Inflammatory response in airway epithelial cells isolated from patients with cystic fibrosis

Cystic fibrosis risk variants confer protection against inflammatory bowel disease

Genetic mutations that yield defective cystic fibrosis transmembrane regulator (CFTR) protein cause cystic fibrosis, a life-limiting autosomal recessive Mendelian disorder. A protective role of CFTR loss-of-function mutations in inflammatory bowel disease (IBD) has been suggested, but its evidence has been inconclusive and contradictory. Here, leveraging the largest IBD exome sequencing dataset to date, comprising 38,558 cases and 66,945 controls in the discovery stage, and 35,797 cases and 179,942 controls in the replication stage, we established a protective role of CF-risk variants against IBD based on evidence from the association test of CFTR delF508 (p-value=8.96E-11) and the gene-based burden test of CF-risk variants (p-value=3.9E-07). Furthermore, we assessed variant prioritization methods, including AlphaMissense, using clinically annotated CF-risk variants as the gold standard. Our findings highlight the critical and unmet need for effective variant prioritization in gene-based burden tests.

A functional 3D full-thickness model for comprehending the interaction between airway epithelium and connective tissue in cystic fibrosis

Patients with cystic fibrosis (CF) experience severe lung disease, including persistent infections, inflammation, and irreversible fibrotic remodeling of the airways. Although therapy with transmembrane conductance regulator (CFTR) protein modulators reached optimal results in terms of CFTR rescue, lung transplant remains the best line of care for patients in an advanced stage of CF. Indeed, chronic inflammation and tissue remodeling still represent stumbling blocks during treatment, and underlying mechanisms are still unclear. Nowadays, animal models are not able to fully replicate clinical features of the human disease and the conventional in vitro models lack a stromal compartment undergoing fibrotic remodeling. To address this gap, we show the development of a 3D full-thickness model of CF with a human bronchial epithelium differentiated on a connective airway tissue. We demonstrated that the epithelial cells not only underwent mucociliary differentiation but also migrated in the connective tissue and formed gland-like structures. The presence of the connective tissue stimulated the pro-inflammatory behaviour of the epithelium, which activated the fibroblasts embedded into their own extracellular matrix (ECM). By varying the composition of the model with CF epithelial cells and a CF or healthy connective tissue, it was possible to replicate different moments of CF disease, as demonstrated by the differences in the transcriptome of the CF epithelium in the different conditions. The possibility to faithfully represent the crosstalk between epithelial and connective in CF through the full thickness model, along with inflammation and stromal activation, makes the model suitable to better understand mechanisms of disease genesis, progression, and response to therapy.

Abnormal functional lymphoid tolerance and enhanced myeloid exocytosis are characteristics of resting and stimulated PBMCs in cystic fibrosis patients

Introduction

Cystic Fibrosis (CF) is the commonest genetically inherited disease (1 in 4,500 newborns) and 70% of people with CF (pwCF) harbour the F508Del mutation, resulting in misfolding and incorrect addressing of the channel CFTR to the epithelial membrane and subsequent dysregulation of fluid homeostasis. Although studies have underscored the importance and over-activation of myeloid cells, and in particular neutrophils in the lungs of people with CF (pwCF), relatively less emphasis has been put on the potential immunological bias in CF blood cells, at homeostasis or following stimulation/infection.

Methods

Here, we revisited, in an exhaustive fashion, in pwCF with mild disease (median age of 15, median % FEV1 predicted = 87), whether their PBMCs, unprimed or primed with a 'non specific' stimulus (PMA+ionomycin mix) and a 'specific' one (live P.a =PAO1 strain), were differentially activated, compared to healthy controls (HC) PBMCs.

Results

1) we analysed the lymphocytic and myeloid populations present in CF and Control PBMCs (T cells, NKT, Tgd, ILCs) and their production of the signature cytokines IFN-g, IL-13, IL-17, IL-22. 2) By q-PCR, ELISA and Luminex analysis we showed that CF PBMCs have increased background cytokines and mediators production and a partial functional tolerance phenotype, when restimulated. 3) we showed that CF PBMCs low-density neutrophils release higher levels of granule components (S100A8/A9, lactoferrin, MMP-3, MMP-7, MMP-8, MMP-9, NE), demonstrating enhanced exocytosis of potentially harmful mediators.

Discussion

In conclusion, we demonstrated that functional lymphoid tolerance and enhanced myeloid protease activity are key features of cystic fibrosis PBMCs.

The Impact of Highly Effective Modulator Therapy on Cystic Fibrosis Microbiology and Inflammation

Highly effective cystic fibrosis (CF) transmembrane conductance regulator (CFTR) modulator therapy (HEMT) corrects the underlying molecular defect causing CF disease. HEMT decreases symptom burden and improves clinical metrics and quality of life for most people with CF (PwCF) and eligible cftr mutations. Improvements in measures of pulmonary health suggest that restoration of function of defective CFTR anion channels by HEMT not only enhances airway mucociliary clearance, but also reduces chronic pulmonary infection and inflammation. This article reviews the evidence for how HEMT influences the dynamic and interdependent processes of infection and inflammation in the CF airway, and what questions remain unanswered.

Locally transplanted human urine-induced nephron progenitor cells contribute to renal repair in mice kidney with diabetic nephropathy

Chronic Kidney Disease (CKD) is increasingly recognized as a global public health issue. Diabetic nephropathy (DN), also known as diabetic kidney disease, is a leading cause of CKD. Regenerative medicine strategy employing nephron progenitor cells (NPCs) is worthy of consideration as an alternative to shortage of donor organs for kidney transplantation. In previous study, we successfully generated induced NPCs (iNPCs) from human urine-derived cells that resembled human embryonic stem cell-derived NPCs. Here, we aimed to investigate the therapeutic potential of iNPCs in DN animal model. The results revealed the therapeutic effect of iNPCs as follows: (1) diminished glomerular hypertrophy, (2) reduced tubulointerstitial fibrosis, (3) low blood urea nitrogen, serum creatinine and albuminuria value, (4) decreased inflammation/fibrosis, (5) enhanced renal regeneration and (6) confirmed safety. This study demonstrates that human iNPCs have a therapeutic potential as a cell source for transplantation in patients with kidney diseases.

Ivacaftor partially corrects airway inflammation in a humanized G551D rat

Animal models have been highly informative for understanding the pathogenesis and progression of cystic fibrosis (CF) lung disease. In particular, the CF rat models recently developed have addressed mechanistic causes of the airway mucus defect characteristic of CF, and how these may change when cystic fibrosis transmembrane conductance regulator (CFTR) activity is restored using new modulator therapies. We hypothesized that inflammatory changes to the airway would develop spontaneously and progressively, and that these changes would be resolved with modulator therapy. To test this, we used a humanized-CFTR rat expressing the G551D variant that responds to the CFTR modulator ivacaftor. Markers typically found in the CF lung were assessed, including neutrophil influx, small airway histopathology, and inflammatory cytokine concentration. Young hG551D rats did not express inflammatory cytokines at baseline but did upregulate these in response to inflammatory trigger. As the hG551D rats aged, histopathology worsened, accompanied by neutrophil influx into the airway and increasing concentrations of TNF-α, IL-1α, and IL-6 in the airways. Ivacaftor administration reduced concentrations of these cytokines when administered to the rats at baseline but was less effective in the rats that had also received inflammatory stimulus. Therefore, we conclude that administration of ivacaftor resulted in an incomplete resolution of inflammation when rats received an external trigger, suggesting that CFTR activation may not be enough to resolve inflammation in the lungs of patients with CF.

Dysregulated signalling pathways in innate immune cells with cystic fibrosis mutations

Cystic fibrosis (CF) is one of the most common life-limiting recessive genetic disorders in Caucasians, caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR). CF is a multi-organ disease that involves the lungs, pancreas, sweat glands, digestive and reproductive systems and several other tissues. This debilitating condition is associated with recurrent lower respiratory tract bacterial and viral infections, as well as inflammatory complications that may eventually lead to pulmonary failure. Immune cells play a crucial role in protecting the organs against opportunistic infections and also in the regulation of tissue homeostasis. Innate immune cells are generally affected by CFTR mutations in patients with CF, leading to dysregulation of several cellular signalling pathways that are in continuous use by these cells to elicit a proper immune response. There is substantial evidence to show that airway epithelial cells, neutrophils, monocytes and macrophages all contribute to the pathogenesis of CF, underlying the importance of the CFTR in innate immune responses. The goal of this review is to put into context the important role of the CFTR in different innate immune cells and how CFTR dysfunction contributes to the pathogenesis of CF, highlighting several signalling pathways that may be dysregulated in cells with CFTR mutations.

Deletion of cftr Leads to an Excessive Neutrophilic Response and Defective Tissue Repair in a Zebrafish Model of Sterile Inflammation

Inflammation-related progressive lung destruction is the leading causes of premature death in cystic fibrosis (CF), a genetic disorder caused by a defective cystic fibrosis transmembrane conductance regulator (CFTR). However, therapeutic targeting of inflammation has been hampered by a lack of understanding of the links between a dysfunctional CFTR and the deleterious innate immune response in CF. Herein, we used a CFTR-depleted zebrafish larva, as an innovative in vivo vertebrate model, to understand how CFTR dysfunction leads to abnormal inflammatory status in CF. We show that impaired CFTR-mediated inflammation correlates with an exuberant neutrophilic response after injury: CF zebrafish exhibit enhanced and sustained accumulation of neutrophils at wounds. Excessive epithelial oxidative responses drive enhanced neutrophil recruitment towards wounds. Persistence of neutrophils at inflamed sites is associated with impaired reverse migration of neutrophils and reduction in neutrophil apoptosis. As a consequence, the increased number of neutrophils at wound sites causes tissue damage and abnormal tissue repair. Importantly, the molecule Tanshinone IIA successfully accelerates inflammation resolution and improves tissue repair in CF animal. Our findings bring important new understanding of the mechanisms underlying the inflammatory pathology in CF, which could be addressed therapeutically to prevent inflammatory lung damage in CF patients with potential improvements in disease outcomes.

Progress in Model Systems of Cystic Fibrosis Mucosal Inflammation to Understand Aberrant Neutrophil Activity

In response to recurrent infection in cystic fibrosis (CF), powerful innate immune signals trigger polymorphonuclear neutrophil recruitment into the airway lumen. Exaggerated neutrophil proteolytic activity results in sustained inflammation and scarring of the airways. Consequently, neutrophils and their secretions are reliable clinical biomarkers of lung disease progression. As neutrophils are required to clear infection and yet a direct cause of airway damage, modulating adverse neutrophil activity while preserving their pathogen fighting function remains a key area of CF research. The factors that drive their pathological behavior are still under investigation, especially in early disease when aberrant neutrophil behavior first becomes evident. Here we examine the latest findings of neutrophils in pediatric CF lung disease and proposed mechanisms of their pathogenicity. Highlighted in this review are current and emerging experimental methods for assessing CF mucosal immunity and human neutrophil function in the laboratory.

Increased intracellular Cl- concentration promotes ongoing inflammation in airway epithelium

Airway epithelial cells harbor the capacity of active Cl^- transepithelial transport and play critical roles in modulating innate immunity. However, whether intracellular Cl^- accumulation contributes to relentless airway inflammation remains largely unclear. This study showed that, in airway epithelial cells, intracellular Cl^- concentration ([Cl^-]_i) was increased after Pseudomonas aeruginosa lipopolysaccharide (LPS) stimulation via nuclear factor-κB (NF-κB)-phosphodiesterase 4D (PDE4D)-cAMP signaling pathways. Clamping [Cl^-]_i at high levels or prolonged treatment with LPS augmented serum- and glucocorticoid-inducible protein kinase 1 (SGK1) phosphorylation and subsequently triggered NF-κB activation in airway epithelial cells, whereas inhibition of SGK1 abrogated airway inflammation in vitro and in vivo. Furthermore, Cl^--SGK1 signaling pathway was pronouncedly activated in patients with bronchiectasis, a chronic airway inflammatory disease. Conversely, hydrogen sulfide (H₂S), a sulfhydryl-containing gasotransmitter, confers anti-inflammatory effects through decreasing [Cl^-]_i via activation of cystic fibrosis transmembrane conductance regulator (CFTR). Our study confirms that intracellular Cl^- is a crucial mediator of sustained airway inflammation. Medications that abrogate excessively increased intracellular Cl^- may offer novel targets for the management of airway inflammatory diseases.

Newborn Cystic Fibrosis Pigs Have a Blunted Early Response to an Inflammatory Stimulus

RATIONALE

Studies suggest that inappropriate responses to proinflammatory stimuli might contribute to inflammation in cystic fibrosis (CF) lungs. However, technical challenges have made it difficult to distinguish whether altered responses in CF airways are an intrinsic defect or a secondary effect of chronic disease in their tissue of origin. The CF pig model provides an opportunity to study the inflammatory responses of CF airways at birth, before the onset of infection and inflammation.

OBJECTIVES

To test the hypothesis that acute inflammatory responses are perturbed in porcine CF airways.

METHODS

We investigated the inflammatory responses of newborn CF and non-CF pig airways following a 4-hour exposure to heat-killed Staphylococcus aureus, in vivo and in vitro.

MEASUREMENTS AND MAIN RESULTS

Following an in vivo S. aureus challenge, markers of inflammation were similar between CF and littermate control animals through evaluation of bronchoalveolar lavage and tissues. However, transcriptome analysis revealed genotype-dependent differences as CF pigs showed a diminished host defense response compared with their non-CF counterparts. Furthermore, CF pig airways exhibited an increase in apoptotic pathways and a suppression of ciliary and flagellar biosynthetic pathways. Similar differences were observed in cultured airway epithelia from CF and non-CF pigs exposed to the stimulus.

CONCLUSIONS

Transcriptome profiling suggests that acute inflammatory responses are dysregulated in the airways of newborn CF pigs.

Insulin signaling via the PI3-kinase/Akt pathway regulates airway glucose uptake and barrier function in a CFTR-dependent manner

Cystic fibrosis-related diabetes is the most common comorbidity associated with cystic fibrosis (CF) and correlates with increased rates of lung function decline. Because glucose is a nutrient present in the airways of patients with bacterial airway infections and because insulin controls glucose metabolism, the effect of insulin on CF airway epithelia was investigated to determine the role of insulin receptors and glucose transport in regulating glucose availability in the airway. The response to insulin by human airway epithelial cells was characterized by quantitative PCR, immunoblot, immunofluorescence, and glucose uptake assays. Phosphatidylinositol 3-kinase/protein kinase B (Akt) signaling and cystic fibrosis transmembrane conductance regulator (CFTR) activity were analyzed by pharmacological and immunoblot assays. We found that normal human primary airway epithelial cells expressed glucose transporter 4 and that application of insulin stimulated cytochalasin B-inhibitable glucose uptake, consistent with a requirement for glucose transporter translocation. Application of insulin to normal primary human airway epithelial cells promoted airway barrier function as demonstrated by increased transepithelial electrical resistance and decreased paracellular flux of small molecules. This provides the first demonstration that airway cells express insulin-regulated glucose transporters that act in concert with tight junctions to form an airway glucose barrier. However, insulin failed to increase glucose uptake or decrease paracellular flux of small molecules in human airway epithelia expressing F508del-CFTR. Insulin stimulation of Akt1 and Akt2 signaling in CF airway cells was diminished compared with that observed in airway cells expressing wild-type CFTR. These results indicate that the airway glucose barrier is regulated by insulin and is dysfunctional in CF.

Airway epithelial homeostasis and planar cell polarity signaling depend on multiciliated cell differentiation

Motile airway cilia that propel contaminants out of the lung are oriented in a common direction by planar cell polarity (PCP) signaling, which localizes PCP protein complexes to opposite cell sides throughout the epithelium to orient cytoskeletal remodeling. In airway epithelia, PCP is determined in a 2-phase process. First, cell-cell communication via PCP complexes polarizes all cells with respect to the proximal-distal tissue axis. Second, during ciliogenesis, multiciliated cells (MCCs) undergo cytoskeletal remodeling to orient their cilia in the proximal direction. The second phase not only directs cilium polarization, but also consolidates polarization across the epithelium. Here, we demonstrate that in airway epithelia, PCP depends on MCC differentiation. PCP mutant epithelia have misaligned cilia, and also display defective barrier function and regeneration, indicating that PCP regulates multiple aspects of airway epithelial homeostasis. In humans, MCCs are often sparse in chronic inflammatory diseases, and these airways exhibit PCP dysfunction. The presence of insufficient MCCs impairs mucociliary clearance in part by disrupting PCP-driven polarization of the epithelium. Consistent with defective PCP, barrier function and regeneration are also disrupted. Pharmacological stimulation of MCC differentiation restores PCP and reverses these defects, suggesting its potential for broad therapeutic benefit in chronic inflammatory disease.

Cystic Fibrosis: Microbiology and Host Response

The earliest descriptions of lung disease in people with cystic fibrosis (CF) showed the involvement of 3 interacting pathophysiologic elements in CF airways: mucus obstruction, inflammation, and infection. Over the past 7 decades, our understanding of CF respiratory microbiology and inflammation has evolved with the introduction of new treatments, increased longevity, and increasingly sophisticated laboratory techniques. This article reviews the current understanding of infection and inflammation and their roles in CF lung disease. It also discusses how this constantly evolving information is used to inform current therapeutic strategies, measures and predictors of disease severity, and research priorities.

Highly differentiated human airway epithelial cells: a model to study host cell-parasite interactions in pertussis

BACKGROUND

Bordetella pertussis colonizes the human respiratory mucosa. Most studies on B. pertussis adherence have relied on cultured mammalian cells that lack key features present in differentiated human airway cells or on animal models that are not natural hosts of B. pertussis. The objectives of this work were to evaluate B. pertussis infection in highly differentiated human airway cells in vitro and to show the role of B. pertussis fimbriae in cell adherence.

METHODS

Primary human airway epithelial (PHAE) cells from human bronchi and a human bronchial epithelial (HBE) cell line were grown in vitro under air-liquid interface conditions.

RESULTS

PHAE and HBE cells infected with B. pertussis wild-type strain revealed bacterial adherence to the apical surface of cells, bacteria-induced cytoskeleton changes, and cell detachment. Mutations in the major fimbrial subunits Fim2/3 or in the minor fimbrial adhesin subunit FimD affected B. pertussis adherence to predominantly HBE cells. This cell model recapitulates the morphologic features of the human airway infected by B. pertussis and confirms the role of fimbriae in B. pertussis adherence. Furthermore, HBE cells show that fimbrial subunits, and specifically FimD adhesin, are critical in B. pertussis adherence to airway cells.

CONCLUSIONS

The relevance of this model to study host-parasite interaction in pertussis lies in the striking physiologic and morphologic similarity between the PHAE and HBE cells and the human airway ciliated and goblet cells in vivo. These cells can proliferate in vitro, differentiate, and express the same genetic profile as human respiratory cells in vivo.

Epithelium-Specific Ets-Like Transcription Factor 1, ESE-1, Regulates ICAM-1 Expression in Cultured Lung Epithelial Cell Lines

Cystic fibrosis (CF) patients suffer from chronic airway inflammation with excessive neutrophil infiltration. Migration of neutrophils to the lung requires chemokine and cytokine signaling as well as cell adhesion molecules, such as intercellular adhesion molecule-1 (ICAM-1), which plays an important role in mediating adhesive interactions between effector and target cells in the immune system. In this study, we investigated the relationship between ICAM-1 and epithelium-specific ETS-like transcription factor 1 (ESE-1) and found that ICAM-1 expression is upregulated in cell lines of CF (IB3-1) as well as non-CF (BEAS-2B and A549) epithelial origin in response to inflammatory cytokine stimulation. Since ESE-1 is highly expressed in A549 cells without stimulation, we examined the effect of ESE-1 knockdown on ICAM-1 expression in these cells. We found that ICAM-1 expression was downregulated when ESE-1 was knocked down in A549 cells. We also tested the effect of ESE-1 knockdown on cell-cell interactions and demonstrate that the knocking down ESE-1 in A549 cells reduce their interactions with HL-60 cells (human promyelocytic leukemia cell line). These results suggest that ESE-1 may play a role in regulating airway inflammation by regulating ICAM-1 expression.

Expression of soluble triggering receptor expressed on myeloid cells-1 in childhood CF and non-CF bronchiectasis

BACKGROUND

Soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) is demonstrating promise as an inflammatory biomarker of acute infection in various pulmonary conditions; including community acquired pneumonia, ventilator associated pneumonia and non-tuberculous mycobacterial infection.

INTRODUCTION

The expression of sTREM-1 has been poorly studied in all forms of bronchiectasis, both in the context of cystic fibrosis (CF) and non-cystic fibrosis bronchiectasis.

METHOD

Induced sputum samples were collected for sTREM-1 determination in children with HIV-associated bronchiectasis and CF-bronchiectasis. The presence or absence of an exacerbation was noted at study entry. Lung function parameters (FEV1, FVC, FEV1 /FVC, FEF(25-75)) were measured using the Viasys SpiroPro Jaeger Spirometer (Hoechberg, Germany).

RESULT

A total of twenty-six children with HIV-associated bronchiectasis and seventeen with CF were included. With respect to sTREM-1, the levels were readily detected in both groups, but were significantly higher in children with HIV-associated bronchiectasis (1244.0 pg/ml (iqr 194.5; 3755.3 pg/ml) and 204.9  pg/ml (iqr 66.9; 653.6 pg/ml) P = 0.003. There was a positive correlation between sTREM-1 and IL-8 as well as sputum neutrophil elastase in the HIV-bronchiectasis group (r = 0.715 and r = 0.630), respectively both P < 0.005. sTREM-1 was not further increased in subjects presenting with an acute pulmonary exacerbation in the HIV-associated bronchiectasis and in CF participants (P = 0.971 and P = 0.481), respectively. In the CF group sTREM-1 strongly correlated with FVC% predicted and FEV1 % predicted (r = 0.950 and r = 0.954), both P < 0.005.

CONCLUSION

The pulmonary innate immune functions are over-active in HIV-associated bronchiectasis, with readily detected sTREM-1 values, which were higher than those in CF. sTREM-1 does not correlate with markers of HIV-disease activity but does correlate with markers of neutrophilic inflammation. In CF sTREM-1 has a negative correlation with pulmonary function parameters.

Oxidative stress modulates the expression of genes involved in cell survival in ΔF508 cystic fibrosis airway epithelial cells

Although cystic fibrosis (CF) pathophysiology is explained by a defect in CF transmembrane conductance regulator (CFTR) protein, the broad spectrum of disease severity is the consequence of environmental and genetic factors. Among them, oxidative stress has been demonstrated to play an important role in the evolution of this disease, with susceptibility to oxidative damage, decline of pulmonary function, and impaired lung antioxidant defense. Although oxidative stress has been implicated in the regulation of inflammation, its molecular outcomes in CF cells remain to be evaluated. To address the question, we compared the gene expression profile in NuLi-1 cells with wild-type CFTR and CuFi-1 cells homozygous for ΔF508 mutation cultured at air-liquid interface. We analyzed the transcriptomic response of these cell lines with microarray technology, under basal culture conditions and after 24 h oxidative stress induced by 15 μM 2,3-dimethoxy-1,4-naphtoquinone. In the absence of oxidative conditions, CuFi-1 gene profiling showed typical dysregulated inflammatory responses compared with NuLi-1. In the presence of oxidative conditions, the transcriptome of CuFi-1 cells reflected apoptotic transcript modulation. These results were confirmed in the CFBE41o- and corrCFBE41o- cell lines as well as in primary culture of human CF airway epithelial cells. Altogether, our data point to the influence of oxidative stress on cell survival functions in CF and identify several genes that could be implicated in the inflammation response observed in CF patients.

Normal CFTR inhibits epidermal growth factor receptor-dependent pro-inflammatory chemokine production in human airway epithelial cells

Mutations in cystic fibrosis transmembrane conductance regulator (CFTR) protein cause cystic fibrosis, a disease characterized by exaggerated airway epithelial production of the neutrophil chemokine interleukin (IL)-8, which results in exuberant neutrophilic inflammation. Because activation of an epidermal growth factor receptor (EGFR) signaling cascade induces airway epithelial IL-8 production, we hypothesized that normal CFTR suppresses EGFR-dependent IL-8 production and that loss of CFTR at the surface exaggerates IL-8 production via activation of a pro-inflammatory EGFR cascade. We examined this hypothesis in human airway epithelial (NCI-H292) cells and in normal human bronchial epithelial (NHBE) cells containing normal CFTR treated with a CFTR-selective inhibitor (CFTR-172), and in human airway epithelial (IB3) cells containing mutant CFTR versus isogenic (C38) cells containing wild-type CFTR. In NCI-H292 cells, CFTR-172 induced IL-8 production EGFR-dependently. Pretreatment with an EGFR neutralizing antibody or the metalloprotease TACE inhibitor TAPI-1, or TACE siRNA knockdown prevented CFTR-172-induced EGFR phosphorylation (EGFR-P) and IL-8 production, implicating TACE-dependent EGFR pro-ligand cleavage in these responses. Pretreatment with neutralizing antibodies to IL-1R or to IL-1alpha, but not to IL-1beta, markedly suppressed CFTR-172-induced EGFR-P and IL-8 production, suggesting that binding of IL-1alpha to IL-1R stimulates a TACE-EGFR-IL-8 cascade. Similarly, in NHBE cells, CFTR-172 increased IL-8 production EGFR-, TACE-, and IL-1alpha/IL-1R-dependently. In IB3 cells, constitutive IL-8 production was markedly increased compared to C38 cells. EGFR-P was increased in IB3 cells compared to C38 cells, and exaggerated IL-8 production in the IB3 cells was EGFR-dependent. Activation of TACE and binding of IL-1alpha to IL-1R contributed to EGFR-P and IL-8 production in IB3 cells but not in C38 cells. Thus, we conclude that normal CFTR suppresses airway epithelial IL-8 production that occurs via a stimulatory EGFR cascade, and that loss of normal CFTR activity exaggerates IL-8 production via activation of a pro-inflammatory EGFR cascade.

Anr and its activation by PlcH activity in Pseudomonas aeruginosa host colonization and virulence

Pseudomonas aeruginosa hemolytic phospholipase C (PlcH) degrades phosphatidylcholine (PC), an abundant lipid in cell membranes and lung surfactant. A ΔplcHR mutant, known to be defective in virulence in animal models, was less able to colonize epithelial cell monolayers and was defective in biofilm formation on plastic when grown in lung surfactant. Microarray analyses found that strains defective in PlcH production had lower levels of Anr-regulated transcripts than the wild type. PC degradation stimulated the Anr regulon in an Anr-dependent manner under conditions where Anr activity was submaximal because of the presence of oxygen. Two PC catabolites, choline and glycine betaine (GB), were sufficient to stimulate Anr activity, and their catabolism was required for Anr activation. The addition of choline or GB to glucose-containing medium did not alter Anr protein levels, growth rates, or respiratory activity, and Anr activation could not be attributed to the osmoprotectant functions of GB. The Δanr mutant was defective in virulence in a mouse pneumonia model. Several lines of evidence indicate that Anr is important for the colonization of biotic and abiotic surfaces in both P. aeruginosa PAO1 and PA14 and that increases in Anr activity resulted in enhanced biofilm formation. Our data suggest that PlcH activity promotes Anr activity in oxic environments and that Anr activity contributes to virulence, even in the acute infection phase, where low oxygen tensions are not expected. This finding highlights the relationships among in vivo bacterial metabolism, the activity of the oxygen-sensitive regulator Anr, and virulence.

The antioxidant resveratrol down-regulates inflammation in an in-vitro model of Pseudomonas aeruginosa infection of lung epithelial cells

Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that can cause severe pulmonary infection in immunocompromized individuals. During the infectious process, P. aeruginosa provokes a potent inflammatory response and induces the release of reactive oxygen species (ROS). Cells undergo oxidative stress when cellular antioxidants are unable to effectively scavenge and detoxify ROS, resulting in lung damage. Resveratrol (3,5,4'-trihydroxystilbene) is a natural polyphenolic compound with recognized antioxidant effects. We hypothesized that owing to its antioxidant activities, resveratrol can attenuate an inflammatory response in P. aeruginosa-infected cells. Lung epithelial A549 cells were pre-treated with 100 μmol/L of resveratrol for 5 h, followed by infection with P. aeruginosa. Intracellular ROS generation was used as an indicator of P. aeruginosa-induced oxidative stress, and cell surface expression of Fas receptor and activation of caspases-3 and -7 as indicators of apoptosis. We also measured the surface expression of intercellular adhesion molecule (ICAM)-1 and enzymes related to inflammation and redox signaling. Resveratrol significantly reduced ROS generation, ICAM-1, and human beta-defensin-2 expression, as well as the markers of apoptosis in A549 cells infected with P. aeruginosa, and up-regulated glutathione peroxidase, suggesting its potential therapeutic role in protecting the lungs against the deleterious effects of P. aeruginosa infection.

Does the F508-CFTR mutation induce a proinflammatory response in human airway epithelial cells?

In the clinical setting, mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene enhance the inflammatory response in the lung to Pseudomonas aeruginosa (P. aeruginosa) infection. However, studies on human airway epithelial cells in vitro have produced conflicting results regarding the effect of mutations in CFTR on the inflammatory response to P. aeruginosa, and there are no comprehensive studies evaluating the effect of P. aeruginosa on the inflammatory response in airway epithelial cells with the ΔF508/ΔF508 genotype and their matched CF cell line rescued with wild-type (wt)-CFTR. CFBE41o- cells (ΔF508/ΔF508) and CFBE41o- cells complemented with wt-CFTR (CFBE-wt-CFTR) have been used extensively as an experimental model to study CF. Thus the goal of this study was to examine the effect of P. aeruginosa on gene expression and cytokine/chemokine production in this pair of cells. P. aeruginosa elicited a more robust increase in cytokine and chemokine expression (e.g., IL-8, CXCL1, CXCL2 and TNF-α) in CFBE-wt-CFTR cells compared with CFBE-ΔF508-CFTR cells. These results demonstrate that CFBE41o- cells complemented with wt-CFTR mount a more robust inflammatory response to P. aeruginosa than CFBE41o-ΔF508/ΔF508-CFTR cells. Taken together with other published studies, our data demonstrate that there is no compelling evidence to support the view that mutations in CFTR induce a hyperinflammatory response in human airway epithelial cells in vivo. Although the lungs of patients with CF have abundant levels of proinflammatory cytokines and chemokines, because the lung is populated by immune cells and epithelial cells there is no way to know, a priori, whether airway epithelial cells in the CF lung in vivo are hyperinflammatory in response to P. aeruginosa compared with non-CF lung epithelial cells. Thus studies on human airway epithelial cell lines and primary cells in vitro that propose to examine the effect of mutations in CFTR on the inflammatory response to P. aeruginosa have uncertain clinical significance with regard to CF.

The role of macrolides in childhood non-cystic fibrosis-related bronchiectasis

Non-cystic fibrosis-related bronchiectasis is a chronic inflammatory lung disease, which is regarded as an “orphan” lung disease, with little research devoted to the study of this condition. Bronchiectasis results in impaired quality of life and mortality if left untreated. The tools available in the armamentarium for the management of bronchiectasis entail antibiotic therapy traditionally used to treat exacerbations, stratagems to improve mucociliary clearance, and avoidance of toxins. Macrolides have been known for the last two decades to have not only anti-bacterial effects but immunomodulatory properties as well. In cystic fibrosis, the use of macrolides is well documented in subjects colonized with Pseudomonas aeruginosa, to improve quality of life and lung function. There is currently emerging evidence to suggest the benefit of macrolides in subjects not colonized with Pseudomonas aeruginosa. This beneficial effect has been less explored in the context of bronchiectasis from other causes. The purpose of this paper is to review the current literature on the use of macrolides in non-cystic fibrosis related bronchiectasis in paediatrics.

Lack of an exaggerated inflammatory response on virus infection in cystic fibrosis

Respiratory virus infections play an important role in cystic fibrosis (CF) exacerbations, but underlying pathophysiological mechanisms are poorly understood. We aimed to assess whether an exaggerated inflammatory response of the airway epithelium on virus infection could explain the increased susceptibility of CF patients towards respiratory viruses. We used primary bronchial and nasal epithelial cells obtained from 24 healthy control subjects and 18 CF patients. IL-6, IL-8/CXCL8, IP-10/CXCL10, MCP-1/CCL2, RANTES/CCL5 and GRO-α/CXCL1 levels in supernatants and mRNA expression in cell lysates were measured before and after infection with rhinoviruses (RV-16 and RV-1B) and RSV. Cytotoxicity was assessed by lactate dehydrogenate assay and flow cytometry. All viruses induced strong cytokine release in both control and CF cells. The inflammatory response on virus infection was heterogeneous and depended on cell type and virus used, but was not increased in CF compared with control cells. On the contrary, there was a marked trend towards lower cytokine production associated with increased cell death in CF cells. An exaggerated inflammatory response to virus infection in bronchial epithelial cells does not explain the increased respiratory morbidity after virus infection in CF patients.

Bronchial brushings for investigating airway inflammation and remodelling

Asthma is the commonest medical cause for hospital admission for children in Australia, affects more than 300 million people worldwide, and is incurable, severe in large number and refractory to treatment in many. However, there have been no new significant treatments despite intense research and billions of dollars. The advancement in our understanding in this disease has been limited due to its heterogeneity, genetic complexity and has severely been hampered particularly in children by the difficulty in obtaining relevant target organ tissue. This review attempts to provide an overview of the currently used and recently developed/adapted techniques used to obtain lung tissue with specific reference to the airway epithelium.

Initial interrogation, confirmation and fine mapping of modifying genes: STAT3, IL1B and IFNGR1 determine cystic fibrosis disease manifestation

We have used a stepwise approach consisting of initial interrogation, confirmation and fine mapping to analyze STAT3, IL1B and IFNGR1 as modifiers of cystic fibrosis disease building upon the data and sample collection of the European Cystic Fibrosis Twin and Sibling Study. We have observed direct correlation between the length of the intronic microsatellite STAT3Sat to STAT3 expression levels among F508del-CFTR homozygous patients (P=0.0075), and an association of longer STAT3Sat-alleles with the presence of CFTR-mediated residual chloride secretion (P=0.0031), measured as the manifestation of the CF basic defect in intestinal tissue. Both, family-based analysis by TDT and case-reference comparison identified consistently the same intragenic IL1B haplotype as a risk variant (P(raw)=0.055 for TDT, P(raw)<0.3 for case-reference comparison). Using haplotype-guided hierarchical fine mapping, we have identified two single nucleotide exchanges for which concordant and discordant sibling pairs differ at a 7 kb-spanning core haplotype in IFNGR1 (P(raw)=0.0113). Taken together, our findings imply that immunorelevant pathways and ion secretion, dominated by CFTR in intestinal and respiratory epithelium, merge at the level of the epithelial cell to integrate the signaling of cytokines due to innate and acquired immune defense.

SERCA2 regulates non-CF and CF airway epithelial cell response to ozone

Calcium mobilization can regulate a wide range of essential functions of respiratory epithelium, including ion transport, ciliary beat frequency, and secretion of mucus, all of which are modified in cystic fibrosis (CF). SERCA2, an important controller of calcium signaling, is deficient in CF epithelium. We conducted this study to determine whether SERCA2 deficiency can modulate airway epithelial responses to environmental oxidants such as ozone. This could contribute to the pathogenesis of pulmonary exacerbations, which are important and frequent clinical events in CF. To address this, we used air-liquid interface (ALI) cultures of non-CF and CF cell lines, as well as differentiated cultures of cells derived from non-CF and CF patients. We found that ozone exposure caused enhanced membrane damage, mitochondrial dysfunction and apoptotic cell death in CF airway epithelial cell lines relative to non-CF. Ozone exposure caused increased proinflammatory cytokine production in CF airway epithelial cell lines. Elevated proinflammatory cytokine production also was observed in shRNA-mediated SERCA2 knockdown cells. Overexpression of SERCA2 reversed ozone-induced proinflammatory cytokine production. Ozone-induced proinflammatory cytokine production was NF-κB- dependent. In a stable NF-κB reporter cell line, SERCA2 inhibition and knockdown both upregulated cytomix-induced NF-κB activity, indicating importance of SERCA2 in modulating NF-κB activity. In this system, increased NF-κB activity was also accompanied by increased IL-8 production. Ozone also induced NF-κB activity and IL-8 release, an effect that was greater in SERCA2-silenced NF-κB-reporter cells. SERCA2 overexpression reversed cytomix-induced increased IL-8 release and total nuclear p65 in CFTR-deficient (16HBE-AS) cells. These studies suggest that SERCA2 is an important regulator of the proinflammatory response of airway epithelial cells and could be a potential therapeutic target.

Inhibition by cigarette smoke of nuclear factor-κB-dependent response to bacteria in the airway

Although individuals exposed to cigarette smoke are more susceptible to respiratory infection, the effects of cigarette smoke on pulmonary defense are incompletely understood. Based on the observation that interactions between bacteria and host cells result in the expression of critical defense genes regulated by NF-κB, we hypothesized that cigarette smoke alters NF-κB function. In this study, primary human tracheobronchial epithelial cells were treated with cigarette smoke extract (CSE) and exposed to Haemophilus influenzae, and the effects of CSE on bacteria-induced signaling and gene expression were assessed. CSE inhibited high concentrations of induced NF-κB activation and the consequent expression of defense genes that occurred in airway epithelial cells in response to H. influenzae. This decreased activation of NF-κB was not attributable to cell loss or cytotoxicity. Glutathione augmentation of epithelial cells decreased the effects of CSE on NF-κB-dependent responses, as well as the effects on the inhibitor of κB and the inhibitor of κB kinase, which are upstream NF-κB regulators, suggesting the involvement of reactive oxygen species. The relevance of these findings for lung infection was confirmed using a mouse model of H. influenzae airway infection, in which decreased NF-κB pathway activation, keratinocyte chemoattractant (KC) chemokine expression, and neutrophil recruitment occurred in animals exposed to cigarette smoke. The results indicate that although cigarette smoke can cause inflammation in the lung, exposure to smoke inhibits the robust pulmonary defense response to H. influenzae, thereby providing one explanation for the increased susceptibility to respiratory bacterial infection in individuals exposed to cigarette smoke.

Critical modifier role of membrane-cystic fibrosis transmembrane conductance regulator-dependent ceramide signaling in lung injury and emphysema

Ceramide accumulation mediates the pathogenesis of chronic obstructive lung diseases. Although an association between lack of cystic fibrosis transmembrane conductance regulator (CFTR) and ceramide accumulation has been described, it is unclear how membrane-CFTR may modulate ceramide signaling in lung injury and emphysema. Cftr(+/+) and Cftr(-/-) mice and cells were used to evaluate the CFTR-dependent ceramide signaling in lung injury. Lung tissue from control and chronic obstructive pulmonary disease patients was used to verify the role of CFTR-dependent ceramide signaling in pathogenesis of chronic emphysema. Our data reveal that CFTR expression inversely correlates with severity of emphysema and ceramide accumulation in chronic obstructive pulmonary disease subjects compared with control subjects. We found that chemical inhibition of de novo ceramide synthesis controls Pseudomonas aeruginosa-LPS-induced lung injury in Cftr(+/+) mice, whereas its efficacy was significantly lower in Cftr(-/-) mice, indicating that membrane-CFTR is required for controlling lipid-raft ceramide levels. Inhibition of membrane-ceramide release showed enhanced protective effect in controlling P. aeruginosa-LPS-induced lung injury in Cftr(-/-) mice compared with that in Cftr(+/+) mice, confirming our observation that CFTR regulates lipid-raft ceramide levels and signaling. Our results indicate that inhibition of de novo ceramide synthesis may be effective in disease states with low CFTR expression like emphysema and chronic lung injury but not in complete absence of lipid-raft CFTR as in ΔF508-cystic fibrosis. In contrast, inhibiting membrane-ceramide release has the potential of a more effective drug candidate for ΔF508-cystic fibrosis but may not be effectual in treating lung injury and emphysema. Our data demonstrate the critical role of membrane-localized CFTR in regulating ceramide accumulation and inflammatory signaling in lung injury and emphysema.

Clinical significance of microbial infection and adaptation in cystic fibrosis

A select group of microorganisms inhabit the airways of individuals with cystic fibrosis. Once established within the pulmonary environment in these patients, many of these microbes adapt by altering aspects of their structure and physiology. Some of these microbes and adaptations are associated with more rapid deterioration in lung function and overall clinical status, whereas others appear to have little effect. Here we review current evidence supporting or refuting a role for the different microbes and their adaptations in contributing to poor clinical outcomes in cystic fibrosis.

TLR5 as an anti-inflammatory target and modifier gene in cystic fibrosis

New treatments are needed to improve the health of people with cystic fibrosis (CF). Reducing lung-damaging inflammation is likely to be beneficial, but specific anti-inflammatory targets have not been identified. By combining cellular immunology with a population-based genetic modifier study, we examined TLR5 as an anti-inflammatory target and modifier gene in CF. Using two pairs of human CF and control airway epithelial cells, we demonstrated that the TLR5-flagellin interaction is a major mediator of inflammation following exposure to Pseudomonas aeruginosa. To validate TLR5 as an anti-inflammatory target, we analyzed the disease modifying effects of the TLR5 c.1174C>T single nucleotide polymorphism (rs5744168) in a large cohort of CF patients (n = 2219). rs5744168 encodes a premature stop codon and the T allele is associated with a 45.5-76.3% reduction in flagellin responsiveness (p < 0.0001). To test the hypothesis that reduced TLR5 responsiveness would be associated with improved health in CF patients, we examined the relationship between rs5744168 and two clinical phenotypes: lung function and body weight. Adults with CF carrying the TLR5 premature stop codon (CT or TT genotype) had a higher body mass index than did CF patients homozygous for the fully functional allele (CC genotype) (p = 0.044); however, similar improvements in lung function associated with the T allele were not statistically significant. Although follow-up studies are needed to confirm the impact of TLR5 on nutritional status, this translational research provides evidence that genetic variation in TLR5 resulting in reduced flagellin responsiveness is associated with improved health indicators in adults with CF.

Respiratory syncytial virus limits alpha subunit of eukaryotic translation initiation factor 2 (eIF2alpha) phosphorylation to maintain translation and viral replication

The impact of respiratory syncytial virus (RSV) on morbidity and mortality is significant in that it causes bronchiolitis in infants, exacerbations in patients with obstructive lung disease, and pneumonia in immunocompromised hosts. RSV activates protein kinase R (PKR), a cellular kinase relevant to limiting viral replication (Groskreutz, D. J., Monick, M. M., Powers, L. S., Yarovinsky, T. O., Look, D. C., and Hunninghake, G. W. (2006) J. Immunol. 176, 1733-1740). It is activated by autophosphorylation, likely triggered by a double-stranded RNA intermediate during replication of the virus. In most instances, ph-PKR targets the alpha subunit of eukaryotic translation initiation factor 2 (eIF2alpha) protein via phosphorylation, leading to an inhibition of translation of cellular and viral protein. However, we found that although ph-PKR increases in RSV infection, significant eIF2alpha phosphorylation is not observed, and inhibition of protein translation does not occur. RSV infection attenuates eIF2alpha phosphorylation by favoring phosphatase rather than kinase activity. Although PKR is activated, RSV sequesters PKR away from eIF2alpha by binding of the kinase to the RSV N protein. This occurs in conjunction with an increase in the association of the phosphatase, PP2A, with eIF2alpha following PKR activation. The result is limited phosphorylation of eIF2alpha and continued translation of cellular and viral proteins.

Effect of polarized release of CXC-chemokines from wild-type and cystic fibrosis murine airway epithelial cells

The respiratory epithelium lining the airway relies on mucociliary clearance and a complex network of inflammatory mediators to protect the lung. Alterations in the composition and volume of the periciliary liquid layer, as occur in cystic fibrosis (CF), lead to impaired mucociliary clearance and persistent airway infection. Moreover, the respiratory epithelium releases chemoattractants after infection, inciting airway inflammation. However, characterizing the inflammatory response of primary human airway epithelial cells to infection can be challenging because of genetic heterogeneity. Using well-characterized, differentiated, primary murine tracheal cells grown at an air-liquid interface, which provides an in vitro polarized epithelial model, we compared inflammatory gene expression and secretion in wild-type and ΔF508 CF airway cells after infection with Pseudomonas aeruginosa. The expression of several CXC-chemokines, including macrophage inflammatory protein-2, small inducible cytokine subfamily member 2, lipopolysaccharide-induced chemokine, and interferon-inducible cytokine-10, was markedly increased after infection, and these proinflammatory mediators were asymmetrically released from the airway epithelium, predominantly from the basolateral surface. Equal amounts of CXC-chemokines were released from wild-type and CF cells. Secreted mediators were concentrated in the thin, periciliary fluid layer, and the dehydrated apical microenvironment of CF airway epithelial cells amplified the inflammatory signal, potentially resulting in high chemokine concentration gradients across the epithelium. Consistent with this observation, the enhanced chemotaxis of wild-type neutrophils was detected in CF airway epithelial cultures, compared with wild-type cells. These data suggest that P. aeruginosa infection of the airway epithelium induces the expression and polarized secretion of CXC-chemokines, and the increased concentration gradient across the CF airway leads to an exaggerated inflammatory response.

Inhibition of IFN-gamma-dependent antiviral airway epithelial defense by cigarette smoke

BACKGROUND

Although individuals exposed to cigarette smoke are more susceptible to respiratory infection, the effects of cigarette smoke on lung defense are incompletely understood. Because airway epithelial cell responses to type II interferon (IFN) are critical in regulation of defense against many respiratory viral infections, we hypothesized that cigarette smoke has inhibitory effects on IFN-gamma-dependent antiviral mechanisms in epithelial cells in the airway.

METHODS

Primary human tracheobronchial epithelial cells were first treated with cigarette smoke extract (CSE) followed by exposure to both CSE and IFN-gamma. Epithelial cell cytotoxicity and IFN-gamma-induced signaling, gene expression, and antiviral effects against respiratory syncytial virus (RSV) were tested without and with CSE exposure.

RESULTS

CSE inhibited IFN-gamma-dependent gene expression in airway epithelial cells, and these effects were not due to cell loss or cytotoxicity. CSE markedly inhibited IFN-gamma-induced Stat1 phosphorylation, indicating that CSE altered type II interferon signal transduction and providing a mechanism for CSE effects. A period of CSE exposure combined with an interval of epithelial cell exposure to both CSE and IFN-gamma was required to inhibit IFN-gamma-induced cell signaling. CSE also decreased the inhibitory effect of IFN-gamma on RSV mRNA and protein expression, confirming effects on viral infection. CSE effects on IFN-gamma-induced Stat1 activation, antiviral protein expression, and inhibition of RSV infection were decreased by glutathione augmentation of epithelial cells using N-acetylcysteine or glutathione monoethyl ester, providing one strategy to alter cigarette smoke effects.

CONCLUSIONS

The results indicate that CSE inhibits the antiviral effects of IFN-gamma, thereby presenting one explanation for increased susceptibility to respiratory viral infection in individuals exposed to cigarette smoke.

Cystic fibrosis pigs develop lung disease and exhibit defective bacterial eradication at birth

Lung disease causes most of the morbidity and mortality in cystic fibrosis (CF). Understanding the pathogenesis of this disease has been hindered, however, by the lack of an animal model with characteristic features of CF. To overcome this problem, we recently generated pigs with mutated CFTR genes. We now report that, within months of birth, CF pigs spontaneously developed hallmark features of CF lung disease, including airway inflammation, remodeling, mucus accumulation, and infection. Their lungs contained multiple bacterial species, suggesting that the lungs of CF pigs have a host defense defect against a wide spectrum of bacteria. In humans, the temporal and causal relations between inflammation and infection have remained uncertain. To investigate these processes, we studied newborn pigs. Their lungs showed no inflammation but were less often sterile than controls. Moreover, after introduction of bacteria into their lungs, pigs with CF failed to eradicate bacteria as effectively as wild-type pigs. These results suggest that impaired bacterial elimination is the pathogenic event that initiates a cascade of inflammation and pathology in CF lungs. Our finding that pigs with CF have a host defense defect against bacteria within hours of birth provides an opportunity to further investigate CF pathogenesis and to test therapeutic and preventive strategies that could be deployed before secondary consequences develop.

Vitamin D decreases respiratory syncytial virus induction of NF-kappaB-linked chemokines and cytokines in airway epithelium while maintaining the antiviral state

Epidemiological studies suggest that low vitamin D levels may increase the risk or severity of respiratory viral infections. In this study, we examined the effect of vitamin D on respiratory syncytial virus (RSV)-infected human airway epithelial cells. Airway epithelium converts 25-hydroxyvitamin D3 (storage form) to 1,25-dihydroxyvitamin D3 (active form). Active vitamin D, generated locally in tissues, is important for the nonskeletal actions of vitamin D, including its effects on immune responses. We found that vitamin D induces IkappaBalpha, an NF-kappaB inhibitor, in airway epithelium and decreases RSV induction of NF-kappaB-driven genes such as IFN-beta and CXCL10. We also found that exposing airway epithelial cells to vitamin D reduced induction of IFN-stimulated proteins with important antiviral activity (e.g., myxovirus resistance A and IFN-stimulated protein of 15 kDa). In contrast to RSV-induced gene expression, vitamin D had no effect on IFN signaling, and isolated IFN induced gene expression. Inhibiting NF-kappaB with an adenovirus vector that expressed a nondegradable form of IkappaBalpha mimicked the effects of vitamin D. When the vitamin D receptor was silenced with small interfering RNA, the vitamin D effects were abolished. Most importantly we found that, despite inducing IkappaBalpha and dampening chemokines and IFN-beta, there was no increase in viral mRNA or protein or in viral replication. We conclude that vitamin D decreases the inflammatory response to viral infections in airway epithelium without jeopardizing viral clearance. This suggests that adequate vitamin D levels would contribute to reduced inflammation and less severe disease in RSV-infected individuals.

Cigarette smoke alters respiratory syncytial virus-induced apoptosis and replication

Individuals exposed to cigarette smoke have a greater number and severity of viral infections, including respiratory syncytial virus (RSV) infections, than do nonsmokers, but the cellular mechanism is unknown. Our objective was to determine the mechanism by which cigarette smoke augments viral infection. We hypothesize that cigarette smoke causes necrosis and prevents virus-induced cellular apoptosis, and that this is associated with increased inflammation and viral replication. Primary airway epithelial cells were exposed to cigarette smoke extract for 2 days, followed by 1 day of RSV exposure. Western blot detection of cleaved caspases 3 and 7 showed less apoptosis when cells were treated with cigarette smoke before viral infection. This finding was confirmed with ELISA and TUNEL detection of apoptosis. Measures of cell viability, including propidium iodide staining, ATP assay, and cell counts, indicated that cigarette smoke causes necrosis rather than virus-induced apoptosis. Using plaque assay and fluorescently-labeled RSV, we showed that although there were less live cells in the cigarette smoke-pretreated group, viral load was increased. The effect was inhibited by pretreatment of cells with N-acetylcysteine and aldehyde dehydrogenase, suggesting that the effect was primarily mediated by reactive aldehydes. Cigarette smoke causes necrosis rather than apoptosis in viral infection, resulting in increased inflammation and enhanced viral replication.

TLR-4-mediated innate immunity is reduced in cystic fibrosis airway cells

Airway epithelial cells contribute to the inflammatory response of the lung, and their innate immune response is primarily mediated via Toll-like receptor (TLR) signaling. Cystic fibrosis (CF) airways are chronically infected with Pseudomonas aeruginosa, suggesting a modified immune response in CF. We investigated the TLR-4 expression and the inflammatory profile (IL-8 and IL-6 secretion) in CF bronchial epithelial cell line CFBE41o- and its CF transmembrane ion condcutance regulator (CFTR)-corrected counterpart grown under air-liquid interface conditions after stimulation with lipopolysaccharide (LPS) from gram-negative bacteria. In CFTR-corrected cells, IL-8 and IL-6 secretions were constitutively activated but significantly increased after LPS stimulation compared with CFBE41o-. Blocking TLR-4 by a specific antibody significantly inhibited IL-8 secretion only in CFTR-corrected cells. Transfection with specific siRNA directed against TLR-4 mRNA significantly reduced the response to LPS in both cell lines. Fluorescence-activated cell sorter analysis revealed significantly higher levels of TLR-4 surface expression in CFTR-corrected cells. In histologic lung sections of patients with CF, the TLR-4 expression in the bronchial epithelium was significantly reduced compared with healthy control subjects. In CF the loss of CFTR function appears to decrease innate immune responses, possibly by altering the expression of TLR-4 on airway epithelial cells. This may contribute to chronic bacterial infection of CF airways.

Inhibition of NFkappaB by the natural product Withaferin A in cellular models of Cystic Fibrosis inflammation

Cystic Fibrosis (CF) is one of the most common autosomal genetic disorders in humans. This disease is caused by mutations within a single gene, coding for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. The phenotypic hallmark of CF is chronic lung infection and associated inflammation from opportunistic microbes such as Pseudomonas aeruginosa (PA), Haemophilus influenzae, and Staphylococcus aureus. This eventually leads to deterioration of lung function and death in most CF patients. Unfortunately, there is no approved therapy for correcting the genetic defect causal to the disease. Hence, controlling inflammation and infection in CF patients are critical to disease management. Accordingly, anti-inflammatory agents and antibiotics are used to manage chronic inflammation and infection in CF patients. However, most of the anti-inflammatory agents in CF have severe limitations due to adverse side effects, and resistance to antibiotics is becoming an even more prominent problem. Thus, new agents that can be used to control chronic inflammation in CF are needed in the absence of a cure for the disease. Activation of the transcription factor NFκB through Toll-like receptors (TLR) following bacterial infection is principally involved in regulating lung inflammation in CF. NFκB regulates the transcription of several genes that are involved in inflammation, anti-apoptosis and anti-microbial activity, and hyper-activation of this transcription factor leads to a potent inflammatory response. Thus, NFκB is a potential anti-inflammatory drug target in CF. Screening of several compounds from natural sources in an in vitro model of CF-related inflammation wherein NFκB is activated by filtrates of a clinically isolated strain of PA (PAF) led us to Withaferin A (WFA), a steroidal lactone from the plant Withania Somnifera L. Dunal. Our data demonstrate that WFA blocks PAF-induced activation of NFκB as determined using reporter assays, IL-8 measurements and high-content fluorescent imaging of NFκB subunit p65 translocation. Since the airways of CF patients can be specifically targeted for delivery of therapeutics, we propose that WFA should be further studied as an anti-inflammatory agent in models of CF related inflammation mediated by NFκB.

Cigarette smoke induces cellular senescence via Werner's syndrome protein down-regulation

RATIONALE

Werner's syndrome is a genetic disorder that causes premature aging due to loss-of-function mutations in a gene encoding a member of the RecQ helicase family. Both Werner's syndrome and cigarette smoking accelerate aging. No studies have examined the effect of cigarette smoke on Werner's syndrome protein.

OBJECTIVES

To investigate the role of Werner's syndrome protein in cigarette smoke-induced cellular senescence.

METHODS

Cellular senescence and amounts of Werner's syndrome protein were measured in fibroblasts isolated from patients with emphysema and compared with age-matched nonsmokers. The in vitro effects of cigarette smoke on amounts of Werner's syndrome protein, function, and senescence were also evaluated in primary human lung fibroblasts and epithelial cells.

MEASUREMENTS AND MAIN RESULTS

Cultured lung fibroblasts isolated from patients with emphysema exhibited a senescent phenotype accompanied by a decrease in Werner's syndrome protein. Cigarette smoke extract decreased Werner's syndrome protein in cultured fibroblasts and epithelial cells. Werner's syndrome protein-deficient fibroblasts were more susceptible to cigarette smoke-induced cellular senescence and cell migration impairment. In contrast, exogenous overexpression of Werner's syndrome protein attenuated the cigarette smoke effects.

CONCLUSIONS

Cigarette smoke induces cellular senescence and cell migration impairment via Werner's syndrome protein down-regulation. Rescue of Werner's syndrome protein down-regulation may represent a potential therapeutic target for smoking-related diseases.

Highlights of a workshop to discuss targeting inflammation in cystic fibrosis

A workshop to discuss anti-inflammatory approaches in the treatment of CF was held at Novartis Institutes for Biomedical Research (NIBR, Horsham, UK) in March 2008. Key opinion leaders in the field (Hugo De Jonge, Stuart Elborn, Erich Gulbins, Mike Konstan, Rick Moss, Scott Randell and Adriano Rossi), and NIBR scientists were brought together to collectively address three main aims: (i) to identify anti-inflammatory targets in CF, (ii) to evaluate the pros and cons of targeting specific cell types and (iii) to discuss model systems to profile potential therapeutic agents. The highlights of the workshop are captured in this review.

Respiratory epithelial cells convert inactive vitamin D to its active form: potential effects on host defense

The role of vitamin D in innate immunity is increasingly recognized. Recent work has identified a number of tissues that express the enzyme 1alpha-hydroxylase and are able to activate vitamin D. This locally produced vitamin D is believed to have important immunomodulatory effects. In this paper, we show that primary lung epithelial cells express high baseline levels of activating 1alpha-hydroxylase and low levels of inactivating 24-hydroxylase. The result of this enzyme expression is that airway epithelial cells constitutively convert inactive 25-dihydroxyvitamin D(3) to the active 1,25-dihydroxyvitamin D(3). Active vitamin D that is generated by lung epithelium leads to increased expression of vitamin D-regulated genes with important innate immune functions. These include the cathelicidin antimicrobial peptide gene and the TLR coreceptor CD14. dsRNA increases the expression of 1alpha-hydroxylase, augments the production of active vitamin D, and synergizes with vitamin D to increase expression of cathelicidin. In contrast to induction of the antimicrobial peptide, vitamin D attenuates dsRNA-induced expression of the NF-kappaB-driven gene IL-8. We conclude that primary epithelial cells generate active vitamin D, which then influences the expression of vitamin D-driven genes that play a major role in host defense. Furthermore, the presence of vitamin D alters induction of antimicrobial peptides and inflammatory cytokines in response to viruses. These observations suggest a novel mechanism by which local conversion of inactive to active vitamin D alters immune function in the lung.