Impaired nitric oxide synthase-2 signaling pathway in cystic fibrosis airway epithelium

Inflammation as a Regulator of the Airway Surface Liquid pH in Cystic Fibrosis

The airway surface liquid (ASL) is a thin sheet of fluid that covers the luminal aspect of the airway epithelium. The ASL is a site of several first-line host defenses, and its composition is a key factor that determines respiratory fitness. Specifically, the acid-base balance of ASL has a major influence on the vital respiratory defense processes of mucociliary clearance and antimicrobial peptide activity against inhaled pathogens. In the inherited disorder cystic fibrosis (CF), loss of cystic fibrosis transmembrane conductance regulator (CFTR) anion channel function reduces HCO3- secretion, lowers the pH of ASL (pHASL), and impairs host defenses. These abnormalities initiate a pathologic process whose hallmarks are chronic infection, inflammation, mucus obstruction, and bronchiectasis. Inflammation is particularly relevant as it develops early in CF and persists despite highly effective CFTR modulator therapy. Recent studies show that inflammation may alter HCO3- and H+ secretion across the airway epithelia and thus regulate pHASL. Moreover, inflammation may enhance the restoration of CFTR channel function in CF epithelia exposed to clinically approved modulators. This review focuses on the complex relationships between acid-base secretion, airway inflammation, pHASL regulation, and therapeutic responses to CFTR modulators. These factors have important implications for defining optimal ways of tackling CF airway inflammation in the post-modulator era.

HSP90 Modulates T2R Bitter Taste Receptor Nitric Oxide Production and Innate Immune Responses in Human Airway Epithelial Cells and Macrophages

Bitter taste receptors (T2Rs) are G protein-coupled receptors (GPCRs) expressed in various cell types including ciliated airway epithelial cells and macrophages. T2Rs in these two innate immune cell types are activated by bitter products, including those secreted by Pseudomonas aeruginosa, leading to Ca2+-dependent activation of endothelial nitric oxide (NO) synthase (eNOS). NO enhances mucociliary clearance and has direct antibacterial effects in ciliated epithelial cells. NO also increases phagocytosis by macrophages. Using biochemistry and live-cell imaging, we explored the role of heat shock protein 90 (HSP90) in regulating T2R-dependent NO pathways in primary sinonasal epithelial cells, primary monocyte-derived macrophages, and a human bronchiolar cell line (H441). Immunofluorescence showed that H441 cells express eNOS and T2Rs and that the bitter agonist denatonium benzoate activates NO production in a Ca2+- and HSP90-dependent manner in cells grown either as submerged cultures or at the air-liquid interface. In primary sinonasal epithelial cells, we determined that HSP90 inhibition reduces T2R-stimulated NO production and ciliary beating, which likely limits pathogen clearance. In primary monocyte-derived macrophages, we found that HSP-90 is integral to T2R-stimulated NO production and phagocytosis of FITC-labeled Escherichia coli and pHrodo-Staphylococcus aureus. Our study demonstrates that HSP90 serves as an innate immune modulator by regulating NO production downstream of T2R signaling by augmenting eNOS activation without impairing upstream Ca2+ signaling. These findings suggest that HSP90 plays an important role in airway antibacterial innate immunity and may be an important target in airway diseases such as chronic rhinosinusitis, asthma, or cystic fibrosis.

Nasal Nitric Oxide in the Upper Airway Inflammatory Diseases

Exhaled nitric oxide (eNO) from the lower respiratory tract is used commonly in diagnosis and treatment monitoring of asthma patients. However, nasal nitric oxide (nNO) has not been widely used in patients with upper airway inflammatory diseases due to its lack of standardized measurement methods. Nasal nitric oxide is produced mainly by the paranasal sinus mucosa and partially by the nasal mucosa and increases with inflammation. Nasal nitric oxide not only locally supports the defensive mechanism of the upper respiratory tract, but also remotely controls pulmonary function by acting as an aerocrine. Nasal NO can be affected by various physiologic and pathologic factors of the upper respiratory tract. This article will review the origin of nNO, its function, various measurement methods, and difference in presentation among upper respiratory tract inflammatory diseases such as allergic rhinitis, upper respiratory tract infection, nasal polyp, rhinosinusitis, primary ciliary dyskinesia, cystic fibrosis, Young’s syndrome, diffuse panbronchiolitis, empty nose syndrome, and obstructive sleep apnea. Future studies should identify the mechanism of action of nNO in various upper respiratory tract inflammatory diseases and obtain highly reproducible normal values of nNO based on a standardized measurement method with a deeper understanding of factors affecting nNO. Then, nNO will be useful for more rapid and simpler diagnosis of various upper respiratory tract diseases and for monitoring their treatment.

2-O, 3-O desulfated heparin (ODSH) increases bacterial clearance and attenuates lung injury in cystic fibrosis by restoring HMGB1-compromised macrophage function

BACKGROUND

High mobility group box 1 protein (HMGB1) is an alarmin following its release by immune cells upon cellular activation or stress. High levels of extracellular HMGB1 play a critical role in impairing the clearance of invading pulmonary pathogens and dying neutrophils in the injured lungs of cystic fibrosis (CF) and acute respiratory distress syndrome (ARDS). A heparin derivative, 2-O, 3-O desulfated heparin (ODSH), has been shown to inhibit HMGB1 release from a macrophage cell line and is efficacious in increasing bacterial clearance in a mouse model of pneumonia. Thus, we hypothesized that ODSH can attenuate the bacterial burden and inflammatory lung injury in CF and we conducted experiments to determine the underlying mechanisms.

METHODS

We determined the effects of ODSH on lung injury produced by Pseudomonas aeruginosa (PA) infection in CF mice with the transmembrane conductance regulator gene knockout (CFTR-/-). Mice were given ODSH or normal saline intraperitoneally, followed by the determination of the bacterial load and lung injury in the airways and lung tissues. ODSH binding to HMGB1 was determined using surface plasmon resonance and in silico docking analysis of the interaction of the pentasaccharide form of ODSH with HMGB1.

RESULTS

CF mice given 25 mg/kg i.p. of ODSH had significantly lower PA-induced lung injury compared to mice given vehicle alone. The CF mice infected with PA had decreased levels of nitric oxide (NO), increased levels of airway HMGB1 and HMGB1-impaired macrophage phagocytic function. ODSH partially attenuated the PA-induced alteration in the levels of NO and airway HMGB1 in CF mice. In addition, ODSH reversed HMGB1-impaired macrophage phagocytic function. These effects of ODSH subsequently decreased the bacterial burden in the CF lungs. In a surface plasmon resonance assay, ODSH interacted with HMGB1 with high affinity (KD = 3.89 × 10-8 M) and induced conformational changes that may decrease HMGB1's binding to its membrane receptors, thus attenuating HMGB1-induced macrophage dysfunction.

CONCLUSIONS

The results suggest that ODSH can significantly decrease bacterial infection-induced lung injury in CF mice by decreasing both HMGB1-mediated impairment of macrophage function and the interaction of HMGB1 with membrane receptors. Thus, ODSH could represent a novel approach for treating CF and ARDS patients that have HMGB1-mediated lung injury.

Pseudomonas aeruginosa LasB protease impairs innate immunity in mice and humans by targeting a lung epithelial cystic fibrosis transmembrane regulator-IL-6-antimicrobial-repair pathway

Background

Pseudomonas aeruginosa lung infections are a huge problem in ventilator-associated pneumonia, cystic fibrosis (CF) and in chronic obstructive pulmonary disease (COPD) exacerbations. This bacterium secretes virulence factors that may subvert host innate immunity.

Objective

We evaluated the effect of P. aeruginosa elastase LasB, an important virulence factor secreted by the type II secretion system, on ion transport, innate immune responses and epithelial repair, both in vitro and in vivo.

Methods

Wild-type (WT) or cystic fibrosis transmembrane conductance regulator (CFTR)-mutated epithelial cells (cell lines and primary cells from patients) were treated with WT or ΔLasB pseudomonas aeruginosa O1 (PAO1) secretomes. The effect of LasB and PAO1 infection was also assessed in vivo in murine models.

Results

We showed that LasB was the most abundant protein in WT PAO1 secretomes and that it decreased epithelial CFTR expression and activity. In airway epithelial cell lines and primary bronchial epithelial cells, LasB degraded the immune mediators interleukin (IL)-6 and trappin-2, an important epithelial-derived antimicrobial molecule. We further showed that an IL-6/STAT3 signalling pathway was downregulated by LasB, resulting in inhibition of epithelial cell repair. In mice, intranasally instillated LasB induced significant weight loss, inflammation, injury and death. By contrast, we showed that overexpression of IL-6 and trappin-2 protected mice against WT-PAO1-induced death, by upregulating IL-17/IL-22 antimicrobial and repair pathways.

Conclusions

Our data demonstrate that PAO1 LasB is a major P. aeruginosa secreted factor that modulates ion transport, immune response and tissue repair. Targeting this virulence factor or upregulating protective factors such as IL-6 or antimicrobial molecules such as trappin-2 could be beneficial in P. aeruginosa-infected individuals.

Viral interference and the live-attenuated intranasal influenza vaccine: Results from a pediatric cohort with cystic fibrosis

BACKGROUND

The objective of this study was to explore the effects of viral co-detection in individuals recently vaccinated with the live-attenuated intranasal influenza virus vaccine (LAIV) on the detection of influenza RNA.

METHODS

Before the 2013-2014 influenza season, nasal swabs were obtained from 59 pediatric participants with cystic fibrosis (CF) and 17 of their healthy siblings immediately before vaccination and 4 times during the week of follow-up. Real-time RT-PCR assays were used to detect influenza RNA. Co-detection of a non-influenza respiratory virus (NIRV) at the time of vaccination was determined by a multiplex RT-PCR assay. Differences in the proportions and rates of influenza detection and their 95% credible intervals (CrI) were estimated.

RESULTS

Influenza RNA was detected in 16% fewer participants (95% CrI: -7, 39%) throughout follow-up in the NIRV-positive group compared with the NIRV-negative group (59% vs. 75%). This was also observed in participants with CF alone (66% vs. 74%; RD = 8% 95% CrI: -16, 33%) as well as in healthy participants only (75% vs. 30%; RD = 45%, 95% CrI: -2, 81%). Influenza was detected in NIRV-negative subjects for 0.49 d more compared with NIRV-positive subjects (95% CrI: -0.37, 1.26).

CONCLUSION

The observed proportion of subjects in whom influenza RNA was detected and the duration of detection differed slightly between NIRV- positive and -negative subjects. However, wide credible intervals for the difference preclude definitive conclusions. If true, this observed association may be related to a recent viral respiratory infection, a phenomenon known as viral interference.

The Interaction between Respiratory Pathogens and Mucus

The interaction between respiratory pathogens and their hosts is complex and incompletely understood. This is particularly true when pathogens encounter the mucus layer covering the respiratory tract. The mucus layer provides an essential first host barrier to inhaled pathogens that can prevent pathogen invasion and subsequent infection. Respiratory mucus has numerous functions and interactions, both with the host and with pathogens. This review summarizes the current understanding of respiratory mucus and its interactions with the respiratory pathogens Pseudomonas aeruginosa, respiratory syncytial virus and influenza viruses, with particular focus on influenza virus transmissibility and host-range specificity. Based on current findings we propose that respiratory mucus represents an understudied host-restriction factor for influenza virus.

Frequency and Duration of Rhinovirus Infections in Children With Cystic Fibrosis and Healthy Controls: A Longitudinal Cohort Study

BACKGROUND

Respiratory viral infections are an important cause of morbidity in patients with chronic respiratory diseases, such as cystic fibrosis (CF). We hypothesized that patients with CF are more susceptible to human rhinovirus (HRV) infections than healthy controls.

METHODS

In a 6-month winter period, 20 young children with CF (0-7 years) and 18 age-matched healthy controls were sampled biweekly for HRV-polymerase chain reaction using nasopharyngeal swabs, irrespective of respiratory symptoms. Respiratory symptoms were scored twice a week. If any symptom was present, an additional sample was obtained. All HRV-positive samples were genotyped to distinguish HRV subtypes.

RESULTS

We analyzed 645 samples, with comparable total numbers of samples in both groups. HRV was detected in 40.8% of all analyzed samples. Children with CF had significantly more HRV-positive samples compared with healthy controls, with a mean number (± standard deviation) of 8.1 ± 2.3 versus 5.7 ± 2.9 positive samples per individual (P < 0.01). Prolonged detection (>2 weeks) with the same HRV subtype occurred more frequently in the CF patients (P < 0.01). The genetic distribution and pattern of phylogenetic diversity of the different HRV subtypes were similar in both groups.

CONCLUSIONS

This is the first in vivo longitudinal study showing that HRV is detected more frequently and persists for longer periods in CF patients compared with healthy controls. This might indicate increased viral replication and/or decreased antiviral defense in patients with CF.

Short-chain fatty acids affect cystic fibrosis airway inflammation and bacterial growth

The hypoxic environment of cystic fibrosis airways allows the persistence of facultative anaerobic bacteria, which can produce short-chain fatty acids (SCFAs) through fermentation. However, the relevance of SCFAs in cystic fibrosis lung disease is unknown. We show that SCFAs are present in sputum samples from cystic fibrosis patients in millimolar concentrations (mean±sem1.99±0.36 mM).

SCFAs positively correlated with sputum neutrophil count and higher SCFAs were predictive for impaired nitric oxide production. We studied the effects of the SCFAs acetate, propionate and butyrate on airway inflammatory responses using epithelial cell lines and primary cell cultures. SCFAs in concentrations present in cystic fibrosis airways (0.5–2.5 mM) affected the release of granulocyte-macrophage colony-stimulating factor, granulocyte colony-stimulating factor and interleukin (IL)-6. SCFAs also resulted in higher IL-8 release from stimulated cystic fibrosis transmembrane conductance regulator (CFTR) F508del-mutant compared to wild-type CFTR-corrected bronchial epithelial cells. At 25 mM propionate reduced IL-8 release in control but not primary cystic fibrosis epithelial cells. Low (0.5–2.5 mM) SCFA concentrations increased, while high (25–50 mM) concentrations decreased inducible nitric oxide synthase expression. In addition, SCFAs affected the growth ofPseudomonas aeruginosain a concentration- and pH-dependent manner.

Thus, our data suggest that SCFAs contribute to cystic fibrosis-specific alterations of responses to airway infection and inflammation.

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.

Progress towards next-generation therapeutics for cystic fibrosis

Cystic fibrosis (CF) is the most common inherited genetic condition amongst Caucasian ethnicities, affecting 1 in 2500 live births. There remains a significant unmet medical need for more and better therapies for this chronic, degenerative condition, in particular those that address the respiratory dysfunction and respiratory infections that characterise CF. CF is caused by mutations in the cystic transmembrane conductance regulator gene (CFTR). The key pathology driver of CF is dysregulated ion transport across the epithelial cell barriers that line the respiratory tract, gastrointestinal tract and other organ systems. This review focuses on the state-of-the-art advances and future directions in therapeutic strategies to combat and manage the symptoms of CF and/or restore functionality of the defective CFTR.

Biogeochemical forces shape the composition and physiology of polymicrobial communities in the cystic fibrosis lung

The cystic fibrosis (CF) lung contains thick mucus colonized by opportunistic pathogens which adapt to the CF lung environment over decades. The difficulty associated with sampling airways has impeded a thorough examination of the biochemical microhabitats these pathogens are exposed to. An indirect approach is to study the responses of microbial communities to these microhabitats, facilitated by high-throughput sequencing of microbial DNA and RNA from sputum samples. Microbial metagenomes and metatranscriptomes were sequenced from multiple CF patients, and the reads were assigned taxonomy and function through sequence homology to NCBI and the Kyoto Encyclopedia of Genes and Genomes (KEGG) database hierarchies. For a comparison, saliva microbial metagenomes from the Human Microbiome Project (HMP) were also analyzed. These analyses identified that functions encoded and expressed by CF microbes were significantly enriched for amino acid catabolism, folate biosynthesis, and lipoic acid biosynthesis. The data indicate that the community uses oxidative phosphorylation as a major energy source but that terminal electron acceptors were diverse. Nitrate reduction was the most abundant anaerobic respiratory pathway, and genes for nitrate reductase were largely assigned to Pseudomonas and Rothia. Although many reductive pathways of the nitrogen cycle were present, the cycle was incomplete, because the oxidative pathways were absent. Due to the abundant amino acid catabolism and incomplete nitrogen cycle, the CF microbial community appears to accumulate ammonia. This finding was verified experimentally using a CF bronchiole culture model system. The data also revealed abundant sensing and transport of iron, ammonium, zinc, and other metals along with a low-oxygen environment. This study reveals the core biochemistry and physiology of the CF microbiome.

The cystic fibrosis (CF) microbial community is complex and adapts to the environmental conditions of the lung over the lifetime of a CF patient. This analysis illustrates the core functions of the CF microbial community in the context of CF lung biochemistry. There are many studies of the metabolism and physiology of individual microbes within the CF lung, but none that collectively analyze data from the whole microbiome. Understanding the core metabolism of microbes that inhabit the CF lung can provide new targets for novel therapies. The fundamental processes that CF pathogens rely on for survival may represent an Achilles heel for this pathogenic community. Novel therapies that are designed to disrupt understudied survival strategies of the CF microbial community may succeed against otherwise untreatable or antibiotic-resistant microbes.

The role of respiratory viruses in adult patients with cystic fibrosis receiving intravenous antibiotics for a pulmonary exacerbation

BACKGROUND

Respiratory viruses have become increasingly recognised as important agents in pulmonary exacerbations in infants and children with CF. The aim of this study was to determine the prevalence of respiratory viruses during acute pulmonary exacerbations in adults and compare the severity of these exacerbations with non-viral associated exacerbations.

METHODS

This was a retrospective case control study. Viral throat swabs were taken from all patients presenting with an acute pulmonary exacerbation requiring intravenous antibiotic treatment over a 12 month period.

RESULTS

There were 432 pulmonary exacerbations in 180 adults. A positive viral PCR in 42 exacerbations indicated a prevalence of 9.7%. The commonest virus isolated was rhinovirus (n = 29, 69%) with influenza A/H1N1 in seven patients (16.7%). Exacerbations associated with a positive viral PCR had a greater fall in lung function at presentation with higher levels of inflammatory markers. They received more days of intravenous antibiotics, showed less response to treatment and had a shorter time to next pulmonary exacerbation compared to matched controls.

CONCLUSION

Viral associated pulmonary exacerbations in adults with CF are associated with more severe pulmonary involvement and respond less well to standard treatment.

KLF6 and iNOS regulates apoptosis during respiratory syncytial virus infection

Human respiratory syncytial virus (RSV) is a highly pathogenic lung-tropic virus that causes severe respiratory diseases. Enzymatic activity of inducible nitric oxide (iNOS) is required for NO generation. Although NO contributes to exaggerated lung disease during RSV infection, the role of NO in apoptosis during infection is not known. In addition, host trans-activator(s) required for iNOS gene expression during RSV infection is unknown. In the current study we have uncovered the mechanism of iNOS gene induction by identifying kruppel-like factor 6 (KLF6) as a critical transcription factor required for iNOS gene expression during RSV infection. Furthermore, we have also uncovered the role of iNOS as a critical host factor regulating apoptosis during RSV infection.

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.

Barrier function of airway tract epithelium

Airway epithelium contributes significantly to the barrier function of airway tract. Mucociliary escalator, intercellular apical junctional complexes which regulate paracellular permeability and antimicrobial peptides secreted by the airway epithelial cells are the three primary components of barrier function of airway tract. These three components act cooperatively to clear inhaled pathogens, allergens and particulate matter without inducing inflammation and maintain tissue homeostasis. Therefore impairment of one or more of these essential components of barrier function may increase susceptibility to infection and promote exaggerated and prolonged innate immune responses to environmental factors including allergens and pathogens resulting in chronic inflammation. Here we review the regulation of components of barrier function with respect to chronic airways diseases.

Transactivation of inducible nitric oxide synthase gene by Kruppel-like factor 6 regulates apoptosis during influenza A virus infection

Influenza A virus (flu) is a respiratory tract pathogen causing high morbidity and mortality among the human population. NO is a cellular mediator involved in tissue damage through its apoptosis of target cells and resulting enhancement of local inflammation. Inducible NO synthase (iNOS) is involved in the production of NO following infection. Although NO is a key player in the development of exaggerated lung disease during flu infection, the underlying mechanism, including the role of NO in apoptosis during infection, has not been reported. Similarly, the mechanism of iNOS gene induction during flu infection is not well defined in terms of the host transactivator(s) required for iNOS gene expression. In the current study, we identified Kruppel-like factor 6 (KLF6) as a critical transcription factor essential for iNOS gene expression during flu infection. We also underscored the requirement for iNOS in inducing apoptosis during infection. KLF6 gene silencing in human lung epithelial cells resulted in the drastic loss of NO production, iNOS promoter-specific luciferase activity, and expression of iNOS mRNA following flu infection. Chromatin immunoprecipitation assay revealed a direct interaction of KLF6 with iNOS promoter during in vitro and in vivo flu infection of human lung cells and mouse respiratory tract, respectively. A significant reduction in flu-mediated apoptosis was noted in KLF6-silenced cells, cells treated with iNOS inhibitor, and primary murine macrophages derived from iNOS knockout mice. A similar reduction in apoptosis was noted in the lungs following intratracheal flu infection of iNOS knockout mice.

Exhaled nitric oxide in pediatrics: what is new for practice purposes and clinical research in children?

Fractional exhaled NO (FeNO) is universally considered an indirect marker of eosinophilic airways inflammation, playing an important role in the physiopathology of childhood asthma. Advances in technology and standardization have allowed a wider use of FeNO in clinical practice in children from the age of four years. FeNO measurements add a new dimension to the traditional clinical tools (symptoms scores, lung function tests) in the assessment of asthma. To date a number of studies have suggested a possible use of FeNO in early identification of exacerbation risk and in inhaled corticosteroids titration. The aim of this paper is to address practical issues of interest to paediatric clinicians who are attempting to use FeNO measurements as an adjunctive tool in the diagnosis and management of childhood airway diseases.

Cystic fibrosis: a mucosal immunodeficiency syndrome

Cystic fibrosis transmembrane conductance regulator (CFTR) functions as a channel that regulates the transport of ions and the movement of water across the epithelial barrier. Mutations in CFTR, which form the basis for the clinical manifestations of cystic fibrosis, affect the epithelial innate immune function in the lung, resulting in exaggerated and ineffective airway inflammation that fails to eradicate pulmonary pathogens. Compounding the effects of excessive neutrophil recruitment, the mutant CFTR channel does not transport antioxidants to counteract neutrophil-associated oxidative stress. Whereas mutant CFTR expression in leukocytes outside of the lung does not markedly impair their function, the expected regulation of inflammation in the airways is clearly deficient in cystic fibrosis. The resulting bacterial infections, which are caused by organisms that have substantial genetic and metabolic flexibility, can resist multiple classes of antibiotics and evade phagocytic clearance. The development of animal models that approximate the human pulmonary phenotypes-airway inflammation and spontaneous infection-may provide the much-needed tools to establish how CFTR regulates mucosal immunity and to test directly the effect of pharmacologic potentiation and correction of mutant CFTR function on bacterial clearance.

An official ATS clinical practice guideline: interpretation of exhaled nitric oxide levels (FENO) for clinical applications

BACKGROUND

Measurement of fractional nitric oxide (NO) concentration in exhaled breath (Fe(NO)) is a quantitative, noninvasive, simple, and safe method of measuring airway inflammation that provides a complementary tool to other ways of assessing airways disease, including asthma. While Fe(NO) measurement has been standardized, there is currently no reference guideline for practicing health care providers to guide them in the appropriate use and interpretation of Fe(NO) in clinical practice.

PURPOSE

To develop evidence-based guidelines for the interpretation of Fe(NO) measurements that incorporate evidence that has accumulated over the past decade.

METHODS

We created a multidisciplinary committee with expertise in the clinical care, clinical science, or basic science of airway disease and/or NO. The committee identified important clinical questions, synthesized the evidence, and formulated recommendations. Recommendations were developed using pragmatic systematic reviews of the literature and the GRADE approach.

RESULTS

The evidence related to the use of Fe(NO) measurements is reviewed and clinical practice recommendations are provided.

CONCLUSIONS

In the setting of chronic inflammatory airway disease including asthma, conventional tests such as FEV(1) reversibility or provocation tests are only indirectly associated with airway inflammation. Fe(NO) offers added advantages for patient care including, but not limited to (1) detecting of eosinophilic airway inflammation, (2) determining the likelihood of corticosteroid responsiveness, (3) monitoring of airway inflammation to determine the potential need for corticosteroid, and (4) unmasking of otherwise unsuspected nonadherence to corticosteroid therapy.

Pseudomonas aeruginosa suppresses interferon response to rhinovirus infection in cystic fibrosis but not in normal bronchial epithelial cells

Despite increased morbidity associated with secondary respiratory viral infections in cystic fibrosis (CF) patients with chronic Pseudomonas aeruginosa infection, the underlying mechanisms are not well understood. Here, we investigated the effect of P. aeruginosa infection on the innate immune responses of bronchial epithelial cells to rhinovirus (RV) infection. CF cells sequentially infected with mucoid P. aeruginosa (MPA) and RV showed lower levels of interferons (IFNs) and higher viral loads than those of RV-infected cells. Unlike results for CF cells, normal bronchial epithelial cells coinfected with MPA/RV showed higher IFN expression than RV-infected cells. In both CF and normal cells, the RV-stimulated IFN response requires phosphorylation of Akt and interferon response factor 3 (IRF3). Preinfection with MPA inhibited RV-stimulated Akt phosphorylation and decreased IRF3 phosphorylation in CF cells but not in normal cells. Compared to normal, unstimulated CF cells or normal cells treated with CFTR inhibitor showed increased reactive oxygen species (ROS) production. Treatment of CF cells with antioxidants prior to MPA infection partially reversed the suppressive effect of MPA on the RV-stimulated IFN response. Together, these results suggest that MPA preinfection inhibits viral clearance by suppressing the antiviral response particularly in CF cells but not in normal cells. Further, increased oxidative stress in CF cells appears to modulate the innate immune responses to coinfection.

The airway epithelium: soldier in the fight against respiratory viruses

The airway epithelium acts as a frontline defense against respiratory viruses, not only as a physical barrier and through the mucociliary apparatus but also through its immunological functions. It initiates multiple innate and adaptive immune mechanisms which are crucial for efficient antiviral responses. The interaction between respiratory viruses and airway epithelial cells results in production of antiviral substances, including type I and III interferons, lactoferrin, β-defensins, and nitric oxide, and also in production of cytokines and chemokines, which recruit inflammatory cells and influence adaptive immunity. These defense mechanisms usually result in rapid virus clearance. However, respiratory viruses elaborate strategies to evade antiviral mechanisms and immune responses. They may disrupt epithelial integrity through cytotoxic effects, increasing paracellular permeability and damaging epithelial repair mechanisms. In addition, they can interfere with immune responses by blocking interferon pathways and by subverting protective inflammatory responses toward detrimental ones. Finally, by inducing overt mucus secretion and mucostasis and by paving the way for bacterial infections, they favor lung damage and further impair host antiviral mechanisms.

Retinoic acid inducible gene I activates innate antiviral response against human parainfluenza virus type 3

Human parainfluenza virus type 3 (HPIV3) is a respiratory paramyxovirus that infects lung epithelial cells to cause high morbidity among infants and children. To date, no effective vaccine or antiviral therapy exists for HPIV3 and therefore, it is important to study innate immune antiviral response induced by this virus in infected cells. Type-I interferons (IFN, interferon-alpha/beta) and tumor necrosis factor-alpha (TNFalpha activated by NFkappaB) are potent antiviral cytokines that play an important role during innate immune antiviral response. A wide-spectrum of viruses utilizes pattern recognition receptors (PRRs) like toll-like receptors (TLRs) and RLH (RIG like helicases) receptors such as RIGI (retinoic acid inducible gene -I) and Mda5 to induce innate antiviral response. Previously it was shown that both TNFalpha and IFNbeta are produced from HPIV3 infected cells. However, the mechanism by which infected cells activated innate response following HPIV3 infection was not known. In the current study, we demonstrated that RIGI serves as a PRR in HPIV3 infected cells to induce innate antiviral response by expressing IFNbeta (via activation of interferon regulatory factor-3 or IRF3) and TNFalpha (via activation of NF-kappaB).

Exhaled nitric oxide measurements in the first 2 years of life: methodological issues, clinical and epidemiological applications

Fractional exhaled nitric oxide (FeNO) is a useful tool to diagnose and monitor eosinophilic bronchial inflammation in asthmatic children and adults. In children younger than 2 years of age FeNO has been successfully measured both with the tidal breathing and with the single breath techniques. However, there are a number of methodological issues that need to be addressed in order to increase the reproducibility of the FeNO measurements within and between infants. Indeed, a standardized method to measure FeNO in the first 2 years of life would be extremely useful in order to meaningfully interpret FeNO values in this age group. Several factors related to the measurement conditions have been found to influence FeNO, such as expiratory flow, ambient NO and nasal contamination. Furthermore, the exposure to pre- and postnatal risk factors for respiratory morbidity has been shown to influence FeNO values. Therefore, these factors should always be assessed and their association with FeNO values in the specific study population should be evaluated and, eventually, controlled for.

There is evidence consistently suggesting that FeNO is increased in infants with family history of atopy/atopic diseases and in infants with recurrent wheezing. These findings could support the hypothesis that eosinophilic bronchial inflammation is present at an early stage in those infants at increased risk of developing persistent respiratory symptoms and asthma. Furthermore, it has been shown that FeNO measurements could represent a useful tool to assess bronchial inflammation in other airways diseases, such as primary ciliary dyskinesia, bronchopulmonary dysplasia and cystic fibrosis. Further studies are needed in order to improve the reproducibility of the measurements, and large prospective studies are warranted in order to evaluate whether FeNO values measured in the first years of life can predict the future development of asthma or other respiratory diseases.

The association of oxidative stress and nasal polyposis

Many diseases are linked to damage from reactive oxygen species that occurs from an imbalance between reactive oxygen species and antioxidants, a condition called oxidative stress. Nasal polyposis is considered to be an inflammatory condition in nasal and paranasal sinus cavities and its aetiology is still unclear. There are very few data on epithelial changes in nasal polyposis and their relationship with free radical damage. Malondialdehyde as a major end-product of lipid peroxidation, and superoxide dismutase and nitric oxide as antioxidants play important roles in oxidative stress. In this study, the concentrations of malondialdehyde, superoxide dismutase and nitric oxide were compared in normal and nasal polyposis-affected tissue samples. Malondialdehyde levels were significantly higher, and superoxide dismutase and nitric oxide levels were significantly lower in patients with nasal polyposis compared with the control group. This study demonstrates that there is a strong relationship between oxidative stress and the pathogenesis of nasal polyposis.

Azithromycin reduces exaggerated cytokine production by M1 alveolar macrophages in cystic fibrosis

Macrophages phagocyte pathogenic microorganisms and orchestrate immune responses by producing a variety of inflammatory mediators. The cystic fibrosis (CF) transmembrane conductance regulator chloride channel has been reported to be of pivotal importance for macrophage functions. The exact phenotype and role of macrophages in CF is still unknown. Alveolar and peritoneal macrophages were monitored in CF mice homozygous for the F508 del mutation and in wild-type control animals. Classical (M1) and alternative (M2) macrophage polarization and responses to LPS from Pseudomonas aeruginosa were investigated, and the effect of azithromycin was examined in both cell populations. We show that alveolar macrophage counts were 1.7-fold higher in CF as compared with wild-type mice. The macrophage-related chemokine, chemokine C-C motif ligand (CCL)-2, was found to be at least 10-fold more abundant in the alveolar space of mutant mice. Cell count and CCL-2 protein levels were also increased in the peritoneal cavity of CF mice. Both M1 and M2 macrophage polarization were significantly enhanced in alveolar and peritoneal cells from F508del-CF mice as compared with control animals. LPS-stimulated expression of proinflammatory mediators, such as nitric oxide synthase-2, IL-1beta, and CCL-2, was increased, whereas anti-inflammatory IL-10 expression was decreased in CF macrophages. Azithromycin, added to cell cultures at 1 mg/liter, significantly reduced proinflammatory cytokine expression (IL-1beta, CCL-2, TNF-alpha) in M1-induced CF and wild-type alveolar macrophages. Our findings indicate that CF macrophages are ubiquitously accumulated, and that these cells are polarized toward classical and alternative activation status. Azithromycin down-regulates inflammatory cytokine production by M1-polarized CF alveolar macrophages.

Pivotal role of c-Fos in nitric oxide synthase 2 expression in airway epithelial cells

The regulation of nitric oxide synthase 2 (NOS2) in airway epithelial cells plays a key role in the innate host response to a wide variety of microbial agents and also participates in the generation of pathologic airway inflammation. Among the important signalling cascades that direct NOS2 gene expression are nuclear factor kappaB (NFkappaB) and interferon-gamma (IFNgamma)/signal transducer and activator of transcription 1 (STAT-1). Previous studies suggest activator protein-1 (AP-1), in particular c-Fos component of AP-1, influences NOS2 expression. We investigated the effect of c-Fos modulation using RNA interference siRNA on NOS2 gene expression. A549 cells stably transfected with a plasmid overexpressing a c-Fos siRNA construct (FOSi) resulted in a decrease of NOS2 protein inducibility by IFN gamma. In contrast, classical IFN gamma inducible signal transduction pathways interferon regulated factor-1 (IRF-1) and pSTAT-1 were activated at a similar magnitude in FOSi and control cells. DNA-protein binding assays showed that c-Fos binding was present in wild type cells, but reduced in FOSi clones. FOSi clones had activation of NFkappaB detectable by DNA-protein binding assays, which may have contributed to a decrease of NOS2 expression. Overall, these studies indicate that c-Fos is a requisite and specific component for inducible NOS2 expression.

Prevalence and impact of respiratory viral infections in young children with cystic fibrosis: prospective cohort study

OBJECTIVE

We aimed to investigate differences in upper and lower respiratory tract symptoms in relation to respiratory viral infections detected with polymerase chain reaction assays in young children with cystic fibrosis and healthy control subjects.

METHODS

In a 6-month winter period, 20 young children with cystic fibrosis and 18 age-matched, healthy, control subjects were contacted twice per week for detection of symptoms of an acute respiratory illness. If any symptom was present, then a home visit was made for physical examination and collection of nasopharyngeal swabs for viral analysis. In addition, parents were instructed to collect nasopharyngeal swabs every 2 weeks.

RESULTS

Children with cystic fibrosis and healthy control subjects had similar frequencies of acute respiratory illnesses (3.8+/-1.0 and 4.2+/-1.7 episodes, respectively). Although there were no significant differences in upper respiratory tract symptoms, the children with cystic fibrosis had longer periods of lower respiratory tract symptoms (22.4+/-22.2 vs 12.8+/-13.8 days) and a higher mean severity score per episode (2.35+/-0.64 vs 1.92+/-0.46). In addition, similar increases in upper respiratory tract symptom scores were associated with significantly greater increases in lower respiratory tract symptom scores in children with cystic fibrosis. No differences in the seasonal occurrences and distributions of respiratory viruses were observed, with picornaviruses and coronaviruses being the most prevalent.

CONCLUSIONS

Although there were no differences in the seasonal occurrences and distributions of polymerase chain reaction-detected respiratory viruses, acute respiratory illnesses were frequently associated with increased lower respiratory tract morbidity in young children with cystic fibrosis.

cAMP-mediated regulation of cholesterol accumulation in cystic fibrosis and Niemann-Pick type C cells

The goal of this study was to identify a mechanism regulating cholesterol accumulation in cystic fibrosis (CF) cells. Both CFTR activation and expression are regulated by the cAMP pathway, and it is hypothesized that a feedback response involving this pathway may be involved in the phenotype of cholesterol accumulation. To examine the role of the cAMP pathway in cholesterol accumulation, we treated two CF model cell lines with the Rp diastereomer of adenosine 3',5'-cyclic monophosphorothioate (Rp-cAMPS) and visualized by filipin staining. Rp-cAMPS treatment eliminated cholesterol accumulation in CF cells, whereas 8-bromo-cAMP treatment led to cholesterol accumulation in wild-type cells. To confirm these findings in an independent model system, we also examined the role of cAMP in modulating cholesterol accumulation in Niemann-Pick type C (NPC) fibroblasts. Expression of the protein related to NPC, NPC1, is also directly regulated by cAMP; therefore, it is postulated that NPC cells exhibit the same cAMP-mediated control of cholesterol accumulation. Cholesterol accumulation in NPC cells also was reduced by the presence of Rp-cAMPS. Expression of beta-arrestin-2 (betaarr2), a marker of cellular response to cAMP signaling, was significantly elevated in CF model cells, Cftr(-/-) MNE, primary tissue obtained by nasal scrapes from CF subjects, and in NPC fibroblasts compared with respective controls.

Chronic inflammation in the cystic fibrosis lung: alterations in inter- and intracellular signaling

A vicious cycle of airway obstruction, infection, and inflammation continues to cause most of the morbidity and mortality in cystic fibrosis (CF). Mutations that result in decreased expression or function of the membrane Cl(-) channel, cystic fibrosis transmembrane regulator (CFTR), result in a decrease in the volume (and hence the depth) of liquid on the airway surface, impaired ciliary function, and dehydrated glandular secretions. In turn, these abnormalities contribute to a milieu, which promotes chronic infection with a limited but unique spectrum of microorganisms. Defects in CFTR also perturb regulation of several intracellular signaling pathways including signal transducers and activator of transcription, I-kappaB and nuclear factor-kappa B, and low molecular weight GTPases. Together, these abnormalities result in excessive production of NF-kappaB dependent cytokines such as interleukin (IL)-1, tumor necrosis factor (TNF), IL-6, and IL-8. There are decreased responses to interferon gamma and transforming growth factor beta leading to decreased production of iNOS and NO. Abnormalities of lipid mediators and decreased secretion of counter/regulatory cytokines have also been reported. Together, these effects combine to create a chronic inflammatory process, which damages and obstructs the airways, and eventually claims the life of the patient.

Prophylaxis against respiratory syncytial virus in young children with cystic fibrosis

INTRODUCTION

In cystic fibrosis (CF) patients, respiratory syncytial virus (RSV) infection is associated with significant morbidity. Although passive prophylaxis with palivizumab lowers hospitalization rate for RSV infection in populations at risk of severe infection, its use is not recommended in infants with CF disease.

OBJECTIVE

To determine the effect of palivizumab prophylaxis on hospitalization for acute respiratory illness in young children with CF during the first RSV season following the diagnosis of CF.

METHODS

In this retrospective study, medical records of patients diagnosed with CF between the years 1997 and 2005 inclusively and on whom the diagnosis was made before 18 months of age were reviewed. Collected data included age at diagnosis, palivizumab prophylaxis, occurrence of hospitalization for acute respiratory tract illness during the RSV season and identification of RSV infection.

RESULTS

A diagnosis of CF was made in 76 young children and data collected from 75 children. Of those, 40 did not receive RSV prophylaxis while 35 received palivizumab injection monthly during the RSV season. Among non-recipient children, 7 out of 40 were hospitalized for acute respiratory illness during the RSV season. Of these seven patients, RSV detection was positive in nasopharyngeal secretions in three patients, negative in one patient and not requested in the others. Among palivizumab recipients, 3 out of 35 children were hospitalized for acute respiratory illness (P > 0.05 compared to non-recipients group). In these three palivizumab recipients, RSV detection was negative in nasopharyngeal secretions. Palivizumab recipients experienced fewer hospital days per patient for acute respiratory illness (mean +/- SD: 0.8 +/- 3.07 days) as compared to non-recipients (mean +/- SD: 1.73 +/- 4.27 days) but this difference did not reach statistical significance.

CONCLUSION

CF infants may benefit from RSV immunoprophylaxis with palivizumab.

A potentiating effect of endogenous NO in the physiologic secretion from airway submucosal glands

It is known that several second messengers, such as Ca(2+) or cAMP, play important roles in the intracellular pathway of electrolyte secretion in tracheal submucosal gland. However, the participation of cGMP, and therefore nitric oxide (NO), is not well understood. To investigate the physiologic role of NO, we first examined whether tracheal glands can synthesize NO in response to acetylcholine (ACh), and then whether endogenous NO has some effects on the ACh-triggered ionic currents. From the experiments using the NO-specific fluorescent indicator 4,5-diaminofluorescein diacetate salt (DAF-2DA), we found that a physiologically relevant low dose of ACh (100 nM) stimulated the endogenous NO synthesis, and it was almost completely suppressed in the presence of the nonspecific NO synthase (NOS) inhibitor Nomega-Nitro-L-arginine Methyl Ester Hydrochloride (L-NAME) or the neuronal NOS (nNOS)-specific inhibitor 7-Nitroindazole (7-NI). Patch-clamp experiments revealed that both the NOS inhibitors (L-NAME or 7-NI) and cGK inhibitors (KT-5823 or Rp-8-Br-cGMP) partially decreased ionic currents induced by 30 nM of ACh, but not in the case of 300 nM of ACh. Our results indicate that NO can be synthesized through the activation of nNOS endogenously and has potentiating effects on the gland secretion, under a physiologically relevant ACh stimulation. When cells were stimulated by an inadequately potent dose of ACh, which caused an excess elevation in [Ca(2+)](i), the cells were desensitized. Therefore, due to NO, gland cells become more sensitive to calcium signaling and are able to maintain electrolyte secretion without desensitization.

Cystic fibrosis and normal human airway epithelial cell response to influenza a viral infection

Viral infections produce severe respiratory morbidity in children with cystic fibrosis (CF). CF cells are more susceptible to virus in part because of impaired airway epithelial activation of signal transducer and activator of transcription 1 (Stat1). As Stat1 is a fundamental regulator of antiviral defenses, we hypothesized that there may be multiple alterations in the antiviral defense of CF epithelium compared with normal (NL). To obtain a comprehensive view of mucosal host responses to influenza and characterize the difference between CF and NL responses to influenza, gene expression profiles of primary human airway epithelial cells (HAEC) were evaluated using an interferon (IFN)-stimulated genes/AU/double-stranded RNA (dsRNA) microarray or quantitative real-time polymerase chain reaction (PCR) following influenza A infection. Gene expression was significantly modified by influenza in NL (228 genes) and CF (101 genes), with a similar pattern of gene response but with overall less numbers of responsive genes in CF (p < 0.05). Moreover, CF cells had less IFN-related antiviral gene induction at 24 h but greater inflammatory cytokine gene induction at 1 h after infection. Taken together, the lesser antiviral and greater early inflammatory response likely contribute to the severe respiratory illness of CF patients with viral infections.

Role of epithelial nitric oxide in airway viral infection

The airway mucosal epithelium is the first site of virus contact with the host, and the main site of infection and inflammation. Nitric oxide (NO) produced by the airway epithelium is vital to antiviral inflammatory and immune defense in the lung. Multiple mechanisms function coordinately to support high-level basal NO synthesis in healthy airway epithelium and further induction of NO synthesis in the infected airway of normal hosts. Hosts deficient in NO synthesis, such as those patients with cystic fibrosis, have impaired antiviral defense and may benefit from therapies to augment NO levels in the airways.

Respiratory epithelial gene expression in patients with mild and severe cystic fibrosis lung disease

Despite having identical cystic fibrosis transmembrane conductance regulator genotypes, individuals with DeltaF508 homozygous cystic fibrosis (CF) demonstrate significant variability in severity of pulmonary disease. This investigation used high-density oligonucleotide microarray analysis of nasal respiratory epithelium to investigate the molecular basis of phenotypic differences in CF by (1) identifying differences in gene expression between DeltaF508 homozygotes in the most severe 20th percentile of lung disease by forced expiratory volume in 1 s and those in the most mild 20th percentile of lung disease and (2) identifying differences in gene expression between DeltaF508 homozygotes and age-matched non-CF control subjects. Microarray results from 23 participants (12 CF, 11 non-CF) met the strict quality control guidelines and were used for final data analysis. A total of 652 of the 11,867 genes identified as present in 75% of the samples were significantly differentially expressed in one of the three disease phenotypes: 30 in non-CF, 53 in mild CF, and 569 in severe CF. An analysis of genes differentially expressed by severity of CF lung disease demonstrated significant upregulation in severe CF of genes involved in protein ubiquination (P < 0.04), mitochondrial oxidoreductase activity (P < 0.01), and lipid metabolism (P < 0.03). Analysis of genes with decreased expression in patients with CF compared with control subjects demonstrated significant downregulation of genes involved in airway defense (P < 0.047) and protein metabolism (P < 0.048). This study suggests that differences in CF lung phenotype are associated with differences in expression of genes involving airway defense, protein ubiquination, and mitochondrial oxidoreductase activity and identifies specific new candidate modifiers of the CF phenotype.

Inducible NO synthase expression is low in airway epithelium from young children with cystic fibrosis

BACKGROUND

This is the first study to measure inducible nitric oxide synthase (iNOS) gene and protein expression quantitatively in primary epithelial cells from very young children with cystic fibrosis (CF). Low levels of exhaled nitric oxide (NO) in CF suggest dysregulation of NO production in the airway. Due to the importance of NO in cell homeostasis and innate immunity, any defect in the pathway associated with CF would be a potential target for treatment.

METHODS

Cells were obtained by tracheobronchial brushing from 40 children with CF of mean (SD) age 2.1 (1.5) years and from 12 healthy non-atopic children aged 3.4 (1.2) years. Expression of iNOS mRNA was measured using quantitative PCR and iNOS protein by immunofluorescence and Western blot analysis.

RESULTS

Inducible NOS mRNA expression was significantly lower in CF patients with and without bacterial infection than in healthy children (0.22 and 0.23 v 0.76; p=0.002 and p=0.01, respectively). Low levels of iNOS gene expression were accompanied by low levels of iNOS protein expression as detected by Western blot analysis.

CONCLUSIONS

These results support the findings of previous studies in adult patients with advanced disease, cell lines, and animal models. Our findings reflect the situation in children with mild lung disease. They indicate that low iNOS expression may be an innate defect in CF with potential consequences for local antimicrobial defence and epithelial cell function and provide evidence for an approach to treatment based on increasing epithelial NO production or the sensitivity of NO dependent cellular processes.

Differential effects of TNF-alpha and IFN-gamma on gene transcription mediated by NF-kappaB-Stat1 interactions

Regulation of gene transcription by the cytokines tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) involves complex interactions between NF-kappaB and Stat families of transcription factors. The purpose of this study was to identify the spatial promoter requirements that govern cytokine synergy for gene transcription regulated by NF-kappaB and Stat factors. Using a set of transcription reporter-luciferase constructs, we show that the relative orientation of juxtaposed NF-kappaB-Stat (SIE) cis-elements determines the ability of TNF-alpha and IFN- gamma to induce gene transcription. Further, NF-kappaB and Stat1 proteins directly regulate transcription by interacting cooperatively on NF-kappaB-SIE DNA binding in response to TNF-alpha plus IFN-gamma. Coimmunoprecipitation provides evidence for a direct NF-kappaB/Stat1 protein-protein interaction. In contrast, IFN-gamma inhibits TNF-alpha-induced transcription of an NF-kappaB reporter gene in a Stat1-dependent mechanism in 2fTGH fibroblasts. Similarly, Stat1 is inhibitory to NF-kappaB overexpression-induced transcription. IFN-gamma and Stat1-dependent inhibition of NF-kappaB transcription occurs independent of TNF-alpha-induced NF-kappaB DNA binding. Interestingly, IFN-gamma pretreatment of 2fTGH fibroblasts potentiates TNF-alpha induction of Stat1 DNA binding. Further, ChIP analysis was applied to detect cytokine-induced in vivo binding and transcriptional regulation of the human inducible nitric oxide synthase (iNOS) gene by NF-kappaB and Stat1. These data demonstrate complex transcriptional regulatory mechanisms elicited by TNF-alpha and IFN-gamma and have potentially important implications for other genes differentially controlled by cytokines.

Viral respiratory infections in cystic fibrosis

Viral respiratory infections in CF patients are associated with an increase in morbidity at short and long term. Viral infections have a greater impact on CF patients compared to non-CF controls. They result in increased respiratory symptoms, deterioration of Shwachman and radiological scores, prolonged hospitalizations, a persistent decrease of pulmonary function, increased use of antibiotics and a higher frequency of exacerbations at follow-up. In addition, interaction between viruses and bacteria in CF is suggested. Some studies observe increased new bacterial colonization and raised antipseudomonal antibodies in episodes of viral respiratory infections. Experimental data suggest that increased virus replication, impaired specific anti-bacterial defense and increased adherence of bacteria play a role in the pathogenesis of viral respiratory infections in CF. Further knowledge about the role of viruses and interaction with bacteria in CF lung disease might result in new therapeutic strategies to improve prognosis of CF patients.

Increased Arginase Activity in Cystic Fibrosis Airways

RATIONALE

Airway nitric oxide concentrations are reduced in cystic fibrosis (CF). Arginases compete for L-arginine, the substrate of nitric oxide synthesis.

OBJECTIVES

We hypothesized that increased arginase activity may be one factor contributing to nitric oxide deficiency in CF.

MEASUREMENTS

We therefore studied sputum arginase activity, exhaled nitric oxide, and pulmonary function in patients with cystic fibrosis.

RESULTS

Mean (+/- SEM) sputum arginase activity was significantly higher in patients admitted for pulmonary exacerbation compared with patients with stable disease (1.032 +/- 0.148 vs. 0.370 +/- 0.091 U/mg protein, p = 0.004). Fourteen days of intravenous antibiotic treatment resulted in significantly decreased sputum arginase activity in all patients (p = 0.0002). However, arginase activity was still significantly (p = 0.0001) higher in CF sputum after treatment for exacerbation compared with induced sputum from healthy control subjects (0.026 +/- 0.006 U/mg protein). Negative correlations were found for sputum arginase activity at admission with FEV1 (r = -0.41, p = 0.01), as well as changes in arginase activity with percent change in FEV1 during antibiotic therapy (r = -0.4, p < 0.01) in CF. Exhaled nitric oxide in CF was positively correlated to FEV1 (r = 0.34, p = 0.007), and in patients admitted for pulmonary exacerbation negatively correlated to sputum arginase activity (r = -0.45, p = 0.03).

CONCLUSIONS

These data suggest that increased sputum arginase activity contributes to nitric oxide deficiency in CF lung disease and may be relevant in the pathogenesis of CF airway disease.

Human airway epithelial cell determinants of survival and functional phenotype for primary human mast cells

Mast cells (MCs) are found in increased numbers at airway mucosal surfaces in asthmatic patients. Because human airway epithelial cells (HAECs) actively participate in airway inflammatory responses and are in direct contact with MCs in the mucosa, we hypothesized that HAEC-MC interactions may contribute to the differentiation and survival of MCs in the airway mucosa. Here, we show that HAECs express mRNA and protein for soluble and membrane-bound stem cell factor, releasing soluble stem cell factor into the cell culture supernatant at a concentration of 5.9 +/- 0.1 ng per 10(6) HAEC. HAECs were able to support MC survival in coculture in the absence of any exogenous cytokines for at least 4 d. Before the initiation of coculture, MCs were uniformly tryptase and chymase (MC(TC)) double positive, but by 2 d of coculture the majority of MCs expressed tryptase (MC(T)) alone. MCs supported in coculture generated low amounts of cysteinyl-leukotrienes (cys-LT) after FcepsilonRI-dependent activation (0.2 +/- 0.1 ng of cys-LT per 10(6) cells) and required priming with IL-4 and IL-3 during coculture to achieve a quantity of cys-LT generation within the range expected for human lung mucosal MC (26.5 +/- 16 ng of cys-LT per 10(6) cells). In these culture conditions, HAECs were able to direct mucosal MC protease phenotype, but T cell-derived Th2 cytokines were required for the expression of a functional airway MC eicosanoid phenotype. Thus, distinct cell types may direct unique aspects of reactive mucosal MC phenotype in the airways.

Disease modifying genes in cystic fibrosis

The variation in cystic fibrosis (CF) lung disease and development of CF related complications correlates poorly with the genotype of the CF transmembrane regulator (CFTR) and with environmental factors. Increasing evidence suggests that phenotypic variation in CF can be attributed to genetic variation in genes other than the CFTR gene, so-called modifier genes. In recent years, multiple candidate modifier genes have been investigated in CF, especially genes that are involved in the control of infection, immunity and inflammation. Some of these genes have been rather conclusively identified as modifiers of the CF phenotype, whereas associations found in other genes have not been confirmed or are conflicting. Identification of genetic variation in modifier genes, obtained by genotype-phenotype studies in well-defined patient populations, may be used as an aid to prognosis and may provide the possibility of new therapeutic interventions.

Nitric oxide in cystic fibrosis

Cystic fibrosis (CF) is characterized by chronic airway infection and inflammation, which accounts for most morbidity and deaths. Exhaled nitric oxide (NO), elevated in most inflammatory lung diseases, is decreased in CF, suggesting decreased formation, increased metabolism or loss of NO. The nitrogen oxide metabolism in CF airways is complex and not yet fully understood. In this article we will summarize current understanding of the origin and function of NO in (patho)physiological processes in the lung of normal subjects and CF patients, possible explanations for and consequences of reduced NO concentrations in CF and possible therapetic strategies for treatment of CF patients.

Potential genetic modifiers of the cystic fibrosis intestinal inflammatory phenotype on mouse chromosomes 1, 9, and 10

Background

Although cystic fibrosis is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, the severity of disease is highly variable indicating the influence of modifier genes. The intestines of Cftr deficient mice (CF mice: Cftr^tm1Unc) are prone to obstruction by excessive mucus accumulation and are used as a model of meconium ileus and distal intestinal obstruction syndrome. This phenotype is strongly dependent on the genetic background of the mice. On the C57Bl/6 background, the majority of CF mice cannot survive on solid mouse chow, have inflammation of the small intestine, and are about 30% smaller than wild type littermates. In this work potential modifier loci of the CF intestinal phenotype were identified.

Results

CF mice on a mixed genetic background (95% C57Bl/6 and 5% 129Sv) were compared to CF mice congenic on the C57Bl/6 background for several parameters of the intestinal CF phenotype. CF mice on the mixed background exhibit significantly greater survival when fed dry mouse chow, have reduced intestinal inflammation as measured by quantitative RT-PCR for marker genes, have near normal body weight gain, and have reduced mucus accumulation in the intestinal crypts. There was an indication of a gender effect for body weight gain: males did not show a significant improvement at 4 weeks of age, but were of normal weight at 8 weeks, while females showed improvement at both 4 and 8 weeks. By a preliminary genome-wide PCR allele scanning, three regions were found to be potentially associated with the milder phenotype. One on chr.1, defined by marker D1Mit36, one on chr. 9 defined by marker D9Mit90, and one on chr. 10, defined by marker D10Mit14.

Conclusion

Potential modifier regions were found that have a positive impact on the inflammatory phenotype of the CF mouse small intestine and animal survival. Identification of polymorphisms in specific genes in these regions should provide important new information about genetic modifiers of the CF intestinal phenotype.

Lung inflammation as a therapeutic target in cystic fibrosis

Cystic fibrosis (CF) lung disease is characterized by chronic neutrophilic inflammation and infection. Effective management of airway inflammation could complement other therapies for the treatment of CF. Recent progress has been made in understanding the signaling pathways regulating inflammatory cytokines in the lung. Here we examine the mechanisms responsible for inflammation in the CF lung, and discuss potential therapeutic strategies targeting inflammation.