Gene expression of osteoclast differentiation factor is induced by lipopolysaccharide in mouse osteoblasts via Toll-like receptors.
Osteoclast differentiation factor (ODF), a recently identified cytokine of the TNF family, is expressed as a membrane-associated protein in osteoblasts and stromal cells. ODF stimulates the differentiation of osteoclast precursors into osteoclasts in the presence of M-CSF. Here we investigated the effects of LPS on the gene expression of ODF in mouse osteoblasts and an osteoblast cell line and found that LPS increased the ODF mRNA level. A specific inhibitor of extracellular signal-regulated kinase or protein kinase C inhibited this up-regulation, indicating that extracellular signal-regulated kinase and protein kinase C activation was involved. A protein synthesis inhibitor, cycloheximide, rather enhanced the LPS-mediated increase of ODF mRNA, and both a neutralizing Ab of TNF-alpha and a specific inhibitor of PGE synthesis failed to block the ODF mRNA increase by native LPS. Thus, LPS directly induced ODF mRNA. Mouse osteoblasts and an osteoblast cell line constitutively expressed Toll-like receptor (TLR) 2 and 4, which are known as putative LPS receptors. ODF mRNA increases in response to synthetic lipid A were defective in primary osteoblasts from C3H/HeJ mice that contain a nonfunctional mutation in the TLR4 gene, suggesting that TLR4 plays an essential role in the process. Altogether, our results indicate that ODF gene expression is directly increased in osteoblasts by LPS treatment via TLR, and this pathway may play an important role in the pathogenesis of LPS-mediated bone disorders, such as periodontitis.
Kikuchi
T
T
Laboratory of Host Defense and Germfree Life, Research Institute for Disease Mechanism and Control, Nagoya University School of Medicine, Nagoya, Japan.
Matsuguchi
T
T
Tsuboi
N
N
Mitani
A
A
Tanaka
S
S
Matsuoka
M
M
Yamamoto
G
G
Hishikawa
T
T
Noguchi
T
T
Yoshikai
Y
Y
D000818:Animals; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics*; D002460:Cell Line; D029721:Drosophila Proteins; D004789:Enzyme Activation / Q000276:immunology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology*; D006023:Glycoproteins / Q000096:biosynthesis / Q000235:genetics; D008050:Lipid A / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000235:genetics* / Q000502:physiology*; D051379:Mice; D008809:Mice, Inbred C3H; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010006:Osteoblasts / Q000187:drug effects / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D010010:Osteoclasts / Q000378:metabolism*; D053244:Osteoprotegerin; D053245:RANK Ligand; D012333:RNA, Messenger / Q000096:biosynthesis; D053246:Receptor Activator of Nuclear Factor-kappa B; D011956:Receptors, Cell Surface / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000096:biosynthesis / Q000235:genetics; D018124:Receptors, Tumor Necrosis Factor; D015398:Signal Transduction / Q000276:immunology; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D015854:Up-Regulation / Q000235:genetics / Q000276:immunology
D002352:Carrier Proteins; D029721:Drosophila Proteins; D006023:Glycoproteins; D008050:Lipid A; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D053244:Osteoprotegerin; D053245:RANK Ligand; D012333:RNA, Messenger; D053246:Receptor Activator of Nuclear Factor-kappa B; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; C505687:Tnfrsf11a protein, mouse; C506031:Tnfrsf11b protein, mouse; C505689:Tnfsf11 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D020928:Mitogen-Activated Protein Kinases