Examining the potential protective effect of Vasaka tea extract on lung cells exposted to Pine wood smoke
This study tested the hypothesis that a medicinal plant, Vasaka, typically consumed as a tea to treat respiratory malaise, could protect airway epithelial cells (AECs) from wood smoke particle-induced damage and prevent pathological mucus expression. Wood/biomass smoke is a common pneumotoxic air pollutant that activates transient receptor potential ankyrin 1 (TRPA1) and causes endoplasmic reticulum (ER) stress and AEC damage. This stimulates epidermal growth factor receptor and mucin 5AC (MUC5AC) production by AECs. Mucus normally protects the airways, but excessive MUC5AC production can obstruct airflow and cause respiratory distress. Vasaka tea pre- and co-treatment dose-dependently inhibited MUC5AC mRNA induction in cells treated with wood smoke particles. This correlated with TRPA1 inhibition, an attenuation of ER stress, and AEC damage/death, among other effects. Induction of mRNA for Anterior Gradient 2 (AGR2), an ER chaperone/disulfide isomerase required for MUC5AC production, and TRP vanilloid-3 (TRPV3), a gene that suppresses ER stress and wood smoke particle-induced cell death, were also attenuated. Variable inhibition of TRPA1, ER stress, and MUC5AC mRNA induction was observed using selected chemicals identified in Vasaka tea including vasicine, vasicinone, apigenin, 9-oxoODE, and 9,10-EpOME. 9,10-EpOME and apigenin were the most cytoprotective and mucosuppressive.  Cytochrome P450 1A1 mRNA was also induced by Vasaka tea and wood smoke particles. Inhibition of CYP1A1 enhanced ER stress and MUC5AC mRNA expression, suggesting a role in producing protective oxylipins in stressed cells. The results provide mechanistic insights and support for the purported benefits of Vasaka tea in treating lung inflammatory conditions, raising the possibility of further development as a preventative therapy. Overall design: This study examines gene expression changes in HBEC-3KT cells after a 24 hr treatment with (n=3) vehicle, pine, vasaka, or Pine + Vasaka.