title: Interferon-γ is increased in the gut of patients with irritable bowel syndrome and modulates serotonin metabolism.
abstract: Mucosal immune activation and altered serotonin metabolism participate in the pathophysiology of irritable bowel syndrome (IBS). However, the reciprocal interplay between these two systems remains unknown. We evaluated the expression and release of interferon (IFN)-γ from the colonic mucosa of patients with IBS and its impact on serotonin reuptake transporter (SERT) gene expression in Caco-2 cells. qPCR was used to evaluate IFN-γ gene expression in colonic mucosal biopsies, whereas IFN-γ protein amount was assessed by ELISA. Colonic T box expressed in T cells (T-bet) and phosphorylated signal transducer and activator of transcription 4 protein amount were evaluated by Western blot. The impact of colonic mucosal mediators on SERT gene expression was evaluated in Caco-2 cells using qPCR. IFN-γ receptor was silenced in Caco-2 cells to determine the effect of IFN-γ released by mucosal biopsies. Compared with asymptomatic controls (ACs), the expression of IFN-γ gene and its transcription factor T-bet were markedly increased in the colonic mucosa of patients with IBS. Compared with ACs, IFN-γ protein tissue levels and its release by mucosal biopsies were significantly increased in IBS. The exposure of Caco-2 cells to IBS supernatants induced a significant decrease in SERT gene expression, independently of IBS subtypes, compared with AC mucosal supernatants. In Caco-2 cells, IFN-γ receptor silencing reversed the reduction of SERT expression evoked by IBS supernatants vs. nonsilenced cell lines. IFN-γ gene, its transcription factor T-bet, IFN-γ protein expression, and its release are increased in the colonic mucosa of patients with IBS and downregulate SERT gene expression in vitro. These results suggest that IFN-γ downregulates SERT expression, hence likely playing a role in altered serotonin metabolism of patients with IBS.
authors.affiliation: Department of Medical and Surgical Sciences and Center for Applied Biomedical Research (CRBA), University of Bologna, Bologna, Italy;
authors.forename: Maria Raffaella
authors.initials: MR
authors.lastname: Barbaro
authors.affiliation: First Department of Internal Medicine, S. Matteo Hospital Foundation, University of Pavia, Pavia, Italy;
authors.forename: Antonio
authors.initials: A
authors.lastname: Di Sabatino
authors.affiliation: Department of Medical and Surgical Sciences and Center for Applied Biomedical Research (CRBA), University of Bologna, Bologna, Italy;
authors.forename: Cesare
authors.initials: C
authors.lastname: Cremon
authors.affiliation: First Department of Internal Medicine, S. Matteo Hospital Foundation, University of Pavia, Pavia, Italy;
authors.forename: Paolo
authors.initials: P
authors.lastname: Giuffrida
authors.affiliation: Department of Hematology, Oncology and Laboratory Medicine, University of Bologna, Bologna, Italy.
authors.forename: Michelangelo
authors.initials: M
authors.lastname: Fiorentino
authors.affiliation: Department of Hematology, Oncology and Laboratory Medicine, University of Bologna, Bologna, Italy.
authors.forename: Annalisa
authors.initials: A
authors.lastname: Altimari
authors.affiliation: Department of Medical and Surgical Sciences and Center for Applied Biomedical Research (CRBA), University of Bologna, Bologna, Italy;
authors.forename: Lara
authors.initials: L
authors.lastname: Bellacosa
authors.affiliation: Department of Medical and Surgical Sciences and Center for Applied Biomedical Research (CRBA), University of Bologna, Bologna, Italy;
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Stanghellini
authors.affiliation: Department of Medical and Surgical Sciences and Center for Applied Biomedical Research (CRBA), University of Bologna, Bologna, Italy; giovanni.barbara@unibo.it.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Barbara
mesh_terms: D000328:Adult; D018938:Caco-2 Cells; D005260:Female; D041981:Gastrointestinal Tract / Q000378:metabolism*; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000378:metabolism; D043183:Irritable Bowel Syndrome / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D012313:RNA / Q000096:biosynthesis / Q000302:isolation & purification; D034622:RNA Interference; D050797:STAT4 Transcription Factor / Q000096:biosynthesis / Q000235:genetics; D012701:Serotonin / Q000378:metabolism*; D050486:Serotonin Plasma Membrane Transport Proteins / Q000378:metabolism; D020825:T-Box Domain Proteins / Q000096:biosynthesis / Q000235:genetics
chemical_list: C493230:SLC6A4 protein, human; D050797:STAT4 Transcription Factor; C494090:STAT4 protein, human; D050486:Serotonin Plasma Membrane Transport Proteins; D020825:T-Box Domain Proteins; D012701:Serotonin; D012313:RNA; D007371:Interferon-gamma
keywords: T box expressed in T cells; gut mucosa; interferon-γ; irritable bowel syndrome; serotonin reuptake transporter