Effects Of Staphylococcus Aureus Invasion On Lactoproteins Synthesis In Human Breast Epithelial Cells

Staphylococcus aureus(S.aureus)is the most common contagious pathogen associated with mastitis,which has been described earlier as an extracellular pahtogen and also been recoginized as an invasive pathogen with an intracellular lifestyle.The milk production and qualities are disturbed under the condition of breast inflammation,especially for the component and content of milk protein.The milk protein secreted by the mammary gland is produced in a pattern of de novo synthesis in the mammary epithelial cells using amino acids.It is not clear that whether the Staphylococcus aureus invasion could affect the amino acid absorption and result in inhibition of milk protein synthesis and secretion.In order to explore the effect of S.aureus invasion on ability of absorbing extracellular amino acids and lactoprotein de novo synthesis of cells,we designed experiments which Staphylococcus aureus invades human mammary epithelial cell(MCF-10A)and then the intracellular bacteria were observed by laser confocal microscope and counted by bacterial colony counting.Furthermore,the contents of animo acids in cell medium and lactoprotein both extracellular and intracellular were detected by ELISA.The effective mechanism of S.aureus invasion on the amino acidabsorption and milk protein synthesis was investigated by qPCR and western blot.The results showed that 1)S.aureus internalized into the MCF-10 A and proliferated within the cells.2)The gene transcription,synthesis and secretion of three components of milk protein—?-la,?-lg and Csn2 were promoted by the Glu,Asp,Leu and multiple amino acids added in the cell culture medium(p < 0.05).3)S.aureus invasion affects the absorption of Glu,Asp and Leu and milk protein synthesis and secretion(p<0.05).4)The ERK/mTORC1 pathway activation was inhibited by S.aureus invasion over 8 h and caspase-1 was activated with secretion of IL-1? and IL-18,indicating S.aureus invasion induced cell pyroptosis.In a word,S.aureus internalized into the MCF-10 A and proliferated within the cells.S.aureus invasion inhibits the capacity of cells to absorb amino acids from cell medium and introcellular lactoprotein synthesis.S.aureus invasion attenuates ERK/mTORC1 signaling activation and induces cell pyroptosis.These results provide basic data to further explore the molecular mechanism of amino acid absorption and lactoprotein synthesis affected by S.aureus invasion,and a theoretical basis for the prevention and treatment of mastitis.