Abstract 3892: A Small Molecule Activator of AMP-Activated Protein Kinase Protects the Heart against Ischemia-Reperfusion Injury
AMP-activated protein kinase (AMPK) plays a pivotal role in the ischemic stress response. Impaired AMPK activation during ischemia and reperfusion (I/R) increases injury in transgenic mouse hearts expressing a kinase dead catalytic subunit. We examined whether pharmacologic treatment with a small molecule specific AMPK activator, A-769662, protects the heart against I/R injury. C57BL/6 hearts were perfused in Langendorff mode with Krebs-Henseleit buffer containing 7 mM glucose, 0.4 mM oleate, and 10 μU/ml insulin and atrial-paced at 450 bpm. Hearts were perfused with or without A-769662 (100 μM) for 30 minutes (n=5/group) prior to no-flow ischemia for 25 minutes. All hearts were reperfused without A-769662 for 30 minutes. A-769662 activated the AMPK pathway in the pre-ischemic period, as evidenced by a 1.8-fold increase in the phosphorylation of downstream acetyl-CoA carboxylase (p=0.03 vs. vehicle control). A-769662 did not affect pre-ischemic LV developed pressure (92 +/−10 vs. 98 +/−15 mmHg; p=ns vs. control) or LV dP/dt. During post-ischemic reperfusion, hearts pre-treated with A-769662 had better functional recovery compared to hearts pre-treated with vehicle control (58 +/−7% vs. 11 +/−2% of baseline rate-pressure product; p=0.001). There was also a reduction in infarct size, measured by TTC staining, in A-769662 vs. control hearts (26 +/−6% vs. 48 +/−4% infarct volume/volume at risk (IV/VAR); p=0.025), accompanied by a 64% reduction in cardiac CK release (p<0.05 vs. control). To determine whether A-769662 also has a cardioprotective effect in the intact animal, C57BL/6 mice were subjected to in vivo regional ischemia by left coronary artery occlusion for 20 minutes followed by 4 hours of reperfusion. Mice were pre-treated with either A-769662 (6 mg/kg, IP) or vehicle (n=4/group) 30 minutes prior to the induction of ischemia. The A-769662 treated mice had a 58% reduction in infarct size (by dual blue dye and TTC staining) compared to control mice (18 +/−3% vs. 43 +/−9% IV/VAR; p=0.04).
CONCLUSION: Pharmacologic stimulation of AMPK using a small molecule activator prior to ischemia reduced I/R damage in both the isolated heart and in vivo. These data indicate that AMPK is a therapeutic target to protect against cardiac I/R injury.