Total Flavonoids of Rhizoma Drynariae Restore the MMP/TIMP Balance in Models of Osteoarthritis by Inhibiting the Activation of the NF-κB and PI3K/AKT Pathways

Total flavonoids of Rhizoma Drynariae (TFRD) have been shown to have beneficial effects on osteoarthritis (OA) clinically, but the mechanisms have not been elucidated. In this study, we investigated the effect of TFRD on articular cartilage in an OA rat model established by the Hulth method and in SW1353 chondrocytes induced by the proinflammatory factor interleukin-1β (IL-1β). The results showed that TFRD could alleviate the pathological changes in knee cartilage in OA model rats. In vivo, the qPCR analysis indicated that the mRNA levels of matrix metalloproteinases, MMP-1, MMP-3, and MMP-13, were decreased, while tissue inhibitor of matrix metalloproteinases- (TIMP-) 4 was increased in cartilage, and these changes could be partially prevented by TFRD. In vitro experiments showed that IL-1β could significantly increase the expression of MMP-1, MMP-3, and MMP-13 and decrease the expression of TIMP-4 in SW1353 cells at the mRNA and protein levels. TFRD could increase the expression of MMP-3 and MMP-13 and decrease the expression of TIMP-4. Transfection of siRNA and addition of pathway inhibitors were used to clarify that inhibition of NF-κB and PI3K/AKT pathway decreased MMP-1, MMP-3, and MMP-13 and increased TIMP-4 expression. We also found that in IL-1β-induced SW1353 cells, TFRD pretreatment had a modest inhibitory effect on p-AKT (Ser473) and reversed the increase of nuclear factor kappa-B (NF-κB) p65 in nuclear fraction and the decrease of inhibitor of NF-κB(IκB)-α in the cytosolic fraction. Further immunofluorescence confirmed that TFRD can inhibit IL-1β-induced NF-κB p65 translocation to the nucleus to some extent. In conclusion, TFRD showed chondroprotective effects by restoring the MMP/TIMP balance in OA models by suppressing the activation of the NF-κB and PI3K/AKT pathways.