Inhibition of interleukin-1-induced proteoglycan degradation and nitric oxide production in bovine articular cartilage/chondrocyte cultures by the natural product, hymenialdisine.

The effects of hymenialdisine (SK&F 108752) were evaluated on interleukin-1 (IL-1)-induced proteoglycan (PG) degradation, PG synthesis, nitric oxide (NO) production, and inducible nitric oxide synthase (iNOS) gene expression in bovine articular cartilage (BAC) and/or cartilage-derived chondrocytes. Cartilage disks from 0- to 3-month-old calves were treated with IL-1alpha or retinoic acid. PG release was determined by measuring glycosaminoglycan release, and nitrite production was measured as a readout for NO. Inhibition of iNOS gene expression was measured by Northern blot analysis in IL-1alpha-stimulated, cartilage-derived chondrocytes. To measure PG synthesis, chondrocytes were established in alginate beads and treated with hymenialdisine, and then [(35)S]sulfate incorporation into PGs was determined. Hymenialdisine inhibited IL-1alpha-stimulated PG breakdown in BAC in a dose-related manner with an IC(50) of approximately 0.6 microM. Herbimycin, a protein tyrosine kinase inhibitor, also inhibited PG breakdown, whereas RO 32-0432, a protein kinase C inhibitor, had no effect. Both hymenialdisine and herbimycin also were able to inhibit retinoic acid-stimulated PG release. IL-1alpha-stimulated NO production in BAC was inhibited by hymenialdisine and herbimycin at similar concentrations. The effect on iNOS gene expression was determined by Northern blot analysis in chondrocytes grown in monolayer, and inhibition by hymenialdisine was observed with an IC(50) of approximately 0.8 microM. In chondrocytes cultured in alginate beads, IL-1alpha inhibited PG synthesis, whereas hymenialdisine stimulated synthesis at low concentrations (0.6 and 1.25 microM), and higher doses (2.5 microM) were not stimulatory. Compounds with this profile may have utility in the treatment of osteoarthritis.