Effects of 17β-estradiol on growth and apoptosis in human vascular endothelial cells: Influence of mechanical strain and tumor necrosis factor-α

Vascular endothelial cell (EC) integrity is key to arterial health; endothelial dysfunction is linked to atherogenesis. Atherosclerosis shows a male preponderance, possibly related to the protective effect of estrogens in women. This study examined the effect of estrogens on growth, apoptosis and adhesion molecule expression in cultured human EC. The effects of 17β-estradiol (E2) were studied in human umbilical vein endothelial cells (HUVEC) under normal culture conditions, and following exposure to cyclic mechanical strain or tumor necrosis factor α (TNFα). E2 enhanced HUVEC growth in serum-enriched media, in a concentration-dependent manner. This up-regulation of EC growth by E2 was associated with an increase in telomerase activity, assessed by PCR-based TRAP analysis. Cyclic strain enhanced [3H]-thymidine incorporation into DNA, and increased activation of mitogen-activated protein (MAP) kinase ERK1/2 and expression of early growth genes (Egr-1 and Sp-1); E2 attenuated the strain-induced ERK1/2 activation but not the early growth gene expression or DNA synthesis. TNFα (20 ng/mL) induced apoptosis in HUVEC, causing a decrease in DNA synthesis, increase in floating and Annexin-V-stained cell numbers, and morphological changes. TNFα also upregulated ERK1/2 activity and expression of adhesion molecules (ICAM-1, VCAM-1 and E-selectin). E2 significantly attenuated the effects of TNFα on ERK1/2 activity, apoptosis, and E-selectin expression in the cells. Thus, estradiol enhances growth and reduces TNFα-induced apoptosis in EC; enhanced EC growth may be mediated via upregulation of telomerase activity. These effects are possible cellular mechanisms underlying female gender-associated cardiovascular protection.