title: Cyclic tension force activates nitric oxide production in cultured human periodontal ligament cells.
abstract: BACKGROUND
  Nitric oxide (NO) is involved in a number of physiological and pathophysiological processes. The aim of this study was to examine the ability of human periodontal ligament (PDL) cells to produce NO and whether mechanical forces could induce NO production in the PDL cells.
  
  
  METHODS
  Human PDL cells were seeded onto flexible bottoms of a culture plate and subjected to cyclic tension forces. NO production was evaluated by measuring concentration of NO2- and NO3- (NO2-/NO3-), the oxidized products of NO, in the culture medium. We employed reverse transcription polymerase chain reaction (RT-PCR) methods to detect NO synthase mRNA in the PDL cells. NO synthase immunoreactivity was also evaluated in both stimulated and unstimulated PDL cells.
  
  
  RESULTS
  In unstimulated PDL cell culture, NO2-/NO3- increased to 140% of the initial value in 12 hours. In contrast, NO2-/NO3- showed a 3-fold increase when the cells had been subjected to cyclic tension forces for 12 hours. The increase in NO production was blocked by NG-monomethyl-L-arginine (5 x 10(-4) M), an inhibitor of NO synthase. Endothelial NO synthase (ecNOS) mRNA was expressed in both stimulated and unstimulated PDL cells, whereas inducible NO synthase (iNOS) mRNA was detected in neither culturing condition. We found strong ecNOS but not iNOS immunoreactivity in the stimulated PDL cells.
  
  
  CONCLUSIONS
  These results suggest that human PDL cells produce NO by ecNOS and that the production is enhanced by stimulating the cells with cyclic tension forces. Mechanically stimulated PDL cells may modulate the function of periodontium by the upregulated NO production.
authors.affiliation: Department of Pediatric Dentistry, School of Dentistry, Hokkaido University, Sapporo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kikuiri
authors.forename: T
authors.initials: T
authors.lastname: Hasegawa
authors.forename: Y
authors.initials: Y
authors.lastname: Yoshimura
authors.forename: T
authors.initials: T
authors.lastname: Shirakawa
authors.forename: H
authors.initials: H
authors.lastname: Oguchi
mesh_terms: D000293:Adolescent; D000704:Analysis of Variance; D015153:Blotting, Western; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D003470:Culture Media; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007150:Immunohistochemistry; D009566:Nitrates / Q000032:analysis; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000032:analysis / Q000037:antagonists & inhibitors / Q000235:genetics; D009573:Nitrites / Q000032:analysis; D010507:Periodicity; D010513:Periodontal Ligament / Q000166:cytology / Q000201:enzymology / Q000378:metabolism* / Q000502:physiology; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D013314:Stress, Mechanical; D015854:Up-Regulation; D019323:omega-N-Methylarginine / Q000494:pharmacology
chemical_list: D003470:Culture Media; D004791:Enzyme Inhibitors; D009566:Nitrates; D009573:Nitrites; D012333:RNA, Messenger; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase