Macrophage-Lipoprotein Interactions

与细胞外基质紧密交联的脂蛋白聚集体是脂蛋白的主要类型。 脂蛋白在动脉粥样硬化病变中的作用。这些聚集体中的大多数胆固醇是未酯化的，但它 一直不清楚胆固醇酯在保留和聚集的细胞外低密度脂蛋白的核心， 水解-特别是因为已经报道涉及溶酶体水解酶。我们最近的研究 证明了胆固醇酯在保留和聚集的核心水解的新机制， LDL，其中巨噬细胞（M β）产生紧密密封的隔室，包围聚集的LDL的一部分， 低密度脂蛋白然后它们酸化这些隔室并向其中分泌溶酶体酶， 突触已经表明，在一种酶促反应中，溶酶体酸性脂肪酶对胆固醇酯的细胞外水解是一种酶促反应。 一种称为消化性外食的过程，导致细胞外产生未酯化的胆固醇， 这种胆固醇转运到细胞中导致泡沫细胞形成。体内高浓度的胆固醇 在初步研究中观察到聚集的LDL导致细胞外胆固醇的形成 晶体，这可能会导致炎症反应的M。这一提议的首要假设是， 这种降解脂蛋白的机制与常规的吞噬细胞相比具有显著的不同 或内吞机制，并且这些差异在肿瘤的病理生理学中具有重要的后果。 动脉粥样硬化此外，了解这一过程可能会导致改善治疗干预。 第一个目标的工作将描述消化外食的分子机制。这将 包括对溶酶体胞吐所需的Rab和SNARE蛋白的研究。通过Tlr 4的信号传导， Myd 88、PI 3-激酶、Akt、Syk、Vav、Cdc 42和其他分子已被证明对消化系统的重要性。 外食，和额外的信号分子的作用将被探讨。 高浓度的胆固醇在聚集的LDL中产生，并且在Aim 2形成中， 将检查胆固醇晶体和由此产生的炎症性激活的M β。 第三个目标的工作将使用光学成像和三维电子显微镜（FIB-SEM）来检查 小鼠动脉粥样硬化模型中溶酶体突触的3D结构。溶酶体突触的形成， 胆固醇晶体与保留和聚集的LDL的结合，以及炎症激活将是一个重要的因素。 通过光学显微镜在各种动脉粥样硬化小鼠模型中进行研究。 更好地理解动脉粥样硬化病变中发生的细胞和分子事件可以导致 更好的风险评估和潜在的新疗法。

Aggregates of lipoproteins that are tightly crosslinked to the extracellular matrix are the major type of lipoprotein in atherosclerotic lesions. The majority of the cholesterol in these aggregates is unesterified, but it has been unclear how the cholesteryl esters in the core of retained and aggregated extracellular LDL are hydrolyzed – especially because a lysosomal hydrolase has been reported to be involved. Our recent studies demonstrate a novel mechanism for the hydrolysis of cholesteryl esters in the core of retained and aggregated LDL in which macrophages (M) create tightly sealed compartments that surround portions of the aggregated LDL. They then acidify these compartments and secrete lysosomal enzymes into them, creating a lysosomal synapse. It has been shown that the extracellular hydrolysis of cholesteryl esters by lysosomal acid lipase, in a process called digestive exophagy, leads to production of unesterified cholesterol outside the cell, and transport of this cholesterol into the cell leads to foam cell formation. The high concentrations of cholesterol in the aggregated LDL were observed in a preliminary study to lead to the formation of extracellular cholesterol crystals, which can cause inflammatory responses in M . The overarching hypothesis of this proposal is that this mechanism for degrading lipoproteins has significant differences as compared to conventional phagocytic or endocytic mechanisms and that these differences have important consequences in the pathophysiology of atherosclerosis. Furthermore, understanding this process may lead to improved therapeutic interventions. Work in the first aim will characterize the molecular mechanisms of digestive exophagy. This will include a study of the Rab and SNARE proteins that are required for lysosomal exocytosis. Signaling by Tlr4, Myd88, PI3-kinase, Akt, Syk, Vav, Cdc42, and other molecules has been shown to be important for digestive exophagy, and the roles of additional signaling molecules will be explored. High concentrations of cholesterol are generated in aggregated LDL, and in Aim 2 formation of cholesterol crystals and resulting inflammatory activation of M will be examined. Work in the third aim will use optical imaging and 3-D electron microscopy (FIB-SEM) to examine the 3D structures of lysosomal synapses in a mouse atherosclerosis model. Formation of lysosomal synapses, association of cholesterol crystals with retained and aggregated LDL, and inflammatory activation will be studied in various mouse models of atherosclerosis by optical microscopy. Better understanding of the cellular and molecular events occurring in atherosclerotic lesions can lead to better risk assessments and potentially new therapies.