BackgroundThe use of electronic (e)-cigarettes is increasing rapidly, but their lung health effects are not established. Clinical studies examining the potential long-term impact of e-cigarette use on lung health will take decades. To address this gap in knowledge, this study investigated the effects of exposure to aerosolised nicotine-free and nicotine-containing e-cigarette fluid on mouse lungs and normal human airway epithelial cells.MethodsMice were exposed to aerosolised phosphate-buffered saline, nicotine-free or nicotine-containing e-cigarette solution, 1-hour daily for 4 months. Normal human bronchial epithelial (NHBE) cells cultured at an air-liquid interface were exposed to e-cigarette vapours or nicotine solutions using a Vitrocell smoke exposure robot.ResultsInhalation of nicotine-containing e-cigarettes increased airway hyper-reactivity, distal airspace enlargement, mucin production, cytokine and protease expression. Exposure to nicotine-free e-cigarettes did not affect these lung parameters. NHBE cells exposed to nicotine-containing e-cigarette vapour showed impaired ciliary beat frequency, airway surface liquid volume, cystic fibrosis transmembrane regulator and ATP-stimulated K+ ion conductance and decreased expression of FOXJ1 and KCNMA1. Exposure of NHBE cells to nicotine for 5 days increased interleukin (IL)-6 and IL-8 secretion.ConclusionsExposure to inhaled nicotine-containing e-cigarette fluids triggered effects normally associated with the development of COPD including cytokine expression, airway hyper-reactivity and lung tissue destruction. These effects were nicotine-dependent both in the mouse lung and in human airway cells, suggesting that inhaled nicotine contributes to airway and lung disease in addition to its addictive properties. Thus, these findings highlight the potential dangers of nicotine inhalation during e-cigarette use.

Circulating levels of fibroblast growth factor (FGF) 23 are associated with systemic inflammation and increased mortality in chronic kidney disease. α-klotho, a co-receptor for FGF23, is downregulated in chronic obstructive pulmonary disease (COPD). However, whether FGF23 and klotho-mediated FGFR activation delineates a pathophysiologic mechanism in COPD remains unclear. We hypothesized that FGF23 can potentiate airway inflammation via klotho independent FGFR4 activation. FGF23 and its effect were studied using plasma and transbronchial biopsies from COPD and control patients and primary human bronchial epithelial cells isolated from COPD patients as well as a murine COPD model. Plasma FGF23 levels were significantly elevated in COPD patients. Exposure of airway epithelial cells to cigarette smoke and FGF23 led to a significant increase in IL-1β release via klotho-independent FGFR4-mediated activation of phospholipase Cγ (PLCγ)/nuclear factor of activated T-cells (NFAT) signaling. In addition, klotho knockout mice developed COPD and showed airway inflammation and elevated FGFR4 expression in their lungs, whereas overexpression of klotho led to an attenuation of airway inflammation. In conclusion, cigarette smoke induces airway inflammation by downregulation of klotho and activation of FGFR4 in the airway epithelium in COPD. Inhibition of FGF23 or FGFR4 might serve as a novel anti-inflammatory strategy in COPD.

The epithelium that lines the conducting airways is composed of several distinct cell types that differentiate from common progenitor cells. The signals that control fate selection and differentiation of ciliated cells, a major component of the epithelium, are not completely understood. Ciliated cell differentiation can be accomplished in vitro when primary normal human bronchial epithelial (NHBE) cells are cultured at an air-liquid interface, but is inhibited when NHBE cells are cultured under submerged conditions. The mechanism by which submersion prevents ciliogenesis is not understood, but may provide clues to in vivo regulation of ciliated cell differentiation. We hypothesized that submersion creates a hypoxic environment that prevents ciliated cell differentiation by blocking the gene expression program required for ciliogenesis. This was confirmed by showing that expression of multicilin and Forkhead box J1, key factors needed for ciliated cell differentiation, was inhibited when NHBE cells were cultured in submerged and hypoxic conditions. Multicilin and Forkhead box J1 expression and ciliated cell differentiation were restored in submerged and hypoxic cells upon treatment with the g-secretase inhibitor, N-[(3,5-difluorophenyl)acetyl]-L-alanyl-2-phenyl] glycine-1,1-dimethylethyl ester (DAPT), which suggested that Notch signaling was involved. Overexpression of Notch intracellular domain inhibited differentiation in the presence of DAPT, confirming the role of Notch signaling. These results indicate that submersion and hypoxia prevent ciliated cell differentiation by maintaining Notch signaling, which represses genes necessary for ciliogenesis. These data provide new insights into the molecular mechanisms that control human bronchial differentiation.

of Health (NIH) -F32-HL140729 (to S.C.) and R01 HL139365 (to M.S.) RUNNING TITLE: Vaped nicotine impairs mucociliary function preferentially via TRPA1 SUBJECT CATEGORY DESCRIPTOR: 6.17 Smoking Health Effects TOTAL WORD COUNT: 3985 AT A GLANCE COMMENTARY: Scientific Knowledge on the Subject E-cigarettes are marketed as safer alternatives to conventional cigarettes due to their defined composition and noncombustible nature. However, it is unclear how exposure to e-cigarette vapor, colloquially referred to as "vape", affects naïve airway epithelia. It is largely unknown to what extent individual constituents of vape, such as nicotine and flavoring agents, influence pulmonary function, if at all. The transient receptor potential ankyrin 1 (TRPA1) is a molecular target for vape effects due to its expression in airway epithelia and its reported gating by nicotine, reactive oxidants, and flavors, especially cinnamaldehyde. What This Study Adds to the FieldThis study implicates nicotine as a key "vape" constituent that acutely impairs airway mucociliary functions in vitro and in vivo (sheep). A functional, nicotine-sensitive TRPA1 receptor is natively expressed in human and sheep bronchial epithelial cells and mediates the effects of nicotine and e-cigarette vapors. Importantly, its inhibition prevents mucociliary dysfunction in vitro and in vivo. These findings implicate TRPA1 as a driver of mucociliary dysfunction induced by nicotine-containing e-cigarette vapor.ABSTRACT RATIONALE: 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. OBJECTIVES:Effects of nicotine-containing e-cig vapors on airway mucociliary function were tested in differentiated human bronchial epithelial cells (HBECs) isolated from never-smokers and in the airways of a novel, ovine large animal model. METHODS:Mucociliary parameters were measured in HBECs and in sheep. Systemic nicotine delivery to sheep was quantified using plasma cotinine levels, measured by ELISA. MEASUREMENTS AND MAIN RESULTS:In vitro, exposure to e-cig vapor reduced airway surface liquid hydration and increased mucus viscosity of HBECs in a nicotinedependent manner. Acute nicotine exposure increased intracellular calcium levels, an effect primarily dependent on transient receptor potential ankyrin 1 (TRPA1). TRPA1 inhibition with A967079 restored nicotine-mediated impairment of mucociliary parameters including mucus transport in vitro. Sheep tracheal mucus velocity (TMV), an in vivo measure of mucociliary clearance, was also reduced by e-cig vapor. Nebulized e-cig liquid containing nicotine also reduced TMV in a dose-dependent manner and elevated plasma cotinine levels. Importantly, nebulized A967079 reversed the effects of e-cig liquid on sheep TMV. CONCLUSIONS:Our findings show that inhalation of e-cig vapor causes airway mucociliary dysfunction in vitro and in vivo. Furthermore, they suggest that the main Page 4 of 64 2 nicotine effect on mucociliary ...