Mechanisms and Consequences of Stress-Induced Macrophage Death in Atherosclerosis

描述（由申请人提供）：动脉粥样硬化性血管疾病是大多数人群的主要死亡原因。只有少数动脉粥样硬化病变实际上会引起临床疾病，而这些病变的一个关键区别特征是斑块坏死。该提案的总体目标是深入了解斑块坏死中涉及的信号通路，最终目标是为高风险个体开发新的治疗措施。我们和其他人以前的工作提供了证据表明，斑块坏死和炎症是由晚期病变中的白细胞/巨噬细胞（Mf）凋亡促进的，其主要原因是暴露于内质网（ER）应激和活性氧/氮物质。然而，在我们对触发这些应激途径的机制以及它们如何导致细胞凋亡的理解方面存在重大差距。基于PI实验室的新数据，该提案将通过关注参与Mf凋亡的新的上游和下游信号通路来解决这些差距。我们推测，氧化应激来源于线粒体，称为“mitoOS”，发挥了关键的上游作用，一种新的Bax/Bak-caspase 8（caspase 8）途径发挥了重要的下游作用，在先进的病变MF凋亡和斑块坏死。在目的1中，我们将阐明mitoOS如何诱导ER应激凋亡效应子CHOP;评估除了CHOP之外，mitoOS通路是否促进Mf凋亡;并探索mitoOS、Drp 1和线粒体Ca 2+摄取的2种诱导剂的作用。最重要的是，我们将研究脂肪喂养的Ldlr-/-小鼠，其中（a）Mfs表达靶向过氧化氢酶，其抑制线粒体OS和凋亡;和（B）Mfs中不存在Drp 1，其阻断线粒体分裂、线粒体OS和凋亡。在目标2中，我们将探索新的Bax/Bak-Casp 8凋亡途径的机制，并研究与目标1中的mitoOS-CHOP途径的联系。然后，我们将按照与目标1相同的总体策略，使用两种独特的模型来测试晚期动脉粥样硬化中的因果关系：Mfs缺乏Bax/巴克的小鼠和表达一种特异性阻断其在细胞凋亡中的作用的Casp 8形式的小鼠。我们还将探讨act-casp 8在晚期人类动脉粥样硬化中的存在。这些联合研究将显著增加我们对临床危险的动脉粥样硬化斑块如何形成以及如何治疗抑制该过程的知识。相关性总结：冠状动脉疾病是大多数人群的主要杀手。目前的治疗集中在减少风险因素。直接针对病变进展的补充方法在减少心脏病方面可能非常有价值。该提案的重点是已知促进动脉粥样硬化进展的特定过程，并且根据本文获得的知识，这些过程可能成为优秀的药物靶点。

DESCRIPTION (provided by applicant): Atherosclerotic vascular disease is the leading cause of death in most populations. Only a minority of atherosclerotic lesions actually cause clinical disease, and a key, distinguishing feature of those that do is plaque necrosis. The overall objective of this proposal is to gain in-depth understanding of the signaling pathways involved in plaque necrosis, with the ultimate goal of developing novel therapeutic measures for high-risk individuals. Our and others' previous work has provided evidence that plaque necrosis and inflammation are promoted by leukocyte/macrophage (Mf) apoptosis in advanced lesions, a major cause of which is exposure to endoplasmic reticulum (ER) stress and reactive oxygen/nitrogen species. However, there are critical gaps in our understanding of the mechanisms that trigger these stress pathways and how they lead to apoptosis. Based on new data in the PI's lab, the proposal will address these gaps by focusing on new upstream and downstream signaling pathways involved in Mf apoptosis. We hypothesize that oxidative stress originating from the mitochondria, referred to as "mitoOS," plays a key upstream role and that a novel Bax/Bak-caspase 8 (casp8) pathway plays a major downstream role in advanced lesional Mf apoptosis and plaque necrosis. In Aim 1, we will elucidate how mitoOS induces the ER- stress apoptosis effector CHOP; evaluate whether mitoOS pathways in addition to CHOP promote Mf apoptosis; and explore the role of 2 inducers of mitoOS, Drp1 and mitochondrial Ca2+ uptake. Most importantly, we will study fat-fed Ldlr-/- mice in which (a) Mfs express mitochondria-targeted catalase, which suppresses mitoOS and apoptosis; and (b) Drp1 is absent in Mfs, which blocks mitochondrial fission, mitoOS, and apoptosis. In Aim 2, we will explore the mechanism of the new Bax/Bak-casp8 apoptosis pathway and investigate links to the mitoOS-CHOP pathway in Aim 1. We will then test causation in advanced atherosclerosis, following the same overall strategy as in Aim 1, using two unique models: mice whose Mfs lack Bax/Bak and mice expressing a form of casp8 that specifically blocks its role in apoptosis. We will also explore the presence of act-casp8 in advanced human atheromata. These combined studies will add significantly to our knowledge of how clinically dangerous atherosclerotic plaques form and how the process may be therapeutically suppressed. Summary of Relevance: Coronary artery disease is the leading killer in most populations. Current therapies are focused on risk factor reduction. A complementary approach directly targeting lesion progression could be extremely valuable in decreasing heart disease. This proposal is focused on specific processes that are known to promote atherosclerosis progression and which, with knowledge gained herein, could be excellent drug targets.