title: Regulation of hepatic CYP1A isozymes by piperonyl butoxide and acenaphthylene in the mouse.
abstract: The regulation of CYP1A1 and CYP1A2 isozymes by piperonyl butoxide (PBO) and acenaphthylene (ACN) was studied in the liver of male C57BL/6 and DBA/2 mice. These two cytochrome P450 genes are known to be regulated by the aromatic hydrocarbon-responsive receptor (AHR); however, it has been suggested that CYP1A2 is also induced by an AHR-independent mechanism. In this study, PBO induced hepatic CYP1A1 considerably more in C57BL/6 (Ahrb-I) than in DBA/2 (Ahrd) mice. In addition, the superinduction of CYP1A1 in wildtype hepa1c1c7 cells, which is AHR-dependent, resulted from PBO and cycloheximide treatment of the cells. In other studies in this laboratory using AHR knock-out (AHR-/-) mice, a hybrid of 129/SV and C57BL/6 strains, no induction of CYP1A1 occurred with PBO or ACN. [D.-Y. Ryu, P.E. Levi, P. Fernandez-Salguero, F.J. Gonzalez, E. Hodgson, Mol. Pharmacol., 50 (1996) 443-446.] ACN, however, did not induce CYP1A1 under the experimental conditions used. These results suggest that PBO, but not ACN, induces CYP1A1 through a weak activation of AHR. On the other hand, hepatic CYP1A2 mRNA and hnRNA were induced by PBO in both C57BL/6 and DBA/2 strains, but were not induced by ACN, a strong inducer of CYP1A2 in the B6C3F1 strain. However, both PBO and ACN induced CYP1A2 in AHR-/- mice. It is assumed, therefore, that the transcriptional induction of CYP1A2 by PBO and ACN is AHR-independent. In addition, the induction of CYP1A2 by ACN depends upon the strain of mice. Immunohistochemical studies for CYP1A1/CYP1A2 apoproteins showed that PBO induced CYP1A1/CYP1A2 around the central veins as did 3-methylcholanthrene (3-MC). The induction of CYP1A1/CYP1A2 by ACN, however, was not observed, consistent with the northern blot results.
authors.affiliation: Department of Toxicology, North Carolina State University, Raleigh 27695, USA.
authors.forename: D Y
authors.initials: DY
authors.lastname: Ryu
authors.forename: P E
authors.initials: PE
authors.lastname: Levi
authors.forename: E
authors.initials: E
authors.lastname: Hodgson
mesh_terms: D000073:Acenaphthenes / Q000494:pharmacology*; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D003513:Cycloheximide / Q000494:pharmacology; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics; D019388:Cytochrome P-450 CYP1A2 / Q000235:genetics; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D015971:Gene Expression Regulation, Enzymologic; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000235:genetics*; D008099:Liver / Q000201:enzymology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D010882:Piperonyl Butoxide / Q000494:pharmacology*; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology; D016133:Polymerase Chain Reaction / Q000379:methods; D012332:RNA, Heterogeneous Nuclear / Q000032:analysis; D012194:RNA-Directed DNA Polymerase; D013723:Teratogens / Q000494:pharmacology
chemical_list: D000073:Acenaphthenes; D007527:Isoenzymes; D000072317:Polychlorinated Dibenzodioxins; D012332:RNA, Heterogeneous Nuclear; D013723:Teratogens; C042553:acenaphthylene; D003577:Cytochrome P-450 Enzyme System; D003513:Cycloheximide; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2; D012194:RNA-Directed DNA Polymerase; D010882:Piperonyl Butoxide