Hypoxia‐induced vascular endothelial growth factor secretion by retinal pigment epithelial cells is inhibited by melatonin via decreased accumulation of hypoxia‐inducible factors‐1α protein

Abstract

Abstract Background Hypoxia is the most important stimulus leading to up‐regulation of vascular endothelial growth factor (VEGF) in the retina via elevation of hypoxia‐inducible factors‐1α (HIF‐1α) protein. The purpose of this study was to test the effects of melatonin on the expression of VEGF and HIF‐1α in the cultured human retinal pigment epithelial (RPE) cells under normoxia and hypoxia. Method An in vitro RPE cell hypoxia model was established by placing cells under 1% oxygen pressure or by adding cobalt chloride (CoCl 2 ) to the culture medium. RPE cells and conditioned media were collected from cultures treated with and without melatonin under normoxia and hypoxia. The protein and RNA levels of VEGF and HIF‐1α were measured by ELISA kits and RT‐PCR, respectively. Result Hypoxia induced a significant increase of expression and secretion of VEGF and accumulation of HIF‐1α protein in RPE cells ( P < 0.05). Melatonin at 10 −5 to 10 −8 M significantly inhibited hypoxia‐induced expression, the secretion of VEGF and the accumulation of HIF‐1α protein ( P < 0.05), but not affected expression of VEGF and HIF‐1α under normoxia ( P > 0.05). Conclusion This study suggests that melatonin may have potential value in the prevention and treatment of various retinal diseases associated with increase of VEGF, vascular leakage and angiogenesis.