Acid, Succinate and Glyoxal Metabolism in Ischemia

摘要 在美国，每年有70万新的心脏病发作(急性心肌梗死)，30万患者 在心脏手术期间接受预定的缺血。超越组织再灌注(血管成形术、溶栓) 目前还没有FDA批准的干预措施来限制由缺血和再灌注(IR)引起的急性心脏损伤。这 续订提案支持我们正在进行的心脏代谢研究计划，并专注于新的 糖酵解下游的心脏保护性代谢信号事件。它是建立在以下前提下的：(I) IR期间的酸性pH对心脏有保护作用，许多促进糖酵解的疗法部分是通过增强 代谢性酸中毒。(Ii)琥珀酸蓄积是缺血的关键事件，其在再灌流时的氧化 促进了活性氧物种的生成。我们认为酸可以调节琥珀酸动力学(积累， 氧化、运输)。(Iii)糖酵解副产物甲基乙二醛(MGO)会引起糖尿病患者的糖化压力，但 I型糖尿病心脏对IR损伤有强烈的保护作用，而氧化镁抑制线粒体通透性 过渡性(PT)孔是IR损伤的关键事件。一些心脏保护干预措施也会提高MGO。(Iv) 线粒体酶ALKBH7是坏死所必需的。抑制或消融ALKBH7具有心脏保护作用， 而这种保护需要MGO代谢酶GLO-1。基于这些已发表的和初步的 结果，我们的中心假设是糖酵解升高的心脏保护作用是中介的 由pH、琥珀酸和氧化镁组成。这一假设将通过解决3个相关的目标…来检验目标1将 研究琥珀酸在IR损伤中的动态变化及pH的影响。目标2将调查MGO作为一个 急性心脏保护信号，包括识别其在线粒体中的靶点。目标3将研究ALKBH7，确定 其底物，并开发ALKBH7抑制剂作为心脏保护药物。目标将使用既定的 实验系统(成人心肌细胞，灌流心脏，基于LC-MS的代谢组学，体内IR损伤， 和高脂饮食糖尿病模型)和基因工程小鼠，包括ALKBH7-/-，Glo1-/-和hGlo1TG。创新 植根于这样一种想法，即MGO可以发挥急性保护性信号作用，而不是众所周知的 慢性病理效应(即兴奋)。这项工作将增进对缺血性心脏的基本知识 新陈代谢，将发展小分子疗法，并将为其他病理学提供机械性的见解 超越IR。

ABSTRACT In the US there are >700,000 new heart attacks (acute myocardial infarctions) a year, and >300,000 patients undergo scheduled ischemia during cardiac surgery. Beyond tissue reperfusion (angioplasty, thrombolysis) there are no FDA-approved interventions to limit acute cardiac injury due to ischemia and reperfusion (IR). This renewal proposal supports our ongoing research program in cardiac metabolism, and is focused on novel cardioprotective metabolic signaling events downstream of glycolysis. It is built on the following premise: (i) Acidic pH during IR is cardioprotective, and many therapies that boost glycolysis work in-part by enhancing metabolic acidosis. (ii) Succinate accumulation is a key event in ischemia, and its oxidation at reperfusion drives reactive oxygen species generation. We propose acid can regulate succinate dynamics (accumulation, oxidation, transport). (iii) The glycolytic byproduct methylglyoxal (MGO) causes glycative stress in diabetes, but type-I diabetic hearts are acutely protected against IR injury, and MGO inhibits the mitochondrial permeability transition (PT) pore, a key event in IR injury. Some cardioprotective interventions also elevate MGO. (iv) The mitochondrial enzyme ALKBH7 is necessary for necrosis. Inhibition or ablation of ALKBH7 is cardioprotective, and this protection requires the MGO metabolizing enzyme GLO-1. Based on these published and preliminary findings, our central hypothesis is that the cardioprotective effects of elevated glycolysis are mediated by pH, succinate, and MGO. This hypothesis will be tested by addressing 3 related aims… Aim 1 will investigate succinate dynamics in IR injury and the impact of pH. Aim 2 will investigate the role of MGO as an acute cardioprotective signal, including identifying its targets in mitochondria. Aim 3 will study ALKBH7, identify its substrates, and develop ALKBH7 inhibitors as cardioprotective drugs. The aims will use established experimental systems (adult cardiomyocytes, perfused hearts, LC-MS based metabolomics, in-vivo IR injury, and a high-fat diet model of diabetes) and engineered mice including Alkbh7-/-, Glo1-/- and hGlo1TG. Innovation is embedded in the idea that MGO can serve an acute protective signaling role separate from its well-known chronic pathologic effects (i.e. hormesis). This work will advance basic knowledge on ischemic cardiac metabolism, will develop small molecule therapeutics, and will offer mechanistic insights to other pathologies beyond IR.