ERK5 and CD36 link oxidative stress to platelet dysfunction and ischemic injury

动脉血栓形成的风险，包括心肌梗死(MI)和中风，在系统性心脏病的环境中增加 与慢性炎症相关的疾病状态，包括癌症、糖尿病、动脉粥样硬化和肥胖。 在这些环境和最近的研究中，不适当的血小板激活是血栓形成的驱动机制 提示疾病状态下的血小板激活机制可能与正常健康状态下的不同 条件。剖析这些新的机制是这个多PI提案的中心目标。最近出版的 初步研究表明，众所周知，内源性危险信号是在疾病发生期间产生的 状态，包括氧化低密度脂蛋白、高级糖化蛋白、细胞来源的微粒和 S100A多肽都与特定的血小板受体CD36相互作用，启动细胞内信号，促进 血小板活化和血栓形成。此外，还发现血小板表达MAP激酶ERK5，这是一种已知的 活性氧(ROS)传感器。随后显示，血小板ERK5作为氧化还原开关对 细胞外ROS在缺血条件下促进血小板活化和加强心肌损伤 在心肌梗死期间，发现ERK5在CD36下游被激活，以响应oxLDL介导的ROS 一代。血小板特异性ERK5基因缺失可改善血小板活化和血栓前状态 与高脂血症氧化应激有关。因此，我们假设ERK5在 病理性血小板活化，对CD36和非CD36触发的受体介导的细胞内信号的反应 受体介导的细胞外信号(ROS)在组织缺血中的作用 监管活动。特定目标1将测试CD36信号产生的特定ROS的假设 通过激活ERK5维持血小板处于激活状态。人体体外和小鼠体内研究将 使用遗传模型、饮食诱导的疾病模型和高度特异的CD36配体来识别关键细胞 CD36介导的ERK5激活所必需的膜伙伴以及ROS的下游效应分子 和ERK5；并确定ERK5信号如何与血小板的“经典”途径相结合 激活以促进血栓形成。目的2将验证ERK5调节血小板蛋白表达的假设 通过调节血小板蛋白翻译和/或蛋白泛素化。体外和体内模型将被用于 确定ROS引起的血小板蛋白表达的变化是否依赖于蛋白质 合成、降解或两者兼而有之。AIM 3将确定血小板ERK5在环境中激活的机制 组织缺血和细胞外ROS增加组织和器官功能障碍。遗传学和药理学 将使用心肌梗死和氧化应激的方法和体内模型。通过了解血小板的作用机制 ERK5的激活和下游途径这些研究将为研究“失调”的血小板功能提供洞察力 在病理条件和缺血环境中可能导致新的治疗靶点和更好的 理解为什么目前基于健康条件下的血小板功能的治疗是不充分的。

Risk of arterial thrombosis, including myocardial infarction (MI) and stroke, is increased in the setting of systemic disease states associated with chronic inflammation, including cancer, diabetes, atherosclerosis and obesity. Inappropriate platelet activation is a driving mechanism of thrombosis in these settings and recent studies suggest that mechanisms of platelet activation in diseased states may be different from those in normal healthy conditions. Dissecting these novel mechanisms is the central goal of this multi-PI proposal. Recent published and preliminary studies showed that endogenous danger signals well known to be generated during diseased states, including oxidized low density lipoprotein, advanced glycated proteins, cell-derived microparticles, and S100A peptides all interact with a specific platelet receptor, CD36, to initiate intracellular signals that promote platelet activation and thrombosis. Furthemore platelets were found to express the MAP kinase ERK5, a known sensor of reactive oxygen species (ROS). Platelet ERK5 was then shown to act as a redox switch responsive to extracellular ROS under ischemic conditions, promoting platelet activation and enhancing myocardial damage during MI; and ERK5 was found to be activated downstream of CD36 in response to oxLDL-mediated ROS generation. Platelet specific deletion of ERK5 ameliorated platelet activation and the pro-thrombotic state associated with hyperlipidemic oxidant stress. We thus hypothesize that ERK5 serves as a central “node” in pathologic platelet activation, responding to receptor-mediated intracellular signals triggered by CD36 and non- receptor mediated extracellular signals (ROS) mediated by tissue ischemia, through both its signaling and protein regulation activities. Specific aim 1 will test the hypothesis that specific ROS generated by CD36 signaling maintains platelets in a pro-activated state via activation of ERK5. Human In vitro and mouse in vivo studies will use genetic models, diet-induced disease models, and highly specific CD36 ligands to identify critical cell membrane partners necessary for CD36-mediated ERK5 activation, as well as downstream effectors of ROS and ERK5 in platelets; and to determine how ERK5 signaling integrates with “classic” pathways of platelet activation to promote thrombosis. Aim 2 will test the hypothesis that ERK5 regulates platelet protein expression by modulating platelet protein translation and/or protein ubiquitination. In vitro and in vivo models will be used to determine whether changes in platelet protein expression in response to ROS are dependent on protein synthesis, degradation, or both. Aim 3 will determine mechanisms by which platelet ERK5 activation in the setting of tissue ischemia and extracellular ROS increases tissue and organ dysfunction. Genetic and pharmacologic approaches and in vivo models of MI and oxidant stress will be used. By understanding mechanisms of platelet ERK5 activation and downstream pathways these studies will provide insights into `dysregulated' platelet function in pathologic conditions and ischemic environments that may lead to new therapeutic targets and better understanding of why current therapies based on platelet function in healthy conditions are inadequate.