Effects of 17β-estradiol on glucose transporter 1 expression and endothelial cell survival following focal ischemia in the rats

Abstract 

Estrogen replacement therapy in postmenopausal women is associated with a decreased mortality and morbidity from stroke. The present study was undertaken to investigate the effects of estrogen on endothelial cell glucose transporter 1 (GLUT 1) and on the cell viability during focal ischemia in a rat model. Female rats were ovariectomized (OVX) and 2 weeks later 17β-estradiol (E₂) was injected subcutaneously at a dose of 100 μg/kg 2 h before unilateral middle cerebral artery (MCA) occlusion. Ischemic lesion size was quantified using 2,3,5-triphenyl tetrazolium chloride (TTC) staining and GLUT 1 protein was analyzed by Western blotting. E₂ treatment decreased ischemic lesion size in slices taken at 9 and 11 mm posterior from the olfactory bulb by 46.3% and 44.1%, respectively (P < 0.05). GLUT 1 protein decreased in both OVX and E₂ groups by 24.6% and 22.7% respectively (P < 0.05) compared with the non-lesioned side in the core ischemic region, including the basal ganglia. GLUT 1 protein was increased in the E₂-treated group compared with the control group (23.3%, P < 0.05) in the penumbral ischemic region of the cortex. Primary rat brain capillary endothelial cell (BCEC) cultures were established as an in vitro model for ischemic effects on endothelial cells. Estrogen reduced BCEC loss by 35.9%, 28.4% and 23.5% (P < 0.05) when glucose in the culture medium was reduced to 50%, 20% and 10%, respectively; and by 28.4% and 18.4% (P < 0.05) following 1 or 4 h of anoxia, respectively. This study demonstrates that estrogen treatment increases GLUT 1 transporters and protects BCEC loss which may in turn reduce focal ischemic brain damage.