Molecular Basis of Oxidative Modification of LDL

描述(由申请人提供)：大量证据表明，动脉壁巨噬细胞对氧化修饰的低密度脂蛋白(OxLDL)的积累和随后的不良处理有助于动脉粥样硬化形成的初始阶段。低密度脂蛋白的氧化修饰涉及其组成成分载脂蛋白B被包括HNE在内的脂质过氧化的反应性醛分解产物的衍生化。这些醛对蛋白质的加合作用是非常复杂的，而且包括交联键。当前资助期的一个重大突破是发现巨噬细胞对oxLDL的摄取可能在很大程度上是通过CD36识别oxLDL中的氧化磷脂来调节的。我们进一步发现，由磷脂的花生四烯基链和亚油基链“镜像”氧化产生的类HNE产物(及其衍生物)作为CD36配体。建议进行进一步的研究，以彻底定义巨噬细胞识别和积聚oxLDL的结构基础。最近的初步研究表明，oxLDL中的氧化成分不仅可能干扰体内脂蛋白的加工，还可能干扰暴露于oxLDL的巨噬细胞的胆固醇外流。下一个资助期的一个主要新目标是澄清oxLDL对胆固醇外流的抑制作用的性质。 我们的工作假设是，对低密度脂蛋白的氧化改变有助于其被巨噬细胞摄取并在巨噬细胞内缺乏处理，而氧化低密度脂蛋白本身或从其发出的成分抑制胆固醇外流的一个或多个机制，所有这些共同起到泡沫细胞形成的重要决定因素的作用。我们将继续定义脂氧化依赖的蛋白质加合化学，包括鉴定巨噬细胞蛋白质的质谱学方法，这些蛋白质特别容易因暴露于oxLDL而发生修饰。后一个目标将得到针对特定加合物的免疫化学探针的持续发展的帮助，这也有助于识别存在于人类动脉粥样硬化中的晚期加合物的性质。拟议的新工作继续利用邻近研究机构的三名研究人员汇集的专业知识，特别是在将新颖的特定结构试剂和工具应用于细胞生物学研究方面。 与公众健康相关：在动脉粥样硬化的初始阶段，血液中主要携带胆固醇的脂蛋白低密度脂蛋白会受到氧化损伤(OxLDL)，导致动脉壁内的细胞试图清除oxLDL并将其分解。我们的研究旨在了解为什么这些细胞中会有胆固醇的积累，因为它们无法有效地分解oxLDL并清除释放的胆固醇。

DESCRIPTION (provided by applicant): Substantial evidence suggests that the accumulation and subsequent poor processing of oxidatively modified low density lipoprotein (oxLDL) by macrophages in the arterial wall contributes to the initial stages of atherogenesis. Oxidative modification of LDL involves the derivatization of its constituent apolipoprotein B by reactive aldehydic breakdown products of lipid peroxidation, including HNE. The chemistry of protein adduction by these aldehydes is highly complex and includes cross-linking. A major breakthrough of the current funding period was the finding that uptake of oxLDL by macrophages may be largely mediated by the recognition of oxidized phospholipids in oxLDL by CD36. We further discovered that the HNE-like products (and their derivatives) resulting from "mirror-image" oxidation of the arachidonyl and linoleyl chains of phospholipids serve as CD36 ligands. Further studies are proposed to bring thorough definition to the structural basis of oxLDL recognition by and accumulation within macrophage cells. Recent pilot studies suggest that oxidized constituents in oxLDL may interfere not only with lipoprotein processing within, but also cholesterol efflux from macrophage cells exposed to oxLDL. A major new aim of the next funding period is to clarify the nature of the inhibitory effects of oxLDL on cholesterol efflux. Our working hypothesis is that oxidative changes to LDL contribute to its uptake into and deficient processing within macrophage cells, and that oxLDL itself or constituents emanating from it inhibit one or more mechanisms of cholesterol efflux, all of which together act as an important determinant of foam cell formation. We will continue to define lipoxidation-dependent protein adduction chemistry, including mass spectrometric approaches to identifying macrophage proteins that are particularly susceptible to modification as a result of exposure of these cells to oxLDL. This latter aim will be aided by continued development of immunochemical probes for specific adducts, also useful for identifying the nature of late-stage adducts present in human atheroma. The new work proposed continues to take advantage of the pooled expertise of three individual investigators at neighboring research institutions, particularly with respect to the application of novel structurally-specific reagents and tools to cell biological studies. Relevance to public health: In the initial stages of atherosclerosis, the main cholesterol-carrying lipoprotein in blood, LDL, becomes oxidatively damaged (oxLDL), resulting in an attempt by cells lining the artery wall to scavenge the oxLDL and break it down. Our research is aimed at understanding why there is an accumulation of cholesterol in these cells because of their inability to efficiently break down the oxLDL and clear the released cholesterol.