Effects of long-term intravenous administration of adrenomedullin (AM) plus hANP therapy in acute decompensated heart failure: a pilot study

Endothelial Dysfunction in Heart Failure: What Is Its Role?

The endothelium is a continuous layer of cells that coats the interior walls of arteries, capillaries, and veins. It has an essential regulatory role in hemostatic function, vascular tone, inflammation, and platelet activity. Endothelial dysfunction is characterized by a shift to a proinflammatory and prothrombic state, and it could have a bidirectional relationship with heart failure (HF). Due to neurohormonal activation and shear stress, HFrEF may promote endothelial dysfunction, increase ROS synthesis, and reduce nitric oxide production. Different studies have also shown that endothelium function is damaged in HFpEF because of a systemic inflammatory state. Some clinical trials suggest that drugs that have an effect on endothelial dysfunction in patients with HF or cardiovascular disease may be a therapeutic option. The aim of this review is to highlight the pathogenetic correlation between endothelial dysfunction and heart failure and the related potential therapeutic options.

Mid-Regional Proadrenomedullin in COVID-19-May It Act as a Predictor of Prolonged Cardiovascular Complications?

The rising prevalence of cardiovascular disease (CVD) and the impact of the SARS-CoV-2 pandemic have both led to increased mortality rates, affecting public health and the global economy. Therefore, it is essential to find accessible, non-invasive prognostic markers capable of identifying patients at high risk. One encouraging avenue of exploration is the potential of mid-regional proadrenomedullin (MR-proADM) as a biomarker in various health conditions, especially in the context of CVD and COVID-19. MR-proADM presents the ability to predict mortality, heart failure, and adverse outcomes in CVD, offering promise for improved risk assessment and treatment strategies. On the other hand, an elevated MR-proADM level is associated with disease severity and cytokine storms in patients with COVID-19, making it a predictive indicator for intensive care unit admissions and mortality rates. Moreover, MR-proADM may have relevance in long COVID, aiding in the risk assessment, triage, and monitoring of individuals at increased risk of developing prolonged cardiac issues. Our review explores the potential of MR-proADM as a predictor of enduring cardiovascular complications following COVID-19 infection.

Acute heart failure: mechanisms and pre-clinical models-a Scientific Statement of the ESC Working Group on Myocardial Function

While chronic heart failure (CHF) treatment has considerably improved patient prognosis and survival, the therapeutic management of acute heart failure (AHF) has remained virtually unchanged in the last decades. This is partly due to the scarcity of pre-clinical models for the pathophysiological assessment and, consequently, the limited knowledge of molecular mechanisms involved in the different AHF phenotypes. This scientific statement outlines the different trajectories from acute to CHF originating from the interaction between aetiology, genetic and environmental factors, and comorbidities. Furthermore, we discuss the potential molecular targets capable of unveiling new therapeutic perspectives to improve the outcome of the acute phase and counteracting the evolution towards CHF.

Clinical Potential of Adrenomedullin Signaling in the Cardiovascular System

Numerous clinical studies have revealed the utility of circulating AM (adrenomedullin) or MR-proAM (mid-regional proAM 45-92) as an effective prognostic and diagnostic biomarker for a variety of cardiovascular-related pathophysiologies. Thus, there is strong supporting evidence encouraging the exploration of the AM-CLR (calcitonin receptor-like receptor) signaling pathway as a therapeutic target. This is further bolstered because several drugs targeting the shared CGRP (calcitonin gene-related peptide)-CLR pathway are already Food and Drug Administration-approved and on the market for the treatment of migraine. In this review, we summarize the AM-CLR signaling pathway and its modulatory mechanisms and provide an overview of the current understanding of the physiological and pathological roles of AM-CLR signaling and the yet untapped potentials of AM as a biomarker or therapeutic target in cardiac and vascular diseases and provide an outlook on the recently emerged strategies that may provide further boost to the possible clinical applications of AM signaling.

Sustained Activation of CLR/RAMP Receptors by Gel-Forming Agonists

Background: Adrenomedullin (ADM), adrenomedullin 2 (ADM2), and CGRP family peptides are important regulators of vascular vasotone and integrity, neurotransmission, and fetoplacental development. These peptides signal through CLR/RAMP1, 2, and 3 receptors, and protect against endothelial dysfunction in disease models. As such, CLR/RAMP receptor agonists are considered important therapeutic candidates for various diseases. Methods and Results: Based on the screening of a series of palmitoylated chimeric ADM/ADM2 analogs, we demonstrated a combination of lipidation and accommodating motifs at the hinge region of select peptides is important for gaining an enhanced receptor-activation activity and improved stimulatory effects on the proliferation and survival of human lymphatic endothelial cells when compared to wild-type peptides. In addition, by serendipity, we found that select palmitoylated analogs self-assemble to form liquid gels, and subcutaneous administration of an analog gel led to the sustained presence of the peptide in the circulation for >2 days. Consistently, subcutaneous injection of the analog gel significantly reduced the blood pressure in SHR rats and increased vasodilation in the hindlimbs of adult rats for days. Conclusions: Together, these data suggest gel-forming adrenomedullin analogs may represent promising candidates for the treatment of various life-threatening endothelial dysfunction-associated diseases such as treatment-resistant hypertension and preeclampsia, which are in urgent need of an effective drug.

Endogenous Vasoactive Peptides and Vascular Aging-Related Diseases

Vascular aging is a specific type of organic aging that plays a central role in the morbidity and mortality of cardiovascular and cerebrovascular diseases among the elderly. It is essential to develop novel interventions to prevent/delay age-related vascular pathologies by targeting fundamental cellular and molecular aging processes. Endogenous vasoactive peptides are compounds formed by a group of amino acids connected by peptide chains that exert regulatory roles in intercellular interactions involved in a variety of biological and pathological processes. Emerging evidence suggests that a variety of vasoactive peptides play important roles in the occurrence and development of vascular aging and related diseases such as atherosclerosis, hypertension, vascular calcification, abdominal aortic aneurysms, and stroke. This review will summarize the cumulative roles and mechanisms of several important endogenous vasoactive peptides in vascular aging and vascular aging-related diseases. In addition, we also aim to explore the promising diagnostic function as biomarkers and the potential therapeutic application of endogenous vasoactive peptides in vascular aging-related diseases.

Translational studies of adrenomedullin and related peptides regarding cardiovascular diseases

Adrenomedullin (AM) is a vasodilative peptide with various physiological functions, including the maintenance of vascular tone and endothelial barrier function. AM levels are markedly increased during severe inflammation, such as that associated with sepsis; thus, AM is expected to be a useful clinical marker and therapeutic agent for inflammation. However, as the increase in AM levels in cardiovascular diseases (CVDs) is relatively low compared to that in infectious diseases, the value of AM as a marker of CVDs seems to be less important. Limitations pertaining to the administrative route and short half-life of AM in the bloodstream (<30 min) restrict the therapeutic applications of AM for CVDs. In early human studies, various applications of AM for CVDs were attempted, including for heart failure, myocardial infarction, pulmonary hypertension, and peripheral artery disease; however, none achieved success. We have developed AM as a therapeutic agent for inflammatory bowel disease in which the vasodilatory effect of AM is minimized. A clinical trial evaluating this AM formulation for acute cerebral infarction is ongoing. We have also developed AM derivatives that exhibit a longer half-life and less vasodilative activity. These AM derivatives can be administered by subcutaneous injection at long-term intervals. Accordingly, these derivatives will reduce the inconvenience in use compared to that for native AM and expand the possible applications of AM for treating CVDs. In this review, we present the latest translational status of AM and its derivatives.

Elevated Plasma Bioactive Adrenomedullin and Mortality in Cardiogenic Shock: Results from the OptimaCC Trial

Aims: Bioactive adrenomedullin (bio-ADM) was recently shown to be a prognostic marker in patients with acute circulatory failure. We investigate the association of bio-ADM with organ injury, functional impairment, and survival in cardiogenic shock (CS). Methods: OptimaCC was a multicenter and randomized trial in 57 patients with CS. In this post-hoc analysis, the primary endpoint was to assess the association between bio-ADM and 30-day all-cause mortality. Secondary endpoints included adverse events and parameters of organ injury or functional impairment. Results: Bio-ADM values were higher in 30-day non-survivors than 30-day survivors at inclusion (median (interquartile range) 67.0 (54.6–142.9) pg/mL vs. 38.7 (23.8–63.6) pg/mL, p = 0.010), at 24 h (p = 0.012), and up to 48 h (p = 0.027). Using a bio-ADM cutoff of 53.8 pg/mL, patients with increased bio-ADM had a HR of 3.90 (95% confidence interval 1.43–10.68, p = 0.008) for 30-day all-cause mortality, and similar results were observed even after adjustment for severity scores. Patients with the occurrence of refractory CS had higher bio-ADM value at inclusion (90.7 (59.9–147.7) pg/mL vs. 40.7 (23.0–64.7) pg/mL p = 0.005). Bio-ADM values at inclusion were correlated with pulmonary vascular resistance index, estimated glomerular filtration rate, and N-terminal pro-B-type natriuretic peptide (r = 0.49, r = –0.47, and r = 0.64, respectively; p < 0.001). Conclusions: In CS patients, the values of bio-ADM are associated with some parameters of organ injury and functional impairment and are prognostic for the occurrence of refractory CS and 30-day mortality.

Mid-Regional Proadrenomedullin as a New Biomarker of Kidney and Cardiovascular Diseases-Is It the Future?

The increasing prevalence of cardiovascular disease and concomitant chronic kidney disease among the aging populations is responsible for considerable growth of mortality. Additionally, frequent, prolonged hospitalizations and long-term treatment generates progressive decline in bodily functions as well as substantial public health and economic burden. Accessibility to easy, non-invasive prognostic markers able to detect patients at risk of cardiovascular events may improve effective therapy and mitigate disease progression. Moreover, an early diagnosis allows time for implementation of prophylactic and educational programs that may result in decreased morbidity, improved quality of life and reduced public health expenditure. One of the promising candidates for a novel cardiovascular biomarker is mid-regional proadrenomedullin, a derivative of adrenomedullin. Adrenomedullin is a peptide hormone known for its vasodilatory, antioxidant, antiapoptotic and antifibrotic effects. A remarkable advantage of mid-regional proadrenomedullin is its longer half-life which is a prerequisite for plasma measurements. These review aims to discuss the importance of mid-regional proadrenomedullin with reference to its usefulness as a biomarker of increased cardiovascular risk and kidney disease progression.

Adrecizumab: an investigational agent for the biomarker-guided treatment of sepsis

Introduction: Sepsis is a major health problem with a high incidence and mortality. ADM, a free-circulating peptide mainly expressed and secreted by vascular endothelial cells, shows vasodilatory properties and causes hypotension when present in higher concentrations during sepsis. Areas covered: Adrecizumab (ADZ) (HAM 8101) is a humanized targeted therapy directed against the N-terminus of adrenomedullin (ADM). ADZ inhibits excessive circulating sepsis-induced ADM and stimulates protective effects on the endothelial barrier, and decreases interstitial vasodilatory effects. ADZ demonstrated a promising safety profile in healthy subjects in phase I studies. According to these results, a phase II proof of concept study enrolling 300 septic patients is currently in course (NCT03085758). Expert opinion: ADZ is the first humanized antibody directed against ADM. The main interest of ADZ is its potential use as a 'biomarker-guided therapy' in septic patients with high circulating ADM. ADZ is increasingly seen as a potential adjunct therapy to restore endothelial function in septic shock. A positive pivotal phase III trial is indeed needed to convince the intensive care community to prescribe ADZ in septic shock patients. Further, it would be of interest to see whether ADZ might also benefit other critical diseases such as cardiogenic shock where endothelial dysfunction has also been described.

20 kDa PEGylated Adrenomedullin as a New Therapeutic Candidate for Inflammatory Bowel Disease

Human adrenomedullin (AM), a hypotensive peptide, also has anti-colitis activity. We prepared a polyethylene glycol (PEG) ylated form of AM through the conjugation of PEG-AM (1–15) and AM (15–52). Highly pure monomeric 20 kDa PEG-AM (20kPEG-AM) stimulated cyclic adenosine monophosphate production in HEK-293 cells stably expressing the type 1 AM receptor in a dose-dependent manner. The half-life of 20kPEG-AM was 7.4 h following subcutaneous administration in mice. We assessed the anti-colitis effect of subcutaneous 20kPEG-AM administration in the dextran sodium sulfate murine colitis model. Single and double subcutaneous injection of 20kPEG-AM significantly reduced total inflammation scores. These results suggest that 20kPEG-AM is a promising therapeutic candidate for the treatment of human inflammatory bowel diseases.

Adrenomedullin in heart failure: pathophysiology and therapeutic application

Adrenomedullin (ADM) is a peptide hormone first discovered in 1993 in pheochromocytoma. It is synthesized by endothelial and vascular smooth muscle cells and diffuses freely between blood and interstitium. Excretion of ADM is stimulated by volume overload to maintain endothelial barrier function. Disruption of the ADM system therefore results in vascular leakage and systemic and pulmonary oedema. In addition, ADM inhibits the renin-angiotensin-aldosterone system. ADM is strongly elevated in patients with sepsis and in patients with acute heart failure. Since hallmarks of both conditions are vascular leakage and tissue oedema, we hypothesize that ADM plays a compensatory role and may exert protective properties against fluid overload and tissue congestion. Recently, a new immunoassay that specifically measures the biologically active ADM (bio-ADM) has been developed, and might become a biomarker for tissue congestion. As a consequence, measurement of bio-ADM might potentially be used to guide diuretic therapy in patients with heart failure. In addition, ADM might be used to guide treatment of (pulmonary) oedema or even become a target for therapy. Adrecizumab is a humanized, monoclonal, non-neutralizing ADM-binding antibody with a half-life of 15 days. Adrecizumab binds at the N-terminal epitope of ADM, leaving the C-terminal side intact to bind to its receptor. Due to its high molecular weight, the antibody adrecizumab cannot cross the endothelial barrier and consequently remains in the circulation. The observation that adrecizumab increases plasma concentrations of ADM indicates that ADM-binding by adrecizumab is able to drain ADM from the interstitium into the circulation. We therefore hypothesize that administration of adrecizumab improves vascular integrity, leading to improvement of tissue congestion and thereby may improve clinical outcomes in patients with acute decompensated heart failure. A phase II study with adrecizumab in patients with sepsis is ongoing and a phase II study on the effects of adrecizumab in patients with acute decompensated heart failure with elevated ADM is currently in preparation.

Adrenomedullin: Continuing to explore cardioprotection

Adrenomedullin (AM), a peptide isolated from an extract of human pheochromocytoma, comprises 52 amino acids with an intramolecular disulfide bond and amidation at the carboxy-terminus. AM is present in various tissues and organs in rodents and humans, including the heart. The peptide concentration increases with cardiac hypertrophy, acute myocardial infarction, and overt heart failure in the plasma and the myocardium. The principal function of AM in the cardiovascular system is the regulation of the vascular tone by vasodilation and natriuresis via cyclic adenosine monophosphate-dependent or -independent mechanism. In addition, AM may possess unique properties that inhibit aldosterone secretion, oxidative stress, apoptosis, and stimulation of angiogenesis, resulting in the protection of the structure and function of the heart. The AM receptor comprises a complex between calcitonin receptor-like receptor (CLR) and receptor activity-modifying protein (RAMP) 2 or 3, and the AM-CLR/RAMP2 system is essential for heart development during embryogenesis. Small-scale clinical trials have proven the efficacy and safety of recombinant AM peptide therapy for heart failure. Gene delivery and a modified AM peptide that prolongs the half-life of the native peptide could be an innovative method to improve the efficacy and benefit of AM in clinical settings. In this review, we focus on the pathophysiological roles of AM and its receptor system in the heart and describe the advances in AM and proAM-derived peptides as diagnostic biomarkers as well as the therapeutic application of AM and modified AM for cardioprotection.

Natural and synthetic peptides in the cardiovascular diseases: An update on diagnostic and therapeutic potentials

Several peptides play an important role in physiological and pathological conditions into the cardiovascular system. In addition to well-known vasoactive agents such as angiotensin II, endothelin, serotonin or natriuretic peptides, the vasoconstrictor Urotensin-II (Uro-II) and the vasodilators Urocortins (UCNs) and Adrenomedullin (AM) have been implicated in the control of vascular tone and blood pressure as well as in cardiovascular disease states including congestive heart failure, atherosclerosis, coronary artery disease, and pulmonary and systemic hypertension. Therefore these peptides, together with their receptors, become important therapeutic targets in cardiovascular diseases (CVDs). Circulating levels of these agents in the blood are markedly modified in patients with specific CVDs compared with those in healthy patients, becoming also potential biomarkers for these pathologies. This review will provide an overview of current knowledge about the physiological roles of Uro-II, UCN and AM in the cardiovascular system and their implications in cardiovascular diseases. It will further focus on the structural modifications carried out on original peptide sequences in the search of analogues with improved physiochemical properties as well as in the delivery methods. Finally, we have overviewed the possible application of these peptides and/or their precursors as biomarkers of CVDs.

Adrenomedullin and Adrenomedullin-Targeted Therapy As Treatment Strategies Relevant for Sepsis

Sepsis remains a major medical challenge, for which, apart from improvements in supportive care, treatment has not relevantly changed over the last few decades. Vasodilation and vascular leakage play a pivotal role in the development of septic shock, with vascular leakage being caused by disrupted endothelial integrity. Adrenomedullin (ADM), a free circulating peptide involved in regulation of endothelial barrier function and vascular tone, is implicated in the pathophysiology of sepsis. ADM levels are increased during sepsis, and correlate with extent of vasodilation, as well as with disease severity and mortality. In vitro and preclinical in vivo data show that administration of ADM exerts anti-inflammatory, antimicrobial, and protective effects on endothelial barrier function during sepsis, but other work suggests that it may also decrease blood pressure, which could be detrimental for patients with septic shock. Work has been carried out to negate ADMs putative negative effects, while preserving or even potentiating its beneficial actions. Preclinical studies have demonstrated that the use of antibodies that bind to the N-terminus of ADM results in an overall increase of circulating ADM levels and improves sepsis outcome. Similar beneficial effects were obtained using coadministration of ADM and ADM-binding protein-1. It is hypothesized that the mechanism behind the beneficial effects of ADM binding involves prolongation of its half-life and a shift of ADM from the interstitium to the circulation. This in turn results in increased ADM activity in the blood compartment, where it exerts beneficial endothelial barrier-stabilizing effects, whereas its detrimental vasodilatory effects in the interstitium are reduced. Up till now, in vivo data on ADM-targeted treatments in humans are lacking; however, the first study in septic patients with an N-terminus antibody (Adrecizumab) is currently being conducted.

Epicardial-derived adrenomedullin drives cardiac hyperplasia during embryogenesis

BACKGROUND

Growth promoting signals from the epicardium are essential for driving myocardial proliferation during embryogenesis. In adults, these signals become reactivated following injury and promote angiogenesis and myocardial repair. Therefore, identification of such paracrine factors could lead to novel therapeutic strategies. The multi-functional peptide adrenomedullin (Adm 5 gene, AM 5 protein) is required for normal heart development. Moreover, elevated plasma AM following myocardial infarction offers beneficial cardioprotection and serves as a powerful diagnostic and prognostic indication of disease severity.

RESULTS

Here, we developed a new model of Adm overexpression by stabilizing the Adm mRNA through gene-targeted replacement of the endogenous 30 untranslated region. As expected, Admhi/hi mice express three-times more AM than controls in multiple tissues, including the heart. Despite normal blood pressures, Admhi/hi mice unexpectedly showed significantly enlarged hearts due to increased cardiac hyperplasia during development. The targeting vector was designed to allow for reversion to wild-type levels by means of Cre-mediated modification. Using this approach, we demonstrate that AM derived from the epicardium, but not the myocardium or cardiac fibroblast, is responsible for driving cardiomyocyte hyperplasia.

CONCLUSIONS

AM is produced by the epicardium and drives myocyte proliferation during development, thus representing a novel and clinically relevant factor potentially related to mechanisms of cardiac repair after injury.

Adrenomedullin and adrenotensin regulate collagen synthesis and proliferation in pulmonary arterial smooth muscle cells

To understand the pathophysiological mechanisms of pulmonary arterial smooth muscle cell (PASMC) proliferation and extracellular-matrix accumulation in the development of pulmonary hypertension and remodeling, this study determined the effects of different doses of adrenomedullin (ADM) and adrenotensin (ADT) on PASMC proliferation and collagen synthesis. The objective was to investigate whether extracellular signal-regulated kinase (ERK1/2) signaling was involved in ADM- and ADT-stimulated proliferation of PASMCs in 4-week-old male Wistar rats (body weight: 100-150 g, n=10). The proliferation of PASMCs was examined by 5-bromo-2-deoxyuridine incorporation. A cell growth curve was generated by the Cell Counting Kit-8 method. Expression of collagen I, collagen III, and phosphorylated ERK1/2 (p-ERK1/2) was evaluated by immunofluorescence. The effects of different concentrations of ADM and ADT on collagen I, collagen III, and p-ERK1/2 protein expression were determined by immunoblotting. We also investigated the effect of PD98059 inhibition on the expression of p-ERK1/2 protein by immunoblotting. ADM dose-dependently decreased cell proliferation, whereas ADT dose-dependently increased it; and ADM and ADT inhibited each other with respect to their effects on the proliferation of PASMCs. Consistent with these results, the expression of collagen I, collagen III, and p-ERK1/2 in rat PASMCs decreased after exposure to ADM but was upregulated after exposure to ADT. PD98059 significantly inhibited the downregulation by ADM and the upregulation by ADT of p-ERK1/2 expression. We conclude that ADM inhibited, and ADT stimulated, ERK1/2 signaling in rat PASMCs to regulate cell proliferation and collagen expression.

Adrenomedullin and cardiovascular diseases

The cardiovascular system is regulated by the autonomic nervous system, the renin-angiotensin-aldosterone system, nitric oxide (NO) and other factors including neuropeptides. Research in neurohumoral factors has led to the development of many cardiovascular drugs. Adrenomedullin (ADM), initially isolated from the adrenal gland, has diverse physiological and pathophysiological functions in the cardiovascular system. It is produced in many organs and tissues including the vasculature. ADM has numerous actions, including vasodilation, natriuresis, antiapoptosis and stimulation of NO production. It might play a protective role in various cardiovascular pathologies, and its plasma level is elevated in patients with hypertension and heart failure. Administration of ADM is a possible therapeutic approach for treating cardiovascular diseases. A number of studies have investigated the infusion of ADM in humans, which seems to be benficial in heart failure and myocardial infarction. Instead of ADM infusion, augmentation of its endogenous level is another possible strategy. Gene therapy is feasible in animal models, but its application in humans is limited. At present, the most promising clinical application of ADM is the use of the plasma level of mid-regional proadrenomedullin as a biomarker in cardiovascular diseases. It is a good marker of prognosis and survival in patients with coronary aretery disease or heart failure.

Conflicting effects of nitric oxide and oxidative stress in chronic heart failure: potential therapeutic strategies

Chronic heart failure (CHF) is characterized by decreased nitric oxide (NO) bioavailability. In addition, the beneficial NO turns to be deleterious when it reacts with superoxide anion, leading to peroxynitrite formation. Numerous experimental and clinical studies have reported increased production of reactive oxygen species (superoxide, hydrogen peroxide, hydroxyl radical) both in animals and patients with CHF. Moreover, there are indicative data suggesting mechanisms associated with endothelial dysfunction in states of CHF, mainly attributed to decreased NO bioavailability and enhanced inactivation of the latter. Thus, such molecules appear to be potential targets in patients with CHF. These patients are strong candidates to receive a variety of therapeutic agents, some of which have known antioxidant effects. Classic treatment with statins or angiotensin converting enzyme inhibitors has been found to be beneficial in restoring NO and improving myocardial function and structure. Other agents such as sildenafil and b-blockers along with novel agents such as NO synthase transcription enhancers have been proved to be also beneficial, but their use for such a purpose is still controversial. Approaches using more-effective antioxidants or targeting myocardial oxidant-producing enzymes and oxidative or nitrosative stress might be promising strategies in the future.

Distribution of urocortins and corticotropin-releasing factor receptors in the cardiovascular system

Urocortins are human homologues of urotensin I, a fish corticotropin-releasing-factor- (CRF-) like peptide secreted from the urophysis. There are three urocortins: urocortin 1, urocortin 2, and urocortin 3 in mammals. We have shown that urocortin 1 and urocortin 3 are endogenously synthesized in the myocardial cells of human heart and may act on CRF type 2 receptor (CRFR2) expressed in the heart. Expression levels of urocortin 1 in the heart and plasma urocortin 1 levels are elevated in patients with heart failure. Recent studies have shown that urocortins have various biological actions in the cardiovascular system, such as a vasodilator action, a positive inotropic action, a cardioprotective action against ischemia/reperfusion injury, and suppressive actions against the renin angiotensin system and the sympathetic nervous system. Urocortins and CRFR2 may therefore be a potential therapeutic target for cardiovascular diseases, such as congestive heart failure, hypertension, and myocardial infarction.

Impact of adrenomedullin on dextran sulfate sodium-induced inflammatory colitis in mice: insights from in vitro and in vivo experimental studies

BACKGROUND

Although adrenomedullin (AM) is known to ameliorate inflammatory processes, few data exist regarding the effect of AM on inflammatory colitis. Therefore, we examined the effect of AM on inflammatory response in vitro and in vivo colitis model.

METHODS

In mice experimental colitis induced by 3% dextran sulfate sodium (DSS) in drinking water for 7 days, AM with 225-900 μg/kg in 0.5 ml of saline or saline alone were given intraperitoneally once a day. In the in vitro experiment, we determined the cytokine response in THP-1 cell activated by lipopolysaccharide with or without AM of 10 nM. Additionally, we performed wound healing assay in Caco-2 cell interfered by DSS with or without AM of 100 nM.

RESULTS

In the colitis model, AM significantly reduced the disease activity index, histological score, and local production of inflammatory cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 in accordance with reduction of serum amyloid A levels. Secretion of TNF-α in lipopolysaccharide-stimulated THP-1 cells was significantly reduced in the presence of AM. The distance of wound healing interfered by 0.25% DSS was significantly improved in the presence of AM of 100 nM.

CONCLUSIONS

These results demonstrate that AM could ameliorate DSS-induced experimental colitis possibly through suppression of systemic and local production of cytokines such as TNF-α, associated with acceleration of ulcer reepithelialization and colon tissue regeneration.

Myocardial protective effect of human atrial natriuretic Peptide in cardiac surgery. -hANP Shot” in clinical safety trial-

BACKGROUND

We studied low-dose human atrial natriuretic peptide (hANP) infusion therapy during cardiac surgery and reported the cardiac and renal protective effects. The efficacy of a bolus injection of hANP (the "hANP shot") simultaneously with induction of cardioplegia has been proven in animal experiments. In the present study the clinical effects of this "hANP shot" were examined.

METHODS AND RESULTS

The subjects were 67 patients undergoing Coronary artery bypass grafting. At the time of inducing cardioplegia, 1 group received a simultaneous bolus injection of 100 μg of hANP (hANP group) and the other group received an injection of physiological saline (placebo group). The primary endpoints were (1) operative mortality and complications, and (2) the creatine kinase isoenzyme MB (CPK-MB), troponin-I, and human heart fatty acid binding protein (H-FABP) levels. The secondary endpoints were (1) the incidence of arrhythmia, and levels of (2) atrial and B-type natriuretic peptides, and cyclic guanosine monophosphate (cGMP), and (3) renin, angiotensin II, and aldosterone. Postoperative CPK-MB, troponin-I, and H-FABP levels were significantly lower in the hANP group than in the placebo group. Postoperative arrhythmia was significantly less frequent in the hANP group than in the placebo group.

CONCLUSIONS

It is possible to achieve cardioprotective effects based on the safety of the "hANP shot", as well as from biomarkers of ischemia and results related to arrhythmia. The "hANP shot" should also be evaluated as a safer and new cardioprotective method for cardiac surgery.

Shared and separate functions of the RAMP-based adrenomedullin receptors

Adrenomedullin (AM) is a novel hypotensive peptide that exerts a variety of strongly protective effects against multiorgan damage. AM-specific receptors were first identified as heterodimers composed of calcitonin-receptor-like receptor (CLR), a G protein coupled receptor, and one of two receptor activity-modifying proteins (RAMP2 or RAMP3), which are accessory proteins containing a single transmembrane domain. RAMPs are required for the surface delivery of CLR and the determination of its phenotype. CLR/RAMP2 (AM₁ receptor) is more highly AM-specific than CLR/RAMP3 (AM₂ receptor). Although there have been no reports showing differences in intracellular signaling via the two AM receptors, in vitro studies have shed light on their distinct trafficking and functionality. In addition, the tissue distributions of RAMP2 and RAMP3 differ, and their gene expression is differentially altered under pathophysiological conditions, which is suggestive of the separate roles played by AM₁ and AM₂ receptors in vivo. Both AM and the AM₁ receptor, but not the AM₂ receptor, are crucial for the development of the fetal cardiovascular system and are able to effectively protect against various vascular diseases. However, AM₂ receptors reportedly play an important role in maintaining a normal body weight in old age and may be involved in immune function. In this review article, we focus on the shared and separate functions of the AM receptor subtypes and also discuss the potential for related drug discovery. In addition, we mention their possible function as receptors for AM2 (or intermedin), an AM-related peptide whose biological functions are similar to those of AM.

The future of pharmacological therapy for heart failure

Current pharmacological therapy for heart failure (HF) is based on improved understanding of the pathophysiological mechanisms of HF progression. In particular, inhibition of key activated neurohormonal systems (eg, the renin-angiotensin-aldosterone system) and the sympathetic nervous system has been the cornerstone of drug therapy for this condition. However, despite these major advances, many HF patients still only marginally respond to these therapies. Novel therapeutic approaches have been tested. Several recent phase III studies have failed, however, despite intriguing pathophysiological concepts and promising pilot data. In other studies, significant benefits have been observed in certain subgroups only, suggesting the need for a more tailored approach to individual risk and comorbidity. This review will focus on recent and potential future pharmacological HF therapies and where drug treatment may be in the next few years. In discussing future pharmacological therapy for HF, 3 key strategies will be considered: (1) optimization of conventional therapies, (2) a focus on new drug development within areas not yet adequately represented by major clinical data and (3) new drugs affecting novel therapeutic targets.

Beneficial effects of growth hormone-releasing peptide on myocardial oxidative stress and left ventricular dysfunction in dilated cardiomyopathic hamsters

BACKGROUND

Growth hormone-releasing peptide (GHRP) may act directly on the myocardium and improve left ventricular (LV) function, suggesting a potential new approach to the treatment of cardiomyopathic hearts. The present study tested the hypothesis that the beneficial cardiac effects of GHRP might include attenuation of myocardial oxidative stress.

METHODS AND RESULTS

Dilated cardiomyopathic TO-2 hamsters were injected with GHRP-2 (1 mg/kg) or saline from 6 to 12 weeks of age. F1B hamsters served as controls. Untreated TO-2 hamsters progressively developed LV dilation, wall thinning, and systolic dysfunction between 6 and 12 weeks of age. Marked myocardial fibrosis was apparent in untreated hamsters at 12 weeks of age in comparison with F1B controls. The ratio of reduced to oxidized glutathione (GSH/GSSG) was decreased and the concentration of 4-hydroxynonenal (4-HNE) was increased in the hearts of untreated TO-2 hamsters. Treatment with GHRP-2 attenuated the progression of LV remodeling and dysfunction, as well as myocardial fibrosis, in TO-2 hamsters. GHRP-2 also inhibited both the decrease in the GSH/GSSG ratio and the increase in the concentration of 4-HNE in the hearts of TO-2 hamsters.

CONCLUSIONS

GHRP-2 can suppress the increase in the level of myocardial oxidative stress, leading to attenuation of progressive LV remodeling and dysfunction in dilated cardiomyopathic hamsters. (Circ J 2010; 74: 163 - 170).