title: Role of mitogen-activated protein kinase in osteoblast differentiation.
abstract: Local control of osteoblast differentiation and bone formation is not well understood. We have previously seen biphasic effects on cell differentiation in response to the short- and long-term exposure to IL-1β in rat calvarial osteoblasts. To characterize the signaling pathway mechanisms regulating IL-1β biphasic effects, we examined the contribution of mitogen-activated protein kinase (MAPK) family. Cells were pretreated with specific inhibitors to extracellular signal-regulated kinase (ERK, PD98059), p38 (SB203580), and c-JUN N-terminal kinase (JNK, SP600125), then co-cultured with IL-1β for 2, 4, and 6 days. Cell differentiation was determined by measuring bone nodules after 10 days of culture. These inhibitors did not alter biphasic effects of IL-1β on cell differentiation. However, PD98059 and U2016, another inhibitor of ERK activation robustly increased osteoblast differentiation compared to vehicle-treated control in a time- and dose-dependent manner. PD98059 appears to stimulate alkaline phosphatase (ALP) activity to promote cell differentiation, where IL-1β appears to suppress it. Interestingly, continuous ERK inhibition with PD98059, after 2 and 4 days of IL-1β treatment, enhanced the IL-1β anabolic effect by increasing bone nodules formed. These observations provide a potential mechanism involving ERK pathway in osteoblasts differentiation and suggest that MAPK family may not directly regulate IL-1β biphasic effects.
authors.affiliation: Division of Orthopaedic Surgery, Department of Surgery, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: Fu-Hsiung
authors.initials: FH
authors.lastname: Lin
authors.forename: Jessica B
authors.initials: JB
authors.lastname: Chang
authors.forename: Brian E
authors.initials: BE
authors.lastname: Brigman
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D002070:Butadienes; D002454:Cell Differentiation; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000378:metabolism; D005419:Flavonoids; D053583:Interleukin-1beta / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D009570:Nitriles; D010006:Osteoblasts / Q000166:cytology / Q000201:enzymology*; D010012:Osteogenesis; D051381:Rats; D012886:Skull / Q000166:cytology
chemical_list: D002070:Butadienes; D005419:Flavonoids; D053583:Interleukin-1beta; D009570:Nitriles; C113580:U 0126; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D051546:Cyclooxygenase 2; C489691:Ptgs2 protein, rat; D020928:Mitogen-Activated Protein Kinases; D000469:Alkaline Phosphatase; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one