B26-07 Airspace Enlargement Due to E-Cigarette Nicotine Exposure

Abstract Rationale Smoking of combustible nicotine delivery devices (cigarettes, cigars) has been documented to cause airspace enlargement and emphysema due to the loss of alveoli including cells and matrix. These effects are thought to be caused by two main mechanisms: a) elaboration of proteases with insuffcient control by protease inhibitors, b) inflammation that leads to increased protease release. Therefore, nicotine habits in the US have changed with the belief that new nicotine delivery devices, e.g. e-cigarettes (e-cigs) are safer. Particularly young people, including high school students, together about 16 million Americans, are currently consuming e-cigs, or are dual users of e-cigs and cigarettes. Here we focus on airspace enlargement by exposure to a toxic substance, such as nicotine, delivered by e-cig aerosols. Methods Four groups of male and female C57BL/6 mice were exposed for a total of either 3 weeks or 5 weeks (3 hours/day, 5 days/week) via whole body inhalation to: 1) filtered room air; 2) propylene glycol and vegetable glycerin (50:50 PG-VG); 3) PG-VG and 36 mg/mL nicotine; or 4) PG-VG and nicotine and 5 mg/ml menthol. The animals were euthanized directly after exposure (3-weeks exposure group) or 3-weeks post exposure, during which the animals got a secondary Streptococcus challenge (5-weeks exposure group), and the lungs were harvested. Lung sections were digitally scanned and analyzed using QuPath(R) and a self-made software add-on to optimize the counting of cells in the alveolar walls. Results We observed patchy airspace enlargement areas interspersed with airspaces that had normal appearance in the non-inflamed parts of the lungs (Fig.1). Because of the patchy nature, the enlargement was hard to quantify. Therefore, we matched normal areas to areas with airspace enlargement in each lung lobe. The number of cells in the enlarged (cells/area) divided by number of cells in the normal areas (cells/area) was determined. Pilot analysis compared the combined controls (air and PG-VG) with the combined nicotine exposed groups (nicotine and nicotine-menthol). The analysis showed a significant decrease in the numbers of cells in the enlarged areas compared to the normal looking areas in nicotine exposed mice (Fig.1). Conclusions We detected enlarged, abnormally looking airspaces in animals exposed to e-cig aerosol containing nicotine, in a patchy manner throughout the lungs. This observation was supported by image analysis. Toxic exposures should be considered as a potential third mechanism of airspace cell rarefication and enlargement, besides the known mechanisms of protease-excess, or inflammation. This abstract is funded by: NHLBI R21 HL142507-02 (JZ, GG), NYU P30 Center ES001247-57