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Background: Fraction of exhaled nitric oxide (FENO) is a promising non-invasive index of airway inflammation that may be used to assess respiratory effects of air pollution. We evaluated FENO as a measure of airway inflammation after controlled exposure to diesel exhaust or ozone. Methods: Healthy volunteers were exposed to either diesel exhaust (particle concentration 300 mu g/m(3)) and filtered air for one hour, or ozone (300 ppb) and filtered air for 75 minutes. FENO was measured in duplicate at expiratory flow rates of 10, 50, 100 and 270 mL/s before, 6 and 24 hours after each exposure. Results: Exposure to diesel exhaust increased FENO at 6 hours compared with air at expiratory flow rates of 10 mL/s (p = 0.01) and at 50 mL/s (p = 0.011), but FENO did not differ significantly at higher flow rates. Increases in FENO following diesel exhaust were attenuated at 24 hours. Ozone did not affect FENO at any flow rate or time point. Conclusions: Exposure to diesel exhaust, but not ozone, increased FENO concentrations in healthy subjects. Differences in the induction of airway inflammation may explain divergent responses to diesel exhaust and ozone, with implications for the use of FENO as an index of exposure to air pollution.

Exposure to particulate matter and ozone cause adverse airway reactions. Individual pollutant effects are often addressed separately, despite coexisting in ambient air. The present investigation was performed to study the effects of sequential exposures to diesel exhaust (DE) and ozone on airway inflammation in human subjects. Healthy subjects underwent bronchoscopy with bronchoalveolar lavage (BAL) and bronchial wash (BW) sampling on two occasions. Once following a DE exposure (with 300 mug.m(-3) particles with a 50% cut-off aerodynamic diameter of 10 mum) with subsequent exposure to O(3) (0.2 ppm) 5 h later. The other bronchoscopy was performed after a filtered air exposure followed by an ozone exposure, using an identical protocol. Bronchoscopy was performed 24 h after the start of the initial exposure. Significant increases in neutrophil and macrophage numbers were found in BW after DE followed by ozone exposure versus air followed by ozone exposure. DE pre-exposure also raised eosinophil protein X levels in BAL compared with air. The present study indicates additive effects of diesel exhaust on the ozone-induced airway inflammation. Together with similar results from a recent study with sequential diesel exhaust and ozone exposures, the present data stress a need to consider the interaction and cumulative effects of different air pollutants.

BACKGROUND: The relationship between eosinophilic airway inflammation and exercise-induced bronchoconstriction (EIB), and the response to inhaled corticosteroid (ICS) therapy was examined. METHODS: Twenty-six steroid-naïve asthmatic patients with EIB were randomized to two parallel, double-blind, crossover study arms (13 subjects in each arm). Each arm compared two dose levels of inhaled ciclesonide that were administered for 3 weeks with a washout period of 3 to 8 weeks, as follows: (1) 40 vs 160 microg daily; and (2) 80 vs 320 microg daily. Baseline and weekly assessments with exercise challenge and sputum analysis were performed. RESULTS: Data were pooled and demonstrated that 10 subjects had baseline sputum eosinophilia >or= 5%. Only high-dose ICS therapy (ie, 160 and 320 microg) significantly attenuated the sputum eosinophil percentage. Sputum eosinophil percentage significantly correlated with EIB severity, and predicted the magnitude and temporal response of EIB to high-dose therapy, but not to low-dose therapy (ie, 40 and 80 microg). Low-dose ICS therapy provided a significant reduction in EIB at 1 week, with little additional improvement thereafter, irrespective of baseline sputum eosinophil counts. In contrast, high-dose ICS therapy provided a significantly greater improvement in EIB in subjects with sputum eosinophilia compared to those with an eosinophil count of < 5%. The difference between the eosinophilic groups in the magnitude of improvement in EIB was evident after the first week of high-dose ICS therapy and increased with time. CONCLUSIONS: These results suggest that eosinophilic airway inflammation may be important in modifying the severity of EIB and the response to ICS therapy. Measurements of sputum eosinophil percentage may, therefore, be useful in predicting the magnitude and temporal response of EIB to different dose levels of ICSs. Trial registration: clinicaltrial.gov; Identifier: NCT00525772.

Exposure to air pollution is associated with adverse health effects, with particulate matter (PM) and ozone (O(3)) both indicated to be of considerable importance. Diesel engine exhaust (DE) and O(3) generate substantial inflammatory effects in the airways. However, as yet it has not been determined whether a subsequent O(3) exposure would add to the diesel-induced airway inflammatory effects. Healthy subjects underwent two separate exposure series: A 1-h DE exposure at a PM-concentration of 300 microg/m(3), followed after 5h by a 2-h exposure to filtered air and 0.2 ppm O(3), respectively. Induced sputum was collected 18 h after the second exposure. A significant increase in the percentage of neutrophils (PMN) and concentration of myeloperoxidase (MPO) was seen in sputum post DE+O(3) vs. DE+air (p<0.05 and <0.05, respectively). Significant associations were observed between the responses in MPO concentration and total PMN cells (p=0.001), and also between MPO and matrix metalloproteinase-9 (MMP-9) (p<0.001). The significant increase of PMN and MPO after the DE+O(3) exposures, compared to DE+air, denotes an O(3)-induced magnification of the DE-induced inflammation. Furthermore, the correlation between responses in MPO and number of PMNs and MMP-9 illustrate that the PMNs are activated, resulting in a more potent inflammatory response. The present study indicates that O(3) exposure adds significantly to the inflammatory response that is established by diesel exhaust. This interaction between exposure to particulate pollution and O(3) in sequence should be taken into consideration when health effects of air pollution are considered.