<i>Lactobacillus reuteri</i> LR1 Improved Expression of Genes of Tight Junction Proteins via the MLCK Pathway in IPEC-1 Cells during Infection with Enterotoxigenic <i>Escherichia coli</i> K88

Abstract

Intestinal epithelial barrier damage disrupts immune homeostasis and leads to many intestinal disorders. <i>Lactobacillus reuteri</i> strains have probiotic functions in their modulation of the microbiota and immune system in intestines. In this study, the effects of <i>L. reuteri</i> LR1, a new strain isolated from the feces of weaning piglets, on intestinal epithelial barrier damage in IPEC-1 cells caused by challenge with enterotoxigenic <i>Escherichia coli</i> (ETEC) K88 were examined. It was found that <i>L. reuteri</i> LR1, in large part, offset the ETEC K88-induced increase in permeability of IPEC-1 cell monolayers and decreased the adhesion and invasion of the coliform in IPEC-1 cells. In addition, <i>L. reuteri</i> LR1 increased transcript abundance and protein contents of tight junction (TJ) proteins zonula occluden-1 (ZO-1) and occludin in ETEC K88-infected IPEC-1 cells, whereas it had no effects on claudin-1 and F-actin expression. Using colloidal gold immunoelectron microscopy, these effects of <i>L. reuteri</i> LR1 on ZO-1 and occludin content in IPEC-1 cells were confirmed. By using ML-7, a selective inhibitor of myosin light-chain kinase (MLCK), the beneficial effect of <i>L. reuteri</i> LR1 on contents of ZO-1 and occludin was shown to be dependent on the MLCK pathway. In conclusion, <i>L. reuteri</i> LR1 had beneficial effects on epithelial barrier function consistent with increasing ZO-1 and occludin expression via a MLCK-dependent manner in IPEC-1 cells during challenge with ETEC K88.