WASHINGTON, D.C. — Today, more U.S. teens vape than smoke. Many of those teens may have assumed that electronic cigarettes are a safe, high-tech alternative to tobacco. And it’s true that e-cigs don’t emit many of the 7,000 chemicals found in tobacco smoke. Still, teens are fooling themselves if they think vaping is harmless, scientists reported February 11 and 12 at a major science meeting.

The new data — from animals and human cells — show that the vapors released by e-cigarettes can alter the activity of genes. Many, many genes. One study also linked e-cig vapors to reproductive harm in males. And data emerging in yet another study linked e-cigarette use to a form of heart disease. The toxicologists shared their findings, here, at the American Association for the Advancement of Science (AAAS) annual meeting.

If used as a means to eventually give up tobacco altogether, then vaping might have some value, says Ilona Jaspers. She works at the University of North Carolina at Chapel Hill. Still, Jaspers is not sure. And for teens who never smoked, vaping “may actually be introducing new [health] risks,” she worries.

Hurting the infection-fighters

Jaspers’ team studied cells that they had scraped from the inside of the noses of healthy people. Some were smokers. Some vaped. Others did neither. The researchers then measured the activity of 594 genes in these cells. All of the genes had earlier been linked with the immune system, which plays a major role in fighting infections.

Among smokers, the activity of 53 genes was depressed, or lower than usual, when compared to those who neither smoked nor vaped. Among vapers, the activity of those same 53 genes was depressed, Jaspers reports. But so was the activity of another 305 genes. By this measure, vaping had a bigger effect on genes related to immunity than smoking did.

Some flavorings used in the liquids converted to vapors by an electronic cigarette appeared especially potent at lowering the activity of immune cells. Among them: cinnamon flavorings. This new research suggests such flavorings might reduce the body’s ability to fight infections. FROM THE COLLECTION OF STANFORD RESEARCH INTO THE IMPACT OF TOBACCO ADVERTISING (TOBACCO.STANFORD.EDU)

The affected genes normally recruit and aid the body’s cells in fighting bacteria or other germs. So the new data suggest that smokers — but especially vapers — “may be more susceptible to any kind of infection,” Jaspers says.

To test that, Jaspers’ team collected immune cells from healthy people. The scientists then exposed those cells to the flavored liquids used to create vapors in e-cigarettes. Tested cells included blood neutrophils (NU-trah-fils) and lung macrophages (MAK-row-FAY-gez). The body normally tasks both with gobbling up and killing bacteria.

Some of the liquids proved disturbingly effective at preventing those immune cells from doing their job. One example was a cinnamon-flavored compound. It was found in several e-juices, including flavorings not associated with cinnamon, such as cola.

Vaping’s impact on behavior

Judy Zelikoff works at New York University’s Langone Medical Center in Tuxedo. Her team also found vaping-related changes in genes. In their case, they focused on genes in the brain that play a role in behavior and mental health.

The scientists exposed pregnant mice to e-cig vapors. Then, once the pups were born, they too got exposed for a month. That is when mice reach young-adulthood. The animals breathed in vapors at concentrations scaled to be similar to what a vaping person might encounter. Then Zelikoff’s group tracked the activity of genes in the animals’ frontal cortex. This brain region is associated with planning and using inputs from the senses (like sight, smell and sound) to understand their environment.

In these animals, whether the e-cig vapors contained nicotine made a big difference. Nicotine is the addictive substance in tobacco that keep smokers yearning for another puff.

Male mice exposed to nicotine-laced vapors showed no gene-activity changes. Among females, however, vapors laced with nicotine altered the activity levels of 148 genes in the brain’s frontal cortex. But among rodents exposed to vapors free of nicotine, a whopping 830 or more genes in the frontal cortex showed substantially altered activity. That activity was either much higher or lower than in unexposed mice. Usually, over- or under-activity of genes is not considered healthy. Both males and females were about equally affected.

“We were so surprised” by the exaggerated effect of no-nicotine vapors, Zelikoff says. In fact, she notes, her team was so shocked “that we repeated the [experiment] two more times.”

The nature of the affected genes would suggest the animals could behave differently than normal. Some of those changes might even point to possible mental illness, Zelikoff says. To probe that a bit further, her group teamed up with researchers at the University of Rochester in New York. They found that mice in both the nicotine and no-nicotine group indeed showed altered behavior.

Young-adult mice exposed to nicotine-free e-cig vapors in the womb tended to move at almost twice the pace of unexposed mice. 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 reports. These behaviors also might be a sign the mice were stressed or agitated. Her group is now exploring possible effects of vaping on memory and mental disorders.

Yet more signs of potential problems

The New York University group also uncovered reproductive problems in the young-adult male mice that had been exposed to e-cig vapors in the womb. Concentrations of their sperm, the male cells used in mating, were only about half as high as in unexposed mice. For mating to be successful, sperm have to move and find an egg to fertilize. But the share of motile sperm — those moving normally — was only a fifth as high as in unexposed males. This suggests that such mice might have a hard time producing a new generation of mice.

Finally, exposing mice to e-cig vapors increased a buildup in their arteries and blood vessels of plaque (PLAK), reports Daniel Conklin. He’s a toxicologist at the University of Louisville in Kentucky. The increased plaque is a sign of emerging atherosclerosis (ATH-ur-oh-sklair-OH-sis). Cigarette smoke also boosted the buildup of plaque.

In both vaping and smoking, he notes, it appears that toxic aldehydes are contributors. Among such compounds are acrolein (AK-roh-leen), formaldehyde (For-MAL-duh-hyde) and acetaldehyde (AA-sit-AL-duh-hyde). These findings, he says, appear to indicate that electronic cigarette vapors “could adversely impact the cardiovascular health of users.”

“We’re really at the beginning of understanding the toxicity of emerging [tobacco] products” such as e-cigs, says Neal Benowitz. He’s a physician who studies tobacco and health at the University of California, San Francisco. Certainly, he says, there has been a general perception that vaping is safer than smoking. The challenge to science is teasing out if that is true. For now, he says, “We really don’t know.”

Adds Zelikoff, “I’m a firm believer in the precautionary principle.” This means that where there are warning signs, they should be heeded. So if she were pregnant, she says, “I would look at these animal data with a great deal of respect.”

Power Words

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acrolein A liquid that’s clear or yellowy and has an odor that can create a choking sensation. In high concentrations it’s a known poison. Manufacturers add it to plastics, medicines, pesticides, resins and more.

aldehydes A family of chemical compounds that contain a “carbonyl group,” which is a carbon and oxygen atom linked chemically with a double bond. Examples of these compounds include acrolein, formaldehyde and acetaldehyde.

atherosclerosis A form of heart disease where the vessels and arteries can be narrowed dangerously (threatening to clog completely) by the buildup of fatty deposits known as plaque.

bacterium (plural bacteria) A single-celled organism. These dwell nearly everywhere on Earth, from the bottom of the sea to inside animals.

behavior The way a person or other organism acts towards others, or conducts itself.

cancer Any of more than 100 different diseases, each characterized by the rapid, uncontrolled growth of abnormal cells. The development and growth of cancers, also known as malignancies, can lead to tumors, pain and death.

cardiovascular An adjective that refers to things that affect or are part of the heart and the system of vessels and arteries that move blood through the heart and tissues of the body.

cell The smallest structural and functional unit of an organism. Typically too small to see with the naked eye, it consists of watery fluid surrounded by a membrane or wall. Animals are made of anywhere from thousands to trillions of cells, depending on their size.

chemical A substance formed from two or more atoms that unite (become bonded together) in a fixed proportion and structure. For example, water is a chemical made of two hydrogen atoms bonded to one oxygen atom. Its chemical symbol is H 2 O. Chemical can also be an adjective that describes properties of materials that are the result of various reactions between different compounds.

concentration (in chemistry) A measurement of how much of one substance has been dissolved into another.

depression A mental illness characterized by persistent sadness and apathy. Although these feelings can be triggered by events, such as the death of a loved one or the move to a new city, that isn’t typically considered an “illness” — unless the symptoms are prolonged and harm an individual’s ability to perform normal daily tasks (such as working, sleeping or interacting with others). People suffering from depression often feel they lack the energy needed to get anything done. They may have difficulty concentrating on things or showing an interest in normal events. Many times, these feelings seem to be triggered by nothing; they can appear out of nowhere.

e-cigarette (short for electronic cigarette) Battery-powered devices that disperse nicotine and other chemicals as tiny airborne particles that users can inhale. They were originally developed as a safer alternative to cigarettes that users could use as they tried to slowly break their addiction to the nicotine in tobacco products.

environment The sum of all of the things that exist around some organism or the process and the condition those things create for that organism or process. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature, humidity and placement of components in some electronics system or product.

frontal cortex Also known as the frontal lobe, it’s a part of the brain, just behind the face that plays a pivotal role in many skills involving movement, in decision-making, in problem-solving and in many behaviors.

gene (adj. genetic) A segment of DNA that codes, or holds instructions, for producing a protein. Offspring inherit genes from their parents. Genes influence how an organism looks and behaves.

germ Any one-celled microorganism, such as a bacterium, fungal species or virus particle. Some germs cause disease. Others can promote the health of higher-order organisms, including birds and mammals. The health effects of most germs, however, remain unknown.

immune system The collection of cells and their responses that help the body fight off infections and deal with foreign substances that may provoke allergies.

immunity The ability of an organism to resist a particular infection or poison by producing and releasing special protective cells.

infection A disease that can spread from one organism to another.

macrophage A type of white blood cell dispatched by the immune system. Like janiters of the body, they gobble up germs, wastes and debris for disposal. These cells also stimulate other immune cells by exposing them to small bits of the invaders.

neutrophil A type of white blood cell released by the immune system. It gobbles up wastes and release chemicals that can digest cells, including germs.

nicotine A colorless, oily chemical produced in tobacco and certain other plants. It creates the ‘buzz’ effect associated with smoking. It also is highly addictive, making it hard for smokers to give us their use of cigarettes. The chemical is also a poison, sometimes used as a pesticide to kill insects and even some invasive snakes or frogs.

sperm The reproductive cell produced by a male animal (or, in plants, produced by male organs). When one joins with an egg, the sperm cell initiates fertilization. This is the first step in creating a new organism.

tobacco A plant cultivated for its leaves. Dried tobacco leaves are burned in cigars, cigarettes, and pipes. Tobacco leaves are also sometimes chewed. The main constituent of tobacco leaves is nicotine.

toxicology The branch of science that probes poisons and how they disrupt the health of people and other organisms. Scientists who work in this field are called toxicologists.

vaping A slang term for the use of e-cigarettes because these devices emit vapor, not smoke. People who do this are referred to as vapers.