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-1 alpha or or retinoic acid. PG release was determined by measuring glycosaminoglyc an release, and nitrite production was measured as a readout for NO. Inhibi tion of iNOS gene expression was measured by Northern blot analysis in IL-1 alpha-stimulated, cartilage-derived chondrocytes. To measure PG synthesis, chondrocytes were established in alginate beads and treated with hymeniald isine, and then [S-35]sulfate incorporation into PGs was determined. Hymeni aldisine inhibited IL-1 alpha-stimulated PG breakdown in BAC in a dose-rela ted manner with an IC50 of approximately 0.6 mu M. Herbimycin, a protein ty rosine kinase inhibitor, also inhibited PG breakdown, whereas RO 32-0432, a protein kinase C inhibitor, had no effect. Both hymenialdisine and herbimy cin also were able to inhibit retinoic acid-stimulated PG release. IL-1 alp ha-stimulated NO production in BAC was inhibited by hymenialdisine and herb imycin at similar concentrations. The effect on iNOS gene expression was de termined by Northern blot analysis in chondrocytes grown in monolayer, and inhibition by hymenialdisine was observed with an IC50 of approximately 0.8 mu M In chondrocytes cultured in alginate beads, IL-1 alpha inhibited PG s ynthesis, whereas hymenialdisine stimulated synthesis at low concentrations (0.6 and 1.25 mu M), and higher doses (2.5 mu M) were not stimulatory. Com pounds with this profile may have utility in the treatment of osteoarthriti s.