title: Reduced glutathione prevents camphorquinone-induced apoptosis in human oral keratinocytes.
abstract: OBJECTIVE
  Camphorquinone (CQ) is a widely used photoinitiator in dental visible light (VL)-cured resinous materials. However, little is known about the toxicity of CQ in human cells. This study was designed to investigate CQ induced oxidative strain and apoptosis in cultured human oral keratinocytes (OKF6/TERT 2). Furthermore, the effects of visible-light (VL)-irradiation and the reducing agent N,N-dimethyl-p-toluidine (DMT) were investigated. In addition, the preventive potential of the antioxidant glutathione (GSH) against CQ induced toxicity was analyzed as well.
  
  
  METHODS
  The fluorescent DNA-staining dye Hoechst 33342 was used to quantify total cell numbers. Intracellular levels of reactive oxygen species (ROS) were measured by the fluorescent probe 2',7'-dichlorofluorescein diacetate (DCFH-DA). Apoptosis was determined by FACS analysis (Annexin V-FITC/propidium iodide), by measuring caspase-3/7 activity (ELISA) and by DNA laddering.
  
  
  RESULTS
  Our data show that CQ was dose-dependent cytotoxic and caused oxidative stress by inducing reactive oxygen species (ROS). The redistribution of phosphatidylserine (PS) to the outer layer of the plasma membrane, induction of caspase-3 enzyme activity and DNA fragmentation were also observed in CQ exposed cells. Interestingly, CQ-induced ROS generation enhanced by VL irradiation or a simultaneous treatment with DMT showed no quantitative effect on apoptosis. However, co-exposure of cells with GSH significantly reduced the intracellular ROS generation as well as apoptosis caused by CQ.
  
  
  CONCLUSIONS
  This is the first report showing that ROS-induced apoptosis, which is caused by CQ, is prevented by GSH.
authors.affiliation: Department of Conservative Dentistry, Periodontology and Preventive Dentistry, Hannover Medical School, Hannover 30625, Germany. Electronic address: volk.joachim@mh-hannover.de.
authors.forename: Joachim
authors.initials: J
authors.lastname: Volk
authors.affiliation: Department of Conservative Dentistry, Periodontology and Preventive Dentistry, Hannover Medical School, Hannover 30625, Germany.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Leyhausen
authors.affiliation: Department of Conservative Dentistry, Periodontology and Preventive Dentistry, Hannover Medical School, Hannover 30625, Germany.
authors.forename: Miriam
authors.initials: M
authors.lastname: Wessels
authors.affiliation: Department of Conservative Dentistry, Periodontology and Preventive Dentistry, Hannover Medical School, Hannover 30625, Germany.
authors.forename: Werner
authors.initials: W
authors.lastname: Geurtsen
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D002164:Camphor / Q000031:analogs & derivatives* / Q000633:toxicity; D002461:Cell Line, Transformed; D005978:Glutathione / Q000494:pharmacology*; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009055:Mouth / Q000166:cytology* / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D017382:Reactive Oxygen Species; D002164:Camphor; D005978:Glutathione; C553149:camphorquinone
keywords: Apoptosis; Camphorquinone; Glutathione; Oral keratinocytes