The Effect And Regulation Mechanism Of Se On The Mastitis Of Staphylococcus Aureus Infection

Mastitis is a common disease with serious harm in dairy cows.No effective vaccine was produced for the prevention of this disease.The antibiotic was commonly used for mastitis treatment.The pathogen infection is a major etiology of mastitis.There was a variety of microorganisms,including viruses,parasites,mycoplasma,fungi and bacteria,and so on.It was shown that bacterial infection was the main reason for inducing mastitis.Staphylococcus aureus(S.aureus)is one of the main pathogenic bacteria of dairy cow mastitis.S.aureus induced mastitis should led to the decrease of the amount of lactation,affect the quality of dairy products.Although the vaccine and drug of prevention had research and development,there was no very effective product and specific medicine treatment.How to effectively control S.aureus mastitis has become an important task for vet.S.aureus bacteria can activate the innate or natural immunity,promoting the disease resistance of the body.The S.aureus also escape the host's immune response to save themselves.The clinical investigation found that it was not induced mastitis with S.aureus infection in all cows.The occurrence of S.aureus induced mastitis is close relation with the body's immune.The energy metabolism was enhanced in the postpartum lactation of cows.If feed poor quality or nutritional imbalance in the postpartum lactation,it will causes the cow lowered immunity,reducing defense ability against S.aureus,and proning severe inflammatory injury with mastitis.Cows were the selenium(Se)deficiency of critical state for a long time,which could increase suffering from mastitis,endometritis and retained placenta.Se deficiency is directly related to the occurrence of early lactation mastitis,and increasing the intake of Se can enhance the phagocytosis and reduce the occurrence of mastitis.The prevalence of S.aureus induced mastitis was negatively correlated to the level of Se content in milk.Fodder with adding Se can decrease the pathogen infection and reduce high somatic cell count of milk in early lactation,significantly reducing the incidence of mastitis.The present study was aim to analyze the effects and potential mechanisms of Se on the S.aureus induced mastitis via the perspective of local immune regulation of Se on the mammary gland.In the present study,the experimental basal diets was obtained from Se deficiency,and then make different Se concentrations of food fed to mice.The S.aureus suspension was injected via teat canal to induce mastitis.In present study,the result showed,S.aureus had induced serious injury to mammary gland,damaging the structure of the breast tissue and lactation function.Se deficiency exacerbated the inflammation of S.aureus infection in mammary gland.But the selenium-rich feeding mice inflammation changes relatively slight.It was preliminary judgment that Se play a role in the process of S.aureus induced mastitis.Se deficiency promoted inflammation,but selenium-rich reduce inflammation.In order to further improve our results,the inflammatory cytokines was analyses.The results showed the productions of IL-1?,TNF-?,IL-6,12,IFN-? and NO were significantly increased in infection of S.aureus,and the Se deficiency were lead to a burst of S.aureus-stimulated proinflammatory cytokines,inhibiting the IL-10 expression.Se-enriched feeding can inhibit secretion of proinflammatory factor,increase anti-inflammatory factor secretion.The effects of different Se concentrations on the mammary gland epithelial cells were consistent with the tissues results.The S.aureus were recognition with activation of TLR2 signaling mediates immune cell activation in various systems.Productions of TNF-?,IL-1? and IL-6 are modulated by the NF-?B and MAPK pathways.To further characterize the nature of Se on cytokine production,the effects of Se on TLR2 and the expressions of NF-?B and MAPKs signal path were examined.The results showed once Se deficiency mice was infected with S.aureus,the TLR2 expressions were explosive increase with out of control.Se deficiency led the phosphorylation of I?B,NF-?B,ERK,JNK and p38 to explosive increase.It had confirmed that S.aureus could induce mammary gland cell apoptosis and destruction of breast tissue structure.In order to further parsing the role of Se,we analyzed the factors related to cell apoptosis.The results showed that the Se played a regulatory role in the breast tissue cell apoptosis induced by S.aureus.Selenium deficiency could increase the phosphorylation of P53 protein molecules,enhance the value of BAX/BCL-2,and improve the cleaving of Caspase 3,6,7 proteins,exacerbating the apoptosis induced by S.aureus.Se-rich can very good ease the biology effect to protect the mammary tissue.The above analysis confirmed the regulation function of Se in the process of S.aureus induced mastitis.It is well known that selenoprotein was the biology function embodier of Se.In many of selenoproteins,the selenoprotein S(Sel S)was closely associated with inflammation.For further study of regulatory mechanism of Se in S.aureus induced mastitis,we studied the Sel S via RNA interference.The results showed that Se influenced the expression of Sel S,resulting to regulation of the NF-?B and MAPK signal transduction pathway of key protein phosphorylation levels,p53 phosphorylation levels,Bax and Bcl-2 protein expressions and Caspase 3,6,7 apoptosis factor protein decomposition.In conclusion,the Se played a regulatory effect on the occurrence and development of S.aureus induced mastitis.The Sel S played an important role in this process.The present study was further elucidated the pathogenesis of S.aureus induced mastitis.It was showed a new target for the prevention and control of mastitis and rich selenium biology function.The present study provide theoretical basis and help on the development of nutritional immunology in animal diseases.