The Mechanism Of Forsythiaside A Inhibiting Osteoclast Differentiation And Its Therapeutic Application

Objective:The balance of osteoclast and osteoblast differentiation maintains the normal physiological function.The dysregulation of osteoclastogenesis is involved in osteoporosis and inflammatory osteolysis.To identify novel and effective therapeutic targets to treat these diseases,it is important to explore the mechanisms underlying them.Methods:To explore the role of FT-A in inflammatory osteolysis and osteoclast differentiation,we first constructed a model of LPS-induced mouse skull osteolysis using microCT and histological analysis.Subsequently,the effect of FT-A on osteoclast differentiation and its underlying mechanism were explored by means of quantitative PCR,Western blot,TRAP staining and plasmid transfection.Finally,OVX-induced mouse osteoporosis model was constructed to verify the protective effect of FT-A.Results:We first found that Forsythiaside A(FT-A)inhibits LPS-induced calvaria osteolysis in mice by inhibiting the formation or recruitment of osteoclasts.Our in vitro experiments demonstrated that FT-A inhibited osteoclast differentiation and bone resorption and downregulated the osteoclast markers c-FOS and NFATcl.Mechanically,FT-A inhibited RANKL-induced NF-?B signaling via suppressing the polyubiquitination of TRAF6 on lysine 63,the degradation of I?B?,and the nuclear translocation of P65.A constitutive active form of P65(CA-P65)could only partially restore osteoclastogenesis.We then found that the Notch pathway was altered in this process.The expression of Notch intracellular domain(NICD)decreased upon treatment of the cells with FT-A,which was also associated with the enhanced expression of recombination signal binding protein for immunoglobulin kappa J region(RBPJ-K)and the switch in RBPJ-K activity as a transcriptional repressor of osteoclastogenesis.Attenuation of RBPJK expression using RNAi could significantly rescue the expression of NFATcl and the osteoclast differentiation.What was more,FT-A was proved to attenuate the ovariectomy(OVX)-induced bone loss in vivo.Conclusions:Collectively,we found that FT-A attenuated the inflammatory bone resorption and OVX-induced osteoporosis via suppressing osteoclastogenesis through the NF-?B and Notch pathways.