Changes in the expression of calcitonin receptor-like receptor, receptor activity-modifying protein (RAMP) 1, RAMP2, and RAMP3 in rat uterus during pregnancy, labor, and by steroid hormone treatments

Animal models of the placenta accreta spectrum: current status and further perspectives

Placenta accreta spectrum disorder (PAS) is a kind of disease of placentation defined as abnormal trophoblast invasion of part or all of the placenta into the myometrium, even penetrating the uterus. Decidual deficiency, abnormal vascular remodeling in the maternal-fetal interface, and excessive invasion by extravillous trophoblast (EVT) cells contribute to its onset. However, the mechanisms and signaling pathways underlying such phenotypes are not fully understood, partly due to the lack of suitable experimental animal models. Appropriate animal models will facilitate the comprehensive and systematic elucidation of the pathogenesis of PAS. Due to the remarkably similar functional placental villous units and hemochorial placentation to humans, the current animal models of PAS are based on mice. There are various mouse models induced by uterine surgery to simulate different phenotypes of PAS, such as excessive invasion of EVT or immune disturbance at the maternal-fetal interface, which could define the pathological mechanism of PAS from the perspective of the "soil." Additionally, genetically modified mouse models could be used to study PAS, which is helpful to exploring the pathogenesis of PAS from the perspectives of both "soil" and "seed," respectively. This review details early placental development in mice, with a focus on the approaches of PAS modeling. Additionally, the strengths, limitations and the applicability of each strategy and further perspectives are summarized to provide the theoretical foundation for researchers to select appropriate animal models for various research purposes. This will help better determine the pathogenesis of PAS and even promote possible therapy.

Involvement of the calcitonin gene-related peptide system in the modulation of inflamed uterus contractile function in pigs

This study analyzed severe acute endometritis action on myometrial density and distribution of protein gene product (PGP)9.5- and calcitonin gene-related peptide (CGRP)-like immunoreactive nerve fibers and calcitonin receptor-like receptor (CLR) expression, and on CGRP receptor (CGRPR) participation in uterine contractility in pigs. E. coli suspension (E. coli group) or saline (SAL group) were injected into the uteri, or only laparotomy was performed (CON group). In the E. coli group myometrium, a lack of significant changes in PGP9.5 and CGRP innervation patterns and increased CLR protein level were revealed. In all groups, compared to the pretreatment period, human αCGRP increased amplitude in the myometrium, while reducing it in endometrium/myometrium. In the E. coli group endometrium/myometrium, human αCGRP lowered amplitude vs other groups. Human αCGRP reduced frequency in CON and SAL groups and enhanced it in the E. coli group endometrium/myometrium. The frequency in E. coli group increased vs other groups. CGRPR antagonist, human αCGRP8-37, reversed (CON, SAL groups) and eliminated (E. coli group) the rise in human αCGRP-induced myometrial amplitude. In endometrium/myometrium, human αCGRP8-37 abolished (CON group) and reversed (SAL group) a decrease in frequency, and reduced the rise in frequency (E. coli group) caused by human αCGRP. Collectively, in the myometrium, endometritis did not change PGP9.5 and CGRP innervation patterns and enhanced CLR protein level. CGRPR also mediated in CGRP action on inflamed uterus contractility.

Whole‐genome sequencing reveals the artificial selection and local environmental adaptability of pigeons ( Columba livia )

To meet human needs, domestic pigeons (Columba livia) with various phenotypes have been bred to provide genetic material for our research on artificial selection and local environmental adaptation. Seven pigeon breeds were resequenced and can be divided into commercial varieties (Euro‐pigeon, Shiqi, Shen King, Taishen, and Silver King), ornamental varieties (High Fliers), and local varieties (Tarim pigeon). Phylogenetic analysis based on population resequencing showed that one group contained local breeds and ornamental pigeons from China, whereas all commercial varieties were clustered together. It is revealed that the traditional Chinese ornamental pigeon is a branch of Tarim pigeon. Runs of homozygosity (ROH) and linkage disequilibrium (LD) analyses revealed significant differences in the genetic diversity of the three types of pigeons. Genome sweep analysis revealed that the selected genes of commercial breeds were related to body size, reproduction, and plumage color. The genomic imprinting genes left by the ornamental pigeon breeds were mostly related to special human facial features and muscular dystrophy. The Tarim pigeon has evolved genes related to chemical ion transport, photoreceptors, oxidative stress, organ development, and olfaction in order to adapt to local environmental stress. This research provides a molecular basis for pigeon genetic resource evaluation and genetic improvement and suggests that the understanding of adaptive evolution should integrate the effects of various natural environmental characteristics.

Differential Synovial CGRP/RAMP1 Expression in Men and Women With Knee Osteoarthritis

Background

Female patients with osteoarthritis report more severe knee pain compared to men. However, the mechanism underlying sex differences in pain remains unclear. We previously found that calcitonin gene-related peptide (CGRP) was expressed in synovial tissue and that this localization may play a role in pain associated with knee osteoarthritis (KOA). Several animal studies have shown that the expression of CGRP and its receptor (receptor activity modifying protein 1, RAMP1) differs by sex. Here, we investigated synovial CGRP and RAMP1 expression in male and female patients with KOA.

Methods

Synovial tissue (ST) was harvested from male and female subjects (n=30 each) with radiographically confirmed unilateral Kellgren/Lawrence grade 3-4 KOA during total knee arthroplasty. Patients’ subjective pain severity was scored on a 0 to 10 cm visual analog scale (VAS). We compared the expression of CGRP and RAMP1 in ST from men and women and examined the correlation between mRNA levels of CGRP and RAMP1 and pain severity.

Results

Synovial expression of CGRP and RAMP1 was significantly elevated in women compared to men (CGRP, P=0.017; RAMP1, P=0.028). While CGRP expression was positively correlated with pain severity in females (ρ=0.443, P=0.014), no correlation was observed in men (ρ=-0.021, P=0.913). RAMP1 expression was not correlated with pain severity in either men or women (male, ρ=-0.114, P=0.939; female, ρ=-0.047, P=0.807).

Conclusion

CGRP and RAMP1 expression levels differ between men and women. Differential CGRP levels may suggest the presence of different pain mechanisms in men and women with KOA.

Amylin brain circuitry

Amylin is a peptide hormone that is mainly known to be produced by pancreatic β-cells in response to a meal but amylin is also produced by brain cells in discrete brain areas albeit in a lesser amount. Amylin receptor (AMY) is composed of the calcitonin core-receptor (CTR) and one of the 3 receptor activity modifying protein (RAMP), thus forming AMY1-3; RAMP enhances amylin binding properties to the CTR. However, amylin receptor agonist such as salmon calcitonin is able to bind CTR alone. Peripheral amylin's main binding site is located in the area postrema (AP) which then propagate the signal to the nucleus of the solitary tract and lateral parabrachial nucleus (LPBN) and it is then transmitted to the forebrain areas such as central amygdala and bed nucleus of the stria terminalis. Amylin's activation of these different brain areas mediates eating and other metabolic pathways controlling energy expenditure and glucose homeostasis. Peripheral amylin can also bind in the arcuate nucleus of the hypothalamus where it acts independently of the AP to activate POMC and NPY neurons. Amylin activation of NPY neurons has been shown to be transmitted to LPBN neurons to act on eating while amylin POMC signaling affects energy expenditure and locomotor activity. While a large amount of experiments have already been conducted, future studies will have to further investigate how amylin is taken up by forebrain areas and deepen our understanding of amylin action on peripheral metabolism.

The role of erenumab in the treatment of migraine

Calcitonin gene related peptide (CGRP) monoclonal antibodies (mAbs) have been the first class of specifically developed preventive treatments for migraine. Clinical trials data suggest superiority of the CGRP mAbs to placebo in terms of prevention of migraine symptoms, migraine-specific quality of life and headache related disability. Treatment-related side effects overall did not differ significantly from placebo and discontinuation rate due to side effects has been low across the clinical trials, perhaps in view of their peripheral mode of action. Along with their route and frequency of administration, these novel class of drugs may constitute an improvement compared with the established arsenal of migraine treatments. Erenumab is a fully human antibody and the only mAb acting on the CGRP pathway by blocking its receptor. It is the first of the CGRP mAb class approved by the US Food and Drug Administration (May 2018) and the European Medicines Agency (July 2018). Erenumab exists in two different doses (70 mg and 140 mg) and it is administered with monthly subcutaneous injections. This review summarises erenumab pharmacological characteristics, clinical trials data, focusing on the potential role of this treatment in clinical practice.

Human Placental Vascular Reactivity in Health and Disease: Implications for the Treatment of Pre-eclampsia

Adequate development of the placenta is essential for optimal pregnancy outcome. Pre-eclampsia (PE) is increasingly recognized to be a consequence of placental dysfunction and can cause serious maternal and fetal complications during pregnancy. Furthermore, PE increases the risk of neonatal problems and has been shown to be a risk factor for cardiovascular disease of the mother later in life. Currently, there is no adequate treatment for PE, mainly because its multifactorial pathophysiology remains incompletely understood. It originates in early pregnancy with abnormal placentation and involves a cascade of dysregulated systems in the placental vasculature. To investigate therapeutic strategies it is essential to understand the regulation of vascular reactivity and remodeling of blood vessels in the placenta. Techniques using human tissue such as the ex vivo placental perfusion model provide insight in the vasoactive profile of the placenta, and are essential to study the effects of drugs on the fetal vasculature. This approach highlights the different pathways that are involved in the vascular regulation of the human placenta, changes that occur during PE and the importance of focusing on restoring these dysfunctional systems when studying treatment strategies for PE.

RAMP1 and RAMP3 Differentially Control Amylin's Effects on Food Intake, Glucose and Energy Balance in Male and Female Mice

Amylin is a pancreatic peptide, which acts as a key controller of food intake and energy balance and predominately binds to three receptors (AMY 1-3). AMY 1-3 are composed of a calcitonin core receptor (CTR) and associated receptor-activity modifying proteins (RAMPs) 1-3. Using RAMP1, RAMP3 and RAMP1/3 global KO mice, this study aimed to determine whether the absence of one or two RAMP subunits affects food intake, glucose homeostasis and metabolism. Of all the RAMP-deficient mice, only high-fat diet fed RAMP1/3 KO mice had increased body weight. Chow-fed RAMP3 KO and high-fat diet fed 1/3 KO male mice were glucose intolerant. Fat depots were increased in RAMP1 KO male mice. No difference in energy expenditure was observed but the respiratory exchange ratio (RER) was elevated in RAMP1/3 KO. RAMP1 and 1/3 KO male mice displayed an increase in intermeal interval (IMI) and meal duration, whereas IMI was decreased in RAMP3 KO male and female mice. WT and RAMP1, RAMP3, and RAMP1/3 KO male and female littermates were then assessed for their food intake response to an acute intraperitoneal injection of amylin or its receptor agonist, salmon calcitonin (sCT). RAMP1/3 KO were insensitive to both, while RAMP3 KO were responsive to sCT only and RAMP1 KO to amylin only. While female mice generally weighed less than male mice, only RAMP1 KO showed a clear sex difference in meal pattern and food intake tests. Lastly, a decrease in CTR fibers did not consistently correlate with a decrease in amylin- induced c-Fos expression in the area postrema (AP). Ultimately, the results from this study provide evidence for a role of RAMP1 in mediation of fat utilization and a role for RAMP3 in glucose homeostasis and amylin's anorectic effect.

Mechanisms of pain modulation by sex hormones in migraine

A number of pain conditions, acute as well as chronic, are much more prevalent in women, such as temporomandibular disorder (TMD), irritable bowel syndrome, fibromyalgia, and migraine. The association of female sex steroids with these nociceptive conditions is well known, but the mechanisms of their effects on pain signaling are yet to be deciphered. We reviewed the mechanisms through which female sex steroids might influence the trigeminal nociceptive pathways with a focus on migraine. Sex steroid receptors are located in trigeminal circuits, providing the molecular substrate for direct effects. In addition to classical genomic effects, sex steroids exert rapid nongenomic actions to modulate nociceptive signaling. Although there are only a handful of studies that have directly addressed the effect of sex hormones in animal models of migraine, the putative mechanisms can be extrapolated from observations in animal models of other trigeminal pain disorders, like TMD. Sex hormones may regulate sensitization of trigeminal neurons by modulating expression of nociceptive mediator such as calcitonin gene-related peptide. Its expression is mostly positively regulated by estrogen, although a few studies also report an inverse relationship. Serotonin (5-Hydroxytryptamine [5-HT]) is a neurotransmitter implicated in migraine; its synthesis is enhanced in most parts of brain by estrogen, which increases expression of the rate-limiting enzyme tryptophan hydroxylase and decreases expression of the serotonin re-uptake transporter. Downstream signaling, including extracellular signal-regulated kinase activation, calcium-dependent mechanisms, and cAMP response element-binding activation, are thought to be the major signaling events affected by sex hormones. These findings need to be confirmed in migraine-specific animal models that may also provide clues to additional ion channels, neuropeptides, and intracellular signaling cascades that contribute to the increased prevalence of migraine in women.

Fetal-derived adrenomedullin mediates the innate immune milieu of the placenta

The remodeling of maternal uterine spiral arteries (SAs) is an essential process for ensuring low-resistance, high-capacitance blood flow to the growing fetus. Failure of SAs to remodel is causally associated with preeclampsia, a common and life-threatening complication of pregnancy that is harmful to both mother and fetus. Here, using both loss-of-function and gain-of-function genetic mouse models, we show that expression of the pregnancy-related peptide adrenomedullin (AM) by fetal trophoblast cells is necessary and sufficient to promote appropriate recruitment and activation of maternal uterine NK (uNK) cells to the placenta and ultimately facilitate remodeling of maternal SAs. Placentas that lacked either AM or its receptor exhibited reduced fetal vessel branching in the labyrinth, failed SA remodeling and reendothelialization, and markedly reduced numbers of maternal uNK cells. In contrast, overexpression of AM caused a reversal of these phenotypes with a concomitant increase in uNK cell content in vivo. Moreover, AM dose-dependently stimulated the secretion of numerous chemokines, cytokines, and MMPs from uNK cells, which in turn induced VSMC apoptosis. These data identify an essential function for fetal-derived factors in the maternal vascular adaptation to pregnancy and underscore the importance of exploring AM as a biomarker and therapeutic agent for preeclampsia.

Transcriptional profiling reveals elevated Sox2 in DNA polymerase ß null mouse embryonic fibroblasts

There are over 150 human proteins that have been categorized as bona fide DNA repair proteins. These DNA repair proteins maintain the integrity of the genome, reducing the onset of cancer, disease and aging phenotypes. Variations in expression and/or function would therefore impact genome integrity as well as the cellular response to genotoxins. Global gene expression analysis is an effective approach to uncover defects in DNA repair gene expression and to discover cellular and/or organismal effects brought about by external stimuli such as environmental genotoxicants, chemotherapeutic regimens, viral infections as well as developmental and age-related stimuli. Given the significance of genome stability in cell survival and response to stimuli, we have hypothesized that cells may undergo transcriptional re-programming to accommodate defects in basal DNA repair capacity to promote survival. As a test of this hypothesis, we have compared the transcriptome in three DNA polymerase ß knockout (Polß-KO) mouse embryonic fibroblasts (MEFs) and the corresponding wild-type (WT) littermate control cell lines. Each Polß-KO cell line was found to have a range of genes up-regulated, when compared to its WT littermate control cell line. Interestingly, six (6) genes were commonly up regulated in all three Polß-KO cell lines, including Sox2, one of several genes associated with the induction of pluripotent stem cells. Herein, we present these findings and suggest that loss of DNA repair and the induction of cellular transcriptional re-programming may, in part, contribute to tumor formation and the cellular response to external stimuli.

Effects of continuous intermedin infusion on blood pressure and hemodynamic function in spontaneously hypertensive rats

OBJECTIVE

To examine the effects of exogenously administered intermedin (IMD, adrenomedullin-2) on arterial blood pressure, cardiac function and the cardiovascular IMD receptor system in spontaneously hypertensive rats (SHRs) as well as to investigate the associated mechanisms.

METHODS

Thirteen week-old male rats were divided in Wistar Kyoto (WKY) group (n = 12), SHR group (n = 12), IMD group (SHRs infused with IMD 1-47 500 ng/kg per hour, n = 12), and ADM group (SHRs infused with adrenomedullin 500 ng/kg per hour, n = 12).

RESULTS

A two-week continuous administration of low dose IMD 1-47 via mini-osmotic pumps markedly reduced blood pressure, the maximal rates of increase and decrease of left-ventricle pressure development (LV ± dp/dt(max)), left ventricular systolic pressure and heart rate in SHRs. Furthermore, IMD also inhibited protein over-expression of cardiovascular IMD receptors, myocardial Receptor Activity-Modifying Proteins (RAMP1 and RAMP2), aortic RAMP1, RAMP2, RAMP3, and calcitonin receptor-like receptor (CRLR); suppressed up-regulation of aortic RAMP1, RAMP2, RAMP3 and CRLR gene expression; and markedly elevated the mRNA abundance of myocardial atrial natriuretic peptide (ANP) and myocardial brain natriuretic peptide (BNP). Additionally, IMD 1-47 administration in SHRs increased aortic cAMP concentration and reduced myocardial cAMP concentration.

CONCLUSION

These findings support the speculation that IMD, as a cardiovascular active peptide, is involved in blood pressure reduction and cardiac function amelioration during hypertension. The mechanism underlying this effect may involve IMD binding of a receptor complex formed by RAMPs and CRLR, and consequential regulation of cAMP levels and other cardiovascular active factors, such as ANP and BNP.

Vascular reactivity to calcitonin gene-related peptide is enhanced in subtotal nephrectomy-salt induced hypertension

In subtotal nephrectomy (SN)- and salt-induced hypertension, calcitonin gene-related peptide (CGRP) plays a compensatory role to attenuate the blood pressure increase in the absence of an increase in the neuronal synthesis and release of this peptide. Therefore, the purpose of this study was to determine whether the mechanism of this antihypertensive activity is through enhanced sensitivity of the vasculature to the dilator actions of this neuropeptide. Hypertension was induced in Sprague-Dawley rats by SN and 1% saline drinking water. Control rats were sham-operated and given tap water to drink. After 11 days, rats had intravenous (drug administration) and arterial (continuous mean arterial pressure recording) catheters surgically placed and were studied in a conscious unrestrained state. Baseline mean arterial pressure was higher in the SN-salt rats (157 ± 5 mmHg) compared with controls (128 ± 3 mmHg). Administration of CGRP (and adrenomedullin) produced a significantly greater dose-dependent decrease in mean arterial pressure in SN-salt rats compared with controls (∼2.0-fold for both the low and high doses). Interestingly, isolated superior mesenteric arterioles from SN-salt rats were significantly more responsive to the dilator effects of CGRP (but not adenomedullin) than the controls (pEC(50), SN-salt, 14.0 ± 0.1 vs. control, 12.0 ± 0.1). Analysis of the CGRP receptor proteins showed that only the receptor component protein was increased significantly in arterioles from SN-salt rats. These data indicate that the compensatory antihypertensive effects of CGRP result from an increased sensitivity of the vasculature to dilator activity of this peptide. The mechanism may be via the upregulation of receptor component protein, thereby providing a more efficient coupling of the receptor to the signal transduction pathways.

Adrenomedullin relaxes rat uterine artery: mechanisms and influence of pregnancy and estradiol

Uterine arteries play a major role in regulating uteroplacental blood flow. Failure to maintain blood flow to the uteroplacental compartment during pregnancy often results in intrauterine growth retardation. Immunohistochemical staining of adrenomedullin (AM), an endogenous vasoactive peptide, in uterine artery was intense in pregnant compared to nonpregnant rats, but it is not known whether AM directly relaxes uterine artery or not. In this study, we elucidated the mechanisms of uterine artery relaxation by AM and its regulation by pregnancy and female sex steroids. AM was able to relax uterine artery, and this relaxation was influenced positively by pregnancy and estradiol as evidenced by the increased pD(2) and E(max) values of AM. Both pregnancy and estradiol treatment to ovariectomized rats amplified RAMP(3) expression in uterine arteries while progesterone had no effect. AM-induced uterine artery relaxation is predominantly endothelium-dependent. The AM receptor antagonist CGRP(8-37) is more potent than AM(22-52) in inhibiting the AM relaxation, indicating the involvement of AM(2) receptor subtype. Moreover, AM uses the classical nitric oxide-cyclic guanosine monophosphate pathway along with K(Ca) channels to mediate the vasodilatory effect in uterine artery. In conclusion, sensitivity of uterine artery to AM-induced relaxation is increased with pregnancy or estradiol treatment by increasing RAMP(3) expression, suggesting an important role for AM in regulating the uterine hemodynamics, probably maintaining uterine blood flow during pregnancy and in pre- and postmenopausal cardiovascular adaptation differences.

Receptor activity modifying proteins and their potential as drug targets

The receptor activity modifying proteins (RAMPs) are a family of membrane proteins that interact with some G protein-coupled receptors (GPCRs) to regulate their function. RAMPs can alter GPCR pharmacology and can regulate their signaling as well as trafficking to and from the cell surface. GPCRs have been successfully exploited as drug targets for many years. RAMPs therefore provide a new avenue for drug development, offering opportunities for regulating the function of therapeutically relevant RAMP-interacting GPCRs. RAMPs could be directly targeted themselves or advantage could be taken of the unique RAMP/GPCR interfaces for generating more selective drugs.

Calcitonin gene-related peptide, adrenomedullin and flushing

Administration of calcitonin gene-related peptide (CGRP) or adrenomedullin (AM) can cause facial flushing, suggesting that the peptides may be important in hot flushes experienced particularly by post-menopausal women. Five studies have measured plasma CGRP concentrations in post-menopausal women who suffer from flushes; all demonstrated elevations of between 170% and 320% over control. Three of the studies showed a temporal relationship between flushes and CGRP elevation. A further study has shown that CGRP is elevated in the urine of women who suffer from flushes. Only a single study has investigated flushes in pre-menopausal women; no elevation of CGRP was observed. Flushes are also experienced by men undergoing androgen deprivation therapy. Whilst one study failed to find any increase in CGRP in the urine of these individuals, a small study has identified an increase in plasma CGRP. No studies have investigated plasma AM or the related peptide, intermedin/AM2. Overall, there is good evidence to show that flushes in post-menopausal women are accompanied by an increase in CGRP. CGRP could act centrally on the thermoregulatory centre of the hypothalamus as well as peripherally to cause vasodilation and sweating. However, it remains to be demonstrated that the elevated CGRP causes flushes. Recently developed CGRP antagonists provide an opportunity to test this hypothesis. If they are successful, they may represent a useful alternative to oestrogen replacement therapy.

Mechanisms leading to increased vasodilator responses to calcitonin-gene-related peptide in mesenteric resistance arteries of early pregnant rats

The objective of this study was to explore the mechanism responsible for the higher relaxing responses of mesenteric arteries to calcitonin-gene-related peptide (CGRP) in pregnancy. We performed myograph and ligand binding studies to determine the role of matrix metalloproteinase-2 (MMP-2) and CGRP receptor density. MMP activity was manipulated in isolated arteries by exposing them to the blocking effects of doxycycline. Vascular activity of MMP-2 was studied by gelatin zymography, and CGRP receptor density was determined by ligand binding analysis. Compared to nonpregnant rats, CGRP elicited stronger arterial relaxation in pregnant rats. The latter effect was neither accompanied by a change in relaxing responses to direct activation of adenylyl cyclase by forskolin nor by a change in the response to stimulation of G-protein-coupled adrenergic receptors by isoproterenol. Doxycycline did not affect the stronger arterial relaxation in pregnancy in spite of the observed more than threefold higher arterial MMP-2 activity. Density of binding sites for [(125)I]CGRP in arteries from pregnant rats (64 +/- 14 fmol/mg protein) and from virgin rats (54 +/- 5 fmol/mg protein) were comparable. The results of this study provide evidence for increased coupling of CGRP receptors to adenylyl cyclase in early pregnancy.

Distal control of the pig whey acidic protein (WAP) locus in transgenic mice

Distal control of the whey acidic protein (WAP) locus was studied using a transgenic approach. A series of pig genomic fragments encompassing increasing DNA lengths upstream of the mammary specific whey acidic protein (WAP) gene transcription start point (tsp) and 5 kb downstream were used for microinjection in mouse fertilized eggs. Our data pointed out three regions as potent regulators for WAP but not for RAMP3 gene expression (a non mammary-specific gene located 30 kb upstream of the WAP gene). WAP gene activating elements were present in the -80 kb to -30 kb and -145 kb to -130 kb regions whereas inhibitors were present in the -130 kb to -80 kb region. The stimulatory regions were characterized by peaks of histone H4 acetylation and a poor nucleosome occupancy in lactating sow mammary glands but not in liver. These data reveal for the first time the existence of several remote potent regulatory regions of the pig WAP gene.

Effect of betamethasone in vivo on placental adrenomedullin in human pregnancy

OBJECTIVE

The aim of the current study was to determine the effects of in vivo administration of prenatal betamethasone in patients at risk for preterm delivery on adrenomedullin (AM) concentrations in maternal and fetal plasma and on AM localization in placenta and fetal membranes.

METHODS

A total of 62 pregnant women between 25 and 35 weeks' gestation were studied. Forty-seven pregnant women received betamethasone (2 x 12 mg intramuscularly given 24 hours apart) for stimulation of fetal lung maturity. Blood samples were collected before betamethasone administration and at different time points after the first and the second dose. Further samples were collected at delivery and, in women who did not deliver, after 1 week and 30 days from betamethasone administration. At delivery, placenta and membranes were collected. Fifteen patients who delivered at the same gestational age not receiving betamethasone represented the control group. AM concentration was determined by radioimmunoassay. Localization of AM in placental tissues was assessed by immunohistochemistry.

RESULTS

Betamethasone caused approximately 50% increase in maternal plasma AM at 1 week after administration, whereas in fetal plasma AM levels increased by about 90% at 48 hours after betamethasone administration. There was increased immunohistochemical staining for AM in fetoplacental tissues collected after betamethasone administration.

CONCLUSION

These results provide the first evidence for in vivo stimulation of AM, likely of placental origin, by glucocorticoids in the third trimester human pregnancy.

Labor-associated gene expression in the human uterine fundus, lower segment, and cervix

BACKGROUND

Preterm labor, failure to progress, and postpartum hemorrhage are the common causes of maternal and neonatal mortality or morbidity. All result from defects in the complex mechanisms controlling labor, which coordinate changes in the uterine fundus, lower segment, and cervix. We aimed to assess labor-associated gene expression profiles in these functionally distinct areas of the human uterus by using microarrays.

METHODS AND FINDINGS

Samples of uterine fundus, lower segment, and cervix were obtained from patients at term (mean +/- SD = 39.1 +/- 0.5 wk) prior to the onset of labor (n = 6), or in active phase of labor with spontaneous onset (n = 7). Expression of 12,626 genes was evaluated using microarrays (Human Genome U95A; Affymetrix) and compared between labor and non-labor samples. Genes with the largest labor-associated change and the lowest variability in expression are likely to be fundamental for parturition, so gene expression was ranked accordingly. From 500 genes with the highest rank we identified genes with similar expression profiles using two independent clustering techniques. Sets of genes with a probability of chance grouping by both techniques less than 0.01 represented 71.2%, 81.8%, and 79.8% of the 500 genes in the fundus, lower segment, and cervix, respectively. We identified 14, 14, and 12 those sets of genes in the fundus, lower segment, and cervix, respectively. This enabled networks of co-regulated and co-expressed genes to be discovered. Many genes within the same cluster shared similar functions or had functions pertinent to the process of labor.

CONCLUSIONS

Our results provide support for many of the established processes of parturition and also describe novel-to-labor genes not previously associated with this process. The elucidation of these mechanisms likely to be fundamental for controlling labor is an important prerequisite to the development of effective treatments for major obstetric problems--including prematurity, with its long-term consequences to the health of mother and offspring.

Calcitonin gene-related peptide receptor activation by receptor activity-modifying protein-1 gene transfer to vascular smooth muscle cells

The neuropeptide calcitonin gene-related peptide (CGRP) is a potent vasodilator that plays a protective role in the cardiovascular system. The receptor for CGRP is an unusual complex of the G protein-coupled calcitonin-like receptor and an obligate receptor activity modifying protein-1 (RAMP1). In this report we provide the first evidence that RAMP1 is rate limiting in vascular smooth muscle cells. Although cultured rat aorta smooth muscle cells express calcitonin like-receptor and RAMP1, we found that CGRP is not a potent activator of the receptor. After overexpression of RAMP1 by adenoviral gene transfer, there was a striking increase in CGRP-induced production of cAMP, with a 75-fold decrease in the EC(50) and a 1.5-fold increase in the maximal response. The biological consequence of this increased receptor activity was observed in three different paradigms. First, RAMP1 gene transfer caused a CGRP-dependent decrease in cell proliferation. Second, RAMP1 and CGRP treatment led to a 3-fold greater free radical-induced reduction in cell number. Finally, RAMP1 gene transfer resulted in a 5-fold CGRP-dependent increase in terminal deoxynucleotidyltransferase-mediated deoxyuridine triphosphate nick end labeling-positive apoptotic cells upon serum withdrawal. The mechanisms underlying these effects involved cAMP-dependent pathways. We propose that RAMP1 gene transfer may be an effective strategy for increasing the effectiveness of CGRP-induced decrease in restenosis after aortic angioplasty.

Female sex steroids increase adrenomedullin-induced vasodilation by increasing the expression of adrenomedullin2 receptor components in rat mesenteric artery

Based on the favorable effects of female sex steroids in vascular functions and the potent hypotensive effects of adrenomedullin (AM), we hypothesized that AM-induced vasodilation is gender dependent, and female sex steroids enhance this effect. In endothelium-intact rat mesenteric artery, AM (1 nm-0.3 microM)-induced concentration-dependent relaxation was significantly (P < 0.05) higher in females [pD2(-log EC50 of the molar concentration), 7.05 +/- 0.10; maximal relaxation response (Emax), 69.2 +/- 3.46%] than males (pD2, 6.53 +/- 0.08; Emax, 53.28 +/- 4.86%). The increased relaxation was lost when the females were ovariectomized (OVX) (pD2, 6.14 +/- 0.24; Emax, 39.68 +/- 5.68%). The reduced relaxation response in OVX rats was reversed by administration of either progesterone (P4; pD2, 7.18 +/- 0.07; Emax, 72.4 +/- 2.76%) or 17beta-estradiol (E2; pD2, 7.00 +/- 0.14; Emax, 70.4 +/- 4.79%). AM mediates its effects through either AM(22-52)-sensitive AM1 receptors [composed of calcitonin receptor-like receptors (CLs) and receptor activity-modifying protein (RAMP)2] or AM2 receptors (CL/RAMP3), which can be antagonized more potently by calcitonin gene-related peptide(8-37) than AM(22-52). Pharmacological characterization suggested the involvement of AM2 receptors in the increased vasodilatory effect of AM in both P4- and E2-treated animals as calcitonin gene-related peptide(8-37) (10 microM) was more potent in antagonizing the AM effects (Emax, P(4): 25.92 +/- 5.32%; E2: 29.11 +/- 7.41%) than AM(22-52) (100 microM). RT-PCR studies also supported the involvement of AM2 receptors because expression of mRNA levels encoding CL (previously reported) and RAMP3 were increased in P4- or E2-treated OVX rats. In conclusion, AM-induced vasodilation is gender-dependent and increased by female sex steroids by increased expression of AM2 receptor components.

GPCR modulation by RAMPs

Our conceptual understanding of the molecular architecture of G-protein coupled receptors (GPCRs) has transformed over the last decade. Once considered as largely independent functional units (aside from their interaction with the G-protein itself), it is now clear that a single GPCR is but part of a multifaceted signaling complex, each component providing an additional layer of sophistication. Receptor activity-modifying proteins (RAMPs) provide a notable example of proteins that interact with GPCRs to modify their function. They act as pharmacological switches, modifying GPCR pharmacology for a particular subset of receptors. However, there is accumulating evidence that these ubiquitous proteins have a broader role, regulating signaling and receptor trafficking. This article aims to provide the reader with a comprehensive appraisal of RAMP literature and perhaps some insight into the impact that their discovery has had on those who study GPCRs.

Progesterone upregulates calcitonin gene-related peptide and adrenomedullin receptor components and cyclic adenosine 3'5'-monophosphate generation in Eker rat uterine smooth muscle cell line

Calcitonin gene-related peptide (CGRP) and adrenomedullin (AM), two potent smooth-muscle relaxants, have been shown to cause uterine relaxation. Both CGRP- and AM-binding sites in the uterus increase during pregnancy and decrease at labor and postpartum. These changes in binding sites appear to be related to the changes in calcitonin receptor-like receptor (CRLR), receptor activity-modified protein 1 (RAMP1), RAMP2, and RAMP3 mRNA levels. It is not clear, however, whether the changes in the receptor components occur in the myometrial cells and whether the steroid hormones can directly alter these receptor components in the muscle cells. In addition, the mechanism of CGRP and AM signaling in the rat myometrium is not well understood. Therefore, we examined the mRNA expression of CGRP- and AM-receptor components, G protein Galphas, CGRP, and AM stimulation of cAMP and cGMP, and the effects of progesterone on these parameters in the Eker rat uterine myometrial smooth-muscle cell line (ELT3). ELT3 cells expressed CGRP- and AM-receptor components CRLR, RAMP1, RAMP2, and RAMP3. Expression of CRLR and RAMP1 mRNA increased with progesterone treatment and decreased with estradiol-17beta treatment. However, RAMP2 and RAMP3 mRNA expressions were unaltered by both progesterone and estradiol. Progesterone increased (P<0.05) Galphas expression and augmented CGRP- and AM-induced increases in cAMP levels. In uterine smooth-muscle cells, the antagonist to Galphas protein NF449 decreased basal as well as CGRP- and AM-stimulated cAMP levels. None of the cell treatments affected cyclic GMP production. Our results suggest that the progesterone-stimulated increases in CGRP and AM receptors, Galphas protein levels, and cAMP generation in the myometrial cells may be responsible for increased uterine relaxation sensitivity to CGRP and AM during pregnancy.

RAMPs and CRLR expressions in osteoblastic cells after dexamethasone treatment

Adrenomedullin (ADM) is a potent stimulator of osteoblastic activity and promotes bone growth in vivo. ADM receptors are formed by heterodimerization of the CRLR and a RAMP2 or RAMP3 molecule. Since glucocorticoid responsive elements were recently identified in the human CRLR promoter and that glucocorticoids exert a major action in bones, we investigated the acute effect of dexamethasone (Dex) treatment on ADM receptor components in osteoblastic cell types: the MC3T3-E1 cells and calvaria-derived osteoblastic cells. Changes in expression of CRLR and RAMPs molecules were evaluated at mRNA levels using RT-PCR and at protein levels by Western blot analysis. We found that Dex increased expression of RAMP1 and RAMP2 mRNA in a time-dependent but dose-independent manner, while RAMP3 was unchanged. In contrast, Dex decreased the CRLR mRNA expression and these changes were reflected at protein levels. We suggest that Dex, in osteoblastic cells, altered ADM receptor by inhibition of CRLR expression and consequently could impair the ADM anabolic effect on bone. Our findings could explain in part, the detrimental side effects observed at bone level during glucocorticoid therapy.

Estrogen and phytoestrogen regulate the mRNA expression of adrenomedullin and adrenomedullin receptor components in the rat uterus

The serum estrogen surge in the uterus triggers precisely-timed physiological and biochemical responses required establishing and maintaining pregnancy. Previous reports have shown that consumption of phytoestrogen-containing plants may disrupt the precise control of pregnancy. To evaluate the effects of phytoestrogens in the uterus, we screened for estradiol (E2)-inducible genes in immature rat uteri. We identified the gene for receptor-activity-modifying protein 2 (Ramp2), known to be a component of the adrenomedullin (ADM) receptor, as responsive to both E2 and the phytoestrogen coumestrol (Cou). We further examined the expression of ADM and ADM signaling components Ramp2, Ramp3, and CRLR in the immature rat uterus and found that both E2 and Cou regulated these genes expression. In addition, treatment with ADM increased uterine weight and edema similar to that observed after Cou treatment. Our findings indicated that the phytoestrogen caused the abnormal induction of vasoactive factors in the uterus.

RAMPs: 5 years on, where to now?

It is now approximately 5 years since the identification of the family of receptor activity modifying proteins (RAMPs). This finding revolutionized concepts of the pharmacology of G-protein-coupled receptors (GPCRs) and revealed that GPCR accessory proteins not only assist trafficking and folding but also define receptor type. Since the identification of RAMPs as modulators of the trafficking and properties of the calcitonin-receptor-like receptor, much work has focused on improving our understanding of the nature of RAMP-GPCR dimers, the extent to which they occur, and the consequence of this association. In this article, we review recent developments, including the identification of new receptor partners and novel roles for RAMPs.

The receptor activity modifying protein family of G protein coupled receptor accessory proteins

Receptor diversity for the calcitonin peptide family is created by the interaction of two 7-transmembrane proteins--the calcitonin receptor (CTR) or the calcitonin receptor-like receptor (CL-R)--with the receptor activity modifying protein (RAMP) family. The discovery of heterodimeric complexes of these proteins heralded a new era in the study of G protein coupled receptors (GPCRs), whereby receptor phenotype is no longer governed by just the GPCR. In this article, recent advances in the study of RAMPs are discussed--from our current understanding of the molecular basis of RAMP-receptor interaction to a broader role for RAMPs outside the calcitonin receptor family.

Adrenomedullin: Multiple functions in human pregnancy

Adrenomedullin is a 52 amino acid peptide originally isolated from human phaeochromocytoma in 1993. It was initially demonstrated to have profound effects on the vasculature including vasodilatation and subsequently promotion of angiogenesis. Since then it has become apparent that it has a wide range of other biological actions including regulation of cell growth and differentiation. Successful pregnancy outcome relies on establishing and maintaining throughout gestation an efficient blood supply to the fetus. This allows the exchange of nutrients, oxygenation of fetal blood and removal of cytotoxins from the fetus, such as carbon dioxide. One of the most important local adaptations to pregnancy is the change in maternal blood flow to the implantation site. Evidence now points towards a vital role for adrenomedullin in the regulation of placentation. It appears that adrenomedullin may play important roles in the regulation of fetal perfusion both in normal and in compromised pregnancies. However, most studies have focused on measuring adrenomedullin levels and studying its expression as well as that of its receptors. More functional studies are now required to elucidate the underlying mechanisms involved.