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Sample records for replicative senescence model

  1. A stochastic step model of replicative senescence explains ROS production rate in ageing cell populations.

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    Conor Lawless

    Full Text Available Increases in cellular Reactive Oxygen Species (ROS concentration with age have been observed repeatedly in mammalian tissues. Concomitant increases in the proportion of replicatively senescent cells in ageing mammalian tissues have also been observed. Populations of mitotic human fibroblasts cultured in vitro, undergoing transition from proliferation competence to replicative senescence are useful models of ageing human tissues. Similar exponential increases in ROS with age have been observed in this model system. Tracking individual cells in dividing populations is difficult, and so the vast majority of observations have been cross-sectional, at the population level, rather than longitudinal observations of individual cells.One possible explanation for these observations is an exponential increase in ROS in individual fibroblasts with time (e.g. resulting from a vicious cycle between cellular ROS and damage. However, we demonstrate an alternative, simple hypothesis, equally consistent with these observations which does not depend on any gradual increase in ROS concentration: the Stochastic Step Model of Replicative Senescence (SSMRS. We also demonstrate that, consistent with the SSMRS, neither proliferation-competent human fibroblasts of any age, nor populations of hTERT overexpressing human fibroblasts passaged beyond the Hayflick limit, display high ROS concentrations. We conclude that longitudinal studies of single cells and their lineages are now required for testing hypotheses about roles and mechanisms of ROS increase during replicative senescence.

  2. Biomarkers of replicative senescence revisited

    DEFF Research Database (Denmark)

    Nehlin, Jan

    2016-01-01

    Biomarkers of replicative senescence can be defined as those ultrastructural and physiological variations as well as molecules whose changes in expression, activity or function correlate with aging, as a result of the gradual exhaustion of replicative potential and a state of permanent cell cycle...... with their chronological age and present health status, help define their current rate of aging and contribute to establish personalized therapy plans to reduce, counteract or even avoid the appearance of aging biomarkers....

  3. Identification of 30 protein species involved in replicative senescence and stress-induced premature senescence

    DEFF Research Database (Denmark)

    Dierick, Jean François; Kalume, Dário E; Wenders, Frédéric

    2002-01-01

    Exposure of human proliferative cells to subcytotoxic stress triggers stress-induced premature senescence (SIPS) which is characterized by many biomarkers of replicative senescence. Proteomic comparison of replicative senescence and stress-induced premature senescence indicates that, at the level....... These changes affect different cell functions, including energy metabolism, defense systems, maintenance of the redox potential, cell morphology and transduction pathways.......Exposure of human proliferative cells to subcytotoxic stress triggers stress-induced premature senescence (SIPS) which is characterized by many biomarkers of replicative senescence. Proteomic comparison of replicative senescence and stress-induced premature senescence indicates that, at the level...... of protein expression, stress-induced premature senescence and replicative senescence are different phenotypes sharing however similarities. In this study, we identified 30 proteins showing changes of expression level specific or common to replicative senescence and/or stress-induced premature senescence...

  4. Attenuation of Replication Stress–Induced Premature Cellular Senescence to Assess Anti-Aging Modalities

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    Zhao, Hong; Darzynkiewicz, Zbigniew

    2014-01-01

    Described is an in vitro model of premature senescence in pulmonary adenocarcinoma A549 cells induced by persistent DNA replication stress in response to treatment with the DNA damaging drug mitoxantrone (Mxt). The degree of cellular senescence, based on characteristic changes in cell morphology, is measured by laser scanning cytometry. Specifically, the flattening of cells grown on slides (considered the hallmark of cellular senescence) is measured as the decline in local intensity of DNA-as...

  5. Piper betle L. Modulates Senescence-Associated Genes Expression in Replicative Senescent Human Diploid Fibroblasts

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    Lina Wati Durani

    2017-01-01

    Full Text Available Piper betle (PB is a traditional medicine that is widely used to treat different diseases around Asian region. The leaf extracts contain various bioactive compounds, which were reported to have antidiabetic, antibacterial, anti-inflammatory, antioxidant, and anticancer effects. In this study, the effect of PB aqueous extracts on replicative senescent human diploid fibroblasts (HDFs was investigated by determining the expressions of senescence-associated genes using quantitative PCR. Our results showed that PB extracts at 0.4 mg/ml can improve cell proliferation of young (143%, presenescent (127.3%, and senescent (157.3% HDFs. Increased expressions of PRDX6, TP53, CDKN2A, PAK2, and MAPK14 were observed in senescent HDFs compared to young and/or presenescent HDFs. Treatment with PB extracts modulates the transcriptional profile changes in senescent HDFs. By contrast, expressions of SOD1 increased, whereas GPX1, PRDX6, TP53, CDKN2A, PAK2, and MAPK14 were decreased in PB-treated senescent HDFs compared to untreated senescent HDFs. In conclusion, this study indicates the modulation of PB extracts on senescence-associated genes expression of replicative senescent HDFs. Further studies warrant determining the mechanism of PB in modulating replicative senescence of HDFs through these signaling pathways.

  6. Donor's age and replicative senescence favour the in-vitro mineralization potential of human fibroblasts.

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    Boraldi, Federica; Bartolomeo, Angelica; Di Bari, Caterina; Cocconi, Andrea; Quaglino, Daniela

    2015-12-01

    Aberrant mineralization of soft connective tissues (ectopic calcification) may occur as a frequent age-related complication. Still, it remains unclear the role of mesenchymal cell donor's age and of replicative senescence on ectopic calcification. Therefore, the ability of cells to deposit in-vitro hydroxyapatite crystals and the expression of progressive ankylosis protein homolog (ANKH), ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1), tissue non specific alkaline phosphatase (TNAP) and osteopontin (OPN) have been evaluated in human dermal fibroblasts derived from neonatal (nHDF) and adult (aHDF) donors (ex-vivo ageing model) or at low and high cumulative population doublings (CPD) up to replicative senescence (in-vitro ageing model). This study demonstrates that: 1) replicative senescence favours hydroxyapatite formation in cultured fibroblasts; 2) donor's age acts as a major modulator of the mineralizing potential of HDF, since nHDF are less prone than aHDF to induce calcification; 3) donor's age and replicative senescence play in concert synergistically increasing the calcification process; 4) the ANKH+ENPP1/TNAP ratio, being crucial for pyrophosphate/inorganic phosphate balance, is greatly influenced by donor's age, as well as by replicative senescence, and regulates mineral deposition; 5) OPN is only modulated by replicative senescence.

  7. Quantitative and integrated proteome and microRNA analysis of endothelial replicative senescence.

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    Yentrapalli, Ramesh; Azimzadeh, Omid; Kraemer, Anne; Malinowsky, Katharina; Sarioglu, Hakan; Becker, Karl-Friedrich; Atkinson, Michael J; Moertl, Simone; Tapio, Soile

    2015-08-01

    Age-related changes in vascular functioning are a harbinger of cardiovascular disease but the biological mechanisms during the progression of endothelial senescence have not been studied. We investigated alterations in the proteome and miRNA profiles in the course of replicative senescence using primary human umbilical vein endothelial cells as an in vitro vascular model. Quantitative proteomic profiling from early growth stage to senescence was performed by isotope-coded protein label coupled to LC-ESI-MS/MS analysis. Some proteins consistently changed their expression during the senescence whereas others appeared as deregulated only during the late senescence. The latter was accompanied by alterations in morphology of senescent endothelial cells. MicroRNA expression profiling revealed transient changes in the level of miR-16-5p, miR-28-3p and miR-886-5p in the early senescence, decrease in the level of miR-106b-3p at the late stage, and continuous changes in the expression of miR-181a-5p and miR-376a-3p during the whole senescence process. Integrating data on proteomic and microRNA changes indicated potential crosstalk between specific proteins and non-coding RNAs in the regulation of metabolism, cell cycle progression and cytoskeletal organization in the endothelial senescence. The knowledge of molecular targets that change during the senescence can ultimately contribute to a better understanding and prevention of age-related vascular diseases.

  8. ATM Couples Replication Stress and Metabolic Reprogramming during Cellular Senescence

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    Katherine M. Aird

    2015-05-01

    Full Text Available Replication stress induced by nucleotide deficiency plays an important role in cancer initiation. Replication stress in primary cells typically activates the cellular senescence tumor-suppression mechanism. Senescence bypass correlates with development of cancer, a disease characterized by metabolic reprogramming. However, the role of metabolic reprogramming in the cellular response to replication stress has been little explored. Here, we report that ataxia telangiectasia mutated (ATM plays a central role in regulating the cellular response to replication stress by shifting cellular metabolism. ATM inactivation bypasses senescence induced by replication stress triggered by nucleotide deficiency. This was due to restoration of deoxyribonucleotide triphosphate (dNTP levels through both upregulation of the pentose phosphate pathway via increased glucose-6-phosphate dehydrogenase (G6PD activity and enhanced glucose and glutamine consumption. These phenotypes were mediated by a coordinated suppression of p53 and upregulation of c-MYC downstream of ATM inactivation. Our data indicate that ATM status couples replication stress and metabolic reprogramming during senescence.

  9. Aminoguanidine delays the replicative senescence of human diploid fibroblasts

    Institute of Scientific and Technical Information of China (English)

    WANG Pei-chang; ZHANG Jian; ZHANG Zong-yu; TONG Tan-jun

    2007-01-01

    advanced glycation end products; comet assayBackground The accumulation of free radicals and advanced glycation end products (AGEs) in cell plays a very important role in replicative senescence. Aminoguanidine (AG) has potential antioxidant effects and decreases AGE levels. This study aimed to investigate its effect on replicative senescence in vitro.Methods The effects of aminoguanidine on morphology, replicative lifespan, cell growth and proliferation, AGEs, DNA damage, DNA repair ability and telomere length were observed in human fetal lung diploid fibroblasts (2BS).Results Aminoguanidine maintained the non-senescent phenotype of 2BS cells even at late population doubling (PD) and increased cumulative population doublings by at least 17-21 PDs. Aminoguanidine also improved the potentials of growth and proliferation of 2BS cells as detected by the MTT assay. The AGE levels of late PD cells grown from early PD in DMEM containing aminiguanidine decreased significantly compared with those of late PD control cells and were similar to those of young control cells. In addition, the cells pretreated with aminoguanidine had a significant reduction in DNA strand breaks when they were exposed to 200 μmol/L H2O2 for 5 minutes which indicated that the compound had a strong potential to protect genomic DNA against oxidative stress. And most of the cells exposed to 100 μmol/L H2O2 had much shorter comet tails and smaller tail areas after incubation with aminoguanidine-supplemented DMEM, which indicated that the compound strongly improved the DNA repair abilities of 2BS cells. Moreover, PD55 cells grown from PD28 in 2 mmol/L or 4 mmol/L aminoguanidine retain telomere lengths of 7.94 kb or 8.12 kb, which was 0.83 kb or 1.11kb longer than that of the control cells.Conclusion Aminoguanidine delays replicative senescence of 2BS cells and the senescence-delaying effect of aminoguanidine appear to be due to its many biological properties including its potential for proliferation

  10. Attenuation of Replication Stress–Induced Premature Cellular Senescence to Assess Anti-Aging Modalities

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    Zhao, Hong; Darzynkiewicz, Zbigniew

    2014-01-01

    Described is an in vitro model of premature senescence in pulmonary adenocarcinoma A549 cells induced by persistent DNA replication stress in response to treatment with the DNA damaging drug mitoxantrone (Mxt). The degree of cellular senescence, based on characteristic changes in cell morphology, is measured by laser scanning cytometry. Specifically, the flattening of cells grown on slides (considered the hallmark of cellular senescence) is measured as the decline in local intensity of DNA-associated DAPI fluorescence (represented by maximal pixels). This change is paralleled by an increase in nuclear area. Thus, the ratio of mean intensity of maximal pixels to nuclear area provides a very sensitive morphometric biomarker for the degree of senescence. This analysis is combined with immunocytochemical detection of senescence markers, such as overexpression of cyclin kinase inhibitors (e.g., p21WAF1) and phosphorylation of ribosomal protein S6 (rpS6), a key marker associated with aging/senescence that is detected using a phospho-specific antibody. These biomarker indices are presented in quantitative terms defined as a senescence index (SI), which is the fraction of the marker in test cultures relative to the same marker in exponentially growing control cultures. This system can be used to evaluate the anti-aging potential of test agents by assessing attenuation of maximal senescence. As an example, the inclusion of berberine, a natural alkaloid with reported anti-aging properties and a long history of use in traditional Chinese medicine, is shown to markedly attenuate the Mxt-induced SI and phosphorylation of rpS6. The multivariate analysis of senescence markers by laser scanning cytometry offers a promising tool to explore the potential anti-aging properties of a variety agents. PMID:24984966

  11. Attenuation of replication stress-induced premature cellular senescence to assess anti-aging modalities.

    Science.gov (United States)

    Zhao, Hong; Darzynkiewicz, Zbigniew

    2014-01-01

    Described is an in vitro model of premature senescence in pulmonary adenocarcinoma A549 cells induced by persistent DNA replication stress in response to treatment with the DNA damaging drug mitoxantrone (Mxt). The degree of cellular senescence, based on characteristic changes in cell morphology, is measured by laser scanning cytometry. Specifically, the flattening of cells grown on slides (considered the hallmark of cellular senescence) is measured as the decline in local intensity of DNA-associated DAPI fluorescence (represented by maximal pixels). This change is paralleled by an increase in nuclear area. Thus, the ratio of mean intensity of maximal pixels to nuclear area provides a very sensitive morphometric biomarker for the degree of senescence. This analysis is combined with immunocytochemical detection of senescence markers, such as overexpression of cyclin kinase inhibitors (e.g., p21(WAF1) ) and phosphorylation of ribosomal protein S6 (rpS6), a key marker associated with aging/senescence that is detected using a phospho-specific antibody. These biomarker indices are presented in quantitative terms defined as a senescence index (SI), which is the fraction of the marker in test cultures relative to the same marker in exponentially growing control cultures. This system can be used to evaluate the anti-aging potential of test agents by assessing attenuation of maximal senescence. As an example, the inclusion of berberine, a natural alkaloid with reported anti-aging properties and a long history of use in traditional Chinese medicine, is shown to markedly attenuate the Mxt-induced SI and phosphorylation of rpS6. The multivariate analysis of senescence markers by laser scanning cytometry offers a promising tool to explore the potential anti-aging properties of a variety agents.

  12. Replicatively senescent cells are arrested in G1 and G2 phases

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    Mao, Zhiyong; Ke, Zhonghe; Gorbunova, Vera; Seluanov, Andrei

    2012-01-01

    Most human somatic cells do not divide indefinitely but enter a terminal growth arrest termed replicative senescence. Replicatively senescent cells are generally believed to arrest in G1 or G0 stage of the cell cycle. While doing cell cycle analysis on three different lines of normal human fibroblasts we observed that 36-60% of the replicatively senescent cells had 4N DNA content. Only up to 5% of senescent cells had more than one nucleus ruling out the possibility that the 4N cell population were G1-arrested bi-nucleated cells. Furthermore, it is unlikely that the 4N cells are tetraploids, because actively dividing pre-senescent cultures lacked the 8N tetraploid G2 population. Collectively these results suggest that the 4N population consists of G2 arrested cells. The notion that a large fraction of senescent cell population is arrested in G2 is important for understanding the biology of replicative senescence. PMID:22745179

  13. Rplp1 bypasses replicative senescence and contributes to transformation

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    Artero-Castro, A. [Pathology Department, Fundacio Institut de Recerca Hospital Vall d' Hebron, Passeig Vall d' Hebron 119-129, 08035 Barcelona (Spain); Kondoh, H. [Department of Geriatric Medicine, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507 (Japan); Fernandez-Marcos, P.J.; Serrano, M. [Spanish National Cancer Research Center (CNIO), 3 Melchor Fernandez Almagro St, Madrid 28029 (Spain); Ramon y Cajal, S. [Pathology Department, Fundacio Institut de Recerca Hospital Vall d' Hebron, Passeig Vall d' Hebron 119-129, 08035 Barcelona (Spain); LLeonart, M.E., E-mail: melleona@ir.vhebron.net [Pathology Department, Fundacio Institut de Recerca Hospital Vall d' Hebron, Passeig Vall d' Hebron 119-129, 08035 Barcelona (Spain)

    2009-05-01

    To determine whether genes expressed by embryonic stem cells have a proliferative effect in primary cells, primary mouse embryonic fibroblasts were infected with an ES cell cDNA library. This led to identification of the ribosomal protein, Rplp1, a member of the P group of ribosomal proteins, whose putative role for bypassing replicative senescence in MEFs was investigated. Our results show that Rplp1 produces a two-fold increase in the expression of an E2F1 promoter and upregulation of cyclin E in MEFs. Therefore, this study is the first to show that overexpression of a single ribosomal protein, Rplp1, is a cause and not a consequence of cell proliferation. In addition, co-expression of Rplp1 with mutant ras{sup Val12} contributed to transformation in NIH3T3 cells, as was evidenced by colony production in soft-agar assays. Moreover, the Rplp1 protein was upregulated in MEFs and NIH3T3 cells upon expression of a p53 dominant negative mutant gene designated p53R175H. Hence, mutation of p53 may facilitate immortalization in vitro by upregulating Rplp1. Lastly, Rplp1 mRNA was found to be upregulated in 16 of 26 human colon cancer biopsy specimens, a finding that may be of relevance to cancer research.

  14. MicroRNA-33 promotes the replicative senescence of mouse embryonic fibroblasts by suppressing CDK6

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    Xu, Shun; Huang, Haijiao; Li, Nanhong; Zhang, Bing; Jia, Yubin; Yang, Yukun; Yuan, Yuan; Xiong, Xing-dong; Wang, Dengchuan; Zheng, Hui-ling [Institute of Aging Research, Guangdong Medical University, Dongguan (China); Guangdong Provincial Key Laboratory of Medical Molecular Diagnostics, Dongguan (China); Institute of Biochemistry & Molecular Biology, Guangdong Medical University, Zhanjiang (China); Liu, Xinguang, E-mail: xgliu64@126.com [Institute of Aging Research, Guangdong Medical University, Dongguan (China); Guangdong Provincial Key Laboratory of Medical Molecular Diagnostics, Dongguan (China); Institute of Biochemistry & Molecular Biology, Guangdong Medical University, Zhanjiang (China)

    2016-05-13

    MicroRNAs are a large class of tiny noncoding RNAs, which have emerged as critical regulators of gene expression, and thus are involved in multiple cellular processes, including cellular senescence. MicroRNA-33 has previously been established to exert crucial effect on cell proliferation, lipid metabolism and cholesterol metabolism. Nonetheless, the association between microRNA-33 and cellular senescence and its underlying molecular mechanism are far to be elucidated. The present study has attempted to probe into the effect of microRNA-33 on MEFs senescence. Our data unveiled that microRNA-33 was dramatically down-regulated in senescent MEFs compared to the young MEFs, and ectopic expression of microRNA-33 promoted MEFs senescence, while knock-down of microRNA-33 exhibited a protective effect against senescence phenotype. Moreover, we verified CDK6 as a direct target of microRNA-33 in mouse. Silencing of CDK6 induced the premature senescence phenotype of MEFs similarly as microRNA-33, while enforced expression of CDK6 significantly reverse the senescence-induction effect of microRNA-33. Taken together, our results suggested that microRNA-33 enhanced the replicative senescence of MEFs potentially by suppressing CDK6 expression. -- Highlights: •MicroRNA-33 was dramatically down-regulated in senescent MEF cells. •Altered expression of microRNA-33 exerted a critical role in MEFs senescence. •MicroRNA-33 promoted the replicative senescence of MEFs via targeting of CDK6.

  15. Persistent Amplification of DNA Damage Signal Involved in Replicative Senescence of Normal Human Diploid Fibroblasts

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    Masatoshi Suzuki

    2012-01-01

    Full Text Available Foci of phosphorylated histone H2AX and ATM are the surrogate markers of DNA double strand breaks. We previously reported that the residual foci increased their size after irradiation, which amplifies DNA damage signals. Here, we addressed whether amplification of DNA damage signal is involved in replicative senescence of normal human diploid fibroblasts. Large phosphorylated H2AX foci (>1.5 μm diameter were specifically detected in presenescent cells. The frequency of cells with large foci was well correlated with that of cells positive for senescence-associated β-galactosidase staining. Hypoxic cell culture condition extended replicative life span of normal human fibroblast, and we found that the formation of large foci delayed in those cells. Our immuno-FISH analysis revealed that large foci partially localized at telomeres in senescent cells. Importantly, large foci of phosphorylated H2AX were always colocalized with phosphorylated ATM foci. Furthermore, Ser15-phosphorylated p53 showed colocalization with the large foci. Since the treatment of senescent cells with phosphoinositide 3-kinase inhibitor, wortmannin, suppressed p53 phosphorylation, it is suggested that amplification of DNA damage signaling sustains persistent activation of ATM-p53 pathway, which is essential for replicative senescence.

  16. Polycomb Mediated Epigenetic Silencing and Replication Timing at the INK4a/ARF Locus during Senescence

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    Verthuy, Christophe; Chasson, Lionel; Serrano, Manuel; Djabali, Malek

    2009-01-01

    Background The INK4/ARF locus encodes three tumor suppressor genes (p15Ink4b, Arf and p16Ink4a) and is frequently inactivated in a large number of human cancers. Mechanisms regulating INK4/ARF expression are not fully characterized. Principal Findings Here we show that in young proliferating embryonic fibroblasts (MEFs) the Polycomb Repressive Complex 2 (PRC2) member EZH2 together with PRC1 members BMI1 and M33 are strongly expressed and localized at the INK4/ARF regulatory domain (RD) identified as a DNA replication origin. When cells enter senescence the binding to RD of both PRC1 and PRC2 complexes is lost leading to a decreased level of histone H3K27 trimethylation (H3K27me3). This loss is accompanied with an increased expression of the histone demethylase Jmjd3 and with the recruitment of the MLL1 protein, and correlates with the expression of the Ink4a/Arf genes. Moreover, we show that the Polycomb protein BMI1 interacts with CDC6, an essential regulator of DNA replication in eukaryotic cells. Finally, we demonstrate that Polycomb proteins and associated epigenetic marks are crucial for the control of the replication timing of the INK4a/ARF locus during senescence. Conclusions We identified the replication licencing factor CDC6 as a new partner of the Polycomb group member BMI1. Our results suggest that in young cells Polycomb proteins are recruited to the INK4/ARF locus through CDC6 and the resulting silent locus is replicated during late S-phase. Upon senescence, Jmjd3 is overexpressed and the MLL1 protein is recruited to the locus provoking the dissociation of Polycomb from the INK4/ARF locus, its transcriptional activation and its replication during early S-phase. Together, these results provide a unified model that integrates replication, transcription and epigenetics at the INK4/ARF locus. PMID:19462008

  17. Polycomb mediated epigenetic silencing and replication timing at the INK4a/ARF locus during senescence.

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    Hanane Agherbi

    Full Text Available BACKGROUND: The INK4/ARF locus encodes three tumor suppressor genes (p15(Ink4b, Arf and p16(Ink4a and is frequently inactivated in a large number of human cancers. Mechanisms regulating INK4/ARF expression are not fully characterized. PRINCIPAL FINDINGS: Here we show that in young proliferating embryonic fibroblasts (MEFs the Polycomb Repressive Complex 2 (PRC2 member EZH2 together with PRC1 members BMI1 and M33 are strongly expressed and localized at the INK4/ARF regulatory domain (RD identified as a DNA replication origin. When cells enter senescence the binding to RD of both PRC1 and PRC2 complexes is lost leading to a decreased level of histone H3K27 trimethylation (H3K27me3. This loss is accompanied with an increased expression of the histone demethylase Jmjd3 and with the recruitment of the MLL1 protein, and correlates with the expression of the Ink4a/Arf genes. Moreover, we show that the Polycomb protein BMI1 interacts with CDC6, an essential regulator of DNA replication in eukaryotic cells. Finally, we demonstrate that Polycomb proteins and associated epigenetic marks are crucial for the control of the replication timing of the INK4a/ARF locus during senescence. CONCLUSIONS: We identified the replication licencing factor CDC6 as a new partner of the Polycomb group member BMI1. Our results suggest that in young cells Polycomb proteins are recruited to the INK4/ARF locus through CDC6 and the resulting silent locus is replicated during late S-phase. Upon senescence, Jmjd3 is overexpressed and the MLL1 protein is recruited to the locus provoking the dissociation of Polycomb from the INK4/ARF locus, its transcriptional activation and its replication during early S-phase. Together, these results provide a unified model that integrates replication, transcription and epigenetics at the INK4/ARF locus.

  18. Modelling transcriptional networks in leaf senescence.

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    Penfold, Christopher A; Buchanan-Wollaston, Vicky

    2014-07-01

    The process of leaf senescence is induced by an extensive range of developmental and environmental signals and controlled by multiple, cross-linking pathways, many of which overlap with plant stress-response signals. Elucidation of this complex regulation requires a step beyond a traditional one-gene-at-a-time analysis. Application of a more global analysis using statistical and mathematical tools of systems biology is an approach that is being applied to address this problem. A variety of modelling methods applicable to the analysis of current and future senescence data are reviewed and discussed using some senescence-specific examples. Network modelling with a senescence transcriptome time course followed by testing predictions with gene-expression data illustrates the application of systems biology tools.

  19. Modeling DNA Replication.

    Science.gov (United States)

    Bennett, Joan

    1998-01-01

    Recommends the use of a model of DNA made out of Velcro to help students visualize the steps of DNA replication. Includes a materials list, construction directions, and details of the demonstration using the model parts. (DDR)

  20. Ameliorating replicative senescence of human bone marrow stromal cells by PSMB5 overexpression

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    Lu, Li, E-mail: luli7300@126.com [Department of Anatomy, Shanxi Medical University, Taiyuan 030001 (China); Song, Hui-Fang; Wei, Jiao-Long; Liu, Xue-Qin [Department of Anatomy, Shanxi Medical University, Taiyuan 030001 (China); Song, Wen-Hui [Department of Orthopaedics, The Second Affiliated Hospital of Shanxi Medical University, Taiyuan 030001 (China); Yan, Ba-Yi; Yang, Gui-Jiao [Department of Anatomy, Shanxi Medical University, Taiyuan 030001 (China); Li, Ang [Department of Medicine, University of Hong Kong Faculty of Medicine, Hong Kong (Hong Kong); Department of Anatomy, University of Hong Kong Faculty of Medicine, Hong Kong (Hong Kong); Yang, Wu-Lin, E-mail: wulinyoung@163.com [School of Biotechnology and Food Engineering, Hefei University of Technology, Hefei 230009 (China); Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium (SBIC), Agency for Science, Technology and Research - A*STAR (Singapore)

    2014-01-24

    Highlights: • PSMB5 overexpression restores the differentiation potential of aged hBMSCs. • PSMB5 overexpression enhances the proteasomal activity of late-stage hBMSCs. • PSMB5 overexpression inhibits replicative senescence and improved cell viability. • PSMB5 overexpression promotes cell growth by upregulating the Cyclin D1/CDK4 complex. - Abstract: Multipotent human bone marrow stromal cells (hBMSCs) potentially serve as a source for cell-based therapy in regenerative medicine. However, in vitro expansion was inescapably accompanied with cell senescence, characterized by inhibited proliferation and compromised pluripotency. We have previously demonstrated that this aging process is closely associated with reduced 20S proteasomal activity, with down-regulation of rate-limiting catalytic β-subunits particularly evident. In the present study, we confirmed that proteasomal activity directly contributes to senescence of hBMSCs, which could be reversed by overexpression of the β5-subunit (PSMB5). Knocking down PSMB5 led to decreased proteasomal activity concurrent with reduced cell proliferation in early-stage hBMSCs, which is similar to the senescent phenotype observed in late-stage cells. In contrast, overexpressing PSMB5 in late-stage cells efficiently restored the normal activity of 20S proteasomes and promoted cell growth, possibly via upregulating the Cyclin D1/CDK4 complex. Additionally, PSMB5 could enhance cell resistance to oxidative stress, as evidenced by the increased cell survival upon exposing senescent hBMSCs to hydrogen peroxide. Furthermore, PSMB5 overexpression retained the pluripotency of late-stage hBMSCs by facilitating their neural differentiation both in vitro and in vivo. Collectively, our work reveals a critical role of PSMB5 in 20S proteasome-mediated protection against replicative senescence, pointing to a possible strategy for maintaining the integrity of culture-expanded hBMSCs by manipulating the expression of PSMB5.

  1. MiRNA profile associated with replicative senescence, extended cell culture, and ectopic telomerase expression in human foreskin fibroblasts.

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    Laura N Bonifacio

    Full Text Available Senescence is a highly regulated process that limits cellular replication by enforcing a G1 arrest in response to various stimuli. Replicative senescence occurs in response to telomeric DNA erosion, and telomerase expression can offset replicative senescence leading to immortalization of many human cells. Limited data exists regarding changes of microRNA (miRNA expression during senescence in human cells and no reports correlate telomerase expression with regulation of senescence-related miRNAs. We used miRNA microarrays to provide a detailed account of miRNA profiles for early passage and senescent human foreskin (BJ fibroblasts as well as early and late passage immortalized fibroblasts (BJ-hTERT that stably express the human telomerase reverse transcriptase subunit hTERT. Selected miRNAs that were differentially expressed in senescence were assayed for expression in quiescent cells to identify miRNAs that are specifically associated with senescence-associated growth arrest. From this group of senescence-associated miRNAs, we confirmed the ability of miR-143 to induce growth arrest after ectopic expression in young fibroblasts. Remarkably, miR-143 failed to induce growth arrest in BJ-hTERT cells. Importantly, the comparison of late passage immortalized fibroblasts to senescent wild type fibroblasts reveals that miR-146a, a miRNA with a validated role in regulating the senescence associated secretory pathway, is also regulated during extended cell culture independently of senescence. The discovery that miRNA expression is impacted by expression of ectopic hTERT as well as extended passaging in immortalized fibroblasts contributes to a comprehensive understanding of the connections between telomerase expression, senescence and processes of cellular aging.

  2. Modulation of Cell Cycle Profile by Chlorella vulgaris Prevents Replicative Senescence of Human Diploid Fibroblasts

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    Tayyebeh Saberbaghi

    2013-01-01

    Full Text Available In this study, the effects of Chlorella vulgaris (CV on replicative senescence of human diploid fibroblasts (HDFs were investigated. Hot water extract of CV was used to treat HDFs at passages 6, 15, and 30 which represent young, presenescence, and senescence ages, respectively. The level of DNA damage was determined by comet assay while apoptosis and cell cycle profile were determined using FACSCalibur flow cytometer. Our results showed direct correlation between increased levels of damaged DNA and apoptosis with senescence in untreated HDFs (P<0.05. Cell cycle profile showed increased population of untreated senescent cells that enter G0/G1 phase while the cell population in S phase decreased significantly (P<0.05. Treatment with CV however caused a significant reduction in the level of damaged DNA and apoptosis in all age groups of HDFs (P<0.05. Cell cycle analysis showed that treatment with CV increased significantly the percentage of senescent HDFs in S phase and G2/M phases but decreased the population of cells in G0/G1 phase (P<0.05. In conclusion, hot water extract of Chlorella vulgaris effectively decreased the biomarkers of ageing, indicating its potential as an antiageing compound.

  3. Modulation of Cell Cycle Profile by Chlorella vulgaris Prevents Replicative Senescence of Human Diploid Fibroblasts.

    Science.gov (United States)

    Saberbaghi, Tayyebeh; Abbasian, Firouz; Mohd Yusof, Yasmin Anum; Makpol, Suzana

    2013-01-01

    In this study, the effects of Chlorella vulgaris (CV) on replicative senescence of human diploid fibroblasts (HDFs) were investigated. Hot water extract of CV was used to treat HDFs at passages 6, 15, and 30 which represent young, presenescence, and senescence ages, respectively. The level of DNA damage was determined by comet assay while apoptosis and cell cycle profile were determined using FACSCalibur flow cytometer. Our results showed direct correlation between increased levels of damaged DNA and apoptosis with senescence in untreated HDFs (P < 0.05). Cell cycle profile showed increased population of untreated senescent cells that enter G0/G1 phase while the cell population in S phase decreased significantly (P < 0.05). Treatment with CV however caused a significant reduction in the level of damaged DNA and apoptosis in all age groups of HDFs (P < 0.05). Cell cycle analysis showed that treatment with CV increased significantly the percentage of senescent HDFs in S phase and G2/M phases but decreased the population of cells in G0/G1 phase (P < 0.05). In conclusion, hot water extract of Chlorella vulgaris effectively decreased the biomarkers of ageing, indicating its potential as an antiageing compound.

  4. p38 (MAPK) stress signalling in replicative senescence in fibroblasts from progeroid and genomic instability syndromes.

    Science.gov (United States)

    Tivey, Hannah S E; Brook, Amy J C; Rokicki, Michal J; Kipling, David; Davis, Terence

    2013-02-01

    Werner Syndrome (WS) is a human segmental progeria resulting from mutations in a DNA helicase. WS fibroblasts have a shortened replicative capacity, an aged appearance, and activated p38 MAPK, features that can be modulated by inhibition of the p38 pathway. Loss of the WRNp RecQ helicase has been shown to result in replicative stress, suggesting that a link between faulty DNA repair and stress-induced premature cellular senescence may lead to premature ageing in WS. Other progeroid syndromes that share overlapping pathophysiological features with WS also show defects in DNA processing, raising the possibility that faulty DNA repair, leading to replicative stress and premature cellular senescence, might be a more widespread feature of premature ageing syndromes. We therefore analysed replicative capacity, cellular morphology and p38 activation, and the effects of p38 inhibition, in fibroblasts from a range of progeroid syndromes. In general, populations of young fibroblasts from non-WS progeroid syndromes do not have a high level of cells with an enlarged morphology and F-actin stress fibres, unlike young WS cells, although this varies between strains. p38 activation and phosphorylated HSP27 levels generally correlate well with cellular morphology, and treatment with the p38 inhibitor SB203580 effects cellular morphology only in strains with enlarged cells and phosphorylated HSP27. For some syndromes fibroblast replicative capacity was within the normal range, whereas for others it was significantly shorter (e.g. HGPS and DKC). However, although in most cases SB203580 extended replicative capacity, with the exception of WS and DKC the magnitude of the effect was not significantly different from normal dermal fibroblasts. This suggests that stress-induced premature cellular senescence via p38 activation is restricted to a small subset of progeroid syndromes.

  5. Resveratrol sequentially induces replication and oxidative stresses to drive p53-CXCR2 mediated cellular senescence in cancer cells.

    Science.gov (United States)

    Li, Boxuan; Hou, Dong; Guo, Haiyang; Zhou, Haibin; Zhang, Shouji; Xu, Xiuhua; Liu, Qiao; Zhang, Xiyu; Zou, Yongxin; Gong, Yaoqin; Shao, Changshun

    2017-03-16

    Resveratrol (RSV) acts either as an antioxidant or a pro-oxidant depending on contexts. RSV-treated cancer cells may experience replication stress that can lead to cellular senescence or apoptosis. While both oxidative and replication stresses may mediate the anti-proliferation effect of RSV, to what extent each contributes to the impaired proliferation in response to RSV remains uncharacterized. We here report the study of the roles of replication and oxidative stresses in mediating cellular senescence in cancer cells treated with RSV. RSV induced S-phase arrest and cellular senescence in a dose-dependent manner in U2OS and A549 cancer cells as well as in normal human fibroblasts. We observed that nucleosides significantly alleviated RSV-induced replication stress and DNA damage response, and consequently attenuating cellular senescence. While the elevation of reactive oxygen species (ROS) also mediated the pro-senescent effect of RSV, it occurred after S-phase arrest. However, the induction of ROS by RSV was independent of S-phase arrest and actually reinforced the latter. We also demonstrated a critical role of the p53-CXCR2 axis in mediating RSV-induced senescence. Interestingly, CXCR2 also functioned as a barrier to apoptosis. Together, our results provided more insights into the biology of RSV-induced stress and its cellular consequences.

  6. Tocotrienol-Rich Fraction Ameliorates Antioxidant Defense Mechanisms and Improves Replicative Senescence-Associated Oxidative Stress in Human Myoblasts

    Directory of Open Access Journals (Sweden)

    Shy Cian Khor

    2017-01-01

    Full Text Available During aging, oxidative stress affects the normal function of satellite cells, with consequent regeneration defects that lead to sarcopenia. This study aimed to evaluate tocotrienol-rich fraction (TRF modulation in reestablishing the oxidative status of myoblasts during replicative senescence and to compare the effects of TRF with other antioxidants (α-tocopherol (ATF and N-acetyl-cysteine (NAC. Primary human myoblasts were cultured to young, presenescent, and senescent phases. The cells were treated with antioxidants for 24 h, followed by the assessment of free radical generation, lipid peroxidation, antioxidant enzyme mRNA expression and activities, and the ratio of reduced to oxidized glutathione. Our data showed that replicative senescence increased reactive oxygen species (ROS generation and lipid peroxidation in myoblasts. Treatment with TRF significantly diminished ROS production and decreased lipid peroxidation in senescent myoblasts. Moreover, the gene expression of superoxide dismutase (SOD2, catalase (CAT, and glutathione peroxidase (GPX1 was modulated by TRF treatment, with increased activity of superoxide dismutase and catalase and reduced glutathione peroxidase in senescent myoblasts. In comparison to ATF and NAC, TRF was more efficient in heightening the antioxidant capacity and reducing free radical insults. These results suggested that TRF is able to ameliorate antioxidant defense mechanisms and improves replicative senescence-associated oxidative stress in myoblasts.

  7. Sirtuin 6 (SIRT6) rescues the decline of homologous recombination repair during replicative senescence

    Science.gov (United States)

    Mao, Zhiyong; Tian, Xiao; Van Meter, Michael; Ke, Zhonghe; Gorbunova, Vera; Seluanov, Andrei

    2012-01-01

    Genomic instability is a hallmark of aging tissues. Genomic instability may arise from the inefficient or aberrant function of DNA double-stranded break (DSB) repair. DSBs are repaired by homologous recombination (HR) and nonhomologous DNA end joining (NHEJ). HR is a precise pathway, whereas NHEJ frequently leads to deletions or insertions at the repair site. Here, we used normal human fibroblasts with a chromosomally integrated HR reporter cassette to examine the changes in HR efficiency as cells progress to replicative senescence. We show that HR declines sharply with increasing replicative age, with an up to 38-fold decrease in efficiency in presenescent cells relative to young cells. This decline is not explained by a reduction of the number of cells in S/G2/M stage as presenescent cells are actively dividing. Expression of proteins involved in HR such as Rad51, Rad51C, Rad52, NBS1, and Sirtuin 6 (SIRT6) diminished with cellular senescence. Supplementation of Rad51, Rad51C, Rad52, and NBS1 proteins, either individually or in combination, did not rescue the senescence-related decline of HR. However, overexpression of SIRT6 in “middle-aged” and presenescent cells strongly stimulated HR repair, and this effect was dependent on mono-ADP ribosylation activity of poly(ADP-ribose) polymerase (PARP1). These results suggest that in aging cells, the precise HR pathway becomes repressed giving way to a more error-prone NHEJ pathway. These changes in the processing of DSBs may contribute to age-related genomic instability and a higher incidence of cancer with age. SIRT6 activation provides a potential therapeutic strategy to prevent the decline in genome maintenance. PMID:22753495

  8. Microarray analysis of E-box binding-related gene expression in young and replicatively senescent human fibroblasts.

    Science.gov (United States)

    Semov, Alexandre; Marcotte, Richard; Semova, Natalie; Ye, Xiangyun; Wang, Eugenia

    2002-03-01

    An E-box (CACGTG) designer microarray was developed to monitor a group of genes whose expressions share a particular regulatory mode. Sensitivity and specificity of microarray hybridization, as well as variability of microarray data, were evaluated. This designer microarray was used to generate expression profiles of E-box binding-related genes in WI-38 fibroblast cultures at three different growth states: low-passage replicating, low-passage contact-inhibited quiescent, and replicatively senescent. Microarray gene screening reveals that quiescent and senescent cells, in comparison with replicating ones, are characterized by downregulation of Pam, a protein associated with c-Myc, and upregulation of Mad family genes, Max dimerization proteins. Moreover, quiescence and senescence can be distinguished by increased expression of Irlb, c-Myc transcription factor, and Miz-1, c-Myc-interacting Zn finger protein 1, only in the former state. Senescence is characterized by downregulation of Id4, inhibitor of DNA binding 4, and Mitf, microphthalmia-associated transcription factor, in comparison with young replicating and quiescent states. Differential expression of genes detected by microarray hybridization was independently confirmed by reverse transcription polymerase chain reaction technique. Alterations in the expression of E-box-binding transcription factors and c-Myc-binding proteins demonstrate the importance of these genes in establishing the contact-inhibited quiescent or senescent phenotypes.

  9. Modeling inhomogeneous DNA replication kinetics.

    Directory of Open Access Journals (Sweden)

    Michel G Gauthier

    Full Text Available In eukaryotic organisms, DNA replication is initiated at a series of chromosomal locations called origins, where replication forks are assembled proceeding bidirectionally to replicate the genome. The distribution and firing rate of these origins, in conjunction with the velocity at which forks progress, dictate the program of the replication process. Previous attempts at modeling DNA replication in eukaryotes have focused on cases where the firing rate and the velocity of replication forks are homogeneous, or uniform, across the genome. However, it is now known that there are large variations in origin activity along the genome and variations in fork velocities can also take place. Here, we generalize previous approaches to modeling replication, to allow for arbitrary spatial variation of initiation rates and fork velocities. We derive rate equations for left- and right-moving forks and for replication probability over time that can be solved numerically to obtain the mean-field replication program. This method accurately reproduces the results of DNA replication simulation. We also successfully adapted our approach to the inverse problem of fitting measurements of DNA replication performed on single DNA molecules. Since such measurements are performed on specified portion of the genome, the examined DNA molecules may be replicated by forks that originate either within the studied molecule or outside of it. This problem was solved by using an effective flux of incoming replication forks at the model boundaries to represent the origin activity outside the studied region. Using this approach, we show that reliable inferences can be made about the replication of specific portions of the genome even if the amount of data that can be obtained from single-molecule experiments is generally limited.

  10. Accelerated Telomere Shortening and Replicative Senescence in Human Fibroblasts Overexpressing Mutant and Wild Type Lamin A

    Science.gov (United States)

    Huang, Shurong; Risques, Rosa Ana; Martin, George M.; Rabinovitch, Peter S.; Oshima, Junko

    2008-01-01

    LMNA mutations are responsible for a variety of genetic disorders, including muscular dystrophy, lipodystrophy, and certain progeroid syndromes, notably Hutchinson-Gilford Progeria. Although a number of clinical features of these disorders are suggestive of accelerated aging, it is not known whether cells derived from these patients exhibit cellular phenotypes associated with accelerated aging. We examined a series of isogenic skin fibroblast lines transfected with LMNA constructs bearing known pathogenic point mutations or deletion mutations found in progeroid syndromes. Fibroblasts overexpressing mutant lamin A exhibited accelerated rates of loss of telomeres and shortened replicative lifespans, in addition to abnormal nuclear morphology. To our surprise, these abnormalities were also observed in lines overexpressing wild-type lamin A. Copy number variants are common in human populations; those involving LMNA, whether arising meiotically or mitotically, might lead to progeroid phenotypes. In an initial pilot study of 23 progeroid cases without detectible WRN or LMNA mutations, however, no cases of altered LMNA copy number were detected. Nevertheless, our findings raise a hypothesis that changes in lamina organization may cause accelerated telomere attrition, with different kinetics for overexpession of wild-type and mutant lamin A, which leads to rapid replicative senescence and progroid phenotypes. PMID:17870066

  11. Testing evolutionary models of senescence: traditional approaches and future directions.

    Science.gov (United States)

    Robins, Chloe; Conneely, Karen N

    2014-12-01

    From an evolutionary perspective, the existence of senescence is a paradox. Why has senescence not been more effectively selected against given its associated decreases in Darwinian fitness? Why does senescence exist and how has it evolved? Three major theories offer explanations: (1) the theory of mutation accumulation suggested by PB Medawar; (2) the theory of antagonistic pleiotropy suggested by GC Williams; and (3) the disposable soma theory suggested by TBL Kirkwood. These three theories differ in the underlying causes of aging that they propose but are not mutually exclusive. This paper compares the specific biological predictions of each theory and discusses the methods and results of previous empirical tests. Lifespan is found to be the most frequently used estimate of senescence in evolutionary investigations. This measurement acts as a proxy for an individual's rate of senescence, but provides no information on an individual's senescent state or "biological age" throughout life. In the future, use of alternative longitudinal measures of senescence may facilitate investigation of previously neglected aspects of evolutionary models, such as intra- and inter-individual heterogeneity in the process of aging. DNA methylation data are newly proposed to measure biological aging and are suggested to be particularly useful for such investigations.

  12. Insulin-like growth factor binding protein-6 delays replicative senescence of human fibroblasts

    DEFF Research Database (Denmark)

    Micutkova, Lucia; Diener, Thomas; Li, Chen;

    2011-01-01

    and apoptotic cell death was increased. Furthermore, downregulation of IGFBP-6 led to premature entry into cellular senescence. Since IGFBP-6 overexpression increased cellular lifespan, the data suggest that IGFBP-6, in contrast to other IGF binding proteins, is a negative regulator of cellular senescence...

  13. Quantitative model of cell cycle arrest and cellular senescence in primary human fibroblasts.

    Directory of Open Access Journals (Sweden)

    Sascha Schäuble

    Full Text Available Primary human fibroblasts in tissue culture undergo a limited number of cell divisions before entering a non-replicative "senescent" state. At early population doublings (PD, fibroblasts are proliferation-competent displaying exponential growth. During further cell passaging, an increasing number of cells become cell cycle arrested and finally senescent. This transition from proliferating to senescent cells is driven by a number of endogenous and exogenous stress factors. Here, we have developed a new quantitative model for the stepwise transition from proliferating human fibroblasts (P via reversibly cell cycle arrested (C to irreversibly arrested senescent cells (S. In this model, the transition from P to C and to S is driven by a stress function γ and a cellular stress response function F which describes the time-delayed cellular response to experimentally induced irradiation stress. The application of this model based on senescence marker quantification at the single-cell level allowed to discriminate between the cellular states P, C, and S and delivers the transition rates between the P, C and S states for different human fibroblast cell types. Model-derived quantification unexpectedly revealed significant differences in the stress response of different fibroblast cell lines. Evaluating marker specificity, we found that SA-β-Gal is a good quantitative marker for cellular senescence in WI-38 and BJ cells, however much less so in MRC-5 cells. Furthermore we found that WI-38 cells are more sensitive to stress than BJ and MRC-5 cells. Thus, the explicit separation of stress induction from the cellular stress response, and the differentiation between three cellular states P, C and S allows for the first time to quantitatively assess the response of primary human fibroblasts towards endogenous and exogenous stress during cellular ageing.

  14. The Tocotrienol-Rich Fraction Is Superior to Tocopherol in Promoting Myogenic Differentiation in the Prevention of Replicative Senescence of Myoblasts.

    Directory of Open Access Journals (Sweden)

    Shy Cian Khor

    Full Text Available Aging results in a loss of muscle mass and strength. Myoblasts play an important role in maintaining muscle mass through regenerative processes, which are impaired during aging. Vitamin E potentially ameliorates age-related phenotypes. Hence, this study aimed to determine the effects of the tocotrienol-rich fraction (TRF and α-tocopherol (ATF in protecting myoblasts from replicative senescence and promoting myogenic differentiation. Primary human myoblasts were cultured into young and senescent stages and were then treated with TRF or ATF for 24 h, followed by an analysis of cell proliferation, senescence biomarkers, cellular morphology and differentiation. Our data showed that replicative senescence impaired the normal regenerative processes of myoblasts, resulting in changes in cellular morphology, cell proliferation, senescence-associated β-galactosidase (SA-β-gal expression, myogenic differentiation and myogenic regulatory factors (MRFs expression. Treatment with both TRF and ATF was beneficial to senescent myoblasts in reclaiming the morphology of young cells, improved cell viability and decreased SA-β-gal expression. However, only TRF treatment increased BrdU incorporation in senescent myoblasts, as well as promoted myogenic differentiation through the modulation of MRFs at the mRNA and protein levels. MYOD1 and MYOG gene expression and myogenin protein expression were modulated in the early phases of myogenic differentiation. In conclusion, the tocotrienol-rich fraction is superior to α-tocopherol in ameliorating replicative senescence-related aberration and promoting differentiation via modulation of MRFs expression, indicating vitamin E potential in modulating replicative senescence of myoblasts.

  15. A two-step model for senescence triggered by a single critically short telomere

    DEFF Research Database (Denmark)

    Abdallah, Pauline; Luciano, Pierre; Runge, Kurt W;

    2009-01-01

    Telomeres protect chromosome ends from fusion and degradation. In the absence of a specific telomere elongation mechanism, their DNA shortens progressively with every round of replication, leading to replicative senescence. Here, we show that telomerase-deficient cells bearing a single, very short...... telomere senesce earlier, demonstrating that the length of the shortest telomere is a major determinant of the onset of senescence. We further show that Mec1p-ATR specifically recognizes the single, very short telomere causing the accelerated senescence. Strikingly, before entering senescence, cells divide...... for several generations despite complete erosion of their shortened telomeres. This pre-senescence growth requires RAD52 (radiation sensitive) and MMS1 (methyl methane sulfonate sensitive), and there is no evidence for major inter-telomeric recombination. We propose that, in the absence of telomerase, a very...

  16. Catastrophic senescence and semelparity in the Penna aging model

    CERN Document Server

    Pinol, C M N

    2010-01-01

    The catastrophic senescence of the Pacific salmon is among the initial tests used to validate the Penna aging model. Based on the mutation accumulation theory, the sudden decrease in fitness following reproduction may be solely attributed to the semelparity of the species. In this work, we report other consequences of mutation accumulation. Contrary to earlier findings, such dramatic manifestation of aging depends not only on the choice of breeding strategy but also on the value of the reproduction age, R, and the mutation threshold, T. Senescence is catastrophic when T\\leq R. As the organism's tolerance for harmful genetic mutations increases, the aging process becomes more gradual. We observe senescence that is threshold dependent whenever T>R. That is, the sudden drop in survival rate occurs at age equal to the mutation threshold value.

  17. Cellular Senescence: A Translational Perspective

    Directory of Open Access Journals (Sweden)

    James L. Kirkland

    2017-07-01

    Full Text Available Cellular senescence entails essentially irreversible replicative arrest, apoptosis resistance, and frequently acquisition of a pro-inflammatory, tissue-destructive senescence-associated secretory phenotype (SASP. Senescent cells accumulate in various tissues with aging and at sites of pathogenesis in many chronic diseases and conditions. The SASP can contribute to senescence-related inflammation, metabolic dysregulation, stem cell dysfunction, aging phenotypes, chronic diseases, geriatric syndromes, and loss of resilience. Delaying senescent cell accumulation or reducing senescent cell burden is associated with delay, prevention, or alleviation of multiple senescence-associated conditions. We used a hypothesis-driven approach to discover pro-survival Senescent Cell Anti-apoptotic Pathways (SCAPs and, based on these SCAPs, the first senolytic agents, drugs that cause senescent cells to become susceptible to their own pro-apoptotic microenvironment. Several senolytic agents, which appear to alleviate multiple senescence-related phenotypes in pre-clinical models, are beginning the process of being translated into clinical interventions that could be transformative.

  18. The profile of lysosomal exoglycosidases in replicative and stress-induced senescence in early passage human fibroblasts

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    Małgorzata Knaś

    2012-07-01

    Full Text Available The aim of the present study was to assess the profiles of the exoglycosidases: N-acetyl-β-hexosoaminidase, β glucuronidase and β galactosidase, α mannosidase and α fucosidase in fibroblast culture undergoing replicative and stress-induced senescence. Half of the cell culture was grown in normal conditions, without the stressor, and the other half of the cell was treated with 0.15 mM tert-butylhydroperoxide. The activities of total N-acetyl-β-hexosoaminidase as well as β glucuronidase in the cell lysate were determined in duplicates using the method of Marciniak et al. The activities of β galactosidase, α mannosidase and α fucosidase in the cell lysate were determined in duplicates using the method of Chatteriee et al. with the modification by Zwierz et al. The activities of the exoglycosidases examined, with the exception of β glucuronidase, showed a significant increase between individual days of the experiment in both non-stressed and stressed fibroblast cell culture. On each day of the experiment, in the cell lysate of stressed fibroblasts, the activities of exoglycosidases were significantly higher compared to the non-stressed cells. There were very strong correlations between SA-β-GAL staining and b galactosidase activity on individual days of the experiment in both non-stressed and stressed fibroblast cell culture. Replicative and stress-induced senescence results in significant changes to the level of lysosomal exoglycosidases, and results in enhanced lysosomal degradative capacity.

  19. Cellular senescence mediates fibrotic pulmonary disease

    Science.gov (United States)

    Schafer, Marissa J.; White, Thomas A.; Iijima, Koji; Haak, Andrew J.; Ligresti, Giovanni; Atkinson, Elizabeth J.; Oberg, Ann L.; Birch, Jodie; Salmonowicz, Hanna; Zhu, Yi; Mazula, Daniel L.; Brooks, Robert W.; Fuhrmann-Stroissnigg, Heike; Pirtskhalava, Tamar; Prakash, Y. S.; Tchkonia, Tamara; Robbins, Paul D.; Aubry, Marie Christine; Passos, João F.; Kirkland, James L.; Tschumperlin, Daniel J.; Kita, Hirohito; LeBrasseur, Nathan K.

    2017-01-01

    Idiopathic pulmonary fibrosis (IPF) is a fatal disease characterized by interstitial remodelling, leading to compromised lung function. Cellular senescence markers are detectable within IPF lung tissue and senescent cell deletion rejuvenates pulmonary health in aged mice. Whether and how senescent cells regulate IPF or if their removal may be an efficacious intervention strategy is unknown. Here we demonstrate elevated abundance of senescence biomarkers in IPF lung, with p16 expression increasing with disease severity. We show that the secretome of senescent fibroblasts, which are selectively killed by a senolytic cocktail, dasatinib plus quercetin (DQ), is fibrogenic. Leveraging the bleomycin-injury IPF model, we demonstrate that early-intervention suicide-gene-mediated senescent cell ablation improves pulmonary function and physical health, although lung fibrosis is visibly unaltered. DQ treatment replicates benefits of transgenic clearance. Thus, our findings establish that fibrotic lung disease is mediated, in part, by senescent cells, which can be targeted to improve health and function. PMID:28230051

  20. Cellular replication limits in the Luria-Delbrück mutation model

    Science.gov (United States)

    Rodriguez-Brenes, Ignacio A.; Wodarz, Dominik; Komarova, Natalia L.

    2016-08-01

    Originally developed to elucidate the mechanisms of natural selection in bacteria, the Luria-Delbrück model assumed that cells are intrinsically capable of dividing an unlimited number of times. This assumption however, is not true for human somatic cells which undergo replicative senescence. Replicative senescence is thought to act as a mechanism to protect against cancer and the escape from it is a rate-limiting step in cancer progression. Here we introduce a Luria-Delbrück model that explicitly takes into account cellular replication limits in the wild type cell population and models the emergence of mutants that escape replicative senescence. We present results on the mean, variance, distribution, and asymptotic behavior of the mutant population in terms of three classical formulations of the problem. More broadly the paper introduces the concept of incorporating replicative limits as part of the Luria-Delbrück mutational framework. Guidelines to extend the theory to include other types of mutations and possible applications to the modeling of telomere crisis and fluctuation analysis are also discussed.

  1. Embryonic senescence and laminopathies in a progeroid zebrafish model.

    Directory of Open Access Journals (Sweden)

    Eriko Koshimizu

    Full Text Available BACKGROUND: Mutations that disrupt the conversion of prelamin A to mature lamin A cause the rare genetic disorder Hutchinson-Gilford progeria syndrome and a group of laminopathies. Our understanding of how A-type lamins function in vivo during early vertebrate development through aging remains limited, and would benefit from a suitable experimental model. The zebrafish has proven to be a tractable model organism for studying both development and aging at the molecular genetic level. Zebrafish show an array of senescence symptoms resembling those in humans, which can be targeted to specific aging pathways conserved in vertebrates. However, no zebrafish models bearing human premature senescence currently exist. PRINCIPAL FINDINGS: We describe the induction of embryonic senescence and laminopathies in zebrafish harboring disturbed expressions of the lamin A gene (LMNA. Impairments in these fish arise in the skin, muscle and adipose tissue, and sometimes in the cartilage. Reduced function of lamin A/C by translational blocking of the LMNA gene induced apoptosis, cell-cycle arrest, and craniofacial abnormalities/cartilage defects. By contrast, induced cryptic splicing of LMNA, which generates the deletion of 8 amino acid residues lamin A (zlamin A-Δ8, showed embryonic senescence and S-phase accumulation/arrest. Interestingly, the abnormal muscle and lipodystrophic phenotypes were common in both cases. Hence, both decrease-of-function of lamin A/C and gain-of-function of aberrant lamin A protein induced laminopathies that are associated with mesenchymal cell lineages during zebrafish early development. Visualization of individual cells expressing zebrafish progerin (zProgerin/zlamin A-Δ37 fused to green fluorescent protein further revealed misshapen nuclear membrane. A farnesyltransferase inhibitor reduced these nuclear abnormalities and significantly prevented embryonic senescence and muscle fiber damage induced by zProgerin. Importantly, the adult

  2. The Redox-sensitive Induction of the Local Angiotensin System Promotes Both Premature and Replicative Endothelial Senescence: Preventive Effect of a Standardized Crataegus Extract.

    Science.gov (United States)

    Khemais-Benkhiat, Sonia; Idris-Khodja, Noureddine; Ribeiro, Thais Porto; Silva, Grazielle Caroline; Abbas, Malak; Kheloufi, Marouane; Lee, Jung-Ok; Toti, Florence; Auger, Cyril; Schini-Kerth, Valérie B

    2016-12-01

    Endothelial senescence, characterized by an irreversible cell cycle arrest, oxidative stress, and downregulation of endothelial nitric oxide synthase (eNOS), has been shown to promote endothelial dysfunction leading to the development of age-related vascular disorders. This study has assessed the possibility that the local angiotensin system promotes endothelial senescence in coronary artery endothelial cells and also the protective effect of the Crataegus extract WS1442, a quantified hawthorn extract. Serial passaging from P1 to P4 (replicative senescence) and treatment of P1 endothelial cells with the eNOS inhibitor L-NAME (premature senescence) promoted acquisition of markers of senescence, enhanced ROS formation, decreased eNOS expression, and upregulation of angiotensin-converting enzyme (ACE) and AT1 receptors. Increased SA-β-gal activity and the upregulation of ACE and AT1R in senescent cells were prevented by antioxidants, an ACE inhibitor, and by an AT1 receptor blocker. WS1442 prevented SA-β-gal activity, the downregulation of eNOS, and oxidative stress in P3 cells. These findings indicate that the impairment of eNOS-derived nitric oxide formation favors a pro-oxidant response triggering the local angiotensin system, which, in turn, promotes endothelial senescence. Such a sequence of events can be effectively inhibited by a standardized polyphenol-rich extract mainly by targeting the oxidative stress. © The Author 2015. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  3. Antrodia camphorata extract induces replicative senescence in superficial TCC, and inhibits the absolute migration capability in invasive bladder carcinoma cells.

    Science.gov (United States)

    Peng, Chiung-Chi; Chen, Kuan-Chou; Peng, Robert Y; Chyau, Charng-Cherng; Su, Ching-Hua; Hsieh-Li, Hsiu Mei

    2007-01-01

    The Antrodia camphorata crude extract (ACCE), an extract obtained from a precious traditional Chinese folkloric herbal medicine Zhan-Ku (a camphor tree mushroom) since the 18th century, has showed rather significant inhibitory effects on the growth and proliferation of the transitional cell carcinomas (TCC) cell lines RT4, TSGH-8301, and T24. On treatment with ACCE at 100 microg/mL, the p53-independent overexpression of p21 with simultaneous down alteration of pRb was observed in RT4, which was thus speculative of proceeding through a mechanism of replicative senescence. On the contrary treatment with ACCE, at 50 microg/mL, resulting in simultaneous down-regulations of Cdc2 and Cyclin B1, with suppression of the absolute migrating capability of the two cell lines TSGH-8301 and T24, and eventually the cell deaths. We conclude that ACCE can be rather effective and beneficial in suppression of both the superficial cancer cell line RT4 and the metastatic cell lines (TSGH-8301 and T24) through different mechanisms.

  4. Semiconservative replication in the quasispecies model

    Science.gov (United States)

    Tannenbaum, Emmanuel; Deeds, Eric J.; Shakhnovich, Eugene I.

    2004-06-01

    This paper extends Eigen’s quasispecies equations to account for the semiconservative nature of DNA replication. We solve the equations in the limit of infinite sequence length for the simplest case of a static, sharply peaked fitness landscape. We show that the error catastrophe occurs when μ , the product of sequence length and per base pair mismatch probability, exceeds 2 ln [2/ ( 1+1/k ) ] , where k>1 is the first-order growth rate constant of the viable “master” sequence (with all other sequences having a first-order growth rate constant of 1 ). This is in contrast to the result of ln k for conservative replication. In particular, as k→∞ , the error catastrophe is never reached for conservative replication, while for semiconservative replication the critical μ approaches 2 ln 2 . Semiconservative replication is therefore considerably less robust than conservative replication to the effect of replication errors. We also show that the mean equilibrium fitness of a semiconservatively replicating system is given by k ( 2 e-μ/2 -1 ) below the error catastrophe, in contrast to the standard result of k e-μ for conservative replication (derived by Kimura and Maruyama in 1966). From this result it is readily shown that semiconservative replication is necessary to account for the observation that, at sufficiently high mutagen concentrations, faster replicating cells will die more quickly than more slowly replicating cells. Thus, in contrast to Eigen’s original model, the semiconservative quasispecies equations are able to provide a mathematical basis for explaining the efficacy of mutagens as chemotherapeutic agents.

  5. Concurrence of replicative senescence and elevated expression of p16(INK4A) with subculture-induced but not calcium-induced differentiation in normal human oral keratinocytes.

    Science.gov (United States)

    Lee, G; Park, B S; Han, S E; Oh, J E; You, Y O; Baek, J H; Kim, G S; Min, B M

    2000-10-01

    Primary normal human oral keratinocytes (NHOKs) undergo differentiation in the presence of calcium concentrations higher than 0.15 mM in vitro, which is useful in investigating the mechanisms involved in the differentiation of epithelial cells. Serial subculture of NHOKs to the postmitotic stage also induces terminal differentiation. However, the detailed mechanisms of both differentiation processes remain substantially unknown. To investigate the molecular differences in these processes, NHOKs were induced to differentiate by exposure to 1.2 mM of calcium and by serial subculture to the postmitotic stage. To study whether the cells were induced to differentiate and to undergo replicative senescence, the amount of cellular involucrin and the expression of senescence-associated beta-galactosidase (SA-beta-gal) were measured respectively. The expression of replicative senescence-associated genes and the activity of telomerase from the differentiated cells were also determined. Both calcium treatment and serial subculture to the postmitotic stage notably elevated the cellular involucrin. The percentage of SA-beta-gal-positive cells was significantly elevated by the continued subculture, but such changes were not observed in keratinocytes exposed to calcium. The concentration of cellular p16(INK4A) protein was progressively increased by the continued subculture but was not changed by calcium treatment. On the other hand, the concentrations of cellular p53 were similar in both differentiation processes. However, telomerase activity was lost in NHOKs that had undergone differentiation by both calcium treatment and serial subculture. The results indicate that calcium-induced differentiation of NHOKs has similar characteristics to their serial subculture-induced differentiation, but that the differentiation processes are not identical, because calcium-induced differentiation does not concur with either replicative senescence or the gradually increased concentration of p16

  6. Preventive Effects of Epigallocatechin-3-O-Gallate against Replicative Senescence Associated with p53 Acetylation in Human Dermal Fibroblasts

    Directory of Open Access Journals (Sweden)

    Dong-Wook Han

    2012-01-01

    Full Text Available Considering the various pharmacological activities of epigallocatechin-3-O-gallate (EGCG including anticancer, and anti-inflammatory, antidiabetic, and so forth, relatively less attention has been paid to the antiaging effect of EGCG on primary cells. In this study, the preventive effects of EGCG against serial passage-induced senescence were investigated in primary cells including rat vascular smooth muscle cells (RVSMCs, human dermal fibroblasts (HDFs, and human articular chondrocytes (HACs. The involvement of Sirt1 and acetylated p53 was examined as an underlying mechanism for the senescence preventive activity of EGCG in HDFs. All cells were employed with the initial passage number (PN between 3 and 7. For inducing senescence, the cells were serially passaged at the predetermined times and intervals in the absence or presence of EGCG (50 or 100 μM. Serial passage-induced senescence in RVSMCs and HACs was able to be significantly prevented at 50 μM EGCG, while in HDFs, 100 μM EGCG could significantly prevent senescence and recover their cell cycle progression close to the normal level. Furthermore, EGCG was found to prevent serial passage- and H2O2-induced senescence in HDFs by suppressing p53 acetylation, but the Sirt1 activity was unaffected. In addition, proliferating HDFs showed similar cellular uptake of FITC-conjugated EGCG into the cytoplasm with their senescent counterparts but different nuclear translocation of it from them, which would partly account for the differential responses to EGCG in proliferating versus senescent cells. Taking these results into consideration, it is suggested that EGCG may be exploited to craft strategies for the development of an antiaging or age-delaying agent.

  7. Stable cellular senescence is associated with persistent DDR activation.

    Science.gov (United States)

    Fumagalli, Marzia; Rossiello, Francesca; Mondello, Chiara; d'Adda di Fagagna, Fabrizio

    2014-01-01

    The DNA damage response (DDR) is activated upon DNA damage generation to promote DNA repair and inhibit cell cycle progression in the presence of a lesion. Cellular senescence is a permanent cell cycle arrest characterized by persistent DDR activation. However, some reports suggest that DDR activation is a feature only of early cellular senescence that is then lost with time. This challenges the hypothesis that cellular senescence is caused by persistent DDR activation. To address this issue, we studied DDR activation dynamics in senescent cells. Here we show that normal human fibroblasts retain DDR markers months after replicative senescence establishment. Consistently, human fibroblasts from healthy aged donors display markers of DDR activation even three years in culture after entry into replicative cellular senescence. However, by extending our analyses to different human cell strains, we also observed an apparent DDR loss with time following entry into cellular senescence. This though correlates with the inability of these cell strains to survive in culture upon replicative or irradiation-induced cellular senescence. We propose a model to reconcile these results. Cell strains not suffering the prolonged in vitro culture stress retain robust DDR activation that persists for years, indicating that under physiological conditions persistent DDR is causally involved in senescence establishment and maintenance. However, cell strains unable to maintain cell viability in vitro, due to their inability to cope with prolonged cell culture-associated stress, show an only-apparent reduction in DDR foci which is in fact due to selective loss of the most damaged cells.

  8. Adressing Replication and Model Uncertainty

    DEFF Research Database (Denmark)

    Ebersberger, Bernd; Galia, Fabrice; Laursen, Keld

    Many fields of strategic management are subject to an important degree of model uncertainty. This is because the true model, and therefore the selection of appropriate explanatory variables, is essentially unknown. Drawing on the literature on the determinants of innovation, and by analyzing inno...

  9. Adressing Replication and Model Uncertainty

    DEFF Research Database (Denmark)

    Ebersberger, Bernd; Galia, Fabrice; Laursen, Keld

    Many fields of strategic management are subject to an important degree of model uncertainty. This is because the true model, and therefore the selection of appropriate explanatory variables, is essentially unknown. Drawing on the literature on the determinants of innovation, and by analyzing inno...

  10. Multiseason occupancy models for correlated replicate surveys

    Science.gov (United States)

    Hines, James; Nichols, James; Collazo, Jaime

    2014-01-01

    Occupancy surveys collecting data from adjacent (sometimes correlated) spatial replicates have become relatively popular for logistical reasons. Hines et al. (2010) presented one approach to modelling such data for single-season occupancy surveys. Here, we present a multiseason analogue of this model (with corresponding software) for inferences about occupancy dynamics. We include a new parameter to deal with the uncertainty associated with the first spatial replicate for both single-season and multiseason models. We use a case study, based on the brown-headed nuthatch, to assess the need for these models when analysing data from the North American Breeding Bird Survey (BBS), and we test various hypotheses about occupancy dynamics for this species in the south-eastern United States. The new model permits inference about local probabilities of extinction, colonization and occupancy for sampling conducted over multiple seasons. The model performs adequately, based on a small simulation study and on results of the case study analysis. The new model incorporating correlated replicates was strongly favoured by model selection for the BBS data for brown-headed nuthatch (Sitta pusilla). Latitude was found to be an important source of variation in local colonization and occupancy probabilities for brown-headed nuthatch, with both probabilities being higher near the centre of the species range, as opposed to more northern and southern areas. We recommend this new occupancy model for detection–nondetection studies that use potentially correlated replicates.

  11. Cold-Inducible RNA-Binding Protein Bypasses Replicative Senescence in Primary Cells through Extracellular Signal-Regulated Kinase 1 and 2 Activation▿ †

    Science.gov (United States)

    Artero-Castro, Ana; Callejas, Francisco B.; Castellvi, Josep; Kondoh, Hiroshi; Carnero, Amancio; Fernández-Marcos, Pablo J.; Serrano, Manuel; Ramón y Cajal, Santiago; Lleonart, Matilde E.

    2009-01-01

    Embryonic stem cells are immortalized cells whose proliferation rate is comparable to that of carcinogenic cells. To study the expression of embryonic stem cell genes in primary cells, genetic screening was performed by infecting mouse embryonic fibroblasts (MEFs) with a cDNA library from embryonic stem cells. Cold-inducible RNA-binding protein (CIRP) was identified due to its ability to bypass replicative senescence in primary cells. CIRP enhanced extracellular signal-regulated kinase 1 and 2 (ERK1/2) phosphorylation, and treatment with an MEK inhibitor decreased the proliferation caused by CIRP. In contrast to CIRP upregulation, CIRP downregulation decreased cell proliferation and resulted in inhibition of phosphorylated ERK1/2 inhibition. This is the first evidence that ERK1/2 activation, through the same mechanism as that described for a Val12 mutant K-ras to induce premature senescence, is able to bypass senescence in the absence of p16INK4a, p21WAF1, and p19ARF upregulation. Moreover, these results show that CIRP functions by stimulating general protein synthesis with the involvement of the S6 and 4E-BP1 proteins. The overall effect is an increase in kinase activity of the cyclin D1-CDK4 complex, which is in accordance with the proliferative capacity of CIRP MEFs. Interestingly, CIRP mRNA and protein were upregulated in a subgroup of cancer patients, a finding that may be of relevance for cancer research. PMID:19158277

  12. Frailty in state-space models: application to actuarial senescence in the Dipper.

    Science.gov (United States)

    Marzolin, Gilbert; Charmantier, Anne; Gimenez, Olivier

    2011-03-01

    Senescence, a decrease in life history traits with age, is a within-individual process. The lack of suitable methods to deal with individual heterogeneity has long impeded progress in exploring senescence in wild populations. Analyses of survival senescence are additionally complicated by the often neglected issue of imperfect detectability. To deal with both these issues, we developed state-space models to analyze capture-mark-recapture data while accounting for individual heterogeneity by incorporating random effects. We illustrated our approach by applying it to 29 years of data on breeding females in a Dipper (Cinclus cinclus) population. We highlighted patterns of age-related variation in annual survival by statistical comparisons of piecewise linear, quadratic, Gompertz, and Weibull survival models. The Gompertz model was ranked first in our set. It provided strong evidence for actuarial senescence with an onset of senescence estimated at about 2.3 years. The probability for this model to involve a frailty was 0.15, and the probability to involve an individual latent effect in detection was about 0.4. The estimated mean age at first reproduction was 1.2 years. The general case model described here in detail should encourage the reanalysis of actuarial senescence in cases where imperfect detection or individual heterogeneity is suspected.

  13. The essence of senescence

    National Research Council Canada - National Science Library

    Kuilman, Thomas; Michaloglou, Chrysiis; Mooi, Wolter J; Peeper, Daniel S

    2010-01-01

    Almost half a century after the first reports describing the limited replicative potential of primary cells in culture, there is now overwhelming evidence for the existence of "cellular senescence" in vivo...

  14. Markers of cellular senescence. Telomere shortening as a marker of cellular senescence.

    Science.gov (United States)

    Bernadotte, Alexandra; Mikhelson, Victor M; Spivak, Irina M

    2016-01-01

    The cellular senescence definition comes to the fact of cells irreversible proliferation disability. Besides the cell cycle arrest, senescent cells go through some morphological, biochemical, and functional changes which are the signs of cellular senescence. The senescent cells (including replicative senescence and stress-induced premature senescence) of all the tissues look alike. They are metabolically active and possess the set of characteristics in vitro and in vivo, which are known as biomarkers of aging and cellular senescence. Among biomarkers of cellular senescence telomere shortening is a rather elegant frequently used biomarker. Validity of telomere shortening as a marker for cellular senescence is based on theoretical and experimental data.

  15. Redox-dependent induction of antioxidant defenses by phenolic diterpenes confers stress tolerance in normal human skin fibroblasts: Insights on replicative senescence.

    Science.gov (United States)

    Carvalho, Ana C; Gomes, Andreia C; Pereira-Wilson, Cristina; Lima, Cristovao F

    2015-06-01

    Mild stress-induced hormesis represents a promising strategy for targeting the age-related accumulation of molecular damage and, therefore, for preventing diseases and achieving healthy aging. Fruits, vegetables, and spices contain a wide variety of hormetic phytochemicals, which may explain the beneficial health effects associated with the consumption of these dietary components. In the present study, the induction of cellular antioxidant defenses by the phenolic diterpenes carnosic acid (CA) and carnosol (CS) were studied in normal human skin fibroblasts, and insights into the aging process at the cellular level investigated. We observed that CA and CS induced several cytoprotective enzymes and antioxidant defenses in human fibroblasts, whose induction was dependent on the cellular redox state for CS and associated with Nrf2 signaling for both compounds. The stress response elicited by preincubation with CS conferred a cytoprotective action against a following oxidant challenge with tert-butyl hydroperoxide, confirming its hormetic effect. Preincubation of normal fibroblasts with CS also protected against hydrogen peroxide-induced premature senescence. Furthermore, cultivation of middle passage normal human skin fibroblasts in the presence of CS ameliorated the physiological state of cells during replicative senescence. Our results support the view that mild stress-induced antioxidant defenses by CS can confer stress tolerance in normal cells and may have important implications in the promotion of healthy aging.

  16. Multiscale modeling of virus replication and spread.

    Science.gov (United States)

    Kumberger, Peter; Frey, Felix; Schwarz, Ulrich S; Graw, Frederik

    2016-07-01

    Replication and spread of human viruses is based on the simultaneous exploitation of many different host functions, bridging multiple scales in space and time. Mathematical modeling is essential to obtain a systems-level understanding of how human viruses manage to proceed through their life cycles. Here, we review corresponding advances for viral systems of large medical relevance, such as human immunodeficiency virus-1 (HIV-1) and hepatitis C virus (HCV). We will outline how the combination of mathematical models and experimental data has advanced our quantitative knowledge about various processes of these pathogens, and how novel quantitative approaches promise to fill remaining gaps.

  17. Replicatively senescent human fibroblasts reveal a distinct intracellular metabolic profile with alterations in NAD+ and nicotinamide metabolism.

    Science.gov (United States)

    James, Emma L; Lane, James A E; Michalek, Ryan D; Karoly, Edward D; Parkinson, E Kenneth

    2016-12-07

    Cellular senescence occurs by proliferative exhaustion (PEsen) or following multiple cellular stresses but had not previously been subject to detailed metabolomic analysis. Therefore, we compared PEsen fibroblasts with proliferating and transiently growth arrested controls using a combination of different mass spectroscopy techniques. PEsen cells showed many specific alterations in both the NAD+ de novo and salvage pathways including striking accumulations of nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR) in the amidated salvage pathway despite no increase in nicotinamide phosphoribosyl transferase or in the NR transport protein, CD73. Extracellular nicotinate was depleted and metabolites of the deamidated salvage pathway were reduced but intracellular NAD+ and nicotinamide were nevertheless maintained. However, sirtuin 1 was downregulated and so the accumulation of NMN and NR was best explained by reduced flux through the amidated arm of the NAD+ salvage pathway due to reduced sirtuin activity. PEsen cells also showed evidence of increased redox homeostasis and upregulated pathways used to generate energy and cellular membranes; these included nucleotide catabolism, membrane lipid breakdown and increased creatine metabolism. Thus PEsen cells upregulate several different pathways to sustain their survival which may serve as pharmacological targets for the elimination of senescent cells in age-related disease.

  18. 人胚肺成纤维细胞复制性衰老过程中端粒相关因子的表达*★%Telomere-associated factor expression in replicative senescence of human embryonic lung fibroblasts

    Institute of Scientific and Technical Information of China (English)

    杜华; 徐晓艳; 海玲; 师迎旭

    2013-01-01

    BACKGROUND: Telomere-associated proteins wil directly affect the function of telomeres, adjust the length of telomeric DNA, which are closely related with cellsenescence and carcinogenesis. OBJECTIVE: To find the key regulatory molecules in the cellsenescence process through observing the telomere-associated factor expression in normal cel replicative senescence process. METHODS: Based on established cel replicative senescence model, reverse transcription-PCR and western blot were used to detect the telomere-associated factor expression on the molecular and protein levels, including the telomere-associated factor human telomere binding protein 1, tankyrase 1, telomerase RNA, telomere protection protein 1 and P53 expressions in the human embryonic lung fibroblast replicative senescence. RESULTS AND CONCLUSION: The results showed that with the cellsenescence, transcription of human telomere binding protein 1 did not changed, while the protein expression of human telomere binding protein 1 was increased gradual y and then decreased rapidly; mRNA and protein expressions of telomere protection protein 1 did not changed; with the human embryonic lung fibroblast replicative senescence, expression of telomere protection protein 1 was decreased gradual y; with cellsenescence, telomerase RNA component showed an increasing trend; protein expression of P53 did not changed. Human telomere binding protein 1, telomere protection protein 1 and telomerase RNA play an important role in cellsenescence.%  背景:端粒相关蛋白直接影响端粒的功能,调节端粒 DNA 的长度,与细胞的衰老和癌变密切相关。目的:通过观察正常细胞复制性衰老过程中端粒相关因子的变化来找寻细胞正常衰老过程中的关键调控分子。方法:在构建好的细胞复制性衰老模型基础上,利用 RT-PCR 与 western blot 方法在分子与蛋白水平检测端粒相关因子的表达变化,主要检测人胚肺成纤维细胞在复制

  19. Replicator-dynamics models of sexual conflict.

    Science.gov (United States)

    Kimura, Mariko; Ihara, Yasuo

    2009-09-07

    Evolutionary conflict between the sexes has been studied in various taxa and in various contexts. When the sexes are in conflict over mating rates, natural selection favors both males that induce higher mating rates and females that are more successful at resisting mating attempts. Such sexual conflict may result in an escalating coevolutionary arms race between males and females. In this article, we develop simple replicator-dynamics models of sexual conflict in order to investigate its evolutionary dynamics. Two specific models of the dependence of a female's fitness on her number of matings are considered: in model 1, female fitness decreases linearly with increasing number of matings and in model 2, there is an optimal number of matings that maximizes female fitness. For each of these models, we obtain the conditions for a coevolutionary process to establish costly male and female traits and examine under what circumstances polymorphism is maintained at equilibrium. Then we discuss how assumptions in previous models of sexual conflict are translated to fit to our model framework and compare our results with those of the previous studies. The simplicity of our models allows us to consider sexual conflict in various contexts within a single framework. In addition, we find that our model 2 shows more complicated evolutionary dynamics than model 1. In particular, the population exhibits bistability, where the evolutionary outcome depends on the initial state, only in model 2.

  20. SIRT1 and AMPK in regulating mammalian senescence: a critical review and a working model.

    Science.gov (United States)

    Wang, Yu; Liang, Yan; Vanhoutte, Paul M

    2011-04-06

    Ageing in mammals remains an unsolved mystery. Anti-ageing is a recurring topic in the history of scientific research. Lifespan extension evoked by Sir2 protein in lower organisms has attracted a large amount of interests in the last decade. This review summarizes recent evidence supporting the role of a Sir2 mammalian homologue, SIRT1 (Silent information regulator T1), in regulating ageing and cellular senescence. The various signaling networks responsible for the anti-ageing and anti-senescence activity of SIRT1 have been discussed. In particular, a counter-balancing model involving the cross-talks between SIRT1 and AMP-activated protein kinase (AMPK), another stress and energy sensor, is suggested for controlling the senescence program in mammalian cells.

  1. Factor Copula Models for Replicated Spatial Data

    KAUST Repository

    Krupskii, Pavel

    2016-12-19

    We propose a new copula model that can be used with replicated spatial data. Unlike the multivariate normal copula, the proposed copula is based on the assumption that a common factor exists and affects the joint dependence of all measurements of the process. Moreover, the proposed copula can model tail dependence and tail asymmetry. The model is parameterized in terms of a covariance function that may be chosen from the many models proposed in the literature, such as the Matérn model. For some choice of common factors, the joint copula density is given in closed form and therefore likelihood estimation is very fast. In the general case, one-dimensional numerical integration is needed to calculate the likelihood, but estimation is still reasonably fast even with large data sets. We use simulation studies to show the wide range of dependence structures that can be generated by the proposed model with different choices of common factors. We apply the proposed model to spatial temperature data and compare its performance with some popular geostatistics models.

  2. Entanglement Swapping Model of DNA Replication

    CERN Document Server

    Pusuluk, Onur

    2011-01-01

    Molecular biology explains function of molecules by their geometric and electronic structures which are mainly determined by utilization of quantum effects in chemistry. However, further quantum effects are not thought to play any significant role in the essential processes of life. On the contrary, consideration of quantum circuits/protocols and organic molecules as software and hardware of living systems that are co-optimized during evolution, may be useful to pass over the difficulties raised by biochemical complexity and to understand the physics of life. In this sense, we model DNA replication with a reliable qubit representation of the nucleotides: 1) molecular recognition of a nucleotide is assumed to trigger an intrabase entanglement corresponding to a superposition of different tautomer forms and 2) pairing of complementary nucleotides is described by swapping intrabase entanglements with interbase entanglements. We examine possible realizations of quantum circuits/protocols to be used to obtain intr...

  3. Stable cellular senescence is associated with persistent DDR activation.

    Directory of Open Access Journals (Sweden)

    Marzia Fumagalli

    Full Text Available The DNA damage response (DDR is activated upon DNA damage generation to promote DNA repair and inhibit cell cycle progression in the presence of a lesion. Cellular senescence is a permanent cell cycle arrest characterized by persistent DDR activation. However, some reports suggest that DDR activation is a feature only of early cellular senescence that is then lost with time. This challenges the hypothesis that cellular senescence is caused by persistent DDR activation. To address this issue, we studied DDR activation dynamics in senescent cells. Here we show that normal human fibroblasts retain DDR markers months after replicative senescence establishment. Consistently, human fibroblasts from healthy aged donors display markers of DDR activation even three years in culture after entry into replicative cellular senescence. However, by extending our analyses to different human cell strains, we also observed an apparent DDR loss with time following entry into cellular senescence. This though correlates with the inability of these cell strains to survive in culture upon replicative or irradiation-induced cellular senescence. We propose a model to reconcile these results. Cell strains not suffering the prolonged in vitro culture stress retain robust DDR activation that persists for years, indicating that under physiological conditions persistent DDR is causally involved in senescence establishment and maintenance. However, cell strains unable to maintain cell viability in vitro, due to their inability to cope with prolonged cell culture-associated stress, show an only-apparent reduction in DDR foci which is in fact due to selective loss of the most damaged cells.

  4. Senescence vs. sustenance

    DEFF Research Database (Denmark)

    Baudisch, Annette; Vaupel, James W.

    2010-01-01

    Humans, and many other species, suffer senescence: mortality increases and fertility decreases with adult age. Some species, however, enjoy sustenance: mortality and fertility remain constant. Here we develop simple but general evolutionary-demographic models to explain the conditions that favor...... senescence vs. sustenance. The models illustrate how mathematical demography can deepen understanding of the evolution of aging....

  5. Raman and infrared spectroscopy differentiate senescent from proliferating cells in a human dermal fibroblast 3D skin model.

    Science.gov (United States)

    Eberhardt, Katharina; Matthäus, Christian; Winter, Doreen; Wiegand, Cornelia; Hipler, Uta-Christina; Diekmann, Stephan; Popp, Jürgen

    2017-08-15

    Senescent cells contribute to tissue aging and dysfunction. Therefore, detecting senescent cells in skin is of interest for skin tumor diagnostics and therapy. Here, we studied the transition into senescence of human dermal fibroblasts (HDFs) in a three-dimensional (3D) human fibroblast-derived matrix (FDM). Senescent and proliferating cells were imaged by Raman spectroscopy (RS) and Fourier transform infrared (FTIR) spectroscopy. The obtained averaged spectra were analyzed using PLS-LDA. For these 3D cultured cells, RS and FTIR could clearly distinguish senescent from proliferating cells. For both techniques, we detected senescence-associated alterations in almost all cellular macromolecules. Furthermore, we identified different biochemical properties of 3D compared to two-dimensional (2D) cultured cells, indicating that cells in their natural, skin-like 3D environment act differently than in (2D) cell cultivations in vitro. Compared to 2D cultured cells, cells grown in 3D models displayed a sharper contrast between the proliferating and senescent state, also affecting the abundance of biomolecules including nucleic acids. The training accuracies of both vibrational spectroscopic techniques were >96%, demonstrating the suitability of these label-free measurements for detecting these cellular states in 3D skin models.

  6. The sulfated polysaccharide fucoidan rescues senescence of endothelial colony-forming cells for ischemic repair.

    Science.gov (United States)

    Lee, Jun Hee; Lee, Sang Hun; Choi, Sung Hyun; Asahara, Takayuki; Kwon, Sang-Mo

    2015-06-01

    The efficacy of cell therapy using endothelial colony-forming cells (ECFCs) in the treatment of ischemia is limited by the replicative senescence of isolated ECFCs in vitro. Such senescence must therefore be overcome in order for such cell therapies to be clinically applicable. This study aimed to investigate the potential of sulfated polysaccharide fucoidan to rescue ECFCs from cellular senescence and to improve in vivo vascular repair by ECFCs. Fucoidan-preconditioning of senescent ECFCs was shown by flow cytometry to restore the expression of functional ECFC surface markers (CD34, c-Kit, VEGFR2, and CXCR4) and stimulate the in vitro tube formation capacity of ECFCs. Fucoidan also promoted the expression of cell cycle-associated proteins (cyclin E, Cdk2, cyclin D1, and Cdk4) in senescent ECFCs, significantly reversed cellular senescence, and increased the proliferation of ECFCs via the FAK, Akt, and ERK signaling pathways. Fucoidan was found to enhance the survival, proliferation, incorporation, and endothelial differentiation of senescent ECFCs transplanted in ischemic tissues in a murine hind limb ischemia model. Moreover, ECFC-induced functional recovery and limb salvage were markedly improved by fucoidan pretreatment of ECFCs. To our knowledge, the findings of our study are the first to demonstrate that fucoidan enhances the neovasculogenic potential of ECFCs by rescuing them from replicative cellular senescence. Pretreatment of ECFCs with fucoidan may thus provide a novel strategy for the application of senescent stem cells to therapeutic neovascularization.

  7. Cisplatin-induced premature senescence with concomitant reduction of gap junctions in human fibroblasts

    Institute of Scientific and Technical Information of China (English)

    Wei ZHAO; Zhong Xiang LIN; Zhi Qian ZHANG

    2004-01-01

    To examine the role of gap junctions in cell senescence,the changes of gap junctions in cisplatin-induced premature senescence of primary cultured fibroblasts were studied and compared with the replicative senescent human fibroblasts.Dye transfer assay for gap junction function and immunofluorescent staining for connexin 43 protein distribution were done respectively. Furthermore,cytofluorimetry and DAPI fluorescence staining were performed for cell cycle and apoptosis analysis. p53 gene expression level was detected with indirect immunofluorescence. We found that cisplatin (10 mM) treatment could block cell growth cycle at G1 and induced premature senescence. The premature senescence changes included high frequency of apoptosis,elevation of p53 expression,loss of membranous gap junctions and reduction of dye-transfer capacity. These changes were comparable to the changes of replicative senescence of human fibroblasts. It was also concluded that cisplatin could induce premature senescence concomitant with inhibition of gap junctions in the fibroblasts. Loss of functional gap junctions from the cell membrane may account for the reduced intercellular communication in the premature senescent fibroblasts. The cell system we used may provide a model useful for the study of the gap junction thus promoting agents against premature senescence.

  8. A theoretical model of the evolution of actuarial senescence under environmental stress.

    Science.gov (United States)

    Watson, H; Cohen, A A; Isaksson, C

    2015-11-01

    Free-living organisms are exposed to a wide range of stressors, all of which can disrupt components of stress-related and detoxification physiology. The subsequent accumulation of somatic damage is widely believed to play a major role in the evolution of senescence. Organisms have evolved sophisticated physiological regulatory mechanisms to maintain homeostasis in response to environmental perturbations, but these systems are likely to be constrained in their ability to optimise robustness to multiple stressors due to functional correlations among related traits. While evolutionary change can accelerate due to human ecological impacts, it remains to be understood how exposure to multiple environmental stressors could affect senescence rates and subsequently population dynamics and fitness. We used a theoretical evolutionary framework to quantify the potential consequences for the evolution of actuarial senescence in response to exposure to simultaneous physiological stressors--one versus multiple and additive versus synergistic--in a hypothetical population of avian "urban adapters". In a model in which multiple stressors have additive effects on physiology, species may retain greater capacity to recover, or respond adaptively, to environmental challenges. However, in the presence of high synergy, physiological dysregulation suddenly occurs, leading to a rapid increase in age-dependent mortality and subsequent population collapse. Our results suggest that, if the synergistic model is correct, population crashes in environmentally-stressed species could happen quickly and with little warning, as physiological thresholds of stress resistance are overcome.

  9. The case for negative senescence

    DEFF Research Database (Denmark)

    Vaupel, James W; Baudisch, Annette; Dölling, Martin

    2004-01-01

    kinds of animals that may experience negative senescence and conclude that negative senescence may be widespread, especially in indeterminate-growth species for which size and fertility increase with age. We develop optimization models of life-history strategies that demonstrate that negative senescence...

  10. Hepatoprotective Effects of Swimming Exercise against D-Galactose-Induced Senescence Rat Model

    Directory of Open Access Journals (Sweden)

    Chi-Chang Huang

    2013-01-01

    Full Text Available This study investigates whether a 12-week swimming exercise training can prevent liver damage or senescence associated biomarkers in an experimental aging model in rats. Twenty-three male Sprague-Dawley rats were divided into four groups: vehicle treatment with sedentary control (C, , aging induction with sedentary (A, , vehicle treatment with swimming exercise (SW, , and aging induction with swimming exercise (A + SW, . Rats in groups A and AS received intraperitoneal D-galactose injections (150 mg/kg/day for 12 weeks to induce aging. Rats in groups SW and A + SW were subjected to swimming exercise training for 12 weeks. Body weight, liver weight, epididymal fat mass, blood biochemistry, and liver pathology were performed at the end of the experiment. Hepatic senescence protein markers such as β-galactosidase, p53, and p21, as well as the inflammatory mediator, IL-6, were examined. The D-galactose-treated rats exhibited increases in AST and γ-GT plasma levels and β-galactosidase protein expression compared to the control group. Swimming exercise significantly reduced BW, epididymal fat mass, γ-GT activity, and p53, p21, and IL-6 protein levels compared to the aging group. These results suggest that a 12-week swimming exercise program suppresses senescence markers and downregulates inflammatory mediator in the liver tissues of D-galactose-induced aging rats.

  11. Photobiomodulation on senescence

    Science.gov (United States)

    Liu, Timon Cheng-Yi; Cheng, Lei; Rong, Dong-Liang; Xu, Xiao-Yang; Cui, Li-Ping; Lu, Jian; Deng, Xiao-Yuan; Liu, Song-Hao

    2006-09-01

    Photobiomodulation (PBM) is an effect oflow intensity monochromatic light or laser irradiation (LIL) on biological systems. which stimulates or inhibits biological functions but does not result in irreducible damage. It has been observed that PBM can suppress cellular senescence, reverse skin photoageing and improve fibromyalgia. In this paper, the biological information model of photobiomodulation (BIMP) is used to discuss its mechanism. Cellular senescence can result from short, dysfunctional telomeres, oxidative stress, or oncogene expression, and may contribute to aging so that it can be seen as a decline of cellular function in which cAMP plays an important role, which provide a foundation for PBM on senescence since cellular senescence is a reasonable model of senescence and PBM is a cellular rehabilitation in which cAMP also plays an important role according to BIMP. The PBM in reversing skin photoageing and improving fibromyalgia are then discussed in detail.

  12. WNT16B is a new marker of cellular senescence that regulates p53 activity and the phosphoinositide 3-kinase/AKT pathway.

    Science.gov (United States)

    Binet, Romuald; Ythier, Damien; Robles, Ana I; Collado, Manuel; Larrieu, Delphine; Fonti, Claire; Brambilla, Elisabeth; Brambilla, Christian; Serrano, Manuel; Harris, Curtis C; Pedeux, Rémy

    2009-12-15

    Senescence is a tumor suppression mechanism that is induced by several stimuli, including oncogenic signaling and telomere shortening, and controlled by the p53/p21(WAF1) signaling pathway. Recently, a critical role for secreted factors has emerged, suggesting that extracellular signals are necessary for the onset and maintenance of senescence. Conversely, factors secreted by senescent cells may promote tumor growth. By using expression profiling techniques, we searched for secreted factors that were overexpressed in fibroblasts undergoing replicative senescence. We identified WNT16B, a member of the WNT family of secreted proteins. We found that WNT16B is overexpressed in cells undergoing stress-induced premature senescence and oncogene-induced senescence in both MRC5 cell line and the in vivo murine model of K-Ras(V12)-induced senescence. By small interfering RNA experiments, we observed that both p53 and WNT16B are necessary for the onset of replicative senescence. WNT16B expression is required for the full transcriptional activation of p21(WAF1). Moreover, WNT16B regulates activation of the phosphoinositide 3-kinase (PI3K)/AKT pathway. Overall, we identified WNT16B as a new marker of senescence that regulates p53 activity and the PI3K/AKT pathway and is necessary for the onset of replicative senescence.

  13. Application of hepatitis B virus replication mouse model

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    AIM:To evaluate the value of the hepatitis B virus(HBV) replication mouse model with regard to several aspects of the study of HBV biology.METHODS:To evaluate the HBV replication mouse model in detecting the efficacy of anti-HBV agents,the interferon inducer polyinosinic-polytidylin acid(polyIC) and nucleotide analogues adefovir and entecavir were administered to mice injected with wild type pHBV4.1,and the inhibiting effect of these agents on HBV DNA replication was evaluated.To identify the model's value ...

  14. A Cognitive Developmental Model of Rigidity in Senescence.

    Science.gov (United States)

    Lapsley, Daniel K.; Enright, Robert D.

    1983-01-01

    The rigidity construct is reinterpreted in terms of the cognitive developmental approach. A review reveals both cognitive and developmental themes, with an emphasis on the structural and operational properties of rigidity. Notes weaknesses of previous approaches to rigidity and discusses implications and predictions from the proposed model.…

  15. Senescence rates in patients with end-stage renal disease: a critical appraisal of the Gompertz model.

    Science.gov (United States)

    Koopman, J J E; Rozing, M P; Kramer, A; de Jager, D J; Ansell, D; De Meester, J M J; Prütz, K G; Finne, P; Heaf, J G; Palsson, R; Kramar, R; Jager, K J; Dekker, F W; Westendorp, R G J

    2011-04-01

    The most frequently used model to describe the exponential increase in mortality rate over age is the Gompertz equation. Logarithmically transformed, the equation conforms to a straight line, of which the slope has been interpreted as the rate of senescence. Earlier, we proposed the derivative function of the Gompertz equation as a superior descriptor of senescence rate. Here, we tested both measures of the rate of senescence in a population of patients with end-stage renal disease. It is clinical dogma that patients on dialysis experience accelerated senescence, whereas those with a functional kidney transplant have mortality rates comparable to the general population. Therefore, we calculated the age-specific mortality rates for European patients on dialysis (n=274 221; follow-up=594 767 person-years), for European patients with a functioning kidney transplant (n=61 286; follow-up=345 024 person-years), and for the general European population. We found higher mortality rates, but a smaller slope of logarithmic mortality curve for patients on dialysis compared with both patients with a functioning kidney transplant and the general population (PGompertz model would imply that the rate of senescence in patients on dialysis is lower than in patients with a functioning transplant and lower than in the general population. In contrast, the derivative function of the Gompertz equation yielded the highest senescence rates for patients on dialysis, whereas the rate was similar in patients with a functioning transplant and the general population. We conclude that the rate of senescence is better described by the derivative function of the Gompertz equation.

  16. Amyloid β Protein Aggravates Neuronal Senescence and Cognitive Deficits in 5XFAD Mouse Model of Alzheimer's Disease

    Institute of Scientific and Technical Information of China (English)

    Zhen Wei; Xiao-Chun Chen; Yue Song; Xiao-Dong Pan; Xiao-Man Dai; Jing Zhang; Xiao-Li Cui

    2016-01-01

    Background:Amyloid β (Aβ) has been established as a key factor for the pathological changes in the brains of patients with Alzheimer's disease (AD),and cellular senescence is closely associated with aging and cognitive impairment.However,it remains blurred whether,in the AD brains,Aβ accelerates the neuronal.senescence and whether this senescence,in turn,impairs the cognitive function.This study aimed to explore the expression of senescence-associated genes in the hippocampal tissue from young to aged 5XFAD mice and their age-matched wild type (WT) mice to determine whether senescent neurons are present in the transgenic AD mouse model.Methods:The 5XFAD mice and age-matched wild type mice,both raised from 1 to 18 months,were enrolled in the study.The senescence-associated genes in the hippocampus were analyzed and differentially expressed genes (DEGs) were screened by quantitative real-time polymerase chain reaction.Cognitive performance of the mice was evaluated by Y-maze and Morris water maze tests.Oligomeric Aβ (oAβ) (1-42) was applied to culture primary neurons to simulate the in vivo manifestation.Aging-related proteins were detected by Western blotting analysis and immunofluorescence.Results:In 5XFAD mice,of all the DEGs,the senescence-associated marker p 16 was most significantly increased,even at the early age.It was mainly localized in neurons,with a marginal expression in astrocytes (labeled as glutamine synthetase),nil expression in activated microglia (labeled as Iba1),and negatively correlated with the spatial cognitive impairments of 5XFAD mice.oAβ (1-42) induced the production of senescence-related protein p 16,but not p53 in vitro,which was in line with the in vivo manifestation.Conclusions:oAβ-accelerated neuronal senescence may be associated with the cognitive impairment in 5XFAD mice.Senescence-associated marker p 16 can serve as an indicator to estimate the cognitive prognosis for AD population.

  17. Sabin-to-Mahoney Transition Model of Quasispecies Replication

    Energy Technology Data Exchange (ETDEWEB)

    2009-05-31

    Qspp is an agent-based stochastic simulation model of the Poliovirus Sabin-to-Mahoney transition. This code simulates a cell-to-cell model of Poliovirus replication. The model tracks genotypes (virus genomes) as they are replicated in cells, and as the cells burst and release particles into the medium of a culture dish. An inoculum is then taken from the pool of virions and is used to inoculate cells on a new dish. This process repeats. The Sabin genotype comprises the initial inoculum. Nucleotide positions that match the Sabin1 (vaccine strain) and Mahoney (wild type) genotypes, as well as the neurovirulent phenotype (from the literature) are enumerated as constants.

  18. Transcriptional activation of p21(WAF¹/CIP¹) is mediated by increased DNA binding activity and increased interaction between p53 and Sp1 via phosphorylation during replicative senescence of human embryonic fibroblasts.

    Science.gov (United States)

    Kim, Hyun-Seok; Heo, Jee-In; Park, Seong-Hoon; Shin, Jong-Yeon; Kang, Hong-Jun; Kim, Min-Ju; Kim, Sung Chan; Kim, Jaebong; Park, Jae-Bong; Lee, Jae-Yong

    2014-01-01

    Although p21(WAF1/CIP1) is known to be elevated during replicative senescence of human embryonic fibroblasts (HEFs), the mechanism for p21 up-regulation has not been elucidated clearly. In order to explore the mechanism, we analyzed expression of p21 mRNA and protein and luciferase activity of full-length p21 promoter. The result demonstrated that p21 up-regulation was accomplished largely at transcription level. The promoter assay using serially-deleted p21 promoter constructs revealed that p53 binding site was the most important site and Sp1 binding sites were necessary but not sufficient for transcriptional activation of p21. In addition, p53 protein was shown to interact with Sp1 protein. The interaction was increased in aged fibroblasts and was regulated by phosphorylation of p53 and Sp1. DNA binding activity of p53 was significantly elevated in aged fibroblasts but that of Sp1 was not. DNA binding activities of p53 and Sp1 were also regulated by phosphorylation. Phosphorylation of p53 at serine-15 and of Sp1 at serines appears to be involved. Taken together, the result demonstrated that p21 transcription during replicative senescence of HEFs is up-regulated by increase in DNA binding activity and interaction between p53 and Sp1 via phosphorylation.

  19. Characterisation of a divergent progenitor cell sub-populations in human osteoarthritic cartilage: the role of telomere erosion and replicative senescence

    Science.gov (United States)

    Fellows, Christopher R.; Williams, Rebecca; Davies, Iwan R.; Gohil, Kajal; Baird, Duncan M.; Fairclough, John; Rooney, Paul; Archer, Charles W.; Khan, Ilyas M.

    2017-01-01

    In recent years it has become increasingly clear that articular cartilage harbours a viable pool of progenitor cells and interest has focussed on their role during development and disease. Analysis of progenitor numbers using fluorescence-activated sorting techniques has resulted in wide-ranging estimates, which may be the result of context-dependent expression of cell surface markers. We have used a colony-forming assay to reliably determine chondroprogenitor numbers in normal and osteoarthritic cartilage where we observed a 2-fold increase in diseased tissue (P  < 0.0001). Intriguingly, cell kinetic analysis of clonal isolates derived from single and multiple donors of osteoarthritic cartilage revealed the presence of a divergent progenitor subpopulation characterised by an early senescent phenotype. Divergent sub-populations displayed increased senescence-associated β–galactosidase activity, lower average telomere lengths but retained the capacity to undergo multi-lineage differentiation. Osteoarthritis is an age-related disease and cellular senescence is predicted to be a significant component of the pathological process. This study shows that although early senescence is an inherent property of a subset of activated progenitors, there is also a pool of progenitors with extended viability and regenerative potential residing within osteoarthritic cartilage. PMID:28150695

  20. A Paper Model of DNA Structure and Replication.

    Science.gov (United States)

    Sigismondi, Linda A.

    1989-01-01

    A paper model which is designed to give students a hands-on experience during lecture and blackboard instruction on DNA structure is provided. A list of materials, paper patterns, and procedures for using the models to teach DNA structure and replication are given. (CW)

  1. Senescence and antibiotic resistance in an age-structured population model.

    Science.gov (United States)

    De Leenheer, Patrick; Dockery, Jack; Gedeon, Tomás; Pilyugin, Sergei S

    2010-10-01

    Different theories have been proposed to understand the growing problem of antibiotic resistance of microbial populations. Here we investigate a model that is based on the hypothesis that senescence is a possible explanation for the existence of so-called persister cells which are resistant to antibiotic treatment. We study a chemostat model with a microbial population which is age-structured and show that if the growth rates of cells in different age classes are sufficiently close to a scalar multiple of a common growth rate, then the population will globally stabilize at a coexistence steady state. This steady state persists under an antibiotic treatment if the level of antibiotics is below a certain threshold; if the level exceeds this threshold, the washout state becomes a globally attracting equilibrium.

  2. Senescence rates in patients with end-stage renal disease: a critical appraisal of the Gompertz model

    NARCIS (Netherlands)

    J.J.E. Koopman; M.P. Rozing; A. Kramer; D.J. de Jager; D. Ansell; J.M.J. de Meester; K.G. Prütz; P. Finne; J.G. Heaf; R. Palsson; R. Kramar; K.J. Jager; F.W. Dekker; R.G.J. Westendorp

    2011-01-01

    P>The most frequently used model to describe the exponential increase in mortality rate over age is the Gompertz equation. Logarithmically transformed, the equation conforms to a straight line, of which the slope has been interpreted as the rate of senescence. Earlier, we proposed the derivative fun

  3. Experiments in Model-Checking Optimistic Replication Algorithms

    CERN Document Server

    Boucheneb, Hanifa

    2008-01-01

    This paper describes a series of model-checking experiments to verify optimistic replication algorithms based on Operational Transformation (OT) approach used for supporting collaborative edition. We formally define, using tool UPPAAL, the behavior and the main consistency requirement (i.e. convergence property) of the collaborative editing systems, as well as the abstract behavior of the environment where these systems are supposed to operate. Due to data replication and the unpredictable nature of user interactions, such systems have infinitely many states. So, we show how to exploit some features of the UPPAAL specification language to attenuate the severe state explosion problem. Two models are proposed. The first one, called concrete model, is very close to the system implementation but runs up against a severe explosion of states. The second model, called symbolic model, aims to overcome the limitation of the concrete model by delaying the effective selection and execution of editing operations until th...

  4. Autophagy-independent senescence and genome instability driven by targeted telomere dysfunction.

    Science.gov (United States)

    Mar, Florie A; Debnath, Jayanta; Stohr, Bradley A

    2015-01-01

    Telomere dysfunction plays a complex role in tumorigenesis. While dysfunctional telomeres can block the proliferation of incipient cancer clones by inducing replicative senescence, fusion of dysfunctional telomeres can drive genome instability and oncogenic genomic rearrangements. Therefore, it is important to define the regulatory pathways that guide these opposing effects. Recent work has shown that the autophagy pathway regulates both senescence and genome instability in various contexts. Here, we apply models of acute telomere dysfunction to determine whether autophagy modulates the resulting genome instability and senescence responses. While telomere dysfunction rapidly induces autophagic flux in human fibroblast cell lines, inhibition of the autophagy pathway does not have a significant impact upon the transition to senescence, in contrast to what has previously been reported for oncogene-induced senescence. Our results suggest that this difference may be explained by disparities in the development of the senescence-associated secretory phenotype. We also show that chromosome fusions induced by telomere dysfunction are comparable in autophagy-proficient and autophagy-deficient cells. Altogether, our results highlight the complexity of the senescence-autophagy interface and indicate that autophagy induction is unlikely to play a significant role in telomere dysfunction-driven senescence and chromosome fusions.

  5. Replicating hedge fund returns: A factor model approach

    OpenAIRE

    Naser, Omar

    2007-01-01

    Growth in the Hedge Fund industry mirrors the growth in the Mutual Fund industry. This raises the possibility of creating a passive strategy that replicates Hedge Fund returns at lower cost using liquid, exchange-traded instruments. Using monthly returns for the period 1991-2005 on thirteen Hedge Fund strategies, I build a linear factor models (“clones”) that replicate Hedge Fund returns. I use six common factors to determine the amount of expected return and variation in returns that can be ...

  6. NF1 loss induces senescence during human melanocyte differentiation in an iPSC-based model.

    Science.gov (United States)

    Larribere, Lionel; Wu, Huizi; Novak, Daniel; Galach, Marta; Bernhardt, Mathias; Orouji, Elias; Weina, Kasia; Knappe, Nathalie; Sachpekidis, Christos; Umansky, Ludmila; Beckhove, Philipp; Umansky, Viktor; De Schepper, Sofie; Kaufmann, Dieter; Ballotti, Robert; Bertolotto, Corine; Utikal, Jochen

    2015-07-01

    Neurofibromatosis type 1 (NF1) is a frequent genetic disease leading to the development of Schwann cell-derived neurofibromas or melanocytic lesions called café-au-lait macules (CALMs). The molecular mechanisms involved in CALMs formation remain largely unknown. In this report, we show for the first time pathophysiological mechanisms of abnormal melanocyte differentiation in a human NF1(+/-) -induced pluripotent stem cell (iPSC)-based model. We demonstrate that NF1 patient-derived fibroblasts can be successfully reprogrammed in NF1(+/-) iPSCs with active RAS signaling and that NF1 loss induces senescence during melanocyte differentiation as well as in patient's-derived CALMs, revealing a new role for NF1 in the melanocyte lineage.

  7. Angelica Sinensis Polysaccharide Prevents Hematopoietic Stem Cells Senescence in D-Galactose-Induced Aging Mouse Model

    Directory of Open Access Journals (Sweden)

    Xinyi Mu

    2017-01-01

    Full Text Available Age-related regression in hematopoietic stem/progenitor cells (HSC/HPCs limits replenishment of the blood and immune system and hence contributes to hematopoietic diseases and declined immunity. In this study, we employed D-gal-induced aging mouse model and observed the antiaging effects of Angelica Sinensis Polysaccharide (ASP, a major active ingredient in dong quai (Chinese Angelica Sinensis, on the Sca-1+ HSC/HPCs in vivo. ASP treatment prevents HSC/HPCs senescence with decreased AGEs levels in the serum, reduced SA-β-Gal positive cells, and promoted CFU-Mix formation in the D-gal administrated mouse. We further found that multiple mechanisms were involved: (1 ASP treatment prevented oxidative damage as total antioxidant capacity was increased and levels of reactive oxygen species (ROS, 8-OHdG, and 4-HNE were declined, (2 ASP reduced the expression of γ-H2A.X which is a DNA double strand breaks (DSBs marker and decreased the subsequent ectopic expressions of effectors in p16Ink4a-RB and p19Arf-p21Cip1/Waf senescent pathways, and (3 ASP inhibited the excessive activation of Wnt/β-catenin signaling in aged HSC/HPCs, as the expressions of β-catenin, phospho-GSK-3β, and TCF-4 were decreased, and the cyto-nuclear translocation of β-catenin was inhibited. Moreover, compared with the positive control of Vitamin E, ASP exhibited a better antiaging effect and a weaker antioxidation ability, suggesting a novel protective role of ASP in the hematopoietic system.

  8. A quantitative model of DNA replication in Xenopus embryos: reliable replication despite stochasticity

    Science.gov (United States)

    Cheng-Hsin Yang, Scott; Bechhoefer, John

    2008-03-01

    DNA synthesis in Xenopus frog embryos initiates stochastically in time at many sites (origins) along the chromosome. Stochastic initiation implies fluctuations in the replication time and may lead to cell death if replication takes longer than the cell cycle time (˜ 25 min.). Surprisingly, although the typical replication time is about 20 min., in vivo experiments show that replication fails to complete only about 1 in 250 times. How is replication timing accurately controlled despite the stochasticity? Biologists have proposed two mechanisms: the first uses a regular spatial distribution of origins, while the second uses randomly located origins but increases their probability of initiation as the cell cycle proceeds. Here, we show that both mechanisms yield similar end-time distributions, implying that regular origin spacing is not needed for control of replication time. Moreover, we show that the experimentally inferred time-dependent initiation rate satisfies the observed low failure probability and nearly optimizes the use of replicative proteins.

  9. Stress-Induced Premature Senescence or Stress-Induced Senescence-Like Phenotype: One In Vivo Reality, Two Possible Definitions?

    Directory of Open Access Journals (Sweden)

    Olivier Toussaint

    2002-01-01

    Full Text Available No consensus exists so far on the definition of cellular senescence. The narrowest definition of senescence is irreversible growth arrest triggered by telomere shortening counting cell generations (definition 1. Other authors gave an enlarged functional definition encompassing any kind of irreversible arrest of proliferative cell types induced by damaging agents or cell cycle deregulations after overexpression of proto-oncogenes (definition 2. As stress increases, the proportion of cells in “stress-induced premature senescence-like phenotype” according to definition 1 or “stress-induced premature senescence,” according to definition 2, should increase when a culture reaches growth arrest, and the proportion of cells that reached telomere-dependent replicative senescence due to the end-replication problem should decrease. Stress-induced premature senescence-like phenotype and telomere-dependent replicatively senescent cells share basic similarities such as irreversible growth arrest and resistance to apoptosis, which may appear through different pathways. Irreversible growth arrest after exposure to oxidative stress and generation of DNA damage could be as efficient in avoiding immortalisation as “telomere-dependent” replicative senescence. Probabilities are higher that the senescent cells (according to definition 2 appearing in vivo are in stress-induced premature senescence rather than in telomere-dependent replicative senescence. Examples are given suggesting these cells affect in vivo tissue (pathophysiology and aging.

  10. Senescence induction; a possible cancer therapy

    Directory of Open Access Journals (Sweden)

    Kondoh Hiroshi

    2009-01-01

    Full Text Available Abstract Cellular immortalization is a crucial step during the development of human cancer. Primary mammalian cells reach replicative exhaustion after several passages in vitro, a process called replicative senescence. During such a state of permanent growth arrest, senescent cells are refractory to physiological proliferation stimuli: they have altered cell morphology and gene expression patterns, although they remain viable with preserved metabolic activity. Interestingly, senescent cells have also been detected in vivo in human tumors, particularly in benign lesions. Senescence is a mechanism that limits cellular lifespan and constitutes a barrier against cellular immortalization. During immortalization, cells acquire genetic alterations that override senescence. Tumor suppressor genes and oncogenes are closely involved in senescence, as their knockdown and ectopic expression confer immortality and senescence induction, respectively. By using high throughput genetic screening to search for genes involved in senescence, several candidate oncogenes and putative tumor suppressor genes have been recently isolated, including subtypes of micro-RNAs. These findings offer new perspectives in the modulation of senescence and open new approaches for cancer therapy.

  11. Widening Disparity and its Suppression in a Stochastic Replicator Model

    CERN Document Server

    Sakaguchi, Hidetsugu

    2016-01-01

    Winner-take-all phenomena are observed in various competitive systems. We find similar phenomena in replicator models with randomly fluctuating growth rates. The disparity between winners and losers increases indefinitely, even if all elements are statistically equivalent. A lognormal distribution describes well the nonstationary time evolution. If a nonlinear load corresponding to progressive taxation is introduced, a stationary distribution is obtained and disparity widening is suppressed.

  12. Nitric oxide prevents alveolar senescence and emphysema in a mouse model.

    Directory of Open Access Journals (Sweden)

    Amanda E Boe

    Full Text Available Nω-nitro-L-arginine methyl ester (L-NAME treatment induces arteriosclerosis and vascular senescence. Here, we report that the systemic inhibition of nitric oxide (NO production by L-NAME causes pulmonary emphysema. L-NAME-treated lungs exhibited both the structural (alveolar tissue destruction and functional (increased compliance and reduced elastance characteristics of emphysema development. Furthermore, we found that L-NAME-induced emphysema could be attenuated through both genetic deficiency and pharmacological inhibition of plasminogen activator inhibitor-1 (PAI-1. Because PAI-1 is an important contributor to the development of senescence both in vitro and in vivo, we investigated whether L-NAME-induced senescence led to the observed emphysematous changes. We found that L-NAME treatment was associated with molecular and cellular evidence of premature senescence in mice, and that PAI-1 inhibition attenuated these increases. These findings indicate that NO serves to protect and defend lung tissue from physiological aging.

  13. Long-term Neuroglial Cocultures as a Brain Aging Model: Hallmarks of Senescence, MicroRNA Expression Profiles, and Comparison With In Vivo Models.

    Science.gov (United States)

    Bigagli, Elisabetta; Luceri, Cristina; Scartabelli, Tania; Dolara, Piero; Casamenti, Fiorella; Pellegrini-Giampietro, Domenico E; Giovannelli, Lisa

    2016-01-01

    Our purpose was to evaluate long-term neuroglial cocultures as a model for investigating senescence in the nervous system and to assess its similarities with in vivo models. To this aim, we maintained the cultures from 15 days in vitro (mature cultures) up to 27 days in vitro (senescent cultures), measuring senescence-associated, neuronal, dendritic, and astrocytic markers. Whole microRNA expression profiles were compared with those measured in the cortex of 18- and 24-month-old C57Bl/6J aged mice and of transgenic TgCRND8 mice, a model of amyloid-β deposition. Neuroglial cocultures displayed features of cellular senescence (increased senescence-associated-β-galactosidase activity, oxidative stress, γ-H2AX expression, IL-6 production, astrogliosis) that were concentration dependently counteracted by the antiaging compound resveratrol (1-5 µM). Among the 1,080 microRNAs analyzed, 335 were downregulated or absent in 27 compared with 15 days in vitro and resveratrol reversed this effect. A substantial overlapping was found between age-associated changes in microRNA expression profiles in vitro and in TgCRND8 mice but not in physiologically aged mice, indicating that this culture model displays more similarities with pathological than physiological brain aging. Our results demonstrate that neuroglial cocultures aged in vitro can be useful for investigating the cellular and molecular mechanisms of brain aging and for preliminary testing of protective compounds.

  14. HDACs and the senescent phenotype of WI-38 cells

    Directory of Open Access Journals (Sweden)

    Noonan Emily J

    2005-10-01

    Full Text Available Abstract Background Normal cells possess a limited proliferative life span after which they enter a state of irreversible growth arrest. This process, known as replicative senescence, is accompanied by changes in gene expression that give rise to a variety of senescence-associated phenotypes. It has been suggested that these gene expression changes result in part from alterations in the histone acetylation machinery. Here we examine the influence of HDAC inhibitors on the expression of senescent markers in pre- and post-senescent WI-38 cells. Results Pre- and post-senescent WI-38 cells were treated with the HDAC inhibitors butyrate or trichostatin A (TSA. Following HDAC inhibitor treatment, pre-senescent cells increased p21WAF1 and β-galactosidase expression, assumed a flattened senescence-associated morphology, and maintained a lower level of proteasome activity. These alterations also occurred during normal replicative senescence of WI-38 cells, but were not accentuated further by HDAC inhibitors. We also found that HDAC1 levels decline during normal replicative senescence. Conclusion Our findings indicate that HDACs impact numerous phenotypic changes associated with cellular senescence. Reduced HDAC1 expression levels in senescent cells may be an important event in mediating the transition to a senescent phenotype.

  15. Using Model Replication to Improve the Reliability of Agent-Based Models

    Science.gov (United States)

    Zhong, Wei; Kim, Yushim

    The basic presupposition of model replication activities for a computational model such as an agent-based model (ABM) is that, as a robust and reliable tool, it must be replicable in other computing settings. This assumption has recently gained attention in the community of artificial society and simulation due to the challenges of model verification and validation. Illustrating the replication of an ABM representing fraudulent behavior in a public service delivery system originally developed in the Java-based MASON toolkit for NetLogo by a different author, this paper exemplifies how model replication exercises provide unique opportunities for model verification and validation process. At the same time, it helps accumulate best practices and patterns of model replication and contributes to the agenda of developing a standard methodological protocol for agent-based social simulation.

  16. Limited impairments of associative learning in a mouse model of accelerated senescence.

    Science.gov (United States)

    Yang, Yi; Wu, Guang-yan; Li, Xuan; Huang, He; Hu, Bo; Yao, Juan; Wu, Bing; Sui, Jian-feng

    2013-11-15

    Research concerning impairment of associative learning during aging remains limited. The senescence-accelerated mice (SAM) prone/8 (P8) has been proposed as a useful model for the study of aging, and SAM resistant/1(SAMR1) is its control as a normal aging strain. Classical eyeblink conditioning has long been served as a model of associative learning. In order to explore the effects of aging on associative learning in SAM, the present study successively tested three paradigms of eyeblink conditioning in SAMP8 and SAMR1: classical single cue trace eyeblink conditioning (TEC), discriminative trace eyeblink conditioning and reversal learning of TEC. Behavioral performance indicated that SAMP8 could acquire limited single-cue trace eyeblink conditioning task and two-tone discrimination trace eyeblink conditioning with a relative lower acquisition rate compared to SAMR1. Both SAMP8 and SAMR1 failed to acquire reversal learning of discriminative TEC, and SAMP8' startle reflex to tone CS was lower than SAMR1. These results indicated that the impairments of aging on associative learning were incomplete in SAMP8.

  17. Stability analysis of a model gene network links aging, stress resistance, and negligible senescence.

    Science.gov (United States)

    Kogan, Valeria; Molodtsov, Ivan; Menshikov, Leonid I; Shmookler Reis, Robert J; Fedichev, Peter

    2015-08-28

    Several animal species are considered to exhibit what is called negligible senescence, i.e. they do not show signs of functional decline or any increase of mortality with age. Recent studies in naked mole rat and long-lived sea urchins showed that these species do not alter their gene-expression profiles with age as much as other organisms do. This is consistent with exceptional endurance of naked mole rat tissues to various genotoxic stresses. We conjectured, therefore, that the lifelong transcriptional stability of an organism may be a key determinant of longevity. We analyzed the stability of a simple genetic-network model and found that under most common circumstances, such a gene network is inherently unstable. Over a time it undergoes an exponential accumulation of gene-regulation deviations leading to death. However, should the repair systems be sufficiently effective, the gene network can stabilize so that gene damage remains constrained along with mortality of the organism. We investigate the relationship between stress-resistance and aging and suggest that the unstable regime may provide a mathematical basis for the Gompertz "law" of aging in many species. At the same time, this model accounts for the apparently age-independent mortality observed in some exceptionally long-lived animals.

  18. Tetraploid cells produced by absence of substrate adhesion during cytokinesis are limited in their proliferation and enter senescence after DNA replication.

    Science.gov (United States)

    De Santis Puzzonia, Marco; Gonzalez, Laetitia; Ascenzi, Sonia; Cundari, Enrico; Degrassi, Francesca

    2016-01-01

    Tetraploidy has been proposed as an intermediate state in neoplastic transformation due to the intrinsic chromosome instability of tetraploid cells. Despite the identification of p53 as a major factor in growth arrest of tetraploid cells, it is still unclear whether the p53-dependent mechanism for proliferation restriction is intrinsic to the tetraploid status or dependent on the origin of tetraploidy. Substrate adherence is fundamental for cytokinesis completion in adherent untransformed cells. Here we show that untransformed fibroblast cells undergoing mitosis in suspension produce binucleated tetraploid cells due to defective cleavage furrow constriction that leads to incomplete cell abscission. Binucleated cells obtained after loss of substrate adhesion maintain an inactive p53 status and are able to progress into G1 and S phase. However, binucleated cells arrest in G2, accumulate p53 and are not able to enter mitosis as no tetraploid metaphases were recorded after one cell cycle time. In contrast, tetraploid metaphases were found following pharmacological inhibition of Chk1 kinase, suggesting the involvement of the ATR/Chk1 pathway in the G2 arrest of binucleated cells. Interestingly, after persistence in the G2 phase of the cell cycle, a large fraction of binucleated cells become senescent. These findings identify a new pathway of proliferation restriction for tetraploid untransformed cells that seems to be specific for loss of adhesion-dependent cytokinesis failure. This involves Chk1 and p53 activation during G2. Inhibition of growth and entrance into senescence after cytokinesis in suspension may represent an important mechanism to control tumor growth. In fact, anchorage independent growth is a hallmark of cancer and it has been demonstrated that binucleated transformed cells can enter a cycle of anchorage independent growth.

  19. Tissue formation and tissue engineering through host cell recruitment or a potential injectable cell-based biocomposite with replicative potential: Molecular mechanisms controlling cellular senescence and the involvement of controlled transient telomerase activation therapies.

    Science.gov (United States)

    Babizhayev, Mark A; Yegorov, Yegor E

    2015-12-01

    . Nuclear export is initiated by ROS-induced phosphorylation of tyrosine 707 within hTERT by the Src kinase family. It might be presumed that protection of mitochondria against oxidative stress is an important telomere length-independent function for telomerase in cell survival. Biotechnology companies are focused on development of therapeutic telomerase vaccines, telomerase inhibitors, and telomerase promoter-driven cell killing in oncology, have a telomerase antagonist in late preclinical studies. Anti-aging medicine-oriented groups have intervened on the market with products working on telomerase activation for a broad range of degenerative diseases in which replicative senescence or telomere dysfunction may play an important role. Since oxidative damage has been shown to shorten telomeres in tissue culture models, the adequate topical, transdermal, or systemic administration of antioxidants (such as, patented ocular administration of 1% N-acetylcarnosine lubricant eye drops in the treatment of cataracts) may be beneficial at preserving telomere lengths and delaying the onset or in treatment of disease in susceptible individuals. Therapeutic strategies toward controlled transient activation of telomerase are targeted to cells and replicative potential in cell-based therapies, tissue engineering and regenerative medicine.

  20. AcMNPV As A Model for Baculovirus DNA Replication

    Institute of Scientific and Technical Information of China (English)

    Eric B. Carstens

    2009-01-01

    Baculoviruses were first identified as insect-specific pathogens, and it was this specificity that lead to their use as safe, target specific biological pesticides. For the past 30 years, AcMNPV has served as the subject of intense basic molecular research into the baculovirus infectious cycle including the interaction of the virus with a continuous insect cell line derived from Spodoptera frugiperda. The studies on baculoviruese have led to an in-depth understanding of the physical organization of the viral genomes including many complete genomic sequences, the time course of gene expression, and the application of this basic research to the use of baculoviruses not only as insecticides, but also as a universal eukaryotic protein expression system, and a potential vector in gene therapy. A great deal has also been discovered about the viral genes required for the replication of the baculovirus genome, while much remains to be learned about the mechanism of viral DNA replication. This report outlines the current knowledge of the factors involved in baculovirus DNA replication, using data on AcMNPV as a model for most members of the Baculoviridae.

  1. Replicating vesicles as models of primitive cell growth and division.

    Science.gov (United States)

    Hanczyc, Martin M; Szostak, Jack W

    2004-12-01

    Primitive cells, lacking the complex bio-machinery present in modern cells, would have had to rely on the self-organizing properties of their components and on interactions with their environment to achieve basic cellular functions such as growth and division. Many bilayer-membrane vesicles, depending on their composition and environment, can exhibit complex morphological changes such as growth, fusion, fission, budding, internal vesicle assembly and vesicle-surface interactions. The rich dynamic properties of these vesicles provide interesting models of how primitive cellular replication might have occurred in response to purely physical and chemical forces.

  2. Downregulation of APE1/Ref-1 is involved in the senescence of mesenchymal stem cells.

    Science.gov (United States)

    Heo, Jun-Young; Jing, Kaipeng; Song, Kyoung-Sub; Seo, Kang-Sik; Park, Ji-Hoon; Kim, Jong-Seok; Jung, Yeon-Joo; Hur, Gang-Min; Jo, Deog-Yeon; Kweon, Gi-Ryang; Yoon, Wan-Hee; Lim, Kyu; Hwang, Byung-Doo; Jeon, Byeong Hwa; Park, Jong-Il

    2009-06-01

    The senescence of human mesenchymal stem cells (hMSCs) causes disruption of tissue and organ maintenance, and is thus an obstacle to stem cell-based therapies for disease. Although some researchers have studied changes in the characteristics of hMSCs (decreases in differentiation ability and self-renewal), comparing young and old ages, the mechanisms of stem cell senescence have not yet been defined. In this study, we developed a growth curve for human bone marrow derived MSCs (hBMSCs) which changes into a hyperbolic state after passage number 7. Senescence associated beta-galactosidase (SA beta-gal) staining of hBMSCs showed 10% in passage 9 and 45% in passage 11. We detected an increase in endogenous superoxide levels during senescence that correlated with senescence markers (SA beta-gal, hyperbolic growth curve). Interestingly, even though endogenous superoxide increased in a replicative senescence model, the expression of APE1/Ref-1, which is sensitive to intracellular redox state, decreased. These effects were confirmed in a stress-induced senescence model by exogenous treatment with H(2)O(2). This change is related to the p53 activity that negatively regulates APE1/Ref-1. p21 expression levels, which represent p53 activity, were transiently increased in passage 9, meaning that they correlated with the expression of APE1/Ref-1. Overexpression of APE1/Ref-1 suppressed superoxide production and decreased SA beta-gal in hBMSCs. In conclusion, intracellular superoxide accumulation appears to be the main cause of the senescence of hBMSCs, and overexpression of APE1/Ref-1 can rescue cells from the senescence phenotype. Maintaining characteristics of hBMSCs by regulating intracellular reactive oxygen species production can contribute to tissue regeneration and to improved cell therapy.

  3. Epigenetic clock analyses of cellular senescence and ageing.

    Science.gov (United States)

    Lowe, Donna; Horvath, Steve; Raj, Kenneth

    2016-02-23

    A confounding aspect of biological ageing is the nature and role of senescent cells. It is unclear whether the three major types of cellular senescence, namely replicative senescence, oncogene-induced senescence and DNA damage-induced senescence are descriptions of the same phenomenon instigated by different sources, or if each of these is distinct, and how they are associated with ageing. Recently, we devised an epigenetic clock with unprecedented accuracy and precision based on very specific DNA methylation changes that occur in function of age. Using primary cells, telomerase-expressing cells and oncogene-expressing cells of the same genetic background, we show that induction of replicative senescence (RS) and oncogene-induced senescence (OIS) are accompanied by ageing of the cell. However, senescence induced by DNA damage is not, even though RS and OIS activate the cellular DNA damage response pathway, highlighting the independence of senescence from cellular ageing. Consistent with this, we observed that telomerase-immortalised cells aged in culture without having been treated with any senescence inducers or DNA-damaging agents, re-affirming the independence of the process of ageing from telomeres and senescence. Collectively, our results reveal that cellular ageing is distinct from cellular senescence and independent of DNA damage response and telomere length.

  4. Preon Model and Family Replicated E_6 Unification

    Science.gov (United States)

    Das, Chitta Ranjan; Laperashvili, Larisa V.

    2008-02-01

    Previously we suggested a new preon model of composite quark-leptons and bosons with the 'flipped' E6 × ˜E6 gauge symmetry group. We assumed that preons are dyons having both hyper-electric g and hyper-magnetic ˜g charges, and these preons-dyons are confined by hyper-magnetic strings which are an N = 1 supersymmetric non-Abelian flux tubes created by the condensation of spreons near the Planck scale. In the present paper we show that the existence of the three types of strings with tensions Tk = kT0 (k = 1,2,3) producing three (and only three) generations of composite quark-leptons, also provides three generations of composite gauge bosons ('hyper-gluons') and, as a consequence, predicts the family replicated [E6]3 unification at the scale ~1017 GeV. This group of unification ha! s the possibility of breaking to the group of symmetry: [SU(3)C]3 × [SU(2)L]3 × [U(1)Y]3 × [U(1)(B-L)]3 which undergoes the breakdown to the Standard Model at lower energies. Some predictive advantages of the family replicated gauge groups of symmetry are briefly discussed.

  5. Preon Model and Family Replicated E_6 Unification

    Directory of Open Access Journals (Sweden)

    Larisa V. Laperashvili

    2008-02-01

    Full Text Available Previously we suggested a new preon model of composite quark-leptons and bosons with the 'flipped' $E_6imes widetilde{E_6}$ gauge symmetry group. We assumed that preons are dyons having both hyper-electric $g$ and hyper-magnetic $ilde g$ charges, and these preons-dyons are confined by hyper-magnetic strings which are an ${f N}=1$ supersymmetric non-Abelian flux tubes created by the condensation of spreons near the Planck scale. In the present paper we show that the existence of the three types of strings with tensions $T_k=k T_0$ $(k = 1,2,3$ producing three (and only three generations of composite quark-leptons, also provides three generations of composite gauge bosons ('hyper-gluons' and, as a consequence, predicts the family replicated $[E_6]^3$ unification at the scale $sim 10^{17}$ GeV. This group of unification has the possibility of breaking to the group of symmetry: $ [SU(3_C]^3imes [SU(2_L]^3imes [U(1_Y]^3 imes [U(1_{(B-L}]^3$ which undergoes the breakdown to the Standard Model at lower energies. Some predictive advantages of the family replicated gauge groups of symmetry are briefly discussed.

  6. Supplementary Material for: Factor Copula Models for Replicated Spatial Data

    KAUST Repository

    Krupskii, Pavel

    2016-01-01

    We propose a new copula model that can be used with replicated spatial data. Unlike the multivariate normal copula, the proposed copula is based on the assumption that a common factor exists and affects the joint dependence of all measurements of the process. Moreover, the proposed copula can model tail dependence and tail asymmetry. The model is parameterized in terms of a covariance function that may be chosen from the many models proposed in the literature, such as the Matérn model. For some choice of common factors, the joint copula density is given in closed form and therefore likelihood estimation is very fast. In the general case, one-dimensional numerical integration is needed to calculate the likelihood, but estimation is still reasonably fast even with large data sets. We use simulation studies to show the wide range of dependence structures that can be generated by the proposed model with different choices of common factors. We apply the proposed model to spatial temperature data and compare its performance with some popular geostatistics models.

  7. Amyloid β Protein Aggravates Neuronal Senescence and Cognitive Deficits in 5XFAD Mouse Model of Alzheimer's Disease

    Directory of Open Access Journals (Sweden)

    Zhen Wei

    2016-01-01

    Conclusions: oAβ-accelerated neuronal senescence may be associated with the cognitive impairment in 5XFAD mice. Senescence-associated marker p16 can serve as an indicator to estimate the cognitive prognosis for AD population.

  8. The effect of overexpression of PGC-1α on the mtDNA4834 common deletion in a rat cochlear marginal cell senescence model.

    Science.gov (United States)

    Zhao, Xue-Yan; Sun, Jin-Li; Hu, Yu-Juan; Yang, Yang; Zhang, Wen-Juan; Hu, Yuan; Li, Jun; Sun, Yu; Zhong, Yi; Peng, Wei; Zhang, Hong-Lian; Kong, Wei-Jia

    2013-02-01

    Aging is a natural process usually defined as a progressive loss of function with an accumulation of senescent cells. The clinical manifestations of this process include age-related hearing loss (AHL)/presbycusis. Several investigations indicated the association between a mitochondrial common deletion (CD) (mtDNA 4977-bp deletion in humans, corresponding to 4834-bp deletion in rats) and presbycusis. Previous researches have shown that peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α) is a key regulator of mitochondrial biogenesis and energy metabolism. However, the expression of PGC-1α in the inner ear and the possible effect of PGC-1α on presbycusis are not clear. Our data demonstrated the distribution of PGC-1α and its downstream transcription factors nuclear respiratory factor-1 (NRF-1), mitochondrial transcription factor A (Tfam) and nuclear factor κB (NF-κB) in marginal cells (MCs) for the first time. To explore the role of PGC-1α in cellular senescence, we established a model of marginal cell senescence harboring the mtDNA4834 common deletion induced by d-galactose. We also found that PGC-1α and its downstream transcription factors compensatorily increased in our cell senescence model. Furthermore, the overexpression of PGC-1α induced by transfection largely increased the expression levels of NRF-1 and TFAM and significantly decreased the expression level of NF-κB in the cell senescence model. And the levels of CD, senescent cells and apoptotic cells in the cell model decreased after PGC-1α overexpression. These results suggested that PGC-1α might protect MCs in this cell model from senescence through a nuclear-mitochondrial interaction and against apoptosis. Our study may shed light on the pathogenesis of presbycusis and provide a new therapeutic target for presbycusis.

  9. Replication of urban innovations - prioritization of strategies for the replication of Dhaka's community-based decentralized composting model.

    Science.gov (United States)

    Yedla, Sudhakar

    2012-01-01

    Dhaka's community-based decentralized composting (DCDC) is a successful demonstration of solid waste management by adopting low-cost technology, local resources community participation and partnerships among the various actors involved. This paper attempts to understand the model, necessary conditions, strategies and their priorities to replicate DCDC in the other developing cities of Asia. Thirteen strategies required for its replication are identified and assessed based on various criteria, namely transferability, longevity, economic viability, adaptation and also overall replication. Priority setting by multi-criteria analysis by applying analytic hierarchy process revealed that immediate transferability without long-term and economic viability consideration is not advisable as this would result in unsustainable replication of DCDC. Based on the analysis, measures to ensure the product quality control; partnership among stakeholders (public-private-community); strategies to achieve better involvement of the private sector in solid waste management (entrepreneurship in approach); simple and low-cost technology; and strategies to provide an effective interface among the complementing sectors are identified as important strategies for its replication.

  10. Slow and Fast Neocortical Oscillations in the Senescence-Accelerated Mouse Model SAMP8

    Directory of Open Access Journals (Sweden)

    Patricia Castano-Prat

    2017-05-01

    Full Text Available The senescence-accelerated mouse prone 8 (SAMP8 model is characterized by accelerated, progressive cognitive decline as well as Alzheimer’s disease (AD-like neurodegenerative changes, and resembles the etiology of multicausal, sporadic late-onset/age-related AD in humans. Our aim was to find whether these AD-like pathological features, together with the cognitive deficits present in the SAMP8 strain, are accompanied by disturbances in cortical network activity with respect to control mice (SAM resistance 1, SAMR1 and, if so, how the alterations in cortical activity progress with age. For this purpose, we characterized the extracellular spontaneous oscillatory activity in different regions of the cerebral cortex of SAMP8 and SAMR1 mice under ketamine anesthesia at 5 and 7 months of age. Under these conditions, slow oscillations and fast rhythms generated in the cortical network were recorded and different parameters of these oscillations were quantified and compared between SAMP8 and their control, SAMR1 mice. The average frequency of slow oscillations in SAMP8 mice was decreased with respect to the control mice at both studied ages. An elongation of the silent periods or Down states was behind the decreased slow oscillatory frequency while the duration of active or Up states remained stable. SAMP8 mice also presented increased cycle variability and reduced high frequency components during Down states. During Up states, the power peak in the gamma range was displaced towards lower frequencies in all the cortical areas of SAMP8 with respect to control mice suggesting that the spectral profile of SAMP8 animals is shifted towards lower frequencies. This shift is reminiscent to one of the principal hallmarks of electroencephalography (EEG abnormalities in patients with Alzheimer’s disease, and adds evidence in support of the suitability of the SAMP8 mouse as a model of this disease. Although some of the differences between SAMP8 and control mice

  11. Uncoupling the senescent phenotype from telomere shortening in hydrogen peroxide-treated fibroblasts

    NARCIS (Netherlands)

    Chen, QM; Prowse, KR; Tu, VC; Purdom, S; Linskens, MHK; Chen, Qin M.; Prowse, Karen R.; Tu, Victoria C.

    2001-01-01

    Normal human cells have a limited replicative potential and inevitably reach replicative senescence in culture. Replicatively senescent cells show multiple molecular changes, some of which are related to the irreversible growth arrest in culture, whereas others resemble the changes occurring during

  12. Preon model and family replicated E_6 unification

    CERN Document Server

    Das, C R

    2007-01-01

    Previously we suggested a new preon model of composite quark-leptons and bosons with the 'flipped' E_6\\times \\tilde{E_6} gauge symmetry group. We assumed that preons are dyons having both hyper-electric g and hyper-magnetic \\tilde g charges, and these preons-dyons are confined by hyper-magnetic strings which are an N=1 supersymmetric non-Abelian flux tubes created by the condensation of spreons near the Planck scale. In the present talk we show that the existence of the three types of strings with tensions T_k=k T_0 (k=1,2,3) producing three (and only three) generations of composite quark-leptons, also provides three generations of composite gauge bosons ('hyper-gluons') and, as a consequence, predicts the family replicated [E_6]^3 unification near the Planck scale. This group of unification has the possibility of breaking to the group of symmetry: [SU(3)_C]^3\\times [SU(2)_L]^3\\times [U(1)_Y]^3 \\times [U(1)_{(B-L)}]^3 which undergoes the breakdown to the Standard Model at lower energies. The AntiGUT scenario ...

  13. Experimental Models in Syrian Golden Hamster Replicate Human Acute Pancreatitis.

    Science.gov (United States)

    Wang, Yunan; Kayoumu, Abudurexiti; Lu, Guotao; Xu, Pengfei; Qiu, Xu; Chen, Liye; Qi, Rong; Huang, Shouxiong; Li, Weiqin; Wang, Yuhui; Liu, George

    2016-06-15

    The hamster has been shown to share a variety of metabolic similarities with humans. To replicate human acute pancreatitis with hamsters, we comparatively studied the efficacy of common methods, such as the peritoneal injections of caerulein, L-arginine, the retrograde infusion of sodium taurocholate, and another novel model with concomitant administration of ethanol and fatty acid. The severity of pancreatitis was evaluated by serum amylase activity, pathological scores, myeloperoxidase activity, and the expression of inflammation factors in pancreas. The results support that the severity of pathological injury is consistent with the pancreatitis induced in mice and rat using the same methods. Specifically, caerulein induced mild edematous pancreatitis accompanied by minimal lung injury, while L-arginine induced extremely severe pancreatic injury including necrosis and neutrophil infiltration. Infusion of Na-taurocholate into the pancreatic duct induced necrotizing pancreatitis in the head of pancreas and lighter inflammation in the distal region. The severity of acute pancreatitis induced by combination of ethanol and fatty acids was between the extent of caerulein and L-arginine induction, with obvious inflammatory cells infiltration. In view of the advantages in lipid metabolism features, hamster models are ideally suited for the studies of pancreatitis associated with altered metabolism in humans.

  14. Replication of a Career Academy Model: The Georgia Central Educational Center and Four Replication Sites. Summary. Issues & Answers. REL 2011-No. 101

    Science.gov (United States)

    Detgen, Amy; Alfeld, Corinne

    2011-01-01

    The study surveyed four career academies in Georgia that replicated the model of the Georgia Central Educational Center, which integrates technical instruction and academics at the high school level. The four replication sites adhered to the major tenets of the model. The model's flexibility helped the new sites meet community needs. [For the main…

  15. Evolution of maternal effect senescence.

    Science.gov (United States)

    Moorad, Jacob A; Nussey, Daniel H

    2016-01-12

    Increased maternal age at reproduction is often associated with decreased offspring performance in numerous species of plants and animals (including humans). Current evolutionary theory considers such maternal effect senescence as part of a unified process of reproductive senescence, which is under identical age-specific selective pressures to fertility. We offer a novel theoretical perspective by combining William Hamilton's evolutionary model for aging with a quantitative genetic model of indirect genetic effects. We demonstrate that fertility and maternal effect senescence are likely to experience different patterns of age-specific selection and thus can evolve to take divergent forms. Applied to neonatal survival, we find that selection for maternal effects is the product of age-specific fertility and Hamilton's age-specific force of selection for fertility. Population genetic models show that senescence for these maternal effects can evolve in the absence of reproductive or actuarial senescence; this implies that maternal effect aging is a fundamentally distinct demographic manifestation of the evolution of aging. However, brief periods of increasingly beneficial maternal effects can evolve when fertility increases with age faster than cumulative survival declines. This is most likely to occur early in life. Our integration of theory provides a general framework with which to model, measure, and compare the evolutionary determinants of the social manifestations of aging. Extension of our maternal effects model to other ecological and social contexts could provide important insights into the drivers of the astonishing diversity of lifespans and aging patterns observed among species.

  16. Changes in autophagy, proteasome activity and metabolism to determine a specific signature for acute and chronic senescent mesenchymal stromal cells.

    Science.gov (United States)

    Capasso, Stefania; Alessio, Nicola; Squillaro, Tiziana; Di Bernardo, Giovanni; Melone, Mariarosa A; Cipollaro, Marilena; Peluso, Gianfranco; Galderisi, Umberto

    2015-11-24

    A sharp definition of what a senescent cell is still lacking since we do not have in depth understanding of mechanisms that induce cellular senescence. In addition, senescent cells are heterogeneous, in that not all of them express the same genes and present the same phenotype. To further clarify the classification of senescent cells, hints may be derived by the study of cellular metabolism, autophagy and proteasome activity. In this scenario, we decided to study these biological features in senescence of Mesenchymal Stromal Cells (MSC). These cells contain a subpopulation of stem cells that are able to differentiate in mesodermal derivatives (adipocytes, chondrocytes, osteocytes). In addition, they can also contribute to the homeostatic maintenance of many organs, hence, their senescence could be very deleterious for human body functions. We induced MSC senescence by oxidative stress, doxorubicin treatment, X-ray irradiation and replicative exhaustion. The first three are considered inducers of acute senescence while extensive proliferation triggers replicative senescence also named as chronic senescence. In all conditions, but replicative and high IR dose senescence, we detected a reduction of the autophagic flux, while proteasome activity was impaired in peroxide-treated and irradiated cells. Differences were observed also in metabolic status. In general, all senescent cells evidenced metabolic inflexibility and prefer to use glucose as energy fuel. Irradiated cells with low dose of X-ray and replicative senescent cells show a residual capacity to use fatty acids and glutamine as alternative fuels, respectively. Our study may be useful to discriminate among different senescent phenotypes.

  17. Aggregate and Individual Replication Probability within an Explicit Model of the Research Process

    Science.gov (United States)

    Miller, Jeff; Schwarz, Wolf

    2011-01-01

    We study a model of the research process in which the true effect size, the replication jitter due to changes in experimental procedure, and the statistical error of effect size measurement are all normally distributed random variables. Within this model, we analyze the probability of successfully replicating an initial experimental result by…

  18. Aggregate and Individual Replication Probability within an Explicit Model of the Research Process

    Science.gov (United States)

    Miller, Jeff; Schwarz, Wolf

    2011-01-01

    We study a model of the research process in which the true effect size, the replication jitter due to changes in experimental procedure, and the statistical error of effect size measurement are all normally distributed random variables. Within this model, we analyze the probability of successfully replicating an initial experimental result by…

  19. IL1- and TGFβ-Nox4 signaling, oxidative stress and DNA damage response are shared features of replicative, oncogene-induced, and drug-induced paracrine 'bystander senescence'

    National Research Council Canada - National Science Library

    Hubackova, Sona; Krejcikova, Katerina; Bartek, Jiri; Hodny, Zdenek

    2012-01-01

    ...)-mediated DNA damage response (DDR). Persistent cytokine signaling and activated DDR evoke senescence in normal bystander cells, accompanied by activation of the JAK/STAT, TGFβ/SMAD and IL1/NFκ...

  20. Cellular senescence regulated by SWI/SNF complex subunits through p53/p21 and p16/pRB pathway.

    Science.gov (United States)

    He, Ling; Chen, Ying; Feng, Jianguo; Sun, Weichao; Li, Shun; Ou, Mengting; Tang, Liling

    2017-09-01

    SWI/SNF complex is an evolutionarily well-conserved chromatin-remodeling complex, which is implicated in the nucleosomes removing or sliding, impacting on the DNA repair, replication and genes expression regulation. The SWI/SNF complex consists up to 12 protein subunits. The catalytic subunits are BRG1 or BRM, which are exclusive ATPase subunits. BRG1 has been reported to play an important role in cellular senescence. However, The function of non-catalytic subunits involved in cellular senescence is rarely investigated. Therefore, we focused on the senescence regulation roles of SWI/SNF non-catalytic subunits in cellular senescent model induced by H2O2. H2O2 treatment was used to induce cellular senescence models in vitro. Screening the candidate subunits involved in this process by comparing the expression levels of SWI/SNF subunits with/without H2O2 treatment. Over-expression and knockdown the candidate subunits were utilized to investigate the functions and mechanism of the subunits involved in senescence regulation. The expressions of BAF57, BAF60a and SNF5 were changed significantly after H2O2 treatment. Overexpression of the three subunits separately induced cell growth arrest in both HaCaT and GLL19 cells, while knockdown of the subunits separately eased the senescence induced by H2O2 treatment. Results further showed that BAF57, BAF60a and SNF5 regulated cellular senescence via both p53/p21 and p16/pRB pathways, and the three subunits all had a directly interaction with p53. These results indicated that BAF57, BAF60a and SNF5 might act as novel pro-senescence factors in both normal and tumor human skin cells. Therefore, inhibiting expression of the three factors might delay the cellular senescence process. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Senescence from glioma stem cell differentiation promotes tumor growth

    Energy Technology Data Exchange (ETDEWEB)

    Ouchi, Rie [Division of Molecular Biotherapy, Cancer Chemotherapy Center, Japanese Foundation for Cancer Research, 3-8-31 Ariake, Koto-ku, Tokyo 135-8550 (Japan); Laboratory of Molecular Target Therapy of Cancer, Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 3-8-31 Ariake, Koto-ku, Tokyo 135-8550 (Japan); Okabe, Sachiko; Migita, Toshiro [Division of Molecular Biotherapy, Cancer Chemotherapy Center, Japanese Foundation for Cancer Research, 3-8-31 Ariake, Koto-ku, Tokyo 135-8550 (Japan); Nakano, Ichiro [Department of Neurosurgery, Comprehensive Cancer Center, University of Alabama at Birmingham, 1824 6th Avenue South, Birmingham, AL 35233 (United States); Seimiya, Hiroyuki, E-mail: hseimiya@jfcr.or.jp [Division of Molecular Biotherapy, Cancer Chemotherapy Center, Japanese Foundation for Cancer Research, 3-8-31 Ariake, Koto-ku, Tokyo 135-8550 (Japan); Laboratory of Molecular Target Therapy of Cancer, Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 3-8-31 Ariake, Koto-ku, Tokyo 135-8550 (Japan)

    2016-02-05

    Glioblastoma (GBM) is a lethal brain tumor composed of heterogeneous cellular populations including glioma stem cells (GSCs) and differentiated non-stem glioma cells (NSGCs). While GSCs are involved in tumor initiation and propagation, NSGCs' role remains elusive. Here, we demonstrate that NSGCs undergo senescence and secrete pro-angiogenic proteins, boosting the GSC-derived tumor formation in vivo. We used a GSC model that maintains stemness in neurospheres, but loses the stemness and differentiates into NSGCs upon serum stimulation. These NSGCs downregulated telomerase, shortened telomeres, and eventually became senescent. The senescent NSGCs released pro-angiogenic proteins, including vascular endothelial growth factors and senescence-associated interleukins, such as IL-6 and IL-8. Conditioned medium from senescent NSGCs promoted proliferation of brain microvascular endothelial cells, and mixed implantation of GSCs and senescent NSGCs into mice enhanced the tumorigenic potential of GSCs. The senescent NSGCs seem to be clinically relevant, because both clinical samples and xenografts of GBM contained tumor cells that expressed the senescence markers. Our data suggest that senescent NSGCs promote malignant progression of GBM in part via paracrine effects of the secreted proteins. - Highlights: • Non-stem glioma cells (NSGCs) lose telomerase and eventually become senescent. • Senescent NSGCs secrete pro-angiogenic proteins, such as VEGFs, IL-6, and IL-8. • Senescent NSGCs enhance the growth of brain microvascular endothelial cells. • Senescent NSGCs enhance the tumorigenic potential of glioma stem cells in vivo.

  2. Jasmonates during senescence

    Science.gov (United States)

    Seltmann, Martin A; Hussels, Wiebke

    2010-01-01

    Jasmonic acid and derivatives are oxylipin signaling compounds derived from linolenic acid. Jasmonates accumulate during natural and dark-induced senescence but the increase in these compounds is not essential for the initiation or progression of these senescence processes. Here we report that during natural and dark-induced senescence the increase in jasmonate levels does not trigger jasmonate signaling. Furthermore we provide evidence that jasmonate production might result from membrane turnover during dark-induced senescence. PMID:21057217

  3. Role of endonuclease G in senescence-associated cell death of human endothelial cells

    OpenAIRE

    2011-01-01

    Mitotic cells in culture show a limited replicative potential and after extended subculturing undergo a terminal growth arrest termed cellular senescence. When cells reach the senescent phenotype, this is accompanied by a significant change in the cellular phenotype and massive changes in gene expression, including the upregulation of secreted factors. In human fibroblasts, senescent cells also acquire resistance to apoptosis. In contrary, in human endothelial cells, both replicative and stre...

  4. Behaviour and cognitive changes correlated with hippocampal neuroinflammaging and neuronal markers in female SAMP8, a model of accelerated senescence.

    Science.gov (United States)

    Griñan-Ferré, Christian; Palomera-Ávalos, Verónica; Puigoriol-Illamola, Dolors; Camins, Antoni; Porquet, David; Plá, Virginia; Aguado, Fernando; Pallàs, Mercè

    2016-07-01

    Senescence accelerated mice P8 (SAMP8) is a phenotypic model of age, characterized by deficits in memory and altered behaviour. Here, we determined the effect of age in SAMP8, and compared with the resistant strain, SAMR1, in behaviour and learning parameters linking these disturbances with oxidative stress environment. We found impairment in emotional behaviour with regard to fear and anxiety in young SAMP8 vs. age-mated SAMR1. Differences were attenuated with age. In contrast, learning capabilities are worse in SAMP8, both in young and aged animals, with regard to SAMR1. These waves in behaviour and cognition were correlated with an excess of oxidative stress (OS) in SAMP8 at younger ages that diminished with age. In this manner, we found changes in the hippocampal expression of ALDH2, IL-6, HMOX1, COX2, CXCL10, iNOS, and MCP-1 with an altered amyloidogenic pathway by increasing the Amyloid beta precursor protein (APP) and BACE1, and reduced ADAM10 expression; in addition, astrogliosis and neuronal markers decreased. Moreover, Superoxide dismutase 1 (SOD1) and Nuclear factor-kappa beta (NF-kβ) expression and protein levels were higher in younger SAMP8 than in SAMR1. In conclusion, the accelerated senescence process present in SAMP8 can be linked with an initial deregulation in redox homeostasis, named neuroinflammaging, by inducing molecular changes that lead to neuroinflammation and the neurodegenerative process. These changes are reflected in the emotional and cognitive behaviour of SAMP8 that differs from that of SAMR1 and that highlighted the importance of earlier oxidative processes in the onset of neurodegeneration. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. Quasispecies spatial models for RNA viruses with different replication modes and infection strategies.

    Directory of Open Access Journals (Sweden)

    Josep Sardanyés

    Full Text Available Empirical observations and theoretical studies suggest that viruses may use different replication strategies to amplify their genomes, which impact the dynamics of mutation accumulation in viral populations and therefore, their fitness and virulence. Similarly, during natural infections, viruses replicate and infect cells that are rarely in suspension but spatially organized. Surprisingly, most quasispecies models of virus replication have ignored these two phenomena. In order to study these two viral characteristics, we have developed stochastic cellular automata models that simulate two different modes of replication (geometric vs stamping machine for quasispecies replicating and spreading on a two-dimensional space. Furthermore, we explored these two replication models considering epistatic fitness landscapes (antagonistic vs synergistic and different scenarios for cell-to-cell spread, one with free superinfection and another with superinfection inhibition. We found that the master sequences for populations replicating geometrically and with antagonistic fitness effects vanished at low critical mutation rates. By contrast, the highest critical mutation rate was observed for populations replicating geometrically but with a synergistic fitness landscape. Our simulations also showed that for stamping machine replication and antagonistic epistasis, a combination that appears to be common among plant viruses, populations further increased their robustness by inhibiting superinfection. We have also shown that the mode of replication strongly influenced the linkage between viral loci, which rapidly reached linkage equilibrium at increasing mutations for geometric replication. We also found that the strategy that minimized the time required to spread over the whole space was the stamping machine with antagonistic epistasis among mutations. Finally, our simulations revealed that the multiplicity of infection fluctuated but generically increased along

  6. MicroRNA-15b regulates mitochondrial ROS production and the senescence-associated secretory phenotype through sirtuin 4/SIRT4

    Science.gov (United States)

    Lang, Alexander; Grether-Beck, Susanne; Singh, Madhurendra; Kuck, Fabian; Jakob, Sascha; Kefalas, Andreas; Altinoluk-Hambüchen, Simone; Graffmann, Nina; Schneider, Maren; Lindecke, Antje; Brenden, Heidi; Felsner, Ingo; Ezzahoini, Hakima; Marini, Alessandra; Weinhold, Sandra; Vierkötter, Andrea; Tigges, Julia; Schmidt, Stephan; Stühler, Kai; Köhrer, Karl; Uhrberg, Markus; Haendeler, Judith; Krutmann, Jean; Piekorz, Roland P.

    2016-01-01

    Mammalian sirtuins are involved in the control of metabolism and life-span regulation. Here, we link the mitochondrial sirtuin SIRT4 with cellular senescence, skin aging, and mitochondrial dysfunction. SIRT4 expression significantly increased in human dermal fibroblasts undergoing replicative or stress-induced senescence triggered by UVB or gamma-irradiation. In-vivo, SIRT4 mRNA levels were upregulated in photoaged vs. non-photoaged human skin. Interestingly, in all models of cellular senescence and in photoaged skin, upregulation of SIRT4 expression was associated with decreased levels of miR-15b. The latter was causally linked to increased SIRT4 expression because miR-15b targets a functional binding site in the SIRT4 gene and transfection of oligonucleotides mimicking miR-15b function prevented SIRT4 upregulation in senescent cells. Importantly, increased SIRT4 negatively impacted on mitochondrial functions and contributed to the development of a senescent phenotype. Accordingly, we observed that inhibition of miR-15b, in a SIRT4-dependent manner, increased generation of mitochondrial reactive oxygen species, decreased mitochondrial membrane potential, and modulated mRNA levels of nuclear encoded mitochondrial genes and components of the senescence-associated secretory phenotype (SASP). Thus, miR-15b is a negative regulator of stress-induced SIRT4 expression thereby counteracting senescence associated mitochondrial dysfunction and regulating the SASP and possibly organ aging, such as photoaging of human skin. PMID:26959556

  7. PKCι depletion initiates mitotic slippage-induced senescence in glioblastoma.

    Science.gov (United States)

    Restall, Ian J; Parolin, Doris A E; Daneshmand, Manijeh; Hanson, Jennifer E L; Simard, Manon A; Fitzpatrick, Megan E; Kumar, Ritesh; Lavictoire, Sylvie J; Lorimer, Ian A J

    2015-01-01

    Cellular senescence is a tumor suppressor mechanism where cells enter a permanent growth arrest following cellular stress. Oncogene-induced senescence (OIS) is induced in non-malignant cells following the expression of an oncogene or inactivation of a tumor suppressor. Previously, we have shown that protein kinase C iota (PKCι) depletion induces cellular senescence in glioblastoma cells in the absence of a detectable DNA damage response. Here we demonstrate that senescent glioblastoma cells exhibit an aberrant centrosome morphology. This was observed in basal levels of senescence, in p21-induced senescence, and in PKCι depletion-induced senescence. In addition, senescent glioblastoma cells are polyploid, Ki-67 negative and arrest at the G1/S checkpoint, as determined by expression of cell cycle regulatory proteins. These markers are all consistent with cells that have undergone mitotic slippage. Failure of the spindle assembly checkpoint to function properly can lead to mitotic slippage, resulting in the premature exit of mitotic cells into the G1 phase of the cell cycle. Although in G1, these cells have the replicated DNA and centrosomal phenotype of a cell that has entered mitosis and failed to divide. Overall, we demonstrate that PKCι depletion initiates mitotic slippage-induced senescence in glioblastoma cells. To our knowledge, this is the first evidence of markers of mitotic slippage directly in senescent cells by co-staining for senescence-associated β-galactosidase and immunofluorescence markers in the same cell population. We suggest that markers of mitotic slippage be assessed in future studies of senescence to determine the extent of mitotic slippage in the induction of cellular senescence.

  8. Significant demographic and fine-scale genetic structure in expanding and senescing populations of the terrestrial orchid Cymbidium goeringii (Orchidaceae)

    National Research Council Canada - National Science Library

    Mi Yoon Chung; John D. Nason; Myong Gi Chung

    2011-01-01

    .... To determine how demographic structure and FSGS change with stages of population succession, we studied replicate expanding and senescing populations of the Asian terrestrial orchid Cymbidium goeringii. Methods...

  9. ASYMPTOTIC NORMALITY OF PARAMETERS ESTIMATION IN EV MODEL WITH REPLICATED OBSERVATIONS

    Institute of Scientific and Technical Information of China (English)

    张三国; 陈希孺

    2002-01-01

    This paper based on the essay [1], studies in case that replicated observations are available in some experimental points, the parameters estimation of one dimensional linear errors-in-variables (EV) models. Asymptotic normality is established.

  10. Establishment and primary application of a mouse model with hepatitis B virus replication

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    AIM: To establish a rapid and convenient animal model with hepatitis B virus (HBV) replication. METHODS: A naked DNA solution of HBV-replicationcompetent plasmid was transferred to BALB/C mice via the tail vein, using a hydrodynamic in vivo transfection procedure. After injection, these mice were sacrificed on d 1, 3, 4, 5, 7 and 10. HBV DNA replication intermediates in the liver were analyzed by Southern blot hybridization. The expression of hepatitis B core antigen (HBcAg) and hepatitis B surface antigen (HBsAg) in the liver was checked by immunohistochemistry. Serum HBsAg and hepatitis B e antigen (HBeAg) was detected by enzymelinked immunosorbent assay (ELISA). Inhibition of HBV replication was compared in HBV replication model mice treated intraperitoneally with polyinosinic-polytidylin acid (polyIC) or phosphate-buffered saline (PBS). RESULTS: After hydrodynamicin vivo transfection, HBV DNA replication intermediates in the mouse liver were detectable on d 1 and abundant on d 3 and 4, the levels were slightly decreased and remained relatively stable between d 5 and 7, and were almost undetectable on d 10. The expression patterns of HBcAg and HBsAg were similar to that of HBV replication intermediate DNA, except that they reached a peak on d 1 after injection. No obvious differences in HBV DNA replication intermediates were observed in the left, right and middle lobes of the liver. After treatment with polyIC, the level of HBV intermediate DNA in the liver was lower than that in the control mice injected with PBS. CONCLUSION: A rapid and convenient mouse model with a high level of HBV replication was developed and used to investigate the inhibitory effect of polyIC on HBV replication, which provides a useful tool for future functional studies of the HBV genome.

  11. YAP/TEAD-mediated transcription controls cellular senescence.

    Science.gov (United States)

    Xie, Qi; Chen, Jing; Feng, Han; Peng, Shengyi; Adams, Ursula; Bai, Yujie; Huang, Li; Li, Ji; Huang, Junjian; Meng, Songshu; Yuan, Zengqiang

    2013-06-15

    Transcription coactivator Yes-associated protein (YAP) plays an important role in the regulation of cell proliferation and apoptosis. Here, we identify a new role of YAP in the regulation of cellular senescence. We find that the expression levels of YAP proteins decrease following the replication-induced cellular senescence in IMR90 cells. Silencing of YAP inhibits cell proliferation and induces premature senescence. In additional experiments, we observe that cellular senescence induced by YAP deficiency is TEAD- and Rb/p16/p53-dependent. Furthermore, we show that Cdk6 is a direct downstream target gene of YAP in the regulation of cellular senescence, and the expression of Cdk6 is through the YAP-TEAD complex. Ectopic expression of Cdk6 rescued YAP knockdown-induced senescence. Finally, we find that downregulation of YAP in tumor cells increases senescence in response to chemotherapeutic agents, and YAP or Cdk6 expression rescues cellular senescence. Taken together, our findings define the critical role of YAP in the regulation of cellular senescence and provide a novel insight into a potential chemotherapeutic avenue for tumor suppression. ©2013 AACR.

  12. Using the life history model to set the stage(s) of growth and senescence in bioarchaeology and paleodemography.

    Science.gov (United States)

    Roksandic, Mirjana; Armstrong, Stephanie D

    2011-07-01

    Paleodemography, the study of demographic parameters of past human populations, relies on assumptions including biological uniformitarianism, stationary populations, and the ability to determine point age estimates from skeletal material. These assumptions have been widely criticized in the literature and various solutions have been proposed. The majority of these solutions rely on statistical modeling, and have not seen widespread application. Most bioarchaeologists recognize that our ability to assess chronological age is inherently limited, and have instead resorted to large, qualitative, age categories. However, there has been little attempt in the literature to systematize and define the stages of development and ageing used in bioarchaeology. We propose that stages should be based in the human life history pattern, and their skeletal markers should have easily defined and clear endpoints. In addition to a standard five-stage developmental model based on the human life history pattern, current among human biologists, we suggest divisions within the adult stage that recognize the specific nature of skeletal samples. We therefore propose the following eight stages recognizable in human skeletal development and senescence: infancy, early childhood, late childhood, adolescence, young adulthood, full adulthood, mature adulthood, and senile adulthood. Striving toward a better prediction of chronological ages will remain important and could eventually help us understand to what extent past societies differed in the timing of these life stages. Furthermore, paleodemographers should try to develop methods that rely on the type of age information accessible from the skeletal material, which uses life stages, rather than point age estimates.

  13. Discrimination thresholds of normal and anomalous trichromats: Model of senescent changes in ocular media density on the Cambridge Colour Test.

    Science.gov (United States)

    Shinomori, Keizo; Panorgias, Athanasios; Werner, John S

    2016-03-01

    Age-related changes in chromatic discrimination along dichromatic confusion lines were measured with the Cambridge Colour Test (CCT). One hundred and sixty-two individuals (16 to 88 years old) with normal Rayleigh matches were the major focus of this paper. An additional 32 anomalous trichromats classified by their Rayleigh matches were also tested. All subjects were screened to rule out abnormalities of the anterior and posterior segments. Thresholds on all three chromatic vectors measured with the CCT showed age-related increases. Protan and deutan vector thresholds increased linearly with age while the tritan vector threshold was described with a bilinear model. Analysis and modeling demonstrated that the nominal vectors of the CCT are shifted by senescent changes in ocular media density, and a method for correcting the CCT vectors is demonstrated. A correction for these shifts indicates that classification among individuals of different ages is unaffected. New vector thresholds for elderly observers and for all age groups are suggested based on calculated tolerance limits.

  14. [Senescence and cellular immortality].

    Science.gov (United States)

    Trentesaux, C; Riou, J-F

    2010-11-01

    Senescence was originally described from the observation of the limited ability of normal cells to grow in culture, and may be generated by telomere erosion, accumulation of DNA damages, oxidative stress and modulation of oncogenes or tumor suppressor genes. Senescence corresponds to a cellular response aiming to control tumor progression by limiting cell proliferation and thus constitutes an anticancer barrier. Senescence is observed in pre-malignant tumor stages and disappears from malignant tumors. Agents used in standard chemotherapy also have the potential to induce senescence, which may partly explain their therapeutic activities. It is possible to restore senescence in tumors using targeted therapies that triggers telomere dysfunction or reactivates suppressor genes functions, which are essential for the onset of senescence.

  15. A dynamic stochastic model for DNA replication initiation in early embryos.

    Directory of Open Access Journals (Sweden)

    Arach Goldar

    Full Text Available BACKGROUND: Eukaryotic cells seem unable to monitor replication completion during normal S phase, yet must ensure a reliable replication completion time. This is an acute problem in early Xenopus embryos since DNA replication origins are located and activated stochastically, leading to the random completion problem. DNA combing, kinetic modelling and other studies using Xenopus egg extracts have suggested that potential origins are much more abundant than actual initiation events and that the time-dependent rate of initiation, I(t, markedly increases through S phase to ensure the rapid completion of unreplicated gaps and a narrow distribution of completion times. However, the molecular mechanism that underlies this increase has remained obscure. METHODOLOGY/PRINCIPAL FINDINGS: Using both previous and novel DNA combing data we have confirmed that I(t increases through S phase but have also established that it progressively decreases before the end of S phase. To explore plausible biochemical scenarios that might explain these features, we have performed comparisons between numerical simulations and DNA combing data. Several simple models were tested: i recycling of a limiting replication fork component from completed replicons; ii time-dependent increase in origin efficiency; iii time-dependent increase in availability of an initially limiting factor, e.g. by nuclear import. None of these potential mechanisms could on its own account for the data. We propose a model that combines time-dependent changes in availability of a replication factor and a fork-density dependent affinity of this factor for potential origins. This novel model quantitatively and robustly accounted for the observed changes in initiation rate and fork density. CONCLUSIONS/SIGNIFICANCE: This work provides a refined temporal profile of replication initiation rates and a robust, dynamic model that quantitatively explains replication origin usage during early embryonic S phase

  16. Salidroside protects human fibroblast cells from premature senescence induced by H(2)O(2) partly through modulating oxidative status.

    Science.gov (United States)

    Mao, Gen-xiang; Wang, Yan; Qiu, Qiang; Deng, Hong-bin; Yuan, Long-guo; Li, Rui-guo; Song, Dan-qing; Li, Yi-yang Yvonne; Li, Dian-dong; Wang, Zhen

    2010-01-01

    Although salidroside and salidroside-like compounds are considered as most critical constitutes needed and responsible for multiple therapeutic benefits of Rhodiola rosea L., including anti-aging, direct demonstration regarding the role of salidroside in anti-aging process is still deficient. In this study, we selected the H(2)O(2)-induced premature senescence model in human fetal lung diploid fibroblasts to investigate the protection of salidroside against aging in vitro and associated molecular mechanisms. We found that salidroside considerably reversed senescence-like phenotypes in the oxidant challenged model, including alterations of morphology, cell cycle, SA-β-gal staining, DNA damage, as well as related molecules expression such as p53, p21 and p16. The protection occurred in a dose-dependent manner, with 5μM offering best efficacy. The proposed antioxidant property of the compound was confirmed in this cellular system, and thus at least partially accounted for the protection of the compound against premature senescence. Similar protection of salidroside against replicative senescence was observed as well. Interestingly, the regulation of senescence-related molecules by salidroside involved ROS-irrelevant mechanisms in both models. This finding presents salidroside as an attractive agent with potential to retard aging and attenuate age-related diseases in humans. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

  17. Ginsenoside Rg1 prevents cognitive impairment and hippocampus senescence in a rat model of D-galactose-induced aging.

    Directory of Open Access Journals (Sweden)

    Jiahong Zhu

    Full Text Available Neurogenesis continues throughout the lifetime in the hippocampus, while the rate declines with brain aging. It has been hypothesized that reduced neurogenesis may contribute to age-related cognitive impairment. Ginsenoside Rg1 is an active ingredient of Panax ginseng in traditional Chinese medicine, which exerts anti-oxidative and anti-aging effects. This study explores the neuroprotective effect of ginsenoside Rg1 on the hippocampus of the D-gal (D-galactose induced aging rat model. Sub-acute aging was induced in male SD rats by subcutaneous injection of D-gal (120 mg/kg·d for 42 days, and the rats were treated with ginsenoside Rg1 (20 mg/kg·d, intraperitoneally or normal saline for 28 days after 14 days of D-gal injection. In another group, normal male SD rats were treated with ginsenoside Rg1 alone (20 mg/kg·d, intraperitoneally for 28 days. It showed that administration of ginsenoside Rg1 significantly attenuated all the D-gal-induced changes in the hippocampus, including cognitive capacity, senescence-related markers and hippocampal neurogenesis, compared with the D-gal-treated rats. Further investigation showed that ginsenoside Rg1 protected NSCs/NPCs (neural stem cells/progenitor cells shown by increased level of SOX-2 expression; reduced astrocytes activation shown by decrease level of Aeg-1 expression; increased the hippocampal cell proliferation; enhanced the activity of the antioxidant enzymes GSH-Px (glutathione peroxidase and SOD (Superoxide Dismutase; decreased the levels of IL-1β, IL-6 and TNF-α, which are the proinflammatory cytokines; increased the telomere lengths and telomerase activity; and down-regulated the mRNA expression of cellular senescence associated genes p53, p21Cip1/Waf1 and p19Arf in the hippocampus of aged rats. Our data provides evidence that ginsenoside Rg1 can improve cognitive ability, protect NSCs/NPCs and promote neurogenesis by enhancing the antioxidant and anti-inflammatory capacity in the

  18. The replication domain model: regulating replicon firing in the context of large-scale chromosome architecture.

    Science.gov (United States)

    Pope, Benjamin D; Gilbert, David M

    2013-11-29

    The "Replicon Theory" of Jacob, Brenner, and Cuzin has reliably served as the paradigm for regulating the sites where individual replicons initiate replication. Concurrent with the replicon model was Taylor's demonstration that plant and animal chromosomes replicate segmentally in a defined temporal sequence, via cytologically defined units too large to be accounted for by a single replicon. Instead, there seemed to be a program to choreograph when chromosome units replicate during S phase, executed by initiation at clusters of individual replicons within each segment. Here, we summarize recent molecular evidence for the existence of such units, now known as "replication domains", and discuss how the organization of large chromosomes into structural units has added additional layers of regulation to the original replicon model.

  19. Caenorhabditis elegans as an alternative model to study senescence of host defense and the prevention by immunonutrition.

    Science.gov (United States)

    Komura, Tomomi; Ikeda, Takanori; Hoshino, Kaori; Shibamura, Ayumi; Nishikawa, Yoshikazu

    2012-01-01

    Whether nutritional control can retard senescence of immune function and decrease mortality from infectious diseases has not yet been established; the difficulty of establishing a model has made this a challenging topic to investigate. Caenorhabditis elegans has been extensively used as an experimental system for biological studies. Particularly for aging studies, the worm has the advantage of a short and reproducible life span. The organism has also been recognized as an alternative to mammalian models of infection with bacterial pathogens in this decade. Hence we have studied whether the worms could be a model host in the fields of immunosenescence and immunonutrition. Feeding nematodes lactic acid bacteria (LAB) resulted in increases in average life span of the nematodes compared to those fed Escherichia coli strain OP50, a standard food bacteria. The 7-day-old nematodes fed LAN from age 3 days were clearly endurable to subsequent salmonella infection compared with nematodes fed OP50 before the salmonella infection. The worm could be a unique model to study effects of food factors on longevity and host defense, so-called immunonutrition. Then we attempted to establish an immunosenescence model using C. elegans. We focused on the effects of worm age on the Legionella infection and the prevention by immunonutrition. No significant differences in survival were seen between 3-day-old worms fed OP50 and 3-day-old worms infected with virulent Legionella strains. However, when the worms were infected from 7.5 days after hatching, the virulent Legionella strains were obviously nematocidal for the worms' immunosenescence. In contrast, nematodes fed with bifidobacteria prior to Legionella infection were resistant to Legionella. C. elegans could act as a unique alternative host for immunosenescence and resultant opportunistic infection, and immunonutrition researches.

  20. Beneficial effect of melatonin treatment on inflammation, apoptosis and oxidative stress on pancreas of a senescence accelerated mice model.

    Science.gov (United States)

    Cuesta, Sara; Kireev, Roman; García, Cruz; Forman, Katherine; Escames, Germaine; Vara, Elena; Tresguerres, Jesús A F

    2011-01-01

    This study has investigated the effect of aging on parameters of inflammation, oxidative stress and apoptosis in pancreas obtained from two types of male mice models: senescence-accelerated prone (SAMP8) and resistant mice (SAMR1). Animals of 2 (young) and 10 months of age (old) were used (n = 64). The influence of the administration of melatonin in the drinking water for one month at two different dosages (1 and 10mg/(kg day) on old SAMP8 mice on these parameters was also studied. SAMP8 mice showed with age a significant increase in the relative expression of pancreatic genes involved in inflammation, oxidative stress and apoptosis. Furthermore the protein expression of several NFκB subunits was also enhanced. On the contrary aged SAMR1 mice did not show significant increases in these parameters. Melatonin administration to SAMP8 mice was able to reduce these age related alterations at the two used dosages. Copyright © 2011. Published by Elsevier Ireland Ltd.

  1. Beryllium induces premature senescence in human fibroblasts.

    Science.gov (United States)

    Coates, Shannon S A; Lehnert, Bruce E; Sharma, Sunil; Kindell, Susan M; Gary, Ronald K

    2007-07-01

    After cells have completed a sufficient number of cell divisions, they exit the cell cycle and enter replicative senescence. Here, we report that beryllium causes proliferation arrest with premature expression of the principal markers of senescence. After young presenescent human fibroblasts were treated with 3 microM BeSO(4) for 24 h, p21 cyclin-dependent kinase inhibitor mRNA increased by >200%. Longer periods of exposure caused mRNA and protein levels to increase for both p21 and p16(Ink4a), a senescence regulator that prevents pRb-mediated cell cycle progression. BeSO(4) also caused dose-dependent induction of senescence-associated beta-galactosidase activity (SA-beta-gal). Untreated cells had 48 relative fluorescence units (RFU)/microg/h of SA-beta-gal, whereas 3 microM BeSO(4) caused activity to increase to 84 RFU/microg/h. In chromatin immunoprecipitation experiments, BeSO(4) caused p53 protein to associate with its DNA binding site in the promoter region of the p21 gene, indicating that p53 transcriptional activity is responsible for the large increase in p21 mRNA elicited by beryllium. Forced expression of human telomerase reverse transcriptase (hTERT) rendered HFL-1 cells incapable of normal replicative senescence. However, there was no difference in the responsiveness of normal HFL-1 fibroblasts (IC(50) = 1.9 microM) and hTERT-immortalized cells (IC(50) = 1.7 microM) to BeSO(4) in a 9-day proliferation assay. The effects of beryllium resemble those of histone deacetylase-inhibiting drugs, which also cause large increases in p21. However, beryllium produced no changes in histone acetylation, suggesting that Be(2+) acts as a novel and potent pharmacological inducer of premature senescence.

  2. Theoretical models for the regulation of DNA replication in fast-growing bacteria

    Science.gov (United States)

    Creutziger, Martin; Schmidt, Mischa; Lenz, Peter

    2012-09-01

    Growing in always changing environments, Escherichia coli cells are challenged by the task to coordinate growth and division. In particular, adaption of their growth program to the surrounding medium has to guarantee that the daughter cells obtain fully replicated chromosomes. Replication is therefore to be initiated at the right time, which is particularly challenging in media that support fast growth. Here, the mother cell initiates replication not only for the daughter but also for the granddaughter cells. This is possible only if replication occurs from several replication forks that all need to be correctly initiated. Despite considerable efforts during the last 40 years, regulation of this process is still unknown. Part of the difficulty arises from the fact that many details of the relevant molecular processes are not known. Here, we develop a novel theoretical strategy for dealing with this general problem: instead of analyzing a single model, we introduce a wide variety of 128 different models that make different assumptions about the unknown processes. By comparing the predictions of these models we are able to identify the key quantities that allow the experimental discrimination of the different models. Analysis of these quantities yields that out of the 128 models 94 are not consistent with available experimental data. From the remaining 34 models we are able to conclude that mass growth and DNA replication need either to be truly coupled, by coupling DNA replication initiation to the event of cell division, or to the amount of accumulated mass. Finally, we make suggestions for experiments to further reduce the number of possible regulation scenarios.

  3. Mitochondria change dynamics and morphology during grapevine leaf senescence.

    Directory of Open Access Journals (Sweden)

    Cristina Ruberti

    Full Text Available Leaf senescence is the last stage of development of an organ and is aimed to its ordered disassembly and nutrient reallocation. Whereas chlorophyll gradually degrades during senescence in leaves, mitochondria need to maintain active to sustain the energy demands of senescing cells. Here we analysed the motility and morphology of mitochondria in different stages of senescence in leaves of grapevine (Vitis vinifera, by stably expressing a GFP (green fluorescent protein reporter targeted to these organelles. Results show that mitochondria were less dynamic and markedly changed morphology during senescence, passing from the elongated, branched structures found in mature leaves to enlarged and sparse organelles in senescent leaves. Progression of senescence in leaves was not synchronous, since changes in mitochondria from stomata were delayed. Mitochondrial morphology was also analysed in grapevine cell cultures. Mitochondria from cells at the end of their growth curve resembled those from senescing leaves, suggesting that cell cultures might represent a useful model system for senescence. Additionally, senescence-associated mitochondrial changes were observed in plants treated with high concentrations of cytokinins. Overall, morphology and dynamics of mitochondria might represent a reliable senescence marker for plant cells.

  4. Mitochondria change dynamics and morphology during grapevine leaf senescence.

    Science.gov (United States)

    Ruberti, Cristina; Barizza, Elisabetta; Bodner, Martina; La Rocca, Nicoletta; De Michele, Roberto; Carimi, Francesco; Lo Schiavo, Fiorella; Zottini, Michela

    2014-01-01

    Leaf senescence is the last stage of development of an organ and is aimed to its ordered disassembly and nutrient reallocation. Whereas chlorophyll gradually degrades during senescence in leaves, mitochondria need to maintain active to sustain the energy demands of senescing cells. Here we analysed the motility and morphology of mitochondria in different stages of senescence in leaves of grapevine (Vitis vinifera), by stably expressing a GFP (green fluorescent protein) reporter targeted to these organelles. Results show that mitochondria were less dynamic and markedly changed morphology during senescence, passing from the elongated, branched structures found in mature leaves to enlarged and sparse organelles in senescent leaves. Progression of senescence in leaves was not synchronous, since changes in mitochondria from stomata were delayed. Mitochondrial morphology was also analysed in grapevine cell cultures. Mitochondria from cells at the end of their growth curve resembled those from senescing leaves, suggesting that cell cultures might represent a useful model system for senescence. Additionally, senescence-associated mitochondrial changes were observed in plants treated with high concentrations of cytokinins. Overall, morphology and dynamics of mitochondria might represent a reliable senescence marker for plant cells.

  5. Autocrine IL-6 mediates pituitary tumor senescence

    Science.gov (United States)

    Fuertes, Mariana; Ajler, Pablo; Carrizo, Guillermo; Cervio, Andrés; Sevlever, Gustavo; Stalla, Günter K.; Arzt, Eduardo

    2017-01-01

    Cellular senescence is a stable proliferative arrest state. Pituitary adenomas are frequent and mostly benign, but the mechanism for this remains unknown. IL-6 is involved in pituitary tumor progression and is produced by the tumoral cells. In a cell autonomous fashion, IL-6 participates in oncogene-induced senescence in transduced human melanocytes. Here we prove that autocrine IL-6 participates in pituitary tumor senescence. Endogenous IL-6 inhibition in somatotroph MtT/S shRNA stable clones results in decreased SA-β-gal activity and p16INK4a but increased pRb, proliferation and invasion. Nude mice injected with IL-6 silenced clones develop tumors contrary to MtT/S wild type that do not, demonstrating that clones that escape senescence are capable of becoming tumorigenic. When endogenous IL-6 is silenced, cell cultures derived from positive SA-β-gal human tumor samples decrease the expression of the senescence marker. Our results establish that IL-6 contributes to maintain senescence by its autocrine action, providing a natural model of IL-6 mediated benign adenoma senescence. PMID:27902467

  6. Senescence and immortality in hepatocellular carcinoma.

    Science.gov (United States)

    Ozturk, Mehmet; Arslan-Ergul, Ayca; Bagislar, Sevgi; Senturk, Serif; Yuzugullu, Haluk

    2009-12-01

    Cellular senescence is a process leading to terminal growth arrest with characteristic morphological features. This process is mediated by telomere-dependent, oncogene-induced and ROS-induced pathways, but persistent DNA damage is the most common cause. Senescence arrest is mediated by p16(INK4a)- and p21(Cip1)-dependent pathways both leading to retinoblastoma protein (pRb) activation. p53 plays a relay role between DNA damage sensing and p21(Cip1) activation. pRb arrests the cell cycle by recruiting proliferation genes to facultative heterochromatin for permanent silencing. Replicative senescence that occurs in hepatocytes in culture and in liver cirrhosis is associated with lack of telomerase activity and results in telomere shortening. Hepatocellular carcinoma (HCC) cells display inactivating mutations of p53 and epigenetic silencing of p16(INK4a). Moreover, they re-express telomerase reverse transcriptase required for telomere maintenance. Thus, senescence bypass and cellular immortality is likely to contribute significantly to HCC development. Oncogene-induced senescence in premalignant lesions and reversible immortality of cancer cells including HCC offer new potentials for tumor prevention and treatment.

  7. Defective ATM-Kap-1-mediated chromatin remodeling impairs DNA repair and accelerates senescence in progeria mouse model.

    Science.gov (United States)

    Liu, Baohua; Wang, Zimei; Ghosh, Shrestha; Zhou, Zhongjun

    2013-04-01

    ATM-mediated phosphorylation of KAP-1 triggers chromatin remodeling and facilitates the loading and retention of repair proteins at DNA lesions. Mouse embryonic fibroblasts (MEFs) derived from Zmpste24(-/-) mice undergo early senescence, attributable to delayed recruitment of DNA repair proteins. Here, we show that ATM-Kap-1 signaling is compromised in Zmpste24(-/-) MEFs, leading to defective DNA damage-induced chromatin remodeling. Knocking down Kap-1 rescues impaired chromatin remodeling, defective DNA repair and early senescence in Zmpste24(-/-) MEFs. Thus, ATM-Kap-1-mediated chromatin remodeling plays a critical role in premature aging, carrying significant implications for progeria therapy.

  8. Estimation in partial linear EV models with replicated observations

    Institute of Scientific and Technical Information of China (English)

    CUI; Hengjian

    2004-01-01

    The aim of this work is to construct the parameter estimators in the partial linear errors-in-variables (EV) models and explore their asymptotic properties. Unlike other related References, the assumption of known error covariance matrix is removed when the sample can be repeatedly drawn at each designed point from the model. The estimators of interested regression parameters, and the model error variance, as well as the nonparametric function, are constructed. Under some regular conditions, all of the estimators prove strongly consistent. Meanwhile, the asymptotic normality for the estimator of regression parameter is also presented. A simulation study is reported to illustrate our asymptotic results.

  9. PML, SUMOylation and senescence

    Directory of Open Access Journals (Sweden)

    Hugues eDe Thé

    2013-07-01

    Full Text Available Since its discovery, 25 years ago, PML has been an enigma. Implicated in the oncogenic PML/RARA fusion, forming elusive intranuclear domains, triggering cell death or senescence, controlled by and perhaps controlling SUMOylation... there are multiple PML-related issues. Here we review the reciprocal interactions between PML, senescence and SUMOylation, notably in the context of cellular transformation.

  10. Senescence Meets Dedifferentiation

    Directory of Open Access Journals (Sweden)

    Yemima Givaty Rapp

    2015-06-01

    Full Text Available Senescence represents the final stage of leaf development but is often induced prematurely following exposure to biotic and abiotic stresses. Leaf senescence is manifested by color change from green to yellow (due to chlorophyll degradation or to red (due to de novo synthesis of anthocyanins coupled with chlorophyll degradation and frequently culminates in programmed death of leaves. However, the breakdown of chlorophyll and macromolecules such as proteins and RNAs that occurs during leaf senescence does not necessarily represent a one-way road to death but rather a reversible process whereby senescing leaves can, under certain conditions, re-green and regain their photosynthetic capacity. This phenomenon essentially distinguishes senescence from programmed cell death, leading researchers to hypothesize that changes occurring during senescence might represent a process of trans-differentiation, that is the conversion of one cell type to another. In this review, we highlight attributes common to senescence and dedifferentiation including chromatin structure and activation of transposable elements and provide further support to the notion that senescence is not merely a deterioration process leading to death but rather a unique developmental state resembling dedifferentiation.

  11. Senescence is not inevitable

    DEFF Research Database (Denmark)

    Jones, Owen; Vaupel, James W.

    2017-01-01

    Senescence, the physiological deterioration resulting in an increase in mortality and decline in fertility with age, is widespread in the animal kingdom and has often been regarded as an inescapable feature of all organisms. This essay briefly describes the history of the evolutionary theoretical...... of biogerontology, it is clear that senescence is not inevitable....

  12. Modelling protocells the emergent synchronization of reproduction and molecular replication

    CERN Document Server

    Serra, Roberto

    2017-01-01

    The monograph discusses models of synthetic protocells, which are cell-like structures obtained from non-living matter endowed with some rudimentary kind of metabolism and genetics, but much simpler than biological cells. They should grow and proliferate, generating offsprings that resemble in some way the parent protocells with some variation, so that selection may take place. Sustainable protocell populations have not yet been obtained experimentally and mathematical models are therefore extremely important to address key questions concerning their synthesis and behavior. Different protocell “architectures” have been proposed and high-level abstract models like those that are presented in this book are particularly relevant to gain a better understanding of the different properites. These models are able to treat all the major dynamical phenomena in a unified framework, so they can be seen as “virtual laboratories” for protocell research. Particular attention is paid to the problem of synchronizatio...

  13. 3D Spatially Resolved Models of the Intracellular Dynamics of the Hepatitis C Genome Replication Cycle

    KAUST Repository

    Knodel, Markus

    2017-10-02

    Mathematical models of virus dynamics have not previously acknowledged spatial resolution at the intracellular level despite substantial arguments that favor the consideration of intracellular spatial dependence. The replication of the hepatitis C virus (HCV) viral RNA (vRNA) occurs within special replication complexes formed from membranes derived from endoplasmatic reticulum (ER). These regions, termed membranous webs, are generated primarily through specific interactions between nonstructural virus-encoded proteins (NSPs) and host cellular factors. The NSPs are responsible for the replication of the vRNA and their movement is restricted to the ER surface. Therefore, in this study we developed fully spatio-temporal resolved models of the vRNA replication cycle of HCV. Our simulations are performed upon realistic reconstructed cell structures-namely the ER surface and the membranous webs-based on data derived from immunostained cells replicating HCV vRNA. We visualized 3D simulations that reproduced dynamics resulting from interplay of the different components of our models (vRNA, NSPs, and a host factor), and we present an evaluation of the concentrations for the components within different regions of the cell. Thus far, our model is restricted to an internal portion of a hepatocyte and is qualitative more than quantitative. For a quantitative adaption to complete cells, various additional parameters will have to be determined through further in vitro cell biology experiments, which can be stimulated by the results deccribed in the present study.

  14. Evolution of plant senescence

    Directory of Open Access Journals (Sweden)

    Young Mike

    2009-07-01

    Full Text Available Abstract Background Senescence is integral to the flowering plant life-cycle. Senescence-like processes occur also in non-angiosperm land plants, algae and photosynthetic prokaryotes. Increasing numbers of genes have been assigned functions in the regulation and execution of angiosperm senescence. At the same time there has been a large expansion in the number and taxonomic spread of plant sequences in the genome databases. The present paper uses these resources to make a study of the evolutionary origins of angiosperm senescence based on a survey of the distribution, across plant and microbial taxa, and expression of senescence-related genes. Results Phylogeny analyses were carried out on protein sequences corresponding to genes with demonstrated functions in angiosperm senescence. They include proteins involved in chlorophyll catabolism and its control, homeoprotein transcription factors, metabolite transporters, enzymes and regulators of carotenoid metabolism and of anthocyanin biosynthesis. Evolutionary timelines for the origins and functions of particular genes were inferred from the taxonomic distribution of sequences homologous to those of angiosperm senescence-related proteins. Turnover of the light energy transduction apparatus is the most ancient element in the senescence syndrome. By contrast, the association of phenylpropanoid metabolism with senescence, and integration of senescence with development and adaptation mediated by transcription factors, are relatively recent innovations of land plants. An extended range of senescence-related genes of Arabidopsis was profiled for coexpression patterns and developmental relationships and revealed a clear carotenoid metabolism grouping, coordinated expression of genes for anthocyanin and flavonoid enzymes and regulators and a cluster pattern of genes for chlorophyll catabolism consistent with functional and evolutionary features of the pathway. Conclusion The expression and phylogenetic

  15. Cristacarpin promotes ER stress-mediated ROS generation leading to premature senescence by activation of p21(waf-1).

    Science.gov (United States)

    Chakraborty, Souneek; Rasool, Reyaz Ur; Kumar, Sunil; Nayak, Debasis; Rah, Bilal; Katoch, Archana; Amin, Hina; Ali, Asif; Goswami, Anindya

    2016-06-01

    Stress-induced premature senescence (SIPS) is quite similar to replicative senescence that is committed by cells exposed to various stress conditions viz. ultraviolet radiation (DNA damage), hydrogen peroxide (oxidative stress), chemotherapeutic agents (cytotoxic threat), etc. Here, we report that cristacarpin, a natural product obtained from the stem bark of Erythrina suberosa, promotes endoplasmic reticulum (ER) stress, leading to sub-lethal reactive oxygen species (ROS) generation and which eventually terminates by triggering senescence in pancreatic and breast cancer cells through blocking the cell cycle in the G1 phase. The majority of cristacarpin-treated cells responded to conventional SA-β-gal stains; showed characteristic p21(waf1) upregulation along with enlarged and flattened morphology; and increased volume, granularity, and formation of heterochromatin foci-all of these features are the hallmarks of senescence. Inhibition of ROS generation by N-acetyl-L-cysteine (NAC) significantly reduced the expression of p21(waf1), confirming that the modulation in p21(waf1) by anti-proliferative cristacarpin was ROS dependent. Further, the elevation in p21(waf1) expression in PANC-1 and MCF-7 cells was consistent with the decrease in the expression of Cdk-2 and cyclinD1. Here, we provide evidence that cristacarpin promotes senescence in a p53-independent manner. Moreover, cristacarpin treatment induced p38MAPK, indicating the ROS-dependent activation of the MAP kinase pathway, and thus abrogates the tumor growth in mouse allograft tumor model.

  16. Mutation accumulation and the catastrophic senescence of Pacific salmon

    CERN Document Server

    Penna, T J P; Stauffer, D; Stauffer, Dietrich

    1995-01-01

    The bit-string model of biological aging is used to simulate the catastrophic senescence of Pacific Salmon. We have shown that reproduction occuring only once and at a fixed age is the only ingredient needed to explain the catastrophic senescence according the mutation accumulation theory. Several results are presented, some of them with up to 10^8 fishes, showing how the survival rates in catastrophic senescence are affected by changes in the parameters of the model.

  17. Artefactual effects of oxygen on cell culture models of cellular senescence and stem cell biology.

    Science.gov (United States)

    Toussaint, Olivier; Weemaels, Geoffroy; Debacq-Chainiaux, Florence; Scharffetter-Kochanek, Karin; Wlaschek, Meinhard

    2011-02-01

    In life sciences, modelling of the in vivo conditions using in vitro models is an important tool to generate knowledge. Although aerobic organisms including mammals depend on accurate oxygen tension, mimicking physiological conditions in cell culture experiments is not very common. Due to the need for simple technical and experimental design, the requirement for simulating the in vivo oxygen tension parameters has been neglected over long time. Fortunately, due to increasing knowledge in recent years the attention has shifted towards this scientific demand. In this short review, we summarize data substantiating the necessity to adequately mimic physiological oxygen tension using cell culture models in life science research. © 2010 Wiley-Liss, Inc.

  18. Mitochondria, telomeres and cell senescence: Implications for lung ageing and disease.

    Science.gov (United States)

    Birch, Jodie; Barnes, Peter J; Passos, Joao F

    2017-10-04

    Cellular senescence, the irreversible loss of replicative capacity in somatic cells, plays a causal role in the development of age-related pathology and in a number of age-related chronic inflammatory diseases. The ageing lung is marked by an increasing number of senescent cells, and evidence is mounting that senescence may directly contribute to a number of age-related respiratory diseases, including chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF). Telomere dysfunction and alterations in mitochondrial homeostasis frequently occur in cellular senescence and are important to the development of the often detrimental senescence-associated secretory phenotype (SASP). The roles of telomeres, the mitochondria and cellular senescence in lung ageing and disease are discussed. Therapeutic interventions targeting cellular senescence are considered for delaying or potentially reversing age-related respiratory disease. Copyright © 2017. Published by Elsevier Inc.

  19. Determining host metabolic limitations on viral replication via integrated modeling and experimental perturbation.

    Directory of Open Access Journals (Sweden)

    Elsa W Birch

    Full Text Available Viral replication relies on host metabolic machinery and precursors to produce large numbers of progeny - often very rapidly. A fundamental example is the infection of Escherichia coli by bacteriophage T7. The resource draw imposed by viral replication represents a significant and complex perturbation to the extensive and interconnected network of host metabolic pathways. To better understand this system, we have integrated a set of structured ordinary differential equations quantifying T7 replication and an E. coli flux balance analysis metabolic model. Further, we present here an integrated simulation algorithm enforcing mutual constraint by the models across the entire duration of phage replication. This method enables quantitative dynamic prediction of virion production given only specification of host nutritional environment, and predictions compare favorably to experimental measurements of phage replication in multiple environments. The level of detail of our computational predictions facilitates exploration of the dynamic changes in host metabolic fluxes that result from viral resource consumption, as well as analysis of the limiting processes dictating maximum viral progeny production. For example, although it is commonly assumed that viral infection dynamics are predominantly limited by the amount of protein synthesis machinery in the host, our results suggest that in many cases metabolic limitation is at least as strict. Taken together, these results emphasize the importance of considering viral infections in the context of host metabolism.

  20. MicroRNA-191 triggers keratinocytes senescence by SATB1 and CDK6 downregulation

    Energy Technology Data Exchange (ETDEWEB)

    Lena, A.M.; Mancini, M.; Rivetti di Val Cervo, P. [University of ' Tor Vergata' , Department of Experimental Medicine and Biochemical Sciences, Via Montpellier 1, Rome 00133 (Italy); Istituto Dermopatico dell' Immacolata-Istituto di Ricovero e Cura a Carattere Scientifico (IDI-IRCCS), Laboratory of Biochemistry c/o Department of Experimental Medicine and Biochemical Sciences, University of Rome ' Tor Vergata' , Rome 00133 (Italy); Saintigny, G.; Mahe, C. [CHANEL Parfums Beaute, 135 av. Charles de Gaulle, F 92521, Neuilly/Seine (France); Melino, G., E-mail: gerry.melino@uniroma2.it [University of ' Tor Vergata' , Department of Experimental Medicine and Biochemical Sciences, Via Montpellier 1, Rome 00133 (Italy); Istituto Dermopatico dell' Immacolata-Istituto di Ricovero e Cura a Carattere Scientifico (IDI-IRCCS), Laboratory of Biochemistry c/o Department of Experimental Medicine and Biochemical Sciences, University of Rome ' Tor Vergata' , Rome 00133 (Italy); Association Cell Death and Differentiation c/o Department of Experimental Medicine and Biochemical Sciences, University of Rome ' Tor Vergata' , Rome 00133 (Italy); and others

    2012-07-06

    Highlights: Black-Right-Pointing-Pointer miR-191 expression is upregulated in senescencent human epidermal keratinocytes. Black-Right-Pointing-Pointer miR-191 overexpression is sufficient per se to induce senescence in keratinocytes. Black-Right-Pointing-Pointer SATB1 and CDK6 are downregulated in senescence and are direct miR-191 targets. Black-Right-Pointing-Pointer SATB1 and CDK6 silencing by siRNA triggers senescence in HEKn cells. -- Abstract: Keratinocyte replicative senescence has an important role in time-dependent changes of the epidermis, a tissue with high turnover. Senescence encompasses growth arrest during which cells remain metabolically active but acquire a typical enlarged, vacuolar and flattened morphology. It is also accompanied by the expression of endogenous senescence-associated-{beta}-galactosidase and specific gene expression profiles. MicroRNAs levels have been shown to be modulated during keratinocytes senescence, playing key roles in inhibiting proliferation and in the acquisition of senescent markers. Here, we identify miR-191 as an anti-proliferative and replicative senescence-associated miRNA in primary human keratinocytes. Its overexpression is sufficient per se to induce senescence, as evaluated by induction of several senescence-associated markers. We show that SATB1 and CDK6 3 Prime UTRs are two miR-191 direct targets involved in this pathway. Cdk6 and Satb1 protein levels decrease during keratinocytes replicative senescence and their silencing by siRNA is able to induce a G1 block in cell cycle, accompanied by an increase in senescence-associated markers.

  1. Consistency of modified MLE in EV model with replicated observations

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Sanguo

    2001-01-01

    [1]Kendall, M., Stuart, A., The Advanced Theory of Statistics, Vol. 2, New York: Charles Griffin, 1979.[2]Anderson, T. W., Estimating linear statistical relationships, Ann. Statist., 1984, 12: 1.[3]Cui Hengjian, Asymptotic normality of M-estimates in the EV model, Sys. Sci. and Math. Sci., 1997, 10(3): 225.[4]Madansky, A., The fitting of straight lines when both variables are subject to error, JASA, 1959, 54: 173.[5]Villegas, C., Maximum likelihood estimations of a linear functional relationship, Ann. Math. Statist., 1961, 32(4): 1048.[6]Stout, W. F., Almost Sure Convergence, New York: Academic Press, 1974.[7]Petrov, V. V., Sums of Independent Random Variables, New York: Springer-Verlag, 1975.[8]Lai, T. L., Robbins, H., Wei, C. Z., Strong consistency of least squares estimates in multiple regression, J. Multivariate Anal., 1979, 9: 343.[9]Chen Xiru, On limiting properties of U-statistics and von-Mises statistics, Scientia Sinica (in Chinese), 1980, (6): 522.

  2. A two-substrate Michaelis-Menten model for the growth of self-replicating polymers.

    Science.gov (United States)

    Ferreira, R

    1987-10-07

    A two-substrate Michaelis-Menten model is proposed for the growth of autocatalytic self-replicating polymers. Selective growth depends on the existence of two complementary pairs of monomers. Discrimination among sequences results from different products of binding constants, KCGnKAUm. The results support an earlier renormalization group treatment (Ferreira & Tsallis, 1985).

  3. Modeling a Dynamic Data Replication Strategy to Increase System Availability in Cloud Computing Environments

    Institute of Scientific and Technical Information of China (English)

    Da-Wei Sun; Gui-Ran Chang; Shang Gao; Li-Zhong Jin; Xing-Wei Wang

    2012-01-01

    Failures are normal rather than exceptional in the cloud computing environmcnts.To improve system availability,replicating the popular data to multiple suitable locations is an advisable choice,as users can access the data from a nearby site.This is,however,not the case for replicas which must have a fixed number of copies on several locations.How to decide a reasonable number and right locations for replicas has become a challenge in the cloud computing.In this paper,a dynamic data replication strategy is put forward with a brief survey of replication strategy suitable for distributed computing environments.It includes:1) analyzing and modeling the relationship between system availability and the number of replicas; 2) evaluating and identifying the popular data and triggering a replication operation when the popularity data passes a dynamic threshold; 3) calculating a suitable number of copies to meet a reasonable system byte effective rate requirement and placing replicas among data nodes in a balanced way; 4) designing the dynamic data replication algorithm in a cloud.Experimental results demonstrate the efficiency and effectiveness of the improved system brought by the proposed strategy in a cloud.

  4. Antiaging Effect of Metformin on Brain in Naturally Aged and Accelerated Senescence Model of Rat.

    Science.gov (United States)

    Garg, Geetika; Singh, Sandeep; Singh, Abhishek Kumar; Rizvi, Syed Ibrahim

    2017-01-09

    Metformin, a biguanide, is a widely used antidiabetic drug, which inhibits gluconeogenesis and is used to treat hyperglycemia in type 2 diabetes. Through activation of AMPK (AMP-activated protein kinase) pathway, metformin also mimics caloric restriction health benefits. Aging causes substantial molecular to morphological changes in brain, the brain cells being more susceptible toward oxidative stress mediated damages due to the presence of high lipid content and higher oxygen consumption. Wistar rats (naturally aged and d-galactose induced rat model) were supplemented with metformin (300 mg/kg b.w. orally) for 6 weeks. The biomarkers of oxidative stress such as antioxidant capacity (ferric reducing antioxidant potential [FRAP]), malondialdehyde (MDA), reduced glutathione (GSH), protein carbonyl (PCO), reactive oxygen species (ROS), acetylcholinesterase (AChE) activity, and nitric oxide (NO) were measured in brain tissues of control and experimental groups. The results indicate that metformin treatment augmented the levels of FRAP and GSH in naturally aged, and d-gal induced aging model groups compared to the respective controls. In contrast, metformin treated groups exhibited significant reduction in MDA, PCO, ROS, and NO levels and a significant increase in AChE activity in induced aging rats. The administration of d-galactose upregulated the expression of sirtuin-2, interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) and downregulated the expression of Beclin-1. Metformin supplementation downregulated the d-galactose induced expressions of sirtuin-2, IL-6, and TNF-α expression, whereas upregulated the Beclin-1 expression. Our data confirm that metformin restores the antioxidant status and improves healthy brain aging through the activation of autophagy and reduction in inflammation.

  5. Planarians as a model of aging to study the interaction between stem cells and senescent cells in vivo

    Directory of Open Access Journals (Sweden)

    Patrick M. Perrigue

    2015-12-01

    Full Text Available The depletion of stem cell pools and the accumulation of senescent cells in animal tissues are linked to aging. Planarians are invertebrate flatworms and are unusual in that their stem cells, called neoblasts, are constantly replacing old and dying cells. By eliminating neoblasts in worms via irradiation, the biological principles of aging are exposed in the absence of wound healing and regeneration, making planaria a powerful tool for aging research.

  6. Canard explosion of limit cycles in templator models of self-replication mechanisms

    DEFF Research Database (Denmark)

    Brøns, Morten

    2011-01-01

    Templators are differential equation models for self-replicating chemical systems. Beutel and Peacock-López [J. Chem. Phys. 126, 125104 (2007)]10.1063/1.2716396 have numerically analyzed a model for a cross-catalytic self-replicating system and found two cases of canard explosion, that is......, a substantial change of amplitude of a limit cycle over a very short parameter interval. We show how the model can be reduced to a two-dimensional system and how canard theory for slow-fast equations can be applied to yield analytic information about the canard explosion. In particular, simple expressions...... for the parameter value where the canard explosion occurs are obtained. The connection to mixed-mode oscillations also observed in the model is briefly discussed. © 2011 American Institute of Physics....

  7. Calculating the Rate of Senescence From Mortality Data

    DEFF Research Database (Denmark)

    Koopman, Jacob J E; Rozing, Maarten P; Kramer, Anneke

    2016-01-01

    The rate of senescence can be inferred from the acceleration by which mortality rates increase over age. Such a senescence rate is generally estimated from parameters of a mathematical model fitted to these mortality rates. However, such models have limitations and underlying assumptions. Notably...

  8. Barriers and facilitators to replicating an evidence-based palliative care model.

    Science.gov (United States)

    Davis, E Maxwell; Jamison, Paula; Brumley, Richard; Enguídanos, Susan

    2006-01-01

    Recognition of the difficulties involved in replicating evidence- based interventions is well documented in the literature within the medical field. Promising research findings are often not translated into practice, and if they are, there is a significant time gap between study conclusion and practice adoption. The purpose of this article is to describe the barriers and facilitators encountered by two managed care organizations while replicating an evidence-based end of life in-home palliative care model. Using Diffusion of Innovation Theory as a theoretical framework, results from focus groups and interviews with the project's clinical, administrative and research teams are presented and recommendations made for improving translational efforts. The process of replicating the end of life in-home palliative care model clearly illustrated the key elements required for successfully diffusing innovation. These key elements include marketing and communication, leadership, organizational support and training and mentorship. This qualitative process study provides clear, real world perspectives of the myriad of challenges encountered in replicating an evidence-based project.

  9. Deterministic slope failure hazard assessment in a model catchment and its replication in neighbourhood terrain

    Directory of Open Access Journals (Sweden)

    Kiran Prasad Acharya

    2016-01-01

    Full Text Available In this work, we prepare and replicate a deterministic slope failure hazard model in small-scale catchments of tertiary sedimentary terrain of Niihama city in western Japan. It is generally difficult to replicate a deterministic model from one catchment to another due to lack of exactly similar geo-mechanical and hydrological parameters. To overcome this problem, discriminant function modelling was done with the deterministic slope failure hazard model and the DEM-based causal factors of slope failure, which yielded an empirical parametric relationship or a discriminant function equation. This parametric relationship was used to predict the slope failure hazard index in a total of 40 target catchments in the study area. From ROC plots, the prediction rate between 0.719–0.814 and 0.704–0.805 was obtained with inventories of September and October slope failures, respectively. This means September slope failures were better predicted than October slope failures by approximately 1%. The results show that the prediction of the slope failure hazard index is possible, even in a small catchment scale, in similar geophysical settings. Moreover, the replication of the deterministic model through discriminant function modelling was found to be successful in predicting typhoon rainfall-induced slope failures with moderate to good accuracy without any use of geo-mechanical and hydrological parameters.

  10. RNA methyltransferase NSUN2 promotes stress-induced HUVEC senescence.

    Science.gov (United States)

    Cai, Xiaoyu; Hu, Yuanyuan; Tang, Hao; Hu, Han; Pang, Lijun; Xing, Junyue; Liu, Zhenyun; Luo, Yuhong; Jiang, Bin; Liu, Te; Gorospe, Myriam; Chen, Chuan; Wang, Wengong

    2016-04-12

    The tRNA methyltransferase NSUN2 delays replicative senescence by regulating the translation of CDK1 and CDKN1B mRNAs. However, whether NSUN2 influences premature cellular senescence remains untested. Here we show that NSUN2 methylates SHC mRNA in vitro and in cells, thereby enhancing the translation of the three SHC proteins, p66SHC, p52SHC, and p46SHC. Our results further show that the elevation of SHC expression by NSUN2-mediated mRNA methylation increased the levels of ROS, activated p38MAPK, thereby accelerating oxidative stress- and high-glucose-induced senescence of human vascular endothelial cells (HUVEC). Our findings highlight the critical impact of NSUN2-mediated mRNA methylation in promoting premature senescence.

  11. Gas6 Delays Senescence in Vascular Smooth Muscle Cells through the PI3K/ Akt/FoxO Signaling Pathway

    Directory of Open Access Journals (Sweden)

    Cheng-wei Jin

    2015-02-01

    Full Text Available Background/Aims: Growth arrest-specific protein 6 (Gas6 is a cytokine that can be synthesized by a variety of cell types and secreted into the extracellular matrix. Previous studies have confirmed that Gas6 is involved in certain pathophysiological processes of the cardiovascular system through binding to its receptor, Axl. In the present study, we investigated the role of Gas6 in cellular senescence and explored the mechanisms underlying its activity. Methods: We used vascular smooth muscle cells (VSMCs to create two cellular senescence models, one for replicative senescence (RS and one for induced senescence (IS, to test the hypothesis that Gas6 delays senescence. Results: Gas6-treated cells appear relatively younger compared with non-Gas6-treated cells. In particular, Gas6-treated cells displayed decreased staining for SA-β-Gal, fewer G1 phase cells, and decreased levels of p16INK4a and p21Cip1 expression; conversely, Gas6-treated cells displayed more S phase cells and significantly increased proliferation indexes. Furthermore, in both the IS and RS models with Gas6 treatment, the levels of PI3K, p-Akt, and p-FoxO3a decreased following Axl inhibition by R428; similarly, the levels of p-Akt and p-FoxO3a also decreased following PI3K inhibition by LY294002. Conclusion: Gas6/Axl signaling is essential for delaying the cellular senescence process regulated by the PI3K/Akt/FoxO signaling pathway.

  12. Transcriptional networks in leaf senescence.

    Science.gov (United States)

    Schippers, Jos H M

    2015-10-01

    Plant senescence is a natural phenomenon known for the appearance of beautiful autumn colors and the ripening of cereals in the field. Senescence is a controlled process that plants utilize to remobilize nutrients from source leaves to developing tissues. While during the past decades, molecular components underlying the onset of senescence have been intensively studied, knowledge remains scarce on the age-dependent mechanisms that control the onset of senescence. Recent advances have uncovered transcriptional networks regulating the competence to senesce. Here, gene regulatory networks acting as internal timing mechanisms for the onset of senescence are highlighted, illustrating that early and late leaf developmental phases are highly connected.

  13. Aberrant localization of lamin B receptor (LBR) in cellular senescence in human cells

    Energy Technology Data Exchange (ETDEWEB)

    Arai, Rumi; En, Atsuki; Ukekawa, Ryo [Graduate School of Nanobioscience, Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama 236-0027 (Japan); Miki, Kensuke [Graduate School of Nanobioscience, Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama 236-0027 (Japan); Ichiban Life Corporation, 1-1-7 Horai-cho, Naka-ku, Yokohama 231-0048 (Japan); Fujii, Michihiko, E-mail: mifuji@yokohama-cu.ac.jp [Graduate School of Nanobioscience, Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama 236-0027 (Japan); Ayusawa, Dai [Graduate School of Nanobioscience, Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama 236-0027 (Japan); Ichiban Life Corporation, 1-1-7 Horai-cho, Naka-ku, Yokohama 231-0048 (Japan)

    2016-05-13

    5-Bromodeoxyuridine (BrdU), a thymidine analogue, induces cellular senescence in mammalian cells. BrdU induces cellular senescence probably through the regulation of chromatin because BrdU destabilizes or disrupts nucleosome positioning and decondenses heterochromatin. Since heterochromatin is tethered to the nuclear periphery through the interaction with the nuclear envelope proteins, we examined the localization of the several nuclear envelope proteins such as lamins, lamin-interacting proteins, nuclear pore complex proteins, and nuclear transport proteins in senescent cells. We have shown here that lamin B receptor (LBR) showed a change in localization in both BrdU-induced and replicative senescent cells.

  14. Senescence and nutrient remobilization in crop plants

    DEFF Research Database (Denmark)

    Gregersen, Per L

    2011-01-01

    Summary This chapter contains sections titled: Abstract Introduction The senescence process Degradation and transport Regulation of senescence Conclusions: the dilemma of senescence Reference......Summary This chapter contains sections titled: Abstract Introduction The senescence process Degradation and transport Regulation of senescence Conclusions: the dilemma of senescence Reference...

  15. Computational Investigations on Polymerase Actions in Gene Transcription and Replication Combining Physical Modeling and Atomistic Simulations

    CERN Document Server

    Yu, Jin

    2015-01-01

    Polymerases are protein enzymes that move along nucleic acid chains and catalyze template-based polymerization reactions during gene transcription and replication. The polymerases also substantially improve transcription or replication fidelity through the non-equilibrium enzymatic cycles. We briefly review computational efforts that have been made toward understanding mechano-chemical coupling and fidelity control mechanisms of the polymerase elongation. The polymerases are regarded as molecular information motors during the elongation process. It requires a full spectrum of computational approaches from multiple time and length scales to understand the full polymerase functional cycle. We keep away from quantum mechanics based approaches to the polymerase catalysis due to abundant former surveys, while address only statistical physics modeling approach and all-atom molecular dynamics simulation approach. We organize this review around our own modeling and simulation practices on a single-subunit T7 RNA poly...

  16. Fractional Response Models - A Replication Exercise of Papke and Wooldridge (1996

    Directory of Open Access Journals (Sweden)

    Harald Oberhofer

    2012-09-01

    Full Text Available This paper replicates the estimates of a fractional response model for share data reported in the seminal paper of Leslie E. Papke and Jeffrey M. Wooldridge published in the Journal of Applied Econometrics 11(6, 1996, pp.619-632. We have been able to replicate all of the reported estimation results concerning the determinants of employee participation rates in 401(k pension plans using the standard routines provided in Stata. As an alternative, we estimate a two-part model that is capable of coping with the excessive number of boundary values equalling one in the data. The estimated marginal effects are similar to those derived in the paper. A small-scale Monte Carlo simulation exercise suggests that the RESET tests proposed by Papke and Wooldridge in their robust form are useful for detecting neglected non-linearities in small samples.

  17. The M-type receptor PLA2R regulates senescence through the p53 pathway.

    Science.gov (United States)

    Augert, Arnaud; Payré, Christine; de Launoit, Yvan; Gil, Jesus; Lambeau, Gérard; Bernard, David

    2009-03-01

    Senescence is a stable proliferative arrest induced by various stresses such as telomere erosion, oncogenic or oxidative stress. Compelling evidence suggests that it acts as a barrier against tumour development. Describing new mechanisms that favour an escape from senescence can thus reveal new insights into tumorigenesis. To identify new genes controlling the senescence programme, we performed a loss-of-function genetic screen in primary human fibroblasts. We report that knockdown of the M-type receptor PLA2R (phospholipase A2 receptor) prevents the onset of replicative senescence and diminishes stress-induced senescence. Interestingly, expression of PLA2R increases during replicative senescence, and its ectopic expression results in premature senescence. We show that PLA2R regulates senescence in a reactive oxygen species-DNA damage-p53-dependent manner. Taken together, our study identifies PLA2R as a potential new tumour suppressor gene crucial in the induction of cellular senescence through the activation of the p53 pathway.

  18. A small molecule inhibitor of PAI-1 protects against doxorubicin-induced cellular senescence.

    Science.gov (United States)

    Ghosh, Asish K; Rai, Rahul; Park, Kitae E; Eren, Mesut; Miyata, Toshio; Wilsbacher, Lisa D; Vaughan, Douglas E

    2016-11-08

    Doxorubicin, an anthracycline antibiotic, is a commonly used anticancer drug. In spite of its widespread usage, its therapeutic effect is limited by its cardiotoxicity. On the cellular level, Doxorubicin-induced cardiotoxicity manifests as stress induced premature senescence. Previously, we demonstrated that plasminogen activator inhibitor-1 (PAI-1), a potent inhibitor of serine proteases, is an important biomarker and regulator of cellular senescence and aging. Here, we tested the hypothesis that pharmacological inhibition of cellular PAI-1 protects against stress- and aging-induced cellular senescence and delineated the molecular basis of protective action of PAI-1 inhibition. Results show that TM5441, a potent small molecule inhibitor of PAI-1, effectively prevents Doxorubicin-induced senescence in cardiomyocytes, fibroblasts and endothelial cells. TM5441 exerts its inhibitory effect on Doxorubicin-induced cellular senescence by decreasing reactive oxygen species generation, induction of antioxidants like catalase and suppression of stress-induced senescence cadre p53, p21, p16, PAI-1 and IGFBP3. Importantly, TM5441 also reduces replicative senescence of fibroblasts. Together these results for the first time demonstrate the efficacy of PAI-1 inhibitor in prevention of Doxorubicin-induced and replicative senescence in normal cells. Thus PAI-1 inhibitor may form an important adjuvant component of chemotherapy regimens, limiting not only Doxorubicin-induced cardiac senescence but also ameliorating the prothrombotic profile.

  19. Investigating the conformational stability of prion strains through a kinetic replication model.

    Directory of Open Access Journals (Sweden)

    Mattia Zampieri

    2009-07-01

    Full Text Available Prion proteins are known to misfold into a range of different aggregated forms, showing different phenotypic and pathological states. Understanding strain specificities is an important problem in the field of prion disease. Little is known about which PrP(Sc structural properties and molecular mechanisms determine prion replication, disease progression and strain phenotype. The aim of this work is to investigate, through a mathematical model, how the structural stability of different aggregated forms can influence the kinetics of prion replication. The model-based results suggest that prion strains with different conformational stability undergoing in vivo replication are characterizable in primis by means of different rates of breakage. A further role seems to be played by the aggregation rate (i.e. the rate at which a prion fibril grows. The kinetic variability introduced in the model by these two parameters allows us to reproduce the different characteristic features of the various strains (e.g., fibrils' mean length and is coherent with all experimental observations concerning strain-specific behavior.

  20. A Self-Replication Model for Long Channelized Lava Flows on the Mars Plains

    Science.gov (United States)

    Baloga, S. M.; Glaze, L. S.

    2008-01-01

    A model is presented for channelized lava flows emplaced by a self-replicating, levee-building process over long distances on the plains of Mars. Such flows may exhibit morphologic evidence of stagnation, overspills, and upstream breakouts. However, these processes do not inhibit the formation and persistence of a prominent central channel that can often be traced for more than 100 km. The two central assumptions of the self-replication model are (1) the flow advances at the average upstream velocity of the molten core and (2) the fraction of the lava that travels faster than the average upstream velocity forms stationary margins in the advancing distal zone to preserve the self-replication process. For an exemplary 300 km long flow north of Pavonis Mons, the model indicates that 8 m of crust must have formed during emplacement, as determined from the channel and levee dimensions. When combined with independent thermal dynamic estimates for the crustal growth rate, relatively narrow constraints are obtained for the flow rate (2250 m3 s 1), emplacement duration (600 d), and the lava viscosity of the molten interior (106 Pa s). Minor, transient overspills and breakouts increase the emplacement time by only a factor of 2. The primary difference between the prodigious channelized Martian flows and their smaller terrestrial counterparts is that high volumetric flow rates must have persisted for many hundreds of days on Mars, in contrast to a few hours or days on Earth.

  1. Small rodent models of hepatitis B and C virus replication and pathogenesis

    Institute of Scientific and Technical Information of China (English)

    Mark A.Feitelson; Alla Arzumanyan; Marcia M.Clayton

    2012-01-01

    The narrow host range of infection supporting the long-term propagation of hepatitis B and C viruses is a major limitation that has prevented a more thorough understanding of persistent infection and the pathogenesis of chronic liver disease (CLD).With hepatitis B virus (HBV),this has been partially overcome by the discovery and characterization of HBV-like viruses in wild animals.With hepatitis C virus (HCV),related Fiaviviruses have been used as surrogate systems for such studies.Independent work has developed various mouse strains for the transplantation of human hepatocytes,which are then susceptible to infection with HBV and HCV.Other laboratories have developed transgenic mice that express virus gene products and/or support virus replication.Some HBV transgenic mouse models develop fulminant hepatitis,acute hepatitis,or CLD following adoptive transfer,while others spontaneously develop hepatocellular carcinoma (HCC),as in human infections.Among HCV transgenic mice,most develop no disease,but acute hepatitis has been observed in one model,while HCC appears in another.Other mouse models include the introduction of xenographs that replicate HBV or HCV.Although mice are not susceptible to these viruses,their ability to support virus replication and to develop liver disease characteristic of human infections,provides new opportunities to study pathogenesis and develop novel therapeutics.

  2. Sensitive detection and monitoring of senescence-associated secretory phenotype by SASP-RAP assay.

    Science.gov (United States)

    Gu, Liubao; Kitamura, Masanori

    2012-01-01

    Senescence-associated secretory phenotype (SASP) is characterized by abundant secretion of various proteins in senescent cells and implicated in tumor progression and inflammatory responses. However, the profile of secreted proteins in SASP is different from cell type to cell type, and currently, universal markers for SASP have not been reported. In the present investigation, we show that SASP-responsive alkaline phosphatase (SASP-RAP) serves as a sensitive, general and convenient marker for SASP. Etoposide-treated cells exhibited a senescent phenotype characterized by senile morphology, positive staining for senescence-associated β-galactosidase, growth arrest and induction of p53 and p21(WAF1/CIP1). In SASP-RAP-transfected cells, exposure to etoposide increased secretion of SASP-RAP time-dependently. The kinetics of secretion was closely correlated with that of activation of the p21(WAF1/CIP1) promoter and the p16(INK4a) promoter. The enhanced secretion of SASP-RAP by senescence was also observed in cells treated with other senescence inducers such as trichostatin A, doxorubicin and 4-phenylbutylic acid. The induction of SASP-RAP by senescence was similarly observed in natural replicative senescence. To confirm selectivity of the SASP-RAP response, cells were treated with senescence-related and -unrelated stimuli (IL-1β, LPS, TNF-α and TGF-β), and induction of senescence markers and activity of SASP-RAP were evaluated in parallel. Unlike etoposide, senescence-unrelated stimuli did not induce p53 and p21(WAF1/CIP1), and it was correlated with lack of induction of SASP-RAP. In contrast, senescence-unrelated stimuli up-regulated conventional indicators for SASP, e.g., MMP-3, IL-6 and TIMP, without induction of senescence. SASP-RAP thus serves as a selective, convenient and general marker for detection and monitoring of SASP during cellular senescence.

  3. A new stochastic model for subgenomic hepatitis C virus replication considers drug resistant mutants.

    Directory of Open Access Journals (Sweden)

    Nikita V Ivanisenko

    Full Text Available As an RNA virus, hepatitis C virus (HCV is able to rapidly acquire drug resistance, and for this reason the design of effective anti-HCV drugs is a real challenge. The HCV subgenomic replicon-containing cells are widely used for experimental studies of the HCV genome replication mechanisms, for drug testing in vitro and in studies of HCV drug resistance. The NS3/4A protease is essential for virus replication and, therefore, it is one of the most attractive targets for developing specific antiviral agents against HCV. We have developed a stochastic model of subgenomic HCV replicon replication, in which the emergence and selection of drug resistant mutant viral RNAs in replicon cells is taken into account. Incorporation into the model of key NS3 protease mutations leading to resistance to BILN-2061 (A156T, D168V, R155Q, VX-950 (A156S, A156T, T54A and SCH 503034 (A156T, A156S, T54A inhibitors allows us to describe the long term dynamics of the viral RNA suppression for various inhibitor concentrations. We theoretically showed that the observable difference between the viral RNA kinetics for different inhibitor concentrations can be explained by differences in the replication rate and inhibitor sensitivity of the mutant RNAs. The pre-existing mutants of the NS3 protease contribute more significantly to appearance of new resistant mutants during treatment with inhibitors than wild-type replicon. The model can be used to interpret the results of anti-HCV drug testing on replicon systems, as well as to estimate the efficacy of potential drugs and predict optimal schemes of their usage.

  4. Therapeutic targeting of replicative immortality.

    Science.gov (United States)

    Yaswen, Paul; MacKenzie, Karen L; Keith, W Nicol; Hentosh, Patricia; Rodier, Francis; Zhu, Jiyue; Firestone, Gary L; Matheu, Ander; Carnero, Amancio; Bilsland, Alan; Sundin, Tabetha; Honoki, Kanya; Fujii, Hiromasa; Georgakilas, Alexandros G; Amedei, Amedeo; Amin, Amr; Helferich, Bill; Boosani, Chandra S; Guha, Gunjan; Ciriolo, Maria Rosa; Chen, Sophie; Mohammed, Sulma I; Azmi, Asfar S; Bhakta, Dipita; Halicka, Dorota; Niccolai, Elena; Aquilano, Katia; Ashraf, S Salman; Nowsheen, Somaira; Yang, Xujuan

    2015-12-01

    One of the hallmarks of malignant cell populations is the ability to undergo continuous proliferation. This property allows clonal lineages to acquire sequential aberrations that can fuel increasingly autonomous growth, invasiveness, and therapeutic resistance. Innate cellular mechanisms have evolved to regulate replicative potential as a hedge against malignant progression. When activated in the absence of normal terminal differentiation cues, these mechanisms can result in a state of persistent cytostasis. This state, termed "senescence," can be triggered by intrinsic cellular processes such as telomere dysfunction and oncogene expression, and by exogenous factors such as DNA damaging agents or oxidative environments. Despite differences in upstream signaling, senescence often involves convergent interdependent activation of tumor suppressors p53 and p16/pRB, but can be induced, albeit with reduced sensitivity, when these suppressors are compromised. Doses of conventional genotoxic drugs required to achieve cancer cell senescence are often much lower than doses required to achieve outright cell death. Additional therapies, such as those targeting cyclin dependent kinases or components of the PI3K signaling pathway, may induce senescence specifically in cancer cells by circumventing defects in tumor suppressor pathways or exploiting cancer cells' heightened requirements for telomerase. Such treatments sufficient to induce cancer cell senescence could provide increased patient survival with fewer and less severe side effects than conventional cytotoxic regimens. This positive aspect is countered by important caveats regarding senescence reversibility, genomic instability, and paracrine effects that may increase heterogeneity and adaptive resistance of surviving cancer cells. Nevertheless, agents that effectively disrupt replicative immortality will likely be valuable components of new combinatorial approaches to cancer therapy. Copyright © 2015 The Authors

  5. Regulations of Reversal of Senescence by PKC Isozymes in Response to 12-O-Tetradecanoylphorbol-13-Acetate via Nuclear Translocation of pErk1/2.

    Science.gov (United States)

    Lee, Yun Yeong; Ryu, Min Sook; Kim, Hong Seok; Suganuma, Masami; Song, Kye Yong; Lim, In Kyoung

    2016-03-01

    The mechanism by which 12-O-tetradecanoylphorbol-13-acetate (TPA) bypasses cellular senescence was investigated using human diploid fibroblast (HDF) cell replicative senescence as a model. Upon TPA treatment, protein kinase C (PKC) α and PKCβ1 exerted differential effects on the nuclear translocation of cytoplasmic pErk1/2, a protein which maintains senescence. PKCα accompanied pErk1/2 to the nucleus after freeing it from PEA-15pS(104) via PKCβ1 and then was rapidly ubiquitinated and degraded within the nucleus. Mitogen-activated protein kinase docking motif and kinase activity of PKCα were both required for pErk1/2 transport to the nucleus. Repetitive exposure of mouse skin to TPA downregulated PKCα expression and increased epidermal and hair follicle cell proliferation. Thus, PKCα downregulation is accompanied by in vivo cell proliferation, as evidenced in 7, 12-dimethylbenz(a)anthracene (DMBA)-TPA-mediated carcinogenesis. The ability of TPA to reverse senescence was further demonstrated in old HDF cells using RNA-sequencing analyses in which TPA-induced nuclear PKCα degradation freed nuclear pErk1/2 to induce cell proliferation and facilitated the recovery of mitochondrial energy metabolism. Our data indicate that TPA-induced senescence reversal and carcinogenesis promotion share the same molecular pathway. Loss of PKCα expression following TPA treatment reduces pErk1/2-activated SP1 biding to the p21(WAF1) gene promoter, thus preventing senescence onset and overcoming G1/S cell cycle arrest in senescent cells.

  6. The rolling-circle melting-pot model for porcine circovirus DNA replication

    Science.gov (United States)

    A stem-loop structure, formed by a pair of inverted repeats during DNA replication, is a conserved feature at the origin of DNA replication (Ori) among plant and animal viruses, bacteriophages and plasmids that replicate their genomes via the rolling-circle replication (RCR) mechanism. Porcine circo...

  7. Active Degradation Explains the Distribution of Nuclear Proteins during Cellular Senescence.

    Directory of Open Access Journals (Sweden)

    Enrico Giampieri

    Full Text Available The amount of cellular proteins is a crucial parameter that is known to vary between cells as a function of the replicative passages, and can be important during physiological aging. The process of protein degradation is known to be performed by a series of enzymatic reactions, ranging from an initial step of protein ubiquitination to their final fragmentation by the proteasome. In this paper we propose a stochastic dynamical model of nuclear proteins concentration resulting from a balance between a constant production of proteins and their degradation by a cooperative enzymatic reaction. The predictions of this model are compared with experimental data obtained by fluorescence measurements of the amount of nuclear proteins in murine tail fibroblast (MTF undergoing cellular senescence. Our model provides a three-parameter stationary distribution that is in good agreement with the experimental data even during the transition to the senescent state, where the nuclear protein concentration changes abruptly. The estimation of three parameters (cooperativity, saturation threshold, and maximal velocity of the reaction, and their evolution during replicative passages shows that only the maximal velocity varies significantly. Based on our modeling we speculate the reduction of functionality of the protein degradation mechanism as a possible competitive inhibition of the proteasome.

  8. Active Degradation Explains the Distribution of Nuclear Proteins during Cellular Senescence.

    Science.gov (United States)

    Giampieri, Enrico; De Cecco, Marco; Remondini, Daniel; Sedivy, John; Castellani, Gastone

    2015-01-01

    The amount of cellular proteins is a crucial parameter that is known to vary between cells as a function of the replicative passages, and can be important during physiological aging. The process of protein degradation is known to be performed by a series of enzymatic reactions, ranging from an initial step of protein ubiquitination to their final fragmentation by the proteasome. In this paper we propose a stochastic dynamical model of nuclear proteins concentration resulting from a balance between a constant production of proteins and their degradation by a cooperative enzymatic reaction. The predictions of this model are compared with experimental data obtained by fluorescence measurements of the amount of nuclear proteins in murine tail fibroblast (MTF) undergoing cellular senescence. Our model provides a three-parameter stationary distribution that is in good agreement with the experimental data even during the transition to the senescent state, where the nuclear protein concentration changes abruptly. The estimation of three parameters (cooperativity, saturation threshold, and maximal velocity of the reaction), and their evolution during replicative passages shows that only the maximal velocity varies significantly. Based on our modeling we speculate the reduction of functionality of the protein degradation mechanism as a possible competitive inhibition of the proteasome.

  9. Immunosuppressive drugs modulate the replication of hepatitis B virus (HBV in a hydrodynamic injection mouse model.

    Directory of Open Access Journals (Sweden)

    Junzhong Wang

    Full Text Available Hepatitis B virus (HBV reactivation and recurrence are common in patients under immunosuppression and can be controlled by hepatitis B immunoglobulin, antivirals, and hepatitis B vaccine. However, the detailed analysis of HBV infection under immunosuppression is essential for the prophylaxis and therapy for HBV reactivation and recurrence. In this study, HBV replication and T cell responses were analyzed in a HBV-transfected mouse model under immunosuppressive therapy. During the treatment, HBV replication was at a high level in mice treated with dexamethasone, cyclosporine, and cyclophosphamide, whereas was terminated in mice treated with mycophenolate mofetil. After the withdrawal, HBV replication was at low or high levels in the dexamethasone-treated mice or in both cyclosporine- and cyclophosphamide-treated mice. The early withdrawal of cyclosporine allowed the recovery of suppressed T cell responses and led to subsequent HBV clearance, while the adoptive immune transfer to the mice with HBV persistence led to HBV suppression. Taken together, long-term HBV persistence under immunosuppression depends on the immunosuppressive drugs used and on the treatment duration and is mediated by the suppressed intrahepatic CD8 T cell response. These data may be helpful for individualized immunosuppressive therapy in patients with high risk of HBV reactivation and recurrence, and the mouse system is suitable for studying HBV reactivation and recurrence under immunosuppression.

  10. Resveratrol Attenuates Copper-Induced Senescence by Improving Cellular Proteostasis

    Science.gov (United States)

    2017-01-01

    Copper sulfate-induced premature senescence (CuSO4-SIPS) consistently mimetized molecular mechanisms of replicative senescence, particularly at the endoplasmic reticulum proteostasis level. In fact, disruption of protein homeostasis has been associated to age-related cell/tissue dysfunction and human disorders susceptibility. Resveratrol is a polyphenolic compound with proved antiaging properties under particular conditions. In this setting, we aimed to evaluate resveratrol ability to attenuate cellular senescence induction and to unravel related molecular mechanisms. Using CuSO4-SIPS WI-38 fibroblasts, resveratrol is shown to attenuate typical senescence alterations on cell morphology, senescence-associated beta-galactosidase activity, and cell proliferation. The mechanisms implicated in this antisenescence effect seem to be independent of senescence-associated genes and proteins regulation but are reliant on cellular proteostasis improvement. In fact, resveratrol supplementation restores copper-induced increased protein content, attenuates BiP level, and reduces carbonylated and polyubiquitinated proteins by autophagy induction. Our data provide compelling evidence for the beneficial effects of resveratrol by mitigating CuSO4-SIPS stressful consequences by the modulation of protein quality control systems. These findings highlight the importance of a balanced cellular proteostasis and add further knowledge on molecular mechanisms mediating resveratrol antisenescence effects. Moreover, they contribute to identifying specific molecular targets whose modulation will prevent age-associated cell dysfunction and improve human healthspan. PMID:28280523

  11. Resveratrol Attenuates Copper-Induced Senescence by Improving Cellular Proteostasis

    Directory of Open Access Journals (Sweden)

    Liliana Matos

    2017-01-01

    Full Text Available Copper sulfate-induced premature senescence (CuSO4-SIPS consistently mimetized molecular mechanisms of replicative senescence, particularly at the endoplasmic reticulum proteostasis level. In fact, disruption of protein homeostasis has been associated to age-related cell/tissue dysfunction and human disorders susceptibility. Resveratrol is a polyphenolic compound with proved antiaging properties under particular conditions. In this setting, we aimed to evaluate resveratrol ability to attenuate cellular senescence induction and to unravel related molecular mechanisms. Using CuSO4-SIPS WI-38 fibroblasts, resveratrol is shown to attenuate typical senescence alterations on cell morphology, senescence-associated beta-galactosidase activity, and cell proliferation. The mechanisms implicated in this antisenescence effect seem to be independent of senescence-associated genes and proteins regulation but are reliant on cellular proteostasis improvement. In fact, resveratrol supplementation restores copper-induced increased protein content, attenuates BiP level, and reduces carbonylated and polyubiquitinated proteins by autophagy induction. Our data provide compelling evidence for the beneficial effects of resveratrol by mitigating CuSO4-SIPS stressful consequences by the modulation of protein quality control systems. These findings highlight the importance of a balanced cellular proteostasis and add further knowledge on molecular mechanisms mediating resveratrol antisenescence effects. Moreover, they contribute to identifying specific molecular targets whose modulation will prevent age-associated cell dysfunction and improve human healthspan.

  12. Quality of life among people with multiple sclerosis: Replication of a three-factor prediction model.

    Science.gov (United States)

    Bishop, Malachy; Rumrill, Phillip D; Roessler, Richard T

    2015-01-01

    This article presents a replication of Rumrill, Roessler, and Fitzgerald's 2004 analysis of a three-factor model of the impact of multiple sclerosis (MS) on quality of life (QOL). The three factors in the original model included illness-related, employment-related, and psychosocial adjustment factors. To test hypothesized relationships between QOL and illness-related, employment-related, and psychosocial variables using data from a survey of the employment concerns of Americans with MS (N = 1,839). An ex post facto, multiple correlational design was employed incorporating correlational and multiple regression analyses. QOL was positively related to educational level, employment status, job satisfaction, and job-match, and negatively related to number of symptoms, severity of symptoms, and perceived stress level. The three-factor model explained approximately 37 percent of the variance in QOL scores. The results of this replication confirm the continuing value of the three-factor model for predicting the QOL of adults with MS, and demonstrate the importance of medical, mental health, and vocational rehabilitation interventions and services in promoting QOL.

  13. Two different pathogenic mechanisms, dying-back axonal neuropathy and pancreatic senescence, are present in the YG8R mouse model of Friedreich’s ataxia

    Directory of Open Access Journals (Sweden)

    Belén Mollá

    2016-06-01

    Full Text Available Frataxin (FXN deficiency causes Friedreich’s ataxia (FRDA, a multisystem disorder with neurological and non-neurological symptoms. FRDA pathophysiology combines developmental and degenerative processes of dorsal root ganglia (DRG, sensory nerves, dorsal columns and other central nervous structures. A dying-back mechanism has been proposed to explain the peripheral neuropathy and neuropathology. In addition, affected individuals have non-neuronal symptoms such as diabetes mellitus or glucose intolerance. To go further in the understanding of the pathogenic mechanisms of neuropathy and diabetes associated with the disease, we have investigated the humanized mouse YG8R model of FRDA. By biochemical and histopathological studies, we observed abnormal changes involving muscle spindles, dorsal root axons and DRG neurons, but normal findings in the posterior columns and brain, which agree with the existence of a dying-back process similar to that described in individuals with FRDA. In YG8R mice, we observed a large number of degenerated axons surrounded by a sheath exhibiting enlarged adaxonal compartments or by a thin disrupted myelin sheath. Thus, both axonal damage and defects in Schwann cells might underlie the nerve pathology. In the pancreas, we found a high proportion of senescent islets of Langerhans in YG8R mice, which decreases the β-cell number and islet mass to pathological levels, being unable to maintain normoglycemia. As a whole, these results confirm that the lack of FXN induces different pathogenic mechanisms in the nervous system and pancreas in the mouse model of FRDA: dying back of the sensory nerves, and pancreatic senescence.

  14. Identification of replication-competent HSV-1 Cgal+ strain targets in a mouse model of human hepatocarcinoma xenograft

    OpenAIRE

    Santamaria, E. (Enrique); Mora, M.I.; Carro-Roldan, E. (Elvira); M Molina; Fernandez-Irigoyen, J. (Joaquín); Marconi, P; Manservigi, R; Greco, A.; Epstein, A L; Prieto, J.; Hernandez-Alcoceba, R. (Rubén); Corrales, F. J.

    2009-01-01

    Recent studies based on animal models have shown the advantages and potential of oncolytic viral therapy using HSV-1 -based replication-competent vectors in the treatment of liver tumors, but little is known about the cellular targets that are modulated during viral infection. In the present work, we have studied the effects of intratumoral injections of HSV-1 Cgal(+) strain in a murine model of human hepatoma xenografts. Viral replication was assessed for more than 1month, leading to a signi...

  15. Immunosuppression enhances oncolytic adenovirus replication and antitumor efficacy in the Syrian hamster model.

    Science.gov (United States)

    Thomas, Maria A; Spencer, Jacqueline F; Toth, Karoly; Sagartz, John E; Phillips, Nancy J; Wold, William S M

    2008-10-01

    We recently described an immunocompetent Syrian hamster model for oncolytic adenoviruses (Ads) that permits virus replication in tumor cells as well as some normal tissues. This model allows exploration of interactions between the virus, tumor, normal organs, and host immune system that could not be examined in the immunodeficient or nonpermissive animal models previously used in the oncolytic Ad field. Here we asked whether the immune response to oncolytic Ad enhances or limits antitumor efficacy. We first determined that cyclophosphamide (CP) is a potent immunosuppressive agent in the Syrian hamster and that CP alone had no effect on tumor growth. Importantly, we found that the antitumor efficacy of oncolytic Ads was significantly enhanced in immunosuppressed animals. In animals that received virus therapy plus immunosuppression, significant differences were observed in tumor histology, and in many cases little viable tumor remained. Notably, we also determined that immunosuppression allowed intratumoral virus levels to remain elevated for prolonged periods. Although favorable tumor responses can be achieved in immunocompetent animals, the rate of virus clearance from the tumor may lead to varied antitumor efficacy. Immunosuppression, therefore, allows sustained Ad replication and oncolysis, which leads to substantially improved suppression of tumor growth.

  16. From discrete to continuous evolution models: a unifying approach to drift-diffusion and replicator dynamics

    CERN Document Server

    Chalub, Fabio A C C

    2008-01-01

    We study the large population limit of the Moran process, assuming weak-selection, and for different scalings. Depending on the particular choice of scalings, we obtain a continuous model that may highlight the genetic-drift (neutral evolution) or natural selection; for one precise scaling, both effects are present. For the scalings that take the genetic-drift into account, the continuous model is given by a singular diffusion equation, together with two conservation laws that are already present at the discrete level. For scalings that take into account only natural selection, we obtain a hyperbolic singular equation that embeds the Replicator Dynamics and satisfies only one conservation law. The derivation is made in two steps: a formal one, where the candidate limit model is obtained, and a rigorous one, where convergence of the probability density is proved. Additional results on the fixation probabilities are also presented.

  17. Melatonin decreases the expression of inflammation and apoptosis markers in the lung of a senescence-accelerated mice model.

    Science.gov (United States)

    Puig, Ángela; Rancan, Lisa; Paredes, Sergio D; Carrasco, Adrián; Escames, Germaine; Vara, Elena; Tresguerres, Jesús A F

    2016-03-01

    Aging is associated with an increase in oxidative stress and inflammation. The aging lung is particularly affected since it is continuously exposed to environmental oxidants while antioxidant machinery weakens with age. Melatonin, a free radical scavenger, counteracts inflammation and apoptosis in healthy cells from several tissues. Its effects on the aging lung are, however, not yet fully understood. This study aimed to investigate the effect of chronic administration of melatonin on the expression of inflammation markers (TNF-α, IL-1β, NFκB2, HO-1) and apoptosis parameters (BAD, BAX, AIF) in the lung tissue of male senescence-accelerated prone mice (SAMP8). In addition, RNA oxidative damage, as the formation of 8-hydroxyguanosine (8-OHG), was also evaluated. Young and old animals, aged 2 and 10 months respectively, were divided into 4 groups: untreated young, untreated old, old mice treated with 1mg/kg/day melatonin, and old animals treated with 10mg/kg/day melatonin. Untreated young and old male senescence accelerated resistant mice (SAMR1) were used as controls. After 30 days of treatment, animals were sacrificed. Lungs were collected and immediately frozen in liquid nitrogen. mRNA and protein expressions were measured by RT-PCR and Western blotting, respectively. Levels of 8-OHG were quantified by ELISA. Mean values were analyzed using ANOVA. Old nontreated SAMP8 animals showed increased (p<0.05) mRNA and protein levels of TNF-α, IL-1β, NFκB2, and HO-1 compared to young mice and SAMR1 mice. Melatonin treatment with either dose reversed the aging-derived inflammation (p<0.05). BAD, BAX and AIF expressions also rose with aging, the effect being counteracted with melatonin (p<0.05). Aging also caused a significant elevation (p<0.05) in SAMP8 8-OHG values. This increase was not observed in animals treated with melatonin (p<0.05). In conclusion, melatonin treatment was able to modulate the inflammatory and apoptosis status of the aging lungs, exerting a

  18. Scalable spheroid model of human hepatocytes for hepatitis C infection and replication.

    Science.gov (United States)

    Ananthanarayanan, Abhishek; Nugraha, Bramasta; Triyatni, Miriam; Hart, Stefan; Sankuratri, Suryanarayana; Yu, Hanry

    2014-07-07

    Developing effective new drugs against hepatitis C (HCV) virus has been challenging due to the lack of appropriate small animal and in vitro models recapitulating the entire life cycle of the virus. Current in vitro models fail to recapitulate the complexity of human liver physiology. Here we present a method to study HCV infection and replication on spheroid cultures of Huh 7.5 cells and primary human hepatocytes. Spheroid cultures are constructed using a galactosylated cellulosic sponge with homogeneous macroporosity, enabling the formation and maintenance of uniformly sized spheroids. This facilitates easy handling of the tissue-engineered constructs and overcomes limitations inherent of traditional spheroid cultures. Spheroids formed in the galactosylated cellulosic sponge show enhanced hepatic functions in Huh 7.5 cells and maintain liver-specific functions of primary human hepatocytes for 2 weeks in culture. Establishment of apical and basolateral polarity along with the expression and localization of all HCV specific entry proteins allow for a 9-fold increase in viral entry in spheroid cultures over conventional monolayer cultures. Huh 7.5 cells cultured in the galactosylated cellulosic sponge also support replication of the HCV clone, JFH (Japanese fulminant hepatitis)-1 at higher levels than in monolayer cultures. The advantages of our system in maintaining liver-specific functions and allowing HCV infection together with its ease of handling make it suitable for the study of HCV biology in basic research and pharmaceutical R&D.

  19. Solving Two Deadlock Cycles through Neighbor Replication on Grid Deadlock Detection Model

    Directory of Open Access Journals (Sweden)

    Ahmed N. Abdalla

    2012-01-01

    Full Text Available A data grid is compose of hundreds of geographically distributed computers and storage resources usually locate under different places and enables users to share data and other resources. Problem statement: Data replication is one of the mechanisms in managing data grid architecture that receive particular attention since it can provide efficient access to data, fault tolerance, reduce access latency and also can enhance the performance of the system. However, during transaction deadlock may occur that can reduce the throughput by minimizing the available resources, so it becomes an important resource management problem in distributed systems. Approach: The Neighbor Replication on Grid Deadlock Detection (NRGDD transaction model has been developed to handle two deadlock cycle problems on grid. By deploying this method, the transactions communicate with each other by passing the probe messages. The victim message has been used to detect the deadlock when the number of waiting resource by other transaction is highest and become as the cause of deadlock occurs. In addition, this transaction must be aborted to solve the problem. Results: NRGDD transaction model are able to detect and solve more than one cycle of deadlocks. Conclusion: NRGDD has resolve the deadlock problem by sending the minimum number of probes message to detect the deadlock and it can resolve the deadlock to ensure the transaction can be done smoothly.

  20. Assessing senescence patterns in populations of large mammals

    Directory of Open Access Journals (Sweden)

    Gaillard, J.-M.

    2004-06-01

    Full Text Available Theoretical models such as those of Gompertz and Weibull are commonly used to study senescence in survival for humans and laboratory or captive animals. For wild populations of vertebrates, senescence in survival has more commonly been assessed by fitting simple linear or quadratic relationships between survival and age. By using appropriate constraints on survival parameters in Capture-Mark-Recapture (CMR models, we propose a first analysis of the suitability of the Gompertz and the two-parameter Weibull models for describing aging-related mortality in free-ranging populations of ungulates. We first show how to handle the Gompertz and the two-parameter Weibull models in the context of CMR analyses. Then we perform a comparative analysis of senescence patterns in both sexes of two ungulate species highly contrasted according to the intensity of sexual selection. Our analyses provide support to the Gompertz model for describing senescence patterns in ungulates. Evolutionary implications of our results are discussed

  1. The behavioral, pathological and therapeutic features of the senescence-accelerated mouse prone 8 strain as an Alzheimer's disease animal model.

    Science.gov (United States)

    Cheng, Xiao-rui; Zhou, Wen-xia; Zhang, Yong-xiang

    2014-01-01

    Alzheimer's disease (AD) is a widespread and devastating progressive neurodegenerative disease. Disease-modifying treatments remain beyond reach, and the etiology of the disease is uncertain. Animal model are essential for identifying disease mechanisms and developing effective therapeutic strategies. Research on AD is currently being carried out in rodent models. The most common transgenic mouse model mimics familial AD, which accounts for a small percentage of cases. The senescence-accelerated mouse prone 8 (SAMP8) strain is a spontaneous animal model of accelerated aging. Many studies indicate that SAMP8 mice harbor the behavioral and histopathological signatures of AD, namely AD-like cognitive and behavioral alterations, neuropathological phenotypes (neuron and dendrite spine loss, spongiosis, gliosis and cholinergic deficits in the forebrain), β-amyloid deposits resembling senile plaques, and aberrant hyperphosphorylation of Tau-like neurofibrillary tangles. SAMP8 mice are useful in the development of novel therapies, and many pharmacological agents and approaches are effective in SAMP8 mice. SAMP8 mice are considered a robust model for exploring the etiopathogenesis of sporadic AD and a plausible experimental model for developing preventative and therapeutic treatments for late-onset/age-related AD, which accounts for the vast majority of cases.

  2. Mathematical modelling of DNA replication reveals a trade-off between coherence of origin activation and robustness against rereplication.

    Directory of Open Access Journals (Sweden)

    Anneke Brümmer

    2010-05-01

    Full Text Available Eukaryotic genomes are duplicated from multiple replication origins exactly once per cell cycle. In Saccharomyces cerevisiae, a complex molecular network has been identified that governs the assembly of the replication machinery. Here we develop a mathematical model that links the dynamics of this network to its performance in terms of rate and coherence of origin activation events, number of activated origins, the resulting distribution of replicon sizes and robustness against DNA rereplication. To parameterize the model, we use measured protein expression data and systematically generate kinetic parameter sets by optimizing the coherence of origin firing. While randomly parameterized networks yield unrealistically slow kinetics of replication initiation, networks with optimized parameters account for the experimentally observed distribution of origin firing times. Efficient inhibition of DNA rereplication emerges as a constraint that limits the rate at which replication can be initiated. In addition to the separation between origin licensing and firing, a time delay between the activation of S phase cyclin-dependent kinase (S-Cdk and the initiation of DNA replication is required for preventing rereplication. Our analysis suggests that distributive multisite phosphorylation of the S-Cdk targets Sld2 and Sld3 can generate both a robust time delay and contribute to switch-like, coherent activation of replication origins. The proposed catalytic function of the complex formed by Dpb11, Sld3 and Sld2 strongly enhances coherence and robustness of origin firing. The model rationalizes how experimentally observed inefficient replication from fewer origins is caused by premature activation of S-Cdk, while premature activity of the S-Cdk targets Sld2 and Sld3 results in DNA rereplication. Thus the model demonstrates how kinetic deregulation of the molecular network governing DNA replication may result in genomic instability.

  3. Computational investigations on polymerase actions in gene transcription and replication: Combining physical modeling and atomistic simulations

    Science.gov (United States)

    Jin, Yu

    2016-01-01

    Polymerases are protein enzymes that move along nucleic acid chains and catalyze template-based polymerization reactions during gene transcription and replication. The polymerases also substantially improve transcription or replication fidelity through the non-equilibrium enzymatic cycles. We briefly review computational efforts that have been made toward understanding mechano-chemical coupling and fidelity control mechanisms of the polymerase elongation. The polymerases are regarded as molecular information motors during the elongation process. It requires a full spectrum of computational approaches from multiple time and length scales to understand the full polymerase functional cycle. We stay away from quantum mechanics based approaches to the polymerase catalysis due to abundant former surveys, while addressing statistical physics modeling approaches along with all-atom molecular dynamics simulation studies. We organize this review around our own modeling and simulation practices on a single subunit T7 RNA polymerase, and summarize commensurate studies on structurally similar DNA polymerases as well. For multi-subunit RNA polymerases that have been actively studied in recent years, we leave systematical reviews of the simulation achievements to latest computational chemistry surveys, while covering only representative studies published very recently, including our own work modeling structure-based elongation kinetic of yeast RNA polymerase II. In the end, we briefly go through physical modeling on elongation pauses and backtracking activities of the multi-subunit RNAPs. We emphasize on the fluctuation and control mechanisms of the polymerase actions, highlight the non-equilibrium nature of the operation system, and try to build some perspectives toward understanding the polymerase impacts from the single molecule level to a genome-wide scale. Project supported by the National Natural Science Foundation (Grant No. 11275022).

  4. The Song Remains the Same: A Replication and Extension of the MUSIC Model.

    Science.gov (United States)

    Rentfrow, Peter J; Goldberg, Lewis R; Stillwell, David J; Kosinski, Michal; Gosling, Samuel D; Levitin, Daniel J

    2012-12-01

    There is overwhelming anecdotal and empirical evidence for individual differences in musical preferences. However, little is known about what drives those preferences. Are people drawn to particular musical genres (e.g., rap, jazz) or to certain musical properties (e.g., lively, loud)? Recent findings suggest that musical preferences can be conceptualized in terms of five orthogonal dimensions: Mellow, Unpretentious, Sophisticated, Intense, and Contemporary (conveniently, MUSIC). The aim of the present research is to replicate and extend that work by empirically examining the hypothesis that musical preferences are based on preferences for particular musical properties and psychological attributes as opposed to musical genres. Findings from Study 1 replicated the five-factor MUSIC structure using musical excerpts from a variety of genres and subgenres and revealed musical attributes that differentiate each factor. Results from Studies 2 and 3 show that the MUSIC structure is recoverable using musical pieces from only the jazz and rock genres, respectively. Taken together, the current work provides strong evidence that preferences for music are determined by specific musical attributes and that the MUSIC model is a robust framework for conceptualizing and measuring such preferences.

  5. Animal models for the study of hepatitis C virus infection and replication

    Institute of Scientific and Technical Information of China (English)

    Kristin L MacArthur; Catherine H Wu; George Y Wu

    2012-01-01

    Hepatitis C virus (HCV) hepatitis,initially termed non-A,non-B hepatitis,has become one of the leading causes of cirrhosis and hepatocellular carcinoma worldwide.With the help of animal models,our understanding of the virus has grown substantially from the time of initial discovery.There is a paucity of available animal models for the study of HCV,mainly because of the selective susceptibility limited to humans and primates.Recent work has focused modification of animals to permit HCV entry,replication and transmission.In this review,we highlight the currently available models for the study of HCV including chimpanzees,tupaia,mouse and rat models.Discussion will include methods of model design as well as the advantages and disadvantages of each model.Particular focus is dedicated to knowledge of pathophysiologic mechanisms of HCV infection that have been elucidated through animal studies.Research within animal models is critically important to establish a complete understanding of HCV infection,which will ultimately form the basis for future treatments and prevention of disease.

  6. Irreparable telomeric DNA damage and persistent DDR signalling as a shared causative mechanism of cellular senescence and ageing.

    Science.gov (United States)

    Rossiello, Francesca; Herbig, Utz; Longhese, Maria Pia; Fumagalli, Marzia; d'Adda di Fagagna, Fabrizio

    2014-06-01

    The DNA damage response (DDR) orchestrates DNA repair and halts cell cycle. If damage is not resolved, cells can enter into an irreversible state of proliferative arrest called cellular senescence. Organismal ageing in mammals is associated with accumulation of markers of cellular senescence and DDR persistence at telomeres. Since the vast majority of the cells in mammals are non-proliferating, how do they age? Are telomeres involved? Also oncogene activation causes cellular senescence due to altered DNA replication and DDR activation in particular at the telomeres. Is there a common mechanism shared among apparently distinct types of cellular senescence? And what is the role of telomeric DNA damage?

  7. Interaction Mortality: Senescence May Have Evolved because It Increases Lifespan

    DEFF Research Database (Denmark)

    Wensink, M. J.; Wrycza, T. F.; Baudisch, A.

    2014-01-01

    Given an extrinsic challenge, an organism may die or not depending on how the threat interacts with the organism's physiological state. To date, such interaction mortality has been only a minor factor in theoretical modeling of senescence. We describe a model of interaction mortality that does...... not involve specific functions, making only modest assumptions. Our model distinguishes explicitly between the physiological state of an organism and potential extrinsic, age-independent threats. The resulting mortality may change with age, depending on whether the organism's state changes with age. We find...... that depending on the physiological constraints, any outcome, be it 'no senescence' or 'high rate of senescence', can be found in any environment; that the highest optimal rate of senescence emerges for an intermediate physiological constraint, i.e. intermediate strength of trade-off; and that the optimal rate...

  8. Mitochondrial dysfunction accounts for the stochastic heterogeneity in telomere-dependent senescence.

    Directory of Open Access Journals (Sweden)

    João F Passos

    2007-05-01

    Full Text Available Aging is an inherently stochastic process, and its hallmark is heterogeneity between organisms, cell types, and clonal populations, even in identical environments. The replicative lifespan of primary human cells is telomere dependent; however, its heterogeneity is not understood. We show that mitochondrial superoxide production increases with replicative age in human fibroblasts despite an adaptive UCP-2-dependent mitochondrial uncoupling. This mitochondrial dysfunction is accompanied by compromised [Ca(2+]i homeostasis and other indicators of a retrograde response in senescent cells. Replicative senescence of human fibroblasts is delayed by mild mitochondrial uncoupling. Uncoupling reduces mitochondrial superoxide generation, slows down telomere shortening, and delays formation of telomeric gamma-H2A.X foci. This indicates mitochondrial production of reactive oxygen species (ROS as one of the causes of replicative senescence. By sorting early senescent (SES cells from young proliferating fibroblast cultures, we show that SES cells have higher ROS levels, dysfunctional mitochondria, shorter telomeres, and telomeric gamma-H2A.X foci. We propose that mitochondrial ROS is a major determinant of telomere-dependent senescence at the single-cell level that is responsible for cell-to-cell variation in replicative lifespan.

  9. Scoring of senescence signalling in multiple human tumour gene expression datasets, identification of a correlation between senescence score and drug toxicity in the NCI60 panel and a pro-inflammatory signature correlating with survival advantage in peritoneal mesothelioma

    Directory of Open Access Journals (Sweden)

    Burns Sharon

    2010-10-01

    Full Text Available Abstract Background Cellular senescence is a major barrier to tumour progression, though its role in pathogenesis of cancer and other diseases is poorly understood in vivo. Improved understanding of the degree to which latent senescence signalling persists in tumours might identify intervention strategies to provoke "accelerated senescence" responses as a therapeutic outcome. Senescence involves convergence of multiple pathways and requires ongoing dynamic signalling throughout its establishment and maintenance. Recent discovery of several new markers allows for an expression profiling approach to study specific senescence phenotypes in relevant tissue samples. We adopted a "senescence scoring" methodology based on expression profiles of multiple senescence markers to examine the degree to which signals of damage-associated or secretory senescence persist in various human tumours. Results We first show that scoring captures differential induction of damage or inflammatory pathways in a series of public datasets involving radiotherapy of colon adenocarcinoma, chemotherapy of breast cancer cells, replicative senescence of mesenchymal stem cells, and progression of melanoma. We extended these results to investigate correlations between senescence score and growth inhibition in response to ~1500 compounds in the NCI60 panel. Scoring of our own mesenchymal tumour dataset highlighted differential expression of secretory signalling pathways between distinct subgroups of MPNST, liposarcomas and peritoneal mesothelioma. Furthermore, a pro-inflammatory signature yielded by hierarchical clustering of secretory markers showed prognostic significance in mesothelioma. Conclusions We find that "senescence scoring" accurately reports senescence signalling in a variety of situations where senescence would be expected to occur and highlights differential expression of damage associated and secretory senescence pathways in a context-dependent manner.

  10. Replication Stress: A Lifetime of Epigenetic Change

    Directory of Open Access Journals (Sweden)

    Simran Khurana

    2015-09-01

    Full Text Available DNA replication is essential for cell division. Challenges to the progression of DNA polymerase can result in replication stress, promoting the stalling and ultimately collapse of replication forks. The latter involves the formation of DNA double-strand breaks (DSBs and has been linked to both genome instability and irreversible cell cycle arrest (senescence. Recent technological advances have elucidated many of the factors that contribute to the sensing and repair of stalled or broken replication forks. In addition to bona fide repair factors, these efforts highlight a range of chromatin-associated changes at and near sites of replication stress, suggesting defects in epigenome maintenance as a potential outcome of aberrant DNA replication. Here, we will summarize recent insight into replication stress-induced chromatin-reorganization and will speculate on possible adverse effects for gene expression, nuclear integrity and, ultimately, cell function.

  11. Senescence-accelerated OXYS rats

    Science.gov (United States)

    Stefanova, Natalia A; Kozhevnikova, Oyuna S; Vitovtov, Anton O; Maksimova, Kseniya Yi; Logvinov, Sergey V; Rudnitskaya, Ekaterina A; Korbolina, Elena E; Muraleva, Natalia A; Kolosova, Nataliya G

    2014-01-01

    Senescence-accelerated OXYS rats are an experimental model of accelerated aging that was established from Wistar stock via selection for susceptibility to cataractogenic effects of a galactose-rich diet and via subsequent inbreeding of highly susceptible rats. Currently, we have the 102nd generation of OXYS rats with spontaneously developing cataract and accelerated senescence syndrome, which means early development of a phenotype similar to human geriatric disorders, including accelerated brain aging. In recent years, our group found strong evidence that OXYS rats are a promising model for studies of the mechanisms of brain aging and neurodegenerative processes similar to those seen in Alzheimer disease (AD). The manifestation of behavioral alterations and learning and memory deficits develop since the fourth week of age, i.e., simultaneously with first signs of neurodegeneration detectable on magnetic resonance imaging and under a light microscope. In addition, impaired long-term potentiation has been demonstrated in OXYS rats by the age of 3 months. With age, neurodegenerative changes in the brain of OXYS rats become amplified. We have shown that this deterioration happens against the background of overproduction of amyloid precursor protein (AβPP), accumulation of β-amyloid (Aβ), and hyperphosphorylation of the tau protein in the hippocampus and cortex. The development of AMD-like retinopathy in OXYS rats is also accompanied by increased accumulation of Aβ in the retina. These published data suggest that the OXYS strain may serve as a spontaneous rat model of AD-like pathology and could help to decipher the pathogenesis of AD. PMID:24552807

  12. Measuring senescence in human populations

    NARCIS (Netherlands)

    Koopman, Jacob Jan Egbert

    2015-01-01

    In this thesis, senescence is measured in human populations according to its definition of an increase in the risks of dysfunction, disease, and death with chronological age. Part I of this thesis investigates how a population’s senescence rate can be measured through the increase in mortality rate

  13. Glycerophospholipid profile in oncogene-induced senescence.

    Science.gov (United States)

    Cadenas, Cristina; Vosbeck, Sonja; Hein, Eva-Maria; Hellwig, Birte; Langer, Alice; Hayen, Heiko; Franckenstein, Dennis; Büttner, Bettina; Hammad, Seddik; Marchan, Rosemarie; Hermes, Matthias; Selinski, Silvia; Rahnenführer, Jörg; Peksel, Begüm; Török, Zsolt; Vígh, László; Hengstler, Jan G

    2012-09-01

    Alterations in lipid metabolism and in the lipid composition of cellular membranes are linked to the pathology of numerous diseases including cancer. However, the influence of oncogene expression on cellular lipid profile is currently unknown. In this work we analyzed changes in lipid profiles that are induced in the course of ERBB2-expression mediated premature senescence. As a model system we used MCF-7 breast cancer cells with doxycycline-inducible expression of NeuT, an oncogenic ERBB2 variant. Affymetrix gene array data showed NeuT-induced alterations in the transcription of many enzymes involved in lipid metabolism, several of which (ACSL3, CHPT1, PLD1, LIPG, MGLL, LDL and NPC1) could be confirmed by quantitative realtime PCR. A study of the glycerophospholipid and lyso-glycerophospholipid profiles, obtained by high performance liquid chromatography coupled to Fourier-transform ion cyclotron resonance-mass spectrometry revealed senescence-associated changes in numerous lipid species, including mitochondrial lipids. The most prominent changes were found in PG(34:1), PG(36:1) (increased) and LPE(18:1), PG(40:7) and PI(36:1) (decreased). Statistical analysis revealed a general trend towards shortened phospholipid acyl chains in senescence and a significant trend to more saturated acyl chains in the class of phosphatidylglycerol. Additionally, the cellular cholesterol content was elevated and accumulated in vacuoles in senescent cells. These changes were accompanied by increased membrane fluidity. In mitochondria, loss of membrane potential along with altered intracellular distribution was observed. In conclusion, we present a comprehensive overview of altered cholesterol and glycerophospholipid patterns in senescence, showing that predominantly mitochondrial lipids are affected and lipid species less susceptible to peroxidation are increased.

  14. Approximating uncertainty of annual runoff and reservoir yield using stochastic replicates of global climate model data

    Science.gov (United States)

    Peel, M. C.; Srikanthan, R.; McMahon, T. A.; Karoly, D. J.

    2015-04-01

    Two key sources of uncertainty in projections of future runoff for climate change impact assessments are uncertainty between global climate models (GCMs) and within a GCM. Within-GCM uncertainty is the variability in GCM output that occurs when running a scenario multiple times but each run has slightly different, but equally plausible, initial conditions. The limited number of runs available for each GCM and scenario combination within the Coupled Model Intercomparison Project phase 3 (CMIP3) and phase 5 (CMIP5) data sets, limits the assessment of within-GCM uncertainty. In this second of two companion papers, the primary aim is to present a proof-of-concept approximation of within-GCM uncertainty for monthly precipitation and temperature projections and to assess the impact of within-GCM uncertainty on modelled runoff for climate change impact assessments. A secondary aim is to assess the impact of between-GCM uncertainty on modelled runoff. Here we approximate within-GCM uncertainty by developing non-stationary stochastic replicates of GCM monthly precipitation and temperature data. These replicates are input to an off-line hydrologic model to assess the impact of within-GCM uncertainty on projected annual runoff and reservoir yield. We adopt stochastic replicates of available GCM runs to approximate within-GCM uncertainty because large ensembles, hundreds of runs, for a given GCM and scenario are unavailable, other than the Climateprediction.net data set for the Hadley Centre GCM. To date within-GCM uncertainty has received little attention in the hydrologic climate change impact literature and this analysis provides an approximation of the uncertainty in projected runoff, and reservoir yield, due to within- and between-GCM uncertainty of precipitation and temperature projections. In the companion paper, McMahon et al. (2015) sought to reduce between-GCM uncertainty by removing poorly performing GCMs, resulting in a selection of five better performing GCMs from

  15. Plant senescence and crop productivity

    DEFF Research Database (Denmark)

    Gregersen, Per L.; Culetic, Andrea; Boschian, Luca

    2013-01-01

    Senescence is a developmental process which in annual crop plants overlaps with the reproductive phase. Senescence might reduce crop yield when it is induced prematurely under adverse environmental conditions. This review covers the role of senescence for the productivity of crop plants....... With the aim to enhance productivity, a number of functional stay-green cultivars have been selected by conventional breeding, in particular of sorghum and maize. In many cases, a positive correlation between leaf area duration and yield has been observed, although in a number of other cases, stay...... plants, the expression of the IPT gene under control of senescence-associated promoters has been the most successful. The promoters employed for senescence-regulated expression contain cis-elements for binding of WRKY transcription factors and factors controlled by abscisic acid. In most crops...

  16. High concentrations of NaCl induce cell swelling leading to senescence in human cells.

    Science.gov (United States)

    Yamakami, Yoshimi; Yonekura, Ryuzo; Matsumoto, Yuko; Takauji, Yuki; Miki, Kensuke; Fujii, Michihiko; Ayusawa, Dai

    2016-01-01

    Cell swelling and retardation in DNA replication are always observed in senescent cells. When DNA replication is slowed down with RNA and protein syntheses unchanged in proliferating cells, it causes a phenomenon known as unbalanced growth. The purpose of this study is to assess the role of cell swelling in unbalanced growth in terms of senescence and investigate the mechanism underlying this phenomenon. We tried to induce cell swelling with minimum damage to cells in this study. We perturbed the osmoregulatory functions to induce cell swelling under hypotonic and hypertonic conditions in normal human fibroblasts. Addition of excess NaCl was found to induce significant cell and nuclear swelling in dose- and time-dependent manners. Excess NaCl immediately retarded DNA replication, accumulated cells at G1 phase of the cell cycle, and eventually deprived division potential of the cells. Such cells showed typical senescent cell shape followed by expression of the typical senescence-associated genes. Excess NaCl also activated ERK1/2, p38, and JNK of the mitogen activated protein kinase family. Addition of U0126, an inhibitor of ERK1/2, prevented appearance of senescent features induced by excess NaCl. These results suggest that hypertonic conditions induce cell swelling due to unbalanced growth, thereby leading to cellular senescence.

  17. The splicing factor ASF/SF2 and intron retention as markers of endothelial senescence

    Directory of Open Access Journals (Sweden)

    Francisco Javier Blanco

    2012-03-01

    Full Text Available Aging is the major risk factor per se for the development of cardiovascular diseases. The senescence of endothelial cells, that line the lumen of blood vessels, is at the cellular basis of these age-dependent vascular pathologies, including atherosclerosis and hypertension. Along their lifespan, endothelial cells may reach the senescence stage by two different pathways, the replicative one derived from their finite number of divisions, and the one induced by stress stimuli. Also, certain physiological stimuli, such as TGF-β are able to modulate cellular senescence. Currently, the cellular aging process is being widely studied to identify novel molecular markers whose changes correlate with senescence. This review focuses on the regulation of alternative splicing mediated by the serine-arginine splicing factor 1 (SRSF1, or ASF/SF2 during endothelial senescence, a process that is associated with a differential subcellular localization of SRSF1, showing a scattered distribution throughout the cytoplasm. Based on its senescence-dependent involvement in alternative splicing, we postulate that SRSF1 is a key marker of endothelial cell senescence regulating the expression of alternative isoforms of target genes such as ENG, VEGFA, T3 or LMNA that integrate a common molecular senescence program.

  18. Overexpression of the novel senescence marker β-galactosidase (GLB1 in prostate cancer predicts reduced PSA recurrence.

    Directory of Open Access Journals (Sweden)

    Jennifer Wagner

    Full Text Available Senescence is a terminal growth arrest that functions as a tumor suppressor in aging and precancerous cells and is a response to selected anticancer compounds. Lysosomal-β-galactosidase (GLB1 hydrolyzes β-galactose from glycoconjugates and is the origin of senescence-associated β-gal activity (SA-β-gal. Using a new GLB1 antibody, senescence biology was investigated in prostate cancer (PCa tissues.In vitro characterization of GLB1 was determined in primary prostate epithelial cell cultures passaged to replicative senescence and in therapy-induced senescence in PCa lines using chemotherapeutic agents. FFPE tissue microarrays were subjected to immunofluorescent staining for GLB1, Ki67 and HP1γ and automated quantitative imaging initially using AQUA in exploratory samples and Vectra in a validation series.GLB1 expression accumulates in replicative and induced senescence and correlates with senescent morphology and P16 (CDKN2 expression. In tissue arrays, quantitative imaging detects increased GLB1 expression in high-grade prostatic intraepithelial neoplasia (HGPIN, known to contain senescent cells, and cancer compared to benign prostate tissues (p<0.01 and senescent cells contain low Ki67 and elevated HP1γ. Within primary tumors, elevated GLB1 associates with lower T stage (p=0.01, localized versus metastatic disease (p=0.0003 and improved PSA-free survival (p=0.03. Increased GLB1 stratifies better PSA-free survival in intermediate grade PCa (0.01. Tissues that elaborate higher GLB1 display increased uniformity of expression.Increased GLB1 is a valuable marker in formalin-fixed paraffin-embedded (FFPE tissues for the senescence-like phenotype and associates with improved cancer outcomes. This protein addresses a lack of senescence markers and should be applicable to study the biologic role of senescence in other cancers.

  19. Factor Analytic Replication and Model Comparison of the BASC-2 Behavioral and Emotional Screening System.

    Science.gov (United States)

    Splett, Joni Williams; Raborn, Anthony; Lane, Kathleen Lynne; Binney, Alexandra J; Chafouleas, Sandra M

    2017-03-06

    We conducted this study to add to literature of previous conflicting factorial examinations of the BASC-2 Behavioral and Emotional Screening System (BESS), Teacher Form-Child/Adolescent. Data were collected by an urban school district in the southeastern United States including 2,228 students rated by 120 teachers in Fall 2014 and 1,955 students rated by 104 teachers in Spring 2015. In both samples, we replicated and then conceptually and statistically compared factor models to examine the (a) 4-factor structure from which the BESS Teacher Form was developed, and (b) existence of a general factor currently being used. Previous studies examined the 4-factor and bifactor structure of the BESS Teacher Form on separate samples. Our model comparison results support a multidimensional interpretation. We recovered similar fit statistics and standardized factor loadings as previous factor analyses. However, measures of variance accounted for by the general factor were below recommended thresholds of a unidimensional construct. We recommend advancing a factorial model that represents a weighted combination of general and specific factors, but do not support continued use of a unidimensional total T score. Limitations and implications of the study are discussed. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  20. A bridging model for persistence of a polycomb group protein complex through DNA replication in vitro.

    Science.gov (United States)

    Lo, Stanley M; Follmer, Nicole E; Lengsfeld, Bettina M; Madamba, Egbert V; Seong, Samuel; Grau, Daniel J; Francis, Nicole J

    2012-06-29

    Epigenetic regulation may involve heritable chromatin states, but how chromatin features can be inherited through DNA replication is incompletely understood. We address this question using cell-free replication of chromatin. Previously, we showed that a Polycomb group complex, PRC1, remains continuously associated with chromatin through DNA replication. Here we investigate the mechanism of persistence. We find that a single PRC1 subunit, Posterior sex combs (PSC), can reconstitute persistence through DNA replication. PSC binds nucleosomes and self-interacts, bridging nucleosomes into a stable, oligomeric structure. Within these structures, individual PSC-chromatin contacts are dynamic. Stable association of PSC with chromatin, including through DNA replication, depends on PSC-PSC interactions. Our data suggest that labile individual PSC-chromatin contacts allow passage of the DNA replication machinery while PSC-PSC interactions prevent PSC from dissociating, allowing it to rebind to replicated chromatin. This mechanism may allow inheritance of chromatin proteins including PRC1 through DNA replication to maintain chromatin states.

  1. Interaction mortality: senescence may have evolved because it increases lifespan.

    Directory of Open Access Journals (Sweden)

    Maarten J Wensink

    Full Text Available Given an extrinsic challenge, an organism may die or not depending on how the threat interacts with the organism's physiological state. To date, such interaction mortality has been only a minor factor in theoretical modeling of senescence. We describe a model of interaction mortality that does not involve specific functions, making only modest assumptions. Our model distinguishes explicitly between the physiological state of an organism and potential extrinsic, age-independent threats. The resulting mortality may change with age, depending on whether the organism's state changes with age. We find that depending on the physiological constraints, any outcome, be it 'no senescence' or 'high rate of senescence', can be found in any environment; that the highest optimal rate of senescence emerges for an intermediate physiological constraint, i.e. intermediate strength of trade-off; and that the optimal rate of senescence as a function of the environment is driven by the way the environment changes the effect of the organism's state on mortality. We conclude that knowledge about the environment, physiology and their interaction is necessary before reasonable predictions about the evolution of senescence can be made.

  2. Memory Enhancement of Acteoside (Verbascoside) in a Senescent Mice Model Induced by a Combination of D-gal and AlCl3.

    Science.gov (United States)

    Gao, Li; Peng, Xiao-Ming; Huo, Shi-Xia; Liu, Xin-Ming; Yan, Ming

    2015-08-01

    Acteoside, also known as verbascoside or orobanchin, is a common compound found in many important medicinal plants including the Chinese herb Cistanche deserticola Y. C. Ma, which is used for its neuroprotective and memory enhancement properties. We have investigated the effects of acteoside using a senescent mouse model induced by a combination of chronic intraperitoneal administration of d-gal (60 mg/kg/day) and oral administration AlCl3 (5 mg/kg/day) once daily for 90 days. After 60 days, acteoside (30, 60, and 120 mg/kg/day) was orally administered once daily for 30 days. The memory enhancing effects of acteoside were evaluated using the Morris water maze test. The results showed that 30-120 mg/kg/day of acteoside reduced the escape latency in finding the platform, and increased the number of crossings of the platform. A 30-120 mg/kg/day of acteoside increased significantly the expression of nerve growth factor and tropomycin receptor kinase A mRNA and protein in the hippocampus, measured using real-time RT-PCR, immunohistochemical analysis, and western blotting. These results support the use of C. deserticola for memory enhancement and indicate that the effects of acteoside are induced via promotion of nerve growth factor and tropomycin receptor kinase A expression.

  3. Cutthroat trout virus as a surrogate in vitro infection model for testing inhibitors of hepatitis E virus replication

    Science.gov (United States)

    Debing, Yannick; Winton, James; Neyts, Johan; Dallmeier, Kai

    2013-01-01

    Hepatitis E virus (HEV) is one of the most important causes of acute hepatitis worldwide. Although most infections are self-limiting, mortality is particularly high in pregnant women. Chronic infections can occur in transplant and other immune-compromised patients. Successful treatment of chronic hepatitis E has been reported with ribavirin and pegylated interferon-alpha, however severe side effects were observed. We employed the cutthroat trout virus (CTV), a non-pathogenic fish virus with remarkable similarities to HEV, as a potential surrogate for HEV and established an antiviral assay against this virus using the Chinook salmon embryo (CHSE-214) cell line. Ribavirin and the respective trout interferon were found to efficiently inhibit CTV replication. Other known broad-spectrum inhibitors of RNA virus replication such as the nucleoside analog 2′-C-methylcytidine resulted only in a moderate antiviral activity. In its natural fish host, CTV levels largely fluctuate during the reproductive cycle with the virus detected mainly during spawning. We wondered whether this aspect of CTV infection may serve as a surrogate model for the peculiar pathogenesis of HEV in pregnant women. To that end the effect of three sex steroids on in vitro CTV replication was evaluated. Whereas progesterone resulted in marked inhibition of virus replication, testosterone and 17β-estradiol stimulated viral growth. Our data thus indicate that CTV may serve as a surrogate model for HEV, both for antiviral experiments and studies on the replication biology of the Hepeviridae.

  4. Metabolically Coupled Replicator Systems: Overview of an RNA-world model concept of prebiotic evolution on mineral surfaces.

    Science.gov (United States)

    Czárán, Tamás; Könnyű, Balázs; Szathmáry, Eörs

    2015-09-21

    Metabolically Coupled Replicator Systems (MCRS) are a family of models implementing a simple, physico-chemically and ecologically feasible scenario for the first steps of chemical evolution towards life. Evolution in an abiotically produced RNA-population sets in as soon as any one of the RNA molecules become autocatalytic by engaging in template directed self-replication from activated monomers, and starts increasing exponentially. Competition for the finite external supply of monomers ignites selection favouring RNA molecules with catalytic activity helping self-replication by any possible means. One way of providing such autocatalytic help is to become a replicase ribozyme. An additional way is through increasing monomer supply by contributing to monomer synthesis from external resources, i.e., by evolving metabolic enzyme activity. Retroevolution may build up an increasingly autotrophic, cooperating community of metabolic ribozymes running an increasingly complicated and ever more efficient metabolism. Maintaining such a cooperating community of metabolic replicators raises two serious ecological problems: one is keeping the system coexistent in spite of the different replicabilities of the cooperating replicators; the other is constraining parasitism, i.e., keeping "cheaters" in check. Surface-bound MCRS provide an automatic solution to both problems: coexistence and parasite resistance are the consequences of assuming the local nature of metabolic interactions. In this review we present an overview of results published in previous articles, showing that these effects are, indeed, robust in different MCRS implementations, by considering different environmental setups and realistic chemical details in a few different models. We argue that the MCRS model framework naturally offers a suitable starting point for the future modelling of membrane evolution and extending the theory to cover the emergence of the first protocell in a self-consistent manner. The

  5. Near-atomic structural model for bacterial DNA replication initiation complex and its functional insights.

    Science.gov (United States)

    Shimizu, Masahiro; Noguchi, Yasunori; Sakiyama, Yukari; Kawakami, Hironori; Katayama, Tsutomu; Takada, Shoji

    2016-12-13

    Upon DNA replication initiation in Escherichia coli, the initiator protein DnaA forms higher-order complexes with the chromosomal origin oriC and a DNA-bending protein IHF. Although tertiary structures of DnaA and IHF have previously been elucidated, dynamic structures of oriC-DnaA-IHF complexes remain unknown. Here, combining computer simulations with biochemical assays, we obtained models at almost-atomic resolution for the central part of the oriC-DnaA-IHF complex. This complex can be divided into three subcomplexes; the left and right subcomplexes include pentameric DnaA bound in a head-to-tail manner and the middle subcomplex contains only a single DnaA. In the left and right subcomplexes, DnaA ATPases associated with various cellular activities (AAA+) domain III formed helices with specific structural differences in interdomain orientations, provoking a bend in the bound DNA. In the left subcomplex a continuous DnaA chain exists, including insertion of IHF into the DNA looping, consistent with the DNA unwinding function of the complex. The intervening spaces in those subcomplexes are crucial for DNA unwinding and loading of DnaB helicases. Taken together, this model provides a reasonable near-atomic level structural solution of the initiation complex, including the dynamic conformations and spatial arrangements of DnaA subcomplexes.

  6. Cellular senescence and autophagy of myoepithelial cells are involved in the progression of in situ areas of carcinoma ex-pleomorphic adenoma to invasive carcinoma. An in vitro model.

    Science.gov (United States)

    Silva, Carolina Amália Barcellos; Martinez, Elizabeth Ferreira; Demasi, Ana Paula Dias; Altemani, Albina; da Silveira Bossonaro, Jeruza Pinheiro; Araújo, Ney Soares; de Araújo, Vera Cavalcanti

    2015-09-01

    During tumor invasion, benign myoepithelial cells of carcinoma ex-pleomorphic adenoma (CXPA) surround malignant epithelial cells and disappear. The mechanisms involved in the death and disappearance of these myoepithelial cells were investigated via analysis of the expression of regulatory proteins for apoptosis, autophagy and cellular senescence in an in situ in vitro model. Protein expression relating to apoptosis (Bax, Bcl-2, Survivin), autophagy (Beclin-1, LC3B) and cellular senescence (p21, p16) was evaluated using indirect immunofluorescence. β-galactosidase expression was assessed via histochemistry. Biopsies of CXPA (ex vivo) allowed immunhistochemical evaluation of p21 and p16, whilst LC3B, p21 and p16 protein expression was analyzed by western blotting. In the in vitro model, the myoepithelial cells were positive for LC3B (cytoplasm) and p21 (nucleus), whilst in vivo positivity for p21 and p16 was observed. In vitro, β-galactosidase activity increased in the myoepithelial cells over time. Western blotting analysis revealed an increased LC3B, p16 and p21 expression in the myoepithelial cells with previous contact with the malignant cells when compared with those without contact. The investigation of behavior of benign myoepithelial cells in ductal areas of CXAP revealed that the myoepithelial cells are involved in the autophagy-senescence phenotype that subsequently leads to their disappearance.

  7. Androgen receptor drives cellular senescence.

    Directory of Open Access Journals (Sweden)

    Yelena Mirochnik

    Full Text Available The accepted androgen receptor (AR role is to promote proliferation and survival of prostate epithelium and thus prostate cancer progression. While growth-inhibitory, tumor-suppressive AR effects have also been documented, the underlying mechanisms are poorly understood. Here, we for the first time link AR anti-cancer action with cell senescence in vitro and in vivo. First, AR-driven senescence was p53-independent. Instead, AR induced p21, which subsequently reduced ΔN isoform of p63. Second, AR activation increased reactive oxygen species (ROS and thereby suppressed Rb phosphorylation. Both pathways were critical for senescence as was proven by p21 and Rb knock-down and by quenching ROS with N-Acetyl cysteine and p63 silencing also mimicked AR-induced senescence. The two pathways engaged in a cross-talk, likely via PML tumor suppressor, whose localization to senescence-associated chromatin foci was increased by AR activation. All these pathways contributed to growth arrest, which resolved in senescence due to concomitant lack of p53 and high mTOR activity. This is the first demonstration of senescence response caused by a nuclear hormone receptor.

  8. NAC transcription factors in senescence

    DEFF Research Database (Denmark)

    Podzimska-Sroka, Dagmara; O'Shea, Charlotte; Gregersen, Per L.;

    2015-01-01

    Within the last decade, NAC transcription factors have been shown to play essential roles in senescence, which is the focus of this review. Transcriptome analyses associate approximately one third of Arabidopsis NAC genes and many crop NAC genes with senescence, thereby implicating NAC genes...... as important regulators of the senescence process. The consensus DNA binding site of the NAC domain is used to predict NAC target genes, and protein interaction sites can be predicted for the intrinsically disordered transcription regulatory domains of NAC proteins. The molecular characteristics...

  9. ING proteins in cellular senescence.

    Science.gov (United States)

    Menéndez, Camino; Abad, María; Gómez-Cabello, Daniel; Moreno, Alberto; Palmero, Ignacio

    2009-05-01

    Cellular senescence is an effective anti-tumor barrier that acts by restraining the uncontrolled proliferation of cells carrying potentially oncogenic alterations. ING proteins are putative tumor suppressor proteins functionally linked to the p53 pathway and to chromatin regulation. ING proteins exert their tumor-protective action through different types of responses. Here, we review the evidence on the participation of ING proteins, mainly ING1 and ING2, in the implementation of the senescent response. The currently available data support an important role of ING proteins as regulators of senescence, in connection with the p53 pathway and chromatin organization.

  10. The ING tumor suppressors in cellular senescence and chromatin.

    Science.gov (United States)

    Ludwig, Susann; Klitzsch, Alexandra; Baniahmad, Aria

    2011-07-18

    The Inhibitor of Growth (ING) proteins represent a type II tumor suppressor family comprising five conserved genes, ING1 to ING5. While ING1, ING2 and ING3 proteins are stable components of the mSIN3a-HDAC complexes, the association of ING1, ING4 and ING5 with HAT protein complexes was also reported. Among these the ING1 and ING2 have been analyzed more deeply. Similar to other tumor suppressor factors the ING proteins are also involved in many cellular pathways linked to cancer and cell proliferation such as cell cycle regulation, cellular senescence, DNA repair, apoptosis, inhibition of angiogenesis and modulation of chromatin.A common structural feature of ING factors is the conserved plant homeodomain (PHD), which can bind directly to the histone mark trimethylated lysine of histone H3 (H3K4me3). PHD mutants lose the ability to undergo cellular senescence linking chromatin mark recognition with cellular senescence. ING1 and ING2 are localized in the cell nucleus and associated with chromatin modifying enzymes, linking tumor suppression directly to chromatin regulation. In line with this, the expression of ING1 in tumors is aberrant or identified point mutations are mostly localized in the PHD finger and affect histone binding. Interestingly, ING1 protein levels increase in replicative senescent cells, latter representing an efficient pathway to inhibit cancer proliferation. In association with this, suppression of p33ING1 expression prolongs replicative life span and is also sufficient to bypass oncogene-induced senescence. Recent analyses of ING1- and ING2-deficient mice confirm a tumor suppressive role of ING1 and ING2 and also indicate an essential role of ING2 in meiosis.Here we summarize the activity of ING1 and ING2 as tumor suppressors, chromatin factors and in development.

  11. Information management in DNA replication modeled by directional, stochastic chains with memory

    Science.gov (United States)

    Arias-Gonzalez, J. Ricardo

    2016-11-01

    Stochastic chains represent a key variety of phenomena in many branches of science within the context of information theory and thermodynamics. They are typically approached by a sequence of independent events or by a memoryless Markov process. Stochastic chains are of special significance to molecular biology, where genes are conveyed by linear polymers made up of molecular subunits and transferred from DNA to proteins by specialized molecular motors in the presence of errors. Here, we demonstrate that when memory is introduced, the statistics of the chain depends on the mechanism by which objects or symbols are assembled, even in the slow dynamics limit wherein friction can be neglected. To analyze these systems, we introduce a sequence-dependent partition function, investigate its properties, and compare it to the standard normalization defined by the statistical physics of ensembles. We then apply this theory to characterize the enzyme-mediated information transfer involved in DNA replication under the real, non-equilibrium conditions, reproducing measured error rates and explaining the typical 100-fold increase in fidelity that is experimentally found when proofreading and edition take place. Our model further predicts that approximately 1 kT has to be consumed to elevate fidelity in one order of magnitude. We anticipate that our results are necessary to interpret configurational order and information management in many molecular systems within biophysics, materials science, communication, and engineering.

  12. Computational Investigations on Polymerase Actions in Gene Transcription and Replication Combining Physical Modeling and Atomistic Simulations

    OpenAIRE

    Yu, Jin

    2015-01-01

    Polymerases are protein enzymes that move along nucleic acid chains and catalyze template-based polymerization reactions during gene transcription and replication. The polymerases also substantially improve transcription or replication fidelity through the non-equilibrium enzymatic cycles. We briefly review computational efforts that have been made toward understanding mechano-chemical coupling and fidelity control mechanisms of the polymerase elongation. The polymerases are regarded as molec...

  13. Regulation of a senescence checkpoint response by the E2F1 transcription factor and p14ARF tumor suppressor

    Energy Technology Data Exchange (ETDEWEB)

    Dimri, Goberdhan P.; Itahana, Koji; Acosta, Meileen; Campisi, Judith

    1999-11-05

    Normal cells do not divide indefinitely due to a process known as replicative senescence. Human cells arrest growth with a senescent phenotype when they acquire one or more critically short telomere as a consequence of cell division. Recent evidence suggests that certain types of DNA damage, chromatin remodeling, or oncogenic forms of Rasor Raf can also elicit a senescence response. We show here that E2F1, a multifunctional transcription factor that binds the retinoblastoma (pRb) tumor suppressor and can either promote or suppress tumorigenesis, induces a senescent phenotype when overexpressed in normal human fibroblasts. Normal human cells stably arrested proliferation and expressed several markers of replicative senescence in response to E2F1. This activity of E2F1 was independent of its pRb binding activity, but dependent on its ability to stimulate gene expression. The E2F1 target gene critical for the senescence response appeared to be the p14ARF tumor suppressor. Replicatively senescent human fibroblasts overexpressed p14ARF, and ectopic expression of p14ARF in presenescent cells induced a phenotype similar to that induced by E2F1. Consistent with a critical role for p14ARF, cells with compromised p53 function were immune to senescence induction by E2F1, as were cells deficient in p14ARF. Our findings support the idea that the senescence response is a critical tumor suppressive mechanism, provide an explanation for the apparently paradoxical roles of E2F1 in oncogenesis, and identify p14ARF as a potentially important mediator of the senescent phenotype.

  14. Essential and non-essential DNA replication genes in the model halophilic Archaeon, Halobacterium sp. NRC-1

    Directory of Open Access Journals (Sweden)

    DasSarma Shiladitya

    2007-06-01

    Full Text Available Abstract Background Information transfer systems in Archaea, including many components of the DNA replication machinery, are similar to those found in eukaryotes. Functional assignments of archaeal DNA replication genes have been primarily based upon sequence homology and biochemical studies of replisome components, but few genetic studies have been conducted thus far. We have developed a tractable genetic system for knockout analysis of genes in the model halophilic archaeon, Halobacterium sp. NRC-1, and used it to determine which DNA replication genes are essential. Results Using a directed in-frame gene knockout method in Halobacterium sp. NRC-1, we examined nineteen genes predicted to be involved in DNA replication. Preliminary bioinformatic analysis of the large haloarchaeal Orc/Cdc6 family, related to eukaryotic Orc1 and Cdc6, showed five distinct clades of Orc/Cdc6 proteins conserved in all sequenced haloarchaea. Of ten orc/cdc6 genes in Halobacterium sp. NRC-1, only two were found to be essential, orc10, on the large chromosome, and orc2, on the minichromosome, pNRC200. Of the three replicative-type DNA polymerase genes, two were essential: the chromosomally encoded B family, polB1, and the chromosomally encoded euryarchaeal-specific D family, polD1/D2 (formerly called polA1/polA2 in the Halobacterium sp. NRC-1 genome sequence. The pNRC200-encoded B family polymerase, polB2, was non-essential. Accessory genes for DNA replication initiation and elongation factors, including the putative replicative helicase, mcm, the eukaryotic-type DNA primase, pri1/pri2, the DNA polymerase sliding clamp, pcn, and the flap endonuclease, rad2, were all essential. Targeted genes were classified as non-essential if knockouts were obtained and essential based on statistical analysis and/or by demonstrating the inability to isolate chromosomal knockouts except in the presence of a complementing plasmid copy of the gene. Conclusion The results showed that ten

  15. Density dependence triggers runaway selection of reduced senescence.

    Directory of Open Access Journals (Sweden)

    Robert M Seymour

    2007-12-01

    Full Text Available In the presence of exogenous mortality risks, future reproduction by an individual is worth less than present reproduction to its fitness. Senescent aging thus results inevitably from transferring net fertility into younger ages. Some long-lived organisms appear to defy theory, however, presenting negligible senescence (e.g., hydra and extended lifespans (e.g., Bristlecone Pine. Here, we investigate the possibility that the onset of vitality loss can be delayed indefinitely, even accepting the abundant evidence that reproduction is intrinsically costly to survival. For an environment with constant hazard, we establish that natural selection itself contributes to increasing density-dependent recruitment losses. We then develop a generalized model of accelerating vitality loss for analyzing fitness optima as a tradeoff between compression and spread in the age profile of net fertility. Across a realistic spectrum of senescent age profiles, density regulation of recruitment can trigger runaway selection for ever-reducing senescence. This novel prediction applies without requirement for special life-history characteristics such as indeterminate somatic growth or increasing fecundity with age. The evolution of nonsenescence from senescence is robust to the presence of exogenous adult mortality, which tends instead to increase the age-independent component of vitality loss. We simulate examples of runaway selection leading to negligible senescence and even intrinsic immortality.

  16. Actuarial senescence in a long-lived orchid challenges our current understanding of ageing.

    Science.gov (United States)

    Dahlgren, Johan Petter; Colchero, Fernando; Jones, Owen R; Øien, Dag-Inge; Moen, Asbjørn; Sletvold, Nina

    2016-11-16

    The dominant evolutionary theory of actuarial senescence-an increase in death rate with advancing age-is based on the concept of a germ cell line that is separated from the somatic cells early in life. However, such a separation is not clear in all organisms. This has been suggested to explain the paucity of evidence for actuarial senescence in plants. We used a 32 year study of Dactylorhiza lapponica that replaces its organs each growing season, to test whether individuals of this tuberous orchid senesce. We performed a Bayesian survival trajectory analysis accounting for reproductive investment, for individuals under two types of land use, in two climatic regions. The mortality trajectory was best approximated by a Weibull model, showing clear actuarial senescence. Rates of senescence in this model declined with advancing age, but were slightly higher in mown plots and in the more benign climatic region. At older ages, senescence was evident only when accounting for a positive effect of reproductive investment on mortality. Our results demonstrate actuarial senescence as well as a survival-reproduction trade-off in plants, and indicate that environmental context may influence senescence rates. This knowledge is crucial for understanding the evolution of demographic senescence and for models of plant population dynamics.

  17. Phenotyping jasmonate regulation of senescence.

    Science.gov (United States)

    Seltmann, Martin A; Berger, Susanne

    2013-01-01

    Osmotic stress induces several senescence-like processes in leaves, such as specific changes in gene expression and yellowing. These processes are dependent on the accumulation of jasmonates and on intact jasmonate signaling. This chapter describes the treatment of Arabidopsis thaliana leaves with sorbitol as an osmotic stress agent and the determination of the elicited phenotypes encompassing chlorophyll loss, degradation of plastidial membrane lipids, and induction of genes regulated by senescence and jasmonate.

  18. NAC Transcription Factors of Barley (Hordeum vulgare L.) and their Involvement in Leaf Senescence

    DEFF Research Database (Denmark)

    Wagner, Michael

    yielding cereal crops are generated. In cereals, the process of leaf senescence is of utmost relevance when discussing yield. It is during the senescence process that all nutrients are transported from the withering leaf to the developing grains. Furthermore, the timing of senescence determines...... parts of the senescence process. The specific aims of this study were therefore (1) to establish and characterise the NAC transcription factors of the model cereal crop barley (Hordeum vulgare L.) (2) to identify and study putative barley NAC transcription factors involved in the regulation of leaf...

  19. HBP1-Mediated Transcriptional Regulation of DNA Methyltransferase 1 and Its Impact on Cell Senescence

    Science.gov (United States)

    Pan, Kewu; Chen, Yifan; Roth, Mendel; Wang, Weibin; Wang, Shuya; Yee, Amy S.

    2013-01-01

    The activity of DNA methyltransferase 1 (DNMT1) is associated with diverse biological activities, including cell proliferation, senescence, and cancer development. In this study, we demonstrated that the HMG box-containing protein 1 (HBP1) transcription factor is a new repressor of DNMT1 in a complex mechanism during senescence. The DNMT1 gene contains an HBP1-binding site at bp −115 to −134 from the transcriptional start site. HBP1 repressed the endogenous DNMT1 gene through sequence-specific binding, resulting in both gene-specific (e.g., p16INK4) and global DNA hypomethylation changes. The HBP1-mediated repression by DNMT1 contributed to replicative and premature senescence, the latter of which could be induced by Ras and HBP1 itself. A detailed investigation unexpectedly revealed that HBP1 has dual and complex transcriptional functions, both of which contribute to premature senescence. HBP1 both repressed the DNMT1 gene and activated the p16 gene in premature senescence. The opposite transcriptional functions proceeded through different DNA sequences and differential protein acetylation. While intricate, the reciprocal partnership between HBP1 and DNMT1 has exceptional importance, since its abrogation compromises senescence and promotes tumorigenesis. Together, our results suggest that the HBP1 transcription factor orchestrates a complex regulation of key genes during cellular senescence, with an impact on overall DNA methylation state. PMID:23249948

  20. Changes in the level and distribution of Ku proteins during cellular senescence

    Science.gov (United States)

    Seluanov, Andrei; Danek, Jacquelynn; Hause, Nola; Gorbunova, Vera

    2009-01-01

    Aging is associated with accumulation of genomic rearrangements consistent with aberrant repair of DNA breaks. We have shown previously that DNA repair by nonhomologous end joining (NHEJ) becomes less efficient and more error-prone in senescent cells. Here we show that the levels of Ku70 and Ku80 drop approximately two fold in replicatively senescent cells. Intracellular distribution of Ku also changes. In the young cells roughly half of Ku is located in the nucleus and half in the cytoplasm. In senescent cells the nuclear levels of Ku do not change, while the cytoplasmic Ku fraction disappears. Upon treatment with gamma-irradiation, in the young cells cytoplasmic Ku moved into the nuclear and membrane fractions, while no change in the Ku distribution occurred in senescent cells. Upon treatment with UVC Ku moved out of the nucleus in the young cells, while most Ku remained nuclear in senescent cells. This suggests that the nuclear Ku in senescent cells is unable to respond to DNA damage. We hypothesize that overall decline in Ku levels, changes in Ku intracellular distribution, and the loss of appropriate response of Ku to DNA damage in senescent cells contribute to the decline of NHEJ and to age-related genomic instability. PMID:17686666

  1. Immunotherapeutics to prevent the replication of Brucella in a treatment failure mouse model.

    Science.gov (United States)

    Jain-Gupta, N; Contreras-Rodriguez, A; Smith, G P; Garg, V K; Witonsky, S G; Isloor, S; Vemulapalli, R; Boyle, S M; Sriranganathan, N

    2014-02-12

    Outer membrane vesicles (OMVs) from Brucella melitensis and irradiated Brucella neotomae have been shown to be effective vaccines against a B. melitensis challenge in a mouse model. The present study evaluates the efficacy of these two vaccines as immuno-therapeutics in combination with conventional antibiotics against a B. melitensis infection. BALB/c mice chronically infected with B. melitensis were treated for 4 weeks with doxycycline and gentamicin and vaccinated twice during the course of therapy. Antibiotics in sub-therapeutic concentrations were chosen in such a way that the treatment would result in a therapeutic failure in mice. Although no additive effect of vaccines and antibiotics was seen on the clearance of B. melitensis, mice receiving vaccines along with antibiotics exhibited no Brucella replication post-treatment compared to mice treated only with antibiotics. Administration of irradiated B. neotomae along with antibiotics led to higher production of IFN-γ ex vivo by splenocytes upon stimulation with heat inactivated B. melitensis while no such effect was seen by splenocytes from mice vaccinated with OMVs. OMV vaccinated mice developed significantly higher anti-Brucella IgG antibody titers at the end of the treatment compared to the mice that received only antibiotics. The mice that received only vaccines did not show any significant clearance of Brucella from spleens and livers compared to non-treated control mice. This study suggests that incorporating OMVs or irradiated B. neotomae along with conventional antibiotics might be able to improve therapeutic efficacy and control the progression of disease in treatment failure cases.

  2. In vitro model for lytic replication, latency, and transformation of an oncogenic alphaherpesvirus.

    Science.gov (United States)

    Schermuly, Julia; Greco, Annachiara; Härtle, Sonja; Osterrieder, Nikolaus; Kaufer, Benedikt B; Kaspers, Bernd

    2015-06-09

    Marek's disease virus (MDV) is an alphaherpesvirus that causes deadly T-cell lymphomas in chickens and serves as a natural small animal model for virus-induced tumor formation. In vivo, MDV lytically replicates in B cells that transfer the virus to T cells in which the virus establishes latency. MDV also malignantly transforms CD4+ T cells with a T(reg) signature, ultimately resulting in deadly lymphomas. No in vitro infection system for primary target cells of MDV has been available due to the short-lived nature of these cells in culture. Recently, we characterized cytokines and monoclonal antibodies that promote survival of cultured chicken B and T cells. We used these survival stimuli to establish a culture system that allows efficient infection of B and T cells with MDV. We were able to productively infect with MDV B cells isolated from spleen, bursa or blood cultured in the presence of soluble CD40L. Virus was readily transferred from infected B to T cells stimulated with an anti-TCRαVβ1 antibody, thus recapitulating the in vivo situation in the culture dish. Infected T cells could then be maintained in culture for at least 90 d in the absence of TCR stimulation, which allowed the establishment of MDV-transformed lymphoblastoid cell lines (LCL). The immortalized cells had a signature comparable to MDV-transformed CD4+ α/β T cells present in tumors. In summary, we have developed a novel in vitro system that precisely reflects the life cycle of an oncogenic herpesivrus in vivo and will allow us to investigate the interaction between virus and target cells in an easily accessible system.

  3. Informatics and Physics Models of Recognitions of DNA Replication and Their Biological Applications

    Directory of Open Access Journals (Sweden)

    Kang Cheng

    2006-01-01

    Full Text Available We initially propose concepts of Informative Intensity, Informative Response Intensity and Informative Flux, with different expressions. In a special expression of electrostatics, we describe Informative Intensity, Informative Response Intensity and Informative Flux in terms of electric field intensity, electric field force and electric field flux respectively. In a special expression of quantum mechanics, we originally propose a concept of Probability Flux. Then we present Informative Intensity in terms of a wave function of Schrödinger equation and Informative Response Intensity in terms of an interactive force between or among objects, Informative Flux in terms of a probability flux. Based on these concepts, we develop our Informatics and physics models of recognitions between a DNA polymerase and an initiation site and of pairing deoxyribonucleotides, for a natural DNA replication, beyond lengths of chemical bounds and half quantitatively explain a probability of the wrong paring. We originally hypothesize the information is, stored in structured charges or masses, transmitted with Informative Intensity in a media and recognized with an Informative Response Intensity by other structured charges or masses. We further generalize, Informative Intensity as multiple layers of fields, potentials or waves, Informative Response Intensity as multiple layers of forces and Informative Flux as an integration of Informative Intensity. We also initially define Transverse Information: Informative Intensity is perpendicular to the direction of information propagation, e.g. electromagnetic wave or magnetic field; and Longitudinal Information: Informative Intensity is parallel or antiparalell to the direction of information propagation, e.g. electric field or gravitational field.

  4. The thorny path linking cellular senescence to organismalaging

    Energy Technology Data Exchange (ETDEWEB)

    Patil, Christopher K.; Mian, Saira; Campisi, Judith

    2005-08-09

    Half a century is fast approaching since Hayflick and colleagues formally described the limited ability of normal human cells to proliferate in culture (Hayflick and Moorhead, 1961). This finding--that normal somatic cells, in contrast to cancer cells, cannot divide indefinitely--challenged the prevailing idea that cells from mortal multicellular organisms were intrinsically ''immortal'' (Carrell, 1912). It also spawned two hypotheses, essential elements of which persist today. The first held that the restricted proliferation of normal cells, now termed cellular senescence, suppresses cancer (Hayflick, 1965; Sager, 1991; Campisi, 2001). The second hypothesis, as explained in the article by Lorenzini et al., suggested that the limited proliferation of cells in culture recapitulated aspects of organismal aging (Hayflick, 1965; Martin, 1993). How well have these hypotheses weathered the ensuing decades? Before answering this question, we first consider current insights into the causes and consequences of cellular senescence. Like Lorenzini et al., we limit our discussion to mammals. We also focus on fibroblasts, the cell type studied by Lorenzini et al., but consider other types as well. We suggest that replicative capacity in culture is not a straightforward assessment, and that it correlates poorly with both longevity and body mass. We speculate this is due to the malleable and variable nature of replicative capacity, which renders it an indirect metric of qualitative and quantitative differences among cells to undergo senescence, a response that directly alters cellular phenotype and might indirectly alter tissue structure and function.

  5. Senescence in fishes

    Energy Technology Data Exchange (ETDEWEB)

    Woodhead, A.D.

    1979-01-01

    A long-standing theory, that there is a fundamental difference in aging between fishes and higher vertebrates, is still alive in the minds of many. In 1932, Bidder proposed that aging was causatively related to the cessation of growth at sexual maturity. Fish, which continue to grow throughout their lives, would not age, and therefore were potentially immortal. His ideas were clearly disproven by Comfort, who established that the survival curves of a laboratory population of guppies, Poecilia reticulata, were very similar to those of a small mammal population under laboratory conditions. Recent data from field and laboratory studies, including histological evidence, amply confirm the occurrence of senescence in fishes. Natural death in fish has been associated with reproduction. There is good evidence for a number of species which shows that, with increasing size, the gonad forms a greater proportion of total body weight. In older, larger fish, extensive energy depletion for reproduction is suggested as an important factor in mortality. Reproductive modifications in older fish are also noted.

  6. hnRNP A1 antagonizes cellular senescence and senescence-associated secretory phenotype via regulation of SIRT1 mRNA stability.

    Science.gov (United States)

    Wang, Hui; Han, Limin; Zhao, Ganye; Shen, Hong; Wang, Pengfeng; Sun, Zhaomeng; Xu, Chenzhong; Su, Yuanyuan; Li, Guodong; Tong, Tanjun; Chen, Jun

    2016-09-09

    Senescent cells display a senescence-associated secretory phenotype (SASP) which contributes to tumor suppression, aging, and cancer. However, the underlying mechanisms for SASP regulation are not fully elucidated. SIRT1, a nicotinamide adenosine dinucleotide-dependent deacetylase, plays multiple roles in metabolism, inflammatory response, and longevity, etc. However, its posttranscriptional regulation and its roles in cellular senescence and SASP regulation are still elusive. Here, we identify the RNA-binding protein hnRNP A1 as a posttranscriptional regulator of SIRT1, as well as cell senescence and SASP regulator. hnRNP A1 directly interacts with the 3' untranslated region of SIRT1 mRNA, promotes its stability, and increases SIRT1 expression. hnRNP A1 delays replicative cellular senescence and prevents from Ras OIS via upregulation of SIRT1 expression to deacetylate NF-κB, thus blunting its transcriptional activity and subsequent IL-6/IL-8 induction. hnRNP A1 overexpression promotes cell transformation and tumorigenesis in a SIRT1-dependent manner. Together, our findings unveil a novel posttranscriptional regulation of SIRT1 by hnRNP A1 and uncover a critical role of hnRNP A1-SIRT1-NF-κB pathway in regulating cellular senescence and SASP expression. © 2016 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.

  7. CAROTENOID CLEAVAGE DIOXYGENASE 7 modulates plant growth, reproduction, senescence, and determinate nodulation in the model legume Lotus japonicas

    NARCIS (Netherlands)

    Liu, J.; Novero, M.; Charnikhova, T.; Ferrandino, A.; Schubert, A.; Ruyter-Spira, C.P.; Biofante, P.; Lovisolo, C.; Bouwmeester, H.J.

    2013-01-01

    Strigolactones (SLs) are newly identified hormones that regulate multiple aspects of plant development, infection by parasitic weeds, and mutualistic symbiosis in the roots. In this study, the role of SLs was studied for the first time in the model plant Lotus japonicus using transgenic lines silenc

  8. Biological varience in the colour of Granny Smith apples Modelling the effect of senescence and chilling injury

    NARCIS (Netherlands)

    Tijskens, L.M.M.; Konopacki, P.; Schouten, R.E.; Hribar, J.; Simcic, M.

    2008-01-01

    The colour of `Granny Smith¿ apples, harvested from three orchards at two stages of maturity, was measured individually using the CIE L*a*b* system during storage in regular atmosphere at three temperatures: 1, 4 and 10 °C. A model was developed based on a simplified mechanism to describe the develo

  9. Database Replication

    CERN Document Server

    Kemme, Bettina

    2010-01-01

    Database replication is widely used for fault-tolerance, scalability and performance. The failure of one database replica does not stop the system from working as available replicas can take over the tasks of the failed replica. Scalability can be achieved by distributing the load across all replicas, and adding new replicas should the load increase. Finally, database replication can provide fast local access, even if clients are geographically distributed clients, if data copies are located close to clients. Despite its advantages, replication is not a straightforward technique to apply, and

  10. Chitosan Treatment Delays the Induction of Senescence in Human Foreskin Fibroblast Strains.

    Directory of Open Access Journals (Sweden)

    Ching-Wen Tsai

    Full Text Available Fibroblasts have been extensively used as a model to study cellular senescence. The purpose of this study was to investigate whether the human foreskin fibroblast aging process could be regulated by using the biomaterial chitosan. Fibroblasts cultured on commercial tissue culture polystyrene (TCPS entered senescence after 55-60 population doublings (PDs, and were accompanied by larger cell shape, higher senescence-associated β-galactosidase (SA β-gal activity, lower proliferation capacity, and upregulation of senescence-associated molecular markers p21, p53, retinoblastoma (pRB, and p16. Before senescence was reached, PD48 cells were collected from TCPS and seeded on chitosan for three days (PD48-Cd3 to form multicellular spheroids. The protein expression of senescence-associated secretory phenotypes (SASPs and senescence-associated molecular markers of these cells in PD48-Cd3 spheroids were downregulated significantly. Following chitosan treatment, fibroblasts reseeded on TCPS showed lower SA β-gal activity, increased cellular motility, and a higher proliferation ability of 70-75 PDs. These phenotypic changes were not accompanied by colonies forming in soft agar and a continuous decrease in the senescence-associated proteins p53 and pRB which act as a barrier to tumorigenesis. These results demonstrate that chitosan treatment could delay the induction of senescence which may be useful and safe for future tissue engineering applications.

  11. Replicating animal mitochondrial DNA

    Directory of Open Access Journals (Sweden)

    Emily A. McKinney

    2013-01-01

    Full Text Available The field of mitochondrial DNA (mtDNA replication has been experiencing incredible progress in recent years, and yet little is certain about the mechanism(s used by animal cells to replicate this plasmid-like genome. The long-standing strand-displacement model of mammalian mtDNA replication (for which single-stranded DNA intermediates are a hallmark has been intensively challenged by a new set of data, which suggests that replication proceeds via coupled leading-and lagging-strand synthesis (resembling bacterial genome replication and/or via long stretches of RNA intermediates laid on the mtDNA lagging-strand (the so called RITOLS. The set of proteins required for mtDNA replication is small and includes the catalytic and accessory subunits of DNA polymerase y, the mtDNA helicase Twinkle, the mitochondrial single-stranded DNA-binding protein, and the mitochondrial RNA polymerase (which most likely functions as the mtDNA primase. Mutations in the genes coding for the first three proteins are associated with human diseases and premature aging, justifying the research interest in the genetic, biochemical and structural properties of the mtDNA replication machinery. Here we summarize these properties and discuss the current models of mtDNA replication in animal cells.

  12. Modelling of the isothermal replication of surface microstructures in polymer melts

    DEFF Research Database (Denmark)

    Rasmussen, Henrik Koblitz; Eriksson, Torbjörn Gerhard

    2005-01-01

    to the incoming molten plastic flow. Just before the flow-front of the melt reached the end of the inserts the polymer was frozen. The replicated PC and PS micro-structures were examined using a confocal laser scanning microscope. Uniaxial elongational viscosity and linear viscoelasticity were used...

  13. Interactions Between Temperature and Sugars in the Regulation of Leaf Senescence in the Perennial Herb Arabis alpina L.

    Institute of Scientific and Technical Information of China (English)

    Astrid Wingler; Emma Josefine Stangberg; Triambak Saxena; Rupal Mistry

    2012-01-01

    Annual plants usually flower and set seed once before senescence results in the death of the whole plant (monocarpic senescence).Leaf senescence also occurs in polycarpic perennials; even in "evergreen" species individual leaves senesce.In the annual model Arabidopsis thaliana sugars accumulate in the senescent leaves and senescence is accelerated by high sugar availability.Similar to A.thaliana,sugar contents increased with leaf age in the perennial Arabis alpina grown under warm conditions (22 ℃day/18 night).At 5 ℃,sugar contents in non-senescent leaves were higher than at a warm temperature,but dependent on the accession,either sugars did not accumulate or their contents decreased in old leaves.In A.alpina plants grown in their natural habitat in the Alps,sugar contents declined with leaf age.Growth at a cold temperature slightly delayed senescence in A.alpina.In both warm and cold conditions,an external glucose supply accelerated senescence,but natural variation was found in this response.In conclusion,sugar accumulation under warm conditions could accelerate leaf senescence in A.alpina plants,but genotype-specific responses and interactions with growth temperature are likely to influence senescence under natural conditions.

  14. A primary care Web-based Intervention Modeling Experiment replicated behavior changes seen in earlier paper-based experiment

    OpenAIRE

    Treweek, S.; Francis, JJ; Bonetti, D; Barnett, K; Eccles, MP; Hudson, J.; Jones, C.; Pitts, NB; Ricketts, IW; Sullivan, F; Weal, M; MacLennan, G.

    2016-01-01

    OBJECTIVES: Intervention Modeling Experiments (IMEs) are a way of developing and testing behavior change interventions before a trial. We aimed to test this methodology in a Web-based IME that replicated the trial component of an earlier, paper-based IME. STUDY DESIGN AND SETTING: Three-arm, Web-based randomized evaluation of two interventions (persuasive communication and action plan) and a "no intervention" comparator. The interventions were designed to reduce the number of antibiotic p...

  15. Oxidative stress and leaf senescence

    Directory of Open Access Journals (Sweden)

    Sedigheh Hatami

    2011-11-01

    Full Text Available Abstract Background Senescence is an important developmental process that leads to the cell death through highly regulated genetically controlled processes in plants. Biotic and abiotic Oxidative stresses can also artificially induce senescence and increase the production of reactive oxygen species (ROS specifically in chloroplast. One of the important oxidative stresses is paraquat that induces deviation of electron from photosynthesis electron chain and lead to the production of more ROS in chloroplast. Plants have evolved special adoptive mechanism to reallocate nutrient to reproductive and juvenile organs in senescence and different oxidative stresses. Rubisco seems to be the most abundant protein in plants and is involved in many changes during senescence. Results In the present study, the effects of ROS on Rubisco during senescence and oxidative stresses were evaluated by measuring photosynthesis factors such as net photosynthesis rate (Pn, stomatal conductance (G, evaporation rate (E, intra cellular CO2 concentration (Ci, fluorescence and total protein during three stages of development. Our results showed that in paraquat treated plants, CO2 assimilation is the most effective factor that refers to Rubisco damages. The highest correlation and regression coefficient belonged to Ci, while correlation coefficient between photosynthesis rate and total protein was much smaller. Conclusion It appears in the early stage of oxidative stresses such as exposing to paraquat, ROS has the most effect on Rubisco activity that induces more susceptibility to Rubisco specific protease. Moreover, Rubisco deactivation acts as an initiative signal for Rubisco degradation.

  16. miR-29c-3p promotes senescence of human mesenchymal stem cells by targeting CNOT6 through p53-p21 and p16-pRB pathways.

    Science.gov (United States)

    Shang, Jin; Yao, Yuan; Fan, Xin; Shangguan, Lei; Li, Jie; Liu, Huan; Zhou, Yue

    2016-04-01

    Mesenchymal stem cells (MSCs) are important seed cells for tissue engineering and are promising targets for cell-based therapies. However, the replicative senescence of MSCs during in vitro culture limits their research and clinical applications. The molecular mechanisms underlying the replicative senescence of MSCs are not fully understood. Evidence suggests that miRNAs play important roles in replicative senescence. A microarray analysis found that the miR-29c-3p level was significantly increased during the MSC senescence process. In our study, we investigated the roles of miR-29c-3p in senescence of MSCs. We cultured MSCs for long periods of time, up and down-regulated the miR-29c-3p expression in MSCs, and examined the senescent phenotype changes. The over-expression of miR-29c-3p led to enhanced senescence-associated-β-galactosidase (SA-β-gal) staining, senescence associated secretory phenotype (SASP), senescence associated heterochromatic foci (SAHF), reduced proliferation ability, retarded osteogenic differentiation and corresponding changes in senescence markers, whereas the miR-29c-3p down-regulation had the opposite results. Dual-luciferase reporter assays demonstrated that CNOT6 is the target gene of miR-29c-3p. Knockdown of CNOT6 confirmed its inhibitory effects on the senescence of MSCs. In addition, Western blot results showed that both the p53-p21 and the p16-pRB pathways were activated during the miR-29c-3p-induced senescence of MSCs. In conclusion, our results demonstrate that miR-29c-3p promotes the senescence of MSCs by targeting CNOT6 through p53-p21 and p16-pRB pathways and highlight the contribution of post-transcriptional regulation to stem cell senescence.

  17. Validation, replication, and sensitivity testing of Heckman-type selection models to adjust estimates of HIV prevalence.

    Directory of Open Access Journals (Sweden)

    Samuel J Clark

    Full Text Available A recent study using Heckman-type selection models to adjust for non-response in the Zambia 2007 Demographic and Health Survey (DHS found a large correction in HIV prevalence for males. We aim to validate this finding, replicate the adjustment approach in other DHSs, apply the adjustment approach in an external empirical context, and assess the robustness of the technique to different adjustment approaches. We used 6 DHSs, and an HIV prevalence study from rural South Africa to validate and replicate the adjustment approach. We also developed an alternative, systematic model of selection processes and applied it to all surveys. We decomposed corrections from both approaches into rate change and age-structure change components. We are able to reproduce the adjustment approach for the 2007 Zambia DHS and derive results comparable with the original findings. We are able to replicate applying the approach in several other DHSs. The approach also yields reasonable adjustments for a survey in rural South Africa. The technique is relatively robust to how the adjustment approach is specified. The Heckman selection model is a useful tool for assessing the possibility and extent of selection bias in HIV prevalence estimates from sample surveys.

  18. Escape from premature senescence is not sufficient for oncogenic transformation by Ras

    NARCIS (Netherlands)

    Peeper, D.S.; Dannenberg, J.-H.; Douma, S.; Riele, H. te; Bernards, R.A.

    2001-01-01

    Resistance of primary cells to transformation by oncogenic Ras has been attributed to the induction of replicative growth arrest1, 2, 3. This irreversible 'fail-safe mechanism' resembles senescence and requires induction by Ras of p19ARF and p53 (refs 3−5). Mutation of either p19ARF or p53 alleviate

  19. Nuclear accumulation of Yes-Associated Protein (YAP) maintains the survival of doxorubicin-induced senescent cells by promoting survivin expression.

    Science.gov (United States)

    Ma, Kai; Xu, Qing; Wang, Shuren; Zhang, Weina; Liu, Mei; Liang, Shufang; Zhu, Hongxia; Xu, Ningzhi

    2016-05-28

    Although chemotherapeutic drugs can induce senescence to prohibit further division of tumor cells, senescence could also promote tumorigenesis mainly through a senescence-associated secretory phenotype. Therefore, senescent tumor cells should be eliminated immediately to prevent drug resistance and recurrence. Here, we used a doxorubicin-induced senescence model to explore the mechanism underlying the survival of therapy-induced senescent cells. After low-dose doxorubicin treatment, tumor cells turned on a senescence program and became large and flattened, increasing their contact area with the extracellular matrix (ECM). Furthermore, Yes-associated protein (YAP) accumulated in the nucleus and YAP activity was increased in doxorubicin-induced senescent cells. Knockdown of YAP increased the sensitivity of cells to low-dose doxorubicin treatment, causing apoptosis rather than senescence. Moreover, the anti-apoptotic gene survivin, a YAP target gene, was overexpressed in senescent cells. Inhibition of survivin could lead to selective elimination of senescent cells through apoptosis. Our study indicates that nuclear accumulation of YAP could promote the survival of senescent cells by increasing survivin expression. Therefore, targeting YAP or survivin might be a new strategy for clearing senescent cancer cells during drug treatment.

  20. Predatory senescence in ageing wolves

    Science.gov (United States)

    MacNulty, D.R.; Smith, D.W.; Vucetich, J.A.; Mech, L.D.; Stahler, D.R.; Packer, C.

    2009-01-01

    It is well established that ageing handicaps the ability of prey to escape predators, yet surprisingly little is known about how ageing affects the ability of predators to catch prey. Research into long-lived predators has assumed that adults have uniform impacts on prey regardless of age. Here we use longitudinal data from repeated observations of individually-known wolves (Canis lupus) hunting elk (Cervus elaphus) in Yellowstone National Park to demonstrate that adult predatory performance declines with age and that an increasing ratio of senescent individuals in the wolf population depresses the rate of prey offtake. Because this ratio fluctuates independently of population size, predatory senescence may cause wolf populations of equal size but different age structure to have different impacts on prey populations. These findings suggest that predatory senescence is an important, though overlooked, factor affecting predator-prey dynamics. ?? 2009 Blackwell Publishing Ltd/CNRS.

  1. Selective insulin resistance in hepatocyte senescence

    Energy Technology Data Exchange (ETDEWEB)

    Aravinthan, Aloysious [Division of Gastroenterology and Hepatology, Department of Medicine, University of Cambridge, Cambridge (United Kingdom); Challis, Benjamin [Institute of Metabolic Sciences, University of Cambridge, Cambridge (United Kingdom); Shannon, Nicholas [Cancer Research UK Cambridge Institute, Cambridge (United Kingdom); Hoare, Matthew [Division of Gastroenterology and Hepatology, Department of Medicine, University of Cambridge, Cambridge (United Kingdom); Cancer Research UK Cambridge Institute, Cambridge (United Kingdom); Heaney, Judith [Division of Gastroenterology and Hepatology, Department of Medicine, University of Cambridge, Cambridge (United Kingdom); Foundation for Liver Research, Institute of Hepatology, London (United Kingdom); Alexander, Graeme J.M., E-mail: gja1000@doctors.org.uk [Division of Gastroenterology and Hepatology, Department of Medicine, University of Cambridge, Cambridge (United Kingdom)

    2015-02-01

    Insulin resistance has been described in association with chronic liver disease for decades. Hepatocyte senescence has been demonstrated in chronic liver disease and as many as 80% of hepatocytes show a senescent phenotype in advanced liver disease. The aim of this study was to understand the role of hepatocyte senescence in the development of insulin resistance. Senescence was induced in HepG2 cells via oxidative stress. The insulin metabolic pathway was studied in control and senescent cells following insulin stimulation. GLUT2 and GLUT4 expressions were studied in HepG2 cells and human liver tissue. Further, GLUT2 and GLUT4 expressions were studied in three independent chronic liver disease cohorts. Signalling impairment distal to Akt in phosphorylation of AS160 and FoxO1 was evident in senescent HepG2 cells. Persistent nuclear localisation of FoxO1 was demonstrated in senescent cells despite insulin stimulation. Increased GLUT4 and decreased GLUT2 expressions were evident in senescent cells, human cirrhotic liver tissue and publically available liver disease datasets. Changes in GLUT expressions were associated with a poor clinical prognosis. In conclusion, selective insulin resistance is evident in senescent HepG2 cells and changes in GLUT expressions can be used as surrogate markers of hepatocyte senescence. - Highlights: • Senescent hepatocytes demonstrate selective insulin resistance. • GLUT changes act as markers of hepatocyte senescence and have prognostic value. • Study offers insight into long noticed intimacy of cirrhosis and insulin resistance.

  2. Cluster-cluster aggregation with particle replication and chemotaxy: a simple model for the growth of animal cells in culture

    Science.gov (United States)

    Alves, S. G.; Martins, M. L.

    2010-09-01

    Aggregation of animal cells in culture comprises a series of motility, collision and adhesion processes of basic relevance for tissue engineering, bioseparations, oncology research and in vitro drug testing. In the present paper, a cluster-cluster aggregation model with stochastic particle replication and chemotactically driven motility is investigated as a model for the growth of animal cells in culture. The focus is on the scaling laws governing the aggregation kinetics. Our simulations reveal that in the absence of chemotaxy the mean cluster size and the total number of clusters scale in time as stretched exponentials dependent on the particle replication rate. Also, the dynamical cluster size distribution functions are represented by a scaling relation in which the scaling function involves a stretched exponential of the time. The introduction of chemoattraction among the particles leads to distribution functions decaying as power laws with exponents that decrease in time. The fractal dimensions and size distributions of the simulated clusters are qualitatively discussed in terms of those determined experimentally for several normal and tumoral cell lines growing in culture. It is shown that particle replication and chemotaxy account for the simplest cluster size distributions of cellular aggregates observed in culture.

  3. Calculating the Rate of Senescence From Mortality Data: An Analysis of Data From the ERA-EDTA Registry.

    Science.gov (United States)

    Koopman, Jacob J E; Rozing, Maarten P; Kramer, Anneke; Abad, José M; Finne, Patrik; Heaf, James G; Hoitsma, Andries J; De Meester, Johan M J; Palsson, Runolfur; Postorino, Maurizio; Ravani, Pietro; Wanner, Christoph; Jager, Kitty J; van Bodegom, David; Westendorp, Rudi G J

    2016-04-01

    The rate of senescence can be inferred from the acceleration by which mortality rates increase over age. Such a senescence rate is generally estimated from parameters of a mathematical model fitted to these mortality rates. However, such models have limitations and underlying assumptions. Notably, they do not fit mortality rates at young and old ages. Therefore, we developed a method to calculate senescence rates from the acceleration of mortality directly without modeling the mortality rates. We applied the different methods to age group-specific mortality data from the European Renal Association-European Dialysis and Transplant Association Registry, including patients with end-stage renal disease on dialysis, who are known to suffer from increased senescence rates (n = 302,455), and patients with a functioning kidney transplant (n = 74,490). From age 20 to 70, senescence rates were comparable when calculated with or without a model. However, when using non-modeled mortality rates, senescence rates were yielded at young and old ages that remained concealed when using modeled mortality rates. At young ages senescence rates were negative, while senescence rates declined at old ages. In conclusion, the rate of senescence can be calculated directly from non-modeled mortality rates, overcoming the disadvantages of an indirect estimation based on modeled mortality rates.

  4. Senescent mesenchymal cells accumulate in human fibrosis by a telomere-independent mechanism and ameliorate fibrosis through matrix metalloproteinases.

    Science.gov (United States)

    Pitiyage, Gayani Nadika; Slijepcevic, Predrag; Gabrani, Aliya; Chianea, Yaghoub Gozaly; Lim, Kue Peng; Prime, Stephen Stewart; Tilakaratne, Wanninayake Mudiyanselage; Fortune, Farida; Parkinson, Eric Kenneth

    2011-04-01

    Fibrosis can occur in many organs, where it is a debilitating and preneoplastic condition. The senescence of activated fibroblasts has been proposed to ameliorate fibrosis via the innate immune system but its role in humans has not been investigated. The availability of oral submucous fibrosis (OSMF) biopsies at different stages of disease progression allowed us to test the hypothesis that senescent fibroblasts accumulate with the progression of human fibrosis in vivo, and also to examine the mechanism of senescence. We tested the hypothesis that senescent cells may ameliorate fibrosis by increasing the secretion of matrix metalloproteinases (MMPs). We have used a combination of in situ immunodetection techniques, drug treatments, fluorescence-activated cell sorting and enzyme-linked absorbance assays on tissue samples and fibroblast cultures. We report a novel panning technique, based on fibronectin adhesion rates, to enrich and deplete senescent cells from fibroblast populations. Senescent fibroblasts, as determined by the presence of senescence-associated heterochromatic foci, accumulated with OSMF progression (R(2) = 0.98) and possessed a reduced replicative lifespan in vitro. Unlike wounds, however, OSMF fibroblasts were quiescent in vivo and consistent with this observation, possessed functional telomeres of normal length. Senescence was associated in vivo and in vitro with oxidative damage, DNA damage foci and p16(INK4A) accumulation and required the production of reactive oxygen species (ROS), perhaps from damaged mitochondria, but not the continuous presence of the disease stimulus (areca nut and tobacco), the tissue environment or other cell types. Depletion of OSMF fibroblasts of senescent cells showed that these cells accounted for 25-83 times more MMP-1 and -2 than their pre-senescent counterparts. The results show that the accumulation of senescent fibroblasts in human fibrosis occurs by a telomere-independent mechanism involving ROS and may locally

  5. The inhibitory mechanism of Cordyceps sinensis on cigarette smoke extract-induced senescence in human bronchial epithelial cells.

    Science.gov (United States)

    Liu, Ailing; Wu, Jinxiang; Li, Aijun; Bi, Wenxiang; Liu, Tian; Cao, Liuzhao; Liu, Yahui; Dong, Liang

    2016-01-01

    Cellular senescence is a state of irreversible growth arrest induced either by telomere shortening (replicative senescence) or stress. The bronchial epithelial cell is often injured by inhaled toxic substances, such as cigarette smoke. In the present study, we investigated whether exposure to cigarette smoke extract (CSE) induces senescence of bronchial epithelial cells; and Cordyceps sinensis mechanism of inhibition of CSE-induced cellular senescence. Human bronchial epithelial cells (16HBE cells) cultured in vitro were treated with CSE and/or C. sinensis. p16, p21, and senescence-associated-galactosidase activity were used to detect cellular senescence with immunofluorescence, quantitative polymerase chain reaction, and Western blotting. Reactive oxygen species (ROS), PI3K/AKT/mTOR and their phosphorylated proteins were examined to testify the activation of signaling pathway by ROS fluorescent staining and Western blotting. Then, inhibitors of ROS and PI3K were used to further confirm the function of this pathway. Cellular senescence was upregulated by CSE treatment, and C. sinensis can decrease CSE-induced cellular senescence. Activation of ROS/PI3K/AKT/mTOR signaling pathway was enhanced by CSE treatment, and decreased when C. sinensis was added. Blocking ROS/PI3K/AKT/mTOR signaling pathway can attenuate CSE-induced cellular senescence. CSE can induce cellular senescence in human bronchial epithelial cells, and ROS/PI3K/AKT/mTOR signaling pathway may play an important role in this process. C. sinensis can inhibit the CSE-induced senescence.

  6. [Research progress of cellular senescence and senescent secretary phenotype in intervertebral disc degeneration].

    Science.gov (United States)

    Wang, Feng; Zheng, Chenjingmei; Wu, Xiaotao

    2012-12-01

    To summarize the role of cellular senescence and senescent secretary phenotype in the intervertebral disc (IVD) degeneration. Relevant articles that discussed the roles of cellular senescence in the IVD degeneration were extensively reviewed, and retrospective and comprehensive analysis was performed. The senescent phenomenon during IVD degeneration, senescent secretary phenotype of the disc cells, senescent pathways within the IVD microenvironment, as well as the anti-senescent approaches for IVD regeneration were systematically reviewed. During aging and degeneration, IVD cells gradually and/or prematurely undergo senescence by activating p53-p21-retinoblastoma (RB) or p161NK4A-RB senescent pathways. The accumulation of senescent cells not only decreases the self-renewal ability of IVD, but also deteriorates the disc microenvironment by producing more inflammatory cytokines and matrix degrading enzymes. More specific senescent biomarkers are required to fully understand the phenotype change of senescent disc cells during IVD degeneration. Molecular analysis of the senescent disc cells and their intracellular signaling pathways are needed to get a safer and more efficient anti-senescence strategy for IVD regeneration. Cellular senescence is an important mechanism by which IVD cells decrease viability and degenerate biological behaviors, which provide a new thinking to understand the pathogenesis of IVD degeneration.

  7. Actuarial senescence in a long-lived orchid challenges our current understanding of ageing

    DEFF Research Database (Denmark)

    Dahlgren, Johan; Colchero, Fernando; Jones, Owen

    2016-01-01

    The dominant evolutionary theory of actuarial senescence – an increase in death rate with advancing age – is based on the concept of a germ cell line that is separated from the somatic cells early in life. However, such a separation is not clear in all organisms. This has been suggested to explain...... the paucity of evidence for actuarial senescence in plants. We used a 32-year study of Dactylorhiza lapponica that replaces its organs each growing season, to test whether individuals of this tuberous orchid senesce. We performed a Bayesian survival trajectory analysis accounting for reproductive investment......, for individuals under two types of land-use, in two climatic regions. The mortality trajectory was best-approximated by a Weibull model, showing clear actuarial senescence. Rates of senescence in this model declined with advancing age, but were slightly higher in mown plots and in the more benign climatic region...

  8. Actuarial senescence in a long-lived orchid challenges our current understanding of ageing

    DEFF Research Database (Denmark)

    Dahlgren, Johan; Colchero, Fernando; Jones, Owen;

    2016-01-01

    The dominant evolutionary theory of actuarial senescence – an increase in death rate with advancing age – is based on the concept of a germ cell line that is separated from the somatic cells early in life. However, such a separation is not clear in all organisms. This has been suggested to explain...... the paucity of evidence for actuarial senescence in plants. We used a 32-year study of Dactylorhiza lapponica that replaces its organs each growing season, to test whether individuals of this tuberous orchid senesce. We performed a Bayesian survival trajectory analysis accounting for reproductive investment......, for individuals under two types of land-use, in two climatic regions. The mortality trajectory was best-approximated by a Weibull model, showing clear actuarial senescence. Rates of senescence in this model declined with advancing age, but were slightly higher in mown plots and in the more benign climatic region...

  9. Detection of cellular senescence within human invasive breast carcinomas distinguishes different breast tumor subtypes.

    Science.gov (United States)

    Cotarelo, Cristina L; Schad, Arno; Kirkpatrick, Charles James; Sleeman, Jonathan P; Springer, Erik; Schmidt, Marcus; Thaler, Sonja

    2016-11-15

    Oncogene-induced senescence is thought to act as a barrier to tumorigenesis by arresting cells at risk of malignant transformation. Nevertheless, numerous findings suggest that senescent cells may conversely promote tumor progression through the development of the senescence-associated secretome they produce. It is likely that the composition and the physiological consequences mediated by the senescence secretome are dependent on the oncogenes that trigger the senescence program. Breast cancer represents a heterogenous disease that can be divided into breast cancer subtypes due to different subsets of genetic and epigenetic abnormalities. As tumor initiation and progression of these breast cancer subtypes is triggered by diverse oncogenic stimuli, differences in the senescence secretomes within breast tumors might be responsible for tumor initiation, progression, metastasis and therapeutic response. Many studies have addressed the role of senescence as a barrier to tumor progression using murine xenograft models. However, few investigations have been performed to elucidate the degree to which senescent tumor cells are present within untreated human tumors, and if present, whether these senescent tumor cells may play a role in disease progression. In the present study we analysed the appearance of senescent cells within invasive breast cancers. Detection of cellular senescence by the use of SAβ-galactosidase (SAβ-gal) staining within invasive breast carcinoms from 129 untreated patients revealed differences in the amount of SAβ-gal+ tumor cells between breast cancer subtypes. The highest percentages of SAβ-gal+ tumor cells were found in HER2-positive and luminal A breast carcinomas whereas triple negative tumors showed either little or no positivity.

  10. [Replication of the subgenomic hepatitis C virus replicon in the presence of the NS3 protease inhibitors: a stochastic model].

    Science.gov (United States)

    Ivanisenko, N V; Mishchenko, E L; Akberdin, I R; Demenkov, P S; Likhoshvai, V A; Kozlov, K N; Todorov, D I; Samsonova, M G; Samsonov, A M; Kolchanov, N A; Ivanisenko, V A

    2013-01-01

    The hepatitis C virus (HCV) belongs to Flaviviridae family and causes hazardous liver diseases leading frequently to cirrhosis and hepatocellular carcinoma. HCV is able to rapidly acquire drug resistance and for this reason there is currently no effective anti-HCV therapy in spite of appearance of new potential drugs. Mathematical models are relevant to predict the efficacy of potential drugs against virus or host targets. One of the promising targets for development of new drugs is the viral NS3 protease. Here we developed a stochastic model of the subgenomic HCV replicon replication in Huh-7 cells and in the presence of the NS3 protease inhibitors. Along with consideration of the stochastic nature of the subgenomic HCV replicon replication the model takes into account the existence and generation of main NS3 protease drug resistant mutants, namely BILN-2061 (A156T, D168V, R155Q), VX-950 (A156S, A156T, T54A) and SCH-503034 (A156T, A156S, T54A). The model reproduces well the viral RNA kinetics in the cell from the moment of the subgenomic HCV replicon transfection to steady state, as well as the viral RNA suppression kinetics in the presence of NS3 protease inhibitors BILN-2061, VX-950 and SCH-503034. We showed that the resistant mutants should be taken into account for the correct description of biphasic kinetics of the viral RNA suppression. The mutants selected in the presence of different inhibitor concentrations have maximal replication capacity in the given inhibitor concentration range. Our model can be used to interpret the results of the new anti-HCV drug testing in replicon systems, as well as to predict the efficacy of new potential drugs and optimize the regimen of their use.

  11. Effect of cell cycle inhibitor p19ARF on senescence of human diploid cell

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    To investigate the effect of cell cycle inhibitor p19ARF on replicative senescence of human diploid cell, recombinant p19ARF eukaryotic expression vector was constructed and p19ARF gene was transfected into human diploid fibroblasts (WI-38 cells) by liposome-mediated transfection for overexpression. Then, the effects of p19ARF on replicative senescence of WI-38 cells were observed. The results re- vealed that, compared with control cells, the WI-38 cells in which p19ARF gene was introduced showed significant up-regulation of p53 and p21 expression level, decrease of cell generation by 10 12 generations, decline of cell growth rate with cell cycle being arrested at G1 phase, increase of positive rate of senescent marker SA-β-gal staining, and decrease of mitochondrial membrane potential. The morphology of the transfected fibroblasts presented the characteristics changes similar to senescent cells. These results indicated that high expression of p19ARF may promote the senescent process of human diploid cells.

  12. The microtubule stabilizing agent discodermolide is a potent inducer of accelerated cell senescence.

    Science.gov (United States)

    Klein, Laura E; Freeze, B Scott; Smith, Amos B; Horwitz, Susan Band

    2005-03-01

    Discodermolide is a microtubule stabilizing agent that suppresses dynamic instability and blocks cells in mitosis. Selection of A549 nonsmall cell lung carcinoma cells with increasing concentrations of discodermolide yielded a clone that proliferated in 8 nM. When these cells were exposed to any concentration greater than 8 nM, replication ceased and the cells developed a flattened, enlarged, granular morphology. Accelerated senescence was demonstrated by a functional beta-galactosidase activity at pH 6. When parental A549 cells were treated with IC50-concentrations of doxorubicin, Taxol or discodermolide, the latter two drugs quickly produced aberrant mitosis. However, discodermolide, but not Taxol, also produced a large increase in senescence-associated beta-galactosidase activity and altered levels of known senescence markers. Although some of these differences between Taxol and discodermolide were dose dependent, only discodermolide produced a doxorubicin-like induction of a senescence phenotype, including a senescence-associated beta-galactosidase activity, up-regulation of PAI-1 and p66Shc, and a strong, sustained, Erk1/2 activation. This research provides insights into the mechanism of action of discodermolide and provides the first demonstration of a microtubule stabilizing agent that inhibits tumor cell growth with a powerful induction of accelerated senescence.

  13. Herança da senescência retardada em milho Inheritance of the delayed senescence in maize

    Directory of Open Access Journals (Sweden)

    Emiliano Fernandes Nassau Costa

    2008-02-01

    Full Text Available O objetivo deste trabalho foi estudar a herança da senescência retardada em milho. Foram realizados cruzamentos dialélicos parciais entre 50 linhagens e cinco testadores. Os 250 cruzamentos resultantes, além de seis híbridos comerciais utilizados como testemunhas, foram avaliados em oito ambientes, no delineamento látice simples 16x16, com duas repetições por ambiente. Os cruzamentos dialélicos foram analisados utilizando o método 4 do modelo 1 de Griffing, adaptado para múltiplos ambientes. A contribuição da capacidade geral de combinação (CGC para a expressão do caráter "stay-green" (69,06% foi maior que a da capacidade específica de combinação (CEC (30,94%, evidenciando que os efeitos aditivos são mais importantes que os efeitos não aditivos na expressão deste caráter. Tanto a CGC como a CEC interagiram significativamente com o ambiente, indicando que a seleção para este caráter deve ser realizada com base nas médias de experimentos em diversos ambientes.The objective of this research was to study the inheritance of delayed senescence in maize. Partial diallel crosses among 50 inbred lines and five testers were made. The 250 crosses, along with six commercial hybrids used as checks, were evaluated at eight environments in lattices 16x16 with two replications per environment. The diallel crosses were analyzed following the method 4 model 1 of Griffing, extended to multiple environments. The contribution of the general combining ability (CGA for the expression of the stay-green trait (69.06% was greater than the specific combining ability (SCA (30.94%, showing that additive effects are more important than non-additive effects for the expression of this trait. Both GCA and SCA interacted significantly with the environments, indicating that the selection for this trait should be based on the means across environments.

  14. The Yin-Yang of DNA Damage Response: Roles in Tumorigenesis and Cellular Senescence

    Directory of Open Access Journals (Sweden)

    Sang Soo Kim

    2013-01-01

    Full Text Available Senescent cells are relatively stable, lacking proliferation capacity yet retaining metabolic activity. In contrast, cancer cells are rather invasive and devastating, with uncontrolled proliferative capacity and resistance to cell death signals. Although tumorigenesis and cellular senescence are seemingly opposite pathological events, they are actually driven by a unified mechanism: DNA damage. Integrity of the DNA damage response (DDR network can impose a tumorigenesis barrier by navigating abnormal cells to cellular senescence. Compromise of DDR, possibly due to the inactivation of DDR components, may prevent cellular senescence but at the expense of tumor formation. Here we provide an overview of the fundamental role of DDR in tumorigenesis and cellular senescence, under the light of the Yin-Yang concept of Chinese philosophy. Emphasis is placed on discussing DDR outcome in the light of in vivo models. This information is critical as it can help make better decisions for clinical treatments of cancer patients.

  15. Hematopoietic stem cell ageing is uncoupled from p16 INK4A-mediated senescence.

    Science.gov (United States)

    Attema, J L; Pronk, C J H; Norddahl, G L; Nygren, J M; Bryder, D

    2009-06-04

    Somatic stem cells are ultimately responsible for mediating appropriate organ homeostasis and have therefore been proposed to represent a cellular origin of the ageing process-a state often characterized by inappropriate homeostasis. Specifically, it has been suggested that ageing stem cells might succumb to replicative senescence by a mechanism involving the cyclin-dependent kinase inhibitor p16(INK4A). Here, we tested multiple functional and molecular parameters indicative of p16(INK4A) activity in primary aged murine hematopoietic stem cells (HSCs). We found no evidence that replicative senescence accompanies stem cell ageing in vivo, and in line with p16(INK4A) being a critical determinant of such processes, most aged HSCs (>99%) failed to express p16(INK4A) at the mRNA level. Moreover, whereas loss of epigenetically guided repression of the INK4A/ARF locus accompanied replicative senescent murine embryonic fibroblasts, such repression was maintained in aged stem cells. Taken together, these studies indicate that increased senescence as mediated by the p16(INK4A) tumor suppressor has only a minor function as an intrinsic regulator of steady-state HSC ageing in vivo.

  16. Intracellular Oxidant Activity, Antioxidant Enzyme Defense System, and Cell Senescence in Fibroblasts with Trisomy 21

    Directory of Open Access Journals (Sweden)

    Víctor Rodríguez-Sureda

    2015-01-01

    Full Text Available Down’s syndrome (DS is characterized by a complex phenotype associated with chronic oxidative stress and mitochondrial dysfunction. Overexpression of genes on chromosome-21 is thought to underlie the pathogenesis of the major phenotypic features of DS, such as premature aging. Using cultured fibroblasts with trisomy 21 (T21F, this study aimed to ascertain whether an imbalance exists in activities, mRNA, and protein expression of the antioxidant enzymes SOD1, SOD2, glutathione-peroxidase, and catalase during the cell replication process in vitro. T21F had high SOD1 expression and activity which led to an interenzymatic imbalance in the antioxidant defense system, accentuated with replicative senescence. Intracellular ROS production and oxidized protein levels were significantly higher in T21F compared with control cells; furthermore, a significant decline in intracellular ATP content was detected in T21F. Cell senescence was found to appear prematurely in DS cells as shown by SA-β-Gal assay and p21 assessment, though not apoptosis, as neither p53 nor the proapoptotic proteins cytochrome c and caspase 9 were altered in T21F. These novel findings would point to a deleterious role of oxidatively modified molecules in early cell senescence of T21F, thereby linking replicative and stress-induced senescence in cultured cells to premature aging in DS.

  17. Eukaryotic DNA Replication Fork.

    Science.gov (United States)

    Burgers, Peter M J; Kunkel, Thomas A

    2017-06-20

    This review focuses on the biogenesis and composition of the eukaryotic DNA replication fork, with an emphasis on the enzymes that synthesize DNA and repair discontinuities on the lagging strand of the replication fork. Physical and genetic methodologies aimed at understanding these processes are discussed. The preponderance of evidence supports a model in which DNA polymerase ε (Pol ε) carries out the bulk of leading strand DNA synthesis at an undisturbed replication fork. DNA polymerases α and δ carry out the initiation of Okazaki fragment synthesis and its elongation and maturation, respectively. This review also discusses alternative proposals, including cellular processes during which alternative forks may be utilized, and new biochemical studies with purified proteins that are aimed at reconstituting leading and lagging strand DNA synthesis separately and as an integrated replication fork.

  18. The many unknowns concerning the bioenergetics of exhaustion and senescence during chronic viral infection

    Directory of Open Access Journals (Sweden)

    Anna eSchurich

    2014-09-01

    Full Text Available The immune system cannot be continuously reactivated throughout the lifetime of an organism, there is a finite point at which repeated antigenic challenge leads to the loss of lymphocyte function or the cells themselves. Antigen-specific T cells can be compromised in two ways through the distinct processes of replicative senescence and exhaustion. Senescence is initiated by a DNA damage response whereas exhaustion triggers inhibitory receptors to dampen the immune response. These two distinct pathways not only differ in their initiation but growing evidence suggests that their bioenergetics is also different. We review here recent findings uncovering the metabolism of these unique states.

  19. Empirical evidence of senescence in adult damselflies (Odonata: Zygoptera).

    Science.gov (United States)

    Sherratt, T N; Laird, R A; Hassall, C; Lowe, C D; Harvey, I F; Watts, P C; Cordero-Rivera, A; Thompson, D J

    2010-09-01

    1. Age-dependent increases in mortality have been documented in a variety of species of insect under laboratory conditions. However, while strong statistical evidence has been presented for senescence in vertebrate populations in the wild, we know little about the rate and shape of senescence in wild populations of insects. 2. Odonates (damselflies and dragonflies) provide excellent candidate species for evaluating demographic senescence as they are large enough to be marked individually and they are easily re-sighted without recapture. The prevailing opinion - based entirely on qualitative examination of the declines in log numbers alive with time since marking - is that odonates exhibit age-independent daily survivorship. 3. Here, we examine mark-recapture data on the Azure Damselfly Coenagrion puella over two consecutive seasons. For the first time, we evaluate and compare the fit of quantitative models that not only account for weather-dependent daily variation in daily re-sighting rates, but also age-dependent variation in daily survivorship. 4. Models with age-dependent declines in daily survivorship provide a more parsimonious explanation for the data than similar models without these age-dependent effects. In general, models in which mortality increases in an exponential (Gompertz) fashion explain the mark-recapture sequences more efficiently than a range of alternative models, including those in which mortality increases as a power function (Weibull) or reaches a plateau (logistic). These results are indicative of a general senescent decline in physiological functioning, which is particularly marked after 15 days as a mature adult. 5. Weather (temperature, sun and precipitation) and initial mite load influenced the probability of daily re-sighting. Weather and mite load also influenced daily survivorship, but their effects differed between seasons. 6. Overall, fitting models with age as an explicit covariate demonstrates that odonates do indeed senesce

  20. Myc and Ras oncogenes engage different energy metabolism programs and evoke distinct patterns of oxidative and DNA replication stress.

    Science.gov (United States)

    Maya-Mendoza, Apolinar; Ostrakova, Jitka; Kosar, Martin; Hall, Arnaldur; Duskova, Pavlina; Mistrik, Martin; Merchut-Maya, Joanna Maria; Hodny, Zdenek; Bartkova, Jirina; Christensen, Claus; Bartek, Jiri

    2015-03-01

    Both Myc and Ras oncogenes impact cellular metabolism, deregulate redox homeostasis and trigger DNA replication stress (RS) that compromises genomic integrity. However, how are such oncogene-induced effects evoked and temporally related, to what extent are these kinetic parameters shared by Myc and Ras, and how are these cellular changes linked with oncogene-induced cellular senescence in different cell context(s) remain poorly understood. Here, we addressed the above-mentioned open questions by multifaceted comparative analyses of human cellular models with inducible expression of c-Myc and H-RasV12 (Ras), two commonly deregulated oncoproteins operating in a functionally connected signaling network. Our study of DNA replication parameters using the DNA fiber approach and time-course assessment of perturbations in glycolytic flux, oxygen consumption and production of reactive oxygen species (ROS) revealed the following results. First, overabundance of nuclear Myc triggered RS promptly, already after one day of Myc induction, causing slow replication fork progression and fork asymmetry, even before any metabolic changes occurred. In contrast, Ras overexpression initially induced a burst of cell proliferation and increased the speed of replication fork progression. However, after several days of induction Ras caused bioenergetic metabolic changes that correlated with slower DNA replication fork progression and the ensuing cell cycle arrest, gradually leading to senescence. Second, the observed oncogene-induced RS and metabolic alterations were cell-type/context dependent, as shown by comparative analyses of normal human BJ fibroblasts versus U2-OS sarcoma cells. Third, the energy metabolic reprogramming triggered by Ras was more robust compared to impact of Myc. Fourth, the detected oncogene-induced oxidative stress was due to ROS (superoxide) of non-mitochondrial origin and mitochondrial OXPHOS was reduced (Crabtree effect). Overall, our study provides novel

  1. Differential senescence in feto-maternal tissues during mouse pregnancy.

    Science.gov (United States)

    Bonney, Elizabeth A; Krebs, Kendall; Saade, George; Kechichian, Talar; Trivedi, Jayshil; Huaizhi, Yin; Menon, Ramkumar

    2016-07-01

    Human studies show that fetal membranes have a limited lifespan and undergo telomere-dependent cellular senescence that is augmented by oxidative stress and mediated by p38 mitogen activated protein kinase (MAPK). Further, these studies suggest that fetal membranes are anatomically and physiologically positioned to transmit senescence signals that may initiate parturition at term. Longitudinal evaluation of feto-maternal tissues from mouse pregnancies was undertaken to determine the molecular progression of senescence during normal pregnancy. On days 10-18 of gestation, C57BL/6 mice were euthanized. Fetal membranes, placenta, and decidua/uterus were collected. Tissues were examined for Telomere length (TL) and the presence of Phosphorylated (P) p38MAPK and p53, p21 and senescence associated β-Galactosidase (SA- β-Gal). Linear regression modeling of observed telomere length as a function of gestational age revealed that beta (β), the slope of the linear regression was negative and significantly different from zero for each tissue (fetal membranes, β = -0.1901 ± 0.03125, p < 0.0001; placenta β = -0.09000 ± 0.03474, p = 0.0135; decidua/uterus β = -0.1317 ± 0.03264, p = 0.0003). Progressive activation p38MAPK was observed in all tissues from days 10 to day18, with the highest activation observed in fetal membranes. Activation of p53 was progressive in fetal membranes. In contrast, active p53 was constitutive in placenta and decidua/uterus throughout gestation. Detection of p21 indicated that pro-senescent change was higher in all compartments on day 18 as compared to other days. The number of SA-β-Gal positive cells increased in fetal membranes as gestation progressed. However, in placenta and uterus and decidua/uterus SA-β-Gal was seen only in days 15 and 18. Telomere dependent p38 and p53 mediated senescence progressed in mouse fetal membranes as gestation advanced. Although senescence is evident, telomere dependent events were not

  2. A genetic analysis of senescence in Drosophila.

    Science.gov (United States)

    Hughes, K A; Charlesworth, B

    1994-01-06

    Two attractive theories for the evolution of senescence are based on the principle that the force of natural selection decreases with age. The theories differ in the type of age-specific gene action that they assume. Antagonistic pleiotropy postulates that pleiotropic genes with positive effects early in life and negative effects of comparable magnitude late in life are favoured by selection, whereas genes with the reverse pattern of action are selected against. Mutation accumulation assumes that deleterious mutant alleles with age-specific effects will equilibrate at a lower frequency if their effects are expressed early rather than late in life. Explicit models demonstrate that both mechanisms can lead to the evolution of senescent life histories under reasonable conditions. Antagonistic pleiotropy has gained considerable empirical support, but the evidence in support of mutation accumulation is more sparse. Here we report that the genetic variability of mortality in male Drosophila melanogaster increases greatly at very late ages, as predicted by the mutation accumulation hypothesis. The rate of increase in mortality with age exhibits substantial genetic and environmental variability. This result provides a possible explanation for recent observations of non-increasing mortality rates in very old flies.

  3. Cellular senescence and the aging brain.

    Science.gov (United States)

    Chinta, Shankar J; Woods, Georgia; Rane, Anand; Demaria, Marco; Campisi, Judith; Andersen, Julie K

    2015-08-01

    Cellular senescence is a potent anti-cancer mechanism that arrests the proliferation of mitotically competent cells to prevent malignant transformation. Senescent cells accumulate with age in a variety of human and mouse tissues where they express a complex 'senescence-associated secretory phenotype' (SASP). The SASP includes many pro-inflammatory cytokines, chemokines, growth factors and proteases that have the potential to cause or exacerbate age-related pathology, both degenerative and hyperplastic. While cellular senescence in peripheral tissues has recently been linked to a number of age-related pathologies, its involvement in brain aging is just beginning to be explored. Recent data generated by several laboratories suggest that both aging and age-related neurodegenerative diseases are accompanied by an increase in SASP-expressing senescent cells of non-neuronal origin in the brain. Moreover, this increase correlates with neurodegeneration. Senescent cells in the brain could therefore constitute novel therapeutic targets for treating age-related neuropathologies.

  4. The oxidative hypothesis of senescence.

    Science.gov (United States)

    Gilca, M; Stoian, I; Atanasiu, V; Virgolici, B

    2007-01-01

    The oxidative hypothesis of senescence, since its origin in 1956, has garnered significant evidence and growing support among scientists for the notion that free radicals play an important role in ageing, either as "damaging" molecules or as signaling molecules. Age-increasing oxidative injuries induced by free radicals, higher susceptibility to oxidative stress in short-lived organisms, genetic manipulations that alter both oxidative resistance and longevity and the anti-ageing effect of caloric restriction and intermittent fasting are a few examples of accepted scientific facts that support the oxidative theory of senescence. Though not completely understood due to the complex "network" of redox regulatory systems, the implication of oxidative stress in the ageing process is now well documented. Moreover, it is compatible with other current ageing theories (e.g, those implicating the mitochondrial damage/mitochondrial-lysosomal axis, stress-induced premature senescence, biological "garbage" accumulation, etc). This review is intended to summarize and critically discuss the redox mechanisms involved during the ageing process: sources of oxidant agents in ageing (mitochondrial -electron transport chain, nitric oxide synthase reaction- and non-mitochondrial- Fenton reaction, microsomal cytochrome P450 enzymes, peroxisomal beta -oxidation and respiratory burst of phagocytic cells), antioxidant changes in ageing (enzymatic- superoxide dismutase, glutathione-reductase, glutathion peroxidase, catalase- and non-enzymatic glutathione, ascorbate, urate, bilirubine, melatonin, tocopherols, carotenoids, ubiquinol), alteration of oxidative damage repairing mechanisms and the role of free radicals as signaling molecules in ageing.

  5. The oxidative hypothesis of senescence

    Directory of Open Access Journals (Sweden)

    Gilca M

    2007-01-01

    Full Text Available The oxidative hypothesis of senescence, since its origin in 1956, has garnered significant evidence and growing support among scientists for the notion that free radicals play an important role in ageing, either as "damaging" molecules or as signaling molecules. Age-increasing oxidative injuries induced by free radicals, higher susceptibility to oxidative stress in short-lived organisms, genetic manipulations that alter both oxidative resistance and longevity and the anti-ageing effect of caloric restriction and intermittent fasting are a few examples of accepted scientific facts that support the oxidative theory of senescence. Though not completely understood due to the complex "network" of redox regulatory systems, the implication of oxidative stress in the ageing process is now well documented. Moreover, it is compatible with other current ageing theories (e.g., those implicating the mitochondrial damage/mitochondrial-lysosomal axis, stress-induced premature senescence, biological "garbage" accumulation, etc. This review is intended to summarize and critically discuss the redox mechanisms involved during the ageing process: sources of oxidant agents in ageing (mitochondrial -electron transport chain, nitric oxide synthase reaction- and non-mitochondrial- Fenton reaction, microsomal cytochrome P450 enzymes, peroxisomal β -oxidation and respiratory burst of phagocytic cells, antioxidant changes in ageing (enzymatic- superoxide dismutase, glutathione-reductase, glutathion peroxidase, catalase- and non-enzymatic glutathione, ascorbate, urate, bilirubine, melatonin, tocopherols, carotenoids, ubiquinol, alteration of oxidative damage repairing mechanisms and the role of free radicals as signaling molecules in ageing.

  6. The SETD8/PR-Set7 Methyltransferase Functions as a Barrier to Prevent Senescence-Associated Metabolic Remodeling

    Directory of Open Access Journals (Sweden)

    Hiroshi Tanaka

    2017-02-01

    Full Text Available Cellular senescence is an irreversible growth arrest that contributes to development, tumor suppression, and age-related conditions. Senescent cells show active metabolism compared with proliferating cells, but the underlying mechanisms remain unclear. Here we show that the SETD8/PR-Set7 methyltransferase, which catalyzes mono-methylation of histone H4 at lysine 20 (H4K20me1, suppresses nucleolar and mitochondrial activities to prevent cellular senescence. SETD8 protein was selectively downregulated in both oncogene-induced and replicative senescence. Inhibition of SETD8 alone was sufficient to trigger senescence. Under these states, the expression of genes encoding ribosomal proteins (RPs and ribosomal RNAs as well as the cyclin-dependent kinase (CDK inhibitor p16INK4A was increased, with a corresponding reduction of H4K20me1 at each locus. As a result, the loss of SETD8 concurrently stimulated nucleolar function and retinoblastoma protein-mediated mitochondrial metabolism. In conclusion, our data demonstrate that SETD8 acts as a barrier to prevent cellular senescence through chromatin-mediated regulation of senescence-associated metabolic remodeling.

  7. Proteome oxidative carbonylation during oxidative stress-induced premature senescence of WI-38 human fibroblasts

    DEFF Research Database (Denmark)

    Le Boulch, Marine; Ahmed, Emad K; Rogowska-Wrzesinska, Adelina

    2017-01-01

    Accumulation of oxidatively damaged proteins is a hallmark of cellular and organismal ageing, and is also a phenotypic feature shared by both replicative senescence and stress-induced premature senescence of human fibroblasts. Moreover, proteins that are building up as oxidized (i.e. the "Oxi......-proteome") during ageing and age-related diseases represent a restricted set of cellular proteins, indicating that certain proteins are more prone to oxidative carbonylation and subsequent intracellular accumulation. The occurrence of specific carbonylated proteins upon oxidative stress induced premature senescence...... of WI-38 human fibroblasts and their follow-up identification have been addressed in this study. Indeed, it was expected that the identification of these proteins would give insights into the mechanisms by which oxidatively damaged proteins could affect cellular function. Among these proteins, some...

  8. Replication of type 5 adenovirus promotes middle ear infection by Streptococcus pneumoniae in the chinchilla model of otitis media

    Science.gov (United States)

    Murrah, Kyle A.; Turner, Roberta L.; Pang, Bing; Perez, Antonia C.; Reimche, Jennifer L.; King, Lauren B.; Wren, John; Gandhi, Uma; Swords, W. Edward; Ornelles, David A.

    2015-01-01

    Adenoviral infection is a major risk factor for otitis media. We hypothesized that adenovirus promotes bacterial ascension into the middle ear through the disruption of normal function in the Eustachian tubes due to inflammation-induced changes. An intranasal infection model of the chinchilla was used to test the ability of type 5 adenovirus to promote middle ear infection by Streptococcus pneumoniae. The hyperinflammatory adenovirus mutant dl327 and the nonreplicating adenovirus mutant H5wt300ΔpTP were used to test the role of inflammation and viral replication, respectively, in promotion of pneumococcal middle ear infection. Precedent infection with adenovirus resulted in a significantly greater incidence of middle ear disease by S. pneumoniae as compared to nonadenovirus infected animals. Infection with the adenovirus mutant dl327 induced a comparable degree of bacterial ascension into the middle ear as did infection with the wild-type virus. By contrast, infection with the nonreplicating adenovirus mutant H5wt300ΔpTP resulted in less extensive middle ear infection compared to the wild-type adenovirus. We conclude that viral replication is necessary for adenoviral-induced pneumococcal middle ear disease. PMID:25251686

  9. A primary care Web-based Intervention Modeling Experiment replicated behavior changes seen in earlier paper-based experiment.

    Science.gov (United States)

    Treweek, Shaun; Francis, Jill J; Bonetti, Debbie; Barnett, Karen; Eccles, Martin P; Hudson, Jemma; Jones, Claire; Pitts, Nigel B; Ricketts, Ian W; Sullivan, Frank; Weal, Mark; MacLennan, Graeme

    2016-12-01

    Intervention Modeling Experiments (IMEs) are a way of developing and testing behavior change interventions before a trial. We aimed to test this methodology in a Web-based IME that replicated the trial component of an earlier, paper-based IME. Three-arm, Web-based randomized evaluation of two interventions (persuasive communication and action plan) and a "no intervention" comparator. The interventions were designed to reduce the number of antibiotic prescriptions in the management of uncomplicated upper respiratory tract infection. General practitioners (GPs) were invited to complete an online questionnaire and eight clinical scenarios where an antibiotic might be considered. One hundred twenty-nine GPs completed the questionnaire. GPs receiving the persuasive communication did not prescribe an antibiotic in 0.70 more scenarios (95% confidence interval [CI] = 0.17-1.24) than those in the control arm. For the action plan, GPs did not prescribe an antibiotic in 0.63 (95% CI = 0.11-1.15) more scenarios than those in the control arm. Unlike the earlier IME, behavioral intention was unaffected by the interventions; this may be due to a smaller sample size than intended. A Web-based IME largely replicated the findings of an earlier paper-based study, providing some grounds for confidence in the IME methodology. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. Targeting DNA Replication Stress for Cancer Therapy

    Science.gov (United States)

    Zhang, Jun; Dai, Qun; Park, Dongkyoo; Deng, Xingming

    2016-01-01

    The human cellular genome is under constant stress from extrinsic and intrinsic factors, which can lead to DNA damage and defective replication. In normal cells, DNA damage response (DDR) mediated by various checkpoints will either activate the DNA repair system or induce cellular apoptosis/senescence, therefore maintaining overall genomic integrity. Cancer cells, however, due to constitutive growth signaling and defective DDR, may exhibit “replication stress” —a phenomenon unique to cancer cells that is described as the perturbation of error-free DNA replication and slow-down of DNA synthesis. Although replication stress has been proven to induce genomic instability and tumorigenesis, recent studies have counterintuitively shown that enhancing replicative stress through further loosening of the remaining checkpoints in cancer cells to induce their catastrophic failure of proliferation may provide an alternative therapeutic approach. In this review, we discuss the rationale to enhance replicative stress in cancer cells, past approaches using traditional radiation and chemotherapy, and emerging approaches targeting the signaling cascades induced by DNA damage. We also summarize current clinical trials exploring these strategies and propose future research directions including the use of combination therapies, and the identification of potential new targets and biomarkers to track and predict treatment responses to targeting DNA replication stress. PMID:27548226

  11. Targeting DNA Replication Stress for Cancer Therapy

    Directory of Open Access Journals (Sweden)

    Jun Zhang

    2016-08-01

    Full Text Available The human cellular genome is under constant stress from extrinsic and intrinsic factors, which can lead to DNA damage and defective replication. In normal cells, DNA damage response (DDR mediated by various checkpoints will either activate the DNA repair system or induce cellular apoptosis/senescence, therefore maintaining overall genomic integrity. Cancer cells, however, due to constitutive growth signaling and defective DDR, may exhibit “replication stress” —a phenomenon unique to cancer cells that is described as the perturbation of error-free DNA replication and slow-down of DNA synthesis. Although replication stress has been proven to induce genomic instability and tumorigenesis, recent studies have counterintuitively shown that enhancing replicative stress through further loosening of the remaining checkpoints in cancer cells to induce their catastrophic failure of proliferation may provide an alternative therapeutic approach. In this review, we discuss the rationale to enhance replicative stress in cancer cells, past approaches using traditional radiation and chemotherapy, and emerging approaches targeting the signaling cascades induced by DNA damage. We also summarize current clinical trials exploring these strategies and propose future research directions including the use of combination therapies, and the identification of potential new targets and biomarkers to track and predict treatment responses to targeting DNA replication stress.

  12. Early needle senescence and thinning of the crown structure of Picea abies as induced by chronic SO{sub 2} pollution. 1. Model deduction and analysis

    Energy Technology Data Exchange (ETDEWEB)

    Slovik, S. [Universitaet Wuerzburg, Wuerzburg (Germany). Julius von Sachs Inst. fuer Biowissenschaften

    1996-10-01

    Regarding time ranges of years, a rationale has been developed which is capable of explaining `spruce decline` symptoms observed when spruce is exposed to air containing ambient levels of SO{sub 2}. It integrates and interrelates (1) ecophysiological data (tree morphology, assimilate partitioning, canopy turnover, senescence physiology, stomatal conductance, canopy throughfall, sulphur metabolism, tonoplast symport), (2) pedological data (soil leaching, cation recycling, litter decomposition, forest nutrition), and (3) meteorological data (site elevation, length of the annual trunk growth period, SO{sub 2}-pollution). It can also explain field observations at numerous sites of spruce decline in central Europe where SO{sub 2} is implicated as a factor of forest decline: (1) thinning of the canopy structure; (2) early needle senescence; (3) cation deficiency; (4) low SO{sub 2} tolerance at sites with depleted soils in the mountains; (5) synergism of SO{sub 2} pollution and acidic precipitation; (6) recovery after liming, fertilization and after decreasing SO{sub 2} pollution; and (7) higher SO{sub 2} tolerances of deciduous angiosperms. Different SO{sub 2} tolerance strategies are identified. Ecophysiological SO{sub 2} tolerance factors interact in a complex synergistic or antagonistic manner. It is concluded that chronic SO{sub 2} pollution at ambient concentrations predisposes evergreen gymnosperms to suffer under synergistic environmental stresses (frost, drought, pathogenes, etc.). Thinning of the crown structure is massive at extreme sites, where several stresses act simultaneously on the trees. This universal rationale, which is applicable to all tree species, is exemplified here for Norway spruce (Picea abies).

  13. Universal sequence replication, reversible polymerization and early functional biopolymers: a model for the initiation of prebiotic sequence evolution.

    Directory of Open Access Journals (Sweden)

    Sara Imari Walker

    Full Text Available Many models for the origin of life have focused on understanding how evolution can drive the refinement of a preexisting enzyme, such as the evolution of efficient replicase activity. Here we present a model for what was, arguably, an even earlier stage of chemical evolution, when polymer sequence diversity was generated and sustained before, and during, the onset of functional selection. The model includes regular environmental cycles (e.g. hydration-dehydration cycles that drive polymers between times of replication and functional activity, which coincide with times of different monomer and polymer diffusivity. Template-directed replication of informational polymers, which takes place during the dehydration stage of each cycle, is considered to be sequence-independent. New sequences are generated by spontaneous polymer formation, and all sequences compete for a finite monomer resource that is recycled via reversible polymerization. Kinetic Monte Carlo simulations demonstrate that this proposed prebiotic scenario provides a robust mechanism for the exploration of sequence space. Introduction of a polymer sequence with monomer synthetase activity illustrates that functional sequences can become established in a preexisting pool of otherwise non-functional sequences. Functional selection does not dominate system dynamics and sequence diversity remains high, permitting the emergence and spread of more than one functional sequence. It is also observed that polymers spontaneously form clusters in simulations where polymers diffuse more slowly than monomers, a feature that is reminiscent of a previous proposal that the earliest stages of life could have been defined by the collective evolution of a system-wide cooperation of polymer aggregates. Overall, the results presented demonstrate the merits of considering plausible prebiotic polymer chemistries and environments that would have allowed for the rapid turnover of monomer resources and for

  14. Universal Sequence Replication, Reversible Polymerization and Early Functional Biopolymers: A Model for the Initiation of Prebiotic Sequence Evolution

    Science.gov (United States)

    Walker, Sara Imari; Grover, Martha A.; Hud, Nicholas V.

    2012-01-01

    Many models for the origin of life have focused on understanding how evolution can drive the refinement of a preexisting enzyme, such as the evolution of efficient replicase activity. Here we present a model for what was, arguably, an even earlier stage of chemical evolution, when polymer sequence diversity was generated and sustained before, and during, the onset of functional selection. The model includes regular environmental cycles (e.g. hydration-dehydration cycles) that drive polymers between times of replication and functional activity, which coincide with times of different monomer and polymer diffusivity. Template-directed replication of informational polymers, which takes place during the dehydration stage of each cycle, is considered to be sequence-independent. New sequences are generated by spontaneous polymer formation, and all sequences compete for a finite monomer resource that is recycled via reversible polymerization. Kinetic Monte Carlo simulations demonstrate that this proposed prebiotic scenario provides a robust mechanism for the exploration of sequence space. Introduction of a polymer sequence with monomer synthetase activity illustrates that functional sequences can become established in a preexisting pool of otherwise non-functional sequences. Functional selection does not dominate system dynamics and sequence diversity remains high, permitting the emergence and spread of more than one functional sequence. It is also observed that polymers spontaneously form clusters in simulations where polymers diffuse more slowly than monomers, a feature that is reminiscent of a previous proposal that the earliest stages of life could have been defined by the collective evolution of a system-wide cooperation of polymer aggregates. Overall, the results presented demonstrate the merits of considering plausible prebiotic polymer chemistries and environments that would have allowed for the rapid turnover of monomer resources and for regularly varying monomer

  15. Modelling of the isothermal replication of surface microstructures in polymer melts

    DEFF Research Database (Denmark)

    Rasmussen, Henrik Koblitz; Eriksson, Torbjörn Gerhard

    2005-01-01

    The forming of micro surface structures on polymer materials is well established in polymer-processing operations. Numerical flow calculations were performed using the Lagrangian Integral Method where the fluid was described by a MSF constitutive model. The numerical modelling of the flow was per...

  16. A transcriptional roadmap to the senescence and differentiation of human oral keratinocytes.

    Science.gov (United States)

    Jang, Da Hyun; Bhawal, Ujjal K; Min, Hong-Ki; Kang, Hyun Ki; Abiko, Yoshimitsu; Min, Byung-Moo

    2015-01-01

    Human epithelial cells undergo morphological and molecular changes leading to terminal differentiation and replicative senescence after a finite number of cell divisions during serial subculture. However, the target genes and their functional significance in the senescence and differentiation in normal human oral keratinocytes have been poorly defined. Here, we demonstrated normal human oral keratinocytes transcriptional signature profiling to senescence and differentiation. Using microarray analysis, our findings indicated that the gene expression profiles induced by serial subculture are distinct classes of gene. The greatest number of these altered genes was identified as being related to biological pathways of transport, cell proliferation, cell cycle, defense and immune response, cell death, transcription, apoptosis, and inflammatory response, suggesting that the serial subculture is able to induce a multitude of specific gene expression changes during senescence and differentiation. Several highly upregulated genes (IL-1β, S100A8, S100A9, MMP1, MMP9, IL-8, BHLHB2, HES1, and TWIST1) in response to the serial subculture in normal human oral keratinocytes were observed. In vitro and in vivo studies also exhibited a close relationship between senescence and differentiation of primary oral keratinocytes and expression of inflammatory molecules. These results suggest a new approach to determine the biological events underlying the pathogenesis of oral keratinocyte aging. © The Author 2014. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  17. Regulation of cellular senescence by the essential caveolar component PTRF/Cavin-1

    Institute of Scientific and Technical Information of China (English)

    Lin Bai; Xiaoli Deng; Juanjuan Li; Miao Wang; Qian Li; Wei An; Deli A; Yu-Sheng Cong

    2011-01-01

    Polymerase I and transcript release factor (PTRF, also known as Cavin-1) is an essential component in the biogenesis and function of caveolae. Here, we show that PTRF expression is increased in senescent human fibroblasts.Importantly, overexpression of PTRF induced features characteristic of cellular senescence, whereas reduced PTRF expression extended the cellular replicative lifespan. Interestingly, we found that PTRF localized primarily to the nuclei of young and quiescent WI-38 human fibroblasts, but translocated to the cytosol and plasma membrane during cellular senescence. Furthermore, electron microscopic analysis demonstrated an increased number of caveolar structures in senescent and PTRF-transfected WI-38 cells. Our data suggest that the role of PTRF in cellular senes cence is dependent on its targeting to caveolae and its interaction with caveolin-l, which appeared to be regulated by the phosphorylation of PTRF. Taken together, our findings identify PTRF as a novel regulator of cellular senescence that acts through the p53/p21 and caveolar pathways.

  18. Rescuing loading induced bone formation at senescence.

    Directory of Open Access Journals (Sweden)

    Sundar Srinivasan

    Full Text Available The increasing incidence of osteoporosis worldwide requires anabolic treatments that are safe, effective, and, critically, inexpensive given the prevailing overburdened health care systems. While vigorous skeletal loading is anabolic and holds promise, deficits in mechanotransduction accrued with age markedly diminish the efficacy of readily complied, exercise-based strategies to combat osteoporosis in the elderly. Our approach to explore and counteract these age-related deficits was guided by cellular signaling patterns across hierarchical scales and by the insight that cell responses initiated during transient, rare events hold potential to exert high-fidelity control over temporally and spatially distant tissue adaptation. Here, we present an agent-based model of real-time Ca(2+/NFAT signaling amongst bone cells that fully described periosteal bone formation induced by a wide variety of loading stimuli in young and aged animals. The model predicted age-related pathway alterations underlying the diminished bone formation at senescence, and hence identified critical deficits that were promising targets for therapy. Based upon model predictions, we implemented an in vivo intervention and show for the first time that supplementing mechanical stimuli with low-dose Cyclosporin A can completely rescue loading induced bone formation in the senescent skeleton. These pre-clinical data provide the rationale to consider this approved pharmaceutical alongside mild physical exercise as an inexpensive, yet potent therapy to augment bone mass in the elderly. Our analyses suggested that real-time cellular signaling strongly influences downstream bone adaptation to mechanical stimuli, and quantification of these otherwise inaccessible, transient events in silico yielded a novel intervention with clinical potential.

  19. Evidence that a RecQ helicase slows senescence by resolving recombining telomeres.

    Directory of Open Access Journals (Sweden)

    Julia Y Lee

    2007-06-01

    Full Text Available RecQ helicases, including Saccharomyces cerevisiae Sgs1p and the human Werner syndrome protein, are important for telomere maintenance in cells lacking telomerase activity. How maintenance is accomplished is only partly understood, although there is evidence that RecQ helicases function in telomere replication and recombination. Here we use two-dimensional gel electrophoresis (2DGE and telomere sequence analysis to explore why cells lacking telomerase and Sgs1p (tlc1 sgs1 mutants senesce more rapidly than tlc1 mutants with functional Sgs1p. We find that apparent X-shaped structures accumulate at telomeres in senescing tlc1 sgs1 mutants in a RAD52- and RAD53-dependent fashion. The X-structures are neither Holliday junctions nor convergent replication forks, but instead may be recombination intermediates related to hemicatenanes. Direct sequencing of examples of telomere I-L in senescing cells reveals a reduced recombination frequency in tlc1 sgs1 compared with tlc1 mutants, indicating that Sgs1p is needed for tlc1 mutants to complete telomere recombination. The reduction in recombinants is most prominent at longer telomeres, consistent with a requirement for Sgs1p to generate viable progeny following telomere recombination. We therefore suggest that Sgs1p may be required for efficient resolution of telomere recombination intermediates, and that resolution failure contributes to the premature senescence of tlc1 sgs1 mutants.

  20. Parser for Sabin-to-Mahoney Transition Model of Quasispecies Replication

    Energy Technology Data Exchange (ETDEWEB)

    2016-01-03

    This code is a data parse for preparing output from the Qspp agent-based stochastic simulation model for plotting in Excel. This code is specific to a set of simulations that were run for the purpose of preparing data for a publication. It is necessary to make this code open-source in order to publish the model code (Qspp), which has already been released. There is a necessity of assuring that results from using Qspp for a publication

  1. Matching allele dynamics and coevolution in a minimal predator-prey replicator model

    Energy Technology Data Exchange (ETDEWEB)

    Sardanyes, Josep [Complex Systems Lab (ICREA-UPF), Barcelona Biomedical Research Park (PRBB-GRIB), Dr. Aiguader 88, 08003 Barcelona (Spain)], E-mail: josep.sardanes@upf.edu; Sole, Ricard V. [Complex Systems Lab (ICREA-UPF), Barcelona Biomedical Research Park (PRBB-GRIB), Dr. Aiguader 88, 08003 Barcelona (Spain); Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501 (United States)

    2008-01-21

    A minimal Lotka-Volterra type predator-prey model describing coevolutionary traits among entities with a strength of interaction influenced by a pair of haploid diallelic loci is studied with a deterministic time continuous model. We show a Hopf bifurcation governing the transition from evolutionary stasis to periodic Red Queen dynamics. If predator genotypes differ in their predation efficiency the more efficient genotype asymptotically achieves lower stationary concentrations.

  2. Knockin mice expressing a chimeric p53 protein reveal mechanistic differences in how p53 triggers apoptosis and senescence

    OpenAIRE

    2008-01-01

    The contribution of transcriptional activation to the p53 effector functions critical for tumor suppression, apoptosis and cellular senescence, remains unclear because of p53's ability to regulate diverse cellular processes in a transactivation-independent manner. Dissociating the importance of transactivation from other p53 functions, including regulating transcriptional repression, DNA replication, homologous recombination, centrosome duplication, and mitochondrial function, has been diffic...

  3. The load of short telomeres, estimated by a new method, Universal STELA, correlates with number of senescent cells

    DEFF Research Database (Denmark)

    Bendix, Laila; Horn, Peer Bendix; Jensen, Uffe Birk;

    2010-01-01

    Short telomeres are thought to trigger senescence, most likely through a single - or a group of few - critically shortened telomeres. Such short telomeres are thought to result from a combination of gradual linear shortening resulting from the end replication problem, reflecting the division hist...

  4. Oncogenic senescence: a multi-functional perspective

    NARCIS (Netherlands)

    Baker, D.J.; Alimirah, F.; Deursen, J.M.A. van; Campisi, J.; Hildesheim, J.

    2017-01-01

    Cellular senescence is defined as an irreversible growth arrest with the acquisition of a distinctive secretome. The growth arrest is a potent anticancer mechanism whereas the secretome facilitates wound healing, tissue repair, and development. The senescence response has also become increasingly

  5. Physiology and molecular biology of petal senescence

    NARCIS (Netherlands)

    Doorn, van W.G.; Woltering, E.J.

    2008-01-01

    Petal senescence is reviewed, with the main emphasis on gene expression in relation to physiological functions. Autophagy seems to be the major mechanism for large-scale degradation of macromolecules, but it is still unclear if it contributes to cell death. Depending on the species, petal senescence

  6. Physiology and molecular biology of petal senescence

    NARCIS (Netherlands)

    Doorn, van W.G.; Woltering, E.J.

    2008-01-01

    Petal senescence is reviewed, with the main emphasis on gene expression in relation to physiological functions. Autophagy seems to be the major mechanism for large-scale degradation of macromolecules, but it is still unclear if it contributes to cell death. Depending on the species, petal senescence

  7. Petal Senescence: New Concepts for Ageing Cells

    NARCIS (Netherlands)

    Woltering, E.J.; Doorn, van W.G.

    2009-01-01

    Senescence in flower petals can be regarded as a form of programmed cell death (PCD), being a process where cells or tissues are broken down in an orderly and predictable manner, whereby nutrients are re-used by other cells, tissues or plant parts. The process of petal senescence shows many

  8. Screening of microRNAs associated with Alzheimer's disease using oxidative stress cell model and different strains of senescence accelerated mice.

    Science.gov (United States)

    Zhang, Rui; Zhang, Qingfu; Niu, Jingya; Lu, Kang; Xie, Bing; Cui, Dongsheng; Xu, Shunjiang

    2014-03-15

    Oxidative stress plays a critical role in the etiology and pathogenesis of Alzheimer's disease (AD), and the molecular mechanisms that control the neuron response to oxidative stress have been extensively studied. However, the effects of oxidative stress on miRNA expression in hippocampal neurons has not been investigated, and little is known about the roles of ROS-modulated miRNAs in cell function as yet. In this study, miRNA microarray technology was used to analyze the expression of miRNAs in the oxidative stressed primary hippocampal neurons, hippocampus of senescence accelerated mouse prone 8 (SAMP8) and prone 10 (SAMP10). The targets of co-regulated microRNAs were also selected for computational prediction using miRWalk software and functional analysis by the DAVID software. In addition, the changes of co-regulated microRNA expression were validated by quantitative real-time PCR. The results of microarray analysis showed that miR-329, miR-193b, miR-20a, miR-296, and miR-130b were all upregulated in H2O2-induced primary hippocampal neurons and different strains of senescence accelerated mice. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that these co-regulated microRNAs may be involved in the regulation of cell growth, apoptosis, signal transmission and cancer development. In which, mitogen-activated protein kinase (MAPK) signaling pathway was one of the most significant pathways to be affected by 83 target genes of miR-329, miR-193b, miR-20a miR-296, and miR-130b. The quantitative real-time PCR data confirmed the alterations of the co-upregulated miRNAs. These results suggested that oxidative stress alters the miRNA expression profile of hippocampal neurons, and the deregulated miRNAs might play potential roles in the pathogenesis of neurodegenerative diseases, such as Alzheimer's disease (AD). This study provided a strong basis for the future study aiming at contributions of miRNAs induced by oxidative stress in AD.

  9. Anthropometric dependence of the response of a thorax FE model under high speed loading: validation and real world accident replication.

    Science.gov (United States)

    Roth, Sébastien; Torres, Fabien; Feuerstein, Philippe; Thoral-Pierre, Karine

    2013-05-01

    Finite element analysis is frequently used in several fields such as automotive simulations or biomechanics. It helps researchers and engineers to understand the mechanical behaviour of complex structures. The development of computer science brought the possibility to develop realistic computational models which can behave like physical ones, avoiding the difficulties and costs of experimental tests. In the framework of biomechanics, lots of FE models have been developed in the last few decades, enabling the investigation of the behaviour of the human body submitted to heavy damage such as in road traffic accidents or in ballistic impact. In both cases, the thorax/abdomen/pelvis system is frequently injured. The understanding of the behaviour of this complex system is of extreme importance. In order to explore the dynamic response of this system to impact loading, a finite element model of the human thorax/abdomen/pelvis system has, therefore, been developed including the main organs: heart, lungs, kidneys, liver, spleen, the skeleton (with vertebrae, intervertebral discs, ribs), stomach, intestines, muscles, and skin. The FE model is based on a 3D reconstruction, which has been made from medical records of anonymous patients, who have had medical scans with no relation to the present study. Several scans have been analyzed, and specific attention has been paid to the anthropometry of the reconstructed model, which can be considered as a 50th percentile male model. The biometric parameters and laws have been implemented in the dynamic FE code (Radioss, Altair Hyperworks 11©) used for dynamic simulations. Then the 50th percentile model was validated against experimental data available in the literature, in terms of deflection, force, whose curve must be in experimental corridors. However, for other anthropometries (small male or large male models) question about the validation and results of numerical accident replications can be raised.

  10. Possible Roles of Strigolactones during Leaf Senescence

    Directory of Open Access Journals (Sweden)

    Yusuke Yamada

    2015-09-01

    Full Text Available Leaf senescence is a complicated developmental process that involves degenerative changes and nutrient recycling. The progress of leaf senescence is controlled by various environmental cues and plant hormones, including ethylene, jasmonic acid, salicylic acid, abscisic acid, cytokinins, and strigolactones. The production of strigolactones is induced in response to nitrogen and phosphorous deficiency. Strigolactones also accelerate leaf senescence and regulate shoot branching and root architecture. Leaf senescence is actively promoted in a nutrient-poor soil environment, and nutrients are transported from old leaves to young tissues and seeds. Strigolactones might act as important signals in response to nutrient levels in the rhizosphere. In this review, we discuss the possible roles of strigolactones during leaf senescence.

  11. Replication of a Crisis Shelter Model of Care in Staff Secure Detention Programs.

    Science.gov (United States)

    Teare, John F.; Castrianno, Lynn M.; Novicoff, Carolyn D.; Peterson, Roger; Authier, Karen; Daly, Daniel

    This paper presents preliminary evidence for the effectiveness of a model of care designed to provide safe and effective services in both short-term shelter and short-term staff secure detention programs. Boys Town short-term crisis shelter programs were designed to provide a safe and therapeutic environment for homeless and runaway youth in need…

  12. Two different template replicators coexisting in the same protocell: stochastic simulation of an extended chemoton model.

    Directory of Open Access Journals (Sweden)

    István Zachar

    Full Text Available The simulation of complex biochemical systems, consisting of intertwined subsystems, is a challenging task in computational biology. The complex biochemical organization of the cell is effectively modeled by the minimal cell model called chemoton, proposed by Gánti. Since the chemoton is a system consisting of a large but fixed number of interacting molecular species, it can effectively be implemented in a process algebra-based language such as the BlenX programming language. The stochastic model behaves comparably to previous continuous deterministic models of the chemoton. Additionally to the well-known chemoton, we also implemented an extended version with two competing template cycles. The new insight from our study is that the coupling of reactions in the chemoton ensures that these templates coexist providing an alternative solution to Eigen's paradox. Our technical innovation involves the introduction of a two-state switch to control cell growth and division, thus providing an example for hybrid methods in BlenX. Further developments to the BlenX language are suggested in the Appendix.

  13. Learning from Television and Books: A Dutch Replication Study Based on Salomon's Model.

    Science.gov (United States)

    Beentjes, Johannes W. J.

    1989-01-01

    Discussion of the amount of mental effort children invest in television viewing versus book reading focuses on a Dutch study based on Salomon's model and his studies with children in Israel and the United States. The depth of information processed is discussed, and differences in results are examined. (18 references) (LRW)

  14. Economic Pressure in African American Families: A Replication and Extension of the Family Stress Model.

    Science.gov (United States)

    Conger, Rand D.; Wallace, Lora Ebert; Sun, Yumei; Simons, Ronald L.; McLoyd, Vonnie C.; Brody, Gene H.

    2002-01-01

    Evaluated applicability of family stress model of economic hardship for understanding economic influences on child development among African American families with a 10- or 11-year-old child. Found that economic hardship positively related to economic pressure in families, and to emotional distress of caregivers, which in turn damaged the…

  15. Replicating the Ice-Volume Signal of the Early Pleistocene with a Complex Earth System Model

    Science.gov (United States)

    Tabor, C. R.; Poulsen, C. J.; Pollard, D.

    2013-12-01

    Milankovitch theory proposes high-latitude summer insolation intensity paces the ice ages by controlling perennial snow cover amounts (Milankovitch, 1941). According to theory, the ~21 kyr cycle of precession should dominate the ice-volume records since it has the greatest influence on high-latitude summer insolation. Modeling experiments frequently support Milankovitch theory by attributing the majority of Northern Hemisphere high-latitude summer snowmelt to changes in the cycle of precession (e.g. Jackson and Broccoli, 2003). However, ice-volume proxy records, especially those of the Early Pleistocene (2.6-0.8 Ma), display variability with a period of ~41 kyr (Raymo and Lisiecki, 2005), indicative of insolation forcing from obliquity, which has a much smaller influence on summer insolation intensity than precession. Several hypotheses attempt to explain the discrepancies between Milkankovitch theory and the proxy records by invoking phenomena such as insolation gradients (Raymo and Nisancioglu, 2003), hemispheric offset (Raymo et al., 2006; Lee and Poulsen, 2009), and integrated summer energy (Huybers, 2006); however, all of these hypotheses contain caveats (Ruddiman, 2006) and have yet to be supported by modeling studies that use a complex GCM. To explore potential solutions to this '41 kyr problem,' we use an Earth system model composed of the GENESIS GCM and Land Surface model, the BIOME4 vegetation model, and the Pennsylvania State ice-sheet model. Using an asynchronous coupling technique, we run four idealized transient combinations of obliquity and precession, representing the orbital extremes of the Pleistocene (Berger and Loutre, 1991). Each experiment is run through several complete orbital cycles with a dynamic ice domain spanning North America and Greenland, and fixed preindustrial greenhouse-gas concentrations. For all orbital configurations, model results produce greater ice-volume spectral power at the frequency of obliquity despite significantly

  16. Validation of the Cyberchondria Severity Scale (CSS): replication and extension with bifactor modeling.

    Science.gov (United States)

    Norr, Aaron M; Allan, Nicholas P; Boffa, Joseph W; Raines, Amanda M; Schmidt, Norman B

    2015-04-01

    Internet help seeking behaviors are increasingly common. Despite the positives associated with technology, cyberchondria, or the process of increased anxiety in response to internet medical information seeking, is on the rise. The Cyberchondria Severity Scale (CSS) was recently developed to provide a valid measure of cyberchondria across multiple dimensions. The current study sought to extend previous work on the CSS factor structure by examining a bifactor model. Participants (N=526) from a community sample completed the CSS via online crowd sourcing. Results revealed that the bifactor model of the CSS provided superior fit to the data, suggesting that it is useful to conceptualize the CSS as containing a General Cyberchondria factor that is orthogonal to its subfactors. Similar to previous work, the CSS Mistrust factor does not appear to be necessary to this construct. Finally, results revealed unique relations between General and Specific Cyberchondria factors with lower-order health anxiety dimensions. Copyright © 2015. Published by Elsevier Ltd.

  17. Investigations for modelling hardness of biomedical implant during replication of FDM-based patterns by vacuum moulding

    Indian Academy of Sciences (India)

    RUPINDER SINGH; GURINDER SINGH

    2017-03-01

    In the present work, effort has been made for modelling the microhardness of biomedical implant prepared by combining fused deposition modelling, vacuum moulding and stir casting (SC) process. A dynamic condylar screw (DCS) plate was selected as a real ‘3D’ biomedical implant for this case study. The DCS plate,made of acrylonitrile butadiene styrene material, was fabricated as a master pattern by fused deposition modelling. After preparation of the master pattern, the mould cavity was fabricated by the vacuum moulding process.Finally a metal–matrix composite of Al and Al2O3 prepared by SC process has been poured in the vacuum mould for fabrication of DCS plate. This study outlines the replication procedure of DCS plate in detail from the master pattern to final product. The contribution of the paper is towards finding out the effect and optimumvalues of three different process parameters (namely: percentage composition of Al and Al2O3, vacuum pressure and grain size of silica) towards microhardness of the DCS plate manufactured by the combined process.

  18. Charter School Replication. Policy Guide

    Science.gov (United States)

    Rhim, Lauren Morando

    2009-01-01

    "Replication" is the practice of a single charter school board or management organization opening several more schools that are each based on the same school model. The most rapid strategy to increase the number of new high-quality charter schools available to children is to encourage the replication of existing quality schools. This policy guide…

  19. [Cellular senescence and chronic inflammation].

    Science.gov (United States)

    Ohtani, Naoko

    2014-01-01

    It has recently become apparent that obesity is associated with chronic inflammation and several common types of cancer development. Although several events were proposed to be involved in these pathologies, the precise mechanisms underlying obesity-associated inflammation and cancer largely remain unclear. Here, we show that senescence-associated secretory phenotype (SASP) plays crucial roles in promoting obesity-associated hepatocellular carcinoma (HCC) development in mice. Dietary or genetic obesity induces alterations of gut microbiota, thereby increasing the levels of a bacterial metabolite that cause DNA damage. The enterohepatic circulation of the bacterial metabolites provokes SASP phenotype in hepatic stellate cells (HSCs), which in turn, secretes various inflammatory and tumour promoting factors in the liver, thus facilitating HCC development in mice after exposure to chemical carcinogen. Importantly, reducing gut bacteria efficiently prevents HCC development in obese mice. Similar results were also observed in mice lacking an SASP inducer or depleted of senescent HSCs, indicating that the induction of SASP by the gut bacterial metabolite in HSCs plays key roles in obesity-associated HCC development. Interestingly, moreover, signs of SASP were also observed in the HSCs in the area of HCC arising in patients with nonalcoholic steatohepatitis (NASH), implying that a similar pathway may contribute to at least certain aspects of obesity-associated HCC development in humans as well. These findings provide valuable new insights into the development of obesity-associated cancer.

  20. msCentipede: Modeling Heterogeneity across Genomic Sites and Replicates Improves Accuracy in the Inference of Transcription Factor Binding.

    Science.gov (United States)

    Raj, Anil; Shim, Heejung; Gilad, Yoav; Pritchard, Jonathan K; Stephens, Matthew

    2015-01-01

    Understanding global gene regulation depends critically on accurate annotation of regulatory elements that are functional in a given cell type. CENTIPEDE, a powerful, probabilistic framework for identifying transcription factor binding sites from tissue-specific DNase I cleavage patterns and genomic sequence content, leverages the hypersensitivity of factor-bound chromatin and the information in the DNase I spatial cleavage profile characteristic of each DNA binding protein to accurately infer functional factor binding sites. However, the model for the spatial profile in this framework fails to account for the substantial variation in the DNase I cleavage profiles across different binding sites. Neither does it account for variation in the profiles at the same binding site across multiple replicate DNase I experiments, which are increasingly available. In this work, we introduce new methods, based on multi-scale models for inhomogeneous Poisson processes, to account for such variation in DNase I cleavage patterns both within and across binding sites. These models account for the spatial structure in the heterogeneity in DNase I cleavage patterns for each factor. Using DNase-seq measurements assayed in a lymphoblastoid cell line, we demonstrate the improved performance of this model for several transcription factors by comparing against the Chip-seq peaks for those factors. Finally, we explore the effects of DNase I sequence bias on inference of factor binding using a simple extension to our framework that allows for a more flexible background model. The proposed model can also be easily applied to paired-end ATAC-seq and DNase-seq data. msCentipede, a Python implementation of our algorithm, is available at http://rajanil.github.io/msCentipede.

  1. msCentipede: Modeling Heterogeneity across Genomic Sites and Replicates Improves Accuracy in the Inference of Transcription Factor Binding.

    Directory of Open Access Journals (Sweden)

    Anil Raj

    Full Text Available Understanding global gene regulation depends critically on accurate annotation of regulatory elements that are functional in a given cell type. CENTIPEDE, a powerful, probabilistic framework for identifying transcription factor binding sites from tissue-specific DNase I cleavage patterns and genomic sequence content, leverages the hypersensitivity of factor-bound chromatin and the information in the DNase I spatial cleavage profile characteristic of each DNA binding protein to accurately infer functional factor binding sites. However, the model for the spatial profile in this framework fails to account for the substantial variation in the DNase I cleavage profiles across different binding sites. Neither does it account for variation in the profiles at the same binding site across multiple replicate DNase I experiments, which are increasingly available. In this work, we introduce new methods, based on multi-scale models for inhomogeneous Poisson processes, to account for such variation in DNase I cleavage patterns both within and across binding sites. These models account for the spatial structure in the heterogeneity in DNase I cleavage patterns for each factor. Using DNase-seq measurements assayed in a lymphoblastoid cell line, we demonstrate the improved performance of this model for several transcription factors by comparing against the Chip-seq peaks for those factors. Finally, we explore the effects of DNase I sequence bias on inference of factor binding using a simple extension to our framework that allows for a more flexible background model. The proposed model can also be easily applied to paired-end ATAC-seq and DNase-seq data. msCentipede, a Python implementation of our algorithm, is available at http://rajanil.github.io/msCentipede.

  2. The inhibitory mechanism of Cordyceps sinensis on cigarette smoke extract-induced senescence in human bronchial epithelial cells

    Directory of Open Access Journals (Sweden)

    Liu AL

    2016-07-01

    Full Text Available Ailing Liu,1,2,* Jinxiang Wu,1,* Aijun Li,2 Wenxiang Bi,3 Tian Liu,1 Liuzhao Cao,1 Yahui Liu,1 Liang Dong1 1Department of Pulmonary Diseases, Qilu Hospital, Shandong University, Jinan, Shandong, People’s Republic of China; 2Department of Pulmonary Diseases, Weihai Municipal Hospital, Weihai, Shandong, People’s Republic of China; 3Institute of Biochemistry and Molecular Biology, School of Medicine, Shandong University, Jinan, Shandong, People’s Republic of China *These authors contributed equally to this work Objectives: Cellular senescence is a state of irreversible growth arrest induced either by telomere shortening (replicative senescence or stress. The bronchial epithelial cell is often injured by inhaled toxic substances, such as cigarette smoke. In the present study, we investigated whether exposure to cigarette smoke extract (CSE induces senescence of bronchial epithelial cells; and Cordyceps sinensis mechanism of inhibition of CSE-induced cellular senescence.Methods: Human bronchial epithelial cells (16HBE cells cultured in vitro were treated with CSE and/or C. sinensis. p16, p21, and senescence-associated-galactosidase activity were used to detect cellular senescence with immunofluorescence, quantitative polymerase chain reaction, and Western blotting. Reactive oxygen species (ROS, PI3K/AKT/mTOR and their phosphorylated proteins were examined to testify the activation of signaling pathway by ROS fluorescent staining and Western blotting. Then, inhibitors of ROS and PI3K were used to further confirm the function of this pathway.Results: Cellular senescence was upregulated by CSE treatment, and C. sinensis can decrease CSE-induced cellular senescence. Activation of ROS/PI3K/AKT/mTOR signaling pathway was enhanced by CSE treatment, and decreased when C. sinensis was added. Blocking ROS/PI3K/AKT/mTOR signaling pathway can attenuate CSE-induced cellular senescence.Conclusion: CSE can induce cellular senescence in human bronchial

  3. The song of the old mother: reproductive senescence in female drosophila.

    Science.gov (United States)

    Miller, Paige B; Obrik-Uloho, Oghenemine T; Phan, Mai H; Medrano, Christian L; Renier, Joseph S; Thayer, Joseph L; Wiessner, Gregory; Bloch Qazi, Margaret C

    2014-01-01

    Among animals with multiple reproductive episodes, changes in adult condition over time can have profound effects on lifetime reproductive fitness and offspring performance. The changes in condition associated with senescence can be particularly acute for females who support reproductive processes from oogenesis through fertilization. The pomace fly Drosophila melanogaster is a well-established model system for exploring the physiology of reproduction and senescence. In this review, we describe how increasing maternal age in Drosophila affects reproductive fitness and offspring performance as well as the genetic foundation of these effects. Describing the processes underlying female reproductive senescence helps us understand diverse phenomena including population demographics, condition-dependent selection, sexual conflict, and transgenerational effects of maternal condition on offspring fitness. Understanding the genetic basis of reproductive senescence clarifies the nature of life-history trade-offs as well as potential ways to augment and/or limit female fertility in a variety of organisms.

  4. NACSA Charter School Replication Guide: The Spectrum of Replication Options. Authorizing Matters. Replication Brief 1

    Science.gov (United States)

    O'Neill, Paul

    2010-01-01

    One of the most important and high-profile issues in public education reform today is the replication of successful public charter school programs. With more than 5,000 failing public schools in the United States, there is a tremendous need for strong alternatives for parents and students. Replicating successful charter school models is an…

  5. Combinatorial effects of continuous protein synthesis, ERK-signaling, and reactive oxygen species on induction of cellular senescence.

    Science.gov (United States)

    Takauji, Yuki; En, Atsuki; Miki, Kensuke; Ayusawa, Dai; Fujii, Michihiko

    2016-07-15

    Mammalian cells, when treated with sub-lethal doses of genotoxic stresses, slow down DNA synthesis but continue protein synthesis. Thus, these cells show an accumulation of proteins and undergo unbalanced growth. In the previous studies, we have shown that HeLa cells treated with excess thymidine or camptothecin undergo unbalanced growth, and prolonged unbalanced growth causes induction of cellular senescence, which is suppressed by restriction of protein synthesis or inhibition of ERK-signaling. In this study, we found that restriction of protein synthesis, inhibition of ERK-signaling, and elimination of reactive oxygen species showed a combinatorial effect on suppression of cellular senescence induced by excess thymidine or camptothecin. Of these, restriction of protein synthesis most effectively suppressed cellular senescence. Importantly, a similar combinatorial effect was observed in replicative senescence in normal human diploid fibroblasts. Our findings suggested that various stresses were cumulatively involved in cellular senescence, and suppression of cellular senescence was improved by combining the treatments that reduce the stresses.

  6. LHCb experience with LFC replication

    CERN Document Server

    Bonifazi, F; Perez, E D; D'Apice, A; dell'Agnello, L; Düllmann, D; Girone, M; Re, G L; Martelli, B; Peco, G; Ricci, P P; Sapunenko, V; Vagnoni, V; Vitlacil, D

    2008-01-01

    Database replication is a key topic in the framework of the LHC Computing Grid to allow processing of data in a distributed environment. In particular, the LHCb computing model relies on the LHC File Catalog, i.e. a database which stores information about files spread across the GRID, their logical names and the physical locations of all the replicas. The LHCb computing model requires the LFC to be replicated at Tier-1s. The LCG 3D project deals with the database replication issue and provides a replication service based on Oracle Streams technology. This paper describes the deployment of the LHC File Catalog replication to the INFN National Center for Telematics and Informatics (CNAF) and to other LHCb Tier-1 sites. We performed stress tests designed to evaluate any delay in the propagation of the streams and the scalability of the system. The tests show the robustness of the replica implementation with performance going much beyond the LHCb requirements.

  7. LHCb experience with LFC replication

    CERN Document Server

    Carbone, Angelo; Dafonte Perez, Eva; D'Apice, Antimo; dell'Agnello, Luca; Duellmann, Dirk; Girone, Maria; Lo Re, Giuseppe; Martelli, Barbara; Peco, Gianluca; Ricci, Pier Paolo; Sapunenko, Vladimir; Vagnoni, Vincenzo; Vitlacil, Dejan

    2007-01-01

    Database replication is a key topic in the framework of the LHC Computing Grid to allow processing of data in a distributed environment. In particular, the LHCb computing model relies on the LHC File Catalog, i.e. database which stores information about files spread across the GRID, their logical names and the physical locations of all the replicas. The LHCb computing model requires the LFC to be replicated at Tier-1s. The LCG 3D project deals with the database replication issue and provides a replication service based on Oracle Streams technology. This paper describes the deployment of the LHC File Catalog replication to the INFN National Center for Telematics and Informations (CNAF) and to other LHCb Tier-1 sites. We performed stress tests designed to evaluate any delay in the propagation of the streams and the scalability of the system. The tests show the robustness of the replica implementation with performance going much beyond the LHCb requirements.

  8. NCOA4 transcriptional coactivator inhibits activation of DNA replication origins.

    Science.gov (United States)

    Bellelli, Roberto; Castellone, Maria Domenica; Guida, Teresa; Limongello, Roberto; Dathan, Nina Alayne; Merolla, Francesco; Cirafici, Anna Maria; Affuso, Andrea; Masai, Hisao; Costanzo, Vincenzo; Grieco, Domenico; Fusco, Alfredo; Santoro, Massimo; Carlomagno, Francesca

    2014-07-01

    NCOA4 is a transcriptional coactivator of nuclear hormone receptors that undergoes gene rearrangement in human cancer. By combining studies in Xenopus laevis egg extracts and mouse embryonic fibroblasts (MEFs), we show here that NCOA4 is a minichromosome maintenance 7 (MCM7)-interacting protein that is able to control DNA replication. Depletion-reconstitution experiments in Xenopus laevis egg extracts indicate that NCOA4 acts as an inhibitor of DNA replication origin activation by regulating CMG (CDC45/MCM2-7/GINS) helicase. NCOA4(-/-) MEFs display unscheduled origin activation and reduced interorigin distance; this results in replication stress, as shown by the presence of fork stalling, reduction of fork speed, and premature senescence. Together, our findings indicate that NCOA4 acts as a regulator of DNA replication origins that helps prevent inappropriate DNA synthesis and replication stress.

  9. Chlamydia pneumoniae replicates in Kupffer cells in mouse model of liver infection

    Institute of Scientific and Technical Information of China (English)

    Antonella Marangoni; Manuela Donati; Francesca Cavrini; Rita Aldini; Silvia Accardo; Vittorio Sambri; Marco Montagnani; Roberto Cevenini

    2006-01-01

    AIM: To develop an animal model of liver infection with Chlamydia pneumoniae (C.pneumoniae) in intraperitoneally infected mice for studying the presence of chlamydiae in Kupffer cells and hepatocytes.METHODS: A total of 80 BALB/c mice were inoculated intraperitoneally with C. pneumoniae and sacrificed at various time points after infection. Chlamydiae were looked for in liver homogenates as well as in Kupffer cells and hepatocytes separated by liver perfusion with collagenase. C. pneumoniae was detected by both isolation in LLC-MK2 cells and fluorescence in situ hybridization (FISH). The releasing of TNFA-α by C. pneumoniae in vitro stimulated Kupffer cells was studied by enzymelinked immunosorbent assay.RESULTS: C. pneumoniae isolation from liver homogenates reached a plateau on d 7 after infection when 6 of 10 animals were positive, then decreased, and became negative by d 20. C. pneumoniae isolation from separated Kupffer cells reached a plateau on d 7 when 5 of 10 animals were positive, and became negative by d 20.The detection of C. pneumoniae in separated Kupffer cells by FISH, confirmed the results obtained by culture.Isolated hepatocytes were always negative. Stimulation of Kupffer cells by alive C. pneumoniae elicited high TNF-α levels.CONCLUSION: A productive infection by C. pneumoniae may take place in Kupffer cells and C. pneumoniae induces a local pro-inflammatory activity. C. pneumoniae is therefore, able to act as antigenic stimulus when localized in the liver. One could speculate that C. pneumoniae infection, involving cells of the innate immunity such as Kupffer cells, could also trigger pathological immune reactions involving the liver, as observed in human patients with primary biliary cirrhosis.

  10. AMPK induces vascular smooth muscle cell senescence via LKB1 dependent pathway

    Energy Technology Data Exchange (ETDEWEB)

    Sung, Jin Young; Woo, Chang-Hoon [Department of Pharmacology, College of Medicine, Yeungnam University, Daegu 705-717 (Korea, Republic of); Aging-associated Vascular Disease Research Center, College of Medicine, Yeungnam University, Daegu 705-717 (Korea, Republic of); Kang, Young Jin; Lee, Kwang Youn [Department of Pharmacology, College of Medicine, Yeungnam University, Daegu 705-717 (Korea, Republic of); Choi, Hyoung Chul, E-mail: hcchoi@med.yu.ac.kr [Department of Pharmacology, College of Medicine, Yeungnam University, Daegu 705-717 (Korea, Republic of); Aging-associated Vascular Disease Research Center, College of Medicine, Yeungnam University, Daegu 705-717 (Korea, Republic of)

    2011-09-16

    Highlights: {yields} An aging model was established by stimulating VSMC with adriamycin. {yields} Adriamycin increased p-LKB1, p-AMPK, p53 and p21 expressions. {yields} Inhibition of AMPK diminished SA-{beta}-gal staining and restored VSMC proliferation. {yields} p53 and p21 siRNA attenuated adriamycin-induced SA-{beta}-gal staining in VSMC. {yields} p53-p21 pathway is a mediator of LKB1/AMPK induced VSMC senescence. -- Abstract: Vascular cells have a limited lifespan with limited cell proliferation and undergo cellular senescence. The functional changes associated with cellular senescence are thought to contribute to age-related vascular disorders. AMP-activated protein kinase (AMPK) has been discussed in terms of beneficial or harmful effects for aging-related diseases. However, the detailed functional mechanisms of AMPK are largely unclear. An aging model was established by stimulating vascular smooth muscle cell (VSMC) with adriamycin. Adriamycin progressively increased the mRNA and protein expressions of AMPK. The phosphorylation levels of LKB1 and acetyl-CoA carboxylase (ACC), the upstream and downstream of AMPK, were dramatically increased by adriamycin stimulation. The expressions of p53 and p21, which contribute to vascular senescence, were also increased. Inhibition of AMPK diminished senescence-associated {beta}-galactosidase (SA-{beta}-gal) staining, and restored VSMC proliferation. Cytosolic translocation of LKB1 by adriamycin could be a mechanism for AMPK activation in senescence. Furthermore, p53 siRNA and p21 siRNA transfection attenuated adriamycin-induced SA-{beta}-gal staining. These results suggest that LKB1 dependent AMPK activation elicits VSMC senescence and p53-p21 pathway is a mediator of LKB1/AMPK-induced senescence.

  11. Twist1 suppresses senescence programs and thereby accelerates and maintains mutant Kras-induced lung tumorigenesis.

    Directory of Open Access Journals (Sweden)

    Phuoc T Tran

    Full Text Available KRAS mutant lung cancers are generally refractory to chemotherapy as well targeted agents. To date, the identification of drugs to therapeutically inhibit K-RAS have been unsuccessful, suggesting that other approaches are required. We demonstrate in both a novel transgenic mutant Kras lung cancer mouse model and in human lung tumors that the inhibition of Twist1 restores a senescence program inducing the loss of a neoplastic phenotype. The Twist1 gene encodes for a transcription factor that is essential during embryogenesis. Twist1 has been suggested to play an important role during tumor progression. However, there is no in vivo evidence that Twist1 plays a role in autochthonous tumorigenesis. Through two novel transgenic mouse models, we show that Twist1 cooperates with Kras(G12D to markedly accelerate lung tumorigenesis by abrogating cellular senescence programs and promoting the progression from benign adenomas to adenocarcinomas. Moreover, the suppression of Twist1 to physiological levels is sufficient to cause Kras mutant lung tumors to undergo senescence and lose their neoplastic features. Finally, we analyzed more than 500 human tumors to demonstrate that TWIST1 is frequently overexpressed in primary human lung tumors. The suppression of TWIST1 in human lung cancer cells also induced cellular senescence. Hence, TWIST1 is a critical regulator of cellular senescence programs, and the suppression of TWIST1 in human tumors may be an effective example of pro-senescence therapy.

  12. Temporally distinct roles of ATM and ROS in genotoxic-stress-dependent induction and maintenance of cellular senescence.

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    Nair, Raji R; Bagheri, Meisam; Saini, Deepak Kumar

    2015-01-15

    Cells exposed to genotoxic stress induce cellular senescence through a DNA damage response (DDR) pathway regulated by ATM kinase and reactive oxygen species (ROS). Here, we show that the regulatory roles for ATM kinase and ROS differ during induction and maintenance of cellular senescence. Cells treated with different genotoxic agents were analyzed using specific pathway markers and inhibitors to determine that ATM kinase activation is directly proportional to the dose of the genotoxic stress and that senescence initiation is not dependent on ROS or the p53 status of cells. Cells in which ROS was quenched still activated ATM and initiated the DDR when insulted, and progressed normally to senescence. By contrast, maintenance of a viable senescent state required the presence of ROS as well as activated ATM. Inhibition or removal of either of the components caused cell death in senescent cells, through a deregulated ATM-ROS axis. Overall, our work demonstrates existence of an intricate temporal hierarchy between genotoxic stress, DDR and ROS in cellular senescence. Our model reports the existence of different stages of cellular senescence with distinct regulatory networks.

  13. Legume nodule senescence: roles for redox and hormone signalling in the orchestration of the natural aging process.

    Science.gov (United States)

    Puppo, Alain; Groten, Karin; Bastian, Fabiola; Carzaniga, Raffaella; Soussi, Mariam; Lucas, M Mercedes; de Felipe, Maria Rosario; Harrison, Judith; Vanacker, Hélène; Foyer, Christine H

    2005-03-01

    Research on legume nodule development has contributed greatly to our current understanding of plant-microbe interactions. However, the factors that orchestrate root nodule senescence have received relatively little attention. Accumulating evidence suggests that redox signals contribute to the establishment of symbiosis and senescence. Although degenerative in nature, nodule senescence is an active process programmed in development in which reactive oxygen species (ROS), antioxidants, hormones and proteinases have key roles. Nodules have high levels of the redox buffers, ascorbate and glutathione, which are important in the nodulation process and in senescence. These metabolites decline with N-fixation as the nodule ages but the resultant decrease in redox buffering capacity does not necessarily lead to enhanced ROS or oxidative stress. We propose models by which ROS and antioxidants interact with hormones such as abscisic acid in the orchestration of nodule senescence.

  14. Perturbation of Ribosome Biogenesis Drives Cells into Senescence through 5S RNP-Mediated p53 Activation

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    Kazuho Nishimura

    2015-03-01

    Full Text Available The 5S ribonucleoprotein particle (RNP complex, consisting of RPL11, RPL5, and 5S rRNA, is implicated in p53 regulation under ribotoxic stress. Here, we show that the 5S RNP contributes to p53 activation and promotes cellular senescence in response to oncogenic or replicative stress. Oncogenic stress accelerates rRNA transcription and replicative stress delays rRNA processing, resulting in RPL11 and RPL5 accumulation in the ribosome-free fraction, where they bind MDM2. Experimental upregulation of rRNA transcription or downregulation of rRNA processing, mimicking the nucleolus under oncogenic or replicative stress, respectively, also induces RPL11-mediated p53 activation and cellular senescence. We demonstrate that exogenous expression of certain rRNA-processing factors rescues the processing defect, attenuates p53 accumulation, and increases replicative lifespan. To summarize, the nucleolar-5S RNP-p53 pathway functions as a senescence inducer in response to oncogenic and replicative stresses.

  15. Perturbation of ribosome biogenesis drives cells into senescence through 5S RNP-mediated p53 activation.

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    Nishimura, Kazuho; Kumazawa, Takuya; Kuroda, Takao; Katagiri, Naohiro; Tsuchiya, Mai; Goto, Natsuka; Furumai, Ryohei; Murayama, Akiko; Yanagisawa, Junn; Kimura, Keiji

    2015-03-03

    The 5S ribonucleoprotein particle (RNP) complex, consisting of RPL11, RPL5, and 5S rRNA, is implicated in p53 regulation under ribotoxic stress. Here, we show that the 5S RNP contributes to p53 activation and promotes cellular senescence in response to oncogenic or replicative stress. Oncogenic stress accelerates rRNA transcription and replicative stress delays rRNA processing, resulting in RPL11 and RPL5 accumulation in the ribosome-free fraction, where they bind MDM2. Experimental upregulation of rRNA transcription or downregulation of rRNA processing, mimicking the nucleolus under oncogenic or replicative stress, respectively, also induces RPL11-mediated p53 activation and cellular senescence. We demonstrate that exogenous expression of certain rRNA-processing factors rescues the processing defect, attenuates p53 accumulation, and increases replicative lifespan. To summarize, the nucleolar-5S RNP-p53 pathway functions as a senescence inducer in response to oncogenic and replicative stresses. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  16. Novel inhibitors of neurotropic alphavirus replication that improve host survival in a mouse model of acute viral encephalitis.

    Science.gov (United States)

    Sindac, Janice A; Yestrepsky, Bryan D; Barraza, Scott J; Bolduc, Kyle L; Blakely, Pennelope K; Keep, Richard F; Irani, David N; Miller, David J; Larsen, Scott D

    2012-04-12

    Arboviral encephalitis is a potentially devastating human disease with no approved therapies that target virus replication. We previously discovered a novel class of thieno[3,2-b]pyrrole-based inhibitors active against neurotropic alphaviruses such as western equine encephalitis virus (WEEV) in cultured cells. In this report, we describe initial development of these novel antiviral compounds, including bioisosteric replacement of the 4H-thieno[3,2-b]pyrrole core with indole to improve metabolic stability and the introduction of chirality to assess target enantioselectivity. Selected modifications enhanced antiviral activity while maintaining low cytotoxicity, increased stability to microsomal metabolism, and also revealed striking enantiospecific activity in cultured cells. Furthermore, we demonstrate improved outcomes (both symptoms and survival) following treatment with indole analogue 9h (CCG-203926) in an in vivo mouse model of alphaviral encephalitis that closely correlate with the enantiospecific in vitro antiviral activity. These results represent a substantial advancement in the early preclinical development of a promising class of novel antiviral drugs against virulent neurotropic alphaviruses.

  17. Senescence is more important in the natural lives of long- than short-lived mammals.

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    Christopher Turbill

    Full Text Available BACKGROUND: Senescence has been widely detected among mammals, but its importance to fitness in wild populations remains controversial. According to evolutionary theories, senescence occurs at an age when selection is relatively weak, which in mammals can be predicted by adult survival rates. However, a recent analysis of senescence rates found more age-dependent mortalities in natural populations of longer lived mammal species. This has important implications to ageing research and for understanding the ecological relevance of senescence, yet so far these have not been widely appreciated. We re-address this question by comparing the mean and maximum life span of 125 mammal species. Specifically, we test the hypothesis that senescence occurs at a younger age relative to the mean natural life span in longer lived species. METHODOLOGY/PRINCIPAL FINDINGS: We show, using phylogenetically-informed generalised least squares models, a significant log-log relationship between mean life span, as calculated from estimates of adult survival for natural populations, and maximum recorded life span among mammals (R2=0.57, p10 in short-lived to approximately 1.5 in long-lived mammal species. CONCLUSIONS/SIGNIFICANCE: We interpret the ratio of maximum to mean life span to be an index of the likelihood an individual will experience senescence, which largely determines maximum life span. Our results suggest that senescence occurs at an earlier age relative to the mean life span, and therefore is experienced by more individuals and remains under selection pressure, in long- compared to short-lived mammals. A minimum rate of somatic degradation may ultimately limit the natural life span of mammals. Our results also indicate that senescence and modulating factors like oxidative stress are increasingly important to the fitness of longer lived mammals (and vice versa.

  18. The viral polymerase inhibitor 2'-C-methylcytidine inhibits Norwalk virus replication and protects against norovirus-induced diarrhea and mortality in a mouse model.

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    Rocha-Pereira, Joana; Jochmans, Dirk; Debing, Yannick; Verbeken, Erik; Nascimento, Maria S J; Neyts, Johan

    2013-11-01

    Human noroviruses are a major cause of food-borne illness, accountable for 50% of all-etiologies outbreaks of acute gastroenteritis (in both developing and developed countries). There is no vaccine or antiviral drug for the prophylaxis or treatment of norovirus-induced gastroenteritis. We recently reported the inhibitory effect of 2'-C-methylcytidine (2CMC), a hepatitis C virus polymerase inhibitor, on the in vitro replication of murine norovirus (MNV). Here we evaluated the inhibitory effect of 2CMC on in vitro human norovirus replication through a Norwalk virus replicon model and in a mouse model by using AG129 mice orally infected with MNV. Survival, weight, and fecal consistency were monitored, and viral loads in stool samples and organs were quantified. Intestines were examined histologically. 2CMC reduced Norwalk virus replicon replication in a dose-dependent manner and was able to clear cells of the replicon. Treatment of MNV-infected AG129 mice with 2CMC (i) prevented norovirus-induced diarrhea; (ii) markedly delayed the appearance of viral RNA and reduced viral RNA titers in the intestine, mesenteric lymph nodes, spleen, lungs, and stool; (iii) completely prevented virus-induced mortality; and (iv) resulted in protective immunity against a rechallenge. We demonstrate for the first time that a small-molecule inhibitor of norovirus replication protects from virus-induced disease and mortality in a relevant animal model. These findings pave the way for the development of potent and safe antivirals as prophylaxis and therapy of norovirus infection.

  19. Limited Role of Murine ATM in Oncogene-Induced Senescence and p53-Dependent Tumor Suppression

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    Martinez-Pastor, Barbara; Ortega-Molina, Ana; Soria, Rebeca; Collado, Manuel; Fernandez-Capetillo, Oscar; Serrano, Manuel

    2009-01-01

    Recent studies in human fibroblasts have provided a new general paradigm of tumor suppression according to which oncogenic signaling produces DNA damage and this, in turn, results in ATM/p53-dependent cellular senescence. Here, we have tested this model in a variety of murine experimental systems. Overexpression of oncogenic Ras in murine fibroblasts efficiently induced senescence but this occurred in the absence of detectable DNA damage signaling, thus suggesting a fundamental difference between human and murine cells. Moreover, lung adenomas initiated by endogenous levels of oncogenic K-Ras presented abundant senescent cells, but undetectable DNA damage signaling. Accordingly, K-Ras-driven adenomas were also senescent in Atm-null mice, and the tumorigenic progression of these lesions was only modestly accelerated by Atm-deficiency. Finally, we have examined chemically-induced fibrosarcomas, which possess a persistently activated DNA damage response and are highly sensitive to the activity of p53. We found that the absence of Atm favored genomic instability in the resulting tumors, but did not affect the persistent DNA damage response and did not impair p53-dependent tumor suppression. All together, we conclude that oncogene-induced senescence in mice may occur in the absence of a detectable DNA damage response. Regarding murine Atm, our data suggest that it plays a minor role in oncogene-induced senescence or in p53-dependent tumor suppression, being its tumor suppressive activity probably limited to the maintenance of genomic stability. PMID:19421407

  20. Connecting radiation-induced bystander effects and senescence to improve radiation response prediction.

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    Poleszczuk, Jan; Krzywon, Aleksandra; Forys, Urszula; Widel, Maria

    2015-05-01

    For the last two decades radiation-induced bystander effects (RIBEs) have attracted significant attention due to their possible implications for radiotherapy. However, despite extensive research, the molecular pathways associated with RIBEs are still not completely known. In the current study we investigated the role of senescence in the bystander response. Irradiated (2, 4, 6 and 8 Gy) human colorectal carcinoma cells (HCT116) with p53(+/+) (wild-type) or p53(-/-) (knockout) gene were co-incubated with nonirradiated cells of the same type. Clonogenic and senescence assays were used for both irradiated and co-incubated bystander cell populations. We also performed additional measurements on the number of remaining cells after the whole co-incubation period. For radiation doses larger than 2 Gy we observed much larger fractions of senescent cells in p53-positive populations compared to their p53-negative counterparts (15.81% vs. 3.63% in the irradiated population; 2.89% vs. 1.05% in the bystander population; 8 Gy; P bystander population; 8 Gy; P bystander population. We also extended the standard linear-quadratic radiation response model by incorporating the influence of the signals released by the senescent cells, which accurately described the radiation response in the bystander population. Our findings suggest that radiation-induced senescence might be a key player in RIBE, i.e., the strength of RIBE depends on the amount of radiation-induced senescence.

  1. Limited role of murine ATM in oncogene-induced senescence and p53-dependent tumor suppression.

    Directory of Open Access Journals (Sweden)

    Alejo Efeyan

    Full Text Available Recent studies in human fibroblasts have provided a new general paradigm of tumor suppression according to which oncogenic signaling produces DNA damage and this, in turn, results in ATM/p53-dependent cellular senescence. Here, we have tested this model in a variety of murine experimental systems. Overexpression of oncogenic Ras in murine fibroblasts efficiently induced senescence but this occurred in the absence of detectable DNA damage signaling, thus suggesting a fundamental difference between human and murine cells. Moreover, lung adenomas initiated by endogenous levels of oncogenic K-Ras presented abundant senescent cells, but undetectable DNA damage signaling. Accordingly, K-Ras-driven adenomas were also senescent in Atm-null mice, and the tumorigenic progression of these lesions was only modestly accelerated by Atm-deficiency. Finally, we have examined chemically-induced fibrosarcomas, which possess a persistently activated DNA damage response and are highly sensitive to the activity of p53. We found that the absence of Atm favored genomic instability in the resulting tumors, but did not affect the persistent DNA damage response and did not impair p53-dependent tumor suppression. All together, we conclude that oncogene-induced senescence in mice may occur in the absence of a detectable DNA damage response. Regarding murine Atm, our data suggest that it plays a minor role in oncogene-induced senescence or in p53-dependent tumor suppression, being its tumor suppressive activity probably limited to the maintenance of genomic stability.

  2. Genome-Wide Overexpression Screen Identifies Genes Able to Bypass p16-Mediated Senescence in Melanoma.

    Science.gov (United States)

    Lee, Won Jae; Škalamera, Dubravka; Dahmer-Heath, Mareike; Shakhbazov, Konstanin; Ranall, Max V; Fox, Carly; Lambie, Duncan; Stevenson, Alexander J; Yaswen, Paul; Gonda, Thomas J; Gabrielli, Brian

    2017-03-01

    Malignant melanomas often arise from nevi, which result from initial oncogene-induced hyperproliferation of melanocytes that are maintained in a CDKN2A/p16-mediated senescent state. Thus, genes that can bypass this senescence barrier are likely to contribute to melanoma development. We have performed a gain-of-function screen of 17,030 lentivirally expressed human open reading frames (ORFs) in a melanoma cell line containing an inducible p16 construct to identify such genes. Genes known to bypass p16-induced senescence arrest, including the human papilloma virus 18 E7 gene ( HPV18E7), and genes such as the p16-binding CDK6 with expected functions, as well as panel of novel genes, were identified, including high-mobility group box (HMGB) proteins. A number of these were further validated in two other models of p16-induced senescence. Tissue immunohistochemistry demonstrated higher levels of CDK6 in primary melanomas compared with normal skin and nevi. Reduction of CDK6 levels drove melanoma cells expressing functional p16 into senescence, demonstrating its contribution to bypass senescence.

  3. Repression of cancer cell senescence by PKCι.

    Science.gov (United States)

    Paget, J A; Restall, I J; Daneshmand, M; Mersereau, J A; Simard, M A; Parolin, D A E; Lavictoire, S J; Amin, M S; Islam, S; Lorimer, I A J

    2012-08-02

    Senescence is an irreversible growth arrest phenotype adopted by cells that has a key role in protecting organisms from cancer. There is now considerable interest in therapeutic strategies that reactivate this process to control the growth of cancer cells. Protein kinase-Cι (PKCι) is a member of the atypical PKC family and an important downstream mediator in the phosphoinositide-3-kinase (PI-3-kinase) pathway. PKCι expression was found to be upregulated in a subset of breast cancers and breast cancer cell lines. Activation of the PI-3-kinase pathway by introduction of mutant, oncogenic PIK3CA into breast mammary epithelial cells increased both the expression and activation of PKCι. In breast cancer cells lines overexpressing PKCι, depletion of PKCι increased the number of senescent cells, as assessed by senescence-associated β-galactosidase, morphology and bromodeoxyuridine incorporation. This phenomenon was not restricted to breast cancer cells, as it was also seen in glioblastoma cells in which PKCι is activated by loss of PTEN. Senescence occurred in the absence of a detectable DNA-damage response, was dependent on p21 and was enhanced by the aurora kinase inhibitor VX-680, suggesting that senescence is triggered by defects in mitosis. Depletion of PKCι had no effect on senescence in normal mammary epithelial cell lines. We conclude that PKCι is overexpressed in a subset of cancers where it functions to suppress premature senescence. This function appears to be restricted to cancer cells and inhibition of PKCι may therefore be an effective way to selectively activate premature senescence in cancer cells.

  4. Chorioamniotic membrane senescence: a signal for parturition?

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    Behnia, Faranak; Taylor, Brandie D; Woodson, Michael; Kacerovsky, Marian; Hawkins, Hal; Fortunato, Stephen J; Saade, George R; Menon, Ramkumar

    2015-09-01

    Senescence is an important biological phenomenon involved in both physiologic and pathologic processes. We propose that chorioamniotic membrane senescence is a mechanism associated with human parturition. The present study was conducted to explore the association between senescence and normal term parturition by examining the morphologic and biochemical evidences in chorioamniotic membranes. Chorioamniotic membranes were collected from normal term deliveries; group 1: term labor and group 2: term, not in labor. Senescence-related morphologic changes were determined by transmission electron microscopy and biochemical changes were studied by senescence-associated (SA) β-galactosidase staining. Amniotic fluid samples collected from both term labor and term not in labor were analyzed for 14 SA secretory phenotype (SASP) markers. Morphologic evidence of cellular senescence (enlarged cells and organelles) and a higher number of SA β-galactosidase-stained amnion and chorion cells were observed in chorioamniotic membranes obtained from women in labor at term, when compared to term not in labor. The concentration of proinflammatory SASP markers (granulocyte macrophage colony-stimulating factor, interleukin-6 and -8) was significantly higher in the amniotic fluid of women in labor at term than women not in labor. In contrast, SASP factors that protect against cell death (eotaxin-1, soluble Fas ligand, osteoprotegerin, and intercellular adhesion molecule-1) were significantly lower in the amniotic fluid samples from term labor. Morphologic and biochemical features of senescence were more frequent in chorioamniotic membranes from women who experienced term labor. Senescence of chorioamniotic membranes were also associated with amniotic fluid SASP markers. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. Archaeal DNA replication.

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    Kelman, Lori M; Kelman, Zvi

    2014-01-01

    DNA replication is essential for all life forms. Although the process is fundamentally conserved in the three domains of life, bioinformatic, biochemical, structural, and genetic studies have demonstrated that the process and the proteins involved in archaeal DNA replication are more similar to those in eukaryal DNA replication than in bacterial DNA replication, but have some archaeal-specific features. The archaeal replication system, however, is not monolithic, and there are some differences in the replication process between different species. In this review, the current knowledge of the mechanisms governing DNA replication in Archaea is summarized. The general features of the replication process as well as some of the differences are discussed.

  6. Keratinocytes derived from chicken embryonic stem cells support Marek's disease virus infection: a highly differentiated cell model to study viral replication and morphogenesis.

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    Couteaudier, Mathilde; Courvoisier, Katia; Trapp-Fragnet, Laetitia; Denesvre, Caroline; Vautherot, Jean-François

    2016-01-07

    Marek's disease is a virus disease with worldwide distribution that causes major losses to poultry production. Vaccines against Marek's disease virus, an oncogenic alphaherpesvirus, reduce tumour formation but have no effect on virus shedding. Successful horizontal virus transmission is linked to the active viral replication in feather follicle epithelial cells of infected chickens, from which infectious viral particles are shed into the environment. The feather follicle epithelium is the sole tissue in which those infectious particles are produced and no in vitro cell-systems can support this highly efficient morphogenesis. We previously characterized embryonic stem-cell-derived keratinocytes, showing they display a marker-gene profile similar to skin keratinocytes, and therefore we tested their susceptibility to Marek's disease virus infection. We show herein that keratinocytes derived from chicken embryonic stem-cells are fully permissive to the replication of either non-pathogenic or pathogenic Marek's disease viruses. All viruses replicated on all three keratinocyte lines and kinetics of viral production as well as viral loads were similar to those obtained on primary cells. Morphogenesis studies were conducted on infected keratinocytes and on corneocytes, showing that all types of capsids/virions were present inside the cells, but extracellular viruses were absent. The keratinocyte lines are the first epithelial cell-line showing ectodermal specific markers supporting Marek's disease virus replication. In this in vitro model the replication lead to the production of cell-associated viral progeny. Further work will be devoted to the study of relationship between 3D differentiation of keratinocytes and Marek's disease virus replication.

  7. Intermittent Stem Cell Cycling Balances Self-Renewal and Senescence of the C. elegans Germ Line.

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    Amanda Cinquin

    2016-04-01

    Full Text Available Self-renewing organs often experience a decline in function in the course of aging. It is unclear whether chronological age or external factors control this decline, or whether it is driven by stem cell self-renewal-for example, because cycling cells exhaust their replicative capacity and become senescent. Here we assay the relationship between stem cell cycling and senescence in the Caenorhabditis elegans reproductive system, defining this senescence as the progressive decline in "reproductive capacity," i.e. in the number of progeny that can be produced until cessation of reproduction. We show that stem cell cycling diminishes remaining reproductive capacity, at least in part through the DNA damage response. Paradoxically, gonads kept under conditions that preclude reproduction keep cycling and producing cells that undergo apoptosis or are laid as unfertilized gametes, thus squandering reproductive capacity. We show that continued activity is in fact beneficial inasmuch as gonads that are active when reproduction is initiated have more sustained early progeny production. Intriguingly, continued cycling is intermittent-gonads switch between active and dormant states-and in all likelihood stochastic. Other organs face tradeoffs whereby stem cell cycling has the beneficial effect of providing freshly-differentiated cells and the detrimental effect of increasing the likelihood of cancer or senescence; stochastic stem cell cycling may allow for a subset of cells to preserve proliferative potential in old age, which may implement a strategy to deal with uncertainty as to the total amount of proliferation to be undergone over an organism's lifespan.

  8. Intermittent Stem Cell Cycling Balances Self-Renewal and Senescence of the C. elegans Germ Line.

    Science.gov (United States)

    Cinquin, Amanda; Chiang, Michael; Paz, Adrian; Hallman, Sam; Yuan, Oliver; Vysniauskaite, Indre; Fowlkes, Charless C; Cinquin, Olivier

    2016-04-01

    Self-renewing organs often experience a decline in function in the course of aging. It is unclear whether chronological age or external factors control this decline, or whether it is driven by stem cell self-renewal-for example, because cycling cells exhaust their replicative capacity and become senescent. Here we assay the relationship between stem cell cycling and senescence in the Caenorhabditis elegans reproductive system, defining this senescence as the progressive decline in "reproductive capacity," i.e. in the number of progeny that can be produced until cessation of reproduction. We show that stem cell cycling diminishes remaining reproductive capacity, at least in part through the DNA damage response. Paradoxically, gonads kept under conditions that preclude reproduction keep cycling and producing cells that undergo apoptosis or are laid as unfertilized gametes, thus squandering reproductive capacity. We show that continued activity is in fact beneficial inasmuch as gonads that are active when reproduction is initiated have more sustained early progeny production. Intriguingly, continued cycling is intermittent-gonads switch between active and dormant states-and in all likelihood stochastic. Other organs face tradeoffs whereby stem cell cycling has the beneficial effect of providing freshly-differentiated cells and the detrimental effect of increasing the likelihood of cancer or senescence; stochastic stem cell cycling may allow for a subset of cells to preserve proliferative potential in old age, which may implement a strategy to deal with uncertainty as to the total amount of proliferation to be undergone over an organism's lifespan.

  9. New Experimental Models of Diabetic Nephropathy in Mice Models of Type 2 Diabetes: Efforts to Replicate Human Nephropathy

    Directory of Open Access Journals (Sweden)

    María José Soler

    2012-01-01

    Full Text Available Diabetic nephropathy (DN is the leading cause of end-stage renal disease. The use of experimental models of DN has provided valuable information regarding many aspects of DN, including pathophysiology, progression, implicated genes, and new therapeutic strategies. A large number of mouse models of diabetes have been identified and their kidney disease was characterized to various degrees. Most experimental models of type 2 DN are helpful in studying early stages of DN, but these models have not been able to reproduce the characteristic features of more advanced DN in humans such as nodules in the glomerular tuft or glomerulosclerosis. The generation of new experimental models of DN created by crossing, knockdown, or knockin of genes continues to provide improved tools for studying DN. These models provide an opportunity to search for new mechanisms involving the development of DN, but their shortcomings should be recognized as well. Moreover, it is important to recognize that the genetic background has a substantial effect on the susceptibility to diabetes and kidney disease development in the various models of diabetes.

  10. Ageing induced vascular smooth muscle cell senescence in atherosclerosis.

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    Uryga, Anna K; Bennett, Martin R

    2016-04-15

    Atherosclerosis is a disease of ageing in that its incidence and prevalence increase with age. However, atherosclerosis is also associated with biological ageing, manifest by a number of typical hallmarks of ageing in the atherosclerotic plaque. Thus, accelerated biological ageing may be superimposed on the effects of chronological ageing in atherosclerosis. Tissue ageing is seen in all cells that comprise the plaque, but particularly in vascular smooth muscle cells (VSMCs). Hallmarks of ageing include evidence of cell senescence, DNA damage (including telomere attrition), mitochondrial dysfunction, a pro-inflammatory secretory phenotype, defects in proteostasis, epigenetic changes, deregulated nutrient sensing, and exhaustion of progenitor cells. In this model, initial damage to DNA (genomic, telomeric, mitochondrial and epigenetic changes) results in a number of cellular responses (cellular senescence, deregulated nutrient sensing and defects in proteostasis). Ultimately, ongoing damage and attempts at repair by continued proliferation overwhelm reparative capacity, causing loss of specialised cell functions, cell death and inflammation. This review summarises the evidence for accelerated biological ageing in atherosclerosis, the functional consequences of cell ageing on cells comprising the plaque, and the causal role that VSMC senescence plays in atherogenesis. © 2015 The Authors. The Journal of Physiology © 2015 The Physiological Society.

  11. The Identification of Senescence-Specific Genes during the Induction of Senescence in Prostate Cancer Cells

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    Steven R. Schwarze

    2005-09-01

    Full Text Available Classic mechanisms of tumor response to chemotherapy include apoptosis, mitotic catastrophe. Recent studies have suggested that cellular senescence, a terminal proliferation arrest seen in vitro, may be invoked during the exposure of cancer cells to chemotherapeutic agents. To identify markers associated specifically with the cellular senescence phenotype, we utilized expression data from cDNA microarray experiments identifying transcripts whose expression levels increased as human prostate epithelial cells progressed to senescence. When screened against other growth-inhibitory conditions, including quiescence, apoptosis, many of these transcripts were also upregulated, indicating that similar pathways occur between apoptosis, senescence. A senescent-like phenotype was then induced in several prostate cancer cell lines using 5-aza-2′-deoxycytidine, doxorubicin, or Docetaxel. Treatment with these agents resulted in a significant increase in the induction of senescence-specific genes when compared to nonsenescent conditions. The performance of the panel was improved with fluorescence-activated cell sorting using PKH26 to isolate nonproliferating, viable, drug-treated populations, indicating that a heterogeneous response occurs with chemotherapy. We have defined an RNA-based gene panel that characterizes the senescent phenotype induced in cancer cells by drug treatment. These data also indicate that a panel of genes, rather than one marker, needs to be utilized to identify senescence.

  12. Bisdemethoxycurcumin Increases Sirt1 to Antagonize t-BHP-Induced Premature Senescence in WI38 Fibroblast Cells

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    Ying-Bo Li

    2013-01-01

    Full Text Available Curcuminoids are well known for their capabilities to combat risk factors that are associated with ageing and cellular senescence. Recent reports have demonstrated that curcuminoids can extend the lifespan of model organisms. However, the underlying mechanisms by which these polyphenic compounds exert these beneficial effects remain unknown. In this study, t-BHP-induced premature senescence model in human fibroblasts was chosen to explore the protective effects of a curcuminoid, bisdemethoxycurcumin (BDMC, on cellular senescence. The results demonstrated that BDMC attenuated oxidative stress-induced senescence-like features which include the induction of an enlarged cellular appearance, higher frequency of senescence-associated β-galactosidase staining activity, appearance of senescence-associated heterochromatic foci in nuclei, decrease in proliferation capability, and alteration in related molecules such as p16 and retinoblastoma protein. Notably, we found that BDMC treatment activated Sirt1/AMPK signaling pathway. Moreover, downregulating Sirt1 by the pharmacological inhibitor nicotianamine or small interfering RNA blocked BDMC-mediated protection against t-BHP-mediated decrease in proliferation. These results suggested that BDMC prevented t-BHP-induced cellular senescence, and BDMC-induced Sirt1 may be a mechanism mediating its beneficial effects.

  13. Gene Network Analysis and Functional Studies of Senescence-associated Genes Reveal Novel Regulators of Arabidopsis Leaf Senescence

    Institute of Scientific and Technical Information of China (English)

    Zhonghai Li; Jinying Peng; Xing Wen; Hongwei Guo

    2012-01-01

    Plant leaf senescence has been recognized as the last phase of plant development,a highly ordered process regulated by genes known as senescence associated genes (SAGs).However,the function of most of SAGs in regulating leaf senescence as well as regulators of those functionally known SAGs are still unclear.We have previously developed a curated database of genes potentially associated with leaf senescence,the Leaf Senescence Database (LSD).In this study,we built gene networks to identify common regulators of leaf senescence in Arabidopsis thaliana using promoting or delaying senescence genes in LSD.Our results demonstrated that plant hormones cytokinin,auxin,nitric oxide as well as small molecules,such as Ca2+,delay leaf senescence.By contrast,ethylene,ABA,SA and JA as well as small molecules,such as oxygen,promote leaf senescence,altogether supporting the idea that phytohormones play a critical role in regulating leaf senescence.Functional analysis of candidate SAGs in LSD revealed that a WRKY transcription factor WRKY75 and a Cys2/His2-type transcription factor AZF2 are positive regulators of leaf senescence and loss-of-function of WRKY75 or AZF2 delayed leaf senescence.We also found that silencing of a protein phosphatase,AtMKP2,promoted early senescence.Collectively,LSD can serve as a comprehensive resource for systematic study of the molecular mechanism of leaf senescence as well as offer candidate genes for functional analyses.

  14. Alisporivir inhibits MERS- and SARS-coronavirus replication in cell culture, but not SARS-coronavirus infection in a mouse model.

    Science.gov (United States)

    de Wilde, Adriaan H; Falzarano, Darryl; Zevenhoven-Dobbe, Jessika C; Beugeling, Corrine; Fett, Craig; Martellaro, Cynthia; Posthuma, Clara C; Feldmann, Heinz; Perlman, Stanley; Snijder, Eric J

    2017-01-15

    Currently, there is no registered treatment for infections with emerging zoonotic coronaviruses like SARS- and MERS-coronavirus. We here report that in cultured cells low-micromolar concentrations of alisporivir, a non-immunosuppressive cyclosporin A-analog, inhibit the replication of four different coronaviruses, including MERS- and SARS-coronavirus. Ribavirin was found to further potentiate the antiviral effect of alisporivir in these cell culture-based infection models, but this combination treatment was unable to improve the outcome of SARS-CoV infection in a mouse model. Nevertheless, our data provide a basis to further explore the potential of Cyp inhibitors as host-directed, broad-spectrum inhibitors of coronavirus replication.

  15. Jnk2 effects on tumor development, genetic instability and replicative stress in an oncogene-driven mouse mammary tumor model.

    Directory of Open Access Journals (Sweden)

    Peila Chen

    Full Text Available Oncogenes induce cell proliferation leading to replicative stress, DNA damage and genomic instability. A wide variety of cellular stresses activate c-Jun N-terminal kinase (JNK proteins, but few studies have directly addressed the roles of JNK isoforms in tumor development. Herein, we show that jnk2 knockout mice expressing the Polyoma Middle T Antigen transgene developed mammary tumors earlier and experienced higher tumor multiplicity compared to jnk2 wildtype mice. Lack of jnk2 expression was associated with higher tumor aneuploidy and reduced DNA damage response, as marked by fewer pH2AX and 53BP1 nuclear foci. Comparative genomic hybridization further confirmed increased genomic instability in PyV MT/jnk2-/- tumors. In vitro, PyV MT/jnk2-/- cells underwent replicative stress and cell death as evidenced by lower BrdU incorporation, and sustained chromatin licensing and DNA replication factor 1 (CDT1 and p21(Waf1 protein expression, and phosphorylation of Chk1 after serum stimulation, but this response was not associated with phosphorylation of p53 Ser15. Adenoviral overexpression of CDT1 led to similar differences between jnk2 wildtype and knockout cells. In normal mammary cells undergoing UV induced single stranded DNA breaks, JNK2 localized to RPA (Replication Protein A coated strands indicating that JNK2 responds early to single stranded DNA damage and is critical for subsequent recruitment of DNA repair proteins. Together, these data support that JNK2 prevents replicative stress by coordinating cell cycle progression and DNA damage repair mechanisms.

  16. SENESCENCE-SUPPRESSED PROTEIN PHOSPHATASE Directly Interacts with the Cytoplasmic Domain of SENESCENCE-ASSOCIATED RECEPTOR-LIKE KINASE and Negatively Regulates Leaf Senescence in Arabidopsis.

    Science.gov (United States)

    Xiao, Dong; Cui, Yanjiao; Xu, Fan; Xu, Xinxin; Gao, Guanxiao; Wang, Yaxin; Guo, Zhaoxia; Wang, Dan; Wang, Ning Ning

    2015-10-01

    Reversible protein phosphorylation mediated by protein kinases and phosphatases plays an important role in the regulation of leaf senescence. We previously reported that the leucine-rich repeat receptor-like kinase SENESCENCE-ASSOCIATED RECEPTOR-LIKE KINASE (AtSARK) positively regulates leaf senescence in Arabidopsis (Arabidopsis thaliana). Here, we report the involvement of a protein serine/threonine phosphatase 2C-type protein phosphatase, SENESCENCE-SUPPRESSED PROTEIN PHOSPHATASE (SSPP), in the negative regulation of Arabidopsis leaf senescence. SSPP transcript levels decreased greatly during both natural senescence and SARK-induced precocious senescence. Overexpression of SSPP significantly delayed leaf senescence in Arabidopsis. Protein pull-down and bimolecular fluorescence complementation assays demonstrated that the cytosol-localized SSPP could interact with the cytoplasmic domain of the plasma membrane-localized AtSARK. In vitro assays showed that SSPP has protein phosphatase function and can dephosphorylate the cytosolic domain of AtSARK. Consistent with these observations, overexpression of SSPP effectively rescued AtSARK-induced precocious leaf senescence and changes in hormonal responses. All our results suggested that SSPP functions in sustaining proper leaf longevity and preventing early senescence by suppressing or perturbing SARK-mediated senescence signal transduction.

  17. Nampt Expression Decreases Age-Related Senescence in Rat Bone Marrow Mesenchymal Stem Cells by Targeting Sirt1

    Science.gov (United States)

    Ma, Cao; Pi, Chenchen; Yang, Yue; Lin, Lin; Shi, Yingai; Li, Yan; Li, Yulin; He, Xu

    2017-01-01

    Senescence restricts the development of applications involving mesenchymal stem cells (MSCs) in research fields, such as tissue engineering, and stem cell therapeutic strategies. Understanding the mechanisms underlying natural aging processes may contribute to the development of novel approaches to preventing age-related diseases or slowing individual aging processes. Nampt is a rate-limiting NAD biosynthetic enzyme that plays critical roles in energy metabolism, cell senescence and maintaining life spans. However, it remains unknown whether Nampt influences stem cell senescence. In this study, the function of Nampt was investigated using a rat model of natural aging. Our data show that Nampt expression was significantly lower in MSCs obtained from aged rats than in those obtained from young rats during physiological aging. Reducing the level of Nampt in aged MSCs resulted in lower intracellular concentrations of NAD+ and downregulated Sirt1 expression and activity. After the Nampt inhibitor FK866 was added, young MSCs were induced to become aged cells. The enhanced senescence was correlated with NAD+ depletion and Sirt1 activity attenuation. In addition, Nampt overexpression attenuated cell senescence in aged MSCs. Our findings provide a new explanation for the mechanisms underlying stem cell senescence and a novel target for delaying stem cell senescence and preventing and treating age-related diseases. PMID:28125705

  18. Significant demographic and fine-scale genetic structure in expanding and senescing populations of the terrestrial orchid Cymbidium goeringii (Orchidaceae).

    Science.gov (United States)

    Chung, Mi Yoon; Nason, John D; Chung, Myong Gi

    2011-12-01

    Fine-scale genetic structure (FSGS) in plants is influenced by variation in spatial and temporal demographic processes. To determine how demographic structure and FSGS change with stages of population succession, we studied replicate expanding and senescing populations of the Asian terrestrial orchid Cymbidium goeringii. We used spatial autocorrelation methods (O-ring and kinship statistics) to quantify spatial demographic structure and FSGS in two expanding and two senescing populations, also measuring genetic diversity and inbreeding in each. All populations exhibited significant aggregation of individuals and FSGS at short spatial scales. In expanding populations, this finding was associated with high recruitment rates, suggesting restricted seed dispersal. In senescing populations, recruitment was minimal, suggesting alternative mechanisms of aggregation, perhaps including spatial associations with mycorrhizal fungi. All populations had significant evidence of genetic bottlenecks, and inbreeding levels were consistently high. Our results indicate that different successional stages can generate similar patterns of spatial demographic and genetic structure, but as a consequence of different processes. These results contrast with the only other study of senescence effects on population genetic structure in an herbaceous perennial, which found little to no FSGS in senescing populations. With the exception of populations subject to mass collection by orchid sellers, significant FSGS is characteristic of the 16 terrestrial orchid species examined to date. From a conservation perspective, this result suggests that inference of orchid population history will benefit from analyses of both FSGS and demographic structure in combination with other ecological field data.

  19. Cellular Senescence: Many Roads, One Final Destination

    Directory of Open Access Journals (Sweden)

    Raya Saab

    2010-01-01

    Full Text Available Cellular senescence is a tumor-suppressor mechanism that has been shown to occur in response to multiple signals, including oncogenic stress, DNA damage, oxidative stress, telomere shortening, and other tumor-promoting insults. Over the past decade, much has been uncovered regarding the phenotype of this tumor-suppressor response and the underlying pathways necessary for its establishment. However, we have also learned that the intricate details of signaling pathways underlying senescence as a tumor-suppressor response are very much context dependent. In addition, cross-talk among pathways, and negative and positive feedback loops, all complicate our understanding of this process. This short review attempts to summarize what is known to date regarding senescence in tumor suppression, both in vitro and in vivo. Further insights into pathways necessary for senescence will hopefully identify appropriate targets for interventions to not only induce senescence as a treatment of cancerous lesions, but also to maintain this state in premalignant lesions in an effort to prevent progression to cancer.

  20. Acrylamide induces accelerated endothelial aging in a human cell model.

    Science.gov (United States)

    Sellier, Cyril; Boulanger, Eric; Maladry, François; Tessier, Frédéric J; Lorenzi, Rodrigo; Nevière, Rémi; Desreumaux, Pierre; Beuscart, Jean-Baptiste; Puisieux, François; Grossin, Nicolas

    2015-09-01

    Acrylamide (AAM) has been recently discovered in food as a Maillard reaction product. AAM and glycidamide (GA), its metabolite, have been described as probably carcinogenic to humans. It is widely established that senescence and carcinogenicity are closely related. In vitro, endothelial aging is characterized by replicative senescence in which primary cells in culture lose their ability to divide. Our objective was to assess the effects of AAM and GA on human endothelial cell senescence. Human umbilical vein endothelial cells (HUVECs) cultured in vitro were used as model. HUVECs were cultured over 3 months with AAM or GA (1, 10 or 100 μM) until growth arrest. To analyze senescence, β-galactosidase activity and telomere length of HUVECs were measured by cytometry and semi-quantitative PCR, respectively. At all tested concentrations, AAM or GA reduced cell population doubling compared to the control condition (p < 0.001). β-galactosidase activity in endothelial cells was increased when exposed to AAM (≥10 μM) or GA (≥1 μM) (p < 0.05). AAM (≥10 μM) or GA (100 μM) accelerated telomere shortening in HUVECs (p < 0.05). In conclusion, in vitro chronic exposure to AAM or GA at low concentrations induces accelerated senescence. This result suggests that an exposure to AAM might contribute to endothelial aging.

  1. Accelerated cellular senescence phenotype of GAPDH-depleted human lung carcinoma cells

    Energy Technology Data Exchange (ETDEWEB)

    Phadke, Manali; Krynetskaia, Natalia [Temple University School of Pharmacy, Philadelphia, PA 19140 (United States); Mishra, Anurag [Jayne Haines Center for Pharmacogenomics, Temple University School of Pharmacy, Philadelphia, PA 19140 (United States); Krynetskiy, Evgeny, E-mail: ekrynets@temple.edu [Temple University School of Pharmacy, Philadelphia, PA 19140 (United States); Jayne Haines Center for Pharmacogenomics, Temple University School of Pharmacy, Philadelphia, PA 19140 (United States)

    2011-07-29

    Highlights: {yields} We examined the effect of glyceraldehyde 3-phosphate (GAPDH) depletion on proliferation of human carcinoma A549 cells. {yields} GAPDH depletion induces accelerated senescence in tumor cells via AMPK network, in the absence of DNA damage. {yields} Metabolic and genetic rescue experiments indicate that GAPDH has regulatory functions linking energy metabolism and cell cycle. {yields} Induction of senescence in LKB1-deficient lung cancer cells via GAPDH depletion suggests a novel strategy to control tumor cell proliferation. -- Abstract: Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is a pivotal glycolytic enzyme, and a signaling molecule which acts at the interface between stress factors and the cellular apoptotic machinery. Earlier, we found that knockdown of GAPDH in human carcinoma cell lines resulted in cell proliferation arrest and chemoresistance to S phase-specific cytotoxic agents. To elucidate the mechanism by which GAPDH depletion arrests cell proliferation, we examined the effect of GAPDH knockdown on human carcinoma cells A549. Our results show that GAPDH-depleted cells establish senescence phenotype, as revealed by proliferation arrest, changes in morphology, SA-{beta}-galactosidase staining, and more than 2-fold up-regulation of senescence-associated genes DEC1 and GLB1. Accelerated senescence following GAPDH depletion results from compromised glycolysis and energy crisis leading to the sustained AMPK activation via phosphorylation of {alpha} subunit at Thr172. Our findings demonstrate that GAPDH depletion switches human tumor cells to senescent phenotype via AMPK network, in the absence of DNA damage. Rescue experiments using metabolic and genetic models confirmed that GAPDH has important regulatory functions linking the energy metabolism and the cell cycle networks. Induction of senescence in LKB1-deficient non-small cell lung cancer cells via GAPDH depletion suggests a novel strategy to control tumor cell proliferation.

  2. YAP/TEAD-mediated transcription controls cellular senescence

    National Research Council Canada - National Science Library

    Xie, Qi; Chen, Jing; Feng, Han; Peng, Shengyi; Adams, Ursula; Bai, Yujie; Huang, Li; Li, Ji; Huang, Junjian; Meng, Songshu; Yuan, Zengqiang

    2013-01-01

    .... Silencing of YAP inhibits cell proliferation and induces premature senescence. In additional experiments, we observe that cellular senescence induced by YAP deficiency is TEAD- and Rb/p16/p53-dependent...

  3. Senescence-associated β-galactosidase activity in the in vitro ovarian stromal fibroblasts

    Directory of Open Access Journals (Sweden)

    Lilian Chuaire-Noack

    2011-04-01

    Full Text Available A growing biological research field is the cellular senescence, a mechanism that has been associated, under certain circumstances, withmalignant transformation. Given the high incidence of ovarian cancerand its main origin from the ovarian surface epithelium, as well asthe possibility that an epithelial-mesenchymal transition occurs, weevaluated both the in vitro growth of stromal fibroblasts from the ovarian cortex and their β-galactosidase activity at pH 6,enzyme whose expression is considered as a marker of replicativesenescence. Methods: 48 samples of ovarian cortical fibroblasts fromdonors without a history of cancer were serially cultured untilthe end of their replicative life. β-galactosidase activity at pH 6was quantified in each passage by the chemiluminiscent method. Ascontrol, we used ovarian epithelial cell cultures from the samedonors. The enzyme activity was also evaluated in fibroblastspreviously induced to senescence by exposure to hydrogen peroxide.Results: The analysis of the enzyme activity and the replicativecapacity taken together showed that the fibroblast cultures reachedthe senescent state at passages 4-5, as what happened with the control epithelial cells. Fibroblasts induced to senescence showed high variability in the values of enzymatic activity. Conclusions:The similarity between both types of cells in reaching the senescent state deserves to be taken into account in relation to theepithelialmesenchymal transition that has been proposed to explaintheir behavior in the genesis of cancer arising from ovarian surfaceepithelium. Low β-galactosidase activity values at pH 6 would suggestpossible inactivation of the response pathways to oxidative stress.

  4. Mitochondrial functional changes characterization in young and senescent human adipose derived MSCs

    Directory of Open Access Journals (Sweden)

    Bernd Robert Stab II

    2016-12-01

    Full Text Available Mitochondria are highly dynamic organelles that in response to the cell’s bio-energetic state continuously undergo structural remodeling fission and fusion processes. This mitochondrial dynamic activity has been implicated in cell cycle, autophagy and age-related diseases. Adult tissue-derived mesenchymal stromal/stem cells present a therapeutic potential. However, to obtain an adequate mesenchymal stromal/stem cell number for clinical use, extensive in vitro expansion is required. Unfortunately, these cells undergo replicative senescence rapidly by mechanisms that are not well understood. Senescence has been associated with metabolic changes in the oxidative state of the cell, a process that has been also linked to mitochondrial fission and fusion events, suggesting an association between mitochondrial dynamic and senescence. In the present work, we studied the mitochondrial structural remodeling process of mesenchymal stromal/stem cells isolated from adipose tissue in vitro to determine if mitochondrial phenotypic changes are associated with mesenchymal stromal/stem cell senescence. For this purpose, mitochondrial dynamics and oxidative state of stromal/stem cell were compared between young and old cells. With increased cell passage, we observed a significant change in cell morphology that is associated with an increase in β-galactosidase activity. In addition, old cells (population doubling seven also showed increased mitochondrial mass, augmented superoxide production, and decreased mitochondrial membrane potential. These changes in morphology were related to slightly levels increases in mitochondrial fusion proteins, Mitofusion 1 (MFN1 and Dynamin-realted GTPase (OPA1. Collectively, our results showed that adipose tissue-derived MSCs at population doubling seven develop a senescent phenotype that is characterized by metabolic cell changes that can lead to mitochondrial fusion.

  5. Jasmonates during senescence: signals or products of metabolism?

    Science.gov (United States)

    Seltmann, Martin A; Hussels, Wiebke; Berger, Susanne

    2010-11-01

    Jasmonic acid and derivatives are oxylipin signaling compounds derived from linolenic acid. Jasmonates accumulate during natural and dark-induced senescence but the increase in these compounds is not essential for the initiation or progression of these senescence processes. Here we report that during natural and dark-induced senescence the increase in jasmonate levels does not trigger jasmonate signaling. Furthermore we provide evidence that jasmonate production might result from membrane turnover during dark-induced senescence.

  6. The organotypic multicellular spheroid is a relevant three-dimensional model to study adenovirus replication and penetration in human tumors in vitro.

    Science.gov (United States)

    Grill, Jacques; Lamfers, Martine L M; van Beusechem, Victor W; Dirven, Clemens M; Pherai, D Shareen; Kater, Mathijs; Van der Valk, Paul; Vogels, Ronald; Vandertop, W Peter; Pinedo, Herbert M; Curiel, David T; Gerritsen, Winald R

    2002-11-01

    The use of adenoviruses for gene transfer and as oncolytic agents is currently receiving widespread attention. As specific constraints to adenovirus distribution and spread cannot be studied in cell cultures, there is a need for an in vitro three-dimensional (3D) model mimicking the in vivo biology of tumors. We studied the interactions between tumor and adenoviruses using multicellular spheroids grown from primary brain tumor material. Using beta-galactosidase and luciferase reporter genes expressed by replication-defective adenoviruses, we showed that infection was restricted to the first layer of cells. Using a replication-competent adenovirus expressing the luciferase gene, we showed that transgene expression in the spheroid was considerably enhanced and that viral spreading deep into the 3D structure took place. In addition, a tetrazolium salt-based metabolic assay could be used to compare the oncolytic activity of different concentrations of replication-competent adenoviruses. We can conclude that organotypic spheroids offer a versatile in vitro system for studying distribution, spread, and oncolysis by adenoviruses in a clinically relevant model.

  7. Drying Without Senescence in Resurrection Plants

    Directory of Open Access Journals (Sweden)

    Cara Ashleigh Griffiths

    2014-02-01

    Full Text Available Research into extreme drought tolerance in resurrection plants using species such as Craterostigma plantagineum, Craterostigma wilmsii, Xerophyta humilis, Tortula ruralis and Sporobolus stapfianus has provided some insight into the desiccation tolerance mechanisms utilized by these plants to allow them to persist under extremely adverse environmental conditions. Some of the mechanisms used to ensure cellular preservation during severe dehydration appear to be peculiar to resurrection plants. Apart from the ability to preserve vital cellular components during drying and rehydration, such mechanisms include the ability to down-regulate growth-related metabolism rapidly in response to changes in water availability, and the ability to inhibit dehydration-induced senescence programs enabling reconstitution of photosynthetic capacity quickly following a rainfall event. Currently, very little is known about the molecular mechanisms that resurrection plants employ to avoid undergoing drought-related senescence during the desiccation process. To survive desiccation, dehydration in the perennial resurrection grass S. stapfianus must proceed slowly over a period of 7 days or more. Leaves detached from the plant before 60% relative water content (RWC is attained are desiccation-sensitive indicating that desiccation tolerance is conferred in vegetative tissue of S. stapfianus when the leaf RWC has declined to 60%. Whilst some older leaves remaining attached to the plant during dehydration will senesce, suggesting dehydration-induced senescence may be influenced by leaf age or the rate of dehydration in individual leaves, the majority of leaves do not senesce. Rather these leaves dehydrate to air-dryness and revive fully following rehydration. Hence it seems likely that there are genes expressed in younger leaf tissues of resurrection plants that enable suppression of drought-related senescence pathways. As very few studies have directly addressed this

  8. Simvastatin suppresses breast cancer cell proliferation induced by senescent cells

    NARCIS (Netherlands)

    Liu, Su; Uppal, Harpreet; Demaria, Marco; Desprez, Pierre-Yves; Campisi, Judith; Kapahi, Pankaj

    2015-01-01

    Cellular senescence suppresses cancer by preventing the proliferation of damaged cells, but senescent cells can also promote cancer though the pro-inflammatory senescence-associated secretory phenotype (SASP). Simvastatin, an HMG-coA reductase inhibitor, is known to attenuate inflammation and preven

  9. The Pace and Shape of Senescence in Angiosperms

    DEFF Research Database (Denmark)

    Baudisch, Annette; Salguero-Gómez, Roberto; Jones, Owen

    2013-01-01

    1. Demographic senescence, the decay in fertility and increase in the risk of mortality with age, is one of the most striking phenomena in ecology and evolution. Comparative studies of senescence patterns of plants are scarce, and consequently, little is known about senescence and its determinant...

  10. Senescence rates in patients with end-stage renal disease

    DEFF Research Database (Denmark)

    Koopman, J J E; Rozing, M P; Kramer, Ada;

    2011-01-01

    function of the Gompertz equation as a superior descriptor of senescence rate. Here, we tested both measures of the rate of senescence in a population of patients with end-stage renal disease. It is clinical dogma that patients on dialysis experience accelerated senescence, whereas those with a functional...

  11. Mitochondrial DNA damage induces apoptosis in senescent cells

    NARCIS (Netherlands)

    Laberge, R-M; Adler, D; DeMaria, M; Mechtouf, N; Teachenor, R; Cardin, G B; Desprez, P-Y; Campisi, J; Rodier, F

    2013-01-01

    Senescence is a cellular response to damage and stress. The senescence response prevents cancer by suppressing the proliferation of cells with a compromised genome and contributes to optimal wound healing in normal tissues. Persistent senescent cells are also thought to drive aging and age-associate

  12. Identification and replication of prediction models for ovulation, pregnancy and live birth in infertile women with polycystic ovary syndrome.

    Science.gov (United States)

    Kuang, Hongying; Jin, Susan; Hansen, Karl R; Diamond, Michael P; Coutifaris, Christos; Casson, Peter; Christman, Gregory; Alvero, Ruben; Huang, Hao; Bates, G Wright; Usadi, Rebecca; Lucidi, Scott; Baker, Valerie; Santoro, Nanette; Eisenberg, Esther; Legro, Richard S; Zhang, Heping

    2015-09-01

    Can we build and validate predictive models for ovulation and pregnancy outcomes in infertile women with polycystic ovary syndrome (PCOS)? We were able to develop and validate a predictive model for pregnancy outcomes in women with PCOS using simple clinical and biochemical criteria particularly duration of attempting conception, which was the most consistent predictor among all considered factors for pregnancy outcomes. Predictive models for ovulation and pregnancy outcomes in infertile women with polycystic ovary syndrome have been reported, but such models require validation. This is a secondary analysis of the data from the Pregnancy in Polycystic Ovary Syndrome I and II (PPCOS-I and -II) trials. Both trials were double-blind, randomized clinical trials that included 626 and 750 infertile women with PCOS, respectively. PPCOS-I participants were randomized to either clomiphene citrate (CC), metformin, or their combination, and PPCOS-II participants to either letrozole or CC for up to five treatment cycles. Linear logistic regression models were fitted using treatment, BMI, and other published variables as predictors of ovulation, conception, clinical pregnancy, and live birth as the outcome one at a time. We first evaluated previously reported significant predictors, and then constructed new prediction models. Receiver operating characteristic (ROC) curves were constructed and the area under the curves (AUCs) was calculated to compare performance using different models and data. Chi-square tests were used to examine the goodness-of-fit and prediction power of logistic regression model. Predictive factors were similar between PPCOS-I and II, but the two participant samples differed statistically significantly but the differences were clinically minor on key baseline characteristics and hormone levels. Women in PPCOS-II had an overall more severe PCOS phenotype than women in PPCOS-I. The clinically minor but statistically significant differences may be due to the

  13. Drying without senescence in resurrection plants.

    Science.gov (United States)

    Griffiths, Cara A; Gaff, Donald F; Neale, Alan D

    2014-01-01

    Research into extreme drought tolerance in resurrection plants using species such as Craterostigma plantagineum, C. wilmsii, Xerophyta humilis, Tortula ruralis, and Sporobolus stapfianus has provided some insight into the desiccation tolerance mechanisms utilized by these plants to allow them to persist under extremely adverse environmental conditions. Some of the mechanisms used to ensure cellular preservation during severe dehydration appear to be peculiar to resurrection plants. Apart from the ability to preserve vital cellular components during drying and rehydration, such mechanisms include the ability to down-regulate growth-related metabolism rapidly in response to changes in water availability, and the ability to inhibit dehydration-induced senescence programs enabling reconstitution of photosynthetic capacity quickly following a rainfall event. Extensive research on the molecular mechanism of leaf senescence in non-resurrection plants has revealed a multi-layered regulatory network operates to control programed cell death pathways. However, very little is known about the molecular mechanisms that resurrection plants employ to avoid undergoing drought-related senescence during the desiccation process. To survive desiccation, dehydration in the perennial resurrection grass S. stapfianus must proceed slowly over a period of 7 days or more. Leaves detached from the plant before 60% relative water content (RWC) is attained are desiccation-sensitive indicating that desiccation tolerance is conferred in vegetative tissue of S. stapfianus when the leaf RWC has declined to 60%. Whilst some older leaves remaining attached to the plant during dehydration will senesce, suggesting dehydration-induced senescence may be influenced by leaf age or the rate of dehydration in individual leaves, the majority of leaves do not senesce. Rather these leaves dehydrate to air-dryness and revive fully following rehydration. Hence it seems likely that there are genes expressed in

  14. Cancer stem cells display extremely large evolvability: alternating plastic and rigid networks as a potential Mechanism: network models, novel therapeutic target strategies, and the contributions of hypoxia, inflammation and cellular senescence.

    Science.gov (United States)

    Csermely, Peter; Hódsági, János; Korcsmáros, Tamás; Módos, Dezső; Perez-Lopez, Áron R; Szalay, Kristóf; Veres, Dániel V; Lenti, Katalin; Wu, Ling-Yun; Zhang, Xiang-Sun

    2015-02-01

    Cancer is increasingly perceived as a systems-level, network phenomenon. The major trend of malignant transformation can be described as a two-phase process, where an initial increase of network plasticity is followed by a decrease of plasticity at late stages of tumor development. The fluctuating intensity of stress factors, like hypoxia, inflammation and the either cooperative or hostile interactions of tumor inter-cellular networks, all increase the adaptation potential of cancer cells. This may lead to the bypass of cellular senescence, and to the development of cancer stem cells. We propose that the central tenet of cancer stem cell definition lies exactly in the indefinability of cancer stem cells. Actual properties of cancer stem cells depend on the individual "stress-history" of the given tumor. Cancer stem cells are characterized by an extremely large evolvability (i.e. a capacity to generate heritable phenotypic variation), which corresponds well with the defining hallmarks of cancer stem cells: the possession of the capacity to self-renew and to repeatedly re-build the heterogeneous lineages of cancer cells that comprise a tumor in new environments. Cancer stem cells represent a cell population, which is adapted to adapt. We argue that the high evolvability of cancer stem cells is helped by their repeated transitions between plastic (proliferative, symmetrically dividing) and rigid (quiescent, asymmetrically dividing, often more invasive) phenotypes having plastic and rigid networks. Thus, cancer stem cells reverse and replay cancer development multiple times. We describe network models potentially explaining cancer stem cell-like behavior. Finally, we propose novel strategies including combination therapies and multi-target drugs to overcome the Nietzschean dilemma of cancer stem cell targeting: "what does not kill me makes me stronger".

  15. Melatonin can improve insulin resistance and aging-induced pancreas alterations in senescence-accelerated prone male mice (SAMP8)

    OpenAIRE

    Cuesta, Sara; Kireev, Roman; García, Cruz; Rancan, Lisa; Vara, Elena; Jesús A. F. Tresguerres

    2012-01-01

    The aim of the present study was to investigate the effect of aging on several parameters related to glucose homeostasis and insulin resistance in pancreas and how melatonin administration could affect these parameters. Pancreas samples were obtained from two types of male mice models: senescence-accelerated prone (SAMP8) and senescence-accelerated-resistant mice (SAMR1). Insulin levels in plasma were increased with aging in both SAMP8 and SAMR1 mice, whereas insulin content in pancreas was d...

  16. Western diet consumption promotes vascular remodeling in non-senescent mice consistent with accelerated senescence, but does not modify vascular morphology in senescent ones.

    Science.gov (United States)

    Dantas, Ana Paula; Onetti, Yara; Oliveira, María Aparecida; Carvalho, Maria Helena; Heras, Magda; Vila, Elisabet; Jiménez-Altayó, Francesc

    2014-07-01

    Senescence accelerated mice (SAM) are susceptible to developing vascular dysfunction and remodeling. Food intake and type of diet have also been identified as determining factors in vascular remodeling. However, the interplay between senescence and diet in vascular remodeling is largely unknown. We aimed to analyze structure of large (aorta) and small (mesenteric; MA) arteries from seven-month-old SAM prone (SAMP8) and resistant (SAMR1) mice that received a Western-type high-fat diet (WD; 8weeks). Aortic structure was assessed by morphometric analysis of hematoxylin and eosin-stained cross sections, and collagen content by qRT-PCR, immunofluorescence and picrosirius red. In MAs, structural and mechanical properties were measured by pressure myography; elastin and collagen content by qRT-PCR and immunofluorescence; nuclei distribution by confocal microscopy; and apoptosis by qRT-PCR and TUNEL assay. In aorta, wall thickness (WT), but not cross-sectional area (CSA), was increased by senescence, and WD only increased WT in SAMR1. WD intake, but not senescence, was associated with increased collagen deposition. In MAs, senescence diminished WT and CSA, without altering collagen and elastin deposition, reduced the number of MA wall cells, and increased pro apoptotic activation. WD consumption promoted in SAMR1 the same remodeling observed with senescence, while in SAMP8 the senescence-associated changes remained unaffected. The mechanisms involved in WD-induced MA remodeling in SAMR1 mimicked those observed in senescence per se. Our study reveals qualitatively different remodeling in aortas and MAs from senescent mice. Consumption of a WD induced remodeling of the SAMR1 vasculature similar to that induced by senescence, while it did not promote any further alteration in the latter. Therefore, we propose that increased consumption of fat-enriched diets could promote accelerated senescence of the non-senescent vasculature, although it does not exacerbate vascular

  17. Maladaptation as a source of senescence in habitats variable in space and time.

    Science.gov (United States)

    Cotto, Olivier; Ronce, Ophélie

    2014-09-01

    In this study, we use a quantitative genetics model of structured populations to investigate the evolution of senescence in a variable environment. Adaptation to local environments depends on phenotypic traits whose optimal values vary with age and with environmental conditions. We study different scenarios of environmental heterogeneity, where the environment changes abruptly, gradually, or cyclically with time and where the environment is heterogeneous in space with different populations connected by migration. The strength of selection decreases with age, which predicts slower adaptation of traits expressed late in the life cycle, potentially generating stronger senescence in habitats where selection changes in space or in time. This prediction is however complicated by the fact that the genetic variance also increases with age. Using numerical calculations, we found that the rate of senescence is generally increased when the environment varies. In particular, migration between different habitats is a source of senescence in heterogeneous landscapes. We also show that the rate of senescence can vary transiently when the population is not at equilibrium, with possible implications for experimental evolution and the study of invasive species. Our results highlight the need to study age-specific adaptation, as a changing environment can have a different impact on different age classes.

  18. Adiponectin Suppresses UVB-Induced Premature Senescence and hBD2 Overexpression in Human Keratinocytes.

    Science.gov (United States)

    Kim, MinJeong; Park, Kui Young; Lee, Mi-Kyung; Jin, Taewon; Seo, Seong Jun

    2016-01-01

    Recent studies have revealed that adiponectin can suppress cellular inflammatory signaling pathways. This study aimed to elucidate the effect of adiponectin on the unregulated production of hBD2 in UVB-induced premature senescent keratinocytes. We constructed an in vitro model of premature senescent keratinocytes through repeated exposure to low energy UVB. After repeated low energy UVB exposure, there was significant generation of reactive oxygen species (ROS) and induction of senescence-associated markers, including senescence associated beta-galactosidase activity and expression of p16INK4a and histone H2AX. In addition, the present clinical study showed higher expression of hBD2 in sun-exposed skin of elderly group, and the overexpression of hBD2 was observed by c-Fos activation in vitro. Adiponectin has the ability to scavenge ROS and consequently inhibit MAPKs and SA-markers in UVB-exposed keratinocytes. An inhibitor study demonstrated that adiponectin downregulated hBD2 mRNA expression through suppression of the AP-1 transcription factor components c-Fos via inactivation of p38 MAPK. Collectively, the dysregulated production of hBD2 by the induction of oxidative stress was attenuated by adiponectin through the suppression of p38 and JNK/SAPK MAPK signaling in UVB-mediated premature senescent inducible conditions. These results suggest the feasibility of adiponectin as an anti-photoaging and anti-inflammatory agent in the skin.

  19. Low zinc environment induces stress signaling, senescence and mixed cell death modalities in colon cancer cells.

    Science.gov (United States)

    Rudolf, Emil; Rudolf, Kamil

    2015-12-01

    Currently it is not clear what type of the final cellular response (i.e. cell death modality or senescence) is induced upon chronic intracellular zinc depletion in colon cancer cells. To address this question, isogenic colon cancer lines SW480 and SW620 exposed to low zinc environment were studied over the period of 6 weeks. Low zinc environment reduced total as well as free intracellular zinc content in both cell lines. Decreased intracellular zinc content resulted in changes in cellular proliferation, cell cycle distribution and activation of stress signaling. In addition, colonocytes with low zinc content displayed increased levels of oxidative stress, changes in mitochondrial activity but in the absence of significant DNA damage. Towards the end of treatment (4th-6th week), exposed cells started to change morphologically, and typical markers of senescence as well as cell death appeared. Of two examined colon cancer cell lines, SW480 cells proved to activate predominantly senescent phenotype, with frequent form of demise being necrosis and mixed cell death modality but not apoptosis. Conversely, SW620 cells activated mostly cell death, with relatively equal distribution of apoptosis and mixed types, while senescent phenotypes and necrosis were present only in a small fraction of cell populations. Addition of zinc at the beginning of 4th week of treatment significantly suppressed cell death phenotypes in both cell lines but had no significant effect on senescence. In conclusion, presented results demonstrate variability of responses to chronic zinc depletion in colon cancer as modeled in vitro.

  20. Comparison of three replication strategies in complex multicellular organisms: Asexual replication, sexual replication with identical gametes, and sexual replication with distinct sperm and egg gametes

    Science.gov (United States)

    Tannenbaum, Emmanuel

    2008-01-01

    This paper studies the mutation-selection balance in three simplified replication models. The first model considers a population of organisms replicating via the production of asexual spores. The second model considers a sexually replicating population that produces identical gametes. The third model considers a sexually replicating population that produces distinct sperm and egg gametes. All models assume diploid organisms whose genomes consist of two chromosomes, each of which is taken to be functional if equal to some master sequence, and defective otherwise. In the asexual population, the asexual diploid spores develop directly into adult organisms. In the sexual populations, the haploid gametes enter a haploid pool, where they may fuse with other haploids. The resulting immature diploid organisms then proceed to develop into mature organisms. Based on an analysis of all three models, we find that, as organism size increases, a sexually replicating population can only outcompete an asexually replicating population if the adult organisms produce distinct sperm and egg gametes. A sexual replication strategy that is based on the production of large numbers of sperm cells to fertilize a small number of eggs is found to be necessary in order to maintain a sufficiently low cost for sex for the strategy to be selected for over a purely asexual strategy. We discuss the usefulness of this model in understanding the evolution and maintenance of sexual replication as the preferred replication strategy in complex, multicellular organisms.

  1. Nucleotide Metabolism and DNA Replication.

    Science.gov (United States)

    Warner, Digby F; Evans, Joanna C; Mizrahi, Valerie

    2014-10-01

    The development and application of a highly versatile suite of tools for mycobacterial genetics, coupled with widespread use of "omics" approaches to elucidate the structure, function, and regulation of mycobacterial proteins, has led to spectacular advances in our understanding of the metabolism and physiology of mycobacteria. In this article, we provide an update on nucleotide metabolism and DNA replication in mycobacteria, highlighting key findings from the past 10 to 15 years. In the first section, we focus on nucleotide metabolism, ranging from the biosynthesis, salvage, and interconversion of purine and pyrimidine ribonucleotides to the formation of deoxyribonucleotides. The second part of the article is devoted to DNA replication, with a focus on replication initiation and elongation, as well as DNA unwinding. We provide an overview of replication fidelity and mutation rates in mycobacteria and summarize evidence suggesting that DNA replication occurs during states of low metabolic activity, and conclude by suggesting directions for future research to address key outstanding questions. Although this article focuses primarily on observations from Mycobacterium tuberculosis, it is interspersed, where appropriate, with insights from, and comparisons with, other mycobacterial species as well as better characterized bacterial models such as Escherichia coli. Finally, a common theme underlying almost all studies of mycobacterial metabolism is the potential to identify and validate functions or pathways that can be exploited for tuberculosis drug discovery. In this context, we have specifically highlighted those processes in mycobacterial DNA replication that might satisfy this critical requirement.

  2. Replication Restart in Bacteria.

    Science.gov (United States)

    Michel, Bénédicte; Sandler, Steven J

    2017-07-01

    In bacteria, replication forks assembled at a replication origin travel to the terminus, often a few megabases away. They may encounter obstacles that trigger replisome disassembly, rendering replication restart from abandoned forks crucial for cell viability. During the past 25 years, the genes that encode replication restart proteins have been identified and genetically characterized. In parallel, the enzymes were purified and analyzed in vitro, where they can catalyze replication initiation in a sequence-independent manner from fork-like DNA structures. This work also revealed a close link between replication and homologous recombination, as replication restart from recombination intermediates is an essential step of DNA double-strand break repair in bacteria and, conversely, arrested replication forks can be acted upon by recombination proteins and converted into various recombination substrates. In this review, we summarize this intense period of research that led to the characterization of the ubiquitous replication restart protein PriA and its partners, to the definition of several replication restart pathways in vivo, and to the description of tight links between replication and homologous recombination, responsible for the importance of replication restart in the maintenance of genome stability. Copyright © 2017 American Society for Microbiology.

  3. Leaf senescence and nutrient remobilisation in barley and wheat

    DEFF Research Database (Denmark)

    Gregersen, P L; Holm, P B; Krupinska, K

    2008-01-01

    Extensive studies have been undertaken on senescence processes in barley and wheat and their importance for the nitrogen use efficiency of these crop plants. During the senescence processes, proteins are degraded and nutrients are re-mobilised from senescing leaves to other organs, especially...... in degradative, metabolic and regulatory processes that could be used in future strategies aimed at modifying the senescence process. The breeding of crops for characters related to senescence processes, e.g. higher yields and better nutrient use efficiency, is complex. Such breeding has to cope with the dilemma...

  4. Prophylactic use of Ganoderma lucidum extract may inhibit Mycobacterium tuberculosis replication in a new mouse model of spontaneous latent tuberculosis infection

    Directory of Open Access Journals (Sweden)

    Chuan eQin

    2016-01-01

    Full Text Available A mouse model of spontaneous latent tuberculosis infection (LTBIthat mimics latent tuberculosis infection in humans is valuable for drug/vaccine development and the study of tuberculosis. However, most LTBI mouse models require interventions, and a spontaneous LTBI mouse model with a low bacterial load is difficult to establish. In this study, mice were IV-inoculated with 100 CFU Mycobacterium tuberculosis H37Rv, and a persistent LTBI was established with low bacterial loads (0.5~1.5log10 CFU in the lung; <4log10 CFU in the spleen. Histopathological changes in the lung, spleen, and liver were mild during the first 20 weeks post-inoculation. The model was used to demonstrate the comparative effects of prophylactic and therapeutic administration of Ganoderma lucidum extract (spores and spores lipid in preventing H37Rv replication in both lung and spleen. H37Rv was inhibited with prophylactic use of G. lucidum extract relative to that of the untreated control and therapy groups, and observed in the spleen as early as post-inoculation week 3. H37Rv infection in the therapy group was comparable to that of the untreated control mice. No significant mitigation of pathological changes was observed in either the prophylactic or therapeutic groups. Our results suggest that this LTBI model is an efficient means of testing anti-tuberculosis vaccines and drugs. The use of G. lucidum extract prior to M. tuberculosis infection may protect the host against bacterial replication to some extent.

  5. The role of cellular senescence during vascular calcification: a key paradigm in aging research.

    Science.gov (United States)

    Mackenzie, N C W; MacRae, V E

    2011-07-01

    Vascular calcification has severe clinical consequences and is considered an accurate predictor of future adverse cardiovascular events. Vascular calcification refers to the deposition of calcium phosphate mineral, most often hydroxyapatite, in arteries. Extensive calcification of the vascular system is a key characteristic of aging. In this article, we outline the mechanisms governing vascular calcification and highlight its association with cellular senescence. This review discusses the molecular mechanisms of cellular senescence and its affect on calcification of vascular cells, the relevance of phosphate regulation and the function of FGF23 and Klotho proteins. The association of vascular calcification and cellular senescence with the rare human aging disorder Hutchison-Gilford Progeria Syndrome (HGPS) is highlighted and the mouse models used to try to determine the underlying pathways are discussed. By understanding the pathways involved in these processes novel drug targets may be elucidated in an effort to reduce the effects of cellular aging as a risk factor in cardiovascular disease.

  6. Use of two-part regression calibration model to correct for measurement error in episodically consumed foods in a single-replicate study design: EPIC case study.

    Directory of Open Access Journals (Sweden)

    George O Agogo

    Full Text Available In epidemiologic studies, measurement error in dietary variables often attenuates association between dietary intake and disease occurrence. To adjust for the attenuation caused by error in dietary intake, regression calibration is commonly used. To apply regression calibration, unbiased reference measurements are required. Short-term reference measurements for foods that are not consumed daily contain excess zeroes that pose challenges in the calibration model. We adapted two-part regression calibration model, initially developed for multiple replicates of reference measurements per individual to a single-replicate setting. We showed how to handle excess zero reference measurements by two-step modeling approach, how to explore heteroscedasticity in the consumed amount with variance-mean graph, how to explore nonlinearity with the generalized additive modeling (GAM and the empirical logit approaches, and how to select covariates in the calibration model. The performance of two-part calibration model was compared with the one-part counterpart. We used vegetable intake and mortality data from European Prospective Investigation on Cancer and Nutrition (EPIC study. In the EPIC, reference measurements were taken with 24-hour recalls. For each of the three vegetable subgroups assessed separately, correcting for error with an appropriately specified two-part calibration model resulted in about three fold increase in the strength of association with all-cause mortality, as measured by the log hazard ratio. Further found is that the standard way of including covariates in the calibration model can lead to over fitting the two-part calibration model. Moreover, the extent of adjusting for error is influenced by the number and forms of covariates in the calibration model. For episodically consumed foods, we advise researchers to pay special attention to response distribution, nonlinearity, and covariate inclusion in specifying the calibration model.

  7. A mouse model based on replication-competent Tiantan vaccinia expressing luciferase/HIV-1 Gag fusion protein for the evaluation of protective efficacy of HIV vaccine

    Institute of Scientific and Technical Information of China (English)

    HUANG Yang; QIU Chao; LIU Lian-xing; FENG Yan-meng; ZHU Ting; XU Jian-qing

    2009-01-01

    Background Developing an effective vaccine against human immunodeficiency virus type 1 (HIV-1) remains a grand challenge after more than two decades of intensive effort. It is partially due to the lack of suitable animal models for screening and prioritizing vaccine candidates. In this study, we aim to develop a mice model to test HIV-1 vaccine efficacy. Methods We constructed a recombinant vaccinia expressing firefly luciferase and HIV-1 Gag fusion protein based on Tiantan strain, an attenuated but replication-competent poxvirus (rTTV-lucgag). By quantifying the luciferase activity as its read out, we defined the biodistribution of Tiantan strain poxvirus in mice inoculated intraperitoneally and attempted to apply this model to evaluate the HIV-1 vaccine efficacy. Results Our data demonstrated that the rTTV-lucgag was able to express high level of luciferase (≤106 relative luciferase units (RLU)/mg protein) and HIV-1 Gag (>3 folds increase comparing to the control). After intraperitoneal inoculation, this virus had dominant replication in the ovary, uterus, and cervix of mice and the luciferase activities in those organs are significantly correlated with viral titers (r2=0.71, P <0.01). Pre-immunization with an HIV gag DNA vaccine reduced the luciferase activity in ovary from (6006+3141) RLU/mg protein in control group to (1538±463) RLU/mg protein in vaccine group (P=0.1969). Conclusions The luciferase activity in ovary could represent viral replication in vivo;, this rTTV-lucgag/mice model may be suitable to assess the protective efficacy of cytotoxic T-cell responses to HIV Gag with less tedious work and high through-put.

  8. T cell senescence and cardiovascular diseases.

    Science.gov (United States)

    Yu, Hee Tae; Park, Sungha; Shin, Eui-Cheol; Lee, Won-Woo

    2016-08-01

    Age-related changes in the immune system, commonly termed "immunosenescence," contribute to deterioration of the immune response and fundamentally impact the health and survival of elderly individuals. Immunosenescence affects both the innate and adaptive immune systems; however, the most notable changes are in T cell immunity and include thymic involution, the collapse of T cell receptor (TCR) diversity, an imbalance in T cell populations, and the clonal expansion of senescent T cells. Senescent T cells have the ability to produce large quantities of proinflammatory cytokines and cytotoxic mediators; thus, they have been implicated in the pathogenesis of many chronic inflammatory diseases. Recently, an increasing body of evidence has suggested that senescent T cells also have pathogenic potential in cardiovascular diseases, such as hypertension, atherosclerosis, and myocardial infarction, underscoring the detrimental roles of these cells in various chronic inflammatory responses. Given that cardiovascular disease is the number one cause of death worldwide, there is great interest in understanding the contribution of age-related immunological changes to its pathogenesis. In this review, we discuss general features of age-related alterations in T cell immunity and the possible roles of senescent T cells in the pathogenesis of cardiovascular disease.

  9. Use of NAP gene to manipulate leaf senescence in plants

    Science.gov (United States)

    Gan, Susheng; Guo, Yongfeng

    2013-04-16

    The present invention discloses transgenic plants having an altered level of NAP protein compared to that of a non-transgenic plant, where the transgenic plants display an altered leaf senescence phenotype relative to a non-transgenic plant, as well as mutant plants comprising an inactivated NAP gene, where mutant plants display a delayed leaf senescence phenotype compared to that of a non-mutant plant. The present invention also discloses methods for delaying leaf senescence in a plant, as well as methods of making a mutant plant having a decreased level of NAP protein compared to that of a non-mutant plant, where the mutant plant displays a delayed leaf senescence phenotype relative to a non-mutant plant. Methods for causing precocious leaf senescence or promoting leaf senescence in a plant are also disclosed. Also disclosed are methods of identifying a candidate plant suitable for breeding that displays a delayed leaf senescence and/or enhanced yield phenotype.

  10. Regulation of beta cell replication

    DEFF Research Database (Denmark)

    Lee, Ying C; Nielsen, Jens Høiriis

    2008-01-01

    Beta cell mass, at any given time, is governed by cell differentiation, neogenesis, increased or decreased cell size (cell hypertrophy or atrophy), cell death (apoptosis), and beta cell proliferation. Nutrients, hormones and growth factors coupled with their signalling intermediates have been...... suggested to play a role in beta cell mass regulation. In addition, genetic mouse model studies have indicated that cyclins and cyclin-dependent kinases that determine cell cycle progression are involved in beta cell replication, and more recently, menin in association with cyclin-dependent kinase...... inhibitors has been demonstrated to be important in beta cell growth. In this review, we consider and highlight some aspects of cell cycle regulation in relation to beta cell replication. The role of cell cycle regulation in beta cell replication is mostly from studies in rodent models, but whether...

  11. Human myotubes from myoblast cultures undergoing senescence exhibit defects in glucose and lipid metabolism

    DEFF Research Database (Denmark)

    Nehlin, Jan O; Just, Marlene; Rustan, Arild C

    2011-01-01

    that the observed metabolic defects accompany the induction of a senescent state. The main function of SCs is regeneration and skeletal muscle-build up. Thus, the metabolic defects observed during aging of SC-derived myotubes could have a role in sarcopenia, the gradual age-related loss of muscle mass and strength.......Adult stem cells are known to have a finite replication potential. Muscle biopsy-derived human satellite cells (SCs) were grown at different passages and differentiated to human myotubes in culture to analyze the functional state of various carbohydrate and lipid metabolic pathways...

  12. Senescence and programmed cell death in plants: polyamine action mediated by transglutaminase

    Directory of Open Access Journals (Sweden)

    Stefano eDel Duca

    2014-04-01

    Full Text Available Research on polyamines in plants laps a long way of about 50 years and many roles have been discovered for these aliphatic cations. Polyamines regulate cell division, differentiation, organogenesis, reproduction, dormancy-break and senescence, homeostatic adjustments in response to external stimuli and stresses. Nevertheless, the molecular mechanisms of their multiple activities are still matter of research. Polyamines are present in free and bound forms and interact with several important cell molecules; some of these interactions may occur by covalent linkages catalyzed by transglutaminase, giving rise to ‘cationisation’ or cross-links among specific proteins. Senescence and PCD can be delayed by polyamines; in order to re-interpret some of these effects and to obtain new insights into their molecular mechanisms, their conjugation has been revised here. The transglutaminase-mediated interactions between proteins and polyamines are the main target of this review. After an introduction on the characteristics of this enzyme, on its catalysis and role in PCD in animals, the plant senescence and PCD models in which TGase has been studied, are presented: the corolla of naturally senescing or excised flowers, the leaves senescing, either excised or not, the pollen during self-incompatible pollination, the hypersensitive response and the tuber storage parenchyma during dormancy release. In all the models examined, transglutaminase appears to be involved by a similar molecular mechanism as described during apoptosis in animal cells, even though several substrates are different. Its effect is probably related to the type of PCD, but mostly to the substrate to be modified in order to achieve the specific PCD program. As a cross-linker of polyamines and proteins, transglutaminase is an important factor involved in multiple, sometimes controversial, roles of polyamines during senescence and PCD.

  13. Characterizing the Final Steps of Chromosomal Replication at the Single-molecule Level in the Model System Escherichia coli

    KAUST Repository

    Elshenawy, Mohamed M.

    2015-12-01

    In the circular Escherichia coli chromosome, two replisomes are assembled at the unique origin of replication and drive DNA synthesis in opposite directions until they meet in the terminus region across from the origin. Despite the difference in rates of the two replisomes, their arrival at the terminus is synchronized through a highly specialized system consisting of the terminator protein (Tus) bound to the termination sites (Ter). This synchronicity is mediated by the polarity of the Tus−Ter complex that stops replisomes from one direction (non-permissive face) but not the other (permissive face). Two oppositely oriented clusters of five Tus–Ters that each block one of the two replisomes create a “replication fork trap” for the first arriving replisome while waiting for the late arriving one. Despite extensive biochemical and structural studies, the molecular mechanism behind Tus−Ter polar arrest activity remained controversial. Moreover, none of the previous work provided answers for the long-standing discrepancy between the ability of Tus−Ter to permanently stop replisomes in vitro and its low efficiency in vivo. Here, I spearheaded a collaborative project that combined single-molecule DNA replication assays, X-ray crystallography and binding studies to provide a true molecular-level understanding of the underlying mechanism of Tus−Ter polar arrest activity. We showed that efficiency of Tus−Ter is determined by a head-to-head kinetic competition between rate of strand separation by the replisome and rate of rearrangement of Tus−Ter interactions during the melting of the first 6 base pairs of Ter. This rearrangement maintains Tus’s strong grip on the DNA and stops the advancing replisome from breaking into Tus−Ter central interactions, but only transiently. We further showed how this kinetic competition functions within the context of two mechanisms to impose permanent fork stoppage. The rate-dependent fork arrest activity of Tus

  14. Senescence-Associated Molecular and Epigenetic Alterations in Mesenchymal Stem Cell Cultures from Amniotic Fluid of Normal and Fetus-Affected Pregnancy

    Directory of Open Access Journals (Sweden)

    Jūratė Savickienė

    2016-01-01

    Full Text Available Human amniotic-fluid-derived mesenchymal stem cells (AF-MSCs are interesting for their multilineage differentiation potential and wide range of therapeutic applications due to the ease of culture expansion. However, MSCs undergo replicative senescence. So far, the molecular mechanisms that underlie fetal diseases and cell senescence are still poorly understood. Here, we analyzed senescence-associated morphologic, molecular, and epigenetic characteristics during propagation of MSCs derived from AF of normal and fetus-affected pregnancy. AF-MSCs cultures from both cell sources displayed quite similar morphology and expression of specific cell surface (CD44, CD90, and CD105 and stemness (Oct4, Nanog, Sox2, and Rex1 markers but had interindividual variability in proliferation capability and time to reach senescence. Within passages 4 and 8, senescent cultures exhibited typical morphological features, senescence-associated β-galactosidase activity, increased levels of p16, and decreased levels of miR-17 and miR-21 but showed differential expression of p21, p53, and ATM dependently on the onset of cell senescence. These differences correlated with changes in the level of chromatin modifiers (DNMT1 and HDAC1 and polycomb group proteins (EZH2, SUZ12, and BMI1 paralleling with changes in the expression of repressive histone marks (H3K9me3 and H3K27me3 and stemness markers (Oct4, Nanog, Sox2, and Rex1. Therefore epigenetic factors are important for AF-MSCs senescence process that may be related with individuality of donor or a fetus malignancy status.

  15. MicroRNA-34a Induces Vascular Smooth Muscle Cells Senescence by SIRT1 Downregulation and Promotes the Expression of Age-Associated Pro-inflammatory Secretory Factors.

    Science.gov (United States)

    Badi, Ileana; Burba, Ilaria; Ruggeri, Clarissa; Zeni, Filippo; Bertolotti, Matteo; Scopece, Alessandro; Pompilio, Giulio; Raucci, Angela

    2015-11-01

    Arterial aging is a major risk factor for the occurrence of cardiovascular diseases. The aged artery is characterized by endothelial dysfunction and vascular smooth muscle cells altered physiology together with low-grade chronic inflammation. MicroRNA-34a (miR-34a) has been recently implicated in cardiac, endothelial, and endothelial progenitor cell senescence; however, its contribution to aging-associated vascular smooth muscle cells phenotype has not been explored so far. We found that miR-34a was highly expressed in aortas isolated from old mice. Moreover, its well-known target, the longevity-associated protein SIRT1, was significantly downregulated during aging in both endothelial cells and vascular smooth muscle cells. Increased miR-34a as well as decreased SIRT1 expression was also observed in replicative-senescent human aortic smooth muscle cells. miR-34a overexpression in proliferative human aortic smooth muscle cells caused cell cycle arrest along with enhanced p21 protein levels and evidence of cell senescence. Furthermore, miR-34a ectopic expression induced pro-inflammatory senescence-associated secretory phenotype molecules. Finally, SIRT1 protein significantly decreased upon miR-34a overexpression and restoration of its levels rescued miR-34a-dependent human aortic smooth muscle cells senescence, but not senescence-associated secretory phenotype factors upregulation. Taken together, our findings suggest that aging-associated increase of miR-34a expression levels, by promoting vascular smooth muscle cells senescence and inflammation through SIRT1 downregulation and senescence-associated secretory phenotype factors induction, respectively, may lead to arterial dysfunctions.

  16. Expression of Senescence-Associated microRNAs and Target Genes in Cellular Aging and Modulation by Tocotrienol-Rich Fraction

    Directory of Open Access Journals (Sweden)

    Sharon Gwee Sian Khee

    2014-01-01

    Full Text Available Emerging evidences highlight the implication of microRNAs as a posttranscriptional regulator in aging. Several senescence-associated microRNAs (SA-miRNAs are found to be differentially expressed during cellular senescence. However, the role of dietary compounds on SA-miRNAs remains elusive. This study aimed to elucidate the modulatory role of tocotrienol-rich fraction (TRF on SA-miRNAs (miR-20a, miR-24, miR-34a, miR-106a, and miR-449a and established target genes of miR-34a (CCND1, CDK4, and SIRT1 during replicative senescence of human diploid fibroblasts (HDFs. Primary cultures of HDFs at young and senescent were incubated with TRF at 0.5 mg/mL. Taqman microRNA assay showed significant upregulation of miR-24 and miR-34a and downregulation of miR-20a and miR-449a in senescent HDFs (P<0.05. TRF reduced miR-34a expression in senescent HDFs and increased miR-20a expression in young HDFs and increased miR-449a expression in both young and senescent HDFs. Our results also demonstrated that ectopic expression of miR-34a reduced the expression of CDK4 significantly (P<0.05. TRF inhibited miR-34a expression thus relieved its inhibition on CDK4 gene expression. No significant change was observed on the expression of CCND1, SIRT1, and miR-34a upstream transcriptional regulator, TP53. In conclusion tocotrienol-rich fraction prevented cellular senescence of human diploid fibroblasts via modulation of SA-miRNAs and target genes expression.

  17. Senescence-Associated Molecular and Epigenetic Alterations in Mesenchymal Stem Cell Cultures from Amniotic Fluid of Normal and Fetus-Affected Pregnancy

    Science.gov (United States)

    Savickienė, Jūratė; Baronaitė, Sandra; Zentelytė, Aistė; Treigytė, Gražina

    2016-01-01

    Human amniotic-fluid-derived mesenchymal stem cells (AF-MSCs) are interesting for their multilineage differentiation potential and wide range of therapeutic applications due to the ease of culture expansion. However, MSCs undergo replicative senescence. So far, the molecular mechanisms that underlie fetal diseases and cell senescence are still poorly understood. Here, we analyzed senescence-associated morphologic, molecular, and epigenetic characteristics during propagation of MSCs derived from AF of normal and fetus-affected pregnancy. AF-MSCs cultures from both cell sources displayed quite similar morphology and expression of specific cell surface (CD44, CD90, and CD105) and stemness (Oct4, Nanog, Sox2, and Rex1) markers but had interindividual variability in proliferation capability and time to reach senescence. Within passages 4 and 8, senescent cultures exhibited typical morphological features, senescence-associated β-galactosidase activity, increased levels of p16, and decreased levels of miR-17 and miR-21 but showed differential expression of p21, p53, and ATM dependently on the onset of cell senescence. These differences correlated with changes in the level of chromatin modifiers (DNMT1 and HDAC1) and polycomb group proteins (EZH2, SUZ12, and BMI1) paralleling with changes in the expression of repressive histone marks (H3K9me3 and H3K27me3) and stemness markers (Oct4, Nanog, Sox2, and Rex1). Therefore epigenetic factors are important for AF-MSCs senescence process that may be related with individuality of donor or a fetus malignancy status. PMID:27803714

  18. Inhibition of severe acute respiratory syndrome coronavirus replication in a lethal SARS-CoV BALB/c mouse model by stinging nettle lectin, Urtica dioica agglutinin

    Science.gov (United States)

    Kumaki, Yohichi; Wandersee, Miles K.; Smith, Aaron J.; Zhou, Yanchen; Simmons, Graham; Nelson, Nathan M.; Bailey, Kevin W.; Vest, Zachary G.; Li, Joseph K.-K.; Chan, Paul Kay-Sheung; Smee, Donald F.; Barnard, Dale L.

    2011-01-01

    Urtica dioica agglutinin (UDA) is a small plant monomeric lectin, 8.7 kDa in size, with an N-acetylglucosamine specificity that inhibits viruses from Nidovirales in vitro. In the current study, we first examined the efficacy of UDA on the replication of different SARS-CoV strains in Vero 76 cells. UDA inhibited virus replication in a dose-dependent manner and reduced virus yields of the Urbani strain by 90% at 1.1 ± 0.4 µg/ml in Vero 76 cells. Then, UDA was tested for efficacy in a lethal SARS-CoV-infected BALB/c mouse model. BALB/c mice were infected with two LD50 (575 PFU) of virus for 4 hours before the mice were treated intraperitoneally with UDA at 20, 10, 5 or 0 mg/kg/day for 4 days. Treatment with UDA at 5 mg/kg significantly protected the mice against a lethal infection with mouse-adapted SARS-CoV (pSARS infection in mice leads to a substantial therapeutic effect that protects mice against death and weight loss. Furthermore, the mode of action of UDA in vitro was further investigated using live SARS-CoV Urbani strain virus and retroviral particles pseudotyped with SARS-CoV spike (S). UDA specifically inhibited the replication of live SARS-CoV or SARS-CoV pseudotyped virus when added just before, but not after, adsorption. These data suggested that UDA likely inhibits SARS-CoV infection by targeting early stages of the replication cycle, namely, adsorption or penetration. In addition, we demonstrated that UDA neutralizes the virus infectivity, presumably by binding to the SARS-CoV spike (S) glycoprotein. Finally, the target molecule for inhibition of virus replication was partially characterized. When UDA was exposed to N-acetylglucosamine and then UDA was added to cells just prior to adsorption, UDA did not inhibit the virus infection. These data support the conclusion that UDA might bind to N-acetylglucosamine-like residues present on the glycosylated envelope glycoproteins, thereby preventing virus attachment to cells. PMID:21338626

  19. Telomere shortening and cell senescence induced by perylene derivatives in A549 human lung cancer cells.

    Science.gov (United States)

    Taka, Thanachai; Huang, Liming; Wongnoppavich, Ariyaphong; Tam-Chang, Suk-Wah; Lee, T Randall; Tuntiwechapikul, Wirote

    2013-02-15

    Cancer cells evade replicative senescence by re-expressing telomerase, which maintains telomere length and hence chromosomal integrity. Telomerase inhibition would lead cancer cells to senesce and therefore prevent cancer cells from growing indefinitely. G-quadruplex ligands can attenuate telomerase activity by inducing G-quadruplex formation at the 3'-overhang of telomere and at the human telomerase reverse transcriptase (hTERT) promoter; the former prevents telomerase from accessing the telomere, and the latter acts as a transcriptional silencer. The present investigation found that perylene derivatives PM2 and PIPER induced G-quadruplex formation from both telomeric DNA and the hTERT promoter region in vitro. Further, TRAP assay showed that these compounds inhibited telomerase in a dose-dependent manner. When A549 human lung cancer cells were treated with these compounds, hTERT expression was down-regulated. Moreover, the crude protein extract from these treated cells exhibited less telomerase activity. In the long-term treatment of A549 lung cancer cells with sub-cytotoxic dose of these perylenes, telomere shortening, reduction of cell proliferation and tumorigenicity, and cell senescence were observed. The results of this study indicate that perylene derivatives warrant further consideration as effective agents for cancer therapy.

  20. Biochemical Genetics of Short-Season Cotton Cultivars that Express Early Maturity Without Senescence

    Institute of Scientific and Technical Information of China (English)

    Shu-Xun YU; Mei-Zhen SONG; Shu-Li FAN; Wu WANG; Ri-Hong YUAN

    2005-01-01

    The present study is aimed to investigate the mechanism of the biochemical genetic in shortseasoned cotton (Gossypium hirsutum L.) (SSC). Ten cultivars from two types of SSC were selected, five SSC with no prematuresenescence crossed with five SSC with premature senescence. The parents, F1, and F2 from the reciprocal crosses were field tested in replication in 2001 and 2002. The results indicated that the activities of protective enzymes of the antioxidant system, such as catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD), were higher in the early maturing SSC with premature senescence compared with activities in the SSC parental cultivars that showed premature senescence, whereas the malondialdehyde (MDA) content in former group was lower than that in latter group. Various genetic variances and heritabilities for these biochemical traits and auxin (IAA), abscisic acid (ABA), and chlorophyll (Chl a+b) contents were also estimated. Significant additive variance for CAT, POD, ABA, and IAA existed, whereas CAT specific activity and SOD activity were largely controlled by dominant effects. Both maternal and dominant variances played equally predominant roles in the specific activity of POD and SOD, MDA, and soluble portents. The relative contribution of the various genetic components to the phenotypic variation varied in the boll-setting period.

  1. Chronic DNA Replication Stress Reduces Replicative Lifespan of Cells by TRP53-Dependent, microRNA-Assisted MCM2-7 Downregulation.

    Directory of Open Access Journals (Sweden)

    Gongshi Bai

    2016-01-01

    Full Text Available Circumstances that compromise efficient DNA replication, such as disruptions to replication fork progression, cause a state known as DNA replication stress (RS. Whereas normally proliferating cells experience low levels of RS, excessive RS from intrinsic or extrinsic sources can trigger cell cycle arrest and senescence. Here, we report that a key driver of RS-induced senescence is active downregulation of the Minichromosome Maintenance 2-7 (MCM2-7 factors that are essential for replication origin licensing and which constitute the replicative helicase core. Proliferating cells produce high levels of MCM2-7 that enable formation of dormant origins that can be activated in response to acute, experimentally-induced RS. However, little is known about how physiological RS levels impact MCM2-7 regulation. We found that chronic exposure of primary mouse embryonic fibroblasts (MEFs to either genetically-encoded or environmentally-induced RS triggered gradual MCM2-7 repression, followed by inhibition of replication and senescence that could be accelerated by MCM hemizygosity. The MCM2-7 reduction in response to RS is TRP53-dependent, and involves a group of Trp53-dependent miRNAs, including the miR-34 family, that repress MCM expression in replication-stressed cells before they undergo terminal cell cycle arrest. miR-34 ablation partially rescued MCM2-7 downregulation and genomic instability in mice with endogenous RS. Together, these data demonstrate that active MCM2-7 repression is a physiologically important mechanism for RS-induced cell cycle arrest and genome maintenance on an organismal level.

  2. Clearance of senescent cells by ABT263 rejuvenates aged hematopoietic stem cells in mice

    NARCIS (Netherlands)

    Chang, Jianhui; Wang, Yingying; Shao, Lijian; Laberge, Remi-Martin; Demaria, Marco; Campisi, Judith; Janakiraman, Krishnamurthy; Sharpless, Norman E; Ding, Sheng; Feng, Wei; Luo, Yi; Wang, Xiaoyan; Aykin-Burns, Nukhet; Krager, Kimberly; Ponnappan, Usha; Hauer-Jensen, Martin; Meng, Aimin; Zhou, Daohong

    2015-01-01

    Senescent cells (SCs) accumulate with age and after genotoxic stress, such as total-body irradiation (TBI). Clearance of SCs in a progeroid mouse model using a transgenic approach delays several age-associated disorders, suggesting that SCs play a causative role in certain age-related pathologies. T

  3. Oncogene-induced senescence is part of the tumorigenesis barrier imposed by DNA damage checkpoints

    DEFF Research Database (Denmark)

    Bartkova, Jirina; Rezaei, Nousin; Liontos, Michalis

    2006-01-01

    and DNA double-strand breaks. Inhibiting the DNA double-strand break response kinase ataxia telangiectasia mutated (ATM) suppressed the induction of senescence and in a mouse model led to increased tumour size and invasiveness. Analysis of human precancerous lesions further indicated that DNA damage...

  4. Gene expression profiles deciphering leaf senescence variation between early- and late-senescence cotton lines.

    Directory of Open Access Journals (Sweden)

    Xiangqiang Kong

    Full Text Available Leaf senescence varies greatly among genotypes of cotton (Gossypium hirsutium L, possibly due to the different expression of senescence-related genes. To determine genes involved in leaf senescence, we performed genome-wide transcriptional profiling of the main-stem leaves of an early- (K1 and a late-senescence (K2 cotton line at 110 day after planting (DAP using the Solexa technology. The profiling analysis indicated that 1132 genes were up-regulated and 455 genes down-regulated in K1 compared with K2 at 110 DAP. The Solexa data were highly consistent with, and thus were validated by those from real-time quantitative PCR (RT-PCR. Most of the genes related to photosynthesis, anabolism of carbohydrates and other biomolecules were down-regulated, but those for catabolism of proteins, nucleic acids, lipids and nutrient recycling were mostly up-regulated in K1 compared with K2. Fifty-one differently expressed hormone-related genes were identified, of which 5 ethylene, 3 brassinosteroid (BR, 5 JA, 18 auxin, 8 GA and 1 ABA related genes were up-regulated in K1 compared with K2, indicating that these hormone-related genes might play crucial roles in early senescence of K1 leaves. Many differently expressed transcription factor (TF genes were identified and 11 NAC and 8 WRKY TF genes were up-regulated in K1 compared with K2, suggesting that TF genes, especially NAC and WRKY genes were involved in early senescence of K1 leaves. Genotypic variation in leaf senescence was attributed to differently expressed genes, particularly hormone-related and TF genes.

  5. Evidences for Chlorogenic Acid--A Major Endogenous Polyphenol Involved in Regulation of Ripening and Senescence of Apple Fruit.

    Directory of Open Access Journals (Sweden)

    Yu Xi

    Full Text Available To learn how the endogenous polyphenols may play a role in fruit ripening and senescence, apple pulp discs were used as a model to study the influences of chlorogenic acid (CHA, a major polyphenol in apple pulp on fruit ripening and senescence. Apple ('Golden Delicious' pulp discs prepared from pre-climacteric fruit were treated with 50 mg L(-1 CHA and incubated in flasks with 10 mM MES buffer (pH 6.0, 11% sorbitol. Compared to the control samples, treatment with CHA significantly reduced ethylene production and respiration rate, and enhanced levels of firmness and soluble solids content of the pulp discs during incubation at 25°C. These results suggested that CHA could retard senescence of the apple pulp discs. Proteomics analysis with sodium dodecyl sulfate-polyacrylamide gel electrophoresis and mass spectrometry (MALDI-TOF/TOF revealed that the expressions of several key proteins correlated to fruit ripening and senescence were affected by the treatment with CHA. Further study showed that treating the pulp discs with CHA remarkably reduced levels of lipoxygenase, β-galactosidase, NADP-malic enzyme, and enzymatic activities of lipoxygenase and UDP-glucose pyrophosphorylase, all of which are known as promoters of fruit ripening and senescence. These results could provide new insights into the functions of endogenous phenolic compounds in fruit ripening and senescence.

  6. Histone deacetylase inhibitor valproic acid promotes the induction of pluripotency in mouse fibroblasts by suppressing reprogramming-induced senescence stress

    Energy Technology Data Exchange (ETDEWEB)

    Zhai, Yingying; Chen, Xi; Yu, Dehai [Stem Cell and Cancer Center, First Affiliated Hospital, Jilin University, Changchun, Jilin 130061 (China); Stanford University Medical School, Palo Alto Veterans Institute for Research, Palo Alto, CA 94304 (United States); Li, Tao [Stanford University Medical School, Palo Alto Veterans Institute for Research, Palo Alto, CA 94304 (United States); Cui, Jiuwei; Wang, Guanjun [Stem Cell and Cancer Center, First Affiliated Hospital, Jilin University, Changchun, Jilin 130061 (China); Hu, Ji-Fan, E-mail: jifan@stanford.edu [Stem Cell and Cancer Center, First Affiliated Hospital, Jilin University, Changchun, Jilin 130061 (China); Stanford University Medical School, Palo Alto Veterans Institute for Research, Palo Alto, CA 94304 (United States); Li, Wei, E-mail: jdyylw@163.com [Stem Cell and Cancer Center, First Affiliated Hospital, Jilin University, Changchun, Jilin 130061 (China)

    2015-09-10

    Histone deacetylase inhibitor valproic acid (VPA) has been used to increase the reprogramming efficiency of induced pluripotent stem cell (iPSC) from somatic cells, yet the specific molecular mechanisms underlying this effect is unknown. Here, we demonstrate that reprogramming with lentiviruses carrying the iPSC-inducing factors (Oct4-Sox2-Klf4-cMyc, OSKM) caused senescence in mouse fibroblasts, establishing a stress barrier for cell reprogramming. Administration of VPA protected cells from reprogramming-induced senescent stress. Using an in vitro pre-mature senescence model, we found that VPA treatment increased cell proliferation and inhibited apoptosis through the suppression of the p16/p21 pathway. In addition, VPA also inhibited the G2/M phase blockage derived from the senescence stress. These findings highlight the role of VPA in breaking the cell senescence barrier required for the induction of pluripotency. - Highlights: • Histone deacetylase inhibitor valproic acid enhances iPSC induction. • Valproic acid suppresses reprogramming-induced senescence stress. • Valproic acid downregulates the p16/p21 pathway in reprogramming. • This study demonstrates a new mechanistic role of valproic acid in enhancing reprogramming.

  7. A human-like senescence-associated secretory phenotype is conserved in mouse cells dependent on physiological oxygen.

    Directory of Open Access Journals (Sweden)

    Jean-Philippe Coppé

    Full Text Available Cellular senescence irreversibly arrests cell proliferation in response to oncogenic stimuli. Human cells develop a senescence-associated secretory phenotype (SASP, which increases the secretion of cytokines and other factors that alter the behavior of neighboring cells. We show here that "senescent" mouse fibroblasts, which arrested growth after repeated passage under standard culture conditions (20% oxygen, do not express a human-like SASP, and differ from similarly cultured human cells in other respects. However, when cultured in physiological (3% oxygen and induced to senesce by radiation, mouse cells more closely resemble human cells, including expression of a robust SASP. We describe two new aspects of the human and mouse SASPs. First, cells from both species upregulated the expression and secretion of several matrix metalloproteinases, which comprise a conserved genomic cluster. Second, for both species, the ability to promote the growth of premalignant epithelial cells was due primarily to the conserved SASP factor CXCL-1/KC/GRO-alpha. Further, mouse fibroblasts made senescent in 3%, but not 20%, oxygen promoted epithelial tumorigenesis in mouse xenographs. Our findings underscore critical mouse-human differences in oxygen sensitivity, identify conditions to use mouse cells to model human cellular senescence, and reveal novel conserved features of the SASP.

  8. DNA replication and cancer

    DEFF Research Database (Denmark)

    Boyer, Anne-Sophie; Walter, David; Sørensen, Claus Storgaard

    2016-01-01

    A dividing cell has to duplicate its DNA precisely once during the cell cycle to preserve genome integrity avoiding the accumulation of genetic aberrations that promote diseases such as cancer. A large number of endogenous impacts can challenge DNA replication and cells harbor a battery of pathways...... causing DNA replication stress and genome instability. Further, we describe cellular and systemic responses to these insults with a focus on DNA replication restart pathways. Finally, we discuss the therapeutic potential of exploiting intrinsic replicative stress in cancer cells for targeted therapy....

  9. Identification of candidate genes associated with leaf senescence in cultivated sunflower (Helianthus annuus L.).

    Science.gov (United States)

    Moschen, Sebastian; Bengoa Luoni, Sofia; Paniego, Norma B; Hopp, H Esteban; Dosio, Guillermo A A; Fernandez, Paula; Heinz, Ruth A

    2014-01-01

    Cultivated sunflower (Helianthus annuus L.), an important source of edible vegetable oil, shows rapid onset of senescence, which limits production by reducing photosynthetic capacity under specific growing conditions. Carbon for grain filling depends strongly on light interception by green leaf area, which diminishes during grain filling due to leaf senescence. Transcription factors (TFs) regulate the progression of leaf senescence in plants and have been well explored in model systems, but information for many agronomic crops remains limited. Here, we characterize the expression profiles of a set of putative senescence associated genes (SAGs) identified by a candidate gene approach and sunflower microarray expression studies. We examined a time course of sunflower leaves undergoing natural senescence and used quantitative PCR (qPCR) to measure the expression of 11 candidate genes representing the NAC, WRKY, MYB and NF-Y TF families. In addition, we measured physiological parameters such as chlorophyll, total soluble sugars and nitrogen content. The expression of Ha-NAC01, Ha-NAC03, Ha-NAC04, Ha-NAC05 and Ha-MYB01 TFs increased before the remobilization rate increased and therefore, before the appearance of the first physiological symptoms of senescence, whereas Ha-NAC02 expression decreased. In addition, we also examined the trifurcate feed-forward pathway (involving ORE1, miR164, and ethylene insensitive 2) previously reported for Arabidopsis. We measured transcription of Ha-NAC01 (the sunflower homolog of ORE1) and Ha-EIN2, along with the levels of miR164, in two leaves from different stem positions, and identified differences in transcription between basal and upper leaves. Interestingly, Ha-NAC01 and Ha-EIN2 transcription profiles showed an earlier up-regulation in upper leaves of plants close to maturity, compared with basal leaves of plants at pre-anthesis stages. These results suggest that the H. annuus TFs characterized in this work could play important

  10. Adiponectin corrects premature cellular senescence and normalizes antimicrobial peptide levels in senescent keratinocytes.

    Science.gov (United States)

    Jin, Taewon; Kim, Min Jeong; Heo, Won Il; Park, Kui Young; Choi, Sun Young; Lee, Mi-Kyung; Hong, Seung-Phil; Kim, Seong-Jin; Im, Myung; Moon, Nam Ju; Seo, Seong Jun

    2016-09-02

    Stress-induced premature senescence or aging causes dysfunction in the human somatic system. Adiponectin (Acrp30) plays a role in functional recovery, especially with adenosine 3',5'-monophosphate (AMP)-activated protein kinase (AMPK) and silent mating type information regulation 2 homolog 1 (SIRT1). Acrp30 stimulation reduced the premature senescence positive ratio induced by hydrogen peroxide (H2O2) and restituted human β-defensin 2 (hBD-2) levels in senescent keratinocytes. Acrp30 recovered AMPK activity in senescent keratinocytes and increased SIRT1 deacetylation activity. As a result, FoxO1 and FoxO3 transcription activity was recovered. Additionally, Acrp30 stimulation suppresses NFκB p65, which induces abnormal expression of hBD-2 induced by H2O2. In the present study, we have shown that Acrp30 reduces premature senescence and recovers cellular function in keratinocytes. These results suggest a role for Acrp30 as an anti-aging agent to improve impaired skin immune barriers. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. Overexpression of HDAC1 induces cellular senescence by Sp1/PP2A/pRb pathway

    Energy Technology Data Exchange (ETDEWEB)

    Chuang, Jian-Ying [Department of Pharmacology, National Cheng-Kung University, Tainan 701, Taiwan (China); Hung, Jan-Jong, E-mail: petehung@mail.ncku.edu.tw [Department of Pharmacology, National Cheng-Kung University, Tainan 701, Taiwan (China); Institute of Bioinformatics and Biosignal Transduction, National Cheng-Kung University, Tainan 701, Taiwan (China)

    2011-04-15

    Highlights: {yields} Overexpression of HDAC1 induces Sp1 deacetylation and raises Sp1/p300 complex formation to bind to PP2Ac promoter. {yields} Overexpression of HDAC1 strongly inhibits the phosphorylation of pRb through up-regulation of PP2A. {yields} Overexpressed HDAC1 restrains cell proliferaction and induces cell senescence though a novel Sp1/PP2A/pRb pathway. -- Abstract: Senescence is associated with decreased activities of DNA replication, protein synthesis, and cellular division, which can result in deterioration of cellular functions. Herein, we report that the growth and division of tumor cells were significantly repressed by overexpression of histone deacetylase (HDAC) 1 with the Tet-off induced system or transient transfection. In addition, HDAC1 overexpression led to senescence through both an accumulation of hypophosphorylated active retinoblastoma protein (pRb) and an increase in the protein level of protein phosphatase 2A catalytic subunit (PP2Ac). HDAC1 overexpression also increased the level of Sp1 deacetylation and elevated the interaction between Sp1 and p300, and subsequently that Sp1/p300 complex bound to the promoter of PP2Ac, thus leading to induction of PP2Ac expression. Similar results were obtained in the HDAC1-Tet-off stable clone. Taken together, these results indicate that HDAC1 overexpression restrained cell proliferation and induced premature senescence in cervical cancer cells through a novel Sp1/PP2A/pRb pathway.

  12. A viscous solvent enables information transfer from gene-length nucleic acids in a model prebiotic replication cycle

    Science.gov (United States)

    He, Christine; Gállego, Isaac; Laughlin, Brandon; Grover, Martha A.; Hud, Nicholas V.

    2017-04-01

    Many hypotheses concerning the nature of early life assume that genetic information was once transferred through the template-directed synthesis of RNA, before the emergence of coded enzymes. However, attempts to demonstrate enzyme-free, template-directed synthesis of nucleic acids have been limited by 'strand inhibition', whereby transferring information from a template strand in the presence of its complementary strand is inhibited by the stability of the template duplex. Here, we use solvent viscosity to circumvent strand inhibition, demonstrating information transfer from a gene-length template (>300 nt) within a longer (545 bp or 3 kb) duplex. These results suggest that viscous environments on the prebiotic Earth, generated periodically by water evaporation, could have facilitated nucleic acid replication—particularly of long, structured sequences such as ribozymes. Our approach works with DNA and RNA, suggesting that viscosity-mediated replication is possible for a range of genetic polymers, perhaps even for informational polymers that may have preceded RNA.

  13. An epigenome-wide association meta-analysis of prenatal maternal stress in neonates: A model approach for replication.

    Science.gov (United States)

    Rijlaarsdam, Jolien; Pappa, Irene; Walton, Esther; Bakermans-Kranenburg, Marian J; Mileva-Seitz, Viara R; Rippe, Ralph C A; Roza, Sabine J; Jaddoe, Vincent W V; Verhulst, Frank C; Felix, Janine F; Cecil, Charlotte A M; Relton, Caroline L; Gaunt, Tom R; McArdle, Wendy; Mill, Jonathan; Barker, Edward D; Tiemeier, Henning; van IJzendoorn, Marinus H

    2016-01-01

    Prenatal maternal stress exposure has been associated with neonatal differential DNA methylation. However, the available evidence in humans is largely based on candidate gene methylation studies, where only a few CpG sites were evaluated. The aim of this study was to examine the association between prenatal exposure to maternal stress and offspring genome-wide cord blood methylation using different methods. First, we conducted a meta-analysis and follow-up pathway analyses. Second, we used novel region discovery methods [i.e., differentially methylated regions (DMRs) analyses]. To this end, we used data from two independent population-based studies, the Generation R Study (n = 912) and the Avon Longitudinal Study of Parents and Children (ALSPAC, n = 828), to (i) measure genome-wide DNA methylation in cord blood and (ii) extract a prenatal maternal stress composite. The meta-analysis (ntotal = 1,740) revealed no epigenome-wide (meta P meta-analysis (meta P meta-analysis, the current study indicates that there are no large effects of prenatal maternal stress exposure on neonatal DNA methylation. Such replication efforts are essential in the search for robust associations, whether derived from candidate gene methylation or epigenome-wide studies.

  14. Insights into the role of immunosenescence during varicella zoster virus infection (shingles) in the aging cell model.

    Science.gov (United States)

    Kim, Ji-Ae; Park, Seul-Ki; Kumar, Mukesh; Lee, Chan-Hee; Shin, Ok Sarah

    2015-11-03

    Varicella zoster virus (VZV) is the etiological agent of shingles, a painful skin rash that affects a significant proportion of the elderly population. In the present study, we used two aging cell models, Hutchinson-Gilford progeria syndrome (HGPS) fibroblasts and stress or replicative senescence-induced normal human dermal fibroblasts (NHDFs), to investigate age-associated susceptibility to VZV infection. VZV infectivity titers were significantly associated with donor age in HGPS fibroblasts and senescence induction in NHDFs. High throughput RNA-sequencing (RNA-seq) analysis was performed to assess global and dynamic changes in the host transcriptomes of VZV-infected aging cells. Analysis of differentially expressed genes (DEGs) indicated that VZV infection in aged HGPS fibroblasts resembled that in senescent NHDFs, particularly in terms of genes associated with pattern recognition receptors in virus sensing network, providing novel insights into the mechanisms of senescence-associated susceptibility to VZV infection. Additionally, we identified stimulator of interferon genes (STING) as a potential VZV sensing receptor. Knockdown of STING expression resulted in increased viral replication in primary fibroblasts, whereas STING overexpression led to suppression of VZV plaque formation. In conclusion, our findings highlight the important role of immunosenescence following VZV infection and provide significant insights into the mechanisms underlying cellular sensing of VZV infection and the induction of immune responses in aged skin cells.

  15. Skeletal Analysis: Investigating Senescence in Ancient Nubia

    OpenAIRE

    Reavis, Katelyn

    2014-01-01

    The understanding of older adult life experiences is deficient when compared to younger adults and children in the archaeological record. Research has been devoted toward aging techniques and studies of osteoarthritis, but there are few discussions describing senescence, the cumulative process of aging, in the past. Most research includes the oldest cohort (45 years and above) within the broad category of adults, but it is useful to look at this demographic separately. Skeletal remains were a...

  16. Cellular senescence in normal and premature lung aging.

    Science.gov (United States)

    Bartling, B

    2013-10-01

    The incidence of chronic respiratory diseases (e.g., chronic obstructive pulmonary disease, COPD) and interstitial lung diseases (e.g., pneumonia and lung fibrosis) increases with age. In addition to immune senescence, the accumulation of senescent cells directly in lung tissue might play a critical role in the increased prevalence of these pulmonary diseases. In the last couple of years, detailed studies have identified the presence of senescent cells in the aging lung and in diseased lungs of patients with COPD and lung fibrosis. Cellular senescence has been shown for epithelial cells of bronchi and alveoli as well as mesenchymal and vascular cells. Known risk factors for pulmonary diseases (cigarette smoke, air pollutions, bacterial infections, etc.) were identified in experimental studies as being possible mediators in the development of cellular senescence. The present findings indicate the importance of cellular senescence in normal lung aging and in premature aging of the lung in patients with COPD, lung fibrosis, and probably other respiratory diseases.

  17. Evolutionary genetic bases of longevity and senescence.

    Science.gov (United States)

    Govindaraju, Diddahally R

    2015-01-01

    Senescence, as a time-dependent developmental process, affects all organisms at every stage in their development and growth. During this process, genetic, epigenetic and environmental factors are known to introduce a wide range of variation for longevity among individuals. As an important life-history trait, longevity shows ontogenetic relationships with other complex traits, and hence may be viewed as a composite trait. Factors that influence the origin and maintenance of diversity of life are ultimately governed by Darwinian processes. Here we review evolutionary genetic mechanisms underlying longevity and senescence in humans from a life-history and genotype-epigenetic-phenotype (G-E-P) map prospective. We suggest that synergistic and cascading effects of cis-ruptive mechanisms in the genome, and epigenetic disruptive processes in relation to environmental factors may lead to sequential slippage in the G-E-P space. These mechanisms accompany age, stage and individual specific senescent processes, influenced by positive pleiotropy of certain genes, superior genome integrity, negative-frequency dependent selection and other factors that universally regulate rarity in nature. Finally we interpret life span as an inherent property of self-organizing systems that, accordingly, maintain species-specific limits for the entire complex of fitness traits. We conclude that Darwinian approaches provide unique opportunities to discover the biological bases of longevity as well as devise individual specific medical or other interventions toward improving health span.

  18. Markers of T Cell Senescence in Humans

    Directory of Open Access Journals (Sweden)

    Weili Xu

    2017-08-01

    Full Text Available Many countries are facing the aging of their population, and many more will face a similar obstacle in the near future, which could be a burden to many healthcare systems. Increased susceptibility to infections, cardiovascular and neurodegenerative disease, cancer as well as reduced efficacy of vaccination are important matters for researchers in the field of aging. As older adults show higher prevalence for a variety of diseases, this also implies higher risk of complications, including nosocomial infections, slower recovery and sequels that may reduce the autonomy and overall quality of life of older adults. The age-related effects on the immune system termed as “immunosenescence” can be exemplified by the reported hypo-responsiveness to influenza vaccination of the elderly. T cells, which belong to the adaptive arm of the immune system, have been extensively studied and the knowledge gathered enables a better understanding of how the immune system may be affected after acute/chronic infections and how this matters in the long run. In this review, we will focus on T cells and discuss the surface and molecular markers that are associated with T cell senescence. We will also look at the implications that senescent T cells could have on human health and diseases. Finally, we will discuss the benefits of having these markers for investigators and the future work that is needed to advance the field of T cell senescence markers.

  19. Tumor senescence and radioresistant tumor-initiating cells (TICs): let sleeping dogs lie!

    Science.gov (United States)

    Zafarana, Gaetano; Bristow, Robert G

    2010-01-01

    Preclinical data from cell lines and experimental tumors support the concept that breast cancer-derived tumor-initiating cells (TICs) are relatively resistant to ionizing radiation and chemotherapy. This could be a major determinant of tumor recurrence following treatment. Increased clonogenic survival is observed in CD24-/low/CD44+ TICs derived from mammosphere cultures and is associated with (a) reduced production of reactive oxygen species, (b) attenuated activation of γH2AX and CHK2-p53 DNA damage signaling pathways, (c) reduced propensity for ionizing radiation-induced apoptosis, and (d) altered DNA double-strand or DNA single-strand break repair. However, recent data have shed further light on TIC radioresistance as irradiated TICs are resistant to tumor cell senescence following DNA damage. Taken together, the cumulative data support a model in which DNA damage signaling and repair pathways are altered in TICs and lead to an altered mode of cell death with unique consequences for long-term clonogen survival. The study of TIC senescence lays the foundation for future experiments in isogenic models designed to directly test the capacity for senescence and local control (that is, not solely local regression) and spontaneous metastases following treatment in vivo. The study also supports the targeting of tumor cell senescence pathways to increase TIC clonogen kill if the targeting also maintains the therapeutic ratio.

  20. The evolution of senescence in the tree of life

    DEFF Research Database (Denmark)

    Salguero-Gómez, Roberto

    and eco-evolutionary research. This book is the first to offer interdisciplinary perspectives on the evolution of senescence in many species, setting the stage for further developments. It brings together new insights from a wide range of scientific fields and cutting-edge research done on a multitude......The existing theories on the evolution of senescence assume that senescence is inevitable in all organisms. However, recent studies have shown that this is not necessarily true. A better understanding of senescence and its underlying mechanisms could have far-reaching consequences for conservation...

  1. Demographic analysis reveals gradual senescence in the flatworm Macrostomum lignano

    Directory of Open Access Journals (Sweden)

    Braeckman Bart P

    2009-07-01

    Full Text Available Abstract Free-living flatworms ("Turbellaria" are appropriate model organisms to gain better insight into the role of stem cells in ageing and rejuvenation. Ageing research in flatworms is, however, still scarce. This is partly due to culture difficulties and the lack of a complete set of demographic data, including parameters such as median lifespan and age-specific mortality rate. In this paper, we report on the first flatworm survival analysis. We used the species Macrostomum lignano, which is an emerging model for studying the reciprocal influence between stem cells, ageing and rejuvenation. This species has a median lifespan of 205 ± 13 days (average ± standard deviation [SD] and a 90th percentile lifespan of 373 ± 32 days. The maximum lifespan, however, is more than 745 days, and the average survival curve is characterised by a long tail because a small number of individuals lives twice as long as 90% of the population. Similar to earlier observations in a wide range of animals, in M. lignano the age-specific mortality rate increases exponentially, but levels off at the oldest ages. To compare the senescence of M. lignano with that of other ageing models, we determined the mortality rate doubling time, which is 0.20 ± 0.02 years. As a result, we can conclude that M. lignano shows gradual senescence at a rate similar to the vertebrate ageing models Rattus norvegicus and Mus musculus. We argue that M. lignano is a suitable model for ageing and rejuvenation research, and especially for the role of stem cells in these processes, due to its accessible stem cell system and regeneration capacity, and the possibility of combining stem cell studies with demographic analyses.

  2. Resveratrol induces cellular senescence with attenuated mono-ubiquitination of histone H2B in glioma cells

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Zhen; Xu, Michael S.; Barnett, Tamara L. [Nevada Cancer Institute, Las Vegas, NV 89135 (United States); Xu, C. Wilson, E-mail: wxu@nvcancer.org [Nevada Cancer Institute, Las Vegas, NV 89135 (United States)

    2011-04-08

    Research highlights: {yields} Resveratrol induces cellular senescence in glioma cell. {yields} Resveratrol inhibits mono-ubiquitination of histone H2B at K120. {yields} Depletion of RNF20, phenocopies the inhibitory effects of resveratrol. {yields} Mono-ubiquitination of histone H2B at K120 is a novel target of resveratrol. {yields} RNF20 inhibits cellular senescence in proliferating glioma cells. -- Abstract: Resveratrol (3,4',5-trihydroxy-trans-stilbene), a polyphenol naturally occurring in grapes and other plants, has cancer chemo-preventive effects and therapeutic potential. Although resveratrol modulates multiple pathways in tumor cells, how resveratrol or its affected pathways converge on chromatin to mediate its effects is not known. Using glioma cells as a model, we showed here that resveratrol inhibited cell proliferation and induced cellular hypertrophy by transforming spindle-shaped cells to enlarged, irregular and flatten-shaped ones. We further showed that resveratrol-induced hypertrophic cells expressed senescence-associated-{beta}-galactosidase, suggesting that resveratrol-induced cellular senescence in glioma cells. Consistent with these observations, we demonstrated that resveratrol inhibited clonogenic efficiencies in vitro and tumor growth in a xenograft model. Furthermore, we found that acute treatment of resveratrol inhibited mono-ubiquitination of histone H2B at K120 (uH2B) in breast, prostate, pancreatic, lung, brain tumor cells as well as primary human cells. Chronic treatment with low doses of resveratrol also inhibited uH2B in the resveratrol-induced senescent glioma cells. Moreover, we showed that depletion of RNF20, a ubiquitin ligase of histone H2B, inhibited uH2B and induced cellular senescence in glioma cells in vitro, thereby recapitulated the effects of resveratrol. Taken together, our results suggest that uH2B is a novel direct or indirect chromatin target of resveratrol and RNF20 plays an important role in inhibiting cellular

  3. Acute MUS81 depletion leads to replication fork slowing and a constitutive DNA damage response

    DEFF Research Database (Denmark)

    Xing, Meichun; Wang, Xiaohui; Palmai-Pallag, Timea;

    2015-01-01

    The MUS81 protein belongs to a conserved family of DNA structure-specific nucleases that play important roles in DNA replication and repair. Inactivation of the Mus81 gene in mice has no major deleterious consequences for embryonic development, although cancer susceptibility has been reported. We...... have investigated the role of MUS81 in human cells by acutely depleting the protein using shRNAs. We found that MUS81 depletion from human fibroblasts leads to accumulation of ssDNA and a constitutive DNA damage response that ultimately activates cellular senescence. Moreover, we show that MUS81...... is required for efficient replication fork progression during an unperturbed S-phase, and for recovery of productive replication following replication stalling. These results demonstrate essential roles for the MUS81 nuclease in maintenance of replication fork integrity....

  4. Detecting and measuring senescence in wild birds: experience with long-lived seabirds.

    Science.gov (United States)

    Nisbet, I C

    2001-04-01

    This paper points out and discusses several practical and methodological problems that arise in attempts to detect and measure senescent declines in survival or breeding performance of wild animals, with specific emphasis on long-lived seabirds. Birds have no anatomical markers of age, so studies of age-related biology require marking individuals at the time of hatching and following them throughout their lives. Seabirds live longer than the working lifespan of biologists, and longer than the turnover times of study techniques or theories of senescence. Seabirds are exposed to changing environmental and demographic conditions and cannot be assumed to be in demographic equilibrium. Sample sizes of the oldest age-classes are always small, requiring either marking very large numbers of birds at hatching or continuing studies of old birds over many years. Incomplete sampling requires the use of mark-recapture models that have only been developed in the last 20years. Mortality selection resulting from demographic heterogeneity (selective survival of high-quality individuals) can offset or confound the effects of senescent changes within individuals. Many of these problems are amenable to solution and will be probably solved within a few years. In the meantime, this paper recommends that reviewers should be cautious about accepting published reports of senescent declines in natural populations.

  5. Recovery of the pubic symphysis on primiparous young and multiparous senescent mice at postpartum.

    Science.gov (United States)

    Consonni, Silvio Roberto; Rosa, Renata Giardini; Nascimento, Maria Amália Cavinato; Vinagre, Cristiane Mendes; Toledo, Olga Maria Szymanski; Joazeiro, Paulo Pinto

    2012-07-01

    It has been observed that parturition has a significant effect on female skeletal architecture and that age alters musculoskeletal tissues and their functions. We therefore hypothesized that multiparity affects the recovery of the pubic symphysis in senescent mice at postpartum and the morphology of the interpubic tissues. The pubic symphysis of primiparous young, virgin senescent (VS) and multiparous senescent (MS) Swiss mice was examined by light microscopy, transmission electron microscopy, morphometric analysis and immunohistochemistry. The mouse pubic symphysis was remodeled during the first pregnancy: the cellular phenotype and morphology changed to ensure a structurally safe birth canal, followed by recovery of the interpubic articulation after birth. The morphology of the pubic symphysis in the VS group was maintained in a state similar to that observed in virgin young mice. In contrast, MS mice exhibited an interpubic ligament characterized by extended fibrocyte-like cells, an opened interpubic articulation gap, compacted and thin collagen fibrils and scarce galectin-3-positive cells. Thus, we found that the cellular and extracellular characteristics of the pubic symphysis were altered by multiparity in senescent mice. These particular tissue characteristics of the MS group might be associated with an impaired recovery process at postpartum. Thus, a better understanding of the alterations that occur in the birth canal, including the pubic symphysis, due to multiparity in reproductively aged mice may contribute to our comprehension of the biological mechanisms that modify the skeleton and pelvic ligaments and even play a role in the murine model of pelvic organ prolapse.

  6. The p53-reactivating small molecule RITA induces senescence in head and neck cancer cells.

    Directory of Open Access Journals (Sweden)

    Hui-Ching Chuang

    Full Text Available TP53 is the most commonly mutated gene in head and neck cancer (HNSCC, with mutations being associated with resistance to conventional therapy. Restoring normal p53 function has previously been investigated via the use of RITA (reactivation of p53 and induction of tumor cell apoptosis, a small molecule that induces a conformational change in p53, leading to activation of its downstream targets. In the current study we found that RITA indeed exerts significant effects in HNSCC cells. However, in this model, we found that a significant outcome of RITA treatment was accelerated senescence. RITA-induced senescence in a variety of p53 backgrounds, including p53 null cells. Also, inhibition of p53 expression did not appear to significantly inhibit RITA-induced senescence. Thus, this phenomenon appears to be partially p53-independent. Additionally, RITA-induced senescence appears to be partially mediated by activation of the DNA damage response and SIRT1 (Silent information regulator T1 inhibition, with a synergistic effect seen by combining either ionizing radiation or SIRT1 inhibition with RITA treatment. These data point toward a novel mechanism of RITA function as well as hint to its possible therapeutic benefit in HNSCC.

  7. Arabidopsis CPR5 is a senescence-regulatory gene with pleiotropic functions as predicted by the evolutionary theory of senescence.

    Science.gov (United States)

    Jing, Hai-Chun; Anderson, Lisa; Sturre, Marcel J G; Hille, Jacques; Dijkwel, Paul P

    2007-01-01

    Evolutionary theories of senescence predict that genes with pleiotropic functions are important for senescence regulation. In plants there is no direct molecular genetic test for the existence of such senescence-regulatory genes. Arabidopsis cpr5 mutants exhibit multiple phenotypes including hypersensitivity to various signalling molecules, constitutive expression of pathogen-related genes, abnormal trichome development, spontaneous lesion formation, and accelerated leaf senescence. These indicate that CPR5 is a beneficial gene which controls multiple facets of the Arabidopsis life cycle. Ectopic expression of CPR5 restored all the mutant phenotypes. However, in transgenic plants with increased CPR5 transcripts, accelerated leaf senescence was observed in detached leaves and at late development around 50 d after germination, as illustrated by the earlier onset of senescence-associated physiological and molecular markers. Thus, CPR5 has early-life beneficial effects by repressing cell death and insuring normal plant development, but late-life deleterious effects by promoting developmental senescence. As such, CPR5 appears to function as a typical senescence-regulatory gene as predicted by the evolutionary theories of senescence.

  8. Antisense targeting human papillomavirus type 16 E6 and E7 genes contributes to apoptosis and senescence in SiHa cervical carcinoma cells.

    Science.gov (United States)

    Sima, Ni; Wang, Shixuan; Wang, Wei; Kong, Debo; Xu, Qian; Tian, Xu; Luo, Aiyue; Zhou, Jianfeng; Xu, Gang; Meng, Li; Lu, Yunping; Ma, Ding

    2007-08-01

    Human papillomavirus type 16 (HPV-16) is a high-risk DNA tumor virus involved in the development of cervical carcinomas. Substantial studies have demonstrated that E6 and E7 oncoproteins of HPV-16 could induce cell proliferation and immortalization. Repression of E6 and/or E7 oncogenes may induce cervical cancer cells to undergo apoptosis or senescence. The purpose of this study was to determine whether activation of the p53 and retinoblastoma (Rb) pathway by HPV-16 E6 and E7 repression was responsible for apoptosis and senescence of cervical cancer cells and to explore the potential of an antisense RNA (AS) transcript for gene therapy of cervical cancer. The antisense RNA directed against HPV-16 E6 and E7 (16AS) was constructed, and its effects on cell apoptosis and senescence of SiHa cervical carcinoma cells harboring HPV-16 were analyzed. The efficiency of 16AS was evaluated with RT-PCR, Western blotting, flow cytometry analysis, Hoechst 33258 staining, senescent cell morphology observation and senescence-associated beta-galactosidase staining. The sufficient repression of HPV-16 E6 and E7 oncogenes were achieved in 16AS-transfected SiHa cells, which led to obvious apoptosis and replicative senescence of tumor cells. Furthermore, the downregulation of HPV-16 E6 and E7 by 16AS transfection resulted in remarkable increase of both p53 expression and hypophosphorylated p105Rb level in SiHa cells. These results demonstrate that reduction of E6 and E7 expression is sufficient to induce SiHa cells to undergo apoptosis and senescence and suggest that transfection of cervical cancer cells with HPV-16 E6 and E7 antisense RNA is a potential approach to treat HPV-16-positive cervical cancers.

  9. Constructive Replication of the Visual-Perceptual-Image Rotation Model in Thurstone's (1941) Battery of 60 Tests of Mental Ability

    Science.gov (United States)

    Johnson, W.; Bouchard, T.J.

    2005-01-01

    We recently evaluated the relative statistical performance of the Cattell-Horn fluid-crystallized model and the Vernon verbal-perceptual model of the structure of human intelligence in a sample of 436 adults heterogeneous for age, place of origin, and educational background who completed 42 separate tests of mental ability from three test…

  10. Hyperthermia stimulates HIV-1 replication.

    Directory of Open Access Journals (Sweden)

    Ferdinand Roesch

    Full Text Available HIV-infected individuals may experience fever episodes. Fever is an elevation of the body temperature accompanied by inflammation. It is usually beneficial for the host through enhancement of immunological defenses. In cultures, transient non-physiological heat shock (42-45°C and Heat Shock Proteins (HSPs modulate HIV-1 replication, through poorly defined mechanisms. The effect of physiological hyperthermia (38-40°C on HIV-1 infection has not been extensively investigated. Here, we show that culturing primary CD4+ T lymphocytes and cell lines at a fever-like temperature (39.5°C increased the efficiency of HIV-1 replication by 2 to 7 fold. Hyperthermia did not facilitate viral entry nor reverse transcription, but increased Tat transactivation of the LTR viral promoter. Hyperthermia also boosted HIV-1 reactivation in a model of latently-infected cells. By imaging HIV-1 transcription, we further show that Hsp90 co-localized with actively transcribing provirus, and this phenomenon was enhanced at 39.5°C. The Hsp90 inhibitor 17-AAG abrogated the increase of HIV-1 replication in hyperthermic cells. Altogether, our results indicate that fever may directly stimulate HIV-1 replication, in a process involving Hsp90 and facilitation of Tat-mediated LTR activity.

  11. Hyperthermia stimulates HIV-1 replication.

    Science.gov (United States)

    Roesch, Ferdinand; Meziane, Oussama; Kula, Anna; Nisole, Sébastien; Porrot, Françoise; Anderson, Ian; Mammano, Fabrizio; Fassati, Ariberto; Marcello, Alessandro; Benkirane, Monsef; Schwartz, Olivier

    2012-01-01

    HIV-infected individuals may experience fever episodes. Fever is an elevation of the body temperature accompanied by inflammation. It is usually beneficial for the host through enhancement of immunological defenses. In cultures, transient non-physiological heat shock (42-45°C) and Heat Shock Proteins (HSPs) modulate HIV-1 replication, through poorly defined mechanisms. The effect of physiological hyperthermia (38-40°C) on HIV-1 infection has not been extensively investigated. Here, we show that culturing primary CD4+ T lymphocytes and cell lines at a fever-like temperature (39.5°C) increased the efficiency of HIV-1 replication by 2 to 7 fold. Hyperthermia did not facilitate viral entry nor reverse transcription, but increased Tat transactivation of the LTR viral promoter. Hyperthermia also boosted HIV-1 reactivation in a model of latently-infected cells. By imaging HIV-1 transcription, we further show that Hsp90 co-localized with actively transcribing provirus, and this phenomenon was enhanced at 39.5°C. The Hsp90 inhibitor 17-AAG abrogated the increase of HIV-1 replication in hyperthermic cells. Altogether, our results indicate that fever may directly stimulate HIV-1 replication, in a process involving Hsp90 and facilitation of Tat-mediated LTR activity.

  12. Transcriptional factor HBP1 targets P16(INK4A), upregulating its expression and consequently is involved in Ras-induced premature senescence.

    Science.gov (United States)

    Li, H; Wang, W; Liu, X; Paulson, K E; Yee, A S; Zhang, X

    2010-09-09

    Oncogene-mediated premature senescence has emerged as a potential tumor-suppressive mechanism in early cancer transitions. Many studies showed that Ras and p38 mitogen-activated protein kinase (MAPK) participate in premature senescence. Our previous work indicated that the HMG box-containing protein 1 (HBP1) transcription factor is involved in Ras- and p38 MAPK-induced premature senescence, but the mechanism of which has not yet been identified. Here, we showed that the p16(INK4A) cyclin-dependent kinase inhibitor is a novel target of HBP1 participating in Ras-induced premature senescence. The promoter of the p16(INK4A) gene contains an HBP1-binding site at position -426 to -433 bp from the transcriptional start site. HBP1 regulates the expression of the endogenous p16(INK4A) gene through direct sequence-specific binding. With HBP1 expression and the subsequent increase of p16(INK4A) gene expression, Ras induces premature senescence in primary cells. The data suggest a model in which Ras and p38 MAPK signaling engage HBP1 and p16(INK4A) to trigger premature senescence. In addition, we report that HBP1 knockdown is also required for Ras-induced transformation. All the data indicate that the mechanism of HBP1-mediated transcriptional regulation is important for not only premature senescence but also tumorigenesis.

  13. MicroRNA-34a regulation of endothelial senescence

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Takashi; Yagi, Shusuke [Department of Medicine, Aab Cardiovascular Research Institute, University of Rochester School of Medicine and Dentistry, West Henrietta, NY 14586 (United States); Yamakuchi, Munekazu, E-mail: munekazu_yamakuchi@urmc.rochester.edu [Department of Medicine, Aab Cardiovascular Research Institute, University of Rochester School of Medicine and Dentistry, West Henrietta, NY 14586 (United States)

    2010-08-06

    Research highlights: {yields} MicroRNA-34a (miR-34a) regulates senescence and cell cycle progression in endothelial cells. {yields} MiR-34a expression increases during endothelial cell senescence and in older mice. {yields} SIRT1 is a miR-34a target gene in endothelial cells. {yields} SIRT1 mediates the effects of miR-34a upon cell senescence in endothelial cells. -- Abstract: Endothelial senescence is thought to play a role in cardiovascular diseases such as atherosclerosis. We hypothesized that endothelial microRNAs (miRNAs) regulate endothelial survival and senescence. We found that miR-34a is highly expressed in primary endothelial cells. We observed that miR-34a expression increases in senescent human umbilical cord vein endothelial cells (HUVEC) and in heart and spleen of older mice. MiR-34a over-expression induces endothelial cell senescence and also suppresses cell proliferation by inhibiting cell cycle progression. Searching for how miR-34a affects senescence, we discovered that SIRT1 is a target of miR-34a. Over-expressing miR-34a inhibits SIRT1 protein expression, and knocking down miR-34a enhances SIRT1 expression. MiR-34a triggers endothelial senescence in part through SIRT1, since forced expression of SIRT1 blocks the ability of miR-34a to induce senescence. Our data suggest that miR-34a contributes to endothelial senescence through suppression of SIRT1.

  14. Effect of SIRT1 and its alternative splicing variant SIRT1-ΔExon8 on senescence model of 293T cells%SIRT1及其选择性剪接变异体SIRT1-ΔExon8在293T细胞衰老模型中的作用研究

    Institute of Scientific and Technical Information of China (English)

    王玥; 杨小荣; 张策

    2015-01-01

    Objective To investigate the effect of silent mating type information regulation 2 homolog 1-full long (SIRT1-FL) and its alternative splicing variant SIRT1-ΔExon8 on the aging process of 293T cells by observing the expression changes of SIRT1 and SIRT1-ΔExon8 in the D-galactose (D-gal) induced senescence model of 293T cells. Methods ①Cell Counting Kit-8 (CCK8) was used to determine the effect of D-gal on 293T cells viability at different concentrations (0, 5, 10, 15, 20 g/L). ②The 293T cells were cultured in DMEM high-glucose medium con-taining 10 g/L D-gal at the third passage and amplified to the sixth passage, and the senescence model of the 293T cells was established. β-galactosidase (SA-β-Gal) staining was used to determine the positive rate of senescent cells.③The mRNA expression levels of SIRT1 and SIRT1-ΔExon8 were measured in the 293T cells of the D-gal induced group and the control group by RT-PCR assay. Results ①The CCK-8 assay showed that the 10 g/L D-gal could in-duce 293T cells senescence and avoid extensive injuries. ②The positive rate of senescent cells in the D-gal induced group (74.2±3.6)%was higher than that in the control group (7.7±1.4)% (P<0.05). ③The findings of RT-PCR showed that the mRNA expression levels of SIRT1-FL and SIRT1-ΔExon8 in the 293T cells in the D-gal induced group were decreased by (78.26±0.05)%and (88.03±0.03)%compared with those in the control group, respectively (P<0.05). Conclusion ①SA-β-gal staining shows that the D-gal can induce the senescence model of 293T cells successfully.②The mRNA expression levels of SIRT1-FL and SIRT1-ΔExon8 in the senescence cells group are significantly de-creased compared with those in the control group, suggesting SIRT1-FL and SIRT1-ΔExon8 may be involved in the regulation of 293T cells senescence.%目的:通过观察SIRT1全长(SIRT1-FL)及缺失第8外显子的SIRT1选择性剪接变异体(SIRT1-ΔExon8)在D-半乳糖诱导的293T细胞衰老模型

  15. The Replication Recipe: What makes for a convincing replication?

    NARCIS (Netherlands)

    Brandt, M.J.; IJzerman, H.; Dijksterhuis, A.J.; Farach, F.J.; Geller, J.; Giner-Sorolla, R.; Grange, J.A.; Perugini, M.; Spies, J.R.; Veer, A. van 't

    2014-01-01

    Psychological scientists have recently started to reconsider the importance of close replications in building a cumulative knowledge base; however, there is no consensus about what constitutes a convincing close replication study. To facilitate convincing close replication attempts we have developed

  16. Replication and extension of a hierarchical model of social anxiety and depression: fear of positive evaluation as a key unique factor in social anxiety.

    Science.gov (United States)

    Weeks, Justin W

    2015-01-01

    Wang, Hsu, Chiu, and Liang (2012, Journal of Anxiety Disorders, 26, 215-224) recently proposed a hierarchical model of social interaction anxiety and depression to account for both the commonalities and distinctions between these conditions. In the present paper, this model was extended to more broadly encompass the symptoms of social anxiety disorder, and replicated in a large unselected, undergraduate sample (n = 585). Structural equation modeling (SEM) and hierarchical regression analyses were employed. Negative affect and positive affect were conceptualized as general factors shared by social anxiety and depression; fear of negative evaluation (FNE) and disqualification of positive social outcomes were operationalized as specific factors, and fear of positive evaluation (FPE) was operationalized as a factor unique to social anxiety. This extended hierarchical model explicates structural relationships among these factors, in which the higher-level, general factors (i.e., high negative affect and low positive affect) represent vulnerability markers of both social anxiety and depression, and the lower-level factors (i.e., FNE, disqualification of positive social outcomes, and FPE) are the dimensions of specific cognitive features. Results from SEM and hierarchical regression analyses converged in support of the extended model. FPE is further supported as a key symptom that differentiates social anxiety from depression.

  17. How frog embryos replicate their DNA reliably

    Science.gov (United States)

    Bechhoefer, John; Marshall, Brandon

    2007-03-01

    Frog embryos contain three billion base pairs of DNA. In early embryos (cycles 2-12), DNA replication is extremely rapid, about 20 min., and the entire cell cycle lasts only 25 min., meaning that mitosis (cell division) takes place in about 5 min. In this stripped-down cell cycle, there are no efficient checkpoints to prevent the cell from dividing before its DNA has finished replication - a disastrous scenario. Even worse, the many origins of replication are laid down stochastically and are also initiated stochastically throughout the replication process. Despite the very tight time constraints and despite the randomness introduced by origin stochasticity, replication is extremely reliable, with cell division failing no more than once in 10,000 tries. We discuss a recent model of DNA replication that is drawn from condensed-matter theories of 1d nucleation and growth. Using our model, we discuss different strategies of replication: should one initiate all origins as early as possible, or is it better to hold back and initiate some later on? Using concepts from extreme-value statistics, we derive the distribution of replication times given a particular scenario for the initiation of origins. We show that the experimentally observed initiation strategy for frog embryos meets the reliability constraint and is close to the one that requires the fewest resources of a cell.

  18. The telomeric protein AKTIP interacts with A- and B-type lamins and is involved in regulation of cellular senescence

    Science.gov (United States)

    Burla, Romina; Carcuro, Mariateresa; Torre, Mattia La; Fratini, Federica; Crescenzi, Marco; D'Apice, Maria Rosaria; Spitalieri, Paola; Raffa, Grazia Daniela; Astrologo, Letizia; Lattanzi, Giovanna; Cundari, Enrico; Raimondo, Domenico; Biroccio, Annamaria; Gatti, Maurizio

    2016-01-01

    AKTIP is a shelterin-interacting protein required for replication of telomeric DNA. Here, we show that AKTIP biochemically interacts with A- and B-type lamins and affects lamin A, but not lamin C or B, expression. In interphase cells, AKTIP localizes at the nuclear rim and in discrete regions of the nucleoplasm just like lamins. Double immunostaining revealed that AKTIP partially co-localizes with lamin B1 and lamin A/C in interphase cells, and that proper AKTIP localization requires functional lamin A. In mitotic cells, AKTIP is enriched at the spindle poles and at the midbody of late telophase cells similar to lamin B1. AKTIP-depleted cells show senescence-associated markers and recapitulate several aspects of the progeroid phenotype. Collectively, our results indicate that AKTIP is a new player in lamin-related processes, including those that govern nuclear architecture, telomere homeostasis and cellular senescence. PMID:27512140

  19. Replicator dynamics in value chains

    DEFF Research Database (Denmark)

    Cantner, Uwe; Savin, Ivan; Vannuccini, Simone

    2016-01-01

    The pure model of replicator dynamics though providing important insights in the evolution of markets has not found much of empirical support. This paper extends the model to the case of firms vertically integrated in value chains. We show that i) by taking value chains into account, the replicator...... dynamics may revert its effect. In these regressive developments of market selection, firms with low fitness expand because of being integrated with highly fit partners, and the other way around; ii) allowing partner's switching within a value chain illustrates that periods of instability in the early...... stage of industry life-cycle may be the result of an 'optimization' of partners within a value chain providing a novel and simple explanation to the evidence discussed by Mazzucato (1998); iii) there are distinct differences in the contribution to market selection between the layers of a value chain...

  20. Abiotic self-replication.

    Science.gov (United States)

    Meyer, Adam J; Ellefson, Jared W; Ellington, Andrew D

    2012-12-18

    The key to the origins of life is the replication of information. Linear polymers such as nucleic acids that both carry information and can be replicated are currently what we consider to be the basis of living systems. However, these two properties are not necessarily coupled. The ability to mutate in a discrete or quantized way, without frequent reversion, may be an additional requirement for Darwinian evolution, in which case the notion that Darwinian evolution defines life may be less of a tautology than previously thought. In this Account, we examine a variety of in vitro systems of increasing complexity, from simple chemical replicators up to complex systems based on in vitro transcription and translation. Comparing and contrasting these systems provides an interesting window onto the molecular origins of life. For nucleic acids, the story likely begins with simple chemical replication, perhaps of the form A + B → T, in which T serves as a template for the joining of A and B. Molecular variants capable of faster replication would come to dominate a population, and the development of cycles in which templates could foster one another's replication would have led to increasingly complex replicators and from thence to the initial genomes. The initial genomes may have been propagated by RNA replicases, ribozymes capable of joining oligonucleotides and eventually polymerizing mononucleotide substrates. As ribozymes were added to the genome to fill gaps in the chemistry necessary for replication, the backbone of a putative RNA world would have emerged. It is likely that such replicators would have been plagued by molecular parasites, which would have been passively replicated by the RNA world machinery without contributing to it. These molecular parasites would have been a major driver for the development of compartmentalization/cellularization, as more robust compartments could have outcompeted parasite-ridden compartments. The eventual outsourcing of metabolic

  1. Adenovirus DNA Replication

    OpenAIRE

    Hoeben, Rob C.; Uil, Taco G.

    2013-01-01

    Adenoviruses have attracted much attention as probes to study biological processes such as DNA replication, transcription, splicing, and cellular transformation. More recently these viruses have been used as gene-transfer vectors and oncolytic agents. On the other hand, adenoviruses are notorious pathogens in people with compromised immune functions. This article will briefly summarize the basic replication strategy of adenoviruses and the key proteins involved and will deal with the new deve...

  2. A role for p53 in selenium-induced senescence

    Science.gov (United States)

    The tumor suppressor p53 and the ataxia-telangiectasia mutated (ATM) kinase play important roles in the senescence response to oncogene activation and DNA damage. We have previously shown that selenium-containing compounds can activate an ATM-dependent senescence response in MRC-5 normal fibroblasts...

  3. Delay of Iris flower senescence by protease inhibitors

    NARCIS (Netherlands)

    Pak, C.; Doorn, van W.G.

    2005-01-01

    asterisk inside a circle sign Visible senescence of the flag tepals in Iris x hollandica (cv. Blue Magic) was preceded by a large increase in endoprotease activity. Just before visible senescence about half of total endoprotease activity was apparently due to cysteine proteases, somewhat less than h

  4. Exercise Prevents Diet-Induced Cellular Senescence in Adipose Tissue

    NARCIS (Netherlands)

    Schafer, M.J.; White, T.A.; Evans, G.; Tonne, J.M.; Verzosa, G.C.; Stout, M.B.; Mazula, D.L.; Palmer, A.K.; Baker, D.J.; Jensen, M.D.; Torbenson, M.S.; Miller, J.D.; Ikeda, Y.; Tchkonia, T.; Deursen, J.M.A. van; Kirkland, J.L.; LeBrasseur, N.K.

    2016-01-01

    Considerable evidence implicates cellular senescence in the biology of aging and chronic disease. Diet and exercise are determinants of healthy aging; however, the extent to which they affect the behavior and accretion of senescent cells within distinct tissues is not clear. Here we tested the

  5. Leaf senescence in alstroemeria: regulation by phytochrome gibberellins and cytokinins.

    NARCIS (Netherlands)

    Kappers, I.

    1998-01-01

    Leaf senescence in plants is a regulated process influenced by light as well as phytohormones. In the present study the putative role of the phytohormones cytokinins and gibberellins as mediators for the light signal on leaf senescence in alstroemeria was studied. It was found that low photon fluenc

  6. Global Reorganization of the Nuclear Landscape in Senescent Cells

    Directory of Open Access Journals (Sweden)

    Tamir Chandra

    2015-02-01

    Full Text Available Cellular senescence has been implicated in tumor suppression, development, and aging and is accompanied by large-scale chromatin rearrangements, forming senescence-associated heterochromatic foci (SAHF. However, how the chromatin is reorganized during SAHF formation is poorly understood. Furthermore, heterochromatin formation in senescence appears to contrast with loss of heterochromatin in Hutchinson-Gilford progeria. We mapped architectural changes in genome organization in cellular senescence using Hi-C. Unexpectedly, we find a dramatic sequence- and lamin-dependent loss of local interactions in heterochromatin. This change in local connectivity resolves the paradox of opposing chromatin changes in senescence and progeria. In addition, we observe a senescence-specific spatial clustering of heterochromatic regions, suggesting a unique second step required for SAHF formation. Comparison of embryonic stem cells (ESCs, somatic cells, and senescent cells shows a unidirectional loss in local chromatin connectivity, suggesting that senescence is an endpoint of the continuous nuclear remodelling process during differentiation.

  7. Life table tests of evolutionary theories of senescence.

    Science.gov (United States)

    Nesse, R M

    1988-01-01

    The phenomenon of senescence requires both evolutionary and proximate explanations. The most widely accepted evolutionary explanation for senescence is that it never gets exposed to natural selection because environmental hazards kill all individuals before the age at which senescence causes decreased fitness. If this explanation is sufficient, wild populations should not demonstrate senescence, and their mortality rates should therefore remain constant during adult life, except when environmental causes of mortality have recently decreased. The alternative explanation for the persistence of the genes that cause senescence is that they have been selected for because they have pleiotropic effects that are beneficial early in life when the force of selection is strongest. Where this is the case, mortality rates should increase with age in wild populations. A method is described for using life table data to calculate an estimate of the intensity of selection acting on senescence in wild populations. This method is applied to a variety of life tables. The results suggest that pleiotropic genes may be important causes of senescence in some populations, but not in others. This has implications for research on the proximate mechanisms of senescence.

  8. Dissecting the metabolic role of mitochondria during developmental leaf senescence

    NARCIS (Netherlands)

    Chrobok, Daria; Law, Simon R.; Brouwer, Bas; Lindén, Pernilla; Ziolkowska, Agnieszka; Liebsch, Daniela; Narsai, Reena; Szal, Bozena; Moritz, Thomas; Rouhier, Nicolas; Whelan, James; Gardeström, Per; Keech, Olivier

    2016-01-01

    The functions of mitochondria during leaf senescence, a type of programmed cell death aimed at the massive retrieval of nutrients from the senescing organ to the rest of the plant, remain elusive. Here, combining experimental and analytical approaches, we showed that mitochondrial integrity in

  9. Biological Impact of Senescence Induction in Prostate Cancer

    Science.gov (United States)

    2010-01-01

    that identifies senescent human cells in culture and in aging skin in vivo. Proc Natl Acad Sci USA 1995;92:9363-9367. 3. Collado M, Gil J, Efeyan A... Collado , M, Gil, J, Efeyan, A, et al. Tumour biology: senescence in premalignant tumours. Nature, 2005; 436(7051): 642. 15. Choi, J, Shendrik, I

  10. Role of p53 in Mammary Epithelial Cell Senescence

    Science.gov (United States)

    2007-05-01

    Cell, 2005. 7(6): p. 505-12. 3. Collado , M., et al., Tumour biology: senescence in premalignant tumours. Nature, 2005. 436(7051): p. 642. 4... Collado , M. and M. Serrano, The power and the promise of oncogene-induced senescence markers. Nat Rev Cancer, 2006. 6(6): p. 472-6. 5. Hofseth, L.J., S.P

  11. Global reorganization of the nuclear landscape in senescent cells.

    Science.gov (United States)

    Chandra, Tamir; Ewels, Philip Andrew; Schoenfelder, Stefan; Furlan-Magaril, Mayra; Wingett, Steven William; Kirschner, Kristina; Thuret, Jean-Yves; Andrews, Simon; Fraser, Peter; Reik, Wolf

    2015-02-03

    Cellular senescence has been implicated in tumor suppression, development, and aging and is accompanied by large-scale chromatin rearrangements, forming senescence-associated heterochromatic foci (SAHF). However, how the chromatin is reorganized during SAHF formation is poorly understood. Furthermore, heterochromatin formation in senescence appears to contrast with loss of heterochromatin in Hutchinson-Gilford progeria. We mapped architectural changes in genome organization in cellular senescence using Hi-C. Unexpectedly, we find a dramatic sequence- and lamin-dependent loss of local interactions in heterochromatin. This change in local connectivity resolves the paradox of opposing chromatin changes in senescence and progeria. In addition, we observe a senescence-specific spatial clustering of heterochromatic regions, suggesting a unique second step required for SAHF formation. Comparison of embryonic stem cells (ESCs), somatic cells, and senescent cells shows a unidirectional loss in local chromatin connectivity, suggesting that senescence is an endpoint of the continuous nuclear remodelling process during differentiation. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  12. Delay of Iris flower senescence by protease inhibitors

    NARCIS (Netherlands)

    Pak, C.; Doorn, van W.G.

    2005-01-01

    asterisk inside a circle sign Visible senescence of the flag tepals in Iris x hollandica (cv. Blue Magic) was preceded by a large increase in endoprotease activity. Just before visible senescence about half of total endoprotease activity was apparently due to cysteine proteases, somewhat less than

  13. Senescence and programmed cell death : substance or semantics?

    NARCIS (Netherlands)

    Doorn, van W.G.; Woltering, E.J.

    2004-01-01

    The terms senescence and programmed cell death (PCD) have led to some confusion. Senescence as visibly observed in, for example, leaf yellowing and petal wilting, has often been taken to be synonymous with the programmed death of the constituent cells. PCD also obviously refers to cells, which show

  14. Cellular senescence and tumor promotion : Is aging the key?

    NARCIS (Netherlands)

    Loaiza, Natalia; Demaria, Marco

    The senescence response is a potent tumor suppressor mechanism characterized by an irreversible growth arrest in response to potentially oncogenic signals to prevent the proliferation of damaged cells. Late in life, some of the features of senescent cells seem to mediate the development of

  15. Cellular and molecular aspects of quinoa leaf senescence.

    Science.gov (United States)

    López-Fernández, María Paula; Burrieza, Hernán Pablo; Rizzo, Axel Joel; Martínez-Tosar, Leandro Julián; Maldonado, Sara

    2015-09-01

    During leaf senescence, degradation of chloroplasts precede to changes in nuclei and other cytoplasmic organelles, RuBisCO stability is progressively lost, grana lose their structure, plastidial DNA becomes distorted and degraded, the number of plastoglobuli increases and abundant senescence-associated vesicles containing electronically dense particles emerge from chloroplasts pouring their content into the central vacuole. This study examines quinoa leaf tissues during development and senescence using a range of well-established markers of programmed cell death (PCD), including: morphological changes in nuclei and chloroplasts, degradation of RuBisCO, changes in chlorophyll content, DNA degradation, variations in ploidy levels, and changes in nuclease profiles. TUNEL reaction and DNA electrophoresis demonstrated that DNA fragmentation in nuclei occurs at early senescence, which correlates with induction of specific nucleases. During senescence, metabolic activity is high and nuclei endoreduplicate, peaking at 4C. At this time, TEM images showed some healthy nuclei with condensed chromatin and nucleoli. We have found that DNA fragmentation, induction of senescence-associated nucleases and endoreduplication take place during leaf senescence. This provides a starting point for further research aiming to identify key genes involved in the senescence of quinoa leaves.

  16. Identification of microRNAs dysregulated in cellular senescence driven by endogenous genotoxic stress

    Science.gov (United States)

    Nidadavolu, Lolita S.; Niedernhofer, Laura J.; Khan, Saleem A.

    2013-01-01

    XFE progeroid syndrome, a disease of accelerated aging caused by deficiency in the DNA repair endonuclease XPF-ERCC1, is modeled by Ercc1 knockout and hypomorphic mice. Tissues and primary cells from these mice senesce prematurely, offering a unique opportunity to identify factors that regulate senescence and aging. We compared microRNA (miRNA) expression in Ercc1−/− primary mouse embryonic fibroblasts (MEFs) and wild-type (WT) MEFs in different growth conditions to identify miRNAs that drive cellular senescence. Microarray analysis showed three differentially expressed miRNAs in passage 7 (P7) Ercc1−/− MEFs grown at 20% O2 compared to Ercc1−/− MEFs grown at 3% O2. Thirty-six differentially expressed miRNAs were identified in Ercc1−/− MEFs at P7 compared to early passage (P3) in 3% O2. Eight of these miRNAs (miR-449a, miR-455*, miR-128, miR-497, miR-543, miR-450b-3p, miR-872 and miR-10b) were similarly downregulated in the liver of progeroid Ercc1−/Δ and old WT mice compared to adult WT mice, a tissue that senesces with aging. Three miRNAs (miR-449a, miR-455* and miR-128) were also downregulated in Ercc1−/Δ and WT old mice kidneys compared to young WT mice. We also discovered that the miRNA expression regulator Dicer is significantly downregulated in tissues of old mice and late passage cells compared to young controls. Collectively these results support the conclusion that the miRNAs identified may play an important role in staving off cellular senescence and their altered expression could be indicative of aging. PMID:23852002

  17. Escalation of error catastrophe for enzymatic self-replicators

    Science.gov (United States)

    Obermayer, B.; Frey, E.

    2009-11-01

    It is a long-standing question in origin-of-life research whether the information content of replicating molecules can be maintained in the presence of replication errors. Extending standard quasispecies models of non-enzymatic replication, we analyze highly specific enzymatic self-replication mediated through an otherwise neutral recognition region, which leads to frequency-dependent replication rates. We find a significant reduction of the maximally tolerable error rate, because the replication rate of the fittest molecules decreases with the fraction of functional enzymes. Our analysis is extended to hypercyclic couplings as an example for catalytic networks.

  18. Mental Effort and Perceptions of TV and Books: A Dutch Replication Study Based on Salomon's Model of Learning.

    Science.gov (United States)

    Beentjes, Hans W. J.

    This comparison of students' learning from reading books and from watching television uses Gavriel Salomon's model of learning effects, which is based on the amount of mental effort invested (AIME) in a medium as determining how deeply the information from that medium is processed. Mental effort, in turn, is predicted to depend on two perceptions…

  19. Senescence gives insights into the morphogenetic evolution of anamniotes

    Directory of Open Access Journals (Sweden)

    Éric Villiard

    2017-06-01

    Full Text Available Senescence represents a mechanism to avoid undesired cell proliferation that plays a role in tumor suppression, wound healing and embryonic development. In order to gain insight on the evolution of senescence, we looked at its presence in developing axolotls (urodele amphibians and in zebrafish (teleost fish, which are both anamniotes. Our data indicate that cellular senescence is present in various developing structures in axolotls (pronephros, olfactory epithelium of nerve fascicles, lateral organs, gums and in zebrafish (epithelium of the yolk sac and in the lower part of the gut. Senescence was particularly associated with transient structures (pronephros in axolotls and yolk sac in zebrafish suggesting that it may play a role in the elimination of these tissues. Our data supports the notion that cellular senescence evolved early in vertebrate evolution to influence embryonic development.

  20. Control of senescence in rumex leaf discs by gibberellic Acid.

    Science.gov (United States)

    Goldthwaite, J J; Laetsch, W M

    1968-11-01

    The kinetics of chlorophyll and protein decomposition and the effect of gibberellic acid (GA) were examined in senescing leaf discs of Rumex crispus and R. obtusifolius. Loss of Rumex total chlorophyll proceeds at a slow rate for about 2 days followed by a period of rapid logarithmic decline. Chlorophyll b is lost at a slightly faster rate than chlorophyll a during senescence in discs as well as in situ. GA causes a complete cessation of net chlorophyll and protein degradation for several days in Rumex, in contrast to the incomplete senescence inhibition generally observed with cytokinins. GA is fully effective even when added at the middle of the logarithmic phase of chlorophyll loss. Senescence inhibition by GA is apparently gradually reversed upon GA removal. The cytokinins, kinetin and 6-benzylaminopurine, were also effective in Rumex leaf discs, indicating that the senescence retarding effect was not restricted to the gibberellins.

  1. Emerging roles of lncRNAs in senescence

    DEFF Research Database (Denmark)

    Montes Resano, Marta; Lund, Anders H

    2016-01-01

    Cellular senescence is a complex stress response that leads to an irreversible state of cell growth arrest. Senescence may be induced by different stimuli such as telomere shortening, DNA damage or oncogenic insult among others. Senescent cells are metabolically highly active producing a wealth...... of cytokines and chemokines that depending on the context may have a beneficial or deleterious impact on the organism. Senescence is considered a tightly regulated stress response that is largely governed by the p53/p21 and p16/Rb pathways. Many molecules have been identified as regulators of these two...... networks, such as transcription factors, chromatin modifiers and recently, non-coding RNAs. The expression level of several long non-coding RNAs is affected during different types of senescence, however, which of these are important for the biological function remains poorly understood. We review here our...

  2. A comparative analysis of senescence in adult damselflies and dragonflies (Odonata).

    Science.gov (United States)

    Sherratt, T N; Hassall, C; Laird, R A; Thompson, D J; Cordero-Rivera, A

    2011-04-01

    Any population whose members are subject to extrinsic mortality should exhibit an increase in mortality with age. Nevertheless, the prevailing opinion is that populations of adult damselflies and dragonflies do not exhibit such senescence. Here, we challenge this contention by fitting a range of demographic models to the data on which these earlier conclusions were based. We show that a model with an exponential increase in age-related mortality (Gompertz) generally provides a more parsimonious fit than alternative models including age-independent mortality, indicating that many odonates do indeed senesce. Controlling for phylogeny, a comparison of the daily mortality of 35 odonate species indicates that although male and female mortalities are positively correlated, mortality tends to be higher in males of those species that exhibit territoriality. Hence, we show for the first time that territoriality may impose a survivorship cost on males, once the underlying phylogenetic relationships are accounted for.

  3. Minichromosome replication in vitro: inhibition of re-replication by replicatively assembled nucleosomes.

    Science.gov (United States)

    Krude, T; Knippers, R

    1994-08-19

    Single-stranded circular DNA, containing the SV40 origin sequence, was used as a template for complementary DNA strand synthesis in cytosolic extracts from HeLa cells. In the presence of the replication-dependent chromatin assembly factor CAF-1, defined numbers of nucleosomes were assembled during complementary DNA strand synthesis. These minichromosomes were then induced to semiconservatively replicate by the addition of the SV40 initiator protein T antigen (re-replication). The results indicate that re-replication of minichromosomes appears to be inhibited by two independent mechanisms. One acts at the initiation of minichromosome re-replication, and the other affects replicative chain elongation. To directly demonstrate the inhibitory effect of replicatively assembled nucleosomes, two types of minichromosomes were prepared: (i) post-replicative minichromosomes were assembled in a reaction coupled to replication as above; (ii) pre-replicative minichromosomes were assembled independently of replication on double-stranded DNA. Both types of minichromosomes were used as templates for DNA replication under identical conditions. Replicative fork movement was found to be impeded only on post-replicative minichromosome templates. In contrast, pre-replicative minichromosomes allowed one unconstrained replication cycle, but re-replication was inhibited due to a block in fork movement. Thus, replicatively assembled chromatin may have a profound influence on the re-replication of DNA.

  4. Arabidopsis CPR5 is a senescence-regulatory gene with pleiotropic functions as predicted by the evolutionary theory of senescence

    NARCIS (Netherlands)

    Jing, Hai-Chun; Anderson, Lisa; Sturre, Marcel J. G.; Hille, Jacques; Dijkwel, Paul P.

    2007-01-01

    Arabidopsis CPR5 is a senescence-regulatory gene with pleiotropic functions as predicted by the evolutionary theory of senescence Hai-Chun Jing1,2, Lisa Anderson3, Marcel J.G. Sturre1, Jacques Hille1 and Paul P. Dijkwel1,* 1Molecular Biology of Plants, Groningen Biomolecular Sciences and Biotechnolo

  5. Arabidopsis CPR5 is a senescence-regulatory gene with pleiotropic functions as predicted by the evolutionary theory of senescence

    NARCIS (Netherlands)

    Jing, Hai-Chun; Anderson, Lisa; Sturre, Marcel J. G.; Hille, Jacques; Dijkwel, Paul P.

    2007-01-01

    Arabidopsis CPR5 is a senescence-regulatory gene with pleiotropic functions as predicted by the evolutionary theory of senescence Hai-Chun Jing1,2, Lisa Anderson3, Marcel J.G. Sturre1, Jacques Hille1 and Paul P. Dijkwel1,* 1Molecular Biology of Plants, Groningen Biomolecular Sciences and

  6. Biomolecular bases of the senescence process and cancer. A new approach to oncological treatment linked to ageing.

    Science.gov (United States)

    Badiola, Iker; Santaolalla, Francisco; Garcia-Gallastegui, Patricia; Ana, Sánchez-Del Rey; Unda, Fernando; Ibarretxe, Gaskon

    2015-09-01

    Human ageing is associated with a gradual decline in the physiological functions of the body at multiple levels and it is a key risk factor for many diseases, including cancer. Ageing process is intimately related to widespread cellular senescence, characterised by an irreversible loss of proliferative capacity and altered functioning associated with telomere attrition, accumulation of DNA damage and compromised mitochondrial and metabolic function. Tumour and senescent cells may be generated in response to the same stimuli, where either cellular senescence or transformation would constitute two opposite outcomes of the same degenerative process. This paper aims to review the state of knowledge on the biomolecular relationship between cellular senescence, ageing and cancer. Importantly, many of the cell signalling pathways that are found to be altered during both cellular senescence and tumourigenesis are regulated through shared epigenetic mechanisms and, therefore, they are potentially reversible. MicroRNAs are emerging as pivotal players linking ageing and cancer. These small RNA molecules have generated great interest from the point of view of future clinical therapy for cancer because successful experimental results have been obtained in animal models. Micro-RNA therapies for cancer are already being tested in clinical phase trials. These findings have potential importance in cancer treatment in aged people although further research-based knowledge is needed to convert them into an effective molecular therapies for cancer linked to ageing. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Identification and characterization of contrasting sunflower genotypes to early leaf senescence process combining molecular and physiological studies (Helianthus annuus L.).

    Science.gov (United States)

    López Gialdi, A I; Moschen, S; Villán, C S; López Fernández, M P; Maldonado, S; Paniego, N; Heinz, R A; Fernandez, P

    2016-09-01

    Leaf senescence is a complex mechanism ruled by multiple genetic and environmental variables that affect crop yields. It is the last stage in leaf development, is characterized by an active decline in photosynthetic rate, nutrients recycling and cell death. The aim of this work was to identify contrasting sunflower inbred lines differing in leaf senescence and to deepen the study of this process in sunflower. Ten sunflower genotypes, previously selected by physiological analysis from 150 inbred genotypes, were evaluated under field conditions through physiological, cytological and molecular analysis. The physiological measurement allowed the identification of two contrasting senescence inbred lines, R453 and B481-6, with an increase in yield in the senescence delayed genotype. These findings were confirmed by cytological and molecular analysis using TUNEL, genomic DNA gel electrophoresis, flow sorting and gene expression analysis by qPCR. These results allowed the selection of the two most promising contrasting genotypes, which enables future studies and the identification of new biomarkers associated to early senescence in sunflower. In addition, they allowed the tuning of cytological techniques for a non-model species and its integration with molecular variables.

  8. A validation test for Adagio through replication of Big Hill and Bayou Choctaw JAS3D models.

    Energy Technology Data Exchange (ETDEWEB)

    Park, Byoung Yoon

    2013-06-01

    JAS3D, a three dimensional iterative solid mechanics code, has been used for structural analyses for the Strategic Petroleum Reserve system since the 1990s. JAS3D is no longer supported by Sandia National Laboratories, and has been replaced by Adagio. To validate the transition from JAS3D to Adagio, the existing JAS3D input decks and user subroutines for Bayou Choctaw and Big Hill models were converted for use with Adagio. The calculation results from the Adagio runs are compared to the JAS3D. Since the Adagio results are very similar to the JAS3D results, Adagio is judged to be performing satisfactorily.

  9. Investigating variation in replicability: A "Many Labs" replication project

    NARCIS (Netherlands)

    Klein, R.A.; Ratliff, K.A.; Vianello, M.; Adams, R.B.; Bahnik, S.; Bernstein, M.J.; Bocian, K.; Brandt, M.J.; Brooks, B.; Brumbaugh, C.C.; Cemalcilar, Z.; Chandler, J.; Cheong, W.; Davis, W.E.; Devos, T.; Eisner, M.; Frankowska, N.; Furrow, D.; Galliani, E.M.; Hasselman, F.W.; Hicks, J.A.; Hovermale, J.F.; Hunt, S.J.; Huntsinger, J.R.; IJzerman, H.; John, M.S.; Joy-Gaba, J.A.; Kappes, H.B.; Krueger, L.E.; Kurtz, J.; Levitan, C.A.; Mallett, R.K.; Morris, W.L.; Nelson, A.J.; Nier, J.A.; Packard, G.; Pilati, R.; Rutchick, A.M.; Schmidt, K.; Skorinko, J.L.M.; Smith, R.; Steiner, T.G.; Storbeck, J.; Van Swol, L.M.; Thompson, D.; Veer, A.E. van 't; Vaughn, L.A.; Vranka, M.; Wichman, A.L.; Woodzicka, J.A.; Nosek, B.A.

    2014-01-01

    Although replication is a central tenet of science, direct replications are rare in psychology. This research tested variation in the replicability of 13 classic and contemporary effects across 36 independent samples totaling 6,344 participants. In the aggregate, 10 effects replicated consistently.

  10. Hepatitis B virus replication

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Hepadnaviruses, including human hepatitis B virus (HBV), replicate through reverse transcription of an RNA intermediate, the pregenomic RNA (pgRNA). Despite this kinship to retroviruses, there are fundamental differences beyond the fact that hepadnavirions contain DNA instead of RNA. Most peculiar is the initiation of reverse transcription: it occurs by protein-priming, is strictly committed to using an RNA hairpin on the pgRNA,ε, as template, and depends on cellular chaperones;moreover, proper replication can apparently occur only in the specialized environment of intact nucleocapsids.This complexity has hampered an in-depth mechanistic understanding. The recent successful reconstitution in the test tube of active replication initiation complexes from purified components, for duck HBV (DHBV),now allows for the analysis of the biochemistry of hepadnaviral replication at the molecular level. Here we review the current state of knowledge at all steps of the hepadnaviral genome replication cycle, with emphasis on new insights that turned up by the use of such cellfree systems. At this time, they can, unfortunately,not be complemented by three-dimensional structural information on the involved components. However, at least for the s RNA element such information is emerging,raising expectations that combining biophysics with biochemistry and genetics will soon provide a powerful integrated approach for solving the many outstanding questions. The ultimate, though most challenging goal,will be to visualize the hepadnaviral reverse transcriptase in the act of synthesizing DNA, which will also have strong implications for drug development.

  11. Tinospora cordifolia Induces Differentiation and Senescence Pathways in Neuroblastoma Cells.

    Science.gov (United States)

    Mishra, Rachana; Kaur, Gurcharan

    2015-08-01

    Children diagnosed with neuroblastomas often suffer from severe side as well as late effects of conventional treatments like chemotherapy and radiotherapy. Recent advances in understanding of molecular pathways involved in cellular differentiation and apoptosis have helped in the development of new therapeutic approach based on differentiation-based therapy of malignant tumours. Natural medicines with their holistic therapeutic approach are known to selectively eliminate cancer cells thus provide a better substitute for the conventional treatment modes. The current study was aimed to investigate the anti-cancer potential of aqueous ethanolic extract of Tinospora cordifolia (TCE) using IMR-32 human neuroblastoma cell line as a model system. TCE is highly recommended in Ayurveda for its general body and metal health-promoting properties. TCE treatment was seen to arrest the majority of cells in G0/G1 phase and modulated the expression of DNA clamp sliding protein (PCNA) and cyclin D1. Further, TCE-treated cells showed differentiation as revealed by their morphology and the expression of neuronal cell specific differentiation markers NF200, MAP-2 and NeuN in neuroblastoma cells. The differentiated phenotype was associated with induction of senescence and pro-apoptosis pathways by enhancing expression of senescence marker mortalin and Rel A subunit of nuclear factor kappa beta (NFkB) along with decreased expression of anti-apoptotic marker, Bcl-xl. TCE exhibited anti-metastatic activity and significantly reduced cell migration in the scratched area along with downregulation of neural cell adhesion molecule (NCAM) polysialylation and secretion of matrix metalloproteinases (MMPs). Our data suggest that crude extract or active phytochemicals from this plant may be a potential candidate for differentiation-based therapy of malignant neuroblastoma cells.

  12. Identification of Senescent Cells in the Bone Microenvironment

    Science.gov (United States)

    Farr, Joshua N; Fraser, Daniel G; Wang, Haitao; Jaehn, Katharina; Ogrodnik, Mikolaj B; Weivoda, Megan M; Drake, Matthew T; Tchkonia, Tamara; LeBrasseur, Nathan K; Kirkland, James L; Bonewald, Lynda F; Pignolo, Robert J; Monroe, David G; Khosla, Sundeep

    2017-01-01

    Cellular senescence is a fundamental mechanism by which cells remain metabolically active yet cease dividing and undergo distinct phenotypic alterations, including upregulation of p16Ink4a, profound secretome changes, telomere shortening, and decondensation of pericentromeric satellite DNA. Because senescent cells accumulate in multiple tissues with aging, these cells and the dysfunctional factors they secrete, termed the senescence-associated secretory phenotype (SASP), are increasingly recognized as promising therapeutic targets to prevent age-related degenerative pathologies, including osteoporosis. However, the cell type(s) within the bone microenvironment that undergoes senescence with aging in vivo has remained poorly understood, largely because previous studies have focused on senescence in cultured cells. Thus in young (age 6 months) and old (age 24 months) mice, we measured senescence and SASP markers in vivo in highly enriched cell populations, all rapidly isolated from bone/marrow without in vitro culture. In both females and males, p16Ink4a expression by real-time quantitative polymerase chain reaction (rt-qPCR) was significantly higher with aging in B cells, T cells, myeloid cells, osteoblast progenitors, osteoblasts, and osteocytes. Further, in vivo quantification of senescence-associated distension of satellites (SADS), ie, large-scale unraveling of pericentromeric satellite DNA, revealed significantly more senescent osteocytes in old compared with young bone cortices (11% versus 2%, p < 0.001). In addition, primary osteocytes from old mice had sixfold more (p < 0.001) telomere dysfunction-induced foci (TIFs) than osteocytes from young mice. Corresponding with the age-associated accumulation of senescent osteocytes was significantly higher expression of multiple SASP markers in osteocytes from old versus young mice, several of which also showed dramatic age-associated upregulation in myeloid cells. These data show that with aging, a subset of cells