E-cigarette Aerosol Enhances Inflammatory Response in Oral Cells
Objectives: The use of E-cigarette is increasing at an alarming rate worldwide for it is considered safer than conventional tobacco cigarettes. It raises public concern for the side-effect caused by E-cigarettes on the oral health due to various components like nicotine, polypropylene glycol and other diluents contained in the e-cigarette liquid (e-liquid). The initial host interaction of e-cigarette aerosol produces derivatives which may lead to severe oral complications. Here, we examined the effect of e-cigarettes on bacterial infection and pro-inflammatory factors in the oral environment.
Methods: We exposed oral cells to e-cigarette aerosol with the presence of oral anaerobic bacteria including Fusobacterium nucleatum and Porphyromonas gingivalis stained with FITC to assess the extent of bacterial infection. To explore the inflammatory response to e-cigarette in the oral environment, multiple oral cell lines were chosen to be exposed to e-cigarette aerosol with the presence of oral anaerobic bacteria in a chamber designed for aerosol delivery. To compare the effect of pure nicotine with the e-liquid, we exposed the oral cells to the aerosol derived from pure nicotine solution.
Results: Flow cytometry showed that exposure to e-cigarette aerosol increases the bacterial infection by up to 35%. qPCR array showed that two of the key pro-inflammatory cytokines TNF-α and IL-8 are increased significantly. The qPCR and ELISA results reveal that pure nicotine induces less TNF-α and IL-8 as compared to the e-liquid, indicating other components in e-liquid are involved in inducing an inflammatory response. Consistently, HPLC showed that multiple non-nicotine peaks exist in the e-liquid.
Conclusions: Based on our research, we conclude that the use of e-cigarette aerosol enhances the oral bacterial infection and inflammatory response. Specifically, e-liquid increases TNF-α and IL-8 in the presence of oral anaerobic bacteria. Further investigations are required to identify the derivatives present in e-liquid and their impact on oral health.