Abstract 15983: Increased Mitochondrial Reactive Oxygen Species Lead to Deleterious JNK Signaling and Ischemia-Reperfusion Injury in AMPK-Inactivated Hearts
AMP-activated kinase (AMPK) is a key stress responsive kinase that regulates cellular adaptation to metabolic stress. Inactivation of AMPK in “kinase-dead” (KD) mice increases myocardial damage following ischemia-reperfusion (IR). We have also shown decreased mitochondrial respiration and increased mitochondrial reactive oxygen species (ROS) production and susceptibility to mitochondrial transition pore opening in KD hearts following IR. The aim of this study was to establish the importance of mitochondrial ROS production and downstream deleterious signaling to mediate tissue damage in absence of active AMPK in the heart. Detoxification of mitochondrial ROS requires conversion of hydrogen peroxide to water, therefore, we studied the effect of transgenic expression of mitochondrial catalase (MCAT) in wild type (WT) and KD mice. MCAT prevents mitochondrial hydrogen peroxide production independent of mitochondrial energy production. Myocardial necrosis was assessed in vitro after global ischemia-reperfusion and in vivo after LAD ligation and reperfusion. Mitogen activated protein kinase kinase 4 (MKK4) and downstream c-Jun terminal kinase (JNK) expression and phosphorylation was assessed in vivo. Increased necrosis in KD hearts following mild global ischemia (15 minutes) - reperfusion (10 minutes) in vitro, was prevented by expression of MCAT (WT vs. KD 17.8±4.1 vs. 50±4.1%, p<0.05 and MCAT-WT vs. MCAT-KD 16.9±4.8 vs. 29.3±4.4%, n.s., and factorial p<0.05). Total JNK protein was not increased in WT and KD hearts with or without expression of MCAT. After coronary occlusion in vivo, KD mice showed increased cardiac activation of MKK4/JNK pathway (p<0.05) as well as greater myocardial necrosis (p<0.05). MCAT expression prevented the excessive cardiac JNK activation observed during IR in KD mice in vivo. Inhibition of JNK with SP600125 (10μM) during in vivo IR also resulted in a significant decrease in necrosis in KD hearts (WT vs. KD 9.1±0.7 vs. 28.2±2.9%, p<0.05 and WT vs. KD with SP600125 8.5±0.5 vs. 10.2±1.1%, n.s. and factorial p<0.05, percentage of equivalent area at risk). Thus, AMPK activation during IR prevents excess mitochondrial reactive oxygen production and consequent JNK signaling, thus protecting against myocardial injury.
Author Disclosures: V.G. Zaha: None. D. Qi: None. H. Lee: None. X. Hu: None. X. Wu: None. G.I. Shulman: None. P.S. Rabinovitch: None. L.H. Young: None.
- © 2014 by American Heart Association, Inc.