Fig. 4

The bacterial supernatants promote 5-HT synthesis in RIN-14B cells. A The effect of 1%, 5%, and 10% bacterial supernatant on cell viability. The effect of 10% bacterial supernatant on TPH1 (B), IDO1 (C), and SERT (D) mRNA expression. E The Western blot strip of β-actin, TPH1, and IDO1. The effect of 10% bacterial supernatant on TPH1 (F) and IDO1 (G) protein level. The effect of 10% bacterial supernatant on cell supernatant (H) and intracellular (I) 5-HT concentration. All values are mean ± SEM. n = 4–6 per group. The one-way ANOVA and multiple comparisons in Fisher’s LSD test were performed while asterisks mean statistically significant difference: ^*P < 0.05, ^**P < 0.01. TPH1: Tryptophan hydroxylase 1; IDO1: Indoleamine 2,3-dioxygenase 1; SERT: Serotonin reuptake transporter