Coexpression of adrenomedullin and its receptor component proteins in the reproductive system of the rat during gestation

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.

Local adrenomedullin gene delivery inhibits Leydig cell dysfunction by rescuing steroidogenic enzymes in vivo

Adrenomedullin (ADM) has beneficial effects on Leydig cells under pathological conditions, including lipopolysaccharide (LPS)-induced orchitis. Our previous studies demonstrated that ADM exerts a restorative effect on steroidogenesis in LPS-treated primary rat Leydig cells by attenuating oxidative stress, inflammation and apoptosis. In this study, we aim to investigate whether ADM inhibits Leydig cell dysfunction by rescuing steroidogenic enzymes in vivo. Rats were administered with LPS and injected with Ad-ADM, an adeno-associated virus vector that expressed ADM. Then, rat testes were collected for 3β-hydroxysteroid dehydrogenase (3β-HSD) immunofluorescence staining. Steroidogenic enzymes or steroidogenic regulatory factors or protein, including steroidogenic factor-1 (SF-1), liver receptor homologue-1 (LRH1), Nur77, steroidogenic acute regulatory protein (StAR), cytochrome P450 cholesterol side chain cleavage enzyme (P450scc), 3β-HSD, cytochrome P450 17α-hydroxylase/17, 20 lyase (CYP17) and 17β-hydroxysteroid dehydrogenase (17β-HSD), were detected via gene expression profiling and western blot analysis. Plasma testosterone concentrations were measured. Results showed that ADM may inhibit Leydig cell dysfunction by rescuing steroidogenic enzymes and steroidogenic regulatory factors in vivo. The reduction in the number of Leydig cells after LPS exposure was reversed by ADM. ADM rescued the gene or protein levels of SF-1, LRH1, Nur77, StAR, P450scc, 3β-HSD, CYP17 and 17β-HSD and plasma testosterone concentrations. To summarize ADM could rescue some important steroidogenic enzymes, steroidogenic regulatory factors and testosterone production in Leydig cells in vivo.

Oocyte-specific disruption of adrenomedullin 2 gene enhances ovarian follicle growth after superovulation

BACKGROUND

Adrenomedullin 2 (ADM2), adrenomedullin (ADM), and calcitonin gene-related peptides (α- and β-CGRPs) signal through heterodimeric calcitonin receptor-like receptor/receptor activity-modifying protein 1, 2 and 3 (CLR/RAMP1, 2 and 3) complexes. These peptides are important regulators of neurotransmission, vasotone, cardiovascular development, and metabolic homeostasis. In rodents, ADM is essential for regulating embryo implantation, fetal-placental development, and hemodynamic adaptation during pregnancy. On the other hand, ADM2 was shown to affect vascular lumen enlargement, and cumulus cell-oocyte complex (COC) communication in rodent and bovine ovarian follicles. To investigate whether oocyte-derived ADM2 plays a physiological role in regulating ovarian folliculogenesis, we generated mice with oocyte-specific disruption of the Adm2 gene using a LoxP-flanked Adm2 transgene (Adm2 loxP/loxP) and crossed them with Zp3-Cre mice which carry a zona pellucida 3 (Zp3) promoter-Cre recombinase transgene.

RESULTS

While heterozygous Adm2 +/-/Zp3-Cre and homozygous Adm2 -/-/Zp3-Cre mice were fertile, Adm2 disruption in oocytes significantly increased the number of ovulated oocytes following a superovulation treatment. Oocyte-specific Adm2 disruption also significantly impaired the developmental capacity of fertilized eggs and decreased the size of the corpus luteum following superovulation, perhaps due to a reduction of ovarian cyclin D2-associated signaling.

CONCLUSIONS

The disruption of intrafollicular ADM2 signaling leads to follicular dysfunction. These data suggested that oocyte-derived ADM2 plays a facilitative role in the regulation of hormonal response and follicle growth independent of the closely related ADM and CGRP peptides, albeit in a subtle manner.

Potential effect of adrenomedullin on metabolic and endocrinal dysfunctions in the experimentally induced polycystic ovary: Targeting implication of endoplasmic reticulum stress

This study investigated the potential effect of adrenomedullin (ADM) on metabolic and endocrinal dysfunctions in experimentally induced polycystic ovary. Twenty-four female Wistar rats were allocated into three groups: control; polycystic ovary syndrome (PCOS) in which PCOS was induced by letrozole, orally in a dose of 1 mg/kg once daily for 3 weeks; and ADM group in which ADM was injected intraperitonally in a dose of 3.5/μg/twice daily for 4 weeks. At the end of the experimental period, the serum sex hormone profile, ADM, fasting glucose, insulin, homeostatic model assessment of insulin resistance, and lipid parameters were determined. Ovarian tissue homogenates were used to determine malondialdehyde, total antioxidant capacity, glutathione peroxidase activity, tumor necrosis factor α, interleukin 6, B cell lymphoma-2 (Bcl-2), and Bcl-2 associated X protein. The profibrotic growth factors, including transforming growth factor β1 and connective tissue growth factor, were determined; and also, the relative gene expression of endoplasmic reticulum (ER) stress, including (Xbox-binding protein-1 [XBP-1], activating transcription factor 6 [ATF6], and homologous protein [CHOP]), serine/threonine kinase 1 (Akt1), phosphatidylinositol 3-kinase (PI3K), and peroxisome proliferator-activated receptor γ (PPAR-γ) were determined. Finally, histopathological analysis of the ovaries was evaluated. PCOS group exhibited increased ER stress, suppressing of PI3K/Akt1 and PPAR-γ pathways, imbalance of sex hormonal profile, hyperglycemia, insulin resistance, dyslipidemia, increased profibrotic factors, and abnormal ovarian histopathological picture, while ADM treatment alleviated these disturbances occurring in the PCOS model. We concluded that ADM mitigated PCOS via attenuating the ER stress, in addition to activation of PI3K/Akt1 and PPAR-γ pathways, its antioxidant, anti-inflammatory, antiapoptotic, and antifibrotic properties.

Adrenomedullin2 (ADM2)/intermedin (IMD) in rat ovary: changes in estrous cycle and pregnancy and its role in ovulation and steroidogenesis

Adrenomedullin2 (ADM2) is reported to facilitate embryo implantation and placental development. Therefore, the current study was undertaken to identify if ADM2 has a functional role in ovary to facilitate its reproductive actions. This study shows that the expression of ADM2 is differentially regulated in rat estrous cycle and that ADM2 increases the synthesis and secretion of 17beta-estradiol accompanied with an increase in the expression of steroidogenic factor 1 (Sf1), estrogen receptor Esr1, and enzymes involved in steroidogenesis in equine chorionic gonadotropin (eCG)-treated rat ovaries. In addition, inhibition of endogenous ADM2 function in eCG-treated immature rats caused impaired ovulation. Furthermore, the mRNA expression of Adm2 and receptor activity modifying protein 3 is higher in the ovary on Day 18 compared to nonpregnant and pregnant rats on Day 22. ADM2-like immunoreactivity is localized in granulosa cells, blood vessels, oocytes, cumulous oophorus, and corpus luteum of pregnant ovaries, suggesting a potential role for ADM2 in the ovary. This is supported by the presence of ADM2-like immunoreactivity in the corpus luteum during pregnancy and a decline in aromatase immunoreactivity in corpus luteum on Day 9 of gestation in rats infused with ADM2 antagonist during implantation and decidualization phase. Taken together, this study suggests a potential involvement of ADM2 in the rat ovary in regulating synthesis of estradiol to support ovulation and facilitate efficient implantation and placental development for a successful pregnancy.

Adrenomedullin and endocrine control of immune cells during pregnancy

The immunology of pregnancy is complex and incompletely understood. Aberrant immune activity in the decidua and in the placenta is believed to play a role in diseases of pregnancy, such as infertility, miscarriage, fetal growth restriction and preeclampsia. Here, we briefly review the endocrine control of uterine natural killer cell populations and their functions by the peptide hormone adrenomedullin. Studies in genetic animal models have revealed the critical importance of adrenomedullin dosage at the maternal-fetal interface, with cells from both the maternal and fetal compartments contributing to essential aspects underlying appropriate uterine receptivity, implantation and vascular remodeling of spiral arteries. These basic insights into the crosstalk between the endocrine and immune systems within the maternal-fetal interface may ultimately translate to a better understanding of the functions and consequences of dysregulated adrenomedullin levels in clinically complicated pregnancies.

Adrenomedullin increases the short-circuit current in the rat prostate: Receptors, chloride channels, the effects of cAMP and calcium ions and implications on fluid secretion

In this study, we have investigated the effects of adrenomedullin on chloride and fluid secretion in the rat prostate. The presence of adrenomedullin (ADM) in rat prostate was confirmed using immunostaining, and the molecular species was determined using gel filtration chromatography coupled with an enzyme-linked assay for ADM. The effects of ADM on fluid secretion were studied by short-circuit current technique in a whole mount preparation of the prostate in an Ussing chamber. The results indicated that the ADM level was higher in the ventral than the dorso-lateral prostate and the major molecular species was the active peptide. ADM increased the short-circuit current through both the cAMP- and calcium-activated chloride channels in the ventral lobe, but only through the calcium-activated channels in the dorso-lateral lobe. These stimulatory effects were blocked by the calcitonin gene-related peptide (CGRP) receptor antagonist, hCGRP8-37. We conclude that ADM may regulate prostatic fluid secretion through the chloride channels, which may affect the composition of the seminal plasma bathing the spermatozoa and hence fertility.

Calcitonin gene related family peptides: importance in normal placental and fetal development

Synchronized molecular and cellular events occur between the uterus and the implanting embryo to facilitate successful pregnancy outcome. Nevertheless, the molecular signaling network that coordinates strategies for successful decidualization, placentation and fetal growth are not well understood. The discovery of calcitonin/calcitonin gene-related peptides (CT/CGRP) highlighted new signaling mediators in various physiological processes, including reproduction. It is known that CGRP family peptides including CGRP, adrenomedulin and intermedin play regulatory functions during implantation, trophoblast proliferation and invasion, and fetal organogenesis. In addition, all the CGRP family peptides and their receptor components are found to be expressed in decidual, placental and fetal tissues. Additionally, plasma levels of peptides of the CGRP family were found to fluctuate during normal gestation and to induce placental cellular differentiation, proliferation, and critical hormone signaling. Moreover, aberrant signaling of these CGRP family peptides during gestation has been associated with pregnancy disorders. It indicates the existence of a possible regulatory role for these molecules during decidualization and placentation processes, which are known to be particularly vulnerable. In this review, the influence of the CGRP family peptides in these critical processes is explored and discussed.

Temporo-spatial expression of adrenomedullin and its receptors in the bovine placenta

BACKGROUND

Adrenomedullin (AM) is a potent vasodilator peptide and is also involved in various physiological activities. In humans and rodents, AM is found in the uteroplacental unit and may be responsible for fetal development and maintenance of placental function. This study investigated 1) the mRNA expression patterns of AM and its receptor components (calcitonin receptor-like receptor (CRLR), receptor activity modifying protein (RAMP) 2 and RAMP3) during pregnancy and 2) mRNA and protein localization of AM, CRLR and RAMPs in the bovine placentome.

METHODS

For real-time quantitative RT-PCR, bovine uteroplacental tissues were collected from Day 25, 60, 100, 150, 200 and 250 of gestation and separated into uterine caruncle (CAR), intercaruncular endometrium (ICAR), extra-embryonic membranes on Day 25 and cotyledonary villous after Day 60 (EEM-COT) and intercotyledonary chorion (ICOT). In situ hybridization and immunohistochemistry was performed to investigate the cellular localization of mRNA and protein of AM, CRLR, RAMP2 and RAMP3 in the placentome on Day 56, 150 and 230 of gestation and interplacentomal tissues on Day 56 of gestation.

RESULTS

AM mRNA was highly expressed on Day 200 in EEM-COT, CAR and ICAR. CRLR mRNA was highly expressed on Day 60 in all portions. RAMP2 mRNA was also highly expressed on Day 60 in ICOT and ICAR. In EEM-COT, mRNA expression of CRLR and RAMP2 decreased from Day 150 to 250. RAMP3 mRNA was highly expressed on Day 150 in EEM-COT, ICOT and ICAR. A distinct AM mRNA and protein signal were only found in trophoblast binucleate cells (BNCs), whereas those of CRLR, RAMP2 and RAMP3 were detected in cotyledonary villous and caruncular epithelial cells. In interplacentomal tissues, AM was detected in BNCs of fetal membrane and a small part of luminal epithelium, endothelial lineage of blood vessels and glandular epithelium of the endometrium. Distinct signals of CRLR, RAMP2 and RAMP3 were found in trophoblast cells, luminal epithelium, stroma under the epithelium, endothelial lineage of blood vessels and glandular epithelium.

CONCLUSIONS

Our results indicate that the AM system in the bovine uteroplacental unit may be activated at placentation and transition from the mid to late gestation period. Locally produced AM in the BNCs may play a crucial role in regulation of placental vascular and cellular functions during pregnancy.

Intermedin in rat uterus: changes in gene expression and peptide levels across the estrous cycle and its effects on uterine contraction

BACKGROUND

The present study demonstrates the expression of intermedin (IMD) and its receptor components in the uterus of the female rat during the estrous cycle and its effect on uterine contraction.

METHODS

The gene expression level of intermedin and its receptor components and the peptide level of intermedin were studied by real-time RT-PCR and enzyme immunoassay (EIA) respectively. The separation of precursor and mature IMD was studied by gel filtration chromatography and EIA. The localization of IMD in the uterus was investigated by immunohistochemistry. The effect of IMD on in vitro uterine contraction was studied by organ bath technique.

RESULTS

Uterine mRNAs of Imd and its receptor components and IMD levels displayed cyclic changes across the estrous cycle. Imd mRNA level was the highest at proestrus while the IMD level was the highest at diestrus. IMD was found in the luminal and glandular epithelia and IMD treatment significantly reduced the amplitude and frequency of uterine contraction but not the basal tone. Both calcitonin gene-related peptide (CGRP) receptor antagonist hCGRP8-37 and adrenomedullin (ADM) receptor antagonist hADM22-52 partially abolished the inhibitory effect of IMD on uterine contraction while the specific IMD receptor antagonist hIMD17-47 completely blocked the actions. The enzyme inhibitors of NO (L-NAME) and PI3K (Wortmannin) pathways diminished the IMD effects on uterine contraction while the cAMP/PKA blocker, KT5720, had no effect, indicating an involvement of NO and PI3K/Akt but not PKA.

CONCLUSIONS

IMD and the gene expression of its receptor components are differentially regulated in the uterus during the estrous cycle and IMD inhibits uterine contraction by decreasing the amplitude and frequency.

Intermedin/adrenomedullin 2 is associated with implantation and placentation via trophoblast invasion in human pregnancy

RATIONALE

Intermedin (IMD) is a novel peptide expressed in trophoblast cells in human placenta and enhances the invasion, migration, and human leukocyte antigen class I, G (HLA-G) expression in first-trimester HTR-8SV/neo cells. We recently reported that infusion of IMD antagonist in pregnant rats is detrimental to pregnancy outcome, resulting in impaired fetoplacental growth and deformed placental vasculature.

OBJECTIVE

This study was undertaken to assess expression of IMD and its involvement in human implantation and early placentation and assess whether its expression is altered in spontaneous abortion.

FINDINGS AND CONCLUSIONS

We demonstrate for the first time that IMD is present in day 5 embryonic secretome; villous and decidual expression of IMD is higher at 6-8 weeks after a decline as gestation advances toward the second trimester; first-trimester spontaneous abortion is associated with a lower expression of IMD in serum, villi, and decidua; IMD stimulates the invasive capacity of first-trimester primary Extravillous cytotrophoblast cells; and IMD decreases elevated levels of tumor suppressor Kangia-1 in decidual explants from first-trimester spontaneous abortion. In conclusion, this study is the first to demonstrate a potential involvement of IMD in human embryo implantation and placental development via regulation of trophoblast invasion at the maternal-fetal interface and suggests a physiological role for this novel peptide in establishment of human pregnancy.

The role of estrogen in the pathophysiology of tubal ectopic pregnancy

17β-estradiol, acting through estrogen receptors α and β, plays a fundamental role in the regulation of Fallopian tube cell homeostasis and in the modulation of normal tubal physiological processes. Fluctuations in E2 levels also play crucial roles in the initiation or progression of numerous human diseases. Fallopian tube malfunction often results in tubal ectopic pregnancy, which is one cause of maternal morbidity and mortality in women. Several factors have been proposed to be associated with increased risk of tubal ectopic pregnancy, but whether these factors are the cause of, or are merely symptoms of, such pregnancies remains unresolved due to the lack of knowledge in regards to the mechanisms by which embryos inadvertently implant in the Fallopian tube. This review summarizes recent findings, including data from our own laboratory, on E2 metabolism and estrogen receptor (ER) subtype expression within the Fallopian tube in humans and rodents. This review also outlines several important, unresolved questions in the field that, once addressed, could offer important clues into how E2/ER signaling contributes to the pathology of tubal function. A better understanding of the specific functions of estrogen receptor subtypes in vivo, as well as of the mechanism and consequences of receptor subtype interactions is critical to understanding their respective roles in Fallopian tube physiology and in the pathophysiology and etiology of tubal ectopic pregnancy.

Possible role of adrenomedullin in the pathogenesis of tubal ectopic pregnancy

CONTEXT

Tubal ectopic pregnancy (tEP) is currently the leading cause of pregnancy-related deaths during the first trimester. Our current knowledge on the molecular pathogenesis is limited.

OBJECTIVE

The objective of the study was to find out the possible role of adrenomedullin (ADM) in the pathogenesis of tEP.

DESIGN

This was an experimental in vitro study on oviductal tissue.

SETTING

The study was conducted at a university teaching hospital.

PATIENTS AND INTERVENTIONS

Patients included those having oviducts removed surgically during salpingectomy for tEP or hysterectomy for benign gynecological conditions. Oviductal tissues were incubated in hormonal condition mimicking early pregnancy before used for in vitro experiments.

MAIN OUTCOME MEASURES

Plasma ADM concentration, oviductal expression of ADM and its receptors, ciliary beat frequency, smooth muscle contraction were measured.

RESULTS

The ciliary beat frequency and frequency of muscle contraction were lower in the oviducts from patients with tEP than those from simulated normal pregnancy. The plasma and oviductal tissue ADM levels were also lower. The decreases in ciliary beat and frequency of contraction were restored to normal after ADM treatment.

CONCLUSIONS

The results suggest that the lower ADM level in the oviducts of tEP may lead to the decrease in ciliary beating and muscle contraction, with the result that the embryo is retained and implanted in the oviduct. Our findings explain for the first time the etiology of tubal pregnancy on the basis of an impairment of the transport of the fertilized ovum resulting from an ADM deficiency and raise the possibility of using the plasma ADM level as a predictor for tubal ectopic pregnancy.