Dichotomous Role of Endothelial SR-BI in Atherosclerosis

项目摘要/摘要 高密度脂蛋白(HDL)胆固醇丰度和功能的差异可能会影响 高密度脂蛋白对心血管的保护作用。高密度脂蛋白经典地调节胆固醇的反向运输(RCT) 通过包括高密度脂蛋白中载脂蛋白A-I(apoA-I)与清道夫结合的过程进入肝脏 肝细胞B型受体I型(SR-BI)。HDL/SR-BI串联的其他动作也可以是 保护性，如它们激活内皮NO的产生和修复的能力，通过激酶信号转导 唯一需要的是接头蛋白PDZK1。然而，我们惊讶地发现，内皮细胞- 高极低密度脂蛋白/低密度脂蛋白和低高密度脂蛋白的apoE-/-小鼠的特异性SR-BI缺失导致减少 动脉硬化。我们进一步发现，这与将低密度脂蛋白输送给 动脉壁，揭示了动脉粥样硬化形成的关键步骤的机制。因此，可能会有一个 内皮SR-BI在动脉粥样硬化中的作用及其在低高密度脂蛋白环境中的促进作用 在高密度脂蛋白环境下提供动脉粥样硬化保护。这一新颖的概念及其机制 基础将在小鼠和人类内皮细胞中进行询问。目标1是比较 内皮SR-BI在相对低与高高密度脂蛋白的环境中影响动脉粥样硬化。动脉硬化 将通过人类转基因表达上调的内皮SR-BI和高密度脂蛋白进行评估 ApoA-I，并将结果与低高密度脂蛋白的结果进行比较。内皮细胞SR-BI的影响 通过删除内皮细胞PDZK1，也将在低和高高密度脂蛋白水平下评估动脉粥样硬化的信号转导。 目的2确定内皮SR-BI和PDZK1在血管紧张素转换酶可能的动脉粥样硬化保护作用中的作用。 高密度脂蛋白。为了评估高密度脂蛋白在体内的抗炎作用，内皮细胞与白细胞的黏附将 通过活体显微镜以及高密度脂蛋白、SR-BI和PDZK1对内皮基因的调控进行评估 对血管炎症的影响也将被盘问。内皮细胞SR-BI和PDZK1在血管内皮细胞中的作用 RCT将在查询血液和淋巴管内皮细胞过程的模型中确定，并在 包括微血管和动脉。目标3是确定内皮SR-BI是如何控制动脉壁低密度脂蛋白的 证词。将研究培养的内皮细胞对低密度脂蛋白的摄取，表达突变形式的SR-BI 脂质通量、质膜胆固醇运动或C末端的特异性功能丧失 蛋白质相互作用。进一步的培养研究将评估其他低密度脂蛋白受体的可能作用，并共同 低密度脂蛋白和SR-BI在血管内皮细胞中的运输。将在活体模型中评估主动脉低密度脂蛋白的摄取 测试PDZK1的作用，高密度脂蛋白升高的影响，以及是否针对SR-BI的药物干预 可以减少低密度脂蛋白的沉积。通过实现这些目标，我们将阐明血管健康是如何 受内皮SR-BI的影响，这可能是动脉粥样硬化调控的关键交叉点 高密度脂蛋白和低密度脂蛋白。所获得的新知识将有可能确定动脉粥样硬化的新疗法。

Project Summary/ Abstract Differences in both high density lipoprotein (HDL) cholesterol abundance and function likely impact the cardiovascular protective potential of HDL. HDL classically mediates reverse cholesterol transport (RCT) to the liver via processes that include the binding of apolipoprotein A-I (apoA-I) in HDL to scavenger receptor class B, type I (SR-BI) in hepatocytes. Other actions of the HDL/SR-BI tandem may also be protective, such as their capacity to activate endothelial NO production and repair via kinase signaling that uniquely requires the adaptor protein PDZK1. However, we surprisingly discovered that endothelial- specific SR-BI deletion in apoE-/- mice, which have high VLDL/LDL and low HDL, results in decreased atherosclerosis. We have further discovered that this is related to a >80% decline in LDL delivery to the artery wall, revealing the mechanism underlying a critical step in atherogenesis. As such, there may be a dichotomous role for endothelial SR-BI in atherosclerosis, promoting it in the setting of low HDL yet affording atheroprotection in the setting of high HDL. This novel concept and its mechanistic underpinnings will be interrogated in mice and in human endothelial cells. Aim 1 is to compare how endothelial SR-BI influences atherosclerosis in the setting of relatively low vs. high HDL. Atherosclerosis will be evaluated with vs. without endothelial SR-BI and HDL raised via transgenic expression of human apoA-I, and findings will be compared with those made with low HDL. The impact of endothelial SR-BI signaling on atherosclerosis will also be evaluated at low vs. high HDL by deleting endothelial PDZK1. Aim 2 is to determine the roles of endothelial SR-BI and PDZK1 in the putative atheroprotective actions of HDL. To assess HDL's anti-inflammatory actions in vivo, endothelial cell-leukocyte adhesion will be evaluated by intravital microscopy, and HDL, SR-BI and PDZK1 modulation of endothelial genes that influence vascular inflammation will also be interrogated. The roles of endothelial SR-BI and PDZK1 in RCT will be determined in models that query processes in both blood and lymphatic endothelium, and in both microvasculature and arteries. Aim 3 is to determine how endothelial SR-BI governs artery wall LDL deposition. LDL uptake will be studied in cultured endothelium expressing mutant forms of SR-BI with specific loss-of-function for lipid flux, sensing of plasma membrane cholesterol movement, or C-terminal protein interaction. Further studies in culture will evaluate possible roles of other LDL receptors, and co- trafficking of LDL and SR-BI across the endothelium. Aorta LDL uptake will be evaluated in vivo in models testing the role of PDZK1, the impact of elevated HDL, and if pharmacologic intervention targeting SR-BI can decrease LDL deposition. By accomplishing these aims, we will elucidate how vascular health is influenced by endothelial SR-BI, which may be a critical point of intersection of atherosclerosis modulation by HDL and LDL. The new knowledge gained will potentially identify novel therapies for atherosclerosis.