Role of human CYP1A1 and NAT2 in 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine-induced mutagenicity and DNA adducts.
2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is carcinogenic in multiple organs and numerous species. Bioactivation of PhIP is initiated by PhIP N(2)-hydroxylation catalysed by cytochrome P450s. Following N-hydroxylation, O-acetylation catalysed by N-acetyltransferase 2 (NAT2) is considered a further possible activation pathway. Genetic polymorphisms in NAT2 may modify cancer risk following exposure. Nucleotide excision repair-deficient Chinese hamster ovary (CHO) cells stably transfected with human cytochrome P4501A1 (CYP1A1) and a single copy of either NAT2*4 (rapid acetylator) or NAT2*5B (slow acetylator) alleles were used to test the effect of CYP1A1 and NAT2 polymorphism on PhIP genotoxicity. Cells transfected with NAT2*4 had significantly higher levels of N-hydroxy-PhIP O-acetyltransferase (p = 0.0150) activity than cells transfected with NAT2*5B. Following PhIP treatment, CHO cell lines transfected with CYP1A1, CYP1A1/NAT2*4 and CYP1A1/NAT2*5B each showed concentration-dependent cytotoxicity and hypoxanthine phosphoribosyl transferase (hprt) mutagenesis not observed in untransfected CHO cells. dG-C8-PhIP was the primary DNA adduct formed and levels were dose dependent in transfected CHO cells in the order: CYP1A1 < CYP1A1 and NAT2*5B < CYP1A1 and NAT2*4, although levels did not differ significantly (p > 0.05) following one-way analysis of variance. These results strongly support activation of PhIP by CYP1A1 with little effect of human NAT2 genetic polymorphism on mutagenesis and DNA damage.
Bendaly
J
J
Department of Pharmacology and Toxicology, James Graham Brown Cancer Center, and Center for Environmental Genomics and Integrative Biology, University of Louisville School of Medicine, Louisville, KY, USA.
Metry
K J
KJ
Doll
M A
MA
Jiang
G
G
States
J C
JC
Smith
N B
NB
Neale
J R
JR
Holloman
J L
JL
Pierce
W M
WM
Hein
D W
DW
D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000235:genetics / Q000378:metabolism*; D016466:CHO Cells; D002273:Carcinogens / Q000494:pharmacology*; D006224:Cricetinae; D003412:Cricetulus; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000378:metabolism*; D018736:DNA Adducts / Q000378:metabolism*; D004249:DNA Damage; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D016296:Mutagenesis; D009153:Mutagens / Q000494:pharmacology*; D011110:Polymorphism, Genetic; D014162:Transfection
D002273:Carcinogens; D018736:DNA Adducts; D007093:Imidazoles; D009153:Mutagens; C049584:2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine; D019363:Cytochrome P-450 CYP1A1; D001191:Arylamine N-Acetyltransferase; C478900:NAT2 protein, human