Rosenblat M, Aviram M
Lipid Research Laboratory, Technion Faculty of Medicine, The Rappaport Family Institute for Research in the Medical Sciences and Rambam Medical Center, Haifa, Israel.
Free Radic Biol Med. 1998 Jan 15;24(2):305-17. doi: 10.1016/s0891-5849(97)00231-1.
Macrophage-mediated oxidation of low-density lipoprotein (LDL) is thought to play a key role during early atherogenesis, and cellular oxygenases were shown to mediate this process. As macrophage antioxidants may also contribute to the extent of cell-mediated oxidation of LDL, we analyzed the role of cellular reduced glutathione (GSH) and glutathione peroxidase (GPx) in LDL oxidation. The present study examined the effect of the macrophage GSH-GPx status on the ability of the cells to oxidize LDL. Upon incubation of J-774 A.1 macrophages for 20 h at 37 degrees C with 50 microM of buthionine sulfoximine (BSO), an inhibitor of glutathione synthesis, cellular GSH content and GPx activity were reduced by 89 and 50%, respectively, and this effect was associated with a twofold elevation in macrophage-mediated oxidation of LDL. The BSO-treated cells contained high levels of peroxides, and released 32% more superoxide anions than nontreated cells in response to their stimulation with LDL in the presence of copper ions. To increase macrophage GSH content and GPx activity we have used L-2-oxothiazolidine-4-carboxylic acid (OTC), which delivers cysteine residues to the cells for GSH synthesis, and also selenium, which activates GPx and increases cellular glutathione synthesis. GSH content and GPx activity in J-774 A.1 macrophages were increased by 80 and 50%, respectively, following cells incubation with 2 mM OTC for 20 h at 37 degrees C, and this was paralleled by a 47% inhibition in LDL oxidation by these cells. An inverse correlation was found between the extent of macrophage-mediated oxidation of LDL and cellular GSH content (r = .97), or GPx activity (r = .95). Upon incubation of J-774 A.1 macrophages with selenomethionine (10 ng/ml) for 1 week, cellular GSH content and GPx activity were increased by about twofold compared to control cells, and this effect was associated with a 30% reduction in cell-mediated oxidation of LDL. Dietary selenium supplementation (1 microg/d/mouse) to the atherosclerotic apolipoprotein E-deficient mice for a 6-month period, increased GSH content and GPx activity in the mice peritoneal macrophages by 36 and 30%, respectively, and this effect was associated with a 46% reduction in cell-mediated oxidation of LDL. Finally, the atherosclerotic lesion area in the aortas derived from these mice after selenium supplementation was found to be reduced by 30% compared to the lesion area found in nontreated mice. Our results demonstrate an inverse relationship between macrophage GSH content/GPx activity and cell-mediated oxidation of LDL. Intervention means to enhance the macrophage GSH-GPx status may thus contribute to attenuation of the atherosclerotic process.
巨噬细胞介导的低密度脂蛋白（LDL）氧化被认为在动脉粥样硬化早期发展过程中起关键作用，并且细胞加氧酶被证明可介导这一过程。由于巨噬细胞抗氧化剂也可能影响细胞介导的LDL氧化程度，我们分析了细胞内还原型谷胱甘肽（GSH）和谷胱甘肽过氧化物酶（GPx）在LDL氧化中的作用。本研究检测了巨噬细胞GSH - GPx状态对细胞氧化LDL能力的影响。将J - 774 A.1巨噬细胞在37℃下与50μM的丁硫氨酸亚砜胺（BSO，一种谷胱甘肽合成抑制剂）孵育20小时后，细胞内GSH含量和GPx活性分别降低了89%和50%，并且这种效应与巨噬细胞介导的LDL氧化增加两倍相关。经BSO处理的细胞含有高水平的过氧化物，并且在铜离子存在下用LDL刺激时，释放的超氧阴离子比未处理的细胞多32%。为了增加巨噬细胞GSH含量和GPx活性，我们使用了L - 2 - 氧代噻唑烷 - 4 - 羧酸（OTC），它为细胞提供半胱氨酸残基用于GSH合成，还使用了硒，它可激活GPx并增加细胞内谷胱甘肽合成。将J - 774 A.1巨噬细胞在37℃下与2 mM OTC孵育20小时后，细胞内GSH含量和GPx活性分别增加了80%和50%，同时这些细胞对LDL的氧化作用受到47%的抑制。发现巨噬细胞介导的LDL氧化程度与细胞内GSH含量（r = 0.97）或GPx活性（r = 0.95）呈负相关。将J - 774 A.1巨噬细胞与硒代蛋氨酸（10 ng/ml）孵育1周后，细胞内GSH含量和GPx活性相比对照细胞增加了约两倍，并且这种效应与细胞介导的LDL氧化减少30%相关。给动脉粥样硬化的载脂蛋白E缺陷小鼠补充膳食硒（1μg/天/小鼠）6个月，小鼠腹腔巨噬细胞内GSH含量和GPx活性分别增加了36%和30%，并且这种效应与细胞介导的LDL氧化减少46%相关。最后，发现这些小鼠补充硒后主动脉中的动脉粥样硬化病变面积与未处理小鼠相比减少了30%。我们的结果表明巨噬细胞GSH含量/GPx活性与细胞介导的LDL氧化之间存在负相关关系。因此，增强巨噬细胞GSH - GPx状态的干预手段可能有助于减轻动脉粥样硬化进程。
