title: Monitoring intracellular redox changes in ozone-exposed airway epithelial cells.
abstract: BACKGROUND
  The toxicity of many xenobiotic compounds is believed to involve oxidative injury to cells. Direct assessment of mechanistic events involved in xenobiotic-induced oxidative stress is not easily achievable. Development of genetically encoded probes designed for monitoring intracellular redox changes represents a methodological advance with potential applications in toxicological studies.
  
  
  OBJECTIVE
  We tested the utility of redox-sensitive green fluorescent protein (roGFP)-based redox sensors for monitoring real-time intracellular redox changes induced by xenobiotics in toxicological studies.
  
  
  METHODS
  roGFP2, a reporter of the glutathione redox potential (E(GSH)), was used to monitor EGSH in cultured human airway epithelial cells (BEAS-2B cells) undergoing exposure to 0.15-1.0 ppm ozone (O(3)). Cells were imaged in real time using a custom-built O(3) exposure system coupled to a confocal microscope.
  
  
  RESULTS
  O(3) exposure induced a dose- and time-dependent increase of the cytosolic EGSH. Additional experiments confirmed that roGFP2 is not directly oxidized, but properly equilibrates with the glutathione redox couple: Inhibition of endogenous glutaredoxin 1 (Grx1) disrupted roGFP2 responses to O(3), and a Grx1-roGFP2 fusion protein responded more rapidly to O(3) exposure. Selenite-induced up-regulation of GPx (glutathione peroxidase) expression-enhanced roGFP2 responsiveness to O(3), suggesting that (hydro)peroxides are intermediates linking O(3) exposure to glutathione oxidation.
  
  
  CONCLUSIONS
  Exposure to O(3) induces a profound increase in the cytosolic E(GSH) of airway epithelial cells that is indicative of an oxidant-dependent impairment of glutathione redox homeostasis. These studies demonstrate the utility of using genetically encoded redox reporters in making reliable assessments of cells undergoing exposure to xenobiotics with strong oxidizing properties.
authors.affiliation: Curriculum in Toxicology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7310, USA.
authors.forename: Eugene A
authors.initials: EA
authors.lastname: Gibbs-Flournoy
authors.forename: Steven O
authors.initials: SO
authors.lastname: Simmons
authors.forename: Philip A
authors.initials: PA
authors.lastname: Bromberg
authors.forename: Tobias P
authors.initials: TP
authors.lastname: Dick
authors.forename: James M
authors.initials: JM
authors.lastname: Samet
mesh_terms: D001980:Bronchi / Q000166:cytology / Q000187:drug effects*; D002460:Cell Line; D004847:Epithelial Cells / Q000187:drug effects; D005947:Glucose / Q000008:administration & dosage; D005978:Glutathione / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D010084:Oxidation-Reduction; D010126:Ozone / Q000633:toxicity*
chemical_list: D049452:Green Fluorescent Proteins; D010126:Ozone; D005978:Glutathione; D005947:Glucose