Oxalomalate, a competitive inhibitor of NADP+-dependent isocitrate dehydrogenase, enhances lipid peroxidation-mediated oxidative damage in U937 cells.
Membrane lipid peroxidation processes yield products that may react with DNA and proteins to cause oxidative modifications. Cytosolic NADP+-dependent isocitrate dehydrogenase (ICDH) in U937 cells produces NADPH, an essential reducing equivalent for the antioxidant system. The protective role of ICDH against lipid peroxidation-mediated oxidative damage in U937 cells was investigated in control cells pre-treated with oxalomalate, a competitive inhibitor of ICDH. Upon exposure to 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH) to U937 cells, which induces lipid peroxidation in membranes, the viability was lower and the protein oxidation, lipid peroxidation, and oxidative DNA damage, reflected by an increase in 8-hydroxy-2'-deoxyguanosine, were higher in oxalomalate-treated cells as compared to control cells. We also observed the significant increase in the endogenous production of reactive oxygen species, as measured by the oxidation of 2',7'-dichlorodihydrofluorescin, as well as the significant decrease in the intracellular GSH level in oxalomalate-treated U937 cells upon exposure to AAPH. These results suggest that ICDH plays an important role as an antioxidant enzyme in cellular defense against lipid peroxidation-mediated oxidative damage through the removal of reactive oxygen species.
Yang
Joon-Hyuck
JH
Department of Biochemistry, College of Natural Sciences, Kyungpook National University, 702-701, Taegu, Republic of Korea.
Park
Jeen-Woo
JW
D000578:Amidines / Q000494:pharmacology; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D007521:Isocitrate Dehydrogenase / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D015227:Lipid Peroxidation / Q000187:drug effects* / Q000502:physiology; D008315:Malondialdehyde / Q000032:analysis / Q000378:metabolism; D018613:Microscopy, Confocal / Q000379:methods; D009249:NADP / Q000378:metabolism*; D009943:Organophosphorus Compounds / Q000032:analysis / Q000378:metabolism; D010070:Oxalates / Q000494:pharmacology*; D016877:Oxidants / Q000494:pharmacology; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D011721:Pyrenes / Q000032:analysis / Q000378:metabolism; D020298:U937 Cells
D000578:Amidines; D004791:Enzyme Inhibitors; D009943:Organophosphorus Compounds; D010070:Oxalates; D016877:Oxidants; D011721:Pyrenes; C066322:diphenyl-1-pyrenylphosphine; C015407:oxalomalic acid; D008315:Malondialdehyde; D009249:NADP; C046728:2,2'-azobis(2-amidinopropane); D007521:Isocitrate Dehydrogenase; C039355:isocitrate dehydrogenase (NADP+); D005978:Glutathione