title: Induction of cytochrome P-450 1A2 by oxidized tryptophan in Hepa lclc7 cells.
abstract: Recent studies from this laboratory have demonstrated that L-tryptophan, after oxidation either by UV-irradiation or ozone, induces aryl hydrocarbon receptor (AhR) activation and binding of the liganded AhR complex to its specific DNA recognition site, thereby initiating transcription of the cytochrome P-450 1a1 (Cyp1a1) gene with concomitant increase of CYP1A1 protein and 7-ethoxyresorufin O-deethylase activity in wild-type mouse hepatoma cells, Hepa lclc7 (Hepa-1), in culture. Temporary inhibition of protein synthesis by cycloheximide resulted in superinduction of oxidized tryptophan-inducible CYP1A1 mRNA, protein, and 7-ethoxyresorufin O-deethylase activity in Hepa-1 cells. In the present communication, the results obtained by immunoblot analyses with monoclonal CYP1A1/1A2 antibody (NIH 1-7-1) demonstrate that both UV- or ozone-oxidized tryptophan also induce CYP1A2 protein in Hepa-1 cells. CYP1A2 mRNA, detected by reverse transcription-polymerase chain reaction, was markedly induced in the UV- or ozone-oxidized tryptophan-treated cells. Temporary inhibition of protein synthesis by cycloheximide further induced oxidized tryptophan-inducible CYP1A2 mRNA as well as the protein in Hepa-1 cells. This is the first report demonstrating the induction of CYP1A2 mRNA and protein in Hepa-1 cells.
authors.affiliation: Department of Pathology, College of Medicine, University of California-Irvine, Irvine, California, USA.
authors.forename: R K
authors.initials: RK
authors.lastname: Sindhu
authors.forename: M
authors.initials: M
authors.lastname: Mitsuhashi
authors.forename: Y
authors.initials: Y
authors.lastname: Kikkawa
mesh_terms: D000818:Animals; D003513:Cycloheximide / Q000494:pharmacology; D019363:Cytochrome P-450 CYP1A1 / Q000096:biosynthesis; D019388:Cytochrome P-450 CYP1A2 / Q000096:biosynthesis* / Q000235:genetics; D018076:DNA, Complementary / Q000737:chemistry; D004790:Enzyme Induction / Q000187:drug effects; D051379:Mice; D010084:Oxidation-Reduction; D012333:RNA, Messenger / Q000032:analysis; D018336:Receptors, Aryl Hydrocarbon / Q000502:physiology; D014364:Tryptophan / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D014364:Tryptophan; D003513:Cycloheximide; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2