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Keywords:

  • chondrocyte;
  • IL-1β;
  • NF-κB;
  • MMP-3;
  • curcumin

Abstract: Curcumin (diferuloylmethane) is a nontoxic dietary pigment in tumeric and curry and a potent inhibitor of the common transcription factor Nuclear Factor κB (NF-κB) in several cell types. It is well established that some of the catabolic effects of the proinflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α in osteoarthritis are regulated by the activation of NF-κB. Therefore, the aim of this study was to determine whether curcumin modifies the catabolic response of chondrocytes to IL-1β. Human articular chondrocytes were prestimulated with 10 ng/mL IL-1β for 0, 4, 8, 12, or 24 h and then cotreated with 50 μM curcumin for 0, 12, 24, 36, or 48 h. Synthesis of the cartilage-specific collagen type II and matrix-degrading enzyme matrix metalloproteinase-3 (MMP-3) was investigated in chondrocytes by Western blot analysis. Activation and nuclear translocation of NF-κB were observed by immunofluorescence microscopy. IL-1β induced a decrease in collagen type II and upregulation of MMP-3 in a time-dependent manner. Upregulation of MMP-3 was inhibited by curcumin in a time-dependent manner. In addition, IL-1β-induced a decrease in type II collagen, which was relieved by curcumin treatment. In response to IL-1β, NF-κB translocated to the nucleus, but translocation was inhibited by curcumin, as revealed by immunofluorescence microscopy. Taken together, these results confirmed an IL-1β-mediated upregulation of proinflammatory MMP-3 in chondrocytes via an NF-κB activation mechanism. Curcumin protected chondrocytes from the catabolic effects of IL-1β, such as MMP-3 upregulation, and interestingly also relieved cytokine-induced suppression of matrix protein synthesis. Therefore, curcumin antagonizes crucial catabolic effects of IL-1β signaling that are known to contribute to the pathogenesis of osteoarthritis.