Abstract 3237: Electronic cigarettes and inflammation in the human lung
Authors: Song Min-Ae , Brasky Theodore M. , Freudenheim Jo L. , McElroy Joseph P. , Weng Daniel Y. , Ying Kevin L. , Nickerson Quentin A. , Reisinger Sarah A. , Wewers Mark D. , Shields Peter G. 
Published: August 2018

Background: The use of electronic cigarettes (e-cigs) is increasing rapidly among both adults and youth, including among both smokers and never-smokers, and is thought to be less harmful than cigarettes. However, biological changes including inflammation have not been studied in target organs such as the lung, particularly for e-cigs; further, it is not known if changes are reversible in smokers who switch to e-cigs.

Methods: We conducted a cross-sectional bronchoscopy study of e-cig users (n=13), cigarette smokers (n=16), and never-smokers (n=40), age 21-30, to assess inflammatory cell counts and cytokines in bronchoalveolar lavages (BAL) fluids. BAL total cell counts were measured using the Countess Automated Cell Counter. Differential cells were performed on stained cytospins by a blinded clinical histopathologist. Smoking-associated inflammatory cytokines were measured using a V-PLEX Plus Pro-inflammatory Panel. Non-parametric Mann-Whitney and Kruskal-Wallis tests were used for cell counts. Log10 transformed cytokines were used for 1-way ANOVA.

Results: Smokers averaged 16 cigarettes/day (SD: 4.7) for 7 years (SD: 4.1). E-cig users vaped an average e-liquid nicotine content of 12 mg/ml (SD: 7.6) and 8 ml/day (SD: 3.9), for an average of 3 years (SD: 0.9); mean time since smoking among e-cig users was 24 months (SD: 16) (2 were never-smokers). Smokers compared to never-smokers had significantly increased total cell counts, macrophages and neutrophils, and decreased lymphocytes (7.15E-05&lt;P&lt;0.05). Total cell concentration for the e-cig users were 35% lower than the smokers and 30% higher than the never smokers (overall P=0.0005). Total and differential cell counts were borderline or significantly different for the smokers compared to e-cig users, and followed the same trends for never-smokers compared to e-cig users. Inflammatory cytokines IL-1β, IL-6, and IL-8 were significantly higher for smokers compared to never-smokers, and were lower for IL-2 and IFN-γ (all P's &lt;0.002). Levels of these cytokines in e-cig users were corroborated by patterns of differences for the cell counts, where overall differences were highly significantly different; e-cig users were intermediate. IL-4, IL-10, IL-12p70, IL-13, and TNF-α did not differ across the groups. Time since last cigarette and cigarettes/day among e-cig users was not significantly correlated with any of the cell counts or cytokine levels.

Discussion: Inflammation differed for never-smokers and smokers, with markers of inflammation intermediate for e-cig users, consistent with the hypothesis that e-cigs are less harmful. Study of whether e-cig use is more harmful than never-use and never-smoking is warranted. Because this cross-sectional study provides only indirect evidence of causation, additional observation studies and randomized trials are needed to understand changes in inflammation for e-cig users, both former- never-smokers.

Citation Format: Min-Ae Song, Theodore M. Brasky, Jo L. Freudenheim, Joseph P. McElroy, Daniel Y. Weng, Kevin L. Ying, Quentin A. Nickerson, Sarah A. Reisinger, Mark D. Wewers, Peter G. Shields. Electronic cigarettes and inflammation in the human lung [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3237.