Expression of adrenomedullin (ADM) and its binding sites in the rat uterus: increased number of binding sites and ADM messenger ribonucleic acid in 20-day pregnant rats compared with nonpregnant rats

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.

Advances in Understanding the Initial Steps of Pruritoceptive Itch: How the Itch Hits the Switch

Pruritoceptive (dermal) itch was long considered an accompanying symptom of diseases, a side effect of drug applications, or a temporary sensation induced by invading pruritogens, as produced by the stinging nettle. Due to extensive research in recent years, it was possible to provide detailed insights into the mechanism of itch mediation and modulation. Hence, it became apparent that pruritus is a complex symptom or disease in itself, which requires particular attention to improve patients’ health. Here, we summarize recent findings in pruritoceptive itch, including how this sensation is triggered and modulated by diverse endogenous and exogenous pruritogens and their receptors. A differentiation between mediating pruritogen and modulating pruritogen seems to be of great advantage to understand and decipher the molecular mechanism of itch perception. Only a comprehensive view on itch sensation will provide a solid basis for targeting this long-neglected adverse sensation accompanying numerous diseases and many drug side effects. Finally, we identify critical aspects of itch perception that require future investigation.

Equine Chorionic Gonadotropin Modulates the Expression of Genes Related to the Structure and Function of the Bovine Corpus Luteum

We hypothesized that stimulatory and superovulatory treatments, using equine chorionic gonadotropin (eCG), modulate the expression of genes related to insulin, cellular modelling and angiogenesis signaling pathways in the bovine corpus luteum (CL). Therefore, we investigated: 1—the effect of these treatments on circulating insulin and somatomedin C concentrations and on gene and protein expression of INSR, IGF1 and IGFR1, as well as other insulin signaling molecules; 2—the effects of eCG on gene and protein expression of INSR, IGF1, GLUT4 and NFKB1A in bovine luteal cells; and 3—the effect of stimulatory and superovulatory treatments on gene and protein expression of ANG, ANGPT1, NOS2, ADM, PRSS2, MMP9 and PLAU. Serum insulin did not differ among groups (P = 0.96). However, serum somatomedin C levels were higher in both stimulated and superovulated groups compared to the control (P = 0.01). In stimulated cows, lower expression of INSR mRNA and higher expression of NFKB1A mRNA and IGF1 protein were observed. In superovulated cows, lower INSR mRNA expression, but higher INSR protein expression and higher IGF1, IGFR1 and NFKB1A gene and protein expression were observed. Expression of angiogenesis and cellular modelling pathway-related factors were as follows: ANGPT1 and PLAU protein expression were higher and MMP9 gene and protein expression were lower in stimulated animals. In superovulated cows, ANGPT1 mRNA expression was higher and ANG mRNA expression was lower. PRSS2 gene and protein expression were lower in both stimulated and superovulated animals related to the control. In vitro, eCG stimulated luteal cells P4 production as well as INSR and GLUT4 protein expression. In summary, our results suggest that superovulatory treatment induced ovarian proliferative changes accompanied by increased expression of genes providing the CL more energy substrate, whereas stimulatory treatment increased lipogenic activity, angiogenesis and plasticity of the extracellular matrix (ECM).

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.

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.

Adrenomedullin in rat follicles and corpora lutea: expression, functions and interaction with endothelin-1

BACKGROUND

Adrenomedullin (ADM), a novel vasorelaxant peptide, was found in human/rat ovaries. The present study investigated the interaction of ADM and endothelin-1 (ET-1) in follicles and newly formed corpora lutea (CL) and the actions of ADM on progesterone production in CL during pregnancy.

METHODS

The peptide and gene expression level of adrenomedullin in small antral follicles, large antral follicles and CL was studied by real-time RT-PCR and EIA. The effect of ADM treatment on oestradiol production in 5-day follicular culture and on progesterone production from CL of different pregnant stages was measured by EIA. The interaction of ADM and ET-1 in follicles and CL at their gene expression level was studied by real-time RT-PCR.

RESULTS

In the rat ovary, the gene expression of Adm increased during development from small antral follicles to large antral follicles and CL. In vitro treatment of preantral follicular culture for 5 days with ADM increased oestradiol production but did not affect follicular growth or ovulation rate. The regulation of progesterone production by ADM in CL in culture was pregnancy-stage dependent, inhibitory at early and late pregnancy but stimulatory at mid-pregnancy, which might contribute to the high progesterone production rate of the CL at mid-pregnancy. Moreover, the interaction between ADM and ET-1 at both the production and functional levels indicates that these two vasoactive peptides may form an important local, fine-tuning regulatory system together with LH and prolactin for progesterone production in rat CL.

CONCLUSIONS

As the CL is the major source of progesterone production even after the formation of placenta in rats, ADM may be an important regulator in progesterone production to meet the requirement of pregnancy.

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

BACKGROUND

Adrenomedullin (ADM), a novel vasorelaxant peptide, was found in human/rat ovaries and uteri. Plasma ADM level increases in pregnant women and pregnant rats.

METHODS

The gene expression levels of Adm and its receptor components - Crlr, Ramp1, Ramp2 and Ramp3, the ADM peptide concentration and localization in the rat female reproductive system during gestation were studied by real-time RT-PCR, EIA and immunohistochemical techniques.

RESULTS

The mRNAs of Adm and its receptor component and ADM were differentially distributed between implantation sites and inter-implantation sites of the pregnant uterus. The day on which vaginal sperm were found was taken to be pregnancy day 1. The Adm mRNA levels in the implantation sites of the uteri in mid- (day 12) and late pregnancy (day 17) were more than 10-fold higher than those in nonpregnancy, pre-implantation (day 3) or early (day 7) pregnancy. ADM was localized in the endometrial stroma with increased immunoreactivity from nonpregnancy to pregnancy. The ADM level and the mRNA levels of Adm, Crlr, Ramp2 and Ramp3 in the corpus luteum all increased in late pregnancy compared with early pregnancy. The gene expression of Adm and it receptor components and intense immunostaining of ADM were also found in the oviduct during pregnancy.

CONCLUSIONS

The gene expressions levels of Adm and its receptor components - Crlr, Ramp1, Ramp2 and Ramp3, and ADM peptide concentration exhibited a spatio-temporal pattern in the rat female reproductive system during gestation and this suggests that ADM may play important roles in gestation.

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.

Adrenomedullin Peptide: Gene Expression of Adrenomedullin, its Receptors and Receptor Activity Modifying Proteins, and Receptor Binding in Rat Testis—Actions on Testosterone Secretion1

Adrenomedullin (ADM) has been shown to be present in the human and rat male reproductive systems. This study demonstrates the expression of ADM in the rat testis and its effect on the secretion of testosterone. Whole testicular extracts had 5.43 +/- 0.42 fmol of immunoreactive ADM per milligram of protein and 84 +/- 8 fg of ADM mRNA per picogram of Actb (beta-actin) mRNA. Immunocytochemical studies showed positive ADM immunostaining in the Leydig cells and in the Sertoli cells. Gel filtration chromatography of testicular extracts showed two peaks, with the predominant one eluting at the position of the ADM precursor. Furthermore, the testis was shown to coexpress mRNAs encoding the calcitonin receptor-like receptor and receptor activity modifying protein 1 (Ramp1), Ramp2, and Ramp3. These account for the specific binding of ADM to the testis, which was partially inhibited by human ADM (22-52) and by human calcitonin gene-related peptide (8-37), the ADM and calcitonin gene-related peptide receptor antagonists, respectively. Administration of ADM to testicular blocks in vitro resulted in a dose-dependent inhibition of hCG-stimulated release of testosterone, which was abolished by the administration of ADM (22-52). Our results suggest a paracrine effect of ADM on testicular steroidogenesis.

Expression of adrenomedullin mRNA is altered with gestation and labour in human placenta and fetal membranes

The aim of the present study was to investigate whether placental and fetal membrane AdM (adrenomedullin) mRNA expression changes with gestation and human labour, as we have previously found labour-associated changes in AdM content in fetal membranes [Al-Ghafra, Gude, Brennecke and King (2003) Clin. Sci. 105, 419-423]. Placentas and fetal membranes were collected either at term or pre-term from women either in-labour or not-in-labour, and AdM mRNA abundance was measured in tissue extracts by Northern blot analysis. Increases were found in the relative abundance of amniotic tissue AdM mRNA in both in-labour and not-in-labour groups at term compared with those at pre-term, and there were positive correlations with gestational age. Relative abundance of choriodecidual tissue AdM mRNA was also significantly elevated in the not-in-labour groups between pre-term and term tissues, although there was no significant correlation with gestational age. However, placental AdM mRNA expression was neither significantly increased at term (compared with pre-term) nor correlated with gestational age. In addition, there were significant increases in AdM mRNA in amnion and choriodecidua in the in-labour group compared with the not-in-labour group for both pre-term and term gestations. There was no difference in AdM mRNA in placental tissues between labour groups. In conclusion, the present study provides evidence that AdM production by fetal membranes is increased in amniotic and choriodecidual tissues at term, compared with pre-term, and in response to labour.

Influence of misoprostol (PGE1) on amniotic fluid and maternal serum adrenomedullin levels

OBJECTIVE

The purpose of this study was to determine the levels of adrenomedullin (AdM) in amniotic fluid (AF) and maternal serum of misoprostol (PGE1)-induced pregnant women.

MATERIALS AND METHODS

A total of 40 women were included in the study: 20 were in active labor and were delivered vaginally and a further 20 were not in labor and misoprostol induction was performed. Women who were undergoing labor induction received 50 microg of misoprostol, which was placed in the posterior fornix of the vagina every 4 hrs until the onset of labor. In each patient, maternal plasma and AF samples were collected. Samples of AF were collected by transvaginal route at the time of rupture of the membranes. The labor was at the same stage in both the groups during the sample collection. In all pregnant subjects, maternal blood samples were drawn from the cubital vein at the time of AF sampling. Amniotic fluid and serum AdM concentration was measured by using reverse-phase high-performance liquid chromatography.

RESULTS

Misoprostol-induced pregnant women showed significantly higher AdM concentrations than control pregnant women in AF (79.48 +/- 6.14 pmol/ml versus 21.28 +/- 0.90 pmol/ml, P = 0.000) and maternal serum (88.20 +/- 4.34 pmol/ml versus 29.78 +/- 4.51 pmol/ml, P = 0.000). There was no significant difference between maternal serum and AF-AdM concentrations in misoprostol and control subjects.

CONCLUSION

Increased serum and AF-AdM concentrations may be necessary to initiate cervical ripening in misoprostol-induced pregnant women.

Role of the N-terminal domain of the calcitonin receptor-like receptor in ligand binding

Calcitonin receptor-like receptor (CRLR) is a seven-transmembrane (7-TM) domain class B G protein-coupled receptor (GPCR) which requires coexpression of different receptor activity modifying proteins (RAMP) to become a functional calcitonin gene-related peptide (CGRP) receptor or an adrenomedullin (AM) receptor. The N-terminal (Nt) extracellular region of class B GPCRs in ligand binding has been reported for receptors such as glucagon and parathyroid hormone. We hypothesize that the Nt-domain of CRLR (Nt-CRLR) is an autonomously folded unit possessing a well-defined structure and is involved in ligand binding and specificity. To obtain structural and functional information on the Nt-CRLR, we cloned and expressed the Nt-CRLR as a fusion protein in Escherichia coli. Overexpressed protein formed an inclusion body, which was refolded and purified, resulting in a soluble monomeric protein. Far-UV CD and fluorescence spectra of Nt-CRLR showed characteristics of a folded protein. The ability of Nt-CRLR to bind CGRP and AM independent of RAMPs was determined by studying inhibition of (125)I-CGRP and (125)I-AM binding to pregnant rat uterine membrane in the presence of Nt-CRLR protein. We observe that Nt-CRLR inhibits (125)I-CGRP and (125)I-AM binding to rat uterus in a dose-dependent fashion (IC(50) = 0.25 and 0.29 muM, respectively). Taken together, our data provide evidence that Nt-CRLR is structured and further that a significant part of the binding affinity comes from binding to the Nt-domain.

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.

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.

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

Calcitonin gene-related peptide (CGRP) and its related peptide, adrenomedullin (AM), are potent smooth muscle relaxants in a variety of tissues. The CGRP has been reported to play an important role in maintaining uterine relaxation during pregnancy. We have previously reported that CGRP-induced uterine relaxation was gestationally regulated. Calcitonin receptor-like receptor (CRLR), a seven-domain transmembrane protein functions as CGRP-A receptor, in association with receptor activity-modifying protein (RAMP) 1, a single-domain transmembrane protein, whereas CRLR and RAMP2 or RAMP3 constitute a receptor for AM. In the present investigation, we examined the mRNA expression of CRLR, RAMP1, RAMP2, and RAMP3 in rat uterus (n = 8) by reverse transcriptional analysis and polymerase chain reaction to assess the changes in the expression of CGRP-A- and AM-receptor components during pregnancy and labor and by steroid hormone treatments in adult ovariectomized rats. The changes in mRNA are expressed relative to the 18S mRNA in the uterus of rats at various stages: nonpregnant, pregnant on Day 18, spontaneous labor at term, Day 2 postpartum, and in pregnant rats on treatment with RU486. Ovariectomized rats treated for 3 days twice daily s.c. with estradiol-17beta (2.5 microg/injection), progesterone (2 mg/injection), and the combination of estradiol-17beta and progesterone (same doses as above) were also examined for the expression of various receptor components. Results showed that mRNA expression of the receptor components was significantly higher (P < 0.001 for CRLR, P < 0.01 for RAMP1, P < 0.05 for RAMP2, and P < 0.01 for RAMP3) in pregnant compared to nonpregnant rats. Except for RAMP3, expression of all the other three genes decreased significantly (P < 0.05) during labor. A progesterone antagonist, RU486 significantly decreased (P < 0.01 for CRLR, P < 0.05 for RAMP1, RAMP2, and RAMP3) all the receptor components during pregnancy. In adult ovariectomized rats, progesterone caused significant increases in CRLR (P < 0.001), RAMP1 (P < 0.05), and RAMP2 (P < 0.01). Levels of RAMP3 were unaffected by the progesterone treatment. Estradiol-17beta treatment decreased all of the four receptor components significantly (P < 0.01 for CRLR, P < 0.05 for RAMP1, RAMP2, and RAMP3). Our results demonstrate that both CGRP and AM may play a role in uterine quiescence during pregnancy and that their receptor components are regulated by the steroid hormones.

Co-expression of adrenomedullin and adrenomedullin receptors in rat epididymis: distinct physiological actions on anion transport

Adrenomedullin (AM) has been found in the brain as well as in various peripheral tissues, including reproductive organs such as the testis and the prostate. Here, we report the expression of AM in the rat epididymis and its role in anion secretion. Whole-epididymal extracts had 35.3 +/- 1.4 fmol of immunoreactive AM per mg of protein, and immunocytochemical studies showed positive AM immunostaining in the epithelial cells. By solution-hybridization-RNase protection assay, preproAM mRNA was detected at high levels in the epididymis. Gel filtration chromatography of AM showed two peaks, with the predominant one eluting at the position of authentic rat AM (1-50). Specific binding of AM to the epididymis, which could be displaced by calcitonin gene-related peptide, was observed. The epididymis also bound to calcitonin gene-related peptide, and this was displaceable by AM. Furthermore, the epididymis was shown to co-express mRNA encoding the calcitonin receptor-like receptor and receptor activity-modifying proteins, RAMP1/RAMP2. The corpus region had the highest AM level and gene expression and the lowest active peptide:precursor ratio. However, mRNA levels of the receptor and the receptor activity-modifying proteins were similar in all regions. In monolayer cultures derived from the rat epididymal cells, AM stimulated short-circuit current on the luminal side in a dose-dependent manner. Our results demonstrate the presence of AM, preproAM mRNA, AM receptors, and specific-binding sites in the rat epididymis as well as the possible role of AM in the regulation of electrolyte and fluid secretion in the epididymis.

Comparison of the expression of calcitonin receptor-like receptor (CRLR) and receptor activity modifying proteins (RAMPs) with CGRP and adrenomedullin binding in cell lines

1. The calcitonin receptor-like receptor (CRLR) and specific receptor activity modifying proteins (RAMPs) together form receptors for calcitonin gene-related peptide (CGRP) and/or adrenomedullin in transfected cells. 2. There is less evidence that innate CGRP and adrenomedullin receptors are formed by CRLR/RAMP combinations. We therefore examined whether CGRP and/or adrenomedullin binding correlated with CRLR and RAMP mRNA expression in human and rat cell lines known to express these receptors. Specific human or rat CRLR antibodies were used to examine the presence of CRLR in these cells. 3. We confirmed CGRP subtype 1 receptor (CGRP(1)) pharmacology in SK-N-MC neuroblastoma cells. L6 myoblast cells expressed both CGRP(1) and adrenomedullin receptors whereas Rat-2 fibroblasts expressed only adrenomedullin receptors. In contrast we could not confirm CGRP(2) receptor pharmacology for Col-29 colonic epithelial cells, which, instead were CGRP(1)-like in this study. 4. L6, SK-N-MC and Col-29 cells expressed mRNA for RAMP1 and RAMP2 but Rat-2 fibroblasts had only RAMP2. No cell line had detectable RAMP3 mRNA. 5. SK-N-MC, Col-29 and Rat-2 fibroblast cells expressed CRLR mRNA. By contrast, CRLR mRNA was undetectable by Northern analysis in one source of L6 cells. Conversely, a different source of L6 cells had mRNA for CRLR. All of the cell lines expressed CRLR protein. Thus, circumstances where CRLR mRNA is apparently absent by Northern analysis do not exclude the presence of this receptor. 6. These data strongly support CRLR, together with appropriate RAMPs as binding sites for CGRP and adrenomedullin in cultured cells.

Adrenomedullin in mammalian embryogenesis

Here are summarized data supporting that adrenomedullin (AM) is a multifunctional factor involved in the complex regulatory mechanisms of mammalian development. During rodent embryogenesis, AM is first expressed in the heart, followed by a broader but also defined spatio-temporal pattern of expression in vascular, neural, and skeletal-forming tissues as well as in the main embryonic internal organs. AM pattern of expression is suggestive of its involvement in the control of embryonic invasion, proliferation, and differentiation processes, probably through autocrine or paracrine modes of action. AM levels in fetoplacental tissues, uterus, maternal and umbilical plasma are highly increased during normal gestation. These findings in addition to other physiological and gene targeting studies support the importance of AM as a vasorelaxant factor implicated in the regulation of maternal vascular adaptation to pregnancy, as well as of fetal and fetoplacental circulations. AM is also present in amniotic fluid and milk, which is suggestive of additional functions in the maturation and immunological protection of the fetus. Altered expression of AM has been found in some gestational pathologies, although it is not yet clear whether this corresponds to causative or compensatory mechanisms. Future studies in regard to the distribution and expression levels of the molecules known to function as AM receptors, together with data on the action of complement factor H (an AM binding protein), may help to better define the roles of AM during embryonic development.

Adrenomedullin, calcitonin gene-related peptide and their receptors: evidence for a decreased placental mRNA content in preeclampsia and HELLP syndrome

OBJECTIVE

The human placenta expresses a variety of vasoactive substances and neuropeptides, which play an important role in the regulation of placental blood flow in both the maternal and foetal compartment and are therefore of critical importance for foetal growth and development. Our study was planned to examine placental mRNA amounts of vasodilatory adrenomedullin (AM), calcitonin gene-related peptide (CGRP) and their receptors (AM-R and CGRP-R) in preeclampsia and HELLP syndrome (hemolysis, elevated liver enzymes, low platelets). These are severe maternal conditions leading to an altered uteroplacental and fetoplacental perfusion and a higher risk for foetal growth retardation, premature delivery, infant mortality, and even maternal death.

STUDY DESIGN

We included 17 patients with preeclampsia, four women with HELLP syndrome and 34 controls. After delivery, the mRNA levels of AM, AM-R, CGRP, CGRP-R, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and -actin were measured in placental villi and chorionic plates using quantitative real-time PCR.

RESULTS

AM/-actin and AM/GAPDH mRNA ratios were significantly lower in placental villi in preeclampsia than in controls (P<0.05) as were CGRP/-actin and CGRP/GAPDH mRNA ratios in chorionic plates (P<0.05). Placental AM-R and CGRP-R mRNA amounts were unaffected.

CONCLUSION

Our data show a reduction of AM and CGRP mRNAs in contrast to unchanged mRNA levels of their receptors in placenta specimens of women with preeclampsia or HELLP syndrome.

Adrenomedullin expression in rat uterus is correlated with plasma estradiol

Levels of expression of adrenomedullin (AM) in the uterus have been reported to vary with the reproductive cycle. This study examines the relationships among uterine AM mRNA, the stage of the estrous cycle, and circulating estradiol and progesterone in cycling rats and in ovariectomized (OVX) rats without or with estrogen replacement (ER). Strong AM mRNA, AM immunoreactivity, and pro-AM NH2-terminal 20 peptide (PAMP) immunoreactivity were observed in endometrial stroma by use of in situ hybridization and immunocytochemistry. Endometrial expression was particularly intense at proestrus and estrus, with weaker expression in the myometrium. By RNase protection assay, significant differences in AM mRNA between the stages of the estrous cycle could not be established. However, levels of AM mRNA were positively correlated with plasma estradiol in cycling rats (r = 0.56, P < 0.005) and in OVX and ER rats (r = 0.92, P < 0.001) and were not correlated with plasma progesterone. Levels of AM mRNA were significantly reduced after OVX compared with cycling rats, and ER restored AM mRNA to levels equivalent to those seen at the peak of the cycle (proestrus). In conclusion, although AM expression in the uterus varies throughout the estrous cycle, it is more closely correlated with circulating estradiol levels than with the stage of the cycle itself.

Influence of labor on fetoplacental adrenomedullin concentrations

OBJECTIVE

Circulating adrenomedullin is increased in pregnancy, and placental and fetal membranes participate significantly in its secretion. Recent studies have suggested a potential role for this peptide in the regulation of fetoplacental circulation and placental hormonal secretion. Because adrenomedullin acts also as a uterorelaxant in rats, this study was designed to investigate whether fetoplacental adrenomedullin production changes with human labor, either at term or preterm.

STUDY DESIGN

Eighty pregnant women grouped according to gestational age and presence of labor were studied. Adrenomedullin concentrations in plasma, amniotic fluid, and placental tissue extracts were measured by means of radioimmunoassay and immunohistochemistry. In addition, the ability of amnion and chorion-decidua to secrete adrenomedullin was investigated in vitro.

RESULTS

Adrenomedullin concentrations in amniotic fluid were higher in preterm labor, whereas no differences were found in adrenomedullin expression or concentrations in tissues or in maternal and fetal plasma between vaginal delivery or elective cesarean section, both at term and preterm. During term labor (8 patients), maternal plasma adrenomedullin concentration decreased with advancing cervical dilatation, being 173 pg/mL at the beginning of the active stage of labor and 57 pg/mL at the time of delivery. Adrenomedullin concentration in the medium of amnion- and chorion-decidua-cultured cells was higher after vaginal delivery.

CONCLUSION

These results suggest that a decrease in adrenomedullin production is not involved in the onset of labor in human subjects but rather that it may play a role other than that of a myometrial relaxant in human parturition.

Coordinated Up-regulation by hypoxia of adrenomedullin and one of its putative receptors (RDC-1) in cells of the rat blood-brain barrier

Adrenomedullin (ADM) is a potent hypotensive peptide, which is produced during sepsis and ischemia. We demonstrate here that hypoxia induced a time-dependent increase of both ADM mRNA and protein expressions in cultured astrocytes and endothelial cells from rat brain microvessels. Gene reporter analyses showed a 2-fold increase in ADM gene transcription which was suppressed when the ADM promoter was deleted of its hypoxia responsive element. Hypoxia increased 7-fold the stability of pre-formed ADM mRNAs. Rat brain microvessels expressed mRNAs coding for the different putative ADM receptors but they did not respond to exogenous ADM and calcitonin gene-related peptide by the formation of cAMP. In contrast, ADM and calcitonin gene-related peptide increased the formation of cAMP in astrocytes and their actions were potentiated about 2-fold after hypoxia. Messenger RNA species coding for three putative ADM receptors (the L1 orphan receptor, RDC-1, and calcitonin receptor-like receptor) and accessory proteins (receptor-activity modifying proteins) were present in astrocytes. Hypoxia selectively up-regulated expression of RDC-1 receptor mRNAs. The results indicate that ADM and RDC-1 are hypoxia-sensitive genes and that RDC-1 receptors may mediate some actions of ADM in hypoxic astrocytes.

Adrenomedullin inhibits spontaneous and bradykinin-induced but not oxytocin- or prostaglandin F(2alpha)-induced periodic contraction of rat uterus

In isolated rat uterine strips, adrenomedullin (AM) inhibited the spontaneous periodic contraction in a concentration-dependent manner (IC(50)=22.3+/-0.7 nM). The inhibitory effect of AM was prevented by either AM(22-52), a putative antagonist for AM receptors, or calcitonin gene-related peptide (CGRP)(8-37), a putative antagonist for CGRP receptors. AM also attenuated bradykinin (BK)-induced periodic uterine contraction, which was blocked by AM(22-52) or CGRP(8-37), whereas AM had no effect on the periodic contraction caused by oxytocin or prostaglandin F(2alpha) (PGF(2alpha)). RT-PCR analysis showed that mRNAs for calcitonin receptor-like receptor (CRLR), receptor-activity-modifying protein (RAMP)1, RAMP2 and RAMP3 were expressed in the rat uterus. These results demonstrate that AM selectively inhibits spontaneous and BK-induced periodic contraction via activating receptors for AM and CGRP.

Adrenomedullin, a multifunctional regulatory peptide

Since the discovery of adrenomedullin in 1993 several hundred papers have been published regarding the regulation of its secretion and the multiplicity of its actions. It has been shown to be an almost ubiquitous peptide, with the number of tissues and cell types synthesizing adrenomedullin far exceeding those that do not. In Section II of this paper we give a comprehensive review both of tissues and cell lines secreting adrenomedullin and of the mechanisms regulating gene expression. The data on circulating adrenomedullin, obtained with the various assays available, are also reviewed, and the disease states in which plasma adrenomedullin is elevated are listed. In Section III the pharmacology and biochemistry of adrenomedullin binding sites, both specific sites and calcitonin gene-related peptide (CGRP) receptors, are discussed. In particular, the putative adrenomedullin receptor clones and signal transduction pathways are described. In Section IV the various actions of adrenomedullin are discussed: its actions on cellular growth, the cardiovascular system, the central nervous system, and the endocrine system are all considered. Finally, in Section V, we consider some unresolved issues and propose future areas for research.

Characterization and distribution of prolactin releasing peptide (PrRP) binding sites in the rat--evidence for a novel binding site subtype in cardiac and skeletal muscle

Prolactin releasing peptide (PrRP) was recently purified from bovine hypothalamus and binds to the orphan receptor, UHR-1. We examined the distribution and kinetics of (125)I-PrRP binding in rat tissues together with molecular characterization by chemical cross-linking and Northern blotting. In this study (125)I-PrRP binding showed specificity and rapid association and dissociation. Specific binding was found in membranes from rat tissues including brain (hypothalamus, medulla oblongata and cerebellum), pituitary, heart, soleus muscle, adipose tissue, kidney, adrenal gland, testis and small intestine. In hypothalamus, pituitary, heart and soleus competition analysis indicated only one class of binding site in each tissue. Binding affinity for PrRP (IC(50)) and binding site density (B(max)) respectively were 5.2+/-0.9 nM and 674+/-97 fmol mg protein(-1) in hypothalamus (n = 5), 1.4+/-0.6 nM and 541+/-126 fmol mg protein(-1) in pituitary (n = 3), 6.6+/-0.7 nM and 628+/-74 fmol mg protein(-1) in heart (n = 4) and 9.8+/-0.9 nM and 677+/-121 fmol mg protein(-1) in soleus muscle (n = 4). Analysis of (125)I-PrRP-binding site complexes by chemical cross-linking showed a binding site M(r) of 69,000 in hypothalamus and 41,000 in heart and soleus. Northern analysis of polyA(+) RNA from hypothalamus showed a 4.2 kb band as expected for UHR-1, but heart and soleus showed a 4.8 kb band. Taken together these results indicate that there may be different subtypes of PrRP binding sites in rat tissues which may differ from UHR-1.

Ethanol injury triggers activation of adrenomedullin and its receptor genes in gastric mucosa

Adrenomedullin (AM) is a potent vasodilatory peptide, which is present in the stomach. However, its precise function in the gastric mucosa is unknown. The expression and localization of AM and its receptor in gastric mucosa injured by ethanol also have not been explored, forming the basis for this study. Gastric samples of rats were obtained at 0 and 8 hr and 1, 2, and 4 days after intragastric administration of 100% ethanol. By RT-PCR, AM mRNA expression in gastric mucosa at 8 and 24 hr following ethanol injury was increased by 2-fold and by 2.5-fold (both P<0.01), respectively, and returned to normal at two days. AM receptor mRNA expression was increased by 2.7-fold, 2.3-fold, and 2.4-fold at 8, 24, and 48 hr, respectively (all P<0.01), and returned to normal at four days. By in situ hybridization, AM and AM receptor mRNAs were present in normal gastric mucosa and up-regulated in gastric mucosa following ethanol injury. The immunohistochemical signal for AM was significantly increased in the mucosa bordering erosion sites. We conclude that ethanol injury up-regulates the expression of both AM and AM receptor in gastric mucosa.

Adrenomedullin attenuates the hypertension in hypertensive pregnant rats induced by N(G)-nitro-L-arginine methyl ester

We examined the effect of adrenomedullin on the cardiovascular system of an animal model for preeclampsia. An inhibitor of nitric oxide synthase, N(G)-nitro-L-arginine methyl ester (L-NAME), was infused subcutaneously into rats at a constant rate from day 14 of pregnancy to make an animal model for preeclampsia. Adrenomedullin was continuously infused intravenously at a dose of 3 or 10 pmol/h from day 17 of pregnancy. The basal systolic blood pressure was significantly higher in the L-NAME treated rats than in the control rats. The adrenomedullin administration at day 19 of pregnancy showed a significant decrease in the blood pressure in the L-NAME treated rats than in vehicle rats during infusion. The blood pressure of normal pregnant rats did not significantly decrease by adrenomedullin infusion. The adrenomedullin decreased pup mortality of the L-NAME treated rats. Adrenomedullin attenuated the L-NAME induced hypertension and pup mortality. On the other hand, adrenomedullin administration in both pregnant rats in early gestation (5-11 days of pregnancy) and in non-pregnant rats did not show any significant effect on L-NAME-induced hypertension. The adrenomedullin mRNA level was predominantly expressed at high levels in the ovary, uterus and placenta, but at low levels in other tissues in pregnant rats in late gestation. The adrenomedullin mRNA level of the L-NAME treated rats in placenta decreased more than in the normal pregnant rats in late gestation (P < 0.05). These findings suggest that the adrenomedullin might play an important role in the regulation of the cardiovascular system of the mother and fetoplacental unit in rats.

Characterization of receptors for calcitonin gene-related peptide and adrenomedullin on the guinea-pig vas deferens

1. The receptors which mediate the effects of calcitonin gene-related peptide (CGRP), amylin and adrenomedullin on the guinea-pig vas deferens have been investigated. 2. All three peptides cause concentration dependant inhibitions of the electrically stimulated twitch response (pD2s for CGRP, amylin and adrenomedullin of 7.90+/-0.11, 7.70+/-0.19 and 7.25+/-0.10 respectively). 3. CGRP8-37 (1 microM) and AC187 (10 microM) showed little antagonist activity against adrenomedullin. 4. Adrenomedullin22-52 by itself inhibited the electrically stimulated contractions of the vas deferens and also antagonized the responses to CGRP, amylin and adrenomedullin. 5. [125I]-adrenomedullin labelled a single population of binding sites in vas deferens membranes with a pIC50 of 8.91 and a capacity of 643 fmol mg(-1). Its selectivity profile was adrenomedullin> AC187>CGRP=amylin. It was clearly distinct from a site labelled by [125I]-CGRP (pIC50=8.73, capacity=114 fmol mg(-1), selectivity CGRP>amylin=AC187>adrenomedullin). [125I]-amylin bound to two sites with a total capacity of 882 fmol mg(-1). 6. Although CGRP has been shown to act at a CGRP2 receptor on the vas deferens with low sensitivity to CGRP8-37, this antagonist displaced [125I]-CGRP with high affinity from vas deferens membranes. This affinity was unaltered by increasing the temperature from 4 degrees C to 25 degrees C, suggesting the anomalous behaviour of CGRP8-37 is not due to temperature differences between binding and functional assays.

New peptides, hormones and parturition

This brief review emphasizes the importance of three novel discovered factors produced by fetal membranes, placenta and/or by the fetus itself in regulating uterine contractility. We have shown that, as reported for other hormones and substances, nitric oxide and endothelin may influence myometrial activity in an autocrine/paracrine manner interacting with other well-known agents such as prostaglandins, oxytocin and hormones. We also demonstrated that different isoforms of nitric oxide synthase (NOS) may play different roles throughout gestation and during labor. We have suggested that another peptide produced by trophoblast cells, adrenomedullin, may affect, directly or indirectly, myometrial contractility during pregnancy, although much remains to be learned about the mechanisms controlling adrenomedullin expression by the feto-placental tissues cells during pregnancy. Continued research is necessary to better define the complex interactions that result in parturition, both at term and preterm, and to allow a more rational approach to management of the premature labor, exploring new possible pharmacological solutions.

Adrenomedullin, a new vasoactive peptide, is increased in preeclampsia

Adrenomedullin is a novel peptide that elicits a long-lasting vasorelaxant activity. Recently, we found high concentrations of adrenomedullin in maternal and umbilical cord plasma and in amniotic fluid in full-term human pregnancy, indicating a role of this peptide during gestation. To investigate the possibility that adrenomedullin is involved in the pathophysiology of preeclampsia, we measured its concentration in maternal and fetoplacental compartments. We studied 12 normotensive nonpregnant women, 13 hypertensive nonpregnant subjects, 29 patients with preeclampsia, and 30 normotensive pregnant women. In all patients, plasma was collected from the cubital vein, and amniotic fluid samples were obtained by transabdominal amniocentesis or at elective cesarean section. Plasma samples from umbilical vein and placental tissues were collected at delivery. Adrenomedullin was assayed on plasma and amniotic fluid samples using a specific radioimmunoassay, and its localization and distribution on placental sections was determined by immunohistochemistry. Adrenomedullin concentrations were higher in hypertensive than in normotensive nonpregnant patients. Pregnant women had higher adrenomedullin levels than nonpregnant subjects, although maternal plasma adrenomedullin concentrations did not differ between normal pregnant and preeclamptic women. Preeclamptic patients showed higher concentrations (P<0.01) than normotensive pregnant women of adrenomedullin in amniotic fluid (252+/-29 versus 112+/-10 fmol/ micromol creatinine) and umbilical vein plasma (18.1+/-2.1 versus 8. 5+/-1.1 fmol/mL). Increased local production of adrenomedullin is associated with preeclampsia. The fetus seems to be responsible for the higher levels of this hormone. Increased adrenomedullin concentrations may be necessary to maintain placental vascular resistance and/or fetal circulation at a physiological level.

Immunoreactive adrenomedullin in human fetoplacental tissues

OBJECTIVE

Adrenomedullin is increased in maternal plasma in pregnancy and has been found in very high concentrations in amniotic fluid and umbilical plasma. To identify adrenomedullin-producing tissue in pregnancy we measured adrenomedullin concentration and distribution in fetoplacental tissues.

STUDY DESIGN

By use of a specific radioimmunoassay we determined the concentrations of adrenomedullin and, by immunohistochemical studies, its localization and distribution in fetal membranes and placentas collected at elective cesarean section from 11 healthy pregnant women at term.

RESULTS

The content of adrenomedullin in placentas (117.7 +/- 7.8 pg/mg wet tissue) and fetal membranes (168.7 +/- 2.3 pg/mg wet tissue) was similar to the adrenomedullin concentration in adrenal medulla (157.3 +/- 4.4 pg/mg wet tissue). Adrenomedullin staining appears to be greater in fetal membranes than in placentas and was localized in amnion and trophoblast cells. In term placentas positive staining was detected predominantly in extravillous trophoblast cells, although a few syncytiotrophoblast cells and endothelial cells of primary villi stained for adrenomedullin.

CONCLUSION

This study provides evidence that is consistent with fetoplacental tissues as a site of synthesis or action of adrenomedullin during pregnancy.