Sophoricoside reduces inflammation in type II collagen-induced arthritis by downregulating NLRP3 signaling

Immune responses, especially NLRP3 signaling in macrophages, play critical roles in rheumatoid arthritis (RA), an autoimmune and inflammatory disease. In this study, we aimed to identify novel therapies for RA. We focused on sophoricoside (SOP), an isoflavone glycoside isolated from Sophora japonica. We predicted the targets of SOP and performed a Gene Ontology analysis to assess its effects. The results suggested that SOP is related to inflammation regulation. We verified these findings by performing in vitro experiments with M1 macrophages differentiated from human peripheral blood monocytes (THP-1 cells). Sophoricoside administration reduced inflammatory activity and NLRP3, Caspase-1, and IL-1β protein levels in macrophages. In addition, SOP and triptolide (TP) was administered intragastrically to male SD rats (n = 40) in a collagen-induced arthritis model. We observed that SOP and TP reduced the inflammatory responses and symptoms of RA. Moreover, unlike TP, SOP showed no liver or kidney toxicity in rats. In conclusion, SOP reduces inflammation in type II collagen-induced arthritis by downregulating NLRP3 signaling and has potential for future clinical applications as an ideal therapy for RA.