Quantitative assessment of protein-bound tyrosine nitration in airway secretions from patients with inflammatory airway disease.

Because reactive nitrogen species (RNS) have potent inflammatory activity, they may be involved in the inflammatory process in pulmonary diseases. We recently reported increased numbers of 3-nitrotyrosine immunopositive cells, which are evidences of RNS production, in the sputum of patients with chronic obstructive pulmonary disease (COPD) and patients with asthma compared with healthy subjects. In the present study, we attempted to quantify this protein nitration in the airways by means of high-performance liquid chromatography (HPLC) used together with an electrochemical detection system that we developed. Sputum samples were obtained from 15 stable COPD patients, 9 asthmatic patients and 7 healthy subjects by using hypertonic saline inhalation. The values for the molar ratio of protein-bound 3-nitrotyrosine/tyrosine in patients with asthma (4.31±1.13 × 10-6, p<0.05) and patients with COPD (3.04±0.36 × 10-6, p<0.01) were significantly higher than those in healthy subjects (1.37±0.19 × 10-6). The levels ...