Effects of Electronic (E)‐cigarette Vapor and Cigarette Smoke in Cultured Vocal Fold Fibroblasts

Abstract

Objective: The public use of electronic-cigarettes (e-cigs) is rapidly growing. When heated, e-cigs produce a vapor that is inhaled. The vocal folds are among the first tissues exposed to this insult. However, the impact of e-cigs on vocal fold health is almost entirely unknown. Our objective was to evaluate the effects of e-cig vapor on cultured human vocal fold fibroblasts (hVFFs), the primary cell type of the lamina propria. We compared the cellular effects of e-cig vapor without and with nicotine and conventional cigarette smoke.Study Design: In vitro.Methods: E-cig vapor extract (EVE) and cigarette smoke extract (CSE) were created by bubbling vapor and smoke, respectively, into the cell culture medium. hVFFs were exposed to EVE without or with nicotine or CSE for 24 hours. Untreated cells were used as a control group. Cells were harvested, and cytotoxicity, extracellular matrix and inflammatory gene expression, and DNA damage were assessed.Results: Undiluted EVE without and with nicotine reduced the viability of hVFFs to a cytotoxic level. CSE reduced hVFFs viability to a greater extent than EVE and induced DNA damage as measured by DNA double-strand breaks. No changes in gene expression were observed following EVE or CSE exposure.Conclusion: EVE induces cytotoxicity in hVFFs. However, cellular responses were greater following exposure to CSE, suggesting cigarette smoke may induce more harm, at least in the short term. Findings from this investigation improve our understanding of responses of hVFFs to e-cigs and form the basis for an in vitro methodology to study the vocal fold responses to these products.

Effects of Short‐term Electronic(e)‐Cigarette Aerosol Exposure in the Mouse Larynx

“…11 E-cigarette extract also reduced human VF fibroblast viability to a cytotoxic level. 12 Preliminary in vivo studies have targeted mostly inflammatory responses in the laryngeal mucosa of rodents following e-cigarette exposure. A 1-month exposure in rats revealed no significant changes in epithelial distribution and inflammation, 13 while 4 months of exposure in mice induced elevated levels of the inflammatory cytokine, IL-4.…”

“…Exposure of human‐engineered vocal fold (VF) mucosa to e‐cigarette extract in vitro disrupted innate immune responses and induced epithelial remodeling 11 . E‐cigarette extract also reduced human VF fibroblast viability to a cytotoxic level 12 . Preliminary in vivo studies have targeted mostly inflammatory responses in the laryngeal mucosa of rodents following e‐cigarette exposure.…”

The Toxicological Effects of e‐Cigarette Use in the Upper Airway: A Scoping Review

“…16,18,25,28,30,35,40,[42][43][44][45][46]49,53,62 Genotoxicity was seen primarily in the oral cavity, but also in the oropharynx and larynx, and was detected by increased DNA fragmentation, adducts, double-or single-strand breaks, appearance of micronuclei or metanuclear abnormalities, or increased expression of genes or proteins involved with DNA damage or repair pathways. 14,19,[22][23][24][25]27,32,51 Histological changes associated with acute and subchronic e-cigarette aerosol exposure in animal models were seen in the oral cavity, submandibular gland, nasal cavity, larynx, and trachea; however, the majority of these changes were considered adaptive and resolved following a recovery period. 30,31,37,47,50,52,[56][57][58][59]61,64 Persistent histological changes in the nasal cavity and larynx included: mild epithelial hyperplasia and squamous metaplasia, and mucus hypersecretion.…”

Impact of Electronic Cigarettes on the Upper Aerodigestive Tract: A Comprehensive Review for Otolaryngology Providers

“… 172 , 173 In the larynx, rats exposed to e‐cig aerosols showed early evidence of hyperplasia and metaplasia of the mucosa, 174 although the results were not statistically significant in this limited study, and increases in IL‐4. 175 In addition, both nicotine‐containing and nicotine‐free e‐juice have been found to cause biologic disruptions including oxidative stress, DNA breakage, metanuclear anomalies, liposomal dysfunction, and solvent and lipid accumulation, and cytotoxicity in human gingival fibroblasts, 67 , 176 , 177 , 178 , 179 , 180 vocal fold epithelial cells and fibroblasts, 181 , 182 head and neck squamous cell carcinoma cell lines, 67 , 183 , 184 , 185 noncancerous oral and oropharyngeal epithelial cells, 139 , 178 , 186 , 187 , 188 , 189 , 190 , 191 , 192 middle ear epithelial cells, 193 , 194 , 195 nasal epithelial cells, 196 , 197 and organotypic cultures/organoids. 178 , 182 , 197 Interestingly, a recent study found that oral cancer cells exposed to e‐cig aerosols increased cell resistance to cisplatin through changes in drug transporters, suggesting a mechanism for e‐cig‐induced chemotherapy resistance.…”