E-cigarettes alter the inflammatory state of multiple organs in the body, which can influence how they respond to infections, according to a report published Tuesday by researchers at UC San Diego School of Medicine.
Daily use of pod-based e-cigarettes alters inflammation in multiple organ systems including the brain, heart, lungs and colon, the researchers found. Effects also vary depending on the e-cigarette flavor, and can influence how organs respond to infections, such as SARS-CoV-2.
The study, published Tuesday in the journal eLife, is the first to assess JUUL devices and their flavorants in a multi-organ fashion.
"These pod-based e-cigarettes have only become popular in the last five or so years, so we don't know much about their long-term effects on health," said senior study author Dr. Laura Crotty Alexander, associate professor of medicine at UCSD School of Medicine and section chief of pulmonary critical care at Veterans Affairs San Diego Healthcare System.
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More than 12 million adults in the United States use e-cigarettes, with the highest rates of use among those aged 18-24. Despite their popularity, research on e-cigarettes has been largely limited to studies of short-term use, older devices such as vape pens or box mods, and e-liquids with significantly lower nicotine concentrations than the modern rechargeable pod-based systems.
Crotty Alexander's team focused on the current most prominent e-cigarette brand, JUUL, and its most popular flavors: mint and mango. To model chronic e-cigarette use, young adult mice were exposed to flavored JUUL aerosols three times a day for three months. Researchers then looked for signs of inflammation across the body.
The report's authors saw the most striking effects in the brain, where several inflammatory markers were elevated including a brain region critical for motivation and reward-processing. The findings raise major concerns, the researchers said, as inflammation in this region has been linked to anxiety, depression and addictive behaviors.
"Many JUUL users are adolescents or young adults whose brains are still developing, so it's pretty terrifying to learn what may be happening in their brains considering how this could affect their mental health and behavior down the line," Crotty Alexander said.
Inflammation also increased in the colon, particularly after one month of e-cigarette exposure, which could increase risk of gastrointestinal disease. In contrast, the heart showed decreased levels of inflammatory markers. Authors said this could make cardiac tissue more vulnerable to infection.
Researchers also found that while lungs did not show tissue-level signs of inflammation, numerous changes were observed in the samples, calling for further study on pulmonary health.
The study also found that the inflammatory response varied depending on which JUUL flavor was used. For example, the hearts of mice who inhaled mint aerosols were much more sensitive to the effects of bacterial pneumonia compared to those who inhaled mango aerosols.
"This was a real surprise to us," Crotty Alexander said. "This shows us that the flavor chemicals themselves are also causing pathological changes. If someone who frequently uses menthol-flavored JUUL e-cigarettes was infected with COVID-19, it's possible their body would respond differently to the infection."
The study can be found here.