Nicotine-Free e-Cigarette Vapor Exposure Stimulates IL6 and Mucin Production in Human Primary Small Airway Epithelial Cells

Purpose: Electronic cigarettes (e-cigs) are relatively new devices that allow the user to inhale a heated and aerosolized solution. At present, little is known about their health effects in the human lung, particularly in the small airways (<2 mm in diameter), a key site of airway obstruction and destruction in chronic obstructive pulmonary disease and other acute and chronic lung conditions. The aim of this study was to investigate the effect of e-cigarettes on human distal airway inflammation and remodeling. Methods: We isolated primary small airway epithelial cells from donor lungs without known lung disease. Small airway epithelial cells were cultured at air-liquid interface and exposed to 15 puffs vapor obtained by heating a commercially available e-cigarette solution (e-vapor) with or without nicotine. After 24 hrs of e-vapor exposure, basolateral and apical media as well as cell lysates were collected to measure the pleiotropic cytokine interleukin 6 (IL6) and MUC5AC, one of the major components in mucus. Results: Unlike the nicotine-containing e-vapor, nicotine-free e-vapor significantly increased the amount of IL6, which was coupled with increased levels of intracellular MUC5AC protein. Importantly, a neutralizing IL6 antibody (vs an IgG isotype control) significantly inhibited the production of MUC5AC induced by nicotine-free e-vapor. Conclusion: Our results suggest that human small airway epithelial cells exposed to nicotine-free e-vapor increase the inflammatory response and mucin production, which may contribute to distal lung airflow limitation and airway obstruction.