Wedelolactone alleviates rheumatoid arthritis by gut microbiota-dependent immunomodulation and p53-mediated inhibition of fibroblast-like synoviocytes.

BACKGROUND

Rheumatoid arthritis (RA) is characterized by synovial hyperplasia and a parallel dysbiosis of the gut microbiota. Wedelolactone (WL), a natural bioactive compound, exhibits potent anti-inflammatory and immunomodulatory activities; however, its therapeutic potential in RA is unknown.

PURPOSE: This study aimed to evaluate the potential effect of WL on RA and explore its underlying mechanism.

METHODS

The anti-arthritic activity of WL was assessed in wild-type and antibiotic‑treated (ABX) collagen‑induced arthritis (CIA) mice in vivo and in human rheumatoid-arthritis synovial fibroblasts (MH7A) cells and murine rheumatoid-arthritis fibroblast-like synoviocytes (RA-FLS) cells in vitro. Additionally, fecal microbiota transplantation (FMT), 16S rDNA sequencing, intestinal barrier integrity assays, splenic and colonic Th17/Treg analyses and targeted metabolomics of short-chain fatty acids (SCFAs) were performed to clarify its microbiota-directed actions. Finally, RNA-seq coupled with chemical inhibition and genetic knockdown with siRNA were employed to explore its effect on the hyperproliferation of synoviocytes.

RESULTS

WL attenuated RA symptoms in CIA mice as evidenced by delayed disease onset, decreased joint swelling, less bone invasion and lower cumulative incidence. WL also reduced the Th17/Treg cell ratio in the spleen and colon and improved the intestinal barrier by inhibiting colonic inflammation and up-regulating tight junction proteins ZO-1 and Occludin. Concomitantly, WL reversed the RA-induced dysbiosis of gut microbiota and markedly elevated SCFAs levels, thereby restoring intestinal barrier integrity and re-establishing Th17/Treg homeostasis. FMT significantly ameliorated arthritis, further verifying the role of the gut microbiota-joint axis in the anti-arthritic effect of WL. However, FMT only partially mimicked the efficacy of WL, which was comparable to that of WL in ABX mice, indicating an additional microbiota-independent pathway. Additionally, WL directly inhibited the proliferation and migration of both MH7A and RA-FLS cells and induced G0/G1 cell cycle arrest. Transcriptomic profiling revealed that WL up-regulated p53-pathway genes including MDM2 and CDKN1A. Subsequently, pharmacologic blockade and genetic knockdown of the p53 axis abolished WL-induced decreases in cell viability and EdU positive cells and reversed the up-regulation expression of CDKN1A and HMOX1. Mechanistically, WL directly bound to p53, disrupted the p53-MDM2 interaction, suppressed p53 ubiquitination and proteasomal degradation, thereby stabilizing and upregulating p53 expression.

CONCLUSION

WL mitigated CIA in mice by modulating gut microbiota-SCFAs-Th17/Treg axis and inhibiting proliferation of RA-FLS via p53 pathway. The findings provide the pre-clinical foundation for the development of WL as an anti-RA agent.