Effects of exposure to e-cigarette aerosols compared with cigarette smoke on 3D human buccal and small airway cultures: a systems toxicology assessment
Considerable attention has been given toward the reduced risk potential of e-cigarettes (e-cigs). Most in vitro studies have focused on testing e-liquid formulations directly on submerged 2D cultures. Here, we examined the effects of exposure to the whole e-cig aerosols compared with the mainstream cigarette smoke (CS) using human 3D organotypic cultures. Buccal and small airway cultures were exposed at the air-liquid interface over 28 min to 112-puffs of undiluted aerosols generated from an e-vapor product, containing different e-liquids [with aerosol formers alone (CARRIER), with 4 % nicotine (BASE), with 4 % nicotine and flavors (TESTMIX)] or to diluted CS in a Vitrocell® exposure system. Nine independent exposures were conducted for a robust assessment. Concentrations of the deposited nicotine and carbonyls in the exposure chamber were measured as markers of exposure. Biological endpoints include histology, cytotoxicity, pro-inflammatory mediators, and gene microarray. Alterations in morphology and cytotoxicity were not observed in buccal culture exposed to undiluted e-cig aerosols, despite a 2-fold higher nicotine deposition compared to the diluted CS exposures. A similar lack of cytotoxicity and morphology changes was observed in the small airway following e-cig aerosol exposures (with a 10-fold higher nicotine deposition compared to CS exposures). CS exposures resulted in an increase in pro-inflammatory mediators in the media in both buccal and small airway cultures. In addition, compared with e-cig aerosols, CS exposures showed greater biological impacts in the global gene expression, including impacts on cell fate, proliferation, stress, and inflammatory respoe lnse networks. Following 24 h post exposure, e-cig aerosol-induced changes in small airway cultures reverted to the levels of the air-control cultures. Among different e-vapor aerosols, there were no significant differences in any of the biological end points tested.