Comparison between in vitro toxicities of tobacco- and menthol-flavored electronic cigarette liquids on human middle ear epithelial cells

• Published in: Scientific reports 2020-02, Vol.10 (1), p.2544, Article 2544
• Main Authors: Go, Yoon Young, Mun, Ji Yoen, Chae, Sung-Won, Chang, Jiwon, Song, Jae-Jun
• Format: Article
• Language: English
• Subjects: 13; 13/2; 14; 14/19; 14/63; 38; 38/1; 38/77; 631/80/82/39; 692/308; Apoptosis; Autophagy; Cell death; Cell Death - drug effects; Cell Line; Cigarettes; Cytotoxicity; Ear diseases; Ear, Middle - cytology; Ear, Middle - drug effects; Electronic cigarettes; Electronic Nicotine Delivery Systems; Epithelial cells; Epithelial Cells - drug effects; Flavoring Agents - adverse effects; Gene Expression Regulation - drug effects; Humanities and Social Sciences; Humans; Inflammation; Longitudinal Studies; Lung - drug effects; Lung - pathology; Menthol; Menthol - chemistry; Microtubule-Associated Proteins - genetics; Middle ear; mRNA; Mucin; multidisciplinary; Otitis media; Phagocytosis; Risk factors; Science; Science (multidisciplinary); Sodium channels; Tobacco; Tobacco Products; Tobacco smoking
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-020-59290-y

Since electronic-cigarettes (e-cigarettes) are considered less toxic than conventional tobacco smoking, the use of e-cigarettes has increased, and the market for e-cigarette liquids (e-liquids) is continuously increasing. However, many studies showed that e-cigarettes may cause various harmful effects in lung, oral and heart. In this study, we investigated the effects of e-liquids on otitis media (OM) using human middle ear epithelial cells (HMEECs). Menthol-flavored e-liquid induced significant cell death in HMEECs (IC 50 : 1.45 ± 0.14%) and tobacco-flavored e-liquid led to increase in inflammatory cytokine levels and higher mucin production. Flavored e-liquids decreased the mRNA levels of genes encoding epithelial sodium channels (ENaCs) in HMEECs. Apoptosis and autophagy reactions were induced by exposure of HMEECs to menthol- and tobacco-flavored e-liquids. Tobacco-flavored e-liquids caused a greater increase in the levels of autophagosome marker, LC3-II, compared to menthol-flavored e-liquids, which was followed by cell death. These results demonstrate that flavored e-liquids cause cytotoxicity via apoptosis, autophagy, inflammatory response, and mucin production in HMEECs. The flavors present in e-liquids might be a risk factor for the development of otitis media.