adrenomedullin and Cardiomegaly

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.

Topics: Adrenomedullin; Animals; Calcitonin Receptor-Like Protein; Cardiomegaly; Heart Failure; Humans; Receptor Activity-Modifying Protein 2; Receptor Activity-Modifying Protein 3

Co-localization of adrenomedullin (AM) and its receptor components such as calcitonin receptor like receptor (CRLR), receptor activity modifying protein (RAMP)2 and RAMP3 in peripheral tissues, including the heart, kidney, and vasculature, suggests an important role for the peptide as a regulator of cardiovascular function. Indeed, we previously reported that AM gene expression and / or immunoreactivity are increased in the ventricles of cardiac hypertrophy and heart failure. Recently, we also found that not only levels of AM peptide and AM gene expression, but also mRNA levels of CRLR, RAMP2 and RAMP3 are increased in cardiac hypertrophy and failing heart. Cardiac myocytes and fibroblast produce and secrete two molecular forms of AM and express CRLR, RAMP2 and RAMP3, and AM is known to have inhibitory effect of collagen synthesis and antiproliferative effect in cardiac fibroblasts. Stimulation by IL-1beta significantly increased gene expression of AM and its receptor components in cardiac fibroblasts. Preincubated IL-1beta elevated the intracellular cAMP response to exogenous administered AM. AM antisense oligodeoxynucleotide treatment significantly lowered AM levels in cultured medium. IL-1beta significantly increased (3)H-proline incorporation and AM antisense oligodeoxynucleotide treatment further increased (3)H-proline incorporation. Collectively, these results support a protective role for increased AM in the cardiac hypertrophy and heart failure. Then, we tested the effects of acute administration of AM in experimental and human heart failure, because AM has hemodynamic effects including vasodilation, increases in cardiac contractility, cardiac output, diuresis, and natriuresis. We observed profound and sustained cardiovascular, hormonal and renal effects. These effects may incorporate many of the therapeutic goals of heart failure management.

Topics: Adrenomedullin; Animals; Calcitonin Receptor-Like Protein; Cardiomegaly; Heart Failure; Humans; Peptides; Protein Processing, Post-Translational; Receptors, Adrenomedullin; Receptors, Calcitonin; Receptors, Peptide

Topics: Adrenomedullin; Angiotensin II; Animals; Apoptosis; Calcium; Cardiomegaly; Cell Division; Cyclic AMP; Endothelin-1; Heart Failure; Humans; Myoblasts, Cardiac; Myocardial Contraction; Myocytes, Cardiac; Nitric Oxide; Peptides; Protein Kinase C; Signal Transduction; Tumor Necrosis Factor-alpha; Ventricular Remodeling

Topics: Adrenomedullin; Animals; Cardiomegaly; Humans; Hypertension; Peptides

Adrenomedullin (ADM) is a vasoactive and natriuretic peptide. While it is known that ADM is increased in failing human ventricles, the expression of ADM in human ventricular allografts remains unknown. The present study was designed to investigate tissue localization and intensity of ADM expression in ventricular biopsy specimens and to characterize ventricular ADM in human cardiac allografts. Thirty-three post-transplant endomyocardial biopsy specimens were examined immunohistochemically. The average score (range: 0-4) of ADM immunoreactivity (IR) was 2.4+/-0.9 (mean+/-standard deviation). Right ventricular (RV) systolic pressure was significantly increased with high ADM-IR (p=0.048) and the ADM-IR positively associated with myocyte size (r(2)=0.23, p=0.010). In contrast, ADM-IR was not associated with systemic blood pressure, serum creatinine, cyclosporine concentration, cardiac fibrosis, or allograft rejection. The present study shows that ADM-IR is present in human ventricular endomyocardium after transplantation, and ADM-IR is associated with the magnitude of RV pressure and myocyte size, suggesting an important role for ventricular ADM in the counteraction against overload as well as in the progress of myocyte hypertrophy after heart transplantation.

Topics: Adolescent; Adrenomedullin; Adult; Aged; Biopsy; Blood Pressure; Cardiomegaly; Cell Size; Cyclosporine; Female; Graft Rejection; Heart Transplantation; Heart Ventricles; Humans; Immunohistochemistry; Male; Middle Aged; Myocardium; Myocytes, Cardiac; Peptides

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.

Topics: Adrenomedullin; Animals; Animals, Newborn; Cardiomegaly; Cardiovascular System; Cells, Cultured; Constriction, Pathologic; Coronary Stenosis; Hemodynamics; Homeostasis; Mice; Mice, Knockout; Myocytes, Cardiac; Oxidative Stress; Receptor Activity-Modifying Protein 2; Receptor Activity-Modifying Protein 3; Receptor Activity-Modifying Proteins; Signal Transduction; Stress, Physiological

Intermedin (IMD), a novel member of the calcitonin/calcitonin gene-related peptide family, is involved in maintaining circulatory homeostasis and is a protective factor of heart and vessel. Here, we investigated the effects of IMD on cardiac hypertrophy in vivo and in vitro and explored the mechanisms involved.. IMD1-53 (100 ng/kg/h) was systemically administered to rats with cardiac hypertrophy induced by abdominal aortic constriction (AAC) by a mini-osmotic pump the next day after surgery continuously for 4 weeks. The AAC-treated rats before IMD infusion showed increased IMD content and expression of its receptors in the hearts. In-vivo administration of IMD1-53 greatly attenuated the cardiac hypertrophy as shown by heart weight to body weight ratio (HW/BW), haemodynamics, echocardiography, histological analyses and expression of hypertrophic markers atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) induced by AAC. IMD1-53 treatment significantly reduced the myocardial protein expression of endoplasmic reticulum stress (ERS) markers such as glucose-regulated protein 78 (GRP78), CCAAT/enhancer binding protein homologous protein (CHOP) and caspase-12, whereas the protein level of phosphorylated AMP-activated protein kinase (p-AMPK) was upregulated with IMD1-53 treatment, which was further confirmed in cultured cardiomyocytes. Concurrently, cardiomyocyte apoptosis in vivo and in vitro was ameliorated by IMD1-53 treatment. The inhibitory effects of IMD1-53 on ERS and apoptosis were eliminated on pretreatment with compound C, an AMPK inhibitor.. IMD1-53 could exert its cardioprotective effect on cardiac hypertrophy by inhibiting myocardial ERS and apoptosis, possibly via activation of AMPK signalling.

Topics: Adrenomedullin; AMP-Activated Protein Kinases; Animals; Apoptosis; Atrial Natriuretic Factor; Cardiomegaly; Caspase 12; CCAAT-Enhancer-Binding Proteins; Cells, Cultured; Echocardiography; Endoplasmic Reticulum; Endoplasmic Reticulum Stress; Heat-Shock Proteins; Male; Myocardium; Myocytes, Cardiac; Natriuretic Peptide, Brain; Neuropeptides; Organ Size; Phosphorylation; Rats

Intermedin (IMD), a novel peptide related to calcitonin gene-related peptide (CGRP) and adrenomedullin (ADM), may have localized actions as a modulator of cardiac function. The aim of the study is to explore the effect of IMD on angiotensin II (Ang II) and endothelin-1 (ET-1) induced hypertrophy in ventricular myocytes of neonatal rat and to try to elucidate the possible mechanism.. Neonatal rat cardiomyocytes were cultured in serum-free medium with and without AngII (1 micromol/L) or ET-1 (60 micromol/L) in the presence and absence of IMD (1 micromol/L). Hypertrophic responses (including cell surface area, alpha-actin, and beta-myosin heavy chain mRNA expression) and cardiomyocyte expression of NADPH oxidase gp91phox were determined.. Ang II induced increases in cardiomyocyte size to 305 +/- 32 microm2 (n = 198, p < 0.05, at 48 hours), alpha-actin expression to 4 +/- 2.8-fold (n = 6, p < 0.05, at 48 hours) and beta-myosin heavy chain expression to 11 +/- 4.8-fold (n = 6, p < 0.05, at 48 hours), and expression of the gp91phox subunit of NADPH oxidase to 29.4 +/- 12.7-fold (n = 6, p < 0.05, at 48 hours). These effects were all significantly inhibited by IMD; cardiomyocyte size, alpha-actin expression, beta-myosin heavy chain expression, and gp91phox expression were reduced to 265 +/- 32 microm2 (n = 374, p < 0.05), 3.0 +/- 1.7-fold (n = 6, p < 0.05), 8.7 +/- 4.9-fold (n = 6, p < 0.05), 3.9 +/- 3-fold (n = 6, p < 0.05), respectively. IMD also significantly inhibited ET1-induced increases in cardiomyocyte size and superoxide generation.. IMD exerts an antihypertrophic effect on neonatal cardiomyocytes by reduced levels of superoxide, suggesting that an antioxidant action contributes to the antihypertrophic actions of IMD.

Topics: Actins; Adrenomedullin; Analysis of Variance; Angiotensin II; Animals; Animals, Newborn; Cardiomegaly; Cell Size; Cells, Cultured; Drug Interactions; Endothelin-1; Gene Expression; Heart Ventricles; Membrane Glycoproteins; Myocytes, Cardiac; Myosin Heavy Chains; NADPH Oxidase 2; NADPH Oxidases; Neuropeptides; Protective Agents; Rats; Rats, Sprague-Dawley; Real-Time Polymerase Chain Reaction

Adrenomedullin (ADM) has been recognized as a multipotent multifunctional peptide. To explore the pathophysiological roles of ADM in insulin resistance (IR), we studied the changes in ADM mRNA level in the myocardium and vessels and the effect of ADM supplementation on rats with IR induced by fructose feeding. Rats were fed 4% fructose in drinking water for 8 weeks, and ADM was administered subcutaneously in pure water through an Alzet Mini-osmotic Pump at 300 ng/kg/h for the last 4 weeks. Compared with controls, rats with IR showed increased levels of fasting blood sugar and serum insulin, by 95% and 67%, respectively (all P<0.01), and glycogen synthesis and glucose transport activity of the soleus decreased by 54% and 55% (all P<0.01). mRNA level and content of brain natriuretic peptide (BNP) in myocardial were all increased significantly. Fructose-fed rats showed increased immunoreactive-ADM content in plasma by 110% and in myocardia by 55% and increased mRNA level in myocardia and vessels (all P<0.01). ADM administration ameliorated the induced IR and myocardial hypertrophy. The glycogen synthesis and glucose transport activity of the soleus muscle increased by 41% (P<0.01) and 32% (P<0.05). ADM therapy attenuated myocardial and soleus lipid peroxidation injury and enhanced the antioxidant ability. Our results showed upregulation of endogenous ADM during fructose-induced IR and the protective effect of ADM on fructose-induced IR and concomitant cardiovascular hypertrophy probably by its antioxidant effect, which suggests that ADM could be an endogenous protective factor in IR.

Topics: Adrenomedullin; Animals; Blood Glucose; Cardiomegaly; Cardiotonic Agents; Fructose; Glycogen; Infusion Pumps; Infusions, Subcutaneous; Insulin; Insulin Resistance; Lipid Peroxidation; Male; Malondialdehyde; Muscle, Skeletal; Myocardium; Natriuretic Peptide, Brain; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger

Left ventricular hypertrophy (LVH) is a risk factor for cardiovascular disease. Elevated natriuretic peptides in LVH have spurred interest that biomarkers may play a role in screening programs. Adrenomedullin (ADM) is a 52-amino acid peptide mediating vasorelaxation, natriuresis, and diuresis. The midregional portion of proADM (MRproADM) is secreted stoichiometrically with ADM; hence, it can be used as a surrogate marker of ADM. We compared the diagnostic performance of MRproADM for the detection of LVH with N-terminal pro-B-type natriuretic peptide (NTproBNP). Two hundred fifty-three hypertensive patients were derived from a local screening study. The MRproADM and NTproBNP levels were assayed using immunoluminometric assays. The MRproADM levels were significantly elevated in patients with LVH than those without (mean [SD]: 0.73 [0.25] vs 0.59 [0.18] nmol/L, P < .001). In multivariate analyses, male sex (P < .001) and log MRproADM (P = .003) retained significance for detecting LVH. Receiver operating characteristic curve for MRproADM yielded an area under the curve of 0.71; confidence interval, 0.62-0.81; P < .001, superior to NTproBNP. An optimal cutoff value for MRproADM as an indicator of LVH was 0.50 nmol/L, with a sensitivity, specificity, and negative predictive value of 90.5%, 36.5%, and 95.1%, respectively. The high negative predictive value of the MRproADM assay allows it to be used as a rule-out test for LVH when stratifying patients into high or low risk. Patients who test positive would necessitate echocardiography, enabling better resource allocation.

Topics: Adrenomedullin; Aged; Cardiomegaly; Electrocardiography; Female; Heart Ventricles; Humans; Hypertension; Male; Middle Aged; Organ Size; Protein Precursors

Intermedin (IMD) is coexpressed in the heart with its receptor, which suggests that it may have localized actions as a modulator of cardiac function. The present study was designed to observe the interaction between IMD and cardiac hypertrophy and the possible mechanism involved in the antihypertrophic effects of IMD1-53 in cultured neonatal ventricular myocytes.. Myocyte hypertrophy was induced by treating the cells with angiotensin II, and the hypertrophic response was characterized by a significant increase in cell surface area, protein synthesis, and BNP mRNA expression.. Our results showed that angiotensin II led to an obvious decrease in the production, secretion, and mRNA expression of IMD and increase receptor activity modifying proteins 1, 3 mRNA expression. Moreover, IMD1-53 inhibited the angiotensin II-induced hypertrophic response and the effects of IMD1-53 were similar to those of equivalent-dose adrenomedullin and could been blocked by H89. Otherwise, in our study, IMD1-53 resulted in dose-dependent increases of cAMP production in cardiomyocytes.. Thus, IMD and its receptor system are involved in cardiac hypertrophy, and like adrenomedullin, IMD1-53 exerts an antihypertrophic effect on neonatal cardiomyocytes and the effect can be mediated by the cAMP/PKA pathway.

Topics: Adrenomedullin; Angiotensin II; Animals; Animals, Newborn; Cardiomegaly; Cells, Cultured; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Heart Ventricles; Myocytes, Cardiac; Natriuretic Peptide, Brain; Neuropeptides; Rats; Rats, Wistar; RNA, Messenger

Chronic inhibition of nitric oxide (NO) synthesis is associated with hypertension, myocardial ischemia, oxidative stress and hypertrophy; expression of the vasodilator peptide, adrenomedullin (AM) and its receptors is augmented in cardiomyocytes, indicating that the myocardial AM system may be activated in response to pressure loading and ischemic insult to serve a counter-regulatory, cardio-protective role. The study examined the hypothesis that oxidative stress and hypertrophic remodeling in NO-deficient cardiomyocytes are attenuated by adenoviral vector-mediated delivery of the human adrenomedullin (hAM) gene in vivo.. The NO synthesis inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME, 15mg . kg(-1) . day(-1)) was given to rats for 4 weeks following systemic administration via the tail vein of a single injection of either adenovirus harbouring hAM cDNA under the control of the cytomegalovirus promoter-enhancer (Ad.CMV-hAM-4F2), or for comparison, adenovirus alone (Ad.Null) or saline. Cardiomyocytes were subsequently isolated for assessment of the influence of each intervention on parameters of oxidative stress and hypertrophic remodelling.. Cardiomyocyte expression of the transgene persisted for > or =4 weeks following systemic administration of adenoviral vector. In L-NAME treated rats, relative to Ad.Null or saline administration, Ad.CMV-hAM-4F2 (i) reduced augmented cardiomyocyte membrane protein oxidation and mRNA expression of pro-oxidant (p22phox) and anti-oxidant (SOD-3, GPx) genes; (ii) attenuated increased cardiomyocyte width and mRNA expression of hypertrophic (sk-alpha-actin) and cardio-endocrine (ANP) genes; (iii) did not attenuate hypertension.. Adenoviral vector mediated delivery of hAM resulted in attenuation of myocardial oxidative stress and hypertrophic remodelling in the absence of blood pressure reduction in this model of chronic NO-deficiency. These findings are consistent with a direct cardio-protective action in the myocardium of locally-derived hAM which is not dependant on NO generation.

Topics: Adrenomedullin; Animals; Atrial Natriuretic Factor; Cardiomegaly; Disease Models, Animal; Gene Transfer Techniques; Genetic Vectors; Humans; Myocytes, Cardiac; NADPH Oxidases; NG-Nitroarginine Methyl Ester; Nitric Oxide; Oxidative Stress; Pressure; Rats; Superoxide Dismutase

The vasodilator and vascular regulatory peptide adrenomedullin (AM), a member of the calcitonin gene-related peptide family of peptides, is predicted to play a pivotal protective role in cardiovascular dysfunction. The principle AM (AM1) receptor is composed of a G protein-linked calcitonin receptor-like receptor and a receptor activity-modifying protein (receptor activity-modifying protein 2). There is little knowledge of the receptors via which AM acts in diseases. Using smooth muscle-targeted receptor activity-modifying protein 2 transgenic mice with increased vascular density of functional AM1 receptors, we demonstrate that receptor activity-modifying protein 2 transgenic mice are not protected against angiotensin II-induced hypertension or cardiac hypertrophy. However, vascular hypertrophy, together with vascular cell adhesion molecule 1 and monocyte chemotactic protein 1 expression, is significantly reduced in the aortic walls of transgenic mice, as determined by histological techniques. This indicates that the AM1 vascular smooth muscle receptor can mediate local protection in vivo. This is supported by proliferation studies in cultured smooth muscle cells. By comparison, levels of hypotension and inflammation in a shock model were similar to those in wild-type mice. Thus, a role of the AM1 receptor in the vasoactive component could not be detected, and evidence is provided to show that the hypotensive response to AM is subject to desensitization in vivo. The finding that the vascular smooth muscle AM1 receptor acts at a local level to protect against hypertension-induced vascular hypertrophy and inflammation provides evidence that targeting this receptor may be a beneficial therapeutic approach.

Topics: Adrenomedullin; Angiotensin II; Animals; Blood Pressure; Cardiomegaly; Cells, Cultured; Disease Models, Animal; Female; Hypertension; Hypertrophy; Hypotension; Intracellular Signaling Peptides and Proteins; Lipopolysaccharides; Male; Membrane Proteins; Mice; Mice, Inbred C57BL; Mice, Transgenic; Muscle, Smooth, Vascular; Receptor Activity-Modifying Proteins; Receptors, Adrenomedullin; Receptors, Peptide; Vasculitis

This experiment on rats was aimed to investigate the expression of intermedin (IMD) in hypertrophic cardiac myoctye of renal vascular hypertension induced by incomplete ligation of the left renal artery, and so to detect and compare the changes of the expression after administration of Valsartan, Amlodipine and Enalapril respectively. The criterion for standard modeling was systolic pressure > or = 140 mmHg. At 4 weeks after successful modeling, 60 SD male rats were randomly divided into 5 groups, namely the hypertrophy group, the 3 drug-treatment groups, and the sham-operation group as control. Blood pressure, left ventricular mass index (LVMI), and the left ventricular mean transverse diameter of myocardial cell (LVTDM) were investigated at the 10th week after model establishment. Gene expression of IMD mRNA was detected by reverse transcription-polymerase chain reaction (RT-PCR), and the optical density of the band was measured by use of the Gel Documentation System. The ratio of IMD mRNA to beta-actin mRNA was considered the relative amount of IMD. When compared with control, the blood pressure increased significantly in the hypertrophy group. There was no statistically significant difference between the treatment groups. No significant difference in heart rate was noted at 4 weeks after operation in all groups. LVMI and LVTDM levels were significantly higher in the hypertrophy group than in the other groups; LVMI and LVTDM levels showed no significant difference among the treatment groups but they were obviously higher than those of the Sham-operation group. The gene expression of IMD mRNA in the hypertrophy group was upregulated in the myocardium, when compared with that in the other groups. Meanwhile, although IMD mRNA in the treament groups was higher than that in the Sham-operation group, no statistically significant difference of myocardial IMD mRNA was found between the treament groups. These results suggested that, in this experiment, intracardiac IMD mRNA was upregulated and could participate in the regulation of cardiac remodeling in renal vascular hypertension-induced cardiac hypertrophy. This upregulation could improve the pathologic and physiologic process of cardiac hypertrophy, and could associate with the pressure loading or myocardia hypertrophy. However, the change did not display any difference that could be attributed to the variety of hypotensive drugs.

Topics: Adrenomedullin; Amlodipine; Animals; Antihypertensive Agents; Cardiomegaly; Enalapril; Hypertension, Renovascular; Male; Myocardium; Neuropeptides; Random Allocation; Rats; Rats, Sprague-Dawley; RNA, Messenger; Tetrazoles; Valine; Valsartan

Chronic inhibition of nitric oxide (NO) synthesis is associated with hypertension, myocardial oxidative stress and hypertrophic remodeling. Up-regulation of the cardiomyocyte adrenomedullin (AM) / intermedin (IMD) receptor signaling cascade is also apparent in NO-deficient cardiomyocytes: augmented expression of AM and receptor activity modifying proteins RAMP2 and RAMP3 is prevented by blood pressure normalization while that of RAMP1 and intermedin (IMD) is not, indicating that the latter is regulated by a pressure-independent mechanism.. to verify the ability of an anti-oxidant intervention to normalize cardiomyocyte oxidant status and to investigate the influence of such an intervention on expression of AM, IMD and their receptor components in NO-deficient cardiomyocytes.. NO synthesis inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME, 35 mg/kg/day) was given to rats for 8 weeks, with/without con-current administration of antioxidants (Vitamin C (25mg/kg/day) and Tempol (25mg/kg/day)).. In left ventricular cardiomyocytes isolated from L-NAME treated rats, increased oxidative stress was indicated by augmented (3.6 fold) membrane protein oxidation, enhanced expression of catalytic and regulatory subunits of pro-oxidant NADPH oxidases (NOX1, NOX2) and compensatory increases in expression of anti-oxidant glutathione peroxidase and Cu/Zn superoxide dismutases (SOD1, SOD3). Vitamin C plus Tempol did not reduce systolic blood pressure but normalized augmented plasma levels of IMD, but not of AM, and in cardiomyocytes: (i) abolished increased membrane protein oxidation; (ii) normalized augmented expression of prepro-IMD and RAMP1, but not prepro-AM, RAMP2 and RAMP3; (iii) attenuated (by 42%) increased width and normalized expression of hypertrophic markers, skeletal-alpha-actin and prepro-endothelin-1 similarly to blood pressure normalization but in contrast to blood pressure normalization did not attenuate augmented brain natriuretic peptide (BNP) expression.. normalization specifically of augmented IMD/RAMP1 expression in NO-deficient cardiomyocytes by antioxidant intervention in the absence of blood pressure reduction indicates that these genes are likely to be induced directly by myocardial oxidative stress. Although oxidative stress contributed to cardiomyocyte hypertrophy, induction of IMD and RAMP1 is unlikely to be secondary to cardiomyocyte hypertrophy.

Topics: Adrenomedullin; Animals; Antioxidants; Blood Pressure; Cardiomegaly; Hypertension; Male; Myocytes, Cardiac; Neuropeptides; Nitric Oxide; Oxidative Stress; Rats; Rats, Sprague-Dawley; Receptors, Peptide

Adrenomedullin may provide a compensatory mechanism to attenuate left ventricular hypertrophy (LVH). Nitric oxide synthase inhibition, induced by chronic administration of N(omega)-nitro-L-arginine methyl ester (L-NAME) to rats, induces cardiac hypertrophy in some, but not all cases; there are few reports of direct assessment of cardiomyocyte parameters. The objective was to characterize hypertrophic parameters in left (LV) and right ventricular (RV) cardiomyocytes after administration of L-NAME to rats for 8 wk and to determine whether adrenomedullin and its receptor components were upregulated. After treatment with L-NAME (20 and 50 mg x kg(-1) x day(-1)), compared with nontreated animals, 1) systolic blood pressure increased (by 34.2 and 104.9 mmHg), 2) heart weight-to-body wt ratio increased 24.1% at the higher dose (P < 0.05), 3) cardiomyocyte protein mass increased (P = NS), 4) cardiomyocyte protein synthesis ([14C]phenylalanine incorporation) increased (P < 0.05), 5) expression of skeletal alpha-actin, atrial natriuretic peptide, brain natriuretic peptide, and ET-1 mRNAs was enhanced (P < 0.05) in LV but not RV cardiomyocytes at 20 and 50 mg x kg(-1) x day(-1), respectively, and 6) expression of adrenomedullin, receptor activity-modifying protein 3 (RAMP3), and RAMP2 (but not calcitonin receptor-like receptor and RAMP1) mRNAs was increased by L-NAME (20 mg x kg(-1) x day(-1)) in LV. In conclusion, L-NAME enhanced protein synthesis in both LV and RV cardiomyocytes but elicited a hypertrophic phenotype accompanied by altered expression of the counterregulatory peptide adrenomedullin and receptor components (RAMP2, RAMP3) in LV only, indicating that the former is due to impaired nitric oxide synthesis, whereas the phenotypic changes are due to pressure overload.

Topics: Adrenomedullin; Animals; Blood Pressure; Body Weight; Cardiomegaly; Drug Administration Schedule; Enzyme Inhibitors; Heart Ventricles; Intracellular Signaling Peptides and Proteins; Male; Membrane Proteins; Myocardium; Myocytes, Cardiac; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Organ Size; Peptides; Rats; Rats, Sprague-Dawley; Receptor Activity-Modifying Proteins; Receptors, Adrenomedullin; Receptors, Peptide; Up-Regulation

Adrenomedullin (AM) is a multifunctional regulatory peptide, and endogenous AM is an important factor in regulating cardiovascular and renal homeostasis as a potent cardio-reno-protective factor. To illustrate the protective mechanism of adrenomedullin (AM) on the cardiovascular system by observing (1) the changes in mRNA and protein levels of AM and its receptor-calcitonin receptor-like receptor (CL) and receptor activity-modifying proteins (RAMPs)-in myocardia and aortas of spontaneously hypertensive rats (SHRs) and (2) the response of cardiovascular tissue to AM. The AM content and cyclic adenosine monophosphate (cAMP) production in myocardia and aortas were measured in SHRs and Wistar Kyoto (WKY) rats (11-week-old) by radioimmunoassay (RIA). The mRNA levels of brain natriuretic peptide (BNP), AM, CL, RAMP1, -2, -3 were determined by semi-quantitative RTPCR. Protein levels of CL, RAMP1, -2, -3 were assayed by Western blotting. SHRs had severe hypertension, and the tail-blood pressure was 76.7% higher, the ratio of heart weight to body weight (heart coefficient) 45.5% higher, and the BNP gene expression 4.5-fold higher than that of WKY rats (all p < 0.01). The AM-ir content in plasma, myocardia and aortas of SHRs increased by 42.5%, 68.3% and 80.4%, respectively (all p < 0.01) compared with WKY rats. Furthermore, the mRNA levels of AM, CL, RAMP1, RAMP2 and RAMP3 were elevated by 46% (p < 0.01), 62% (p < 0.05), 51.2% (p < 0.01), 41% (p < 0.01) and 54% (p < 0.01), respectively, in myocardia and by 72%, 87%, 155%, 53% and 74% (all p < 0.01), respectively, in aortas. The elevated mRNA level of CL, RAMP1 RAMP2 and RAMP3 correlated positively with that of AM mRNA in hypertrophic myocardia (r= 0.943, 0.621, 0.688 and 0.633, respectively, all p < 0.01) and aortas (r = 0.762, 0.892, 0.828 and 0.736, respectively, all p < 0.01). The protein levels of CL, RAMP1, RAMP2 and RAMP3 in myocardia and aortas of SHRs were increased compared with that of WKY rats. The response to AM was potentiated in myocardia and aortas in SHRs, and the production of cAMP was increased by 47% and 65% (both p < 0.01), respectively. AM-stimulated cAMP generation in myocardia and aortas was blocked by both AM(22-52), the specific antagonist of AM, and calcitonin gene-related peptide (CGRP)(8-37), the antagonist of the CGRP1 receptor. In myocardia and aortas of SHRs, the gene expressions and protein levels of AM, CL, RAMP1, RAMP2 and RAMP3 were increased, and the response to AM was potentiat

Topics: Adrenomedullin; Animals; Aorta; Blood Pressure; Blotting, Western; Calcitonin Receptor-Like Protein; Cardiomegaly; Cyclic AMP; Hypertension; Intracellular Signaling Peptides and Proteins; Male; Membrane Proteins; Myocardium; Natriuretic Peptide, Brain; Radioimmunoassay; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Receptor Activity-Modifying Protein 1; Receptor Activity-Modifying Protein 2; Receptor Activity-Modifying Protein 3; Receptor Activity-Modifying Proteins; Receptors, Calcitonin; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Up-Regulation

Intermedin (IMD) is a novel member of the calcitonin/calcitonin gene-related peptide (CGRP). The present study aimed to investigate the cardiovascular effects of IMDs (IMD1-47 and IMD8-47) in rats. Intravenous administration of 150 nmol IMDs continuously decreased mean arterial pressure and inhibited cardiac function. Administration with IMDs decreased left ventricular end-systolic pressure (LVESP) and maximal rate of left-ventricle pressure development (+/-LVdp/dt(max)), and elevated left ventricular end-diastolic pressure (LVEDP). Changes with IMD1-47 treatment were close to that with IMD8-47 (P>0.05). Perfusion of isolated rat hearts in vitro with IMD8-47 (10(-8) and 10(-7)mol/L) resulted in lower LVSP, by 40 and 56% (P<0.01); lower +LVdp/dt (max), by 33 and 47% (P<0.01); lower -LVdp/dt(max), by 25 and 39% (P<0.01); but higher coronary perfusion flow (CPF), by 25% (P<0.05) and 33% (P<0.01), respectively, than controls. However, both IMD8-47 and IMD1-47 (from 10(-13) to 10(-7)mol/L) relaxed preconstricted aortic rings in a dose-dependent manner. Intravenous administration of IMD1-47 and IMD8-47 (10(-7)mol/L) in vivo increased the cyclic adenosine monophosphate (cAMP) content by 68 and 150% (both P<0.01), respectively, in myocardia and 320 and 281% (both P<0.01), respectively, in aortas, compared with controls. Perfusion of isolated hearts with IMD1-47 and IMD8-47 (10(-7)mol/L) enhanced cAMP content by 24% (P<0.05) and 73% (P<0.01), respectively, compared with controls. IMDs inhibited 3H-Leucine incorporation in cardiomyocytes in a concentration-dependent manner. IMD1-47 and IMD8-47 (10(-7) and 10(-8)mol/L) decreased 3H-Leucine incorporation by 12-25% (P<0.01) and 14-18% (P<0.01), respectively. IMD mRNA was detected in cultured neonatal cardiomyocytes and isoproterenol-induced hypertrophic myocardia but not normal myocardia of adult rats. These results suggest that IMD might be a regulatory factor for cardiovascular function and myocardial hypertrophy as a cardiovascular active peptide.

Topics: Adrenomedullin; Animals; Animals, Newborn; Aorta; Blood Pressure; Cardiomegaly; Cardiovascular Physiological Phenomena; Cardiovascular System; Cells, Cultured; Coronary Circulation; Cyclic AMP; Gene Expression; Heart; Heart Rate; Leucine; Male; Muscle Contraction; Muscle, Smooth, Vascular; Myocardium; Myocytes, Cardiac; Neuropeptides; Peptide Fragments; Perfusion; Rats; Rats, Sprague-Dawley; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Ventricular Function, Left

We developed a transgenic (Tg) rat model that overexpresses human proadrenomedullin N-terminal 20 peptide (PAMP) only and then compared the effects of unilateral nephrectomy followed by a high salt diet for five weeks in Tg and wild-type rats. We found that systolic blood pressure was significantly lower in Tg UNX rats and cardiac hypertrophy and myocardial fibrosis was also attenuated in Tg rats. Evaluation of gene expression showed suppression of cardiac local renin-angiotensin system (RAS) in Tg rat. These results suggest that in addition to reducing blood pressure, PAMP suppresses cardiac hypertrophy through negative regulation of the local cardiac RAS.

Topics: Adrenomedullin; Animals; Animals, Genetically Modified; Blood Pressure; Cardiomegaly; Diet; Fibrosis; Humans; Hypertension; Kidney; Myocardium; Peptide Fragments; Protein Precursors; Proteins; Rats; Renin-Angiotensin System; Salts; Transgenes

Experimental pulmonary hypertension induced in a hypobaric hypoxic environment (HHE) is characterized by structural remodeling of the heart and pulmonary arteries. Adrenomedullin (AM) has diuretic, natriuretic, and hypotensive effects. To study the possible effects of HHE on the AM synthesis system, 150 male Wistar rats were housed in a chamber at the equivalent of a 5,500-m altitude level for 21 days. After 14 days of exposure to HHE, pulmonary arterial pressure (PAP) was significantly increased (compared with control rats). The plasma AM protein level was significantly increased on day 21 of exposure to HHE. In the right ventricle (RV), right atrium, and left atrium of the heart, the expressions of AM mRNA and protein were increased in the middle to late phase (5-21 days) of HHE, whereas in the brain and lung they were increased much earlier (0.5-5 days). In situ hybridization and immunohistochemistry showed AM mRNA and protein staining to be more intense in the RV in animals in the middle to late phase of HHE exposure than in the controls. During HHE, these changes in AM synthesis, which occurred strongly in the RV, occurred alongside the increase in PAP. Conceivably, AM may play a role in modulating pulmonary hypertension in HHE.

Topics: Adrenomedullin; Animals; Atmosphere Exposure Chambers; Body Weight; Cardiomegaly; Hematocrit; Hypertension, Pulmonary; Hypoxia; Immunohistochemistry; In Situ Hybridization; Male; Peptides; Pulmonary Wedge Pressure; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger

Adrenomedullin (AM) is a novel vasodilating peptide thought to have important effects on cardiovascular function. The aim of this study was to assess the activity of endogenous AM in the cardiovascular system using AM knockout mice.. Mice heterozygous for an AM-null mutation (AM+/-) and their wild-type littermates were subjected to aortic constriction or angiotensin II (Ang II) infusion. The resultant cardiovascular stress led to increases in heart weight/body weight ratios, left ventricular wall thickness, and perivascular fibrosis, as well as expression of genes encoding angiotensinogen, ACE, transforming growth factor-beta, collagen type I, brain natriuretic peptide, and c-fos. In addition, renal damage characterized by decreased creatinine clearance with glomerular sclerosis was noted. In all cases, the effects were significantly more pronounced in AM+/- mice. Hearts from adult mice subjected to aortic constriction showed enhanced extracellular signal-regulated kinase (ERK) activation, as did cardiac myocytes from neonates treated acutely with Ang II. Again the effect was more pronounced in AM+/- mice, which showed increases in cardiac myocyte size, protein synthesis, and fibroblast proliferation. ERK activation was suppressed by protein kinase C inhibition to a greater degree in AM+/- myocytes. In addition, treatment of cardiac myocytes with recombinant AM suppressed Ang II-induced ERK activation via a protein kinase A-dependent pathway.. Endogenous AM exerts a protective effect against stress-induced cardiac hypertrophy via protein kinase C- and protein kinase A-dependent regulation of ERK activation. AM may thus represent a useful new tool for the treatment of cardiovascular disease.

Topics: Adrenomedullin; Angiotensin II; Angiotensinogen; Animals; Aorta, Abdominal; Cardiomegaly; Collagen Type I; Constriction; Enzyme Activation; Enzyme Inhibitors; Fibroblasts; Fibrosis; Gene Expression Regulation; Genes, fos; Genes, Lethal; Glomerulosclerosis, Focal Segmental; Heterozygote; Male; MAP Kinase Signaling System; Mice; Mice, Knockout; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Mitogen-Activated Protein Kinases; Myocytes, Cardiac; Natriuretic Peptide, Brain; Peptides; Peptidyl-Dipeptidase A; Protein Kinase C; Proto-Oncogene Proteins c-fos; Transforming Growth Factor beta; Ventricular Remodeling

Adrenomedullin (AM) is a potent vasodilating and natriuretic peptide that is thought to play important roles in cardiovascular function. Whether or not AM is involved in the development of cardiac hypertrophy and renal damage remains controversial. In the present study, using heterozygote knockout mice of the AM gene (AM +/-), we analyzed the physiological and pathological roles of the endogenous AM gene. There were no differences in body size or heart and kidney weight compared with wild-type (AM +/+) mice. However, angiotensin II (Ang II) infusion resulted in more severe cardiac hypertrophy in AM +/- mice. The increases in the heart weight-to-body weight ratio and wall thickness of the left ventricle were more prominent in the AM +/- mice. Renal dysfunction characterized by decreased creatinine clearance (C(cr)) was more severe in AM +/- after Ang II infusion. These results suggest that AM plays critical roles in the defense mechanism against cardiac hypertrophy and renal dysfunction. An improved understanding of these roles may pave the way to a novel pharmacological approach for the prevention of cardiovascular diseases.

Topics: Adrenomedullin; Angiotensin II; Animals; Cardiomegaly; Male; Mice; Mice, Knockout; Peptides; Renal Insufficiency; Time Factors; Vasoconstrictor Agents; Vasodilator Agents

To explore the changes in adrenomedullin (ADM) and receptor activity-modifying protein 2 (RAMP2) mRNA in myocardium and vessels in hypertension, a hypertensive rat model was prepared by administering L-NNA. Contents of ADM in plasma, myocardium and vessels were measured by radioimmunoassay (RIA). The levels of pro-ADM mRNA of myocardium and vessels were determined by competitive quantitative RT-PCR. The results showed that L-NNA induced hypertension and cardiomegaly. The ratio of heart to body weight increased by 35.5% (P<0.01). In hypertensive rats the ir-ADM in plasma, myocardium and vessels was increased by 80%, 72% and 57% (P<0.01), respectively compared with the control. The amounts of ADM mRNA in myocardium and vessels were increased by 50% and 109.2% (P<0.05), respectively, and the amounts of RAMP2 mRNA was increased by 132% and 87% (P<0.01), respectively, compared with control. The levels of ADM in myocardium and vessels were positively correlated with RAMP2 mRNA, the correlation coefficients were 0.741 and 0.885 (P<0.01), respectively. The results obtained indicate that in hypertensive rats, ADM is elevated in plasma, myocardium and ves-myocardium and vessel, and ADM and RAMP2 mRNA are up-regulated in myocardium and vessel. The ADM/RAMP2 system may play an important role in the pathogenesis of hypertension.

Topics: Adrenomedullin; Animals; Cardiomegaly; Hypertension; Myocardium; Nitroarginine; Rats; Receptor Activity-Modifying Protein 2; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Up-Regulation

Adrenomedullin (AM) is a potent vasodilator and natriuretic peptide that plays an important role in cardiovascular function. In this study, we employed a somatic gene delivery approach to explore its potential protective role in renovascular hypertension. A single tail vein injection of adenovirus harboring the human AM gene significantly blunted a blood pressure increase that lasted for more than 3 wk in two-kidney one-clip (2K1C) hypertensive rats. The expression of human AM mRNA was detected in the kidney, adrenal gland, heart, lung, and liver, and immunoreactive human AM was detected in the plasma and urine of 2K1C rats after human AM gene delivery. A maximal blood pressure difference of 28 mmHg was observed 10 days after AM gene delivery, compared with that in rats injected with the control virus carrying the LacZ gene. Human AM gene delivery significantly attenuated increases in the ratio of left ventricular weight to heart weight, cardiomyocyte diameter, and fibrosis in the heart, as well as glomerular sclerosis, tubular injuries, and protein casts in the kidney. The beneficial effects of AM gene delivery were accompanied by increased urinary cAMP levels, indicating activation of AM receptors. These findings provide new insights into the role of AM in renovascular hypertension and may have significance in therapeutic applications in cardiovascular diseases.

Topics: Adenoviridae; Adrenomedullin; Animals; Blood Pressure; Cardiomegaly; Disease Models, Animal; Fibrosis; Gene Expression; Gene Transfer Techniques; Genetic Therapy; Glomerulosclerosis, Focal Segmental; Humans; Hypertension, Renovascular; Male; Organ Size; Peptides; Radioimmunoassay; Rats; Rats, Wistar; RNA, Messenger

Adrenomedullin is a potent hypotensive, natriuretic and diuretic peptide that is coexpressed in the heart with its receptor, suggesting that it may have localized actions as a modulator of cardiac function. Although expression of adrenomedullin is upregulated in the pathological heart, its cardiac function has not been clearly elucidated and it is not known whether this represents a common feature of cardiac hypertrophy, nor whether this is restricted to cardiac myocytes. We have determined the direct effects of hypertrophic agents on cardiomyocyte adrenomedullin gene expression and peptide secretion and have examined the effects of adrenomedullin on biochemical markers of cardiomyocyte hypertrophy.. Regulation of adrenomedullin expression and its effects on the hypertrophic response were studied in cultured rat neonatal ventricular cardiomyocytes.. Incubation with phenylephrine or endothelin for 48 h led to a hypertrophic response with an associated fivefold stimulation of ANP gene expression. In contrast, adrenomedullin mRNA was inhibited by 30-50% in response to phenylephrine or endothelin-mediated hypertrophy, and this was associated with a 35-45% reduction in secretion of immunoreactive adrenomedullin. Phorbol ester mediated activation of protein kinase C and increasing intracellular Ca(2+) with ionomycin led to significant downregulation of adrenomedullin gene expression in cardiomyocytes. Co-incubation with 100 nM adrenomedullin for 48 h inhibited phenylephrine-induced cardiomyocyte hypertrophy as determined by protein:DNA ratio. Adrenomedullin partially blocked phenylephrine-mediated transcriptional activation of ANP and MLC-2 reporter gene expression in cardiomyocytes and this effect was mimicked by 2 microM forskolin, suggesting that this response was mediated via the activation of adenylate cyclase.. These data demonstrate that the cardiomyocyte adrenomedullin gene is repressed by phenylephrine or endothelin-mediated hypertrophy. The inhibitory effects of adrenomedullin on the cardiomyocyte hypertrophic response suggests that this peptide acts as a regulated autocrine or paracrine modulator of cardiomyocyte function and that downregulation of adrenomedullin expression may play a role in induction and maintenance of cardiomyocyte hypertrophy.

Topics: Adenylyl Cyclases; Adrenomedullin; Analysis of Variance; Animals; Atrial Natriuretic Factor; Calcium; Cardiomegaly; Cells, Cultured; Colforsin; Endothelin-1; Enzyme Activation; Gene Expression Regulation; Myocardium; Peptides; Phenylephrine; Protein Kinase C; Radioimmunoassay; Rats; Rats, Sprague-Dawley; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Transcription, Genetic

Pressure overload, such as hypertension, to the heart causes pathological cardiac hypertrophy, whereas chronic exercise causes physiological cardiac hypertrophy, which is defined as athletic heart. There are differences in cardiac properties between these two types of hypertrophy. We investigated whether mRNA expression of various cardiovascular regulating factors differs in rat hearts that are physiologically and pathologically hypertrophied, because we hypothesized that these two types of cardiac hypertrophy induce different molecular phenotypes. We used the spontaneously hypertensive rat (SHR group; 19 wk old) as a model of pathological hypertrophy and swim-trained rats (trained group; 19 wk old, swim training for 15 wk) as a model of physiological hypertrophy. We also used sedentary Wistar-Kyoto rats as the control group (19 wk old). Left ventricular mass index for body weight was significantly higher in SHR and trained groups than in the control group. Expression of brain natriuretic peptide, angiotensin-converting enzyme, and endothelin-1 mRNA in the heart was significantly higher in the SHR group than in control and trained groups. Expression of adrenomedullin mRNA in the heart was significantly lower in the trained group than in control and SHR groups. Expression of beta(1)-adrenergic receptor mRNA in the heart was significantly higher in SHR and trained groups than in the control group. Expression of beta(1)-adrenergic receptor kinase mRNA, which inhibits beta(1)-adrenergic receptor activity, in the heart was markedly higher in the SHR group than in control and trained groups. We demonstrated for the first time that the manner of mRNA expression of various cardiovascular regulating factors in the heart differs between physiological and pathological cardiac hypertrophy.

Topics: Actins; Adrenomedullin; Animals; Blood Pressure; Body Weight; Cardiomegaly; Disease Models, Animal; Gene Expression Regulation; Hemodynamics; Natriuretic Peptide, Brain; Peptides; Peptidyl-Dipeptidase A; Phenotype; Physical Conditioning, Animal; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Receptor, Muscarinic M2; Receptors, Adrenergic, beta-1; Receptors, Muscarinic; Reference Values; Swimming; Transcription, Genetic

We investigated the potential roles of adrenomedullin (AM) in cardiovascular and renal function by somatic gene delivery. We showed that a single intravenous injection of the human AM gene under the control of cytomegalovirus promoter/enhancer induces a prolonged delay in blood pressure rise for several weeks in spontaneously hypertensive rats, Dahl salt-sensitive, DOCA-salt, and two-kidney one-clip hypertensive rats as compared to their respective controls injected with a reporter gene. Expression of the human AM transcript was identified in the heart, kidney, lung, liver and aorta of the rat after adenovirus-mediated AM gene delivery by RT-PCR followed by Southern blot analysis. Immunoreactive human AM levels were measured in rat plasma and urine following AM gene delivery. AM gene delivery induced significant reduction of left ventricular mass in these hypertensive animal models. It also reduces urinary protein excretion and increases glomerular filtration rate, renal blood flow and urinary cAMP levels. AM gene transfer attenuated cardiomyocyte diameter and interstitial fibrosis in the heart, and reduced glomerular sclerosis, tubular disruption, protein cast accumulation and renal cell proliferation in the kidney. In the rat model with myocardial ischemia/reperfusion injury, AM gene delivery significantly reduced myocardial infarction, apoptosis, and superoxide production. Furthermore, local AM gene delivery significantly inhibited arterial thickening, promoted re-endothelialization and increased vascular cGMP levels in rat artery after balloon angioplasty. Collectively, these results indicate that human AM gene delivery attenuates hypertension, myocardial infarction, renal injury and cardiovascular remodeling in animal models via cAMP and cGMP signaling pathways. These findings provide new insights into the role of AM in cardiovascular and renal function.

Topics: Adenoviridae; Adrenomedullin; Animals; Cardiomegaly; Cardiomyopathies; Disease Models, Animal; Gene Transfer Techniques; Genetic Therapy; Genetic Vectors; Humans; Hypertension; Kidney Diseases; Male; Myocardial Infarction; Peptides; Rats; Rats, Inbred Dahl; Rats, Inbred SHR; Streptozocin; Tunica Intima; Ventricular Remodeling

We examined whether adrenomedullin (AM), a vasoactive peptide with significant expression and binding sites in the heart, modulates the hypertrophic response in cultured neonatal rat ventricular myocytes. Myocyte hypertrophy was induced by treating the cells with angiotensin II (Ang II), endothelin-1 (ET-1) or alpha-adrenergic agonist, L-phenylephrine (PHE). All treatments resulted in a hypertrophic response as reflected by increased protein synthesis and expression of atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) genes. AM treatment resulted in a complete inhibition of the Ang II-induced increase in ANP and BNP gene expression and secretion. In contrast, no inhibitory effect was seen in either ET-1-induced natriuretic peptide gene expression or PHE-induced ANP and BNP gene expression and secretion. AM had only a modest effect on basal levels of natriuretic peptide secretion and gene expression. When AM mRNA levels in isolated neonatal rat myocytes treated for 48 h with Ang II, ET-1 or PHE were measured, only Ang II induced a consistent increase in AM gene expression. These results indicate that AM is not invariably associated with attenuation of the hypertrophic response but its effect is dependent on the stimulus activating myocyte hypertrophy. AM may form an important autocrine/paracrine growth-inhibitory loop in Ang II-induced myocyte hypertrophy.

Topics: Adrenomedullin; Angiotensin II; Animals; Atrial Natriuretic Factor; Cardiomegaly; Cyclic AMP; Cyclic GMP; Drug Interactions; Endothelin-1; Gene Expression; Heart; Heart Ventricles; In Vitro Techniques; Myocardium; Natriuretic Peptide, Brain; Peptides; Phenylephrine; Rats; Sarcomeres

Plasma adrenomedullin (AM) has been shown to increase in the early phase of acute myocardial infarction (MI). However, little information is available regarding cardiac AM synthesis after MI. Accordingly, we examined the time course of ventricular AM production and potential stimulation of AM in the infarcted and noninfarcted regions in MI rats produced by coronary artery ligation. Compared with sham-operated rats, the ventricular AM peptide level 6 h after MI increased 1.5-fold in the infarcted region and 1.7-fold in the noninfarcted region in association with increased left ventricular end-diastolic pressure (EDP). Northern blot analysis also showed marked induction of AM gene expression in the infarcted region (11-fold) and the noninfarcted region (6-fold) 6 h after MI. The AM peptide level in the infarcted region reached its peak (2. 6-fold) 1 wk postinfarction and thereafter decreased to normal. In the noninfarcted region, however, the AM level remained elevated for at least 4 wk. Immunohistochemical studies demonstrated that intense immunostaining for AM was limited to myocytes in both the infarcted and noninfarcted regions. Interestingly, the AM level in the noninfarcted region correlated positively with infarct size (r = 0. 40, P < 0.01) and EDP (r = 0.52, P < 0.001). An oral angiotensin-converting enzyme inhibitor suppressed the overproduction of AM 1 wk postinfarction in association with decreases in EDP and mean arterial pressure. In summary, cardiac AM synthesis was rapidly induced in both the infarcted and noninfarcted regions after MI. The subsequent ventricular AM in the two regions demonstrated different time-concentration curves during 4 wk after MI. AM may be synthesized predominantly by cardiac myocytes, but not by fibroblasts, at least in part, in association with increased ventricular load after MI.

Topics: Adrenomedullin; Angiotensin-Converting Enzyme Inhibitors; Animals; Cardiomegaly; Gene Expression; Male; Muscle Fibers, Skeletal; Myocardial Infarction; Myocardium; Organ Size; Peptides; Rats; Rats, Wistar; RNA, Messenger; Ventricular Function, Left; Ventricular Remodeling

Adrenomedullin (AM) is a potent vasodilator expressed in tissues relevant to cardiac and renal functions. Our previous study showed that delivery of the human AM gene in the form of naked DNA caused a prolonged reduction of blood pressure in genetically hypertensive rats. In this study, we evaluated potential protective effects of adenovirus-mediated AM gene delivery on salt-induced cardiorenal lesions in hypertensive Dahl saltsensitive (DSS) rats. Adenovirus carrying the human AM cDNA under the control of the cytomegalovirus promoter-enhancer (Ad.CMV-hAM) was generated by homologous recombination of E. coli. Expression of recombinant human AM was detected by a radioimmunoassay in the medium of human embryonic kidney 293 cells transfected with Ad.CMV-hAM. A single intravenous injection of Ad.CMV-hAM caused a significant reduction of systolic blood pressure for 4 weeks in DSS rats compared with control rats with or without injection of adenovirus carrying the green fluorescent protein gene. AM gene delivery significantly reduced left ventricular mass and urinary protein, increased cAMP levels, and enhanced renal function as evidenced by increases in glomerular filtration rate and renal blood flow. Morphological investigations showed that AM gene transfer reduced cardiomyocyte diameter and interstitial fibrosis in the heart as well as glomerular sclerosis, tubular disruption, and protein cast accumulation in the kidney. Expression of human AM mRNA was identified in rat heart, kidney, lung, liver, and aorta, and immunoreactive human AM levels were measured in rat plasma and urine. These results indicate that human AM gene delivery protects against salt-induced hypertension and cardiac and renal lesions in DSS rats via activation of cAMP as a second messenger. These findings provide new insights into the role of AM in salt-induced hypertension and may have implications in therapeutic applications to salt-related cardiovascular and renal diseases.

Topics: Adenoviridae; Adrenomedullin; Animals; Blood Pressure; Cardiomegaly; Cell Line; Cyclic AMP; Fibrosis; Genetic Therapy; Humans; Hypertension; Kidney; Kidney Function Tests; Male; Peptides; Proteinuria; Rats; Rats, Inbred Dahl; Recombinant Proteins; Salts

Adrenomedullin (AM) is a potent vasodilator and natriuretic peptide that plays an important role in cardiorenal function. In this study, we explored the potential protective role of AM in volume-dependent hypertension by somatic gene delivery. Adenovirus containing the human AM cDNA under the control of the cytomegalovirus promoter/enhancer was administered into deoxycorticosterone acetate (DOCA)-salt hypertensive rats via tail vein injection. A single injection of the human AM gene resulted in a prolonged reduction of blood pressure with a maximal reduction of 41 mm Hg 9 days after gene delivery. Human AM gene delivery enhanced renal function, as indicated by a 3-fold increase in renal blood flow and a 2-fold increase in glomerular filtration rate (n=5, P<0.05). Histological examination of the kidney revealed a significant reduction in glomerular sclerosis, tubular injury, luminol protein cast accumulation, and interstitial fibrosis as well as urinary protein. Human AM gene delivery caused significant decreases in left ventricular weight and cardiomyocyte diameter, which were accompanied by reduced interstitial fibrosis and extracellular matrix formation within the heart. Expression of human AM mRNA was detected in the kidney, adrenal gland, heart, aorta, lung, and liver; immunoreactive human AM levels were measured in urine and plasma. Significant increases in urinary and cardiac cAMP levels were observed in DOCA-salt rats receiving the human AM gene, indicating activation of the AM receptor. These findings showed that AM gene delivery attenuates hypertension, protects against cardiac remodeling and renal damage in volume-overload hypertension, and may have significance in therapeutic applications in cardiovascular and renal diseases.

Topics: Adenoviridae; Adrenomedullin; Animals; Cardiomegaly; Cyclic AMP; Cyclic GMP; Desoxycorticosterone; Disease Models, Animal; Fibrosis; Gene Transfer Techniques; Genetic Therapy; Genetic Vectors; Humans; Hypertension; Kidney Diseases; Male; Peptides; Rats; Rats, Sprague-Dawley; Systole

To study the effects of long-term treatment with the type 1 angiotensin (AT1) receptor antagonist losartan and the angiotensin-converting enzyme (ACE) inhibitor enalapril, on cardiac adrenomedullin (ADM), atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) gene expression.. Spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats were given losartan (15 mg/kg per day) or enalapril (4 mg/kg per day) orally for 10 weeks. The effects of drugs on systolic blood pressure, cardiac hypertrophy, ANP, BNP and ADM mRNA and immunoreactive-ANP (IR)-ANP, IR-BNP and IR-ADM levels in the left ventricle and atria were compared.. Losartan and enalapril treatments completely inhibited the increase of systolic blood pressure occurring with ageing in SHR. The ratio of heart to body weight was reduced in both losartan- and enalapril-treated SHR and WKY rats. Treatment with losartan or enalapril reduced left ventricular ANP mRNA and IR-ANP in both strains, and ventricular BNP mRNA levels in SHR rats. Inhibition of ACE, AT1 receptor antagonism, changes in blood pressure or cardiac mass had no effect on left ventricular ADM gene expression in SHR and WKY rats. In addition, atrial IR-ANP and IR-ADM levels increased in SHR whereas IR-BNP levels decreased in WKY and SHR rats in response to drug treatments.. Our results show that ventricular ADM synthesis is an insensitive marker of changes in haemodynamic load or cardiac hypertrophy. Furthermore, the expression of ADM, ANP and BNP genes is differently regulated both in the left ventricle and atria in response to AT1 receptor antagonism and ACE inhibition.

Topics: Adrenomedullin; Angiotensin Receptor Antagonists; Angiotensin-Converting Enzyme Inhibitors; Animals; Atrial Natriuretic Factor; Blood Pressure; Cardiomegaly; Enalapril; Gene Expression; Heart; Hypertension; Losartan; Male; Natriuretic Peptide, Brain; Peptides; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Receptor, Angiotensin, Type 1; Receptor, Angiotensin, Type 2; Reference Values

1. Adrenomedullin is a recently discovered vasodilating and natriuretic peptide whose physiological and pathophysiological roles remain to be established. Like atrial natiuretic peptide adrenomedullin is expressed in the left ventricle. Ventricular expression of atrial natriuretic peptide is known to be markedly increased by volume or pressure overload. In this study we investigated whether ventricular expression of adrenomedullin is similarly stimulated under such conditions. 2. Ventricular adrenomedullin and atrial natriuretic peptide mRNA levels as well as those of a loading control mRNA (glyceraldehyde-3-phosphate dehydrogenase) were quantified by Northern blot analysis in (a) rats with severe post-infarction heart failure induced by left coronary ligation at 30 days post-surgery and (b) in rats with pressure-related cardiac hypertrophy induced by aortic banding at several time points (0.5, 1 and 4 h, and 1, 4, 7 and 28 days) after surgery. Levels were compared with those in matched sham-operated controls. 3. The mRNA level of atrial natriuretic peptide was markedly increased (8-10-fold) in the left ventricle of animals with post-infarction heart failure. In contrast, there was only a modest (40%) increase in the level of adrenomedullin mRNA. In rats with pressure-induced cardiac hypertrophy the ventricular level of atrial natriuretic peptide mRNA was again markedly increased (maximum 10-fold). The increase was first noticeable at 24 h post-banding and persisted until 28 days. In contrast, there was no change in adrenomedullin mRNA level compared with sham-operated rats at any time point. 4. Despite having similar systemic effects, the expression of adrenomedullin and atrial natriuretic peptide in the left ventricle is differently regulated. The findings imply distinct roles for the two peptides. The results do not support an important role for ventricular adrenomedullin expression in the remodelling process that occurs during the development of cardiac hypertrophy but suggest that ventricular adrenomedullin participates in the local and/or systemic response to heart failure.

Topics: Adrenomedullin; Animals; Atrial Natriuretic Factor; Blotting, Northern; Cardiomegaly; Gene Expression Regulation; Heart Failure; Heart Ventricles; Male; Myocardium; Peptides; Rats; Rats, Inbred WKY; Rats, Wistar; RNA, Messenger

The aim of this study was to investigate the relationships between levels of natriuretic peptides and adrenomedullin and 24 h blood pressure levels in elderly hypertensives.. We performed both 24 h ambulatory blood pressure monitoring and measurement of plasma levels of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and adrenomedullin in 118 asymptomatic hypertensive elderly (> 60 years old) patients. We classified the subjects into groups with isolated clinic hypertension (n = 40) and sustained hypertension (n = 78). We also measured the levels of these peptides in 37 elderly normotensive subjects.. Plasma ANP and BNP levels were slightly increased in patients with isolated clinic hypertension compared with elderly normotensives. Among the hypertensives, plasma ANP and BNP levels were more closely related to 24 h blood pressure levels than to office blood pressure levels. Sustained hypertensives showed significantly increased plasma levels of ANP and BNP compared with isolated clinic hypertensives, while adrenomedullin levels were similar in the two groups. Elderly hypertensives with left ventricular hypertrophy detected by electrocardiography had significantly higher levels of ANP and BNP, and higher BNP/ANP ratios than those without left ventricular hypertrophy, while there was no significant difference in adrenomedullin levels between the two groups.. Our results suggest that measurements of ANP and BNP may be useful in detecting left ventricular hypertrophy and in differentiating isolated clinic hypertension from sustained hypertension in elderly hypertensive patients.

Topics: Adrenomedullin; Aged; Atrial Natriuretic Factor; Blood Pressure; Cardiomegaly; Circadian Rhythm; Echocardiography; Female; Humans; Hypertension; Male; Middle Aged; Natriuretic Peptide, Brain; Peptides

It has been reported that plasma concentrations of adrenomedullin (AM), a novel vasodilator peptide, are higher in patients with essential hypertension than those in normotensive subjects. To clarify the clinical significance of increased levels of AM in patients with essential hypertension, in this study we examined the relationship between plasma concentrations of AM and the structure of the left ventricle or carotid artery. Plasma AM concentrations; renin activity; and norepinephrine, epinephrine, and creatinine concentrations in 50 patients with untreated essential hypertension without renal dysfunction and heart failure were measured. We also measured the mean wall thickness of the left ventricle and left ventricular mass index by M-mode echocardiography and intimal-medial thickness and arterial distensibility of the carotid artery by ultrasonography. Hypertensive patients were divided into two groups: hypertensives with and those without left ventricular hypertrophy. Plasma AM concentrations in hypertensive patients with left ventricular hypertrophy were significantly higher than in hypertensive patients without left ventricular hypertrophy (7.87+/-2.70 vs 5.74+/-1.65 fmol/mL, P<.01). In all hypertensive patients, plasma AM concentrations were not correlated with blood pressure, plasma renin activity, plasma norepinephrine, plasma epinephrine, or plasma creatinine concentration. Plasma AM concentrations were positively correlated with left ventricular mass index or mean wall thickness (r=.37, P=.009; r=.40, P=.004, respectively) and inversely correlated with carotid artery distensibility (r=-.33, P=.02), whereas plasma AM concentrations were not correlated with intimal-medial thickness. These results suggest that the observed elevation of plasma AM in patients with essential hypertension with normal renal function may be partly related to cardiac hypertrophy and decreased carotid artery distensibility.

Topics: Adrenomedullin; Adult; Aged; Cardiomegaly; Carotid Arteries; Female; Humans; Hypertension; Hypertrophy; Male; Middle Aged; Peptides