title: Nitrogen dioxide induces death in lung epithelial cells in a density-dependent manner.
abstract: Nitrogen dioxide (*NO2) is commonly known as an indoor and outdoor air pollutant. Inhalation of *NO2 is associated with epithelial cell injury, inflammation, and the aggravation of asthma. *NO2 can also be formed during inflammation, by the metabolism of nitric oxide. We describe a gas-phase exposure system for in vitro exposure of lung epithelial cells to *NO2. Immunofluorescence revealed 3-nitrotyrosine immunoreactivity of rat alveolar type II epithelial cells exposed to 5 parts per million of *NO2 for 4 h. Comparative analysis of log-phase and confluent cultures demonstrated that cell death occurred extensively in log-phase cells, whereas minimal death was observed in confluent cultures. Peroxynitrite (ONOO-) or the ONOO- generator 3-morpholinosydnonimine (SIN-1) caused similar amounts of death. Further, exposure of wounded cell cultures to *NO(2) or SIN-1 revealed that death was restricted to cells repopulating a wounded area. Cycloheximide or actinomycin D, inhibitors or protein and messenger RNA synthesis, respectively, significantly reduced terminal transferase reactivity, suggesting that a new protein(s) may be required for cell death. These results suggest that during restitution after pulmonary injury, epithelium may be sensitive to cell death by reactive nitrogen species.
authors.affiliation: Department of Pathology, University of Vermont College of Medicine, Burlington, Vermont 05405, USA.
authors.forename: R L
authors.initials: RL
authors.lastname: Persinger
authors.forename: W M
authors.initials: WM
authors.lastname: Blay
authors.forename: N H
authors.initials: NH
authors.lastname: Heintz
authors.forename: D R
authors.initials: DR
authors.lastname: Hemenway
authors.forename: Y M
authors.initials: YM
authors.lastname: Janssen-Heininger
mesh_terms: D002452:Cell Count; D016923:Cell Death / Q000187:drug effects*; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D004277:DNA, Single-Stranded / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D008168:Lung / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008981:Molsidomine / Q000031:analogs & derivatives / Q000494:pharmacology; D009566:Nitrates / Q000378:metabolism / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009573:Nitrites / Q000378:metabolism; D009585:Nitrogen Dioxide / Q000494:pharmacology*; D018384:Oxidative Stress / Q000187:drug effects; D020545:Respiratory Mucosa / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism
chemical_list: D017077:Culture Media, Conditioned; D004277:DNA, Single-Stranded; D009566:Nitrates; D020030:Nitric Oxide Donors; D009573:Nitrites; C039642:peroxynitric acid; C002385:linsidomine; D008981:Molsidomine; D009585:Nitrogen Dioxide