Peripheral inflammation is more important than central inflammation

Small airways in asthma: From inflammation and pathophysiology to treatment response

Small airways are characterized as those with an inner diameter less than 2 mm and constitute a major site of pathology and inflammation in asthma disease. It is estimated that small airways dysfunction may occur before the emergence of noticeable symptoms, spirometric abnormalities and imaging findings, thus characterizing them as "the quiet or silent zone" of the lungs. Despite their importance, measuring and quantifying small airways dysfunction presents a considerable challenge due to their inaccessibility in usual functional measurements, primarily due to their size and peripheral localization. Several pulmonary function tests have been proposed for the assessment of the small airways, including impulse oscillometry, nitrogen washout, body plethysmography, as well as imaging methods. Nevertheless, none of these methods has been established as the definitive "gold standard," thus, a combination of them should be used for an effective assessment of the small airways. Widely used asthma treatments seem to also affect several parameters of the small airways. Emerging biologic treatments show promising results in reducing small airways inflammation and remodelling, providing evidence for potential alterations in the disease's progression and outcomes. These novel therapies have implications not only in the clinical aspects of asthma but also in its inflammatory and functional aspects.

[Small airway: from definition to treatment]

The small airway, present since the origins of humanity and described barely a century ago, has recently been discovered as the anatomical site where inflammation begins in some obstructive lung diseases, such as asthma and Chronic Obstructive Pulmonary Disease (COPD), per se. Small airway dysfuction was identified in up to 91% of asthmatic patients and in a large proportion of COPD patients. In subjects without pathology, small airway represent 98.8% (approximately 4500 ml) of the total lung volume, contributing only between 10-25% of the total lung resistance; however, in subjects with obstruction, it can represent up to 90% of the total resistance. Despite this, its morphological and functional characteristics allow its dysfunction to remain undetected by conventional diagnostic methods, such as spirometry. Hence the importance of this review, which offers an overview of the tools available to assess small airway dysfunction and the possible therapies that act in this silent zone.

Elevated air quality index and fine particulate matter levels contribute to the poor prognosis and progression of nonsmall-cell lung cancer: A cohort study combined with external validation

Background

Poor air quality can result in a variety of respiratory disorders. However, the air quality index (AQI) and the level of fine particulate matter (PM2.5) on the progression and prognosis of nonsmall‐cell lung cancer (NSCLC) are unclear.

Methods

We launched a cohort study focused on the relationship between air quality and overall survival as well as progression, incorporating data from 590 patients with NSCLC in our medical center between November 1, 2013 and March 1, 2016. Forty‐nine patients from Sichuan Cancer Hospital were used for validation.

Results

Cases with poorer AQI 6 months before NSCLC diagnosis were more likely to progress to stage III to IV NSCLC than controls (OR = 2.61, 95% CI 1.35–5.24, p = 0.005). Similarly, if exposed to high levels of PM2.5 during these 6 months, overall survival was poor (HR [95% CI] = 1.53 [1.13, 2.07], p = 0.006). According to multivariate analysis, age, gender, KPS, PM2.5, hyperlipemia, and NSCLC stage were independent risk factors of overall survival. A predictive model developed by these factors above yielded a favorable agreement (C‐index = 0.758) on the calibration curve. External validation was conducted by 46 patients from Sichuan Cancer Hospital displaying an AUC of 0.724 (0.684–0.763).

Conclusions

PM2.5 and AQI levels affect disease progression and long‐term survival in NSCLC patients. An overall survival prediction model based on the PM2.5 level can help clinicians predict the risk of death in NSCLC.

Real-Life Effectiveness of Mepolizumab on Forced Expiratory Flow between 25% and 75% of Forced Vital Capacity in Patients with Severe Eosinophilic Asthma

Severe eosinophilic asthma (SEA) is associated with high peripheral blood and airway eosinophilia, recurrent disease exacerbations and severe airflow limitation. Eosinophilic inflammation is also responsible for small airway disease (SAD) development. SEA patients experience poor disease control and response to standard therapy and are prime candidates for anti-IL5 biologicals, such as mepolizumab, but the effect of treatment on SAD is unclear. We investigated the effect of mepolizumab on lung function in SEA patients, focusing on SAD parameters, and searched for an association between patients' phenotypic characteristics and changes in small airways function. In this real-life study, data from 105 patients with SEA were collected at baseline and after 6, 12 and 18 months of mepolizumab treatment. Along with expected improvements in clinical and lung function parameters brought by Mepolizumab treatment, FEF2525-75% values showed a highly significant, gradual and persistent increase (from 32.7 ± 18.2% at baseline to 48.6 ± 18.4% after 18 months) and correlated with ACT scores at 18 months (r = 0.566; p ≤ 0.0001). A patient subgroup analysis showed that changes in FEF25-75% values were higher in patients with a baseline peripheral blood eosinophil count ≥400 cells/μL and oral corticosteroid use. Mepolizumab significantly improves small airway function. This effect correlates with clinical benefits and may represent an accessible parameter through which to evaluate therapeutic response. This study provides novel insights into the phenotypic characteristics associated with the improved functional outcome provided by mepolizumab treatment.

Association Between Bedroom Particulate Matter Filtration and Changes in Airway Pathophysiology in Children With Asthma

Importance

Fine particles (particulate matter 2.5 μm [PM2.5]), a ubiquitous air pollutant, can deposit in the small airways that play a vital role in asthma. It appears to be unknown whether the use of a PM2.5 filtration device can improve small airway physiology and respiratory inflammation in children with asthma.

Objective

To discover what pathophysiological changes in the small airways are associated with using a PM2.5-removing device in the bedrooms of children with asthma.

Design, Setting, and Participants

Children with mild or moderate asthma were enrolled in this double-blind, crossover study. The participants used a true filtration device and a sham filtration device in their bedrooms in a random order for 2 weeks each with a 2-week washout interval. The study was conducted in a suburb of Shanghai, China, during a low-ozone season.

Exposures

Ozone and PM2.5 were measured inside bedrooms and outside a window.

Main Outcomes and Measures

Impulse oscillometry, spirometry, and fractional exhaled nitric oxide were measured at the beginning and the end of each intervention. Peak expiratory flow was measured twice daily at home.

Results

Forty-three children (5-13 years old; 26 boys [60%]) participated. Outdoor 24-hour mean PM2.5 concentrations were moderately high, ranging from 28.6 to 69.8 μg/m3 (median, 53 μg/m3). During true filtration, bedroom PM2.5 concentrations were a mean (SD) of 63.4% (35.9%) lower than during sham filtration. Compared with sham filtration, true filtration was significantly associated with improved airway mechanics, reflected in a 24.4% (95% CI, 11.8%-37.1%) reduction in total airway resistance, a 43.5% (95% CI, 13.7%-73.3%) reduction in small airway resistance, a 22.2% (95% CI, 2.2%-42.2%) reduction in resonant frequency, and a 73.1% (95% CI, 0.3%-145.8%) increase in airway reactance. True filtration was also associated with significant improvements in fractional exhaled nitric oxide (a 27.6% [95% CI, 8.9%-42.4%] reduction) and peak expiratory flow (a 1.6% [95% CI, 0.8%-2.5%] increase). These improvements were significantly associated with bedroom PM2.5 reduction. Improvements in small airway function were nonsignificant (8.4% [95% CI, -1.4% to 18.3%]) in all participants but significant (13.2% [95% CI, 1.2%-25.1%]) in participants without eosinophilic airway inflammation at baseline. No improvements were observed for forced vital capacity, forced expiratory volume during the first second, and the ratio of these in all participants or subgroups.

Conclusions and Relevance

Per these results, indoor PM2.5 filtration can be a practical method to improve air flow in an asthmatic lung through improved airway mechanics and function as well as reduced inflammation. This warrants a clinical trial to confirm.

Trial Registration

ClinicalTrials.gov Identifier: NCT03282864.

Small airway impairment and bronchial hyperresponsiveness in asthma onset

Purpose

Our study tried to find a relationship between baseline FEF_25-75% and airway hyperresponsiveness (AHR) and whether a greater FEF_25-75% impairment may be a marker of a more severe hyperresponsiveness in subjects with normal FEV1 and FEV1/FVC and suggestive asthma symptoms. Besides, we tried to asses a FEF_25-75% cut-off value to identify hyper-reactive subjects.

Methods

4,172 subjects (2,042 M; mean age: 38.3±14.9; mean FEV1 % predicted: 100.5±12.7 and FEV1/FVC: 85.4±6.8) were examined after performing a methacholine (Mch) test. All subjects reported a symptom onset within 3 years before the test. Subjects with PD20<400 or >400 µg were arbitrarily considered affected by moderate/severe and borderline AHR, respectively.

Results

PD20 values were 213 (IQR:86-557), 340 (IQR:157-872) and 433 (IQR:196-1032) µg in subjects with baseline FEF_25-75≤50%, FEF_25-75 between 50 and 70% and FEF_25-75>70% respectively (P<0.0001). Only in moderate/severe hyper-reactive subjects (excluded borderlines), PD20 was lower in the FEF_25-75≤50% subgroup than in the 1 with FEF_25-75>70%. The hyperreactive subjects percentage, was higher in those with FEF_25-75≤50% and lower in those with FEF_25-75>70% (P<0.0001). FEF_25-75<50% (compared to FEF_25-75>70%) was a higher AHR risk factor, especially in subjects with moderate/severe AHR (OR: 2.18 [IQR:1.41-3.37]; P<0.0001). Thresholds yielding the highest combined sensitivity/specificity for FEF_25-75% were 75.19 (area under curve [AUC]: 0.653) and 74.95 (AUC:0.688) in subjects with PD20<2,400 and <400 µg respectively. FEV1, FVC, and FEV1/FVC measured in subjects with different FEF_25-75≤50%, FEF_25-75>50 and ≤70% or FEF_25-75>70% levels were similar both in normoreactive and hyperreactive subjects.

Conclusions

At asthma onset, reduced baseline FEF_25-75 values with normal FEV1 and FEV1/FVC may predict AHR. Detectable predictive cut-off values do not exist because even normoreactive subjects can show lower FEF_25-75 values. Furthermore, a greater FEF_25-75 reduction may be associated to a more severe AHR, suggesting a possible FEF_25-75 role in the management of asthma when FEV1 and FEV1/FVC are normal.

Assessing and accessing the small airways; implications for asthma management

Despite the wealth of experience in the management of asthma, the disease remains inadequately controlled in some patients, who face long-term respiratory impairment and disability. The disease has been characterised as an inflammatory condition affecting first the larger airways and eventually the smaller airways, but there is evidence that peripheral airway involvement defines a particular and more severe phenotype of asthma. For this reason, assessing functional and biological parameters reflective of small airways involvement is important prognostically. No assessment method is universally and directly representative of peripheral airway function, but the traditional spirometric tests, including vital capacity, residual volume and forced vital capacity, are somewhat correlated with this function; useful methods for further assessment include the single-breath nitrogen wash-out test, impulse oscillometry, nitrous oxide and exhaled breath concentrate measurements, as well as computed tomography to reflect air trapping and response to treatment. Formulation advancements have made for easier treatment access to the smaller airways, with the new extrafine formulations resulting in better asthma control compared with non-extrafine formulations.

Pathogenesis of small airways in asthma

Asthma is a lung disease characterized by inflammation and remodeling of the airways. It is now widely accepted that airway inflammation and remodeling occur not only in the central airways but also in the small airways and even in the lung parenchyma. Inflammation of the distal lung can be observed even in mild asthmatics with normal or noncompromised lung function. Moreover, the small airways and the lung parenchyma can produce many Th2 cytokines and chemokines involved in initiation and perpetuation of the inflammatory process. In addition, the distal parts of the bronchial tree have been recognized as a predominant site of airflow obstruction in many asthmatics. In fact, the inflammation at this distal site has been described as more severe when compared to the large airway inflammation, and evidence of remodeling in the lung periphery is emerging. Recognition of asthma as a disease of the entire respiratory tract has an important clinical significance, highlighting the need to also consider the distal lung as a target in any therapeutic strategy for effective treatment of this disease.

[Inflammation and remodeling of the distal airways: studies in humans and experimental models]

Asthma is characterized by inflammation and remodeling of the airways, giving rise to airway obstruction and symptoms of wheezing, chest tightness, cough and dyspnea. Most of these observations arise from the study of samples obtained from the central airways by distinct methods. However, it is currently accepted that this inflammatory process occurs not only in the central airway but also in the small airway and even in the pulmonary parenchyma of all asthmatic patients, even those with mild asthma. CD4+ lymphocytes, activated eosinophils and IL-5 mRNA expression are present in a greater quantity in the small airways. Also present is remodeling, with an increase in submucosal thickness, the muscular layer and adventitia. This inflammatory process causes a disconnection between the pulmonary parenchyma and the airway, giving rise to obstruction of the small airway, which is currently considered to be predominant in asthmatic patients. Likewise, studies of experimental asthma in animals support the substantial role of the distal airway. Recognition that asthma affects the entire airway could be clinically important and lead to the distal lung being considered as a target in any effective therapeutic strategy. However, longitudinal studies are required to evaluate the impact of distal airway inflammation and its treatment in asthma.

[Physiology and physiopathology of the distal airways in asthma]

The small airways are those with an internal diameter of less than 2 mm. The contribution of these airways to total airflow resistance is small in healthy individuals but can represent 50-90 % of total airflow resistance in asthmatics. Suspicion of small airways disease has been based on reduction of midexpiratory and instantaneous flows, although wide variability in their values and the absence of a sufficiently validated cut-off point has limited their clinical application. Static pulmonary volumes can provide indirect evidence of the state of the most distal airways, revealing two effects of their alteration: air trapping and dynamic hyperinflation. While determination of airway resistance by plethysmography and of respiratory system resistance measured by flow interruption are highly non-specific, the forced oscillation technique allows obstruction of the small airways to be distinguished from that of medium-caliber airways. The characteristic pattern of peripheral obstruction includes a decrease in frequency-dependent resistance, reduced reactivity and an increase in resonance frequency. Single-or multiple-breath nitrogen washout can also provide specific information on the small airways, although the apparatus required is less frequently available. Analysis through bicompartmental models of exhaled nitric oxide allows alveolar nitric oxide concentrations to be determined, which seems to provide information on inflammatory activity in the small airways.

Scientific respiratory symposium, paris june 2010

At a 2010 Respiratory Symposium in Paris, chaired by Professors Bousquet and Roche of the University of Paris, recent trends in research, therapy and treatment guidelines for asthma and chronic obstructive pulmonary disease (COPD) were reviewed and discussed by a faculty of expert European and US respiratory physicians. This article reviews five key clinical presentations with particular emphasis given to the importance of small airways in the pathology and treatment of asthma and COPD. Further analysis of the economics of treatment in Europe and the US shows a wide variance in direct and indirect costs.

The effect of intranasal corticosteroids on asthma control and quality of life in allergic rhinitis with mild asthma

BACKGROUND

The mechanisms through which rhinitis affects asthma have not been completely elucidated. We explored whether the effect of nasal treatment on asthma control and respiratory-related quality of life (HRQoL) is mediated by inflammatory changes of the upper and lower airways.

METHODS

Allergic rhinitics with mild asthma were randomized to a 14-day treatment period with either nasal budesonide 100 μg, 1 puff per nostril twice a day, or placebo. Clinical, functional, and biological evaluations were performed before and after treatment.

RESULTS

Twenty subjects (M/F: 10/10; age: 31 ± 15 years; mean ± SD) were enrolled, and a total of 17 individuals completely participated in the study. Lung function was within the normal range. The total asthma control test (ACT) score was 20 ± 5.3 and the RHINASTHMA Global Summary (GS) was 44 ± 15. The percentage proportion of eosinophils in nasal lavage was 9.9% and significantly correlated with spirometric parameters reflecting peripheral airway function (for FEF(50): r = 0.48, p = .03; for FEF(25): r = 0.47, p = .03). The pH of the exhaled breath condensate (EBC) was 7.33 ± 0.4. After nasal treatment, the percentage proportion of eosinophils fell significantly (p = .002), and changes in percentage proportion of eosinophils were associated with changes both in the ACT score (r = 0.76, p = .04) and in the RHINASTHMA GS (r = 0.77, p = .02). The increase in the pH of the EBC was not associated with changes in the ACT score or with the RHINASTHMA GS.

CONCLUSIONS

These findings confirm that, in subjects with allergic rhinitis with mild asthma, nasal inflammation impacts on asthma control and HRQoL. The improved control of respiratory symptoms obtained with nasal corticosteroids seems to be mediated by functional changes in the peripheral airways.

New insights into the pathophysiology of the small airways in asthma

Asthma is a lung disease characterized by inflammation and remodeling of the airways, which leads to airflow obstruction and symptoms of wheeze, chest tightness, cough and dyspnea. It is now widely accepted that airway inflammation and remodeling occur not only in the central airways but also in the small airways and even in the lung parenchyma. Inflammation of the distal lung can be observed even in mild asthmatics with normal or noncompromised lung function. Moreover, the small airways and the lung parenchyma can produce many Th2 cytokines and chemokines involved in initiation and perpetuation of the inflammatory process. In addition, the distal parts of the lung have been recognized as a predominant site of airflow obstruction in asthmatics. In fact, the inflammation at this distal site has been described as more severe when compared to the large airway inflammation, and evidence of remodeling in the lung periphery is emerging. Recognition of asthma as a disease of the entire respiratory tract has an important clinical significance, highlighting the need to also consider the distal lung as a target in any therapeutic strategy for effective treatment of this disease.

The small airways and distal lung compartment in asthma and COPD: a time for reappraisal

The involvement of small airways in the pathogenesis of asthma and chronic obstructive pulmonary disease (COPD) has been debated for a long time. However, a proper definition of small airway disease is still lacking, and neither a widely accepted biomarker nor a functional parameter to assess small airway abnormalities and to explore the effect of tested compounds on small airways is available. Aiming towards increased knowledge and consensus on this topic, this perspective paper intends to (i) strengthen awareness among the scientific community on the role of small airways in asthma and COPD; (ii) examine the pros and cons of some biological, functional and imaging parameters in the assessment of small airway abnormalities; and (iii) discuss the evidence for distal airway pharmacological targeting in asthma and COPD.

Sputum eosinophilia, airway hyperresponsiveness and airway narrowing in young adults with former asthma

BACKGROUND

30-80% of outgrown asthma subjects develop symptoms again later in life. We investigated inflammation and function of lower airway in adolescents with former asthma.

METHODS

326 never-smoking young adults (mean age 24.0 years) were interviewed with special emphasis on history of asthma. Diagnosis of asthma was based on GINA guidelines. Former asthma subjects consisted of ones with a history of physician-diagnosed childhood asthma, who had been free of asthma symptoms without the use of medication for at least 10 years prior to the study. Provocative concentration of methacholine causing a 20% fall in forced expiratory volume in 1 second (FEV(1))(PC(20)) and eosinophil percentage in induced sputum were measured.

RESULTS

31 subjects were former asthma subjects (FBA), 11 subjects were current asthma subjects (CBA) and 284 subjects had no history of asthma (non-BA). PC(20) and FEV(1)/FVC ratio were significantly lower in the FBA group than in the non-BA group (P < 0.01). Maximal mid-expiratory flow (MMF) was significantly lower in the FBA group than in the non-BA group (P < 0.05). Sputum eosinophil percentage was significantly increased in the FBA group compared with the non-BA group (P < 0.01). PC(20) was significantly lower in the CBA group than in the FBA and non-BA groups (P < 0.01). FEV(1), FEV(1)/FVC ratio and MMF were significantly lower in the CBA group than in the FBA group (P < 0.05, P < 0.05 and P < 0.05, respectively) and the non-BA group (P < 0.01, P < 0.01 and P < 0.05, respectively). Sputum eosinophils were significantly higher in the CBA group than in the FBA and non-BA groups (P < 0.01).

CONCLUSIONS

This study shows that subjects with long-term outgrown asthma continue to have airway eosinophilic inflammation, airway hyperresponsiveness and airway narrowing.

Posture-dependent human 3He lung imaging in an open-access MRI system: initial results

RATIONALE AND OBJECTIVES

The human lung and its functions are extremely sensitive to orientation and posture, and debate continues as to the role of gravity and the surrounding anatomy in determining lung function and heterogeneity of perfusion and ventilation. However, study of these effects is difficult. The conventional high-field magnets used for most hyperpolarized (3)He magnetic resonance imaging (MRI) of the human lung, and most other common radiologic imaging modalities including positron emission tomography and computed tomography, restrict subjects to lying horizontally, minimizing most gravitational effects.

MATERIALS AND METHODS

In this article, we review the motivation for posture-dependent studies of human lung function and present initial imaging results of human lungs in the supine and vertical body orientations using inhaled hyperpolarized (3)He gas and an open-access MRI instrument. The open geometry of this MRI system features a "walk-in" capability that permits subjects to be imaged in vertical and horizontal positions and potentially allows for complete rotation of the orientation of the imaging subject in a two-dimensional plane.

RESULTS

Initial results include two-dimensional lung images acquired with approximately 4 x 8 mm in-plane resolution and three-dimensional images with approximately 2-cm slice thickness.

CONCLUSIONS

Effects of posture variation are observed, including posture-related effects of the diaphragm and distension of the lungs while vertical.

Regional differences in the pattern of airway remodeling following chronic allergen exposure in mice

Background

Airway remodeling present in the large airways in asthma or asthma models has been associated with airway dysfunction in humans and mice. It is not clear if airways distal to the large conducting airways have similar degrees of airway remodeling following chronic allergen exposure in mice. Our objective was to test the hypothesis that airway remodeling is heterogeneous by optimizing a morphometric technique for distal airways and applying this to mice following chronic exposure to allergen or saline.

Methods

In this study, BALB/c mice were chronically exposed to intranasal allergen or saline. Lung sections were stained for smooth muscle, collagen, and fibronectin content. Airway morphometric analysis of small (0–50000 μm²), medium (50000 μm²–175000 μm²) and large (>175000 μm²) airways was based on quantifying the area of positive stain in several defined sub-epithelial regions of interest. Optimization of this technique was based on calculating sample sizes required to detect differences between allergen and saline exposed animals.

Results

Following chronic allergen exposure BALB/c mice demonstrate sustained airway hyperresponsiveness. BALB/c mice demonstrate an allergen-induced increase in smooth muscle content throughout all generations of airways, whereas changes in subepithelial collagen and fibronectin content are absent from distal airways.

Conclusion

We demonstrate for the first time, a systematic objective analysis of allergen induced airway remodeling throughout the tracheobronchial tree in mice. Following chronic allergen exposure, at the time of sustained airway dysfunction, BALB/c mice demonstrate regional differences in the pattern of remodeling. Therefore results obtained from limited regions of lung should not be considered representative of the entire airway tree.

New insights into the pathophysiology of the small airways in asthma

Airway inflammation and remodeling in asthma occur in the central airways and also in the small airways and in the lung parenchyma. The small airways and the lung parenchyma can produce many Th2 cytokines, chemokines, and mediators involved in initiation and perpetuation of the inflammatory process. The distal lung has been recognized as a predominant site of airflow obstruction in asthmatics. Distal inflammation has been described as more severe than large airway inflammation, and strong evidence of remodeling in the lung periphery is emerging. Recognition of asthma as a disease of the entire respiratory tract has clinical significance, highlighting the need to target the distal lung in any strategy for effective treatment of this disease.

Involvement of distal airways in a chronic model of experimental asthma

BACKGROUND

Bronchial asthma is characterized by chronic airway inflammation and airway remodelling which occurs in both proximal and distal airways. These changes are associated with development of airway hyper-responsiveness and airflow limitation.

OBJECTIVE

This study was aimed to analyse whether chronic inhalative allergen challenges in mice lead to morphological and physiological changes comparable with this phenotype.

METHODS

For this purpose, BALB/c mice were systemically sensitized to ovalbumin (OVA) followed by aerosol allergen challenges on 2 consecutive days per week for 12 weeks.

RESULTS

In chronically challenged mice, tissue inflammation in proximal as well as distal airways was observed with a predominance of lymphocytes within the cellular infiltrate. In contrast, inflammation in the airway lumen decreased over time. These changes were associated by a shift in bronchoalveolar lavage-cytokine levels from IL-4, IL-5 and TNF-alpha production (during the acute phase) towards markedly increased levels of TGF-beta during the chronic phase. Goblet cell hyperplasia and subepithelial fibrosis occurred throughout the airway tree. In terms of lung function, chronically challenged mice developed persistent bronchial hyper-responsiveness and progressive airflow limitation. Six weeks after OVA aerosol discontinuation, airway inflammation still persisted although lung function was normalized.

CONCLUSION

These data indicate that our model of chronic aerosol allergen challenges leads to a phenotype of experimental asthma with participation of distal airways and persistence of inflammation thereby resembling many morphological and physiological aspects of human bronchial asthma.

Dry powder inhalers for pulmonary drug delivery

The pulmonary route is an interesting route for drug administration, both for effective local therapy (asthma, chronic obstructive pulmonary disease or cystic fibrosis) and for the systemic administration of drugs (e.g., peptides and proteins). Well-designed dry powder inhalers are highly efficient systems for pulmonary drug delivery. However, they are also complicated systems, the the performance of which relies on many aspects, including the design of the inhaler (e.g., resistance to air flow and the used de-agglomeration principle to generate the inhalation aerosol), the powder formulation and the air flow generated by the patient. The technical background of these aspects, and how they may be tuned in order to obtain desired performance profiles, is reviewed. In light of the technical background, new developments and possibilities for further improvements are discussed.

Deposition and effects of inhaled corticosteroids

Inhaled corticosteroids are now recommended as maintenance therapy for all but the mildest cases of asthma, and may be delivered by a variety of devices and formulations. Drug delivery may be assessed by both in vitro and in vivo methods. Although drug deposition in the lungs is expected to predict clinical response, this relationship is often masked by the flat nature of corticosteroid dose-response curves. The effects of inhaled corticosteroids depend not only upon the pharmacology of the drug being administered, but also upon its delivery system, with more efficient devices not only improving therapeutic effect but also potentially increasing systemic adverse effects. Modern delivery systems that enhance drug targeting to the lungs make it possible to use lower dosages of inhaled corticosteroid, such that the clinical response is maintained but systemic exposure reduced.

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.

Contribution of the distal lung to the pathologic and physiologic changes in asthma: potential therapeutic target Roger S. Mitchell lecture

Pathologic and physiologic evidence has emerged in the last few years suggesting that the airway inflammation and remodeling that characterize asthma occur not only in the central airways but extend to the distal lung and the lung parenchyma. The distal airways are capable of producing T helper (Th) type 2 cytokines and chemokines, and, more recently, they have been recognized as a predominant site of airflow obstruction in asthmatic patients. In the lung parenchyma, a similar Th2 cytokine profile and infiltration of inflammatory cells also has been reported. The inflammation at this distal site has been described as being more severe when compared to the large amount of airway inflammation, and evidence of remodeling in the lung periphery is emerging. The recognition of asthma as a disease of the entire respiratory tract has an important clinical significance highlighting the need to also consider the distal lung as a target in any therapeutic strategy for effective treatment of this disease.

Small airway inflammation in asthma

Asthma was originally described as an inflammatory disease that predominantly involves the central airways. Pathological and physiological evidence reported during the past few years suggests that the inflammatory process extends beyond the central airways to the peripheral airways and the lung parenchyma. The small airways are capable of producing T-helper-2 cytokines, as well as chemokines, and they have recently been recognized as a predominant site of airflow obstruction in asthmatic persons. The inflammation at this distal site has been described as more severe than large airway inflammation. These findings are of great clinical significance, and highlight the need to consider the peripheral airways as a target in any therapeutic strategy for treatment of asthma.