Abstract 1815: Resveratrol, an Activator of Protein Deacetylase SIRT1, Suppresses Oxidative Stress-Induced Cell Death by Upregulating MnSOD Expression through Transactivation of FOXO3a
[Purpose] SIRT1, a class III protein deacetylase, contributes to cell survival under oxidative stress. Although MnSOD plays a crucial role in prevention of oxidant-induced cell death, its expression is reduced in failing hearts, and there are few currently available interventions to upregulate MnSOD in the myocardium. Here, we examined whether and how resveratrol (RSV), an activator of SIRT1, upregulates MnSOD and reduces oxidative stress-induced cell death.
[Methods and Results] First, the effect of RSV on activity of SIRT1 was examined in C2C12 myoblast cells. RSV deacetylated histone H3 Lys 9 and histone H4 Lys 16, both of which are targets of SIRT1, in the presence of a class I and II HDAC inhibitor, trichostatin A. The deacetylation by RSV was completely inhibited by SIRT1-siRNA, confirming that SIRT1 is essential for deacetylation by RSV. Next, we examined the effect of RSV on oxidative stress-induced apoptosis detected by nuclear condensation with Hoechst 33342 staining. Exposure of C2C12 cells to antimycin A (AA), an oxidant stressor, enhanced the dichlorofluorescein (DCF) signal and induced apoptosis. RSV significantly decreased DCF signal and suppressed the apoptosis compared with those in the case of a vehicle (24.9Â ±1.7% vs. 33.3Â ±1.7%, p=0.04). Although inhibition of p53 is known to play a role in cytoprotection by SIRT1, this mechanism is unlikely to operate in our model because AA failed to upregulate p53 mRNA. In contrast, MnSOD protein was increased by 31% after RSV treatment in the presence of AA, and siRNA-mediated knockdown of MnSOD abolished RSV-induced protection, demonstrating that upregulation of MnSOD is indispensable in the protection. Finally, we examined the role of forkhead box O transcription factors (FOXO), a target of SIRT1, in the MnSOD induction under oxidative stress. Chromatin immunoprecipitation assay revealed that the amount of FOXO3a, but not that of FOXO1 or FOXO4, bound in the MnSOD promoter region was significantly increased by AA treatment.
[Conclusion] RSV promotes MnSOD expression under oxidative stress via FOXO3a transactivation in a SIRT1-dependent manner, which affords protection against oxidant-induced cell death. RSV may be applicable for restoration of MnSOD level in failing hearts.