α-Hemolysin Suppresses Osteogenesis By Inducing Lipid Raft Accumulation In Bone Marrow Stromal Cells

α-hemolysin(Hla)is considered an essential virulent factor for S.aureus toxicity,the cellular and molecular mechanism by which Hla affect bone metabolism is still poorly understood.In the present study,2-month-old C57BL/6 mice were treated with Hla(40 μg/kg every three days)by intraperitoneal injection.Microcomputed tomography(Micro-CT)analysis showed progressive bone loss from week 2 to week 4 after treatment,accompanied by a decreased osteoblasts and increased osteoclasts in femoral metaphysic.In vitro,Hla stimulates the expression of Caveolin-1 and activate lipid rafts accumulation in membrane of bone marrow stromal cells(BMSCs),and suppress osteogenesis of BMSCs.In addition,destruction of lipid rafts with methyl-β-cyclodextrin(MβCD)blocked the detrimental effect of Hla on osteogenesis of BMSCs.Interestingly,Hla does not affect osteoclastogenesis in vitro,whereas up-regulates the expression of RANKL and down-regulates the expression of OPG.Importantly,treating mice with MβCD rescues the loss of osteoblasts and increased osteoclastogenesis induced by Hla.Together,we demonstrate that Hla induced bone destruction directly by suppressing osteogenesis and indirectly by stimulating osteoclastogenesis,and that lipid rafts may mediate the detrimental effect of Hla on osteogenesis.