Corticosteroid treatment selectively decreases mast cells in the smooth muscle and epithelium of asthmatic bronchi

BACKGROUND

Mast cells are important in the pathophysiology of airway inflammation and evidence suggests their sub-localisation within the airway is altered in asthma. Little is known about the effect of corticosteroids on mast cell localisation within the bronchi.

METHODS

We therefore performed an immunohistochemical analysis of mast cell numbers within the smooth muscle, epithelium and submucosa of healthy subjects (n = 10) and well-characterised asthmatic patients, using either β(2)-agonists alone (n = 10) or β(2)-agonists and inhaled corticosteroids (n = 10).

RESULTS

Patients using inhaled corticosteroids displayed significantly lower numbers of mast cells within their epithelium and smooth muscle compared to those not treated with inhaled corticosteroids. Submucosal mast cells were not affected by corticosteroid treatment. Numbers of smooth muscle mast cells correlated with bronchial responsiveness and epithelial mast cells with exhaled NO.

CONCLUSION

We demonstrate that glucocorticosteroids differentially affect mast cell numbers within specific airway sub-locations highlighting the importance of mast cell and smooth muscle/epithelial interactions in asthma pathogenesis.

Increased levels of cysteinyl-leukotrienes in saliva, induced sputum, urine and blood from patients with aspirin-intolerant asthma

BACKGROUND

A diagnosis of aspirin-intolerant asthma requires aspirin provocation in specialist clinics. Urinary leukotriene E(4) (LTE(4)) is increased in aspirin-intolerant asthma. A study was undertaken to investigate new biomarkers of aspirin intolerance by comparing basal levels of cysteinyl-leukotrienes (CysLTs) and leukotriene B(4) (LTB(4)) in saliva, sputum and ex vivo stimulated blood in subjects with aspirin-intolerant and aspirin-tolerant asthma. The effects of aspirin- and allergen-induced bronchoconstriction on leukotriene levels in saliva and ex vivo stimulated blood were also compared with the effects of the provocations on urinary mediators.

METHODS

Induced sputum, saliva, urine and blood were obtained at baseline from 21 subjects with asthma. At a separate visit, 11 subjects showed a positive response to lysine-aspirin inhalation and 10 were aspirin tolerant. Saliva, blood and urine were also collected on the provocation day. Analyses of CysLTs and LTB(4) and the prostaglandin D(2) metabolite 9alpha,11beta-prostaglandin F(2) were performed and the fraction of exhaled nitric oxide was measured.

RESULTS

Subjects with aspirin-intolerant asthma had higher exhaled nitric oxide levels and higher baseline levels of CysLTs in saliva, sputum, blood ex vivo and urine than subjects with aspirin-tolerant asthma. There were no differences in LTB(4) levels between the groups. Levels of urinary LTE(4) and 9alpha,11beta-prostaglandin F(2) increased after aspirin provocation whereas leukotriene levels in saliva and ex vivo stimulated blood did not increase.

CONCLUSION

These findings support a global and specific increase in CysLT production in aspirin-intolerant asthma. Measurement of CysLTs in saliva has the potential to be a new and convenient non-invasive biomarker of aspirin-intolerant asthma.

Early rise in exhaled nitric oxide and mast cell activation in repeated low-dose allergen challenge

Repeated low-dose allergen inhalation challenge mimics natural allergen exposure, providing a model for early mechanisms in the triggering of asthma. The current authors performed a controlled study to evaluate the time course of changes in exhaled nitric oxide fraction (F(e,NO)) and urinary biomarkers of airway inflammation. Eight subjects with mild allergic asthma completed two 7-day repeated low-dose challenge periods, with diluent and allergen, respectively. Subjects were symptom free at inclusion and were investigated when not exposed to specific allergen. Pulmonary function and symptoms were followed, and F(e,NO) and urinary mediators were correlated to changes in airway responsiveness to histamine and adenosine. Despite no change in pulmonary function (forced expiratory volume in one second mean+/-sem fall 0.3+/-0.7 versus 0.6+/-1.0%, for diluent and allergen, respectively) and no asthma symptoms, repeated allergen exposure, in contrast to diluent, caused significant increases in histamine responsiveness (2.3 doubling doses), an early and gradual increase in F(e,NO) (up to a doubling from baseline) and a small increase in the mast cell marker 9alpha11beta-prostaglandin F(2) after adenosine challenge. In conclusion, serial measurements of exhaled nitric oxide fraction have the potential to provide a very sensitive strategy for early detection of emerging airway inflammation and subsequent changes in airway hyperresponsiveness to histamine.

Relation between bronchial responsiveness to inhaled leukotriene D4 and markers of leukotriene biosynthesis

BACKGROUND

While clinical trials with antileukotrienes have shown overall beneficial effects in asthma, the factors that determine leukotriene dependent asthma are still unclear. A study was undertaken to determine whether or not leukotriene responsiveness in the airways correlates with endogenous leukotriene biosynthesis.

METHODS

Bronchial responsiveness to leukotriene (LT) D4 was assessed as PD20FEV1 in 20 subjects with mild asthma and 10 healthy controls, and compared with bronchial responsiveness to methacholine and two global measures of leukotriene production-urinary LTE4 and ex vivo production of LTB4 in whole blood.

RESULTS

In patients with asthma the bronchoconstrictor activity of LTD4 was about 1300 times greater than methacholine (geometric mean PD20 0.69 nmol v 887 nmol). Those who were most responsive to LTD4 were relatively less responsive to methacholine (p<0.01). There was, however, no correlation between bronchial responsiveness to LTD4 and urinary LTE4 or blood ex vivo LTB4 levels in asthmatic subjects or healthy controls. Subjects with asthma treated with inhaled corticosteroids produced higher levels of LTB4 (p<0.05).

CONCLUSIONS

General measures of leukotriene production cannot predict bronchial responsiveness to LTD4. The unique bronchoconstrictive potency of LTD4 on human airways may relate to the locally regulated expression of the cysteinyl LT1 receptor.