Adrenomedullin: molecular mechanisms and its role in cardiac disease

Adrenomedullin improved endothelial dysfunction via receptor-Akt pathway in rats with obesity-related hypertension

Obesity-related hypertension (OH) is accompanied by obvious endothelial dysfunction, which contributes to increased peripheral vascular resistance and hypertension. Adrenomedullin (ADM), a multifunctional active peptide, is elevated in obese humans. The OH rats induced by high fat diet (HFD) for 28 weeks and the human umbilical vein endothelial cells (HUVECs)-treated by palmitic acid (PA) were used to investigate the effects of ADM on endothelial dysfunction and the underlying mechanisms. Vascular reactivity was assessed using mesenteric arteriole rings, and the protein expression levels were examined by Western blot analysis. Compared with the control rats, OH rats exhibited hypertension and endothelial dysfunction, along with reduced eNOS protein expression and Akt activation, and increased protein expression of proinflammatory cytokines and ROS levels. Four-week ADM administration improved hypertension and endothelial function, increased eNOS protein expression and Akt activation, and attenuated endothelial inflammation and oxidative stress in OH rats. In vitro experiment, the antagonism of ADM receptors with ADM22-52 and the suppression of Akt signaling with A6730 significantly blocked ADM-caused increase of NO content and activation of eNOS and Akt, and inhibited the anti-inflammatory and anti-oxidant effect of ADM in PA-stimulated HUVECs. These data indicate that endothelial dysfunction in OH rats is partially attributable to the decreased NO level, and the increased inflammation and oxidative stress. ADM improves endothelial function and exerts hypotensive effect depending on the increase of NO, and its anti-inflammatory and anti-oxidant effect via receptor-Akt pathway.

Identification and validation of potential hypoxia-related genes associated with coronary artery disease

Introduction: Coronary artery disease (CAD) is one of the most life-threatening cardiovascular emergencies with high mortality and morbidity. Increasing evidence has demonstrated that the degree of hypoxia is closely associated with the development and survival outcomes of CAD patients. However, the role of hypoxia in CAD has not been elucidated. Methods: Based on the GSE113079 microarray dataset and the hypoxia-associated gene collection, differential analysis, machine learning, and validation of the screened hub genes were carried out. Results: In this study, 54 differentially expressed hypoxia-related genes (DE-HRGs), and then 4 hub signature genes (ADM, PPFIA4, FAM162A, and TPBG) were identified based on microarray datasets GSE113079 which including of 93 CAD patients and 48 healthy controls and hypoxia-related gene set. Then, 4 hub genes were also validated in other three CAD related microarray datasets. Through GO and KEGG pathway enrichment analyses, we found three upregulated hub genes (ADM, PPFIA4, TPBG) were strongly correlated with differentially expressed metabolic genes and all the 4 hub genes were mainly enriched in many immune-related biological processes and pathways in CAD. Additionally, 10 immune cell types were found significantly different between the CAD and control groups, especially CD8 T cells, which were apparently essential in cardiovascular disease by immune cell infiltration analysis. Furthermore, we compared the expression of 4 hub genes in 15 cell subtypes in CAD coronary lesions and found that ADM, FAM162A and TPBG were all expressed at higher levels in endothelial cells by single-cell sequencing analysis. Discussion: The study identified four hypoxia genes associated with coronary heart disease. The findings provide more insights into the hypoxia landscape and, potentially, the therapeutic targets of CAD.

The ebb and flow of cardiac lymphatics: a tidal wave of new discoveries

The heart is imbued with a vast lymphatic network that is responsible for fluid homeostasis and immune cell trafficking. Disturbances in the forces that regulate microvascular fluid movement can result in myocardial edema, which has profibrotic and proinflammatory consequences and contributes to cardiovascular dysfunction. This review explores the complex relationship between cardiac lymphatics, myocardial edema, and cardiac disease. It covers the revised paradigm of microvascular forces and fluid movement around the capillary as well as the arsenal of preclinical tools and animal models used to model myocardial edema and cardiac disease. Clinical studies of myocardial edema and their prognostic significance are examined in parallel to the recent elegant animal studies discerning the pathophysiological role and therapeutic potential of cardiac lymphatics in different cardiovascular disease models. This review highlights the outstanding questions of interest to both basic scientists and clinicians regarding the roles of cardiac lymphatics in health and disease.

Immunomodulatory Role of Neuropeptides in the Cornea

The transparency of the cornea along with its dense sensory innervation and resident leukocyte populations make it an ideal tissue to study interactions between the nervous and immune systems. The cornea is the most densely innervated tissue of the body and possesses both immune and vascular privilege, in part due to its unique repertoire of resident immune cells. Corneal nerves produce various neuropeptides that have a wide range of functions on immune cells. As research in this area expands, further insights are made into the role of neuropeptides and their immunomodulatory functions in the healthy and diseased cornea. Much remains to be known regarding the details of neuropeptide signaling and how it contributes to pathophysiology, which is likely due to complex interactions among neuropeptides, receptor isoform-specific signaling events, and the inflammatory microenvironment in disease. However, progress in this area has led to an increase in studies that have begun modulating neuropeptide activity for the treatment of corneal diseases with promising results, necessitating the need for a comprehensive review of the literature. This review focuses on the role of neuropeptides in maintaining the homeostasis of the ocular surface, alterations in disease settings, and the possible therapeutic potential of targeting these systems.

A Review of Adrenomedullin in Pediatric Patients: A Useful Biomarker

Adrenomedullin has several properties. It acts as a potent vasodilator, has natriuretic effects, and reduces endothelial permeability. It also plays a role in initiating the early hyperdynamic phase of sepsis. Since its discovery, many articles have been published studying the uses and benefits of this biomarker. The aim of this review is to determine the usefulness of adrenomedullin in pediatric patients. Relevant studies covering adrenomedullin in pediatrics (<18 years) and published up until August 2021 were identified through a search of MEDLINE, PubMed, Embase, Web of Science, Scopus, and Cochrane. Seventy studies were included in the present review, most of them with a low level of evidence (IV to VI). Research on adrenomedullin has primarily been related to infection and the cardiovascular field. The performance of adrenomedullin to quantify infection in children seems satisfactory, especially in sepsis. In congenital heart disease, this biomarker seems to be a useful indicator before, during, and after cardiopulmonary bypass. Adrenomedullin seems to be useful in the pediatric population for a large variety of pathologies, especially regarding infection and cardiovascular conditions. However, it should be used in combination with other biomarkers and clinical or analytical variables, rather than as a single tool.

Hypoxia Inducible Factors as Central Players in the Pathogenesis and Pathophysiology of Cardiovascular Diseases

Cardiovascular (CV) diseases are the major cause of death in industrialized countries. The main function of the CV system is to deliver nutrients and oxygen to all tissues. During most CV pathologies, oxygen and nutrient delivery is decreased or completely halted. Several mechanisms, including increased oxygen transport and delivery, as well as increased blood flow are triggered to compensate for the hypoxic state. If the compensatory mechanisms fail to sufficiently correct the hypoxia, irreversible damage can occur. Thus, hypoxia plays a central role in the pathogenesis and pathophysiology of CV diseases. Hypoxia inducible factors (HIFs) orchestrate the gene transcription for hundreds of proteins involved in erythropoiesis, glucose transport, angiogenesis, glycolytic metabolism, reactive oxygen species (ROS) handling, cell proliferation and survival, among others. The overall regulation of the expression of HIF-dependent genes depends on the severity, duration, and location of hypoxia. In the present review, common CV diseases were selected to illustrate that HIFs, and proteins derived directly or indirectly from their stabilization and activation, are related to the development and perpetuation of hypoxia in these pathologies. We further classify CV diseases into acute and chronic hypoxic states to better understand the temporal relevance of HIFs in the pathogenesis, disease progression and clinical outcomes of these diseases. We conclude that HIFs and their derived factors are fundamental in the genesis and progression of CV diseases. Understanding these mechanisms will lead to more effective treatment strategies leading to reduced morbidity and mortality.

Adrenomedullin-RAMP2 and -RAMP3 Systems Regulate Cardiac Homeostasis during Cardiovascular Stress

Adrenomedullin (AM) is a peptide hormone with multiple physiological functions, which are regulated by its receptor activity-modifying proteins, RAMP2 and RAMP3. We previously reported that AM or RAMP2 knockout (KO) (AM-/-, RAMP2-/-) is embryonically lethal in mice, whereas RAMP3-/- mice are apparently normal. AM, RAMP2, and RAMP3 are all highly expressed in the heart; however, their functions there are not fully understood. Here, we analyzed the pathophysiological functions of the AM-RAMP2 and AM-RAMP3 systems in hearts subjected to cardiovascular stress. Cardiomyocyte-specific RAMP2-/- (C-RAMP2-/-) and RAMP3-/- showed no apparent heart failure at base line. After 1 week of transverse aortic constriction (TAC), however, C-RAMP2-/- exhibited significant cardiac hypertrophy, decreased ejection fraction, and increased fibrosis compared with wild-type mice. Both dP/dtmax and dP/dtmin were significantly reduced in C-RAMP2-/-, indicating reduced ventricular contractility and relaxation. Exposing C-RAMP2-/- cardiomyocytes to isoproterenol enhanced their hypertrophy and oxidative stress compared with wild-type cells. C-RAMP2-/- cardiomyocytes also contained fewer viable mitochondria and showed reduced mitochondrial membrane potential and respiratory capacity. RAMP3-/- also showed reduced systolic function and enhanced fibrosis after TAC, but those only became apparent after 4 weeks. A reduction in cardiac lymphatic vessels was the characteristic feature in RAMP3-/-. These observations indicate the AM-RAMP2 system is necessary for early adaptation to cardiovascular stress through regulation of cardiac mitochondria. AM-RAMP3 is necessary for later adaptation through regulation of lymphatic vessels. The AM-RAMP2 and AM-RAMP3 systems thus play separate critical roles in the maintenance of cardiovascular homeostasis against cardiovascular stress.

An update on the use and discovery of prognostic biomarkers in acute decompensated heart failure

Introduction: Acute decompensated heart failure (ADHF) remains a significant health care burden as evidenced by high readmission rates and mortality. Over the years, the care of patients with ADHF has been transformed by the use of biomarkers, specifically to aid in the diagnosis and prognosis. Patients with HF follow a variable course given the complex and heterogenous pathophysiological processes, thus it is imperative for clinicians to have tools to predict short and long-term outcomes in order to educate patients and optimize management. Areas Covered: The natriuretic peptides, including B-type natriuretic peptide and N-terminal pro-B-type natriuretic peptide, are considered the gold standard biomarkers. Yet, other emerging biomarkers such as suppression of tumerogenicity-2, cardiac troponin, galectin-2, mid-regional pro-adrenomedullin, copeptin, cystatin, and neutrophil gelatinase-associated lipocalin have increasingly shown promise in evaluating prognosis in patients with ADHF. This article reviews the pathophysiology and utility of both established and emerging biomarkers for the prognostication of patients with ADHF. Expert Opinion: As of 2019, the most validated biomarkers for use in decompensated heart failure include natriuretic peptides, high sensitivity troponin, and sST2. These biomarkers are involved in the underlying pathophysiology of disease and as such provide added information to that of exam, x-ray, and echocardiography.

[Indicators of the left ventricular-arterial coupling interaction in chronic forms of ischemic heart disease: relationships of the protradenomedullin and N-terminal probrain natriuretic peptide]

PURPOSE OF THE STUDY

Analyze the parameters of the interaction between the left ventricle and the arterial system in patients with chronic forms of coronary heart disease and to identify relationships with levels of proadrenomedullin (MR‑proADM) and N‑terminal precursor of the brain natriuretic peptide B (NT‑proBNP).

MATERIALS AND METHODS

240 patients with chronic forms of coronary heart disease (median - 55,9 [43; 63] years) and Q‑forming myocardial infarction in the past were examined. Of these, 110 patients with myocardial infarction and preserved lef ventricular ejection fraction and 130 patients with ischemic cardiomyopathy. All patients were calculated parameters of lef ventricular‑arterial interaction and the determination in blood serum levels of MR‑proADM and NT‑proBNP.

RESULTS

In patients with ischemic cardiomyopathy, an increase in the lef ventricular‑arterial interaction index was detected (2,51 [1,18; 5,00]), which reflects a decrease in the functional abilities and efficiency of the heart. In patients with myocardial infarction and a preserved left ventricular ejection fraction, this indicator was in the range of normal values (0,78 [0,55; 1,07]), which indicates an effective cardiac work. A study of MR‑proADM and NT‑proBNP levels demonstrated an increase in both groups (1,72 [1,56; 1,98] nmol/l and 779,3 [473; 2193] pg/ml in the group of patients with ischemic cardiomyopathy; 0,89 [0,51; 1,35] nmol/l and 246 [118; 430] pg/ml in the group of patients with myocardial infarction and preserved left ventricular ejection fraction), and the correlation analysis with left ventricular‑arterial coupling interaction parameters allowed identify statistically significant connections (in the group of patients with ischemic cardiomyopathy: with the level of MR‑proADM ‑ r=0,67, p=0,006, with the level of NT‑proBNP ‑ r=0,78, p&lt;0,001; in the group of patients with myocardial infarction and preserved left ventricular ejection fraction: with MR‑proADM level ‑ r=‑0,52, p=0,024, with NT‑proBNP level ‑ r =‑0,38, p=0,037).

CONCLUSION

The findings suggest a pathogenetic association between the biomarkers under study and the parameters of left ventricular‑arterial coupling interaction.

Al[18F]F-complexation of DFH17, a NOTA-conjugated adrenomedullin analog, for PET imaging of pulmonary circulation

INTRODUCTION

Adrenomedullin receptors are highly expressed in human alveolar capillaries and provide a molecular target for imaging the integrity of pulmonary microcirculation. In this work, we aimed to develop a NOTA-derivatized adrenomedullin analog (DFH17), radiolabeled with [¹⁸F]AlF, for PET imaging of pulmonary microcirculation.

METHODS

Highly concentrated [¹⁸F](AlF)²⁺ (15 μL) was produced from purified fluorine-18 in NaCl 0.9%. Various complexation experiments were carried out at Al-to-NOTA molar ratios ranging from 1:1 to 1:40 to assess optimal radiolabeling conditions before using the peptide. DFH17 peptide (2 mM, pH 4) was radiolabeled with [¹⁸F](AlF)²⁺ for 15 min at 100 °C in a total volume of 60 μL. As part of the radiolabeling process, parameters such as fluorine-18 activity (~37 and 1480 MBq), concentration of AlCl₃ (0.75, 2, 3, 6 or 10 mM) and the effects of hydrophilic organic solvent (aqueous vs ethanol 50%) were studied. The final formulation was tested for purity, identity and stability in saline. Initial in vivo evaluation of [¹⁸F]AlF-DFH17 was performed in normal rats by PET/CT.

RESULTS

The scaled-up production of [¹⁸F]AlF-DFH17 was performed in high radiochemical and chemical purities in an overall radiochemical yield of 22-38% (at end-of-synthesis) within 60 min. The final formulation was stable in saline at different radioactive concentrations for 8 h. PET evaluation in rats revealed high lung-to-background ratios and no defluorination in vivo up to 1 h post-injection.

CONCLUSION

The novel radioconjugate [¹⁸F]AlF-DFH17 appears to be a promising PET ligand for pulmonary microcirculation imaging.

Adrenomedullin Is Associated With Surgical Trauma and Impaired Renal Function in Vascular Surgery Patients

BACKGROUND:

Patients undergoing vascular surgery are prone to perioperative organ injury because of both higher prevalence of cardiovascular risk factors and the extent of surgery. Early detection of organ failure is essential to facilitate appropriate medical care. Midregional pro-adrenomedullin (MR-proADM) has been investigated in acute medical care settings to guide clinical decision-making regarding patient pathways and to identify patients prone to imminent cardiovascular or inflammatory complications. In this study, we evaluated the impact of perioperative MR-proADM levels as an early marker of perioperative cardiovascular and inflammatory stress reactions and kidney injury.

METHODS:

The study was conducted as a monocentric, prospective, noninterventional trial at Hannover Medical School, Germany. A total of 454 consecutive patients who underwent open vascular surgery were followed from the day prior to until 30 days after surgery. The composite primary end point was defined as the occurrence of major adverse cardiac events (MACEs), acute kidney injury (AKI), or systemic inflammatory response syndrome (SIRS). Measurements were correlated with both medical history and postoperative MACE, AKI, or SIRS using univariate and multivariate regression analysis.

RESULTS:

One hundred thirty-nine (31%) of the patients reached the primary end point within the study interval. Midregional pro-adrenomedullin change was associated with the combined primary end point and with the intensity of surgical trauma. Midregional pro-adrenomedullin change was increased in patients reaching the secondary end points, SIRS (optimal cutoff: 0.2 nmol/L) and AKI (optimal cutoff: 0.7 nmol/L), but not in patients with MACEs.

CONCLUSION:

Increased levels of MR-proADM within the perioperative setting (1) were linked to the invasiveness of surgery and (2) identified patients with ongoing loss of renal function. Increased MR-proADM levels may therefore identify a subgroup of patients prone to excessive cardiovascular stress but did not directly correlate with adverse cardiac events. Consistently low levels of MR-proADM may identify a subgroup of patients with acceptable low risk to guide discharge from high-density care units.

Plasma mid-regional pro-adrenomedullin levels are inversely associated with anxiety but unrelated to depression: Results from the observational DIAST-CHF study in patients with cardiovascular risk factors

OBJECTIVES

It has been postulated that patients with heart failure have a high risk of ventricular arrhythmias and sudden cardiac death resulting from anxiety-induced autonomic arousal. In the prospective and multicenter DIAST-CHF (Diagnostic Trial on Prevalence and Clinical Course of Diastolic Dysfunction and Heart Failure) study, we therefore, tested the hypothesis that adrenomedullin (ADM), a well-established predictor for cardiovascular outcome, is associated with self-rated anxiety symptoms in patients at risk of suffering from or actually with overt heart failure.

PARTICIPANTS AND MEASURES

Study participants with risk factors for diastolic dysfunction were requested to complete the Hospital Anxiety and Depression Scale (HADS), and plasma mid-regional pro-adrenomedullin (MR-proADM) concentrations were measured.

RESULTS

In bivariate analysis, we found significantly lower plasma MR-proADM levels in patients with elevated HADS-anxiety scores above the clinically relevant cut-off level of ≥11 (n=118, 536pmol/l, interquartile range [IQR] 449-626) as compared to non-anxious study participants (n=1,292, 573pmol/l, IQR 486-702, p=0.001). A set of multivariate models adjusted for potential confounders confirmed the negative association between self-rated anxiety symptoms and plasma MR-proADM. In similar models, no significant association was detected between HADS-depression scores and MR-proADM.

CONCLUSIONS

The inverse relationship between plasma MR-proADM and anxiety observed in patients with cardiovascular risk factors supports a previous experimental study using a mutant mouse line with a brain-specific loss of ADM expression which displayed hyperactive and over-anxious behavior. Further experimental and clinical studies are warranted to test the hypothesis that also in humans ADM acts as a neuromodulator with anxiolytic properties.

Midregional proadrenomedullin predicts mortality and major adverse cardiac events in patients presenting with chest pain: results from the CHOPIN trial

OBJECTIVES

Chest pain is a common complaint to emergency departments (EDs) and clinical risk factors are used to predict which patients are at risk for worse outcomes and mortality. The goal was to assess the novel biomarker midregional proadrenomedullin (MR-proADM) in prediction of mortality and major adverse cardiac events (MACE).

METHODS

This was a subanalysis of the CHOPIN study, a 16-center prospective trial that enrolled 2,071 patients presenting with chest pain within 6 hours of onset. The primary endpoint was 6-month all-cause mortality and the secondary endpoint was 30-day and 6-month MACE: ED visits or hospitalization for acute myocardial infarction, unstable angina, reinfarction, revascularization, and heart failure.

RESULTS

MR-proADM performed similarly to troponin (cTnI; c-statistic = 0.845 and 0.794, respectively) for mortality prediction in all subjects and had similar results in those with noncardiac diagnoses. MR-proADM concentrations were stratified by decile, and the cohort in the top decile had a 9.8% 6-month mortality risk versus 0.9% risk for those in the bottom nine deciles (p < 0.0001). MR-proADM, history of coronary artery disease (CAD), and hypertension were predictors of short-term MACE, while history of CAD, hypertension, cTnI, and MR-proADM were predictors of long-term MACE.

CONCLUSIONS

In patients with chest pain, MR-proADM predicts mortality and MACE in all-comers with chest pain and has similar prediction in those with a noncardiac diagnosis. This exploratory analysis is primarily hypotheses-generating and future prospective studies to identify its utility in risk stratification should be considered.

Study of the association of adrenomedullin and basic-fibroblast growth factors with the peripheral arterial blood flow and endothelial dysfunction biomarkers in type 2 diabetic patients with peripheral vascular insufficiency

Background

Progressive micro-vascular vaso-degeneration is the major factor in progression of diabetic complications. Adrenomedullin (AM) and basic-Fibroblast growth factor (b-FGF) are strongly correlated with angiogenesis in vascular diseases. This study aims to provide base line data regarding the vascular effects and correlation of AM, and b-FGF with the peripheral blood flow in diabetic patients with peripheral vascular disease (PVD), and their effect on endothelial dysfunction markers. Ninety age- and sex matched females were enrolled in the study: 30 were controls, 30 had diabetes without complications (group II) and 30 had diabetes with PVD (group III) diagnosed by ankle/ brachial index (A/BI). Plasma levels of AM, b-FGF, intercellular adhesion molecule −1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) were measured by indirect enzyme immunoassay (ELISA).

Results

There was a significant increase in plasma AM, VCAM-1and ICAM-1, while a significant decrease in plasma b-FGF in diabetic patients with PVD (p < 0.05). A positive correlation was observed between plasma AM, b-FGF and A/BI and a negative correlation with VCAM −1 and ICAM in diabetic PVD. AM was not a predictor, while b-FG, VCAM-1 and ICAM-1 could be predictors for peripheral blood flow in diabetic PVD.

Conclusion

This study elucidates for the first time that AM and b-FGF are correlated and have a direct impact on the peripheral blood flow, the rise of AM in diabetic PVD may be a consecutive and compensatory vasculo-protective effect as its angiogenic and anti-inflammatory properties act to relief the endothelial insult. Down expression of b-FGF may be a predisposing factor for micro-vascular derangement. It is not clear if the rise of AM and the decline of b- FGF levels may be consequences or predisposing factors for VCAM-1 and ICAM-1 elevation as these endothelial dysfunction biomarkers could reduce peripheral blood flow and vascular integrity. It is optimistic to believe that drug intervention through AM and b-FGF administration together with reversing the endothelial inflammatory process by targeting VCAM and ICAM could reduce the prevalence of diabetic vascular complications, reduce the risk of cerebrovascular and cardiovascular morbidity in diabetes through normalizing vascular endothelium function and peripheral blood flow.

Pharmacological characterization of the relaxant effect induced by adrenomedullin in rat cavernosal smooth muscle

The aim of the present study was to determine the mechanisms underlying the relaxant effect of adrenomedullin (AM) in rat cavernosal smooth muscle (CSM) and the expression of AM system components in this tissue. Functional assays using standard muscle bath procedures were performed in CSM isolated from male Wistar rats. Protein and mRNA levels of pre-pro-AM, calcitonin receptor-like receptor (CRLR), and Subtypes 1, 2 and 3 of the receptor activity-modifying protein (RAMP) family were assessed by Western immunoblotting and quantitative real-time polymerase chain reaction, respectively. Nitrate and 6-keto-prostaglandin F_1α (6-keto-PGF_1α; a stable product of prostacyclin) levels were determined using commercially available kits. Protein and mRNA of AM, CRLR, and RAMP 1, -2, and -3 were detected in rat CSM. Immunohistochemical assays demonstrated that AM and CRLR were expressed in rat CSM. AM relaxed CSM strips in a concentration-dependent manner. AM_22-52, a selective antagonist for AM receptors, reduced the relaxation induced by AM. Conversely, CGRP_8-37, a selective antagonist for calcitonin gene-related peptide receptors, did not affect AM-induced relaxation. Preincubation of CSM strips with N^G-nitro-L-arginine-methyl-ester (L-NAME, nitric oxide synthase inhibitor), 1H-(1,2,4)oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, quanylyl cyclase inhibitor), Rp-8-Br-PET-cGMPS (cGMP-dependent protein kinase inhibitor), SC560 [5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethyl pyrazole, selective cyclooxygenase-1 inhibitor], and 4-aminopyridine (voltage-dependent K⁺ channel blocker) reduced AM-induced relaxation. On the other hand, 7-nitroindazole (selective neuronal nitric oxide synthase inhibitor), wortmannin (phosphatidylinositol 3-kinase inhibitor), H89 (protein kinase A inhibitor), SQ22536 [9-(tetrahydro-2-furanyl)-9H-purin-6-amine, adenylate cyclase inhibitor], glibenclamide (selective blocker of ATP-sensitive K⁺ channels), and apamin (Ca²⁺-activated channel blocker) did not affect AM-induced relaxation. AM increased nitrate levels and 6-keto-PGF_1α in rat CSM. The major new contribution of this research is that it demonstrated expression of AM and its receptor in rat CSM. Moreover, we provided evidence that AM-induced relaxation in this tissue is mediated by AM receptors by a mechanism that involves the nitric oxide-cGMP pathway, a vasodilator prostanoid, and the opening of voltage-dependent K⁺ channels.

Cardiac biomarkers in heart failure

BACKGROUND

Heart failure is a syndrome characterized by the inability of the heart to meet the body's circulatory demands. Heart failure is a growing health issue worldwide and the prevalence of heart failure is expected to rise as populations age. Therapies and interventions for a variety of cardiac conditions continue to advance and biomarkers will play an increasing role in patient management.

METHODS

This is a review of the clinical research in blood based biomarkers for diagnosis, prognosis and therapeutic guidance of heart failure. The focus of this review is biomarkers that are currently available for clinical measurement, and their current and potential for applications for managing heart failure patients.

RESULTS

The various biologic pathways and physiologic processes of heart failure biomarkers represent a host of different including inflammation, remodeling, strain, neurohormonal activation, metabolism and cardiac myocyte injury. The clinical characteristics and applications of each heart failure biomarker are discussed.

CONCLUSION

As populations age and effective treatments and interventions for coronary artery disease improve, heart failure will increase in incidence and prevalence. Blood biomarkers will play an increasing role in the early diagnosis, therapeutic monitoring and management of heart failure patients in the future.

An exploratory panel of biomarkers for risk prediction in pulmonary hypertension: emerging role of CT-proET-1

BACKGROUND

Pulmonary arterial hypertension (PAH) is a rare, deadly condition. Although risk stratification is extremely important for assessment of prognosis and to guide therapy, there is lack of evidence concerning the role of novel biomarkers. In a pivotal study, we sought to comparatively investigate the predictive power of several new biomarkers in PAH.

METHODS

Patients with prevalent PAH were enrolled in the study protocol, which included clinical, functional and echocardiographic assessment. Blood samples were collected at baseline for determination of NT-proBNP, CT-proET-1, MR-proANP, MR-proADM, copeptin and troponin I. Patients were clinically followed-up up to 12 months for first occurrence of hospital admission due to PAH-related clinical worsening, heart/lung transplantation or all-cause mortality.

RESULTS

Among the 28 included patients the pre-specified end-point occurred in 8 (29% event rate). There were higher baseline levels of CT-proET-1, copeptin, MR-proANP, NT-proBNP and troponin I in patients who reached the composite end-point. They also had larger right atria. In multivariate Cox regression, CT-proET-1 was the only biomarker associated with increased hazard of reaching the primary composite end-point (hazard ratio per tertile increase = 10.1; 95% CI 2.0 to 50.6).

CONCLUSIONS

CT-proET-1 provided prognostic information independent of other biomarkers. Importantly, we have provided the first evidence that CT-proET-1 may be superior to commonly used biomarkers.

Novel regulation of cardiac metabolism and homeostasis by the adrenomedullin-receptor activity-modifying protein 2 system

Adrenomedullin (AM) was identified as a vasodilating and hypotensive peptide mainly produced by the cardiovascular system. The AM receptor calcitonin receptor-like receptor associates with receptor activity-modifying protein (RAMP), one of the subtypes of regulatory proteins. Among knockout mice ((-/-)) of RAMPs, only RAMP2(-/-) is embryonically lethal with cardiovascular abnormalities that are the same as AM(-/-). This suggests that the AM-RAMP2 system is particularly important for the cardiovascular system. Although AM and RAMP2 are highly expressed in the heart from embryo to adulthood, their analysis has been limited by the embryonic lethality of AM(-/-) and RAMP2(-/-). For this study, we generated inducible cardiac myocyte-specific RAMP2(-/-) (C-RAMP2(-/-)). C-RAMP2(-/-) exhibited dilated cardiomyopathy-like heart failure with cardiac dilatation and myofibril disruption. C-RAMP2(-/-) hearts also showed changes in mitochondrial structure and downregulation of mitochondria-related genes involved in oxidative phosphorylation, β-oxidation, and reactive oxygen species regulation. Furthermore, the heart failure was preceded by changes in peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α), a master regulator of mitochondrial biogenesis. Metabolome and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF-MS) imaging analyses revealed early downregulation of cardiolipin, a mitochondrial membrane-specific lipid. Furthermore, primary-cultured cardiac myocytes from C-RAMP2(-/-) showed reduced mitochondrial membrane potential and enhanced reactive oxygen species production in a RAMP2 deletion-dependent manner. C-RAMP2(-/-) showed downregulated activation of cAMP response element binding protein (CREB), one of the main regulators of mitochondria-related genes. These data demonstrate that the AM-RAMP2 system is essential for cardiac metabolism and homeostasis. The AM-RAMP2 system is a promising therapeutic target of heart failure.

Role of adrenomedullin in the growth and differentiation of stem and progenitor cells

Stem cells have captured the imagination of the general public by their potential as new therapeutic tools in the fight against degenerative diseases. This potential is based on their capability for self-renewal and at the same time for producing progenitor cells that will eventually provide the building blocks for tissue and organ regeneration. These processes are carefully orchestrated in the organism by means of a series of molecular cues. An emerging molecule which is responsible for some of these physiological responses is adrenomedullin, a 52-amino acid regulatory peptide which increases proliferation and regulates cell fate of stem cells of different origins. Adrenomedullin binds to specific membrane receptors in stem cells and induces several intracellular pathways such as those involving cAMP, Akt, or MAPK. Regulation of adrenomedullin levels may help in directing the growth and differentiation of stem cells for applications (e.g., cell therapy) both in vitro and in vivo.

Midregional proadrenomedullin (MR-proADM) is a powerful predictor of early death in AL amyloidosis

BACKGROUND

Cardiac biomarkers play a major role in the identification of patients at risk of early death in AL amyloidosis, and a staging system based on amino-terminal pro-natriuretic peptide type-B (NT-proBNP) and troponins (cTn) is used for prognostic stratification. Adrenomedullin is produced by several tissues including the heart, and portends a poor prognosis in heart diseases. We investigated the ability of midregional proadrenomedullin (MR-proADM) to predict early death in AL amyloidosis.

METHODS

One-hundred and thirty consecutive patients with newly-diagnosed AL amyloidosis were prospectively enrolled. The impact on survival of NT-proBNP, cTnI and MR-proADM was evaluated.

RESULTS

The concentration of MR-proADM correlated with systolic and diastolic function, but did not reflect the amount of amyloid deposited in the heart. Moreover, MR-proADM was associated with non-cardiac markers of advanced disease. The staging system based on NT-proBNP and cTnI identified high-risk subjects, but could not discriminate good-risk and intermediate-risk patients. Conversely, a staging system based on MR-proADM and cTnI identified 3 groups with significantly different survivals.

CONCLUSIONS

Midregional-proADM is a powerful prognostic marker in AL amyloidosis, which may not only reflect cardiac dysfunction but also widespread systemic disease, and can be combined with cTn for detecting patients at risk of early death.

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.

Chronic ethanol consumption reduces adrenomedullin-induced relaxation in the isolated rat aorta

Adrenomedullin (AM) is a peptide that displays cardiovascular protective activity. We investigated the effects of chronic ethanol consumption on vascular reactivity to AM and the expression of AM system components in the rat aorta. Male Wistar rats were treated with ethanol (20% vol/vol) for 6 weeks. Vascular reactivity experiments were performed in the isolated rat aorta. Metalloproteinase-2 (MMP-2) levels were determined by gelatin zymography. Nitrite and nitrate generation was measured by chemiluminescence. Protein and mRNA levels of pre-pro-AM, calcitonin receptor-like receptor (CRLR) and RAMP1, 2, and 3 (receptor-activity-modifying proteins) were assessed by western blot and quantitative real-time polymerase chain reaction, respectively. Ethanol intake reduced AM-induced relaxation in endothelium-intact rat aortas, whereas calcitonin gene-related peptide-, acetylcholine-, and sodium nitroprusside-induced relaxation were not affected by ethanol intake. N(G)-nitro-l-arginine-methyl-ester (l-NAME), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, and tetraethylammonium reduced AM-induced relaxation in aortic rings from both control and ethanol-treated rats. Ethanol consumption did not alter basal levels of nitrate and nitrite, nor did it affect the expression of MMP-2 in the rat aorta. Ethanol consumption increased mRNA levels of pre-pro-AM and RAMP1. Protein levels of AM, CRLR, and RAMP1, 2, and 3 were not affected by ethanol consumption. The major findings of the present study are that ethanol consumption reduces the vascular relaxation induced by AM and changes the mRNA expression of the components of the AM system in the vasculature. This response could be one of the mechanisms by which ethanol predisposes individuals to vascular dysfunction and hypertension.

Ethanol consumption alters the expression and reactivity of adrenomedullin in the rat mesenteric arterial bed

AIMS

Adrenomedullin (AM) is a peptide that displays cardiovascular protective activity. We investigated the effects of chronic ethanol consumption on arterial blood pressure, vascular reactivity to AM and the expression of AM system components in the rat mesenteric arterial bed (MAB).

METHODS

Male Wistar rats were treated with ethanol (20% vol/vol) for 6 weeks. Systolic, diastolic and mean arterial blood pressure were monitored in conscious rats. Vascular reactivity experiments were performed on isolated rat MAB. Matrix metalloproteinase-2 (MMP-2) levels were determined by gelatin zymography. Nitrite and nitrate generation were measured by chemiluminescence. Protein and mRNA levels of pre-pro-AM, CRLR (calcitonin receptor-like receptor) and RAMP1, 2 and 3 (receptor activity-modifying proteins) were assessed by western blot and quantitative real-time polymerase chain reaction, respectively.

RESULTS

Ethanol consumption induced hypertension and decreased the relaxation induced by AM and acetylcholine in endothelium-intact rat MAB. Phenylephrine-induced contraction was increased in endothelium-intact MAB from ethanol-treated rats. Ethanol consumption did not alter basal levels of nitrate and nitrite, nor did it affect the expression of MMP-2 or the net MMP activity in the rat MAB. Ethanol consumption increased mRNA levels of pre-pro-AM and protein levels of AM in the rat MAB. Finally, no differences in protein levels or mRNA of CRLR and RAMP1, 2 and 3 were observed after treatment with ethanol.

CONCLUSION

Our study demonstrates that ethanol consumption increases blood pressure and the expression of AM in the vasculature and reduces the relaxation induced by this peptide in the rat MAB.

Myocardial AKT: the omnipresent nexus

One of the greatest examples of integrated signal transduction is revealed by examination of effects mediated by AKT kinase in myocardial biology. Positioned at the intersection of multiple afferent and efferent signals, AKT exemplifies a molecular sensing node that coordinates dynamic responses of the cell in literally every aspect of biological responses. The balanced and nuanced nature of homeostatic signaling is particularly essential within the myocardial context, where regulation of survival, energy production, contractility, and response to pathological stress all flow through the nexus of AKT activation or repression. Equally important, the loss of regulated AKT activity is primarily the cause or consequence of pathological conditions leading to remodeling of the heart and eventual decompensation. This review presents an overview compendium of the complex world of myocardial AKT biology gleaned from more than a decade of research. Summarization of the widespread influence that AKT exerts upon myocardial responses leaves no doubt that the participation of AKT in molecular signaling will need to be reckoned with as a seemingly omnipresent regulator of myocardial molecular biological responses.

Adrenomedullin augments the angiogenic potential of late outgrowth endothelial progenitor cells

The therapeutic utility of endothelial progenitor cells (EPCs) in cardiovascular disease is potentially hampered by their low numbers in the circulation, impaired functional activity, and inhibitory factors in the recipient. These obstacles can possibly be circumvented by the use of proangiogenic cytokines and peptides. We sought to examine the effect of the endogenous vasoactive peptide adrenomedullin (AM) on the angiogenic potential of late outgrowth EPCs and their release of proangiogenic and proinflammatory cytokines/chemokines. Human peripheral blood mononuclear cells were cultured until the appearance of typical late outgrowth EPC colonies. The effect of AM on EPC proliferation was assessed using a colorimetric MTS proliferation assay while differentiation and formation of tubular structures in an EPC/fibroblast coculture or matrigel assay was used to assess the angiogenic potential of the cells. Finally, the release and mRNA transcripts of cytokines/chemokines were quantified in stimulated vs. nonstimulated EPCs using real-time PCR and a bead-based multiplex assay. The cultured EPCs possessed an endothelial phenotype and expressed the AM receptor (calcitonin receptor-like receptor/receptor activity modifying protein-2). AM stimulation induced proliferation of EPCs compared with controls ( P < 0.05). Furthermore, AM produced a 36% and 80% increase in the formation of tubular networks in the EPC/fibroblast coculture and matrigel assay, respectively ( P < 0.05). These effects seemed to be mediated through the phosphatidylinositol 3-kinase/Akt signaling pathway. AM did not seem to significantly influence the release or production of IL-6, IL-8, VEGF, stromal cell-derived factor 1, or the expression of CXCR-4 or VEGF receptor 2. In conclusion, adrenomedullin augmented the growth and angiogenic properties of late outgrowth EPCs, but did not influence their paracrine properties.

Adrenomedullin up-regulates osteopontin and attenuates vascular calcification via the cAMP/PKA signaling pathway

AIM

To determine whether adrenomedullin (ADM) attenuates vascular calcification (VC) by inducing osteopontin (OPN) expression.

METHODS

A VC model of rat aorta was induced with vitamin D3 plus nicotine (VDN), and vascular smooth muscle cell (VSMC) calcification was induced with beta-glycerophosphate. Von Kossa staining and alizarin red staining were assessed. Alkaline phosphatase (ALP) activity was measured. Immunohistochemical analysis was used to detect alpha-actin, while RT-PCR and Western blot analysis were used to quantify OPN expression.

RESULTS

Administration of ADM greatly reduced VC in VDN-treated aortas compared with controls, which was confirmed in calcified VSMCs. The decrease in alpha-actin expression was ameliorated by ADM both in vivo and in vitro. Moreover, mRNA and protein expression levels of OPN were significantly up-regulated in calcified aortas, and ADM increased OPN expression in calcified aortas. Furthermore, ADM up-regulated OPN expression in normal aortas and VSMCs. The ADM-mediated effects were similar to that of forskolin, which activates adenylyl cyclase; additionally, while the PKA inhibitor H89 and Ca²(+) chelator Fura-2 blocked the effect of ADM. However, the MEK/ERK inhibitor PD98509 had no effect on ADM induction of OPN mRNA expression. An OPN polyclonal antibody inhibited ADM-mediated attenuation of VC.

CONCLUSION

ADM up-regulates OPN expression and thus attenuates VC via PKA. ADM appears to be an endogenous cardiovascular protective peptide and may represent a new therapeutic target for VC treatment.

Adrenomedullin ameliorates the development of atherosclerosis in apoE-/- mice

Adrenomedullin (ADM) is a multifunctional peptide regulating cardiovascular homeostasis. We studied the role of ADM in the pathogenesis of atherosclerosis by investigating changes in ADM and its receptors - calcitonin receptor-like receptor (CRLR) and receptor activity-modifying proteins (RAMPs) - in aorta of apoE-/- mice and the effect of exogenous ADM administration. ApoE-/- mice were fed an atherogenic diet for 4 weeks, and apoE-/-+ADM mice were additionally given subcutaneous injections of ADM, 300ng/kg/h, for 4 weeks. ApoE-/- mice fed an atherogenic diet showed hyperlipidemia, a large plaque area and increased vessel wall thickness. The mRNA expression and protein level of ADM/ADM receptors were increased in the aorta, compared with C57BL/6J mice. The elevated mRNA level of CRLR and RAMPs correlated positively with ADM mRNA level. Radioimmunoassay revealed a higher plasma and aorta ADM content, by 61.6% and 285% (both P<0.01), respectively, in apoE-/- mice than that in C57BL/6J mice. Exogenous ADM significantly ameliorated dyslipidemia in apoE-/- mice. ADM-treated mice showed fewer aortic plaques, decreased plaque area, by 76% (P<0.01), and reduced ratio of plaque area to luminal area, by 65% (P<0.01), and ultrasonography revealed significantly reduced intima-media thickness of the ascending branch and abdominal aorta. The results suggest that atherosclerotic apoE-/- mice fed an atherogenic diet showed upregulated endogenous ADM and its receptors, and exogenous ADM treatment ameliorated the dyslipidemia and vascular atherosclerotic lesions. ADM/ADM receptors might be an important protective system against atherosclerosis and could become a new target of prevention and therapy for atherosclerosis.

Use of adrenomedullin derivatives for molecular imaging of pulmonary circulation

Currently, there is no low-molecular-weight agent for imaging of the pulmonary circulation. Adrenomedullin (AM) is a peptide predominantly cleared by the pulmonary circulation through specific endothelial receptors. We developed human AM derivatives radiolabeled with 99mTc and evaluated their biodistribution, plasma kinetics, and utility as pulmonary vascular imaging agents.

METHODS

Two derivatives radiolabeled with 99mTc were evaluated: the natural cyclic form of the peptide, to which the chelator diethylenetriaminepentaacetic acid was added (C-DTPA-AM), and the linear form, which allows direct labeling (L-AM). The compounds were injected into dogs, and the activities of the tracers in blood and in organs were determined with a nuclear medicine camera. Single-pass pulmonary clearance was measured by the indicator dilution technique. The capacity to image perfusion defects was evaluated after surgical pulmonary artery ligation.

RESULTS

Both derivatives were rapidly cleared from plasma, with elimination half-lives of 42 and 32 min for C-DTPA-AM and L-AM, respectively. The lungs retained most of the activity after 30 min; this activity was higher (P = 0.02) for L-AM (42% +/- 5% [mean +/- SEM]) than for C-DTPA-AM (27% +/- 1%). Lung activity slowly declined over time but was maintained after 2 h at approximately 20% for both tracers. The single-pass pulmonary clearance of plasma L-AM was 414 +/- 85 mL/min. There was a higher level of urinary excretion of L-AM than of C-DTPA-AM. After pulmonary artery ligation, perfusion defects were easily detectable by external imaging.

CONCLUSION

AM derivatives are promising compounds for molecular imaging of the pulmonary circulation. L-AM displayed higher levels of initial lung retention and of kidney excretion.

Receptor activity-modifying proteins: RAMPing up adrenomedullin signaling

Adrenomedullin (AM) is a 52-amino-acid multifunctional peptide that circulates in the plasma in the low picomolar range and can exert a multitude of biological effects through an autocrine/paracrine mode of action. The mechanism by which AM transduces its signal represents a novel and pharmacologically tractable paradigm in G protein-coupled receptor signaling. Since its discovery in 1993, the study of AM has emerged into a new field of research with nearly 1800 publications that rivals the renown of other common factors like angiopoetin (1015 publications) and ghrelin (1550 publications). Despite the tremendous strides made in recent years toward unveiling the biochemical and cellular functions of AM, we are still lagging in our understanding of the essential roles of AM in normal and disease physiology. As discussed in this current review, a concerted effort to combine information from clinical, genomic, biochemical, and genetic mouse model sources can provide a focused view to help define the physiological functions of AM. Specifically, we find that certain conditions, such as pregnancy, cardiovascular disease, and sepsis, are associated with robust and dynamic changes in the expression of AM and AM receptor proteins, which together represent an elegant mechanism for altering the physiological responsiveness or function of AM. Thus, the modulation of AM signaling may be further exploited for therapeutic strategies in the management and treatment of human disease.