Simultaneous expression of human CYP3A7 and N-acetyltransferase in Chinese hamster CHL cells results in high cytotoxicity for carcinogenic heterocyclic amines.
To investigate whether several food-derived heterocyclic amines are activated to genotoxic products in human fetal livers, cell lines stably expressing CYP3A7, a human fetus-specific form of cytochrome P450, NADPH-cytochrome P450 reductase, and human monomorphic or polymorphic N-acetyltransferase (NAT1 or NAT2) were established. The expression of CYP3A7 mRNAs and proteins was determined by RNA blot and immunoblot analyses, respectively. The introduction of CYP3A7 cDNA to CR-68 cells which had been transfected with guinea pig NADPH-cytochrome P450 reductase, NAT1, or NAT2 cDNA resulted in increased sensitivity of the cells to aflatoxin B1 compared to parental cells. The cytotoxicity assay for 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) showed that 7P-145 cells, which expressed the reductase, CYP3A7, and NAT2, were approximately 4-, 30-, and 14-fold more sensitive to respective IQ, MeIQ, and MeIQx than parental CR-68 cells. There were no clear differences in sensitivity to these compounds among CHL, CR-68, and the cells which expressed the reductase and CYP3A7 (7R-54), the reductase and NAT1 (CNM-4), the reductase and NAT2 (CNP-40), and the reductase, NAT1, and CYP3A7 (7M-124). From these results, it was suggested that both CYP3A7 and polymorphic NAT2 are required for mutagenic activation of several heterocyclic amines in human fetal livers.
Hashimoto
H
H
Division of Drug Metabolism, Faculty of Pharmaceutical Sciences, Hokkaido University, Japan.
Yanagawa
Y
Y
Sawada
M
M
Itoh
S
S
Deguchi
T
T
Kamataki
T
T
D000588:Amines / Q000633:toxicity*; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D001191:Arylamine N-Acetyltransferase / Q000096:biosynthesis* / Q000235:genetics; D002273:Carcinogens / Q000633:toxicity*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects*; D006224:Cricetinae; D003412:Cricetulus; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000235:genetics; D015870:Gene Expression; D018014:Gene Transfer Techniques; D006801:Humans; D011804:Quinolines / Q000633:toxicity; D011810:Quinoxalines / Q000633:toxicity
D000588:Amines; D002273:Carcinogens; D011804:Quinolines; D011810:Quinoxalines; C029216:2-amino-3-methylimidazo(4,5-f)quinoline; C036990:2-amino-3,8-dimethylimidazo(4,5-f)quinoxaline; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C103123:CYP3A7 protein, human; D051544:Cytochrome P-450 CYP3A; D001191:Arylamine N-Acetyltransferase; C036989:2-amino-3,4-dimethylimidazo(4,5-f)quinoline