potential, dV/dtmax, was increased and action potential duration was reduced in HZ versus WT. θ was similar in the two genotypes. Computer simulation of propagation and dV/dtmax showed a relatively small dependence of θ on gap junction coupling, thus explaining the lack of observed differences in θ between WT and HZ. Importantly, the simulations suggested that the difference in dV/dtmax is due to an upregulation of INa in HZ versus WT. Thus, heterozygote-null mutation of Cx43 produces a complex electrical phenotype in synthetic strands that is characterized by both changes in ion channel function and cell-to-cell coupling. The lack of changes in θ in this tissue is explained by the dominating role of myoplasmic resistance and the compensatory increase of dV/dtmax. PMID:12730095

  5. Diabetic cardiomyopathy: from the pathophysiology of the cardiac myocytes to current diagnosis and management strategies

    Directory of Open Access Journals (Sweden)

    Christina Voulgari

    2010-10-01

    Full Text Available Christina Voulgari, Dimitrios Papadogiannis, Nicholas TentolourisFirst Department of Propaedeutic and Internal Medicine, Athens University Medical School, Laiko General Hospital, Athens, GreeceAbstract: Diabetic cardiomyopathy (DCM, although a distinct clinical entity, is also a part of the diabetic atherosclerosis process. It may be independent of the coexistence of ischemic heart disease, hypertension, or other macrovascular complications. Its pathological substrate is characterized by the presence of myocardial damage, reactive hypertrophy, and intermediary fibrosis, structural and functional changes of the small coronary vessels, disturbance of the management of the metabolic cardiovascular load, and cardiac autonomic neuropathy. These alterations make the diabetic heart susceptible to ischemia and less able to recover from an ischemic attack. Arterial hypertension frequently coexists with and exacerbates cardiac functioning, leading to the premature appearance of heart failure. Classical and newer echocardiographic methods are available for early diagnosis. Currently, there is no specific treatment for DCM; targeting its pathophysiological substrate by effective risk management protects the myocardium from further damage and has a recognized primary role in its prevention. Its pathophysiological substrate is also the objective for the new therapies and alternative remedies.Keywords: cardiovascular disease, atherosclerosis, cardiac autonomic neuropathy, echocardiography, treatment strategies

  6. Differential extracellular signal-regulated kinases 1 and 2 activation by the angiotensin type 1 receptor supports distinct phenotypes of cardiac myocytes

    DEFF Research Database (Denmark)

    Aplin, Mark; Christensen, Gitte Lund; Schneider, Mikael

    2007-01-01

    The angiotensin II (AngII) type 1 receptor (AT(1)R) is a seven-transmembrane receptor well established to activate extracellular signal-regulated kinases 1 and 2 (ERK1/2) by discrete G protein-dependent and beta-arrestin2-dependent pathways. The biological importance of this, however, remains obs...... obscure. Application of the modified analogue [Sar(1), Ile(4), Ile(8)]-AngII ([SII] AngII) allowed us to dissect the two pathways of ERK1/2 activation in native cardiac myocytes. Although cytosol-retained, the beta-arrestin2-bound pool of ERK1/2 represents an active signalling component...... that phosphorylates p90 Ribosomal S6 Kinase, a ubiquitous and versatile mediator of ERK1/2 signal transduction. Moreover, the beta-arrestin2-dependent ERK1/2 signal supports intact proliferation of cardiac myocytes. In contrast to G(q)-activated ERK1/2, and in keeping with its failure to translocate to the nucleus......, the beta-arrestin2-scaffolded pool of ERK1/2 does not phosphorylate the transcription factor Elk-1, induces no increased transcription of the immediate-early gene c-Fos, and does not entail myocyte hypertrophy. These results clearly demonstrate the biological significance of differential signalling...

  7. Sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA) gene silencing and remodeling of the Ca2+ signaling mechanism in cardiac myocytes.

    Science.gov (United States)

    Seth, M; Sumbilla, C; Mullen, S P; Lewis, D; Klein, M G; Hussain, A; Soboloff, J; Gill, D L; Inesi, G

    2004-11-23

    Transient elevations of cytosolic Ca2+ are a common mechanism of cellular signaling. In striated muscle, the sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA) plays an important role in terminating Ca2+ transients by returning cytosolic Ca2+ to intracellular stores. Stored Ca2+ can then be released again for subsequent signaling. We down-regulated SERCA2 gene expression in cultured cardiac myocytes by means of endogenous transcription of small interfering RNA encoded by an exogenous cDNA template. The cDNA template was delivered by adenovirus vector. Reduction of SERCA expression in all myocytes in culture was documented by immunochemistry, real-time RT-PCR, and determination of ATP-dependent Ca2+ transport. The reduction of SERCA2 expression was associated with the up-regulation of transient receptor potential (TRP) channel proteins (TRPC4 and TRPC5) and Na+/Ca2+ exchanger, indicating that intracellular store deficiency was compensated for by Ca2+ fluxes through the plasma membrane. In fact, SERCA silencing was followed by increased transcription of Na+/Ca2+ exchanger, TRPC4, TRPC5, and related transcriptional factors, such as stimulating protein 1, myocyte enhancer factor 2, and nuclear factor of activated cells 4, through activation of calcineurin. This finding demonstrates that the observed compensation occurs through transcriptional crosstalk and the remodeling of Ca2+ signaling pathways. The wide significance of this regulatory mechanism is related to its general involvement in Ca2+ signaling dynamics and in cardiac development and hypertrophy.

  8. An increased TREK-1-like potassium current in ventricular myocytes during rat cardiac hypertrophy.

    Science.gov (United States)

    Wang, Weiping; Zhang, Man; Li, Pingping; Yuan, Hui; Feng, Nan; Peng, Ying; Wang, Ling; Wang, Xiaoliang

    2013-04-01

    To elucidate the expression and identify the functional changes of 2 pore domain potassium channel TREK-1 during cardiac hypertrophy in rats, left ventricular hypertrophy was induced by subcutaneous injection with isoproterenol. Western blot was used to detect the expression of TREK-1 channel protein, and inside-out and whole-cell recordings were used to record TREK-1 currents. The results showed that TREK-1 protein expression in endocardium was slightly higher than that in epicardium in control left ventricles. However, it was obviously upregulated by 89.8% during hypertrophy, 2.3-fold higher than in epicardium. Mechanical stretch, intracellular acidification, and arachidonic acid could activate a TREK-1-like current in cardiomyocytes. The slope conductances of cardiac TREK-1 and CHO/TREK-1 channels were 123 ± 7 and 113 ± 17 pS, respectively. The TREK-1 inhibitor L-3-n-butylphthalide (10 μM) reduced the currents in CHO/TREK-1 cells, normal cardiomyocytes, and hypertrophic cardiomyocytes by 48.5%, 54.3%, and 55.5%, respectively. The percentage of L-3-n-butylphthalide-inhibited outward whole-cell current in hypertrophic cardiomyocytes (23.7%) was larger than that in normal cardiomyocytes (14.2%). The percentage of chloroform-activated outward whole-cell current in hypertrophic cardiomyocytes (58.3%) was also larger than normal control (40.2%). Our results demonstrated that in hypertrophic rats, TREK-1 protein expression in endocardium was specifically increased and the ratio of TREK-1 channel current in cardiac outward currents was also enhanced. TREK-1 might balance potassium ion flow during hypertrophy and might be a potential drug target for heart protection.

  9. Tomato-oleoresin supplement prevents doxorubicin-induced cardiac myocyte oxidative DNA damage in rats.

    Science.gov (United States)

    Ferreira, Ana Lucia Anjos; Salvadori, Daisy Maria Favero; Nascimento, Maria Carolina Munhoz Oliveira; Rocha, Noeme Souza; Correa, Camila R; Pereira, Elenize Jamas; Matsubara, Luiz Shiguero; Matsubara, Beatriz Bojikian; Ladeira, Marcelo Sady Plácido

    2007-07-10

    Doxorubicin (DOX) is an efficient chemotherapeutic agent used against several types of tumors; however, its use is limited due to severe cardiotoxicity. Since it is accepted that reactive oxygen species are involved in DOX-induced cardiotoxicity, antioxidant agents have been used to attenuate its side effects. To determine tomato-oleoresin protection against cardiac oxidative DNA damage induced by DOX, we distributed Wistar male rats in control (C), lycopene (L), DOX (D) and DOX+lycopene (DL) groups. They received corn oil (C, D) or tomato-oleoresin (5mg/kg body wt. day) (L, DL) by gavage for a 7-week period. They also received saline (C, L) or DOX (4mg/kg body wt.) (D, DL) intraperitoneally at the 3rd, 4th, 5th, and at 6th week. Lycopene absorption was checked by HPLC. Cardiac oxidative DNA damage was evaluated by the alkaline Comet assay using formamidopyrimidine-DNA glycosylase (FPG) and endonuclease III (endo III). Cardiomyocyte levels of SBs, SBs FPG and SBs Endo III were higher in rats from D when compared to other groups. DNA damage levels in cardiomyocytes from DL were not different when compared to C and L groups. The viability of cardiomyocytes from D or DL was lower than C or L groups (poleoresin supplementation protected against cardiomyocyte oxidative DNA damage.

  10. Differential Sarcomere and Electrophysiological Maturation of Human iPSC-Derived Cardiac Myocytes in Monolayer vs. Aggregation-Based Differentiation Protocols

    Directory of Open Access Journals (Sweden)

    Dorota Jeziorowska

    2017-06-01

    Full Text Available Human induced pluripotent stem cells (iPSCs represent a powerful human model to study cardiac disease in vitro, notably channelopathies and sarcomeric cardiomyopathies. Different protocols for cardiac differentiation of iPSCs have been proposed either based on embroid body formation (3D or, more recently, on monolayer culture (2D. We performed a direct comparison of the characteristics of the derived cardiomyocytes (iPSC-CMs on day 27 ± 2 of differentiation between 3D and 2D differentiation protocols with two different Wnt-inhibitors were compared: IWR1 (inhibitor of Wnt response or IWP2 (inhibitor of Wnt production. We firstly found that the level of Troponin T (TNNT2 expression measured by FACS was significantly higher for both 2D protocols as compared to the 3D protocol. In the three methods, iPSC-CM show sarcomeric structures. However, iPSC-CM generated in 2D protocols constantly displayed larger sarcomere lengths as compared to the 3D protocol. In addition, mRNA and protein analyses reveal higher cTNi to ssTNi ratios in the 2D protocol using IWP2 as compared to both other protocols, indicating a higher sarcomeric maturation. Differentiation of cardiac myocytes with 2D monolayer-based protocols and the use of IWP2 allows the production of higher yield of cardiac myocytes that have more suitable characteristics to study sarcomeric cardiomyopathies.

  11. Cardiac sodium channel NaV1.5 distribution in myocytes via interacting proteins: the multiple pool model.

    Science.gov (United States)

    Shy, Diana; Gillet, Ludovic; Abriel, Hugues

    2013-04-01

    The cardiac sodium current (INa) is responsible for the rapid depolarization of cardiac cells, thus allowing for their contraction. It is also involved in regulating the duration of the cardiac action potential (AP) and propagation of the impulse throughout the myocardium. Cardiac INa is generated by the voltage-gated Na(+) channel, NaV1.5, a 2016-residue protein which forms the pore of the channel. Over the past years, hundreds of mutations in SCN5A, the human gene coding for NaV1.5, have been linked to many cardiac electrical disorders, including the congenital and acquired long QT syndrome, Brugada syndrome, conduction slowing, sick sinus syndrome, atrial fibrillation, and dilated cardiomyopathy. Similar to many membrane proteins, NaV1.5 has been found to be regulated by several interacting proteins. In some cases, these different proteins, which reside in distinct membrane compartments (i.e. lateral membrane vs. intercalated disks), have been shown to interact with the same regulatory domain of NaV1.5, thus suggesting that several pools of NaV1.5 channels may co-exist in cardiac cells. The aim of this review article is to summarize the recent works that demonstrate its interaction with regulatory proteins and illustrate the model that the sodium channel NaV1.5 resides in distinct and different pools in cardiac cells. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Cardiac Pathways of Differentiation, Metabolism and Contraction. Copyright © 2012 Elsevier B.V. All rights reserved.

  12. Ryanodine receptor gating controls generation of diastolic calcium waves in cardiac myocytes

    Science.gov (United States)

    Petrovič, Pavol; Valent, Ivan; Cocherová, Elena; Pavelková, Jana

    2015-01-01

    The role of cardiac ryanodine receptor (RyR) gating in the initiation and propagation of calcium waves was investigated using a mathematical model comprising a stochastic description of RyR gating and a deterministic description of calcium diffusion and sequestration. We used a one-dimensional array of equidistantly spaced RyR clusters, representing the confocal scanning line, to simulate the formation of calcium sparks. Our model provided an excellent description of the calcium dependence of the frequency of diastolic calcium sparks and of the increased tendency for the production of calcium waves after a decrease in cytosolic calcium buffering. We developed a hypothesis relating changes in the propensity to form calcium waves to changes of RyR gating and tested it by simulation. With a realistic RyR gating model, increased ability of RyR to be activated by Ca2+ strongly increased the propensity for generation of calcium waves at low (0.05–0.1-µM) calcium concentrations but only slightly at high (0.2–0.4-µM) calcium concentrations. Changes in RyR gating altered calcium wave formation by changing the calcium sensitivity of spontaneous calcium spark activation and/or the average number of open RyRs in spontaneous calcium sparks. Gating changes that did not affect RyR activation by Ca2+ had only a weak effect on the propensity to form calcium waves, even if they strongly increased calcium spark frequency. Calcium waves induced by modulating the properties of the RyR activation site could be suppressed by inhibiting the spontaneous opening of the RyR. These data can explain the increased tendency for production of calcium waves under conditions when RyR gating is altered in cardiac diseases. PMID:26009544

  13. Urokinase plasminogen activator protects cardiac myocytes from oxidative damage and apoptosis via hOGG1 induction.

    Science.gov (United States)

    Hohensinner, Philipp J; Takacs, Nikol; Kaun, Christoph; Thaler, Barbara; Krychtiuk, Konstantin A; Pfaffenberger, Stefan; Aliabadi, Arezu; Zuckermann, Andreas; Huber, Kurt; Wojta, Johann

    2017-08-01

    The role of uPA in tissue remodeling and cell migration is already well established. In addition, uPA was reported to stabilize p53, a key cell cycle control, DNA repair and apoptosis initiation protein. We aimed to determine the role of uPA-uPAR signaling towards cell survival or apoptosis in human adult cardiac myocytes (HACM). HACM were stimulated with uPA and DNA damage was inflicted by incubating cells with 200 µM H2O2. To analyze for apoptotic cells we applied TUNEL staining. Oxidative damage foci were analyzed by staining for 8-oxoguanine base pairs. In vivo qPCR analysis from RNA extracted from failing human hearts demonstrated a close relation of uPA with apoptosis and the p53 pathway. Furthermore, we observed a close correlation of uPA and p53 protein in homogenized tissue lysates. In vitro studies revealed that uPA preincubation protected HACM from oxidative damage induced cell death and reduced oxidative damage foci. uPA protection is independent of its catalytic activity, as the amino terminal fragment of uPA showed similar protection. A key enzyme for repairing oxidative DNA damage is the p53 target hOGG1. We found a significant increase of hOGG1 after pretreatment of HACM with uPA. Knockdown of hOGG1 completely abrogated the protective effect of uPA. We conclude that uPA might have a tissue protective role in human hearts besides its role in tissue remodeling. Tissue protection is mediated by the DNA repair protein hOGG1. This might be beneficial during tissue remodeling and thus could be a target for therapeutic approaches in the diseased heart.

  14. Calcium-mediated coupling between mitochondrial substrate dehydrogenation and cardiac workload in single guinea-pig ventricular myocytes.

    Science.gov (United States)

    Jo, Hikari; Noma, Akinori; Matsuoka, Satoshi

    2006-03-01

    We measured mitochondrial NADH autofluorescence or Ca(2+) using Rhod-2, simultaneously with cell shortening in isolated guinea-pig ventricular myocytes. When both frequency and amplitude of twitch shortening (work intensity) were increased by raising stimulus frequency in incremental steps from 0.1 to 3.3 Hz, the steady level of NADH signal increased in a frequency-dependent manner. Mitochondrial Ca(2+) also increased with increasing work intensity. Applying Ru360, an inhibitor of mitochondrial Ca(2+) uniporter, largely attenuated the response of both NADH fluorescence and mitochondrial Ca(2+). The increase in mitochondrial Ca(2+) was slow with t(1/2)=~12 s and no obvious cyclic changes were observed in the NADH signal. When a step change from 0.1 to 3.3 Hz stimulation was applied, the NADH signal first decreased to 83% and then increased to 155% of the control level. Upon returning to 0.1 Hz, the NADH signal showed an overshoot before declining to the control level. The biphasic onset time course was well explained by the delayed Ca(2+) activation of the substrate dehydrogenation superimposed on the feedback control of the ATP synthesis, while the offset time course with a delayed deactivation of dehydrogenation. A computer simulation using an oxidative phosphorylation linked to the cardiac excitation contraction model well reconstructed the response of NADH. This model simulation predicts that the activation of substrate dehydrogenation provides ~23% of driving force of the ATP synthesis to meet the increased workload induced by the jump of stimulus from 0.1 to 3.3 Hz, and remaining ~77% is supplied by the feedback control.

  15. Athletic Cardiac Adaptation in Males Is a Consequence of Elevated Myocyte Mass.

    Science.gov (United States)

    McDiarmid, Adam K; Swoboda, Peter P; Erhayiem, Bara; Lancaster, Rosalind E; Lyall, Gemma K; Broadbent, David A; Dobson, Laura E; Musa, Tarique A; Ripley, David P; Garg, Pankaj; Greenwood, John P; Ferguson, Carrie; Plein, Sven

    2016-04-01

    Cardiac remodeling occurs in response to regular athletic training, and the degree of remodeling is associated with fitness. Understanding the myocardial structural changes in athlete's heart is important to develop tools that differentiate athletic from cardiomyopathic change. We hypothesized that athletic left ventricular hypertrophy is a consequence of increased myocardial cellular rather than extracellular mass as measured by cardiovascular magnetic resonance. Forty-five males (30 athletes and 15 sedentary age-matched healthy controls) underwent comprehensive cardiovascular magnetic resonance studies, including native and postcontrast T1 mapping for extracellular volume calculation. In addition, the 30 athletes performed a maximal exercise test to assess aerobic capacity and anaerobic threshold. Participants were grouped by athleticism: untrained, low performance, and high performance (O2max 60 mL/kg per min, respectively). In athletes, indexed cellular mass was greater in high- than low-performance athletes 60.7±7.5 versus 48.6±6.3 g/m(2); Pfitness. Cardiovascular magnetic resonance ECV quantification may have a future role in differentiating athlete's heart from change secondary to cardiomyopathy. © 2016 The Authors.

  16. Antiapoptotic Actions of Methyl Gallate on Neonatal Rat Cardiac Myocytes Exposed to H2O2

    Directory of Open Access Journals (Sweden)

    Sandhya Khurana

    2014-01-01

    Full Text Available Reactive oxygen species trigger cardiomyocyte cell death via increased oxidative stress and have been implicated in the pathogenesis of cardiovascular diseases. The prevention of cardiomyocyte apoptosis is a putative therapeutic target in cardioprotection. Polyphenol intake has been associated with reduced incidences of cardiovascular disease and better overall health. Polyphenols like epigallocatechin gallate (EGCG can reduce apoptosis of cardiomyocytes, resulting in better health outcomes in animal models of cardiac disorders. Here, we analyzed whether the antioxidant N-acetyl cysteine (NAC or polyphenols EGCG, gallic acid (GA or methyl gallate (MG can protect cardiomyocytes from cobalt or H2O2-induced stress. We demonstrate that MG can uphold viability of neonatal rat cardiomyocytes exposed to H2O2 by diminishing intracellular ROS, maintaining mitochondrial membrane potential, augmenting endogenous glutathione, and reducing apoptosis as evidenced by impaired Annexin V/PI staining, prevention of DNA fragmentation, and cleaved caspase-9 accumulation. These findings suggest a therapeutic value for MG in cardioprotection.

  17. Conditional FKBP12.6 overexpression in mouse cardiac myocytes prevents triggered ventricular tachycardia through specific alterations in excitation-contraction coupling.

    Science.gov (United States)

    Gellen, Barnabas; Fernández-Velasco, María; Briec, François; Vinet, Laurent; LeQuang, Khai; Rouet-Benzineb, Patricia; Bénitah, Jean-Pierre; Pezet, Mylène; Palais, Gael; Pellegrin, Noémie; Zhang, Andy; Perrier, Romain; Escoubet, Brigitte; Marniquet, Xavier; Richard, Sylvain; Jaisser, Fréderic; Gómez, Ana María; Charpentier, Flavien; Mercadier, Jean-Jacques

    2008-04-08

    Ca(2+) release from the sarcoplasmic reticulum via the ryanodine receptor (RyR2) activates cardiac myocyte contraction. An important regulator of RyR2 function is FKBP12.6, which stabilizes RyR2 in the closed state during diastole. Beta-adrenergic stimulation has been suggested to dissociate FKBP12.6 from RyR2, leading to diastolic sarcoplasmic reticulum Ca(2+) leakage and ventricular tachycardia (VT). We tested the hypothesis that FKBP12.6 overexpression in cardiac myocytes can reduce susceptibility to VT in stress conditions. We developed a mouse model with conditional cardiac-specific overexpression of FKBP12.6. Transgenic mouse hearts showed a marked increase in FKBP12.6 binding to RyR2 compared with controls both at baseline and on isoproterenol stimulation (0.2 mg/kg i.p.). After pretreatment with isoproterenol, burst pacing induced VT in 10 of 23 control mice but in only 1 of 14 transgenic mice (P<0.05). In isolated transgenic myocytes, Ca(2+) spark frequency was reduced by 50% (P<0.01), a reduction that persisted under isoproterenol stimulation, whereas the sarcoplasmic reticulum Ca(2+) load remained unchanged. In parallel, peak I(Ca,L) density decreased by 15% (P<0.01), and the Ca(2+) transient peak amplitude decreased by 30% (P<0.001). A 33.5% prolongation of the caffeine-evoked Ca(2+) transient decay was associated with an 18% reduction in the Na(+)-Ca(2+) exchanger protein level (P<0.05). Increased FKBP12.6 binding to RyR2 prevents triggered VT in normal hearts in stress conditions, probably by reducing diastolic sarcoplasmic reticulum Ca(2+) leak. This indicates that the FKBP12.6-RyR2 complex is an important candidate target for pharmacological prevention of VT.

  18. Tissue-Mimicking Geometrical Constraints Stimulate Tissue-Like Constitution and Activity of Mouse Neonatal and Human-Induced Pluripotent Stem Cell-Derived Cardiac Myocytes

    Directory of Open Access Journals (Sweden)

    Götz Pilarczyk

    2016-01-01

    Full Text Available The present work addresses the question of to what extent a geometrical support acts as a physiological determining template in the setup of artificial cardiac tissue. Surface patterns with alternating concave to convex transitions of cell size dimensions were used to organize and orientate human-induced pluripotent stem cell (hIPSC-derived cardiac myocytes and mouse neonatal cardiac myocytes. The shape of the cells, as well as the organization of the contractile apparatus recapitulates the anisotropic line pattern geometry being derived from tissue geometry motives. The intracellular organization of the contractile apparatus and the cell coupling via gap junctions of cell assemblies growing in a random or organized pattern were examined. Cell spatial and temporal coordinated excitation and contraction has been compared on plain and patterned substrates. While the α-actinin cytoskeletal organization is comparable to terminally-developed native ventricular tissue, connexin-43 expression does not recapitulate gap junction distribution of heart muscle tissue. However, coordinated contractions could be observed. The results of tissue-like cell ensemble organization open new insights into geometry-dependent cell organization, the cultivation of artificial heart tissue from stem cells and the anisotropy-dependent activity of therapeutic compounds.

  19. Changes in T-Tubules and Sarcoplasmic Reticulum in Ventricular Myocytes in Early Cardiac Hypertrophy in a Pressure Overload Rat Model

    Directory of Open Access Journals (Sweden)

    Perla Pérez-Treviño

    2015-10-01

    Full Text Available Background/Aims: Pressure-overload (PO causes cardiac hypertrophy (CH, and eventually leads to heart failure (HF. HF ventricular myocytes present transverse-tubules (TT loss or disarrangement and decreased sarcoplasmic reticulum (SR density, and both contribute to altered Ca2+ signaling and heart dysfunction. It has been shown that TT remodeling precedes HF, however, it is unknown whether SR structural and functional remodeling also starts early in CH. Methods: Using confocal microscopy, we assessed TT (with Di-8-ANNEPS and SR (with SR-trapped Mag-Fluo-4 densities, as well as SR fluorophore diffusion (fluorescence recovery after photobleach; FRAP, cytosolic Ca2+ signaling and ex vivo cardiac performance in a PO rat hypertrophy model induced by abdominal aortic constriction (at 6 weeks. Results: Rats developed CH, while cardiac performance, basal and upon β-adrenergic stimulation, remained unaltered. TT density decreased by ∼14%, without spatial disarrangement, while SR density decreased by ∼7%. More important, FRAP was ∼30% slower, but with similar maximum recovery, suggesting decreased SR interconnectivity. Systolic and diastolic Ca2+ signaling and SR Ca2+ content were unaltered. Conclusion: SR remodeling is an early CH event, similar to TT remodeling, appearing during compensated hypertrophy. Nevertheless, myocytes can withstand those moderate structural changes in SR and TT, preserving normal Ca2+ signaling and contractility.

  20. A pharmaceutical preparation of Salvia miltiorrhiza protects cardiac myocytes from tumor necrosis factor-induced apoptosis and reduces angiotensin II-stimulated collagen synthesis in fibroblasts.

    Science.gov (United States)

    Ling, Shanhong; Luo, Ruizhi; Dai, Aozhi; Guo, Zhixin; Guo, Ruoling; Komesaroff, Paul A

    2009-01-01

    Salvia miltiorrhiza is a medicinal herb commonly used in traditional Chinese medicine for the prevention and treatment of cardiovascular disease. This study investigated the effects of Cardiotonic Pill (CP), a pharmaceutical preparation of Salvia miltiorrhiza, on cardiac myocytes and fibroblasts with respect to the viability, proliferation, and collagen synthesis in these cells under various conditions. A cardiac myocyte line, H9c2, and primarily cultured fibroblasts from rat hearts were incubated with CP over a broad concentration range (50-800 microg/ml) under normal cultures, conditions of ischemia (serum-free culture), and stimulation by angiotensin II (AII, 100 nM), hydrogen peroxide (H(2)O(2), 50-200 microM), or tumor necrosis factor alpha (TNFalpha, 40 ng/ml) for 24-48 h. Cell growth, apoptosis, DNA and collagen synthesis, and expression of relevant genes were assessed via cell number study, morphological examination, Annexin-V staining, flow-cytometry, [(3)H]-thymidine or [(3)H]-proline incorporation assay, and Western blotting analysis. It was found that (1) at therapeutic (50 microg/ml) and double therapeutic (100 microg/ml) concentrations, CP did not significantly affect normal DNA synthesis and cell growth in these cardiac cells, while at higher (over 4-fold therapeutic) concentrations (200-800 microg/ml), CP decreased DNA synthesis and cell growth and increased cell death; (2) CP treatment (50 microg/ml) significantly inhibited TNFalpha-induced apoptosis in myocytes, with 12.3+/-1.46% cells being apoptosis in CP treatment group and 37.0+/-7.34% in the control (pSalvia miltiorrhiza preparation CP is physiologically active on cardiac cells. The actions by CP to reduce apoptotic damage in myocytes and collagen synthesis in fibroblasts may help to preserve the heart function and reduce heart failure risk. The actions by CP to inhibit DNA synthesis and cell growth, which occurred at over therapeutic doses, may weaken the ability of heart repair. Further

  1. Pre-Conditioning with CDP-Choline Attenuates Oxidative Stress-Induced Cardiac Myocyte Death in a Hypoxia/Reperfusion Model

    Science.gov (United States)

    González-Pacheco, Héctor; Méndez-Domínguez, Aurelio; Hernández, Salomón; López-Marure, Rebeca; Vazquez-Mellado, Maria J.; Aguilar, Cecilia; Rocha-Zavaleta, Leticia

    2014-01-01

    Background. CDP-choline is a key intermediate in the biosynthesis of phosphatidylcholine, which is an essential component of cellular membranes, and a cell signalling mediator. CDP-choline has been used for the treatment of cerebral ischaemia, showing beneficial effects. However, its potential benefit for the treatment of myocardial ischaemia has not been explored yet. Aim. In the present work, we aimed to evaluate the potential use of CDP-choline as a cardioprotector in an in vitro model of ischaemia/reperfusion injury. Methods. Neonatal rat cardiac myocytes were isolated and subjected to hypoxia/reperfusion using the coverslip hypoxia model. To evaluate the effect of CDP-choline on oxidative stress-induced reperfusion injury, the cells were incubated with H2O2 during reperfusion. The effect of CDP-choline pre- and postconditioning was evaluated using the cell viability MTT assay, and the proportion of apoptotic and necrotic cells was analyzed using the Annexin V determination by flow cytometry. Results. Pre- and postconditioning with 50 mg/mL of CDP-choline induced a significant reduction of cells undergoing apoptosis after hypoxia/reperfusion. Preconditioning with CDP-choline attenuated postreperfusion cell death induced by oxidative stress. Conclusion. CDP-choline administration reduces cell apoptosis induced by oxidative stress after hypoxia/reperfusion of cardiac myocytes. Thus, it has a potential as cardioprotector in ischaemia/reperfusion-injured cardiomyocytes. PMID:24578622

  2. The angiotensin type 1 receptor activates extracellular signal-regulated kinases 1 and 2 by G protein-dependent and -independent pathways in cardiac myocytes and langendorff-perfused hearts

    DEFF Research Database (Denmark)

    Aplin, Mark; Christensen, Gitte Lund; Schneider, Mikael

    2007-01-01

    II) analogue in native preparations of cardiac myocytes and beating hearts. We found that [SII] AngII does not activate G(q)-coupling, yet stimulates the beta-arrestin2-dependent ERK1/2. The G(q)-activated pool of ERK1/2 rapidly translocates to the nucleus, while the beta-arrestin2-scaffolded pool remains...

  3. Na/K pump inactivation, subsarcolemmal Na measurements, and cytoplasmic ion turnover kinetics contradict restricted Na spaces in murine cardiac myocytes.

    Science.gov (United States)

    Lu, Fang-Min; Hilgemann, Donald W

    2017-07-03

    Decades ago, it was proposed that Na transport in cardiac myocytes is modulated by large changes in cytoplasmic Na concentration within restricted subsarcolemmal spaces. Here, we probe this hypothesis for Na/K pumps by generating constitutive transsarcolemmal Na flux with the Na channel opener veratridine in whole-cell patch-clamp recordings. Using 25 mM Na in the patch pipette, pump currents decay strongly during continuous activation by extracellular K (τ, ∼2 s). In contradiction to depletion hypotheses, the decay becomes stronger when pump currents are decreased by hyperpolarization. Na channel currents are nearly unchanged by pump activity in these conditions, and conversely, continuous Na currents up to 0.5 nA in magnitude have negligible effects on pump currents. These outcomes are even more pronounced using 50 mM Li as a cytoplasmic Na congener. Thus, the Na/K pump current decay reflects mostly an inactivation mechanism that immobilizes Na/K pump charge movements, not cytoplasmic Na depletion. When channel currents are increased beyond 1 nA, models with unrestricted subsarcolemmal diffusion accurately predict current decay (τ ∼15 s) and reversal potential shifts observed for Na, Li, and K currents through Na channels opened by veratridine, as well as for Na, K, Cs, Li, and Cl currents recorded in nystatin-permeabilized myocytes. Ion concentrations in the pipette tip (i.e., access conductance) track without appreciable delay the current changes caused by sarcolemmal ion flux. Importantly, cytoplasmic mixing volumes, calculated from current decay kinetics, increase and decrease as expected with osmolarity changes (τ >30 s). Na/K pump current run-down over 20 min reflects a failure of pumps to recover from inactivation. Simulations reveal that pump inactivation coupled with Na-activated recovery enhances the rapidity and effectivity of Na homeostasis in cardiac myocytes. In conclusion, an autoregulatory mechanism enhances cardiac Na/K pump activity when

  4. Effects of adding intravenous nicorandil to standard therapy on cardiac sympathetic nerve activity and myocyte dysfunction in patients with acute decompensated heart failure

    Energy Technology Data Exchange (ETDEWEB)

    Kasama, Shu [Gunma University Graduate School of Medicine, Department of Medicine and Biological Science (Cardiovascular Medicine), Maebashi, Gunma (Japan); Cardiovascular Hospital of Central Japan (Kitakanto Cardiovascular Hospital), Department of Cardiovascular Medicine, Gunma (Japan); Toyama, Takuji; Funada, Ryuichi; Takama, Noriaki; Koitabashi, Norimichi; Kurabayashi, Masahiko [Gunma University Graduate School of Medicine, Department of Medicine and Biological Science (Cardiovascular Medicine), Maebashi, Gunma (Japan); Ichikawa, Shuichi [Cardiovascular Hospital of Central Japan (Kitakanto Cardiovascular Hospital), Department of Cardiovascular Medicine, Gunma (Japan); Suzuki, Yasuyuki; Matsumoto, Naoya [Nihon University School of Medicine, Department of Cardiology, Tokyo (Japan); Sato, Yuichi [Health Park Clinic, Department of Imaging, Takasaki, Gunma (Japan)

    2015-04-01

    Nicorandil, an adenosine triphosphate-sensitive potassium channel opener, improves cardiac sympathetic nerve activity (CSNA) in ischemic heart disease or chronic heart failure. However, its effects on CSNA and myocyte dysfunction in acute heart failure (AHF) remain unclear. We investigated the effects of adding intravenous nicorandil to standard therapy on CSNA and myocyte dysfunction in AHF. We selected 70 patients with mild to moderate nonischemic AHF who were treated with standard conventional therapy soon after admission. Thirty-five patients were assigned to additionally receive intravenous nicorandil (4-12 mg/h; group A), whereas the remaining patients continued their current drug regimen (group B). Delayed total defect score (TDS), delayed heart to mediastinum count (H/M) ratio, and washout rate (WR) were determined by {sup 123}I-metaiodobenzylguanidine (MIBG) scintigraphy within 3 days of admission and 4 weeks later. High sensitivity troponin T (hs-TnT) level was also measured at the same time points. After treatment, MIBG scintigraphic parameters significantly improved in both groups. However, the extent of the changes in these parameters in group A significantly exceeded the extent of the changes in group B [TDS -11.3 ± 4.3 in group A vs -4.0 ± 6.0 in group B (p < 0.01); H/M ratio 0.31 ± 0.16 vs 0.14 ± 0.16 (p < 0.01); WR -13.8 ± 7.8 % vs -6.1 ± 8.9 % (p < 0.01)]. The hs-TnT level decreased significantly from 0.052 ± 0.043 to 0.041 ± 0.033 ng/ml (p < 0.05) in group A, but showed no significant change in group B. Moreover, in both groups, no relationships between the extent of changes in MIBG parameters and hs-TnT level were observed. Adding intravenous nicorandil to standard therapy provides additional benefits for CSNA and myocyte dysfunction over conventional therapy alone in AHF patients. Furthermore, the mechanisms of improvement in CSNA and myocyte dysfunction after nicorandil treatment in AHF patients were distinct. (orig.)

  5. Use of Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes (hiPSC-CMs) to Monitor Compound Effects on Cardiac Myocyte Signaling Pathways.

    Science.gov (United States)

    Guo, Liang; Eldridge, Sandy; Furniss, Mike; Mussio, Jodie; Davis, Myrtle

    2015-09-01

    There is a need to develop mechanism-based assays to better inform risk of cardiotoxicity. Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are rapidly gaining acceptance as a biologically relevant in vitro model for use in drug discovery and cardiotoxicity screens. Utilization of hiPSC-CMs for mechanistic investigations would benefit from confirmation of the expression and activity of cellular pathways that are known to regulate cardiac myocyte viability and function. This unit describes an approach to demonstrate the presence and function of signaling pathways in hiPSC-CMs and the effects of treatments on these pathways. We present a workflow that employs protocols to demonstrate protein expression and functional integrity of signaling pathway(s) of interest and to characterize biological consequences of signaling modulation. These protocols utilize a unique combination of structural, functional, and biochemical endpoints to interrogate compound effects on cardiomyocytes. Copyright © 2015 John Wiley & Sons, Inc.

  6. Basic FGF enhances calcium permeable channel openings in adult rat cardiac myocytes: implication in the bFGF-induced increase of free Ca2+ content.

    Science.gov (United States)

    Merle, P L; Usson, Y; Robert-Nicoud, M; Verdetti, J

    1997-10-01

    Basic fibroblast growth factor (bFGF) has been implicated in the changes in gene expression that, under pathological conditions such as ischemia or volume overload, lead to adult cardiomyocyte hypertrophy. In many tissues, one of the first events following cell activation by growth factors is an enhancement of the intracellular free calcium concentration, generated by fluxes from internal storage compartments and through channels of the plasma membrane. The present study was undertaken to determine whether cardiac myocytes isolated from adult rat ventricles express Ca2+-permeable channels activated by bFGF. Using the cell-attached mode of the patch-clamp technique, we observed that bFGF (from 0.1-10 nM) induced an increase of fast burst openings, mediated by Ca2+-permeable channels with low conductance (15 pS) and voltage-independence. Inside-out patch-clamp experiments revealed that inositol 1,4,5-trisphosphate (5 microM) enhanced the opening of Ca2+-permeable channels with similar properties as the bFGF-induced channels, indicating that IP3 may be a second messenger of this process. Confocal fluorescence imaging of intracellular free calcium provided direct evidence that bFGF induced an increase of cytoplasmic and nucleoplasmic free Ca2+ concentrations which were generated, in part, by Ca2+ influx through the plasma membrane. In conclusion, this study supports the presence, in the plasma membrane of adult cardiac myocytes, of messenger-activated calcium channels which could play key roles in the calcium-dependent pathways that are activated in response to growth factors. Copyright 1997 Academic Press Limited.

  7. The study of simulated microgravity effects on cardiac myocytes using a 3D heart tissue-equivalent model encapsulated in alginate microbeads

    Science.gov (United States)

    Li, Yu; Tian, Weiming; Zheng, Hongxia; Yu, Lei; Zhang, Yao; Han, Fengtong

    Long duration spaceflight may increase the risk and occurrence of potentially life-threatening heart rhythm disturbances associated with alterations of cardiac myocytes, myocyte connec-tivity, and extracellular matrix resulting from prolonged exposure to zero-or low-gravity. For understanding of the effects of microgravity, either traditional 2-dimensional (2D) cell cultures of adherent cell populations or animal models were typically used. The 2D in vitro systems do not allow assessment of the dynamic effects of intercellular interactions within tissues, whereas potentially confounding factors tend to be overlooked in animal models. Therefore novel cell culture model representative of the cellular interactions and with extracellular matrix present in tissues needs to be used. In this study, 3D multi-cellular heart tissue-equivalent model was constructed by culturing neonatal rat myocardial cells in alginate microbeads for one week. With this model we studied the simulated microgravity effects on myocardiocytes by incubat-ing the microbeads in NASA rotary cell culture system with a rate of 15rpm. Cytoskeletal changes, mitochondrial membrane potential and reactive oxygen production were studied after incubating for 24h, 48h and 72h respectively. Compared with 3D ground-culture group, sig-nificant cytoskeleton depolymerization characterized by pseudo-feet disappearance, significant increase of mitochondrial membrane potential, and greater reactive oxygen production were observed in after incubating 24h, 48h, and 72h, in NASA system. The beating rate of 3D heart tissue-equivalent decreased significantly at 24h, and all the samples stopped beating after 48h incubation while the beating rate of control group did not change. This study indicated that mi-crogravity affects both the structure and function of myocardial cells. Our results suggest that a 3D heart tissue-equivalent model maybe better for attempting to elucidate the microgravity effects on myocardiocytes in

  8. Stretch-induced regulation of angiotensinogen gene expression in cardiac myocytes and fibroblasts: opposing roles of JNK1/2 and p38alpha MAP kinases.

    Science.gov (United States)

    Lal, Hind; Verma, Suresh K; Golden, Honey B; Foster, Donald M; Smith, Manuela; Dostal, David E

    2008-12-01

    The cardiac renin-angiotensin system (RAS) has been implicated in mediating myocyte hypertrophy, remodeling, and fibroblast proliferation in the hemodynamically overloaded heart. However, the intracellular signaling mechanisms responsible for regulation of angiotensinogen (Ao), a substrate of the RAS system, are largely unknown. Here we report the identification of JNK1/2 as a negative, and p38alpha as a major positive regulator of Ao gene expression. Isolated neonatal rat ventricular myocytes (NRVM) and fibroblasts (NRFB) plated on deformable membranes coated with collagen IV, were exposed to 20% equiaxial static-stretch (0-24 h). Mechanical stretch initially depressed Ao gene expression (4 h), whereas after 8 h, Ao gene expression increased in a time-dependent manner. Blockade of JNK1/2 with SP600125 increased basal Ao gene expression in NRVM (10.52+/-1.98 fold, Pstretch-mediated (24 h) Ao gene expression, showing both JNK1 and JNK2 to be negative regulators of Ao gene expression in NRVM and NRFB. Blockade of p38alpha/beta by SB202190 or p38alpha by SB203580 significantly inhibited stretch-induced (24 h) Ao gene expression, whereas expression of wild-type p38alpha increased stretch-induced Ao gene expression in both NRVM (8.41+/-1.50 fold, Pstretch response. Moreover, expression of constitutively active MKK6b (E) significantly stimulated Ao gene expression in the absence of stretch, indicating that p38 activation alone is sufficient to induce Ao gene expression. Taken together p38alpha was demonstrated to be a positive regulator, whereas JNK1/2 was found to be a negative regulator of Ao gene expression. Prolonged stretch diminished JNK1/2 activation, which was accompanied by a reciprocal increase in p38 activation and Ao gene expression. This suggests that a balance in JNK1/2 and p38alpha activation determines the level of Ao gene expression in myocardial cells.

  9. The AMPK gamma1 R70Q mutant regulates multiple metabolic and growth pathways in neonatal cardiac myocytes

    Science.gov (United States)

    Although mutations in the gamma-subunit of AMP-activated protein kinase (AMPK) can result in excessive glycogen accumulation and cardiac hypertrophy, the mechanisms by which this occurs have not been well defined. Because >65% of cardiac AMPK activity is associated with the gamma1-subunit of AMPK, w...

  10. The nitric oxide donor sodium nitroprusside stimulates the Na+-K+ pump in isolated rabbit cardiac myocytes.

    Science.gov (United States)

    William, Maged; Vien, Jimmy; Hamilton, Elisha; Garcia, Alvaro; Bundgaard, Henning; Clarke, Ronald J; Rasmussen, Helge H

    2005-06-15

    Nitric oxide (NO) affects the membrane Na(+)-K(+) pump in a tissue-dependent manner. Stimulation of intrinsic pump activity, stimulation secondary to NO-induced Na(+) influx into cells or inhibition has been reported. We used the whole-cell patch clamp technique to measure electrogenic Na(+)-K(+) pump current (I(p)) in rabbit ventricular myocytes. Myocytes were voltage clamped with wide-tipped patch pipettes to achieve optimal perfusion of the intracellular compartment, and I(p) was identified as the shift in holding current induced by 100 microm ouabain. The NO donor sodium nitroprusside (SNP) in concentrations of 1, 10, 50 or 100 microm induced a significant increase in I(p) when the intracellular compartment was perfused with pipette solutions containing 10 mm Na(+), a concentration near physiological levels. SNP had no effect when the pump was near-maximally activated by 80 mm Na(+) in pipette solutions. Stimulation persisted in the absence of extracellular Na(+), indicating its independence of transmembrane Na(+) influx. The SNP-induced pump stimulation was abolished by inhibition of soluble guanylyl cyclase (sGC) with 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one, by inhibition of protein kinase G (PKG) with KT-5823 or by inhibition of protein phosphatase with okadaic acid. Inclusion of the non-hydrolysable cGMP analogue 8pCPT-cGMP, activated recombinant PKG or the sGC-activator YC-1 in patch pipette filling solutions reproduced the SNP-induced pump stimulation. Pump stimulation induced by YC-1 was dependent on the Na(+) concentration but not the K(+) concentration in pipette filling solutions, suggesting an altered sensitivity of the Na(+)-K(+) pump to intracellular Na(+).

  11. Acyloxy nitroso compounds inhibit LIF signaling in endothelial cells and cardiac myocytes: evidence that STAT3 signaling is redox-sensitive.

    Directory of Open Access Journals (Sweden)

    Carlos Zgheib

    Full Text Available We previously showed that oxidative stress inhibits leukemia inhibitory factor (LIF signaling by targeting JAK1, and the catalytic domains of JAK 1 and 2 have a cysteine-based redox switch. Thus, we postulated that the NO sibling and thiophylic compound, nitroxyl (HNO, would inhibit LIF-induced JAK-STAT3 activation. Pretreatment of human microvascular endothelial cells (HMEC-1 or neonatal rat cardiomyocytes with the HNO donors Angeli's salt or nitrosocyclohexyl acetate (NCA inhibited LIF-induced STAT3 activation. NCA pretreatment also blocked the induction of downstream inflammatory genes (e.g. intercellular adhesion molecule 1, CCAAT/enhancer binding protein delta. The related 1-nitrosocyclohexyl pivalate (NCP; not a nitroxyl donor was equally effective in inhibiting STAT3 activation, suggesting that these compounds act as thiolate targeting electrophiles. The JAK1 redox switch is likely not a target of acyloxy nitroso compounds, as NCA had no effect on JAK1 catalytic activity and only modestly affected JAK1-induced phosphorylation of the LIF receptor. However, pretreatment of recombinant human STAT3 with NCA or NCP reduced labeling of free sulfhydryl residues. We show that NCP in the presence of diamide enhanced STAT3 glutathionylation and dimerization in adult mouse cardiac myocytes and altered STAT3 under non-reducing conditions. Finally, we show that monomeric STAT3 levels are decreased in the Gαq model of heart failure in a redox-sensitive manner. Altogether, our evidence indicates that STAT3 has redox-sensitive cysteines that regulate its activation and are targeted by HNO donors and acyloxy nitroso compounds. These findings raise the possibility of new therapeutic strategies to target STAT3 signaling via a redox-dependent manner, particularly in the context of cardiac and non-cardiac diseases with prominent pro-inflammatory signaling.

  12. Terminal differentiation of cardiac and skeletal myocytes induces permissivity to AAV transduction by relieving inhibition imposed by DNA damage response proteins.

    Science.gov (United States)

    Lovric, Jasmina; Mano, Miguel; Zentilin, Lorena; Eulalio, Ana; Zacchigna, Serena; Giacca, Mauro

    2012-11-01

    Gene therapy vectors based on the adeno-associated virus (AAV) are extremely efficient for gene transfer into post-mitotic cells of heart, muscle, brain, and retina. The reason for their exquisite tropism for these cells has long remained elusive. Here, we show that upon terminal differentiation, cardiac and skeletal myocytes downregulate proteins of the DNA damage response (DDR) and that this markedly induces permissivity to AAV transduction. We observed that expression of members of the MRN complex (Mre11, Rad50, Nbs1), which bind the incoming AAV genomes, faded in cardiomyocytes at ~2 weeks after birth, as well as upon myoblast differentiation in vitro; in both cases, withdrawal of the cells from the cell cycle coincided with increased AAV permissivity. Treatment of proliferating cells with short-interfering RNAs (siRNAs) against the MRN proteins, or with microRNA-24, which is normally upregulated upon terminal differentiation and negatively controls the Nbs1 levels, significantly increased permissivity to AAV transduction. Consistently, delivery of these small RNAs to the juvenile liver concomitant with AAV markedly improved in vivo hepatocyte transduction. Collectively, these findings support the conclusion that cellular DDR proteins inhibit AAV transduction and that terminal cell differentiation relieves this restriction.

  13. Hypotonic swelling promotes nitric oxide release in cardiac ventricular myocytes: impact on swelling-induced negative inotropic effect.

    Science.gov (United States)

    Gonano, Luis Alberto; Morell, Malena; Burgos, Juan Ignacio; Dulce, Raul Ariel; De Giusti, Verónica Celeste; Aiello, Ernesto Alejandro; Hare, Joshua Michael; Vila Petroff, Martin

    2014-12-01

    Cardiomyocyte swelling occurs in multiple pathological situations and has been associated with contractile dysfunction, cell death, and enhanced propensity to arrhythmias. We investigate whether hypotonic swelling promotes nitric oxide (NO) release in cardiomyocytes, and whether it impacts on swelling-induced contractile dysfunction. Superfusing rat cardiomyocytes with a hypotonic solution (HS; 217 mOsm), increased cell volume, reduced myocyte contraction and Ca(2+) transient, and increased NO-sensitive 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM) fluorescence. When cells were exposed to HS + 2.5 mM of the NO synthase inhibitor l-NAME, cell swelling occurred in the absence of NO release. Swelling-induced NO release was also prevented by the nitric oxide synthase 1 (NOS1) inhibitor, nitroguanidine, and significantly reduced in NOS1 knockout mice. Additionally, colchicine (inhibitor of microtubule polymerization) prevented the increase in DAF-FM fluorescence induced by HS, indicating that microtubule integrity is necessary for swelling-induced NO release. The swelling-induced negative inotropic effect was exacerbated in the presence of either l-NAME, nitroguandine, the guanylate cyclase inhibitor, ODQ, or the PKG inhibitor, KT5823, suggesting that NOS1-derived NO provides contractile support via a cGMP/PKG-dependent mechanism. Indeed, ODQ reduced Ca(2+) wave velocity and both ODQ and KT5823 reduced the HS-induced increment in ryanodine receptor (RyR2, Ser2808) phosphorylation, suggesting that in this context, cGMP/PKG may contribute to preserve contractile function by enhancing sarcoplasmic reticulum Ca(2+) release. Our findings suggest a novel mechanism for NO release in cardiomyocytes with putative pathophysiological relevance determined, at least in part, by its capability to reduce the extent of contractile dysfunction associated with hypotonic swelling. Published on behalf of the European Society of Cardiology. All rights reserved. © The

  14. Mst1 inhibition rescues β1-adrenergic cardiomyopathy by reducing myocyte necrosis and non-myocyte apoptosis rather than myocyte apoptosis

    Science.gov (United States)

    Lee, Grace J.; Yan, Lin; Vatner, Dorothy E.

    2015-01-01

    It is generally held that inhibition of mammalian sterile 20-like kinase 1 (Mst1) protects the heart through reducing myocyte apoptosis. We determined whether inhibition with a dominant-negative Mst1 (DN-Mst1) would protect against the cardiomyopathy induced by chronic β1-adrenergic receptor (β1-AR) stimulation by preventing myocyte apoptosis. DN-Mst1 mice were mated with β1-AR transgenic (Tg) mice and followed for 20 months. β1-AR Tg mice developed cardiomyopathy as they aged, as reflected by premature mortality and depressed cardiac function, which were rescued in β1-AR × DN-Mst1 bigenic mice. Surprisingly, myocyte apoptosis did not significantly decrease with Mst1 inhibition. Instead, Mst1 inhibition predominantly reduced non-myocyte apoptosis, e.g., fibroblasts, macrophages, neutrophils and endothelial cells. Fibrosis in the hearts with cardiomyopathy increased fivefold and this increase was nearly abolished in the bigenic mice with Mst1 inhibition. Regression analysis showed no correlation between myocyte apoptosis and cardiac function or myocyte number, whereas the latter two correlated significantly, p myocyte necrosis, chronic β-AR stimulation with isoproterenol was induced for 24 h and myocyte necrosis was assessed by 1 % Evans blue dye. Compared to WT, DN-Mst1 mice showed significant inhibition, p myocyte necrosis. We confirmed this result in Mst1-knockout mice, which also showed significant protection, p myocyte necrosis compared to WT. These data indicate that Mst1 inhibition rescued cardiac fibrosis and myocardial dysfunction in β1-AR cardiomyopathy. However, this did not occur through Mst1 inhibition of myocyte apoptosis but rather by inhibition of cardiomyocyte necrosis and non-myocyte apoptosis, features of Mst1 not considered previously. PMID:25600225

  15. Cell volume control in phospholemman (PLM) knockout mice: do cardiac myocytes demonstrate a regulatory volume decrease and is this influenced by deletion of PLM?

    Science.gov (United States)

    Bell, James R; Lloyd, David; Curl, Claire L; Delbridge, Lea M D; Shattock, Michael J

    2009-03-01

    In addition to modulatory actions on Na+-K+-ATPase, phospholemman (PLM) has been proposed to play a role in cell volume regulation. Overexpression of PLM induces ionic conductances, with 'PLM channels' exhibiting selectivity for taurine. Osmotic challenge of host cells overexpressing PLM increases taurine efflux and augments the cellular regulatory volume decrease (RVD) response, though a link between PLM and cell volume regulation has not been studied in the heart. We recently reported a depressed cardiac contractile function in PLM knockout mice in vivo, which was exacerbated in crystalloid-perfused isolated hearts, indicating that these hearts were osmotically challenged. To address this, the present study investigated the role of PLM in osmoregulation in the heart. Isolated PLM wild-type and knockout hearts were perfused with a crystalloid buffer supplemented with mannitol in a bid to prevent perfusate-induced cell swelling and maintain function. Accordingly, and in contrast to wild-type control hearts, contractile function was improved in PLM knockout hearts with 30 mM mannitol. To investigate further, isolated PLM wild-type and knockout cardiomyocytes were subjected to increasing hyposmotic challenges. Initial validation studies showed the IonOptix video edge-detection system to be a simple and accurate 'real-time' method for tracking cell width as a marker of cell size. Myocytes swelled equally in both genotypes, indicating that PLM, when expressed at physiological levels in cardiomyocytes, is not essential to limit water accumulation in response to a hyposmotic challenge. Interestingly, freshly isolated adult cardiomyocytes consistently failed to mount RVDs in response to cell swelling, adding to conflicting reports in the literature. A proposed perturbation of the RVD response as a result of the cell isolation process was not restored, however, with short-term culture in either adult or neonatal cardiomyocytes.

  16. Ca2+ ionophores are not suitable for inducing mPTP opening in murine isolated adult cardiac myocytes.

    Science.gov (United States)

    Panel, Mathieu; Ghaleh, Bijan; Morin, Didier

    2017-06-27

    Opening of the mitochondrial permeability transition pore (mPTP) plays a major role in cell death during cardiac ischaemia-reperfusion. Adult isolated rodent cardiomyocytes are valuable cells to study the effect of drugs targeting mPTP. This study investigated whether the use of Ca2+ ionophores (A23187, ionomycin and ETH129) represent a reliable model to study inhibition of mPTP opening in cardiomyocytes. We monitored mPTP opening using the calcein/cobalt fluorescence technique in adult rat and wild type or cyclophilin D (CypD) knock-out mice cardiomyocytes. Cells were either treated with Ca2+ ionophores or subjected to hypoxia followed by reoxygenation. The ionophores induced mPTP-dependent swelling in isolated mitochondria. A23187, but not ionomycin, induced a decrease in calcein fluorescence. This loss could not be inhibited by CypD deletion and was explained by a direct interaction between A23187 and cobalt. ETH129 caused calcein loss, mitochondrial depolarization and cell death but CypD deletion did not alleviate these effects. In the hypoxia-reoxygenation model, CypD deletion delayed both mPTP opening and cell death occurring at the time of reoxygenation. Thus, Ca2+ ionophores are not suitable to induce CypD-dependent mPTP opening in adult murine cardiomyocytes. Hypoxia-reoxygenation conditions appear therefore as the most reliable model to investigate mPTP opening in these cells.

  17. Cardiac phosphatase-deficient 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase increases glycolysis, hypertrophy, and myocyte resistance to hypoxia

    OpenAIRE

    Wang, Qianwen; Donthi, Rajakumar V.; Wang, Jianxun; Alex J. Lange; Watson, Lewis J.; Steven P Jones; Epstein, Paul N.

    2008-01-01

    During ischemia and heart failure, there is an increase in cardiac glycolysis. To understand if this is beneficial or detrimental to the heart, we chronically elevated glycolysis by cardiac-specific overexpression of phosphatase-deficient 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2) in transgenic mice. PFK-2 controls the level of fructose-2,6-bisphosphate (Fru-2,6-P2), an important regulator of phosphofructokinase and glycolysis. Transgenic mice had over a threefold elevation ...

  18. Unusual localization and translocation of TRPV4 protein in cultured ventricular myocytes of the neonatal rat

    Directory of Open Access Journals (Sweden)

    Y. Zhao

    2012-07-01

    Full Text Available TRPV4 protein forms a Ca2+-permeable channel that is sensitive to osmotic and mechanical stimuli and responds to warm temperatures, and expresses widely in various kinds of tissues. As for cardiac myocytes, TRPV4 has been detected only at the mRNA level and there were few reports about subcellular localization of the protein. The purpose of the present study was to investigate the expression profile of TRPV4 protein in cultured neonatal rat ventricular myocytes. Using Western blots, immunofluorescence, confocal microscopy and immuno-electron microscopy, we have shown that TRPV4 protein was predominantly located in the nucleus of cultured neonatal myocytes. Furthermore, cardiac myocytes responded to hypotonic stimulation by translocating TRPV4 protein out of the nucleus. The significance and mechanism concerning the unusual distribution and translocation of TRPV4 protein in cardiac myocytes remain to be clarified.

  19. Cardiac phosphatase-deficient 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase increases glycolysis, hypertrophy, and myocyte resistance to hypoxia.

    Science.gov (United States)

    Wang, Qianwen; Donthi, Rajakumar V; Wang, Jianxun; Lange, Alex J; Watson, Lewis J; Jones, Steven P; Epstein, Paul N

    2008-06-01

    During ischemia and heart failure, there is an increase in cardiac glycolysis. To understand if this is beneficial or detrimental to the heart, we chronically elevated glycolysis by cardiac-specific overexpression of phosphatase-deficient 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2) in transgenic mice. PFK-2 controls the level of fructose-2,6-bisphosphate (Fru-2,6-P2), an important regulator of phosphofructokinase and glycolysis. Transgenic mice had over a threefold elevation in levels of Fru-2,6-P2. Cardiac metabolites upstream of phosphofructokinase were significantly reduced, as would be expected by the activation of phosphofructokinase. In perfused hearts, the transgene caused a significant increase in glycolysis that was less sensitive to inhibition by palmitate. Conversely, oxidation of palmitate was reduced by close to 50%. The elevation in glycolysis made isolated cardiomyocytes highly resistant to contractile inhibition by hypoxia, but in vivo the transgene had no effect on ischemia-reperfusion injury. Transgenic hearts exhibited pathology: the heart weight-to-body weight ratio was increased 17%, cardiomyocyte length was greater, and cardiac fibrosis was increased. However, the transgene did not change insulin sensitivity. These results show that the elevation in glycolysis provides acute benefits against hypoxia, but the chronic increase in glycolysis or reduction in fatty acid oxidation interferes with normal cardiac metabolism, which may be detrimental to the heart.

  20. Cardiac expression of kinase-deficient 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase inhibits glycolysis, promotes hypertrophy, impairs myocyte function, and reduces insulin sensitivity.

    Science.gov (United States)

    Donthi, Rajakumar V; Ye, Gang; Wu, Chaodong; McClain, Donald A; Lange, Alex J; Epstein, Paul N

    2004-11-12

    Glycolysis is important to cardiac metabolism and reduced glycolysis may contribute to diabetic cardiomyopathy. To understand its role independent of diabetes or hypoxic injury, we modulated glycolysis by cardiac-specific overexpression of kinase-deficient 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (kd-PFK-2). PFK-2 controls the level of fructose 2,6-bisphosphate (Fru-2,6-P(2)), an important regulator of glycolysis. Transgenic mice had over 2-fold reduced levels of Fru-2,6-P(2). Heart weight/body weight ratio indicated mild hypertrophy. Sirius red staining for collagen was significantly increased. We observed a 2-fold elevation in glucose 6-phosphate and fructose 6-phosphate levels, whereas fructose 1,6-bisphosphate was reduced 2-fold. Pathways branching off of glycolysis above phosphofructokinase were activated as indicated by over 2-fold elevated UDP-N-acetylglucosamine and glycogen. The kd-PFK-2 transgene significantly inhibited glycolysis in perfused hearts. Insulin stimulation of metabolism and Akt phosphorylation were sharply reduced. In addition, contractility of isolated cardiomyocytes was impaired during basal and hypoxic incubations. The present study shows that cardiac overexpression of kinase-deficient PFK-2 reduces cardiac glycolysis that produced negative consequences to the heart including hypertrophy, fibrosis, and reduced cardiomyocyte function. In addition, metabolic and signaling responses to insulin were significantly decreased.

  1. Complement and Dilated Cardiomyopathy: A Role of Sublytic Terminal Complement Complex-Induced Tumor Necrosis Factor-α Synthesis in Cardiac Myocytes

    OpenAIRE

    Zwaka, Thomas P.; Manolov, Dimitar; Özdemir, Cüneyt; Marx, Nikolaus; Kaya, Ziya; Kochs, Matthias; Höher, Martin; Hombach, Vinzenz; Torzewski, Jan

    2002-01-01

    Dilated cardiomyopathy is a syndrome characterized by cardiac enlargement and impaired systolic function of the heart. Tumor necrosis factor (TNF)-α, a pleiotropic cytokine, seems to play a central role in the progression of dilated cardiomyopathy. Recent data suggest that ongoing inflammation in the myocardium may, in many cases, contribute to the development of disease. Chronic generation of autoantibodies to myocardial antigens or, in some cases, viral infection are pathobiologically invol...

  2. Modulation of membrane potential by an acetylcholine-activated potassium current in trout atrial myocytes

    DEFF Research Database (Denmark)

    Molina, C.E.; Gesser, Hans; Llach, A.

    2007-01-01

    Application of the current-clamp technique in rainbow trout atrial myocytes has yielded resting membrane potentials that are incompatible with normal atrial function. To investigate this paradox, we recorded the whole membrane current (Im) and compared membrane potentials recorded in isolated...... cardiac myocytes and multicellular preparations. Atrial tissue and ventricular myocytes had stable resting potentials of -87 ± 2 mV and -83.9 ± 0.4 mV, respectively. In contrast, 50 out of 59 atrial myocytes had unstable depolarized membrane potentials that were sensitive to the holding current. We...... hypothesized that this is at least partly due to a small slope conductance of Im around the resting membrane potential in atrial myocytes. In accordance with this hypothesis, the slope conductance of Im was about sevenfold smaller in atrial than in ventricular myocytes. Interestingly, ACh increased Im at -120...

  3. Time-resolved fluorescence spectroscopy investigation of the effect of 4-hydroxynonenal on endogenous NAD(P)H in living cardiac myocytes.

    Science.gov (United States)

    Chorvatova, Alzbeta; Aneba, Swida; Mateasik, Anton; Chorvat, Dusan; Comte, Blandine

    2013-06-01

    Lipid peroxidation is a major biochemical consequence of the oxidative deterioration of polyunsaturated lipids in cell membranes and causes damage to membrane integrity and loss of protein function. 4-hydroxy-2-nonenal (HNE), one of the most reactive products of n-6 polyunsaturated fatty acid peroxidation of membrane phospholipids, has been shown to be capable of affecting both nicotinamide adenine dinucleotide (phosphate) reduced [NAD(P)H] as well as NADH production. However, the understanding of its effects in living cardiac cells is still lacking. Our goal was to therefore investigate HNE effects on NAD(P)H noninvasively in living cardiomyocytes. Spectrally resolved lifetime detection of endogenous fluorescence, an innovative noninvasive technique, was employed. Individual fluorescence components were resolved by spectral linear unmixing approach. Gathered results revealed that HNE reduced the amplitude of both resolved NAD(P)H components in a concentration-dependent manner. In addition, HNE increased flavoprotein fluorescence and responsiveness of the NAD(P)H component ratio to glutathione reductase (GR) inhibitor. HNE also increased the percentage of oxidized nucleotides and decreased maximal NADH production. Presented data indicate that HNE provoked an important cell oxidation by acting on NAD(P)H regulating systems in cardiomyocytes. Understanding the precise role of oxidative processes and their products in living cells is crucial for finding new noninvasive tools for biomedical diagnostics of pathophysiological states.

  4. Effects of Na+ Current and Mechanogated Channels in Myofibroblasts on Myocyte Excitability and Repolarization

    Directory of Open Access Journals (Sweden)

    Heqing Zhan

    2016-01-01

    Full Text Available Fibrotic remodeling, characterized by fibroblast phenotype switching, is often associated with atrial fibrillation and heart failure. This study aimed to investigate the effects on electrotonic myofibroblast-myocyte (Mfb-M coupling on cardiac myocytes excitability and repolarization of the voltage-gated sodium channels (VGSCs and single mechanogated channels (MGCs in human atrial Mfbs. Mathematical modeling was developed from a combination of (1 models of the human atrial myocyte (including the stretch activated ion channel current, ISAC and Mfb and (2 our formulation of currents through VGSCs (INa_Mfb and MGCs (IMGC_Mfb based upon experimental findings. The effects of changes in the intercellular coupling conductance, the number of coupled Mfbs, and the basic cycle length on the myocyte action potential were simulated. The results demonstrated that the integration of ISAC, INa_Mfb, and IMGC_Mfb reduced the amplitude of the myocyte membrane potential (Vmax and the action potential duration (APD, increased the depolarization of the resting myocyte membrane potential (Vrest, and made it easy to trigger spontaneous excitement in myocytes. For Mfbs, significant electrotonic depolarizations were exhibited with the addition of INa_Mfb and IMGC_Mfb. Our results indicated that ISAC, INa_Mfb, and IMGC_Mfb significantly influenced myocytes and Mfbs properties and should be considered in future cardiac pathological mathematical modeling.

  5. Stroke and cardiac cell death: Two peas in a pod.

    Science.gov (United States)

    Gonzales-Portillo, Chiara; Ishikawa, Hiroto; Shinozuka, Kazutaka; Tajiri, Naoki; Kaneko, Yuji; Borlongan, Cesar V

    2016-03-01

    A close pathological link between stroke brain and heart failure may exist. Here, we discuss relevant laboratory and clinical reports demonstrating neural and cardiac myocyte cell death following ischemic stroke. Although various overlapping risk factors exist between cerebrovascular incidents and cardiac incidents, stroke therapy has largely neglected the cardiac pathological consequences. Recent preclinical stroke studies have implicated an indirect cell death pathway, involving toxic molecules, that originates from the stroke brain and produces cardiac cell death. In concert, previous laboratory reports have revealed a reverse cell death cascade, in that cardiac arrest leads to ischemic cell death in the brain. A deeper understanding of the crosstalk of cell death pathways between stroke and cardiac failure will facilitate the development of novel treatments designed to arrest the global pathology of both diseases thereby improving the clinical outcomes of patients diagnosed with stroke and heart failure. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Biocompatibility of calcined mesoporous silica particles with ventricular myocyte structure and function.

    Science.gov (United States)

    Aburawi, Elhadi H; Qureshi, Mohammed Anwar; Oz, Deniz; Jayaprakash, Petrilla; Tariq, Saeed; Hameed, Rashed S; Das, Sayantani; Goswami, Anandarup; Biradar, Ankush V; Asefa, Tewodros; Souid, Abdul-Kader; Adeghate, Ernest; Howarth, Frank Christopher

    2013-01-18

    In vivo and in vitro systems were employed to investigate the biocompatibility of two forms of calcined mesoporous silica microparticles, MCM41-cal and SBA15-cal, with ventricular myocytes. These particles have potential clinical use in delivering bioactive compounds to the heart. Ventricular myocytes were isolated from 6 to 8 week male Wistar rats. The distribution of the particles in ventricular myocytes was investigated by transmission electron microscopy and scanning electron microscopy. The distribution of particles was also examined in cardiac muscle 10 min after intravenous injection of 2.0 mg/mL MCM41-cal. Myocyte shortening and the Ca(2+) transient were determined following exposure to 200 μg/mL MCM41-cal or SBA15-cal for 10 min. Within 10 min of incubation at 25 °C, both MCM41-cal and SBA15-cal were found attached to the plasma membrane, and some particles were observed inside ventricular myocytes. MCM41-cal was more abundant inside the myocytes than SBA15-cal. The particles had a notable affinity to mitochondrial membranes, where they eventually settled. Within 10 min of intravenous injection (2.0 mg/mL), MCM41-cal traversed the perivascular space, and some particles entered ventricular myocytes and localized around the mitochondrial membranes. The amplitude of shortening was slightly reduced in myocytes superperfused with MCM41-cal or SBA15-cal. The amplitude of the Ca(2+) transient was significantly reduced in myocytes superperfused with MCM41-cal but was only slightly reduced with SBA15-cal. Overall, the results show reasonable bioavailability and biocompatibility of MCM41-cal and SBA15-cal with ventricular myocytes.

  7. The influence of body mass index on outcomes in patients undergoing cardiac surgery: does the obesity paradox really exist?

    Directory of Open Access Journals (Sweden)

    Juan Carlos Lopez-Delgado

    Full Text Available Obesity influences risk stratification in cardiac surgery in everyday practice. However, some studies have reported better outcomes in patients with a high body mass index (BMI: this is known as the obesity paradox. The aim of this study was to quantify the effect of diverse degrees of high BMI on clinical outcomes after cardiac surgery, and to assess the existence of an obesity paradox in our patients.A total of 2,499 consecutive patients requiring all types of cardiac surgery with cardiopulmonary bypass between January 2004 and February 2009 were prospectively studied at our institution. Patients were divided into four groups based on BMI: normal weight (18.5-24.9 kg∙m-2; n = 523; 21.4%, overweight (25-29.9 kg∙m-2; n = 1150; 47%, obese (≥ 30-≤ 34.9 kg∙m-2; n = 624; 25.5% and morbidly obese (≥ 35kg∙m-2; n = 152; 6.2%. Follow-up was performed in 2,379 patients during the first year.After adjusting for confounding factors, patients with higher BMI presented worse oxygenation and better nutritional status, reflected by lower PaO2/FiO2 at 24h and higher albumin levels 48 h after admission respectively. Obese patients showed a higher risk for Perioperative Myocardial Infarction (OR: 1.768; 95% CI: 1.035-3.022; p = 0.037 and septicaemia (OR: 1.489; 95% CI: 1.282-1.997; p = 0.005. In-hospital mortality was 4.8% (n = 118 and 1-year mortality was 10.1% (n = 252. No differences were found regarding in-hospital mortality between BMI groups. The overweight group showed better 1-year survival than normal weight patients (91.2% vs. 87.6%; Log Rank: p = 0.029. HR: 1.496; 95% CI: 1.062-2.108; p = 0.021.In our population, obesity increases Perioperative Myocardial Infarction and septicaemia after cardiac surgery, but does not influence in-hospital mortality. Although we found better 1-year survival in overweight patients, our results do not support any protective effect of obesity in patients undergoing cardiac surgery.

  8. Decreased expression of natriuretic peptides associated with lipid accumulation in cardiac ventricle of obese mice

    DEFF Research Database (Denmark)

    Bartels, E.D.; Nielsen, J.M.; Bisgaard, L.S.

    2010-01-01

    % (P myocytes. The data suggest that obesity and altered cardiac lipid metabolism are associated with reduced production of ANP and BNP in the cardiac ventricles in the setting of normal as well as impaired cardiac function....

  9. Assessment of the quality of existing patient educational tools focused on sudden cardiac arrest: a systematic evaluation by the Sudden Cardiac Arrest Thought Leadership Alliance

    Directory of Open Access Journals (Sweden)

    Hazelton G

    2013-04-01

    Full Text Available Garrett Hazelton,1 Sana M Al-Khatib,2,3 Gregg C Fonarow,4 Kevin L Thomas,3 David Hayes,5 Gillian D Sanders,2,3 Susan M Campbell,6 Clyde Yancy,7 Eric D Peterson,2,3 Samuel Sears8 1Department of Psychiatric Medicine, East Carolina University, Greenville, NC, 2Duke Clinical Research Institute, 3Department of Medicine, Duke University School of Medicine, Durham, NC, 4Division of Cardiology, Geffen School of Medicine at UCLA, Los Angeles, CA, 5Mayo Clinic, Rochester, MN, 6WomenHeart, The National Coalition for Women with Heart Disease, Washington, DC, 7Division of Cardiology, Feinburg School of Medicine, Northwestern University, Chicago, IL, 8Departments of Psychology and Cardiology, East Carolina University, Greenville, NC, USA Background: Conveying contemporary treatment options for those at risk of sudden cardiac arrest (SCA is challenging. The purpose of the present research was to evaluate the quality and usability of available patient educational tools relevant to SCA and its treatment options, such as implantable cardioverter defibrillators (ICDs. We hypothesized that this review would identify gaps in areas of information for the enhancement of patient education and decision-making materials. Methods: We used a formal instrument to assess specific domains of content, development, and effectiveness of 18 available SCA and ICD educational tools. The multidisciplinary review panel included two electrophysiologists, two general cardiologists, a cardiac psychologist, a health services researcher, and a patient advocate. Results: Of the 18 education tools, four were rated as “good, may need revisions, but sufficient for use”, 12 were rated as “marginal, needs revision prior to use”, and two were rated as “poor, inadequate for use”. None of the tools were rated as being of “very good” or “excellent” quality. Conclusion: There appear to be opportunities to improve the quality and completeness of existing educational tools for

  10. Increased sarcolemmal Na+/H+ exchange activity in hypertrophied myocytes from dogs with chronic atrioventricular block

    NARCIS (Netherlands)

    van Borren, Marcel M. G. J.; Vos, Marc A.; Houtman, Marien J. C.; Antoons, Gudrun; Ravesloot, Jan H.

    2013-01-01

    Dogs with compensated biventricular hypertrophy due to chronic atrioventricular block (cAVB), are more susceptible to develop drug-induced Torsade-de-Pointes arrhythmias and sudden cardiac death. It has been suggested that the increased Na+ influx in hypertrophied cAVB ventricular myocytes

  11. Dual effects of amiodarone on pacemaker currents in hypertrophied ventricular myocytes isolated from spontaneously hypertensive rats.

    Science.gov (United States)

    Li, Hongxia; Zhou, Yafeng; Jiang, Bin; Zhao, Xin; Li, Xun; Yang, Xiangjun; Jiang, Wenping

    2014-09-01

    The pacemaker current If conducted by hyperpolarization-activated cyclic nucleotide-gated (HCN) channels plays a critical role in the regulation of cardiac automaticity, with If density increased in hypertrophied ventricular myocytes. Amiodarone, a highly effective anti-arrhythmic agent, blocks human HCN currents and native If under normal conditions. To determine the effects of amiodarone under pathological conditions, we monitored If under after both acute (0.01, 0.1, 1, 10 and 100 μmol/L) and chronic (10 μmol/L) amiodarone treatment in ventricular myocytes from spontaneously hypertensive rats (SHR) with left ventricular hypertrophy using the whole-cell patch-clamp technique. The If current density was significantly greater in SHR ventricular myocytes than in cells from healthy normotensive control Wistar-Kyoto (WKY) rats. Acute application of amiodarone significantly decreased If density in myocytes from both SHR and WKY rats. The inhibition was concentration dependent with an IC50 of 4.9 ± 1.2 and 6.9 ± 1.3 μmol/L in myocytes from SHR and WKY rats, respectively. Amiodarone increased the activation and deactivation times of If in myocytes from SHR, although it did not alter the relationship of voltage-dependent activation and the reversal potential of If in myocytes from SHR. Chronic exposure of myocytes from SHR to amiodarone potently inhibited If and downregulated HCN2 and HCN4, the major channel subtypes underlying native If , at both the mRNA and protein level. These findings indicate that amiodarone inhibits If under hypertrophied conditions through dual mechanisms: (i) direct channel blockade of If currents; and (ii) indirect suppression via negative regulation of HCN channel gene expression. These unique properties of amiodarone may contribute to its anti-arrhythmic properties under pathological conditions. © 2014 Wiley Publishing Asia Pty Ltd.

  12. Myocyte TLR4 enhances enteric and systemic inflammation driving late murine endotoxic ileus

    Science.gov (United States)

    Buchholz, Bettina M.; Shapiro, Richard A.; Vodovotz, Yoram; Billiar, Timothy R.; Sodhi, Chhinder P.; Hackam, David J.

    2015-01-01

    Myocytes are nonhemopoietic in origin and functionally essential in generating gastrointestinal motility. In endotoxemia, a rapid-onset nonhemopoietic mechanism potently triggers early ileus in a Toll-like receptor 4 (TLR4)/myeloid differentiation primary response gene 88 (MyD88)-dependent manner. Moreover, synergistically with hemopoietic cells, nonhemopoietic cells escalate late ileus via an IL-6 receptor-dependent inflammation-driven pathway. We therefore specifically investigated the role of myocytes in TLR4-triggered inflammation and ileus. TLR4+/+, TLR4−/−, bmTLR4+/+/TLR4−/− chimera, SM22-Cre−/−TLR4flox/flox, and selective myocyte TLR4-deficient (SM22-Cre+/−TLR4flox/flox) mice were injected intraperitoneally with purified lipopolysaccharide. SM22-driven Cre recombinase activity was selectively detected in cardiac, gastrointestinal, skeletal, and vascular myocytes, of small-sized vessels in a two-color fluorescent Cre reporter mouse. In contrast to nonhemopoietic TLR4 deficiency, deletion of myocyte TLR4 signaling prevented neither endotoxin-induced suppression of spontaneous jejunal contractility in vitro nor early ileus in vivo at 6 h. Circulating plasma colony-stimulating factor 3 was greatly elevated during endotoxemia, independent of myocyte TLR4 signaling or time. TLR4 activation of myocytes contributed significantly to an early enteric IL-6 mRNA induction and systemic IL-6 release, as well as to a late increase in circulating chemokine (C-X-C motif) ligand 1 (CXCL1) and IL-17. Consequently, inhibition of myocyte TLR4 signaling allowed functional recovery of motility by preventing inflammation-driven late ileus at 24 h. Direct TLR4 activation of myocytes is not responsible for nonhemopoietic-mediated early ileus. However, myocytes are proinflammatory cells that potently drive enteric and systemic inflammation, subsequently fueling late mediator-triggered ileus. Specifically, the myocyte TLR4-dependent inflammatory signature of elevated

  13. Altered distribution of ICa impairs Ca release at the t-tubules of ventricular myocytes from failing hearts.

    Science.gov (United States)

    Bryant, Simon M; Kong, Cherrie H T; Watson, Judy; Cannell, Mark B; James, Andrew F; Orchard, Clive H

    2015-09-01

    In mammalian cardiac ventricular myocytes, Ca influx and release occur predominantly at t-tubules, ensuring synchronous Ca release throughout the cell. Heart failure is associated with disrupted t-tubule structure, but its effect on t-tubule function is less clear. We therefore investigated Ca influx and release at the t-tubules of ventricular myocytes isolated from rat hearts ~18weeks after coronary artery ligation (CAL) or corresponding Sham operation. L-type Ca current (ICa) was recorded using the whole-cell voltage-clamp technique in intact and detubulated myocytes; Ca release at t-tubules was monitored using confocal microscopy with voltage- and Ca-sensitive fluorophores. CAL was associated with cardiac and cellular hypertrophy, decreased ejection fraction, disruption of t-tubule structure and a smaller, slower Ca transient, but no change in ryanodine receptor distribution, L-type Ca channel expression, or ICa density. In Sham myocytes, ICa was located predominantly at the t-tubules, while in CAL myocytes, it was uniformly distributed between the t-tubule and surface membranes. Inhibition of protein kinase A with H-89 caused a greater decrease of t-tubular ICa in CAL than in Sham myocytes; in the presence of H-89, t-tubular ICa density was smaller in CAL than in Sham myocytes. The smaller t-tubular ICa in CAL myocytes was accompanied by increased latency and heterogeneity of SR Ca release at t-tubules, which could be mimicked by decreasing ICa using nifedipine. These data show that CAL decreases t-tubular ICa via a PKA-independent mechanism, thereby impairing Ca release at t-tubules and contributing to the altered excitation-contraction coupling observed in heart failure. Copyright © 2015. Published by Elsevier Ltd.

  14. Interleukin-6-induced reciprocal expression of SERCA and natriuretic peptides mRNA in cultured rat ventricular myocytes.

    Science.gov (United States)

    Tanaka, T; Kanda, T; Takahashi, T; Saegusa, S; Moriya, J; Kurabayashi, M

    2004-01-01

    We investigated the effect of interleukin-6 (IL-6) expression on sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA), atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) mRNA levels in cultured rat neonatal ventricular myocytes. IL-6 plays a key role in regulating cardiac hypertrophy and the development of heart failure, and SERCA, ANP and BNP are all cardiac hormones with regulatory properties. Compared with baseline measurements, treatment with 50 U/ml IL-6 significantly decreased SERCA gene expression, but significantly increased ANP and BNP gene expression in the cardiac myocytes. These results suggest that the clinical overproduction of IL-6 in response to infection, autoimmune disease and cancer might be responsible for cardiac hypertrophy. Cardiac hypertrophy may result from the imbalance of both natriuretic peptides and SERCA transcription levels, caused by elevated IL-6 expression.

  15. Calcium response of KCl-excited populations of ventricular myocytes from the European sea bass (Dicentrarchus labrax): a promising approach to integrate cell-to-cell heterogeneity in studying the cellular basis of fish cardiac performance.

    Science.gov (United States)

    Ollivier, Hélène; Marchant, James; Le Bayon, Nicolas; Servili, Arianna; Claireaux, Guy

    2015-10-01

    Climate change challenges the capacity of fishes to thrive in their habitat. However, through phenotypic diversity, they demonstrate remarkable resilience to deteriorating conditions. In fish populations, inter-individual variation in a number of fitness-determining physiological traits, including cardiac performance, is classically observed. Information about the cellular bases of inter-individual variability in cardiac performance is scarce including the possible contribution of excitation-contraction (EC) coupling. This study aimed at providing insight into EC coupling-related Ca(2+) response and thermal plasticity in the European sea bass (Dicentrarchus labrax). A cell population approach was used to lay the methodological basis for identifying the cellular determinants of cardiac performance. Fish were acclimated at 12 and 22 °C and changes in intracellular calcium concentration ([Ca(2+)]i) following KCl stimulation were measured using Fura-2, at 12 or 22 °C-test. The increase in [Ca(2+)]i resulted primarily from extracellular Ca(2+) entry but sarcoplasmic reticulum stores were also shown to be involved. As previously reported in sea bass, a modest effect of adrenaline was observed. Moreover, although the response appeared relatively insensitive to an acute temperature change, a difference in Ca(2+) response was observed between 12- and 22 °C-acclimated fish. In particular, a greater increase in [Ca(2+)]i at a high level of adrenaline was observed in 22 °C-acclimated fish that may be related to an improved efficiency of adrenaline under these conditions. In conclusion, this method allows a rapid screening of cellular characteristics. It represents a promising tool to identify the cellular determinants of inter-individual variability in fishes' capacity for environmental adaptation.

  16. Improved out-of-hospital cardiac arrest survival through the inexpensive optimization of an existing defibrillation program: OPALS study phase II. Ontario Prehospital Advanced Life Support.

    Science.gov (United States)

    Stiell, I G; Wells, G A; Field, B J; Spaite, D W; De Maio, V J; Ward, R; Munkley, D P; Lyver, M B; Luinstra, L G; Campeau, T; Maloney, J; Dagnone, E

    1999-04-07

    Survival rates for out-of-hospital cardiac arrest are low; published survival rates in Ontario are only 2.5%. This study represents phase II of the Ontario Prehospital Advanced Life Support (OPALS) study, which is designed to systematically evaluate the effectiveness and efficiency of various prehospital interventions for patients with cardiac arrest, trauma, and critical illnesses. To assess the impact on out-of-hospital cardiac arrest survival of the implementation of a rapid defibrillation program in a large multicenter emergency medical services (EMS) system with existing basic life support and defibrillation (BLS-D) level of care. Controlled clinical trial comparing survival for 36 months before (phase I) and 12 months after (phase II) system optimization. Nineteen urban and suburban Ontario communities (populations ranging from 16 000 to 750 000 [total, 2.7 million]). All patients who had out-of-hospital cardiac arrest in the study communities for whom resuscitation was attempted by emergency responders. Study communities optimized their EMS systems to achieve the target response interval from when a call was received until a vehicle stopped with a defibrillator of 8 minutes or less for 90% of cardiac arrest cases. Working both locally and provincially, communities implemented multiple measures, including defibrillation by firefighters, base paging, tiered response agreements with fire departments, continuous quality improvement for response intervals, and province-wide revision and implementation of standard dispatch policies. All response times were obtained from a central dispatch system. Survival to hospital discharge. The 4690 cardiac arrest patients studied in phase I and the 1641 in phase II were similar for all clinical and demographic characteristics, including age, sex, witnessed status, rhythm, and receipt of bystander cardiopulmonary resuscitation. The proportion of cases meeting the 8-minute response criterion improved (76.7% vs 92

  17. Effects of clenbuterol on contractility and Ca2+ homeostasis of isolated rat ventricular myocytes

    OpenAIRE

    Siedlecka, U; Arora, M.; Kolettis, T; Soppa, G. K. R.; Lee, J.; Stagg, M. A.; Harding, S E; Yacoub, M H; Terracciano, C. M. N.

    2008-01-01

    Clenbuterol, a compound classified as a β2-adrenoceptor (AR) agonist, has been employed in combination with left ventricular assist devices (LVADs) to treat patients with severe heart failure. Previous studies have shown that chronic administration of clenbuterol affects cardiac excitation-contraction coupling. However, the acute effects of clenbuterol and the signaling pathway involved remain undefined. We investigated the acute effects of clenbuterol on isolated ventricular myocyte sarcomer...

  18. Longitudinal shortening of sub-epicardial myocytes in severe ischaemic cardiomyopathy

    DEFF Research Database (Denmark)

    Bjerre, Jenny; Kyhl, Kasper; Gustafsson, Finn

    2017-01-01

    We present two patients with three-vessel disease and severely depressed left ventricular (LV) systolic function where viability analysis by cardiac magnetic resonance imaging demonstrated areas of near-transmural sub-endocardial fibrosis and hence little chance of regaining systolic function as ....... The cases highlight that sub-epicardial, longitudinally oriented myocytes can contribute to overall LV systolic function and suggest taking their 'piston-function' into consideration when analysing viability....

  19. Fetal myocardium in the kidney capsule: an in vivo model of repopulation of myocytes by bone marrow cells.

    Directory of Open Access Journals (Sweden)

    Eric Y Zhang

    Full Text Available Debate surrounds the question of whether the heart is a post-mitotic organ in part due to the lack of an in vivo model in which myocytes are able to actively regenerate. The current study describes the first such mouse model--a fetal myocardial environment grafted into the adult kidney capsule. Here it is used to test whether cells descended from bone marrow can regenerate cardiac myocytes. One week after receiving the fetal heart grafts, recipients were lethally irradiated and transplanted with marrow from green fluorescent protein (GFP-expressing C57Bl/6J (B6 donors using normal B6 recipients and fetal donors. Levels of myocyte regeneration from GFP marrow within both fetal myocardium and adult hearts of recipients were evaluated histologically. Fetal myocardium transplants had rich neovascularization and beat regularly after 2 weeks, continuing at checkpoints of 1, 2, 4, 6, 8 and12 months after transplantation. At each time point, GFP-expressing rod-shaped myocytes were found in the fetal myocardium, but only a few were found in the adult hearts. The average count of repopulated myocardium with green rod-shaped myocytes was 996.8 cells per gram of fetal myocardial tissue, and 28.7 cells per adult heart tissue, representing a thirty-five fold increase in fetal myocardium compared to the adult heart at 12 months (when numbers of green rod-shaped myocytes were normalized to per gram of myocardial tissue. Thus, bone marrow cells can differentiate to myocytes in the fetal myocardial environment. The novel in vivo model of fetal myocardium in the kidney capsule appears to be valuable for testing repopulating abilities of potential cardiac progenitors.

  20. TNF-α- Mediated-p38-Dependent Signaling Pathway Contributes to Myocyte Apoptosis in Rats Subjected to Surgical Trauma

    Directory of Open Access Journals (Sweden)

    Huaxing Wu

    2015-03-01

    Full Text Available Background: The accumulation of cytokines in the plasma after trauma can induce myocyte apoptosis. We aimed to identify which cytokine(s present in the plasma responsible for myocyte apoptosis, and delineated the signal transduction mechanism in rats subjected to surgical trauma. Methods: Rats were randomized into two groups: control and trauma groups, which was divided into five subgroups: posttraumatic 0, 3, 6, 12, and 24 h subgroups. Cardiomyocytes isolated from traumatized rats were incubated with one of the factors for 12 h (normal plasma; Cytomix; TNF-α; IL-1β; IFN-γ; trauma plasma; anti-TNF-α antibody; SB203580. Myocyte apoptosis, cytokine levels, and MAPKs activation, as the primary experimental outcomes, were measured by TUNEL, flow cytometry, ELISA and Western blot, respectively. Results: Myocyte apoptosis was induced by surgical trauma during the early stage after trauma. Accompanying this change, plasma TNF-α, IL-1β, and IFN-γ levels were elevated in traumatized rats. Incubation of traumatized cardiomyocytes with cytomix or TNF-α alone induced myocyte apoptosis, and increased the activation of p38 and ERK1/2. Myocyte apoptosis and p38 activation were elevated in traumatized cardiomyocytes with trauma plasma, and these increases were partly abolished by anti-TNF-α antibody or SB203580. Conclusion: Our study demonstrated that there exists the TNF-α-mediated-p38-dependent signaling pathway that contributed to posttraumatic myocyte apoptosis of rats undergoing surgical trauma.

  1. A method to increase reproducibility in adult ventricular myocyte sizing and flow cytometry: Avoiding cell size bias in single cell preparations.

    Directory of Open Access Journals (Sweden)

    Javier E López

    Full Text Available Flow cytometry (FCM of ventricular myocytes (VMs is an emerging technology in adult cardiac research that is challenged by the wide variety of VM shapes and sizes. Cellular variability and cytometer flow cell size can affect cytometer performance. These two factors of variance limit assay validity and reproducibility across laboratories. Washing and filtering of ventricular cells in suspension are routinely done to prevent cell clumping and minimize data variability without the appropriate standardization. We hypothesize that washing and filtering arbitrarily biases towards sampling smaller VMs than what actually exist in the adult heart.To determine the impact of washing and filtering on adult ventricular cells for cell sizing and FCM.Left ventricular cardiac cells in single-cell suspension were harvested from New Zealand White rabbits and fixed prior to analysis. Each ventricular sample was aliquoted before washing or filtering through a 40, 70, 100 or 200μm mesh. The outcomes of the study are VM volume by Coulter Multisizer and light-scatter signatures by FCM. Data are presented as mean±SD. Myocyte volumes without washing or filtering (NF served as the "gold standard" within the sample and ranged from 11,017 to 46,926μm3. Filtering each animal sample through a 200μm mesh caused no variation in the post-filtration volume (1.01+0.01 fold vs. NF, n = 4 rabbits, p = 0.999 with an intra-assay coefficient of variation (%CV of <5% for all 4 samples. Filtering each sample through a 40, 70 or 100μm mesh invariably reduced the post-filtration volume by 41±10%, 9.0±0.8% and 8.8±0.8% respectively (n = 4 rabbits, p<0.0001, and increased the %CV (18% to 1.3%. The high light-scatter signature by FCM, a simple parameter for the identification of ventricular myocytes, was measured after washing and filtering. Washing discarded VMs and filtering cells through a 40 or 100μm mesh reduced larger VM by 46% or 11% respectively (n = 6 from 2 rabbits, p<0

  2. Stimulating endogenous cardiac regeneration

    Directory of Open Access Journals (Sweden)

    Amanda eFinan

    2015-09-01

    Full Text Available The healthy adult heart has a low turnover of cardiac myocytes. The renewal capacity, however, is augmented after cardiac injury. Participants in cardiac regeneration include cardiac myocytes themselves, cardiac progenitor cells, and peripheral stem cells, particularly from the bone marrow compartment. Cardiac progenitor cells and bone marrow stem cells are augmented after cardiac injury, migrate to the myocardium, and support regeneration. Depletion studies of these populations have demonstrated their necessary role in cardiac repair. However, the potential of these cells to completely regenerate the heart is limited. Efforts are now being focused on ways to augment these natural pathways to improve cardiac healing, primarily after ischemic injury but in other cardiac pathologies as well. Cell and gene therapy or pharmacological interventions are proposed mechanisms. Cell therapy has demonstrated modest results and has passed into clinical trials. However, the beneficial effects of cell therapy have primarily been their ability to produce paracrine effects on the cardiac tissue and recruit endogenous stem cell populations as opposed to direct cardiac regeneration. Gene therapy efforts have focused on prolonging or reactivating natural signaling pathways. Positive results have been demonstrated to activate the endogenous stem cell populations and are currently being tested in clinical trials. A potential new avenue may be to refine pharmacological treatments that are currently in place in the clinic. Evidence is mounting that drugs such as statins or beta blockers may alter endogenous stem cell activity. Understanding the effects of these drugs on stem cell repair while keeping in mind their primary function may strike a balance in myocardial healing. To maximize endogenous cardiac regeneration,a combination of these approaches couldameliorate the overall repair process to incorporate the participation ofmultiple cell players.

  3. Transient left bundle branch block induced by left-sided cardiac catheterization in patients without pre-existing conduction abnormalities.

    Science.gov (United States)

    Shimamoto, T; Nakata, Y; Sumiyoshi, M; Ogura, S; Takaya, J; Sakurai, H; Yamaguchi, H

    1998-02-01

    A traumatic left bundle branch block (LBBB) is uncommon in a patient with intact atrioventricular conduction. Three of our patients developed LBBB during a left-sided catheterization. Two patients suffered from angina pectoris and the other had an abdominal aneurysm. Two of them had a history of hypertension. None of the patients had ever shown any conduction abnormalities before the catheterization. The electrocardiogram just before the examination was normal in all 3 patients. LBBB was observed when a catheter was introduced into the left ventricle, and lasted 2--4 min without significant change in heart rates. Examination revealed no significant stenosis proximal to the first septal perforator and normal left ventricular contraction in all patients. One patient developed permanent LBBB 14 months later. Catheter-induced LBBB may occur easily with certain anatomical characteristics of the left bundle branch or the distal His bundle, with or without some concealed damage to the conduction system. It is important to keep this complication in mind and to pay adequate attention to patients' electrocardiograms as well as their angiographical findings, especially in those with pre-existing right bundle branch block.

  4. Some growth factors stimulate cultured adult rabbit ventricular myocyte hypertrophy in the absence of mechanical loading

    Science.gov (United States)

    Decker, R. S.; Cook, M. G.; Behnke-Barclay, M.; Decker, M. L.

    1995-01-01

    Cultured adult rabbit cardiac myocytes treated with recombinant growth factors display enhanced rates of protein accumulation (ie, growth) in response to insulin and insulin-like growth factors (IGFs), but epidermal growth factor, acidic or basic fibroblast growth factor, and platelet-derived growth factor failed to increase contractile protein synthesis or growth of the heart cells. Insulin and IGF-1 increased growth rates by stimulating anabolic while simultaneously inhibiting catabolic pathways, whereas IGF-2 elevated growth modestly by apparently inhibiting lysosomal proteolysis. Neutralizing antibodies directed against either IGF-1 or IGF-2 or IGF binding protein 3 blocked protein accumulation. A monoclonal antibody directed against the IGF-1 receptor also inhibited changes in protein turnover provoked by recombinant human IGF-1 but not IGF-2. Of the other growth factors tested, only transforming growth factor-beta 1 increased the fractional rate of myosin heavy chain (MHC) synthesis, with beta-MHC synthesis being elevated and alpha-MHC synthesis being suppressed. However, the other growth factors were able to modestly stimulate the rate of DNA synthesis in this preparation. Bromodeoxyuridine labeling revealed that these growth factors increased DNA synthesis in myocytes and nonmyocytes alike, but the heart cells displayed neither karyokinesis or cytokinesis. In contrast, cocultures of cardiac myocytes and nonmyocytes and nonmyocyte-conditioned culture medium failed to enhance the rate of cardiac MHC synthesis or its accumulation, implying that quiescent heart cells do not respond to "conditioning" by cardiac nonmyocytes. These findings demonstrated that insulin and the IGFs promote passively loaded cultured adult rabbit heart cells to hypertrophy but suggest that other growth factors tested may be limited in this regard.

  5. Selective Endothelin-1 Receptor type-A Inhibition in Cardiac Surgery Subjects with Pre-Existing LV Dysfunction: Influence on Early Post-Operative Hemodynamics

    Science.gov (United States)

    Toole, John M.; Ikonomidis, John S.; Szeto, Wilson Y.; Zellner, James L.; Mulcahy, John; Deardorff, Rachael L.; Spinale, Francis G.

    2010-01-01

    Background and Objective A robust release of endothelin-1-1 (ET) with subsequent ETA subtype receptor (ET-AR) activation occurs in patients following cardiac surgery requiring cardiopulmonary bypass (CPB). Increased ET-AR activation has been identified in patients with poor LV function (reduced ejection fraction; EF). Accordingly, this study tested the hypothesis that a selective ET-AR antagonist (ET-ARA) administered peri-operatively would favorably affect post-CPB hemodynamic profiles in patients with a pre-existing poor LVEF. Methods and Results Patients (n=29; 66±2 yrs) with a reduced LVEF (37±2%) were prospectively randomized, in a blinded fashion, at the time of elective coronary revascularization and/or valve replacement requiring CPB, to infusion of the highly-selective and potent ET-ARA, sitaxsentan at 1 or 2 mg/kg (IV bolus; n=9, 10 respectively) or vehicle (saline; n=10). Infusion of the ET-ARA/vehicle was performed immediately prior to separation from CPB and again at 12 hrs post-CPB. ET and hemodynamic measurements were performed at baseline, at separation from CPB (Time 0) and at 0.5, 6, 12, 24 hrs post-CPB. Baseline plasma ET (4.0±0.3 fmol/mL) was identical across all 3 groups, but when compared to pre-operative, baseline values obtained from age matched subjects with a normal LVEF (n=37;LVEF>50%), were significantly increased (2.9±0.2 fmol/mL, pTime 0, SVR changed in an equivalent fashion in the post-CPB period, but a significant ET-ARA effect was observed for PVR (ANOVA; p<0.05). For example at 24 hrs post-CPB, PVR increased by 40 d.scm-5 in the vehicle group, but directionally decreased by over 40 d·s·cm-5 in the 2 mg/kg ETARA group (p<0.05). Total adverse events were equivalently distributed across the ET-ARA/placebo groups. Conclusions These unique findings demonstrated that infusion of an ET-ARA in high risk cardiac surgery patients was not associated with significant hemodynamic compromise. Moreover, ET-ARA favorably affected PVR in the

  6. Allicin inhibits transient outward potassium currents in mouse ventricular myocytes

    OpenAIRE

    CAO, HONG; HUANG, CONGXIN; WANG, XIN

    2016-01-01

    Allicin is the active constituent of garlic, a widely used spice and food. The remedial properties of garlic have also been extensively researched and it has been demonstrated that allicin is able to inhibit the transient outward potassium current (Ito) in atrial myocytes. However, the direct effect of allicin on Ito in ventricular myocytes has yet to be elucidated. In the present study, the effects of allicin on Ito in ventricular myocytes isolated from mice were investigated, using the whol...

  7. Spiral-Wave Dynamics in a Mathematical Model of Human Ventricular Tissue with Myocytes and Fibroblasts

    Science.gov (United States)

    Nayak, Alok Ranjan; Shajahan, T. K.; Panfilov, A. V.; Pandit, Rahul

    2013-01-01

    Cardiac fibroblasts, when coupled functionally with myocytes, can modulate the electrophysiological properties of cardiac tissue. We present systematic numerical studies of such modulation of electrophysiological properties in mathematical models for (a) single myocyte-fibroblast (MF) units and (b) two-dimensional (2D) arrays of such units; our models build on earlier ones and allow for zero-, one-, and two-sided MF couplings. Our studies of MF units elucidate the dependence of the action-potential (AP) morphology on parameters such as , the fibroblast resting-membrane potential, the fibroblast conductance , and the MF gap-junctional coupling . Furthermore, we find that our MF composite can show autorhythmic and oscillatory behaviors in addition to an excitable response. Our 2D studies use (a) both homogeneous and inhomogeneous distributions of fibroblasts, (b) various ranges for parameters such as , and , and (c) intercellular couplings that can be zero-sided, one-sided, and two-sided connections of fibroblasts with myocytes. We show, in particular, that the plane-wave conduction velocity decreases as a function of , for zero-sided and one-sided couplings; however, for two-sided coupling, decreases initially and then increases as a function of , and, eventually, we observe that conduction failure occurs for low values of . In our homogeneous studies, we find that the rotation speed and stability of a spiral wave can be controlled either by controlling or . Our studies with fibroblast inhomogeneities show that a spiral wave can get anchored to a local fibroblast inhomogeneity. We also study the efficacy of a low-amplitude control scheme, which has been suggested for the control of spiral-wave turbulence in mathematical models for cardiac tissue, in our MF model both with and without heterogeneities. PMID:24023798

  8. Angiogenesis and cardiac hypertrophy: maintenance of cardiac function and causative roles in heart failure.

    Science.gov (United States)

    Oka, Toru; Akazawa, Hiroshi; Naito, Atsuhiko T; Komuro, Issei

    2014-01-31

    Cardiac hypertrophy is an adaptive response to physiological and pathological overload. In response to the overload, individual cardiac myocytes become mechanically stretched and activate intracellular hypertrophic signaling pathways to re-use embryonic transcription factors and to increase the synthesis of various proteins, such as structural and contractile proteins. These hypertrophic responses increase oxygen demand and promote myocardial angiogenesis to dissolve the hypoxic situation and to maintain cardiac contractile function; thus, these responses suggest crosstalk between cardiac myocytes and microvasculature. However, sustained pathological overload induces maladaptation and cardiac remodeling, resulting in heart failure. In recent years, specific understanding has increased with regard to the molecular processes and cell-cell interactions that coordinate myocardial growth and angiogenesis. In this review, we summarize recent advances in understanding the regulatory mechanisms of coordinated myocardial growth and angiogenesis in the pathophysiology of cardiac hypertrophy and heart failure.

  9. Cardiac catheterization

    Science.gov (United States)

    Catheterization - cardiac; Heart catheterization; Angina - cardiac catheterization; CAD - cardiac catheterization; Coronary artery disease - cardiac catheterization; Heart valve - cardiac catheterization; ...

  10. Atrial myocyte function and Ca2+ handling is associated with inborn aerobic capacity.

    Directory of Open Access Journals (Sweden)

    Anne Berit Johnsen

    Full Text Available Although high aerobic capacity is associated with effective cardiac function, the effect of aerobic capacity on atrial function, especially in terms of cellular mechanisms, is not known. We aimed to investigate whether rats with low inborn maximal oxygen uptake (VO2 max had impaired atrial myocyte contractile function when compared to rats with high inborn VO2 max.Atrial myocyte function was depressed in Low Capacity Runners (LCR relative to High Capacity Runners (HCR which was associated with impaired Ca(2+ handling. Fractional shortening was 52% lower at 2 Hz and 60% lower at 5 Hz stimulation while time to 50% relengthening was 43% prolonged and 55% prolonged, respectively. Differences in Ca(2+ amplitude and diastolic Ca(2+ level were observed at 5 Hz stimulation where Ca(2+ amplitude was 70% lower and diastolic Ca(2+ level was 11% higher in LCR rats. Prolonged time to 50% Ca(2+ decay was associated with reduced sarcoplasmic reticulum (SR Ca(2+ ATPase function in LCR (39%. Na(+/Ca(2+ exchanger activity was comparable between the groups. Diastolic SR Ca(2+ leak was increased by 109%. This could be partly explained by increased ryanodine receptors phosphorylation at the Ca(2+-calmodulin-dependent protein kinase-II specific Ser-2814 site in LCR rats. T-tubules were present in 68% of HCR cells whereas only 33% LCR cells had these structures. In HCR, the significantly higher numbers of cells with T-tubules were combined with greater numbers of myocytes where Ca(2+ release in the cell occurred simultaneously in central and peripheral regions, giving rise to faster and more spatial homogenous Ca(2+-signal onset.This data demonstrates that contrasting for low or high aerobic capacity leads to diverse functional and structural remodelling of atrial myocytes, with impaired contractile function in LCR compared to HCR rats.

  11. Class II HDACs mediate CaMK-dependent signaling to NRSF in ventricular myocytes.

    Science.gov (United States)

    Nakagawa, Yasuaki; Kuwahara, Koichiro; Harada, Masaki; Takahashi, Nobuki; Yasuno, Shinji; Adachi, Yuichiro; Kawakami, Rika; Nakanishi, Michio; Tanimoto, Keiji; Usami, Satoru; Kinoshita, Hideyuki; Saito, Yoshihiko; Nakao, Kazuwa

    2006-12-01

    We recently reported that a transcriptional repressor, neuron-restrictive silencer factor (NRSF), represses expression of fetal cardiac genes, including atrial and brain natriuretic peptide (ANP and BNP), by recruiting class I histone deacetylase (HDAC) and that attenuation of NRSF-mediated repression contributes to the reactivation of fetal gene expression during cardiac hypertrophy. The molecular mechanism by which the activity of the NRSF-HDAC complex is inhibited in cardiac hypertrophy remains unresolved, however. In the present study, we show that class II HDACs (HDAC4 and 5), which are Ca/calmodulin-dependent kinase (CaMK)-responsive repressors of hypertrophic signaling, associate with NRSF and participate in NRSF-mediated repression. Blockade of the CaMK-class II HDAC signaling pathway using a CaMK-resistant HDAC5 mutant, a CaMK inhibitor (KN62) or a dominant-negative CaMK mutant inhibited ET-1-inducible ANP and BNP promoter activity, but that inhibitory effect was abolished by mutation of the neuron-restrictive silencer element (NRSE) within the ANP and BNP promoter. In addition, adenovirus-mediated expression of a dominant-negative NRSF mutant abolished the inhibitory effect of KN62 on ET-1-inducible endogenous ANP gene expression in ventricular myocytes. Finally, the interaction between NRSF and class II HDACs was decreased in both in vitro and in vivo models of cardiac hypertrophy. These findings show that ET-1-induced CaMK signaling disrupts class II HDAC-NRSF repressor complexes, thereby enabling activation of ANP and BNP gene transcription in ventricular myocytes, and shed light on a novel mechanism by which the fetal cardiac gene program is reactivated.

  12. Novel mechanisms for caspase inhibition protecting cardiac function with chronic pressure overload

    OpenAIRE

    Park, Misun; Vatner, Stephen F.; Yan, Lin; Gao, Shumin; Yoon, Seunghun; Lee, Grace Jung Ah; Xie, Lai-Hua; Kitsis, Richard N.; Vatner, Dorothy E.

    2013-01-01

    Myocyte apoptosis is considered a major mechanism in the pathogenesis of heart failure. Accordingly, manipulations that inhibit apoptosis are assumed to preserve cardiac function by maintaining myocyte numbers. We tested this assumption by examining the effects of caspase inhibition (CI) on cardiac structure and function in C57BL/6 mouse with pressure overload model induced by transverse aortic constriction (TAC). CI preserved left ventricular (LV) function following TAC compared with the veh...

  13. Biosynthesis of cardiac natriuretic peptides

    DEFF Research Database (Denmark)

    Goetze, Jens Peter

    2010-01-01

    Cardiac-derived peptide hormones were identified more than 25 years ago. An astonishing amount of clinical studies have established cardiac natriuretic peptides and their molecular precursors as useful markers of heart disease. In contrast to the clinical applications, the biogenesis of cardiac....... An inefficient post-translational prohormone maturation will also affect the biology of the cardiac natriuretic peptide system. This review aims at summarizing the myocardial synthesis of natriuretic peptides focusing on B-type natriuretic peptide, where new data has disclosed cardiac myocytes as highly...... competent endocrine cells. The structurally related atrial natriuretic peptide will be mentioned where appropriate, whereas C-type natriuretic peptide will not be considered as a cardiac peptide of relevance in mammalian physiology....

  14. Modeling CICR in rat ventricular myocytes: voltage clamp studies

    Directory of Open Access Journals (Sweden)

    Palade Philip T

    2010-11-01

    Full Text Available Abstract Background The past thirty-five years have seen an intense search for the molecular mechanisms underlying calcium-induced calcium-release (CICR in cardiac myocytes, with voltage clamp (VC studies being the leading tool employed. Several VC protocols including lowering of extracellular calcium to affect Ca2+ loading of the sarcoplasmic reticulum (SR, and administration of blockers caffeine and thapsigargin have been utilized to probe the phenomena surrounding SR Ca2+ release. Here, we develop a deterministic mathematical model of a rat ventricular myocyte under VC conditions, to better understand mechanisms underlying the response of an isolated cell to calcium perturbation. Motivation for the study was to pinpoint key control variables influencing CICR and examine the role of CICR in the context of a physiological control system regulating cytosolic Ca2+ concentration ([Ca2+]myo. Methods The cell model consists of an electrical-equivalent model for the cell membrane and a fluid-compartment model describing the flux of ionic species between the extracellular and several intracellular compartments (cell cytosol, SR and the dyadic coupling unit (DCU, in which resides the mechanistic basis of CICR. The DCU is described as a controller-actuator mechanism, internally stabilized by negative feedback control of the unit's two diametrically-opposed Ca2+ channels (trigger-channel and release-channel. It releases Ca2+ flux into the cyto-plasm and is in turn enclosed within a negative feedback loop involving the SERCA pump, regulating[Ca2+]myo. Results Our model reproduces measured VC data published by several laboratories, and generates graded Ca2+ release at high Ca2+ gain in a homeostatically-controlled environment where [Ca2+]myo is precisely regulated. We elucidate the importance of the DCU elements in this process, particularly the role of the ryanodine receptor in controlling SR Ca2+ release, its activation by trigger Ca2+, and its

  15. Myocardial deletion of transcription factor CHF1/Hey2 results in altered myocyte action potential and mild conduction system expansion but does not alter conduction system function or promote spontaneous arrhythmias

    OpenAIRE

    Matthew E Hartman; Liu, Yonggang; Zhu, Wei-Zhong; Chien, Wei-Ming; Chad S. Weldy; Fishman, Glenn I.; Laflamme, Michael A.; Chin, Michael T.

    2014-01-01

    CHF1/Hey2 is a Notch-responsive basic helix–loop-helix transcription factor involved in cardiac development. Common variants in Hey2 are associated with Brugada syndrome. We hypothesized that absence of CHF1/Hey2 would result in abnormal cellular electrical activity, altered cardiac conduction system (CCS) development, and increased arrhythmogenesis. We isolated neonatal CHF/Hey2-knockout (KO) cardiac myocytes and measured action potentials and ion channel subunit gene expression. We also cro...

  16. Selective activation of heteromeric SK channels contributes to action potential repolarization in mouse atrial myocytes.

    Science.gov (United States)

    Hancock, Jane M; Weatherall, Kate L; Choisy, Stéphanie C; James, Andrew F; Hancox, Jules C; Marrion, Neil V

    2015-05-01

    Activation of small conductance calcium-activated potassium (SK) channels is proposed to contribute to repolarization of the action potential in atrial myocytes. This role is controversial, as these cardiac SK channels appear to exhibit an uncharacteristic pharmacology. The objectives of this study were to resolve whether activation of SK channels contributes to atrial action potential repolarization and to determine the likely subunit composition of the channel. The effect of 2 SK channel inhibitors was assessed on outward current evoked in voltage clamp and on action potential duration in perforated patch and whole-cell current clamp recording from acutely isolated mouse atrial myocytes. The presence of SK channel subunits was assessed using immunocytochemistry. A significant component of outward current was reduced by the SK channel blockers apamin and UCL1684. Block by apamin displayed a sensitivity indicating that this current was carried by homomeric SK2 channels. Action potential duration was significantly prolonged by UCL1684, but not by apamin. This effect was accompanied by an increase in beat-to-beat variability and action potential triangulation. This pharmacology was matched by that of expressed heteromeric SK2-SK3 channels in HEK293 cells. Immunocytochemistry showed that atrial myocytes express both SK2 and SK3 channels with an overlapping expression pattern. Only proposed heteromeric SK2-SK3 channels are physiologically activated to contribute to action potential repolarization, which is indicated by the difference in pharmacology of evoked outward current and prolongation of atrial action potential duration. The effect of blocking this channel on the action potential suggests that SK channel inhibition during cardiac function has the potential to be proarrhythmic. Copyright © 2015 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

  17. The proarrhythmic antihistaminic drug terfenadine increases spontaneous calcium release in human atrial myocytes.

    Science.gov (United States)

    Hove-Madsen, Leif; Llach, Anna; Molina, Cristina E; Prat-Vidal, Cristina; Farré, Jordi; Roura, Santiago; Cinca, Juan

    2006-12-28

    Spontaneous calcium release from the sarcoplasmic reticulum in cardiac myocytes plays a central role in cardiac arrhythmogenesis. Compounds intended for therapeutical use that interfere with intracellular calcium handling may therefore have an undesired proarrhythmic potential. Here we have used isolated human atrial myocytes to compare the effect of the proarrhythmic antihistaminic drug terfenadine with the non-proarrhythmic antihistaminic drugs fexofenadine and rupatadine on intracellular calcium homeostasis. Perforated patch-clamp technique was used to measure ionic currents and to detect spontaneous calcium release from the sarcoplasmic reticulum. Our results show that the compound terfenadine, with known arrhythmogenic effects, inhibits L-type calcium current (I(Ca)) with an IC(50) of 185 nM when cells are stimulated at 1.0 Hz. The inhibitory effect of 0.3 muM terfenadine increased from 19+/-4% at stimulation frequency of 0.2 Hz to 63+/-6% at 2.0 Hz. Moreover, terfenadine also increased spontaneous calcium release from the sarcoplasmic reticulum. At a concentration of 1 muM, terfenadine significantly increased the spontaneous Na-Ca exchange current (I(NCX)) frequency from 0.48+/-0.25 to 1.93+/-0.67 s(-1). In contrast, fexofenadine and rupatadine did not change I(Ca) or the frequency of spontaneous I(NCX). We conclude that the proarrhythmic antihistaminic drug terfenadine alters intracellular calcium handling in isolated human atrial myocytes. This experimental model may be suitable to screen for potential arrhythmogenic side-effects of compounds intended for therapeutical use.

  18. α-Catenin localization and sarcomere self-organization on N-cadherin adhesive patterns are myocyte contractility driven.

    Directory of Open Access Journals (Sweden)

    Anant Chopra

    Full Text Available The N-cadherin (N-cad complex plays a crucial role in cardiac cell structure and function. Cadherins are adhesion proteins linking adjacent cardiac cells and, like integrin adhesions, are sensitive to force transmission. Forces through these adhesions are capable of eliciting structural and functional changes in myocytes. Compared to integrins, the mechanisms of force transduction through cadherins are less explored. α-catenin is a major component of the cadherin-catenin complex, thought to provide a link to the cell actin cytoskeleton. Using N-cad micropatterned substrates in an adhesion constrainment model, the results from this study show that α-catenin localizes to regions of highest internal stress in myocytes. This localization suggests that α-catenin acts as an adaptor protein associated with the cadherin mechanosensory apparatus, which is distinct from mechanosensing through integrins. Myosin inhibition in cells bound by integrins to fibronectin-coated patterns disrupts myofibiril organization, whereas on N-cad coated patterns, myosin inhibition leads to better organized myofibrils. This result indicates that the two adhesion systems provide independent mechanisms for regulating myocyte structural organization.

  19. Global Optimization of Ventricular Myocyte Model to Multi-Variable Objective Improves Predictions of Drug-Induced Torsades de Pointes

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    Trine Krogh-Madsen

    2017-12-01

    Full Text Available In silico cardiac myocyte models present powerful tools for drug safety testing and for predicting phenotypical consequences of ion channel mutations, but their accuracy is sometimes limited. For example, several models describing human ventricular electrophysiology perform poorly when simulating effects of long QT mutations. Model optimization represents one way of obtaining models with stronger predictive power. Using a recent human ventricular myocyte model, we demonstrate that model optimization to clinical long QT data, in conjunction with physiologically-based bounds on intracellular calcium and sodium concentrations, better constrains model parameters. To determine if the model optimized to congenital long QT data better predicts risk of drug-induced long QT arrhythmogenesis, in particular Torsades de Pointes risk, we tested the optimized model against a database of known arrhythmogenic and non-arrhythmogenic ion channel blockers. When doing so, the optimized model provided an improved risk assessment. In particular, we demonstrate an elimination of false-positive outcomes generated by the baseline model, in which simulations of non-torsadogenic drugs, in particular verapamil, predict action potential prolongation. Our results underscore the importance of currents beyond those directly impacted by a drug block in determining torsadogenic risk. Our study also highlights the need for rich data in cardiac myocyte model optimization and substantiates such optimization as a method to generate models with higher accuracy of predictions of drug-induced cardiotoxicity.

  20. Modulation of sarcoplasmic reticulum Ca2+ release by glycolysis in cat atrial myocytes.

    Science.gov (United States)

    Kockskämper, Jens; Zima, Aleksey V; Blatter, Lothar A

    2005-05-01

    In cardiac myocytes, glycolysis and excitation-contraction (E-C) coupling are functionally coupled. We studied the effects of inhibitors (2-deoxy-D-glucose (2-DG), iodoacetate (IAA)), intermediates (glucose-6-phosphate (G6P), fructose-6-phosphate (F6P), fructose-1,6-bisphosphate (FBP), phosphoenolpyruvate (PEP)) and products (pyruvate, L-lactate) of glycolysis on sarcoplasmic reticulum (SR) Ca(2+) release and uptake in intact and permeabilized cat atrial myocytes. In field-stimulated (0.5-0.7 Hz) intact myocytes, 2-DG (10 mm) and IAA (1 mm) caused elevation of diastolic [Ca(2+)](i) and [Ca(2+)](i) transient alternans (Ca(2+) alternans) followed by a decrease of the amplitude of the [Ca(2+)](i) transient. Focal application of 2-DG resulted in local Ca(2+) alternans that was confined to the region of exposure. 2-DG and IAA slowed the decay kinetics of the [Ca(2+)](i) transient and delayed its recovery (positive staircase) after complete SR depletion, suggesting impaired activity of the SR Ca(2+)-ATPase (SERCA). 2-DG and IAA reduced the rate of reuptake of Ca(2+) into the SR which was accompanied by a 15-20% decrease of SR Ca(2+) load. Major changes of mitochondrial redox state (measured as FAD autofluorescence) were not observed after inhibition of glycolysis. Pyruvate (10 mm) and L-lactate (10 mm) elicited similar changes of the [Ca(2+)](i) transient. Pyruvate, L-lactate and IAA - but not 2-DG - induced intracellular acidosis. Recording of single channel activity of ryanodine receptors (RyRs) incorporated into lipid bilayers revealed complex modulation by glycolytic intermediates and products (1 mm each): some were without effect (G6P, PEP, L-lactate) while others either increased (F6P, +40%; FBP, +265%) or decreased (pyruvate, -58%) the open probability of the RyR. Consistent with these findings, spontaneous SR Ca(2+) release (Ca(2+) sparks) in permeabilized myocytes was facilitated by FBP and inhibited by pyruvate. The results indicate that in atrial myocytes

  1. Acute CD47 Blockade During Ischemic Myocardial Reperfusion Enhances Phagocytosis-Associated Cardiac Repair

    Directory of Open Access Journals (Sweden)

    Shuang Zhang, BS

    2017-08-01

    Full Text Available Our data suggest that, after a myocardial infarction, integrin-associated protein CD47 on cardiac myocytes is elevated. In culture, increased CD47 on the surface of dying cardiomyocytes impairs phagocytic removal by immune cell macrophages. After myocardial ischemia and reperfusion, acute CD47 inhibition with blocking antibodies enhanced dead myocyte clearance by cardiac phagocytes and also improved the resolution of cardiac inflammation, reduced infarct size, and preserved cardiac contractile function. Early targeting of CD47 in the myocardium after reperfusion may be a new strategy to enhance wound repair in the ischemic heart.

  2. [Cardiac fibroma: A rare cause of sudden child death].

    Science.gov (United States)

    Humez, Sarah; Gibier, Jean-Baptiste; Recher, Morgan; Leteurtre, Stéphane; Leroy, Xavier; Devisme, Louise

    2015-10-01

    We report the case of a 3-year-old child who died from the consequences of a cardio-respiratory arrest despite reanimation procedures. Echocardiography and magnetic resonance imaging (MRI) revealed a mass of the free wall of the left ventricle. Autopsy confirmed the existence of a solitary myocardial tumor, well-circumscribed, firm, with a whitish and trabeculated cut surface. Histologically, the tumor consisted of bundles of spindle-shaped and regular cells mingling with collagen and elastic fibers, insinuating themselves between myocytes in periphery. Calcifications were present. After immunohistochemistry, the cells were highlighted by anti-actin smooth muscle antibody; but they were not highlighted by anti-desmin, anti-β catenin and anti-Ki67 antibodies. The diagnosis of cardiac fibroma was made. The primary cardiac tumors of child are rare and usually benign. They are essentially represented by rhabdomyoma and fibroma. Cardiac fibroma mostly occurs during the first year of life. It can be revealed by cardiac insufficiency, arrhythmia, chest pain or sudden death. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  3. Induced Pluripotent Stem Cells 10 Years Later: For Cardiac Applications.

    Science.gov (United States)

    Yoshida, Yoshinori; Yamanaka, Shinya

    2017-06-09

    Induced pluripotent stem cells (iPSCs) are reprogrammed cells that have features similar to embryonic stem cells, such as the capacity of self-renewal and differentiation into many types of cells, including cardiac myocytes. Although initially the reprogramming efficiency was low, several improvements in reprogramming methods have achieved robust and efficient generation of iPSCs without genomic insertion of transgenes. iPSCs display clonal variations in epigenetic and genomic profiles and cellular behavior in differentiation. iPSC-derived cardiac myocytes (iPSC cardiac myocytes) recapitulate phenotypic differences caused by genetic variations, making them attractive human disease models, and are useful for drug discovery and toxicology testing. In addition, iPSC cardiac myocytes can help with patient stratification in regard to drug responsiveness. Furthermore, they can be used as source cells for cardiac regeneration in animal models. Here, we review recent progress in iPSC technology and its applications to cardiac diseases. © 2017 American Heart Association, Inc.

  4. Cardiac Malpositions

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Shi Joon; Im, Chung Gie; Yeon, Kyung Mo; Hasn, Man Chung [Seoul National University College of Medicine, Seoul (Korea, Republic of)

    1979-06-15

    Cardiac Malposition refers to any position of the heart other than a left-sided heart in a situs solitus individual. Associated cardiac malformations are so complex that even angiocardiographic and autopsy studies may not afford an accurate information. Although the terms and classifications used to describe the internal cardiac anatomy and their arterial connections in cardiac malpositions differ and tend to be confusing, common agreement exists on the need for a segmental approach to diagnosis. Authors present 18 cases of cardiac malpositions in which cardiac catheterization and angiocardiography were done at the Department of Radiology, Seoul National University Hospital between 1971 and 1979. Authors analyzed the clinical, radiographic, operative and autopsy findings with the emphasis on the angiocardiographic findings. The results are as follows: 1. Among 18 cases with cardiac malpositions, 6 cases had dextrocardia with situs inversus, 9 cases had dextrocardia with situs solitus and 3 cases had levocardia with situs inversus. 2. There was no genuine exception to visceroatrial concordance rule. 3. Associated cardiac malpositions were variable and complex with a tendency of high association of transposition and double outlet varieties with dextrocardia in situs solitus and levocardia in situs inversus. Only one in 6 cases of dextrocardia with situs inversus had pure transposition. 4. In two cases associated pulmonary atresia was found at surgery which was not predicted by angiocardiography. 5. Because many of the associated complex lesions can be corrected surgically provided the diagnosis is accurate, the selective biplane angiocardiography with or without cineradiography is essential.

  5. Effects of clenbuterol on contractility and Ca2+ homeostasis of isolated rat ventricular myocytes.

    Science.gov (United States)

    Siedlecka, U; Arora, M; Kolettis, T; Soppa, G K R; Lee, J; Stagg, M A; Harding, S E; Yacoub, M H; Terracciano, C M N

    2008-11-01

    Clenbuterol, a compound classified as a beta2-adrenoceptor (AR) agonist, has been employed in combination with left ventricular assist devices (LVADs) to treat patients with severe heart failure. Previous studies have shown that chronic administration of clenbuterol affects cardiac excitation-contraction coupling. However, the acute effects of clenbuterol and the signaling pathway involved remain undefined. We investigated the acute effects of clenbuterol on isolated ventricular myocyte sarcomere shortening, Ca2+ transients, and L-type Ca2+ current and compared these effects to two other clinically used beta2-AR agonists: fenoterol and salbutamol. Clenbuterol (30 microM) produced a negative inotropic response, whereas fenoterol showed a positive inotropic response. Salbutamol had no significant effects. Clenbuterol reduced Ca2+ transient amplitude and L-type Ca2+ current. Selective beta1-AR blockade did not affect the action of clenbuterol on sarcomere shortening but significantly reduced contractility in the presence of fenoterol and salbutamol (P clenbuterol. In addition, overexpression of inhibitory G protein (Gi) by adenoviral transfection induced a stronger clenbuterol-mediated negative inotropic effect, suggesting the involvement of the Gi protein. We conclude that clenbuterol does not increase and, at high concentrations, significantly depresses contractility of isolated ventricular myocytes, an effect not seen with fenoterol or salbutamol. In its negative inotropism, clenbuterol predominantly acts through Gi, and the consequent downstream signaling pathways activation may explain the beneficial effects observed during chronic administration of clenbuterol in patients treated with LVADs.

  6. Sustained exposure to catecholamines affects cAMP/PKA compartmentalised signalling in adult rat ventricular myocytes.

    Science.gov (United States)

    Fields, Laura A; Koschinski, Andreas; Zaccolo, Manuela

    2016-07-01

    In the heart compartmentalisation of cAMP/protein kinase A (PKA) signalling is necessary to achieve a specific functional outcome in response to different hormonal stimuli. Chronic exposure to catecholamines is known to be detrimental to the heart and disrupted compartmentalisation of cAMP signalling has been associated to heart disease. However, in most cases it remains unclear whether altered local cAMP signalling is an adaptive response, a consequence of the disease or whether it contributes to the pathogenetic process. We have previously demonstrated that isoforms of PKA expressed in cardiac myocytes, PKA-I and PKA-II, localise to different subcellular compartments and are selectively activated by spatially confined pools of cAMP, resulting in phosphorylation of distinct downstream targets. Here we investigate cAMP signalling in an in vitro model of hypertrophy in primary adult rat ventricular myocytes. By using a real time imaging approach and targeted reporters we find that that sustained exposure to catecholamines can directly affect cAMP/PKA compartmentalisation. This appears to involve a complex mechanism including both changes in the subcellular localisation of individual phosphodiesterase (PDE) isoforms as well as the relocalisation of PKA isoforms. As a result, the preferential coupling of PKA subsets with different PDEs is altered resulting in a significant difference in the level of cAMP the kinase is exposed to, with potential impact on phosphorylation of downstream targets. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  7. Immune modulation of cardiac repair and regeneration: the art of mending broken hearts

    Directory of Open Access Journals (Sweden)

    Ivana Zlatanova

    2016-10-01

    Full Text Available The accumulation of immune cells is amongst the earliest responses that manifest in the cardiac tissue after injury. Both innate and adaptive immunity coordinate distinct and mutually non-exclusive events governing cardiac repair including elimination of the cellular debris, compensatory growth of the remaining cardiac tissue, activation of resident or circulating precursor cells, quantitative and qualitative modifications of the vascular network and formation of a fibrotic scar. The present review summarizes the mounting evidence suggesting that the inflammatory response also guides the regenerative process following cardiac damage. In particular, recent literature has reinforced the central role of monocytes/macrophages in poising the refreshment of cardiomyocytes in myocardial infarction- or apical resection-induced cardiac insult. Macrophages dictate cardiac myocyte renewal through stimulation of pre-existing cardiomyocyte proliferation and/or neovascularization. Nevertheless, substantial efforts are required to identify the nature of these macrophage-derived factors as well as the molecular mechanisms engendered by the distinct subsets of macrophages pertaining in the cardiac tissue. Among the growing inflammatory intermediaries that have been recognized as essential player in heart regeneration, we will focus on the role of interleukin-6 and interleukin-13. Finally, it is likely that within the mayhem of the injured cardiac tissue, additional types of inflammatory cells, such as neutrophils, will enter the dance to ignite and refresh the broken heart. However, the protective and detrimental inflammatory pathways have been mainly deciphered in animal models. Future research should be focused on understanding the cellular effectors and molecular signals regulating inflammation in human heart to pave the way for the development of factual therapies targeting the inflammatory compartment in cardiac diseases.

  8. Larger late sodium current density as well as greater sensitivities to ATX II and ranolazine in rabbit left atrial than left ventricular myocytes.

    Science.gov (United States)

    Luo, Antao; Ma, Jihua; Song, Yejia; Qian, Chunping; Wu, Ying; Zhang, Peihua; Wang, Leilei; Fu, Chen; Cao, Zhenzhen; Shryock, John C

    2014-02-01

    An increase of cardiac late sodium current (INa.L) is arrhythmogenic in atrial and ventricular tissues, but the densities of INa.L and thus the potential relative contributions of this current to sodium ion (Na(+)) influx and arrhythmogenesis in atria and ventricles are unclear. In this study, whole-cell and cell-attached patch-clamp techniques were used to measure INa.L in rabbit left atrial and ventricular myocytes under identical conditions. The density of INa.L was 67% greater in left atrial (0.50 ± 0.09 pA/pF, n = 20) than in left ventricular cells (0.30 ± 0.07 pA/pF, n = 27, P ATX II) increased INa.L with an EC50 value of 14 ± 2 nM and a Hill slope of 1.4 ± 0.1 (n = 9) in atrial myocytes and with an EC50 of 21 ± 5 nM and a Hill slope of 1.2 ± 0.1 (n = 12) in ventricular myocytes. Na(+) channel open probability (but not mean open time) was greater in atrial than in ventricular cells in the absence and presence of ATX II. The INa.L inhibitor ranolazine (3, 6, and 9 μM) reduced INa.L more in atrial than ventricular myocytes in the presence of 40 nM ATX II. In summary, rabbit left atrial myocytes have a greater density of INa.L and higher sensitivities to ATX II and ranolazine than rabbit left ventricular myocytes.

  9. Circulating interleukin-1β promotes endoplasmic reticulum stress-induced myocytes apoptosis in diabetic cardiomyopathy via interleukin-1 receptor-associated kinase-2.

    Science.gov (United States)

    Liu, Zhongwei; Zhao, Na; Zhu, Huolan; Zhu, Shunming; Pan, Shuo; Xu, Jing; Zhang, Xuejun; Zhang, Yong; Wang, Junkui

    2015-09-23

    IL-1β was considered as an important inflammatory cytokine in diabetic cardiovascular complications. DCM is one of the major manifestations of diabetic cardiovascular complications whose specific mechanisms are still unclear. In this study, we investigated the role of IL-1β in myocytes apoptosis in DCM. In the in vitro study, high- glucose medium and/or IL-1β were used to incubate the isolated primary myocytes. siRNA was used to knockdown the irak2 gene expression. Apoptosis was evaluated by Hoechst and TUNEL staining. In the in vivo study, DCM in rats was induced by STZ injection and confirmed by cardiac hemodynamic determinations. The IL-1 receptor antagonist, IL-1Ra was also used to treat DCM rats. Myocardial apoptosis was assessed by TUNEL assay. In both in vitro and in vivo studies, expression levels of GRP-78, IRAK-2 and CHOP were analyzed by Western Blotting. ELISA was employed to exam the IL-1β content in serum and cell supernatants. Myocytes were not identified as the source of IL-1β secretion under high- glucose incubation. High glucose incubation and/or IL-1β incubation elevated ER- stress mediated myocytes apoptosis which was attenuated by irak2 silencing. Dramatically increased circulating and myocardial IL-1β levels were found in DCM rats which stimulated activation of ER stress and lead to elevated myocytes apoptosis. The administration of IL-1Ra, however, attenuated IRAK2/CHOP induced apoptosis without affecting fasting blood glucose concentration. Elevated circulating IL-1β contributed to promote ER stress- induced myocytes apoptosis by affecting IRAK-2/CHOP pathway in DCM.

  10. IGF-1 induces skeletal myocyte hypertrophy through calcineurin in association with GATA-2 and NF-ATc1

    Science.gov (United States)

    Musaro, A.; McCullagh, K. J.; Naya, F. J.; Olson, E. N.; Rosenthal, N.

    1999-01-01

    Localized synthesis of insulin-like growth factors (IGFs) has been broadly implicated in skeletal muscle growth, hypertrophy and regeneration. Virally delivered IGF-1 genes induce local skeletal muscle hypertrophy and attenuate age-related skeletal muscle atrophy, restoring and improving muscle mass and strength in mice. Here we show that the molecular pathways underlying the hypertrophic action of IGF-1 in skeletal muscle are similar to those responsible for cardiac hypertrophy. Transfected IGF-1 gene expression in postmitotic skeletal myocytes activates calcineurin-mediated calcium signalling by inducing calcineurin transcripts and nuclear localization of calcineurin protein. Expression of activated calcineurin mimics the effects of IGF-1, whereas expression of a dominant-negative calcineurin mutant or addition of cyclosporin, a calcineurin inhibitor, represses myocyte differentiation and hypertrophy. Either IGF-1 or activated calcineurin induces expression of the transcription factor GATA-2, which accumulates in a subset of myocyte nuclei, where it associates with calcineurin and a specific dephosphorylated isoform of the transcription factor NF-ATc1. Thus, IGF-1 induces calcineurin-mediated signalling and activation of GATA-2, a marker of skeletal muscle hypertrophy, which cooperates with selected NF-ATc isoforms to activate gene expression programs.

  11. Protective effect of piperine on electrophysiology abnormalities of left atrial myocytes induced by hydrogen peroxide in rabbits.

    Science.gov (United States)

    Liu, Yan; Zhang, Yu; Lin, Kun; Zhang, De-Xian; Tian, Miao; Guo, Hong-Yang; Wang, Yu-Tang; Li, Yang; Shan, Zhao-Liang

    2014-01-17

    Piperine had protective effects on oxidative stress damage of ventricular myocytes by hydrogen peroxide (H2O2). In this study we aimed to explore the protective effect of piperine on abnormalities of the cardiac action potential (AP) and several ion currents induced by hydrogen peroxide (H2O2) in single rabbit left atrial myocyte. Conventional microelectrodes were used to record action potential duration (APD), resting membrane potential (RMP) and some ion currents (ICa,L,Ito,IK1 and Ikur,ect.), before and after H2O2 administration with or without piperine. The piperine (7 μmol/L) had no significant effect on APD, ICa,L,Ito,IK1 and Ikur and their channel dynamics. In the presence of 50 μmol/L H2O2, APD50 and APD90 shortened (PPiperine (7 μmol/L) significantly alleviated the inhibiting effect of H2O2 on APD and ICa,L (PPiperine (7 μmol/L) significantly alleviated the inhibiting effect of H2O2 on Ito (Ppiperine protected the changes of Ito dynamics induced by H2O2. The peak current of IK1 and IKUr was significantly reduced (PPiperine (7 μmol/L) alleviated the inhibiting effect of H2O2 on IK1 and IKUr significantly (Ppiperine protected the changes of IKUr dynamics induced by H2O2. These results suggest that piperine effectively protects atrial myocytes from oxidative stress injury in atrial electrophysiology. © 2013.

  12. Regulatory effect of connexin 43 on basal Ca2+ signaling in rat ventricular myocytes.

    Directory of Open Access Journals (Sweden)

    Chen Li

    Full Text Available BACKGROUND: It has been found that gap junction-associated intracellular Ca(2+ [Ca(2+](i disturbance contributes to the arrhythmogenesis and hyperconstriction in diseased heart. However, whether functional gaps are also involved in the regulation of normal Ca(2+ signaling, in particular the basal [Ca(2+](i activities, is unclear. METHODS AND RESULTS: Global and local Ca(2+ signaling and gap permeability were monitored in cultured neonatal rat ventricular myocytes (NRVMs and freshly isolated mouse ventricular myocytes by Fluo4/AM and Lucifer yellow (LY, respectively. The results showed that inhibition of gap communication by heptanol, Gap 27 and flufenamic acid or interference of connexin 43 (Cx43 with siRNA led to a significant suppression of LY uptake and, importantly, attenuations of global Ca(2+ transients and local Ca(2+ sparks in monolayer NRVMs and Ca(2+ sparks in adult ventricular myocytes. In contrast, overexpression of rat-Cx43 in NRVMs induced enhancements in the above measurements, and so did in HEK293 cells expressing rat Cx43. Additionally, membrane-permeable inositol 1,4,5-trisphosphate (IP(3 butyryloxymethyl ester and phenylephrine, an agonist of adrenergic receptor, could relieve the inhibited Ca(2+ signal and LY uptake by gap uncouplers, whereas blockade of IP(3 receptor with xestospongin C or 2-aminoethoxydiphenylborate mimicked the effects of gap inhibitors. More importantly, all these gap-associated effects on Ca(2+ signaling were also found in single NRVMs that only have hemichannels instead of gap junctions. Further immunostaining/immunoblotting single myocytes with antibody against Cx43 demonstrated apparent increases in membrane labeling of Cx43 and non-junctional Cx43 in overexpressed cells, suggesting functional hemichannels exist and also contribute to the Ca(2+ signaling regulation in cardiomyocytes. CONCLUSIONS: These data demonstrate that Cx43-associated gap coupling plays a role in the regulation of resting Ca(2

  13. Cardiac overexpression of Mammalian enabled (Mena) exacerbates heart failure in mice

    OpenAIRE

    Belmonte, Stephen L.; Ram, Rashmi; Mickelsen, Deanne M.; Gertler, Frank B.; Blaxall, Burns C.

    2013-01-01

    Mammalian enabled (Mena) is a key regulator of cytoskeletal actin dynamics, which has been implicated in heart failure (HF). We have previously demonstrated that cardiac Mena deletion produced cardiac dysfunction with conduction abnormalities and hypertrophy. Moreover, elevated Mena expression correlates with HF in human and animal models, yet the precise role of Mena in cardiac pathophysiology is unclear. In these studies, we evaluated mice with cardiac myocyte-specific Mena overexpression (...

  14. G protein-coupled receptor kinase 2 promotes cardiac hypertrophy

    Science.gov (United States)

    Tscheschner, Henrike; Gao, Erhe; Schumacher, Sarah M.; Yuan, Ancai; Backs, Johannes; Most, Patrick; Wieland, Thomas; Koch, Walter J.; Katus, Hugo A.; Raake, Philip W.

    2017-01-01

    The increase in protein activity and upregulation of G-protein coupled receptor kinase 2 (GRK2) is a hallmark of cardiac stress and heart failure. Inhibition of GRK2 improved cardiac function and survival and diminished cardiac remodeling in various animal heart failure models. The aim of the present study was to investigate the effects of GRK2 on cardiac hypertrophy and dissect potential molecular mechanisms. In mice we observed increased GRK2 mRNA and protein levels following transverse aortic constriction (TAC). Conditional GRK2 knockout mice showed attenuated hypertrophic response with preserved ventricular geometry 6 weeks after TAC operation compared to wild-type animals. In isolated neonatal rat ventricular cardiac myocytes stimulation with angiotensin II and phenylephrine enhanced GRK2 expression leading to enhanced signaling via protein kinase B (PKB or Akt), consecutively inhibiting glycogen synthase kinase 3 beta (GSK3β), such promoting nuclear accumulation and activation of nuclear factor of activated T-cells (NFAT). Cardiac myocyte hypertrophy induced by in vitro GRK2 overexpression increased the cytosolic interaction of GRK2 and phosphoinositide 3-kinase γ (PI3Kγ). Moreover, inhibition of PI3Kγ as well as GRK2 knock down prevented Akt activation resulting in halted NFAT activity and reduced cardiac myocyte hypertrophy. Our data show that enhanced GRK2 expression triggers cardiac hypertrophy by GRK2-PI3Kγ mediated Akt phosphorylation and subsequent inactivation of GSK3β, resulting in enhanced NFAT activity. PMID:28759639

  15. Contribution of mineralocorticoid and glucocorticoid receptors to the chronotropic and hypertrophic actions of aldosterone in neonatal rat ventricular myocytes.

    Science.gov (United States)

    Rossier, Michel F; Python, Magaly; Maturana, Andrés D

    2010-06-01

    Mineralocorticoids and glucocorticoids have been involved in the genesis of ventricular arrhythmias associated with pathological heart hypertrophy. We previously observed, using isolated neonate rat ventricular cardiomyocytes, that both aldosterone (Aldo) and corticosterone induced in vitro a marked acceleration of the spontaneous contractions of these cells, a phenomenon dependent on the expression of the low threshold T-type calcium channels. Because both mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) mediated the chronotropic response to corticosteroids, we characterized the role of each receptor using spironolactone and mifepristone (RU-486) as specific antagonists. We first observed that GR antagonism, but not MR antagonism, completely disrupted the significant correlation existing between the level of T channel mRNA and the beating frequency; this difference could not be explained by a specific regulation of channel expression or activity by one of the receptors. Moreover, the chronotropic action of Aldo was additive to that of forskolin, a direct activator of the cAMP pathway. This additive response was selectively abolished upon GR inhibition. Finally, myocyte hypertrophy induced in vitro by Aldo was completely prevented by GR antagonism, whereas spironolactone had only a marginal effect. These results suggest that, in isolated rat ventricular cardiomyocytes, the activation of both MR and GR is necessary for a complete electrical remodeling and a maximal chronotropic response to corticosteroids. However, GR alone appears involved in the sensitization of the cells to the chronotropic regulation through the cAMP pathway and in the hypertrophic response to steroids. These observations have therapeutic implications given the fact that MR becomes a major target of pharmacological drugs in the clinical practice for preventing cardiac function decompensation and evolution toward heart failure and lethal arrhythmias.

  16. Basal late sodium current is a significant contributor to the duration of action potential of guinea pig ventricular myocytes.

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    Song, Yejia; Belardinelli, Luiz

    2017-05-01

    In cardiac myocytes, an enhancement of late sodium current ( I N aL ) under pathological conditions is known to cause prolongation of action potential duration (APD). This study investigated the contribution of I N aL under basal, physiological conditions to the APD Whole-cell I N aL and the APD of ventricular myocytes isolated from healthy adult guinea pigs were measured at 36°C. The I N aL inhibitor GS967 or TTX was applied to block I N aL The amplitude of basal I N aL and the APD at 50% repolarization in myocytes stimulated at a frequency of 0.17 Hz were -0.24 ± 0.02 pA/pF and 229 ± 6 msec, respectively. GS967 (0.01-1  μ mol/L) concentration dependently reduced the basal I NaL by 18 ± 3-82 ± 4%. At the same concentrations, GS967 shortened the APD by 9 ± 2 to 25 ± 1%. Similarly, TTX at 0.1-10  μ mol/L decreased the basal I NaL by 13 ± 1-94 ± 1% and APD by 8 ± 1-31 ± 2%. There was a close correlation ( R 2  = 0.958) between the percentage inhibition of I N aL and the percentage shortening of APD caused by either GS967 or TTX MTSEA (methanethiosulfonate ethylammonium, 2 mmol/L), a Na V 1.5 channel blocker, reduced the I NaL by 90 ± 5%, suggesting that the Na V 1.5 channel isoform is the major contributor to the basal I NaL KN-93 (10  μ mol/L) and AIP (2  μ mol/L), blockers of CaMKII, moderately reduced the basal I NaL Thus, this study provides strong evidence that basal endogenous I NaL is a significant contributor to the APD of cardiac myocytes. In addition, the basal I NaL of guinea pig ventricular myocytes is mainly generated from Na V 1.5 channel isoform and is regulated by CaMKII. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

  17. Jamb and Jamc Are Essential for Vertebrate Myocyte Fusion

    Science.gov (United States)

    Powell, Gareth T.; Wright, Gavin J.

    2011-01-01

    Cellular fusion is required in the development of several tissues, including skeletal muscle. In vertebrates, this process is poorly understood and lacks an in vivo-validated cell surface heterophilic receptor pair that is necessary for fusion. Identification of essential cell surface interactions between fusing cells is an important step in elucidating the molecular mechanism of cellular fusion. We show here that the zebrafish orthologues of JAM-B and JAM-C receptors are essential for fusion of myocyte precursors to form syncytial muscle fibres. Both jamb and jamc are dynamically co-expressed in developing muscles and encode receptors that physically interact. Heritable mutations in either gene prevent myocyte fusion in vivo, resulting in an overabundance of mononuclear, but otherwise overtly normal, functional fast-twitch muscle fibres. Transplantation experiments show that the Jamb and Jamc receptors must interact between neighbouring cells (in trans) for fusion to occur. We also show that jamc is ectopically expressed in prdm1a mutant slow muscle precursors, which inappropriately fuse with other myocytes, suggesting that control of myocyte fusion through regulation of jamc expression has important implications for the growth and patterning of muscles. Our discovery of a receptor-ligand pair critical for fusion in vivo has important implications for understanding the molecular mechanisms responsible for myocyte fusion and its regulation in vertebrate myogenesis. PMID:22180726

  18. The evolutionary origin of bilaterian smooth and striated myocytes

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    Brunet, Thibaut; Fischer, Antje HL; Steinmetz, Patrick RH; Lauri, Antonella; Bertucci, Paola; Arendt, Detlev

    2016-01-01

    The dichotomy between smooth and striated myocytes is fundamental for bilaterian musculature, but its evolutionary origin is unsolved. In particular, interrelationships of visceral smooth muscles remain unclear. Absent in fly and nematode, they have not yet been characterized molecularly outside vertebrates. Here, we characterize expression profile, ultrastructure, contractility and innervation of the musculature in the marine annelid Platynereis dumerilii and identify smooth muscles around the midgut, hindgut and heart that resemble their vertebrate counterparts in molecular fingerprint, contraction speed and nervous control. Our data suggest that both visceral smooth and somatic striated myocytes were present in the protostome-deuterostome ancestor and that smooth myocytes later co-opted the striated contractile module repeatedly – for example, in vertebrate heart evolution. During these smooth-to-striated myocyte conversions, the core regulatory complex of transcription factors conveying myocyte identity remained unchanged, reflecting a general principle in cell type evolution. DOI: http://dx.doi.org/10.7554/eLife.19607.001 PMID:27906129

  19. Myomaker mediates fusion of fast myocytes in zebrafish embryos

    Energy Technology Data Exchange (ETDEWEB)

    Landemaine, Aurélie; Rescan, Pierre-Yves; Gabillard, Jean-Charles, E-mail: Jean-charles.gabillard@rennes.inra.fr

    2014-09-05

    Highlights: • Myomaker is transiently expressed in fast myocytes during embryonic myogenesis. • Myomaker is essential for fast myocyte fusion in zebrafish. • The function of myomaker is conserved among Teleostomi. - Abstract: Myomaker (also called Tmem8c), a new membrane activator of myocyte fusion was recently discovered in mice. Using whole mount in situ hybridization on zebrafish embryos at different stages of embryonic development, we show that myomaker is transiently expressed in fast myocytes forming the bulk of zebrafish myotome. Zebrafish embryos injected with morpholino targeted against myomaker were alive after yolk resorption and appeared morphologically normal, but they were unable to swim, even under effect of a tactile stimulation. Confocal observations showed a marked phenotype characterized by the persistence of mononucleated muscle cells in the fast myotome at developmental stages where these cells normally fuse to form multinucleated myotubes. This indicates that myomaker is essential for myocyte fusion in zebrafish. Thus, there is an evolutionary conservation of myomaker expression and function among Teleostomi.

  20. Allicin inhibits transient outward potassium currents in mouse ventricular myocytes.

    Science.gov (United States)

    Cao, Hong; Huang, Congxin; Wang, Xin

    2016-05-01

    Allicin is the active constituent of garlic, a widely used spice and food. The remedial properties of garlic have also been extensively researched and it has been demonstrated that allicin is able to inhibit the transient outward potassium current (I to ) in atrial myocytes. However, the direct effect of allicin on I to in ventricular myocytes has yet to be elucidated. In the present study, the effects of allicin on I to in ventricular myocytes isolated from mice were investigated, using the whole-cell patch recording technique. The results revealed that I to current was not significantly suppressed by allicin in the low-dose group (10 µmol/l; P>0.05). However, I to was significantly inhibited by higher doses of allicin (30, 100 and 300 µmol/l; Pallicin (≥100 µmol/l) was able to accelerate the voltage-dependent inactivation of I to in mouse ventricular myocytes. In conclusion, the present study revealed that allicin inhibited the I to in mouse ventricular myocytes, which may be the mechanism through which allicin exerts its antiarrhythmic effect.

  1. Cardiac current density distribution by electrical pulses from TASER devices.

    Science.gov (United States)

    Stratbucker, Robert A; Kroll, Mark W; McDaniel, Wayne; Panescu, Dorin

    2006-01-01

    TASERs deliver electrical pulses that can temporarily incapacitate subjects. The goal of this paper is to analyze the distribution of TASER currents in the heart and understand their chances of triggering cardiac arrhythmias. The models analyzed herein describe strength-duration thresholds for myocyte excitation and ventricular fibrillation induction. Finite element modeling is used to compute current density in the heart for worst-case TASER electrode placement. The model predicts a maximum TASER current density of 0.27 mA/cm(2) in the heart. It is conclude that the numerically simulated TASER current density in the heart is about half the threshold for myocytes excitation and more than 500 times lower than the threshold required for inducing ventricular fibrillation. Showing a substantial cardiac safety margin, TASER devices do not generate currents in the heart that are high enough to excite myocytes or trigger VF.

  2. Longstanding hyperthyroidism is associated with normal or enhanced intrinsic cardiomyocyte function despite decline in global cardiac function.

    Directory of Open Access Journals (Sweden)

    Nathan Y Weltman

    Full Text Available Thyroid hormones (THs play a pivotal role in cardiac homeostasis. TH imbalances alter cardiac performance and ultimately cause cardiac dysfunction. Although short-term hyperthyroidism typically leads to heightened left ventricular (LV contractility and improved hemodynamic parameters, chronic hyperthyroidism is associated with deleterious cardiac consequences including increased risk of arrhythmia, impaired cardiac reserve and exercise capacity, myocardial remodeling, and occasionally heart failure. To evaluate the long-term consequences of chronic hyperthyroidism on LV remodeling and function, we examined LV isolated myocyte function, chamber function, and whole tissue remodeling in a hamster model. Three-month-old F1b hamsters were randomized to control or 10 months TH treatment (0.1% grade I desiccated TH. LV chamber remodeling and function was assessed by echocardiography at 1, 2, 4, 6, 8, and 10 months of treatment. After 10 months, terminal cardiac function was assessed by echocardiography and LV hemodynamics. Hyperthyroid hamsters exhibited significant cardiac hypertrophy and deleterious cardiac remodeling characterized by myocyte lengthening, chamber dilatation, decreased relative wall thickness, increased wall stress, and increased LV interstitial fibrotic deposition. Importantly, hyperthyroid hamsters demonstrated significant LV systolic and diastolic dysfunction. Despite the aforementioned remodeling and global cardiac decline, individual isolated cardiac myocytes from chronically hyperthyroid hamsters had enhanced function when compared with myocytes from untreated age-matched controls. Thus, it appears that long-term hyperthyroidism may impair global LV function, at least in part by increasing interstitial ventricular fibrosis, in spite of normal or enhanced intrinsic cardiomyocyte function.

  3. Longstanding Hyperthyroidism Is Associated with Normal or Enhanced Intrinsic Cardiomyocyte Function despite Decline in Global Cardiac Function

    Science.gov (United States)

    Redetzke, Rebecca A.; Gerdes, A. Martin

    2012-01-01

    Thyroid hormones (THs) play a pivotal role in cardiac homeostasis. TH imbalances alter cardiac performance and ultimately cause cardiac dysfunction. Although short-term hyperthyroidism typically leads to heightened left ventricular (LV) contractility and improved hemodynamic parameters, chronic hyperthyroidism is associated with deleterious cardiac consequences including increased risk of arrhythmia, impaired cardiac reserve and exercise capacity, myocardial remodeling, and occasionally heart failure. To evaluate the long-term consequences of chronic hyperthyroidism on LV remodeling and function, we examined LV isolated myocyte function, chamber function, and whole tissue remodeling in a hamster model. Three-month-old F1b hamsters were randomized to control or 10 months TH treatment (0.1% grade I desiccated TH). LV chamber remodeling and function was assessed by echocardiography at 1, 2, 4, 6, 8, and 10 months of treatment. After 10 months, terminal cardiac function was assessed by echocardiography and LV hemodynamics. Hyperthyroid hamsters exhibited significant cardiac hypertrophy and deleterious cardiac remodeling characterized by myocyte lengthening, chamber dilatation, decreased relative wall thickness, increased wall stress, and increased LV interstitial fibrotic deposition. Importantly, hyperthyroid hamsters demonstrated significant LV systolic and diastolic dysfunction. Despite the aforementioned remodeling and global cardiac decline, individual isolated cardiac myocytes from chronically hyperthyroid hamsters had enhanced function when compared with myocytes from untreated age-matched controls. Thus, it appears that long-term hyperthyroidism may impair global LV function, at least in part by increasing interstitial ventricular fibrosis, in spite of normal or enhanced intrinsic cardiomyocyte function. PMID:23056390

  4. Myocyte necrosis underlies progressive myocardial dystrophy in mouse dsg2-related arrhythmogenic right ventricular cardiomyopathy.

    Science.gov (United States)

    Pilichou, Kalliopi; Remme, Carol Ann; Basso, Cristina; Campian, Maria E; Rizzo, Stefania; Barnett, Phil; Scicluna, Brendon P; Bauce, Barbara; van den Hoff, Maurice J B; de Bakker, Jacques M T; Tan, Hanno L; Valente, Marialuisa; Nava, Andrea; Wilde, Arthur A M; Moorman, Antoon F M; Thiene, Gaetano; Bezzina, Connie R

    2009-08-03

    Mutations in the cardiac desmosomal protein desmoglein-2 (DSG2) are associated with arrhythmogenic right ventricular cardiomyopathy (ARVC). We studied the explanted heart of a proband carrying the DSG2-N266S mutation as well as transgenic mice (Tg-NS) with cardiac overexpression of the mouse equivalent of this mutation, N271S-dsg2, with the aim of investigating the pathophysiological mechanisms involved. Transgenic mice recapitulated the clinical features of ARVC, including sudden death at young age, spontaneous ventricular arrhythmias, cardiac dysfunction, and biventricular dilatation and aneurysms. Investigation of transgenic lines with different levels of transgene expression attested to a dose-dependent dominant-negative effect of the mutation. We demonstrate for the first time that myocyte necrosis is the key initiator of myocardial injury, triggering progressive myocardial damage, including an inflammatory response and massive calcification within the myocardium, followed by injury repair with fibrous tissue replacement, and myocardial atrophy. These observations were supported by findings in the explanted heart from the patient. Insight into mechanisms initiating myocardial damage in ARVC is a prerequisite to the future development of new therapies aimed at delaying onset or progression of the disease.

  5. The Drosophila Transcription Factors Tinman and Pannier Activate and Collaborate with Myocyte Enhancer Factor-2 to Promote Heart Cell Fate.

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    TyAnna L Lovato

    Full Text Available Expression of the MADS domain transcription factor Myocyte Enhancer Factor 2 (MEF2 is regulated by numerous and overlapping enhancers which tightly control its transcription in the mesoderm. To understand how Mef2 expression is controlled in the heart, we identified a late stage Mef2 cardiac enhancer that is active in all heart cells beginning at stage 14 of embryonic development. This enhancer is regulated by the NK-homeodomain transcription factor Tinman, and the GATA transcription factor Pannier through both direct and indirect interactions with the enhancer. Since Tinman, Pannier and MEF2 are evolutionarily conserved from Drosophila to vertebrates, and since their vertebrate homologs can convert mouse fibroblast cells to cardiomyocytes in different activator cocktails, we tested whether over-expression of these three factors in vivo could ectopically activate known cardiac marker genes. We found that mesodermal over-expression of Tinman and Pannier resulted in approximately 20% of embryos with ectopic Hand and Sulphonylurea receptor (Sur expression. By adding MEF2 alongside Tinman and Pannier, a dramatic expansion in the expression of Hand and Sur was observed in almost all embryos analyzed. Two additional cardiac markers were also expanded in their expression. Our results demonstrate the ability to initiate ectopic cardiac fate in vivo by the combination of only three members of the conserved Drosophila cardiac transcription network, and provide an opportunity for this genetic model system to be used to dissect the mechanisms of cardiac specification.

  6. Alternans promotion in cardiac electrophysiology models by delay differential equations

    Science.gov (United States)

    Gomes, Johnny M.; dos Santos, Rodrigo Weber; Cherry, Elizabeth M.

    2017-09-01

    Cardiac electrical alternans is a state of alternation between long and short action potentials and is frequently associated with harmful cardiac conditions. Different dynamic mechanisms can give rise to alternans; however, many cardiac models based on ordinary differential equations are not able to reproduce this phenomenon. A previous study showed that alternans can be induced by the introduction of delay differential equations (DDEs) in the formulations of the ion channel gating variables of a canine myocyte model. The present work demonstrates that this technique is not model-specific by successfully promoting alternans using DDEs for five cardiac electrophysiology models that describe different types of myocytes, with varying degrees of complexity. By analyzing results across the different models, we observe two potential requirements for alternans promotion via DDEs for ionic gates: (i) the gate must have a significant influence on the action potential duration and (ii) a delay must significantly impair the gate's recovery between consecutive action potentials.

  7. Alternans promotion in cardiac electrophysiology models by delay differential equations.

    Science.gov (United States)

    Gomes, Johnny M; Dos Santos, Rodrigo Weber; Cherry, Elizabeth M

    2017-09-01

    Cardiac electrical alternans is a state of alternation between long and short action potentials and is frequently associated with harmful cardiac conditions. Different dynamic mechanisms can give rise to alternans; however, many cardiac models based on ordinary differential equations are not able to reproduce this phenomenon. A previous study showed that alternans can be induced by the introduction of delay differential equations (DDEs) in the formulations of the ion channel gating variables of a canine myocyte model. The present work demonstrates that this technique is not model-specific by successfully promoting alternans using DDEs for five cardiac electrophysiology models that describe different types of myocytes, with varying degrees of complexity. By analyzing results across the different models, we observe two potential requirements for alternans promotion via DDEs for ionic gates: (i) the gate must have a significant influence on the action potential duration and (ii) a delay must significantly impair the gate's recovery between consecutive action potentials.

  8. Cardiac mitochondria exhibit dynamic functional clustering

    Directory of Open Access Journals (Sweden)

    Felix Tobias Kurz

    2014-09-01

    Full Text Available Multi-oscillatory behavior of mitochondrial inner membrane potential ΔΨm in self-organized cardiac mitochondrial networks can be triggered by metabolic or oxidative stress. Spatio-temporal analyses of cardiac mitochondrial networks have shown that mitochondria are heterogeneously organized in synchronously oscillating clusters in which the mean cluster frequency and size are inversely correlated, thus suggesting a modulation of cluster frequency through local inter-mitochondrial coupling. In this study, we propose a method to examine the mitochondrial network's topology through quantification of its dynamic local clustering coefficients. Individual mitochondrial ΔΨm oscillation signals were identified for each cardiac myocyte and cross-correlated with all network mitochondria using previously described methods (Kurz et al., 2010. Time-varying inter-mitochondrial connectivity, defined for mitochondria in the whole network whose signals are at least 90% correlated at any given time point, allowed considering functional local clustering coefficients. It is shown that mitochondrial clustering in isolated cardiac myocytes changes dynamically and is significantly higher than for random mitochondrial networks that are constructed using the Erdös-Rényi model based on the same sets of vertices. The network's time-averaged clustering coefficient for cardiac myocytes was found to be 0.500 ± 0.051 (N=9 versus 0.061 ± 0.020 for random networks, respectively. Our results demonstrate that cardiac mitochondria constitute a network with dynamically connected constituents whose topological organization is prone to clustering. Cluster partitioning in networks of coupled oscillators has been observed in scale-free and chaotic systems and is therefore in good agreement with previous models of cardiac mitochondrial networks (Aon et al., 2008.

  9. Micromolded gelatin hydrogels for extended culture of engineered cardiac tissues.

    Science.gov (United States)

    McCain, Megan L; Agarwal, Ashutosh; Nesmith, Haley W; Nesmith, Alexander P; Parker, Kevin Kit

    2014-07-01

    Defining the chronic cardiotoxic effects of drugs during preclinical screening is hindered by the relatively short lifetime of functional cardiac tissues in vitro, which are traditionally cultured on synthetic materials that do not recapitulate the cardiac microenvironment. Because collagen is the primary extracellular matrix protein in the heart, we hypothesized that micromolded gelatin hydrogel substrates tuned to mimic the elastic modulus of the heart would extend the lifetime of engineered cardiac tissues by better matching the native chemical and mechanical microenvironment. To measure tissue stress, we used tape casting, micromolding, and laser engraving to fabricate gelatin hydrogel muscular thin film cantilevers. Neonatal rat cardiac myocytes adhered to gelatin hydrogels and formed aligned tissues as defined by the microgrooves. Cardiac tissues could be cultured for over three weeks without declines in contractile stress. Myocytes on gelatin had higher spare respiratory capacity compared to those on fibronectin-coated PDMS, suggesting that improved metabolic function could be contributing to extended culture lifetime. Lastly, human induced pluripotent stem cell-derived cardiac myocytes adhered to micromolded gelatin surfaces and formed aligned tissues that remained functional for four weeks, highlighting their potential for human-relevant chronic studies. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Anabolic steroids impair the exercise-induced growth of the cardiac capillary bed.

    Science.gov (United States)

    Tagarakis, C V; Bloch, W; Hartmann, G; Hollmann, W; Addicks, K

    2000-08-01

    Concomitant application of anabolic-androgenic steroids and physical exercise can induce cardiac hypertrophy. These experiments investigate the still unknown response of the cardiac myocytes and capillaries to the combined influence of various anabolic steroids and muscular exercise. Female SPF-NMRI mice were divided into the following groups: a) sedentary control, b) exercise (treadmill running); c) sedentary receiving Dianabol; d) exercise + Dianabol; e) exercise + Oral-Turinabol. After 3 and 6 weeks the left ventricular papillary muscles were studied morphometrically. Evaluated variables: minimal myocyte diameter, number of capillaries around a single myocyte, capillary density and intercapillary distance. Only the anabolic steroids + exercise groups showed a mild myocyte hypertrophy. In contrast, only exercise alone caused a significant increase of the capillary density after both experimental periods; e.g. capillary density after 6 weeks (capillaries/mm2, mean values +/- standard deviation, p Anabolic steroids combined with exercise: 1) induce mild hypertrophy of the cardiac myocytes, 2) impair the cardiac microvascular adaptation to physical conditioning. The microvascular impairment may cause a detrimental alteration of the myocardial oxygen supply, especially during muscular exercise.

  11. Regulation of the cardiac sodium pump.

    Science.gov (United States)

    Fuller, W; Tulloch, L B; Shattock, M J; Calaghan, S C; Howie, J; Wypijewski, K J

    2013-04-01

    In cardiac muscle, the sarcolemmal sodium/potassium ATPase is the principal quantitative means of active transport at the myocyte cell surface, and its activity is essential for maintaining the trans-sarcolemmal sodium gradient that drives ion exchange and transport processes that are critical for cardiac function. The 72-residue phosphoprotein phospholemman regulates the sodium pump in the heart: unphosphorylated phospholemman inhibits the pump, and phospholemman phosphorylation increases pump activity. Phospholemman is subject to a remarkable plethora of post-translational modifications for such a small protein: the combination of three phosphorylation sites, two palmitoylation sites, and one glutathionylation site means that phospholemman integrates multiple signaling events to control the cardiac sodium pump. Since misregulation of cytosolic sodium contributes to contractile and metabolic dysfunction during cardiac failure, a complete understanding of the mechanisms that control the cardiac sodium pump is vital. This review explores our current understanding of these mechanisms.

  12. Toll-like receptor 9 mediated responses in cardiac fibroblasts.

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    Ingrid Kristine Ohm

    Full Text Available Altered cardiac Toll-like receptor 9 (TLR9 signaling is important in several experimental cardiovascular disorders. These studies have predominantly focused on cardiac myocytes or the heart as a whole. Cardiac fibroblasts have recently been attributed increasing significance in mediating inflammatory signaling. However, putative TLR9-signaling through cardiac fibroblasts remains non-investigated. Thus, our aim was to explore TLR9-signaling in cardiac fibroblasts and investigate the consequence of such receptor activity on classical cardiac fibroblast cellular functions. Cultivated murine cardiac fibroblasts were stimulated with different TLR9 agonists (CpG A, B and C and assayed for the secretion of inflammatory cytokines (tumor necrosis factor α [TNFα], CXCL2 and interferon α/β. Expression of functional cardiac fibroblast TLR9 was proven as stimulation with CpG B and -C caused significant CXCL2 and TNFα-release. These responses were TLR9-specific as complete inhibition of receptor-stimulated responses was achieved by co-treatment with a TLR9-antagonist (ODN 2088 or chloroquine diphosphate. TLR9-stimulated responses were also found more potent in cardiac fibroblasts when compared with classical innate immune cells. Stimulation of cardiac fibroblasts TLR9 was also found to attenuate migration and proliferation, but did not influence myofibroblast differentiation in vitro. Finally, results from in vivo TLR9-stimulation with subsequent fractionation of specific cardiac cell-types (cardiac myocytes, CD45+ cells, CD31+ cells and cardiac fibroblast-enriched cell-fractions corroborated our in vitro data and provided evidence of differentiated cell-specific cardiac responses. Thus, we conclude that cardiac fibroblast may constitute a significant TLR9 responder cell within the myocardium and, further, that such receptor activity may impact important cardiac fibroblast cellular functions.

  13. Influence of infrasound exposure on the whole L-type calcium currents in rat ventricular myocytes.

    Science.gov (United States)

    Pei, Zhaohui; Zhuang, Zhiqiang; Xiao, Pingxi; Chen, Jingzao; Sang, Hanfei; Ren, Jun; Wu, Zhenbiao; Yan, Guangmei

    2009-06-01

    This study was designed to examine the effect of infrasound exposure (5 Hz at 130 dB) on whole-cell L-type Ca2+ currents (WLCC) in rat ventricular myocytes and the underlying mechanism(s) involved. Thirty-two adult Sprague-Dawley rats were randomly assigned to infrasound exposure and control groups. [Ca2+](i), WLCC, mRNA expression of the a(1c) subunit of L-type Ca2+ channels (LCC), and SERCA2 protein were examined on day 1, 7, and 14 after initiation of infrasound exposure. Fluo-3/AM fluorescence and the laser scanning confocal microscope techniques were used to measure [Ca2+](i) in freshly isolated ventricular myocytes. The Ca2+ fluorescence intensity (FI), denoting [Ca2+](i) in cardiomyocytes, was significantly elevated in a time-dependent manner in the exposure groups. There was a significant increase in WLCC in the 1-day group and a further significant increase in the 7- and 14-day groups. LCC mRNA expression measured by RT-PCR revealed a significant rise in the 1-day group and a significant additional rise in the 7- and 14-day groups compared with control group. SERCA2 expression was significantly upregulated in the 1-day group followed by an overt decrease in the 7- and 14-day groups. Prolonged exposure of infrasound altered WLCC in rat cardiomyocytes by shifting the steady-state inactivation curves to the right (more depolarized direction) without altering the slope and biophysical properties of I (Ca,L). Taken together, our data suggest that changes in [Ca2+](I) levels as well as expression of LCC and SERCA2 may contribute to the infrasound exposure-elicited cardiac response.

  14. Comprehensive analyses of ventricular myocyte models identify targets exhibiting favorable rate dependence.

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    Megan A Cummins

    2014-03-01

    Full Text Available Reverse rate dependence is a problematic property of antiarrhythmic drugs that prolong the cardiac action potential (AP. The prolongation caused by reverse rate dependent agents is greater at slow heart rates, resulting in both reduced arrhythmia suppression at fast rates and increased arrhythmia risk at slow rates. The opposite property, forward rate dependence, would theoretically overcome these parallel problems, yet forward rate dependent (FRD antiarrhythmics remain elusive. Moreover, there is evidence that reverse rate dependence is an intrinsic property of perturbations to the AP. We have addressed the possibility of forward rate dependence by performing a comprehensive analysis of 13 ventricular myocyte models. By simulating populations of myocytes with varying properties and analyzing population results statistically, we simultaneously predicted the rate-dependent effects of changes in multiple model parameters. An average of 40 parameters were tested in each model, and effects on AP duration were assessed at slow (0.2 Hz and fast (2 Hz rates. The analysis identified a variety of FRD ionic current perturbations and generated specific predictions regarding their mechanisms. For instance, an increase in L-type calcium current is FRD when this is accompanied by indirect, rate-dependent changes in slow delayed rectifier potassium current. A comparison of predictions across models identified inward rectifier potassium current and the sodium-potassium pump as the two targets most likely to produce FRD AP prolongation. Finally, a statistical analysis of results from the 13 models demonstrated that models displaying minimal rate-dependent changes in AP shape have little capacity for FRD perturbations, whereas models with large shape changes have considerable FRD potential. This can explain differences between species and between ventricular cell types. Overall, this study provides new insights, both specific and general, into the determinants of

  15. Role of the T-type calcium channel CaV3.2 in the chronotropic action of corticosteroids in isolated rat ventricular myocytes.

    Science.gov (United States)

    Maturana, Andrés; Lenglet, Sébastien; Python, Magaly; Kuroda, Shun'ichi; Rossier, Michel F

    2009-08-01

    The mineralocorticoid receptor is involved in the development of several cardiac dysfunctions, including lethal ventricular arrhythmias associated with heart failure or hyperaldosteronism, but the molecular mechanisms responsible for these effects remain to be clarified. Reexpression of low voltage-activated T-type calcium channels in ventricular myocytes together with other fetal genes during cardiac pathologies could confer automaticity to these cells and would represent a pro-arrhythmogenic condition if occurring in vivo. In the present study, we demonstrated that in isolated neonatal rat ventricular myocytes, corticosteroids selectively induced the expression of a particular isoform of T channel, Ca(V)3.2/alpha1H. This response was accompanied by an increase of the Ca(V)3.2 T-type current, identified with the patch clamp technique by its sensitivity to nickel, and a concomitant acceleration of the myocyte spontaneous contractions. Silencing Ca(V)3.2 expression markedly reduced the chronotropic response to steroids. Moreover, modulation of the frequency of cell contractions by different redox agents was independent of channel expression but involved a direct regulation of channel activity. Although oxidants increased both Ca(V)3.2 current amplitude and beating frequency, they decreased L-type channel activity. Reducing agents had the opposite effect on these parameters. In conclusion, the acceleration of ventricular myocyte spontaneous contractions induced by corticosteroids in vitro appears dependent on the expression of the Ca(V)3.2 T channel isoform and modulated by the redox potential of the cells. These results provide a molecular model that could explain the high incidence of arrhythmias observed in patients upon combination of inappropriate activation of the mineralocorticoid receptor and oxidative stress.

  16. Reduced contraction and altered frequency response of isolated ventricular myocytes from patients with heart failure.

    Science.gov (United States)

    Davies, C H; Davia, K; Bennett, J G; Pepper, J R; Poole-Wilson, P A; Harding, S E

    1995-11-01

    Previous work has failed to demonstrate reduced maximal contraction of isolated ventricular myocytes from failing human hearts compared with nonfailing control hearts. The effect of alterations in stimulation frequency and temperature on the contraction of isolated ventricular myocytes has been investigated. Left ventricular myocytes were isolated from the hearts of patients with severe heart failure undergoing heart transplantation and compared with myocytes isolated from myocardial biopsies from patients with coronary disease but preserved left ventricular systolic function or from myocytes from rejected donor hearts. Myocytes were exposed to either a maximally activating level of extracellular calcium at 37 degrees C or to 2 mmol/L calcium at 32 degrees C. There was no significant difference in the contraction amplitude between myocytes from failing and nonfailing hearts at 0.2 Hz. With increasing stimulation frequency, there was a reduction in contraction amplitude in cells from failing hearts relative to control hearts in both maximal calcium from 0.33 Hz (4.5% versus 6.6%) to 1.4 Hz (3.9% versus 8.8%) (ANCOVA, P contraction and the times to 50% and 90% relaxation were prolonged in myocytes from failing hearts at stimulation rate of 0.2 Hz (P contraction, slowed relaxation, and impaired frequency response occurring at the level of the individual ventricular myocyte can be demonstrated in human heart failure. This demonstrates that disruption of myocyte function can contribute to both the systolic and the diastolic abnormalities that occur in the failing human heart.

  17. Inflammation and cardiac dysfunction during sepsis, muscular dystrophy, and myocarditis

    Directory of Open Access Journals (Sweden)

    Ying Li

    2013-12-01

    Full Text Available Inflammation plays an important role in cardiac dysfunction under different situations. Acute systemic inflammation occurring in patients with severe burns, trauma, and inflammatory diseases causes cardiac dysfunction, which is one of the leading causes of mortality in these patients. Acute sepsis decreases cardiac contractility and impairs myocardial compliance. Chronic inflammation such as that occurring in Duchenne muscular dystropshy and myocarditis may cause adverse cardiac remodeling including myocyte hypertrophy and death, fibrosis, and altered myocyte function. However, the underlying cellular and molecular mechanisms for inflammatory cardiomyopathy are still controversial probably due to multiple factors involved. Potential mechanisms include the change in circulating blood volume; a direct inhibition of myocyte contractility by cytokines (tumor necrosis factor (TNF-a, interleukin (IL-1b; abnormal nitric oxide and reactive oxygen species (ROS signaling; mitochondrial dysfunction; abnormal excitation-contraction coupling; and reduced calcium sensitivity at the myofibrillar level and blunted b-adrenergic signaling. This review will summarize recent advances in diagnostic technology, mechanisms, and potential therapeutic strategies for inflammation-induced cardiac dysfunction.

  18. Omentin functions to attenuate cardiac hypertrophic response.

    Science.gov (United States)

    Matsuo, Kazuhiro; Shibata, Rei; Ohashi, Koji; Kambara, Takahiro; Uemura, Yusuke; Hiramatsu-Ito, Mizuho; Enomoto, Takashi; Yuasa, Daisuke; Joki, Yusuke; Ito, Masanori; Hayakawa, Satoko; Ogawa, Hayato; Kihara, Shinji; Murohara, Toyoaki; Ouchi, Noriyuki

    2015-02-01

    Cardiac hypertrophy occurs in many obesity-related conditions. Omentin is an adipose-derived plasma protein that is downregulated under obese conditions. Here, we investigated whether omentin modulates cardiac hypertrophic responses in vivo and in vitro. Systemic administration of an adenoviral vector expressing human omentin (Ad-OMT) to wild-type (WT) mice led to the attenuation of cardiac hypertrophy, fibrosis and ERK phosphorylation induced by transverse aortic constriction (TAC) or angiotensin II infusion. In cultured cardiomyocytes, stimulation with phenylephrine (PE) led to an increase in myocyte size, which was prevented by pretreatment with human omentin protein. Pretreatment of cardiomyocytes with omentin protein also reduced ERK phosphorylation in response to PE stimulation. Ad-OMT enhanced phosphorylation of AMP-activated protein kinase (AMPK) in the heart of WT mice after TAC operation. Blockade of AMPK activation by transduction with dominant-negative mutant forms of AMPK reversed the inhibitory effect of omentin on myocyte hypertrophy and ERK phosphorylation following PE stimulation. Moreover, fat-specific transgenic mice expressing human omentin showed reduced cardiac hypertrophy and ERK phosphorylation following TAC surgery compared to littermate controls. These data suggest that omentin functions to attenuate the pathological process of myocardial hypertrophy via the activation of AMPK in the heart, suggesting that omentin may represent a target molecule for the treatment of cardiac hypertrophy. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Urocortin2 prolongs action potential duration and modulates potassium currents in guinea pig myocytes and HEK293 cells.

    Science.gov (United States)

    Yang, Li-Zhen; Zhu, Yi-Chun

    2015-07-05

    We previously reported that activation of corticotropin releasing factor receptor type 2 by urocortin2 up-regulates both L-type Ca(2+) channels and intracellular Ca(2+) concentration in ventricular myocytes and plays an important role in cardiac contractility and arrhythmogenesis. This study goal was to further test the hypothesis that urocortin2 may modulate action potentials as well as rapidly and slowly activating delayed rectifier potassium currents. With whole cell patch-clamp techniques, action potentials and slowly activating delayed rectifier potassium currents were recorded in isolated guinea pig ventricular myocytes, respectively. And rapidly activating delayed rectifier potassium currents were tested in hERG-HEK293 cells. Urocortin2 produced a time- and concentration-dependent prolongation of action potential duration. The EC50 values of action potential duration and action potential duration at 90% of repolarization were 14.73 and 24.3nM respectively. The prolongation of action potential duration of urocortin2 was almost completely or partly abolished by H-89 (protein kinase A inhibitor) or KB-R7943 (Na(+)/Ca(2+) exchange inhibitor) pretreatment respectively. And urocortin2 caused reduction of rapidly activating delayed rectifier potassium currents in hERG-HEK293 cells. In addition, urocortin2 slowed the rate of slowly activating delayed rectifier potassium channel activation, and rightward shifted the threshold of slowly activating delayed rectifier potassium currents to more positive potentials. Urocortin2 prolonged action potential duration via activation of protein kinase A and Na(+)/ Ca(2+) exchange in isolated guinea pig ventricular myocytes in a time- and concentration- dependent manner. In hERG-HEK293 cells, urocortin2 reduced rapidly activating delayed rectifier potassium current density which may contribute to action potential duration prolongation. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Differentiated vascular myocytes: are they involved in neointimal formation?

    OpenAIRE

    Holifield, B; Helgason, T; Jemelka, S; Taylor, A; Navran, S; Allen, J; Seidel, C

    1996-01-01

    The role of differentiated vascular myocytes are neointimal formation in canine carotid artery was investigated. Using antibodies and cDNA probes, cells were characterized in situ and after isolation. In situ characterization indicated the majority of medial cells expressed both smooth muscle myosin and alpha actin but many cells were negative to these markers. All adventitial cells were negative for these proteins. The muscle protein-positive cells were designated differentiated, vascular my...

  1. Electrophysiological effects of Chinese medicine Shen song Yang xin (SSYX) on Chinese miniature swine heart and isolated guinea pig ventricular myocytes.

    Science.gov (United States)

    Feng, Li; Gong, Jing; Jin, Zhen-yi; Li, Ning; Sun, Li-ping; Wu, Yi-ling; Pu, Jie-lin

    2009-07-05

    Shen song Yang xin (SSYX) is a compound of Chinese medicine with the effect of increasing heart rate (HR). This study aimed to evaluate its electrophysiological properties at heart and cellular levels. The Chinese miniature swines were randomly assigned to two groups, administered with SSYX or placebo for 4 weeks (n = 8 per group). Cardiac electrophysiological study (EPS) was performed before and after drug administration. The guinea pig ventricular myocytes were enzymatically isolated and whole cell voltage-clamp technique was used to evaluate the effect of SSYX on cardiac action potential (AP). SSYX treatment accelerated the HR from (141.8 +/- 36.0) beats per minute to (163.0 +/- 38.0) beats per minute (P = 0.013) without changing the other parameters in surface electrocardiogram. After blockage of the autonomic nervous system with metoprolol and atropin, SSYX had no effect on intrinsic HR (IHR), but decreased corrected sinus node recovery time (CSNRT) and sinus atrium conducting time (SACT). Intra cardiac EPS showed that SSYX significantly decreased the A-H and A-V intervals as well as shortened the atrial (A), atrioventricular node (AVN) and ventricular (V) effective refractory period (ERP). In isolated guinea pig ventricular myocytes, the most obvious effect of SSYX on action potential was a shortening of the action potential duration (APD) without change in shape of action potential. The shortening rates of APD(30), APD(50) and APD(90) were 19.5%, 17.8% and 15.3%, respectively. The resting potential (Em) and the interval between the end of APD(30) and APD(90) did not significantly change. The present study demonstrates that SSYX increases the HR and enhances the conducting capacity of the heart in the condition of the intact autonomic nervous system. SSYX homogenously decreases the ERP of the heart and shortens the APD of the myocytes, suggesting its antiarrhythmic effect without proarrhythmia.

  2. Myocyte performance during evolution of myocardial infarction in rats: effects of propionyl-L-carnitine.

    Science.gov (United States)

    Li, P; Park, C; Micheletti, R; Li, B; Cheng, W; Sonnenblick, E H; Anversa, P; Bianchi, G

    1995-04-01

    To determine whether alterations in the mechanical properties and calcium transients of myocytes are important factors in the evolution of the postinfarcted heart, these physiological parameters were measured in the viable muscle cells of the left ventricle 6 h, 2-3 days, 1 wk, and 1 mo after coronary artery occlusion and the documentation of left ventricular failure. In addition, the effects of propionyl-L-carnitine (PLC) on shortening properties and calcium dynamics of single myocytes were established to demonstrate whether the potential increase in ATP generation by this intervention improved myocyte cell function. Myocardial infarction was associated with a progressive increase in length of the spared myocytes, whereas the changes in myocyte diameter were apparent only at the 1-mo interval. Mechanically, myocyte shortening was decreased 43% at 6 h, 34% at 2-3 days, 26% at 1 wk, and 41% at 1 mo after infarction. Similar abnormalities were noted in the velocity of myocyte shortening. Peak systolic calcium was decreased at all intervals after infarction. In contrast, diastolic calcium remained within control values. PLC was capable of ameliorating the mechanical behavior and calcium transients of myocytes, particularly 1 mo after infarction. Thus alterations in muscle cell performance may be important determinants in the development and progression of ischemic cardiomyopathy, and interventions improving myocyte contractility may interfere with the unfavorable outcome of the disease.

  3. Potassium Currents in Freshly Dissociated Uterine Myocytes from Nonpregnant and Late-Pregnant Rats

    OpenAIRE

    Wang, S. Y.; Yoshino, M; Sui, J.L.; Wakui, M; Kao, P.N.; Kao, C. Y.

    1998-01-01

    In freshly dissociated uterine myocytes, the outward current is carried by K+ through channels highly selective for K+. Typically, nonpregnant myocytes have rather noisy K+ currents; half of them also have a fast-inactivating transient outward current (ITO). In contrast, the current records are not noisy in late pregnant myocytes, and ITO densities are low. The whole-cell IK of nonpregnant myocytes respond strongly to changes in [Ca2+]o or changes in [Ca2+]i caused by photolysis of caged Ca2+...

  4. STAT3 balances myocyte hypertrophy vis-à-vis autophagy in response to Angiotensin II by modulating the AMPKα/mTOR axis.

    Science.gov (United States)

    Chen, Lei; Zhao, Lin; Samanta, Anweshan; Mahmoudi, Seyed Morteza; Buehler, Tanner; Cantilena, Amy; Vincent, Robert J; Girgis, Magdy; Breeden, Joshua; Asante, Samuel; Xuan, Yu-Ting; Dawn, Buddhadeb

    2017-01-01

    Signal transducers and activators of transcription 3 (STAT3) is known to participate in various cardiovascular signal transduction pathways, including those responsible for cardiac hypertrophy and cytoprotection. However, the role of STAT3 signaling in cardiomyocyte autophagy remains unclear. We tested the hypothesis that Angiotensin II (Ang II)-induced cardiomyocyte hypertrophy is effected, at least in part, through STAT3-mediated inhibition of cellular autophagy. In H9c2 cells, Ang II treatment resulted in STAT3 activation and cellular hypertrophy in a dose-dependent manner. Ang II enhanced autophagy, albeit without impacting AMPKα/mTOR signaling or cellular ADP/ATP ratio. Pharmacologic inhibition of STAT3 with WP1066 suppressed Ang II-induced myocyte hypertrophy and mRNA expression of hypertrophy-related genes ANP and β-MHC. These molecular events were recapitulated in cells with STAT3 knockdown. Genetic or pharmacologic inhibition of STAT3 significantly increased myocyte ADP/ATP ratio and enhanced autophagy through AMPKα/mTOR signaling. Pharmacologic activation and inhibition of AMPKα attenuated and exaggerated, respectively, the effects of Ang II on ANP and β-MHC gene expression, while concomitant inhibition of STAT3 accentuated the inhibition of hypertrophy. Together, these data indicate that novel nongenomic effects of STAT3 influence myocyte energy status and modulate AMPKα/mTOR signaling and autophagy to balance the transcriptional hypertrophic response to Ang II stimulation. These findings may have significant relevance for various cardiovascular pathological processes mediated by Ang II signaling.

  5. Reciprocal Modulation of IK1-INa Extends Excitability in Cardiac Ventricular Cells.

    Science.gov (United States)

    Varghese, Anthony

    2016-01-01

    The inwardly rectifying potassium current (IK1) and the fast inward sodium current (INa) are reciprocally modulated in mammalian ventricular myocytes. An increase in the expression of channels responsible for one of these two currents results in a corresponding increase in expression of the other. These currents are critical in the propagation of action potentials (AP) during the normal functioning of the heart. This study identifies a physiological role for IK1-INa reciprocal modulation in ventricular fiber activation thresholds and conduction. Simulations of action potentials in single cells and propagating APs in cardiac fibers were carried out using an existing model of electrical activity in cardiac ventricular myocytes. The conductances, GK1, of the inwardly rectifying potassium current, and GNa, of the fast inward sodium current were modified independently and in tandem to simulate reciprocal modulation. In single cells, independent modulation of GK1 alone resulted in changes in activation thresholds that were qualitatively similar to those for reciprocal GK1-GNa modulation and unlike those due to independent modulation of GNa alone, indicating that GK1 determines the cellular activation threshold. On the other hand, the variations in conduction velocity in cardiac cell fibers were similar for independent GNa modulation and for tandem changes in GK1-GNa, suggesting that GNa is primarily responsible for setting tissue AP conduction velocity. Conduction velocity dependence on GK1-GNa is significantly affected by the intercellular gap junction conductance. While the effects on the passive fiber space constant due to changes in both GK1 and the intercellular gap junction conductance, Ggj, were in line with linear cable theory predictions, both conductances had surprisingly large effects on fiber activation thresholds. Independent modulation of GK1 rendered cardiac fibers inexcitable at higher levels of GK1 whereas tandem GK1-GNa changes allowed fibers to remain

  6. The decrease of expression of ryanodine receptor sub-type 2 is reversed by gentamycin sulphate in vascular myocytes from mdx mice.

    Science.gov (United States)

    Morel, Jean-Luc; Dabertrand, Fabrice; Fritz, Nicolas; Henaff, Morgana; Mironneau, Jean; Macrez, Nathalie

    2009-09-01

    The mdx mouse, a model of the human Duchenne muscular dystrophy, displays impaired contractile function in skeletal, cardiac and smooth muscles. We explored the possibility that ryanodine receptor (RYR) expression could be altered in vascular muscle. The three RYR sub-types were expressed in portal vein myocytes. As observed through mRNA and protein levels, RYR2 expression was strongly decreased in mdx myocytes, whereas RYR3 and RYR1 expression were unaltered. The use of antisense oligonucleotide directed against RYR sub-types indicated that caffeine-induced Ca(2+) response and Ca(2+) spark frequency depended on RYR2 and RYR1. In mdx mice, caffeine-induced Ca(2+) responses were decreased in both amplitude and maximal rate of rise, and the frequency of Ca(2+) sparks was also strongly decreased. The gentamycin treatment was able to increase both the expression of RYR2 and the caffeine-induced Ca(2+) response to the same level as that observed in wild-type mice. Taken together, these results confirm that both RYR1 and RYR2 are required for vascular Ca(2+) signalling and indicate that inhibition of RYR2 expression may account for the decreased Ca(2+) release from the SR in mdx vascular myocytes. Finally, we suggest that gentamycin can restore the Ca(2+) signalling in smooth muscle from mdx mice by increasing RYR2 and dystrophin expression. These results may help explain the reduced efficacy of contraction in vascular myocytes of mdx mice and Duchenne muscular dystrophy-afflicted patients. Gentamycin treatment could be a good therapeutic tool to restore the vascular function.

  7. Swimming training increases cardiac vagal activity and induces cardiac hypertrophy in rats

    Directory of Open Access Journals (Sweden)

    A. Medeiros

    2004-12-01

    Full Text Available The effect of swimming training (ST on vagal and sympathetic cardiac effects was investigated in sedentary (S, N = 12 and trained (T, N = 12 male Wistar rats (200-220 g. ST consisted of 60-min swimming sessions 5 days/week for 8 weeks, with a 5% body weight load attached to the tail. The effect of the autonomic nervous system in generating training-induced resting bradycardia (RB was examined indirectly after cardiac muscarinic and adrenergic receptor blockade. Cardiac hypertrophy was evaluated by cardiac weight and myocyte morphometry. Plasma catecholamine concentrations and citrate synthase activity in soleus muscle were also determined in both groups. Resting heart rate was significantly reduced in T rats (355 ± 16 vs 330 ± 20 bpm. RB was associated with a significantly increased cardiac vagal effect in T rats (103 ± 25 vs 158 ± 40 bpm, since the sympathetic cardiac effect and intrinsic heart rate were similar for the two groups. Likewise, no significant difference was observed for plasma catecholamine concentrations between S and T rats. In T rats, left ventricle weight (13% and myocyte dimension (21% were significantly increased, suggesting cardiac hypertrophy. Skeletal muscle citrate synthase activity was significantly increased by 52% in T rats, indicating endurance conditioning. These data suggest that RB induced by ST is mainly mediated parasympathetically and differs from other training modes, like running, that seems to mainly decrease intrinsic heart rate in rats. The increased cardiac vagal activity associated with ST is of clinical relevance, since both are related to increased life expectancy and prevention of cardiac events.

  8. Astragaloside IV Prevents Cardiac Remodeling in the Apolipoprotein E-Deficient Mice by Regulating Cardiac Homeostasis and Oxidative Stress

    Directory of Open Access Journals (Sweden)

    Xiong-Zhi Li

    2017-12-01

    Full Text Available Background: Hypercholesterolemia is a risk factor for the development of cardiac hypertrophy. Astragaloside IV (AST-IV possesses cardiovascular protective properties. We hypothesize that AST-IV prevents cardiac remodeling with hypercholesterolemia via modulating tissue homeostasis and alleviating oxidative stress. Methods: The ApoE-/- mice were treated with AST-IV at 1 or 10 mg/kg for 8 weeks. The blood lipids tests, echocardiography, and TUNEL were performed. The mRNA expression profile was detected by real-time PCR. The myocytes size and number, and the expressions of proliferation (ki67, senescence (p16INK4a, oxidant (NADPH oxidase 4, NOX4 and antioxidant (superoxide dismutase, SOD were observed by immunofluorescence staining. Results: Neither 1 mg/kg nor 10 mg/kg AST-IV treatment could decrease blood lipids in ApoE-/- mice. However, the decreased left ventricular ejection fraction (LVEF and fractional shortening (FS in ApoE–/– mice were significantly improved after AST-IV treatment. The cardiac collagen volume fraction declined nearly in half after AST-IV treatment. The enlarged myocyte size was suppressed, and myocyte number was recovered, and the alterations of genes expressions linked to cell cycle, proliferation, senescence, p53-apoptosis pathway and oxidant-antioxidants in the hearts of ApoE-/- mice were reversed after AST-IV treatment. The decreased ki67 and increased p16INK4a in the hearts of ApoE-/- mice were recovered after AST-IV treatment. The percentages of apoptotic myocytes and NOX4-positive cells in AST-IV treated mice were decreased, which were consistent with the gene expressions. Conclusion: AST-IV treatment could prevent cardiac remodeling and recover the impaired ventricular function induced by hypercholesterolemia. The beneficial effect of AST-IV might partly be through regulating cardiac homeostasis and anti-oxidative stress.

  9. Comparison of Detailed and Simplified Models of Human Atrial Myocytes to Recapitulate Patient Specific Properties.

    Directory of Open Access Journals (Sweden)

    Daniel M Lombardo

    2016-08-01

    Full Text Available Computer studies are often used to study mechanisms of cardiac arrhythmias, including atrial fibrillation (AF. A crucial component in these studies is the electrophysiological model that describes the membrane potential of myocytes. The models vary from detailed, describing numerous ion channels, to simplified, grouping ionic channels into a minimal set of variables. The parameters of these models, however, are determined across different experiments in varied species. Furthermore, a single set of parameters may not describe variations across patients, and models have rarely been shown to recapitulate critical features of AF in a given patient. In this study we develop physiologically accurate computational human atrial models by fitting parameters of a detailed and of a simplified model to clinical data for five patients undergoing ablation therapy. Parameters were simultaneously fitted to action potential (AP morphology, action potential duration (APD restitution and conduction velocity (CV restitution curves in these patients. For both models, our fitting procedure generated parameter sets that accurately reproduced clinical data, but differed markedly from published sets and between patients, emphasizing the need for patient-specific adjustment. Both models produced two-dimensional spiral wave dynamics for that were similar for each patient. These results show that simplified, computationally efficient models are an attractive choice for simulations of human atrial electrophysiology in spatially extended domains. This study motivates the development and validation of patient-specific model-based mechanistic studies to target therapy.

  10. Effect of gap junction distribution on impulse propagation in a monolayer of myocytes: a model study.

    Science.gov (United States)

    Hubbard, Marjorie Letitia; Ying, Wenjun; Henriquez, Craig S

    2007-11-01

    To use microstructural computer models to study how four features of myocardial architecture affect propagation: brick wall tissue structures, jutting at cell ends, gap junction distribution and conductance along cell borders, and increased structural discontinuity. Simulations of longitudinal and transverse plane wave propagation and point propagation were performed in several two-dimensional (2D) microstructural models of adult cardiac tissue. Conduction velocities and maximum upstroke velocities were measured for a range of gap junction conductances and distributions. In tissue models with normal to low connectivity, brick wall architecture and jutting decrease cell-to-cell delay, increase longitudinal conduction velocity, and decrease longitudinal maximum upstroke velocity. Transverse conduction velocity also increases if the overlap or jutting introduces additional lateral (side-to-side) connections between myocytes. Both end-to-end and side-to-side interplicate gap junctions increase longitudinal and transverse conduction velocity; however, side-to-side interplicate gap junctions have the greatest influence on transverse conduction velocity and longitudinal and transverse maximum upstroke velocity. The complex structure of myocardium creates additional pathways of current flow that enhance both longitudinal and transverse propagation. These alternative pathways of current help to maintain conduction as connectivity between cells decreases.

  11. Myocyte Dedifferentiation Drives Extraocular Muscle Regeneration in Adult Zebrafish.

    Science.gov (United States)

    Saera-Vila, Alfonso; Kasprick, Daniel S; Junttila, Tyler L; Grzegorski, Steven J; Louie, Ke'ale W; Chiari, Estelle F; Kish, Phillip E; Kahana, Alon

    2015-07-01

    The purpose of this study was to characterize the injury response of extraocular muscles (EOMs) in adult zebrafish. Adult zebrafish underwent lateral rectus (LR) muscle myectomy surgery to remove 50% of the muscle, followed by molecular and cellular characterization of the tissue response to the injury. Following myectomy, the LR muscle regenerated an anatomically correct and functional muscle within 7 to 10 days post injury (DPI). Following injury, the residual muscle stump was replaced by a mesenchymal cell population that lost cell polarity and expressed mesenchymal markers. Next, a robust proliferative burst repopulated the area of the regenerating muscle. Regenerating cells expressed myod, identifying them as myoblasts. However, both immunofluorescence and electron microscopy failed to identify classic Pax7-positive satellite cells in control or injured EOMs. Instead, some proliferating nuclei were noted to express mef2c at the very earliest point in the proliferative burst, suggesting myonuclear reprogramming and dedifferentiation. Bromodeoxyuridine (BrdU) labeling of regenerating cells followed by a second myectomy without repeat labeling resulted in a twice-regenerated muscle broadly populated by BrdU-labeled nuclei with minimal apparent dilution of the BrdU signal. A double-pulse experiment using BrdU and 5-ethynyl-2'-deoxyuridine (EdU) identified double-labeled nuclei, confirming the shared progenitor lineage. Rapid regeneration occurred despite a cell cycle length of 19.1 hours, whereas 72% of the regenerating muscle nuclei entered the cell cycle by 48 hours post injury (HPI). Dextran lineage tracing revealed that residual myocytes were responsible for muscle regeneration. EOM regeneration in adult zebrafish occurs by dedifferentiation of residual myocytes involving a muscle-to-mesenchyme transition. A mechanistic understanding of myocyte reprogramming may facilitate novel approaches to the development of molecular tools for targeted therapeutic

  12. Mitochondrial function in engineered cardiac tissues is regulated by extracellular matrix elasticity and tissue alignment.

    Science.gov (United States)

    Lyra-Leite, Davi M; Andres, Allen M; Petersen, Andrew P; Ariyasinghe, Nethika R; Cho, Nathan; Lee, Jezell A; Gottlieb, Roberta A; McCain, Megan L

    2017-10-01

    Mitochondria in cardiac myocytes are critical for generating ATP to meet the high metabolic demands associated with sarcomere shortening. Distinct remodeling of mitochondrial structure and function occur in cardiac myocytes in both developmental and pathological settings. However, the factors that underlie these changes are poorly understood. Because remodeling of tissue architecture and extracellular matrix (ECM) elasticity are also hallmarks of ventricular development and disease, we hypothesize that these environmental factors regulate mitochondrial function in cardiac myocytes. To test this, we developed a new procedure to transfer tunable polydimethylsiloxane disks microcontact-printed with fibronectin into cell culture microplates. We cultured Sprague-Dawley neonatal rat ventricular myocytes within the wells, which consistently formed tissues following the printed fibronectin, and measured oxygen consumption rate using a Seahorse extracellular flux analyzer. Our data indicate that parameters associated with baseline metabolism are predominantly regulated by ECM elasticity, whereas the ability of tissues to adapt to metabolic stress is regulated by both ECM elasticity and tissue alignment. Furthermore, bioenergetic health index, which reflects both the positive and negative aspects of oxygen consumption, was highest in aligned tissues on the most rigid substrate, suggesting that overall mitochondrial function is regulated by both ECM elasticity and tissue alignment. Our results demonstrate that mitochondrial function is regulated by both ECM elasticity and myofibril architecture in cardiac myocytes. This provides novel insight into how extracellular cues impact mitochondrial function in the context of cardiac development and disease.NEW & NOTEWORTHY A new methodology has been developed to measure O2 consumption rates in engineered cardiac tissues with independent control over tissue alignment and matrix elasticity. This led to the findings that matrix

  13. Cardiac MR imaging: current status and future direction

    Science.gov (United States)

    Van, Tu Anh; Krug, Roland; Hetts, Steven W.; Wilson, Mark W.

    2015-01-01

    Coronary artery disease is currently a worldwide epidemic with increasing impact on healthcare systems. Magnetic resonance imaging (MRI) sequences give complementary information on LV function, regional perfusion, angiogenesis, myocardial viability and orientations of myocytes. T2-weighted short-tau inversion recovery (T2-STIR), fat suppression and black blood sequences have been frequently used for detecting edematous area at risk (AAR) of infarction. T2 mapping, however, indicated that the edematous reaction in acute myocardial infarct (AMI) is not stable and warranted the use of edematous area in evaluating therapies. On the other hand, cine MRI demonstrated reproducible data on LV function in healthy volunteers and LV remodeling in patients. Noninvasive first pass perfusion, using exogenous tracer (gadolinium-based contrast media) and arterial spin labeling MRI, using endogenous tracer (water), are sensitive and useful techniques for evaluating myocardial perfusion and angiogenesis. Recently, new strategies have been developed to quantify myocardial viability using T1-mapping and equilibrium contrast enhanced MR techniques because existing delayed contrast enhancement MRI (DE-MRI) sequences are limited in detecting patchy microinfarct and diffuse fibrosis. These new techniques were successfully used for characterizing diffuse myocardial fibrosis associated with myocarditis, amyloidosis, sarcoidosis heart failure, aortic hypertrophic cardiomyopathy, congenital heart disease, restrictive cardiomyopathy, arrhythmogenic right ventricular dysplasia and hypertension). Diffusion MRI provides information regarding microscopic tissue structure, while diffusion tensor imaging (DTI) helps to characterize the myocardium and monitor the process of LV remodeling after AMI. Novel trends in hybrid imaging, such as cardiac positron emission tomography (PET)/MRI and optical imaging/MRI, are recently under intensive investigation. With the promise of higher spatial

  14. Cardiac MR imaging: current status and future direction.

    Science.gov (United States)

    Saeed, Maythem; Van, Tu Anh; Krug, Roland; Hetts, Steven W; Wilson, Mark W

    2015-08-01

    Coronary artery disease is currently a worldwide epidemic with increasing impact on healthcare systems. Magnetic resonance imaging (MRI) sequences give complementary information on LV function, regional perfusion, angiogenesis, myocardial viability and orientations of myocytes. T2-weighted short-tau inversion recovery (T2-STIR), fat suppression and black blood sequences have been frequently used for detecting edematous area at risk (AAR) of infarction. T2 mapping, however, indicated that the edematous reaction in acute myocardial infarct (AMI) is not stable and warranted the use of edematous area in evaluating therapies. On the other hand, cine MRI demonstrated reproducible data on LV function in healthy volunteers and LV remodeling in patients. Noninvasive first pass perfusion, using exogenous tracer (gadolinium-based contrast media) and arterial spin labeling MRI, using endogenous tracer (water), are sensitive and useful techniques for evaluating myocardial perfusion and angiogenesis. Recently, new strategies have been developed to quantify myocardial viability using T1-mapping and equilibrium contrast enhanced MR techniques because existing delayed contrast enhancement MRI (DE-MRI) sequences are limited in detecting patchy microinfarct and diffuse fibrosis. These new techniques were successfully used for characterizing diffuse myocardial fibrosis associated with myocarditis, amyloidosis, sarcoidosis heart failure, aortic hypertrophic cardiomyopathy, congenital heart disease, restrictive cardiomyopathy, arrhythmogenic right ventricular dysplasia and hypertension). Diffusion MRI provides information regarding microscopic tissue structure, while diffusion tensor imaging (DTI) helps to characterize the myocardium and monitor the process of LV remodeling after AMI. Novel trends in hybrid imaging, such as cardiac positron emission tomography (PET)/MRI and optical imaging/MRI, are recently under intensive investigation. With the promise of higher spatial

  15. Differences in affinity of cardiac beta-adrenergic receptors for (3H)dihydroalprenolol

    Energy Technology Data Exchange (ETDEWEB)

    Muntz, K.H.; Calianos, T.A.; Vandermolen, D.T.; Willerson, J.T.; Buja, L.M.

    1986-03-01

    We performed quantitative light microscopic autoradiography of (3H)dihydroalprenolol (DHA) binding to frozen sections of canine myocardium to test the hypothesis that there are differences in the density or affinity of beta-adrenergic receptors on various tissue compartments. In one study, with concentrations of (3H)DHA from 0.34 to 5.1 nM, specific binding to cardiac myocytes was saturable, whereas nonspecific binding was linear with ligand concentration. Arterioles had more specific grain counts than muscle cells (P less than 0.0001), and Scatchard analysis showed that the arterioles had a much higher affinity for (3H)DHA than myocytes. In a second study with lower concentrations of (3H)DHA (0.19-1.98 nM), binding to the arterioles saturated, whereas binding to the cardiac myocytes did not. Specific binding to arterioles was significantly higher (P less than 0.0001) than binding to myocytes at all concentrations of (3H)DHA. The dissociation constants for the subendocardial and subepicardial myocytes were 1.57 and 1.71 nM, respectively, while the dissociation constant for the arterioles was 0.26 nM. The maximum number of binding sites was 911 grains/0.9 X 10(-2) mm2 for subepicardial myocytes, 936 for subendocardial myocytes, and 986 for arterioles. The large nerves accompanying an epicardial artery also demonstrated specific (3H)DHA binding. Thus this study has demonstrated major differences in the distribution and affinity of beta-adrenergic receptors, which may help to explain various physiological responses to beta-adrenergic stimulation.

  16. Modulation of KCNQ1 alternative splicing regulates cardiac IKs and action potential repolarization.

    Science.gov (United States)

    Lee, Hsiang-Chun; Rudy, Yoram; Po-Yuan, Phd; Sheu, Sheng-Hsiung; Chang, Jan-Gowth; Cui, Jianmin

    2013-08-01

    Slow delayed-rectifier potassium current (IKs) channels, made of the pore-forming KCNQ1 and auxiliary KCNE1 subunits, play a key role in determining action potential duration (APD) in cardiac myocytes. The consequences of drug-induced KCNQ1 splice alteration remain unknown. To study the modulation of KCNQ1 alternative splicing by amiloride and the consequent changes in IKs and action potentials (APs) in ventricular myocytes. Canine endocardial, midmyocardial, and epicardial ventricular myocytes were isolated. Levels of KCNQ1a and KCNQ1b as well as a series of splicing factors were quantified by using the reverse transcriptase-polymerase chain reaction and Western blot. The effect of amiloride-induced changes in the KCNQ1b/total KCNQ1 ratio on AP was measured by using whole-cell patch clamp with and without isoproterenol. With 50 μmol/L of amiloride for 6 hours, KCNQ1a at transcriptional and translational levels increased in midmyocardial myocytes but decreased in endo- and epicardial myocytes. Likewise, changes in splicing factors in midmyocardial were opposite to that in endo- and epicardial myocytes. In midmyocardial myocytes amiloride shortened APD and decreased isoproterenol-induced early afterdepolarizations significantly. The same amiloride-induced effects were demonstrated by using human ventricular myocyte model for AP simulations under beta-adrenergic stimulation. Moreover, amiloride reduced the transmural dispersion of repolarization in pseudo-electrocardiogram. Amiloride regulates IKs and APs with transmural differences and reduces arrhythmogenicity through the modulation of KCNQ1 splicing. We suggested that the modulation of KCNQ1 splicing may help prevent arrhythmia. Copyright © 2013 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

  17. Uso de fluorescência em um método de dissector modificado para estimar o número de miócitos no tecido cardíaco Uso de fluorescencia en un método de disector modificado para estimar el número de miocitos en el tejido cardíaco Use of fluorescence in a modified disector method to estimate the number of myocytes in cardiac tissue

    Directory of Open Access Journals (Sweden)

    Rômulo Dias Novaes

    2012-03-01

    rea de 3D. OBJETIVO: Usar la microscopia de fluorescencia en un método de disector modificado para determinar el número de miocitos en el tejido cardíaco en condiciones normales y patológicas. MÉTODOS: El estudio empleó ratones Wistar machos de cuatro meses de edad y peso de 366,25 ± 88,21 g randomizados en grupos controles (GC, n = 8 e infectados (GI, n = 8. Los animales del GI fueron inoculados con cepa Y de T. cruzi (300.000 tripomastigotas/50 g. Después de ocho semanas, los animales fueron pesados y sacrificados. Los Ventrículos Izquierdos (VI fueron removidos para análisis estereológico de la densidad numérica de cardiomiocitos (Nv [c] y el número total de esas células en el VI (N [c]. Esos parámetros fueron estimados usando un disector fluorescente (FD y comparados con los métodos convencionales de disector óptico (OD y disector físico (PD. RESULTADOS: En ambos métodos de disector, los animales del GI presentaron caída significativa de Nv[c] y N[c] en comparación con los animales del GC (P > 0,05. Una correlación fuerte, igual o superior a 96%, fue obtenida entre FD, OD y PD. CONCLUSIÓN: El método FD parece ser igualmente confiable para determinar Nv[c] y N[c] en condiciones normales y patológicas, presentando algunas ventajas en relación a los métodos convencionales de disector: reducción de cortes histológicos e imágenes en el análisis estereológico, reducción del tiempo de análisis de las imágenes, la construcción de FD en microscopios simples, utilizando el modo de epifluorescencia, distinción de planos de disector en ampliaciones inferiores.BACKGROUND: Conventional disector methods currently require considerable financial, technical and operational costs to estimate the number of cells, including cardyomyocytes, in a 3D area. OBJECTIVE: To use fluorescence microscopy in a modified disector method to determine the number of myocytes in cardiac tissue in normal and pathological conditions. METHODS: The study employed four

  18. Nitrate-containing beetroot enhances myocyte metabolism and mitochondrial content

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    Roger A. Vaughan

    2016-01-01

    Full Text Available Beetroot (甜菜 tián cài juice consumption is of current interest for improving aerobic performance by acting as a vasodilator and possibly through alterations in skeletal muscle metabolism and physiology. This work explored the effects of a commercially available beetroot supplement on metabolism, gene expression, and mitochondrial content in cultured myocytes. C2C12 myocytes were treated with various concentrations of the beetroot supplement for various durations. Glycolytic metabolism and oxidative metabolism were quantified via measurement of extracellular acidification and oxygen consumption, respectively. Metabolic gene expression was measured using quantitative reverse transcription–polymerase chain reaction, and mitochondrial content was assessed with flow cytometry and confocal microscopy. Cells treated with beetroot exhibited significantly increased oxidative metabolism, concurrently with elevated metabolic gene expression including peroxisome proliferator-activated receptor gamma coactivator-1 alpha, nuclear respiratory factor 1, mitochondrial transcription factor A, and glucose transporter 4, leading to increased mitochondrial biogenesis. Our data show that treatment with a beetroot supplement increases basal oxidative metabolism. Our observations are also among the first to demonstrate that beetroot extract is an inducer of metabolic gene expression and mitochondrial biogenesis. These observations support the need for further investigation into the therapeutic and pharmacological effects of nitrate-containing supplements for health and athletic benefits.

  19. Differentiated vascular myocytes: are they involved in neointimal formation?

    Science.gov (United States)

    Holifield, B; Helgason, T; Jemelka, S; Taylor, A; Navran, S; Allen, J; Seidel, C

    1996-02-01

    The role of differentiated vascular myocytes are neointimal formation in canine carotid artery was investigated. Using antibodies and cDNA probes, cells were characterized in situ and after isolation. In situ characterization indicated the majority of medial cells expressed both smooth muscle myosin and alpha actin but many cells were negative to these markers. All adventitial cells were negative for these proteins. The muscle protein-positive cells were designated differentiated, vascular myocytes (VSMC). The others were designated type 2 cells. Sequential enzyme digestion from lumenal surface yielded VSMC ( > 90%) while digestions from the adventitial surface yielded type 2 cells ( > 90%). VSMC were viable in culture but did not spread, proliferate, or alter expression of muscle proteins. Type 2 cells proliferated and increased their expression of muscle actin but did not express muscle myosin. Characterization of neointimal cells from injured carotid arteries indicated they were morphologically and immunologically identical to cultured type 2 cells. We concluded that: (a) canine carotid artery media consists of a heterogeneous cell population: (b) serum does not stimulate isolated VSMC to undergo phenotypic modulation or proliferate: and (c) type 2 cells may be responsible for neointimal formation because they proliferate and acquire a phenotype identical to in situ neointimal cells.

  20. Micro and Nano-mediated 3D Cardiac Tissue Engineering

    Science.gov (United States)

    2010-10-01

    digital camera was mounted inside the sterilized hood to precisely cut the segments of the heart. The camera, Dnt Mikroskopkamera Digimicro 2.0 Scale...molecular medicine: Tissue engineering. Totowa, New Jersey: Humana Press Inc.; 2007:291-307. 41. Geisse NA. Control of myocyte remodeling in vitro with...biology, cardiac gene expression: Methods and protocols. Totowa, New Jersey: Humana Press Inc.; 2007:321-330. 52. Chlopcíková S, Psotová J, Miketová

  1. Inibição da corrente de cálcio tipo L por tramadol e enantiômeros em miócitos cardíacos de ratos Inhibition of L-type calcium current by tramadol and enantiomers in cardiac myocytes from rats

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    Emiliano Medei

    2011-10-01

    -L, in which the peak amplitude was reduced by 64.4 ± 2.8% and 68.9 ± 5.8%, respectively at 0 mV (p > 0.05. Tramadol, (+- and (--tramadol shifted the steady-state inactivation of I Ca-L to more negative membrane potentials. Also, tramadol and (+-tramadol markedly shifted the time-dependent recovery curve of I Ca-L to the right and slowed down the recovery of I Ca-L from inactivation. The time constant was increased from 175.6 ± 18.6 to 305.0 ± 32.9 ms (p < 0.01 for tramadol and from 248.1 ± 28.1 ms to 359.0 ± 23.8 ms (p < 0.05 for (+-tramadol. The agonist of µ-opioid receptor DAMGO had no effect on the I Ca-L. CONCLUSION: The inhibition of I Ca-L induced by tramadol and its enantiomers was unrelated to the activation of opioid receptors and could explain, at least in part, their negative cardiac inotropic effect.

  2. Instability of spiral and scroll waves in the presence of a gradient in the fibroblast density: the effects of fibroblast-myocyte coupling

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    Zimik, Soling; Pandit, Rahul

    2016-12-01

    Fibroblast-myocyte coupling can modulate electrical-wave dynamics in cardiac tissue. In diseased hearts, the distribution of fibroblasts is heterogeneous, so there can be gradients in the fibroblast density (henceforth we call this GFD) especially from highly injured regions, like infarcted or ischemic zones, to less-wounded regions of the tissue. Fibrotic hearts are known to be prone to arrhythmias, so it is important to understand the effects of GFD in the formation and sustenance of arrhythmic re-entrant waves, like spiral or scroll waves. Therefore, we investigate the effects of GFD on the stability of spiral and scroll waves of electrical activation in a state-of-the-art mathematical model for cardiac tissue in which we also include fibroblasts. By introducing GFD in controlled ways, we show that spiral and scroll waves can be unstable in the presence of GFDs because of regions with varying spiral- or scroll-wave frequency ω, induced by the GFD. We examine the effects of the resting membrane potential of the fibroblast and the number of fibroblasts attached to the myocytes on the stability of these waves. Finally, we show that the presence of GFDs can lead to the formation of spiral waves at high-frequency pacing.

  3. Calcium-activated chloride current determines action potential morphology during calcium alternans in atrial myocytes.

    Science.gov (United States)

    Kanaporis, Giedrius; Blatter, Lothar A

    2016-02-01

    Cardiac alternans--periodic beat-to-beat alternations in contraction, action potential (AP) morphology or cytosolic calcium transient (CaT) amplitude--is a high risk indicator for cardiac arrhythmias and sudden cardiac death. However, it remains an unresolved issue whether beat-to-beat alternations in intracellular Ca(2+) ([Ca(2+)]i ) or AP morphology are the primary cause of pro-arrhythmic alternans. Here we show that in atria AP alternans occurs secondary to CaT alternans. CaT alternans leads to complex beat-to-beat changes in Ca(2+)-regulated ion currents that determine alternans of AP morphology. We report the novel finding that alternans of AP morphology is largely sustained by the activity of Ca(2+)-activated Cl(-) channels (CaCCs). Suppression of the CaCCs significantly reduces AP alternans, while CaT alternans remains unaffected. The demonstration of a major role of CaCCs in the development of AP alternans opens new possibilities for atrial alternans and arrhythmia prevention. Cardiac alternans, described as periodic beat-to-beat alternations in contraction, action potential (AP) morphology or cytosolic Ca transient (CaT) amplitude, is a high risk indicator for cardiac arrhythmias and sudden cardiac death. We investigated mechanisms of cardiac alternans in single rabbit atrial myocytes. CaTs were monitored simultaneously with membrane currents or APs recorded with the patch clamp technique. Beat-to-beat alternations of AP morphology and CaT amplitude revealed a strong quantitative correlation. Application of voltage clamp protocols in the form of pre-recorded APs (AP-clamp) during pacing-induced CaT alternans revealed a Ca(2+)-dependent current consisting of a large outward component (4.78 ± 0.58 pA pF(-1) in amplitude) coinciding with AP phases 1 and 2 that was followed by an inward current (-0.42 ± 0.03 pA pF(-1); n = 21) during AP repolarization. Approximately 90% of the initial outward current was blocked by substitution of Cl(-) ions or application

  4. Cardiac catheterization - discharge

    Science.gov (United States)

    Catheterization - cardiac - discharge; Heart catheterization - discharge: Catheterization - cardiac; Heart catheterization; Angina - cardiac catheterization discharge; CAD - cardiac catheterization discharge; Coronary ...

  5. Eicosapentaenoic acid ameliorates palmitate-induced lipotoxicity via the AMP kinase/dynamin-related protein-1 signaling pathway in differentiated H9c2 myocytes.

    Science.gov (United States)

    Sakamoto, Atsushi; Saotome, Masao; Hasan, Prottoy; Satoh, Terumori; Ohtani, Hayato; Urushida, Tsuyoshi; Katoh, Hideki; Satoh, Hiroshi; Hayashi, Hideharu

    2017-02-01

    Emerging evidence suggested the preferable effects of eicosapentaenoic acid (EPA; n-3 polyunsaturated fatty acid) against cardiac lipotoxicity, which worsens cardiac function by means of excessive serum free fatty acids due to chronic adrenergic stimulation under heart failure. Nonetheless, the precise molecular mechanisms remain elusive. In this study, we focused on dynamin-related protein-1 (Drp1) as a possible modulator of the EPA-mediated cardiac protection against cardiac lipotoxicity, and investigated the causal relation between AMP-activated protein kinase (AMPK) and Drp1. When differentiated H9c2 myocytes were exposed to palmitate (PAL; saturated fatty acid, 400µM) for 24h, these myocytes showed activation of caspases 3 and 7, enhanced caspase 3 cleavage, depolarized mitochondrial membrane potential, depleted intracellular ATP, and enhanced production of intracellular reactive oxygen species. These changes suggested lipotoxicity due to excessive PAL. PAL enhanced mitochondrial fragmentation with increased Drp1 expression, as well. EPA (50µM) restored the PAL-induced apoptosis, mitochondrial dysfunction, and mitochondrial fragmentation with increased Drp1 expression by PAL. EPA activated phosphorylation of AMPK, and pharmacological activation of AMPK by 5-aminoimidazole-4-carboxamide ribonucleotide ameliorated the PAL-induced apoptosis, mitochondrial dysfunction, and downregulated Drp1. An AMPK knockdown via RNA interference enhanced Drp1 expression and attenuated the protective effects of EPA against the PAL-induced lipotoxicity. EPA ameliorates the PAL-induced lipotoxicity via AMPK activation, which subsequently suppresses mitochondrial fragmentation and Drp1 expression. Our findings may provide new insights into the molecular mechanisms of EPA-mediated myocardial protection in heart failure. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. Spatiotemporal intracellular calcium dynamics during cardiac alternans

    Science.gov (United States)

    Restrepo, Juan G.; Karma, Alain

    2009-09-01

    Cellular calcium transient alternans are beat-to-beat alternations in the peak cytosolic calcium concentration exhibited by cardiac cells during rapid electrical stimulation or under pathological conditions. Calcium transient alternans promote action potential duration alternans, which have been linked to the onset of life-threatening ventricular arrhythmias. Here we use a recently developed physiologically detailed mathematical model of ventricular myocytes to investigate both stochastic and deterministic aspects of intracellular calcium dynamics during alternans. The model combines a spatially distributed description of intracellular calcium cycling, where a large number of calcium release units are spatially distributed throughout the cell, with a full set of ionic membrane currents. The results demonstrate that ion channel stochasticity at the level of single calcium release units can influence the whole-cell alternans dynamics by causing phase reversals over many beats during fixed frequency pacing close to the alternans bifurcation. They also demonstrate the existence of a wide range of dynamical states. Depending on the sign and magnitude of calcium-voltage coupling, calcium alternans can be spatially synchronized or desynchronized, in or out of phase with action potential duration alternans, and the node separating out-of-phase regions of calcium alternans can be expelled from or trapped inside the cell. This range of states is found to be larger than previously anticipated by including a robust global attractor where calcium alternans can be spatially synchronized but out of phase with action potential duration alternans. The results are explained by a combined theoretical analysis of alternans stability and node motion using general iterative maps of the beat-to-beat dynamics and amplitude equations.

  7. Species-dependent adaptation of the cardiac Na+/K+ pump kinetics to the intracellular Na+ concentration.

    Science.gov (United States)

    Lewalle, Alexandre; Niederer, Steven A; Smith, Nicolas P

    2014-12-15

    The Na(+)/K(+) ATPase (NKA) plays a critical role in maintaining ionic homeostasis and dynamic function in cardiac myocytes, within both the in vivo cell and in silico models. Physiological conditions differ significantly between mammalian species. However, most existing formulations of NKA used to simulate cardiac function in computational models are derived from a broad range of experimental sources spanning many animal species. The resultant inability of these models to discern species-specific features is a significant obstacle to achieving a detailed quantitative and comparative understanding of physiological behaviour in different biological contexts. Here we present a framework for characterising the steady-state NKA current using a biophysical mechanistic model specifically designed to provide a mechanistic explanation of the NKA flux supported by self-consistent species-specific data. We thus compared NKA kinetics specific to guinea- pig and rat ventricular myocytes. We observe that the apparent binding affinity for sodium in the rat is significantly lower, whereas the overall pump cycle rate is doubled, in comparison to the guinea pig. This sensitivity of NKA to its regulatory substrates compensates for the differences in Na(+) concentrations between the cell types. NKA is thereby maintained within its dynamic range over a wide range of pacing frequencies in these two species, despite significant disparities in sodium concentration. Hence, by replacing a conventional generic NKA model with our rat-specific NKA formula into a whole-cell simulation, we have, for the first time, been able to accurately reproduce the action potential duration and the steady-state sodium concentration as functions of pacing frequency. © 2014 The Authors. The Journal of Physiology © 2014 The Physiological Society.

  8. Revascularization of chronic hibernating myocardium stimulates myocyte proliferation and partially reverses chronic adaptations to ischemia.

    Science.gov (United States)

    Page, Brian J; Banas, Michael D; Suzuki, Gen; Weil, Brian R; Young, Rebeccah F; Fallavollita, James A; Palka, Beth A; Canty, John M

    2015-02-24

    The time course and extent of recovery after revascularization of viable dysfunctional myocardium are variable. Although fibrosis is a major determinant, myocyte structural and molecular remodeling may also play important roles. This study sought to determine whether persistent myocyte loss and/or irreversibility of protein changes that develop in hibernating myocardium have an impact on functional recovery in the absence of infarction. Swine implanted with a chronic left anterior descending artery (LAD) stenosis to produce hibernating myocardium underwent percutaneous revascularization, with serial functional recovery evaluated for 1 month (n = 12). Myocardial tissue was evaluated to assess myocyte size, nuclear density, and proliferation indexes in comparison with those of normal animals and nonrevascularized controls. Proteomic analysis by 2-dimensional differential in-gel electrophoresis was used to determine the reversibility of molecular adaptations of hibernating myocytes. At 3 months, physiological features of hibernating myocardium were confirmed, with depressed LAD wall thickening and no significant infarction. Revascularization normalized LAD flow reserve, with no immediate change in LAD wall thickening. Regional LAD wall thickening slowly improved but remained depressed 1 month post-percutaneous coronary intervention. Surprisingly, revascularization was associated with histological evidence of myocytes re-entering the growth phase of the cell cycle and increases in the number of c-Kit(+) cells. Myocyte nuclear density returned to normal, whereas regional myocyte hypertrophy regressed. Proteomic analysis demonstrated heterogeneous effects of revascularization. Up-regulated stress and cytoskeletal proteins normalized, whereas reduced contractile and metabolic proteins persisted. Delayed recovery of hibernating myocardium in the absence of scar may reflect persistent reductions in the amounts of contractile and metabolic proteins. Although

  9. Revascularization of Chronic Hibernating Myocardium Stimulates Myocyte Proliferation and Partially Reverses Chronic Adaptations to Ischemia

    Science.gov (United States)

    Page, Brian J.; Banas, Michael D.; Suzuki, Gen; Weil, Brian R.; Young, Rebeccah F.; Fallavollita, James A.; Palka, Beth A.; Canty, John M.

    2014-01-01

    Background The time course and extent of recovery after revascularization of viable dysfunctional myocardium is variable. While fibrosis is a major determinant, myocyte structural and molecular remodeling may also play important roles. Objective This study sought to determine whether persistent myocyte loss and/or irreversibility of protein changes that develop in hibernating myocardium have an impact on functional recovery in the absence of infarction. Methods Swine instrumented with a chronic left anterior descending artery (LAD) stenosis to produce hibernating myocardium underwent percutaneous revascularization with serial functional recovery evaluated for 1 month (n = 12). Myocardial tissue was evaluated to assess myocyte size, nuclear density, and proliferation indexes in comparison to normal animals and nonrevascularized controls. Proteomic analysis by 2-dimensional differential in-gel electrophoresis (2D-DIGE) was used to determine the reversibility of molecular adaptations of hibernating myocytes. Results At 3 months, physiological features of hibernating myocardium were confirmed, with depressed LAD wall thickening and no significant infarction. Revascularization normalized LAD flow reserve, with no immediate change in LAD wall thickening. Regional LAD wall thickening slowly improved, but remained depressed 1 month post-percutaneous coronary intervention (PCI). Surprisingly, revascularization was associated with histological evidence of myocytes reentering the growth phase of the cell cycle and increased cKit+ cells. Myocyte nuclear density returned to normal, while regional myocyte hypertrophy regressed. Proteomic analysis demonstrated heterogeneous effects of revascularization. Up-regulated stress and cytoskeletal proteins normalized, while reduced contractile and metabolic proteins persisted. Conclusions Delayed recovery of hibernating myocardium in the absence of scar may reflect persistent reductions in contractile and metabolic proteins. While

  10. The ShcA Phosphotyrosine Docking Protein Uses Distinct Mechanisms to Regulate Myocyte and Global Heart Function

    Science.gov (United States)

    Vanderlaan, Rachel D.; Hardy, W. Rod; Kabir, M. Golam; Pasculescu, Adrian; Jones, Nina; deTombe, Pieter P.; Backx, Peter H.; Pawson, Tony

    2011-01-01

    Rationale Although tyrosine kinases (TKs) are important for cardiac function, their relevant downstream targets in the adult heart are unknown. The ShcA docking protein binds specific phosphotyrosine (pTyr) sites on activated TKs through its N-terminal pTyr-binding (PTB) and C-terminal SH2 domains and stimulates downstream pathways through motifs such as pTyr sites in its central CH1 region. Therefore, ShcA could be a potential hub for downstream TK signaling in the myocardium. Objective To define the role of ShcA, a TK scaffold, in the adult heart using a myocardial-specific knockout of murine ShcA (ShcA CKO) and domain knock-in models. Methods and Results ShcA CKO mice developed a dilated cardiomyopathy phenotype involving impaired systolic function with enhanced cardiomyocyte contractility. This uncoupling of global heart and intrinsic myocyte functions was associated with altered collagen and extracellular matrix compliance properties, suggesting disruption of mechanical coupling. In vivo dissection of ShcA signaling properties revealed that selective inactivation of the PTB domain in the myocardium had effects resembling those seen in ShcA CKO mice, whereas disruption of the SH2 domain caused a less severe cardiac phenotype. Downstream signaling through the CH1 pTyr sites was dispensable for baseline cardiac function but necessary to prevent adverse remodeling after hemodynamic overload. Conclusions These data demonstrate a requirement for TK-ShcA PTB domain signaling to maintain cardiac function. In addition, analysis of the SH2 domain and CH1 pTyr sites reveals that ShcA mediates pTyr signaling in the adult heart through multiple distinct signaling elements that control myocardial functions and response to stresses. PMID:21148430

  11. Vector-averaged gravity alters myocyte and neuron properties in cell culture

    Science.gov (United States)

    Gruener, Raphael; Hoeger, Glenn

    1991-01-01

    The effect of changes in the gravitational field of developing neurons and myocytes on the development of these cells was investigated using observations of rotated cultures of embryonic spinal neurons and myocytes in a horizontal clinostat, in which rotation produces, from the cells' perspective, a 'vector-free' gravity environment by continous averaging of the vector, thus simulating the microgravity of space. It was found that, at rotation rates between 1 and 50 rpm, cellular and nuclear areas of myocytes become significantly enlarged and the number of presumptive nucleoli increase; in neurons, frequent and large swellings appeared along neuritic shafts. Some of these changes were reversible after the cessation of rotation.

  12. Contribution of the late sodium current to intracellular sodium and calcium overload in rabbit ventricular myocytes treated by anemone toxin.

    Science.gov (United States)

    Kornyeyev, Dmytro; El-Bizri, Nesrine; Hirakawa, Ryoko; Nguyen, Steven; Viatchenko-Karpinski, Serge; Yao, Lina; Rajamani, Sridharan; Belardinelli, Luiz

    2016-02-01

    Pathological enhancement of late Na(+) current (INa) can potentially modify intracellular ion homeostasis and contribute to cardiac dysfunction. We tested the hypothesis that modulation of late INa can be a source of intracellular Na(+) ([Na(+)]i) overload. Late INa was enhanced by exposing rabbit ventricular myocytes to Anemonia sulcata toxin II (ATX-II) and measured using whole cell patch-clamp technique. [Na(+)]i was determined with fluorescent dye Asante NaTRIUM Green-2 AM. Pacing-induced changes in the dye fluorescence measured at 37°C were more pronounced in ATX-II-treated cells than in control (dye washout prevented calibration). At 22-24°C, resting [Na(+)]i was 6.6 ± 0.8 mM. Treatment with 5 nM ATX-II increased late INa 8.7-fold. [Na(+)]i measured after 2 min of electrical stimulation (1 Hz) was 10.8 ± 1.5 mM and 22.1 ± 1.6 mM (P < 0.001) in the absence and presence of 5 nM ATX-II, respectively. Inhibition of late INa with GS-967 (1 μM) prevented Na(+) i accumulation. A strong positive correlation was observed between the late INa and the pacing-induced increase of [Na(+)]i (R(2) = 0.88) and between the rise in [Na(+)]i and the increases in cytosolic Ca(2+) (R(2) = 0.96). ATX-II, tetrodotoxin, or GS-967 did not affect [Na(+)]i in quiescent myocytes suggesting that late INa was solely responsible for triggering the ATX-II effect on [Na(+)]i. Experiments with pinacidil and E4031 indicate that prolongation of the action potential contributes to as much as 50% of the [Na(+)]i overload associated with the increase in late INa caused by ATX-II. Enhancement of late INa can cause intracellular Na(+) overload in ventricular myocytes. Copyright © 2016 the American Physiological Society.

  13. Extracellular high-mobility group box 1 mediates pressure overload-induced cardiac hypertrophy and heart failure.

    Science.gov (United States)

    Zhang, Lei; Liu, Ming; Jiang, Hong; Yu, Ying; Yu, Peng; Tong, Rui; Wu, Jian; Zhang, Shuning; Yao, Kang; Zou, Yunzeng; Ge, Junbo

    2016-03-01

    Inflammation plays a key role in pressure overload-induced cardiac hypertrophy and heart failure, but the mechanisms have not been fully elucidated. High-mobility group box 1 (HMGB1), which is increased in myocardium under pressure overload, may be involved in pressure overload-induced cardiac injury. The objectives of this study are to determine the role of HMGB1 in cardiac hypertrophy and cardiac dysfunction under pressure overload. Pressure overload was imposed on the heart of male wild-type mice by transverse aortic constriction (TAC), while recombinant HMGB1, HMGB1 box A (a competitive antagonist of HMGB1) or PBS was injected into the LV wall. Moreover, cardiac myocytes were cultured and given sustained mechanical stress. Transthoracic echocardiography was performed after the operation and sections for histological analyses were generated from paraffin-embedded hearts. Relevant proteins and genes were detected. Cardiac HMGB1 expression was increased after TAC, which was accompanied by its translocation from nucleus to both cytoplasm and intercellular space. Exogenous HMGB1 aggravated TAC-induced cardiac hypertrophy and cardiac dysfunction, as demonstrated by echocardiographic analyses, histological analyses and foetal cardiac genes detection. Nevertheless, the aforementioned pathological change induced by TAC could partially be reversed by HMGB1 inhibition. Consistent with the in vivo observations, mechanical stress evoked the release and synthesis of HMGB1 in cultured cardiac myocytes. This study indicates that the activated and up-regulated HMGB1 in myocardium, which might partially be derived from cardiac myocytes under pressure overload, may be of crucial importance in pressure overload-induced cardiac hypertrophy and cardiac dysfunction. © 2015 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.

  14. Chaos in the Genesis and Maintenance of Cardiac Arrhythmias

    Science.gov (United States)

    Qu, Zhilin

    2010-01-01

    Dynamical chaos, an irregular behavior of deterministic systems, has been widely shown in nature. It also has been demonstrated in cardiac myocytes in many studies, including rapid pacing induced irregular beat-to-beat action potential alterations and slow pacing induced irregular early afterdepolarizations, etc. Here we review the roles of chaos in the genesis of cardiac arrhythmias, the transition to ventricular fibrillation, and the spontaneous termination of fibrillation, based on evidence from computer simulation of mathematical models and experiments of animal models. PMID:21078337

  15. Pitx2c increases in atrial myocytes from chronic atrial fibrillation patients enhancing IKs and decreasing ICa,L.

    Science.gov (United States)

    Pérez-Hernández, Marta; Matamoros, Marcos; Barana, Adriana; Amorós, Irene; Gómez, Ricardo; Núñez, Mercedes; Sacristán, Sandra; Pinto, Ángel; Fernández-Avilés, Francisco; Tamargo, Juan; Delpón, Eva; Caballero, Ricardo

    2016-03-01

    Atrial fibrillation (AF) produces rapid changes in the electrical properties of the atria (electrical remodelling) that promote its own recurrence. In chronic AF (CAF) patients, up-regulation of the slow delayed rectifier K(+) current (IKs) and down-regulation of the voltage-gated Ca(2+) current (ICa,L) are hallmarks of electrical remodelling and critically contribute to the abbreviation of action potential duration and atrial refractory period. Recent evidences suggested that Pitx2c, a bicoid-related homeodomain transcription factor involved in directing cardiac asymmetric morphogenesis, could play a role in atrial remodelling. However, its effects on IKs and ICa,L are unknown. Real-time quantitative polymerase chain reaction analysis showed that Pitx2c mRNA expression was significantly higher in human atrial myocytes from CAF patients than those from sinus rhythm patients. The expression of Pitx2c was positively and negatively correlated with IKs and ICa,L densities, respectively. Expression of Pitx2c in HL-1 cells increased IKs density and reduced ICa,L density. Luciferase assays demonstrated that Pitx2c increased transcriptional activity of KCNQ1 and KCNE1 genes. Conversely, its effects on ICa,L could be mediated by the atrial natriuretic peptide. Our results demonstrated for the first time that CAF increases Pitx2c expression in isolated human atrial myocytes and suggested that this transcription factor could contribute to the CAF-induced IKs increase and ICa,L reduction observed in humans. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For permissions please email: journals.permissions@oup.com.

  16. Cardiac Alpha1-Adrenergic Receptors: Novel Aspects of Expression, Signaling Mechanisms, Physiologic Function, and Clinical Importance

    Science.gov (United States)

    O’Connell, Timothy D.; Jensen, Brian C.; Baker, Anthony J.

    2014-01-01

    Adrenergic receptors (AR) are G-protein-coupled receptors (GPCRs) that have a crucial role in cardiac physiology in health and disease. Alpha1-ARs signal through Gαq, and signaling through Gq, for example, by endothelin and angiotensin receptors, is thought to be detrimental to the heart. In contrast, cardiac alpha1-ARs mediate important protective and adaptive functions in the heart, although alpha1-ARs are only a minor fraction of total cardiac ARs. Cardiac alpha1-ARs activate pleiotropic downstream signaling to prevent pathologic remodeling in heart failure. Mechanisms defined in animal and cell models include activation of adaptive hypertrophy, prevention of cardiac myocyte death, augmentation of contractility, and induction of ischemic preconditioning. Surprisingly, at the molecular level, alpha1-ARs localize to and signal at the nucleus in cardiac myocytes, and, unlike most GPCRs, activate “inside-out” signaling to cause cardioprotection. Contrary to past opinion, human cardiac alpha1-AR expression is similar to that in the mouse, where alpha1-AR effects are seen most convincingly in knockout models. Human clinical studies show that alpha1-blockade worsens heart failure in hypertension and does not improve outcomes in heart failure, implying a cardioprotective role for human alpha1-ARs. In summary, these findings identify novel functional and mechanistic aspects of cardiac alpha1-AR function and suggest that activation of cardiac alpha1-AR might be a viable therapeutic strategy in heart failure. PMID:24368739

  17. A compartmentalized mathematical model of the β1-adrenergic signaling system in mouse ventricular myocytes.

    Directory of Open Access Journals (Sweden)

    Vladimir E Bondarenko

    Full Text Available The β1-adrenergic signaling system plays an important role in the functioning of cardiac cells. Experimental data shows that the activation of this system produces inotropy, lusitropy, and chronotropy in the heart, such as increased magnitude and relaxation rates of [Ca(2+]i transients and contraction force, and increased heart rhythm. However, excessive stimulation of β1-adrenergic receptors leads to heart dysfunction and heart failure. In this paper, a comprehensive, experimentally based mathematical model of the β1-adrenergic signaling system for mouse ventricular myocytes is developed, which includes major subcellular functional compartments (caveolae, extracaveolae, and cytosol. The model describes biochemical reactions that occur during stimulation of β1-adrenoceptors, changes in ionic currents, and modifications of Ca(2+ handling system. Simulations describe the dynamics of major signaling molecules, such as cyclic AMP and protein kinase A, in different subcellular compartments; the effects of inhibition of phosphodiesterases on cAMP production; kinetics and magnitudes of phosphorylation of ion channels, transporters, and Ca(2+ handling proteins; modifications of action potential shape and duration; magnitudes and relaxation rates of [Ca(2+]i transients; changes in intracellular and transmembrane Ca(2+ fluxes; and [Na(+]i fluxes and dynamics. The model elucidates complex interactions of ionic currents upon activation of β1-adrenoceptors at different stimulation frequencies, which ultimately lead to a relatively modest increase in action potential duration and significant increase in [Ca(2+]i transients. In particular, the model includes two subpopulations of the L-type Ca(2+ channels, in caveolae and extracaveolae compartments, and their effects on the action potential and [Ca(2+]i transients are investigated. The presented model can be used by researchers for the interpretation of experimental data and for the developments of

  18. Calcium and IP3 dynamics in cardiac myocytes: Experimental and computational perspectives and approaches

    Directory of Open Access Journals (Sweden)

    Felix eHohendanner

    2014-03-01

    Full Text Available Calcium plays a crucial role in excitation-contraction coupling (ECC, but it is also a pivotal second messenger activating Ca2+-dependent transcription factors in a process termed excitation-transcription coupling (ETC. Evidence accumulated over the past decade indicates a pivotal role of inositol 1,4,5-trisphosphate receptor (IP3R-mediated Ca2+ release in the regulation of cytosolic and nuclear Ca2+ signals. IP3 is generated by stimulation of plasma membrane receptors that couple to phospholipase C (PLC, liberating IP3 from phosphatidylinositol 4,5-bisphosphate (PIP2. An intriguing aspect of IP3 signaling is the presence of the entire PIP2-PLC-IP3 signaling cascade as well as the presence of IP3Rs at the inner and outer membranes of the nuclear envelope (NE which functions as a Ca2+ store. The observation that the nucleus is surrounded by its own putative Ca2+ store raises the possibility that nuclear IP3-dependent Ca2+ release plays a critical role in ETC. This provides a potential mechanism of regulation that acts locally and autonomously from the global cytosolic Ca2+ signal underlying ECC. Moreover, there is evidence that: (i the sarcoplasmic reticulum (SR and NE are a single contiguous Ca2+ store; (ii the nuclear pore complex is the major gateway for Ca2+ and macromolecules to pass between the cytosol and the nucleoplasm; (iii the inner membrane of the NE hosts key Ca2+ handling proteins including the Na+/Ca2+ exchanger (NCX/GM1 complex, ryanodine receptors (RyRs, nicotinic acid adenine dinucleotide phosphate receptors (NAADPRs, Na+/K+ ATPase and Na+/H+ exchanger. Thus, it appears that the nucleus represents a Ca2+ signaling domain equipped with its own ion channels and transporters that allow for complex local Ca2+ signals. Many experimental and modeling approaches have been used for the study of intracellular Ca2+ signaling but the key to understanding of the dual role of Ca2+ mediating ECC and ECT lays in quantitative differences of local [Ca2+

  19. Diabetic cardiomyopathy: from the pathophysiology of the cardiac myocytes to current diagnosis and management strategies

    OpenAIRE

    Voulgari, Christina; Papadogiannis, Dimitrios; Tentolouris, Nicholas

    2010-01-01

    Christina Voulgari, Dimitrios Papadogiannis, Nicholas TentolourisFirst Department of Propaedeutic and Internal Medicine, Athens University Medical School, Laiko General Hospital, Athens, GreeceAbstract: Diabetic cardiomyopathy (DCM), although a distinct clinical entity, is also a part of the diabetic atherosclerosis process. It may be independent of the coexistence of ischemic heart disease, hypertension, or other macrovascular complications. Its pathological substrate is characterized by the...

  20. Stem cells can form gap junctions with cardiac myocytes and exert pro-arrhythmic effects

    Directory of Open Access Journals (Sweden)

    Nicoline Willemijn Smit

    2014-10-01

    Full Text Available Stem cell therapy has been suggested to be a promising option for regeneration of injured myocardium, for example following a myocardial infarction. For clinical use cell-based therapies have to be safe and applicable and are aimed to renovate the architecture of the heart. Yet for functional and coordinated activity synchronized with the host myocardium stem cells have to be capable of forming electrical connections with resident cardiomyocytes. In this paper we discuss whether stem cells are capable of establishing functional electrotonic connections with cardiomyocytes and whether these may generate a risk for arrhythmias. Application of stem cells in the clinical setting with outcomes concerning arrhythmogenic safety and future perspectives will also briefly be touched upon.

  1. When is a Cardiac Arrest Non-Cardiac?

    Science.gov (United States)

    Carter, Ryan M; Cone, David C

    2017-10-01

    Introduction While the overall survival rate for out-of-hospital cardiac arrest (OHCA) is low, ranging from 5%-10%, several characteristics have been shown to decrease mortality, such as presence of bystander cardiopulmonary resuscitation (CPR), witnessed vs unwitnessed events, and favorable initial rhythm (VF/VT). More recently, studies have shown that modified CPR algorithms, such as chest-compression only or cardio-cerebral resuscitation, can further increase survival rates in OHCA. Most of these studies have included only OHCA patients with "presumed cardiac etiology," on the assumption that airway management is of lesser impact than chest compressions in these patients. However, prehospital personnel often lack objective and consistent criteria to assess whether an OHCA is of cardiac or non-cardiac etiology. Hypothesis/Problem The relative proportions of cardiac vs non-cardiac etiology in published data sets of OHCA in the peer-reviewed literature were examined in order to assess the variability of prehospital clinical etiology assessment. A Medline (US National Library of Medicine, National Institutes of Health; Bethesda, Maryland USA) search was performed using the subject headings "OHCA" and "Emergency Medical Services" (EMS). Studies were included if they reported prevalence of cardiac etiology among OHCA in the entire patient sample, or in all arms of a comparison study. Studies that either did not report etiology of OHCA, or that excluded all cardiac or non-cardiac etiologies prior to reporting clinical data, were excluded. Twenty-four studies were identified, containing 27 datasets of OHCA which reported the prevalence of presumed cardiac vs non-cardiac etiology. These 27 datasets were drawn from 15 different countries. The prevalence of cardiac etiology among OHCA ranged from 50% to 91%. No obvious patterns were found regarding database size, year of publication, or global region (continent) of origin. There exists significant variation in published

  2. Leptin modulates electrophysiological characteristics and isoproterenol-induced arrhythmogenesis in atrial myocytes

    OpenAIRE

    Lin, Yung-Kuo; Chen, Yao-Chang; Huang, Jen-Hung; Lin, Yenn-Jiang; Huang, Shiang-Suo; Chen, Shih-Ann; Chen, Yi-Jen

    2013-01-01

    Background Obesity is an important risk factor for atrial fibrillation (AF). Leptin is an important adipokine. However, it is not clear whether leptin directly modulates the electrophysiological characteristics of atrial myocytes. Results Whole cell patch clamp and indo-1 fluorescence were used to record the action potentials (APs) and ionic currents in isolated rabbit left atrial (LA) myocytes incubated with and without (control) leptin (100 nM) for 1 h to investigate the role of leptin on a...

  3. Standard and Strain Measurements by Echocardiography Detect Early Overloaded Right Ventricular Dysfunction: Validation against Hemodynamic and Myocyte Contractility Changes in a Large Animal Model.

    Science.gov (United States)

    Hodzic, Amir; Bobin, Pierre; Mika, Delphine; Ly, Mohamed; Lefebvre, Florence; Lechêne, Patrick; Le Bret, Emmanuel; Gouadon, Elodie; Coblence, Mathieu; Vandecasteele, Grégoire; Capderou, André; Leroy, Jérôme; Rucker-Martin, Catherine; Lambert, Virginie

    2017-11-01

    Early detection of right ventricular (RV) failure is required to improve the management of patients with congenital heart diseases. The aim of this study was to validate echocardiography for the early detection of overloaded RV dysfunction, compared with hemodynamic and myocyte contractility assessment. Using a porcine model reproducing repaired tetralogy of Fallot, RV function was evaluated over 4 months using standard echocardiography and speckle-tracking compared with hemodynamic parameters (conductance catheter). Sarcomere shortening and calcium transients were recorded in RV isolated myocytes. Contractile reserve (ΔEmax) was assessed by β-adrenergic stimulation in vivo (dobutamine 5 μg/kg) and ex vivo (isoproterenol 100 nM). Six operated animals were compared with four age- and sex-matched controls. In the operated group, hemodynamic RV efficient ejection fraction was significantly decreased (29.7% [26.2%-34%] vs 42.9% [40.7%-48.6%], P < .01), and inotropic responses to dobutamine were attenuated (ΔEmax was 51% vs 193%, P < .05). Echocardiographic measurements of fraction of area change, tricuspid annular plane systolic excursion, tricuspid annular peak systolic velocity (S') and RV free wall longitudinal systolic strain and strain rate were significantly decreased. Strain rate, S', and tricuspid annular plane systolic excursion were correlated with ΔEmax (r = 0.75, r = 0.78, and r = 0.65, respectively, P < .05). These alterations were associated in RV isolated myocytes with the decrease of sarcomere shortening in response to isoproterenol and perturbations of calcium homeostasis assessed by the increase of spontaneous calcium waves. In this porcine model, both standard and strain echocardiographic parameters detected early impairments of RV function and cardiac reserve, which were associated with cardiomyocyte excitation-contraction coupling alterations. Copyright © 2017 American Society of Echocardiography. Published by Elsevier Inc

  4. miR-28 promotes cardiac ischemia by targeting mitochondrial aldehyde dehydrogenase 2 (ALDH2) in mus musculus cardiac myocytes.

    Science.gov (United States)

    Li, S-P; Liu, B; Song, B; Wang, C-X; Zhou, Y-C

    2015-01-01

    Aldehyde dehydrogenase 2 (ALDH2) is a crucial enzyme involved in protecting the heart from ischemic. MicroRNAs (miRNAs) are involved in gene down-regulation. However, this mechanism is unclear. The aim of this study was to investigate the role of miR-28 in the regulation of ALDH2 and to explore the mechanism of miR-28 in musculus of myocardial ischemia. To evaluate the role of miR-28, we assessed cellular apoptosis. In addition, the regulation of ALDH2 by miR-199b was evaluated by Western blotting and luciferase assay. MiR-28 was up-regulated, while ALDH2 expression decreased in a time-dependent manner under normoxic conditions. The miR-28-transfected cells showed a significant decrease in the cellular apoptosis. Compared with the negative control 1 precursor molecules, miR-28 over-expression caused about 55% increase in myocardial apoptosis under hypoxic conditions, and miR-28 silencing by anti-miR-28 attenuated a 41% decreasing in apoptosis. MiR-28 and pGL3-ALDH2 vector-transfected cells showed that ALDH2 protein expression was suppressed and luciferase activity was reduced. These findings suggest that miR-28 promotes myocardial ischemia through the inhibition of ALDH2 expression in mus. miRNAs is as a probable index in identification of myocardial ischemia after acute myocardial infarction.

  5. Acute Simvastatin Inhibits KATP Channels of Porcine Coronary Artery Myocytes

    Science.gov (United States)

    Zhang, Qian; Li, Rachel Wai Sum; Kong, Siu Kai; Ngai, Sai Ming; Wan, Song; Ho, Ho Pui; Lee, Simon Ming Yuen; Hoi, Maggie Pui Man; Chan, Shun Wan; Leung, George Pak Heng; Kwan, Yiu Wa

    2013-01-01

    Background Statins (3-hydroxy-3-methyl-glutaryl coenzyme A (HMG-CoA) reductase inhibitors) consumption provides beneficial effects on cardiovascular systems. However, effects of statins on vascular KATP channel gatings are unknown. Methods Pig left anterior descending coronary artery and human left internal mammary artery were isolated and endothelium-denuded for tension measurements and Western immunoblots. Enzymatically-dissociated/cultured arterial myocytes were used for patch-clamp electrophysiological studies and for [Ca2+]i, [ATP]i and [glucose]o uptake measurements. Results The cromakalim (10 nM to 10 µM)- and pinacidil (10 nM to 10 µM)-induced concentration-dependent relaxation of porcine coronary artery was inhibited by simvastatin (3 and 10 µM). Simvastatin (1, 3 and 10 µM) suppressed (in okadaic acid (10 nM)-sensitive manner) cromakalim (10 µM)- and pinacidil (10 µM)-mediated opening of whole-cell KATP channels of arterial myocytes. Simvastatin (10 µM) and AICAR (1 mM) elicited a time-dependent, compound C (1 µM)-sensitive [3H]-2-deoxy-glucose uptake and an increase in [ATP]i levels. A time (2–30 min)- and concentration (0.1–10 µM)-dependent increase by simvastatin of p-AMPKα-Thr172 and p-PP2A-Tyr307 expression was observed. The enhanced p-AMPKα-Thr172 expression was inhibited by compound C, ryanodine (100 µM) and KN93 (10 µM). Simvastatin-induced p-PP2A-Tyr307 expression was suppressed by okadaic acid, compound C, ryanodine, KN93, phloridzin (1 mM), ouabain (10 µM), and in [glucose]o-free or [Na+]o-free conditions. Conclusions Simvastatin causes ryanodine-sensitive Ca2+ release which is important for AMPKα-Thr172 phosphorylation via Ca2+/CaMK II. AMPKα-Thr172 phosphorylation causes [glucose]o uptake (and an [ATP]i increase), closure of KATP channels, and phosphorylation of AMPKα-Thr172 and PP2A-Tyr307 resulted. Phosphorylation of PP2A-Tyr307 occurs at a site downstream of AMPKα-Thr172 phosphorylation. PMID:23799098

  6. The effects of aging on the regulation of t-tubular ICa by caveolin in mouse ventricular myocytes.

    Science.gov (United States)

    Kong, Cherrie H T; Bryant, Simon M; Watson, Judy J; Gadeberg, Hanne C; Roth, David M; Patel, Hemal H; Cannell, Mark B; Orchard, Clive H; James, Andrew F

    2017-12-09

    Aging is associated with diminished cardiac function in males. Cardiac excitation-contraction coupling in ventricular myocytes involves Ca influx via the Ca current (ICa) and Ca release from the sarcoplasmic reticulum, which occur predominantly at t-tubules. Caveolin-3 regulates t-tubular ICa, partly through PKA, and both ICa and caveolin-3 decrease with age. We therefore investigated ICa and t-tubule structure and function in cardiomyocytes from male WT and caveolin-3-overexpressing (Cav-3OE) mice at 3 and 24 months of age. In WT cardiomyocytes, t-tubular ICa-density was reduced by ~50% with age while surface ICa density was unchanged. Although regulation by PKA was unaffected by age, inhibition of caveolin-3-binding reduced t-tubular ICa at 3-mo, but not 24-mo. While Cav-3OE increased cardiac caveolin-3 protein expression ~2.5-fold at both ages, the age-dependent reduction in caveolin-3 (WT ~35%) was preserved in transgenic mice. Overexpression of caveolin-3 reduced t-tubular ICa density at 3-mo but prevented further ICa loss with age. Measurement of Ca release at the t-tubules revealed that the triggering of local Ca release by t-tubular ICa was unaffected by age. In conclusion, the data suggest that the reduction in ICa density with age is associated with the loss of a caveolin-3-dependent mechanism that augments t-tubular ICa density. © The Author(s) 2017. Published by Oxford University Press on behalf of The Gerontological Society of America.

  7. Overview of cardiac markers in heart disease.

    Science.gov (United States)

    Jarolim, Petr

    2014-03-01

    Cardiac troponins I and T have been the cornerstone of diagnostics of acute coronary syndrome for almost 20 years. Natriuretic peptides have established themselves in heart failure during the last decade. These and additional promising biomarkers, such as ST-2, galectin-3, GDF-15, copeptin, midregional proadrenomedullin, and the markers of glomerular filtration rate and kidney injury, are reviewed in groups corresponding to the pathophysiological processes they probe--cardiomyocyte injury, myocyte stress, inflammation, oxidative stress, plaque instability, extracellular-matrix remodeling, or those markers grouped in the neurohormone category. Biomarkers linking the renal and cardiac functions and microRNAs and metabolomic markers are addressed as well. Copyright © 2014 Elsevier Inc. All rights reserved.

  8. Syzygium aromaticum L. (Clove) extract regulates energy metabolism in myocytes.

    Science.gov (United States)

    Tu, Zheng; Moss-Pierce, Tijuana; Ford, Paul; Jiang, T Alan

    2014-09-01

    The prevalence of metabolic syndrome and type 2 diabetes is increasing worldwide. Herbs and spices have been used for the treatment of diabetes for centuries in folk medicine. Syzygium aromaticum L. (Clove) extracts (SE) have been shown to perform comparably to insulin by significantly reducing blood glucose levels in animal models; however, the mechanisms are not well understood. We investigated the effects of clove on metabolism in C2C12 myocytes and demonstrated that SE significantly increases glucose consumption. The phosphorylation of AMP-activated protein kinase (AMPK), as well as its substrate, acetyl-CoA carboxylase (ACC) was increased by SE treatment. SE also transcriptionally regulates genes involved in metabolism, including sirtuin 1 (SIRT1) and PPARγ coactivator 1α (PGC1α). Nicotinamide, an SIRT1 inhibitor, diminished SE's effects on glucose consumption. Furthermore, treatment with SE dose-dependently increases muscle glycolysis and mitochondrial spare respiratory capacity. Overall, our study suggests that SE has the potential to increase muscle glycolysis and mitochondria function by activating both AMPK and SIRT1 pathways.

  9. Growth hormone regulates the expression of UCP2 in myocytes.

    Science.gov (United States)

    Futawaka, Kumi; Tagami, Tetsuya; Fukuda, Yuki; Koyama, Rie; Nushida, Ayaka; Nezu, Syoko; Imamoto, Miyuki; Kasahara, Masato; Moriyama, Kenji

    2016-08-01

    To determine if and how growth hormone (GH) signaling is involved in energy metabolism. We used human embryonic kidney TSA201 cells, human H-EMC-SS chondrosarcoma cells, rat L6 skeletal muscle cells, and murine C2C12 skeletal muscle myoblasts to investigate GH-induced expression of uncoupling protein2 (UCP2) to the GHR/JAK/STAT5 pathway by a combination of a reporter assay, electrophoretic mobility shift assay (EMSA), real-time quantitative PCR, Western blotting. We demonstrated that the regulation energy metabolism, which was hypothesized to be directly acted on by GH, involves UCP2 via activated STAT5B, a signal transducer downstream of GH. We also showed that the sequence at the -586 'TTCnGA' may function as a novel putative consensus sequence of STAT5s. The results suggest that GH regulates energy metabolism directly in myocytes and that UCP2 participates in the signal transduction pathway that functions downstream of the GHR/JAK/STAT. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Comparison of fractal dimension and Shannon entropy in myocytes from rats treated with histidine-tryptophan-glutamate and histidine-tryptophan cetoglutarate

    Science.gov (United States)

    de Oliveira, Marcos Aurélio Barboza; Brandi, Antônio Carlos; dos Santos, Carlos Alberto; Botelho, Paulo Henrique Husseni; Cortez, José Luís Lasso; de Godoy, Moacir Fernandes; Braile, Domingo Marcolino

    2014-01-01

    Introduction Solutions that cause elective cardiac arrest are constantly evolving, but the ideal compound has not yet been found. The authors compare a new cardioplegic solution with histidine-tryptophan-glutamate (Group 2) and other one with histidine-tryptophan-cetoglutarate (Group 1) in a model of isolated rat heart. Objective To quantify the fractal dimension and Shannon entropy in rat myocytes subjected to cardioplegia solution using histidine-tryptophan with glutamate in an experimental model, considering the caspase markers, IL-8 and KI-67. Methods Twenty male Wistar rats were anesthetized and heparinized. The chest was opened, the heart was withdrawn and 40 ml/kg of cardioplegia (with histidine-tryptophan-cetoglutarate or histidine-tryptophan-glutamate solution) was infused. The hearts were kept for 2 hours at 4ºC in the same solution, and thereafter placed in the Langendorff apparatus for 30 min with Ringer-Locke solution. Analyzes were performed for immunohistochemical caspase, IL-8 and KI-67. Results The fractal dimension and Shannon entropy were not different between groups histidine-tryptophan-glutamate and histidine-tryptophan-acetoglutarate. Conclusion The amount of information measured by Shannon entropy and the distribution thereof (given by fractal dimension) of the slices treated with histidine-tryptophan-cetoglutarate and histidine-tryptophan-glutamate were not different, showing that the histidine-tryptophan-glutamate solution is as good as histidine-tryptophan-acetoglutarate to preserve myocytes in isolated rat heart. PMID:25140464

  11. Iodine 125-phenylpentadecanoic acid and its beta-methyl substitute metabolism in cultured mouse embryonal myocytes; Iodine-labelled fatty acids as tracers of myocardial high energy phosphate

    Energy Technology Data Exchange (ETDEWEB)

    Okano, Mitsuji; Ohsuzu, Fumitaka; Sakata, Nobuhiro; Katsushika, Shuuichi; Nakamura, Haruo (National Defense Medical Coll., Tokorozawa, Saitama (Japan)); Ishida, Hideyuki; Aosaki, Noboru

    1993-02-01

    Iodine-labelled fatty acids have been proposed as new tracers of cardiac metabolisms. However, it is not clear how these tracers would reflect the intracellular metabolism. Therefore, we measured the uptake and release of iodine 125-labelled phenylpentadecanoic acid (IPPA), its [beta]-methyl substitute (BMIPP) and [sup 201]Tl in cultured myocytes of mouse embryos, and compared these values to intracellular adenosine triphosphate (ATP) content after metabolic inhibitions of oxidative phosphorylation by sodium cyanide (CN), glycolysis by 2-deoxyglucose (2-DG) or fatty acid [beta]-oxidation by lactate. The uptake and release of BMIPP was not changed by any inhibitors suggesting BMIPP would not be metabolized in the myocytes. The uptake of IPPA was significantly reduced by 2DG and 60-80% of IPPA was metabolized to hydrophilic catabolites. The correlation of BMIPP and IPPA uptake to intracellular ATP content were high (r=0.89, p<0.05; r=0.86, p<0.1), but there was poor correlation of [sup 201]Tl to ATP values (r=0.53, n.s.). These results suggested that iodine-labelled fatty acids could be used as better tracers of myocardial metabolism than [sup 201]Tl. (author).

  12. Naturally occurring cardiac glycosides.

    Science.gov (United States)

    Radford, D J; Gillies, A D; Hinds, J A; Duffy, P

    1986-05-12

    Cardiac glycoside poisoning from the ingestion of plants, particularly of oleanders, occurs with reasonable frequency in tropical and subtropical areas. We have assessed a variety of plant specimens for their cardiac glycoside content by means of radioimmunoassays with antibodies that differ in their specificity for cardiac glycosides. Significant amounts of immunoreactive cardiac glycoside were found to be present in the ornamental shrubs: yellow oleander (Thevetia peruviana); oleander (Nerium oleander); wintersweet (Carissa spectabilis); bushman's poison (Carissa acokanthera); sea-mango (Cerbera manghas); and frangipani (Plumeria rubra); and in the milkweeds: redheaded cotton-bush (Asclepias curassavica); balloon cotton (Asclepias fruiticosa); king's crown (Calotropis procera); and rubber vine (Cryptostegia grandifolia). The venom gland of the cane toad (Bufo marinus) also contained large quantities of cardiac glycosides. The competitive immunoassay method permits the rapid screening of specimens that are suspected to contain cardiac glycosides. Awareness of the existence of these plant and animal toxins and their dangers allows them to be avoided and poisoning prevented. The method is also useful for the confirmation of the presence of cardiac glycosides in serum in cases of poisoning.

  13. Dose-dependent apoptotic and necrotic myocyte death induced by the beta2-adrenergic receptor agonist, clenbuterol.

    Science.gov (United States)

    Burniston, Jatin G; Chester, Neil; Clark, William A; Tan, Lip-Bun; Goldspink, David F

    2005-12-01

    We have investigated the dose- and time-dependency of myocyte apoptosis and necrosis induced by the beta2-adrenergic receptor agonist, clenbuterol, with the aim of determining whether myocyte apoptosis and necrosis are two separate processes or a continuum of events. Male Wistar rats were administered subcutaneous injections of clenbuterol, and immunohistochemistry was used to detect myocyte-specific apoptosis and necrosis. Myocyte apoptosis peaked 4 h after, and necrosis 12 h after, clenbuterol administration. In the soleus, peak apoptosis (5.8 +/- 2.0%; P clenbuterol. Twelve hours after clenbuterol administration, 73% of damaged myocytes labeled as necrotic, 27% as apoptotic and necrotic, and 0% as purely apoptotic. Administrations of clenbuterol (10 microg x kg(-1)) at 48-h intervals induced cumulative myocyte death over 8 days. These data show that the phenotype of myocyte death is dependent on the magnitude of the insult and the time at which it is investigated. Only very low doses induced apoptosis alone; in most cases apoptotic myocytes lysed and became necrotic and the magnitude of necrosis was greater than that of apoptosis. Thus, it is important to investigate both apoptotic and necrotic myocyte death, contrary to the current trend of only investigating apoptotic cell death.

  14. Dose-dependent apoptotic and necrotic myocyte death induced by the β2-adrenergic receptor agonist, clenbuterol

    Science.gov (United States)

    Burniston, Jatin G; Chester, Neil; Clark, William A; Tan, Lip-Bun; Goldspink, David F

    2007-01-01

    We have investigated the dose- and time-dependency of myocyte apoptosis and necrosis induced by the β2-adrenergic receptor agonist, clenbuterol, with the aim of determining whether myocyte apoptosis and necrosis are two separate processes or a continuum of events. Male Wistar rats were administered subcutaneous injections of clenbuterol, and immunohistochemistry was used to detect myocyte specific apoptosis and necrosis. Myocyte apoptosis peaked 4 h after, and necrosis 12 h after, clenbuterol administration. In the soleus, peak apoptosis (5.8 ± 2.0 %; Pclenbuterol kg-1. Twelve hours after clenbuterol administration, 73 % of damaged myocytes labelled as necrotic, 27 % as apoptotic and necrotic and none labelled as purely apoptotic. Bi-daily administrations of 10 μg of clenbuterol kg-1 induced cumulative myocyte death over 8 days. These data show that the phenotype of myocyte death is dependent on the magnitude of the insult and the time at which it is investigated. Only very low doses induced only apoptosis, in most cases apoptotic myocytes lysed and became necrotic and the magnitude of necrosis was greater than that of apoptosis. Thus, it is important to investigate both apoptotic and necrotic myocyte death, this being contrary to the current trend of only investigating apoptotic cell death. PMID:16007677

  15. Cardiac-specific overexpression of the human short CLC-3 chloride channel isoform in mice.

    Science.gov (United States)

    Xiong, Dazhi; Wang, Ge-Xin; Burkin, Dean J; Yamboliev, Ilia A; Singer, Cherie A; Rawat, Shanti; Scowen, Paul; Evans, Rebecca; Ye, Linda; Hatton, William J; Tian, Honglin; Keller, Phillip S; McCloskey, Diana T; Duan, Dayue; Hume, Joseph R

    2009-04-01

    1. ClC-3 has been proposed as a molecular candidate responsible for volume-sensitive outwardly rectifying anion channels (VSOAC) in cardiac and smooth muscle cells. To further test this hypothesis, we produced a novel line of transgenic mice with cardiac-specific overexpression of the human short ClC-3 isoform (hsClC-3). 2. Northern and western blot analyses demonstrated that mRNA and protein levels of the short isoform (sClC-3) in the heart were significantly increased in hsClC-3-overexpressing (OE) mice compared with wild-type (WT) mice. Heart weight : bodyweight ratios for OE mice were significantly smaller compared with age-matched WT mice. 3. Electrocardiogram recordings indicated no difference at rest, whereas echocardiographic recordings revealed consistent reductions in left ventricular diastolic diameter, left ventricular posterior wall thickness at end of diastole and interventricular septum thickness in diastole in OE mice. 4. The VSOAC current densities in atrial cardiomyocytes were significantly increased by ClC-3 overexpression compared with WT cells. No differences in VSOAC current properties in OE and WT atrial myocytes were observed in terms of outward rectification, anion permeability (I(-) > Cl(-) > Asp(-)) and inhibition by 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid and glibenclamide. The VSOAC in atrial myocytes from both groups were totally abolished by phorbol-12,13-dibutyrate (a protein kinase C activator) and by intracellular dialysis of an N-terminal anti-ClC-3 antibody. 5. Cardiac cell volume measurements revealed a significant acceleration of the rate of regulatory volume decrease (RVD) in OE myocytes compared with WT. 6. In conclusion, enhanced VSOAC currents and acceleration of the time-course of RVD in atrial myocytes of OE mice is strong evidence supporting an essential role of sClC-3 in native VSOAC function in mouse atrial myocytes.

  16. Leptin modulates electrophysiological characteristics and isoproterenol-induced arrhythmogenesis in atrial myocytes.

    Science.gov (United States)

    Lin, Yung-Kuo; Chen, Yao-Chang; Huang, Jen-Hung; Lin, Yenn-Jiang; Huang, Shiang-Suo; Chen, Shih-Ann; Chen, Yi-Jen

    2013-12-20

    Obesity is an important risk factor for atrial fibrillation (AF). Leptin is an important adipokine. However, it is not clear whether leptin directly modulates the electrophysiological characteristics of atrial myocytes. Whole cell patch clamp and indo-1 fluorescence were used to record the action potentials (APs) and ionic currents in isolated rabbit left atrial (LA) myocytes incubated with and without (control) leptin (100 nM) for 1 h to investigate the role of leptin on atrial electrophysiology. Leptin-treated LA myocytes (n = 19) had longer 20% of AP duration (28 ± 3 vs. 21 ± 2 ms, p  0.05), and 90% of AP duration (89 ± 5 vs. 94 ± 4 ms, p > 0.05), as compared to the control (n = 22). In the presence of isoproterenol (10 nM), leptin-treated LA myocytes (n = 21) showed a lower incidence (19% vs. 54.2%, p Leptin-treated LA myocytes showed a larger sodium current, but a smaller ultra-rapid delayed rectifier potassium current, and sodium-calcium exchanger current than the control. Leptin-treated and control LA myocytes exhibited a similar late sodium current, inward rectifier potassium current, transient outward current and L-type calcium current. In addition, the leptin-treated LA myocytes (n = 38) exhibited a smaller intracellular Ca2+ transient (0.21 ± 0.01 vs. 0.26 ± 0.01 R410/485, p Leptin regulates the LA electrophysiological characteristics and attenuates isoproterenol-induced arrhythmogenesis.

  17. Effects of Potassium-Channel Opener on Thallium-201 Kinetics: In-vitro Study in Rat Myocyte Preparations and In-vivo Mice Biodistribution Study

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jae Tae; Kim, Eun Ji; Ahn, Byeong Cheol; Son, Kang Kyun; Lee, Kyu Bo [Kyungpook National University School of Medicine, Taegu (Korea, Republic of); Ha, Jeoung Hee [Youngnam University Medical School, Taegu (Korea, Republic of); Kim, Chun Ki [Mt. Sinai School of Medicine, New York (United States)

    1996-10-15

    Potassium channel opener (K-opener) opens ATP-sensitive K{sup +}-channel located at membrane and induces potassium efflux from cytosol, resulting in intracellular hyperpolarization. Newly synthesized K-opener is currently examined for pharmacologic potency by means of rubidium release test from smooth muscle strip preincubated with Rb-86. Since in-vive behavior of thallium is similar to that of rubidium, we hypothesized that K-opener can alter T1-201 kinetics in vivo. This study was prepared to investigate the effects of pinacidil (one of potent K-openers) on the T1-201 uptake and clearance in cultured myocyte, and in-vivo biodistribution in mice. Spontaneous contracting myocytes were prepared to imitate in-vivo condition from 20 hearts of 3-5 days old Sprague-Dawley rat and cultured for 3-5 days before use (5 X 105 cells/ml). Pinacidil was dissolved in 10% DMSO solution at a final concentration of 100nM or 10uM and was co-incubated with T1-201 in HBSS buffer for 20-min to evaluate its effect on cellular T1-uptake, or challenged to cell preparation pre-incubated with T1-201 for washout study. Two, 40 or 100 mg of pinacidil was injected intravenously into ICR mice at 10 min after 5 muCi T1-201 injection, and organ uptake and whole body retention rate were measured at different time points. Co-incubation of pinacidil with T1-201 resulted in a decrease in T1-201 uptake into cultured myocyte by 1.6 to 2.5 times, depending on pinacidil concentration and activity of T1-201 used. Pinacidil enhanced T1-201 washout by 1.6-3.1 times from myocyte preparations pre-incubated with T1-201. Pinacidil treatment appears to be resulted in mild decreases in blood and liver activity in normal mice, in contrast, renal and cardiac uptake were mildly decreased in a dose dependent manner. Whole body retention ratios of T1-201 were lower at 24 hour after injection with 100 mg of pinacidil than control. These results suggest that treatment with K-opener may affect the interpretation of T1

  18. Advanced glycation end product cross-link breaker attenuates diabetes-induced cardiac dysfunction by improving sarcoplasmic reticulum calcium handling

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    Allyson eKranstuber

    2012-07-01

    Full Text Available Diabetic heart disease is a distinct clinical entity that can progress to heart failure and sudden death. However, the mechanisms responsible for the alterations in excitation-contraction coupling leading to cardiac dysfunction during diabetes are not well known. Hyperglycemia, the landmark of diabetes, leads to the formation of advanced glycation end products (AGE on long-lived proteins, including SR Ca2+ regulatory proteins. However, their pathogenic role on SR Ca2+ handling in cardiac myocytes is unknown. Therefore, we investigated whether an AGE cross-link breaker could prevent the alterations in SR Ca2+ cycling that lead to in vivo cardiac dysfunction during diabetes. Streptozotocin-induced diabetic rats were treated with Alagebrium Chloride (ALT-711 for 8 weeks and compared to age-matched placebo-treated diabetic rats and healthy rats. Cardiac function was assessed by echocardiographic examination. Ventricular myocytes were isolated to assess SR Ca2+ cycling by confocal imaging and quantitative Western blots. Diabetes resulted in in vivo cardiac dysfunction and ALT-711 therapy partially alleviated diastolic dysfunction by decreasing isovolumetric relaxation time and myocardial performance index (by 27 and 41% vs. untreated diabetic rats, respectively, P<0.05. In cardiac myocytes, diabetes induced prolongation of cytosolic Ca2+ transient clearance by 43% and decreased SR Ca2+ load by 25% (P<0.05; these parameters were partially improved after ALT-711 therapy. SERCA2a and RyR2 protein expression was significantly decreased in the myocardium of untreated diabetic rats (by 64 and 36% vs. controls, respectively, P<0.05, but preserved in the treated diabetic group compared to controls. Collectively, our result suggest that, in a model of type 1 diabetes, AGE accumulation primarily impairs SR Ca2+ reuptake in cardiac myocytes and that long term treatment with an AGE cross-link breaker partially normalized SR Ca2+ handling and improved diabetic

  19. Cardiac Physiology of Aging: Extracellular Considerations.

    Science.gov (United States)

    Horn, Margaux A

    2015-07-01

    Aging is a major risk factor for the development of cardiovascular disease, with the majority of affected patients being elderly. Progressive changes to myocardial structure and function occur with aging, often in concert with underlying pathologies. However, whether chronological aging results in a remodeled "aged substrate" has yet to be established. In addition to myocyte contractility, myocardial performance relies heavily on the cardiac extracellular matrix (ECM), the roles of which are as dynamic as they are significant; including providing structural integrity, assisting in force transmission throughout the cardiac cycle and acting as a signaling medium for communication between cells and the extracellular environment. In the healthy heart, ECM homeostasis must be maintained, and matrix deposition is in balance with degradation. Consequently, alterations to, or misregulation of the cardiac ECM has been shown to occur in both aging and in pathological remodeling with disease. Mounting evidence suggests that age-induced matrix remodeling may occur at the level of ECM control; including collagen synthesis, deposition, maturation, and degradation. Furthermore, experimental studies using aged animal models not only suggest that the aged heart may respond differently to insult than the young, but the identification of key players specific to remodeling with age may hold future therapeutic potential for the treatment of cardiac dysfunction in the elderly. This review will focus on the role of the cardiac interstitium in the physiology of the aging myocardium, with particular emphasis on the implications to age-related remodeling in disease. © 2015 American Physiological Society.

  20. 3-OST-7 Regulates BMP-Dependent Cardiac Contraction

    Science.gov (United States)

    Samson, Shiela C.; Ferrer, Tania; Jou, Chuanchau J.; Sachse, Frank B.; Shankaran, Sunita S.; Shaw, Robin M.; Chi, Neil C.; Tristani-Firouzi, Martin; Yost, H. Joseph

    2013-01-01

    The 3-O-sulfotransferase (3-OST) family catalyzes rare modifications of glycosaminoglycan chains on heparan sulfate proteoglycans, yet their biological functions are largely unknown. Knockdown of 3-OST-7 in zebrafish uncouples cardiac ventricular contraction from normal calcium cycling and electrophysiology by reducing tropomyosin4 (tpm4) expression. Normal 3-OST-7 activity prevents the expansion of BMP signaling into ventricular myocytes, and ectopic activation of BMP mimics the ventricular noncontraction phenotype seen in 3-OST-7 depleted embryos. In 3-OST-7 morphants, ventricular contraction can be rescued by overexpression of tropomyosin tpm4 but not by troponin tnnt2, indicating that tpm4 serves as a lynchpin for ventricular sarcomere organization downstream of 3-OST-7. Contraction can be rescued by expression of 3-OST-7 in endocardium, or by genetic loss of bmp4. Strikingly, BMP misregulation seen in 3-OST-7 morphants also occurs in multiple cardiac noncontraction models, including potassium voltage-gated channel gene, kcnh2, affected in Romano-Ward syndrome and long-QT syndrome, and cardiac troponin T gene, tnnt2, affected in human cardiomyopathies. Together these results reveal 3-OST-7 as a key component of a novel pathway that constrains BMP signaling from ventricular myocytes, coordinates sarcomere assembly, and promotes cardiac contractile function. PMID:24311987

  1. 3-OST-7 regulates BMP-dependent cardiac contraction.

    Directory of Open Access Journals (Sweden)

    Shiela C Samson

    2013-12-01

    Full Text Available The 3-O-sulfotransferase (3-OST family catalyzes rare modifications of glycosaminoglycan chains on heparan sulfate proteoglycans, yet their biological functions are largely unknown. Knockdown of 3-OST-7 in zebrafish uncouples cardiac ventricular contraction from normal calcium cycling and electrophysiology by reducing tropomyosin4 (tpm4 expression. Normal 3-OST-7 activity prevents the expansion of BMP signaling into ventricular myocytes, and ectopic activation of BMP mimics the ventricular noncontraction phenotype seen in 3-OST-7 depleted embryos. In 3-OST-7 morphants, ventricular contraction can be rescued by overexpression of tropomyosin tpm4 but not by troponin tnnt2, indicating that tpm4 serves as a lynchpin for ventricular sarcomere organization downstream of 3-OST-7. Contraction can be rescued by expression of 3-OST-7 in endocardium, or by genetic loss of bmp4. Strikingly, BMP misregulation seen in 3-OST-7 morphants also occurs in multiple cardiac noncontraction models, including potassium voltage-gated channel gene, kcnh2, affected in Romano-Ward syndrome and long-QT syndrome, and cardiac troponin T gene, tnnt2, affected in human cardiomyopathies. Together these results reveal 3-OST-7 as a key component of a novel pathway that constrains BMP signaling from ventricular myocytes, coordinates sarcomere assembly, and promotes cardiac contractile function.

  2. Cardiac metabolism in myocardial ischemia.

    Science.gov (United States)

    Rosano, Giuseppe M C; Fini, Massimo; Caminiti, Giuseppe; Barbaro, Giuseppe

    2008-01-01

    Myocardial ischemia occurs for a mismatch between blood flow and metabolic requirements, when the rate of oxygen and metabolic substrates delivery to the myocardium is insufficient to meet the myocardial energy requirements for a given myocardial workload. During ischemia, substantial changes occur in cardiac energy metabolism, as a consequence of the reduced oxygen availability. Some of these metabolic changes are beneficial and may help the heart adapt to the ischemic condition. However, most of the changes are maladaptive and contribute to the severity of the ischemic injury leading stunned or hibernating myocardium, cell death and ultimately to contractile disfunction. Dramatic changes in cardiac metabolism and contractile function, also occur during myocardial reperfusion as a consequence of the generation of oxygen free radicals, loss of cation homeostasis, depletion of energy stores, and changes in subcellular activities. The reperfusion injury may cause in the death of cardiac myocytes that were still viable immediately before myocardial reperfusion. This form of myocardial injury, by itself can induce cardiomyocyte death and increase infarct size. During acute ischemia the relative substrate concentration is the prime factor defining preference and utilization rate. Allosteric enzyme regulation and protein phosphorylation cascades, partially controlled by hormones such as insulin, modulate the concentration effect; together they provide short-term adjustments of cardiac energy metabolism. The expression of metabolic genes is also dynamically regulated in response to developmental and (patho)physiological conditions, leading to long-term adjustments. Specific nuclear receptor transcription factors and co-activators regulate the expression of these genes. Understanding the functional role of these changes is critical for developing the concept of metabolic intervention for heart disease. The paper will review the alterations in energy metabolism that occur

  3. Electrical stimulation directs engineered cardiac tissue to an age-matched native phenotype

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    Richard A Lasher

    2012-12-01

    Full Text Available Quantifying structural features of native myocardium in engineered tissue is essential for creating functional tissue that can serve as a surrogate for in vitro testing or the eventual replacement of diseased or injured myocardium. We applied three-dimensional confocal imaging and image analysis to quantitatively describe the features of native and engineered cardiac tissue. Quantitative analysis methods were developed and applied to test the hypothesis that environmental cues direct engineered tissue toward a phenotype resembling that of age-matched native myocardium. The analytical approach was applied to engineered cardiac tissue with and without the application of electrical stimulation as well as to age-matched and adult native tissue. Individual myocytes were segmented from confocal image stacks and assigned a coordinate system from which measures of cell geometry and connexin-43 spatial distribution were calculated. The data were collected from 9 nonstimulated and 12 electrically stimulated engineered tissue constructs and 5 postnatal day 12 and 7 adult hearts. The myocyte volume fraction was nearly double in stimulated engineered tissue compared to nonstimulated engineered tissue (0.34 ± 0.14 vs 0.18 ± 0.06 but less than half of the native postnatal day 12 (0.90 ± 0.06 and adult (0.91 ± 0.04 myocardium. The myocytes under electrical stimulation were more elongated compared to nonstimulated myocytes and exhibited similar lengths, widths, and heights as in age-matched myocardium. Furthermore, the percentage of connexin-43-positive membrane staining was similar in the electrically stimulated, postnatal day 12, and adult myocytes, whereas it was significantly lower in the nonstimulated myocytes. Connexin-43 was found to be primarily located at cell ends for adult myocytes and irregularly but densely clustered over the membranes of nonstimulated, stimulated, and postnatal day 12 myocytes. These findings support our hypothesis and reveal

  4. Myocyte growth, repair, and oxidative stress following pediatric heart transplantation.

    Science.gov (United States)

    Dipchand, Anne I; White, Michel; Manlhiot, Cedric; Pollock-BarZiv, Stacey; Allain-Rooney, Tina; West, Lori; He, Ying; Touyz, Rhian M

    2014-11-01

    Cardiac remodeling is associated with plasma biomarkers of fibrinogenesis, inflammation, and oxidative stress, and upregulation of mitogenic, pro-fibrotic, and apoptotic signaling pathways. Our primary objective was to evaluate biomarker and subcellular myocardial changes in pediatric heart transplant recipients. Fifty-two-week prospective, randomized (tacrolimus, Tac, vs. cyclosporine, CsA), open-label, parallel group study. Serial myocardial biopsies were probed for mitogenic and pro-inflammatory proteins. Plasma biomarkers of oxidative stress (F2α isoprostanes, nitrotyrosine), and inflammation and oxidation (hsCRP and cystatin-C) were measured. Nine of 11 randomized patients completed the study (four Tac, five CsA). Mean levels of F2α isoprostanes, hsCRP, and cystatin-C were maximal at Week 2. Peak activation of all MAP kinases in myocardial tissue was maximal at Week 10; no association was seen with rejection. Cardiac Bax/Bcl-2 levels (index of apoptosis) correlated negatively with F2α isoprostanes at Week 2 (r = -0.88) and with hsCRP at Week 52 (r = -0.67). At Week 52, hsCRP levels correlated positively with molecular indices of cardiac cell growth. We found evidence of systemic and myocardial oxidative damage and inflammation early posttransplant, which may be related to the remodeling process. Further study is needed to better understand the cardiac and systemic repair processes following pediatric heart transplantation. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  5. Inhibitory Effects of Glycyrrhetinic Acid on the Delayed Rectifier Potassium Current in Guinea Pig Ventricular Myocytes and HERG Channel

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    Delin Wu

    2013-01-01

    Full Text Available Background. Licorice has long been used to treat many ailments including cardiovascular disorders in China. Recent studies have shown that the cardiac actions of licorice can be attributed to its active component, glycyrrhetinic acid (GA. However, the mechanism of action remains poorly understood. Aim. The effects of GA on the delayed rectifier potassium current (IK, the rapidly activating (IKr and slowly activating (IKs components of IK, and the HERG K+ channel expressed in HEK-293 cells were investigated. Materials and Methods. Single ventricular myocytes were isolated from guinea pig myocardium using enzymolysis. The wild type HERG gene was stably expressed in HEK293 cells. Whole-cell patch clamping was used to record IK (IKr, IKs and the HERG K+ current. Results. GA (1, 5, and 10 μM inhibited IK (IKr, IKs and the HERG K+ current in a concentration-dependent manner. Conclusion. GA significantly inhibited the potassium currents in a dose- and voltage-dependent manner, suggesting that it exerts its antiarrhythmic action through the prolongation of APD and ERP owing to the inhibition of IK (IKr, IKs and HERG K+ channel.

  6. Elevated NF-κB activation is conserved in human myocytes cultured from obese type 2 diabetic patients and attenuated by AMP-activated protein kinase

    DEFF Research Database (Denmark)

    Green, Charlotte Jane; Pedersen, Maria; Pedersen, Bente K

    2011-01-01

    To examine whether the inflammatory phenotype found in obese and diabetic individuals is preserved in isolated, cultured myocytes and to assess the effectiveness of pharmacological AMP-activated protein kinase (AMPK) activation upon the attenuation of inflammation in these myocytes....

  7. Raman probing of lipids, proteins, and mitochondria in skeletal myocytes: a case study on obesity

    DEFF Research Database (Denmark)

    Brazhe, Nadezda A.; Nikelshparg, Evelina I.; Prats, Clara

    2017-01-01

    We propose a novel approach to assess simultaneously lipid composition in lipid droplets, the redox state of cytochromes, and the relative amount of [Fe–S] clusters in the electron transport chain in the mitochondria of skeletal myocytes by means of near-infrared Raman spectroscopy. Mitochondria...... demonstrate the applicability of the proposed approach in a case study of myocytes of an obese patient before and after the gastric bypass surgery in comparison with a healthy lean donor. Ratios from chosen Raman peaks were calculated and compared between the different subjects. We show that the suggested...... technique allows to estimate qualitatively the relative amount of cholesterol and unsaturated lipids, ordering of lipid phase in lipid droplets, changes in the redox state of c-type and b-type cytochromes, and the relative amount of [Fe–S] clusters in the mitochondria of intact myocytes. The proposed...

  8. A separate pool of cardiac phospholemman that does not regulate or associate with the sodium pump: multimers of phospholemman in ventricular muscle.

    Science.gov (United States)

    Wypijewski, Krzysztof J; Howie, Jacqueline; Reilly, Louise; Tulloch, Lindsay B; Aughton, Karen L; McLatchie, Linda M; Shattock, Michael J; Calaghan, Sarah C; Fuller, William

    2013-05-10

    Phospholemman regulates the plasmalemmal sodium pump in excitable tissues. In cardiac muscle, a subpopulation of phospholemman with a unique phosphorylation signature associates with other phospholemman molecules but not with the pump. Phospholemman oligomers exist in cardiac muscle. Much like phospholamban regulation of SERCA, phospholemman exists as both a sodium pump inhibiting monomer and an unassociated oligomer. Phospholemman (PLM), the principal quantitative sarcolemmal substrate for protein kinases A and C in the heart, regulates the cardiac sodium pump. Much like phospholamban, which regulates the related ATPase SERCA, PLM is reported to oligomerize. We investigated subpopulations of PLM in adult rat ventricular myocytes based on phosphorylation status. Co-immunoprecipitation identified two pools of PLM: one not associated with the sodium pump phosphorylated at Ser(63) and one associated with the pump, both phosphorylated at Ser(68) and unphosphorylated. Phosphorylation of PLM at Ser(63) following activation of PKC did not abrogate association of PLM with the pump, so its failure to associate with the pump was not due to phosphorylation at this site. All pools of PLM co-localized to cell surface caveolin-enriched microdomains with sodium pump α subunits, despite the lack of caveolin-binding motif in PLM. Mass spectrometry analysis of phosphospecific immunoprecipitation reactions revealed no unique protein interactions for Ser(63)-phosphorylated PLM, and cross-linking reagents also failed to identify any partner proteins for this pool. In lysates from hearts of heterozygous transgenic animals expressing wild type and unphosphorylatable PLM, Ser(63)-phosphorylated PLM co-immunoprecipitated unphosphorylatable PLM, confirming the existence of PLM multimers. Dephosphorylation of the PLM multimer does not change sodium pump activity. Hence like phospholamban, PLM exists as a pump-inhibiting monomer and an unassociated oligomer. The distribution of different PLM

  9. Assembly of a functional 3D primary cardiac construct using magnetic levitation

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    Glauco Souza

    2016-07-01

    Full Text Available Easily assembled organotypic co-cultures have long been sought in medical research. In vitro tissue constructs with faithful representation of in vivo tissue characteristics are highly desirable for screening and characteristic assessment of a variety of tissue types. Cardiac tissue analogs are particularly sought after due to the phenotypic degradation and difficulty of culture of primary cardiac myocytes. This study utilized magnetic nanoparticles and primary cardiac myocytes in order to levitate and culture multicellular cardiac aggregates (MCAs. Cells were isolated from 2 day old Sprague Dawley rat hearts and subsequently two groups were incubated with either C1: 33 µL nanoshell/million cells or C2: 50 µL nanoshell/million cells. Varying numbers of cells for each concentration were cultured in a magnetic field in a 24 well plate and observed over a period of 12 days. Constructs generally formed spherical structures. Masson’s trichrome staining of a construct shows the presence of extracellular matrix protein, indicating the presence of functional fibroblasts. Many constructs exhibited noticeable contraction after 4 days of culture and continued contracting noticeably past day 9 of culture. Noticeable contractility indicates the presence of functional primary cardiac myocytes in culture. Phenotypic conservation of cardiac cells was ascertained using IHC staining by α-actinin and collagen. CD31 and fibrinogen were probed in order to assess localization of fibroblasts and endothelial cells. The study verifies a protocol for the use of magnetic levitation in order to rapidly assemble 3D cardiac like tissue with phenotypic and functional stability.

  10. Satellite cells derived from obese humans with type 2 diabetes and differentiated into myocytes in vitro exhibit abnormal response to IL-6

    DEFF Research Database (Denmark)

    Scheele, Camilla; Nielsen, Søren; Broholm, Christa

    2012-01-01

    isolated satellite cells from skeletal muscle of people that were healthy (He), obese (Ob) or were obese and had type 2 diabetes (DM), and differentiated them in vitro into myocytes. Down-regulation of IL-6Rα was conserved in Ob myocytes. In addition, acute IL-6 administration for 30, 60 and 120 minutes......, resulted in a down-regulation of IL-6Rα protein in Ob myocytes compared to both He myocytes (P...

  11. Cell-specific cardiac electrophysiology models.

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    Willemijn Groenendaal

    2015-04-01

    Full Text Available The traditional cardiac model-building paradigm involves constructing a composite model using data collected from many cells. Equations are derived for each relevant cellular component (e.g., ion channel, exchanger independently. After the equations for all components are combined to form the composite model, a subset of parameters is tuned, often arbitrarily and by hand, until the model output matches a target objective, such as an action potential. Unfortunately, such models often fail to accurately simulate behavior that is dynamically dissimilar (e.g., arrhythmia to the simple target objective to which the model was fit. In this study, we develop a new approach in which data are collected via a series of complex electrophysiology protocols from single cardiac myocytes and then used to tune model parameters via a parallel fitting method known as a genetic algorithm (GA. The dynamical complexity of the electrophysiological data, which can only be fit by an automated method such as a GA, leads to more accurately parameterized models that can simulate rich cardiac dynamics. The feasibility of the method is first validated computationally, after which it is used to develop models of isolated guinea pig ventricular myocytes that simulate the electrophysiological dynamics significantly better than does a standard guinea pig model. In addition to improving model fidelity generally, this approach can be used to generate a cell-specific model. By so doing, the approach may be useful in applications ranging from studying the implications of cell-to-cell variability to the prediction of intersubject differences in response to pharmacological treatment.

  12. Changes of Ventricular Myocytes Membrane Capacitance in Rabbit with Myocardial Infarction and Effects of Carvedilol

    DEFF Research Database (Denmark)

    Niu, Hui-Yan; Liang, Bo; Liu, Nian

    2005-01-01

    Objective: To investigate effects of long-term treatment of oral Carvedilol on ventricular myocytes membrane capacitance in HMI. Methods: 30 rabbits were randomly assigned in three groups: HMI group, ligation of circumflex coronary artery; Carvedilol group, with operation the same as HMI group......, and administration of oral Carvedilol 0.33 mg/kg×3 months beginning on the day of operation; Sham group, left thoracotomy with no coronary artery ligation. 3 months after surgery, rabbits were harvested. Myocytes were isolated by enzymatic method. The cell membrane capacitance was recorded by using the whole cell...

  13. Type 2 diabetes and obesity induce similar transcriptional reprogramming in human myocytes

    DEFF Research Database (Denmark)

    Väremo, Leif; Henriksen, Tora Ida; Scheele, Camilla

    2017-01-01

    used to characterize the different myocytes. RESULTS: We found that the transcriptional program associated with obesity alone was strikingly similar to that induced specifically by T2D. We identified a candidate epigenetic mechanism, H3K27me3 histone methylation, mediating these transcriptional...... in sphingolipid metabolism was transcriptionally regulated. CONCLUSIONS: Our findings identify inherent characteristics in myocytes, as a memory of the in vivo phenotype, without the influence from a diabetic or obese extracellular environment, highlighting their importance in the development of T2D....

  14. Functional reentrant waves propagate outwardly in cardiac tissue

    Energy Technology Data Exchange (ETDEWEB)

    Gong Yunfan [Department of Medicine, Division of Cardiology, Weill Medical College of Cornell University, New York, NY 10021 (United States)]. E-mail: yug2002@med.cornell.edu; Christini, David J. [Department of Medicine, Division of Cardiology, Weill Medical College of Cornell University, New York, NY 10021 (United States) and Department of Physiology and Biophysics, Weill Graduate School of Medical Sciences of Cornell University, New York, NY 10021 (United States)]. E-mail: dchristi@med.cornell.edu

    2004-10-18

    The dynamical nature of cardiac arrhythmias has been investigated for decades by researchers from a wide range of disciplines. One long-standing unsettled issue involves whether the mechanism of functional reentry should be described by the 'leading-circle' hypothesis or the 'spiral-wave' hypothesis, which rely on inward and outward wave propagation, respectively. To address this issue, we investigated two-dimensional FitzHugh-Nagumo type models and found that inwardly propagating waves could occur in the spontaneous oscillatory mode, but not the excitable mode. However, such spontaneous oscillatory behavior is characterized by small-amplitude, sinusoidal oscillations that are fundamentally different from the stimulus-driven, excitable behavior of cardiac myocytes. This finding suggests that inward wave propagation, which is posited by the leading-circle hypothesis for the purpose of maintaining functional reentry, is unlikely to occur in cardiac tissue.

  15. Cardiac cAMP: production, hydrolysis, modulation and detection

    Directory of Open Access Journals (Sweden)

    Cédric eBOULARAN

    2015-10-01

    Full Text Available Cyclic adenosine 3’,5’-monophosphate (cAMP modulates a broad range of biological processes including the regulation of cardiac myocyte contractile function where it constitutes the main second messenger for β-adrenergic receptors’ signaling to fulfill positive chronotropic, inotropic and lusitropic effects. A growing number of studies pinpoint the role of spatial organization of the cAMP signaling as an essential mechanism to regulate cAMP outcomes in cardiac physiology. Here, we will briefly discuss the complexity of cAMP synthesis and degradation in the cardiac context, describe the way to detect it and review the main pharmacological arsenal to modulate its availability.

  16. Stochastic modelling of cardiac cell structure.

    Science.gov (United States)

    Theakston, Elizabeth; Walker, Cameron; O'Sullivan, Michael; Rajagopal, Vijay

    2010-01-01

    Anatomically realistic and biophysically based computational models of the heart have provided valuable insights into cardiac function in health and disease. Nevertheless, these models typically use a "black-box" approach to describe the cellular level processes that underlie the heart beat. We are developing techniques to stochastically generate three-dimensional models of mammalian ventricular myocytes that exhibit salient characteristics of the spatial organisation of key cellular organelles in cardiac cell excitation and contraction. Such anatomically detailed models will facilitate a deeper understanding of cardiac function at multiple scales. This paper presents an important first step towards understanding and modelling the spatial distribution of two key organelles in cardiac cell contraction - myofibrils and mitochondria. The sarcolemma, myofibrils and mitochondria were segmented from transmission electron micrographs of ventricular cells from a healthy wistar rat. The centroids of the myofibrils and mitochondria were calculated, and various spatial statistical techniques for characterising the centroid distribution and inter-point interactions were investigated and implemented using the R spatstat package. Techniques for modelling the observed spatial patterns were also investigated, and preliminary results indicate that the Strauss Hard-core model best captures the interaction observed. We intend to confirm these results with larger sample of cells.

  17. Multiscale Characterization of Engineered Cardiac Tissue Architecture.

    Science.gov (United States)

    Drew, Nancy K; Johnsen, Nicholas E; Core, Jason Q; Grosberg, Anna

    2016-11-01

    In a properly contracting cardiac muscle, many different subcellular structures are organized into an intricate architecture. While it has been observed that this organization is altered in pathological conditions, the relationship between length-scales and architecture has not been properly explored. In this work, we utilize a variety of architecture metrics to quantify organization and consistency of single structures over multiple scales, from subcellular to tissue scale as well as correlation of organization of multiple structures. Specifically, as the best way to characterize cardiac tissues, we chose the orientational and co-orientational order parameters (COOPs). Similarly, neonatal rat ventricular myocytes were selected for their consistent architectural behavior. The engineered cells and tissues were stained for four architectural structures: actin, tubulin, sarcomeric z-lines, and nuclei. We applied the orientational metrics to cardiac cells of various shapes, isotropic cardiac tissues, and anisotropic globally aligned tissues. With these novel tools, we discovered: (1) the relationship between cellular shape and consistency of self-assembly; (2) the length-scales at which unguided tissues self-organize; and (3) the correlation or lack thereof between organization of actin fibrils, sarcomeric z-lines, tubulin fibrils, and nuclei. All of these together elucidate some of the current mysteries in the relationship between force production and architecture, while raising more questions about the effect of guidance cues on self-assembly function. These types of metrics are the future of quantitative tissue engineering in cardiovascular biomechanics.

  18. Phospholemman: a novel cardiac stress protein.

    Science.gov (United States)

    Cheung, Joseph Y; Zhang, Xue-Qian; Song, Jianliang; Gao, Erhe; Rabinowitz, Joseph E; Chan, Tung O; Wang, Jufang

    2010-08-01

    Phospholemman (PLM), a member of the FXYD family of regulators of ion transport, is a major sarcolemmal substrate for protein kinases A and C in cardiac and skeletal muscle. In the heart, PLM co-localizes and co-immunoprecipitates with Na(+)-K(+)-ATPase, Na(+)/Ca(2+) exchanger, and L-type Ca(2+) channel. Functionally, when phosphorylated at serine(68), PLM stimulates Na(+)-K(+)-ATPase but inhibits Na(+)/Ca(2+) exchanger in cardiac myocytes. In heterologous expression systems, PLM modulates the gating of cardiac L-type Ca(2+) channel. Therefore, PLM occupies a key modulatory role in intracellular Na(+) and Ca(2+) homeostasis and is intimately involved in regulation of excitation-contraction (EC) coupling. Genetic ablation of PLM results in a slight increase in baseline cardiac contractility and prolongation of action potential duration. When hearts are subjected to catecholamine stress, PLM minimizes the risks of arrhythmogenesis by reducing Na(+) overload and simultaneously preserves inotropy by inhibiting Na(+)/Ca(2+) exchanger. In heart failure, both expression and phosphorylation state of PLM are altered and may partly account for abnormalities in EC coupling. The unique role of PLM in regulation of Na(+)-K(+)-ATPase, Na(+)/Ca(2+) exchanger, and potentially L-type Ca(2+) channel in the heart, together with the changes in its expression and phosphorylation in heart failure, make PLM a rational and novel target for development of drugs in our armamentarium against heart failure. Clin Trans Sci 2010; Volume 3: 189-196.

  19. Mechanotransduction in cardiac hypertrophy and failure.

    Science.gov (United States)

    Lyon, Robert C; Zanella, Fabian; Omens, Jeffrey H; Sheikh, Farah

    2015-04-10

    Cardiac muscle cells have an intrinsic ability to sense and respond to mechanical load through a process known as mechanotransduction. In the heart, this process involves the conversion of mechanical stimuli into biochemical events that induce changes in myocardial structure and function. Mechanotransduction and its downstream effects function initially as adaptive responses that serve as compensatory mechanisms during adaptation to the initial load. However, under prolonged and abnormal loading conditions, the remodeling processes can become maladaptive, leading to altered physiological function and the development of pathological cardiac hypertrophy and heart failure. Although the mechanisms underlying mechanotransduction are far from being fully elucidated, human and mouse genetic studies have highlighted various cytoskeletal and sarcolemmal structures in cardiac myocytes as the likely candidates for load transducers, based on their link to signaling molecules and architectural components important in disease pathogenesis. In this review, we summarize recent developments that have uncovered specific protein complexes linked to mechanotransduction and mechanotransmission within the sarcomere, the intercalated disc, and at the sarcolemma. The protein structures acting as mechanotransducers are the first step in the process that drives physiological and pathological cardiac hypertrophy and remodeling, as well as the transition to heart failure, and may provide better insights into mechanisms driving mechanotransduction-based diseases. © 2015 American Heart Association, Inc.

  20. Unique Properties of the ATP-Sensitive K+ Channel in the Mouse Ventricular Cardiac Conduction System

    Science.gov (United States)

    Bao, Li; Kefalogianni, Eirini; Lader, Joshua; Hong, Miyoun; Morley, Gregory; Fishman, Glenn I.; Sobie, Eric A.; Coetzee, William A.

    2011-01-01

    Background The specialized cardiac conduction system (CCS) expresses a unique complement of ion channels that confer a specific electrophysiological profile. ATP sensitive potassium (KATP) channels in these myocytes have not been systemically investigated. Methods and Results We recorded KATP channels in isolated CCS myocytes using Cntn2-EGFP reporter mice. The CCS KATP channels were less sensitive to inhibitory cytosolic ATP compared to ventricular channels and more strongly activated by MgADP. They also had a smaller slope conductance. The two types of channels had similar intraburst open and closed times, but the CCS KATP channel had a prolonged interburst closed time. CCS KATP channels were strongly activated by diazoxide and less by levcromakalim, whereas the ventricular KATP channel had a reverse pharmacological profile. CCS myocytes express elevated levels of Kir6.1, but reduced Kir6.2 and SUR2A mRNA compared to ventricular myocytes (SUR1 expression was negligible). SUR2B mRNA expression was higher in CCS myocytes relative to SUR2A. Canine Purkinje fibers expressed higher levels of Kir6.1 and SUR2B protein relative to the ventricle. Numerical simulation predicts a high sensitivity of the Purkinje action potential to changes in ATP:ADP ratio. Cardiac conduction time was prolonged by low-flow ischemia in isolated, perfused mouse hearts, which was prevented by glibenclamide. Conclusions These data imply a differential electrophysiological response (and possible contribution to arrhythmias) of the ventricular CCS to KATP channel opening during periods of ischemia. PMID:21984445

  1. Cardiac sarcoidosis

    Directory of Open Access Journals (Sweden)

    Costello BT

    2016-04-01

    Full Text Available Benedict T Costello,1,2 James Nadel,3 Andrew J Taylor,1,21Department of Cardiovascular Medicine, The Alfred Hospital, 2Baker IDI Heart and Diabetes Research Institute, Melbourne, VIC, 3School of Medicine, University of Notre Dame, Sydney, NSW, Australia Abstract: Cardiac sarcoidosis is a rare but life-threatening condition, requiring a high degree of clinical suspicion and low threshold for investigation to make the diagnosis. The cardiac manifestations include heart failure, conducting system disease, and arrhythmias predisposing to sudden cardiac death. A number of investigations are available to assist in making the diagnosis. The diagnosis may be made from the clinical history and evidence of inflammation on imaging modalities in the active phase and evidence of myocardial scarring in the chronic phase. Keywords: cardiac magnetic resonance, positron emission tomography, sarcoidosis, sudden cardiac death

  2. Cardiac ablation procedures

    Science.gov (United States)

    Catheter ablation; Radiofrequency catheter ablation; Cryoablation - cardiac ablation; AV nodal reentrant tachycardia - cardiac ablation; AVNRT - cardiac ablation; Wolff-Parkinson-White Syndrome - cardiac ablation; Atrial fibrillation - cardiac ablation; Atrial flutter - ...

  3. Raf-mediated cardiac hypertrophy in adult Drosophila

    Science.gov (United States)

    Yu, Lin; Daniels, Joseph; Glaser, Alex E.; Wolf, Matthew J.

    2013-01-01

    SUMMARY In response to stress and extracellular signals, the heart undergoes a process called cardiac hypertrophy during which cardiomyocytes increase in size. If untreated, cardiac hypertrophy can progress to overt heart failure that causes significant morbidity and mortality. The identification of molecular signals that cause or modify cardiomyopathies is necessary to understand how the normal heart progresses to cardiac hypertrophy and heart failure. Receptor tyrosine kinase (RTK) signaling is essential for normal human cardiac function, and the inhibition of RTKs can cause dilated cardiomyopathies. However, neither investigations of activated RTK signaling pathways nor the characterization of hypertrophic cardiomyopathy in the adult fly heart has been previously described. Therefore, we developed strategies using Drosophila as a model to circumvent some of the complexities associated with mammalian models of cardiovascular disease. Transgenes encoding activated EGFRA887T, Ras85DV12 and Ras85DV12S35, which preferentially signal to Raf, or constitutively active human or fly Raf caused hypertrophic cardiomyopathy as determined by decreased end diastolic lumen dimensions, abnormal cardiomyocyte fiber morphology and increased heart wall thicknesses. There were no changes in cardiomyocyte cell numbers. Additionally, activated Raf also induced an increase in cardiomyocyte ploidy compared with control hearts. However, preventing increases in cardiomyocyte ploidy using fizzy-related (Fzr) RNAi did not rescue Raf-mediated cardiac hypertrophy, suggesting that Raf-mediated polyploidization is not required for cardiac hypertrophy. Similar to mammals, the cardiac-specific expression of RNAi directed against MEK or ERK rescued Raf-mediated cardiac hypertrophy. However, the cardiac-specific expression of activated ERKD334N, which promotes hyperplasia in non-cardiac tissues, did not cause myocyte hypertrophy. These results suggest that ERK is necessary, but not sufficient, for

  4. Comprehensive cardiac rehabilitation

    DEFF Research Database (Denmark)

    Kruse, Marie; Hochstrasser, Stefan; Zwisler, Ann-Dorthe O

    2006-01-01

    OBJECTIVES: The costs of comprehensive cardiac rehabilitation are established and compared to the corresponding costs of usual care. The effect on health-related quality of life is analyzed. METHODS: An unprecedented and very detailed cost assessment was carried out, as no guidelines existed...... for the situation at hand. Due to challenging circumstances, the cost assessment turned out to be ex-post and top-down. RESULTS: Cost per treatment sequence is estimated to be approximately euro 976, whereas the incremental cost (compared with usual care) is approximately euro 682. The cost estimate is uncertain...... and may be as high as euro 1.877. CONCLUSIONS: Comprehensive cardiac rehabilitation is more costly than usual care, and the higher costs are not outweighed by a quality of life gain. Comprehensive cardiac rehabilitation is, therefore, not cost-effective....

  5. Effects of phytoestrogens on protein turnover in rainbow trout primary myocytes

    Science.gov (United States)

    Soybean-derived ingredients used in aquaculture feeds may contain phytoestrogens, but it is unknown if these compounds can mimic the catabolic effects of estradiol in fish muscle. Six day-old rainbow trout primary myocytes were exposed to increasing concentrations (10 nM – 100 µM) of either geniste...

  6. Beta-adrenergic receptor subtypes differentially affect apoptosis in adult rat ventricular myocytes

    National Research Council Canada - National Science Library

    Zaugg, M; Xu, W; Lucchinetti, E; Shafiq, S A; Jamali, N Z; Siddiqui, M A

    2000-01-01

    .... METHODS AND RESULTS-Myocytes were first exposed to norepinephrine (NE) alone (10 mcmol/L) or NE+atenolol (AT) (10 mcmol/L) for 12 hours. AT, a beta(1)-selective AR antagonist, abolished the NE-induced increase in nick end-labeling...

  7. Cortical Bone Stem Cell Therapy Preserves Cardiac Structure and Function After Myocardial Infarction.

    Science.gov (United States)

    Sharp, Thomas E; Schena, Giana J; Hobby, Alexander R; Starosta, Timothy; Berretta, Remus M; Wallner, Markus; Borghetti, Giulia; Gross, Polina; Yu, Daohai; Johnson, Jaslyn; Feldsott, Eric; Trappanese, Danielle M; Toib, Amir; Rabinowitz, Joseph E; George, Jon C; Kubo, Hajime; Mohsin, Sadia; Houser, Steven R

    2017-11-10

    Cortical bone stem cells (CBSCs) have been shown to reduce ventricular remodeling and improve cardiac function in a murine myocardial infarction (MI) model. These effects were superior to other stem cell types that have been used in recent early-stage clinical trials. However, CBSC efficacy has not been tested in a preclinical large animal model using approaches that could be applied to patients. To determine whether post-MI transendocardial injection of allogeneic CBSCs reduces pathological structural and functional remodeling and prevents the development of heart failure in a swine MI model. Female Göttingen swine underwent left anterior descending coronary artery occlusion, followed by reperfusion (ischemia-reperfusion MI). Animals received, in a randomized, blinded manner, 1:1 ratio, CBSCs (n=9; 2×10 7 cells total) or placebo (vehicle; n=9) through NOGA-guided transendocardial injections. 5-ethynyl-2'deoxyuridine (EdU)-a thymidine analog-containing minipumps were inserted at the time of MI induction. At 72 hours (n=8), initial injury and cell retention were assessed. At 3 months post-MI, cardiac structure and function were evaluated by serial echocardiography and terminal invasive hemodynamics. CBSCs were present in the MI border zone and proliferating at 72 hours post-MI but had no effect on initial cardiac injury or structure. At 3 months, CBSC-treated hearts had significantly reduced scar size, smaller myocytes, and increased myocyte nuclear density. Noninvasive echocardiographic measurements showed that left ventricular volumes and ejection fraction were significantly more preserved in CBSC-treated hearts, and invasive hemodynamic measurements documented improved cardiac structure and functional reserve. The number of EdU + cardiac myocytes was increased in CBSC- versus vehicle- treated animals. CBSC administration into the MI border zone reduces pathological cardiac structural and functional remodeling and improves left ventricular functional reserve

  8. Systematic reduction of a detailed atrial myocyte model

    Science.gov (United States)

    Lombardo, Daniel M.; Rappel, Wouter-Jan

    2017-09-01

    Cardiac arrhythmias are a major health concern and often involve poorly understood mechanisms. Mathematical modeling is able to provide insights into these mechanisms which might result in better treatment options. A key element of this modeling is a description of the electrophysiological properties of cardiac cells. A number of electrophysiological models have been developed, ranging from highly detailed and complex models, containing numerous parameters and variables, to simplified models in which variables and parameters no longer directly correspond to electrophysiological quantities. In this study, we present a systematic reduction of the complexity of the detailed model of Koivumaki et al. using the recently developed manifold boundary approximation method. We reduce the original model, containing 42 variables and 37 parameters, to a model with only 11 variables and 5 parameters and show that this reduced model can accurately reproduce the action potential shape and restitution curve of the original model. The reduced model contains only five currents and all variables and parameters can be directly linked to electrophysiological quantities. Due to its reduction in complexity, simulation times of our model are decreased more than three-fold. Furthermore, fitting the reduced model to clinical data is much more efficient, a potentially important step towards patient-specific modeling.

  9. Caveolin-3 Overexpression Attenuates Cardiac Hypertrophy via Inhibition of T-type Ca2+ Current Modulated by Protein Kinase Cα in Cardiomyocytes*

    Science.gov (United States)

    Markandeya, Yogananda S.; Phelan, Laura J.; Woon, Marites T.; Keefe, Alexis M.; Reynolds, Courtney R.; August, Benjamin K.; Hacker, Timothy A.; Roth, David M.; Patel, Hemal H.; Balijepalli, Ravi C.

    2015-01-01

    Pathological cardiac hypertrophy is characterized by subcellular remodeling of the ventricular myocyte with a reduction in the scaffolding protein caveolin-3 (Cav-3), altered Ca2+ cycling, increased protein kinase C expression, and hyperactivation of calcineurin/nuclear factor of activated T cell (NFAT) signaling. However, the precise role of Cav-3 in the regulation of local Ca2+ signaling in pathological cardiac hypertrophy is unclear. We used cardiac-specific Cav-3-overexpressing mice and in vivo and in vitro cardiac hypertrophy models to determine the essential requirement for Cav-3 expression in protection against pharmacologically and pressure overload-induced cardiac hypertrophy. Transverse aortic constriction and angiotensin-II (Ang-II) infusion in wild type (WT) mice resulted in cardiac hypertrophy characterized by significant reduction in fractional shortening, ejection fraction, and a reduced expression of Cav-3. In addition, association of PKCα and angiotensin-II receptor, type 1, with Cav-3 was disrupted in the hypertrophic ventricular myocytes. Whole cell patch clamp analysis demonstrated increased expression of T-type Ca2+ current (ICa, T) in hypertrophic ventricular myocytes. In contrast, the Cav-3-overexpressing mice demonstrated protection from transverse aortic constriction or Ang-II-induced pathological hypertrophy with inhibition of ICa, T and intact Cav-3-associated macromolecular signaling complexes. siRNA-mediated knockdown of Cav-3 in the neonatal cardiomyocytes resulted in enhanced Ang-II stimulation of ICa, T mediated by PKCα, which caused nuclear translocation of NFAT. Overexpression of Cav-3 in neonatal myocytes prevented a PKCα-mediated increase in ICa, T and nuclear translocation of NFAT. In conclusion, we show that stable Cav-3 expression is essential for protecting the signaling mechanisms in pharmacologically and pressure overload-induced cardiac hypertrophy. PMID:26170457

  10. Cardiac Rehabilitation

    Science.gov (United States)

    Cardiac rehabilitation (rehab) is a medically supervised program to help people who have A heart attack Angioplasty or coronary artery bypass grafting for coronary heart disease A heart valve repair or replacement A ...

  11. Cardiac rehabilitation

    Science.gov (United States)

    ... ncbi.nlm.nih.gov/pubmed/25503364 . Balady GJ, Williams MA, Ades PA, et al. Core components of ... ncbi.nlm.nih.gov/pubmed/22070836 . Thompson PD. Exercise-based, comprehensive cardiac rehabilitation. In: Mann DL, Zipes ...

  12. Cardiac arrest

    Science.gov (United States)

    ... also run other tests, depending on your health history and the results of these tests. Treatment Cardiac arrest needs emergency treatment right away to get the heart started again. Cardiopulmonary resuscitation (CPR) . This is often the first type of ...

  13. Norepinephrine-induced apoptotic and hypertrophic responses in H9c2 cardiac myoblasts are characterized by different repertoire of reactive oxygen species generation

    Directory of Open Access Journals (Sweden)

    Anita Thakur

    2015-08-01

    Full Text Available Despite recent advances, the role of ROS in mediating hypertrophic and apoptotic responses in cardiac myocytes elicited by norepinephrine (NE is rather poorly understood. We demonstrate through our experiments that H9c2 cardiac myoblasts treated with 2 µM NE (hypertrophic dose generate DCFH-DA positive ROS only for 2 h; while those treated with 100 µM NE (apoptotic dose sustains generation for 48 h, followed by apoptosis. Though the levels of DCFH fluorescence were comparable at early time points in the two treatment sets, its quenching by DPI, catalase and MnTmPyP suggested the existence of a different repertoire of ROS. Both doses of NE also induced moderate levels of H2O2 but with different kinetics. Sustained but intermittent generation of highly reactive species detectable by HPF was seen in both treatment sets but no peroxynitrite was generated in either conditions. Sustained generation of hydroxyl radicals with no appreciable differences were noticed in both treatment sets. Nevertheless, despite similar profile of ROS generation between the two conditions, extensive DNA damage as evident from the increase in 8-OH-dG content, formation of γ-H2AX and PARP cleavage was seen only in cells treated with the higher dose of NE. We therefore conclude that hypertrophic and apoptotic doses of NE generate distinct but comparable repertoire of ROS/RNS leading to two very distinct downstream responses.

  14. Cardiac Angiosarcoma

    Directory of Open Access Journals (Sweden)

    Monique Esteves Cardoso

    2011-01-01

    Full Text Available Despite cardiac metastases are found in about 20% of cancer deaths, the presence of primary cardiac tumors is rare. Most primary tumors are benign, and malignant tumors comprise about 15%. We report a 21-year-old man with fever, dyspnea, and hemoptysis that was diagnosed with angiosarcoma of the right atrium and pulmonary metastasis. Patient was submitted to surgical tumor resection without adjuvant therapy and died four months after diagnosis.

  15. Cardiac Angiosarcoma

    OpenAIRE

    Cardoso, Monique Esteves; Canale, Leonardo Secchin; Ramos, Rosana Grandelle; Salvador Junior, Edson da Silva; Lachtermacher, Stephan

    2011-01-01

    Despite cardiac metastases are found in about 20% of cancer deaths, the presence of primary cardiac tumors is rare. Most primary tumors are benign, and malignant tumors comprise about 15%. We report a 21-year-old man with fever, dyspnea, and hemoptysis that was diagnosed with angiosarcoma of the right atrium and pulmonary metastasis. Patient was submitted to surgical tumor resection without adjuvant therapy and died four months after diagnosis.

  16. Cardiac Angiosarcoma

    Science.gov (United States)

    Cardoso, Monique Esteves; Canale, Leonardo Secchin; Ramos, Rosana Grandelle; Salvador Junior, Edson da Silva; Lachtermacher, Stephan

    2011-01-01

    Despite cardiac metastases are found in about 20% of cancer deaths, the presence of primary cardiac tumors is rare. Most primary tumors are benign, and malignant tumors comprise about 15%. We report a 21-year-old man with fever, dyspnea, and hemoptysis that was diagnosed with angiosarcoma of the right atrium and pulmonary metastasis. Patient was submitted to surgical tumor resection without adjuvant therapy and died four months after diagnosis. PMID:24826214

  17. SR-targeted CaMKII inhibition improves SR Ca2+ handling, but accelerates cardiac remodeling in mice overexpressing CaMKIIδC

    Science.gov (United States)

    Huke, Sabine; DeSantiago, Jaime; Kaetzel, Marcia A.; Mishra, Shikha; Brown, Joan H.; Dedman, John R.; Bers, Donald M.

    2010-01-01

    Cardiac myocyte overexpression of CaMKIIδC leads to cardiac hypertrophy and heart failure (HF) possibly caused by altered myocyte Ca2+ handling. A central defect might be the marked CaMKII-induced increase in diastolic sarcoplasmic reticulum (SR) Ca2+ leak which decreases SR Ca2+ load and Ca2+ transient amplitude. We hypothesized that inhibition of CaMKII near the SR membrane would decrease the leak, improve Ca2+ handling and prevent the development of contractile dysfunction and HF. To test this hypothesis we crossbred CaMKIIδC overexpressing mice (CaMK) with mice expressing the CaMKII-inhibitor AIP targeted to the SR via a modified phospholamban (PLB)-transmembrane-domain (SR-AIP). There was a selective decrease in the amount of activated CaMKII in the microsomal (SR/membrane) fraction prepared from these double-transgenic mice (CaMK/SR-AIP) mice. In ventricular cardiomyocytes from CaMK/SR-AIP mice, SR Ca2+ leak, assessed both as diastolic Ca2+ shift into SR upon tetracaine in intact myocytes or integrated Ca2+ spark release in permeabilized myocytes, was significantly reduced. The reduced leak was accompanied by enhanced SR Ca2+ load and twitch amplitude in double-transgenic mice (vs. CaMK), without changes in SERCA expression or NCX function. However, despite the improved myocyte Ca2+ handling, cardiac hypertrophy and remodeling was accelerated in CaMK/SR-AIP and cardiac function worsened. We conclude that while inhibition of SR localized CaMKII in CaMK mice improves Ca2+ handling, it does not necessarily rescue the HF phenotype. This implies that a non-SR CaMKIIδC exerts SR-independent effects that contribute to hypertrophy and HF, and this CaMKII pathway may be exacerbated by the global enhancement of Ca transients. PMID:20971119

  18. Cardiac hypertrophy in mice expressing unphosphorylatable phospholemman.

    Science.gov (United States)

    Boguslavskyi, Andrii; Pavlovic, Davor; Aughton, Karen; Clark, James E; Howie, Jacqueline; Fuller, William; Shattock, Michael J

    2014-10-01

    Elevation of intracellular Na in the failing myocardium contributes to contractile dysfunction, the negative force-frequency relationship, and arrhythmias. Although phospholemman (PLM) is recognized to form the link between signalling pathways and Na/K pump activity, the possibility that defects in its regulation contribute to elevation of intracellular Na has not been investigated. Our aim was to test the hypothesis that the prevention of PLM phosphorylation in a PLM(3SA) knock-in mouse (in which PLM has been rendered unphosphorylatable) will exacerbate cardiac hypertrophy and cellular Na overload. Testing this hypothesis should determine whether changes in PLM phosphorylation are simply bystander effects or are causally involved in disease progression. In wild-type (WT) mice, aortic constriction resulted in hypophosphorylation of PLM with no change in Na/K pump expression. This under-phosphorylation of PLM occurred at 3 days post-banding and was associated with a progressive decline in Na/K pump current and elevation of [Na]i. Echocardiography, morphometry, and pressure-volume (PV) catheterization confirmed remodelling, dilation, and contractile dysfunction, respectively. In PLM(3SA) mice, expression of Na/K ATPase was increased and PLM decreased such that net Na/K pump current under quiescent conditions was unchanged (cf. WT myocytes); [Na(+)]i was increased and forward-mode Na/Ca exchanger was reduced in paced PLM(3SA) myocytes. Cardiac hypertrophy and Na/K pump inhibition were significantly exacerbated in banded PLM(3SA) mice compared with banded WT. Decreased phosphorylation of PLM reduces Na/K pump activity and exacerbates Na overload, contractile dysfunction, and adverse remodelling following aortic constriction in mice. This suggests a novel therapeutic target for the treatment of heart failure. © The Author 2014. Published by Oxford University Press on behalf of the European Society of Cardiology.

  19. Exercise training prior to myocardial infarction attenuates cardiac deterioration and cardiomyocyte dysfunction in rats.

    Science.gov (United States)

    Bozi, Luiz Henrique Marchesi; Maldonado, Izabel Regina dos Santos Costa; Baldo, Marcelo Perim; Silva, Márcia Ferreira da; Moreira, José Bianco Nascimento; Novaes, Rômulo Dias; Ramos, Regiane Maria Soares; Mill, José Geraldo; Brum, Patricia Chakur; Felix, Leonardo Bonato; Gomes, Thales Nicolau Prímola; Natali, Antônio José

    2013-04-01

    The present study was performed to investigate 1) whether aerobic exercise training prior to myocardial infarction would prevent cardiac dysfunction and structural deterioration and 2) whether the potential cardiac benefits of aerobic exercise training would be associated with preserved morphological and contractile properties of cardiomyocytes in post-infarct remodeled myocardium. Male Wistar rats underwent an aerobic exercise training protocol for eight weeks. The rats were then assigned to sham surgery (SHAM), sedentary lifestyle and myocardial infarction or exercise training and myocardial infarction groups and were evaluated 15 days after the surgery. Left ventricular tissue was analyzed histologically, and the contractile function of isolated myocytes was measured. Student's t-test was used to analyze infarct size and ventricular wall thickness, and the other parameters were analyzed by the Kruskal-Wallis test followed by Dunn's test or a one-way analysis of variance followed by Tukey's test (pmyocardial infarction extension, a thicker infarcted wall and less collagen accumulation as compared to myocardial infarctions in sedentary animals. Myocardial infarction-induced left ventricular dilation and cardiac dysfunction, as evaluated by +dP/dt and -dP/dt, were both prevented by previous aerobic exercise training. Moreover, aerobic exercise training preserved cardiac myocyte shortening, improved the maximum shortening and relengthening velocities in infarcted hearts and enhanced responsiveness to calcium. Previous aerobic exercise training attenuated the cardiac dysfunction and structural deterioration promoted by myocardial infarction, and such benefits were associated with preserved cardiomyocyte morphological and contractile properties.

  20. Rhabdomyosarcoma cells show an energy producing anabolic metabolic phenotype compared with primary myocytes

    Directory of Open Access Journals (Sweden)

    Higashi Richard M

    2008-10-01

    Full Text Available Abstract Background The functional status of a cell is expressed in its metabolic activity. We have applied stable isotope tracing methods to determine the differences in metabolic pathways in proliferating Rhabdomysarcoma cells (Rh30 and human primary myocytes in culture. Uniformly 13C-labeled glucose was used as a source molecule to follow the incorporation of 13C into more than 40 marker metabolites using NMR and GC-MS. These include metabolites that report on the activity of glycolysis, Krebs' cycle, pentose phosphate pathway and pyrimidine biosynthesis. Results The Rh30 cells proliferated faster than the myocytes. Major differences in flux through glycolysis were evident from incorporation of label into secreted lactate, which accounts for a substantial fraction of the glucose carbon utilized by the cells. Krebs' cycle activity as determined by 13C isotopomer distributions in glutamate, aspartate, malate and pyrimidine rings was considerably higher in the cancer cells than in the primary myocytes. Large differences were also evident in de novo biosynthesis of riboses in the free nucleotide pools, as well as entry of glucose carbon into the pyrimidine rings in the free nucleotide pool. Specific labeling patterns in these metabolites show the increased importance of anaplerotic reactions in the cancer cells to maintain the high demand for anabolic and energy metabolism compared with the slower growing primary myocytes. Serum-stimulated Rh30 cells showed higher degrees of labeling than serum starved cells, but they retained their characteristic anabolic metabolism profile. The myocytes showed evidence of de novo synthesis of glycogen, which was absent in the Rh30 cells. Conclusion The specific 13C isotopomer patterns showed that the major difference between the transformed and the primary cells is the shift from energy and maintenance metabolism in the myocytes toward increased energy and anabolic metabolism for proliferation in the Rh30 cells

  1. Pathfinder to EXIST: ProtoEXIST

    Science.gov (United States)

    Garson, A. B., III; Allen, B.; Baker, R. G.; Barthelmy, S. D.; Burke, M.; Burnham, J.; Chammas, N.; Collins, J.; Cook, W. R.; Copete, A.; Gehrels, N.; Gauron, T.; Grindlay, J.; Harrison, F. A.; Hong, J.; Howell, J.; Krawczynski, H.; Labov, S.; Said, B.; Sheikh Sheikh, S.

    2008-04-01

    We describe the ProtoEXIST instrument, our fist-generation wide-field hard X-ray imaging (20 - 600 keV) balloon-borne telescope. The ProtoEXIST program is a pathfinder for the Energetic X-ray Imaging Survey Telescope (EXIST), a candidate for the Black Hole Finder Probe. ProtoEXIST consists of two independent coded-aperture telescopes using pixellated (2.5mm pitch) CZT detectors. The two telescopes will provide performance comparison of two shielding configurations, for optimization of the EXIST design. We report on the science goals and designs of both ProtoEXIST and EXIST and their implications for hard X-ray astronomy and astrophysics.

  2. β(3) adrenergic stimulation of the cardiac Na+-K+ pump by reversal of an inhibitory oxidative modification

    DEFF Research Database (Denmark)

    Bundgaard, Henning; Liu, Chia-Chi; Garcia, Alvaro

    2010-01-01

    inhibition of L-type Ca(2+) current contributes to negative inotropy of β(3) adrenergic receptor (β(3) AR) activation, but effects on other determinants of excitation-contraction coupling are not known. Of these, the Na(+)-K(+) pump is of particular interest because of adverse effects attributed ...... to high cardiac myocyte Na(+) levels and upregulation of the β(3) AR in heart failure....

  3. ß(3) adrenergic stimulation of the cardiac Na+-K+ pump by reversal of an inhibitory oxidative modification

    DEFF Research Database (Denmark)

    Bundgaard, Henning; Liu, Chia-Chi; Garcia, Alvaro

    2010-01-01

    inhibition of L-type Ca(2+) current contributes to negative inotropy of ß(3) adrenergic receptor (ß(3) AR) activation, but effects on other determinants of excitation-contraction coupling are not known. Of these, the Na(+)-K(+) pump is of particular interest because of adverse effects attributed ...... to high cardiac myocyte Na(+) levels and upregulation of the ß(3) AR in heart failure....

  4. Cardiac echinococcosis

    Directory of Open Access Journals (Sweden)

    Ivanović-Krstić Branislava A.

    2002-01-01

    Full Text Available Cardiac hydatid disease is rare. We report on an uncommon hydatid cyst localized in the right ventricular wall, right atrial wall tricuspid valve left atrium and pericard. A 33-year-old woman was treated for cough, fever and chest pain. Cardiac echocardiograpic examination revealed a round tumor (5.8 x 4 cm in the right ventricular free wall and two smaller cysts behind that tumor. There were cysts in right atrial wall and tricuspidal valve as well. Serologic tests for hydatidosis were positive. Computed tomography finding was consistent with diagnosis of hydatid cyst in lungs and right hylar part. Surgical treatment was rejected due to great risk of cardiac perforation. Medical treatment with albendazole was unsuccessful and the patient died due to systemic hydatid involvement of the lungs, liver and central nervous system.

  5. [Cardiac amyloidosis].

    Science.gov (United States)

    Boussabah, Elhem; Zakhama, Lilia; Ksontini, Iméne; Ibn Elhadj, Zied; Boukhris, Besma; Naffeti, Sana; Thameur, Moez; Ben Youssef, Soraya

    2008-09-01

    PREREQUIS: Amyloidosis is a rare infiltrative disease characterized by multiple clinical features. Various organs are involved and the cardiovascular system is a common target of amyloidosis. Cardiac involvement may occur with or without clinical manifestations and is considered as a major prognostic factor. To analyze the clinical features of cardiac involvement, to review actual knowledgement concerning echocardiographic diagnostic and to evaluate recent advances in treatment of the disease. An electronic search of the relevant literature was carried out using Medline and Pubmed. Keys words used for the final search were amyloidosis, cardiopathy and echocardiography. We considered for analysis reviews, studies and articles between 1990 and 2007. Amyloidosis represents 5 to 10% of non ischemic cardiomyoparhies. Cardiac involvement is the first cause of restrictive cardiomyopathy witch must be evoked in front of every inexplained cardiopathy after the age of forty. The amyloid nature of cardiopathy is suggered if some manifestations were associated as a peripheric neuropathy, a carpal tunnel sydrome and proteinuria > 3g/day. Echocardiography shows dilated atria, a granular sparkling appearance of myocardium, diastolic dysfunction and thickened left ventricle contrasting with a low electric voltage. The proof of amyloidosis is brought by an extra-cardiac biopsy, the indications of endomyocardial biopsy are very limited. The identification of the amyloid nature of cardiopathy has an direct therapeutic implication: it indicates the use of digitalis, calcium channel blockers and beta-blockers. Today the treatment of amyloidosis remains very unsatisfactory especially in the cardiac involvement. An early diagnosis before the cardiac damage may facilitate therapy and improve prognosis.

  6. The plasma membrane calcium ATPase 4 signalling in cardiac fibroblasts mediates cardiomyocyte hypertrophy

    Science.gov (United States)

    Mohamed, Tamer M. A.; Abou-Leisa, Riham; Stafford, Nicholas; Maqsood, Arfa; Zi, Min; Prehar, Sukhpal; Baudoin-Stanley, Florence; Wang, Xin; Neyses, Ludwig; Cartwright, Elizabeth J.; Oceandy, Delvac

    2016-01-01

    The heart responds to pathological overload through myocyte hypertrophy. Here we show that this response is regulated by cardiac fibroblasts via a paracrine mechanism involving plasma membrane calcium ATPase 4 (PMCA4). Pmca4 deletion in mice, both systemically and specifically in fibroblasts, reduces the hypertrophic response to pressure overload; however, knocking out Pmca4 specifically in cardiomyocytes does not produce this effect. Mechanistically, cardiac fibroblasts lacking PMCA4 produce higher levels of secreted frizzled related protein 2 (sFRP2), which inhibits the hypertrophic response in neighbouring cardiomyocytes. Furthermore, we show that treatment with the PMCA4 inhibitor aurintricarboxylic acid (ATA) inhibits and reverses cardiac hypertrophy induced by pressure overload in mice. Our results reveal that PMCA4 regulates the development of cardiac hypertrophy and provide proof of principle for a therapeutic approach to treat this condition. PMID:27020607

  7. Type 2 diabetes and obesity induce similar transcriptional reprogramming in human myocytes

    DEFF Research Database (Denmark)

    Väremo, Leif; Henriksen, Tora Ida; Scheele, Camilla

    2017-01-01

    BACKGROUND: Skeletal muscle is one of the primary tissues involved in the development of type 2 diabetes (T2D). The close association between obesity and T2D makes it difficult to isolate specific effects attributed to the disease alone. Therefore, here we set out to identify and characterize...... used to characterize the different myocytes. RESULTS: We found that the transcriptional program associated with obesity alone was strikingly similar to that induced specifically by T2D. We identified a candidate epigenetic mechanism, H3K27me3 histone methylation, mediating these transcriptional...... in sphingolipid metabolism was transcriptionally regulated. CONCLUSIONS: Our findings identify inherent characteristics in myocytes, as a memory of the in vivo phenotype, without the influence from a diabetic or obese extracellular environment, highlighting their importance in the development of T2D....

  8. Effect of siRNA silencing of inducible co-stimulatory molecule on myocardial cell hypertrophy after cardiac infarction in rats.

    Science.gov (United States)

    Wang, W M; Liu, Z; Chen, G

    2016-05-20

    As the most common cardiac disease, myocardial infarction is followed by hypertrophy of cardiac myocytes and reconstruction of ventricular structure. The up-regulation of a series of factors including metalloproteinases, inflammatory factors, and growth factors after primary infarction lead to the hypertrophy, apoptosis, necrosis, and fibroblast proliferation in cardiac muscle tissues. Recent studies have reported on the potency of small interfering RNA (siRNA) in treating cardiac diseases. We thus investigated the efficacy of inducible co-stimulatory molecule (ICOS)-specific siRNA silencing in myocardial hypertrophy in a cardiac infarction rat model. This cardiac infarction model was prepared by ligating the left anterior descending coronary artery. ICOS-siRNA treatment was administered in parallel with non-sense siRNA. After 18 days, the cross-sectional area of cardiac muscle tissues and the left ventricle weight index were measured, along with ICOS mRNA and protein expression levels, and pathological staining. Compared to those in the control groups, in myocardial infarcted rats, the application of ICOS-siRNA effectively decreased the left ventricle weight index, as well as the surface area of cardiac myocytes. Both mRNA and protein levels of ICOS were also significantly decreased. HE staining was consistent with these results. In conclusion, ICOS-targeted siRNA can effectively silence gene expression of ICOS, and provided satisfactory treatment efficacy for myocardial cell hypertrophy after infarction.

  9. Cardiac Dysrhythmias and Neurological Dysregulation: Manifestations of Profound Hypomagnesemia

    Directory of Open Access Journals (Sweden)

    Sagger Mawri

    2017-01-01

    Full Text Available Magnesium is the second most common intracellular cation and serves as an important metabolic cofactor to over 300 enzymatic reactions throughout the human body. Among its various roles, magnesium modulates calcium entry and release from sarcoplasmic reticulum and regulates ATP pumps in myocytes and neurons, thereby regulating cardiac and neuronal excitability. Therefore, deficiency of this essential mineral may result in serious cardiovascular and neurologic derangements. In this case, we present the clinical course of a 76-year-old woman who presented with marked cardiac and neurological signs and symptoms which developed as a result of severe hypomagnesemia. The patient promptly responded to magnesium replacement once the diagnosis was established. We herein discuss the clinical presentation, pathophysiology, diagnosis, and management of severe hypomagnesemia and emphasize the implications of magnesium deficiency in the cardiovascular and central nervous systems. Furthermore, this case highlights the importance of having high vigilance for hypomagnesemia in the appropriate clinical setting.

  10. Stimulation of ICa by basal PKA activity is facilitated by caveolin-3 in cardiac ventricular myocytes☆

    Science.gov (United States)

    Bryant, Simon; Kimura, Tomomi E.; Kong, Cherrie H.T.; Watson, Judy J.; Chase, Anabelle; Suleiman, M. Saadeh; James, Andrew F.; Orchard, Clive H.

    2014-01-01

    L-type Ca channels (LTCC), which play a key role in cardiac excitation–contraction coupling, are located predominantly at the transverse (t-) tubules in ventricular myocytes. Caveolae and the protein caveolin-3 (Cav-3) are also present at the t-tubules and have been implicated in localizing a number of signaling molecules, including protein kinase A (PKA) and β2-adrenoceptors. The present study investigated whether disruption of Cav-3 binding to its endogenous binding partners influenced LTCC activity. Ventricular myocytes were isolated from male Wistar rats and LTCC current (ICa) recorded using the whole-cell patch-clamp technique. Incubation of myocytes with a membrane-permeable peptide representing the scaffolding domain of Cav-3 (C3SD) reduced basal ICa amplitude in intact, but not detubulated, myocytes, and attenuated the stimulatory effects of the β2-adrenergic agonist zinterol on ICa. The PKA inhibitor H-89 also reduced basal ICa; however, the inhibitory effects of C3SD and H-89 on basal ICa amplitude were not summative. Under control conditions, myocytes stained with antibody against phosphorylated LTCC (pLTCC) displayed a striated pattern, presumably reflecting localization at the t-tubules. Both C3SD and H-89 reduced pLTCC staining at the z-lines but did not affect staining of total LTCC or Cav-3. These data are consistent with the idea that the effects of C3SD and H-89 share a common pathway, which involves PKA and is maximally inhibited by H-89, and suggest that Cav-3 plays an important role in mediating stimulation of ICa at the t-tubules via PKA-induced phosphorylation under basal conditions, and in response to β2-adrenoceptor stimulation. PMID:24412535

  11. 9-Phenanthrol inhibits recombinant and arterial myocyte TMEM16A channels

    Science.gov (United States)

    Burris, Sarah K; Wang, Qian; Bulley, Simon; Neeb, Zachary P; Jaggar, Jonathan H

    2015-01-01

    Background and Purpose In arterial smooth muscle cells (myocytes), intravascular pressure stimulates membrane depolarization and vasoconstriction (the myogenic response). Ion channels proposed to mediate pressure-induced depolarization include several transient receptor potential (TRP) channels, including TRPM4, and transmembrane protein 16A (TMEM16A), a Ca2+-activated Cl− channel (CaCC). 9-Phenanthrol, a putative selective TRPM4 channel inhibitor, abolishes myogenic tone in cerebral arteries, suggesting that either TRPM4 is essential for pressure-induced depolarization, upstream of activation of other ion channels or that 9-phenanthrol is non-selective. Here, we tested the hypothesis that 9-phenanthrol is also a TMEM16A channel blocker, an ion channel for which few inhibitors have been identified. Experimental Approach Patch clamp electrophysiology was used to measure rat cerebral artery myocyte and human recombinant TMEM16A (rTMEM16A) currents or currents generated by recombinant bestrophin-1, another Ca2+-activated Cl− channel, expressed in HEK293 cells. Key Results 9-Phenanthrol blocked myocyte TMEM16A currents activated by either intracellular Ca2+ or Eact, a TMEM16A channel activator. In contrast, 9-phenanthrol did not alter recombinant bestrophin-1 currents. 9-Phenanthrol reduced arterial myocyte TMEM16A currents with an IC50 of ∼12 μM. Cell-attached patch recordings indicated that 9-phenanthrol reduced single rTMEM16A channel open probability and mean open time, and increased mean closed time without affecting the amplitude. Conclusions and Implications These data identify 9-phenanthrol as a novel TMEM16A channel blocker and provide an explanation for the previous observation that 9-phenanthrol abolishes myogenic tone when both TRPM4 and TMEM16A channels contribute to this response. 9-Phenanthrol may be a promising candidate from which to develop TMEM16A channel-specific inhibitors. PMID:25573456

  12. Type 2 diabetes and obesity induce similar transcriptional reprogramming in human myocytes.

    Science.gov (United States)

    Väremo, Leif; Henriksen, Tora Ida; Scheele, Camilla; Broholm, Christa; Pedersen, Maria; Uhlén, Mathias; Pedersen, Bente Klarlund; Nielsen, Jens

    2017-05-25

    Skeletal muscle is one of the primary tissues involved in the development of type 2 diabetes (T2D). The close association between obesity and T2D makes it difficult to isolate specific effects attributed to the disease alone. Therefore, here we set out to identify and characterize intrinsic properties of myocytes, associated independently with T2D or obesity. We generated and analyzed RNA-seq data from primary differentiated myotubes from 24 human subjects, using a factorial design (healthy/T2D and non-obese/obese), to determine the influence of each specific factor on genome-wide transcription. This setup enabled us to identify intrinsic properties, originating from muscle precursor cells and retained in the corresponding myocytes. Bioinformatic and statistical methods, including differential expression analysis, gene-set analysis, and metabolic network analysis, were used to characterize the different myocytes. We found that the transcriptional program associated with obesity alone was strikingly similar to that induced specifically by T2D. We identified a candidate epigenetic mechanism, H3K27me3 histone methylation, mediating these transcriptional signatures. T2D and obesity were independently associated with dysregulated myogenesis, down-regulated muscle function, and up-regulation of inflammation and extracellular matrix components. Metabolic network analysis identified that in T2D but not obesity a specific metabolite subnetwork involved in sphingolipid metabolism was transcriptionally regulated. Our findings identify inherent characteristics in myocytes, as a memory of the in vivo phenotype, without the influence from a diabetic or obese extracellular environment, highlighting their importance in the development of T2D.

  13. Triggered intracellular calcium waves in dog and human left atrial myocytes from normal and failing hearts.

    Science.gov (United States)

    Aistrup, Gary L; Arora, Rishi; Grubb, Søren; Yoo, Shin; Toren, Benjamin; Kumar, Manvinder; Kunamalla, Aaron; Marszalec, William; Motiwala, Tej; Tai, Shannon; Yamakawa, Sean; Yerrabolu, Satya; Alvarado, Francisco J; Valdivia, Hector H; Cordeiro, Jonathan M; Shiferaw, Yohannes; Wasserstrom, John Andrew

    2017-11-01

    Abnormal intracellular Ca2+ cycling contributes to triggered activity and arrhythmias in the heart. We investigated the properties and underlying mechanisms for systolic triggered Ca2+ waves in left atria from normal and failing dog hearts. Intracellular Ca2+ cycling was studied using confocal microscopy during rapid pacing of atrial myocytes (36 °C) isolated from normal and failing canine hearts (ventricular tachypacing model). In normal atrial myocytes (NAMs), Ca2+ waves developed during rapid pacing at rates ≥ 3.3 Hz and immediately disappeared upon cessation of pacing despite high sarcoplasmic reticulum (SR) load. In heart failure atrial myocytes (HFAMs), triggered Ca2+ waves (TCWs) developed at a higher incidence at slower rates. Because of their timing, TCW development relies upon action potential (AP)-evoked Ca2+ entry. The distribution of Ca2+ wave latencies indicated two populations of waves, with early events representing TCWs and late events representing conventional spontaneous Ca2+ waves. Latency analysis also demonstrated that TCWs arise after junctional Ca2+ release has occurred and spread to non-junctional (cell core) SR. TCWs also occurred in intact dog atrium and in myocytes from humans and pigs. β-adrenergic stimulation increased Ca2+ release and abolished TCWs in NAMs but was ineffective in HFAMs making this a potentially effective adaptive mechanism in normals but potentially arrhythmogenic in HF. Block of Ca-calmodulin kinase II also abolished TCWs, suggesting a role in TCW formation. Pharmacological manoeuvres that increased Ca2+ release suppressed TCWs as did interventions that decreased Ca2+ release but these also severely reduced excitation-contraction coupling. TCWs develop during the atrial AP and thus could affect AP duration, producing repolarization gradients and creating a substrate for reentry, particularly in HF where they develop at slower rates and a higher incidence. TCWs may represent a mechanism for the initiation

  14. c-MET regulates myoblast motility and myocyte fusion during adult skeletal muscle regeneration.

    Science.gov (United States)

    Webster, Micah T; Fan, Chen-Ming

    2013-01-01

    Adult muscle stem cells, satellite cells (SCs), endow skeletal muscle with tremendous regenerative capacity. Upon injury, SCs activate, proliferate, and migrate as myoblasts to the injury site where they become myocytes that fuse to form new muscle. How migration is regulated, though, remains largely unknown. Additionally, how migration and fusion, which both require dynamic rearrangement of the cytoskeleton, might be related is not well understood. c-MET, a receptor tyrosine kinase, is required for myogenic precursor cell migration into the limb for muscle development during embryogenesis. Using a genetic system to eliminate c-MET function specifically in adult mouse SCs, we found that c-MET was required for muscle regeneration in response to acute muscle injury. c-MET mutant myoblasts were defective in lamellipodia formation, had shorter ranges of migration, and migrated slower compared to control myoblasts. Surprisingly, c-MET was also required for efficient myocyte fusion, implicating c-MET in dual functions of regulating myoblast migration and myocyte fusion.

  15. Tetrodotoxin Sensitivity of the Vertebrate Cardiac Na+ Current

    Directory of Open Access Journals (Sweden)

    Jaakko Haverinen

    2011-11-01

    Full Text Available Evolutionary origin and physiological significance of the tetrodotoxin (TTX resistance of the vertebrate cardiac Na+ current (INa is still unresolved. To this end, TTX sensitivity of the cardiac INa was examined in cardiac myocytes of a cyclostome (lamprey, three teleost fishes (crucian carp, burbot and rainbow trout, a clawed frog, a snake (viper and a bird (quail. In lamprey, teleost fishes, frog and bird the cardiac INa was highly TTX-sensitive with EC50-values between 1.4 and 6.6 nmol·L−1. In the snake heart, about 80% of the INa was TTX-resistant with EC50 value of 0.65 μmol·L−1, the rest being TTX-sensitive (EC50 = 0.5 nmol·L−1. Although TTX-resistance of the cardiac INa appears to be limited to mammals and reptiles, the presence of TTX-resistant isoform of Na+ channel in the lamprey heart suggest an early evolutionary origin of the TTX-resistance, perhaps in the common ancestor of all vertebrates.

  16. Global intracoronary infusion of allogeneic cardiosphere-derived cells improves ventricular function and stimulates endogenous myocyte regeneration throughout the heart in swine with hibernating myocardium.

    Directory of Open Access Journals (Sweden)

    Gen Suzuki

    Full Text Available Cardiosphere-derived cells (CDCs improve ventricular function and reduce fibrotic volume when administered via an infarct-related artery using the "stop-flow" technique. Unfortunately, myocyte loss and dysfunction occur globally in many patients with ischemic and non-ischemic cardiomyopathy, necessitating an approach to distribute CDCs throughout the entire heart. We therefore determined whether global intracoronary infusion of CDCs under continuous flow improves contractile function and stimulates new myocyte formation.Swine with hibernating myocardium from a chronic LAD occlusion were studied 3-months after instrumentation (n = 25. CDCs isolated from myocardial biopsies were infused into each major coronary artery (∼ 33 × 10(6 icCDCs. Global icCDC infusion was safe and while ∼ 3% of injected CDCs were retained, they did not affect ventricular function or myocyte proliferation in normal animals. In contrast, four-weeks after icCDCs were administered to animals with hibernating myocardium, %LADWT increased from 23 ± 6 to 51 ± 5% (p<0.01. In diseased hearts, myocyte proliferation (phospho-histone-H3 increased in hibernating and remote regions with a concomitant increase in myocyte nuclear density. These effects were accompanied by reductions in myocyte diameter consistent with new myocyte formation. Only rare myocytes arose from sex-mismatched donor CDCs.Global icCDC infusion under continuous flow is feasible and improves contractile function, regresses myocyte cellular hypertrophy and increases myocyte proliferation in diseased but not normal hearts. New myocytes arising via differentiation of injected cells are rare, implicating stimulation of endogenous myocyte regeneration as the primary mechanism of repair.

  17. The heart remembers : observations of cardiac memory in the Dorper sheep heart

    Directory of Open Access Journals (Sweden)

    J. Ker

    2003-11-01

    Full Text Available Memory is a property common to a diverse range of tissues. Cardiac memory has been demonstrated in the human, dog, rat and rabbit. This is a peculiar phenomenon, reflected in the T wave of the electrocardiogram. The heart is able to remember periods of alterations in the sequence of ventricular activation and once there is a return to a normal sequence of ventricular activation the T waves may manifest memory. Cardiac memory is noted when the T wave during normal ventricular activation retains the vector of the previous abnormal QRS complex, caused by a period of altered ventricular activation. Possible mechanisms of memory in the heart are alterations of the transient outward potassium current (Ito in ventricular myocytes and new protein synthesis inside myocytes. These two mechanisms operate in short- and long-term cardiac memory respectively. Currently, it is unknown whether memory may have adverse structural consequences in the heart. We were able to demonstrate memory in the hearts of Dorper wethers and this is the first report of cardiac memory in Dorper sheep.

  18. Estimating the probabilities of rare arrhythmic events in multiscale computational models of cardiac cells and tissue.

    Directory of Open Access Journals (Sweden)

    Mark A Walker

    2017-11-01

    Full Text Available Ectopic heartbeats can trigger reentrant arrhythmias, leading to ventricular fibrillation and sudden cardiac death. Such events have been attributed to perturbed Ca2+ handling in cardiac myocytes leading to spontaneous Ca2+ release and delayed afterdepolarizations (DADs. However, the ways in which perturbation of specific molecular mechanisms alters the probability of ectopic beats is not understood. We present a multiscale model of cardiac tissue incorporating a biophysically detailed three-dimensional model of the ventricular myocyte. This model reproduces realistic Ca2+ waves and DADs driven by stochastic Ca2+ release channel (RyR gating and is used to study mechanisms of DAD variability. In agreement with previous experimental and modeling studies, key factors influencing the distribution of DAD amplitude and timing include cytosolic and sarcoplasmic reticulum Ca2+ concentrations, inwardly rectifying potassium current (IK1 density, and gap junction conductance. The cardiac tissue model is used to investigate how random RyR gating gives rise to probabilistic triggered activity in a one-dimensional myocyte tissue model. A novel spatial-average filtering method for estimating the probability of extreme (i.e. rare, high-amplitude stochastic events from a limited set of spontaneous Ca2+ release profiles is presented. These events occur when randomly organized clusters of cells exhibit synchronized, high amplitude Ca2+ release flux. It is shown how reduced IK1 density and gap junction coupling, as observed in heart failure, increase the probability of extreme DADs by multiple orders of magnitude. This method enables prediction of arrhythmia likelihood and its modulation by alterations of other cellular mechanisms.

  19. Does cirrhotic cardiomyopathy exist? 50 years of uncertainty.

    Science.gov (United States)

    Pellicori, Pierpaolo; Torromeo, Concetta; Calicchia, Angela; Ruffa, Alessandra; Di Iorio, Martina; Cleland, John G F; Merli, Manuela

    2013-12-01

    Subtle abnormalities of cardiac structure or function are often identified in patients with liver cirrhosis and have been termed cirrhotic cardiomyopathy. However, in the absence of a precise definition, its diagnosis remains a challenge. Cardiac dysfunction in patients with cirrhosis can often be attributed to concomitant diseases such as hypertension, ischaemic heart disease or excess alcohol consumption in many patients. Further research is required to identify the existence, origin and importance of abnormal cardiac function due specifically to liver disease. Cardiac dysfunction may be masked by treatments given to cirrhotic patients, such as mineral-corticoid receptor antagonists, or by co-existing conditions, such as anaemia. New imaging tests or plasma biomarkers might be able to detect abnormal cardiac function at an early stage of its development.

  20. Corin, a transmembrane cardiac serine protease, acts as a pro-atrial natriuretic peptide-converting enzyme

    OpenAIRE

    Yan, Wei; Wu, Faye; Morser, John; Wu, Qingyu

    2000-01-01

    Atrial natriuretic peptide (ANP) is a cardiac hormone essential for the regulation of blood pressure. In cardiac myocytes, ANP is synthesized as a precursor, pro-ANP, that is converted to biologically active ANP by an unknown membrane-associated protease. Recently, we cloned a transmembrane serine protease, corin, that is highly expressed in the heart. In this study, we examine effects of corin on pro-ANP processing. Our results show that recombinant human corin converts pro-ANP to ANP and th...

  1. Lack of effect of prolonged treatment with liraglutide on cardiac remodeling in rats after acute myocardial infarction

    DEFF Research Database (Denmark)

    Kyhl, Kasper; Lønborg, Jacob; Hartmann, Bolette

    2017-01-01

    Following the acute phase of a myocardial infarction, a set of structural and functional changes evolves in the myocardium, collectively referred to as cardiac remodeling. This complex set of processes, including interstitial fibrosis, inflammation, myocyte hypertrophy and apoptosis may progress...... to heart failure. Analogs of the incretin hormone glucagon-like peptide 1 (GLP-1) have shown some promise as cardioprotective agents. We hypothesized that a long-acting GLP-1 analog liraglutide would ameliorate cardiac remodeling over the course of 4 weeks in a rat model of non-reperfused myocardial...

  2. A Separate Pool of Cardiac Phospholemman That Does Not Regulate or Associate with the Sodium Pump

    Science.gov (United States)

    Wypijewski, Krzysztof J.; Howie, Jacqueline; Reilly, Louise; Tulloch, Lindsay B.; Aughton, Karen L.; McLatchie, Linda M.; Shattock, Michael J.; Calaghan, Sarah C.; Fuller, William

    2013-01-01

    Phospholemman (PLM), the principal quantitative sarcolemmal substrate for protein kinases A and C in the heart, regulates the cardiac sodium pump. Much like phospholamban, which regulates the related ATPase SERCA, PLM is reported to oligomerize. We investigated subpopulations of PLM in adult rat ventricular myocytes based on phosphorylation status. Co-immunoprecipitation identified two pools of PLM: one not associated with the sodium pump phosphorylated at Ser63 and one associated with the pump, both phosphorylated at Ser68 and unphosphorylated. Phosphorylation of PLM at Ser63 following activation of PKC did not abrogate association of PLM with the pump, so its failure to associate with the pump was not due to phosphorylation at this site. All pools of PLM co-localized to cell surface caveolin-enriched microdomains with sodium pump α subunits, despite the lack of caveolin-binding motif in PLM. Mass spectrometry analysis of phosphospecific immunoprecipitation reactions revealed no unique protein interactions for Ser63-phosphorylated PLM, and cross-linking reagents also failed to identify any partner proteins for this pool. In lysates from hearts of heterozygous transgenic animals expressing wild type and unphosphorylatable PLM, Ser63-phosphorylated PLM co-immunoprecipitated unphosphorylatable PLM, confirming the existence of PLM multimers. Dephosphorylation of the PLM multimer does not change sodium pump activity. Hence like phospholamban, PLM exists as a pump-inhibiting monomer and an unassociated oligomer. The distribution of different PLM phosphorylation states to different pools may be explained by their differential proximity to protein phosphatases rather than a direct effect of phosphorylation on PLM association with the pump. PMID:23532852

  3. Components of the interleukin-33/ST2 system are differentially expressed and regulated in human cardiac cells and in cells of the cardiac vasculature.

    Science.gov (United States)

    Demyanets, Svitlana; Kaun, Christoph; Pentz, Richard; Krychtiuk, Konstantin A; Rauscher, Sabine; Pfaffenberger, Stefan; Zuckermann, Andreas; Aliabadi, Arezu; Gröger, Marion; Maurer, Gerald; Huber, Kurt; Wojta, Johann

    2013-07-01

    Interleukin-33 (IL-33) is a recently described member of the IL-1 family of cytokines, which was identified as a ligand for the ST2 receptor. Components of the IL-33/ST2 system were shown to be expressed in normal and pressure overloaded human myocardium, and soluble ST2 (sST2) has emerged as a prognostic biomarker in myocardial infarction and heart failure. However, expression and regulation of IL-33 in human adult cardiac myocytes and fibroblasts was not tested before. In this study we found that primary human adult cardiac fibroblasts (HACF) and human adult cardiac myocytes (HACM) constitutively express nuclear IL-33 that is released during cell necrosis. Tumor necrosis factor (TNF)-α, interferon (IFN)-γ and IL-1β significantly increased both IL-33 protein and IL-33 mRNA expression in HACF and HACM as well as in human coronary artery smooth muscle cells (HCASMC). The nuclear factor-κB (NF-κB) inhibitor dimethylfumarate inhibited TNF-α- and IL-1β-induced IL-33 production as well as nuclear translocation of p50 and p65 NF-κB subunits in these cells. Mitogen-activated protein/extracellular signal-regulated kinase inhibitor U0126 abrogated TNF-α-, IFN-γ-, and IL-1β-induced and Janus-activated kinase inhibitor I reduced IFN-γ-induced IL-33 production. We detected IL-33 mRNA in human myocardial tissue from patients undergoing heart transplantation (n=27) where IL-33 mRNA levels statistically significant correlated with IFN-γ (r=0.591, p=0.001) and TNF-α (r=0.408, p=0.035) mRNA expression. Endothelial cells in human heart expressed IL-33 as well as ST2 protein. We also reveal that human cardiac and vascular cells have different distribution patterns of ST2 isoforms (sST2 and transmembrane ST2L) mRNA expression and produce different amounts of sST2 protein. Both human macrovascular (aortic and coronary artery) and heart microvascular endothelial cells express specific mRNA for both ST2 isoforms (ST2L and sST2) and are a source for sST2 protein, whereas

  4. Boosters and barriers for direct cardiac reprogramming.

    Science.gov (United States)

    Talkhabi, Mahmood; Zonooz, Elmira Rezaei; Baharvand, Hossein

    2017-06-01

    Heart disease is currently the most significant cause of morbidity and mortality worldwide, which accounts for approximately 33% of all deaths. Recently, a promising and alchemy-like strategy has been developed called direct cardiac reprogramming, which directly converts somatic cells such as fibroblasts to cardiac lineage cells such as cardiomyocytes (CMs), termed induced CMs or iCMs. The first in vitro cardiac reprogramming study, mediated by cardiac transcription factors (TFs)-Gata4, Tbx5 and Mef2C-, was not enough efficient to produce an adequate number of fully reprogrammed, functional iCMs. As a result, numerous combinations of cardiac TFs exist for direct cardiac reprogramming of mouse and human fibroblasts. However, the efficiency of direct cardiac reprogramming remains low. Recently, a number of cellular and molecular mechanisms have been identified to increase the efficiency of direct cardiac reprogramming and the quality of iCMs. For example, microgrooved substrate, cardiogenic growth factors [VEGF, FGF, BMP4 and Activin A], and an appropriate stoichiometry of TFs boost the direct cardiac reprogramming. On the other hand, serum, TGFβ signaling, activators of epithelial to mesenchymal transition, and some epigenetic factors (Bmi1 and Ezh2) are barriers for direct cardiac reprogramming. Manipulating these mechanisms by the application of boosters and removing barriers can increase the efficiency of direct cardiac reprogramming and possibly make iCMs reliable for cell-based therapy or other potential applications. In this review, we summarize the latest trends in cardiac TF- or miRNA-based direct cardiac reprogramming and comprehensively discuses all molecular and cellular boosters and barriers affecting direct cardiac reprogramming. Copyright © 2017 Elsevier Inc. All rights reserved.

  5. Components of the interleukin-33/ST2 system are differentially expressed and regulated in human cardiac cells and in cells of the cardiac vasculature

    OpenAIRE

    Demyanets, Svitlana; Kaun, Christoph; Pentz, Richard; Krychtiuk, Konstantin A.; Rauscher, Sabine; Pfaffenberger, Stefan; Zuckermann, Andreas; Aliabadi, Arezu; Gröger, Marion; Maurer, Gerald; Huber, Kurt; Wojta, Johann

    2013-01-01

    Interleukin-33 (IL-33) is a recently described member of the IL-1 family of cytokines, which was identified as a ligand for the ST2 receptor. Components of the IL-33/ST2 system were shown to be expressed in normal and pressure overloaded human myocardium, and soluble ST2 (sST2) has emerged as a prognostic biomarker in myocardial infarction and heart failure. However, expression and regulation of IL-33 in human adult cardiac myocytes and fibroblasts was not tested before. In this study we foun...

  6. Global Intracoronary Infusion of Allogeneic Cardiosphere-Derived Cells Improves Ventricular Function and Stimulates Endogenous Myocyte Regeneration throughout the Heart in Swine with Hibernating Myocardium

    Science.gov (United States)

    Suzuki, Gen; Weil, Brian R.; Leiker, Merced M.; Ribbeck, Amanda E.; Young, Rebeccah F.; Cimato, Thomas R.; Canty, John M.

    2014-01-01

    Background Cardiosphere-derived cells (CDCs) improve ventricular function and reduce fibrotic volume when administered via an infarct-related artery using the “stop-flow” technique. Unfortunately, myocyte loss and dysfunction occur globally in many patients with ischemic and non-ischemic cardiomyopathy, necessitating an approach to distribute CDCs throughout the entire heart. We therefore determined whether global intracoronary infusion of CDCs under continuous flow improves contractile function and stimulates new myocyte formation. Methods and Results Swine with hibernating myocardium from a chronic LAD occlusion were studied 3-months after instrumentation (n = 25). CDCs isolated from myocardial biopsies were infused into each major coronary artery (∼33×106 icCDCs). Global icCDC infusion was safe and while ∼3% of injected CDCs were retained, they did not affect ventricular function or myocyte proliferation in normal animals. In contrast, four-weeks after icCDCs were administered to animals with hibernating myocardium, %LADWT increased from 23±6 to 51±5% (pmyocyte proliferation (phospho-histone-H3) increased in hibernating and remote regions with a concomitant increase in myocyte nuclear density. These effects were accompanied by reductions in myocyte diameter consistent with new myocyte formation. Only rare myocytes arose from sex-mismatched donor CDCs. Conclusions Global icCDC infusion under continuous flow is feasible and improves contractile function, regresses myocyte cellular hypertrophy and increases myocyte proliferation in diseased but not normal hearts. New myocytes arising via differentiation of injected cells are rare, implicating stimulation of endogenous myocyte regeneration as the primary mechanism of repair. PMID:25402428

  7. LabHEART: an interactive computer model of rabbit ventricular myocyte ion channels and Ca transport

    Science.gov (United States)

    Puglisi, J. L.; Bers, D. M.

    2001-01-01

    An interactive computer program, LabHEART, was developed to simulate the action potential (AP), ionic currents, and Ca handling mechanisms in a rabbit ventricular myocyte. User-oriented, its design allows switching between voltage and current clamp and easy on-line manipulation of key parameters to change the original formulation. The model reproduces normal rabbit ventricular myocyte currents, Ca transients, and APs. We also changed parameters to simulate data from heart failure (HF) myocytes, including reduced transient outward (I(to)) and inward rectifying K currents (I(K1)), enhanced Na/Ca exchange expression, and reduced sarcoplasmic reticulum Ca-ATPase function, but unaltered Ca current density. These changes caused reduced Ca transient amplitude and increased AP duration (especially at lower frequency) as observed experimentally. The model shows that the increased Na/Ca exchange current (I(NaCa)) in HF lowers the intracellular [Ca] threshold for a triggered AP from 800 to 540 nM. Similarly, the decrease in I(K1) reduces the threshold to 600 nM. Changes in I(to) have no effect. Combining enhanced Na/Ca exchange with reduced I(K1) (as in HF) lowers the threshold to trigger an AP to 380 nM. These changes reproduce experimental results in HF, where the contributions of different factors are not readily distinguishable. We conclude that the triggered APs that contribute to nonreentrant ventricular tachycardia in HF are due approximately equally (and nearly additively) to alterations in I(NaCa) and I(K1). A free copy of this software can be obtained at http://www.meddean.luc.edu/lumen/DeptWebs/physio/bers.html.

  8. Dynamics of Muscle Microcirculatory and Blood-myocyte O2 Flux During Contractions

    Science.gov (United States)

    Poole, David C.; Copp, Steven W.; Hirai, Daniel M.; Musch, Timothy I.

    2011-01-01

    The O2 requirements of contracting skeletal muscle may increase 100-fold above rest. In 1919 August Krogh’s brilliant insights recognized the capillary as the principal site for this increased blood-myocyte O2 flux. Based on the premise that most capillaries did not sustain RBC flux at rest Krogh proposed that capillary recruitment (i.e., initiation of red blood cell (RBC) flux in previously non-flowing capillaries) increased the capillary surface area available for O2 flux and reduced mean capillary-to-mitochondrial diffusion distances. More modern experimental approaches reveal that most muscle capillaries may support RBC flux at rest. Thus, rather than contraction-induced capillary recruitment per se, increased RBC flux and hematocrit within already-flowing capillaries likely elevate perfusive and diffusive O2 conductances and hence blood-myocyte O2 flux. Additional surface area for O2 exchange is recruited but, crucially, this may occur along the length of already-flowing capillaries (i.e. longitudinal recruitment). Today, the capillary is still considered the principal site for O2 and substrate delivery to contracting skeletal muscle. Indeed, the presence of very low intramyocyte O2 partial pressures (PO2’s) and the absence of PO2 gradients, whilst refuting the relevance of diffusion distances, place an even greater importance on capillary hemodynamics. This emergent picture calls for a paradigm-shift in our understanding of the function of capillaries by de-emphasizing de novo ‘capillary recruitment.’ Diseases such as heart failure impair blood-myocyte O2 flux, in part, by decreasing the proportion of RBC-flowing capillaries. Knowledge of capillary function in healthy muscle is requisite for identification of pathology and efficient design of therapeutic treatments. PMID:21199399

  9. The Unfolded Protein Response Regulates Uterine Myocyte Antioxidant Responsiveness During Pregnancy.

    Science.gov (United States)

    Ramnarayanan, Saiprasad; Kyathanahalli, Chandrashekara; Ingles, Judith; Park-York, MieJung; Jeyasuria, Pancharatnam; Condon, Jennifer C

    2016-12-01

    There is considerable evidence that implicates oxidative stress in the pathophysiology of human pregnancy complications. However, the role and the mechanism of maintaining an antioxidant prosurvival uterine environment during normal pregnancy is largely unresolved. Herein we report that the highly active uterine unfolded protein response plays a key role in promoting antioxidant activity in the uterine myocyte across gestation. The unfolded protein response (UPR) senses the accumulation of misfolded proteins in the endoplasmic reticulum (ER) and activates a signaling network that consists of the transmembrane protein kinase eukaryotic translation initiation factor 2 alpha kinase 3/PKR-like-ER kinase (EIF2AK3), which acts to decrease protein translation levels, allowing for a lowered need for protein folding during periods of ER stress. However, independent of its translational regulatory capacity, EIF2AK3-dependent signals elicit the activation of the transcription factor, nuclear factor erythroid 2-like 2 (NFE2L2) in response to oxidative stress. NFE2L2 binds to antioxidant response elements in the promoters of a variety of antioxidant genes that minimize the opportunities for generation of reactive oxygen intermediates. Our analysis demonstrates that in the absence of EIF2AK3, the uterine myocyte experiences increased levels of reactive oxygen species due to decreased NFE2L2 activation. Elevated levels of intracellular reactive oxygen species were observed in the EIF2AK3 null cells, and this was associated with the onset of apoptotic cell death. These findings confirm the prosurvival and antioxidant role of UPR-mediated EIF2AK3 activation in the context of the human uterine myocyte. © 2016 by the Society for the Study of Reproduction, Inc.

  10. The Unfolded Protein Response Regulates Uterine Myocyte Antioxidant Responsiveness During Pregnancy1

    Science.gov (United States)

    Ramnarayanan, Saiprasad; Kyathanahalli, Chandrashekara; Ingles, Judith; Park-York, MieJung; Jeyasuria, Pancharatnam; Condon, Jennifer C.

    2016-01-01

    There is considerable evidence that implicates oxidative stress in the pathophysiology of human pregnancy complications. However, the role and the mechanism of maintaining an antioxidant prosurvival uterine environment during normal pregnancy is largely unresolved. Herein we report that the highly active uterine unfolded protein response plays a key role in promoting antioxidant activity in the uterine myocyte across gestation. The unfolded protein response (UPR) senses the accumulation of misfolded proteins in the endoplasmic reticulum (ER) and activates a signaling network that consists of the transmembrane protein kinase eukaryotic translation initiation factor 2 alpha kinase 3/PKR-like-ER kinase (EIF2AK3), which acts to decrease protein translation levels, allowing for a lowered need for protein folding during periods of ER stress. However, independent of its translational regulatory capacity, EIF2AK3-dependent signals elicit the activation of the transcription factor, nuclear factor erythroid 2-like 2 (NFE2L2) in response to oxidative stress. NFE2L2 binds to antioxidant response elements in the promoters of a variety of antioxidant genes that minimize the opportunities for generation of reactive oxygen intermediates. Our analysis demonstrates that in the absence of EIF2AK3, the uterine myocyte experiences increased levels of reactive oxygen species due to decreased NFE2L2 activation. Elevated levels of intracellular reactive oxygen species were observed in the EIF2AK3 null cells, and this was associated with the onset of apoptotic cell death. These findings confirm the prosurvival and antioxidant role of UPR-mediated EIF2AK3 activation in the context of the human uterine myocyte. PMID:27733380

  11. Regional acidosis locally inhibits but remotely stimulates Ca2+ waves in ventricular myocytes.

    Science.gov (United States)

    Ford, Kerrie L; Moorhouse, Emma L; Bortolozzi, Mario; Richards, Mark A; Swietach, Pawel; Vaughan-Jones, Richard D

    2017-07-01

    Spontaneous Ca2+ waves in cardiomyocytes are potentially arrhythmogenic. A powerful controller of Ca2+ waves is the cytoplasmic H+ concentration ([H+]i), which fluctuates spatially and temporally in conditions such as myocardial ischaemia/reperfusion. H+-control of Ca2+ waves is poorly understood. We have therefore investigated how [H+]i co-ordinates their initiation and frequency. Spontaneous Ca2+ waves were imaged (fluo-3) in rat isolated ventricular myocytes, subjected to modest Ca2+-overload. Whole-cell intracellular acidosis (induced by acetate-superfusion) stimulated wave frequency. Pharmacologically blocking sarcolemmal Na+/H+ exchange (NHE1) prevented this stimulation, unveiling inhibition by H+. Acidosis also increased Ca2+ wave velocity. Restricting acidosis to one end of a myocyte, using a microfluidic device, inhibited Ca2+ waves in the acidic zone (consistent with ryanodine receptor inhibition), but stimulated wave emergence elsewhere in the cell. This remote stimulation was absent when NHE1 was selectively inhibited in the acidic zone. Remote stimulation depended on a locally evoked, NHE1-driven rise of [Na+]i that spread rapidly downstream. Acidosis influences Ca2+ waves via inhibitory Hi+ and stimulatory Nai+ signals (the latter facilitating intracellular Ca2+-loading through modulation of sarcolemmal Na+/Ca2+ exchange activity). During spatial [H+]i-heterogeneity, Hi+-inhibition dominates in acidic regions, while rapid Nai+ diffusion stimulates waves in downstream, non-acidic regions. Local acidosis thus simultaneously inhibits and stimulates arrhythmogenic Ca2+-signalling in the same myocyte. If the principle of remote H+-stimulation of Ca2+ waves also applies in multicellular myocardium, it raises the possibility of electrical disturbances being driven remotely by adjacent ischaemic areas, which are known to be intensely acidic.

  12. Phos-tag-based analysis of myosin regulatory light chain phosphorylation in human uterine myocytes.

    Directory of Open Access Journals (Sweden)

    Hector N Aguilar

    Full Text Available The 'phosphate-binding tag' (phos-tag reagent enables separation of phospho-proteins during SDS-PAGE by impeding migration proportional to their phosphorylation stoichiometry. Western blotting can then be used to detect and quantify the bands corresponding to the phospho-states of a target protein. We present a method for quantification of data regarding phospho-states derived from phos-tag SDS-PAGE. The method incorporates corrections for lane-to-lane loading variability and for the effects of drug vehicles thus enabling the comparison of multiple treatments by using the untreated cellular set-point as a reference. This method is exemplified by quantifying the phosphorylation of myosin regulatory light chain (RLC in cultured human uterine myocytes.We have evaluated and validated the concept that, when using an antibody (Ab against the total-protein, the sum of all phosphorylation states in a single lane represents a 'closed system' since all possible phospho-states and phosphoisotypes are detected. Using this approach, we demonstrate that oxytocin (OT and calpeptin (Calp induce RLC kinase (MLCK- and rho-kinase (ROK-dependent enhancements in phosphorylation of RLC at T18 and S19. Treatment of myocytes with a phorbol ester (PMA induced phosphorylation of S1-RLC, which caused a mobility shift in the phos-tag matrices distinct from phosphorylation at S19.We have presented a method for analysis of phospho-state data that facilitates quantitative comparison to a reference control without the use of a traditional 'loading' or 'reference' standard. This analysis is useful for assessing effects of putative agonists and antagonists where all phospho-states are represented in control and experimental samples. We also demonstrated that phosphorylation of RLC at S1 is inducible in intact uterine myocytes, though the signal in the resting samples was not sufficiently abundant to allow quantification by the approach used here.

  13. Regression of cardiac hypertrophy in the SHR by combined renin-angiotensin system blockade and dietary sodium restriction

    Directory of Open Access Journals (Sweden)

    Emad Abro

    2001-03-01

    Full Text Available Altered operation of the renin-angiotensin-aldosterone system (RAAS and dietary sodium intake have been identified as independent risk factors for cardiac hypertrophy. The way in which sodium intake and the operation of the renin-angiotensin-aldosterone system interact in the pathogenesis of cardiac hypertrophy is poorly understood. The aims of this study were to investigate the cardiac effects of the renin-angiotensin system (RAS blockade in the spontaneously hypertensive rat (SHR, using co-treatment with an angiotensin II receptor blocker (ARB and an angiotensin-converting enzyme (ACE inhibitor with different sodium intakes. Our experiments with SHR show that, at high levels of sodium intake (4.0%, aggressive RAS blockade treatment with candesartan (3 mg/kg and perindopril (6 mg/kg does not result in regression of cardiac hypertrophy. In contrast, RAS blockade coupled with reduced sodium diet (0.2% significantly regresses cardiac hypertrophy, impairs animal growth and is associated with elevated plasma renin and dramatically suppressed plasma angiotensinogen levels. Histological analyses indicate that the differential effect of reduced sodium on heart growth during RAS blockade is not associated with any change in myocardial interstitial collagen, but reflects modification of cellular geometry. Dimensional measurements of enzymatically-isolated ventricular myocytes show that, in the RAS blocked, reduced sodium group, myocyte length and width were decreased by about 16—19% compared with myocytes from the high sodium treatment group. Our findings highlight the importance of `titrating' sodium intake with combined RAS blockade in the clinical setting to optimise therapeutic benefit.

  14. Requirements for existing buildings

    DEFF Research Database (Denmark)

    Thomsen, Kirsten Engelund; Wittchen, Kim Bjarne

    This report collects energy performance requirements for existing buildings in European member states by June 2012.......This report collects energy performance requirements for existing buildings in European member states by June 2012....

  15. Accumulation of slowly activating delayed rectifier potassium current (IKs) in canine ventricular myocytes

    DEFF Research Database (Denmark)

    Stengl, Milan; Volders, Paul G A; Thomsen, Morten Bækgaard

    2003-01-01

    the deactivation is much faster, is still unclear. In this study the conditions under which accumulation occurs in canine ventricular myocytes were studied with regard to its physiological relevance in controlling action potential duration (APD). At baseline, square pulse voltage clamp experiments revealed...... that the accumulation of canine IKs could occur, but only at rather short interpulse intervals (... in the presence of isoproterenol. Block of IKs, however, led to a reverse rate-dependent prolongation of APD indicating that IKs does not have a dominant role at short cycle lengths....

  16. Cardiac conduction system

    Science.gov (United States)

    The cardiac conduction system is a group of specialized cardiac muscle cells in the walls of the heart that send signals to the ... contract. The main components of the cardiac conduction system are the SA node, AV node, bundle of ...

  17. Sudden Cardiac Arrest (SCA)

    Science.gov (United States)

    ... Arrest (SCA) Back to Heart Diseases & Disorders Sudden Cardiac Arrest (SCA) Sudden Cardiac Arrest ( SCA ) occurs when the heart stops beating, abruptly ... to saving someone who is having a sudden cardiac arrest , it is important to understand the difference. The ...

  18. Cardiac electrophysiology and the athlete: a primer for the sports clinician.

    Science.gov (United States)

    Stoebner, Richard; Bellin, Daniel A; Haigney, Mark C

    2012-01-01

    Intense exercise requires a significant increase in cardiac output in order to meet the needs of the skeletal muscles for oxygenated blood. In order to improve cardiac performance, the autonomic nervous system increases sympathetic tone primarily through release of norepinephrine from postganglionic receptors to stimulate the β-adrenergic receptors of the nodal and muscle tissue of the heart. This event initiates a signaling cascade focused on increasing the amount of calcium available to the contractile myofilaments in the cardiac cell. Failure of the myocytes to counterbalance the increase in inward ion flow or adequately sequester cytosolic calcium during diastole leads to potentially catastrophic electrical instability. In this review, the relationship between the cellular events initiated by exercise and the induction of arrhythmias associated with the long QT, Brugada, and Wolff-Parkinson-White syndromes; catecholaminergic polymorphic ventricular tachycardia; and the heritable cardiomyopathies are explored.

  19. Heparin-binding EGF-like growth factor mediates oxyhemoglobin-induced suppression of voltage-dependent potassium channels in rabbit cerebral artery myocytes.

    Science.gov (United States)

    Koide, Masayo; Penar, Paul L; Tranmer, Bruce I; Wellman, George C

    2007-09-01

    Oxyhemoglobin (OxyHb) can suppress voltage-dependent K(+) channel (K(V)) currents through protein tyrosine kinase activation, which may contribute to cerebral vasospasm following subarachnoid hemorrhage. Here we have tested the hypothesis that shedding of heparin-binding EGF-like growth factor (HB-EGF) and the resulting activation of the tyrosine kinase EGF receptor (EGFR) underlie OxyHb-induced K(V) channel suppression in the cerebral vasculature. With the use of the conventional whole cell patch-clamp technique, two EGFR ligands, EGF and HB-EGF, were found to mimic OxyHb-induced K(V) suppression in rabbit cerebral artery myocytes. K(V) current suppression by OxyHb or EGF ligands was eliminated by a specific EGFR inhibitor, AG-1478, but was unaffected by PKC inhibition. Compounds (heparin and CRM-197) that specifically interfere with HB-EGF signaling eliminated OxyHb-induced K(V) suppression, suggesting that HB-EGF is the EGFR ligand involved in this pathway. HB-EGF exists as a precursor protein that, when cleaved by matrix metalloproteases (MMPs), causes EGFR activation. MMP activation was detected in OxyHb-treated arteries by gelatin zymography. Furthermore, the MMP inhibitor (GM-6001) abolished OxyHb-induced K(V) current suppression. We also observed K(V) current suppression due to EGFR activation in human cerebral artery myocytes. In conclusion, these data demonstrate that OxyHb induces MMP activation, causing HB-EGF shedding and enhanced EGFR activity, ultimately leading to K(V) channel suppression. We propose that EGFR-mediated K(V) suppression contributes to vascular pathologies, such as cerebral vasospasm, and may play a more widespread role in the regulation of regional blood flow and peripheral resistance.

  20. Distinct Effects of Abelson Kinase Mutations on Myocytes and Neurons in Dissociated Drosophila Embryonic Cultures: Mimicking of High Temperature

    Science.gov (United States)

    Liu, Lijuan; Wu, Chun-Fang

    2014-01-01

    Abelson tyrosine kinase (Abl) is known to regulate axon guidance, muscle development, and cell-cell interaction in vivo. The Drosophila primary culture system offers advantages in exploring the cellular mechanisms mediated by Abl with utilizing various experimental manipulations. Here we demonstrate that single-embryo cultures exhibit stage-dependent characteristics of cellular differentiation and developmental progression in neurons and myocytes, as well as nerve-muscle contacts. In particular, muscle development critically depends on the stage of dissociated embryos. In wild-type (WT) cultures derived from embryos before stage 12, muscle cells remained within cell clusters and were rarely detected. Interestingly, abundant myocytes were spotted in Abl mutant cultures, exhibiting enhanced myocyte movement and fusion, as well as neuron-muscle contacts even in cultures dissociated from younger, stage 10 embryos. Notably, Abl myocytes frequently displayed well-expanded lamellipodia. Conversely, Abl neurons were characterized with fewer large veil-like lamellipodia, but instead had increased numbers of filopodia and darker nodes along neurites. These distinct phenotypes were equally evident in both homo- and hetero-zygous cultures (Abl/Abl vs. Abl/+) of different alleles (Abl1 and Abl4) indicating dominant mutational effects. Strikingly, in WT cultures derived from stage 10 embryos, high temperature (HT) incubation promoted muscle migration and fusion, partially mimicking the advanced muscle development typical of Abl cultures. However, HT enhanced neuronal growth with increased numbers of enlarged lamellipodia, distinct from the characteristic Abl neuronal morphology. Intriguingly, HT incubation also promoted Abl lamellipodia expansion, with a much greater effect on nerve cells than muscle. Our results suggest that Abl is an essential regulator for myocyte and neuron development and that high-temperature incubation partially mimics the faster muscle development

  1. Effect of Commiphora mukul extract on cardiac dysfunction and ventricular function in isoproterenol-induced myocardial infarction.

    Science.gov (United States)

    Ojha, Shreesh K; Nandave, Mukesh; Arora, Sachin; Mehra, Raj D; Joshi, Sujata; Narang, Rajiv; Arya, D S

    2008-09-01

    In present study, hydroalcoholic extract of C. mukul significantly improved the cardiac function and prevented myocardial ischemic impairment manifested in the form of increased heart rate, decreased arterial pressure, increased left ventricular end diastolic pressure, and altered myocardial contractility indices. C. mukul treatment additionally also produced a significant increase in lactate dehydrogenase levels and prevented decline of protein content in heart. C. mukul preserved the structural integrity of myocardium. Reduced leakage of myocyte enzyme lactate dehydrogenase and maintenance of structural integrity of myocardium along with favorable modulation of cardiac function and improved cardiac performance indicate the salvage of myocardium with C. mukul treatment. Guggulsterones which are considered to be responsible for most of the therapeutic properties of C. mukul may underlie the observed cardioprotective effect of C. mukul against cardiac dysfunction in isoproterenol-induced ischemic rats.

  2. AVE 0991 attenuates cardiac hypertrophy through reducing oxidative stress.

    Science.gov (United States)

    Ma, Yuedong; Huang, Huiling; Jiang, Jingzhou; Wu, Lingling; Lin, Chunxi; Tang, Anli; Dai, Gang; He, Jiangui; Chen, Yili

    2016-06-10

    AVE 0991, the nonpeptide angiotensin-(1-7) (Ang-(1-7)) analog, is recognized as having beneficial cardiovascular effects. However, the mechanisms have not been fully elucidated. This study was designed to investigate the effects of AVE 0991 on cardiac hypertrophy and the mechanisms involved. Mice were underwent aortic banding to induce cardiac hypertrophy followed by the administration of AVE 0991 (20 mg kg·day (-1)) for 4 weeks. It was shown that AVE 0991 reduced left ventricular hypertrophy and improved heart function, characterized by decreases in left ventricular weight and left ventricular end-diastolic diameter, and increases in ejection fraction. Moreover, AVE 0991 significantly down-regulated mean myocyte diameter and attenuate the gene expression of the hypertrophic markers. Furthermore, AVE 0991 inhibited the expression of NOX 2 and NOX 4, meaning that AVE 0991 reduced oxidative stress of cardiac hypertrophy mice. Our data showed that AVE 0991 treatment could attenuate cardiac hypertrophy and improve heart function, which may be due to reduce oxidative stress. Copyright © 2016. Published by Elsevier Inc.

  3. Cardiac myofibrillar contractile properties during the progression from hypertension to decompensated heart failure.

    Science.gov (United States)

    Hanft, Laurin M; Emter, Craig A; McDonald, Kerry S

    2017-07-01

    Heart failure arises, in part, from a constellation of changes in cardiac myocytes including remodeling, energetics, Ca 2+ handling, and myofibrillar function. However, little is known about the changes in myofibrillar contractile properties during the progression from hypertension to decompensated heart failure. The aim of the present study was to provide a comprehensive assessment of myofibrillar functional properties from health to heart disease. A rodent model of uncontrolled hypertension was used to test the hypothesis that myocytes in compensated hearts exhibit increased force, higher rates of force development, faster loaded shortening, and greater power output; however, with progression to overt heart failure, we predicted marked depression in these contractile properties. We assessed contractile properties in skinned cardiac myocyte preparations from left ventricles of Wistar-Kyoto control rats and spontaneous hypertensive heart failure (SHHF) rats at ~3, ~12, and >20 mo of age to evaluate the time course of myofilament properties associated with normal aging processes compared with myofilaments from rats with a predisposition to heart failure. In control rats, the myofilament contractile properties were virtually unchanged throughout the aging process. Conversely, in SHHF rats, the rate of force development, loaded shortening velocity, and power all increased at ~12 mo and then significantly fell at the >20-mo time point, which coincided with a decrease in left ventricular fractional shortening. Furthermore, these changes occurred independent of changes in β-myosin heavy chain but were associated with depressed phosphorylation of myofibrillar proteins, and the fall in loaded shortening and peak power output corresponded with the onset of clinical signs of heart failure. NEW & NOTEWORTHY This novel study systematically examined the power-generating capacity of cardiac myofilaments during the progression from hypertension to heart disease. Previously

  4. Natriuretic peptides in developing medaka embryos: implications in cardiac development by loss-of-function studies.

    Science.gov (United States)

    Miyanishi, Hiroshi; Okubo, Kataaki; Nobata, Shigenori; Takei, Yoshio

    2013-01-01

    Cardiac natriuretic peptides (NPs), atrial NP (ANP) and B-type NP (BNP), and their receptor, guanylyl cyclase (GC)-A have attracted attention of many basic and clinical researchers because of their potent renal and cardiovascular actions. In this study, we used medaka, Oryzias latipes, as a model species to pursue the physiological functions of NPs because it is a suitable model for developmental analyses. Medaka has two ligands, BNP and C-type NP3 (CNP3) (but not ANP), that have greater affinity for the two O. latipes GC-A receptors (OLGC), OLGC7 and OLGC2, respectively. CNP3 is the ancestral molecule of cardiac NPs. Initially, we examined developmental expression of cardiac NP/receptor combinations, BNP/OLGC7 and CNP3/OLGC2, using quantitative real-time PCR and in situ hybridization. BNP and CNP3 mRNA increased at stages 25 (onset of ventricular formation) and 22 (appearance of heart anlage), respectively, whereas both receptor mRNAs increased at as early as stage 12. BNP/OLGC7 transcripts were found in arterial/ventricular tissues and CNP3/OLGC2 transcripts in venous/atrial tissues by in situ hybridization. Thus, BNP and CNP3 can act locally on cardiac myocytes in a paracrine/autocrine fashion. Double knockdown of BNP/OLGC7 genes impaired ventricular development by causing hypoplasia of ventricular myocytes as evidenced by reduced bromodeoxyuridine incorporation. CNP3 knockdown induced hypertrophy of atria and activated the renin-angiotensin system. Collectively, it appears that BNP is important for normal ventricular, whereas CNP3 is important for normal atrial development and performance, a role usually taken by ANP in other vertebrates. The current study provides new insights into the role of cardiac NPs in cardiac development in vertebrates.

  5. Phospholemman-mediated activation of Na/K-ATPase limits [Na]i and inotropic state during beta-adrenergic stimulation in mouse ventricular myocytes.

    Science.gov (United States)

    Despa, Sanda; Tucker, Amy L; Bers, Donald M

    2008-04-08

    Cardiac Na/K-ATPase (NKA) regulates intracellular Na ([Na](i)), which in turn affects intracellular Ca and thus contractility via Na/Ca exchange. Recent evidence shows that phosphorylation of the NKA-associated small transmembrane protein phospholemman (PLM) mediates beta-adrenergic-induced NKA stimulation. Here, we tested whether PLM phosphorylation during beta-adrenergic activation limits the rise in [Na](i), Ca transient amplitude, and triggered arrhythmias in mouse ventricular myocytes. In myocytes from wild-type (WT) mice, [Na](i) increased on field stimulation at 2 Hz from 11.1+/-1.8 mmol/L to a plateau of 15.2+/-1.5 mmol/L. Isoproterenol induced a decrease in [Na](i) to 12.0+/-1.2 mmol/L. In PLM knockout (PLM-KO) mice in which beta-adrenergic stimulation does not activate NKA, [Na](i) also increased at 2 Hz (from 10.4+/-1.2 to 17.0+/-1.5 mmol/L) but was unaltered by isoproterenol. The PLM-mediated decrease in [Na](i) in WT mice could limit the isoproterenol-induced inotropic state. Indeed, the isoproterenol-induced increase in the amplitude of Ca transients was significantly smaller in the WT mice (5.2+/-0.4- versus 7.1+/-0.5-fold in PLM-KO mice). This also was the case for the sarcoplasmic reticulum Ca content, which increased by 1.27+/-0.09-fold in WT mice versus 1.53+/-0.09-fold in PLM-KO mice. The higher sarcoplasmic reticulum Ca content in PLM-KO versus WT mice was associated with an increased propensity for spontaneous Ca transients and contractions in PLM-KO mice. These data suggest that PLM phosphorylation and NKA stimulation are an integral part of the sympathetic fight-or-flight response, tempering the rise in [Na](i) and cellular Ca loading and perhaps limiting Ca overload-induced arrhythmias.

  6. Development of the excitation-contraction coupling machinery and its relation to myofibrillogenesis in human iPSC-derived skeletal myocytes.

    Science.gov (United States)

    Lainé, Jeanne; Skoglund, Gunnar; Fournier, Emmanuel; Tabti, Nacira

    2018-01-05

    Human induced pluripotent stem cells-derived myogenic progenitors develop functional and ultrastructural features typical of skeletal muscle when differentiated in culture. Besides disease-modeling, such a system can be used to clarify basic aspects of human skeletal muscle development. In the present study, we focus on the development of the excitation-contraction (E-C) coupling, a process that is essential both in muscle physiology and as a tool to differentiate between the skeletal and cardiac muscle. The occurrence and maturation of E-C coupling structures (Sarcoplasmic Reticulum-Transverse Tubule (SR-TT) junctions), key molecular components, and Ca2+ signaling were examined, along with myofibrillogenesis. Pax7+-myogenic progenitors were differentiated in culture, and developmental changes were examined from a few days up to several weeks. Ion channels directly involved in the skeletal muscle E-C coupling (RyR1 and Cav1.1 voltage-gated Ca2+ channels) were labeled using indirect immunofluorescence. Ultrastructural changes of differentiating cells were visualized by transmission electron microscopy. On the functional side, depolarization-induced intracellular Ca2+ transients mediating E-C coupling were recorded using Fura-2 ratiometric Ca2+ imaging, and myocyte contraction was captured by digital photomicrography. We show that the E-C coupling machinery occurs and operates within a few days post-differentiation, as soon as the myofilaments align. However, Ca2+ transients become effective in triggering myocyte contraction after 1 week of differentiation, when nascent myofibrils show alternate A-I bands. At later stages, myofibrils become fully organized into adult-like sarcomeres but SR-TT junctions do not reach their triadic structure and typical A-I location. This is mirrored by the absence of cross-striated distribution pattern of both RyR1 and Cav1.1 channels. The E-C coupling machinery occurs and operates within the first week of muscle cells differentiation

  7. What Causes Sudden Cardiac Arrest?

    Science.gov (United States)

    ... Back To Health Topics / Sudden Cardiac Arrest Sudden Cardiac Arrest Also known as Cardiac Arrest , Sudden Cardiac Death ... the condition For People Who Have Survived Sudden Cardiac Arrest If you've already had SCA, you're ...

  8. What Is Sudden Cardiac Arrest?

    Science.gov (United States)

    ... Back To Health Topics / Sudden Cardiac Arrest Sudden Cardiac Arrest Also known as Cardiac Arrest , Sudden Cardiac Death ... the condition For People Who Have Survived Sudden Cardiac Arrest If you've already had SCA, you're ...

  9. Ectopic automaticity induced in ventricular myocytes by transgenic overexpression of HCN2.

    Science.gov (United States)

    Oshita, Kensuke; Itoh, Masayuki; Hirashima, Shingo; Kuwabara, Yoshihiro; Ishihara, Keiko; Kuwahara, Koichiro; Nakao, Kazuwa; Kimura, Takeshi; Nakamura, Kei-Ichiro; Ushijima, Kazuo; Takano, Makoto

    2015-03-01

    Hyperpolarization-activated cyclic nucleotide-gated channels (HCNs) are expressed in the ventricles of fetal hearts but are normally down-regulated as development progresses. In the hypertrophied heart, however, these channels are re-expressed and generate a hyperpolarization-activated, nonselective cation current (Ih), which evidence suggests may increase susceptibility to arrhythmia. To test this hypothesis, we generated and analyzed transgenic mice overexpressing HCN2 specifically in their hearts (HCN2-Tg). Under physiological conditions, HCN2-Tg mice exhibited no discernible abnormalities. After the application of isoproterenol (ISO), however, ECG recordings from HCN2-Tg mice showed intermittent atrioventricular dissociation followed by idioventricular rhythm. Consistent with this observation, 0.3 μmol/L ISO-induced spontaneous action potentials (SAPs) in 76% of HCN2-Tg ventricular myocytes. In the remaining 24%, ISO significantly depolarized the resting membrane potential (RMP), and the late repolarization phase of evoked action potentials (APs) was significantly longer than in WT myocytes. Analysis of membrane currents revealed that these differences are attributable to the Ih tail current. These findings suggest HCN2 channel activity reduces the repolarization reserve of the ventricular action potential and increases ectopic automaticity under pathological conditions such as excessive β-adrenergic stimulation. Copyright © 2015. Published by Elsevier Ltd.

  10. Cardiomyocyte-enriched protein CIP protects against pathophysiological stresses and regulates cardiac homeostasis.

    Science.gov (United States)

    Huang, Zhan-Peng; Kataoka, Masaharu; Chen, Jinghai; Wu, Gengze; Ding, Jian; Nie, Mao; Lin, Zhiqiang; Liu, Jianming; Hu, Xiaoyun; Ma, Lixin; Zhou, Bin; Wakimoto, Hiroko; Zeng, Chunyu; Kyselovic, Jan; Deng, Zhong-Liang; Seidman, Christine E; Seidman, J G; Pu, William T; Wang, Da-Zhi

    2015-11-02

    Cardiomyopathy is a common human disorder that is characterized by contractile dysfunction and cardiac remodeling. Genetic mutations and altered expression of genes encoding many signaling molecules and contractile proteins are associated with cardiomyopathy; however, how cardiomyocytes sense pathophysiological stresses in order to then modulate cardiac remodeling remains poorly understood. Here, we have described a regulator in the heart that harmonizes the progression of cardiac hypertrophy and dilation. We determined that expression of the myocyte-enriched protein cardiac ISL1-interacting protein (CIP, also known as MLIP) is reduced in patients with dilated cardiomyopathy. As CIP is highly conserved between human and mouse, we evaluated the effects of CIP deficiency on cardiac remodeling in mice. Deletion of the CIP-encoding gene accelerated progress from hypertrophy to heart failure in several cardiomyopathy models. Conversely, transgenic and AAV-mediated CIP overexpression prevented pathologic remodeling and preserved cardiac function. CIP deficiency combined with lamin A/C deletion resulted in severe dilated cardiomyopathy and cardiac dysfunction in the absence of stress. Transcriptome analyses of CIP-deficient hearts revealed that the p53- and FOXO1-mediated gene networks related to homeostasis are disturbed upon pressure overload stress. Moreover, FOXO1 overexpression suppressed stress-induced cardiomyocyte hypertrophy in CIP-deficient cardiomyocytes. Our studies identify CIP as a key regulator of cardiomyopathy that has potential as a therapeutic target to attenuate heart failure progression.

  11. Cardiac Niche Influences the Direct Reprogramming of Canine Fibroblasts into Cardiomyocyte-Like Cells

    Directory of Open Access Journals (Sweden)

    Giacomo Palazzolo

    2016-01-01

    Full Text Available The Duchenne and Becker muscular dystrophies are caused by mutation of dystrophin gene and primarily affect skeletal and cardiac muscles. Cardiac involvement in dystrophic GRMD dogs has been demonstrated by electrocardiographic studies with the onset of a progressive cardiomyopathy similar to the cardiac disease in DMD patients. In this respect, GRMD is a useful model to explore cardiac and skeletal muscle pathogenesis and for developing new therapeutic protocols. Here we describe a protocol to convert GRMD canine fibroblasts isolated from heart and skin into induced cardiac-like myocytes (ciCLMs. We used a mix of transcription factors (GATA4, HAND2, TBX5, and MEF2C, known to be able to differentiate mouse and human somatic cells into ciCLMs. Exogenous gene expression was obtained using four lentiviral vectors carrying transcription factor genes and different resistance genes. Our data demonstrate a direct switch from fibroblast into ciCLMs with no activation of early cardiac genes. ciCLMs were unable to contract spontaneously, suggesting, differently from mouse and human cells, an incomplete differentiation process. However, when transplanted in neonatal hearts of SCID/Beige mice, ciCLMs participate in cardiac myogenesis.

  12. Understanding cardiac extracellular matrix remodeling to develop biomarkers of myocardial infarction outcomes

    DEFF Research Database (Denmark)

    Nielsen, Signe Holm; Mouton, Alan J.; DeLeon-Pennell, Kristine Y.

    2017-01-01

    Cardiovascular Disease (CVD) is the most common cause of death in industrialized countries, and myocardial infarction (MI) is a major CVD with significant morbidity and mortality. Following MI, the left ventricle (LV) undergoes a wound healing response to ischemia that results in extracellular...... matrix (ECM) scar formation to replace necrotic myocytes. While ECM accumulation following MI is termed cardiac fibrosis, this is a generic term that does not differentiate between ECM accumulation that occurs in the infarct region to form a scar that is structurally necessary to preserve left ventricle...

  13. Contemporary Breast Radiotherapy and Cardiac Toxicity.

    Science.gov (United States)

    Yeboa, Debra Nana; Evans, Suzanne Buckley

    2016-01-01

    Long-term cardiac effects are an important component of survivorship after breast radiotherapy. The pathophysiology of cardiotoxicity, history of breast radiotherapy, current methods of cardiac avoidance, modern outcomes, context of historical outcomes, quantifying cardiac effects, and future directions are reviewed in this article. Radiation-induced oxidative stress induces proinflammatory cytokines and is a process that potentiates late effects of fibrosis and intimal proliferation in endothelial vasculature. Breast radiation therapy has changed substantially in recent decades. Several modern technologies exist to improve cardiac avoidance such as deep inspiration breath hold, gating, accelerated partial breast irradiation, and use of modern 3-dimensional planning. Modern outcomes may vary notably from historical long-term cardiac outcomes given the differences in cardiac dose with modern techniques. Methods of quantifying radiation-related cardiotoxicity that correlate with future cardiac risks are needed with current data exploring techniques such as measuring computed tomography coronary artery calcium score, single-photon emission computed tomography imaging, and biomarkers. Placing historical data, dosimetric correlations, and relative cardiac risk in context are key when weighing the benefits of radiotherapy in breast cancer control and survival. Estimating present day cardiac risk in the modern treatment era includes challenges in length of follow-up and the use of confounding cardiotoxic agents such as evolving systemic chemotherapy and targeted therapies. Future directions in both multidisciplinary management and advancing technology in radiation oncology may provide further improvements in patient risk reduction and breast cancer survivorship. Copyright © 2016 Elsevier Inc. All rights reserved.

  14. Cardiac dynamics: Alternans and arrhythmogenesis

    Directory of Open Access Journals (Sweden)

    Gary Tse, BA Hons MBBS MA PhD

    2016-10-01

    Full Text Available Pre-existing heterogeneities present in cardiac tissue are essential for maintaining the normal electrical and mechanical functions of the heart. Exacerbation of such heterogeneities or the emergence of dynamic factors can produce repolarization alternans, which are beat-to-beat alternations in the action potential time course. Traditionally, this was explained by restitution, but additional factors, such as cardiac memory, calcium handling dynamics, refractory period restitution, and mechano-electric feedback, are increasingly recognized as the underlying causes. The aim of this article is to review the mechanisms that generate cardiac repolarization alternans and convert spatially concordant alternans to the more arrhythmogenic spatially discordant alternans. This is followed by a discussion on how alternans generate arrhythmias in a number of clinical scenarios, and concluded by an outline of future therapeutic targets for anti-arrhythmic therapy.

  15. Overexpression myocardial inducible nitric oxide synthase exacerbates cardiac dysfunction and beta-adrenergic desensitization in experimental hypothyroidism.

    Science.gov (United States)

    Shao, Qun; Cheng, Heng-Jie; Callahan, Michael F; Kitzman, Dalane W; Li, Wei-Min; Cheng, Che Ping

    2016-02-01

    Altered nitric oxide synthase (NOS) has been implicated in the pathophysiology of heart failure (HF). Recent evidence links hypothyroidism to the pathology of HF. However, the precise mechanisms are incompletely understood. The alterations and functional effects of cardiac NOS in hypothyroidism are unknown. We tested the hypothesis that hypothyroidism increases cardiomyocyte inducible NOS (iNOS) expression, which plays an important role in hypothyroidism-induced depression of cardiomyocyte contractile properties, [Ca(2+)]i transient ([Ca(2+)]iT), and β-adrenergic hyporesponsiveness. We simultaneously evaluated LV functional performance and compared myocyte three NOS, β-adrenergic receptors (AR) and SERCA2a expressions and assessed cardiomyocyte contractile and [Ca(2+)]iT responses to β-AR stimulation with and without pretreatment of iNOS inhibitor (1400 W, 10(-5)mol/L) in 26 controls and 26 rats with hypothyroidism induced by methimazole (~30 mg/kg/day for 8 weeks in the drinking water). Compared with controls, in hypothyroidism, total serum T3 and T4 were significantly reduced followed by significantly decreased LV contractility (EES) with increased LV time constant of relaxation. These LV abnormalities were accompanied by concomitant significant decreases in myocyte contraction (dL/dtmax), relaxation (dR/dtmax), and [Ca(2+)]iT. In hypothyroidism, isoproterenol (10(-8)M) produced significantly smaller increases in dL/dtmax, dR/dtmax and [Ca(2+)]iT. These changes were associated with decreased β1-AR and SERCA2a, but significantly increased iNOS. Moreover, only in hypothyroidism, pretreatment with iNOS inhibitor significantly improved basal and isoproterenol-stimulated myocyte contraction, relaxation and [Ca(2+)]iT. Hypothyroidism produces intrinsic defects of LV myocyte force-generating capacity and relaxation with β-AR desensitization. Up-regulation of cardiomyocyte iNOS may promote progressive cardiac dysfunction in hypothyroidism. Copyright © 2015 Elsevier

  16. Overexpression Myocardial Inducible Nitric Oxide Synthase Exacerbates Cardiac Dysfunction and Beta-Adrenergic Desensitization in Experimental Hypothyroidism☆,☆☆

    Science.gov (United States)

    Shao, Qun; Cheng, Heng-Jie; Callahan, Michael F.; Kitzman, Dalane W; Li, Wei-Min; Cheng, Che Ping

    2015-01-01

    Background Altered nitric oxide synthase (NOS) has been implicated in the pathophysiology of heart failure (HF). Recent evidence links hypothyroidism to the pathology of HF. However, the precise mechanisms are incompletely understood. The alterations and functional effects of cardiac NOS in hypothyroidism are unknown. We tested the hypothesis that hypothyroidism increases cadiomyocyte inducible NOS (iNOS) expression, which plays an important role in hypothyroidism-induced depression of cardiomyocyte contractile properties, [Ca2+]i transient ([Ca2+]iT), and β-adrenergic hyporesponsiveness. Methods and Results We simultaneously evaluated LV functional performance and compared myocyte three NOS, β-adrenergic receptors (AR) and SERCA2a expressions and assessed cardiomyocyte contractile and [Ca2+]iT responses to β-AR stimulation with and without pretreatment of iNOS inhibitor (1400W, 10−5 mol/L) in 26 controls and 26 rats with hypothyroidism induced by methimazole (~30 mg/kg/day for 8 weeks in the drinking water). Compared with controls, in hypothyroidism, total serum T3 and T4 were significantly reduced followed by significantly decreased LV contractility (EES) with increased LV time constant of relaxation. These LV abnormalities were accompanied by concomitant significant decreases in myocyte contraction (dL/dtmax), relaxation (dR/dtmax), and [Ca2+]iT. In hypothyroidism, isoproterenol (10−8 M) produced significantly smaller increases in dL/dtmax, dR/dtmax and [Ca2+]iT. These changes were associated with decreased β1-AR and SERCA2a, but significantly increased iNOS. Moreover, only in hypothyroidism, pretreatment with iNOS inhibitor significantly improved basal and isoproterenol-stimulated myocyte contraction, relaxation and [Ca2+]iT. Conclusions Hypothyroidism produces intrinsic defects of LV myocyte force-generating capacity and relaxation with β-AR desensitization. Up-regulation of cadiomyocyte iNOS may promote progressive cardiac dysfunction in

  17. About Cardiac Arrest

    Science.gov (United States)

    ... Artery Disease Venous Thromboembolism Aortic Aneurysm More About Cardiac Arrest Updated:Mar 10,2017 What is cardiac arrest? ... and procedures related to heart disease and stroke. Cardiac Arrest • Home • About Cardiac Arrest • Understand Your Risk for ...

  18. Cardiac MRI in Athletes

    NARCIS (Netherlands)

    Luijkx, T.

    2012-01-01

    Cardiac magnetic resonance imaging (CMR) is often used in athletes to image cardiac anatomy and function and is increasingly requested in the context of screening for pathology that can cause sudden cardiac death (SCD). In this thesis, patterns of cardiac adaptation to sports are investigated with

  19. Animal models of cardiac cachexia.

    Science.gov (United States)

    Molinari, Francesca; Malara, Natalia; Mollace, Vincenzo; Rosano, Giuseppe; Ferraro, Elisabetta

    2016-09-15

    Cachexia is the loss of body weight associated with several chronic diseases including chronic heart failure (CHF). The cachectic condition is mainly due to loss of skeletal muscle mass and adipose tissue depletion. The majority of experimental in vivo studies on cachexia rely on animal models of cancer cachexia while a reliable and appropriate model for cardiac cachexia has not yet been established. A critical issue in generating a cardiac cachexia model is that genetic modifications or pharmacological treatments impairing the heart functionality and used to obtain the heart failure model might likely impair the skeletal muscle, this also being a striated muscle and sharing with the myocardium several molecular and physiological mechanisms. On the other hand, often, the induction of heart damage in the several existing models of heart failure does not necessarily lead to skeletal muscle loss and cachexia. Here we describe the main features of cardiac cachexia and illustrate some animal models proposed for cardiac cachexia studies; they include the genetic calsequestrin and Dahl salt-sensitive models, the monocrotaline model and the surgical models obtained by left anterior descending (LAD) ligation, transverse aortic constriction (TAC) and ascending aortic banding. The availability of a specific animal model for cardiac cachexia is a crucial issue since, besides the common aspects of cachexia in the different syndromes, each disease has some peculiarities in its etiology and pathophysiology leading to cachexia. Such peculiarities need to be unraveled in order to find new targets for effective therapies. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  20. Protection of myocytes against free radical-induced damage by accelerated turnover of the glutathione redox cycle

    NARCIS (Netherlands)

    Le, C. T.; Hollaar, L.; van der Valk, E. J.; Franken, N. A.; van Ravels, F. J.; Wondergem, J.; van der Laarse, A.

    1995-01-01

    The primary defence mechanism of myocytes against peroxides and peroxide-derived peroxyl and alkoxyl radicals is the glutathione redox cycle. The purpose of the present study was to increase the turnover rate of this cycle by stimulating the glutathione peroxidase catalysed reaction (2GSH-->GSSG),

  1. Calpain inhibition prevents pacing-induced cellular remodeling in a HL-1 myocyte model for atrial fibrillation

    NARCIS (Netherlands)

    Brundel, BJJM; Kampinga, HH; Henning, RH

    2004-01-01

    Objective: Atrial fibrillation (AF) is a progressive disease. Previously, clinical and animal experimental studies in AF revealed a variety of myocyte remodeling processes including L-type Ca(2+) channel reduction and structural changes, which finally result in electrical remodeling and contractile

  2. Targeted intracellular catalase delivery protects neonatal rat myocytes from hypoxia-reoxygenation and ischemia-reperfusion injury

    Science.gov (United States)

    Undyala, Vishnu; Terlecky, Stanley R.; Vander Heide, Richard S.

    2010-01-01

    Hypoxia followed by reoxygenation (HR) and ischemia-reperfusion (IR) cause cell death in neonatal rat ventricular myocytes (NRVM) primarily through the generation of oxidative stress. Extracellular catalase (CAT) has not been effective in reducing or eliminating IR or HR-induced cell death due both to extracellular degradation and poor cellular uptake. Aims 1) to determine if a cell penetrating catalase derivative with enhanced peroxisome targeting efficiency (catalase-SKL) increases intracellular levels of the antioxidant enzyme in NVRM; and 2) to determine if catalase-SKL protects against both HR and IR injury. Methods NRVM were subjected to 3 or 6 hr of HR or 1 hr of IR. CAT concentration, activity, and subcellular distribution were determined using standard techniques. Reactive oxygen species (ROS) and related oxidative stress were visualized using 2’,7’-dichlorofluorescin diacetate. Cell death was measured using trypan blue exclusion or lactate dehydrogenase (LDH) release assays. Results CAT activity was higher in (catalase-SKL) transduced myocytes, was concentrated in a membranous cellular fraction, and potently inhibited oxidative stress. In contrast to non-transducible (unmodified) CAT, catalase-SKL-treated myocytes were protected against both HR and IR. Conclusions 1) catalase-SKL increased myocyte CAT content and activity and dramatically increased resistance to hydrogen peroxide-induced oxidation; 2) catalase-SKL protects against both HR and IR; 3) catalase-SKL may represent a new therapeutic approach to protect hearts against myocardial HR or IR. PMID:20708413

  3. Free fatty acids act as endogenous ionophores, resulting in Na+ and Ca2+ influx and myocyte apoptosis.

    Science.gov (United States)

    Fang, Kwang-Ming; Lee, An-Sheng; Su, Ming-Jai; Lin, Chien-Liang; Chien, Chung-Liang; Wu, Mei-Lin

    2008-06-01

    Disturbances in lipid metabolism have been suggested to play an important role in myocardial damage. Marked accumulation of free fatty acids (FFAs), including arachidonic acid (AA), palmitic acid, oleic acid, and linoleic acid, occurs during post-ischaemia and reperfusion (post-I/R). Possible cellular mechanisms of AA/FFAs-induced myocyte apoptosis were investigated. In neonatal rat ventricular myocytes, AA/FFAs activate a novel non-selective cation conductance (NSCC), resulting in both intracellular Ca(2+) and Na(+) overload. AA caused sustained cytosolic [Na(+)](cyt) and [Ca(2+)](cyt) overload, resulting in mitochondrial [Na(+)](m) and [Ca(2+)](m) overload, which induced caspase-3-mediated apoptosis. Similar apoptotic effects were seen using Na(+) ionophore cocktail/Ca(2+)-free medium, which induced [Na(+)](cyt) and [Na(+)](m), but not [Ca(2+)](cyt) and [Ca(2+)](m) overload. Electron microscopy showed that inhibition of [Na(+)](m) overload prevented disruption of the mitochondrial membrane, showing that [Na(+)](m) overload is an important upstream signal in AA- and FFA-induced myocyte apoptosis. AA and FFAs, which accumulate in the myocardium during post-I/R, may therefore act as naturally occurring endogenous ionophores and contribute to the myocyte death seen during post-I/R.

  4. Transcription factor-induced activation of cardiac gene expression in human c-kit+ cardiac progenitor cells.

    Directory of Open Access Journals (Sweden)

    Tareq Al-Maqtari

    Full Text Available Although transplantation of c-kit+ cardiac progenitor cells (CPCs significantly alleviates post-myocardial infarction left ventricular dysfunction, generation of cardiomyocytes by exogenous CPCs in the recipient heart has often been limited. Inducing robust differentiation would be necessary for improving the efficacy of the regenerative cardiac cell therapy. We assessed the hypothesis that differentiation of human c-kit+ CPCs can be enhanced by priming them with cardiac transcription factors (TFs. We introduced five different TFs (Gata4, MEF2C, NKX2.5, TBX5, and BAF60C into CPCs, either alone or in combination, and then examined the expression of marker genes associated with the major cardiac cell types using quantitative RT-PCR. When introduced individually, Gata4 and TBX5 induced a subset of myocyte markers. Moreover, Gata4 alone significantly induced smooth muscle cell and fibroblast markers. Interestingly, these gene expression changes brought by Gata4 were also accompanied by morphological changes. In contrast, MEF2C and NKX2.5 were largely ineffective in initiating cardiac gene expression in CPCs. Surprisingly, introduction of multiple TFs in different combinations mostly failed to act synergistically. Likewise, addition of BAF60C to Gata4 and/or TBX5 did not further potentiate their effects on cardiac gene expression. Based on our results, it appears that GATA4 is able to potentiate gene expression programs associated with multiple cardiovascular lineages in CPCs, suggesting that GATA4 may be effective in priming CPCs for enhanced differentiation in the setting of stem cell therapy.

  5. Evaluation of ischemic heart disease and viability by cardiac MRI

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    Mona Bhatia

    2014-01-01

    Full Text Available In ischemic heart disease, cardiac MRI, besides being the gold standard for evaluation of quantitative ventricular function, enables evaluation of myocardial wall thickness, T2-weighted imaging for myocardial edema and infarct quantification and transmurality. Delayed hyperenhancement sequences are highly predictive of scar formation, being associated with myocyte necrosis. The extent and transmurality of delayed hyperenhancement has prognostic implications and is inversely proportional to the degree of functional recovery after acute myocardial infarction. A greater transmural extent of infarction (eg, hyperenhancement involving >50% of the wall thickness can predict regions that are less likely to improve in function after therapy. The ultimate focus of MRI in ischemic heart disease is in diagnosis, quantification of myocardium at risk, salvageable myocardium, perfusion defects and differentiation of viable myocardium from non viable myocardium to enable prognostication.

  6. Taxifolin protects against cardiac hypertrophy and fibrosis during biomechanical stress of pressure overload

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    Guo, Haipeng; Zhang, Xin [Department of Critical Care Medicine, Qilu Hospital of Shandong University, Jinan (China); Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Health, Qilu Hospital of Shandong University, Jinan (China); Cui, Yuqian [Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Health, Qilu Hospital of Shandong University, Jinan (China); Zhou, Heng [Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan (China); Xu, Dachun [Department of Cardiology, Shanghai Tenth People' s Hospital of Tongji University, Shanghai (China); Shan, Tichao; Zhang, Fan [Department of Critical Care Medicine, Qilu Hospital of Shandong University, Jinan (China); Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Health, Qilu Hospital of Shandong University, Jinan (China); Guo, Yuan [Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Health, Qilu Hospital of Shandong University, Jinan (China); Chen, Yuguo, E-mail: chen919085@163.com [Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Health, Qilu Hospital of Shandong University, Jinan (China); Department of Emergency, Qilu Hospital of Shandong University, Jinan (China); Wu, Dawei, E-mail: wdwu55@163.com [Department of Critical Care Medicine, Qilu Hospital of Shandong University, Jinan (China); Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Health, Qilu Hospital of Shandong University, Jinan (China)

    2015-09-01

    Cardiac hypertrophy is a key pathophysiological component to biomechanical stress, which has been considered to be an independent and predictive risk factor for adverse cardiovascular events. Taxifolin (TAX) is a typical plant flavonoid, which has long been used clinically for treatment of cardiovascular and cerebrovascular diseases. However, very little is known about whether TAX can influence the development of cardiac hypertrophy. In vitro studies, we found that TAX concentration-dependently inhibited angiotensin II (Ang II) induced hypertrophy and protein synthesis in cardiac myocytes. Then we established a mouse model by transverse aortic constriction (TAC) to further confirm our findings. It was demonstrated that TAX prevented pressure overload induced cardiac hypertrophy in mice, as assessed by ventricular mass/body weight, echocardiographic parameters, myocyte cross-sectional area, and the expression of ANP, BNP and β-MHC. The excess production of reactive oxygen species (ROS) played critical role in the development of cardiac hypertrophy. TAX arrested oxidative stress and decreased the expression of 4-HNE induced by pressure overload. Moreover, TAX negatively modulated TAC-induced phosphorylation of ERK1/2 and JNK1/2. Further studies showed that TAX significantly attenuated left ventricular fibrosis and collagen synthesis through abrogating the phosphorylation of Smad2 and Smad2/3 nuclear translocation. These results demonstrated that TAX could inhibit cardiac hypertrophy and attenuate ventricular fibrosis after pressure overload. These beneficial effects were at least through the inhibition of the excess production of ROS, ERK1/2, JNK1/2 and Smad signaling pathways. Therefore, TAX might be a potential candidate for the treatment of cardiac hypertrophy and fibrosis. - Highlights: • We focus on the protective effect of taxifolin on cardiac remodeling. • Taxifolin inhibited cardiac hypertrophy and attenuated ventricular fibrosis. • Taxifolin

  7. Loss of T-tubules and other changes to surface topography in ventricular myocytes from failing human and rat heart.

    Science.gov (United States)

    Lyon, Alexander R; MacLeod, Ken T; Zhang, Yanjun; Garcia, Edwin; Kanda, Gaelle Kikonda; Lab, Max J; Korchev, Yuri E; Harding, Sian E; Gorelik, Julia

    2009-04-21

    T-tubular invaginations of the sarcolemma of ventricular cardiomyocytes contain junctional structures functionally coupling L-type calcium channels to the sarcoplasmic reticulum calcium-release channels (the ryanodine receptors), and therefore their configuration controls the gain of calcium-induced calcium release (CICR). Studies primarily in rodent myocardium have shown the importance of T-tubular structures for calcium transient kinetics and have linked T-tubule disruption to delayed CICR. However, there is disagreement as to the nature of T-tubule changes in human heart failure. We studied isolated ventricular myocytes from patients with ischemic heart disease, idiopathic dilated cardiomyopathy, and hypertrophic obstructive cardiomyopathy and determined T-tubule structure with either the fluorescent membrane dye di-8-ANNEPs or the scanning ion conductance microscope (SICM). The SICM uses a scanning pipette to produce a topographic representation of the surface of the live cell by a non-optical method. We have also compared ventricular myocytes from a rat model of chronic heart failure after myocardial infarction. T-tubule loss, shown by both ANNEPs staining and SICM imaging, was pronounced in human myocytes from all etiologies of disease. SICM imaging showed additional changes in surface structure, with flattening and loss of Z-groove definition common to all etiologies. Rat myocytes from the chronic heart failure model also showed both T-tubule and Z-groove loss, as well as increased spark frequency and greater spark amplitude. This study confirms the loss of T-tubules as part of the phenotypic change in the failing human myocyte, but it also shows that this is part of a wider spectrum of alterations in surface morphology.

  8. Angiotensin II Facilitates Matrix Metalloproteinase-9-Mediated Myosin Light Chain Kinase Degradation in Pressure Overload-Induced Cardiac Hypertrophy

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    Shun Wang

    2017-12-01

    Full Text Available Background/Aims: Angiotensin II (Ang II has been shown to promote cardiac remodeling during the process of hypertrophy. Myosin light chain kinase (MLCK, a specific kinase for the phosphorylation of myosin light chain 2 (MLC2, plays an important role in regulating cardiac muscle contraction and hypertrophy. However, whether Ang II could facilitate cardiac hypertrophy by altering the expression of MLCK remains unclear. This study aimed to investigate this effect and the underlying mechanisms. Methods: Cardiac hypertrophy was induced via pressure overload in rats, which were then evaluated via histological and biochemical measurements and echocardiography. Angiotensin-converting enzyme inhibitor (ACEI was used to inhibit Ang II. Neonatal rat cardiomyocytes were stimulated with Ang II to induce hypertrophy and were treated with a matrix metalloproteinase 9 (MMP9 inhibitor. Myocyte hypertrophy was evaluated using immunofluorescence and qRT-PCR. Degradation of recombinant human MLCK by recombinant human MMP9 was tested using a cleavage assay. The expression levels of MLCK, MLC2, phospho-myosin light chain 2 (p-MLC2, myosin phosphatase 2 (MYPT2, and calmodulin (CaM were measured using western blotting. Results: ACEI improved cardiac function and remodeling and increased the levels of MLCK and p-MLC2 as well as reduced the expression of MMP9 in pressure overload-induced cardiac hypertrophy. Moreover, the MMP9 inhibitor alleviated myocyte hypertrophy and upregulated the levels of MLCK and p-MLC2 in Ang II-induced cardiomyocyte hypertrophy. Recombinant human MLCK was concentration- and time-dependently degraded by recombinant human MMP9 in vitro, and this process was prevented by the MMP9 inhibitor. Conclusion: Our results suggest that Ang II is involved in the degradation of MLCK in pressure overload-induced cardiac hypertrophy and that this process was mediated by MMP9.

  9. Exercise training prior to myocardial infarction attenuates cardiac deterioration and cardiomyocyte dysfunction in rats

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    Luiz Henrique Marchesi Bozi

    2013-04-01

    Full Text Available OBJECTIVES: The present study was performed to investigate 1 whether aerobic exercise training prior to myocardial infarction would prevent cardiac dysfunction and structural deterioration and 2 whether the potential cardiac benefits of aerobic exercise training would be associated with preserved morphological and contractile properties of cardiomyocytes in post-infarct remodeled myocardium. METHODS: Male Wistar rats underwent an aerobic exercise training protocol for eight weeks. The rats were then assigned to sham surgery (SHAM, sedentary lifestyle and myocardial infarction or exercise training and myocardial infarction groups and were evaluated 15 days after the surgery. Left ventricular tissue was analyzed histologically, and the contractile function of isolated myocytes was measured. Student's t-test was used to analyze infarct size and ventricular wall thickness, and the other parameters were analyzed by the Kruskal-Wallis test followed by Dunn's test or a one-way analysis of variance followed by Tukey's test (p<0.05. RESULTS: Myocardial infarctions in exercise-trained animals resulted in a smaller myocardial infarction extension, a thicker infarcted wall and less collagen accumulation as compared to myocardial infarctions in sedentary animals. Myocardial infarction-induced left ventricular dilation and cardiac dysfunction, as evaluated by +dP/dt and -dP/dt, were both prevented by previous aerobic exercise training. Moreover, aerobic exercise training preserved cardiac myocyte shortening, improved the maximum shortening and relengthening velocities in infarcted hearts and enhanced responsiveness to calcium. CONCLUSION: Previous aerobic exercise training attenuated the cardiac dysfunction and structural deterioration promoted by myocardial infarction, and such benefits were associated with preserved cardiomyocyte morphological and contractile properties.

  10. Enhanced basal late sodium current appears to underlie the age-related prolongation of action potential duration in guinea pig ventricular myocytes.

    Science.gov (United States)

    Song, Yejia; Belardinelli, Luiz

    2017-12-14

    Aging hearts have prolonged QT interval and are vulnerable to oxidative stress. Because the QT interval indirectly reflects the action potential duration (APD), we examined the hypotheses that 1) the APD of ventricular myocytes increases with age; 2) the age-related prolongation of APD is due to an enhancement of basal late Na + current (I NaL ); 3) inhibition of I NaL may protect aging hearts from arrhythmogenic effects of hydrogen peroxide (H 2 O 2 ). Experiments were performed on ventricular myocytes isolated from one-month (young) and one-year (old) guinea pigs (GPs). The APD of myocytes from old GPs was significantly longer than that from young GPs and was shortened by the I NaL inhibitors GS967 and tetrodotoxin. The magnitude of I NaL was significantly larger in myocytes from old than from young GPs. The CaMKII inhibitors KN-93 and AIP and the Na V 1.5-channel blocker MTSEA blocked the I NaL . There were no significant differences between myocytes from young and old GPs in L-type Ca 2+ current and the rapidly- and slowly-activating delayed rectifier K + currents, although the inward rectifier K + current was slightly decreased in myocytes from old GPs. H 2 O 2 induced more early afterdepolarizations in myocytes from old than from young GPs. The effect of H 2 O 2 was attenuated by GS967. The results suggest that 1) the APD of myocytes from old GPs is prolonged, 2) a CaMKII-mediated increase in Na V 1.5-channel I NaL is responsible for the prolongation of APD, and 3) Inhibition of I NaL may be beneficial for maintaining electrical stability under oxidative stress in myocytes of old GPs.

  11. Myocyte necrosis underlies progressive myocardial dystrophy in mouse dsg2-related arrhythmogenic right ventricular cardiomyopathy

    NARCIS (Netherlands)

    Pilichou, K.; Remme, C.A.; Basso, C.; Campian, M.E.; Rizzo, S.; Barnett, P.; Scicluna, B.P.; Bauce, B.; van den Hoff, M.J.B.; de Bakker, J.M.T.; Tan, H.L.; Valente, M.; Nava, A.; Wilde, A.A.M.; Moorman, A.F.M.; Thiene, G.; Bezzina, C.R.

    2009-01-01

    Mutations in the cardiac desmosomal protein desmoglein-2 (DSG2) are associated with arrhythmogenic right ventricular cardiomyopathy (ARVC). We studied the explanted heart of a proband carrying the DSG2-N266S mutation as well as transgenic mice (Tg-NS) with cardiac overexpression of the mouse

  12. Local stimulation of cultured myocyte cells by femtosecond laser-induced stress wave

    Science.gov (United States)

    Kuo, Yung-En; Wu, Cheng-Chi; Hosokawa, Yoichiroh; Maezawa, Yasuyo; Okano, Kazunori; Masuhara, Hiroshi; Kao, Fu-Jen

    2010-12-01

    When an 800 nm femtosecond laser is tightly focused into cell culture medium a stress wave is generated at the laser focal point. Since the stress wave localizes in a few tens of μm, it is possible to locally stimulate single cells in vitro. In this work, several kinds of cultured mammalian cells, HeLa, PC12, P19CL6, and C2C12, were stimulated by the stress wave and the cell growth after the stress loading with the laser irradiation was investigated. In comparison with the control conditions, cell growth after the laser irradiation was enhanced for the cells of C2C12 and P19CL6, which can differentiate into myocytes, and suppressed for PC12 and HeLa cell lines. These results suggest a possibility of cell growth enhancement due to myogenic cells response to the femtosecond laser-induced stress.

  13. Inducible and Deterministic Forward Programming of Human Pluripotent Stem Cells into Neurons, Skeletal Myocytes, and Oligodendrocytes

    Directory of Open Access Journals (Sweden)

    Matthias Pawlowski

    2017-04-01

    Full Text Available The isolation or in vitro derivation of many human cell types remains challenging and inefficient. Direct conversion of human pluripotent stem cells (hPSCs by forced expression of transcription factors provides a potential alternative. However, deficient inducible gene expression in hPSCs has compromised efficiencies of forward programming approaches. We have systematically optimized inducible gene expression in hPSCs using a dual genomic safe harbor gene-targeting strategy. This approach provides a powerful platform for the generation of human cell types by forward programming. We report robust and deterministic reprogramming of hPSCs into neurons and functional skeletal myocytes. Finally, we present a forward programming strategy for rapid and highly efficient generation of human oligodendrocytes.

  14. Inducible and Deterministic Forward Programming of Human Pluripotent Stem Cells into Neurons, Skeletal Myocytes, and Oligodendrocytes.

    Science.gov (United States)

    Pawlowski, Matthias; Ortmann, Daniel; Bertero, Alessandro; Tavares, Joana M; Pedersen, Roger A; Vallier, Ludovic; Kotter, Mark R N

    2017-04-11

    The isolation or in vitro derivation of many human cell types remains challenging and inefficient. Direct conversion of human pluripotent stem cells (hPSCs) by forced expression of transcription factors provides a potential alternative. However, deficient inducible gene expression in hPSCs has compromised efficiencies of forward programming approaches. We have systematically optimized inducible gene expression in hPSCs using a dual genomic safe harbor gene-targeting strategy. This approach provides a powerful platform for the generation of human cell types by forward programming. We report robust and deterministic reprogramming of hPSCs into neurons and functional skeletal myocytes. Finally, we present a forward programming strategy for rapid and highly efficient generation of human oligodendrocytes. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  15. Modeling the cardiac surgery workforce in Canada.

    Science.gov (United States)

    Vanderby, Sonia A; Carter, Michael W; Latham, Timothy; Ouzounian, Maral; Hassan, Ansar; Tang, Gilbert H; Teng, Carolyn J; Kingsbury, Kori; Feindel, Christopher M

    2010-08-01

    Limited employment opportunities for recently trained cardiac surgeons are deterring medical students from entering cardiac surgery residency programs. Given the lengthy training period and the aging of both the general population and currently practicing cardiac surgeons, this reduced enrollment raises concerns about the adequacy of the future cardiac surgery workforce. A workforce model was developed to explore the future need for cardiac surgeons in Canada. A novel system dynamics model was developed to simulate the supply and demand for cardiac surgery in Canada between 2008 and 2030 to identify whether an excess or shortage of surgeons would exist. Several different scenarios were examined, including varying surgeon productivity, revascularization rates, and residency enrollment rates. The simulation results of various scenarios are presented. In the base case, a surgeon shortage is expected to develop by 2025, although this depends on surgeons' response to demand-supply gap changes. An alternative scenario in which residency enrollment directly relates to the presence of unemployed surgeons also projects substantial shortages after 2021. The model results indicate that if residency enrollment rates remain at the 2009 level an alarming shortage may develop soon, possibly reaching almost 50% of the Canadian cardiac surgical workforce. These workforce model results project an eventual cardiac surgeon shortage in Canada. This study highlights the possibility of a crisis in cardiac surgery and emphasizes the urgency with which enrollment into cardiac surgery training programs and the employability of recently trained cardiac surgery graduates need to be addressed. Copyright 2010 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

  16. Cellular Trafficking of Phospholamban and Formation of Functional Sarcoplasmic Reticulum During Myocyte DIfferentiation

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    Stenoien, David L.; Knyushko, Tatyana V.; Londono, Monica P.; Opresko, Lee; Mayer, M. Uljana; Brady, Scott T.; Squier, Thomas C.; Bigelow, Diana J.

    2007-06-01

    The sarco/endoplasmic reticulum Ca-ATPase (SERCA) family members are transmembrane proteins that play an essential role in regulating intracellular calcium levels. Phospholamban (PLB), a 52 amino acid phosphoprotein, regulates SERCA activity in adult heart and skeletal muscle. Using the C2C12 myocyte cell line, we find endogenous PLB constitutively expressed in both myoblasts and myotubes, whereas SERCA expression coincides with activation of the differentiation program. PLB has a punctuate distribution in myoblasts changing to a reticular distribution in myotubes where it colocalizes with SERCAs. To examine the distribution and dynamics of PLB and SERCA, we expressed fluorescent fusion proteins (GFP, CFP, and YFP) of PLB and SERCA in myoblasts. Coexpressed PLB and SERCA localize to distinct cellular compartments in myoblasts but begin to colocalize as cells differentiate. Fluorescence Recovery After Photobleaching (FRAP) studies show different recovery patterns for each protein in myoblasts confirming their localization to distinct compartments. To extend these studies, we created stable cell lines expressing O6-alkylguanine-DNA alkyltransferase (AGT) fusions with PLB or SERCA to track their localization as myocytes differentiate. These experiments demonstrate that PLB localizes to punctate vesicles in myoblasts and adopts a reticular distribution that coincides with SERCA distribution after differentiation. Colocalization experiments indicate that a subset of PLB in myoblasts colocalizes with endosomes, Golgi, and the plasma membrane however PLB also localizes to other, as yet unidentified vesicles. Our results indicate that differentiation plays a critical role in regulating PLB distribution to ensure its colocalization within the same cellular compartment as SERCA in differentiated cells. The presence and altered distribution of PLB in undifferentiated myoblasts raises the possibility that this protein has additional functions distinct from SERCA regulation.

  17. Phosphorylation of the ryanodine receptor mediates the cardiac fight or flight response in mice.

    Science.gov (United States)

    Shan, Jian; Kushnir, Alexander; Betzenhauser, Matthew J; Reiken, Steven; Li, Jingdong; Lehnart, Stephan E; Lindegger, Nicolas; Mongillo, Marco; Mohler, Peter J; Marks, Andrew R

    2010-12-01

    During the classic "fight-or-flight" stress response, sympathetic nervous system activation leads to catecholamine release, which increases heart rate and contractility, resulting in enhanced cardiac output. Catecholamines bind to β-adrenergic receptors, causing cAMP generation and activation of PKA, which phosphorylates multiple targets in cardiac muscle, including the cardiac ryanodine receptor/calcium release channel (RyR2) required for muscle contraction. PKA phosphorylation of RyR2 enhances channel activity by sensitizing the channel to cytosolic calcium (Ca²+). Here, we found that mice harboring RyR2 channels that cannot be PKA phosphorylated (referred to herein as RyR2-S2808A+/+ mice) exhibited blunted heart rate and cardiac contractile responses to catecholamines (isoproterenol). The isoproterenol-induced enhancement of ventricular myocyte Ca²+ transients and fractional shortening (contraction) and the spontaneous beating rate of sinoatrial nodal cells were all blunted in RyR2-S2808A+/+ mice. The blunted cardiac response to catecholamines in RyR2-S2808A+/+ mice resulted in impaired exercise capacity. RyR2-S2808A+/+ mice were protected against chronic catecholaminergic-induced cardiac dysfunction. These studies identify what we believe to be new roles for PKA phosphorylation of RyR2 in both the heart rate and contractile responses to acute catecholaminergic stimulation.

  18. Cardiac ATP-sensitive K+ channel associates with the glycolytic enzyme complex

    Science.gov (United States)

    Hong, Miyoun; Kefaloyianni, Eirini; Bao, Li; Malester, Brian; Delaroche, Diane; Neubert, Thomas A.; Coetzee, William A.

    2011-01-01

    Being gated by high-energy nucleotides, cardiac ATP-sensitive potassium (KATP) channels are exquisitely sensitive to changes in cellular energy metabolism. An emerging view is that proteins associated with the KATP channel provide an additional layer of regulation. Using putative sulfonylurea receptor (SUR) coiled-coil domains as baits in a 2-hybrid screen against a rat cardiac cDNA library, we identified glycolytic enzymes (GAPDH and aldolase A) as putative interacting proteins. Interaction between aldolase and SUR was confirmed using GST pulldown assays and coimmunoprecipitation assays. Mass spectrometry of proteins from KATP channel immunoprecipitates of rat cardiac membranes identified glycolysis as the most enriched biological process. Coimmunoprecipitation assays confirmed interaction for several glycolytic enzymes throughout the glycolytic pathway. Immunocytochemistry colocalized many of these enzymes with KATP channel subunits in rat cardiac myocytes. The catalytic activities of aldolase and pyruvate kinase functionally modulate KATP channels in patch-clamp experiments, whereas d-glucose was without effect. Overall, our data demonstrate close physical association and functional interaction of the glycolytic process (particularly the distal ATP-generating steps) with cardiac KATP channels.—Hong, M., Kefaloyianni, E., Bao, L., Malester, B., Delaroche, D., Neubert, T. A., Coetzee, W. A. Cardiac ATP-sensitive K+ channel associates with the glycolytic enzyme complex. PMID:21482559

  19. Erythropoietin protects myocardin-expressing cardiac stem cells against cytotoxicity of tumor necrosis factor-{alpha}

    Energy Technology Data Exchange (ETDEWEB)

    Madonna, Rosalinda [The Center for Cardiovascular Biology and Atherosclerosis Research, The University of Texas Health Science Center at Houston, Texas (United States); Institute of Cardiology, and Center of Excellence on Aging, ' G. d' Annunzio' University, Chieti (Italy); Shelat, Harnath; Xue, Qun; Willerson, James T. [The Center for Cardiovascular Biology and Atherosclerosis Research, The University of Texas Health Science Center at Houston, Texas (United States); The Texas Heart Institute at St. Luke' s Episcopal Hospital, Houston, Texas (United States); De Caterina, Raffaele [Institute of Cardiology, and Center of Excellence on Aging, ' G. d' Annunzio' University, Chieti (Italy); Geng, Yong-Jian, E-mail: yong-jian.geng@uth.tmc.edu [The Center for Cardiovascular Biology and Atherosclerosis Research, The University of Texas Health Science Center at Houston, Texas (United States); The Texas Heart Institute at St. Luke' s Episcopal Hospital, Houston, Texas (United States)

    2009-10-15

    Cardiac stem cells are vulnerable to inflammation caused by infarction or ischemic injury. The growth factor, erythropoietin (Epo), ameliorates the inflammatory response of the myocardium to ischemic injury. This study was designed to assess the role of Epo in regulation of expression and activation of the cell death-associated intracellular signaling components in cardiac myoblasts stimulated with the proinflammatory cytokine tumor necrosis factor (TNF)-{alpha}. Cardiac myoblasts isolated from canine embryonic hearts characterized by expression of myocardin A, a promyogenic transcription factor for cardiovascular muscle development were pretreated with Epo and then exposed to TNF-{alpha}. Compared to untreated cells, the Epo-treated cardiac myoblasts exhibited better morphology and viability. Immunoblotting revealed lower levels of active caspase-3 and reductions in iNOS expression and NO production in Epo-treated cells. Furthermore, Epo pretreatment reduced nuclear translocation of NF-{kappa}B and inhibited phosphorylation of inhibitor of kappa B (I{kappa}B) in TNF-{alpha}-stimulated cardiac myoblasts. Thus, Epo protects cardiac myocyte progenitors or myoblasts against the cytotoxic effects of TNF-{alpha} by inhibiting NF-{kappa}B-mediated iNOS expression and NO production and by preventing caspase-3 activation.

  20. COMPARISON OF CARDIAC BIOMARKERS AND ECHOCARDIOGRAPHY IN DIAGNOSING MYOCARDITIS

    Directory of Open Access Journals (Sweden)

    Nimi Bharathan

    2017-03-01

    Full Text Available BACKGROUND Conventional methods used to diagnose or rule out myocarditis is not useful in detecting cardiac myocyte injury in clinically suspected cases. Endomyocardial biopsy and histopathological examination is not feasible in most government hospitals in India. Sensitive parameters have yet to be found out. The study was conducted to find out whether diagnosis of myocarditis in clinically suspected cases can be done by measurement of serum levels of cardiac troponinI (cTnI and MB isoform of creatine kinase (CK-MB. MATERIALS AND METHODS 19 patients with clinically suspected myocarditis were screened for CK-MB activity and cTnI. Echocardiography, ECG and IgM for leptospirosis were also checked in these patients. RESULTS cTnI was elevated in 10 out of 19 patients with clinically suspected myocarditis. CK-MB was elevated in 7 patients. CONCLUSION Elevation of cTnI level in blood can be taken as an indicator of cardiac muscle cell injury in suspected cases of myocarditis.

  1. Cardiac involvement in Wegener granulomatosis diagnosed at autopsy.

    Science.gov (United States)

    Mukhopadhyay, Sanjay; Hensley, Richard G; Tazelaar, Henry D

    2010-01-01

    Wegener granulomatosis (WG) is a systemic vasculitis classically involving the lungs, kidneys, and upper respiratory tract. Involvement of other sites does occur but is less frequent. Clinically evident cardiac involvement is uncommon. There are only a few cases in the literature with documentation of the histologic appearance of cardiac involvement in WG. We report a case of a previously healthy 37-year-old man who presented with a one-week history of cough and weakness and a one-day history of shortness of breath. At presentation, he was hypoxic and required intubation. Upon hospitalization, he deteriorated rapidly, became bradycardic and expired the same night. Infection was suspected clinically as the cause of illness and death. At autopsy, the lungs showed diffuse alveolar hemorrhage with capillaritis, diffuse alveolar damage, and parenchymal necrosis with necrotizing granulomas. The heart was enlarged and showed a mixed inflammatory infiltrate composed of neutrophils, eosinophils, and histiocytes, with focal myocyte necrosis. Granulomas, giant cells, and vasculitis were absent. The esophagus showed submucosal vasculitis. A diagnosis of WG was made. Postmortem serology for c-ANCA was positive, and all cultures were negative, confirming the diagnosis. Cardiac involvement is an underrecognized and potentially fatal complication of WG. The histologic findings in the heart may consist of a non-specific inflammatory infiltrate without granulomas or vasculitis, raising a wide differential diagnosis. Copyright 2010 Elsevier Inc. All rights reserved.

  2. The EXIST OIRT

    Science.gov (United States)

    Allen, Branden; Golisano, C.; Kutyrev, A.; Moseley, H.; Grindlay, J.; Hong, J.; EXIST Team

    2009-01-01

    The EXIST Optical / Infrared Telescope (OIRT) has been integrated into the EXIST concept design for the determination GRB redshifts on orbit and to preform follow up source identification and studies following the generation of a trigger from the EXIST high energy telescope (HET). The base OIRT main design has been inherited from the NextView OIRT has been operating in low earth orbit since September of 2007 and is currently being used for the acquisition of geospatial data. After reconfiguration of the instrumentation for astrophysical observations the OIRT will have an angular resolution of 0.15" and a 5'×5' field of view and be sensitive to emission in the range of 0.4 $\\mu$m - 2.2 $\\mu$m. Passive cooling of the tertiary, secondary, and primary mirrors will enable observation into the Ks$ band.

  3. Angiotensin II reduces the surface abundance of KV 1.5 channels in arterial myocytes to stimulate vasoconstriction.

    Science.gov (United States)

    Kidd, Michael W; Bulley, Simon; Jaggar, Jonathan H

    2017-03-01

    Several different voltage-dependent K+ (KV ) channel isoforms are expressed in arterial smooth muscle cells (myocytes). Vasoconstrictors inhibit KV currents, but the isoform selectivity and mechanisms involved are unclear. We show that angiotensin II (Ang II), a vasoconstrictor, stimulates degradation of KV 1.5, but not KV 2.1, channels through a protein kinase C- and lysosome-dependent mechanism, reducing abundance at the surface of mesenteric artery myocytes. The Ang II-induced decrease in cell surface KV 1.5 channels reduces whole-cell KV 1.5 currents and attenuates KV 1.5 function in pressurized arteries. We describe a mechanism by which Ang II stimulates protein kinase C-dependent KV 1.5 channel degradation, reducing the abundance of functional channels at the myocyte surface. Smooth muscle cells (myocytes) of resistance-size arteries express several different voltage-dependent K+ (KV ) channels, including KV 1.5 and KV 2.1, which regulate contractility. Myocyte KV currents are inhibited by vasoconstrictors, including angiotensin II (Ang II), but the mechanisms involved are unclear. Here, we tested the hypothesis that Ang II inhibits KV currents by reducing the plasma membrane abundance of KV channels in myocytes. Angiotensin II (applied for 2 h) reduced surface and total KV 1.5 protein in rat mesenteric arteries. In contrast, Ang II did not alter total or surface KV 2.1, or KV 1.5 or KV 2.1 cellular distribution, measured as the percentage of total protein at the surface. Bisindolylmaleimide (BIM; a protein kinase C blocker), a protein kinase C inhibitory peptide or bafilomycin A (a lysosomal degradation inhibitor) each blocked the Ang II-induced decrease in total and surface KV 1.5. Immunofluorescence also suggested that Ang II reduced surface KV 1.5 protein in isolated myocytes; an effect inhibited by BIM. Arteries were exposed to Ang II or Ang II plus BIM (for 2 h), after which these agents were removed and contractility measurements

  4. Does Unconscious Racism Exist?

    Science.gov (United States)

    Quillian, Lincoln

    2008-01-01

    This essay argues for the existence of a form of unconscious racism. Research on implicit prejudice provides good evidence that most persons have deeply held negative associations with minority groups that can lead to subtle discrimination without conscious awareness. The evidence for implicit attitudes is briefly reviewed. Criticisms of the…

  5. Long Term Ablation of Protein Kinase A (PKA)-mediated Cardiac Troponin I Phosphorylation Leads to Excitation-Contraction Uncoupling and Diastolic Dysfunction in a Knock-in Mouse Model of Hypertrophic Cardiomyopathy*

    Science.gov (United States)

    Dweck, David; Sanchez-Gonzalez, Marcos A.; Chang, Audrey N.; Dulce, Raul A.; Badger, Crystal-Dawn; Koutnik, Andrew P.; Ruiz, Edda L.; Griffin, Brittany; Liang, Jingsheng; Kabbaj, Mohamed; Fincham, Frank D.; Hare, Joshua M.; Overton, J. Michael; Pinto, Jose R.

    2014-01-01

    The cardiac troponin I (cTnI) R21C (cTnI-R21C) mutation has been linked to hypertrophic cardiomyopathy and renders cTnI incapable of phosphorylation by PKA in vivo. Echocardiographic imaging of homozygous knock-in mice expressing the cTnI-R21C mutation shows that they develop hypertrophy after 12 months of age and have abnormal diastolic function that is characterized by longer filling times and impaired relaxation. Electrocardiographic analyses show that older R21C mice have elevated heart rates and reduced cardiovagal tone. Cardiac myocytes isolated from older R21C mice demonstrate that in the presence of isoproterenol, significant delays in Ca2+ decay and sarcomere relaxation occur that are not present at 6 months of age. Although isoproterenol and stepwise increases in stimulation frequency accelerate Ca2+-transient and sarcomere shortening kinetics in R21C myocytes from older mice, they are unable to attain the corresponding WT values. When R21C myocytes from older mice are treated with isoproterenol, evidence of excitation-contraction uncoupling is indicated by an elevation in diastolic calcium that is frequency-dissociated and not coupled to shorter diastolic sarcomere lengths. Myocytes from older mice have smaller Ca2+ transient amplitudes (2.3-fold) that are associated with reductions (2.9-fold) in sarcoplasmic reticulum Ca2+ content. This abnormal Ca2+ handling within the cell may be attributed to a reduction (2.4-fold) in calsequestrin expression in conjunction with an up-regulation (1.5-fold) of Na+-Ca2+ exchanger. Incubation of permeabilized cardiac fibers from R21C mice with PKA confirmed that the mutation prevents facilitation of mechanical relaxation. Altogether, these results indicate that the inability to enhance myofilament relaxation through cTnI phosphorylation predisposes the heart to abnormal diastolic function, reduced accessibility of cardiac reserves, dysautonomia, and hypertrophy. PMID:24973218

  6. Functional Cross-Talk between the α1- and β1-Adrenergic Receptors Modulates the Rapidly Activating Delayed Rectifier Potassium Current in Guinea Pig Ventricular Myocytes

    Directory of Open Access Journals (Sweden)

    Di Xu

    2014-08-01

    Full Text Available The rapidly activating delayed rectifier potassium current (IKr plays a critical role in cardiac repolarization. Although IKr is known to be regulated by both α1- and β1-adrenergic receptors (ARs, the cross-talk and feedback mechanisms that dictate its response to α1- and β1-AR activation are not known. In the present study, IKr was recorded using the whole-cell patch-clamp technique. IKr amplitude was measured before and after the sequential application of selective adrenergic agonists targeting α1- and β1-ARs. Stimulation of either receptor alone (α1-ARs using 1 μM phenylephrine (PE or β1-ARs using 10 μM xamoterol (Xamo reduced IKr by 0.22 ± 0.03 and 0.28 ± 0.01, respectively. The voltage-dependent activation curve of IKr shifted in the negative direction. The half-maximal activation voltage (V0.5 was altered by −6.35 ± 1.53 and −1.95 ± 2.22 mV, respectively, with no major change in the slope factor (k. When myocytes were pretreated with Xamo, PE-induced reduction in IKr was markedly blunted and the corresponding change in V0.5 was significantly altered. Similarly, when cells were pretreated with PE, Xamo-induced reduction of IKr was significantly attenuated. The present results demonstrate that functional cross-talk between α1- and β1-AR signaling regulates IKr. Such non-linear regulation may form a protective mechanism under excessive adrenergic stimulation.

  7. Cardiac arrhythmias in stroke unit patients. Evaluation of the cardiac monitoring data.

    Science.gov (United States)

    Fernández-Menéndez, S; García-Santiago, R; Vega-Primo, A; González Nafría, N; Lara-Lezama, L B; Redondo-Robles, L; Montes-Montes, M; Riveira-Rodríguez, M C; Tejada-García, J

    2016-06-01

    Cardiac arrhythmias are frequent in acute stroke. Stroke units are widely equipped with cardiac monitoring systems. Pre-existing heart diseases and heart-brain interactions may be implicated in causing cardiac arrhythmias in acute stroke. This article analyses cardiac arrhythmias detected in patients hospitalised in a stroke unit. Prospective observational study of consecutive patients admitted to a stroke unit with cardiac monitoring. We collected clinical data from patients and the characteristics of their cardiac arrhythmias over a 1-year period (2013). Time of arrhythmia onset, associated predisposing factors, and the therapeutic decisions made after detection of arrhythmia were examined. All patients underwent continuous cardiac monitoring during no less than 48hours. Of a total of 332 patients admitted, significant cardiac arrhythmias occurred in 98 patients (29.5%) during their stay in the stroke unit. Tachyarrhythmia (ventricular tachyarrhythmias, supraventricular tachyarrhythmias, complex ventricular ectopy) was present in 90 patients (27.1%); bradyarrhythmia was present in 13 patients (3.91%). Arrhythmias were independently associated with larger size of brain lesion and older age. In 10% of the patient total, therapeutic actions were taken after detection of significant cardiac arrhythmias. Most events occurred within the first 48hours after stroke unit admission. Systematic cardiac monitoring in patients with acute stroke is useful for detecting clinically relevant cardiac arrhythmias. Incidence of arrhythmia is higher in the first 48hours after stroke unit admission. Age and lesion size were predicted appearance of arrhythmias. Detection of cardiac arrhythmias in a stroke unit has important implications for treatment. Copyright © 2014 Sociedad Española de Neurología. Published by Elsevier España, S.L.U. All rights reserved.

  8. What Is Cardiac Rehabilitation?

    Science.gov (United States)

    ANSWERS by heart Treatments + Tests What Is Cardiac Rehabilitation? A cardiac rehabilitation (rehab) program takes place in a hospital or ... special help in making lifestyle changes. During your rehabilitation program you’ll… • Have a medical evaluation to ...

  9. Cardiac Syndrome X

    Science.gov (United States)

    ... Stroke Sudden Cardiac Arrest Valve Disease Vulnerable Plaque Coronary Microvascular Disease (CMD) Related terms: angina, cardiac syndrome X, CMD, MVD, microvascular angina Coronary Microvascular Disease (CMD or MVD) is a type of heart ...

  10. Proteome- and transcriptome-driven reconstruction of the human myocyte metabolic network and its use for identification of markers for diabetes

    DEFF Research Database (Denmark)

    Väremo, Leif; Scheele, Camilla; Broholm, Christa

    2015-01-01

    Skeletal myocytes are metabolically active and susceptible to insulin resistance and are thus implicated in type 2 diabetes (T2D). This complex disease involves systemic metabolic changes, and their elucidation at the systems level requires genome-wide data and biological networks. Genome......-scale metabolic models (GEMs) provide a network context for the integration of high-throughput data. We generated myocyte-specific RNA-sequencing data and investigated their correlation with proteome data. These data were then used to reconstruct a comprehensive myocyte GEM. Next, we performed a meta......-analysis of six studies comparing muscle transcription in T2D versus healthy subjects. Transcriptional changes were mapped on the myocyte GEM, revealing extensive transcriptional regulation in T2D, particularly around pyruvate oxidation, branched-chain amino acid catabolism, and tetrahydrofolate metabolism...

  11. Specific inhibition of stretch‐induced increase in L‐type calcium channel currents by herbimycin A in canine basilar arterial myocytes

    National Research Council Canada - National Science Library

    Kimura, Makoto; Obara, Kazuo; Sasase, Tomohiko; Ishikawa, Tomohisa; Tanabe, Yoshiyuki; Nakayama, Koichi

    2000-01-01

    ...‐activated barium currents (I Ba ) through L‐type calcium channels increased by hypotonic solution were investigated in canine basilar arterial myocytes by the whole‐cell patch‐clamp technique...

  12. Tumor Suppressor A20 Protects against Cardiac Hypertrophy and Fibrosis through Blocking TAK1-Dependent Signaling

    Science.gov (United States)

    Huang, He; Tang, Qi-Zhu; Wang, Ai-Bing; Chen, Manyin; Zhou, Heng; Liu, Chen; Jiang, Hong; Yang, Qinglin; Bian, Zhou-Yan; Bai, Xue; Zhu, Li-Hua; Wang, Lang; Li, Hongliang

    2010-01-01

    A20 or tumor necrosis factor–induced protein 3 is a negative regulator of nuclear factor κB signaling. A20 has been shown previously to attenuate cardiac hypertrophy in vitro and postmyocardial infarction remodeling in vivo. In the present study, we tested the hypothesis that overexpression of A20 in the murine heart would protect against cardiac hypertrophy in vivo. The effects of constitutive human A20 expression on cardiac hypertrophy were investigated using in vitro and in vivo models. Cardiac hypertrophy was produced by aortic banding in A20 transgenic mice and control animals. The extent of cardiac hypertrophy was quantitated by echocardiography, as well as by pathological and molecular analyses of heart samples. Constitutive overexpression of human A20 in the murine heart attenuated the hypertrophicresponse and markedly reduced inflammation, apoptosis, and fibrosis. Cardiac function was also preserved in hearts with increased A20 levels in response to hypertrophic stimuli. Western blot experiments further showed A20 expression markedly blocked transforming growth factor-β–activated kinase 1–dependent c-Jun N-terminal kinase/p38 signaling cascade but with no difference in either extracellular signal-regulated kinase 1/2 or AKT activation in vivo and in vitro. In cultured neonatal rat cardiac myocytes, [3H]proline incorporation and Western blot assays revealed that A20 expression suppressed transforming growth factor-β–induced collagen synthesis and transforming growth factor-β–activated kinase 1–dependent Smad 2/3/4 activation. In conclusion, A20 improves cardiac functions and inhibits cardiac hypertrophy, inflammation, apoptosis, and fibrosis by blocking transforming growth factor-β–activated kinase 1–dependent signaling. PMID:20585109

  13. Background Studies for EXIST

    Science.gov (United States)

    Wilson, Colleen A.; Pendleton, G. N.; Fishman, G. J.

    2004-01-01

    We present results from a study of the trapped proton and electron background for several orbital inclinations and altitudes. This study includes time dependent effects. In addition we describe a 3 component cosmic background model developed at the University of Southampton, UK. The three components are cosmic diffuse gamma rays, atmospheric albedo gamma rays, and cosmic ray protons. We present examples of how this model was applied to BATSE and discuss its application to EXIST.

  14. Cardiac MRI in a Patient with Coincident Left Ventricular Non-Compaction and Hypertrophic Cardiomyopathy

    Directory of Open Access Journals (Sweden)

    Zahra Alizadeh-Sani

    2011-12-01

    Full Text Available Left ventricular non-compaction cardiomyopathy is a rare congenital cardiomyopathy that affects both children and adults. Since the clinical manifestations are not sufficient to establish diagnosis, echocardiography is the diagnostic tool that makes it possible to document ventricular non-compaction and establish prognostic factors. We report a 47-year-old woman with a history of dilated cardiomyopathy with unknown etiology. Echocardiography showed mild left ventricular enlargement with severe systolic dysfunction (EF = 20-25%. According to cardiac magnetic resonance imaging findings non-compaction left ventricle with hypertrophic cardiomyopathy was considered, and right ventricular septal biopsy was recommended. Right ventricular endomyocardial biopsy showed moderate hypertrophy of cardiac myocytes with foci of myocytolysis and moderate interstitial fibrosis. No evidence of infiltrative deposition was seen.

  15. Cardiac MRI in a Patient with Coincident Left Ventricular Non-Compaction and Hypertrophic Cardiomyopathy

    Science.gov (United States)

    Alizadeh-Sani, Zahra; Madadi, Shabnam; Sadeghpour, Anita; Khajali, Zahra; Golnari, Pedram; Kiavar, Majid

    2011-01-01

    Left ventricular non-compaction cardiomyopathy is a rare congenital cardiomyopathy that affects both children and adults. Since the clinical manifestations are not sufficient to establish diagnosis, echocardiography is the diagnostic tool that makes it possible to document ventricular non-compaction and establish prognostic factors. We report a 47-year-old woman with a history of dilated cardiomyopathy with unknown etiology. Echocardiography showed mild left ventricular enlargement with severe systolic dysfunction (EF = 20–25%). According to cardiac magnetic resonance imaging findings non-compaction left ventricle with hypertrophic cardiomyopathy was considered, and right ventricular septal biopsy was recommended. Right ventricular endomyocardial biopsy showed moderate hypertrophy of cardiac myocytes with foci of myocytolysis and moderate interstitial fibrosis. No evidence of infiltrative deposition was seen. PMID:23074372

  16. The cardiac sodium channel displays differential distribution in the conduction system and transmural heterogeneity in the murine ventricular myocardium.

    Science.gov (United States)

    Remme, C A; Verkerk, A O; Hoogaars, W M H; Aanhaanen, W T J; Scicluna, B P; Annink, C; van den Hoff, M J B; Wilde, A A M; van Veen, T A B; Veldkamp, M W; de Bakker, J M T; Christoffels, V M; Bezzina, C R

    2009-09-01

    Cardiac sodium channels are responsible for conduction in the normal and diseased heart. We aimed to investigate regional and transmural distribution of sodium channel expression and function in the myocardium. Sodium channel Scn5a mRNA and Na(v)1.5 protein distribution was investigated in adult and embryonic mouse heart through immunohistochemistry and in situ hybridization. Functional sodium channel availability in subepicardial and subendocardial myocytes was assessed using patch-clamp technique. Adult and embryonic (ED14.5) mouse heart sections showed low expression of Na(v)1.5 in the HCN4-positive sinoatrial and atrioventricular nodes. In contrast, high expression levels of Na(v)1.5 were observed in the HCN4-positive and Cx43-negative AV or His bundle, bundle branches and Purkinje fibers. In both ventricles, a transmural gradient was observed, with a low Na(v)1.5 labeling intensity in the subepicardium as compared to the subendocardium. Similar Scn5a mRNA expression patterns were observed on in situ hybridization of embryonic and adult tissue. Maximal action potential upstroke velocity was significantly lower in subepicardial myocytes (mean +/- SEM 309 +/- 32 V/s; n = 14) compared to subendocardial myocytes (394 +/- 32 V/s; n = 11; P channel availability in subepicardium compared to subendocardium. Scn5a and Na(v)1.5 show heterogeneous distribution patterns within the cardiac conduction system and across the ventricular wall. This differential distribution of the cardiac sodium channel may have profound consequences for conduction disease phenotypes and arrhythmogenesis in the setting of sodium channel disease.

  17. Cardiac sodium channelopathies

    NARCIS (Netherlands)

    Amin, Ahmad S.; Asghari-Roodsari, Alaleh; Tan, Hanno L.

    2010-01-01

    Cardiac sodium channel are protein complexes that are expressed in the sarcolemma of cardiomyocytes to carry a large inward depolarizing current (I-Na) during phase 0 of the cardiac action potential. The importance of I-Na for normal cardiac electrical activity is reflected by the high incidence of

  18. Altered cardiac electrophysiology and SUDEP in a model of Dravet syndrome.

    Directory of Open Access Journals (Sweden)

    David S Auerbach

    Full Text Available OBJECTIVE: Dravet syndrome is a severe form of intractable pediatric epilepsy with a high incidence of SUDEP: Sudden Unexpected Death in epilepsy. Cardiac arrhythmias are a proposed cause for some cases of SUDEP, yet the susceptibility and potential mechanism of arrhythmogenesis in Dravet syndrome remain unknown. The majority of Dravet syndrome patients have de novo mutations in SCN1A, resulting in haploinsufficiency. We propose that, in addition to neuronal hyperexcitability, SCN1A haploinsufficiency alters cardiac electrical function and produces arrhythmias, providing a potential mechanism for SUDEP. METHODS: Postnatal day 15-21 heterozygous SCN1A-R1407X knock-in mice, expressing a human Dravet syndrome mutation, were used to investigate a possible cardiac phenotype. A combination of single cell electrophysiology and in vivo electrocardiogram (ECG recordings were performed. RESULTS: We observed a 2-fold increase in both transient and persistent Na(+ current density in isolated Dravet syndrome ventricular myocytes that resulted from increased activity of a tetrodotoxin-resistant Na(+ current, likely Nav1.5. Dravet syndrome myocytes exhibited increased excitability, action potential duration prolongation, and triggered activity. Continuous radiotelemetric ECG recordings showed QT prolongation, ventricular ectopic foci, idioventricular rhythms, beat-to-beat variability, ventricular fibrillation, and focal bradycardia. Spontaneous deaths were recorded in 2 DS mice, and a third became moribund and required euthanasia. INTERPRETATION: These data from single cell and whole animal experiments suggest that altered cardiac electrical function in Dravet syndrome may contribute to the susceptibility for arrhythmogenesis and SUDEP. These mechanistic insights may lead to critical risk assessment and intervention in human patients.

  19. The effects of halothane, isoflurane, and sevoflurane on Ca2+ current and transient outward K+ current in subendocardial and subepicardial myocytes from the rat left ventricle.

    Science.gov (United States)

    Rithalia, Amber; Hopkins, Philip M; Harrison, Simon M

    2004-12-01

    Halothane, isoflurane, and sevoflurane abbreviate ventricular action potential duration (APD), and for halothane this effect is greater in the subendocardium than in the subepicardium. In this study we investigated mechanisms underlying the regional effects of these anesthetics on APD. The effect of 0.6 mM halothane, isoflurane, and sevoflurane on the action potential, L-type Ca(2+) current, transient outward K(+) current (I(to)), and steady-state current was recorded in rat left ventricular subendocardial and subepicardial myocytes. Halothane and isoflurane (but not sevoflurane) reduced APD significantly (P subendocardial than subepicardial myocytes. Peak L-type Ca(2+) current did not differ between regions and, compared with control, was reduced significantly in both regions by 40% (P subendocardial (1.12 +/- 0.05 nA) myocytes. In subepicardial myocytes, peak I(to) was reduced significantly by halothane (P subendocardial myocytes with the three anesthetics. The steady-state current was increased significantly (P subendocardial myocytes by halothane and isoflurane could underlie their transmural effects on APD.

  20. Existing chemicals: international activities.

    Science.gov (United States)

    Purchase, J F

    1989-01-01

    The standards of care used in the protection of the health and safety of people exposed to chemicals has increased dramatically in the last decade. Standards imposed by regulation and those adopted by industry have required a greater level of knowledge about the hazards of chemicals. In the E.E.C., the 6th amendment of the dangerous substances directive imposed the requirement that al new chemicals should be tested according to prescribed programme before introduction on to the market. The development of a European inventory of existing chemicals was an integral part of the 6th amendment. It has now become clear that increased standards of care referred to above must be applied to the chemicals on the inventory list. There is, however, a considerable amount of activity already under way in various international agencies. The OECD Chemicals Programme has been involved in considering the problem of existing chemicals for some time, and is producing a priority list and action programme. The International Programme on Chemical Safety produces international chemical safety cards, health and safety guides and environmental health criteria documents. The international register of potentially toxic compounds (part of UNEP) has prepared chemical data profiles on 990 compounds. The International Agency for Research on Cancer prepared monographs on the carcinogenic risk of chemicals to man. So far 42 volumes have been prepared covering about 900 substances. IARC and IPCS also prepare periodic reports on ongoing research on carcinogenicity or toxicity (respectively) of chemicals. The chemical industry through ECETOC (the European Chemical Industry Ecology and Toxicology Centre) has mounted a major initiative on existing chemicals. Comprehensive reviews of the toxicity of selected chemicals are published (Joint Assessment of Commodity Chemicals). In its technical report no. 30 ECETOC lists reviews and evaluations by major national and international organisations, which provides

  1. Do multiquark hadrons exist

    Energy Technology Data Exchange (ETDEWEB)

    Weinstein, J.; Isgur, N.

    1982-03-08

    The qqq-barq-bar system has been examined by solving the four-particle Schroedinger equation variationally. The main findings are that: (1) qqq-barq-bar bound states normally do not exist, (2) the cryptoexotic 0/sup + +/ sector of this system with KK-bar quantum numbers is probably the only exception to (1) and its bound states can be identified with the S* and delta just below KK-bar threshold, (3) qqq-barq-bar bound states provide a model for the weak binding and color-singlet clustering observed in nuclei, and (4) there is no indication that this system has strong resonances.

  2. Repowering existing plants

    Energy Technology Data Exchange (ETDEWEB)

    Steazel, W.C.; Sopocy, D.M.; Pace, S.E.

    1998-07-01

    Increased competition among power generation companies, changes in generating system load requirements, lower allowable plant emissions, and changes in fuel availability and cost accentuate the need to closely assess the economics and performances of older electric generation units. Generally, decisions must be made as to whether these units should be retired and replaced with new generation capacity, whether capacity should be purchased from other generation companies, or if these existing units should be repowered. These decisions usually require the evaluation of many factors including; environmental discharge limits, permitting requirements, generating load demand increases, options for increasing the benefits of using existing facilities (e.g.; increasing efficiency and output), fuel cost increases, transmission requirements and access, optional plant designs. Many of these factors need to be used in the analysis based on a range rather than one specific value to test for changes in the selection of the best option because of future uncertainties. Usually complicated analysis results because of all the factors involved. Computer products that integrate performance and financial analysis can provide substantial value by enabling the user to evaluate the applicable plant options and range of input. The SOAPP (State-of-the-Art Power Plant) family of software products provides easy to use tools for rapid, thorough and economical evaluation of plant option. Repowering evaluation methodology typically used in the US, technology options, and available SOAPP repowering software are reviewed in this paper.

  3. Acute simvastatin inhibits K ATP channels of porcine coronary artery myocytes.

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    Sai Wang Seto

    Full Text Available BACKGROUND: Statins (3-hydroxy-3-methyl-glutaryl coenzyme A (HMG-CoA reductase inhibitors consumption provides beneficial effects on cardiovascular systems. However, effects of statins on vascular KATP channel gatings are unknown. METHODS: Pig left anterior descending coronary artery and human left internal mammary artery were isolated and endothelium-denuded for tension measurements and Western immunoblots. Enzymatically-dissociated/cultured arterial myocytes were used for patch-clamp electrophysiological studies and for [Ca(2+]i, [ATP]i and [glucose]o uptake measurements. RESULTS: The cromakalim (10 nM to 10 µM- and pinacidil (10 nM to 10 µM-induced concentration-dependent relaxation of porcine coronary artery was inhibited by simvastatin (3 and 10 µM. Simvastatin (1, 3 and 10 µM suppressed (in okadaic acid (10 nM-sensitive manner cromakalim (10 µM- and pinacidil (10 µM-mediated opening of whole-cell KATP channels of arterial myocytes. Simvastatin (10 µM and AICAR (1 mM elicited a time-dependent, compound C (1 µM-sensitive [(3H]-2-deoxy-glucose uptake and an increase in [ATP]i levels. A time (2-30 min- and concentration (0.1-10 µM-dependent increase by simvastatin of p-AMPKα-Thr(172 and p-PP2A-Tyr(307 expression was observed. The enhanced p-AMPKα-Thr(172 expression was inhibited by compound C, ryanodine (100 µM and KN93 (10 µM. Simvastatin-induced p-PP2A-Tyr(307 expression was suppressed by okadaic acid, compound C, ryanodine, KN93, phloridzin (1 mM, ouabain (10 µM, and in [glucose]o-free or [Na(+]o-free conditions. CONCLUSIONS: Simvastatin causes ryanodine-sensitive Ca(2+ release which is important for AMPKα-Thr(172 phosphorylation via Ca(2+/CaMK II. AMPKα-Thr(172 phosphorylation causes [glucose]o uptake (and an [ATP]i increase, closure of KATP channels, and phosphorylation of AMPKα-Thr(172 and PP2A-Tyr(307 resulted. Phosphorylation of PP2A-Tyr(307 occurs at a site downstream of AMPKα-Thr(172 phosphorylation.

  4. The Myocyte Expression of Adiponectin Receptors and PPARδ Is Highly Coordinated and Reflects Lipid Metabolism of the Human Donors

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    Anna-Maria Ordelheide

    2011-01-01

    Full Text Available Muscle lipid oxidation is stimulated by peroxisome proliferator-activated receptor (PPAR δ or adiponectin receptor signalling. We studied human myocyte expression of the PPARδ and adiponectin receptor genes and their relationship to lipid parameters of the donors. The mRNA levels of the three adiponectin receptors, AdipoR1, AdipoR2, and T-cadherin, were highly interrelated (r≥0.91. However, they were not associated with GPBAR1, an unrelated membrane receptor. In addition, the adiponectin receptors were positively associated with PPARδ expression (r≥0.75. However, they were not associated with PPARα. Using stepwise multiple linear regression analysis, PPARδ was a significant determinant of T-cadherin (P=.0002. However, pharmacological PPARδ activation did not increase T-cadherin expression. The myocyte expression levels of AdipoR1 and T-cadherin were inversely associated with the donors' fasting plasma triglycerides (P<.03. In conclusion, myocyte expression of PPARδ and the adiponectin receptors are highly coordinated, and this might be of relevance for human lipid metabolism in vivo.

  5. Adenoviral gene transfer of mutant phospholamban rescues contractile dysfunction in failing rabbit myocytes with relatively preserved SERCA function.

    Science.gov (United States)

    Ziolo, Mark T; Martin, Jody L; Bossuyt, Julie; Bers, Donald M; Pogwizd, Steven M

    2005-04-29

    In heart failure (HF) a main factor in reduced contractility is reduced SR Ca2+ content and reversed force-frequency response (FFR), ie, from positive to negative. Our arrhythmogenic rabbit H