Fu-zi decoction attenuate rheumatoid arthritis and by modulating RANK/RANKL signaling pathway.

BACKGROUND

Fu-zi decoction (FZD) has a long history of application for treating Rheumatoid arthritis (RA) as a classic formulation. However, its underlying mechanisms have not been fully elucidated. This study aimed to decipher the potential mechanism of FZD in treating RA, with a specific focus on receptor activator of nuclear factor κB/receptor activator of nuclear factor κB ligand (RANK/RANKL) signaling pathway.

METHODS

The impact of FZD on RA was investigated in collagen-induced arthritis rats (CIA), and the underlying mechanism was investigated in an osteoclast differentiation cell model. , the antiarthritic effect of FZD at various doses (2.3, 4.6, 9.2 g/kg/day) was evaluated by arthritis index score, paw volume, toe thickness and histopathological examination of inflamed joints. Additionally, the ankle joint tissues were determined with micro-CT and safranin O fast green staining to evaluate synovial hyperplasia and articular cartilage damage. , osteoclast differentiation and maturation were evaluated by TRAP staining in RANKL-induced bone marrow mononuclear cells. The levels of pro- and anti-inflammatory cytokines as well as RANKL and OPG were evaluated by ELISA kits. In addition, Western blotting was used to investigate the effect of FZD on RANK/RANKL pathway activation both and .

RESULTS

FZD significantly diminished the arthritis index score, paw volume, toe thickness and weigh loss in CIA rats, alleviated the pathological joint alterations. Consistent with results, FZD markedly inhibited RANKL-induced osteoclast differentiation by decreasing osteoclast numbers in a dose-dependent manner. Moreover, FZD decreased the levels of pro-inflammatory cytokines IL-6, IL-1β and TNF-α, while increasing anti-inflammatory cytokine IL-10 level both in serum and culture supernatants. Treatment with FZD significantly reduced serum RANKL levels, increased OPG levels, and decreased the RANKL/OPG ratio. In both and settings, FZD downregulated the protein expressions of RANK, RANKL, and c-Fos, while elevating OPG levels, further decreasing the RANKL/OPG ratio.

CONCLUSION

In conclusion, FZD exerts a therapeutic effect in CIA rats by inhibiting RANK/RANKL-mediated osteoclast differentiation, which suggested that FZD is a promising treatment for RA.