AMP-Activated Protein Kinase Activation Preconditions the Heart against Ischemic Injury

Abstract AMP-ACTIVATED PROTEIN KINASE ACTIVATION PRECONDITIONS THE HEART AGAINST ISCHEMIC INJURY. Tracy M. Wright, Agnes S. Kim, Lawrence H. Young. Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT. AMP-activated protein kinase (AMPK) is a well-established regulator of cellular energy status and metabolic function, and is a vital molecule during the acute response to ischemic stress in the heart. However, its role in preconditioning against ischemic injury is still not clearly defined. Using a novel and specific AMPK activator, A-769662, we wanted to determine if pharmacologic, pre-ischemic activation of AMPK is sufficient to protect the heart against subsequent ischemia-reperfusion injury. Using two mouse models of ischemia: 1) the Langendorff perfused heart and 2) in vivo coronary occlusion, we investigated whether A-769662 treatment would activate the AMPK pathway and if pre-ischemic AMPK activation was cardioprotective. In these models, wild type C57BL/6 and transgenic AMPK kinase dead (KD) mice hearts were subjected to ischemia for 25 minutes (perfused heart) or 20 minutes (in vivo), followed by reperfusion. A-769662 or vehicle control was administered in the perfusion buffer (100uM, perfused heart) or by intra-peritoneal injection (6mg/kg, in vivo), prior to ischemia. A-769662 treatment resulted in AMPK activation in the perfused heart and in the intact heart in vivo in the absence of ischemia, and decreased myocardial injury when administered prior to ischemia in both models. These cardioprotective effects were abolished in the AMPK deficient AMPK KD hearts. In the wild type perfused heart, we found evidence that pre-ischemic A-769662 treatment leads to increased end-ischemia adenosine triphosphate (ATP) content, increased end-ischemia phosphorylation of eukaryotic elongation factor 2 (eEF2) at threonine 56, and increased endothelial nitric oxide synthase (eNOS) phosphorylation at serine 1177 residue. These findings show that A-769662 treatment leads to myocardial AMPK activation, and preconditions the heart against ischemia in an AMPK dependent manner, possibly through an AMPK-eEF2 or AMPK-eNOS signaling pathway