Oxidative stress, apoptosis and survival in human gingival fibroblasts exposed to e-cigarette fluids.

In the last years, electronic (e-)cigarettes have been marketed as a safe alternative to the traditional ones. However, despite the facts that no combustion occurs and that all the ingredients contained in the liquid of e-cigarettes are approved as food additives, the harmlessness of these electronic devices is still not fully proven. The aim of this work was to investigate the effects of the liquids of e-cigarettes on human gingival fibroblasts (HGFs) and to compare the effects of nicotine-containing fluid to the fluid itself. HGFs were treated with 1 mg/mL of fluids of e-cigarettes for different times (0–48 h). Fluids were administered also after being vaped (e.g., warmed into the cartomizer). Apoptosis occurrence and Bax expression were evaluated by flow cytometry; ROS production was analyzed by fluorescence optical microscopy. Electron microscopy analyses were performed and collagen production and lysosome compartment changes were evaluated. Both nicotine-containing and nicotine-free fluids induced an increased ROS production after 24 h, along with an increased Bax expression, followed by apoptosis occurrence after 48 h of exposure. The nicotine containing fluids, both vaped and not vaped, showed the presence of vacuoles into the cytoplasm and a reduced collagen production, while the lysosome compartment appeared augmented in HGFs treated with nicotine-free fluids. E-cigarette fluids are toxic for HGFs and the cytotoxicity exerted on HGFs is not entirely ascribable to nicotine. Because the e-cigarettes are advertised as a safer alternative to traditional tobacco cigarettes, especially for the possibility of “smoking” nicotine-free fluids, further studies are necessary to clarify the mechanism involved in the occurrence of cytotoxicity exerted by such compounds.