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Sample records for calcium channels inhibits

  1. Calcium channel blockers for inhibiting preterm labour and birth.

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    Flenady, Vicki; Wojcieszek, Aleena M; Papatsonis, Dimitri N M; Stock, Owen M; Murray, Linda; Jardine, Luke A; Carbonne, Bruno

    2014-06-05

    Preterm birth is a major contributor to perinatal mortality and morbidity, affecting around 9% of births in high-income countries and an estimated 13% of births in low- and middle-income countries. Tocolytics are drugs used to suppress uterine contractions for women in preterm labour. The most widely used tocolytic are the betamimetics, however, these are associated with a high frequency of unpleasant and sometimes severe maternal side effects. Calcium channel blockers (CCBs) (such as nifedipine) may have similar tocolytic efficacy with less side effects than betamimetics. Oxytocin receptor antagonists (ORAs) (e.g. atosiban) also have a low side-effect profile. To assess the effects on maternal, fetal and neonatal outcomes of CCBs, administered as a tocolytic agent, to women in preterm labour. We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (12 November 2013). All published and unpublished randomised trials in which CCBs were used for tocolysis for women in labour between 20 and 36 completed weeks' gestation. Two review authors independently assessed trial eligibility, undertook quality assessment and data extraction. Results are presented using risk ratio (RR) for categorical data and mean difference (MD) for data measured on a continuous scale with the 95% confidence interval (CI). The number needed to treat to benefit (NNTB) and the number needed to treat to harm (NNTH) were calculated for categorical outcomes that were statistically significantly different. This update includes 26 additional trials involving 2511 women, giving a total of 38 included trials (3550 women). Thirty-five trials used nifedipine as the CCB and three trials used nicardipine. Blinding of intervention and outcome assessment was undertaken in only one of the trials (a placebo controlled trial). However, objective outcomes defined according to timing of birth and perinatal mortality were considered to have low risk of detection bias.Two small trials comparing CCBs

  2. Aluminium and hydrogen ions inhibit a mechanosensory calcium-selective cation channel

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    Ding, J. P.; Pickard, B. G.

    1993-01-01

    The tension-dependent activity of mechanosensory calcium-selective cation channels in excised plasmalemmal patches from onion bulb scale epidermis is modulated by pH in the physiologically meaningful range between 4.5 and 7.2. It is rapidly lowered by lowering pH and rapidly raised by raising pH. Channel activity is effectively inhibited by low levels of aluminium ions and activity can be partially restored by washing for a few minutes. We suggest that under normal conditions the sensitivity of the mechanosensory channels to pH of the wall free space plays important roles in regulation of plant activities such as growth. We further suggest that, when levels of acid and aluminium ions in the soil solution are high, they might inhibit similar sensory channels in cells of the root tip, thus contributing critically to the acid soil syndrome.

  3. Activation and inhibition of TMEM16A calcium-activated chloride channels.

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    Yu-Li Ni

    Full Text Available Calcium-activated chloride channels (CaCC encoded by family members of transmembrane proteins of unknown function 16 (TMEM16 have recently been intensely studied for functional properties as well as their physiological roles as chloride channels in various tissues. One technical hurdle in studying these channels is the well-known channel rundown that frequently impairs the precision of electrophysiological measurements for the channels. Using experimental protocols that employ fast-solution exchange, we circumvented the problem of channel rundown by normalizing the Ca(2+-induced current to the maximally-activated current obtained within a time period in which the channel rundown was negligible. We characterized the activation of the TMEM16A-encoded CaCC (also called ANO1 by Ca(2+, Sr(2+, and Ba(2+, and discovered that Mg(2+ competes with Ca(2+ in binding to the divalent-cation binding site without activating the channel. We also studied the permeability of the ANO1 pore for various anions and found that the anion occupancy in the pore-as revealed by the permeability ratios of these anions-appeared to be inversely correlated with the apparent affinity of the ANO1 inhibition by niflumic acid (NFA. On the other hand, the NFA inhibition was neither affected by the degree of the channel activation nor influenced by the types of divalent cations used for the channel activation. These results suggest that the NFA inhibition of ANO1 is likely mediated by altering the pore function but not through changing the channel gating. Our study provides a precise characterization of ANO1 and documents factors that can affect divalent cation activation and NFA inhibition of ANO1.

  4. Dehydroepiandrosterone (DHEA) inhibits voltage-gated T-type calcium channels.

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    Chevalier, M; Gilbert, G; Lory, P; Marthan, R; Quignard, J F; Savineau, J P

    2012-06-01

    Dehydroepiandrosterone (DHEA) and its sulfated form, DHEAS, are the most abundant steroid hormones in the mammalian blood flow. DHEA may have beneficial effects in various pathophysiological conditions such as cardiovascular diseases or deterioration of the sense of well-being. However to date, the cellular mechanism underlying DHEA action remains elusive and may involve ion channel modulation. In this study, we have characterized the effect of DHEA on T-type voltage-activated calcium channels (T-channels), which are involved in several cardiovascular and neuronal diseases. Using the whole-cell patch-clamp technique, we demonstrate that DHEA inhibits the three recombinant T-channels (Ca(V)3.1, Ca(V)3.2 and Ca(V)3.3) expressed in NG108-15 cell line, as well as native T-channels in pulmonary artery smooth muscle cells. This effect of DHEA is both concentration (IC(50) between 2 and 7μM) and voltage-dependent and results in a significant shift of the steady-state inactivation curves toward hyperpolarized potentials. Consequently, DHEA reduces window T-current and inhibits membrane potential oscillations induced by Ca(V)3 channels. DHEA inhibition is not dependent on the activation of nuclear androgen or estrogen receptors and implicates a PTX-sensitive Gi protein pathway. Functionally, DHEA and the T-type inhibitor NNC 55-0396 inhibited KCl-induced contraction of pulmonary artery rings and their effect was not cumulative. Altogether, the present data demonstrate that DHEA inhibits T-channels by a Gi protein dependent pathway. DHEA-induced alteration in T-channel activity could thus account for its therapeutic action and/or physiological effects. Copyright © 2012 Elsevier Inc. All rights reserved.

  5. Clofazimine inhibits human Kv1.3 potassium channel by perturbing calcium oscillation in T lymphocytes.

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    Yunzhao R Ren

    Full Text Available The Kv1.3 potassium channel plays an essential role in effector memory T cells and has been implicated in several important autoimmune diseases including multiple sclerosis, psoriasis and type 1 diabetes. A number of potent small molecule inhibitors of Kv1.3 channel have been reported, some of which were found to be effective in various animal models of autoimmune diseases. We report herein the identification of clofazimine, a known anti-mycobacterial drug, as a novel inhibitor of human Kv1.3. Clofazimine was initially identified as an inhibitor of intracellular T cell receptor-mediated signaling leading to the transcriptional activation of human interleukin-2 gene in T cells from a screen of the Johns Hopkins Drug Library. A systematic mechanistic deconvolution revealed that clofazimine selectively blocked the Kv1.3 channel activity, perturbing the oscillation frequency of the calcium-release activated calcium channel, which in turn led to the inhibition of the calcineurin-NFAT signaling pathway. These effects of clofazimine provide the first line of experimental evidence in support of a causal relationship between Kv1.3 and calcium oscillation in human T cells. Furthermore, clofazimine was found to be effective in blocking human T cell-mediated skin graft rejection in an animal model in vivo. Together, these results suggest that clofazimine is a promising immunomodulatory drug candidate for treating a variety of autoimmune disorders.

  6. Effect of gingerol on colonic motility via inhibition of calcium channel currents in rats.

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    Cai, Zheng-Xu; Tang, Xu-Dong; Wang, Feng-Yun; Duan, Zhi-Jun; Li, Yu-Chun; Qiu, Juan-Juan; Guo, Hui-Shu

    2015-12-28

    To investigate the effect of gingerol on colonic motility and the action of L-type calcium channel currents in this process. The distal colon was cut along the mesenteric border and cleaned with Ca(2+)-free physiological saline solution. Muscle strips were removed and placed in Ca(2+)-free physiological saline solution, which was oxygenated continuously. Longitudinal smooth muscle samples were prepared by cutting along the muscle strips and were then placed in a chamber. Mechanical contractile activities of isolated colonic segments in rats were recorded by a 4-channel physiograph. Colon smooth muscle cells were dissociated by enzymatic digestion. L-type calcium currents were recorded using the conventional whole-cell patch-clamp technique. Gingerol inhibited the spontaneous contraction of colonic longitudinal smooth muscle in a dose-dependent manner with inhibition percentages of 13.3% ± 4.1%, 43.4% ± 3.9%, 78.2% ± 3.6% and 80.5% ± 4.5% at 25 μmol/L, 50 μmol/L, 75 μmol/L and 100 μmol/L, respectively (P gingerol. Gingerol inhibited L-type calcium channel currents in colonic longitudinal myocytes of rats. At a 75 μmol/L concentration of gingerol, the percentage of gingerol-induced inhibition was diminished by nifedipine from 77.1% ± 4.2% to 42.6% ± 3.6% (P Gingerol suppressed IBa in a dose-dependent manner, and the inhibition rates were 22.7% ± 2.38%, 35.77% ± 3.14%, 49.78% ± 3.48% and 53.78% ± 4.16% of control at 0 mV, respectively, at concentrations of 25 μmol/L, 50 μmol/L, 75 μmol/L and 100 μmol/L (P gingerol. The value of half activation was -14.23 ± 1.12 mV in the control group and -10.56 ± 1.04 mV in the 75 μmol/L group (P gingerol group (P > 0.05), and a slope factor, K, of 13.24 ± 1.62 in the control group and 13.45 ± 1.68 (P > 0.05) in the 75 μmol/L gingerol group. Gingerol inhibits colonic motility by preventing Ca(2+) influx through L-type calcium channels.

  7. Stereoselective inhibition of thromboxane-induced coronary vasoconstriction by 1,4-dihydropyridine calcium channel antagonists

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    Eltze, M.; Boer, R.; Sanders, K.H.; Boss, H.; Ulrich, W.R.; Flockerzi, D. (Byk Gulden Pharmaceuticals, Konstanz (Germany F.R.))

    1990-01-01

    The biological activity of the (+)-S- and (-)-R-enantiomers of niguldipine, of the (-)-S- and (+)-R-enantiomers of felodipine and nitrendipine, and of rac-nisoldipine and rac-nimodipine was investigated in vitro and in vivo. Inhibition of coronary vasoconstriction due to the thromboxane A2 (TxA2)-mimetic U-46619 in guinea pig Langendorff hearts, displacement of (+)-({sup 3}H)isradipine from calcium channel binding sites of guinea pig skeletal muscle T-tubule membranes, and blood pressure reduction in spontaneously hypertensive rats were determined. The enantiomers were obtained by stereoselective synthesis. Cross-contamination was less than 0.5% for both S- and R-enantiomers of niguldipine and nitrendipine and less than 1% for those of felodipine. From the doses necessary for a 50% inhibition of coronary vasoconstriction, stereoselectivity ratios for (+)-(S)-/(-)-(R)-niguldipine, (-)-(S)-/(+)-(R)-felodipine, and (-)-(S)-/(+)-(R)-nitrendipine of 28, 13, and 7, respectively, were calculated. The potency ratio rac-nisoldipine/rac-nimodipine was 3.5. Ratios obtained from binding experiments and antihypertensive activity were (+)-(S)-/(-)-(R)-niguldipine = 45 and 35, (-)-(S)-/(+)-(R)-felodipine = 12 and 13, (-)-(S)-/(+)-(R)-nitrendipine = 8 and 8, and rac-nisoldipine/rac-nimodipine = 8 and 7, respectively. Highly significant correlations were found between the in vitro potency of the substances to prevent U-46619-induced coronary vasoconstriction and their affinity for calcium channel binding sites as well as their antihypertensive activity.

  8. Brain-derived neurotrophic factor inhibits calcium channel activation, exocytosis, and endocytosis at a central nerve terminal.

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    Baydyuk, Maryna; Wu, Xin-Sheng; He, Liming; Wu, Ling-Gang

    2015-03-18

    Brain-derived neurotrophic factor (BDNF) is a neurotrophin that regulates synaptic function and plasticity and plays important roles in neuronal development, survival, and brain disorders. Despite such diverse and important roles, how BDNF, or more generally speaking, neurotrophins affect synapses, particularly nerve terminals, remains unclear. By measuring calcium currents and membrane capacitance during depolarization at a large mammalian central nerve terminal, the rat calyx of Held, we report for the first time that BDNF slows down calcium channel activation, including P/Q-type channels, and inhibits exocytosis induced by brief depolarization or single action potentials, inhibits slow and rapid endocytosis, and inhibits vesicle mobilization to the readily releasable pool. These presynaptic mechanisms may contribute to the important roles of BDNF in regulating synapses and neuronal circuits and suggest that regulation of presynaptic calcium channels, exocytosis, and endocytosis are potential mechanisms by which neurotrophins achieve diverse neuronal functions. Copyright © 2015 the authors 0270-6474/15/354676-07$15.00/0.

  9. Calcium channel blocker overdose

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    ... page: //medlineplus.gov/ency/article/002580.htm Calcium-channel blocker overdose To use the sharing features on this page, please enable JavaScript. Calcium-channel blockers are a type of medicine used to ...

  10. 5,6-EET potently inhibits T-type calcium channels

    DEFF Research Database (Denmark)

    Cazade, M.; Bidaud, I.; Hansen, Pernille B. Lærkegaard

    2014-01-01

    T-type calcium channels (T-channels) are important actors in neuronal pacemaking, in heart rhythm, and in the control of the vascular tone. T-channels are regulated by several endogenous lipids including the primary eicosanoid arachidonic acid (AA), which display an important role in vasodilation...

  11. Gynura procumbens Merr. decreases blood pressure in rats by vasodilatation via inhibition of calcium channels

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    See-Ziau Hoe

    2011-01-01

    Full Text Available INTRODUCTION: Gynura procumbens has been shown to decrease blood pressure via inhibition of the angiotensinconverting enzyme. However, other mechanisms that may contribute to the hypotensive effect have not been studied. OBJECTIVES: To investigate the cardiovascular effects of a butanolic fraction of Gynura procumbens in rats. METHODS: Anaesthetized rats were given intravenous bolus injections of butanolic fraction at doses of 2.5-20 mg/kg in vivo. The effect of butanolic fraction on vascular reactivity was recorded in isolated rat aortic rings in vitro. RESULTS: Intravenous administrations of butanolic fraction elicited significant (p<0.001 and dose-dependent decreases in the mean arterial pressure. However, a significant (p<0.05 decrease in the heart rate was observed only at the higher doses (10 and 20 mg/kg. In isolated preparations of rat aortic rings, phenylephrine (1×10-6 M- or potassium chloride (8×10-2 M-precontracted endothelium-intact and -denuded tissue; butanolic fraction (1×10-6-1×10-1 g/ml induced similar concentration-dependent relaxation of the vessels. In the presence of 2.5×10-3 and 5.0×10-3 g/ml butanolic fraction, the contractions induced by phenylephrine (1×10-9-3×10-5 M and potassium chloride (1×10-2-8×10-2 M were significantly antagonized. The calcium-induced vasocontractions (1×10-4-1×10-2 M were antagonized by butanolic fraction concentration-dependently in calcium-free and high potassium (6×10-2 M medium, as well as in calcium- and potassium-free medium containing 1×10-6 M phenylephrine. However, the contractions induced by noradrenaline (1×10-6 M and caffeine (4.5×10-2 M were not affected by butanolic fraction. CONCLUSION: Butanolic fraction contains putative hypotensive compounds that appear to inhibit calcium influx via receptor-operated and/or voltage-dependent calcium channels to cause vasodilation and a consequent fall in blood pressure.

  12. Eugenol dilates rat cerebral arteries by inhibiting smooth muscle cell voltage-dependent calcium channels.

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    Peixoto-Neves, Dieniffer; Leal-Cardoso, Jose Henrique; Jaggar, Jonathan H

    2014-11-01

    Plants high in eugenol, a phenylpropanoid compound, are used as folk medicines to alleviate diseases including hypertension. Eugenol has been demonstrated to relax conduit and ear arteries and reduce systemic blood pressure, but mechanisms involved are unclear. Here, we studied eugenol regulation of resistance-size cerebral arteries that control regional brain blood pressure and flow and investigated mechanisms involved. We demonstrate that eugenol dilates arteries constricted by either pressure or membrane depolarization (60 mM K) in a concentration-dependent manner. Experiments performed using patch-clamp electrophysiology demonstrated that eugenol inhibited voltage-dependent calcium (Ca) currents, when using Ba as a charge carrier, in isolated cerebral artery smooth muscle cells. Eugenol inhibition of voltage-dependent Ca currents involved pore block, a hyperpolarizing shift (∼-10 mV) in voltage-dependent inactivation, an increase in the proportion of steady-state inactivating current, and acceleration of inactivation rate. In summary, our data indicate that eugenol dilates cerebral arteries by means of multimodal inhibition of voltage-dependent Ca channels.

  13. Calcium channel blocker poisoning

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    Miran Brvar

    2005-04-01

    Full Text Available Background: Calcium channel blockers act at L-type calcium channels in cardiac and vascular smooth muscles by preventing calcium influx into cells with resultant decrease in vascular tone and cardiac inotropy, chronotropy and dromotropy. Poisoning with calcium channel blockers results in reduced cardiac output, bradycardia, atrioventricular block, hypotension and shock. The findings of hypotension and bradycardia should suggest poisoning with calcium channel blockers.Conclusions: Treatment includes immediate gastric lavage and whole-bowel irrigation in case of ingestion of sustainedrelease products. All patients should receive an activated charcoal orally. Specific treatment includes calcium, glucagone and insulin, which proved especially useful in shocked patients. Supportive care including the use of catecholamines is not always effective. In the setting of failure of pharmacological therapy transvenous pacing, balloon pump and cardiopulmonary by-pass may be necessary.

  14. Calcium-dependent inhibition of T-type calcium channels by TRPV1 activation in rat sensory neurons.

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    Comunanza, Valentina; Carbone, Emilio; Marcantoni, Andrea; Sher, Emanuele; Ursu, Daniel

    2011-11-01

    We studied the inhibitory effects of transient receptor potential vanilloid-1 (TRPV1) activation by capsaicin on low-voltage-activated (LVA, T-type) Ca(2+) channel and high-voltage-activated (HVA; L, N, P/Q, R) currents in rat DRG sensory neurons, as a potential mechanism underlying capsaicin-induced analgesia. T-type and HVA currents were elicited in whole-cell clamped DRG neurons using ramp commands applied before and after 30-s exposures to 1 μM capsaicin. T-type currents were estimated at the first peak of the I-V characteristics and HVA at the second peak, occurring at more positive potentials. Small and medium-sized DRG neurons responded to capsaicin producing transient inward currents of variable amplitudes, mainly carried by Ca(2+). In those cells responding to capsaicin with a large Ca(2+) influx (59% of the total), a marked inhibition of both T-type and HVA Ca(2+) currents was observed. The percentage of T-type and HVA channel inhibition was prevented by replacing Ca(2+) with Ba(2+) during capsaicin application or applying high doses of intracellular BAPTA (20 mM), suggesting that TRPV1-mediated inhibition of T-type and HVA channels is Ca(2+)-dependent and likely confined to membrane nano-microdomains. Our data are consistent with the idea that TRPV1-induced analgesia may derive from indirect inhibition of both T-type and HVA channels which, in turn, would reduce the threshold of nociceptive signals generation (T-type channel inhibition) and nociceptive synaptic transmission (HVA-channels inhibition).

  15. Amyloid Beta Peptides Block New Synapse Assembly by Nogo Receptor-Mediated Inhibition of T-Type Calcium Channels.

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    Zhao, Yanjun; Sivaji, Sivaprakash; Chiang, Michael C; Ali, Haadi; Zukowski, Monica; Ali, Sareen; Kennedy, Bryan; Sklyar, Alex; Cheng, Alice; Guo, Zihan; Reed, Alexander K; Kodali, Ravindra; Borowski, Jennifer; Frost, Georgia; Beukema, Patrick; Wills, Zachary P

    2017-10-11

    Compelling evidence links amyloid beta (Aβ) peptide accumulation in the brains of Alzheimer's disease (AD) patients with the emergence of learning and memory deficits, yet a clear understanding of the events that drive this synaptic pathology are lacking. We present evidence that neurons exposed to Aβ are unable to form new synapses, resulting in learning deficits in vivo. We demonstrate the Nogo receptor family (NgR1-3) acts as Aβ receptors mediating an inhibition of synapse assembly, plasticity, and learning. Live imaging studies reveal Aβ activates NgRs on the dendritic shaft of neurons, triggering an inhibition of calcium signaling. We define T-type calcium channels as a target of Aβ-NgR signaling, mediating Aβ's inhibitory effects on calcium, synapse assembly, plasticity, and learning. These studies highlight deficits in new synapse assembly as a potential initiator of cognitive pathology in AD, and pinpoint calcium dysregulation mediated by NgRs and T-type channels as key components. VIDEO ABSTRACT. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. Assay for calcium channels

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    Glossmann, H.; Ferry, D.R.

    1985-01-01

    This chapter focuses on biochemical assays for Ca/sup 2 +/-selective channels in electrically excitable membranes which are blocked in electrophysiological and pharmacological experiments by verapamil, 1,4-dihydropyridines, diltiazen (and various other drugs), as well as inorganic di- or trivalent cations. The strategy employed is to use radiolabeled 1,4-dihydropyridine derivatives which block calcium channels with ED/sub 50/ values in the nanomolar range. Although tritiated d-cis-diltiazem and verapamil can be used to label calcium channels, the 1,4-dihydropyridines offer numerous advantages. The various sections cover tissue specificity of channel labeling, the complex interactions of divalent cations with the (/sup 3/H)nimodipine-labeled calcium channels, and the allosteric regulation of (/sup 3/H)nimodipine binding by the optically pure enantiomers of phenylalkylamine and benzothiazepine calcium channel blockers. A comparison of the properties of different tritiated 1,4-dihydropyridine radioligands and the iodinated channel probe (/sup 125/I)iodipine is given.

  17. Postsynaptic GABABRs Inhibit L-Type Calcium Channels and Abolish Long-Term Potentiation in Hippocampal Somatostatin Interneurons.

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    Booker, Sam A; Loreth, Desiree; Gee, Annabelle L; Watanabe, Masahiko; Kind, Peter C; Wyllie, David J A; Kulik, Ákos; Vida, Imre

    2018-01-02

    Inhibition provided by local GABAergic interneurons (INs) activates ionotropic GABAA and metabotropic GABAB receptors (GABABRs). Despite GABABRs representing a major source of inhibition, little is known of their function in distinct IN subtypes. Here, we show that, while the archetypal dendritic-inhibitory somatostatin-expressing INs (SOM-INs) possess high levels of GABABR on their somato-dendritic surface, they fail to produce significant postsynaptic inhibitory currents. Instead, GABABRs selectively inhibit dendritic CaV1.2 (L-type) Ca2+ channels on SOM-IN dendrites, leading to reduced calcium influx and loss of long-term potentiation at excitatory input synapses onto these INs. These data provide a mechanism by which GABABRs can contribute to disinhibition and control the efficacy of extrinsic inputs to hippocampal networks. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

  18. Lipid Storage Disorders Block Lysosomal Trafficking By Inhibiting TRP Channel and Calcium Release

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    Shen, Dongbiao; Wang, Xiang; Li, Xinran; Zhang, Xiaoli; Yao, Zepeng; Dibble, Shannon; Dong, Xian-ping; Yu, Ting; Lieberman, Andrew P.; Showalter, Hollis D.; Xu, Haoxing

    2012-01-01

    Lysosomal lipid accumulation, defects in membrane trafficking, and altered Ca2+ homeostasis are common features in many lysosomal storage diseases. Mucolipin TRP channel 1 (TRPML1) is the principle Ca2+ channel in the lysosome. Here we show that TRPML1-mediated lysosomal Ca2+ release, measured using a genetically-encoded Ca2+ indicator (GCaMP3) attached directly to TRPML1 and elicited by a potent membrane-permeable synthetic agonist, is dramatically reduced in Niemann-Pick (NP) disease cells. Sphingomyelins (SMs) are plasma membrane lipids that undergo Sphingomyelinase (SMase)-mediated hydrolysis in the lysosomes of normal cells, but accumulate distinctively in NP cell lysosomes. Patch-clamp analyses revealed that TRPML1 channel activity is inhibited by SMs, but potentiated by SMases. In NP type C (NPC) cells, increasing TRPML1’s expression/activity was sufficient to correct the trafficking defects and reduce lysosome storage and cholesterol accumulation. We propose that abnormal accumulation of luminal lipids causes secondary lysosome storage by blocking TRPML1- and Ca2+-dependent lysosomal trafficking. PMID:22415822

  19. Lipid storage disorders block lysosomal trafficking by inhibiting a TRP channel and lysosomal calcium release.

    Science.gov (United States)

    Shen, Dongbiao; Wang, Xiang; Li, Xinran; Zhang, Xiaoli; Yao, Zepeng; Dibble, Shannon; Dong, Xian-ping; Yu, Ting; Lieberman, Andrew P; Showalter, Hollis D; Xu, Haoxing

    2012-03-13

    Lysosomal lipid accumulation, defects in membrane trafficking and altered Ca(2+) homoeostasis are common features in many lysosomal storage diseases. Mucolipin transient receptor potential channel 1 (TRPML1) is the principle Ca(2+) channel in the lysosome. Here we show that TRPML1-mediated lysosomal Ca(2+) release, measured using a genetically encoded Ca(2+) indicator (GCaMP3) attached directly to TRPML1 and elicited by a potent membrane-permeable synthetic agonist, is dramatically reduced in Niemann-Pick (NP) disease cells. Sphingomyelins (SMs) are plasma membrane lipids that undergo sphingomyelinase (SMase)-mediated hydrolysis in the lysosomes of normal cells, but accumulate distinctively in lysosomes of NP cells. Patch-clamp analyses revealed that TRPML1 channel activity is inhibited by SMs, but potentiated by SMases. In NP-type C cells, increasing TRPML1's expression or activity was sufficient to correct the trafficking defects and reduce lysosome storage and cholesterol accumulation. We propose that abnormal accumulation of luminal lipids causes secondary lysosome storage by blocking TRPML1- and Ca(2+)-dependent lysosomal trafficking.

  20. TRAM-34, a putatively selective blocker of intermediate-conductance, calcium-activated potassium channels, inhibits cytochrome P450 activity.

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    Jay J Agarwal

    Full Text Available TRAM-34, a clotrimazole analog characterized as a potent and selective inhibitor of intermediate-conductance, calcium-activated K(+ (IKCa channels, has been used extensively in vitro and in vivo to study the biological roles of these channels. The major advantage of TRAM-34 over clotrimazole is the reported lack of inhibition of the former drug on cytochrome P450 (CYP activity. CYPs, a large family of heme-containing oxidases, play essential roles in endogenous signaling and metabolic pathways, as well as in xenobiotic metabolism. However, previously published work has only characterized the effects of TRAM-34 on a single CYP isoform. To test the hypothesis that TRAM-34 may inhibit some CYP isoforms, the effects of this compound were presently studied on the activities of four rat and five human CYP isoforms. TRAM-34 inhibited recombinant rat CYP2B1, CYP2C6 and CYP2C11 and human CYP2B6, CYP2C19 and CYP3A4 with IC50 values ranging from 0.9 µM to 12.6 µM, but had no inhibitory effects (up to 80 µM on recombinant rat CYP1A2, human CYP1A2, or human CYP19A1. TRAM-34 also had both stimulatory and inhibitory effects on human CYP3A4 activity, depending on the substrate used. These results show that low micromolar concentrations of TRAM-34 can inhibit several rat and human CYP isoforms, and suggest caution in the use of high concentrations of this drug as a selective IKCa channel blocker. In addition, in vivo use of TRAM-34 could lead to CYP-related drug-drug interactions.

  1. Diabetes-Induced Inhibition of Voltage-Dependent Calcium Channels in the Retinal Microvasculature: Role of Spermine

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    Matsushita, Kenji; Fukumoto, Masanori; Kobayashi, Takatoshi; Kobayashi, Masato; Ishizaki, Eisuke; Minami, Masahiro; Katsumura, Kozo; Liao, Sophie D.; Wu, David M.; Zhang, Ting

    2010-01-01

    Purpose. Although decentralized control of blood flow is particularly important in the retina, knowledge of the functional organization of the retinal microvasculature is limited. Here, the authors characterized the distribution and regulation of L-type voltage-dependent calcium channels (VDCCs) within the most decentralized operational complex of the retinal vasculature—the feeder vessel/capillary unit—which consists of a capillary network plus the vessel linking it with a myocyte-encircled arteriole. Methods. Perforated-patch recordings, calcium-imaging, and time-lapse photography were used to assess VDCC-dependent changes in ionic currents, intracellular calcium, abluminal cell contractility, and lumen diameter, in microvascular complexes freshly isolated from the rat retina. Results. Topographical heterogeneity was found in the distribution of functional VDCCs; VDCC activity was markedly greater in feeder vessels than in capillaries. Experiments showed that this topographical distribution occurs, in large part, because of the inhibition of capillary VDCCs by a mechanism dependent on the endogenous polyamine spermine. An operational consequence of functional VDCCs predominantly located in the feeder vessels is that voltage-driven vasomotor responses are generated chiefly in this portion of the feeder vessel/capillary unit. However, early in the course of diabetes, this ability to generate voltage-driven vasomotor responses becomes profoundly impaired because of the inhibition of feeder vessel VDCCs by a spermine-dependent mechanism. Conclusions. The regulation of VDCCs by endogenous spermine not only plays a critical role in establishing the physiological organization of the feeder vessel/capillary unit, but also may contribute to dysfunction of this decentralized operational unit in the diabetic retina. PMID:20484578

  2. Inhibition of collagen synthesis by select calcium and sodium channel blockers can be mitigated by ascorbic acid and ascorbyl palmitate.

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    Ivanov, Vadim; Ivanova, Svetlana; Kalinovsky, Tatiana; Niedzwiecki, Aleksandra; Rath, Matthias

    2016-01-01

    Calcium, sodium and potassium channel blockers are widely prescribed medications for a variety of health problems, most frequently for cardiac arrhythmias, hypertension, angina pectoris and other disorders. However, chronic application of channel blockers is associated with numerous side effects, including worsening cardiac pathology. For example, nifedipine, a calcium-channel blocker was found to be associated with increased mortality and increased risk for myocardial infarction. In addition to the side effects mentioned above by different channel blockers, these drugs can cause arterial wall damage, thereby contributing to vascular wall structure destabilization and promoting events facilitating rupture of plaques. Collagen synthesis is regulated by ascorbic acid, which is also essential for its optimum structure as a cofactor in lysine and proline hydroxylation, a precondition for optimum crosslinking of collagen and elastin. Therefore, the main objective in this study was to evaluate effects of various types of channel blockers on intracellular accumulation and cellular functions of ascorbate, specifically in relation to formation and extracellular deposition of major collagen types relevant for vascular function. Effects of select Na- and Ca- channel blockers on collagen synthesis and deposition were evaluated in cultured human dermal fibroblasts and aortic smooth muscle cells by immunoassay. All channel blockers tested demonstrated inhibitory effects on collagen type I deposition to the ECM by fibroblasts, each to a different degree. Ascorbic acid significantly increased collagen I ECM deposition. Nifedipine (50 µM), a representative of channel blockers tested, significantly reduced ascorbic acid and ascorbyl palmitate-dependent ECM deposition of collagen type l and collagen type lV by cultured aortic smooth muscle cells. In addition, nifedipine (50 µM) significantly reduced ascorbate-dependent collagen type l and type lV synthesis by cultured aortic smooth

  3. Lipid Storage Disorders Block Lysosomal Trafficking By Inhibiting TRP Channel and Calcium Release

    OpenAIRE

    Shen, Dongbiao; Wang, Xiang; Li, Xinran; Zhang, Xiaoli; Yao, Zepeng; Dibble, Shannon; Dong, Xian-Ping; Yu, Ting; Lieberman, Andrew P.; Showalter, Hollis D.; Xu, Haoxing

    2012-01-01

    Lysosomal lipid accumulation, defects in membrane trafficking, and altered Ca2+ homeostasis are common features in many lysosomal storage diseases. Mucolipin TRP channel 1 (TRPML1) is the principle Ca2+ channel in the lysosome. Here we show that TRPML1-mediated lysosomal Ca2+ release, measured using a genetically-encoded Ca2+ indicator (GCaMP3) attached directly to TRPML1 and elicited by a potent membrane-permeable synthetic agonist, is dramatically reduced in Niemann-Pick (NP) disease cells....

  4. Antagonism of T-type calcium channels inhibits high-fat diet-induced weight gain in mice.

    Science.gov (United States)

    Uebele, Victor N; Gotter, Anthony L; Nuss, Cindy E; Kraus, Richard L; Doran, Scott M; Garson, Susan L; Reiss, Duane R; Li, Yuxing; Barrow, James C; Reger, Thomas S; Yang, Zhi-Qiang; Ballard, Jeanine E; Tang, Cuyue; Metzger, Joseph M; Wang, Sheng-Ping; Koblan, Kenneth S; Renger, John J

    2009-06-01

    The epidemics of obesity and metabolic disorders have well-recognized health and economic burdens. Pharmacologic treatments for these diseases remain unsatisfactory with respect to both efficacy and side-effect profiles. Here, we have identified a potential central role for T-type calcium channels in regulating body weight maintenance and sleep. Previously, it was shown that mice lacking CaV3.1 T-type calcium channels have altered sleep/wake activity. We found that these mice were also resistant to high-fat diet-induced weight gain, without changes in food intake or sensitivity to high-fat diet-induced disruptions of diurnal rhythm. Administration of a potent and selective antagonist of T-type calcium channels, TTA-A2, to normal-weight animals prior to the inactive phase acutely increased sleep, decreased body core temperature, and prevented high-fat diet-induced weight gain. Administration of TTA-A2 to obese rodents reduced body weight and fat mass while concurrently increasing lean muscle mass. These effects likely result from better alignment of diurnal feeding patterns with daily changes in circadian physiology and potentially an increased metabolic rate during the active phase. Together, these studies reveal what we believe to be a previously unknown role for T-type calcium channels in the regulation of sleep and weight maintenance and suggest the potential for a novel therapeutic approach to treating obesity.

  5. The ?2? Subunit and Absence Epilepsy: Beyond Calcium Channels?

    National Research Council Canada - National Science Library

    Roberta Celli; Ines Santolini; Michela Guiducci; Gilles van Luijtelaar; Pasquale Parisi; Pasquale Striano; Roberto Gradini; Giuseppe Battaglia; Richard T. Ngomba; Ferdinando Nicoletti

    2017-01-01

    .... Activation of T-type voltage-sensitive calcium channels (VSCCs) contributes to the pathological oscillatory activity of this network, and some of the first-line drugs used in the treatment of absence epilepsy inhibit T-type calcium channels. The ?2...

  6. Resveratrol Protects Against Ultraviolet A-Mediated Inhibition of the Phagocytic Function of Human Retinal Pigment Epithelial Cells Via Large-Conductance Calcium-Activated Potassium Channels

    Directory of Open Access Journals (Sweden)

    Shwu-Jiuan Sheu

    2009-07-01

    Full Text Available This study was undertaken to examine the protective effect of resveratrol on human retinal pigment epithelial (RPE cell phagocytosis against ultraviolet irradiation damage. Cultured RPE cells were exposed to ultraviolet A (UVA, 20 minutes irradiation, and treated with meclofenamic acid (30μM, 20 minutes, paxilline (100 μM, 20 minutes or resveratrol (10μM, 20 minutes. Meclofenamic acid and resveratrol were given after exposure to UVA. Pretreatment with meclofenamic acid, resveratrol or paxilline before UVA irradiation was also performed. Fluorescent latex beads were then fed for 4 hours and the phagocytotic function was assessed by flow cytometry. UVA irradiation inhibited the phagocytic function of human RPE cells. The large-conductance calcium-activated potassium channel activator meclofenamic acid ameliorated the damage caused by UVA irradiation. Pretreatment with resveratrol acid also provided protection against damage caused by UVA. Posttreatment with meclofenamic acid offered mild protection, whereas resveratrol did not. In conclusion, the red wine flavonoid resveratrol ameliorated UVA-mediated inhibition of human RPE phagocytosis. The underlying mechanism might involve the large-conductance calcium-activated potassium channels.

  7. Inhibition of transmembrane member 16A calcium-activated chloride channels by natural flavonoids contributes to flavonoid anticancer effects.

    Science.gov (United States)

    Zhang, Xuan; Li, Honglin; Zhang, Huiran; Liu, Yani; Huo, Lifang; Jia, Zhanfeng; Xue, Yucong; Sun, Xiaorun; Zhang, Wei

    2017-07-01

    Natural flavonoids are ubiquitous in dietary plants and vegetables and have been proposed to have antiviral, antioxidant, cardiovascular protective and anticancer effects. Transmembrane member 16A (TMEM16A)-encoded Ca(2+) -activated Cl(-) channels play a variety of physiological roles in many organs and tissues. Overexpression of TMEM16A is also believed to be associated with cancer progression. Therefore, inhibition of TMEM16A current may be a potential target for cancer therapy. In this study, we screened a broad spectrum of flavonoids for their inhibitory activities on TMEM16A currents. A whole-cell patch technique was used to record the currents. The BrdU assay and transwell technique were used to investigate cell proliferation and migration. At a concentration of 100 μM, 10 of 20 compounds caused significant (>50%) inhibition of TMEM16A currents. The four most potent compounds - luteolin, galangin, quercetin and fisetin - had IC50 values ranging from 4.5 to 15 μM). To examine the physiological relevance of these findings, we also studied the effects of these flavonoids on endogenous TMEM16A currents in addition to cell proliferation and migration in LA795 cancer cells. Among the flavonoids tested, we detected a highly significant correlation between TMEM16A current inhibition and cell proliferation or reduction of migration. This study demonstrates that flavonoids inhibit TMEM16A currents and suggests that flavonoids could have anticancer effects via this mechanism. © 2017 The British Pharmacological Society.

  8. Modulation of L-type calcium channels by sodium ions.

    OpenAIRE

    Balke, C W; Wier, W G

    1992-01-01

    It is universally believed that the removal of external sodium ions is without effect on calcium current. We now report that in enzymatically isolated guinea pig ventricular cells, the replacement of external sodium ions with certain other cations causes a 3- to 6-fold increase in peak L-type calcium current. The increase in current is reversibly blocked by L-type calcium-channel antagonists, not mediated by changes in internal calcium, and is inhibited by intracellular 5'-adenylyl imidodipho...

  9. 20-O-β-d-glucopyranosyl-20(S)-protopanaxadiol, a metabolite of ginseng, inhibits colon cancer growth by targeting TRPC channel-mediated calcium influx.

    Science.gov (United States)

    Hwang, Jeong Ah; Hwang, Mun Kyung; Jang, Yongwoo; Lee, Eun Jung; Kim, Jong-Eun; Oh, Mi Hyun; Shin, Dong Joo; Lim, Semi; Ji, Geun og; Oh, Uhtaek; Bode, Ann M; Dong, Zigang; Lee, Ki Won; Lee, Hyong Joo

    2013-06-01

    Abnormal regulation of Ca(2+) mediates tumorigenesis and Ca(2+) channels are reportedly deregulated in cancers, indicating that regulating Ca(2+) signaling in cancer cells is considered as a promising strategy to treat cancer. However, little is known regarding the mechanism by which Ca(2+) affects cancer cell death. Here, we show that 20-O-β-d-glucopyranosyl-20(S)-protopanaxadiol (20-GPPD), a metabolite of ginseng saponin, causes apoptosis of colon cancer cells through the induction of cytoplasmic Ca(2+). 20-GPPD decreased cell viability, increased annexin V-positive early apoptosis and induced sub-G1 accumulation and nuclear condensation of CT-26 murine colon cancer cells. Although 20-GPPD-induced activation of AMP-activated protein kinase (AMPK) played a key role in the apoptotic death of CT-26 cells, LKB1, a well-known upstream kinase of AMPK, was not involved in this activation. To identify the upstream target of 20-GPPD for activating AMPK, we examined the effect of Ca(2+) on apoptosis of CT-26 cells. A calcium chelator recovered 20-GPPD-induced AMPK phosphorylation and CT-26 cell death. Confocal microscopy showed that 20-GPPD increased Ca(2+) entry into CT-26 cells, whereas a transient receptor potential canonical (TRPC) blocker suppressed Ca(2+) entry. When cells were treated with a TRPC blocker plus an endoplasmic reticulum (ER) calcium blocker, 20-GPPD-induced calcium influx was completely inhibited, suggesting that the ER calcium store, as well as TRPC, was involved. In vivo mouse CT-26 allografts showed that 20-GPPD significantly suppressed tumor growth, volume and weight in a dose-dependent manner. Collectively, 20-GPPD exerts potent anticarcinogenic effects on colon carcinogenesis by increasing Ca(2+) influx, mainly through TRPC channels, and by targeting AMPK. Copyright © 2013 Elsevier Inc. All rights reserved.

  10. Chronic inhibition of endoplasmic reticulum calcium-release channels and calcium-ATPase lengthens the period of hepatic clock gene Per1

    Directory of Open Access Journals (Sweden)

    Díaz-Muñoz Mauricio

    2011-07-01

    Full Text Available Abstract Background The role played by calcium as a regulator of circadian rhythms is not well understood. The effect of the pharmacological inhibition of the ryanodine receptor (RyR, inositol 1,4,5-trisphosphate receptor (IP3R, and endoplasmic-reticulum Ca2+-ATPase (SERCA, as well as the intracellular Ca2+-chelator BAPTA-AM was explored on the 24-h rhythmicity of the liver-clock protein PER1 in an experimental model of circadian synchronization by light and restricted-feeding schedules. Methods Liver explants from Period1-luciferase (Per1-luc transgenic rats with either free food access or with a restricted meal schedule were treated for several days with drugs to inhibit the activity of IP3Rs (2-APB, RyRs (ryanodine, or SERCA (thapsigargin as well as to suppress intracellular calcium fluctuations (BAPTA-AM. The period of Per1-luc expression was measured during and after drug administration. Results Liver explants from rats fed ad libitum showed a lengthened period in response to all the drugs tested. The pharmacological treatments of the explants from meal-entrained rats induced the same pattern, with the exception of the ryanodine treatment which, unexpectedly, did not modify the Per1-luc period. All effects associated with drug application were reversed after washout, indicating that none of the pharmacological treatments was toxic to the liver cultures. Conclusions Our data suggest that Ca2+ mobilized from internal deposits modulates the molecular circadian clock in the liver of rats entrained by light and by restricted meal access.

  11. Antidepressants Rescue Stress-Induced Disruption of Synaptic Plasticity via Serotonin Transporter-Independent Inhibition of L-Type Calcium Channels.

    Science.gov (United States)

    Normann, Claus; Frase, Sibylle; Haug, Verena; von Wolff, Gregor; Clark, Kristin; Münzer, Patrick; Dorner, Alexandra; Scholliers, Jonas; Horn, Max; Vo Van, Tanja; Seifert, Gabriel; Serchov, Tsvetan; Biber, Knut; Nissen, Christoph; Klugbauer, Norbert; Bischofberger, Josef

    2017-10-19

    Long-term synaptic plasticity is a basic ability of the brain to dynamically adapt to external stimuli and regulate synaptic strength and ultimately network function. It is dysregulated by behavioral stress in animal models of depression and in humans with major depressive disorder. Antidepressants have been shown to restore disrupted synaptic plasticity in both animal models and humans; however, the underlying mechanism is unclear. We examined modulation of synaptic plasticity by selective serotonin reuptake inhibitors (SSRIs) in hippocampal brain slices from wild-type rats and serotonin transporter (SERT) knockout mice. Recombinant voltage-gated calcium (Ca 2+ ) channels in heterologous expression systems were used to determine the modulation of Ca 2+ channels by SSRIs. We tested the behavioral effects of SSRIs in the chronic behavioral despair model of depression both in the presence and in the absence of SERT. SSRIs selectively inhibited hippocampal long-term depression. The inhibition of long-term depression by SSRIs was mediated by a direct block of voltage-activated L-type Ca 2+ channels and was independent of SERT. Furthermore, SSRIs protected both wild-type and SERT knockout mice from behavioral despair induced by chronic stress. Finally, long-term depression was facilitated in animals subjected to the behavioral despair model, which was prevented by SSRI treatment. These results showed that antidepressants protected synaptic plasticity and neuronal circuitry from the effects of stress via a modulation of Ca 2+ channels and synaptic plasticity independent of SERT. Thus, L-type Ca 2+ channels might constitute an important signaling hub for stress response and for pathophysiology and treatment of depression. Copyright © 2017 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

  12. Activation of MrgC receptor inhibits N-type calcium channels in small-diameter primary sensory neurons in mice.

    Science.gov (United States)

    Li, Zhe; He, Shao-Qiu; Xu, Qian; Yang, Fei; Tiwari, Vinod; Liu, Qin; Tang, Zongxiang; Han, Liang; Chu, Yu-Xia; Wang, Yun; Hin, Niyada; Tsukamoto, Takashi; Slusher, Barbara; Guan, Xiaowei; Wei, Feng; Raja, Srinivasa N; Dong, Xinzhong; Guan, Yun

    2014-08-01

    Mas-related G-protein-coupled receptor subtype C (mouse MrgC11 and rat rMrgC), expressed specifically in small-diameter primary sensory neurons, may constitute a novel pain inhibitory mechanism. We have shown previously that intrathecal administration of MrgC-selective agonists can strongly attenuate persistent pain in various animal models. However, the underlying mechanisms for MrgC agonist-induced analgesia remain elusive. Here, we conducted patch-clamp recordings to test the effect of MrgC agonists on high-voltage-activated (HVA) calcium current in small-diameter dorsal root ganglion (DRG) neurons. Using pharmacological approaches, we show for the first time that an MrgC agonist (JHU58) selectively and dose-dependently inhibits N-type, but not L- or P/Q-type, HVA calcium channels in mouse DRG neurons. Activation of HVA calcium channels is important to neurotransmitter release and synaptic transmission. Patch-clamp recordings in spinal cord slices showed that JHU58 attenuated the evoked excitatory postsynaptic currents in substantia gelatinosa (SG) neurons in wild-type mice, but not in Mrg knockout mice, after peripheral nerve injury. These findings indicate that activation of endogenously expressed MrgC receptors at central terminals of primary sensory fibers may decrease peripheral excitatory inputs onto SG neurons. Together, these results suggest potential cellular and molecular mechanisms that may contribute to intrathecal MrgC agonist-induced analgesia. Because MrgC shares substantial genetic homogeneity with human MrgX1, our findings may suggest a rationale for developing intrathecally delivered MrgX1 receptor agonists to treat pathological pain in humans and provide critical insight regarding potential mechanisms that may underlie its analgesic effects. Copyright © 2014 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

  13. 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...

  14. Nitric oxide synthase inhibition exaggerates the hypotensive response to ghrelin: role of calcium-activated potassium channels.

    Science.gov (United States)

    Shinde, Urmila A; Desai, Kaushik M; Yu, Changhua; Gopalakrishnan, Venkat

    2005-04-01

    To investigate the mechanism underlying the observation that infusion of the growth hormone secretagogue peptide, ghrelin, produces a decrease in mean arterial pressure (MAP) with no change in heart rate. The effect of a single bolus infusion of ghrelin (12 nmol/kg intravenously) on the changes in MAP and heart rate was determined in 12-week-old male anaesthetized Sprague-Dawley rats subjected to pretreatment with either the nitric oxide synthase (NOS) inhibitor, N-nitro-L-arginine methyl ester (L-NAME; 0.7 mg/ml by mouth for 5 days), or vehicle (control). Ghrelin produced a significant decrease in MAP at 20 min (P ghrelin-evoked decrease in MAP was much greater (P ghrelin in both control and NOS-inhibited rats. A sodium nitroprusside-induced decrease in MAP was unaffected in the presence of apamin-ChTX, but acetylcholine-evoked hypotension was significantly reduced in both groups. These data suggest that the Ca-activated, K-channel-mediated, ghrelin-evoked decrease in MAP may be significant in states of endothelial dysfunction associated with reduced nitric oxide availability.

  15. Inhibition of CaV3.2 T-type calcium channels in peripheral sensory neurons contributes to analgesic properties of epipregnanolone.

    Science.gov (United States)

    Ayoola, Christine; Hwang, Sung Mi; Hong, Sung Jun; Rose, Kirstin E; Boyd, Christopher; Bozic, Neda; Park, Ji-Yong; Osuru, Hari Prasad; DiGruccio, Michael R; Covey, Douglas F; Jevtovic-Todorovic, Vesna; Todorovic, Slobodan M

    2014-09-01

    T-type calcium channels (T-channels) play an important role in controlling excitability of nociceptors. We have previously shown that a synthetic series of 5β-reduced steroids induce a voltage-dependent blockade of T-currents in rat dorsal root ganglia (DRG) cells in vitro and induce potent analgesia to thermal stimuli in rats in vivo (Mol Pharmacol 66:1223-1235, 2004). Here, we investigated the effects of the endogenous 5β-reduced neuroactive steroid molecule, epipregnanolone [(3β,5β)-3-hydroxypregnan-20-one], on peripheral nociception. We used acutely dissociated DRG cells in vitro from adult rats as well as in vivo pain studies in mice and rats to investigate the effects of epipregnanolone on DRG T-channels. We found that epipregnanolone reversibly blocked DRG T-currents with a half-maximal inhibitory concentration (IC50) of 2 μM and stabilized the channel in the inactive state. However, sodium, potassium, and gamma-aminobutyric acid (GABA)-gated ionic currents were not sensitive to the blocking effects of epipregnanolone even at 10 μM. In ensuing in vivo studies, we found that intraplantar (i.pl.) injections of epipregnanolone directly into peripheral receptive fields reduced responses to nociceptive heat stimuli in rats in a dose-dependent fashion. Furthermore, i.pl. epipregnanolone injections effectively reduced responses to peripheral nociceptive thermal and mechanical stimuli in wild-type mice but had no effect on the responses of CaV3.2 knockout mice. We conclude that the inhibition of peripheral CaV3.2 T-channels contributes to the potent analgesic effect of the endogenous steroid epipregnanolone.

  16. Estradiol inhibits depolarization-evoked exocytosis in PC12 cells via N-type voltage-gated calcium channels.

    NARCIS (Netherlands)

    Adams, K.L.; Maxson, M.M.; Mellander, L.; Westerink, R.H.S.|info:eu-repo/dai/nl/239425952; Ewing, A.G.

    2010-01-01

    Fast neuromodulatory effects of 17-β-estradiol (E2) on cytosolic calcium concentration ([Ca(2+)](i)) have been reported in many cell types, but little is known about its direct effects on vesicular neurotransmitter secretion (exocytosis). We examined the effects of E2 on depolarization-evoked

  17. Localization and pharmacological characterization of voltage dependent calcium channels in cultured neocortical neurons

    DEFF Research Database (Denmark)

    Timmermann, D B; Lund, Trine Meldgaard; Belhage, B

    2001-01-01

    The physiological significance and subcellular distribution of voltage dependent calcium channels was defined using calcium channel blockers to inhibit potassium induced rises in cytosolic calcium concentration in cultured mouse neocortical neurons. The cytosolic calcium concentration was measured...... channels were differentially distributed in somata, neurites and nerve terminals. omega-conotoxin MVIIC (omega-CgTx MVIIC) inhibited approximately 40% of the Ca(2+)-rise in both somata and neurites and 60% of the potassium induced [3H]GABA release, indicating that the Q-type channel is the quantitatively...... using the fluorescent calcium chelator fura-2. The types of calcium channels present at the synaptic terminal were determined by the inhibitory action of calcium channel blockers on potassium-induced [3H]GABA release in the same cell preparation. L-, N-, P-, Q- and R-/T-type voltage dependent calcium...

  18. Inhibition of Intermediate-Conductance Calcium-Activated K Channel (KCa3.1) and Fibroblast Mitogenesis by α-Linolenic Acid and Alterations of Channel Expression in the Lysosomal Storage Disorders, Fabry Disease, and Niemann Pick C.

    Science.gov (United States)

    Oliván-Viguera, Aida; Lozano-Gerona, Javier; López de Frutos, Laura; Cebolla, Jorge J; Irún, Pilar; Abarca-Lachen, Edgar; García-Malinis, Ana J; García-Otín, Ángel Luis; Gilaberte, Yolanda; Giraldo, Pilar; Köhler, Ralf

    2017-01-01

    The calcium/calmodulin-gated KCa3.1 channel regulates normal and abnormal mitogenesis by controlling K+-efflux, cell volume, and membrane hyperpolarization-driven calcium-entry. Recent studies suggest modulation of KCa3.1 by omega-3 fatty acids as negative modulators and impaired KCa3.1 functions in the inherited lysosomal storage disorder (LSD), Fabry disease (FD). In the first part of present study, we characterize KCa3.1 in murine and human fibroblasts and test the impact of omega-3 fatty acids on fibroblast proliferation. In the second, we study whether KCa3.1 is altered in the LSDs, FD, and Niemann-Pick disease type C (NPC). Our patch-clamp and mRNA-expression studies on murine and human fibroblasts show functional expression of KCa3.1. KCa currents display the typical pharmacological fingerprint of KCa3.1: Ca2+-activation, potentiation by the positive-gating modulators, SKA-31 and SKA-121, and inhibition by TRAM-34, Senicapoc (ICA-17043), and the negative-gating modulator, 13b. Considering modulation by omega-3 fatty acids we found that α-linolenic acid (α-LA) and docosahexanenoic acid (DHA) inhibit KCa3.1 currents and strongly reduce fibroblast growth. The α-LA-rich linseed oil and γ-LA-rich borage oil at 0.5% produce channel inhibition while α-LA/γ-LA-low oils has no anti-proliferative effect. Concerning KCa3.1 in LSD, mRNA expression studies, and patch-clamp on primary fibroblasts from FD and NPC patients reveal lower KCa3.1-gene expression and membrane expression than in control fibroblasts. In conclusion, the omega-3 fatty acid, α-LA, and α-LA/γ-LA-rich plant oils, inhibit fibroblast KCa3.1 channels and mitogenesis. Reduced fibroblast KCa3.1 functions are a feature and possible biomarker of cell dysfunction in FD and NPC and supports the concept that biased lipid metabolism is capable of negatively modulating KCa3.1 expression.

  19. Voltage-Gated Calcium Channels in Nociception

    Science.gov (United States)

    Yasuda, Takahiro; Adams, David J.

    Voltage-gated calcium channels (VGCCs) are a large and functionally diverse group of membrane ion channels ubiquitously expressed throughout the central and peripheral nervous systems. VGCCs contribute to various physiological processes and transduce electrical activity into other cellular functions. This chapter provides an overview of biophysical properties of VGCCs, including regulation by auxiliary subunits, and their physiological role in neuronal functions. Subsequently, then we focus on N-type calcium (Cav2.2) channels, in particular their diversity and specific antagonists. We also discuss the role of N-type calcium channels in nociception and pain transmission through primary sensory dorsal root ganglion neurons (nociceptors). It has been shown that these channels are expressed predominantly in nerve terminals of the nociceptors and that they control neurotransmitter release. To date, important roles of N-type calcium channels in pain sensation have been elucidated genetically and pharmacologically, indicating that specific N-type calcium channel antagonists or modulators are particularly useful as therapeutic drugs targeting chronic and neuropathic pain.

  20. A toxin from the spider Phoneutria nigriventer that blocks calcium channels coupled to exocytosis

    Science.gov (United States)

    Guatimosim, C; Romano-Silva, M A; Cruz, J S; Beirão, P S L; Kalapothakis, E; Moraes-Santos, T; Cordeiro, M N; Diniz, C R; Gomez, M V; Prado, M A M

    1997-01-01

    The aim of the present experiments was to investigate the pharmacological action of a toxin from the spider Phoneutria nigriventer, Tx3-3, on the function of calcium channels that control exocytosis of synaptic vesicles. Tx3-3, in confirmation of previous work, diminished the intracellular calcium increase induced by membrane depolarization with KCl (25 mM) in rat cerebrocortical synaptosomes. The toxin was very potent (IC50 0.9 nM) at inhibiting calcium channels that regulate calcium entry in synaptosomes. In addition, Tx3-3 blocked the exocytosis of synaptic vesicles, as measured with the fluorescent dye FM1-43. Using ω-toxins that interact selectively with distinct neuronal calcium channels, we investigated whether the target of Tx3-3 overlaps with known channels that mediate exocytosis. The results indicate that the main population of voltage-sensitive calcium channels altered by Tx3-3 can also be inhibited by ω-agatoxin IVA, an antagonist of P/Q calcium channels. ω-conotoxin GVIA, which inhibits N type calcium channels did not decrease significantly the entry of calcium or exocytosis of synaptic vesicles in depolarized synaptosomes. It is concluded that Tx3-3 potently inhibits ω-agatoxin IVA-sensitive calcium channels, which are involved in controlling exocytosis in rat brain cortical synaptosomes. PMID:9351520

  1. Effect of activation on adhesion of flowing neutrophils to cultured endothelium: time course and inhibition by a calcium channel blocker (nitrendipine).

    OpenAIRE

    Perry, I.; Buttrum, S. M.; Nash, G. B.

    1993-01-01

    1. Adhesion of neutrophils to vascular endothelium plays an important role in inflammation and thrombosis. Modulation of adhesion may be therapeutic in these conditions. 2. A flow model was used to quantify adhesion of neutrophils to human cultured umbilical vein endothelial cells. The time course of the neutrophil response to activation by N-formyl-methionyl-leucylphenylalanine (fMLP, 10(-7) M) was studied and the inhibitory effects of the calcium-channel blockers, nitrendipine and nifedipin...

  2. Localization and pharmacological characterization of voltage dependent calcium channels in cultured neocortical neurons

    DEFF Research Database (Denmark)

    Timmermann, D B; Lund, T M; Belhage, B

    2001-01-01

    using the fluorescent calcium chelator fura-2. The types of calcium channels present at the synaptic terminal were determined by the inhibitory action of calcium channel blockers on potassium-induced [3H]GABA release in the same cell preparation. L-, N-, P-, Q- and R-/T-type voltage dependent calcium...... channels were differentially distributed in somata, neurites and nerve terminals. omega-conotoxin MVIIC (omega-CgTx MVIIC) inhibited approximately 40% of the Ca(2+)-rise in both somata and neurites and 60% of the potassium induced [3H]GABA release, indicating that the Q-type channel is the quantitatively...... in cytosolic calcium concentration. The results of this investigation demonstrate that pharmacologically distinct types of voltage dependent calcium channels are differentially localized in cell bodies, neurites and nerve terminals of mouse cortical neurons but that the Q-type calcium channel appears...

  3. Inhibition of late sodium current suppresses calcium-related ventricular arrhythmias by reducing the phosphorylation of CaMK-II and sodium channel expressions.

    Science.gov (United States)

    Wei, Xiao-Hong; Yu, Shan-Dong; Ren, Lu; Huang, Si-Hui; Yang, Qiao-Mei; Wang, Ping; Chu, Yan-Peng; Yang, Wei; Ding, Yan-Sheng; Huo, Yong; Wu, Lin

    2017-04-20

    Cardiac arrhythmias associated with intracellular calcium inhomeostasis are refractory to antiarrhythmic therapy. We hypothesized that late sodium current (I Na) contributed to the calcium-related arrhythmias. Monophasic action potential duration at 90% completion of repolarization (MAPD90) was significantly increased and ventricular arrhythmias were observed in hearts with increased intracellular calcium concentration ([Ca(2+)]i) by using Bay K 8644, and the increase became greater in hearts treated with a combination of ATX-II and Bay K 8644 compared to Bay K 8644 alone. The prolongations caused by Bay K 8644 and frequent episodes of ventricular tachycardias, both in absence and presence of ATX-II, were significantly attenuated or abolished by late I Na inhibitors TTX and eleclazine. In rabbit ventricular myocytes, Bay K 8644 increased I CaL density, calcium transient and myocyte contraction. TTX and eleclazine decreased the amplitude of late I Na, the reverse use dependence of MAPD90 at slower heart rate, and attenuated the increase of intracellular calcium transient and myocyte contraction. TTX diminished the phosphorylation of CaMKII-δ and Nav 1.5 in hearts treated with Bay K 8644 and ATX-II. In conclusion, late I Na contributes to ventricular arrhythmias and its inhibition is plausible to treat arrhythmias in hearts with increased [Ca(2+)]i.

  4. Effects of Calcium Ion, Calpains, and Calcium Channel Blockers on Retinitis Pigmentosa

    Directory of Open Access Journals (Sweden)

    Mitsuru Nakazawa

    2011-01-01

    Full Text Available Recent advances in molecular genetic studies have revealed many of the causative genes of retinitis pigmentosa (RP. These achievements have provided clues to the mechanisms of photoreceptor degeneration in RP. Apoptosis is known to be a final common pathway in RP and, therefore, a possible therapeutic target for photoreceptor rescue. However, apoptosis is not a single molecular cascade, but consists of many different reactions such as caspase-dependent and caspase-independent pathways commonly leading to DNA fractionation and cell death. The intracellular concentration of calcium ions is also known to increase in apoptosis. These findings suggest that calpains, one of the calcium-dependent proteinases, play some roles in the process of photoreceptor apoptosis and that calcium channel antagonists may potentially inhibit photoreceptor apoptosis. Herein, the effects of calpains and calcium channel antagonists on photoreceptor degeneration are reviewed.

  5. The α2δ subunit and absence epilepsy: Beyond calcium channels?

    National Research Council Canada - National Science Library

    Celli, R; Santolini, I; Guiducci, M; Luijtelaar, E.L.J.M. van; Parisi, P; Striano, P; Gradini, R; Battaglia, G; Ngomba, R.T; Nicoletti, F

    2017-01-01

    .... Activation of T-type voltage-sensitive calcium channels (VSCCs) contributes to the pathological oscillatory activity of this network, and some of the first-line drugs used in the treatment of absence epilepsy inhibit T-type calcium channels. The α2δ...

  6. Computational study of a calcium release-activated calcium channel

    Science.gov (United States)

    Talukdar, Keka; Shantappa, Anil

    2016-05-01

    The naturally occurring proteins that form hole in membrane are commonly known as ion channels. They play multiple roles in many important biological processes. Deletion or alteration of these channels often leads to serious problems in the physiological processes as it controls the flow of ions through it. The proper maintenance of the flow of ions, in turn, is required for normal health. Here we have investigated the behavior of a calcium release-activated calcium ion channel with pdb entry 4HKR in Drosophila Melanogaster. The equilibrium energy as well as molecular dynamics simulation is performed first. The protein is subjected to molecular dynamics simulation to find their energy minimized value. Simulation of the protein in the environment of water and ions has given us important results too. The solvation energy is also found using Charmm potential.

  7. Inhibition of large conductance calcium-dependent potassium ...

    African Journals Online (AJOL)

    We tested the hypothesis that Rho-kinase inhibits the large-conductance, calcium and voltage dependent potassium (BKCa) channels thereby promoting vasoconstriction. Our results show that the Rho-kinase inhibitor, Y-27632, induced concentration-dependent relaxation in rat mesenteric artery. The selective BKCa ...

  8. Pharmacologic inhibition of small-conductance calcium-activated potassium (SK) channels by NS8593 reveals atrial antiarrhythmic potential in horses

    DEFF Research Database (Denmark)

    Haugaard, Maria Mathilde; Hesselkilde, Eva Zander; Pehrson, Steen Michael

    2015-01-01

    . The electrophysiologic and anti-AF effects of the relative selective SK channel inhibitor NS8593 (5 mg/kg IV) were evaluated in anesthetized horses, focusing on the potential of NS8593 to terminate acute pacing-induced AF, drug-induced changes in atrial effective refractory period, AF duration and vulnerability...... and ventricular cardiomyocytes and contribute to atrial repolarization. Inhibition by NS8593 terminates pacing-induced AF of short duration and decreases AF duration and vulnerability without affecting ventricular conduction and repolarization. Thus, inhibition by NS8593 demonstrates clear atrial antiarrhythmic...

  9. Discovery and Development of Calcium Channel Blockers

    Directory of Open Access Journals (Sweden)

    Théophile Godfraind

    2017-05-01

    Full Text Available In the mid 1960s, experimental work on molecules under screening as coronary dilators allowed the discovery of the mechanism of calcium entry blockade by drugs later named calcium channel blockers. This paper summarizes scientific research on these small molecules interacting directly with L-type voltage-operated calcium channels. It also reports on experimental approaches translated into understanding of their therapeutic actions. The importance of calcium in muscle contraction was discovered by Sidney Ringer who reported this fact in 1883. Interest in the intracellular role of calcium arose 60 years later out of Kamada (Japan and Heibrunn (USA experiments in the early 1940s. Studies on pharmacology of calcium function were initiated in the mid 1960s and their therapeutic applications globally occurred in the the 1980s. The first part of this report deals with basic pharmacology in the cardiovascular system particularly in isolated arteries. In the section entitled from calcium antagonists to calcium channel blockers, it is recalled that drugs of a series of diphenylpiperazines screened in vivo on coronary bed precontracted by angiotensin were initially named calcium antagonists on the basis of their effect in depolarized arteries contracted by calcium. Studies on arteries contracted by catecholamines showed that the vasorelaxation resulted from blockade of calcium entry. Radiochemical and electrophysiological studies performed with dihydropyridines allowed their cellular targets to be identified with L-type voltage-operated calcium channels. The modulated receptor theory helped the understanding of their variation in affinity dependent on arterial cell membrane potential and promoted the terminology calcium channel blocker (CCB of which the various chemical families are introduced in the paper. In the section entitled tissue selectivity of CCBs, it is shown that characteristics of the drug, properties of the tissue, and of the stimuli are

  10. D1 receptors physically interact with N-type calcium channels to regulate channel distribution and dendritic calcium entry.

    Science.gov (United States)

    Kisilevsky, Alexandra E; Mulligan, Sean J; Altier, Christophe; Iftinca, Mircea C; Varela, Diego; Tai, Chao; Chen, Lina; Hameed, Shahid; Hamid, Jawed; Macvicar, Brian A; Zamponi, Gerald W

    2008-05-22

    Dopamine signaling through D1 receptors in the prefrontal cortex (PFC) plays a critical role in the maintenance of higher cognitive functions, such as working memory. At the cellular level, these functions are predicated to involve alterations in neuronal calcium levels. The dendrites of PFC neurons express D1 receptors and N-type calcium channels, yet little information exists regarding their coupling. Here, we show that D1 receptors potently inhibit N-type channels in dendrites of rat PFC neurons. Using coimmunoprecipitation, we demonstrate the existence of a D1 receptor-N-type channel signaling complex in this region, and we provide evidence for a direct receptor-channel interaction. Finally, we demonstrate the importance of this complex to receptor-channel colocalization in heterologous systems and in PFC neurons. Our data indicate that the N-type calcium channel is an important physiological target of D1 receptors and reveal a mechanism for D1 receptor-mediated regulation of cognitive function in the PFC.

  11. Functional and pharmacological consequences of the distribution of voltage-gated calcium channels in the renal blood vessels

    DEFF Research Database (Denmark)

    Hansen, P B L

    2013-01-01

    Calcium channel blockers are widely used to treat hypertension because they inhibit voltage-gated calcium channels that mediate transmembrane calcium influx in, for example, vascular smooth muscle and cardiomyocytes. The calcium channel family consists of several subfamilies, of which the L......-type is usually associated with vascular contractility. However, the L-, T- and P-/Q-types of calcium channels are present in the renal vasculature and are differentially involved in controlling vascular contractility, thereby contributing to regulation of kidney function and blood pressure. In the preglomerular...... vascular bed, all the three channel families are present. However, the T-type channel is the only channel in cortical efferent arterioles which is in contrast to the juxtamedullary efferent arteriole, and that leads to diverse functional effects of L- and T-type channel inhibition. Furthermore...

  12. Inhibition of cancer cell growth by exposure to a specific time-varying electromagnetic field involves T-type calcium channels.

    Directory of Open Access Journals (Sweden)

    Carly A Buckner

    Full Text Available Electromagnetic field (EMF exposures affect many biological systems. The reproducibility of these effects is related to the intensity, duration, frequency, and pattern of the EMF. We have shown that exposure to a specific time-varying EMF can inhibit the growth of malignant cells. Thomas-EMF is a low-intensity, frequency-modulated (25-6 Hz EMF pattern. Daily, 1 h, exposures to Thomas-EMF inhibited the growth of malignant cell lines including B16-BL6, MDA-MB-231, MCF-7, and HeLa cells but did not affect the growth of non-malignant cells. Thomas-EMF also inhibited B16-BL6 cell proliferation in vivo. B16-BL6 cells implanted in syngeneic C57b mice and exposed daily to Thomas-EMF produced smaller tumours than in sham-treated controls. In vitro studies showed that exposure of malignant cells to Thomas-EMF for > 15 min promoted Ca(2+ influx which could be blocked by inhibitors of voltage-gated T-type Ca(2+ channels. Blocking Ca(2+ uptake also blocked Thomas-EMF-dependent inhibition of cell proliferation. Exposure to Thomas-EMF delayed cell cycle progression and altered cyclin expression consistent with the decrease in cell proliferation. Non-malignant cells did not show any EMF-dependent changes in Ca(2+ influx or cell growth. These data confirm that exposure to a specific EMF pattern can affect cellular processes and that exposure to Thomas-EMF may provide a potential anti-cancer therapy.

  13. Inhibition of cancer cell growth by exposure to a specific time-varying electromagnetic field involves T-type calcium channels.

    Science.gov (United States)

    Buckner, Carly A; Buckner, Alison L; Koren, Stan A; Persinger, Michael A; Lafrenie, Robert M

    2015-01-01

    Electromagnetic field (EMF) exposures affect many biological systems. The reproducibility of these effects is related to the intensity, duration, frequency, and pattern of the EMF. We have shown that exposure to a specific time-varying EMF can inhibit the growth of malignant cells. Thomas-EMF is a low-intensity, frequency-modulated (25-6 Hz) EMF pattern. Daily, 1 h, exposures to Thomas-EMF inhibited the growth of malignant cell lines including B16-BL6, MDA-MB-231, MCF-7, and HeLa cells but did not affect the growth of non-malignant cells. Thomas-EMF also inhibited B16-BL6 cell proliferation in vivo. B16-BL6 cells implanted in syngeneic C57b mice and exposed daily to Thomas-EMF produced smaller tumours than in sham-treated controls. In vitro studies showed that exposure of malignant cells to Thomas-EMF for > 15 min promoted Ca(2+) influx which could be blocked by inhibitors of voltage-gated T-type Ca(2+) channels. Blocking Ca(2+) uptake also blocked Thomas-EMF-dependent inhibition of cell proliferation. Exposure to Thomas-EMF delayed cell cycle progression and altered cyclin expression consistent with the decrease in cell proliferation. Non-malignant cells did not show any EMF-dependent changes in Ca(2+) influx or cell growth. These data confirm that exposure to a specific EMF pattern can affect cellular processes and that exposure to Thomas-EMF may provide a potential anti-cancer therapy.

  14. Structures and functions of calcium channel beta subunits.

    Science.gov (United States)

    Birnbaumer, L; Qin, N; Olcese, R; Tareilus, E; Platano, D; Costantin, J; Stefani, E

    1998-08-01

    Calcium channel beta subunits have profound effects on how alpha1 subunits perform. In this article we summarize our present knowledge of the primary structures of beta subunits as deduced from cDNAs and illustrate their different properties. Upon co-expression with alpha1 subunits, the effects of beta subunits vary somewhat between L-type and non-L-type channels mostly because the two types of channels have different responses to voltage which are affected by beta subunits, such as long-lasting prepulse facilitation of alpha1C (absent in alpha1E) and inhibition by G protein betagamma dimer of alpha1E, absent in alpha1C. One beta subunit, a brain beta2a splice variant that is palmitoylated, has several effects not seen with any of the others, and these are due to palmitoylation. We also illustrate the finding that functional expression of alpha1 in oocytes requires a beta subunit even if the final channel shows no evidence for its presence. We propose two structural models for Ca2+ channels to account for "alpha1 alone" channels seen in cells with limited beta subunit expression. In one model, beta dissociates from the mature alpha1 after proper folding and membrane insertion. Regulated channels seen upon co-expression of high levels of beta would then have subunit composition alpha1beta. In the other model, the "chaperoning" beta remains associated with the mature channel and "alpha1 alone" channels would in fact be alpha1beta channels. Upon co-expression of high levels of beta the regulated channels would have composition [alpha1beta]beta.

  15. Calcium channel blocker inhibition of AGE and RAGE axis limits renal injury in nondiabetic patients with stage I or II chronic kidney disease.

    Science.gov (United States)

    Nakamura, Tsukasa; Sato, Eiichi; Fujiwara, Nobuharu; Kawagoe, Yasuhiro; Koide, Hikaru; Ueda, Yoshihiko; Takeuchi, Masayoshi; Yamagishi, Sho-ichi

    2011-06-01

    There is a growing body of evidence that advanced glycation end products (AGE) and their receptor (RAGE) system are implicated in chronic kidney disease (CKD). We have previously found that a long-acting calcium channel blocker, azelnidipine, but not amlodipine, improves renal injury in CKD patients. However, little is known about the effect of azelnidipine on the AGE-RAGE axis in humans. In this study, we examined whether azelnidipine addition could have renoprotective properties in hypertensive CKD patients by reducing serum levels of AGE and soluble form of RAGE (sRAGE). Thirty nondiabetic stage I or II CKD patients who had already been treated with angiotensin II receptor blockers were enrolled in this study. We hypothesized that azelnidipine treatment could limit renal injury partly by blocking the AGE-RAGE axis. Patients were randomly divided into 2 groups; one group was treated with 16 mg azelnidipine and the other with 5 mg amlodipine once daily. They were followed up for 6 months. Proteinuria was positively correlated with circulating AGE and sRAGE levels in our subjects. Both drugs exhibited comparable and significant blood pressure (BP)-lowering effects. Although neither of them affected glucose, glycated hemoglobin, lipid levels, and estimated glomerular filtration rate, treatment with azelnidipine, but not amlodipine, decreased circulating AGE, sRAGE, proteinuria, and urinary levels of liver-type fatty acid binding protein, a marker of tubular injury, in a BP-lowering-independent manner. Our present results suggest that azelnidipine may exert renoprotective properties in nondiabetic hypertensive CKD patients via its unique inhibitory effects on the AGE-RAGE axis. © 2011 Wiley Periodicals, Inc.

  16. Inhibition of late sodium current suppresses calcium-related ventricular arrhythmias by reducing the phosphorylation of CaMK-II and sodium channel expressions

    OpenAIRE

    Xiao-Hong Wei; Shan-Dong Yu; Lu Ren; Si-Hui Huang; Qiao-Mei Yang; Ping Wang; Yan-Peng Chu; Wei Yang; Yan-Sheng Ding; Yong Huo; Lin Wu

    2017-01-01

    Cardiac arrhythmias associated with intracellular calcium inhomeostasis are refractory to antiarrhythmic therapy. We hypothesized that late sodium current (I Na) contributed to the calcium-related arrhythmias. Monophasic action potential duration at 90% completion of repolarization (MAPD90) was significantly increased and ventricular arrhythmias were observed in hearts with increased intracellular calcium concentration ([Ca2+]i) by using Bay K 8644, and the increase became greater in hearts t...

  17. Nocistatin inhibits pregnant rat uterine contractions in vitro: roles of calcitonin gene-related peptide and calcium-dependent potassium channel.

    Science.gov (United States)

    Deák, Beáta H; Klukovits, Anna; Tekes, Kornélia; Ducza, Eszter; Falkay, George; Gáspár, Róbert

    2013-08-15

    The endogenous neuropeptide nociceptin/orphanin FQ, translated from the prepronociceptin gene, exerts a contraction-inhibitory effect on the rat uterus. As nocistatin has been reported to cause functional antagonism of the pro-nociceptive effects of nociceptin, we set out to investigate its effects on the pregnant rat uterus and to elucidate its signalling pathway. The expression of prepronociceptin mRNA in the uterus and nocistatin levels in the uterus and the plasma were confirmed by RT-PCR and radioimmunoassay. The uterine levels of prepronociceptin mRNA and nocistatin were significantly increased by the last day of pregnancy, while the plasma nocistatin levels remained unchanged. In the isolated organ bath studies nocistatin inhibited the prostaglandin- and the KCl-evoked contractions in the uterus dose-dependently. This latter effect was decreased by preincubation with capsaicin. Incubation with calcitonin gene-related peptide after capsaicin treatment caused an elevation in the contraction-inhibitory effect of nocistatin. The effect of nocistatin was also decreased by the Ca(2+)-dependent K(+) channel inhibitor paxilline, against spontaneous uterine contractions. Nociceptin potentiated the action of nocistatin. Naloxone decreased the effect of nocistatin administered either alone or in combination with nociceptin. In Ca(2+)-poor environment, this effect of naloxone was suspended. Enzyme immunoassay for the uterine intracellular cAMP levels partially confirmed the results of in vitro contractility studies. We conclude that nocistatin, generated locally in the uterus, exerts an inhibitory effect, the mechanism being mediated in part by Ca(2+)-dependent K(+) channels, the elevation of cAMP levels and sensory neuropeptides. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. Different calcium sources control somatic versus dendritic SK channel activation during action potentials.

    Science.gov (United States)

    Jones, Scott L; Stuart, Greg J

    2013-12-11

    Small-conductance calcium-activated potassium (SK) channels play an important role in regulating neuronal excitability. While SK channels at the soma have long been known to contribute to the medium afterhyperpolarization (mAHP), recent evidence indicates they also regulate NMDA receptor activation in dendritic spines. Here we investigate the activation of SK channels in spines and dendrites of rat cortical pyramidal neurons during action potentials (APs), and compare this to SK channel activation at the soma. Using confocal calcium imaging, we demonstrate that the inhibition of SK channels with apamin results in a location-dependent increase in calcium influx into dendrites and spines during backpropagating APs (average increase, ~40%). This effect was occluded by block of R-type voltage-dependent calcium channels (VDCCs), but not by inhibition of N- or P/Q-type VDCCs, or block of calcium release from intracellular stores. During these experiments, we noticed that the calcium indicator (Oregon Green BAPTA-1) blocked the mAHP. Subsequent experiments using low concentrations of EGTA (1 mm) produced the same result, suggesting that somatic SK channels are not tightly colocalized with their calcium source. Consistent with this idea, all known subtypes of VDCCs except R-type were calcium sources for the apamin-sensitive mAHP at the soma. We conclude that SK channels in spines and dendrites of cortical pyramidal neurons regulate calcium influx during backpropagating APs in a distance-dependent manner, and are tightly coupled to R-type VDCCs. In contrast, SK channels activated by APs at the soma of these neurons are weakly coupled to a variety of VDCCs.

  19. Divergent action of calcium channel blockers on ATP-binding cassette protein expression.

    Science.gov (United States)

    Hasegawa, Kazuhiro; Wakino, Shu; Kanda, Takeshi; Yoshioka, Kyoko; Tatematsu, Satoru; Homma, Koichiro; Takamatsu, Ichiro; Sugano, Naoki; Hayashi, Koichi

    2005-12-01

    Calcium channel blockers (CCBs) are widely used in clinical practice, and have been reported to be effective in preventing the progression of atherosclerosis. We examined whether various types of calcium channel blockers affected the expression of ATP binding cassette transporter A1 (ABCA1), a factor contributing to anti-atherogenesis. Undifferentiated monocytic cell line, THP-1 cells were maintained in RPMI 1640 medium and treated with different kinds of calcium channel blockers. Among the calcium channel blockers tested, aranidipine and efonidipine increased ABCA1 protein expression without an increase in ABCA1 mRNA expression, whereas other calcium channel blockers (eg, nifedipine, amlodipine, and nicardipine) or T-type calcium channel blockers (eg, mibefradil and nickel chloride) failed to upregulate ABCA1 expression. H89, a protein kinase A inhibitor inhibited the aranidipine-induced ABCA1 protein expression, whereas genistein (a tyrosine kinase inhibitor), or AG490 (a JAK-2 inhibitor) had no effects. Neither of these inhibitors suppressed the efonidipine-induced ABCA1 protein expression. Intracellular cAMP levels were elevated only by aranidipine, but not by efonidipine. In conclusion, aranidipine and efonidipine have the ability to induce ABCA1 protein by distinct mechanisms; protein kinase A is involved in the aranidipine-induced ABCA1 upregulation. This non-class effect of calcium channel blockers may potentially offer beneficial action in the treatment of hypertensive subjects with atherosclerosis.

  20. Analytical models of calcium binding in a calcium channel

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jinn-Liang [Department of Applied Mathematics, National Hsinchu University of Education, Hsinchu 300, Taiwan (China); Eisenberg, Bob [Department of Molecular Biophysics and Physiology, Rush University, Chicago, Illinois 60612 (United States)

    2014-08-21

    The anomalous mole fraction effect of L-type calcium channels is analyzed using a Fermi like distribution with the experimental data of Almers and McCleskey [J. Physiol. 353, 585 (1984)] and the atomic resolution model of Lipkind and Fozzard [Biochemistry 40, 6786 (2001)] of the selectivity filter of the channel. Much of the analysis is algebraic, independent of differential equations. The Fermi distribution is derived from the configuration entropy of ions and water molecules with different sizes, different valences, and interstitial voids between particles. It allows us to calculate potentials and distances (between the binding ion and the oxygen ions of the glutamate side chains) directly from the experimental data using algebraic formulas. The spatial resolution of these results is comparable with those of molecular models, but of course the accuracy is no better than that implied by the experimental data. The glutamate side chains in our model are flexible enough to accommodate different types of binding ions in different bath conditions. The binding curves of Na{sup +} and Ca{sup 2+} for [CaCl{sub 2}] ranging from 10{sup −8} to 10{sup −2} M with a fixed 32 mM background [NaCl] are shown to agree with published Monte Carlo simulations. The Poisson-Fermi differential equation—that includes both steric and correlation effects—is then used to obtain the spatial profiles of energy, concentration, and dielectric coefficient from the solvent region to the filter. The energy profiles of ions are shown to depend sensitively on the steric energy that is not taken into account in the classical rate theory. We improve the rate theory by introducing a steric energy that lumps the effects of excluded volumes of all ions and water molecules and empty spaces between particles created by Lennard-Jones type and electrostatic forces. We show that the energy landscape varies significantly with bath concentrations. The energy landscape is not constant.

  1. STIM and calcium channel complexes in cancer.

    Science.gov (United States)

    Jardin, Isaac; Rosado, Juan A

    2016-06-01

    The ion Ca(2+) is a ubiquitous second messenger that mediates a variety of cellular functions. Dysfunction of the mechanisms involved in Ca(2+) homeostasis underlies a number of pathological processes, including cancer. Store-operated Ca(2+) entry (SOCE) is a major mechanism for Ca(2+) entry modulated by the intracellular Ca(2+) stores. The Ca(2+)-selective store-operated current (ICRAC) is mediated by the endoplasmic reticulum (ER) Ca(2+) sensor STIM1 and the store-operated Ca(2+) (SOC) channel Orai1, while other non-selective cation currents (ISOC) involves the participation of members of the canonical transient receptor potential (TRPC) channel family, including TRPC1. Distinct isoforms of the key components of SOCE have been described in mammalian cells, STIM1 and 2, Orai1-3 and TRPC1-7. In cancer cells, SOCE has been reported to play an important role in cell cycle progression and proliferation, migration, metastasis and evasion of apoptosis. Changes in the expression of the key elements of SOCE and Ca(2+) homeostasis remodeling have been account to play important roles in the phenotypic changes observed in transformed cells. Despite there are differences in the expression level of the molecular components of SOCE, as well as in the relevance of the STIM, Orai and TRPC isoforms in SOCE and tumorigenesis among cancer cell types, there is a body of evidence supporting an important role for SOCE underlying the phenotypic modifications of cancer cells that propose STIM and the SOC channels as suitable candidate targets for future prognostic or therapeutic strategies. This article is part of a Special Issue entitled: Calcium and Cell Fate. Guest Editors: Jacques Haiech, Claus Heizmann, Joachim Krebs, Thierry Capiod and Olivier Mignen. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. Low threshold T-type calcium channels as targets for novel epilepsy treatments.

    Science.gov (United States)

    Powell, Kim L; Cain, Stuart M; Snutch, Terrance P; O'Brien, Terence J

    2014-05-01

    Low voltage-activated T-type calcium channels were originally cloned in the 1990s and much research has since focused on identifying the physiological roles of these channels in health and disease states. T-type calcium channels are expressed widely throughout the brain and peripheral tissues, and thus have been proposed as therapeutic targets for a variety of diseases such as epilepsy, insomnia, pain, cancer and hypertension. This review discusses the literature concerning the role of T-type calcium channels in physiological and pathological processes related to epilepsy. T-type calcium channels have been implicated in pathology of both the genetic and acquired epilepsies and several anti-epileptic drugs (AEDs) in clinical use are known to suppress seizures via inhibition of T-type calcium channels. Despite the fact that more than 15 new AEDs have become clinically available over the past 20 years at least 30% of epilepsy patients still fail to achieve seizure control, and many patients experience unwanted side effects. Furthermore there are no treatments that prevent the development of epilepsy or mitigate the epileptic state once established. Therefore there is an urgent need for the development of new AEDs that are effective in patients with drug resistant epilepsy, are anti-epileptogenic and are better tolerated. We also review the mechanisms of action of the current AEDs with known effects on T-type calcium channels and discuss novel compounds that are being investigated as new treatments for epilepsy. © 2013 The British Pharmacological Society.

  3. Spontaneous and CRH-Induced Excitability and Calcium Signaling in Mice Corticotrophs Involves Sodium, Calcium, and Cation-Conducting Channels.

    Science.gov (United States)

    Zemkova, Hana; Tomić, Melanija; Kucka, Marek; Aguilera, Greti; Stojilkovic, Stanko S

    2016-04-01

    Transgenic mice expressing the tdimer2(12) form of Discosoma red fluorescent protein under control of the proopiomelanocortin gene's regulatory elements are a useful model for studying corticotrophs. Using these mice, we studied the ion channels and mechanisms controlling corticotroph excitability. Corticotrophs were either quiescent or electrically active, with a 22-mV difference in the resting membrane potential (RMP) between the 2 groups. In quiescent cells, CRH depolarized the membrane, leading to initial single spiking and sustained bursting; in active cells, CRH further facilitated or inhibited electrical activity and calcium spiking, depending on the initial activity pattern and CRH concentration. The stimulatory but not inhibitory action of CRH on electrical activity was mimicked by cAMP independently of the presence or absence of arachidonic acid. Removal of bath sodium silenced spiking and hyperpolarized the majority of cells; in contrast, the removal of bath calcium did not affect RMP but reduced CRH-induced depolarization, which abolished bursting electrical activity and decreased the spiking frequency but not the amplitude of single spikes. Corticotrophs with inhibited voltage-gated sodium channels fired calcium-dependent action potentials, whereas cells with inhibited L-type calcium channels fired sodium-dependent spikes; blockade of both channels abolished spiking without affecting the RMP. These results indicate that the background voltage-insensitive sodium conductance influences RMP, the CRH-depolarization current is driven by a cationic conductance, and the interplay between voltage-gated sodium and calcium channels plays a critical role in determining the status and pattern of electrical activity and calcium signaling.

  4. Functional and pharmacological consequences of the distribution of voltage-gated calcium channels in the renal blood vessels.

    Science.gov (United States)

    Hansen, P B L

    2013-04-01

    Calcium channel blockers are widely used to treat hypertension because they inhibit voltage-gated calcium channels that mediate transmembrane calcium influx in, for example, vascular smooth muscle and cardiomyocytes. The calcium channel family consists of several subfamilies, of which the L-type is usually associated with vascular contractility. However, the L-, T- and P-/Q-types of calcium channels are present in the renal vasculature and are differentially involved in controlling vascular contractility, thereby contributing to regulation of kidney function and blood pressure. In the preglomerular vascular bed, all the three channel families are present. However, the T-type channel is the only channel in cortical efferent arterioles which is in contrast to the juxtamedullary efferent arteriole, and that leads to diverse functional effects of L- and T-type channel inhibition. Furthermore, by different mechanisms, T-type channels may contribute to both constriction and dilation of the arterioles. Finally, P-/Q-type channels are involved in the regulation of human intrarenal arterial contractility. The calcium blockers used in the clinic affect not only L-type but also P-/Q- and T-type channels. Therefore, the distinct effect obtained by inhibiting a given subtype or set of channels under experimental settings should be considered when choosing a calcium blocker for treatment. T-type channels seem to be crucial for regulating the GFR and the filtration fraction. Use of blockers is expected to lead to preferential efferent vasodilation, reduction of glomerular pressure and proteinuria. Therefore, renovascular T-type channels might provide novel therapeutic targets, and may have superior renoprotective effects compared to conventional calcium blockers. Acta Physiologica © 2013 Scandinavian Physiological Society.

  5. Inhibitory effect of calcium channel blockers on proliferation of human glioma cells in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Kunert-Radek, J.; Stepien, H.; Lyson, K.; Pawlikowski, M.; Radek, A.

    1989-01-01

    The effects of 2 specific calcium channel blockers, verapamil and nimodipine, on the proliferation of human glioma tumour cells were investigated in vitro. Tumour tissues for primary cell cultures were obtained bioptically from 3 patients with the histopathological diagnosis of glioblastoma. The (/sup 3/H)-thymidine incorporation into glioma tumour cells DNA was used as a sensitive index of the cell proliferation. It was found that varapamil (10/sup 4/-10/sup 5/M) and nimodipine (10/sup 4/-10/sup 6/M) significantly inhibited the (/sup 3/H)-thymidine uptake in a dose-related manner. The inhibitory effect of both calcium channel antagonists was reversed by stimultancous addition of calcium chloride (5x10/sup 3/M). These results indicate that verapamil and nimodipine may exert an antiproliferative effect on glioma cells growth acting through a blokade of specific voltage-dependent calcium channels.

  6. Inhibition of Cancer Cell Growth by Exposure to a Specific Time-Varying Electromagnetic Field Involves T-Type Calcium Channels

    OpenAIRE

    Carly A Buckner; Buckner, Alison L.; Koren, Stan A.; Michael A. Persinger; Lafrenie, Robert M.

    2015-01-01

    Electromagnetic field (EMF) exposures affect many biological systems. The reproducibility of these effects is related to the intensity, duration, frequency, and pattern of the EMF. We have shown that exposure to a specific time-varying EMF can inhibit the growth of malignant cells. Thomas-EMF is a low-intensity, frequency-modulated (25-6 Hz) EMF pattern. Daily, 1 h, exposures to Thomas-EMF inhibited the growth of malignant cell lines including B16-BL6, MDA-MB-231, MCF-7, and HeLa cells but di...

  7. Calcium channels in the brain as targets for the calcium-channel modulators used in the treatment of neurological disorders

    NARCIS (Netherlands)

    Peters, Thies; WILFFERT, B; VANHOUTTE, PM; VANZWIETEN, PA

    1991-01-01

    Recent investigations of calcium channels in brain cells by voltage-clamp techniques have revealed that, in spite of electrophysiological similarities, the pharmacological properties of these channels differ considerably from channels in peripheral tissues, e.g., heart and smooth muscle. Therefore,

  8. Inhibition of Enterococcus faecalis by Calcium Peroxide.

    Science.gov (United States)

    Su, Yong Liang; Wang, Xiao Yan

    2016-06-01

    To investigate the inhibition of Enterococcus faecalis by calcium peroxide (CaO₂). The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Enterococcus faecalis by CaO₂ and calcium hydroxide (Ca(OH)₂) were determined by direct exposure tests (n = 10). The inhibition zone of E. faecalis mycoderm treated with CaO₂ and Ca(OH)₂ paste (53% w/w) was observed using agar diffusion tests (n = 20). The inhibition of E. faecalis biofilms by CaO₂/phosphate-buffered saline (PBS) and Ca(OH)₂/PBS suspensions were observed using confocal laser scanning microscopy and the percentages of live bacteria in the biofilms calculated. The MIC of Ca(OH)₂ (4.5 to 5.5 mg/ml) was higher than the MIC of CaO₂ (2.0 to 2.5 mg/ml) (P faecalis biofilms after treatment (P faecalis by CaO₂ was greater than that by Ca(OH)₂.

  9. Calcium-activated chloride channels in the apical region of mouse vomeronasal sensory neurons.

    Science.gov (United States)

    Dibattista, Michele; Amjad, Asma; Maurya, Devendra Kumar; Sagheddu, Claudia; Montani, Giorgia; Tirindelli, Roberto; Menini, Anna

    2012-07-01

    The rodent vomeronasal organ plays a crucial role in several social behaviors. Detection of pheromones or other emitted signaling molecules occurs in the dendritic microvilli of vomeronasal sensory neurons, where the binding of molecules to vomeronasal receptors leads to the influx of sodium and calcium ions mainly through the transient receptor potential canonical 2 (TRPC2) channel. To investigate the physiological role played by the increase in intracellular calcium concentration in the apical region of these neurons, we produced localized, rapid, and reproducible increases in calcium concentration with flash photolysis of caged calcium and measured calcium-activated currents with the whole cell voltage-clamp technique. On average, a large inward calcium-activated current of -261 pA was measured at -50 mV, rising with a time constant of 13 ms. Ion substitution experiments showed that this current is anion selective. Moreover, the chloride channel blockers niflumic acid and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid partially inhibited the calcium-activated current. These results directly demonstrate that a large chloride current can be activated by calcium in the apical region of mouse vomeronasal sensory neurons. Furthermore, we showed by immunohistochemistry that the calcium-activated chloride channels TMEM16A/anoctamin1 and TMEM16B/anoctamin2 are present in the apical layer of the vomeronasal epithelium, where they largely colocalize with the TRPC2 transduction channel. Immunocytochemistry on isolated vomeronasal sensory neurons showed that TMEM16A and TMEM16B coexpress in the neuronal microvilli. Therefore, we conclude that microvilli of mouse vomeronasal sensory neurons have a high density of calcium-activated chloride channels that may play an important role in vomeronasal transduction.

  10. Voltage gated calcium channels negatively regulate protective immunity to Mycobacterium tuberculosis.

    Directory of Open Access Journals (Sweden)

    Shashank Gupta

    Full Text Available Mycobacterium tuberculosis modulates levels and activity of key intracellular second messengers to evade protective immune responses. Calcium release from voltage gated calcium channels (VGCC regulates immune responses to pathogens. In this study, we investigated the roles of VGCC in regulating protective immunity to mycobacteria in vitro and in vivo. Inhibiting L-type or R-type VGCC in dendritic cells (DCs either using antibodies or by siRNA increased calcium influx in an inositol 1,4,5-phosphate and calcium release calcium activated channel dependent mechanism that resulted in increased expression of genes favoring pro-inflammatory responses. Further, VGCC-blocked DCs activated T cells that in turn mediated killing of M. tuberculosis inside macrophages. Likewise, inhibiting VGCC in infected macrophages and PBMCs induced calcium influx, upregulated the expression of pro-inflammatory genes and resulted in enhanced killing of intracellular M. tuberculosis. Importantly, compared to healthy controls, PBMCs of tuberculosis patients expressed higher levels of both VGCC, which were significantly reduced following chemotherapy. Finally, blocking VGCC in vivo in M. tuberculosis infected mice using specific antibodies increased intracellular calcium and significantly reduced bacterial loads. These results indicate that L-type and R-type VGCC play a negative role in M. tuberculosis infection by regulating calcium mobilization in cells that determine protective immunity.

  11. Activation of L-type calcium channels is required for gap junction-mediated intercellular calcium signaling in osteoblastic cells

    DEFF Research Database (Denmark)

    Jørgensen, Niklas Rye; Teilmann, Stefan Cuoni; Henriksen, Zanne

    2003-01-01

    The propagation of mechanically induced intercellular calcium waves (ICW) among osteoblastic cells occurs both by activation of P2Y (purinergic) receptors by extracellular nucleotides, resulting in "fast" ICW, and by gap junctional communication in cells that express connexin43 (Cx43), resulting...... in "slow" ICW. Human osteoblastic cells transmit intercellular calcium signals by both of these mechanisms. In the current studies we have examined the mechanism of slow gap junction-dependent ICW in osteoblastic cells. In ROS rat osteoblastic cells, gap junction-dependent ICW were inhibited by removal......43 (UMR/Cx43) we confirmed that nifedipine sensitivity of ICW required Cx43 expression. In human osteoblastic cells, gap junction-dependent ICW also required activation of L-type calcium channels and influx of extracellular calcium....

  12. Ziconotide: neuronal calcium channel blocker for treating severe chronic pain.

    Science.gov (United States)

    Miljanich, G P

    2004-12-01

    Ziconotide (PRIALT) is a neuroactive peptide in the final stages of clinical development as a novel non-opioid treatment for severe chronic pain. It is the synthetic equivalent of omega-MVIIA, a component of the venom of the marine snail, Conus magus. The mechanism of action underlying ziconotide's therapeutic profile derives from its potent and selective blockade of neuronal N-type voltage-sensitive calcium channels (N-VSCCs). Direct blockade of N-VSCCs inhibits the activity of a subset of neurons, including pain-sensing primary nociceptors. This mechanism of action distinguishes ziconotide from all other analgesics, including opioid analgesics. In fact, ziconotide is potently anti-nociceptive in animal models of pain in which morphine exhibits poor anti-nociceptive activity. Moreover, in contrast to opiates, tolerance to ziconotide is not observed. Clinical studies of ziconotide in more than 2,000 patients reveal important correlations to ziconotide's non-clinical pharmacology. For example, ziconotide provides significant pain relief to severe chronic pain sufferers who have failed to obtain relief from opiate therapy and no evidence of tolerance to ziconotide is seen in these patients. Contingent on regulatory approval, ziconotide will be the first in a new class of neurological drugs: the N-type calcium channel blockers, or NCCBs. Its novel mechanism of action as a non-opioid analgesic suggests ziconotide has the potential to play a valuable role in treatment regimens for severe chronic pain. If approved for clinical use, ziconotide will further validate the neuroactive venom peptides as a source of new and useful medicines.

  13. Reporting sodium channel activity using calcium flux: pharmacological promiscuity of cardiac Nav1.5.

    Science.gov (United States)

    Zhang, Hongkang; Zou, Beiyan; Du, Fang; Xu, Kaiping; Li, Min

    2015-02-01

    Voltage-gated sodium (Nav) channels are essential for membrane excitability and represent therapeutic targets for treating human diseases. Recent reports suggest that these channels, e.g., Nav1.3 and Nav1.5, are inhibited by multiple structurally distinctive small molecule drugs. These studies give reason to wonder whether these drugs collectively target a single site or multiple sites in manifesting such pharmacological promiscuity. We thus investigate the pharmacological profile of Nav1.5 through systemic analysis of its sensitivity to diverse compound collections. Here, we report a dual-color fluorescent method that exploits a customized Nav1.5 [calcium permeable Nav channel, subtype 5 (SoCal5)] with engineered-enhanced calcium permeability. SoCal5 retains wild-type (WT) Nav1.5 pharmacological profiles. WT SoCal5 and SoCal5 with the local anesthetics binding site mutated (F1760A) could be expressed in separate cells, each with a different-colored genetically encoded calcium sensor, which allows a simultaneous report of compound activity and site dependence. The pharmacological profile of SoCal5 reveals a hit rate (>50% inhibition) of around 13% at 10 μM, comparable to that of hERG. The channel activity is susceptible to blockage by known drugs and structurally diverse compounds. The broad inhibition profile is highly dependent on the F1760 residue in the inner cavity, which is a residue conserved among all nine subtypes of Nav channels. Both promiscuity and dependence on F1760 seen in Nav1.5 were replicated in Nav1.4. Our evidence of a broad inhibition profile of Nav channels suggests a need to consider off-target effects on Nav channels. The site-dependent promiscuity forms a foundation to better understand Nav channels and compound interactions. Copyright © 2014 by The American Society for Pharmacology and Experimental Therapeutics.

  14. Anoctamin Calcium-Activated Chloride Channels May Modulate Inhibitory Transmission in the Cerebellar Cortex.

    Directory of Open Access Journals (Sweden)

    Weiping Zhang

    Full Text Available Calcium-activated chloride channels of the anoctamin (alias TMEM16 protein family fulfill critical functions in epithelial fluid transport, smooth muscle contraction and sensory signal processing. Little is known, however, about their contribution to information processing in the central nervous system. Here we examined the recent finding that a calcium-dependent chloride conductance impacts on GABAergic synaptic inhibition in Purkinje cells of the cerebellum. We asked whether anoctamin channels may underlie this chloride conductance. We identified two anoctamin channel proteins, ANO1 and ANO2, in the cerebellar cortex. ANO1 was expressed in inhibitory interneurons of the molecular layer and the granule cell layer. Both channels were expressed in Purkinje cells but, while ANO1 appeared to be retained in the cell body, ANO2 was targeted to the dendritic tree. Functional studies confirmed that ANO2 was involved in a calcium-dependent mode of ionic plasticity that reduces the efficacy of GABAergic synapses. ANO2 channels attenuated GABAergic transmission by increasing the postsynaptic chloride concentration, hence reducing the driving force for chloride influx. Our data suggest that ANO2 channels are involved in a Ca2+-dependent regulation of synaptic weight in GABAergic inhibition. Thus, in balance with the chloride extrusion mechanism via the co-transporter KCC2, ANO2 appears to regulate ionic plasticity in the cerebellum.

  15. T-type calcium channel: a privileged gate for calcium entry and control of adrenal steroidogenesis

    Directory of Open Access Journals (Sweden)

    Michel Florian Rossier

    2016-05-01

    Full Text Available Intracellular calcium plays a crucial role in modulating a variety of functions such as muscle contraction, hormone secretion, gene expression or cell growth. Calcium signaling has been however shown to be more complex than initially thought. Indeed, it is confined within cell microdomains and different calcium channels are associated with different functions, as shown by various channelopathies.Sporadic mutations on voltage-operated L-type calcium channels in adrenal glomerulosa cells have been shown recently to be the second most prevalent genetic abnormalities present in human aldosterone-producing adenoma. The observed modification of the threshold of activation of the mutated channels not only provides an explanation for this gain of function but reminds us on the importance of maintaining adequate electrophysiological characteristics to make channels able to exert specific cellular functions. Indeed, the contribution to steroid production of the various calcium channels expressed in adrenocortical cells is not equal and the reason has been investigated for a long time. Given the very negative resting potential of these cells, and the small membrane depolarization induced by their physiological agonists, low threshold T-type calcium channels are particularly well suited for responding under these conditions and conveying calcium into the cell, at the right place for controlling steroidogenesis. In contrast, high threshold L-type channels are normally activated by much stronger cell depolarizations. The fact that dihydropyridine calcium antagonists, specific for L-type channels, are poorly efficient for reducing aldosterone secretion either in vivo or in vitro, strongly supports the view that these two types of channels differently affect steroid biosynthesis.Whether a similar analysis is transposable to fasciculata cells and cortisol secretion is one of the questions addressed in the present review. No similar mutations on L-type or T

  16. Putative calcium-binding domains of the Caenorhabditis elegans BK channel are dispensable for intoxication and ethanol activation

    Science.gov (United States)

    Davis, S. J.; Scott, L. L.; Ordemann, G.; Philpo, A.; Cohn, J.; Pierce-Shimomura, J. T.

    2016-01-01

    Alcohol modulates the highly conserved, voltage- and calcium-activated potassium (BK) channel, which contributes to alcohol-mediated behaviors in species from worms to humans. Previous studies have shown that the calcium-sensitive domains, RCK1 and the Ca2+ bowl, are required for ethanol activation of the mammalian BK channel in vitro. In the nematode Caenorhabditis elegans, ethanol activates the BK channel in vivo, and deletion of the worm BK channel, SLO-1, confers strong resistance to intoxication. To determine if the conserved RCK1 and calcium bowl domains were also critical for intoxication and basal BK channel-dependent behaviors in C. elegans, we generated transgenic worms that express mutated SLO-1 channels predicted to have the RCK1, Ca2+ bowl or both domains rendered insensitive to calcium. As expected, mutating these domains inhibited basal function of SLO-1 in vivo as neck and body curvature of these mutants mimicked that of the BK null mutant. Unexpectedly, however, mutating these domains singly or together in SLO-1 had no effect on intoxication in C. elegans. Consistent with these behavioral results, we found that ethanol activated the SLO-1 channel in vitro with or without these domains. By contrast, in agreement with previous in vitro findings, C. elegans harboring a human BK channel with mutated calcium-sensing domains displayed resistance to intoxication. Thus, for the worm SLO-1 channel, the putative calcium-sensitive domains are critical for basal in vivo function but unnecessary for in vivo ethanol action. PMID:26113050

  17. T-type calcium channels in synaptic plasticity.

    Science.gov (United States)

    Leresche, Nathalie; Lambert, Régis C

    2017-03-04

    The role of T-type calcium currents is rarely considered in the extensive literature covering the mechanisms of long-term synaptic plasticity. This situation reflects the lack of suitable T-type channel antagonists that till recently has hampered investigations of the functional roles of these channels. However, with the development of new pharmacological and genetic tools, a clear involvement of T-type channels in synaptic plasticity is starting to emerge. Here, we review a number of studies showing that T-type channels participate to numerous homo- and hetero-synaptic plasticity mechanisms that involve different molecular partners and both pre- and post-synaptic modifications. The existence of T-channel dependent and independent plasticity at the same synapse strongly suggests a subcellular localization of these channels and their partners that allows specific interactions. Moreover, we illustrate the functional importance of T-channel dependent synaptic plasticity in neocortex and thalamus.

  18. Regulation of CaV2 calcium channels by G protein coupled receptors

    Science.gov (United States)

    Zamponi, Gerald W.; Currie, Kevin P.M.

    2012-01-01

    Voltage gated calcium channels (Ca2+ channels) are key mediators of depolarization induced calcium influx into excitable cells, and thereby play pivotal roles in a wide array of physiological responses. This review focuses on the inhibition of CaV2 (N- and P/Q-type) Ca2+-channels by G protein coupled receptors (GPCRs), which exerts important autocrine/paracrine control over synaptic transmission and neuroendocrine secretion. Voltage-dependent inhibition is the most widespread mechanism, and involves direct binding of the G protein βγ dimer (Gβγ) to the α1 subunit of CaV2 channels. GPCRs can also recruit several other distinct mechanisms including phosphorylation, lipid signaling pathways, and channel trafficking that result in voltage-independent inhibition. Current knowledge of Gβγ-mediated inhibition is reviewed, including the molecular interactions involved, determinants of voltage-dependence, and crosstalk with other cell signaling pathways. A summary of recent developments in understanding the voltage-independent mechanisms prominent in sympathetic and sensory neurons is also included. PMID:23063655

  19. Endothelin induces two types of contractions of rat uterus: phasic contractions by way of voltage-dependent calcium channels and developing contractions through a second type of calcium channels

    Energy Technology Data Exchange (ETDEWEB)

    Kozuka, M.; Ito, T.; Hirose, S.; Takahashi, K.; Hagiwara, H.

    1989-02-28

    Effects of endothelin on nonvascular smooth muscle have been examined using rat uterine horns and two modes of endothelin action have been revealed. Endothelin (0.3 nM) caused rhythmic contractions of isolated uterus in the presence of extracellular calcium. The rhythmic contractions were completely inhibited by calcium channel antagonists. These characteristics of endothelin-induced contractions were very similar to those induced by oxytocin. Binding assays using /sup 125/I-endothelin showed that endothelin and the calcium channel blockers did not compete for the binding sites. However, endothelin was unique in that it caused, in addition to rhythmic contractions, a slowly developing monophasic contraction that was insensitive to calcium channel blockers. This developing contraction became dominant at higher concentrations of endothelin and was also calcium dependent.

  20. High affinity complexes of pannexin channels and L-type calcium channel splice-variants in human lung: Possible role in clevidipine-induced dyspnea relief in acute heart failure

    Directory of Open Access Journals (Sweden)

    Gerhard P. Dahl

    2016-08-01

    Research in Context: Clevidipine lowers blood pressure by inhibiting calcium channels in vascular smooth muscle. In patients with acute heart failure, clevidipine was shown to relieve breathing problems. This was only partially related to the blood pressure lowering actions of clevidipine and not conferred by another calcium channel inhibitor. We here found calcium channel variants in human lung that are more selectively inhibited by clevidipine, especially when associated with pannexin channels. This study gives a possible mechanism for clevidipine's relief of breathing problems and supports future clinical trials testing the role of clevidipine in the treatment of acute heart failure.

  1. Active Dendrites and Differential Distribution of Calcium Channels Enable Functional Compartmentalization of Golgi Cells.

    Science.gov (United States)

    Rudolph, Stephanie; Hull, Court; Regehr, Wade G

    2015-11-25

    Interneurons are essential to controlling excitability, timing, and synaptic integration in neuronal networks. Golgi cells (GoCs) serve these roles at the input layer of the cerebellar cortex by releasing GABA to inhibit granule cells (grcs). GoCs are excited by mossy fibers (MFs) and grcs and provide feedforward and feedback inhibition to grcs. Here we investigate two important aspects of GoC physiology: the properties of GoC dendrites and the role of calcium signaling in regulating GoC spontaneous activity. Although GoC dendrites are extensive, previous studies concluded they are devoid of voltage-gated ion channels. Hence, the current view holds that somatic voltage signals decay passively within GoC dendrites, and grc synapses onto distal dendrites are not amplified and are therefore ineffective at firing GoCs because of strong passive attenuation. Using whole-cell recording and calcium imaging in rat slices, we find that dendritic voltage-gated sodium channels allow somatic action potentials to activate voltage-gated calcium channels (VGCCs) along the entire dendritic length, with R-type and T-type VGCCs preferentially located distally. We show that R- and T-type VGCCs located in the dendrites can boost distal synaptic inputs and promote burst firing. Active dendrites are thus critical to the regulation of GoC activity, and consequently, to the processing of input to the cerebellar cortex. In contrast, we find that N-type channels are preferentially located near the soma, and control the frequency and pattern of spontaneous firing through their close association with calcium-activated potassium (KCa) channels. Thus, VGCC types are differentially distributed and serve specialized functions within GoCs. Interneurons are essential to neural processing because they modulate excitability, timing, and synaptic integration within circuits. At the input layer of the cerebellar cortex, a single type of interneuron, the Golgi cell (GoC), carries these functions. The

  2. The TRPM7 channel kinase regulates store-operated calcium entry.

    Science.gov (United States)

    Faouzi, Malika; Kilch, Tatiana; Horgen, F David; Fleig, Andrea; Penner, Reinhold

    2017-05-15

    Pharmacological and molecular inhibition of transient receptor potential melastatin 7 (TRPM7) reduces store-operated calcium entry (SOCE). Overexpression of TRPM7 in TRPM7-/- cells restores SOCE. TRPM7 is not a store-operated calcium channel. TRPM7 kinase rather than channel modulates SOCE. TRPM7 channel activity contributes to the maintenance of store Ca2+ levels at rest. The transient receptor potential melastatin 7 (TRPM7) is a protein that combines an ion channel with an intrinsic kinase domain, enabling it to modulate cellular functions either by conducting ions through the pore or by phosphorylating downstream proteins via its kinase domain. In the present study, we report store-operated calcium entry (SOCE) as a novel target of TRPM7 kinase activity. TRPM7-deficient chicken DT40 B lymphocytes exhibit a strongly impaired SOCE compared to wild-type cells as a result of reduced calcium release activated calcium currents, and independently of potassium channel regulation, membrane potential changes or changes in cell-cycle distribution. Pharmacological blockade of TRPM7 with NS8593 or waixenicin A in wild-type B lymphocytes results in a significant decrease in SOCE, confirming that TRPM7 activity is acutely linked to SOCE, without TRPM7 representing a store-operated channel itself. Using kinase-deficient mutants, we find that TRPM7 regulates SOCE through its kinase domain. Furthermore, Ca2+ influx through TRPM7 is essential for the maintenance of endoplasmic reticulum Ca2+ concentration in resting cells, and for the refilling of Ca2+ stores after a Ca2+ signalling event. We conclude that the channel kinase TRPM7 and SOCE are synergistic mechanisms regulating intracellular Ca2+ homeostasis. © 2017 The Authors. The Journal of Physiology © 2017 The Physiological Society.

  3. Diltiazem and verapamil preferentially block inactivated cardiac calcium channels.

    Science.gov (United States)

    Kanaya, S; Arlock, P; Katzung, B G; Hondeghem, L M

    1983-02-01

    Diltiazem has been proposed to act by blocking calcium channels of cardiac and smooth muscle since it has pharmacological [12-14] and clinical [10] effects that resemble those of verapamil, an agent that has been shown to block these channels [3]. However, block of the slow inward current by diltiazem has not been directly demonstrated. In fact, it has been suggested that diltiazem has an entirely different mechanism of action [7]. We therefore studied the blocking effects of diltiazem and verapamil on cardiac calcium channels by measuring the slow inward current in voltage-clamped ferret myocardium. Both drugs blocked the slow inward current in a use-dependent fashion, i.e. the block was enhanced by increased frequency of activating clamps and by more positive holding potentials. However, we found that short single activating clamps resulted in minimal block, whereas prolonging the clamp step progressively enhanced the blockade. Thus, a single long clamp caused as much blockade as a train of shorter pulses. These results demonstrate that diltiazem and verapamil block the slow inward current by binding to calcium channels in a state-dependent fashion, i.e. inactivated channels have a high affinity for the drugs, while rested and open channels have a lower affinity.

  4. TRPV5: an ingeniously controlled calcium channel.

    NARCIS (Netherlands)

    Groot, T. de; Bindels, R.J.M.; Hoenderop, J.G.J.

    2008-01-01

    Body Ca(2+) homeostasis is tightly controlled and slight disturbances in renal Ca(2+) reabsorption can lead to excessive urine Ca(2+) excretion and promote kidney stone formation. The epithelial Ca(2+) channel TRPV5 constitutes the rate-limiting step of active Ca(2+) reabsorption in the kidney.

  5. Caffeine-Induced Suppression of GABAergic Inhibition and Calcium-Independent Metaplasticity

    Directory of Open Access Journals (Sweden)

    Masako Isokawa

    2016-01-01

    Full Text Available GABAergic inhibition plays a critical role in the regulation of neuron excitability; thus, it is subject to modulations by many factors. Recent evidence suggests the elevation of intracellular calcium ([Ca2+]i and calcium-dependent signaling molecules underlie the modulations. Caffeine induces a release of calcium from intracellular stores. We tested whether caffeine modulated GABAergic transmission by increasing [Ca2+]i. A brief local puff-application of caffeine to hippocampal CA1 pyramidal cells transiently suppressed GABAergic inhibitory postsynaptic currents (IPSCs by 73.2 ± 6.98%. Time course of suppression and the subsequent recovery of IPSCs resembled DSI (depolarization-induced suppression of inhibition, mediated by endogenous cannabinoids that require a [Ca2+]i rise. However, unlike DSI, caffeine-induced suppression of IPSCs (CSI persisted in the absence of a [Ca2+]i rise. Intracellular applications of BAPTA and ryanodine (which blocks caffeine-induced calcium release from intracellular stores failed to prevent the generation of CSI. Surprisingly, ruthenium red, an inhibitor of multiple calcium permeable/release channels including those of stores, induced metaplasticity by amplifying the magnitude of CSI independently of calcium. This metaplasticity was accompanied with the generation of a large inward current. Although ionic basis of this inward current is undetermined, the present result demonstrates that caffeine has a robust Ca2+-independent inhibitory action on GABAergic inhibition and causes metaplasticity by opening plasma membrane channels.

  6. Calcium channel blockers and cancer risk using the UK CPRD

    NARCIS (Netherlands)

    Grimaldi-Bensouda, Lamiae; De Groot, Mark; Reynolds, Robert; Klungel, Olaf; Rossignol, Michel

    2014-01-01

    Background: This study was part of the Pharmacoepidemiological Research on Outcomes (PROTECT) project which aims at monitoring of the benefit-risk of medicines in Europe. Few epidemiological studies have investigated the association between calcium channel blockers (CCB) and cancer, and have

  7. [Obtaining antibodies to 1,4-dihydropyridine calcium channel blockers].

    Science.gov (United States)

    Burkin, A A; Murkin, M A

    2008-01-01

    Immunization of rabbits with amlodipine conjugated with horseradish peroxidase resulted in raising polyclonal antibodies that allowed group determination of 1,4-dihydropyridine calcium channel blockers in aqueous solutions by ELISA with a sensitivity of 0.1 to 1.0 ng/ml for amlodipine, felodipine, nifedipine, and isradipine.

  8. Evaluation of nitrendipine -a new calcium channel blocker ...

    African Journals Online (AJOL)

    Nitrendipine (Baypress; Bayer-Miles), a new calcium channel blocker, was administered to 38 hypertensive patients in an oral dose of 20 mg once or twice daily. Both systolic and diastolic blood pressures were reduced to a clinically relevant extent within 2 hours of taking the medication. There was no loss of effect during ...

  9. Calcium channel-dependent molecular maturation of photoreceptor synapses.

    Directory of Open Access Journals (Sweden)

    Nawal Zabouri

    Full Text Available Several studies have shown the importance of calcium channels in the development and/or maturation of synapses. The Ca(V1.4(α(1F knockout mouse is a unique model to study the role of calcium channels in photoreceptor synapse formation. It features abnormal ribbon synapses and aberrant cone morphology. We investigated the expression and targeting of several key elements of ribbon synapses and analyzed the cone morphology in the Ca(V1.4(α(1F knockout retina. Our data demonstrate that most abnormalities occur after eye opening. Indeed, scaffolding proteins such as Bassoon and RIM2 are properly targeted at first, but their expression and localization are not maintained in adulthood. This indicates that either calcium or the Ca(V1.4 channel, or both are necessary for the maintenance of their normal expression and distribution in photoreceptors. Other proteins, such as Veli3 and PSD-95, also display abnormal expression in rods prior to eye opening. Conversely, vesicle related proteins appear normal. Our data demonstrate that the Ca(V1.4 channel is important for maintaining scaffolding proteins in the ribbon synapse but less vital for proteins related to vesicular release. This study also confirms that in adult retinae, cones show developmental features such as sprouting and synaptogenesis. Overall we present evidence that in the absence of the Ca(V1.4 channel, photoreceptor synapses remain immature and are unable to stabilize.

  10. Regulation of voltage-gated calcium channels by proteolysis

    Science.gov (United States)

    Kathryn, ABELE; Jian, YANG

    2015-01-01

    Voltage gated calcium channels (VGCCs) are multi-subunit membrane proteins present in a variety of tissues and control many essential physiological processes. Due to their vital importance, VGCCs are regulated by a myriad of proteins and signaling pathways. Here we review the literature on the regulation of VGCCs by proteolysis of the pore-forming α1 subunit, Cavα1. This form of regulation modulates channel function and degradation and affects cellular gene expression and excitability. L-type Ca2+ channels are proteolyzed in two ways, depending on tissue localization. In the heart and skeletal muscle, the distal C-terminus of Cavα1 is cleaved and acts as an autoinhibitor when it reassociates with the proximal C-terminus. Relief of this autoinhibition underlies the β-adrenergic stimulation-induced enhancement of cardiac and skeletal muscle calcium currents, part of the “fight or flight” response. Proteolysis of the distal C-terminus of L-type channels also occurs in the brain and is probably catalyzed by a calpain-like protease. In some brain regions, the entire C-terminus of L-type Ca2+ channels can be cleaved by an unknown protease and translocates to the nucleus acting as a transcription factor. The distal C-terminus of P/Q-channel Cavα1 is also proteolyzed and translocates to the nucleus. Truncated forms of the PQ-channel Cavα1 are produced by many disease-causing mutations and interfere with the function of full-length channels. Truncated forms of N-type channel Cavα1, generated by mutagenesis, affect the expression of full-length channels. New forms of proteolysis of VGCC subunits remain to be discovered and may represent a fruitful area of VGCC research. PMID:23090491

  11. Calcium-activated SK channels control firing regularity by modulating sodium channel availability in midbrain dopamine neurons.

    Science.gov (United States)

    Iyer, Rajeshwari; Ungless, Mark A; Faisal, Aldo A

    2017-07-12

    Dopamine neurons in the substantia nigra pars compacta and ventral tegmental area regulate behaviours such as reward-related learning, and motor control. Dysfunction of these neurons is implicated in Schizophrenia, addiction to drugs, and Parkinson's disease. While some dopamine neurons fire single spikes at regular intervals, others fire irregular single spikes interspersed with bursts. Pharmacological inhibition of calcium-activated potassium (SK) channels increases the variability in their firing pattern, sometimes also increasing the number of spikes fired in bursts, indicating that SK channels play an important role in maintaining dopamine neuron firing regularity and burst firing. However, the exact mechanisms underlying these effects are still unclear. Here, we develop a biophysical model of a dopamine neuron incorporating ion channel stochasticity that enabled the analysis of availability of ion channels in multiple states during spiking. We find that decreased firing regularity is primarily due to a significant decrease in the AHP that in turn resulted in a reduction in the fraction of available voltage-gated sodium channels due to insufficient recovery from inactivation. Our model further predicts that inhibition of SK channels results in a depolarisation of action potential threshold along with an increase in its variability.

  12. Localization of calcium channels in Paramecium caudatum.

    Science.gov (United States)

    Dunlap, K

    1977-01-01

    1. Electrical recordings from Paramecium caudatum were made after removal of the cilia with chloral hydrate and during ciliary regrowth to study the electrical properties of that portion of the surface membrane enclosing the ciliary axoneme. 2. Removal of the somatic cilia (a 50% reduction in membrane surface area) results in an almost complete elimination of the regenerative Ca response, all-or-none Ba2+ spike, and delayed rectification. 3. A twofold increase in input resistance resulted from the 50% reduction in membrane surface area. 4. The electrical properties remained unchanged, despite prolonged exposure to the chloral hydrate, until the cilia were mechanically removed. 5. Restoration of the Ca response accompanied ciliary regrowth, so that complete excitability returns when the cilia regain their original lengths. 6. It is concluded that the voltage-sensitive Ca channels are localized to that portion of surface membrane surrounding the cilia. 7. Measurements of membrane constants before and after deciliation and estimations of the cable constants of a single cilium suggest that the cilia of Paramecium may be fully isopotential along their length and with the major cell compartment. Images Plate 1 Plate 2 PMID:915829

  13. Calcium signalling through L-type calcium channels: role in pathophysiology of spinal nociceptive transmission.

    Science.gov (United States)

    Roca-Lapirot, Olivier; Radwani, Houda; Aby, Franck; Nagy, Frédéric; Landry, Marc; Fossat, Pascal

    2017-02-18

    L-type voltage-gated calcium channels are ubiquitous channels in the CNS. L-type calcium channels (LTCs) are mostly post-synaptic channels regulating neuronal firing and gene expression. They play a role in important physio-pathological processes such as learning and memory, Parkinson's disease, autism and, as recognized more recently, in the pathophysiology of pain processes. Classically, the fundamental role of these channels in cardiovascular functions has limited the use of classical molecules to treat LTC-dependent disorders. However, when applied locally in the dorsal horn of the spinal cord, the three families of LTC pharmacological blockers - dihydropyridines (nifedipine), phenylalkylamines (verapamil) and benzothiazepines (diltiazem) - proved effective in altering short-term sensitization to pain, inflammation-induced hyperexcitability and neuropathy-induced allodynia. Two subtypes of LTCs, Cav 1.2 and Cav 1.3, are expressed in the dorsal horn of the spinal cord, where Cav 1.2 channels are localized mostly in the soma and proximal dendritic shafts, and Cav 1.3 channels are more distally located in the somato-dendritic compartment. Together with their different kinetics and pharmacological properties, this spatial distribution contributes to their separate roles in shaping short- and long-term sensitization to pain. Cav 1.3 channels sustain the expression of plateau potentials, an input/output amplification phenomenon that contributes to short-term sensitization to pain such as prolonged after-discharges, dynamic receptive fields and windup. The Cav 1.2 channels support calcium influx that is crucial for the excitation-transcription coupling underlying nerve injury-induced dorsal horn hyperexcitability. These subtype-specific cellular mechanisms may have different consequences in the development and/or the maintenance of pathological pain. Recent progress in developing more specific compounds for each subunit will offer new opportunities to modulate LTCs

  14. Chemical analysis and calcium channel blocking activity of the essential oil of Perovskia abrotanoides.

    Science.gov (United States)

    Shah, Abdul Jabbar; Rasheed, Munawwer; Jabeen, Qaiser; Ahmed, Amir; Tareen, Rasool Bakhsh; Gilani, Anwarul Hassan; Nadir, Muhammad; Ahmad, Viqar Uddin

    2013-11-01

    The aim of this study was to investigate the chemical composition and provide a pharmacological base for the medicinal use of the essential oil of Perovskia abrotanoides (Pa.Oil) in gastrointestinal disorders, such as colic. The chemical investigation resulted in the identification of 26 compounds, of which tricyclene, beta-trans-ocimene, terpinene-4-acetate, terpinen-4-ol, caran-3beta-ol, linalyl acetate, beta-caryophyllene oxide and alpha-elemene had not previously been reported from P. abrotanoides. Major constituents were 1,8-cineol and delta-3-carene, which constituting 50% of the oil. In the isolated rabbit jejunum preparation Pa.Oil caused inhibition of spontaneous and high K+ (80 mM)-induced contractions, with respective EC50 values of 0.13 (0.08-0.20; n = 4) and 0.90 mg/mL (0.50-1.60; n = 5), thus showing that spasmolytic activity is mediated possibly through calcium channel blockade (CCB). The CCB activity was confirmed when pre-treatment of the tissue with Pa.Oil (0.03-0.1 mg/mL) caused a rightward shift in the Ca++ concentration-response curves, similar to that caused by verapamil, a standard calcium channel blocker. These data indicate that the essential oil of P. abrotanoides possesses spasmolytic activity mediated possibly through inhibition of voltage-dependent calcium channels, which may explain its medicinal use in colic and possibly diarrhea.

  15. Serum and immunoglobulin G from the mother of a child with congenital heart block induce conduction abnormalities and inhibit L-type calcium channels in a rat heart model.

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    Boutjdir, M; Chen, L; Zhang, Z H; Tseng, C E; El-Sherif, N; Buyon, J P

    1998-07-01

    Although a strong clinical association exists between congenital heart block (CHB) and an immune response to SSA/Ro and SSB/La proteins, a causative role of these antibodies in the pathogenesis is just emerging. In a preliminary report, we have demonstrated that IgG fractions isolated from the sera of mothers whose children have CHB are arrhythmogenic in the human fetal heart. To more precisely define the arrhythmogenic effect of anti-SSA/Ro-SSB/La antibodies, we used the readily available rat heart model to record: 1) ECGs from Langendorff beating hearts; 2) action potentials from atrioventricular (AV) nodal preparations; 3) L-type Ca currents, I(Ca) at the whole-cell and single channel levels; and 4) other currents such as the transient outward K+ current, I(to), the inward rectifier K+ current, I(K1), and the Na+ current, I(Na). Perfusion of hearts with purified IgG (800 microg/mL), isolated from the serum of a mother with SSA/Ro and SSB/La antibodies whose child had CHB, resulted in bradycardia associated with 2:1 AV block. Simultaneous action potentials were recorded from dissected atrial and AV nodal areas of the rat heart. Superfusion of these preparations with the same mother's IgG fraction resulted in 2:1 AV block followed by complete inhibition of AV nodal action potential. Because AV nodal electrogenesis is largely dependent on I(Ca), the effect of these antibodies on I(Ca) was subsequently determined. Superfusion of myocytes with whole serum or purified IgG (80 microg/mL) from the same mother consistently inhibited whole cell I(Ca), ensemble average Ba2+ currents (I(Ba)) and open state probability, p(o), without affecting the channel conductance. IgG had no significant effect on I(to), I(K1), or I(Na). Whole sera and IgG fractions from a healthy mother with no detectable anti-SSA/Ro or SSB/La antibodies did not inhibit I(Ca) or I(Ba). These results demonstrate that IgG containing anti-SSA/Ro and -SSB/La antibodies induces complete AV block in beating

  16. Regulation of calcium signalling by docosahexaenoic acid in human T-cells. Implication of CRAC channels.

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    Bonin, A; Khan, N A

    2000-02-01

    We elucidated the role of docosahexaenoic acid (DHA) on the increases in free intracellular calcium concentrations, [Ca(2+)]i, in human (Jurkat) T-cell lines. DHA evoked an increase in [Ca(2+)]i in a dose-dependent manner in these cells. Anti-CD3 antibody, known to stimulate increases in Ca(2+) from endoplasmic reticulum (ER) via the production of inositol trisphosphate, also evoked increases in [Ca(2+)]i in Jurkat T-cells. We also used thapsigargin which inhibits Ca(2+)-ATPase of the ER and, therefore, increases Ca(2+) in the cytosol. Interestingly, addition of DHA during the thapsigargin-induced peak response exerted an additive effect on the increases in [Ca(2+)]i in human T-cells, indicating that the mechanisms of action of these two agents are different. However, the DHA-induced calcium response was not observed when this agent was added during the anti-CD3-induced calcium peak, though its addition resulted in a prolonged and sustained calcium response as a function of time, suggesting that DHA recruits calcium, in part, from the ER pool and the prolonged response may be due to Ca(2+) influx. In the medium containing 0% Ca(2+), the DHA-evoked response on the increases in [Ca(2+)]i was significantly curtailed as compared to that in 100% Ca(2+) medium, supporting the notion that the response of the DHA is also due, in part, to the opening of calcium channels. Furthermore, preincubation of cells with tyrphostin A9, an inhibitor of Ca(2+) release-activated Ca(2+) (CRAC) channels also significantly curtailed the DHA-induced sustained response on the increases in [Ca(2+)]i in these cells. These results suggest that DHA induces an increase in [Ca(2+)]i via the ER pool and the opening of CRAC channels in human T-cells.

  17. Understanding alternative splicing of Cav1.2 calcium channels for a new approach towards individualized medicine

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    Liao, Ping; Soong, Tuck Wah

    2010-01-01

    Calcium channel blockers (CCBs) are widely used to treat cardiovascular diseases such as hypertension, angina pectoris, hypertrophic cardiomyopathy, and supraventricular tachycardia. CCBs selectively inhibit the inward flow of calcium ions through voltage-gated calcium channels, particularly Cav1.2, that are expressed in the cardiovascular system. Changes to the molecular structure of Cav1.2 channels could affect sensitivity of the channels to blockade by CCBs. Recently, extensive alternative splicing was found in Cav1.2 channels that generated wide phenotypic variations. Cardiac and smooth muscles express slightly different, but functionally important Cav1.2 splice variants. Alternative splicing could also modulate the gating properties of the channels and giving rise to different responses to inhibition by CCBs. Importantly, alternative splicing of Cav1.2 channels may play an important role to influence the outcome of many cardiovascular disorders. Therefore, the understanding of how alternative splicing impacts Cav1.2 channels pharmacology in various diseases and different organs may provide the possibility for individualized therapy with minimal side effects. PMID:23554629

  18. Zebrafish CaV2.1 Calcium Channels Are Tailored for Fast Synchronous Neuromuscular Transmission

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    Naranjo, David; Wen, Hua; Brehm, Paul

    2015-01-01

    The CaV2.2 (N-type) and CaV2.1 (P/Q-type) voltage-dependent calcium channels are prevalent throughout the nervous system where they mediate synaptic transmission, but the basis for the selective presence at individual synapses still remains an open question. The CaV2.1 channels have been proposed to respond more effectively to brief action potentials (APs), an idea supported by computational modeling. However, the side-by-side comparison of CaV2.1 and CaV2.2 kinetics in intact neurons failed to reveal differences. As an alternative means for direct functional comparison we expressed zebrafish CaV2.1 and CaV2.2 α-subunits, along with their accessory subunits, in HEK293 cells. HEK cells lack calcium currents, thereby circumventing the need for pharmacological inhibition of mixed calcium channel isoforms present in neurons. HEK cells also have a simplified morphology compared to neurons, which improves voltage control. Our measurements revealed faster kinetics and shallower voltage-dependence of activation and deactivation for CaV2.1. Additionally, recordings of calcium current in response to a command waveform based on the motorneuron AP show, directly, more effective activation of CaV2.1. Analysis of calcium currents associated with the AP waveform indicate an approximately fourfold greater open probability (PO) for CaV2.1. The efficient activation of CaV2.1 channels during APs may contribute to the highly reliable transmission at zebrafish neuromuscular junctions. PMID:25650925

  19. Voltage sensitive calcium channels (VSCC) in cultured neuronal hybrid cells

    Energy Technology Data Exchange (ETDEWEB)

    Richard, C.L.; U' Prichard, D.C.; Noronha-Blob, L.

    1986-03-01

    Calcium entry via VSCC has been identified in selected, neuronal clonal cell lines using /sup 45/Ca uptake and the fluorescent calcium indicator, quin 2. VSCC in NG108-15 hybrid cells, differentiated with dibutyryl cyclic AMP (1 mM, 4 days) have been further characterized. Depolarization (50 mM K/sup +/, dp) resulted in a rapid (15 sec) influx of Ca/sup 2 +/. Intracellular calcium concentrations were elevated approx. 3 fold from 223 +- 68 nM to 666 +- 74 nM. Dp-sensitive calcium entry was voltage dependent, independent of Na/sup +/, stimulated (40%) by the agonist Bay K 8644 (1..mu..M) and blocked by divalent cations (..mu..M range) and organic calcium channel antagonists (nM range) Bay K 8644, in the absence of KCl, failed to stimulate Ca/sup 2 +/ influx. Tetrodotoxin (TTX) and tetraethylammonium had no effect on VSCC activity. Blockage of VSCC by nimodipine was reversed by increasing Ca/sup 2 +/ ions. IC/sub 50/ values were right shifted from 6.5 nM (1mM/sup 0/Ca/sup 2 +/) to 840 nM (10 mM Ca/sup 2 +/). Ca/sup 2 +/ entry was also stimulated by veratridine (VE), in a Na/sup +//sub 0/-sensitive manner. VE-induced Ca/sup 2 +/ entry was voltage-independent, TTX-sensitive, and was only 25% of dp-sensitive Ca/sup 2 +/ entry. These results together indicate that VSCC in neuronal cells offer a useful system for studying ion channel regulation.

  20. Iron overload and apoptosis of HL-1 cardiomyocytes: effects of calcium channel blockade.

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    Mei-pian Chen

    Full Text Available Iron overload cardiomyopathy that prevails in some forms of hemosiderosis is caused by excessive deposition of iron into the heart tissue and ensuing damage caused by a raise in labile cell iron. The underlying mechanisms of iron uptake into cardiomyocytes in iron overload condition are still under investigation. Both L-type calcium channels (LTCC and T-type calcium channels (TTCC have been proposed to be the main portals of non-transferrinic iron into heart cells, but controversies remain. Here, we investigated the roles of LTCC and TTCC as mediators of cardiac iron overload and cellular damage by using specific Calcium channel blockers as potential suppressors of labile Fe(II and Fe(III ingress in cultured cardiomyocytes and ensuing apoptosis.Fe(II and Fe(III uptake was assessed by exposing HL-1 cardiomyocytes to iron sources and quantitative real-time fluorescence imaging of cytosolic labile iron with the fluorescent iron sensor calcein while iron-induced apoptosis was quantitatively measured by flow cytometry analysis with Annexin V. The role of calcium channels as routes of iron uptake was assessed by cell pretreatment with specific blockers of LTCC and TTCC.Iron entered HL-1 cardiomyocytes in a time- and dose-dependent manner and induced cardiac apoptosis via mitochondria-mediated caspase-3 dependent pathways. Blockade of LTCC but not of TTCC demonstrably inhibited the uptake of ferric but not of ferrous iron. However, neither channel blocker conferred cardiomyocytes with protection from iron-induced apoptosis.Our study implicates LTCC as major mediators of Fe(III uptake into cardiomyocytes exposed to ferric salts but not necessarily as contributors to ensuing apoptosis. Thus, to the extent that apoptosis can be considered a biological indicator of damage, the etiopathology of cardiosiderotic damage that accompanies some forms of hemosiderosis would seem to be unrelated to LTCC or TTCC, but rather to other routes of iron ingress present in

  1. Physiology and Regulation of Calcium Channels in Stomatal Guard Cells

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, Julian I.

    2007-05-02

    Stomatal pores in the epidermis of leaves regulate the diffusion of CO2 into leaves for photosynthetic carbon fixation and control water loss of plants during drought periods. Guard cells sense CO2, water status, light and other environmental conditions to regulate stomatal apertures for optimization of CO2 intake and plant growth under drought stress. The cytosolic second messenger calcium contributes to stomatal movements by transducing signals and regulating ion channels in guard cells. Studies suggest that both plasma membrane Ca2+ influx channels and vacuolar/organellar Ca2+ release channels contribute to ABA-induced Ca2+ elevations in guard cells. Recent research in the P.I.'s laboratory has led to identification of a novel major cation-selective Ca2+-permeable influx channel (Ica) in the plasma membrane of Arabidopsis guard cells. These advances will allow detailed characterization of Ica plasma membrane Ca2+ influx channels in guard cells. The long term goal of this research project is to gain a first detailed characterization of these novel plasma membrane Ca2+-permeable channel currents in Arabidopsis guard cells. The proposed research will investigate the hypothesis that Ica represents an important Ca2+ influx pathway for ABA and CO2 signal transduction in Arabidopsis guard cells. These studies will lead to elucidation of key signal transduction mechanisms by which plants balance CO2 influx into leaves and transpirational water loss and may contribute to future strategies for manipulating gas exchange for improved growth of crop plants and for biomass production.

  2. Sigma-1 Receptor Plays a Negative Modulation on N-type Calcium Channel

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    Kang Zhang

    2017-05-01

    Full Text Available The sigma-1 receptor is a 223 amino acids molecular chaperone with a single transmembrane domain. It is resident to eukaryotic mitochondrial-associated endoplasmic reticulum and plasma membranes. By chaperone-mediated interactions with ion channels, G-protein coupled receptors and cell-signaling molecules, the sigma-1 receptor performs broad physiological and pharmacological functions. Despite sigma-1 receptors have been confirmed to regulate various types of ion channels, the relationship between the sigma-1 receptor and N-type Ca2+ channel is still unclear. Considering both sigma-1 receptors and N-type Ca2+ channels are involved in intracellular calcium homeostasis and neurotransmission, we undertake studies to explore the possible interaction between these two proteins. In the experiment, we confirmed the expression of the sigma-1 receptors and the N-type calcium channels in the cholinergic interneurons (ChIs in rat striatum by using single-cell reverse transcription-polymerase chain reaction (scRT-PCR and immunofluorescence staining. N-type Ca2+ currents recorded from ChIs in the brain slice of rat striatum was depressed when sigma-1 receptor agonists (SKF-10047 and Pre-084 were administrated. The inhibition was completely abolished by sigma-1 receptor antagonist (BD-1063. Co-expression of the sigma-1 receptors and the N-type calcium channels in Xenopus oocytes presented a decrease of N-type Ca2+ current amplitude with an increase of sigma-1 receptor expression. SKF-10047 could further depress N-type Ca2+ currents recorded from oocytes. The fluorescence resonance energy transfer (FRET assays and co-immunoprecipitation (Co-IP demonstrated that sigma-1 receptors and N-type Ca2+ channels formed a protein complex when they were co-expressed in HEK-293T (Human Embryonic Kidney -293T cells. Our results revealed that the sigma-1 receptors played a negative modulation on N-type Ca2+ channels. The mechanism for the inhibition of sigma-1 receptors on

  3. Putative calcium-binding domains of the Caenorhabditis elegans BK channel are dispensable for intoxication and ethanol activation.

    Science.gov (United States)

    Davis, S J; Scott, L L; Ordemann, G; Philpo, A; Cohn, J; Pierce-Shimomura, J T

    2015-07-01

    Alcohol modulates the highly conserved, voltage- and calcium-activated potassium (BK) channel, which contributes to alcohol-mediated behaviors in species from worms to humans. Previous studies have shown that the calcium-sensitive domains, RCK1 and the Ca(2+) bowl, are required for ethanol activation of the mammalian BK channel in vitro. In the nematode Caenorhabditis elegans, ethanol activates the BK channel in vivo, and deletion of the worm BK channel, SLO-1, confers strong resistance to intoxication. To determine if the conserved RCK1 and calcium bowl domains were also critical for intoxication and basal BK channel-dependent behaviors in C. elegans, we generated transgenic worms that express mutated SLO-1 channels predicted to have the RCK1, Ca(2+) bowl or both domains rendered insensitive to calcium. As expected, mutating these domains inhibited basal function of SLO-1 in vivo as neck and body curvature of these mutants mimicked that of the BK null mutant. Unexpectedly, however, mutating these domains singly or together in SLO-1 had no effect on intoxication in C. elegans. Consistent with these behavioral results, we found that ethanol activated the SLO-1 channel in vitro with or without these domains. By contrast, in agreement with previous in vitro findings, C. elegans harboring a human BK channel with mutated calcium-sensing domains displayed resistance to intoxication. Thus, for the worm SLO-1 channel, the putative calcium-sensitive domains are critical for basal in vivo function but unnecessary for in vivo ethanol action. © 2015 John Wiley & Sons Ltd and International Behavioural and Neural Genetics Society.

  4. Magnesium: Effect on ocular health as a calcium channel antagonist

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    Şafak Korkmaz

    2013-06-01

    Full Text Available Magnesium is the physiologic calcium channel blocker,involving in many different metabolic processes by maintainingcell membrane function, modulating smooth musclecontraction and influencing enzymatic activities. Magnesiumhas been shown to increase blood flow to tissuesby modifying endothelial function via endothelin-1 (ET-1and nitric Oxide (NO pathways. Magnesium also exhibitsneuroprotective role by blocking N-methyl-D-aspartate(NMDA receptor related calcium influx and by inhibitingthe release of glutamate, hence protects the cell againstoxidative stress and apoptosis. Both increase in bloodflow and its neuroprotective effect make magnesium agood candidate for glaucoma studies. Magnesium hasbeen shown to decrease oxidative stress and apoptosisin retinal tissue and to have retinal ganglion cell sparingeffect. A series of studies has been conducted aboutmagnesium could decrease insulin resistance in diabeticpatients, ease glycemia control and prevent diabetic retinopathy.Magnesium is found to be critically important inmaintaining normal ionic homeostasis of lens. Magnesiumdeficiency has been shown to cause increased lenticularoxidative stress and ionic imbalance in the lens so triggercataractogenesis. J Clin Exp Invest 2013; 4 (2: 244-251Key words: Magnesium, calcium channel blockage,glaucoma, neuroprotection, diabetic retinopathy, cataract

  5. The L-type Ca(2+) Channel Blocker Nifedipine Inhibits Mycelial Growth, Sporulation, and Virulence of Phytophthora capsici.

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    Liu, Peiqing; Gong, Jie; Ding, Xueling; Jiang, Yue; Chen, Guoliang; Li, Benjin; Weng, Qiyong; Chen, Qinghe

    2016-01-01

    The oomycete vegetable pathogen Phytophthora capsici causes significant losses of important vegetable crops worldwide. Calcium and other plant nutrients have been used in disease management of oomycete pathogens. Calcium homeostasis and signaling is essential for numerous biological processes, and Ca(2+) channel blockers prevent excessive Ca(2+) influx into the fungal cell. However, it is not known whether voltage-gated Ca(2+) channel blockers improve control over oomycete pathogens. In the present study, we compared the inhibitory effects of CaCl2 and the extracellular Ca(2+) chelator EDTA on mycelial growth and found that calcium assimilation plays a key role in P. capsici mycelial growth. Next, we involved the voltage-gated Ca(2+) channel blockers verapamil (VP) and nifedipine (NFD) to analyze the effect of Ca(2+) channel blockers on mycelial growth and sporulation; the results suggested that NFD, but not VP, caused significant inhibition. Ion rescue in an NFD-induced inhibition assay suggested that NFD-induced inhibition is calcium-dependent. In addition, NFD increased P. capsici sensitivity to H2O2 in a calcium-dependent manner, and extracellular calcium rescued it. Furthermore, NFD inhibited the virulence and gene expression related to its pathogenicity. These results suggest that NFD inhibits mycelial growth, sporulation, and virulence of P. capsici.

  6. Mechanism of sodium hydrosulfide modulation of L-type calcium channels in rat colonic smooth muscle cells.

    Science.gov (United States)

    Tang, Qincai; Quan, Xiaojing; Yan, Lin; Ren, Haixia; Chen, Wei; Xia, Hong; Luo, Hesheng

    2018-01-05

    Hydrogen sulfide (H 2 S) can exert different effects on the gastrointestinal tract by modulating ion channels. Previously, we found that H 2 S donor sodium hydrosulfide (NaHS) regulates colonic motility through L-type calcium channels, but the molecular mechanism remains unknown. The present study was designed to investigate possible mechanisms underlying the modulation of L-type calcium channels by NaHS in rat colonic smooth muscle cells. L-type calcium currents in colonic smooth muscle cells were recorded using the whole-cell patch-clamp technique. Spontaneous contractions of mid-colonic smooth muscle strips were measured in an organ bath system and a biological signal acquisition system. NaHS evoked a significant rightward shift in the steady-state activation curve of L-type calcium channels, changed the shape of the current-voltage (I-V) curve, and decreased the peak current density at 0mV, although it significantly increased with higher stimulatory voltage. The sulfhydryl-modifying reagent DL-dithiothreitol (DTT) enhanced the effects of NaHS on L-type calcium channels, while diamide (DM) and reduced L-glutathione (GSH) alleviated the effects of NaHS. Additionally, NaHS inhibited the spontaneous high-amplitude contractions of both longitudinal and circular smooth muscle strips in a dose-dependent manner. The inhibitory effects were reversible. DTT and GSH enhanced the effects of NaHS, while DM attenuated the effects of NaHS. In conclusion, NaHS modulates L-type calcium channels in rat colonic smooth muscle cells and regulates the contractile activity of colonic smooth muscle, potentially by modifying the free sulfhydryl groups of L-type calcium channels. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. The concentration of adrenaline and noradrenaline in the serum of dogs under the influence of calcium channels blockers

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    Milanović Tamara

    2015-01-01

    Full Text Available The most important characteristic of calcium channels is selective regulation of slow incoming stream of calcium into the cell tissue providing the slow increasement of action potential. Such tissues include smooth muscles of blood vessels, cardiocytes and heart noduses (AV and SA node. Different calcium antagonists have different effects on previous tissues due to their different chemical formula. Verapamile, Nifedipin and Diltiazem are the most frequently used of all. Their commonest characteristic is blocking the calcium channels causing vasodilatation of blood vessels as well as negative inotropic and chronotropic influence. By blocking the incoming calcium through slow channels of myofibrils of smooth muscles, the antagonists of calcium decrease the quantity of available calcium for contraction which causes vasodilatation. The most famous and most frequently used calcium antagonist is Verapamile. In terms of electrophysiology, Verapamile inhibits action potentials of heart noduses, especially the AV node, where the slow incoming of calcium is the most important for depolarization. Prolongation of the efective refractory period of SA node causes the heart frequency decreasement while prolongation of the effective refractory period of AV node slows down the work of chambers in case of flater and fibrillation of atriums. The molecules of calcium-bonding protein called kalmodulin are located in synaptic endings. Each kalmodulin can bond four calcium ions providing transfer into active calcium-kalmodulin complex which activates the kinase protein. Activated kinase protein starts the exocytosis of neurotransmitters into synaptic gap. Apart from activating kinase protein, calcium-kalmodulin complex also starts the activity of calcium pump presynaptic membrane which pumps calcium out of presynaptic ending stopping the further exocytosis of neurotransmitters into synaptic gap. Taking into consideration the fact that opening the calcium channels on

  8. Support for calcium channel gene defects in autism spectrum disorders

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    Lu Ake Tzu-Hui

    2012-12-01

    Full Text Available Abstract Background Alternation of synaptic homeostasis is a biological process whose disruption might predispose children to autism spectrum disorders (ASD. Calcium channel genes (CCG contribute to modulating neuronal function and evidence implicating CCG in ASD has been accumulating. We conducted a targeted association analysis of CCG using existing genome-wide association study (GWAS data and imputation methods in a combined sample of parent/affected child trios from two ASD family collections to explore this hypothesis. Methods A total of 2,176 single-nucleotide polymorphisms (SNP (703 genotyped and 1,473 imputed covering the genes that encode the α1 subunit proteins of 10 calcium channels were tested for association with ASD in a combined sample of 2,781 parent/affected child trios from 543 multiplex Caucasian ASD families from the Autism Genetics Resource Exchange (AGRE and 1,651 multiplex and simplex Caucasian ASD families from the Autism Genome Project (AGP. SNP imputation using IMPUTE2 and a combined reference panel from the HapMap3 and the 1,000 Genomes Project increased coverage density of the CCG. Family-based association was tested using the FBAT software which controls for population stratification and accounts for the non-independence of siblings within multiplex families. The level of significance for association was set at 2.3E-05, providing a Bonferroni correction for this targeted 10-gene panel. Results Four SNPs in three CCGs were associated with ASD. One, rs10848653, is located in CACNA1C, a gene in which rare de novo mutations are responsible for Timothy syndrome, a Mendelian disorder that features ASD. Two others, rs198538 and rs198545, located in CACN1G, and a fourth, rs5750860, located in CACNA1I, are in CCGs that encode T-type calcium channels, genes with previous ASD associations. Conclusions These associations support a role for common CCG SNPs in ASD.

  9. Nifedipine, a calcium channel blocker, inhibits advanced glycation end product (AGE)-elicited mesangial cell damage by suppressing AGE receptor (RAGE) expression via peroxisome proliferator-activated receptor-gamma activation

    Energy Technology Data Exchange (ETDEWEB)

    Matsui, Takanori [Department of Pathophysiology and Therapeutics of Diabetic Vascular Complications, Kurume University School of Medicine, 67 Asahi-machi, Kurume 830-0011 (Japan); Yamagishi, Sho-ichi, E-mail: shoichi@med.kurume-u.ac.jp [Department of Pathophysiology and Therapeutics of Diabetic Vascular Complications, Kurume University School of Medicine, 67 Asahi-machi, Kurume 830-0011 (Japan); Takeuchi, Masayoshi [Department of Pathophysiological Science, Faculty of Pharmaceutical Science, Hokuriku University, Kanazawa (Japan); Ueda, Seiji; Fukami, Kei; Okuda, Seiya [Department of Medicine, Kurume University School of Medicine, Kurume (Japan)

    2009-07-24

    The interaction between advanced glycation end products (AGE) and their receptor RAGE mediates the progressive alteration in renal architecture and loss of renal function in diabetic nephropathy. Oxidative stress generation and inflammation also play a central role in diabetic nephropathy. This study investigated whether and how nifedipine, a calcium channel blocker (CCB), blocked the AGE-elicited mesangial cell damage in vitro. Nifedipine, but not amlodipine, a control CCB, down-regulated RAGE mRNA levels and subsequently reduced reactive oxygen species (ROS) generation in AGE-exposed mesangial cells. AGE increased mRNA levels of vascular cell adhesion molecule-1 (VCAM-1) and induced monocyte chemoattractant protein-1 (MCP-1) production in mesangial cells, both of which were prevented by the treatment with nifedipine, but not amlodipine. The beneficial effects of nifedipine on AGE-exposed mesangial cells were blocked by the simultaneous treatment of GW9662, an inhibitor of peroxisome proliferator-activated receptor-{gamma} (PPAR-{gamma}). Although nifedipine did not affect expression levels of PPAR-{gamma}, it increased the PPAR-{gamma} transcriptional activity in mesangial cells. Our present study provides a unique beneficial aspect of nifedipine on diabetic nephropathy; it could work as an anti-inflammatory agent against AGE by suppressing RAGE expression in cultured mesangial cells via PPAR-{gamma} activation.

  10. Regulation of Spinal Substance P Release by Intrathecal Calcium Channel Blockade

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    Takasusuki, Toshifumi; Yaksh, Tony L.

    2012-01-01

    Background We investigated the role of different voltage sensitive calcium channels expressed at presynaptic afferent terminals in substance P release and on nociceptive behavior evoked by intraplantar formalin by examining the effects of intrathecally delivered N- (ziconotide), T- (mibefradil) and L-type voltage sensitive calcium channels blockers (diltiazem and verapamil). Methods Rats received intrathecal pretreatment with saline or doses of morphine, ziconotide, mibefradil, diltiazem or verapamil. The effect of these injections upon flinching evoked by intraplantar formalin (5%, 50μl) was quantified. To assess substance P release, the incidence of neurokinin 1 receptor internalization in the ipsilateral and contralateral lamina I was determined in immunofluorescent stained tissues. Results Intrathecal morphine (20μg), ziconotide (0.3, 0.6 and 1μg), mibefradil (100μg, but not 50μg), diltiazem (500μg, but not 300μg) and verapamil (200μg, but not 50 and 100μg) reduced paw flinching in phase 2 as compared to vehicle control (P Ziconotide (0.3, 0.6 and 1μg) and morphine (20μg) significantly inhibited neurokinin 1 receptor internalization (P < 0.05), but mibefradil, diltiazem and verapamil at the highest doses had no effect. Conclusion These results emphasize the role in vivo of N-, but not T- and L-type voltage sensitive calcium channels in mediating the stimulus evoked substance P release from small primary afferents and suggest that T- and L-type voltage sensitive calcium channels blockers exert antihyperalgesic effects by an action on other populations of afferents or mechanisms involving post synaptic excitability. PMID:21577088

  11. Interaction of H2S with Calcium Permeable Channels and Transporters

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    Weihua Zhang

    2015-01-01

    Full Text Available A growing amount of evidence has suggested that hydrogen sulfide (H2S, as a gasotransmitter, is involved in intensive physiological and pathological processes. More and more research groups have found that H2S mediates diverse cellular biological functions related to regulating intracellular calcium concentration. These groups have demonstrated the reciprocal interaction between H2S and calcium ion channels and transporters, such as L-type calcium channels (LTCC, T-type calcium channels (TTCC, sodium/calcium exchangers (NCX, transient receptor potential (TRP channels, β-adrenergic receptors, and N-methyl-D-aspartate receptors (NMDAR in different cells. However, the understanding of the molecular targets and mechanisms is incomplete. Recently, some research groups demonstrated that H2S modulates the activity of calcium ion channels through protein S-sulfhydration and polysulfide reactions. In this review, we elucidate that H2S controls intracellular calcium homeostasis and the underlying mechanisms.

  12. Effect of antiarrhythmic drugs on small conductance calcium - activated potassium channels.

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    Simó-Vicens, Rafel; Sauter, Daniel R P; Grunnet, Morten; Diness, Jonas G; Bentzen, Bo H

    2017-05-15

    Atrial fibrillation (AF) is the most common type of arrhythmia. Current pharmacological treatment for AF is moderately effective and/or increases the risk of serious ventricular adverse effects. To avoid ventricular adverse effects, a new target has been considered, the small conductance calcium-activated K+ channels (KCa2.X, SK channels). In the heart, KCa2.X channels are functionally more important in atria compared to ventricles, and pharmacological inhibition of the channel confers atrial selective prolongation of the cardiac action potential and converts AF to sinus rhythm in animal models of AF. Whether antiarrhythmic drugs (AADs) recommended for treating AF target KCa2.X channels is unknown. To this end, we tested a large number of AADs on the human KCa2.2 and KCa2.3 channels to assess their effect on this new target using automated whole-cell patch clamp. Of the AADs recommended for treatment of AF only dofetilide and propafenone inhibited hKCa2.X channels, with no subtype selectivity. The calculated IC50 were 90±10µmol/l vs 60±10µmol/l for dofetilide and 42±4µmol/l vs 80±20µmol/l for propafenone (hKCa2.3 vs hKCa2.2). Whether this inhibition has clinical importance for their antiarrhythmic effect is unlikely, as the calculated IC50 values are very high compared to the effective free therapeutic plasma concentration of the drugs when used for AF treatment, 40,000-fold for dofetilide and 140-fold higher for propafenone. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Voltage-Gated Calcium Channel Antagonists and Traumatic Brain Injury

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    Bruce Lyeth

    2013-06-01

    Full Text Available Traumatic brain injury (TBI is a leading cause of death and disability in the United States. Despite more than 30 years of research, no pharmacological agents have been identified that improve neurological function following TBI. However, several lines of research described in this review provide support for further development of voltage gated calcium channel (VGCC antagonists as potential therapeutic agents. Following TBI, neurons and astrocytes experience a rapid and sometimes enduring increase in intracellular calcium ([Ca2+]i. These fluxes in [Ca2+]i drive not only apoptotic and necrotic cell death, but also can lead to long-term cell dysfunction in surviving cells. In a limited number of in vitro experiments, both L-type and N-type VGCC antagonists successfully reduced calcium loads as well as neuronal and astrocytic cell death following mechanical injury. In rodent models of TBI, administration of VGCC antagonists reduced cell death and improved cognitive function. It is clear that there is a critical need to find effective therapeutics and rational drug delivery strategies for the management and treatment of TBI, and we believe that further investigation of VGCC antagonists should be pursued before ruling out the possibility of successful translation to the clinic.

  14. Calcium Channel Blockers and Esophageal Sclerosis: Should We Expect Exacerbation of Interstitial Lung Disease

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    Charalampos Seretis

    2012-01-01

    Full Text Available Esophageal sclerosis is the most common visceral manifestation of systemic sclerosis, resulting in impaired esophageal clearance and retention of ingested food; in addition, co-existence of lung fibrosis with esophageal scleroderma is not uncommon. Both the progression of generalized connective tissue disorders and the damaging effect of chronic aspiration due to esophageal dysmotility appear to be involved in this procedure of interstitial fibrosis. Nifedipine is a widely prescribed calcium antagonist in a significant percentage of rheumatologic patients suffering from Raynaud syndrome, in order to inhibit peripheral vasospasm. Nevertheless, blocking calcium channels has proven to contribute to exacerbation of gastroesophageal reflux, which consequently can lead to chronic aspiration. We describe the case of severe exacerbation of interstitial lung disease in a 76-year-old female with esophageal sclerosis who was treated with oral nifedipine for Raynaud syndrome.

  15. ATP-sensitive voltage- and calcium-dependent chloride channels in sarcoplasmic reticulum vesicles from rabbit skeletal muscle.

    Science.gov (United States)

    Kourie, J I

    1997-05-01

    Chloride channels in the sarcoplasmic reticulum (SR) are thought to play an essential role in excitation-contraction (E-C) coupling by balancing charge movement during calcium release and uptake. In this study the nucleotide-sensitivity of Cl- channels in the SR from rabbit skeletal muscle was investigated using the lipid bilayer technique. Two distinct ATP-sensitive Cl- channels that differ in their conductance and kinetic properties and in the mechanism of ATP-induced channel inhibition were observed. The first, a nonfrequent 150 pS channel was inhibited by trans (luminal) ATP, and the second, a common 75 pS small chloride (SCl) channel was inhibited by cis (cytoplasmic) ATP. In the case of the SCl channel the ATP-induced reversible decline in the values of current (maximal current amplitude, Imax and integral current, I') and kinetic parameters (frequency of opening FO, probability of the channel being open PO, mean open TO and closed Tc times) show a nonspecific block of the voltage- and Ca2+-dependent SCl channel. ATP was a more potent blocker from the cytoplasmic side than from the luminal side of the channel. The SCl channel block was not due to Ca2+ chelation by ATP, nor to phosphorylation of the channel protein. The inhibitory action of ATP was mimicked by the nonhydrolyzable analogue adenylylimidodiphosphate (AMP-PNP) in the absence of Mg2+. The inhibitory potency of the adenine nucleotides was charge dependent in the following order ATP4- > ADP3- > > > AMP2-. The data suggest that ATP-induced effects are mediated via an open channel block mechanism. Modulation of the SCl channel by [ATP]cis and [Ca2+]cis indicates that (i) this channel senses the bioenergetic state of the muscle fiber and (ii) it is linked to the ATP-dependent cycling of the Ca2+ between the SR and the sarcoplasm.

  16. Lavender oil-potent anxiolytic properties via modulating voltage dependent calcium channels.

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    Anita M Schuwald

    Full Text Available Recent clinical data support the clinical use of oral lavender oil in patients suffering from subsyndromal anxiety. We identified the molecular mechanism of action that will alter the perception of lavender oil as a nonspecific ingredient of aromatherapy to a potent anxiolytic inhibiting voltage dependent calcium channels (VOCCs as highly selective drug target. In contrast to previous publications where exorbitant high concentrations were used, the effects of lavender oil in behavioral, biochemical, and electrophysiological experiments were investigated in physiological concentrations in the nanomolar range, which correlate to a single dosage of 80 mg/d in humans that was used in clinical trials. We show for the first time that lavender oil bears some similarities with the established anxiolytic pregabalin. Lavender oil inhibits VOCCs in synaptosomes, primary hippocampal neurons and stably overexpressing cell lines in the same range such as pregabalin. Interestingly, Silexan does not primarily bind to P/Q type calcium channels such as pregabalin and does not interact with the binding site of pregabalin, the α2δ subunit of VOCCs. Lavender oil reduces non-selectively the calcium influx through several different types of VOCCs such as the N-type, P/Q-type and T-type VOCCs. In the hippocampus, one brain region important for anxiety disorders, we show that inhibition by lavender oil is mainly mediated via N-type and P/Q-type VOCCs. Taken together, we provide a pharmacological and molecular rationale for the clinical use of the oral application of lavender oil in patients suffering from anxiety.

  17. Glucocorticoids specifically enhance L-type calcium current amplitude and affect calcium channel subunit expression in the mouse hippocampus.

    Science.gov (United States)

    Chameau, Pascal; Qin, Yongjun; Spijker, Sabine; Smit, August Benjamin; Smit, Guus; Joëls, Marian

    2007-01-01

    Previous studies have shown that corticosterone enhances whole cell calcium currents in CA1 pyramidal neurons, through a pathway involving binding of glucocorticoid receptor homodimers to the DNA. We examined whether glucocorticoids show selectivity for L- over N-type of calcium currents. Moreover, we addressed the putative gene targets that eventually lead to the enhanced calcium currents. Electrophysiological recordings were performed in nucleated patches that allow excellent voltage control. Calcium currents in these patches almost exclusively involve N- and L-type channels. We found that L- but not N-type calcium currents were largely enhanced after treatment with a high dose of corticosterone sufficient to activate glucocorticoid receptors. Voltage dependency and kinetic properties of the currents were unaffected by the hormone. Nonstationary noise analysis suggests that the increased current is not caused by a larger unitary conductance, but rather to a doubling of the number of functional channels. Quantitative real-time PCR revealed that transcripts of the Ca(v)1 subunits encoding for the N- or L-type calcium channels are not upregulated in the mouse CA1 area; instead, a strong, direct, and consistent upregulation of the beta4 subunit was observed. This indicates that the corticosteroid-induced increase in number of L-type calcium channels is not caused by a simple transcriptional regulation of the pore-forming subunit of the channels.

  18. AMP-activated protein kinase inhibits TREK channels.

    Science.gov (United States)

    Kréneisz, Orsolya; Benoit, Justin P; Bayliss, Douglas A; Mulkey, Daniel K

    2009-12-15

    AMP-activated protein kinase (AMPK) is a serine/threonine kinase activated by conditions that increase the AMP : ATP ratio. In carotid body glomus cells, AMPK is thought to link changes in arterial O(2) with activation of glomus cells by inhibition of unidentified background K(+) channels. Modulation by AMPK of individual background K(+) channels has not been described. Here, we characterize effects of activated AMPK on recombinant TASK-1, TASK-3, TREK-1 and TREK-2 background K(+) channels expressed in HEK293 cells. We found that TREK-1 and TREK-2 channels but not TASK-1 or TASK-3 channels are inhibited by AMPK. AMPK-mediated inhibition of TREK involves key serine residues in the C-terminus that are also known to be important for PKA and PKC channel modulation; inhibition of TREK-1 requires Ser-300 and Ser-333 and inhibition of TREK-2 requires Ser-326 and Ser-359. Metabolic inhibition by sodium azide can also inhibit both TREK and TASK channels. The effects of azide on TREK occlude subsequent channel inhibition by AMPK and are attenuated by expression of a dominant negative catalytic subunit of AMPK (dnAMPK), suggesting that metabolic stress modulates TREK channels by an AMPK mechanism. By contrast, inhibition of TASK channels by azide was unaffected by expression of dnAMPK, suggesting an AMPK-independent mechanism. In addition, prolonged exposure (6-7 min) to hypoxia ( = 11 +/- 1 mmHg) inhibits TREK channels and this response was blocked by expression of dnAMPK. Our results identify a novel modulation of TREK channels by AMPK and indicate that select residues in the C-terminus of TREK are points of convergence for multiple signalling cascades including AMPK, PKA and PKC. To the extent that carotid body O(2) sensitivity is dependent on AMPK, our finding that TREK-1 and TREK-2 channels are inhibited by AMPK suggests that TREK channels may represent the AMPK-inhibited background K(+) channels that mediate activation of glomus cells by hypoxia.

  19. Calcium and Vitamin D increase mRNA levels for the growth control hIK1 channel in human epidermal keratinocytes but functional channels are not observed

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    Rossie Sandra

    2004-06-01

    Full Text Available Abstract Background Intermediate-conductance, calcium-activated potassium channels (IKs modulate proliferation and differentiation in mesodermal cells by enhancing calcium influx, and they contribute to the physiology of fluid movement in certain epithelia. Previous reports suggest that IK channels stimulate proliferative growth in a keratinocyte cell line; however, because these channels indirectly promote calcium influx, a critically unique component of the keratinocyte differentiation program, an alternative hypothesis is that they would be anti-proliferative and pro-differentiating. This study addresses these hypotheses. Methods Real-time PCR, patch clamp electrophysiology, and proliferation assays were used to determine if human IK1 (hIK1 expression and function are correlated with either proliferation or differentiation in cultured human skin epidermal keratinocytes, and skin biopsies grown in explant culture. Results hIK1 mRNA expression in human keratinocytes and skin was increased in response to anti-proliferative/pro-differentiating stimuli (elevated calcium and Vitamin D. Correspondingly, the hIK1 agonist 1-EBIO inhibited keratinocyte proliferation suggesting that the channel could be anti-proliferative and pro-differentiating. However, this proliferative inhibition by 1-EBIO was not reversed by a panel of hIK1 blockers, calling into question the mechanism of 1-EBIO action. Subsequent patch clamp electrophysiological analysis failed to detect hIK1 channel currents in keratinocytes, even those expressing substantial hIK1 mRNA in response to calcium and Vitamin D induced differentiation. Identical electrophysiological recording conditions were then used to observe robust IK1 currents in fibroblasts which express IK1 mRNA levels comparable to those of keratinocytes. Thus, the absence of observable hIK1 currents in keratinocytes was not a function of the electrophysiological techniques. Conclusion Human keratinocyte differentiation is

  20. Actions of Calcium Channel Blockers on Vascular Proteoglycan Synthesis: Relationship to Atherosclerosis

    Science.gov (United States)

    Survase, Soniya; Ivey, Melanie E; Nigro, Julie; Osman, Narin; Little, Peter J

    2005-01-01

    Calcium channel blockers (CCBs) are a widely used group of antihypertensive agents. CCBs are efficacious in the reduction of blood pressure but the extent to which they manifest beneficial effects on cardiovascular disease is variable. Clinical studies indicate that pleiotropic actions make significant contributions to the efficacy of agents aimed at preventing atherosclerosis. The “response to retention” hypothesis implicates the binding and retention of lipoproteins by glycosaminoglycan chains on proteoglycans as an initiating step in atherogenesis. Atherogenic factors act as agonists and several classes of drugs including peroxisome proliferating-activated receptor (PPAR)-α and -γ ligands act as antagonists in this model. Initial data have demonstrated that high concentrations of CCBs inhibit proteoglycan synthesis. Newer preliminary data show that the action is very modest at reasonable concentrations and appears to be independent of calcium channel blocking activity. We have reviewed the role of cardiovascular drugs acting on vascular smooth muscle proteoglycan synthesis and considered the potential action of CCBs in this model. We conclude that the inhibition of proteoglycan synthesis by CCBs does not play a role in the attenuation of atherosclerosis; however, the antihypertensive efficacy and alternative beneficial actions provide support for the use of CCBs in the therapy of cardiovascular disease. PMID:17319105

  1. Plasma membrane calcium channels in cancer: Alterations and consequences for cell proliferation and migration.

    Science.gov (United States)

    Déliot, Nadine; Constantin, Bruno

    2015-10-01

    The study of calcium channels in molecular mechanisms of cancer transformation is still a novel area of research. Several studies, mostly conducted on cancer cell lines, however support the idea that a diversity of plasma membrane channels participates in the remodeling of Ca2+ homeostasis, which regulates various cancer hallmarks such as uncontrolled multiplication and increase in migration and invasion abilities. However few is still understood concerning the intracellular signaling cascades mobilized by calcium influx participating to cancer cell behavior. This review intends to gather some of these pathways dependent on plasma membrane calcium channels and described in prostate, breast and lung cancer cell lines. In these cancer cell types, the calcium channels involved in calcium signaling pathways promoting cancer behaviors are mostly non-voltage activated calcium channels and belong to the TRP superfamily (TRPC, TPRPV and TRPM families) and the Orai family. TRP and Orai channels are part of many signaling cascades involving the activation of transmembrane receptors by extracellular ligand from the tumor environment. TRPV can sense changes in the physical and chemical environment of cancer cells and TRPM7 are stretch activated and sensitive to cholesterol. Changes in activation and or expression of plasma-membrane calcium channels affect calcium-dependent signaling processes relevant to tumorigenesis. The studies cited in this review suggest that an increase in plasma membrane calcium channel expression and/or activity sustain an elevated calcium entry (constitutive or under the control of extracellular signals) promoting higher cell proliferation and migration in most cases. A variety of non-voltage-operated calcium channels display change expression and/or activity in a same cancer type and cooperate to the same process relevant to cancer cell behavior, or can be involved in a different sequence of events during the tumorigenesis. This article is part of a

  2. T-Type Calcium Channels Are Required to Maintain Viability of Neural Progenitor Cells.

    Science.gov (United States)

    Kim, Ji-Woon; Oh, Hyun Ah; Lee, Sung Hoon; Kim, Ki Chan; Eun, Pyung Hwa; Ko, Mee Jung; Gonzales, Edson Luck T; Seung, Hana; Kim, Seonmin; Bahn, Geon Ho; Shin, Chan Young

    2018-02-21

    T-type calcium channels are low voltage-activated calcium channels that evoke small and transient calcium currents. Recently, T-type calcium channels have been implicated in neurodevelopmental disorders such as autism spectrum disorder and neural tube defects. However, their function during embryonic development is largely unknown. Here, we investigated the function and expression of T-type calcium channels in embryonic neural progenitor cells (NPCs). First, we compared the expression of T-type calcium channel subtypes (CaV3.1, 3.2, and 3.3) in NPCs and differentiated neural cells (neurons and astrocytes). We detected all subtypes in neurons but not in astrocytes. In NPCs, CaV3.1 was the dominant subtype, whereas CaV3.2 was weakly expressed, and CaV3.3 was not detected. Next, we determined CaV3.1 expression levels in the cortex during early brain development. Expression levels of CaV3.1 in the embryonic period were transiently decreased during the perinatal period and increased at postnatal day 11. We then pharmacologically blocked T-type calcium channels to determine the effects in neuronal cells. The blockade of T-type calcium channels reduced cell viability, and induced apoptotic cell death in NPCs but not in differentiated astrocytes. Furthermore, blocking T-type calcium channels rapidly reduced AKT-phosphorylation (Ser473) and GSK3β-phosphorylation (Ser9). Our results suggest that T-type calcium channels play essential roles in maintaining NPC viability, and T-type calcium channel blockers are toxic to embryonic neural cells, and may potentially be responsible for neurodevelopmental disorders.

  3. Role of L-type calcium-channel modulation in nonconvulsive epilepsy in rats

    NARCIS (Netherlands)

    Luijtelaar, E.L.J.M. van; Ates, N.; Coenen, A.M.L.

    1995-01-01

    Old male Wistar rats spontaneously showing hundreds of spike-wave discharges daily were used to investigate the role of calcium ions in nonconvulsive epilepsy. The effects of the L-type calcium channel blocker nimodipine and the L-type channel opener BAY K 8644 on number and duration of these

  4. Small and Intermediate Calcium-Activated Potassium Channel Openers Improve Rat Endothelial and Erectile Function

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    Simon G. Comerma-Steffensen

    2017-09-01

    Full Text Available Modulation of endothelial calcium-activated potassium (KCa channels has been proposed as an approach to restore endothelial function. The present study investigated whether novel openers of KCa channels with small (KCa2.x and intermediate (KCa3.1 conductance, NS309 and NS4591, improve endothelium-dependent relaxation and erectile function. Rat corpus cavernosum (CC strips were mounted for isometric tension recording and processed for immunoblotting. Mean arterial pressure (MAP, intracavernosal pressure (ICP, and electrocardiographic (ECG measurements were conducted in anesthetized rats. Immunoblotting revealed the presence of KCa2.3 and large KCa conductance (KCa1.1 channels in the corpus cavernosum. NS309 and NS4591 increased current in CC endothelial cells in whole cell patch clamp experiments. Relaxation induced by NS309 (<1 μM was inhibited by endothelial cell removal and high extracellular potassium. An inhibitor of nitric oxide (NO synthase, and blockers of KCa2.x and KCa1.1 channels, apamin and iberiotoxin also inhibited NS309 relaxation. Incubation with NS309 (0.5 μM markedly enhanced acetylcholine relaxation. Basal erectile function (ICP/MAP increased during administration of NS309. Increases in ICP/MAP after cavernous nerve stimulation with NS309 were unchanged, whereas NS4591 significantly improved erectile function. Administration of NS309 and NS4591 caused small changes in the electrocardiogram, but neither arrhythmic events nor prolongation of the QTc interval were observed. The present study suggests that openers of KCa2.x and KCa3.1 channels improve endothelial and erectile function. The effects of NS309 and NS4591 on heart rate and ECG are small, but will require additional safety studies before evaluating whether activation of KCa2.3 channels has a potential for treatment of erectile dysfunction.

  5. Nitric oxide regulates neuronal activity via calcium-activated potassium channels.

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    Lei Ray Zhong

    Full Text Available Nitric oxide (NO is an unconventional membrane-permeable messenger molecule that has been shown to play various roles in the nervous system. How NO modulates ion channels to affect neuronal functions is not well understood. In gastropods, NO has been implicated in regulating the feeding motor program. The buccal motoneuron, B19, of the freshwater pond snail Helisoma trivolvis is active during the hyper-retraction phase of the feeding motor program and is located in the vicinity of NO-producing neurons in the buccal ganglion. Here, we asked whether B19 neurons might serve as direct targets of NO signaling. Previous work established NO as a key regulator of growth cone motility and neuronal excitability in another buccal neuron involved in feeding, the B5 neuron. This raised the question whether NO might modulate the electrical activity and neuronal excitability of B19 neurons as well, and if so whether NO acted on the same or a different set of ion channels in both neurons. To study specific responses of NO on B19 neurons and to eliminate indirect effects contributed by other cells, the majority of experiments were performed on single cultured B19 neurons. Addition of NO donors caused a prolonged depolarization of the membrane potential and an increase in neuronal excitability. The effects of NO could mainly be attributed to the inhibition of two types of calcium-activated potassium channels, apamin-sensitive and iberiotoxin-sensitive potassium channels. NO was found to also cause a depolarization in B19 neurons in situ, but only after NO synthase activity in buccal ganglia had been blocked. The results suggest that NO acts as a critical modulator of neuronal excitability in B19 neurons, and that calcium-activated potassium channels may serve as a common target of NO in neurons.

  6. The influence of environmental calcium concentrations on calcium flux, compensatory drinking and epithelial calcium channel expression in a freshwater cartilaginous fish.

    Science.gov (United States)

    Allen, Peter J; Weihrauch, Dirk; Grandmaison, Vanessa; Dasiewicz, Patricia; Peake, Stephan J; Anderson, W Gary

    2011-03-15

    Calcium metabolism and mRNA levels of the epithelial calcium channel (ECaC) were examined in a freshwater cartilaginous fish, the lake sturgeon Acipenser fulvescens. Lake sturgeon were acclimated for ≥2 weeks to 0.1 (low), 0.4 (normal) or 3.3 (high) mmol l(-1) environmental calcium. Whole-body calcium flux was examined using (45)Ca as a radioactive marker. Net calcium flux was inward in all treatment groups; however, calcium influx was greatest in the low calcium environment and lowest in the high calcium environment, whereas efflux had the opposite relationship. A significant difference in the concentration of (45)Ca in the gastrointestinal tract (GIT) of fish in the low calcium environment led to the examination of drinking rate and calcium flux across the anterior-middle (mid) intestine. Drinking rate was not different between treatments; however, calcium influx across the mid-intestine in the low calcium treatment was significantly greater than that in both the normal and high calcium treatments. The lake sturgeon ECaC was 2831 bp in length, with a predicted protein sequence of 683 amino acids that shared a 66% identity with the closest sequenced ECaCs from the vertebrate phyla. ECaC mRNA levels were examined in the gills, kidney, pyloric caeca, mid-intestine and spiral intestine. Expression levels were highest in the gills, then the kidneys, and were orders of magnitude lower in the GIT. Contrary to existing models for calcium uptake in the teleost gill, ECaC expression was greatest in high calcium conditions and kidney ECaC expression was lowest in low calcium conditions, suggesting that cellular transport mechanisms for calcium may be distinctly different in these freshwater cartilaginous fishes.

  7. Inhibition of mitochondrial calcium uptake 1 in Drosophila neurons.

    Science.gov (United States)

    M'Angale, P G; Staveley, B E

    2017-02-08

    The mitochondrial calcium uptake 1 (MICU1) is a regulatory subunit of the mitochondrial calcium uniporter that plays an important role in calcium sensing. It contains two EF-hand domains that are well conserved across diverse species from protozoa to plants and metazoans. The loss of MICU1 function in mammals is attributed to several neurological disorders that involve movement dysfunction. The CG4495 gene in Drosophila melanogaster was identified as a putative homolog of MICU1 in the HomoloGene database of the National Centre for Biotechnology Information (NCBI). In agreement with previous studies that have shown the development of neurological disorders and movement defects in MICU1 loss-of-function organisms, we attempted to identify the function of CG4495/MICU1 in Drosophila neurons. We analyzed survival and locomotor ability of these flies and additionally performed biometric analysis of the Drosophila developing eye. The inducible RNA interference-mediated inhibition of CG4495/MICU1 in the Ddc-Gal4-expressing neurons of Drosophila presented with reduction in survival coupled with a precocious loss of locomotor ability. Since the pro-survival Bcl-2 family genes have been shown to be protective towards mitochondria, and CG4495/MICU1 has a mitochondrial targeting sequence, we attempted to rescue the phenotypes resulting from the inhibition of CG4495/MICU1 by overexpressing Buffy, the sole Bcl-2 homologue in Drosophila. The co-expression of CG4495/MICU1-RNAi along with Buffy resulted in the suppression of the phenotypes induced by the inhibition of CG4495/MICU1. Subsequently, the inhibition of CG4495/MICU1 in the Drosophila developing eye, a neuron-rich organ, resulted in reduced number of ommatidia and a highly fused ommatidial array. These developmental eye defects were rescued by the overexpression of Buffy. Our study suggests an important role for MICU1 in the normal function of neurons in Drosophila.

  8. Modulation of the N-type calcium channel gene expression by the alpha subunit of Go.

    Science.gov (United States)

    Kim, Bum-Jun; Ghil, Sung-Ho; Kim, Min-Ji; Yun Park, So; Kim, Dong-Sun; Hwan Kim, Sung; Chin, Hemin; Birnbaumer, Lutz; Jiang, Meisheng; Hong, Sung Youl; Suh-Kim, Haeyoung; Lee, Young-Don

    2003-04-10

    Go, a heterotrimeric G-protein, is enriched in brain and neuronal growth cones. Although several reports suggest that Go may be involved in modulation of neuronal differentiation, the precise role of Go is not clear. To investigate the function of Go in neuronal differentiation, we determined the effect of Goalpha, the alpha subunit of Go, on the expression of Ca(v)2.2, the pore-forming unit of N-type calcium channels, at the transcription level. Treatment with cyclic AMP (cAMP), which triggers neurite outgrowth in neuroblastoma F11 cells, increased the mRNA level and the promoter activity of the Ca(v)2.2 gene. Overexpression of Goalpha inhibited neurite extension in F11 cells and simultaneously repressed the stimulatory effect of cAMP on the Ca(v)2.2 gene expression to the basal level. Targeted mutation of the Goalpha gene also increased the level of Ca(v)2.2 in the brain. These results suggest that Go may regulate neuronal differentiation through modulation of gene expression of target genes such as N-type calcium channels.

  9. A functional tandem between transient receptor potential canonical channels 6 and calcium-dependent chloride channels in human epithelial cells.

    Science.gov (United States)

    Bertrand, Johanna; Dannhoffer, Luc; Antigny, Fabrice; Vachel, Laura; Jayle, Christophe; Vandebrouck, Clarisse; Becq, Frédéric; Norez, Caroline

    2015-10-15

    TRPC6 plays important human physiological functions, notably in artery and arterioles constriction, in regulation of vascular volume and in bronchial muscle constriction. It is implicated in pulmonary hypertension, cardiovascular disease, and focal segmental glomerulosclerosis and seems to play a role in cancer development. Previously, we identified Guanabenz, an α2-adrenergic agonist used for hypertension treatment (Wytensin®), as an activator of calcium-dependent chloride channels (CaCC) in human Cystic Fibrosis (CF) nasal epithelial cells by transiently increasing [Ca2+]i via an influx of extracellular Ca2+. In this study, using assays to measure chloride channel activity, we show that guanabenz is an activator of CaCC in freshly dissociated human bronchial epithelial cells from three CF patients with various genotypes (F508del/F508del, F508del/R1066C, F508del/H1085R). We further characterised the effect of guanabenz and show that it is independent of α-adrenergic receptors, is inhibited by the TRPC family inhibitor SKF-96365 but not by the TRPV family inhibitor ruthenium red. Using western-blotting, Ca2+ measurements and iodide efflux assay, we found that TRPC1 siRNA has no effect on guanabenz induced responses whereas TRPC6 siRNA prevented the guanabenz-dependent Ca2+ influx and the CaCC-dependent activity stimulated by guanabenz. In conclusion, we show that TRPC6 channel is pivotal for the activation of CaCC by guanabenz through a α2-adrenergic-independent pathway in human airway epithelial cells. We suggest propose a functional coupling between TRPC6 and CaCC and guanabenz as a potential TRPC6 activator for exploring TRPC6 and CaCC channel functions and corresponding channelopathies. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Immunolocalization and expression of small-conductance calcium-activated potassium channels in human myometrium

    DEFF Research Database (Denmark)

    Rosenbaum, Sofia T; Svalø, Julie; Nielsen, Karsten

    2012-01-01

    Small-conductance calcium-activated potassium (SK3) channels have been detected in human myometrium and we have previously shown a functional role of SK channels in human myometrium in vitro. The aims of this study were to identify the precise localization of SK3 channels and to quantify SK3 mRNA...

  11. New Role of P/Q-type Voltage-gated Calcium Channels

    DEFF Research Database (Denmark)

    Hansen, Pernille B L

    2015-01-01

    Voltage-gated calcium channels are important for the depolarization-evoked contraction of vascular smooth muscle cells (SMCs), with L-type channels being the classical channel involved in this mechanism. However, it has been demonstrated that the CaV2.1 subunit, which encodes a neuronal isoform o...

  12. Signal processing by T-type calcium channel interactions in the cerebellum.

    Science.gov (United States)

    Engbers, Jordan D T; Anderson, Dustin; Zamponi, Gerald W; Turner, Ray W

    2013-11-27

    T-type calcium channels of the Cav3 family are unique among voltage-gated calcium channels due to their low activation voltage, rapid inactivation, and small single channel conductance. These special properties allow Cav3 calcium channels to regulate neuronal processing in the subthreshold voltage range. Here, we review two different subthreshold ion channel interactions involving Cav3 channels and explore the ability of these interactions to expand the functional roles of Cav3 channels. In cerebellar Purkinje cells, Cav3 and intermediate conductance calcium-activated potassium (IKCa) channels form a novel complex which creates a low voltage-activated, transient outward current capable of suppressing temporal summation of excitatory postsynaptic potentials (EPSPs). In large diameter neurons of the deep cerebellar nuclei, Cav3-mediated calcium current (I T) and hyperpolarization-activated cation current (I H) are activated during trains of inhibitory postsynaptic potentials. These currents have distinct, and yet synergistic, roles in the subthreshold domain with I T generating a rebound burst and I H controlling first spike latency and rebound spike precision. However, by shortening the membrane time constant the membrane returns towards resting value at a faster rate, allowing I H to increase the efficacy of I T and increase the range of burst frequencies that can be generated. The net effect of Cav3 channels thus depends on the channels with which they are paired. When expressed in a complex with a KCa channel, Cav3 channels reduce excitability when processing excitatory inputs. If functionally coupled with an HCN channel, the depolarizing effect of Cav3 channels is accentuated, allowing for efficient inversion of inhibitory inputs to generate a rebound burst output. Therefore, signal processing relies not only on the activity of individual subtypes of channels but also on complex interactions between ion channels whether based on a physical complex or by indirect

  13. Signal processing by T-type calcium channel interactions in the cerebellum

    Directory of Open Access Journals (Sweden)

    Jordan D.T. Engbers

    2013-11-01

    Full Text Available T-type calcium channels of the Cav3 family are unique among voltage-gated calcium channels due to their low activation voltage, rapid inactivation, and small single channel conductance. These special properties allow Cav3 calcium channels to regulate neuronal processing in the subthreshold voltage range. Here, we review two different subthreshold ion channel interactions involving Cav3 channels and explore the ability of these interactions to expand the functional roles of Cav3 channels. In cerebellar Purkinje cells, Cav3 and intermediate conductance calcium-activated potassium (IKCa channels form a novel complex which creates a low voltage-activated, transient outward current capable of suppressing temporal summation of excitatory postsynaptic potentials (EPSPs. In large diameter neurons of the deep cerebellar nuclei, Cav3-mediated calcium current (IT and hyperpolarization-activated cation current (IH are activated during trains of IPSPs. These currents have distinct, and yet synergistic, roles in the subthreshold domain with IT generating a rebound burst and IH controlling first spike latency and rebound spike precision. However, by shortening the membrane time constant the membrane returns towards resting value at a faster rate, allowing IH to increase the efficacy of IT, and increase the range of burst frequencies that can be generated. The net effect of Cav3 channels thus depends on the channels with which they are paired. When expressed in a complex with a KCa channel, Cav3 channels reduce excitability when processing excitatory inputs. If functionally coupled with an HCN channel, the depolarizing effect of Cav3 channels is accentuated, allowing for efficient inversion of inhibitory inputs to generate a rebound burst output. Therefore, signal processing relies not only on the activity of individual subtypes of channels but also on complex interactions between ion channels whether based on a physical complex or by indirect effects on

  14. Protons inhibit anoctamin 1 by competing with calcium.

    Science.gov (United States)

    Chun, Hyeyeon; Cho, Hawon; Choi, Jimi; Lee, Jesun; Kim, Sung Min; Kim, Hyungsup; Oh, Uhtaek

    2015-11-01

    Cl(-) efflux through Ca(2+)-activated Cl(-) channels (CaCCs) in secretory epithelial cells plays a key role in the regulation of fluid secretion. The fluid and electrolyte secretion is closely related to intracellular pH. CaCCs have been known to be inhibited by intracellular acid. However, the molecular mechanism for the inhibition remains unknown. Anoctamin 1 (ANO1) is a Ca(2+)-activated Cl(-) channel that mediates numerous physiological functions including fluid secretion in secretory epithelia. However, little is known about whether ANO1 can be modulated by change of intracellular pH. Here, we demonstrate that Ca(2+)-induced activation of ANO1 and its homolog ANO2 are strongly inhibited by intracellular acid. Intracellular acid caused a rightward shift of the concentration-response curve of Ca(2+) in activating ANO1 and ANO2. To identify the location of the acid-induced inhibition, mutations were made on each of all histidine residues in cytoplasmic part of ANO1. However, none of the His-mutant showed the reduction in the acid-induced inhibition. Furthermore, mutation on Glu- or Asp-residues in the multiple acidic-amino acid regions was ineffective in blocking the acid-induced inhibition. Because the Ca(2+)-binding site of a fungal anoctamin (nhTMEM16) was uncovered by crystallography, mutagenesis was performed in this region. Surprisingly, mutations at Glu, Asp or Asn residues in the hydrophobic core that are known to be essential for Ca(2+)-induced activation of ANO1 blocked the acid-induced inhibition. These results suggest that protons interfere with Ca(2+) at the Ca(2+) binding site of ANO1. These findings provide a molecular mechanism underlying the acid-induced inhibition of ANO1, which may contribute to control fluid and electrolyte secretion in the secretory epithelia. Copyright © 2015. Published by Elsevier Ltd.

  15. The role of T-type calcium channel genes in absence seizures

    Directory of Open Access Journals (Sweden)

    Yucai eChen

    2014-05-01

    Full Text Available The thalamic relay neurons, reticular thalamic nucleus, and neocortical pyramidal cells form a circuit that sustains oscillatory burst firing, and is regarded as the underlying mechanism of absence seizures. T-type calcium channels play a key role in this circuit. Here we review the role of T-type calcium channel genes in the development of absence seizures, and emphasize gain or loss of function mutations, and other variations that alter both quantity and quality of transcripts, and methylation status of isoforms of T-type calcium channel proteins might be of equal importance in understanding the pathological mechanism of absence seizures.

  16. Calcium channels and their blockers in intraocular pressure and glaucoma.

    Science.gov (United States)

    Mayama, Chihiro

    2014-09-15

    Several factors besides high intraocular pressure assumed to be associated with the development and progression of glaucoma, and calcium channel blockers (CCBs) have been an anticipated option for glaucoma treatment by improving ocular perfusion and/or exerting neuroprotective effects on retinal ganglion cells with safety established in wide and long-term usage. Decrease in IOP has been reported after topical application of CCBs, however, the effect is much smaller and almost negligible after systemic application. Various CCBs have been reported to increase posterior ocular blood flow in vivo and to exert direct neuroprotection in neurons in vitro. Distribution of the drug at a pharmacologically active concentration in the posterior ocular tissues across the blood-brain barrier or blood-retina barrier, especially in the optic nerve head and retina where the ganglion cells mainly suffer from glaucomatous damage, is essential for clinical treatment of glaucoma. Improved visual functions such as sensitivity in the visual field test have been reported after administration of CCBs, but evidences from the randomized studies have been limited and effects of CCBs on blood flow and direct neuroprotection are hardly distinguished from each other. © 2013 Published by Elsevier B.V.

  17. NSAIDs acutely inhibit TRPC channels in freshly isolated rat glomeruli

    Energy Technology Data Exchange (ETDEWEB)

    Ilatovskaya, Daria V. [Department of Physiology, Medical College of Wisconsin, Milwaukee, WI (United States); Institute of Cytology RAS, St. Petersburg (Russian Federation); Levchenko, Vladislav; Ryan, Robert P.; Cowley, Allen W. [Department of Physiology, Medical College of Wisconsin, Milwaukee, WI (United States); Staruschenko, Alexander, E-mail: Staruschenko@mcw.edu [Department of Physiology, Medical College of Wisconsin, Milwaukee, WI (United States)

    2011-05-06

    Highlights: {yields} We have established a unique approach to search for physiologically relevant mechanisms of TRPC channels in podocytes. {yields} This study describes endogenous TRPC channels in the isolated decapsulated glomeruli preparation. {yields} We report for the first time that NSAIDs inhibit TRPC channels in podocytes. -- Abstract: Using a novel approach for analysis of TRPC channel activity, we report here that NSAIDs are involved into regulation of TRPC channels in the podocytes of the freshly isolated decapsulated glomeruli. Fluorescence and electron microscopy techniques confirmed the integrity of podocytes in the glomeruli. Western blotting showed that TRPC1, 3 and 6 are highly expressed in the glomeruli. Single-channel patch clamp analysis revealed cation currents with distinct TRPC properties. This is the first report describing single TRPC-like currents in glomerular podocytes. Furthermore, our data provide a novel mechanism of NSAIDs regulation of TRPC channels, which might be implicated in maintaining the glomerular filtration barrier.

  18. Anti-neuroinflammatory effects of the calcium channel blocker nicardipine on microglial cells: implications for neuroprotection.

    Directory of Open Access Journals (Sweden)

    Bor-Ren Huang

    Full Text Available BACKGROUND/OBJECTIVE: Nicardipine is a calcium channel blocker that has been widely used to control blood pressure in severe hypertension following events such as ischemic stroke, traumatic brain injury, and intracerebral hemorrhage. However, accumulating evidence suggests that inflammatory processes in the central nervous system that are mediated by microglial activation play important roles in neurodegeneration, and the effect of nicardipine on microglial activation remains unresolved. METHODOLOGY/PRINCIPAL FINDINGS: In the present study, using murine BV-2 microglia, we demonstrated that nicardipine significantly inhibits microglia-related neuroinflammatory responses. Treatment with nicardipine inhibited microglial cell migration. Nicardipine also significantly inhibited LPS plus IFN-γ-induced release of nitric oxide (NO, and the expression of inducible nitric oxide synthase (iNOS and cyclooxygenase-2 (COX-2. Furthermore, nicardipine also inhibited microglial activation by peptidoglycan, the major component of the Gram-positive bacterium cell wall. Notably, nicardipine also showed significant anti-neuroinflammatory effects on microglial activation in mice in vivo. CONCLUSION/SIGNIFICANCE: The present study is the first to report a novel inhibitory role of nicardipine on neuroinflammation and provides a new candidate agent for the development of therapies for inflammation-related neurodegenerative diseases.

  19. Blockade of L-type calcium channel in myocardium and calcium-induced contractions of vascular smooth muscle by CPU 86017.

    Science.gov (United States)

    Dai, De-zai; Hu, Hui-juan; Zhao, Jing; Hao, Xue-mei; Yang, Dong-mei; Zhou, Pei-ai; Wu, Cai-hong

    2004-04-01

    To assess the blockade by CPU 86017 on the L-type calcium channels in the myocardium and on the Ca(2+)-related contractions of vascular smooth muscle. The whole-cell patch-clamp was applied to investigate the blocking effect of CPU 86017 on the L-type calcium current in isolated guinea pig myocytes and contractions by KCl or phenylephrine (Phe) of the isolated rat tail arteries were measured. Suppression of the L-type current of the isolated myocytes by CPU 86017 was moderate, in time- and concentration-dependent manner and with no influence on the activation and inactivation curves. The IC(50) was 11.5 micromol/L. Suppressive effect of CPU 86017 on vaso-contractions induced by KCl 100 mmol/L, phenylephrine 1 micromol/L in KH solution (phase 1), Ca(2+) free KH solution ( phase 2), and by addition of CaCl(2) into Ca(2+)-free KH solution (phase 3) were observed. The IC(50) to suppress vaso-contractions by calcium entry via the receptor operated channel (ROC) and voltage-dependent channel (VDC) was 0.324 micromol/L and 16.3 micromol/L, respectively. The relative potency of CPU 86017 to suppress vascular tone by Ca(2+) entry through ROC and VDC is 1/187 of prazosin and 1/37 of verapamil, respectively. The blocking effects of CPU 86017 on the L-type calcium channel of myocardium and vessel are moderate and non-selective. CPU 86017 is approximately 50 times more potent in inhibiting ROC than VDC.

  20. Use of clopidogrel and calcium channel blockers and risk of major adverse cardiovascular events

    DEFF Research Database (Denmark)

    Schmidt, Morten; Johansen, Martin B; Robertson, Douglas J

    2012-01-01

    Eur J Clin Invest 2011 ABSTRACT: Background  The CYP3A4 inhibition by calcium channel blockers (CCBs) may attenuate the effectiveness of clopidogrel. Using time-varying drug exposure ascertainment, we examined whether CCB use modified the association between clopidogrel use and major adverse......-month follow-up, we tracked the use of clopidogrel and CCBs and the rate of MACE (composite of myocardial infarction, ischaemic stroke, stent thrombosis, target lesion revascularization, or cardiac death). We used Cox regression to compute hazard ratios, controlling for potential confounders. Results......  Overall, the 12-month risk for MACE was 14·5%. The rate was 130 per 1000 person years for concomitant clopidogrel and CCB use, 106 for clopidogrel without CCB use, 213 for CCB without clopidogrel use, and 248 for no use of either drug. The adjusted hazard ratio for MACE comparing clopidogrel use...

  1. Extracellular protons enable activation of the calcium-dependent chloride channel TMEM16A.

    Science.gov (United States)

    Cruz-Rangel, Silvia; De Jesús-Pérez, José J; Aréchiga-Figueroa, Iván A; Rodríguez-Menchaca, Aldo A; Pérez-Cornejo, Patricia; Hartzell, H Criss; Arreola, Jorge

    2017-03-01

    The calcium-activated chloride channel TMEM16A provides a pathway for chloride ion movements that are key in preventing polyspermy, allowing fluid secretion, controlling blood pressure, and enabling gastrointestinal activity. TMEM16A is opened by voltage-dependent calcium binding and regulated by permeant anions and intracellular protons. Here we show that a low proton concentration reduces TMEM16A activity while maximum activation is obtained when the external proton concentration is high. In addition, protonation conditions determine the open probability of TMEM16A without changing its calcium sensitivity. External glutamic acid 623 (E623) is key for TMEM16A's ability to respond to external protons. At physiological pH, E623 is un-protonated and TMEM16A is activated when intracellular calcium increases; however, under acidic conditions E623 is partially protonated and works synergistically with intracellular calcium to activate the channel. These findings are critical for understanding physiological and pathological processes that involve changes in pH and chloride flux via TMEM16A. Transmembrane protein 16A (TMEM16A), also known as ANO1, the pore-forming subunit of a Ca(2+) -dependent Cl(-) channel (CaCC), is activated by direct, voltage-dependent, binding of intracellular Ca(2+) . Endogenous CaCCs are regulated by extracellular protons; however, the molecular basis of such regulation remains unidentified. Here, we evaluated the effects of different extracellular proton concentrations ([H(+) ]o ) on mouse TMEM16A expressed in HEK-293 cells using whole-cell and inside-out patch-clamp recordings. We found that increasing the [H(+) ]o from 10(-10) to 10(-5.5)  m caused a progressive increase in the chloride current (ICl ) that is described by titration of a protonatable site with pK = 7.3. Protons regulate TMEM16A in a voltage-independent manner, regardless of channel state (open or closed), and without altering its apparent Ca(2+) sensitivity. Noise analysis

  2. Inhibition of HERG potassium channels by celecoxib and its mechanism.

    Directory of Open Access Journals (Sweden)

    Roman V Frolov

    Full Text Available Celecoxib (Celebrex, a widely prescribed selective inhibitor of cyclooxygenase-2, can modulate ion channels independently of cyclooxygenase inhibition. Clinically relevant concentrations of celecoxib can affect ionic currents and alter functioning of neurons and myocytes. In particular, inhibition of Kv2.1 channels by celecoxib leads to arrhythmic beating of Drosophila heart and of rat heart cells in culture. However, the spectrum of ion channels involved in human cardiac excitability differs from that in animal models, including mammalian models, making it difficult to evaluate the relevance of these observations to humans. Our aim was to examine the effects of celecoxib on hERG and other human channels critically involved in regulating human cardiac rhythm, and to explore the mechanisms of any observed effect on the hERG channels.Celecoxib inhibited the hERG, SCN5A, KCNQ1 and KCNQ1/MinK channels expressed in HEK-293 cells with IC(50s of 6.0 µM, 7.5 µM, 3.5 µM and 3.7 µM respectively, and the KCND3/KChiP2 channels expressed in CHO cells with an IC(50 of 10.6 µM. Analysis of celecoxib's effects on hERG channels suggested gating modification as the mechanism of drug action.The above channels play a significant role in drug-induced long QT syndrome (LQTS and short QT syndrome (SQTS. Regulatory guidelines require that all new drugs under development be tested for effects on the hERG channel prior to first administration in humans. Our observations raise the question of celecoxib's potential to induce cardiac arrhythmias or other channel related adverse effects, and make a case for examining such possibilities.

  3. Stretch induced endothelin-1 secretion by adult rat astrocytes involves calcium influx via stretch-activated ion channels (SACs)

    Energy Technology Data Exchange (ETDEWEB)

    Ostrow, Lyle W., E-mail: lostrow1@jhmi.edu [Department of Neurology, Johns Hopkins School of Medicine, Baltimore, MD 21205 (United States); Suchyna, Thomas M.; Sachs, Frederick [Department of Physiology and Biophysical Sciences, State University of New York at Buffalo, Buffalo, NY 14214 (United States)

    2011-06-24

    Highlights: {yields} Endothelin-1 expression by adult rat astrocytes correlates with cell proliferation. {yields} Stretch-induced ET-1 is inhibited by GsMtx-4, a specific inhibitor of Ca{sup 2+} permeant SACs. {yields} The less specific SAC inhibitor streptomycin also inhibits ET-1 secretion. {yields} Stretch-induced ET-1 production depends on a calcium influx. {yields} SAC pharmacology may provide a new class of therapeutic agents for CNS pathology. -- Abstract: The expression of endothelins (ETs) and ET-receptors is often upregulated in brain pathology. ET-1, a potent vasoconstrictor, also inhibits the expression of astrocyte glutamate transporters and is mitogenic for astrocytes, glioma cells, neurons, and brain capillary endothelia. We have previously shown that mechanical stress stimulates ET-1 production by adult rat astrocytes. We now show in adult astrocytes that ET-1 production is driven by calcium influx through stretch-activated ion channels (SACs) and the ET-1 production correlates with cell proliferation. Mechanical stimulation using biaxial stretch (<20%) of a rubber substrate increased ET-1 secretion, and 4 {mu}M GsMTx-4 (a specific inhibitor of SACs) inhibited secretion by 30%. GsMTx-4 did not alter basal ET-1 levels in the absence of stretch. Decreasing the calcium influx by lowering extracellular calcium also inhibited stretch-induced ET-1 secretion without effecting ET-1 secretion in unstretched controls. Furthermore, inhibiting SACs with the less specific inhibitor streptomycin also inhibited stretch-induced ET-1 secretion. The data can be explained with a simple model in which ET-1 secretion depends on an internal Ca{sup 2+} threshold. This coupling of mechanical stress to the astrocyte endothelin system through SACs has treatment implications, since all pathology deforms the surrounding parenchyma.

  4. Low threshold T‐type calcium channels as targets for novel epilepsy treatments

    National Research Council Canada - National Science Library

    Powell, Kim L; Cain, Stuart M; Snutch, Terrance P; O'Brien, Terence J

    2014-01-01

    .... T ‐type calcium channels are expressed widely throughout the brain and peripheral tissues, and thus have been proposed as therapeutic targets for a variety of diseases such as epilepsy, insomnia, pain...

  5. A deleterious gene-by-environment interaction imposed by calcium channel blockers in Marfan syndrome.

    NARCIS (Netherlands)

    Doyle, J.J.; Doyle, A.J.; Wilson, N.K.; Habashi, J.P.; Bedja, D.; Whitworth, R.E.; Lindsay, M.E.; Schoenhoff, F.; Myers, L.; Huso, N.; Bachir, S.; Squires, O.; Rusholme, B.; Ehsan, H.; Huso, D.; Thomas, C.J.; Caulfield, M.J.; Eyk, J.E. Van; Judge, D.P.; Dietz, H.C.; Loeys, B.L.

    2015-01-01

    Calcium channel blockers (CCBs) are prescribed to patients with Marfan syndrome for prophylaxis against aortic aneurysm progression, despite limited evidence for their efficacy and safety in the disorder. Unexpectedly, Marfan mice treated with CCBs show accelerated aneurysm expansion, rupture, and

  6. Plasma Membrane Cyclic Nucleotide Gated Calcium Channels Control Land Plant Thermal Sensing and Acquired Thermotolerance

    National Research Council Canada - National Science Library

    Andrija Finka; America Farinia Henriquez Cuendet; Frans J.M. Maathuis; Younousse Saidi; Pierre Goloubinoff

    2012-01-01

    .... Here, we found that the cyclic nucleotide gated calcium channel (CNGC) CNGCb gene from Physcomitrella patens and its Arabidopsis thaliana ortholog CNGC2, encode a component of cyclic nucleotide gated Ca²...

  7. The Physiology, Pathology, and Pharmacology of Voltage-Gated Calcium Channels and Their Future Therapeutic Potential

    Science.gov (United States)

    Zamponi, Gerald W.; Striessnig, Joerg; Koschak, Alexandra

    2015-01-01

    Voltage-gated calcium channels are required for many key functions in the body. In this review, the different subtypes of voltage-gated calcium channels are described and their physiologic roles and pharmacology are outlined. We describe the current uses of drugs interacting with the different calcium channel subtypes and subunits, as well as specific areas in which there is strong potential for future drug development. Current therapeutic agents include drugs targeting L-type CaV1.2 calcium channels, particularly 1,4-dihydropyridines, which are widely used in the treatment of hypertension. T-type (CaV3) channels are a target of ethosuximide, widely used in absence epilepsy. The auxiliary subunit α2δ-1 is the therapeutic target of the gabapentinoid drugs, which are of value in certain epilepsies and chronic neuropathic pain. The limited use of intrathecal ziconotide, a peptide blocker of N-type (CaV2.2) calcium channels, as a treatment of intractable pain, gives an indication that these channels represent excellent drug targets for various pain conditions. We describe how selectivity for different subtypes of calcium channels (e.g., CaV1.2 and CaV1.3 L-type channels) may be achieved in the future by exploiting differences between channel isoforms in terms of sequence and biophysical properties, variation in splicing in different target tissues, and differences in the properties of the target tissues themselves in terms of membrane potential or firing frequency. Thus, use-dependent blockers of the different isoforms could selectively block calcium channels in particular pathologies, such as nociceptive neurons in pain states or in epileptic brain circuits. Of important future potential are selective CaV1.3 blockers for neuropsychiatric diseases, neuroprotection in Parkinson’s disease, and resistant hypertension. In addition, selective or nonselective T-type channel blockers are considered potential therapeutic targets in epilepsy, pain, obesity, sleep, and

  8. Involvement of Potassium Channels and Calcium-Independent Mechanisms in Hydrogen Sulfide-Induced Relaxation of Rat Mesenteric Small Arteries.

    Science.gov (United States)

    Hedegaard, Elise R; Gouliaev, Anja; Winther, Anna K; Arcanjo, Daniel D R; Aalling, Mathilde; Renaltan, Nirthika S; Wood, Mark E; Whiteman, Matthew; Skovgaard, Nini; Simonsen, Ulf

    2016-01-01

    Endogenous hydrogen sulfide (H2S) is involved in the regulation of vascular tone. We hypothesized that the lowering of calcium and opening of potassium (K) channels as well as calcium-independent mechanisms are involved in H2S-induced relaxation in rat mesenteric small arteries. Amperometric recordings revealed that free [H2S] after addition to closed tubes of sodium hydrosulfide (NaHS), Na2S, and GYY4137 [P-(4-methoxyphenyl)-P-4-morpholinyl-phosphinodithioic acid] were, respectively, 14%, 17%, and 1% of added amount. The compounds caused equipotent relaxations in isometric myographs, but based on the measured free [H2S], GYY4137 caused more relaxation in relation to released free H2S than NaHS and Na2S in rat mesenteric small arteries. Simultaneous measurements of [H2S] and tension showed that 15 µM of free H2S caused 61% relaxation in superior mesenteric arteries. Simultaneous measurements of smooth muscle calcium and tension revealed that NaHS lowered calcium and caused relaxation of NE-contracted arteries, while high extracellular potassium reduced NaHS relaxation without corresponding calcium changes. In NE-contracted arteries, NaHS (1 mM) lowered the phosphorylation of myosin light chain, while phosphorylation of myosin phosphatase target subunit 1 remained unchanged. Protein kinase A and G, inhibitors of guanylate cyclase, failed to reduce NaHS relaxation, whereas blockers of voltage-gated KV7 channels inhibited NaHS relaxation, and blockers of mitochondrial complex I and III abolished NaHS relaxation. Our findings suggest that low micromolar concentrations of free H2S open K channels followed by lowering of smooth muscle calcium, and by another mechanism involving mitochondrial complex I and III leads to uncoupling of force, and hence vasodilation. Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.

  9. Adenosine versus intravenous calcium channel antagonists for supraventricular tachycardia.

    Science.gov (United States)

    Alabed, Samer; Sabouni, Ammar; Providencia, Rui; Atallah, Edmond; Qintar, Mohammed; Chico, Timothy Ja

    2017-10-12

    People with supraventricular tachycardia (SVT) frequently are symptomatic and present to the emergency department for treatment. Although vagal manoeuvres may terminate SVT, they often fail, and subsequently adenosine or calcium channel antagonists (CCAs) are administered. Both are known to be effective, but both have a significant side effect profile. This is an update of a Cochrane review previously published in 2006. To review all randomised controlled trials (RCTs) that compare effects of adenosine versus CCAs in terminating SVT. We identified studies by searching CENTRAL, MEDLINE, Embase, and two trial registers in July 2017. We checked bibliographies of identified studies and applied no language restrictions. We planned to include all RCTs that compare adenosine versus a CCA for patients of any age presenting with SVT. We used standard methodological procedures as expected by Cochrane. Two review authors independently checked results of searches to identify relevant studies and resolved differences by discussion with a third review author. At least two review authors independently assessed each included study and extracted study data. We entered extracted data into Review Manager 5. Primary outcomes were rate of reversion to sinus rhythm and major adverse effects of adenosine and CCAs. Secondary outcomes were rate of recurrence, time to reversion, and minor adverse outcomes. We measured outcomes by calculating odds ratios (ORs) and assessed the quality of primary outcomes using the GRADE approach through the GRADEproGDT website. We identified two new studies for inclusion in the review update; the review now includes seven trials with 622 participants who presented to an emergency department with SVT. All included studies were RCTs, but only three described the randomisation process, and none had blinded participants, personnel, or outcome assessors to the intervention given. Moderate-quality evidence shows no differences in the number of people reverting to

  10. Calcium current-dependent and voltage-dependent inactivation of calcium channels in Helix aspersa

    Science.gov (United States)

    Brown, A. M.; Morimoto, K.; Tsuda, Y.; Wilson, D. L.

    1981-01-01

    -exponential inactivation process that persists in the presence of EGTAi is similar to that occurring when extracellular Ba ion carries current through the Ca channel. Steady-state inactivation also persists and is similar in the two cases. Therefore it is concluded that inactivation is voltage-dependent as well as Ca current-dependent. 8. Diffusion models that included reasonable values for the effect of binding on diffusion, even when combined with declining influxes, did not account for this `mixed' form of calcium- and voltage-dependent inactivation. A compartmental model in which the particular kinetic model of voltage-dependent inactivation was not critical described the Ca current-dependent inactivation. PMID:6275075

  11. Ryanodine receptor/calcium release channel PKA phosphorylation: A critical mediator of heart failure progression

    OpenAIRE

    Wehrens, Xander H. T.; Lehnart, Stephan E.; Reiken, Steven; Vest, John A.; Wronska, Anetta; Marks, Andrew R.

    2006-01-01

    Defective regulation of the cardiac ryanodine receptor (RyR2)/calcium release channel, required for excitation-contraction coupling in the heart, has been linked to cardiac arrhythmias and heart failure. For example, diastolic calcium “leak” via RyR2 channels in the sarcoplasmic reticulum has been identified as an important factor contributing to impaired contractility in heart failure and ventricular arrhythmias that cause sudden cardiac death. In patients with heart failure, chronic activat...

  12. Role of T-type calcium channels in myogenic tone of skeletal muscle resistance arteries

    DEFF Research Database (Denmark)

    VanBavel, Ed; Sorop, Oana; Andreasen, Ditte

    2002-01-01

    T-type calcium channels may be involved in the maintenance of myogenic tone. We tested their role in isolated rat cremaster arterioles obtained after CO(2) anesthesia and decapitation. Total RNA was analyzed by RT-PCR and Southern blotting for calcium channel expression. We observed expression......); K(+) -5.4 +/- 0.3 (n = 4); all log(IC(50)) P maintenance of myogenic tone in rat cremaster muscle arterioles....

  13. Glycosylation of voltage-gated calcium channels in health and disease

    Czech Academy of Sciences Publication Activity Database

    Lazniewska, Joanna; Weiss, Norbert

    2017-01-01

    Roč. 1859, č. 5 (2017), s. 662-668 ISSN 0005-2736 R&D Projects: GA ČR GA15-13556S; GA MŠk 7AMB15FR015 Institutional support: RVO:61388963 Keywords : calcium channels * voltage-gated calcium channels * N-glycosylation * ancillary subunit * trafficking * stability Subject RIV: CE - Biochemistry Impact factor: 3.498, year: 2016

  14. Phylogeny unites animal sodium leak channels with fungal calcium channels in an ancient, voltage-insensitive clade.

    Science.gov (United States)

    Liebeskind, Benjamin J; Hillis, David M; Zakon, Harold H

    2012-12-01

    Proteins in the superfamily of voltage-gated ion channels mediate behavior across the tree of life. These proteins regulate the movement of ions across cell membranes by opening and closing a central pore that controls ion flow. The best-known members of this superfamily are the voltage-gated potassium, calcium (Ca(v)), and sodium (Na(v)) channels, which underlie impulse conduction in nerve and muscle. Not all members of this family are opened by changes in voltage, however. NALCN (NA(+) leak channel nonselective) channels, which encode a voltage-insensitive "sodium leak" channel, have garnered a growing interest. This study examines the phylogenetic relationship among Na(v)/Ca(v) voltage-gated and voltage-insensitive channels in the eukaryotic group Opisthokonta, which includes animals, fungi, and their unicellular relatives. We show that NALCN channels diverged from voltage-gated channels before the divergence of fungi and animals and that the closest relatives of NALCN channels are fungal calcium channels, which they functionally resemble.

  15. T-type calcium channels, but not Cav3.2, in the peripheral sensory afferents are involved in acute itch in mice.

    Science.gov (United States)

    Lin, Si-Fang; Wang, Bing; Zhang, Feng-Ming; Fei, Yuan-Hui; Gu, Jia-Hui; Li, Jie; Bi, Ling-Bo; Liu, Xing-Jun

    2017-06-10

    T-type calcium channels are prominently expressed in primary nociceptive fibers and well characterized in pain processes. Although itch and pain share many similarities including primary sensory fibers, the function of T-type calcium channels on acute itch has not been explored. We investigated whether T-type calcium channels expressed within primary sensory fibers of mouse skin, especially Cav3.2 subtype, involve in chloroquine-, endothelin-1- and histamine-evoked acute itch using pharmacological, neuronal imaging and behavioral analyses. We found that pre-locally blocking three subtypes of T-type calcium channels in the peripheral afferents of skins, yielded an inhibition in acute itch or pain behaviors, while selectively blocking the Cav3.2 channel in the skin peripheral afferents only inhibited acute pain but not acute itch. These results suggest that T-type Cav3.1 or Cav3.3, but not Cav3.2 channel, have an important role in acute itch processing, and their distinctive roles in modulating acute itch are worthy of further investigation. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. Englerin A Agonizes the TRPC4/C5 Cation Channels to Inhibit Tumor Cell Line Proliferation.

    Directory of Open Access Journals (Sweden)

    Cheryl Carson

    Full Text Available Englerin A is a structurally unique natural product reported to selectively inhibit growth of renal cell carcinoma cell lines. A large scale phenotypic cell profiling experiment (CLiP of englerin A on ¬over 500 well characterized cancer cell lines showed that englerin A inhibits growth of a subset of tumor cell lines from many lineages, not just renal cell carcinomas. Expression of the TRPC4 cation channel was the cell line feature that best correlated with sensitivity to englerin A, suggesting the hypothesis that TRPC4 is the efficacy target for englerin A. Genetic experiments demonstrate that TRPC4 expression is both necessary and sufficient for englerin A induced growth inhibition. Englerin A induces calcium influx and membrane depolarization in cells expressing high levels of TRPC4 or its close ortholog TRPC5. Electrophysiology experiments confirmed that englerin A is a TRPC4 agonist. Both the englerin A induced current and the englerin A induced growth inhibition can be blocked by the TRPC4/C5 inhibitor ML204. These experiments confirm that activation of TRPC4/C5 channels inhibits tumor cell line proliferation and confirms the TRPC4 target hypothesis generated by the cell line profiling. In selectivity assays englerin A weakly inhibits TRPA1, TRPV3/V4, and TRPM8 which suggests that englerin A may bind a common feature of TRP ion channels. In vivo experiments show that englerin A is lethal in rodents near doses needed to activate the TRPC4 channel. This toxicity suggests that englerin A itself is probably unsuitable for further drug development. However, since englerin A can be synthesized in the laboratory, it may be a useful chemical starting point to identify novel modulators of other TRP family channels.

  17. [Biological activity of Ungernia victoris extract in the Escherichia coli CaCl2-transformation system in the presence of calcium channel modulators].

    Science.gov (United States)

    Miriuta, A Iu; Pererva, T P

    2008-01-01

    Furosemid and verapamil appear to have an effect on the yield of E. coli plasmid transformants according to their properties as calcium channel regulators in eukaryotes. It means that furosemid stimulates and verapamil inhibits transforming DNA penetration into competent cell. PHB/Ca2+ polyP complex does not function only as a channel for transforming DNA penetration but appears to be one of the targets for transformation blocking U. victoris extract.

  18. Lithium prevents early cytosolic calcium increase and secondary injurious calcium overload in glycolytically inhibited endothelial cells

    Energy Technology Data Exchange (ETDEWEB)

    Bosche, Bert, E-mail: bert.bosche@uk-essen.de [Department of Neurology, University of Duisburg-Essen (Germany); Max Planck Institute for Neurological Research with Klaus-Joachim-Zülch Laboratories of the Max Planck Society and the Medical Faculty of the University of Cologne (Germany); Schäfer, Matthias, E-mail: matthias.schaefer@sanofi.com [Institute of Physiology, Justus-Liebig-University Giessen (Germany); Graf, Rudolf, E-mail: rudolf.graf@nf.mpg.de [Max Planck Institute for Neurological Research with Klaus-Joachim-Zülch Laboratories of the Max Planck Society and the Medical Faculty of the University of Cologne (Germany); Härtel, Frauke V., E-mail: frauke.haertel@tu-dresden.de [Institute of Physiology, Medical Faculty Carl Gustav Carus, Technical University Dresden (Germany); Schäfer, Ute, E-mail: ute.schaefer@medunigraz.at [Research Unit for Experimental Neurotraumatology, Medical University of Graz (Austria); Noll, Thomas, E-mail: thomas.noll@tu-dresden.de [Institute of Physiology, Medical Faculty Carl Gustav Carus, Technical University Dresden (Germany)

    2013-05-03

    Highlights: •We investigate free calcium as a central signalling element in endothelial cells. •Inhibition of glycolysis with 2-deoxy-D-glucose reduces cellular ATP. •This manoeuvre leads to a biphasic increase and overload of free calcium. •Pre-treatment with lithium for 24 h abolishes both phases of the calcium increase. •This provides a new strategy to protect endothelial calcium homeostasis and barrier function. -- Abstract: Cytosolic free calcium concentration ([Ca{sup 2+}]{sub i}) is a central signalling element for the maintenance of endothelial barrier function. Under physiological conditions, it is controlled within narrow limits. Metabolic inhibition during ischemia/reperfusion, however, induces [Ca{sup 2+}]{sub i} overload, which results in barrier failure. In a model of cultured porcine aortic endothelial monolayers (EC), we addressed the question of whether [Ca{sup 2+}]{sub i} overload can be prevented by lithium treatment. [Ca{sup 2+}]{sub i} and ATP were analysed using Fura-2 and HPLC, respectively. The combined inhibition of glycolytic and mitochondrial ATP synthesis by 2-desoxy-D-glucose (5 mM; 2-DG) plus sodium cyanide (5 mM; NaCN) caused a significant decrease in cellular ATP content (14 ± 1 nmol/mg protein vs. 18 ± 1 nmol/mg protein in the control, n = 6 culture dishes, P < 0.05), an increase in [Ca{sup 2+}]{sub i} (278 ± 24 nM vs. 71 ± 2 nM in the control, n = 60 cells, P < 0.05), and the formation of gaps between adjacent EC. These observations indicate that there is impaired barrier function at an early state of metabolic inhibition. Glycolytic inhibition alone by 10 mM 2-DG led to a similar decrease in ATP content (14 ± 2 nmol/mg vs. 18 ± 1 nmol/mg in the control, P < 0.05) with a delay of 5 min. The [Ca{sup 2+}]{sub i} response of EC was biphasic with a peak after 1 min (183 ± 6 nM vs. 71 ± 1 nM, n = 60 cells, P < 0.05) followed by a sustained increase in [Ca{sup 2+}]{sub i}. A 24-h pre-treatment with 10 mM of lithium

  19. Probenecid, a gout remedy, inhibits pannexin 1 channels.

    Science.gov (United States)

    Silverman, William; Locovei, Silviu; Dahl, Gerhard

    2008-09-01

    Probenecid is a well-established drug for the treatment of gout and is thought to act on an organic anion transporter, thereby affecting uric acid excretion in the kidney by blocking urate reuptake. Probenecid also has been shown to affect ATP release, leading to the suggestion that ATP release involves an organic anion transporter. Other pharmacological evidence and the observation of dye uptake, however, suggest that the nonvesicular release of ATP is mediated by large membrane channels, with pannexin 1 being a prominent candidate. In the present study we show that probenecid inhibited currents mediated by pannexin 1 channels in the same concentration range as observed for inhibition of transport processes. Probenecid did not affect channels formed by connexins. Thus probenecid allows for discrimination between channels formed by connexins and pannexins.

  20. Calcium channel TRPV6 is involved in murine maternal-fetal calcium transport.

    Science.gov (United States)

    Suzuki, Yoshiro; Kovacs, Christopher S; Takanaga, Hitomi; Peng, Ji-Bin; Landowski, Christopher P; Hediger, Matthias A

    2008-08-01

    Maternal-fetal calcium (Ca(2+)) transport is crucial for fetal Ca(2+) homeostasis and bone mineralization. In this study, the physiological significance of the transient receptor potential, vanilloid 6 (TRPV6) Ca(2+) channel in maternal-fetal Ca(2+) transport was investigated using Trpv6 knockout mice. The Ca(2+) concentration in fetal blood and amniotic fluid was significantly lower in Trpv6 knockout fetuses than in wildtypes. The transport activity of radioactive Ca(2+) ((45)Ca) from mother to fetuses was 40% lower in Trpv6 knockout fetuses than in wildtypes. The ash weight was also lower in Trpv6 knockout fetuses compared with wildtype fetuses. TRPV6 mRNA and protein were mainly localized in intraplacental yolk sac and the visceral layer of extraplacental yolk sac, which are thought to be the places for maternal-fetal Ca(2+) transport in mice. These expression sites were co-localized with calbindin D(9K) in the yolk sac. In wildtype mice, placental TRPV6 mRNA increased 14-fold during the last 4 days of gestation, which coincides with fetal bone mineralization. These results provide the first in vivo evidence that TRPV6 is involved in maternal-fetal Ca(2+) transport. We propose that TRPV6 functions as a Ca(2+) entry pathway, which is critical for fetal Ca(2+) homeostasis.

  1. Pharmacological efficacy of CPU 86017 on hypoxic pulmonary hypertension in rats: mediated by direct inhibition of calcium channels and antioxidant action, but indirect effects on the ET-1 pathway.

    Science.gov (United States)

    Zhang, Tian-Tai; Cui, Bing; Dai, De-Zai; Tang, Xiao-Yun

    2005-12-01

    Endothelin-1 (ET-1) plays a key role in the pathogenesis of pulmonary hypertension. The present study was conducted to examine the effects of a novel compound p-chlorobenzyltetrahydroberberine (CPU 86017) on endothelin-1 system of hypoxia-induced pulmonary hypertension in rats. SD male rats were divided into control, untreated pulmonary hypertension, nifedipine (10 mg/kg p.o.), and CPU 86017 (80, 40, and 20 mg/kg p.o.) groups. The pulmonary hypertension was established by housing the rats in a hypoxic (10 +/- 0.5% oxygen) chamber 8 hours per day for 4 weeks. Hemodynamic and morphologic assessment exhibited a significant increase in the central vein pressure (CVP), right ventricular systolic pressure (RVSP), and pulmonary arteriole remodeling in the pulmonary hypertensive rats, which were improved by CPU 86017 80 and 40 mg/kg administration (P CPU 86017 groups. The maladjustment of redox enzyme system in pulmonary hypertension rats was corrected after treatment. We concluded that CPU 86017 improves pulmonary hypertension mainly to suppress the endothelin-1 pathway at the upstream and downstream via calcium antagonism and antioxidative action, then, resulting in a relief in pathogenesis of the disease.

  2. Antimicrobial, anti-oxidant and calcium channel blocking activities of Amberboa divaricata

    Directory of Open Access Journals (Sweden)

    Shahid Muhammad Iqbal

    2014-03-01

    Full Text Available Traditional healers in Pakistan use the herb Amberboa divaricata as tonic, aperiant, deobstruent, febrifuge, anti-diarrheal, antiperiodic, antipyretic, anti-cough and in skin disorders. In vitro tissue experiments were carried out on rabbit jejunum to elucidate the possible mechanism of its prescribed effects on gastrointestinal tract, while antibacterial and antioxidant experiments were performed to provide pharmacological evidence of its traditional use in skin disorders. The 70%methanolic crude extract of A. divaricata produced dose dependent relaxation in isolated rabbit jejunum tissue in a concentration range of 0.1–3.0 mg/mL (n=5. Calcium response curves were constructed at concen-tration of 0.03 and 0.1 mg/mL (n=5, which produced rightward shift in a pattern similar to that of verapamil, confirming the calcium channel blocking activity. Agar disc diffusion assay at a concentration of 10 mg crude extract/disc showed clear zones of inhibition.

  3. Effect of L- type Calcium Channel Blocker Nimodipine and T-type Calcium Channel Blocker Flunarizine on Motor Control in Mice

    Directory of Open Access Journals (Sweden)

    Swapnil Balkrishna Kaikade

    2015-05-01

    Full Text Available Objective: To study the effect of L-type of Calcium channel blocker nimodipine and T-type of calcium channel blocker funarizine on locomotor activity in mice without pretreatment by any other drug. Materials and method: The study was carried out following permission from the Institutional animal ethics committee. Healthy Swiss albino mice of either sex were selected by the strict inclusion and exclusion criteria and the grouping is done. Group A is control treated with normal saline, Group B and C received two titrated doses of nimodipine while Group D and E received two titrated doses of flunarizine. The animals were then observed for motor control on inclined plane and the Statistical analysis was done by using unpaired‘t’ test. Results: L-type calcium channel blocker nimodipine has dose dependent effect on motor control on inclined plane while the T- type calcium channel blocker flunarizine has no effect on motor control. Conclusion: Nimodipine has significant dose dependent depressant action on motor control on inclined plane while flunarizine has no effect on the above mentioned parameter.

  4. T-type voltage-gated calcium channels regulate the tone of mouse efferent arterioles

    DEFF Research Database (Denmark)

    Poulsen, Christian B; Al-Mashhadi, Rozh H; Cribbs, Leanne L

    2011-01-01

    Voltage-gated calcium channels are important for the regulation of renal blood flow and the glomerular filtration rate. Excitation-contraction coupling in afferent arterioles is known to require activation of these channels and we studied their role in the regulation of cortical efferent arteriol...... publication, 10 November 2010; doi:10.1038/ki.2010.429....

  5. The TRPV5/6 calcium channels contain multiple calmodulin binding sites with differential binding properties.

    NARCIS (Netherlands)

    Kovalevskaya, N.V.; Bokhovchuk, F.M.; Vuister, G.W.

    2012-01-01

    The epithelial Ca(2+) channels TRPV5/6 (transient receptor potential vanilloid 5/6) are thoroughly regulated in order to fine-tune the amount of Ca(2+) reabsorption. Calmodulin has been shown to be involved into calcium-dependent inactivation of TRPV5/6 channels by binding directly to the distal

  6. The genetic background affects the vascular response in T-type calcium channels 3.2 deficient mice

    DEFF Research Database (Denmark)

    Svenningsen, Per; Hansen, Pernille B L

    2016-01-01

    Voltage-gated calcium channels (Cav ) are important regulators of vascular tone and are attractive targets for pharmacological treatment of hypertension. The clinical used calcium blockers are often not selective for one channel but affect several types of calcium channels (Hansen 2015). L......-type channels are the dominant Ca(2+) entry pathway in vascular smooth muscle cells, however, T-type calcium channels are also expressed in the cardiovascular system where they play a functional role in the regulation of both contraction and vasodilation in (Chen et al. 2003; Hansen et al. 2001). This article...... is protected by copyright. All rights reserved....

  7. Lack of direct evidence for a functional role of voltage-operated calcium channels in juxtaglomerular cells

    DEFF Research Database (Denmark)

    Kurtz, A; Skott, O; Chegini, S

    1990-01-01

    In this study we have examined the role of voltage-gated calcium channels in the regulation of calcium in juxtaglomerular cells. Using a combination of patch-clamp and single-cell calcium measurement we obtained evidence neither for voltage-operated calcium currents nor for changes of the intrace...

  8. Differential effects of organic calcium-channel blockers on diastolic SR calcium-handling in the frog heart.

    Science.gov (United States)

    Subramani, Sathya; Vijayanand, Caroline; Tharion, Elizabeth

    2002-11-01

    1. Gradual loss of sarcoplasmic reticular (SR) calcium during a rest-period is responsible for the rest-induced decay (RID) of force in mammalian myocardium. Effect of verapamil and diltiazem on a similar RID in the frog myocardium suggests a new mechanism of action of these drugs. 2. Strips of frog-ventricle were paced at 0.2 Hz and the rhythm was interrupted by varying rest-periods ranging from 10 to 180 s. In control conditions, the amplitude of the post-rest beat was significantly lower than that of the pre-rest beat for rest-periods more than 40 s (RID). 3. Verapamil and diltiazem (which are organic calcium-channel blockers (OCCB)) changed the pattern of RID in the control solution to a 'rest-induced potentiation' (RIP) in the same preparation while another OCCB nifedipine and the inorganic calcium-channel blocker cadmium did not alter the post-rest phenomenon. 4. We propose that verapamil and diltiazem produce an RIP due to either blockade of SR calcium-leak during rest or enhancement of SR calcium-uptake during rest.

  9. A Calcium-Dependent Plasticity Rule for HCN Channels Maintains Activity Homeostasis and Stable Synaptic Learning

    Science.gov (United States)

    Honnuraiah, Suraj; Narayanan, Rishikesh

    2013-01-01

    Theoretical and computational frameworks for synaptic plasticity and learning have a long and cherished history, with few parallels within the well-established literature for plasticity of voltage-gated ion channels. In this study, we derive rules for plasticity in the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, and assess the synergy between synaptic and HCN channel plasticity in establishing stability during synaptic learning. To do this, we employ a conductance-based model for the hippocampal pyramidal neuron, and incorporate synaptic plasticity through the well-established Bienenstock-Cooper-Munro (BCM)-like rule for synaptic plasticity, wherein the direction and strength of the plasticity is dependent on the concentration of calcium influx. Under this framework, we derive a rule for HCN channel plasticity to establish homeostasis in synaptically-driven firing rate, and incorporate such plasticity into our model. In demonstrating that this rule for HCN channel plasticity helps maintain firing rate homeostasis after bidirectional synaptic plasticity, we observe a linear relationship between synaptic plasticity and HCN channel plasticity for maintaining firing rate homeostasis. Motivated by this linear relationship, we derive a calcium-dependent rule for HCN-channel plasticity, and demonstrate that firing rate homeostasis is maintained in the face of synaptic plasticity when moderate and high levels of cytosolic calcium influx induced depression and potentiation of the HCN-channel conductance, respectively. Additionally, we show that such synergy between synaptic and HCN-channel plasticity enhances the stability of synaptic learning through metaplasticity in the BCM-like synaptic plasticity profile. Finally, we demonstrate that the synergistic interaction between synaptic and HCN-channel plasticity preserves robustness of information transfer across the neuron under a rate-coding schema. Our results establish specific physiological roles

  10. Inhibition of Calcium Influx Reduces Dysfunction and Apoptosis in Lipotoxic Pancreatic β-Cells via Regulation of Endoplasmic Reticulum Stress.

    Directory of Open Access Journals (Sweden)

    Yuren Zhou

    Full Text Available Lipotoxicity plays an important role in pancreatic β-cell failure during the development of type 2 diabetes. Prolonged exposure of β-cells to elevated free fatty acids level could cause deterioration of β-cell function and induce cell apoptosis. Therefore, inhibition of fatty acids-induced β-cell dysfunction and apoptosis might provide benefit for the therapy of type 2 diabetes. The present study examined whether regulation of fatty acids-triggered calcium influx could protect pancreatic β-cells from lipotoxicity. Two small molecule compounds, L-type calcium channel blocker nifedipine and potassium channel activator diazoxide were used to inhibit palmitic acid-induced calcium influx. And whether the compounds could reduce palmitic acid-induced β-cell failure and the underlying mechanism were also investigated. It was found that both nifedipine and diazoxide protected MIN6 pancreatic β-cells and primary cultured murine islets from palmitic acid-induced apoptosis. Meanwhile, the impaired insulin secretion was also recovered to varying degrees by these two compounds. Our results verified that nifedipine and diazoxide could reduce palmitic acid-induced endoplasmic reticulum stress to generate protective effects on pancreatic β-cells. More importantly, it suggested that regulation of calcium influx by small molecule compounds might provide benefits for the prevention and therapy of type 2 diabetes.

  11. Phosphocitrate inhibits mitochondrial and cytosolic accumulation of calcium in kidney cells in vivo.

    OpenAIRE

    Tew, W P; Malis, C D; Howard, J. E.; Lehninger, A L

    1981-01-01

    Synthetic 3-phosphocitrate, an extremely potent inhibitor of calcium phosphate crystallization as determined in a nonbiological physical-chemical assay, has many similarities to a mitochondrial factor that inhibits crystallization of nondiffracting amorphous calcium phosphate. In order to determine whether phosphocitrate can prevent uptake and crystallization of calcium phosphate in mitochondria in vivo, it was administered intraperitoneally to animals given large daily doses of calcium gluco...

  12. Inhibiting the mitochondrial calcium uniporter during development impairs memory in adult Drosophila

    OpenAIRE

    Drago, Ilaria; Davis, Ronald L.

    2016-01-01

    The uptake of cytoplasmic calcium into mitochondria is critical for a variety of physiological processes, including calcium buffering, metabolism and cell survival. We demonstrate here that inhibiting the mitochondrial calcium uniporter in the Drosophila mushroom body neurons (MBn) – a brain region critical for olfactory memory formation – causes memory impairment without altering the capacity to learn. Inhibiting uniporter activity only during pupation impaired adult memory, whereas the same...

  13. Interactions of divalent cations with single calcium channels from rat brain synaptosomes.

    Science.gov (United States)

    Nelson, M T

    1986-02-01

    Voltage-dependent calcium channels from a rat brain membrane preparation ("synaptosomes") were incorporated into planar lipid bilayers. The effects of calcium, barium, strontium, manganese, and cadmium ions on the amplitudes and kinetics of single channel currents were examined. The order of single channel conductances was gBa greater than gSr greater than gMn, which was the inverse of the order of the mean channel open times: TMn greater than TCa = TSr greater than TBa. In contrast, the identity of the charge carrier had little or no effect on the mean closed times of the channel. Manganese, in the absence of other permeant ions, can pass through single channels (gMn = 4 pS). However, when added to a solution that contained another type of permeant divalent cation, manganese reduced the single channel current in a voltage-dependent manner. Cadmium, a potent blocker of macroscopic "ensemble" calcium currents in many preparations, reduced the current through an open channel in a manner consistent with Cd ions both not being measurably permeant and interacting with a single site. The permeant ions competed with cadmium for this site with the following order: Mn greater than Sr = Ca greater than Ba. These results are consistent with the existence of no less than one divalent cation binding site in the channel that regulates ion permeation.

  14. Inhibition of voltage-gated sodium channels by sumatriptan bioisosteres

    Directory of Open Access Journals (Sweden)

    Roberta eCarbonara

    2015-07-01

    Full Text Available Voltage-gated sodium channels are known to play a pivotal role in perception and transmission of pain sensations. Gain-of-function mutations in the genes encoding the peripheral neuronal sodium channels, hNav1.7-1.9, cause human painful diseases. Thus while treatment of chronic pain remains an unmet clinical need, sodium channel blockers are considered as promising druggable targets. In a previous study, we evaluated the analgesic activity of sumatriptan, an agonist of serotonin 5HT1B/D receptors, and some new chiral bioisosteres, using the hot plate test in the mouse. Interestingly, we observed that the analgesic effectiveness was not necessarily correlated to serotonin agonism. In this study, we evaluated whether sumatriptan and its congeners may inhibit heterologously-expressed hNav1.7 sodium channels using the patch-clamp method. We show that sumatriptan blocks hNav1.7 channels only at very high, supratherapeutic concentrations. In contrast, its three analogues, namely 20b, (R-31b, and (S-22b, exert a dose and use-dependent sodium channel block. At 0.1 and 10 Hz stimulation frequencies, the most potent compound, (S-22b, was 4.4 and 1.7 fold more potent than the well-known sodium channel blocker mexiletine. The compound induces a negative shift of voltage dependence of fast inactivation, suggesting higher affinity to the inactivated channel. Accordingly, we show that (S-22b likely binds the conserved local anesthetic receptor within voltage-gated sodium channels. Combining these results with the previous ones, we hypothesize that use-dependent sodium channel blockade contributes to the analgesic activity of (R-31b and (S-22b. These later compounds represent promising lead compounds for the development of efficient analgesics, the mechanism of action of which may include a dual action on sodium channels and 5HT1D receptors.

  15. Inhibition of voltage-gated sodium channels by sumatriptan bioisosteres.

    Science.gov (United States)

    Carbonara, Roberta; Carocci, Alessia; Roussel, Julien; Crescenzo, Giuseppe; Buonavoglia, Canio; Franchini, Carlo; Lentini, Giovanni; Camerino, Diana Conte; Desaphy, Jean-François

    2015-01-01

    Voltage-gated sodium channels are known to play a pivotal role in perception and transmission of pain sensations. Gain-of-function mutations in the genes encoding the peripheral neuronal sodium channels, hNav1.7-1.9, cause human painful diseases. Thus while treatment of chronic pain remains an unmet clinical need, sodium channel blockers are considered as promising druggable targets. In a previous study, we evaluated the analgesic activity of sumatriptan, an agonist of serotonin 5HT1B/D receptors, and some new chiral bioisosteres, using the hot plate test in the mouse. Interestingly, we observed that the analgesic effectiveness was not necessarily correlated to serotonin agonism. In this study, we evaluated whether sumatriptan and its congeners may inhibit heterologously expressed hNav1.7 sodium channels using the patch-clamp method. We show that sumatriptan blocks hNav1.7 channels only at very high, supratherapeutic concentrations. In contrast, its three analogs, namely 20b, (R)-31b, and (S)-22b, exert a dose and use-dependent sodium channel block. At 0.1 and 10 Hz stimulation frequencies, the most potent compound, (S)-22b, was 4.4 and 1.7 fold more potent than the well-known sodium channel blocker mexiletine. The compound induces a negative shift of voltage dependence of fast inactivation, suggesting higher affinity to the inactivated channel. Accordingly, we show that (S)-22b likely binds the conserved local anesthetic receptor within voltage-gated sodium channels. Combining these results with the previous ones, we hypothesize that use-dependent sodium channel blockade contributes to the analgesic activity of (R)-31b and (S)-22b. These later compounds represent promising lead compounds for the development of efficient analgesics, the mechanism of action of which may include a dual action on sodium channels and 5HT1D receptors.

  16. /sup 3/H)Nitrendipine binding to calcium channels in bovine and rat pituitary

    Energy Technology Data Exchange (ETDEWEB)

    Titeler, M.; De Souza, E.B.; Kuhar, M.J.

    1985-06-01

    (/sup 3/H)Nitrendipine was used to label sites in homogenates of bovine anterior and neurointermediate lobes of the pituitary gland. The amount of specific binding in the anterior lobe was 1.82 +/- 0.30 pmol/g wet weight of tissue and the KD was 1.44 +/- 0.02 X 10(-10) M. Preliminary experiments indicated a similar amount of binding in bovine neurointermediate lobe. In competition studies nimodipine and nisoldipine (two potent voltage-sensitive calcium channel blockers) displayed IC50 values of 1.6 and 6.8 X 10(-10) M, respectively. Verapamil and the verapamil-like calcium channel blockers D-600 and tiapamil competed in a complex manner for the (/sup 3/H)nitrendipine specific binding to bovine anterior pituitary homogenates. Autoradiographical studies demonstrated specific (/sup 3/H)nitrendipine binding sites distributed approximately equally in the anterior and posterior lobes, but not in the intermediate lobe of the rat pituitary. In general the properties of (/sup 3/H)nitrendipine binding in the pituitary tissue resemble strongly the properties of (/sup 3/H)nitrendipine binding in the brain which is believed to be to voltage-sensitive calcium channels. These results provide support for the hypothesis that calcium channels are involved in pituitary hormone secretion and that drugs that interact with calcium channels may modulate the secretory process directly at the level of the pituitary.

  17. L-type calcium channels regulate filopodia stability and cancer cell invasion downstream of integrin signalling.

    Science.gov (United States)

    Jacquemet, Guillaume; Baghirov, Habib; Georgiadou, Maria; Sihto, Harri; Peuhu, Emilia; Cettour-Janet, Pierre; He, Tao; Perälä, Merja; Kronqvist, Pauliina; Joensuu, Heikki; Ivaska, Johanna

    2016-12-02

    Mounting in vitro, in vivo and clinical evidence suggest an important role for filopodia in driving cancer cell invasion. Using a high-throughput microscopic-based drug screen, we identify FDA-approved calcium channel blockers (CCBs) as potent inhibitors of filopodia formation in cancer cells. Unexpectedly, we discover that L-type calcium channels are functional and frequently expressed in cancer cells suggesting a previously unappreciated role for these channels during tumorigenesis. We further demonstrate that, at filopodia, L-type calcium channels are activated by integrin inside-out signalling, integrin activation and Src. Moreover, L-type calcium channels promote filopodia stability and maturation into talin-rich adhesions through the spatially restricted regulation of calcium entry and subsequent activation of the protease calpain-1. Altogether we uncover a novel and clinically relevant signalling pathway that regulates filopodia formation in cancer cells and propose that cycles of filopodia stabilization, followed by maturation into focal adhesions, directs cancer cell migration and invasion.

  18. Substance P Depolarizes Lamprey Spinal Cord Neurons by Inhibiting Background Potassium Channels.

    Directory of Open Access Journals (Sweden)

    Carolina Thörn Pérez

    Full Text Available Substance P is endogenously released in the adult lamprey spinal cord and accelerates the burst frequency of fictive locomotion. This is achieved by multiple effects on interneurons and motoneurons, including an attenuation of calcium currents, potentiation of NMDA currents and reduction of the reciprocal inhibition. While substance P also depolarizes spinal cord neurons, the underlying mechanism has not been resolved. Here we show that effects of substance P on background K+ channels are the main source for this depolarization. Hyperpolarizing steps induced inward currents during whole-cell voltage clamp that were reduced by substance P. These background K+ channels are pH sensitive and are selectively blocked by anandamide and AVE1231. These blockers counteracted the effect of substance P on these channels and the resting membrane potential depolarization in spinal cord neurons. Thus, we have shown now that substance P inhibits background K+ channels that in turn induce depolarization, which is likely to contribute to the frequency increase observed with substance P during fictive locomotion.

  19. Voltage-gated calcium channels of Paramecium cilia.

    Science.gov (United States)

    Lodh, Sukanya; Yano, Junji; Valentine, Megan S; Van Houten, Judith L

    2016-10-01

    Paramecium cells swim by beating their cilia, and make turns by transiently reversing their power stroke. Reversal is caused by Ca2+ entering the cilium through voltage-gated Ca2+ (CaV) channels that are found exclusively in the cilia. As ciliary Ca2+ levels return to normal, the cell pivots and swims forward in a new direction. Thus, the activation of the CaV channels causes cells to make a turn in their swimming paths. For 45 years, the physiological characteristics of the Paramecium ciliary CaV channels have been known, but the proteins were not identified until recently, when the P. tetraurelia ciliary membrane proteome was determined. Three CaVα1 subunits that were identified among the proteins were cloned and confirmed to be expressed in the cilia. We demonstrate using RNA interference that these channels function as the ciliary CaV channels that are responsible for the reversal of ciliary beating. Furthermore, we show that Pawn (pw) mutants of Paramecium that cannot swim backward for lack of CaV channel activity do not express any of the three CaV1 channels in their ciliary membrane, until they are rescued from the mutant phenotype by expression of the wild-type PW gene. These results reinforce the correlation of the three CaV channels with backward swimming through ciliary reversal. The PwB protein, found in endoplasmic reticulum fractions, co-immunoprecipitates with the CaV1c channel and perhaps functions in trafficking. The PwA protein does not appear to have an interaction with the channel proteins but affects their appearance in the cilia. © 2016. Published by The Company of Biologists Ltd.

  20. Acetaldehyde - ethanol interactions on calcium-activated potassium (BK channels in pituitary tumor (GH3 cells

    Directory of Open Access Journals (Sweden)

    Astrid G. Handlechner

    2013-06-01

    Full Text Available Background: In the central nervous system ethanol (EtOH is metabolized to acetaldehyde (ACA primarily by the oxidative enzyme catalase. Evidence suggests that ACA is responsible for at least some of the effects on the brain that have been attributed to EtOH. Various types of ion channels which are involved in electrical signaling are targets of EtOH like maxi calcium-activated potassium (BK channels. BK channels exhibit various functions like action potential repolarization, blood pressure regulation, hormone secretion, or transmitter release. In most neuronal and neuroendocrine preparations at physiological intracellular calcium levels, EtOH increases BK channel activity. The simultaneous presence of ACA and EtOH reflects the physiological situation after drinking and may result in synergistic as well as antagonistic actions compared to a single application of either drug. The action of ACA on electrical activity has yet not been fully established.Methods: GH3 pituitary tumor cells were used for outside-out and inside-out patch-clamp recordings of BK activity in excised patches. Unitary current amplitude, open probability and channel mean open time of BK channels were measured. Results: Extracellular EtOH raised BK channel activity. In the presence of intracellular ACA this increment of BK activity was suppressed in a dose- as well as calcium-dependent manner. Mean channel open time was significantly reduced by internal ACA, whereas BK channel amplitudes were not affected. The EtOH counteracting effect of ACA was found to depend on succession of application. EtOH was prevented from activating BK channels by pre-exposure of membrane patches to ACA. In contrast BK activation by a hypotonic solution was not affected by internal ACA. Conclusions: Our data suggest an inhibitory impact of ACA on BK activation by EtOH. ACA appears to interact specifically with EtOH at BK channels since intracellular ACA had no effect when BK channels were activated by

  1. Spatial distribution of calcium-gated chloride channels in olfactory cilia.

    Science.gov (United States)

    French, Donald A; Badamdorj, Dorjsuren; Kleene, Steven J

    2010-12-30

    In vertebrate olfactory receptor neurons, sensory cilia transduce odor stimuli into changes in neuronal membrane potential. The voltage changes are primarily caused by the sequential openings of two types of channel: a cyclic-nucleotide-gated (CNG) cationic channel and a calcium-gated chloride channel. In frog, the cilia are 25 to 200 µm in length, so the spatial distributions of the channels may be an important determinant of odor sensitivity. To determine the spatial distribution of the chloride channels, we recorded from single cilia as calcium was allowed to diffuse down the length of the cilium and activate the channels. A computational model of this experiment allowed an estimate of the spatial distribution of the chloride channels. On average, the channels were concentrated in a narrow band centered at a distance of 29% of the ciliary length, measured from the base of the cilium. This matches the location of the CNG channels determined previously. This non-uniform distribution of transduction proteins is consistent with similar findings in other cilia. On average, the two types of olfactory transduction channel are concentrated in the same region of the cilium. This may contribute to the efficient detection of weak stimuli.

  2. Oxidative Regulation of Large Conductance Calcium-Activated Potassium Channels

    Science.gov (United States)

    Tang, Xiang D.; Daggett, Heather; Hanner, Markus; Garcia, Maria L.; McManus, Owen B.; Brot, Nathan; Weissbach, Herbert; Heinemann, Stefan H.; Hoshi, Toshinori

    2001-01-01

    Reactive oxygen/nitrogen species are readily generated in vivo, playing roles in many physiological and pathological conditions, such as Alzheimer's disease and Parkinson's disease, by oxidatively modifying various proteins. Previous studies indicate that large conductance Ca2+-activated K+ channels (BKCa or Slo) are subject to redox regulation. However, conflicting results exist whether oxidation increases or decreases the channel activity. We used chloramine-T, which preferentially oxidizes methionine, to examine the functional consequences of methionine oxidation in the cloned human Slo (hSlo) channel expressed in mammalian cells. In the virtual absence of Ca2+, the oxidant shifted the steady-state macroscopic conductance to a more negative direction and slowed deactivation. The results obtained suggest that oxidation enhances specific voltage-dependent opening transitions and slows the rate-limiting closing transition. Enhancement of the hSlo activity was partially reversed by the enzyme peptide methionine sulfoxide reductase, suggesting that the upregulation is mediated by methionine oxidation. In contrast, hydrogen peroxide and cysteine-specific reagents, DTNB, MTSEA, and PCMB, decreased the channel activity. Chloramine-T was much less effective when concurrently applied with the K+ channel blocker TEA, which is consistent with the possibility that the target methionine lies within the channel pore. Regulation of the Slo channel by methionine oxidation may represent an important link between cellular electrical excitability and metabolism. PMID:11222629

  3. The medieval physician Avicenna used an herbal calcium channel blocker, Taxus baccata L.

    Science.gov (United States)

    Tekol, Yalcin

    2007-07-01

    Calcium channel blockers are drugs which are important for current medical therapy. The first examples of synthetic congeners of this class of drugs appear around at the beginning of the 1960s. Review of the current and historical literature shows that Avicenna (Ibn Sina) (980-1037) had used the herbal drug 'Zarnab' (Taxus baccata L.) as a cardiac remedy. The leaves of T. baccata contain an alkaloid mixture (taxines). It was recently demonstrated that this drug possessed calcium channel blocking activity. So, it is evident that Avicenna used a drug with calcium channel blocking activity much earlier than the arrival of synthetic drugs belonging to the same pharmacological group. Copyright 2007 John Wiley & Sons, Ltd.

  4. How voltage-gated calcium channels gate forms of homeostatic synaptic plasticity

    Directory of Open Access Journals (Sweden)

    C. Andrew eFrank

    2014-02-01

    Full Text Available Throughout life, animals face a variety of challenges such as developmental growth, the presence of toxins, or changes in temperature. Neuronal circuits and synapses respond to challenges by executing an array of neuroplasticity paradigms. Some paradigms allow neurons to up- or downregulate activity outputs, while countervailing ones ensure that outputs remain within appropriate physiological ranges. A growing body of evidence suggests that homeostatic synaptic plasticity (HSP is critical in the latter case. Voltage-gated calcium channels gate forms of HSP. Presynaptically, the aggregate data show that when synapse activity is weakened, homeostatic signaling systems can act to correct impairments, in part by increasing calcium influx through presynaptic CaV2-type channels. Increased calcium influx is often accompanied by parallel increases in the size of active zones and the size of the readily releasable pool of presynaptic vesicles. These changes coincide with homeostatic enhancements of neurotransmitter release. Postsynaptically, there is a great deal of evidence that reduced network activity and loss of calcium influx through CaV1-type calcium channels also results in adaptive homeostatic signaling. Some adaptations drive presynaptic enhancements of vesicle pool size and turnover rate via retrograde signaling, as well as de novo insertion of postsynaptic neurotransmitter receptors. Enhanced calcium influx through CaV1 after network activation or single cell stimulation can elicit the opposite response – homeostatic depression via removal of excitatory receptors.There exist intriguing links between HSP and calcium channelopathies – such as forms of epilepsy, migraine, ataxia, and myasthenia. The episodic nature of some of these disorders suggests alternating periods of stable and unstable function. Uncovering information about how calcium channels are regulated in the context of HSP could be relevant toward understanding these and other

  5. AHR-16303B, a novel antagonist of 5-HT2 receptors and voltage-sensitive calcium channels

    Energy Technology Data Exchange (ETDEWEB)

    Barrett, R.J.; Appell, K.C.; Kilpatrick, B.F.; Proakis, A.G.; Nolan, J.C.; Walsh, D.A. (A. H. Robins Research Labs., Richmond, VA (USA))

    1991-01-01

    In vivo and in vitro methods were used to characterize AHR-16303B, a novel compound with antagonistic action at 5-HT2 receptors and voltage-sensitive calcium channels. The 5-HT2 receptor-antagonistic properties of AHR-16303B were demonstrated by inhibition of (a) (3H)ketanserin binding to rat cerebral cortical membranes (IC50 = 165 nM); (b) 5-hydroxytryptamine (5-HT)-induced foot edema in rats (minimum effective dose, (MED) = 0.32 mg/kg orally, p.o.); (c) 5-HT-induced vasopressor responses in spontaneously hypertensive rats (SHR) (ID50 = 0.18 mg/kg intravenously (i.v.), 1.8 mg/kg p.o.), (d) 5-HT-induced antidiuresis in rats (MED = 1 mg/kg p.o.), and (e) platelet aggregation induced by 5-HT + ADP (IC50 = 1.5 mM). The calcium antagonist properties of AHR-16303B were demonstrated by inhibition of (a) (3H)nimodipine binding to voltage-sensitive calcium channels on rabbit skeletal muscle membranes (IC50 = 15 nM), (b) KCl-stimulated calcium flux into cultured PC12 cells (IC50 = 81 nM), and (c) CaCl2-induced contractions of rabbit thoracic aortic strips (pA2 = 8.84). AHR-16303B had little or no effect on binding of radioligands to dopamine2 (DA2) alpha 1, alpha 2, H1, 5-HT1 alpha, beta 2, muscarinic M1, or sigma opioid receptors; had no effect on 5-HT3 receptor-mediated vagal bradycardia; and had only minor negative inotropic, chronotropic, and dromotropic effects on isolated guinea pig atria. In conscious SHR, 30 mg/kg p.o. AHR-16303B completely prevented the vasopressor responses to i.v. 5-HT, and decreased blood pressure (BP) by 24% 3 h after dosing.

  6. Emerging roles of calcium-activated K channels and TRPV4 channels in lung oedema and pulmonary circulatory collapse.

    Science.gov (United States)

    Simonsen, U; Wandall-Frostholm, C; Oliván-Viguera, A; Köhler, R

    2017-01-01

    It has been suggested that the transient receptor potential cation (TRP) channel subfamily V (vanilloid) type 4 (TRPV4) and intermediate conductance calcium-activated potassium (KCa3.1) channels contribute to endothelium-dependent vasodilation. Here, we summarize very recent evidence for a synergistic interplay of TRPV4 and KCa3.1 channels in lung disease. Among the endothelial Ca2+ -permeable TRPs, TRPV4 is best characterized and produces arterial dilation by stimulating Ca2+ -dependent nitric oxide synthesis and endothelium-dependent hyperpolarization. Besides these roles, some TRP channels control endothelial/epithelial barrier functions and vascular integrity, while KCa3.1 channels provide the driving force required for Cl- and water transport in some cells and most secretory epithelia. The three conditions, increased pulmonary venous pressure caused by left heart disease, high inflation pressure and chemically induced lung injury, may lead to activation of TRPV4 channels followed by Ca2+ influx leading to activation of KCa3.1 channels in endothelial cells ultimately leading to acute lung injury. We find that a deficiency in KCa3.1 channels protects against TRPV4-induced pulmonary arterial relaxation, fluid extravasation, haemorrhage, pulmonary circulatory collapse and cardiac arrest in vivo. These data identify KCa3.1 channels as crucial molecular components in downstream TRPV4 signal transduction and as a potential target for the prevention of undesired fluid extravasation, vasodilatation and pulmonary circulatory collapse. © 2016 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

  7. Testosterone increases urinary calcium excretion and inhibits expression of renal calcium transport proteins

    DEFF Research Database (Denmark)

    Hsu, Yu-Juei; Dimke, Henrik Anthony; Schoeber, Joost P H

    2010-01-01

    Although gender differences in the renal handling of calcium have been reported, the overall contribution of androgens to these differences remains uncertain. We determined here whether testosterone affects active renal calcium reabsorption by regulating calcium transport proteins. Male mice had...... higher urinary calcium excretion than female mice and their renal calcium transporters were expressed at a lower level. We also found that orchidectomized mice excreted less calcium in their urine than sham-operated control mice and that the hypocalciuria was normalized after testosterone replacement...... calcium transport. Thus, our study shows that gender differences in renal calcium handling are, in part, mediated by the inhibitory actions of androgens on TRPV5-mediated active renal calcium transport....

  8. Nuclear-localized cyclic nucleotide-gated channels mediate symbiotic calcium oscillations.

    Science.gov (United States)

    Charpentier, Myriam; Sun, Jongho; Vaz Martins, Teresa; Radhakrishnan, Guru V; Findlay, Kim; Soumpourou, Eleni; Thouin, Julien; Véry, Anne-Aliénor; Sanders, Dale; Morris, Richard J; Oldroyd, Giles E D

    2016-05-27

    Nuclear-associated Ca(2+) oscillations mediate plant responses to beneficial microbial partners--namely, nitrogen-fixing rhizobial bacteria that colonize roots of legumes and arbuscular mycorrhizal fungi that colonize roots of the majority of plant species. A potassium-permeable channel is known to be required for symbiotic Ca(2+) oscillations, but the calcium channels themselves have been unknown until now. We show that three cyclic nucleotide-gated channels in Medicago truncatula are required for nuclear Ca(2+) oscillations and subsequent symbiotic responses. These cyclic nucleotide-gated channels are located at the nuclear envelope and are permeable to Ca(2+) We demonstrate that the cyclic nucleotide-gated channels form a complex with the postassium-permeable channel, which modulates nuclear Ca(2+) release. These channels, like their counterparts in animal cells, might regulate multiple nuclear Ca(2+) responses to developmental and environmental conditions. Copyright © 2016, American Association for the Advancement of Science.

  9. Zn2+Interaction with Alzheimer Amyloid β Protein Calcium Channels

    National Research Council Canada - National Science Library

    Nelson Arispe; Harvey B. Pollard; Eduardo Rojas

    1996-01-01

    The Alzheimer disease 40-residue amyloid β protein (Aβ P[1-40]) forms cation-selective channels across acidic phospholipid bilayer membranes with spontaneous transitions over a wide range of conductances ranging from 40 to 4000 pS...

  10. Effects of low-dose ionising radiation on pituitary adenoma: is there a role for L-type calcium channel?

    Energy Technology Data Exchange (ETDEWEB)

    Soares, Marcella Araugio; Santos, Raquel Gouvea dos [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN), Belo Horizonte, MG (Brazil). Lab. de Radiobiologia]. E-mail: santosr@cdtn.br

    2005-10-15

    Pituitary adenomas constitute about 6-18% of brain tumours in adults. Activation of voltage gated calcium currents can account for growth hormone over secretion in some GH-secreting pituitary adenomas that produce an acromegaly appearance and increase mortality. Ca{sup 2+} ions, as mediators of intracellular signalling, are crucial for the development of apoptosis. However, the role of [Ca{sup 2+}] in the development of apoptosis is ambiguous. In this study, the effects of low-dose ionising gamma radiation ({sup 60} Co) on rat pituitary adenoma cells survival and proliferation and the role of calcium channels on the apoptosis radio-induced were evaluated. Doses as low as 3 Gy were found to inhibit GH3 cell proliferation. Even though there was a significant number of live cells,168 hours following irradiation, they were not able to proliferate. The results indicate that the blockade of extracellular calcium influx through these channels does not interfere in the radiation-induced apoptosis in GH3 cells. (author)

  11. Role for voltage gated calcium channels in calcitonin gene-related peptide release in the rat trigeminovascular system

    DEFF Research Database (Denmark)

    Amrutkar, D V; Ploug, K B; Olesen, J

    2011-01-01

    Clinical and genetic studies have suggested a role for voltage gated calcium channels (VGCCs) in the pathogenesis of migraine. Release of calcitonin gene-related peptide (CGRP) from trigeminal neurons has also been implicated in migraine. The VGCCs are located presynaptically on neurons and are i......Clinical and genetic studies have suggested a role for voltage gated calcium channels (VGCCs) in the pathogenesis of migraine. Release of calcitonin gene-related peptide (CGRP) from trigeminal neurons has also been implicated in migraine. The VGCCs are located presynaptically on neurons...... and are involved in the release of these peptides to different stimuli. We have examined the presence and importance of VGCCs in controlling the CGRP release from rat dura mater, freshly isolated trigeminal ganglion (TG) and trigeminal nucleus caudalis (TNC). Each of the four VGCCs, P/Q-, N-, and L- and T...... the potassium induced CGRP release. In the absence of calcium ions (Ca2+) and in the presence of a cocktail of blockers, the stimulated CGRP release from dura mater was reduced almost to the same level as basal CGRP release. In the TG ¿-conotoxin GVIA inhibited the potassium induced CGRP release significantly...

  12. Role for voltage gated calcium channels in calcitonin gene-related peptide release in the rat trigeminovascular system

    DEFF Research Database (Denmark)

    Amrutkar, D V; Ploug, K B; Olesen, J

    2011-01-01

    Clinical and genetic studies have suggested a role for voltage gated calcium channels (VGCCs) in the pathogenesis of migraine. Release of calcitonin gene-related peptide (CGRP) from trigeminal neurons has also been implicated in migraine. The VGCCs are located presynaptically on neurons and are i......Clinical and genetic studies have suggested a role for voltage gated calcium channels (VGCCs) in the pathogenesis of migraine. Release of calcitonin gene-related peptide (CGRP) from trigeminal neurons has also been implicated in migraine. The VGCCs are located presynaptically on neurons...... and are involved in the release of these peptides to different stimuli. We have examined the presence and importance of VGCCs in controlling the CGRP release from rat dura mater, freshly isolated trigeminal ganglion (TG) and trigeminal nucleus caudalis (TNC). Each of the four VGCCs, P/Q-, N-, and L- and T...... the potassium induced CGRP release. In the absence of calcium ions (Ca2+) and in the presence of a cocktail of blockers, the stimulated CGRP release from dura mater was reduced almost to the same level as basal CGRP release. In the TG ω-conotoxin GVIA inhibited the potassium induced CGRP release significantly...

  13. Calcium-activated chloride channel ANO1 promotes breast cancer progression by activating EGFR and CAMK signaling.

    Science.gov (United States)

    Britschgi, Adrian; Bill, Anke; Brinkhaus, Heike; Rothwell, Christopher; Clay, Ieuan; Duss, Stephan; Rebhan, Michael; Raman, Pichai; Guy, Chantale T; Wetzel, Kristie; George, Elizabeth; Popa, M Oana; Lilley, Sarah; Choudhury, Hedaythul; Gosling, Martin; Wang, Louis; Fitzgerald, Stephanie; Borawski, Jason; Baffoe, Jonathan; Labow, Mark; Gaither, L Alex; Bentires-Alj, Mohamed

    2013-03-12

    The calcium-activated chloride channel anoctamin 1 (ANO1) is located within the 11q13 amplicon, one of the most frequently amplified chromosomal regions in human cancer, but its functional role in tumorigenesis has remained unclear. The 11q13 region is amplified in ∼15% of breast cancers. Whether ANO1 is amplified in breast tumors, the extent to which gene amplification contributes to ANO1 overexpression, and whether overexpression of ANO1 is important for tumor maintenance have remained unknown. We have found that ANO1 is amplified and highly expressed in breast cancer cell lines and primary tumors. Amplification of ANO1 correlated with disease grade and poor prognosis. Knockdown of ANO1 in ANO1-amplified breast cancer cell lines and other cancers bearing 11q13 amplification inhibited proliferation, induced apoptosis, and reduced tumor growth in established cancer xenografts. Moreover, ANO1 chloride channel activity was important for cell viability. Mechanistically, ANO1 knockdown or pharmacological inhibition of its chloride-channel activity reduced EGF receptor (EGFR) and calmodulin-dependent protein kinase II (CAMKII) signaling, which subsequently attenuated AKT, v-src sarcoma viral oncogene homolog (SRC), and extracellular signal-regulated kinase (ERK) activation in vitro and in vivo. Our results highlight the involvement of the ANO1 chloride channel in tumor progression and provide insights into oncogenic signaling in human cancers with 11q13 amplification, thereby establishing ANO1 as a promising target for therapy in these highly prevalent tumor types.

  14. LRRK2 regulates voltage-gated calcium channel function.

    Directory of Open Access Journals (Sweden)

    Cade eBedford

    2016-05-01

    Full Text Available Voltage-gated Ca2+ (CaV channels enable Ca2+ influx in response to membrane depolarization. CaV2.1 channels are localized to the presynaptic membrane of many types of neurons where they are involved in triggering neurotransmitter release. Several signaling proteins have been identified as important CaV2.1 regulators including protein kinases, G-proteins and Ca2+ binding proteins. Recently, we discovered that leucine rich repeat kinase 2 (LRRK2, a protein associated with inherited Parkinson’s disease, interacts with specific synaptic proteins and influences synaptic transmission. Since synaptic proteins functionally interact with CaV2.1 channels and synaptic transmission is triggered by Ca2+ entry via CaV2.1, we investigated whether LRRK2 could impact CaV2.1 channel function. CaV2.1 channel properties were measured using whole cell patch clamp electrophysiology in HEK293 cells transfected with CaV2.1 subunits and various LRRK2 constructs. Our results demonstrate that both wild type LRRK2 and the G2019S LRRK2 mutant caused a significant increase in whole cell Ca2+ current density compared to cells expressing only the CaV2.1 channel complex. In addition, LRRK2 expression caused a significant hyperpolarizing shift in voltage-dependent activation while having no significant effect on inactivation properties. These functional changes in CaV2.1 activity are likely due to a direct action of LRRK2 as we detected a physical interaction between LRRK2 and the β3 CaV channel subunit via coimmunoprecipitation. Furthermore, effects on CaV2.1 channel function are dependent on LRRK2 kinase activity as these could be reversed via treatment with a LRRK2 inhibitor. Interestingly, LRRK2 also augmented endogenous voltage-gated Ca2+ channel function in PC12 cells suggesting other CaV channels could also be regulated by LRRK2. Overall, our findings support a novel physiological role for LRRK2 in regulating CaV2.1 function that could have implications for how

  15. Pyrethroids inhibit K2P channels and activate sensory neurons: basis of insecticide-induced paraesthesias.

    Science.gov (United States)

    Castellanos, Aida; Andres, Alba; Bernal, Laura; Callejo, Gerard; Comes, Nuria; Gual, Arcadi; Giblin, Jonathan P; Roza, Carolina; Gasull, Xavier

    2017-09-25

    Pyrethroid insecticides are widely used for pest control in agriculture or in human public health commonly as a topical treatment for scabies and head lice. Exposure to pyrethroids such as permethrin or tetramethrin (TM) causes sensory alterations such as transient pain, burning, stinging sensations, and paraesthesias. Despite the well-known effects of pyrethroids on sodium channels, actions on other channels that control sensory neuron excitability are less studied. Given the role of 2-pore domain potassium (K2P) channels in modulating sensory neuron excitability and firing, both in physiological and pathological conditions, we examined the effect of pyrethroids on K2P channels mainly expressed in sensory neurons. Through electrophysiological and calcium imaging experiments, we show that a high percentage of TM-responding neurons were nociceptors, which were also activated by TRPA1 and/or TRPV1 agonists. This pyrethroid also activated and enhanced the excitability of peripheral saphenous nerve fibers. Pyrethroids produced a significant inhibition of native TRESK, TRAAK, TREK-1, and TREK-2 currents. Similar effects were found in transfected HEK293 cells. At the behavioral level, intradermal TM injection in the mouse paw produced nocifensive responses and caused mechanical allodynia, demonstrating that the effects seen on nociceptors in culture lead to pain-associated behaviors in vivo. In TRESK knockout mice, pain-associated behaviors elicited by TM were enhanced, providing further evidence for a role of this channel in preventing excessive neuronal activation. Our results indicate that inhibition of K2P channels facilitates sensory neuron activation and increases their excitability. These effects contribute to the generation of paraesthesias and pain after pyrethroid exposure.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and

  16. A promoter in the coding region of the calcium channel gene CACNA1C generates the transcription factor CCAT.

    Directory of Open Access Journals (Sweden)

    Natalia Gomez-Ospina

    Full Text Available The C-terminus of the voltage-gated calcium channel Cav1.2 encodes a transcription factor, the calcium channel associated transcriptional regulator (CCAT, that regulates neurite extension and inhibits Cav1.2 expression. The mechanisms by which CCAT is generated in neurons and myocytes are poorly understood. Here we show that CCAT is produced by activation of a cryptic promoter in exon 46 of CACNA1C, the gene that encodes CaV1.2. Expression of CCAT is independent of Cav1.2 expression in neuroblastoma cells, in mice, and in human neurons derived from induced pluripotent stem cells (iPSCs, providing strong evidence that CCAT is not generated by cleavage of CaV1.2. Analysis of the transcriptional start sites in CACNA1C and immune-blotting for channel proteins indicate that multiple proteins are generated from the 3' end of the CACNA1C gene. This study provides new insights into the regulation of CACNA1C, and provides an example of how exonic promoters contribute to the complexity of mammalian genomes.

  17. Effect of propionyl-L-carnitine on L-type calcium channels in human heart sarcolemma

    Energy Technology Data Exchange (ETDEWEB)

    Bevilacqua, M.; Vago, T.; Norbiato, G. (Servizio di Endocrinologia, Milano, (Italy))

    1991-02-01

    Propionyl-L-carnitine (PC) protects perfused rat hearts against damage by ischemia-reperfusion. Activation of L-type calcium channel play a role on ischemia-reperfusion damage. Therefore, we studied the effect of PC on some properties of L-type calcium channels in an in vitro preparation from human myocardium sarcolemma (from patients with idiopathic dilated cardiomyopathy). Binding of the L-type calcium channel blockers isradipine ({sup 3}H)-PN 200-110 (PN) to plasma membrane preparations revealed a single population of binding sites (total number: Bmax = 213 +/- 34 fM/mg protein and affinity: Kd = 152 +/- 19 nM; n = 6). The characteristics of these binding sites were evaluated in the presence and in the absence of Ca{sup 2}{sup +} and of calcium blockers (D-888, a verapamillike drug, and diltiazem). Incubation in a Ca{sup 2}{sup +}-containing buffer increased the affinity of PN binding sites. Binding sites for PN were modulated by organic calcium channel blockers; in competition isotherms at 37{degree}C, D-888 (desmethoxyverapamil) decreased the PN binding, whereas diltiazem increased it. These results strongly suggest that the site labelled by PN is the voltage-operated calcium channel of the human myocardium. The addition of PC (1 mM) to plasma membranes labelled with PN at 37{degree}C decreased the affinity of the binding; this effect was counteracted by the addition of Ca{sup 2}{sup +} to the medium. This result was consistent with a competition between Ca{sup 2}{sup +} and PC. The effect of PC incubation at 4{degree}C was the opposite; at this temperature PC increased the affinity of the binding sites and the effect was obscured by Ca{sup 2}{sup +}.

  18. Noradrenaline upregulates T-type calcium channels in rat pinealocytes.

    Science.gov (United States)

    Yu, Haijie; Seo, Jong Bae; Jung, Seung-Ryoung; Koh, Duk-Su; Hille, Bertil

    2015-02-15

    The mammalian pineal gland is a neuroendocrine organ that responds to circadian and seasonal rhythms. Its major function is to secrete melatonin as a hormonal night signal in response to nocturnal delivery of noradrenaline from sympathetic neurons. Culturing rat pinealocytes in noradrenaline for 24 h induced a low-voltage activated transient Ca(2+) current whose pharmacology and kinetics corresponded to a CaV3.1 T-type channel. The upregulation of the T-type Ca(2+) current is initiated by β-adrenergic receptors, cyclic AMP and cyclic AMP-dependent protein kinase. Messenger RNA for CaV3.1 T-type channels is significantly elevated by noradrenaline at 8 h and 24 h. The noradrenaline-induced T-type channel mediated an increased Ca(2+) entry and supported modest transient electrical responses to depolarizing stimuli, revealing the potential for circadian regulation of pinealocyte electrical excitability and Ca(2+) signalling. Our basic hypothesis is that mammalian pinealocytes have cycling electrical excitability and Ca(2+) signalling that may contribute to the circadian rhythm of pineal melatonin secretion. This study asked whether the functional expression of voltage-gated Ca(2+) channels (CaV channels) in rat pinealocytes is changed by culturing them in noradrenaline (NA) as a surrogate for the night signal. Channel activity was assayed as ionic currents under patch clamp and as optical signals from a Ca(2+)-sensitive dye. Channel mRNAs were assayed by quantitative polymerase chain reaction. Cultured without NA, pinealocytes showed only non-inactivating L-type dihydropyridine-sensitive Ca(2+) current. After 24 h in NA, additional low-voltage activated transient Ca(2+) current developed whose pharmacology and kinetics corresponded to a T-type CaV3.1 channel. This change was initiated by β-adrenergic receptors, cyclic AMP and protein kinase A as revealed by pharmacological experiments. mRNA for CaV3.1 T-type channels became significantly elevated, but mRNA for

  19. Identifying Calcium Channels and Porters in Plant Membranes

    Energy Technology Data Exchange (ETDEWEB)

    Sze, Heven

    1998-04-01

    The overall objectives of the proposal submitted in 6/90 was to understand how Ca was transported across plant membranes, and how these transport pathways were regulated. Ca participates in many cellular processes, including the transduction of hormonal and environmental signals, secretion, and protein folding. These processes depend on the coordination of passive Ca fluxes via channels and active Ca pumps; however these transport pathways are poorly understood in plants. We had, therefore, proposed to identify and characterize Ca transport proteins, such as the inositol-1 ,4,5-trisphosphate (IP3)-sensitive Ca channels and Ca pumps. We have had difficulties characterizing and cloning the IP3-sensitive Ca channel, but have made considerable progress on the biochemical characterization, and partial purification of a 120 kD Ca-pumping ATPase. We have begun to determine the structure of Ca pumps by molecular cloning and have already obtained a partial cDNA with features characteristic of Ca pumps.

  20. TRESK background K(+ channel is inhibited by PAR-1/MARK microtubule affinity-regulating kinases in Xenopus oocytes.

    Directory of Open Access Journals (Sweden)

    Gabriella Braun

    Full Text Available TRESK (TWIK-related spinal cord K(+ channel, KCNK18 is a major background K(+ channel of sensory neurons. Dominant-negative mutation of TRESK is linked to familial migraine. This important two-pore domain K(+ channel is uniquely activated by calcineurin. The calcium/calmodulin-dependent protein phosphatase directly binds to the channel and activates TRESK current several-fold in Xenopus oocytes and HEK293 cells. We have recently shown that the kinase, which is responsible for the basal inhibition of the K(+ current, is sensitive to the adaptor protein 14-3-3. Therefore we have examined the effect of the 14-3-3-inhibited PAR-1/MARK, microtubule-associated-protein/microtubule affinity-regulating kinase on TRESK in the Xenopus oocyte expression system. MARK1, MARK2 and MARK3 accelerated the return of TRESK current to the resting state after the calcium-dependent activation. Several other serine-threonine kinase types, generally involved in the modulation of other ion channels, failed to influence TRESK current recovery. MARK2 phosphorylated the primary determinant of regulation, the cluster of three adjacent serine residues (S274, 276 and 279 in the intracellular loop of mouse TRESK. In contrast, serine 264, the 14-3-3-binding site of TRESK, was not phosphorylated by the kinase. Thus MARK2 selectively inhibits TRESK activity via the S274/276/279 cluster, but does not affect the direct recruitment of 14-3-3 to the channel. TRESK is the first example of an ion channel phosphorylated by the dynamically membrane-localized MARK kinases, also known as general determinants of cellular polarity. These results raise the possibility that microtubule dynamics is coupled to the regulation of excitability in the neurons, which express TRESK background potassium channel.

  1. Microdamage induced calcium efflux from bone matrix activates intracellular calcium signaling in osteoblasts via L-type and T-type voltage-gated calcium channels.

    Science.gov (United States)

    Jung, Hyungjin; Best, Makenzie; Akkus, Ozan

    2015-07-01

    Mechanisms by which bone microdamage triggers repair response are not completely understood. It has been shown that calcium efflux ([Ca(2+)]E) occurs from regions of bone undergoing microdamage. Such efflux has also been shown to trigger intracellular calcium signaling ([Ca(2+)]I) in MC3T3-E1 cells local to damaged regions. Voltage-gated calcium channels (VGCCs) are implicated in the entry of [Ca(2+)]E to the cytoplasm. We investigated the involvement of VGCC in the extracellular calcium induced intracellular calcium response (ECIICR). MC3T3-E1 cells were subjected to one dimensional calcium efflux from their basal aspect which results in an increase in [Ca(2+)]I. This increase was concomitant with membrane depolarization and it was significantly reduced in the presence of Bepridil, a non-selective VGCC inhibitor. To identify specific type(s) of VGCC in ECIICR, the cells were treated with selective inhibitors for different types of VGCC. Significant changes in the peak intensity and the number of [Ca(2+)]I oscillations were observed when L-type and T-type specific VGCC inhibitors (Verapamil and NNC55-0396, respectively) were used. So as to confirm the involvement of L- and T-type VGCC in the context of microdamage, cells were seeded on devitalized notched bone specimen, which were loaded to induce microdamage in the presence and absence of Verapamil and NNC55-0396. The results showed significant decrease in [Ca(2+)]I activity of cells in the microdamaged regions of bone when L- and T-type blockers were applied. This study demonstrated that extracellular calcium increase in association with damage depolarizes the cell membrane and the calcium ions enter the cell cytoplasm by L- and T-type VGCCs. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. Mechanism of magnesium activation of calcium-activated potassium channels.

    Science.gov (United States)

    Shi, Jingyi; Krishnamoorthy, Gayathri; Yang, Yanwu; Hu, Lei; Chaturvedi, Neha; Harilal, Dina; Qin, Jun; Cui, Jianmin

    2002-08-22

    Large-conductance (BK type) Ca(2+)-dependent K(+) channels are essential for modulating muscle contraction and neuronal activities such as synaptic transmission and hearing. BK channels are activated by membrane depolarization and intracellular Ca(2+) and Mg(2+) (refs 6-10). The energy provided by voltage, Ca(2+) and Mg(2+) binding are additive in activating the channel, suggesting that these signals open the activation gate through independent pathways. Here we report a molecular investigation of a Mg(2+)-dependent activation mechanism. Using a combined site-directed mutagenesis and structural analysis, we demonstrate that a structurally new Mg(2+)-binding site in the RCK/Rossman fold domain -- an intracellular structural motif that immediately follows the activation gate S6 helix -- is responsible for Mg(2+)-dependent activation. Mutations that impair or abolish Mg(2+) sensitivity do not affect Ca(2+) sensitivity, and vice versa. These results indicate distinct structural pathways for Mg(2+)- and Ca(2+)-dependent activation and suggest a possible mechanism for the coupling between Mg(2+) binding and channel opening.

  3. Calcium channels blocked activity: Providing the basis for medicinal use of Abies pindrow in diarrhea and bronchitis

    Directory of Open Access Journals (Sweden)

    Sohaib Mushtaq

    2015-06-01

    Full Text Available Abies pindrow is widely used in traditional practice for the treatment of diarrhea and bronchitis and the present study was designed to validate its folkloric uses. The crude extract of A. pindrow inhibit spontaneously contracting (1-10 mg/mL and high K+ (80 mM-induced pre-contracted rabbit jejun-um (3 mg/mL in concentration dependent manner. A rightward shift in Ca+2 concentration response curves was seen in the presence of crude extract (0.1-0.3, similar to verapamil. In isolated tracheal tissue, A. pindrow inhibited, high K+ and carbachol (1 µM-induced contractions, at 3 mg/mL and 10 mg/mL respectively, similar to that caused by verapamil. These results indicate the presence of calcium channels blocked activity in crude extract of A. pindrow, which provide sound basis for medicinal uses of A. pindrow in diarrhea and bronchitis.

  4. Sarcoplasmic Reticulum Calcium Release Channels in Ventricles of Older Adult Hamsters

    Science.gov (United States)

    Nicholl, Peter A.; Howlett, Susan E.

    2006-01-01

    Whether the density of sarcoplasmic reticulum (SR) calcium release channels/ryanodine receptors in the heart declines with age is not clear. We investigated age-related changes in the density of [3H]-ryanodine receptors in crude ventricular homogenates, which contained all ligand binding sites in heart and in isolated junctional SR membranes.…

  5. The ethanol withdrawal syndrome: A role for dihydropyridine-sensitive calcium channels in neuronal hyperexcitability states

    Energy Technology Data Exchange (ETDEWEB)

    Whittington, M.A.

    1990-01-01

    This project investigated the effects of dihydropyridine calcium channel blockers on behavioral and electrophysiological aspects of ethanol withdrawal. The effects of the dihydropyridine (+)-PN 200-110, on changes in neuronal function during ethanol withdrawal, were compared with effects on changes caused by the GABAergic convulsant drug bicuculline. Behavioral correlates of ethanol withdrawal were measured in two strains of mice using a rating of handling-induced convulsions. Concurrent chronic treatment with ethanol and the dihydropyridine calcium channel blockers ([plus minus])-nitrendipine, ([plus minus])-nimodipine or ([plus minus])-PN 200-110 prevented withdrawal-induced increased in convulsive behavior. This effect was dose dependent. The duration of chronic treatment with calcium channel blocker affected the degree of protection against increases in convulsive behavior seen during ethanol withdrawal. Concurrent chronic treatment with ethanol, and the mixed calcium channel activator/blocker ([plus minus])-BAY K 8644, prevented ethanol withdrawal-induced increases in convulsive behavior. Single acute injections of nitrendipine immediately on cessation of chronic treatment with ethanol, or 2h later, reduced withdrawal-induced increases in convulsive behavior in a dose-dependent manner throughout the 12h test period. Slices isolated from mice after chronic ethanol treatment showed a complex, time-dependent pattern of changes in the above measurements, culminating in epileptiform discharges seen from 4h to 7h into withdrawal.

  6. [Expression of L-type calcium channel alpha1C subunit in adult rat heart].

    Science.gov (United States)

    Ou, Yan; Niu, Xiao-lin; Ren, Fu-xian; Zhang, Ying; Ling, Feng-dong

    2005-11-01

    To investigate the expression and distribution of L-type calcium channel alpha1C subunits in adult rat heart. HE staining was applied on the frozen sections of adult rat heart to identify the sinoatrial node (SAN), atrioventricular node (AVN), and posterior nodal extension (PNE). The protein expression of L-type calcium channel alpha1C in adult rat heart and its cellular localization were examined by Western blotting and immunohistochemistry, respectively. L-type calcium channel alpha1C subunit was immunolocalized on the membrane of the myocardial cells, and its expression increased gradually in the SAN, AVN, PNE, right atrium and right ventricle. The protein level of L-type calcium channel alpha1C in the AVN was similar to that in the PNE (P>0.05), and its level in the right atrium and ventricle were significantly higher than those in the SAN and AVN (Pchannel alpha1C subunit may play a role in the electrophysiological functions of the heart.

  7. The α2δ subunit and absence epilepsy: Beyond calcium channels?

    NARCIS (Netherlands)

    Celli, R.; Santolini, I.; Guiducci, M.; Luijtelaar, E.L.J.M. van; Parisi, P.; Striano, P.; Gradini, R.; Battaglia, G.; Ngomba, R.T.; Nicoletti, F.

    2017-01-01

    Spike-wave discharges, underlying absence seizures, are generated within a cortico-thalamo-cortical network that involves the somatosensory cortex, the reticular thalamic nucleus, and the ventrobasal thalamic nuclei. Activation of T-type voltage-sensitive calcium channels (VSCCs) contributes to the

  8. Fetal calcium regulates branching morphogenesis in the developing human and mouse lung: involvement of voltage-gated calcium channels.

    Directory of Open Access Journals (Sweden)

    Sarah C Brennan

    Full Text Available Airway branching morphogenesis in utero is essential for optimal postnatal lung function. In the fetus, branching morphogenesis occurs during the pseudoglandular stage (weeks 9-17 of human gestation, embryonic days (E11.5-16.5 in mouse in a hypercalcaemic environment (~1.7 in the fetus vs. ~1.1-1.3 mM for an adult. Previously we have shown that fetal hypercalcemia exerts an inhibitory brake on branching morphogenesis via the calcium-sensing receptor. In addition, earlier studies have shown that nifedipine, a selective blocker of L-type voltage-gated Ca(2+ channels (VGCC, inhibits fetal lung growth, suggesting a role for VGCC in lung development. The aim of this work was to investigate the expression of VGCC in the pseudoglandular human and mouse lung, and their role in branching morphogenesis. Expression of L-type (CaV1.2 and CaV1.3, P/Q type (CaV2.1, N-type (CaV2.2, R-type (CaV2.3, and T-type (CaV3.2 and CaV3.3 VGCC was investigated in paraffin sections from week 9 human fetal lungs and E12.5 mouse embryos. Here we show, for the first time, that Cav1.2 and Cav1.3 are expressed in both the smooth muscle and epithelium of the developing human and mouse lung. Additionally, Cav2.3 was expressed in the lung epithelium of both species. Incubating E12.5 mouse lung rudiments in the presence of nifedipine doubled the amount of branching, an effect which was partly mimicked by the Cav2.3 inhibitor, SNX-482. Direct measurements of changes in epithelial cell membrane potential, using the voltage-sensitive fluorescent dye DiSBAC2(3, demonstrated that cyclic depolarisations occur within the developing epithelium and coincide with rhythmic occlusions of the lumen, driven by the naturally occurring airway peristalsis. We conclude that VGCC are expressed and functional in the fetal human and mouse lung, where they play a role in branching morphogenesis. Furthermore, rhythmic epithelial depolarisations evoked by airway peristalsis would allow for branching to

  9. Absence epilepsy in tottering mutant mice is associated with calcium channel defects.

    Science.gov (United States)

    Fletcher, C F; Lutz, C M; O'Sullivan, T N; Shaughnessy, J D; Hawkes, R; Frankel, W N; Copeland, N G; Jenkins, N A

    1996-11-15

    Mutations at the mouse tottering (tg) locus cause a delayed-onset, recessive neurological disorder resulting in ataxia, motor seizures, and behavioral absence seizures resembling petit mal epilepsy in humans. A more severe allele, leaner (tg(la)), also shows a slow, selective degeneration of cerebellar neurons. By positional cloning, we have identified an alpha1A voltage-sensitive calcium channel gene that is mutated in tg and tg(la) mice. The alpha1A gene is widely expressed in the central nervous system with prominent, uniform expression in the cerebellum. alpha1A expression does not mirror the localized pattern of cerebellar degeneration observed in tg(la) mice, providing evidence for regional differences in biological function of alpha1A channels. These studies define the first mutations in a mammalian central nervous system-specific voltage-sensitive calcium channel and identify the first gene involved in absence epilepsy.

  10. AII amacrine cells express L-type calcium channels at their output synapses.

    Science.gov (United States)

    Habermann, Christopher J; O'Brien, Brendan J; Wässle, Heinz; Protti, Dario A

    2003-07-30

    AII amacrine cells play a critical role in the high-fidelity signal transmission pathways involved with nighttime vision. The temporal properties of the light responses strongly depend on the transfer function at different synaptic stages and consequently on presynaptic calcium influx. AII light responses are complex waveforms generated by graded input, they comprise Na+-based spikes as well as a sustained component, and they are transferred to graded cone bipolar cells. It is, therefore, of interest to determine the properties of AII voltage-dependent calcium channels (VDCCs) to establish whether these cells express N-type and/or P/Q-type VDCCs, characteristic of spiking neurons, or whether they are more like graded neurons, which mostly use L-type VDCCs. We combined electrophysiological, molecular biological, and imaging techniques to characterize calcium currents and their sites of origin in mouse AII amacrine cells. Calcium currents activated at potentials more positive than -60 mV (maximally between -50 and -20 mV) and inactivated slowly. These currents were blocked by dihydropyridine (DHP) antagonists and were enhanced by the DHP agonist BayK 8644. Single-cell RT-PCR analysis of mRNA encoding for different calcium channel alpha subunits in AIIs revealed a consistent expression of the alpha1-D subunit. Calcium imaging of AII cells showed that the greatest change in intracellular calcium occurred in the lobular appendages, with minor changes being observed in the arboreal dendrites. Depolarization-induced calcium rises were also modulated by DHPs, suggesting that a particular kind of L-type VDCC, mainly localized to the lobular appendages, enables these spiking-capable neurons to release neurotransmitter in a sustained manner onto OFF-cone bipolar cells.

  11. Calcium channels and pumps in cancer: changes and consequences.

    Science.gov (United States)

    Monteith, Gregory R; Davis, Felicity M; Roberts-Thomson, Sarah J

    2012-09-14

    Increases in intracellular free Ca(2+) play a major role in many cellular processes. The deregulation of Ca(2+) signaling is a feature of a variety of diseases, and modulators of Ca(2+) signaling are used to treat conditions as diverse as hypertension to pain. The Ca(2+) signal also plays a role in processes important in cancer, such as proliferation and migration. Many studies in cancer have identified alterations in the expression of proteins involved in the movement of Ca(2+) across the plasma membrane and subcellular organelles. In some cases, these Ca(2+) channels or pumps are potential therapeutic targets for specific cancer subtypes or correlate with prognosis.

  12. Calcium Channels and Pumps in Cancer: Changes and Consequences*

    Science.gov (United States)

    Monteith, Gregory R.; Davis, Felicity M.; Roberts-Thomson, Sarah J.

    2012-01-01

    Increases in intracellular free Ca2+ play a major role in many cellular processes. The deregulation of Ca2+ signaling is a feature of a variety of diseases, and modulators of Ca2+ signaling are used to treat conditions as diverse as hypertension to pain. The Ca2+ signal also plays a role in processes important in cancer, such as proliferation and migration. Many studies in cancer have identified alterations in the expression of proteins involved in the movement of Ca2+ across the plasma membrane and subcellular organelles. In some cases, these Ca2+ channels or pumps are potential therapeutic targets for specific cancer subtypes or correlate with prognosis. PMID:22822055

  13. Curcumin inhibits activation of TRPM2 channels in rat hepatocytes

    Directory of Open Access Journals (Sweden)

    E. Kheradpezhouh

    2016-04-01

    Full Text Available Oxidative stress is a hallmark of many liver diseases including viral and drug-induced hepatitis, ischemia-reperfusion injury, and non-alcoholic steatohepatitis. One of the consequences of oxidative stress in the liver is deregulation of Ca2+ homeostasis, resulting in a sustained elevation of the free cytosolic Ca2+ concentration ([Ca2+]c in hepatocytes, which leads to irreversible cellular damage. Recently it has been shown that liver damage induced by paracetamol and subsequent oxidative stress is, in large part, mediated by Ca2+ entry through Transient Receptor Potential Melastatin 2 (TRPM2 channels. Involvement of TRPM2 channels in hepatocellular damage induced by oxidative stress makes TRPM2 a potential therapeutic target for treatment of a range of oxidative stress-related liver diseases. We report here the identification of curcumin ((1E,6E-1,7-bis(4-hydroxy-3-methoxyphenyl-1,6-heptadiene-3,5-dione, a natural plant-derived polyphenol in turmeric spice, as a novel inhibitor of TRPM2 channel. Presence of 5 µM curcumin in the incubation medium prevented the H2O2- and paracetamol-induced [Ca2+]c rise in rat hepatocytes. Furthermore, in patch clamping experiments incubation of hepatocytes with curcumin inhibited activation of TRPM2 current by intracellular ADPR with IC50 of approximately 50 nM. These findings enhance understanding of the actions of curcumin and suggest that the known hepatoprotective properties of curcumin are, at least in part, mediated through inhibition of TRPM2 channels.

  14. Inhibition of choroidal angiogenesis by calcium dobesilate in normal Wistar and diabetic GK rats.

    Science.gov (United States)

    Lameynardie, Stéphane; Chiavaroli, Carlo; Travo, Pierre; Garay, Ricardo P; Parés-Herbuté, Núria

    2005-03-07

    Calcium dobesilate reduces vascular endothelial growth factor (VEGF) over-expression in diabetic rat retina, but its effect on intraocular angiogenesis is unknown. Therefore, we tested calcium dobesilate for its in vitro and ex vivo effects on choroidal explant angiogenesis in spontaneously diabetic Goto-Kakizaki (GK) rats. Choroidal explants were cultured in gels of collagen. Budded microvessels numbers and VEGF formation were taken as markers of angiogenesis. Ex vivo studies were performed in GK rats orally given 100 mg/kg/day calcium dobesilate for 10 days. In vitro, calcium dobesilate dose- and time-dependently inhibited both microvessel formation and VEGF production, at concentrations >or=25 mug/ml (i.e. >or=60 microM), with complete inhibition at 100 microg/ml. Oral treatment of diabetic GK rats with calcium dobesilate induced a significant reduction of choroidal angiogenesis ex vivo (38.8% after 3 days of culture). In conclusion, calcium dobesilate inhibited choroidal explant angiogenesis both in vitro and ex vivo. This effect may be due, at least in part, to inhibition of VEGF production. Antiangiogenesis by calcium dobesilate can be involved in its therapeutic benefit in diabetic retinopathy.

  15. Acetate transiently inhibits myocardial contraction by increasing mitochondrial calcium uptake.

    Science.gov (United States)

    Schooley, James F; Namboodiri, Aryan M A; Cox, Rachel T; Bünger, Rolf; Flagg, Thomas P

    2014-12-09

    There is a close relationship between cardiovascular disease and cardiac energy metabolism, and we have previously demonstrated that palmitate inhibits myocyte contraction by increasing Kv channel activity and decreasing the action potential duration. Glucose and long chain fatty acids are the major fuel sources supporting cardiac function; however, cardiac myocytes can utilize a variety of substrates for energy generation, and previous studies demonstrate the acetate is rapidly taken up and oxidized by the heart. In this study, we tested the effects of acetate on contractile function of isolated mouse ventricular myocytes. Acute exposure of myocytes to 10 mM sodium acetate caused a marked, but transient, decrease in systolic sarcomere shortening (1.49 ± 0.20% vs. 5.58 ± 0.49% in control), accompanied by a significant increase in diastolic sarcomere length (1.81 ± 0.01 μm vs. 1.77 ± 0.01 μm in control), with a near linear dose response in the 1-10 mM range. Unlike palmitate, acetate caused no change in action potential duration; however, acetate markedly increased mitochondrial Ca(2+) uptake. Moreover, pretreatment of cells with the mitochondrial Ca(2+) uptake blocker, Ru-360 (10 μM), markedly suppressed the effect of acetate on contraction. Lehninger and others have previously demonstrated that the anions of weak aliphatic acids such as acetate stimulate Ca(2+) uptake in isolated mitochondria. Here we show that this effect of acetate appears to extend to isolated cardiac myocytes where it transiently modulates cell contraction.

  16. Fear conditioning suppresses large-conductance calcium-activated potassium channels in lateral amygdala neurons.

    Science.gov (United States)

    Sun, P; Zhang, Q; Zhang, Y; Wang, F; Wang, L; Yamamoto, R; Sugai, T; Kato, N

    2015-01-01

    It was previously shown that depression-like behavior is accompanied with suppression of the large-conductance calcium activated potassium (BK) channel in cingulate cortex pyramidal cells. To test whether BK channels are also involved in fear conditioning, we studied neuronal properties of amygdala principal cells in fear conditioned mice. After behavior, we made brain slices containing the amygdala, the structure critically relevant to fear memory. The resting membrane potential in lateral amygdala (LA) neurons obtained from fear conditioned mice (FC group) was more depolarized than in neurons from naïve controls. The frequencies of spikes evoked by current injections were higher in neurons from FC mice, demonstrating that excitability of LA neurons was elevated by fear conditioning. The depolarization in neurons from FC mice was shown to depend on BK channels by using the BK channel blocker charybdotoxin. Suppression of BK channels in LA neurons from the FC group was further confirmed on the basis of the spike width, since BK channels affect the descending phase of spikes. Spikes were broader in the FC group than those in the naïve control in a manner dependent on BK channels. Consistently, quantitative real-time PCR revealed a decreased expression of BK channel mRNA. The present findings suggest that emotional disorder manifested in the forms of fear conditioning is accompanied with BK channel suppression in the amygdala, the brain structure critical to this emotional disorder. Copyright © 2014 Elsevier Inc. All rights reserved.

  17. Ryanodine receptor/calcium release channel PKA phosphorylation: A critical mediator of heart failure progression

    Science.gov (United States)

    Wehrens, Xander H. T.; Lehnart, Stephan E.; Reiken, Steven; Vest, John A.; Wronska, Anetta; Marks, Andrew R.

    2006-01-01

    Defective regulation of the cardiac ryanodine receptor (RyR2)/calcium release channel, required for excitation-contraction coupling in the heart, has been linked to cardiac arrhythmias and heart failure. For example, diastolic calcium “leak” via RyR2 channels in the sarcoplasmic reticulum has been identified as an important factor contributing to impaired contractility in heart failure and ventricular arrhythmias that cause sudden cardiac death. In patients with heart failure, chronic activation of the “fight or flight” stress response leads to protein kinase A (PKA) hyperphosphorylation of RyR2 at Ser-2808. PKA phosphorylation of RyR2 Ser-2808 reduces the binding affinity of the channel-stabilizing subunit calstabin2, resulting in leaky RyR2 channels. We developed RyR2-S2808A mice to determine whether Ser-2808 is the functional PKA phosphorylation site on RyR2. Furthermore, mice in which the RyR2 channel cannot be PKA phosphorylated were relatively protected against the development of heart failure after myocardial infarction. Taken together, these data show that PKA phosphorylation of Ser-2808 on the RyR2 channel appears to be a critical mediator of progressive cardiac dysfunction after myocardial infarction. PMID:16407108

  18. The Peptide PnPP-19, a Spider Toxin Derivative, Activates μ-Opioid Receptors and Modulates Calcium Channels

    Directory of Open Access Journals (Sweden)

    Ana C. N. Freitas

    2018-01-01

    Full Text Available The synthetic peptide PnPP-19 comprehends 19 amino acid residues and it represents part of the primary structure of the toxin δ-CNTX-Pn1c (PnTx2-6, isolated from the venom of the spider Phoneutria nigriventer. Behavioural tests suggest that PnPP-19 induces antinociception by activation of CB1, μ and δ opioid receptors. Since the peripheral and central antinociception induced by PnPP-19 involves opioid activation, the aim of this work was to identify whether this synthetic peptide could directly activate opioid receptors and investigate the subtype selectivity for μ-, δ- and/or κ-opioid receptors. Furthermore, we also studied the modulation of calcium influx driven by PnPP-19 in dorsal root ganglion neurons, and analyzed whether this modulation was opioid-mediated. PnPP-19 selectively activates μ-opioid receptors inducing indirectly inhibition of calcium channels and hereby impairing calcium influx in dorsal root ganglion (DRG neurons. Interestingly, notwithstanding the activation of opioid receptors, PnPP-19 does not induce β-arrestin2 recruitment. PnPP-19 is the first spider toxin derivative that, among opioid receptors, selectively activates μ-opioid receptors. The lack of β-arrestin2 recruitment highlights its potential for the design of new improved opioid agonists.

  19. Activation of KCNN3/SK3/K(Ca)2.3 channels attenuates enhanced calcium influx and inflammatory cytokine production in activated microglia.

    Science.gov (United States)

    Dolga, Amalia M; Letsche, Till; Gold, Maike; Doti, Nunzianna; Bacher, Michael; Chiamvimonvat, Nipavan; Dodel, Richard; Culmsee, Carsten

    2012-12-01

    In neurons, small-conductance calcium-activated potassium (KCNN/SK/K(Ca)2) channels maintain calcium homeostasis after N-methyl-D-aspartate (NMDA) receptor activation, thereby preventing excitotoxic neuronal death. So far, little is known about the function of KCNN/SK/K(Ca)2 channels in non-neuronal cells, such as microglial cells. In this study, we addressed the question whether KCNN/SK/K(Ca)2 channels activation affected inflammatory responses of primary mouse microglial cells upon lipopolysaccharide (LPS) stimulation. We found that N-cyclohexyl-N-[2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-4-pyrimidinamine (CyPPA), a positive pharmacological activator of KCNN/SK/K(Ca)2 channels, significantly reduced LPS-stimulated activation of microglia in a concentration-dependent manner. The general KCNN/SK/K(Ca)2 channel blocker apamin reverted these effects of CyPPA on microglial proliferation. Since calcium plays a central role in microglial activation, we further addressed whether KCNN/SK/K(Ca)2 channel activation affected the changes of intracellular calcium levels, [Ca(2+)](i), in microglial cells. Our data show that LPS-induced elevation of [Ca(2+)](i) was attenuated following activation of KCNN2/3/K(Ca)2.2/K(Ca)2.3 channels by CyPPA. Furthermore, CyPPA reduced downstream events including tumor necrosis factor alpha and interleukin 6 cytokine production and nitric oxide release in activated microglia. Further, we applied specific peptide inhibitors of the KCNN/SK/K(Ca)2 channel subtypes to identify which particular channel subtype mediated the observed anti-inflammatory effects. Only inhibitory peptides targeting KCNN3/SK3/K(Ca)2.3 channels, but not KCNN2/SK2/K(Ca)2.2 channel inhibition, reversed the CyPPA-effects on LPS-induced microglial proliferation. These findings revealed that KCNN3/SK3/K(Ca)2.3 channels can modulate the LPS-induced inflammatory responses in microglial cells. Thus, KCNN3/SK3/K(Ca)2.3 channels may serve as a therapeutic target for reducing microglial

  20. Antihypertensive and vasorelaxant activities of Laelia autumnalis are mainly through calcium channel blockade.

    Science.gov (United States)

    Vergara-Galicia, Jorge; Ortiz-Andrade, Rolffy; Castillo-España, Patricia; Ibarra-Barajas, Maximiliano; Gallardo-Ortiz, Itzell; Villalobos-Molina, Rafael; Estrada-Soto, Samuel

    2008-07-01

    The aim of the present study was to evaluate the possible mechanism of the vasorelaxant action of methanol extract from Laelia autumnalis (MELa) in isolated rat aortic rings, and to establish its antihypertensive activity in vivo. MELa (0.15-->50 microg/mL) induced relaxation in aortic rings pre-contracted with KCl (80 mM), showing an IC50 value of 34.61+/-1.41 microg/mL and E max value of 85.0+/-4.38% (in endothelium-intact rings) and an IC50 value of 45.11+/-4.17 microg/mL and E max value of 80.0+/-12.1% (in endothelium-denuded rings). Serotonin (5-HT, 1 x 10(-4) M) provoked sustained contraction, which was markedly inhibited by MELa (0.15-->50 microg/mL) in a concentration-dependent and endothelium-independent manner. Pretreatment with MELa (15, 46, 150, 300 and 1500 microg/mL) also inhibited contractile responses to norepinephrine (NE 1 x 10(-11) M to 1 x 10(-5.5) M). In endothelium-denuded rings, the vasorelaxant effect of MELa was reduced partially by ODQ (1 microM), but not by tetraethylammonium (5 microM), glibenclamide (10 microM), and 2-aminopyridine (100 microM). The extract also reduced NE-induced transient contraction in Ca2+-free solution, and inhibited contraction induced by increasing external calcium in Ca2+-free medium plus high KCl (80 mM). The antihypertensive effect of MELa was determined in spontaneously hypertensive rats (SHR). A single oral administration of the extract (100 mg/kg) exhibited a significant decrease in systolic and diastolic blood pressure and heart rate (p<0.05) in SHR rats. Our results suggest that MELa induces relaxation in rat aortic rings through an endothelium-independent pathway, involving blockade of Ca2+ channels and a possible cGMP enhanced concentrations and also causes an antihypertensive effect.

  1. GABA(A) Increases Calcium in Subventricular Zone Astrocyte-Like Cells Through L- and T-Type Voltage-Gated Calcium Channels

    DEFF Research Database (Denmark)

    Young, Stephanie Z; Platel, Jean-Claude; Nielsen, Jakob V

    2010-01-01

    induced Ca(2+) increases in 40-50% of SVZ astrocytes. GABA(A)-induced Ca(2+) increases were prevented with nifedipine and mibefradil, blockers of L- and T-type voltage-gated calcium channels (VGCC). The L-type Ca(2+) channel activator BayK 8644 increased the percentage of GABA(A)-responding astrocyte...

  2. Voltage-dependent sodium channels and calcium-activated potassium channels in human odontoblasts in vitro.

    Science.gov (United States)

    Ichikawa, Hideki; Kim, Hyong-Jung; Shuprisha, Apichai; Shikano, Tetsuo; Tsumura, Maki; Shibukawa, Yoshiyuki; Tazaki, Masakazu

    2012-10-01

    Transmembrane ionic signaling regulates many cellular processes in both physiological and pathologic settings. In this study, the biophysical properties of voltage-dependent Na(+) channels in odontoblasts derived from human dental pulp (HOB cells) were investigated together with the effect of bradykinin on intracellular Ca(2+) signaling and expression of Ca(2+)-activated K(+) channels. Ionic channel activity was characterized by using whole-cell patch-clamp recording and fura-2 fluorescence. Mean resting membrane potential in the HOB cells was -38 mV. Depolarizing steps from a holding potential of -80 mV activated transient voltage-dependent inward currents with rapid activation/inactivation properties. At a holding potential of -50 mV, no inward current was recorded. Fast-activation kinetics exhibited dependence on membrane potential, whereas fast-inactivation kinetics did not. Steady-state inactivation was described by a Boltzmann function with a half-maximal inactivation potential of -70 mV, indicating that whereas the channels were completely inactivated at physiological resting membrane potential, they could be activated when the cells were hyperpolarized. Inward currents disappeared in Na(+)-free extracellular solution. Bradykinin activated intracellular Ca(2+)-releasing and influx pathways. When the HOB cells were clamped at a holding potential of -50 mV, outward currents were recorded at positive potentials, indicating sensitivity to inhibitors of intermediate-conductance Ca(2+)-activated K(+) channels. Human odontoblasts expressed voltage-dependent Na(+) channels, bradykinin receptors, and Ca(2+)-activated K(+) channels, which play an important role in driving cellular functions by channel-receptor signal interaction and membrane potential regulation. Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  3. Calcium signaling in lymphocytes and ELF fields. Evidence for an electric field metric and a site of interaction involving the calcium ion channel.

    Science.gov (United States)

    Liburdy, R P

    1992-04-13

    Calcium influx increased during mitogen-activated signal transduction in thymic lymphocytes exposed to a 22 mT, 60 Hz magnetic field (E induced = 1.7 mV/cm, 37 degrees C, 60 min). To distinguish between an electric or a magnetic field dependence a special multi-ring annular cell culture plate based on Faraday's Law of Induction was employed. Studies show a dependence on the strength of the induced electric field at constant magnetic flux density. Moreover, exposure to a pure 60 Hz electric field or to a magnetically-induced electric field of identical strength resulted in similar changes in calcium transport. The first real-time monitoring of [Ca2+]i during application of a 60 Hz electric field revealed an increase in [Ca2+]i observed 100 s after mitogen stimulation; this suggests that the plateau phase rather than the early phase of calcium signaling was influenced. The hypothesis was tested by separating, in time, the early release of calcium from intracellular stores from the influx of extracellular calcium. In calcium-free buffer, 60 Hz field exerted little influence on the early release of calcium from intracellular stores. In contrast, addition of extracellular calcium during exposure enhanced calcium influx through the plasma membrane. Alteration of the plateau phase of calcium signaling implicates the calcium channel as a site of field interaction. In addition, an electric field exposure metric is mechanistically consistent with a cell-surface interaction site.

  4. A combined role of calcium channel blockers and angiotensin receptor blockers in stroke prevention

    Directory of Open Access Journals (Sweden)

    Ji-Guang Wang

    2009-07-01

    Full Text Available Ji-Guang WangCentre for Epidemiological Studies and Clinical Trials, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, ChinaAbstract: Stroke is a leading cause of death and disability worldwide. The importance of lowering blood pressure for reducing the risk of stroke is well established. However, not all the benefits of antihypertensive treatments in stroke can be accounted for by reductions in BP and there may be differences between antihypertensive classes as to which provides optimal protection. Dihydropyridine calcium channel blockers, such as amlodipine, and angiotensin receptor blockers, such as valsartan, represent the two antihypertensive drug classes with the strongest supportive data for the prevention of stroke. Therefore, when combination therapy is required, a combination of these two antihypertensive classes represents a logical approach.Keywords: stroke, angiotensin, calcium channel, cerebrovascular, hypertension, blood pressure

  5. [Results of an intervention to reduce potentially inappropriate prescriptions of beta blockers and calcium channel blockers].

    Science.gov (United States)

    Machado-Alba, J E; Giraldo-Giraldo, C; Aguirre Novoa, A

    2016-01-01

    To determine the frequency of simultaneous prescription of β-blockers and calcium channel blockers, notify the cardiovascular risk of these patients to the health care professionals in charge of them, and achieve a reduction in the number of those who use them. Quasi-experimental, prospective study by developing an intervention on medical prescriptions of patients older than 65 years treated between January 1 and July 30, 2014, affiliated to the Health System in 101 cities in Colombia. A total of 43,180 patients received a β-blocker each month, and 14,560 receiving a calcium channel blocker were identified. Educational interventions were performed and an evaluation was made, using sociodemographic and pharmacological variables, on the number of patients that stopped taking any of the two drugs in the following three months. A total of 535 patients, with a mean age 75.8±6.7 years received concomitant β-blockers plus calcium channel blockers. Modification of therapy was achieved in 235 patients (43.9% of users) after 66 educational interventions. In 209 cases (88.9%) one of the two drugs was suspended, and 11.1% changed to other antihypertensive drugs. The variable of being more than 85 years old (OR: 1.93; 95% CI: 1.07-3.50), and receiving concomitant medication with inhibitors of the renin-angiotensin system (OR: 2.16; 95% CI: 1.28-3.65) were associated with increased risk of their doctor changing or stopping the prescription. An improved adherence to recommendations for appropriate use of β-blockers and calcium channel blockers by health service providers was achieved. Intervention programs that reduce potentially inappropriate prescriptions for patients treated for cardiovascular disease should be used more frequently. Copyright © 2015 SECA. Published by Elsevier Espana. All rights reserved.

  6. Calcium Channels: Structure and Function (Annals of the New York Academy of Sciences. Volume 560)

    Science.gov (United States)

    1989-06-26

    of the Calcium-Channel Agonist CGP 28392 on Transmitter Release at Mouse Neuromuscular Junctions. By J. BURGES and D . W .-W RAY...for example, CGP 28392 (most likely (S)- CGP 28392, see Refs. 12 and 13), (S)-(+)-202-791, or (- )-Bay K 8644 are always inhibitory." Interestingly...electric organ synapse in an elasmobranch is reversibly blocked by wCgTX," whereas synapses in amphibia, |2 reptiles , and birds (D.Y., unpublished) are

  7. Effects of Calcium Channel Blockers on Antidepressant Action of Alprazolam and Imipramine

    Directory of Open Access Journals (Sweden)

    Gorash ZM

    2007-01-01

    Full Text Available Alprazolam is effective as an anxiolytic and in the adjunct treatment of depression. In this study, the effects of calcium channel antagonists on the antidepressant action of alprazolam and imipramine were investigated. A forced swimming maze was used to study behavioral despair in albino mice. Mice were divided into nine groups (n = 7 per group. One group received a single dose of 1% Tween 80; two groups each received a single dose of the antidepressant alone (alprazolam or imipramine; two groups each received a single dose of the calcium channel blocker (nifedipine or verapamil; four groups each received a single dose of the calcium channel blocker followed by a single dose of the antidepressant (with same doses used for either in the previous four groups. Drug administration was performed concurrently on the nine groups. Our data confirmed the antidepressant action of alprazolam and imipramine. Both nifedipine and verapamil produced a significant antidepressant effect (delay the onset of immobility when administered separately. Verapamil augmented the antidepressant effects of alprazolam and imipramine (additive antidepressant effect. This may be due to the possibility that verapamil might have antidepressant-like effect through different mechanism. Nifedipine and imipramine combined led to a delay in the onset of immobility greater than their single use but less than the sum of their independent administration. This may be due to the fact that nifedipine on its own might act as an antidepressant but blocks one imipramine mechanism that depends on L-type calcium channel activation. Combining nifedipine with alprazolam produced additional antidepressant effects, which indicates that they exert antidepressant effects through different mechanisms.

  8. An expert protocol for immunofluorescent detection of calcium channels in tsA-201 cells.

    Science.gov (United States)

    Koch, Peter; Herzig, Stefan; Matthes, Jan

    Pore-forming subunits of voltage gated calcium channels (VGCC) are large membrane proteins (260kDa) containing 24 transmembrane domains. Despite transfection with viral promoter driven vectors, biochemical analysis of VGCC is often hampered by rather low expression levels in heterologous systems rendering VGCC challenging targets. Especially in immunofluorescent detection, calcium channels are demanding proteins. We provide an expert step-by-step protocol with adapted conditions for handling procedures (tsA-201 cell culture, transient transfection, incubation time and temperature at 28°C or 37°C and immunostaining) to address the L-type calcium-channel pore Cav1.2 in an immunofluorescent approach. We performed immunocytochemical analysis of Cav1.2 expression at single-cell level in combination with detection of different markers for cellular organelles. We show confluency levels and shapes of tsA-201 cells at different time points during an experiment. Our experiments reveal sufficient levels of Cav1.2 protein and a correct Cav1.2 expression pattern in polygonal shaped cells already 12h after transfection. A sequence of elaborated protocol modifications allows subcellular localization analysis of Cav1.2 in an immunocytochemical approach. We provide a protocol that may be used to achieve insights into physiological and pathophysiological processes involving voltage gated calcium channels. Our protocol may be used for expression analysis of other challenging proteins and efficient overexpression may be exploited in related biochemical techniques requiring immunolabels. Copyright © 2016 Elsevier Inc. All rights reserved.

  9. Interactions between calcium channel blockers and the anticonvulsants carbamazepine and phenytoin.

    Science.gov (United States)

    Bahls, F H; Ozuna, J; Ritchie, D E

    1991-05-01

    We describe a retrospective analysis of the frequency of adverse interactions between calcium channel blockers and anticonvulsant drugs (phenytoin and carbamazepine) in a series of 43 patients. Ten patients receiving carbamazepine and three patients receiving phenytoin exhibited symptoms or signs of toxicity. Toxicity occurred with both diltiazem and verapamil, but not with nifedipine. These results emphasize the need for careful clinical and laboratory monitoring of patients receiving both classes of medication.

  10. Role of calcium influx through voltage-operated calcium channels and of calcium mobilization in the physiology of Schistosoma mansoni muscle contractions.

    Science.gov (United States)

    Mendonça-Silva, D L; Novozhilova, E; Cobbett, P J R; Silva, C L M; Noël, F; Totten, M I J; Maule, A G; Day, T A

    2006-07-01

    We tested the hypothesis that voltage-operated Ca2+ channels mediate an extracellular Ca2+ influx in muscle fibres from the human parasite Schistosoma mansoni and, along with Ca2+ mobilization from the sarcoplasmic reticulum, contribute to muscle contraction. Indeed, whole-cell voltage clamp revealed voltage-gated inward currents carried by divalent ions with a peak current elicited by steps to +20 mV (from a holding potential of -70 mV). Depolarization of the fibres by elevated extracellular K+ elicited contractions that were completely dependent on extracellular Ca2+ and inhibited by nicardipine (half inhibition at 4.1 microM). However these contractions were not very sensitive to other classical blockers of voltage-gated Ca2+ channels, indicating that the schistosome muscle channels have an atypical pharmacology when compared to their mammalian counterparts. Futhermore, the contraction induced by 5 mM caffeine was inhibited after depletion of the sarcoplasmic reticulum either with thapsigargin (10 microM) or ryanodine (10 microM). These data suggest that voltage-operated Ca2+ channels do contribute to S. mansoni contraction as does the mobilization of stored Ca2+, despite the small volume of sarcoplasmic reticulum in schistosome smooth muscles.

  11. Vasorelaxant and antihypertensive effects of methanolic extract from roots of Laelia anceps are mediated by calcium-channel antagonism.

    Science.gov (United States)

    Vergara-Galicia, Jorge; Ortiz-Andrade, Rolffy; Rivera-Leyva, Julio; Castillo-España, Patricia; Villalobos-Molina, Rafael; Ibarra-Barajas, Maximiliano; Gallardo-Ortiz, Itzell; Estrada-Soto, Samuel

    2010-07-01

    RMELanc-induced relaxation in aortic rings precontracted with NE, 5-HT and KCl. It also reduced NE-induced transient contraction in Ca(2+)-free solution and inhibited contraction induced by increasing external calcium. Nevertheless, the vasorelaxant effect of RMELanc was not reduced by ODQ, 1-alprenolol, TEA, glibenclamide, and 2-AP. Oral administration of 100 mg/kg of RMELanc exhibited a significant decrease in systolic and diastolic blood pressures in SHR rats. HPLC analysis allowed us to detect the presence of 2,7-dihydroxy-3,4,9-trimethoxyphenantrene (1), which induced a significant relaxation effect. Therefore, our results suggest that RMELanc induces vasorelaxant and antihypertensive effects by blockade of Ca(2+) channels. Copyright 2009 Elsevier B.V. All rights reserved.

  12. Calcium-channel blockers do not alter the clinical efficacy of clopidogrel after myocardial infarction: a nationwide cohort study

    DEFF Research Database (Denmark)

    Olesen, Jonas B; Gislason, Gunnar H; Charlot, Mette G

    2011-01-01

    Objectives The purpose of this study was to determine the risk of adverse cardiovascular events associated with concomitant use of clopidogrel and calcium-channel blockers (CCBs) in patients with myocardial infarction (MI). Background CCBs inhibit a variety of cytochrome P-450 enzymes, some...... of which contribute to clopidogrel metabolic activation. This interaction may diminish the efficacy of clopidogrel. Methods All patients surviving 30 days after a first-time MI in the period 2000 to 2006 in Denmark were identified by individual-level linkage of nationwide administrative registers....... The cohort was divided into patients treated with and without clopidogrel and followed for 1 year after discharge. The risk of a composite of cardiovascular death, MI, or stroke and the risk of the individual components of the composite end point and all-cause death associated with CCBs were analyzed...

  13. Calcium channel TRPV6 as a potential therapeutic target in estrogen receptor-negative breast cancer.

    Science.gov (United States)

    Peters, Amelia A; Simpson, Peter T; Bassett, Johnathon J; Lee, Jane M; Da Silva, Leonard; Reid, Lynne E; Song, Sarah; Parat, Marie-Odile; Lakhani, Sunil R; Kenny, Paraic A; Roberts-Thomson, Sarah J; Monteith, Gregory R

    2012-10-01

    Calcium signaling is a critical regulator of cell proliferation. Elevated expression of calcium channels and pumps is a characteristic of some cancers, including breast cancer. We show that the plasma membrane calcium channel TRPV6, which is highly selective for Ca(2+), is overexpressed in some breast cancer cell lines. Silencing of TRPV6 expression in a breast cancer cell line with increased endogenous TRPV6 expression leads to a reduction in basal calcium influx and cellular proliferation associated with a reduction in DNA synthesis. TRPV6 gene amplification was identified as one mechanism of TRPV6 overexpression in a subset of breast cancer cell lines and breast tumor samples. Analysis of two independent microarray expression datasets from breast tumor samples showed that increased TRPV6 expression is a feature of estrogen receptor (ER)-negative breast tumors encompassing the basal-like molecular subtype, as well as HER2-positive tumors. Breast cancer patients with high TRPV6 levels had decreased survival compared with patients with low or intermediate TRPV6 expression. Our findings suggest that inhibitors of TRPV6 may offer a novel therapeutic strategy for the treatment of ER-negative breast cancers.

  14. Inhibition of large conductance calcium-dependent potassium ...

    African Journals Online (AJOL)

    Cachero, T.G., Morielli, A.D., Peralta, E.G., 1998. The small GTP-binding protein RhoA regulates a delayed rectifier potassium channel. Cell. 93, 1077-1085. Callera, G.E., Yogi, A., Tostes, R.C., Rossoni, L.V.,. Bendhack, L.M., 2004. Ca2+- Activated K+. Channels Underlying the Impaired Acetylcholine-. Induced Vasodilation ...

  15. The mode of inhibition of the Na+-K+ pump activity in mast cells by calcium

    DEFF Research Database (Denmark)

    Knudsen, T; Johansen, Torben

    1989-01-01

    1 The inhibition by calcium of the Na(+)-K+ pump in the plasma membrane of rat peritoneal mast cells was studied in pure populations of the cells by measuring the ouabain-sensitive uptake of the radioactive potassium analogue, 86rubidium (86Rb+). 2 Exposure of the cells to calcium induced a time...... not develop when the mast cells were incubated in a potassium-free medium, which is known to block Na(+)-K+ pump activity and allow accumulation of sodium inside the cells. Likewise, increasing the sodium permeability of the plasma membrane by monensin abolished the inhibition of the pump activity. In both...... peritoneal mast cells in a calcium-free medium increases the permeability of the plasma membrane to sodium, and the consequent increase in the intracellular concentration of sodium causes an increase in the activity of the pump. Addition of calcium to the cell suspension decreases the sodium permeability...

  16. Unexpected Effect of Calcium Channel Blockers on the Optic Nerve Compartment Syndrome.

    Science.gov (United States)

    Konieczka, K; Todorova, M G; Bojinova, R I; Binggeli, T; Chackathayil, T N; Flammer, J

    2016-04-01

    The optic nerve compartment syndrome is a pathological condition in which cerebrospinal fluid of the subarachnoid space surrounding the optic nerve is partly or totally segregated from the cerebrospinal fluid of the intracranial subarachnoid space, leading - inter alia - to an increase in the diameter of the optic nerve sheath. The pathogenesis of this condition remains unclear. We have observed clinically that optic nerve compartment syndrome often occurs in normal tension glaucoma patients with Flammer syndrome. To treat Flammer syndrome, some glaucoma patients received a low dose of a calcium channel blocker and we analysed whether this treatment also had an effect on the optic nerve compartment syndrome. We retrospectively analysed the data of 10 eyes of seven patients suffering from a combination of primary open angle glaucoma, optic nerve compartment syndrome, and Flammer syndrome. We included subjects who had eye socket echography before and after a few months of therapy with a calcium channel blocker. All patients received a low dose of a calcium channel blocker (nifedipine or amlodipine) to treat Flammer syndrome. As expected, the symptoms of Flammer syndrome were mitigated. To our surprise, the optic nerve compartment syndrome also improved in eight of the 10 eyes (80 %), but remained unchanged in the remainder. To some extent, the optic nerve compartment syndrome is related to the combination of primary open angle glaucoma and Flammer syndrome. On the basis of our results, we hypothesise that treatment of Flammer syndrome may also improve the optic nerve compartment syndrome. Georg Thieme Verlag KG Stuttgart · New York.

  17. The effect of calcium channel blockers on prevention of preeclampsia in pregnant women with chronic hypertension.

    Science.gov (United States)

    Jiang, N; Liu, Q; Liu, L; Yang, W W; Zeng, Y

    2015-01-01

    Pregnant women with chronic hypertension are at increased risk for complications. This study aims to investigate whether calcium channel blockers plus low dosage aspirin therapy can reduce the incidence of complications during pregnancy with chronic hypertension and improve the prognosis of neonates. From March 2011 to June 2013, 33 patients were selected to join this trial according to the chronic hypertension criteria set by the Preface Bulletin of American College of Obstetricians and Gynecologists, (ACOG). Patients were administrated calcium channel blockers plus low-dosage aspirin and vitamin C. The statistic data of baseline and prognosis from the patients were retrospectively reviewed and compared. Blood pressure of patients was controlled by these medicines with average systolic pressure from 146.3 to 148.7 mmHg and average diastolic pressure from 93.8 to 97.9 mmHg; 39.4% patients complicated mild preeclampsia; however, none of them developed severe preeclampsia or eclampsia, or complicate placental abruption. 30.3% patients delivered at preterm labour; 84.8% patients underwent cesarean section. The neonatal average weight was 3,008 ± 629.6 g, in which seven neonatal weights were less than 2,500 g. All of the neonatal Apgar scores were 9 to 10 at one to five minutes. Small for gestational age (SGA) occurred in five (15%). Calcium channel blockers can improve the outcome of pregnancy women with chronic hypertension to avoid the occurrence of severe pregnancy complication or neonatal morbidity.

  18. The effect of calcium channel blockers and calmodulin inhibitors on the macrophage factor-stimulated synthesis of collagenase by rabbit chondrocytes.

    Science.gov (United States)

    Nolan, J C; Gathright, C E; Wagner, L E

    1988-08-01

    Macrophages and monocytes secrete a factor(s) which can stimulate the synthesis of collagenase in synovial cells and in chondrocytes. Incubation of rabbit chondrocytes with macrophage conditioned medium (MCM) and with the calcium channel blockers, nifedipine, verapamil or diltiazem (up to 200 microM) had no effect on collagenase synthesis. However, TMB-8 (8-[N,N-diethylamino]-octyl 3,4,5-trimethoxybenzoate hydrochloride), an inhibitor of internal calcium movement, did inhibit the process with an IC50 of approximately 130 microM. The calmodulin antagonists, trifluoperazine, chlorpromazine and calmidazolium (R-24571) were effective inhibitors of the process with IC50's of 40 microM, 18 microM and 3.5 microM, respectively. Collagenase activity itself was not affected by these agents. The data suggests that calmodulin and/or internal calcium movement may play a role in the macrophage factor-stimulated synthesis of collagenase in rabbit chondrocytes.

  19. Long-Term Blocking of Calcium Channels in mdx Mice Results in Differential Effects on Heart and Skeletal Muscle

    DEFF Research Database (Denmark)

    Jørgensen, Louise Helskov; Blain, Alison; Greally, Elizabeth

    2011-01-01

    calcium ions to enter the cell. The objective of this study was to investigate the effect of chronically blocking calcium channels with the aminoglycoside antibiotic streptomycin from onset of disease in the mdx mouse model of Duchenne muscular dystrophy (DMD). Treatment in utero onwards delayed onset......The disease mechanisms underlying dystrophin-deficient muscular dystrophy are complex, involving not only muscle membrane fragility, but also dysregulated calcium homeostasis. Specifically, it has been proposed that calcium channels directly initiate a cascade of pathological events by allowing...... in older mice. However, streptomycin treatment did not show positive effects in diaphragm or heart muscle, and heart pathology was worsened. Thus, blocking calcium channels even before disease onset does not prevent dystrophy, making this an unlikely treatment for DMD. These findings highlight...

  20. Involvement of Nitric Oxide in the Inhibition of Aortic Smooth Muscle Cell Proliferation by Calcium Dobesilate.

    Science.gov (United States)

    Parés-Herbuté; Fliche; Monnier

    1999-01-01

    Vascular smooth muscle cell (SMC) proliferation is a key process in the pathogenesis of atherosclerosis. Numerous factors are involved in the regulation of SMC growth. Nitric oxide (NO) induces the inhibition of SMC proliferation whereas oxidized low-density lipoproteins (LDL) have a mitogenic effect. Calcium dobesilate (Doxium) is an angioprotective agent for treating vascular diseases. It has been shown to increase NO production and to have antioxidant properties but its mechanism of action is not yet fully understood. This study investigated the effect of calcium dobesilate on proliferation of rat aortic SMC in culture. Proliferation was evaluated by cell number and DNA synthesis. Orally administered calcium dobesilate (30, 100, or 200 mg/kg/day for 7 days) induced a dose-dependent decrease of proliferation of SMC in primary culture compared with controls. In vitro treatment with calcium dobesilate (0.05-5 mM) inhibited both DNA synthesis and proliferation in a time- and concentration-dependent manner. In both ex vivo and in vitro models, the inhibition was reversible upon removal of the drug. Calcium dobesilate also stimulated NO production and NO synthase activity. Inhibitors of NO synthesis attenuated the inhibitory effect of calcium dobesilate (300 µM) on DNA synthesis. In addition, calcium dobesilate (2.5-40 µM) induced a dose-dependent protection of cooper-induced LDL oxidation. These results showed that calcium dobesilate inhibits SMC proliferation, partly by a NO-dependent mechanism, and suggest that it could be effective in the treatment of pathological disorders associated with vascular SMC proliferation.

  1. The effect of calcium hardness on hatching success of channel catfish x blue catfish hybrid catfish eggs

    Science.gov (United States)

    The present study was designed to determine the optimal level of calcium hardness in hatching waters to incubate channel catfish Ictalurus punctatus ' x blue catfish I. furcatus ' hybrid catfish eggs. Hatching success of hybrid catfish eggs was higher (phardness (C...

  2. Efficacy and safety of calcium channel blockers in heart failure : Focus on recent trials with second-generation dihydropyridines

    NARCIS (Netherlands)

    de Vries, RJM; van Veldhuisen, DJ; Dunselman, PHJM

    Background Chronic heart failure (CHF) has high morbidity and mortality rates despite treatment with angiotensin-converting-enzyme inhibitors, diuretics, and digoxin. Adjunctive-vasodilation through calcium channel blockade has been suggested as potentially useful, However, the first-generation

  3. Design and Synthesis of a Conformationally Rigid Mimic of the Dihydropyrimidine Calcium Channel Modulator SQ 32,926

    Directory of Open Access Journals (Sweden)

    Birgit Jauk

    2000-03-01

    Full Text Available A conformationally rigid polyheterocycle (3 which mimics the putative receptorbound conformation of dihydropyridine-type calcium channel modulators is prepared in a seven-step reaction sequence based on a Biginelli-type cyclocondensation reaction.

  4. Design and Synthesis of a Conformationally Rigid Mimic of the Dihydropyrimidine Calcium Channel Modulator SQ 32,926

    OpenAIRE

    Birgit Jauk; Tetiana Pernat; Oliver Kappe, C.

    2000-01-01

    A conformationally rigid polyheterocycle (3) which mimics the putative receptorbound conformation of dihydropyridine-type calcium channel modulators is prepared in a seven-step reaction sequence based on a Biginelli-type cyclocondensation reaction.

  5. Anion-sensitive regions of L-type CaV1.2 calcium channels expressed in HEK293 cells.

    Directory of Open Access Journals (Sweden)

    Norbert Babai

    2010-01-01

    Full Text Available L-type calcium currents (I(Ca are influenced by changes in extracellular chloride, but sites of anion effects have not been identified. Our experiments showed that CaV1.2 currents expressed in HEK293 cells are strongly inhibited by replacing extracellular chloride with gluconate or perchlorate. Variance-mean analysis of I(Ca and cell-attached patch single channel recordings indicate that gluconate-induced inhibition is due to intracellular anion effects on Ca(2+ channel open probability, not conductance. Inhibition of CaV1.2 currents produced by replacing chloride with gluconate was reduced from approximately 75%-80% to approximately 50% by omitting beta subunits but unaffected by omitting alpha(2delta subunits. Similarly, gluconate inhibition was reduced to approximately 50% by deleting an alpha1 subunit N-terminal region of 15 residues critical for beta subunit interactions regulating open probability. Omitting beta subunits with this mutant alpha1 subunit did not further diminish inhibition. Gluconate inhibition was unchanged with expression of different beta subunits. Truncating the C terminus at AA1665 reduced gluconate inhibition from approximately 75%-80% to approximately 50% whereas truncating it at AA1700 had no effect. Neutralizing arginines at AA1696 and 1697 by replacement with glutamines reduced gluconate inhibition to approximately 60% indicating these residues are particularly important for anion effects. Expressing CaV1.2 channels that lacked both N and C termini reduced gluconate inhibition to approximately 25% consistent with additive interactions between the two tail regions. Our results suggest that modest changes in intracellular anion concentration can produce significant effects on CaV1.2 currents mediated by changes in channel open probability involving beta subunit interactions with the N terminus and a short C terminal region.

  6. Inhibiting the Mitochondrial Calcium Uniporter during Development Impairs Memory in Adult Drosophila.

    Science.gov (United States)

    Drago, Ilaria; Davis, Ronald L

    2016-09-06

    The uptake of cytoplasmic calcium into mitochondria is critical for a variety of physiological processes, including calcium buffering, metabolism, and cell survival. Here, we demonstrate that inhibiting the mitochondrial calcium uniporter in the Drosophila mushroom body neurons (MBn)-a brain region critical for olfactory memory formation-causes memory impairment without altering the capacity to learn. Inhibiting uniporter activity only during pupation impaired adult memory, whereas the same inhibition during adulthood was without effect. The behavioral impairment was associated with structural defects in MBn, including a decrease in synaptic vesicles and an increased length in the axons of the αβ MBn. Our results reveal an in vivo developmental role for the mitochondrial uniporter complex in establishing the necessary structural and functional neuronal substrates for normal memory formation in the adult organism. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  7. Inhibiting the Mitochondrial Calcium Uniporter during Development Impairs Memory in Adult Drosophila

    Directory of Open Access Journals (Sweden)

    Ilaria Drago

    2016-09-01

    Full Text Available The uptake of cytoplasmic calcium into mitochondria is critical for a variety of physiological processes, including calcium buffering, metabolism, and cell survival. Here, we demonstrate that inhibiting the mitochondrial calcium uniporter in the Drosophila mushroom body neurons (MBn—a brain region critical for olfactory memory formation—causes memory impairment without altering the capacity to learn. Inhibiting uniporter activity only during pupation impaired adult memory, whereas the same inhibition during adulthood was without effect. The behavioral impairment was associated with structural defects in MBn, including a decrease in synaptic vesicles and an increased length in the axons of the αβ MBn. Our results reveal an in vivo developmental role for the mitochondrial uniporter complex in establishing the necessary structural and functional neuronal substrates for normal memory formation in the adult organism.

  8. Inhibition of herpes simplex virus type 1 entry by chloride channel inhibitors tamoxifen and NPPB

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Kai [Guangzhou Jinan Biomedicine Research and Development Center, National Engineering Research Center of Genetic Medicine, Jinan University, Guangzhou (China); College of Life Science and Technology, Jinan University, Guangzhou (China); Chen, Maoyun [Guangzhou Jinan Biomedicine Research and Development Center, National Engineering Research Center of Genetic Medicine, Jinan University, Guangzhou (China); College of pharmacy, Jinan University, Guangzhou (China); Xiang, Yangfei; Ma, Kaiqi [Guangzhou Jinan Biomedicine Research and Development Center, National Engineering Research Center of Genetic Medicine, Jinan University, Guangzhou (China); Jin, Fujun [Guangzhou Jinan Biomedicine Research and Development Center, National Engineering Research Center of Genetic Medicine, Jinan University, Guangzhou (China); College of pharmacy, Jinan University, Guangzhou (China); Wang, Xiao [School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006 (China); Wang, Xiaoyan; Wang, Shaoxiang [Guangzhou Jinan Biomedicine Research and Development Center, National Engineering Research Center of Genetic Medicine, Jinan University, Guangzhou (China); Wang, Yifei, E-mail: twang-yf@163.com [Guangzhou Jinan Biomedicine Research and Development Center, National Engineering Research Center of Genetic Medicine, Jinan University, Guangzhou (China)

    2014-04-18

    Highlights: • We analyze the anti-HSV potential of chloride channel inhibitors. • Tamoxifen and NPPB show anti-HSV-1 and anti-ACV-resistant HSV-1 activities. • HSV-1 infection induces intracellular chloride concentration increasing. • Tamoxifen and NPPB inhibit HSV-1 early infection. • Tamoxifen and NPPB prevent the fusion process of HSV-1. - Abstract: Herpes simplex virus type 1 (HSV-1) infection is very common worldwide and can cause significant health problems from periodic skin and corneal lesions to encephalitis. Appearance of drug-resistant viruses in clinical therapy has made exploring novel antiviral agents emergent. Here we show that chloride channel inhibitors, including tamoxifen and 5-nitro-2-(3-phenyl-propylamino) benzoic acid (NPPB), exhibited extensive antiviral activities toward HSV-1 and ACV-resistant HSV viruses. HSV-1 infection induced chloride ion influx while treatment with inhibitors reduced the increase of intracellular chloride ion concentration. Pretreatment or treatment of inhibitors at different time points during HSV-1 infection all suppressed viral RNA synthesis, protein expression and virus production. More detailed studies demonstrated that tamoxifen and NPPB acted as potent inhibitors of HSV-1 early entry step by preventing viral binding, penetration and nuclear translocation. Specifically the compounds appeared to affect viral fusion process by inhibiting virus binding to lipid rafts and interrupting calcium homeostasis. Taken together, the observation that tamoxifen and NPPB can block viral entry suggests a stronger potential for these compounds as well as other ion channel inhibitors in antiviral therapy against HSV-1, especially the compound tamoxifen is an immediately actionable drug that can be reused for treatment of HSV-1 infections.

  9. Enigma homolog 1 scaffolds protein kinase D1 to regulate the activity of the cardiac L-type voltage-gated calcium channel.

    Science.gov (United States)

    Maturana, Andrés D; Wälchli, Sébastien; Iwata, Miki; Ryser, Stephan; Van Lint, Johannes; Hoshijima, Masahiko; Schlegel, Werner; Ikeda, Yasuhiro; Tanizawa, Katsuyuki; Kuroda, Shun'ichi

    2008-06-01

    In cardiomyocytes, protein kinase D1 (PKD1) plays a central role in the response to stress signals. From a yeast two-hybrid assay, we have identified Enigma Homolog 1 (ENH1) as a new binding partner of PKD1. Since in neurons, ENH1, associated with protein kinase Cepsilon, was shown to modulate the activity of N-type calcium channels, and the pore-forming subunit of the cardiac L-type voltage-gated calcium channel, alpha1C, possesses a potential phosphorylation site for PKD1, we studied here a possible role of ENH1 and PKD1 in the regulation of the cardiac L-type voltage-gated calcium channel. PKD1-interacting proteins were searched by yeast two-hybrid screening. In vivo protein interactions in cardiomyocytes isolated from heart ventricles of newborn rats were tested by co-immunoprecipitation. Small interfering RNA and a dominant negative mutant of PKD1 were delivered into cardiomyocytes by use of an adenovirus. Calcium currents were measured by the patch-clamp technique. Both ENH1 and PKD1 interact with alpha1C in cardiomyocytes. This interaction is increased upon stimulation. Silencing of ENH1 prevented the binding of PKD1 to alpha1C. Moreover, a dominant negative mutant of PKD1 or the silencing of ENH1 inhibited the alpha-adrenergic-induced increase of L-type calcium currents. We found a new binding partner, ENH1, and a new target, alpha1C, for PKD1 in neonatal rat cardiomyocytes. We propose a model where ENH1 scaffolds PKD1 to alpha1C in order to form a signalling complex that regulates the activity of cardiac L-type voltage-gated Ca(2+) channels.

  10. Evidence for the Involvement of Potassium Channel Inhibition in the Antidepressant-Like Effects of Hesperidin in the Tail Suspension Test in Mice.

    Science.gov (United States)

    Donato, Franciele; Borges Filho, Carlos; Giacomeli, Renata; Alvater, Elza Eliza Tenório; Del Fabbro, Lucian; Antunes, Michele da Silva; de Gomes, Marcelo Gomes; Goes, André Tiago Rossito; Souza, Leandro Cattelan; Boeira, Silvana Peterini; Jesse, Cristiano Ricardo

    2015-07-01

    The administration of hesperidin elicits an antidepressant-like effect in mice by a mechanism dependent on an interaction with the L-arginine-nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) pathway, whose stimulation is associated with the activation of potassium (K(+)) channels. Thus, this study investigated the involvement of different types of K(+) channels in the antidepressant-like effect of hesperidin in the mice tail suspension test (TST). The intracerebroventricular administration of tetraethylammonium (TEA, a nonspecific blocker of K(+) channels), glibenclamide (an ATP-sensitive K(+) channel blocker), charybdotoxin (a large- and intermediate-conductance calcium-activated K(+) channel blocker) or apamin (a small-conductance calcium-activated K(+) channel blocker) combined with a subeffective dose of hesperidin (0.01 mg/kg, intraperitoneally [i.p.]) was able to produce a synergistic antidepressant-like effect in the mice TST. Moreover, the antidepressant-like effect elicited by an effective dose of hesperidin (0.3 mg/kg, i.p.) in TST was abolished by the treatment of mice with pharmacological compounds K(+) channel openers (cromakalim and minoxidil). Results showed that the antidepressant-like effect of hesperidin in TST may involve, at least in part, the modulation of neuronal excitability through inhibition of K(+) channels and may act through a mechanism dependent on the inhibition of L-arginine-NO pathway.

  11. H2O2augments cytosolic calcium in nucleus tractus solitarii neurons via multiple voltage-gated calcium channels.

    Science.gov (United States)

    Ostrowski, Tim D; Dantzler, Heather A; Polo-Parada, Luis; Kline, David D

    2017-05-01

    Reactive oxygen species (ROS) play a profound role in cardiorespiratory function under normal physiological conditions and disease states. ROS can influence neuronal activity by altering various ion channels and transporters. Within the nucleus tractus solitarii (nTS), a vital brainstem area for cardiorespiratory control, hydrogen peroxide (H 2 O 2 ) induces sustained hyperexcitability following an initial depression of neuronal activity. The mechanism(s) associated with the delayed hyperexcitability are unknown. Here we evaluate the effect(s) of H 2 O 2 on cytosolic Ca 2+ (via fura-2 imaging) and voltage-dependent calcium currents in dissociated rat nTS neurons. H 2 O 2 perfusion (200 µM; 1 min) induced a delayed, slow, and moderate increase (~27%) in intracellular Ca 2+ concentration ([Ca 2+ ] i ). The H 2 O 2 -mediated increase in [Ca 2+ ] i prevailed during thapsigargin, excluding the endoplasmic reticulum as a Ca 2+ source. The effect, however, was abolished by removal of extracellular Ca 2+ or the addition of cadmium to the bath solution, suggesting voltage-gated Ca 2+ channels (VGCCs) as targets for H 2 O 2 modulation. Recording of the total voltage-dependent Ca 2+ current confirmed H 2 O 2 enhanced Ca 2+ entry. Blocking VGCC L, N, and P/Q subtypes decreased the number of cells and their calcium currents that respond to H 2 O 2 The number of responder cells to H 2 O 2 also decreased in the presence of dithiothreitol, suggesting the actions of H 2 O 2 were dependent on sulfhydryl oxidation. In summary, here, we have shown that H 2 O 2 increases [Ca 2+ ] i and its Ca 2+ currents, which is dependent on multiple VGCCs likely by oxidation of sulfhydryl groups. These processes presumably contribute to the previously observed delayed hyperexcitability of nTS neurons in in vitro brainstem slices. Copyright © 2017 the American Physiological Society.

  12. Alzheimer disease amyloid beta protein forms calcium channels in bilayer membranes: blockade by tromethamine and aluminum.

    Science.gov (United States)

    Arispe, N; Rojas, E; Pollard, H B

    1993-01-15

    Amyloid beta protein (A beta P) is the 40- to 42-residue polypeptide implicated in the pathogenesis of Alzheimer disease. We have incorporated this peptide into phosphatidylserine liposomes and then fused the liposomes with a planar bilayer. When incorporated into bilayers the A beta P forms channels, which generate linear current-voltage relationships in symmetrical solutions. A permeability ratio, PK/PCl, of 11 for the open A beta P channel was estimated from the reversal potential of the channel current in asymmetrical KCl solutions. The permeability sequence for different cations, estimated from the reversal potential of the A beta P-channel current for each system of asymmetrical solutions, is Pcs > PLi > PCa > or = PK > PNa. A beta P-channel current (either CS+ or Ca2+ as charge carriers) is blocked reversibly by tromethamine (millimolar range) and irreversibly by Al3+ (micromolar range). The inhibition of the A beta P-channel current by these two substances depends on transmembrane potential, suggesting that the mechanism of blockade involves direct interaction between tromethamine (or Al3+) and sites within the A beta P channel. Hitherto, A beta P has been presumed to be neurotoxic. On the basis of the present data we suggest that the channel activity of the polypeptide may be responsible for some or all of its neurotoxic effects. We further propose that a useful strategy for drug discovery for treatment of Alzheimer disease may include screening compounds for their ability to block or otherwise modify A beta P channels.

  13. 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

  14. The involvement of the Mid1/Cch1/Yvc1 calcium channels in Aspergillus fumigatus virulence.

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    Patrícia Alves de Castro

    Full Text Available Aspergillus fumigatus is a major opportunistic pathogen and allergen of mammals. Calcium homeostasis and signaling is essential for numerous biological processes and also influences A. fumigatus pathogenicity. The presented study characterized the function of the A. fumigatus homologues of three Saccharomyces cerevisiae calcium channels, voltage-gated Cch1, stretch-activated Mid1 and vacuolar Yvc1. The A. fumigatus calcium channels cchA, midA and yvcA were regulated at transcriptional level by increased calcium levels. The YvcA::GFP fusion protein localized to the vacuoles. Both ΔcchA and ΔmidA mutant strains showed reduced radial growth rate in nutrient-poor minimal media. Interestingly, this growth defect in the ΔcchA strain was rescued by the exogenous addition of CaCl2. The ΔcchA, ΔmidA, and ΔcchA ΔmidA strains were also sensitive to the oxidative stress inducer, paraquat. Restriction of external Ca(2+ through the addition of the Ca(2+-chelator EGTA impacted upon the growth of the ΔcchA and ΔmidA strains. All the A. fumigatus ΔcchA, ΔmidA, and ΔyvcA strains demonstrated attenuated virulence in a neutropenic murine model of invasive pulmonary aspergillosis. Infection with the parental strain resulted in a 100% mortality rate at 15 days post-infection, while the mortality rate of the ΔcchA, ΔmidA, and ΔyvcA strains after 15 days post-infection was only 25%. Collectively, this investigation strongly indicates that CchA, MidA, and YvcA play a role in A. fumigatus calcium homeostasis and virulence.

  15. The transition from proliferation to differentiation in colorectal cancer is regulated by the calcium activated chloride channel A1.

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    Bo Yang

    Full Text Available Breaking the balance between proliferation and differentiation in animal cells can lead to cancer, but the mechanisms maintaining this balance remain largely undefined. The calcium activated chloride channel A1 (CLCA1 is a member of the calcium sensitive chloride conductance family of proteins and is expressed mainly in the colon, small intestine and appendix. We show that CLCA1 plays a functional role in differentiation and proliferation of Caco-2 cells and of intestinal tissue. Caco-2 cells spontaneously differentiate either in confluent culture or when treated with butyrate, a molecule present naturally in the diet. Here, we compared CLCA1 expressional levels between patients with and without colorectal cancer (CRC and determined the functional role of CLCA1 in differentiation and proliferation of Caco-2 cells. We showed that: 1 CLCA1 and CLCA4 expression were down-regulated significantly in CRC patients; 2 CLCA1 expression was up-regulated in Caco-2 cells induced to differentiate by confluent culture or by treatment with sodium butyrate (NaBT; 3 Knockdown of CLCA1 with siRNA significantly inhibited cell differentiation and promoted cell proliferation in Caco-2 confluent cultures, and 4 In Caco-2 3D culture, suppression of CLCA1 significantly increased cell proliferation and compromised NaBT-induced inhibition of proliferation. In conclusion, CLCA1 may contribute to promoting spontaneous differentiation and reducing proliferation of Caco-2 cells and may be a target of NaBT-induced inhibition of proliferation and therefore a potential diagnostic marker for CRC prognosis.

  16. α-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid receptor activation protects against phencyclidine-induced caspase-3 activity by activating voltage-gated calcium channels.

    Science.gov (United States)

    Timpe, Jennifer M; Wang, Cheng Z; Kim, Jisoo; Johnson, Kenneth M

    2014-12-01

    Phencyclidine (PCP) is a noncompetitive, open channel blocker of the N-methyl-D-aspartate (NMDA) receptor-ion channel complex. When administered to immature animals, it is known to cause apoptotic neurodegeneration in several regions, and this is followed by olanzapine-sensitive, schizophrenia-like behaviors in late adolescence and adulthood. Clarification of its mechanism of action could yield data that would help to inform the treatment of schizophrenia. In our initial experiments, we found that α-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid (AMPA) inhibited PCP-induced apoptosis in organotypic neonatal rat brain slices in a concentration-dependent and 6-cyano-7-nitroquinoxaline-2,3-dione-sensitive manner. Calcium signaling pathways are widely implicated in apoptosis, and PCP prevents calcium influx through NMDA receptor channels. We therefore hypothesized that AMPA could protect against this effect by activation of voltage-dependent calcium channels (VDCCs). In support of this hypothesis, pretreatment with the calcium channel blocker cadmium chloride eliminated AMPA-mediated protection against PCP. Furthermore, the L-type VDCC inhibitor nifedipine (10 µM) fully abrogated the effects of AMPA, suggesting that L-type VDCCs are required for AMPA-mediated protection against PCP-induced neurotoxicity. Whereas the P/Q-type inhibitor ω-agatoxin TK (200 nM) reduced AMPA protection by 51.7%, the N-type VDCC inhibitor ω-conotoxin (2 µM) had no effect. Decreased AMPA-mediated protection following cotreatment with K252a, a TrkB inhibitor, suggests that brain-derived neurotrophic factor signaling plays an important role. By analogy, these results suggest that activation of L-type, and to a lesser extent P/Q-type, VDCCs might be advantageous in treating conditions associated with diminished NMDAergic activity during early development. © 2014 Wiley Periodicals, Inc.

  17. Selectivity and permeation in calcium release channel of cardiac muscle: alkali metal ions.

    Science.gov (United States)

    Chen, D P; Xu, L; Tripathy, A; Meissner, G; Eisenberg, B

    1999-03-01

    Current was measured from single open channels of the calcium release channel (CRC) of cardiac sarcoplasmic reticulum (over the range +/-180 mV) in pure and mixed solutions (e.g., biionic conditions) of the alkali metal ions Li+, K+, Na+, Rb+, Cs+, ranging in concentration from 25 mM to 2 M. The current-voltage (I-V) relations were analyzed by an extension of the Poisson-Nernst-Planck (PNP) formulation of electrodiffusion, which includes local chemical interaction described by an offset in chemical potential, which likely reflects the difference in dehydration/solvation/rehydration energies in the entry/exit steps of permeation. The theory fits all of the data with few adjustable parameters: the diffusion coefficient of each ion species, the average effective charge distribution on the wall of the pore, and an offset in chemical potential for lithium and sodium ions. In particular, the theory explains the discrepancy between "selectivities" defined by conductance sequence and "selectivities" determined by the permeability ratios (i.e., reversal potentials) in biionic conditions. The extended PNP formulation seems to offer a successful combined treatment of selectivity and permeation. Conductance selectivity in this channel arises mostly from friction: different species of ions have different diffusion coefficients in the channel. Permeability selectivity of an ion is determined by its electrochemical potential gradient and local chemical interaction with the channel. Neither selectivity (in CRC) seems to involve different electrostatic interaction of different ions with the channel protein, even though the ions have widely varying diameters.

  18. Large conductance, calcium- and voltage-gated potassium (BK) channels: regulation by cholesterol.

    Science.gov (United States)

    Dopico, Alejandro M; Bukiya, Anna N; Singh, Aditya K

    2012-08-01

    Cholesterol (CLR) is an essential component of eukaryotic plasma membranes. CLR regulates the membrane physical state, microdomain formation and the activity of membrane-spanning proteins, including ion channels. Large conductance, voltage- and Ca²⁺-gated K⁺ (BK) channels link membrane potential to cell Ca²⁺ homeostasis. Thus, they control many physiological processes and participate in pathophysiological mechanisms leading to human disease. Because plasmalemma BK channels cluster in CLR-rich membrane microdomains, a major driving force for studying BK channel-CLR interactions is determining how membrane CLR controls the BK current phenotype, including its pharmacology, channel sorting, distribution, and role in cell physiology. Since both BK channels and CLR tissue levels play a pathophysiological role in human disease, identifying functional and structural aspects of the CLR-BK channel interaction may open new avenues for therapeutic intervention. Here, we review the studies documenting membrane CLR-BK channel interactions, dissecting out the many factors that determine the final BK current response to changes in membrane CLR content. We also summarize work in reductionist systems where recombinant BK protein is studied in artificial lipid bilayers, which documents a direct inhibition of BK channel activity by CLR and builds a strong case for a direct interaction between CLR and the BK channel-forming protein. Bilayer lipid-mediated mechanisms in CLR action are also discussed. Finally, we review studies of BK channel function during hypercholesterolemia, and underscore the many consequences that the CLR-BK channel interaction brings to cell physiology and human disease. Copyright © 2012 Elsevier Inc. All rights reserved.

  19. Inhibitors of arachidonate-regulated calcium channel signaling suppress triggered activity induced by the late sodium current.

    Science.gov (United States)

    Wolkowicz, Paul; Umeda, Patrick K; Sharifov, Oleg F; White, C Roger; Huang, Jian; Mahtani, Harry; Urthaler, Ferdinand

    2014-02-05

    Disturbances in myocyte calcium homeostasis are hypothesized to be one cause for cardiac arrhythmia. The full development of this hypothesis requires (i) the identification of all sources of arrhythmogenic calcium and (ii) an understanding of the mechanism(s) through which calcium initiates arrhythmia. To these ends we superfused rat left atria with the late sodium current activator type II Anemonia sulcata toxin (ATXII). This toxin prolonged atrial action potentials, induced early afterdepolarization, and provoked triggered activity. The calmodulin-dependent protein kinase II (CaMKII) inhibitor KN-93 (N-[2-[[[3-(4-chlorophenyl)-2-propenyl]methylamino]methyl]phenyl]-N-(2-hydroxyethyl)-4-methoxybenzenesulphon-amide) suppressed ATXII triggered activity but its inactive congener KN-92 (2-[N-(4-methoxy benzenesulfonyl)]amino-N-(4-chlorocinnamyl)-N-methylbenzylamine) did not. Neither drug affected normal atrial contractility. Calcium entry via L-type channels or calcium leakage from sarcoplasmic reticulum stores are not critical for this type of ectopy as neither verapamil ((RS)-2-(3,4-dimethoxyphenyl)-5-{[2-(3,4-dimethoxyphenyl)ethyl]-(methyl)amino}-2-prop-2-ylpentanenitrile) nor ryanodine affected ATXII triggered activity. By contrast, inhibitors of the voltage independent arachidonate-regulated calcium (ARC) channel and the store-operated calcium channel specifically suppressed ATXII triggered activity without normalizing action potentials or affecting atrial contractility. Inhibitors of cytosolic calcium-dependent phospholipase A2 also suppressed triggered activity suggesting that this lipase, which generates free arachidonate, plays a key role in ATXII ectopy. Thus, increased left atrial late sodium current appears to activate atrial Orai-linked ARC and store operated calcium channels, and these voltage-independent channels may be unexpected sources for the arrhythmogenic calcium that underlies triggered activity. Copyright © 2013 Elsevier B.V. All rights reserved.

  20. Combined oral administration of bovine collagen peptides with calcium citrate inhibits bone loss in ovariectomized rats.

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    JunLi Liu

    Full Text Available Collagen peptides (CPs and calcium citrate are commonly used as bone health supplements for treating osteoporosis. However, it remains unknown whether the combination of oral bovine CPs with calcium citrate is more effective than administration of either agent alone.Forty 12-week-old Sprague-Dawley rats were randomly divided into five groups (n = 8 for once-daily intragastric administration of different treatments for 3 months at 3 months after ovariectomy (OVX as follows: sham + vehicle; OVX + vehicle; OVX + 750 mg/kg CP; OVX + CP-calcium citrate (75 mg/kg; OVX + calcium citrate (75 mg/kg. After euthanasia, the femurs were removed and analyzed by dual energy X-ray absorptiometry and micro-computed tomography, and serum samples were analyzed for bone metabolic markers.OVX rats supplemented with CPs or CP-calcium citrate showed osteoprotective effects, with reductions in the OVX-induced decreases in their femoral bone mineral density. Moreover, CP-calcium citrate prevented trabecular bone loss, improved the microarchitecture of the distal femur, and significantly inhibited bone loss with increased bone volume, connectivity density, and trabecular number compared with OVX control rats. CP or CP-calcium citrate administration significantly increased serum procollagen type I N-terminal propeptide levels and reduced serum bone-specific alkaline phosphatase, osteocalcin, and C-telopeptide of type I collagen levels.Our data indicate that combined oral administration of bovine CPs with calcium citrate inhibits bone loss in OVX rats. The present findings suggest that combined oral administration of bovine CPs with calcium citrate is a promising alternative for reducing bone loss in osteopenic postmenopausal women.

  1. FM dyes enter via a store-operated calcium channel and modify calcium signaling of cultured astrocytes

    Science.gov (United States)

    Li, Dongdong; Hérault, Karine; Oheim, Martin; Ropert, Nicole

    2009-01-01

    The amphiphilic fluorescent styryl pyridinium dyes FM1-43 and FM4-64 are used to probe activity-dependent synaptic vesicle cycling in neurons. Cultured astrocytes can internalize FM1-43 and FM4-64 inside vesicles but their uptake is insensitive to the elevation of cytosolic calcium (Ca2+) concentration and the underlying mechanism remains unclear. Here we used total internal reflection fluorescence microscopy and pharmacological tools to study the mechanisms of FM4-64 uptake into cultured astrocytes from mouse neocortex. Our data show that: (i) endocytosis is not a major route for FM4-64 uptake into astrocytes; (ii) FM4-64 enters astrocytes through an aqueous pore and strongly affects Ca2+ homeostasis; (iii) partitioning of FM4-64 into the outer leaflet of the plasma membrane results in a facilitation of store-operated Ca2+ entry (SOCE) channel gating; (iv) FM4-64 permeates and competes with Ca2+ for entry through a SOCE channel; (v) intracellular FM4-64 mobilizes Ca2+ from the endoplasmic reticulum stores, conveying a positive feedback to activate SOCE and to sustain dye uptake into astrocytes. Our study demonstrates that FM dyes are not markers of cycling vesicles in astrocytes and calls for a careful interpretation of FM fluorescence. PMID:20007370

  2. Peptides of Matrix Gla protein inhibit nucleation and growth of hydroxyapatite and calcium oxalate monohydrate crystals.

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    Maria Goiko

    Full Text Available Matrix Gla protein (MGP is a phosphorylated and γ-carboxylated protein that has been shown to prevent the deposition of hydroxyapatite crystals in the walls of blood vessels. MGP is also expressed in kidney and may inhibit the formation of kidney stones, which mainly consist of another crystalline phase, calcium oxalate monohydrate. To determine the mechanism by which MGP prevents soft-tissue calcification, we have synthesized peptides corresponding to the phosphorylated and γ-carboxylated sequences of human MGP in both post-translationally modified and non-modified forms. The effects of these peptides on hydroxyapatite formation and calcium oxalate crystallization were quantified using dynamic light scattering and scanning electron microscopy, respectively. Peptides YGlapS (MGP1-14: YγEpSHEpSMEpSYELNP, YEpS (YEpSHEpSMEpSYELNP, YGlaS (YγESHESMESYELNP and SK-Gla (MGP43-56: SKPVHγELNRγEACDD inhibited formation of hydroxyapatite in order of potency YGlapS > YEpS > YGlaS > SK-Gla. The effects of YGlapS, YEpS and YGlaS on hydroxyapatite formation were on both crystal nucleation and growth; the effect of SK-Gla was on nucleation. YGlapS and YEpS significantly inhibited the growth of calcium oxalate monohydrate crystals, while simultaneously promoting the formation of calcium oxalate dihydrate. The effects of these phosphopeptides on calcium oxalate monohydrate formation were on growth of crystals rather than nucleation. We have shown that the use of dynamic light scattering allows inhibitors of hydroxyapatite nucleation and growth to be distinguished. We have also demonstrated for the first time that MGP peptides inhibit the formation of calcium oxalate monohydrate. Based on the latter finding, we propose that MGP function not only to prevent blood-vessel calcification but also to inhibit stone formation in kidney.

  3. Ziconotide, an intrathecally administered N-type calcium channel antagonist for the treatment of chronic pain.

    Science.gov (United States)

    Wermeling, Daniel P

    2005-08-01

    Ziconotide is a novel peptide that blocks the entry of calcium into neuronal N-type voltage-sensitive calcium channels, preventing the conduction of nerve signals. N-type calcium channels are present in the superficial laminae of the dorsal horn of the spinal cord. In various animal models of pain, intrathecal administration of ziconotide blocked nerve transmission and nociception. The United States Food and Drug Administration recently approved ziconotide intrathecal infusion for the management of severe chronic pain in patients who require intrathecal therapy and who are intolerant of or refractory to other treatment, such as systemic analgesics, adjunctive therapies, or intrathecal morphine. The drug has a narrow therapeutic window and a lag time for the onset and offset of analgesia and adverse events. In early clinical trials, frequent and severe psychiatric and central nervous system adverse effects were associated with rapid intrathecal infusion (0.4 microg/hr) and frequent up-titration (every 12 hrs). Therefore, patients with psychiatric symptoms are not candidates for this drug. Drug trials of external intrathecal catheters and microinfusion devices demonstrated a 3% risk of meningitis. A low initial infusion rate of 0.1 microg/hour and limiting infusion rate increases to 2-3 times/week are now recommended. Patients responsive to intrathecal ziconotide require an implanted infusion system to receive long-term therapy.

  4. CRAC channels, calcium, and cancer in light of the driver and passenger concept.

    Science.gov (United States)

    Hoth, Markus

    2016-06-01

    Advances in next-generation sequencing allow very comprehensive analyses of large numbers of cancer genomes leading to an increasingly better characterization and classification of cancers. Comparing genomic data predicts candidate genes driving development, growth, or metastasis of cancer. Cancer driver genes are defined as genes whose mutations are causally implicated in oncogenesis whereas passenger mutations are defined as not being oncogenic. Currently, a list of several hundred cancer driver mutations is discussed including prominent members like TP53, BRAF, NRAS, or NF1. According to the vast literature on Ca(2+) and cancer, Ca(2+) signals and the underlying Ca(2+) channels and transporters certainly influence the development, growth, and metastasis of many cancers. In this review, I focus on the calcium release-activated calcium (CRAC) channel genes STIM and Orai and their role for cancer development, growth, and metastasis. STIM and Orai genes are being discussed in the context of current cancer concepts with a focus on the driver-passenger hypothesis. One result of this discussion is the hypothesis that a driver analysis of Ca(2+) homeostasis-related genes should not be carried out by looking at isolated genes. Rather a pool of “Ca(2+) genes” might be considered to act as one potential cancer driver. This article is part of a Special Issue entitled: Calcium and Cell Fate. Guest Editors: Jacques Haiech, Claus Heizmann, Joachim Krebs, Thierry Capiod and Olivier Mignen.

  5. Inhibition of T cell proliferation by selective block of Ca(2+)-activated K(+) channels

    DEFF Research Database (Denmark)

    Jensen, B S; Odum, Niels; Jorgensen, N K

    1999-01-01

    established. The recent cloning of the Ca(2+)-activated, intermediate-conductance K(+) channel (IK channel) has enabled a detailed investigation of the role of this highly Ca(2+)-sensitive K(+) channel in the calcium signaling and subsequent regulation of T cell proliferation. The role IK channels play in T...... cell activation and proliferation has been investigated by using various blockers of IK channels. The Ca(2+)-activated K(+) current in human T cells is shown by the whole-cell voltage-clamp technique to be highly sensitive to clotrimazole, charybdotoxin, and nitrendipine, but not to ketoconazole...

  6. Expression profiling of colorectal cancer cells reveals inhibition of DNA replication licensing by extracellular calcium.

    Science.gov (United States)

    Aggarwal, Abhishek; Schulz, Herbert; Manhardt, Teresa; Bilban, Martin; Thakker, Rajesh V; Kallay, Enikö

    2017-06-01

    Colorectal cancer is one of the most common cancers in industrialised societies. Epidemiological studies, animal experiments, and randomized clinical trials have shown that dietary factors can influence all stages of colorectal carcinogenesis, from initiation through promotion to progression. Calcium is one of the factors with a chemoprophylactic effect in colorectal cancer. The aim of this study was to understand the molecular mechanisms of the anti-tumorigenic effects of extracellular calcium ([Ca(2+)]o) in colon cancer cells. Gene expression microarray analysis of colon cancer cells treated for 1, 4, and 24h with 2mM [Ca(2+)]o identified significant changes in expression of 1571 probe sets (ANOVA, pcalcium-sensing receptor (CaSR), a G protein-coupled receptor is a mediator involved in this process. To test whether these results were physiologically relevant, we fed mice with a standard diet containing low (0.04%), intermediate (0.1%), or high (0.9%) levels of dietary calcium. The main molecules regulating replication licensing were inhibited also in vivo, in the colon of mice fed high calcium diet. We show that among the mechanisms behind the chemopreventive effect of [Ca(2+)]o is inhibition of replication licensing, a process often deregulated in neoplastic transformation. Our data suggest that dietary calcium is effective in preventing replicative stress, one of the main drivers of cancer and this process is mediated by the calcium-sensing receptor. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  7. Small-conductance calcium-activated potassium (SK) channels contribute to action potential repolarization in human atria

    DEFF Research Database (Denmark)

    Skibsbye, Lasse; Poulet, Claire; Diness, Jonas Goldin

    2014-01-01

    AIMS: Small-conductance calcium-activated potassium (SK) channels are expressed in the heart of various species, including humans. The aim of the present study was to address whether SK channels play a functional role in human atria. METHODS AND RESULTS: Quantitative real-time PCR analyses showed...

  8. Presynaptic Localization and Possible Function of Calcium-Activated Chloride Channel Anoctamin 1 in the Mammalian Retina.

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    Ji Hyun Jeon

    Full Text Available Calcium (Ca(2+-activated chloride (Cl(- channels (CaCCs play a role in the modulation of action potentials and synaptic responses in the somatodendritic regions of central neurons. In the vertebrate retina, large Ca(2+-activated Cl(- currents (ICl(Ca regulate synaptic transmission at photoreceptor terminals; however, the molecular identity of CaCCs that mediate ICl(Ca remains unclear. The transmembrane protein, TMEM16A, also called anoctamin 1 (ANO1, has been recently validated as a CaCC and is widely expressed in various secretory epithelia and nervous tissues. Despite the fact that tmem16a was first cloned in the retina, there is little information on its cellular localization and function in the mammalian retina. In this study, we found that ANO1 was abundantly expressed as puncta in 2 synaptic layers. More specifically, ANO1 immunoreactivity was observed in the presynaptic terminals of various retinal neurons, including photoreceptors. ICl(Ca was first detected in dissociated rod bipolar cells expressing ANO1. ICl(Ca was abolished by treatment with the Ca(2+ channel blocker Co(2+, the L-type Ca(2+ channel blocker nifedipine, and the Cl(- channel blockers 5-nitro-2-(3-phenylpropylamino benzoic acid (NPPB and niflumic acid (NFA. More specifically, a recently discovered ANO1-selective inhibitor, T16Ainh-A01, and a neutralizing antibody against ANO1 inhibited ICl(Ca in rod bipolar cells. Under a current-clamping mode, the suppression of ICl(Ca by using NPPB and T16Ainh-A01 caused a prolonged Ca(2+ spike-like depolarization evoked by current injection in dissociated rod bipolar cells. These results suggest that ANO1 confers ICl(Ca in retinal neurons and acts as an intrinsic regulator of the presynaptic membrane potential during synaptic transmission.

  9. Micromolar-Affinity Benzodiazepine Receptors Regulate Voltage-Sensitive Calcium Channels in Nerve Terminal Preparations

    Science.gov (United States)

    Taft, William C.; Delorenzo, Robert J.

    1984-05-01

    Benzodiazepines in micromolar concentrations significantly inhibit depolarization-sensitive Ca2+ uptake in intact nerve-terminal preparations. Benzodiazepine inhibition of Ca2+ uptake is concentration dependent and stereospecific. Micromolar-affinity benzodiazepine receptors have been identified and characterized in brain membrane and shown to be distinct from nanomolar-affinity benzodiazepine receptors. Evidence is presented that micromolar, and not nanomolar, benzodiazepine binding sites mediate benzodiazepine inhibition of Ca2+ uptake. Irreversible binding to micromolar benzodiazepine binding sites also irreversibly blocked depolarization-dependent Ca2+ uptake in synaptosomes, indicating that these compounds may represent a useful marker for identifying the molecular components of Ca2+ channels in brain. Characterization of benzodiazepine inhibition of Ca2+ uptake demonstrates that these drugs function as Ca2+ channel antagonists, because benzodiazepines effectively blocked voltage-sensitive Ca2+ uptake inhibited by Mn2+, Co2+, verapamil, nitrendipine, and nimodipine. These results indicate that micromolar benzodiazepine binding sites regulate voltage-sensitive Ca2+ channels in brain membrane and suggest that some of the neuronal stabilizing effects of micromolar benzodiazepine receptors may be mediated by the regulation of Ca2+ conductance.

  10. Na+ -K+ pump activity in rat peritoneal mast cells: inhibition by extracellular calcium

    DEFF Research Database (Denmark)

    Knudsen, Torben; Johansen, Torben

    1989-01-01

    1. Pure populations of rat peritoneal mast cells were used to study cellular potassium uptake. The radioactive potassium analogue, 86rubidium, was used as a tracer for potassium for measurements of the activity of the cellular potassium uptake process. 2. The ouabain-sensitive and the ouabain......-resistant potassium (86rubidium) uptake of mast cells incubated in the presence of calcium, 1 mmol l-1, were very low, 52 and 147 pmol per 10(6) cells min-1. 3. Calcium-deprivation of the cells uncovered a large capacity ouabain-sensitive potassium (86rubidium) uptake mechanism. The activity of the uptake mechanism...... of an enzyme, and it is mediated by the Na+ -K+ pump located in the plasma membrane. It is demonstrated that the activity of the Na+ -K+ pump mechanism is inhibited by low concentrations of extracellular calcium (0.1-1.2 mmol l-1). The possibility is discussed that calcium-deprivation may increase the pump...

  11. Aristoyunnolin H attenuates extracellular matrix secretion in cardiac fibroblasts by inhibiting calcium influx.

    Science.gov (United States)

    Chen, Shao-Rui; Zhang, Wen-Ping; Bao, Jing-Mei; Cheng, Zhong-Bin; Yin, Sheng

    2017-01-01

    Aristoyunnolin H is a novel aristophyllene sesquiterpenoid isolated from the traditional Chinese medicine Aristolochia yunnanensis Franch. The present research was designed to explore the anti-fibrotic effects of aristoyunnolin H in adult rat cardiac fibroblasts (CFs) stimulated with angiotensin II (Ang II). Western blot analysis data showed that aristoyunnolin H reduced the upregulation of fibronectin (FN), connective tissue growth factor and collagen I(Col I) production induced by Ang II in CFs. By studying the dynamic intracellular changes of Ca(2+), we further found that while aristoyunnolin H relieved the calcium influx, it has no effect on intracellular calcium store release. Meanwhile, aristoyunnolin H also inhibited the Ang II-stimulated phosphorylation of Ca(2+)/calmodulin-dependent protein kinase II. In conclusion, aristoyunnolin H may attenuate extracellular matrix secretion in vitro by inhibiting Ang II-induced calcium signaling.

  12. Note: Inhibiting bottleneck corrosion in electrical calcium tests for ultra-barrier measurements

    Energy Technology Data Exchange (ETDEWEB)

    Nehm, F., E-mail: frederik.nehm@iapp.de; Müller-Meskamp, L.; Klumbies, H.; Leo, K. [Institut für Angewandte Photophysik, Technische Universität Dresden, George-Bähr-Straße 1, 01069 Dresden (Germany)

    2015-12-15

    A major failure mechanism is identified in electrical calcium corrosion tests for quality assessment of high-end application moisture barriers. Accelerated calcium corrosion is found at the calcium/electrode junction, leading to an electrical bottleneck. This causes test failure not related to overall calcium loss. The likely cause is a difference in electrochemical potential between the aluminum electrodes and the calcium sensor, resulting in a corrosion element. As a solution, a thin, full-area copper layer is introduced below the calcium, shifting the corrosion element to the calcium/copper junction and inhibiting bottleneck degradation. Using the copper layer improves the level of sensitivity for the water vapor transmission rate (WVTR) by over one order of magnitude. Thin-film encapsulated samples with 20 nm of atomic layer deposited alumina barriers this way exhibit WVTRs of 6 × 10{sup −5} g(H{sub 2}O)/m{sup 2}/d at 38 °C, 90% relative humidity.

  13. New Conotoxin SO-3 Targeting N-type Voltage-Sensitive Calcium Channels

    Directory of Open Access Journals (Sweden)

    Lei Wen

    2006-04-01

    Full Text Available Selective blockers of the N-type voltage-sensitive calcium (CaV channels are useful in the management of severe chronic pain. Here, the structure and function characteristics of a novel N-type CaV channel blocker, SO-3, are reviewed. SO-3 is a 25-amino acid conopeptide originally derived from the venom of Conus striatus, and contains the same 4-loop, 6-cysteine framework (C-C-CC-C-C as O-superfamily conotoxins. The synthetic SO-3 has high analgesic activity similar to ω-conotoxin MVIIA (MVIIA, a selective N-type CaV channel blocker approved in the USA and Europe for the alleviation of persistent pain states. In electrophysiological studies, SO-3 shows more selectivity towards the N-type CaV channels than MVIIA. The dissimilarity between SO-3 and MVIIA in the primary and tertiary structures is further discussed in an attempt to illustrate the difference in selectivity of SO-3 and MVIIA towards N-type CaV channels.

  14. Small and Intermediate Calcium-Activated Potassium Channel Openers Improve Rat Endothelial and Erectile Function

    Science.gov (United States)

    Comerma-Steffensen, Simon G.; Carvacho, Ingrid; Hedegaard, Elise R.; Simonsen, Ulf

    2017-01-01

    Modulation of endothelial calcium-activated potassium (KCa) channels has been proposed as an approach to restore endothelial function. The present study investigated whether novel openers of KCa channels with small (KCa2.x) and intermediate (KCa3.1) conductance, NS309 and NS4591, improve endothelium-dependent relaxation and erectile function. Rat corpus cavernosum (CC) strips were mounted for isometric tension recording and processed for immunoblotting. Mean arterial pressure (MAP), intracavernosal pressure (ICP), and electrocardiographic (ECG) measurements were conducted in anesthetized rats. Immunoblotting revealed the presence of KCa2.3 and large KCa conductance (KCa1.1) channels in the corpus cavernosum. NS309 and NS4591 increased current in CC endothelial cells in whole cell patch clamp experiments. Relaxation induced by NS309 (cavernous nerve stimulation with NS309 were unchanged, whereas NS4591 significantly improved erectile function. Administration of NS309 and NS4591 caused small changes in the electrocardiogram, but neither arrhythmic events nor prolongation of the QTc interval were observed. The present study suggests that openers of KCa2.x and KCa3.1 channels improve endothelial and erectile function. The effects of NS309 and NS4591 on heart rate and ECG are small, but will require additional safety studies before evaluating whether activation of KCa2.3 channels has a potential for treatment of erectile dysfunction. PMID:28993731

  15. Dendritic and Axonal L-Type Calcium Channels Cooperate to Enhance Motoneuron Firing Output duringDrosophilaLarval Locomotion.

    Science.gov (United States)

    Kadas, Dimitrios; Klein, Aylin; Krick, Niklas; Worrell, Jason W; Ryglewski, Stefanie; Duch, Carsten

    2017-11-08

    Behaviorally adequate neuronal firing patterns are critically dependent on the specific types of ion channel expressed and on their subcellular localization. This study combines in situ electrophysiology with genetic and pharmacological intervention in larval Drosophila melanogaster of both sexes to address localization and function of L-type like calcium channels in motoneurons. We demonstrate that Dmca1D (Ca v 1 homolog) L-type like calcium channels localize to both the somatodendritic and the axonal compartment of larval crawling motoneurons. In situ patch-clamp recordings in genetic mosaics reveal that Dmca1D channels increase burst duration and maximum intraburst firing frequencies during crawling-like motor patterns in semi-intact animals. Genetic and acute pharmacological manipulations suggest that prolonged burst durations are caused by dendritically localized Dmca1D channels, which activate upon cholinergic synaptic input and amplify EPSPs, thus indicating a conserved function of dendritic L-type channels from Drosophila to vertebrates. By contrast, maximum intraburst firing rates require axonal calcium influx through Dmca1D channels, likely to enhance sodium channel de-inactivation via a fast afterhyperpolarization through BK channel activation. Therefore, in unmyelinated Drosophila motoneurons different functions of axonal and dendritic L-type like calcium channels likely operate synergistically to maximize firing output during locomotion. SIGNIFICANCE STATEMENT Nervous system function depends on the specific excitabilities of different types of neurons. Excitability is largely shaped by different combinations of voltage-dependent ion channels. Despite a high degree of conservation, the huge diversity of ion channel types and their differential localization pose challenges in assigning distinct functions to specific channels across species. We find a conserved role, from fruit flies to mammals, for L-type calcium channels in augmenting motoneuron

  16. Activation of endogenous c-Src or a related tyrosine kinase by intracellular (pY)EEI peptide increases voltage-operated calcium channel currents in rabbit ear artery cells.

    Science.gov (United States)

    Wijetunge, S; Hughes, A D

    1996-12-09

    The effect of activation of endogenous c-Src tyrosine kinase by (pY)EEI peptide was examined on voltage-operated calcium channel (VOC) currents in arterial smooth muscle cells. In single rabbit ear artery cells intracellular application of (pY)EEI peptide increased calcium channel currents. Inactive, non-phosphorylated YEEI peptide had no effect on currents. Peptide-A, a 21 amino acid inhibitor of c-Src inhibited currents and prevented the effect of (pY)EEI peptide on calcium channel currents. These results indicate that activation of intrinsic c-Src increases VOC and support a role for c-Src in the regulation of VOC in vascular smooth muscle cells.

  17. L-type calcium channels refine the neural population code of sound level.

    Science.gov (United States)

    Grimsley, Calum Alex; Green, David Brian; Sivaramakrishnan, Shobhana

    2016-12-01

    The coding of sound level by ensembles of neurons improves the accuracy with which listeners identify how loud a sound is. In the auditory system, the rate at which neurons fire in response to changes in sound level is shaped by local networks. Voltage-gated conductances alter local output by regulating neuronal firing, but their role in modulating responses to sound level is unclear. We tested the effects of L-type calcium channels (CaL: CaV1.1-1.4) on sound-level coding in the central nucleus of the inferior colliculus (ICC) in the auditory midbrain. We characterized the contribution of CaL to the total calcium current in brain slices and then examined its effects on rate-level functions (RLFs) in vivo using single-unit recordings in awake mice. CaL is a high-threshold current and comprises ∼50% of the total calcium current in ICC neurons. In vivo, CaL activates at sound levels that evoke high firing rates. In RLFs that increase monotonically with sound level, CaL boosts spike rates at high sound levels and increases the maximum firing rate achieved. In different populations of RLFs that change nonmonotonically with sound level, CaL either suppresses or enhances firing at sound levels that evoke maximum firing. CaL multiplies the gain of monotonic RLFs with dynamic range and divides the gain of nonmonotonic RLFs with the width of the RLF. These results suggest that a single broad class of calcium channels activates enhancing and suppressing local circuits to regulate the sensitivity of neuronal populations to sound level. Copyright © 2016 the American Physiological Society.

  18. α-SNAP regulates dynamic, on-site assembly and calcium selectivity of Orai1 channels.

    Science.gov (United States)

    Li, Peiyao; Miao, Yong; Dani, Adish; Vig, Monika

    2016-08-15

    Orai1 forms a highly calcium-selective pore of the calcium release activated channel, and α-SNAP is necessary for its function. Here we show that α-SNAP regulates on-site assembly of Orai1 dimers into calcium-selective multimers. We find that Orai1 is a dimer in resting primary mouse embryonic fibroblasts but displays variable stoichiometry in the plasma membrane of store-depleted cells. Remarkably, α-SNAP depletion induces formation of higher-order Orai1 oligomers, which permeate significant levels of sodium via Orai1 channels. Sodium permeation in α-SNAP-deficient cells cannot be corrected by tethering multiple Stim1 domains to Orai1 C-terminal tail, demonstrating that α-SNAP regulates functional assembly and calcium selectivity of Orai1 multimers independently of Stim1 levels. Fluorescence nanoscopy reveals sustained coassociation of α-SNAP with Stim1 and Orai1, and α-SNAP-depleted cells show faster and less constrained mobility of Orai1 within ER-PM junctions, suggesting Orai1 and Stim1 coentrapment without stable contacts. Furthermore, α-SNAP depletion significantly reduces fluorescence resonance energy transfer between Stim1 and Orai1 N-terminus but not C-terminus. Taken together, these data reveal a unique role of α-SNAP in the on-site functional assembly of Orai1 subunits and suggest that this process may, in part, involve enabling crucial low-affinity interactions between Orai1 N-terminus and Stim1. © 2016 Li, Miao, et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

  19. Efficacy of Methylene Blue in an Experimental Model of Calcium Channel Blocker Induced Shock

    Science.gov (United States)

    Jang, David H.; Donovan, Sean; Nelson, Lewis S.; Bania, Theodore C.; Hoffman, Robert S.; Chu, Jason

    2014-01-01

    BACKGROUND Calcium channel blocker poisonings account for a substantial number of reported deaths from cardiovascular drugs. While supportive care is the mainstay of treatment, experimental therapies such as high dose insulin-euglycemia and lipid emulsion have been studied in animal models and used in humans. In the most severe cases even aggressive care is inadequate and deaths occur. In both experimental models and clinical cases of vasodilatory shock, methylene blue improves hemodynamic measures. Methylene blue acts as both a nitric oxide scavenger and inhibits guanylate cyclase that is responsible for the production of cGMP. Excessive cGMP production is associated with refractory vasodilatory shock in sepsis and anaphylaxis. The aim of this study was to determine the efficacy of methylene blue in an animal model of amlodipine-induced shock. METHODS Sprague-Dawley rats were anesthetized, ventilated and instrumented for continuous blood pressure and heart rate monitoring. The dose of amlodipine that produced death within 60 minutes was 17 mg/kg/hour (LD50). Rats were divided into 2 groups: amlodipine followed by methylene blue or amlodipine followed by normal saline (NS) with 15 rats in each group. Rats received methylene blue at 2 mg/kg over 5 mins or an equivalent amount of NS in three intervals from the start of the protocol: Minute 5, 30, and 60. The animals were observed for a total of 2 hours after the start of the protocol. Mortality risk and survival time were analyzed using Fisher’s exact test and Kaplan Meier survival analysis with the log rank test. RESULTS Overall, 1/15 (7%) rats in the saline-treated group survived to 120 minutes compared with 5/15 (33%) rats in the methylene blue-treated group (difference −26%, 95% CI –54%, 0.3%). The median survival time for the NS group was 42 min (95% CI, 28.1,55.9) and the methylene blue group was 109 min (95% CI, 93.9,124.1). Heart rate and MAP differences between groups were analyzed until 60 minutes

  20. Calcium

    Science.gov (United States)

    ... Turn to calcium-fortified (or "calcium-set") tofu, soy milk, tempeh, soy yogurt, and cooked soybeans (edamame). Calcium-fortified foods. Look for calcium-fortified orange juice, soy or rice milk, breads, and cereal. Beans. You can get decent ...

  1. POSITIONS OF CALCIUM CHANNEL BLOCKER LERCANIDIPINE ACCORDING TO EVIDENCE BASED CARDIOLOGY

    Directory of Open Access Journals (Sweden)

    Yu. V. Lukina

    2010-01-01

    Full Text Available Data of evidence based cardiology including results of international clinical trials on efficacy and safety of the modern calcium channel blocker (CCB, lercanidipine, are presented. Results of these trials show the firm position of lercanidipine in the modern cardiology and confirm that treatment with lercanidipine leads to significant reduction of systolic and diastolic blood pressure (BP with no effect on heart rate (HR. Peripheral edema (the common side effect of CCBs occurs rarer with lercanidipine treatment than this with any other CCB treatment. Lercanidipine can be recommended to patients with concomitant diseases due to its additional features.

  2. Mechanism of preservation of myocardial calcium channel function by pyruvate cardioplegic solution.

    Science.gov (United States)

    Ono, K; Wada, T; Lee, T S; Gondo, N; Hadama, T; Arita, M

    1998-02-01

    We evaluated the effects of adding pyruvate to a cardioplegic solution on the preservation of the dihydropyridine-sensitive calcium (Ca2+) current responses to beta-adrenergic stimulation in rabbit cardiac myocytes by measurement of single-channel open probability. Single ventricular myocytes were isolated and stored in St. Thomas' solution with or without pyruvate at 4 degrees C for 2, 6, 12, or 24 hours, and cell-attached single Ca2+ channel currents recordings were made at 20 degrees to 22 degrees C after each storage period. When 0.1 micromol/L isoproterenol (ISO) was applied to the cells, the percent mean open probability of the Ca2+ channels tested in freshly isolated cells was 181% +/- 27% (n = 12) of control values. These responses decreased with an increasing duration of the hypothermic storage and were only 112% +/- 22% (n = 5) of control values after 24 hours of storage in the absence of pyruvate. Conversely, the responses were significantly preserved, to as much as 143% +/- 17% (n = 7), in the presence of 10 mmol/L pyruvate in the storage solution. The application of forskolin to stimulate adenylate cyclase or a membrane-permeable cyclic adenosine monophosphate mimicked the effects of ISO when the myocytes were stored with pyruvate. Pyruvate did not alter the open-channel kinetics or single-channel conductance and lacked any apparent direct effect on the Ca2+ channel activity. We suggest that pyruvate added to the hypothermic storage solution preserves the high-energy phosphates in myocytes that are responsible for Ca2+ channel phosphorylation via beta-adrenergic stimulation. (J Lab

  3. Activation and inhibition of thermosensitive TRP channels by voacangine, an alkaloid present in Voacanga africana, an African tree.

    Science.gov (United States)

    Terada, Yuko; Horie, Syunji; Takayama, Hiromitsu; Uchida, Kunitoshi; Tominaga, Makoto; Watanabe, Tatsuo

    2014-02-28

    Voacangine (1) is an alkaloid found in the root bark of Voacanga africana. Our previous work has suggested that 1 is a novel transient receptor potential vanilloid type 1 (TRPV1) antagonist. In this study, the agonist and antagonist activities of 1 were examined against thermosensitive TRP channels. Channel activity was evaluated mainly using TRP channel-expressing HEK cells and calcium imaging. Herein, it was shown that 1 acts as an antagonist for TRPV1 and TRPM8 but as an agonist for TRPA1 (EC50, 8 μM). The compound competitively blocked capsaicin binding to TRPV1 (IC50, 50 μM). Voacangine (1) competitively inhibited the binding of menthol to TRPM8 (IC50, 9 μM), but it showed noncompetitive inhibition against icilin (IC50, 7 μM). Moreover, the compound selectively abrogated chemical agonist-induced TRPM8 activation and did not affect cold-induced activation. Among these effects, the TRPM8 inhibition profile is unique and noteworthy, because to date no studies have reported a menthol competitive inhibitor of TRPM8 derived from a natural source. Furthermore, this is the first report of a stimulus-selective TRPM8 antagonist. Accordingly, 1 may contribute to the development of a novel class of stimulus-selective TRPM8 blockers.

  4. Calcium signaling of in situ chondrocytes in articular cartilage under compressive loading: Roles of calcium sources and cell membrane ion channels.

    Science.gov (United States)

    Lv, Mengxi; Zhou, Yilu; Chen, Xingyu; Han, Lin; Wang, Liyun; Lu, X Lucas

    2017-10-05

    Mechanical loading on articular cartilage can induce many physical and chemical stimuli on chondrocytes residing in the extracellular matrix (ECM). Intracellular calcium ([Ca2+ ]i ) signaling is among the earliest responses of chondrocytes to physical stimuli, but the [Ca2+ ]i signaling of in situ chondrocytes in loaded cartilage is not fully understood due to the technical challenges in [Ca2+ ]i imaging of chondrocytes in a deforming ECM. This study developed a novel bi-directional microscopy loading device that enables the record of transient [Ca2+ ]i responses of in situ chondrocytes in loaded cartilage. It was found that compressive loading significantly promoted [Ca2+ ]i signaling in chondrocytes with faster [Ca2+ ]i oscillations in comparison to the non-loaded cartilage. Seven [Ca2+ ]i signaling pathways were further investigated by treating the cartilage with antagonists prior to and/or during the loading. Removal of extracellular Ca2+ ions completely abolished the [Ca2+ ]i responses of in situ chondrocytes, suggesting the indispensable role of extracellular Ca2+ sources in initiating the [Ca2+ ]i signaling in chondrocytes. Depletion of intracellular Ca2+ stores, inhibition of PLC-IP3 pathway, and block of purinergic receptors on plasma membrane led to significant reduction in the responsive rate of cells. Three types of ion channels that are regulated by different physical signals, TRPV4 (osmotic and mechanical stress), T-type VGCCs (electrical potential), and mechanical sensitive ion channels (mechanical loading) all demonstrated critical roles in controlling the [Ca2+ ]i responses of in situ chondrocyte in the loaded cartilage. This study provided new knowledge about the [Ca2+ ]i signaling and mechanobiology of chondrocytes in its natural residing environment. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

  5. Revealing calcium fluxes by analyzing inhibition dynamics in action potential clamp.

    Science.gov (United States)

    Laasmaa, Martin; Birkedal, Rikke; Vendelin, Marko

    2016-11-01

    In cardiac excitation-contraction coupling (ECC), calcium enters the cytosol via L-type Ca 2+ channels (LTCC) and reverse Na + /Ca 2+ -exchange (NCX rev ), or is released from the sarcoplasmic reticulum (SR) by Ca 2+ -induced Ca 2+ -release (CICR). The magnitude of Ca 2+ influx via the different pathways varies with the state of the cell and is difficult to assess quantitatively, because changes in Ca 2+ influx through one pathway affect the others. In rainbow trout ventricular myocytes, the role of the SR has been uncertain for decades. The aim of this work was therefore two-fold: 1) to develop a method to quantify the Ca 2+ influx pathways, and 2) to determine the role of CICR from the SR in trout ventricular myocytes. The novelty of our developed method lies in the mathematical analysis of measured transsarcolemmal Ca 2+ currents and their impact on the corresponding Ca 2+ transient during gradual inhibition of the currents in action potential (AP) clamp. We tested the developed method using an excitation-contraction model and showed that the method was able to recover calcium fluxes from noisy synthetic data. We applied the approach to trout ventricular myocytes and quantified the relative contributions of different Ca 2+ influx pathways in ECC and determined the kinetics of these fluxes. Under baseline conditions, NCX rev is the main transmembrane Ca 2+ influx pathway contributing 29 ± 6% (of the Ca 2+ influx), LTCC 18 ± 7%, and CICR 53 ± 10% to overall Ca 2+ transient. Thus, NCX rev is an important regulator of contractility and probably plays a role in the negative force-frequency relationship of trout ventricular preparations. These results demonstrate that trout and neonatal mammalian cardiomyocytes resemble each other not only in terms of morphology and energetics but ECC as well. In summary, the developed method resolves the major problem how to separate highly interconnected fluxes in AP clamp and allows to study Ca 2+ fluxes in cardiomyocytes under

  6. Effect of antiarrhythmic drugs on small conductance calcium –activated potassium channels

    DEFF Research Database (Denmark)

    Simo Vicens, Rafel; Sauter, Daniel Rafael Peter; Grunnet, Morten

    2017-01-01

    . Whether antiarrhythmic drugs (AADs) recommended for treating AF target KCa2.X channels is unknown. To this end, we tested a large number of AADs on the human KCa2.2 and KCa2.3 channels to assess their effect on this new target using automated whole-cell patch clamp. Of the AADs recommended for treatment...... for their antiarrhythmic effect is unlikely, as the calculated IC50 values are very high compared to the effective free therapeutic plasma concentration of the drugs when used for AF treatment, 40,000-fold for dofetilide and 140- fold higher for propafenone.......Atrial fibrillation (AF) is the most common type of arrhythmia. Current pharmacological treatment for AF is moderately effective and/or increases the risk of serious ventricular adverse effects. To avoid ventricular adverse effects, a new target has been considered, the small conductance calcium...

  7. Blockade of chloride channels by DIDS stimulates renin release and inhibits contraction of afferent arterioles

    DEFF Research Database (Denmark)

    Jensen, B L; Skøtt, O

    1996-01-01

    arterioles with the chloride channel blocker 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). Renin secretion was equally enhanced by omission of extracellular calcium and by addition of 0.5 mM DIDS. The inhibitory effect of calcium was blocked by DIDS. The stimulatory effects of low calcium [with......Calcium-activated chloride channels have been proposed to control renin release from juxtaglomerular cells and to be involved in the excitation-contraction coupling of the renal afferent arteriole. The hypothesis was tested on renin release from rat glomeruli and in microperfused rabbit afferent...... or without ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid] and DIDS were not additive. In the absence of chloride, basal renin release was suppressed and the stimulatory effect of DIDS was abolished. The DIDS-induced enhancement of renin release was not dependent on bicarbonate...

  8. Development of multiple calcium channel types in cultured mouse hippocampal neurons.

    Science.gov (United States)

    Chameau, P; Lucas, P; Melliti, K; Bournaud, R; Shimahara, T

    1999-05-01

    The development of multiple calcium channel activities was studied in mouse hippocampal neurons in culture, using the patch-clamp technique. A depolarizing pulse (40-50 ms duration) from the holding potential of -80 mV to levels more depolarized than -40 mV produced a low threshold T-type current. The T-type current was observed in 52% of four days in vitro neurons. The number of neurons which expressed T-type current decreased with age of culture, so that the current was detected in only 18% of neurons after 16 days in vitro. The T-type current densities varied between 1.9 pA/pF and 3.29 pA/pF in the mean values during the period studied (4-16 days in vitro). A depolarizing pulse from -80 mV to levels more depolarized than -35 mV evoked a high threshold calcium channel current. The high threshold current density increased in the mean values from 3.9 pA/pF in four days in vitro neurons to 28 pA/pF in 16 days in vitro neurons. We have then examined the effect of nifedipine, omega-Agatoxin IVA and omega-conotoxin GVIA on the high threshold current. Nifedipine (1-5 microM) sensitive current density stayed in the range of 1.9-2.1 pA/pF during 4-16 days in vitro, while omega-Agatoxin IVA (200 nM) sensitive current density increased in the mean values from 1.54 pA/pF in four days in vitro neurons to 21.5 pA/pF in 16 days in vitro neurons. The omega-conotoxin GVIA sensitive N-type channel current was maximum at eight days in vitro (5.44 pA/pF) and it reduced progressively to reach almost half (2.46 pA/pF) in 16 days in vitro neurons. These results showed that diverse subtypes of calcium channels change in density during the early period of culture. We suggest that the temporal expression of each type of channel may be linked to the development of neural activities.

  9. Inhibition of ANO1/TMEM16A Chloride Channel by Idebenone and Its Cytotoxicity to Cancer Cell Lines.

    Directory of Open Access Journals (Sweden)

    Yohan Seo

    Full Text Available The expression levels of anoctamin 1 (ANO1, TMEM16A, a calcium-activated chloride channel (CaCC, are significantly increased in several tumors, and inhibition of ANO1 is known to reduce cell proliferation and migration. Here, we performed cell-based screening of a collection of natural products and drug-like compounds to identify inhibitors of ANO1. As a result of the screening, idebenone, miconazole and plumbagin were identified as novel ANO1 inhibitors. Electrophysiological studies showed that idebenone, a synthetic analog of coenzyme Q10, completely blocked ANO1 activity in FRT cells expressing ANO1 without any effect on intracellular calcium signaling and CFTR, a cAMP-regulated chloride channel. The CaCC activities in PC-3 and CFPAC-1 cells expressing abundant endogenous ANO1 were strongly blocked by idebenone. Idebenone inhibited cell proliferation and induced apoptosis in PC-3 and CFPAC-1 cells, but not in A549 cells, which do not express ANO1. These data suggest that idebenone, a novel ANO1 inhibitor, has potential for use in cancer therapy.

  10. In vivo impact of presynaptic calcium channel dysfunction on motor axons in episodic ataxia type 2.

    Science.gov (United States)

    Tomlinson, Susan E; Tan, S Veronica; Burke, David; Labrum, Robyn W; Haworth, Andrea; Gibbons, Vaneesha S; Sweeney, Mary G; Griggs, Robert C; Kullmann, Dimitri M; Bostock, Hugh; Hanna, Michael G

    2016-02-01

    Ion channel dysfunction causes a range of neurological disorders by altering transmembrane ion fluxes, neuronal or muscle excitability, and neurotransmitter release. Genetic neuronal channelopathies affecting peripheral axons provide a unique opportunity to examine the impact of dysfunction of a single channel subtype in detail in vivo. Episodic ataxia type 2 is caused by mutations in CACNA1A, which encodes the pore-forming subunit of the neuronal voltage-gated calcium channel Cav2.1. In peripheral motor axons, this channel is highly expressed at the presynaptic neuromuscular junction where it contributes to action potential-evoked neurotransmitter release, but it is not expressed mid-axon or thought to contribute to action potential generation. Eight patients from five families with genetically confirmed episodic ataxia type 2 underwent neurophysiological assessment to determine whether axonal excitability was normal and, if not, whether changes could be explained by Cav2.1 dysfunction. New mutations in the CACNA1A gene were identified in two families. Nerve conduction studies were normal, but increased jitter in single-fibre EMG studies indicated unstable neuromuscular transmission in two patients. Excitability properties of median motor axons were compared with those in 30 age-matched healthy control subjects. All patients had similar excitability abnormalities, including a high electrical threshold and increased responses to hyperpolarizing (P ataxia type 2 thus has unexpected effects on axon excitability, which may reflect an indirect effect of abnormal calcium current fluxes during development. © The Author (2016). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved.

  11. Alternative Splicing at C Terminus of CaV1.4 Calcium Channel Modulates Calcium-dependent Inactivation, Activation Potential, and Current Density

    Science.gov (United States)

    Tan, Gregory Ming Yeong; Yu, Dejie; Wang, Juejin; Soong, Tuck Wah

    2012-01-01

    The CaV1.4 voltage-gated calcium channel is predominantly expressed in the retina, and mutations to this channel have been associated with human congenital stationary night blindness type-2. The L-type CaV1.4 channel displays distinct properties such as absence of calcium-dependent inactivation (CDI) and slow voltage-dependent inactivation (VDI) due to the presence of an autoinhibitory domain (inhibitor of CDI) in the distal C terminus. We hypothesized that native CaV1.4 is subjected to extensive alternative splicing, much like the other voltage-gated calcium channels, and employed the transcript scanning method to identify alternatively spliced exons within the CaV1.4 transcripts isolated from the human retina. In total, we identified 19 alternative splice variations, of which 16 variations have not been previously reported. Characterization of the C terminus alternatively spliced exons using whole-cell patch clamp electrophysiology revealed a splice variant that exhibits robust CDI. This splice variant arose from the splicing of a novel alternate exon (43*) that can be found in 13.6% of the full-length transcripts screened. Inclusion of exon 43* inserts a stop codon that truncates half the C terminus. The CaV1.4 43* channel exhibited robust CDI, a larger current density, a hyperpolarized shift in activation potential by ∼10 mV, and a slower VDI. Through deletional experiments, we showed that the inhibitor of CDI was responsible for modulating channel activation and VDI, in addition to CDI. Calcium currents in the photoreceptors were observed to exhibit CDI and are more negatively activated as compared with currents elicited from heterologously expressed full-length CaV1.4. Naturally occurring alternative splice variants may in part contribute to the properties of the native CaV1.4 channels. PMID:22069316

  12. TMEM16 proteins: the long awaited calcium-activated chloride channels?

    Directory of Open Access Journals (Sweden)

    C.A. Flores

    2009-11-01

    Full Text Available Currents mediated by calcium-activated chloride channels (CaCCs, observed for the first time in Xenopus oocytes, have been recorded in many cells and tissues ranging from different types of neurons to epithelial and muscle cells. CaCCs play a role in the regulation of excitability in neurons including sensory receptors. In addition, they are crucial mediators of chloride movements in epithelial cells where their activity regulates electrolyte and fluid transport. The roles of CaCCs, particularly in epithelia, are briefly reviewed with emphasis on their function in secretory epithelia. The recent identification by three independent groups, using different strategies, of TMEM16A as the molecular counterpart of the CaCC is discussed. TMEM16A is part of a family that has 10 other members in mice. The discovery of the potential TMEM16 anion channel activity opens the way for the molecular investigation of the role of these anion channels in specific cells and in organ physiology and pathophysiology. The identification of TMEM16A protein as a CaCC chloride channel molecule represents a great triumph of scientific perseverance and ingenuity. The varied approaches used by the three independent research groups also augur well for the solidity of the discovery.

  13. Distribution of high-conductance calcium-activated potassium channels in rat vestibular epithelia.

    Science.gov (United States)

    Schweizer, Felix E; Savin, David; Luu, Cindy; Sultemeier, David R; Hoffman, Larry F

    2009-11-10

    Voltage- and calcium-activated potassium channels (BK) are important regulators of neuronal excitability. BK channels seem to be crucial for frequency tuning in nonmammalian vestibular and auditory hair cells. However, there are a paucity of data concerning BK expression in mammalian vestibular hair cells. We therefore investigated the localization of BK channels in mammalian vestibular hair cells, specifically in rat vestibular neuroepithelia. We find that only a subset of hair cells in the utricle and the crista ampullaris express BK channels. BK-positive hair cells are located mainly in the medial striolar region of the utricle, where they constitute at most 12% of hair cells, and in the central zone of the horizontal crista. A majority of BK-positive hair cells are encapsulated by a calretinin-positive calyx defining them as type I cells. The remainder are either type I cells encapsulated by a calretinin-negative calyx or type II hair cells. Surprisingly, the number of BK-positive hair cells in the utricle peaks in juvenile rats and declines in early adulthood. BK channels were not found in vestibular afferent dendrites or somata. Our data indicate that BK channel expression in the mammalian vestibular system differs from the expression pattern in the mammalian auditory and the nonmammalian vestibular system. The molecular diversity of vestibular hair cells indicates a functional diversity that has not yet been fully characterized. The predominance of BK-positive hair cells within the medial striola of juvenile animals suggests that they contribute to a scheme of highly lateralized coding of linear head movements during late development.

  14. Synergistic Effect of Fluconazole and Calcium Channel Blockers against Resistant Candida albicans.

    Directory of Open Access Journals (Sweden)

    Shuyuan Liu

    Full Text Available Candidiasis has increased significantly recently that threatens patients with low immunity. However, the number of antifungal drugs on the market is limited in comparison to the number of available antibacterial drugs. This fact, coupled with the increased frequency of fungal resistance, makes it necessary to develop new therapeutic strategies. Combination drug therapy is one of the most widely used and effective strategy to alleviate this problem. In this paper, we were aimed to evaluate the combined antifungal effects of four CCBs (calcium channel blockers, amlodipine (AML, nifedipine (NIF, benidipine (BEN and flunarizine (FNZ with fluconazole against C. albicans by checkerboard and time-killing method. In addition, we determined gene (CCH1, MID1, CNA1, CNB1, YVC1, CDR1, CDR2 and MDR1 expression by quantitative PCR and investigated the efflux pump activity of resistant candida albicans by rhodamine 6G assay to reveal the potential mechanisms. Finally, we concluded that there was a synergy when fluconazole combined with the four tested CCBs against resistant strains, with fractional inhibitory concentration index (FICI <0.5, but no interaction against sensitive strains (FICI = 0.56 ~ 2. The mechanism studies revealed that fluconazole plus amlodipine caused down-regulating of CNA1, CNB1 (encoding calcineurin and YVC1 (encoding calcium channel protein in vacuole membrane.

  15. Synergistic Effect of Fluconazole and Calcium Channel Blockers against Resistant Candida albicans

    Science.gov (United States)

    Liu, Shuyuan; Yue, Longtao; Gu, Wenrui; Li, Xiuyun; Zhang, Liuping; Sun, Shujuan

    2016-01-01

    Candidiasis has increased significantly recently that threatens patients with low immunity. However, the number of antifungal drugs on the market is limited in comparison to the number of available antibacterial drugs. This fact, coupled with the increased frequency of fungal resistance, makes it necessary to develop new therapeutic strategies. Combination drug therapy is one of the most widely used and effective strategy to alleviate this problem. In this paper, we were aimed to evaluate the combined antifungal effects of four CCBs (calcium channel blockers), amlodipine (AML), nifedipine (NIF), benidipine (BEN) and flunarizine (FNZ) with fluconazole against C. albicans by checkerboard and time-killing method. In addition, we determined gene (CCH1, MID1, CNA1, CNB1, YVC1, CDR1, CDR2 and MDR1) expression by quantitative PCR and investigated the efflux pump activity of resistant candida albicans by rhodamine 6G assay to reveal the potential mechanisms. Finally, we concluded that there was a synergy when fluconazole combined with the four tested CCBs against resistant strains, with fractional inhibitory concentration index (FICI) fluconazole plus amlodipine caused down-regulating of CNA1, CNB1 (encoding calcineurin) and YVC1 (encoding calcium channel protein in vacuole membrane). PMID:26986478

  16. Castration prevents calcium channel blocker-induced gingival hyperplasia in beagle dogs.

    Science.gov (United States)

    Dayan, D; Kozlovsky, A; Tal, H; Kariv, N; Shemesh, M; Nyska, A

    1998-07-01

    1. The purpose of this study was to investigate testosterone's role on the calcium channel antagonist oxodipine-inducing gingival hyperplasia in a dog model. 2. Two experiments were conducted using castrated and intact male dogs. Oxodipine was administered orally for 90 days, at a dose of 24 mg/kg/day. In the first experiment, the occurrence of gingival hyperplasia was evaluated. In the second, the gingival index (GI) and gingival hyperplasia index (GHI) were recorded and correlated with serum levels of testosterone. 3. A significant positive correlation between GI, GHI and plasma testosterone was noted. Castrated dogs were injected with testosterone, 4 months after the start of oxodipine treatment, while in the non-castrated dogs, administration of oxodipine was stopped. Castration correlated with lack of GH, while testosterone injection to the same dogs was associated with an increase of GI and GHI. 4. Since it is known that testosterone receptors are present in the gingiva, it is proposed that oxodipine-induced gingival hyperplasia could be mediated by the calcium channel blocker on plasma testosterone levels.

  17. High-dose insulin therapy in beta-blocker and calcium channel-blocker poisoning.

    Science.gov (United States)

    Engebretsen, Kristin M; Kaczmarek, Kathleen M; Morgan, Jenifer; Holger, Joel S

    2011-04-01

    INTRODUCTION. High-dose insulin therapy, along with glucose supplementation, has emerged as an effective treatment for severe beta-blocker and calcium channel-blocker poisoning. We review the experimental data and clinical experience that suggests high-dose insulin is superior to conventional therapies for these poisonings. PRESENTATION AND GENERAL MANAGEMENT. Hypotension, bradycardia, decreased systemic vascular resistance (SVR), and cardiogenic shock are characteristic features of beta-blocker and calcium-channel blocker poisoning. Initial treatment is primarily supportive and includes saline fluid resuscitation which is essential to correct vasodilation and low cardiac filling pressures. Conventional therapies such as atropine, glucagon and calcium often fail to improve hemodynamic status in severely poisoned patients. Catecholamines can increase blood pressure and heart rate, but they also increase SVR which may result in decreases in cardiac output and perfusion of vascular beds. The increased myocardial oxygen demand that results from catecholamines and vasopressors may be deleterious in the setting of hypotension and decreased coronary perfusion. METHODS. The Medline, Embase, Toxnet, and Google Scholar databases were searched for the years 1975-2010 using the terms: high-dose insulin, hyperinsulinemia-euglycemia, beta-blocker, calcium-channel blocker, toxicology, poisoning, antidote, toxin-induced cardiovascular shock, and overdose. In addition, a manual search of the Abstracts of the North American Congress of Clinical Toxicology and the Congress of the European Association of Poisons Centres and Clinical Toxicologists published in Clinical Toxicology for the years 1996-2010 was undertaken. These searches identified 485 articles of which 72 were considered relevant. MECHANISMS OF HIGH-DOSE INSULIN BENEFIT. There are three main mechanisms of benefit: increased inotropy, increased intracellular glucose transport, and vascular dilatation. EFFICACY OF HIGH

  18. Mechanism of HERG potassium channel inhibition by tetra-n-octylammonium bromide and benzethonium chloride

    Energy Technology Data Exchange (ETDEWEB)

    Long, Yan; Lin, Zuoxian [Key Laboratory of Regenerative Biology, Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530 (China); Xia, Menghang; Zheng, Wei [National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20892 (United States); Li, Zhiyuan, E-mail: li_zhiyuan@gibh.ac.cn [Key Laboratory of Regenerative Biology, Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530 (China)

    2013-03-01

    Tetra-n-octylammonium bromide and benzethonium chloride are synthetic quaternary ammonium salts that are widely used in hospitals and industries for the disinfection and surface treatment and as the preservative agent. Recently, the activities of HERG channel inhibition by these compounds have been found to have potential risks to induce the long QT syndrome and cardiac arrhythmia, although the mechanism of action is still elusive. This study was conducted to investigate the mechanism of HERG channel inhibition by these compounds by using whole-cell patch clamp experiments in a CHO cell line stably expressing HERG channels. Tetra-n-octylammonium bromide and benzethonium chloride exhibited concentration-dependent inhibitions of HERG channel currents with IC{sub 50} values of 4 nM and 17 nM, respectively, which were also voltage-dependent and use-dependent. Both compounds shifted the channel activation I–V curves in a hyperpolarized direction for 10–15 mV and accelerated channel activation and inactivation processes by 2-fold. In addition, tetra-n-octylammonium bromide shifted the inactivation I–V curve in a hyperpolarized direction for 24.4 mV and slowed the rate of channel deactivation by 2-fold, whereas benzethonium chloride did not. The results indicate that tetra-n-octylammonium bromide and benzethonium chloride are open-channel blockers that inhibit HERG channels in the voltage-dependent, use-dependent and state-dependent manners. - Highlights: ► Tetra-n-octylammonium and benzethonium are potent HERG channel inhibitors. ► Channel activation and inactivation processes are accelerated by the two compounds. ► Both compounds are the open-channel blockers to HERG channels. ► HERG channel inhibition by both compounds is use-, voltage- and state dependent. ► The in vivo risk of QT prolongation needs to be studied for the two compounds.

  19. The β1 Subunit Enhances Oxidative Regulation of Large-Conductance Calcium-activated K+ Channels

    Science.gov (United States)

    Santarelli, Lindsey Ciali; Chen, Jianguo; Heinemann, Stefan H.; Hoshi, Toshinori

    2004-01-01

    Oxidative stress may alter the functions of many proteins including the Slo1 large conductance calcium-activated potassium channel (BKCa). Previous results demonstrated that in the virtual absence of Ca2+, the oxidant chloramine-T (Ch-T), without the involvement of cysteine oxidation, increases the open probability and slows the deactivation of BKCa channels formed by human Slo1 (hSlo1) α subunits alone. Because native BKCa channel complexes may include the auxiliary subunit β1, we investigated whether β1 influences the oxidative regulation of hSlo1. Oxidation by Ch-T with β1 present shifted the half-activation voltage much further in the hyperpolarizing direction (−75 mV) as compared with that with α alone (−30 mV). This shift was eliminated in the presence of high [Ca2+]i, but the increase in open probability in the virtual absence of Ca2+ remained significant at physiologically relevant voltages. Furthermore, the slowing of channel deactivation after oxidation was even more dramatic in the presence of β1. Oxidation of cysteine and methionine residues within β1 was not involved in these potentiated effects because expression of mutant β1 subunits lacking cysteine or methionine residues produced results similar to those with wild-type β1. Unlike the results with α alone, oxidation by Ch-T caused a significant acceleration of channel activation only when β1 was present. The β1 M177 mutation disrupted normal channel activation and prevented the Ch-T–induced acceleration of activation. Overall, the functional effects of oxidation of the hSlo1 pore-forming α subunit are greatly amplified by the presence of β1, which leads to the additional increase in channel open probability and the slowing of deactivation. Furthermore, M177 within β1 is a critical structural determinant of channel activation and oxidative sensitivity. Together, the oxidized BKCa channel complex with β1 has a considerable chance of being open within the physiological voltage

  20. Effects of low-dose ionising radiation on pituitary adenoma: is there a role for L-type calcium channel?

    Directory of Open Access Journals (Sweden)

    Marcella Araugio Soares

    2005-10-01

    Full Text Available Pituitary adenomas constitute about 6-18% of brain tumours in adults. Activation of voltage gated calcium currents can account for growth hormone oversecretion in some GH-secreting pituitary adenomas that produce an acromegaly appearance and increase mortality. Ca2+ ions, as mediators of intracellular signalling, are crucial for the development of apoptosis. However, the role of [Ca2+] in the development of apoptosis is ambiguous. In this study, the effects of low-dose ionising gamma radiation (60Co on rat pituitary adenoma cells survival and proliferation and the role of calcium channels on the apoptosis radio-induced were evaluated. Doses as low as 3 Gy were found to inhibit GH3 cell proliferation. Even though there was a significant number of live cells,168 hours following irradiation, they were not able to proliferate. The results indicate that the blockade of extracellular calcium influx through these channels does not interfere in the radiation-induced apoptosis in GH3 cells.Adenomas de pituitária constituem cerca de 6-18% dos tumores cerebrais em adultos. A ativação de correntes de cálcio dependentes de voltagem podem levar à super-excreção de hormônio do crescimento produzindo acromegalia e aumentando a mortalidade. Íons Ca2+ como mediadores de sinalização intracelular são cruciais no desenvolvimento da apoptose. No entanto, o papel da [Ca 2+] no desenvolvimento da apoptose é ambíguo. Neste estudo nós avaliamos os efeitos de baixas doses de radiação gama (60Co na sobrevivência e proliferação de células de adenoma de pituitária de rato e o papel do cálcio na apoptose radio-induzida. Nossos resultados mostraram que a dose de 3Gy foi suficiente para inibir a proliferação das células GH3. Apesar de existir um número significativo de células vivas após 168 horas do tratamento com radiação, elas não estavam aptas a proliferar. Nossos resultados também indicaram que bloqueio do influxo de cálcio extracelular n

  1. Lotus japonicus CASTOR and POLLUX are ion channels essential for perinuclear calcium spiking in legume root endosymbiosis.

    Science.gov (United States)

    Charpentier, Myriam; Bredemeier, Rolf; Wanner, Gerhard; Takeda, Naoya; Schleiff, Enrico; Parniske, Martin

    2008-12-01

    The mechanism underlying perinuclear calcium spiking induced during legume root endosymbioses is largely unknown. Lotus japonicus symbiosis-defective castor and pollux mutants are impaired in perinuclear calcium spiking. Homology modeling suggested that the related proteins CASTOR and POLLUX might be ion channels. Here, we show that CASTOR and POLLUX form two independent homocomplexes in planta. CASTOR reconstituted in planar lipid bilayers exhibited ion channel activity, and the channel characteristics were altered in a symbiosis-defective mutant carrying an amino acid replacement close to the selectivity filter. Permeability ratio determination and competition experiments reveled a weak preference of CASTOR for cations such as potassium over anions. POLLUX has an identical selectivity filter region and complemented a potassium transport-deficient yeast mutant, suggesting that POLLUX is also a potassium-permeable channel. Immunogold labeling localized the endogenous CASTOR protein to the nuclear envelope of Lotus root cells. Our data are consistent with a role of CASTOR and POLLUX in modulating the nuclear envelope membrane potential. They could either trigger the opening of calcium release channels or compensate the charge release during the calcium efflux as counter ion channels.

  2. Aptamer-Conjugated Calcium Phosphate Nanoparticles for Reducing Diabetes Risk via Retinol Binding Protein 4 Inhibition.

    Science.gov (United States)

    Torabi, Raheleh; Ghourchian, Hedayatollah; Amanlou, Massoud; Pasalar, Parvin

    2017-06-01

    Inhibition of the binding of retinol to its carrier, retinol binding protein 4, is a new strategy for treating type 2 diabetes; for this purpose, we have provided an aptamer-functionalized multishell calcium phosphate nanoparticle. First, calcium phosphate nanoparticles were synthesized and conjugated to the aptamer. The cytotoxicity of nanoparticles releases the process of aptamer from nanoparticles and their inhibition function of binding retinol to retinol binding protein 4. After synthesizing and characterizing the multishell calcium phosphate nanoparticles and observing the noncytotoxicity of conjugate, the optimum time (48 hours) and the pH (7.4) for releasing the aptamer from the nanoparticles was determined. The half-maximum inhibitory concentration (IC 50 ) value for inhibition of retinol binding to retinol binding protein 4 was 210 femtomolar (fmol). The results revealed that the aptamer could prevent connection between retinol and retinol binding protein 4 at a very low IC 50 value (210 fmol) compared to other reported inhibitors. It seems that this aptamer could be used as an efficient candidate not only for decreasing the insulin resistance in type 2 diabetes, but also for inhibiting the other retinol binding protein 4-related diseases. Copyright © 2017 Diabetes Canada. Published by Elsevier Inc. All rights reserved.

  3. Evaluating state dependence and subtype selectivity of calcium channel modulators in automated electrophysiology assays.

    Science.gov (United States)

    Kuryshev, Yuri A; Brown, Arthur M; Duzic, Emir; Kirsch, Glenn E

    2014-03-01

    Voltage-gated Ca2+ channels play essential roles in control of neurosecretion and muscle contraction. The pharmacological significance of Cav channels stem from their identification as the molecular targets of calcium blockers used in the treatment of cardiovascular diseases, such as hypertension, angina, and arrhythmia, and neurologic diseases, such as pain and seizure. It has been proposed that state-dependent Cav inhibitors, that is, those that preferentially bind to channels in open or inactivated states, may improve the therapeutic window over relatively state-independent Cav inhibitors. High-throughput fluorescent-based functional assays have been useful in screening chemical libraries to identify Cav inhibitors. However, hit confirmation, mechanism of action, and subtype selectivity are better suited to automated patch clamp assays that have sufficient capacity to handle the volume of compounds identified during screening, even of modest sized libraries (≤500,000 compounds), and the flexible voltage control that allows evaluation of state-dependent drug blocks. IonWorks Barracuda (IWB), the newest generation of IonWorks instruments, provides the opportunity to accelerate the Cav drug discovery studies in an automated patch clamp platform in 384-well format capable of medium throughput screening and profiling studies. We have validated hCav1.2, hCav2.1, hCav2.2, and hCav3.2 channels assays on the IWB platform (population patch clamp mode) and demonstrated that the biophysical characteristics of the channels (activation, inactivation, and steady-state inactivation) obtained with the IWB system are consistent with known subtype-specific characteristics. Using standard reference compounds (nifedipine, BAY K8644, verapamil, mibefradil, and pimozide), we demonstrated subtype-selective and state- and use-dependent characteristics of drug-channel interactions. Here we describe the design and validation of novel robust high-throughput Cav channel assays on the IWB

  4. Turtle Flexion Reflex Motor Patterns Show Windup, Mediated Partly by L-type Calcium Channels

    Directory of Open Access Journals (Sweden)

    Keith P. Johnson

    2017-10-01

    Full Text Available Windup is a form of multisecond temporal summation in which identical stimuli, delivered seconds apart, trigger increasingly strong neuronal responses. L-type Ca2+ channels have been shown to play an important role in the production of windup of spinal cord neuronal responses, initially in studies of turtle spinal cord and later in studies of mammalian spinal cord. L-type Ca2+ channels have also been shown to contribute to windup of limb withdrawal reflex (flexion reflex in rats, but flexion reflex windup has not previously been described in turtles and its cellular mechanisms have not been studied. We studied windup of flexion reflex motor patterns, evoked with weak mechanical and electrical stimulation of the dorsal hindlimb foot skin and assessed via a hip flexor (HF nerve recording, in spinal cord-transected and immobilized turtles in vivo. We found that an L-type Ca2+ channel antagonist, nifedipine, applied at concentrations of 50 μM or 100 μM to the hindlimb enlargement spinal cord, significantly reduced windup of flexion reflex motor patterns, while lower concentrations of nifedipine had no such effect. Nifedipine similarly reduced the amplitude of an individual flexion reflex motor pattern evoked by a stronger mechanical stimulus, in a dose-dependent manner, suggesting that L-type Ca2+ channels contribute to each flexion reflex as well as to multisecond summation of flexion reflex responses in turtles. We also found that we could elicit flexion reflex windup consistently using a 4-g von Frey filament, which is not usually considered a nociceptive stimulus. Thus, it may be that windup can be evoked by a wide range of tactile stimuli and that L-type calcium channels contribute to multisecond temporal summation of diverse tactile stimuli across vertebrates.

  5. Calcium-activated potassium (BK) channels are encoded by duplicate slo1 genes in teleost fishes.

    Science.gov (United States)

    Rohmann, Kevin N; Deitcher, David L; Bass, Andrew H

    2009-07-01

    Calcium-activated, large conductance potassium (BK) channels in tetrapods are encoded by a single slo1 gene, which undergoes extensive alternative splicing. Alternative splicing generates a high level of functional diversity in BK channels that contributes to the wide range of frequencies electrically tuned by the inner ear hair cells of many tetrapods. To date, the role of BK channels in hearing among teleost fishes has not been investigated at the molecular level, although teleosts account for approximately half of all extant vertebrate species. We identified slo1 genes in teleost and nonteleost fishes using polymerase chain reaction and genetic sequence databases. In contrast to tetrapods, all teleosts examined were found to express duplicate slo1 genes in the central nervous system, whereas nonteleosts that diverged prior to the teleost whole-genome duplication event express a single slo1 gene. Phylogenetic analyses further revealed that whereas other slo1 duplicates were the result of a single duplication event, an independent duplication occurred in a basal teleost (Anguilla rostrata) following the slo1 duplication in teleosts. A third, independent slo1 duplication (autotetraploidization) occurred in salmonids. Comparison of teleost slo1 genomic sequences to their tetrapod orthologue revealed a reduced number of alternative splice sites in both slo1 co-orthologues. For the teleost Porichthys notatus, a focal study species that vocalizes with maximal spectral energy in the range electrically tuned by BK channels in the inner ear, peripheral tissues show the expression of either one (e.g., vocal muscle) or both (e.g., inner ear) slo1 paralogues with important implications for both auditory and vocal physiology. Additional loss of expression of one slo1 paralogue in nonneural tissues in P. notatus suggests that slo1 duplicates were retained via subfunctionalization. Together, the results predict that teleost fish achieve a diversity of BK channel subfunction via

  6. Conotoxins as Tools to Understand the Physiological Function of Voltage-Gated Calcium (CaV Channels

    Directory of Open Access Journals (Sweden)

    David Ramírez

    2017-10-01

    Full Text Available Voltage-gated calcium (CaV channels are widely expressed and are essential for the completion of multiple physiological processes. Close regulation of their activity by specific inhibitors and agonists become fundamental to understand their role in cellular homeostasis as well as in human tissues and organs. CaV channels are divided into two groups depending on the membrane potential required to activate them: High-voltage activated (HVA, CaV1.1–1.4; CaV2.1–2.3 and Low-voltage activated (LVA, CaV3.1–3.3. HVA channels are highly expressed in brain (neurons, heart, and adrenal medulla (chromaffin cells, among others, and are also classified into subtypes which can be distinguished using pharmacological approaches. Cone snails are marine gastropods that capture their prey by injecting venom, “conopeptides”, which cause paralysis in a few seconds. A subset of conopeptides called conotoxins are relatively small polypeptides, rich in disulfide bonds, that target ion channels, transporters and receptors localized at the neuromuscular system of the animal target. In this review, we describe the structure and properties of conotoxins that selectively block HVA calcium channels. We compare their potency on several HVA channel subtypes, emphasizing neuronal calcium channels. Lastly, we analyze recent advances in the therapeutic use of conotoxins for medical treatments.

  7. Altered voltage-gated calcium channels in rat inferior colliculus neurons contribute to alcohol withdrawal seizures

    Science.gov (United States)

    N’Gouemo, Prosper

    2015-01-01

    We have previously reported that enhanced susceptibility to alcohol withdrawal seizures (AWS) parallels the enhancement of the current density of high-threshold voltage-gated Ca2+ (CaV) channels in rat inferior colliculus (IC) neurons. However, whether this increased current density is a cause or consequence of AWS is unclear. Here, I report changes in the current density of CaV channels in IC neurons during the course of alcohol withdrawal and the potential anticonvulsant effect of intra-IC infusions of L- and P-type CaV channel antagonists. Whole-cell currents were activated by depolarizing pulses using barium as the charge carrier. Currents and seizure susceptibility were evaluated in control animals 3 h after alcohol intoxication, as well as 3 h (before AWS), 24 h (when AWS susceptibility is maximal), and 48 h (when AWS susceptibility is no longer present) after alcohol withdrawal. Nifedipine, nimodipine (L-type antagonists) or ω-agatoxin TK (P-type antagonist) were infused intra-IC to probe the role of CaV channels in the pathogenesis of AWS. CaV current density and conductance in IC neurons were significantly increased 3 and 24 h after alcohol withdrawal compared with the control group or the group tested 3 h following ethanol intoxication. Blockade of L-type CaV channels within the IC completely suppressed AWS, and inhibition of P-type channels reduced AWS severity. These findings suggest that the enhancement of CaV currents in IC neurons occurs prior to AWS onset and that alterations in L- and P-type CaV channels in these neurons may underlie the pathogenesis of AWS. PMID:25914156

  8. n-Alcohols Inhibit Voltage-Gated Na+ Channels Expressed in Xenopus Oocytes

    Science.gov (United States)

    Horishita, Takafumi; Harris, R. Adron

    2008-01-01

    Voltage-gated sodium channels are essential for the initiation and propagation of action potentials in excitable cells and are known as a target of local anesthetics. In addition, inhibition of sodium channels by volatile anesthetics has been proposed as a mechanism of general anesthesia. The n-alcohols produce anesthesia, and their potency increases with carbon number until a “cut-off” is reached. In this study, we examined effects of a range of n-alcohols on Nav1.2 subunits to determine the alcohol cut-off for this channel. We also studied the effect of a short-chain alcohol (ethanol) and a long-chain alcohol (octanol) on Nav1.2, Nav1.4, Nav1.6, and Nav1.8 subunits, and we investigated the effects of alcohol on channel kinetics. Ethanol and octanol inhibited sodium currents of all subunits, and the inhibition of the Nav1.2 channel by n-alcohols indicated a cut-off at nonanol. Ethanol and octanol produced open-channel block, which was more pronounced for Nav1.8 than for the other sodium channels. Inhibition of Nav1.2 was due to decreased activation and increased inactivation. These results suggest that sodium channels may have a hydrophobic binding site for n-alcohols and demonstrate the differences in the kinetic mechanisms of inhibition for n-alcohols and inhaled anesthetics. PMID:18434586

  9. Stimulation of NOX2 in isolated hearts reversibly sensitizes RyR2 channels to activation by cytoplasmic calcium.

    Science.gov (United States)

    Donoso, Paulina; Finkelstein, José Pablo; Montecinos, Luis; Said, Matilde; Sánchez, Gina; Vittone, Leticia; Bull, Ricardo

    2014-03-01

    The response of ryanodine receptor (RyR) channels to cytoplasmic free calcium concentration ([Ca(2+)]) is redox sensitive. Here, we report the effects of a mild oxidative stress on cardiac RyR (RyR2) channels in Langendorff perfused rat hearts. Single RyR2 channels from control ventricles displayed the same three responses to Ca(2+) reported in other mammalian tissues, characterized by low, moderate, or high maximal activation. A single episode of 5 min of global ischemia, followed by 1 min of reperfusion, enhanced 2.3-fold the activity of NOX2 compared to controls and changed the frequency distribution of the different responses of RyR2 channels to calcium, favoring the more active ones: high activity response increased and low activity response decreased with respect to controls. This change was fully prevented by perfusion with apocynin or VAS 2870 before ischemia and totally reversed by the extension of the reperfusion period to 15 min. In vitro activation of NOX2 in control SR vesicles mimicked the effect of the ischemia/reperfusion episode on the frequencies of emergence of single RyR2 channel responses to [Ca(2+)] and increased 2.2-fold the rate of calcium release in Ca(2+)-loaded SR vesicles. In vitro changes were reversed at the single channel level by DTT and in isolated SR vesicles by glutaredoxin. Our results indicate that in whole hearts a mild oxidative stress enhances the response of cardiac RyR2 channels to calcium via NOX2 activation, probably by S-glutathionylation of RyR2 protein. This change is transitory and fully reversible, suggesting a possible role of redox modification in the physiological response of cardiac RyR2 to cellular calcium influx. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Protein kinase D regulates the human cardiac L-type voltage-gated calcium channel through serine 1884.

    Science.gov (United States)

    Aita, Yusuke; Kurebayashi, Nagomi; Hirose, Shigehisa; Maturana, Andrés D

    2011-12-15

    Protein kinase D (PKD) regulates the activity of the L-type calcium channel in rat ventricular cardiomyocytes. However, the functional target residues of PKD on the L-type calcium channel remain to be identified. Our aim was to identify the functional phosphorylation sites of PKD on the human L-type calcium channel. The pore subunit of the human CaV1.2 (hCaV1.2) was stably expressed in HEK293 cells. Both the expression of a dominant-negative mutant of PKD and the mutation of serine 1884 but not serine 1930, putative targets of PKD, strongly reduced L-type calcium currents and single channel activity without affecting the channel's expression at the plasma membrane. Our results suggest that serine 1884 is essential for the regulation of hCaV1.2 by PKD. Copyright © 2011 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  11. Consequences of activating the calcium-permeable ion channel TRPV1 in breast cancer cells with regulated TRPV1 expression.

    Science.gov (United States)

    Wu, Tina T L; Peters, Amelia A; Tan, Ping T; Roberts-Thomson, Sarah J; Monteith, Gregory R

    2014-08-01

    Increased expression of specific calcium channels in some cancers and the role of calcium signaling in proliferation and invasion have led to studies assessing calcium channel inhibitors as potential therapies for some cancers. The use of channel activators to promote death of cancer cells has been suggested, but the risk of activators promoting cancer cell proliferation and the importance of the degree of channel over-expression is unclear. We developed an MCF-7 breast cancer cell line with inducible TRPV1 overexpression and assessed the role of TRPV1 levels on cell death mediated by the TRPV1 activator capsaicin and the potential for submaximal activation to promote proliferation. The TRPV1 level was a determinant of cell death induced by capsaicin. A concentration response curve with varying TRPV1 expression levels identified the minimum level of TRPV1 required for capsaicin induced cell death. At no level of TRPV1 over-expression or capsaicin concentration did TRPV1 activation enhance proliferation. Cell death induced by capsaicin was necrotic and associated with up-regulation of c-Fos and RIP3. These studies suggest that activators of specific calcium channels may be an effective way to induce necrosis and that this approach may not always be associated with enhancement of cancer cell proliferation. Copyright © 2014 Elsevier Ltd. All rights reserved.

  12. TRPV6 calcium channel translocates to the plasma membrane via Orai1-mediated mechanism and controls cancer cell survival.

    Science.gov (United States)

    Raphaël, Maylis; Lehen'kyi, V'yacheslav; Vandenberghe, Matthieu; Beck, Benjamin; Khalimonchyk, Sergiy; Vanden Abeele, Fabien; Farsetti, Leonardo; Germain, Emmanuelle; Bokhobza, Alexandre; Mihalache, Adriana; Gosset, Pierre; Romanin, Christoph; Clézardin, Philippe; Skryma, Roman; Prevarskaya, Natalia

    2014-09-16

    Transient receptor potential vanilloid subfamily member 6 (TRPV6) is a highly selective calcium channel that has been considered as a part of store-operated calcium entry (SOCE). Despite its first discovery in the early 2000s, the role of this channel in prostate cancer (PCa) remained, until now, obscure. Here we show that TRPV6 mediates calcium entry, which is highly increased in PCa due to the remodeling mechanism involving the translocation of the TRPV6 channel to the plasma membrane via the Orai1/TRPC1-mediated Ca(2+)/Annexin I/S100A11 pathway, partially contributing to SOCE. The TRPV6 calcium channel is expressed de novo by the PCa cell to increase its survival by enhancing proliferation and conferring apoptosis resistance. Xenografts in nude mice and bone metastasis models confirmed the remarkable aggressiveness of TRPV6-overexpressing tumors. Immunohistochemical analysis of these demonstrated the increased expression of clinical markers such as Ki-67, prostate specific antigen, synaptophysin, CD31, and CD56, which are strongly associated with a poor prognosis. Thus, the TRPV6 channel acquires its oncogenic potential in PCa due to the remodeling mechanism via the Orai1-mediated Ca(2+)/Annexin I/S100A11 pathway.

  13. TRPV6 calcium channel translocates to the plasma membrane via Orai1-mediated mechanism and controls cancer cell survival

    Science.gov (United States)

    Raphaël, Maylis; Lehen’kyi, V’yacheslav; Vandenberghe, Matthieu; Beck, Benjamin; Khalimonchyk, Sergiy; Vanden Abeele, Fabien; Farsetti, Leonardo; Germain, Emmanuelle; Bokhobza, Alexandre; Mihalache, Adriana; Gosset, Pierre; Romanin, Christoph; Clézardin, Philippe; Skryma, Roman; Prevarskaya, Natalia

    2014-01-01

    Transient receptor potential vanilloid subfamily member 6 (TRPV6) is a highly selective calcium channel that has been considered as a part of store-operated calcium entry (SOCE). Despite its first discovery in the early 2000s, the role of this channel in prostate cancer (PCa) remained, until now, obscure. Here we show that TRPV6 mediates calcium entry, which is highly increased in PCa due to the remodeling mechanism involving the translocation of the TRPV6 channel to the plasma membrane via the Orai1/TRPC1-mediated Ca2+/Annexin I/S100A11 pathway, partially contributing to SOCE. The TRPV6 calcium channel is expressed de novo by the PCa cell to increase its survival by enhancing proliferation and conferring apoptosis resistance. Xenografts in nude mice and bone metastasis models confirmed the remarkable aggressiveness of TRPV6-overexpressing tumors. Immunohistochemical analysis of these demonstrated the increased expression of clinical markers such as Ki-67, prostate specific antigen, synaptophysin, CD31, and CD56, which are strongly associated with a poor prognosis. Thus, the TRPV6 channel acquires its oncogenic potential in PCa due to the remodeling mechanism via the Orai1-mediated Ca2+/Annexin I/S100A11 pathway. PMID:25172921

  14. INHIBITION OF CALCIUM OXALATE CRYSTALLIZATION IN-VITRO BY VARIOUS EXTRACTS OF HYPTIS SUAVEOLENS (L.) POIT.

    OpenAIRE

    Agarwal Kumkum; Varma Ranjana

    2012-01-01

    Hyptis suaveolens (L) Poit. commonly known as Vilayati tulsi, belongs to the Mint family Lamiaceae. The inhibition of in-vitro calcium-oxalate crystal (a major component of most urinary stones) formation by various extracts of Hyptis was investigated by titrimetric method. The inhibitor potency of alcohol extracts of Hyptis suaveolens (L.) Poit was found to be comparable to that of cystone (a proprietary drug for dissolving kidney stones). Thus alcohol extract could be further analyzed in viv...

  15. Antispasmodic and vasodilator activities of Morinda citrifolia root extract are mediated through blockade of voltage dependent calcium channels.

    Science.gov (United States)

    Gilani, Anwarul Hassan; Mandukhail, Saf-ur-Rehman; Iqbal, Javeid; Yasinzai, Masoom; Aziz, Nauman; Khan, Aslam; Najeeb-ur-Rehman

    2010-01-13

    Morinda citrifolia (Noni) is an edible plant with wide range of medicinal uses. It occurs exclusively in tropical climate zone from India through Southeast Asia and Australia to Eastern Polynesia and Hawaii. The objective of this study was to explore the possible mode(s) of action for its antispasmodic, vasodilator and cardio-suppressant effects to rationalize its medicinal use in gut and cardiovascular disorders. Isolated tissue preparations such as, rabbit jejunum, rat and rabbit aorta and guinea pig atria were used to test the antispasmodic and cardiovascular relaxant effects and the possible mode of action(s) of the 70% aqueous-ethanolic extract of Morinda citrifolia roots (Mc.Cr). The Mc.Cr produced a concentration-dependent relaxation of spontaneous and high K(+) induced contractions in isolated rabbit jejunum preparations. It also caused right ward shift in the concentration response curves of Ca(++), similar to that of verapamil. In guinea-pig right atria, Mc.Cr caused inhibition of both atrial force and rate of spontaneous contractions. In rabbit thoracic aortic preparations, Mc.Cr also suppressed contractions induced by phenylephrine (1.0 μM) in normal- Ca(++) and Ca(++)-free kreb solutions and by high K(+), similar to that of verapamil. In rat thoracic aortic preparations, Mc.Cr also relaxed the phenylephrine (1.0 μM)-induced contractions. The vasodilatory responses were not altered in the presence of L-NAME (0.1 mM) or atropine (1.0 μM) and removal of endothelium. These results suggest that the spasmolytic and vasodilator effects of Mc.Cr root extract are mediated possibly through blockade of voltage-dependent calcium channels and release of intracellular calcium, which may explain the medicinal use of Morinda citrifolia in diarrhea and hypertension. However, more detailed studies are required to assess the safety and efficacy of this plant.

  16. [Low conductivity calcium channels in the plasmatic membrane of macrophages: activation with inositol 1,4,5-triphosphate].

    Science.gov (United States)

    Semenova, S B; Kiselev, K I; Mozhaeva, G N

    1998-01-01

    Using patch-clamp technique we have shown that the plasma membrane of mouse macrophages contains calcium channels that are activated by inositol (1, 4, 5)-trisphosphate (IP3) and blocked by heparine. Their conductivity properties strongly differentiate them from IP3-activated channels of endoplasmic reticulum, but make it possible to include them to the ICRAC family. By the other hand, properties of the IP3 receptor (IP3R) of our channels are similar to those of endoplasmic IP3R. Basing on these data we suggest that IP3R could be located out of the plasma membrane, and by some conformational changes transduces the signal to the high selective Ca2+ channel in the plasma membrane. This model well conforms with the known in the literature "coupling model" of calcium signalling [1].

  17. Efficacy of methylene blue in an experimental model of calcium channel blocker-induced shock.

    Science.gov (United States)

    Jang, David H; Donovan, Sean; Nelson, Lewis S; Bania, Theodore C; Hoffman, Robert S; Chu, Jason

    2015-04-01

    Calcium channel blocker poisonings account for a substantial number of reported deaths from cardiovascular drugs. Although supportive care is the mainstay of treatment, experimental therapies such as high-dose insulin-euglycemia and lipid emulsion have been studied in animal models and used in humans. In the most severe cases, even aggressive care is inadequate and deaths occur. In both experimental models and clinical cases of vasodilatory shock, methylene blue improves hemodynamic measures. It acts as a nitric oxide scavenger and inhibits guanylate cyclase that is responsible for the production of cyclic guanosine monophosphate (cGMP). Excessive cGMP production is associated with refractory vasodilatory shock in sepsis and anaphylaxis. The aim of this study is to determine the efficacy of methylene blue in an animal model of amlodipine-induced shock. Sprague-Dawley rats were anesthetized, ventilated, and instrumented for continuous blood pressure and pulse rate monitoring. The dose of amlodipine that produced death within 60 minutes was 17 mg/kg per hour (LD50). Rats were divided into 2 groups: amlodipine followed by methylene blue or amlodipine followed by normal saline solution, with 15 rats in each group. Rats received methylene blue at 2 mg/kg during 5 minutes or an equivalent amount of normal saline solution in 3 intervals from the start of the protocol: minutes 5, 30, and 60. The animals were observed for a total of 2 hours after the start of the protocol. Mortality risk and survival time were analyzed with Fisher's exact test and Kaplan-Meier survival analysis with the log rank test. Overall, 1 of 15 rats (7%) in the saline solution-treated group survived to 120 minutes compared with 5 of 15 (33%) in the methylene blue-treated group (difference -26%; 95% confidence interval [CI] -54% to 0.3%). The median survival time for the normal saline solution group was 42 minutes (95% CI 28.1 to 55.9 minutes); for the methylene blue group, 109 minutes (95% CI 93.9 to

  18. Exclusion of alternative exon 33 of CaV1.2 calcium channels in heart is proarrhythmogenic.

    Science.gov (United States)

    Li, Guang; Wang, Juejin; Liao, Ping; Bartels, Peter; Zhang, Hengyu; Yu, Dejie; Liang, Mui Cheng; Poh, Kian Keong; Yu, Chye Yun; Jiang, Fengli; Yong, Tan Fong; Wong, Yuk Peng; Hu, Zhenyu; Huang, Hua; Zhang, Guangqin; Galupo, Mary Joyce; Bian, Jin-Song; Ponniah, Sathivel; Trasti, Scott Lee; See, Kelvin; Foo, Roger; Hoppe, Uta C; Herzig, Stefan; Soong, Tuck Wah

    2017-05-23

    Alternative splicing changes the CaV1.2 calcium channel electrophysiological property, but the in vivo significance of such altered channel function is lacking. Structure-function studies of heterologously expressed CaV1.2 channels could not recapitulate channel function in the native milieu of the cardiomyocyte. To address this gap in knowledge, we investigated the role of alternative exon 33 of the CaV1.2 calcium channel in heart function. Exclusion of exon 33 in CaV1.2 channels has been reported to shift the activation potential -10.4 mV to the hyperpolarized direction, and increased expression of CaV1.2Δ33 channels was observed in rat myocardial infarcted hearts. However, how a change in CaV1.2 channel electrophysiological property, due to alternative splicing, might affect cardiac function in vivo is unknown. To address these questions, we generated mCacna1c exon 33(-/-)-null mice. These mice contained CaV1.2Δ33 channels with a gain-of-function that included conduction of larger currents that reflects a shift in voltage dependence and a modest increase in single-channel open probability. This altered channel property underscored the development of ventricular arrhythmia, which is reflected in significantly more deaths of exon 33(-/-) mice from β-adrenergic stimulation. In vivo telemetric recordings also confirmed increased frequencies in premature ventricular contractions, tachycardia, and lengthened QT interval. Taken together, the significant decrease or absence of exon 33-containing CaV1.2 channels is potentially proarrhythmic in the heart. Of clinical relevance, human ischemic and dilated cardiomyopathy hearts showed increased inclusion of exon 33. However, the possible role that inclusion of exon 33 in CaV1.2 channels may play in the pathogenesis of human heart failure remains unclear.

  19. Molecular simulations study of novel 1,4-dihydropyridines derivatives with a high selectivity for Cav3.1 calcium channel

    Science.gov (United States)

    Liu, Xiaoguang; Yu, Hui; Zhao, Xi; Huang, Xu-Ri

    2015-01-01

    1,4-Dihydropyridines (DHPs) have been developed to treat hypertension, angina, and nerve system disease. They are thought to mainly target the L-type calcium channels, but low selectivity prompts them to block Cav1.2 and Cav3.1 channels simultaneously. Recently, some novel DHPs with different hydrophobic groups have been synthesized and among them M12 has a higher selectivity for Cav3.1. However, the structural information about Cav3.1-DHPs complexes is not available in the experiment. Thus, we combined homology modeling, molecular docking, molecular dynamics simulations, and binding free energy calculations to quantitatively elucidate the inhibition mechanism of DHPs. The calculated results indicate that our model is in excellent agreement with experimental results. On the basis of conformational analysis, we identify the main interactions between DHPs and calcium channels and further elaborate on the different selectivity of ligands from the micro perspective. In conjunction with energy distribution, we propose that the binding sites of Cav3.1-DHPs is characterized by several interspersed hydrophobic amino acid residues on the IIIS6 and IVS6 segments. We also speculate the favorable function groups on prospective DHPs. Besides, our model provides important information for further mutagenesis experiments. PMID:26256672

  20. Calcium Activated K+ Channels in The Electroreceptor of the Skate Confirmed by Cloning. Details of Subunits and Splicing

    OpenAIRE

    King, Benjamin L.; Shi, Ling Fang; Kao, Peter; Clusin, William T.

    2015-01-01

    Elasmobranchs detect small potentials using excitable cells of the ampulla of Lorenzini which have calcium-activated K+ channels, first described in l974. A distinctive feature of the outward current in voltage clamped ampullae is its apparent insensitivity to voltage. The sequence of a BK channel ? isoform expressed in the ampulla of the skate was characterized. A signal peptide is present at the beginning of the gene. When compared to human isoform 1 (the canonical sequence), the largest di...

  1. It takes two T to shape immunity: emerging role for T-type calcium channels in immune cells

    Czech Academy of Sciences Publication Activity Database

    Lacinová, L.; Weiss, Norbert

    2016-01-01

    Roč. 35, č. 4 (2016), s. 393-396 ISSN 0231-5882 R&D Projects: GA ČR GA15-13556S; GA MŠk 7AMB15FR015 Institutional support: RVO:61388963 Keywords : calcium channel * T-type channel * Ca(v)3.1 * immune cells Subject RIV: CE - Biochemistry Impact factor: 1.170, year: 2016

  2. NP-313, 2-acetylamino-3-chloro-1,4-naphthoquinone, a novel antithrombotic agent with dual inhibition of thromboxane A(2) synthesis and calcium entry.

    Science.gov (United States)

    Kuo, Heng-Lan; Lien, Jin-Cherng; Chang, Chien-Hsin; Chung, Ching-Hu; Kuo, Sheng-Chu; Hsu, Chun-Chieh; Peng, Hui-Chin; Huang, Tur-Fu

    2011-04-01

    1,4-Naphthoquinones exhibit antiplatelet activity both in vivo and in vitro. In the present study, we investigated the antiplatelet effect of a novel naphthoquinone derivative NP-313, 2-acetylamino-3-chloro-1,4-naphthoquinone and its mechanism of action. We measured platelet aggregation, Ca(2+) mobilization, thromboxane B2 formation and P-selectin expression and examined several enzymatic activities. Furthermore, we used the irradiated mesenteric venules in fluorescein sodium-treated mice to monitor the antithrombotic effect of NP-313 in vivo. NP-313 concentration-dependently inhibited human platelet aggregation induced by collagen, arachidonic acid, thapsigargin, thrombin and A23187. NP-313 also inhibited P-selectin expression, thromboxane B(2) formation and [Ca(2+) ](i) elevation in platelets stimulated by thrombin and collagen. NP-313 at 10 µM inhibited cyclooxygenase, thromboxane A(2) synthase, and protein kinase Cα, whereas it did not affect phospholipase A(2) or phospholipase C activity. In the presence of indomethacin and an adenosine 5-diphosphate scavenger, NP-313 concentration-dependently inhibited thrombin- and A23187-induced [Ca(2+)](i) increase through its inhibitory effects on Ca(2+) influx, rather than blocking Ca(2+) release from intracellular stores. NP-313 also inhibited thapsigargin-mediated Ca(2+) influx through store-operated calcium channel but had no effect on Ca(2+) influx through store-independent calcium channel evoked by the diacylglycerol analogue 1-oleoyl-2-acetyl-sn-glycerol. Nevertheless, it had little effect on cyclic AMP and cyclic GMP levels. Also, intravenously administered NP-313 dose-dependently inhibited the thrombus occlusion of the irradiated mesenteric vessels of fluorescein-pretreated mice. Taken together, these results indicate that NP-313 exerts its antithrombotic activity through dual inhibition of thromboxane A(2) synthesis and Ca(2+) influx through SOCC. © 2011 The Authors. British Journal of Pharmacology © 2011

  3. Orai and TRPC channel characterization in FcεRI-mediated calcium signaling and mediator secretion in human mast cells.

    Science.gov (United States)

    Wajdner, Hannah E; Farrington, Jasmine; Barnard, Claire; Peachell, Peter T; Schnackenberg, Christine G; Marino, Joseph P; Xu, Xiaoping; Affleck, Karen; Begg, Malcolm; Seward, Elizabeth P

    2017-03-01

    Inappropriate activation of mast cells via the FcεRI receptor leads to the release of inflammatory mediators and symptoms of allergic disease. Calcium influx is a critical regulator of mast cell signaling and is required for exocytosis of preformed mediators and for synthesis of eicosanoids, cytokines and chemokines. Studies in rodent and human mast cells have identified Orai calcium channels as key contributors to FcεRI-initiated mediator release. However, until now the role of TRPC calcium channels in FcεRI-mediated human mast cell signaling has not been published. Here, we show evidence for the expression of Orai 1,2, and 3 and TRPC1 and 6 in primary human lung mast cells and the LAD2 human mast cell line but, we only find evidence of functional contribution of Orai and not TRPC channels to FcεRI-mediated calcium entry. Calcium imaging experiments, utilizing an Orai selective antagonist (Synta66) showed the contribution of Orai to FcεRI-mediated signaling in human mast cells. Although, the use of a TRPC3/6 selective antagonist and agonist (GSK-3503A and GSK-2934A, respectively) did not reveal evidence for TRPC6 contribution to FcεRI-mediated calcium signaling in human mast cells. Similarly, inactivation of STIM1-regulated TRPC1 in human mast cells (as tested by transfecting cells with STIM1-KK684-685EE - TRPC1 gating mutant) failed to alter FcεRI-mediated calcium signaling in LAD2 human mast cells. Mediator release assays confirm that FcεRI-mediated calcium influx through Orai is necessary for histamine and TNFα release but is differentially involved in the generation of cytokines and eicosanoids. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

  4. Differential effects of voltage-gated calcium channel blockers on calcium channel alpha-2-delta-1 subunit protein-mediated nociception.

    Science.gov (United States)

    Chang, E; Chen, X; Kim, M; Gong, N; Bhatia, S; Luo, Z D

    2015-05-01

    Overexpression of the voltage-gated calcium channel (VGCC) alpha-2-delta1 subunit protein (Cav α2 δ1 ) has been shown to cause pain states. However, whether VGCC are involved in pain states driven by abnormal Cav α2 δ1 expression is not known. Intrathecal injection of N-, P/Q- and L-type VGCC blockers were tested in two models: a transgenic neuronal Cav α2 δ1 overexpression (TG) model with behavioural hypersensitivity and a spinal nerve ligation (SNL) model with Cav α2 δ1 overexpression in sensory pathways and neuropathy pain states. The nociceptive response to mechanical stimuli was significantly attenuated in both models with ω-conotoxin GVIA (an N-type VGCC blocker) and nifedipine (an L-type VGCC blocker), in which ω-conotoxin GVIA appeared more potent than nifedipine. Treatments with ω-agatoxin IVA (P-VGCC blocker), but not ω-conotoxin MVIIC (Q-VGCC blocker) had similar potency in the TG model as the N-type VGCC blocker, while both ω-agatoxin IVA and ω-conotoxin MVIIC had minimal effects in the SNL model compared with controls. These findings suggest that, at the spinal level, N- and L-type VGCC are likely involved in behavioural hypersensitivity states driven by Cav α2 δ1 overexpression. Q-type VGCC has minimal effects in both models. The anti-nociceptive effects of P-type VGCC blocker in the Cav α2 δ1 TG mice, but minimally at the SNL model with presynaptic Cav α2 δ1 up-regulation, suggest that its potential action site(s) is at the post-synaptic and/or supraspinal level. These findings support that N-, L- and P/Q-type VGCC have differential contributions to behavioural hypersensitivity modulated by Cav α2 δ1 dysregulation at the spinal cord level. © 2014 European Pain Federation - EFIC®

  5. 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.

  6. S-petasin and butterbur lactones dilate vessels through blockage of voltage gated calcium channels and block DNA synthesis.

    Science.gov (United States)

    Sheykhzade, Majid; Smajilovic, Sanela; Issa, Ali; Haunso, Stig; Christensen, Søren Brøgger; Tfelt-Hansen, Jacob

    2008-09-28

    Eremophilanlactones isolated from roots of Petasites hybridus (L.) G.M. et Sch. (Asteraceae) and S-petasin have vasodilatory effects with pD(2) -log (EC(50)) values of 6.01+/-0.08, 5.24+/-0.10, 4.74+/-0.13, and 5.43+/-0.06 for S-petasin, the (Z)-3-methylthioacrylic ester of 2beta-hydroxy-8betaH-7(11)-eremophilene-12,8-olide, the angelic ester of 2beta-hydroxy-8alphaH-7(11)-eremophilene-12,8-olide, and the angelic ester of 2beta-hydroxy-8betaH-7(11)-eremophilene-12,8-olide, respectively, in the mesenteric arteries. The pD(2) values were somewhat lower for all compounds in aortic segments. The vasodilation was caused by a blockage of the voltage gated calcium channels. S-petasin, (Z)-3-methylthioacrylic ester of 2beta-hydroxy-8betaH-7(11)-eremophilene-12,8-olide, and the angelic ester of 2beta-hydroxy-8alphaH-7(11)-eremophilene-12,8-olide displayed similar potencies in inhibiting DNA synthesis in cardiomyocytes and vascular smooth muscle cells.

  7. Different effects of dihydropyridine calcium channel antagonists on CYP3A4 enzyme of human liver microsomes.

    Science.gov (United States)

    Xia, Zongling; Wang, Mingli; Zou, Sulan; Chen, Rong

    2012-09-01

    The present study investigated inhibitory effects of 1,4-dihydropyridines (1,4-DHPs) calcium channel antagonists (1,4-DHP-CCAs) on cytochromeP450 3A4 (CYP3A4) of human liver microsomes and further explored importance of 1,4-DHPs molecular structural descriptors. Partial Least Squares method was applied to probe the quantitative relationships between the 1,4-DHPs molecular structural descriptors and its inhibitory actions, which demonstrated that different 1,4-DHP-CCAs could inhibit CYP3A4 enzyme's activity differently. The K (i) values of nicardipine, lercandipine, cilnidipine, nitrendipine, lacidipine, nifedipine, felodipine were 10.13, 10.17, 11.44, 23.90, 29.34, 29.06 and 32.64 μmol L⁻¹, respectively. It is suggested that the 1,4-DHPs molecular structural descriptors are the most important for its inhibitory effects based on the quantitative structure-activity relationship (QSAR) formula. The LogP was positively correlated to the K (i), whereas molecular weight and molecule volume were negatively correlated. It is concluded that analysis of K (i) of 1,4-DHPs derivatives on the CYP3A4 activity may apply for the QSAR formula at the initial stage of clinical application of new drugs.

  8. Targeting voltage-gated calcium channels: developments in peptide and small-molecule inhibitors for the treatment of neuropathic pain

    Science.gov (United States)

    Vink, S; Alewood, PF

    2012-01-01

    Chronic pain affects approximately 20% of people worldwide and places a large economic and social burden on society. Despite the availability of a range of analgesics, this condition is inadequately treated, with complete alleviation of symptoms rarely occurring. In the past 30 years, the voltage-gated calcium channels (VGCCs) have been recognized as potential targets for analgesic development. Although the majority of the research has been focused on Cav2.2 in particular, other VGCC subtypes such as Cav3.2 have recently come to the forefront of analgesic research. Venom peptides from marine cone snails have been proven to be a valuable tool in neuroscience, playing a major role in the identification and characterization of VGCC subtypes and producing the first conotoxin-based drug on the market, the ω-conotoxin, ziconotide. This peptide potently and selectively inhibits Cav2.2, resulting in analgesia in chronic pain states. However, this drug is only available via intrathecal administration, and adverse effects and a narrow therapeutic window have limited its use in the clinic. Other Cav2.2 inhibitors are currently in development and offer the promise of an improved route of administration and safety profile. This review assesses the potential of targeting VGCCs for analgesic development, with a main focus on conotoxins that block Cav2.2 and the developments made to transform them into therapeutics. PMID:22725651

  9. A key role for STIM1 in store operated calcium channel activation in airway smooth muscle

    Directory of Open Access Journals (Sweden)

    Peel Samantha E

    2006-09-01

    Full Text Available Abstract Background Control of cytosolic calcium plays a key role in airway myocyte function. Changes in intracellular Ca2+ stores can modulate contractile responses, modulate proliferation and regulate synthetic activity. Influx of Ca2+ in non excitable smooth muscle is believed to be predominantly through store operated channels (SOC or receptor operated channels (ROC. Whereas agonists can activate both SOC and ROC in a range of smooth muscle types, the specific trigger for SOC activation is depletion of the sarcoplasmic reticulum Ca2+ stores. The mechanism underlying SOC activation following depletion of intracellular Ca2+ stores in smooth muscle has not been identified. Methods To investigate the roles of the STIM homologues in SOC activation in airway myocytes, specific siRNA sequences were utilised to target and selectively suppress both STIM1 and STIM2. Quantitative real time PCR was employed to assess the efficiency and the specificity of the siRNA mediated knockdown of mRNA. Activation of SOC was investigated by both whole cell patch clamp electrophysiology and a fluorescence based calcium assay. Results Transfection of 20 nM siRNA specific for STIM1 or 2 resulted in robust decreases (>70% of the relevant mRNA. siRNA targeted at STIM1 resulted in a reduction of SOC associated Ca2+ influx in response to store depletion by cyclopiazonic acid (60% or histamine but not bradykinin. siRNA to STIM2 had no effect on these responses. In addition STIM1 suppression resulted in a more or less complete abrogation of SOC associated inward currents assessed by whole cell patch clamp. Conclusion Here we show that STIM1 acts as a key signal for SOC activation following intracellular Ca2+ store depletion or following agonist stimulation with histamine in human airway myocytes. These are the first data demonstrating a role for STIM1 in a physiologically relevant, non-transformed endogenous expression cell model.

  10. Anti-Convulsant Activity of Boerhaavia diffusa: Plausible Role of Calcium Channel Antagonism

    Directory of Open Access Journals (Sweden)

    Mandeep Kaur

    2011-01-01

    Full Text Available “Ethnopharmacological” use of roots of Boerhaavia diffusa (B. diffusa in the treatment of epilepsy in Nigerian folk medicine and reports showing the presence of a calcium channel antagonistic compound “liriodendrin” in its roots, led us to undertake the present study. The study was designed to investigate the methanolic root extract of B. diffusa and its different fractions including liriodendrin-rich fraction for exploring the possible role of liriodendrin in its anti-convulsant activity. Air-dried roots of B. diffusa were extracted with methanol by cold maceration. The methanol soluble fraction of extract thus obtained was successively extracted to obtain liriodendrin-rich fraction and two side fractions, that is, chloroform fraction and phenolic compound fraction. Anti-convulsant activity of methanolic extract (1000, 1500 and 2000 mg kg-1, intraperitoneally (i.p. and its different fractions, that is, liriodendrin-rich fraction (10, 20 and 40 mg kg-1, i.p., chloroform fraction (20 mg kg-1, i.p. and phenolic compound fraction (1 mg kg-1, i.p. were studied in pentylenetetrazol (PTZ-induced seizures (75 mg kg-1, i.p.. The crude methanolic extract of B. diffusa and only its liriodendrin-rich fraction showed a dose-dependent protection against PTZ-induced convulsions. The liriodendrin-rich fraction also showed significant protection against seizures induced by BAY k-8644. These findings reiterated the anti-convulsant activity of methanolic extract of B. diffusa roots. Furthermore, it can be concluded that the observed anti-convulsant activity was due to its calcium channel antagonistic action as this activity was retained only in the liodendrin-rich fraction, which has additionally been confirmed by significant anti-convulsant activity of liriodendrin-rich fraction in BAY k-8644-induced seizures.

  11. Reversal of acute theophylline toxicity by calcium channel blockers in dogs and rats.

    Science.gov (United States)

    Whitehurst, V E; Joseph, X; Vick, J A; Alleva, F R; Zhang, J; Balazs, T

    1996-06-17

    Theophylline, widely used in the treatment of pulmonary diseases, has a narrow therapeutic index; the recommended plasma levels being 10-20 micrograms/ml in humans. The misuse or abuse of theophylline can cause life-threatening central nervous system and cardiovascular effects. Increased intracellular Ca2+ levels are thought to play an important role in theophylline toxicity and death. The objective of this study was to determine whether Ca2+ channel blockers, e.g. verapamil, nifedipine, or diltiazem, prevent sudden death caused by theophylline treatment in rats and dogs. Groups of Sprague-Dawley rats were treated with theophylline alone (150 mg/kg i.p.) or with theophylline pretreatment followed by administration of verapamil (0.25 to 0.5 mg/kg i.p.), nifedipine (0.25 to 1.0 mg/kg i.p.), or diltiazem (0.5 to 1.0 mg/kg i.p.), 2.5 to 15 min later. The rats were observed for toxic signs and survival over a period of 15 days. All three calcium channel blockers significantly reduced the theophylline-induced sudden death in rats. In a separate study, neither verapamil (0.5 mg/kg i.p.) nor nifedipine (1.0 mg/kg i.p.) prevented the theophylline-induced myocardial necrosis in the rat. In beagle dogs, verapamil (0.5 mg/kg i.v.) prevented theophylline (15 mg/kg/min i.v. for 10 min)-induced hypotension, arrhythmias, and sudden death. Our results support previously reported findings that calcium plays a major role in theophylline-induced toxicity and death.

  12. Cloning, chromosomal localization, and functional expression of the alpha 1 subunit of the L-type voltage-dependent calcium channel from normal human heart

    NARCIS (Netherlands)

    Schultz, D; Mikala, G; Yatani, A; Engle, D B; Iles, D E; Segers, B; Sinke, R J; Weghuis, D O; Klöckner, U; Wakamori, M

    1993-01-01

    A unique structural variant of the cardiac L-type voltage-dependent calcium channel alpha 1 subunit cDNA was isolated from libraries derived from normal human heart mRNA. The deduced amino acid sequence shows significant homology to other calcium channel alpha 1 subunits. However, differences from

  13. Severe beta blocker and calcium channel blocker overdose: Role of high dose insulin.

    Science.gov (United States)

    Seegobin, Karan; Maharaj, Satish; Deosaran, Ansuya; Reddy, Pramod

    2018-01-10

    A 54-year-old female presented after taking an overdose of an unknown amount of hydrochlorothiazide, doxazocin, atenolol and amlodipine. She was initially refractory to treatment with conventional therapy (intravenous fluids, activated charcoal, glucagon 5 mg followed with glucagon drip, calcium gluconate 10%, and atropine). Furthermore, insulin at 4 U/kg was not effective in improving her hemodynamics. Shortly after high dose insulin was achieved with 10 U/kg, there was dramatic improvement in hemodynamics resulting in three of five vasopressors being weaned off in 8 h. She was subsequently off all vasopressors after six additional hours. The role of high dose insulin has been documented in prior cases, however it is generally recommended after other conventional therapies have failed. However, there are other reports that suggest it as initial therapy. Our patient failed conventional therapies and responded well only with maximum dose of insulin. Physicians should consider high dose insulin early in severe beta blocker or calcium channel blocker overdose for improvement in hemodynamics. This leads to early discontinuation of vasopressors. It is important that emergency physicians be aware of the beneficial effects of high dose insulin when initiated early as opposed to waiting for conventional therapy to fail; as these patients often present first to the emergency department. Early initiation in the emergency department can be beneficial in these patients. Copyright © 2018. Published by Elsevier Inc.

  14. Glucocorticoids specifically enhance L-type calcium current amplitude and affect calcium channel subunit expression in the mouse hippocampus

    NARCIS (Netherlands)

    Chameau, P.; Qin, Y.; Spijker, S.; Smit, A.B.; Joels, M.

    2007-01-01

    Previous studies have shown that corticosterone enhances whole cell calcium currents in CA1 pyramidal neurons, through a pathway involving binding of glucocorticoid receptor homodimers to the DNA. We examined whether glucocorticoids show selectivity for L- over N-type of calcium currents. Moreover,

  15. Glucocorticoids specifically enhance L-type calcium current amplitude and affect calcium channel subunit expression in the mouse hippocampus.

    NARCIS (Netherlands)

    Chameau, P.J.P.; Qin, Y.J.; Smit, G.; Joëls, M.

    2007-01-01

    Previous studies have shown that corticosterone enhances whole cell calcium currents in CA1 pyramidal neurons, through a pathway involving binding of glucocorticoid receptor homodimers to the DNA. We examined whether glucocorticoids show selectivity for L- over N-type of calcium currents. Moreover,

  16. Anti-addiction drug ibogaine inhibits voltage-gated ionic currents: A study to assess the drug's cardiac ion channel profile

    Energy Technology Data Exchange (ETDEWEB)

    Koenig, Xaver; Kovar, Michael; Rubi, Lena; Mike, Agnes K.; Lukacs, Peter; Gawali, Vaibhavkumar S.; Todt, Hannes [Center for Physiology and Pharmacology, Department of Neurophysiology and -pharmacology, Medical University of Vienna, 1090 Vienna (Austria); Hilber, Karlheinz, E-mail: karlheinz.hilber@meduniwien.ac.at [Center for Physiology and Pharmacology, Department of Neurophysiology and -pharmacology, Medical University of Vienna, 1090 Vienna (Austria); Sandtner, Walter [Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, 1090 Vienna (Austria)

    2013-12-01

    The plant alkaloid ibogaine has promising anti-addictive properties. Albeit not licenced as a therapeutic drug, and despite hints that ibogaine may perturb the heart rhythm, this alkaloid is used to treat drug addicts. We have recently reported that ibogaine inhibits human ERG (hERG) potassium channels at concentrations similar to the drugs affinity for several of its known brain targets. Thereby the drug may disturb the heart's electrophysiology. Here, to assess the drug's cardiac ion channel profile in more detail, we studied the effects of ibogaine and its congener 18-Methoxycoronaridine (18-MC) on various cardiac voltage-gated ion channels. We confirmed that heterologously expressed hERG currents are reduced by ibogaine in low micromolar concentrations. Moreover, at higher concentrations, the drug also reduced human Na{sub v}1.5 sodium and Ca{sub v}1.2 calcium currents. Ion currents were as well reduced by 18-MC, yet with diminished potency. Unexpectedly, although blocking hERG channels, ibogaine did not prolong the action potential (AP) in guinea pig cardiomyocytes at low micromolar concentrations. Higher concentrations (≥ 10 μM) even shortened the AP. These findings can be explained by the drug's calcium channel inhibition, which counteracts the AP-prolonging effect generated by hERG blockade. Implementation of ibogaine's inhibitory effects on human ion channels in a computer model of a ventricular cardiomyocyte, on the other hand, suggested that ibogaine does prolong the AP in the human heart. We conclude that therapeutic concentrations of ibogaine have the propensity to prolong the QT interval of the electrocardiogram in humans. In some cases this may lead to cardiac arrhythmias. - Highlights: • We study effects of anti-addiction drug ibogaine on ionic currents in cardiomyocytes. • We assess the cardiac ion channel profile of ibogaine. • Ibogaine inhibits hERG potassium, sodium and calcium channels. • Ibogaine’s effects on

  17. Extremely Low Frequency Electromagnetic Fields Facilitate Vesicle Endocytosis by Increasing Presynaptic Calcium Channel Expression at a Central Synapse.

    Science.gov (United States)

    Sun, Zhi-cheng; Ge, Jian-long; Guo, Bin; Guo, Jun; Hao, Mei; Wu, Yi-chen; Lin, Yi-an; La, Ting; Yao, Pan-tong; Mei, Yan-ai; Feng, Yi; Xue, Lei

    2016-02-18

    Accumulating evidence suggests significant biological effects caused by extremely low frequency electromagnetic fields (ELF-EMF). Although exo-endocytosis plays crucial physical and biological roles in neuronal communication, studies on how ELF-EMF regulates this process are scarce. By directly measuring calcium currents and membrane capacitance at a large mammalian central nervous synapse, the calyx of Held, we report for the first time that ELF-EMF critically affects synaptic transmission and plasticity. Exposure to ELF-EMF for 8 to 10 days dramatically increases the calcium influx upon stimulation and facilitates all forms of vesicle endocytosis, including slow and rapid endocytosis, endocytosis overshoot and bulk endocytosis, but does not affect the RRP size and exocytosis. Exposure to ELF-EMF also potentiates PTP, a form of short-term plasticity, increasing its peak amplitude without impacting its time course. We further investigated the underlying mechanisms and found that calcium channel expression, including the P/Q, N, and R subtypes, at the presynaptic nerve terminal was enhanced, accounting for the increased calcium influx upon stimulation. Thus, we conclude that exposure to ELF-EMF facilitates vesicle endocytosis and synaptic plasticity in a calcium-dependent manner by increasing calcium channel expression at the nerve terminal.

  18. Role of calcium-activated potassium channels with small conductance in bradykinin-induced vasodilation of porcine retinal arterioles

    DEFF Research Database (Denmark)

    Dalsgaard, Thomas; Kroigaard, Christel; Bek, Toke

    2009-01-01

    PURPOSE: Endothelial dysfunction and impaired vasodilation may be involved in the pathogenesis of retinal vascular diseases. In the present study, the mechanisms underlying bradykinin vasodilation were examined and whether calcium-activated potassium channels of small (SK(Ca)) and intermediate (I...

  19. Dopamine Induces LTP Differentially in Apical and Basal Dendrites through BDNF and Voltage-Dependent Calcium Channels

    Science.gov (United States)

    Navakkode, Sheeja; Sajikumar, Sreedharan; Korte, Martin; Soong, Tuck Wah

    2012-01-01

    The dopaminergic modulation of long-term potentiation (LTP) has been studied well, but the mechanism by which dopamine induces LTP (DA-LTP) in CA1 pyramidal neurons is unknown. Here, we report that DA-LTP in basal dendrites is dependent while in apical dendrites it is independent of activation of L-type voltage-gated calcium channels (VDCC).…

  20. The calcium-activated potassium channel KCa3.1 is an important modulator of hepatic injury

    DEFF Research Database (Denmark)

    Møller, Linda Maria Sevelsted; Fialla, Annette Dam; Schierwagen, Robert

    2016-01-01

    The calcium-activated potassium channel KCa3.1 controls different cellular processes such as proliferation and volume homeostasis. We investigated the role of KCa3.1 in experimental and human liver fibrosis. KCa3.1 gene expression was investigated in healthy and injured human and rodent liver. Ef...

  1. Calcium channel blockade limits cardiac remodeling and improves cardiac function in myocardial infarction-induced heart failure in rats

    NARCIS (Netherlands)

    Sandmann, S.; Claas, R.; Cleutjens, J. P.; Daemen, M. J.; Unger, T.

    2001-01-01

    Calcium channel antagonists (CCAs) have been proposed to prevent cardiac events after myocardial infarction (MI). However, unwanted effects, such as negative inotropy, limit their use in many cases. The aim of this study was to compare the effects of long-term treatment with the CCAs, mibefradil,

  2. Calcium

    Science.gov (United States)

    ... and blood vessels contract and expand, to secrete hormones and enzymes and to send messages through the nervous system. It is important to get plenty of calcium in the foods you eat. Foods rich in calcium include Dairy products such as milk, cheese, and yogurt Leafy, green vegetables Fish with ...

  3. Mice with deficient BK channel function show impaired prepulse inhibition and spatial learning, but normal working and spatial reference memory.

    Science.gov (United States)

    Typlt, Marei; Mirkowski, Magdalena; Azzopardi, Erin; Ruettiger, Lukas; Ruth, Peter; Schmid, Susanne

    2013-01-01

    Genetic variations in the large-conductance, voltage- and calcium activated potassium channels (BK channels) have been recently implicated in mental retardation, autism and schizophrenia which all come along with severe cognitive impairments. In the present study we investigate the effects of functional BK channel deletion on cognition using a genetic mouse model with a knock-out of the gene for the pore forming α-subunit of the channel. We tested the F1 generation of a hybrid SV129/C57BL6 mouse line in which the slo1 gene was deleted in both parent strains. We first evaluated hearing and motor function to establish the suitability of this model for cognitive testing. Auditory brain stem responses to click stimuli showed no threshold differences between knockout mice and their wild-type littermates. Despite of muscular tremor, reduced grip force, and impaired gait, knockout mice exhibited normal locomotion. These findings allowed for testing of sensorimotor gating using the acoustic startle reflex, as well as of working memory, spatial learning and memory in the Y-maze and the Morris water maze, respectively. Prepulse inhibition on the first day of testing was normal, but the knockout mice did not improve over the days of testing as their wild-type littermates did. Spontaneous alternation in the y-maze was normal as well, suggesting that the BK channel knock-out does not impair working memory. In the Morris water maze knock-out mice showed significantly slower acquisition of the task, but normal memory once the task was learned. Thus, we propose a crucial role of the BK channels in learning, but not in memory storage or recollection.

  4. Mice with deficient BK channel function show impaired prepulse inhibition and spatial learning, but normal working and spatial reference memory.

    Directory of Open Access Journals (Sweden)

    Marei Typlt

    Full Text Available Genetic variations in the large-conductance, voltage- and calcium activated potassium channels (BK channels have been recently implicated in mental retardation, autism and schizophrenia which all come along with severe cognitive impairments. In the present study we investigate the effects of functional BK channel deletion on cognition using a genetic mouse model with a knock-out of the gene for the pore forming α-subunit of the channel. We tested the F1 generation of a hybrid SV129/C57BL6 mouse line in which the slo1 gene was deleted in both parent strains. We first evaluated hearing and motor function to establish the suitability of this model for cognitive testing. Auditory brain stem responses to click stimuli showed no threshold differences between knockout mice and their wild-type littermates. Despite of muscular tremor, reduced grip force, and impaired gait, knockout mice exhibited normal locomotion. These findings allowed for testing of sensorimotor gating using the acoustic startle reflex, as well as of working memory, spatial learning and memory in the Y-maze and the Morris water maze, respectively. Prepulse inhibition on the first day of testing was normal, but the knockout mice did not improve over the days of testing as their wild-type littermates did. Spontaneous alternation in the y-maze was normal as well, suggesting that the BK channel knock-out does not impair working memory. In the Morris water maze knock-out mice showed significantly slower acquisition of the task, but normal memory once the task was learned. Thus, we propose a crucial role of the BK channels in learning, but not in memory storage or recollection.

  5. [Distribution diversity of integrins and calcium channels on major human and mouse host cells of Leptospira species].

    Science.gov (United States)

    Li, Cheng-xue; Zhao, Xin; Qian, Jing; Yan, Jie

    2012-07-01

    To determine the distribution of integrins and calcium channels on major human and mouse host cells of Leptospira species. The expression of β1, β2 and β3 integrins was detected with immunofluorescence assay on the surface of human monocyte line THP-1, mouse mononuclear-macrophage-like cell line J774A.1, human vascular endothelial cell line HUVEC, mouse vascular endothelial cell EOMA, human hepatocyte line L-02, mouse hepatocyte line Hepa1-6, human renal tubular epithelial cell line HEK-293, mouse glomerular membrane epithelial cell line SV40-MES13, mouse collagen blast line NIH/3T3, human and mouse platelets. The distribution of voltage gate control calcium channels Cav3.1, Cav3.2, Cav3.3 and Cav2.3, and receptor gate calcium channels P(2)X(1), P(2)2X(2), P(2)X(3), P(2)X(4), P(2)X(5), P(2)X(6) and P(2)X(7) were determined with Western blot assay. β1 integrin proteins were positively expressed on the membrane surface of J774A.1, THP-1, HUVEC, EOMA, L-02, Hepa1-6 and HEK-239 cells as well as human and mouse platelets. β2 integrin proteins were expressed on the membrane surface of J774A.1, THP-1, HUVEC, EOMA, and NIH/3T3 cells. β3 integrin proteins were expressed on the membrane surface of J774A.1, THP-1, HUVEC, EOMA, Hepa1-6, HEK-239 and NIH/3T3 cells as well as human and mouse platelets. P(2)X(1) receptor gate calcium channel was expressed on the membrane surface of human and mouse platelets, while P(2)X(5) receptor gate calcium channel was expressed on the membrane surface of J774A.1, THP-1, L-02, Hepa1-6, HEK-239 and HUVEC cells. However, the other calcium channels were not detected on the tested cell lines or platelets. There is a large distribution diversity of integrins and calcium channel proteins on the major human and mouse host cells of Leptospira species, which may be associated with the differences of leptospira-induced injury in different host cells.

  6. Establishing homology between mitochondrial calcium uniporters, prokaryotic magnesium channels and chlamydial IncA proteins.

    Science.gov (United States)

    Lee, Andre; Vastermark, Ake; Saier, Milton H

    2014-08-01

    Mitochondrial calcium uniporters (MCUs) (TC no. 1.A.77) are oligomeric channel proteins found in the mitochondrial inner membrane. MCUs have two well-conserved transmembrane segments (TMSs), connected by a linker, similar to bacterial MCU homologues. These proteins and chlamydial IncA proteins (of unknown function; TC no. 9.B.159) are homologous to prokaryotic Mg(2+) transporters, AtpI and AtpZ, based on comparison scores of up to 14.5 sds. A phylogenetic tree containing all of these proteins showed that the AtpZ proteins cluster coherently as a subset within the large and diverse AtpI cluster, which branches separately from the MCUs and IncAs, both of which cluster coherently. The MCUs and AtpZs share the same two TMS topology, but the AtpIs have four TMSs, and IncAs can have either two (most frequent) or four (less frequent) TMSs. Binary alignments, comparison scores and motif analyses showed that TMSs 1 and 2 align with TMSs 3 and 4 of the AtpIs, suggesting that the four TMS AtpI proteins arose via an intragenic duplication event. These findings establish an evolutionary link interconnecting eukaryotic and prokaryotic Ca(2+) and Mg(2+) transporters with chlamydial IncAs, and lead us to suggest that all members of the MCU superfamily, including IncAs, function as divalent cation channels. © 2014 The Authors.

  7. The effects of propofol and enflurane on single calcium channel currents of guinea-pig isolated ventricular myocytes.

    OpenAIRE

    Takahashi, H.; Puttick, R. M.; Terrar, D. A.

    1994-01-01

    1. The effects of the anaesthetics, propofol (100 microM) and enflurane (3%, 1.46 mM), on single L type calcium channel currents were investigated in single myocytes isolated from guinea-pig ventricles. Channel activity was recorded from membrane patches by use of the 'cell-attached' patch-clamp technique (pipette solution containing 110 mM BaCl2, 5 microM Bay K 8644, 5 microM HEPES, pH 7.4; temperature 36 degrees C). 2. Channel conductance was calculated from the slope of the relationship be...

  8. The calcium channel β2 (CACNB2 subunit repertoire in teleosts

    Directory of Open Access Journals (Sweden)

    Mueller Rachel

    2008-04-01

    Full Text Available Abstract Background Cardiomyocyte contraction is initiated by influx of extracellular calcium through voltage-gated calcium channels. These oligomeric channels utilize auxiliary β subunits to chaperone the pore-forming α subunit to the plasma membrane, and to modulate channel electrophysiology 1. Several β subunit family members are detected by RT-PCR in the embryonic heart. Null mutations in mouse β2, but not in the other three β family members, are embryonic lethal at E10.5 due to defects in cardiac contractility 2. However, a drawback of the mouse model is that embryonic heart rhythm is difficult to study in live embryos due to their intra-uterine development. Moreover, phenotypes may be obscured by secondary effects of hypoxia. As a first step towards developing a model for contributions of β subunits to the onset of embryonic heart rhythm, we characterized the structure and expression of β2 subunits in zebrafish and other teleosts. Results Cloning of two zebrafish β2 subunit genes (β2.1 and β2.2 indicated they are membrane-associated guanylate kinase (MAGUK-family genes. Zebrafish β2 genes show high conservation with mammals within the SH3 and guanylate kinase domains that comprise the "core" of MAGUK proteins, but β2.2 is much more divergent in sequence than β2.1. Alternative splicing occurs at the N-terminus and within the internal HOOK domain. In both β2 genes, alternative short ATG-containing first exons are separated by some of the largest introns in the genome, suggesting that individual transcript variants could be subject to independent cis-regulatory control. In the Tetraodon nigrovidis and Fugu rubripes genomes, we identified single β2 subunit gene loci. Comparative analysis of the teleost and human β2 loci indicates that the short 5' exon sequences are highly conserved. A subset of 5' exons appear to be unique to teleost genomes, while others are shared with mammals. Alternative splicing is temporally and

  9. Alternative splicing modulates diltiazem sensitivity of cardiac and vascular smooth muscle Cav1.2 calcium channels

    Science.gov (United States)

    Zhang, Heng Yu; Liao, Ping; Wang, Jue Jin; Yu, De Jie; Soong, Tuck Wah

    2010-01-01

    Background and purpose: As a calcium channel blocker, diltiazem acts mainly on the voltage-gated calcium channels, Cav1.2, for its beneficial effects in cardiovascular diseases such as hypertension, angina and/or supraventricular arrhythmias. However, the effects of diltiazem on different isoforms of Cav1.2 channels expressed in heart and vascular smooth muscles remain to be investigated. Here, we characterized the effects of diltiazem on the splice variants of Cav1.2 channels, predominant in cardiac and vascular smooth muscles. Experimental approach: Cardiac and smooth muscle isoforms of Cav1.2 channels were expressed in human embryonic kidney cells and their electrophysiological properties were characterized using whole-cell patch-clamp techniques. Key results: Under closed-channel and use-dependent block (0.03 Hz), cardiac splice variant Cav1.2CM was less sensitive to diltiazem than two major smooth muscle splice variants, Cav1.2SM and Cav1.2b. Cav1.2CM has a more positive half-inactivation potential than the smooth muscle channels, and diltiazem shifted it less to negative potential. Additionally, the current decay was slower in Cav1.2CM channels. When we modified alternatively spliced exons of cardiac Cav1.2CM channels into smooth muscle exons, we found that all three loci contribute to the different diltiazem sensitivity between cardiac and smooth muscle splice isoforms. Conclusions and implications: Alternative splicing of Cav1.2 channels modifies diltiazem sensitivity in the heart and blood vessels. Gating properties altered by diltiazem are different in the three channels. PMID:20649567

  10. The Need for a Rational Approach to Vasoconstrictive Syndromes: Transcranial Doppler and Calcium Channel Blockade in Reversible Cerebral Vasoconstriction Syndrome

    Directory of Open Access Journals (Sweden)

    Elisabeth B. Marsh

    2016-07-01

    Full Text Available Introduction: Reversible cerebral vasoconstriction syndrome (RCVS typically affects young patients and left untreated can result in hemorrhage or ischemic stroke. Though the disorder has been well characterized in the literature, the most appropriate way to diagnose, treat, and evaluate therapeutic response remains unclear. In previous studies, transcranial Doppler ultrasound (TCD has shown elevated velocities indicative of vasospasm. This imaging modality is noninvasive and inexpensive; an attractive option for diagnosis and therapeutic monitoring if it is sensitive enough to detect changes in the acute setting given that RCVS often affects the distal vessels early in the course of disease. There is also limited data that calcium channel blockade may be effective in treating vasospasm secondary to RCVS, though the agent of choice, formulation, and dose are unclear. Methods: We report a small cohort of seven patients presenting with thunderclap headache whose vascular imaging was consistent with RCVS. All were treated with calcium channel blockade and monitored with TCD performed every 1–2 days. Results: On presentation, TCD correlated with standard neuroimaging findings of vasospasm (on MR, CT, and conventional angiography. TCD was also able to detect improvement in velocities in the acute setting that correlated well with initiation of calcium channel blockade. Long-acting verapamil appeared to have the greatest effect on velocities compared to nimodipine and shorter-acting calcium channel blockers. Conclusion: Though small, our cohort demonstrates potential utility of TCD to monitor RCVS, and relative superiority of extended-release verapamil over other calcium channel blockers, illustrating the need for larger randomized trials.

  11. Sociability impairments in Genetic Absence Epilepsy Rats from Strasbourg: Reversal by the T-type calcium channel antagonist Z944.

    Science.gov (United States)

    Henbid, Mark T; Marks, Wendie N; Collins, Madeline J; Cain, Stuart M; Snutch, Terrance P; Howland, John G

    2017-10-01

    Childhood absence epilepsy (CAE) is associated with interictal co-morbid symptoms including abnormalities in social behaviour. Genetic Absence Epilepsy Rats from Strasbourg (GAERS) is a model of CAE that exhibits physiological and behavioural alterations characteristic of the human disorder. However, it is unknown if GAERS display the social deficits often observed in CAE. Sociability in rodents is thought to be mediated by neural circuits densely populated with T-type calcium channels and GAERS contain a missense mutation in the Cav3.2 T-type calcium channel gene. Thus, the objective of this study was to examine the effects of the clinical stage pan-T-type calcium channel blocker, Z944, on sociability behaviour in male and female GAERS and non-epileptic control (NEC) animals. Female GAERS showed reduced sociability in a three-chamber sociability task whereas male GAERS, male NECs, and female NECs all showed a preference for the chamber containing a stranger rat. In drug trials, pre-treatment with 5mg/kg of Z944 normalized sociability in female GAERS. In contrast, female NECs showed impaired sociability following Z944 treatment. Dose-dependent decreases in locomotor activity were noted following Z944 treatment in both strains. Treatment with 10mg/kg of Z944 altered exploration such that only 8 of the 16 rats tested explored both sides of the testing chamber. In those that explored the chamber, significant preference for the stranger rat was observed in GAERS but not NECs. Overall, the data suggest that T-type calcium channels are critical in regulating sociability in both GAERS and NEC animals. Future research should focus on T-type calcium channels in the treatment of sociability deficits observed in disorders such as CAE. Copyright © 2017 Elsevier Inc. All rights reserved.

  12. Dual pathways of calcium entry in spike and plateau phases of luteinizing hormone release from chicken pituitary cells: sequential activation of receptor-operated and voltage-sensitive calcium channels by gonadotropin-releasing hormone

    Energy Technology Data Exchange (ETDEWEB)

    Davidson, J.S.; Wakefield, I.K.; King, J.A.; Mulligan, G.P.; Millar, R.P.

    1988-04-01

    It has previously been shown that, in pituitary gonadotrope cells, the initial rise in cytosolic Ca2+ induced by GnRH is due to a Ca2+ mobilization from intracellular stores. This raises the possibility that the initial transient spike phase of LH release might be fully or partially independent of extracellular Ca2+. We have therefore characterized the extracellular Ca2+ requirements, and the sensitivity to Ca2+ channel blockers, of the spike and plateau phases of secretion separately. In the absence of extracellular Ca2+ the spike and plateau phases were inhibited by 65 +/- 4% and 106 +/- 3%, respectively. Both phases exhibited a similar dependence on concentration of extracellular Ca2+. However, voltage-sensitive Ca2+ channel blockers D600 and nifedipine had a negligible effect on the spike phase, while inhibiting the plateau phase by approximately 50%. In contrast, ruthenium red, Gd3+ ions, and Co2+ ions inhibited both spike and plateau phases to a similar extent as removal of extracellular Ca2+. A fraction (35 +/- 4%) of spike phase release was resistant to removal of extracellular Ca2+. This fraction was abolished after calcium depletion of the cells by preincubation with EGTA in the presence of calcium ionophore A23187, indicating that it depends on intracellular Ca2+ stores. Neither absence of extracellular Ca2+, nor the presence of ruthenium red or Gd3+ prevented mobilization of 45Ca2+ from intracellular stores by GnRH. We conclude that mobilization of intracellular stored Ca2+ is insufficient by itself to account for full spike phase LH release.

  13. Expression and cellular localization of the voltage-gated calcium channel α2δ3 in the rodent retina

    Science.gov (United States)

    Müller, Luis Pérez de Sevilla; Sargoy, Allison; Fernández-Sánchez, Laura; Rodriguez, Allen; Liu, Janelle; Cuenca, Nicolás; Brecha, Nicholas

    2015-01-01

    High voltage activated calcium channels are hetero-oligomeric protein complexes that mediate multiple cellular processes including the influx of extracellular Ca2+, neurotransmitter release, gene transcription and synaptic plasticity. These channels consist of a primary α1 pore-forming subunit, which is associated with an extracellular α2δ subunit and an intracellular β auxiliary subunit, which alter the gating properties and trafficking of the calcium channel. The cellular localization of the α2δ3 subunit in the mouse and rat retina is unknown. In this study, using RT-PCR a single band at ~305 bp corresponding to the predicted size of the α2δ3 subunit fragment was in mouse and rat retina and brain homogenates. Western blotting of rodent retina and brain homogenates showed a single 123 kDa band. Immunohistochemistry using an affinity purified antibody to the α2δ3 subunit revealed immunoreactive cell bodies in the ganglion cell layer (GCL) and inner nuclear layer (INL), and immunoreactive processes in the inner plexiform layer (IPL) and the outer plexiform layer (OPL). α2δ3 immunoreactivity was localized to multiple cell types, including ganglion, amacrine and bipolar cells, and photoreceptors, but not by horizontal cells. The expression of the α2δ3 calcium channel subunit to multiple cell types suggests this subunit participates widely in Ca channel-mediated signaling in the retina. PMID:25631988

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

    National Research Council Canada - National Science Library

    Seto, Sai Wang; Au, Alice Lai Shan; Poon, Christina Chui Wa; Zhang, Qian; Li, Rachel Wai Sum; Yeung, John Hok Keung; 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

    ...]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...

  15. Mapping of dihydropyridine binding residues in a less sensitive invertebrate L-type calcium channel (LCa v 1).

    Science.gov (United States)

    Senatore, Adriano; Boone, Adrienne; Lam, Stanley; Dawson, Taylor F; Zhorov, Boris; Spafford, J David

    2011-01-01

    Invertebrate L-type calcium channel, LCa(v) 1, isolated from the pond snail Lymnaea stagnalis is nearly indistinguishable from mammalian Ca(v) 1.2 (α1C) calcium channel in biophysical characteristics observed in vitro. These L-type channels are likely constrained within a narrow range of biophysical parameters to perform similar functions in the snail and mammalian cardiovascular systems. What distinguishes snail and mammalian L-type channels is a difference in dihydropyridine sensitivity: 100 nM isradipine exhibits a significant block of mammalian Ca(v) 1.2 currents without effect on snail LCa(v)1 currents. The native snail channel serves as a valuable surrogate for validating key residue differences identified from previous experimental and molecular modeling work. As predicted, three residue changes in LCa(v)1 (N_3o18, F_3i10, and I_4i12) replaced with DHP-sensing residues in respective positions of Ca(v) 1.2, (Q_3o18, Y_3i10, and M_4i12) raises the potency of isradipine block of LCa(v)1 channels to that of mammalian Ca(v) 1.2. Interestingly, the single N_3o18_Q mutation in LCa(v) 1 channels lowers DHP sensitivity even further and the triple mutation bearing enhanced isradipine sensitivity, still retains a reduced potency of agonist, (S)-Bay K8644.

  16. ω-Tbo-IT1-New Inhibitor of Insect Calcium Channels Isolated from Spider Venom.

    Science.gov (United States)

    Mikov, Alexander N; Fedorova, Irina M; Potapieva, Natalia N; Maleeva, Ekaterina E; Andreev, Yaroslav A; Zaitsev, Alexey V; Kim, Kira K; Bocharov, Eduard V; Bozin, Timur N; Altukhov, Dmitry A; Lipkin, Alexey V; Kozlov, Sergey A; Tikhonov, Denis B; Grishin, Eugene V

    2015-11-27

    Novel disulfide-containing polypeptide toxin was discovered in the venom of the Tibellus oblongus spider. We report on isolation, spatial structure determination and electrophysiological characterization of this 41-residue toxin, called ω-Tbo-IT1. It has an insect-toxic effect with LD50 19 μg/g in experiments on house fly Musca domestica larvae and with LD50 20 μg/g on juvenile Gromphadorhina portentosa cockroaches. Electrophysiological experiments revealed a reversible inhibition of evoked excitatory postsynaptic currents in blow fly Calliphora vicina neuromuscular junctions, while parameters of spontaneous ones were not affected. The inhibition was concentration dependent, with IC50 value 40 ± 10 nM and Hill coefficient 3.4 ± 0.3. The toxin did not affect frog neuromuscular junctions or glutamatergic and GABAergic transmission in rat brains. Ca(2+) currents in Calliphora vicina muscle were not inhibited, whereas in Periplaneta americana cockroach neurons at least one type of voltage gated Ca(2+) current was inhibited by ω-Tbo-IT1. Thus, the toxin apparently acts as an inhibitor of presynaptic insect Ca(2+) channels. Spatial structure analysis of the recombinant ω-Tbo-IT1 by NMR spectroscopy in aqueous solution revealed that the toxin comprises the conventional ICK fold containing an extended β-hairpin loop and short β-hairpin loop which are capable of making "scissors-like mutual motions".

  17. Antiarrhythmic Mechanisms of SK Channel Inhibition in the Rat Atrium

    DEFF Research Database (Denmark)

    Skibsbye, Lasse; Wang, Xiaodong; Axelsen, Lene Nygaard

    2015-01-01

    -clamping and two-electrode voltage-clamp was used to access INa and IK,ACh respectively. RESULTS: The SK channel inhibitor N-(pyridin-2-yl)-4-(pyridin-2-yl)thiazol-2-amine (ICA) exhibited antiarrhythmic effects. ICA prevented electrically induced runs of atrial fibrillation in the isolated right atrium and induced...

  18. Calcium

    Science.gov (United States)

    ... from dietary supplements are linked to a greater risk of kidney stones, especially among older adults. But calcium from foods does not appear to cause kidney stones. For most people, other factors (such as not drinking enough fluids) probably have ...

  19. Quercetin inhibits acid-sensing ion channels through a putative binding site in the central vestibular region.

    Science.gov (United States)

    Mukhopadhyay, Mohona; Singh, Anurag; Sachchidanand, S; Bera, Amal Kanti

    2017-04-21

    Acid-sensing ion channels (ASICs) are associated with many pathophysiological processes, such as neuronal death during ischemic stroke, epileptic seizure and nociception. However, there is a dearth of ASIC-specific therapeutic blockers. Here we report that quercetin, a plant flavonoid, which is known for its neuroprotective effect, reversibly inhibits homomeric rat ASIC1a, ASIC2a and ASIC3 with an IC50 of about 2µM. Also, quercetin prevents low pH-induced intracellular calcium rise and cell death in HEK-293 cells, which have endogenous expression of ASIC1a and 2a. The inhibitory effect of quercetin on ASICs is not due to membrane perturbation, as it did not have any effect on other channels, like NMDA receptor, GABAA receptor and P2X4 receptor. Unlike quercetin, another flavonoid resveratrol had no effect on ASIC1a. Computational analysis revealed that quercetin binds to the channel in a cavity at the central vestibule, lined by several charged residues like Q276, R369, E373 and E416 in ASIC1a. Mutation of Arg369 to Ala or Glu416 to Gln abolished the inhibitory effect of quercetin on rat ASIC1a completely, while Glu373 to Gln showed reduced sensitivity. Our results raise the possibility of using quercetin for targeting ASICs in vivo. Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

  20. Calcium-Activated Chloride Channels (CaCCs) Regulate Action Potential and Synaptic Response in Hippocampal Neurons

    Science.gov (United States)

    Huang, Wendy C.; Xiao, Shaohua; Huang, Fen; Harfe, Brian D.; Jan, Yuh Nung; Jan, Lily Yeh

    2012-01-01

    SUMMARY Central neurons respond to synaptic inputs from other neurons by generating synaptic potentials. Once the summated synaptic potentials reach threshold for action potential firing, the signal propagates leading to transmitter release at the synapse. The calcium influx accompanying such signaling opens calcium-activated ion channels for feedback regulation. Here we report a novel mechanism for modulating hippocampal neuronal signaling that involves calcium-activated chloride channels (CaCCs). We present the first evidence that CaCCs reside in hippocampal neurons and are in close proximity of calcium channels and NMDA receptors to shorten action potential duration, dampen excitatory synaptic potentials, impede temporal summation, and raise the threshold for action potential generation by synaptic potential. Having recently identified TMEM16A and TMEM16B as CaCCs, we further show that TMEM16B but not TMEM16A is important for hippocampal CaCC, laying the groundwork for deciphering the dynamic CaCC modulation of neuronal signaling in neurons important for learning and memory. PMID:22500639

  1. Probenecid, a gout remedy, inhibits pannexin 1 channels

    OpenAIRE

    Silverman, William; Locovei, Silviu; Dahl, Gerhard

    2008-01-01

    Probenecid is a well-established drug for the treatment of gout and is thought to act on an organic anion transporter, thereby affecting uric acid excretion in the kidney by blocking urate reuptake. Probenecid also has been shown to affect ATP release, leading to the suggestion that ATP release involves an organic anion transporter. Other pharmacological evidence and the observation of dye uptake, however, suggest that the nonvesicular release of ATP is mediated by large membrane channels, wi...

  2. Single calcium channel domain gating of synaptic vesicle fusion at fast synapses; analysis by graphic modeling

    Science.gov (United States)

    Stanley, Elise F

    2015-01-01

    At fast-transmitting presynaptic terminals Ca2+ enter through voltage gated calcium channels (CaVs) and bind to a synaptic vesicle (SV) -associated calcium sensor (SV-sensor) to gate fusion and discharge. An open CaV generates a high-concentration plume, or nanodomain of Ca2+ that dissipates precipitously with distance from the pore. At most fast synapses, such as the frog neuromuscular junction (NMJ), the SV sensors are located sufficiently close to individual CaVs to be gated by single nanodomains. However, at others, such as the mature rodent calyx of Held (calyx of Held), the physiology is more complex with evidence that CaVs that are both close and distant from the SV sensor and it is argued that release is gated primarily by the overlapping Ca2+ nanodomains from many CaVs. We devised a 'graphic modeling' method to sum Ca2+ from individual CaVs located at varying distances from the SV-sensor to determine the SV release probability and also the fraction of that probability that can be attributed to single domain gating. This method was applied first to simplified, low and high CaV density model release sites and then to published data on the contrasting frog NMJ and the rodent calyx of Held native synapses. We report 3 main predictions: the SV-sensor is positioned very close to the point at which the SV fuses with the membrane; single domain-release gating predominates even at synapses where the SV abuts a large cluster of CaVs, and even relatively remote CaVs can contribute significantly to single domain-based gating. PMID:26457441

  3. Would calcium or potassium channels be responsible for cardiac arrest produced by adenosine and ATP in the right atria of Wistar rats?

    Science.gov (United States)

    Camara, Henrique; Rodrigues, Juliano Quintella Dantas; Alves, Gabriel Andrade; da Silva Junior, Edilson Dantas; Caricati-Neto, Afonso; Garcia, Antônio G; Jurkiewicz, Aron

    2015-12-05

    Autonomic nerves release ATP, which is processed into adenosine in the synaptic cleft. Adenosine and ATP exert a negative chronotropic effect in the heart. This study aims to evaluate adenosine and P2 receptors and cellular signalling in cardiac arrest produced by purines in the heart. Right atria of adult Wistar rats were used to evaluate the effects of adenosine, ATP and CPA (an adenosine A1 receptor agonist), in the presence and absence of DPCPX, an adenosine A1 receptor antagonist. Effects of adenosine A2 and A3 receptors agonists and antagonists were also investigated. Finally, involvement of calcium and potassium channels in these responses was assessed using BayK 8644 and 4-Aminopyridine. Cumulative concentration-effect curves of adenosine and CPA resulted in a negative chronotropic effect culminating in cardiac arrest at 1000μM (adenosine) and 1µM (CPA). Furthermore, ATP produced a negative chronotropic effect at 1-300µM and cardiac arrest at 1000μM in the right atrium. ATPγS (a non-hydrolysable analogue of ATP) reduced chronotropism only. The effects of adenosine, CPA and ATP were inhibited by DPCPX, a selective adenosine A1 receptor antagonist. The selective adenosine A2 and A3 receptors antagonists did not alter the chronotropic response of adenosine. 4-Aminopyridine, a blocker of potassium channels at 10mM, prevented the cardiac arrest produced by adenosine and ATP, while BayK 8644, activator of calcium channels, did not prevent cardiac arrest. Adenosine A1 receptor activation by adenosine and ATP produces cardiac arrest in the right atrium of Wistar rats predominantly through activation of potassium channels. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Use of calcium channel blockers in cardiovascular risk reduction: issues in Latin America.

    Science.gov (United States)

    Alcocer, Luis; Bendersky, Mario; Acosta, Julio; Urina-Triana, Miguel

    2010-01-01

    Cardiovascular disease (CVD) is a continuum that begins with the presence of several risk factors for CVD, including smoking, hypertension, obesity, diabetes mellitus, and high levels of cholesterol, and if unaddressed can result in premature death, ischemic heart disease, stroke, congestive heart failure, and end-stage renal disease. Hypertension is associated with a significant increase in cardiovascular (CV) morbidity and mortality, raising the risk of stroke, myocardial infarction, heart failure, kidney disease, and peripheral arterial disease. In Latin America, the prevalence of hypertension and other CV risk factors has become similar to that seen in more developed countries, increasing the proportion of the population at high risk for CVD and congestive heart failure; however, it is hypertension that is a key driving force behind CV risk in Latin America. Despite the existence of a wide range of antihypertensive agents, BP control and reductions in CV risk remain poor in Latin America and in Hispanics living in the US. Ethnic differences in treatment rates and disease awareness have been well documented. Studies have shown that calcium channel blockers (CCBs; calcium channel antagonists) are at least as effective in reducing BP and improving the CV risk profile as other classes of antihypertensive agents when administered as monotherapy. CCBs have also been shown to be effective when administered as part of combination therapy in both low- and high-risk hypertensive patients, suggesting that CCBs can easily be combined with other antihypertensive classes in order to achieve BP control and CV risk reduction. In patients with hypertension, coronary artery disease, and high cholesterol, CCBs have been associated with beneficial effects on a range of other aspects of the CV continuum, including the vasculature, coronary calcification, and progression of atherosclerosis. CCBs have also been shown to preserve renal function. Unlike diuretics and beta

  5. Spasmolytic activity of Rosmarinus officinalis L. involves calcium channels in the guinea pig ileum.

    Science.gov (United States)

    Ventura-Martínez, Rosa; Rivero-Osorno, Oscar; Gómez, Claudia; González-Trujano, María Eva

    2011-10-11

    Rosmarinus officinalis L. is a plant used around the world for its properties to cure pain in several conditions, such as arthritic and abdominal pain or as an antispasmodic; however, there are no scientific studies demonstrating its spasmolytic activity. Therefore, the aim of the present study was to investigate the effect of an ethanol extract from Rosmarinus officinalis aerial parts and the possible mechanism involved by using rings from the isolated guinea pig ileum (IGPI). The IGPI rings were pre-contracted with potassium chloride (KCl; 60 mM), acetylcholine (ACh; 1 × 10(-9) to 1 × 10(-5)M) or electrical field stimulation (EFS; 0.3 Hz of frequency, 3.0 ms of duration and 14 V intensity) and tested in the presence of the Rosmarinus officinalis ethanol extract (150, 300, 600 and 1 200 μg/mL) or a referenced smooth muscle relaxant (papaverine, 30 μM). In addition, the possible mechanism of action was analyzed in the presence of hexametonium (a ganglionic blocker), indomethacine (an inhibitor of prostaglandins), l-NAME (a selective inhibitor of the nitric oxide synthase) and nifedipine (a calcium channel blocker). Rosmarinus officinalis ethanol extract exhibited a significant and concentration-dependent spasmolytic activity on the contractions induced by KCl (CI(50) = 661.06 ± 155.91 μg/mL); ACh (CI(50) = 464.05 ± 16.85 μg/mL) and EFS (CI(50) = 513.72 ± 34.13 μg/mL). Spasmolytic response of Rosmarinus officinalis (600 μg/mL) was reverted in the presence of nifedipine 1 μM, but not in the presence of hexamethonium 0.5mM, indomethacine 1 μM or L-NAME 100 μM. The present results reinforce the use of Rosmarinus officinalis as antispasmodic in folk medicine. Moreover, it is demonstrated the involvement of calcium channels in this activity, but not the participation of nicotinic receptors, prostaglandins or nitric oxide. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  6. Alcohol Dependence Disrupts Amygdalar L-Type Voltage-Gated Calcium Channel Mechanisms.

    Science.gov (United States)

    Varodayan, Florence P; de Guglielmo, Giordano; Logrip, Marian L; George, Olivier; Roberto, Marisa

    2017-04-26

    L-type voltage-gated calcium channels (LTCCs) are implicated in several psychiatric disorders that are comorbid with alcoholism and involve amygdala dysfunction. Within the amygdala, the central nucleus (CeA) is critical in acute alcohol's reinforcing actions, and its dysregulation in human alcoholics drives their negative emotional state and motivation to drink. Here we investigated the specific role of CeA LTCCs in the effects of acute alcohol at the molecular, cellular physiology, and behavioral levels, and their potential neuroadaptation in alcohol-dependent rats. Alcohol increases CeA activity (neuronal firing rates and GABA release) in naive rats by engaging LTCCs, and intra-CeA LTCC blockade reduces alcohol intake in nondependent rats. Alcohol dependence reduces CeA LTCC membrane abundance and disrupts this LTCC-based mechanism; instead, corticotropin-releasing factor type 1 receptors (CRF1s) mediate alcohol's effects on CeA activity and drive the escalated alcohol intake of alcohol-dependent rats. Collectively, our data indicate that alcohol dependence functionally alters the molecular mechanisms underlying the CeA's response to alcohol (from LTCC- to CRF1-driven). This mechanistic switch contributes to and reflects the prominent role of the CeA in the negative emotional state that drives excessive drinking.SIGNIFICANCE STATEMENT The central amygdala (CeA) plays a critical role in the development of alcohol dependence. As a result, much preclinical alcohol research aims to identify relevant CeA neuroadaptions that promote the transition to dependence. Here we report that acute alcohol increases CeA neuronal activity in naive rats by engaging L-type calcium channels (LTCCs) and that intra-CeA LTCC blockade reduces alcohol intake in nondependent rats. Alcohol dependence disrupts this LTCC-based mechanism; instead, corticotropin-releasing factor type 1 receptors (CRF1s) mediate alcohol's effects on CeA activity and drive the escalated alcohol intake of alcohol

  7. Endoxifen, the active metabolite of tamoxifen, inhibits cloned hERG potassium channels.

    Science.gov (United States)

    Chae, Yun Ju; Lee, Keon Jin; Lee, Hong Joon; Sung, Ki-Wug; Choi, Jin-Sung; Lee, Eun Hui; Hahn, Sang June

    2015-04-05

    The effects of tamoxifen, and its active metabolite endoxifen (4-hydroxy-N-desmethyl-tamoxifen), on hERG currents stably expressed in HEK cells were investigated using the whole-cell patch-clamp technique and an immunoblot assay. Tamoxifen and endoxifen inhibited hERG tail currents at -50mV in a concentration-dependent manner with IC50 values of 1.2 and 1.6μM, respectively. The steady-state activation curve of the hERG currents was shifted to the hyperpolarizing direction in the presence of endoxifen. The voltage-dependent inhibition of hERG currents by endoxifen increased steeply in the voltage range of channel activation. The inhibition by endoxifen displayed a shallow voltage dependence (δ=0.18) in the full activation voltage range. A fast application of endoxifen induced a reversible block of hERG tail currents during repolarization in a concentration-dependent manner, which suggested an interaction with the open state of the channel. Endoxifen also decreased the hERG current elicited by a 5s depolarizing pulse to +60mV to inactivate the hERG currents, suggesting an interaction with the activated (open and/or inactivated) states of the channels. Tamoxifen and endoxifen inhibited the hERG channel protein trafficking to the plasma membrane in a concentration-dependent manner with endoxifen being more potent than tamoxifen. These results indicated that tamoxifen and endoxifen inhibited the hERG current by direct channel blockage and by the disruption of channel trafficking to the plasma membrane in a concentration-dependent manner. A therapeutic concentration of endoxifen inhibited the hERG current by preferentially interacting with the activated (open and/or inactivated) states of the channel. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Inhibition of HERG potassium channels by domiphen bromide and didecyl dimethylammonium bromide.

    Science.gov (United States)

    Long, Yan; Chen, Wanjuan; Lin, Zuoxian; Sun, Hongmao; Xia, Menghang; Zheng, Wei; Li, Zhiyuan

    2014-08-15

    Domiphen bromide and didecyl dimethylammonium bromide were widely used environmental chemicals with potent activity on blockade of human ether-a-go-go related gene (HERG) channels. But the mechanism of their action is not clear. The kinetics of block of HERG channels by domiphen bromide and didecyl dimethylammonium bromide was studied in order to characterize the inhibition of HERG currents by these quaternary ammonium compounds (QACs). Domiphen bromide and didecyl dimethylammonium bromide inhibited HERG channel currents in a dose-dependent manner with IC50 values of 9nM and 5nM, respectively. Block of HERG channel by domiphen bromide and didecyl dimethylammonium bromide was voltage-dependent and use-dependent. Domiphen bromide and didecyl dimethylammonium bromide caused substantial negative shift of the activation curves, accelerated activated process, but had no effects on the deactivation and reactivation processes. The docking models implied that these two compounds bound to PAS domain of HERG channels and inhibited its function. Our data demonstrated that domiphen bromide and didecyl dimethylammonium bromide blocked the HERG channel with a preference for the activated channel state. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Store-operated calcium entry and increased endothelial cell permeability.

    Science.gov (United States)

    Norwood, N; Moore, T M; Dean, D A; Bhattacharjee, R; Li, M; Stevens, T

    2000-11-01

    We hypothesized that myosin light chain kinase (MLCK) links calcium release to activation of store-operated calcium entry, which is important for control of the endothelial cell barrier. Acute inhibition of MLCK caused calcium release from inositol trisphosphate-sensitive calcium stores and prevented subsequent activation of store-operated calcium entry by thapsigargin, suggesting that MLCK serves as an important mechanism linking store depletion to activation of membrane calcium channels. Moreover, in voltage-clamped single rat pulmonary artery endothelial cells, thapsigargin activated an inward calcium current that was abolished by MLCK inhibition. F-actin disruption activated a calcium current, and F-actin stabilization eliminated the thapsigargin-induced current. Thapsigargin increased endothelial cell permeability in the presence, but not in the absence, of extracellular calcium, indicating the importance of calcium entry in decreasing barrier function. Although MLCK inhibition prevented thapsigargin from stimulating calcium entry, it did not prevent thapsigargin from increasing permeability. Rather, inhibition of MLCK activity increased permeability that was especially prominent in low extracellular calcium. In conclusion, MLCK links store depletion to activation of a store-operated calcium entry channel. However, inhibition of calcium entry by MLCK is not sufficient to prevent thapsigargin from increasing endothelial cell permeability.

  10. Chronic Hypoxia Inhibits Pregnancy-Induced Upregulation of SKCa Channel Expression and Function in Uterine Arteries

    Science.gov (United States)

    Zhu, Ronghui; Hu, Xiang-Qun; Xiao, Daliao; Yang, Shumei; Wilson, Sean M.; Longo, Lawrence D.; Zhang, Lubo

    2013-01-01

    Summary Small conductance Ca2+-activated K+ (SKCa) channels are crucial in regulating vascular tone and blood pressure. The present study tested the hypothesis that SKCa channels play an important role in uterine vascular adaptation in pregnancy, which is inhibited by chronic hypoxia during gestation. Uterine arteries were isolated from nonpregnant and near-term pregnant sheep maintained at sea level (~300 m) or exposed to high-altitude (3801 m) hypoxia for 110 days. Immunohistochemistry revealed the presence of SKCa channels type 2 (SK2) and type 3 (SK3) in both smooth muscle and endothelium of uterine arteries. The expression of SK2 and SK3 channels was significantly increased during pregnancy, which was inhibited by chronic hypoxia. In normoxic animals, both SKCa channel opener NS309 and a large-conductance (BKCa) channel opener NS1619 relaxed norepinephrine-contracted uterine arteries in pregnant but not nonpregnant sheep. These relaxations were inhibited by selective SKCa and BKCa channel blockers, respectively. NS309-induced relaxation was largely endothelium-independent. In high altitude hypoxic animals, neither NS1691 nor NS309 produced significant relaxation of uterine arteries in either nonpregnant or pregnant sheep. Similarly, the role of SKCa channels in regulating myogenic reactivity of uterine arteries in pregnant animals was abrogated by chronic hypoxia. Accordingly, the enhanced SKCa channel activity in uterine arterial myocytes of pregnant animals was ablated by chronic hypoxia. The findings suggest a novel mechanism of SKCa channels in regulating myogenic adaptation of uterine arteries in pregnancy, and in the maladaptation of uteroplacental circulation caused by chronic hypoxia during gestation. PMID:23716582

  11. Antagonism of Lidocaine Inhibition by Open-Channel Blockers That Generate Resurgent Na Current

    Science.gov (United States)

    Bant, Jason S.; Aman, Teresa K.; Raman, Indira M.

    2013-01-01

    Na channels that generate resurgent current express an intracellular endogenous open-channel blocking protein, whose rapid binding upon depolarization and unbinding upon repolarization minimizes fast and slow inactivation. Na channels also bind exogenous compounds, such as lidocaine, which functionally stabilize inactivation. Like the endogenous blocking protein, these use-dependent inhibitors bind most effectively at depolarized potentials, raising the question of how lidocaine-like compounds affect neurons with resurgent Na current. We therefore recorded lidocaine inhibition of voltage-clamped, tetrodotoxin-sensitive Na currents in mouse Purkinje neurons, which express a native blocking protein, and in mouse hippocampal CA3 pyramidal neurons with and without a peptide from the cytoplasmic tail of NaVβ4 (the β4 peptide), which mimics endogenous open-channel block. To control channel states during drug exposure, lidocaine was applied with rapid-solution exchange techniques during steps to specific voltages. Inhibition of Na currents by lidocaine was diminished by either the β4 peptide or the native blocking protein. In peptide-free CA3 cells, prolonging channel opening with a site-3 toxin, anemone toxin II, reduced lidocaine inhibition; this effect was largely occluded by open-channel blockers, suggesting that lidocaine binding is favored by inactivation but prevented by open-channel block. In constant 100 μM lidocaine, current-clamped Purkinje cells continued to fire spontaneously. Similarly, the β4 peptide reduced lidocaine-dependent suppression of spiking in CA3 neurons in slices. Thus, the open-channel blocking protein responsible for resurgent current acts as a natural antagonist of lidocaine. Neurons with resurgent current may therefore be less susceptible to use-dependent Na channel inhibitors used as local anesthetic, antiarrhythmic, and anticonvulsant drugs. PMID:23486968

  12. Connexin mimetic peptides fail to inhibit vascular conducted calcium responses in renal arterioles

    DEFF Research Database (Denmark)

    Sørensen, Charlotte Mehlin; Salomonsson, Max; Braunstein, Thomas Hartig

    2008-01-01

    in transmission of conducted vasoconstrictor signals in the preglomerular arterioles is unknown. Connexin mimetic peptides were previously reported to target and inhibit specific connexins. We, therefore, investigated whether conducted vasoconstriction in isolated renal arterioles could be blocked by the use...... of mimetic peptides directed against one or more connexins. Preglomerular resistance vessels were microdissected from kidneys of Sprague-Dawley rats and loaded with fura 2. The vessels were stimulated locally by applying electrical current through a micropipette, and the conducted calcium response...... was measured 500 mum from the site of stimulation. Application of connexin mimetic peptides directed against Cx40, 37/43, 45, or a cocktail with equimolar amounts of each, did not inhibit the propagated response, whereas the nonselective gap junction uncoupler carbenoxolone completely abolished the propagated...

  13. Drug inhibition and proton conduction mechanisms of the influenza a M2 proton channel.

    Science.gov (United States)

    Gu, Ruoxu; Liu, Limin Angela; Wei, Dongqing

    2015-01-01

    The influenza A virus matrix protein 2 (M2 protein) is a pH-regulated proton channel embedded in the viral membrane. Inhibition of the M2 proton channel has been used to treat influenza infections for decades due to the crucial role of this protein in viral infection and replication. However, the widely-used M2 inhibitors, amantadine and rimantadine, have gradually lost their efficiencies because of naturally-occurring drug resistant mutations. Therefore, investigation of the structure and function of the M2 proton channel will not only increase our understanding of this important biological system, but also lead to the design of novel and effective anti-influenza drugs. Despite the simplicity of the M2 molecular structure, the M2 channel is highly flexible and there have been controversies and arguments regarding the channel inhibition mechanism and the proton conduction mechanism. In this book chapter, we will first carefully review the experimental and computational studies of the two possible drug binding sites on the M2 protein and explain the mechanisms regarding how inhibitors prevent proton conduction. Then, we will summarize our recent molecular dynamics simulations of the drug-resistant mutant channels and propose mechanisms for drug resistance. Finally, we will discuss two existing proton conduction mechanisms and talk about the remaining questions regarding the proton-relay process through the channel. The studies reviewed here demonstrate how molecular modeling and simulations have complemented experimental work and helped us understand the M2 channel structure and function.

  14. S-acylation dependent post-translational cross-talk regulates large conductance calcium- and voltage- activated potassium (BK channels

    Directory of Open Access Journals (Sweden)

    Michael J Shipston

    2014-08-01

    Full Text Available Mechanisms that control surface expression and/or activity of large conductance calcium-activated potassium (BK channels are important determinants of their (pathophysiological function. Indeed, BK channel dysfunction is associated with major human disorders ranging from epilepsy to hypertension and obesity. S-acylation (S-palmitoylation represents a major reversible, post-translational modification controlling the properties and function of many proteins including ion channels. Recent evidence reveals that both pore-forming and regulatory subunits of BK channels are S-acylated and control channel trafficking and regulation by AGC-family protein kinases. The pore-forming α-subunit is S-acylated at two distinct sites within the N- and C-terminus, each site being regulated by different palmitoyl acyl transferases (zDHHCs and acyl thioesterases. (APTs. S-acylation of the N-terminus controls channel trafficking and surface expression whereas S-acylation of the C-terminal domain determines regulation of channel activity by AGC-family protein kinases. S-acylation of the regulatory β4-subunit controls ER exit and surface expression of BK channels but does not affect ion channel kinetics at the plasma membrane. Furthermore, a significant number of previously identified BK-channel interacting proteins have been shown, or are predicted to be, S-acylated. Thus, the BK channel multi-molecular signalling complex may be dynamically regulated by this fundamental post-translational modification and thus S-acylation likely represents an important determinant of BK channel physiology in health and disease.

  15. L-type calcium channel blockers, morphine and pain: Newer insights

    Directory of Open Access Journals (Sweden)

    Rakesh Kumar

    2010-01-01

    Full Text Available Earlier, we had reported that co-administration of opioids and L-type calcium channel blockers (L-CCBs like diltiazem could prove useful in the treatment of cancer pain. Much of this report was based upon earlier published work involving animal models of pain exposed to brief periods of noxious radiant heat without any tissue injury. However, pain in clinical situations usually result from tissue injury. Thus, the aim of the current investigation was to study the analgesic effect of this combination of drugs in the rat formalin test which is associated with actual tissue injury. Wistar rats (n=60 received either L-CCB (nifedipine/nimodipine/verapamil/diltiazem i.p. or morphine (s.c. or both drugs. The formalin test was done 30 min after morphine or placebo injection. The naloxone reversal test was also done. Administration of L-CCBs alone, particularly diltiazem, increased pain in the formalin test. In contrast, co-administration of these L-CCBs with morphine led to decreased pain response, though statistically significant decrease was noted only with nimodipine + morphine. Naloxone reversed this analgesic effect, indicating that it was primarily an opioid-mediated effect. The results show that administration of L-CCBs alone may prove counterproductive in the therapeutic management of pain (anti-analgesic effect. However, co-administration of both drugs (morphine and nimodipine in quick succession could lead to adequate pain relief.

  16. Genetic analysis of hyperemesis gravidarum reveals association with intracellular calcium release channel (RYR2).

    Science.gov (United States)

    Fejzo, Marlena Schoenberg; Myhre, Ronny; Colodro-Conde, Lucía; MacGibbon, Kimber W; Sinsheimer, Janet S; Reddy, M V Prasad Linga; Pajukanta, Päivi; Nyholt, Dale R; Wright, Margaret J; Martin, Nicholas G; Engel, Stephanie M; Medland, Sarah E; Magnus, Per; Mullin, Patrick M

    2017-01-05

    Hyperemesis Gravidarum (HG), severe nausea/vomiting in pregnancy (NVP), can cause poor maternal/fetal outcomes. Genetic predisposition suggests the genetic component is essential in discovering an etiology. We performed whole-exome sequencing of 5 families followed by analysis of variants in 584 cases/431 controls. Variants in RYR2 segregated with disease in 2 families. The novel variant L3277R was not found in any case/control. The rare variant, G1886S was more common in cases (p = 0.046) and extreme cases (p = 0.023). Replication of G1886S using Norwegian/Australian data was supportive. Common variants rs790899 and rs1891246 were significantly associated with HG and weight loss. Copy-number analysis revealed a deletion in a patient. RYR2 encodes an intracellular calcium release channel involved in vomiting, cyclic-vomiting syndrome, and is a thyroid hormone target gene. Additionally, RYR2 is a downstream drug target of Inderal, used to treat HG and CVS. Thus, herein we provide genetic evidence for a pathway and therapy for HG. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  17. Effect of Calcium Channel Blockers on Lower Urinary Tract Symptoms: A Systematic Review

    Directory of Open Access Journals (Sweden)

    Muhammad Salman

    2017-01-01

    Full Text Available Background. Numerous medications are known to be associated with the development of lower urinary tract symptoms (LUTS. One such medication group is calcium channel blockers (CCB. Objective. To critically examine the literature regarding the involvement of CCB in manifestation of LUTS in humans. Methods. A systematic literature search was conducted on PubMed, SciELO, Scopus, and OpenGrey databases to find all potentially relevant research studies before August 2016. Results. Five studies met the inclusion criteria and were included in this review. Three out of five studies stated that CCB were involved in either precipitation or exacerbation of LUTS. As for the remaining two studies, one study found out that only the monotherapy of CCB was associated with increased prevalence of nocturia and voiding symptoms in young females, whereas the other study reported an inverse association of CCB with LUTS. The methodological quality of studies was considered high for four studies and low for one study. Conclusion. Healthcare providers should make efforts for an earlier identification of the individuals at risk of LUTS prior to the commencement of CCB therapy. Moreover, patients should be counselled to notify their healthcare provider if they notice urinary symptoms after the initiation of CCB.

  18. Differential effects of calcium channel blockers on size selectivity of proteinuria in diabetic glomerulopathy.

    Science.gov (United States)

    Smith, A C; Toto, R; Bakris, G L

    1998-09-01

    Calcium channel blockers (CCBs) are known to have differential effects on both changes in proteinuria as well as progression of diabetic nephropathy. No clinical study, however, has evaluated whether the differential antiproteinuric effects of CCBs may be explained by their effect on glomerular membrane permeability. We, therefore, tested the hypothesis that certain subclasses of CCBs reduce proteinuria by changing size selectivity of the glomerular membrane, hence changing its permeability. Twenty-one patients with type 2 diabetes and the presence of nephropathy with hypertension were randomized to receive either diltiazem CD or nifedipine GITS after baseline data for mean systolic and diastolic pressure, urinary protein excretion, glomerular filtration rate, renal plasma flow, neutral dextran and IgG clearances were obtained. Glomerular filtration rate, renal plasma flow, neutral dextran and IgG clearance were measured every three months, arterial pressure and heart rate every month. Patients were followed for 21 months. At 21 months, both patient groups had similar levels of blood pressure control, however, only the diltiazem group had a change in proteinuria (4+/-10%delta, nifedipine vs. -57+/-18%delta, diltiazem; P proteinuria do so, in part, by improving glomerular size permselectivity.

  19. The effect of the molecular properties of calcium channel blockers on their elimination route

    Directory of Open Access Journals (Sweden)

    Trbojević-Stanković Jasna B.

    2015-01-01

    Full Text Available Calcium channel blockers (CCBs are among the most widely used drugs in cardiovascular medicine. In this study, nine CCBs (amlodipine, felodipine, isradipine, nicardipine, nifedipine, nimodipine, nisoldipine, verapamil and diltiazem were investigated to assess the relationship between their molecular properties and elimination data obtained from literature. The descriptors of the molecular properties of CCBs were calculated using three software packages. The relationship between computed molecular properties and elimination data collected from relevant literature, initially investigated with simple linear regression analysis, showed poor correlation (R2 <0.25. Application of molecular weight or volume data as additional independent variable, multiple linear regression (MLR revealed better correlations (R2 ~ 0.38 between CCB renal and fecal elimination data and their lipophilicity. Excluding nimodipine from the calculations resulted in more acceptable correlations. The best correlations were established after computed lipophilicity descriptor and molecular weight were applied (R2 = 0.66 with acceptable probability value. [Projekat Ministarstva nauke Republike Srbije, br. TR34031

  20. The Low-Threshold Calcium Channel Cav3.2 Determines Low-Threshold Mechanoreceptor Function

    Directory of Open Access Journals (Sweden)

    Amaury François

    2015-01-01

    Full Text Available The T-type calcium channel Cav3.2 emerges as a key regulator of sensory functions, but its expression pattern within primary afferent neurons and its contribution to modality-specific signaling remain obscure. Here, we elucidate this issue using a unique knockin/flox mouse strain wherein Cav3.2 is replaced by a functional Cav3.2-surface-ecliptic GFP fusion. We demonstrate that Cav3.2 is a selective marker of two major low-threshold mechanoreceptors (LTMRs, Aδ- and C-LTMRs, innervating the most abundant skin hair follicles. The presence of Cav3.2 along LTMR-fiber trajectories is consistent with critical roles at multiple sites, setting their strong excitability. Strikingly, the C-LTMR-specific knockout uncovers that Cav3.2 regulates light-touch perception and noxious mechanical cold and chemical sensations and is essential to build up that debilitates allodynic symptoms of neuropathic pain, a mechanism thought to be entirely A-LTMR specific. Collectively, our findings support a fundamental role for Cav3.2 in touch/pain pathophysiology, validating their critic pharmacological relevance to relieve mechanical and cold allodynia.

  1. eNOS-dependent antisenscence effect of a calcium channel blocker in human endothelial cells.

    Directory of Open Access Journals (Sweden)

    Toshio Hayashi

    Full Text Available Senescence of vascular endothelial cells is an important contributor to the pathogenesis of age-associated vascular disorders such as atherosclerosis. We investigated the effects of antihypertensive agents on high glucose-induced cellular senescence in human umbilical venous endothelial cells (HUVECs. Exposure of HUVECs to high glucose (22 mM for 3 days increased senescence-associated- β-galactosidase (SA-β-gal activity, a senescence marker, and decreased telomerase activity, a replicative senescence marker. The calcium channel blocker nifedipine, but not the β1-adrenergic blocking agent atenolol or the angiotensin-converting enzyme inhibitor perindopril, reduced SA-β-gal positive cells and prevented a decrease in telomerase activity in a high-glucose environment. This beneficial effect of nifedipine was associated with reduced reactive oxygen species (ROS and increased endothelial nitric oxide synthase (eNOS activity. Thus, nifedipine prevented high glucose-induced ROS generation and increased basal eNOS phosphorylation level at Ser-1177. Treatment with N (G-nitro-L-arginine (L-NAME and transfection of small interfering RNA (siRNA targeting eNOS eliminated the anti-senscence effect of nifedipine. These results demonstrate that nifedipine can prevent endothelial cell senescence in an eNOS-dependent manner. The anti-senescence action of nifedipine may represent a novel mechanism by which it protects against atherosclerosis.

  2. Amlodipine, a long-acting calcium channel blocker, attenuates morning blood pressure rise in hypertensive patients.

    Science.gov (United States)

    Ishimitsu, T; Minami, J; Kawano, Y; Numabe, A; Takishita, S; Matsuoka, H

    1999-07-01

    1. The effects of once-daily calcium channel blockers with different plasma half-lives on diurnal blood pressure changes were examined in hypertensive patients. 2. Patients with essential hypertension, nine men and 13 women aged 61 +/- 2 years, were treated with amlodipine or nitrendipine in a random cross-over design for 12-16 weeks each. The study drugs were given once daily as monotherapy (n = 8) or in combination with other classes of antihypertensive drugs (n = 14). The plasma half-life of amlodipine is as long as 36 h, while that of nitrendipine is 10 h. At the end of each treatment period, 24 h ambulatory blood pressure and pulse rate were monitored. 3. Average office blood pressure was comparably controlled below 140/90 mmHg by either amlodipine or nitrendipine, both in the monotherapy and the combination therapy groups; however, pulse rate was greater in nitrendipine than in amlodipine either in the monotherapy (by 6 b.p.m., P morning (05.30-09.00 h) blood pressure was higher in nitrendipine than in amlodipine by 6/4 mmHg in the monotherapy (P morning blood pressure and mitigating reflex activation of the sympathetic nervous system.

  3. Calcium-dependent expression of transient receptor potential canonical type 3 channels in patients with chronic kidney disease

    DEFF Research Database (Denmark)

    Liu, Ying; Krueger, Katharina; Hovsepian, Anahit

    2011-01-01

    It is unknown whether extracellular calcium may regulate the expression of transient receptor potential canonical type 3 (TRPC3) channels in patients with chronic kidney disease. Using quantitative in-cell Western assay we compared the expression of TRPC3 channel protein in monocytes from 20...... patients with chronic kidney disease and 19 age- and sex-matched healthy control subjects. TRPC3 channels were identified by immunoblotting using specific antibodies and TRPC3 protein was further confirmed by mass spectrometry. We observed a significant increase of TRPC3 channel protein expression...... in patients with chronic kidney disease compared to healthy control subjects (normalized expression, 0.42±0.06 vs. 0.19±0.03; p...

  4. Acepromazine inhibits hERG potassium ion channels expressed in human embryonic kidney 293 cells.

    Science.gov (United States)

    Joo, Young Shin; Lee, Hong Joon; Choi, Jin-Sung; Sung, Ki-Wug

    2017-01-01

    The effects of acepromazine on human ether-à-go-go-related gene (hERG) potassium channels were investigated using whole-cell voltage-clamp technique in human embryonic kidney (HEK293) cells transfected with hERG. The hERG currents were recorded with or without acepromazine, and the steady-state and peak tail currents were analyzed for the evaluating the drug effects. Acepromazine inhibited the hERG currents in a concentration-dependent manner with an IC50 value of 1.5 µM and Hill coefficient of 1.1. Acepromazine blocked hERG currents in a voltage-dependent manner between -40 and +10 mV. Before and after application of acepromazine, the half activation potentials of hERG currents changed to hyperpolarizing direction. Acepromazine blocked both the steady-state hERG currents by depolarizing pulse and the peak tail currents by repolarizing pulse; however, the extent of blocking by acepromazine in the repolarizing pulse was more profound than that in the depolarizing pulse, indicating that acepromazine has a high affinity for the open state of the channels, with a relatively lower affinity for the closed state of hERG channels. A fast application of acepromazine during the tail currents inhibited the open state of hERG channels in a concentration-dependent. The steady-state inactivation of hERG currents shifted to the hyperpolarized direction by acepromazine. These results suggest that acepromazine inhibits the hERG channels probably by an open- and inactivated-channel blocking mechanism. Regarding to the fact that the hERG channels are the potential target of drug-induced long QT syndrome, our results suggest that acepromazine can possibly induce a cardiac arrhythmia through the inhibition of hERG channels.

  5. Short-term exposure to L-type calcium channel blocker, verapamil, alters the expression pattern of calcium-binding proteins in the brain of goldfish, Carassius auratus.

    Science.gov (United States)

    Palande, Nikhil V; Bhoyar, Rahul C; Biswas, Saikat P; Jadhao, Arun G

    2015-01-01

    The influx of calcium ions (Ca(2+)) is responsible for various physiological events including neurotransmitter release and synaptic modulation. The L-type voltage dependent calcium channels (L-type VDCCs) transport Ca(2+) across the membrane. Calcium-binding proteins (CaBPs) bind free cytosolic Ca(2+) and prevent excitotoxicity caused by sudden increase in cytoplasmic Ca(2+). The present study was aimed to understand the regulation of expression of neuronal CaBPs, namely, calretinin (CR) and parvalbumin (PV) following blockade of L-type VDCCs in the CNS of Carassius auratus. Verapamil (VRP), a potent L-type VDCC blocker, selectively blocks Ca(2+) entry at the plasma membrane level. VRP present in the aquatic environment at a very low residual concentration has shown ecotoxicological effects on aquatic animals. Following acute exposure for 96h, median lethal concentration (LC50) for VRP was found to be 1.22mg/L for goldfish. At various doses of VRP, the behavioral alterations were observed in the form of respiratory difficulty and loss of body balance confirming the cardiovascular toxicity caused by VRP at higher doses. In addition to affecting the cardiovascular system, VRP also showed effects on the nervous system in the form of altered expression of PV. When compared with controls, the pattern of CR expression did not show any variations, while PV expression showed significant alterations in few neuronal populations such as the pretectal nucleus, inferior lobes, and the rostral corpus cerebellum. Our result suggests possible regulatory effect of calcium channel blockers on the expression of PV. Copyright © 2015 Elsevier Inc. All rights reserved.

  6. Mechanism of inhibition by olanzapine of cloned hERG potassium channels.

    Science.gov (United States)

    Lee, Hong Joon; Choi, Jin-Sung; Hahn, Sang June

    2015-11-16

    Olanzapine is widely used in the treatment of schizophrenia and related psychoses. We investigated the effects of olanzapine on human ether-a-go-go related gene (hERG) channels stably expressed in human embryonic kidney (HEK) cells using the whole-cell patch-clamp technique. Olanzapine inhibited hERG tail currents at -50mV in a concentration-dependent manner with an IC50 value of 8.0μM and a Hill coefficient of 0.9. The voltage-dependent inhibition of the hERG currents by olanzapine increased steeply in the voltage range of channel activation. Olanzapine also shifted the steady-state activation curve of the hERG currents in a hyperpolarizing direction. At more depolarized potentials where the channels were fully activated (between 0 and +50mV), the olanzapine inhibition was voltage-independent. The steady-state inactivation curve of the hERG currents was shifted in the hyperpolarizing direction in the presence of olanzapine. A fast application of olanzapine induced a reversible inhibition of the hERG tail currents during repolarization in a concentration-dependent manner with an IC50 value of 11.9μM, suggesting an open-channel block. Olanzapine also decreased the hERG current elicited by a 5s depolarizing pulse to +60mV to inactivate the hERG currents, suggesting an inhibition of the activated (open and/or inactivated) states of the channels. These results indicated that olanzapine inhibited the hERG current by preferentially interacting with the activated states of the channel. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  7. Comprehensive behavioral analysis of voltage-gated calcium channel beta-anchoring and -regulatory protein knockout mice

    Science.gov (United States)

    Nakao, Akito; Miki, Takafumi; Shoji, Hirotaka; Nishi, Miyuki; Takeshima, Hiroshi; Miyakawa, Tsuyoshi; Mori, Yasuo

    2015-01-01

    Calcium (Ca2+) influx through voltage-gated Ca2+ channels (VGCCs) induces numerous intracellular events such as neuronal excitability, neurotransmitter release, synaptic plasticity, and gene regulation. It has been shown that genes related to Ca2+ signaling, such as the CACNA1C, CACNB2, and CACNA1I genes that encode VGCC subunits, are associated with schizophrenia and other psychiatric disorders. Recently, VGCC beta-anchoring and -regulatory protein (BARP) was identified as a novel regulator of VGCC activity via the interaction of VGCC β subunits. To examine the role of the BARP in higher brain functions, we generated BARP knockout (KO) mice and conducted a comprehensive battery of behavioral tests. BARP KO mice exhibited greatly reduced locomotor activity, as evidenced by decreased vertical activity, stereotypic counts in the open field test, and activity level in the home cage, and longer latency to complete a session in spontaneous T-maze alteration test, which reached “study-wide significance.” Acoustic startle response was also reduced in the mutants. Interestingly, they showed multiple behavioral phenotypes that are seemingly opposite to those seen in the mouse models of schizophrenia and its related disorders, including increased working memory, flexibility, prepulse inhibition, and social interaction, and decreased locomotor activity, though many of these phenotypes are statistically weak and require further replications. These results demonstrate that BARP is involved in the regulation of locomotor activity and, possibly, emotionality. The possibility was also suggested that BARP KO mice may serve as a unique tool for investigating the pathogenesis/pathophysiology of schizophrenia and related disorders. Further evaluation of the molecular and physiological phenotypes of the mutant mice would provide new insights into the role of BARP in higher brain functions. PMID:26136667

  8. Sigma-1 receptor agonist increases axon outgrowth of hippocampal neurons via voltage-gated calcium ions channels.

    Science.gov (United States)

    Li, Dong; Zhang, Shu-Zhuo; Yao, Yu-Hong; Xiang, Yun; Ma, Xiao-Yun; Wei, Xiao-Li; Yan, Hai-Tao; Liu, Xiao-Yan

    2017-12-01

    Sigma-1 receptors (Sig-1Rs) are unique endoplasmic reticulum proteins that have been implicated in both neurodegenerative and ischemic diseases, such as Alzheimer's disease and stroke. Accumulating evidence has suggested that Sig-1R plays a role in neuroprotection and axon outgrowth. The underlying mechanisms of Sig-1R-mediated neuroprotection have been well elucidated. However, the mechanisms underlying the effects of Sig-1R on axon outgrowth are not fully understood. To clarify this issue, we utilized immunofluorescence to compare the axon lengths of cultured naïve hippocampal neurons before and after the application of the Sig-1R agonist, SA4503. Then, electrophysiology and immunofluorescence were used to examine voltage-gated calcium ion channel (VGCCs) currents in the cell membranes and growth cones. We found that Sig-1R activation dramatically enhanced the axonal length of the naïve hippocampal neurons. Application of the Sig-1R antagonist NE100 and gene knockdown techniques both demonstrated the effects of Sig-1R. The growth-promoting effect of SA4503 was accompanied by the inhibition of voltage-gated Ca2+ influx and was recapitulated by incubating the neurons with the L-type, N-type, and P/Q-type VGCC blockers, nimodipine, MVIIA and ω-agatoxin IVA, respectively. This effect was unrelated to glial cells. The application of SA4503 transformed the growth cone morphologies from complicated to simple, which favored axon outgrowth. Sig-1R activation can enhance axon outgrowth and may have a substantial influence on neurogenesis and neurodegenerative diseases. © 2017 John Wiley & Sons Ltd.

  9. Mechanisms of NMDA Receptor- and Voltage-Gated L-Type Calcium Channel-Dependent Hippocampal LTP Critically Rely on Proteolysis That Is Mediated by Distinct Metalloproteinases.

    Science.gov (United States)

    Wiera, Grzegorz; Nowak, Daria; van Hove, Inge; Dziegiel, Piotr; Moons, Lieve; Mozrzymas, Jerzy W

    2017-02-01

    Long-term potentiation (LTP) is widely perceived as a memory substrate and in the hippocampal CA3-CA1 pathway, distinct forms of LTP depend on NMDA receptors (nmdaLTP) or L-type voltage-gated calcium channels (vdccLTP). LTP is also known to be effectively regulated by extracellular proteolysis that is mediated by various enzymes. Herein, we investigated whether in mice hippocampal slices these distinct forms of LTP are specifically regulated by different metalloproteinases (MMPs). We found that MMP-3 inhibition or knock-out impaired late-phase LTP in the CA3-CA1 pathway. Interestingly, late-phase LTP was also decreased by MMP-9 blockade. When both MMP-3 and MMP-9 were inhibited, both early- and late-phase LTP was impaired. Using immunoblotting, in situ zymography, and immunofluorescence, we found that LTP induction was associated with an increase in MMP-3 expression and activity in CA1 stratum radiatum. MMP-3 inhibition and knock-out prevented the induction of vdccLTP, with no effect on nmdaLTP. L-type channel-dependent LTP is known to be impaired by hyaluronic acid digestion. We found that slice treatment with hyaluronidase occluded the effect of MMP-3 blockade on LTP, further confirming a critical role for MMP-3 in this form of LTP. In contrast to the CA3-CA1 pathway, LTP in the mossy fiber-CA3 projection did not depend on MMP-3, indicating the pathway specificity of the actions of MMPs. Overall, our study indicates that the activation of perisynaptic MMP-3 supports L-type channel-dependent LTP in the CA1 region, whereas nmdaLTP depends solely on MMP-9. Various types of long-term potentiation (LTP) are correlated with distinct phases of memory formation and retrieval, but the underlying molecular signaling pathways remain poorly understood. Extracellular proteases have emerged as key players in neuroplasticity phenomena. The present study found that L-type calcium channel-dependent LTP in the CA3-CA1 hippocampal projection is critically regulated by the activity

  10. A high-throughput assay for evaluating state dependence and subtype selectivity of Cav2 calcium channel inhibitors.

    Science.gov (United States)

    Dai, Ge; Haedo, Rodolfo J; Warren, Vivien A; Ratliff, Kevin S; Bugianesi, Randal M; Rush, Alison; Williams, Mark E; Herrington, James; Smith, McHardy M; McManus, Owen B; Swensen, Andrew M

    2008-04-01

    Cav2.2 channels play a critical role in pain signaling by controlling synaptic transmission between dorsal root ganglion neurons and dorsal horn neurons. The Cav2.2-selective peptide blocker ziconotide (Prialt, Elan Pharmaceuticals, Dublin, Ireland) has proven efficacious in pain relief, but has a poor therapeutic index and requires intrathecal administration. This has provided impetus for finding an orally active, state-dependent Cav2.2 inhibitor with an improved safety profile. Members of the Cav2 subfamily of calcium channels are the main contributors to central and peripheral synaptic transmission, but the pharmacological effects of blocking each subtype is not yet defined. Here we describe a high-throughput fluorescent assay using a fluorometric imaging plate reader (FLIPR [Molecular Devices, Sunnyvale, CA]) designed to quickly evaluate the state dependence and selectivity of inhibitors across the Cav2 subfamily. Stable cell lines expressing functional Cav2 channels (Ca(V)alpha, beta(3), and alpha(2)delta subunits) were co-transfected with an inward rectifier (Kir2.3) so that membrane potential, and therefore channel state, could be controlled by external potassium concentration. Following cell incubation in drug with varying concentrations of potassium, a high potassium trigger was added to elicit calcium influx through available, unblocked channels. State-dependent inhibitors that preferentially bind to channels in the open or inactivated state can be identified by their increased potency at higher potassium concentrations, where cells are depolarized and channels are biased towards these states. Although the Cav2 channel subtypes differ in their voltage dependence of inactivation, by adjusting pre-trigger potassium concentrations, the degree of steady-state inactivation can be more closely matched across Cav2 subtypes to assess molecular selectivity.

  11. Selective Small Molecule Activators of TREK-2 Channels Stimulate Dorsal Root Ganglion c-Fiber Nociceptor Two-Pore-Domain Potassium Channel Currents and Limit Calcium Influx.

    Science.gov (United States)

    Dadi, Prasanna K; Vierra, Nicholas C; Days, Emily; Dickerson, Matthew T; Vinson, Paige N; Weaver, C David; Jacobson, David A

    2017-03-15

    The two-pore-domain potassium (K2P) channel TREK-2 serves to modulate plasma membrane potential in dorsal root ganglia c-fiber nociceptors, which tunes electrical excitability and nociception. Thus, TREK-2 channels are considered a potential therapeutic target for treating pain; however, there are currently no selective pharmacological tools for TREK-2 channels. Here we report the identification of the first TREK-2 selective activators using a high-throughput fluorescence-based thallium (Tl+) flux screen (HTS). An initial pilot screen with a bioactive lipid library identified 11-deoxy prostaglandin F2α as a potent activator of TREK-2 channels (EC50 ≈ 0.294 μM), which was utilized to optimize the TREK-2 Tl+ flux assay (Z' = 0.752). A HTS was then performed with 76 575 structurally diverse small molecules. Many small molecules that selectively activate TREK-2 were discovered. As these molecules were able to activate single TREK-2 channels in excised membrane patches, they are likely direct TREK-2 activators. Furthermore, TREK-2 activators reduced primary dorsal root ganglion (DRG) c-fiber Ca2+ influx. Interestingly, some of the selective TREK-2 activators such as 11-deoxy prostaglandin F2α were found to inhibit the K2P channel TREK-1. Utilizing chimeric channels containing portions of TREK-1 and TREK-2, the region of the TREK channels that allows for either small molecule activation or inhibition was identified. This region lies within the second pore domain containing extracellular loop and is predicted to play an important role in modulating TREK channel activity. Moreover, the selective TREK-2 activators identified in this HTS provide important tools for assessing human TREK-2 channel function and investigating their therapeutic potential for treating chronic pain.

  12. Fragile X mental retardation protein controls synaptic vesicle exocytosis by modulating N-type calcium channel density

    Science.gov (United States)

    Ferron, Laurent; Nieto-Rostro, Manuela; Cassidy, John S.; Dolphin, Annette C.

    2014-04-01

    Fragile X syndrome (FXS), the most common heritable form of mental retardation, is characterized by synaptic dysfunction. Synaptic transmission depends critically on presynaptic calcium entry via voltage-gated calcium (CaV) channels. Here we show that the functional expression of neuronal N-type CaV channels (CaV2.2) is regulated by fragile X mental retardation protein (FMRP). We find that FMRP knockdown in dorsal root ganglion neurons increases CaV channel density in somata and in presynaptic terminals. We then show that FMRP controls CaV2.2 surface expression by targeting the channels to the proteasome for degradation. The interaction between FMRP and CaV2.2 occurs between the carboxy-terminal domain of FMRP and domains of CaV2.2 known to interact with the neurotransmitter release machinery. Finally, we show that FMRP controls synaptic exocytosis via CaV2.2 channels. Our data indicate that FMRP is a potent regulator of presynaptic activity, and its loss is likely to contribute to synaptic dysfunction in FXS.

  13. First direct electron microscopic visualization of a tight spatial coupling between GABAA-receptors and voltage-sensitive calcium channels

    DEFF Research Database (Denmark)

    Hansen, G H; Belhage, B; Schousboe, A

    1992-01-01

    Using cerebellar granule neurons in culture it was demonstrated that exposure of the cells to the GABAA receptor agonist 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP) leads to an increase in the number of voltage-gated calcium channels as revealed by quantitative preembedding indirect imm...... of THIP-treated cultures. This suggests that primarily low affinity GABAA-receptors are closely associated with Ca2+ channels and this may be important for the ability of these receptors to mediate an inhibitory action on transmitter release even under extreme depolarizing conditions....

  14. The effects of calcium channel blockade on agouti-induced obesity

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jung Han; Moustaid, N.; Zemel, M.B. [Univ. of Tennessee, Knoxville, TN (United States)] [and others

    1996-12-01

    We have previously observed that obese viable yellow (A{sup vy}/a) mice exhibit increased intracellular Ca{sup 2+} ([Ca{sup 2+}]i) and fatty acid synthase (FAS) gene expression; further, recombinant agouti protein increases in cultured adipocytes and these effects are inhibited by Ca{sup 2+} channel blockade. Accordingly, we determined the effect of Ca{sup 2+} channel blockade (nifedipine for 4 wk) on FAS and obesity in transgenic mice expressing the agouti gene in a ubiquitous manner. The transgenic mice initially were significantly heavier (30.5 {+-} 0.6 vs. 27.3 {+-} 0.3 g; P<0.001) and exhibited a 0.81{degrees}C lower initial core temperature (P<0.0005), an approximately twofold increase in fat pad weights (P=0.002), a sevenfold increase in adipose FAS activity (P=0.009), and a twofold increase in plasma insulin level (P<0.05) compared to control mice. Nifedipine treatment resulted in an 18% decrease in fat pad weights (P<0.007) and a 74% decrease in adipose FAS activity (P=0.03), normalized circulating insulin levels and insulin sensitivity (P,0.05), and transiently elevated core temperature in the transgenic mice, but was without effect in the control mice. These data suggest that agouti regulates FAS, fat storage, and possibly thermogenesis, at least partially, via a [Ca{sup 2+}]{sub i}-dependent mechanism, and that Ca{sup 2+} channel blockade may partially attenuate agouti-induced obesity. 42 refs., 4 figs., 1 tab.

  15. NecroX-5 prevents breast cancer metastasis by AKT inhibition via reducing intracellular calcium levels.

    Science.gov (United States)

    Park, Jin-Hee; Kim, Hyoung Kyu; Jung, Hana; Kim, Ki Hyang; Kang, Mi Seon; Hong, Jun Hyuk; Yu, Byeng Chul; Park, Sungjae; Seo, Su-Kil; Choi, Il Whan; Kim, Soon Ha; Kim, Nari; Han, Jin; Park, Sae Gwang

    2017-01-01

    A major goal of breast cancer research is to prevent the molecular events that lead to tumour metastasis. It is well-established that both cytoplasmic and mitochondrial reactive oxygen species (ROS) play important roles in cell migration and metastasis. Accordingly, this study examined the molecular mechanisms of the anti-metastatic effects of NecroX-5, a mitochondrial ROS scavenger. NecroX-5 inhibited lung cancer metastasis by ameliorating migration in a mouse model. In human cancer cells, the inhibition of migration by NecroX-5 is cell type-dependent. We observed that the effect of NecroX-5 correlated with a reduction in mitochondrial ROS, but mitochondrial ROS reduction by MitoQ did not inhibit cell migration. NecroX-5 decreased intracellular calcium concentration by blocking Ca2+ influx, which mediated the inhibition of cell migration, AKT downregulation and the reduction of mitochondrial ROS levels. However, the reduction of mitochondrial ROS was not associated with supressed migration and AKT downregulation. Our study demonstrates the potential of NecroX-5 as an inhibitor of breast cancer metastasis.

  16. Calcium Dobesilate Prevents Diabetic Kidney Disease by Decreasing Bim and Inhibiting Apoptosis of Renal Proximal Tubular Epithelial Cells.

    Science.gov (United States)

    Cai, Tian; Wu, Xiao-Yun; Zhang, Xiao-Qian; Shang, Hong-Xia; Zhang, Zhong-Wen; Liao, Lin; Dong, Jian-Jun

    2017-04-01

    Apoptosis of renal proximal tubular epithelial cells (PTECs) plays a vital role in the pathogenesis and progression of diabetic kidney disease (DKD). Calcium dobesilate is a vascular protective compound used for treatment of diabetic retinopathy and chronic venous insufficiency. The aim of this study was to determine whether calcium dobesilate can protect PTECs from glucose-induced apoptosis and the potential mechanism of this effect. It is indicated that high glucose promoted abnormal apoptosis of HK2 cells, which was inhibited by treatment of calcium dobesilate, while Bim expression decreased in response to calcium dobesilate in high-glucose-treated HK2 cells. These findings confirmed the therapeutic effects of calcium dobesilate on DKD and emphasized the importance of it as a potentially crucial drug in treatment of DKD.

  17. Electromagnetic fields act via activation of voltage-gated calcium channels to produce beneficial or adverse effects

    OpenAIRE

    Pall, Martin L

    2013-01-01

    The direct targets of extremely low and microwave frequency range electromagnetic fields (EMFs) in producing non-thermal effects have not been clearly established. However, studies in the literature, reviewed here, provide substantial support for such direct targets. Twenty-three studies have shown that voltage-gated calcium channels (VGCCs) produce these and other EMF effects, such that the L-type or other VGCC blockers block or greatly lower diverse EMF effects. Furthermore, the voltage-gat...

  18. High Glucose Represses hERG K+ Channel Expression through Trafficking Inhibition.

    Science.gov (United States)

    Shi, Yuan-Qi; Yan, Meng; Liu, Li-Rong; Zhang, Xiao; Wang, Xue; Geng, Huai-Ze; Zhao, Xin; Li, Bao-Xin

    2015-01-01

    Abnormal QT prolongation is the most prominent cardiac electrical disturbance in patients with diabetes mellitus (DM). It is well known that the human ether-ago-go-related gene (hERG) controls the rapid delayed rectifier K+ current (IKr) in cardiac cells. The expression of the hERG channel is severely down-regulated in diabetic hearts, and this down-regulation is a critical contributor to the slowing of repolarization and QT prolongation. However, the intracellular mechanisms underlying the diabetes-induced hERG deficiency remain unknown. The expression of the hERG channel was assessed via western blot analysis, and the hERG current was detected with a patch-clamp technique. The results of our study revealed that the expression of the hERG protein and the hERG current were substantially decreased in high-glucose-treated hERG-HEK cells. Moreover, we demonstrated that the high-glucose-mediated damage to the hERG channel depended on the down-regulation of protein levels but not the alteration of channel kinetics. These discoveries indicated that high glucose likely disrupted hERG channel trafficking. From the western blot and immunoprecipitation analyses, we found that high glucose induced trafficking inhibition through an effect on the expression of Hsp90 and its interaction with hERG. Furthermore, the high-glucose-induced inhibition of hERG channel trafficking could activate the unfolded protein response (UPR) by up-regulating the expression levels of activating transcription factor-6 (ATF-6) and the ER chaperone protein calnexin. In addition, we demonstrated that 100 nM insulin up-regulated the expression of the hERG channel and rescued the hERG channel repression caused by high glucose. The results of our study provide the first evidence of a high-glucose-induced hERG channel deficiency resulting from the inhibition of channel trafficking. Furthermore, insulin promotes the expression of the hERG channel and ameliorates the high-glucose-induced inhibition of the h

  19. High Glucose Represses hERG K+ Channel Expression through Trafficking Inhibition

    Directory of Open Access Journals (Sweden)

    Yuan-Qi Shi

    2015-08-01

    Full Text Available Background/Aims: Abnormal QT prolongation is the most prominent cardiac electrical disturbance in patients with diabetes mellitus (DM. It is well known that the human ether-ago-go-related gene (hERG controls the rapid delayed rectifier K+ current (IKr in cardiac cells. The expression of the hERG channel is severely down-regulated in diabetic hearts, and this down-regulation is a critical contributor to the slowing of repolarization and QT prolongation. However, the intracellular mechanisms underlying the diabetes-induced hERG deficiency remain unknown. Methods: The expression of the hERG channel was assessed via western blot analysis, and the hERG current was detected with a patch-clamp technique. Results: The results of our study revealed that the expression of the hERG protein and the hERG current were substantially decreased in high-glucose-treated hERG-HEK cells. Moreover, we demonstrated that the high-glucose-mediated damage to the hERG channel depended on the down-regulation of protein levels but not the alteration of channel kinetics. These discoveries indicated that high glucose likely disrupted hERG channel trafficking. From the western blot and immunoprecipitation analyses, we found that high glucose induced trafficking inhibition through an effect on the expression of Hsp90 and its interaction with hERG. Furthermore, the high-glucose-induced inhibition of hERG channel trafficking could activate the unfolded protein response (UPR by up-regulating the expression levels of activating transcription factor-6 (ATF-6 and the ER chaperone protein calnexin. In addition, we demonstrated that 100 nM insulin up-regulated the expression of the hERG channel and rescued the hERG channel repression caused by high glucose. Conclusion: The results of our study provide the first evidence of a high-glucose-induced hERG channel deficiency resulting from the inhibition of channel trafficking. Furthermore, insulin promotes the expression of the hERG channel

  20. Structure-function of proteins interacting with the α1 pore-forming subunit of high-voltage-activated calcium channels

    Science.gov (United States)

    Neely, Alan; Hidalgo, Patricia

    2014-01-01

    Openings of high-voltage-activated (HVA) calcium channels lead to a transient increase in calcium concentration that in turn activate a plethora of cellular functions, including muscle contraction, secretion and gene transcription. To coordinate all these responses calcium channels form supramolecular assemblies containing effectors and regulatory proteins that couple calcium influx to the downstream signal cascades and to feedback elements. According to the original biochemical characterization of skeletal muscle Dihydropyridine receptors, HVA calcium channels are multi-subunit protein complexes consisting of a pore-forming subunit (α1) associated with four additional polypeptide chains β, α2, δ, and γ, often referred to as accessory subunits. Twenty-five years after the first purification of a high-voltage calcium channel, the concept of a flexible stoichiometry to expand the repertoire of mechanisms that regulate calcium channel influx has emerged. Several other proteins have been identified that associate directly with the α1-subunit, including calmodulin and multiple members of the small and large GTPase family. Some of these proteins only interact with a subset of α1-subunits and during specific stages of biogenesis. More strikingly, most of the α1-subunit interacting proteins, such as the β-subunit and small GTPases, regulate both gating and trafficking through a variety of mechanisms. Modulation of channel activity covers almost all biophysical properties of the channel. Likewise, regulation of the number of channels in the plasma membrane is performed by altering the release of the α1-subunit from the endoplasmic reticulum, by reducing its degradation or enhancing its recycling back to the cell surface. In this review, we discuss the structural basis, interplay and functional role of selected proteins that interact with the central pore-forming subunit of HVA calcium channels. PMID:24917826

  1. Structure-function of proteins interacting with the alpha1 pore-forming subunit of high voltage-activated calcium channel

    Directory of Open Access Journals (Sweden)

    Alan eNeely

    2014-06-01

    Full Text Available Openings of high-voltage-activated calcium channels lead to a transient increase in calcium concentration that in turn activate a plethora of cellular functions, including muscle contraction, secretion and gene transcription. To coordinate all these responses calcium channels form supramolecular assemblies containing effectors and regulatory proteins that couple calcium influx to the downstream signal cascades and to feedback elements. According to the original biochemical characterization of skeletal muscle Dihydropyridine receptors, high-voltage-activated calcium channels are multi-subunit protein complexes consisting of a pore-forming subunit (α1 associated with four additional polypeptide chains β, α2, δ and γ, often referred to as accessory subunits. Twenty-five years after the first purification of a high-voltage calcium channel, the concept of a flexible stoichiometry to expand the repertoire of mechanisms that regulate calcium channel influx has emerged. Several other proteins have been identified that associate directly with the α1-subunit, including calmodulin and multiple members of the small and large GTPase family. Some of these proteins only interact with a subset of α1-subunits and during specific stages of biogenesis. More strikingly, most of the α1-subunit interacting proteins, such as the β-subunit and small GTPases, regulate both gating and trafficking through a variety of mechanisms. Modulation of channel activity covers almost all biophysical properties of the channel. Likewise, regulation of the number of channels in the plasma membrane is performed by altering the release of the α1-subunit from the endoplasmic reticulum, by reducing its degradation or enhancing its recycling back to the cell surface. In this review, we discuss the structural basis, interplay and functional role of selected proteins that interact with the central pore-forming subunit of high-voltage-activated calcium channels.

  2. Channelrhodopsin-2-expressed dorsal root ganglion neurons activates calcium channel currents and increases action potential in spinal cord.

    Science.gov (United States)

    Zhang, Yi; Yue, Jing; Ai, Midan; Ji, Zhigang; Liu, Zhiguo; Cao, Xuehong; Li, Li

    2014-07-01

    We used optogenetic techniques in spinal cord and dorsal root ganglion (DRG) neuron studies. This study investigated changes in channelrhodopsin-2 (ChR2) expression in the spinal cord and DRG neurons using optogenetic techniques. The results show the possibility of using optogenetics to treat neuropathic pain. Previous studies have shown that activated ChR2 induces an increase in DRG neuron action potential. Western blot analysis was used to measure ChR2 protein levels in the spinal cord and DRG neurons or rats intrathecally injected with ChR2 lentivirus. Electrophysiology recording was used to detect differences in action potential levels in the spinal cord and calcium channel currents in the DRG neurons. Our studies showed that ChR2 expression increased the action potential in the spinal cord and increased calcium channel currents in DRG neurons. We successfully expressed the ChR2 protein in the spinal cord and DRG neurons. We also found that ChR2 increased the action potential in the spinal cord and activated the calcium channel in DRG neurons. These findings support the research possibilities of using optogenetic studies to improve treatment for neuropathic pain. N/A.

  3. Clinical features of neuromuscular disorders in patients with N-type voltage-gated calcium channel antibodies

    Directory of Open Access Journals (Sweden)

    Andreas Totzeck

    2016-09-01

    Full Text Available Neuromuscular junction disorders affect the pre- or postsynaptic nerve to muscle transmission due to autoimmune antibodies. Members of the group like myasthenia gravis and Lambert-Eaton syndrome have pathophysiologically distinct characteristics. However, in practice, distinction may be difficult. We present a series of three patients with a myasthenic syndrome, dropped-head syndrome, bulbar and respiratory muscle weakness and positive testing for anti-N-type voltage-gated calcium channel antibodies. In two cases anti-acetylcholin receptor antibodies were elevated, anti-P/Q-type voltage-gated calcium channel antibodies were negative. All patients initially responded to pyridostigmine with a non-response in the course of the disease. While one patient recovered well after treatment with intravenous immunoglobulins, 3,4-diaminopyridine, steroids and later on immunosuppression with mycophenolate mofetil, a second died after restriction of treatment due to unfavorable cancer diagnosis, the third patient declined treatment. Although new antibodies causing neuromuscular disorders were discovered, clinical distinction has not yet been made. Our patients showed features of pre- and postsynaptic myasthenic syndrome as well as severe dropped-head syndrome and bulbar and axial muscle weakness, but only anti-N-type voltage-gated calcium channel antibodies were positive. When administered, one patient benefited from 3,4-diaminopyridine. We suggest that this overlap-syndrome should be considered especially in patients with assumed seronegative myasthenia gravis and lack of improvement under standard therapy.

  4. Effect of MCI-176, a new calcium channel blocker, on large and small coronary arteries in dogs.

    Science.gov (United States)

    Ishibashi, T; Nakazawa, M; Imai, S

    1989-04-01

    MCI-176, a new calcium channel blocker, increases coronary blood flow and may improve perfusion in ischaemic areas. Its vasodilating effects on large conductive coronary arteries and the resistive arterioles were therefore compared with those of diltiazem, nifedipine, glyceryl trinitrate and adenosine in anaesthetised open chest beagle dogs. Intracoronary injection of these compounds caused dose dependent increases in coronary flow associated with decreases in the resistance of resistive arterioles, and the rank order of potency was nifedipine greater than adenosine greater than MCI-176 greater than diltiazem greater than glyceryl trinitrate. The resistance of the large conductive vessels was likewise reduced by these agents, except for adenosine. Glyceryl trinitrate showed the highest selectivity to the large conductive vessels, while adenosine showed the lowest and calcium channel blockers were intermediate. Among three calcium channel blockers, MCI-176 had the highest selectivity to the large conductive vessels, while the duration of action was the longest with diltiazem; the duration of action of MCI-176 was intermediate. Thus, MCI-176 is a coronary vasodilator, the potency of which is intermediate between nifedipine and diltiazem, but it has the highest selectivity to the large conductive vessels among these three compounds.

  5. Small-cell lung cancer with voltage-gated calcium channel antibody-positive paraneoplastic limbic encephalitis: a case report.

    Science.gov (United States)

    Kaira, Kyoichi; Okamura, Takashi; Takahashi, Hiroki; Horiguchi, Norio; Sunaga, Noriaki; Hisada, Takeshi; Yamada, Masanobu

    2014-04-08

    Paraneoplastic limbic encephalitis is a rare neurological syndrome and clinically characterized by cognitive dysfunction, memory impairment, seizures and psychiatric symptoms. Paraneoplastic limbic encephalitis is most frequently found in small-cell lung cancer, among various malignancies, and antineuronal antibodies are related to the autoimmune mechanism. We experienced a rare case of a patient with small-cell lung cancer with anti-voltage-gated calcium channel antibody-positive paraneoplastic limbic encephalitis. A 61-year-old Japanese man with a history of smoking cigarettes presented with seizure, confusion and personality change in acute onset. Brain magnetic resonance imaging showed high signal intensity on T2-weighted image in his right temporal lobe, suggestive of limbic encephalitis. A mediastinoscopy of the lymph node revealed small-cell lung carcinoma, and he was staged as having limited stage disease. Antibodies against P/Q-type and N-type voltage-gated calcium channel were positive and Hu antibody was negative. He was started on chemotherapy of carboplatin plus etoposide with concurrent thoracic radiotherapy. Neurological symptoms were gradually improved after systemic chemotherapy. We should be alert to the potential of malignant neoplasms associated with paraneoplastic limbic encephalitis when we examine a patient with cancer with neurological disorders such as personality change, disorientation, unconsciousness and memory loss. A clinical marker such as voltage-gated calcium channel antibody may help our diagnosis in clinical practice.

  6. Calcium channel blockers shorten the periodicity of ultradian variation in blood pressure in patients with essential hypertension.

    Science.gov (United States)

    Kawamura, H; Mitsubayashi, H; Saito, T; Kanmatsuse, K; Saito, N

    1998-09-01

    We studied ultradian and circadian variations in blood pressure (BP) in patients with essential hypertension who were receiving antihypertensive agents. No patient had previously received antihypertensive agents before this study began. After a 2-wk control period, we performed ambulatory blood pressure monitoring (ABPM) in 86 patients with essential hypertension (WHO stages I or II). The patients were then given a long-acting angiotensin converting enzyme inhibitor (ACEI) (captopril or imidapril), a beta-receptor blocker (arotinolol or bisoprolol), or a calcium channel blocker (nisoldipine or benidipine) twice daily to control BP. We evaluated the patients' BP once every 2 wk to ensure optimal control. After 12 wk, ultradian and circadian variations in BP were analyzed by the maximum entropy method (MEM). All antihypertensive agents decreased office systolic BP (SBP), office diastolic BP (DBP), 24-h SBP, and 24-h DBP. ACEI did not change office, 24-h, daytime, or nighttime pulse rate (PR). Arotinolol and bisoprolol decreased 24-h PR. All antihypertensive agents decreased 24-h, daytime, and nighttime pressure rate product. MEM showed that no antihypertensive agent affected the circadian variation in the 1st peak (24-h periodicity) of SBP, DBP, or PR. However, calcium channel blockers shortened the periodicity of circadian variations in the 2nd peak (12-h periodicity) of SBP and the 3rd peak (8 to 6 h periodicity) of SBP. Therefore, ultradian variations in BP should be carefully monitored in hypertensive patients treated with calcium channel blockers.

  7. Synthesis and Effects of Novel Dihydropyridines as Dual Calcium Channel Blocker and Angiotensin Antagonist on Isolated Rat Aorta

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    Farzin Hadizadeh

    2010-01-01

    Full Text Available Four novel losartan analogues 5a-d were synthesized by connecting a dihydropyridine nucleus to imidazole ring. The effects of 5a and 5b on angiotensin receptors (AT1 and L-type calcium channels were investigated on isolated rat aorta. Materials and MethodsAortic rings were pre-contracted with 1 µM Angiotensin II or 80 mM KCl and relaxant effects of losartan, nifedipine, 5a and 5b were evaluated by cumulative addition of these drugs to the bath solution.ResultsThe results showed that compounds 5a and 5b have both L-type calcium channel and AT1 receptor blocking activity. Their effects on AT1 receptors are 1000 and 100,000 times more than losartan respectively. The activity of compound 5b on L-type calcium channel is significantly less than nifedipine but compound 5a has comparable effect with nifedipine. ConclusionFinally we concluded that these two new Compounds can be potential candidates to be used as effective antihypertensive agents.

  8. Concentrative biliary secretion of ceftriaxone. Inhibition of lipid secretion and precipitation of calcium ceftriaxone in bile.

    Science.gov (United States)

    Xia, Y; Lambert, K J; Schteingart, C D; GU, J J; Hofmann, A F

    1990-08-01

    The hepatic transport of ceftriaxone, a third-generation cephalosporin, was characterized in the rat and hamster; its effect on bile flow and bile acid-induced biliary lipid secretion was also measured. In anesthetized rats with biliary fistulae, the Tmax was about 5 mumol.min-1.kg-1, and in the hamster the Tmax was about 1 mumol.min-1.kg-1. The compound was not biotransformed. At high secretion rates, the concentration of cephalosporin in bile increased to 27 mmol/L, a concentration far exceeding the solubility product of its calcium salt [2 x 10(-6) (mol/L)2], which precipitated from bile. In the rat, ceftriaxone induced choleresis (22 microL/mumol ceftriaxone, the expected value for a dianionic compound). In the isolated perfused rat liver, ceftriaxone had a fractional hepatic extraction rate averaging 3%; the compound was concentratively secreted into bile, the bile-perfusate ratio ranging from 35-250. Ceftriaxone inhibited phospholipid and cholesterol secretion induced by endogenous or exogenous bile acids; the rate of inhibition was linearly proportional to the canalicular secretion rate of ceftriaxone. Hepatic transport of ceftriaxone had no influence on hepatic secretion of ursodeoxycholyltaurine. In contrast, the net hepatic transport of ursodeoxycholic acid, ursodeoxycholyltaurine, or cholyltaurine inhibited ceftriaxone transport in a dose-dependent manner. It is concluded that ceftriaxone and bile acids share a common mechanism for hepatic transport in the rat and also interact in the processes involved in biliary lipid secretion. Biliary secretion of unbiotransformed ceftriaxone occurs at high concentrations; secondary Ca2+ entry results in the formation of supersaturated canalicular bile and subsequent precipitation as a calcium salt in the biliary tract. These data explain the formation of biliary sludge that occurs in patients undergoing high-dose ceftriaxone therapy.

  9. Vasorelaxant and antihypertensive effects of ZCM298, a dihydropyridine derivative, are through inhibiting extracellular calcium influx.

    Science.gov (United States)

    Zhang, Li-Xin; Chen, Xin-lin; Yang, Peng-bo; Zhang, San-Qi; Cao, Yong-Xiao

    2013-01-01

    ZCM298 is a novel 1,4-dihydropyridine derivative. The aim of the study was to investigate its vasodilation and hypotension, and the related mechanisms. The isometric tension of artery ring segments was recorded using an in vitro myography system. The blood pressure of spontaneously hypertensive rats (SHRs) was measured in vivo using a non-invasive tail cuff blood pressure system. Changes in the intracellular calcium concentration ([Ca2+]i) in the mesenteric artery were surveyed using real-time confocal microscopy. Regional cerebral blood flow (rCBF) in the pia mater was monitored by laser-Doppler flowmetry (LDP). ZCM298 (10(-9)-10(-4) M) relaxed rat mesenteric artery obviously and concentration-dependently, which was not affected by the removal of the endothelium. ZCM298 shifted the concentration-contractile curves of mesenteric arteries in response to phenylephrine, U46619, KCl and CaCl2 towards the right in a non-parallel manner. The potency of ZCM298 on relaxing basilar artery was much higher than on mesenteric artery. ZCM298 did not depress the phenylephrine-induced vasoconstriction; however, it inhibited the contraction caused by the addition of CaCl2 in Ca2+-free solution. ZCM298 (10(-6) M) inhibited the increase of [Ca2+]i induced by KCl in the artery. ZCM298 improved the rCBF in the pia mater of rats at 0.03 and 0.06 mg/kg. ZCM298 depressed the systolic and diastolic blood pressure of SHRs in a dose-dependent manner. ZCM298 relaxes arteries probably through inhibiting extracellular calcium influx and decreases the blood pressure of SHRs. ZCM298 is more potent in the basilar artery than in the mesenteric artery and improves rCBF in the pia mater of rats.

  10. Activation of L-type calcium channel in twitch skeletal muscle fibres of the frog.

    Science.gov (United States)

    Francini, F; Bencini, C; Squecco, R

    1996-07-01

    1. The activation of the L-type calcium current (ICa) was studied in normally polarized (-100 mV) cut skeletal muscle fibres of the frog with the double Vaseline-gap voltage-clamp technique. Both external and internal solutions were Ca2+ buffered. Solutions were made in order to minimize all but the Ca2+ current. 2. The voltage-dependent components of the time course of activation were determined by two procedures: fast and slow components were evaluated by multiexponential fitting to current traces elicited by long voltage pulses (5 s) after removing inactivation; fast components were also determined by short voltage pulses having different duration (0.5-70 ms). 3. The components of deactivation were evaluated after removing the charge-movement current from the total tail current by the difference between two short (50 and 70 ms) voltage pulses to 10 mV, moving the same intramembrane charge. Two exponential components, fast and slow (time constants, 6 +/- 0.3 and 90 +/- 7 ms at -100 mV; n = 26), were found. 4. The time onset of ICa was evaluated either by multiexponential fitting to the ICa activation or by pulses of different duration to test the beginning of the 'on' and 'off' inequality. This was at about 2 ms, denoting that it was very early. 5. The time constant vs. voltage plots indicated the presence of four voltage-dependent components in the activation pathway. Various kinetic models are discussed. Models with independent transitions, like a Hodgkin-Huxley scheme, were excluded. Suitable models were a five-state sequential and a four-state cyclic with a branch scheme. The latter gave the best simulation of the data. 6. The steady-state activation curve saturated at high potentials. It had a half-voltage value of 1 +/- 0.2 mV and the opening probability was only 0.82 +/- 0.2 at 20 mV (n = 32). This result implies a larger number of functional calcium channels than was previously supposed and is in agreement with the number of dihydropyridine (DHP

  11. Inhibition of cloned hERG potassium channels by risperidone and paliperidone.

    Science.gov (United States)

    Lee, Hong Joon; Choi, Jin-Sung; Choi, Bok Hee; Hahn, Sang June

    2017-06-01

    Risperidone and one of its active metabolites, paliperidone, are widely used for the treatment of schizophrenia. We used a patch-clamp study to investigate the effects of paliperidone on hERG potassium channels expressed in HEK cells. Western blot analyses were used to study the effects of risperidone and paliperidone on hERG and hERG 3.1 isoform channel trafficking. Risperidone and paliperidone inhibited the hERG tail currents in a concentration-dependent manner with IC 50 values of 0.16 and 0.57 μM, respectively. The block of hERG currents by paliperidone was voltage-dependent, increasing over a range of voltages for channel activation. A fast application of paliperidone inhibited the hERG current elicited by a 5-s depolarizing pulse to +60 mV to fully inactivate the hERG currents, suggesting an inactivated state block. A fast application of paliperidone during repolarization reversibly inhibited the hERG tail currents in a concentration-dependent manner with a IC 50 value of 1.26 μM. Kinetic analysis of paliperidone interaction with the open state of the hERG channels showed that the rate constants of association (k +1 ) and dissociation (k -1 ) for paliperidone were 0.45 μM -1  s -1 and 1.07 s -1 , respectively. Paliperidone shifted the steady-state inactivation curve of the hERG currents in a hyperpolarizing direction and also produced a use-dependent block. Risperidone and paliperidone had no effect on hERG and hERG 3.1 channel trafficking to the cell membrane. Our results indicated that paliperidone inhibited the hERG current by preferentially interacting with the open and inactivated states of the channel, but not by disruption of hERG channel protein trafficking.

  12. Amino acid substitutions in the FXYD motif enhance phospholemman-induced modulation of cardiac L-type calcium channels.

    Science.gov (United States)

    Guo, Kai; Wang, Xianming; Gao, Guofeng; Huang, Congxin; Elmslie, Keith S; Peterson, Blaise Z

    2010-11-01

    We have found that phospholemman (PLM) associates with and modulates the gating of cardiac L-type calcium channels (Wang et al., Biophys J 98: 1149-1159, 2010). The short 17 amino acid extracellular NH(2)-terminal domain of PLM contains a highly conserved PFTYD sequence that defines it as a member of the FXYD family of ion transport regulators. Although we have learned a great deal about PLM-dependent changes in calcium channel gating, little is known regarding the molecular mechanisms underlying the observed changes. Therefore, we investigated the role of the PFTYD segment in the modulation of cardiac calcium channels by individually replacing Pro-8, Phe-9, Thr-10, Tyr-11, and Asp-12 with alanine (P8A, F9A, T10A, Y11A, D12A). In addition, Asp-12 was changed to lysine (D12K) and cysteine (D12C). As expected, wild-type PLM significantly slows channel activation and deactivation and enhances voltage-dependent inactivation (VDI). We were surprised to find that amino acid substitutions at Thr-10 and Asp-12 significantly enhanced the ability of PLM to modulate Ca(V)1.2 gating. T10A exhibited a twofold enhancement of PLM-induced slowing of activation, whereas D12K and D12C dramatically enhanced PLM-induced increase of VDI. The PLM-induced slowing of channel closing was abrogated by D12A and D12C, whereas D12K and T10A failed to impact this effect. These studies demonstrate that the PFXYD motif is not necessary for the association of PLM with Ca(V)1.2. Instead, since altering the chemical and/or physical properties of the PFXYD segment alters the relative magnitudes of opposing PLM-induced effects on Ca(V)1.2 channel gating, PLM appears to play an important role in fine tuning the gating kinetics of cardiac calcium channels and likely plays an important role in shaping the cardiac action potential and regulating Ca(2+) dynamics in the heart.

  13. A blocker of N- and T-type voltage-gated calcium channels attenuates ethanol-induced intoxication, place preference, self-administration, and reinstatement.

    Science.gov (United States)

    Newton, Philip M; Zeng, Lily; Wang, Victoria; Connolly, Jacklyn; Wallace, Melisa J; Kim, Chanki; Shin, Hee-Sup; Belardetti, Francesco; Snutch, Terrance P; Messing, Robert O

    2008-11-05

    There is a clear need for new therapeutics to treat alcoholism. Here, we test our hypothesis that selective inhibitors of neuronal calcium channels will reduce ethanol consumption and intoxication, based on our previous studies using knock-out mice and cell culture systems. We demonstrate that pretreatment with the novel mixed N-type and T-type calcium channel antagonist 1-(6,6-bis(4-fluorophenyl)hexyl)-4-(3,4,5-trimethoxybenzyl)piperazine (NP078585) reduced ethanol intoxication. NP078585 also attenuated the reinforcing and rewarding properties of ethanol, measured by operant self-administration and the expression of an ethanol conditioned place preference, and abolished stress-induced reinstatement of ethanol seeking. NP078585 did not affect alcohol responses in mice lacking N-type calcium channels. These results suggest that selective calcium channel inhibitors may be useful in reducing acute ethanol intoxication and alcohol consumption by human alcoholics.

  14. Anesthetic drug midazolam inhibits cardiac human ether-à-go-go-related gene channels: mode of action

    Directory of Open Access Journals (Sweden)

    Vonderlin N

    2015-02-01

    Full Text Available Nadine Vonderlin,1 Fathima Fischer,1 Edgar Zitron,1,2 Claudia Seyler,1 Daniel Scherer,1 Dierk Thomas,1,2 Hugo A Katus,1,2 Eberhard P Scholz1 1Department of Internal Medicine III, University Hospital Heidelberg, 2German Centre for Cardiovascular Research, Partner Site Heidelberg/Mannheim, Heidelberg, Germany Abstract: Midazolam is a short-acting benzodiazepine that is in wide clinical use as an anxiolytic, sedative, hypnotic, and anticonvulsant. Midazolam has been shown to inhibit ion channels, including calcium and potassium channels. So far, the effects of midazolam on cardiac human ether-à-go-go-related gene (hERG channels have not been analyzed. The inhibitory effects of midazolam on heterologously expressed hERG channels were analyzed in Xenopus oocytes using the double-electrode voltage clamp technique. We found that midazolam inhibits hERG channels in a concentration-dependent manner, yielding an IC50 of 170 µM in Xenopus oocytes. When analyzed in a HEK 293 cell line using the patch-clamp technique, the IC50 was 13.6 µM. Midazolam resulted in a small negative shift of the activation curve of hERG channels. However, steady-state inactivation was not significantly affected. We further show that inhibition is state-dependent, occurring within the open and inactivated but not in the closed state. There was no frequency dependence of block. Using the hERG pore mutants F656A and Y652A we provide evidence that midazolam uses a classical binding site within the channel pore. Analyzing the subacute effects of midazolam on hERG channel trafficking, we further found that midazolam does not affect channel surface expression. Taken together, we show that the anesthetic midazolam is a low-affinity inhibitor of cardiac hERG channels without additional effects on channel surface expression. These data add to the current understanding of the pharmacological profile of the anesthetic midazolam. Keywords: midazolam, anesthetics, human ether

  15. Tissue transglutaminase inhibits the TRPV5-dependent calcium transport in an N-glycosylation-dependent manner

    DEFF Research Database (Denmark)

    Boros, Sandor; Xi, Qi; Dimke, Henrik Anthony

    2011-01-01

    Tissue transglutaminase (tTG) is a multifunctional Ca(2+)-dependent enzyme, catalyzing protein crosslinking. The transient receptor potential vanilloid (TRPV) family of cation channels was recently shown to contribute to the regulation of TG activities in keratinocytes and hence skin barrier...... of polarized cultures of rabbit connecting tubule and cortical collecting duct (CNT/CCD) cells. Extracellular application of tTG significantly reduced TRPV5 activity in human embryonic kidney cells transiently expressing the channel. Similarly, a strong inhibition of transepithelial Ca(2+) transport...... was observed after apical application of purified tTG to polarized rabbit CNT/CCD cells. Furthermore, tTG promoted the aggregation of the plasma membrane-associated fraction of TRPV5. Using patch clamp analysis, we observed a reduction in the pore diameter after tTG treatment, suggesting distinct structural...

  16. Parathyroid Hormone Induces Bone Cell Motility and Loss of Mature Osteocyte Phenotype through L-Calcium Channel Dependent and Independent Mechanisms.

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    Matthew Prideaux

    Full Text Available Parathyroid Hormone (PTH can exert both anabolic and catabolic effects on the skeleton, potentially through expression of the PTH type1 receptor (PTH1R, which is highly expressed in osteocytes. To determine the cellular and molecular mechanisms responsible, we examined the effects of PTH on osteoblast to osteocyte differentiation using primary osteocytes and the IDG-SW3 murine cell line, which differentiate from osteoblast to osteocyte-like cells in vitro and express GFP under control of the dentin matrix 1 (Dmp1 promoter. PTH treatment resulted in an increase in some osteoblast and early osteocyte markers and a decrease in mature osteocyte marker expression. The gene expression profile of PTH-treated Day 28 IDG-SW3 cells was similar to PTH treated primary osteocytes. PTH treatment induced striking changes in the morphology of the Dmp1-GFP positive cells in IDG-SW3 cultures and primary cells from Dmp1-GFP transgenic mice. The cells changed from a more dendritic to an elongated morphology and showed increased cell motility. E11/gp38 has been shown to be important for cell migration, however, deletion of the E11/gp38/podoplanin gene had no effect on PTH-induced motility. The effects of PTH on motility were reproduced using cAMP, but not with protein kinase A (PKA, exchange proteins activated by cAMP (Epac, protein kinase C (PKC or phosphatidylinositol-4,5-bisphosphonate 3-kinase (Pi3K agonists nor were they blocked by their antagonists. However, the effects of PTH were mediated through calcium signaling, specifically through L-type channels normally expressed in osteoblasts but decreased in osteocytes. PTH was shown to increase expression of this channel, but decrease the T-type channel that is normally more highly expressed in osteocytes. Inhibition of L-type calcium channel activity attenuated the effects of PTH on cell morphology and motility but did not prevent the downregulation of mature osteocyte marker expression. Taken together, these

  17. Oxidized Low-density Lipoprotein (ox-LDL) Cholesterol Induces the Expression of miRNA-223 and L-type Calcium Channel Protein in Atrial Fibrillation

    Science.gov (United States)

    He, Fengping; Xu, Xin; Yuan, Shuguo; Tan, Liangqiu; Gao, Lingjun; Ma, Shaochun; Zhang, Shebin; Ma, Zhanzhong; Jiang, Wei; Liu, Fenglian; Chen, Baofeng; Zhang, Beibei; Pang, Jungang; Huang, Xiuyan; Weng, Jiaqiang

    2016-08-01

    Atrial fibrillation (AF) is the most common sustained arrhythmia causing high morbidity and mortality. While changing of the cellular calcium homeostasis plays a critical role in AF, the L-type calcium channel α1c protein has suggested as an important regulator of reentrant spiral dynamics and is a major component of AF-related electrical remodeling. Our computational modeling predicted that miRNA-223 may regulate the CACNA1C gene which encodes the cardiac L-type calcium channel α1c subunit. We found that oxidized low-density lipoprotein (ox-LDL) cholesterol significantly up-regulates both the expression of miRNA-223 and L-type calcium channel protein. In contrast, knockdown of miRNA-223 reduced L-type calcium channel protein expression, while genetic knockdown of endogenous miRNA-223 dampened AF vulnerability. Transfection of miRNA-223 by adenovirus-mediated expression enhanced L-type calcium currents and promoted AF in mice while co-injection of a CACNA1C-specific miR-mimic counteracted the effect. Taken together, ox-LDL, as a known factor in AF-associated remodeling, positively regulates miRNA-223 transcription and L-type calcium channel protein expression. Our results implicate a new molecular mechanism for AF in which miRNA-223 can be used as an biomarker of AF rheumatic heart disease.

  18. Lessons learned from a novel calcium-channel protagonist and person.

    Science.gov (United States)

    Dillon, Margaret

    2015-11-15

    A long time ago (circa 1976), David C. Triggle was Chair of the Department of Biochemical Pharmacology at S.U.N.Y. Buffalo where he led the faculty and staff in the education and mentoring of countless pharmacy and graduate students who passed through the hallowed halls of the University. Trained as a chemist, David spent his days synthesizing new and improved calcium channel blockers in a cramped, makeshift organic chemistry lab while a lab full of aspiring pharmacologists measured their effects on contractile responses of various smooth muscle preparations. I was a graduate student fortunate enough to land in David's laboratory, and thanks to him, I successfully navigated out with a Ph.D. in hand. That being said, his influence was less through his role as thesis advisor and more by the example he set in his simple, everyday life in Buffalo, N.Y: his love for - and dedication to - his family, his concern for the environment and his health, his perseverance in that tiny organic chemistry closet, his command of the English language, his unbridled honesty and cynicism, and his quiet pursuit of excellence. This article chronicles student life during that particular time period and provides a glimpse into David's unique personality and lifestyle that made him a role model to me and others. Interwoven is my own circuitous career path both before and after leaving S.U.N.Y. Buffalo that culminated in a productive career at the opposite end of the drug development process from where it all started in pharmacology. Copyright © 2015. Published by Elsevier Inc.

  19. Enhancement of Tissue Expansion by Calcium Channel Blocker: A preliminary study

    Directory of Open Access Journals (Sweden)

    Aktas Alper

    2003-10-01

    Full Text Available Abstract Background Reconstruction of the defects after surgical resection of tumors is one of the important issues in surgical oncology. It is essential that the defect should be covered with a tissue quite similar to the original one and is best achieved by harvesting tissue from an area adjacent to the defect. Tissue expansion is one of the most frequently used reconstructive techniques. A number of studies evaluated blood circulation, capsule formation, tissue tolerance, histomorphological changes and complications of expander placement. However, only a few attempted to enhance tissue expansion. This study we aimed to evaluate verapamil, a calcium channel blocker, to enhance tissue expansion. Material and method Twelve New Zealand rabbits weighing between 900 gm and 1200 gm were assigned into study and control groups. High volume expanders (100, 200 or 300 cc were placed into the subcutaneous tissue. Rabbits in the study group received verapamil. Expanders in the control group were inflated every three days to achieve same pressure as the study group. The size of the flaps was assessed by applying pressure on tip of the flap to demonstrate the contraction. Histopathological examinations were performed. Results By administering liquid earlier and more quickly less flap retraction was observed in the study group. In the control group expanders were exposed in two rabbits while no complication occurred in the study group. Following extraction of the expanders, the flaps were elevated and less retraction was observed in the study group compared to controls. Conclusion Verapamil is safe when used topically and provides less retracted flaps. It can be suggested that verapamil acts on the myofibroblasts in the capsule around tissue expanders and thus increases efficiency of the expanders.

  20. Effect of a calcium channel blocker and antispasmodic in diarrhoea-predominant irritable bowel syndrome.

    Science.gov (United States)

    Lu, C L; Chen, C Y; Chang, F Y; Chang, S S; Kang, L J; Lu, R H; Lee, S D

    2000-08-01

    Irritable bowel syndrome (IBS) is a colonic function disorder. Both pinaverlum bromide (a selective calcium channel blocker) and mebeverine (an antispasmodic) are reported to be effective in the long-term (12-16 weeks) treatment of IBS patients. Their efficacy in the short-term treatment of IBS patients and colonic transit time is unclear. Furthermore, substance P and neuropeptide Y have either excitatory or inhibitory effects on colonic motility. Whether the efficacy of both drugs is mediated through these neuropeptides remains unknown. A clinical trial was conducted with 91 patients with diarrhoea-predominant IBS. After basal measurement of the total colonic transit time, IBS patients were randomized to receive either pinaverlum bromide (50 mg, t.i.d.) or mebeverine (100 mg, t.i.d.) for 2 weeks. The symptomatic scores regarding defaecation, total colonic transit time and serum levels of substance P and neuropeptide Y were measured before and after treatments. The daily defaecation frequency was markedly decreased after treatment (pinaverlum bromide, 2.9+/-1.2 vs 2.0+/-1.0, Pmebeverine, 2.7+/-1.1 vs 2.1+/-1.0, Pmebeverine 73.4 vs 71.8%, P> 0.05). The total colonic transit time was significantly prolonged only after pinaverlum bromide treatment (21.4+/-15.5 vs 30.8+/-14.8 h, Pmebeverine have similar therapeutic efficacies on diarrhoea-predominant IBS patients. Prolonged colonic transit time may be one of the factors responsible for the efficacy of pinaverlum bromide on the IBS patients. Substance P and neuropeptideY appear less important in the pathogenesis of diarrhoea-predominant IBS.

  1. Molecular Basis for Allosteric Inhibition of Acid-Sensing Ion Channel 1a by Ibuprofen

    DEFF Research Database (Denmark)

    Lynagh, Timothy; Romero-Rojo, José Luis; Lund, Camilla

    2017-01-01

    -clamp fluorometry. Our results show that ibuprofen is an allosteric inhibitor of ASIC1a, which binds to a crucial site in the agonist transduction pathway and causes conformational changes that oppose channel activation. Ibuprofen inhibits several ASIC subtypes, but certain ibuprofen derivatives show some...

  2. Alternative Splicing of L-type CaV1.2 Calcium Channels: Implications in Cardiovascular Diseases

    Directory of Open Access Journals (Sweden)

    Zhenyu Hu

    2017-11-01

    Full Text Available L-type Cav1.2 calcium channels are the major pathway for Ca2+ influx to initiate the contraction of smooth and cardiac muscles. Alteration of Cav1.2 channel function has been implicated in multiple cardiovascular diseases, such as hypertension and cardiac hypertrophy. Alternative splicing is a post-transcriptional mechanism that expands Cav1.2 channel structures to modify function, pharmacological and biophysical property such as calcium/voltage-dependent inactivation (C/VDI, or to influence its post-translational modulation by interacting proteins such as Galectin-1. Alternative splicing has generated functionally diverse Cav1.2 isoforms that can be developmentally regulated in the heart, or under pathophysiological conditions such as in heart failure. More importantly, alternative splicing of certain exons of Cav1.2 has been reported to be regulated by splicing factors such as RNA-binding Fox-1 homolog 1/2 (Rbfox 1/2, polypyrimidine tract-binding protein (PTBP1 and RNA-binding motif protein 20 (RBM20. Understanding how Cav1.2 channel function is remodelled in disease will provide better information to guide the development of more targeted approaches to discover therapeutic agents for cardiovascular diseases.

  3. Alternative Splicing of L-type CaV1.2 Calcium Channels: Implications in Cardiovascular Diseases.

    Science.gov (United States)

    2017-11-24

    L-type Cav1.2 calcium channels are the major pathway for Ca2+ influx to initiate the contraction of smooth and cardiac muscles. Alteration of Cav1.2 channel function has been implicated in multiple cardiovascular diseases, such as hypertension and cardiac hypertrophy. Alternative splicing is a post-transcriptional mechanism that expands Cav1.2 channel structures to modify function, pharmacological and biophysical property such as calcium/voltage-dependent inactivation (C/VDI), or to influence its post-translational modulation by interacting proteins such as Galectin-1. Alternative splicing has generated functionally diverse Cav1.2 isoforms that can be developmentally regulated in the heart, or under pathophysiological conditions such as in heart failure. More importantly, alternative splicing of certain exons of Cav1.2 has been reported to be regulated by splicing factors such as RNA-binding Fox-1 homolog 1/2 (Rbfox 1/2), polypyrimidine tract-binding protein (PTBP1) and RNA-binding motif protein 20 (RBM20). Understanding how Cav1.2 channel function is remodelled in disease will provide better information to guide the development of more targeted approaches to discover therapeutic agents for cardiovascular diseases.

  4. Effects on atrial fibrillation in aged hypertensive rats by Ca(2+)-activated K(+) channel inhibition

    DEFF Research Database (Denmark)

    Diness, Jonas Goldin; Skibsbye, Lasse; Jespersen, Thomas

    2011-01-01

    hypertensive rats were more vulnerable to AF induction both by S2 stimulation and burst pacing. Vehicle affected neither the atrial effective refractory period nor AF duration. SK channel inhibition with NS8593 and UCL1684 significantly increased the atrial effective refractory period and decreased AF duration......We have shown previously that inhibition of small conductance Ca(2+)-activated K(+) (SK) channels is antiarrhythmic in models of acutely induced atrial fibrillation (AF). These models, however, do not take into account that AF derives from a wide range of predisposing factors, the most prevalent...... being hypertension. In this study we assessed the effects of two different SK channel inhibitors, NS8593 and UCL1684, in aging, spontaneously hypertensive rats to examine their antiarrhythmic properties in a setting of hypertension-induced atrial remodeling. Male spontaneously hypertensive rats...

  5. A Secondary Gate As a Mechanism for Inhibition of the M2 Proton Channel by Amantadine

    Science.gov (United States)

    Yi, Myunggi; Cross, Timothy A.; Zhou, Huan-Xiang

    2013-01-01

    The mechanism of inhibition of the influenza A virus M2 proton channel by the antiviral drug amantadine has been under intense investigation. The importance of a mechanistic understanding is heightened by the prevalence of amantadine-resistant mutations. To gain mechanistic insight at the molecular level, we carried out extensive molecular dynamics simulations of the tetrameric M2 proton channel in both apo and amantadine-bound forms in a lipid bilayer. The simulation of the apo form revealed that Val27 from the four M2 subunits can form a secondary gate near the channel entrance and break the water wire in the channel pore. This gate arises from physical occlusion and the elimination of hydrogen-bonding partners for water molecules. In the presence of amantadine, the secondary gate formed by Val27 and the drug molecule lying just below form an extended blockage, which breaks the water wire throughout the simulation. The location and orientation of amantadine inside of the channel pore as found in our simulation are supported by a host of experimental observations. Our study suggests a novel role for Val27 in the inhibition of the M2 proton channel by amantadine. PMID:18476738

  6. [Gentamicin on inner hair cells ribbon synapses CaV1.3 calcium ion channel protein expression].

    Science.gov (United States)

    Sun, Jianhua; Wang, Xuefeng; Liu, Ke

    2014-02-01

    To learn the influence the gentamycin on C57BL/6J mice hear and cochlear hair cell ribbon synapses CaV1.3 calcium protein amount. To explore the relationship between hear loss and its dosage correlation change and significance. The fixed amino glucoside to C57BL/6J mice was used to make abdominal cavity injection mold every day. The auditory brain-stem response ABR was used to measure the hear of mice in 7th, 14th, 28th after the injection. Immunofluorescence method was used to observe cochlear basement membrane of hair ribbon synapse CaV1.3 calcium channel proteins in the distribution and expression. Inner hair cells synaptic membrane was immune fluorescent tags with CtbP2 and CaV1. 3. With the growth of the injected drugs, ABR threshold increased,but all the hair cells and shape had no obvious change. However the amount of hair rib bon synapse CaV1.3 calcium ion channel proteins in the expression had significant differences (P < 0.01). CaV1.3 calcium ion channel proteins increased slightly lower than normal at 7th day, significantly decreased at 14th day, had increased, increased quantity compare with 14th day, but at 28th day after intraperitoneal injection of gentamicin. The increasing,decreasing and increasing trend of cochlear hair cells CaV1.3 proteins in the environment of amino glucoside drug toxicity showed that the increase of hair ribbon synapse CaV1.3 proteins may have a compensatory effect on the drug toxicity. With the increase of the drug toxicity effect, this kind of decompensated function could be the listening decline, which may be one of the mechanism of damage to hearing.

  7. Calcium regulation by temperature-sensitive transient receptor potential channels in human uveal melanoma cells.

    Science.gov (United States)

    Mergler, Stefan; Derckx, Raissa; Reinach, Peter S; Garreis, Fabian; Böhm, Arina; Schmelzer, Lisa; Skosyrski, Sergej; Ramesh, Niraja; Abdelmessih, Suzette; Polat, Onur Kerem; Khajavi, Noushafarin; Riechardt, Aline Isabel

    2014-01-01

    Uveal melanoma (UM) is both the most common and fatal intraocular cancer among adults worldwide. As with all types of neoplasia, changes in Ca(2+) channel regulation can contribute to the onset and progression of this pathological condition. Transient receptor potential channels (TRPs) and cannabinoid receptor type 1 (CB1) are two different types of Ca(2+) permeation pathways that can be dysregulated during neoplasia. We determined in malignant human UM and healthy uvea and four different UM cell lines whether there is gene and functional expression of TRP subtypes and CB1 since they could serve as drug targets to either prevent or inhibit initiation and progression of UM. RT-PCR, Ca(2+) transients, immunohistochemistry and planar patch-clamp analysis probed for their gene expression and functional activity, respectively. In UM cells, TRPV1 and TRPM8 gene expression was identified. Capsaicin (CAP), menthol or icilin induced Ca(2+) transients as well as changes in ion current behavior characteristic of TRPV1 and TRPM8 expression. Such effects were blocked with either La(3+), capsazepine (CPZ) or BCTC. TRPA1 and CB1 are highly expressed in human uvea, but TRPA1 is not expressed in all UM cell lines. In UM cells, the CB1 agonist, WIN 55,212-2, induced Ca(2+) transients, which were suppressed by La(3+) and CPZ whereas CAP-induced Ca(2+) transients could also be suppressed by CB1 activation. Identification of functional TRPV1, TRPM8, TRPA1 and CB1 expression in these tissues may provide novel drug targets for treatment of this aggressive neoplastic disease. © 2013.

  8. Allitridi inhibits multiple cardiac potassium channels expressed in HEK 293 cells.

    Directory of Open Access Journals (Sweden)

    Xiao-Hui Xu

    Full Text Available Allitridi (diallyl trisulfide is an active compound (volatile oil from garlic. The previous studies reported that allitridi had anti-arrhythmic effect. The potential ionic mechanisms are, however, not understood. The present study was designed to determine the effects of allitridi on cardiac potassium channels expressed in HEK 293 cells using a whole-cell patch voltage-clamp technique and mutagenesis. It was found that allitridi inhibited hKv4.3 channels (IC(50 = 11.4 µM by binding to the open channel, shifting availability potential to hyperpolarization, and accelerating closed-state inactivation of the channel. The hKv4.3 mutants T366A, T367A, V392A, and I395A showed a reduced response to allitridi with IC(50s of 35.5 µM, 44.7 µM, 23.7 µM, and 42.4 µM. In addition, allitridi decreased hKv1.5, hERG, hKCNQ1/hKCNE1 channels stably expressed in HEK 293 cells with IC(50s of 40.2 µM, 19.6 µM and 17.7 µM. However, it slightly inhibited hKir2.1 current (100 µM, inhibited by 9.8% at -120 mV. Our results demonstrate for the first time that allitridi preferably blocks hKv4.3 current by binding to the open channel at T366 and T367 of P-loop helix, and at V392 and I395 of S6 domain. It has a weak inhibition of hKv1.5, hERG, and hKCNQ1/hKCNE1 currents. These effects may account for its anti-arrhythmic effect observed in experimental animal models.

  9. Inhibition of G protein-activated inwardly rectifying K+ channels by different classes of antidepressants.

    Directory of Open Access Journals (Sweden)

    Toru Kobayashi

    Full Text Available Various antidepressants are commonly used for the treatment of depression and several other neuropsychiatric disorders. In addition to their primary effects on serotonergic or noradrenergic neurotransmitter systems, antidepressants have been shown to interact with several receptors and ion channels. However, the molecular mechanisms that underlie the effects of antidepressants have not yet been sufficiently clarified. G protein-activated inwardly rectifying K(+ (GIRK, Kir3 channels play an important role in regulating neuronal excitability and heart rate, and GIRK channel modulation has been suggested to have therapeutic potential for several neuropsychiatric disorders and cardiac arrhythmias. In the present study, we investigated the effects of various classes of antidepressants on GIRK channels using the Xenopus oocyte expression assay. In oocytes injected with mRNA for GIRK1/GIRK2 or GIRK1/GIRK4 subunits, extracellular application of sertraline, duloxetine, and amoxapine effectively reduced GIRK currents, whereas nefazodone, venlafaxine, mianserin, and mirtazapine weakly inhibited GIRK currents even at toxic levels. The inhibitory effects were concentration-dependent, with various degrees of potency and effectiveness. Furthermore, the effects of sertraline were voltage-independent and time-independent during each voltage pulse, whereas the effects of duloxetine were voltage-dependent with weaker inhibition with negative membrane potentials and time-dependent with a gradual decrease in each voltage pulse. However, Kir2.1 channels were insensitive to all of the drugs. Moreover, the GIRK currents induced by ethanol were inhibited by sertraline but not by intracellularly applied sertraline. The present results suggest that GIRK channel inhibition may reveal a novel characteristic of the commonly used antidepressants, particularly sertraline, and contributes to some of the therapeutic effects and adverse effects.

  10. Arctigenin, a Potential Anti-Arrhythmic Agent, Inhibits Aconitine-Induced Arrhythmia by Regulating Multi-Ion Channels

    Directory of Open Access Journals (Sweden)

    Zhenying Zhao

    2013-11-01

    Full Text Available Background/Aims: Arctigenin possesses biological activities, but its underlying mechanisms at the cellular and ion channel levels are not completely understood. Therefore, the present study was designed to identify the anti-arrhythmia effect of arctigenin in vivo, as well as its cellular targets and mechanisms. Methods: A rat arrhythmia model was established via continuous aconitine infusion, and the onset times of ventricular premature contraction, ventricular tachycardia and death were recorded. The Action Potential Duration (APD, sodium current (INa, L-type calcium current (ICa, L and transient outward potassium current (Ito were measured and analysed using a patch-clamp recording technique in normal rat cardiomyocytes and myocytes of arrhythmia aconitine-induced by. Results: Arctigenin significantly delayed the arrhythmia onset in the aconitine-induced rat model. The 50% and 90% repolarisations (APD50 and APD90 were shortened by 100 µM arctigenin; the arctigenin dose also inhibited the prolongation of APD50 and APD90 caused by 1 µM aconitine. Arctigenin inhibited INa and ICa,L and attenuated the aconitine-increased INa and ICa,L by accelerating the activation process and delaying the inactivation process. Arctigenin enhanced Ito by facilitating the activation process and delaying the inactivation process, and recoverd the decreased Ito induced by aconitine. Conclusions: Arctigenin has displayed anti-arrhythmia effects, both in vivo and in vitro. In the context of electrophysiology, INa, ICa, L, and Ito may be multiple targets of arctigenin, leading to its antiarrhythmic effect.

  11. Physiology and Evolution of Voltage-Gated Calcium Channels in Early Diverging Animal Phyla: Cnidaria, Placozoa, Porifera and Ctenophora

    Science.gov (United States)

    Senatore, Adriano; Raiss, Hamad; Le, Phuong

    2016-01-01

    Voltage-gated calcium (Cav) channels serve dual roles in the cell, where they can both depolarize the membrane potential for electrical excitability, and activate transient cytoplasmic Ca2+ signals. In animals, Cav channels play crucial roles including driving muscle contraction (excitation-contraction coupling), gene expression (excitation-transcription coupling), pre-synaptic and neuroendocrine exocytosis (excitation-secretion coupling), regulation of flagellar/ciliary beating, and regulation of cellular excitability, either directly or through modulation of other Ca2+-sensitive ion channels. In recent years, genome sequencing has provided significant insights into the molecular evolution of Cav channels. Furthermore, expanded gene datasets have permitted improved inference of the species phylogeny at the base of Metazoa, providing clearer insights into the evolution of complex animal traits which involve Cav channels, including the nervous system. For the various types of metazoan Cav channels, key properties that determine their cellular contribution include: Ion selectivity, pore gating, and, importantly, cytoplasmic protein-protein interactions that direct sub-cellular localization and functional complexing. It is unclear when these defining features, many of which are essential for nervous system function, evolved. In this review, we highlight some experimental observations that implicate Cav channels in the physiology and behavior of the most early-diverging animals from the phyla Cnidaria, Placozoa, Porifera, and Ctenophora. Given our limited understanding of the molecular biology of Cav channels in these basal animal lineages, we infer insights from better-studied vertebrate and invertebrate animals. We also highlight some apparently conserved cellular functions of Cav channels, which might have emerged very early on during metazoan evolution, or perhaps predated it. PMID:27867359

  12. Physiology and evolution of voltage-gated calcium channels in early diverging animal phyla: Cnidaria, Placozoa, Porifera and Ctenophora

    Directory of Open Access Journals (Sweden)

    Adriano Senatore

    2016-11-01

    Full Text Available Voltage-gated calcium (Cav channels serve dual roles in the cell, where they can both depolarize the membrane potential for electrical excitability, and activate transient cytoplasmic Ca2+ signals. In animals, Cav channels play crucial roles including driving muscle contraction (excitation-contraction coupling, gene expression (excitation-transcription coupling, pre-synaptic and neuroendocrine exocytosis (excitation-secretion coupling, regulation of flagellar/ciliary beating, and regulation of cellular excitability, either directly or through modulation of other Ca2+-sensitive ion channels. In recent years, genome sequencing has provided significant insights into the molecular evolution of Cav channels. Furthermore, expanded gene datasets have permitted improved inference of the species phylogeny at the base of Metazoa, providing clearer insights into the evolution of complex animal traits which involve Cav channels, including the nervous system. For the various types of metazoan Cav channels, key properties that determine their cellular contribution include: ion selectivity, pore gating, and, importantly, cytoplasmic protein-protein interactions that direct sub-cellular localization and functional complexing. It is unclear when many of these defining features, many of which are essential for nervous system function, evolved. In this review, we highlight some experimental observations that implicate Cav channels in the physiology and behavior of the most early-diverging animals from the phyla Cnidaria, Placozoa, Porifera and Ctenophora. Given our limited understanding of the molecular biology of Cav channels in these basal animal lineages, we infer insights from better-studied vertebrate and invertebrate animals. We also highlight some apparently conserved cellular functions of Cav channels, which might have emerged very early on during metazoan evolution, or perhaps predated it.

  13. Physiology and Evolution of Voltage-Gated Calcium Channels in Early Diverging Animal Phyla: Cnidaria, Placozoa, Porifera and Ctenophora.

    Science.gov (United States)

    Senatore, Adriano; Raiss, Hamad; Le, Phuong

    2016-01-01

    Voltage-gated calcium (Cav) channels serve dual roles in the cell, where they can both depolarize the membrane potential for electrical excitability, and activate transient cytoplasmic Ca(2+) signals. In animals, Cav channels play crucial roles including driving muscle contraction (excitation-contraction coupling), gene expression (excitation-transcription coupling), pre-synaptic and neuroendocrine exocytosis (excitation-secretion coupling), regulation of flagellar/ciliary beating, and regulation of cellular excitability, either directly or through modulation of other Ca(2+)-sensitive ion channels. In recent years, genome sequencing has provided significant insights into the molecular evolution of Cav channels. Furthermore, expanded gene datasets have permitted improved inference of the species phylogeny at the base of Metazoa, providing clearer insights into the evolution of complex animal traits which involve Cav channels, including the nervous system. For the various types of metazoan Cav channels, key properties that determine their cellular contribution include: Ion selectivity, pore gating, and, importantly, cytoplasmic protein-protein interactions that direct sub-cellular localization and functional complexing. It is unclear when these defining features, many of which are essential for nervous system function, evolved. In this review, we highlight some experimental observations that implicate Cav channels in the physiology and behavior of the most early-diverging animals from the phyla Cnidaria, Placozoa, Porifera, and Ctenophora. Given our limited understanding of the molecular biology of Cav channels in these basal animal lineages, we infer insights from better-studied vertebrate and invertebrate animals. We also highlight some apparently conserved cellular functions of Cav channels, which might have emerged very early on during metazoan evolution, or perhaps predated it.

  14. Novel bioactive root canal sealer to inhibit endodontic multispecies biofilms with remineralizing calcium phosphate ions.

    Science.gov (United States)

    Wang, Lin; Xie, Xianju; Li, Chunyan; Liu, Huaibing; Zhang, Ke; Zhou, Yanmin; Chang, Xiaofeng; Xu, Hockin H K

    2017-05-01

    The objectives of this study were to: (1) develop a bioactive endodontic sealer via dimethylaminohexadecyl methacrylate (DMAHDM), 2-methacryloyloxyethyl phosphorylcholine (MPC) and nanoparticles of amorphous calcium phosphate (NACP) for the first time; and (2) evaluate inhibition of early-stage and mature multispecies endodontic biofilm, bond strength to root canal dentine, and calcium (Ca) and phosphate (P) ion release. A series of bioactive endodontic sealers were formulated with DMAHDM, MPC, and NACP. Root dentine bond strength was measured via a push-out test. Three endodontic strains, Enterococcus faecalis, Actinomyces naeslundii, and Fusobacterium nucleatum, were grown on endodontic sealer disks to form multispecies biofilms. Biofilms were grown for 3 days (early) and 14 days (mature). Colony-forming units (CFU), live/dead assay, metabolic activity and polysaccharide were determined. Ca and P ion release from endodontic sealer was measured. Incorporating DMAHDM, MPC and NACP did not decrease the push-out bond strength (p>0.1). Adding DMAHDM and MPC reduced endodontic biofilm CFU by 3 log. DMAHDM or MPC each greatly decreased the biofilm CFU (pEndodontic sealer with DMAHDM+MPC had much greater killing efficacy than DMAHDM or MPC alone (pEndodontic sealer with DMAHDM+MPC had slightly lower, but not significantly lower, Ca and P ion release compared to that without DMAHDM+MPC (p>0.1). A novel bioactive endodontic sealer was developed with potent inhibition of multispecies endodontic biofilms, reducing biofilm CFU by 3 log, while containing NACP for remineralization and possessing good bond strength to root canal dentine walls. The new bioactive endodontic sealer is promising for endodontic applications to eradicate endodontic biofilms and strengthen root structures. The combination of DMAHDM, MPC and NACP may be applicable to other preventive and restoration resins. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Calcium Oxalate Stone Agglomeration Inhibition [tm] Reflects Renal Stone-Forming Activity

    Science.gov (United States)

    Lindberg, Jill S.; Cole, Francis E.; Romani, William; Husserl, Fred E.; Fuselier, Harold A.; Kok, Dirk J.; Erwin, Donald T.

    2000-01-01

    Louisiana and other Gulf South states comprise a “Stone Belt” where calcium oxalate stone formers (CaOx SFs) are found at a high rate of approximately 5%. In these patients, the agglomeration of small stone crystals, which are visible in nearly all morning urine collections, forms stones that can become trapped in the renal parenchyma and the renal pelvis. Without therapy, about half of CaOx SFs repeatedly form kidney stones, which can cause excruciating pain that can be relieved by passage, fragmentation (lithotripsy), or surgical removal. The absence of stones in “normal” patients suggests that there are stone inhibitors in “normal” urines. At the Ochsner Renal Stone Clinic, 24-hour urine samples are collected by the patient and sent to the Ochsner Renal Stone Research Program where calcium oxalate stone agglomeration inhibition [tm] measurements are performed. Urine from healthy subjects and inactive stone formers has demonstrated strongly inhibited stone growth [tm] in contrast to urine from recurrent CaOx SFs. [tm] data from 1500 visits of 700 kidney stone patients have been used to evaluate the risk of recurrence in Ochsner's CaOx SF patients. These data have also been used to demonstrate the interactive roles of certain identified urinary stone-growth inhibitors, citrate and Tamm-Horsfall protein (THP), which can be manipulated with medication to diminish recurrent stone formation. Our goal is to offer patients both financial and pain relief by reducing their stones with optimized medication, using medical management to avoid costly treatments. PMID:21811395

  16. Seeing the forest through the trees: towards a unified view on physiological calcium regulation of voltage-gated sodium channels.

    Science.gov (United States)

    Van Petegem, Filip; Lobo, Paolo A; Ahern, Christopher A

    2012-12-05

    Voltage-gated sodium channels (Na(V)s) underlie the upstroke of the action potential in the excitable tissues of nerve and muscle. After opening, Na(V)s rapidly undergo inactivation, a crucial process through which sodium conductance is negatively regulated. Disruption of inactivation by inherited mutations is an established cause of lethal cardiac arrhythmia, epilepsy, or painful syndromes. Intracellular calcium ions (Ca(2+)) modulate sodium channel inactivation, and multiple players have been suggested in this process, including the cytoplasmic Na(V) C-terminal region including two EF-hands and an IQ motif, the Na(V) domain III-IV linker, and calmodulin. Calmodulin can bind to the IQ domain in both Ca(2+)-bound and Ca(2+)-free conditions, but only to the DIII-IV linker in a Ca(2+)-loaded state. The mechanism of Ca(2+) regulation, and its composite effect(s) on channel gating, has been shrouded in much controversy owing to numerous apparent experimental inconsistencies. Herein, we attempt to summarize these disparate data and propose a novel, to our knowledge, physiological mechanism whereby calcium ions promote sodium current facilitation due to Ca(2+) memory at high-action-potential frequencies where Ca(2+) levels may accumulate. The available data suggest that this phenomenon may be disrupted in diseases where cytoplasmic calcium ion levels are chronically high and where targeted phosphorylation may decouple the Ca(2+) regulatory machinery. Many Na(V) disease mutations associated with electrical dysfunction are located in the Ca(2+)-sensing machinery and misregulation of Ca(2+)-dependent channel modulation is likely to contribute to disease phenotypes. Copyright © 2012 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  17. Expanded alternative splice isoform profiling of the mouse Cav3.1/α1G T-type calcium channel

    Directory of Open Access Journals (Sweden)

    Ernst Wayne L

    2009-05-01

    Full Text Available Abstract Background Alternative splicing of low-voltage-activated T-type calcium channels contributes to the molecular and functional diversity mediating complex network oscillations in the normal brain. Transcript scanning of the human CACNA1G gene has revealed the presence of 11 regions within the coding sequence subjected to alternative splicing, some of which enhance T-type current. In mouse models of absence epilepsy, elevated T-type calcium currents without clear increases in channel expression are found in thalamic neurons that promote abnormal neuronal synchronization. To test whether enhanced T-type currents in these models reflect pathogenic alterations in channel splice isoforms, we determined the extent of alternative splicing of mouse Cacna1g transcripts and whether evidence of altered transcript splicing could be detected in mouse absence epilepsy models. Results Transcript scanning of the murine Cacna1g gene detected 12 regions encoding alternative splice isoforms of Cav3.1/α1G T-type calcium channels. Of the 12 splice sites, six displayed homology to the human CACNA1G splice sites, while six novel mouse-specific splicing events were identified, including one intron retention, three alternative acceptor sites, one alternative donor site, and one exon exclusion. In addition, two brain region-specific alternative splice patterns were observed in the cerebellum. Comparative analyses of brain regions from four monogenic absence epilepsy mouse models with altered thalamic T-type currents and wildtype controls failed to reveal differences in Cacna1g splicing patterns. Conclusion The determination of six novel alternative splice sites within the coding region of the mouse Cacna1g gene greatly expands the potential biophysical diversity of voltage-gated T-type channels in the mouse central nervous system. Although alternative splicing of Cav3.1/α1G channels does not explain the enhancement of T-type current identified in four mouse

  18. Anti-Epileptic Drugs Delay Age-Related Loss of Spiral Ganglion Neurons via T-type Calcium Channel

    Science.gov (United States)

    Lei, Debin; Gao, Xia; Perez, Philip; Ohlemiller, Kevin K; Chen, Chien-Chang; Campbell, Kevin P.; Hood, Aizhen Yang; Bao, Jianxin

    2011-01-01

    Loss of spiral ganglion neurons is a major cause of age-related hearing loss (presbycusis). Despite being the third most prevalent condition afflicting elderly persons, there are no known medications to prevent presbycusis. Because calcium signaling has long been implicated in age-related neuronal death, we investigated T-type calcium channels. This family is comprised of three members (Cav3.1, Cav3.2, and Cav3.3), based on their respective main pore-forming alpha subunits: α1G, α1H, and α1I. In the present study, we report a significant delay of age-related loss of cochlear function and preservation of spiral ganglion neurons in α1H null and heterozygous mice, clearly demonstrating an important role for Cav3.2 in age-related neuronal loss. Furthermore, we show that anticonvulsant drugs from a family of T-type calcium channel blockers can significantly preserve spiral ganglion neurons during aging. To our knowledge, this is the first report of drugs capable of diminishing age-related loss of spiral ganglion neurons. PMID:21640179

  19. Propofol inhibits hERG K+ channels and enhances the inhibition effects on its mutations in HEK293 cells.

    Science.gov (United States)

    Han, Sheng-Na; Jing, Ying; Yang, Lin-Lin; Zhang, Zhao; Zhang, Li-Rong

    2016-11-15

    QT interval prolongation, a potential risk for arrhythmias, may result from gene polymorphisms relevant to cardiomyocyte repolarization. Another noted cause of QT interval prolongation is the administration of chemical compounds such as anesthetics, which may affect a specific type of cardiac K+ channel encoded by the human ether-a-go-go-related gene (hERG). hERG K+ current was recorded using whole-cell patch clamp in human embryonic kidney (HEK293) cells expressing wild type (WT) or mutated hERG channels. Expression of hERG K+ channel proteins was evaluated using western blot and confirmed by fluorescent staining and imaging. Computational modeling was adopted to identify the possible binding site(s) of propofol with hERG K+ channels. Propofol had a significant inhibitory effect on WT hERG K+ currents in a concentration-dependent manner, with a half-maximal inhibitory concentration (IC50) of 60.9±6.4μM. Mutations in drug-binding sites (Y652A or F656C) of the hERG channel were found to attenuate hERG current blockage by propofol. However, propofol did not inhibit the trafficking of hERG protein to the cell membrane. Meanwhile, for the three selective hERG K+ channel mutant heterozygotes WT/Q738X-hERG, WT/A422T-hERG, and WT/H562P-hERG, the IC50 of propofol was calculated as 14.2±2.8μM, 3.3±1.2μM, and 5.9±1.9μM, respectively, which were much lower than that for the wild type. These findings indicate that propofol may potentially increase QT interval prolongation risk in patients via direct inhibition of the hERG K+ channel, especially in those with other concurrent triggering factors such as hERG gene mutations. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. A New Negative Allosteric Modulator AP14145 for the Study of Small Conductance Calcium-Activated Potassium Channels

    DEFF Research Database (Denmark)

    Simo Vicens, Rafel; Kirchhoff, Jeppe Egedal; Dolce, Bernardo

    2017-01-01

    Background and purpose: Small conductance Ca2+-activated K+ (KCa2) channels represent a promising atrial-selective target for treatment of atrial fibrillation (AF). Here, we establish the mechanism of KCa2