Production of reactive oxygen species by microsomes enriched in specific human cytochrome P450 enzymes.
Few studies have evaluated the production of reactive oxygen intermediates by human microsomes, especially the influence of the specific form of cytochrome P450. Experiments were carried out to evaluate the ability of CYP1A1, 1A2, 2B6, and 3A4 to consume NADPH, reduce iron, and catalyze production of reactive oxygen species. Microsomes enriched in each of these CYPs were obtained from commercial +/- lymphoblast cells that had been transfected with cDNA encoding the specific human CYP. On a per nanomole cytochrome P450 basis, CYP3A4 was the most active P450 evaluated in catalyzing NADPH oxidation, production of superoxide anion radical, NADPH-dependent chemiluminescence, oxidation of dichlorofluorescein diacetate, and reduction of either ferric-EDTA or ferric-citrate. CYP1A1 was the next most reactive CYP, whereas CYP1A2 and 2B6 displayed a comparable, lower activity. Nitric oxide, which reacts with and inactivates hemoproteins, inhibited superoxide production by all the CYPs to a similar extent. Because CYP3A4 is present in high amounts in human liver microsomes and is active in catalyzing the formation of reactive oxygen species, this CYP may make an important contribution in the overall ability of human liver microsomes to generate active oxygen species.
Puntarulo
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S
School of Pharmacy and Biochemistry, University of Buenos Aires, Argentina.
Cederbaum
A I
AI
D001189:Aryl Hydrocarbon Hydroxylases; D002460:Cell Line; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000378:metabolism; D019388:Cytochrome P-450 CYP1A2 / Q000235:genetics / Q000378:metabolism; D065702:Cytochrome P-450 CYP2B6; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007501:Iron / Q000378:metabolism; D007700:Kinetics; D015227:Lipid Peroxidation; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism*; D008862:Microsomes, Liver / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D009569:Nitric Oxide / Q000494:pharmacology; D010084:Oxidation-Reduction; D010089:Oxidoreductases, N-Demethylating / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism; D014162:Transfection
D017382:Reactive Oxygen Species; D013481:Superoxides; D009569:Nitric Oxide; D009249:NADP; D003577:Cytochrome P-450 Enzyme System; D007501:Iron; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C585599:CYP2B6 protein, human; C104464:CYP3A protein, human; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2; D065702:Cytochrome P-450 CYP2B6; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D010089:Oxidoreductases, N-Demethylating