Mechanisms of Defective Efferocytosis in Atherosclerosis

描述（由申请人提供）：动脉粥样硬化性血栓性血管疾病的一个关键事件是亚临床病变转化为破坏斑块，从而引发急性管腔血栓形成。PI的实验室专注于参与危险斑块关键特征的细胞和分子过程，即坏死核心，它有助于炎症、斑块破坏和血栓形成。坏死核心是由晚期病变巨噬细胞的凋亡和凋亡巨噬细胞的吞噬清除缺陷或“efferocytosis”引起的。本研究的目的是阐明在晚期动脉粥样硬化中，巨噬细胞和树突状细胞（dc）这两种主要的单核细胞来源细胞群体中，有缺陷的efferocytosis的机制和后果。目的1将探讨adam17介导的晚期病变巨噬细胞中efferocytosis受体MerTK的裂解导致efferocytosis缺陷和斑块坏死的假设。Subaim 1A将在体外和体内探索一种导致MerTK分裂的新机制，该机制涉及CD36/ toll样受体2/NADPH氧化酶/PKC4途径的动脉粥样硬化相关激活因子。其中一种激活剂是载脂蛋白(a)，它与载脂蛋白ob结合形成脂蛋白(a) [Lp(a)]，并与人类CAD有遗传关系。Subaim 1B将首先研究小鼠和人类动脉粥样硬化中病变的sol-Mer和斑块阶段之间的时间和定量关系，然后使用具有不可切割MerTK的小鼠来测试因果关系，我们预测在病变进展过程中，MerTK将免受有缺陷的efferocysis和斑块坏死的影响。目的2将探讨一种假设，即在动脉粥样硬化中，成熟的dc （mDCs）的富集会导致efferocytosis缺陷和斑块坏死，而这些dc会失去efferocytosis能力。我们已经证明富含mDCs的晚期斑块区域，就像那些富含巨噬细胞的区域一样，位于斑块坏死区域附近，并且比富含巨噬细胞的区域有更严重的efferocytosis。Subaim 2A将通过炎症信号传导促进DC成熟，从而验证DC中MerTK的切割导致细胞凋亡缺陷的假设。Subaim 2B将首先研究人类颈动脉粥样硬化和脂肪喂养的Ldlr-/-和Apoe-/-小鼠斑块中病变DC、efferocytosis和斑块坏死之间的关系，然后通过评估两种抑制DC发育或成熟的基因操作（gm - csf缺乏和DC MyD88缺乏）的效果来测试因果关系。实现上述目标将为了解坏死核心如何形成提供关键信息，并可能有助于设计新的治疗策略，以防止动脉粥样硬化病变的临床进展。

DESCRIPTION (provided by applicant): A key event in atherothrombotic vascular disease is the conversion of subclinical lesions to disrupted plaques that trigger acute lumenal thrombosis. The PI's laboratory is focused on cellular and molecular processes involved in a critical feature of dangerous plaques, the necrotic core, which contributes to inflammation, plaque disruption, and thrombosis. Necrotic cores arise from the apoptosis of advanced lesional macrophages coupled with defective phagocytic clearance, or "efferocytosis," of the apoptotic macrophages. The objective of this proposal is to elucidate mechanisms and consequences of defective efferocytosis in the two major populations of monocyte-derived cells in advanced atherosclerosis, macrophages and dendritic-like cells (DCs). Aim 1 will explore the hypothesis that ADAM17-mediated cleavage of the efferocytosis receptor MerTK in advanced lesional macrophages contributes to defective efferocytosis and plaque necrosis. Subaim 1A will explore in vitro and in vivo a new mechanism that leads to MerTK cleavage involving athero-relevant activators of a CD36/Toll-like receptor 2/NADPH oxidase/PKC4 pathway. One such activator is apolipoprotein(a), which associates with apoB to form lipoprotein(a) [Lp(a)] and is genetically associated with human CAD. Subaim 1B will first investigate the temporal and quantitative relationships between lesional sol-Mer and plaque stage in murine and human atheromata and then will test causation by using a mouse with non-cleavable MerTK, which we predict will be protected from defective efferocytosis and plaque necrosis during lesion progression. Aim 2 will explore the hypothesis that enrichment of atheromata with mature DCs (mDCs), which lose efferocytic capacity, contributes to defective efferocytosis and plaque necrosis. We have shown that areas of advanced plaques enriched in mDCs, like those enriched in macrophages, are located near areas of plaque necrosis and have even worse efferocytosis than macrophage-rich regions. Subaim 2A will test the hypothesis that MerTK cleavage in DCs leads to defective efferocytosis by promoting DC maturation through inflammatory signaling. Subaim 2B will first study the relationships among lesional DCs, efferocytosis, and plaque necrosis in human carotid atheromata and in plaques of fat-fed Ldlr-/- and Apoe-/- mice and will then test causation by assessing the effect of two genetic manipulations that suppress DC development or maturation-GM-CSF deficiency and DC MyD88 deficiency. Achieving the stated objective will provide critical information for understanding how necrotic cores form and may help in the design of new therapeutic strategies to prevent the clinical progression of atherosclerotic lesions.