Using e-cigarettes may be just as harmful to health as smoking regular cigarettes, according to researchers at the University of North Carolina, Chapel Hill. Their analysis of sputum samples from nonsmokers, e-cigarette users, and cigarette smokers found that e-cigarettes triggered unique and potentially damaging immune responses, as well as changes to protein expression and mucus composition that are linked to the adverse lung effects caused by cigarette smoking.
“There is confusion about whether e-cigarettes are ‘safer’ than cigarettes because the potential adverse effects of e-cigarettes are only beginning to be studied,” claims Mehmet Kesimer, Ph.D., associated professor of pathology. “Our results suggest that e-cigarettes might be just as bad as cigarettes.” The team reports its findings in the American Journal of Respiratory and Critical Care Medicine, in a paper entitled “E-Cigarette Use Causes a Unique Innate Immune Response in the Lung, Involving Increased Neutrophilic Activation and Altered Mucin Secretion.”
E-cigarettes represent a $3.5 billion business in the U.S., and their use among high school students increased 900% between 2011 to 2015, according to a 2016 Surgeon General’s report. The FDA now regulates multiple aspects of e-cigarette manufacture, importation, advertising, distribution, and sale in the U.S., but not all areas of regulation have been put in place, primarily because the potential adverse health effects and risks of their use aren’t known, the researchers state.
The upward trend in e-cigarette usage is also “supported by a common assumption that e-cigarettes are harmless and a safe alternative to cigarette smoking,” they suggest. Some healthcare practices even promote e-cigarettes as a smoking cessation aid. However, the researchers stress, “… little is known about the potential adverse health effects of e-cigarette use on the lungs.”
In what they claim is the first study using human airway mucus samples to investigate the effects of e-cigarette use on the airways, Dr. Kesimer’s team analyzed sputum from 15 e-cigarette users, 14 current cigarette smokers, and 15 nonsmokers. Their results showed that compared with sputum samples from nonsmokers, those from e-cigarette users contained approximately 81 proteins with significantly altered abundance. There were 44 proteins with altered abundance identified in sputum from cigarette smokers.
The samples from e-cigarette users commonly, and uniquely, exhibited significant increases in neutrophil granulocyte- and neutrophil-extracellular-trap (NET)-related proteins and enzymes, including myeloperoxidase, azurocidin, and protein-arginine deiminase 4, but without increased numbers of neutrophils. NET formation is part of the natural antibacterial response by neutrophils that helps to maintain and protect the airways. However, “among other functions, these neutrophilic enzymes are inflammatory mediators and major contributors to the pathogenesis of chronic lung diseases, such as COPD [chronic obstructive pulmonary disease],” the researchers note. They also suggest that NET formation in peripheral blood neutrophils from e-cigarette users should be evaluated in the context of some systemic diseases, including systemic lupus erythematosus, vasculitis, and psoriasis.
In contrast to changes that were specific to e-cigarette use, both e-cigarette users and cigarette smokers demonstrated significant increases in biomarkers of oxidative stress and the activation of innate defense mechanisms that are associated with lung diseases. Of particular note were increases in biomarkers of aldehyde-detoxification and oxidative-stress-related proteins, thioredoxin (TXN), and matrix metalloproteinase-9 (MMP9). E-cigarette use and cigarette smoking were, in addition, associated with changes in airway mucus composition and particularly levels of mucin 5AC (MUC5AC), which is known to be altered in COPD patients, and overproduction of which is associated with other lung disorders, including chronic bronchitis and asthma.
“This study describes a unique e-cigarette–induced innate lung response that includes markers of aberrant neutrophilic response and altered mucin secretion and indicate that the effects of e-cigarettes are overlapping with yet distinct from those observed in otherwise healthy cigarette smokers,” the authors conclude. “Comparing the harm of e-cigarettes with cigarettes is a little like comparing apples to oranges,” Dr. Kesimer said. “Our data shows that e-cigarettes have a signature of harm in the lung that is both similar and unique, which challenges the concept that switching from cigarettes to e-cigarettes is a healthier alternative.”