title: PGE2 inhibits chondrocyte differentiation through PKA and PKC signaling.
abstract: Prostaglandins are ubiquitous metabolites of arachidonic acid, and cyclooxygenase inhibitors prevent their production and secretion. Animals with loss of cyclooxygenase-2 function have reduced reparative bone formation, but the role of prostaglandins during endochondral bone formation is not defined. The role of PGE2 as a regulator of chondrocyte differentiation in chick growth plate chondrocytes (GPCs) was examined. While PGE2, PGD2, PGF2alpha, and PGJ2 all inhibited colX expression, approximately 80% at 10(-6) M, PGE2 was the most potent activator of cAMP response element (CRE)-mediated transcription. PGE2 dose-dependently inhibited the expression of the differentiation-related genes, colX, VEGF, MMP-13, and alkaline phosphatase gene, and enzyme activity with significant effects at concentrations as low as 10(-10) M. PGE2 induced cyclic AMP response element binding protein (CREB) phosphorylation and increased c-Fos protein levels by 5 min, and activated transcription at CRE-Luc, AP-1-Luc, and c-Fos promoter constructs. The protein kinase A (PKA) inhibitor, H-89, completely blocked PGE2-mediated induction of CRE-Luc and c-Fos promoter-Luc promoters, and partially inhibited induction of AP-1-Luc, while the protein kinase C (PKC) inhibitor Go-6976 partially inhibited all three promoters, demonstrating substantial cross-talk between these signaling pathways. PGE2 inhibition of colX gene expression was dependent upon both PKA and PKC signaling. These observations demonstrate potent prostaglandin regulatory effects on chondrocyte maturation and show a role for both PKA and PKC signaling in PGE2 regulatory events.
authors.affiliation: Center for Musculoskeletal Research, School of Medicine and Dentistry, University of Rochester, Rochester, NY 14642, USA.
authors.forename: Tian-Fang
authors.initials: TF
authors.lastname: Li
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Zuscik
authors.forename: Andreia M
authors.initials: AM
authors.lastname: Ionescu
authors.forename: Xinping
authors.initials: X
authors.lastname: Zhang
authors.forename: Randy N
authors.initials: RN
authors.lastname: Rosier
authors.forename: Edward M
authors.initials: EM
authors.lastname: Schwarz
authors.forename: Hicham
authors.initials: H
authors.lastname: Drissi
authors.forename: Regis J
authors.initials: RJ
authors.lastname: O'Keefe
mesh_terms: D000469:Alkaline Phosphatase / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D002356:Cartilage / Q000254:growth & development / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D002645:Chickens; D019902:Chondrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D024121:Collagen Type X / Q000187:drug effects / Q000378:metabolism; D017364:Collagenases / Q000187:drug effects / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000187:drug effects / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D015232:Dinoprostone / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D053509:Matrix Metalloproteinase 13; D010012:Osteogenesis / Q000187:drug effects / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D011493:Protein Kinase C / Q000187:drug effects / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D042461:Vascular Endothelial Growth Factor A / Q000187:drug effects / Q000378:metabolism
chemical_list: D024121:Collagen Type X; D017362:Cyclic AMP Response Element-Binding Protein; D004791:Enzyme Inhibitors; D016760:Proto-Oncogene Proteins c-fos; D042461:Vascular Endothelial Growth Factor A; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D000469:Alkaline Phosphatase; D017364:Collagenases; D053509:Matrix Metalloproteinase 13; D015232:Dinoprostone