Abstract 11004: Activated Protein C Protects Human Cardiomyocytes Against Hypoxia Reoxygenation Stress-Induced Injury Through Maintaining Mitochondrial Integrity

Abstract

Introduction: Activated protein C (APC) is a vitamin-K-dependent plasma serine protease that functions as a natural anticoagulant to downregulate thrombin generation in the clotting cascade. Endothelial protein C receptor (EPCR) mediates APC's cytoprotective properties. We found that cardiac EPCR expression is downregulated in aging, leading to cardiac intolerance to ischemic insults. However, the role of APC in the human heart under ischemic stress remains unclear. Hypothesis: APC-EPCR axis protects human cardiomyocytes against hypoxia-reoxygenation stress-induced damage through maintaining mitochondrial integrity. Methods: The left ventricles of 38 adult human donor hearts underwent proteomic analysis of myocardial EPCR. Viable human cardiomyocytes were isolated and challenged by 30 min hypoxia/30 min reoxygenation (H/R) with or without APC treatment. Cardiomyocyte contractile properties were determined by IonOptix Imaging System, while the mitochondrial functional integrity and reactive oxygen species (ROS) were determined with Seahorse XF analyzer and MitoSox staining. Results: Immunoblotting data demonstrated that EPCR expression levels are declined in human hearts along with aging. H/R-stress reduced contractile functions of human cardiomyocytes, and the cardiomyocytes from aged adults (>65 years) versus cardiomyocytes from young adults (<65 years) were more vulnerable to H/R-induced insults. Interestingly, the administration of APC significantly improved the contractile functions of both young and aged human cardiomyocytes under H/R stress. APC also stabilizes EPCR levels and modulates the calcium flux homeostasis in both young and aged human cardiomyocytes under H/R. The mitochondrial respiration experimental data demonstrated that APC treatment ameliorates the mitochondrial dysfunction induced by H/R stress in both young and aged human cardiomyocytes. Since the ROS generations in human cardiomyocytes during H/R stress were attenuated with APC administration. Conclusions: Cardiac EPCR levels are downregulated with aging. The administration of APC can rescue the cardiac intolerance to ischemic insults in aging through stabilizing receptor EPCR and maintaining cardiomyocyte mitochondrial integrity.