Statins Decrease VEGF Expression in Retinal Pigment Epithelial Cells by Downregulation of Receptor for AGE (RAGE)

Age-related macular degeneration (AMD) is one of the most important causes of blindness in the elderly patients. Statins, inhibitors for HMG-CoA reductase, are recently reported to be useful for decreasing the risk of wet-type AMD. However, the molecular mechanisms how statins reduce the risk of AMD remain unclear. In this study, we examined the effects of statins (atorvastatin and lovastatin) on the expression of VEGF and RAGE in human retinal pigment epithelial (RPE) cells. We used h1RPE7, human RPE cells, damaged by 20 µM hydroquinone (HQ)+300 µg/mL advanced glycation end-product (AGE) as an experimental AMD model. These cells were treated with atorvastatin (100 nM) or lovastatin (2 µM) for 24 hours. After the treatment, the expression of VEGF and RAGE was evaluated by real-time RT-PCR, and we found that the mRNA levels of VEGF and RAGE in the HQ+AGE treated cells were increased. The additions of statins significantly attenuated the HQ+AGE-induced VEGF and RAGE mRNA expression. We also measured the VEGF concentration in the cell culture medium by ELISA and found that it was markedly decreased by the addition of statins. In order to know the impact of RAGE on the VEGF expression, small interfering RNA (siRNA) for RAGE (siRAGE) was introduced into h1RPE7 cells by lipofection method and the VEGF expression was measured by real-time RT-PCR. The RT-PCR results show that siRAGE attenuated the up-regulation of VEGF in the HQ+AGE treated cells. The luciferase reporter assays for RAGE and VEGF transcription showed that the RAGE expression in the statin-treated cells was regulated at the transcriptional level, and that the VEGF expression in these cells was regulated by a post-transcriptional mechanism. These results indicate that statins attenuated the HQ+AGE-induced VEGF expression via decreasing RAGE expression. As VEGF is an important factor for the development of wet-type AMD, statins could decrease the risk of wet-type AMD and be a preventive medicine for diabetic patients.