Abstract：The occurrence of cow (Bos taurus) mastitis has restricted the development of dairy industry. It damages the cow health and reduces the quality of dairy products.The main cause of mastitis is pathogenic microorganism. Pathogenic microorganisms could induce cell apoptosis and thus interfere the development of the disease process. The purpose of this study was to explore the expression of cytokines and receptors, and the level of cell apoptosis in bovine mammary epithelial cells (BMECs) infected by Staphylococcus aureus and Escherichia coli. This study was intended to explore the S. aureus and E. coli (with fabrication: Oli) infected BMECs on the expression of cytokine. The BMECs were cultured in vitro and identified by immunohistochemistry, then the purified fifth generation of BMECs were selected and infected S. aureus or E. coli with the concentration of 0, 101, 102, 103, 104 CFU/mL, respectively. By the formula computing, the best infected quantity of S. aureus and E.coil was 0.6 mL; and the number of cell apoptosis was detected by one-step TUNEL (terminal dexynucleotidyl transferase (TdT)-mediated dUTP nick end labeling). The expression of interleukin-1β (IL-1β), IL1RⅠ and TNF-α were detected by means of qRT-PCR detection. The results showed that cells expressed not only keratin 18 also beta casein. In addition, the BMECs didn't express vimentin. The cultured cells were identified as BMECs. The highest mRNA expression of IL1RⅠ, IL-1β and TNF-α were at the S.aureus concentrations of 102 CFU/mL, 104 CFU/mL and 103 CFU/mL, respectively. The highest mRNA expression of IL1RⅠ, IL-1β and TNF-α were at the E. coli concentrations of 101 CFU/mL, 103 CFU/mL and 104 CFU/mL, respectively. The apoptosis rate was the highest at 104 CFU/mL with a concentration of cells treated by S.aureus or E. coli. The result indicated that different concentrations of bacterial infecting BMEC could increase the expression of cell factor, while decreased the expression of the receptor, which led to apoptosis of BMEC. This consequence could provide scientific basis for the pathogenesis of mastitis caused by bacterial infection .
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