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. 2015 Apr 8;12(4):3915-25.
doi: 10.3390/ijerph120403915.

Evaluation of E-cigarette liquid vapor and mainstream cigarette smoke after direct exposure of primary human bronchial epithelial cells

Stefanie Scheffler  1 , Hauke Dieken  2 , Olaf Krischenowski  3 , Christine Förster  4 , Detlev Branscheid  5 , Michaela Aufderheide  6
Affiliations

Evaluation of E-cigarette liquid vapor and mainstream cigarette smoke after direct exposure of primary human bronchial epithelial cells

Stefanie Scheffler et al. Int J Environ Res Public Health. .

Abstract

E-cigarettes are emerging products, often described as "reduced-risk" nicotine products or alternatives to combustible cigarettes. Many smokers switch to e-cigarettes to quit or significantly reduce smoking. However, no regulations for e-cigarettes are currently into force, so that the quality and safety of e-liquids is not necessarily guaranteed. We exposed primary human bronchial epithelial cells of two different donors to vapor of e-cigarette liquid with or without nicotine, vapor of the carrier substances propylene glycol and glycerol as well as to mainstream smoke of K3R4F research cigarettes. The exposure was done in a CULTEX® RFS compact module, allowing the exposure of the cells at the air-liquid interface. 24 h post-exposure, cell viability and oxidative stress levels in the cells were analyzed. We found toxicological effects of e-cigarette vapor and the pure carrier substances, whereas the nicotine concentration did not have an effect on the cell viability. The viability of mainstream smoke cigarette exposed cells was 4.5-8 times lower and the oxidative stress levels 4.5-5 times higher than those of e-cigarette vapor exposed cells, depending on the donor. Our experimental setup delivered reproducible data and thus provides the opportunity for routine testing of e-cigarette liquids to ensure safety and quality for the user.

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Figures

Figure 1
Figure 1
Cell viability of NHBE cells after exposure. The results are given as mean of five (NHBE48) and three (NHBE33) independent experiments with three samples each + standard deviation. The asterisks indicate the statistical significance compared to clean air exposed cells, the hash marks compared to cells exposed to e-cigarette vapor with 0% nicotine. The relevance of the significance is explained in Section 2.5.
Figure 2
Figure 2
Oxidative stress levels in NHBE cells after exposure. The results are given as mean of five (NHBE48) and three (NHBE33) independent experiments with three samples each + standard deviation. The asterisks indicate the statistical significance compared to clean air exposed cells, the hash marks compared to cells exposed to e-cigarette vapor with 0% nicotine. The relevance of the significance is explained in Section 2.5.
Figure 3
Figure 3
Puff-adjusted values for cell viability of NHBE cells after exposure. The results are given as mean of five (NHBE48) and three (NHBE33) independent experiments with three samples each + standard deviation. The asterisks indicate the statistical significance compared to clean air exposed cells, the hash marks compared to cells exposed to e-cigarette vapor with 0% nicotine. The relevance of the significance is explained in Section 2.5.
Figure 4
Figure 4
Puff-adjusted values for oxidative stress levels in NHBE cells after exposure. The results are given as mean of five (NHBE48) and three (NHBE33) independent experiments with three samples each + standard deviation. The asterisks indicate the statistical significance compared to clean air exposed cells, the hash marks compared to cells exposed to e-cigarette vapor with 0% nicotine. The relevance of the significance is explained in Section 2.5.
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