Free radical-generated F2α-isoprostanes are a group of compounds with vasoconstrictor properties and have been recognized as a stable, good biomarker for in vivo oxidative stress. Oestradiol (E2) has been proposed to exert antioxidant effects, a property related to the cardiovascular effects of oestrogens, but controversial results have been reported with the use of different doses and methods to study that antioxidant capacity. We investigated whether E2 exerts anti-oxidant actions modifying F2α-isoprostane production.
Cultured human umbilical vein endothelial cells were exposed to different physiological concentrations (0.1-10 nM) of E2 for different times of incubation, up to 48 h. In some experiments, anti-oestrogens (ICI 182780 or EM-652) or progestogens were added. Total (free plus esterified) F2α-isoprostanes were measured in culture medium after extraction with specific F2α-isoprostane affinity columns and assayed by using a commercial F2α-isoprostane EIA kit. Repeated-measures ANOVA was applied for comparisons of means, and then Student’s unpaired t test was performed. P values < 0.05 were considered significant.
Exposure to different E2 dosages for less than 8 h did not modify F2α-isoprostane production. Exposure to 1 nM E2 decreased F2α-isoprostane production only after 24 h, whereas the 10 nM E2-induced reduction was already significant after 16 h. The rest of the experiments were performed at 24 h of incubation with different compounds. E2 (1 and 10 nM) inhibited F2α-isoprostane production by 36 and 49 %, respectively (P < 0.001 vs. control, for both values). Exposure to anti-oestrogens alone (ICI 182780 or EM-652) slightly reduced F2α-isoprostanes (P < 0.05 vs. control), but much less than E2 (P < 0.05). ICI 182780 reversed the E2-induced reduction of F2α-isoprostane production (P < 0.05 vs. E2 values). Along with time course analysis, these results suggest that E2 effects were mediated through both oestrogen receptor-dependent and -independent mechanisms. The effect of two progestogens was also tested. Neither natural progesterone nor medroxyprogesterone acetate (a progestogen used in postmenopausal hormone therapy) changed F2α-isoprostane production at any of the tested concentrations (1, 10 and 100 nM). Combined exposure to E2 plus progesterone or medroxyprogesterone modified the endothelial cell production of F2α-isoprostanes in a different way: progesterone reversed the E2-induced reduction of F2α-isoprostane production while medroxyprogesterone did not.
This work was supported by grants 00/0960 and 01/0197 from FIS (Spanish Ministerio de Sanidad) and GV01-69 from the Generalitat Valenciana.