Biological Impact of the Ratio of E-Cigarette Liquid Base Constituents, Propylene Glycol and Vegetable Glycerin, on Primary Human Melanocytes

Oral cavity is the first site to encounter e-cigarette (EC) or tobacco smoke. Increased gingival pigmentation can lead aesthetic concerns and hinder successful outcomes of depigmentation procedures as well color alterations in patients with dental restorations. While effects smoke nicotine increasing gingiva smoker have been well-documented, EC on not explored. Due large variations e-liquids from different sources, this study focused liquid base constituents, propylene glycol (PG) vegetable glycerin (VG), which are a universal constituent all e-liquids. Effects PG VG solutions mixed at ratios (0/100, 20/80, 55/45, 80/20, 100/0 % v/v) were examined using primary human melanocytes obtained neonatal foreskin; cell model representative physiological has used our previous study. Results showed significant concentration-dependent cytotoxicity for groups, although mixtures higher content cells compared those VG. Melanogenesis was robustly activated by PG-containing greatest effect 80/20 PG/VG mixture other ratios, while itself did activate melanogenesis. The activation melanin synthesis within correlated intracellular tyrosinase activity that suppressed ratios. Morphological changes multidendritic phenotype observed exposed mixtures, markedly greater groups content. Taken together, results pilot demonstrate time constituents possess capacity significantly melanogenesis nontoxic concentrations, dominant ratio indicative nonlinear response concentrations PG. Moreover, further studies address impact addition flavors underway. Future elucidate mechanisms increased investigate presence oral types components microenvironment such saliva bacterial flora warranted. This research emphasizes need reconsider regulation these compounds cause differential effects.