Regulation of cyclooxygenase-2 expression in normal human articular chondrocytes.
This study analyzes cyclooxygenase II (COX-2) gene expression, protein synthesis, and PGE2 release in normal human articular chondrocytes. Stimulation of chondrocytes in primary culture resulted in a dose-dependent induction of COX-2 mRNA in response to IL-1 with an ED50 between 0.1 and 1 ng/ml. COX-2 mRNA was detectable after 2 h, reached high levels at 6 h, and showed a remarkably long duration of expression for at least 72 h. Analysis of other extracellular stimuli showed that COX-2 mRNA was inducible by other cytokines including TNF-alpha, IL-6, and LIF and by bacterial LPS. Dexamethasone completely inhibited IL-1-induced COX-2 mRNA expression. Analysis of signaling pathways showed that PMA and calcium ionophore A23187, but not dibutyryl cAMP, induced COX-2 mRNA. The combination of IL-1 and A23187 resulted in synergistic increases. IL-1 effects were not reduced by the protein kinase C inhibitor staurosporine or by the protein kinase A inhibitor H89 but blocked by the protein tyrosine kinase inhibitor herbimycin A. COX-2 protein was detected at 71 kDa by Western blotting in IL-1-stimulated, and to almost similar levels in A23187-treated, cells. Flow cytometric analysis showed that after IL-1 stimulation 78% of the chondrocytes expressed COX-2 protein. The patterns of COX-2 protein expression and the levels of PGE2 release correlated with the effects of the different stimuli and inhibitors on mRNA expression.
Geng
Y
Y
Sam and Rose Stein Institute for Research on Aging, University of California, San Diego, La Jolla 92093, USA.
Blanco
F J
FJ
Cornelisson
M
M
Lotz
M
M
D002358:Cartilage, Articular / Q000166:cytology / Q000378:metabolism*; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology; D015232:Dinoprostone / Q000096:biosynthesis; D005786:Gene Expression Regulation; D006801:Humans; D007375:Interleukin-1 / Q000502:physiology; D011451:Prostaglandin-Endoperoxide Synthases / Q000187:drug effects / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis; D015398:Signal Transduction / Q000502:physiology
D007375:Interleukin-1; D012333:RNA, Messenger; D003907:Dexamethasone; D011451:Prostaglandin-Endoperoxide Synthases; D015232:Dinoprostone