Therapeutic significance of distal airway inflammation in asthma

Presence of activated mobile fibroblasts in bronchoalveolar lavage from patients with mild asthma

Activated fibroblasts are suggested to be involved in the deposition of extracellular matrix in the formation of peribronchial fibrosis in asthma. We report the novel finding of activated elongated fibroblasts accompanied by elevated numbers of eosinophils in bronchoalveolar lavage fluid from 5 out of 12 patients with mild asthma (= 42%), whereas no fibroblasts were observed in the control subjects without asthma (n = 17). The elongated fibroblasts migrated twice as far when compared with fibroblasts from corresponding bronchial biopsies from the same patients, accompanied by an induced expression of RhoA and Rac1, indicating that the increased expression of these proteins are linked to increased migratory capabilities. Moreover, the elongated fibroblasts had an elevated production of the proteoglycans biglycan, versican, perlecan, and decorin, which correlated to an active cytoplasm in these cells. Differential expression patterns between the two fibroblast groups in motility-regulating proteins, such as cofilin, nuclear chloride ion channel protein, and heat-shock protein 20, were identified by two-dimensional electrophoresis and mass spectrometry. These findings indicate the presence of activated and mobile fibroblasts accompanied by an induced inflammatory response outside the airway epithelium in patients with mild asthma, results that may play a role in formation of airway fibrosis.

Increase in alveolar nitric oxide in the presence of symptoms in childhood asthma

STUDY OBJECTIVES

To determine respective contributions of alveolar and proximal airway compartments in exhaled nitric oxide (NO) output (QNO) in pediatric patients with asthma and to correlate their variations with mild symptoms or bronchial obstruction.

PATIENTS AND DESIGN

In 15 asthmatic children with recent mild symptoms, 30 asymptomatic asthmatic children, and 15 healthy children, exhaled NO concentration was measured at multiple expiratory flow (V) rates allowing the calculation of alveolar and proximal airway contributions in QNO, using two approaches, ie, linear and nonlinear models.

MEASUREMENTS AND RESULTS

Asymptomatic and recently symptomatic patients were not significantly different regarding FEV(1) and maximum V between 25% and 75% of FVC (MEF(25-75)): FEV(1), 93.3 +/- 13.4% vs 90 +/- 7.5%; MEF(25-75), 70 +/- 22% vs 68 +/- 28% of predicted values, respectively (mean +/- SD). Maximal airway QNO output was significantly higher in recently symptomatic vs asymptomatic patients (p < 0.0001), and in asymptomatic patients vs healthy children (p < 0.02): 134 +/- 7 nl/min, 55 +/- 43 nl/min, and 19 +/- 8 nl/min, respectively. In a multiple regression analysis, variables that influenced airway QNO output were symptoms (p < 0.0001) and distal airway obstruction as assessed by MEF(25-75) (p < 0.05). Alveolar NO concentration (FANO) was significantly (p < 0.03) higher in recently symptomatic than in patients without symptoms, whereas it was not significantly different between asymptomatic patients and healthy children: 7.2 +/- 2.4 parts per billion (ppb), 5.5 +/- 2.7 ppb, and 4.2 +/- 2.0 ppb, respectively.

CONCLUSIONS

An increase in FANO was observed in the presence of symptoms, and proximal airway NO output was correlated with distal obstruction during asthma.

Exhaled nitric oxide in the assessment of asthma

PURPOSE

Asthma is now defined as a TH2-mediated inflammatory disease involving both large and small airways. However, assessment of airways inflammation is limited by techniques that are time consuming and possibly distressing to the patient. Exhaled nitric oxide, an easily and rapidly obtained noninvasive study, is a potential surrogate for measuring airways inflammation, but its clinical utility remains to be determined. This review examines the role of exhaled nitric oxide in assessing and directing therapy of asthmatic airways inflammation.

RECENT FINDINGS

It is well established that exhaled nitric oxide is increased in patients with untreated asthma and decreases with corticosteroid treatment. Exhaled nitric oxide also generally correlates with eosinophilic inflammation in asthmatic patients. Recent studies show that this correlation is especially pronounced in atopic subjects with asthma when compared with nonatopic subgroups. Recent studies also show that exhaled nitric oxide may be useful in identifying subclinical inflammation, assessing the antiinflammatory effects of asthma medications other than inhaled or oral corticosteroids, and heralding an asthma exacerbation. A number of new studies assert the utility of exhaled nitric oxide as a diagnostic tool for asthma.

SUMMARY

Exhaled nitric oxide may be a useful parameter for monitoring asthmatic inflammation, adjusting therapy, and diagnosing asthma, although prospective longitudinal trials investigating the correlation between exhaled nitric oxide and clinical outcomes are necessary to determine its utility.

Role of muscarinic receptor subtypes in the constriction of peripheral airways: studies on receptor-deficient mice

In the airways, increases in cholinergic nerve activity and cholinergic hypersensitivity are associated with chronic obstructive pulmonary disease and asthma. However, the contribution of individual muscarinic acetylcholine receptor subtypes to the constriction of smaller intrapulmonary airways that are primarily responsible for airway resistance has not been analyzed. To address this issue, we used videomicroscopy and digital imaging of precision-cut lung slices derived from wild-type mice and mice deficient in either the M1 (mAChR1-/- mice), M2 (mAChR2-/- mice), or M3 receptor subtype (mAChR3-/- mice) or lacking both the M2 and M3 receptor subtypes (mAChR2/3-/- double-knockout mice). In peripheral airways from wild-type mice (mAChR+/+ mice), muscarine induced a triphasic concentration-dependent response, characterized by an initial constriction, a transient relaxation, and a sustained constriction. The bronchoconstriction was diminished by up to 60% in mAChR3-/- lungs and was completely abolished in mAChR2/3-/- lungs. The sustained bronchoconstriction was reduced in mAChR2-/- bronchi, and, interestingly, the transient relaxation was absent; the bronchoconstriction in response to 10-8 M muscarine was increased by 158% in mAChR1-/- mice. Quantitative reverse transcriptase-polymerase chain reaction analysis revealed that the disruption of specific mAChR genes had no significant effect on the expression levels of the remaining mAChR subtypes. These results demonstrate that cholinergic constriction of murine peripheral airways is mediated by the concerted action of the M2 and M3 receptor subtypes and suggest the existence of pulmonary M1 receptor activation, which counteracts cholinergic bronchoconstriction. Given the important role of muscarinic cholinergic mechanisms in pulmonary disease, these findings should be of considerable therapeutic relevance.

Effects of cysteinyl leukotrienes in small human bronchus and antagonist activity of montelukast and its metabolites

BACKGROUND

Evidence suggests that small airways contribute to clinically significant processes in asthma. Cysteinyl leukotrienes (CysLTs) are considered to be pivotal mediators in the pathogenesis of asthma. Montelukast (MK), a specific CysLT1 receptor antagonist, is metabolized in two main hydroxylated metabolites (termed M5 and M6, respectively).

OBJECTIVES

The aims of this study were to compare the responsiveness of small and large human bronchi to the three CysLTs, to evaluate the antagonist activity of MK, M5 and M6 in these preparations of human bronchi, and to characterize the CysLT receptors involved in the contractile response.

METHODS AND RESULTS

In isolated small bronchus (i.d. 0.5-2 mm), the potencies (-log molar EC50) of LTC4, LTD4 and LTE4 were 9.3 (n=11), 9.1 (n=30) and 8.4 (n=14), respectively. The three CysLTs were about 30-fold more potent in small bronchi than in larger bronchi (i.d. 4-6 mm). In small bronchi, MK significantly shifted to the right the CysLT concentration-effect curves with pA2 values against LTC4, LTD4 and LTE4 of 9.1 (n=3), 9.0 (n=11) and 8.7 (n=5), respectively. The antagonist potencies of M6 and M5 were similar to MK and fivefold lower, respectively. A similar activity of MK against the three CysLTs suggested that CysLT1 receptors are involved in the contraction of human bronchus. Analysis by RT-PCR also indicated that human bronchus mainly expressed CysLT1 receptors.

CONCLUSION

MK exerts a potent antagonist activity against the particularly potent constricting effects of CysLTs in isolated human small bronchi, which only expressed the CysLT1 receptor subtype. The metabolites of MK are also potent in vitro antagonists, but may not participate in the therapeutic activity of MK due to their low plasma concentrations in patients treated with the recommended dose of MK.

Effect of HFA-flunisolide on peripheral lung inflammation in asthma

BACKGROUND

New hydrofluoroalkane (HFA) formulations of glucocorticoids have been shown to effectively control asthma. HFA glucocorticoids are deposited across all sizes of airways, including the small ones. However, it is not clear whether they can suppress peripheral airway inflammation.

OBJECTIVE

We sought to determine whether HFA-flunisolide could suppress peripheral inflammation in asthma.

METHODS

Twelve patients with mild to moderate asthma received HFA-flunisolide for 6 weeks. Transbronchial and endobronchial biopsy specimens were obtained before and after treatment, and spirometry was performed. Changes in inflammatory cells (eosinophils, neutrophils, lymphocytes, macrophages, basophils) and IL-5 and eotaxin were measured by using immunocytochemistry and in situ hybridization.

RESULTS

Lung function significantly improved after treatment (P <.05). HFA-flunisolide significantly reduced eosinophils, IL-5, and eotaxin in both peripheral and central airways (P <.01). Neutrophils significantly increased after treatment in peripheral and central airways (P <.05). The numbers of lymphocytes remained unchanged.

CONCLUSIONS

These results show that HFA-flunisolide effectively suppressed eosinophilic inflammation in peripheral and central airways. These changes were accompanied by improvement in lung function.

Evaluation of efficacy and safety of flunisolide hydrofluoroalkane for the treatment of asthma

BACKGROUND

Inhaled corticosteroids are currently recommended as first-line therapy for the long-term control and management of persistent asthma. Flunisolide hydrofluoroalkane (HFA) is a new formulation of the corticosteroid flunisolide that is delivered by a metered-dose inhaler containing an HFA propellant. HFA replaces the chlorofluorocarbon (CFC) propellant of the previous formulation, producing aerosols of smaller average particle size.

OBJECTIVE

This article reviews the physical and pharmacologic properties, deposition profile, and potential clinical benefits of flunisolide HFA for the treatment of asthma.

METHODS

Data included in this review were found via MEDLINE (search term, flunisolide HFA).

RESULTS

Flunisolide HFA has a mass median aerodynamic diameter (MMAD) of 1.2 microm, smaller than the 3.8 microm MMAD of the CFC formulation. Compared with flunisolide CFC, more of each flunisolide HFA dose reaches the lungs and less is deposited in the oropharynx. In addition, scintigraphic studies have found that the extra-fine particle size of flunisolide HFA gives it better access to small airways. In short- and long-term clinical studies, flunisolide HFA has been found to significantly increase pulmonary function relative to placebo. Although not statistically superior to the previous CFC formulation, flunisolide HFA exhibited small improvements in secondary efficacy measures, such as as-needed albuterol use and asthma symptoms, relative to flunisolide CFC. Furthermore, research suggests that the new HFA formulation has a low risk of systemic corticosteroid effects (eg, hypothalamic-pituitary-adrenal axis suppression, growth inhibition in children). Also, lower levels of oropharyngeal deposition, such as those seen with flunisolide HFA, are associated with lower incidence of local effects (eg, candidiasis).

CONCLUSION

Flunisolide HFA offers effective asthma control with a high level of tolerability in an extra-fine particle formulation that distributes corticosteroid to all areas of the lung, including small airways.

Management of persistent symptoms in patients with asthma

The main goals of asthma therapy are to control symptoms, prevent acute attacks, and maintain lung function as close to normal as possible. Customizing the regimen to relieve the patient's symptoms and control airway inflammation is important. If asthma is not well controlled, an initial inhaled corticosteroid boost will treat the underlying heightened airway inflammation, and the addition of a long-acting beta2-adrenergic agonist or leukotriene receptor antagonist will rapidly control symptoms. Most patients do not require prolonged treatment with expensive combination or additive agents. Exercise-induced bronchoconstriction is a common source of symptoms. Treatments for scheduled and unscheduled exercises differ. Inhaled corticosteroids prevent frequent and severe asthma exacerbations. When patients have persistent symptoms despite a pharmacological regimen, environmental factors and nonpharmacological interventions must be considered before medication is increased. When an inhaled corticosteroid is being considered, issues of compliance, drug delivery device, and proper inhaler techniques are as important as issues of potency, clinical efficacy, and adverse effects. The new hydrofluoroalkane preparations offer more lung deposition and may be important in treating inflammation of the small airways in patients with asthma.

Thoracic CT in pediatric patients with difficult-to-treat asthma

OBJECTIVE

. The aim of this study was to establish objective, simple criteria for bronchial wall thickening in children with difficult-to-treat asthma.

SUBJECTS AND METHODS

. Bronchial sections were counted at five levels in both lungs and at three levels in the right lung on high-resolution CT and plotted against lung function. Findings from 27 children with persistent symptoms of asthma (mean age, 11.4 years; SD, +/-3.1 years) that were severe (group A, n = 15) or moderate (group B, n = 12) were compared with findings from 21 control subjects (mean age, 10.8 years; SD, +/-3.0 years) using the Student's t test, analysis of variance, and Dunn-Bonferroni test.

RESULTS

. A bronchial wall thickening score based on the number of visible bronchi at three levels (three-level score) proved to be as valuable as and simpler to obtain than a score based on the number of bronchi at five levels (five-level score). The three-level scores for groups A and B were similar (mean +/- SD, 16.8 +/- 4.2 vs 18.4 +/- 3.4, respectively; p = not significant), but these scores were significantly higher than those for the control subjects (mean +/- SD, 8.2 +/- 3.4, respectively; p < 0.001). There was no correlation between the three-level score and forced expiratory volume in 1 sec or forced expiratory flow between 25% and 75% of forced vital capacity. In contrast with adults with severe asthma, our pediatric patients with difficult-to-treat asthma did not have CT evidence of mucoid impaction, emphysema, areas of hyperlucency, bronchiectasis, or sequellar line shadows.

CONCLUSION

. Bronchial wall thickening visible on high-resolution CT may constitute an additional criterion of asthma severity in children. CT evidence of bronchial wall thickening might help to identify patients with a higher risk of airway remodeling.