title: Characterisation of an aerosol exposure system to evaluate the genotoxicity of whole mainstream cigarette smoke using the in vitro γH2AX assay by high content screening.
abstract: BACKGROUND
  The genotoxic effect of cigarette smoke is routinely measured by treating cells with cigarette Particulate Matter (PM) at different dose levels in submerged cell cultures. However, PM exposure cannot be considered as a complete exposure as it does not contain the gas phase component of the cigarette smoke. The in vitro γH2AX assay by High Content Screening (HCS) has been suggested as a complementary tool to the standard battery of genotoxicity assays as it detects DNA double strand breaks in a high-throughput fashion. The aim of this study was to further optimise the in vitro γH2AX assay by HCS to enable aerosol exposure of human bronchial epithelial BEAS-2B cells at the air-liquid interface (ALI).
  
  
  METHODS
  Whole mainstream cigarette smoke (WMCS) from two reference cigarettes (3R4F and M4A) were assessed for their genotoxic potential. During the study, a further characterisation of the Borgwaldt RM20S® aerosol exposure system to include single dilution assessment with a reference gas was also carried out.
  
  
  RESULTS
  The results of the optimisation showed that both reference cigarettes produced a positive genotoxic response at all dilutions tested. However, the correlation between dose and response was low for both 3R4F and M4A (Pearson coefficient, r = -0.53 and -0.44 respectively). During the additional characterisation of the exposure system, it was observed that several pre-programmed dilutions did not perform as expected.
  
  
  CONCLUSIONS
  Overall, the in vitro γH2AX assay by HCS could be used to evaluate WMCS in cell cultures at the ALI. Additionally, the extended characterisation of the exposure system indicates that assessing the performance of the dilutions could improve the existing routine QC checks.
authors: British American Tobacco, Group Research and Development, Regents Park Road, Southampton, Hampshire SO15 8TL, UK. Carolina_Garcia-Canton@bat.com.
authors: Carolina
authors: C
authors: Garcia-Canton
authors: Graham
authors: G
authors: Errington
authors: Arturo
authors: A
authors: Anadon
authors: Clive
authors: C
authors: Meredith
mesh_terms: D000336:Aerosols; D002460:Cell Line; D006657:Histones / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D009152:Mutagenicity Tests; D012906:Smoke; D014026:Nicotiana
chemical_list: D000336:Aerosols; C468783:H2AX protein, human; D006657:Histones; D012906:Smoke