The Study Of Corticotropin-Releasing Hormone Regulating Steroid Hormones Production In Human Placental Cells And Its Mechanisms

Estrogen and progesterone produced by the human placenta play pivotal roles in the regulation of pregnancy and parturition. Progesterone is crucial for maintaining the uterus in a quiescent state in order to prevent premature onset of labor. In contrast, estrogen augments the capacity for uterine contraction and promotes parturition. The human placenta produces large amounts of estrogen and progesterone, which increases progressively through pregnancy but there is an increase in the ratio estrogen/progesterone in maternal plasma at the term, which may contribute to the process of parturition in humans.Placental CRH play a major role in the mechanisms controlling human parturition, but the mechanism by which the CRH regulating estrogen and progesterone production is unclear. To examine the role of CRH in the placenta, we studied its effects on estrogen and progesterone release in cultured human placental cells. In this study we firstly observed the effects of CRH on estradiol and progesterone, and determined whether the CRH effects on the production of placental estradiol and progesterone were receptor-mediated. Secondly, we studied the regulation of estradiol and progesterone by H-89, the inhibitor of PKA, and GO6976, the inhibitor of PKA , and examined whether PKA/PKC pathway may be involved in the production of placental estradiol and progesterone. Finally we examined the expression of the messenger RNA transcripts encoding P-450aromatase (P-450arom), the key enzyme for estrogen synthesis and 3p-Hydroxysteroid dehydrogenase(Sp-HSD) and cytochrome P450 cholesterol side chain cleavage (P450scc), the enzymes for progesterone synthesis.Main results and conclusions are as followings:1. CRH caused an increase of E2 release in cultured human placentalcells, which was dose-dependent. The CRH receptor antagonist, a-helical CRH, not only blocked the increase of estradiol release by exogenous CRH, but inhibited the basal estradiol release, suggesting endogenous CRH has a tonic stimulatory effect on estradiol release, and the effect of CRH was receptor-mediated. Exposure of to H-89 and G06976 caused a reduction of E2 concentrations in the media, indicating that CRH stimulates placental E2 secretion with the PKA and PKC pathway. Using Northern blot analysis, we found that the expression of mRNA encoding P450arom were up-regulated by CRH, but decreased with exposure to a-Helical CRH9₄1p H-89 and G06976, indicating that CRH stimulate mRNA expression of P450arom and the biosynthesis of E2 through the PKA and PKC pathways.2. CRH decreased progesterone secretion, which was dose-dependent, and the a-Helical CRH9-4i reversed the CRH effect and increased the basal progesterone production, indicating that the effect of CRH was mediated by CRH receptor. H-89 produced a decrease and G06976 caused an increase of progesterone concentrations in the media, indicating that CRH stimulates placental E2 secretion through the PKC pathway. The expressions of 3p-HSD1 and P450scc were significantly inhibited by CRH, but augmented by CRH receptor antagonist. H-89 decreased the expressions of 3p-HSD1 and P450scc, and G06976 increased the expressions of 3J5-HSD1 and P450scc, indicating that CRH repressed mRNA expression of 3P-HSD1 and P450scc, and decreased progesterone secretion through PKC pathway in the cultured human placental cells.In conclusion, CRH stimulates expression of P450arom through PKA and PKC pathway and then increases placental E2 production. CRH repress expression of 3p-HSD1 and P450scc through PKC pathway, and in turn inhibits placental progesterone production.