Identification of a genotoxic mechanism for 2-nitroanisole carcinogenicity and of its carcinogenic potential for humans.
2-Nitroanisole (2-NA) is an important industrial pollutant and a potent bladder carcinogen for rodents. The mechanism of its carcinogenicity was investigated in this study. Here we have used two independent methods, (32)P-post-labeling and (3)H-labeled 2-NA, to show that 2-NA binds covalently to DNA in vitro after reductive activation by human hepatic cytosol and xanthine oxidase (XO). We also investigated the capacity of 2-NA to form DNA adducts in vivo. Male Wistar rats were treated i.p. with 2-NA (0.15 mg/kg body wt daily for 5 days) and DNA from several organs was analyzed by (32)P-post-labeling. Two 2-NA-specific DNA adducts, identical to those found in DNA incubated with 2-NA and human hepatic cytosol or XO in vitro, were detected in the urinary bladder (3.4 adducts/10(7) nt), the target organ, and, to a lesser extent, in liver, kidney and spleen. The two DNA adducts found in rat tissues in vivo were identified as deoxyguanosine adducts derived from a 2-NA reductive metabolite, N-(2-methoxyphenyl)hydroxylamine. This reactive metabolite of 2-NA was identified in incubations with human hepatic cytosol, besides 2-methoxyaniline (o-anisidine). The results of our study, the first report on the potential of human cytosolic enzymes to contribute to the activation of 2-NA by nitroreduction, strongly suggest a carcinogenic potency of this rodent carcinogen for humans.
Stiborová
Marie
M
Department of Biochemistry, Faculty of Science, Charles University, Albertov 2030, 128 40 Prague 2, Czech Republic. stiborov@natur.cuni.cz
Miksanová
Markéta
M
Smrcek
Stanislav
S
Bieler
Christian A
CA
Breuer
Andrea
A
Klokow
Karl A
KA
Schmeiser
Heinz H
HH
Frei
Eva
E
D000293:Adolescent; D000328:Adult; D000368:Aged; D042931:Aldehyde Oxidase / Q000378:metabolism; D000814:Aniline Compounds / Q000378:metabolism; D000818:Animals; D000840:Anisoles / Q000493:pharmacokinetics / Q000633:toxicity*; D002273:Carcinogens / Q000493:pharmacokinetics / Q000633:toxicity*; D002648:Child; D002675:Child, Preschool; D003600:Cytosol / Q000201:enzymology*; D004247:DNA / Q000378:metabolism*; D018736:DNA Adducts; D005260:Female; D006801:Humans; D007668:Kidney / Q000187:drug effects / Q000201:enzymology; D008099:Liver / Q000187:drug effects / Q000201:enzymology; D008297:Male; D008875:Middle Aged; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000378:metabolism; D010759:Phosphorus Isotopes; D051381:Rats; D017208:Rats, Wistar; D013154:Spleen / Q000187:drug effects / Q000201:enzymology; D001743:Urinary Bladder / Q000187:drug effects / Q000201:enzymology; D014969:Xanthine Oxidase / Q000378:metabolism*
D000814:Aniline Compounds; D000840:Anisoles; D002273:Carcinogens; D018736:DNA Adducts; D010759:Phosphorus Isotopes; D004247:DNA; D014969:Xanthine Oxidase; D042931:Aldehyde Oxidase; D016660:NAD(P)H Dehydrogenase (Quinone); C447479:NQO1 protein, human; C003898:2-anisidine; C005328:2-nitroanisole