Peptidoglycan derived from Lactobacillus rhamnosusMLGA up-regulates the expression of chicken β-defensin 9 without triggering an inflammatory response

Defensins are critical components of the innate immune system and play an important role in the integration of innate and adaptive immune responses. Although information on the immunomodulatory properties of peptidoglycan from bacteria is abundant, little is known about the β-defensin induction effect of peptidoglycan from the probiotic Lactobacillus. This study investigated the effect of intact peptidoglycan from L. rhamnosusMLGA on the induction of avian β-defensin 9 in chicken immune cells and intestinal explants. Peptidoglycan from Lactobacillus rhamnosusMLGA dose dependently promoted avian β-defensin 9 mRNA expression in chicken PBMCs, splenocytes, thymocytes, hepatocytes, and chicken embryo jejunum, ileum, and cecum explants and increased the capacity of PBMC or splenocyte lysates to inhibit the growth of SalmonellaEnteritidis. In contrast to the effect of L. rhamnosusMLGA-derived peptidoglycan, peptidoglycan derived from pathogenic Staphylococcus aureusreduced avian β-defensin 9 mRNA expression in chicken PBMCs and splenocytes. The inducible effect of peptidoglycan from L. rhamnosusMLGA on avian β-defensin 9 expression in PBMCs and splenocytes was observed without activation of the expression of associated pro-inflammatory cytokines IL-1β, IL-8, and IL-12p40, whereas these cytokine expressions were suppressed by peptidoglycan hydrolysate obtained by lysozyme digestion. The results of the present study show the capability of peptidoglycan derived from L. rhamnosusMLGA to induce the antimicrobial peptide defensin while simultaneously avoiding the deleterious risks of an inflammatory response.