Ambient level of NO2 augments the inflammatory response to inhaled allergen in asthmatics.

Air pollution constitutes an important factor for asthma aggravation, and there is increased concern about respiratory health effects of common air pollutants. The purpose of this study was to examine how exposure to a high ambient concentration nitrogen dioxide (NO2) prior to a bronchial allergen challenge modulated the inflammatory response in the bronchi. Thirteen subjects with mild asthma and allergy were exposed at rest to either purified air or 500 microg x m 3 NO2 for 30 min, followed 4 h later by an allergen inhalation challenge. The exposures (NO2 or air) were performed in random order and at least 4 weeks apart. Lung function during NO2/air exposure and allergen challenge was measured by plethysmography, and then hourly by portable spirometry after exposures. Subjective symptoms were recorded during and after exposure. Bronchoscopy with bronchial wash (BW) and bronchoalveolar lavage (BAL) was performed 19 h after allergen challenge. NO2+allergen enhanced the percentage of neutrophils in both BW and BAL compared to air+allergen (BW 19 vs. 11, P=0.05; BAL 3 vs. 1, P=0.02 median values). The levels of eosinophil cationic protein (ECP) in BW was higher after NO2+allergen compared to air+allergen (90 vs. 3.6 microg/l; P=0.02, median values). There was no NO2-associated effect on symptoms or pulmonary function. These data suggest that ambient NO2 can enhance allergic inflammatory reaction in the airways without causing symptoms or pulmonary dysfunction.

Brief exposures to NO2 augment the allergic inflammation in asthmatics.

Exposure to high ambient levels of nitrogen dioxide (NO2) enhances the airway reaction in humans to allergen, measured as decreased pulmonary function. We tested whether this NO2 effect is associated with an increased inflammatory response to allergen in the airways. To mimic real-life conditions, in which exposure to high ambient levels of NO2 occurs only during short periods of time but often several times a day, we used a repeated-exposure model. On day 1, 18 subjects with allergic asthma were exposed, in randomized order, to purified air or to 500 microg/m3 NO2 for 15 min, and on day 2 for 2 x 15 min. Allergen was inhaled 3-4h after the NO2 exposures on both days. Symptoms, pulmonary function, and inflammatory response in sputum and blood were measured daily. Eosinophil cationic protein in both sputum and blood increased more from day 1 to day 3 after NO2+allergen than after air+allergen, whereas eosinophil counts did not differ. The change in myeloperoxidase was significantly greater after NO2+allergen than after air+allergen in blood but not in sputum. This finding was not accompanied by raised levels of neutrophils in sputum and blood. Symptoms and pulmonary function were equally affected by NO2+allergen and air+allergen. We conclude that two to three brief exposures to ambient levels of NO2 can prime circulating eosinophils and enhance the eosinophilic activity in sputum in response to inhaled allergen. This might be an important mechanism by which air pollutants amplify the inflammatory reactions in the airways.

Allergen challenge alters intracellular cytokine expression.

The pathophysiology of asthma is complex and engages cascades of events in the cytokine network. We, therefore, investigated the impact of bronchial allergen challenge in humans on the cytokine profile of circulating lymphocytes. Peripheral blood samples from 10 patients with allergic asthma were collected before and 24 h after allergen provocation. Patients who mounted a late-phase reaction were designated dual responders opposite to single responders. Whole blood cells were stimulated by mitogen and intracellular interleukin (IL)-4 and interferon (IFN)-gamma were detected by flow cytometry. The allergen challenge induced a decrease in IL-4+CD4+ cells in the patients (P = 0.05), and a significant decrease (P < 0.05) in IFN-gamma+CD4+ cells was noted in single, but not dual, responders. In addition, there was a significant difference (P < 0.01) with respect to the changes in the IFN-gamma+CD4+ cells comparing dual and single responders. No corresponding changes were observed in CD8+ cells. The data suggest a possible on-going traffic of IFN-gamma and IL-4+CD4+ lymphocytes into the bronchial mucosa in relation to an allergen challenge and generate the hypothesis that a difference exists between single and dual responders in this respect. Because the CD4+IFN-gamma-producing cells have the capacity to downregulate the T-helper type 2 response, a reduced capacity in this aspect might contribute to the pathophysiology in dual responders.

Different functional and morphological characteristics in a nonadherent subpopulation of human macrophages recovered by bronchoalveolar lavage.

The alveolar macrophages (AMs) constitute a morphologically and functionally heterogenous cell population. The adhesive properties of these cells are important for their role in host defence. To focus on the heterogeneity, a population of nonadherent macrophages were characterized functionally and morphologically. These cells were then compared with the total alveolar macrophage population. Alveolar cells (> 95% alveolar macrophages), were recovered by bronchoalveolar lavage (BAL) from healthy smokers. Nonadherent macrophages were separated by adhesion. The phagocytic capacity and the autofluorescent properties of the cell populations were determined in flow cytofluorometric assays. In addition, electron microscopic evaluation was performed. The alveolar macrophage adhesion to wells coated with albumin increased in a time-dependent manner. After 15 min, median 47%, interquartile range 42-52% (uncoated wells 68%, 67-72%) of the alveolar macrophages were attached; and after 60 min, 56%, 51-58% (uncoated wells 73%, 71-76%) of the alveolar macrophages were attached. The nonadherent alveolar macrophage population had less phagocytic capacity. The cell autofluorescence increased with increasing cell size and cell complexity/granularity in both populations. The nonadherent cells were more autofluorescent, indicating an increased granularity/complexity. These findings were confirmed with electron microscopy. Thus, the nonadherent alveolar macrophages had more cytoplasmic inclusions than the total alveolar macrophage population (volume density median 0.39, interquartile range 0.35-0.46 and 0.31, 0.26-0.34, respectively), but less surface protusions. We conclude that in lavage fluid from human smokers there is an ultrastructurally specific subpopulation of alveolar macrophages, showing less adhesive properties and impaired phagocytic capacity in vitro. These macrophages may be older alveolar cells or, alternatively, airway macrophages. Since only alveolar macrophages from smokers were investigated, we cannot draw any conclusions regarding alveolar cells from nonsmokers. Nevertheless, the heterogeneity of the lavaged cells should be taken into consideration when the functional ability of the alveolar macrophages are evaluated.

The immotile cilia syndrome: characterization of the inflammatory response in nonsmoking patients with dysfunction of the cilia.

In order to demonstrate how patients with immotile cilia syndrome (ICS) are associated with lower respiratory tract inflammation, bronchoscopy and fractionated BAL were performed on eight ICS patients. Their VC was 84.5 +/- 16.7% (mean +/- SD) and FEV1 73.1 +/- 19.9% of predicted. Endobronchial signs of bronchitis were observed in all patients. The total cell concentrations in the BAL fluid were increased, compared to healthy nonsmokers (n = 10), both in the bronchial (BP) and alveolar portion (AP) (p < 0.01 for both). In the BP, this was mainly due to a high concentration of neutrophils (p < 0.001), whereas in the AP, the concentrations of lymphocytes (p < 0.01) as well as all types of granulocytes (p < 0.001-0.01) were elevated. The signs of active inflammation in the lower respiratory tract were confirmed by the concomitantly elevated (p < 0.001-0.05) concentrations of the soluble BAL components albumin, fibronectin and hyaluronan. Thus, the inflammatory response is not restricted to the ciliated conducting airways, but also occurs in the alveolar space and results-surprisingly-in only a slightly impaired lung function.

Clearance in small ciliated airways in allergic asthmatics after bronchial allergen provocation.

BACKGROUND: Asthma tends to affect mucociliary clearance, as assessed from measurements in large airways. However, there is no knowledge about clearance in the smallest airways of the tracheobronchial region in acute exacerbation of asthma. OBJECTIVE: The aim of the study was to investigate clearance from the bronchiolar region in patients with allergic asthma in a situation resembling a mild acute exacerbation of the disease. We also aimed to compare clearance data with corresponding data found for healthy subjects and asthmatics on therapy. METHODS: Tracheobronchial clearance was studied twice in 9 patients with mild asthma of the allergic type after inhalation of 6 microm (aerodynamic diameter) monodisperse Teflon particles labelled with 111In. At one exposure, inhalation was performed 4 h after bronchial provocation with an allergen the patients were allergic to. The second exposure was a control measurement. The particles were inhaled at an extremely slow flow, 0.05 liter/s, which gives deposition mainly in the small ciliated airways (bronchioles). Lung retention was measured at 0, 24, 48 and 72 h. RESULTS: All patients demonstrated an early asthmatic reaction of varying degree after bronchial provocation. There was significant clearance of radioaerosol in each 24-hour period for both exposures, with the possible exception of the period between 24 and 48 h for the provocation exposure, with similar fractions of retained particles at all points of time. The retained fractions were significantly larger compared to a group of healthy subjects and asthmatics on regular treatment with anti-inflammatory drugs. CONCLUSIONS: Our results indicate that in allergic asthmatics a bronchial allergen provocation with an early asthmatic reaction does not significantly influence overall clearance from the bronchiolar region. However, in the present group of patients, retention in small ciliated airways was significantly higher compared to healthy subjects and asthmatics on regular treatment.

Repeated exposure to an ambient level of NO2 enhances asthmatic response to a nonsymptomatic allergen dose.

We investigated the effects of NO2 and allergen on lung function in a repeated exposure model. For 4 subsequent days, 16 subjects with mild asthma and allergy to birch or grass pollen were exposed at rest to either purified air or 500 microg x m(-3) NO2 for 30 min in an exposure chamber. Four hours later, an individually determined nonsymptomatic allergen dose was inhaled. Lung function (forced expiratory volume in one second (FEV1)) was measured by a portable spirometer at early phase (EP) 15 min after allergen and at late phase (LP) 3-10 h after allergen. Subjective symptoms and medication were followed by diary cards. Asthmatic response was significantly increased after repeated exposure to NO2 and allergen compared to air and allergen. The 4-day mean fall in FEV1 after NO2 was at EP -25% versus -0.4% for air (p=0.02) and at LP -4.4% versus -1.9% for air (p=0.01, ANOVA). An increase in EP response was seen already after a single NO2 exposure (p=0.03). There was a tendency (p=0.07) towards increased night-time symptoms of asthma after NO2 plus allergen. Although the effects were small, the results indicate that a repeated short exposure to an ambient level of NO2 enhances the airway response to a nonsymptomatic allergen dose.