Avicularin suppresses cartilage extracellular matrix degradation and inflammation via TRAF6/MAPK activation

Background: Osteoarthritis (OA) is an intractable degenerative disease of the whole joint, which is characterized by synovitis inflammation, cartilage damage, and chronic pain. Tumor necrosis factor receptor (TNFR)-associated factor 6 (TRAF6) performs an important role in OA.

Purpose: We aim to investigate avicularin to protect cartilage extracellular matrix degradation (ECM) and suppresses inflammation both in rat and human chondrocytes.

Methods: 5-Ethynyl-2'-deoxyuridine (EdU) staining, Quantitative Real-Time PCR, TRAF6 plasmid transfection, Western blot, Measurement of nitric oxide (NO), ROS detection and Immunofluorescence were utilized in vitro. micro-CT scanning, Safranin O-Fast Green, toluidine blue and immunohistochemistry staining were performed in vivo.

Results: In vitro, avicularin attenuates the degradation of ECM and inflammation, which could inhibit the activation of TRAF6/MAPK pathway via targeting TRAF6. Increased MMP3 and MMP13 expressions and decreased Aggrecan and Collagen Ⅱ levels were observed in anterior cruciate ligament transection (ACLT) induced osteoarthritic rats. Interestingly, intra-articular injection of avicularin attenuates this phenomenon.

Conclusions: Taken together, our results indicate that avicularin suppresses cartilage extracellular matrix degradation and inflammation via TRAF6/MAPK activation by targeting TRAF6. These observations identify TRAF6 as a relevant drug target, and avicularin may as a potential therapeutic agent in osteoarthritis.