EFFECT OF 17 β -ESTRADIOL ON BRAIN MICROVASCULAR ENDOTHELIAL CELL OXIDATIVE STRESS, APOPTOTIC SUSCEPTIBILITY AND FIBRINOLYTIC CAPACITY

The experimental aim of this study was to determine, in vitro, the effect of estrogen on brain endothelial cell oxidative stress, apoptotic susceptibility and tissue-type plasminogen activator (t-PA) release. Human cerebral microvascular endothelial cells (hCMECs) were cultured and treated with 17β-estradiol (100 nM), the primary and most biologically active endogenous form of estrogen in humans, for 24 hours. Intracellular reactive oxygen species production was significantly lower (∼15%; P>0.01) in hCMECs treated with 17β-estradiol; however, antioxidant proteins superoxide dismutase-1 (28.6±11.0 vs 36.2±11.9 AU) and catalase (33.6±14.0 vs 32.1±14.7 AU) were not significantly altered by 17β-estradiol. Although, there were no significant differences in the basal intracellular expression of either total caspase-3 (159.8±84.9 vs 143.6±39.2 AU) or active caspase-3 (13.5±4.5 vs 15.4±6.7 AU) between untreated and 17β-estradiol-treated hCMECs; the increase in active caspase-3 in response to the apoptosis stimulus staurosporine was significantly lower (∼30%; P=0.02) in 17β-estradiol-treated (from 15.5±6.7 to 184.5±43.8 AU) compared with untreated (from 13.5±4.5 to 257.6±34.4 pg/mL) hCMECs. t-PA release in response to thrombin was significantly higher (P=0.02) in 17β-estradiol-treated (from 41.6±10.8 to 61.1±9.2 pg/mL; ∼45% increase) compared with untreated (43.4±9.2 to 48.0±11.5 pg/mL; ∼10% increase) hCMECs. In summary, 17β-estradiol decreases oxidative stress, enhances apoptotic resistance and increases fibrinolytic capacity in human brain microvascular endothelial cells in vitro. Reduced risk of cerebrovascular disease and thrombotic events attributed to estrogen may be mediated, in part, by these beneficial endothelial effects.