Dendrobine Inhibits Osteoclastogenesis And Attenuates Inflammatory Osteolysis

Background and purpose:Destructive erosion of bone or osteolysis is a major complication of inflammatory conditions such as rheumatoid arthritis(RA),Paget's and periodontal disease etc.,mainly manifested as excessive bone loss.With the development of the diseases,they can lead to a series of bone related events such as bone pain and bone deformity.As the only cells in the body responsible for absorbing bone,osteoclasts and osteoblasts are restrained by each other in a dynamic equilibrium,to maintain bone renewal and remodeling.The over-activation of oteoclasts will cause a series of bone destruction related diseases and bring a great economic burden on society.Recently,targeting osteoclast differentiation has become a feasible therapeutic strategy for alleviating the above diseases,the representative clinical drugs mainly include bisphosphonates and denosumab at present,but they can lead to osteonecrosis of the jaw and all require intravenous or subcutaneous injection,and costly.It is a promising way to dig out new drugs from traditional Chinese medicines with less side effects,and possible to find safe,effective,convenient and affordable drugs targeting osteoclast differentiation,for reducing the burden of bone destruction diseases and improving the poor quality of life of patients.It has been reported that Dendrobii Caulis can nourish the Yin,tonify the kidney,and can be used to alleviate rheumatoid arthritis.Fresh or dried stems of Dendrobium nobile are major raw materials of Dendrobii Caulis,and it's active component dendrobine possesses analgesic effect,but the study of how dendrobine affects osteoclastogenesis has not been reported,and the study of how dendrobine affects osteoclast-related osteolysis has not been reported.Therefore,in order to explore the new role and mechanisms of the drug,and provide a new treatment for bone destruction,this study mainly focuses on the effects of dendrobine on RANKL-induced osteoclast formation and function in vitro and its related molecular mechanisms,and the protective effect on inflammatory osteolysis induced by LPS in vivo.Methods:1.BMMs and RAW264.7 cells were stimulated by RANKL to establish a model of osteoclast differentiation in vitro.The effects of dendrobine on the survival of BMMs and RAW264.7 cells were detected by MTT.The effects of dendrobine on osteoclastogenesis and resorption function were detected by TRAP staining and pits assay.2.To explore the molecular mechanisms,the effect of dendrobine on ROS production was observed by fluorescence microscope and flow cytometry.NF-?B and NFATcl transcriptional activity were detected by luciferase reporter gene.The protein expression of NF-?B,MAPKs(p38,JNK,ERK1/2),c-Fos,NFATcl,MMP9 signal pathways were tested by western blot during osteoclastogenesis.qRT-PCR were used to measure c-Fos,NFATcl mRNA and osteoclast related genes(TRAP,c-src,DC-STAMP,cathepsin K,MMP9)expression.3.The model of LPS-induced inflammatory bone lytic mice was established in vivo.The effects of dendrobine on bone parameters and osteoclastogenesis were detected by Micro-CT and TRAP staining in bone loss mice.Results:1.Dendrobine significantly inhibited RANKL-induced osteoclast formation and bone resorption in vitro.2.Dendrobine can inhibit RANKL-induced osteoclastogenesis in vitro by directly eliminating ROS production,p38 MAPK-c-Fos and NFATcl-MMP9 pathways,but has little effects on NF-?B activity and the phosphorylation of JNK and ERK.3.In vivo,dendrobine effectively alleviated the inflammatory osteolysis induced by LPS via inhibiting bone loss and trabecular bone damage,but increasing bone density.Also dendrobine significantly reduced osteoclast numbers in lytic bone loss mice.Conclusion:1.The new pharmacological function of dendrobine in osteoclasts has been demonstrated.2.Dendrobine can be used as a potential osteoclast differentiation inhibitor to treat lytic bone disease.