Abstract
BackgroundEnterotoxigenic Escherichia coli (ETEC) K88 commonly colonize in the small intestine and keep releasing enterotoxins to impair the intestinal barrier function and trigger inflammatory reaction. Although Lactobacillus salivarius (L. salivarius) has been reported to enhance intestinal health, it remains to be seen whether there is a functional role of L. salivarius in intestinal inflammatory response in intestinal porcine epithelial cell line (IPEC-J2) when stimulated with ETEC K88. In the present study, IPEC-J2 cells were first treated with L. salivarius followed by the stimulation of ETEC K88 for distinct time period. ETEC K88 adherent status, pattern recognition receptors (PRRs) mRNA, mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) activation, the release of pro-inflammation cytokines and cell integrity were examined.ResultsAside from an inhibited adhesion of ETEC K88 to IPEC-J2 cells, L. salivarius was capable of remarkably attenuating the expression levels of interleukin (IL)-1β, tumor necrosis factor-α (TNF-α), IL-8, Toll-like receptor (TLR) 4, nucleotide-binding oligomerization domain (NOD)-like receptor pyrin domain-containing protein (NLRP) 3 and NLRP6. This alternation was accompanied by a significantly decreased phosphorylation of p38 MAPK and p65 NF-κB during ETEC K88 infection with L. salivarius pretreatment. Western blot analysis revealed that L. salivarius increased the expression levels of zona occludens 1 (ZO-1) and occludin (P < 0.05) in ETEC K88-infected IPEC-J2 cells. Compared with ETEC K88-infected groups, the addition of L. salivarius as well as extra inhibitors for MAPKs and NF-κB to ETEC K88-infected IPEC-J2 cells had the capability to reduce pro-inflammatory cytokines.ConclusionsCollectively, our results suggest that L. salivarius might reduce inflammation-related cytokines through attenuating phosphorylation of p38 MAPK and blocking the NF-κB signaling pathways. Besides, L. salivarius displayed a potency in the enhancement of IPEC-J2 cell integrity.
Highlights
Enterotoxigenic Escherichia coli (ETEC) K88 commonly colonize in the small intestine and keep releasing enterotoxins to impair the intestinal barrier function and trigger inflammatory reaction
Inhibited adhesion of ETEC K88 to IPEC-J2 cells The adhesion of ETEC K88 to L. salivarius-pretreated IPEC-J2 cells was reduced to varying degrees during the infection
Effects of L. salivarius on Toll-like receptor (TLR)- and nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs)-mediated signaling pathways To investigate the effects of L. salivarius on the inflammatory process triggered in ETEC K88-challenge Intestinal porcine epithelial cell line (IPECJ2) cells, mRNA levels of TLRs and NLRs were basically detected in three different groups, namely the group of IPEC-J2 cells treated with ETEC K88 alone, the group of cells preincubated with L. salivarius before ETEC K88 infection and the control group without any stimulation
Summary
Enterotoxigenic Escherichia coli (ETEC) K88 commonly colonize in the small intestine and keep releasing enterotoxins to impair the intestinal barrier function and trigger inflammatory reaction. A large number of studies have shown that Lactobacillus, an extensively used species both in humans and animals [2, 3], is widely known for its capability to improve intestinal health and promote growth performance. This improvement could be obtained by preventing other pathogenic bacteria from attaching to the intestine [4, 5], alleviating existed intestinal damage [6], restoring impaired intestinal barrier [7] and enhancing inadequate immune system [8]. The exact mechanisms concerning L. salivarius on health modulation, such as inflammatory response and immunology regulation, have not yet been elucidated
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