Influence of coexistence of mild OSA on airway mucus hypersecretion in patients with COPD

The coexistence of chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA) can cause multiple system damage, and the main physiological mechanisms are continuous hypoxia and intermittent hypoxia (IH). Airway mucus hypersecretion is an important clinical feature of COPD, which can cause a progressive decline of lung function, acute COPD aggravation, and disease progression. The purpose of our study is to determine the influence of the coexistence of mild OSA on airway mucus hypersecretion. Clinical data and airway epithelial samples of 36 subjects were collected. The average fluorescence intensity of MUC5AC and the number of goblet cells were measured through immunofluorescence staining. MUC5AC expression was measured in human bronchial epithelial (HBE) cells exposed to normoxia, IH, particulate matter (PM), and PM + IH using real-time quantitative polymerase chain reaction and western blotting. FEV₁% pred and FEV₁/FVC were higher in patients with COPD-OSA overlap syndrome (OS) than in patients with COPD alone. Patients with OS had less sputum volume than patients with COPD alone. MUC5AC expression and the number of goblet cells in the airway epithelium in the COPD alone group were significantly higher than those in the OS groups. The PM + IH group had lower MUC5AC mRNA and protein expression in HBE cells than the PM group. The coexistence of mild OSA may reduce goblet cell proliferation and MUC5AC expression in the airway epithelium of patients with COPD. Mild IH inhibited PM-induced up-regulation of MUC5AC expression in the mRNA and protein levels in HBE cells.