Abstract 10639: 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<0.05). APC augmented the activation of AMP-activated protein kinase (AMPK) in ischemic hearts (1.5 fold vs. saline control, p<0.05). In mouse hearts with AMPKα2 deletion, APC has less discernable protective effect against myocardial infarction (35±4% 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<0.05 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<0.05), with the augmentation of glucose uptake in the ischemic heart when compared to the control group (0.58 ± 0.1 vs. 0.38 ± 0.13 µmol/min/g, p<0.05). However, the fatty acid oxidation during reperfusion was inhibited by APC (0.007 ± 0.0003 vs. 0.011 ± 0.004 µmol/min/g, p<0.05).
Conclusions- APC protects against myocardial ischemic injury by triggering AMPK signaling pathway, which modulates substrate metabolism and inflammatory response.
- © 2011 by American Heart Association, Inc.