Abstract
Purpose:
Epithelial-to-mesenchymal transition (EMT) of the retinal pigment epithelium (RPE) is a critical event in the pathogenesis of proliferative vitreoretinopathy (PVR). However, the underlying mechanisms through which RPE undergo EMT are still not fully elucidated. Resveratrol (trans-3, 4, 5-trihydroxystilbene, RSV), a natural compound, is a sirtuin1 (sirt1) activator and possesses a wide spectrum of pharmacological properties, including anti-tumor invasion and EMT. The aim of this study was to investigate the effects of RSV on EMT induced by TGF-β in RPE cells in vitro.
Methods:
All experiments were conducted in primary cultured human fetal RPE cells from passages two to four. The RPE cells were pretreated with RSV (at 25, 50 and 100 mM) for 24hs and then stimulated with recombinant TGF-β2 (10ng/ml) for additional 48hs. The expression of E-cadherin (epithelial phenotype marker) and α-SMA (EMT marker) were examined by Western blotting, Real time RT-PCR and immunofluorescent staining. To confirm the role of RSV inhibition of EMT through activation of sirt1, RPE cells were transfected with sirt1 siRNA and experiments were performed as described above.
Results:
Resveratrol treatment caused a significant up-regulation of E-cadherin and down-regulation of α-SMA in a dose-dependent manner in mRNA and protein compared with controls (p<0.05). Furthermore, TGF-β2 induced down -regulation of E-cadherin and up-regulation of α-SMA were significantly reversed by RSV (p<0.05 vs controls). Immunofluorescent staining confirmed the findings by Western blot as indicated above. Importantly, after knocking down sirt1 using specific siRNA, the expression of E-cadherin and α-SMA induced by TGF-β2 was not altered in the presence of RSV.
Conclusions:
Taken together, the current results indicate that RSV suppresses TGF-β2 induced RPE EMT through activation of sirt1. This study suggests that RSV should be evaluated further for the treatment of PVR.