Electronic Cigarette Vapor with Nicotine Causes Airway Mucociliary Dysfunction Preferentially via TRPA1 Receptors

Abstract

<b>Rationale:</b> Electronic cigarette (e-cig) use has been widely adopted under the perception of safety. However, possibly adverse effects of e-cig vapor in never-smokers are not well understood.<b>Objectives:</b> To test the effects of nicotine-containing e-cig vapors on airway mucociliary function in differentiated human bronchial epithelial cells isolated from never-smokers and in the airways of a novel, ovine large animal model.<b>Methods:</b> Mucociliary parameters were measured in human bronchial epithelial cells and in sheep. Systemic nicotine delivery to sheep was quantified using plasma cotinine levels, measured by ELISA.<b>Measurements and Main Results:</b><i>In vitro</i>, exposure to e-cig vapor reduced airway surface liquid hydration and increased mucus viscosity of human bronchial epithelial cells in a nicotine-dependent manner. Acute nicotine exposure increased intracellular calcium levels, an effect primarily dependent on TRPA1 (transient receptor potential ankyrin 1). TRPA1 inhibition with A967079 restored nicotine-mediated impairment of mucociliary parameters including mucus transport <i>in vitro</i>. Sheep tracheal mucus velocity, an <i>in vivo</i> measure of mucociliary clearance, was also reduced by e-cig vapor. Nebulized e-cig liquid containing nicotine also reduced tracheal mucus velocity in a dose-dependent manner and elevated plasma cotinine levels. Importantly, nebulized A967079 reversed the effects of e-cig liquid on sheep tracheal mucus velocity.<b>Conclusions:</b> Our findings show that inhalation of e-cig vapor causes airway mucociliary dysfunction <i>in vitro</i> and <i>in vivo</i>. Furthermore, they suggest that the main nicotine effect on mucociliary function is mediated by TRPA1 and not nicotinic acetylcholine receptors.