Macrophage, ABCA1, Inflammation, and Atherosclerosis

描述(申请人提供)：三磷酸腺苷结合盒转运体A1(ABCA1)是一种膜蛋白，需要从巨噬细胞中去除多余的脂肪。最近的数据表明，巨噬细胞ABCA1的表达具有抗炎和预防胰岛素抵抗的作用。然而，由于ABCA1在体内几乎所有组织中都有表达，因此很难确定巨噬细胞ABCA1在炎症、动脉粥样硬化发展和胰岛素抵抗中的具体作用。为了解决这些知识上的差距，我们开发了一种巨噬细胞特异性ABCA1基因敲除(MSKO)小鼠。我们的目标是利用这些小鼠来确定巨噬细胞特异性ABCA1表达缺失的机制：1)增加巨噬细胞炎症，2)影响动脉粥样硬化的发展，以及3)增加肥胖和胰岛素抵抗的发展。我们发现MSKO小鼠的巨噬细胞对Toll样受体(TLR)激动剂高度敏感，这似乎与膜上游离胆固醇和脂筏的增加有关。在特定的目标1中，我们假设MSKO小鼠的巨噬细胞有一个I，导致TLR和接头蛋白募集到脂筏中，增加了信号转导效率，并处于促炎状态。2)TLR4及其接头蛋白在脂筏与非脂筏膜区的分布。基于初步研究，我们在特定目标2中假设，与LDLrKO小鼠相比，低密度脂蛋白受体(LDLR)KO背景下的MSKO小鼠的动脉粥样硬化病变中富含CE的巨噬细胞较少，导致类似程度的动脉粥样硬化。我们将确定：1)血浆脂蛋白表型，2)体内巨噬细胞胆固醇的反向转运，3)动脉粥样硬化程度，4)主动脉病变巨噬细胞数量、脂质含量和基因表达，以及5)对饲喂致动脉粥样硬化饲料的MSKO-LDLrKO和LDLrKO小鼠的影响。在具体目标3中，我们的初步数据表明，与WT小鼠相比，高脂肪/高蔗糖(HF/HS)饮食的MSKO小鼠体重增加，肝脏脂肪含量增加，全身胰岛素抵抗。我们假设，HF/HS饮食导致促炎巨噬细胞减少胰岛素信号并增加外周组织和肝脏中的脂肪储存。用HF/HS饲料喂养的WT和MSKO小鼠，测定血脂/脂蛋白表型、巨噬细胞炎症状态和组织内的浸润、全身代谢表型以及肝脏和外周组织的胰岛素信号转导。这些研究的结果将填补在体内巨噬细胞特异性ABCA1表达在动脉粥样硬化、胰岛素抵抗和肥胖等慢性炎症性疾病发病机制中的具体作用的知识空白。 公共卫生相关性：慢性炎症会导致肥胖和胰岛素抵抗。在这个提案中，我们试图了解由于膜胆固醇转运蛋白的特定缺失而导致的巨噬细胞炎症与动脉粥样硬化、肥胖和胰岛素抵抗的发展之间的关系。

DESCRIPTION (provided by applicant): ATP binding cassette transporter A1 (ABCA1) is a membrane protein that is required to remove excess lipid from macrophages. Recent data have suggested that macrophage ABCA1 expression is anti-inflammatory and protects against development of insulin resistance. However, since Abca1 is expressed in nearly all tissues in the body, it is difficult to determine the specific role of macrophage Abca1 with regard to inflammation, atherosclerosis development, and insulin resistance. To address these gaps in knowledge, we have developed a macrophage-specific Abca1 knockout (MSKO) mouse. Our goal is to use these mice to determine the mechanisms by which macrophage-specific deletion of Abca1 expression: 1) increases macrophage inflammation, 2) affects atherosclerosis development, and 3) increases development of obesity and insulin resistance. We have found that macrophages from MSKO mice are hypersensitive to Toll-like receptor (TLR) agonists, which appears related to an increase in membrane free cholesterol and lipid rafts. In Specific aim 1, we hypothesize that macrophages from MSKO mice have an i , resulting in increased TLR and adapter protein recruitment into lipid rafts, increased signaling efficiency, , and a pro-inflammatory state. 2) the distribution of TLR4 and adapter proteins in lipid raft vs. non-raft membrane regions 1 TLR4 stimulation. Based on preliminary studies, we hypothesize in Specific aim 2 that atherosclerotic lesions in MSKO mice in the low density lipoprotein receptor (LDLr) KO background have fewer macrophages that are CE-enriched relative to LDLrKO mice, resulting in a similar degree of atherosclerosis. We will determine: 1) plasma lipoprotein phenotype, 2) in vivo reverse cholesterol transport from macrophages, 3) atherosclerosis extent, 4) aortic lesion macrophage number, lipid content, and gene expression, and 5) effect on MSKO-LDLrKO and LDLrKO mice fed an atherogenic diet. In Specific aim 3, our preliminary data demonstrated that MSKO mice fed a high fat/high sucrose (HF/HS) diet have increased body weight, increased hepatic lipid content, and systemic insulin resistance compared to WT mice. We hypothesize that the HF/HS diet results in pro-inflammatory macrophages that reduce insulin signaling and increase fat storage in peripheral tissues and liver. Using HF/HS diet-fed WT and MSKO mice ' , we will determine plasma lipid/lipoprotein phenotype, macrophage inflammatory state and infiltration into tissues, whole body metabolic phenotype, and insulin signaling in liver and peripheral tissues. Results from these studies will fill gaps in knowledge on the specific role of macrophage-specific Abca1 expression in vivo in the pathogenesis of chronic inflammatory diseases such as atherosclerosis, insulin resistance and obesity. PUBLIC HEALTH RELEVANCE: Chronic inflammation results in obesity and insulin resistance. In this proposal, we seek to understand the relationship between macrophage inflammation that results from the specific deletion of a membrane cholesterol transporter on development of atherosclerosis, obesity and insulin resistance.