Hormonal sensitivity of adenylate cyclase from human endometrium: modulation by estradiol

Histamine promotes mouse decidualization through stimulating epithelial amphiregulin release

Accumulating evidence shows that inflammation is essential for embryo implantation and decidualization. Histamine, a proinflammatory factor that is present in almost all mammalian tissues, is synthesized through decarboxylating histidine by histidine decarboxylase (HDC). Although histamine is known to be essential for decidualization, the underlying mechanism remains undefined. In the present study, histamine had no obvious direct effects on in vitro decidualization in mice. However, the obvious differences in HDC protein levels between day 4 of pregnancy and day 4 of pseudopregnancy, as well as between delayed and activated implantation, suggested that the blastocyst may be involved in regulating HDC expression. Furthermore, blastocyst-derived tumor necrosis factor α (TNFα) significantly increased HDC levels in the luminal epithelium. Histamine increased the levels of amphiregulin (AREG) and disintegrin and metalloproteinase domain-containing protein 17 (ADAM17) proteins, which was abrogated by treatment with famotidine, a specific histamine type 2 receptor (H2R) inhibitor, or by TPAI-1 (a specific inhibitor of ADAM17). Intraluminal injection of urocanic acid (HDC inhibitor) on day 4 of pregnancy significantly reduced the number of implantation sites on day 5 of pregnancy. TNFα-stimulated increases in HDC, AREG and ADAM17 protein levels was abrogated by urocanic acid, a specific inhibitor of HDC. Additionally, AREG treatment significantly promoted in vitro decidualization. Collectively, our data suggests that blastocyst-derived TNFα induces luminal epithelial histamine secretion, and histamine increases mouse decidualization through ADAM17-mediated AREG release.

Implantation and Establishment of Pregnancy in Human and Nonhuman Primates

Implantation and the establishment of pregnancy are critical for the propagation of the species, but yet remain the limiting steps in human and primate reproduction. Successful implantation requires a competent blastocyst and a receptive endometrium during a specific window of time during the menstrual cycle to initiate the bilateral communication required for the establishment of a successful pregnancy. This chapter provides an overview of these processes and discusses the molecular mechanisms associated with implantation of the blastocyst and decidualization of the uterus in primates.

Cyclic decidualization of the human endometrium in reproductive health and failure

Decidualization denotes the transformation of endometrial stromal fibroblasts into specialized secretory decidual cells that provide a nutritive and immunoprivileged matrix essential for embryo implantation and placental development. In contrast to most mammals, decidualization of the human endometrium does not require embryo implantation. Instead, this process is driven by the postovulatory rise in progesterone levels and increasing local cAMP production. In response to falling progesterone levels, spontaneous decidualization causes menstrual shedding and cyclic regeneration of the endometrium. A growing body of evidence indicates that the shift from embryonic to maternal control of the decidual process represents a pivotal evolutionary adaptation to the challenge posed by invasive and chromosomally diverse human embryos. This concept is predicated on the ability of decidualizing stromal cells to respond to individual embryos in a manner that either promotes implantation and further development or facilitates early rejection. Furthermore, menstruation and cyclic regeneration involves stem cell recruitment and renders the endometrium intrinsically capable of adapting its decidual response to maximize reproductive success. Here we review the endocrine, paracrine, and autocrine cues that tightly govern this differentiation process. In response to activation of various signaling pathways and genome-wide chromatin remodeling, evolutionarily conserved transcriptional factors gain access to the decidua-specific regulatory circuitry. Once initiated, the decidual process is poised to transit through distinct phenotypic phases that underpin endometrial receptivity, embryo selection, and, ultimately, resolution of pregnancy. We discuss how disorders that subvert the programming, initiation, or progression of decidualization compromise reproductive health and predispose for pregnancy failure.

Nebivolol decreases endothelial cell stiffness via the estrogen receptor beta: a nano-imaging study

BACKGROUND

Nebivolol (NEB) is a [beta]1-receptor blocker with nitric oxide-dependent vasodilating properties. NEB-induced nitric oxide release is mediated through the estrogen receptor.

METHOD

Here, we tested the hypothesis that NEB decreases endothelial cell stiffness and that these effects can be abolished by both endothelial nitric oxide synthase and estrogen receptor blockade. Human endothelial cells (EAHy-926) were incubated with vehicle, NEB 0.7 nmol/l, metoprolol 200 nmol/l, 17[beta]-estradiol (E2) 15 nmol/l, the estrogen receptor antagonists tamoxifen 100 nmol/l and ICI 182780 (ICI) 100 nmol/l, the nitric oxide synthase inhibitor N[omega]-nitro-L-arginine methyl ester 1 mmol/l and combinations of NEB and E2 with either tamoxifen, ICI or N[omega]-nitro-L-arginine methyl ester as well as metoprolol and ICI. Atomic force microscopy was performed to measure cellular stiffness, cell volume and apical surface. Presence of estrogen receptor protein in EAHy-926 was confirmed by western blot analysis; quantification of ER[alpha] and ER[beta] total RNA was performed by semiquantitative PCR.

RESULTS

Both NEB as well as E2 decreased cellular stiffness to a similar extent (NEB: 0.83 +/- 0.03 pN/nm, E2: 0.87 +/- 0.03 pN/nm, vehicle: 2.19 +/- 0.07 pN/nm), whereas metoprolol had no effect on endothelial stiffness (2.07 +/- 0.04 pN/nm, all n = 60, P < 0.01). The decrease in stiffness occurred as soon as 5 min after starting NEB incubation. The effects are mediated through nongenomic ER[beta] pathways, as ER[alpha] is not translated into measurable protein levels in EAHy-926. Furthermore, NEB increased cell volume by 48 +/- 4% and apical surface by 34 +/- 3%. E2 had comparable effects. Tamoxifen, ICI and N[omega]-nitro-L-arginine methyl ester substantially diminished the effects of NEB and E2.

CONCLUSION

NEB decreases cellular stiffness and causes endothelial cell growth. These effects are nitric oxide-dependent and mediated through nongenomic ER[beta] pathways. The morphological and functional alterations observed in endothelial cells may explain improved endothelial function with NEB treatment.

Molecular and cellular mechanisms for differentiation and regeneration of the uterine endometrium

The human endometrium undergoes cyclical changes including proliferation, differentiation, tissue breakdown, and shedding (menstruation) throughout a woman's reproductive life. The postovulatory rise in ovarian progesterone induces profound remodeling and differentiation of the estradiol-primed endometrium. This change, termed decidualization, is crucial for embryo implantation and maintenance of the pregnancy. To date, activation and crosstalk of cAMP- and progesterone-mediated signaling pathways have emerged as key cellular events to drive integrated changes at both the transcriptome and the proteome levels. This results in the induction and maintenance of the decidual phenotype and function. Our recent series of studies highlights the critical role of SRC kinase activation (v-src sarcoma viral oncogene homolog) and STAT5 (signal transducer and activator of transcription 5) phosphorylation in decidualization. After separation of the functional layer of the differentiated endometrium that follows progesterone withdrawal, i.e., menstruation, the basal layer of the endometrium, under the influence of estradiol, regrows and initiates a unique form of angiogenesis and regenerates a new functional layer. The molecular and cellular mechanisms for this process remain elusive, mainly because of difficulties in reproducing menstrual tissue breakdown, shedding, and subsequent tissue regeneration in vitro. We have recently developed a "humanized" mouse model in which a functional human endometrium is reconstituted. It may be used as an in vivo experimental tool for the study of endometrial angiogenesis and regeneration. This model may also be used to identify and test new therapeutic strategies for endometriosis, endometrial cancer, implantation failure, and infertility related to endometrial dysfunction.

Hormone control and expression of androgen receptor coregulator MAGE-11 in human endometrium during the window of receptivity to embryo implantation

The androgen receptor (AR) is a ligand-activated transcription factor of the male and female reproductive tracts whose activity is modulated by coregulator binding. We recently identified melanoma antigen gene protein-11 (MAGE-11) of the MAGEA gene family that functions as an AR coregulator by binding the AR N-terminal FXXLF motif. Here we report that MAGE-11 is expressed in a temporal fashion in endometrium of normally cycling women. Highest levels of MAGE-11 mRNA and protein occur in the mid-secretory stage, coincident with the window of uterine receptivity to embryo implantation. Studies in human endometrial cell lines together with the hormone profile of the menstrual cycle and pattern of estrogen receptor-alpha expression in cycling endometrium suggest the rise in MAGE-11 mRNA results from down-regulation by estradiol during the proliferative phase and up-regulation by cyclic AMP signaling in the early and mid-secretory stage. In agreement with its coregulatory function, MAGE-11 localizes with AR in glandular epithelial cell nuclei in the mid-secretory stage. The increase in AR protein in the mid-secretory endometrium without an increase in AR mRNA suggests MAGE-11 stabilizes AR in glandular epithelial cell nuclei. This was supported by expression studies at low androgen levels indicating AR stabilization by MAGE-11 dependent on the AR N-terminal transactivation domain. The results suggest that MAGE-11 functions as a coregulator that increases AR transcriptional activity during the establishment of uterine receptivity in the human female.

A novel protein Depp, which is induced by progesterone in human endometrial stromal cells activates Elk-1 transcription factor

Decidualization of the endometrial stromal cells (ESC), considered to be stimulated by progesterone and/or cAMP, is crucial for embryo implantation and placentation. In this study, we isolated a novel clone encoding decidual protein induced by progesterone (Depp) from a human ESC cDNA library enriched with progesterone-inducible genes. Depp mRNA was expressed in various human tissues including placenta, ovary and kidney. Increased expression of Depp was observed in endometria during mid- and late-secretory phases and 1st trimester deciduas. In vitro, Depp mRNA was induced in ESC within 30 min of progesterone treatment, which was inhibited by the antiprogestin RU486. Androgen alone also induced Depp expression. Depp increased the level of phosphorylated Erk and activated the Elk-1 transcription factor in human embryonal kidney 293 cells, suggesting that Depp modulates the effects of progesterone during decidualization and in the decidua by affecting gene expression. Elucidation of the biological function of Depp in the endometrium will facilitate our understanding of the molecular mechanisms of decidualization and placental development.

Heparin-binding epidermal growth factor and its receptors mediate decidualization and potentiate survival of human endometrial stromal cells

Heparin-binding epidermal growth factor (HB-EGF) has pleiotropic biological functions in many tissues, including those of the female reproductive tract. It facilitates embryo development and mediates implantation and is thought to have a function in endometrial receptivity and maturation. The mature HB-EGF molecule manifests its activity as either a soluble factor (sol-HB-EGF) or a transmembrane precursor (tm-HB-EGF) and can bind two receptors, EGFR and ErbB4/HER4. In this study, we identify factors that modulate expression of HB-EGF, EGFR, and ErbB4 in endometrial stromal cells in vitro. We demonstrate that levels of sol- and tm-HB-EGF, EGFR, and ErbB4 are increased by cAMP, a potent inducer of decidualization of the endometrial stroma. We also show that production of sol- and tm-HB-EGF is differentially modulated by TNF alpha and TGF beta. Our data suggest that HB-EGF has a function in endometrial maturation in mediating decidualization and attenuating TNF alpha- and TGF beta-induced apoptosis of endometrial stromal cells.

Biology of primate relaxin: a paracrine signal in early pregnancy?

Relaxin is a peptide hormone that exerts numerous effects in a variety of tissues across a broad range of species. Although first identified more than 75 years ago interest in relaxin biology has waxed and waned over the years consistent with peaks and troughs of new experimental data on its wide-ranging biological effects and advances in relaxin enabling technologies. Recent insights into species-dependent differences in relaxin biology during pregnancy have once again stimulated a relative surge of interest in the study of relaxin's reproductive biology. Identification and pharmacological characterization of orphaned relaxin receptors and exploration of its paracrine effects on pregnancy using genomic and proteomic technologies have succeeded in fueling current interest in relaxin research. Primates and non-primate vertebrates exhibit very disparate profiles of relaxin genomics, proteomics and functional biology. Non-human primates appear to exhibit a very close similarity to humans with respect to relaxin reproductive biology but the similarities and subtle differences are only just beginning to be understood. We, and others, have shown that relaxin produces significant changes to the non-human primate endometrium during the peri-implantation period that are consistent with relaxin's long perceived role as a paracrine modulator of pregnancy. The purpose of this review is to summarize the reproductive biology of relaxin in non-human primates with a specific emphasis on the paracrine role of ovarian and endometrial relaxin during embryo implantation and early pregnancy.

Suppression of the nicotinic acetylcholine response in rat superior cervical ganglionic neurons by steroids

The effects of various types of steroids on the nicotinic acetylcholine (ACh) receptor (nAChR)-mediated responses were investigated in superior cervical ganglionic neurons acutely dissociated from rats using nystatin perforated patch recording. ACh induced a peak followed by a gradual decrease in the inward current at a holding potential of -40 mV. Nicotine, but not muscarine, mimicked ACh. Hydrocortisone at a concentration of >10(-6) M reversibly suppressed both the peak and steady-state nicotine-induced currents (Inic) in a noncompetitive manner. The inhibition of Inic by hydrocortisone did not show any voltage dependency and persisted in the presence of either cyclic AMP modulators, forskolin and 3-isobutyl-1-methylxanthine, or a protein kinase A inhibitor, N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide dihydrochloride (H-89). Beta-estradiol, androsterone, aldosterone, and 17alpha-estradiol mimicked hydrocortisone in its inhibitory action on ACh-induced currents (I(ACh)). The potency for the inhibitory actions on I(ACh) was as follows: androsterone > beta-estradiol > hydrocortisone > or = aldosterone = 17alpha-estradiol. Cholesterol had no effect on the I(ACh). In conclusion, the structural characteristics of a steroid are thus considered to be necessary to block nicotinic I(ACh) in rat superior cervical ganglionic cells, whereas the cholesterol side chain might disturb the inhibitory action of the steroid skeleton on nAChRs.

Progesterone-dependent decidualization of the human endometrium is mediated by cAMP

Progesterone is a key factor in regulating endometrial cell decidualization, but the signal transduction pathways involved in mediating the effects of progesterone are not known. A role of the cAMP pathway in decidualization has been suggested by in vitro studies demonstrating that cAMP agonists can stimulate decidualization, in the absence of sex steroids. In this article, we have used an in vitro culture model of progesterone-dependent decidualization of human endometrial stromal cells to examine whether progesterone-induced decidualization is associated with activation of the cAMP signal transduction pathway in which the prolactin gene expression is a marker of decidualization. Following a lag period of approx 3 d, progesterone induced prolactin secretion and elevated intracellular cAMP levels. By d 15, cAMP and prolactin levels were approx 10- and 60-fold greater, respectively, than those on d 3. Changes in cAMP levels showed a positive correlation with prolactin secretion. Prostaglandin E2 (PGE2), which enhances progesterone-dependent decidualization, also increased both prolactin secretion and cAMP levels approx two- to fourfold on d 15 compared with d 3, whereas PGE2 alone, which does not induce decidualization, did not stimulate prolactin secretion or intracellular cAMP accumulation. Conversely, all-trans retinoic acid, which attenuates progesterone-dependent decidualization, significantly (p < 0.05) decreased both prolactin secretion and cAMP levels. Furthermore, the protein kinase A (PKA) inhibitor, 8-bromoadenosine-3',5'-cyclic monophosphorothioate, significantly (p < 0.05) suppressed progesterone-dependent prolactin expression. Since activation of the PGE2 receptor subtype EP2 stimulates adenylate cyclase, reverse transcription-polymerase chain reaction (RT-PCR) analysis of endometrial cells was undertaken. Expression of EP2 mRNA was induced in cells treated with progesterone and estradiol alone or with PGE2, compared with untreated controls. The data suggest that the cAMP signal transduction cascade is activated during progesterone-dependent decidualization.

17 beta-Estradiol potentiates kainate-induced currents via activation of the cAMP cascade

Evidence for nongenomic actions of steroids is now coming from a variety of fields of steroid research. Mechanisms of steroid action are being studied with regard to the membrane receptors and the activation of second messengers. The present study investigated the mechanism for the rapid effect of estrogen on acutely dissociated hippocampal CA1 neurons by using the whole-cell, voltage-clamp recording. Under the perforated patch configuration, 17 beta-estradiol potentiated kainate-induced currents in 38% of tested neurons. The potentiation was stereospecific, rapid in onset, and reversible after the removal of the steroid. Dose-response curves show that the potentiation by 17 beta-estradiol was evident at a concentration as low as 10 nM and saturated at 10 microM. 17 beta-Estradiol did not affect the kinetics (i.e., affinity and cooperativity) and reversal potential of kainate-induced currents. This suggests that the potentiation did not result from direct interaction with kainate receptors nor the activation of ion channels other than kainate receptor-channels. The potentiation by 17 beta-estradiol was similar to the enhancement of kainate-induced currents evoked by 8-bromo-cAMP, and was modulated by an inhibitor of phosphodiesterase (IBMX). The estrogen potentiation was blocked by a specific blocker of PKA (Rp-cAMPS). Under standard recording configuration, the effect was significantly affected by intracellular perfusing with GDP-beta-S or GTP-gamma-S. The data suggest that the potentiation of kainate-induced currents by 17-beta-estradiol was likely a G-protein(s) coupled, cAMP-dependent phosphorylation event. By involvement of this non-genomic mechanism, estrogen may play a role in the modulation of excitatory synaptic transmission in the hippocampus.

Hormone replacement therapy and hemostasis: principles of a complex interaction

Postmenopausal women on hormone replacement therapy (HRT) have been shown to be at reduced risk of arterial thrombotic disease. The risk of venous thrombosis appears not to be increased in HRT users in the absence of specific risk factors. However, while these data refer predominantly to women using conjugated equine estrogens, it is less clear whether the favourable impact on cardiovascular diseases may also be achieved by other preparations. Dose, as well as route of application and, particularly, the combination of steroids have been shown to affect both the clinical and the metabolic profile. With regard to cardiovascular diseases, differential effects on the hemostatic system are of particular interest. The principles of the interaction of steroids with the hemostatic system are reviewed. Also, the principal limitations of the assessment of the hemostatic system, as well as its interpretation, with regard to cardiovascular diseases are discussed. It is proposed to view the hemostatic system predominantly as a monitor of endothelial function rather than as a mediator of potential harmful effects on the cardiovascular system.

Modulation of quail oviduct adenylate cyclase activity by estradiol and progesterone

Oviduct adenylate cyclase activity of the quail was measured by radiochemical analysis following different hormonal treatments. A single injection of estradiol benzoate (EB) to immature female quails resulted in a prereplicative surge of adenylate cyclase activity. A second surge of enzyme activity was observed during the proliferative phase induced by EB. Estradiol-17 alpha, estrone, estriol and testosterone were ineffective. Tamoxifen completely inhibits the growth-promoting effect of EB and the second surge of adenylate cyclase activity but does not inhibit the prereplicative increase of enzyme activity. This prereplicative increase of adenylate cyclase activity was also observed, even in the absence of increased plasma estradiol, when estradiol-17 beta (E2) was perfused through the hepatic portal vein. Moreover, E2 had no effect on enzyme activity when added directly to the oviduct homogenate preparation, at concentrations ranging from 10(-9) to 10(-7) M. In response to progesterone injection, oviduct adenylate cyclase activity followed a different pattern, beginning its increase after 3 h and remaining elevated up to 24 h. The activation by estradiol was independent of the presence of guanylylimidodiphosphate. Moreover, the enzyme was more sensitive to forskolin at submaximal concentration in estradiol treated birds than in control. These results demonstrate that transient activation of adenylate cyclase at the early stages of the action of estradiol does not occur through the classic nuclear receptor-gene activation pathway or a membrane receptor mediated process, but involves an indirect pathway, yet to be defined.

Effect of 17 beta-estradiol on calcium response to phytohaemagglutinin in human lymphocytes

Pre-treatment of human lymphocytes with 17 beta-estradiol diminishes the increase in concentration of cytosolic free calcium after stimulation with phytohaemagglutinin. The effect is dependent on 17 beta-estradiol concentration and on the preincubation time. The effect is not due to an interaction between 17 beta-estradiol and phytohaemagglutinin, but appears to be a consequence of the binding of the hormone to the cell surface. The effect is specific for 17 beta-estradiol, since the alpha isomer and other steroid hormones (progesterone, testosterone, diethylstilbestrol and 5 alpha-androstan) have no effect. Since the effect of the 17 beta-estradiol can be suppressed by treatment of lymphocytes with ouabain, it appears that the effect of estradiol on the rise of cytosolic calcium induced by phytohaemagglutinin is mediated by the (Na, K)-ATPase.

Modification of number and of affinity of endometrial EGF receptors during the menstrual cycle

We have analysed the distribution and the binding properties of the epidermal growth factor (EGF) receptor in human endometrium during the menstrual cycle to validate the proposal that steroids affect the growth rate of target cells via growth factor-related pathways. The total number of EGF receptors and their affinity for the iodinate exogenous ligand are significantly higher during the proliferative than the secretory phase; the binding kinetics appear to be hyperbolic and sigmoid during the proliferative and the secretory phase, respectively. These results suggest that endogenous sex steroids can regulate the levels and the properties of EGF receptors in vivo, and support the possibility that receptor-coupled events may play a role in estrogen-stimulated growth.

Non-genomic effects of estrogens and antiestrogens

In addition to the effects of estrogens on transcription, mediated by the estrogen receptor, and the antiestrogenic effects of triphenylethylene derivatives resulting from their competitive action at the estrogen receptor level, estrogens and antiestrogens can affect cellular processes though other mechanisms. Estrogens can bind and alter enzymatic activities in membranes isolated from target cells, can influence the activities of purified enzymes and can change cell permeability and polarization under conditions excluding transcriptional effects. Triphenylethylene antiestrogens at micromolar concentrations can affect cholinergic, histaminergic and dopaminergic systems, affect calmodulin action and influence protein kinase C activity. Tamoxifen added to suspension of human endometrial adenocarcinoma cells at concentrations greater than 10 microM both increased phosphoinositide hydrolysis and inhibited the stimulatory effect of carbachol on this system. These effects, however, may represent nonspecific actions of the antiestrogens, shared with the structurally related phenothiazines, on the plasma membrane.

Role of estrogens on striatal dopaminergic activity

Studies were undertaken to evaluate the effects of estradiol and prolactin on striatal dopamine receptor activity. Dopamine receptors were quantified in partially purified striatal membranes by equilibrium binding using [3H]spiroperidol. When we investigated whether the D-2 dopamine receptor activity changes during the estrous cycle, the results suggest an increase in dopamine receptor density in diestrous, without modifications in the affinity. The finding that in ovariectomized rats the dopamine receptor binding parameters remained unchanged, suggests that gonadal steroids are not essential in the mechanism of action of this receptor. Results of activity of D-2 dopamine receptors showing that hyperprolactinemia fails to increase the number of these receptors do not support the hypothesis that circulating prolactin regulates the activity of these striatal dopamine receptors. Administration of estradiol benzoate (250 micrograms/kg per day) to hyperprolactinemic rats, by s.c. injection, significantly decreased both the density and the affinity of the striatal dopamine receptors. The present data indicate that, although prolactin does not seem to modify the activity of striatal dopamine receptors, it could modulate the estrogen-induced hypersensitivity of these receptors.

A possible mechanism of action of 17 beta-estradiol in stimulation of fertilization in vitro

The effects of 17 beta-estradiol (E2) on sperm-egg interactions in the mouse were investigated. It was shown that E2 induces adhesiveness of the sperm head, expressed as sperm-sperm and sperm-egg binding. Since the concentration dependence of this process was similar to that observed for stimulation of in vitro fertilization by E2, it is suggested that induction of adhesiveness or initiation of processes that cause adhesiveness of the sperm head are of biological significance as preparatory steps for fertilization. Finally, the content of E2 in mouse eggs was determined and found to be 0.2 pg/egg, equally distributed between the oocyte together with the zona pellucida and the follicular cells with their associated intercellular matrix. The intra-ovum concentration is estimated as 10(-6) M.

Basal and forskolin-stimulated cyclic adenosine monophosphate in intact human platelets during the menstrual cycle

In previous studies we observed modifications of cyclic adenosine monophosphate and adenylate cyclase activity in human endometrium during the menstrual cycle. In the present study our intension was to verify whether these modifications occur in isolated intact platelets. The results demonstrate that in nine normal women platelet cyclic adenosine monophosphate content varies during the menstrual cycle both in basal and in stimulated conditions (in vitro addition of forskolin). In fact, significantly higher levels of cyclic adenosine monophosphate were consistently observed during the proliferative phase. These findings provide evidence that platelet cyclic adenosine monophosphate metabolism normally varies during the menstrual cycle, which suggests a possible involvement of this system in some important clinical events.