Abstract Wed013: The Protective Role of Sirtuin Enzymes in the Development of Cardiac Ischemia in a Rat Model

Introduction: Sirtuins (SIRT) are a family of enzymes that function as NAD+-dependent deacetylases and ribosyltransferases and are implicated in many biological processes. SIRTs 1/6 have been found to directly influence the pathways that regulate cardiac metabolism. SIRT 1 is involved in stress resistance, metabolism, and aging while SIRT 6 is involved in DNA repair, inflammation regulation, and metabolism. Oxidative stress is an effect of cardiac ischemia reperfusion (IR) that contributes towards decreased cardiomyocyte function. Currently, the effects of SIRTs 1/6 in the progression of cardiac ischemia reperfusion is poorly understood. Hypothesis: We hypothesize that SIRTs 1/6 will be downregulated in cardiomyocytes as a result of a IR event. Goals: To reveal patterns in the role of SIRTs 1/6 in rats following IR. Methods: In-vitro: H9C2 cells were cultured and transferred to low glucose media before being placed in a hypoxia chamber with 95% N2/5% CO2 for 1 hour. The cells were removed from the chamber and placed in regular media and incubated for 1 hour before being harvested for protein and mRNA. Cell isolates underwent western blotting and qPCR that probed for expression of SIRTs 1/6. In-vivo: Thoracotomies were performed on Wistar rats and the left anterior descending artery was ligated for 1 hour before reperfusion. The rats were sacrificed 1 hour post reperfusion via excision of the heart and heart tissue was flash frozen. The tissue was processed and underwent western blotting testing for protein expression of SIRTs 1/6. Results: Hypoxia was confirmed in cells via western blotting that probed for Hypoxia Inducing Factor 1 Alpha (HIF1A). The western blotting data demonstrated that H9C2 cells that experienced 1 hour of hypoxia in serum free media had signifficantly decreased protein expression of SIRTs 1/6. The qPCR data showed a decrease in gene expression for SIRTs 1/6 in hypoxic samples. An established rat IR model was utilized and its success was verified via pressure-volume loop data. The western blotting results displayed a significant decrease in protein expression of SIRTs 1/6 in IR samples. Similarly, the qPCR results demonstrated a decrease in gene expression for SIRTs 1/6 in IR samples. Conclusion: SIRTs 1/6 are significantly downregulated 1 hour following an IR event. The decrease in SIRTs 1/6 expressions were apparent in in-vitro and in-vivo experiments. Addressing this deficiency may be a useful way to improve cardiomyocyte recovery following IR.