Long-term use of e-cigarettes and regular cigarettes can have harmful effects on blood vessels

Long-term use of e-cigarettes and regular cigarettes can have harmful effects on blood vessels

Long-term use of electronic cigarettes (e-cigarettes) or vaping can significantly impair the functioning of the body's blood vessels and increase the risk of cardiovascular disease. Additionally, using e-cigarettes and regular cigarettes may pose an even greater risk than using either of these products alone. These results come from two new studies supported by the National Heart, Lung, and Blood Institute (NHLBI), part of the National Institutes of Health (NIH).

The findings, appearing today in the journal Arteriosclerosis, Thrombosis, and Vascular Biology, add to growing evidence that long-term use of e-cigarettes can harm a person's health. Researchers have known for years that tobacco smoking can damage blood vessels. However, the effects of e-cigarettes on cardiovascular health are poorly understood. The two new studies – one on humans, the other on rats – sought to change that.

In our human study, we found that chronic e-cigarette users had impaired blood vessel function, which could put them at increased risk of heart disease. It suggests that chronic e-cigarette users may be at similar risk of vascular disease as chronic smokers.”

Matthew L. Springer, Ph.D., Professor of Medicine, Department of Cardiology, University of California, San Francisco

Springer is the leader of both studies.

In this first study, Springer and his colleagues collected blood samples from a group of 120 volunteers, including long-time e-cigarette users, long-time cigarette smokers and non-users. The researchers defined long-term e-cigarette use as more than five times per week for more than three months and long-term cigarette use as smoking more than five cigarettes per day.

They then exposed each of the blood samples to human blood vessel cells (endothelial cells) cultured in the laboratory and measured the release of nitric oxide, a chemical marker used to assess the proper function of endothelial cells. They also tested cell permeability, the ability of molecules to pass through one layer of cells to the other side. Too much permeability causes vessels to leak, impairing function and increasing the risk of cardiovascular disease.

The researchers found that the blood of e-cigarette users and smokers caused a significantly greater decrease in nitric oxide production by blood vessel cells than the blood of non-users. Remarkably, the researchers found that blood from e-cigarette users also caused more permeability in blood vessel cells than the blood from tobacco smokers and non-users. The blood of e-cigarette users also caused a greater release of hydrogen peroxide by blood vessel cells than the blood of non-users. Any of these three factors may contribute to impaired blood vessel function in e-cigarette users, the researchers said.

Additionally, Springer and his team discovered that e-cigarettes have harmful cardiovascular effects in different ways than tobacco smoke. Specifically, they found that the blood of tobacco smokers had higher levels of certain circulating biomarkers of cardiovascular risk and the blood of e-cigarette users had increased levels of other circulating biomarkers of cardiovascular risk.

“These results suggest that using the two products together, as many people do, could increase their health risks compared to using them individually,” Springer said. “We didn’t expect that.”

In the second study, researchers tried to find out whether there are certain components of tobacco smoke or e-cigarette vapor that are responsible for damaging blood vessels. In studies with rats, they exposed the animals to various substances from tobacco smoke or e-cigarettes. These included nicotine, menthol (a cigarette additive), the gases acrolein and acetaldehyde (two chemicals found in both tobacco smoke and e-cigarette vapor), and inert carbon nanoparticles to represent the particulate nature of smoke and e-cigarette vapor (which contains oily droplets).

Using special arterial flow measurements, the researchers showed 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 irritation of the respiratory tract, which triggers biological signals in the vagus nerve that somehow lead to blood vessel damage, perhaps through an inflammatory process. The vagus is a long nerve that extends from the brain and connects the respiratory tract to the rest of the nervous system and plays a key role in heart rate, breathing and other functions. The researchers showed that severing the nerve in rats prevented blood vessel damage caused by tobacco smoke, demonstrating its key role in the process.

“We were surprised that there was not a single component that could be removed to stop the harmful effects of smoke or fumes on blood vessels,” Springer said. “As long as an irritant is present in the respiratory tract, blood vessel function may be impaired.”

The finding has implications for efforts to regulate tobacco products and e-cigarettes because it underscores how difficult it is to pinpoint an ingredient responsible for damaging blood vessels. “What I like to tell people is this: Just breathe clean air and avoid using these products,” Springer said.

Lisa Postow, Ph.D., an NHLBI program officer in NHLBI's Division of Pulmonary Diseases, agreed that the study results "provide further evidence that exposure to e-cigarettes may result in adverse cardiovascular health effects." She added that more data is needed to fully understand the health effects of e-cigarettes. The NIH and others continue to research this area.

Source:

National Institutes of Health

References:

• Chronischer Gebrauch von E-Zigaretten beeinträchtigt die Endothelfunktion auf physiologischer und zellulärer Ebene. Arteriosklerose, Thrombose und Gefäßbiologie. DOI: 10.1161/ATVBAHA.121.317749
• Die Beeinträchtigung der Endothelfunktion durch Zigarettenrauch wird nicht durch einen bestimmten Rauchbestandteil verursacht, sondern durch vagalen Eintrag aus den Atemwegen. Arteriosklerose, Thrombose und Gefäßbiologie. DOI: 10.1161/ATVBAHA.122.318051

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