Increased cytokine response of rhinovirus-infected airway epithelial cells in chronic obstructive pulmonary disease

HRV16 Impairs Macrophages Cytokine Response to a Secondary Bacterial Trigger

Human rhinovirus is frequently seen as an upper respiratory tract infection but growing evidence proves the virus can cause lower respiratory tract infections in patients with chronic inflammatory lung diseases including chronic obstructive pulmonary disease (COPD). In addition to airway epithelial cells, macrophages are crucial for regulating inflammatory responses to viral infections. However, the response of macrophages to HRV has not been analyzed in detail. We used in vitro monocyte-derived human macrophages to study the cytokine secretion of macrophages in response to the virus. Our results showed that macrophages were competent at responding to HRV, as a robust cytokine response was detected. However, after subsequent exposure to non-typeable Haemophilus influenzae (NTHi) or to LPS, HRV-treated macrophages secreted reduced levels of pro-inflammatory or regulatory cytokines. This “paralyzed” phenotype was not mimicked if the macrophages were pre-treated with LPS or CpG instead of the virus. These results begin to deepen our understanding into why patients with COPD show HRV-induced exacerbations and why they mount a defective response toward NTHi.

Proteomics of Bronchoalveolar Lavage Fluid Reveals a Lung Oxidative Stress Response in Murine Herpesvirus-68 Infection

Murine herpesvirus-68 (MHV-68) productively infects mouse lungs, exhibiting a complex pathology characteristic of both acute viral infections and chronic respiratory diseases. We sought to discover proteins differentially expressed in bronchoalveolar lavage (BAL) from mice infected with MHV-68. Mice were infected intranasally with MHV-68. After nine days, as the lytic phase of infection resolved, differential BAL proteins were identified by two-dimensional (2D) electrophoresis and mass spectrometry. Of 23 unique proteins, acute phase proteins, vitamin A transport, and oxidative stress response factors Pdx6 and EC-SOD (Sod3) were enriched. Correspondingly, iNOS2 was induced in lung tissue by seven days post-infection. Oxidative stress was partly a direct result of MHV-68 infection, as reactive oxygen species (ROS) were induced in cultured murine NIH3T3 fibroblasts and human lung A549 cells infected with MHV-68. Finally, mice infected with a recombinant MHV-68 co-expressing inflammatory cytokine murine interleukin 6 (IL6) showed exacerbated oxidative stress and soluble type I collagen characteristic of tissue recovery. Thus, oxidative stress appears to be a salient feature of MHV-68 pathogenesis, in part caused by lytic replication of the virus and IL6. Proteins and small molecules in lung oxidative stress networks therefore may provide new therapeutic targets to ameliorate respiratory virus infections.

Targeting Cytokines as Evolving Treatment Strategies in Chronic Inflammatory Airway Diseases

Cytokines are key players in the initiation and propagation of inflammation in chronic inflammatory airway diseases such as chronic obstructive pulmonary disease (COPD), bronchiectasis and allergic asthma. This makes them attractive targets for specific novel anti-inflammatory treatment strategies. Recently, both interleukin-1 (IL-1) and IL-6 have been associated with negative health outcomes, mortality and a pro-inflammatory phenotype in COPD. IL-6 in COPD was shown to correlate negatively with lung function, and IL-1beta was induced by cigarette smoke in the bronchial epithelium, causing airway inflammation. Furthermore, IL-8 has been shown to be a pro-inflammatory marker in bronchiectasis, COPD and allergic asthma. Clinical trials using specific cytokine blockade therapies are currently emerging and have contributed to reduce exacerbations and steroid use in COPD. Here, we present a review of the current understanding of the roles of cytokines in the pathophysiology of chronic inflammatory airway diseases. Furthermore, outcomes of clinical trials in cytokine blockade as novel treatment strategies for selected patient populations with those diseases will be discussed.

Modulation of airway hyperresponsiveness by rhinovirus exposure

Rhinovirus (RV) exposure has been implicated in childhood development of wheeze evoking asthma and exacerbations of underlying airways disease. Studies such as the Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) and Childhood Origins of ASThma (COAST) have identified RV as a pathogen inducing severe respiratory disease. RVs also modulate airway hyperresponsiveness (AHR), a key characteristic of such diseases. Although potential factors underlying mechanisms by which RV induces AHR have been postulated, the precise mechanisms of AHR following RV exposure remain elusive.

A challenge to RV-related research stems from inadequate models for study. While human models raise ethical concerns and are relatively difficult in terms of subject recruitment, murine models are limited by susceptibility of infection to the relatively uncommon minor group (RV-B) serotypes, strains that are generally associated with infrequent clinical respiratory virus infections. Although a transgenic mouse strain that has been developed has enhanced susceptibility for infection with the common major group (RV-A) serotypes, few studies have focused on RV in the context of allergic airways disease rather than understanding RV-induced AHR. Recently, the receptor for the virulent RV-C CDHR3, was identified, but a dearth of studies have examined RV-C-induced effects in humans.

Currently, the mechanisms by which RV infections modulate airway smooth muscle (ASM) shortening or excitation-contraction coupling remain elusive. Further, only one study has investigated the effects of RV on bronchodilatory mechanisms, with only speculation as to mechanisms underlying RV-mediated modulation of bronchoconstriction.

Inhibition of C-X-C Motif Chemokine 10 (CXCL10) Protects Mice from Cigarette Smoke-Induced Chronic Obstructive Pulmonary Disease

Background

Chronic obstructive pulmonary disease (COPD) is a type of obstructive lung disease characterized by long-term breathing problems and poor airflow. COPD can progress to persistent decline of pulmonary function. This study explored the effect of CXCL10 on COPD induced by cigarette smoke (CS) and its underlying mechanism.

Material/Methods

Wild-type (WT) mice were randomly assigned into 3 groups: the control group, the CS group, and the intervention group. Mice in the CS group were exposed to CS and mice in the CXCL10 group were exposed to CS and CXCL10 neutralizing antibody. At 24 h after the last CS exposure, body weight and lung functions of each mouse were recorded. Mice were then anesthetized for collecting bronchoalveolar lavage fluid (BALF) and lung tissues. Levels of interleukin-6 (IL-6), keratinocyte chemotactic factor (KC), and monocyte chemoattractant protein-1 (MCP-1) in supernatant and lung homogenate were detected by ELISA and real-time PCR (RT-PCR), respectively. For in vitro experiments, human bronchial epithelial cells 16HBE were stimulated with different concentrations of cigarette smoke extract (CSE) and CXCL10. Cell viability and levels of inflammatory cytokines in the cell supernatant were detected by Cell Counting Kit-8 (CCK-8) and ELISA assay, respectively.

Results

Our data showed significant weight loss and reduction of lung functions in mice in the CS group compared with those in the control group and intervention group. Increased levels of IL-6, KC, and MCP-1 in BALF and lung homogenate were observed in mice in the model group compared to those in the control group and intervention group. In vitro experiments also confirmed that CXCL10-neutralizing antibody can inhibit CSE-induced cell necrosis and activation of inflammatory cytokines.

Conclusions

Inhibited CXCL10 protects against COPD progression by decreasing secretion of inflammatory factors, which provides a new direction for the clinical prevention and treatment of COPD.

Redox Biology of Respiratory Viral Infections

Respiratory viruses cause infections of the upper or lower respiratory tract and they are responsible for the common cold—the most prevalent disease in the world. In many cases the common cold results in severe illness due to complications, such as fever or pneumonia. Children, old people, and immunosuppressed patients are at the highest risk and require fast diagnosis and therapeutic intervention. However, the availability and efficiencies of existing therapeutic approaches vary depending on the virus. Investigation of the pathologies that are associated with infection by respiratory viruses will be paramount for diagnosis, treatment modalities, and the development of new therapies. Changes in redox homeostasis in infected cells are one of the key events that is linked to infection with respiratory viruses and linked to inflammation and subsequent tissue damage. Our review summarizes current knowledge on changes to redox homeostasis, as induced by the different respiratory viruses.

NOTCH3 contributes to rhinovirus-induced goblet cell hyperplasia in COPD airway epithelial cells

RATIONALE

Goblet cell hyperplasia (GCH) is one of the cardinal features of chronic obstructive pulmonary disease (COPD) and contributes to airways obstruction. Rhinovirus (RV), which causes acute exacerbations in patients with COPD, also causes prolonged airways obstruction. Previously, we showed that RV enhances mucin gene expression and increases goblet cell number in a COPD mouse model. This study examines whether RV causes sustained GCH in relevant models of COPD.

METHODS

Mucociliary-differentiated COPD and normal airway epithelial cell cultures and mice with normal or COPD phenotype were infected with RV or sham and examined for GCH by immunofluorescence and/or mucin gene expression. In some experiments, RV-infected COPD cells and mice with COPD phenotype were treated with γ-secretase inhibitor or interleukin-13 neutralising antibody and assessed for GCH. To determine the contribution of NOTCH1/3 in RV-induced GCH, COPD cells transduced with NOTCH1/3 shRNA were used.

RESULTS

RV-infected COPD, but not normal cell cultures, showed sustained GCH and increased mucin genes expression. Microarray analysis indicated increased expression of NOTCH1, NOTCH3 and HEY1 only in RV-infected COPD cells. Blocking NOTCH3, but not NOTCH1, attenuated RV-induced GCH in vitro. Inhibition of NOTCH signalling by γ-secretase inhibitor, but not neutralising antibody to IL-13, abrogated RV-induced GCH and mucin gene expression.

CONCLUSIONS

RV induces sustained GCH via NOTCH3 particularly in COPD cells or mice with COPD phenotype. This may be one of the mechanisms that may contribute to RV-induced prolonged airways obstruction in COPD.

Quercetin prevents rhinovirus-induced progression of lung disease in mice with COPD phenotype

Acute exacerbations are the major cause of morbidity and mortality in patients with chronic obstructive pulmonary disease (COPD). Rhinovirus, which causes acute exacerbations may also accelerate progression of lung disease in these patients. Current therapies reduces the respiratory symptoms and does not treat the root cause of exacerbations effectively. We hypothesized that quercetin, a potent antioxidant and anti-inflammatory agent with antiviral properties may be useful in treating rhinovirus-induced changes in COPD. Mice with COPD phenotype maintained on control or quercetin diet and normal mice were infected with sham or rhinovirus, and after 14 days mice were examined for changes in lung mechanics and lung inflammation. Rhinovirus-infected normal mice showed no changes in lung mechanics or histology. In contrast, rhinovirus-infected mice with COPD phenotype showed reduction in elastic recoiling and increase in lung inflammation, goblet cell metaplasia, and airways cholinergic responsiveness compared to sham-infected mice. Interestingly, rhinovirus-infected mice with COPD phenotype also showed accumulation of neutrophils, CD11b⁺/CD11c⁺ macrophages and CD8+ T cells in the lungs. Quercetin supplementation attenuated rhinovirus-induced all the pathologic changes in mice with COPD phenotype. Together these results indicate that quercetin effectively mitigates rhinovirus-induced progression of lung disease in a mouse model of COPD. Therefore, quercetin may be beneficial in the treatment of rhinovirus-associated exacerbations and preventing progression of lung disease in COPD.

Air-Liquid Interface Culture of Human and Mouse Airway Epithelial Cells

Air-liquid interface culture enables airway epithelial cells to differentiate into a pseudostratified cell layer, consisting of ciliated cells, goblet/secretory cells, and basal cells (Ghio et al., Part Fibre Toxicol 10:25, 2013). This technique is critically important for in vitro studies of lung diseases such as asthma, chronic obstructive pulmonary disease, and cystic fibrosis, since differentiated airway epithelial cells are more representative of the in vivo lung environment than non-differentiated cells (Derichs et al., FASEB J 25:2325-2332, 2011; Hackett et al., Am J Respir Cell Mol Biol 45:1090-1100, 2011;Schneider et al., Am J Respir Crit Care Med 182: 332-340, 2010). Here we describe the process of isolating and expanding human and mouse airway epithelial cells, as well as differentiation of airway epithelial cells by air-liquid interface culture.

The Role of Nicotinamide Adenine Dinucleotide Phosphate Oxidases in Lung Architecture Remodeling

Chronic lung disorders, such as pulmonary artery hypertension (PAH), chronic obstructive pulmonary disease (COPD), asthma and neonatal bronchopulmonary dysplasia (BPD), are characterized by airway and/or vascular remodeling. Despite differences in the pathology, reactive oxygen species (ROS) have been highlighted as a critical contributor to the initiation and development of airway and vascular remodeling. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (Nox) appear to play a pivotal role in lung signaling, leading to marked changes in pulmonary airway and vascular cell phenotypes, including proliferation, hypertrophy and apoptosis. In this review, we summarized the current literature regarding the role of Nox in the airway and vascular remodeling.

Overproduction of growth differentiation factor 15 promotes human rhinovirus infection and virus-induced inflammation in the lung

Human rhinovirus (HRV) is the most common virus contributing to acute exacerbations of chronic obstructive pulmonary disease (COPD) nearly year round, but the mechanisms have not been well elucidated. Recent clinical studies suggest that high levels of growth differentiation factor 15 (GDF15) protein in the blood are associated with an increased yearly rate of all-cause COPD exacerbations. Therefore, in the current study, we investigated whether GDF15 promotes HRV infection and virus-induced lung inflammation. We first examined the role of GDF15 in regulating host defense and HRV-induced inflammation using human GDF15 transgenic mice and cultured human GDF15 transgenic mouse tracheal epithelial cells. Next, we determined the effect of GDF15 on viral replication, antiviral responses, and inflammation in human airway epithelial cells with GDF15 knockdown and HRV infection. Finally, we explored the signaling pathways involved in airway epithelial responses to HRV infection in the context of GDF15. Human GDF15 protein overexpression in mice led to exaggerated inflammatory responses to HRV, increased infectious particle release, and decreased IFN-λ2/3 (IL-28A/B) mRNA expression in the lung. Moreover, GDF15 facilitated HRV replication and inflammation via inhibiting IFN-λ1/IL-29 protein production in human airway epithelial cells. Lastly, Smad1 cooperated with interferon regulatory factor 7 (IRF7) to regulate airway epithelial responses to HRV infection partly via GDF15 signaling. Our results reveal a novel function of GDF15 in promoting lung HRV infection and virus-induced inflammation, which may be a new mechanism for the increased susceptibility and severity of respiratory viral (i.e., HRV) infection in cigarette smoke-exposed airways with GDF15 overproduction.

C-X-C motif chemokine ligand 10 produced by mouse Sertoli cells in response to mumps virus infection induces male germ cell apoptosis

Mumps virus (MuV) infection usually results in germ cell degeneration in the testis, which is an etiological factor for male infertility. However, the mechanisms by which MuV infection damages male germ cells remain unclear. The present study showed that C-X-C motif chemokine ligand 10 (CXCL10) is produced by mouse Sertoli cells in response to MuV infection, which induces germ cell apoptosis through the activation of caspase-3. CXC chemokine receptor 3 (CXCR3), a functional receptor of CXCL10, is constitutively expressed in male germ cells. Neutralizing antibodies against CXCR3 and an inhibitor of caspase-3 activation significantly inhibited CXCL10-induced male germ cell apoptosis. Furthermore, the tumor necrosis factor-α (TNF-α) upregulated CXCL10 production in Sertoli cells after MuV infection. The knockout of either CXCL10 or TNF-α reduced germ cell apoptosis in the co-cultures of germ cells and Sertoli cells in response to MuV infection. Local injection of MuV into the testes of mice confirmed the involvement of CXCL10 in germ cell apoptosis in vivo. These results provide novel insights into MuV-induced germ cell apoptosis in the testis.

Rhinovirus and COPD airway epithelium

Chronic Obstructive Pulmonary Disease (COPD) is characterized by irreversible airflow limitation. It is a global disease and expected to be the third leading cause of death. Respiratory exacerbations are associated with increased mortality and morbidity in this patient population. Respiratory viruses were isolated from at least 30 to 50% of the infectious respiratory COPD exacerbations with rhinovirus being most commonly isolated pathogen. Although rhinovirus does not cause airway epithelial damage like influenza and other respiratory viruses, it may further impair innate immunity of airway epithelium, which is the first line of defense in the lungs. This may increase susceptibility to secondary bacterial infections leading to progression of lung disease. Currently, there arc no therapies available to treat rhinovirus infection in COPD and therefore understanding the mechanisms underlying RV pathogenesis in COPD is essential to identify molecular target to develop new therapeutic strategies. Quercetin, a plant polyphenol, which modulates innate immunity and effectively blocks viral replication may be useful in treating rhinovirus associated COPD exacerbations.

Use of airway epithelial cell culture to unravel the pathogenesis and study treatment in obstructive airway diseases

Asthma and chronic obstructive pulmonary disease (COPD) are considered as two distinct obstructive diseases. Both chronic diseases share a component of airway epithelial dysfunction. The airway epithelium is localized to deal with inhaled substances, and functions as a barrier preventing penetration of such substances into the body. In addition, the epithelium is involved in the regulation of both innate and adaptive immune responses following inhalation of particles, allergens and pathogens. Through triggering and inducing immune responses, airway epithelial cells contribute to the pathogenesis of both asthma and COPD. Various in vitro research models have been described to study airway epithelial cell dysfunction in asthma and COPD. However, various considerations and cautions have to be taken into account when designing such in vitro experiments. Epithelial features of asthma and COPD can be modelled by using a variety of disease-related invoking substances either alone or in combination, and by the use of primary cells isolated from patients. Differentiation is a hallmark of airway epithelial cells, and therefore models should include the ability of cells to differentiate, as can be achieved in air-liquid interface models. More recently developed in vitro models, including precision cut lung slices, lung-on-a-chip, organoids and human induced pluripotent stem cells derived cultures, provide novel state-of-the-art alternatives to the conventional in vitro models. Furthermore, advanced models in which cells are exposed to respiratory pathogens, aerosolized medications and inhaled toxic substances such as cigarette smoke and air pollution are increasingly used to model e.g. acute exacerbations. These exposure models are relevant to study how epithelial features of asthma and COPD are affected and provide a useful tool to study the effect of drugs used in treatment of asthma and COPD. These new developments are expected to contribute to a better understanding of the complex gene-environment interactions that contribute to development and progression of asthma and COPD.

Acute cigarette smoke exposure activates apoptotic and inflammatory programs but a second stimulus is required to induce epithelial to mesenchymal transition in COPD epithelium

Background

Smoking and aberrant epithelial responses are risk factors for lung cancer as well as chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis. In these conditions, disease progression is associated with epithelial damage and fragility, airway remodelling and sub-epithelial fibrosis. The aim of this study was to assess the acute effects of cigarette smoke on epithelial cell phenotype and pro-fibrotic responses in vitro and in vivo.

Results

Apoptosis was significantly greater in unstimulated cells from COPD patients compared to control, but proliferation and CXCL8 release were not different. Cigarette smoke dose-dependently induced apoptosis, proliferation and CXCL8 release with normal epithelial cells being more responsive than COPD patient derived cells. Cigarette smoke did not induce epithelial-mesenchymal transition. In vivo, cigarette smoke exposure promoted epithelial apoptosis and proliferation. Moreover, mimicking a virus-induced exacerbation by exposing to mice to poly I:C, exaggerated the inflammatory responses, whereas expression of remodelling genes was similar in both.

Conclusions

Collectively, these data indicate that cigarette smoke promotes epithelial cell activation and hyperplasia, but a secondary stimulus is required for the remodelling phenotype associated with COPD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-017-0565-2) contains supplementary material, which is available to authorized users.

Mitochondrial alterations during oxidative stress in chronic obstructive pulmonary disease

The high incidence of chronic obstructive pulmonary disease (COPD), one of the most prevalent diseases worldwide, has attracted growing attention. Cigarette smoking is considered a major contributory factor in the pathogenesis and progression of COPD due to the tremendous oxidative burden that it causes, which induces an oxidant/antioxidant imbalance. Excessive oxidation induced by the excessive generation of mitochondrial reactive oxygen species disturbs the antioxidant systems and plays an important role in triggering and promoting chronic inflammation of airways. Given that mitochondria is one of the main sites of reactive oxygen species production by the oxidative phosphorylation process, oxidative stress may affect mitochondrial function by changing its structure and morphology and by affecting a series of mitochondrial proteins. In particular, PTEN-induced putative kinase 1/Parkin and p62 play critical roles in mitophagy. During the process, the Akt ubiquitin E3 ligase is an important mediator associated with cigarette smoke exposure-induced pulmonary endothelial cell death and dysfunction. Thus, understanding the underlying mechanisms of the signaling pathway may provide important information regarding the therapeutic treatment of COPD by application of alternative PTEN-induced putative kinase 1 targets or ubiquitin E3 ligase.

Unexpectedly Higher Morbidity and Mortality of Hospitalized Elderly Patients Associated with Rhinovirus Compared with Influenza Virus Respiratory Tract Infection

Rhinovirus is a common cause of upper and lower respiratory tract infections in adults, especially among the elderly and immunocompromised. Nevertheless, its clinical characteristics and mortality risks have not been well described. A retrospective analysis on a prospective cohort was conducted in a single teaching hospital center over a one-year period. We compared adult patients hospitalized for pneumonia caused by rhinovirus infection with those hospitalized for influenza infection during the same period. All recruited patients were followed up for at least 3 months up to 15 months. Independent risk factors associated with mortality for rhinovirus infection were identified. Between 1 March 2014 and 28 February 2015, a total of 1946 patients were consecutively included for analysis. Of these, 728 patients were hospitalized for rhinovirus infection and 1218 patients were hospitalized for influenza infection. Significantly more rhinovirus patients were elderly home residents and had chronic lung diseases (p < 0.001), whereas more influenza patients had previous stroke (p = 0.02); otherwise, there were no differences in the Charlson comorbidity indexes between the two groups. More patients in the rhinovirus group developed pneumonia complications (p = 0.03), required oxygen therapy, and had a longer hospitalization period (p < 0.001), whereas more patients in the influenza virus group presented with fever (p < 0.001) and upper respiratory tract symptoms of cough and sore throat (p < 0.001), and developed cardiovascular complications (p < 0.001). The 30-day (p < 0.05), 90-day (p < 0.01), and 1-year (p < 0.01) mortality rate was significantly higher in the rhinovirus group than the influenza virus group. Intensive care unit admission (odds ratio (OR): 9.56; 95% confidence interval (C.I.) 2.17–42.18), elderly home residents (OR: 2.60; 95% C.I. 1.56–4.33), requirement of oxygen therapy during hospitalization (OR: 2.62; 95% C.I. 1.62–4.24), and hemoglobin level <13.3 g/dL upon admission (OR: 2.43; 95% C.I. 1.16–5.12) were independent risk factors associated with 1-year mortality in patients hospitalized for rhinovirus infection. Rhinovirus infection in the adults was associated with significantly higher mortality and longer hospitalization when compared with influenza virus infection. Institutionalized older adults were particularly at risk. More stringent infection control among health care workers in elderly homes could lower the infection rate before an effective vaccine and antiviral become available.

Exacerbation of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a disease with high prevalence and substantial associated economical burden. A significant determinant of quality of life, long-term survival, and health care costs is an acute exacerbation of COPD. Acute exacerbations are provoked by respiratory viruses, altered airway microbiome, and environmental factors. The current treatment options are limited. In order to develop specific therapeutic measures, it is important to understand how acute exacerbations evolve. This review focuses on pathophysiology of stable and exacerbated COPD.

Assessment of biological responses of EpiAirway 3-D cell constructs versus A549 cells for determining toxicity of ambient air pollution

CONTEXT

EpiAirway™ 3-D constructs are human-derived cell cultures of differentiated airway epithelial cells that may represent a more biologically relevant model of the human lung. However, limited information is available on their utility for exposures to air pollutants at the air-liquid interface (ALI).

OBJECTIVE

To assess the biological responses of EpiAirway™ cells in comparison to the responses of A549 human alveolar epithelial cells after exposure to air pollutants at ALI.

METHODS

Cells were exposed to filtered air, 400 ppb of ozone (O3) or a photochemically aged Synthetic Urban Mixture (SynUrb54) consisting of hydrocarbons, nitrogen oxides, O3 and other secondary oxidation products for 4 h. Basolateral supernatants and apical washes were collected at 9 and 24 h post-exposure. We assessed cytotoxicity by measuring lactate dehydrogenase (LDH) release into the culture medium and apical surface. Interleukin 6 (IL-6) and interleukin 8 (IL-8) proteins were measured in the culture medium and in the apical washes to determine the inflammatory response after exposure.

RESULTS

Both O3 and SynUrb54 significantly increased basolateral levels of LDH and IL-8 in A549 cells. No significant changes in LDH and IL-8 levels were observed in the EpiAirway™ cells, however, IL-6 in the apical surface was significantly elevated at 24 h after O3 exposure.

CONCLUSION

LDH and IL-8 are robust endpoints for assessing toxicity in A549 cells. The EpiAirway™ cells show minimal adverse effects after exposure suggesting that they are more toxicologically resistant compared to A549 cells. Higher concentrations or longer exposure times are needed to induce effects on EpiAirway™ cells.

The main rhinovirus respiratory tract adhesion site (ICAM-1) is upregulated in smokers and patients with chronic airflow limitation (CAL)

BACKGROUND

ICAM-1 is a major receptor for ~60% of human rhinoviruses, and non-typeable Haemophilus influenzae, two major pathogens in COPD. Increased cell-surface expression of ICAM-1 in response to tobacco smoke exposure has been suggested. We have investigated epithelial ICAM-1 expression in both the large and small airways, and lung parenchyma in smoking-related chronic airflow limitation (CAL) patients.

METHODS

We evaluated epithelial ICAM-1 expression in resected lung tissue: 8 smokers with normal spirometry (NLFS); 29 CAL patients (10 small-airway disease; 9 COPD-smokers; 10 COPD ex-smokers); Controls (NC): 15 normal airway/lung tissues. Immunostaining with anti-ICAM-1 monoclonal antibody was quantified with computerized image analysis. The percent and type of cells expressing ICAM-1 in large and small airway epithelium and parenchyma were enumerated, plus percentage of epithelial goblet and submucosal glands positive for ICAM- 1.

RESULTS

A major increase in ICAM-1 expression in epithelial cells was found in both large (p < 0.006) and small airways (p < 0.004) of CAL subjects compared to NC, with NLFS being intermediate. In the CAL group, both basal and luminal areas stained heavily for ICAM-1, so did goblet cells and sub-mucosal glands, however in either NC or NLFS subjects, only epithelial cell luminal surfaces stained. ICAM-1 expression on alveolar pneumocytes (mainly type II) was slightly increased in CAL and NLFS (p < 0.01). Pack-years of smoking correlated with ICAM-1 expression (r = 0.49; p < 0.03).

CONCLUSION

Airway ICAM-1 expression is markedly upregulated in CAL group, which could be crucial in rhinoviral and NTHi infections. The parenchymal ICAM-1 is affected by smoking, with no further enhancement in CAL subjects.

Rhinovirus Delays Cell Repolarization in a Model of Injured/Regenerating Human Airway Epithelium

Rhinovirus (RV), which causes exacerbation in patients with chronic airway diseases, readily infects injured airway epithelium and has been reported to delay wound closure. In this study, we examined the effects of RV on cell repolarization and differentiation in a model of injured/regenerating airway epithelium (polarized, undifferentiated cells). RV causes only a transient barrier disruption in a model of normal (mucociliary-differentiated) airway epithelium. However, in the injury/regeneration model, RV prolongs barrier dysfunction and alters the differentiation of cells. The prolonged barrier dysfunction caused by RV was not a result of excessive cell death but was instead associated with epithelial-to-mesenchymal transition (EMT)-like features, such as reduced expression of the apicolateral junction and polarity complex proteins, E-cadherin, occludin, ZO-1, claudins 1 and 4, and Crumbs3 and increased expression of vimentin, a mesenchymal cell marker. The expression of Snail, a transcriptional repressor of tight and adherence junctions, was also up-regulated in RV-infected injured/regenerating airway epithelium, and inhibition of Snail reversed RV-induced EMT-like features. In addition, compared with sham-infected cells, the RV-infected injured/regenerating airway epithelium showed more goblet cells and fewer ciliated cells. Inhibition of epithelial growth factor receptor promoted repolarization of cells by inhibiting Snail and enhancing expression of E-cadherin, occludin, and Crumbs3 proteins, reduced the number of goblet cells, and increased the number of ciliated cells. Together, these results suggest that RV not only disrupts barrier function, but also interferes with normal renewal of injured/regenerating airway epithelium by inducing EMT-like features and subsequent goblet cell hyperplasia.

Pathogenesis of Viral Infection in Exacerbations of Airway Disease

Chronic airway diseases are a significant cause of morbidity and mortality worldwide, and their prevalence is predicted to increase in the future. Respiratory viruses are the most common cause of acute pulmonary infection, and there is clear evidence of their role in acute exacerbations of inflammatory airway diseases such as asthma and chronic obstructive pulmonary disease. Studies have reported impaired host responses to virus infection in these diseases, and a better understanding of the mechanisms of these abnormal immune responses has the potential to lead to the development of novel therapeutic targets for virus-induced exacerbations. The aim of this article is to review the current knowledge regarding the role of viruses and immune modulation in acute exacerbations of chronic pulmonary diseases and to discuss exciting areas for future research and novel treatments.

TLR2 Activation Limits Rhinovirus-Stimulated CXCL-10 by Attenuating IRAK-1-Dependent IL-33 Receptor Signaling in Human Bronchial Epithelial Cells

Airway epithelial cells are the major target for rhinovirus (RV) infection and express proinflammatory chemokines and antiviral cytokines that play a role in innate immunity. Previously, we demonstrated that RV interaction with TLR2 causes ILR-associated kinase-1 (IRAK-1) depletion in both airway epithelial cells and macrophages. Further, IRAK-1 degradation caused by TLR2 activation was shown to inhibit ssRNA-induced IFN expression in dendritic cells. Therefore, in this study, we examined the role of TLR2 and IRAK-1 in RV-induced IFN-β, IFN-λ1, and CXCL-10, which require signaling by viral RNA. In airway epithelial cells, blocking TLR2 enhanced RV-induced expression of IFNs and CXCL-10. By contrast, IRAK-1 inhibition abrogated RV-induced expression of CXCL-10, but not IFNs in these cells. Neutralization of IL-33 or its receptor, ST2, which requires IRAK-1 for signaling, inhibited RV-stimulated CXCL-10 expression. In addition, RV induced expression of both ST2 and IL-33 in airway epithelial cells. In macrophages, however, RV-stimulated CXCL-10 expression was primarily dependent on TLR2/IL-1R. Interestingly, in a mouse model of RV infection, blocking ST2 not only attenuated RV-induced CXCL-10, but also lung inflammation. Finally, influenza- and respiratory syncytial virus-induced CXCL-10 was also found to be partially dependent on IL-33/ST2/IRAK-1 signaling in airway epithelial cells. Together, our results indicate that RV stimulates CXCL-10 expression via the IL-33/ST2 signaling axis, and that TLR2 signaling limits RV-induced CXCL-10 via IRAK-1 depletion at least in airway epithelial cells. To our knowledge, this is the first report to demonstrate the role of respiratory virus-induced IL-33 in the induction of CXCL-10 in airway epithelial cells.

Rhinovirus in the Pathogenesis and Clinical Course of Asthma

In healthy individuals, human rhinovirus (HRV) infections are the major cause of the common cold. These are generally uncomplicated infections except for occasional cases of otitis media or sinusitis. In individuals with asthma, however, HRV infections can have a major impact on disease development and progression. HRV-induced wheezing illnesses in early life are a significant risk factor for subsequent development of asthma, and growing evidence supports a role of recurrent HRV infections in the development and progression of several aspects of airway remodeling in asthma. In addition, HRV infections are one of the most common triggers for acute exacerbations of asthma, which represent a major burden to health-care systems around the world. None of the currently prescribed medications for asthma are effective in preventing or reversing asthma development and airway remodeling or are ideal for treating HRV-induced exacerbations of asthma. Thus, a better understanding of the role of HRV in asthma is important if we are to develop more effective therapies. In the past decade, we have gained new insights into the role of HRV infections in the development and progression of airway remodeling as well as a new appreciation for the proinflammatory and host defense responses to HRV infections that may help to regulate susceptibility to asthma exacerbations. This article reviews the current understanding of the role HRV infections play in the pathogenesis of asthma and identifies possible avenues to new therapeutic strategies for limiting the effects of HRV infections in asthma.

Increased rhinovirus replication in nasal mucosa cells in allergic subjects is associated with increased ICAM-1 levels and endosomal acidification and is inhibited by L-carbocisteine

Increased viral replication and cytokine production may be associated with the pathogenesis of asthma attacks in rhinovirus (RV) infections. However, the association between increased RV replication and enhanced expression of intercellular adhesion molecule‐1 (ICAM‐1), a receptor for a major RV group, in airway epithelial cells has remained unclear. Furthermore, the inhibitory effects of mucolytics, which have clinical benefits in asthmatic subjects, are uncertain. Human nasal epithelial (HNE) cells were infected with type 14 rhinovirus (RV14), a major RV group. RV14 titers and cytokine concentrations, including interleukin (IL)‐6 and IL‐8, in supernatants, RV14 RNA replication and susceptibility to RV14 infection were higher in HNE cells obtained from subjects in the allergic group (allergic subjects) than in those from subjects in the non‐allergic group (non‐allergic subjects). ICAM‐1 expression and the number and fluorescence intensity of acidic endosomes from which RV14 RNA enters the cytoplasm were higher in HNE cells from allergic subjects, though substantial amounts of interferon (IFN)‐γ and IFN‐λ were not detected in the supernatant. The abundance of p50 and p65 subunits of transcription factor nuclear factor kappa B (NF‐κB) in nuclear extracts of the cells from allergic subjects was higher compared to non‐allergic subjects, and an inhibitor of NF‐κB, caffeic acid phenethyl ester, reduced the fluorescence intensity of acidic endosomes as well as RV titers and RNA. Furthermore, a mucolytic agent, L‐carbocisteine, reduced RV14 titers and RNA levels, cytokine release, ICAM‐1 expression, the fluorescence intensity of acidic endosomes, and NF‐κB activation. The increased RV14 replication observed in HNE cells from allergic subjects might be partly associated with enhanced ICAM‐1 expression and decreased endosomal pH through NF‐κB activation. L‐Carbocisteine inhibits RV14 infection by reducing ICAM‐1 and acidic endosomes and may, therefore, modulate airway inflammation caused by RV infection in allergic subjects.

The role of viral infections in exacerbations of chronic obstructive pulmonary disease and asthma

Asthma and chronic obstructive pulmonary disease (COPD) are major causes of global morbidity and mortality worldwide. The clinical course of both asthma and COPD are punctuated by the occurrence of exacerbations, acute events characterized by increased symptoms and airflow obstruction. Exacerbations contribute most of the morbidity, mortality and excess healthcare costs associated with both asthma and COPD. COPD and asthma exacerbations are frequently associated with respiratory virus infections and this has led to an intense research focus into the mechanisms of virus-induced exacerbations over the past decade. Current therapies are effective in reducing chronic symptoms but are less effective in preventing exacerbations, particularly in COPD. Understanding the mechanisms of virus-induced exacerbation will lead to the development of new targeted therapies that can reduce the burden of virus-induced exacerbations. In this review we discuss current knowledge of virus-induced exacerbations of asthma and COPD with a particular focus on mechanisms, human studies, virus-bacteria interactions and therapeutic advances.

Altered Expression of IFN-λ2 in Allergic Airway Disorders and Identification of Its Cell Origins

This study investigated the expression levels of interferon- (IFN-) λ2 in peripheral blood and tissues. The results showed that the levels of IFN-λ2 were elevated by 17.9% and 14.2% in the plasma of allergic rhinitis (AR) and combined rhinitis with asthma (AR + AS), which was positively correlated with the level of tryptase but negatively correlated with the level of IL-10. IFN-λ2 was predominately expressed in the CD16+ cells and CD14+ cells in healthy control subjects (HC) but upregulated only in CD8+ cells of AR and in eosinophils of asthma. It was observed that approximately 6.6% and 7.0% dispersed tonsil cells and 5.8% and 0.44% dispersed lung cells are IFN-λ2+ mast cells and macrophages. Moreover, tryptase and agonist peptides of PAR-2 induced enhanced IFN-λ2 mRNA expression in A549 cells. In conclusion, the elevated levels of IFN-λ2 in the plasma of AR and AR + AS indicate that IFN-λ2 is likely to contribute to the pathogenesis of allergic airway disorders. The potential origins of the elevated plasma IFN-λ2 include mast cells, macrophages, and epithelial cells in tissues, neutrophils, monocytes, CD8+ T cells, and eosinophils in peripheral blood. Development of IFN-λ2 related therapy may help to treat or prevent allergic airway disorders.

Critical role of RIG-I-like receptors in inflammation in chronic obstructive pulmonary disease

INTRODUCTION

Viral infection is a significant cause of chronic obstructive pulmonary disease (COPD) and acute exacerbation of COPD. Retinoic acid inducible gene I (RIG-I)-like receptors (RLRs), including RIG-I and melanoma differentiation associated gene 5 (MDA-5), are important pattern recognition receptors for viral elimination.

OBJECTIVE

The study aims to investigate the role of RIG-I and MDA-5 in COPD pathogenesis.

METHODS

We examined the expression of RIG-I and MDA-5 by immunohistochemistry, real-time PCR and Western blots in COPD patients and control subjects.

RESULTS

Our results showed that MDA-5 expression was upregulated in lung tissues and peripheral blood mononuclear cells of COPD patients and there was a negative correlation between MDA-5 mRNA levels and forced expiratory volume in 1 s %pred. COPD patients had higher interleukin (IL)-1 and IL-8 mRNA expression levels, and these inflammatory cytokines positively correlate with MDA-5 levels. However, there was no difference in the expression of RIG-I between COPD patients and control subjects.

CONCLUSION

Our results suggested that MDA-5, but not RIG-I, may play a critical role in airway inflammation in COPD.

Will chronic e-cigarette use cause lung disease?

Chronic tobacco smoking is a major cause of preventable morbidity and mortality worldwide. In the lung, tobacco smoking increases the risk of lung cancer, and also causes chronic obstructive pulmonary disease (COPD), which encompasses both emphysema and chronic bronchitis. E-cigarettes (E-Cigs), or electronic nicotine delivery systems, were developed over a decade ago and are designed to deliver nicotine without combusting tobacco. Although tobacco smoking has declined since the 1950s, E-Cig usage has increased, attracting both former tobacco smokers and never smokers. E-Cig liquids (e-liquids) contain nicotine in a glycerol/propylene glycol vehicle with flavorings, which are vaporized and inhaled. To date, neither E-Cig devices, nor e-liquids, are regulated by the Food and Drug Administration (FDA). The FDA has proposed a deeming rule, which aims to initiate legislation to regulate E-Cigs, but the timeline to take effect is uncertain. Proponents of E-Cigs say that they are safe and should not be regulated. Opposition is varied, with some opponents proposing that E-Cig usage will introduce a new generation to nicotine addiction, reversing the decline seen with tobacco smoking, or that E-Cigs generally may not be safe and will trigger diseases like tobacco. In this review, we shall discuss what is known about the effects of E-Cigs on the mammalian lung and isolated lung cells in vitro. We hope that collating this data will help illustrate gaps in the knowledge of this burgeoning field, directing researchers toward answering whether or not E-Cigs are capable of causing disease.

Interferon response of the cystic fibrosis bronchial epithelium to major and minor group rhinovirus infection

Rhinoviruses (RVs) are associated with exacerbations of cystic fibrosis (CF), asthma and COPD. There is growing evidence suggesting the involvement of the interferon (IFN) pathway in RV-associated morbidity in asthma and COPD. The mechanisms of RV-triggered exacerbations in CF are poorly understood. In a pilot study, we assessed the antiviral response of CF and healthy bronchial epithelial cells (BECs) to RV infection, we measured the levels of IFNs, pattern recognition receptors (PRRs) and IFN-stimulated genes (ISGs) upon infection with major and minor group RVs and poly(IC) stimulation. Major group RV infection of CF BECs resulted in a trend towards a diminished IFN response at the level of IFNs, PRRs and ISGs in comparison to healthy BECs. Contrary to major group RV, the IFN pathway induction upon minor group RV infection was significantly increased at the level of IFNs and PRRs in CF BECs compared to healthy BECs.

A short-term mouse model that reproduces the immunopathological features of rhinovirus-induced exacerbation of COPD

Viral exacerbations of chronic obstructive pulmonary disease (COPD), commonly caused by rhinovirus (RV) infections, are poorly controlled by current therapies. This is due to a lack of understanding of the underlying immunopathological mechanisms. Human studies have identified a number of key immune responses that are associated with RV-induced exacerbations including neutrophilic inflammation, expression of inflammatory cytokines and deficiencies in innate anti-viral interferon. Animal models of COPD exacerbation are required to determine the contribution of these responses to disease pathogenesis. We aimed to develop a short-term mouse model that reproduced the hallmark features of RV-induced exacerbation of COPD. Evaluation of complex protocols involving multiple dose elastase and lipopolysaccharide (LPS) administration combined with RV1B infection showed suppression rather than enhancement of inflammatory parameters compared with control mice infected with RV1B alone. Therefore, these approaches did not accurately model the enhanced inflammation associated with RV infection in patients with COPD compared with healthy subjects. In contrast, a single elastase treatment followed by RV infection led to heightened airway neutrophilic and lymphocytic inflammation, increased expression of tumour necrosis factor (TNF)-α, C-X-C motif chemokine 10 (CXCL10)/IP-10 (interferon γ-induced protein 10) and CCL5 [chemokine (C-C motif) ligand 5]/RANTES (regulated on activation, normal T-cell expressed and secreted), mucus hypersecretion and preliminary evidence for increased airway hyper-responsiveness compared with mice treated with elastase or RV infection alone. In summary, we have developed a new mouse model of RV-induced COPD exacerbation that mimics many of the inflammatory features of human disease. This model, in conjunction with human models of disease, will provide an essential tool for studying disease mechanisms and allow testing of novel therapies with potential to be translated into clinical practice.

Airway epithelial cell PPARγ modulates cigarette smoke-induced chemokine expression and emphysema susceptibility in mice

Chronic obstructive pulmonary disease (COPD) is a highly prevalent, chronic inflammatory lung disease with limited existing therapeutic options. While modulation of peroxisome proliferator-activating receptor (PPAR)-γ activity can modify inflammatory responses in several models of lung injury, the relevance of the PPARG pathway in COPD pathogenesis has not been previously explored. Mice lacking Pparg specifically in airway epithelial cells displayed increased susceptibility to chronic cigarette smoke (CS)-induced emphysema, with excessive macrophage accumulation associated with increased expression of chemokines, Ccl5, Cxcl10, and Cxcl15. Conversely, treatment of mice with a pharmacological PPARγ activator attenuated Cxcl10 and Cxcl15 expression and macrophage accumulation in response to CS. In vitro, CS increased lung epithelial cell chemokine expression in a PPARγ activation-dependent fashion. The ability of PPARγ to regulate CS-induced chemokine expression in vitro was not specifically associated with peroxisome proliferator response element (PPRE)-mediated transactivation activity but was correlated with PPARγ-mediated transrepression of NF-κB activity. Pharmacological or genetic activation of PPARγ activity abrogated CS-dependent induction of NF-κB activity. Regulation of NF-κB activity involved direct PPARγ-NF-κB interaction and PPARγ-mediated effects on IKK activation, IκBα degradation, and nuclear translocation of p65. Our data indicate that PPARG represents a disease-relevant pathophysiological and pharmacological target in COPD. Its activation state likely contributes to NF-κB-dependent, CS-induced chemokine-mediated regulation of inflammatory cell accumulation.

Virus-induced modulation of lower airway diseases: pathogenesis and pharmacologic approaches to treatment

Uncomplicated upper respiratory viral infections are the most common cause of days lost from work and school and exert a major economic burden. In susceptible individuals, however, common respiratory viruses, particularly human rhinoviruses, also can have a major impact on diseases that involve the lower airways, including asthma, chronic obstructive pulmonary diseases (COPD) and cystic fibrosis (CF). Respiratory virus-induced wheezing illnesses in early life are a significant risk factor for the subsequent development of asthma, and virus infections may also play a role in the development and progression of airway remodeling in asthma. It is clear that upper respiratory tract virus infections can spread to the lower airway and trigger acute attacks of asthma, COPD or CF. These exacerbations can be life-threatening, and exert an enormous burden on health care systems. In recent years we have gained new insights into the mechanisms by which respiratory viruses may induce acute exacerbations of lower airway diseases, as well as into host defense pathways that may regulate the outcomes to viral infections. In the current article we review the role of viruses in lower airway diseases, including our current understanding on pathways by which they may cause remodeling and trigger acute exacerbations. We also review the efficacy of current and emerging therapies used to treat these lower airway diseases on the outcomes due to viral infection, and discuss alternative therapeutic approaches for the management of virus-induced airway inflammation.

The role of airway epithelial cells and innate immune cells in chronic respiratory disease

An abnormal immune response to environmental agents is generally thought to be responsible for causing chronic respiratory diseases, such as asthma and chronic obstructive pulmonary disease (COPD). Based on studies of experimental models and human subjects, there is increasing evidence that the response of the innate immune system is crucial for the development of this type of airway disease. Airway epithelial cells and innate immune cells represent key components of the pathogenesis of chronic airway disease and are emerging targets for new therapies. In this Review, we summarize the innate immune mechanisms by which airway epithelial cells and innate immune cells regulate the development of chronic respiratory diseases. We also explain how these pathways are being targeted in the clinic to treat patients with these diseases.

Respiratory viruses in exacerbations of non-cystic fibrosis bronchiectasis in children

BACKGROUND

Respiratory viral infections precipitate exacerbations of chronic respiratory diseases such as asthma and chronic obstructive pulmonary disease though similar data in non-cystic fibrosis (CF) bronchiectasis are missing. Our study aimed to determine the point prevalence of viruses associated with exacerbations and evaluate clinical and investigational differences between virus-positive and -negative exacerbations in children with bronchiectasis.

METHODS

A cohort of 69 children (median age 7 years) with non-CF bronchiectasis was prospectively followed for 900 child-months. PCR for 16 respiratory viruses was performed on nasopharyngeal aspirates collected during 77 paediatric pulmonologist-defined exacerbations. Clinical data, systemic (C reactive protein (CRP), IL-6, procalcitonin, amyloid-A, fibrinogen) and lung function parameters were also collected.

FINDINGS

Respiratory viruses were detected during 37 (48%) exacerbations: human rhinovirus (HRV) in 20; an enterovirus or bocavirus in four each; adenoviruses, metapneumovirus, influenza A virus, respiratory syncytial virus, parainfluenza virus 3 or 4 in two each; coronavirus or parainfluenza virus 1 and 2 in one each. Viral codetections occurred in 6 (8%) exacerbations. HRV-As (n=9) were more likely to be present than HRV-Cs (n=2). Children with virus-positive exacerbations were more likely to require hospitalisation (59% vs 32.5% (p=0.02)) and have fever (OR 3.1, 95% CI 1.2 to 11.1), hypoxia (OR 25.5, 95% CI 2.0 to 322.6), chest signs (OR 3.3, 95% CI 1.1 to 10.2) and raised CRP (OR 4.7, 95% CI 1.7 to 13.1) when compared with virus-negative exacerbations.

INTERPRETATION

Respiratory viruses are commonly detected during pulmonary exacerbations of children with bronchiectasis. HRV-As were the most frequently detected viruses with viral codetection being rare. Time-sequenced cohort studies are needed to determine the role of viral-bacterial interactions in exacerbations of bronchiectasis.

Inflammation-related genetic variants predict toxicity following definitive radiotherapy for lung cancer

Definitive radiotherapy improves locoregional control and survival in inoperable non-small cell lung cancer (NSCLC) patients. However, radiation-induced toxicities (pneumonitis/esophagitis) are common dose-limiting inflammatory conditions. We therefore conducted a pathway-based analysis to identify inflammation-related SNPs associated with radiation-induced pneumonitis or esophagitis. 11,930 SNPs were genotyped in 201 stage I-III NSCLC patients treated with definitive radiotherapy. Validation was performed in an additional 220 NSCLC cases. After validation, 19 SNPs remained significant. A polygenic risk score (PRS) was generated to summarize the effect from validated SNPs. Significant improvements in discriminative ability were observed by adding the PRS into the clinical/epidemiological variable-based model. We then used 277 lymphoblastoid cell-lines to assess radiation sensitivity and eQTL relationships of the identified SNPs. Three genes (PRKCE,DDX58 and TNFSF7) were associated with radiation sensitivity. We concluded that inflammation-related genetic variants could contribute to the development of radiation-induced toxicities. These loci could assist in predicting those unfavorable events.

Formoterol and budesonide inhibit rhinovirus infection and cytokine production in primary cultures of human tracheal epithelial cells

BACKGROUND

Long-acting β(2) agonists (LABAs) and inhaled corticosteroids (ICSs) reduce the frequency of exacerbations of chronic obstructive pulmonary disease and bronchial asthma. However, inhibitory effects of LABAs and ICSs on the replication of rhinovirus (RV), the major cause of exacerbations, have not been demonstrated.

METHODS

Primary cultures of human tracheal epithelial cells were infected with a major group RV, type 14 rhinovirus (RV14), to examine the effects of formoterol and budesonide on RV infection and infection-induced airway inflammation.

RESULTS

Treatment with formoterol and budesonide 72 h before and after RV14 infection reduced RV14 titers and cytokine concentrations, including interleukin (IL)-1β, IL-6 and IL-8, in supernatants and viral RNA within cells. Formoterol and budesonide reduced mRNA expression and protein concentration of intercellular adhesion molecule-1 (ICAM-1), the receptor for RV14. Formoterol reduced the number and fluorescence intensity of acidic endosomes through which RV RNA enters the cytoplasm. Formoterol and budesonide reduced the activation of the nuclear factor kappa-B protein p65 in nuclear extracts. The effects of formoterol plus budesonide were additive with respect to RV14 replication, cytokine production, ICAM-1 expression, acidic endosome fluorescence intensity, and p65 activation. The selective β(2)-adrenergic receptor antagonist, ICI 118551 [erythro-dl-1-(7-methylindan-4-yloxy)-3-isopropylaminobutan-2-ol], reversed the inhibitory effects of formoterol on RV14 titers and RNA levels, the susceptibility of cells to RV14 infection, cytokine production, acidic endosomes, ICAM-1 expression, and p65 activation.

CONCLUSIONS

Formoterol and budesonide may inhibit RV infection by reducing the ICAM-1 levels and/or acidic endosomes and modulate airway inflammation associated with RV infections.

Differential responses to rhinovirus- and influenza-associated pulmonary exacerbations in patients with cystic fibrosis

RATIONALE

The mechanism by which viruses cause exacerbations of chronic airway disease and the capacity of patients with cystic fibrosis (CF) to respond to viral infection are not precisely known.

OBJECTIVES

To determine the antiviral response to infection in patients with CF.

METHODS

Sputum was collected from patients with CF with respiratory exacerbation. Viruses were detected in multiplex polymerase chain reaction (PCR)-based assays. Gene expression of 84 antiviral response genes was measured, using a focused quantitative PCR gene array.

MEASUREMENTS AND MAIN RESULTS

We examined 36 samples from 23 patients with respiratory exacerbation. Fourteen samples tested virus-positive and 22 virus-negative. When we compared exacerbations associated with rhinovirus (RV, n = 9) and influenza (n = 5) with virus-negative specimens, we found distinct patterns of antiviral gene expression. RV was associated with greater than twofold induction of five genes, including those encoding the monocyte-attracting chemokines CXCL10, CXCL11, and CXCL9. Influenza was associated with overexpression of 20 genes, including those encoding the cytokines tumor necrosis factor and IL-12; the kinases MEK, TBK-1, and STAT-1; the apoptosis proteins caspase-8 and caspase-10; the influenza double-stranded RNA receptor RIG-I and its downstream effector MAVS; and pyrin, an IFN-stimulated protein involved in influenza resistance.

CONCLUSIONS

We conclude that virus-induced exacerbations of CF are associated with immune responses tailored to specific infections. Influenza induced a more potent response consisting of inflammation, whereas RV infection had a pronounced effect on chemokine expression. As far as we are aware, this study is the first to compare specific responses to different viruses in live patients with chronic airway disease.

Respiratory syncytial virus infections enhance cigarette smoke induced COPD in mice

Respiratory syncytial viral (RSV) infections are a frequent cause of chronic obstructive pulmonary disease (COPD) exacerbations, which are a major factor in disease progression and mortality. RSV is able to evade antiviral defenses to persist in the lungs of COPD patients. Though RSV infection has been identified in COPD, its contribution to cigarette smoke-induced airway inflammation and lung tissue destruction has not been established. Here we examine the long-term effects of cigarette smoke exposure, in combination with monthly RSV infections, on pulmonary inflammation, protease production and remodeling in mice. RSV exposures enhanced the influx of macrophages, neutrophils and lymphocytes to the airways of cigarette smoke exposed C57BL/6J mice. This infiltration of cells was most pronounced around the vasculature and bronchial airways. By itself, RSV caused significant airspace enlargement and fibrosis in mice and these effects were accentuated with concomitant smoke exposure. Combined stimulation with both smoke and RSV synergistically induced cytokine (IL-1α, IL-17, IFN-γ, KC, IL-13, CXCL9, RANTES, MIF and GM-CSF) and protease (MMP-2, -8, -12, -13, -16 and cathepsins E, S, W and Z) expression. In addition, RSV exposure caused marked apoptosis within the airways of infected mice, which was augmented by cigarette smoke exposure. RSV and smoke exposure also reduced protein phosphatase 2A (PP2A) and protein tyrosine phosphates (PTP1B) expression and activity. This is significant as these phosphatases counter smoke-induced inflammation and protease expression. Together, these findings show for the first time that recurrent RSV infection markedly enhances inflammation, apoptosis and tissue destruction in smoke-exposed mice. Indeed, these results indicate that preventing RSV transmission and infection has the potential to significantly impact on COPD severity and progression.

Combined exposure to cigarette smoke and nontypeable Haemophilus influenzae drives development of a COPD phenotype in mice

BACKGROUND

Cigarette smoke (CS) is the major etiologic factor of chronic obstructive pulmonary disease (COPD). CS-exposed mice develop emphysema and mild pulmonary inflammation but no airway obstruction, which is also a prominent feature of COPD. Therefore, CS may interact with other factors, particularly respiratory infections, in the pathogenesis of airway remodeling in COPD.

METHODS

C57BL/6 mice were exposed to CS for 2 h a day, 5 days a week for 8 weeks. Mice were also exposed to heat-killed non-typeable H. influenzae (HK-NTHi) on days 7 and 21. One day after the last exposure to CS, mice were sacrificed and lung inflammation and mechanics, emphysematous changes, and goblet cell metaplasia were assessed. Mice exposed to CS or HK-NTHi alone or room air served as controls. To determine the susceptibility to viral infections, we also challenged these mice with rhinovirus (RV).

RESULTS

Unlike mice exposed to CS or HK-NTHi alone, animals exposed to CS/HK-NTHi developed emphysema, lung inflammation and goblet cell metaplasia in both large and small airways. CS/HK-NTHi-exposed mice also expressed increased levels of mucin genes and cytokines compared to mice in other groups. CS/HK-NTHi-exposed mice infected with RV demonstrated increased viral persistence, sustained neutrophilia, and further increments in mucin gene and chemokine expression compared to other groups.

CONCLUSIONS

These findings indicate that in addition to CS, bacteria may also contribute to development of COPD, particularly changes in airways. Mice exposed to CS/HK-NTHi are also more susceptible to subsequent viral infection than mice exposed to either CS or HK-NTHi alone.

Nod-like receptor X-1 is required for rhinovirus-induced barrier dysfunction in airway epithelial cells

Barrier dysfunction of airway epithelium may increase the risk for acquiring secondary infections or allergen sensitization. Both rhinovirus (RV) and polyinosinic-polycytidilic acid [poly(I·C)], a double-stranded RNA (dsRNA) mimetic, cause airway epithelial barrier dysfunction, which is reactive oxygen species (ROS) dependent, implying that dsRNA generated during RV replication is sufficient for disrupting barrier function. We also demonstrated that RV or poly(I·C)-stimulated NADPH oxidase 1 (NOX-1) partially accounts for RV-induced ROS generation. In this study, we identified a dsRNA receptor(s) contributing to RV-induced maximal ROS generation and thus barrier disruption. We demonstrate that genetic silencing of the newly discovered dsRNA receptor Nod-like receptor X-1 (NLRX-1), but not other previously described dsRNA receptors, abrogated RV-induced ROS generation and reduction of transepithelial resistance (R(T)) in polarized airway epithelial cells. In addition, both RV and poly(I·C) stimulated mitochondrial ROS, the generation of which was dependent on NLRX-1. Treatment with Mito-Tempo, an antioxidant targeted to mitochondria, abolished RV-induced mitochondrial ROS generation, reduction in R(T), and bacterial transmigration. Furthermore, RV infection increased NLRX-1 localization to the mitochondria. Additionally, NLRX-1 interacts with RV RNA and poly(I·C) in polarized airway epithelial cells. Finally, we show that NLRX-1 is also required for RV-stimulated NOX-1 expression. These findings suggest a novel mechanism by which RV stimulates generation of ROS, which is required for disruption of airway epithelial barrier function.

IMPORTANCE

Rhinovirus (RV), a virus responsible for a majority of common colds, disrupts the barrier function of the airway epithelium by increasing reactive oxygen species (ROS). Poly(I·C), a double-stranded RNA (dsRNA) mimetic, also causes ROS-dependent barrier disruption, implying that the dsRNA intermediate generated during RV replication is sufficient for this process. Here, we demonstrate that both RV RNA and poly(I·C) interact with NLRX-1 (a newly discovered dsRNA receptor) and stimulate mitochondrial ROS. We show for the first time that NLRX-1 is primarily expressed in the cytoplasm and at the apical surface rather than in the mitochondria and that NLRX-1 translocates to mitochondria following RV infection. Together, our results suggest a novel mechanism for RV-induced barrier disruption involving NLRX-1 and mitochondrial ROS. Although ROS is necessary for optimal viral clearance, if not neutralized efficiently, it may increase susceptibility to secondary infections and alter innate immune responses to subsequently inhaled pathogens, allergens, and other environmental factors.

Experimental rhinovirus infection in COPD: implications for antiviral therapies

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COPD exacerbations are a major cause of morbidity and mortality; new treatments are urgently needed.

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Respiratory viruses, particularly rhinoviruses, are a major cause of exacerbations.

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Experimental rhinovirus infection is a valid model of virus-induced COPD exacerbations.

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This model could be used to evaluate new antiviral treatments in COPD.

Chronic obstructive pulmonary disease (COPD) is a major public health problem and will be one of the leading global causes of mortality over the coming decades. Much of the morbidity, mortality and health care costs of COPD are attributable to acute exacerbations, the commonest causes of which are respiratory infections. Respiratory viruses are frequently detected in COPD exacerbations but direct proof of a causative relationship has been lacking. We have developed a model of COPD exacerbation using experimental rhinovirus infection in COPD patients and this has established a causative relationship between virus infection and exacerbations. In addition it has determined some of the molecular mechanisms linking virus infections to COPD exacerbations and identified potential new therapeutic targets. This new data should stimulate research into the role of antiviral agents as potential treatments for COPD exacerbations. Testing of antiviral agents has been hampered by the lack of a small animal model for rhinovirus infection and experimental rhinovirus infection in healthy volunteers has been used to test treatments for the common cold. Experimental rhinovirus infection in COPD subjects offers the prospect of a model that can be used to evaluate the effects of new treatments for virus-induced COPD exacerbations, and provide essential data that can be used in making decisions regarding large scale clinical trials.

Function of NADPH oxidase 1 in pulmonary arterial smooth muscle cells after monocrotaline-induced pulmonary vascular remodeling

AIMS

Chronic hypoxia induces pulmonary hypertension (PH) that is concomitant with pulmonary vascular remodeling. Reactive oxygen species (ROS) are thought to play a major role in this. Recent findings suggest that ROS production by NADPH oxidase 4 (Nox4) is important in this remodeling. We investigated whether ROS production by Nox is also important in an inflammatory model of monocrotaline (MCT)-induced PH. We examined ROS production, their possible sources, and their impact on the function of pulmonary arterial smooth muscle cells (PASMC) isolated from MCT-treated and healthy rats.

RESULTS

MCT-PASMC showed increased intracellular superoxide production, migration, and proliferation compared with healthy controls due to increased Nox1 expression. A comparison of PASMC from MCT- and nontreated rats revealed an up-regulation of Sod2, Nrf2, cyclin D1, and matrix metalloproteinase-9 (MMP-9) as well as an increased phosphorylation of cofilin and extracellular signal-regulated kinases (Erk). Expression of Sod2, Nrf2, and cyclin D1 and phosphorylation of cofilin and Erk were Nox1 dependent.

INNOVATION

The role of ROS in PH is not fully understood. Mitochondria and Nox have been suggested as sources of altered ROS generation in PH, yet it remains unclear whether increased or decreased ROS contributes to the development of PH. Our studies provide evidence that for different triggers of PH, different Nox isoforms regulate proliferation and migration of PASMC.

CONCLUSION

In contrast to hypoxia-induced PH, Nox1 but not Nox4 is responsible for pathophysiological proliferation and migration of PASMC in an inflammatory model of MCT-induced PH via increased superoxide production. Thus, different Nox isoforms may be targeted in different forms of PH.

Viral infections in asthma and COPD

Airway viral infections are associated with the pathogenesis of asthma and COPD. It has been argued that respiratory syncytial virus (RSV) infection in infancy is a probable causal factor in the development of pediatric asthma. RSV infections tend to induce Th2-biased immune responses in the host airways. RSV infection, atopy, and low pulmonary function in neonates may work synergistically toward the development of pediatric asthma. Human rhinovirus (HRV) is a representative virus associated with the exacerbation of asthma in both children and adults. Viral infections trigger innate immune responses including granulocytic inflammation and worsen the underlying inflammation due to asthma and COPD. The innate immune responses involve type-I and -III interferon (IFN) production, which plays an important role in anti-viral responses, and the airway epithelia of asthmatics reportedly exhibit defects in the virus-induced IFN responses, which renders these individuals more susceptible to viral infection. A similarly impaired IFN response is seen in COPD, and several investigators propose that latent adenoviral infection may be involved in COPD development. Persistent RSV infections were detected in a sub-population of patients with COPD and were associated with the accelerated decline of lung function. The virus-induced upregulation of co-inhibitory molecules in the airway epithelium partly accounts for the persistent infections. Experimental animal models for virus-asthma/COPD interactions have shed light on the underlying immune mechanisms and are expected to help develop novel approaches to treat respiratory diseases.

Airway gene expression in COPD is dynamic with inhaled corticosteroid treatment and reflects biological pathways associated with disease activity

Background

A core feature of chronic obstructive pulmonary disease (COPD) is the accelerated decline in forced expiratory volume in one second (FEV₁). The recent Groningen and Leiden Universities study of Corticosteroids in Obstructive Lung Disease (GLUCOLD) study suggested that particular phenotypes of COPD benefit from fluticasone±salmeterol by reducing the rate of FEV₁ decline, yet the underlying mechanisms are unknown.

Methods

Whole-genome gene expression profiling using the Affymetrix Gene ST array (V.1.0) was performed on 221 bronchial biopsies available from 89 COPD patients at baseline and after 6 and 30 months of fluticasone±salmeterol and placebo treatment in GLUCOLD.

Results

Linear mixed effects modelling revealed that the expression of 138 genes decreased, whereas the expression of 140 genes significantly upregulated after both 6 and 30 months of treatment with fluticasone±salmeterol versus placebo. A more pronounced treatment-induced change in the expression of 50 and 55 of these 278 genes was associated with a lower rate of decline in FEV₁ and Saint George Respiratory Questionnaire, respectively. Genes decreasing with treatment were involved in pathways related to cell cycle, oxidative phosphorylation, epithelial cell signalling, p53 signalling and T cell signalling. Genes increasing with treatment were involved in pathways related to focal adhesion, gap junction and extracellular matrix deposition. Finally, the fluticasone-induced gene expression changes were enriched among genes that change in the airway epithelium in smokers with versus without COPD in an independent data set.

Conclusions

The present study suggests that gene expression in biological pathways of COPD is dynamic with treatment and reflects disease activity. This study opens the gate to targeted and molecular phenotype-driven therapy of COPD.

Susceptibility to viral infections in chronic obstructive pulmonary disease: role of epithelial cells

PURPOSE OF REVIEW

The aim is to understand how airway epithelial cells with compromised innate defense mechanisms enhance susceptibility to respiratory virus infections in chronic obstructive pulmonary disease (COPD).

RECENT FINDINGS

Exacerbations associated with respiratory viruses are more severe and increase disease severity in COPD. Airway epithelial cells cultured from COPD patients show excessive innate immune response to viral infection and higher viral load compared with normal cells.

SUMMARY

Airway epithelial cells are the first line of defense in the lung and are equipped with several lines of innate defense mechanisms to fight against invading pathogens including viruses. Under normal conditions, mucociliary and barrier functions of airway epithelial cells prevent virus binding and entry into the cells. Virus-infected airway epithelial cells also express various cytokines, which recruit and activate innate and adaptive immune cells ultimately controlling the infection and tissue damage. In COPD however, compromised mucociliary and barrier functions may increase virus binding and allow virus entry into airway epithelial cells. Virus-infected COPD airway epithelial cells also show disproportionate cytokine expression leading to inappropriate recruitment and activation of innate and adaptive immune cells. COPD airway epithelial cells also show defective antiviral responses. Such defects in innate defense mechanisms may increase susceptibility to viral infections and disease severity in COPD.

Cytokine responses in patients with mild or severe influenza A(H1N1)pdm09

BACKGROUND

Influenza virus affects millions of people worldwide each year. More severe infection occurs in the elderly, very young and immunocompromised. In 2009, a new variant of swine origin (influenza A(H1N1)pdm09 virus) emerged that produced severe disease in young healthy adults.

OBJECTIVES

The aim of this study was to determine whether cytokine concentrations are associated with clinical outcome in patients infected influenza A(H1N1)pdm09 virus.

STUDY DESIGN

Plasma concentration of 32 cytokines and growth factors were measured using a multiplex bead immunoassay and conventional ELISA in four patient groups. Patients with severe and mild influenza A(H1N1)pdm09 virus infection, rhinovirus infection and healthy volunteers were investigated. In addition, serial samples of respiratory secretions from five patients with severe influenza A(H1N1)pdm09 virus infection were examined.

RESULTS

The majority of cytokines measured were elevated in patients with viral respiratory infections compared to the healthy controls. Concentrations of IL-6, IL-10, IL-15, IP-10, IL-2R, HGF, ST2 and MIG were significantly higher (p<0.05) and EGF significantly lower (p=0.0001) in patients with severe influenza A(H1N1)pdm09 virus infection compared to those with mild influenza A(H1N1)pdm09 virus and rhinovirus infection.

CONCLUSIONS

A number of cytokines were found to be substantially elevated in patients with severe influenza A(H1N1)pdm09 virus infection. This supports and extends other published work suggesting a role for proinflammatory cytokines in influenza-induced lung pathology. Interestingly, EGF was significantly lower in patients with severe infection suggesting it is actively suppressed. As EGF has a role in role in cell proliferation and tissue repair, it may protect the lung from host or virus mediated damage.

Repair and Remodeling of airway epithelium after injury in Chronic Obstructive Pulmonary Disease

COPD is thought to develop as a result of chronic exposure to cigarette smoke, occupational or other environmental hazards and it comprises both airways and parenchyma. Acute infections or chronic colonization of airways with bacteria may also contribute to development and/or progression of COPD lung disease. Airway epithelium is the primary target for the inhaled environmental factors and pathogens. The repetitive injury as a result of chronic exposure to environmental factors may result in persistent activation of pathways involved in airway epithelial repair, such as epithelial to mesenchymal transition, altered migration and proliferation of progenitor cells, and abnormal redifferentiation leading to airway remodeling. Development of model systems which mimics chronic airways disease as observed in COPD is required to understand the molecular mechanisms underlying the abnormal airway epithelial repair that are specific to COPD and to also develop novel therapies focused on airway epithelial repair.