RT Journal Article SR Electronic T1 Regulation of Cytochrome P450 2E1 under Hypertonic Environment through TonEBP in Human Hepatocytes JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 173 OP 181 DO 10.1124/mol.106.033480 VO 72 IS 1 A1 Ito, Takashi A1 Asakura, Koko A1 Tougou, Katsuhiko A1 Fukuda, Tsuyoshi A1 Kubota, Ryuji A1 Nonen, Shinpei A1 Fujio, Yasushi A1 Azuma, Junichi YR 2007 UL http://molpharm.aspetjournals.org/content/72/1/173.abstract AB Whereas the liver as well as the other organs are continually exposed to the change of osmotic status, it has never been investigated whether activities and gene expressions of drug-metabolizing enzymes, including cytochromes P450, are dependent on osmotic change in the liver. In the present study, we determined that CYP2E1 is induced under hypertonic environments at a transcriptional level in human primary hepatocytes, as assessed by cDNA microarray and real time-reverse transcription-polymerase chain reaction analyses. Both a protein level and the catalytic activity of CYP2E1 were consistently increased in response to hypertonic conditions. In promoter-reporter assay, it was demonstrated that -586 to -566 in the CYP2E1 5′-flanking region was necessary for 2E1 promoter activation by hypertonic stimulation. It is noteworthy that tonicity-response element (TonE) consensus sequence was found at -578 to -568 in human CYP2E1 5′-flanking region, and electrophoretic mobility shift assay demonstrated the interaction of TonE binding protein (TonEBP) with TonE motif of CYP2E1 promoter. Furthermore, cotransfection of a CYP2E1 promoter construct with wild-type TonEBP expression vector enhanced promoter activity under both isotonic and hypertonic conditions, whereas dominant-negative TonEBP suppressed an induction of CYP2E1 promoter activity. These results indicate that the level of CYP2E1 is induced by hypertonic condition via TonEBP transactivation. The present study suggests that osmotic status may influence individual responses to the substrate of CYP2E1. The American Society for Pharmacology and Experimental Therapeutics