Vasoactive intestinal polypeptide regulates barrier function via mast cells in human intestinal follicle-associated epithelium and during stress in rats

Background Vasoactive intestinal polypeptide (VIP) has been implicated as a regulator of intestinal barrier function and inflammation. Our aim was to elucidate the role of VIP in follicle-associated epithelium (FAE) and villus epithelium (VE) permeability following stress in rats and on human intestinal barrier function. Methods Rats were injected intraperitoneally (i.p.) with VIP receptor-antagonists (anti-VPACs), a mast cell stabilizer, doxantrazole (DOX), or NaCl, and submitted to acute water avoidance stress. Ileal segments were mounted in Ussing chambers to assess 51chromium-edta (51Cr-edta) and Escherichia (E.) coli (strain K-12) permeability. Rat ileal and human ileal and colonic segments were exposed to VIP +/- anti-VPACs or DOX. An in vitro co-culture model of human FAE was used to study epithelial-VIP effects. VIP/VPACs distribution was assessed by microscopy. Key Results Stress increased 51Cr-edta and E.coli permeability in VE and FAE. The increases were abolished by i.p. injection of DOX or anti-VPACs. Ileal VIP-exposure ex vivo increased bacterial passage and this was reduced by DOX. In human FAE ex vivo, VIP treatment doubled bacterial uptake, which was normalized by DOX or anti-VPACs. No barrier effects were observed in human colonic tissue. VPACs were found in rat and human ileal follicles, with partial mast cell co-localization. The co-culture model confirmed VIPmast cellepithelial interactions in the regulation of barrier function. Conclusions & Inferences Stress affects the FAE barrier by mechanisms involving VIP and VPACs on mucosal mast cells. We suggest a regulatory role for VIP in the control of ileal permeability that may be relevant to bacterialepithelial interactions in stress-related intestinal disorders.