Myeloperoxidase of bronchial leucocytes as a biomarker of osmotic bronchial hyperresponsiveness in asthmatics

Introduction: Cell inflammation at asthma plays a key role in the formation of airway hyperresponsiveness. It has not been studied yet whether the activity of myeloperoxidase (MPO) of bronchial leucocytes influences the formation of osmotic airway hyperresponsiveness. Aim: To study the correlation between the airway response to ultrasonically nebulized distilled water (UNDW) and activity of leucocytes MPO in the induced sputum (IS) of asthma patients. Methods: The lung function (FEV1) and the airway response (ΔFEV1) to 3-minute UNDW inhalation were assessed in 33 patients. The activity of leucocytes MPO was identified in cytological smear of IS by the method of Graham-Knoll, the optical density of MPO was measured by summed for eosinophilic and neutrophilic leucocytes mean cytochemical coefficient (MCC) in pixels. Results: The patients were divided into 2 groups according to the response to UNDW: the 1st group with the positive airway response (n=15) and the 2nd group without it (n=18) (mean ΔFEV1 was -18.8±3.5 vs. -1.89±0.97%, respectively; p<0.001). In the 1st group there was a lower level of MPO MCC: 67.7±4.29 vs. 110.0±10.0 in the 2nd group (p<0.001). Close correlation between the level of MPO MCC and ΔFEV1 (r=0.43; p<0.05) was found out. Low cytoplasmatic content of MPO at osmotic hyperresponsiveness proves the high degree of mobilization of enzyme saturated granules in the processes of leucocytes granulation and exocytosis of the granule contents into the extracellular media. Conclusion: The activity of bronchial leucocytes MPO in asthmatics is a biomarker of airway hyperresponsiveness to osmotic stimulus. Supported by the Russian Science Foundation (14-25-00019).