Nose-only Exposure to Cherry and Tobacco Flavored E-cigarettes Induced Lung Inflammation in Mice in a Sex-dependent Manner

Abstract

Flavoring chemicals utilized in electronic nicotine delivery systems (ENDS) have been shown to result in an increase in cellular inflammation, meanwhile, the effects of fruit and tobacco flavors on lung inflammation by nose-only exposures to mice are relatively unknown. We hypothesized that C57BL/6J mice exposed to flavored e-cigarettes would result in an increase in lung inflammation. C57BL/6J mice were exposed to air, propylene glycol/vegetable glycerin (PG/VG), and e-liquids Apple, Cherry, Strawberry, Wintergreen, and Smooth & Mild Tobacco, for one hour per day for a three day exposure. Quantification of flavoring chemicals was measured by proton nuclear magnetic resonance spectroscopy (1H NMR), differential cell counts by flow cytometry, pro-inflammatory cytokines/chemokines by ELISA, and matrix metalloproteinase levels by western blot. Exposure to PG/VG, Apple, and Smooth & Mild Tobacco resulted in an increase in neutrophil cell count in lung bronchoalveolar lavage fluid (BALF). Strawberry exposure increased KC levels in BALF while in lung homogenate KC levels were increased in PG/VG, Cherry, and Smooth & Mild Tobacco exposure. Exposure to PG/VG and Cherry increased IL-6 levels and in all exposed mice there was a male-specific decrease in MCP-1 levels in lung homogenate. Mice exposed to PG and VG, Apple, Cherry, and Wintergreen resulted in an increase in MMP2 levels. Our results indicate that female mice exposed to cherry flavored e-liquids and male mice exposed to tobacco flavored e-liquids resulted in an increase in inflammation, while exposure to mint flavored e-liquids resulted in a decrease in inflammatory cytokine and an increase in tissue repair proteins. This study revealed that flavored-based e-cigarette exposure elicited sex-specific alterations in lung inflammation, with cherry flavors/benzaldehyde eliciting female-specific increases in inflammation. This highlights the toxicity of flavored chemicals and the further need for regulation of flavoring chemicals.

Chronic low‐level JUUL aerosol exposure causes pulmonary immunologic, transcriptomic, and proteomic changes

“…Moreover, as in this study using mango‐flavored‐JUUL products, the impact of different flavors is notable, particularly fruit flavors and tobacco flavors 57,58 . However, not all studies show that e‐cigarettes increase lung neutrophils, 25 and some studies show that PG/VG alone increases neutrophils in the lungs, 58 a finding that contrasts our results. These differences in outcomes may be related to differences in e‐cigarette brand/liquid, exposure regime, and/or mouse strain.…”

“…These findings are in agreement with several other in vivo studies investigating the pulmonary outcomes of e‐cigarette exposure, including the ability of inhaled aerosols to increase lung neutrophils 28,50,57 . Moreover, as in this study using mango‐flavored‐JUUL products, the impact of different flavors is notable, particularly fruit flavors and tobacco flavors 57,58 . However, not all studies show that e‐cigarettes increase lung neutrophils, 25 and some studies show that PG/VG alone increases neutrophils in the lungs, 58 a finding that contrasts our results.…”