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

Introduction:
This text is a scientific report on a study investigating the effects of tobacco and menthol-flavored electronic cigarette (e-cigarette) liquids on human middle ear epithelial cells (hMEECs). The study found that both flavors decreased cell viability and induced cytotoxicity through various mechanisms, including inflammatory response, mucin production, and dysregulation of water channels.

Key Points:

* The study analyzed the cytotoxicity of two flavors of e-cigarette liquids, tobacco and menthol, on hMEECs.
* Both flavors reduced cell viability in a dose-dependent manner, with menthol being significantly more cytotoxic than tobacco.
* Exposure to e-liquids induced inflammatory cytokine expression, with menthol increasing COX-2 and TNF-α expression more than tobacco.
* Mucin production was also increased, with both flavors significantly increasing MUC4 and MUC5aC expression.
* The expression of water channel-related genes was dysregulated, with both flavors significantly increasing aqP4 expression and decreasing ENaC family member expression.
* Tobacco-flavored e-liquid significantly induced COX-2 and Muc5aC expression, while menthol-flavored e-liquid exhibited apoptotic cell death by inducing transcription of Muc4 and aqP4 and inactivating ENaC family members.
* Both flavors stimulated autophagy signaling, with menthol-flavored e-liquid inducing more apoptotic- and necrotic-positive cells than tobacco-flavored e-liquid.

Main Message:
The study suggests that flavor-containing e-cigarettes can cause apoptotic and autophagic cell death in middle ear epithelium by inducing inflammatory responses and mucin production, thus acting as a risk factor for OM incidence. The study highlights the need for further research into the potential health risks associated with e-cigarette use, particularly the effects of flavorings on human cells. as an expert in regulatory matters, it is crucial to consider these findings when developing policies and regulations around e-cigarette use and safety.

Go YY, Mun JY, Chae SW, Chang J, Song JJ. Comparison between in vitro toxicities of tobacco- and menthol-flavored electronic cigarette liquids on human middle ear epithelial cells. Scientific reports. 2020;10(1):2544. doi:10.1038/s41598-020-59290-y