Lung barrier study finds one day of JUUL aerosol opened cell leaks

One day of exposure to aerosol from JUUL Virginia Tobacco 5% pods loosened the barrier between deep-lung cell layers grown in the laboratory, according to a study published in JCI Insight.

Irina Petrache, chief of pulmonary, critical care and sleep medicine at National Jewish Health in Denver, was senior author. Researchers from the University of Colorado and Colorado State University took part.

The study tested cells and hamsters, not people who vape

None of the measurements came from vape users. The team worked with human lung endothelial and epithelial cells, some grown from donated lungs, and precision-cut lung slices from donors who had never smoked and had no lung disease.

A machine drew on the pods for three seconds every 30 seconds. The researchers exposed cells to the vapor, the liquid and the condensed aerosol at doses intended to mimic casual vaping.

Within 24 hours the cell sheets leaked, and leakage rose with the dose. Cells switched on autophagy, the recycling process that breaks down damaged components, but did not complete it; half-processed material accumulated, growth slowed and some cells died.

The team linked the barrier damage to JNK stress signalling. Blocking JNK with a drug before aerosol exposure kept the sheets tighter and moved the recycling process further along.

Hamster lungs showed stress markers 10 days after exposure ended

Six golden Syrian hamsters per group, male and female, inhaled a mist made from condensed aerosol once a day for five days, then breathed clean air for 10 days.

The animals lost no weight and showed no outward illness. Their lungs showed no inflammation or scarring under the microscope, yet the marker of unfinished cell cleanup had risen about fourfold and cells lining small blood vessels carried broken DNA strands.

About 200 genes were more active and about 300 less active than in unexposed animals. Some of the suppressed genes relate to Th1 immunity, which helps fight viruses. The authors noted that many of these gene changes passed a loose statistical threshold but not a strict one, partly because each group held so few animals.

Prior aerosol exposure raised early SARS-CoV-2 levels in a second hamster set

Hamsters that inhaled the mist for five days and then received SARS-CoV-2 through the nose carried more virus in upper-airway swabs than unexposed animals during the first three days of infection.

After a week, their lungs showed weaker antiviral gene activity and stronger activity in genes tied to tissue breakdown and rebuilding. Exposed females lost more weight after infection than unexposed females; exposed males lost less.

Lung tissue inflammation and injury did not differ clearly between the groups. Some animals also received influenza A between the last aerosol dose and the coronavirus infection.

What the design could not separate

The team used one product in one flavour and did not isolate the effect of nicotine from the flavourings or other ingredients. Biosafety rules at the time required hamsters to breathe a condensate rather than fresh aerosol, and a condensate lacks short-lived compounds present in a fresh puff.

The study cannot show whether such early changes lead to chronic conditions such as COPD or fibrosis, which involve similar barrier leaks.

Manufacturers and exporters face a familiar evidence gap

Analysis: the results give regulators and health bodies another citation for aerosol toxicology questions, but they do not identify which ingredients drove the effect, so they cannot be read as a finding about any formulation other than the one tested. Supply-chain teams preparing dossiers for markets that ask for aerosol or cytotoxicity data should expect this kind of in vitro and animal work to be raised in review, and should treat ingredient-level attribution as an open question rather than a settled one.

Human studies are the next step the authors set out

Petrache’s team wrote that research in people who vape would be needed to establish whether similar changes occur in their lungs. Future work could also test whether blocking JNK limits the injury.

The JCI Insight paper follows a 2019 outbreak of severe lung injury among e-cigarette users, which the CDC counted as more than 2,800 people hospitalised or dead; a respiratory infection on top of vaping was one suspected trigger, which the team cited as a reason to test infected lungs.

Questions readers ask

Did the study test people who vape?

No. The experiments used human lung cells and tissue in the laboratory and golden Syrian hamsters; the authors state that studies of people who vape would be needed to show whether similar changes occur in their lungs.

Which product was tested?

A commercial JUUL product in Virginia Tobacco flavour with 5% nicotine. Hamsters breathed a mist made from condensed aerosol rather than fresh aerosol, a choice the team attributes to biosafety rules at the time.

Can the results be attributed to nicotine?

Not from this study. The team did not separate the effects of nicotine from those of the flavourings or other ingredients.