Crocetin inhibits the proliferation, migration and TGF-β2-induced epithelial-mesenchymal transition of retinal pigment epithelial cells.

Retinal pigment epithelial (RPE) cells, the major cell type in the fibrotic membrane of proliferative vitreoretinopathy, display enhanced proliferative and migratory capacities and epithelial-mesenchymal transition (EMT). In this study, we investigated the potential impact of crocetin on the proliferation, migration and EMT of cultured ARPE-19 cells. The cells were treated with crocetin alone or in combination with transforming growth factor-β2 (TGF-β2). Cell proliferation was examined using the CCK-8 assay. Cell cycle distribution was analyzed by flow cytometry after propidium iodide staining. The expression levels of proliferating cell nuclear antigen (PCNA), p21 and p53 were examined by Western blot analysis. Cell migration was assessed by in vitro scratch and Transwell assays. Real-time PCR, Western blotting and immunofluorescence were used to assess EMT features. Treatment of ARPE-19 cells with crocetin (50-200μM) significantly inhibited their proliferation and migration in a concentration- and time-dependent manner. Crocetin induced G1 arrest, reduced PCNA protein expression and increased the p21 and p53 accumulation in ARPE-19 cells. Crocetin inhibited TGF-β2-induced EMT in ARPE-19 cells by maintaining the expression of E-cadherin and ZO-1 and by reducing the expression of vimentin and α-SMA through the suppression of phosphorylation of p38. These results indicate that crocetin is an effective inhibitor of the proliferation, migration and TGF-β2-mediated EMT of ARPE-19 cells.