Inhibition of Interleukin-1β-Induced Matrix Metalloproteinases 1 and 13 Production in Human Osteoarthritic Chondrocytes by Prostaglandin D2

Objective. To investigate the effects of prostaglandin D-2 (PGD(2)) on interieukin-1 beta (IL-1 beta)-induced matrix metalloproteinase 1 (MMP-1) and MMP-13 expression in human chondrocytes and the signaling pathways involved in these effects. Methods. Chondrocytes were stimulated with IL-1 in the presence or absence of PGD(2), and expression of MMP-1. and MMP-13 proteins was evaluated by enzyme-linked immunosorbent assay. Messenger RNA (mRNA) expression and promoter activity were analyzed by real-time reverse transcription-polymerase chain reaction and transient transfections, respectively. The role of the PGD(2) receptors D prostanoid receptor 1 (DP1) and chemoattractant receptor-like molecule expressed on Th2 cells (CRTH2) was evaluated using specific agonists and antibody-blocking experiments. The contribution of the cAMP/protein kinase A (PKA) pathway was determined using cAMP-elevating agents and PKA inhibitors. Results. PGD(2) decreased in a dose-dependent manner IL-1-induced MMP-1 and MMP-13 protein and mRNA expression as well as their promoter activation. DP1 and CRTH2 were expressed and functional in chondrocytes. The effect of PGD(2) was mimicked by BW245C, a selective agonist of DP1, but not by 13,14-dihydro-15-keto-PGD(2), a selective agonist of CRTH2. Furthermore, treatment with an anti-DP1 antibody reversed the effect of PGD(2) indicating that the inhibitory effect of PGD(2) is mediated by DP1. The cAMP-elevating agents 8-Br-cAMP and forskolin suppressed IL-1-induced MMP-1 and MMP-13 expression, and the PKA inhibitors KT5720 and H89 reversed the inhibitory effect of PGD(2) suggesting that the effect of PGD(2) is mediated by the cAMP/PKA pathway. Conclusion. PGD(2) inhibits IL-1-induced production of MMP-1 and MMP-13 by chondrocytes through the DP1/cAMP/PKA signaling pathway. These data also suggest that modulation of PGD(2) levels in the joint may have therapeutic potential in the prevention of cartilage degradation.