Fengshi Qutong capsule ameliorates bone destruction of experimental rheumatoid arthritis by inhibiting osteoclastogenesis

Ethnopharmacological relevance: Bone destruction plays a key role in damaging the joint function of rheumatoid arthritis (RA). Fengshi Qutong capsule (FSQTC) consisting of 19 traditional Chinese medicines has been used for treating RA in China for many years. Preliminary studies show that FSQTC has analgesic activity and inhibits synovial angiogenesis of collagen-induced arthritis (CIA), but its role on bone destruction of RA is still unclear.

Aim of the study: To explore the effect of FSQTC on bone destruction of RA and the possible mechanism of osteoclastogenesis in vivo and in vitro.

Materials and methods: LC-MS system was used to detect the quality control components of FSQTC. The anti-arthritic effect of FSQTC on CIA rats was evaluated by arthritis score, arthritis incidence and histopathology evaluation of inflamed joints. The effect of treatment with FSQTC on bone destruction of joint tissues was determined with X-ray and micro-CT quantification, and on bone resorption marker CTX-I and formation marker osteocalcin in sera were detected by ELISA. Then, osteoclast differentiation and mature were evaluated by TRAP staining, actin ring immunofluorescence and bone resorption assay both in joints and RANKL-induced RAW264.7 cells. In addition, RANKL, OPG, IL-1β and TNFα in sera were evaluated by ELISA. The molecular mechanisms of the inhibitions were elucidated by analyzing the protein and gene expression of osteoclastic markers CTSK, MMP-9 and β3-Integrin, transcriptional factors c-Fos and NFATc1, as well as phosphorylation of ERK1/2, JNK and P38 in joints and in RANKL-induced RAW264.7 cells using western blot and/or qPCR.

Results: In this study, 12 major quality control components were identified. Our data showed that FSQTC significantly increased bone mineral density, volume fraction, trabecular thickness, and decreased trabecular separation of inflamed joints both at periarticular and extra-articular locations in CIA rats. FSQTC also diminished the level of CTX-I and simultaneously increased osteocalcin in sera of CIA rats. The effects were accompanied by reductions of osteoclast differentiation, bone resorption, and expression of osteoclastic markers (CTSK, MMP-9 and β3-Integrin) in joints. Interestingly, FSQTC treatment could reduce the protein level of RANKL, increase the expression of OPG, and decrease the ratio of RANKL to OPG in inflamed joints and sera of CIA rats. In addition, FSQTC inhibited the levels of pro-inflammatory cytokines implicated in bone resorption, such as IL-1β and TNFα in sera. When RAW264.7 cells were treated with RANKL, FSQTC inhibited the formation of TRAP + multinucleated cells, actin ring and the bone-resorbing activity in dose-dependent manners. Furthermore, FSQTC reduced the RANKL-induced expression of osteoclastic genes and proteins and transcriptional factors (c-Fos and NFATc1), as well as phosphorylation of mitogen-activated protein kinases (MAPKs).

Conclusion: FSQTC may inhibit bone destruction of RA by its anti-osteoclastogenic activity both in vivo and in vitro.