The effects of e‐cigarette use on asthma severity in adult BALB/c mice

Electronic cigarettes (e-cigarettes) are often perceived to be a less harmful alternative to tobacco cigarettes. Potentially due to this perception, they are used by people with pre-existing respiratory conditions, such as asthma, who otherwise would not smoke. Despite this, there are few studies exploring the health effects of e-cigarette use on pre-existing asthma. In this study, a house dust mite-induced allergic-airways disease phenotype was generated in adult BALB/c mice over 7 weeks. For the last 2 weeks of this period, mice were also exposed to either medical air, or tobacco smoke or e-cigarette aerosol (with or without nicotine) for 2 h/day. Twenty-four hours later, respiratory parameters including lung volume/function and responsiveness to methacholine were assessed. Biological samples were taken for analysis of pulmonary cellular inflammation and mediator levels, serum IgE and lung/airway structure. There were complex effects of exposure on respiratory outcomes. For example, tobacco smoke-exposed mice of both sexes were the most responsive to methacholine but had suppressed total cellular and eosinophilic inflammation. Female e-cigarette aerosol-exposed mice had impaired parenchymal mechanics at functional residual capacity compared with tobacco smoke-exposed mice, irrespective of nicotine. Interferon γ levels were suppressed in both e-cigarette-exposed groups. There was no effect of any exposure on IgE or lung structural parameters. E-cigarette aerosol exposure exacerbated aspects of an allergic airways disease phenotype in mice. This suggests that asthmatics should exercise increased caution if thinking of using e-cigarettes.