While the health effects of conventional tobacco are well-defined, data on vaping devices, including those for the most popular e-cigarettes that have high levels of nicotine, are less established. Previous studies of e-cigarettes have demonstrated inflammatory and cardiopulmonary physiological changes, while chronic studies have demonstrated extrapulmonary effects, including neurotransmitter alterations in reward pathways.
Now, researchers at the University of California (UC) School of Medicine in San Diego reported that daily use of capsule-based e-cigarettes alters inflammatory status in multiple organ systems, including the brain, heart, lungs, and colon. The effects also vary depending on the taste of the e-cigarette and may influence how organs respond to infections, such as SARS-CoV-2.
The study, published in the journal eLife, is the first to evaluate JUUL branded devices and their flavourings in a multiorganic way. “These cigarettes have only become popular in the last five years, so we don't know much about their long-term health effects,” said Laura Crotty Alexander, lead author of the study, associate professor at UC San Diego School of Medicine and head of the Pulmonary Critical Care section at Veterans Affairs San Diego Healthcare System.
Currently, more than 12 million adults in the United States use e-cigarettes, with the highest rates of use among those between the ages of 18 and 24. Despite their popularity, research on e-cigarettes has largely been limited to studies of short-term use, older devices such as vaping and e-liquids with significantly lower nicotine concentrations than modern systems based on rechargeable pods.
The team of researchers focused on the most prominent electronic cigarette brand in the US today, JUUL, and its most popular flavors: mint and mango. To model chronic e-cigarette use, young adult mice were exposed to JUUL flavored sprays three times daily for three months. The researchers then looked for signs of inflammation throughout the body.
The authors saw the most striking effects on the brain, where several inflammatory markers were elevated. Additional changes in neuroinflammatory gene expression were observed in the nucleus accumbens, a region of the brain critical for motivation and reward processing. The findings raise major concerns, they said, as neuroinflammation in this region has been linked to anxiety, depression and addictive behaviors, which could further exacerbate substance use and addiction. “Many JUUL users are teenagers or young adults whose brains are still developing, so it's quite scary to know what may be happening considering how this might affect their mental health and behavior in the future,” Crotty Alexander warned.
Inflammatory gene expression also increased in the colon, particularly after one month of exposure to e-cigarette, which could increase the risk of gastrointestinal disease. In contrast, the heart showed reduced levels of inflammatory markers. Specialists suggested that this state of immunosuppression could make heart tissue more vulnerable to infection. Although the lungs showed no signs of inflammation at the tissue level, numerous changes in gene expression were observed in the samples, requiring further study of the long-term effects of capsule-based e-cigarettes on lung health, the scientists say in their paper.
The researchers also found that the inflammatory response of each organ varied depending on which flavor of JUUL was used. For example, the hearts of mice that inhaled mint sprays were much more sensitive to the effects of bacterial pneumonia compared to those who inhaled mango sprays. “This was a real surprise for us,” added Crotty Alexander. This shows us that the same flavor chemicals are also causing pathological changes. If someone who frequently uses menthol-flavored JUUL e-cigarettes were infected with COVID-19, their body may respond differently to the infection.”
Each organ has its own finely adjusted immune environment, so disrupting that balance through the use of e-cigarettes could lead to many long-term health effects, the authors wrote in the research. “It is clear that every electronic cigarette device and flavor should be studied to determine how it affects health throughout the body,” concluded Crotty Alexander.
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