Project description:The main constituents of electronic cigarette liquids are nicotine, propylene glycol (PG), and vegetable glycerin (VG), together with distilled water and flavors. To assess the toxicity of PG/VG mixtures with and without nicotine as basic components of liquids used in e-cigarettes, a 90-day rat inhalation study according to the Organization for Economic Co-operation and Development test guideline 413 was conducted. Sprague-Dawley (SD) rats were nose-only exposed, 6 h/day, 5 days/week to filtered air, or nebulized vehicle (saline), or three concentrations of PG/VG (0.174 mg PG/l + 0.210 mg VG/l; 0.520 mg PG/l + 0.630 mg VG/l; 1.520 mg PG/l + 1.890 mg VG/l) – with (test item) and without (reference item) 23 µg nicotine/L. Standard toxicological endpoints were complemented by molecular analyses using transcriptomics, proteomics, and lipidomics. Compared to vehicle exposure, the tested PG/VG aerosols showed only very limited biological effects with no signs of toxicity, both for the standard toxicological endpoints (e.g., histopathology, clinical chemistry) and the systems toxicological analyses (transcriptomics, proteomics, and lipidomics). The addition of nicotine to the PG/VG aerosols (23 µg/l) resulted in effects in line with nicotine effects in previous studies. These included up-regulation of xenobiotic enzymes (Cyp1a1 and Fmo3) in the lung and metabolic effects, e.g., reduction in serum lipid concentrations and changes in the expression of metabolic enzymes in the liver. Signs of a generalized stress response to nicotine exposure such as decreased thymus weights were observed; and likely, a subset of the observed metabolic alterations was interlinked with this generalized stress response. Under the conditions of this 90-day SD rat inhalation study, no toxicologically relevant effects of PG/VG aerosols (up to 1.520 mg PG/l + 1.890 mg VG/l) were observed, and the no observed adverse effect level (NOAEL) for PG/VG/nicotine was determined to be 438/544/6.7 mg/kg/day. Further the study demonstrated how complementary systems toxicology analyses can reveal, also in the absence of observable adverse effects, subtoxic and adaptive responses to pharmacologically active compounds such as nicotine.

Project description:The main constituents of electronic cigarette liquids are nicotine, propylene glycol (PG), and vegetable glycerin (VG), together with distilled water and flavors. To assess the toxicity of PG/VG mixtures with and without nicotine as basic components of liquids used in e-cigarettes, a 90-day rat inhalation study according to the Organization for Economic Co-operation and Development test guideline 413 was conducted. Sprague-Dawley (SD) rats were nose-only exposed, 6â€‰h/day, 5 days/week to filtered air, or nebulized vehicle (saline), or three concentrations of PG/VG (0.174 mg PG/l + 0.210 mg VG/l; 0.520 mg PG/l + 0.630 mg VG/l; 1.520 mg PG/l + 1.890 mg VG/l) with (test item) and without (reference item) 23 µg nicotine/L. Standard toxicological endpoints were complemented by molecular analyses using transcriptomics, proteomics, and lipidomics. Compared to vehicle exposure, the tested PG/VG aerosols showed only very limited biological effects with no signs of toxicity, both for the standard toxicological endpoints (e.g., histopathology, clinical chemistry) and the systems toxicological analyses (transcriptomics, proteomics, and lipidomics). The addition of nicotine to the PG/VG aerosols (23 Âµg/l) resulted in effects in line with nicotine effects in previous studies. These included up-regulation of xenobiotic enzymes (Cyp1a1 and Fmo3) in the lung and metabolic effects, e.g., reduction in serum lipid concentrations and changes in the expression of metabolic enzymes in the liver. Signs of a generalized stress response to nicotine exposure such as decreased thymus weights were observed; and likely, a subset of the observed metabolic alterations was interlinked with this generalized stress response. Under the conditions of this 90-day SD rat inhalation study, no toxicologically relevant effects of PG/VG aerosols (up to 1.520 mg PG/l + 1.890 mg VG/l) were observed, and the no observed adverse effect level (NOAEL) for PG/VG/nicotine was determined to be 438/544/6.7 mg/kg/day. Further the study demonstrated how complementary systems toxicology analyses can reveal, also in the absence of observable adverse effects, subtoxic and adaptive responses to pharmacologically active compounds such as nicotine.

Project description:Smoking cessation is the most effective measure for reducing the risk of smoking-related diseases but switching to less harmful products (modified-risk tobacco products) can be an alternative for smokers who would otherwise not quit. In an 18-month chronic carcinogenicity/toxicity study in A/J mice (OECD Test Guideline 453), we assessed aerosol from the Tobacco Heating System 2.2 (THS 2.2), a candidate modified-risk tobacco product based on the heat-not-burn principle, compared with 3R4F cigarette smoke (CS). To capture toxicity- and disease-relevant mechanisms, we complemented standard toxicology endpoints with in-depth systems toxicology analyses. Briefly, female A/J mice were exposed to fresh air (Sham), three concentrations of THS 2.2 aerosol corresponding to nicotine concentrations of 6.7 (Low; L), 13.4 (Medium; M), and 26.8 (High; H) µg nicotine\L test atmosphere, or to one concentration of 3R4F CS (13.4 µg nicotine\L test atmosphere) in whole-body exposure chambers for 6 h per day, 5 days per week, and up to 18 months. Interim dissections were scheduled for months 1, 5, and 10. Male mice were exposed to either fresh air (Sham) or to the high THS 2.2 aerosol concentration for 15 months. Chronic toxicity and carcinogenicity endpoints outlined in the OECD protocol were assessed; detailed findings will be reported separately (Wong et al.). For evaluation of non-OECD endpoints following a systems toxicology approach (proteomics, transcriptomics, and genomics), several tissues were collected for further analysis. Housing and all procedures involving animals were performed in accordance with the approved Institutional Animal Care and Use Committee protocol in an Agri-Food & Veterinary Authority of Singapore-licensed and Association for Assessment and Accreditation of Laboratory Animal Care International-accredited facility, where the care and use of the animals for scientific purposes were in accordance with the National Advisory Committee for Laboratory Animal Research (NACLAR) Guideline (NACLAR, 2004). Animals allocated to the omics endpoints (N=8-20) were dissected within 16-24 h of the last exposure and following randomization of all planned necropsies for the dissection time point in question. All efforts to minimize potential nucleic acid and protein degradation were made, and samples were frozen as rapidly as possible once ex vivo. Lungs collected after month 1 were snap-frozen and the right caudal lobe was used for proteomics analysis. These are the protein expression data for lung tissue assessed by iTRAQ®-based quantitative proteomics.

Dataset Information

Systems toxicological assessment of the mentholated Tobacco Heating System 2.2 product revealed reduced cellular and molecular exposure effects compared to cigarette smoke [quantitative proteomics of rat nasal epithelium]

Publications

Evaluation of the Tobacco Heating System 2.2. Part 7: Systems toxicological assessment of a mentholated version revealed reduced cellular and molecular exposure effects compared with mentholated and non-mentholated cigarette smoke.

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