Promotion of G1/S Transition and Inhibition of Inflammatory Cytokine Production by Hydroxypyridinone-Coumarin in Osteoarthritis Rats.

BACKGROUND Osteoarthritis is a joint disorder characterized by articular cartilage degradation leading to joint stiffness and pain. The present study investigated the effect of hydroxypyridinone-coumarin on proliferation of chondrocytes. MATERIAL AND METHODS Chondrocyte proliferation was assessed by MTT assay, and distribution of cells in various phases of the cell cycle was determined using flow cytometry. RT-PCR and Western blot assays were used for assessment of mRNA and protein levels, respectively. Osteoarthritis was induced in the rats by injecting monosodium iodoacetate (5 mg/kg) by the intra-articular route. The rats in the treatment groups were intraperitoneally injected with 5, 10, or 15 mg/kg doses of hydroxypyridinone-coumarin alternately for 1 month. RESULTS The proliferation of chondrocytes was increased significantly (P<0.05) by treatment with hydroxypyridinone-coumarin in a concentration-based manner. The increase in chondrocyte proliferation by hydroxypyridinone-coumarin was maximum at 50 µM. Treatment with hydroxypyridinone-coumarin markedly increased chondrocyte population in S and G2/M phases, with subsequent reduction in G0/G1 phase. The cyclin D1, CDK4, and CDK6 levels in the chondrocytes were increased by treatment with hydroxypyridinone-coumarin. The production of IL-6, TNF-alpha, and IL-1ß in the osteoarthritis rats was markedly suppressed by hydroxypyridinone-coumarin. Treatment of the OA rats with hydroxypyridinone-coumarin markedly reduced the expression of IkappaB-alpha and NF-kappaB p65. CONCLUSIONS The present study revealed that the proliferative potential of chondrocytes is increased by hydroxypyridinone-coumarin through acceleration of G1/S transition. Moreover, hydroxypyridinone-coumarin treatment reduced inflammatory cytokine production in the osteoarthritis rats. Therefore, hydroxypyridinone-coumarin should be evaluated further for possible use in the treatment of osteoarthritis.