The Mechanism Of IFN-? On The Increased Susceptibility Of Bovine Mammary Epithelial Cells To Staphylococcus Aureus

Cow mastitis is often accompanied by elevated level of IFN-?.our previous study found that IFN-? increased susceptibility of bovine mammary epithelial cells(BMECs)toStaphylococcus aureus(S.aureus),however,the mechanisms are poorly understood.Therefore,in this study we established gene expression profiles of BMECs,which treatment with or without IFN-?,using transcriptome sequencing,and then obtained differentially expressed genes(DEGs).The present study is mainly aimed to evaluate the effects and underling molecular mechanisms of IFN-? on susceptibility to S.aureus in vitro and in vivo.The transcriptome library about IFN-? treatment for BMECs was successfully constructed by high-throughput sequencing.The enriched pathways included the cell proliferation and differentiation,the formation and maintenance of tissues and organs,the regulation of nucleic acid metabolism and immune responses related signaling pathways.The genes that were differentially expressed in the DEGs were consistent with the q PCR and Western Blot results,revealing that IFN-? promoted the expression of chemokine ligand 5(Chemokine(C-C motif)ligand 5,CCL5)mRNA and protein levels.We established the S.aureus infection model of BMECs to further explore the effects of IFN-? on the susceptibility of BMECs to S.aureus.The results revealed that S.aureus adhesion to and invasion of BMECs increased significantly after cells treatment with IFN-?.And the adhesion of S.aureus to BMECs was increased dramaticallyby up-regulating CCL5,while the increased susceptibility of BMECs to S.aureus could be blocked by specific antibodies against CCL5 and Toll-like receptor 4 inhibitor(TAK-242),indicating that the increased adhesion and invasion depended on IFN-?-induced up-regulation of CCL5.Furthermore,IFN-? treatment prior to S.aureus infection significantly increased the number of S.aureus in mammary glands of mice as well as CCL5 expression in mouse mammary glands.However,the ability of S.aureus to plant in mice mammary gland and spead to blood induced by IFN-? was significantly inhibited by TAK-242.These results suggested that IFN-? promoted CCL5 expression on the BMECs surface and contributed to the infection of mammary gland in vitro/in vivo,and this process was regulated by TLR4 signal pathway.In our previous study,we found that IFN-? increased arginine depletion which leading to autophagy in BMECs.In order to determine the effect of IFN-? on arginine metabolism and the role of arginine onthe susceptibility of BMECs to S.aureus,the liquid chromatography-mass spectrometry(LC-MS)was used and the result confirmed that IFN-? promoted arginine depletion,and the ability of S.aureus to adhere to and invade into BMECs was significantly inhibited by arginine.In this study,the protein level of CCL5 induced by IFN-? was decreased significantly after cells treatment with arginine.Furthermore,arginine treatment prior to S.aureus infection significantly decreased the number of S.aureus in mammary glands of mice,and arginine treatment reduced the lesions and the typical signs of mastitis in mammary gland.Our results found that the increased level of IFN-? acted as an “accomplice” to S.aureus,causing cow mastitis in vitro/in vivo.Therefore,this study provides a basis for controlling mastitis by managing nutrition,which is crucial for preventing and treating mastitis in dairy cows.