An accelerated increase of plasma adrenomedullin in acute asthma

Adrenomedullin as a Protein with Multifunctional Behavior and Effects in Various Organs and Tissues

In literature, it has been reported that adrenomedullin, which is generally thought to have vasodilator, natriuretic and diuretic effects, is synthesized in almost all body, especially CNS, vascular muscles and endothelium, heart, liver, lung, kidney, gastric mocosa, intestinal endothelium and various blood cells. It has been found that the possible effects of adrenomedullin can be demonstrated directly or indirectly by means of active mediators, neuropeptides, enzymes and hormones. It is also suggested that it regulates the endocrine system by affecting the hypothalamic-pituitary axis. It increases in heart failure, acute coronary syndromes, hypertensive conditions, cerebrovascular accessory, chronic renal failure and periodontitis and decreases in peptic ulcer and intestinal diseases. However, it is still not clear whether increase/decrease in adrenomedullin level is a cause of a disease or is a result of damage due to an illness. This peptide, which could be thought to multifunctional, should be considered as a molecule with genetic coding that may have different effects on different tissues and conditions. For all these reasons, we aimed to review the multifonctional behavior of adrenomedullin in the light of the current literature to pioneer new hypotheses and discuss possible mechanisms.

Adrenomedullin mediates pro-angiogenic and pro-inflammatory cytokines in asthma and COPD

PURPOSE

Adrenomedullin (AM) is a pluripotent peptide hormone with contradictory effects in human health and disease. In chronic inflammatory lung diseases, such as asthma and COPD, AM has been shown to inhibit inflammation and cell proliferation. In the present study, we aimed to investigate the effect of AM on pro-angiogenic and pro-inflammatory cytokines in asthma and COPD.

PATIENTS AND METHODS

Serum levels of pro-AM were measured in patients with asthma, COPD and matched controls. The effect of AM on intracellular signaling proteins and cytokine secretion was assessed in primary cultures of epithelial cells (EC) and airway smooth muscle cells (ASMC) established from endo-bronchial biopsies of patients with asthma, COPD and controls.

RESULTS

Serum pro-AM was higher in patients with asthma and COPD, compared to controls. AM stimulated cAMP in ASMC but not in EC. In EC, AM decreased Erk1/2 MAPK expression and activation but in ASMC, AM activated Erk1/2. This effect was similar in asthma, COPD and controls. AM stimulated the secretion of pro-angiogenic CXCL1 by EC of controls and CXCL5 by EC of asthma patients. AM did not affect the secretion of IL-6 or IL-8 by EC but stimulated the secretion of IL-6 by ASMC. In EC, AM inhibited the stimulatory effect of TGF-β and IL-4 on the secretion of IL-6 and IL-8 but had an additive stimulatory effect with TGF-β in ASMC.

CONCLUSIONS

These data suggest that AM mediates the secretion of pro-angiogenic and pro-inflammatory cytokines in a cell-type and/or a disease-specific way, explaining its association with clinical outcomes in COPD.

Stable-State Midrange-Proadrenomedullin Level Is a Strong Predictor of Mortality in Patients With COPD

BACKGROUND

Midrange-proadrenomedullin (MR-proADM) has been shown to be elevated in patients hospitalized for an acute exacerbation of COPD (AECOPD) and in patients with community-acquired pneumonia. When measured during AECOPDs, MR-proADM has also been shown to be a predictor of mortality. We hypothesized that MR-proADM levels measured in a stable state could also predict mortality.

METHODS

We included 181 patients in whom we had paired plasma samples for MR-proADM determinations during a stable state and at hospitalization for an AECOPD when they also produced sputum. Time to death or censoring was compared between patients with MR-proADM above or below the median of 0.71 nmol/L. The predictive value of MR-proADM for survival was determined by calculating the C statistic.

RESULTS

Patients with COPD and MR-proADM levels > 0.71 nmol/L in the stable state had a threefold-higher risk of dying than did patients with MR-proADM levels < 0.71 nmol/L (hazard ratio, 2.98 [95% CI, 1.51-5.90]; C statistic, 0.76). The corrected OR for 1-year mortality was 8.90 (95% CI, 1.94-44.6) in patients with high MR-proADM levels measured in the stable state, compared with patients with low levels measured in the stable state.

CONCLUSIONS

MR-proADM measured in the stable state appeared to be a strong predictor of mortality in patients with COPD. MR-proADM is far easier to measure than other predictors of mortality in COPD, such as BMI, airflow obstruction, dyspnea, and exercise capacity score.

Identification of Adrenomedullin in Avian Type II Pneumocytes: Increased Expression after Exposure to Air Pollutants

Adrenomedullin (AM) is a potent vasodilator peptide present in the lung of mammals where it is expressed mainly in the columnar epithelium and alveolar macrophages. AM increases the secretion of phosphatidylcholine by type II pneumocytes, which suggests a role as an autocrine modulator of surfactant secretion. In this study we show the expression of an AM-like protein in the lung of the pigeon, Columba livia. Using an antibody against its human ortholog, AM-like immunoreactivity was found to be associated with membranous structures of the multivesicular bodies of type II pneumocytes. We also studied the differential expression of AM-like peptide in the lung of pigeons exposed to polluted city air vs cleaner countryside conditions and found that AM-like expression was higher in city animals. Similar results were obtained in an experimental study in which pigeons were exposed to increasing concentrations of a single pollutant, ozone. Taken together, our findings support the implication of AM in the response of type II pneumocytes to air pollutants.

Plasma adrenomedullin levels in children with asthma: any relation with atopic dermatitis?

BACKGROUND

Asthma is a chronic, inflammatory disease of the airway, and adrenomedullin (ADM) may have some effects against bronchoconstriction. However, the role(s) of ADM in asthmatic children have not been evaluated yet. The aims of this study were to determine if there are any changes in plasma ADM levels during acute asthma attack, and to search for any association between allergen sensitivity and ADM level in asthmatic children.

METHODS

Twenty-seven children with acute asthma attack, ranging in age from 5 to 15 years were investigated and compared with 20 controls. Plasma ADM levels (ng/mL) were measured by ELISA method.

RESULTS

No significant difference was found in ADM levels between the controls and patients in either the acute attack or remission period. Plasma ADM levels were significantly higher in the acute attack (p=0.043) compared to the remission period in patients who were considered as having a "severe attack" according to GINA (Global Initiative for Asthma) classification. There were statistically significant correlations between the patients' AlaTOP and Food Panel 7 levels and plasma ADM levels in the acute attack period (p=0.010, p=0.001, respectively). The ADM levels in patients with a history of atopic dermatitis were significantly higher in the acute attack period compared to those without a history of atopic dermatitis (p=0.007).

CONCLUSION

We speculate that ADM may have a role in children with atopic dermatitis, and may also have a role in the immuno-inflammatory process of asthma.

The clinical and environmental determinants of airway transcriptional profiles in allergic asthma

RATIONALE

Gene expression profiling of airway epithelial and inflammatory cells can be used to identify genes involved in environmental asthma.

METHODS

Airway epithelia and inflammatory cells were obtained via bronchial brush and bronchoalveolar lavage (BAL) from 39 subjects comprising three phenotypic groups (nonatopic nonasthmatic, atopic nonasthmatic, and atopic asthmatic) 4 hours after instillation of LPS, house dust mite antigen, and saline in three distinct subsegmental bronchi. RNA transcript levels were assessed using whole genome microarrays.

MEASUREMENTS AND MAIN RESULTS

Baseline (saline exposure) differences in gene expression were related to airflow obstruction in epithelial cells (C3, ALOX5AP, CCL18, and others), and to serum IgE (innate immune genes and focal adhesion pathway) and allergic-asthmatic phenotype (complement genes, histone deacetylases, and GATA1 transcription factor) in inflammatory cells. LPS stimulation resulted in pronounced transcriptional response across all subjects in both airway epithelia and BAL cells, with strong association to nuclear factor-κB and IFN-inducible genes as well as signatures of other transcription factors (NRF2, C/EBP, and E2F1) and histone proteins. No distinct transcriptional profile to LPS was observed in the asthma and atopy phenotype. Finally, although no consistent expression changes were observed across all subjects in response to house dust mite antigen stimulation, we observed subtle differences in gene expression (e.g., GATA1 and GATA2) in BAL cells related to the asthma and atopy phenotype.

CONCLUSIONS

Our results indicate that among individuals with allergic asthma, transcriptional changes in airway epithelia and inflammatory cells are influenced by phenotype as well as environmental exposures.

Adrenomedullin Function in Vascular Endothelial Cells: Insights from Genetic Mouse Models

Adrenomedullin is a highly conserved peptide implicated in a variety of physiological processes ranging from pregnancy and embryonic development to tumor progression. This review highlights past and present studies that have contributed to our current appreciation of the important roles adrenomedullin plays in both normal and disease conditions. We provide a particular emphasis on the functions of adrenomedullin in vascular endothelial cells and how experimental approaches in genetic mouse models have helped to drive the field forward.

Genome-wide analysis reveals the active roles of keratinocytes in oral mucosal adaptive immune response

To elucidate the roles of oral keratinocytes in the adaptive immune response of oral mucosa, global gene expression analysis was performed by microarray technique and integrating computational methods, including hierarchical clustering, biological process Gene Ontology analysis, Kyoto Encyclopedia of Genes and Genomes pathway analysis, self-organizing maps (SOMs) and biological association network analysis (BAN). Raw data from microarray experiments were uploaded to the Gene Expression Omnibus Database, http://www.ncbi.nlm.nih.gov/geo/ (GEO accession GSE28035). We identified 666 differentially expressed genes in the early stage (48 h) and 993 in the late stage (96 h) of the oral mucosal adaptive immune response. The analysis revealed that oral keratinocytes exerted diverse biological functions in different stages of immune response. Specifically, in 48 h the differentially expressed genes encompassed an array of biological ontology associated with immune response, such as antigen processing and presentation, and positive regulation of T-cell-mediated cytotoxicity. Several pathways which have been reported to be critical in inflammation, including mitogen-activated protein kinase pathway, were activated. Furthermore, after BAN construction, some putative hub genes and networks such as interleukin-1α and its subnetwork were recognized. Taken together, these results give substantial evidence to support the active roles of keratinocytes in the oral mucosal adaptive immune response.

Adrenomedullin level in the nasal discharge from allergic rhinitis cohort

Adrenomedullin (AM) is a potent hypotensive and vasodilatory peptide. AM may exert protective actions against the development of many diseases by modulating the blood circulation and body fluid balance. In addition to these functions, it has recently been reported to play important roles in the development of allergy and infections. The purpose of the present study was to demonstrate the existence of AM in the human nasal mucosa and to discuss whether AM might contribute to the pathogenesis of nasal congestion. We measured the total AM concentrations in the nasal discharge. The total AM concentration in the nasal discharge was significantly higher in the non-allergy group (72.1 ± 55.5 fmol/ml) than in the allergy group (37.1 ± 44.2 fmol/ml). By immunohistochemical examination, we identified AM-containing cells in the nasal mucosa from both subjects with and without nasal allergy, and also in nasal polyps. Moreover, those cells were positive for anti-tryptase antibody which recognizes mast cells. In nasal allergy, vasodilatation and increase in vascular permeability are characteristic features of the immediate phase response. Reduced AM levels in the nasal discharge may be associated with attenuation of both of these factors. On the other hand, immunohistochemical analysis demonstrated AM-immunoreactive cells in the chronic phase of rhinosinusitis. In the late and inflammatory phase, mast cells produce AM, which possibly acts as an inhibitor of inflammatory cell migration. In conclusion, AM may be actively secreted into the nasal discharge. AM in the nasal discharge may have protective and anti-inflammatory effects in the nasal mucosa.

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.

Lack of adrenomedullin on antigen-induced bronchoconstriction in guinea pigs in vivo

Antigen challenge can provoke acute bronchoconstriction, recognized as immediate asthmatic response (IAR), but the evolving events in this reaction are not well defined. Recently, a novel peptide, designated adrenomedullin, was isolated from human pheochromocytoma, and has been shown to have potent systemic and pulmonary vasodilator activity.The purpose of this study was to elucidate the influence of adrenomedullin in the development of IAR. Passively sensitized guinea pigs were anesthetized and treated with diphenhydramine hydrochloride, and then artificially ventilated. Ovalbumin was inhaled after an intravenous administration of adrenomedullin. Other studies were performed in naive guinea pigs to investigate the airway responses to inhaled methacholine or histamine after an intravenous administration of adrenomedullin. Antigen challenge caused bronchoconstriction in sensitized guinea pigs. Adrenomedullin did not inhibit the antigen-induced bronchoconstriction in sensitized guinea pigs or the dose-dependent responses to inhaled methacholine or histamine in naive animals in spite of its vasodilating effect. We conclude that an intravenous administration of adrenomedullin does not influence antigen-induced bronchoconstriction or bronchial responsiveness to inhaled methacholine or histamine in vivo.

A review of the biological properties and clinical implications of adrenomedullin and proadrenomedullin N-terminal 20 peptide (PAMP), hypotensive and vasodilating peptides

Adrenomedullin (AM), identified from pheochromocytoma and having 52 amino acids, elicits a long-lasting vasodilatation and diuresis. AM is mainly mediated by the intracellular adenylate cyclase coupled with cyclic adenosine monophosphate (cAMP) and nitric oxide (NO) -cyclic guanosine monophosphate (cGMP) pathway through its specific receptor. The calcitonin receptor-like receptor (CLCR) and receptor-activity modifying protein (RAMP) 2 or RAMP3 models have been proposed as the candidate receptor. AM is produced mainly in cardiovascular tissues in response to stimuli such as shear stress and stretch, hormonal factors and cytokines. Recently established AM knockout mice lines revealed that AM is essential for development of vitelline vessels of embryo. Plasma AM levels elevate in cardiovascular diseases such as heart failure, hypertension and septic shock, where AM may play protective roles through its characteristic biological activities. Human AM gene delivery improves hypertension, renal function, cardiac hypertrophy and nephrosclerosis in the hypertensive rats. AM decreases cardiac preload and afterload and improves cardiac contractility and diuresis in patients with heart failure and hypertension. Advances in gene engineering and receptor studies may contribute to further understandings of biological implication and therapeutic availability of AM.

Adrenomedullin and proadrenomedullin N-terminal 20 peptide induce histamine release from rat peritoneal mast cell

Adrenomedullin (ADM)-induced histamine release from rat peritoneal mast cells was investigated. We compared the ability of full-length ADM to induce histamine release to the fragments ADM-(1-25) and ADM-(22-52), as well as proadrenomedullin N-terminal 20 peptide (PAMP). ADM (10(-8) to 10(-5) M) and PAMP (10(-8) to 10(-5) M) dose-dependently increased histamine release from peritoneal mast cell preparations. The effect of ADM-(1-25) was similar to ADM, whereas ADM-(22-52) did not show any effects. These data suggest the relative importance of the ADM C-terminal fragment, which contains a six-membered ring structure. Histamine release, induced by ADM, was significantly and dose-dependently inhibited by the addition of ADM-(22-52) (10(-5) M), Ca(2+) (0.5 to 2.0 mM), and benzalkonium chloride (3 to 7 microM), a selective inhibitor of Gi type G proteins. In contrast, PAMP (10(-5) M)-induced histamine release was not inhibited by Ca(2+). These results suggest that ADM induce histamine release via a putative ADM receptor in a manner sensitive to Gi-protein function and extracellular Ca(2+) concentration, and that PAMP might produce its effect by a different mechanism than ADM.

Plasma adrenomedullin levels in asthmatic patients

Adrenomedullin (ADM) is a newly discovered endogenous vasorelaxing peptide isolated from pheochromocytoma. Some experimental studies suggest that ADM plays a role in asthma. The purposes of the present study were to assess the plasma ADM levels in adults with mild to severe asthma and controls and to correlate those with the findings on lung function test results and other clinical indices. We recruited 16 mild, 10 moderate, and 11 severely asthmatic patients and 12 healthy controls. We measured the plasma concentrations of ADM in patients with asthma and in healthy subjects using RIA. We assessed FEV1, FEV1 predicted %, FEV1/FVC, symptom score, IgE, ECP, and morning and evening peak expiratory flow measurements. There was no significant difference between the asthmatic and the control group ADM levels, which were 26.3 +/- 24.2 pg/mL and 22.9 +/- 17.6 pg/mL, respectively. Furthermore, plasma ADM levels increased as the severity of the disease increased in asthmatic patients (20.7 +/- 14.4 pg/mL in mild, 25.2 +/- 24.3 pg/mL in moderate, and 35.5 +/- 33.6 pg/mL in severe asthmatics), although they did not result in any statistical significance. However, the plasma ADM levels correlated negatively with the FEV1 levels in the asthmatic group (p < 0.02, r = -0.37). Peripheral blood eosinophilia, IgE, and ECP levels did not correlate with plasma ADM levels. These results suggest that the measurement of ADM concentration in plasma will not be of diagnostic use in asthma, but may be a reflection of the severity of asthma.

Hypoxic induction of adrenomedullin in cultured human umbilical vein endothelial cells

OBJECTIVES

The current study evaluated the hypoxic induction of adrenomedullin gene expression and secretion, and its mechanism in cultured human umbilical vein endothelial cells (HUVEC).

METHODS

HUVEC were exposed to hypoxia or normoxia as controls for 1 to 24 h. Using Northern blot analysis and a radioimmunoassay, we evaluated adrenomedullin expression in HUVEC. The transcriptional component of adrenomedullin gene regulation was assessed by nuclear run-off experiments, and adrenomedullin mRNA half-life was measured by actinomycin D experiments.

RESULTS

We found that hypoxic conditions (1-3% oxygen) significantly increased adrenomedullin mRNA and protein in HUVEC. This increase was inversely proportional to oxygen tension and was reversible upon re-exposure to a 21% oxygen environment Nuclear run-off experiments revealed the enhanced transcriptional rate of adrenomedullin gene. Next, actinomycin D experiments revealed the enhanced adrenomedullin mRNA stability.

CONCLUSIONS

These results indicate that hypoxia increases adrenomedullin gene expression and secretion in HUVEC by transcriptional and post-transcriptional mechanisms. Hypoxic induction of adrenomedullin may play a pathophysiological role in the vascular systems.

Adrenomedullin increases phosphatidylcholine secretion in rat type II pneumocytes

Adrenomedullin, a novel hypotensive peptide, has been reported to be produced in the lung as well as in the adrenal medulla. However, the effect of adrenomedullin on lung function is still poorly understood. In this study, we detected the expression of both adrenomedullin mRNA and putative adrenomedullin receptor mRNA in primary cultures of rat type II pneumocytes. Adrenomedullin increased the secretion of phosphatidylcholine, the predominant component of pulmonary surfactant, by type II pneumocytes. The increase was partly inhibited by pretreatment with the calcitonin gene-related peptide (CGRP) receptor antagonist CGRP-(8-37). Furthermore, the increased phosphatidylcholine secretion was significantly inhibited by several protein kinase C inhibitors, such as sphingosine, 2-[1-(3-dimethylaminopropyl)-5-methoxyindol-3-yl]3-(1H-indol-3-yl) maleimide (Gö6983), 3-[1-(3-amidinothio)-propyl-1H-indoyl-3-yl]3-(1-methyl-1H-++ +indoyl-3-yl ) maleimide methane sulfonate (Ro-31-8220), and staurosporine. Our results suggest that adrenomedullin can be considered a candidate autocrine modulator of surfactant secretion in type II pneumocytes.

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.

Adrenomedullin and the control of fluid and electrolyte homeostasis

Two potent hypotensive peptides, adrenomedullin (AM) and proadrenomedullin N-terminal 20 peptide (PAMP), are encoded by the adrenomedullin gene. AM stimulates nitric oxide production by endothelial cells, whereas PAMP acts presynaptically to inhibit adrenergic nerves that innervate blood vessels. Complementary, but mechanistically unique, actions also occur in the anterior pituitary gland where both peptides inhibit adrenocorticotropin release. In the adrenal gland both AM and PAMP inhibit potassium and angiotensin II-stimulated aldosterone secretion. Natriuretic and diuretic actions of AM reflect unique actions of the peptide on renal blood flow and tubular function. In the brain AM inhibits water intake and, in a physiologically relevant manner, salt appetite. Both AM and PAMP act in the brain to elevate sympathetic tone, effects that mirror the positive inotropic action of AM in the heart. Cardioprotective actions in the brain and heart may be important counter-regulatory actions that buffer the extreme hypotensive actions of the peptides when released in sepsis. Thus the biologic actions of the proadrenomedullin-derived peptides seem well coordinated to contribute to the physiologic regulation of volume and electrolyte homeostasis.

Adrenomedullin concentrations in umbilical cord plasma of uncomplicated term pregnancies

OBJECTIVE

The study's objective was to determine whether there is a difference in the plasma concentration of adrenomedullin, a hypotensive peptide, between arterial and venous umbilical cord blood of uncomplicated gestations with vaginal delivery.

STUDY DESIGN

Arterial and venous umbilical cord blood was obtained immediately after vaginal delivery of 44 term infants with uncomplicated antepartum and intrapartum courses. Radioimmunoassay was performed to assess adrenomedullin concentrations in the plasma. The paired t test was used to compare arterial and venous concentrations. Significance was set at P < .05.

RESULTS

Mean +/- SE adrenomedullin concentrations were 178.7 +/- 4.7 pg/mL and 190.6 +/- 6.3 pg/mL for arterial and venous cord plasma, respectively. The difference between the 2 concentrations was not significant (11.8 pg/mL, P = .09).

CONCLUSION

Arterial and venous umbilical plasma concentrations of adrenomedullin do not differ significantly in uncomplicated gestations terminating with uncomplicated vaginal deliveries. This suggests that in the normal state there is neither net production nor net clearance of adrenomedullin in the placenta.

Proadrenomedullin-derived peptides

Posttranslational processing of the adrenomedullin gene product results in the formation of at least two biologically active peptides, adrenomedullin (AM) and proadrenomedullin N-20 terminal peptide (PAMP). Produced predominantly in the vasculature, both peptides are potent hypotensive agents, albeit via unique mechanisms of action. The gene is transcribed in a variety of other tissues including brain, pituitary, and kidney. Numerous actions have been reported most related to the physiologic control of fluid and electrolyte homeostasis. In the kidney, AM is diuretic and natriuretic, and both AM and PAMP inhibit aldosterone secretion by direct adrenal actions. In pituitary gland, both peptides at physiologically relevant doses inhibit basal ACTH secretion, again by apparently differing mechanisms. Additionally, AM antagonizes CRH-stimulated ACTH release. The peptides are produced in numerous brain sites, including hypothalamus and brainstem. Inhibition of AVP release has been reported and the physiologic significance of AM's ability to inhibit water drinking and salt appetite has been established. Thus the peptides appear to act in brain and pituitary gland to facilitate the loss of plasma volume, actions which complement their hypotensive effects in the blood vessel. Interestingly, direct cardiac effects (positive inotropism and chronotropism) and CNS actions (sympathostimulation) have been reported, leading to the hypothesis that these peptides also can exert important cardioprotective effects, helping to prevent vascular collapse during states of high AM secretion such as sepsis.