JNK-IN-IX Inhibits Osteoclastogenesis And Periodontitis-Induced Alveolar Bone Loss In Rats

Background:Periodontal disease is a common inflammatory disease that usually leads to irreversible alveolar bone resorption and subsequent tooth loss.Studies have shown that OCs are considered to be the only cells in the body responsible for bone resorption.Targeted therapy for the inhibition of OCs activation is considered to be the most effective treatment strategy for reversing bone destruction.NF-?B ligand(RANKL)has been identified as the primary mediator of bone resorption.Agents that inhibit RANKL signaling have the potential to inhibit bone resorption or osteoclastogenesis.Aim:This study was designed to determine the role of JNK-IN-IX in a rat model of LPS-induced periodontitis.Moreover,confirm the truth of this result in vitro and investigate the mechanism of JNK-EN-IX affecting the proliferation and differentiation of osteoclasts.METHODS:The cytotoxicity of JNK-IN-IX on bone marrow mesenchymal cells(BMM)was determined by MTT assay.BMMs were stimulated with M-CSF(30 ng/ml),RANKL(50ng/ml)and different lose of inhibitor(0,12.5,25,or 50nM.After TRAP(anti-tartaric acid phosphatase)test,we calculated the number and area of OCs by Image J software.BMMs were seeded on bone slices and investigate the affection of the inhibitor on bone resorption by SEM.Measuring the expression level of osteoclast-specific gene by q-pcr and detecting the expression of related proteins at different time by western blotting is used for the analysis of the mechanism of JNK-IN-IX inhibiting the differentiation of osteoclasts.The LPS-induced periodontitis rat model was established and the mandible Micro-CT was analyzed,which was to determine the inhibitory effect of JNK-IN-IX on alveolar bone resorption in rats.Results:1.When the inhibitor's concentration is over 128.8?M,we think that JNK-IN-IX has cytotoxic effect on BMMs.2.In the TRAP staining,we found that JNK-IN-IX significantly inhibited the induction and differentiation of osteoclasts,and the effect was enhanced with increasing concentration from 12.5 to 50nM.3.The expression of osteoclast marker genes such as TRAP,cathepsin K(CTSK),calcitonin receptor CTR and Atp6v0d2 was also attenuated by JNK-IN-IX,especially at a concentration of 50 nM.4.JNK-IN-IX was found to inhibit bone resorption in vitro by calculating the area of bone recess.5.JNK-IN-IX inhibits RANKL-induced osteoclasts by inhibiting JNK phosphorylation and its downstream c-Jun,and we found that osteoprotegerin OPG expression was significantly increased after the agent's stimulation.6.We successfully built LPS-induced periodontitis rat model.Micro-CT showed that the agent group effectively inhibited alveolar bone resorption in rat periodontitis,and the high doze group was more effective than the low.Conclusion:1.JNK-IN-IX inhibits the differentiation of BMMs into osteoclasts in a dose-and time-dependent manner.2.JNK-IN-IX inhibits osteoclast function through the JNK/RANKL/OPG signaling pathway in vivo.3.JNK-IN-IX has a therapeutic effect on alveolar bone resorption caused by periodontitis in rats in vitro.