Exposure to nicotine-free and flavor-free e-cigarette vapors modifies the pulmonary response to tobacco cigarette smoke in female mice.

Introduction:
This article explores the impact of electronic cigarette (e-cigarette) vapors, both alone and in combination with tobacco smoke, on pulmonary health in mice. The study is particularly interested in the effects of e-cigarette vapors on lung circadian rhythm regulatory genes and immune cell populations.

Key Points:

* The study used well-established mouse models to investigate the impact of dual exposure to e-cigarette vapors and tobacco smoke on lung homeostasis.
* Mice were exposed to tobacco smoke for 2 hours/day in the morning and to e-cigarette vapors for 2 hours/day in the afternoon, 5 days/week for 8 weeks.
* Exposure to e-cigarette vapors led to significant decreases in the expression of nr1d2 and a tendency for increased expression for arntl and decreased expression for per1.
* Dual exposure to e-cigarette vapors and tobacco smoke resulted in significant changes in the expression of arntl, nr1d1, nr1d2, per2, and per3.
* Exposure to e-cigarette vapors alone did not induce cellular infiltration in the bronchoalveolar lavage (BaL), but it did reduce the size of alveolar macrophages and increase BaL IL-1 levels.
* Dual exposure to e-cigarette vapors and tobacco smoke reduced the size of alveolar macrophages and lung tissue icam1, vcam1, and pigr mRNa levels.
* Exposure to e-cigarette vapors alone or with cigarette smoke caused reduced levels of icam1, vcam1, integrins, and a receptor involved in circadian immune cell recruitment, leading to potential alterations in cell recruitment.
* Dual exposure to e-cigarette vapors and tobacco smoke increased airway resistance and Newtonian resistance.

Main Message:
The study suggests that e-cigarette vapors, even without nicotine or flavors, could affect how the lungs react to tobacco cigarette smoke exposure in dual users, potentially altering the pathological course triggered by smoking. The findings highlight the importance of considering the potential impacts of e-cigarette use on pulmonary health, particularly in the context of dual use with tobacco cigarettes.

Lechasseur a, huppé Ca, Talbot M, et al. Exposure to nicotine-free and flavor-free e-cigarette vapors modifies the pulmonary response to tobacco cigarette smoke in female mice. american journal of physiology Lung cellular and molecular physiology. 2020;319(4):L717-L727. doi:10.1152/ajplung.00037.2020