Airway Surface Dehydration Aggravates Cigarette Smoke-Induced Hallmarks of COPD in Mice

Genetic Deletion of Mmp9 Does Not Reduce Airway Inflammation and Structural Lung Damage in Mice with Cystic Fibrosis-like Lung Disease

Elevated levels of matrix metalloprotease 9 (MMP-9) and neutrophil elastase (NE) are associated with bronchiectasis and lung function decline in patients with cystic fibrosis (CF). MMP-9 is a potent extracellular matrix-degrading enzyme which is activated by NE and has been implicated in structural lung damage in CF. However, the role of MMP-9 in the in vivo pathogenesis of CF lung disease is not well understood. Therefore, we used β-epithelial Na+ channel-overexpressing transgenic (βENaC-Tg) mice as a model of CF-like lung disease and determined the effect of genetic deletion of Mmp9 (Mmp9-/-) on key aspects of the pulmonary phenotype. We found that MMP-9 levels were elevated in the lungs of βENaC-Tg mice compared with wild-type littermates. Deletion of Mmp9 had no effect on spontaneous mortality, inflammatory markers in bronchoalveolar lavage, goblet cell metaplasia, mucus hypersecretion and emphysema-like structural lung damage, while it partially reduced mucus obstruction in βENaC-Tg mice. Further, lack of Mmp9 had no effect on increased inspiratory capacity and increased lung compliance in βENaC-Tg mice, whereas both lung function parameters were improved with genetic deletion of NE. We conclude that MMP-9 does not play a major role in the in vivo pathogenesis of CF-like lung disease in mice.

Role of air pollutants in airway epithelial barrier dysfunction in asthma and COPD

Chronic exposure to environmental pollutants is a major contributor to the development and progression of obstructive airway diseases, including asthma and COPD. Understanding the mechanisms underlying the development of obstructive lung diseases upon exposure to inhaled pollutants will lead to novel insights into the pathogenesis, prevention and treatment of these diseases. The respiratory epithelial lining forms a robust physicochemical barrier protecting the body from inhaled toxic particles and pathogens. Inhalation of airborne particles and gases may impair airway epithelial barrier function and subsequently lead to exaggerated inflammatory responses and airway remodelling, which are key features of asthma and COPD. In addition, air pollutant-induced airway epithelial barrier dysfunction may increase susceptibility to respiratory infections, thereby increasing the risk of exacerbations and thus triggering further inflammation. In this review, we discuss the molecular and immunological mechanisms involved in physical barrier disruption induced by major airborne pollutants and outline their implications in the pathogenesis of asthma and COPD. We further discuss the link between these pollutants and changes in the lung microbiome as a potential factor for aggravating airway diseases. Understanding these mechanisms may lead to identification of novel targets for therapeutic intervention to restore airway epithelial integrity in asthma and COPD.

Exposure to air pollution induces airway epithelial barrier dysfunction through several mechanisms including increased oxidative stress, exaggerated cytokine responses and impaired host defence, which contributes to development of asthma and COPD. https://bit.ly/3DHL1CA

Age-Related Differences in Structure and Function of Nasal Epithelial Cultures From Healthy Children and Elderly People

The nasal epithelium represents the first line of defense against inhaled pathogens, allergens, and irritants and plays a key role in the pathogenesis of a spectrum of acute and chronic airways diseases. Despite age-dependent clinical phenotypes triggered by these noxious stimuli, little is known about how aging affects the structure and function of the airway epithelium that is crucial for lung homeostasis and host defense. The aim of this study was therefore to determine age-related differences in structural and functional properties of primary nasal epithelial cultures from healthy children and non-smoking elderly people. To achieve this goal, highly differentiated nasal epithelial cultures were established from nasal brushes at air–liquid interface and used to study epithelial cell type composition, mucin (MUC5AC and MUC5B) expression, and ion transport properties. Furthermore, we determined age-dependent molecular signatures using global proteomic analysis. We found lower numeric densities of ciliated cells and higher levels of MUC5AC expression in cultures from children vs. elderly people. Bioelectric studies showed no differences in basal ion transport properties, ENaC-mediated sodium absorption, or CFTR-mediated chloride transport, but detected decreased calcium-activated TMEM16A-mediated chloride secretory responses in cultures from children vs. elderly people. Proteome analysis identified distinct age-dependent molecular signatures associated with ciliation and mucin biosynthesis, as well as other pathways implicated in aging. Our data identified intrinsic, age-related differences in structure and function of the nasal epithelium and provide a basis for further studies on the role of these findings in age-dependent airways disease phenotypes observed with a spectrum of respiratory infections and other noxious stimuli.

Postnatal Ozone Exposure Disrupts Alveolar Development, Exaggerates Mucoinflammatory Responses, and Suppresses Bacterial Clearance in Developing Scnn1b-Tg+ Mice Lungs

Increased levels of ambient ozone, one of the six criteria air pollutants, result in respiratory tract injury and worsening of ongoing lung diseases. However, the effect of ozone exposure on the respiratory tract undergoing active lung development and simultaneously experiencing mucoinflammatory lung diseases, such as cystic fibrosis, remains unclear. To address these questions, we exposed Scnn1b transgenic (Scnn1b-Tg⁺) mice, a mouse model of cystic fibrosis-like lung disease, and littermate wild-type (WT) mice to ozone from postnatal days (PND) 3-20 and examined the lung phenotypes at PND21. As compared with filtered air (FA)-exposed WT mice, the ozone-exposed WT mice exhibited marked alveolar space enlargement, in addition to significant eosinophilic infiltration, type 2 inflammation, and mucous cell metaplasia. Ozone-exposed Scnn1b-Tg⁺ mice also exhibited significantly increased alveolar space enlargement, which was also accompanied by exaggerated granulocytic infiltration, type 2 inflammation, and a greater degree of mucus obstruction. The alveolar space enlargement in ozone-exposed WT, FA-exposed Scnn1b-Tg⁺, and ozone-exposed Scnn1b-Tg⁺ mice was accompanied by elevated levels of MMP12 protein in macrophages and Mmp12 mRNA in the lung homogenates. Finally, although bacterial burden was largely resolved by PND21 in FA-exposed Scnn1b-Tg⁺ mice, ozone-exposed Scnn1b-Tg⁺ mice exhibited compromised bacterial clearance, which was also associated with increased levels of IL-10, an immunosuppressive cytokine, and marked mucus obstruction. Taken together, our data show that ozone exposure results in alveolar space remodeling during active phases of lung development and markedly exaggerates the mucoinflammatory outcomes of pediatric-onset lung disease, including bacterial infections, granulocytic inflammation, mucus obstruction, and alveolar space enlargement.

Electronic Cigarette Exposure Enhances Lung Inflammatory and Fibrotic Responses in COPD Mice

Although a few studies show that the use of electronic nicotine delivery systems (ENDS) may ameliorate objective and subjective outcomes in COPD smokers who switched to electronic cigarettes, it is unclear whether e-cigarette exposure alters lung pathological features and inflammatory response in COPD. Here, we employed βENaC-overexpressing mice bearing COPD-like pulmonary abnormality, and exposed them to ENDS. We found that ENDS exposure aggravated airspace enlargement and mucus production in βENaC-overexpressing mice, which was associated with increased MMP12 and Muc5ac, respectively. ENDS exposure to mice significantly increased the numbers of macrophages, particularly in M2 macrophages in bronchoalveolar lavage (BAL) fluid, despite ENDS did not induce M2 macrophage polarization in a cultured murine macrophage cell line (RAW264.7). There were no changes in neutrophils in BAL fluid by ENDS exposure. Multiple cytokine productions were increased including M-CSF, IL-1rα, IL-10, and TGF-β1, in BAL fluid from mice when exposed to ENDS. The Sirius Red staining and hydroxyproline assay showed ENDS-exposed mice displayed enhanced fibrotic phenotypes compared to control mice. In conclusion, ENDS exposure enhances airspace enlargement, mucus secretion, and fibrogenesis in COPD mice. This is associated with increased MMP12, inflammatory responses, and M2 macrophage phenotype. This study provides pre-clinical data implicating that electronic cigarette exposure is not safe in COPD patients who want to replace traditional cigarettes with ENDS.

Trypsin-Like Proteases and Their Role in Muco-Obstructive Lung Diseases

Trypsin-like proteases (TLPs) belong to a family of serine enzymes with primary substrate specificities for the basic residues, lysine and arginine, in the P1 position. Whilst initially perceived as soluble enzymes that are extracellularly secreted, a number of novel TLPs that are anchored in the cell membrane have since been discovered. Muco-obstructive lung diseases (MucOLDs) are characterised by the accumulation of hyper-concentrated mucus in the small airways, leading to persistent inflammation, infection and dysregulated protease activity. Although neutrophilic serine proteases, particularly neutrophil elastase, have been implicated in the propagation of inflammation and local tissue destruction, it is likely that the serine TLPs also contribute to various disease-relevant processes given the roles that a number of these enzymes play in the activation of both the epithelial sodium channel (ENaC) and protease-activated receptor 2 (PAR2). More recently, significant attention has focused on the activation of viruses such as SARS-CoV-2 by host TLPs. The purpose of this review was to highlight key TLPs linked to the activation of ENaC and PAR2 and their association with airway dehydration and inflammatory signalling pathways, respectively. The role of TLPs in viral infectivity will also be discussed in the context of the inhibition of TLP activities and the potential of these proteases as therapeutic targets.

Cigarillos Compromise the Mucosal Barrier and Protein Expression in Airway Epithelia

Smoking remains a leading cause of preventable morbidity and mortality worldwide. Despite a downward trend in cigarette use, less-regulated tobacco products, such as cigarillos, which are often flavored to appeal to specific demographics, such as younger people, are becoming increasingly popular. Cigar/cigarillo smoking has been considered a safer alternative to cigarettes; however, the health risks associated with cigar in comparison with cigarette smoking are not well understood. To address this knowledge gap, we characterized the effects of multiple brands of cigarillos on the airway epithelium using ex vivo and in vivo models. To analyze these effects, we assessed the cellular viability and integrity of smoke-exposed primary airway cell cultures. We also investigated the protein compositions of apical secretions from cigarillo-exposed airway epithelial cultures and BAL fluid of cigarillo-exposed mice through label-free quantitative proteomics and determined the chemical composition of smoke collected from the investigated cigarillo products. We found that cigarillo smoke exerts similar or greater effects than cigarette smoke in terms of reduced cell viability; altered protein levels, including those of innate immune proteins; induced oxidative-stress markers; and greater nicotine delivery to cells. The analysis of the chemical composition of the investigated cigarillo products revealed differences that might be linked to the differential effects of these products on cell viability and protein abundance profiles, which have been associated with a range of health risks in the context of airway biology. These findings contradict the assumption that cigarillos might be safer and less harmful than cigarettes. Instead, our results indicate that cigarillo smoke is associated with equal or greater health risks and the same or increased airway toxicity compared with cigarette smoke.

Mechanisms of Virus-Induced Airway Immunity Dysfunction in the Pathogenesis of COPD Disease, Progression, and Exacerbation

Chronic obstructive pulmonary disease (COPD) is the integrated form of chronic obstructive bronchitis and pulmonary emphysema, characterized by persistent small airway inflammation and progressive irreversible airflow limitation. COPD is characterized by acute pulmonary exacerbations and associated accelerated lung function decline, hospitalization, readmission and an increased risk of mortality, leading to huge social-economic burdens. Recent evidence suggests ~50% of COPD acute exacerbations are connected with a range of respiratory viral infections. Nevertheless, respiratory viral infections have been linked to the severity and frequency of exacerbations and virus-induced secondary bacterial infections often result in a synergistic decline of lung function and longer hospitalization. Here, we review current advances in understanding the cellular and molecular mechanisms underlying the pathogenesis of COPD and the increased susceptibility to virus-induced exacerbations and associated immune dysfunction in patients with COPD. The multiple immune regulators and inflammatory signaling pathways known to be involved in host-virus responses are discussed. As respiratory viruses primarily target airway epithelial cells, virus-induced inflammatory responses in airway epithelium are of particular focus. Targeting virus-induced inflammatory pathways in airway epithelial cells such as Toll like receptors (TLRs), interferons, inflammasomes, or direct blockade of virus entry and replication may represent attractive future therapeutic targets with improved efficacy. Elucidation of the cellular and molecular mechanisms of virus infections in COPD pathogenesis will undoubtedly facilitate the development of these potential novel therapies that may attenuate the relentless progression of this heterogeneous and complex disease and reduce morbidity and mortality.

Conditional deletion of Nedd4-2 in lung epithelial cells causes progressive pulmonary fibrosis in adult mice

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive interstitial lung disease characterized by patchy scarring of the distal lung with limited therapeutic options and poor prognosis. Here, we show that conditional deletion of the ubiquitin ligase Nedd4-2 (Nedd4l) in lung epithelial cells in adult mice produces chronic lung disease sharing key features with IPF including progressive fibrosis and bronchiolization with increased expression of Muc5b in peripheral airways, honeycombing and characteristic alterations in the lung proteome. NEDD4-2 is implicated in the regulation of the epithelial Na⁺ channel critical for proper airway surface hydration and mucus clearance and the regulation of TGFβ signaling, which promotes fibrotic remodeling. Our data support a role of mucociliary dysfunction and aberrant epithelial pro-fibrotic response in the multifactorial disease pathogenesis. Further, treatment with the anti-fibrotic drug pirfenidone reduced pulmonary fibrosis in this model. This model may therefore aid studies of the pathogenesis and therapy of IPF.

Idiopathic pulmonary fibrosis (IPF) is a devastating disease with poor prognosis. Here, the authors show that deficiency of the E3 ubiqutin-protein ligase Nedd4-2 in airway epithelial cells causes IPF-like disease in adult mice. This model may aid studies of the pathogenesis and therapy of IPF.

Bone morphogenetic protein 6 (BMP-6) modulates lung function, pulmonary iron levels and cigarette smoke-induced inflammation

Chronic obstructive pulmonary disease (COPD) is associated with abnormal inflammatory responses and airway wall remodeling, leading to reduced lung function. An association between the bone morphogenetic protein (BMP-6) locus and forced vital capacity has been found in a genome-wide association study. However, the role of BMP-6 in the pathogenesis of COPD remains unknown. The pulmonary expression of BMP-6 was analyzed in patients with COPD and in cigarette smoke (CS)-exposed mice. We evaluated lung function and histology in BMP-6 KO mice at baseline. We exposed BMP-6 KO mice to CS for 4 weeks and measured pulmonary inflammation and iron levels. Pulmonary mRNA levels of BMP-6 were decreased in smokers with and without COPD and in CS-exposed mice. Importantly, BMP-6 expression was lowest in severe COPD. Accordingly, protein levels of BMP-6 were decreased in patients with COPD. Lung function measurements demonstrated a decreased compliance and total lung capacity in BMP-6 KO mice, whereas lung histology was normal. Furthermore, BMP-6 KO mice displayed elevated iron levels and an aggravated CS-induced inflammatory response. These results suggest that BMP-6 is important for normal lung function and that downregulation of BMP-6-as observed in patients with COPD-contributes to pulmonary inflammation after CS exposure.

Cigarette smoke modifies and inactivates SPLUNC1, leading to airway dehydration

Chronic obstructive pulmonary disease (COPD) is a growing cause of morbidity and mortality worldwide. Cigarette smoke (CS) exposure, a major cause of COPD, dysregulates airway epithelial ion transport and diminishes airway surface liquid (ASL) volume. Short palate lung and nasal epithelial clone 1 (SPLUNC1) is secreted into the airway lumen where it maintains airway hydration via interactions with the epithelial Na+ channel (ENaC). Although ASL hydration is dysregulated in CS-exposed/COPD airways, effects of CS on SPLUNC1 have not been elucidated. We hypothesized that CS alters SPLUNC1 activity, therefore contributing to ASL dehydration. CS exposure caused irreversible SPLUNC1 aggregation and prevented SPLUNC1 from internalizing ENaC and maintaining ASL hydration. Proteomic analysis revealed αβ-unsaturated aldehyde modifications to SPLUNC1's cysteine residues. Removal of these cysteines prevented SPLUNC1 from regulating ENaC/ASL volume. In contrast, SPX-101, a peptide mimetic of natural SPLUNC1, that internalizes ENaC, but does not contain cysteines was unaffected by CS. SPX-101 increased ASL hydration and attenuated ENaC activity in airway cultures after CS exposure and prolonged survival in a chronic airway disease model. These findings suggest that the CS-induced defects in SPLUNC1 can be circumvented, thus making SPX-101 a novel candidate for the treatment of mucus dehydration in COPD. -Moore, P. J., Reidel, B., Ghosh, A., Sesma, J., Kesimer, M., Tarran, R. Cigarette smoke modifies and inactivates SPLUNC1, leading to airway dehydration.

A candidate gene identification strategy utilizing mouse to human big-data mining: "3R-tenet" in COPD genetic research

Background

Early life impairments leading to lower lung function by adulthood are considered as risk factors for chronic obstructive pulmonary disease (COPD). Recently, we compared the lung transcriptomic profile between two mouse strains with extreme total lung capacities to identify plausible pulmonary function determining genes using microarray analysis (GSE80078). Advancement of high-throughput techniques like deep sequencing (eg. RNA-seq) and microarray have resulted in an explosion of genomic data in the online public repositories which however remains under-exploited. Strategic curation of publicly available genomic data with a mouse-human translational approach can effectively implement “3R- Tenet” by reducing screening experiments with animals and performing mechanistic studies using physiologically relevant in vitro model systems. Therefore, we sought to analyze the association of functional variations within human orthologs of mouse lung function candidate genes in a publicly available COPD lung RNA-seq data-set.

Methods

Association of missense single nucleotide polymorphisms, insertions, deletions, and splice junction variants were analyzed for susceptibility to COPD using RNA-seq data of a Korean population (GSE57148). Expression of the associated genes were studied using the Gene Paint (mouse embryo) and Human Protein Atlas (normal adult human lung) databases. The genes were also assessed for replication of the associations and expression in COPD−/mouse cigarette smoke exposed lung tissues using other datasets.

Results

Significant association (p <  0.05) of variations in 20 genes to higher COPD susceptibility have been detected within the investigated cohort. Association of HJURP, MCRS1 and TLR8 are novel in relation to COPD. The associated ADAM19 and KIT loci have been reported earlier. The remaining 15 genes have also been previously associated to COPD. Differential transcript expression levels of the associated genes in COPD- and/ or mouse emphysematous lung tissues have been detected.

Conclusion

Our findings suggest strategic mouse-human datamining approaches can identify novel COPD candidate genes using existing datasets in the online repositories. The candidates can be further evaluated for mechanistic role through in vitro studies using appropriate primary cells/cell lines. Functional studies can be limited to transgenic animal models of only well supported candidate genes. This approach will lead to a significant reduction of animal experimentation in respiratory research.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0795-y) contains supplementary material, which is available to authorized users.

Early Postnatal Secondhand Smoke Exposure Disrupts Bacterial Clearance and Abolishes Immune Responses in Muco-Obstructive Lung Disease

Secondhand smoke (SHS) exposure has been linked to the worsening of ongoing lung diseases. However, whether SHS exposure affects the manifestation and natural history of imminent pediatric muco-obstructive airway diseases such as cystic fibrosis remains unclear. To address these questions, we exposed Scnn1b transgenic (Scnn1b-Tg⁺) mice to SHS from postnatal day (PND) 3-21 and lung phenotypes were examined at PND22. Although a majority of filtered air (FA)-exposed Scnn1b-Tg⁺ (FA-Tg⁺) mice successfully cleared spontaneous bacterial infections by PND22, the SHS-exposed Scnn1b-Tg⁺ (SHS-Tg⁺) mice failed to resolve these infections. This defect was associated with suppressed antibacterial defenses, i.e., phagocyte recruitment, IgA secretion, and Muc5b expression. Whereas the FA-Tg⁺ mice exhibited marked mucus obstruction and Th2 responses, SHS-Tg⁺ mice displayed a dramatic suppression of these responses. Mechanistically, downregulated expression of IL-33, a stimulator of type II innate lymphoid cells, in lung epithelial cells was associated with suppression of neutrophil recruitment, IgA secretions, Th2 responses, and delayed bacterial clearance in SHS-Tg⁺ mice. Cessation of SHS exposure for 21 d restored previously suppressed responses, including phagocyte recruitment, IgA secretion, and mucous cell metaplasia. However, in contrast with FA-Tg⁺ mice, the SHS-Tg⁺ mice had pronounced epithelial necrosis, alveolar space consolidation, and lymphoid hyperplasia; indicating lagged unfavorable effects of early postnatal SHS exposure in later life. Collectively, our data show that early postnatal SHS exposure reversibly suppresses IL-33 levels in airspaces which, in turn, results in reduced neutrophil recruitment and diminished Th2 response. Our data indicate that household smoking may predispose neonates with muco-obstructive lung disease to bacterial exacerbations.

Airway mucus, inflammation and remodeling: emerging links in the pathogenesis of chronic lung diseases

Airway mucus obstruction is a hallmark of many chronic lung diseases including rare genetic disorders such as cystic fibrosis (CF) and primary ciliary dyskinesia, as well as common lung diseases such as asthma and chronic obstructive pulmonary disease (COPD), which have emerged as a leading cause of morbidity and mortality worldwide. However, the role of excess airway mucus in the in vivo pathogenesis of these diseases remains poorly understood. The generation of mice with airway-specific overexpression of epithelial Na⁺ channels (ENaC), exhibiting airway surface dehydration (mucus hyperconcentration), impaired mucociliary clearance (MCC) and mucus plugging, led to a model of muco-obstructive lung disease that shares key features of CF and COPD. In this review, we summarize recent progress in the understanding of causes of impaired MCC and in vivo consequences of airway mucus obstruction that can be inferred from studies in βENaC-overexpressing mice. These studies confirm that mucus hyperconcentration on airway surfaces plays a critical role in the pathophysiology of impaired MCC, mucus adhesion and airway plugging that cause airflow obstruction and provide a nidus for bacterial infection. In addition, these studies support the emerging concept that excess airway mucus per se, probably via several mechanisms including hypoxic epithelial necrosis, retention of inhaled irritants or allergens, and potential immunomodulatory effects, is a potent trigger of chronic airway inflammation and associated lung damage, even in the absence of bacterial infection. Finally, these studies suggest that improvement of mucus clearance may be a promising therapeutic strategy for a spectrum of muco-obstructive lung diseases.

Pharmacological and genetic reappraisals of protease and oxidative stress pathways in a mouse model of obstructive lung diseases

Protease-antiprotease imbalance and oxidative stress are considered to be major pathophysiological hallmarks of severe obstructive lung diseases including chronic obstructive pulmonary disease (COPD) and cystic fibrosis (CF), but limited information is available on their direct roles in the regulation of pulmonary phenotypes. Here, we utilized βENaC-transgenic (Tg) mice, the previously established mouse model of severe obstructive lung diseases, to produce lower-mortality but pathophysiologically highly useful mouse model by backcrossing the original line with C57/BL6J mice. C57/BL6J-βENaC-Tg mice showed higher survival rates and key pulmonary abnormalities of COPD/CF, including mucous hypersecretion, inflammatory and emphysematous phenotypes and pulmonary dysfunction. DNA microarray analysis confirmed that protease- and oxidative stress-dependent pathways are activated in the lung tissue of C57/BL6J-βENaC-Tg mice. Treatments of C57/BL6J-βENaC-Tg mice with a serine protease inhibitor ONO-3403, a derivative of camostat methylate (CM), but not CM, and with an anti-oxidant N-acetylcystein significantly improved pulmonary emphysema and dysfunction. Moreover, depletion of a murine endogenous antioxidant vitamin C (VC), by genetic disruption of VC-synthesizing enzyme SMP30 in C57/BL6J-βENaC-Tg mice, exaggerated pulmonary phenotypes. Thus, these assessments clarified that protease-antiprotease imbalance and oxidative stress are critical pathways that exacerbate the pulmonary phenotypes of C57/BL6J-βENaC-Tg mice, consistent with the characteristics of human COPD/CF.

Cigarette smoke causes acute airway disease and exacerbates chronic obstructive lung disease in neonatal mice

Epidemiological evidence demonstrates a strong link between postnatal cigarette smoke (CS) exposure and increased respiratory morbidity in young children. However, how CS induces early onset airway disease in young children, and how it interacts with endogenous risk factors, remains poorly understood. We, therefore, exposed 10-day-old neonatal wild-type and β-epithelial sodium ion channel (β-ENaC)-transgenic mice with cystic fibrosis-like lung disease to CS for 4 days. Neonatal wild-type mice exposed to CS demonstrated increased numbers of macrophages and neutrophils in the bronchoalveolar lavage fluid (BALF), which was accompanied by increased levels of Mmp12 and Cxcl1 BALF from β-ENaC-transgenic mice contained greater numbers of macrophages, which did not increase following acute CS exposure; however, there was significant increase in airway neutrophilia compared with filtered air transgenic and CS-exposed wild-type controls. Interestingly, wild-type and β-ENaC-transgenic mice demonstrated epithelial airway and vascular remodeling following CS exposure. Morphometric analysis of lung sections revealed that CS exposure caused increased mucus accumulation in the airway lumen of neonatal β-ENaC-transgenic mice compared with wild-type controls, which was accompanied by an increase in the number of goblet cells and Muc5ac upregulation. We conclude that short-term CS exposure 1) induces acute airway disease with airway epithelial and vascular remodeling in neonatal wild-type mice; and 2) exacerbates airway inflammation, mucus hypersecretion, and mucus plugging in neonatal β-ENaC-transgenic mice with chronic lung disease. Our results in neonatal mice suggest that young children may be highly susceptible to develop airway disease in response to tobacco smoke exposure, and that adverse effects may be aggravated in children with underlying chronic lung diseases.

Pinellia ternata Attenuates Mucus Secretion and Airway Inflammation after Inhaled Corticosteroid Withdrawal in COPD Rats

Inhaled corticosteroids (ICS) are widely used to manage chronic obstructive pulmonary disease (COPD). However, withdrawal of ICS generally causes various adverse effects, warranting careful management of the ICS withdrawal. Pinellia ternata, a traditional Chinese herbal medicine, has been used to treat respiratory diseases in China for centuries. Here, we investigated its role in antagonizing ICS withdrawal-induced side effects, and explored the underlying mechanisms. The rat COPD model was established using a combination of passive cigarette smoking and intratracheal instillation of lipopolysaccharide (LPS). COPD rats were treated with saline or budesonide inhalation, or with budesonide inhalation followed by saline inhalation or Pinellia ternata gavage. The number of goblet cells and the level of mucin 5AC (MUC5AC) were enhanced by budesonide withdrawal. Pinellia ternata treatment significantly blocked these effects. Further, Pinellia ternata treatment reversed budesonide withdrawal-induced increase of interleukin 1[Formula: see text] (IL-1[Formula: see text] and tumor necrosis factor [Formula: see text] (TNF-[Formula: see text]) levels in bronchoalveolar lavage fluid (BALF). Extracellular signal-regulated kinase (ERK), but neither p38 nor c-Jun N-terminal kinase (JNK), was activated by budesonide withdrawal, and the activation was blocked by Pinellia ternata treatment. The MUC5AC expression was positively correlated with goblet cell number, IL-1[Formula: see text] and TNF-[Formula: see text] levels, and ERK activity. Pinellia ternata treatment protected the airway from ICS withdrawal-induced mucus hypersecretion and airway inflammation by inhibiting ERK activation. Pinellia ternata treatment may represent a novel therapeutic strategy to prevent ICS withdrawal-induced side effects in COPD patients.

Secretory IgA from submucosal glands does not compensate for its airway surface deficiency in chronic obstructive pulmonary disease

Secretory immunoglobulin A (SIgA) reaches the airway lumen by local transcytosis across airway epithelial cells or with tracheobronchial submucosal gland secretions. In chronic obstructive pulmonary disease (COPD), deficiency of SIgA on the airway surface has been reported. However, reduction of SIgA levels in sputum and bronchoalveolar lavage (BAL) fluid has not been consistently observed. To explain this discrepancy, we analyzed BAL fluid and lung tissue from patients with COPD and control subjects. Immunohistochemical analysis of large and small airways of COPD patients showed that MUC5AC is the predominant mucin expressed by airway epithelial cells, whereas MUC5B is expressed in submucosal glands of large airways. Dual immunostaining with anti-IgA and anti-MUC5B antibodies showed reduction of IgA on the airway surface as well as accumulation of IgA within MUC5B-positive luminal mucus plugs, suggesting that luminal SIgA originates from submucosal glands in COPD patients. We found that the concentration of SIgA in BAL is inversely correlated with forced expiratory volume in 1 s (FEV₁) in COPD, but that the ratio of SIgA/MUC5B is a better predictor of FEV₁, particularly in patients with moderate COPD. Together, these findings suggest that SIgA production by submucosal glands, which are expanded in COPD, is insufficient to compensate for reduced SIgA transcytosis by airway epithelial cells. Localized SIgA deficiency on the surface of small airways is associated with COPD progression and represents a potential new therapeutic target in COPD.