Researchers have known for years that tobacco smoking can cause damage to blood vessels.
However, the effects of e-cigarettes on cardiovascular health have been poorly understood. The two new studies—one on humans, the other on rats—aimed to change that.
In two studies from the University of California in San Francisco, scientists found that long-term use of e-cigarettes, or vaping, can strongly impair the function of the body’s blood vessels, increasing the risk for heart disease.
Additionally, the use of both e-cigs and regular cigarettes may cause an even greater risk than the use of either of these products alone.
In the study, researchers found that chronic e-cigarette users had impaired blood vessel function, which may put them at increased risk for heart disease.
It indicates that chronic users of e-cigarettes may experience a risk of vascular disease similar to that of chronic smokers.
In this first study, the team collected blood samples from a group of 120 volunteers that included long-term e-cigarette users, long-term cigarette smokers, and non-users.
The researchers defined long-term e-cigarette use as more than five times/week for more than three months and defined long-term cigarette use as smoking more than five cigarettes per day.
They then exposed each of the blood samples to cultured human blood vessel (endothelial) cells in the laboratory and measured the release of nitric oxide, a chemical marker used to evaluate the proper functioning of endothelial cells.
The researchers found that blood from e-cigarette users and smokers caused a much greater decrease in nitric oxide production by the blood vessel cells than the blood of non-users.
Notably, the researchers found that blood from e-cig users also caused more permeability in the blood vessel cells than the blood from both tobacco smokers and non-users.
The e-cigarette users’ blood also caused a greater release of hydrogen peroxide by the blood vessel cells than the blood of the non-users.
Each of these three factors can contribute to the impairment of blood vessel function in e-cig users, the researchers said.
In addition, the team discovered that e-cigarettes had harmful cardiovascular effects in ways that were different from those caused by tobacco smoke.
Specifically, they found that blood from tobacco smokers had higher levels of certain circulating biomarkers of cardiovascular risks, and the blood from e-cig users had elevated levels of other circulating biomarkers of cardiovascular risks.
In the second study, the researchers exposed rats to various substances found in tobacco smoke or e-cigarettes.
They found that blood vessel damage does not appear to be caused by a specific component of cigarette smoke or e‑cigarette vapor.
Instead, they said, it appears to be caused by airway irritation that triggers biological signals in the vagus nerve that somehow leads to blood vessel damage, possibly through an inflammatory process.
The vagus is a long nerve extending from the brain that connects the airway to the rest of the nervous system and plays a key role in heart rate, breathing, and other functions.
The researchers showed that detaching the nerve in rats prevented blood vessel damage caused by tobacco smoke, demonstrating its key role in this process.
The findings showed that there was not a single component that you could remove to stop the damaging effect of smoke or vapors on the blood vessels.
The finding has implications for efforts to regulate tobacco products and e-cigarettes, as it underscores how difficult it is to pinpoint any one ingredient in them that is responsible for blood vessel damage.
If you care about smoking, please read studies about how to manage chronic lung disease amid COVID-19, and E-cigarettes change inflammation in the brain, heart, lungs, and colon.
For more information about health, please see recent studies about why smokers have a lower risk of COVID-19, and results showing scientists find the cause of lung cancer in never smokers.
The studies were conducted by Matthew L. Springer et al and published in the journal Arteriosclerosis, Thrombosis, and Vascular Biology.
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