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

Exhaled nitric oxide is associated with inflammatory biomarkers and risk of acute respiratory exacerbations in children with HIV-associated chronic lung disease

OBJECTIVES

Chronic lung disease is a recognized complication in children with HIV. Acute respiratory exacerbations (ARE) are common among this group and cause significant morbidity. Exhaled nitric oxide (eNO) is a known marker of local airway inflammation. We investigated the association between eNO and ARE, biomarkers of systemic inflammation, and the effect of azithromycin on eNO levels.

METHODS

Individuals aged 6-19 years with HIV-associated chronic lung disease in Harare, Zimbabwe, were enrolled in a placebo-controlled randomized trial investigating the effect of 48-week azithromycin treatment on lung function and ARE. eNO levels and biomarkers were measured at inclusion and after treatment in a consecutively enrolled subset of participants. Linear regression and generalized linear models were used to study associations between eNO and ARE, biomarkers, and the effect of azithromycin on eNO levels.

RESULTS

In total, 172 participants were included in this sub-study, 86 from the placebo group and 86 from the azithromycin group. Participants experiencing at least one ARE during follow-up had significantly higher eNO levels at baseline than participants who did not (geometric mean ratio 1.13, 95% confidence interval [CI] 1.03-1.24, p = 0.015), adjusted for trial arm, age, sex and history of tuberculosis. Matrix metalloproteinase (MMP)-3, -7, and -10 were significantly associated with higher baseline eNO levels. At 48 weeks, azithromycin treatment did not affect eNO levels (geometric mean ratio 0.86, 95% CI 0.72-1.03, p = 0.103).

CONCLUSION

Higher baseline eNO levels were a risk factor for ARE. eNO was associated with proinflammatory biomarkers previously found to contribute to the development of chronic lung disease. The potential use of eNO as a marker of inflammation and risk factor for ARE in HIV-associated chronic lung disease needs further investigation.

Lower Airway Nitrogen Oxide Levels in Children with Primary Ciliary Dyskinesia Is Linked to Neutrophilic Inflammation

Treatment of primary ciliary dyskinesia pulmonary exacerbations resulted in an increase in sputum nitric oxide (NO) metabolites and decrease in neutrophilic inflammation. The association between the 2 suggests that neutrophilic inflammation contributes to airway NO deficiency in primary ciliary dyskinesia and that reducing inflammation may lead to improved airway NO homeostasis. TRIAL REGISTRY: ClinicalTrials.gov: NCT01155115.

Boosting nitric oxide in stress and respiratory infection: Potential relevance for asthma and COVID-19

Nitric oxide (NO) is a ubiquitous signaling molecule that is critical for supporting a plethora of processes in biological organisms. Among these, its role in the innate immune system as a first line of defense against pathogens has received less attention. In asthma, levels of exhaled NO have been utilized as a window into airway inflammation caused by allergic processes. However, respiratory infections count among the most important triggers of disease exacerbations. Among the multitude of factors that affect NO levels are psychological processes. In particular, longer lasting states of psychological stress and depression have been shown to attenuate NO production. The novel SARS-CoV-2 virus, which has caused a pandemic, and with that, sustained levels of psychological stress globally, also adversely affects NO signaling. We review evidence on the role of NO in respiratory infection, including COVID-19, and stress, and argue that boosting NO bioavailability may be beneficial in protection from infections, thus benefitting individuals who suffer from stress in asthma or SARS-CoV-2 infection.

The Bactericidal Tandem Drug, AB569: How to Eradicate Antibiotic-Resistant Biofilm Pseudomonas aeruginosa in Multiple Disease Settings Including Cystic Fibrosis, Burns/Wounds and Urinary Tract Infections

The life-threatening pandemic concerning multi-drug resistant (MDR) bacteria is an evolving problem involving increased hospitalizations, billions of dollars in medical costs and a remarkably high number of deaths. Bacterial pathogens have demonstrated the capacity for spontaneous or acquired antibiotic resistance and there is virtually no pool of organisms that have not evolved such potentially clinically catastrophic properties. Although many diseases are linked to such organisms, three include cystic fibrosis (CF), burn/blast wounds and urinary tract infections (UTIs), respectively. Thus, there is a critical need to develop novel, effective antimicrobials for the prevention and treatment of such problematic infections. One of the most formidable, naturally MDR bacterial pathogens is Pseudomonas aeruginosa (PA) that is particularly susceptible to nitric oxide (NO), a component of our innate immune response. This susceptibility sets the translational stage for the use of NO-based therapeutics during the aforementioned human infections. First, we discuss how such NO therapeutics may be able to target problematic infections in each of the aforementioned infectious scenarios. Second, we describe a recent discovery based on years of foundational information, a novel drug known as AB569. AB569 is capable of forming a "time release" of NO from S-nitrosothiols (RSNO). AB569, a bactericidal tandem consisting of acidified NaNO₂ (A-NO₂ ^-) and Na₂-EDTA, is capable of killing all pathogens that are associated with the aforementioned disorders. Third, we described each disease state in brief, the known or predicted effects of AB569 on the viability of PA, its potential toxicity and highly remote possibility for resistance to develop. Finally, we conclude that AB569 can be a viable alternative or addition to conventional antibiotic regimens to treat such highly problematic MDR bacterial infections for civilian and military populations, as well as the economical burden that such organisms pose.

Clinical Values of Nitric Oxide Parameters from the Respiratory System

BACKGROUND

Fractional exhaled nitric oxide (FENO) concentration reliably reflects central airway inflammation, but it is not sensitive to changes in the NO dynamics in the lung periphery. By measuring FENO at several different flow rates one can estimate alveolar NO concentration (C_ANO), bronchial NO flux (J_awNO), bronchial wall NO concentration (C_awNO) and the bronchial diffusivity of NO (D_awNO).

OBJECTIVE

We aimed to describe the current knowledge and clinical relevance of NO parameters in different pulmonary diseases.

METHODS

We conducted a systematic literature search to identify publications reporting NO parameters in subjects with pulmonary or systemic diseases affecting the respiratory tract. A narrative review was created for those with clinical relevance.

RESULTS

Estimation of pulmonary NO parameters allows for differentiation between central and peripheral inflammation and a more precise analysis of central airway NO output. C_ANO seems to be a promising marker of parenchymal inflammation in interstitial lung diseases and also a marker of tissue damage and altered gas diffusion in chronic obstructive pulmonary disease and systemic diseases affecting the lung. In asthma, C_ANO can detect small airway involvement left undetected by ordinary FENO measurement. Additionally, C_awNO and D_awNO can be used in asthma to assess if FENO is increased due to enhanced inflammatory activity (increased C_awNO) or tissue changes related to bronchial remodelling (altered D_awNO).

CONCLUSION

NO parameters may be useful for diagnosis, prediction of disease progression and prediction of treatment responses in different parenchymal lung and airway diseases. Formal trials to test the added clinical value of NO parameters are needed.

History of tuberculosis is associated with lower exhaled nitric oxide levels in HIV-infected children

Objective:

HIV disrupts host defense mechanisms and maintains chronic inflammation in the lung. Nitric oxide is a marker of lung inflammation and can be measured in the exhaled air. We investigated the relationship between exhaled nitric oxide (eNO), HIV status and airway abnormalities in perinatally HIV-infected children aged 6–19 years.

Design:

A cross-sectional study.

Methods:

HIV-infected individuals on antiretroviral therapy and HIV-uninfected children with no active tuberculosis (TB) or acute respiratory tract infection were recruited from a public hospital in Harare, Zimbabwe. Clinical history was collected and eNO testing and spirometry was performed. The association between eNO and explanatory variables (HIV, FEV1 z-score, CD4⁺ cell count, viral load, history of TB) was investigated using linear regression analysis adjusted for age, sex and time of eNO testing.

Results:

In total, 222 HIV-infected and 97 HIV-uninfected participants were included. Among HIV-infected participants, 57 (25.7%) had a history of past TB; 56 (25.2%) had airway obstruction, but no prior TB. HIV status was associated with lower eNO level [mean ratio 0.79 (95% confidence interval, 95% CI 0.65–0.97), P = 0.03]. Within the HIV-infected group, history of past TB was associated with lower eNO levels after controlling for age, sex and time of eNO testing [0.79 (95% CI 0.67–0.94), P = 0.007].

Conclusion:

HIV infection and history of TB were associated with lower eNO levels. eNO levels may be a marker of HIV and TB-induced alteration in pulmonary physiology; further studies focused on potential causes for lower eNO levels in HIV and TB are warranted.

Type I interferon induced by TLR2-TLR4-MyD88-TRIF-IRF3 controls Mycobacterium abscessus subsp. abscessus persistence in murine macrophages via nitric oxide

Mycobacterium abscessus (MAB) is an emerging, rapidly growing non-tuberculous Mycobacterium causing therapy-resistant pulmonary disease especially in patients with cystic fibrosis (CF). Smooth and rough colony type MAB can be isolated from infected patients whereby rough colony type MAB are more often associated with severe disease. Disease severity is also associated with an alternated type I interferon (IFN-I) response of the MAB-infected patients. However the relevance of this response for the outcome of MAB infection is still unknown. In this study, we analyzed the IFNβ expression of murine macrophages infected with a MAB rough colony strain (MAB-R) isolated from a patient with progressive CF and compared it to macrophages infected with the MAB smooth colony type reference strain (MAB-S). We found that MAB-R infected macrophages expressed significantly more IFNβ mRNA and protein than MAB-S infected macrophages. Higher IFNβ induction by MAB-R was associated with higher TNF expression and intracellular killing while low IFNβ induction was associated with lower TNF expression and persistence of MAB-S. IFNβ induction was independent of the intracellular cGAS-STING recognition pathway. MAB appeared to be recognized extracellularly and induced IFNβ expression via TLR2-TLR4-MyD88-TRIF-IRF3 dependent pathways. By using macrophages lacking the IFN-I receptor we demonstrate that MAB induced IFN-I response essentially contributed to restricting MAB-R and MAB-S infections by activating macrophage Nos2 expression and nitric oxide production. Thus IFN-I seem to influence the intrinsic ability of macrophages to control MAB infections. As MAB persists over long time periods in susceptible patients, our findings suggest that virulence of MAB strains is promoted by an insufficient IFN-I response of the host.

[Usefulness of measurement of nitric oxide in exhaled air in diagnostics and treatment of allergic rhinitis and asthma in children and adolescents]

Nitric oxide is produced by enzymes called nitric oxide synthases. It fulfills many important functions in the human body, but produced in excess amount has a proinflammatory activity. Fractional exhaled nitric oxide measurements are used in the diagnosis and monitoring of eosinophilic inflammation in the lower airways, but should not be used as an independent parameter to make a diagnosis of asthma or for the monitoring of asthma treatment. Evaluation of fractional exhaled nitric oxide concentrations is also used to determine the pathogenesis of symptoms in patients with rhinitis. In addition, they are helpful in detecting and monitoring eosinophilic inflammation in the lower respiratory tract that coexists with inflammation in the upper airways. Fractional exhaled nitric oxide concentrations may be abnormal (lowered or elevated) in other chronic diseases, such as cystic fibrosis, primary ciliary dyskinesia and inflammatory bowel diseases. Many factors, e.g. atopy, genetic polymorphisms of NOS, and the lipid profile affect the fractional exhaled nitric oxide measurement. Nasal nitric oxide measurement is useful in assessing the prevalence and severity of eosinophilic inflammation in the upper respiratory tract.

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.

Nasal nitric oxide screening for primary ciliary dyskinesia: systematic review and meta-analysis

Nasal nitric oxide (nNO) concentrations are low in patients with primary ciliary dyskinesia (PCD) providing a noninvasive screening test.

We conducted a systematic review of the literature to examine the utility of nNO in screening for PCD, in particular 1) different respiratory manoeuvres during sampling (velum closure, tidal breathing, etc.), 2) accuracy in screening young/uncooperative children, 3) stationary versus portable analysers, and 4) nNO in “atypical” PCD.

96 papers were assessed according to modified PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) criteria and 22 were included in this review.

Meta-analysis of 11 studies comparing nNO during a velum closure breath hold gave a mean±sd nNO of 19.4±18.6 nL·min-1 in PCD (n = 478) and 265.0±118.9 nL·min-1 in healthy controls (n = 338). Weighted mean difference for PCD versus healthy controls was 231.1 nL·min-1 (95% CI 193.3–268.9; n = 338) and 114.1 nL·min-1 (95% CI 101.5–126.8; n = 415) for PCD versus cystic fibrosis. Five studies of nNO measurement during tidal breathing demonstrated that this is an acceptable manoeuvre in young children where velum closure is not possible, but the discriminatory value was reduced. Four small studies of portable NO analysers suggest these are reliable tools for screening for PCD. However, nNO must be interpreted alongside clinical suspicion. Future studies should focus on standardising sampling techniques and reporting.

Determinants of culture success in an airway epithelium sampling program of young children with cystic fibrosis

AIM OF THE STUDY

The bronchial brushing technique presents an opportunity to establish a gold standard in vitro model of Cystic Fibrosis (CF) airway disease. However, unique obstacles exist when establishing CF airway epithelial cells (pAECCF). We aimed to identify determinants of culture success through retrospective analysis of a program of routinely brushing children with CF.

MATERIALS AND METHODS

Anaesthetised children (CF and non-CF) had airway samples taken which were immediately processed for cell culture. Airway data for the CF cohort was obtained from clinical records and the AREST CF database.

RESULTS

Of 260 brushings processed for culture, 114 (43.8%) pAECCF successfully cultured to passage one (P1) and 63 (24.2% of total) progressed to passage two (P2). However, >80% of non-CF specimens (pAECnon-CF) cultured to P2 from similar cell numbers. Within the CF cohort, specimens successfully cultured to P2 had a higher initial cell count and lower proportion of severe CF mutation phenotype than those that did not proliferate beyond initial seeding. Elevated airway IL-8 concentration was also negatively associated with culture establishment. Contamination by opportunistic pathogens was observed in 81 (31.2% of total) cultures and brushings from children with lower respiratory tract infections were more likely to co-culture contaminating flora.

CONCLUSIONS

Lower passage rates of pAECCF cultures uniquely contrasts with pAECnon-CF despite similar cell numbers. An equivalent establishment rate of CF nasal epithelium reported elsewhere, significant associations to CFTR mutation phenotype, elevated airway IL-8 and opportunistic pathogens all suggest this is likely related to the CF disease milieu.

Proteomic biomarker discovery for the monogenic disease cystic fibrosis

Proteomics was initially viewed as a promising new scientific discipline to study complex disorders such as polygenic, infectious and environment-related diseases. However, the first attempts to understand a monogenic disease such as cystic fibrosis (CF) by proteomics-based approaches have proved quite rewarding. In CF, the impairment of a unique protein, the CF transmembrane conductance regulator, does not completely explain the complex and variable CF clinical phenotype. The great advances in our knowledge about the molecular and cellular consequences of such impairment have not been sufficient to be translated into effective treatments, and CF patients are still dying due to chronic progressive lung dysfunction. The progression of proteomics application in CF will certainly unravel new proteins that could be useful as biomarkers either to elucidate CF basic mechanisms and to better monitor the disease progression, or to promote the development of novel therapeutic strategies against CF. This review will summarize the recent technological advances in proteomics and the first results of its application to address the most important issues in the CF field.

Exhaled nitric oxide in symptomatic children at preschool age predicts later asthma

BACKGROUND

Prediction of asthma in young children with respiratory symptoms is hampered by the lack of objective measures applicable in clinical routine. In this prospective study in a preschool children cohort, we assessed whether the fraction of exhaled nitric oxide (FeNO), a biomarker of airway inflammation, is associated with asthma at school age.

METHODS

At baseline, IgE and eosinophils were measured in the blood, and FeNO was measured offline in 391 children aged 3-47 months with lower airway symptoms. We developed an asthma predictive index (API) including high FeNO as major criterion. At follow-up, primary outcome was physician-diagnosed asthma based on standardized interviews in those children reaching school age (n = 166).

RESULTS

FeNO was significantly elevated in those children with later asthma (68/166) as compared to children not developing asthma. Median (IQR) FeNO was 10.5 (6.6-17.2) vs. 7.4 (5.3-10.3) ppb. Per 5 ppb FeNO increase, the odds ratio (95% CI) for asthma increased by 2.44 (1.61-3.70) without changing when adjusting for confounders. Using the new API, children scored at risk had 58.0% probability for later asthma, whereas the negative predictive value was 78.2%, which was comparable to the classical API.

CONCLUSIONS

In this cohort of high-risk preschool children, elevated FeNO is associated with increased risk for school-age asthma. The new API including FeNO identifies children at risk of later asthma comparably to the classical API, but does not require blood sampling.

Gasotransmitters: novel regulators of epithelial na(+) transport?

The vectorial transport of Na(+) across epithelia is crucial for the maintenance of Na(+) and water homeostasis in organs such as the kidneys, lung, or intestine. Dysregulated Na(+) transport processes are associated with various human diseases such as hypertension, the salt-wasting syndrome pseudohypoaldosteronism type 1, pulmonary edema, cystic fibrosis, or intestinal disorders, which indicate that a precise regulation of epithelial Na(+) transport is essential. Novel regulatory signaling molecules are gasotransmitters. There are currently three known gasotransmitters: nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H(2)S). These molecules are endogenously produced in mammalian cells by specific enzymes and have been shown to regulate various physiological processes. There is a growing body of evidence which indicates that gasotransmitters may also regulate Na(+) transport across epithelia. This review will summarize the available data concerning NO, CO, and H(2)S dependent regulation of epithelial Na(+) transport processes and will discuss whether or not these mediators can be considered as true physiological regulators of epithelial Na(+) transport biology.

Bronchial brushings for investigating airway inflammation and remodelling

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

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.

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.

A single dose of Sildenafil does not enhance FeNO: a randomised, cross-over and placebo-controlled study

Monitoring of asthma control can be performed with different means including measurement of the concentration of nitric oxide (NO) in exhaled air. Due to its action on the NO-metabolism; we hypothesized that the intake of Sildenafil might augment and falsify the NO-values in exhaled air of subjects taking the drug to treat erectile dysfunction. This randomised, placebo-controlled cross-over study including 10 male non-asthmatic volunteers taking a single dose of 50 mg Sildenafil did not confirm this assumption in non-asthmatic subjects. We cannot think of any reason why asthmatics should behave differently. On the basis of these results, it does not seem necessary to ask asthma patients with elevated NO-values if they had taken any selective inhibitor of the cGMP-specific phosphodiesterase Type 5 as Sildenafil prior to the test.

Monitoring respiratory disease severity in cystic fibrosis

Measurements of disease severity provide a guide for the physician to tailor therapies, for the patient and family to gauge progress, and are required for clinical trials. For many respiratory diseases, including cystic fibrosis, sensitive, noninvasive measurements are few, and some of those that are available are applicable only to certain subgroups of patients or lack sufficient sensitivity. We discuss currently available measurements in 4 groups: physiology, infection, inflammation, and radiology. For each group we highlight strengths and weaknesses, ask how we could improve upon these, and provide details of alternative methods.

The role of inhaled corticosteroids in the management of cystic fibrosis

The lung disease of cystic fibrosis (CF) is characterized by a vicious cycle of airway obstruction, chronic bacterial infection, and vigorous inflammation, which ultimately results in bronchiectasis. Recognition that excessive and persistent inflammation is a key factor in lung destruction has prompted investigation into anti-inflammatory therapies. Although effective, the use of systemic corticosteroids has been limited by the unacceptable adverse effect profile. Inhaled corticosteroids (ICS) are a widely prescribed anti-inflammatory agent in CF, likely as a result of clinicians' familiarity with these agents and their excellent safety profile at low doses in asthmatic patients. However, while multiple studies are limited by small sample size and short duration, they consistently failed to demonstrate statistically or clinically significant benefits of ICS use in CF. This review provides an overview of the inflammatory response in CF, the mechanisms of action of corticosteroids, the safety of ICS, and the literature relevant to the use of ICS in CF.

Biomarkers in exhaled breath condensate indicate presence and severity of cystic fibrosis in children

Chronic airway inflammation is present in cystic fibrosis (CF). Non-invasive inflammometry may be useful in disease management. The aim of the present cross-sectional study was to investigate: (i) the ability of fractional exhaled nitric oxide and inflammatory markers (IM) [exhaled breath condensate (EBC) acidity, nitrite, nitrate, hydrogen peroxide (H(2)O(2)), 8-isoprostane, Th1/Th2 cytokines] to indicate (exacerbations of) CF; and (ii) the ability of these non-invasive IM to indicate CF disease severity. In 98 children (48 CF/50 controls), exhaled nitric oxide was measured using the NIOX, and condensate was collected using a glass condenser. In CF interferon (IFN-gamma) and nitrite concentrations were significantly higher, whereas exhaled nitric oxide levels were significantly lower compared with controls (3.3 +/- 0.3 pg/ml, 2.2 +/- 0.2 microM, 10.0 +/- 1.2 p.p.b. vs. 2.6 +/- 0.2 pg/ml, 1.4 +/- 0.1 microM, 15.4 +/- 1.4 p.p.b. respectively). Using multivariate logistic regression models, the presence of CF was best indicated by 8-isoprostane, nitrite and IFN-gamma [sensitivity 78%, specificity 83%; area under receiver operating characteristic curve (AUC) 0.906, p < 0.001]. An exacerbation of CF was best indicated by 8-isoprostane and nitrite (sensitivity 40%, specificity 97%, AUC curve 0.838, p = 0.009). Most indicative biomarkers of CF severity were exhaled nitric oxide, and condensate acidity (sensitivity 96%, specificity 67%; AUC curve 0.751, p = 0.008). In this cross-sectional study, the combination of different exhaled IM could indicate (exacerbations of) CF, and severity of the disease in children. Longitudinal data are necessary to further confirm the role of these markers for the management of CF in children.

Assessment and monitoring of cystic fibrosis lung disease in infants and young children

Chronic airway infection and inflammation are the hallmarks of cystic fibrosis (CF) lung disease. As these events occur early in life, it is critical to develop techniques for the assessment and monitoring of early-CF lung disease in infants and young children. In the last several years, there have been major advances in the development of imaging technology to assess structural damage in CF lung disease, noninvasive markers of CF airway inflammation and measurement of lung function in infants and young children with CF. In this article, we will review these advances and techniques, and discuss future directions for research and clinical applications.

Exhaled nitric oxide in childhood asthma: a review

As an 'inflammometer', the fraction of nitric oxide in exhaled air (Fe(NO)) is increasingly used in the management of paediatric asthma. Fe(NO) provides us with valuable, additional information regarding the nature of underlying airway inflammation, and complements lung function testing and measurement of airway hyper-reactivity. This review focuses on clinical applications of Fe(NO) in paediatric asthma. First, Fe(NO) provides us with a practical tool to aid in the diagnosis of asthma and distinguish patients who will benefit from inhaled corticosteroids from those who will not. Second, Fe(NO) is helpful in predicting exacerbations, and predicting successful steroid reduction or withdrawal. In atopic asthmatic children Fe(NO) is beneficial in adjusting steroid doses, discerning those patients who require additional therapy from those whose medication dose could feasibly be reduced. In pre-school children Fe(NO) may be of help in the differential diagnosis of respiratory symptoms, and may potentially allow for better targeting and monitoring of anti-inflammatory treatment.

Alveolar, but not bronchial nitric oxide production is elevated in cystic fibrosis

Exhaled nitric oxide (NO) remains a promising non-invasive marker for measuring inflammation in lung diseases. In cystic fibrosis (CF), exhaled NO measured at a single expiratory flow has been found to be normal or low. However, this measure cannot localize the anatomical site of NO production. The aims of this study were to apply a multiple-flow NO analysis to compare alveolar NO concentration and bronchial NO flux in CF children with healthy controls. Twenty-two children with CF and 17 healthy controls had exhaled NO measured at four different expiratory flows to calculate bronchial NO flux and alveolar NO concentration. Median (range) alveolar NO concentration was 2.2 (0.6-5.6) ppb for children with CF and 1.5 (0.4-2.6) ppb for healthy controls. Median (range) bronchial NO flux was 445 (64-1,256) pL/sec for children with CF and 509 (197-1,913) pL/sec for healthy controls. Children with CF had a significantly higher alveolar NO concentration, but no significant difference in bronchial NO flux compared to healthy children. In conclusion, children with CF have increased alveolar NO production, but not bronchial NO flux compared to healthy controls. The distal airway is a major site of inflammation in CF, and measuring alveolar NO may be a marker of distal inflammation in this disease.

Longitudinal monitoring of pediatric cystic fibrosis lung disease using nitrite in exhaled breath condensate

Cystic fibrosis (CF) lung disease is characterized by airway inflammation and airway infection. Nitrites in exhaled breath condensate (EBC-NO(2)(-)) have been shown to be increased in children and adults with CF compared to healthy controls suggesting its use as a measure of airway inflammation. This longitudinal study aimed to evaluate if repeated measurements of EBC-NO(2)(-) are helpful in monitoring CF lung disease activity in children. Thirty-two children with mild CF lung disease (age 10.6 +/- 3.3 years) were recruited in two study centers. Follow-up visits occurred every 3 months over a period of 1 year with a total of five visits. Each visit included a clinical assessment incorporating a modified Shwachman-Kulczycki (SK) score, spirometry, an oropharyngeal swab, or sputum sample for bacterial analysis and an EBC sample analyzed for NO(2)(-) using a spectrophotometric assay. Furthermore at the first and the last visit a chest radiograph was done and scored (Chrispin-Norman (CN) score). There was no correlation of EBC-NO(2)(-) and parameters of spirometry, SK-score, or CN-score. Furthermore, increased EBC-NO(2)(-) levels did not predict subsequent pulmonary exacerbations. We conclude that repeated measurements of EBC-NO(2)(-) are not helpful in the longitudinal monitoring of mild CF lung disease in children.