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E-cigarettes linked with blood vessel damage

Cigarettes and e-cigarettes both impaired blood vessel function and caused inflammation, researchers found. CatherineLProd / Shutterstock

Smoking cigarettes or other tobacco products has been proven to cause a host of health problems, from lung cancer to heart disease. In the past decade, electronic cigarettes, or e-cigarettes, have risen in popularity as a potentially safer alternative. But recent studies suggest that these products have their own health risks.

To better understand the effects of e-cigarette use, or vaping, on the cardiovascular system, NIH-funded researchers led by Dr. Matthew Springer from the University of California, San Francisco recruited 120 adults aged 21 to 50. The volunteers were in overall good health, with no known heart problems. Of the 120, 42 regularly used e-cigarettes, 28 smoked conventional cigarettes, and 50 used neither.

The researchers tested blood samples from all volunteers for changes in chemicals involved in blood flow. They also used ultrasound to measure blood-vessel function in a subset of people from each group. Results were published on October 26, 2022, in Arteriosclerosis, Thrombosis, and Vascular Biology.

Compared with blood vessels in nonsmokers, those in both cigarette smokers and e-cigarette users were less able to expand. This difference remained when the researchers accounted for differences in age, sex, and other measurements of heart function.

The team next exposed cultured blood-vessel cells to the volunteers’ blood serum. Serum from smokers or e-cigarette users caused less nitric oxide to be released by the cells than serum from nonusers. Nitric oxide helps control the normal flow of blood in the vessels. Serum from e-cigarette users also caused the cells to become more permeable, or leaky, than serum from either from smokers or nonusers. This is a sign of impaired blood vessel function.

The researchers then exposed cultured blood-vessel cells to chemicals isolated from both cigarettes and e-cigarettes. Surprisingly, these exposures didn’t change nitric oxide production or permeability in the cells. This suggested that the body’s response to chemical exposure, not the chemicals directly, was driving the cell damage observed.

The team found that both smokers and e-cigarette users had signs in their blood of increased inflammation and higher risk of blood clots. However, the specific molecules that were altered differed between the two groups. Further experiments revealed that cigarette and e-cigarette use affected cells, at least in part, by different mechanisms.

“These findings suggest that using the two products together, as many people do, could increase their health risks compared to using them individually,” Springer says.

In another study published in the same journal issue, the researchers exposed rats to different components of cigarettes and e-cigarettes. These included nicotine, menthol, and two gasses found in both products. They also tested an inert carbon nanoparticle.

Nicotine, the gasses, and the inert particles all interfered with blood-vessel function. This suggested that a general response in the body to airway irritation, rather than exposure to any one compound, was driving a drop in blood flow. Further work showed that the vagus nerve, which helps the nervous system control the heart and lungs, was driving the response to airway irritation.

“We were surprised to find that there was not a single component that you could remove to stop the damaging effect of smoke or vapors on the blood vessels,” Springer says. “As long as there’s an irritant in the airway, blood vessel function may be impaired.”

Most people in the study used earlier models of e-cigarettes, rather than currently popular ones. More work is needed to understand the health effects of different e-cigarette products.