Hélène Huyvaert

Associations between Nitric Oxide Synthase Genes and Exhaled NO-Related Phenotypes according to Asthma Status

Background The nitric oxide (NO) pathway is involved in asthma, and eosinophils participate in the regulation of the NO pool in pulmonary tissues. We investigated associations between single nucleotide polymorphisms (SNPs) of NO synthase genes (NOS) and biological NO-related phenotypes measured in two compartments (exhaled breath condensate and plasma) and blood eosinophil counts. Methodology SNPs (N = 121) belonging to NOS1, NOS2 and NOS3 genes were genotyped in 1277 adults from the French Epidemiological study on the Genetics and Environment of Asthma (EGEA). Association analyses were conducted on four quantitative phenotypes: the exhaled fraction of NO (Fe NO), plasma and exhaled breath condensate (EBC) nitrite-nitrate levels (NO2–NO3) and blood eosinophils in asthmatics and non-asthmatics separately. Genetic heterogeneity of these phenotypes between asthmatics and non-asthmatics was also investigated. Principal Findings In non-asthmatics, after correction for multiple comparisons, we found significant associations of FeNO levels with three SNPs in NOS3 and NOS2 (P≤0.002), and of EBC NO2–NO3 level with NOS2 (P = 0.002). In asthmatics, a single significant association was detected between Fe NO levels and one SNP in NOS3 (P = 0.004). Moreover, there was significant heterogeneity of NOS3 SNP effect on FeNO between asthmatics and non-asthmatics (P = 0.0002 to 0.005). No significant association was found between any SNP and NO2–NO3 plasma levels or blood eosinophil counts. Conclusions Variants in NO synthase genes influence FeNO and EBC NO2–NO3 levels in adults. These genetic determinants differ according to asthma status. Significant associations were only detected for exhaled phenotypes, highlighting the critical relevance to have access to specific phenotypes measured in relevant biological fluid.

Exhaled nitric oxide, nitrite/nitrate levels, allergy, rhinitis and asthma in the EGEA study

Although interest in biomarkers in the nitrate–nitrite–NO pathway has recently increased, associations between nitrite (NO2−) and nitrate (NO3−), and asthma, allergic sensitisation and rhinitis remain unclear. The study aimed to evaluate the associations between NO2−/NO3− and exhaled fraction of nitric oxide (FeNO) levels with asthma, allergic sensitisation and rhinitis. Plasma and exhaled breath condensate (EBC) NO2−/NO3− and FeNO levels were measured in 523 adults of the French Epidemiological study on Genetics and Environment of Asthma. Allergic sensitisation was defined by a positive skin prick test for at least one aeroallergen. Subjects were classified as non-sensitised, sensitised and as having allergic rhinitis. Plasma NO2−/NO3− level was unrelated to any disease phenotypes. EBC NO2−/NO3− level was unrelated to any asthma phenotypes. EBC NO2−/NO3− and FeNO levels were correlated in sensitised subjects only (r=0.21±0.10, p=0.01). EBC NO2−/NO3− and FeNO levels were higher in sensitised than in non-sensitised subjects (adjusted geometric mean (95% CI): 2.36 (1.96–2.84) versus 1.72 (1.38–2.14) &mgr;mol per mg proteins, p=0.008; and 18.3 (16.7–20.0) versus 14.8 (13.3–16.5) ppb, p=0.0006, respectively), with gradual relationships from sensitised subjects to those with allergic rhinitis (p<0.0001). Results suggest that EBC NO2−/NO3− and FeNO levels may be considered as biological markers of intensity of allergic sensitisation and rhinitis. The EGEA study: exhaled nitrate/nitrite/NO levels may be considered markers for intensity of allergy and rhinitis http://ow.ly/uKbxh

Plasma and exhaled breath condensate nitrite–nitrate level in relation to environmental exposures in adults in the EGEA study

This study evaluated the associations between biological markers in the nitrate-nitrite-NO pathway and four environmental exposures among subjects examined in the second survey (2003-2007) of the French Epidemiological study on Genetics and Environment of Asthma (EGEA). Total nitrite and nitrate (NO(2)(-) /NO(3)(-)) levels were measured both in plasma and in exhaled breath condensate (EBC) in 949 adults. Smoking, diet and exposure to chlorine products were assessed using standardized questionnaires. Exposure to air pollutants was estimated by using geostatistical models. All estimates were obtained with generalized estimating equations for linear regression models. Median levels of NO(2)(-)/NO(3)(-) were 36.3 μM (1st-3rd quartile: 25.7, 51.1) in plasma and 2.0 μmol/mg proteins (1st-3rd quartile 0.9, 3.9) in EBC. After adjustment for asthma, age, sex and menopausal status, plasma NO(2)(-)/NO(3)(-) level increased with leafy vegetable consumption (above versus below median=0.04 (95%CI: 0.001, 0.07)) and decreased in smokers (versus non/ex-smokers=-0.08 (95%CI: -0.11, -0.04). EBC NO(2)(-)/NO(3)(-) level decreased in smokers (-0.08 (95%CI: -0.16, -0.001)) and with exposure to ambient O(3) concentration (above versus below median=-0.10 (95%CI: -0.17, -0.03)). Cured meat, chlorine products, PM(10) and NO(2) concentrations were not associated with NO(2)(-)/NO(3)(-) levels. Results suggest that potential modifiable environmental and behavioral risk factors may modify NO(2)(-)/NO(3)(-) levels in plasma and EBC according to the route of exposure.

Occupational exposures and fluorescent oxidation products in 723 adults of the EGEA study

Occupational asthma can be induced by a variety of agents, including high and low molecular weight sensitisers, and respiratory irritants [1]. The role of exposure to cleaning products and disinfectants in work-related asthma is increasingly recognised, although the specific substances that increase asthma risk are not well identified [2]. Some of the numerous agents contained in these products are chemical sensitisers, but most are hypothesised to act as respiratory irritants [2]. While high molecular weight sensitisers are known to cause occupational asthma through a typical allergic response, the pathophysiological mechanisms involved in occupational asthma induced by low molecular weight (LMW) chemicals, and in irritant-induced asthma, remain poorly understood [1, 3, 4]. Associations between occupational exposures to asthmogenic chemicals and irritants and oxidative stress were found http://ow.ly/K6RSt

Usefulness of a new dialysis device adapted to small volume of red blood cells and its interest in epidemiology

OBJECTIVES We checked the efficiency of a new dialysis device adapted to small volumes to remove glycerol from cryopreserved red blood cells. DESIGN AND METHODS Dialysis was performed on D-Tube96™ Dialyzer Mini device. In a preliminary trial, we measured the residual glycerol before, and 2, 4 and 24 h after dialysis. Glycerol and hemoglobin concentrations and antioxidant enzymes activities were measured in three samples with or without glycerolization/deglycerolization procedure. The mini dialysis was then applied to 96 samples from the French Epidemiological study on the Genetics and Environment of Asthma. RESULTS Ninety-two percent of glycerol was removed after 24 h of dialysis. Hemoglobin content and activities of superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase were recovered. No significant loss of volume was observed. Results obtained for the 96 samples perfectly fitted with reference values of our laboratory. CONCLUSION This new dialysis method seems to be particularly adapted for processing a large number of samples of RBCs cryoconserved in small volumes from epidemiological studies.

Oxidative stress biomarkers and asthma characteristics in adults of the EGEA study

Asthma is an oxidative stress related disease, but associations with asthma outcomes are poorly studied in adults. We aimed to study the associations between several biomarkers related to oxidative stress and various asthma outcomes. Cross-sectional analyses were conducted in 1388 adults (mean age 43 years, 44% with asthma) from the Epidemiological Study of the Genetics and Environment of Asthma (EGEA2). Three blood antioxidant enzyme activities (biomarkers of response to oxidative stress) and exhaled breath condensate 8-isoprostanes and plasma fluorescent oxidation products (FlOPs) levels (two biomarkers of damage) were measured. Associations between biomarkers and 1) ever asthma and 2) asthma attacks, asthma control and lung function in participants with asthma were evaluated using regression models adjusted for age, sex and smoking. Biomarkers of response were unrelated to asthma outcomes. Higher 8-isoprostane levels were significantly associated with ever asthma (odds ratio for one interquartile range increase 1.28 (95% CI 1.06–1.67). Among participants with asthma, 8-isoprostane levels were negatively associated with adult-onset asthma (0.63, 0.41–0.97) and FlOPs levels were positively associated with asthma attacks (1.33, 1.07–1.65), poor asthma control (1.30, 1.02–1.66) and poor lung function (1.34, 1.04–1.74). Our results suggest that 8-isoprostanes are involved in childhood-onset asthma and FlOPs are linked to asthma expression. Oxidative stress-related damage seems to be involved in asthma expression and control http://ow.ly/VSxG30fGNuz