The Role Of EGFR/FAK And Src Pathways In The Internalization Of Staphylococcus Aureus By Osteoblasts

Objective:Chronic osteomyelitis caused by S.aureus is a serious disease which is difficult to treat.Studies have shown that intracellular S.aureus can induce bone infections and can lead to chronic and recrudescent infections.Therefore,inhibiting the internalization of S.aureus by osteoblasts in the early stage of infection may be a new method for prevention and treatment of chronic osteomyelitis.In this study,we aimed to investigate the molecular mechanism of S.aureus internalization by osteoblasts.Methods:We purchased 10-week old male C57BL/6 mice for animal experiments.Osteomyelitis model was induced by intravenous injection of 1× 106 CFU of S.aureus in 100 μl PBS via caudal vein.Mice were injected with gentamicin intraperitoneally to kill the extracellular bacteria.Osteoblastic MC3T3-E1 cell line was cultured for vitro experiments.We used western blotting to detect the expression of related proteins after S.aureus infection.Cells were pretreated with gefitinib(an inhibitor for EGFR),VS6063(an inhibitor for FAK)and AZD0530(an inhibitor for Src)to study the effect of related proteins on the internalization of S.aureus by MC3T3-E1.Results:In vivo experiments,we found that S.aureus could be internalized by osteoblasts,which led to the destruction in bone structure and the loss of osteoblasts.In vitro experiments,we found that S.aureus infection promoted the expression of p-EGFR,p-FAK and p-Src.Meanwhile,the inhibitor for EGFR can normalize the expression of p-FAK.Moreover,inhibition of EGFR/FAK signaling or Src signaling leads to a significantly decrease in S.aureus internalization.Conclusion:S.aureus can be internalized by osteoblasts.EGFR/FAK and Src signaling pathways mediate the internalization of S.aureus by osteoblasts.All these provide new insights into the process of S.aureus internalization and the potential of EGFR/FAK and Src signaling pathways as potential targets for concomitant drugs therapy of chronic S.aureus osteomyelitis.