Gingival Cells Exposed to e-Cigarette Liquid Induce Pro-inflammatory Cytokine Elaboration

Objectives: Over the past few decades, the derivation of electronic cigarettes (eCig) has given rise to a new, largely unregulated market within the smoking industry. eCigs rely on vapor produced by heating an oil based liquid (e-liquid) to deliver flavored nicotine, and while initially considered to be less harmful than traditional tobacco cigarette smoke, little is known about the cellular impact of these electronic devices. The oral environment is anatomically positioned as a significant gateway for exposure to environmental toxicants including eCig delivery. We hypothesize that such exposure specifically compromises oral health by orchestrating inflammation at the cellular level. The purpose of this study was to determine the effects of eCig liquid on oral health by examining the expression of several pro-inflammatory cytokines: interleukin (IL)-1b, IL-6, IL-8 and tumor necrosis factor (TNF)-a.
Methods: Gingival epithelial cells (Ca9-22) were exposed to Cuttwood^TM, a national brand of eCig liquid at concentrations of zero, two, or four percent for 24 hours. After exposure, total RNA and protein were isolated and conditioned media was retained.
Results: Quantitative real-time PCR (qRT-PCR) was conducted and we observed a significant increase in the transcription of IL-1b, IL-6, and TNF-a after 24 hours of exposure to 2% liquid. Compared to controls, 4% caused higher IL-6, and TNF-a, but caused a complete eradication of IL-1b, expression. Interestingly, each eCig liquid dose caused significant inhibition of IL-8 transcription. ELISAs and immunoblotting for specific molecules were used where appropriate to corroborate RNA-protein expression patterns.
Conclusions: Together, these results provide important understanding relative to the inflammatory profile of exposed gingival cells. Further work may show that pro-inflammatory signaling axes exacerbated by eCigs are conserved in comparison to other tobacco based products. This work was supported by institutional research funds from Roseman University and a grant from the Flight Attendant’s Medical Research Institute (FAMRI, P.R.R. and J.A.A.).