https ://doi.org/10.1186/s1293 1-020-01539-1
Rakeysha Pinkston1,2, Hasan Zaman2, Ekhtear Hossain2, Arthur L. Penn2 and Alexandra Noël2
1 Department of Environmental Toxicology, College of Sciences and Engineering, Southern University and A&M College, Baton Rouge, LA 70813, USA.
2 Department of Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, 1909 Skip Bertman Drive, Baton Rouge, LA 70803, USA.
There are thousands of flavors and flavoring combinations of e-liquids on the market with the potential to produce harmful effects when aerosolized through an ENDS device. While more research is needed regarding the potential toxicity associated with inhaling flavoring additives in combination with nicotine salt for future regulation of ENDS products, the present study provides laboratory-based evidence that should be considered regarding regulation of nicotine salt-based products.
Backgroud: JUUL, an electronic nicotine delivery system (ENDS), which first appeared on the US market in 2015, controled more than 75% of the US ENDS sales in 2018. JUUL-type devices are currently the most commonly used form of ENDS among youth in the US. In contrast to free-base nicotine contained in cigarettes and other ENDS, JUUL contains high levels of nicotine salt (35 or 59 mg/mL), whose cellular and molecular effects on lung cells are largely unknown. In the present study, we evaluated the in vitro toxicity of JUUL crème brûlée-flavored aerosols on 2 types of human bronchial epithelial cell lines (BEAS-2B, H292) and a murine macrophage cell line (RAW 264.7).
Methods: Human lung epithelial cells and murine macrophages were exposed to JUUL crème brûlée-flavored aerosols at the air–liquid interface (ALI) for 1-h followed by a 24-h recovery period. Membrane integrity, cytotoxicity, extracellular release of nitrogen species and reactive oxygen species, cellular morphology and gene expression were assessed.
Results: Crème brûlée-flavored aerosol contained elevated concentrations of benzoic acid (86.9 μg/puff), a wellestablished respiratory irritant. In BEAS-2B cells, crème brûlée-flavored aerosol decreased cell viability (≥ 50%) and increased nitric oxide (NO) production (≥ 30%), as well as iNOS gene expression. Crème brûlée-flavored aerosol did not affect the viability of either H292 cells or RAW macrophages, but increased the production of reactive oxygen species (ROS) by ≥ 20% in both cell types. While crème brûlée-flavored aerosol did not alter NO levels in H292 cells, RAW macrophages exposed to crème brûlée-flavored aerosol displayed decreased NO (≥ 50%) and down-regulation of the iNOS gene, possibly due to increased ROS. Additionally, crème brûlée-flavored aerosol dysregulated the expression of several genes related to biotransformation, inflammation and airway remodeling, including CYP1A1, IL-6, and MMP12 in all 3 cell lines.
Conclusion: Our results indicate that crème brûlée-flavored aerosol causes cell-specific toxicity to lung cells. This study contributes to providing scientific evidence towards regulation of nicotine salt-based products.