Ferulic acid inhibits interleukin 17‐dependent expression of nodal pathogenic mediators in fibroblast‐like synoviocytes of rheumatoid arthritis

Interleukin 17 (IL-17), a proinflammatory cytokine produced by T helper (Th) 17 cells, potentially controls fibroblast-like synoviocytes (FLS)-mediated disease activity of rheumatoid arthritis (RA) via IL-17/ IL-17 receptor type A (IL-17RA)/signal transducer and activator of transcription 3 (STAT-3) signaling cascade. This has suggested that targeting IL-17 signaling could serve as an important strategy to treat FLS-mediated RA progression. Ferulic acid (FA), a key polyphenol, attenuates the development of gouty arthritis and cancer through its anti-inflammatory effects, but its therapeutic efficiency on IL-17 signaling in FLS-mediated RA pathogenesis remains unknown. In the current study, FA markedly inhibited the IL-17-mediated expression of its specific transmembrane receptor IL-17RA in FLS isolated from adjuvant-induced arthritis (AA) rats. Importantly, FA dramatically suppressed the IL-17-mediated expression of toll-like receptor 3 (TLR-3), cysteine-rich angiogenic inducer 61 (Cyr61), IL-23, granulocyte-macrophage colony stimulating factor (GM-CSF) in AA-FLS via the inhibition of IL-17/IL-17RA/STAT-3 signaling cascade. In addition, FA significantly decreased the formation of osteoclast cells and bone resorption potential in a coculture system consisting of IL-17 treated AA-FLS and rat bone marrow derived monocytes/macrophages. Furthermore, FA remarkably inhibited the IL-17-mediated expression of receptor activator of nuclear factor κ-Β ligand (RANKL) and increased the expression of osteoprotegerin (OPG) in AA-FLS via the regulation of IL-17/IL-17RA/STAT-3 signaling cascade. The therapeutic efficiency of FA on IL-17 signaling was further confirmed by knockdown of IL-17RA using small interfering RNA or blocking of STAT-3 activation with S3I-201. The molecular docking analysis revealed that FA manifests significant ligand efficiency toward IL-17RA, STAT-3, IL-23, and RANKL proteins. This study provides new evidence that FA can be used as a potential therapeutic agent for inhibiting IL-17-mediated disease severity and bone erosion in RA.