Estradiol antagonism of glucocorticoid-induced GILZ expression in human uterine epithelial cells and murine uterus.

Sex hormone signaling regulates a variety of functions in the uterine endometrium essential for embryo implantation and immunity. Epithelial cells of the uterine endometrium are the target of the coordinated actions of estradiol (E(2)) and progesterone. However, little information exists regarding the interplay of estrogens with glucocorticoids in this tissue. Using the human uterine epithelial cell line ECC1, E(2) was found to antagonize induction of the glucocorticoid-induced leucine zipper (GILZ) gene expression, which is associated with several of the immune-related functions of glucocorticoids. Interestingly, E(2) antagonizes glucocorticoid regulated nascent RNA GILZ expression within 1 h of hormone treatment. Repression of glucocorticoid-induced GILZ expression requires the estrogen receptor (ER), because both treatment with the ER-antagonist ICI 182,780 and small interfering RNA knockdown of ERα block E(2)'s ability to repress GILZ gene expression. Antagonism of glucocorticoid-induced GILZ expression may not be unique to ERα, as the ERβ agonist Liquiritigenin is also able to antagonize glucocorticoid signaling. Transcriptional regulation appears to be at the level of promoter binding. Both the glucocorticoid receptor and ERα are recruited to regions of the GILZ promoter containing glucocorticoid response elements and the transcriptional start site. Glucocorticoid receptor binding to these regions in the presence of dexamethasone decreases with E(2) treatment. GILZ gene expression was also found to be repressed in the whole mouse uterus treated with a combination of dexamethasone and E(2). Regulation of the antiinflammatory gene GILZ by glucocorticoids and E(2) suggests cross talk between the immune modulating functions of glucocorticoids and the reproductive actions of estradiol signaling.