Mechanism of Myocardial Reperfusion Injury in Diabetes

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DESCRIPTION (provided by applicant): Diabetic patients have a higher risk of mortality following an initial myocardial infarction when compared to nondiabetics and myocardial infarction remains the principal cause of death in patients with diabetes mellitus. The increased risk of mortality associated with myocardial infarction in diabetics is believed to be due in part to an increased size of myocardial infarction. Endothelial nitric oxide synthase (eNOS) derived NO protects against myocardial ischemia-reperfusion (MI-R) injury and eNOS-derived NO is markedly attenuated in persons with type 2 diabetes mellitus. Reductions in eNOS-derived NO may contribute to the enhanced severity of myocardial infarction in diabetics. A paucity of information exists regarding the role of eNOS and NO in the diabetic myocardium in the setting of MI-R injury. Preliminary data indicates that NO donors attenuate MI-R injury in the db/db diabetic mouse. Proposed studies will examine the use of NO donors and cardiac-specific gone therapy with eNOS adenoviruses to protect the diabetic myocardium against MI-R injury. We will also examine MI-R injury in a novel eNOS transgenic/db/db diabetic double mutant mouse model. Furthermore, studies proposed in this grant application will examine the mechanisms responsible for the cardioprotective actions of NO therapy following MI-R in the db/db diabetic mouse The proposed studies will examine the role(s) of both the heme oxygenase and soluble guanylate cyclase signaling pathways in NO-mediated cardioprotection in diabetes. The studies will address a number of downstream signaling components including: carbon monoxide (CO), cyclic guanosine-3', 5'-monophosphate (cGMP), cGMP-dependent protein kinase (PKG), p38 mitogen activated protein kinase (p38 MAPK), andmitochondrial ATP-sensitive K+ channels (mitOKATp) in NO-mediated protection of the diabetic myocardium. The specific aims of the proposed studies are: Specific Aim # 1: To investigate the effects of nitric oxide (NO) therapy in the setting of myocardialischemia-reperfusion injury in the diabetic heart. Specific Aim # 2: To examine the effects of NO therapy on home oxygenase-1 (HO-1) activation and myocardial protection in the setting of myocardial reperfusion injury in the diabetic heart. Specific Aim # 3: To examine the effects of NO therapy on soluble guanylate cyclase (sGC) stimulation and myocardial protection in the setting of myocardial reperfusion injury in the diabetic heart.The proposed studies will provide novel insights regarding the complex pathophysiology of myocardial reperfusion injury in the diabetic myocardium. Studies proposed in this grant will also examine the efficacy of various forms of NO therapy (NO donors and gone therapy) in the setting of MI-R injury in diabetes mellitus. Finally, these studies will provide novel insights into the cellular mechanisms responsible for NO-mediated cardioprotection in diabetes.