A new study published in the Journal of Clinical Investigation highlights health concerns related to the use of e-cigarettes. Using a mouse model, researchers from the Baylor College of Medicine have shown that chronic exposure to vapors from e-cigarettes can:
- Disrupt normal lung function
- Reduce the capacity of immune cells within the lungs to respond to viral infection
The above changes were observed in mice exposed to vapors without nicotine, suggesting more extensive investigation may be warranted to determine the safety of solvents in e-cigarettes.
"E-cigarettes currently are the most commonly consumed tobacco substitute in the adolescent population. More than 3 million high school age adolescents as well as about 10 million adults in the U.S. are active users," said corresponding author Farrah Kheradmand, in a recent press release.
Kheradmand explains that it was the discrepancies relating to safety reported in e-cigarette related studies that fueled the team’s efforts to further investigate: “… opposing views on the safety of e-cigarettes prompted one of my graduate students, Matthew Madison, to investigate the effects of chronic exposure to e-cigarette vapors and to conventional tobacco smoke on murine lung function."
As well as exploring effects on lung function the team investigated the impact of vapors on the functioning of immune cells within the lungs – honing in on one type in particular – macrophages.
Macrophages act as a first line of defense against viral infections, for example those caused by the influenza virus.
The study involved four groups of mice:
Group 1: Exposed to e-cigarette vapors with nicotine along with common vaping solvents vegetable glycerin and propylene glycol (in a ratio of 2:3).
Group 2: Exposed to vapors containing only solvents but no nicotine.
Group 3: Exposed to tobacco smoke.
Group 4: Exposed to clean air.
The mice were exposed to the above, for a period of four months, following a regimen that aimed to reflect someone who had begun smoking during their teenage years, until their fifth decade of life. This regimen noticeably increases the chances of someone developing emphysema.
As the team predicted, the mice exposed to cigarette smoke (Group 3) had extremely damaged lungs and excessive inflammation similar to that observed in human smokers with emphysema.
The team were surprised to find that mice treated with e-cigarette vapors made of propylene glycol and vegetable glycerin solvents only (Group 2) also exhibited damage to their lungs. Whilst this group didn’t experience inflammation or emphysema, the researchers did find evidence of excess lipid buildup within the lungs, causing disruption to normal lung function and structure of the lungs.
The excess buildup of lipids was caused by irregular turnover of the protective layer of fluid in the lungs. The buildup was also observed inside macrophages residing in the lungs.
When these lipid-filled macrophages were exposed to the influenza virus, they displayed a “reduced” response to the infection.
Kheradmand concludes: "In summary, our experimental findings reveal that, independent of nicotine, chronic inhalation e-cigarette vapor disrupts normal murine lung function and reduces the ability of resident immune cells to respond to infection, increasing the susceptibility to diseases such as influenza."
"Our experimental findings share similarities with previous multiple case reports describing the presence of lipid-laden macrophages in pulmonary fluid from people with e-cigarette-associated pneumonia. Our results support further investigations into the solvents used in vaping."
Reference: Madison, et al. (2019) Electronic cigarettes disrupt lung lipid homeostasis and innate immunity independent of nicotine. Journal of Clinical Investigation. DOI: https://doi.org/10.1172/JCI128531.