Effect of cigarette smoke exposure on airway epithelial barrier function in never-smokers and ex-smokers with and without COPD

Abstract

<b>Objective:</b> To assess effects of cigarette smoke extract (CSE) on airway epithelial barrier function and anti-oxidant genes in healthy never-smokers, healthy ex-smokers and ex-smoker with COPD of different severity. <b>Methods:</b> Primary bronchial epithelial cells (PBECs) were obtained from bronchial brushings of 7 never- and 7 ex-smokers with normal lung function, 8 mild-moderate and 5 severe COPD patients and treated with/without 10% CSE for 24 hours. Electric cell-surface impedance sensing (ECIS) was used to measure barrier function. qPCR was performed to assess the expression of epithelial barrier and oxidative stress response genes. <b>Results:</b> We observed significantly lower epithelial resistance in PBECs from ex-smokers compared to never-smokers (p&lt;0.01), which was further reduced in PBECs from severe COPD patients (p&lt;0.05). CSE exposure significantly reduced (p&lt;0.001) epithelial resistance in all groups, from which PBECs of never-smokers but not ex-smokers recovered within 24 hours. PBECs from ex-smokers had higher mRNA expression of CDH1, ZO-1 and CLDN7 genes compared to never-smokers, which were significantly upregulated by CSE only in PBECs from never-smokers. Furthermore, we observed higher mRNA expression of catalase and SOD1, 2, and 3 in ex-smokers compared to never-smokers at baseline, which increased upon CSE treatment only in PBECs from controls. <b>Conclusions:</b> Our results show that acute smoke exposure reduces airway epithelial barrier function and that epithelial barrier function is also lower in individuals with long-term smoking history, with a further decline with increasing severity of COPD which is accompanied by an impaired redox mechanism.