Biomarkers of Exposure and Effect in the Lungs of Smokers, Nonsmokers, and Electronic Cigarette Users.

Introduction:
This text provides a detailed analysis of a study examining the effects of electronic cigarette (e-cig) use on the lung, comparing e-cig users, smokers, and never-smokers. The study focuses on in flammatory cells, cytokines, gene methylation, and gene expression in lung samples. The key points and main message of the text are summarized below.

Key Points:

* The study included 73 participants, divided into three groups: never-smokers, e-cig users, and smokers.
* E-cig users had higher in flammatory in filtrates than never-smokers, but lower than for smokers.
* Compared with never-smokers, e-cig users had signi ficantly different levels for IL1 b, IL6, and IFNg, associated with lung cancer and COPD.
* Distinct patterns for DNa methylation and gene expression were found, with e-cig users' levels being intermediate between smokers and never-smokers.
* Genes involved in ahR and aRNT signaling pathways, and CYPs and other xeno-metabolizing enzymes, were affected, increasing DNa damage and associated with lung tumorigenesis.
* The study found lower expression levels of ahR and xenobiotic metabolizing enzymes in e-cig users, consistent with the hypothesis of lower responses with lower carcinogen exposure.
* The study also found effects on NRF2 oxidative stress response pathway, PXR, and RXR pathways, affecting xenobiotic metabolism through cytochrome P450s.

Main Message:
The study suggests that e-cig use may be less harmful than smoking, at least for the smoking-related biomarkers measured. however, e-cig use also has harmful effects compared with never smoking. The findings support the need for further studies, including longitudinal studies and randomized trials, to understand the biological impact of e-cig use on the lung, especially given the high prevalence of e-cig use.

Song Ma, Freudenheim JL, Brasky TM, et al. Biomarkers of Exposure and Effect in the Lungs of Smokers, Nonsmokers, and Electronic Cigarette Users. Cancer epidemiology, biomarkers & prevention : a publication of the american association for Cancer Research, cosponsored by the american Society of Preventive Oncology. 2020;29(2):443-451. doi:10.1158/1055-9965.EPI-19-1245