Hypothermia in Cardiac Arrest: Akt Preservation of Mitochondrial Integrity

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DESCRIPTION (provided by applicant): Project Summary/Abstract Studies and physician-scientist training are proposed to model in vitro and in vivo mechanisms of lethal cardiac reperfusion injury following cardiac arrest resuscitation and therapeutic hypothermia (TH) cardiac protection against this injury. Recent work by the applicant involving mouse cardiac arrest and mouse cardiomyocyte models of ischemia/reperfusion (IR) injury suggests that rapid, early cooling within minutes of resuscitation protects against mitochondrial oxidant injury and preserves contractile function. TH cardioprotection in both these complementary models is associated with Akt1 activation. Finally, cardiomyocytes appear to adapt to oxidant stress within minutes by localization of Akt to the mitochondrial subcellular fraction. The central hypothesis of this proposal is that TH cardioprotection following cardiac arrest is the result of Akt activation and localization to the mitochondria with subsequent inhibition of GSK-32 and activation of hexokinase II. The proposed aims and candidate career development plan will help determine whether: Aim #1) Akt1 activation during cardimyocyte I/R is necessary for TH protection of mitochondrial integrity and is associated with Akt subcellular localization, GSK-32 inhibition and hexokinase II activation; that Aim #2) Overexpression of nuclear versus mitochondrial targeted Akt1 will enhance or replicate TH cardioprotection; and Aim #3) Akt1 phosphorylation and subcellular signaling changes seen in Aims #1 and #2 will also be required for TH cardioprotection in a mouse model of cardiac arrest. The proposed work is a natural progression of Dr Sharp's prior background in cardiac cell biology and training in emergency medicine, and will equip him with several new tools for mitochondrial functional and oxidant stress measures, confocal imaging, targeted transfection strategies, and in vivo as well as in vitro approaches to studies of myocardial I/R injury. The plan will ensure a successful transition from junior faculty to tenure track with independent funding. This proposal addresses a major public health problem that constitutes a leading cause of death in the United States, affecting an estimated 335,000 individuals every year. Rates of cardiac arrest are disproportionately high among African Americans and are rising among young women. Although promising, the effective and rapid implementation of TH during cardiopulmonary resuscitation (CPR) particularly in the out of hospital setting is technically challenging. Understanding the Akt-mediated pathways that improve cardiovascular function and survival with TH could lead to the development of pharmacologic adjuncts that replicate or enhance the protective effects of TH.