Abstract
We previously proposed a systems toxicology framework for in vitro assessment of e-liquids. The framework starts with the first layer aimed at screening the potential toxicity of e-liquids, followed by the second layer aimed at investigating the toxicity-related mechanism of e-liquids, and finally, the third layer aimed at evaluating the toxicity-related mechanism of the corresponding aerosols. In this work, we applied this framework to assess the impact of the e-liquid MESH Classic Tobacco and its aerosol compared with that of cigarette smoke (CS) from the 3R4F reference cigarette. In the first layer, we evaluated the cytotoxicity profile of the MESH Classic Tobacco e-liquid (containing humectants, nicotine, and flavors) and its Base e-liquid (containing humectant and nicotine only) in comparison with total particulate matter (TPM) of 3R4F CS using primary bronchial epithelial cell cultures. In the second layer, the same culture model was used to explore changes in specific markers using high-content screening assays to identify potential toxicity-related mechanisms induced by the MESH Classic Tobacco and Base e-liquids beyond cell viability in comparison with the 3R4F CS TPM-induced effects. Finally, in the third layer, we compared the impact of exposure to the MESH Classic Tobacco or Base aerosols with 3R4F CS using human organotypic air–liquid interface buccal and small airway epithelial cultures. The results showed that the cytotoxicity of the MESH Classic Tobacco liquid was similar to the Base liquid but lower than 3R4F CS TPM at comparable nicotine concentrations. Relative to 3R4F CS exposure, MESH Classic Tobacco aerosol exposure did not cause tissue damage and elicited lower changes in the mRNA, microRNA, and protein markers. In the context of tobacco harm reduction strategy, the framework is suitable to assess the potential-reduced impact of electronic cigarette aerosol relative to CS.
Highlights
The effort to reduce harm caused by smoking has focused on preventing smoking initiation and promoting smoking cessation; a consistent increase in the rate of cessation from 1991 to 2010 failed to be demonstrated (Zhu et al 2012)
We evaluated the impact of MESH Classic Tobacco liquid and Base e-liquids compared with that of 3R4F cigarette smoke (CS) total particulate matter (TPM) on cell viability
A robust approach is needed to test the potential toxicity of the final electronic cigarettes (EC) liquids and, eventually, the aerosolized formulations
Summary
The effort to reduce harm caused by smoking has focused on preventing smoking initiation and promoting smoking cessation; a consistent increase in the rate of cessation from 1991 to 2010 failed to be demonstrated (Zhu et al 2012). The tobacco harm reduction approach, which is designed to reduce health risks associated with tobacco smoking, but may involve the continued use of nicotine (Cox and Dawkins 2018), has been increasingly proposed as a promising complementary strategy to accelerate the decline in smoking prevalence and to reduce. Modified risk tobacco products (Family Smoking Prevention and Tobacco Control Act 2009) are relevant to this effort; they should significantly reduce the harm and risk of smoking-related disease for individual smokers and improve the health of the population as a whole. With more than 8000 flavors available on the market (Bals et al 2019) and around 242 new flavors added every month (Tierney et al 2016), the selection of e-liquids adequate for use with ECs should be driven by relevant toxicological analysis
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