Abstract
Coupled bone turnover is directed by the expression of receptor-activated NF-kappaB ligand (RANKL) and its decoy receptor, osteoprotegerin (OPG). Proinflammatory cytokines, such as interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) induce RANKL expression in bone marrow stromal cells. Here, we report that IL-1beta and TNF-alpha-induced RANKL requires p38 mitogen-activating protein kinase (MAPK) pathway activation for maximal expression. Real-time PCR was used to assess the p38 contribution toward IL-1beta and TNF-alpha-induced RANKL mRNA expression. Steady-state RANKL RNA levels were increased approximately 17-fold by IL-1beta treatment and subsequently reduced approximately 70%-90% when p38 MAPK was inhibited with SB203580. RANKL mRNA stability data indicated that p38 MAPK did not alter the rate of mRNA decay in IL-1beta-induced cells. Using a RANKL-luciferase cell line receptor containing a 120-kB segment of the 5' flanking region of the RANKL gene, reporter expression was stimulated 4-5-fold by IL-1beta or TNF-alpha treatment. IL-1beta-induced RANKL reporter expression was completely blocked with specific p38 inhibitors as well as dominant negative mutant constructs of MAPK kinase-3 and -6. In addition, blocking p38 signaling in bone marrow stromal cells partially inhibited IL-1beta and TNF-alpha-induced osteoclastogenesis in vitro. Results from these studies indicate that p38 MAPK is a major signaling pathway involved in IL-1beta and TNF-alpha-induced RANKL expression in bone marrow stromal cells.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Animals
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Bone Marrow Cells / drug effects
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Bone Marrow Cells / enzymology
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Bone Marrow Cells / metabolism*
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Carrier Proteins / biosynthesis*
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Carrier Proteins / genetics
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Cell Differentiation
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Cell Line
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Cytokines / pharmacology*
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Genes, Reporter
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Imidazoles / pharmacology
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Interleukin-1 / antagonists & inhibitors
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Interleukin-1 / pharmacology
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MAP Kinase Kinase 3 / antagonists & inhibitors
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MAP Kinase Kinase 3 / genetics
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MAP Kinase Kinase 3 / metabolism
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MAP Kinase Kinase 6 / antagonists & inhibitors
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MAP Kinase Kinase 6 / genetics
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MAP Kinase Kinase 6 / metabolism
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MAP Kinase Signaling System / drug effects
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Membrane Glycoproteins / biosynthesis*
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Membrane Glycoproteins / genetics
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Mice
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Mitogen-Activated Protein Kinase Kinases / metabolism*
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Mutation
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Osteoclasts / cytology
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Protein Kinase Inhibitors / pharmacology
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Pyridines / pharmacology
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RANK Ligand
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RNA, Messenger / metabolism
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Receptor Activator of Nuclear Factor-kappa B
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Stromal Cells / drug effects
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Stromal Cells / enzymology
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Stromal Cells / metabolism
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Transcriptional Activation
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Tumor Necrosis Factor-alpha / antagonists & inhibitors
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Tumor Necrosis Factor-alpha / pharmacology
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p38 Mitogen-Activated Protein Kinases / antagonists & inhibitors
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p38 Mitogen-Activated Protein Kinases / metabolism*
Substances
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Carrier Proteins
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Cytokines
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Imidazoles
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Interleukin-1
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Membrane Glycoproteins
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Protein Kinase Inhibitors
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Pyridines
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RANK Ligand
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RNA, Messenger
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Receptor Activator of Nuclear Factor-kappa B
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Tnfrsf11a protein, mouse
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Tnfsf11 protein, mouse
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Tumor Necrosis Factor-alpha
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p38 Mitogen-Activated Protein Kinases
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MAP Kinase Kinase 3
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MAP Kinase Kinase 6
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Mitogen-Activated Protein Kinase Kinases
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SB 203580