The effect of 17 β-estradiol on intracellular calcium homeostasis in human endothelial cells
European Journal of Pharmacology
The cardiovascular effects of estrogen are mediated in part by augmenting the function of endothelial nitric oxide synthase. Endothelial nitric oxide synthase activity is dependent on many cofactors including Ca2+. Hence, we investigated the effect of chronic 17 β-estradiol treatment on the intracellular Ca2+ concentration and endothelial nitric oxide synthase protein expression in the human endothelial cell line, EA.hy926, using spectrofluorometry and Western blot, respectively. Inhibiting the sarco(endo)plasmic reticulum Ca2+ ATPase with thapsigargin caused an increase in the intracellular Ca2+ concentration, which was higher in chronically 17 β-estradiol-treated (1 μM, 24 h) cells loaded with Fura-2-acetoxymethyl ester compared to vehicle-treated cells, suggesting a higher endoplasmic reticulum Ca2+ content in 17 β-estradiol-treated cells. An enhanced Ca2+ influx pathway in chronically 17 β-estradiol-treated cells was also observed. In addition, 17 β-estradiol-treated cells expressed higher levels of endothelial nitric oxide synthase protein in comparison to vehicle-treated cells. The chronic effect of 17 β-estradiol on Ca2+ homeostasis and endothelial nitric oxide synthase expression was attenuated with the nonselective estrogen receptor inhibitor, ICI 182,780 (10 μM, 7α, 17β-[9-[(4,4,5,5,5-Pentafluoropentyl)sulfinyl]nonyl] estra-1,3,5(10)-triene-3,17-diol). Furthermore, analysis of the thapsigargin-evoked Ca2+ response in chronically 17 β-estradiol-treated estrogen receptor α-knockdown cells showed no significant difference in Ca2+ response compared to vehicle-treated estrogen receptor α-knockdown cells, indicating that the regulation of Ca2+ homeostasis by 17 β-estradiol is mediated through an estrogen receptor α-dependent pathway. These data revealed an estrogen receptor α-dependent modulation of Ca2+ homeostasis accompanying the enhancement of endothelial nitric oxide synthase expression in 17 β-estradiol-treated human endothelial cells.
The effect of 17 β-estradiol on intracellular calcium homeostasis in human endothelial cells.
European Journal of Pharmacology, 630(1--3), 92–99.