Proadrenomedullin NH(2)-terminal 20 peptide (PAMP) and adrenomedullin bind to teratocarcinoma cells

Cancer protection elicited by a single nucleotide polymorphism close to the adrenomedullin gene

CONTEXT

The risk of developing cancer is regulated by genetic variants, including polymorphisms. Characterizing such variants may help in developing protocols for personalized medicine.

OBJECTIVE

Adrenomedullin is a regulatory peptide involved in cancer promotion and progression. Carriers of a single nucleotide polymorphism (SNP) in the proximity of the adrenomedullin gene have lower levels of circulating peptide. The aim of the present work was to investigate whether carriers of this SNP (rs4910118) are protected against cancer.

DESIGN

This was a retrospective study. DNA samples were obtained from the Carlos III DNA National Bank (University of Salamanca, Salamanca, Spain).

SETTING

Samples represent a variety of donors and patients from Spain.

PATIENTS OR OTHER PARTICIPANTS

DNA from patients with breast cancer (n = 238), patients with lung cancer (n = 348), patients with cardiac insufficiency (n = 474), and healthy donors of advanced age (n = 500) was used.

INTERVENTIONS

All samples were genotyped using double-mismatch PCR, and confirmation was achieved by direct sequencing.

MAIN OUTCOME MEASURES

The minor allele frequency was calculated in all groups. The Pearson χ(2) was used to compare SNP frequencies.

RESULTS

Of 1560 samples, 14 had the minor allele, with a minor allele frequency in healthy donors of 0.90%. Patients with cancer had a statistically significantly lower frequency than healthy donors (odds ratio = 0.216, 95% confidence interval = 0.048-0.967, P = .028).

CONCLUSIONS

Carriers of the minor allele have a 4.6-fold lower risk of developing cancer than homozygotes for the major allele. Knowledge of the rs4910118 genotype may be useful for stratifying patients in clinical trials and for designing prevention strategies.

Chronic administration of adrenomedullin attenuates hypoxic pulmonary vascular structural remodeling and inhibits proadrenomedullin N-terminal 20-peptide production in rats

Adrenomedullin (ADM) is a novel cardiovascular-active peptide involved in vasodilation, reducing blood pressure and inhibiting vascular smooth muscle cell migration and proliferation. Previous research showed that ADM might be involved in the development of pulmonary hypertension. In this study, we investigated the effect of ADM subcutaneously administered by mini-osmotic pump (300 ng/h) on pulmonary hemodynamics and pulmonary vascular structure in hypoxic rats, as well as the influence of ADM on the proadrenomedullin N-terminal 20-peptide (PAMP) protein and mRNA expressions and its plasma concentrations. The results showed that ADM obviously decreased mean pulmonary artery pressure and the ratio of right ventricular mass to left ventricular plus septal mass in hypoxic rats. Chronic infusion of ADM lessened the muscularization of small pulmonary vessels, attenuated relative medial thickness and relative medial area of pulmonary arteries, and alleviated the ultrastructural changes in pulmonary arteries of hypoxic rats. ADM inhibited the proliferation of pulmonary artery smooth muscle cells, represented by a decrease in the expression of proliferative cell nuclear antigen (PCNA) in the pulmonary artery. Meanwhile, plasma PAMP concentration and the expression of PAMP protein and mRNA by pulmonary arteries in rats of hypoxia with ADM group were markedly decreased compared with those in hypoxic group. The results suggest that ADM ameliorated the development of hypoxic pulmonary vascular structural remodeling. Intramolecular regulation of ADM may play an important role in the regulation of hypoxic pulmonary hypertension by ADM.

Adrenomedullin: a new target for the design of small molecule modulators with promising pharmacological activities

Adrenomedullin (AM) is a 52-amino acid peptide with a pluripotential activity. AM is expressed in many tissues throughout the body, and plays a critical role in several diseases such as cancer, diabetes, cardiovascular and renal disorders, among others. While AM is a protective agent against cardiovascular disorders, it behaves as a stimulating factor in other pathologies such as cancer and diabetes. Therefore, AM is a new and promising target for the development of molecules which, through their ability to regulate AM levels, could be used in the treatment of these pathologies.

Effect of adrenomedullin and proadrenomedullin N-terminal 20 peptide on sugar transport in the rat intestine

Previous studies have shown immunostaining of adrenomedullin (AM) and proadrenomedullin N-terminal 20 peptide (PAMP) throughout the gastrointestinal tract. Based on these data, we decided to investigate the effect of these peptides on intestinal sugar absorption using everted rings from Wistar rat intestine. PAMP increases alpha-methylglucoside (MG) uptake at concentrations ranging from 10(-12) to 10(-7) M. AM shows a dual effect inhibiting sugar absorption at low concentrations (10(-12) to 10(-11) M) and increasing MG uptake at higher concentrations (10(-8) to 10(-6) M). In all cases, the effect is phloridzin-sensitive, indicating that the peptides alter SGLT1 function without modifying the non-mediated component of absorption. The enhancing effect of 10(-8) M AM and PAMP seems to be mediated by elevation of cAMP and is accompanied by an increase on SGLT1 expression in the brush-border membrane of the enterocytes. The inhibitory effect of 10(-12) M AM could be mediated by either cAMP reduction or, more probably, by other second messenger able to inhibit sugar absorption. PKC is not involved in the action of either AM or PAMP. These results demonstrate that both peptides play a role in the regulation of the active transport of sugars in the intestine.

Cell and molecular biology of the multifunctional peptide, adrenomedullin

Adrenomedullin (AM) is a recently discovered regulatory peptide involved in many functions including vasodilatation, electrolyte balance, neurotransmission, growth, and hormone secretion regulation, among others. This 52-amino acid peptide is expressed by specific cell types in many organs throughout the body. A complex receptor system has been described for AM; it requires at least the presence of a seven-transmembrane-domain G-protein-coupled receptor, a single-transmembrane-domain receptor activity modifying protein, and a receptor component protein needed to establish the connection with the downstream signal transduction pathway, which usually involves cyclicAMP. In addition, a serum-binding protein regulates the biological actions of AM, frequently by increasing AM functional attributes. Changes in levels of circulating AM correlate with several critical diseases, including cardiovascular and renal disorders, sepsis, cancer, and diabetes. Whether AM is a causal agent, a protective reaction, or just a marker for these diseases is currently under investigation. New technologies seeking to elevate and/or reduce AM levels are being investigated as potential therapeutic avenues.

Adrenomedullin and cancer

Adrenomedullin (AM) is a pluripotent hormone with structural similarities to calcitonin gene-related peptide (CGRP), which is expressed by many tissues in the body and shows a remarkable range of effects mediated by paracrine/autocrine and possibly endocrine mechanisms. AM has been implicated as a mediator of several pathologies such as cardiovascular and renal disorders, sepsis, inflammation, diabetes and cancer, among others. AM is expressed in a variety of tumors where it aggravates several of the molecular and physiological features of malignant cells. AM has been shown to be a mitogenic factor stimulating growth in several cancer types and to encourage a more aggressive tumor phenotype. In addition, AM is an apoptosis survival factor for cancer cells and an indirect suppressor of the immune response through its binding protein, complement factor H, and regulation in expression of cytokines. AM plays an important role in environments subjected to low oxygen tensions, which is a typical feature in the proximity of solid tumors. Under these conditions, AM is upregulated through a hypoxia-inducible factor 1 (HIF-1)-dependent pathway and acts as a potent angiogenic factor promoting neovascularization. The collective findings brought together over the last years place AM as a major regulator of carcinogenesis-tumor progression and identifies its autocrine loop as a putative target for developing new strategies against human cancers.

Roles of different peptide fragments derived from proadrenomedullin in the regulation of vascular tone in isolated rat aorta

The effects of proadrenomedullin N-terminal 20 peptide (PAMP) and adrenotensin (ADT) on adrenomedullin (ADM)-induced vasodilation were investigated in aortic rings from rat. ADM (10(-9) to 10(-7)M) relaxed the aorta preconstricted with phenylephrine in a concentration-dependent manner. Denudation of endothelium or pretreatment with nitric oxide synthase (NOS) inhibitor, L-NAME, attenuated the vasodilatory action of ADM. ADM-induced vasorelaxation in the aortic rings with endothelium was converted to contraction by PAMP, but not by ADT. The ADM-induced vasodilation was not affected by PAMP in aorta rings without endothelium or in intact aortic rings pretreated with L-NAME. ADM-stimulated nitrite production and NOS activity of the aortas, which was inhibited by PAMP, ADT or PAMP plus ADT. ADM, PAMP, and ADT increased the cyclic adenosine monophosphate (cAMP) contents in vascular tissue. The combination of ADM with PAMP or ADT caused a smaller increase in cAMP level as compared with that of PAMP or ADT alone. These results show that ADM-induced endothelium-dependent vasodilation could be converted to vasoconstriction in the presence of PAMP, probably through a NO-dependent pathway. There was no indication that cAMP was involved in the converting effect of PAMP on ADM vasodilator action.

Regulation of cell growth and apoptosis by adrenomedullin

Adrenomedullin, originally discovered in human pheochromocytoma, has been shown to have potent vasodilatory activity. However, like other vasoactive peptide hormones, its physiological roles have been found to extend far beyond the regulation of vascular tonus, and to include such functions as the regulation of cell proliferation and differentiation. There is a growing body of evidence that adrenomedullin exerts a wide range of effects on cell growth and apoptotic death, and that these effects are dependent on cell type and experimental conditions. Signaling pathways independent of cyclic AMP, such as protein tyrosine kinase(s) and mitogen-activated protein kinases, may play key roles in the regulation of mitogenesis and apoptosis by adrenomedullin.

Coexpression of calcitonin receptor-like receptor and receptor activity-modifying protein 2 or 3 mediates the antimigratory effect of adrenomedullin

Three isoforms of the receptor activity-modifying protein (RAMP) are thought to transport the calcitonin receptor-like receptor (CRLR) to the plasma membrane to function as calcitonin gene-related peptide or adrenomedullin receptors, but their role remains largely unknown. We investigated whether coexpression of RAMP and CRLR are involved in the regulation of cell migration using a monolayer-wounding protocol. Quantification of gene transcripts revealed expression of all RAMP isoforms and CRLR in cultured rat vascular smooth muscle cells (VSMCs), RAMP2 and RAMP3 in rat endothelial cells, and RAMP1 in rat fibroblasts. CRLR expression was minimal in endothelial cells and fibroblasts. Adrenomedullin potently suppressed the migration of VSMCs, whereas calcitonin gene-related peptide did not suppress migration in any cell type. The antimigratory effect of adrenomedullin on VSMCs was potentiated by transfecting CRLR cDNA. Cotransfection of RAMP2 or RAMP3 with CRLR into VSMCs resulted in a slower migratory rate, and this effect was enhanced by adrenomedullin. Migration of fibroblasts was also suppressed after cotransfection of RAMP2 or RAMP3 with CRLR. cAMP agonists had no effect on VSMC migration, and a cAMP antagonist failed to abrogate the antimigratory effect of adrenomedullin. Thus, coexpression of CRLR and RAMP2 or RAMP3 mediates the inhibitory effect of adrenomedullin on cell migration, independent of cAMP-dependent signaling pathways.

Overexpression of adrenomedullin gene markedly inhibits proliferation of PC3 prostate cancer cells in vitro and in vivo

The expression of the gene encoding adrenomedullin (AM), a multifunctional peptide hormone, in the prostate is localized to the epithelial cells. Prostate cancer cells are derived from prostatic epithelial cells. To elucidate the potential role of the AM gene in prostate cancer progression, we have stably-transfected the PC3 human prostate cancer cell line with an AM gene expression vector. The AM-transfected PC3 sublines were studied along with parental and empty vector transfected PC3 cells as controls. The average level of AM in the conditioned media of AM-transfected cells was 0.959+/-0.113 nM, a physiologically relevant concentration. The ectopic expression of AM gene inhibited the proliferation of PC3 cells in culture dishes. In addition, anchorage-independent growth of the transfected sublines was virtually abolished in soft agar assays. Flow cytometry studies showed that overexpression of AM gene caused a very significant G(1)/G(0) cell cycle arrest. In vivo experiments demonstrated that AM gene expression markedly inhibited the growth of xenograft tumors in nude mice. Our in vivo and in vitro studies suggest that AM could strongly suppress the malignancy of prostate cancer cells, via autocrine and/or paracrine mechanisms.

Effects of different peptide fragments derived from proadrenomedullin on gene expression of adrenomedullin gene

Primary culture of vascular smooth muscle cells (VSMC) from rat aorta was used for the study of the effect of different peptides derived from proadrenomedullin on the expression of adrenomedullin (ADM) gene. ADM and preproADM(22-41) (PAMP) secreted by VSMC were measured by radioimmunoassay, and ADM mRNA in VSMC was determined by quantitative RT-PCR. After the incubation of VSMC in 10(-7)M ADM for 24h, PAMP in the medium and ADM mRNA in the VSMC were decreased by 34 and 41.3%, respectively, and cAMP concentration in the VSMC was increased by 385%. After the incubation of VSMC in 10(-7)M PAMP for 24h, ADM in the medium and ADM mRNA in the VSMC were decreased by 12.2 and 39.1%, respectively, and cAMP concentration in the VSMC was increased by 67%. The decreased ADM mRNA in VSMC induced by the ADM and PAMP treatment was completely reversed by the pre-treatment of the cells in 10(-7)M protein kinase inhibitor for 30 min. After the incubation of VSMC in 10(-7)M preproADM(153-185) (ADT) for 24h, however, ADM in the medium and ADM mRNA in the VSMC were increased by 21 and 35.2%. The increased ADM mRNA in VSMC induced by the ADT treatment was partially blocked by the co-incubation in ADM and ADT, and was totally blocked by the co-incubation in PAMP+ADM and ADT, but was not blocked by the co-incubation in PAMP and ADT. Our results suggest that the four peptides derived from proadrenomedullin may have different effects, possibly through a cAMP-dependent pathway, on the expression of ADM gene.

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.

Proadrenomedullin-derived peptides in the paracrine control of the hypothalamo-pituitary-adrenal axis

Adrenomedullin (ADM) and proadrenomedullin N-terminal 20 peptide (PAMP) are widely distributed in various body tissues and organs, including the hypothalamo-pituitary-adrenal (HPA) axis. ADM and PAMP inhibit in vitro release of ACTH from pituitary corticotropes, and findings suggest that this effect may become relevant when an exceedingly high ACTH secretion must be counteracted. ADM directly supresses angiotensin-II- and K+-stimulated aldosterone secretion from ZG cells, acting through calcitonin gene-related peptide (CGRP) type 1 ADM(22-52)-sensitive receptors, the activation of which is likely to impair Ca2+ influx. In contrast, ADM stimulates medullary chromaffin cells to release catecholamines, which in turn enhance aldosterone secretion acting in a paracrine manner. Also this effect of ADM occurs via CGRP1 receptors, which are coupled with the adenylate cyclase-dependent cascade. There is indication that in vivo these two opposite effects of ADM on ZG may interact with each other when normal aldosterone secretion has to be restored. ADM exerts a mitogenic effect on rat ZG, acting via CGRP1 receptors that activate the tyrosine kinase-dependent mitogen-activated protein kinase cascade. These findings, along with the demonstration of a high level of ADM gene expression in adrenocortical adenomas and carcinomas, may suggest a role for ADM as adrenocortical growth stimulator and tumor promoter. PAMP, like ADM, suppresses aldosterone response of ZG cells to Ca2+-dependent agonists, but, in contrast with ADM, it inhibits catecholamine release by adrenal medulla. Both effects of PAMP are mediated by PAMP(12-20)-sensitive receptors, whose signaling mechanism is likely to involve the blockade of voltage-gated Ca2+ channels. The concentrations attained by ADM and PAMP in the blood rule out the possibility that they act as true circulating hormones. Conversely, their content in the hypothalamo-pituitary complex and adrenal gland is consistent with a paracrine mechanism of action, which may play an important role in pathophysiological conditions where the function of the HPA axis has to be reset.

Action sites of adrenomedullin in the rat brain: functional mapping by Fos expression

The effects of intracerebroventricular (icv) administration of adrenomedullin (AM) and proadrenomedullin NH2-terminal 20 peptide (PAMP) on the expression of Fos in the central nervous system (CNS) were examined in conscious rats, using immunohistochemistry. Fos-like immunoreactivity (LI) was detected in various brain areas of the rats, including the supraoptic nucleus, the paraventricular nucleus, the locus coeruleus, the area postrema and the nucleus of the tractus solitarius 90 min after icv administration of AM. Few cells with Fos-LI were found in the CNS 90 min after icv administration of saline. Fos-LI was also detected in the various hypothalamic areas after icv administration of PAMP. These results suggest that centrally administered AM and PAMP may cause physiological responses through the activation of a neural network in the hypothalamus and the brainstem.

Proadrenomedullin N-terminal 20 peptide (PAMP) enhances proliferation of rat zona glomerulosa cells by activating MAPK cascade

The effect of proadrenomedullin N-terminal 20 peptide (PAMP) on the proliferative activity of rat zona glomerulosa (ZG) cells has been investigated. Dispersed rat ZG cells were cultured in vitro for 24 h and then exposed to PAMP for an additional 24 h, and the proliferation rate was assessed by the 5-bromo-2'-deoxyuridine (BrdU) incorporation technique. PAMP dose-dependently increased the percentage of BrdU-positive cells, with a maximal effective concentration observed at 10(-8) M. The tyrosine kinase (TK) inhibitor, tyrphostin-23, and the p42/p44 MAPK inhibitor, PD-98059, abolished the proliferogenic effect of PAMP, while the protein kinase (PK) A inhibitor, H-89, and the PKC inhibitor, calphostin-C, were ineffective in blocking the response to PAMP. PAMP (10(-8) M) enhanced TK and MAPK activity of dispersed rat ZG cells. The stimulatory action of PAMP on TK activity was annulled by tyrphostin-23, while that on MAPK activity was abolished by either tyrphostin-23 or PD-98059. Taken together, these data indicate that PAMP enhances proliferation of cultured rat ZG cells, through the TK-dependent activation of p42/p44 MAPK cascade.

Novel actions of proadrenomedullin N-terminal 20 peptide (PAMP)

Poadrenomedullin N-terminal 20 peptide (PAMP) is a hypotensive peptide derived from the precursor of adrenomedullin. We identified novel actions of proadrenomedullin N-terminal 20 peptide (PAMP) on blood glucose, food intake and gastric emptying after exogenous administration. PAMP elevated blood glucose levels after central injection in fasted mice. PAMP had affinity for bombesin (BN) receptor and the hyperglycemic effect of PAMP was blocked by a BN antagonist, indicating that the elevation of blood glucose after central administration of PAMP was mediated by BN receptor. Centrally administered PAMP inhibited food intake and gastric emptying in fasted conscious mice. However, studies using a BN antagonist and BN receptor knockout mice suggested that the inhibitory effects of PAMP on feeding and gastric emptying were mediated not via BN receptor but via another receptor specific for PAMP. In the present review, we summarize these effects of PAMP and report other novel actions of PAMP on body temperature and oxygen consumption. In addition, the mechanism underlying the cardiovascular functions of PAMP is discussed.

Cancer and diabetes: two pathological conditions in which adrenomedullin may be involved

Adrenomedullin (AM) is a regulatory peptide involved in several physiological processes. Among them, AM has been implicated in the regulation of growth, both with mitogenic and antiproliferative activities on normal cells. AM is widely expressed during embryogenesis and may have a significant role in the proliferation and differentiation processes associated with development. AM is also expressed by cancer cell lines and tumors and has been implicated in the growth of malignant cells. Some additional activities associated with AM (antiapoptotic capabilities, angiogenic potential, and upregulation in hypoxic conditions), together with its wide distribution in cancer, suggest that AM may be an important factor in carcinogenesis. Besides its implication in growth, embryogenesis and tumor biology, AM is also involved in pancreatic regulation and diabetes. AM regulates insulin secretion and is overexpressed in the plasma of diabetic patients. Several findings indicate that AM may participate in the pathogenesis and/or clinical complications of this disease.

Proadrenomedullin N-terminal 20 peptide (PAMP) inhibits food intake and gastric emptying in mice

We found that proadrenomedullin N-terminal 20 peptide (PAMP) decreased dose-dependently (3-30 nmol/mouse) food intake after intra-third cerebroventricular administration in fasted ddY mice. Gastric emptying also was delayed after central injection of PAMP. In our previous study, PAMP was demonstrated to elicit hyperglycemia via bombesin (BN) receptor. Then, we examined whether the effects of PAMP on feeding and gastric emptying were induced through BN receptor. Surprisingly, PAMP-induced reductions in feeding and gastric emptying rate were not blocked by a BN antagonist, [D-Phe(6), Leu-NHEt(13), des-Met(14)]-BN (6-14). PAMP suppressed feeding in mice lacking gastrin-releasing peptide receptor or BN receptor subtype-3. These results indicate that centrally administered PAMP inhibits food intake, involving the delayed gastric emptying, not through BN receptors but through selective PAMP receptor.