The effects of electronic cigarettes on human gingival cells and Candida albicans

Authors: Alanazi, Humidah
Advisor: Rouabhia, Mahmoud
Abstract: Electronic cigarettes (e-cigarettes) were designed to replace regular cigarette smoking and to contribute to smoking cessation. E-cigarettes require the use of vaping liquid that contains propylene glycol (PG) and vegetable glycerin (VG) as well as nicotine in various concentrations and flavours. Several studies comparing ecigarettes to conventional cigarettes show that e-cigarettes contain lower levels of toxic compounds and for this reason are deemed safer. However, a growing body of evidence shows that e-cigarettes contain many chemicals including formaldehyde, acetaldehyde, acrolein, and toluene, which may have adverse effects on different body parts, including the oral cavity. The first objective of this study was to investigate the impact of repeated exposures (1, 2, or 3 times) to e-cigarette condensates with or without nicotine on normal human gingival fibroblast morphology, proliferation, migration, and apoptosis. The second objective was to evaluate the effect of e-cigarettes vapors on the growth changes of C. albicans from blastospore to hyphal form and the expression of secreted aspartic proteinases (SAPs) SAP2, SAP3, and SAP9 genes by C. albicans, with exposure times of 15 min twice a day for 2 and 3 days. The third objective was to shed light on the interaction between e-cigarette-exposed C. albicans and gingival epithelial cells. Various cell biology, molecular biology, and microbiology protocols were deployed. Results show that exposure of gingival fibroblasts to nicotine-rich e-cigarette condensate altered both cell morphology and proliferation rate. Exposure to the ecigarette condensate also increased the levels of apoptotic fibroblasts. Fibroblast migration was delayed after culture scratches were exposed to e-cigarette condensate. Although e-cigarettes are considered to be less harmful than are conventional cigarettes, e-cigarettes significantly harmed the fibroblasts compared to non-exposed cells. E-cigarette exposure also increased C. albicans growth and hyphal length. The exposed C. albicans produced high levels of chitin and expressed high mRNA levels of SAP2, SAP3, and SAP9 genes. When in contact with gingival epithelial cells, e-cigarette-exposed C. albicans adhered better compared to the controls. Indirect communication between e-cigarette-exposed C. albicans and gingival epithelial cells led to epithelial cell differentiation, reduced cell growth, and increased lactate dehydrogenase (LDH) activity. Overall results indicate that e-cigarettes may interact with the user’s oral microbiome. Because e-cigarettes reduce gingival cell growth and increase cell apoptosis, this may decrease the innate immunity in the oral cavity, which could increase the risk of oral infections, such as candidiasis.
Document Type: Thèse de doctorat
Issue Date: 2020
Open Access Date: 5 October 2020
Grantor: Université Laval
Collection:Thèses et mémoires

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