title: NMDA glutamate receptors are expressed by osteoclast precursors and involved in the regulation of osteoclastogenesis.
abstract: We previously identified functional N-methyl-D-aspartate (NMDA) glutamate receptors in mature osteoclasts and demonstrated that they are involved in bone resorption in vitro. In the present work, we studied the expression of NMDA receptors (NMDAR) by osteoclast precursors and their role in osteoclastogenesis using two in vitro models, the murine myelomonocytic RAW 264.7 cell line and mouse bone marrow cells, both of which differentiate into osteoclasts in the presence of macrophage colony-stimulating factor (M-CSF) and Rank ligand (RankL). Using RT-PCR analysis with specific probes, we showed that RAW 264.7 cells and mouse bone marrow cells express mRNA of NMDAR subunits NMDA receptor 1 (NR1) and NMDA receptor 2 (NR2) A, B, and D. These subunits are expressed all along the differentiation sequence from undifferentiated precursors to mature resorbing osteoclasts. Semi-quantitative PCR analysis showed no regulation of the expression of these subunits during the differentiation process. Two specific non competitive antagonists of NMDAR, MK801 and DEP, dose-dependently inhibited osteoclast formation in both models, indicating that osteoclastogenesis requires the activation of NMDAR expressed by osteoclast precursors. MK801 had no effect when added only during the first 2 days of culture, suggesting that NMDAR are rather involved in the late stages of osteoclast formation. Finally, we demonstrated using Western-blotting and immunofluorescence that activation of NMDAR in RAW 264.7 cells by specific agonists induces nuclear translocation of NF-kappa B, a factor required for osteoclast formation. Altogether, our results indicate that osteoclast precursors express NMDAR that are involved in the osteoclast differentiation process through activation of the NF-kappa B pathway.
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D001921:Brain / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000378:metabolism; D016291:Dizocilpine Maleate / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005786:Gene Expression Regulation; D016173:Macrophage Colony-Stimulating Factor / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D022423:Myeloid Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D010010:Osteoclasts / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism*; D021122:Protein Subunits; D021381:Protein Transport; D011759:Pyrrolidines / Q000494:pharmacology; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D002352:Carrier Proteins; D018691:Excitatory Amino Acid Antagonists; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D021122:Protein Subunits; D011759:Pyrrolidines; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D016194:Receptors, N-Methyl-D-Aspartate; C505687:Tnfrsf11a protein, mouse; C505689:Tnfsf11 protein, mouse; C007268:1-(2-(dodecyloxy)ethyl)pyrrolidine hydrochloride; D016291:Dizocilpine Maleate; D016173:Macrophage Colony-Stimulating Factor