title: Mitogen-activated protein kinase p38 mediates regulation of chondrocyte differentiation by parathyroid hormone.
abstract: Parathyroid hormone (PTH) and its related peptide regulate endochondral ossification by inhibiting chondrocyte differentiation toward hypertrophy. However, the intracellular pathway for transducing PTH/PTH-related peptide signals in chondrocytes remains unclear. Here, we show that this pathway is mediated by mitogen-activated protein kinase (MAPK) p38. Incubation of hypertrophic chondrocytes with PTH (1-34) induces an inhibition of p38 kinase activity in a time- and dose-dependent manner. Inhibition of protein kinase C prevents PTH-induced p38 MAPK inhibition, whereas inhibition of protein kinase A has no effect. Thus, protein kinase C, but not protein kinase A, is required for the inhibition of p38 MAPK by PTH. Treatment of hypertrophic chondrocytes by PTH or by p38 MAPK inhibitor SB203580 up-regulates Bcl-2, suggesting that Bcl-2 lies downstream of p38 MAPK in the PTH signaling pathway. Inhibition of p38 MAPK in hypertrophic chondrocytes by either PTH, SB303580, or both together leads to a decrease of hypertrophic marker type X collagen mRNA and an increase of the expression of prehypertrophic marker cartilage matrix protein. Therefore, inhibition of p38 converts a hypertrophic cell phenotype to a prehypertrophic one, thereby preventing precocious chondrocyte hypertrophy. Taken together, these data suggest a major role for p38 MAPK in transmitting PTH signals to regulate chondrocyte differentiation.
authors.affiliation: Musculoskeletal Research Laboratory, Department of Orthopaedics and Rehabilitation, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA.
authors.forename: X
authors.initials: X
authors.lastname: Zhen
authors.forename: L
authors.initials: L
authors.lastname: Wei
authors.forename: Q
authors.initials: Q
authors.lastname: Wu
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: Q
authors.initials: Q
authors.lastname: Chen
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D002642:Chick Embryo; D019902:Chondrocytes / Q000166:cytology / Q000378:metabolism*; D003094:Collagen / Q000096:biosynthesis / Q000235:genetics; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016326:Extracellular Matrix Proteins / Q000096:biosynthesis / Q000235:genetics; D006023:Glycoproteins / Q000096:biosynthesis / Q000235:genetics; D007093:Imidazoles / Q000494:pharmacology; D064235:Matrilin Proteins; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D008954:Models, Biological; D010281:Parathyroid Hormone / Q000494:pharmacology*; D019000:Phosphotyrosine / Q000378:metabolism; D011493:Protein Kinase C / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D004791:Enzyme Inhibitors; D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; D007093:Imidazoles; D064235:Matrilin Proteins; D010281:Parathyroid Hormone; D019253:Proto-Oncogene Proteins c-bcl-2; D011725:Pyridines; D012333:RNA, Messenger; D019000:Phosphotyrosine; D003094:Collagen; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580