E-cigarette Aerosol May Enhance SARS-CoV-2 Infection: Study

In a recent study published on BioRxiv, researchers evaluated whether aerosols from e-cigarettes (EC) promote infection of the novel coronavirus (SARS-CoV-2).

In a recent study published in BioRxiv, researchers evaluated whether the aerosol from electronic cigarettes (EC) facilitated the infection of the novel coronavirus (SARS-CoV-2).

Background

Smoking can lead to lung diseases, including cancer. Although there is great interest in studying the link between tobacco/nicotine use and the 2019 coronavirus disease, these relationships are often contradictory and poorly defined. For example, patient data suggests that smoking can prevent COVID-19, while many studies, including meta-analyses, have found smoking to be a risk factor for the progression of COVID-19.

Furthermore, the increased levels of angiotensin-converting enzyme 2 (ACE2) receptors detected in the respiratory tract biopsies of smokers highlight their heightened susceptibility. E-cigarettes, or EC, are nicotine delivery devices that heat electronic liquid to produce an aerosol containing various chemicals. The aerosol produced by ECs may have adverse effects on the respiratory system.

Research and Discovery.

This study examined whether EC aerosols enhance SARS-CoV-2 infection in human bronchial epithelial cells. BEAS-2B cells were used to examine the impact of "JUUL Virginia Tobacco" liquid, aerosols, and JUUL product components on ACE2 levels.

In underwater cultivation, a mixture was created using 0.5% JUUL Virginia tobacco liquid (diluted to contain 0.3 mg/ml nicotine), either 0.03 or 0.3 mg/ml nicotine, and 0.5% propylene glycol/vegetable glycerin (PG/VG) or 0.5% PG/VG with 0.03 or 0.3 mg/ml nicotine. Microscopic images of cells labeled with ACE2 antibodies showed an increase in ACE2 expression in cells exposed to 0.3 mg/ml nicotine.

An increase in nicotine levels was observed in a dose-dependent manner. The levels of ACE2 in cells treated with JUUL showed a slight increase compared with the control group. Similarly, BEAS-2B cells were cultured on the air-liquid interface (ALI) with either the Cultex exposure system or the Vitrocell cloud system.

The cells were exposed to aerosols produced by phosphate-buffered saline (PBS) or 0.3 or 0.03 mg/ml nicotine. ACE2 expression was higher in cells treated with nicotine. In contrast, cells were exposed to JUUL Virginia Tobacco EC in ten puffs of humidified clean air or aerosol. Additionally, JUUL devices were used with other refillable pods containing laboratory-manufactured liquids (PG/VG or a mixture of PG/VG with 6 or 60 mg/ml nicotine).

The expression of ACE2 increases in cells exposed to PG/VG or JUUL aerosols, although to a negligible extent. In aerosols manufactured in a laboratory, there is a significant increase in ACE2 expression. Next, underwater treatments were performed to examine the effects of nicotine, PG/VG, or JUUL aerosols on the levels and activity of the transmembrane protease serine 2 (TMPRSS2). Expression of TMPRSS2 increases in cells exposed to 0.3 mg/mL nicotine.

Cells exposed to nicotine-containing liquids manufactured in the lab showed a dose-dependent increase in TMPRSS2 levels. When treated with JUUL liquid, TMPRSS2 activity increased as measured by the cleavage of a specific substrate. Similar experiments were repeated using an air-liquid interface (ALI) cloud chamber or exposure system. Results showed that nicotine exposure did not affect TMRPSS2 levels, but enzyme activity significantly increased with 0.3 milligrams/milliliter of nicotine.

In the Cultex system, the level of TMPRSS2 was not significantly different from the control group exposed to normal air. However, the enzyme activity in cells exposed to PG/VG was significantly reduced, while the enzyme activity in cells exposed to PG/VG-nicotine mixture was significantly increased. Despite exposure to JUUL aerosol, there was no change in enzyme activity in the cells.

Lastly, the author examined how JUUL liquid/aerosol or individual components affect SARS-CoV-2 infection in BEAS-2B cells. They created SARS-CoV-2 pseudoviruses expressing SARS-CoV-2 spike protein and containing ZsGreen, a plasmid reportedly used to identify infected cells. After treatment for 24 hours, the pseudoviruses were added to the culture and incubated for an additional 24 hours.

Fluorescence was measured using a flow cytometer and microscope. Virus infection was significantly increased in cells treated with JUUL liquid, while cells treated with PG/VG showed a slight increase. Nicotine treatment induced a dose-dependent increase in virus infection and when used in conjunction with PG/VG, infection rates were even higher.

Similarly, fake virus infections were carried out in ALI. Nicotine (0.3 mg/ml) slightly enhanced virus infections. Increased infections were observed in cells exposed to JUUL aerosols and PG/VG-nicotine mixtures.

Conclusion

Research shows that JUUL liquids and aerosols increase the expression of ACE2, the activity of TMRRPSS2, and the infection of BEAS-2b cells. The impact of electronic cigarettes on virus infection depends on exposure type and chemical composition. In submerged culture and vapor exposure, nicotine enhances the expression of ACE2 and pseudo-viral infection.

In the Cultex system, nicotine and PG/VG are associated with heightened expression and infection of ACE2. While TMPRSS2 levels and activity are higher in submerged cultures, only enzyme activity increases in ALI exposure. Overall, the investigation suggests that JUUL aerosol modulates the cell infection mechanism, enhancing SARS-CoV-2 pseudoparticle infection.

Important Announcement

The preliminary scientific reports published on bioRxiv are not subject to peer review and therefore should not be viewed as conclusive, guiding clinical practice/health-related behavior, or treated as established information.

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