Activated Protein C Protects Against Ischemic Injury By Activating Ampk Signaling And Regulating Substrate Metabolism

Background- Activated Protein C (APC) is a natural anticoagulant protein, with recently discovered anti-inflammatory and anti-apoptotic effects. We recently unveiled that APC can limit cardiac ischemia/reperfusion (I/R) injury and is independent of its anticoagulant activity. Here, we elucidate the signaling pathways by which APC mediates its salutary actions. Methods and Results- FVB/NJ mice were subjected to 20 min ischemia via left coronary artery occlusion followed by 3 hr reperfusion. APC was injected via tail vein (0.2 μg/g) 5 min before reperfusion. Myocardial infarction (MI) was significantly reduced in the APC group (14.4 ± 2.1% vs. 30.9 ± 2.9% saline control, n=4-5 per group, p vs. saline control, p vs. 43±6% control, p =NS), suggesting that AMPK mediates the APC’s cardioprotection against ischemic injury. Moreover, APC attenuated I/R-induced c-Jun N terminal protein kinase (JNK) signaling pathway, and decreased the production of pro-inflammatory cytokines, TNFα and IL-6 (all p vs. I/R alone). However, the inhibition of JNK signaling by APC was abrogated in AMPKα2 KO mice, indicating that AMPK was involved in the regulation of ischemia-induced inflammation. To further address how the APC-AMPK cascade modulates inflammation and metabolism in the ischemic heart, isolated WT hearts (n=4 each group) were subjected to 20 min global ischemia followed by 30 min reperfusion with or without APC treatment in an ex vivo perfused system. The results demonstrated that APC increases cell surface of glucose transporter GLUT4 (2 fold vs. control, p vs. 0.38 ± 0.13 µmol/min/g, p vs. 0.011 ± 0.004 µmol/min/g, p Conclusions- APC protects against myocardial ischemic injury by triggering AMPK signaling pathway, which modulates substrate metabolism and inflammatory response.