Increased Nitrosothiols in Exhaled Breath Condensate in Inflammatory Airway Diseases

Nitrosothiols (RS-NOs) are formed by interaction of nitric oxide (NO) with glutathione and may limit the detrimental effect of NO. Because NO generation is increased in airway inflammation, we have measured RS-NOs in exhaled breath condensate in patients with asthma, cystic fibrosis, or chronic obstructive pulmonary disease (COPD). We also measured exhaled NO and nitrite (NO2 −) in the same subjects. RS-NOs were detectable in exhaled breath condensate of all subjects. RS-NOs were higher in subjects with severe asthma (0.81 ± 0.06 μ M) when compared with normal control subjects (0.11 ± 0.02 μ M, p < 0.01) and with subjects with mild asthma (0.08 ± 0.01 μ M, p < 0.01). Elevated RS-NOs values were also found in patients with cystic fibrosis (0.35 ± 0.07 μ M, p < 0.01), in those with COPD (0.24 ± 0.04 μ M, p < 0.01) and in smokers (0.46 ± 0.09 μ M, p < 0.01). In current smokers there was a correlation (r = 0.8, p < 0.05) between RS-NOs values and smoking history (pack/year). We also found elevated concentrations of NO2 − in patients with severe asthma, cystic fibrosis, or COPD, but not in smokers or patients with mild asthma. This suggests that exhaled NO2 − is less sensitive than exhaled RS-NOs. This study has shown that RS-NOs are detectable in exhaled breath condensate of healthy subjects and are increased in patients with inflammatory airway diseases. As RS-NOs concentrations in exhaled breath condensate vary in the different airway diseases and increase with the severity of asthma, their measurement may have clinical relevance as a noninvasive biomarker of nitrosative stress.