The role of small airways in lung disease

May Small Airways Dysfunction (SAD) Play a Role in the Idiopathic Pulmonary Fibrosis (IPF) and May SAD Be a Therapeutic Target?

Small airway dysfunction (SAD) is a pathological process that affects the bronchioles and non-cartilaginous airways below 2 mm in diameter. This short review presents a link between SAD and IPF. Pathomorphological changes of small airways in fibrotic lungs are discussed. Additionally, functional abnormalities related to SAD measured by spirometry and oscillometry are presented. The problem of early detection and treatment of SAD as a procedure potentially capable of mitigating fibrosis is mentioned.

Small-Molecule Activation of Protein Phosphatase 2A Counters Bleomycin-Induced Fibrosis in Mice

The activity of protein phosphatase 2A (PP2A), a serine-threonine phosphatase, is reduced in the lung fibroblasts of idiopathic pulmonary fibrosis (IPF) patients. The objective of this study was to determine whether the reactivation of PP2A could reduce fibrosis and preserve the pulmonary function in a bleomycin (BLM) mouse model. Here, we present a new class of direct small-molecule PP2A activators, diarylmethyl-pyran-sulfonamide, exemplified by ATUX-1215. ATUX-1215 has improved metabolic stability and bioavailability compared to our previously described PP2A activators. Primary human lung fibroblasts were exposed to ATUX-1215 and an older generation PP2A activator in combination with TGFβ. ATUX-1215 treatment enhanced the PP2A activity, reduced the phosphorylation of ERK and JNK, and reduced the TGFβ-induced expression of ACTA2, FN1, COL1A1, and COL3A1. C57BL/6J mice were administered 5 mg/kg ATUX-1215 daily following intratracheal instillation of BLM. Three weeks later, forced oscillation and expiratory measurements were performed using the Scireq Flexivent System. ATUX-1215 prevented BLM-induced lung physiology changes, including the preservation of normal PV loop, compliance, tissue elastance, and forced vital capacity. PP2A activity was enhanced with ATUX-1215 and reduced collagen deposition within the lungs. ATUX-1215 also prevented the BLM induction of Acta2, Ccn2, and Fn1 gene expression. Treatment with ATUX-1215 reduced the phosphorylation of ERK, p38, JNK, and Akt and the secretion of IL-12p70, GM-CSF, and IL1α in BLM-treated animals. Delayed treatment with ATUX-1215 was also observed to slow the progression of lung fibrosis. In conclusion, our study indicates that the decrease in PP2A activity, which occurs in fibroblasts from the lungs of IPF subjects, could be restored with ATUX-1215 administration as an antifibrotic agent.

Role of transforming growth factor-β in airway remodelling in bronchiolitis obliterans

Airway remodelling is the main pathological mechanism of bronchiolitis obliterans (BO). Several studies have found that transforming growth factor-β (TGF-β) expression is increased in BO during airway remodelling, where it plays an important role in various biological processes by binding to its receptor complex to activate multiple signalling proteins and pathways. This review examines the role of TGF-β in airway remodelling in BO and its potential as a therapeutic target, highlighting the mechanisms of TGF-β activation and signalling, cellular targets of TGF-β actions, and research progress in TGF-β signalling and TGF-β-mediated processes.

TNN: Tree Neural Network for Airway Anatomical Labeling

Detailed anatomical labeling of bronchial trees extracted from CT images can be used as fine-grained maps for intra-operative navigation. To cater to the sparse distribution of airway voxels and large class imbalance in 3D image space, a graph-neural-network-based method is proposed to map branches to nodes in a graph space and assign anatomical labels down to subsegmental level. To address the inherent problem of overlapping distribution of positional and morphological features, especially for subsegmental categories, the proposed method focuses on the relative position between sibling subsegments which is fixed in most cases. The hierarchical nomenclature is represented by multi-level labeling and each category is associated with one or two subtrees in the graph. Hyperedges are used to extract the representation of subtrees while a hypergraph neural network is developed to encode their intrinsic relationship through hyperedge interaction. A filter module is further designed to guide feature aggregation between nodes and hyperedges. With the proposed method, the final accuracies for segmental and subsegmental node classification can achieve 93.6% and 82.0% respectively. The corresponding code is publicly available at https://github.com/haozheng-sjtu/airway-labeling.

Effects of Medication Use on Small Airway Function and Airway Inflammation in Patients with Clinically Controlled Asthma

OBJECTIVE

To observe effects of medication use on small airway function, airway inflammation and acute exacerbations in patients with clinically controlled asthma.

METHODS

Forced expiratory flow over the middle half of the forced expiratory curve (FEF_25%-75%), percentage of eosinophil, concentrations of eosinophil cationic protein (ECP) and interleukin (IL)-5 in induced sputum were assessed in patients with clinically controlled asthma who were given oral anti-inflammatory agents alone or in combination with inhaled therapy and inhaled therapy alone. Subsequently, acute exacerbations were compared between two groups during the 24-week follow-up period.

RESULTS

FEF_25%-75% in 43 patients with clinically controlled asthma given oral anti-inflammatory agents alone or in combination with inhaled therapy was significantly higher than that in 49 patients given inhaled therapy alone. Meanwhile, the percentage of eosinophils and levels of IL-5 and ECP in patients with clinically controlled asthma given oral anti-inflammatory agents alone or in combination with inhaled therapy were significantly lower than those in patients given inhaled therapy alone. Additionally, the patients with clinically controlled asthma given inhaled therapy were likely to have more acute exacerbation than the patients given oral anti-inflammatory agents alone or in combination with inhaled therapy during the 24-week follow-up period.

CONCLUSION

Systemic anti-inflammatory agents may have a greater effect on parameters reflecting small airway patency and reducing acute exacerbations, presumably secondary to reduction in airway inflammation.

Airway-On-A-Chip: Designs and Applications for Lung Repair and Disease

The lungs are affected by illnesses including asthma, chronic obstructive pulmonary disease, and infections such as influenza and SARS-CoV-2. Physiologically relevant models for respiratory conditions will be essential for new drug development. The composition and structure of the lung extracellular matrix (ECM) plays a major role in the function of the lung tissue and cells. Lung-on-chip models have been developed to address some of the limitations of current two-dimensional in vitro models. In this review, we describe various ECM substitutes utilized for modeling the respiratory system. We explore the application of lung-on-chip models to the study of cigarette smoke and electronic cigarette vapor. We discuss the challenges and opportunities related to model characterization with an emphasis on in situ characterization methods, both established and emerging. We discuss how further advancements in the field, through the incorporation of interstitial cells and ECM, have the potential to provide an effective tool for interrogating lung biology and disease, especially the mechanisms that involve the interstitial elements.

Learning Tubule-Sensitive CNNs for Pulmonary Airway and Artery-Vein Segmentation in CT

Training convolutional neural networks (CNNs) for segmentation of pulmonary airway, artery, and vein is challenging due to sparse supervisory signals caused by the severe class imbalance between tubular targets and background. We present a CNNs-based method for accurate airway and artery-vein segmentation in non-contrast computed tomography. It enjoys superior sensitivity to tenuous peripheral bronchioles, arterioles, and venules. The method first uses a feature recalibration module to make the best use of features learned from the neural networks. Spatial information of features is properly integrated to retain relative priority of activated regions, which benefits the subsequent channel-wise recalibration. Then, attention distillation module is introduced to reinforce representation learning of tubular objects. Fine-grained details in high-resolution attention maps are passing down from one layer to its previous layer recursively to enrich context. Anatomy prior of lung context map and distance transform map is designed and incorporated for better artery-vein differentiation capacity. Extensive experiments demonstrated considerable performance gains brought by these components. Compared with state-of-the-art methods, our method extracted much more branches while maintaining competitive overall segmentation performance. Codes and models are available at http://www.pami.sjtu.edu.cn/News/56.

Attenuation of Allergen-, IL-13-, and TGF-α-induced Lung Fibrosis after the Treatment of rIL-15 in Mice

Endogenous IL-15 deficiency promotes lung fibrosis; therefore, we examined the effect of induced IL-15 in restricting the progression of lung fibrosis. Our objective in this work was to establish a novel therapeutic molecule for pulmonary fibrosis. Western blot, qPCR, and ELISA were performed on the lung tissues of IL-15-deficient mice, and recombinant IL-15 (rIL-15)-treated CC10-IL-13 and CC10-TGF-α mice, and allergen-challenged CC10-IL-15 mice were examined to establish the antifibrotic effect of IL-15 in lung fibrosis. We show that endogenous IL-15 deficiency induces baseline profibrotic cytokine and collagen accumulation in the lung, and pharmacological delivery of rIL-15 downregulates Aspergillus antigen-induced lung collagen, the profibrotic cytokines IL-13 and TGF-β1, and α-SMA⁺ and FSP1⁺ cells in mice. To confirm that overexpression of IL-15 diminishes pulmonary fibrosis, we generated CC10-rtTA-tetO7-IL-15 transgenic mice and challenged them with Aspergillus antigen. Aspergillus antigen-challenged, doxycycline (DOX)-treated CC10-IL-15 transgenic mice exhibited decreased collagen accumulation, profibrotic cytokine (IL-13 and TGF-β1) expression, and α-SMA⁺ and FSP1⁺ cells compared with IL-15-overexpressing mice not treated with DOX. Additionally, to establish that the antifibrotic effect of IL-15 is not limited to allergen-induced fibrosis, we showed that rIL-15 or IL-15 agonist treatment restricted pulmonary fibrosis even in CC10-IL-13 and CC10-TGF-α mice. Mechanistically, we show that T-helper cell type 17 suppressor IL-15-responsive RORγ⁺ T regulatory cells are induced in DOX-treated, allergen-challenged IL-15-overexpressing mice, which may be a novel pathway for restricting progression of pulmonary fibrosis. Taken together, our data establishes antifibrotic activity of IL-15 that might be a novel therapeutic molecule to combat the development of pulmonary fibrosis.

Region growing algorithm combined with morphology and skeleton analysis for segmenting airway tree in CT images

BACKGROUND

Automatic segmentation of pulmonary airway tree is a challenging task in many clinical applications, including developing computer-aided detection and diagnosis schemes of lung diseases.

OBJECTIVE

To segment the pulmonary airway tree from the computed tomography (CT) chest images using a novel automatic method proposed in this study.

METHODS

This method combines a two-pass region growing algorithm with gray-scale morphological reconstruction and leakage elimination. The first-pass region growing is implemented to obtain a rough airway tree. The second-pass region growing and gray-scale morphological reconstruction are used to detect the distal airways. Finally, leakage detection is performed to remove leakage and refine the airway tree.

RESULTS

Our methods were compared with the gold standards. Forty-five clinical CT lung image scan cases were used in the experiments. Statistics on tree division order, branch number, and airway length were adopted for evaluation. The proposed method detected up to 12 generations of bronchi. On average, 148.85 branches were extracted with a false positive rate of 0.75%.

CONCLUSIONS

The results show that our method is accurate for pulmonary airway tree segmentation. The strategy of separating the leakage detection from the segmenting process is feasible and promising for ensuring a high branch detected rate with a low leakage volume.

Reduction in mouse allergen exposure is associated with greater lung function growth

BACKGROUND

Current childhood asthma therapies have little effect on lung function trajectory.

OBJECTIVE

We sought to determine whether mouse allergen exposure reduction is associated with lung function growth in mouse-sensitized/exposed asthmatic children.

METHODS

Three hundred fifty mouse-sensitized/exposed asthmatic children (5-17 years old) were enrolled in a 1-year randomized trial of integrated pest management plus education versus education alone. Prebronchodilator/postbronchodilator spirometry was performed at baseline and 6 and 12 months, and bedroom floor mouse allergen levels were measured every 3 months. Mouse allergen reduction was defined as a 75% or greater decrease in mouse allergen levels from baseline. Treatment groups were combined for analyses because there were no differences in outcomes between groups. Changes in lung function over time were modeled, adjusting for age, sex, race, atopy, group, and bronchodilator reversibility and including an interaction term (allergen reduction*time).

RESULTS

The study population was predominantly black (79.4%) and low income (66.3% [<$30,000]). At baseline, the median mouse allergen level was 5.7 μg/g (interquartile range, 1.5-22.8 μg/g), and the mean (SD) prebronchodilator FEV₁/forced vital capacity ratio was 80.2% (9.0%). Ninety-two (26.3%) participants had 75% or greater reduction in mouse allergen levels. For a 10-year-old black boy, 75% or greater allergen reduction was associated with an increase in prebronchodilator FEV₁ of 238 mL/y (95% CI, 177-299 mL/y), whereas less than 75% allergen reduction was associated with an increase in prebronchodilator FEV₁ of 131 mL/y (95% CI, 97-166 mL/y). Estimated differences in prebronchodilator and postbronchodilator FEV₁ growth were as follows: 107 mL/y (95% CI, 37-177 mL/y; P_int = .003) and 48 mL/y (95% CI, -17 to 113 mL/y; P_int = .15), respectively. Estimated differences in prebronchodilator and postbronchodilator forced expiratory flow at 25% to 75% of vital capacity growth were as follows: 182 mL/y (95% CI, 61-304 mL/y; P_int = .003) and 181 mL/y (95% CI, 48-314 mL/y; P_int = .008), respectively.

CONCLUSION

Mouse allergen reduction is associated with greater increases in prebronchodilator FEV₁ and prebronchodilator/postbronchodilator forced expiratory flow at 25% to 75% of vital capacity over 1 year among sensitized/exposed asthmatic children.

Nonhuman Primate Models of Respiratory Disease: Past, Present, and Future

The respiratory system consists of an integrated network of organs and structures that primarily function for gas exchange. In mammals, oxygen and carbon dioxide are transmitted through a complex respiratory tract, consisting of the nasal passages, pharynx, larynx, and lung. Exposure to ambient air throughout the lifespan imposes vulnerability of the respiratory system to environmental challenges that can contribute toward development of disease. The importance of the respiratory system to human health is supported by statistics from the Centers for Disease Control and Prevention; in 2015, chronic lower respiratory diseases were the third leading cause of death in the United States. In light of the significant mortality associated with respiratory conditions that afflict all ages of the human population, this review will focus on basic and preclinical research conducted in nonhuman primate models of respiratory disease. In comparison with other laboratory animals, the nonhuman primate lung most closely resembles the human lung in structure, physiology, and mucosal immune mechanisms. Studies defining the influence of inhaled microbes, pollutants, or allergens on the nonhuman primate lung have provided insight on disease pathogenesis, with the potential for elucidation of molecular targets leading to new treatment modalities. Vaccine trials in nonhuman primates have been crucial for confirmation of safety and protective efficacy against infectious diseases of the lung in a laboratory animal model that recapitulates pathology observed in humans. In looking to the future, nonhuman primate models of respiratory diseases will continue to be instrumental for translating biomedical research for improvement of human health.

Both Ways at Once: Keeping Small Airways Clean

The small airways of the lungs are under constant assault from the pathogens and debris in the air that they must conduct to alveoli. Although hygiene is of paramount importance for respiratory health, the underlying principles of airway clearance have not been well integrated or established. Newly emerging concepts of simultaneous absorption and secretion of airway surface liquid (ASL) and the role of [Formula: see text] in the maturation of mucins have advanced from experimental evidence as well as observations from the congenital disease cystic fibrosis (CF) to present a novel model that integrates microanatomy with organ physiology to meet the constant challenge of cleaning small airways.

Derivation of therapeutic lung spheroid cells from minimally invasive transbronchial pulmonary biopsies

Background

Resident stem and progenitor cells have been identified in the lung over the last decade, but isolation and culture of these cells remains a challenge. Thus, although these lung stem and progenitor cells provide an ideal source for stem-cell based therapy, mesenchymal stem cells (MSCs) remain the most popular cell therapy product for the treatment of lung diseases. Surgical lung biopsies can be the tissue source but such procedures carry a high risk of mortality.

Methods

In this study we demonstrate that therapeutic lung cells, termed “lung spheroid cells” (LSCs) can be generated from minimally invasive transbronchial lung biopsies using a three-dimensional culture technique. The cells were then characterized by flow cytometry and immunohistochemistry. Angiogenic potential was tested by in-vitro HUVEC tube formation assay. In-vivo bio- distribution of LSCs was examined in athymic nude mice after intravenous delivery.

Results

From one lung biopsy, we are able to derive >50 million LSC cells at Passage 2. These cells were characterized by flow cytometry and immunohistochemistry and were shown to represent a mixture of lung stem cells and supporting cells. When introduced systemically into nude mice, LSCs were retained primarily in the lungs for up to 21 days.

Conclusion

Here, for the first time, we demonstrated that direct culture and expansion of human lung progenitor cells from pulmonary tissues, acquired through a minimally invasive biopsy, is possible and straightforward with a three-dimensional culture technique. These cells could be utilized in long-term expansion of lung progenitor cells and as part of the development of cell-based therapies for the treatment of lung diseases such as chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF).

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-017-0611-0) contains supplementary material, which is available to authorized users.

A simple method to reconstruct the molar mass signal of respiratory gas to assess small airways with a double-tracer gas single-breath washout

For the assessment of small airway diseases, a noninvasive double-tracer gas single-breath washout (DTG-SBW) with sulfur hexafluoride (SF₆) and helium (He) as tracer components has been proposed. It is assumed that small airway diseases may produce typical ventilation inhomogeneities which can be detected within one single tidal breath, when using two tracer components. Characteristic parameters calculated from a relative molar mass (MM) signal of the airflow during the washout expiration phase are analyzed. The DTG-SBW signal is acquired by subtracting a reconstructed MM signal without tracer gas from the signal measured with an ultrasonic sensor during in- and exhalation of the double-tracer gas for one tidal breath. In this paper, a simple method to determine the reconstructed MM signal is presented. Measurements on subjects with and without obstructive lung diseases including the small airways have shown high reliability and reproducibility of this method.

Desensitization of idiopathic pulmonary fibrosis fibroblasts to Alternaria alternata extract-mediated necrotic cell death

Alternaria alternata is an allergenic fungus and known to cause an upper respiratory tract infection and asthma in humans with compromised immunity. Although A. alternata's effect on airway epithelial cells has previously been examined, the potential role of A. alternata on lung fibroblast viability is not understood. Since lung fibroblasts derived from patients with idiopathic pulmonary fibrosis (IPF) display a distinct phenotype that is resistant to stress and cell death inducing conditions, the investigation of the role of Alternaria on pathological IPF fibroblasts provides a better understanding of the fibrotic process induced by an allergenic fungus. Therefore, we examined cell viability of control and IPF fibroblasts (n = 8 each) in response to A. alternata extract. Control fibroblast cell death was increased while IPF fibroblasts were resistant when exposed to 50-100 μg/mL of A. alternata extract. However, there was no significant difference in kinetics or magnitude of Ca²⁺ responses from control lung and IPF fibroblasts. In contrast, unlike control fibroblasts, intracellular reactive oxygen species (ROS) levels remained low when IPF cells were treated with A. alternata extracts as a function of time. Caspase 3/7 and TUNEL assay revealed that enhanced cell death caused by A. alternata extract was likely due to necrosis, and 7-AAD assay and the use of sodium pyruvate for ATP generation further supported our findings that IPF fibroblasts become resistant to A. alternata extract-induced necrotic cell death. Our results suggest that exposure to A. alternata potentially worsens the fibrotic process by promoting normal lung fibroblast cell death in patients with IPF.

A morphologic study of the airway structure abnormalities in patients with asthma by high-resolution computed tomography

BACKGROUND

Airway structure changes, termed as airway remodeling, are common in asthma patients due to chronic inflammation, which can be assessed by high-resolution computed tomography (HRCT). Considering the controversial conclusions in the correlation of morphologic abnormalities with clinical feature and outcome, we aimed to further specify and evaluate the structural abnormalities of Chinese asthmatics by HRCT.

METHODS

From August 2012 to February 2015, outpatients with asthma were recruited consecutively in the Asthma Center of West China Hospital, Sichuan University. Standard HRCT and pulmonary function test (PFT) were performed to collect information of bronchial wall thickening, bronchial dilatation, mucus impaction, emphysema, mosaic perfusion, atelectasis, and spirometric parameters. We reported the incidence of each structural abnormality in HRCT and compared it among different asthmatic severities.

RESULTS

A total of 123 asthmatics were enrolled, among which 84 (68.3%) were female and 39 (31.7%) were male. At least one structural abnormality was detected by HRCT in 85.4% asthmatics, and the incidence of bronchial wall thickening, bronchial dilatation, mucus impaction, emphysema, mosaic perfusion, and atelectasis was 57.7%, 51.2%, 22%, 24.4%, 5.7% and 1.6%, respectively. The incidences of bronchial wall thickening, bronchial dilation and emphysema were significantly increased by asthma severity (P<0.05), while incidences of mucus impaction (26/27, 96.30%), mosaic perfusion (6/7, 85.71%) and atelectasis (2/2, 100%) were mainly found in severe asthma. We found a longer asthma history (28.13±18.55 years, P<0.001, P=0.003), older age (51.30±10.70 years, P=0.022, P=0.006) and lower predicted percentage of forced expiratory volume in one second (FEV₁%) (41.97±15.19, P<0.001, P<0.001) and ratio of forced expiratory volume to forced vital capacity (FEV₁/FVC) (48.01±9.55, P<0.001, P<0.001) in patients with severe bronchial dilation compared with those in none and mild bronchial dilation. A negative correlation was also found between the extent of bronchial dilation and FEV₁% as well as FEV₁/FVC (r=-0.359, P=0.004; r=-0.266, P=0.035, respectively).

CONCLUSIONS

The incidences of structural abnormalities detected by HRCT are fairly high in Chinese asthma populations, especially the bronchial wall thickening and bronchial dilation, which are significantly increased in severe asthma, and are potential risk factors of pulmonary function decline in asthmatics.

Site of Fluid Secretion in Small Airways

The secretion and management of readily transportable airway surface liquid (ASL) along the respiratory tract is crucial for the clearance of debris and pathogens from the lungs. In proximal large airways, submucosal glands (SMGs) can produce ASL. However, in distal small airways, SMGs are absent, although the lumens of these airways are, uniquely, highly plicated. Little is known about the production and maintenance of ASL in small airways, but using electrophysiology, we recently found that native porcine small airways simultaneously secrete and absorb. How these airways can concurrently transport ASL in opposite directions is puzzling. Using high expression of the Na-K-2Cl cotransport (NKCC) 1 protein (SLC12a2) as a phenotypic marker for fluid secretory cells, immunofluorescence microscopy of porcine small airways revealed two morphologically separated sets of luminal epithelial cells. NKCC1 was abundantly expressed by most cells in the contraluminal regions of the pleats but highly expressed very infrequently by cells in the luminal folds of the epithelial plications. In larger proximal airways, the acini of SMGs expressed NKCC1 prominently, but cells expressing NKCC1 in the surface epithelium were sparse. Our findings indicate that, in the small airway, cells in the pleats of the epithelium secrete ASL, whereas, in the larger proximal airways, SMGs mainly secrete ASL. We propose a mechanism in which the locations of secretory cells in the base of pleats and of absorptive cells in luminal folds physically help maintain a constant volume of ASL in small airways.

Diagnostic and prognostic utility of mid-expiratory flow rate in older community-dwelling persons with respiratory symptoms, but without chronic obstructive pulmonary disease

BACKGROUND

The maximal expiratory flow at 50 % of the forced vital capacity (MEF50) is the flow where half of forced vital capacity (FVC) remains to be exhaled. A reduced MEF50 has been suggested as a surrogate marker of small airways disease. The diagnostic and prognostic utility of this easy to assess spirometric variable in persons with respiratory symptoms, but without COPD is unclear.

METHODS

We used data from the UHFO-COPD cohort in which 405 community-dwelling persons aged 65 years or over, and a general practitioner's diagnosis of chronic obstructive pulmonary disease (COPD) underwent pulmonary function testing and echocardiography. In total 161 patients had no COPD according to the spirometric GOLD criteria. We considered MEF50 as reduced if < 60 % of predicted.

RESULTS

Of the 161 patients without COPD (mean age 72 ± 5.7 years; 35 % male; follow-up 4.5 ± 1.1 years), 61 (37.9 %) had a reduced MEF50. They were older, had more pack-years of smoking, more respiratory symptoms, and used more frequently inhaled medication than the remaining 100 subjects. A reduced MEF50 was nearly twice as often associated with newly detected heart failure (HF) at assessment (29.5 % vs. 15.6 %, p = 0.045). In age-and sex-adjusted Cox regression analysis, a reduced MEF50 was significantly associated with episodes of acute bronchitis (hazard ratio 2.54 95 % confidence interval (1.26; 5.13) P = 0.009), and in trend with pneumonia (2.14 (0.98; 4.69) P = 0.06) and hospitalizations for pulmonary reasons (2.28 (0.93; 5.62) P = 0.07).

CONCLUSIONS

In older community-dwelling persons with pulmonary symptoms but without COPD, a reduced MEF50 may help to uncover unrecognized HF, and identify those at a higher risk for episodes of acute bronchitis, pneumonia and hospitalizations for pulmonary reasons. Echocardiography and close follow-up should be considered in these patients.

The role of the small airways in the pathophysiology of asthma and chronic obstructive pulmonary disease

Chronic respiratory diseases, such as asthma and chronic obstructive pulmonary disease (COPD), represent a major social and economic burden for worldwide health systems. During recent years, increasing attention has been directed to the role of small airways in respiratory diseases, and their exact contribution to the pathophysiology of asthma and COPD continues to be clarified. Indeed, it has been suggested that small airways play a distinct role in specific disease phenotypes. Besides providing information on small airways structure and diagnostic procedures, this review therefore aims to present updated and evidence-based findings on the role of small airways in the pathophysiology of asthma and COPD. Most of the available information derives from either pathological studies or review articles and there are few data on the natural history of small airways disease in the onset or progression of asthma and COPD. Comparisons between studies on the role of small airways are hard to draw because both asthma and COPD are highly heterogeneous conditions. Most studies have been performed in small population samples, and different techniques to characterize aspects of small airways function have been employed in order to assess inflammation and remodelling. Most methods of assessing small airways dysfunction have been largely confined to research purposes, but some data are encouraging, supporting the utilization of certain techniques into daily clinical practice, particularly for early-stage diseases, when subjects are often asymptomatic and routine pulmonary function tests may be within normal ranges. In this context further clinical trials and real-life feedback on large populations are desirable.

LL-37 secreted by epithelium promotes fibroblast collagen production: a potential mechanism of small airway remodeling in chronic obstructive pulmonary disease

Emerging evidence suggests that the process of small airway remodeling is mediated by profibrotic growth factors produced by epithelium, which are capable of activating the underlying mesenchymal cells with excessive collagen production. It has been demonstrated that human cathelicidin antimicrobial protein LL-37 is highly expressed in small airway epithelium from COPD patients. However, it is unknown whether the increased levels of LL-37 in epithelium are involved in the pathogenesis of small airway remodeling in COPD. In this study, we examined the expression of LL-37 in small airways from smokers with COPD and controls (non-smokers and smokers without COPD) by immunohistochemistry, and then the association between LL-37 expression in epithelium and the structural changes of small airway remodeling was analyzed. In vitro, the effect of CSE-induced epithelial secretion of LL-37 on collagen production in human lung fibroblasts (HFL-1 cell line) was studied in a co-culture system. Finally, the signaling pathways involved in the effect of LL-37 on fibroblast collagen production were evaluated. The results showed that LL-37 immunoreactivity in airway epithelium was significantly elevated in smokers with COPD compared with controls. In addition, the magnitude of LL-37 expression in epithelium was positively correlated with airway wall thickness and collagen deposition. In vitro, CSE-induced epithelial secretion of LL-37 promoted fibroblast collagen production. Finally, we showed that formyl peptide receptor-like 1 (FPRL1)-dependent extracellular signal-regulated kinase (ERK) signaling pathway was essential for LL-37-induced collagen production in HFL-1 cells. These results suggest that after cigarette smoke exposure, the increased levels of LL-37 in airway epithelium could stimulate collagen production in the underlying lung fibroblasts and may contribute to small airway remodeling in COPD.

The RESOLVE concept: approaching pathophysiology of fibroproliferative disease in aged individuals

After reaching adulthood, orderly repair is probably one of the most important mechanisms throughout lifetime. Regular wound healing after an injury consists of a well-ordered sequence of overlapping phases of repair and essentially repeats the complex process of organ development. Organ failure in the ageing organism frequently represents the lost capacity to achieve an orderly reactivation of organ development, yet in varying and complex pathologic settings. One of the most aggressive manifestations of age-dependent and dysbalanced wound healing is a disease called idiopathic pulmonary fibrosis. Essentially, the disease replaces functional lung tissue with spreading scar tissue over a period of just 5 years. By a systematic comparison of wound healing conditions, the large-scale collaborative FP7-EU project RESOLVE has addressed these difficulties in a successful way. Background and outlining of the project are discussed.

Heliox therapy in bronchiolitis: phase III multicenter double-blind randomized controlled trial

BACKGROUND AND OBJECTIVE

Supportive care remains the mainstay of therapy in bronchiolitis. Earlier studies suggest that helium-oxygen therapy may be beneficial, but evidence is limited. We aimed to compare efficacy of 2 treatment gases, Heliox and Airox (21% oxygen + 79% helium or nitrogen, respectively), on length of hospital treatment for bronchiolitis.

METHODS

This was a multicenter randomized blinded controlled trial of 319 bronchiolitic infant subjects randomly assigned to either gas; 281 subjects completed the study (140 Heliox, 141 Airox), whose data was analyzed. Treatment was delivered via facemask (nasal cannula, if the facemask intolerant) ± continuous positive airway pressure (CPAP). Severe bronchiolitics received CPAP from the start. Primary end point was length of treatment (LoT) required to alleviate hypoxia and respiratory distress. Secondary end-points were proportion of subjects needing CPAP; CPAP (LoT); and change in respiratory distress score.

RESULTS

Analysis by intention to treat (all subjects); median LoT (inter-quartile range, days): Heliox 1.90 (1.08-3.17), Airox 1.87 (1.11-3.34), P = .41. Facemask tolerant subgroup: Heliox 1.46 (0.85-1.95), Airox 2.01 (0.93-2.86), P = .03. Nasal cannula subgroup: Heliox 2.51 (1.21-4.32), Airox 2.81 (1.45-4.78), P = .53. Subgroup started on CPAP: Heliox 1.55 (1.38-2.01), Airox 2.26 (1.84-2.73), P = .02. Proportion of subjects needing CPAP: Heliox 17%, Airox 19%, O.R. 0.87 (0.47-1.60), P = .76. Heliox reduced respiratory distress score after 8 hours (mixed models estimate, -0.1298; P < .001). The effect was greater for facemask compared with nasal cannula (mixed models estimate, 0.093; P = .04).

CONCLUSIONS

Heliox therapy does not reduce LoT unless given via a tight-fitting facemask or CPAP. Nasal cannula heliox therapy is ineffective.

Histomorphometric study of the periodontal ligament in the initial period of orthodontic movement in Wistar rats with induced allergic asthma

INTRODUCTION

Asthma is a common systemic disease occurring in infancy and adolescence, time periods that could encompass orthodontic treatment. Asthma is an inflammatory disease; therefore, it might interfere with orthodontic tooth movement. The purpose of the study was to analyze the histomorphologic aspects of the periodontal ligament of asthmatic Wistar rats in the initial period of orthodontic movement.

METHODS

Thirty-two Wistar rats were divided into 4 groups: 2 control groups consisting of rats without induced allergic asthma, and 2 experimental groups consisting of rats with induced allergic asthma. The animals of the first control and experimental groups did not receive orthodontic forces, whereas those in the second control and experimental groups were subjected to mesial movement of the maxillary left first molar for 3 days. The samples were prepared for histomorphometric analysis of the periodontal ligament. The area of the periodontal ligament was calculated as a function of root length in the cervical and apical regions of the distal face of the maxillary first molar mesial root. The Student t test and the Welch correlation test were applied to the data obtained.

RESULTS

There was a statistically significant difference (P <0.05) between the control and experimental groups. An enhanced response to orthodontic force was observed in the asthmatic animals: the periodontal ligament was more compressed at the pressure area and more stretched in the traction area.

CONCLUSIONS

Our findings indicate that experimental allergic asthma seems to exacerbate orthodontic movement in rats.

Assessment of peripheral airway function following chronic allergen challenge in a sheep model of asthma

Background

There is increasing evidence that the small airways contribute significantly to the pathophysiology of asthma. However, due to the difficulty in accessing distal lung regions in clinical settings, functional changes in the peripheral airways are often overlooked in studies of asthmatic patients. The aim of the current study was to characterize progressive changes in small airway function in sheep repeatedly challenged with house dust mite (HDM) allergen.

Methodology/Principal Findings

Four spatially separate lung segments were utilized for HDM challenges. The right apical, right medial, right caudal and left caudal lung segments received 0, 8, 16 and 24 weekly challenges with HDM respectively. A wedged-bronchoscope technique was used to assess changes in peripheral resistance (R_p) at rest, and in response to specific and non-specific stimuli throughout the trial. Allergen induced inflammatory cell infiltration into bronchoalveolar lavage and increases in R_p in response to HDM and methacholine were localized to treated lung segments, with no changes observed in adjacent lung segments. The acute response to HDM was variable between sheep, and was significantly correlated to airway responsiveness to methacholine (r_s = 0.095, P<0.01). There was no correlation between resting R_p and the number of weeks of HDM exposure. Nor was there a correlation between the magnitude of early-phase airway response and the number of HDM-challenges.

Conclusions

Our findings indicate that airway responses to allergic and non-allergic stimuli are localized to specific treated areas of the lung. Furthermore, while there was a decline in peripheral airway function with HDM exposure, this decrease was not correlated with the length of allergen challenge.

Structured tree impedance outflow boundary conditions for 3D lung simulations

In this paper, we develop structured tree outflow boundary conditions for modeling the airflow in patient specific human lungs. The utilized structured tree is used to represent the nonimageable vessels beyond the 3D domain. The coupling of the two different scales (1D and 3D) employs a Dirichlet-Neumann approach. The simulations are performed under a variety of conditions such as light breathing and constant flow ventilation (which is characterized by very rapid acceleration and deceleration). All results show that the peripheral vessels significantly impact the pressure, however, the flow is relatively unaffected, reinforcing the fact that the majority of the lung impedance is due to the lower generations rather than the peripheral vessels. Furthermore, simulations of a hypothetical diseased lung (restricted flow in the superior left lobe) under mechanical ventilation show that the mean pressure at the outlets of the 3D domain is about 28% higher. This hypothetical model illustrates potential causes of volutrauma in the human lung and furthermore demonstrates how different clinical scenarios can be studied without the need to assume the unknown flow distribution into the downstream region.

Review series: Rehabilitation in non COPD: Mechanisms of exercise limitation and pulmonary rehabilitation for patients with pulmonary fibrosis/restrictive lung disease

The standard of care in the treatment of chronic lung disease includes pulmonary rehabilitation (PR). While evidence of the effectiveness of PR in chronic obstructive lung disease (COPD) is robust, that for pulmonary fibrosis and other non-fibrotic restrictive lung diseases is less extensive. However, PR has been shown to improve functional exercise capacity and health-related quality of life in non-COPD patients, primarily those with interstitial lung diseases. This review examines mechanisms of exercise limitation in non-COPD patients and discusses how they might affect both the application of and outcome measures of PR. We also review the assessment of exercise performance, dyspnea, and quality of life as well as special protocols, safety considerations, and special techniques in PR as applied to patients with pulmonary fibrosis or restrictive lung disease. At present, there are no evidence-based guidelines for PR in non-COPD patients whereas PR is firmly recommended in COPD management. More research is needed to strengthen the evidence for the use of PR in non-COPD patients. Meanwhile, the available data, summarized in this review, support the inclusion of PR in the management of all patients with chronic lung disease including pulmonary fibrosis and restrictive lung disease.

Metabolic syndrome and risk of pulmonary involvement

Metabolic syndrome (MS) is a complex disorder recognized clinically by the findings of abdominal obesity, elevated triglycerides, atherogenic dyslipidaemia, elevated blood pressure, high blood glucose and/or insulin resistance. It is associated with a pro-thrombotic and a pro-inflammatory state. A growing body of evidence suggests that individuals in the community with moderate airflow limitation may have co-existing systemic inflammation with this background. Therefore, we examined a population of 237 patients with metabolic disorder for the concomitant presence of functional pulmonary involvement, as assessed by FEV(1) and FVC impairment. Criteria for the identification of the MS included 3 or more of the following: waist circumference: (>102 cm in men, >88 cm in women), triglycerides levels (> or =150 mg/dl), high-density lipoprotein cholesterol levels (<40 mg/dl in men, <50 mg/dl in women), blood pressure (> or =135/> or =85 mmHg), and fasting glucose levels (>100 mg/dl). 119 subjects were diagnosed MS. Non-smokers patients suffering from MS presented lower spirometric values, with a trend to ventilatory restrictive more than obstructive pattern. Also in smokers patients with MS there was a trend to harmonic decrease in FEV(1) and FVC but not in FEV(1)/FVC ratio, although the changes did not reach statistical significance. Mainly abdominal circumference, and also insulin resistance were retained as independent predictors of both FEV(1) and FVC changes. However, HDL-C was the strongest predictor of FEV(1) and FVC changes, with an inverse association.

Small airways obstruction syndrome in clinical practice

BACKGROUND AND OBJECTIVE

Small airways obstruction syndrome (SAOS) is a particular pulmonary function test (PFT) pattern showing decreased VC and FEV(1) but a normal FEV(1)/VC ratio and TLC. The significance of this syndrome in clinical practice has not been comprehensively investigated.

METHODS

This study retrospectively identified all patients who had performed PFT that showed a SAOS pattern at a university teaching hospital over 1 year. A simple algorithm for differential diagnosis was developed and validated.

RESULTS

Of the 3207 PFT performed, 153 (4.8%) showed a pattern indicating SAOS. Among these, a final diagnosis was confirmed for 85 (63.4%) of the patients. The causes of SAOS included both restrictive and obstructive lung diseases with the leading causes being early interstitial lung disease (n = 20; 23.3%), chest wall deformity (n = 12; 14.1%) and asthma (n = 10; 11.6%). Using a cut-off point of TLC of <95% predicted value to identify restrictive ventilatory defects (P = 0.002) and of > or =95% predicted combined with RV/TLC > or =55% to identify obstructive ventilatory defects (P < 0.001), a simplified algorithm with good accuracy (86.6%) was identified. Validation in an independent group showed accuracy of 91%.

CONCLUSIONS

The PFT pattern called SAOS is not uncommon. The most common causes of SAOS were early interstitial lung disease, chest wall deformity and asthma. A diagnostic algorithm was proposed, which may help physicians' decision-making in their daily practice.

Patterns of pulmonary function in smoking and nonsmoking patients with progressive systemic sclerosis

Pulmonary involvement is a prominent feature in systemic sclerosis and a significant cause of morbidity and mortality. A restrictive ventilatory defect is typical and static lung volumes are usually reduced in patients with ILDs. The possibility of obstruction of small airways in progressive systemic sclerosis (SSc) has been suggested by widespread bronchiolectasis and peribronchial fibrosis noted at necropsy. A total of 46 patients with a diagnosis of SSc were retrospectively included in this study. Patients were classified according to their smoking status (never smokers, n = 34 and ex or current smokers, n = 12). Patients were also compared on the basis of the presence or not of an obstructive pattern on spirometry. The purpose of this study was to establish if SSc patients who are smokers have a different pattern of pulmonary function involvement. Our hypothesis was that smoking habit was not the only cause of air trapping and that the existence of small airway involvement secondary to SSc itself cannot be excluded.

Low attenuation area is associated with airflow limitation and airway hyperresponsiveness

BACKGROUND

Asthma is a chronic inflammatory disorder of the airways characterized by airflow limitation and airway hyperresponsiveness. Lung density indices on quantitative computed tomography (QCT) are assumed to reflect the degree of air trapping originated from airflow limitation in airway diseases.

PURPOSE

The present study investigated the availability of lung density indices on QCT in clinical evaluation of asthma.

METHODS

Eleven asthmatic patients and 48 healthy control subjects were prospectively evaluated by QCT, pulmonary function testing, and a methacholine challenge test. High-resolution computed tomography scans were performed at full-inspiratory and full-expiratory phases, and percentage of lung field occupied by low attenuation area (LAA%) and mean lung density (MLD) at both inspiratory and expiratory phases were measured.

RESULTS

MLD values at inspiratory phase were significantly increased in asthmatic patients compared with those in healthy control subjects. Inspiratory LAA% values were significantly decreased in asthmatics compared with the values in control subjects. On expiratory scans, MLD values of asthmatics were significantly lower than the values of control subjects. Expiratory LAA% values of asthmatics were significantly higher than the values of control subjects. The LAA% in the expiratory phase showed significant negative correlation with forced expiratory volume in 1 second (FEV(1)), FEV(1)/forced vital capacity, and the provocative dose of methacholine causing a 20% decrease in FEV(1) in asthmatic patients.

CONCLUSION

These results suggest that lung density indices on QCT may be useful for clinical evaluation of asthmatic patients and increased LAA% in the expiratory phase is associated with airflow limitation and airway hyperresponsiveness in asthma.

Induced sputum and peripheral blood cell profile in chronic obstructive pulmonary disease

OBJECTIVE

To determine cell profiles, as well as to identify CD4+ and CD8+ lymphocyte subgroups, in induced sputum (IS) and peripheral venous blood (PVB) of patients with chronic obstructive pulmonary disease (COPD).

METHODS

Total cell counts and counts of individual cell types, including CD4+ and CD8+ T lymphocytes, were determined in the IS and PVB of 85 subjects (38 with COPD without exacerbation, 29 smokers without obstruction and 18 nonsmokers). Mann-Whitney and Spearman non-parametric tests were used in the statistical analysis, and values of p < 0.05 were considered statistically significant.

RESULTS

Comparing the IS of subjects with COPD to that of nonsmokers, neutrophil, eosinophil and CD8+ T lymphocyte counts were higher (respectively p = 0.005, p < 0.05 and p < 0.05), whereas the percentage of macrophages was lower (p = 0.003). There were weak linear correlations (r(2) < 0.1) between each cell type in IS and forced expiratory volume in one second (FEV1), forced vital capacity (FVC) and FEV1/FVC ratio. Eosinophil and CD8+ T lymphocyte counts were also higher in PVB (p = 0.04 and p = 0.02).

CONCLUSIONS

In patients with stable COPD, CD8+ T lymphocyte counts were higher in PVB, whereas total leukocyte counts were similar to those of the other two groups analyzed, suggesting systemic inflammatory involvement. The CD8+ T lymphocyte count in blood can be a useful marker of systemic inflammation and can help identify smokers who already present a COPD inflammatory pattern.

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.

Distal airways in mice exposed to cigarette smoke: Nrf2-regulated genes are increased in Clara cells

Cigarette smoke (CS) is the main risk factor for chronic obstructive pulmonary disease (COPD). Terminal bronchioles are critical zones in the pathophysiology of COPD, but little is known about the cellular and molecular changes that occur in cells lining terminal bronchioles in response to CS. We subjected C57BL/6 mice to CS (6 d/wk, up to 6 mo), looked for morphologic changes lining the terminal bronchioles, and used laser capture microdissection to selectively isolate cells in terminal bronchioles to study gene expression. Morphologic and immunohistochemical analyses showed that Clara cell predominance remained despite 6 months of CS exposure. Since Clara cells have a role in protection against oxidative stress, we focused on the expression of antioxidant/detoxification genes using microarray analysis. Of the 35 antioxidant/detoxification genes with at least 2.5-fold increased expression in response to 6 months of CS exposure, 21 were NF-E2-related factor 2 (Nrf2)-regulated genes. Among these were cytochrome P450 1b1, glutathione reductase, thioredoxin reductase, and members of the glutathione S-transferase family, as well as Nrf2 itself. In vitro studies using immortalized murine Clara cells (C22) showed that CS induced the stabilization and nuclear translocation of Nrf2, which correlated with the induction of antioxidant and detoxification genes. Furthermore, decreasing Nrf2 expression by siRNA resulted in a corresponding decrease in CS-induced expression of several antioxidant and detoxification genes by C22 cells. These data suggest that the protective response by Clara cells to CS exposure is predominantly regulated by the transcription factor Nrf2.

Dual oxidase 1 and 2 expression in airway epithelium of smokers and patients with mild/moderate chronic obstructive pulmonary disease

Dual oxidase (Duox) 1 and Duox2 are important sources of hydrogen peroxide production and play a role in host defense in airways. Little is known about their regulation in association with smoking or chronic obstructive pulmonary disease (COPD). We investigated the epithelial expression of Duox1 and Duox2 in the airways of smokers, and the relationship between this expression and COPD at early stage. First, using bronchoscopy, we harvested tracheal and bronchial epithelium from individuals who have never smoked and current smokers. Duox1 expression in brushed tracheal and bronchial epithelium was significantly downregulated, whereas Duox2 was upregulated, in current smokers as compared to individuals who have never smoked. Second, laser capture microdissection and microscope-assisted manual dissection were performed in surgically resected lung tissues to collect bronchiolar epithelium and alveolar septa. Subjects with mild/moderate COPD, who were all former smokers, exhibited downregulation of bronchiolar Duox1 and Duox2 when compared to individuals who have never smoked, whereas a difference between former smokers, with and without COPD, was observed only for Duox1. Alveolar Duox1 and Duox2 expression was low and did not differ among the groups. These results imply that the airway expression of Duox1 and Duox2 is diversely associated with smoking and COPD.

Bronchiolar chemokine expression is different after single versus repeated cigarette smoke exposure

BACKGROUND

Bronchioles are critical zones in cigarette smoke (CS)-induced lung inflammation. However, there have been few studies on the in vivo dynamics of cytokine gene expression in bronchiolar epithelial cells in response to CS.

METHODS

We subjected C57BL/6J mice to CS (whole body exposure, 90 min/day) for various periods, and used laser capture microdissection to isolate bronchiolar epithelial cells for analysis of mRNA by quantitative reverse transcription-polymerase chain reaction.

RESULTS

We detected enhanced expression of keratinocyte-derived chemokine (KC), macrophage inflammatory protein-2 (MIP-2), tumor necrosis factor-alpha (TNF-alpha), and interleukin-1beta (IL-1beta) by bronchial epithelial cells after 10 consecutive days of CS exposure. This was mirrored by increases in neutrophils and KC, MIP-2, TNF-alpha, and IL-1beta proteins in the bronchoalveolar lavage (BAL) fluid. The initial inhalation of CS resulted in rapid and robust upregulation of KC and MIP-2 with concomitant DNA oxidation within 1 hr, followed by a return to control values within 3 hrs. In contrast, after CS exposure for 10 days, this initial surge was not observed. As the CS exposure was extended to 4, 12, 18 and 24 weeks, the bronchiolar KC and MIP-2 expression and their levels in BAL fluid were relatively dampened compared to those at 10 days. However, neutrophils in BAL fluid continuously increased up to 24 weeks, suggesting that neutrophil accumulation as a result of long-term CS exposure became independent of KC and MIP-2.

CONCLUSION

These findings indicate variable patterns of bronchiolar epithelial cytokine expression depending on the duration of CS exposure, and that complex mechanisms govern bronchiolar molecular dynamics in vivo.

FVC to slow inspiratory vital capacity ratio: a potential marker for small airways obstruction

BACKGROUND

The ratio of FVC to slow inspiratory vital capacity (SVC) has been reported to reflect small airways obstruction, but its validity as such is still unclear. The aim of this study was to assess the applicability of the FVC/SVC ratio as a marker of small airways function in patients with bronchiolitis obliterans syndrome (BOS) after lung transplantation (LTX), which is a disorder in which predominantly small airways obstruction causes progressive airflow limitation.

METHODS

The FVC/SVC ratio was analyzed both cross-sectionally and longitudinally in 39 patients (26 men) with BOS after bilateral LTX (median age, 47 years; interquartile range [IQR], 35 to 54 years), and 36 bilateral lung transplant recipients without BOS (14 men; median age, 46 years; IQR, 41 to 53 years).

RESULTS

The FVC/SVC ratio decreased significantly during follow-up in patients with BOS stages 1 and 2, by 2.2% and 4.4%, respectively, from baseline (p < 0.001). This decrease was not significantly associated with the decrease in FEV(1). The FVC/SVC ratio increased, though not significantly, in the group in which BOS did not develop by 1.1%, which is a significant difference from the average fall of 4.4% in the group in which BOS developed.

CONCLUSIONS

Significant, yet small decreases in FVC/SVC ratio occur in patients in whom BOS develops, independent from changes in FEV(1). At a group level, FVC/SVC ratio is able to detect small airways changes. These results merit prospective studies to determine the sensitivity of FVC/SVC ratio to quantifying small airways dysfunction at an individual level and in other airway diseases.

Asthma therapy and airway remodeling

Asthma is characterized by variable degrees of chronic inflammation and structural alterations in the airways. The most prominent abnormalities include epithelial denudation, goblet cell metaplasia, subepithelial thickening, increased airway smooth muscle mass, bronchial gland enlargement, angiogenesis, and alterations in extracellular matrix components, involving large and small airways. Chronic inflammation is thought to initiate and perpetuate cycles of tissue injury and repair in asthma, although remodeling may also occur in parallel with inflammation. In the absence of definite evidence on how different remodeling features affect lung function in asthma, the working hypothesis should be that structural alterations can lead to the development of persistent airway hyperresponsiveness and fixed airway obstruction. It is still unanswered whether and when to begin treating patients with asthma to prevent or reverse deleterious remodeling, which components of remodeling to target, and how to monitor remodeling. Consequently, efforts are being made to understand better the effects of conventional anti-inflammatory therapies, such as glucocorticosteroids, on airway structural changes. Animal models, in vitro studies, and some clinical studies have advanced present knowledge on the cellular and molecular pathways involved in airway remodeling. This has encouraged the development of biologicals aimed to target various components of airway remodeling. Progress in this area requires the explicit linking of modern structure-function analysis with innovative biopharmaceutical approaches.

Small Airways Dysfunction and Neutrophilic Inflammation in Bronchial Biopsies and BAL in COPD

BACKGROUND

The single-breath N(2) test (sbN(2)-test) is closely related to small airways pathology in resected lung specimens of smokers. We investigated whether uneven ventilation and airway closure are associated with specific markers of airway inflammation as obtained by bronchial biopsies, BAL, and induced sputum in patients with manifest COPD.

METHODS

Fifty-one patients with stable COPD not receiving corticosteroids were examined in a cross-sectional study (43 men; mean [SD] age, 63 +/- 8 years; exsmokers and smokers; median pack-years, 41 [interquartile range, 31 to 51 pack-years]). Postbronchodilator spirometry (FEV(1), 63 +/- 8% of predicted) and sbN(2)-test (slope of phase III [DeltaN(2)], closing capacity [CC]/total lung capacity [TLC] percentage of predicted) were performed. Inflammatory cell counts were assessed in bronchial biopsies, BAL (only in the first half of patients), and induced sputum. Neutrophil elastase (NE), secretory leukocyte proteinase inhibitor (SLPI), and interleukin-8 levels were determined in BAL fluid.

RESULTS

DeltaN(2) increased with subepithelial neutrophil numbers in bronchial biopsies (rs = 0.337, p = 0.017) and with NE levels (rs = 0.443, p = 0.039), NE/neutrophil ratio (rs = 0.575, p = 0.005) and SLPI levels (rs = 0.484, p = 0.022) in BAL. CC/TLC was associated with BAL neutrophil numbers (rs = 0.448, p = 0.048). The sbN(2)-test was not associated with any other inflammatory cell type in BAL or biopsies, nor with inflammatory cell counts in sputum. Of importance, the correlations between DeltaN(2) and BAL NE/neutrophil ratio, and between CC/TLC and BAL neutrophil numbers remained significant when adjusting for FEV(1) percentage of predicted.

CONCLUSIONS

The results of the sbN(2)-test are associated with neutrophilic inflammation in bronchial biopsies and BAL in patients with COPD. Our findings support a role of neutrophilic inflammation in the pathogenesis of small airways dysfunction in COPD.

Effect of levocetirizine on the contraction induced by histamine on isolated rabbit bronchioles from precision-cut lung slices

The present experiments were designed to study the effects of levocetirizine (a potent selective histamine H(1) antagonist) on the contraction induced by histamine on isolated rabbit bronchioles using the precision-cut lung slice technology. Histamine induced a concentration-dependent contraction of isolated rabbit bronchioles (pD(2) value of 5.6). Mepyramine (0.01-1 micromol/l) induced a shift to the right without any decrease in the concentration-response curve to histamine (pA(2) value of 8.2). Levocetirizine (0.03-0.1 micromol/l) induced both a shift to the right and a decrease in the maximal amplitude of the concentration-response curve to histamine (pA(2) and pD'(2) values of 7.9 and 7.0, respectively). The difference between both compounds could be explained in terms of the difference in the dissociation rate from the histamine H(1) receptor coupled to a putative low receptor reserve present in the rabbit bronchioles.

CD4+25+ regulatory T cells limit Th1-autoimmunity by inducing IL-10 producing T cells following human lung transplantation

Chronic human lung allograft rejection is manifested by bronchiolitis obliterans syndrome (BOS). BOS has a multifactorial etiology. Previous studies have indicated that both cellular and humoral alloimmunity play a significant role in the pathogenesis of BOS. Recently, autoimmunity has also been demonstrated to contribute to lung allograft rejection in animal models. However, the significance of autoimmunity in BOS remains unknown. In this report, we investigated the role of naturally occurring CD4(+)CD25(+) regulatory T cells (T-regs) in modulating cellular autoimmunity to collagen type V (col-V), a 'sequestered' yet immunogenic self-protein present in the lung tissue, following lung transplantation (LT). We demonstrated that col-V reactive CD4(+) T cells could be detected in the peripheral blood of lung transplant recipients. There was a predominance of IL-10 producing T cells (T(IL-10)) reactive to col-V with significantly lower levels of IFN-gamma and IL-2 producing T cells (Th1 cells). The col-V specific T(IL-10) cells suppressed the proliferation and expansion of col-V specific Th1 cells by IL-10-dependent and contact-independent pathways. The T(IL-10) cells were distinct but their development was dependent on the presence of T-regs. Furthermore, during chronic lung allograft rejection there was a significant decline of T(IL-10) cells with concomitant expansion of col-V-specific IFN-gammaproducing Th1 cells.

Early changes in basement membrane thickness in airway walls post-lung transplantation

BACKGROUND

Identification of early histopathologic markers of future bronchiolitis obliterans syndrome (BOS) may enable preemptive targeted intervention, delaying and perhaps preventing the onset of BOS. This study aimed to determine if early changes in airway epithelial basement membrane thickness predisposes transplant recipients to the subsequent development of BOS.

METHODS

Basement membrane thickness was measured in serial endobronchial biopsies taken from 29 initially stable lung transplant recipients (sLTR) recruited 148 +/- 80 days post-transplant and followed for 3 years. A further 2 years of clinical follow-up was undertaken without biopsies to follow lung function and define ultimate BOS status. Nine healthy subjects (non-atopic, non-asthmatic) were recruited as controls. Sections of paraffinized endobronchial biopsies were stained for collagen type I immunohistochemically, and basement membrane thickness was assessed by computer image analysis.

RESULTS

BOS developed in 21 of 29 patients in the 5 years of follow-up, 16 of which had endobronchial biopsies available for analysis before BOS developed (ever-BOS). The first endobronchial biopsies showed increased BMT in the combined sLTR and ever-BOS patients compared with the controls. This initial increase in basement membrane thickness resolved to normal levels within 300 days post-transplant, with a strong negative correlation (r2 = 0.424, p < 0.0001) of basement membrane thickness vs time. Paradoxically, the sLTR tended to have the greatest basement membrane thickness at baseline.

CONCLUSION

An initial increase in basement membrane thickness is seen in the airway walls of all lung transplant recipients. This is transient and does not appear to be a risk factor for the subsequent development of BOS in lung allograft recipients.

Small airways function and molecular markers in exhaled air in mild asthma

BACKGROUND

Several studies suggest that the periphery of the lung is the major site of inflammation in asthma. Fractional exhaled nitric oxide (Feno) and 8-isoprostane have been proposed as biomarkers of inflammation and oxidative stress. We therefore hypothesised that small airway dysfunction in asthma is of inflammatory origin that can be detected by molecular markers in exhaled air. To test this hypothesis, we examined the relationship of Feno and 8-isoprostane in exhaled air with small airways function as assessed by the single breath nitrogen test.

METHODS

Sixteen patients (14 women) with mild atopic asthma (forced expiratory volume in 1 second >80% predicted) of mean (SD) age 23.0 (5.5) years participated in a cross sectional study. Feno was recorded by chemiluminescence and 8-isoprostane was measured by ELISA in concentrated exhaled breath condensate. The slope of phase III (deltaN2) and the closing volume (CV) were assessed from the single breath washout curve.

RESULTS

The median Feno level was 30.4 ppb (range 10.1-82.8), the median 8-isoprostane concentration in exhaled breath condensate was 2.2 pg/ml (range 1.6-2.7), and the mean (SD) deltaN2 value was 1.1 (0.4)% N2/l. Feno was positively associated with deltaN2 (r(s) = 0.54, p = 0.032) while 8-isoprostane was inversely correlated with FEV1% predicted (rs= -0.58; p = 0.017) and CV as a percentage of vital capacity (rs= 0.58; p = 0.019).

CONCLUSIONS

Feno and 8-isoprostane in exhaled air are associated with small airways function in mild asthma. This suggests that these markers reflect small airway inflammation and favours a role for them as disease markers that is complementary to spirometry in the monitoring of patients with asthma.

Predominant constitutive CFTR conductance in small airways

BACKGROUND

The pathological hallmarks of chronic obstructive pulmonary disease (COPD) are inflammation of the small airways (bronchiolitis) and destruction of lung parenchyma (emphysema). These forms of disease arise from chronic prolonged infections, which are usually never present in the normal lung. Despite the fact that primary hygiene and defense of the airways presumably requires a well controlled fluid environment on the surface of the bronchiolar airway, very little is known of the fluid and electrolyte transport properties of airways of less than a few mm diameter.

METHODS

We introduce a novel approach to examine some of these properties in a preparation of minimally traumatized porcine bronchioles of about 1 mm diameter by microperfusing the intact bronchiole.

RESULTS

In bilateral isotonic NaCl Ringer solutions, the spontaneous transepithelial potential (TEP; lumen to bath) of the bronchiole was small (mean +/- sem: -3 +/- 1 mV; n = 25), but when gluconate replaced luminal Cl-, the bionic Cl- diffusion potentials (-58 +/- 3 mV; n = 25) were as large as -90 mV. TEP diffusion potentials from 2:1 NaCl dilution showed that epithelial Cl- permeability was at least 5 times greater than Na+ permeability. The anion selectivity sequence was similar to that of CFTR. The bionic TEP became more electronegative with stimulation by luminal forskolin (5 microM)+IBMX (100 microM), ATP (100 microM), or adenosine (100 microM), but not by ionomycin. The TEP was partially inhibited by NPPB (100 microM), GlyH-101* (5-50 microM), and CFTRInh-172* (5 microM). RT-PCR gave identifying products for CFTR, alpha-, beta-, and gamma-ENaC and NKCC1. Antibodies to CFTR localized specifically to the epithelial cells lining the lumen of the small airways.

CONCLUSION

These results indicate that the small airway of the pig is characterized by a constitutively active Cl- conductance that is most likely due to CFTR.

[Bronchiolitis with airflow obstruction in adults]

PURPOSE

The purpose of this paper is twofold: to describe the clinical and anatomical characteristics of bronchiolitis associated with airflow obstruction in adults; to present through a clinical approach, a classification of the main aetiologies or pathological frames associated with that entity.

KEY POINTS

The constrictive bronchiolitis type is the most frequently encountered. On clinical grounds, cough, crackles, and a progressive dyspnea develop usually within a few weeks. Radiological signs of bronchiolar abnormalities are best visualized on high resolution expiratory CT scan. The decrease in maximal airflows and oxygen tension is of limited amplitude and poorly reversible with bronchodilators. Diagnosis is easily performed when a causative event, or the clinical context, can be delineated: inhalation of toxic fumes, diffuse bronchiectasis, rheumatoid arthritis, lung or bone marrow transplantation. Delayed formation of bronchiectasis in the central airways is common. The treatment is not standardized; corticosteroids are usually prescribed as a first line therapy; the benefit of the addition of, or substitution with immunosuppressive drugs has not been adequately evaluated, but is, on the mean, of limited amplitude.

PERSPECTIVES

Recent advances in the identification of inhaled agents toxic for the distal airways help in establishing appropriate measures of prevention. When the aetiology of the bronchiolitis cannot be suspected, extensive search of a causative agent should be performed, including microbial and mineral analysis of bronchoalveolar products. Negative results should lead to perform a surgical lung biopsy. The study of chronic rejection processes in animal models of lung transplantation, the identification of inhibitory factors of bronchiolar fibrogenesis, and the efficacy of some anti-cytokines on inflammatory processes could result in new therapeutic approaches.

Bronchiolitis obliterans

PURPOSE OF REVIEW

Bronchiolitis obliterans (BO) occurs in both post-lung transplant and nontransplant-related individuals, and is characterized by mainly irreversible airflow obstruction that is often ultimately progressive.

RECENT FINDINGS

While post-lung transplant BO is a major cause of lung allograft dysfunction, and hence is better characterized than nontransplant-related BO, it is likely that many similarities in pathogenesis and treatment apply to both categories.

SUMMARY

Optimal management for BO remains to be established, and the role of retransplantation in this disease requires further consensus. Minimization of risk factors for BO and earlier detection in the form of methacholine challenge testing and HRCT scans of the chest amongst other forms of detection, may help in the stabilization and possible resolution of early BO.