Total Flavonoids of Rhizoma Drynariae Ameliorate Rheumatoid Arthritis by Modulating Macrophage Polarization and HIF-1α-Associated Glycolysis

Objective: Rheumatoid arthritis (RA) is a chronic autoimmune disease with the abnormal accumulation of pro-inflammatory macrophages within the synovial joints. Total flavonoids of Rhizoma Drynariae (TFRD), the major bioactive constituents of the traditional Chinese medical herb Drynariae rhizome, have shown potent activities in treating RA, but their effect and underlying mechanism in modulating macrophage behavior remain unknown. This study aimed to evaluate the therapeutic potential of TFRD in regulating macrophage polarization during RA, and to further elucidate the underlying mechanism. Methods: The therapeutic effects of TFRD were assessed by utilizing a collagen-induced arthritis (CIA) mice model in vivo. A macrophage polarization model was employed to investigate the effect of TFRD on the macrophage pro-inflammatory polarization and glycolytic activity in vitro. Additionally, the role of hypoxia-inducible factor-1α (HIF-1α) in the TFRD-mediated regulation of macrophage glycolysis was examined via plasma transfection. Results: Administration of TFRD significantly reduced the arthritis severity scores and ameliorated joint swelling and bone destruction in CIA mice. The therapeutic efficacy of high-dose TFRD (TFRD-H) was broadly similar to that of MTX in CIA mice. Further, TFRD decreased the proportion of pro-inflammatory macrophages and the expression of HIF-1α within the joints of CIA mice. The in vitro experiments indicated that TFRD inhibited the lipopolysaccharide-induced macrophage pro-inflammatory polarization. Mechanistically, TFRD attenuated glycolytic metabolism and downregulated HIF-1α expression during pro-inflammatory polarization, while HIF-1α overexpression partly reversed these effects. Furthermore, 16S rRNA sequencing analysis revealed the mitigated dysbiosis of the gut microbiota and increased relative abundance of Parabacteroides in CIA mice. Conclusions: These findings indicate that TFRD alleviated RA, which was partly dependent on downregulating pro-inflammatory macrophages and mitigating HIF-1α-associated glycolysis. This study could provide a scientific basis for further research and the clinical use of TFRD.