After uncovering a key mechanism that could explain how e-cigarettes harm the lungs, brain, and cardiovascular system, a team of researchers now calls for much stricter regulation of these electronic devices.
Electronic cigarettes — e-cigarettes, for short — were developed as a safer alternative to traditional cigarettes, in an effort to help wean smokers off their harmful habit.
However, evidence has increasingly come to light that the liquid that goes into an e-cigarette and the materials of the devices themselves contain dangerous levels of toxic substances that can harm health.
Moreover, researchers have found that e-cigarettes can provide a gateway to smoking and other addictive behaviors among teenagers, who may see these devices as a social trend.
And recently, various media outlets have reported several cases of adolescents being hospitalized with severe health problems from e-cigarette use.
The most recent report involves a 17-year-old who experienced such serious lung damage from e-cigarette use that he needed a double lung transplant.
"According to the [United States] Centers for Disease Control and Prevention, over 3.6 million children in the U.S. use e-cigarettes, with a jump of 78% — from 11.7% to 20.8% — among U.S. high school students reporting e-cigarette use from 2017 to 2018," reports Dr. Thomas Münzel, of the University Medical Centre Mainz, in Germany.
He continues, "And in the [United Kingdom], 1.6% of those aged 11–18 use e-cigarettes more than once a week, compared with 0.5% in 2015."
In light of these figures and the reports of dangers associated with e-cigarette use, Dr. Münzel and colleagues have conducted their own study — in humans and mice — to learn more about how and why these devices can damage vital organs.
In response to their findings, which appear in the European Heart Journal, the researchers now actively encourage policymakers to take more decisive measures in regulating e-cigarettes.
Uncovering underlying mechanisms
As part of their research, Dr. Münzel and the team first looked at how e-cigarette vapors would affect blood flow and artery stiffness in 20 "otherwise healthy smokers" both before they used an e-cigarette and 15 minutes after they had used one.
This experiment showed that using an e-cigarette just once increased participants' heart rates, made their arteries stiffer, and affected the functioning of their arterial lining, known as the endothelium, which plays a complex role in circulatory health.
Among other functions, the endothelium helps ensure that vessels dilate and constrict correctly, that toxic substances do not pass into the bloodstream, and that inflammation and blood clotting are regulated, when necessary.
The next step in the research was to find out more about the underlying mechanisms by which e-cigarettes affect health. To do this, the investigators exposed 151 mice to e-cigarette vapor for 20 minutes, six times a day over a period of 1, 3, or 5 days.
In doing so, the researchers found that the artificial vapors caused blood vessel damage in the rodents. The damage was general and, in blood vessels that oxygenate the lungs or brain, it occurred via an enzyme called NOX-2. This, the team explains, may be because NOX-2 plays a key role in regulating cellular health.
In mice that the researchers had engineered not to produce NOX-2, the e-cigarette vapors did not have the same effects. This may be because NOX-2 plays a key role in regulating cellular health.
Next, the investigators treated some mice with macitentan, a drug used to treat endothelial dysfunction and high blood pressure, and others with bepridil, a drug designed to prevent abnormal cell death attributed to high blood pressure or angina.
These mice did not experience endothelial dysfunction, abnormal cell death, or abnormal inflammation when exposed to e-cigarette vapors.
"The results of the present studies identified several molecular mechanisms whereby e-cigarettes can cause damage to the blood vessels, lungs, heart, and brain," says Dr. Münzel.
"This," he goes on to explain, "is a consequence of toxic chemicals that are produced by the vaping process and may also be present at lower concentrations in the liquid itself. Importantly, we identified an enzyme, NOX-2, that mediated all the effects of e-cigarettes on the brain and cardiovascular system, and we found that a toxic chemical called acrolein, which is produced when the liquid in e-cigarettes is vaporized, activated the damaging effects of NOX-2."
"The beneficial effects of macitentan and bepridil indicate that e-cigarettes have the capacity to trigger constriction of blood vessels and to impair our cells' antioxidant and survival systems," the researcher adds.
Study 'should serve as a warning'
In conclusion, Dr. Münzel emphasizes that, according to the current findings, e-cigarettes are harmful. Because of this, he calls on policymakers to regulate these devices much more strictly.
"Our data may indicate that e-cigarettes are not a healthy alternative to traditional cigarettes, and their perceived 'safety' is not warranted. In addition, we still have no experience [of] the health side effects of e-cigarettes arising from long term use," the researcher notes.
"The e-cigarette epidemic in the U.S. and Europe, in particular among our youth, is causing a huge generation of nicotine-addicted people who are being endangered by encouragement to switch from traditional cigarettes to e-cigarettes. Research like ours should serve as a warning [...] and aggressive steps should be taken to protect our children."
Dr. Thomas Münzel
The investigators also warn against trusting biased studies funded by e-cigarette producers, which may attempt to reassure the public about the supposed safety of e-cigarettes.
"Recent studies indicate that e-cigarette industry funding is more likely to lead to results that indicate that e-cigarettes are harmless," the researchers write in their study paper, mentioning that the current study did not receive any financial backing from stakeholders in the e-cigarette industry.