PROSTANOID-INDUCED EXPRESSION OF MATRIX METALLOPROTEINASE-1 MESSENGER-RIBONUCLEIC-ACID IN RAT OSTEOSARCOMA CELLS

Individual prostanoids have distinct potencies in activating intracell ular signaling pathways and regulating gene expression in osteoblastic cells. The E-series prostaglandins (PGs) are known to stimulate matri x metalloproteinase-1 (MMP-1) synthesis and secretion in certain roden t and human osteoblastic cells, yet the intracellular events involved remain unclear. To further characterize this response and its signal t ransduction pathway(s), we examined prostanoid-induced expression of t he MMP-1 gene in the rat osteoblastic osteosarcoma cell line UMR 106-0 1. Northern blot analysis demonstrated that prostaglandin E(2) (PGE(2) ) and PGE(1) were very potent stimulators (40-fold) of MMP-1 transcrip t abundance, PGF(2 alpha) and prostacyclin were weak stimulators (4-fo ld), and thromboxane-B-2 had no effect. The marked increase in MMP-1 t ranscript abundance after PGE(2) treatment was first detected at 2 h, became maximal at 4 h, and persisted beyond 24 h. This response was do se dependent and elicited maximal and half-maximal effects with concen trations of 10(-6) and 0.6 x 10(-7) M, respectively. Cycloheximide, a protein synthesis inhibitor, completely blocked this effect of PGE(2), suggesting that the expression of other genes is required. Nuclear ru n-on experiments demonstrated that PGE(2) rapidly activates MMP-1 gene transcription, with a maximal increase at 2-4 h. The second messenger analog, 8-bromo-cAMP, mimicked the effects of PGE(2) by stimulating a dose-dependent increase in MMP-1 messenger RNA (mRNA) levels, with a maximal effect quantitatively similar to that observed with PGE(2). Th us, in UMR 106-01 cells, different prostanoids have distinct potencies in stimulating MMP-1 mRNA abundance. Our data suggest that PGE2 stimu lation of MMP-1 synthesis is due to activation of MMP-1 gene transcrip tion and a subsequent marked increase in MMP-1 mRNA abundance. This ef fect s dependent on de novo protein synthesis and is mimicked by prote in kinase-A activation.