Eosinophils increase airway sensory nerve density in mice and in human asthma

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Abstract

In asthma, airway nerve dysfunction leads to excessive bronchoconstriction and cough. It is well established that eosinophils alter nerve function and that airway eosinophilia is present in 50 to 60% of asthmatics. However, the effects of eosinophils on airway nerve structure have not been established. We tested whether eosinophils alter airway nerve structure and measured the physiological consequences of those changes. Our results in humans with and without eosinophilic asthma showed that airway innervation and substance P expression were increased in moderate persistent asthmatics compared to mild intermittent asthmatics and healthy subjects. Increased innervation was associated with a lack of bronchodilator responsiveness and increased irritant sensitivity. In a mouse model of eosinophilic airway inflammation, the increase in nerve density and airway hyperresponsiveness were mediated by eosinophils. Our results implicate airway nerve remodeling as a key mechanism for increased irritant sensitivity and exaggerated airway responsiveness in eosinophilic asthma.

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Tiotropium in asthma poorly controlled with standard combination therapy.

Huib A M Kerstjens, Michael Engel, Ronald Dahl … (2012)

Some patients with asthma have frequent exacerbations and persistent airflow obstruction despite treatment with inhaled glucocorticoids and long-acting beta-agonists (LABAs). In two replicate, randomized, controlled trials involving 912 patients with asthma who were receiving inhaled glucocorticoids and LABAs, we compared the effect on lung function and exacerbations of adding tiotropium (a total dose of 5 μg) or placebo, both delivered by a soft-mist inhaler once daily for 48 weeks. All the patients were symptomatic, had a post-bronchodilator forced expiratory volume in 1 second (FEV(1)) of 80% or less of the predicted value, and had a history of at least one severe exacerbation in the previous year. The patients had a mean baseline FEV(1) of 62% of the predicted value; the mean age was 53 years. At 24 weeks, the mean (±SE) change in the peak FEV(1) from baseline was greater with tiotropium than with placebo in the two trials: a difference of 86±34 ml in trial 1 (P=0.01) and 154±32 ml in trial 2 (P<0.001). The predose (trough) FEV(1) also improved in trials 1 and 2 with tiotropium, as compared with placebo: a difference of 88±31 ml (P=0.01) and 111±30 ml (P<0.001), respectively. The addition of tiotropium increased the time to the first severe exacerbation (282 days vs. 226 days), with an overall reduction of 21% in the risk of a severe exacerbation (hazard ratio, 0.79; P=0.03). No deaths occurred; adverse events were similar in the two groups. In patients with poorly controlled asthma despite the use of inhaled glucocorticoids and LABAs, the addition of tiotropium significantly increased the time to the first severe exacerbation and provided modest sustained bronchodilation. (Funded by Boehringer Ingelheim and Pfizer; ClinicalTrials.gov numbers, NCT00772538 and NCT00776984.).

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Charles Irvin, L. Rinaldi, Brian J. Lee … (2004)

Eosinophils are often dominant inflammatory cells present in the lungs of asthma patients. Nonetheless, the role of these leukocytes remains poorly understood. We have created a transgenic line of mice (PHIL) that are specifically devoid of eosinophils, but otherwise have a full complement of hematopoietically derived cells. Allergen challenge of PHIL mice demonstrated that eosinophils were required for pulmonary mucus accumulation and the airway hyperresponsiveness associated with asthma. The development of an eosinophil-less mouse now permits an unambiguous assessment of a number of human diseases that have been linked to this granulocyte, including allergic diseases, parasite infections, and tumorigenesis.

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Tiotropium bromide step-up therapy for adults with uncontrolled asthma.

Susan J Kunselman, David Sutherland, Loren Denlinger … (2010)

Long-acting beta-agonist (LABA) therapy improves symptoms in patients whose asthma is poorly controlled by an inhaled glucocorticoid alone. Alternative treatments for adults with uncontrolled asthma are needed. In a three-way, double-blind, triple-dummy crossover trial involving 210 patients with asthma, we evaluated the addition of tiotropium bromide (a long-acting anticholinergic agent approved for the treatment of chronic obstructive pulmonary disease but not asthma) to an inhaled glucocorticoid, as compared with a doubling of the dose of the inhaled glucocorticoid (primary superiority comparison) or the addition of the LABA salmeterol (secondary noninferiority comparison). The use of tiotropium resulted in a superior primary outcome, as compared with a doubling of the dose of an inhaled glucocorticoid, as assessed by measuring the morning peak expiratory flow (PEF), with a mean difference of 25.8 liters per minute (P<0.001) and superiority in most secondary outcomes, including evening PEF, with a difference of 35.3 liters per minute (P<0.001); the proportion of asthma-control days, with a difference of 0.079 (P=0.01); the forced expiratory volume in 1 second (FEV1) before bronchodilation, with a difference of 0.10 liters (P=0.004); and daily symptom scores, with a difference of -0.11 points (P<0.001). The addition of tiotropium was also noninferior to the addition of salmeterol for all assessed outcomes and increased the prebronchodilator FEV1 more than did salmeterol, with a difference of 0.11 liters (P=0.003). When added to an inhaled glucocorticoid, tiotropium improved symptoms and lung function in patients with inadequately controlled asthma. Its effects appeared to be equivalent to those with the addition of salmeterol. (Funded by the National Heart, Lung, and Blood Institute; ClinicalTrials.gov number, NCT00565266.).