A framework for in vitro systems toxicology assessment of e-liquids

Abstract

Various electronic nicotine delivery systems (ENDS), of which electronic cigarettes (e-cigs) are the most recognized prototype, have been quickly gaining ground on conventional cigarettes because they are perceived as less harmful. Research assessing the potential effects of ENDS exposure in humans is currently limited and inconclusive. New products are emerging with numerous variations in designs and performance parameters within and across brands. Acknowledging these challenges, we present here a proposed framework for an in vitro systems toxicology assessment of e-liquids and their aerosols, intended to complement the battery of assays for standard toxicity assessments. The proposed framework utilizes high-throughput toxicity assessments of e-liquids and their aerosols, in which the device-to-device variability is minimized, and a systems-level investigation of the cellular mechanisms of toxicity is an integral part. An analytical chemistry investigation is also included as a part of the framework to provide accurate and reliable chemistry data solidifying the toxicological assessment. In its simplest form, the framework comprises of three main layers: (1) high-throughput toxicity screening of e-liquids using primary human cell culture systems; (2) toxicity-related mechanistic assessment of selected e-liquids, and (3) toxicity-related mechanistic assessment of their aerosols using organotypic air–liquid interface airway culture systems. A systems toxicology assessment approach is leveraged to enable in-depth analyses of the toxicity-related cellular mechanisms of e-liquids and their aerosols. We present example use cases to demonstrate the suitability of the framework for a robust in vitro assessment of e-liquids and their aerosols.

Keywords:

• e-Cigarette
• ENDS
• high-content screening
• organotypic cultures transcriptomics

Acknowledgements

The authors thank Dr. Walter Schlage for the critical review of the manuscript. The authors also thank the following individuals for contributing their technical expertise: Laura Ortega Torres and Stephanie Johne (the handling and the measurements of cytotoxicity, CYP activity, and cilia beating frequency in 3D culture systems); Alexandra Laurent (the measurement using xCELLigence); Keyur Trivedi and Abdelkader Benyagoub (the histological processing); Celine Merg (the Luminex-based measurement); and Karine Baumer, Remi Dulize, and Dariusz Peric (the microarray experiment), as well as Dr. Markus Nordlund and Dr. Sandro Steiner (the assessment of droplet size distribution of the aerosols). Finally, the authors thank Samantha Elmhurst for illustrating aerosol generation devices, particle size measurement devices, and other laboratory equipment.

Disclosure statement

PMI is developing products with the potential to reduce individual risk and population harm in comparison to smoking combustible cigarettes. This study/research involves PMI investigational products and was conducted by PMI employees/consultants with PMI funding. The authors had full access to all study/research data and ensure their integrity as well as the accuracy of the data analysis.

Funding information

This work was funded by Philip Morris Product SA (a member of Philip Morris International Group of Companies).