Lactobacillus casei prevents impaired barrier function in intestinal epithelial cells

The exact effect of probiotics on epithelial barrier function is not well understood. The aims of this study were to evaluate cytokine-induced epithelial barrier dysfunction in intestinal epithelial cells (IECs) and to study the role of probiotics in the prevention of epithelial barrier dysfunction. Caco-2 cells grown on transwell chambers were stimulated with tumor necrosis factor (TNF)-alpha or interferon (IFN)-gamma basolaterally. Probiotic, Lactobacillus casei, was added 1 h before cytokine stimulation. MAPK inhibitors were added 15 min before L. casei stimulation. The electrical resistance and paracellular permeability of Caco-2 monolayers were measured. Distribution of zonula occludens (ZO)-1 protein was assessed by immunofluorescence, and Western blot analyses for ZO-1, p-Akt, and toll-like receptor (TLR) 2 were performed. Both TNF-alpha and IFN-gamma stimulation on Caco-2 cells decreased transepithelial resistance (TER), increased epithelial permeability, and decreased ZO-1 expression of Caco-2 cells. In contrast, pretreatment of L. casei reversed the cytokine-induced dysfunction of TER, epithelial permeability, and ZO-1 expression. Reversal of cytokine-induced dysfunction of TER and intestinal permeability by L. casei was abrogated with MAPK inhibitor treatment. Lactobacillus casei stimulation on Caco-2 cells increased TLR2 and p-Akt expression. Probiotic, L. casei, prevents cytokine-induced epithelial barrier dysfunctions in IECs.