Determinants of fractional exhaled nitric oxide in healthy men and women from the European Community Respiratory Health Survey III

SNPs inFAM13AandIL2RBgenes are associated with FeNO in adult subjects with asthma

Nitric oxide has different roles in asthma as both an endogenous modulator of airway function and a pro-inflammatory mediator. Fractional exhaled nitric oxide (FeNO) is a reliable, quantitative, non-invasive, simple, and safe biomarker for assessing airways inflammation in asthma. Previous genome-wide and genetic association studies have shown that different genes and single nucleotide polymorphisms (SNPs) are linked to FeNO. We aimed at identifying SNPs in candidate genes or gene regions that are associated with FeNO in asthma. We evaluated 264 asthma cases (median age 42.8 years, female 47.7%) who had been identified in the general adult population within the Gene Environment Interactions in Respiratory Diseases survey in Verona (Italy; 2008-2010). Two hundred and twenty-one tag-SNPs, which are representative of 50 candidate genes, were genotyped by a custom GoldenGate Genotyping Assay. A two-step association analysis was performed without assuming ana priorigenetic model: step (1) a machine learning technique [gradient boosting machine (GBM)] was used to select the 15 SNPs with the highest variable importance measure; step (2) the GBM-selected SNPs were jointly tested in a linear regression model with natural log-transformed FeNO as the normally distributed outcome and with age, sex, and the SNPs as covariates. We replicated our results within an independent sample of 296 patients from the European Community Respiratory Health Survey III. We found that SNP rs987314 in family with sequence similarity 13 member A (FAM13A) and SNP rs3218258 in interleukin 2 receptor subunit beta (IL2RB) gene regions are significantly associated with FeNO in adult subjects with asthma. These genes are involved in different mechanisms that affect smooth muscle constriction and endothelial barrier function responses (FAM13A), or in immune response processes (IL2RB). Our findings contribute to the current knowledge on FeNO in asthma by identifying two novel SNPs associated with this biomarker of airways inflammation.

A cross-sectional analysis of medical conditions and environmental factors associated with fractional exhaled nitric oxide (FeNO) in women and children from the ISA birth cohort, Costa Rica

BACKGROUND

Fractional exhaled nitric oxide (FeNO) is a marker of airway inflammation. Elevated FeNO has been associated with environmental exposures, however, studies from tropical countries are limited. Using data from the Infants' Environmental Health Study (ISA) birth cohort, we evaluated medical conditions and environmental exposures' association with elevated FeNO.

METHODS

We performed a cross-sectional analysis of 277 women and 293 8-year old children who participated in the 8-year post-partum visit in 2019. We measured FeNO and collected information on medical conditions and environmental exposures including smoke from waste burning, work in banana plantations, and home pesticide use. We defined elevated FeNO as >25 ppb for women and >20 ppb for children. To evaluate factors associated with elevated FeNO, we used logistic regression models adjusted for obesity in women and unadjusted in children.

RESULTS

Overall elevated FeNO was common (20% of women, 13% of children). Rhinitis diagnosis was significantly associated with elevated FeNO in both women (odds ratio (OR): 3.67 95% Confidence Interval (CI): 1.81,7.35) and children (OR: 8.18 95%CI: 3.15, 21.22); wheeze was associated with elevated FeNO in women (OR: 4.50 95% CI: 2.25, 8.99). Environmental exposures were associated with elevated FeNO, but not significantly. Waste burning was associated with elevated FeNO in both women (OR: 1.58 95%CI 0.68, 4.15) and children (OR: 2.49 95%CI:0.82, 10.79). Para-occupational pesticide exposures were associated with elevated FeNO in women and children. For women, having a partner working in agriculture was associated with elevated FeNO (OR: 1.61 95%CI:0.77, 3.58) and for children, maternal work in agriculture was associated with elevated FeNO. (OR 2.08 95%CI 0.86, 4.67) CONCLUSION: Rhinitis and wheeze were associated with elevated FeNO in this rural, agricultural population. Smoke from waste burning as well as para-occupational pesticide exposure may contribute to elevated FeNO in rural communities.

Airway inflammation in adolescents and elderly women: Chronic air pollution exposure and polygenic susceptibility

BACKGROUND AND AIM

The fractional exhaled nitric oxide (FeNO) concentration in the exhaled breath is a biomarker for eosinophilic airway inflammation. We explored the interplay between chronic air pollution exposure and polygenic susceptibility to airway inflammation at different critical age stages.

METHODS

Adolescents (15 yr) enrolled in the GINIplus/LISA birth cohorts (n = 2434) and 220 elderly women (75 yr on average) enrolled in the SALIA cohort with FeNO measurements available were investigated. Environmental main effects of the mean of ESCAPE land-use regression air pollutant concentrations within a time window of 15 years and main effects of the polygenic risk scores (PRS) using internal weights from elastic net regression of genome-wide derived single nucleotide polymorphisms were investigated. Furthermore, we examined gene-environment interaction (GxE) effects on natural log-transformed FeNO levels by adjusted linear regression models.

RESULTS

While we observed no significant environmental and polygenic main effects on airway inflammation in either age group, we found robust harmful effects of chronic nitrogen dioxide (NO₂) exposure in the GxE models for elderly women (16.2 % increase in FeNO, p-value = 0.027). Stratified analyses found GxE effects between the PRS and chronic NO₂ exposure in never-smoker elderly women and in adolescents without any inflammatory respiratory conditions.

CONCLUSIONS

FeNO measurement is a useful biomarker to detect higher risk of NO₂-induced eosinophilic airway inflammation in the elderly. There was limited evidence for GxE effects on airway inflammation in adolescents or the elderly. Further GxE studies in subpopulations should be conducted to investigate the assumption that susceptibility to airway inflammation differs between age stages.

Clinical implications of concentration of alveolar nitric oxide in asthmatic and non-asthmatic subacute cough

Asthma is an important cause of subacute cough. The concentration of alveolar nitric oxide (CANO) is a sensitive inflammatory indicator in peripheral airways, and it has received much less attention than the fraction of exhaled nitric oxide (FeNO₅₀). The main objective of this study was to explore the correlation between CANO and clinical parameters in asthmatic and non-asthmatic subacute cough, which might promote understanding of the clinical utility of CANO in these special patient populations. 155 patients with subacute cough were included consecutively, of which 25 were diagnosed as asthmatic. Data for demographic characteristics, FeNO₅₀, CANO, baseline spirometry, bronchial provocation test (or bronchodilation test) and response dose ratio (RDR) were collected. Differences between the asthmatic and non-asthmatic groups were analyzed. Spearman's correlation coefficient (ρ) was used to evaluate the correlation between FeNO₅₀, CANO and other clinical parameters. In patients with subacute cough, baseline CANO values did not differ between asthmatic and non-asthmatic patients (4.4(1.3, 11.4) versus 4.0(2.1, 6.8) ppb,P> 0.05). Besides, CANO exhibited a stronger association with pulmonary function parameters when compared with FeNO₅₀. For asthmatic subacute cough, CANO was inversely correlated with FEV₁/FVC (ρ= -0.69,P< 0.01) and small airway parameters including MEF25 (ρ= -0.47,P< 0.05) and MMEF (ρ= -0.45,P< 0.05). For non-asthmatic subacute cough, CANO was inversely correlated with MEF25 (ρ= -0.19,P< 0.05) and RDR (ρ= -0.21,P< 0.05). In subacute cough, asthmatic and non-asthmatic patients had similar values of baseline CANO. In both asthmatic and non-asthmatic subacute cough, CANO exhibited a stronger association with pulmonary function parameters when compared with FeNO₅₀. A low CANO value in non-asthmatic subacute cough corresponded to a higher value of RDR, which implied a stronger tendency towards airway responsiveness.

Fractional exhaled nitric oxide levels in relation to work-related respiratory burden and sensitization to wheat flour and multigrain in bakers

Background

Work‐related lower airway symptoms (WR‐LAS), rhinitis (WRR), and asthma (WRA) are very common among bakers, due to airborne exposure to wheat flour and multigrain. Limited data is available regarding fractional exhaled nitric oxide (FeNO) in bakers in relation to respiratory burden and occupational sensitization in a real‐life situation.

Objective

To analyze FeNO levels in relation to WRR, WR‐LAS, and WRA with regard to allergic sensitization to occupational allergen in bakers.

Methods

Cross‐sectional, observational study of 174 bakers employed in traditional small bakeries in the Verona District. Subjects did FeNO measurements, spirometry, methacholine challenge, and skin prick test to common inhalant aeroallergens and bakeries occupational allergens.

Results

FeNO levels were higher in subjects sensitized to occupational allergens compared with bakers not sensitized to occupational allergens (22.8 ppb (18.9, 27.6) vs. 12.0 ppb (9.9, 14.5), p < 0.05). FeNO levels were higher in bakers with WRR and occupational sensitization (25.4 (20.6, 31.3)) than in bakers with WRR without occupational sensitization compared and bakers without respiratory burden (13.4 (9.6, 18.6) and 11.9 (9.8, 14.5), both p < 0.001). Similar findings were found for WR‐LAS with regard to the same categories (31.2 (24.1, 40.4) vs 13.3 (11.4, 15.6) and 15.3 (8.5, 27.5), p < 0.001 and p = 0.005). Bakers with WRA, with or without occupational allergic sensitization, had higher levels of FeNO than bakers without respiratory burden (both p ≤ 0.001). These findings were consistent after adjustments for gender, age, height, weight, smoking, and sensitization to common inhalant aeroallergens and lung function.

Conclusions

WRR and lower airway symptoms in bakers sensitized to occupational allergens relate to increased FeNO. Our study suggests that FeNO is associated with work‐related allergic inflammation in occupational sensitized bakers, but future studies are needed to assess how FeNO should be integrated in the diagnostic work‐up of occupational disease in bakers.

Fractional exhaled NO in a metalworking occupational cohort

PURPOSE

Secondary metalworking carries exposure to relatively heavy levels of respirable particulate. We investigated the extent to which metalworking is associated with increased exhaled nitric oxide (FeNO), an established inflammatory biomarker.

METHODS

We studied 80 metalworking factory employees in Kazakhstan. Informed by industrial hygiene data, we categorized them into three groups: (1) machine operators (41%); (2) welders or assemblers (33%); and (3) all others, including administrative and ancillary staff (26%). Participants completed questionnaires covering occupational history, smoking, home particulate sources, respiratory symptoms, and comorbidities. We measured exhaled carbon monoxide (CO), exhaled fractional nitric oxide (FeNO), and spirometric function. We used mixed-effects modeling to test the associations of occupational group with FeNO, adjusted for covariates.

RESULTS

The median age was 51.5 (interquartile range 20.5) years; 7% were women. Occupational group (p < 0.01), daily current cigarette smoking intensity (p < 0.05), and age (p < 0.05), each was statistically associated with FeNO. Welders, or assemblers (Group 2), who had intermediate particulate exposure, manifested significantly higher exhaled FeNO compared to machinists (Group 1, with the highest particulate exposure) and all others (Groups 3, the lowest particulate): adjusted Group 2 mean 44.8 ppb (95% confidence interval (CI) 33.8-55.9) vs. Group 1 24.6 ppb (95% 20.5-28.7) and Group 3, 24.3 ppb (95% CI 17.7-30.9). Secondhand smoking and height were not associated with FeNO.

CONCLUSION

In a metalworking industrial cohort, welders/assemblers manifested significantly higher levels of FeNO. This may reflect respiratory tract inflammation associated with airborne exposures specific to this group.

Importance of type and degree of IgE sensitisation for defining fractional exhaled nitric oxide reference values

BACKGROUND

Fractional exhaled nitric oxide (FE_NO) is a marker of type 2 airway inflammation used in clinical practice in asthma. However, reference values are needed to broaden the clinical use of FE_NO and this is within the scope of a newly started Global Lung Function Initiative task force. We aim to study FE_NO levels with special emphasis on the upper limit of normal (ULN) in relation to the type and degree of IgE sensitisation.

METHODS

FE_NO was measured in 1855 non-smoking, respiratory healthy subjects from the Swedish CArdioPulmonary bioImage Study (SCAPIS). Atopic subjects (n = 424), defined as being IgE-sensitised to aeroallergens (ImmunoCAP Phadiatop™, ≥0.35 PAU/l) were compared to non-atopic subjects (<0.35 PAU/l, n = 1431). Atopic subjects were further characterised according to their grade of IgE sensitisation (IgE antibody tertiles: (T1<1.16, T2 1.16-3.72 and T3 >3.72 PAU/l) and sensitisation to perennial (cat or mite) or seasonal (birch) allergens.

RESULTS

Subjects IgE-sensitised to cat or mite had higher FE_NO compared to non-atopic subjects (FE_NO (ppb): median 20.0 vs. 15.0, and ULN 50.4 vs. 33.0, p < 0.001). This was seen to a lesser extent for subjects IgE-sensitised to birch only (median 18.0 vs. 15.0, and ULN 38.0 vs. 33.0, p = 0.048). Atopic subjects with a high degree of IgE sensitisation (Phadiatop: >3.72 PAU/l) had the highest FE_NO compared to non-atopic subjects (median 20.0 vs. 15.0, and ULN 56.0 vs. 33.0, p < 0.001).

CONCLUSIONS

The type and degree of IgE sensitisation should be considered in generating FE_NO reference values.

Ambient air pollution is associated with airway inflammation in older women: a nested cross-sectional analysis

Background

Air pollution is a risk factor for chronic obstructive pulmonary disease (COPD). Fraction of exhaled nitric oxide (FeNO) could be a useful biomarker for health effects of air pollutants. However, there were limited data from older populations with higher prevalence of COPD and other inflammatory conditions.

Methods

We obtained data from the German Study on the influence of Air pollution on Lung function, Inflammation and Ageing. Spirometry and FeNO were measured by standard techniques. Air pollutant exposures were estimated following the European Study of Cohorts for Air Pollution Effects protocols, and ozone (O₃) measured at the closest ground level monitoring station. Multiple linear regression models were fitted to FeNO with each pollutant separately and adjusted for potential confounders.

Results

In 236 women (mean age 74.6 years), geometric mean FeNO was 15.2ppb. Almost a third (n=71, 30.1%) of the women had some chronic inflammatory respiratory condition. A higher FeNO concentration was associated with exposures to fine particles (PM_2.5), PM_{2.5absorbance} and respirable particles (PM₁₀). There were no significant associations with PM_coarse, NO₂, NO_x, O₃ or length of major roads within a 1 km buffer. Restricting the analysis to participants with a chronic inflammatory respiratory condition, with or without impaired lung function produced similar findings. Adjusting for diabetes did not materially alter the findings. There were no significant interactions between individual pollutants and asthma or current smoking.

Conclusions

This study adds to the evidence to reduce ambient PM_2.5 concentrations as low as possible to protect the health of the general population.

Ratio-Adjustable Upconversion Luminescence Nanoprobe for Ultrasensitive In Vitro Diagnostics

The development of precise medicine requires diagnostic probes to simultaneously satisfy an excellent detection limit and a wide linear analysis range because of enormous individual-discrepancy of disease biomarker concentrations, yet it remains challenging. Herein, an upconverison nanoprobe with a luminescence ratio flexibly tailored was designed for ultrasensitive monitoring exhaled nitric oxide to indicate the clinical course of asthma. Two independent emissions from the same nanoprobe can be discretionarily modulated to vary their intensity ratios for adapting different analysis requirements. Delightfully, this novel nanoprobe demonstrated a 100-fold lower detection limit compared with the traditional ratiometric fluorescence manner and a more broad linear detection range from the subpart per billion (ppb) level to hundreds of ppb. This ratio-adjustable fluorescence detection strategy holds great potential for miscellaneous disease diagnosis applications.

Systemic and breath biomarkers for asthma: an update

PURPOSE OF REVIEW

Finding suitable biomarkers to phenotype asthma, identify individuals at risk of worsening and guide treatment is highly prioritized in asthma research. We aimed to provide an analysis of currently used and upcoming biomarkers, focusing on developments published in the past 2 years.

RECENT FINDINGS

Type 2 inflammation is the most studied asthma mechanism with the most biomarkers in the pipeline. Blood eosinophils and fractional exhaled nitric oxide (FeNO) are those most used clinically. Recent developments include their ability to identify individuals at higher risk of exacerbations, faster decline in lung function and more likely to benefit from anti-IL-5 and anti-IL-4/-13 treatment. Certain patterns of urinary eicosanoid excretion also relate to type 2 inflammation. Results of recent trials investigating the use of serum periostin or dipeptidyl peptidase-4 to guide anti-IL-13 therapy were somewhat disappointing. Less is known about non-type 2 inflammation but blood neutrophils and YKL-40 may be higher in patients with evidence of non-type 2 asthma. Volatile organic compounds show promise in their ability to distinguish both eosinophilic and neutrophilic asthma.

SUMMARY

The ultimate panel of biomarkers for identification of activated inflammatory pathways and treatment strategies in asthma patients still lies in the future, particularly for non-type 2 asthma, but potential candidates are available.

The coexistence of asthma and COPD: risk factors, clinical history and lung function trajectories

RATIONALE

Patients with concomitant features of asthma and chronic obstructive pulmonary disease (COPD) have a heavy disease burden.

OBJECTIVES

Using data collected prospectively in the European Community Respiratory Health Survey, we compared the risk factors, clinical history, and lung function trajectories from early adulthood to the late sixties of middle aged subjects having asthma+COPD (n=179), past (n=263) or current (n=808) asthma alone, COPD alone (n=111), or none of these (n=3477).

METHODS

Interview data and prebronchodilator FEV₁ and FVC were obtained during three clinical examinations in 1991-1993, 1999-2002, and 2010-2013. Disease status was classified in 2010-2013, when the subjects were aged 40-68, according to the presence of fixed airflow obstruction (postbronchodilator FEV₁/FVC below the lower limit of normal), a lifetime history of asthma, and cumulative exposure to tobacco or occupational inhalants. Previous lung function trajectories, clinical characteristics, and risk factors of these phenotypes were estimated.

MAIN RESULTS

Subjects with asthma+COPD reported maternal smoking (28.2%) and respiratory infections in childhood (19.1%) more frequently than subjects with COPD alone (20.9 and 14.0%, respectively). Subjects with asthma+COPD had an impairment of lung function at age 20 that tracked over adulthood, and more than half of them had asthma onset in childhood. Subjects with COPD alone had the highest lifelong exposure to tobacco smoking and occupational inhalants, and they showed accelerated lung function decline during adult life.

CONCLUSIONS

The coexistence between asthma and COPD seems to have its origins earlier in life compared to COPD alone. These findings suggest that prevention of this severe condition, which is typical at older ages, should start in childhood.

Fractional exhaled nitric oxide as a determinant for the clinical course of asthma: a systematic review

Background: Precision medicine means linking the right patient to the right management strategy including best possible pharmacological therapy, considering the individual variability of the disease characteristics, type of inflammation, genes, environment, and lifestyle. For heterogenous diseases such as asthma, reliable biomarkers are needed to facilitate the best possible disease control and reduce the risk of side effects. The present review examines fractional exhaled nitric oxide (FeNO) as a guide for the management strategy of asthma and predictor of its clinical course.

Method: The literature included was identified by searching the PubMed database using specific key words and MeSH terms. Studies were not excluded based on their design alone. The search resulted in 212 hits, of which 35 articles were included in this review.

Results: Several studies support a potential role for high FeNO levels as a prognostic biomarker for accelerated lung function decline in adults with newly diagnosed asthma. Furthermore, studies report an association between high FeNO levels and excess decline in FEV₁ in adults with long-standing moderate to severe asthma despite optimised therapy, whereas the findings for patients with less severe disease are conflicting. Applying a FeNO-based management algorithm reduces the exacerbation rate in adults with asthma. Similar observations are seen in children, though based on fewer studies. The available studies provide evidence that the level of FeNO may be useful as a predictor of subsequent loss of asthma control in adults, though the evidence is somewhat conflicting in children and young adults.

Conclusion: The present review provides evidence of the prognostic value of FeNO as a surrogate biomarker for type 2 inflammation in the airways. FeNO is likely to emerge as an important biomarker in monitoring and tailoring modern asthma treatment, either alone or in combination with other biomarkers.

Novel non-invasive particles in exhaled air method to explore the lining fluid of small airways-a European population-based cohort study

INTRODUCTION

Respiratory tract lining fluid of small airways mainly consists of surfactant that can be investigated by collection of the particles of exhaled aerosol (PExA) method. This offers an exciting prospect to monitor small airway pathology, including subjects with asthma and smokers.

AIM

To explore the influence of anthropometric factors and gender on phospholipids, surfactant protein A (SP-A) and albumin of the lining fluid of small airwaysand to examine the association with asthma and smoking. Furthermore, to examine if the surfactant components can predict lung function in terms of spirometry variables.

METHOD

This study employs the population-based cohort of the European Community Respiratory Health Survey III, including participants from Gothenburg city, Sweden (n=200). The PExA method enabled quantitative description and analytical analysis of phospholipids, SP-A and albumin of the lining fluid of small airways.

RESULTS

Age was a significant predictor of the phospholipids. The components PC14:0/16:0, PC16:0/18:2 (PC, phosphatidylcholine) and SP-A were higher among subjects with asthma, whereas albumin was lower. Among smokers, there were higher levels particularly of di-palmitoyl-di-phosphatidyl-choline compared with non-smokers. Most phospholipids significantly predicted the spirometry variables.

CONCLUSION

This non-invasive PExA method appears to have great potential to explore the role of lipids and proteins of surfactant in respiratory disease.

Developments allergy in 2019 through the eyes of Clinical and Experimental Allergy, Part II clinical allergy

In the second of two linked articles, we describe the development in clinical as described by Clinical & Experimental Allergy and other journals in 2019. Epidemiology, clinical allergy, asthma and rhinitis are all covered. In this article, we described the development in the field of allergy as described by Clinical and Experimental Allergy in 2019. Epidemiology, clinical allergy, asthma and rhinitis are all covered.

Cavity ringdown spectroscopy of nitric oxide in the ultraviolet region for human breath test

We report the spectrum of nitric oxide (NO) in the ultraviolet (UV) (225.4-227.0 nm) region based on cavity ringdown spectroscopy (CRDS). A cavity ringdown system, which consisted of a tunable UV laser source and a vacuum-pumped ringdown cavity, was constructed to measure NO at room temperature and atmospheric or reduced pressure. The measured spectra were validated using LIFBase simulations. The absorption cross-section of NO at the strongest absorption peak at 226.255 nm was measured to be 7.64 × 10^-18 cm² molecule^-1. Using the measured mirror reflectivity of 99.55% at 226.255 nm, the detection limit of NO was determined to be 7.4 ppb (parts per billion) based on the standard 3-σ criteria. The stability and reproducibility of this CRDS system were also tested. Furthermore, exhaled gas samples from 203 human subjects (105 healthy people and 98 lung cancer patients) were measured using the system. Results demonstrated that the cavity ringdown spectroscopy in the deep-UV region has potential for breath NO test.

Formaldehyde, Oxidative Stress, and FeNO in Traffic Police Officers Working in Two Cities of Northern Italy

Personal air formaldehyde (air-FA) was measured as risk factor of airways inflammation and oxidative stress (SO) induction. Overall, 154 police officers were enrolled from two differently urbanised Italian cities, Turin and Pavia. Urinary F2t-isoprostane (15-F2t-IsoP), a prostaglandin-like compound, was quantified as a biomarker of general OS in vivo and fractional exhaled nitric oxide (FeNO) was measured for monitoring local inflammatory processes. Urinary cotinine was quantified as a biomarker of tobacco smoking exposure. Traffic police officers living in Turin showed an increased level of log air-FA (p < 0.001), equal to +53.6% (p < 0.001). Log air-(FA) mean values were 3.38 (C.I. 95% 3.33–3.43) and 2.84 (C.I. 95% 2.77–2.92) in Turin and Pavia, respectively. Log (air-FA) was higher in “outdoor workers” (3.18, C.I. 95% 3.13–3.24, p = 0.035) compared to “indoor workers”, showing an increase of +9.3%, even controlling for sex and city. The analyses on 15-F2t-IsoP and FeNO, both adjusted for log air-FA, highlighted that OS and inflammation were higher (+66.8%, p < 0.001 and +75%, p < 0.001, respectively) in Turin traffic police officers compared to those from Pavia. Our findings suggest that even low exposures to traffic-related emissions and urbanisation may influence both general oxidative stress levels and local inflammation.