| Objective:Angiotensin II (Ang II) stimulates endothelin (ET-1) transcription, which contributes to cardiac hypertrophy and fibrosis. The involvement of the epigenetic machinery in this process is largely undefined.We examined the epigenetic maneuvering underlying ET-1 transactivation by Angâ…¡ and its involvement in cardiac hypertrophy and fibrosis.Methods:When treated with Ang â…¡, mRNA levels and luciferase activities of ET-1 were examined by real-time quantitative PCR (qPCR) in human embryonic umbilical vein endothelial cells (HUVEC), human Pulmonary endothelial cells (HPEC) and mouse embryonic fibroblasts (MEF). Co-Immunoprecipitation and western blotting were performed to examine MRTF-A expression levels,and the interaction of MRTF-A and COMPASS components, as well as c-Jun/c-Fos(AP-1). ChIP assay were performed to detect the effect of Ang â…¡ on promoting MRTF-A, c-Jun/c-Fos, H3K4-me3, H3K4-me2 bounding to the ET-1 promoter.In contrast, silencing MRTF-A with shRNA,and then detect the effects of Ang â…¡ on ET-1 transcriptional regulation. In vivo experiments, we detected Ang â…¡-induced ET-1 transactivation and consequential cardiac hypertrophy and myocardial fibrosis levels in MRTF-A,ASH2,WDR5 knockout mice.Results:Angâ…¡ activated myocardin related transcription factor A (MRTF-A)in vascular endothelial cells. Over-expression of MRTF-A enhanced, whereas depletion of MRTF-A attenuated, transcriptional activation of ET-1 gene by Ang â…¡. MRTF-A deficiency ameliorated Ang â…¡ induced cardiac hypertrophy and fibrosis in mice paralleling diminishedsynthesis and release of ET-1. MRTF-A was recruited to the ET-1 promoter by c-Jun/c-Fos (AP-1) in response to Ang â…¡ treatment. Once bound, MRTF-A brought a histone H3K4 methyltransferase complex (ASH2/WDR5) to activate ET-1 transcription by altering chromatin structure. Endothelial specific depletion of ASH2/WDR5 significantly dampened Angâ…¡ induced cardiac hypertrophy and fibrosis in mice.Conclusions:In conclusion, we data have unveiled a MRTF-A-containing epigenetic complex that links ET-1 transactivation in endothelial cells to cardiac hypertrophy and fibrosis by Ang â…¡.Objective:Epigenetics is a phenomenon of altered heritable phenotypic expression of genetic information occurring without changes in DNA sequence. SIRT1 is one of seven sirtiuns in mammals. SIRT1 regulates ageing-related, tissue-specific pathobiological processes in humans including cardiovascular disease. Recent investigations have shown that SIRT1 can protect the heart against ischemia/reperfusion injury. Despite advances achieved on understanding the transcriptional regulation of SIRT1, the role of histone methylation has not been fully investigated. We examined the role of histone H3K9 trimethylase Suv39H2 on SIRT1 repression in heart diseases.Methods:An SIRT1 promoter luciferase construct was transfected into HEK293 followed by treatment with MTA (a pan-methyltransfersase inhibiter). HMTs (G9a, SET9, EZH1, Suv39H) were silenced with targeted siRNA. We depleted Suv39H2 by special targeted small interference RNA(siRNA) or inhibited Suv39H by Chaetocin (a specific Suv39H inhibitor) followed by oxidative stress and hypoxic/ischemic stress. Male C57BL/6 mice were subjected to permanent ligation of left anterior descending coronary artery (LAD) to induce MI and TAC to induce cardiac hypertrophy.Results:In HEK293 cells, treatment of MTA and Chaetocin augmented SIRT1 transcription and expression. Deleption of Suv39H2 and inhibition of Suv39H activity by Chaetocin restored SIRT1 expression under oxidative stress and hypoxic/ischemic stress. Finally, pretreatment with Chaetocin markedly attenuated MI and cardiac hypertrophy in mice.Conclusion:Oxidative stress and hypoxic/ischemic stress down-regulate SIRT1 expression in heart diseases, leading to cardiac injury. Therefore, targeting Suv39H2 by may protect heart against cardiac injury. |
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