Inhibition of placental 11β-hydroxysteroid dehydrogenase type 2 by catecholamines via α-adrenergic signaling

Abstract

The placenta expresses high levels of 11β-hydroxysteroid dehydrogenase type 2 (11βHSD2) that converts cortisol into inactive 11-keto metabolites and effectively protects the developing fetus from maternal cortisol during pregnancy. Impairment of this glucocorticoid barrier has adverse effects on fetal outcomes. A similar spectrum of adverse fetal effects is induced by antenatal stress during pregnancy. To examine the hypothesis that physiological stress may regulate placental 11βHSD2 gene expression, we examined the effects of the catecholamines norepinephrine (NE) and epinephrine (E) on 11βHSD2 expression in human trophoblastic cells. With the use of Northern blotting and semiquantitative RT-PCR, we determined that NE and E rapidly downregulate 11βHSD2 steady-state mRNA levels in early- and late-gestation human trophoblasts and BeWo trophoblastic cells. Experiments using different adrenoceptor subtype-selective agonists and antagonists demonstrated that this catecholamine suppression of 11βHSD2 mRNA expression is mediated via both α1- and α2-adrenoceptors and is independent of β-adrenergic stimulation. To examine transcriptional regulation, BeWo cells were transiently transfected with a reporter construct in which an 11βHSD2 human promoter sequence was inserted upstream of the luciferase gene. Treatment with 10−7 M NE decreased luciferase activity by ∼60% ( n = 3, P < 0.01). These results suggest the NE/E-mediated decrease in placental 11βHSD2 gene expression is an instance of α-adrenoceptor-specific rapid transcriptional inhibition of an adrenergic target gene. This molecular mechanism may be involved in the deleterious effects of antenatal physiological stress on fetoplacental growth and development.