SEBS colonized in ileal mucosa, optimized bacterial composition, improved Se level and activated TLR2-NF-kB1 signaling pathway to regulate β-defensin 1 expression
Background Both selenium (Se) and probiotic bacillus improve immunity. Beta defensin 1 (BD1), a component of intestinal mucosal immunity, could be up-regulated in dietary selenium enriched bacillus subtilis (SEBS) supplementation. SEBS was supplemented in the culture medium of mouse intestinal crypt cells and the diets of chicks to observe the effects of SEBS on BD1 in the intestine by colonization of bacillus subtilis, its recognition and signaling pathway, bacterial composition optimization,
... nd biological functions of Se. Results BD1 was formed in intestinal crypt cells and secreted into the lumen through the villi brush border. BD1 was up-regulated in distal ileum segments with SEBS and bacillus subtilis colonization. This occurred through the recognition of toll like receptor 2 and the NF-kB1 signaling pathway (TLR2-MyD88།NF-kB1), this increased expression was further enhanced with Se combination. Pro-inflammatory cytokines, TNF-α, IL-1β, and IL-6, were up-regulated with bacillus subtilis supplementation, while this up-regulation was inhibited with Se. Colonization of bacillus subtilis in distal segments of the ileum improved bacterial diversity, while reducing the number of endogenous Salmonella and lactobacilli sp. in ileal mucous membranes with SEBS supplementation. Species of unclassified Lachnospiraceae, uncultured Anaerosporobacter, Ruminococcaceae_UCG-014, Peptococcus, and Lactobacillus salivarius, and unclassified Butyricicoccus were substantial in ileal mucous membranes to promote BD1 concentration. Conclusion SECB, colonized in the ileal mucous membrane, optimized bacterial composition, enhanced BD1 secretion through activation of the TLR2-MyD88།NF-kB1 signaling pathway, and reduced pro-inflammatory factors. Our results suggest a new avenue for the combination of probiotic bacteria and essential micro-element selenium to improve intestinal mucosal immunity, increase defense against cold stress, and reduce illness incidence and mortality.