Role of glucocorticoid receptor and CCAAT/enhancer-binding protein α in the feed-forward induction of 11β-hydroxysteroid dehydrogenase type 1 expression by cortisol in human amnion fibroblasts

Abstract

The amount of cortisol available to its receptors is increased by the pre-receptor enzyme 11b-hydroxysteroid dehydrogenase type 1 (11b-HSD1) which converts cortisone to cortisol. We examined the molecular mechanisms of the feedback effect of cortisol on 11b-HSD1 mRNA expression in human amnion fibroblasts. Our data showed that cortisol-induced 11b-HSD1 mRNA expression dose dependently in amnion fibroblasts, which could be completely blocked both by the mRNA transcription inhibitor 5,6-dichlorobenzimidazole riboside and by the glucocorticoid receptor (GR) antagonist RU486, and partially blocked by global inhibition of CCAAT/enhancerbinding proteins (C/EBPs) with transfection of C/EBP-specific dominant-negative expression CMV500 plasmid (AC/EBP) into the cells. Likewise, the induction of the promoter activity by cortisol could also be completely blocked by RU486 and partially by AC/EBP transfection. Progressive 5 0 deletion of the 11b-HSD1 promoter located the region responsible for cortisol's induction within K204 bp upstream to the transcription start site. Specific nucleotide mutations of the putative glucocorticoid responsive element or CCAAT in this promoter region attenuated the induction by cortisol. Moreover, chromatin immunoprecipitation assay and electrophoretic mobility shift assay showed that GR and C/EBPa but not C/EBPb could bind this promoter region upon cortisol stimulation of amnion fibroblasts. In conclusion, we demonstrated that GR and C/EBPa were involved in cortisol-induced 11b-HSD1 mRNA expression via binding to 11b-HSD1 promoter in amnion fibroblasts, which may cast a feed-forward production of cortisol in the fetal membranes at the end of gestation.

11β-Hydroxysteroid Dehydrogenases: Intracellular Gate-Keepers of Tissue Glucocorticoid Action

“…Two C/EBP sites close to the transcription start and highly conserved between human, rat, and mouse (244,775) are critical for basal and regulated expression (775), either alone or in concert with other transcription factors including GR (789).…”

The Effects of Glucocorticoids on Fetal and Placental Development

“…GR-mediated transcriptional activation is modulated by phosphorylation [29]. GRs are highly expressed in decidua, chorion, amnion, stromal fibroblasts, vascular smooth muscle cells and endothelial cells of human term placentas, with moderate expression in cytotrophoblasts and negligible expression in syncytiotrophoblast [30][31][32][33][34]. Because the significance of glucocorticoids to the early mammalian embryo is clear and glucocorticoid action within the cell is regulated by GR, we investigated GR expression during the course of rat embryogenesis until day 12 of gestation.…”

Role of fetal membranes in signaling of fetal maturation and parturition

“…Glucocorticoids up-regulate 11b-HSD1 expression in a number of tissues or cell types (Tomlinson et al, 2004) and we demonstrated that glucocorticoids induced 11b-HSD1 expression in fibroblast cells and trophoblast cells derived from human fetal membranes at concentrations easily achieved at the end of pregnancy (Sun and Myatt 2003;Li et al 2006;Yang et al 2007). We found this induction of 11β-HSD1 expression by glucocorticoids was a GR mediated on-going transcriptional process and verified the CCAAT consensus sequence and a GRE existing within the promoter region responsible for the induction of 11β-HSD1 by glucocorticoids (Yang et al, 2007).…”