Pro-inflammatory responses of human bronchial epithelial cells to acute nitrogen dioxide exposure

• Published in: Toxicology (Amsterdam) 2004-04, Vol.197 (2), p.148-163
• Main Authors: Ayyagari, Vijayalakshmi N., Januszkiewicz, Adolph, Nath, Jayasree
• Format: Article
• Language: English
• Subjects: Air; Biological and medical sciences; Blotting, Western; Bronchi - cytology; Bronchi - drug effects; Cell Survival - drug effects; Cells, Cultured; cytokines; Cytokinins - biosynthesis; Cytokinins - toxicity; Drug Synergism; Environmental pollutants toxicology; Epithelial Cells - drug effects; Epithelial Cells - enzymology; Epithelial Cells - metabolism; Human bronchial epithelial cells; Humans; Immunohistochemistry; Inflammation Mediators - toxicity; Interleukin-8 (IL-8); Medical sciences; Nitric oxide (NO); Nitric Oxide Synthase - biosynthesis; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Nitrogen dioxide (NO 2); Nitrogen Dioxide - toxicity; Toxicology; Tumor necrosis factor α (TNF-α)
• ISSN: 0300-483X; 1879-3185
• DOI: 10.1016/j.tox.2003.12.017

Nitrogen dioxide (NO 2) is an environmental oxidant, known to be associated with lung epithelial injury. In the present study, cellular pro-inflammatory responses following exposure to a brief high concentration of NO 2 (45 ppm) were assessed, using normal human bronchial epithelial (NHBE) cells as an in vitro model of inhalation injury. Generation and release of pro-inflammatory mediators such as nitric oxide (NO), IL-8, TNF-α, IFN-γ and IL-1β were assessed at different time intervals following NO 2 exposure. Effects of a pre-existing inflammatory condition was tested by treating the NHBE cells with different inflammatory cytokines such as IFN-γ, IL-8, TNF-α, IL-1β, either alone or in combination, before exposing them to NO 2. Immunofluorescence studies confirmed oxidant-induced formation of 3-nitrotyrosine in the NO 2-exposed cells. A marked increase in the levels of nitrite (as an index of NO) and IL-8 were observed in the NO 2-exposed cells, which were further enhanced in the presence of the cytokines. Effects of various NO inhibitors combined, with immunofluorescence and Western blotting data, indicated partial contribution of the nitric oxide synthases (NOSs) toward the observed increase in nitrite levels. Furthermore, a significant increase in IL-1β and TNF-α generation was observed in the NO 2-exposed cells. Although NO 2 exposure alone did induce slight cytotoxicity (