Loss of E-Cadherin Alters Cigarette Smoke Extract (CSE)-Induced Damage and Repair Responses in Human Airway Epithelial Cells; Implications for Chronic Obstructive Pulmonary Disease (COPD).

Abstract

COPD is characterized by airway epithelial barrier dysfunction. We hypothesized that downregulation of E-cadherin results in abnormal responses to cigarette smoke extract (CSE) with impaired repair and increased pro-inflammatory activity. We used CRISPR-Cas9-engineered 16HBE cells with 1-2 copies of the CDH1 gene encoding E-cadherin (CDH1^+/+ or CDH1^+/-) to study effects on tight junctional protein zonula occludens (ZO-1), CSE-induced epithelial barrier dysfunction using electric cell-substrate impedance sensing and pro-inflammatory cytokine production. In airway epithelial cells (AECs) from nine COPD stage IV transplant lungs and tracheobronchial tissue of nine non-COPD donors, we assessed E-cadherin, ZO-1 and pro-inflammatory cytokines. Lower electrical resistance in CDH1^+/- 16HBE cells was accompanied by ZO-1 delocalization. CSE exposure induced transient barrier dysfunction, from which CDH1^+/- cells recovered more slowly than CDH1+/+ cells. Similarly, CDH1^+/- cells showed a delayed repair response upon wounding, while gene expression and secretion of pro-inflammatory cytokines were higher in unexposed cells (CXCL8, IL-1α) and/or showed a stronger CSE-induced increase (IL-1α, GM-CSF). AECs from COPD patients displayed lower E-cadherin and TJP1 levels and higher CSE-induced IL1A expression compared to control. Downregulation of E-cadherin resulted in disrupted ZO-1 expression, aggravated CSE-induced barrier dysfunction, impaired recovery from injury and a more pro-inflammatory epithelial phenotype in 16HBE cells.