ApoE and SR-BI as Determinants of HDL and Macrophage Function in Atherogenesis

描述(申请人提供)：高密度脂蛋白胆固醇的抗动脉粥样硬化功能包括调节胆固醇的反向运输，以及抗氧化和抗炎作用。清道夫受体B类L(SR-BI)和载脂蛋白E(ApoE)在高密度脂蛋白代谢和胆固醇逆向转运中都起着重要作用。在小鼠中，SR-BI和apoE(DKO)的联合缺乏会导致血脂异常，其特征是大量富含游离胆固醇(FC)的高密度脂蛋白颗粒，加速闭塞性冠状动脉疾病，以及因心肌梗死而过早死亡。我们的初步研究表明，DKO高密度脂蛋白颗粒可能通过诱导野生型巨噬细胞Fc超载而功能障碍和致动脉粥样硬化。在特定目标(SA)1中，我们将检验DKO高密度脂蛋白胆固醇颗粒是严重功能障碍和致动脉粥样硬化的假说，促进氧化、炎症和异常的反向胆固醇运输。APOE可能通过SR-BI依赖和独立途径介导RCT，这两条途径的缺失可能是DKO小鼠致死性表型的原因之一。巨噬细胞特异性缺失apoE或SR-BI促进动脉粥样硬化。我们的初步研究表明，apoE和SR-BI的巨噬细胞缺陷导致动脉粥样硬化病变中胆固醇稳态显著受损和凋亡细胞显著增加，这与DKO脂质环境无关。这些结果表明，在动脉粥样硬化中，DKO巨噬细胞可能倾向于FC诱导的细胞凋亡和/或对凋亡细胞的吞噬清除功能受损。SA2的目标是验证巨噬细胞载脂蛋白E和SR-BI协同作用以限制动脉粥样硬化形成和细胞凋亡的假设。DKO巨噬细胞的胆固醇稳态异常提示SR-BI和apoE以协同方式发挥作用，以优化巨噬细胞运输和动员胆固醇。在SA3中，体外研究将检验SR-BI相关的胆固醇结构域和信号调节载脂蛋白E分泌的假设。研究还将检验这一假设，即含有高密度脂蛋白的载脂蛋白E是SR-BI动员的胆固醇最有效的受体。最后，我们将检验SR-BI和apoE表达影响ABCA1和Abcg1介导的胆固醇运输和动员的假设。对载脂蛋白E和SR-BI作为高密度脂蛋白和巨噬细胞胆固醇抗动脉粥样硬化功能决定因素的作用的新见解可能会导致动脉粥样硬化的新的治疗方法。

DESCRIPTION (provided by applicant): Anti-atherogenic functions of HDL cholesterol include mediation of reverse cholesterol transport as well as anti-oxidant and anti-inflammatory effects. Scavenger receptor class B type-l (SR-BI) and apolipoprotein E (apoE) both play crucial roles in HDL metabolism and reverse cholesterol transport. Combined deficiency of SR-BI and apoE (DKO) in mice results in dyslipidemia, characterized by large free cholesterol (FC)-enriched HDL particles, accelerated occlusive coronary disease, and premature death due to myocardial infarction. Our preliminary studies show that DKO HDL particles may be dysfunctional and proatherogenic by inducing FC overload in wild type macrophages. In Specific Aim (SA) 1, we will examine the hypothesis that the DKO HDL cholesterol particles are severely dysfunctional and proatherogenic, promoting oxidation, inflammation, and abnormal reverse cholesterol transport. ApoE may mediate RCT through both SR-BI dependent and independent pathways, and the loss of both pathways may contribute to the lethal phenotype in DKO mice. Macrophage-specific deletion of either apoE or SR-BI promotes atherosclerosis. Our preliminary studies indicate that macrophage deficiency of both apoE and SR-BI results in dramatically impaired cholesterol homeostasis and a striking increase in accumulation of apoptotic cells in atherosclerotic lesions, independent of the DKO lipid environment. These results suggest that DKO macrophages may be prone to FC-induced apoptosis and/or impaired phagocytic clearance of apoptotic cells in atherosclerosis. The goal of SA2 is to test the hypothesis that macrophage apoE and SR-BI cooperate to limit atherogenesis and apoptosis. The abnormal cholesterol homeostasis of DKO macrophages suggests that SR-BI and apoE function in a cooperative fashion to optimize macrophage trafficking and mobilization of cholesterol. In SA3, in vitro studies will examine the hypothesis that SR-BI-associated cholesterol domains and signaling modulate apoE secretion. Studies will also test the hypothesis that apoE containing HDL are the most efficient acceptors of SR-BI mobilized cholesterol. Finally, we will examine the hypothesis that SR-BI and apoE expression impact ABCA1- and ABCG1-mediated trafficking and mobilization of cholesterol. New insights into the roles of apoE and SR-BI as determinants of the anti-atherogenic functions of HDL cholesterol and macrophage cholesterol homeostasis and apoptosis may lead to new therapeutic approaches for atherosclerosis.