Cigarette Smoke Activates NOTCH3 to Promote Goblet Cell Differentiation in Human Airway Epithelial Cells
Chronic obstructive pulmonary disease (COPD) is the 3rd leading cause of death in the United States and is caused primarily by cigarette smoking. Increased numbers of mucus-producing secretory (“goblet”) cells defined as goblet cell metaplasia or hyperplasia (GCMH), contributes significantly to COPD pathophysiology. The objective of this study was to determine whether NOTCH signaling regulates goblet cell differentiation in response to cigarette smoke. To this end, primary human bronchial epithelial cells (HBECs) from nonsmokers and COPD smokers were differentiated in vitro on air-liquid interface and exposed to cigarette smoke extract (CSE) for 7 days. NOTCH signaling activity was modulated using (1) the NOTCH/?-secretase inhibitor Dibenzazepine (DBZ), (2) lentiviral over-expression of the NOTCH3-intracellular domain (NICD3) or (3) NOTCH3-specific siRNA. Cell differentiation and response to CSE were evaluated by qPCR, Western blotting, immunostaining and RNA-Seq. Our data demonstrate that CSE exposure of nonsmoker airway epithelium induced goblet cell differentiation characteristic of GCMH. Treatment with DBZ suppressed CSE-dependent induction of goblet cell differentiation. Furthermore, CSE induced NOTCH3 activation, as revealed by increased NOTCH3 nuclear localization and elevated NICD3 protein levels. Over-expression of NICD3 increased expression of the goblet cell associated genes SPDEF and MUC5AC, whereas NOTCH3 knockdown suppressed CSE-mediated induction of SPDEF and MUC5AC. Finally, CSE exposure of COPD airway epithelium induced goblet cell differentiation in a NOTCH3-dependent manner. These results identify NOTCH3 activation as one of the important mechanisms by which cigarette smoke induces goblet cell differentiation, thus providing a potential strategy to control GCMH-related pathologies in smokers and patients with COPD. Overall design: mRNA profiling of primary human bronchial epithelial cells (HBECs) from nonsmokers and COPD smokers cultured on air-liquid interface (ALI) for 28 days and then exposed to 2.5% cigarette smoke extract (CSE) for 7 days.