FIG. 5.

AhR overexpression enhances the inducing effect of 3-MC on the PON-1 gene promoter activity, and cotreatment with the AhR antagonist 7-KC partially abolishes the effect of synthetic and natural dietary compounds. (A) HuH7 cells were transiently transfected with the pPON1000-FL plasmid and cotransfected with the indicated amount of the AhR-expressing plasmid pSG5-AhR (squares) or its corresponding empty vector pSG5 (circles). Cells were treated for 48 h with 5 μM 3-MC (solid lines) or the solvent vehicle alone (0.1% DMSO; dashed lines). Firefly luciferase was assayed as described in Materials and Methods. Results are means ± SEM (n = 12). A level of 100% corresponds to the luciferase value in cells without cotransfection and treated with DMSO alone (ALU, 3.15 ± 0.79; n = 12). For each group (DMSO or 3-MC treatment; identical amounts of cotransfected plasmid were used), statistically significant differences between pSG5 and pAhR cotransfected conditions are marked with a single asterisk (P < 0.05) or a double asterisk (P < 0.01). (B) HuH7 cells were transiently transfected with the pPON1000-FL plasmid and treated for 48 h with 5 μM 3-MC, 10 μM quercetin (Querc.), 250 μM FA, or the solvent vehicle alone (0.1% DMSO). In addition, cells were treated with the AhR antagonist 7-KC (37) (20 μM) or left untreated. Firefly luciferase was assayed as described in Materials and Methods. Results are means ± SEM (n = 10). A level of 100% corresponds to the luciferase value in cells treated with DMSO alone (ALU, 2.89 ± 0.92; n = 10). For each treatment, statistically significant differences between untreated and 7-KC cotreatment conditions are marked with a single asterisk (P < 0.05) or a double asterisk (P < 0.01).