Fluid flow induces COX-2 expression in MC3T3-E1 osteoblasts via a PKA signaling pathway.
Mechanical loading of bone generates fluid flow within the mineralized matrix which can exert fluid shear stress (FSS) at cell membranes. FSS induces new transcription of cyclooxygenase-2 (COX-2) in MC3T3-E1 osteoblasts, with peak effects at 4-5h. Using MC3T3-E1 cells stably transfected with the COX-2 promoter fused to a luciferase reporter, we examined involvement of the protein kinase A (PKA) and protein kinase C (PKC) signaling pathways in the peak COX-2 mRNA and luciferase responses to FSS (10dyn/cm(2)). Neither inhibition nor down-regulation of the PKC pathway affected the FSS stimulation of COX-2 mRNA or luciferase activity. In contrast, inhibitors of the PKA pathway, used at doses which inhibited forskolin-stimulated luciferase activity by 70-80%, reduced FSS-stimulated COX-2 mRNA expression and luciferase activity by 50-80%. Hence, peak FSS induction of COX-2 expression in MC3T3-E1 osteoblastic cells is largely dependent on the PKA signaling pathway.
Wadhwa
Sunil
S
Department of Orthodontics, School of Dental Medicine, University of Connecticut Health Center, Farmington, CT 06030, USA.
Choudhary
Shilpa
S
Voznesensky
Maria
M
Epstein
Mary
M
Raisz
Lawrence
L
Pilbeam
Carol
C
D000818:Animals; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D051546:Cyclooxygenase 2; D007527:Isoenzymes / Q000096:biosynthesis*; D051379:Mice; D010006:Osteoblasts / Q000201:enzymology* / Q000378:metabolism; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis*; D015398:Signal Transduction / Q000502:physiology*
D007527:Isoenzymes; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D017868:Cyclic AMP-Dependent Protein Kinases