Nasal and exhaled nitric oxide is reduced in adult patients with cystic fibrosis and does not correlate with cystic fibrosis genotype

Reactive nitrogen species in the respiratory tract

Endogenous Nitric Oxide (NO) plays a key role in the physiological regulation of airway functions. In response to various stimuli activated inflammatory cells (e.g., eosinophils and neutrophils) generate oxidants ("oxidative stress") which in conjunction with exaggerated enzymatic release of NO and augmented NO metabolites produce the formation of strong oxidizing reactive nitrogen species, such as peroxynitrite, in various airway diseases including asthma, chronic obstructive pulmonary diseases (COPD), cystic fibrosis and acute respiratory distress syndrome (ARDS). Reactive nitrogen species provoke amplification of inflammatory processes in the airways and lung parenchyma causing DNA damage, inhibition of mitochondrial respiration, protein dysfunction and cell damage ("nitrosative stress"). These effects alter respiratory homeostasis (such as bronchomotor tone and pulmonary surfactant activity) and the long-term persistence of "nitrosative stress" may contribute to the progressive deterioration of pulmonary functions leading to respiratory failure. Recent studies showing that protein nitration can be dynamic and reversible ("denitration mechanisms") open new horizons in the treatment of chronic respiratory diseases affected by the deleterious actions of "nitrosative stress".

Reduced exhaled NO is related to impaired nasal potential difference in patients with cystic fibrosis

Nitric oxide (NO) plays a central role in many airway physiological functions, and its production appears to be related with progression of lung disease in patients with cystic fibrosis (CF). However, underlying mechanisms which specifically link NO and CF-related lung disease remain unclear. Following in vitro and animal studies suggesting a role for NO in ion transport in various epithelia, this work investigates the relationship between transepithelial baseline potential difference (BPD), an index of airway ion transport, and exhaled NO in the airways of adult patients with CF. Association with other phenotypic traits, lung function tests and CFTR genotype was also assessed. Using simple linear regression, F(E)NO and transepithelial BPD values were significantly inversely correlated (p<0.001, r=-0.53). Polynomial analysis evidenced an asymptotic relationship between F(E)NO and BPD values, yielding a plateau for absolute BPD values above 50 mV. This relation was not altered by adjustment for clinical and genetic characteristics of the patients. The relationship between exhaled NO and transepithelial BPD suggests that low NO concentrations likely worsens airway ion transport impairment resulting from CFTR defect. These results fit with experimental studies that suggest the inhibitory effect of NO on sodium absorption, which is the main determinant of airway basal transepithelial conductance.

Nitric oxide in cystic fibrosis

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

Repeatability of standardised nasal nitric oxide measurements in healthy and asthmatic adults and children

Several nasal nitric oxide (NO) measurement techniques have been described, but there is not a widespread measurement technique for measurement of nasal NO. In this study we evaluated the repeatability of one technique of nasal NO measurements using the nasal application of the NIOX system.

METHODS

Three nasal NO measurements (NIOX Nitric Oxide Monitoring System, Aerocrine, Sweden) were made on a single occasion in 22 healthy subjects and 27 patients with asthma, aged 5-69 years. Nasal NO was sampled during breath hold from one nostril at a flow rate of 5 ml/s.

RESULTS

The repeatability of nasal NO assessed by the coefficient of variation (CV) was 12.5% (95% Confidence interval (CI) 11.0-14.7%) for the total population. Healthy adults had a significantly better repeatability than healthy children (P<0.008). The mean NO level for the total population was 837 ppb. The mean NO levels in children were lower than in the adults (751 and 897 ppb, respectively). The mean breath hold length needed to obtain a steady NO plateau for all subject categories combined was 20.4+/-6.01 s. The average number of attempts needed to obtain three approved NO measurements was 5.4 (range 3-13) for the total population. There were no significant differences between the different subject categories. When using two measurements per session instead of three, the overall CV was 10.5% (95% CI 8.8-13.1%). Most subjects found the measurements easy to perform and all of them would accept to do the examination as a routine.

CONCLUSIONS

Nasal NO measurements in NIOX may provide a useful reliable clinical tool to assess and monitor upper airways in different diseases, for example PCD and rhinitis, and are acceptable by both healthy and asthmatic adults and children, as a part of their routine visit to a physician.

Erythrocytes of humans with cystic fibrosis fail to stimulate nitric oxide synthesis in isolated rabbit lungs

Erythrocytes (red blood cells) of either rabbits or healthy humans are required to demonstrate the participation of nitric oxide (NO) in the regulation of pulmonary vascular resistance in the isolated rabbit lung. The property of the erythrocyte that is responsible for the stimulation of NO synthesis was reported to be the ability to release ATP in response to physiological stimuli, including deformation. Moreover, a signal transduction pathway that relates mechanical deformation of erythrocytes to ATP release has been described, and the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) is a component, i.e., erythrocytes of individuals with CF do not release ATP in response to deformation. Here, we investigated the hypothesis that, in contrast to those of healthy humans, erythrocytes of humans with CF fail to stimulate endogenous NO synthesis in the isolated rabbit lung. We report that CFTR is a component of the membranes of both rabbit and human erythrocytes. The addition of the NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 100 muM) produced increases in vascular resistance in isolated rabbit lungs perfused with physiological salt solution (PSS) containing erythrocytes of healthy humans, but L-NAME was without effect when the lungs were perfused with PSS alone or PSS containing erythrocytes of CF patients. These results provide support for the hypothesis that, in CF, a defect in ATP release from erythrocytes could lead to decreased endogenous pulmonary NO synthesis and contribute to pulmonary hypertension.

Dornase alpha and exhaled NO in cystic fibrosis

Nitric oxide (NO) that is produced within the airways can be measured in the exhaled air. Concentrations of exhaled NO (FENO) are decreased in cystic fibrosis (CF) and, in cross sectional studies, have been shown to be even lower in patients with more advanced pulmonary disease. This may result from retention and metabolisation of NO within viscous airway secretions. Treatment with recombinant human DNase I (dornase alpha) modifies the rheological properties of airway secretions and thereby improves pulmonary function even in young and apparently healthy patients with CF. We studied FENO and pulmonary function in children with CF with little clinical evidence of lung morbidity in a two-year randomized double-blind placebo-controlled study with nebulized dornase alpha. Mean age at enrollment was 8 years (range 6 to 11 years), mean forced vital capacity (FVC) was 112% (range 86 to 133%), and mean forced expiratory volume in one second (FEV1)was 109% (range 88 to 128%) of predicted values. In five of six (83%) of the dornase alpha treated patients, FENO changed in parallel to changes in pulmonary function tests while no such correlation was observed in any of the eight patients receiving placebo. This difference between treatment groups was statistically significant for both FVC (P = 0.026, Wilcoxon-test) and FEV1 (P = 0.042). These data suggest that FENO may serve as a surrogate measure for evaluating the effectiveness of interventions that affect airway clearance in CF.

Nitric oxide synthase 1 as a potential modifier gene of decline in lung function in patients with cystic fibrosis

BACKGROUND

The severity of lung disease varies widely in patients with cystic fibrosis (CF) who have the same type of mutations of the cystic fibrosis transmembrane regulator (CFTR) gene, suggesting involvement of "modifier" genes. The nitric oxide synthase 1 (NOS1) gene is a candidate for this role because exhaled nitric oxide (NO) is reduced in patients with CF and NOS1 activity contributes to transepithelial ionic transport, immune defence, and non-specific inflammation of the airways.

METHODS

Dinucleotide GT repeat polymorphism was studied in the 5' untranslated region of the NOS1 gene, immediately upstream from the transcription initiation site, in 59 patients with CF and 59 healthy controls.

RESULTS

Nineteen alleles of the NOS1 gene were identified according to the number of GT repeats (from 18 to 36) in the 5 untranslated region. Exhaled NO levels were significantly correlated with the number of GT repeats. Patients with CF who had the NOS1 genotype associated with high NO production had a slower decline in lung function during the 5 year follow up period. There was no confounding effect of age, chronic bacterial colonisation of the airway, or CFTR genotype.

CONCLUSIONS

These data suggest a possible link between the NOS1 gene locus and the rate of decline in lung function in patients with CF.

Exhaled nitric oxide increases following admission for intravenous antibiotics in children with cystic fibrosis

BACKGROUND

Lack of standardisation for the measurement of exhaled nitric oxide (NO) (FENO) has resulted in conflicting data in cystic fibrosis (CF). The aim of this study was to assess whether FENO is a useful non-invasive marker of lung disease in CF by assessing the effect of intravenous (IV) antibiotics on FENO.

METHODS

FENO was measured on line, according to recently published ERS/ATS guidelines, using a chemiluminescence analyser together with pulmonary function in 14 CF children prior to and following a course of IV antibiotics.

RESULTS

There was a significant improvement in mean (S.E.M.) % FEV1 from 60.0 (6.3) to 68.0 (5.4) (P < 0.05) and mean (S.E.M.) % FVC from 66.3 (5.5) to 75.1 (4.9) (P < 0.01). FENO increased significantly from median (range) 5.8 (2.0-14.3) to 9.2 ppb (0.8-25.1) (P < 0.05). There was no correlation between FE(NO) and lung function. Subgroup analysis on those with chronic Pseudomonas aeruginosa infection (n = 6) demonstrated no significant change in FENO.

CONCLUSIONS

Using a flow of 50 ml/s, FENO increases following admission for IV antibiotic treatment in children with CF but does not correlate with lung function. It is not a useful marker of lung diseases in CF, which has implications for clinical practice.

Comparison of cadmium and enzyme-catalyzed nitrate reduction for determination of NO2-/NO3- in breath condensate

BACKGROUND

Analysis of NO2-/NO3- in expired breath condensate (EBC) has been proposed as a marker of inflammation in various lung diseases.

METHODS

NO2- and total NO3-/NO2- concentrations were determined in EBC collected from healthy and asthmatic subjects. The NO3- was first reduced to NO2-, and total NO2- was detected by colorimetric Griess reaction. Two methods of NO3- reduction were compared. To reduce NO3-, cadmium (600 microl EBC-macromethod) and enzyme-NADPH-nitrate reductase (60 microl EBC-micromethod) were used.

RESULTS

Macromethod: Mean NO2- concentrations in EBC were 1.64 +/- 0.24 micromol/l in healthy subjects and 0.42 +/- 0.17 micromol/l in asthmatic patients. Mean total NO2-/NO3- levels were 3.64 +/- 0.43 micromol/l in healthy subjects and 3.27 +/- 0.34 micromol/l in asthmatic. Micromethod: NO2- level: 1.69 +/- 0.23 micromol/l in healthy subjects and 0.53 +/- 0.21 micromol/l in asthmatics. Total NO2-/NO3- levels: 3.56 +/- 0.37 micromol/l in healthy subjects and 3.57 +/- 1.17 micromol/l in asthmatics. Variability index was 27% and 6% for macro- and micromethod, respectively. Recovery of NO3- added to EBC was 100% for enzymatic and almost 88% for cadmium reduction. There was no correlation between total NO2-/NO3- levels determined by macro- and micromethod.

CONCLUSIONS

We recommend enzymatic reduction as a better method for NO3- determination in EBC.

Effects of nitric oxide on Pseudomonas aeruginosa infection of epithelial cells from a human respiratory cell line derived from a patient with cystic fibrosis

Cystic fibrosis (CF) is characterized by airway inflammation and chronic bacterial lung infection, most commonly with Pseudomonas aeruginosa, an opportunistic human pathogen. Despite the persistent airway inflammation observed in patients with CF, although phagocyte inducible nitric oxide synthase (iNOS) production is upregulated, expression of iNOS in the respiratory epithelium is markedly reduced. Given the antimicrobial action of NO, this may contribute to the chronic airway infection of this disease. To define the role of epithelium-derived NO in airway defense against P. aeruginosa, we infected differentiated human bronchial epithelial cells derived from a patient with CF (CFBE41o- cells) with different strains of this pathogen at low multiplicities of infection. Using cells transfected with human iNOS cDNA, we studied the effect of NO on P. aeruginosa replication, adherence, and internalization. P. aeruginosa adherence to iNOS-expressing cells was reduced by 44 to 72% (P = 0.02) compared with control values. Absolute P. aeruginosa uptake into these cells was reduced by 44%, but uptake expressed as a percentage of adherent bacteria did not differ from the control uptake. Survival of P. aeruginosa within iNOS-expressing cells was reduced at late times postinfection (P = 0.034). NO production did not alter host cell viability. NO production reduced P. aeruginosa adherence to human bronchial epithelial cells and enhanced killing of internalized bacteria, suggesting that a lack of epithelial iNOS in patients with CF may contribute to P. aeruginosa infection and colonization.

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.

Exhaled nitric oxide in cystic fibrosis patients with allergic bronchopulmonary aspergillosis

Exhaled nitric oxide (NO) is thought to be a marker of asthmatic inflammation. Levels in cystic fibrosis (CF) are generally low. This study aimed to measure exhaled NO in CF patients at high risk of developing ABPA and patients at low risk. We studied nine patients at high risk of developing ABPA and 36 at low risk. The two groups were similar in age and spirometry. All patients in the high-risk group were taking oral or inhaled glucocorticoids, compared to 56% in the low-risk group (P=0.02). The exhaled NO levels were lower in the high-risk group than in the low-risk group (2.0 vs. 3.6 ppb), mean difference (95% CI) 1.6 (-3.6 to 0.4) ppb, P=0.001. On subgroup analysis of patients on oral glucocorticoids, the exhaled NO levels were significantly lower in patients with a high risk of developing ABPA (n=7) than patients with a low risk (n=8) (P=0.011). The number of patients who were on inhaled, but not oral glucocorticoids was too small to analyse usefully. Exhaled NO levels were lower in CF patients with a high risk of developing ABPA and on glucocorticoids. This may be because oral glucocorticoids exert a greater effect on exhaled NO than inhaled glucocorticoids. Alternatively, inducible nitric oxide synthase may be down-regulated by Aspergillus toxin.

Nitric oxide in respiratory diseases

The formation and modulation of nitric oxide (NO) in the lungs is reviewed. Its beneficial and deleterious roles in airways diseases, including asthma, chronic obstructive pulmonary disease, and cystic fibrosis, and in animal models is discussed. The pharmacological effects of agents that modulate NO production or act as NO donors are described. The clinical pharmacology of these agents is described and the therapeutic potential for their use in airways disease is considered.

Comparison of exhaled and nasal nitric oxide and exhaled carbon monoxide levels in bronchiectatic patients with and without primary ciliary dyskinesia

BACKGROUND

Primary ciliary dyskinesia (PCD) is associated with chronic airway inflammation resulting in bronchiectasis.

METHODS

The levels of exhaled nitric oxide (eNO), carbon monoxide (eCO) and nasal NO (nNO) from bronchiectatic patients with PCD (n=14) were compared with those from patients with non-PCD bronchiectasis without (n=31) and with cystic fibrosis (CF) (n=20) and from normal subjects (n=37) to assess the clinical usefulness of these measurements in discriminating between PCD and other causes of bronchiectasis.

RESULTS

Exhaled NO levels were lower in patients with PCD than in patients with non-PCD non-CF bronchiectasis or healthy subjects (median (range) 2.1 (1.3-3.5) ppb v 8.7 (4.5-26.0) ppb, p<0.001; 6.7 (2.6-11.9) ppb, p<0.001, respectively) but not lower than bronchiectatic patients with CF (3.0 (1.5-7.5) ppb, p>0.05). Nasal levels of nNO were significantly lower in PCD patients than in any other subjects (PCD: 54.5 (5.0-269) ppb, non-PCD bronchiectasis without CF: 680 (310-1000) ppb, non-PCD bronchiectasis with CF: 343 (30-997) ppb, control: 663 (322-1343) ppb). In contrast, eCO levels were higher in all patient groups than in control subjects (PCD: 4.5 (3.0-24.0) ppm, p<0.01, other bronchiectasis without CF: 5.0 (3.0-15.0) ppm, p<0.001; CF: 5.3 (2.0-23.0) ppm, p<0.001 v 3.0 (0.5-5.0) ppm). Low values in both eNO and nNO readings (<2.4 ppb and <187 ppb, respectively) identified PCD patients from other bronchiectatic patients with a specificity of 98% and a positive predictive value of 92%.

CONCLUSION

The simultaneous measurement of eNO and nNO is a useful screening tool for PCD.

Pharmacological approaches for the discovery and development of new anti-inflammatory agents for the treatment of cystic fibrosis

Some of the most important pathobiology in cystic fibrosis occurs not as a direct result of impaired chloride transport, but the downstream consequences of defective CFTR function, particularly the lung infection and inflammation that ultimately takes the lives of most patients. Interrupting the vicious cycle of infection and inflammation is effective in slowing the course of the disease, and antibiotics have long been the staple of pulmonary therapy. However, limiting the inflammatory response in the CF lung is also effective. High dose ibuprofen clearly retards progression of lung disease, but also entrains adverse events that mar its therapeutic utility, so alternative anti-inflammatory agents are necessary. Because of the remarkable therapeutic success of ibuprofen, consideration should be given to finding less toxic alternatives. However, it is also appropriate to consider the mechanisms by which the inflammatory response occurs in the CF lung, and identify sites to interrupt it. Sites at which therapeutic intervention is possible are the neutralization of cytokines such as tumor necrosis factor-alpha, interleukin (IL)-1beta, or IL-8 with specific antibodies or receptor antagonists, inhibition of the intracellular signaling cascades that result in cytokine production (for example, at the level of p38 MAP kinase), application of cytokines such as Il-10 that are themselves anti-inflammatory, or modulating the arachidonic acid cascade with inhibitors directed at leukotriene B(4). In addition, interventions designed to limit the consequences of the inflammatory response, such as protease inhibitors and reagents to limit the ill effects of DNA accumulation in airways, are in use. To limit adverse effect and concentrate the therapeutic effect, there may be value in targeting delivery of the therapeutic reagents to the inflamed site, either by specifically directing systemic delivery or by exploitation of the aerosol route. Treating the inflammatory response is important, for the data from the ibuprofen study show that the effects of anti-inflammatory therapy are additive or even synergistic with intensive conventional therapy and alter the rate of decline of pulmonary function, and therefore benefits for survival of patients with CF are to be expected.

Low levels of nitric oxide and carbon monoxide in alpha 1-antitrypsin deficiency

Quantitations of exhaled nitric oxide (NO) and carbon monoxide (CO) have been proposed as noninvasive markers of airway inflammation. We hypothesized that exhaled CO is increased in individuals with alpha(1)-antitrypsin (AT) deficiency, who have lung inflammation and injury related to oxidative and proteolytic processes. Nineteen individuals with alpha(1)-AT deficiency, 22 healthy controls, and 12 patients with non-alpha(1)-AT-deficient chronic obstructive pulmonary disease (COPD) had NO, CO, CO(2), and O(2) measured in exhaled breath. Individuals with alpha(1)-AT deficiency had lower levels of NO and CO than control or COPD individuals. Alpha(1)-AT-deficient and COPD patients had lower exhaled CO(2) than controls, although only alpha(1)-AT-deficient patients had higher exhaled O(2) than healthy controls. NO was correlated inversely with exhaled O(2) and directly with exhaled CO(2), supporting a role for NO in regulation of gas exchange. Exhaled gases were not significantly related to corticosteroid use or lung function. Demonstration of lower than normal CO and NO levels may be useful as an additional noninvasive method to evaluate alpha(1)-AT deficiency in individuals with a severe, early onset of obstructive lung disease.

Nitric oxide and protein nitration in the cystic fibrosis airway

Cystic fibrosis (CF), characterized by chronic airway infection and inflammation, ultimately leads to respiratory failure. Exhaled nitric oxide (NO), elevated in most inflammatory airway diseases, is decreased in CF, suggesting either decreased production or accelerated metabolism of NO. The present studies performed on two groups of CF patients provide further support for a disordered NO airway metabolism in CF respiratory tract disease. Despite confirmation of subnormal NOS2 in the CF airway epithelium, alternative isoforms NOS1 and NOS3 were present, and inflammatory cells in the CF airway expressed abundant NOS2. Increased immunohistochemical staining for nitrotyrosine was demonstrated in lung tissues from patients with CF as compared to control. To our knowledge, this is the first report localizing nitrotyrosine in diseased CF lung tissue. While the relative NOS2 deficiency in CF respiratory tract epithelium may contribute to the lower expired NO levels, these results suggest that increased metabolism of NO is also present in advanced CF lung disease. The significance of altered NO metabolism and protein nitration in CF remains to be fully elucidated.

Nasal nitric oxide in children: a novel measurement technique and normal values

OBJECTIVES

To develop and standardize a technique for measuring nasal nitric oxide (NO) output in children and to determine normal values in this population.

STUDY DESIGN

Prospective study evaluating a new technique for measuring nasal nitric oxide in a cohort of normal patients and a cohort of patients with nasal disease.

METHODS

Nasal NO was measured using an aspiration technique, aspirating room air through the nasal cavities by means of a Teflon nozzle placed in one nasal vestibule while maintaining velopharyngeal closure using a party "blow-out" toyRESULTS Nasal NO measurements were performed in 45 children (mean age, 11.0 y; age range, 3.2-17.6 y) There were 20 girls and 25 boys. All children were able to perform the maneuvers necessary for measurement of nasal NO output. Among the subgroup of normal healthy children (30), there was considerable variation in NO output between subjects, with a mean NO output of 481 nL/min and an SD of 283 nL/min.

CONCLUSIONS

Nasal NO can be readily measured in children using the presented technique. There is considerable variability in the values for nasal NO output in normal children.

"CF asthma": what is it and what do we do about it?

The diagnosis of "CF asthma" is problematic and it is difficult to determine which patients have a combination of CF and asthma and which have asthma like symptoms caused by inflammation of the CF lung. This may not matter, however; the relevance lies in the possible approaches to treatment.

One-year low-dose erythromycin treatment of persistent chronic sinusitis after sinus surgery: clinical outcome and effects on mucociliary parameters and nasal nitric oxide

OBJECTIVE

In 17 patients with chronic sinusitis persistent after sinus surgery, long-term, low-dose erythromycin therapy was tested. The aim of the investigation was to study the clinical outcome and effects on nasal nitric oxide (NO), ciliary beat frequency (CBF), and mucociliary transport (saccharine transit time).

STUDY DESIGN AND SETTING

We conducted a prospective open study at a tertiary teaching hospital. Symptoms were assessed using visual analog scales. NO was measured using a chemiluminescence analyzer, and mucociliary transport was measured with the saccharine crystal technique. CBF was measured in nasal brush samples using a phase contrast microscope. All patients were treated with erythromycin succinate 250 mg 2x daily or clarithromycin 250 mg 1x daily and were assessed after 3 months. In cases where there was no response, treatment was abandoned. The remaining patients (responders) were reassessed after 12 months of treatment.

RESULTS

Of 17 patients, 12 responded to treatment. The 12-month follow-up showed an improvement in saccharine transit time (P < 0.05) but no significant change in CBF. There was a trend toward an increase in NO (P = 0.12). Endoscopic nasal examination scoring improved significantly (P < 0.01). In the visual analog scale scoring, the most pronounced improvements were seen in nasal congestion, sticky secretion, and runny nose at 3 and 12 months (P < 0.01). Improvements were also seen in headache (P < 0.05).

CONCLUSION

The present study suggests that long-term, low-dose treatment with erythromycin is effective in persistent chronic sinusitis that does not respond to sinus surgery or systemic steroid/antibiotic treatment.

SIGNIFICANCE

Long-term, low-dose erythromycin therapy seems to be a promising alternative when more conventional therapy fails. However, placebo-controlled studies are needed to validate the potential of this treatment.

Flow-independent nitric oxide exchange parameters in cystic fibrosis

Exhaled nitric oxide (NO) remains a promising noninvasive index for monitoring inflammatory lung diseases; however, the plateau concentration (C(NO,plat)) is nonspecific and requires a constant exhalation flow rate. We utilized a new technique that employs a variable flow rate to estimate key flow-independent parameters characteristic of NO exchange in a group (n = 9) of 10 to 14 yr-old healthy children and children with cystic fibrosis (CF): maximum flux of NO from the airways (J(NO,max'), pl s(-1)), diffusing capacity of NO in the airways (D(NO,air'), pl s(-1) ppb(-1)), steady-state alveolar concentration (C(alv,ss'), ppb), and mean tissue concentration of NO in the airways (C(tiss,air'), ppb). We determined the following mean (+/- SD) values in the healthy children and patients with CF for J(NO,max'), D(NO,air'), C(alv,ss'), and C(tiss,air'), respectively: 784 +/- 465 and 607 +/- 648 pl s(-1); 4.82 +/- 3.07 and 17.6 +/- 12.1 pl s(-1) ppb(-1); 4.63 +/- 3.59 and 1.96 +/- 1.18 ppb; and 198 +/- 131 and 38 +/- 25 ppb. D(NO,air) is elevated (p = 0.007), and both C(alv,ss) and C(tiss,air) are reduced (p = 0.05 and 0.002, respectively) in CF. In contrast, C(NO,plat) for healthy control subjects and patients with CF are not statistically different at both exhalation flow rates of 50 ml/s (17.5 +/- 11.5 and 11.5 +/- 8.97) and at 250 ml/s (7.11 +/- 5.36 and 4.28 +/- 3.43). We conclude that D(NO,air'), C(tiss,air'), and C(alv,ss) may be useful noninvasive markers of CF.

Biomarkers of some pulmonary diseases in exhaled breath

Analysis of various biomarkers in exhaled breath allows completely non-invasive monitoring of inflammation and oxidative stress in the respiratory tract in inflammatory lung diseases, including asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), bronchiectasis and interstitial lung diseases. The technique is simple to perform, may be repeated frequently, and can be applied to children, including neonates, and patients with severe disease in whom more invasive procedures are not possible. Several volatile chemicals can be measured in the breath (nitric oxide, carbon monoxide, ammonia), and many non-volatile molecules (mediators, oxidation and nitration products, proteins) may be measured in exhaled breath condensate. Exhaled breath analysis may be used to quantify inflammation and oxidative stress in the respiratory tract, in differential diagnosis of airway disease and in the monitoring of therapy. Most progress has been made with exhaled nitric oxide (NO), which is increased in atopic asthma, is correlated with other inflammatory indices and is reduced by treatment with corticosteroids and antileukotrienes, but not (beta 2-agonists. In contrast, exhaled NO is normal in COPD, reduced in CF and diagnostically low in primary ciliary dyskinesia. Exhaled carbon monoxide (CO) is increased in asthma, COPD and CF. Increased concentrations of 8-isoprostane, hydrogen peroxide, nitrite and 3-nitrotyrosine are found in exhaled breath condensate in inflammatory lung diseases. Furthermore, increased levels of lipid mediators are found in these diseases, with a differential pattern depending on the nature of the disease process. In the future it is likely that smaller and more sensitive analyzers will extend the discriminatory value of exhaled breath analysis and that these techniques may be available to diagnose and monitor respiratory diseases in the general practice and home setting.

Flow-independent nitric oxide exchange parameters in healthy adults

Currently accepted techniques utilize the plateau concentration of nitric oxide (NO) at a constant exhalation flow rate to characterize NO exchange, which cannot sufficiently distinguish airway and alveolar sources. Using nonlinear least squares regression and a two-compartment model, we recently described a new technique (Tsoukias et al. J Appl Physiol 91: 477-487, 2001), which utilizes a preexpiratory breath hold followed by a decreasing flow rate maneuver, to estimate three flow-independent NO parameters: maximum flux of NO from the airways (J(NO,max), pl/s), diffusing capacity of NO in the airways (D(NO,air), pl x s(-1) x ppb(-1)), and steady-state alveolar concentration (C(alv,ss), ppb). In healthy adults (n = 10), the optimal breath-hold time was 20 s, and the mean (95% intramaneuver, intrasubject, and intrapopulation confidence interval) J(NO,max), D(NO,air), and C(alv,ss) are 640 (26, 20, and 15%) pl/s, 4.2 (168, 87, and 37%) pl x s(-1) x ppb(-1), and 2.5 (81, 59, and 21%) ppb, respectively. J(NO,max) can be estimated with the greatest certainty, and the variability of all the parameters within the population of healthy adults is significant. There is no correlation between the flow-independent NO parameters and forced vital capacity or the ratio of forced expiratory volume in 1 s to forced vital capacity. With the use of these parameters, the two-compartment model can accurately predict experimentally measured plateau NO concentrations at a constant flow rate. We conclude that this new technique is simple to perform and can simultaneously characterize airway and alveolar NO exchange in healthy adults with the use of a single breathing maneuver.

Rethinking cystic fibrosis pathology: the critical role of abnormal reduced glutathione (GSH) transport caused by CFTR mutation

Though the cause of cystic fibrosis (CF) pathology is understood to be the mutation of the CFTR protein, it has been difficult to trace the exact mechanisms by which the pathology arises and progresses from the mutation. Recent research findings have noted that the CFTR channel is not only permeant to chloride anions, but other, larger organic anions, including reduced glutathione (GSH). This explains the longstanding finding of extracellular GSH deficit and dramatically reduced extracellular GSH:GSSG (glutathione disulfide) ratio found to be chronic and progressive in CF patients. Given the vital role of GSH as an antioxidant, a mucolytic, and a regulator of inflammation, immune response, and cell viability via its redox status in the human body, it is reasonable to hypothesize that this condition plays some role in the pathogenesis of CF. This hypothesis is advanced by comparing the literature on pathological phenomena associated with GSH deficiency to the literature documenting CF pathology, with striking similarities noted. Several puzzling hallmarks of CF pathology, including reduced exhaled NO, exaggerated inflammation with decreased immunocompetence, increased mucus viscoelasticity, and lack of appropriate apoptosis by infected epithelial cells, are better understood when abnormal GSH transport from epithelia (those without anion channels redundant to the CFTR at the apical surface) is added as an additional explanatory factor. Such epithelia should have normal levels of total glutathione (though perhaps with diminished GSH:GSSG ratio in the cytosol), but impaired GSH transport due to CFTR mutation should lead to progressive extracellular deficit of both total glutathione and GSH, and, hypothetically, GSH:GSSG ratio alteration or even total glutathione deficit in cells with redundant anion channels, such as leukocytes, lymphocytes, erythrocytes, and hepatocytes. Therapeutic implications, including alternative methods of GSH augmentation, are discussed.

Increased nitrotyrosine in exhaled breath condensate in cystic fibrosis

Exhaled nitric oxide (ENO), a marker of inflammation in airway diseases is decreased in cystic fibrosis (CF) patients, perhaps because nitric oxide (NO) is metabolized to oxidative end-products. A stable product, 3-nitrotyrosine, may indicate local formation of reactive nitrogen species. Whether NO metabolites in exhaled breath condensate may be increased in CF patients was investigated. The fractional concentration of ENO (Feno), nitrotyrosine and oxides of nitrogen in exhaled breath condensate from 36 stable CF patients were compared to 14 normal subjects using an enzyme immunoassay and fluorescence assay. Nitrotyrosine levels in breath condensate were increased significantly in stable CF patients, compared with normal subjects (25.3 +/- 1.5 versus 6.3 +/- 0.8 ng x mL(-1), p<0.0001). There was an inverse correlation between the levels of nitrotyrosine and the severity of lung disease. Feno levels were significantly lower in CF patients than in normal subjects (4.4 +/- 0.3 versus 5.6 +/- 0.4 (parts per billion), p<0.05). No correlation was found between nitrotyrosine and Feno levels in CF. There was no significant difference in the levels of nitrite and nitrate between CF patients and normals. The elevation in nitrotyrosine may reflect increased formation of reactive nitrogen species such as peroxynitrite or direct nitration by granulocyte peroxidases, indicating increased oxidative stress in airways of cystic fibrosis patients.