Abstract 12715: Administration of Activated Protein C Stabilizes Membrane EPCR and Increases Resistance of Heart to Ischemic Insult in Aging

Abstract

Introduction: Activated protein C (APC) is a circulating protease with anti-coagulant property. Endothelial protein C receptor (EPCR) mediates APC's downstream events. We have revealed that APC exerts cardioprotective effects during ischemia and reperfusion (I/R). Hypothesis: There is an impaired APC signaling in aging and administration of APC restores APC signaling of aged heart to improve cardiac tolerance to ischemic insult caused by I/R stress. Methods: Young C57BL/6J (3-4 months), aged C57BL/6J (24-26 months), and EPCR R84A/R84A (3-4 months, C57BL6/J background) transgenic mice without APC binding affinity were subjected to ischemia (45 min) and reperfusion (24 hrs) by ligation/release of left anterior descending coronary artery. APC, signaling selective APC-2Cys, or anticoagulant selective APC-E170A was injected through jugular vein five-minutes before reperfusion. Results: I/R stress triggers APC signaling in both young and aged hearts, but APC activity was significantly impaired in the aged versus young hearts. Serum EPCR measurement demonstrated that membrane EPCR's shedding into circulation was dramatically promoted during I/R stress. Intriguingly, administration of APC significantly reduced EPCR shedding caused by I/R stress in both young and aged hearts but not EPCR R84A/R84A heart. The echocardiography data showed that APC and APC-2Cys but not APC-E170A ameliorated cardiac dysfunction by I/R insult in both young and aged mice. Interestingly, APC and APC-2Cys restored aged heart's resistance to a comparable level as young heart to ischemic damage. The cardioprotective effects of APC and ACP-2Cys are diminished in EPCR R84A/R84A mice. Furthermore, metabolomics analysis and working perfusion heart results demonstrated that AMP-activated protein kinase (AMPK) signaling mediates acute adaptive metabolic response while protein kinase B (Akt) signaling pathway is involved in chronic metabolic programming in the heart with APCs treatments. Conclusions: I/R stress causes membrane EPCR shedding in the heart and APC's cardioprotection against I/R injury is not related with its anti-coagulant activity. Administration of APC prevents I/R-induced cardiac EPCR shedding that is critical for limiting cardiac damage in aging.