Chronological assessment of mast cell-mediated gut dysfunction and mucosal inflammation in a rat model of chronic psychosocial stress.

Life stress and mucosal inflammation may influence symptom onset and severity in certain gastrointestinal disorders, particularly irritable bowel syndrome (IBS), in connection with dysregulated intestinal barrier. However, the mechanism responsible remains unknown. Crowding is a validated animal model reproducing naturalistic psychosocial stress, whose consequences on gut physiology remain unexplored. Our aims were to prove that crowding stress induces mucosal inflammation and intestinal dysfunction, to characterize dynamics in time, and to evaluate the implication of stress-induced mast cell activation on intestinal dysfunction. Wistar-Kyoto rats were submitted to 15 days of crowding stress (8 rats/cage) or sham-crowding (2 rats/cage). We measured spontaneous and corticotropin-releasing factor-mediated release of plasma corticosterone. Stress-induced intestinal chrono-pathobiology was determined by measuring intestinal inflammation, epithelial damage, mast cell activation and infiltration, and intestinal barrier function. Corticosterone release was higher in crowded rats throughout day 15. Stress-induced mild inflammation, manifested earlier in the ileum and the colon than in the jejunum. While mast cell counts remained mostly unchanged, piecemeal degranulation increased along time, as the mucosal content and luminal release of rat mast cell protease-II. Stress-induced mitochondrial injury and increased jejunal permeability, both events strongly correlated with mast cell activation at day 15. Taken together, we have provided evidences that long-term exposure to psychosocial stress promotes mucosal inflammation and mast cell-mediated barrier dysfunction in the rat bowel. The notable resemblance of these findings with those in some IBS patients, support the potential interest and translational validity of this experimental model for the research of stress-sensitive intestinal disorders, particularly IBS.

Host responses to intestinal microbial antigens in gluten-sensitive mice.

BACKGROUND AND AIMS: Excessive uptake of commensal bacterial antigens through a permeable intestinal barrier may influence host responses to specific antigen in a genetically predisposed host. The aim of this study was to investigate whether intestinal barrier dysfunction induced by indomethacin treatment affects the host response to intestinal microbiota in gluten-sensitized HLA-DQ8/HCD4 mice. METHODOLOGY/PRINCIPAL FINDINGS: HLA-DQ8/HCD4 mice were sensitized with gluten, and gavaged with indomethacin plus gluten. Intestinal permeability was assessed by Ussing chamber; epithelial cell (EC) ultra-structure by electron microscopy; RNA expression of genes coding for junctional proteins by Q-real-time PCR; immune response by in-vitro antigen-specific T-cell proliferation and cytokine analysis by cytometric bead array; intestinal microbiota by fluorescence in situ hybridization and analysis of systemic antibodies against intestinal microbiota by surface staining of live bacteria with serum followed by FACS analysis. Indomethacin led to a more pronounced increase in intestinal permeability in gluten-sensitized mice. These changes were accompanied by severe EC damage, decreased E-cadherin RNA level, elevated IFN-gamma in splenocyte culture supernatant, and production of significant IgM antibody against intestinal microbiota. CONCLUSION: Indomethacin potentiates barrier dysfunction and EC injury induced by gluten, affects systemic IFN-gamma production and the host response to intestinal microbiota antigens in HLA-DQ8/HCD4 mice. The results suggest that environmental factors that alter the intestinal barrier may predispose individuals to an increased susceptibility to gluten through a bystander immune activation to intestinal microbiota.