Optimization of aqueous aerosol extract (AqE) generation from e-cigarettes and tobacco heating products for in vitro cytotoxicity testing

• Published in: Toxicology letters 2020-12, Vol.335, p.51-63
• Main Authors: Bozhilova, Stela, Baxter, Andrew, Bishop, Emma, Breheny, Damien, Thorne, David, Hodges, Paul, Gaça, Marianna
• Format: Article
• Language: English
• Subjects: Aerosol; Aerosols; Aqueous extract; Cell Survival - drug effects; Cells, Cultured; Cigarette smoke; e-cigarette; Electronic Nicotine Delivery Systems; Hazardous Substances - toxicity; Heating; Human umbilical vein endothelial cells; Human Umbilical Vein Endothelial Cells - drug effects; Human Umbilical Vein Endothelial Cells - pathology; Humans; In vitro; Smoke - adverse effects; Standardization; Tobacco heating product; Tobacco Products - toxicity; Toxicology; Vapor
• ISSN: 0378-4274; 1879-3169
• DOI: 10.1016/j.toxlet.2020.10.005

[Display omitted] •Novel nicotine products assessed in endothelial cells using cytotoxicity assay.•Standardized method for aqueous aerosol extract generation.•Quality control checks for batch-to-batch consistency and aerosol capture.•Optimized product-by-product assessment approach.•Methods suitably sensitive for inter- and intra-product category comparisons. Electronic cigarettes (e-cigarettes) and tobacco heating products (THPs) have reduced yields of toxicants and have recently emerged as a potentially safer alternative to combustible cigarettes. To understand if reduced toxicant exposure is associated with reductions in biological responses, there is a need for high-quality pre-clinical in vitro studies. Here, we investigated the cytotoxic response of human umbilical vein endothelial cells to conventional cigarette aqueous aerosol extracts (AqE) and highly concentrated AqEs from e-cigarettes (two generations of atomisers) and THPs (two variants). All AqE samples were generated by a standardized methodology and characterized for nicotine, propylene glycol and vegetable glycerol. The cigarette AqE caused a maximum 100 ± 0.00 % reduction in cell viability at 35 % dose (2.80 puffs) as opposed to 96.63 ± 2.73 % at 50 % (20 puffs) and 99.85 ± 0.23 % at 75 % (30 puffs) for the two THP variants (glo Bright Tobacco, glo Rich Tobacco), and 99.07 ± 1.61 % at the neat ePen2.0 e-cigarette (200 puffs). The AqE of the remaining e-cigarettes either resulted in an incomplete dose-response or did not elicit any response. The methods utilized were suitably sensitive to not only differentiate between cigarette, THP and e-cigarette aerosols but also to distinguish between products within each product category.