The effect of inhibitors of free radical generating-enzymes on low-density lipoprotein oxidation by macrophages.
Oxidised low-density lipoprotein (LDL) produced by the action of arterial cells, including macrophages, has been implicated in atherosclerosis. We have investigated the effect of inhibitors of various cellular free-radical generating enzymes on macrophage-mediated LDL oxidation. Xanthine oxidase and nitric oxide synthase are not responsible for LDL modification by resident mouse peritoneal macrophages. Eicosatetraynoic acid, a lipoxygenase inhibitor, produced a dose-dependent irreversible inhibition of macrophage modification of LDL, but at concentrations rather close to those toxic to the cells. Diphenyl and diphenylene iodonium, NADPH oxidase and mitochondrial electron transport inhibitors, inhibited macrophage oxidation of LDL, at concentrations that were not obviously toxic. This suggests that NADPH oxidase, or some other flavin nucleotide-dependent process, may be involved in LDL oxidation by macrophages. Wortmannin and thiopropionic acid dilauryl ester did not inhibit LDL oxidation, suggesting that inhibition of NADPH oxidase may not be the means by which the iodonium compounds inhibit LDL oxidation. Macrophages from C3H/HeJ mice, which lack receptors for lipopolysaccharide, modified LDL normally, suggesting that the inadvertent priming of resident macrophages by traces of lipopolysaccharide bound to LDL was not involved in LDL oxidation.
Wilkins
G M
GM
Department of Biochemistry and Physiology, School of Animal and Microbial Sciences, University of Reading, Whiteknights, Berks, UK.
Leake
D S
DS
D000594:Amino Acid Oxidoreductases / Q000037:antagonists & inhibitors; D000818:Animals; D001161:Arteriosclerosis / Q000209:etiology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D005609:Free Radicals; D008077:Lipoproteins, LDL / Q000378:metabolism*; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology; D017737:Macrophages, Peritoneal / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D008809:Mice, Inbred C3H; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors; D019255:NADPH Oxidases; D019001:Nitric Oxide Synthase; D010084:Oxidation-Reduction; D013482:Superoxide Dismutase / Q000037:antagonists & inhibitors; D014969:Xanthine Oxidase / Q000037:antagonists & inhibitors
D004791:Enzyme Inhibitors; D005609:Free Radicals; D008077:Lipoproteins, LDL; D016859:Lipoxygenase Inhibitors; D019001:Nitric Oxide Synthase; D013482:Superoxide Dismutase; D014969:Xanthine Oxidase; D000594:Amino Acid Oxidoreductases; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases