Prostaglandin inactivation is increased in endometrium after exposure to clomiphene

Expression of reproductive hormone receptors and contraction‑associated genes in porcine uterus during the estrous cycle

Contraction of uterus tissue frequently occurs throughout the estrous cycle and is regulated by several endogenous factors, including estradiol, progesterone, luteinizing hormone, follicle‑stimulating hormone, oxytocin (OXT) and contraction‑associated proteins (CAPs). Contraction activity of uterus tissue according to the estrous cycle is important, due to the fact that it is directly associated with balanced implantation and stable pregnancy. However, few studies have examined the mechanism of uterus contraction activity in a porcine model. In the current study, porcine uterus tissue was separated into the follicular and luteal phases by histological analysis. To investigate regulation of contraction‑associated factors according to the estrous cycle, mRNA and protein expression levels of reproductive hormonal receptors, including estrogen receptors, progesterone receptor and luteinizing hormone/choriogonadotropin receptor in addition to CAPs including OXT, OXT receptor (OXTR), hydroxyprostaglandin dehydrogenase 15‑(NAD) and gap junction α‑1 protein, were examined in the porcine uterus according to the follicular and luteal phases. For the results, hormonal receptors and CAPs were dynamically regulated depending on the estrous cycle. In conclusion, genes associated with uterine contraction and its regulatory hormonal receptors in the porcine uterus were differently regulated in the follicular and luteal phases, suggesting that these genes are critically involved in the remodeling and contraction of uterine tissue and may be required to modulate the physiological status of the uterus.

Adverse effects of 4-tert-octylphenol on the production of oxytocin and hCG in pregnant rats

Endocrine-disrupting chemicals (EDCs) are exogenous substances that alter the structure or function of the endocrine system. 4-Tert-octylphenol (OP) is one of the most representative EDCs and has estrogenic effects. In this study, we examined the effects of ethinyl estradiol (EE) and OP on the pituitary gland, placenta, and uterus of pregnant rats. Expression levels of human chorionic gonadotropin (hCG), oxytocin (OT), and contraction-associated proteins (CAPs) were determined, and uterine contractile activity was measured by uterine contraction assay. EE and OP both increased mRNA expression of OT and hCG in the pituitary gland but not the placenta. Since OT and hCG control uterine contraction, we next examined CAP expression in the uterus. Expression of 15-hydroxyprostaglandin-dehydrogenase (PGDH) was upregulated by OP, whereas expression of other CAPs was unaffected. To clarify the effect of OP on uterine contraction in pregnant rats, uterine contraction assay was performed. The 17β-Estradiol (E2) did not affect contraction of primary uterine cells harvested from pregnant rats in a 3D collagen gel model. However, OP showed different effects from E2 by significantly reducing contraction activity. In summary, we demonstrated that OP interferes with regulation of OT and hCG in the pituitary gland as well as PGDH in the uterus, thereby reducing uterine contraction activity. This result differs from the action of endogenous E2. Collectively, these findings suggest that exposure to EDCs such as OP during pregnancycan reduce uterine contractile ability, which may result in contraction-associated adverse effects such as metratonia, bradytocia, and uterine leiomyomata.

Effects of estrogen and estrogenic compounds, 4-tert-octylphenol, and bisphenol A on the uterine contraction and contraction-associated proteins in rats

We examined the effects of estradiol (E2), 4-tert-octylphenol (OP), and bisphenol A (BPA) on uterine contractions in immature rats. The expression and localization of contraction-associated proteins (CAPs), and contractility of rat uterus with a collagen gel contraction assay were analyzed. E2, OP, and BPA all increased oxytocin (OT)-related pathway, while the prostaglandin-related signaling was reduced. Interestingly, E2 and estrogenic compounds showed distinct effects on the contractile activity of uterine cells. E2 enhanced the contractility, while OP and BPA significantly decreased it. Immunohistochemical analysis of CAPs showed distinct regulation of prostaglandin F receptor localization by E2 and estrogenic compounds, which may explain the different contractile activities of those reagents. In summary, we demonstrate that E2, OP, and BPA regulate CAP expression in a similar manner in the immature rat uterus, however, the effects on contractile activity were modulated differently. These findings suggest that OP and BPA interfere with uterine contractility.

The human NAD+-dependent 15-hydroxyprostaglandin dehydrogenase gene promoter is controlled by Ets and activating protein-1 transcription factors and progesterone

NAD+-dependent 15-hydroxyprostaglandin dehydrogenase (PGDH) is a key catabolic enzyme in the inactivation of PGF2alpha and PGE2 and therefore serves as an important determinant in regulating their local concentrations. To gain insights into the transcriptional regulation of this enzyme, we have isolated 3.5 kb of the 5'-flanking sequence of the human PGDH promoter and characterized its control in hemopoietic cells and cells of myometrial and placental origin. Several potential binding sites for cAMP-responsive element-binding protein (CREB), Ets, and activating protein-1 (AP-1) transcription factors are present within 2368 bp of the 5'-flanking region. This region and deletions thereof were fused to the luciferase reporter gene and used for transient transfection experiments. In Jurkat leukemic T cells, which express PGDH endogenously, the transfected PGDH promoter was strongly induced by phorbol ester. Induction was reversed by coexpression of A-Fos, a dominant negative to AP-1. In primary cultures of myometrial smooth muscle cells (SMC), the Ets family members Ets-1, Ets-2, and PEA3 potently stimulated transcriptional activity of the PGDH promoter. PEA3-mediated activation was partially repressed by A-Fos, suggesting an involvement of AP-1 proteins, which might be conferred by a distal and a proximal Ets/ AP-1 composite element. The distal Ets/AP-1 element is flanked by two CRE-like sequences. Cotransfection of A-CREB, a dominant negative to CREB, inhibited stimulation of PGDH-2368/luc3 by PEA3 in myometrial SMC, whereas treatment with 8-bromo-cAMP moderately enhanced promoter activity. Progesterone is believed to be an important stimulus for PGDH expression in the utero-placental unit, thus contributing to the maintenance of a quiescent uterus during pregnancy. In myometrial SMC, both isoforms of the progesterone receptor, PR-B and PR-A, caused a ligand-dependent activation of PGDH-2368/luc3. Transcriptional activity of PR-B, but not PR-A, was further enhanced by the addition of 8-bromo-cAMP. We could not confirm a recently proposed transcriptional control of PGDH by mineralocorticoid receptor. No effect of mineralocorticoid receptor, in the absence or presence of aldosterone, with or without 8-bromo-cAMP, was observed on PGDH-2368/luc3. Taken together, these findings demonstrate control of the PGDH promoter by multiple pathways and provide evidence for cross-talk among Ets, AP-1, cAMP, and PR-mediated signaling, suggesting complex regulatory mechanisms for the expression of PGDH.

Steroid regulation of prostaglandin dehydrogenase activity and expression in human term placenta and chorio-decidua in relation to labor

NAD+-dependent 15-hydroxyprostaglandin dehydrogenase (PGDH) is the key catabolic enzyme controlling levels of biologically active PGs. PGDH is localized to syncytiotrophoblast in placenta, and to trophoblast cells in chorion. To examine the regulation of PGDH by steroids and to determine any changes with labor, we obtained placenta and chorion from term elective cesarean section or spontaneous delivery and isolated trophoblast cells using a Percoll density gradient. Cells were treated with varying concentrations of cortisol, progesterone, the synthetic progestins R5020, and medroxyprogesterone acetate with or without RU486 or the specific progesterone receptor antagonist, onapristone, and the 3beta-hydroxysteroid dehydrogenase inhibitor, trilostane. The activity of PGDH was assessed by measurement of 13,14-dihydro-15-keto-PGF2alpha. PGDH messenger ribonucleic acid was quantified by in situ hybridization and computerized image analysis. The basal output of 13,14-dihydro-15-keto-PGF2alpha was lower in placenta or chorion collected at spontaneous labor than in that obtained at elective cesarean section. Cortisol had a significant dose-dependent inhibitory effect on PGDH activity in both placental and chorion trophoblast cells and significantly decreased levels of PGDH messenger ribonucleic acid. Responses were similar between tissues from laboring and nonlaboring women. PGDH activity was increased by R5020 and medroxyprogesterone acetate and was inhibited by RU486, onapristone, and trilostane. We conclude that cortisol inhibits PGDH activity and expression and that progestagens increase PGDH activity in human chorion and placenta.