Epigallocatechin gallate & curcumin prevent transforming growth factor beta 1-induced epithelial to mesenchymal transition in ARPE-19 cells

Background & objectives: Proliferative vitreoretinopathy (PVR) is characterized by the presence of epiretinal membrane (ERM), which exerts traction and detaches the retina. Epithelial to mesenchymal transition (EMT) of the retinal pigment epithelial (RPE) cells underlies ERM formation. Adjuvant therapies aimed at preventing recurrence of PVR after surgery mostly failed in clinical trials. This study was aimed to evaluate the anti-EMT properties of bio-active compounds epigallocatechin gallate (EGCG), curcumin and lycopene as inhibitors of EMT induced by transforming growth factor beta 1 (TGF-beta 1) in cultured ARPE-19 cells. Methods: ARPE-19 cells were treated with TGF-beta 1 alone or co-treated with EGCG (1-50 mu M), lycopene (1-10 mu M) and curcumin (1-10 mu M). The mRNA and protein expression of EMT markers, alpha-smooth muscle actin, vimentin, zonula occludens-1 and matrix metalloproteinase-2 (MMP-2), were assessed by reverse transcription polymerase chain reaction/quantitative polymerase chain reaction and immunofluorescence/enzyme linked immunosorbent assay. Activity of MMP-2 was assessed by zymography. Functional implications of EMT were assessed by proliferation assay (MTT assay) and migration assay (scratch assay). Western-blot for phosphorylated Smad-3 and total Smad-3 was done to delineate the mechanism. Results: EGCG and curcumin at 10 mu M concentration reversed EMT, inhibited proliferation and migration through Smad-3 phosphorylation, when induced by TGF-beta 1 in ARPE-19 cells. Lycopene did not prevent EMT in ARPE-19 cells. Interpretation & conclusions: EGCG and curcumin are potent in preventing EMT induced by TGF-beta 1 in ARPE-19 cells and therefore, proposed as potential molecules for further pre-clinical evaluation in PVR management.