Approaches in Hydroxytyrosol Supplementation on Epithelial-Mesenchymal Transition in TGFβ1-Induced Human Respiratory Epithelial Cells

Hydroxytyrosol (HT) is an olive polyphenol with anti-inflammatory and antioxidant properties. This study aimed to investigate the effect of HT treatment on epithelial-mesenchymal transition (EMT) in primary human respiratory epithelial cells (RECs) isolated from human nasal turbinate. HT dose-response study and growth kinetic study on RECs was performed. Several approaches on HT treatment and TGF beta 1 induction with varying durations and methods was studied. RECs morphology and migration ability were evaluated. Vimentin and E-cadherin immunofluorescence staining and Western blotting [E-cadherin, vimentin, SNAIL/SLUG, AKT, phosphorylated (p)AKT, SMAD2/3 and pSMAD2/3] were performed after 72-h treatment. In silico analysis (molecular docking) of HT was performed to evaluate the potential of HT to bind with the TGF beta receptor. The viability of the HT-treated RECs was concentration-dependent, where the median effective concentration (EC50) was 19.04 mu g/mL. Testing of the effects of 1 and 10 mu g/mL HT revealed that HT suppressed expression of the protein markers vimentin and SNAIL/SLUG while preserving E-cadherin protein expression. Supplementation with HT protected against SMAD and AKT pathway activation in the TGF beta 1-induced RECs. Furthermore, HT demonstrated the potential to bind with ALK5 (a TGF beta receptor component) in comparison to oleuropein. TGF beta 1-induced EMT in RECs and HT exerted a positive effect in modulating the effects of EMT.