Potential effects span immunity to mental health and sperm to heart
WASHINGTON — Many people have turned to electronic cigarettes in hopes of avoiding the heart and cancer risks associated with smoking conventional tobacco products. But vaping appears far from benign, a trio of toxicologists reported February 11 and 12 at the American Association for the Advancement of Science annual meeting.
If used as a means to totally wean people off of tobacco products, then e-cigarettes might have value, concedes Ilona Jaspers of the University of North Carolina at Chapel Hill. But she’s not sure. Unpublished data that she and the others presented at the meeting link e-cig products to a host of new risks. So vaping may not eliminate risks associated with conventional smoking, Jaspers maintains — “and may actually be introducing new ones.”
Her group examined scraped cells from the noses of otherwise healthy people who had a history of smoking, vaping or doing neither. The researchers then measured the activity levels in these cells of 594 genes associated with the body’s ability to fight infections. Among smokers, the activity of 53 genes was substantially diminished, compared with people who neither smoked nor vaped. Among vapers, those same 53 genes showed significantly diminished activity, Jaspers reported, as did 305 more.
The normal role of these genes would suggest that the lung tissue as well as nasal tissue of smokers — and especially vapers — “may be more susceptible to any kind of infection.”
To test that possibility, Jaspers’ team collected immune cells from healthy human volunteers, then exposed them to flavored liquids used in e-cigarettes. Tested cells included blood neutrophils and lung macrophages, both normally tasked with gobbling up and killing bacteria. Some of the liquids proved disturbingly effective at suppressing the ability of those immune cells to do their job, Jaspers reported.
One compound with a particularly suppressive effect on immune-gene activity was the cinnamon-flavored cinnamaldehyde. Jaspers said she was surprised to find cinnamaldehyde in some of the liquids, including the cola-flavored one.
Judy Zelikoff of New York University’s Langone Medical Center in Tuxedo looked at genes affected by e-cigarette vapors. Her group exposed mice developing in the womb, and for a month after birth, to vapors at concentrations calculated to be comparable to what a vaping person might encounter. Then she tracked the activity of genes in the animals’ frontal cortex, a brain region associated with planning and integrating the senses to understand the environment.
Whether the e-cig vapors contained nicotine made a big difference.
Males exposed to nicotine-laced vapors showed no gene-activity changes. Among females, vapors laced with nicotine appeared to alter the activity levels of 148 genes in the brain’s frontal cortex. But among rodents exposed to nicotine-free vapors, a whopping 830 or more genes in the frontal cortex showed substantially altered activity — either much higher or lower than in unexposed mice. Here, both males and females were about equally affected.
“Was I surprised” by this exaggerated effect of the no-nicotine group? “We were so surprised,” Zelikoff said, “that we repeated the [experiment] two more times.”
The nature of the gene changes would suggest affected animals would exhibit behavioral changes, including ones associated with mental illness, she said. To probe that a bit further, her group teamed up with researchers at the University of Rochester in New York. Both mice in the nicotine and no-nicotine group showed behavioral changes. When adult mice that had been exposed to e-cig vapors in the womb moved, they tended to do so at almost twice the pace as unexposed mice if the vapors had no nicotine. They moved faster still if they had been exposed to nicotine. Both groups of mice also jumped more. And mice exposed to vapors also stood on their hind legs more than those that had not been exposed. All of these “are behaviors that are reflective of increased — or hyper — activity,” Zelikoff reported, “and possibly agitation.” Her group is now exploring possible effects on memory and mental disorders.
Her group also uncovered reproductive problems in young-adult males exposed to e-cig vapors in the womb. Their sperm concentrations were roughly half the value as those in unexposed mice. And the motility of their sperm was only a fifth as high as in unexposed males.
Finally, exposing mice to e-cig vapors increased plaque buildup, which is a sign of emerging atherosclerosis, reported Daniel Conklin of the University of Louisville in Kentucky. Cigarette smoke did too. In both cases, he noted, it appears that toxic aldehydes, such as acrolein, formaldehyde and acetaldehyde, are contributors. As such, he concluded, it appears electronic cigarette vapors “could adversely impact the cardiovascular health of users.”
“We’re really at the beginning of understanding the toxicity of emerging products,” says Neal Benowitz of the University of California, San Francisco. But as presentations at the science meeting illustrated, he says, there is a lot of complexity to understanding what goes into the vapors and the tissues that may be at risk. Certainly, he says, there has been a general perception that vaping is safer than smoking. “The challenge to science,” he says, will be to tease out: “Is this really true?” For now, he says, “We really don’t know.”
Perhaps it’s true, Zelikoff says. “But I’m a firm believer in the precautionary principle.” If she were pregnant, she says, “I would look at these animal data with a great deal of respect.”
I. Jaspers. Pulmonary effects of exposure to tobacco smoke and tobacco products. American Association for the Advancement of Science annual meeting. February 12, 2016.
J. Zelikoff. Reproductive and developmental effects of exposure to emerging tobacco products. American Association for the Advancement of Science annual meeting. February 12, 2016.
D. Conklin. Cardiovascular effects of exposure to tobacco products and harmful constituents. American Association for the Advancement of Science annual meeting. February 12, 2016.
J. Raloff. E-cigarettes proving to be a danger to teens. Science News. Vol. 188, July 11, 2015, p. 18.