Fig. 4.

Enhancement of aryl hydrocarbon receptor (AhR) binding to the cytochrome P450 (CYP) 1A1 and 1B1 promoters and augmentation of CYP1A1 promoter activity by acute ethanol (EtOH) exposure. (A) Mouse hepatic stellate cells (MHSCs) were treated with 0, 100, or 200 mM of EtOH or 10 nM benzo(a)pyrene (BaP) for 6 hours. AhR binding to the CYP1A1 or 1B1 promoter was assessed by chromatin immunoprecipitation analysis. Genomic DNA bound to AhR was recovered from the immunoprecipitant and quantified by real-time reverse transcription polymerase chain reaction (RT-PCR) using primer pairs specific for the CYP1A1- and 1B1-xenobiotic response element regions. The DNA-binding activity of AhR was expressed as the ratio of the PCR product from the immunoprecipitant to that from the input control. (B) The CYP1A1 promoter activity was determined by luciferase assays. MHSCs were transfected with a CYP1A1 promoter-luciferase reporter plasmid, and then treated with EtOH at the indicated concentrations for 6 hours. Luciferase activity was measured using a luminescence assay and expressed relative to the protein level. Values represent the mean ± SEM of 5 independent experiments. *p < 0.05 versus cells without EtOH treatment.