Macrophage glutathione content and glutathione peroxidase activity are inversely related to cell-mediated oxidation of LDL: in vitro and in vivo studies.
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.
Rosenblat
M
M
Lipid Research Laboratory, Technion Faculty of Medicine, The Rappaport Family Institute for Research in the Medical Sciences and Rambam Medical Center, Haifa, Israel.
Aviram
M
M
D000818:Animals; D001057:Apolipoproteins E / Q000172:deficiency; D001161:Arteriosclerosis / Q000378:metabolism; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D002460:Cell Line; D005978:Glutathione / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005979:Glutathione Peroxidase / Q000378:metabolism*; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D010084:Oxidation-Reduction; D010545:Peroxides / Q000378:metabolism; D011761:Pyrrolidonecarboxylic Acid; D012643:Selenium / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines
D001057:Apolipoproteins E; D008077:Lipoproteins, LDL; D010545:Peroxides; D013844:Thiazoles; D053778:Thiazolidines; C099252:oxidized low density lipoprotein; D013481:Superoxides; D019328:Buthionine Sulfoximine; D005979:Glutathione Peroxidase; D005978:Glutathione; D012643:Selenium; D011761:Pyrrolidonecarboxylic Acid; C029536:2-oxothiazolidine-4-carboxylic acid