Macrophage, ABCA1, Inflammation, and Atherosclerosis

描述（由申请人提供）：ATP结合盒转运蛋白A1 （ABCA1）是一种清除巨噬细胞中多余脂质的膜蛋白。最近的数据表明，巨噬细胞ABCA1表达具有抗炎作用，可以防止胰岛素抵抗的发生。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。为了解决这些知识空白，我们开发了巨噬细胞特异性Abca1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缺失Abca1表达的机制：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。我们发现来自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Specific aim 1中，我们假设来自MSKO小鼠的巨噬细胞有一个i，导致TLR和适配器蛋白募集到脂筏中增加，信号传导效率增加，以及促炎症状态。2) TLR4和转接头蛋白在脂筏区和非筏膜区的分布。基于初步研究，我们在Specific aim 2中假设，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，相对于LDLrKO小鼠，ce富集的巨噬细胞较少，从而导致相似程度的动脉粥样硬化。我们将确定：1)血浆脂蛋白表型，2)体内巨噬细胞逆向胆固醇转运，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，以及5)喂食致动脉粥样硬化饮食对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）饮食的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饮食导致促炎巨噬细胞减少胰岛素信号并增加外周组织和肝脏的脂肪储存。采用HF/HS饮食喂养WT和MSKO小鼠，我们将检测血浆脂/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胰岛素信号。这些研究的结果将填补巨噬细胞特异性Abca1在体内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。

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.