Ohwia caudata extract relieves the IL-17A-induced inflammatory response of synoviocytes through modulation of SOCS3 and JAK2/STAT3 activation.

Fibroblast-like synoviocytes accumulation, proliferation and activation, and the subsequent inflammatory mediators production play a key role in the progression of rheumatoid arthritis (RA). It is well established that Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) signaling triggers inflammation, and induces cytokine levels in RA. Ohwia caudata have long been used against many disorders. However, in RA, the effects of O. caudata have not been elucidated. In the current study, synoviocytes were used to evaluate the suppressive effects of O. caudate extract (OCE) on the pro-inflammatory cytokines production. In vitro, the underlying mechanisms by which OCE inhibits inflammatory response through regulation of suppressors of cytokine signaling 3 (SOCS3) and JAK2/STAT3 expression in IL-17A-treated HIG-82 synoviocytes were investigated. The results demonstrated that the proliferation of IL-17A-challenged cells were increased in comparison with non-stimulated control cells. The synoviocyte proliferation was decreased significantly of OCE concentrations in dose dependent manner. The p-JAK2, p-STAT3, interleukin (IL)-1β, and IL-6 were reduced in IL-17A-challenged cells treated with OCE. Furthermore, AZD1480 (a JAK2-specific inhibitor) or WP1066 (a STAT3-specific inhibitor) affected the inflammatory mediators production in IL-17A-challenged synoviocytes, and OCE failed to mitigate the IL-17A-induced inflammatory mediators and SOCS3, acting as a feedback inhibitor of the JAK/STAT3 pathway, in the presence of SOCS3 siRNA, indicating that the beneficial effects of OCE on the regulation of inflammatory response homeostasis were dependent on SOCS3 and the JAK2/STAT3 signaling pathway. Our study also showed that SOCS3 was markedly activated by OCE in RA fibroblast-like synoviocytes, thereby decreasing the JAK/STAT3 pathway, and the IL-1β, and IL-6 activation. Thus, O. caudate should be further investigated as a candidate anti-inflammatory and anti-arthritic agent.