Michel Boutet

Is reactive airways dysfunction syndrome a variant of occupational asthma

BACKGROUND Reactive airways dysfunction syndrome (RADS) or irritant-induced asthma is a syndrome that leaves subjects with asthma-like symptoms after one or more exposures to a high concentration of an irritant substance. The degree of reversibility of airway obstruction in subjects with RADS is nevertheless unknown, as is the degree of associated lesions at the airway level. METHODS We compared the acute reversibility of forced expiratory volume in 1 second (FEV1) after inhalation of albuterol (200 micrograms) in 15 subjects with RADS (12 cases caused by chlorine inhalation) with that of 30 subjects with occupational asthma (OA) caused by various agents. They were paired according to baseline airway obstruction (61% and 63% of predicted value in the RADS and OA groups), requirement for medication (bronchodilator only--7 of 15 subjects with RADS and 14 of 30 subjects with OA--as compared with bronchodilator + inhaled steroids in 8 of 15 subjects with RADS and 16 of 30 subjects with OA, respectively), and interval since removal from exposure (means of 30 and 24 months in the RADS and OA groups). In addition, five nonsmokers with RADS who had not received inhaled steroids underwent bronchoscopy with lavage and bronchial biopsies less than 2 years after the exposure. RESULTS The percentage increase in FEV1 over baseline after inhalation of albuterol was 10% +/- 9% in the RADS group and 19% +/- 16% in the OA group (p = 0.005). Only 2 of 15 subjects (13%) with RADS and 12 of 30 subjects (40%) with OA showed an improvement in FEV1 of 20% or greater after inhalation of albuterol. Bronchoalveolar lavage showed an increased number of cells with a predominance of lymphocytes, and biopsy specimens showed increased basement membrane thickness in the five subjects with RADS who underwent bronchoscopy. CONCLUSION Subjects with RADS are generally left with less airway reversibility than those with OA. We suggest that this difference is secondary to distinct pathologic changes.

Influence of natural antigenic exposure on expiratory flows, methacholine responsiveness, and airway inflammation in mild allergic asthma

BACKGROUND This study looked at respiratory symptoms, peak expiratory flow rates (PEFRs), airway responsiveness to methacholine and inflammatory changes on bronchial biopsies, bronchial lavage (BL), and bronchoalveolar lavage (BAL) during natural antigenic exposure in nine subjects with pollen-sensitized seasonal asthma. METHODS The subjects recorded daily symptoms of asthma, cough and rhinitis, and morning and evening PEFRs between January and September, during and out of the pollen exposure. Baseline forced expiratory volume in 1 second, forced vital capacity, and methacholine responsiveness were measured every 3 to 4 weeks. BAL, BL, and bronchial biopsies were performed in the pollen season at the initial increase of asthma symptoms and out of pollen exposure. RESULTS At the time of bronchoscopy during the pollen season compared with out of season, asthmatic subjects had an increase in asthma symptom score (1.18 +/- 0.24/0.44 +/- 0.18, p < 0.05), a reduction of PEFR (407 +/- 23/442 +/- 20 L/min, p = 0.02), and a decrease in PC20 (1.15/1.48 mg/ml, p = 0.05). In asthmatic subjects, median BAL and BL cell counts and cell differentials during or out of antigenic exposure were similar, but BAL and BL eosinophils and metachromatic cells counts were always higher than in healthy subjects. In comparison with controls, biopsies obtained in asthmatic subjects showed airway lesions such as epithelial desquamation, squamous cell metaplasia, thickening of basal membrane, inflammatory cells (p < 0.05 for neutrophils), edema, and ciliary abnormalities. During pollen exposure, inflammatory signs increased, but this change was only significant for the extent of epithelial desquamation and neutrophil counts. No significant correlation was found between the intensity of airway inflammation and changes in airway responsiveness. CONCLUSIONS In subjects with mild allergic asthma and pollen-induced asthma, seasonal antigenic exposure was associated with an increase in epithelial shedding and in the number of neutrophils on bronchial biopsies, suggesting a mild increase in baseline airway inflammation. However, these changes were not correlated with increases in airway responsiveness.

Airway inflammation and structural changes in airway hyper-responsiveness and asthma: an overview.

Asthma treatment has moved from bronchodilator therapy to an emphasis on anti-inflammatory therapy. Airway inflammation is believed to induce airway hyper-responsiveness (AHR) through the release of mediators that increase the airway response to agonists. However, the exact contribution of airway inflammation in the physiology of airway hyper-responsiveness remains undefined. Structural modifications in airways resulting from inflammation may contribute to the development and persistence of AHR and the development of asthma. This paper reviews some of the main components of airway inflammation and structural changes in asthma, and discusses how these processes may interact to modify airway function and induce respiratory symptoms.

Airway inflammation after removal from the causal agent in occupational asthma due to high and low molecular weight agents

In order to determine 1) the features of airway inflammation after removal from exposure to high (HMW) and low (LMW) molecular weight agents 2) if there are any differences in the pattern of inflammation induced by these two types of agents, we studied 18 subjects with a recently confirmed diagnosis of occupational asthma (OA) due to HMW (n = 11) and LMW (n = 7) agents. The duration of asthma symptoms varied from 2 to 108 months (mean 33 months), and withdrawal from exposure to the sensitizing agent from 3 to 24 weeks (mean 10 weeks). All subjects underwent measurements of expiratory flow rates, methacholine inhalation tests, and a flexible bronchoscopy with bronchoalveolar lavage (BAL) and bronchial biopsies. Endoscopic findings were compared with a group of 10 normal subjects. At the time of the bronchoscopy, asthma symptoms were minimal in most subjects. Although 15/18 subjects had normal forced expiratory volume in one second (FEV1 > 80% pred), all subjects had increased airway responsiveness to methacholine (provocation concentration producing a 20% fall in FEV1 = 0.2-10.0 mg.ml-1). BAL analysis showed similar median percentages of the total number of cells and differentials in control subjects and those exposed to HMW and LMW agents. Bronchial biopsies showed that mean inflammatory cell count, both epithelial and sub-epithelial, was similarly raised in OA subjects exposed to either HMW or LMW agents, compared to controls, except for epithelial lymphocyte count. In contrast to the controls, bronchial biopsy of both groups with OA also showed other changes such as extensive epithelial desquamation, ciliary abnormalities of the epithelial cells, smooth muscle hyperplasia and subepithelial fibrosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical detection of GM-CSF, IL-4 and IL-5 in a murine model of allergic bronchopulmonary aspergillosis.

Background Granulocyte macrophage‐colony stimulating factor (GM‐CSF), interleukin‐4 (IL‐4) and IL‐5 are important in tissue eosinophil accumulation and high IgE production in allergic inflammatory reaction.

PRODUCTION OF TISSUE-ENGINEERED THREE-DIMENSIONAL HUMAN BRONCHIAL MODELS

SummaryWe have reported morphological and functional features of cells isolated from human bronchial biopsies. Both epithelial and fibroblastic cells were isolated from the same biopsies using collagenase. A few models have been established to study normal bronchial response to various agents and to understand the mechanisms responsible for some disorders, such as asthma. We produced three-dimensional bronchial equivalents in culture, using human epithelial and fibroblastic cells. We previously showed that peripheral anchorage can prevent the dramatic collagen contraction in gels seeded with fibroblasts when properly adapted to the size and type of cultured tissues. Our bilayered bronchial constructs were anchored and cultured under submerged conditions and at the air-liquid interface. Three culture media were compared. Serium-free medium supplemented with retinoic acid (5×10−8M) was found to be the best for maintenance of bronchial cell properties in the reconstructed bronchial tissue. Immunohistological and ultrastructural analyses showed that these equivalents present good structural organization, allowing ciliogenesis to occur in culture. Moreover, human bronchial goblet cells could differentiate and secrete mucus with culture time. Laminin, a major constituent of the basement membrane and basal cells, was also detected at the mesenchymoepithelial interface. Such models with be useful for studying human bronchial properites in vitro.

Effect of salmeterol on allergen‐induced airway inflammation in mild allergic asthma

A previous study suggested that the long‐acting β2‐adrenergic agonist salmeterol (SM) had inhibitory effects on bronchial mucosal inflammation 6 hours after allergen exposure.

Influence of salmeterol on chronic and allergen-induced airway inflammation in mild allergic asthma : A pilot study

Abstract Salmeterol xinafoate, a potent, long-acting, selective beta 2 -agonist, inhibits allergen-induced asthmatic responses. To evaluate if this bronchoprotection was also associated with anti-inflammatory effects, mild asthmatic patients presenting a dual asthmatic response to allergens were randomized in a double-masked, placebo-controlled, parallel-group study to take either salmeterol 50 μg twice daily (n = 7) or placebo (n = 6) for 2 months. At the end of the treatment period, airway inflammation was assessed by bronchoalveolar lavage and bronchial biopsies, both before and after allergen challenge. After treatment, allergen-induced responses were decreased in the salmeterol group and, to a lesser degree, in the placebo group. Postallergen and preallergen challenge, lavage total, and differential cell counts were similar in the two groups. Before allergen challenge, bronchial biopsies of both groups indicated extensive airway inflammation with similar total inflammatory cell counts but with a higher percentage of epithelial desquamation in the salmeterol group. The allergen challenge did not modify the inflammatory variables measured except for an increase in eosinophil counts in connective tissue. Comparison of the postchallenge data of the two groups showed that counts of AA1-, HLA-DR-, and CD45ro-positive cells were reduced in the salmeterol group. When prechallenge and postchallenge data were pooled to compare the two treatments, the salmeterol group had lower numbers of CD3-, CD25-, HLA-DR-, AA1-, CD45-, and CD45ro-positive cells. In conclusion, these results confirmed the bronchodilator and bronchoprotective effects of salmeterol. They also suggested that even though salmeterol did not modify lavage and overall bronchial biopsy cellular infiltrate, the drug apparently reduced expression of some bronchial mucosa activation cell markers. This study, however, was mainly exploratory, and the reproducibility and clinical significance of these observations require further clarification

Increased expression of intercellular adhesion molecule‐1 (ICAM‐1) in a murine model of pulmonary eosinophilia and high IgE level

T lymphocytes and eosinophils are probably involved in the pathogenesis of allergic broncho‐pulmonary aspergillosis (ABPA), a disease characterized by pulmonary eosinophilia and high serum and lavage IgE levels. We recently developed a murine model of ABPA. To investigate the mechanisms of T lymphocyte and eosinophil recruitment to the lung in this disease, we examined the expression of ICAM‐1 In the lung tissue of mouse challenged with Aspergillus fumigatus (Af) antigen. C57B1/6 mice were intranasally exposed to Af (Af group) or saline (control group) three times a week for 1, 2 or 3 weeks. On days 4, 7, 14 and 21, mice were killed and lung tissue was fixed in acetone and embedded in glycol methacrylate. Serial μm sections were stained with chromotrope 2R and MoAbs against ICAM‐I. CD11a/CD18 (LFA‐1) and CD3. Af‐challenged mice presented significant increases in eosinophil, T lymphocyte and LFA‐1‐positive cell count and up‐regulated expression of ICAM‐1 in the lung tissue at all the time points examined. ICAM‐1 expression intensity correlated with the number of T lymphocytes (r= 0·59, P <0·01), LFA‐1‐positive cells (r= 0·68, P < 0·001), but not of eosinophils (r=−0·24, P > 0·05). These findings suggest that up‐regulation of ICAM‐1 expression is involved in the inflammatory process of this murine model of ABPA, and that this up‐regulation may be more relevant to the T lymphocyte accumulation in the lung.

Dexamethasone and cyclosporin A modulation of cytokine expression and specific antibody synthesis in an allergic bronchopulmonary aspergillosis murine model

We previously demonstrated that, in C57B1/6 mice, cyclosporin A enhanced and dexamethasone inhibited the Aspergillus fumigatus‐induced pulmonary eosinophilia and total IgE levels. To evaluate whether these effects were related to the modulation of T‐lymphocyte recruitment and activation and cytokine expression, we performed immunohistochemical staining for T‐cell surface marker CD3 and CD4, cell activation marker CD25, and cytokines granulocyte–macrophage colony‐stimulating factor (GM‐CSF), interleukin‐4 (IL‐4) and interleukin‐5 (IL‐5) on lung tissue sections from mice exposed to Aspergillus fumigatus and treated or not with dexamethasone or cyclosporin A. Dexamethasone significantly inhibited Aspergillus fumigatus‐induced increased number of activated T cells and cytokine‐expressing cells in parallel with a decrease in pulmonary eosinophils. In contrast, cyclosporin A did not decrease these immunological events but enhanced the lung eosinophil recruitment. Moreover, dexamethasone prevented the production of immunoglobulins against 76 and 36 kD antigen proteins and cyclosporin A against 76 and 18 kD antigen proteins. These results indicate that dexamethasone down‐regulates and cyclosporin A up‐regulates lung eosinophil recruitment and total IgE production, probably via the modulation of T‐lymphocyte activation and GM‐CSF, IL‐4 and IL‐5 expression. Both drugs inhibit Aspergillus fumigatus‐specific antibody synthesis, but their suppressive actions are selective to different antigenic components.