Airway neutrophils and myeloperoxidase in asthma patients with cold-induced bronchoconstriction

Introduction. The role of neutrophil inflammation of the bronchi in patients with asthma in the devel­opment and manifestation of cold airway hyperresponsiveness (CAHR) has not been sufficiently studied.Aim. To assess the level of neutrophils and the activity of myeloperoxidase (MPO) in the bronchi of asthma patients with cold-induced bronchospasm.Materials and methods. In 138 patients with mild-to-moderate asthma with CAHR, the level of asthma control (ACT), lung function (FEV1), cellular composition of sputum was examined before and after the bronchoprovo­cation test by isocapnic hyperventilation with cold air (IHCA). In sputum samples, the percentage of neutrophils, eosino­phils, and bronchial epithelial cells (structurally intact cylindrical ciliated and goblet cells) was assessed; the concentration and activity of MPO in neutrophils were studied by the cytochemical method.Results. The patients were divided into three groups: group 1 (n=94) - patients with mild cold-induced bronchospasm, group 2 (n=28) - with moderate broncho­spasm, group 3 (n=16) - with severe bronchospasm (AFEV1=- 13.5±0.3, -24.6±0.5, -36.9±1.5%, respectively). Patients did not differ in the level of asthma control (16 [12; 21]; 16 [13; 20] and 16 [12; 21] ACT points, respectively). Patients of the third group had lower values of bronchial patency in comparison with the first and second groups: FEV1 79.4±3.2; 92.4±1.7 (p<0.01); 92.1±2.9% and FEF25-75 46.4±4.3; 66.1±2.5 (p<0.001); 63.2±4.0% (p<0.01). In sputum after the IHCA test in groups 2 and 3, an increase in the number of neutrophils was recorded from 35.5±3.9 to 46.0±3.8% (p<0.05) and from 39.0±3.8 to 52, 4±4.4% (p<0.05), respectively, while the number of neutrophils in group 1 did not change (43.2±2.4 and 44.3±2.1%). The concentration of MPO in response to the IHCA test in all groups significantly increased by more than 30% (p<0.05).Conclusion. The mobilization of neutrophils in a mixed pattern of airway inflammation in asthma pa­tients is associated with worsening of cold-induced bronchospasm. An increase in the content of MPO in neutrophil gran­ules in response to the action of cold air is aimed at enhancing the secretion of the enzyme in the interstitium, activating its oxidative activity in the respiratory tract, and escalating the oxidative/halogenating stress that accompanies broncho­spasm.