Mechanisms of Myocardial Ischemic Injury in Diabetes

描述（由申请人提供）：本提案的总体目标是阐明高血糖增加心肌缺血和再灌注损伤的机制，目的是降低糖尿病和高血糖患者的心血管发病率和死亡率。一氧化氮受损（NO.）信号传导被认为在糖尿病和高血糖症期间的心血管疾病的发病机制中起关键作用，并且内皮型一氧化氮合酶（eNOS）功能是关键因素。目前的建议将测试的总体假设，即高血糖症损害心脏的心脏保护信号转导机制，通过衰减热休克（HSP）90/eNOS的相互作用，通过涉及活性氧和氮物种和四氢生物蝶呤（BH 4）的途径。在特定目标1中，我们将评估高血糖剂量依赖性地损害eNOS偶联并导致eNOS依赖性NO减少和超氧阴离子（O2.-）增加的假设。通过调节兔体内HSP 90/eNOS伴侣蛋白和BH 4辅因子的可用性以及体外内皮细胞和心肌细胞的可用性。我们将解决的假设，高血糖症诱导的过氧亚硝酸盐（ONOO-）的形成损害HSP 90/eNOS通过减少磷酸酪氨酸-HSP 90和增加硝基酪氨酸-HSP 90;并通过减少BH 4。最后，我们将评估高血糖通过减弱HSP 90/eNOS相互作用和降低体内BH 4的可用性来阻断缺血预处理（IPC）的假设。这些实验将提供新的机制信息HSP 90和高血糖症的作用，通过蛋白质-蛋白质相互作用和改变自由基的形成，使用一个集成的细胞，分子和药理学的方法来调节心脏保护。在具体目标2中，我们将提出以下假设：用磷酸酪氨酸磷酸酶抑制剂增加HSP 90上的磷酸酪氨酸;用外源性BH 4或其代谢前体sepiapterin增加BH 4的可用性;用新型apo A-1模拟物D4-F减少氧化应激将增强HSP 90/eNOS结合;在体外和体内高血糖期间恢复eNOS偶联;并通过HSP 90介导的途径恢复IPC在高血糖存在下产生的心肌梗死保护作用。这些实验将阐明HSP 90在心脏保护过程中的新作用，并将确认治疗糖尿病和高血糖症的潜在新治疗靶点。简单描述：糖尿病患者血糖升高会增加心脏病发作和死亡的风险。这项研究将评估热休克蛋白（HSP）90促进心脏损伤抵抗力的作用;将确定血糖对损害HSP 90作用的不利影响;并将确定潜在的糖尿病新治疗策略。

DESCRIPTION (provided by applicant): The overall objective of this proposal is to elucidate the mechanisms whereby hyperglycemia increases myocardial ischemia and reperfusion injury with the goal of reducing cardiovascular morbidity and mortality in patients with diabetes and hyperglycemia. Impaired nitric oxide (NO.) signaling is believed to play a key role in the pathogenesis of cardiovascular disease during diabetes and hyperglycemia and endothelial nitric oxide synthase (eNOS) function is a critical factor. The current proposal will test the overall hypothesis that hyperglycemia impairs cardioprotective signal transduction mechanisms in the heart by attenuating heat shock (HSP)90/eNOS interactions through a pathway involving reactive oxygen and nitrogen species and tetrahydrobiopterin (BH4). During Specific Aim 1, we will evaluate the hypotheses that hyperglycemia dose-dependently impairs eNOS coupling and results in eNOS-dependent decreases in NO. and increases in superoxide anion (O2.-) by modulation of HSP90/eNOS chaperone and BH4 co-factor availability in rabbits in vivo and in endothelial cells and cardiomyocytes in vitro. We will address the hypotheses that hyperglycemia-induced formation of peroxynitrite (ONOO-) impairs HSP90/eNOS by decreasing phosphotyrosine-HSP90 and increasing nitrotyrosine-HSP90; and by decreasing BH4. Finally, we will evaluate the hypothesis that hyperglycemia blocks ischemic preconditioning (IPC) by attenuating HSP90/eNOS interactions and by decreasing the availability of BH4 in vivo. These experiments will provide novel mechanistic information on the role of HSP90 and hyperglycemia to modulate cardioprotection through protein-protein interactions and altered radical formation using an integrated cellular, molecular and pharmacological approach. During Specific Aim 2, we will address the hypotheses that increasing phosphotyrosine on HSP90 with a phosphotyrosine phosphatase inhibitor; increasing BH4 availability with exogenous BH4 or its metabolic precursor sepiapterin; and decreasing oxidant stress with a novel apo A-1 mimetic D4-F will enhance HSP90 /eNOS association; restore eNOS coupling during hyperglycemia in vitro and in vivo; and restore protection against myocardial infarction produced by IPC in the presence of hyperglycemia through an HSP90-mediated pathway. These experiments will elucidate a novel role for HSP90 during cardioprotection and will confirm potential new therapeutic targets for the treatment of diabetes and hyperglycemia. Lay description: Increases in blood sugar that occur in individuals with diabetes increase the risk of heart attack and death. The proposed research will evaluate the role of heat shock protein (HSP)90 to promote resistance to heart injury; will determine the adverse effects of blood sugar to impair HSP90 effects: and will identify potential new treatment strategies for diabetes.