Michael Anderson

Project title: Effects of common e-cigarette compounds on immortalized mouse hepatocytes and glutathione as a potential modulator of susceptibility

Degree: MS | Program: Environmental Toxicology (Tox) | Project type: Thesis/Dissertation
Completed in: 2020 | Faculty advisor: Terrance J. Kavanagh


In 2018, 3.2% of adults reported currently using an e-cigarette (vaping) at least once in a 30-day period. 20.8% and 4.9% of high school and middle school students, respectively, also reported using e-cigarettes during that same year. Of greater concern, in 2019, 27.5% of high school students and 10.5% of middle school students reported using e-cigarettes. Despite this, comparatively little research has been done on the potential hazards and effects of e-cigarettes. In this study, four compounds were chosen due to their common associations with various aspects of vaping. Formaldehyde and acetaldehyde were chosen as common pyrolysis byproducts of the propylene glycol/vegetable glycerin vehicle found in most vaping formulations; cinnamaldehyde and diacetyl were chosen as common flavoring agents. Immortalized mouse hepatocytes were used as a model system for this study with the hope that this would limit any confounding associated with approaching senescence. Two cell lines—either sufficient or deficient in the production of the antioxidant glutathione (GSH) (Gclm wild-type of null cells, respectively) were exposed to each of the four compounds in culture. Effects on viability, antioxidant response, oxidative stress, and gene expression were then evaluated. Formaldehyde and cinnamaldehyde showed the most profound effects on overall viability, while acetaldehyde showed virtually no effect. Diacetyl only demonstrated nominal effects up to the highest dose. Similarly, formaldehyde and cinnamaldehyde showed drastic decreases in total GSH levels, whereas acetaldehyde and diacetyl showed only modest decreases at low doses that re-approached baseline levels at higher doses. RNAseq revealed differential gene expression in the wild type cells at 100 µM cinnamaldehyde and 1 mM diacetyl; the knockout cells had significant differential gene expression at 250 µM and 1 mM diacetyl. Quantitation of lipid peroxidation levels revealed virtually no significant dose or genotype effects, but even with a lack of significance the Gclm null cells appeared to have higher levels of peroxidized lipids across all four compounds. Despite the preliminary nature of the data and the lack of a concrete physiological context, it demonstrates that some of these compounds could potentially pose a hazard to the liver. Further research is needed to better understand the risks posed by these compounds, especially in the context of in vivo exposures to e-cigarette aerosols. URI