P2‐20: Propylene glycol and glycerol, components of E‐cigarettes and heated tobacco products, damage epithelial cells in human airways

injury, which often leads to radiation pneumonitis. Glucocorticoid (GC) is used for the treatment of radiation pneumonitis. Although alveolar epithelial cells play a pivotal role for the alveolus barrier function, the effects of irradiation and GC on barrier function in alveolar epithelial cell remains unclear. Methods: Alveolar epithelial type II (ATII) cells were isolated from Sprague-Dawley rats. ATII cells were cultured on collagen-coated trans-wells and trans-differentiated into type I-like cells. The cells were treated with 1μM dexamethasone (DEX) right before irradiation (8 Gy of X-ray). Barrier function was evaluated with trans-epithelial electrical resistance (TEER) at 6, 24, and 48 hours (h) and FITC-dextran 4kD (FD4) permeability at 24h. Statistical analysis was done by one-way ANOVA followed by Holm-Sidak test and the relative data was expressed with means SE (n=5). Results and Conclusions: Irradiation reduced TEER by 20 4% at 6h (p=0.02) and 25 5% at 24 h (p=0.03). Conversely, DEX increased TEER by 95 12% at 6h (p<0.01) and 85 15% at 24 h (p=0.01). TEER of irradiated epithelial cells treated with DEX was increased by 70 8% at 6h and by 60 13% at 24 h compared to that of control cells. These effects by irradiation and DEX were disappeared at 48 h. FD4 permeability was decreased by DEX in non-irradiated cells (1.00 for controls vs. 0.51 0.09 for DEX-treated, p=0.01) and in irradiated cells (1.11 0.12 for controls vs. 0.59 0.18 for DEX-treated, p=0.12). In conclusion, these results suggest that irradiation loosens alveolar epithelial cell barrier function, whereas GC tightens it.