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Smokers' nasal damage not repaired by switch to e-cigarettes – small US study

The damage done to the nasal epithelium by smoking may not be repaired by switching to electronic cigarettes, found a University of California study in Toxics.

The University of California, Riverside, researchers report that switching from combustible cigarettes to electronic cigarettes (ECs) does not restore the nasal epithelium to that the epithelium gene expression profiles of EC users do not revert to the typical epithelium gene expression profiles of non-smokers.

“Indeed, compared to non-smokers, the EC group showed molecular alterations in their gene expression profiles that are associated with cigarette smokers,” said Giovanna Pozuelos, the first author of the research paper.

“Specifically, the EC group showed alteration of genes associated with an increase in oxidative stress, immune response, and keratinisation, as well as evidence of ciliary dysfunction, and diminished ciliogenesis.”

The research team, led by Prue Talbot, a professor of cell biology, reports that alterations the team observed in the epithelium gene expression profiles of the EC users suggest that electronic cigarettes may interfere with the recovery of the respiratory epithelium of former smokers.

“ECs are often postulated as a healthier alternative to cigarette smoking,” said Talbot who advised Pozuelos on the study. “Continual EC use, however, may contribute to airway epithelial damage and the progression of respiratory diseases, such as squamous metaplasia.”

Squamous metaplasia refers to benign changes in the epithelium – tissue that lines organs, such as the lungs, throat, and thyroid, and can also be found in the skin. Pozuelos explained that squamous metaplasia is observed in the lungs in response to toxic injury often caused by cigarette smoking.

“It is reversible, however, after smoking cessation,” she said. “In our study molecular markers associated with squamous metaplasia were increased in EC users, suggesting ECs might interfere with the recovery of squamous metaplasia in former smokers.

“We also observed an increase of oxidative stress and inflammation, which may contribute to airway epithelial damage and progression of other respiratory diseases.”

The researchers collected nasal biopsies from three groups of participants and compared their epithelium gene expression readouts. The groups comprised three former smokers who completely switched to second generation ECs for at least six months; three current tobacco cigarette smokers; and three non-smokers.

The researchers then used bioinformatics to identify biological processes, cellular pathways, and diseases. “Alterations in the gene expression profiles of the EC users suggest that electronic cigarettes may interfere with the recovery of the respiratory epithelium of former smokers,” Pozuelos said.

Study details

Transcriptomic Evidence That Switching from Tobacco to Electronic Cigarettes Does Not Reverse Damage to the Respiratory Epithelium

Giovanna L. Pozuelos, Meenakshi Kagda, Matine A. Rubin, Maciej L. Goniewicz,
Thomas Girke, Prue Talbot.

Published in Toxics on 22 April 2022

Abstract

The health benefits of switching from tobacco to electronic cigarettes (ECs) are neither confirmed nor well characterised. To address this problem, we used RNA-seq analysis to compare the nasal epithelium transcriptome from the following groups (n = 3 for each group): (1) former smokers who completely switched to second generation ECs for at least 6 months, (2) current tobacco cigarette smokers (CS), and (3) non-smokers (NS). Group three included one former cigarette smoker. The nasal epithelial biopsies from the EC users vs. NS had a higher number of differentially expressed genes (DEGs) than biopsies from the CS vs. NS and CS vs. EC sets (1817 DEGs total for the EC vs. NS, 407 DEGs for the CS vs. NS, and 116 DEGs for the CS vs. EC comparison). In the EC vs. NS comparison, enriched gene ontology terms for the downregulated DEGs included cilium assembly and organization, whereas gene ontologies for upregulated DEGs included immune response, keratinisation, and NADPH oxidase. Similarly, ontologies for cilium movement were enriched in the downregulated DEGs for the CS vs. NS group. Reactome pathway analysis gave similar results and also identified keratinization and cornified envelope in the upregulated DEGs in the EC vs. NS comparison. In the CS vs. NS comparison, the enriched Reactome pathways for upregulated DEGs included biological oxidations and several metabolic processes. Regulator effects identified for the EC vs. NS comparison were inflammatory response, cell movement of phagocytes and degranulation of phagocytes. Disease Ontology Sematic Enrichment analysis identified lung disease, mouth disease, periodontal disease and pulmonary fibrosis in the EC vs. NS comparison. Squamous metaplasia associated markers, keratin 10, keratin 13 and involucrin, were increased in the EC vs. NS comparison. Our transcriptomic analysis showed that gene expression profiles associated with EC use are not equivalent to those from non-smokers. EC use may interfere with airway epithelium recovery by promoting increased oxidative stress, inhibition of ciliogenesis, and maintaining an inflammatory response. These transcriptomic alterations may contribute to the progression of diseases with chronic EC use.

 

Toxics article – Transcriptomic Evidence That Switching from Tobacco to Electronic Cigarettes Does Not Reverse Damage to the Respiratory Epithelium (Open access)

 

See more from MedicalBrief archives:

 

Vaping causes ‘much less’ DNA damage in cells than cigarettes – Imperial research

 

E-cigarettes linked to heart attacks, coronary artery disease, depression

 

The E-Cigarette Summit 2020 – Less harmful than smoking but not harmless

 

The health pros and cons of e-cigarettes – Evidence ambivalence

 

 

 

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