Effect Of Selenium On The Proliferation Of Bovine Mammary Epithelial Cells Infected By Staphylococcus Aureus

Bovine mastitis is one of the common diseases of bovine,which can cause huge economic losses.Pathogens invade breast tissue and survive in host cells,a process often associated with tissue damage.S.aureus is one of the important pathogens of bovine mastitis.When the mammary gland is infected,it undergoes self-repair under the activation of various signaling pathways and factors,then restores the normal structure and function of the mammary gland.Selenium is usually presented in the body of animals in the form of selenoproteins.A number of studies have confirmed that selenium can regulate cell proliferation,but the effect of selenium for the proliferation in BMECs has not been reported.Therefore,in this study,the effect of selenium on Wnt/p-catenin and PI3K/Akt/mTOR signaling pathways,cell cycle and proliferation factors were studied in vitro culture.We explored the mechanism of selenium on the proliferation of BMECs,which provided a basis for the treatment of selenitis in bovine.(1)In order to study the effect of selenium on the proliferation of BMECs infected by S.aureus,this experiment was set up in the same group as above.The cell cycle was detected by flow cytometry.The results showed that compared with the blank group,4 ?M selenium significantly increased S phase cells compared with the blank group(p<0.01);8 ?M selenium significantly reduced G0/G1 phase cells(p<0.01),increased G2/M phase cells significantly in cells(p<0.01),and PI significantly increased(p<0.01).When S.aureus infected BMECs,the S phase cells of S.aureus group extremely significantly decreased(p<0.01),G2/M phase cells significantly increased(p<0.05).Compared with the S.aureus group,when 2,4,and 8 ?M selenium and S.aureus were co-treated,G0/G1 phase cells showed a significant or extremely significant decrease(p<0.01 or p<0.05),and S phase cells significantly or extremely significant increased(p<0.01 or p<0.05),PI increased significantly(p<0.05).(2)To study the effect of selenium on the proliferative factors of BMECs,the mRNA expression of CTGF,EGFR,TGF-?3,VEGF,ERa and ER? were meassured.The experiment was set up in the same group as above.As a result,compared with the blank group,2 ?M selenium increased CTGF and VEGF expression levels,the difference was significant or extremely significant(p<0.05);4,8 ?M selenium increased the expression levels of CTGF,EGFR,TGF-P3,VEGF,ERa and ER?,the differences was significant or extremely significant(p<0.05 or p<0.01).Compared with the blank group,when S.aureus infected with BMECs,the mRNA expression of CTGF,EGFR,VEGF,ERa,ERP and TGF-?3 in S.aureus group increased,the difference was significant or extremely significant(p<0.05 or p<0.01).Compared with the S.aureus group,the mRNA expression of EGFR,VEGF,TGF-?3 and ER? in 2 ?M selenium and S.aureus cotreatment group increased significantly(p<0.01);the mRNA expression of EGFR,VEGF,CTGF and ERa in 4,8 ?M selenium and S.aureus cotreatment group were increased,the difference was significant or extremely significant(p<0.05 or p<0.01).(3)To investigate the mechanism of effect of selenium on the regulation of Wnt/p-catenin and PI3K/Akt/mTOR signaling pathways when BMECs infected by S.aureus.In this study,BMECs were divided into blank group,S.aureus group(MOI=1:1),selenium group(2,4,8 ?M),and selenium-S.aureus co-treatment group.Western Blot was used to detect the protein expressions of ?-catenin,Cyclin D1,c-Myc,PI3K,p-PI3K,Akt and p-Akt.and distribution of?-catenin was meassured by immunofluorescence.The results showed that compared with the blank group,4 ?M selenium promoted the expression of Cyclin D1 in BMECs,the difference was extremely significant(p<0.05);8 ?M selenium promoted the expression of ?-catenin,Cyclin D1 and c-Myc,the difference was in different degree(p<0.05 or p<0.01),and ?-catenin was widely distributed in cytoplasm and nucleus.2,4 and 8 ?M selenium promoted the phosphorylation level of PI3K,Akt and mTOR,the difference was significant or extremely significant(p<0.05 or p<0.01).When S.aureus was infected with BMECs,compared with the blank group,the expression of ?-catenin was increased(p<0.01),?-catenin was widely distributed in cytoplasm and nucleus;the phosphorylation level of PI3K protein and Akt increased,the difference was extremely significant(p<0.01).Compared with the S.aureus group,2,4 and 8 ?M selenium promoted the expression of ?-catenin,Cyclin D1 and c-Myc in BMECs infected by S.aureus,the difference was significant or extremely significant(p<0.05 or p<0.01),?-catenin was widely distributed in cytoplasm and nucleus;in 4 ?M selenium and S.aureus cotreatment group,phosphorylation levels of PI3K,Akt and mTOR increased to difffeent degree(p<0.05 or p<0.01).In summary,selenium can activate the Wnt/?-catenint pathway and the PI3K/Akt/mTOR pathway,regulate the expression of proliferation factors,improve the cell cycle,and promote the proliferation and repair of BMECs.The results provide a theoretical basis for exploring the self-repair of mammary gland damage and the prevention and treatment of mastitis.