Effects of Ginkgo biloba Extract on Cultured Human Retinal Pigment Epithelial Cells under Chemical Hypoxia

Purpose: To investigate the effects of Ginkgo biloba extract (GBE) on expression of hypoxia-inducible factor (HIF)-1 alpha and vascular endothelial growth factor (VEGF) in retinal pigment epithelial (RPE) cells under chemical hypoxia. Materials and Methods: RPE cells (ARPE-19) were cultured in either untreated media (control group), media treated with 200 mu M cobalt chloride (hypoxia group) or media treated with both 200 mu M cobalt chloride and 100 mu g/ml GBE (hypoxia+GBE group) for various amounts of time. HIF-1 alpha and VEGF expression were compared between groups. HIF-1 alpha and VEGF messenger RNA (mRNA) were quantified using real-time polymerase chain reaction (PCR). HIF-1 alpha of extracted nuclei and VEGF of the media were quantified using enzyme-linked immunosorbent assay (ELISA). The expression of HIF-1 alpha was also assessed with Western blot and immunocytochemistry. Results: HIF-1 alpha mRNA, VEGF mRNA, HIF-1 alpha and VEGF levels were higher in the hypoxia group compared with the control group; however, real-time PCR revealed decreased expression of HIF-1 alpha mRNA and VEGF mRNA in the hypoxia+GBE group compared with the hypoxia group. In the ELISA, the HIF-1 alpha and VEGF protein concentrations also decreased with GBE treatment. Western blot and immunostaining showed that the intensity of HIF-1 alpha signals in the hypoxia+GBE group was lower than that of the hypoxia group. Conclusion: GBE reduced HIF-1 alpha and VEGF expression in RPE cells cultured under chemical hypoxia in vitro.