Electronic cigarette liquid exposure induces flavor-dependent osteotoxicity and increases expression of a key bone marker, collagen type I: OSTEOTOXICITY INDUCED BY ELECTRONIC CIGARETTE FLAVORED LIQUIDS

Electronic cigarettes (e-cigarettes) are nicotine delivery devices advertised as a healthier alternative to conventional tobacco products, but their rapid rise in popularity outpaces research on potential health consequences. Since conventional tobacco use is a risk factor for osteoporosis, this study examines whether exposure to electronic liquid (e-liquid) used in e-cigarettes affects bone-forming osteoblasts. Human MG-63 and Saos-2 osteoblast-like cells were treated for 48 h with 0.004%−4.0% dilutions of commercially available e-liquids of various flavors with or without nicotine. Changes in cell viability and key osteoblast markers, RUNX2 and Col1a1, were assessed. With all e-liquids tested, cell viability decreased in a dose-dependent manner, which was least pronounced in flavorless e-liquids, most pronounced in cinnamon-flavored e-liquids, and occurred independently of nicotine. Col1a1, but not RUNX2, mRNA expression was upregulated in response to coffee-flavored and fruit-flavored e-liquids. Cells treated with a non-cytotoxic concentration of fruit-flavored Mango Blast e-liquid with or without nicotine showed significantly increased collagen type I protein expression compared to culture medium only. We conclude that the degree of osteotoxicity is flavor-dependent and occurs independently of nicotine and that flavored e-liquids reveal collagen type I as a potential target in osteoblasts. This study elucidates potential consequences of e-cigarette use in bone. This study investigates the effects of electronic cigarette liquids on human MG-63 and Saos-2 osteoblast-like cells exposed to dilutions of e-liquids with or without nicotine. All e-liquids decreased cell viability in a dose-dependent manner, which was exacerbated by flavorings but independent of nicotine. Cinnamon-flavored e-liquids were the most osteotoxic. Coffee- and fruit-flavored e-liquids increased collagen type I revealing this matrix protein as a target for e-liquid osteotoxicity and demonstrating further need for research on bone health consequences of e-cigarette use.