Lung Toxicity of Condensed Aerosol from E-CIG Liquids: Influence of the Flavor and the In Vitro Model Used

Introduction:
This article presents a study on the inhalation toxicity of condensed aerosols (CAs) from e-cigarette (e-CIG) liquids with different flavors and nicotine concentrations. The study uses two in vitro models, a monoculture of human epithelial alveolar cells and a three-dimensional (3D) co-culture of alveolar and lung microvascular endothelial cells, to investigate cell viability, pro-inflammatory cytokines release, and alveolar-blood barrier (ABB) integrity.

Key Points:

* The study tested CAs from three main e-liquid categories: tobacco, mint, and cinnamon, with and without nicotine.
* The monoculture of human epithelial alveolar cells and the 3D co-culture of alveolar and lung microvascular endothelial cells were used to evaluate the toxicity of CAs.
* Cell viability, pro-inflammatory cytokines release, and ABB integrity were assessed as inhalation toxicity endpoints.
* Nicotine itself had almost no influence on the modulation of the toxicity response, while flavor composition did have.
* The cell viability was significantly decreased in monoculture and ABB after exposure to the mints and cinnamon CAs.
* The barrier integrity was significantly affected in the ABB after exposure to cytotoxic CAs.
* With the exception of the significant IL-8 release in the monoculture after Cinnamon exposure, no increase of inflammatory cytokines (IL-8 and MCP-1) release was observed.

Main Message:
The study demonstrates that multiple assays with different in vitro models are able to discriminate the acute inhalation toxicity of CAs from liquids with different flavors. This finding provides companies and regulatory bodies with useful tools for the preliminary screening of marketable products. The study also highlights the importance of considering the flavor composition in the assessment of e-CIG safety, as it can significantly contribute to induce cytotoxic effects in lung cells. Therefore, further exploration of the mechanisms of action of the variety of products already in commerce and the potential health hazards deriving from prolonged exposure and abuse of e-CIGs is mandatory.

Bengalli, Rossella, Emanuele Ferri, Massimo Labra, and Paride Mantecca. “Lung Toxicity of Condensed Aerosol from E-CIG Liquids: Influence of the Flavor and the In Vitro Model Used.” International Journal of Environmental Research and Public Health 14, no. 10 (October 20, 2017): 1254. https://doi.org/10.3390/ijerph14101254.