Abstract P217: Activated Protein C Protects Heart against Ischemia Reperfusion Injury via Activating AMPK Signaling Pathway and Decreasing Inflammatory Response
Activated protein C (APC) was first identified as a natural anticoagulant protein. Recently, it has been found that APC elicits cytoprotective signaling responses and reduces brain infarction during ischemia reperfusion (I/R). There is also some evidence linking the signaling activity of APC to cardiac protection against I/R. We hypothesize that APC protects against myocardial ischemic injury by triggering defensive signaling pathways. To test this hypothesis, FVB/NJ mice were subjected to 20 min regional ischemia via left coronary artery occlusion followed by 3 hours reperfusion. Wild-type APC or the APC 2Cys mutant with only signaling activity were injected via tail vein (200 μg/kg) 5 min before reperfusion. Our data showed that APC or 2Cys reduced myocardial infarction from 30.9±2.9% (saline) to 14.4±2.1% or 18.4±1.7% (both p<0.05), respectively. However, another mutant E170A with only anticoagulant activity did not affect cardiac infarction (27.8%±2.8%, p=NS vs. saline). APC or 2Cys stimulated activation of AMP-activated protein kinase (AMPK) as well as phosphorylation of AMPK downstream acetyl-CoA carboxylase in either intact mouse hearts or cardiomyocytes. Furthermore, APC treatment did not significantly decrease the infarction size caused by ischemia (20 min)/reperfusion (3 h) in AMPKα2 KO hearts (35.1%±4.5% vs. 43.1%±6.4%, APC vs. saline, p=NS). These results suggest that AMPK contributes to the cardioprotection of APC against I/R injury. Langendorff system perfused ex vivo mouse hearts, APC or 2Cys treatment improved the recovery of post ischemic cardiac function (78±7% or 74±8% vs. 51±7% recovery; both p<0.05), which was associated with augmented AMPK signaling and enhanced cardiac glucose uptake by APC or 2Cys. On the other hand, APC or 2Cys attenuated in vivo I/R-induced c-Jun N terminal protein kinase (JNK) signaling pathway, which resulted in less production of pro-inflammatory cytokines, TNFα and IL-6 (all p<0.01 vs. I/R alone). In conclusion, APC protects against myocardial ischemic injury by triggering AMPK signaling pathway to modulate substrates metabolism and by attenuating JNK signaling to decrease inflammation under ischemic stress. APC exerts these protective activities independent of its anticoagulant activity.
This research has received full or partial funding support from the American Heart Association, National Center.