Correlation between expressions of myeloperoxidase and eosinophil cationic protein in sputum and clinical features of asthma-chronic obstructive pulmonary disease overlap

Abstract

To observe the role of myeloperoxidase(MPO)and eosinophilic cationic protein(ECP)in the airway inflammation and their correlation with clinical feature in asthma-COPD overlap (ACO) patients. Twenty patients with COPD, 20 with asthma, 20 with ACO and 20 control subjects underwent pulmonary function test for measurement of forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), peak expiratory flow (PEF), and maximum midexpiratory flow (MMF25/75). COPD assessment test (CAT) was used to evaluate the clinical symptoms of the patients with COPD and ACO. The asthma control test (ACT) was used to evaluate the asthma control in the patients with asthma and ACO. Induced sputum samples were collected from the subjects for analysis of neutrophil and eosinophil ratios, and enzyme-linked immunosorbent assay was used to determine the expression levels of MPO and ECP in the sputum. No significant difference was observed in the CAT scores between ACO group and COPD group (P> 0.05). Compared with the asthma group, the patients with ACO had significantly lower ACT scores and lower FEV1, PEF and MMF25/75 (P < 0.05). The patients with ACO had significantly higher FVC and sputum eosinophil ratio than those with COPD (P < 0.05), and a higher sputum neutrophil ratio than those with asthma (P < 0.01). In ACO group, the MPO level in sputum was significantly higher than that in the asthma group (P < 0.05), while sputum ECP level was significantly higher than that in both the asthma group and COPD group (P < 0.05 or 0.01). In ACO group, sputum MPO level was positively correlated with sputum neutrophil ratio (r=0.8358, P < 0.01) but was not correlated with CAT score or FEV1 (P> 0.05); sputum ECP level was positively correlated with sputum eosinophil ratio (r=0.4666, P < 0.05) and was inversely correlated with ACT score (r=-0.4966, P < 0.05) and FEV1 (r=-0.4610, P < 0.05). Both neutrophilic and eosinophilic inflammations occur in the airway of patients with ACO, and their sputum ECP level is negatively correlated with asthma control and obstructive airflow limitation.