Hoff H F, Whitaker T E, O'Neil J
Department of Vascular Cell Biology and Atherosclerosis, Cleveland Clinic Foundation, Ohio 44195.
J Biol Chem. 1992 Jan 5;267(1):602-9.
Oxidized (ox-) low density lipoproteins (LDL) is characterized by the formation of lipid peroxides and their decomposition to reactive aldehydes which covalently link to apoB in LDL. These chemical changes are believed to be responsible for the enhanced recognition of ox-LDL by receptors on macrophages in culture. When oxidation is extensive, particle aggregation also occurs. The aim of this study was to characterize aggregation formation and how this influences the interaction of ox-LDL with macrophages in culture. When LDL was oxidized by incubating at 500 micrograms of protein/ml with 10 microM Cu2+ at 20 degrees C for up to 25 h, time-dependent increases in thiobarbituric acid reactive substances, conjugated diene content, electrophoretic mobility, and fluorescence at 360 excitation/430 emission were found. Particle aggregation increased in parallel with several parameters of oxidation and increased with increasing incubation temperatures and LDL concentrations used. When evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, apoB fragments of reproducible sizes and higher molecular weight species appeared after mild oxidation of LDL. The percent of total apoB remaining aggregated in sodium dodecyl sulfate was 50-80% at high degrees of oxidation, whereas it was far less in LDL that had been aggregated without chemical modification. This suggested that intermolecular cross-linking of apoB had occurred during oxidation of LDL at high concentrations. Degradation of ox-LDL in mouse peritoneal macrophages (MPM) increased in parallel with the degree of oxidation and with particle aggregation but reached a plateau after 12 h. Results from cross-competition studies in MPM with soluble and insoluble portions of extensively ox-LDL and with acetyl-LDL were consistent with uptake of soluble ox-LDL via both the scavenger receptor and another receptor on MPM, and uptake of the insoluble ox-LDL by an alternative mechanism.
氧化型（ox-）低密度脂蛋白（LDL）的特征在于脂质过氧化物的形成及其分解为与LDL中的载脂蛋白B共价连接的反应性醛。这些化学变化被认为是培养的巨噬细胞上的受体对ox-LDL识别增强的原因。当氧化程度较高时，颗粒聚集也会发生。本研究的目的是表征聚集物的形成以及这如何影响培养的巨噬细胞中ox-LDL与巨噬细胞的相互作用。当LDL在20℃下以500微克蛋白质/毫升与10微摩尔Cu2+孵育长达25小时进行氧化时，发现硫代巴比妥酸反应性物质、共轭二烯含量、电泳迁移率以及在360激发/430发射处的荧光随时间增加。颗粒聚集与氧化的几个参数平行增加，并随着孵育温度和所用LDL浓度的增加而增加。通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳评估时，LDL轻度氧化后出现了可重复大小的载脂蛋白B片段和更高分子量的物种。在高度氧化时，在十二烷基硫酸钠中保持聚集的总载脂蛋白B的百分比为50-80%，而在未经化学修饰而聚集的LDL中该百分比要低得多。这表明在高浓度LDL氧化过程中发生了载脂蛋白B的分子间交联。小鼠腹腔巨噬细胞（MPM）中ox-LDL的降解与氧化程度和颗粒聚集平行增加，但在12小时后达到平台期。MPM中广泛氧化的ox-LDL的可溶性和不溶性部分与乙酰-LDL的交叉竞争研究结果表明，可溶性ox-LDL通过清道夫受体和MPM上的另一种受体摄取，不溶性ox-LDL通过另一种机制摄取。
