Glucocorticoid stimulation of corticotropin-releasing hormone gene expression requires a cyclic adenosine 3 ',5 '-monophosphate regulatory element inhuman primary placental cytotrophoblast cells

Production of placental CRH, which is identical to the peptide synthesized and secreted in the hypothalamus, has been linked to human parturition. Glu cocorticoids stimulate placental CRH secretion and messenger ribonucleic ac id expression, in contrast to their inhibition of CRH synthesis in the hypo thalamus. A positive feedforward loop involving glucocorticoid-CRH-ACTH-glu cocorticoid is thought to drive the exponential increase in placental CRH l eading to delivery. Tissue-specific effects of glucocorticoids on CRH expre ssion are therefore of interest. Using human primary placental cells, we in vestigated the mechanism by which glucocorticoids stimulate placental CRH g ene expression. Nuclear run-on transcription shows that in human placental cells glucocorticoids up-regulate transcription of human CRH (hCRH). Using transient transfection assays we demonstrate that dexamethasone up-regulate s both basal and cAMP-stimulated hCRH promoter activity, correlating well w ith the increase in endogenous CRH peptide levels. Through mutagenesis and deletion analyses we show that dexamethasone stimulation of hCRH gene trans cription requires a functional cAMP regulatory element (CRE); this CRE is a dequate to confer dexamethasone stimulation upon a heterologous promoter, a nd electrophoretic mobility shift assay studies show that a placental nucle ar protein specifically binds to the hCRH CRE.