Prostaglandin H synthase-medicated oxidation and binding to DNA of a detoxication metabolite of carcinogenic Sudan I, 1-(phenylazo)-2,6-dihydroxynaphthalene.
The metabolite of the carcinogenic azo dye Sudan I, 1-(phenylazo)-2,6-dihydroxynaphthalene (6-OH-Sudan I), which is considered to be the detoxification product of this dye is metabolized by prostaglandin H synthase (PHS) in the presence of arachidonic acid or H2O2 in vitro. The apparent Michaelis constant value for 6-OH-Sudan I as a substrate is 98.9 microM. 1-(Phenylazo)-2,6-naphthoquinone is a principal product of the 6-OH-Sudan I oxidation. This oxidation is inhibited by radical scavengers nitrosobenzene, ascorbate, glutathione and NADH. This indicates that PHS metabolizes 6-OH-Sudan I through a one-electron oxidation mechanism, giving rise to free radicals. During the PHS-mediated reaction, 6-OH-Sudan I is activated to metabolites binding to protein and DNA. The 32P-postlabeling analysis of DNA modified by activated 6-OH-Sudan I provides evidence that covalent binding to DNA is the principal type of DNA modification. The PHS-mediated binding of 6-OH-Sudan I to DNA presumably proceeds through formation of 1-(phenylazo)-2,6-naphthoquinone. The results suggest strongly that the C-hydroxylated derivative of Sudan I (6-OH-Sudan I) should be evaluated as a proximate carcinogenic metabolite, which may participate in the initiation of Sudan I-carcinogenesis in the urinary bladder.
Stiborová
M
M
Department of Biochemistry, Faculty of Natural Sciences, Charles University, Prague, Czech Republic. stiborov@prfdec.natur.cuni.cz
Schmeiser
H H
HH
Frei
E
E
D000818:Animals; D002273:Carcinogens / Q000378:metabolism*; D004247:DNA / Q000378:metabolism*; D018736:DNA Adducts / Q000378:metabolism*; D008658:Inactivation, Metabolic; D008297:Male; D009281:Naphthalenes / Q000378:metabolism*; D009284:Naphthols / Q000378:metabolism*; D010084:Oxidation-Reduction; D011451:Prostaglandin-Endoperoxide Synthases / Q000502:physiology*; D012756:Sheep
D002273:Carcinogens; D018736:DNA Adducts; D009281:Naphthalenes; D009284:Naphthols; C024336:1-phenylazo-2-naphthol; D004247:DNA; D011451:Prostaglandin-Endoperoxide Synthases