title: Effect of Ga-Al-As laser irradiation on COX-2 and cPLA2-alpha expression in compressed human periodontal ligament cells.
abstract: OBJECTIVE
  Prostaglandin E(2) (PGE(2)), which has bone-resorptive activity, is produced by human periodontal ligament (PDL) cells in response to mechanical stress. We previously reported that low level laser (LLL) irradiation inhibited PGE(2) production in PDL cells in response to mechanical stress; however, the mechanism underlying this inhibitory effect was unclear. Thus, we sought to determine the mechanism underlying the inhibitory effect of LLL on PGE(2) production in compressed PDL cells.
  
  
  METHODS
  A compressive force of 2.0 g/cm(2) was applied for 24 hours to human PDL cells obtained from premolars extracted for orthodontic treatment. LLL irradiation (Ga-Al-As laser, 830 nm, 3.82 J/cm(2)) was applied 6 hours before, 1 hour before, and immediately after the application of compressive force. The mRNA expression of COX-2 and cPLA(2)-alpha was then examined by real-time PCR.
  
  
  RESULTS
  LLL irradiation significantly inhibited COX-2 and cPLA(2)-alpha mRNA expression, which was increased in response to the application of a compressive force. Moreover, LLL irradiation immediately after compression had the strongest inhibitory effect on the expression of these genes.
  
  
  CONCLUSIONS
  The inhibition of PGE(2) production by LLL irradiation in compressed PDL cells may be due to the inhibition of COX-2 and cPLA(2)-alpha expression and is most pronounced immediately after the application of a compressive force.
authors.affiliation: Department of Orthodontics, Nihon University School of Dentistry, 1-8-13 Kanda, Surugadai, Chiyoda-Ku, Tokyo 101-8310, Japan. mayahara@dent.nihon-u.ac.jp
authors.forename: Kotoe
authors.initials: K
authors.lastname: Mayahara
authors.forename: Akikuni
authors.initials: A
authors.lastname: Yamaguchi
authors.forename: Masahito
authors.initials: M
authors.lastname: Sakaguchi
authors.forename: Yu
authors.initials: Y
authors.lastname: Igarashi
authors.forename: Noriyoshi
authors.initials: N
authors.lastname: Shimizu
mesh_terms: D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D054513:Group IV Phospholipases A2 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D054023:Lasers, Semiconductor; D010513:Periodontal Ligament / Q000166:cytology*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D013314:Stress, Mechanical
chemical_list: D012333:RNA, Messenger; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D054513:Group IV Phospholipases A2