Pinocembrin inhibits matrix metalloproteinase expression in chondrocytes

Osteoarthritis (OA), the most common form of arthritis, affects millions of people worldwide. The degradation of extracellular matrix induced by matrix metalloproteinases (MMPs) is an important cause of cartilage destruction. Pinocembrin (PB) is one of the primary flavonoids abundant in propolis and extracted as a pure compound. The protective effects of PB in OA have not been reported before. In this study, we found that PB inhibits the expression of MMP-1, MMP-3, and MMP-13 at both mRNA levels and protein levels in human chondrocytes. Importantly, the results of luciferase reporter assay indicated that tumor necrosis factor-alpha (TNF-α) induced the activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) was inhibited by the treatment with PB. It is also shown that TNF-α-induced p65 nuclear translocation was blocked by the treatment with PB. Mechanistically, PB treatment significantly inhibited TNF-α-induced phosphorylation and degradation of the NF-κB inhibitor IκBα in human chondrocytes. These results suggest a potential protective effect of PB in OA.