Mechanotransduction in bone cells proceeds via activation of COX-2, but not COX-1.
Cyclooxygenase (COX) is the key enzyme in the production of prostaglandins, which are essential for the response of bone to mechanical loading. We determined which COX-isoform, COX-1 or COX-2, determines loading-induced prostaglandin production in primary bone cells in vitro. Mouse and human bone cells reacted to 1 h of pulsating fluid flow (PFF, 0.6+/-0.3 Pa at 5 Hz) with an increased prostaglandin E(2) production, which continued 24 h after cessation of PFF. Inhibition of COX-2 activity with NS-398 abolished the stimulating effect of PFF both at 1 h and at 24 h post-incubation, while inhibition of COX-1 by SC-560 affected neither the early nor the late response to flow. PFF rapidly stimulated COX-2 mRNA expression at 1 h but did not affect COX-1 mRNA expression. COX-2 mRNA expression was still significantly enhanced 24 h after cessation of PFF. We conclude that COX-2 is the mechanosensitive form of COX that determines the response of bone tissue to mechanical loading.
Bakker
A D
AD
Department of Oral Cell Biology, ACTA-Vrije Universiteit, Amsterdam, The Netherlands. AD.Bakker.OCB.ACTA@med.vu.nl
Klein-Nulend
J
J
Burger
E H
EH
D000818:Animals; D001842:Bone and Bones / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D002478:Cells, Cultured; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000096:biosynthesis; D004789:Enzyme Activation; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D040542:Mechanotransduction, Cellular; D008565:Membrane Proteins; D051379:Mice; D009578:Nitrobenzenes / Q000494:pharmacology; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism*; D011720:Pyrazoles / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D013314:Stress, Mechanical; D013449:Sulfonamides / Q000494:pharmacology
D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D007527:Isoenzymes; D008565:Membrane Proteins; D009578:Nitrobenzenes; D011720:Pyrazoles; D012333:RNA, Messenger; C115461:SC 560; D013449:Sulfonamides; C080955:N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; C496511:PTGS1 protein, human; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; C496512:Ptgs1 protein, mouse; D015232:Dinoprostone