Refill liquids for electronic cigarettes display peculiar toxicity on human endothelial cells

The electronic cigarettes mimic combustible cigarettes through a heating technology that vaporizes a refill liquid consisting of solvents, flavors, and nicotine. E-cigarettes are sometimes still used as a support for smoking cessation, even if in 2019 an acute lung injury outbreak occurred in the USA, affecting mainly adolescents and young adults, and was correlated to eCigs. Therefore, due to the lack of a definite knowledge about the mechanism(s) of refill liquid toxicity and considering that previous investigations gave controversial results, the aim of the present study was the cytotoxicity assessment of different refill liquids on human endothelial cells, evaluated by means of two different in vitro approaches, i.e. the resazurin and the LDH release assays. Our results clearly demonstrated that different refill liquids (6 samples) display different levels of cytotoxicity in our cellular model, although their cytotoxicity was always lower than that observed for the condensate obtained from traditional cigarettes (3 samples). These results suggest that accurate evaluations should be provided for refill liquids, in particular to correlate their toxicity to their chemical composition, with the final aim of obtaining useful information for the agencies involved in the regulation of their components.

The flavoring and not the nicotine content is a decisive factor for the effects of refill liquids of electronic cigarette on the redox status of endothelial cells

•

The pattern of the effect on Ea.hy926 redox status differs among flavored e-liquids.

•

Tobacco flavored e-liquids increase ROS generation with concomitant increase in TBARS.

•

Vanilla flavored e-liquids profile depends on the nicotine content.

•

Apple/mint flavored e-liquids activate the cellular antioxidant defense.

•

Flavorings and not the nicotine content play a key role in free radical generation.

Electronic cigarettes are constantly gaining ground as they are considered less harmful than conventional cigarettes, and there is also the perception that they may serve as a potential smoking cessation tool. Although the acute effects of electronic cigarette use have been extensively studied, the long-term potential adverse effects on human health remain largely unknown. It has been well-established that oxidative stress is involved in the development of various pathological conditions. So far, most studies on e-cigarettes concern the effects on the respiratory system while fewer have focused on the vascular system. In the present study, we attempted to reveal the effects of electronic cigarette refill liquids on the redox state of human endothelial cells (EA.hy926 cell line). For this purpose, the cytotoxic effect of three e-liquids with different flavors (tobacco, vanilla, apple/mint) and nicotine concentrations (0, 6, 12, 18 mg/ml) were initially examined for their impact on cell viability of EA.hy926 cells. Then, five redox biomarkers [reduced form of glutathione (GSH), reactive oxygen species (ROS), total antioxidant capacity (TAC), thiobarbituric acid reactive substances (TBARS) and protein carbonyls (CARBS)] were measured. The results showed a disturbance in the redox balance in favor of free radicals in tobacco flavored e-liquids while vanilla flavored e-liquids exhibited a more complex profile depending on the nicotine content. The most interesting finding of the present study concerns the apple/mint flavored e-liquids that seemed to activate the cellular antioxidant defense and, thus, to protect the cells from the adverse effects of free radicals. Conclusively, it appears that the flavorings and not the nicotine content play a key role in the oxidative stress-induced toxicity of the e-liquids.

Perceptions of emerging tobacco products and nicotine replacement therapy among pregnant women and women planning a pregnancy

The increasing availability of emerging non-combusted tobacco products (snus, dissolvables, and electronic nicotine delivery systems or ENDS) may have implications for pregnant women and women of reproductive age. We conducted 15 focus groups to explore how women perceive emerging non-combusted tobacco products and nicotine replacement therapy (NRT) in general, and during pregnancy. Sessions were held in 2013 in four U.S. cities. Participants were 18–40 years old and were pregnant smokers, pregnant quitters, or smokers planning a pregnancy. Responses were coded and analyzed to identify key themes using NVivo 10.0 qualitative software (QSR).

Several themes emerged from focus groups. Participants generally found snus unappealing, but viewed dissolvables as a discreet and stigma-free way to use tobacco during pregnancy. Participants perceived NRT as ineffective and having undesired side effects. ENDS were thought to offer advantages over cigarettes, including use in smoke-free areas, lower cost, appealing flavors, and fewer health effects, and were seen by some as a potential quit aid. Some participants, however, worried that the lack of natural stopping point could lead to excessive use. Many participants felt that the use of any tobacco or NRT product is harmful during pregnancy.

Women seeking to reduce health risks or stigma related to smoking during pregnancy may perceive advantages of using some emerging products over cigarettes. These findings can inform future public health efforts to reduce risks associated with tobacco product use among women of reproductive age.

•

We conducted focus groups with pregnant smokers and quitters, and smokers planning a pregnancy.

•

We assessed perceptions related to emerging non-combusted tobacco products and NRT.

•

Some participants perceived that e-cigarettes are less harmful than combusted cigarettes.

•

Some participants perceived that e-cigarettes can be used as a cessation aid.

•

Participants generally perceived that NRT is ineffective and/or has side effects.