Protective effects of piperlongumine against adjuvant-induced arthritis in rats through modulating OPG/RANKL/NF-κB signaling pathway.

Objectives: We examined the antirheumatoid effects of piperlongumine (PLM) on rat adjuvant-induced arthritis (AIA) and explored the underlying mechanisms involved.

Methods: PLM (2.5, 5, and 10 mg/kg) was administered intraperitoneally to AIA rats to assess its effectiveness. Blood, thymus, spleen, ankle joint, and synovial tissue samples were gathered for subsequent analyses, like enzyme-linked immunosorbent assay, thymus/spleen index measurement, ankle joint pathological examination, immunohistochemistry assay, polymerase chain reaction, and western blot assay. Moreover, the involvement of osteoprotegerin (OPG)/receptor activators of nuclear factor κB ligand (RANKL)/nuclear factor-κB (NF-κB) signaling was investigated.

Key findings: PLM effectively relieved inflammation and joint destruction in AIA rats, as indicated by reductions in hind paw swelling, arthritis index, thymus/spleen index, ankle joint pathological damage, production of TNF-α, IL-1β, and IL-6 in both serum and synovium, and osteoclast formation. Also, PLM treatment raised OPG production, reduced RANKL expression, and elevated the OPG/RANKL ratio in synovial tissues. Furthermore, PLM prevented IκBα degradation and phosphorylation, resulting in a reduced expression of the nuclear NF-κB p65 protein in AIA rat synovial tissues.

Conclusions: PLM demonstrated strong antiarthritic effects in rats with AIA by influencing the OPG/RANKL/NF-κB signaling pathway, highlighting its potential clinical relevance in treating rheumatoid arthritis.