PGE2 induces the gene expression of bone matrix metalloproteinase-1 in mouse osteoblasts by cAMP-PKA signaling pathway.
Prostaglandin E2 (PGE2), an abundant eicosanoid in bone, has been implicated in a number of pathological states associated with bone loss, and is also known to stimulate matrix metalloproteinase (MMP)-1 synthesis and secretion in rat and human osteoblast cells, although the nature of the intracellular reaction remains unclear. Although MMP-1 plays a critical role in bone-remodeling, it would be of interest to examine whether PGE2 regulates MMP-1 expression by mouse osteoblasts or not. Here we demonstrate that PGE2 is a potent inducer of MMP-1 production in fetal osteoblasts and show that PGE2 stimulates the activity of the MMP-1 promoter in osteoblasts, suggesting that PGE2 controls MMP-1 gene expression at least at the transcriptional level. PGE2 induced MMP-1 messenger RNA (mRNA) expression in the cells within 4 h, and this expression was maintained for 36 h. The increase in MMP-1 production with 0.1-2.0 microM PGE2 was dose-dependent. We also found that PGE2 (1.5 microM) up-regulated MMP-1 protein levels in cultured mouse osteoblasts, as evidenced by ELISA. To examine whether PGE2 mediated response and signal pathway are involved in the intracellular action, the PGE2-mediated expression of the MMP-1 gene was investigated in mouse osteoblast cells. A Northern blot analysis showed that PGE2 and PGE1 were potent stimulators of MMP-1 transcription, and the presence of thromboxane B2 had no effect. The increase in MMP-1 transcript after PGE2 treatment was observed at 4h, reaching a maximum at 6h, and persisted for 24h. This response was dose-dependent. Cycloheximide, an inhibitor of protein synthesis, completely blocked this effect by PGE2, indicating that the expression of other genes is also required. The second messenger analog, 8-bromo-cAMP, mimicked the effects of PGE2 by stimulating a dose-dependent increase in MMP-1 mRNA levels, with a maximal effect that was quantitatively similar to that observed with PGE2. Thus, the present results strongly suggest that the PGE2 stimulation of MMP-1 synthesis is due to the activation of MMP-1 gene transcription and a subsequent marked increase in MMP-1 transcription. This effect is dependent on de novo protein synthesis and is mimicked by protein kinase A activation. The findings suggest that PGE2 is involved in the cAMP-PKA signaling pathway in regulating MMP-1 gene expression in osteoblasts.
Kim
Cheorl-Ho
CH
National Research Laboratory for Glycobiology, Ministry of Science and Technology, Kyungju City, Kyungbuk 780-714, Korea. chkimbio@dongguk.ac.kr
Park
Young-Guk
YG
Noh
Sang-Ho
SH
Kim
Yeon-Kye
YK
D000818:Animals; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D015232:Dinoprostone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D020781:Matrix Metalloproteinase 1 / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D008807:Mice, Inbred BALB C; D010006:Osteoblasts / Q000378:metabolism*; D010120:Oxytocics / Q000494:pharmacology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D015290:Second Messenger Systems / Q000187:drug effects*; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics
D010120:Oxytocics; D012333:RNA, Messenger; D017868:Cyclic AMP-Dependent Protein Kinases; D020781:Matrix Metalloproteinase 1; D015232:Dinoprostone