Abstract 2287: The SIRT1 Activator Resveratrol Suppresses Cardiomyocyte Hypertrophy by Promoting Histone H3 Lys9 Deacetylation and Tri-methylation
[Background] SIRT1 not only directly deacetylates histones but also promotes histone methylation by activating histone H3 lys9 (H3K9) tri-methylase SUV39H1, resulting in epigenetic gene silencing. However, its significance in the heart is not fully understood. Here, we examined whether activation of SIRT1 by resveratrol (RSV) promotes histone deacetylation and methylation in cardiomyocytes and whether the histone modification suppresses cardiomyocyte hypertrophy.
[Methods and Results] Immunoblotting showed that treatment of neonatal rat ventricular myocytes (NRVM) with RSV (100 μM, 12 hrs) reduced the global level of acetyl-H3K9/K14 by 36% (p=0.02). This effect of RSV was abolished by knockdown of SIRT1 by siRNA. Furthermore, RSV significantly increased the level of tri-methyl-H3K9. Immunostaining revealed that H3K9 deacetylation and tri-methylation occurred in cells transfected with wild-type SIRT1 but not in those expressing deacetylase-inactive mutant SIRT1. We next examined whether RSV modifies the expression of key molecules for development of cardiomyocyte hypertrophy, resulting in suppression of agonist-induced hypertrophy. Pretreatment of NRVM with RSV (10 μM, 12 hrs) significantly suppressed the phenylephrine (50 μM, 48 hr)-induced myocyte enlargement and elevation of ANP mRNA level by 45% and 70%, respectively. Interestingly, RSV reduced the protein level of the histone acetyltransferase p300, which has been reported to promote cardiac hypertrophy, to 53% of the control (p=0.02). Knockdown of SIRT1 canceled the RSV-induced p300 repression. Finally, immunostatining showed that acetyl-H3K9/K14 level was markedly higher in the failing myocardium of cardimyopathic TO2 hamsters (TO2, 35 weeks old) than in age-matched controls. Oral administration of RSV (4 g/kg chow) to TO2 starting at 6 weeks of age not only significantly changed the tissue level of acetyl-H3K9/K14 (−42%) and tri-methyl-H3K9 (+52%) but also attenuated the increase in heart weight/body weight and preserved cardiac fraction (LVEF=27.9+/−1.6 vs. 34.4+/−2.2%, p=0.02).
[Conclusion] RSV promotes SIRT1-mediated deacetylation and methylation of H3K9 in cardiomyocytes, which may contribute to suppression of myocyte hypertrophy via downregulation of p300.