Rationale?With the sharply increasing use of e-cigarettes worldwide, especially among teenager , all of us are facing a huge public health risk. E-cigarettes or vaping associated pulmonary disease might be a new type of tobacco-related lung disease. Therefore, more information regarding respiratory system effect of e-cigarettes is needed.

Methods?Cultured A549 alveolar type II epithelial cells were exposure to three out of the eight types of JUUL brand e-liquids ( Mint, Menthol and Virginia Tobacco, all containing 3% nicotine ) and assessed for viability using a Resazyrin-based assay. Intracellular calcium(Ca2+) levels were measured using Fluo-4 AM fluorescent indicators. Cultures were also analyzed by flow cytometry to evaluate apoptotic markers  and cell viability. Thapsigargin as a SOCE agonist was added to cultures before or after exposed to e-liquid at a final concentration of 5?M and intracellular calcium(Ca2+) levels were measured using Fluo-4 AM fluorescent indicators.

Results: Mint, VT and Menthol e-liquids inhibit the proliferation of A549 cells in a dose- and time-dependent manner. Acute Mint and VT e-liquids addition increase significant cytoplasmic calcium(Ca2+) levels in A549 cells. Mint e-liquid induces apoptosis of A549 cells.Mint e-liquid induces ER Ca2+ release/store-operated Ca2+ entry in A549 cells. 

Conclusions: JUUL E-liquid increase cytoplasmic calcium(Ca2+) levels in alveolar epithelial cells. 1% Mint induces apoptosis in alveolar epithelial cells.JUUL E-liquid acutely induces ER Ca2+ -release/SOCE in alveolar epithelial cells.