Kritharides L, Jessup W, Dean R T
Cell Biology Group, Heart Research Institute, Camperdown, Sydney, NSW, Australia.
Free Radic Res. 1995 May;22(5):399-417. doi: 10.3109/10715769509147549.
The extent to which cells can oxidize LDL may be underestimated because of the use of standard and arbitrary 24 hour in vitro incubations of cells with LDL. Such incubations have resulted in inconsistent results regarding the ability of cell-mediated LDL oxidation to generate relatively advanced oxidation products such as 7-ketocholesterol (7-KC). We studied prolonged oxidation of low density lipoprotein (LDL) by mouse peritoneal macrophages using HPLC measurement of cholesterol, cholesteryl esters and their oxidation products 7-KC and cholesteryl linoleate hydroperoxide (CL-OOH). Cell-mediated oxidation in Ham's F10 consistently followed the successive stages previously described during 24 hour-10 microM copper-mediated LDL oxidation, always generating 7-KC if allowed to proceed for sufficient time. The degree of inhibition of LDL oxidation achieved by metal chelators EDTA and DTPA at more advanced stages of cell-mediated LDL oxidation was not predictable from the published effects of such chelators upon early stages of metal-mediated and cell-mediated LDL oxidation. EDTA and DTPA only incompletely prevented the consumption of cholesteryl esters and the loss of performed CL-OOH when added after cell-mediated LDL oxidation was established, while effectively concurrently inhibiting the generation of 7-KC. These data indicate that progressive cell-mediated peroxidation of LDL cholesteryl esters and decomposition of CL-OOH may be less dependent upon a continuing supply of redox active metals than is the generation of 7-KC. In addition, they confirm the plausibility of prolonged cell-mediated oxidation of LDL as a source of oxysterols found in human atherosclerotic plaque, and imply that active redox cycling of metals is particularly important for their generation in vivo.
由于采用标准且任意的细胞与低密度脂蛋白（LDL）进行24小时体外孵育的方法，细胞氧化LDL的程度可能被低估。这样的孵育对于细胞介导的LDL氧化生成相对高级的氧化产物（如7-酮胆固醇（7-KC））的能力产生了不一致的结果。我们使用高效液相色谱法测量胆固醇、胆固醇酯及其氧化产物7-KC和亚油酸胆固醇酯氢过氧化物（CL-OOH），研究了小鼠腹腔巨噬细胞对低密度脂蛋白（LDL）的长时间氧化。在Ham's F10培养基中细胞介导的氧化始终遵循先前在24小时-10微摩尔铜介导的LDL氧化过程中所描述的连续阶段，如果允许进行足够长的时间，总是会生成7-KC。在细胞介导的LDL氧化的更后期阶段，金属螯合剂乙二胺四乙酸（EDTA）和二乙烯三胺五乙酸（DTPA）对LDL氧化的抑制程度无法从已发表的这些螯合剂对金属介导和细胞介导的LDL氧化早期阶段的作用中预测出来。当在细胞介导的LDL氧化建立后添加时，EDTA和DTPA只能不完全阻止胆固醇酯的消耗和已生成的CL-OOH的损失，同时有效地抑制7-KC的生成。这些数据表明，LDL胆固醇酯的渐进性细胞介导的过氧化和CL-OOH的分解可能比7-KC的生成对氧化还原活性金属的持续供应依赖性更小。此外，它们证实了LDL的长时间细胞介导氧化作为人类动脉粥样硬化斑块中发现的氧化甾醇来源的合理性，并暗示金属的活跃氧化还原循环对其在体内的生成尤为重要。
