Abstract 16840: AMP-Activated Protein Kinase Prevents Myocardial Injury During Ischemia-Reperfusion by Suppressing the c-Jun Terminal Kinase Pathway and Inhibiting Mitochondrial Transition Permeability Pore Opening
AMP-activated kinase (AMPK) is a stress responsive kinase that coordinates energy conservation, activating catabolic pathways and inhibiting fuel storage and protein synthesis. In the heart, functional AMPK is essential to myocardial survival and functional recovery following ischemia-reperfusion. The mechanisms by which intrinsic AMPK activation protects against ischemic injury are not well understood. We investigated the role of AMPK in modulating mitogen activated protein kinase pathway and mitochondrial integrity during ischemia-reperfusion. Hearts from wild type (WT) and kinase dead AMPK (KD) mice were perfused with 7mM glucose, 0.4 mM oleate, 1% BSA and 10µU/mL insulin in vitro and subjected to 15 min of global ischemia and 10 min reperfusion. KD hearts had similar baseline contractile function, but markedly decreased recovery of left ventricular developed pressure (LVDP) after ischemia-reperfusion compared to WT (4.6±1.4 vs. 26.4±5.2% of baseline, n=9 and 11, p<0.05). Mitochondria isolated from non-ischemic KD and WT hearts had similar calcium induced, cyclosporin-A inhibitable mitochondrial permeability transition pore (mPTP) opening (29.3±1.9 vs. 23.2±1.6µM calcium concentration at mPTP opening, n=4 per group). However, following ischemia-reperfusion mPTP opening was triggered by significantly less calcium in KD mitochondria compared to WT (9.0±0.6 vs. 12.6±1.3µM calcium, n=5 and 6, respectively, p<0.05), indicating higher susceptibility of KD mitochondria to mPTP opening. KD hearts had increased phosphorylation of mitogen activated protein kinase kinase 4 (MKK4) and downstream c-Jun terminal kinase (JNK) during early reperfusion compared to WT hearts (p<0.05). Pharmacologic inhibition of JNK during ischemia-reperfusion with SP600125 (10µM) resulted in improved recovery selectively in KD hearts (4.6±1.4 vs. 15.3±6.5%, of baseline, n=4 and 5, respectively, p<0.05), without changes in WT. JNK inhibition also eliminated the increased susceptibility of mitochondria from KD hearts to mPTP opening. In conclusion, intrinsic AMPK activation prevents cardiac injury during ischemia-reperfusion, suppressing activation of signaling through the MKK4-JNK pathway and inhibiting mitochondrial transition pore opening.
- © 2011 by American Heart Association, Inc.