Comparison of the structural and inflammatory features of COPD and asthma. Giles F. Filley Lecture

Dynamics of Inflammatory and Pathological Changes Induced by Single Exposure of Particulate Matter (PM2.5) in Mice: Potential Implications in COPD

Chronic Obstructive Pulmonary Disease (COPD) is a progressive disorder of lungs marked by chronic bronchitis and emphysema. Particulate matter (PM2.5), a major component of air pollution has been correlated with COPD incidence. The present work aimed to understand dynamics of cellular/molecular players behind PM2.5-mediated COPD pathogenesis in mice by conducting dose and time-course studies. Single intratracheal exposure of PM2.5 at a dose of either 100 or 200 μg induced inflammatory response in lungs at 4 days. Time course studies showed that inflammation once triggered by PM2.5 is progressive in nature as reflected by data on BALF inflammatory cells at 7/14 days. Similarly, various cytokines/chemokines (KC/IL-6/TNF-α/IL-1β/G-CSF/MCP-1) peak at either 7 or 14 days. However, inflammation declined sharply at 21 days. Data on LPO/GSH and activities of SOD/Catalase show induction of continuous oxidative stress in lung tissue. Next, enhanced mtROS in the CD11b+ inflammatory cells confirms the redox imbalance in neutrophils/macrophages. A continuous decline in lung function was observed till 28 days. Further, histological analysis of lung tissues at 28 days confirmed the presence of emphysematous lesions, validating the potency of PM2.5 to cause irreversible damage to lungs through complex interplay of various cellular/molecular players which may be exploited as potential preventive/therapeutic targets.

Pseudomonas aeruginosa breaches respiratory epithelia through goblet cell invasion in a microtissue model

Pseudomonas aeruginosa, a leading cause of severe hospital-acquired pneumonia, causes infections with up to 50% mortality rates in mechanically ventilated patients. Despite some knowledge of virulence factors involved, it remains unclear how P. aeruginosa disseminates on mucosal surfaces and invades the tissue barrier. Using infection of human respiratory epithelium organoids, here we observed that P. aeruginosa colonization of apical surfaces is promoted by cyclic di-GMP-dependent asymmetric division. Infection with mutant strains revealed that Type 6 Secretion System activities promote preferential invasion of goblet cells. Type 3 Secretion System activity by intracellular bacteria induced goblet cell death and expulsion, leading to epithelial rupture which increased bacterial translocation and dissemination to the basolateral epithelium. These findings show that under physiological conditions, P. aeruginosa uses coordinated activity of a specific combination of virulence factors and behaviours to invade goblet cells and breach the epithelial barrier from within, revealing mechanistic insight into lung infection dynamics.

Alterations in the molecular control of mitochondrial turnover in COPD lung and airway epithelial cells

Abnormal mitochondria have been observed in bronchial- and alveolar epithelial cells of patients with chronic obstructive pulmonary disease (COPD). However, it is unknown if alterations in the molecular pathways regulating mitochondrial turnover (mitochondrial biogenesis vs mitophagy) are involved. Therefore, in this study, the abundance of key molecules controlling mitochondrial turnover were assessed in peripheral lung tissue from non-COPD patients (n = 6) and COPD patients (n = 11; GOLDII n = 4/11; GOLDIV n = 7/11) and in both undifferentiated and differentiated human primary bronchial epithelial cells (PBEC) from non-COPD patients and COPD patients (n = 4-7 patients/group). We observed significantly decreased transcript levels of key molecules controlling mitochondrial biogenesis (PPARGC1B, PPRC1, PPARD) in peripheral lung tissue from severe COPD patients. Interestingly, mRNA levels of the transcription factor TFAM (mitochondrial biogenesis) and BNIP3L (mitophagy) were increased in these patients. In general, these alterations were not recapitulated in undifferentiated and differentiated PBECs with the exception of decreased PPARGC1B expression in both PBEC models. Although these findings provide valuable insight in these pathways in bronchial epithelial cells and peripheral lung tissue of COPD patients, whether or not these alterations contribute to COPD pathogenesis, underlie changes in mitochondrial function or may represent compensatory mechanisms remains to be established.

Large airway T cells in adults with former bronchopulmonary dysplasia

BACKGROUND

Bronchopulmonary Dysplasia (BPD) in infants born prematurely is a risk factor for chronic airway obstruction later in life. The distribution of T cell subtypes in the large airways is largely unknown.

OBJECTIVE

To characterize cellular and T cell profiles in the large airways of young adults with a history of BPD.

METHODS

Forty-three young adults born prematurely (preterm (n = 20), BPD (n = 23)) and 45 full-term-born (asthma (n = 23), healthy (n = 22)) underwent lung function measurements, and bronchoscopy with large airway bronchial wash (BW). T-cells subsets in BW were analyzed by immunocytochemistry.

RESULTS

The proportions of both lymphocytes and CD8 + T cells in BW were significantly higher in BPD (median, 6.6%, and 78.0%) when compared with asthma (3.4% and 67.8%, p = 0.002 and p = 0.040) and healthy (3.8% and 40%, p < 0.001 and p < 0.001). In all adults born prematurely (preterm and BPD), lymphocyte proportion correlated negatively with forced vital capacity (r= -0.324, p = 0.036) and CD8 + T cells correlated with forced expiratory volume in one second, FEV1 (r=-0.448, p = 0.048). Correlation-based network analysis revealed that lung function cluster and BPD-birth cluster were associated with lymphocytes and/or CD4 + and CD8 + T cells. Multivariate regression analysis showed that lymphocyte proportions and BPD severity qualified as independent factors associated with FEV1.

CONCLUSIONS

The increased cytotoxic T cells in the large airways in young adults with former BPD, suggest a similar T-cell subset pattern as in the small airways, resembling features of COPD. Our findings strengthen the hypothesis that mechanisms involving adaptive and innate immune responses are involved in the development of airway disease due to preterm birth.

A Survey on Artificial Intelligence in Pulmonary Imaging

Over the last decade, deep learning (DL) has contributed a paradigm shift in computer vision and image recognition creating widespread opportunities of using artificial intelligence in research as well as industrial applications. DL has been extensively studied in medical imaging applications, including those related to pulmonary diseases. Chronic obstructive pulmonary disease, asthma, lung cancer, pneumonia, and, more recently, COVID-19 are common lung diseases affecting nearly 7.4% of world population. Pulmonary imaging has been widely investigated toward improving our understanding of disease etiologies and early diagnosis and assessment of disease progression and clinical outcomes. DL has been broadly applied to solve various pulmonary image processing challenges including classification, recognition, registration, and segmentation. This paper presents a survey of pulmonary diseases, roles of imaging in translational and clinical pulmonary research, and applications of different DL architectures and methods in pulmonary imaging with emphasis on DL-based segmentation of major pulmonary anatomies such as lung volumes, lung lobes, pulmonary vessels, and airways as well as thoracic musculoskeletal anatomies related to pulmonary diseases.

Airway Detection in COPD at Low-Dose CT Using Deep Learning and Multiparametric Freeze and Grow

PURPOSE

To present and validate a fully automated airway detection method at low-dose CT in patients with chronic obstructive pulmonary disease (COPD).

MATERIALS AND METHODS

In this retrospective study, deep learning (DL) and freeze-and-grow (FG) methods were optimized and applied to automatically detect airways at low-dose CT. Four data sets were used: two data sets consisting of matching standard- and low-dose CT scans from the Genetic Epidemiology of COPD (COPDGene) phase II (2014-2017) cohort (n = 2 × 236; mean age ± SD, 70 years ± 9; 123 women); one data set consisting of low-dose CT scans from the COPDGene phase III (2018-2020) cohort (n = 335; mean age ± SD, 73 years ± 8; 173 women); and one data set consisting of low-dose, anonymized CT scans from the 2003 Dutch-Belgian Randomized Lung Cancer Screening trial (n = 55) acquired by using different CT scanners. Performance measures for different methods were computed and compared by using the Wilcoxon signed rank test.

RESULTS

At low-dose CT, 56 294 of 62 480 (90.1%) airways of the reference total airway count (TAC) and 32 109 of 37 864 (84.8%) airways of the peripheral TAC (TAC_p), detected at standard-dose CT, were detected. Significant losses (P < .001) of 14 526 of 76 453 (19.0%) airways and 884 of 6908 (12.8%) airways in the TAC and 12 256 of 43 462 (28.2%) airways and 699 of 3882 (18.0%) airways in the TAC_p were observed, respectively, for the multiprotocol and multiscanner data without retraining. When using the automated low-dose CT method, TAC values of 347, 342, 323, and 266 and TAC_p values of 205, 202, 289, and 141 were observed for those who have never smoked and participants at Global Initiative for Chronic Obstructive Lung Disease stages 0, 1, and 2, respectively, which were superior to the respective values previously reported for matching groups when using a semiautomated method at standard-dose CT.

CONCLUSION

A low-cost, automated CT-based airway detection method was suitable for investigation of airway phenotypes at low-dose CT.Keywords: Airway, Airway Count, Airway Detection, Chronic Obstructive Pulmonary Disease, CT, Deep Learning, Generalizability, Low-Dose CT, Segmentation, Thorax, LungClinical trial registration no. NCT00608764 Supplemental material is available for this article. © RSNA, 2022.

Smoking-Associated Exposure of Human Primary Bronchial Epithelial Cells to Aldehydes: Impact on Molecular Mechanisms Controlling Mitochondrial Content and Function

Chronic obstructive pulmonary disease (COPD) is a devastating lung disease primarily caused by exposure to cigarette smoke (CS). During the pyrolysis and combustion of tobacco, reactive aldehydes such as acetaldehyde, acrolein, and formaldehyde are formed, which are known to be involved in respiratory toxicity. Although CS-induced mitochondrial dysfunction has been implicated in the pathophysiology of COPD, the role of aldehydes therein is incompletely understood. To investigate this, we used a physiologically relevant in vitro exposure model of differentiated human primary bronchial epithelial cells (PBEC) exposed to CS (one cigarette) or a mixture of acetaldehyde, acrolein, and formaldehyde (at relevant concentrations of one cigarette) or air, in a continuous flow system using a puff-like exposure protocol. Exposure of PBEC to CS resulted in elevated IL-8 cytokine and mRNA levels, increased abundance of constituents associated with autophagy, decreased protein levels of molecules associated with the mitophagy machinery, and alterations in the abundance of regulators of mitochondrial biogenesis. Furthermore, decreased transcript levels of basal epithelial cell marker KRT5 were reported after CS exposure. Only parts of these changes were replicated in PBEC upon exposure to a combination of acetaldehyde, acrolein, and formaldehyde. More specifically, aldehydes decreased MAP1LC3A mRNA (autophagy) and BNIP3 protein (mitophagy) and increased ESRRA protein (mitochondrial biogenesis). These data suggest that other compounds in addition to aldehydes in CS contribute to CS-induced dysregulation of constituents controlling mitochondrial content and function in airway epithelial cells.

The new preparation method for paraffin-embedded samples applying scanning electron microscopy revealed characteristic features in asthma-induced mice

In bronchial asthma patients, mucous cell metaplasia (MCM) and fibrosis occur in the bronchial epithelium and interstitium, respectively. The mucus and collagen fibers are identified by Periodic acid-Schiff stain (PAS) or Sirius red stain on optical microscopy. On a scanning electron microscope (SEM) observation, formalin-fixed-paraffin-embedded specimens have high insulation, thereby attenuating the scattered electron signals leading to insufficient contrast. Moreover, there were no staining methods for SEM observation, which characterizes the changes in epithelium and interstitium by enhancing the scattered electrons. In this study, we established a method of coating osmium thin film on pathological tissue specimens using plasma chemical vapor deposition technology. This method ensured the intensity of scattered electron signals and enabled SEM observation. Furthermore, we found that morphological changes in MCM and interstitial fibrosis could be characterized by Grocott stain, which we optimized to evaluate pathological remodeling in bronchial asthma. Using these techniques, we compared asthma-induced mice with Amphiregulin (Areg) knockout mice, and found that Areg induce MCM, but the production of Grocott-stain-positive substrate in the interstitium is Areg-independent. The method developed in this study provides an understanding of the pathological spatial information linked to the ultrastructural changes in cells and interstitium due to disease-related signaling abnormalities.

Leukocyte Function in COPD: Clinical Relevance and Potential for Drug Therapy

Chronic obstructive pulmonary disease (COPD) is a progressive lung condition affecting 10% of the global population over 45 years. Currently, there are no disease-modifying treatments, with current therapies treating only the symptoms of the disease. COPD is an inflammatory disease, with a high infiltration of leukocytes being found within the lung of COPD patients. These leukocytes, if not kept in check, damage the lung, leading to the pathophysiology associated with the disease. In this review, we focus on the main leukocytes found within the COPD lung, describing how the release of chemokines from the damaged epithelial lining recruits these cells into the lung. Once present, these cells become active and may be driven towards a more pro-inflammatory phenotype. These cells release their own subtypes of inflammatory mediators, growth factors and proteases which can all lead to airway remodeling, mucus hypersecretion and emphysema. Finally, we describe some of the current therapies and potential new targets that could be utilized to target aberrant leukocyte function in the COPD lung. Here, we focus on old therapies such as statins and corticosteroids, but also look at the emerging field of biologics describing those which have been tested in COPD already and potential new monoclonal antibodies which are under review.

Epithelial Barrier Dysfunction in Chronic Respiratory Diseases

Mucosal surfaces are lined by epithelial cells, which provide a complex and adaptive module that ensures first-line defense against external toxics, irritants, antigens, and pathogens. The underlying mechanisms of host protection encompass multiple physical, chemical, and immune pathways. In the lung, inhaled agents continually challenge the airway epithelial barrier, which is altered in chronic diseases such as chronic obstructive pulmonary disease, asthma, cystic fibrosis, or pulmonary fibrosis. In this review, we describe the epithelial barrier abnormalities that are observed in such disorders and summarize current knowledge on the mechanisms driving impaired barrier function, which could represent targets of future therapeutic approaches.

CXCR1 and CXCR2 Inhibition by Ladarixin Improves Neutrophil-Dependent Airway Inflammation in Mice

Rationale

Increased IL-8 levels and neutrophil accumulation in the airways are common features found in patients affected by pulmonary diseases such as Asthma, Idiopathic Pulmonary Fibrosis, Influenza-A infection and COPD. Chronic neutrophilic inflammation is usually corticosteroid insensitive and may be relevant in the progression of those diseases.

Objective

To explore the role of Ladarixin, a dual CXCR1/2 antagonist, in several mouse models of airway inflammation with a significant neutrophilic component.

Findings

Ladarixin was able to reduce the acute and chronic neutrophilic influx, also attenuating the Th2 eosinophil-dominated airway inflammation, tissue remodeling and airway hyperresponsiveness. Correspondingly, Ladarixin decreased bleomycin-induced neutrophilic inflammation and collagen deposition, as well as attenuated the corticosteroid resistant Th17 neutrophil-dominated airway inflammation and hyperresponsiveness, restoring corticosteroid sensitivity. Finally, Ladarixin reduced neutrophilic airway inflammation during cigarette smoke-induced corticosteroid resistant exacerbation of Influenza-A infection, improving lung function and mice survival.

Conclusion

CXCR1/2 antagonist Ladarixin offers a new strategy for therapeutic treatment of acute and chronic neutrophilic airway inflammation, even in the context of corticosteroid-insensitivity.

Altered generation of ciliated cells in chronic obstructive pulmonary disease

In COPD, epithelial changes are prominent features in the airways, such as goblet cell hyperplasia and squamous metaplasia. In contrast, it remains unclear whether ciliated cells are reduced and which pathways dysregulate epithelial differentiation. We hypothesized that bronchial epithelial cell lineage specification is dysregulated in COPD because of an aberrant reprogramming through transforming growth factor (TGF)-β1. Surgical lung tissue from 81 COPD and 61 control (smokers and non-smokers) patients was assessed for bronchial epithelial cell phenotyping by immunohistochemistry, both in situ and in vitro in reconstituted air-liquid interface (ALI) cultures. The role of TGF-β1 was studied in vitro. COPD epithelium in large airways, when compared to controls, showed decreased β-tubulin IV + ciliated cells (4.4%, 2.5–8.8% versus 8.5%, 6.3–11.8% of surface staining, median and IQR, p = 0.0009) and increased MUC5AC + goblet cells (34.8%, 24.4–41.9% versus 10.3%, 5.1–17.6%, p < 0.0001). Both features were recapitulated in the ALI-cultured epithelium from COPD patients. Exogenous TGF-β1 reduced mucociliary differentiation while neutralizing TGF-β1 during ALI increased both specialized cell types. The COPD airway epithelium displays altered differentiation for ciliated cells, which recapitulates in vitro, at least in part through TGF-β1.

Interleukin-Mediated Pendrin Transcriptional Regulation in Airway and Esophageal Epithelia

Pendrin (SLC26A4), a Cl⁻/anion exchanger, is expressed at high levels in kidney, thyroid, and inner ear epithelia, where it has an essential role in bicarbonate secretion/chloride reabsorption, iodide accumulation, and endolymph ion balance, respectively. Pendrin is expressed at lower levels in other tissues, such as airways and esophageal epithelia, where it is transcriptionally regulated by the inflammatory cytokines interleukin (IL)-4 and IL-13 through a signal transducer and activator of transcription 6 (STAT6)-mediated pathway. In the airway epithelium, increased pendrin expression during inflammatory diseases leads to imbalances in airway surface liquid thickness and mucin release, while, in the esophageal epithelium, dysregulated pendrin expression is supposed to impact the intracellular pH regulation system. In this review, we discuss some of the recent findings on interleukin-mediated transcriptional regulation of pendrin and how this dysregulation impacts airway and esophagus epithelial homeostasis during inflammatory diseases.

Siglec-8 and Siglec-9 binding specificities and endogenous airway ligand distributions and properties

Siglecs are transmembrane sialoglycan binding proteins, most of which are expressed on leukocyte subsets and have inhibitory motifs that translate cell surface ligation into immune suppression. In humans, Siglec-8 on eosinophils, mast cells and basophils and Siglec-9 on neutrophils, monocytes and some T-cells, mediate immune cell death, inhibition of immune mediator release and/or enhancement of anti-inflammatory mediator release. Endogenous sialoglycan ligands in tissues, mostly uncharacterized, engage siglecs on leukocytes to inhibit inflammation. Glycan array analyses demonstrated that Siglec-8, Siglec-9 and their mouse counterparts Siglec-F and Siglec-E (respectively) have distinct glycan binding specificities, with Siglec-8 more structurally restricted. Since siglecs are involved in lung inflammation, we studied Siglec-8 and Siglec-9 ligands in human lungs and airways. Siglec-8 ligands are in tracheal submucosal glands and cartilage but not airway epithelium or connective tissues, whereas Siglec-9 ligands are broadly distributed. Mouse airways do not have Siglec-8 ligands, whereas Siglec-9 ligands are on airways of both species. Extraction of human airways and lung followed by electrophoretic resolution and siglec blotting revealed Siglec-8 ligands in extracts of human trachea and cultured tracheal gland cells, but not parenchyma or cultured airway epithelial cells whereas Siglec-9 ligands were extracted from all airway and lung tissues and cells tested. Siglec-8 and Siglec-9 ligands in airways appear to be high molecular weight O-linked sialoglycoproteins. These data reveal differential glycan specificities of Siglec-8, Siglec-9 and their mouse counterparts Siglec-F and Siglec-E, and the tissue distributions and molecular characteristics of Siglec-8 and Siglec-9 sialoglycan ligands on human airways and lungs.

Objective Assessment of Lower Airway Involvement in Chronic Rhinosinusitis

Background

When associated with lower airway involvement, the morbidity and the cost of chronic rhinosinusitis (CRS) can increase. The aim of this prospective study was to assess the clinical and radiological characteristics of the upper airways in CRS patients scheduled for functional endoscopic sinus surgery and to correlate these findings with the functional changes of the lower airways.

Methods

Twenty-five adult patients with CRS were subjected to clinical and endoscopic assessments, computed tomography scan, and allergic assessments using validated scoring systems. Lower airways were assessed by clinical history, pulmonary function test, histamine bronchial provocation test, and chest x rays.

Results

Sixty percent of CRS patients were shown to have associated lower airway involvement, i.e., 24% had asthma and 36% had small airway disease (SAD). Nasal congestion and nasal polyps were the most common clinical findings in both of these subgroups of patients. In addition, there was a negative correlation between computed tomography scan findings of the sinuses and the obstructive parameters on pulmonary function test in SAD but not in the asthma subgroup.

Conclusion

These results showed that different kinds of lower airway involvement frequently could be associated with CRS. Some are manifest such as asthma and some are hidden such as SAD and histamine bronchial hyperresponsiveness.

Airway Epithelium Dysfunction in Cystic Fibrosis and COPD

Cystic fibrosis is a genetic disease caused by mutations in the CFTR gene, whereas chronic obstructive pulmonary disease (COPD) is mainly caused by environmental factors (mostly cigarette smoking) on a genetically susceptible background. Although the etiology and pathogenesis of these diseases are different, both are associated with progressive airflow obstruction, airway neutrophilic inflammation, and recurrent exacerbations, suggesting common mechanisms. The airway epithelium plays a crucial role in maintaining normal airway functions. Major molecular and morphologic changes occur in the airway epithelium in both CF and COPD, and growing evidence suggests that airway epithelial dysfunction is involved in disease initiation and progression in both diseases. Structural and functional abnormalities in both airway and alveolar epithelium have a relevant impact on alteration of host defences, immune/inflammatory response, and the repair process leading to progressive lung damage and impaired lung function. In this review, we address the evidence for a critical role of dysfunctional airway epithelial cells in chronic airway inflammation and remodelling in CF and COPD, highlighting the common mechanisms involved in the epithelial dysfunction as well as the similarities and differences of the two diseases.

Multiple-level validation identifies PARK2 in the development of lung cancer and chronic obstructive pulmonary disease

An important precursor to lung cancer development is chronic obstructive pulmonary disease (COPD), independent of exposure to tobacco smoke. Both diseases are associated with increased host susceptibility, inflammation, and genomic instability. However, validation of the candidate genes and functional confirmation to test shared genetic contribution and cellular mechanisms to the development of lung cancer in patients with COPD remains underexplored. Here, we show that loss of PARK2 (encoding Parkin) increases the expression of proinflammation factors as well as nuclear NF-κB localization, suggesting a role of PARK2 loss in inflammation. Additional exploration showed that PARK2 deficiency promotes genomic instability and cell transformation. This role of PARK2 in inflammation and chromosome instability provides a potential link among Parkin, COPD and lung cancer. A further comprehensive validation of 114 informative single nucleotide polymorphism (SNP) variants of PARK2, in 2,484 cases and controls with well-defined lung cancer and COPD phenotypes, found rs577876, rs6455728 and rs9346917 (p<0.01) to be significantly associated with lung cancer development in people with COPD. Our findings support the evidence that PARK2 might have a tumor suppressor role in the development of COPD and lung cancer.

Lung ageing and COPD: is there a role for ageing in abnormal tissue repair?

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death worldwide, with increasing prevalence, in particular in the elderly. COPD is characterised by abnormal tissue repair resulting in (small) airways disease and emphysema. There is accumulating evidence that ageing hallmarks are prominent features of COPD. These ageing hallmarks have been described in different subsets of COPD patients, in different lung compartments and also in a variety of cell types, and thus might contribute to different COPD phenotypes. A better understanding of the main differences and similarities between normal lung ageing and the pathology of COPD may improve our understanding of the mechanisms driving COPD pathology, in particular in those patients that develop the most severe form of COPD at a relatively young age, i.e. severe early-onset COPD patients.In this review, after introducing the main concepts of lung ageing and COPD pathology, we focus on the role of (abnormal) ageing in lung remodelling and repair in COPD. We discuss the current evidence for the involvement of ageing hallmarks in these pathological features of COPD. We also highlight potential novel treatment strategies and opportunities for future research based on our current knowledge of abnormal lung ageing in COPD.

The Role and Immunobiology of Eosinophils in the Respiratory System: a Comprehensive Review

The eosinophil is a fully delineated granulocyte that disseminates throughout the bloodstream to end-organs after complete maturation in the bone marrow. While the presence of eosinophils is not uncommon even in healthy individuals, these granulocytes play a central role in inflammation and allergic processes. Normally appearing in smaller numbers, higher levels of eosinophils in the peripheral blood or certain tissues typically signal a pathologic process. Eosinophils confer a beneficial effect on the host by enhancing immunity against molds and viruses. However, tissue-specific elevation of eosinophils, particularly in the respiratory system, can cause a variety of short-term symptoms and may lead to long-term sequelae. Eosinophils often play a role in more commonly encountered disease processes, such as asthma and allergic responses in the upper respiratory tract. They are also integral in the pathology of less common diseases including eosinophilic pneumonia, allergic bronchopulmonary aspergillosis, hypersensitivity pneumonitis, and drug reaction with eosinophilia and systemic symptoms. They can be seen in neoplastic disorders or occupational exposures as well. The involvement of eosinophils in pulmonary disease processes can affect the method of diagnosis and the selection of treatment modalities. By analyzing the complex interaction between the eosinophil and its environment, which includes signaling molecules and tissues, different therapies have been discovered and created in order to target disease processes at a cellular level. Innovative treatments such as mepolizumab and benralizumab will be discussed. The purpose of this article is to further explore the topic of eosinophilic presence, activity, and pathology in the respiratory tract, as well as discuss current and future treatment options through a detailed literature review.

Chronic inflammatory airway diseases: the central role of the epithelium revisited

The respiratory epithelium plays a critical role for the maintenance of airway integrity and defense against inhaled particles. Physical barrier provided by apical junctions and mucociliary clearance clears inhaled pathogens, allergens or toxics, to prevent continuous stimulation of adaptive immune responses. The "chemical barrier", consisting of several anti-microbial factors such as lysozyme and lactoferrin, constitutes another protective mechanism of the mucosae against external aggressions before adaptive immune response starts. The reconstruction of damaged respiratory epithelium is crucial to restore this barrier. This review examines the role of the airway epithelium through recent advances in health and chronic inflammatory diseases in the lower conducting airways (in asthma and chronic obstructive pulmonary disease). Better understanding of normal and altered epithelial functions continuously provides new insights into the physiopathology of chronic airway diseases and should help to identify new epithelial-targeted therapies.

Convergence in the Epidemiology and Pathogenesis of COPD and Pneumonia

Chronic obstructive pulmonary disease (COPD) is one of the main causes of human mortalities globally after heart disease and stroke. There is increasing evidence of an aetiological association between COPD and pneumonia, the leading infectious cause of death globally in children under 5 years. In this review, we discuss the known risk factors of COPD that are also shared with pneumonia including smoking, air pollution, age and immune suppression. We review how lung pathology linked to a previous history of pneumonia may heighten susceptibility to the development of COPD in later life. Furthermore, we examine how specific aspects of COPD immunology could contribute to the manifestation of pneumonia. Based on the available evidence, a convergent relationship is becoming apparent with respect to the pathogenesis of COPD and pneumonia. This has implications for the management of both diseases, and the development of new interventions.

Tiotropium Attenuates Virus-Induced Pulmonary Inflammation in Cigarette Smoke-Exposed Mice

Viral infections trigger exacerbations in chronic obstructive pulmonary disease (COPD), and tiotropium, a M3 receptor antagonist, reduces exacerbations in patients by unknown mechanisms. In this report, we investigated whether tiotropium has anti-inflammatory effects in mice exposed to cigarette smoke (CS) and infected with influenza virus A/PR/8/34 (H1N1) or respiratory syncytial virus (RSV) and compared these effects with those of steroid fluticasone and PDE4-inhibitor roflumilast. Mice were exposed to CS; infected with H1N1 or RSV; and treated with tiotropium, fluticasone, or roflumilast. The amount of cells and cytokine levels in the airways, lung function, and viral load was determined. NCI-H292 cells were infected with H1N1 or RSV and treated with the drugs. In CS/H1N1-exposed mice, tiotropium reduced neutrophil and macrophage numbers and levels of interleukin-6 (IL-6) and interferon-γ (IFN-γ) in the airways and improved lung function. In contrast, fluticasone increased the loss of body weight; failed to reduce neutrophil or macrophage numbers; increased IL-6, KC, and tumor necrosis factor-α (TNF-α) in the lungs; and worsened lung function. Treatment with roflumilast reduced macrophage numbers, IL-6, and KC in the lungs but had no effect on neutrophil numbers or lung function. In CS/RSV-exposed mice, treatment with tiotropium, but not fluticasone or roflumilast, reduced neutrophil numbers and IL-6 and TNF-α levels in the lungs. Viral load of H1N1 and RSV was significantly elevated in CS/virus-exposed mice and NCI-H292 cells after fluticasone treatment, whereas tiotropium and roflumilast had no effect. In conclusion, tiotropium has anti-inflammatory effects on CS/virus-induced inflammation in mice that are superior to the effects of roflumilast and fluticasone. This finding might help to explain the observed reduction of exacerbation rates in COPD patients.

Enhanced monocyte migration to CXCR3 and CCR5 chemokines in COPD

Chronic obstructive pulmonary disease (COPD) patients exhibit chronic inflammation, both in the lung parenchyma and the airways, which is characterised by an increased infiltration of macrophages and T-lymphocytes, particularly CD8+ cells. Both cell types can express chemokine (C-X-C motif) receptor (CXCR)3 and C-C chemokine receptor 5 and the relevant chemokines for these receptors are elevated in COPD. The aim of this study was to compare chemotactic responses of lymphocytes and monocytes of nonsmokers, smokers and COPD patients towards CXCR3 ligands and chemokine (C-C motif) ligand (CCL)5.

Migration of peripheral blood mononuclear cells, monocytes and lymphocytes from nonsmokers, smokers and COPD patients toward CXCR3 chemokines and CCL5 was analysed using chemotaxis assays.

There was increased migration of peripheral blood mononuclear cells from COPD patients towards all chemokines studied when compared with nonsmokers and smokers. Both lymphocytes and monocytes contributed to this enhanced response, which was not explained by increased receptor expression. However, isolated lymphocytes failed to migrate and isolated monocytes from COPD patients lost their enhanced migratory capacity.

Both monocytes and lymphocytes cooperate to enhance migration towards CXCR3 chemokines and CCL5. This may contribute to increased numbers of macrophages and T-cells in the lungs of COPD patients, and inhibition of recruitment using selective antagonists might be a treatment to reduce the inflammatory response in COPD.

[A case of acute respiratory failure in an elderly patient with elderly asthma-COPD overlap syndrome (ACOS) is differentiated from acute eosinophilic pneumonia]

We report a case of acute respiratory failure in a 77-year-old male with chronic obstructive pulmonary disease (COPD) who showed marked eosinophilia (61.5% of the peripheral total white blood cells [WBCs]; 13,200/mm(3)). The patient was an ex-smoker, but he had started smoking again one month previously, His forced expiratory volume in one second (FEV1) was low and dyspnea symptom was observed. Although rhonchi were detected, wheezing chest sounds were not detected. Chest X-radiography and computed tomography of the lung revealed diffuse bilateral pulmonary infiltrates and emphysematous changes. He was given intravenous methyl prednisolone (1,000 mg) for 3 consecutive days. The abnormal shadows on the chest X-ray film improved remarkably and the eosinophils in his peripheral blood were reduced. Furthermore, it was no longer necessary to administer oxygen to treat his hypoxemia. The symptomatic and clinical course mimicked to a case of acute eosinophilic pneumonia (AEP). However, transbronchial lung biopsy specimens did not reveal eosinophilic infiltration in the alveolar septa. The fraction of eosinophils in the patient's bronchoalveolar lavage was 4.4% and not greater than 25%. After hospitalization, 5-15 mg of prednisolone administered orally in combination with bronchodilators to better manage his clinical symptoms. This case was thus determined to correspond to elderly asthma-COPD overlap syndrome (ACOS).

Klotho Reduction in Alveolar Macrophages Contributes to Cigarette Smoke Extract-induced Inflammation in Chronic Obstructive Pulmonary Disease

Abnormal inflammation and accelerated decline in lung function occur in patients with chronic obstructive pulmonary disease (COPD). Klotho, an anti-aging protein, has an anti-inflammatory function. However, the role of Klotho has never been investigated in COPD. The aim of this study is to investigate the possible role of Klotho by alveolar macrophages in airway inflammation in COPD. Klotho levels were assessed in the lung samples and peripheral blood mononuclear cells of non-smokers, smokers, and patients with COPD. The regulation of Klotho expression by cigarette smoke extract (CSE) was studied in vitro, and small interfering RNA (siRNA) and recombinant Klotho were employed to investigate the role of Klotho on CSE-induced inflammation. Klotho expression was reduced in alveolar macrophages in the lungs and peripheral blood mononuclear cells of COPD patients. CSE decreased Klotho expression and release from MH-S cells. Knockdown of endogenous Klotho augmented the expression of the inflammatory mediators, such as MMP-9, IL-6, and TNF-α, by MH-S cells. Exogenous Klotho inhibited the expression of CSE-induced inflammatory mediators. Furthermore, we showed that Klotho interacts with IκBα of the NF-κB pathway. Dexamethasone treatment increased the expression and release level of Klotho in MH-S cells. Our findings suggest that Klotho plays a role in sustained inflammation of the lungs, which in turn may have therapeutic implications in COPD.

[Regeneration of airway epithelium]

INTRODUCTION

Epithelial regeneration is a complex process. It can lead to the remodeling of the airway epithelium as in asthma, COPD or cystic fibrosis.

BACKGROUND

The development of in vivo and in vitro models has allowed the analysis of remodeling mechanisms and showed the role of components of extracellular matrix, proteases, cytokines and growth factors. Airway epithelial progenitors and stems cells have been studied in these models. However, their identification remains difficult.

CONCLUSION

Identification and characterization of airway epithelial progenitor/stem-cells, and a better knowledge of the regeneration process may allow the development of new therapeutic strategies for airway epithelial reconstitution.

From Childhood Asthma to Chronic Obstructive Pulmonary Disease: Evidence Supporting a Disease Continuum

In this review, we analyze the available evidence showing a link between asthma and chronic obstructive pulmonary disease (COPD). Many features (epidemiologic, physiologic, and histologic) overlap between these two conditions. Both environmental cigarette smoke exposure and early lung development are risk factors for the development of asthma and COPD. However, recent studies suggest that up to 25% of COPD cases were nonsmokers. Asthma during early childhood, independent of smoking history, may be an independent risk factor for the later development of COPD. One explanation for this phenomenon suggests that early small airway dysfunction (including chronic airway inflammation and airway remodeling) can lead to permanent impairment in lung physiology. Several reasons why control of airway inflammation is difficult in some patients are explored. Finally, we examine the available evidence suggesting overlapping histologic features in both asthma and COPD.

The role of macrophages in obstructive airways disease: chronic obstructive pulmonary disease and asthma

Macrophages are a major cellular component of the innate immune system, and play an important role in the recognition of microbes, particulates, and immunogens and to the regulation of inflammatory responses. In the lung, macrophages react with soluble proteins that bind microbial products in order to remove pathogens and particles and to maintain the sterility of the airway tract. Chronic obstructive pulmonary disease and asthma are both obstructive airway diseases that involve chronic inflammation of the respiratory tract which contributes to disease progression. In the case of COPD, there is increasing evidence that lung macrophages orchestrate inflammation through the release of chemokines that attract neutrophils, monocytes and T cells and the release of several proteases. On the other hand, in asthma, it seems that alveolar macrophages are inappropriately activated and are implicated in the development and progression of the disease. In this review we summarize the current basic and clinical research studies which highlight the role of macrophages in asthma and COPD.

Effects of electroacupuncture at Zusanli (ST36) on inflammatory cytokines in a rat model of smoke-induced chronic obstructive pulmonary disease

OBJECTIVE

Improvement in lung function was reported after acupuncture treatment of chronic obstructive pulmonary disease (COPD), but little is known about the underlying mechanisms. Because an immune response imbalance could be seen in COPD, we hypothesize that electroacupuncture (EA) may play a role in regulating inflammatory cytokines and contribute to lung protection in a rat model of smoke-induced COPD.

METHODS

A COPD model using male Sprague-Dawley rats exposed to cigarette smoke was established. The rats were randomly divided into four groups (control, sham, COPD, and COPD plus EA), and COPD model was evaluated by measuring pulmonary pathological changes and lung function. EA was applied to the acupuncture point Zusanli (ST36) for 30 min/d for 14 d in sham and COPD rats. Bronchoalveolar lavage fluid (BALF) was used to measure levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and malonaldehyde (MDA).

RESULTS

Compared with the control rats, COPD rats had significant changes in lung resistance (RL) and lung compliance (CL) (both P<0.01), bronchi and bronchiole airway obstruction (P<0.01), and levels of MDA, TNF-α, and IL-1β (P<0.01). There were no significant differences between the control and the sham groups. Compared with the COPD rats, the COPD plus EA rats had decreased RL and increased CL (both P<0.05), and reduced bronchi and bronchiole airway obstruction (P<0.05, P<0.01, respectively), while levels of TNF-α, IL-1β, and MDA in BALF were lowered (P<0.05 and P<0.01, respectively). However, TNF-α and IL-1β levels of the EA group rats remained higher than those of the control group (P<0.05).

CONCLUSION

EA at ST36 can reduce lung injury in a COPD rat model, and beneficial effects may be related to down-regulation of inflammatory cytokines. The anti-inflammatory and antioxidant effects may prolong the clinical benefit of EA.

Conditional overexpression of receptors for advanced glycation end-products in the adult murine lung causes airspace enlargement and induces inflammation

Receptors for advanced glycation end-products (RAGE) are multiligand surface receptors detected abundantly in pulmonary tissue. Our previous work revealed increased RAGE expression in cells and lungs exposed to tobacco smoke and RAGE-mediated cytokine expression via proinflammatory mechanisms involving NF-κB. RAGE expression is elevated in various pathological states, including chronic obstructive pulmonary disease; however, precise contributions of RAGE to the progression of emphysema and pulmonary inflammation in the adult lung are unknown. In the current study, we generated a RAGE transgenic (RAGE TG) mouse and conditionally induced adult alveolar epithelium to overexpress RAGE. RAGE was induced after the period of alveologenesis, from weaning (20 d of age) until animals were killed at 50, 80, and 110 days (representing 30, 60, and 90 d of RAGE overexpression). Hematoxylin and eosin staining and mean chord length revealed incremental dilation of alveolar spaces as RAGE overexpression persisted. TUNEL staining and electron microscopy confirmed increased apoptosis and blebbing of alveolar epithelium in lungs from RAGE TG mice when compared with control mice. Immunohistochemistry for matrix metalloproteinase 9 revealed an overall increase in matrix metalloproteinase 9, which correlated with decreased elastin expression in RAGE TG mice. Furthermore, RAGE TG mice manifested significant inflammation measured by elevated bronchoalveolar lavage protein, leukocyte infiltration, and secreted cytokines. These data support the concept that innovative transgenic mice that overexpress RAGE may model pulmonary inflammation and alveolar destabilization independent of tobacco smoke and validate RAGE signaling as a target pathway in the prevention or attenuation of smoke-related inflammatory lung diseases.

Andrographolide protects against cigarette smoke-induced lung inflammation through activation of heme oxygenase-1

This study was conducted to check whether andrographolide, a bioactive molecule isolated from Andrographis paniculata, could protect against cigarette smoke (CS)-induced lung injury through activation of heme oxygenase-1 (HO-1). Pretreatment with andrographolide (1 mg/kg body weight) markedly attenuated lung inflammation in CS-exposed mice, coupled with reduced numbers of total cells, neutrophils, and macrophages in bronchial alveolar lavage fluid (BALF) and decreased production of cytokine/chemokine into BALF. Furthermore, andrographolide pretreatment increased the expression and activation of HO-1 in the lung of CS-exposed animals. Notably, these histological and biochemical changes induced by andrographolide were blocked by prior administration of zinc protoporphyrin IX (ZnPP; 20 mg/kg body weight), a potent heme oxygenase inhibitor. Moreover, andrographolide-induced phosphorylation of signal transducer and activator of transcription 3 (STAT3) was attenuated by ZnPP treatment in CS-exposed animals. Our data collectively demonstrate that andrographolide confers protection against CS-induced lung inflammation, partially through activation of HO-1 and STAT3.

Innate immunity to influenza in chronic airways diseases

Influenza presents a unique human infectious disease that has a substantial impact on the public health, in general, and especially for those with chronic airways diseases. People with asthma and chronic obstructive pulmonary disease (COPD) are particularly vulnerable to influenza infection and experience more severe symptoms with the worsening of their pre-existing conditions. Recent advances in reverse genetics and innate immunity has revealed several influenza virulence factors and host factors involved in influenza pathogenesis and the immune responses to infection. Early innate immunity plays a critical role of limiting viral infection and spread; however, the underlying mechanisms that lead to enhanced susceptibility to influenza infection and severe symptoms in those with asthma and COPD to infection remain un-investigated. This review will explore the importance of early innate antiviral responses to influenza infection and how these responses are altered by influenza virus and in those with chronic airways diseases.

IL-8 production in response to cigarette smoke is decreased in epithelial cells from COPD patients

Cigarette smoke is the principal cause of chronic obstructive pulmonary disease (COPD), a disorder characterized by airway inflammation. As epithelial cells are the first line of defense against foreign material, the response of normal epithelial cells to smoke has been extensively studied. However, little is known about how epithelial cells derived from COPD patients respond to ongoing smoke exposure. This study was aimed at comparing the intracellular response of normal human bronchial/tracheal epithelial cells (NHBE) and COPD-diseased human bronchial/tracheal epithelial cells (DHBE) to cigarette smoke. NHBE and DHBE cells were treated with cigarette smoke condensate (CSC) for 24 h. IL-8 production was measured by ELISA and western blot was used to measure TLR4 expression. Cells were pretreated with CLI-095, a TLR4 inhibitor, or the signaling pathway inhibitors PD184352, Helenalin, or PI-103, which inhibit the ERK1/2, NF-κB and PI3K pathways, respectively. NHBE cells increased IL-8 production in a dose-dependent manner in response to CSC while DHBE cells did not show any significant difference and had a much lower production of IL-8 in response to CSC compared to NHBE cells. There was no change in TLR4 expression with CSC exposure. CLI-095 and PD184352 attenuated IL-8 secretion, indicating that CSC-induced inflammation is both TLR4- and ERK1/2-dependent. These results demonstrate that NHBE and DHBE cells differentially respond to cigarette smoke. DHBE cells exhibit a dampened IL-8 release, indicating that COPD is associated with a reduced capacity of airway epithelial cells to respond to foreign material.

Multiple facets of cAMP signalling and physiological impact: cAMP compartmentalization in the lung

Therapies involving elevation of the endogenous suppressor cyclic AMP (cAMP) are currently used in the treatment of several chronic inflammatory disorders, including chronic obstructive pulmonary disease (COPD). Characteristics of COPD are airway obstruction, airway inflammation and airway remodelling, processes encompassed by increased airway smooth muscle mass, epithelial changes, goblet cell and submucosal gland hyperplasia. In addition to inflammatory cells, airway smooth muscle cells and (myo)fibroblasts, epithelial cells underpin a variety of key responses in the airways such as inflammatory cytokine release, airway remodelling, mucus hypersecretion and airway barrier function. Cigarette smoke, being next to environmental pollution the main cause of COPD, is believed to cause epithelial hyperpermeability by disrupting the barrier function. Here we will focus on the most recent progress on compartmentalized signalling by cAMP. In addition to G protein-coupled receptors, adenylyl cyclases, cAMP-specific phospho-diesterases (PDEs) maintain compartmentalized cAMP signalling. Intriguingly, spatially discrete cAMP-sensing signalling complexes seem also to involve distinct members of the A-kinase anchoring (AKAP) superfamily and IQ motif containing GTPase activating protein (IQGAPs). In this review, we will highlight the interaction between cAMP and the epithelial barrier to retain proper lung function and to alleviate COPD symptoms and focus on the possible molecular mechanisms involved in this process. Future studies should include the development of cAMP-sensing multiprotein complex specific disruptors and/or stabilizers to orchestrate cellular functions. Compartmentalized cAMP signalling regulates important cellular processes in the lung and may serve as a therapeutic target.

Increased human Ca²⁺-activated Cl⁻ channel 1 expression and mucus overproduction in airway epithelia of smokers and chronic obstructive pulmonary disease patients

Background

The mechanisms underlying the association between smoking and mucus overproduction remain unknown. Because of its involvement in other airway diseases, such as asthma, we hypothesized that Ca²⁺-activated Cl^- channel 1 (CLCA1) was associated with overproduction of mucus in the airways of smokers and COPD patients.

Methods

Using real-time quantitative PCR analyses, we compared the CLCA1 mRNA expression levels in induced-sputum cells from COPD patients (n = 20), smokers without COPD (n = 5), and non-smokers (n =13). We also examined the relationship between CLCA1 protein expression and mucus production in lung airway epithelia of COPD patients (n = 6), smokers without COPD (n = 7), and non-smokers (n = 7).

Results

CLCA1 mRNA expression was significantly up-regulated in the induced-sputum cells of COPD patients compared with cells of non-smokers (p = 0.02), but there was no significant difference compared with cells of smokers without COPD. Using immunostaining with an anti-CLCA1 antibody, semi-quantitative image analyses of airway epithelium demonstrated significantly increased CLCA1 expression in smokers without COPD (p = 0.02) and in COPD patients (p = 0.002) compared with non-smokers. There were significant negative correlations between CLCA1 protein expression and FEV₁/FVC (r = −0.57, p = 0.01) and %predicted FEV₁ (r = −0.56, p = 0.01). PAS staining for mucus showed that there was a significant positive correlation between CLCA1 protein expression and mucus production (r = 0.67, p = 0.001). These markers were significantly increased in smokers without COPD (p = 0.04) and in COPD patients (p = 0.003) compared with non-smokers (non-smokers < smokers ≤ COPD).

Conclusions

CLCA1 expression is significantly related to mucus production in the airway epithelia of smokers and COPD patients, and may contribute to the development and pathogenesis of COPD by inducing mucus production.

RAGE signaling by alveolar macrophages influences tobacco smoke-induced inflammation

Receptors for advanced glycation end-products (RAGE) are multiligand cell surface receptors of the immunoglobin family expressed by epithelium and macrophages, and expression increases following exposure to cigarette smoke extract (CSE). The present study sought to characterize the proinflammatory contributions of RAGE expressed by alveolar macrophages (AMs) following CSE exposure. Acute exposure of mice to CSE via nasal instillation revealed diminished bronchoalveolar lavage (BAL) cellularity and fewer AMs in RAGE knockout (KO) mice compared with controls. Primary AMs were obtained from BAL, exposed to CSE in vitro, and analyzed. CSE significantly increased RAGE expression by wild-type AMs. Employing ELISAs, wild-type AMs exposed to CSE had increased levels of active Ras, a small GTPase that perpetuates proinflammatory signaling. Conversely, RAGE KO AMs had less Ras activation compared with wild-type AMs after exposure to CSE. In RAGE KO AMs, assessment of p38 MAPK and NF-κB, important intracellular signaling intermediates induced during an inflammatory response, revealed that CSE-induced inflammation may occur in part via RAGE signaling. Lastly, quantitative RT-PCR revealed that the expression of proinflammatory cytokines including TNF-α and IL-1β were detectably decreased in RAGE KO AMs exposed to CSE compared with CSE-exposed wild-type AMs. These results reveal that primary AMs orchestrate CSE-induced inflammation, at least in part, via RAGE-mediated mechanisms.

Airway epithelial cell differentiation during lung organogenesis requires C/EBPα and C/EBPβ

BACKGROUND

CCAAT/enhancer-binding protein (C/EBP)α is crucial for lung development and differentiation of the pulmonary epithelium. Conversely, no lung defects have been observed in C/EBPβ-deficient mice, although C/EBPβ trans-activate pulmonary genes by binding to virtually identical DNA-sequences as C/EBPα. Thus, the pulmonary phenotype of mice lacking C/EBPβ could be explained by functional replacement with C/EBPα. We investigated whether C/EBPα and C/EBPβ have overlapping functions in regulating lung epithelial differentiation during organogenesis. Epithelial differentiation was assessed in mice with a lung epithelial-specific (SFTPC-Cre-mediated) deletion of C/EBPα (Cebpa(ΔLE) ), C/EBPβ (Cebpb(ΔLE) ), or both genes (Cebpa(ΔLE) ; Cebpb(ΔLE) ).

RESULTS

Both Cebpa(ΔLE) mice and Cebpa(ΔLE) ; Cebpb(ΔLE) mice demonstrated severe pulmonary immaturity compared to wild-type littermates, while no differences in lung histology or epithelial differentiation were observed in Cebpb(ΔLE) mice. In contrast to Cebpa(ΔLE) mice, Cebpa(ΔLE) ; Cebpb(ΔLE) mice also displayed undifferentiated Clara cells with markedly impaired protein and mRNA expression of Clara cell secretory protein (SCGB1A1), compared to wild-type littermates. In addition, ectopic mucus-producing cells were observed in the conducting airways of Cebpa(ΔLE) ; Cebpb(ΔLE) mice.

CONCLUSIONS

Our findings demonstrate that C/EBPα and C/EBPβ play pivotal, and partly overlapping roles in determining airway epithelial differentiation, with possible implications for tissue regeneration in lung homeostasis and disease.

Leukocytes are recruited through the bronchial circulation to the lung in a spontaneously hypertensive rat model of COPD

Chronic obstructive pulmonary disease (COPD) kills approximately 2.8 million people each year, and more than 80% of COPD cases can be attributed to smoking. Leukocytes recruited to the lung contribute to COPD pathology by releasing reactive oxygen metabolites and proteolytic enzymes. In this work, we investigated where leukocytes enter the lung in the early stages of COPD in order to better understand their effect as a contributor to the development of COPD. We simultaneously evaluated the parenchyma and airways for neutrophil accumulation, as well as increases in the adhesion molecules and chemokines that cause leukocyte recruitment in the early stages of tobacco smoke induced lung disease. We found neutrophil accumulation and increased expression of adhesion molecules and chemokines in the bronchial blood vessels that correlated with the accumulation of leukocytes recovered from the lung. The expression of adhesion molecules and chemokines in other vascular beds did not correlate with leukocytes recovered in bronchoalveolar lavage fluid (BALF). These data strongly suggest leukocytes are recruited in large measure through the bronchial circulation in response to tobacco smoke. Our findings have important implications for understanding the etiology of COPD and suggest that pharmaceuticals designed to reduce leukocyte recruitment through the bronchial circulation may be a potential therapy to treat COPD.

Artificial airways for the study of respiratory disease

This review will focus on human cell-based experimental models to study respiratory diseases, in particular models of the large airways relevant to asthma and chronic obstructive pulmonary disease. Such models have the advantage of incorporating cells that can be derived from disease-relevant tissue and so have retained important genetic and epigenetic features that contribute to the human disease. These models can be used for mechanistic studies, target identification and validation and toxicological testing. While many models have been developed to varying degrees of sophistication, the challenge remains to develop an integrated system that recapitulates the complex cell-cell and cell-matrix interactions that occur in vivo and to provide these with a 'circulation' to study the dynamics of immune and inflammatory cell influx and efflux.

Acrolein - a pulmonary hazard

Acrolein is a respiratory irritant that can be generated during cooking and is in environmental tobacco smoke. More plentiful in cigarette smoke than polycyclic aromatic hydrocarbons (PAH), acrolein can adduct tumor suppressor p53 (TP53) DNA and may contribute to TP53-mutations in lung cancer. Acrolein is also generated endogenously at sites of injury, and excessive breath levels (sufficient to activate metalloproteinases and increase mucin transcripts) have been detected in asthma and chronic obstructive pulmonary disease (COPD). Because of its reactivity with respiratory-lining fluid or cellular macromolecules, acrolein alters gene regulation, inflammation, mucociliary transport, and alveolar-capillary barrier integrity. In laboratory animals, acute exposures have lead to acute lung injury and pulmonary edema similar to that produced by smoke inhalation whereas lower concentrations have produced bronchial hyperreactivity, excessive mucus production, and alveolar enlargement. Susceptibility to acrolein exposure is associated with differential regulation of cell surface receptor, transcription factor, and ubiquitin-proteasome genes. Consequent to its pathophysiological impact, acrolein contributes to the morbidly and mortality associated with acute lung injury and COPD, and possibly asthma and lung cancer.

Enhancement of lung tumorigenesis in a Gprc5a Knockout mouse by chronic extrinsic airway inflammation

Background

Although cigarette smoking is the principal cause of lung carcinogenesis, chronic obstructive pulmonary disease (COPD), an inflammatory disease of the lung, has been identified as an independent risk factor for lung cancer. Bacterial colonization, particularly with non-typeable Haemophilus influenzae (NTHi), has been implicated as a cause of airway inflammation in COPD besides cigarette smoke. Accordingly, we hypothesized that lung cancer promotion may occur in a chronic inflammatory environment in the absence of concurrent carcinogen exposure.

Results

Herein, we investigated the effects of bacterial-induced COPD-like inflammation and tobacco carcinogen-enhanced tumorigenesis/inflammation in the retinoic acid inducible G protein coupled receptor knock out mouse model (Gprc5a-/- mouse) characterized by late-onset, low multiplicity tumor formation. Three-month-old Gprc5a-/- mice received 4 intraperitoneal injections of the tobacco-specific carcinogen, NNK, followed by weekly exposure to aerosolized NTHi lysate for 6 months. The numbers of inflammatory cells in the lungs and levels of several inflammatory mediators were increased in Gprc5a-/- mice treated with NTHi alone, and even more so in mice pretreated with NNK followed by NTHi. The incidence of spontaneous lung lesions in the Gprc5a-/- mice was low, but NTHi exposure led to enhanced development of hyperplastic lesions. Gprc5a-/- mice exposed to NNK alone developed multiple lung tumors, while NTHi exposure increased the number of hyperplastic foci 6-fold and the tumor multiplicity 2-fold. This was associated with increased microvessel density and HIF-1α expression.

Conclusion

We conclude that chronic extrinsic lung inflammation induced by bacteria alone or in combination with NNK enhances lung tumorigenesis in Gprc5a-/- mice.

The Asthma-COPD Overlap Syndrome: A Common Clinical Problem in the Elderly

Many patients with breathlessness and chronic obstructive lung disease are diagnosed with either asthma, COPD, or—frequently—mixed disease. More commonly, patients with uncharacterized breathlessness are treated with therapies that target asthma and COPD rather than one of these diseases. This common practice represents the difficulty in distinguishing these disorders clinically, particularly in patients with a history that does not easily differentiate asthma from COPD. A common clinical scenario is an older former smoker with partially reversible or fixed airflow obstruction and evidence of atopy, demonstrating “overlap” features of asthma and COPD. We stress that asthma-COPD overlap syndrome becomes more prevalent with advancing age as patients respond less favorably to guideline-recommended drug therapy. We review the similarities and differences in clinical characteristics between these disorders, and their physiologic and inflammatory profiles within the context of the aging patient. We underscore the difficulties in differentiating asthma from COPD in current or former smokers, share our institutional experience with overlap syndrome, and highlight the need for new research to better characterize and investigate this important clinical phenotype.