Induction of Cytochrome P-450 1A2 by Oxidized Tryptophan in Hepa lclc7 Cells

• Published in: The Journal of pharmacology and experimental therapeutics Vol. 292; no. 3; pp. 1008 - 1014
• Main Authors: Sindhu, R K, Mitsuhashi, M, Kikkawa, Y
• Format: Journal Article
• Language: English
• Published: United States American Society for Pharmacology and Experimental Therapeutics 01.03.2000
• Subjects: Animals; Cycloheximide - pharmacology; Cytochrome P-450 CYP1A1 - biosynthesis; Cytochrome P-450 CYP1A2 - biosynthesis; Cytochrome P-450 CYP1A2 - genetics; DNA, Complementary - chemistry; Enzyme Induction - drug effects; Mice; Oxidation-Reduction; Receptors, Aryl Hydrocarbon - physiology; RNA, Messenger - analysis; Tryptophan - pharmacology; Tumor Cells, Cultured
• ISSN: 0022-3565; 1521-0103

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.