Effects of probiotics and commensals on epithelial barrier function

Increased permeability ofthe intestinal epithelium is now recognized as having a role in the pathophysiology of gastrointestinal diseases and is observed in inflammatory bowel disease, irritable bowel disease and celiac disease. Hyperpermeability of the intestinal epithelium is also associated with diabetes, diarrhea in HIV infected patients, atopic eczema and altered sensitivity to food-allergens. Consequently, modulation of epithelial permeability is an interesting target for novel therapeutic or preventative treatments against a range of diseases. Evidence for probiotic effects on barrier function has been demonstrated in humans as well as animal models of chronic stress, DSS-colitis, hemorrhagic shock and sepsis although the mechanisms have not been fully elucidated. Studies with polarised cell models of epithelium suggests that particular strains of probiotics can protect against barrier dysfunctions caused by invasive pathogens or pro-inflammatory cytokines. Here we review recent evidence for the role of innate signalling in the intestinal epithelium and the regulation of tight junction protein composition as probiotic mechanisms to enhance mucosal integrity.