TY - JOUR T1 - Oltipraz Is a Bifunctional Inducer Activating Both Phase I and Phase II Drug-Metabolizing Enzymes via the Xenobiotic Responsive Element JF - Molecular Pharmacology JO - Mol Pharmacol SP - 346 LP - 354 DO - 10.1124/mol.64.2.346 VL - 64 IS - 2 AU - Weimin Miao AU - Lianggao Hu AU - Mustapha Kandouz AU - Gerald Batist Y1 - 2003/08/01 UR - http://molpharm.aspetjournals.org/content/64/2/346.abstract N2 - Oltipraz, a promising cancer chemopreventive agent, has been recognized as a monofunctional inducer selectively activating phase II carcinogen-detoxifying enzymes via the antioxidant responsive element (ARE). However, we report here that oltipraz also induces rat glutathione S-transferase A5 (GSTA5), a potent phase II detoxifying enzyme, by means of the xenobiotic responsive element (XRE). Although an ARE sequence exists in the 5′ upstream of the rGSTA5 gene, this cis-acting regulatory element loses its responsiveness to oltipraz treatment because of extensive mutations in its distal-half site. Our data indicate that a XRE sequence, located downstream of the transcription initiation site of the gene, is another oltipraz-responsive element. Electrophoretic mobility shift assay showed that oltipraz steadily induces XRE-aryl hydrocarbon receptor (AhR) binding, which can be blocked specifically by excess XRE oligonucleotides or by AhR antibody. By cloning different XREs into the pGL3-promoter vector, we found that oltipraz can activate XRE enhancers from several phase II drug metabolism enzymes, including rGSTA5, rGSTA2, NAD(P)H:quinone reductase, and it also activates XRE from the phase I metabolism enzyme CYP1A1. Oltipraz's effect on XRE is AhR-dependent and is independent of the presence of active CYP1A1. Reverse transcriptase-polymerase chain reaction experiments revealed that oltipraz induces gene expression of both phase I and II drug-metabolizing enzymes in rat hepatoma cells. Thus, we conclude that, like ARE, the XRE pathway constitutes an important part of the molecular mechanism contributing to oltipraz-induced expression of the phase II metabolism enzymes. Oltipraz is a bifunctional inducer, modulating both phase I and II drug-metabolizing enzymes to enhance carcinogen detoxification. ER -