Abstract
Sphingosine 1-phosphate (S1P), produced by sphingosine kinase (SPHK), acts both by intracellular and extracellular modes. We evaluated the role of SPHK1 and S1P in osteoclastogenesis using bone marrow-derived macrophage (BMM) single and BMM/osteoblast coculture systems. In BMM single cultures, the osteoclastogenic factor receptor activator of NF-kappaB ligand (RANKL) upregulated SPHK1 and increased S1P production and secretion. SPHK1 siRNA enhanced and SPHK1 overexpression attenuated osteoclastogenesis via modulation of p38 and ERK activities, and NFATc1 and c-Fos levels. Extracellular S1P had no effect in these cultures. These data suggest that intracellular S1P produced in response to RANKL forms a negative feedback loop in BMM single cultures. In contrast, S1P addition to BMM/osteoblast cocultures greatly increased osteoclastogenesis by increasing RANKL in osteoblasts via cyclooxygenase-2 and PGE(2) regulation. S1P also stimulated osteoblast migration and survival. The RANKL elevation and chemotactic effects were also observed with T cells. These results indicate that secreted S1P attracts and acts on osteoblasts and T cells to augment osteoclastogenesis. Taken together, S1P plays an important role in osteoclastogenesis regulation and in communication between osteoclasts and osteoblasts or T cells.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Cell Differentiation / drug effects*
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Cell Survival / drug effects
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Chemotaxis / drug effects
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Coculture Techniques
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Cyclooxygenase 2 / genetics
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Cyclooxygenase 2 / metabolism
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Dinoprostone / metabolism
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Extracellular Signal-Regulated MAP Kinases / metabolism
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Gene Expression Regulation, Enzymologic / drug effects
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HeLa Cells
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Humans
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Lymphocyte Activation / drug effects
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Lysophospholipids / pharmacology*
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Mice
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NFATC Transcription Factors / metabolism
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Osteoblasts / cytology*
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Osteoblasts / drug effects*
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Osteoblasts / metabolism
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Osteoclasts / cytology*
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Osteoclasts / drug effects*
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Osteogenesis / drug effects
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Phosphotransferases (Alcohol Group Acceptor) / genetics
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Phosphotransferases (Alcohol Group Acceptor) / metabolism
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Proto-Oncogene Proteins c-fos / metabolism
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RANK Ligand / genetics
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RANK Ligand / metabolism
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RNA, Messenger / genetics
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RNA, Messenger / metabolism
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Sphingosine / analogs & derivatives*
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Sphingosine / pharmacology
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T-Lymphocytes / cytology
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T-Lymphocytes / drug effects
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p38 Mitogen-Activated Protein Kinases / metabolism
Substances
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Lysophospholipids
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NFATC Transcription Factors
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Proto-Oncogene Proteins c-fos
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RANK Ligand
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RNA, Messenger
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sphingosine 1-phosphate
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Cyclooxygenase 2
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Phosphotransferases (Alcohol Group Acceptor)
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sphingosine kinase
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Extracellular Signal-Regulated MAP Kinases
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p38 Mitogen-Activated Protein Kinases
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Dinoprostone
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Sphingosine