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Article

Effects of E-Cigarette Flavoring Chemicals on Human Macrophages and Bronchial Epithelial Cells

1
Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA
2
Department of Basic Pharmaceutical Sciences, West Virginia University Health Sciences Center, Morgantown, WV 26505, USA
3
Environmental Health Investigations Branch, California Department of Public Health, Richmond, CA 94804, USA
*
Author to whom correspondence should be addressed.
Academic Editors: Alexandra Noël and Meghan Rebuli
Int. J. Environ. Res. Public Health 2021, 18(21), 11107; https://doi.org/10.3390/ijerph182111107
Received: 8 September 2021 / Revised: 18 October 2021 / Accepted: 19 October 2021 / Published: 22 October 2021
E-cigarettes utilize a wide range of flavoring chemicals with respiratory health effects that are not well understood. In this study, we used pulmonary-associated cell lines to assess the in vitro cytotoxic effects of 30 flavoring chemicals. Human bronchial epithelial cells (BEAS-2B) and both naïve and activated macrophages (THP-1) were treated with 10, 100, and 1000 µM of flavoring chemicals and analyzed for changes in viability, cell membrane damage, reactive oxygen species (ROS) production, and inflammatory cytokine release. Viability was unaffected for all chemicals at the 10 and 100 µM concentrations. At 1000 µM, the greatest reductions in viability were seen with decanal, hexanal, nonanal, cinnamaldehyde, eugenol, vanillin, alpha-pinene, and limonene. High amounts of ROS were elicited by vanillin, ethyl maltol, and the diketones (2,3-pentanedione, 2,3-heptanedione, and 2,3-hexanedione) from both cell lines. Naïve THP-1 cells produced significantly elevated levels of IL-1β, IL-8, and TNF-α when exposed to ethyl maltol and hexanal. Activated THP-1 cells released increased IL-1β and TNF-α when exposed to ethyl maltol, but many flavoring chemicals had an apparent suppressive effect on inflammatory cytokines released by activated macrophages, some with varying degrees of accompanying cytotoxicity. The diketones, L-carvone, and linalool suppressed cytokine release in the absence of cytotoxicity. These findings provide insight into lung cell cytotoxicity and inflammatory cytokine release in response to flavorings commonly used in e-cigarettes. View Full-Text
Keywords: electronic cigarettes; e-cigarettes; flavorings; toxicity; airway epithelium; macrophages; inflammation electronic cigarettes; e-cigarettes; flavorings; toxicity; airway epithelium; macrophages; inflammation
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MDPI and ACS Style

Morris, A.M.; Leonard, S.S.; Fowles, J.R.; Boots, T.E.; Mnatsakanova, A.; Attfield, K.R. Effects of E-Cigarette Flavoring Chemicals on Human Macrophages and Bronchial Epithelial Cells. Int. J. Environ. Res. Public Health 2021, 18, 11107. https://doi.org/10.3390/ijerph182111107

AMA Style

Morris AM, Leonard SS, Fowles JR, Boots TE, Mnatsakanova A, Attfield KR. Effects of E-Cigarette Flavoring Chemicals on Human Macrophages and Bronchial Epithelial Cells. International Journal of Environmental Research and Public Health. 2021; 18(21):11107. https://doi.org/10.3390/ijerph182111107

Chicago/Turabian Style

Morris, Anna M., Stephen S. Leonard, Jefferson R. Fowles, Theresa E. Boots, Anna Mnatsakanova, and Kathleen R. Attfield. 2021. "Effects of E-Cigarette Flavoring Chemicals on Human Macrophages and Bronchial Epithelial Cells" International Journal of Environmental Research and Public Health 18, no. 21: 11107. https://doi.org/10.3390/ijerph182111107

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