Jabba Sairam V, Diaz Alexandra N, Erythropel Hanno C, Zimmerman Julie B, Jordt Sven-Eric
Department of Anesthesiology, Duke University School of Medicine, Durham, NC.
Yale Center for the Study of Tobacco Products (YCSTP), Department of Psychiatry, Yale School of Medicine, New Haven, CT.
Nicotine Tob Res. 2020 Dec 15;22(Suppl 1):S25-S34. doi: 10.1093/ntr/ntaa185.
Flavor aldehydes in e-cigarettes, including vanillin, ethyl vanillin (vanilla), and benzaldehyde (berry/fruit), rapidly undergo chemical reactions with the e-liquid solvents, propylene glycol, and vegetable glycerol (PG/VG), to form chemical adducts named flavor aldehyde PG/VG acetals that can efficiently transfer to e-cigarette aerosol. The objective of this study was to compare the cytotoxic and metabolic toxic effects of acetals and their parent aldehydes in respiratory epithelial cells.
Cell metabolic assays were carried out in bronchial (BEAS-2B) and alveolar (A549) epithelial cells assessing the effects of benzaldehyde, vanillin, ethyl vanillin, and their corresponding PG acetals on key bioenergetic parameters of mitochondrial function. The potential cytotoxic effects of benzaldehyde and vanillin and their corresponding PG acetals were analyzed using the LIVE/DEAD cell assay in BEAS-2B cells and primary human nasal epithelial cells (HNEpC). Cytostatic effects of vanillin and vanillin PG acetal were compared using Click-iT EDU cell proliferation assay in BEAS-2B cells.
Compared with their parent aldehydes, PG acetals diminished key parameters of cellular energy metabolic functions, including basal respiration, adenosine triphosphate production, and spare respiratory capacity. Benzaldehyde PG acetal (1-10 mM) increased cell mortality in BEAS-2B and HNEpC, compared with benzaldehyde. Vanillin PG acetal was more cytotoxic than vanillin at the highest concentration tested while both diminished cellular proliferation in a concentration-dependent manner.
Reaction products formed in e-liquids between flavor aldehydes and solvent chemicals have differential toxicological properties from their parent flavor aldehydes and may contribute to the health effects of e-cigarette aerosol in the respiratory system of e-cigarette users.
With no inhalation toxicity studies available for acetals, data from this study will provide a basis for further toxicological studies using in vitro and in vivo models. This study suggests that manufacturers' disclosure of e-liquid ingredients at time of production may be insufficient to inform a comprehensive risk assessment of e-liquids and electronic nicotine delivery systems use, due to the chemical instability of e-liquids over time and the formation of new compounds.
电子烟中的风味醛类，包括香草醛、乙基香草醛（香草味）和苯甲醛（浆果/水果味），会迅速与电子烟烟液溶剂丙二醇和蔬菜甘油（PG/VG）发生化学反应，形成名为风味醛PG/VG缩醛的化学加合物，这些加合物能够有效地转移到电子烟气溶胶中。本研究的目的是比较缩醛及其母体醛类在呼吸道上皮细胞中的细胞毒性和代谢毒性作用。
在支气管（BEAS-2B）和肺泡（A549）上皮细胞中进行细胞代谢测定，评估苯甲醛、香草醛、乙基香草醛及其相应的PG缩醛对线粒体功能关键生物能量参数的影响。使用BEAS-2B细胞和原代人鼻上皮细胞（HNEpC）中的活/死细胞测定法分析苯甲醛和香草醛及其相应PG缩醛的潜在细胞毒性作用。在BEAS-2B细胞中使用Click-iT EDU细胞增殖测定法比较香草醛和香草醛PG缩醛的细胞生长抑制作用。
与它们的母体醛类相比，PG缩醛降低了细胞能量代谢功能的关键参数，包括基础呼吸、三磷酸腺苷生成和备用呼吸能力。与苯甲醛相比，苯甲醛PG缩醛（1-10 mM）增加了BEAS-2B和HNEpC中的细胞死亡率。在测试的最高浓度下，香草醛PG缩醛比香草醛具有更高的细胞毒性，而两者均以浓度依赖性方式降低细胞增殖。
风味醛类与溶剂化学品在电子烟烟液中形成的反应产物具有与其母体风味醛类不同的毒理学特性，可能会对电子烟使用者呼吸系统中电子烟气溶胶的健康影响产生作用。
由于目前尚无关于缩醛的吸入毒性研究，本研究的数据将为使用体外和体内模型进行进一步毒理学研究提供依据。本研究表明，由于电子烟烟液随时间的化学不稳定性以及新化合物的形成，制造商在生产时对电子烟烟液成分的披露可能不足以对电子烟烟液和电子尼古丁传送系统的使用进行全面的风险评估。
