title: Defense mechanism of heme oxygenase-1 against cytotoxic and receptor activator of nuclear factor-kappaB ligand inducing effects of hydrogen peroxide in human periodontal ligament cells.
abstract: OBJECTIVE
  Although induction of heme oxygenase-1 by H2O2 has been reported, the protective role of heme oxygenase-1 against the cytotoxic and osteoclastogenic effects of H2O2 have not been elucidated in human periodontal ligament cells. The aim of this work was to investigate the defense mechanism of heme oxygenase-1 on H2O2-induced cytotoxicity and to analyze the expression of receptor activator of nuclear factor-kappaB ligand (RANKL) and osteoprotegerin as markers for osteoclast differentiation in periodontal ligament cells.
  
  
  METHODS
  Using human periodontal ligament cells, cytotoxicity was measured by the 3,4,5-dimethylthiazol-2-yl-2,5-diphenyl tetrazolium bromide (MTT) assay, and expression of heme oxygenase-1, RANKL, and osteoprotegerin mRNA was determined by reverse transcription-polymerase chain reaction.
  
  
  RESULTS
  H2O2 produced a cytotoxic effect by reducing the cell viability and enhancing the expression of heme oxygenase-1 and RANKL mRNAs in a concentration- and time-dependent manner. Additional experiments revealed that heme oxygenase-1 inducer (hemin), a membrane-permeable cGMP analog (8-bromo-cGMP), carbon monoxide, extracellular signal-regulated kinase, p38 mitogen-activated protein kinase inhibitor, protein kinase inhibitor (KT5823), and nuclear factor-kappaB inhibitor (pyrrolidine dithiocarbamate) also blocked the effects of H2O2 on cell viability and RANKL mRNA expression in periodontal ligament cells.
  
  
  CONCLUSIONS
  These data suggest that heme oxygenase-1 induction plays a protective role in periodontal ligament cells against the cytotoxic and RANKL-inducing effects of H2O2, through multiple signaling pathways.
authors.affiliation: Department of Periodontology, Wonkwang University, Iksan, South Korea.
authors.forename: S-H
authors.initials: SH
authors.lastname: Pi
authors.forename: S-C
authors.initials: SC
authors.lastname: Kim
authors.forename: H-T
authors.initials: HT
authors.lastname: Kim
authors.forename: H-J
authors.initials: HJ
authors.lastname: Lee
authors.forename: S-K
authors.initials: SK
authors.lastname: Lee
authors.forename: E-C
authors.initials: EC
authors.lastname: Kim
mesh_terms: D000704:Analysis of Variance; D002470:Cell Survival / Q000187:drug effects; D019610:Cytoprotection / Q000502:physiology; D051547:Heme Oxygenase-1 / Q000378:metabolism*; D006427:Hemin / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity*; D053244:Osteoprotegerin / Q000032:analysis; D016877:Oxidants / Q000633:toxicity*; D010513:Periodontal Ligament / Q000187:drug effects / Q000201:enzymology*; D053245:RANK Ligand / Q000032:analysis* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*
chemical_list: D053244:Osteoprotegerin; D016877:Oxidants; D053245:RANK Ligand; D012333:RNA, Messenger; D006427:Hemin; D006861:Hydrogen Peroxide; D051547:Heme Oxygenase-1