Airway nitric oxide in patients with cystic fibrosis is associated with pancreatic function, Pseudomonas infection, and polyunsaturated fatty acids

Fatty acid abnormalities in cystic fibrosis-the missing link for a cure?

The care for cystic fibrosis (CF) has dramatically changed with the development of modulators, correctors, and potentiators of the CFTR molecule, which lead to improved clinical status of most people with CF (pwCF). The modulators influence phospholipids and ceramides, but not linoleic acid (LA) deficiency, associated with more severe phenotypes of CF. The LA deficiency is associated with upregulation of its transfer to arachidonic acid (AA). The AA release from membranes is increased and associated with increase of pro-inflammatory prostanoids and the characteristic inflammation is present before birth and bacterial infections. Docosahexaenoic acid is often decreased, especially in associated liver disease Some endogenously synthesized fatty acids are increased. Cholesterol and ceramide metabolisms are disturbed. The lipid abnormalities are present at birth, and before feeding in transgenic pigs and ferrets. This review focus on the lipid abnormalities and their associations to clinical symptoms in CF, based on clinical studies and experimental research.

Elexacaftor/tezacaftor/ivacaftor improves nasal nitric oxide in patients with cystic fibrosis

BACKGROUND

In health, nitric oxide (NO) shows high concentrations in the upper airways, while nasal NO (nNO) is significantly lower in patients with sinonasal inflammation, such as people with cystic fibrosis (PwCF). In PwCF treated with elexacaftor/tezacaftor/ivacaftor (ETI; PwCF-ETI), clinical improvement of sinonasal symptoms and inflammation was observed. We therefore hypothesised that ETI may increase nNO in PwCF.

METHODS

25 PwCF-ETI underwent nNO measurement at baseline and after 3 to 24 months of ETI treatment. NNO was measured using velum closure (VC) techniques in cooperative patients and tidal breathing (TB) for all patients. As controls, 7 CF patients not eligible for ETI (PwCF-non ETI) and 32 healthy controls (HC) were also repeatedly investigated.

RESULTS

In PwCF-ETI, sinonasal symptoms, lung function parameters and sweat chloride levels improved from baseline to follow-up whereas there was no change in PwCF-non ETI and HC. NNO increased from a median (IQR) value at baseline to follow-up from 348.2 (274.4) ppb to 779.6 (364.7) ppb for VC (P < 0.001) and from 198.2 (107.0) ppb to 408.3 (236.1) ppb for TB (P < 0.001). At follow-up, PwCF-ETI reached nNO values in the normal range. In PwCF-non ETI as well as HC, nNO did not change between baseline and follow-up.

CONCLUSIONS

In PwCF-ETI, the nNO values significantly increased after several months of ETI treatment in comparison to baseline and reached values in the normal range. This suggests that nNO is a potential non-invasive biomarker to examine sinonasal inflammatory disease in PwCF and supports the observation of clinical improvement in these patients.

Loss of CFTR function is associated with reduced bitter taste receptor-stimulated nitric oxide innate immune responses in nasal epithelial cells and macrophages

Introduction

Bitter taste receptors (T2Rs) are G protein-coupled receptors identified on the tongue but expressed all over the body, including in airway cilia and macrophages, where T2Rs serve an immune role. T2R isoforms detect bitter metabolites (quinolones and acyl-homoserine lactones) secreted by gram negative bacteria, including Pseudomonas aeruginosa, a major pathogen in cystic fibrosis (CF). T2R activation by bitter bacterial products triggers calcium-dependent nitric oxide (NO) production. In airway cells, the NO increases mucociliary clearance and has direct antibacterial properties. In macrophages, the same pathway enhances phagocytosis. Because prior studies linked CF with reduced NO, we hypothesized that CF cells may have reduced T2R/NO responses, possibly contributing to reduced innate immunity in CF.

Methods

Immunofluorescence, qPCR, and live cell imaging were used to measure T2R localization, calcium and NO signaling, ciliary beating, and antimicrobial responses in air-liquid interface cultures of primary human nasal epithelial cells and immortalized bronchial cell lines. Immunofluorescence and live cell imaging was used to measure T2R signaling and phagocytosis in primary human monocyte-derived macrophages.

Results

Primary nasal epithelial cells from both CF and non-CF patients exhibited similar T2R expression, localization, and calcium signals. However, CF cells exhibited reduced NO production also observed in immortalized CFBE41o- CF cells and non-CF 16HBE cells CRISPR modified with CF-causing mutations in the CF transmembrane conductance regulator (CFTR). NO was restored by VX-770/VX-809 corrector/potentiator pre-treatment, suggesting reduced NO in CF cells is due to loss of CFTR function. In nasal cells, reduced NO correlated with reduced ciliary and antibacterial responses. In primary human macrophages, inhibition of CFTR reduced NO production and phagocytosis during T2R stimulation.

Conclusions

Together, these data suggest an intrinsic deficiency in T2R/NO signaling caused by loss of CFTR function that may contribute to intrinsic susceptibilities of CF patients to P. aeruginosa and other gram-negative bacteria that activate T2Rs.

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

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

Limitations of Nasal Nitric Oxide Measurement for Diagnosis of Primary Ciliary Dyskinesia with Normal Ultrastructure

Rationale Primary ciliary dyskinesia (PCD) is a heterogeneous, multisystem disorder characterized by defective ciliary beating. Diagnostic guidelines of the American Thoracic Society (ATS) and European Respiratory Society (ERS) recommend measurement of nasal nitric oxide (nNO) for PCD diagnosis. Several studies demonstrated low nNO-production rates in PCD individuals but underlying causes remain elusive. Objective To determine nNO-production rates in a well-characterized PCD cohort including subgroup analyses with regard to ultrastructural and ciliary beating phenotypes. Methods This study included 301 individuals assessed according to ERS guidelines. Diagnostic cutoffs for nNO-production rates for this study cohort and subgroups with normal and abnormal ultrastructure were determined. Diagnostic accuracy was also tested for the widely used 77 nl/min-cutoff in this study cohort. The relationship between nNO-production rates and ciliary beat frequencies (CBFs) was evaluated. Results The study cohort comprised 180 individuals with definite PCD diagnosis including 160 individuals with genetic diagnosis, 16 individuals with probable PCD diagnosis and 105 disease controls. The 77 nl/min nNO-cutoff showed a test sensitivity of 0.92 and specificity of 0.86. Test sensitivity was lower (0.85) in the subgroup of 47 PCD individuals with normal ultrastructure compared to 133 PCD individuals with abnormal ultrastructure (0.95). The optimal diagnostic cutoff for the nNO-production rate for the whole study cohort was 69.8 nl/min (sensitivity 0.92, specificity 0.89), however it was 107.8 nl/min (sensitivity 0.89, specificity 0.78) for the subgroup of PCD with normal ultrastructure. PCD individuals with normal ultrastructure compared to abnormal ultrastructure showed higher ciliary motility. Consistently, PCD individuals with higher CBFs showed higher nNO-production rates. In addition, laterality defects occurred less frequently in PCD with normal ultrastructure. Conclusion Measurements of nNO below the widely used 77 nL/min cutoff are less sensitive in detecting PCD individuals with normal ultrastructure. Our findings indicate, that higher nNO-production in this subgroup with a higher cutoff for the nNO-production rate (107.8 nl/min) and higher residual ciliary motility are dependent on the underlying molecular PCD defect. Higher nNO-production rates, higher residual CBFs and the lower prevalence of laterality defects hamper diagnosis of PCD with normal ultrastructure. Adjusting the cutoff of nNO-production rate to 107.8 nl/min might promote diagnosing PCD with normal ultrastructure.

Abnormal n-6 fatty acid metabolism in cystic fibrosis contributes to pulmonary symptoms

Cystic fibrosis (CF) is a recessively inherited fatal disease that is the subject of extensive research and ongoing development of therapeutics targeting the defective protein, cystic fibrosis transmembrane conductance regulator (CFTR). Despite progress, the link between CFTR and clinical symptoms is incomplete. The severe CF phenotypes are associated with a deficiency of linoleic acid, which is the precursor of arachidonic acid. The release of arachidonic acid from membranes via phospholipase A₂ is the rate-limiting step for eicosanoid synthesis and is increased in CF, which contributes to the observed inflammation. A potential deficiency of docosahexaenoic acid may lead to decreased levels of specialized pro-resolving mediators. This pathophysiology may contribute to an early and sterile inflammation, mucus production, and to bacterial colonization, which further increases inflammation and potentiates the clinical symptoms. Advances in lipid technology will assist in elucidating the role of lipid metabolism in CF, and stimulate therapeutic modulations of inflammation.

Fatty acid profile in erythrocytes associated with serum cytokines in pediatric cystic fibrosis patients

ABSTRACT Objective To analyze erythrocyte fatty acid composition and its association with serum cytokine levels in pediatric cystic fibrosis patients. Methods A cross-sectional study was performed at a reference center in Rio de Janeiro, Brazil. We have included all pediatric patients aged 5-19 years with confirmed cystic fibrosis diagnosis. Erythrocyte fatty acid composition and serum cytokine (TNF-α, IL-1β, IL-6 and IL-8) and C-reactive protein levels were measured. The cut-off point to determine essential fatty acids deficiency was the linoleic acid concentration of <21%. Results Twenty-six children (<10 years old) and thirty-one adolescents were studied. Most patients were female and heterozygous for DF508 mutation and suffered from exocrine pancreatic insufficiency. Both children and adolescents had lower linoleic acid concentration (<21%). TNF-α was the only pro-inflammatory marker whose levels were increased; the increase was greater in children. An association between fatty acid composition in erythrocytes and cytokines IL-1β and IL-6 was observed (p<0.05). Conclusion The pediatric cystic fibrosis patients studied presented a deficiency of essential fatty acids, and an association between fatty acid profile in erythrocytes and serum pro-inflammatory cytokines was observed. These findings highlight the importance of this type of assessment that may open new possibilities for studying pathophysiology and treating cystic fibrosis patients, such as the dietary supplementation with n-3 fatty acids (eicosapentaenoic and docosahexaenoic acids). However, further longitudinal studies are needed for better clarification of the imbalance in lipid metabolism and inflammation in cystic fibrosis

Exhaled and nasal nitric oxide in relation to lung function, blood cell counts and disease characteristics in cystic fibrosis

BACKGROUND

Patients with cystic fibrosis (CF) have similar or lower exhaled nitric oxide (FeNO) and lower nasal nitric oxide (nNO) levels than controls. There are divergent results on alveolar NO (Calv_NO) concentrations in relation to CF. There are inconsistent results on correlation between different nitric oxide parameters and lung function and inflammation in CF.

AIM

To compare FeNO, Calv_NO and nNO levels between subjects with CF, asthma and healthy controls and to study whether these parameters are related to lung function, blood cell counts or clinical characteristics in CF patients.

MATERIAL AND METHODS

Measurements of FeNO at multiple exhalation flow rates, nNO and spirometry were done in 38 patients (18 adults) with CF. Blood cell counts and CF clinical characteristics were recorded. Thirty-eight healthy controls and 38 asthma patients, gender- and age-matched, were included as reference groups.

RESULTS

FeNO levels were lower in CF patients (7.2 [4.7-11.2] ppb) than in healthy controls (11.4 [8.3-14.6] ppb) and asthma patients (14.7 [8.7-24.7] ppb) (both p < 0.005). These differences were consistent in adults. No difference in Calv_NO was seen between the groups. nNO levels in CF patients (319 [193-447] ppb) were lower than in healthy controls (797 [664-984] ppb) and asthma patients (780 [619-961] ppb) (both p < 0.001). FeNO positively related to FEV₁ (rho = 0.51, p = 0.001) in CF patients and this was consistent in both adults and children. A negative correlation was found between FeNO and blood neutrophil counts (rho = -0.37, p = 0.03) in CF patients.

CONCLUSION

CF patients have lower FeNO and nNO and similar Calv_NO levels as healthy controls and asthma patients. Lower FeNO related to lower lung function in both adults and children with CF. Furthermore, in CF, lower FeNO also related to higher blood neutrophil counts.

Application of nitric oxide measurements in clinical conditions beyond asthma

Fractional exhaled nitric oxide (FeNO) is a convenient, non-invasive method for the assessment of active, mainly Th2-driven, airway inflammation, which is sensitive to treatment with standard anti-inflammatory therapy. Consequently, FeNO serves as a valued tool to aid diagnosis and monitoring in several asthma phenotypes. More recently, FeNO has been evaluated in several other respiratory, infectious, and/or immunological conditions. In this short review, we provide an overview of several clinical studies and discuss the status of potential applications of NO measurements in clinical conditions beyond asthma.

Clinical application of nasal nitric oxide measurement in pediatric airway diseases

Nitric oxide plays an important role in several physiological and pathophysiological processes in the respiratory tract. Different ways to measure nasal nitric oxide levels in children are currently available. The possibility of obtaining nasal nitric oxide measurement from relatively young children, combined with the availability of portable devices that can be used even in the office setting, opens new perspectives for nasal nitric oxide analysis in the pediatric daily practice. This review presents a synopsis about the current clinical applications of nasal nitric oxide measurement in the pediatric clinical practice. A total of 3,775 articles on the topic were identified, of which 883 duplicates were removed, and 2,803 were excluded based on review of titles and abstracts. Eighty-nine full text articles were assessed for eligibility and 32 additional articles were obtained from the reference lists of the retrieved studies. Since very low nasal nitric oxide levels are found in the majority of patients with primary ciliary dyskinesia, most publications support a central role for nasal nitric oxide to screen the disease, and indicate that it is a very helpful first-line tool in the real-life work-up in all age groups. Decreased nasal nitric oxide concentration is also typical of cystic fibrosis, even though nasal nitric oxide is not as low as in primary ciliary dyskinesia. In other upper airway disorders such as allergic rhinitis, rhinosinusitis, nasal polyposis, and adenoidal hypertrophy, clinical utility of nasal nitric oxide is still critically questioned and remains to be established. Since nNO determination is flow dependent, a general consensus from the major investigators in this area is highly desirable so that future studies will be performed with the same flow rate. A shared nNO methodology will enable to overcome the challenges that lie ahead in incorporating nNO measurement into the mainstream clinical setting of pediatric airway diseases.

Reduced nasal nitric oxide production in cystic fibrosis patients with elevated systemic inflammation markers

Background

Nitric oxide (NO) is produced within the respiratory tract and can be detected in exhaled bronchial and nasal air. The concentration varies in specific diseases, being elevated in patients with asthma and bronchiectasis, but decreased in primary ciliary dyskinesia. In cystic fibrosis (CF), conflicting data exist on NO levels, which are reported unexplained as either decreased or normal. Functionally, NO production in the paranasal sinuses is considered as a location-specific first-line defence mechanism. The aim of this study was to investigate the correlation between upper and lower airway NO levels and blood inflammatory parameters, CF-pathogen colonisation, and clinical data.

Methods and Findings

Nasal and bronchial NO concentrations from 57 CF patients were determined using an electrochemical analyser and correlated to pathogen colonisation of the upper and lower airways which were microbiologically assessed from nasal lavage and sputum samples. Statistical analyses were performed with respect to clinical parameters (lung function, BMI), laboratory findings (CRP, leucocytes, total-IgG, fibrinogen), and anti-inflammatory and antibiotic therapy. There were significant correlations between nasal and bronchial NO levels (rho = 0.48, p<0.001), but no correlation between NO levels and specific pathogen colonisation. In patients receiving azithromycin, significantly reduced bronchial NO and a tendency to reduced nasal NO could be found. Interestingly, a significant inverse correlation of nasal NO to CRP (rho = −0.28, p = 0.04) and to leucocytes (rho = −0.41, p = 0.003) was observed. In contrast, bronchial NO levels showed no correlation to clinical or inflammatory parameters.

Conclusion

Given that NO in the paranasal sinuses is part of the first-line defence mechanism against pathogens, our finding of reduced nasal NO in CF patients with elevated systemic inflammatory markers indicates impaired upper airway defence. This may facilitate further pathogen acquisition in the sinonasal area, with consequences for lung colonisation and the overall outcome in CF.

Exhaled nitric oxide

Nitric oxide (NO) is now considered an important biomarker for respiratory disease. Studies have confirmed that the fractional concentration of exhaled nitric oxide (FENO) is elevated in the airways of patients who have asthma in comparison with controls. The level of FENO correlates well with the presence and level of inflammation, and decreases with glucocorticoid treatment. NO has potential to be used not only as a diagnostic aid but also as a management tool for assessing severity, monitoring response to therapy, and gaining control of asthma symptoms. This article reviews the biology of NO and its role in respiratory disease.

Increased oxidative stress induces apoptosis in human cystic fibrosis cells

Oxidative stress results in deleterious cell function in pathologies associated with inflammation. Here, we investigated the generation of superoxide anion as well as the anti-oxidant defense systems related to the isoforms of superoxide dismutases (SOD) in cystic fibrosis (CF) cells. Pro-apoptotic agents induced apoptosis in CF but not in control cells that was reduced by treatment with SOD mimetic. These effects were associated with increased superoxide anion production, sensitive to the inhibition of IκB-α phosphorylation, in pancreatic but not tracheal CF cells, and reduced upon inhibition of either mitochondrial complex I or NADPH oxidase. CF cells exhibited reduced expression, but not activity, of both Mn-SOD and Cu/Zn-SOD when compared to control cells. Although, expression of EC-SOD was similar in normal and CF cells, its activity was reduced in CF cells. We provide evidence that high levels of oxidative stress are associated with increased apoptosis in CFTR-mutated cells, the sources being different depending on the cell type. These observations underscore a reduced anti-oxidant defense mechanism, at least in part, via diminished EC-SOD activity and regulation of Cu/Zn-SOD and Mn-SOD expressions. These data point to new therapeutic possibilities in targeting anti-oxidant pathways to reduce oxidative stress and apoptosis in CF cells.

Exhaled nitric oxide in pulmonary diseases: a comprehensive review

The upregulation of nitric oxide (NO) by inflammatory cytokines and mediators in central and peripheral airway sites can be monitored easily in exhaled air. It is now possible to estimate the predominant site of increased fraction of exhaled NO (FeNO) and its potential pathologic and physiologic role in various pulmonary diseases. In asthma, increased FeNO reflects eosinophilic-mediated inflammatory pathways moderately well in central and/or peripheral airway sites and implies increased inhaled and systemic corticosteroid responsiveness. Recently, five randomized controlled algorithm asthma trials reported only equivocal benefits of adding measurements of FeNO to usual clinical guideline management including spirometry; however, significant design issues may exist. Overall, FeNO measurement at a single expiratory flow rate of 50 mL/s may be an important adjunct for diagnosis and management in selected cases of asthma. This may supplement standard clinical asthma care guidelines, including spirometry, providing a noninvasive window into predominantly large-airway-presumed eosinophilic inflammation. In COPD, large/central airway maximal NO flux and peripheral/small airway/alveolar NO concentration may be normal and the role of FeNO monitoring is less clear and therefore less established than in asthma. Furthermore, concurrent smoking reduces FeNO. Monitoring FeNO in pulmonary hypertension and cystic fibrosis has opened up a window to the role NO may play in their pathogenesis and possible clinical benefits in the management of these diseases.

Antimicrobial lipids: novel innate defense molecules are elevated in sinus secretions of patients with chronic rhinosinusitis

BACKGROUND

Airway secretions possess intrinsic antimicrobial properties that contribute to the innate host defense of the respiratory tract. These microbicidal capabilities have largely been attributed to the presence of antibacterial polypeptides. However, recent investigation has indicated that host-derived lipids including cholesteryl esters also exhibit antimicrobial properties. The purpose of this study was to determine whether sinus secretions contain such antimicrobial lipids and to compare the lipid composition in patients with and without chronic rhinosinusitis (CRS).

METHODS

Maxillary sinus fluid was obtained via antral lavage from subjects with (seven patients) and without (nine patients) a history of CRS. After specimen collection, total lipid was extracted according to Bligh and Dyer (Bligh EG and Dyer WJ, A rapid method of total lipid extraction and purification, Can J Biochem Physiol 37:911-918, 1959) and lipid profiles were obtained by reverse phase high-performance liquid chromatography on an amide-embedded C18 column. In addition, the neutrophil-specific antimicrobial peptides human neutrophil peptides 1-3 (HNP1-3) were quantified by Western immunoblotting.

RESULTS

Lipids, including cholesteryl esters, were identified in the maxillary sinus secretions of patients with and without CRS. However, levels of lipid composition differed between the two groups with CRS patients exhibiting greater amounts of all classes of lipids, reaching over 10-fold higher concentration when compared with non-CRS patients. This increase was independent of HNP1-3 content.

CONCLUSION

Sinus secretions of patients with CRS appear to show elevated levels of antimicrobial lipids compared with controls independent from neutrophil influx. This up-regulation suggests that host-derived lipids act as mediators of mucosal immunity in CRS. Further study is necessary to determine if such antimicrobial lipids function alone or synergistically with antibacterial peptides in conferring such inherent microbicidal properties.

Supplementation with fatty acids influences the airway nitric oxide and inflammatory markers in patients with cystic fibrosis

OBJECTIVES

To obtain a balance in the fatty acid (FA) metabolism is important for the inflammatory response and of special importance in cystic fibrosis (CF), which is characterized by impaired FA metabolism, chronic inflammation, and infection in the airways. Nitric oxide (NO) has antimicrobial properties and low nasal (nNO) and exhaled NO (FENO), commonly reported in CF that may affect bacterial status. The present study investigates the effect of different FA blends on nNO and FENO and immunological markers in patients with CF.

PATIENTS AND METHODS

Forty-three patients with CF and "severe" mutations were consecutively enrolled in a randomized double-blind placebo-controlled study with 3 FA blends containing mainly n-3 or n-6 FA or saturated FA acting as placebo. FENO, nNO, serum phospholipid concentrations of FA, and biomarkers of inflammation were measured before and after 3 months of supplementation.

RESULTS

Thirty-five patients in clinically stable condition completed the study. The serum phospholipid FA pattern changed significantly in all 3 groups. An increase of the n-6 FA, arachidonic acid, was associated with a decrease of FENO and nNO. The inflammatory biomarkers, erythrocyte sedimentation rate, and interleukin-8 decreased after supplementation with n-3 FA and erythrocyte sedimentation rate increased after supplementation with n-6 FA.

CONCLUSIONS

This small pilot study indicated that the composition of dietary n-3 and n-6 FA influenced the inflammatory markers in CF. FENO and nNO were influenced by changes in the arachidonic acid concentration, supporting previous studies suggesting that both the lipid abnormality and the colonization with Pseudomonas influenced NO in the airways.

Low levels of exhaled nitric oxide are associated with impaired lung function in cystic fibrosis

Fraction of exhaled nitric oxide (FENO) is often reduced in cystic fibrosis (CF). FENO at different expiratory flows can provide an indication of the site of nitric oxide production. The aim of this study was to examine whether NO parameters are related to overall (FEV(1)) or peripheral (lung clearance index, LCI, measured by multiple breath SF(6) washout) airway function and systemic inflammation in CF. Secondary aim was to compare alveolar NO and bronchial NO flux calculated by two different mathematical models, a linear and a nonlinear method. Thirty-five healthy and 45 CF children were recruited. FENO at 50 ml/sec (FENO(50)) and bronchial NO flux were lower in CF than controls, 9.5 (2.7-38.8) (median (range)) versus 12.4 (5.2-40.1) ppb, P = 0.029, and 391 (97-1772) versus 578 (123-1993) (pl/sec), P = 0.036, respectively. No difference in alveolar NO was shown. The nonlinear method resulted in lower alveolar NO and higher bronchial flux, than the linear method, but the result was closely correlated in both groups. LCI was higher in CF than controls, 8.4 (6.5-12.9) versus 5.9 (5.1-7.8), P < 0.001. FENO(50) was negatively correlated with LCI (r = -0.43; P = 0.003) and positively correlated with FEV(1) (r = 0.42, P = 0.004) in CF. Alveolar NO correlated negatively with inflammatory markers: orosomucoid (r = -0.42, P = 0.005), platelets (r = -0.50, P < 0.001) and white blood cell count (r = -0.48, P = 0.001). In conclusion, FENO(50) and bronchial NO flux are reduced in young CF subjects and low FENO(50) is associated with overall and small airway obstruction. NO parameters derived from the different models were closely related but the values differed slightly.

Persistence of essential fatty acid deficiency in cystic fibrosis despite nutritional therapy

To study the evolution of plasma fatty acid composition of patients with cystic fibrosis (CF) in relation to nutritional status, pancreatic function, and development of CF-related liver disease (CFRLD) and diabetes mellitus, 24 CF pediatric patients with stable pulmonary disease were studied before and after an approximate period of 8 y. Nutritional status, pulmonary function, pancreatic function, and presence of CFRLD or diabetes mellitus were recorded. Results were compared with data obtained in 83 healthy children. Patients with CF have significantly lower linoleic acid (LA), docosahexaenoic acid (DHA), lignoceric acid, and LA x DHA product and higher oleic acid, mead acid, dihomo-gamma-linoleic acid, and docosapentaenoic acid (DPA). Comparison of samples taken at first and second studies revealed a significant decrease in LA levels and lignoceric acid associated with a significant increase in dihomo-gamma-linoleic acid levels. Patients with CFRLD showed significantly higher mead acid/arachidonic acid ratio and lower total omega6 polyunsaturated fatty acids content. There was no relation of plasma fatty acids composition with pancreatic function, pulmonary function, or diabetes mellitus. Follow-up of patients with CF shows that essential fatty acids deficiency, particularly in LA and DHA content, persisted unmodified along time despite an adequate nutritional therapy. Future studies after supplementation with omega3 polyunsaturated fatty acids should be undertaken.

Mechanisms of the noxious inflammatory cycle in cystic fibrosis

Multiple evidences indicate that inflammation is an event occurring prior to infection in patients with cystic fibrosis. The self-perpetuating inflammatory cycle may play a pathogenic part in this disease. The role of the NF-κB pathway in enhanced production of inflammatory mediators is well documented. The pathophysiologic mechanisms through which the intrinsic inflammatory response develops remain unclear. The unfolded mutated protein cystic fibrosis transmembrane conductance regulator (CFTRΔF508), accounting for this pathology, is retained in the endoplasmic reticulum (ER), induces a stress, and modifies calcium homeostasis. Furthermore, CFTR is implicated in the transport of glutathione, the major antioxidant element in cells. CFTR mutations can alter redox homeostasis and induce an oxidative stress. The disturbance of the redox balance may evoke NF-κB activation and, in addition, promote apoptosis. In this review, we examine the hypotheses of the integrated pathogenic processes leading to the intrinsic inflammatory response in cystic fibrosis.

Lipids including cholesteryl linoleate and cholesteryl arachidonate contribute to the inherent antibacterial activity of human nasal fluid

Mucosal surfaces provide first-line defense against microbial invasion through their complex secretions. The antimicrobial activities of proteins in these secretions have been well delineated, but the contributions of lipids to mucosal defense have not been defined. We found that normal human nasal fluid contains all major lipid classes (in micrograms per milliliter), as well as lipoproteins and apolipoprotein A-I. The predominant less polar lipids were myristic, palmitic, palmitoleic, stearic, oleic, and linoleic acid, cholesterol, and cholesteryl palmitate, cholesteryl linoleate, and cholesteryl arachidonate. Normal human bronchioepithelial cell secretions exhibited a similar lipid composition. Removal of less-polar lipids significantly decreased the inherent antibacterial activity of nasal fluid against Pseudomonas aeruginosa, which was in part restored after replenishing the lipids. Furthermore, lipids extracted from nasal fluid exerted direct antibacterial activity in synergism with the antimicrobial human neutrophil peptide HNP-2 and liposomal formulations of cholesteryl linoleate and cholesteryl arachidonate were active against P. aeruginosa at physiological concentrations as found in nasal fluid and exerted inhibitory activity against other Gram-negative and Gram-positive bacteria. These data suggest that host-derived lipids contribute to mucosal defense. The emerging concept of host-derived antimicrobial lipids unveils novel roads to a better understanding of the immunology of infectious diseases.

Cystic Fibrosis and Nutrition: Linking Phospholipids and Essential Fatty Acids with Thiol Metabolism

Cystic fibrosis (CF) is the most common lethal inherited disorder among Caucasians and results from mutation in the gene encoding the CF transmembrane conductance regulator. In addition to its multisystem clinical effects, the disease is characterized by increased proinflammatory mediators and oxidant stress, and systemic redox imbalance with reduced glutathione (GSH), together with alterations in circulating and tissue (n-6) and (n-3) fatty acids, particularly a decrease in docosahexaenoic acid. The metabolism of phospholipids and fatty acids is closely related to GSH through the methionine-homocysteine cycle, in which choline via betaine provides methyl groups to regenerate S-adenosylmethionine, important in generating phosphatidylcholine and amino acid precursors for GSH. Current research focuses both on fatty acid supplementations to normalize altered (n-6) to (n-3) fatty acid balance and decrease generation of (n-6) fatty acid-derived inflammatory mediators, and strategies to improve oxidant defenses and redox balance. However, further research is needed before such strategies can be included in clinical care of individuals with CF.

The use of fraction of exhaled nitric oxide in pulmonary practice

The measurement of the fractional concentration of exhaled nitric oxide (FeNO) is a convenient, noninvasive, point-of-service office test for airway inflammation. The first half of this practice management review presents the methodological, interpretative, and clinical applications of FeNO. The second half discusses practical management issues, including current and future technology, equipment specifications, US Food and Drug Administration regulations, cost, current procedural terminology coding, and reimbursement. The measurement of FeNO is helpful in the diagnosis of asthma. It is predictive of a response to inhaled corticosteroids (ICSs). Monitoring FeNO is useful in maintaining asthma control by allowing the assessment of adherence to medication and dose titration of ICSs. An elevated level of FeNO is predictive of asthma relapse following corticosteroid withdrawal especially in children. The advances in technology, ease of use, and clinical utility will lead to greater availability, acceptance, and routine application in the care of asthma.

Exhaled nitric oxide

Exhaled nitric oxide (FENO) is a noninvasive easily measurable biomarker that is proving to be an excellent surrogate for eosinophilic inflammation in the lungs of patients who have asthma. Although large-scale normative data are still awaited, preliminary studies have shown FENO to be helpful in diagnosing and assessing severity and control for asthma. FENO levels have also proven helpful in diagnosing and managing several other inflammatory lung diseases.