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- Holgate, Stephen T, et al.
(author)
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Health effects of acute exposure to air pollution. Part I : Healthy and asthmatic subjects exposed to diesel exhaust
- 2003
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In: Research report (Health Effects Institute). - 1041-5505. ; :112, s. 1-30; discussion 51
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Journal article (peer-reviewed)abstract
- The purpose of this study was to assess the impact of short-term exposure to diluted diesel exhaust on inflammatory parameters in human airways. We previously exposed control subjects for 1 hour to a high ambient concentration of diesel exhaust (particle concentration 300 pg/m3--a level comparable with that found in North Sea ferries, highway underpasses, etc). Although these exposures did not have any measurable effect on standard indices of lung function, there was a marked neutrophilic inflammatory response in the airways accompanied by increases in blood neutrophil and platelet counts. Endothelial adhesion molecules were upregulated, and the expression of interleukin 8 messenger RNA (IL-8 mRNA*) was increased in a pattern consistent with neutrophilia. Individuals with asthma have inflamed airways and are clinically more sensitive to air pollutants than are control subjects. The present study was designed to assess whether this clinical sensitivity can be explained by acute neutrophilic inflammation or an increase in allergic airway inflammation resulting from diesel exhaust exposure. For this study, we used a lower concentration of diesel exhaust (100 microg/m3 PM10) for a 2-hour exposure. At this concentration, both the control subjects and those with asthma demonstrated a modest but statistically significant increase in airway resistance following exposure to diesel exhaust. This increase in airway resistance was associated with an increased number of neutrophils in the bronchial wash (BW) fluid obtained from control subjects (median after diesel exhaust 22.0 vs median after air 17.2; P = 0.015), as well as an increase in lymphocytes obtained through bronchoalveolar lavage (BAL) (15.0% after diesel exhaust vs 12.3% after air; P = 0.017). Upregulation of the endothelial adhesion molecule P-selectin was noted in bronchial biopsy tissues from control subjects (65.4% of vessels after diesel exhaust vs 52.5% after air). There was also a significant increase in IL-8 protein concentrations in BAL fluid and IL-8 mRNA gene expression in the bronchial biopsy tissues obtained from control subjects after diesel exhaust exposure (median IL-8 expression 65.7% of adenine phosphoribosyl transferase [APRT] gene expression value after diesel exhaust vs 51.0% after air; P = 0.007). There were no significant changes in total protein, albumin, or other soluble inflammatory markers in the BW or BAL fluids. Red and white blood cell counts in peripheral blood were unaffected by diesel exhaust exposure. Airway mucosal biopsy tissues from subjects with mild asthma (defined as forced expiratory volume in 1 second [FEV1] greater than or equal to 70% of the predicted value) showed eosinophilic airway inflammation after air exposure compared with the airways of the corresponding control subjects. However, among the subjects with mild asthma, diesel exhaust did not induce any significant change in airway neutrophils, eosinophils, or other inflammatory cells; cytokines; or mediators of inflammation. The only clear effect of diesel exhaust on the airways of subjects with asthma was a significant increase in IL-10 staining in the biopsy tissues. This study demonstrated that modest concentrations of diesel exhaust have clear-cut inflammatory effects on the airways of nonasthmatic (or control) subjects. The data suggest a direct effect of diesel exhaust on IL-8 production leading to upregulation of endothelial adhesion molecules and neutrophil recruitment. Despite clinical reports of increased susceptibility of patients with asthma to diesel exhaust and other forms of air pollution, it does not appear that this susceptibility is caused either directly by induction of neutrophilic inflammation or indirectly by worsening of preexisting asthmatic airway inflammation. The increased level of IL-10 after diesel exhaust exposure in airways of subjects with asthma suggests that this pollutant may induce subtle changes in airway immunobiology. This is an important topic for further investigation. Other possible explanations for the apparent lack of response to diesel exhaust among subjects with asthma include (1) the time course of the response to diesel may differ from the response to allergens, which peaks 6 to 8 hours after exposure; (2) a different type of inflammation may occur that was not detectable by the standard methods used in this study; and (3) the increased sensitivity of patients with asthma to particulate air pollution may reflect the underlying bronchial hyperresponsiveness found in asthma rather than any specific increase in inflammatory responses.
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- Stenfors, Nikolai, et al.
(author)
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Effect of ozone on bronchial mucosal inflammation in asthmatic and healthy subjects
- 2002
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In: Respiratory Medicine. - : Saunders Elsevier. - 0954-6111 .- 1532-3064. ; 96:5, s. 352-358
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Journal article (peer-reviewed)abstract
- Epidemiological studies suggestthat asthmatics are more affected by ozone than healthy people. This study tested three hypotheses (1) that short-term exposure to ozone induces inflammatory cell increases and up-regulation of vascular adhesion molecules in airway lavages and bronchial tissue 6 h after ozone exposure in healthy subjects; (2) these responses are exaggerated in subjects with mild allergic asthma; (3) ozone exacerbates pre-existent allergic airways inflammation. We exposed 15 mild asthmatic and 15 healthy subjects to 0.2 ppm of ozone or filtered air for 2 h on two separate occasions. Airway lavages and bronchial biopsies were obtained 6 h post-challenge. We found that ozone induced similar increases in bronchial wash neutrophils in both groups, although the neutrophil increase in the asthmatic group was on top of an elevated baseline. In healthy subjects, ozone exposure increased the expression of the vascular endothelial adhesion molecules P-selectin and ICAM- 1, as well as increasing tissue neutrophil and mast cell numbers. The asthmatics showed allergic airways inflammation at baseline but ozone did not aggravate this at the investigated time point. At 6 h post-ozone-exposure, we found no evidence that mild asthmatics were more responsive than healthy to ozone in terms of exaggerated neutrophil recruitment or exacerbation of pre-existing allergic inflammation. Further work is needed to assess the possibility of a difference in time kinetics between healthy and asthmatic subjects in their response to ozone.
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