Abstract 18366: Disruption of Histone Deacetylase 4 Sumoylation Promotes Hypoxia-Induced Injury in Cardiomyocytes

Abstract

Background: Histone deacetylase (HDAC) inhibition has been shown to play an important role in eliciting cardioprotection. However, molecular mechanism(s) of HDAC modification that mediate the survival of myocytes remains unknown. Objectives: The goal of this study is to test whether disruption of HDAC4 sumoylation abolishes HDAC inhibitor-induced protective effects in H9c2 cardiomyocytes exposed to hypoxia/reoxygenation, and whether HDAC inhibitor leads HDAC4 sumoylation, which cause subsequent HDAC4 ubiquitination. Methods: Rat H9c2 cardiomyocytes were cultured and then subjected to hypoxia for 48 hours followed by 2 hours of re-oxygenation. Cardiomyocytes were preconditioned with trichostatin A, a selective HDAC inhibitor that blocks HDAC activity. To further examine the function of HDAC4 sumyolation in the regulation of HDAC inhibition-induced protective effects, stable cardiomyocyte lines expressing wild type HDAC4 and dead HDAC4 sumoylation (HDAC4K559R) were established, respectively. Cell cytotoxicities were estimated by the measurement of lactate dehydrogenase (LDH) leakages. The cell viabilities were assessed by MTT assay. Western blot and immunoprecipitation were employed to detect HDAC4 protein sumoylation following HDAC inhibition. Results: Inhibition of HDAC increased the resistance of cardiomyocytes against hypoxia-reoxygenation, as indicated by the reduction in LDH leakage and the increase in cell viabilities. As compared with wild type HDAC4 over-expressing of cardiomyocytes, disruption of HDAC4 sumoylation at lysine 559 increases the susceptibility of cardiomyocytes to hypoxia-reoxygenation injury. Western blot and co-immunoprecipitation assay demonstrated that HDAC inhibition-mediated HDAC4 sumoylation was associated with ubiquitination of HDAC4. Conclusion: Our study demonstrated that HDAC inhibition produces protective effects in cardiomyocytes, which is modulated by specific HDAC4 sumoylation.