Apoptotic effects of high estradiol concentrations on endometrial glandular cells

High serum estradiol (E2) concentrations result in adverse reproductive outcome in in vitro fertilization cycles, and the detrimental effects are probably due to impaired endometrial receptivity.Endometrial glandular cells (EGCs) are the cells that embryos first interact with during implantation. Our objective is to examine the in vitro EGC alterations after high E2 treatment.This was a prospective study.The study was conducted at a tertiary university hospital.Six women in the follicular phase participated in the study.EGCs were purified from human endometrium and cultured with different concentrations (0, 10(-9), 10(-8), 10(-7), 10(-5), 10(-4) M) of E2.EGC apoptosis and its underlying mechanism were measured.In vitro BeWo spheroid-EGC implantation assay demonstrated that the stimulation with 10(-5) and 10(-4) M E2 for 2 days decreased embryo implantation potentials. Presence of apoptotic bodies and DNA fragmentation and an increased percentage of sub-G1 phase were found in EGCs treated with high E2 concentrations. The high E2-treated EGCs could be rescued from apoptosis after the addition of estrogen receptor antagonist ICI 182 780. Western blot revealed increased inhibitory-κB (IκB)-α expression and decreased nuclear factor-κB (NF-κB) expression in high E2-treated EGCs, and NF-κB binding site-driven luciferase activity was decreased as well. When EGCs were pretreated with IκB-α small interfering RNA, high E2-induced B cell lymphoma 2 (Bcl-2) down-regulation did not occur and EGCs apoptosis was reduced. Bcl-2 overexpression also rescued high E2-induced EGCs from apoptosis.High E2 concentrations induced EGCs apoptosis through enhancing IκB-α expression, which in turn suppressed NF-κB expression. The decreased nuclear NF-κB subsequently inhibited Bcl-2 expression and accordingly enhanced EGC apoptosis.