Reduction in leukotriene B4 generation by bronchoalveolar lavage cells in asthma.

Abstract

Background -Leukotrienes are inflammatory mediators implicated in the pathogenesis of asthma. The capacity of inflammatory cells within the airways to generate leukotrienes may be altered in asthma. This hypothesis was tested using bronchoalveolar lavage (BAL) to sample cells within the airways from atopic asthmatic and normal subjects, and by measuring their Asthma is characterised by reversible airflow obstruction, bronchial reactivity, and airways inflammation in which a range of mediators, including leukotrienes, is implicated.' Leukotriene B4 (LTB4) is chemotactic for neutrophils, eosinophils, and mononuclear cells, and activates neutrophils and eosinophils, but also stimulates T suppressor cell function.' The cysteinyl leukotrienes -leukotriene C4 (LTC4), leukotriene D4 (LTD4), and leukotriene E4 (LTE4)-cause bronchoconstriction, increased vascular permeability, and increased mucus secretion.3 The leukotrienes are derived from arachidonic acid by the 5-lipoxygenase pathway and their involvement in asthma is suggested by their increased levels in body fluids of asthmatic patients -for example, LTB4 and LTC4 in bronchoalveolar lavage (BAL) fluid4 and LTE4 in urine.' The most convincing evidence comes from studies of leukotriene antagonists and 5-lipoxygenase inhibitors in asthmatic subjects. These agents reduce bronchoconstriction induced by exercise6 and cold air7 and improve lung function in chronic asthma.8Leukotrienes are produced by a range of cells present in the airways, including eosinophils, mast cells, macrophages/monocytes, and neutrophils.9 Leukotriene generation independent of receptor-associated processes can be studied in vitro using calcium ionophore (A23187). Leukotriene generation by peripheral blood leucocytes from atopic asthmatic subjects is increased in response to ionophore compared with that in normal subjects.'0 We postulated that the capacity of inflammatory cells in the bronchi of asthmatic subjects to generate leukotrienes might also be increased. Inflammatory cells within the bronchi -most of which are alveolar macrophages -can be sampled by BAL and their function studied in vitro. The aim of this study was to investigate whether the capacity of BAL cells to generate leukotrienes when stimulated with ionophore is altered in asthmatic subjects. Methods SUBJECTSTwelve mild asymptomatic atopic asthmatic subjects and 12 normal human volunteers were studied. Between two and seven days before fibreoptic bronchoscopy each subject was assessed for the presence and severity of asthma. Clinical history and examination, standard skin prick tests (Bencard, Idis, Kingston, Surrey, UK), full blood count and differential white blood count, serum IgE, biochemical screen, chest radiography (if not performed within the previous year), spirometry and methacholine challenge were performed. Forced expiratory volume in one second (FEVy) was measured using a Vitallograph dry wedge bellows spirometer; baseline FEV, was recorded after three reproducible values were obtained. Methacholine challe...

Effect of intravenous corticosteroid on ex vivo leukotriene generation by blood leucocytes of normal and asthmatic patients

“…The data are unlikely to be explained by the tendency for eosinophil percentages within PMNL preparations to fall after methylprednisolone (table 1) as these falls did not reach statistical significance and occurred in both subject groups while the fall in LTC 4 synthesis was only seen in the asthmatic subjects. The trend for increased capacity of blood eosinophils from asthmatic subjects to synthesise LTC 4 agrees with significant results in previous studies19 20 and may be due to in vivo priming by eosinophilotactic cytokines implicated in allergic inflammation such as interleukin (IL-)3 and IL-5 22. The ability of methylprednisolone to reduce LTC 4 synthesis in eosinophils in asthmatic subjects may prevent a vicious cycle of eosinophil migration and LTC 4 synthesis.…”

“…20 PMNL and MNC preparations were incubated at 5 × 10 6  cells/ml and BAL cells at 0.5 × 10 6  cells/ml in Ca 2+ /Mg 2+ containing culture medium at 37°C with 25 mM HEPES and 20 mM l -serine (Sigma) to prevent peroxidase dependent catabolism of leukotrienes. Cells were stimulated with calcium ionophore A23187 (Sigma) in dimethylsulfoxide (<0.5% v/v) at a final concentration of 2 μM for PMNL and MNC experiments and 4 μM for BAL cells.…”

Assessment of leukotriene B4 production in leukocytes from horses with recurrent airway obstruction

“…Similarly, cells in BALF samples from humans with asthma but without clinical signs are reported to produce less LTB 4 than cells from nonasthmatic individuals, whereas the concentrations of LTC 4 are similar between the groups (as detected in the horses of our study). 26 Before horses were stabled, the production of LTB 4 was similar in PBNs and BALF leukocytes, but there was significantly less production in RAO-affected horses than there was in control horses. After stabling of RAO-affected horses, there was an influx of neutrophils into the airways (such that the BALF samples contained primarily neutrophils), but the production of LTB 4 per 10 6 cells was 3 to 4 times as great as that of the purified PBNs at the same time period.…”

“…In cells in BALF samples from healthy humans, the ratio of LTB 4 :LTC 4 is similar to that detected in horses (approx 12:1). 26 On stimulation ex vivo, cells in BALF samples obtained from RAO-affected horses before stabling (0 hours) produced significantly less LTB 4 than did cells in BALF samples from control horses, despite there being no differences in cell counts in BALF samples, clinical score, or ∆Ppl max between the groups at this time. Similarly, cells in BALF samples from humans with asthma but without clinical signs are reported to produce less LTB 4 than cells from nonasthmatic individuals, whereas the concentrations of LTC 4 are similar between the groups (as detected in the horses of our study).…”

Platelet Dynamics following Allergen Challenge in Allergic Asthmatics

“…In order to confirm that there was active airway inflammation at 24 h, a subgroup of the asthmatics who underwent allergen challenge (n = 7) were bronchoscoped after the last venesection as described elsewhere [16, 17]. Bronchoalveolar lavage (BAL) of a subsegment of the right middle lobe was performed with three aliquots of 60-ml sterile saline at 37°C.…”