Figure 5.

5-HT induces XRE reporter activity in a SERT-dependent manner. Caco-2 cells were treated beginning 24 h post-transfection. (a) Caco-2 cells were transiently co-transfected with pGudLuc7.5 luciferase XRE-reporter or pGL3-basic along with a β-gal mammalian expression plasmid (CMV-β) by lipofectamine. Cells were treated with 5-HT (10 μM), AhR ligand 6-formylindolo[3,2b]carbazole (FICZ) (10 nM), or vehicle (Con) for 24 h in serum-free medium. Reporter activity was measured by luciferase assay. Assays were performed using quadruplicate wells for each treatment and values were normalized to β-gal activity. Results are expressed as fold-change activity of untreated (Con) pGL3-basic transfected cells. Data analyzed by 1-way ANOVA followed by Tukey’s multiple comparisons test (n = 3). *P < 0.05, ****P < 0.0001 vs. untreated cells transfected with pGudLuc7.5 ^##P < 0.05 vs. pGL3-basic. (b) Caco-2 cells were transiently co-transfected with pGudLuc7.5 Luciferase XRE-reporter, CMV- β, and either a SERT overexpression vector or empty vector (EV) by Amaxa electroporation. Cells were treated with 5-HT (10 μM) for 24 h in serum-free medium. Reporter activity was measured by luciferase assay. Assays were performed using quadruplicate wells for each treatment and values were normalized to β-gal. Results are expressed as fold-change over the activity of untreated cells. Data analyzed by unpaired 2-tailed Student’s t-test (n = 4). *P < 0.05 vs. EV. Red circle = untreated, blue square = 5-HT, black diamond = FICZ.