A119 THE MICROBIAL METABOLITE SENSOR PREGNANE X RECEPTOR (PXR) RESTRAINS FIBROBLASTS FROM PROMOTING INTESTINAL INFLAMMATION AND FIBROSIS IN MICE. (1st March 2018)

• Record Type: Journal Article
• Authors: Flannigan, K L; Alston, L; Mani, S; Hirota, S A
• Is Part Of: Journal of the Canadian Association of Gastroenterology. Volume 1(2018)Supplement 1
• Page Start: 209
• Page End: 210
• Publication Date: 2018-03-01
• Subjects: Gastroenterology -- Periodicals; 616.33005
• DOI: 10.1093/jcag/gwy008.120
• Languages: English
• ISSNs: 2515-2084

Abstract

Abstract: Background: Fibrosis contributes to intestinal stricture and obstruction in 30–50% of Crohn's disease patients. The pathogenesis of fibrosis is incompletely understood and has virtually no effective treatments. The pregnane X receptor (PXR), a xenobiotic receptor involved in detoxification responses, has been identified as a modulator of fibrosis in hepatic stellate cells. Of the number of foreign ligands for the PXR, the tryptophan metabolite indole-3-propionic acid (IPA) produced by the intestinal commensal Clostridium sporogenes can bind to the PXR to mediate signalling events that protect intestinal barrier function. The role of the PXR in intestinal fibrosis and if microbial metabolite sensing can affect intestinal fibrotic responses is unknown. Aims: To examine the role of the PXR and its ability to sense microbial metabolites in the modulation of intestinal fibrosis. Methods: Intestinal inflammation was induced using DSS (3.5%) for 5 days followed by healing for 25 days. Fibrosis was assessed using Masson's trichrome and Sirius Red staining of colonic sections. Mouse primary colonic fibroblasts were grown from wild type (WT) and PXR-/- mice and stimulated with cytomix (TNFα, IL1β, and IFNγ) for 24 hours to assess cytokine production by Luminex. Fibroblasts were also stimulated with cytomix in the presence of the PXR agonists PCN or IPA and assessed for gene expression via qPCR. NFkB activity was assessed by Western blot for phos-p65. To examine the microbiota's role in fibrosis, after the 5-day course of DSS the microbiota was depleted for 25 days with an antibiotic cocktail (vancomycin, neomycin, metronidazole, ampicillin). C. sporogenes DNA was detected in feces using qPCR. Results: Following a 25-day recovery after DSS, WT mice demonstrated clear intestinal fibrosis. When compared to WT mice, PXR-/- mice demonstrated significantly greater levels of fibrosis. Mouse primary fibroblasts were found to express the PXR. Following stimulation with cytomix, PXR-/- fibroblasts produced dramatically higher levels of inflammatory cytokines including eotaxin, CXCL2, G-CSF, GM-CSF, IL-9, and IL-15. Importantly, PCN and the microbial metabolite IPA suppressed the expression of these cytokines. These effects in PXR-/- fibroblasts may be linked to the increased activity of NFkB that was observed both basally and after stimulation with cytomix compared to WT fibroblasts. Depletion of the microbiota supressed levels of C. sporogenes DNA in feces and exacerbated intestinal fibrosis. Conclusions: PXR signaling in intestinal fibroblast appears to be required to restrain inflammation and fibrosis. Luminal sensing of bacterial derived indoles (i.e. IPA) via PXR may be involved in this process, highlighting a xenobiotic-microbiota axis that could be targeted to prevent the intestinal fibrosis observed in Crohn's disease. Funding Agencies: CCCBeverley Phillips Rising Stars Program, The Dr. Lloyd Sutherland Investigator in IBD/GI Research, Canadian Foundation for Innovation, Canada Research Chairs Program, U.S. Department of Defense