The P2X7 Receptor Promotes Intestinal Fibrosis by Modulating the Gut Microbiota and the Inflammasome.

Abstract

BACKGROUND & AIMS: Considering the role of the P2X7 receptor in intestinal inflammation, we examined its potential involvement in fibrosis development. METHODS: Colonic biopsies from patients with inflammatory bowel disease (IBD) were analyzed via double immunofluorescence under confocal microscopy. Colon fibroblasts were used to analyze P2X7 receptor modulation and chemotaxis. Experimental chronic colitis was induced with 3 cycles of oral dextran sodium sulfate (DSS) treatment in P2X7and P2X7mice. The mice were evaluated via follow-up video endoscopy with an endoluminal ultrasound biomicroscopic (eUBM) system, histological scoring, immunohistochemistry, cytokine measurement in colon explants, gene expression analysis of P2X7 signaling targets via quantitative real-time polymerase chain reaction (qRT-PCR), and microbiome composition analysis. RESULTS: Colocalization studies revealed a greater density of P2X7/alpha smooth muscle actin (&#x3b1;-SMA)cells in colon sections from patients than in those from controls, especially in patients with Crohn's disease (P < .05). Activation of the adenosine triphosphate (ATP)-P2X7 pathway in human fibroblasts increased cell migration, calcium influx, and collagen production. Video colonoscopy with the eUBM system revealed significantly more inflammation, with greater wall thickness and stiffness, in P2X7mice than in P2X7and P2X7mice treated with A740003 (a P2X7-selective inhibitor). P2X7mice exhibited increased caspase-1 and NLRP3 expression, as well as nuclear factor &#x3ba;B (NF-&#x3ba;B) and extracellular signal-regulated kinase (ERK) activation, accompanied by decreased peroxisome proliferator-activated receptor gamma (PPAR&#x3b3;) expression. In the supernatants of colon explants, tumor necrosis factor (TNF)-&#x3b1;, interleukin (IL)-1&#x3b2;, interferon (IFN)-&#x3b3;, transforming growth factor (TGF)-&#x3b2;, IL-10, and collagen production were increased in P2X7mice. Various microbial changes were observed in P2X7and P2X7mice. CONCLUSIONS: Regulatory mechanisms downstream of P2X7, combined with signals from a dysbiotic microbiota, activate intracellular signaling pathways and the inflammasome, leading to intestinal inflammation and promoting fibrogenesis.