Isorhynchophylline ameliorates the progression of osteoarthritis by inhibiting the NF-κB pathway

Osteoarthritis (OA), a progressive and degenerative joint disease, is characterized by cartilage degradation, synovitis, subchondral bone remodeling and osteophyte formation. Isorhynchophylline (IRN) is an oxindole alkaloid isolated from the traditional Chinese herb Uncaria rhynchophylla. In this study, we evaluated the protective effects of IRN on human OA chondrocytes. IRN treatment dose-dependently decreased the interleukin-1β (IL-1β)-induced expressions of nitric oxide (NO; p < 0.001), prostaglandin E2 (PGE2; p < 0.001), tumor necrosis factor alpha (TNF-α; p < 0.001), interleukin-6 (IL-6; p < 0.001), cyclooxygenase-2 (COX-2; p < 0.001) and inducible nitric oxide synthase (iNOS; p < 0.001) in chondrocytes. Meanwhile, the production of metalloproteinase 13 (MMP13; p < 0.001) and a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5; p < 0.001) was inhibited by IRN treatment. Molecular docking studies revealed that IRN directly interacted with the nuclear factor kappa B (NF-κB) complex, which was associated with a reduced level of NF-κB nuclear translocation and the inhibition of NF-κB signaling activity. Furthermore, administration of IRN generated marked in vivo protective effects during OA development. Collectively, our results demonstrate that IRN may exhibit therapeutic benefits against OA, potentially by ameliorating the inflammative and degenerative progression of OA via inhibiting the NF-κB pathway.