e-Cigarettes Cause Unique Injury to Lung Immunity, Study Shows

Jennifer Garcia

October 25, 2017

A new study finds that e-cigarettes cause unique harm to innate lung immunity, challenging the concept that they are a healthier alternative to traditional cigarettes.

 "[O]ur results indicate that e-cigarette use alters the profile of innate defense proteins in airway secretions, inducing both similar and unique changes relative to cigarette smoking," write Mehmet Kesimer, PhD, from the University of North Carolina at Chapel Hill, and colleagues. The team published their results online October 20 in the American Journal of Respiratory Critical Care Medicine.

Researchers collected induced sputum samples from 15 current e-cigarette users, 14 current cigarette smokers, and 15 never-smokers. They analyzed the samples using quantitative proteomics, as well as total and individual mucin concentrations. Neutrophil extracellular trap (NET) formation was also analyzed and compared among the groups.

The researchers found that both cigarette smokers and e-cigarette users had a significant increase in oxidative stress-related proteins, such as thioredoxin (TXN), compared with nonsmokers (P ≤ 0.05 for all levels). These proteins are markers of activation of the innate defense mechanisms associated with lung disease, the researchers explain.

Compared with cigarette smokers and nonsmokers, e-cigarette users had higher levels of neutrophil granulocyte- and NET-related proteins, including matrix metalloproteinase-9 (MMP-9), a major contributor to chronic lung disease (P ≤ 0.05 for all levels). Of note, these elevations were seen despite no increase in the sputum neutrophil cell counts.

Total mucin concentrations were highest in the sputum of smokers and were similar among e-cigarette users and nonsmokers. However, mucin composition, which has been correlated to progression of lung disease in previous studies, was similar between smokers and e-cigarette users.

 "[T]he elevated levels of markers known to be associated with cigarette smoke and lung disease/inflammation, such as TXN and MMP-9, in the sputum of both cigarette smokers and e-cigarette users, indicates commonality in the impacts of these products on airway physiology, such as increased oxidative stress and activation of innate defense mechanisms," the authors write.

They note that 12 of the 15 e-cigarette users smoked cigarettes in the past, and 5 said they occasionally still smoked cigarettes. While residual biomarkers have been shown to be absent in the sputum of former smokers, the authors acknowledge that future studies should include e-cigarette users who have never smoked traditional cigarettes.

"In conclusion, our results challenge the concept that e-cigarettes are a healthier alternative to cigarettes and reverse smoking-induced adverse health effects," Dr Kesimer and colleagues write.

The National Institutes of Health Food and Drug Administration Center for Tobacco Products provided funding for this study. The authors have disclosed no relevant financial relationships.

Am J Respit Crit Care Med. Published online October 20, 2017. Abstract

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