Molecular Basis of Oxidative Modification of LDL

大量的证据表明，积累和随后的不良处理的氧化修饰， 动脉壁巨噬细胞活化的低密度脂蛋白（oxLDL）有助于动脉粥样硬化的初始阶段。 动脉粥样硬化LDL的氧化修饰包括其组分载脂蛋白B的衍生化 通过脂质过氧化反应性的代谢产物，包括HNE。蛋白质化学 这些醛的加合是高度复杂的，并且包括交联。一个重大的突破， 目前的资助期是发现巨噬细胞对oxLDL的摄取可能在很大程度上是由 通过CD36识别oxLDL中的氧化磷脂。我们进一步发现，HNE样产物 (and它们的衍生物），其由以下物质的花生四烯基和亚油基链的“镜像”氧化产生： 磷脂用作CD36配体。建议进一步研究，以彻底定义 巨噬细胞识别oxLDL并在其中蓄积的结构基础。最近的试点研究 表明oxLDL中氧化成分不仅可能干扰脂蛋白的加工， 暴露于oxLDL的巨噬细胞的胆固醇流出。下一个供资期的一个主要新目标是 阐明oxLDL对胆固醇流出的抑制作用的性质。 我们的工作假设是LDL的氧化变化有助于其吸收和缺乏 在巨噬细胞内加工，而oxLDL本身或其成分抑制一种或多种细胞因子， 更多的胆固醇流出机制，所有这些共同作为一个重要的决定因素，泡沫细胞 阵我们将继续定义脂氧化依赖的蛋白加合化学，包括质量 鉴定特别易受修饰的巨噬细胞蛋白的光谱方法 因为这些细胞暴露于oxLDL。后一个目标将通过继续发展 特异性加合物的免疫化学探针，也可用于鉴定后期加合物的性质 存在于人类动脉粥样硬化中。拟议的新工作继续利用 三个独立的研究人员在邻近的研究机构，特别是关于申请 新的结构特异性试剂和工具的细胞生物学研究。 与公共卫生的关系 在动脉粥样硬化的初始阶段，血液中主要的携带胆固醇的脂蛋白LDL， 氧化性低密度脂蛋白（oxLDL），导致动脉壁细胞试图破坏oxLDL 把它分解我们的研究旨在了解为什么有胆固醇的积累， 这些细胞因为它们不能有效地分解oxLDL和清除释放的胆固醇。

Substantial evidence suggests that the accumulation and subsequent poor processing of oxidatively modi- fied 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.