Abstract
Objective
To investigate the effects of prostaglandin D~2~ (PGD~2~) on interleukin‐1β (IL‐1β)–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.