Expression and functional role of nitric oxide synthase in osteoblast-like cells.
Nitric oxide synthases (NOS) are enzymes that produce nitric oxide (NO) from L-arginine in a reaction yielding citrulline as a coproduct. Nitric oxide modulates the activity of a wide variety of cells, but little is known about its effects on bone cells. In the present study we report that the NOS inhibitor NG-monomethyl-L-arginine (NMMA) induced a dose-dependent inhibitory effect on the proliferation of the osteoblast-like cell lines MG63 and ROS 17/2.8. The inhibitory effect was prevented by increasing L-arginine concentrations in the medium and by the NO donor sodium nitroprusside. Likewise, NMMA inhibited interleukin-6 secretion, independently of its effect on cell number. NOS expression by MG63 cells was confirmed by measuring their ability to metabolize radiolabeled L-arginine to citrulline. NOS bioactivity was detected in unstimulated cells, but was markedly increased by stimulating the cells with cytokines, lipopolysaccharide, or 1,25-dihydroxyvitamin D3. NOS activity was partially dependent upon the presence of calcium in the medium. Furthermore, constitutive-type NOS (c-NOS) and inducible-type NOS (i-NOS) mRNA expression was detected in ROS 17/2.8 cells after reverse transcription and polymerase chain reaction amplification. In conclusion, osteoblast-like cells express c-NOS and i-NOS, and NOS activity seems to play an important role in the regulation of cell proliferation and function.
Riancho
J A
JA
Department of Internal Medicine, Hospital U.M. Valdecilla, University of Cantabria, Santander, Spain.
Salas
E
E
Zarrabeitia
M T
MT
Olmos
J M
JM
Amado
J A
JA
Fernández-Luna
J L
JL
González-Macías
J
J
D000594:Amino Acid Oxidoreductases / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D001483:Base Sequence; D001859:Bone Neoplasms / Q000473:pathology; D002117:Calcitriol / Q000633:toxicity; D002118:Calcium / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D016207:Cytokines / Q000633:toxicity; D017931:DNA Primers / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000633:toxicity; D008969:Molecular Sequence Data; D009569:Nitric Oxide / Q000037:antagonists & inhibitors*; D019001:Nitric Oxide Synthase; D009599:Nitroprusside / Q000494:pharmacology; D010006:Osteoblasts / Q000166:cytology / Q000201:enzymology*; D012516:Osteosarcoma / Q000473:pathology; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D014158:Transcription, Genetic / Q000235:genetics; D014407:Tumor Cells, Cultured; D019323:omega-N-Methylarginine
D016207:Cytokines; D017931:DNA Primers; D015850:Interleukin-6; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D009599:Nitroprusside; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D002117:Calcitriol; D002118:Calcium