title: Role of benzalkonium chloride in DNA strand breaks in human corneal epithelial cells.
abstract: OBJECTIVE
  To investigate the toxic effects of benzalkonium chloride (BAC), a preservative commonly used in ophthalmic preparations, on DNA single- and double-strand breaks in immortalized human corneal epithelial cells (HCEs).
  
  
  METHODS
  HCEs were treated with BAC in concentrations ranging from 0.00005% to 0.001% for 30 min. Cells were examined immediately after BAC exposure and after 24-h recovery. Alkaline comet assay was used to detect DNA single-strand breaks (SSBs). Immunofluorescence microscope detection of the phosphorylated form of histone variant H2AX (γH2AX) foci indicated DNA double-strand breaks (DSBs). Cell viability was measured by the MTT test.
  
  
  RESULTS
  A significant increase of SSBs, detected by alkaline comet assay, was observed in a dose-dependent manner with BAC exposure in HCEs at concentrations of 0.00005% and higher. Such BAC treatment also exhibited a dose-dependent increase in DSBs, evaluated by number of γH2AX foci. In addition, a significant change in the relative cell survival rate of HCEs was observed after exposure to 0.001% BAC for 30 min. Although the toxic effects of BAC could be partly repaired after 24 h of cell recovery, SSBs and DSBs in HCEs were still present after BAC removal.
  
  
  CONCLUSIONS
  The results demonstrated that exposure to BAC in HCEs, even at low concentrations, could induce DNA strand breaks, which were present after BAC removal. Cell survival analysis indicated that BAC-induced DNA damage was correlated with the cytotoxic effects.
authors.affiliation: Department of Ophthalmology, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, China. yejuan@zju.edu.cn
authors.forename: Juan
authors.initials: J
authors.lastname: Ye
authors.forename: Han
authors.initials: H
authors.lastname: Wu
authors.forename: Huina
authors.initials: H
authors.lastname: Zhang
authors.forename: Yihua
authors.initials: Y
authors.lastname: Wu
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
authors.forename: Xiuming
authors.initials: X
authors.lastname: Jin
authors.forename: Xin
authors.initials: X
authors.lastname: Shi
mesh_terms: D001548:Benzalkonium Compounds / Q000633:toxicity*; D002460:Cell Line; D002470:Cell Survival; D020552:Comet Assay; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects*; D053904:DNA Breaks, Single-Stranded / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D019573:Epithelium, Corneal / Q000187:drug effects*; D006657:Histones / Q000378:metabolism; D006801:Humans; D008856:Microscopy, Fluorescence; D010750:Phosphoproteins / Q000378:metabolism; D011310:Preservatives, Pharmaceutical / Q000633:toxicity*
chemical_list: D001548:Benzalkonium Compounds; C468783:H2AX protein, human; D006657:Histones; D010750:Phosphoproteins; D011310:Preservatives, Pharmaceutical