The use of electronic cigarettes (e-cigarettes) potentially offers a safer alternative to conventional tobacco products. The advance in molecular biology and computational sciences offers new perspective to assess adverse biological responses for product risk assessment by combining omics screens with knowledge-based biological pathways. Our aim was to compare transcriptomic perturbations in MucilAirÔ, a commercially available lung epithelial tissue, after short repeated exposure to cigarette smoke (3R4F) and e-cigarette (Vype ePen) aerosols. We performed deep RNA sequencing and secreted inflammatory cytokine profiling postexposure. One hundred twenty-three genes were differentially expressed at fold change (FC) >1.5 and p-false discovery rate (pFDR) <0.1 for 3R4F exposure and 0 genes for Vype ePen aerosol exposure. When a relaxed filter pFDR <0.5 and FC >1.5 was applied, 29 genes were identified with e-cigarette aerosol exposure and used for validation of potential candidates by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Gene enrichment analysis was conducted and predicted a response to 3R4F smoke exposure in biological processes involving inflammation and oxidative stress pathways. No enrichment could be performed for Vype ePen aerosol exposure due to the lack of regulated gene candidates at those exposure conditions even after qRT-PCR validation. Of a panel of 33 cytokines screened, 8 were upregulated (FC >1.5 p < 0.05) following 3R4F smoke exposure, which was in agreement with our enrichment analysis. In conclusion, aerosol from the tested e-cigarette caused limited perturbations in gene and inflammatory cytokine expression compared to conventional cigarette smoke, as assessed using next-generation sequencing-based systems biology approaches in 3D commercially available reconstituted lung epithelial tissues.

Assessment of novel tobacco and nicotine products for their harm reduction potential compared with cigarettes is of significance for regulators and public health. The National Research Council's report, ''Toxicity Testing in the 21st Century,'' outlines recent advances in molecular biology and the utility of human in vitro systems in toxicity testing. Such approaches could enable efficient, ethical, and economical risk assessment of chemicals and chemical mixtures. We investigated the potential of a simple in vitro lung model to discriminate between a commercially available cigarette (CC) and a reduced toxicant prototype (RTP) cigarette, which yielded significantly reduced toxicant emissions compared with the CC. The investigation compared cytotoxicity, oxidative stressrelated and proinflammatory endpoints, associated with smoking-related disease development. Furthermore, we assessed the discriminatory potential of the model upon exposure to a selection of test matrices, which captured different fractions of the cigarette smoke. RTP whole smoke (WS) was significantly less cytotoxic than CC; however, there was no significant difference with respect to cytokine expression, namely interleukin (IL)-6, IL-8, and matrix-metalloproteinase-1 secretion. The RTP aqueous extract significantly reduced intracellular oxidant production and antioxidant depletion compared with CC. Dose-related responses were observed with some RTP and CC particulate matter (PM) exposures, but they were shown to not be significantly different from each other except for antioxidant depletion. RTP PM induced significantly less depletion of GSH compared with PM from the CC cigarette. The ability of this model to differentiate between CC and RTP WS cytotoxicity and oxidative stress suggests that it could be a useful tool to support regulatory submissions for novel tobacco and nicotine delivery products.