Effects of (-)-epigallocatechin gallate on RPE cell migration and adhesion

PURPOSE In diseases such as proliferative vitreoretinopathy (PVR), proliferative diabetic retinopathy (PDR), and age-related macular degeneration (AMD), retinal pigment epithelial (RPE) cells can initiate proliferation and migration and secrete extracellular matrix (ECM) proteins. (-)-Epigallocatechin gallate (EGCG)-a natural anti-oxidant flavonoid that is abundant in green tea-has been shown to suppress the migration and adhesion of many cell types, but its effects on RPE cell migration and adhesion were unknown. Several studies have shown that platelet-derived growth factor (PDGF) enhances proliferation and migration effects on RPE cells in PVR, and that fibronectin is a major ECM component of PVR tissue. Therefore, we investigated the inhibitory effects of EGCG on RPE cell migration induced by PDGF-BB, an isoform of PDGF, and adhesion by fibronectin. METHODS The migration of RPE cells was detected by an electric cell-substrate impedance sensing (ECIS) migration assay and a Transwell migration assay. Cells were loaded with 2',7'-bis-(carboxyethyl)-5(6')-carboxyfluorescein acetoxymethyl ester (BCECF/AM), and their adhesion to fibronectin was examined. The interactions of EGCG with PDGF-BB were analyzed by a dot binding assay. Cytoskeletal reorganization was examined by immunofluorescence microscopy. The PDGF-BB-induced signaling pathways were detected by western blotting. RESULTS In the present study, we find that EGCG can inhibit PDGF-BB-induced human RPE cell migration and, in a dose-dependent manner, RPE cell adhesion to fibronectin. Our analysis demonstrates that EGCG does not directly bind to PDGF-BB and the inhibition of EGCG against fibronectin-induced cytoskeletal reorganization is observed. Furthermore, EGCG is shown to suppress PDGF-BB-induced PDGF-beta receptors, downstream PI3K/Akt, and MAPK phosphorylation. CONCLUSIONS Our results provide the first evidence that EGCG is an effective inhibitor of RPE cell migration and adhesion to fibronectin and, therefore, may prevent epiretinal membrane formation.