Regulation of estradiol and progesterone production by CRH-R1 and -R2 is through divergent signaling pathways in cultured human placental trophoblasts

Focusing on the role of secretin/adhesion (Class B) G protein-coupled receptors in placental development and preeclampsia

Preeclampsia, a clinical syndrome mainly characterized by hypertension and proteinuria, with a worldwide incidence of 3–8% and high maternal mortality, is a risk factor highly associated with maternal and offspring cardiovascular disease. However, the etiology and pathogenesis of preeclampsia are complicated and have not been fully elucidated. Obesity, immunological diseases and endocrine metabolic diseases are high-risk factors for the development of preeclampsia. Effective methods to treat preeclampsia are lacking, and termination of pregnancy remains the only curative treatment for preeclampsia. The pathogenesis of preeclampsia include poor placentation, uteroplacental malperfusion, oxidative stress, endoplasmic reticulum stress, dysregulated immune tolerance, vascular inflammation and endothelial cell dysfunction. The notion that placenta is the core factor in the pathogenesis of preeclampsia is still prevailing. G protein-coupled receptors, the largest family of membrane proteins in eukaryotes and the largest drug target family to date, exhibit diversity in structure and function. Among them, the secretin/adhesion (Class B) G protein-coupled receptors are essential drug targets for human diseases, such as endocrine diseases and cardiometabolic diseases. Given the great value of the secretin/adhesion (Class B) G protein-coupled receptors in the regulation of cardiovascular system function and the drug target exploration, we summarize the role of these receptors in placental development and preeclampsia, and outlined the relevant pathological mechanisms, thereby providing potential drug targets for preeclampsia treatment.

The role of corticoliberin concentration levels and placental CRH receptors 1 and 2 in the prolongation of pregnancy

OBJECTIVE

To examine the changes in CRH concentrations in the blood serum of pregnant women and in the placenta of patients after the 41st week of gestation, and to determine its influence on the effectiveness of inducing labor and its progress.

MATERIALS AND METHODS

The study group comprised pregnant patients who did not deliver until the 41 week of gestation (n = 114). The control group was divided into two subgroups: patients in whom delivery started spontaneously before the 41st week of gestation (n = 24) and pregnant patients in whom delivery started spontaneously after the 41st week of gestation (n = 23). Blood serum and placenta were obtained from the patients. Corticoliberin originating from blood serum was assessed with the use of ELISA Kit. Parts of the placenta were stained with monoclonal antibodies for the presence of corticoliberin, corticoliberin receptors 1 and 2.

RESULTS

No statistically significant differences were found with regard to corticoliberin concentrations in the blood or during a qualitative assessment of the number of CRH R1 in the placenta between the research groups. However, corticoliberin receptor 2 had a statistically higher expression rate in the control group in which the delivery started spontaneously before the 41st week of gestation.

CONCLUSION

In post-term pregnancy, the up-regulation of CRH R2 receptor is disturbed with no change in CRH R1 expression, which complicates the initiation of labor despite correct corticoliberin levels in both blood serum and the placenta. Pregnancy duration over 41 weeks and the effectiveness of preinducing or inducing labor do not depend on corticoliberin concentrations.

Corticotropin-releasing hormone reduces basal estradiol production in zebrafish follicular cells

Corticotropin-releasing hormone (CRH) plays a key regulatory role in coordinating the regulation of endocrine, autonomic nervous, immune, and reproductive systems. Two CRH (CRHα and CRHβ) and their receptors (CRHR1 and CRHR2) had been identified in zebrafish. However, their functions remained uncovered in the ovary of zebrafish. Therefore, this study aimed to determine whether CRH acts directly on the ovary to regulate steroidogenesis in cultured zebrafish follicular cells. Firstly, CRH and its receptors are expressed in the zebrafish ovary. The expression profile of CRHβ fluctuated during ovarian development in zebrafish, and the highest CRHα mRNA levels were observed at the mature follicle. The highest CRHR1 and CRHR2 mRNA levels existed in mid-vitellogenic (MV) and early vitellogenic (EV) stages, respectively. In primary cultured zebrafish follicular cells, both of the CRHα and CRHβ inhibited expression of hsd17b3 mRNA levels and decreased content of estradiol (E2) in the medium. Furthermore, CRH activated p38 MAPK and p38 MAPK inhibitor SB203580 attenuated the phosphorylation of p38 MAPK induced by CRHα. Simultaneously, SB203580 changed the effect of CRH on cyp19a1a expression but not hsd17b1 and hsd17b3. SB203580 alone or combined with CRH inhibited the E2 content. Finally, the CRHR inhibitor α-helical 9-41 also blocked the phosphorylation of p38 MAPK induced by CRHα but did not change the inhibitory effect of CRH on the mRNA expression of the steroidogenic gene and the content of E2 in the culture medium. Taken together, our findings suggest that the anti-steroidogenic effects of CRH may be mediated partly through activation of the p38 MAPK signaling pathway.

The Role of Corticotropin-Releasing Hormone at Peripheral Nociceptors: Implications for Pain Modulation

Peripheral nociceptors and their synaptic partners utilize neuropeptides for signal transmission. Such communication tunes the excitatory and inhibitory function of nociceptor-based circuits, eventually contributing to pain modulation. Corticotropin-releasing hormone (CRH) is the initiator hormone for the conventional hypothalamic-pituitary-adrenal axis, preparing our body for stress insults. Although knowledge of the expression and functional profiles of CRH and its receptors and the outcomes of their interactions has been actively accumulating for many brain regions, those for nociceptors are still under gradual investigation. Currently, based on the evidence of their expressions in nociceptors and their neighboring components, several hypotheses for possible pain modulations are emerging. Here we overview the historical attention to CRH and its receptors on the peripheral nociception and the recent increases in information regarding their roles in tuning pain signals. We also briefly contemplate the possibility that the stress-response paradigm can be locally intrapolated into intercellular communication that is driven by nociceptor neurons. Such endeavors may contribute to a more precise view of local peptidergic mechanisms of peripheral pain modulation.

Prenatal two-hit stress affects maternal and offspring pregnancy outcomes and uterine gene expression in rats: match or mismatch?

Maternal stress and inflammation excesses can lead to adverse pregnancy outcomes and offspring development. We evaluated whether distinct prenatal stressors affect pregnancy, maternal and offspring outcomes, and uterine gene expression differently when combined than either alone. Long-Evans dams were exposed to psychological or/and (two-hit) immune stress (interleukin-1 beta [IL-1β]), on gestational days 12-18 and 17-delivery, respectively. Gestational length, maternal weight gain, glycaemia and corticosterone levels, offspring weight, and gender effects were recorded. Maternal and offspring uteri were collected at weaning and on postnatal day 160 correspondingly. Uterine expression of genes involved in local progesterone metabolism, neuroendocrine and immune systems were analyzed using quantitative real-time polymerase chain reaction. Maternal two-hit stress increased gestational length variation and the occurrence of adverse pregnancy outcomes while reducing gestational weight gain. Pup weight was negatively affected by prenatal stressors in a gender-specific way. In dams, IL-1β upregulated gene expression of neuroendocrine (Crh, Crhr1) and cytokine genes (Il1b, Il1rn, Il6, and Il10). Conversely, transcriptional patterns in offspring uteri were more variable with gene-specific up- or downregulation by each stressor separately, while exposure to both extensively reduced the expression of neuroendocrine (Hsd11b1), cytokine (Il1a, Il1rn, Il6), and IL-1 receptor genes. In conclusion, maternal stress affects physiological and molecular processes in dams and their offspring; two hits have different effects than single stressors. Outcomes appear generation-, gender-, and stressor-specific. Dampening of offspring uterine gene expression after exposure to multiple stressors could fit within the match/mismatch hypothesis of perinatal programming, with offspring preparing for a stressful life.

Estradiol-Dependent Stimulation and Suppression of Gonadotropin-Releasing Hormone Neuron Firing Activity by Corticotropin-Releasing Hormone in Female Mice

Gonadotropin-releasing hormone (GnRH) neurons are the final central regulators of reproduction, integrating various inputs that modulate fertility. Stress typically inhibits reproduction but can be stimulatory; stress effects can also be modulated by steroid milieu. Corticotropin-releasing hormone (CRH) released during the stress response may suppress reproduction independent of downstream glucocorticoids. We hypothesized CRH suppresses fertility by decreasing GnRH neuron firing activity. To test this, mice were ovariectomized (OVX) and either implanted with an estradiol capsule (OVX+E) or not treated further to examine the influence of estradiol on GnRH neuron response to CRH. Targeted extracellular recordings were used to record firing activity from green fluorescent protein-identified GnRH neurons in brain slices before and during CRH treatment; recordings were done in the afternoon when estradiol has a positive feedback effect to increase GnRH neuron firing. In OVX mice, CRH did not affect the firing rate of GnRH neurons. In contrast, CRH exhibited dose-dependent stimulatory (30 nM) or inhibitory (100 nM) effects on GnRH neuron firing activity in OVX+E mice; both effects were reversible. The dose-dependent effects of CRH appear to result from activation of different receptor populations; a CRH receptor type-1 agonist increased firing activity in GnRH neurons, whereas a CRH receptor type-2 agonist decreased firing activity. CRH and specific agonists also differentially regulated short-term burst frequency and burst properties, including burst duration, spikes/burst, and/or intraburst interval. These results indicate that CRH alters GnRH neuron activity and that estradiol is required for CRH to exert both stimulatory and inhibitory effects on GnRH neurons.

MiR133b is involved in endogenous hydrogen sulfide suppression of sFlt-1 production in human placenta

Increased production of soluble fms-like tyrosine kinase-1 (sFlt-1) from placenta is one of the major contributors to the development of preeclampsia. Our previous study has shown that hydrogen sulfide (H₂S) inhibits sFlt-1 release in placenta. In the present study, we sought to investigate whether endogenous H₂S affects sFlt-1 production and elucidate which H₂S-producing enzyme is responsible for its effect in placenta. It was found that, besides cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE), 3-mercaptopyruvatesulfurtransferase (3-MST) was identified in human placenta and mainly localized in syncytiotrophoblasts. There was no significant difference in expression level of 3-MST among preeclamptic and normal placentas. Treatment of cultured syncytiotrophoblasts with NaHS and l-cysteine suppressed sFlt-1 mRNA expression and caused a decrease in sFlt-1 protein content in culture media of the cells. Transfection of syncytiotrophoblasts with CBS siRNA and CSE siRNA reversed the above effects of l-cysteine. Furthermore, NaHS and l-cysteine treatment decreased the half-life of sFlt-1 mRNA and increased the expression of miR-133b targeting sFlt-1. MiR-133b expression was downregulated in preeclamptic placentas and correlated with the level of CBS and CSE. These results indicate that H₂S is an important regulatory factor in sFlt-1 production in placenta. Reduced H₂S generation in placenta contributes to development of preeclampsia by enhancing sFlt-1 production.

MiR 20a,-20b and -200c are involved in hydrogen sulfide stimulation of VEGF production in human placental trophoblasts

Hydrogen sulfide (H2S) has been implicated to angiogenesis in various tissues. We sought to investigate the role of hydrogen sulfide (H2S) in regulating production of vascular endothelial growth factor (VEGF) proteins, the key factors of angiogenesis and vasculogenesis, in placenta.

METHODS

Placental tissues were obtained from pregnant women with preeclampsia and healthy pregnant women who underwent elective cesarean section. Explants and trophoblasts were isolated from healthy placentas and treated with H2S donor and precursor. Western blotting was used to determine the levels of cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE). The levels of VEGF mRNA, miR miR-200c,-20a and -20b were determined by quantitative real time PCR.

RESULTS

NaHS and l-cysteine increased VEGF but not placenta growth factor (PlGF) production in cultured explants and trophoblasts. Transfection of CBS and CSE siRNA reversed the stimulatory effect of l-cysteine on VEGF production in placental cells. H2S prolonged the half-life of VEGF mRNA and decreased the expression of miR-200c,-20a and -20b in placental cells. MiR-200c mimic and inhibitor affected VEGF mRNA and protein level, whereas miR-20a or -20b mimic and inhibitor affect VEGF protein release but not mRNA expression. The expression level of miR-200c,-20a and -20b as well as the level of CBS, CSE and VEGF were downregulated in preeclamptic placentas.

CONCLUSION

H2S produced via CSE and CBS plays a critical role in VEGF production in human placenta. Reduced expression of CSE and CBS may contribute to the abnormal production of angiogenic factors in preeclamptic placenta.

The endocrine function of human placenta: an overview

During pregnancy, several tightly coordinated and regulated processes take place to enable proper fetal development and gestational success. The formation and development of the placenta is one of these critical pregnancy events. This organ plays essential roles during gestation, including fetal nourishment, support and protection, gas exchange and production of several hormones and other mediators. Placental hormones are mainly secreted by the syncytiotrophoblast, in a highly and tightly regulated way. These hormones are important for pregnancy establishment and maintenance, exerting autocrine and paracrine effects that regulate decidualization, placental development, angiogenesis, endometrial receptivity, embryo implantation, immunotolerance and fetal development. In addition, because they are released into maternal circulation, the profile of their blood levels throughout pregnancy has been the target of intense research towards finding potential robust and reliable biomarkers to predict and diagnose pregnancy-associated complications. In fact, altered levels of these hormones have been associated with some pathologies, such as chromosomal anomalies or pre-eclampsia. This review proposes to revise and update the main pregnancy-related hormones, addressing their major characteristics, molecular targets, function throughout pregnancy, regulators of their expression and their potential clinical interest.

Molecular evolution of GPCRs: CRH/CRH receptors

Corticotrophin-releasing hormone (CRH) is the pivotal neuroendocrine peptide hormone associated with the regulation of the stress response in vertebrates. However, CRH-like peptides are also found in a number of invertebrate species. The origin of this peptide can be traced to a common ancestor of lineages leading to chordates and to arthropods, postulated to occur some 500 million years ago. Evidence indicates the presence of a single CRH-like receptor and a soluble binding protein system that acted to transduce and regulate the actions of the early CRH peptide. In vertebrates, genome duplications led to the divergence of CRH receptors into CRH1 and CRH2 forms in tandem with the development of four paralogous ligand lineages that included CRH; urotensin I/urocortin (Ucn), Ucn2 and Ucn3. In addition, taxon-specific genome duplications led to further local divergences in CRH ligands and receptors. Functionally, the CRH ligand-receptor system evolved initially as a molecular system to integrate early diuresis and nutrient acquisition. As multicellular organisms evolved into more complex forms, this ligand-receptor system became integrated with the organismal stress response to coordinate homoeostatic challenges with internal energy usage. In vertebrates, CRH and the CRH1 receptor became associated with the hypothalamo-pituitary-adrenal/interrenal axis and the initial stress response, whereas the CRH2 receptor was selected to play a greater role in diuresis, nutrient acquisition and the latter aspects of the stress response.

Corticotropin-releasing hormone (CRH) promotes inflammation in human pregnant myometrium: the evidence of CRH initiating parturition?

CONTEXT

An increasing body of evidence indicates that human labor, either term or preterm, is an inflammatory event. CRH has been implicated to be a trigger of human parturition.

OBJECTIVE

To investigate whether CRH induces the cascades of inflammation in human pregnant myometrium, thereby leading to activation of uterus.

DESIGN

The myometrial tissues were obtained from pregnant women who were in labor or not in labor at term. The output of cytokines and prostaglandins (PGs) was determined by Multiplex and ELISA. Western blot analysis was used to determine the levels of uterine activation proteins (UAPs).

RESULTS

The levels of chemokines and cytokines as well as activated nuclear factor-κB (NF-κB) were increased in the term labor group more than the not term labor group. CRH stimulated production of a number of chemokines and cytokines in cultured uterine smooth muscle cells (USMCs), which induced chemotaxis of monocytes. These effects were mediated by CRH receptor 1 (CRHR1) and dependent on adenylyl cyclase/protein kinase (PKA) and NF-κB signaling. Cocultures of CRH-treated USMCs with monocytes greatly enhanced the output of cytokines and chemokines as well as PGs in cultures and increased the expression of uterine activation proteins (UAPs) in USMCs. IL-1β, IL-6, and TNF-α stimulated the expression of UAPs and output of PGs in USMCs.

CONCLUSIONS

CRH induces the production of chemokines and cytokines in myometrium at term and subsequently results in the cascade of inflammation in uterus. The inflammation induced by CRH can lead to activation of uterus.

Effects of corticotrophin releasing hormone (CRH) on cell viability and differentiation in the human BeWo choriocarcinoma cell line: a potential syncytialisation inducer distinct from cyclic adenosine monophosphate (cAMP)

BACKGROUND

Placental production of corticotrophin releasing hormone (CRH) rises exponentially as pregnancy progresses, and has been linked with the onset of normal and preterm labour. CRH is produced in syncytiotrophoblast cells and production is increased by glucocorticoids and cAMP. It remains unclear whether cAMP acts by inducing differentiation of cytotrophoblasts and/or through induction of syncytialisation. As CRH can stimulate cAMP pathways we have tested whether a feed-forward system may exist in placental cells during syncytialisation.

METHODS

The choriocarcinoma BeWo cell line was treated with cAMP, CRH or vehicle. Cell viability was determined by MTT assay, while apoptosis was analysed by DAPI staining and by FACS. Differentiation was measured by assaying message for hCG and ERVW-1 (syncytin1) by qRT-PCR, as well as the respective protein by ELISA. Fusion of BeWo cells was assessed by co-staining cell membrane and nuclei with CellMask and Hoechst 33342. CRHR1 and CRHR2 mRNA levels were measured by qRT-PCR.

RESULTS

We show that cAMP has an inductive effect on syncytialisation, as evidenced by induction of hCG secretion, by ERVW-1 mRNA expression and by formation of multinuclear cells. CRH mRNA expression was found to increase prior to the changes in the other syncytialisation markers. cAMP had an inhibitory effect on BeWo cell viability, but exogenous CRH did not. However, CRH did mimic the differentiation inducing effect of cAMP, suggesting a link between CRH and cAMP signalling in syncytialisation. We also found that treatment of BeWo cells with exogenous CRH resulted in elevated cellular CRHR1 levels.

CONCLUSIONS

This study suggests a positive feed-forward role exists for CRH in trophoblast cell differentiation, which may underlie the exponential rise in CRH observed as gestation advances.