A lower impact of an acute exposure to electronic cigarette aerosols than to cigarette smoke in human organotypic buccal and small airway cultures was demonstrated using systems toxicology assessment

Abstract

In the context of tobacco harm-reduction strategy, the potential reduced impact of electronic cigarette (EC) exposure should be evaluated relative to the impact of cigarette smoke exposure. We conducted a series of in vitro studies to compare the biological impact of an acute exposure to aerosols of “test mix” (flavors, nicotine, and humectants), “base” (nicotine and humectants), and “carrier” (humectants) formulations using MarkTen ® EC devices with the impact of exposure to smoke of 3R4F reference cigarettes, at a matching puff number, using human organotypic air–liquid interface buccal and small airway cultures. We measured the concentrations of nicotine and carbonyls deposited in the exposure chamber after each exposure experiment. The deposited carbonyl concentrations were used as representative measures to assess the reduced exposure to potentially toxic volatile substances. We followed a systems toxicology approach whereby functional biological endpoints, such as histopathology and ciliary beating frequency, were complemented by multiplex and omics assays to measure secreted inflammatory proteins and whole-genome transcriptomes, respectively. Among the endpoints analyzed, the only parameters that showed a significant response to EC exposure were secretion of proteins and whole-genome transcriptomes. Based on the multiplex and omics analyzes, the cellular responses to EC aerosol exposure were tissue type-specific; however, those alterations were much smaller than those following cigarette smoke exposure, even when the EC aerosol exposure under the testing conditions resulted in a deposited nicotine concentration approximately 200 times that in saliva of EC users. Electronic supplementary material The online version of this article (10.1007/s11739-019-02055-x) contains supplementary material, which is available to authorized users.

The in vitro assessment of a novel vaping technology

“…These findings are consistent with previous assessments of e-cig products by our group and others, where reduced biological activity was reported in comparison to that induced by cigarette smoke [ [6] , [7] , [8] , 12 , 29 , 46 ]. It is likely that the biological responses that are seen upon exposure to cigarette smoke may be driven by multiple toxic constituents of that aerosol, and that the specific constituents that drive the response may differ from one biological endpoint to the other.…”

Application of a multi-layer systems toxicology framework for in vitro assessment of the biological effects of Classic Tobacco e-liquid and its corresponding aerosol using an e-cigarette device with MESH™ technology

“…Tissue-specific soluble factors are important to condition the local environment against stimuli or pathogens (Hu and Pasare 2013). Decreased GRO and increased IL-1β secretion following 3R4F CS exposure were only detected in buccal cultures but not in small airway cultures, while marked increased secretion in VEGFA, IL-8, and TIMP-1 following 3R4F CS exposure was seen only in small airway cultures but not in buccal cultures; these observations were consistent with our previous finding (Iskandar et al 2019). These mediators were not altered pronouncedly following exposure to MESH Classic Tobacco or Base aerosols.…”

“…Nonetheless, we were intrigued by the pronounced increase in IL-1α secretion from buccal cultures following exposure to MESH Classic Tobacco or Base aerosols, despite the absence of tissue damage. This observation was also seen previously in buccal cultures following exposure to an EC aerosol of a prototype "Test Mix" and its base formulation (Iskandar et al 2019). The expression of the IL1A gene, however, was not markedly impacted by MESH Classic Tobacco and Base aerosol exposure (data not shown).…”

“…The MESH technology maintains the temperature for the heater between 200 and 220 °C rather than varying the temperature depending on the puff strength. The particle sizes of 3R4F CS, MESH Classic Tobacco aerosol, and Base aerosol were similar; they were measured before entering the exposure system as a quality control following a previously published protocol (Iskandar et al 2019); data are given Supplementary Table 1.…”

Health impact of electronic cigarettes and heated tobacco systems

“…This computation calls for more advanced toxicological research methods. Iskandar et al [18] propose an elegant approach consisting of an in vitro systems toxicology assessment of e-liquids and their aerosols to complement the battery of assays for standard toxicity assessments. The proposed methodology with human organotypic air-liquid interface buccal and small airway cultures compares the biological impact of acute exposure to different e-cigarette aerosols with exposure to cigarette smoke.…”