The contrasting effect of estrogen on mRNA expression of VEGF in bovine retinal vascular endothelial cells under different oxygen conditions

Abstract

To investigate the influence of Estradial (E(2)) at physiological concentration on mRNA expression of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1α(HIF-α1) in bovine retinal vascular endothelial cells (BRECs) under different oxygen conditions. The mRNA expression of VEGF, HIF-1α in BRECs was studied by quantitative reverse-transcription PCR (qRT-PCR), and protein levels were assayed by Western Blot. Different concentrations of E(2) (10(-12), 10(-10), 10(-8) mol/l) and estrogen receptor antagonist Tamoxifen (10(-7) mol/l) were added into the cell culture medium of different groups, while the phosphate-buffered saline (PBS) was added in the control group instead. Culture conditions were set to be under normoxia and hypoxia. The results of each group were detected after 8 hours and 24 hours. (1) Under hypoxia, gene expression of VEGF, HIF-1α in BRECs increased more than that of the control group (P < 0.05). There is evident positive correlation between the mRNA and protein levels of VEGF and HIF-1α (r = 0.82). (2) Treated with 10(-8) mol/l E(2,) the expression of VEGF mRNA was increased in a time-dependent manner (P < 0.05). Treated with the indicated to concentrations of E(2) (10(-12 ∼ -8) mol/l) under normoxia for twenty-four hours, the mRNA expression of VEGF in BRECs was increased in a dose-dependent manner (P < 0.05), whereas E(2) did not influence the mRNA expression of HIF-1α (P > 0.05). (3) Under hypoxia , E(2) reduced the mRNA and protein levels of HIF-1α and VEGF in a concentration-dependent manner (P < 0.05), and the decrease developed in a time-dependent manner (P < 0.05). (4) An overdose of tamoxifen (10(-7) mol/l) reversed the effect of E(2) (10(-8) mol/l) (P < 0.05). E(2) increases the gene expression of VEGF in BRECs under normoxia, whereas E(2) reduces the gene expression of VEGF in BRECs through HIF-1α under hypoxic conditions in a dose-dependent and time-dependent manner. The contrasting effect of E(2) on mRNA expression of VEGF may play a prophylactic role in retinopathy of prematurity (ROP).