ABSTRACT: A 7-month inhalation study in C57BL/6 mice was conducted to evaluate long-term respiratory toxicity of e-vapor aerosols compared to cigarette smoke and to assess the impact of smoking cessation or switching to an e-vapor product after 3 months of exposure to 3R4F cigarette smoke (CS). In this study, we performed a chronic inhalation (4 h/day, 5 d/week, up to 7 months) study in C57BL/6 mice using a commercial (MarkTen®) e-vapor product and a combustible reference cigarette (3R4F) using a Switching and Cessation study design. A commercial e-vapor product (MarkTen® device [version 2.6.8]; “Test Red”) was supplied by Altria Client Services LLC (Richmond, VA, USA). The Test Red formulation was composed of aerosol formers (propylene glycol [PG] and vegetable glycerol [VG]), ~4% nicotine by weight, and flavors (non-menthol). The 3R4F commercial reference cigarettes were purchased from the University of Kentucky (Lexington, KY). HEPA filtered air at the testing facility (Battelle, West Jefferson, OH) was used as Sham Control. General procedures for animal care and housing met the Association for Assessment and Accreditation of Laboratory Animal Care (AAALAC) recommendations and requirements stated in the “Guide for Care and Use of Laboratory Animals” [National Research Council (NRC)] and approved by the Institutional Animal Care and Use Committee (IACUC). Female C57BL/6 mice were received from Charles River Kingston (Stone Ridge, NY). Test atmosphere was generated from smoking machines and delivered to the mice through a nose-only exposure system. The modified Cooperation Centre for Scientific Research Relative to Tobacco (CORESTA) Reference Method 81 regimen (55/30/5: a 55 ± 0.3 mL puff volume, a puff every 30 seconds, a 5-second puff duration) was used to generate e-vapor aerosol for 130 puffs/cartridge. Mainstream smoke from 3R4F cigarette was generated using a modified Health Canada Intense regimen (55/30/2: a 55 ± 0.3 mL puff volume, a puff every 30 seconds, a 2-second puff duration, and a near-square puff profile) for 8 puffs/cigarette. Female C57BL/6 mice (~10 weeks old) were randomly assigned based on body weight to one of five exposure groups: Sham Control, 3R4F CS, Test Red, Switching, and Cessation. Mice were exposed to 3R4F CS (550 µg/L TPM) or e-vapor aerosols (Test Red; 1100 µg/L TPM) via nose-only inhalation up to 4 h/day, 5 d/week for up to 7 months. After the first 3 months of exposure, groups of 3R4F CS mice were subjected to exposures of: (1) Test Red aerosol (“Switching”) or (2) filtered air (“Cessation”), while a group of mice continued to be exposed to 3R4F CS. Here, the protein expression data for lung tissue assessed by iTRAQ®-based quantitative proteomics is reported.
Bjoern Titz 
