Probiotics are beneficial bacteria present in various dietary components and many of these colonize in the human
and animal intestine. In the gut probiotics help the host by assisting in maintenance of normal mucosal homeostasis.
Probiotics not only help maintain normal function of the gut mucosa, but also protect mucosa from injurious factors such
as toxins, allergens and pathogens. The beneficial effect of probiotics is mediated by multiple mechanisms, including cytoprotection,
cell proliferation, cell migration, resistance to apoptosis, synthesis of proteins and gene expression. One of
the important cytoprotective effects of probiotics in the intestinal mucosa is to strengthen the epithelial tight junctions and
preservation of mucosal barrier function. Probiotics not only enhance barrier function by inducing synthesis and assembly
of tight junction proteins, but also by preventing disruption of tight junctions by injurious factors. Bioactive factors released
by probiotics trigger activation of various cell signaling pathways that lead to strengthening of tight junctions and
the barrier function. This article reviews and summarizes the current understanding of various probiotics that are involved
in the protection of gut barrier function, highlights the cellular and molecular mechanisms involved in the protective effect
and addresses the clinical implications of probiotic supplementation.