Effects of indomethacin on the production of matrix metalloproteinase-3 and tissue inhibitor of metalloproteinases-1 by human articular chondrocytes

Objective. To study the action of indomethacin on cartilage catabolic activity by comparing the production of a matrix degrading proteinase and its inhibitor in human articular chondrocyte cultures. Methods. Matrix metalloproteinase-3 (MMP-3) and tissue inhibitor of metalloproteinases-1 (TIMP1) in conditioned medium from human articular chondrocyte cultures were measured using a one-step sandwich enzyme immunoassay. TIMP-1 mRNA expression was analyzed by Northern blotting using a 0.6 kb cDNA probe for human TIMP-1. Results. Human recombinant interleukin 1β (IL-1β) increased MMP-3 levels in primary chondrocyte cultures. Indomethacin at 10^-5 M inhibited this IL-1β stimulation, but had no effect in the therapeutic range (10^-6-10^-7 M). Low levels of indomethacin (10^-7 M) significantly increased the production of TIMP-1 by chondrocytes. Synthesis of TIMP-1 appeared to be inhibited by prostaglandin E₂ (PGE₂), since exogenously added PGE₂ reversed the stimulating effect of indomethacin on TIMP-1 production. Northern blot analysis showed that 10^-7 M indomethacin increased TIMP-1 mRNA levels in chondrocytes. Conclusion. Our findings indicate that low levels of indomethacin can benefit matrix metabolism by affecting the balance of proteinases to their inhibitors in human articular cartilage.