Esculetin suppresses proteoglycan metabolism by inhibiting the production of matrix metalloproteinases in rabbit chondrocytes.

The possible mechanism of the chondroprotective effect of 6,7-dihydroxycoumarin (esculetin) was investigated using primary cultures of rabbit articular chondrocytes. Esculetin (EST) significantly suppressed the proteoglycan depletion and the release of pulse-labeled [35S]proteoglycan from the matrix layer of rabbit chondrocytes treated with recombinant human interleukin-1alpha. The matrix metalloproteinase inhibitor, 1,10-phenanthroline, also blocked the proteoglycan depletion and [35S]proteoglycan release. From these results, it is likely that recombinant human interleukin-1alpha-induced proteoglycan depletion is mediated by matrix metalloproteinases. Although esculetin did not directly inhibit collagenolytic activity in the culture media, it significantly suppressed the production of pro-matrix metalloproteinase-1/interstitial procollagenase and pro-matrix metalloproteinase-3/prostromelysin 1, accompanied by a decrease in the steady-state levels of their mRNAs. These results suggest that esculetin is a therapeutically effective candidate for inhibition of cartilage destruction in osteoarthritis and rheumatoid arthritis.