Philippe Gosset

Among the many possible mediators of the early asthmatic response, prostaglandin D2, a bronchoconstrictor, is the principal cyclooxygenase metabolite of arachidonic acid that is released upon the activation of mast cells and is also synthesized by human alveolar macrophages. We performed bronchoalveolar lavage in five patients with chronic stable asthma, before and up to nine minutes after local provocative challenge with Dermatophagoides pteronyssinus. The lavage fluid was analyzed for products of arachidonic acid metabolism. Prostaglandin D2 levels in all five patients rose an average of 150-fold, from less than 8 to 332 +/- 114 pg per milliliter (mean +/- SEM; P less than 0.050), after local instillation of the antigen. Levels of 15-hydroxyeicosatetraenoic acid, which may also have a role in the pulmonary allergic response, were detectable in lavage fluid before challenge and increased after provocation with the antigen in four of the five patients. The activity of beta-glucuronidase, an enzyme released by macrophages and mast cells upon stimulation, tended to increase in the lavage fluid after provocation in all patients. These studies provide evidence that the release of prostaglandin D2 into the airways is an early event after the instillation of D. pteronyssinus in patients who are sensitive to this antigen.

Cellular events that occur in status asthmaticus (SA) remain poorly investigated. Autopsy studies frequently emphasized about the presence of eosinophils in bronchial airway wall, whereas recent studies reported increased number of neutrophils in patients dying of sudden-onset fatal asthma. Mucus plugs occluding the bronchial lumen are almost constant features during SA. Bronchial lavage (BL) may be useful to remove mucus plugs in cases of atelectasis and/or refractory SA. We investigated the contribution of different cell types and cellular mediators (neutrophil elastase, eosinophil cationic protein [ECP], histamine, interleukin-8 [IL-8]) to the pathogenesis of SA. We studied 16 BL from eight patients undergoing mechanical ventilation (MV) for SA (time interval from onset of MV = Day 0 to Day 11), four BL from patients undergoing MV without preexisting respiratory disease (V), 11 BL from patients with stable asthma (A) and eight BL from healthy controls (C). SA exhibited higher number and percentage of neutrophils (81.5 +/- 4.5%) than V (44.3 +/- 12.2) (p < 0.05), A (6.9 +/- 2.7) and C (9.5 +/- 3.8) (p < 0.0001), and higher number of eosinophils than V, A, and C (p < 0.01). Neutrophil elastase, ECP, and IL-8 levels were dramatically increased in SA. Histamine was higher in SA than in C and V (p < 0.05). Bronchial neutrophilia was not related to concomitant bacterial infection as bacteriological cultures were positive in only three BL. Eosinophils, mast cells and histamine were higher in BL performed within the first 48 h of MV (p < 0.05) than in BL performed later on. Our results indicate that bronchial inflammation in SA differs from bronchial inflammation in mild asthma. Persistent bronchial neutrophilia is associated with increased eosinophils and mast cells in the early phase of SA. Neutrophils may result in tissue damage and participate to the shedding of the epithelium in SA.

Status asthmaticus (SA) is an acute respiratory failure combining an acute bronchospastic reaction with a severe airway inflammation. We previously reported an important influx of neutrophils and an increased secretion of interleukin-8 (IL-8) in patients with SA. The aim of this prospective study was to evaluate in bronchial lavage (BL) of patients with SA (n = 9) under mechanical ventilation (MV) the concentrations of cytokines and related mediators which have the ability to modulate inflammation, either proinflammatory (interleukin-1beta [IL-1beta], IL-6, tumor necrosis factor-alpha [TNF-alpha]), or anti-inflammatory mediators (IL-10, transforming growth factor-beta1 [TGF-beta1]), interleukin-1 receptor antagonist [IL-1Ra], soluble TNF receptor I and II [sTNFRI and II]). To determine the relative importance of both pro- and anti-inflammatory mediators, the net inflammatory activity was analyzed by the capacity of BL fluids (BLF) to increase intercellular adhesion molecule-1 (ICAM-1) expression in the human lung A549 epithelial cell line. These data were compared with those obtained from patients who required MV without respiratory disease (V, n = 4), controlled asthma (A, n = 11), and nonsmoking healthy volunteers (C, n = 8). Levels of IL-1, IL-6, TNF-alpha, and of the active form of TGF-beta1 were significantly higher in SA compared with the other groups. The concentrations of IL-1Ra, IL-10, the latent form of TGF-beta1, and of the sTNFRI and II were not significantly different between SA and V, albeit higher in SA than in A and C. The ratio between IL-1Ra and IL-1beta was significantly higher in patients with SA compared with the other groups, whereas there was no difference for the ratio between both types of sTNFR and TNF-alpha. Despite a marked increase of anti-inflammatory mediators in BL from patients with SA, the net inflammatory activity was found to be proinflammatory and mainly due to the presence of bioactive IL-1beta (79% inhibition of ICAM-1 expression with anti-IL-1beta antibodies) and to a lesser extent TNF-alpha (32% inhibition with anti-TNF-alpha antibodies).