Mo1102 Mechanisms of Stress-Induced Intestinal Barrier Dysfunction in the Porcine Intestine

Abstract

Pathophysiologic and clinicalmanifestations of stress-induced intestinal disorders are initiated by disturbances in intestinal barrier function. Corticotropin releasing factor (CRF) receptor signaling pathways have been shown to be a central pathway by which stress mediates its deleterious effects on the intestinal barrier; however, the precise mechanisms remain poorly understood. In addition, few studies exist that utilize translational large animal models to study CRF pathways in intestinal dysfunction. Here we utilized In Vivo and ex vivo porcine models to investigate the mechanism of intestinal barrier dysfunction mediated by CRF. To determine the role of CRF signaling in stress-induced barrier dysfunction, 16-d old piglets were administered the dual CRF receptor 1 (CRF1)/CRF receptor 2(CRF2) antagonist Astressin B (30 μg/kg), 30 min prior to subjecting pigs to early weaning stress. At 24 h post-weaning stress, ileum was harvested and mounted on Ussing chambers for measurement of intestinal barrier function as determined by transepithelial electrical resistance (TER) and mucosalto-serosal flux of 3H-mannitol. Weaning stress caused significant reductions (p<0.05) in TER and elevations (p<0.01) in 3H-mannitol flux in control pigs; however, pre-treatment with Astressin B ameliorated deleterious changes in barrier function in weaned pigs. In an ex vivo Ussing chamber model, application of CRF to porcine ileum caused elevations in FITC dextran (4 kDa) flux that were blocked by pre-treating tissues with the CRF1 antagonist antalarmin and the CRF1/CRF2 antagonist Astressin B. Application of the selective CRF1 agonist stressin1 to porcine ileum increased FD4 flux and reduced TER compared with CRF and vehicle treatments (p<0.05). CRF and stressin1 were shown to induce mast cell activation and release of mast cell-derived TNF-α and tryptase. CRF and stressin1 mediated increases in FD4 flux were inhibited by pre-treating tissues with protease inhibitors and anti-TNF-α antibodies. These studies demonstrate that in the porcine ileum, stress induces increases in paracellular permeability that is mediated by CRF1. This pathway involves the release of mast cell-derived proteases and TNF-α that contribute to disturbances in intestinal barrier function.