Lactobacillus brevis KB290 enhances IL-8 secretion by Vibrio parahaemolyticus-infected Caco-2 cells

Vibrio parahaemolyticus in uncooked seafood causes acute gastroenteritis. The microorganism has two sets of type III secretion systems and two hemolysins. When it injects its effector proteins into a host cell via type III secretion system 1, one of the type III secretion systems induces secretion of interleukin (IL)-8, a proinflammatory chemokine, through the phosphorylation of ERK 1/2 and p38 MAPK. Although probiotics have beneficial effects on hosts and can help control some infectious diseases, there is little research on the efficacy of probiotics in V. parahaemolyticus infection. Here we pretreated V. parahaemolyticus-infected human intestinal epithelial cells with heat-killed Lactobacillus brevis KB290, a probiotic isolated from fermented vegetables (traditional Japanese pickles) and utilized as an ingredient of beverages and supplementary foods, and demonstrated its efficacy in enhancing IL-8 secretion from V. parahaemolyticus-infected cells. Among the three heat-killed lactic acid bacterial strains we tested, L. brevis KB290 induced the highest level of IL-8 secretions in the infected cells. Relative to control cells (Caco-2 cells pretreated with PBS), V. parahaemolyticus-infected Caco-2 cells pretreated with heat-killed L. brevis KB290 secreted IL-8 earlier, although concentrations were similar 450min after infection. Heat-killed L. brevis KB290 pretreatment also induced earlier ERK 1/2 phosphorylation, greater p38 MAPK phosphorylation, and enhanced IL-8 mRNA expression. Heat-killed L. brevis KB290 accelerated IL-8 secretion, a host cell immune response, in V. parahaemolyticus-infected cells. We consider this to be beneficial because IL-8 plays an important defensive role against infection, and would contribute to the repair of injured epithelial cells.