2-(4'-chlorophenyl)benzothiazole is a potent inducer of cytochrome P450IA1 in a human and a mouse cell line. Anomalous correlation between protein and mRNA induction.
Two benzothiazole derivatives, 2-(4'-chlorophenyl)benzothiazole (CPBT) and 2-(4'-formylphenyl)benzothiazole (FPBT) were studied for their ability to induce aryl hydrocarbon hydroxylase activity in a mouse and a human cell line. In both the mouse hepatoma cell line, Hepa-1, and the human choriocarcinoma cell line, JEG-3, a high aryl hydrocarbon hydroxylase activity was observed after treatment with CPBT. In contrast, FPBT had a very weak inducing capacity in both cell lines. The maximal induction by CPBT was several times (e.g. in Hepa-1 about fourfold on average) greater than that observed with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). A specific cDNA probe for mouse cytochrome P4501A1 gene was used to quantify mRNA levels in Hepa-1 cells. CPBT increased cytochrome P450IA1 mRNA to a level of 88% of that induced by TCDD. Immunoblot analysis with monoclonal antibody 1-7-1, directed against rat liver cytochrome P450IA1 and P450IA2, showed that the amount of P450IA1 is substantially increased in Hepa-1 cells after treatment with CPBT. The observation that CPBT competed TCDD off its specific cytosolic binding site suggests a receptor-mediated induction of cytochrome P450IA1 mRNA. An in vitro activation effect did not explain the exceptionally high hydroxylase activity. The results show that CPBT is a more efficient inducer of aryl hydrocarbon hydroxylase than TCDD in Hepa-1 and JEG-3 cells and that the induction is supported by P450IA1. The discordant effect of CPBT on mRNA and aryl hydrocarbon hydroxylase activity suggests that post-translational modifications of P450IA1 account for a major part of the increased enzyme activity.
Kärenlampi
S O
SO
Department of Biochemistry, University of Kuopio, Finland.
Tuomi
K
K
Korkalainen
M
M
Raunio
H
H
D000818:Animals; D000911:Antibodies, Monoclonal; D001189:Aryl Hydrocarbon Hydroxylases / Q000096:biosynthesis; D052160:Benzothiazoles; D002460:Cell Line; D002822:Choriocarcinoma; D002999:Clone Cells; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000235:genetics*; D004790:Enzyme Induction; D005260:Female; D006801:Humans; D015151:Immunoblotting; D008114:Liver Neoplasms, Experimental; D051379:Mice; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology; D011247:Pregnancy; D012333:RNA, Messenger / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics*; D013329:Structure-Activity Relationship; D013844:Thiazoles / Q000494:pharmacology*; D014594:Uterine Neoplasms
D000911:Antibodies, Monoclonal; D052160:Benzothiazoles; D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D013844:Thiazoles; C059650:2-(4'-chlorophenyl)benzothiazole; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases