Nadif, R; Decoster, B; Huyvaert, H; Briand, G; Le Moual, N; Pin, I; Siroux, V; Varraso, R; Kauffmann, F; Zerimech, F; Matran, R
Rationale - Exhaled Breath Condensate (EBC) is a way of collecting biomarkers of lung disease which may provide valuable information in the understanding of airway inflammation pathways. Regarding asthma and the nitrosative pathway, objectives were to study 1) correlations between nitrite-nitrate (NO2-NO3) levels in plasma and EBC, and 2) their associations with age, sex and smoking, which was never done in large epidemiological study.
Methods – EBC was collected according to standardized method using RTube™. In plasma and EBC, total NO2-NO3 (converted nitrate plus nitrite) was measured by using the Griess reaction. Four markers were considered: NO2-NO3 level, and NO2-NO3 level related to protein concentration (ratios) both in plasma and EBC. Measurements with coefficient of variation>15% were excluded from the analyses (n=246). Participants reporting to have ever had attacks of shortness of breath at rest with wheezing in the chest or asthma attacks, and to have respiratory symptoms in the past 12 months or to have used inhaled and/or oral medicines in the previous 12 months because of breathing problems, were defined as current asthmatics. Association analyses were performed in 1159 adults (43 years, 589 women, 38.7% with current asthma) from the French Epidemiological study on the Genetics and Environment of Asthma.
Results – NO2-NO3 geometric mean (95% CI) was 35.5 µM (11.0–115) in plasma and 5.31 µM (0.76–37) in EBC. Ratio was 0.46 µmol/g (0.15–1.44) in plasma and 1.84 µmol/µg (0.17–19.8) in EBC. Plasma NO2-NO3 and ratio were positively associated with age (both r=0.11, P <0.0001), with highest means in subjects older than 45 yrs: 38.0 vs. 32.3 µM, P<0.0001 for NO2-NO3, and 0.51 vs. 0.43 µmol/g, P<0.0001 for ratio, and whatever the asthma status. Regarding smoking, lower plasma NO2-NO3 (31.0 vs. 36.3 µM, P<0.0001) and ratio (0.40 vs. 0.49 µmol/g, P<0.0001), and EBC NO2-NO3 (1.59 vs. 1.93 µmol/µg, P=0.04) were observed in smokers than in ex-/non-smokers. Stratification according to asthma status showed similar results in plasma, whereas EBC NO2-NO3 was associated with smoking only in asthmatics (1.44 vs. 1.99 µmol/µg, P=0.04). EBC and plasma NO2-NO3 were correlated in all subjects (r=0.10, P=0.001), and whatever the asthma status. No association of markers with sex was found. Multivariate analyses taking into account familial resemblance of the subjects and potential confounders (sex, center) did not change any of the associations.
Conclusion – Nitrite-nitrate in plasma and EBC were correlated and were both found to decrease with smoking, suggesting possible common underlying mechanisms.
