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

AbstractElectronic 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.