Lactobacillus delbrueckii ssp. lactis R4 prevents Salmonella typhimurium SL1344-induced damage to tight junctions and adherens junctions.

Cell junctions are the gatekeepers of the paracellular route and defend the mucosal barrier. Several enteropathogenic bacteria can invade intestinal epithelial cells by targeting and damaging cell junctions. It is not well understood how Salmonella typhimurium is able to overcome the intestinal barrier and gain access to the circulation, nor is it understood how Lactobacillus prevents the invasion of S. typhimurium. Therefore, we sought to determine whether infection with S. typhimurium SL1344 could regulate the molecular composition of cell junctions and whether Lactobacillus delbrueckii ssp. lactis R4 could affect this modification. Our data demonstrated that infection of Caco-2 cells with S. typhimurium over 2 h resulted in a redistribution of claudin-1, ZO-1, occluding, and E-cadherin. Western blot analysis of epithelial cell lysates demonstrated that S. typhimurium could decrease the expression of cell junction proteins. However, L. delbrueckii ssp. lactis R4 ameliorated this destruction and induced increased expression of ZO-1, occludin, and E-cadherin relative to the levels in the control group. The results of these experiments implied that S. typhimurium may facilitate its uptake and distribution within the host by regulating the molecular composition of cell junctions. Furthermore, Lactobacillus may prevent the adhesion and invasion of pathogenic bacteria by maintaining cell junctions and the mucosal barrier.