Effect Of Lipoprotein On Cytokine Expression And Its Regulation Mechanism During Staphylococcus Aureus Infection Of Neutrophil In Dairy Cows

At least one of the diseases,such as suppurative vaginal secretion,endometritis,mastitis and cervicitis,may affect dairy cows during postpartum.These diseases are caused by an inadequate immune response to bacterial infection or by a persistent inflammatory response,which can impair the health of dairy cows and thus affect their economic performance.It was found that staphylococcus aureus(S.aureus)was one of the main pathogenic bacteria causing bacterial infectious diseases in dairy cows.The occurrence of cow mastitis is mainly caused by S.aureus,and the incidence of cow vaginitis and endometritis is also closely related to S.aureus.It has been reported that S.aureus lipoprotein induces inflammatory response by recognizing TLR2,TLR4 and NLRP3 receptors on mouse macrophages.However,the recognition and regulation mechanism of neutrophils in S.aureus infected cows is not clear.In order to further study the regulation mechanism of TLR2,TLR4 and NLRP3 receptors induced by S.aureus lipoprotein in inflammatory response of dairy cows,neutrophils of dairy cows were infected with S.aureus wild strain SA113 and Staphylococcus aureus lipoprotein deficiency strain Δlgt.Fluorescence quantitative PCR,Western Blot and ELISA were used.The secretion of cytokines(IL-1β,IL-6,IL-10,IL-8)and the expression of genes and proteins of natural immune receptors(TLR2,TLR4,NLRP3)were detected.The phosphorylation levels of P38,JNK,ERK and Caspase-1were analyzed.Then,TLR2(C29),TLR4(TAK-242)and NLRP3(MCC950)receptor inhibitors were added to detect the secretion of cytokines(IL-1β,IL-6,IL-10 and IL-8),and the changes of phosphorylation levels of P38,JNK,ERK and Caspase-1 were analyzed.The results show that: Cytokines IL-1β,IL-6,IL-10,IL-8 were detected in bovine neutrophils infected with S.aureus.The expression of natural immune receptor(TLR2,TLR4,NLRP3)receptor genes and proteins,P38,JNK,ERK,caspase-1 phosphorylation levels were significantly up-regulated compared with blank control group(P<0.05).After treatment with TLR2(C29),TLR4(TAK-242)and NLRP3(MCC950)receptor inhibitors,the expression of il-1 β,IL-6,IL-10,IL-8,P38,JNK,ERK and caspase-1 phosphorylation levels were significantly inhibited(P<0.05).Studies have shown that the recognition of natural immune receptors(TLR2,TLR4,NLRP3)in bovine neutrophils infected with S.aureus leads to the occurrence of inflammatory response,and S.aureus lipoprotein is the main immune active substance that induces the activation of natural immune response by bovine neutrophils.