In yet another sign that electronic cigarettes are far from harmless, a new lab study suggests that vaping damages the cells that line the inside walls of blood vessels and could hasten heart trouble.
Lab-grown endothelial cells were more likely to die off or suffer from impaired function when exposed to e-cigarette vapour, the researchers reported.
A critical role in heart health
If this same effect occurs in the human body, then e-cigarette users potentially could be at increased long-term risk of heart disease and stroke, said senior researcher Dr Joseph Wu. He is director of the Stanford Cardiovascular Institute, in California.
"If you're a chronic e-cigarette [user], you're probably going to be prone to more vascular disease in the future," Wu said. "It doesn't have the carcinogens associated with smoking, but don't use e-cigarettes with the assumption that if I switch to e-cigarettes it will be good for my cardiovascular health."
Endothelial cells lining the interior surface of blood vessels play a critical role in heart health, the researchers explained.
These cells need to be flexible to help manage blood pressure, and if damaged they could attract more cholesterol plaques that contribute to narrowing of the arteries, and stroke, Wu said.
For the study, Wu and his colleagues grew endothelial cells from blood samples drawn from five smokers, five non-smokers, two e-cigarette users and two people who use both e-cigarettes and tobacco cigarettes.
These endothelial cells then were exposed to six types of vapour from different e-liquids purchased online by the researchers.
Not perfectly safe
Following exposure, the cells were more likely to die early and showed increased levels of DNA damage, the study authors said.
The cells also were less able to help form new blood vessels or participate in wound healing, the findings showed.
"The big picture is that, contrary to what people think, e-cigarettes are not perfectly safe," Wu said.
Exposure to cinnamon and menthol e-liquids proved particularly damaging to cells, the researchers reported. Caramel and vanilla flavours also disrupted the cells, but not as severely.
The findings were published online in the Journal of the American College of Cardiology.
Dr Rose Marie Robertson is deputy chief medical officer of the American Heart Association. She said, "The remarkable thing was there were very strong effects, both in terms of the specific mechanisms they looked at and that the effects were not very different between cells from e-cigarette smokers and cigarette smokers."
Wu said that the researchers suspect that different components of e-cigarette vapour might harm blood vessel cells in different ways.
Serious detrimental effects on cells
The vapour includes nicotine, flavourings and solvents, and all might contribute in different ways to cell death, oxidative stress on cells and inflammation, the study authors suggested.
Part of the problem is that e-cigarettes are using flavourings that have been approved by the US Food and Drug Administration for ingestion, but not necessarily for inhalation, Robertson noted.
"Gradually, the evidence is accruing that shows these compounds have serious detrimental effects on cells," Robertson said.
Use of e-cigarettes has skyrocketed since their introduction a decade ago.
The FDA estimates that more than 3.5 million middle and high school students used e-cigarettes in 2018, even though sales to minors are prohibited. One in five high school students has tried e-cigarettes.
There's a lot of concern that these teens will wind up using e-cigarettes long-term, and that the damage done to their blood vessels will worsen over time, Wu and Robertson said.
"It's important for e-cigarette users to realise that these chemicals are circulating within their bodies and affecting their vascular health," Wu said.
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