Research Program Area: Health & Exposure
Exposure of healthy subjects to ozone is associated with pulmonary inflammation as evidenced by increased cellular and biochemical markers of inflammation in bronchoalveolar lavage. Collection of bronchoalveolar lavage requires that subjects undergo bronchoscopy, an invasive procedure that requires willing subjects and skilled research personnel. Recently, sputum induction has been proposed as a non invasive method for sampling airway secretions for research purposes. Sputum induction relies on the fact that healthy subjects expectorate sputum when they inhale an aerosol of hypertonic saline. We and others have demonstrated that it is feasible to perform both cellular and biochemical measurements on this "induced sputum." To determine if analysis of induced sputum might reveal the pulmonary inflammatory effects of ozone exposure, we performed cellular and biochemical analysis of induced sputum collected four hours after air and ozone (0.4 ppm for two hours) exposures from ten healthy subjects (age 30 ± 5 years; five females) in a randomized crossover study where exposures were separated by two weeks. We found that the total number of non-squamous cells were significantly higher after ozone exposure than after air exposure (7.4 vs 3.9 x 105/ml, p < 0.05) as were the percentage of the non-squamous cells that were neutrophils (80 ± 7.0 percent vs 51 ± 20 percent, p < 0.05) and the levels of myeploperoxidase in the sputum fluid phase (1,622 ± 635 ng vs. 1,273 ± 578 ng, p < 0.05). In addition, we found a trend for higher levels of IL-6 and IL-8 in induced sputum after ozone than after air exposures. Total protein levels and mucin-like glycoprotein levels were not significantly different between exposures. We conclude that analysis of induced sputum reveals evidence of inflammation similar to that reported from analysis of bronchoalveolar lavage and that sputum induction thus represents a useful non-invasive method for studying the pulmonary response to ozone exposure in healthy subjects.
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