Figure 2.

Induction of CYP1A1 mRNA is independent of 5-HTRs and MAOs but is dependent upon SERT. Caco-2 cells were plated at low density and allowed to differentiate for 10–14 d in medium containing 20% serum before treatments were performed without transfection (a,b,f). When transfection was performed, Caco-2 cells were treated beginning 24 h post-transfection (c–e). (a) Caco-2 cells were treated with vehicle (Con) or 5-HTR antagonists tropisetron or asenapine apically for 1 h before co-treatment with 5-HT for 8 h in serum-free medium (n = 3). (b) Caco-2 cells were treated with vehicle (Con) or fluoxetine (1 μM) for 4 d in serum-containing medium before co-treatment of 5-HT (10 μM) with fluoxetine (1 μM) for 12 h in serum-free medium (n = 4). (c) Caco-2 cells were transiently transfected with SERT overexpression plasmid or empty vector (EV) by Amaxa electroporation before treatment with 5-HT (10 μM) for 24 h (n = 5). (d,e) Caco-2 cells were transfected with EV or SERT by Amaxa electroporation before treatment with vehicle (Con) or AhR ligands 3-methylindole (3-MI, 100 μM), tryptamine (TRYP, 100 μM), or 6-formylindolo[3,2b]carbazole (FICZ, 10 nM) for 24 h in serum-free medium. (d) depicts CYP1A1 expression when transfected with EV while (e) depicts the ratio of CYP1A1 induction between SERT and EV transfected cells, with no difference observed for any treatments other than 5-HT (n = 3). (f) Caco-2 cells were treated with vehicle (Con) or MAO inhibitor pargyline for 1 h before co-treatment with 5-HT for 8 h in serum-free medium (n = 3). Data represent the relative expression of CYP1A1 mRNA quantified by qPCR. Data analyzed by 1-way (a–c,f) or 2-way (d,e) ANOVA followed by Tukey’s (a–c,f) or Bonferroni’s (d,e) multiple comparisons test. *P < 0.05, **P < 0.01, ****P < 0.0001 vs. untreated. ^###P < 0.001 vs. no fluoxetine or EV. Red circle = untreated, blue square = 5-HT, green triangle = 3-MI, yellow triangle = TRYP treated, black diamond = FICZ.