IN-VITRO SUPPRESSION OF TRANSFORMING-GROWTH-FACTOR-BETA INDUCED STIMULATION OF GLYCOSAMINOGLYCAN SYNTHESIS BY ACETYLSALICYLIC-ACID AND ITS REVERSAL BY MISOPROSTOL

Objective. To determine if acetylsalicylic acid (ASA) suppresses the s timulatory effects of transforming growth factor-beta (TGF-beta) and i nsulin-like growth factor-1 (IGF-1) on glycosaminoglycan (GAG) synthes is by cultured bovine articular chondrocytes (BAC), and whether such a suppression can be counteracted by the addition of misoprostol, a pro staglandin (PG) E-1 analog. Methods. Confluent cultures of BAC were pr e-incubated for 2 days with ASA (Aspirin) (250 mu g/ml), TGF-beta (10 ng/ml), IGF-1 (150 ng/ml), and misoprostol (80 ng/ml), separately and in different combinations, and for 2 more days with fresh medium and t he same test agents in the presence of S-35-sulfate (10 mu Ci/ml), The radiolabelled GAG in the medium were then isolated, separated by cell ulose acetate electrophoresis, and assayed for incorporated radioactiv ity, as a measure of GAG synthesis. Results. TGF-beta, IGF-1, at their optimal concentrations, and misoprostol (80 ng/ml) stimulated GAG syn thesis 2.6, 1.8, and 2.4-fold, respectively, of the control value, but ASA (250 mu g/ml) showed no significant effect. ASA in combination wi th TGF-beta or misoprostol markedly suppressed the stimulation of GAG synthesis observed with either TGF-beta or misoprostol alone, but had no effect on the stimulation of GAG synthesis by IGF-1. Addition of mi soprostol together with TGF-beta potentiated the stimulation of GAG sy nthesis by TGF-beta and abolished the suppressive effect of ASA on the stimulation of GAG synthesis by TGF-beta. Also, the magnitude of the stimulatory effect of misoprostol varied from batch to batch of misopr ostol as well as for the same batch when it was added to the cultures either directly or after diluting with serum-free medium. Conclusion. In BAC cultures, ASA suppresses and misoprostol potentiates the stimul ation of GAG synthesis by TGF-beta. Misoprostol also counteracts ASA i nduced suppression of the stimulation of GAG synthesis by TGF-beta.