Role of Endothelial and Macrophage ApoER2 in Atherosclerosis Modulation

项目总结/摘要： 全基因组关联分析已将LRP 8基因的变体联系起来，包括R952 Q LRP 8 变异，与过早动脉粥样硬化和急性心肌梗死在人类，表明其 编码的蛋白质apoE受体-2（apoER 2）对心血管健康和疾病具有重大影响。如何 apoER 2对心血管生物学的影响是完全未知的。我们最近发现apoER 2 LDL受体缺失小鼠动脉粥样硬化形成明显加速， 而不影响血浆脂蛋白代谢。这个多PI项目的总体目标是 确定内皮细胞和巨噬细胞中的apoER 2如何有助于心血管保护。这将 由两个目前正在合作的实验室完成，在研究 脂蛋白、脂蛋白受体和血管生物学。我们最近的细胞培养工作表明， 通过apoER 2，载脂蛋白E3（apoE 3）激活内皮NO合酶（eNOS）， 促进内皮细胞迁移，并且还减弱内皮细胞-单核细胞粘附。与此相反， apoER 2-R952 Q对野生型受体激活eNOS具有显性负性作用。已经进一步 发现Lrp 8-/-小鼠的再内皮化受损。在Aim 1中，apoER 2胞质结构域突变体 不能与衔接蛋白相互作用和候选衔接蛋白敲低将被用于 确定内皮中apoER 2作用的生化基础。apoER 2-R952 Q的基础 功能障碍也将被识别，并且通过apoER 2-R952 Q- 将尝试用NO供体表达内皮细胞。使用最近创建的floxed Lrp 8小鼠， 内皮apoER 2对内皮细胞-白细胞粘附的调节也将在体内通过活体内研究。 显微镜初步研究还表明，在巨噬细胞中，apoER 2缺乏导致 过度oxLDL诱导的中性脂质蓄积和细胞死亡/凋亡。缺乏apoER 2 巨噬细胞还导致PPAR <$和PPAR <$-应答基因表达的增加。重点是 PPAR γ介导的过程，在Aim 2中，apoER 2调节细胞内信号传导的机制 在巨噬细胞中，从而支配它们的功能和命运将被辨别。在目标3中，将进行研究 使用Lrp 8 floxed小鼠或在LDL受体无效背景下的骨髓重建来确定 内皮细胞与巨噬细胞apoER 2对动脉粥样硬化进展的保护作用 和斑块坏死。计划中的研究将提供关键的新的理解的基础上， apoER 2及其主要配体apoE影响心血管健康。获得的新信息有望 以在大量个体中对抗心血管疾病 LRP 8变异体（~1%）和/或apoE多态性（~15%）。普通民众也可受益于 开发新的疗法，利用这些过程来优化心血管保护。

PROJECT SUMMARY/ABSTRACT: Genome-wide association analyses have linked variants of the LRP8 gene, including the R952Q LRP8 variant, with premature atherosclerosis and acute myocardial infarction in humans, indicating that its encoded protein apoE receptor-2 (apoER2) has a major impact on cardiovascular health and disease. How apoER2 influences cardiovascular biology is entirely unknown. We recently discovered that apoER2 deletion in LDL receptor-null mice causes marked acceleration of atherogenesis and promotes lesion necrosis without influencing plasma lipoprotein metabolism. The overall goal of this multiple-PI project is to determine how apoER2 in endothelium and macrophages contributes to cardiovascular protection. This will be accomplished by two currently collaborating laboratories with complementary expertise in the study of lipoproteins, lipoprotein receptors and vascular biology. Our recent cell culture work has revealed that through apoER2, apolipoprotein E3 (apoE3) activates endothelial NO synthase (eNOS) and thereby promotes endothelial cell migration, and also blunts endothelial cell-monocyte adhesion. In contrast, apoER2-R952Q has dominant-negative effect on eNOS activation by wild-type receptor. It has further been found that Lrp8-/- mice have impaired reendothelialization. In Aim 1, an apoER2 cytoplasmic domain mutant incapable of adaptor protein interaction and candidate adaptor protein knockdown will be employed to determine the biochemical basis for apoER2 action in endothelium. The underpinnings of apoER2-R952Q dysfunction will also be discerned, and the rescue of cardioprotective behaviors by apoER2-R952Q- expressing endothelial cells will be attempted with NO donor. Using a recently-created floxed Lrp8 mouse, endothelial apoER2 regulation of endothelial cell-leukocyte adhesion will also be studied in vivo by intravital microscopy. Preliminary work has additionally shown that in macrophages apoER2 deficiency causes exaggerated oxLDL-induced neutral lipid accumulation and cell death/apoptosis. Lack of apoER2 in macrophages also results in increases in PPAR¿ and PPAR¿-responsive gene expression. With a focus on PPAR¿-mediated processes, in Aim 2 the mechanism(s) by which apoER2 modulates intracellular signaling in macrophages and thereby governs their function and fate will be discerned. In Aim 3, studies will be done using the Lrp8 floxed mouse or bone marrow reconstitution on LDL receptor-null background to determine the contributions of endothelial versus macrophage apoER2 to protection from atherosclerosis progression and plaque necrosis. The planned studies will provide critical new understanding of the basis by which apoER2 and its major ligand apoE influence cardiovascular health. The new information gained promises to improve as well as personalize therapies to combat cardiovascular disease in a large number of individuals with LRP8 variants (~1%) and/or apoE polymorphisms (~15%). The general population may also benefit by the development of novel therapies that harness these processes to optimize cardiovascular protection.