Effects Of Peptidoglycan Derived From Lactobacillus Rhamnosus On Avian Antimicrobial Peptides Gene Expression And Signaling Pathway In Chicken Peripheral Blood Monocytes

Antimicrobial peptides are important components of innate immunity. In addition to their broad-spectrum direct microbicidal activity, antimicrobial peptides also act as immune effector molecules between cells to play multiple functions in immune defense against infection. Defensin and Cathelicidins are the two main families of antimicrobial peptides found in animals, and play an important role in disease resistance. The cell wall peptidoglycan extracted from probiotic Lactobacillus rhamnosus, plays an important role in immune regulation especially in promoting the expression of antimicrobial peptides. However, the mechanisms of action by which peptidoglycan promotes the expression of antimicrobial peptides and then improves innate and adaptive immune responses has not yet been fully elucidated. In this experiment, the effects of whole peptidoglycan derived from Lactobacillus rnamnosus MLGA on avain ?-defensin 9(AvBD9) and Cathelicidin-B1(Cath-B1) gene expressions in peripheral blood monocytes of chicken were investigated. Moreover, the quantitative RT-PCR analysis was used to determine the expressions of genes mediating in antimicrobial peptides expression. In addition, anti-TLR2 antibody, specific inhibitors of molecules in thesignaling pathway were used to elucidate the signaling pathway involved in induction of AvBD9 and Cath-B1 expressions by peptidoglycan. The results showed as follows:(1) Peptidoglycan derived from Lactobacillus rhamnosus MIGA at various concentrations used in this experiment promoted AvBD9 and Cath-B1 mRNA expressions with different potential in peripheral blood monocytes of chicken. A 200 ?g/ml of peptidoglycan had the strongest potential in inducing AvBD9 expression and 150?g/ml in inducing Cath-B1 expression.(2) As compared with the control group, 200 ?g/ml of peptidoglycan significantly upregulated TLR2, NALP3(P?0.05)and NOD-like receptors 1(NOD1)(P?0.01) mRNA expression in peripheral blood monocytes of chicken.(3) AvBD9 and Cath-B1 mRNA expression were suppressed and the ratio of phosphorylated NF-?B p65, P38, JNK proteins to respective non-phosphorylated ones were significantly decreased(P <0.05) when TLR2 was blocked by anti-TLR2 specific antibody or NOD1 was inhibited by NOD1 inhibitor.(4) AvBD9 and Cath-B1 induction in chicken peripheral blood monocytes by Lactobacillus rhamnosus-derived WPG was reduced by pretreatment with PDTC, a selective inhibitor of NF-?B, or SP600125, a selective inhibitor of c-Jun N-terminal kinase(JNK), or SB203580, a selective inhibitor of p38 MAPK. Furthermore, the inhibition extent of AvBD9 and Cath-B1 expression by PDTC was bigger than by SP600125 or SB203580. However, AvBD9 and Cath-B1 expressions were increased by SCH772984, a selective inhibitor of ERK1/2 MAPK.In conclusion, Lactobacillus rhamnosus MLGA-derived peptidoglycan could promote AvBD9 and Cath-B1 gene expression in chicken peripheral blood monocytes. The induction of AvBD9 and Cath-B1 mRNA expression by Lactobacillus rhamnosus-derived peptidoglycan in chicken peripheral blood monocytes was mediated by TLR2 or NOD1/NALP3. Lactobacillus rhamnosus MLGA derived-peptidoglycan exerts beneficial effects to the host and enhances the innate defense against infection through the upregulation of antimicrobial peptides such as AvBD9 and Cath-B1 expression mediated by NF-?B/MAPK signaling pathway.