Abstract 18048: Essential Role of Heart AMP-Activated Protein Kinase to Maintain Mitochondrial Respiration, Decrease Mitochondrial Oxidative Stress and Inhibit Mitochondrial Transition Permeability Pore Opening after Ischemia-Reperfusion
AMP-activated kinase (AMPK) is a stress responsive kinase essential to myocardial recovery following ischemia-reperfusion (IR). Recent studies suggest that AMPK signaling regulates mitochondrial integrity during IR. The aim of this study was to investigate the mechanisms by which AMPK modulates mitochondrial activity during IR. Mitochondria were isolated from wild type (WT) and AMPK kinase dead (KD) mouse hearts and analyzed structurally and functionally after control aerobic perfusion in vitro and after 15 min of global ischemia and 10 min reperfusion. KD hearts had similar LV contractile function during baseline Langendorff perfusion (BL), but poor early recovery after IR (KD vs. WT rate pressure product recovery, 3.8±1.4% vs. 22±4.4%, p<0.05). Mitochondrial ultrastructure by electron microscopy and latent to free citrate synthase activity ratios were similar at BL and after IR in KD vs. WT hearts, indicating intact mitochondrial membrane integrity. Respiratory control ratios were similar across all groups and showed good coupling (approx. 14). Oxygen consumption rates with pyruvate/malate (10mM/2mM) and ADP were 24% lower in KD at BL and decreased significantly after IR (KD vs. WT, BL: 405±23 vs. 528±27, IR: 308±20 vs. 423±19 nmol O2/min/mg protein, p<0.05 vs. WT and vs. BL). Hydrogen peroxide production was similar at BL, but increased by 33% in KD after IR compared to WT (KD vs. WT, BL: 1.1±0.1 vs. 1.1±0.1, IR: 1.6±0.1 vs. 1.2±0.1 nmol H2O2/min/mg mitochondrial protein, p<0.05 vs. WT and vs. BL and factorial). Mitochondria from KD hearts also had increased susceptibility to calcium induced mitochondrial permeability transition pore (mPTP) opening after IR (KD vs. WT Ca2+ retention capacity, 36±2.3 vs. 50.4±5.2 nmol/mg protein, p<0.05). Mitochondrial proteome analysis showed decreased expression of several complex I subunits and of anti-oxidative enzymes, including manganese superoxide dismutase, thioredoxin reductase 2 and catalase in mitochondria from KD hearts. Thus, the AMPK pathway prevents cardiac injury during IR, regulating the expression of mitochondrial electron transport chain components and anti-oxidative enzymes, maintaining oxidative metabolism and preventing mPTP opening and irreversible mitochondrial damage.
- © 2012 by American Heart Association, Inc.