Chylomicrons and endothelial biology

摘要 动脉粥样硬化的第一步是血管内皮细胞的跨内皮细胞运动和内皮下堆积。 脂蛋白脂质。低密度脂蛋白的内皮细胞转胞作用涉及清道夫受体-BI(SR-BI)两种受体 和激活素样激酶1(ALK1)。我们发现内皮细胞还通过SR-BI和 在溶酶体中处理它们，导致一些脂肪以脂滴的形式储存，并释放出细胞外的小分子 导致巨噬细胞脂质堆积的囊泡(SEV)。虽然许多人认为乳糜龙是 这个概念不会导致动脉粥样硬化，而且太大，无法越过EC屏障，现在已经过时了，因为人们认识到 脂蛋白进入动脉是一个受体介导的过程。这个项目的总体目标是确定 EC乳胶粒摄取如何影响EC生物学，将脂质输送到动脉，并加速动脉粥样硬化。在……里面 目的1，我们建议确定富含甘油三酯的脂蛋白如何影响脂类在血管中的转移 内皮细胞。我们提供的初步数据表明，N-末端apoB18具有单独的配体结合 ALK1和SR-BI的区域。我们将确定脂蛋白大小或载脂蛋白B长度是否决定暴露于 这两个不同的地区。我们还将确定来自乳胶微粒条件的内皮细胞的SEV是如何引起脂质的 巨噬细胞中的蓄积，并确定对照组和对照组释放的SEV之间的差异 乳糜米隆处理的内皮细胞。在目标2中，我们建议进行活体研究，以确定EC-乳胶粒的作用 组织脂质转运中的摄取途径与动脉粥样硬化。我们提供的初步数据表明 在脂蛋白脂肪酶(LPL)缺乏的小鼠体内积累的乳糜粒会增加动脉粥样硬化。我们将使用 转基因小鼠和基因敲除策略，以评估对低密度脂蛋白和乳清蛋白脂的摄取 并将评估LPL和LPL联合缺乏的小鼠是否出现更广泛的动脉粥样硬化 低密度脂蛋白受体是由高乳糜粒微粒血症引起的。最后，我们将确定AAV介导的 在体内过表达apoB18可减少EC对apoB脂蛋白的摄取，并改变动脉粥样硬化。完成 建议的研究有望改变我们对乳糜粒与血管疾病关系的看法，定义 动脉内致动脉脂类积聚的新途径，并阐明了一种可能的预防方法 这些脂类不能进入动脉。

ABSTRACT The first steps in atherosclerosis are the transendothelial movement and subendothelial accumulation of lipoprotein lipid. Endothelial cell (EC) transcytosis of LDL involves two receptors, scavenger receptor-BI (SR-BI) and activin-like kinase 1 (ALK1). We showed that ECs also internalize undigested chylomicrons via SR-BI and process them in lysosomes, leading to storage of some lipid as lipid droplets and the release of small extracellular vesicles (sEVs) that cause lipid accumulation in macrophages. While many have considered chylomicrons as non-atherogenic and too large to cross the EC barrier, this concept is now outdated with the understanding that lipoprotein entry into the artery is a receptor-mediated process. The overall goal of this project is to determine how EC chylomicron uptake affects EC biology, delivers lipids to the artery, and accelerates atherosclerosis. In Aim 1, we propose to determine how triglyceride-rich lipoproteins affect lipid transfer across the vascular endothelium. We provide preliminary data suggesting that N-terminal apoB18 has separate ligand binding regions for ALK1 and SR-BI. We will determine whether lipoprotein size or apoB length determines exposure of these two different regions. We also will determine how sEVs from chylomicron-conditioned ECs cause lipid accumulation in macrophages and determine the differences between sEVs released from control and chylomicron-treated ECs. In Aim 2, we propose in vivo studies to determine the role of the EC-chylomicron uptake pathway in tissue lipid delivery and atherosclerosis. We provide preliminary data suggesting that chylomicrons that accumulate in lipoprotein lipase (LpL) deficient mice increase atherosclerosis. We will use genetically modified mice and knockdown strategies to assess the uptake of LDL and chylomicron lipids into arteries and will assess whether more extensive atherosclerosis in mice with combined deficiency of LpL and the LDL receptor is due to hyperchylomicronemia. Finally, we will determine whether AAV-mediated overexpression of apoB18 reduces EC uptake of apoB lipoproteins in vivo and alters atherosclerosis. Completion of the proposed studies promises to alter our view of the relationship of chylomicrons to vascular disease, define a novel pathway for arterial accumulation of atherogenic lipids, and illustrate a possible approach to prevent these lipids from entering the artery.