ToxSci Advance Access originally published online on May 28, 2003
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Toxicological Sciences 74, 437-446 (2003)
Copyright © 2003 by the Society of Toxicology
RESPIRATORY TOXICOLOGY |
Ozone Exposure Enhances Endotoxin-Induced Mucous Cell Metaplasia in Rat Pulmonary Airways
Department of Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing, Michigan 48824
Coexposure to different airborne pollutants can be more toxic to airway epithelium than an inhalation exposure to a single pollutant. We have previously reported that coexposure to ozone, the primary oxidant gas in photochemical smog, and unique inflammatory biogenic substances such as allergens or bacterial endotoxin, results in augmented epithelial and inflammatory responses in rat nasal airways (M. V. Fanucchi et al., 1998, Toxicol. Appl. Pharmacol. 152, 1–9; J. G. Wagner et al., 2002a, Toxicol. Sci.67, 284–294). In the present study, we investigated the toxic interaction of ozone and endotoxin on the respiratory epithelium in the pulmonary airways of laboratory rodents. F344 rats were intranasally instilled with 0, 2, or 20 µg endotoxin dissolved in sterile saline (150 µl/ nasal passage). Six h after instillation rats were exposed to air or 1 ppm ozone for 8 h. One day later, endotoxin and ozone exposures were repeated. Three days after the last exposure, rats were sacrificed, the lungs were lavaged with saline, and the collected bronchoalveolar lavage fluid (BALF) was analyzed for inflammatory cells and secreted mucosubstances (mucin 5AC). Lung tissues were processed for light microscopic examination and morphometric analysis of numeric density of epithelial cell populations and volume densities of intraepithelial mucosubstances (IM). Conducting airways were microdissected and analyzed by quantitative RT-PCR to determine steady-state mucin gene (rMuc5AC) mRNA levels in respiratory epithelium. Endotoxin instillation caused a dose-dependent increase in BALF neutrophils that was further increased twofold in ozone-exposed rats given 20 µg endotoxin. Mucin glycoprotein 5AC was elevated in BALF from rats exposed to 20 µg, but not 2 µg endotoxin. Exposure to ozone alone did not cause mucus hypersecretion, but ozone potentiated mucus secretion in rats given 2 or 20 µg endotoxin. Airways of rats exposed to air or ozone alone had scant amounts of IM. Endotoxin instillation induced a dose-dependent increase in IM in airway epithelium that was significantly increased (twofold) in rats that were also exposed to ozone. Expression of rMuc5AC was induced in axial pulmonary airways by 2 and 20 µg endotoxin, and was increased further by ozone-exposure in rats instilled with 20 µg endotoxin. These data demonstrate that ozone exposure potentiates neutrophilic inflammation and mucus production and secretion elicited by a biogenic substance in rat pulmonary airways.
Key Words: ozone; lipopolysaccharide; mucous cell metaplasia; mucin; neutrophil; inflammation.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  T. K. Baginski, K. Dabbagh, C. Satjawatcharaphong, and D. C. Swinney Cigarette Smoke Synergistically Enhances Respiratory Mucin Induction by Proinflammatory Stimuli Am. J. Respir. Cell Mol. Biol., August 1, 2006; 35(2): 165 - 174. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. F. Harris, M. J. Fischer, J. R. Hotchkiss, B. P. Monia, S. H. Randell, J. R. Harkema, and Y. Tesfaigzi Bcl-2 Sustains Increased Mucous and Epithelial Cell Numbers in Metaplastic Airway Epithelium Am. J. Respir. Crit. Care Med., April 1, 2005; 171(7): 764 - 772. [Abstract] [Full Text] [PDF]
|
|