巨噬细胞CGI-58在动脉粥样硬化发生发展中的作用与机制研究

Atherosclerosis (AS) underlines coronary heart disease and ischemic stroke, two leading causes of death worldwide. A hallmark of AS plaques is the deposition of lipid-laden macrophage foam cells in the subendothelial space of arteries. It has long been known that both cholesterol esters and triglycerides (TG) are accumulated in human AS lesional macrophages. TG-rich lipoproteins (TRLs) can cause macrophage foam cell formation. Surprisingly, despite these early observations, research focused on macrophage TG deposition and AS is scarce. Comparative Gene Identification-58 (CGI-58) protein is critically implicated in cellular TG breakdown. We have created a macrophage-specific CGI-58 knockout (MacKO) mouse model. CGI-58-deficient macrophages accumulate both TG and cholesterol, are proinflammatory, and show reduced expression of PPARs and their target genes. We also found that atherogenic factors such as lipopolysaccharide (LPS) and oxidized low-density lipoprotein (ox-LDL) downregulate macrophage CGI-58 expression and that inhibition of CGI-58 in RAW264.7 monocytes reduces LC3B-II, a marker of autophagy. Based on these findings, we hypothesize that macrophage CGI-58 inhibits AS risk factors-induced macrophage foam cell formation by activating both Neutral Lipolysis and Acidic Lipolysis (lipophagy, a lipid-specific macroautophagy) of cytosolic lipid droplets to promote fatty acid oxidation and cholesterol efflux mediated by the PPAR-LXR nuclear receptor signaling pathway, thereby preventing AS development and progression. To test this hypothesis, we will cross our MacKO mice with the low-density lipoprotein receptor (LDLR) knockout mice (an reliable AS model). We will then define how macrophage CGI-58 deficiency influences AS development and progression in this novel animal model by using a series of molecular, cell biology, histology and in vivo approaches. Elevated blood TG has now been accepted as an important biomarker of atherosclerotic cardiovascular disease. The outcomes of these studies will establish macrophage CGI-58 as a novel regulator of AS, a process that underlines major health problems.

血TG升高已被认为是动脉粥样硬化（AS）心血管疾病的重要生物标志物。AS以动脉内皮下聚集富含胆固醇酯和甘油三酯(TG)的泡沫细胞为主要特征。目前对巨噬细胞TG沉积与AS形成关系的研究极少。CGI-58在细胞TG分解中起重要作用。我们发现CGI-58敲除的巨噬细胞出现脂质蓄积和炎症反应，细胞核受体PPAR活性下调；AS因子抑制巨噬细胞CGI-58表达； 抑制CGI-58表达降低自噬标志物LC3B-Ⅱ的水平。因此，推测巨噬细胞CGI-58通过激活中性脂肪水解和脂质特异性巨自噬（Lipophagy），增加PPAR活性，抑制AS危险因素所致的泡沫细胞形成并缓解AS的发生和发展。我们将在LDLR敲除小鼠上特异性敲除巨噬细胞CGI-58，从分子、细胞、组织和整体水平探讨CGI-58在AS发生和发展中的作用及机制，发现CGI-58调控脂肪水解的新机制，为AS防治提供新思路。

心、脑血管疾病的病理基础是以慢性、进行性动脉粥样斑块形成和血管狭窄为主要特征的动脉粥样硬化(Atherosclerosis，AS)。动脉血管内皮下积聚的巨噬细胞大量蓄积脂滴，形成泡沫细胞，是 AS 斑块形成的重要原因。血TG升高已被认为是动脉粥样硬化心血管疾病的重要生物标志物。AS以动脉内皮下聚集富含胆固醇酯和甘油三酯(TG)的泡沫细胞为主要特征。CGI-58在细胞TG分解中起重要作用。我们发现CGI-58敲除的巨噬细胞出现脂质蓄积和炎症反应，细胞核受体PPAR活性下调；AS因子抑制巨噬细胞CGI-58表达； 抑制CGI-58表达降低自噬标志物LC3B-Ⅱ的水平。因此，本课题主要研究巨噬细胞CGI58和动脉粥样硬化的关系。为了阐明其中机制，我们分别以LDLR 和APOE两种小鼠为背景，构建了LDLR/APOE为背景的巨噬细胞CGI58三敲小鼠模型，即LDLR/Mac-CGI-58KO和APOE/Mac-CGI-58KO，从分子/细胞及整体水平分析巨噬细胞CGI58和动脉粥样硬化的关系。通过本基金支持，先后培养博士研究生3名，硕士研究生2名，发表文章5篇。