Macrophage, ABCA1, Inflammation, and Atherosclerosis

描述（由申请方提供）：ATP结合盒转运蛋白A1（ABCA 1）是一种膜蛋白，需要从巨噬细胞中清除过量脂质。最近的数据表明，巨噬细胞ABCA 1表达是抗炎性的，并防止胰岛素抵抗的发展。然而，由于Abca 1在体内几乎所有组织中表达，因此很难确定巨噬细胞Abca 1在炎症、动脉粥样硬化发展和胰岛素抵抗方面的具体作用。为了解决这些知识空白，我们开发了巨噬细胞特异性Abca 1敲除（MSKO）小鼠。我们的目标是使用这些小鼠来确定巨噬细胞特异性Abca 1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，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）激动剂过敏，这似乎与膜游离胆固醇和脂筏的增加有关。在具体目标1中，我们假设来自MSKO小鼠的巨噬细胞具有i，导致TLR和衔接蛋白募集到脂筏中增加，信号传导效率增加，以及促炎状态。 2)TLR 4和接头蛋白在脂筏与非筏膜区域1 TLR 4刺激中的分布。基于初步研究，我们在特定目的2中假设，低密度脂蛋白受体（LDLr）KO背景下MSKO小鼠的动脉粥样硬化病变中CE富集的巨噬细胞相对于LDLrKO小鼠较少，导致动脉粥样硬化程度相似。我们将确定：1）血浆脂蛋白表型，2）来自巨噬细胞的体内反向胆固醇转运，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，和5）对喂食致动脉粥样硬化饮食的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，喂食高脂肪/高蔗糖（HF/HS）饲料的MSKO小鼠体重增加，肝脏脂质含量增加，全身胰岛素抵抗。我们假设HF/HS饮食导致促炎性巨噬细胞减少胰岛素信号传导并增加外周组织和肝脏中的脂肪储存。使用HF/HS饮食喂养的WT和MSKO小鼠，我们将确定血浆脂质/脂蛋白表型、巨噬细胞炎症状态和组织浸润、全身代谢表型以及肝脏和外周组织中的胰岛素信号传导。这些研究的结果将填补巨噬细胞特异性Abca 1在体内表达在慢性炎症性疾病如动脉粥样硬化、胰岛素抵抗和肥胖发病机制中的特定作用的知识空白。 公共卫生相关性：慢性炎症导致肥胖和胰岛素抵抗。在这个提议中，我们试图了解巨噬细胞炎症之间的关系，导致特定的删除膜胆固醇转运蛋白对动脉粥样硬化，肥胖和胰岛素抵抗的发展。

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.