Effects of retinoic acid on the beta-catenin/TCF pathway in cultured porcine tracheobronchial epithelial cells.

The effects of retinoic acid on the beta-catenin/TCF pathway in cultured porcine tracheobronchial epithelial cells (TBEC) were investigated. After TBEC were treated with retinoic acid at various concentrations, mRNA and protein changes of beta-catenin in cytoplasm, nucleus and whole cell of the TBEC were observed by immunocytochemical stain, RT-PCR and Western blotting. And the changes of the target gene cyclinD1 of beta-catenin/TCF pathway were also observed. It was found that there was no significant difference in beta-cat mRNA level after retinoic acid treatment. However, the expression of beta-catenin in the whole cell and cytoplasm was elevated with the increase of retinoic acid concentration (P<0. 01). The nuclear protein beta-catenin and target gene cyclinD1 of beta-catenin/TCF pathway was decreased (P<0.05). It was indicated that retinoic acid could increase beta-catenin level of the whole cell protein and decrease nuclear beta-catenin, downregulating beta-cat/TCF signaling activity and reducing target gene cyclinD1 protein level. As a result, retinoic acid can downregulate beta-catenin/TCF pathway in porcine tracheobronchial epithelial cell, suggesting that retinoic acid can inhibit the proliferation and accelerate differentiation of tracheobronchial epithelial cells.