Up-regulation of HIF-1α and VEGF expression by elevated glucose concentration and hypoxia in cultured human retinal pigment epithelial cells

Abstract

In order to explore the effect of high glucose concentration and high glucose concentration with hypoxia on the production of hypoxia-inducible factor-1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF), human RPE cells were cultured in 5.56 mmol/L glucose (control group), 5.56 mmol/L glucose with 150 micro mol/L CoCl2 (hypoxic group), 25 mmol/L glucose (high glucose group) and 25 mmol/L glucose with 150 micro mol/L CoCl2 (combination group). RT-PCR was used to detect the expression of HIF-1alpha and VEGF mRNAs. Western blot analysis was used to measure the levels of HIF-1alpha and VEGF proteins. Although the small amount of HIF-1alpha protein was able to be detected in high glucose group but not in control group, there was no significant difference between the expression of HIF-1alpha mRNA of RPE cells in high glucose group and that of RPE cells in control group. As compared with RPE cells in control group, the mRNA expression and the protein synthesis of VEGF in high glucose group were up-regulated. As compared with RPE cells in hypoxic group, the expression of HIF-1alpha mRNA of RPE cells in combination group was not different, but the protein synthesis of HIF-1alpha, the mRNA expression and the protein synthesis of VEGF were more obviously up-regulated. In conclusion, high concentration glucose mainly influence the protein synthesis of HIF-1alpha of RPE cell, and HIF-1alpha protein is able to be accumulated in high concentration glucose. Under hypoxia, the HIF-1alpha protein induced by high concentration glucose is more stable, and the expression of VEGF is obviously increased. It is suggested that high concentration glucose may play a role in retinal neovascularization, especially at ischemia stage of diabetic retinopathy.