Regulation of the maturation of osteoblasts and osteoclastogenesis by glutamate.
Glutamate, an important central excitatory neurotransmitter, is also secreted by osteoblasts and may be involved in the regulation of bone metabolism. Glutamate receptors for N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) are demonstrated in bone cells. Here we investigated the in vivo effects of glutamate by local injection of AMPA, NMDA, and their antagonists into tibia as well as their in vitro effects on the maturation of osteoblasts and formation of osteoclasts. AMPA receptor antagonist CNQX and NMDA receptor antagonist MK-801 significantly inhibited the maturation and mineralization of osteoblasts in high-glutamate alpha-MEM. On the other hand, AMPA and NMDA up-regulated the mineralized deposition and osteocalcin mRNA expression of primary osteoblasts cultured in glutamate-free DMEM. AMPA and NMDA induced the phosphorylation of extracellular signal-related kinases (ERK) in osteoblasts within 15 min. In addition, NMDA but not AMPA up-regulated the number of osteoclasts while MK801 antagonized this potentiating effect. To explore the action of glutamate agonists on bone formation in animal model, AMPA was locally injected into tibia and it was found that the bone volume in secondary spongiosa significantly increased and co-treatment of CNQX antagonized the enhancing effect of AMPA. These results suggest that glutamate may play a physiological role in regulating the maturation of osteoblasts and osteoclastogenesis. Activation of both AMPA and NMDA receptors regulates the maturation of osteoblasts. NMDA but not AMPA affects receptor for activation of NF-kappaB ligand (RANKL)-induced osteoclastogenesis.
Department of Pharmacology, College of Medicine, National Taiwan University and Hospital, Taipei, Taiwan.
Tzu-Hung
TH
Lin
Rong-Sen
RS
Yang
Chih-Hsin
CH
Tang
Ming-Yueh
MY
Wu
Wen-Mei
WM
Fu
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism*; D008297:Male; D016202:N-Methylaspartate / Q000378:metabolism; D010006:Osteoblasts / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D015675:Osteocalcin / Q000235:genetics / Q000378:metabolism; D010010:Osteoclasts / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D010012:Osteogenesis / Q000187:drug effects; D010766:Phosphorylation; D053245:RANK Ligand / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000187:drug effects / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000378:metabolism; D013977:Tibia / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D013997:Time Factors; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D053245:RANK Ligand; D012333:RNA, Messenger; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; D015675:Osteocalcin; D018698:Glutamic Acid; D016202:N-Methylaspartate; D016291:Dizocilpine Maleate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D048049:Extracellular Signal-Regulated MAP Kinases