Enhancement of Epithelial Barrier Function by Probiotics

ABSTRACT

Probiotics are microbial organisms that are administered in supplements or foods to enhance the well-being of the host. There exists substantial evidence that in a strain and dose-dependent manner, probiotics can modulate systemic and mucosal immune function, improve intestinal barrier function, alter gut microecology, and exert metabolic effects on the host. Several strains of Lactobacillus and Bifidobacterium are able to compete with pathogens for binding to intestinal epithelial cells, and can displace pathogens. Epithelial cell signalling pathways are stimulated by whole microbes, structural components, and microbial-produced metabolites. In particular, the NF-κB pathway is modulated by probiotics at many different levels with effects seen on IκB degradation and ubiquitination, proteasome function, and nuclearcytoplasmic movement of RelA through a PPAR-gamma dependent pathway. In a strain and dose-dependent manner, probiotic strains have been shown to alter tight junction protein expression and/or localization in both in vivo and in vitro models. Probiotics can also enhance gut barrier function via increased production of cytoprotective molecules such as heat-shock proteins. In addition, probiotics are able to prevent cytokine- and oxidant-induced epithelial damage by promoting cell survival. Lactobacillus GG and soluble factors (p75 and p40) released from LGG prevented epithelial cell apoptosis through activating anti-apoptotic Akt in a phosphatidylinositol-3’-kinase (PI3K)-dependent manner and inhibiting pro-apoptotic p38/MAPK activation. It is clear that host-microbial interactions at the gut mucosal surface are critical for health and overall homeostasis and probiotics may possibly be harnessed to enhance barrier function in order to maintain health and protect against disease.