Inflammation in cystic fibrosis airways: relationship to increased bacterial adherence

Reduced neutrophil elastase inhibitor elafin and elevated transforming growth factor-β1 are linked to inflammatory response in sputum of cystic fibrosis patients with Pseudomonas aeruginosa

Research question

Pulmonary disease progression in patients with cystic fibrosis (CF) is characterised by inflammation and fibrosis and aggravated by Pseudomonas aeruginosa (Pa). We investigated the impact of Pa specifically on: 1) protease/antiprotease balance; 2) inflammation; and 3) the link of both parameters to clinical parameters of CF patients.

Methods

Transforming growth factor-β₁ (TGF-β₁), interleukin (IL)-1β, IL-8, neutrophil elastase (NE) and elastase inhibitor elafin were measured (ELISA assays), and gene expression of the NF-κB pathway was assessed (reverse transcriptase PCR) in the sputum of 60 CF patients with a minimum age of 5 years. Spirometry was assessed according to American Thoracic Society guidelines.

Results

Our results demonstrated the following: 1) NE was markedly increased in Pa-positive sputum, whereas elafin was significantly decreased; 2) increased IL-1β/IL-8 levels were associated with both Pa infection and reduced forced expiratory volume in 1 s, and sputum TGF-β₁ was elevated in Pa-infected CF patients and linked to an impaired lung function; and 3) gene expression of NF-κB signalling components was increased in sputum of Pa-infected patients, and these findings were positively correlated with IL-8.

Conclusion

Our study links Pa infection to an imbalance of NE and NE inhibitor elafin and increased inflammatory mediators. Moreover, our data demonstrate an association between high TGF-β₁ sputum levels and a progress in chronic lung inflammation and pulmonary fibrosis in CF. Controlling the excessive airway inflammation by inhibition of NE and TGF-β₁ might be promising therapeutic strategies in future CF therapy and a possible complement to cystic fibrosis transmembrane conductance regulator (CFTR) modulators.

In Vivo Proteome of Pseudomonas aeruginosa in Airways of Cystic Fibrosis Patients

Chronic airway infection with P. aeruginosa (PA) is a hallmark of cystic fibrosis (CF) disease. The mechanisms producing PA persistence in CF therapies remain poorly understood. To gain insight on PA physiology in patient airways and better understand how in vivo bacterial functioning differs from in vitro conditions, we investigated the in vivo proteomes of PA in 35 sputum samples from 11 CF patients. We developed a novel bacterial-enrichment method that relies on differential centrifugation and detergent treatment to enrich for bacteria to improve identification of PA proteome with CF sputum samples. Using two nonredundant peptides as a cutoff, a total of 1304 PA proteins were identified directly from CF sputum samples. The in vivo PA proteomes were compared with the proteomes of ex vivo-grown PA populations from the same patient sample. Label-free quantitation and proteome comparison revealed the in vivo up-regulation of siderophore TonB-dependent receptors, remodeling in central carbon metabolism including glyoxylate cycle and lactate utilization, and alginate overproduction. Knowledge of these in vivo proteome differences or others derived using the presented methodology could lead to future treatment strategies aimed at altering PA physiology in vivo to compromise infectivity or improve antibiotic efficacy.

Targeting Cytokines as Evolving Treatment Strategies in Chronic Inflammatory Airway Diseases

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

Respiratory viruses are associated with common respiratory pathogens in cystic fibrosis

OBJECTIVES

Test the hypothesis that the link between respiratory viruses and pulmonary exacerbation in cystic fibrosis (CF) reflects increased frequency or severity of lower airways infection.

STUDY DESIGN

Molecular respiratory viral panels (RVPs), cell counts, and quantitative bacterial cultures were assessed in 235 bronchoalveolar lavage fluid (BALF) samples from 138 children with CF. Relationships among the data were analyzed using multivariate methods.

RESULTS

RVPs were positive in 67 (28.5%) BALF samples from 52 (37.7%) patients, with rhinovirus/enterovirus most common (82.4% of RVP+). RVP+ patients were younger (5.4 years, IQR 3.0-9.7 vs. 8.0 years, IQR 3.5-12.9; P < 0.01), more likely to have respiratory symptoms (74.6% vs. 55.2%, P < 0.01), and had higher BALF percent neutrophils (70.5%, IQR 46-85% vs. 59.3%, IQR 34-77%; P < 0.05). Percent predicted FEV1 at bronchoscopy was diminished from baseline in both groups, but recovered in the RVP- (90.2 ± 22.2% vs. 89.6 ± 19.7%, P = 0.62) but not the RVP+ subjects (95.7 ± 21.1% vs. 89.1 ± 18.0%, P < 0.05). RVP status did not alter recovery rates of typical CF respiratory pathogens including Staphylococcus aureus (44.8% vs. 42.9%) and Pseudomonas aeruginosa (25.4% vs. 25.6%). However, common respiratory pathogens (Haemophilus species, Moraxella species, and Streptococcus pneumoniae) were recovered more frequently from RVP+ samples independent of age (OR 3.6, 95% CI 1.8-7.5, P < 0.001).

CONCLUSIONS

Respiratory viruses were frequently detected in BALF from CF patients and associated with markers of disease severity. Respiratory viruses did not impact frequency or severity of infection with typical CF pathogens, but rates of infection with common respiratory pathogens were increased. This finding may have treatment implications.

Intravenous and Inhaled Antimicrobials at Home in Cystic Fibrosis Patients

The primary clinical characteristics of cystic fibrosis (CF) are malnutrition caused by malabsorption secondary to pancreatic insufficiency, chronic pulmonary infections, and male infertility. The major cause of morbidity and mortality are bronchiectasis and obstructive pulmonary disease. Lung disease in CF is manifested by this chronic lung disease progression, with intermittent episodes of acute worsening of symptoms called pulmonary exacerbations. Once the patient has stabilized, and if suitable care can be arranged, these interventions are often transitioned to the home. This review summarizes important points pertinent to the use of intravenous and inhaled antimicrobials that may be encountered by prescribers, nurses, technicians, and case managers in the home health setting. Appropriate dosing, indications, adverse drug reactions, monitoring parameters, and practicality of both intravenous and inhaled antimicrobials are discussed.

TPL2 signalling: from Toll-like receptors-mediated ERK1/ERK2 activation to Cystic Fibrosis lung disease

Cystic Fibrosis (CF) is the most common lethal genetic recessive disorder, with a carrier frequency of 1 in 27 among North American Caucasians. Mitogen-activated protein kinases (MAPKs) and pro-inflammatory cytokines have crucial functions in the innate immune response of epithelial cells. They determine the inflammation status and the host response to pathogenic infections. However, in CF, bacterial-driven inflammation leads to tissue destruction, reduction in lung function and mortality. Recognition of invading pathogens is mediated in part by Toll-like receptors (TLR) activation of intracellular signalling cascade leading to cytokines' synthesis. The protein kinase Tumour Progression Locus 2 (TPL2) is a key molecule in relaying inflammatory stimuli to ERK1/ERK2 MAPKs. In this review, we summarized the recent findings on TPL2 signalling and how TPL2 can contribute to the excessive inflammation found in CF. Pharmacologically targeting this kinase could have a significant benefit for CF patients dealing with chronic bacterial infections such as Pseudomonas aeruginosa. This article is part of a Directed Issue entitled: Cystic Fibrosis: From o-mics to cell biology, physiology, and therapeutic advances.

Pseudomonas pyocyanin stimulates IL-8 expression through MAPK and NF-κB pathways in differentiated U937 cells

Background

Pyocyanin (PCN), an extracellular product of Pseudomonas aeruginosa and a blue redox active secondary metabolite, plays an important role in invasive pulmonary infection. However, the detailed inflammatory response triggered by PCN infection in inflammatory cells (particularly macrophages), if present, remains to be clarified. To investigate the effects of PCN on macrophages, the ability of PCN to induce inflammation reaction and the signaling pathway for IL-8 release in PCN-induced differentiated U937 cells were examined.

Results

It was found that PCN increased IL-8 release and mRNA expression in Phorbol 12-myristate 13-acetate (PMA) differentiated U937 cells in both a concentration- and time-dependent manner by reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). P38 and ERK MAPKs were activated after 10 min of induction with PCN and their levels returned to baselines after 30 min by Western blotting. It was also found that within 10 min of PCN incubation, the level of p-I-κBα in the cytosol was increased, which returned to baseline level after 60 min. Meanwhile, the level of p-p65 was increased in the nuclear extract and cytosol, and maintained high in total cell lysates. The results were further confirmed by the observation that p38, ERK1/2 and NF-κB inhibitors inhibited PCN-induced NF-κB activation and attenuated PCN-induced IL-8 expression in U937 cells as a function of their concentrations. Moreover, it was shown that PCN induced oxidative stress in U937 cells and N-acetyl cysteine, an antioxidant, was able to inhibit PCN-induced IL-8 protein expression.

Conclusions

It is concluded that PCN induces IL-8 secretion and mRNA expression in PMA-differentiated U937 cells in a concentration- and time- dependent manner. Furthermore, p38 and ERK MAPKs and NF-κΒ signaling pathways may be involved in the expression of IL-8 in PCN-incubated PMA-differentiated U937 cells.

The role of mean platelet volume predicting acute exacerbations of cystic fibrosis in children

OBJECTIVE:

The aim of this study is to evaluate the relationship between acute exacerbations and the mean platelet volume (MPV) trend in children with cystic fibrosis (CF), to predict the exacerbations.

METHODS:

A total of 46 children with CF and 37 healthy children were enrolled in the study. White blood cell count (WBC), hemoglobin level, platelet count, mean platelet volume (MPV), and mean corpuscular volume (MCV) were retrospectively recorded.

RESULTS:

Our study population consisted of 25 (54.3%) males and 21 (45.7%) females with CF and 20 (54.0%) males and 17 (46.0%) females in the healthy control group. The mean age of the CF patients was 6.32 ± 4.9 years and that of the healthy subjects was 7.02 ± 3.15 years. In the acute exacerbation period of CF, the MPV values were lower and WBC and platelet counts were higher than those in the healthy controls (P = 0.00, P = 0.00, P = 0.00, respectively). Besides, in acute exacerbation, the MPV values were lower and the WBC count was higher than the values in the non-exacerbation period (P 0= 0.01, P = 0.00, respectively). In the non-exacerbation period MPV was lower and platelet count was higher when compared to healthy subjects (P = 0.02, P = 0.04, respectively).

CONCLUSION:

This study suggests that MPV might be used as a simple, cost effective, diagnostic, predictive indicator for platelet activation in pediatric CF patients related to chronic inflammation, which might be helpful to discriminate or estimate exacerbations.

The Role of Nuclear Factor Kappa B in the Pathogenesis of Pulmonary Diseases: Implications for Therapy

The nuclear factor kappa B (NF-kappaB) transcription factor plays a key role in the induction of pro-inflammatory gene expression, leading to the synthesis of cytokines, adhesion molecules, chemokines, growth factors and enzymes. Results of studies in in vitro and in vivo models of inflammation and malignancy have also suggested central roles for NF-kappaB in programmed cell death, or apoptosis. NF-kappaB plays a central role in a variety of acute and chronic inflammatory diseases. In the common lung diseases associated with a significant inflammatory component such as severe sepsis, acute lung injury, acute respiratory distress syndrome, cystic fibrosis and asthma, the pathogenic roles of NF-kappaB have been extensively investigated. In COPD, activation of NF-kappaB has been implicated in disease pathogenesis but its exact role is less clearly demonstrable in this heterogeneous patient population. However, the principal risk factor for COPD, cigarette smoking, is strongly associated with NF-kappaB activation. Activation of NF-kappaB has been demonstrated in mineral dust diseases and probably plays a role in the pathogenesis of these chronic illnesses. NF-kB also plays a variety of roles in lung cancer including resistance to chemotherapy, inhibition of tumorigenesis and inducing expression of antiapoptotic genes. The complex NF-kappaB pathway offers a variety of potential molecular targets for chemotherapeutic intervention. A variety of agents aimed at modulating NF-kappaB activity are in various stages of investigation.

Role of CFTR expressed by neutrophils in modulating acute lung inflammation and injury in mice

Objective and design

Cystic fibrosis transmembrane conductance regulator (CFTR) regulates infection and inflammation. In this study, we investigated whether a lack of functional CFTR in neutrophils would promote lipopolysaccharide (LPS)-induced lung inflammation and injury.

Materials and methods

CFTR-inhibited or F508del-CFTR-mutated neutrophils were stimulated with LPS and cultured to evaluate production of cytokines and NF-κB activation. Wild-type mice were reconstituted with F508del neutrophils or bone marrow and then intratracheally challenged with LPS to observe lung inflammatory response.

Results

Pharmacologic inhibition and genetic mutation of CFTR in neutrophils activated NF-κB and facilitated macrophage inflammatory protein-2 (MIP-2) and tumor necrosis factor-α (TNF-α) production. Wild-type mice reconstituted with F508del neutrophils and bone marrow had more severe lung inflammation and injury after LPS challenge compared to wild-type mice receiving wild-type neutrophils or bone marrow reconstitution.

Conclusions

Lack of functional CFTR in neutrophils can promote LPS-induced acute lung inflammation and injury.

Mechanisms of action and clinical application of macrolides as immunomodulatory medications

Macrolides have diverse biological activities and an ability to modulate inflammation and immunity in eukaryotes without affecting homeostatic immunity. These properties have led to their long-term use in treating neutrophil-dominated inflammation in diffuse panbronchiolitis, bronchiectasis, rhinosinusitis, and cystic fibrosis. These immunomodulatory activities appear to be polymodal, but evidence suggests that many of these effects are due to inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation and nuclear factor kappa B (NF-kappaB) activation. Macrolides accumulate within cells, suggesting that they may associate with receptors or carriers responsible for the regulation of cell cycle and immunity. A concern is that long-term use of macrolides increases the emergence of antimicrobial resistance. Nonantimicrobial macrolides are now in development as potential immunomodulatory therapies.

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.

Myeloperoxidase-dependent oxidative metabolism of nitric oxide in the cystic fibrosis airway

BACKGROUND

Decreased expired nitric oxide (eNO) is commonly observed in cystic fibrosis (CF) patients and is usually explained by dysregulation of NO synthase (NOS) isoforms in respiratory tract epithelium. Later stages of this disease are accompanied by intense airway infiltration of phagocytes with high NOS activity, abundant levels of the hemoprotein myeloperoxidase (MPO) and significant production of significant reactive oxygen species.

METHODS

This study characterizes the contribution of the high airway levels of MPO to decreased eNO levels in adult CF patients. NO metabolites (NO(x)) and MPO levels in fresh sputum of control and adult CF patients were determined and related to measurements of eNO and to in vitro consumption of NO in CF sputum.

RESULTS

Despite essentially equal levels of NO(x) in sputum, eNO was 2- to 3-fold lower in CF patients compared to healthy controls. In CF patients, eNO levels were negatively associated with sputum peroxidase activity. In vivo correlations were confirmed by ex vivo studies of NO consumption by MPO in CF sputum. Immunodepletion studies confirmed MPO as the major heme peroxidase in CF sputum contributing to the hydrogen peroxide (H(2)O(2))-dependent consumption of NO.

CONCLUSIONS

In CF airways MPO acts as a phagocyte-derived NO oxidase that diminishes NO bioavailability at airway surfaces, possibly identifying this peroxidase as a potential target for therapeutic intervention.

SUMOylation of tissue transglutaminase as link between oxidative stress and inflammation

Cystic fibrosis (CF) is a monogenic disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. CF is characterized by chronic bacterial lung infections and inflammation, and we have previously reported that tissue transglutaminase (TG2), a multifunctional enzyme critical to several diseases, is constitutively up-regulated in CF airways and drives chronic inflammation. Here, we demonstrate that the generation of an oxidative stress induced by CFTR-defective function leads to protein inhibitor of activated STAT (PIAS)y-mediated TG2 SUMOylation and inhibits TG2 ubiquitination and proteasome degradation, leading to sustained TG2 activation. This prevents peroxisome proliferator-activated receptor (PPAR)gamma and IkBalpha SUMOylation, leading to NF-kappaB activation and to an uncontrolled inflammatory response. Cellular homeostasis can be restored by small ubiquitin-like modifier (SUMO)-1 or PIASy gene silencing, which induce TG2 ubiquitination and proteasome degradation, restore PPARgamma SUMOylation, and prevent IkBalpha cross-linking and degradation, thus switching off inflammation. Manganese superoxide dismutase overexpression as well as the treatment with the synthetic superoxide dismutase mimetic EUK-134 control PIASy-TG2 interaction and TG2 SUMOylation. TG2 inhibition switches off inflammation in vitro as well as in vivo in a homozygous F508del-CFTR mouse model. Thus, TG2 may function as a link between oxidative stress and inflammation by driving the decision as to whether a protein should undergo SUMO-mediated regulation or degradation. Targeting TG2-SUMO interactions might represent a new option to control disease evolution in CF patients as well as in other chronic inflammatory diseases, neurodegenerative pathologies, and cancer.

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.

Frequency of cytokine gene promoter polymorphisms in the Northern Ireland Cystic Fibrosis population

It has been postulated that cytokine allele frequencies are gender and perhaps geographically-specific. Cytokine release is crucial in the regulation of the type and magnitude of the immune response. This study observed no differences in the frequency of cytokine promoter polymorphisms associated with variant levels of expression in patients with CF and a non-CF population of Northern Ireland.

Premature cellular senescence induced by pyocyanin, a redox-active Pseudomonas aeruginosa toxin

Pseudomonas aeruginosa is an important nosocomial pathogen that can cause acute and chronic infection, particularly of the respiratory system. Pyocyanin is a major P. aeruginosa virulence factor that displays redox activity and induces oxidative stress in cellular systems. The effect of pyocyanin on replicating human pulmonary epithelial (A549) cells was investigated. Cells were exposed to pyocyanin for 24 h and their subsequent growth and development were followed for 7 days. Pyocyanin (5-10 microM) arrested cell growth and resulted in the development of a morphological phenotype consistent with cellular senescence, that is, an enlarged and flattened appearance. The senescent nature of these cells was supported by positive staining for increased lysosomal content and senescence-associated beta-galactosidase activity. All cells treated with pyocyanin (10 microM) converted to the senescent phenotype, which remained stable for up to 7 days. Exposure to pyocyanin at 25 microM or greater resulted in cell death due to apoptosis. A549 cells exposed to pyocyanin generated hydrogen peroxide in a dose-dependent manner and the senescence-inducing effect of pyocyanin was inhibited by the antioxidant, glutathione, suggesting the involvement of reactive oxygen species. The induction of premature cellular senescence by redox-active bacterial toxins may be a hitherto unrecognized aspect of infection pathology and a limiting factor in the tissue repair response to infection.

Dysregulated interleukin-8 secretion and NF-κB activity in human cystic fibrosis nasal epithelial cells

BACKGROUND

It is not clear whether cystic fibrosis (CF) airway inflammation is a consequence of bacterial infection or is intrinsically dysregulated. The aim of this study was to investigate IL-8 secretion and NF-kappaB activity in primary respiratory epithelial cells cultured from nasal polyps obtained from CF and non-CF subjects.

METHODS

NF-kappaB activity was studied by electrophoretic mobility-shift and quantitative colorimetric assays in nuclear extracts. Immunoreactive IL-8 levels were assessed by ELISA in cell culture supernatants. Both parameters were studied at baseline and following challenge with Pseudomonas aeruginosa or stimulation with pro-inflammatory cytokines.

RESULTS

Under basal conditions, CF cells presented a significant higher activity of NF-kappaB than non-CF cells (P=0.0004). P. aeruginosa challenge and IL-1beta/H2O2 co-stimulation caused four and two fold induction of NF-kappaB activity in non-CF and CF cells, respectively. IL-8 levels in unstimulated CF cells were significantly higher than in non-CF cells (P=0.0025). Upon incubation with P. aeruginosa and IL-1beta/H2O2, non-CF cells produced 6.3 times more IL-8 than unstimulated cells, whereas IL-8 secretion increased only of 1.4 times in CF cells.

CONCLUSIONS

CF respiratory epithelial cells exhibit a basal dysregulated production of IL-8 that partially correlates to enhanced NF-kappaB activity. Our data corroborate the hypothesis of a basal exaggerated inflammatory response in the CF respiratory epithelium.

The inflammatory role of platelets in cystic fibrosis

Platelets are an important, albeit generally underappreciated, component of the inflammatory cascade. Platelets are known to contribute to inflammation in atherosclerosis, stroke, and asthma. They produce a large number of proinflammatory lipid mediators and cytokines, and play a vital role in recruitment of leukocytes into inflamed tissue. We review the role of platelets in inflammation, how they assist in the recruitment of leukocytes into lung tissue in asthma, and evidence of their dysfunction in cystic fibrosis (CF). Platelet dysfunction in CF could contribute to pulmonary inflammation and tissue destruction. We hypothesize that platelet activation is important in CF lung disease and suggest research avenues that might help elucidate the role of activated platelets in CF.

Lower airway inflammation in infants with cystic fibrosis detected by newborn screening

Controversy exists over whether the lower airway inflammation that characterizes cystic fibrosis (CF) is initiated primarily by the genetic defect. To determine if inflammation precedes infection, we examined bronchoalveolar lavage (BAL) fluid cytology, cytokines (interleukin (IL)-1beta, IL-4, IL-5, IL-6, IL-8, IL-10, and tumor necrosis factor-alpha), and free neutrophil elastase activity from 70 CF (aged 1.5-71 months) children detected by newborn screening and 19 (aged 2.0-48 months) controls with chronic stridor. CF subjects were selected and categorized as pristine (13 aged </= 6 months, lacking prior respiratory symptoms and exposure to antibiotics, and without respiratory pathogens on BAL), infected (42 with viruses or >/= 10(5) colony-forming units/ml of pathogenic bacteria in BAL), and uninfected (15 aged > 6 months, asymptomatic, not taking antibiotics at bronchoscopy, and free of pathogens in their BAL). To further resolve if inflammation develops without infection, inflammatory mediators in paired annual BAL samples from 38 CF subjects were measured, and results were grouped according to whether BAL showed persistence (n = 6), acquisition (n = 8), clearance (n = 13), or absence (n = 11) of infection. While pristine, uninfected, and control subjects had similar BAL profiles, infected patients showed elevated inflammatory indices, including increased IL-10 (P < 0.001). Pristine subjects had the fewest signs of inflammation. Analysis of BAL pairs found differences between the four infection groups for changes in neutrophil percentages, IL-8 (P < 0.001), and free neutrophil elastase (P = 0.009). Infection was associated with elevated inflammatory mediators in BAL fluid. In contrast, minimal or reduced signs of inflammation accompanied absence of eradication of infection from BAL fluid. We conclude that in CF, infection initiates and sustains airway inflammation.

Prophylactic antibiotics in cystic fibrosis: a conviction without evidence?

Pulmonary infection with Staphylococcus aureus occurs in young children with cystic fibrosis, and may contribute to the cycle of infection, inflammation, and destruction of lung tissue which leads to bronchiectasis. Practice guidelines in North America and the UK differ greatly with regard to the advice given on prescribing prophylactic antistaphylococcal antibiotics to young children with cystic fibrosis. This article reviews the evidence behind these guidelines, and suggests a pragmatic approach to clinical practice. The implications for research are also discussed, and suggestions are made for clinical trials to inform future guidelines.

Cystic fibrosis in neonates and infants

Cystic fibrosis (CF) is a common autosomal recessive disorder, characterized by chronic bronchopulmonary infection, pancreatic insufficiency, and subsequently, other multisystem complications. Most children are diagnosed before school age. Here we review the pathophysiology of the condition, the age-related presentations of CF up until school age, and the appropriate use of diagnostic tests. A specialist centre should supervise treatment. There are exciting new advances in monitoring techniques in the preschool years, including CT scanning, bronchoscopy and gas mixing indices. Recent advances in the knowledge of the molecular biology of CF hold out the hope of specific therapies which can reverse the underlying defect causing death from CF lung disease.

Pseudomonas aeruginosa: the potential to immunise against infection

Pseudomonas aeruginosa remains a serious pathogen for specific cohorts of patients where chronic infection is a poor prognostic indicator, such as those with cystic fibrosis, burn wounds or those who are immunocompromised. Significant disease burden is associated with a diverse spectrum of both nosocomial and community-acquired infections. To date, vaccines against P. aeruginosa have shown limited and often conflicting efficacy data, especially against heterologous strains, which are increasingly identified as co-colonisers of biofilms. While few studies have gone beyond Phase II clinical trials, a particular concern is the ability of P. aeruginosa to evade the immune system while provoking an immune response that contributes to the destructive nature of infection. Therefore, vaccine development needs to focus on preventing attachment and colonisation, as well as preventing conversion to a mucoid phenotype that is characteristic of the chronic condition that promotes pathology.

Relation of exaggerated cytokine responses of CF airway epithelial cells to PAO1 adherence

In many model systems, cystic fibrosis (CF) phenotype airway epithelial cells in culture respond to P. aeruginosa with greater interleukin (IL)-8 and IL-6 secretion than matched controls. In order to test whether this excess inflammatory response results from the reported increased adherence of P. aeruginosa to the CF cells, we compared the inflammatory response of matched pairs of CF and non CF airway epithelial cell lines to the binding of GFP-PAO1, a strain of pseudomonas labeled with green fluorescent protein. There was no clear relation between GFP-PAO1 binding and cytokine production in response to PAO1. Treatment with exogenous aGM1 resulted in greater GFP-PAO1 binding to the normal phenotype compared to CF phenotype cells, but cytokine production remained greater from the CF cell lines. When cells were treated with neuraminidase, PAO1 adherence was equalized between CF and nonCF phenotype cell lines, but IL-8 production in response to inflammatory stimuli was still greater in CF phenotype cells. The polarized cell lines 16HBEo-Sense (normal phenotype) and Antisense (CF phenotype) cells were used to test the effect of disrupting tight junctions, which allows access of PAO1 to basolateral binding sites in both cell lines. IL-8 production increased from CF, but not normal, cells. These data indicate that increased bacterial binding to CF phenotype cells cannot by itself account for excess cytokine production in CF airway epithelial cells, encourage investigation of alternative hypotheses, and signal caution for therapeutic strategies proposed for CF that include disruption of tight junctions in the face of pseudomonas infection.

Endothelial activation and increased heparan sulfate expression in cystic fibrosis

RATIONALE

Pulmonary disease in cystic fibrosis (CF) is characterized by an exaggerated interleukin (IL)-8-driven, neutrophilic, inflammatory response to infection. Binding of IL-8 to heparan sulfate (HS)-containing proteoglycans (HSPG) facilitates binding of the chemokine to its specific receptor, stabilizes and prolongs IL-8 activity, and protects it from proteolysis. We hypothesized that increased expression of HSPG contributes to the sustained inflammatory response in CF bronchial tissue.

OBJECTIVES

Our objectives were to analyze the distribution and abundance of IL-8 and HS, in intact and cleaved forms, in bronchial tissue from adult patients with CF or chronic obstructive pulmonary disease (COPD) and a control group without inflammatory airway disease.

METHODS

Immunostaining and quantitative image analysis were applied to ethanol-fixed and paraffin-embedded tissue obtained at transplant in patients with CF or COPD, or postmortem in the control group.

MEASUREMENTS AND MAIN RESULTS

Quantitative immunohistochemical analysis demonstrated significant disease-related differences. Intact HS was significantly more abundant in epithelial and endothelial basement membranes in CF than in COPD or the control group. Conversely, cleaved HS was significantly more abundant in COPD than the other groups. More IL-8-positive blood vessels were observed in CF and COPD compared with the control group, whereas more extensive IL-8 expression in the epithelium was observed in CF compared with COPD.

CONCLUSIONS

Sustained neutrophil recruitment in the CF airway may therefore be related not only to increased IL-8 expression but also to the increased stability and prolonged activity and retention of IL-8 when it is bound to HSPG in bronchial tissue.

Cytokines and inflammatory mediators in cystic fibrosis

Airway disease in cystic fibrosis (CF) is characterised by a continuous cycle of chronic infection and inflammation dominated by a neutrophilic infiltrate. This inflammation is characterised by an increased production of pro-inflammatory cytokines in the lung. The relationship between the abnormal CFTR gene product and the development of inflammation and progression of lung disease in CF is not fully understood. This review article studied the mechanisms of pulmonary inflammation in CF, the profiles of cytokines and inflammatory mediators in the lung in CF, the mechanisms that predispose to chronic Pseudomonas aeruginosa infection, cytokine involvement in diseases other than CF and reviewed current therapeutic strategies for CF. Imbalances of cytokine secretion are now better understood due to recent advances in understanding CF at a molecular level and it is increasingly thought that the normal inflammatory process is deranged in CF early in the course of the disease and may occur in the absence of detectable infection. However, the relationship between this unbalanced cytokine production, the mutations in CFTR and its actual consequence for pathogenesis need further investigation.

Cytokine secretion by cystic fibrosis airway epithelial cells

It is controversial whether mutations in cystic fibrosis transmembrane conductance regulator intrinsically dysregulate inflammation. We characterized passage 2 human tracheobronchial epithelial cell cultures morphologically and physiologically and determined whether cytokine production or nuclear factor-kappaB activation was systematically altered in cystic fibrosis (CF) cells. Non-CF and CF cells originating from a total of 33 and 25 lungs, respectively, were available for culture on plastic or at an air-liquid interface until well differentiated. Forskolin-stimulated short-circuit currents were present in representative polarized non-CF cultures and were absent in CF cultures, whereas uridine 5'-triphosphate-stimulated currents were present in both. Constitutive or interleukin (IL)-1beta-induced IL-8 or IL-6 secretion or nuclear factor-kappaB activity was not significantly different between non-CF and CF cells. The cytokines regulated upon activation, normal T cell expressed and secreted (RANTES) and IL-10 were not detectable. Stimulation with tumor necrosis factor-alpha or a synthetic toll-like receptor 2 agonist or variable doses and times of Staphylococcus aureus culture filtrate revealed a single dose- and time-dependent difference in IL-8 production by CF cells. Interestingly, although IL-8 secretion after stimulation with Pseudomonas aeruginosa filtrates was not greater in CF cells in the absence of human serum, it was variably greater in its presence. Thus, although exaggerated responses may develop under certain conditions, our results do not support an overall intrinsically hyperinflammatory phenotype in CF cells.

Inflammation et mucoviscidose

Lung inflammation plays a pivotal role in the pathogenesis of airway disease in cystic fibrosis (CF). Inflammation occurs very early and can be identified in very young infants. Inflammatory response is also more intense in CF than in non-CF airway inflammatory diseases. Among the different cell types involved in the airway inflammation, neutrophils are recognized to play a central role by releasing proinflammatory mediators, such as reactive oxygen species and proteolytic enzymes. Whether inflammation arises independently from infection remains debated. While infection was demonstrated to clearly amplify the inflammation, several studies argue for the possibility of an intrinsic inflammation. Finally, there is also evidence that the severity of pulmonary disease is linked to other genetic factors outside the CFTR gene locus, involved in host defence and inflammation.

State of the art: why do the lungs of patients with cystic fibrosis become infected and why can't they clear the infection?

Cystic Fibrosis (CF) lung disease, which is characterized by airway obstruction, chronic bacterial infection, and an excessive inflammatory response, is responsible for most of the morbidity and mortality. Early in life, CF patients become infected with a limited spectrum of bacteria, especially P. aeruginosa. New data now indicate that decreased depth of periciliary fluid and abnormal hydration of mucus, which impede mucociliary clearance, contribute to initial infection. Diminished production of the antibacterial molecule nitric oxide, increased bacterial binding sites (e.g., asialo GM-1) on CF airway epithelial cells, and adaptations made by the bacteria to the airway microenvironment, including the production of virulence factors and the ability to organize into a biofilm, contribute to susceptibility to initial bacterial infection. Once the patient is infected, an overzealous inflammatory response in the CF lung likely contributes to the host's inability to eradicate infection. In response to increased IL-8 and leukotriene B₄ production, neutrophils infiltrate the lung where they release mediators, such as elastase, that further inhibit host defenses, cripple opsonophagocytosis, impair mucociliary clearance, and damage airway wall architecture. The combination of these events favors the persistence of bacteria in the airway. Until a cure is discovered, further investigations into therapies that relieve obstruction, control infection, and attenuate inflammation offer the best hope of limiting damage to host tissues and prolonging survival.

Growth factors in cystic fibrosis - when more is not enough

In the airways of patients with cystic fibrosis, repeated cycles of infection and inflammation are responsible for bronchial wall thickening, a major determinant of loss of FEV(1) and progressive damage to the small and large airways. Proteolytic degradation of elastin, collagen and fibronectin fibrils in the tissue matrix leads to the loss of normal tissue architecture and the development of bronchiectasis, the most commonly observed morphological change on high-resolution computed tomography examination. We have reviewed the evidence for increased expression of growth factors (TGF, HGF, FGF, EGF, VEGF) and activation of tissue repair processes in cystic fibrosis. Significantly higher concentrations of the growth factors compared with normal do not appear to prevent or reverse structural remodelling in the airways. The reasons why this process appears to be ineffective are discussed and we speculate on alternative strategies that might have a significant impact on the observed structural changes.

Increased leukotriene B4 and interleukin-6 in exhaled breath condensate in cystic fibrosis

Chronic neutrophilic airway inflammation is an important feature of cystic fibrosis (CF). Noninvasive inflammatory markers may be useful in monitoring CF. Leukotriene B4 (LTB4) and interleukin (IL)-6 are inflammatory mediators that are increased in chronic neutrophilic inflammation. The aim of this study was to assess whether LTB4 and IL-6 were increased in exhaled breath condensate of CF patients and whether they could be used to monitor inflammation. Twenty patients with CF (13 males, age of 28 +/- 9 years) were recruited together with 15 age-matched healthy subjects (8 males, age 35 +/- 7 years). LTB4 and IL-6 levels were markedly elevated in patients with acute exacerbations (28.8 +/- 4.3 and 8.7 +/- 0.4 pg/ml) compared with control subjects (6.8 +/- 0.7 and 2.6 +/- 0.1 pg/ml, p < 0.0001). We also observed a decrease of exhaled LTB4 and IL-6 concentrations after antibiotic treatment in six patients who were followed until clinically stable (31.1 +/- 4.4 and 9.5 +/- 0.4 pg/ml vs. 18.8 +/- 0.8 and 6.4 +/- 0.2 pg/ml, respectively) and an increase in 15 CF patients infected with Pseudomonas aeruginosa (34.3 +/- 5.0 and 9.3 +/- 0.3 pg/m) compared with those infected with other bacteria (18.3 +/- 0.7 and 6.9 +/- 0.5 pg/ml). These findings suggest that LTB4 and IL-6 levels are increased in exhaled breath condensate of patients with CF during exacerbation and could be used to monitor airway inflammation in these patients.

CFTR is a pattern recognition molecule that extracts Pseudomonas aeruginosa LPS from the outer membrane into epithelial cells and activates NF-kappa B translocation

Immune cells are activated during cellular responses to antigen by two described mechanisms: (i) direct uptake of antigen and (ii) extraction and internalization of membrane components from antigen-presenting cells. Although endocytosis of microbial antigens by pattern recognition molecules (PRM) also activates innate immunity, it is not known whether this involves extraction and internalization of microbial surface components. Epithelial cells on mucosal surfaces use a variety of receptors that are distinct from the classical endocytic PRM to bind and internalize intact microorganisms. Nonclassical receptor molecules theoretically could act as a type of endocytic PRM if these molecules could recognize, bind, extract, and internalize a pathogen-associated molecule and initiate cell signaling. We report here that the interaction between the cystic fibrosis transmembrane conductance regulator (CFTR) and the outer core oligosaccharide of the lipopolysaccharide (LPS) in the outer membrane of Pseudomonas aeruginosa satisfies all of these conditions. P. aeruginosa LPS was specifically recognized and bound by CFTR, extracted from the organism's surface, and endocytosed by epithelial cells, leading to a rapid (5- to 15-min) and dynamic translocation of nuclear transcription factor NF-kappa B. Inhibition of epithelial cell internalization of P. aeruginosa LPS prevented NF-kappa B activation. Cellular activation depended on expression of wild-type CFTR, because both cultured Delta F508 CFTR human airway epithelial cells and lung epithelial cells of transgenic-CF mice failed to endocytose LPS and translocate NF-kappa B. CFTR serves as a critical endocytic PRM in the lung epithelium, coordinating the effective innate immune response to P. aeruginosa infection.

Cystic fibrosis

Cystic fibrosis is the most common lethal inherited disorder with autosomal recessive inheritance. Major progress has been made in understanding the molecular mechanisms leading to increased susceptibility to Pseudomonas aeruginosa colonization. Persistent respiratory infection with P. aeruginosa leads to progressive pulmonary inflammation and is the major cause of morbidity and mortality. Treatment and prophylaxis of respiratory infection has improved the median survival and quality of life of cystic fibrosis patients. In the future, treatment of the underlying genetic defect may be possible.

Persistent and aggressive bacteria in the lungs of cystic fibrosis children

There have been enormous improvements in life expectancy of patients with cystic fibrosis, especially with improved nutrition and better understanding of the basic cellular defects. However, infection in particular with Pseudomonas aeruginosa and Burkholderia cepacia, has the greatest effect in decreasing life expectancy. Although infections can be prevented by rigorous infection control procedures, early aggressive antimicrobial chemotherapy and established infection managed by antibiotics, they are not completely effective. A greater understanding of how the bacteria evade the host defences and produce infection is needed.