Effects of e-cigarette vapor (with or without nicotine) on airway mucin expression in NCI-H292 cells and human nasal epithelial cells. (A) Real-time polymerase chain reaction (RT-PCR) results showing that e-cigarette vapor (with or without nicotine 24 mg/mL) meaningfully stimulated MUC5AC, but not MUC5B, mRNA expression in NCI-H292 cells. (B) Enzyme-linked immunosorbent assay (ELISA) results showing that e-cigarette vapor (with or without nicotine 24 mg/mL) significantly stimulated MUC5AC, but not MUC5B, protein levels in NCI-H292 cells. (C) RT-PCR results showing that e-cigarette vapor (with or without nicotine 24 mg/mL) meaningfully stimulated MUC5AC, but not MUC5B, mRNA expression in human nasal epithelial cells. (D) ELISA results showing that e-cigarette vapor (with or without nicotine 24 mg/mL) significantly increased MUC5AC, but not MUC5B, protein levels in human nasal epithelial cells. Bars represent mean±standard deviation of three independent experiments performed in triplicate. PG, propylene glycol; VG, vegetable glycerin. a)P<0.05 vs. baseline.