Effects of 17 β-estradiol on lipopolysacharride-induced intracellular adhesion molecule-1 mRNA expression and Ca2+ homeostasis alteration in human endothelial cells

Recent evidence showed that 17 β-estradiol (E2) decreased cytokine-induced expression of cell adhesion molecules (CAM). Changes in intracellular Ca2+ concentration ([Ca2+]i) has been shown to be associated with CAM expression in endothelial cells. Here, the effects of E2 (1 μM, 24 h) on the expression of intracellular adhesion molecule-1 (ICAM-1) and [Ca2+]i were investigated in a lipopolysaccharide (LPS) (100 ng/mL, 18 h)-stimulated human endothelial cell line, EA.hy926, using real-time PCR and spectrofluorometry, respectively. PCR analysis revealed a significant increase in ICAM-1 expression in calcium ionophore A23187 (1 nM)- or LPS-stimulated cells. Pretreatment of cells with E2 significantly inhibited LPS-induced ICAM-1 mRNA expression. [Ca2+]i was monitored in Fura-2 AM-loaded cells in the presence and absence of extracellular Ca2+ with thapsigargin (TG, 1 μM), a sarco/endoplasmic reticulum ATPase inhibitor or ATP (100 μM). The extent of TG- or ATP-induced [Ca2+]i increase was significantly higher in LPS-stimulated cells than in control cells. Pre-treatment of LPS-stimulated cells with E2 limited the Ca2+ response to the same level as in control cells. Furthermore, ICI 182,780, an estrogen receptor antagonist, attenuated the inhibitory actions of E2 on ICAM-1 mRNA expression and Ca2+ responses, suggesting that estrogen receptors mediate, at least in part, the effects of estrogen. These data suggest a potential underlying mechanism for the protective effect of E2 against atherosclerosis.

• In the early stages of atherosclerosis, inflammatory cells are recruited to vascular wall via CAM.
• Estrogen's effect on CAM and a possible link between CAM and Ca2+ contribute to the hypothesis that the anti‐atherogenic effect of E2 is mediated, in part, by the modulatory effects on Ca2+.Figure optionsDownload as PowerPoint slide