PROSTAGLANDINS E(2) AND E(1) INHIBIT CYTOKINE-INDUCED METALLOPROTEASEEXPRESSION IN HUMAN SYNOVIAL FIBROBLASTS - MEDIATION BY CYCLIC-AMP SIGNALING PATHWAY

BACKGROUND: Cytokine modulated matrix metalloprotease (MMP, i.e., coll agenase and stromelysin) synthesis may be associated etiologically wit h osteoarthritic diseases. The aim of this study was to investigate th e mode of action by which interleukin-1 beta (IL-1 beta) induced colla genase and stromelysin mRNA expression and synthesis in normal human s ynoviocytes and to explore mechanisms of suppression of these proteoly tic enzymes by prostaglandins (PG). EXPERIMENTAL DESIGN: Collagenase a nd stromelysin expression and synthesis were induced in cultured human synoviocytes with rhIL-1 beta in the absence or presence of either ch emical inhibitors of protein kinase (PK) A and C, PGE(2) or PGE(1), or cAMP mimetics. We used enzyme immunoassays to determine MMP antigen l evels in spent culture medium and Northern hybridization to measure st eady-state MMP mRNA expression. RESULTS: Dose-response experiments rev ealed that 10 pg/ml of interleukin-1 beta was an effective sub-saturat ing concentration for the induction of collagenase and stromelysin exp ression in normal human synovial fibroblasts. The rate of collagenase and stromelysin expression peaked at 18 to 24 hours after rhIL-1 beta stimulation, whereas stromelysin output increased steadily within the experimental time frame (72 hours). Protein kinase C inhibitors, H-7 a nd staurosporine, prevented the rhIL-1 beta induction of MMP mRNA expr ession and protein synthesis. Pretreatment of synoviocytes with phorbo l myristate acetate for 18 hours abrogated the ability of rhIL-1 beta to induce MMP synthesis. Prostaglandins E(2) and E(1) potently inhibit ed in a dose-dependent fashion rhIL-1 beta induced MMP synthesis: PGE( 2), IC50, collagenase, 2.3 ng/ml; stromelysin, 21.2 ng/ml; PGE(1), IC5 0, collagenase, 2.5 ng/ml; stromelysin, 13.4 ng/ml. MMP mRNA steady-st ate levels were suppressed in a fashion similar to that of the protein synthesis. Forskolin, dibutyryl cAMP, and 3-isobutyl-1-methyl xanthin e mimicked the effects of the prostaglandins (PGs). [N-(2-methyl-amino )-5-isoquinoline-sulfonamide dihydrochloride] (H-8), and inhibitor of PKA activity, could reverse to a large extent, the suppressive effects of the PGs as did cycloheximide when preincubated with PGE(2) before rhIL-1 beta activation of synoviocytes. CONCLUSION: We conclude that I L-1 beta stimulates MMP synthesis by activating PKC but not PKA, and t hat the synthesis of collagenase and stromelysin is discoordinate on a temporal and quantitative basis. PGs inhibit rhIL-1 beta-induced MMP expression and synthesis by virtue of their ability to increase cAMP i ntracellular levels and subsequent activation of signal transduction m echanisms involving PKA. Homeostasis may be maintained in acute episod es of joint inflammation through feedback processes involving locally produced eicosanoids.