Flavored e-cigarettes without nicotine were shown to have differing asthma outcomes on mice based on the flavor, indicating that some flavors may worsen the severity of allergic airways disease, according to a study published today in the journal Scientific Reports.
E-cigarette use has risen to an estimated 9% in 18-24 year-old Americans, possibly correlated to unverified suggestions by e-cig manufacturing companies that their products are safer than traditional cigarettes. Recent cases of mysterious lung illnesses related to vaping have caused federal entities such as the FDA and CDC to conduct public health investigations to determine causes of the growing national outbreak. Due to these events, the Australian Medical Association have already imposed regulations on e-cigarettes.
As flavored vapors in e-cigarettes are preferred by users, researchers from the University of Technology Sydney (UTS), University of Vermont, and the Woolcock Institute of Medical Research, aimed to delineate the respiratory effect of certain flavors on mice.
The study utilized a novel asthma model to investigate the effect of a range of popular e-cig flavors, without or with 12 mg/mL nicotine:
- Mice were challenged with PBS or house dust mite (HDM) (HDM occurred days 0, 7, 14-18) and exposed to room air or e-cig aerosol for 30 minutes daily, 6 days a week for 18 days
- E-cig flavors cinnacide, black licorice, banana pudding, and kola were tested, as well as, a vehicle control (50% vegetable glycerin (VG), 50% propylene glycol (PG))
- Mice assessed 72 hours after final HDM challenge
Data revealed that based on the flavor, e-cigarette vapors without nicotine can alter allergic airways disease. The effect of nicotine-free e-cig exposure varied among the flavors as banana pudding increased soluble lung collagen (P = .049), black licorice increased airway inflammation banana pudding increased soluble lung collagen (P = .089), and cinnicide suppressed airway inflammation (P = .045) while also increasing peripheral airway hyperresponsiveness (AHR) (P = .02). The stark change in conditions for allergic airways disease reveals a distinct effect through each non-nicotine flavor.
Vehicle control PG/VG and flavors with nicotine, however, had no effect on AHR or airway remodeling. The authors noted that the suppressed airway inflammation in the mice exposed to flavors with nicotine was likely caused by nicotine’s known anti-inflammatory properties. Findings with tobacco smoke have associated these properties to abnormal eosinophil migration into the airways. In the study, the mice exposed to allergic airways disease exhibited reduced eosinophilia similar to that of asthmatics who smoke tobacco cigarettes compared with those who do not. This effect reveals consistent findings between mice and asthmatics.
Lead study author David Chapman, MD, translational physiologist at UTS, highlighted that findings were “especially important for those with respiratory disease, whom are vulnerable to the effects of smoking,” said Chapman. For these affected individuals, Chapman described how the distinct effects of each e-cigarette flavor may not all have the same consequences on lung health. Due to potentially increased severity of asthma outcomes in e-cigarette users, the authors noted that restrictions on certain flavors are warranted.
“Future investigation into the individual chemical constituents of e-cigarettes driving these toxic effects may provide important insight for the regulation of e-cigarettes,” said the authors.
Chapman DG, Casey DT, Ather JL, et al. The effect of flavored e-cigarettes on murine allergic airways disease. [published online September 20, 2019]. Sci Rep. doi: 10.1038_s41598-019-50223-y.ris.