Expression of C-type natriuretic peptide and of its receptor NPR-B in normal and failing heart

Cardiomyocyte-derived C-type natriuretic peptide diminishes myocardial ischaemic injury by promoting revascularisation and limiting fibrotic burden

BACKGROUND

C-type natriuretic peptide (CNP) is a significant player in the maintenance of cardiac and vascular homeostasis regulating local blood flow, platelet and leukocyte activation, heart structure and function, angiogenesis and metabolic balance. Since such processes are perturbed in myocardial infarction (MI), we explored the role of cardiomyocyte-derived CNP, and pharmacological administration of the peptide, in offsetting the pathological consequences of MI.

METHODS

Wild type (WT) and cardiomyocyte-restricted CNP null (cmCNP-/-) mice were subjected to left anterior descending coronary artery (LADCA) ligation and acute effects on infarct size and longer-term outcomes of cardiac repair explored. Heart structure and function were assessed by combined echocardiographic and molecular analyses. Pharmacological administration of CNP (0.2 mg/kg/day; s.c.) was utilized to assess therapeutic potential.

RESULTS

Compared to WT littermates, cmCNP-/- mice had a modestly increased infarct size following LADCA ligation but without significant deterioration of cardiac structural and functional indices. However, cmCNP-/- animals exhibited overtly worse heart morphology and contractility 6 weeks following MI, with particularly deleterious reductions in left ventricular ejection fraction, dilatation, fibrosis and revascularization. This phenotype was largely recapitulated in animals with global deletion of natriuretic peptide receptor (NPR)-C (NPR-C-/-). Pharmacological administration of CNP rescued the deleterious pathology in WT and cmCNP-/-, but not NPR-C-/-, animals.

CONCLUSIONS AND IMPLICATIONS

Cardiomyocytes synthesize and release CNP as an intrinsic protective mechanism in response to MI that reduces cardiac structural and functional deficits; these salutary actions are primarily NPR-C-dependent. Pharmacological targeting of CNP may represent a new therapeutic option for MI.

Exploring PKG signaling as a therapeutic avenue for pressure overload, ischemia, and HFpEF

INTRODUCTION

Heart failure (HF) is a complex and heterogeneous syndrome resulting from any diastolic or systolic dysfunction of the cardiac muscle. In addition to comorbid conditions, pressure overload, and myocardial ischemia are associated with cardiac remodeling which manifests as extracellular matrix (ECM) perturbations, impaired cellular responses, and subsequent ventricular dysfunction.

AREAS COVERED

The current review discusses the main aspects of the cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG) pathway (cGMP-PKG) pathway modulators and highlights the promising outcomes of its novel pharmacological boosters.

EXPERT OPINION

Among several signaling pathways involved in the pathogenesis of pressure overload, ischemia and HF with preserved ejection fraction (HFpEF) is cGMP-PKG pathway. This pathway plays a pivotal role in the regulation of cardiac contractility, and modulation of cGMP-PKG signaling, contributing to the development of the diseases. Ventricular cardiomyocytes of HF patients and animal models are known to exhibit reduced cGMP levels and disturbed cGMP signaling including hypophosphorylation of PKG downstream targets. However, restoration of cGMP-PKG signaling improves cardiomyocyte function and promotes cardioprotective effects.

C-type natriuretic peptide (CNP): The cardiovascular system and beyond

C-type natriuretic peptide (CNP) represents the 'local' member of the natriuretic peptide family, functioning in an autocrine or paracrine capacity to modulate a hugely diverse portfolio of physiological processes. Whilst the best-characterised of these regulatory roles are in the cardiovascular system, akin to its predominantly endocrine siblings atrial (ANP) and brain (BNP) natriuretic peptides, CNP governs many additional, unrelated mechanisms including bone growth, gamete maturation, auditory processing, and neuronal integrity. Furthermore, there is currently great interest in mimicking the biological activity of CNP for therapeutic gain in many of these disparate organ systems. Herein, we provide an overview of the physiology, pathophysiology and pharmacology of CNP in both cardiovascular and non-cardiovascular settings.

leptin b and its regeneration enhancer illustrate the regenerative features of zebrafish hearts

BACKGROUND

Zebrafish possess a remarkable regenerative capacity, which is mediated by the induction of various genes upon injury. Injury-dependent transcription is governed by the tissue regeneration enhancer elements (TREEs). Here, we utilized leptin b (lepb), an injury-specific factor, and its TREE to dissect heterogeneity of noncardiomyocytes (CMs) in regenerating hearts.

RESULTS

Our single-cell RNA sequencing (scRNA-seq) analysis demonstrated that the endothelium/endocardium(EC) is activated to induce distinct subpopulations upon injury. We demonstrated that lepb can be utilized as a regeneration-specific marker to subset injury-activated ECs. lepb+ ECs robustly induce pro-regenerative factors, implicating lepb+ ECs as a signaling center to interact with other cardiac cells. Our scRNA-seq analysis identified that lepb is also produced by subpopulation of epicardium (Epi) and epicardium-derived cells (EPDCs). To determine whether lepb labels injury-emerging non-CM cells, we tested the activity of lepb-linked regeneration enhancer (LEN) with chromatin accessibility profiles and transgenic lines. While nondetectable in uninjured hearts, LEN directs EC and Epi/EPDC expression upon injury. The endogenous LEN activity was assessed using LEN deletion lines, demonstrating that LEN deletion abolished injury-dependent expression of lepb, but not other nearby genes.

CONCLUSIONS

Our integrative analyses identify regeneration-emerging cell-types and factors, leading to the discovery of regenerative features of hearts.

Natriuretic Peptide Receptor B Protects Against Atrial Fibrillation by Controlling Atrial cAMP Via Phosphodiesterase 2

BACKGROUND

β-AR (β-adrenergic receptor) stimulation regulates atrial electrophysiology and Ca2+ homeostasis via cAMP-dependent mechanisms; however, enhanced β-AR signaling can promote atrial fibrillation (AF). CNP (C-type natriuretic peptide) can also regulate atrial electrophysiology through the activation of NPR-B (natriuretic peptide receptor B) and cGMP-dependent signaling. Nevertheless, the role of NPR-B in regulating atrial electrophysiology, Ca2+ homeostasis, and atrial arrhythmogenesis is incompletely understood.

METHODS

Studies were performed using atrial samples from human patients with AF or sinus rhythm and in wild-type and NPR-B-deficient (NPR-B+/-) mice. Studies were conducted in anesthetized mice by intracardiac electrophysiology, in isolated mouse atrial preparations using high-resolution optical mapping, in isolated mouse and human atrial myocytes using patch-clamping and Ca2+ imaging, and in mouse and human atrial tissues using molecular biology.

RESULTS

Atrial NPR-B protein levels were reduced in patients with AF, and NPR-B+/- mice were more susceptible to AF. Atrial cGMP levels and PDE2 (phosphodiesterase 2) activity were reduced in NPR-B+/- mice leading to larger increases in atrial cAMP in the presence of the β-AR agonist isoproterenol. NPR-B+/- mice displayed larger increases in action potential duration and L-type Ca2+ current in the presence of isoproterenol. This resulted in the occurrence of spontaneous sarcoplasmic reticulum Ca2+ release events and delayed afterdepolarizations in NPR-B+/- atrial myocytes. Phosphorylation of the RyR2 (ryanodine receptor) and phospholamban was increased in NPR-B+/- atria in the presence of isoproterenol compared with the wildtypes. C-type natriuretic peptide inhibited isoproterenol-stimulated L-type Ca2+ current through PDE2 in mouse and human atrial myocytes.

CONCLUSIONS

NPR-B protects against AF by preventing enhanced atrial responses to β-adrenergic receptor agonists.

NPRC deletion attenuates cardiac fibrosis in diabetic mice by activating PKA/PKG and inhibiting TGF-β1/Smad pathways

Cardiac fibrosis plays a key role in the progression of diabetic cardiomyopathy (DCM). Previous studies demonstrated the cardioprotective effects of natriuretic peptides. However, the effects of natriuretic peptide receptor C (NPRC) on cardiac fibrosis in DCM remains unknown. Here, we observed that myocardial NPRC expression was increased in mice and patients with DCM. NPRC-/- diabetic mice showed alleviated cardiac fibrosis, as well as improved cardiac function and remodeling. NPRC knockdown in both cardiac fibroblasts and cardiomyocytes decreased collagen synthesis and proliferation of cardiac fibroblasts. RNA sequencing identified that NPRC deletion up-regulated the expression of TGF-β-induced factor homeobox 1 (TGIF1), which inhibited the phosphorylation of Smad2/3. Furthermore, TGIF1 up-regulation was mediated by the activation of cAMP/PKA and cGMP/PKG signaling induced by NPRC deletion. These findings suggest that NPRC deletion attenuated cardiac fibrosis and improved cardiac remodeling and function in diabetic mice, providing a promising approach to the treatment of diabetic cardiac fibrosis.

Physiological and Pathophysiological Effects of C-Type Natriuretic Peptide on the Heart

Simple Summary

C-type natriuretic peptide (CNP) is the third member of the natriuretic peptide family. Unlike atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), CNP was not previously regarded as an important cardiac modulator. However, recent studies have revealed the physiological and pathophysiological importance of CNP in the heart; in concert with its cognate natriuretic peptide receptor-B (NPR-B), CNP has come to be regarded as the major heart-protective natriuretic peptide in the failed heart. In this review, I introduce the history of research on CNP in the cardiac field.

Abstract

C-type natriuretic peptide (CNP) is the third member of the natriuretic peptide family. Unlike other members, i.e., atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), which are cardiac hormones secreted from the atrium and ventricle of the heart, respectively, CNP is regarded as an autocrine/paracrine regulator with broad expression in the body. Because of its low expression levels compared to ANP and BNP, early studies failed to show its existence and role in the heart. However, recent studies have revealed the physiological and pathophysiological importance of CNP in the heart; in concert with the distribution of its specific natriuretic peptide receptor-B (NPR-B), CNP has come to be regarded as the major heart-protective natriuretic peptide in the failed heart. NPR-B generates intracellular cyclic guanosine 3′,5′-monophosphate (cGMP) upon CNP binding, followed by various molecular effects including the activation of cGMP-dependent protein kinases, which generates diverse cytoprotective actions in cardiomyocytes, as well as in cardiac fibroblasts. CNP exerts negative inotropic and positive lusitropic responses in both normal and failing heart models. Furthermore, osteocrin, the intrinsic and specific ligand for the clearance receptor for natriuretic peptides, can augment the effects of CNP and may supply a novel therapeutic strategy for cardiac protection.

C-type natriuretic peptide in childhood obesity

According to the World Health Organization obesity is the result of an energy imbalance between calories assumed and expended and over the past 30 years its incidence has dramatically increased. Recently, the problem of obesity has drastically increased also in childhood, assuming a social relevance. Childhood obesity, in fact, increases the possibility to be obese in adulthood, representing a risk for cardiovascular morbidity and mortality. Aim of this review was to carry out a revision of the literature on childhood obesity focusing on natriuretic peptides (NPs) and in particular on the role of C-type natriuretic peptide (CNP). In obesity NPs play a fundamental role in the regulation of body weight and energy metabolism. Data on plasma CNP levels in children are scarce. The review of the literature relating to the role of CNP in adolescents showed a progressive reduction in the CNP plasma levels in overweight/obese adolescents compared to normal-weight subjects, as previously observed in obese adults, as well as a different modulation in CNP mRNA expression. An independent association between CNP levels and obesity as well as a significant association with the endothelial dysfunction index was reported, indicating that the peptide could play a very important role as a marker of risk of developing obesity. The results of these studies indicate the importance of adopting healthy lifestyles to improve glucometabolic control as well as to provide the rationale for designing and developing new drugs to modulate the NPs system.

Natriuretic peptide receptor B maintains heart rate and sinoatrial node function via cyclic GMP-mediated signaling

AIMS

Heart rate (HR) is a critical indicator of cardiac performance that is determined by sinoatrial node (SAN) function and regulation. Natriuretic peptides, including C-type NP (CNP) have been shown to modulate ion channel function in the SAN when applied exogenously. CNP is the only NP that acts as a ligand for natriuretic peptide receptor-B (NPR-B). Despite these properties, the ability of CNP and NPR-B to regulate HR and intrinsic SAN automaticity in vivo, and the mechanisms by which it does so, are incompletely understood. Thus, the objective of this study was to determine the role of NPR-B signaling in regulating HR and SAN function.

METHODS AND RESULTS

We have used NPR-B deficient mice (NPR-B+/-) to study HR regulation and SAN function using telemetry in conscious mice, intracardiac electrophysiology in anesthetized mice, high resolution optical mapping in isolated SAN preparations, patch-clamping in isolated SAN myocytes, and molecular biology in isolated SAN tissue. These studies demonstrate that NPR-B+/- mice exhibit slow HR, increased corrected SAN recovery time, and slowed SAN conduction. Spontaneous AP firing frequency in isolated SAN myocytes was impaired in NPR-B+/- mice due to reductions in the hyperpolarization activated current (If) and L-type Ca2+ current (ICa,L). If and ICa,L were reduced due to lower cGMP levels and increased hydrolysis of cAMP by phosphodiesterase 3 (PDE3) in the SAN. Inhibiting PDE3 or restoring cGMP signaling via application of 8-Br-cGMP abolished the reductions in cAMP, AP firing, If, and ICa,L, and normalized SAN conduction, in the SAN in NPR-B+/- mice. NPR-B+/- mice did not exhibit changes in SAN fibrosis and showed no evidence of cardiac hypertrophy or changes in ventricular function.

CONCLUSIONS

NPR-B plays an essential physiological role in maintaining normal HR and SAN function by modulating ion channel function in SAN myocytes via a cGMP/PDE3/cAMP signaling mechanism.

Piezo1 Mechanosensitive Ion Channel Mediates Stretch-Induced Nppb Expression in Adult Rat Cardiac Fibroblasts

In response to stretch, cardiac tissue produces natriuretic peptides, which have been suggested to have beneficial effects in heart failure patients. In the present study, we explored the mechanism of stretch-induced brain natriuretic peptide (Nppb) expression in cardiac fibroblasts. Primary adult rat cardiac fibroblasts subjected to 4 h or 24 h of cyclic stretch (10% 1 Hz) showed a 6.6-fold or 3.2-fold (p < 0.05) increased mRNA expression of Nppb, as well as induction of genes related to myofibroblast differentiation. Moreover, BNP protein secretion was upregulated 5.3-fold in stretched cardiac fibroblasts. Recombinant BNP inhibited TGFβ1-induced Acta2 expression. Nppb expression was >20-fold higher in cardiomyocytes than in cardiac fibroblasts, indicating that cardiac fibroblasts were not the main source of Nppb in the healthy heart. Yoda1, an agonist of the Piezo1 mechanosensitive ion channel, increased Nppb expression 2.1-fold (p < 0.05) and significantly induced other extracellular matrix (ECM) remodeling genes. Silencing of Piezo1 reduced the stretch-induced Nppb and Tgfb1 expression in cardiac fibroblasts. In conclusion, our study identifies Piezo1 as mediator of stretch-induced Nppb expression, as well as other remodeling genes, in cardiac fibroblasts.

Cardiac morphological and functional changes induced by C-type natriuretic peptide are different in normotensive and spontaneously hypertensive rats

OBJECTIVE

Inflammation and fibrosis are key mechanisms in cardiovascular remodeling. C-type natriuretic peptide (CNP) is an endothelium-derived factor with a cardiovascular protective role, although its in-vivo effect on cardiac remodeling linked to hypertension has not been investigated. The aim of this study was to determine the effects of chronic administration of CNP on inflammatory and fibrotic cardiac mechanisms in normotensive Wistar rats and spontaneously hypertensive rats (SHR).

METHODS

Twelve-week-old male SHR and normotensive rats were infused with CNP (0.75 μg/h/100 g) or isotonic saline (NaCl 0.9%) for 14 days (subcutaneous micro-osmotic pumps). Echocardiograms and electrocardiograms were performed, and SBP was measured. After treatment, transforming growth factor-beta 1, Smad proteins, tumor necrosis factor-alpha, interleukin-1 and interleukin-6, nitric oxide (NO) system and 2-thiobarbituric acid-reactive substances were evaluated in left ventricle. Histological studies were also performed.

RESULTS

SHR showed lower cardiac output with signs of fibrosis and hypertrophy in left ventricle, higher NO-system activity and more oxidative damage, as well as higher pro-inflammatory and pro-fibrotic markers than normotensive rats. Chronic CNP treatment-attenuated hypertension and ventricular hypertrophy in SHR, with no changes in normotensive rats. In left ventricle, CNP induced an anti-inflammatory and antifibrotic response, decreasing both pro-fibrotic and pro-inflammatory cytokines in SHR. In addition, CNP reduced oxidative damage as well as collagen content, and upregulated the NO system in both groups.

CONCLUSION

Chronic CNP treatment appears to attenuate hypertension and associated end-organ damage in the heart by reducing inflammation and fibrosis.

Multiplicity of Nitric Oxide and Natriuretic Peptide Signaling in Heart Failure

Heart failure (HF) is a common consequence of several cardiovascular diseases and is understood as a vicious cycle of cardiac and hemodynamic decline. The current inventory of treatments either alleviates the pathophysiological features (eg, cardiac dysfunction, neurohumoral activation, and ventricular remodeling) and/or targets any underlying pathologies (eg, hypertension and myocardial infarction). Yet, since these do not provide a cure, the morbidity and mortality associated with HF remains high. Therefore, the disease constitutes an unmet medical need, and novel therapies are desperately needed. Cyclic guanosine-3',5'-monophosphate (cGMP), synthesized by nitric oxide (NO)- and natriuretic peptide (NP)-responsive guanylyl cyclase (GC) enzymes, exerts numerous protective effects on cardiac contractility, hypertrophy, fibrosis, and apoptosis. Impaired cGMP signaling, which can occur after GC deactivation and the upregulation of cyclic nucleotide-hydrolyzing phosphodiesterases (PDEs), promotes cardiac dysfunction. In this study, we review the role that NO/cGMP and NP/cGMP signaling plays in HF. After considering disease etiology, the physiological effects of cGMP in the heart are discussed. We then assess the evidence from preclinical models and patients that compromised cGMP signaling contributes to the HF phenotype. Finally, the potential of pharmacologically harnessing cardioprotective cGMP to rectify the present paucity of effective HF treatments is examined.

Cardiac Endocrinology: Heart-Derived Hormones in Physiology and Disease

The heart plays a central role in the circulatory system and provides essential oxygen, nutrients, and growth factors to the whole organism. The heart can synthesize and secrete endocrine signals to communicate with distant target organs. Studies of long-known and recently discovered heart-derived hormones highlight a shared theme and reveal a unified mechanism of heart-derived hormones in coordinating cardiac function and target organ biology. This paper reviews the biochemistry, signaling, function, regulation, and clinical significance of representative heart-derived hormones, with a focus on the cardiovascular system. This review also discusses important and exciting questions that will advance the field of cardiac endocrinology.

The Novel Inodilator ORM-3819 Relaxes Isolated Porcine Coronary Arteries: Role of Voltage-Gated Potassium Channel Activation

Relaxation and changes in the transmembrane potential of vascular smooth muscle induced by ORM-3819, a novel inodilating compound, were investigated in isolated porcine coronary arteries. Isometric tone was studied on arterial rings precontracted by KCl (30 mM), and resting membrane potential was investigated by a conventional microelectrode technique. ORM-3819 in the concentration range 0.38-230.6 µM evoked concentration-dependent relaxation with a maximum value of 58.1% and an effective concentration of the relaxing substance that caused 50% of maximum relaxation of 72.2 µM. The maximum hyperpolarization produced by ORM-3819 at a concentration of 120 µM (-2.6 ± 0.81 mV, N = 10) did not differ significantly from that induced by C-type natriuretic peptide (CNP), an endogenous hyperpolarizing mediator, at a concentration of 1.4 µM (-3.6 ± 0.38 mV, N = 17). The same effect elicited by the known inodilator levosimendan was less pronounced at a concentration of 3.7 µM: -1.82 ± 0.44 mV, N = 22 (P < 0.05 vs. CNP). The voltage-gated potassium channel inhibitor 4-aminopyridine, at a concentration of 5 mM, attenuated the relaxation induced by ORM-3819 at concentrations of 41.6 or 117.2 µM. These results suggest that ORM-3819 is a potent vasodilating agent able to relieve coronary artery vasospasm by causing hyperpolarization of vascular smooth muscle cells through processes involving activation of voltage-gated potassium channels.

C-type natriuretic peptide co-ordinates cardiac structure and function

AIMS

C-type natriuretic peptide (CNP) is an essential endothelium-derived signalling species that governs vascular homoeostasis; CNP is also expressed in the heart but an intrinsic role for the peptide in cardiac function is not established. Herein, we employ unique transgenic strains with cell-specific deletion of CNP to define a central (patho)physiological capacity of CNP in maintaining heart morphology and contractility.

METHODS AND RESULTS

Cardiac structure and function were explored in wild type (WT), cardiomyocyte (cmCNP-/-), endothelium (ecCNP-/-), and fibroblast (fbCNP-/-)-specific CNP knockout mice, and global natriuretic peptide receptor (NPR)-B-/-, and NPR-C-/- animals at baseline and in experimental models of myocardial infarction and heart failure (HF). Endothelium-specific deletion of CNP resulted in impaired coronary responsiveness to endothelium-dependent- and flow-mediated-dilatation; changes mirrored in NPR-C-/- mice. Ex vivo, global ischaemia resulted in larger infarcts and diminished functional recovery in cmCNP-/- and NPR-C-/-, but not ecCNP-/-, vs. WT. The cardiac phenotype of cmCNP-/-, fbCNP-/-, and NPR-C-/- (but not ecCNP-/- or NPR-B-/-) mice was more severe in pressure overload- and sympathetic hyperactivation-induced HF compared with WT; these adverse effects were rescued by pharmacological CNP administration in WT, but not NPR-C-/-, mice. At a molecular level, CNP/NPR-C signalling is impaired in human HF but attenuates activation of well-validated pro-hypertrophic and pro-fibrotic pathways.

CONCLUSION

C-type natriuretic peptide of cardiomyocyte, endothelial and fibroblast origins co-ordinates and preserves cardiac structure, function, and coronary vasoreactivity via activation of NPR-C. Targeting NPR-C may prove an innovative approach to treating HF and ischaemic cardiovascular disorders.

Evaluation of transcriptional levels of the natriuretic peptides, endothelin-1, adrenomedullin, their receptors and long non-coding RNAs in rat cardiac tissue as cardiovascular biomarkers of aging

Chronological age is considered one of the major risk factors for cardiovascular disease and mortality. The study aimed to evaluate the transcriptional levels of the natriuretic peptides (NP), endothelin (ET)-1, adrenomedullin (ADM), their receptors and long non-coding (Lnc) RNA MIAT, MALAT-1, CARMEN and XIST in rat cardiac tissue as cardiovascular biomarkers of aging. Three groups of male Wistar rats were studied: A (n = 6; young), B (n = 13; adult), C (n = 10; old). Total RNA was extracted from left ventricle and analyzed by Real-Time PCR. Echocardiographic and histological analyses were performed. A significant increase of Atrial NP (ANP) and Brain NP (BNP) mRNA was observed in C while C-type NP (CNP) remained in a steady-state in B and C; ET-1 mRNA increased significantly as a function of age. Any difference was observed for NP receptors. ETA expression was statistically lower in B than A while ETB were similar in all the three groups. The ADM showed an opposite trend to that of the other peptides decreasing significantly as a function of age and presenting a counter-regulation of calcitonin receptor-like receptor (CLR) and receptor activity modifying protein (RAMP)-2. LncRNA transcripts decreased significantly as a function of age except for XIST. ADM and LncRNA trend suggest that the animals are subjected to "successful aging" as also confirmed by histological analysis. Applying a multivariate logistic regression analysis, only LnANP (p = 0.003) and LnADM (p = 0.023) resulted significantly associated with aging identifying them, for the first time, as independent markers of aging. The study underlining the importance of a multi-label biomolecular approach in the evaluation of aging.

Tuscany Sangiovese grape juice imparts cardioprotection by regulating gene expression of cardioprotective C-type natriuretic peptide

PURPOSE

A regular intake of red grape juice has cardioprotective properties, but its role on the modulation of natriuretic peptides (NPs), in particular of C-type NP (CNP), has not yet been proven. The aims were to evaluate: (1) in vivo the effects of long-term intake of Tuscany Sangiovese grape juice (SGJ) on the NPs system in a mouse model of myocardial infarction (MI); (2) in vitro the response to SGJ small RNAs of murine MCEC-1 under physiological and ischemic condition; (3) the activation of CNP/NPR-B/NPR-C in healthy human subjects after 7 days' SGJ regular intake.

METHODS

(1) C57BL/6J male and female mice (n = 33) were randomly subdivided into: SHAM (n = 7), MI (n = 15) and MI fed for 4 weeks with a normal chow supplemented with Tuscany SGJ (25% vol/vol, 200 µl/per day) (MI + SGJ, n = 11). Echocardiography and histological analyses were performed. Myocardial NPs transcriptional profile was investigated by Real-Time PCR. (2) MCEC-1 were treated for 24 h with a pool of SGJ small RNAs and cell viability under 24 h exposure to H₂O₂ was evaluated by MTT assay. (3) Human blood samples were collected from seven subjects before and after the 7 days' intake of Tuscany SGJ. NPs and miRNA transcriptional profile were investigated by Real-Time PCR in MCEC-1 and human blood.

RESULTS

Our experimental data, obtained in a multimodal pipeline, suggest that the long-term intake of SGJ promotes an adaptive response of the myocardium to the ischemic microenvironment through the modulation of the cardiac CNP/NPR-B/NPR-C system.

CONCLUSIONS

Our results open new avenue in the development of functional foods aimed at enhancing cardioprotection of infarcted hearts through action on the myocardial epigenome.

C-type Natriuretic Peptide: A Multifaceted Paracrine Regulator in the Heart and Vasculature

C-type natriuretic peptide (CNP) is an autocrine and paracrine mediator released by endothelial cells, cardiomyocytes and fibroblasts that regulates vital physiological functions in the cardiovascular system. These roles are conveyed via two cognate receptors, natriuretic peptide receptor B (NPR-B) and natriuretic peptide receptor C (NPR-C), which activate different signalling pathways that mediate complementary yet distinct cellular responses. Traditionally, CNP has been deemed the endothelial component of the natriuretic peptide system, while its sibling peptides, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), are considered the endocrine guardians of cardiac function and blood volume. However, accumulating evidence indicates that CNP not only modulates vascular tone and blood pressure, but also governs a wide range of cardiovascular effects including the control of inflammation, angiogenesis, smooth muscle and endothelial cell proliferation, atherosclerosis, cardiomyocyte contractility, hypertrophy, fibrosis, and cardiac electrophysiology. This review will focus on the novel physiological functions ascribed to CNP, the receptors/signalling mechanisms involved in mediating its cardioprotective effects, and the development of therapeutics targeting CNP signalling pathways in different disease pathologies.

Immunolocalization of natriuretic peptides and their receptors in goat (Capra hircus) heart

Natriuretic peptides are structurally similar, but genetically distinct, hormones that participate in cardiovascular homeostasis by regulating blood and extracellular fluid volume and blood pressure. We investigated the distribution of natriuretic peptides and their receptors in goat (Capra hircus) heart tissue using the peroxidase-anti-peroxidase (PAP) immunohistochemical method. Strong staining of atrial natriuretic peptide (ANP) was observed in atrial cardiomyocytes, while strong staining for brain natriuretic peptide (BNP) was observed in ventricular cardiomyocytes. Slightly stronger cytoplasmic C-type natriuretic peptide (CNP) immunostaining was detected in the ventricles compared to the atria. Natriuretic peptide receptor-A (NPR-A) immunoreactivity was more prominent in the atria, while natriuretic peptide receptor-B (NPR-B) immunoreactivity was stronger in the ventricles. Cytoplasmic natriuretic peptide receptor-C (NPR-C) immunoreactivity was observed in both the atria and ventricles, although staining was more prominent in the ventricles. ANP immunoreactivity ranged from weak to strong in endothelial and vascular smooth muscle cells. Endothelial cells exhibited moderate to strong BNP immunoreactivity, while vascular smooth cells displayed weak to strong staining. Endothelial cells exhibited weak to strong cytoplasmic CNP immunoreactivity. Vascular smooth muscle cells were labeled moderately to strongly for CNP. Weak to strong cytoplasmic NPR-A immunoreactivity was found in the endothelial cells and vascular smooth muscle cells stained weakly to moderately for NPR-A. Endothelial and vascular smooth cells exhibited weak to strong cytoplasmic NPR-B immunoreactivity. Moderate to strong NPR-C immunoreactivity was observed in the endothelial and smooth muscle cells. Small gender differences in the immunohistochemical distribution of natriuretic peptides and receptors were observed. Our findings suggest that endothelial cells, vascular smooth cells and cardiomyocytes express both natriuretic peptides and their receptors.

Natriuretic Peptides and Normal Body Fluid Regulation

Natriuretic peptides are structurally related, functionally diverse hormones. Circulating atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are delivered predominantly by the heart. Two C-type natriuretic peptides (CNPs) are paracrine messengers, notably in bone, brain, and vessels. Natriuretic peptides act by binding to the extracellular domains of three receptors, NPR-A, NPR-B, and NPR-C of which the first two are guanylate cyclases. NPR-C is coupled to inhibitory proteins. Atrial wall stress is the major regulator of ANP secretion; however, atrial pressure changes plasma ANP only modestly and transiently, and the relation between plasma ANP and atrial wall tension (or extracellular volume or sodium intake) is weak. Absence and overexpression of ANP-related genes are associated with modest blood pressure changes. ANP augments vascular permeability and reduces vascular contractility, renin and aldosterone secretion, sympathetic nerve activity, and renal tubular sodium transport. Within the physiological range of plasma ANP, the responses to step-up changes are unimpressive; in man, the systemic physiological effects include diminution of renin secretion, aldosterone secretion, and cardiac preload. For BNP, the available evidence does not show that cardiac release to the blood is related to sodium homeostasis or body fluid control. CNPs are not circulating hormones, but primarily paracrine messengers important to ossification, nervous system development, and endothelial function. Normally, natriuretic peptides are not powerful natriuretic/diuretic hormones; common conclusions are not consistently supported by hard data. ANP may provide fine-tuning of reno-cardiovascular relationships, but seems, together with BNP, primarily involved in the regulation of cardiac performance and remodeling. © 2017 American Physiological Society. Compr Physiol 8:1211-1249, 2018.

Osteopontin in hepatocellular carcinoma: A possible biomarker for diagnosis and follow-up

Recently osteopontin (OPN), a protein of the extracellular matrix, has generated in hepatocellular carcinoma (HCC) a significant interest as a prognostic factor. Aim of this study was to confirm, in liver tissues of subjects with HCV-positive HCC undergoing liver transplantation (RL, n=10) and of donors (DL, n=14), the increase of OPN plasma and tissue concentration, the OPN splicing isoforms expression profiling together with those of thrombin, and to evaluate a possible association between OPN measurements. Their association with Notch-1, IV-Collagen-7s domain, IL-6 and TNF-α were also evaluated. Real-Time PCR experiments and immunometric assay were performed. mRNA expression resulted higher in RL than in DL for all analyzed genes and several correlations were found between them. The more relevant association were between OPN-a and OPN-b (p<0.0001), between thrombin and OPN-a (p=0.007), between 7s-collagen and OPN isoforms (p<0.05) and between Notch-1 with OPN-c (p=0.004). Both OPN plasma and liver tissue extract concentrations were assessed confirming the trend observed at the mRNA level. An important association was found between OPN plasma and protein (p<0.0001, r=0.96) even splitting patients in DL (p<0.0001, r=0.93) and RL (p<0.0001, r=0.96). A reduction of OPN plasma levels was found at 6months after transplantation. Considering MELD score as liver disease severity, the mRNA expression of our markers as well as of OPN plasma and tissue concentrations resulted increased as a function of clinical severity. Our results might be considered a useful starting point to validate OPN as a prognostic and diagnostic marker of HCC.

Elevated C-type natriuretic peptide elicits exercise preconditioning-induced cardioprotection against myocardial injury probably via the up-regulation of NPR-B

To evaluate exercise preconditioning (EP)-induced cardioprotective effects against exercise-induced acute myocardial injury and investigate the alterations of C-type natriuretic peptide (CNP) and its specific receptor, natriuretic peptide receptor B (NPR-B), during EP-induced cardioprotection. Rats were subjected to treadmill exercise as an EP model (4 periods of 10 min each at 30 m/min with intervening periods of rest lasting 10 min). High-intensity exercise was performed 0.5 and 24 h after the EP. EP attenuated high-intensity exercise-induced myocardial injury in both the early and late phases. After EP and high-intensity exercise, CNP and NPR-B levels increased robustly, but no alterations in the plasma CNP were observed. The enhanced NPR-B, plasma and tissue CNP, and its mRNA levels after high-intensity exercise were significantly elevated by EP. These results suggest that cardiac CNP and NPR-B play an important role in EP-mediated cardioprotection against high-intensity exercise-induced myocardial injury in rats.

A Study of Hyponatremia in Acute Encephalitis Syndrome: A Prospective Study From a Tertiary Care Center in India

PURPOSE:

To evaluate the frequency and causes of hyponatremia in acute encephalitis syndrome (AES) and its effect on outcome.

PATIENTS AND METHODS:

Consecutive patients with AES were subjected to neurological evaluation including Glasgow Coma Scale, focal weakness, movement disorder, and reflex changes. The etiology of AES was based on blood and cerebrospinal fluid enzyme-linked immunosorbent assay and polymerase chain reaction. We have categorized patients into neurological or systemic AES. Hyponatremia was diagnosed if 2 consecutive serum sodium levels were below 135 mEq/L, 24 hours apart. Serum and urinary osmolality and electrolytes were measured on alternate days. Fluid intake, output, and body weight were measured daily. The hyponatremia was categorized into syndrome of inappropriate secretion of antidiuretic hormone (SIADH), cerebral salt wasting (CSW), or miscellaneous group. Outcome at 1 month was assessed by modified Rankin scale.

RESULTS:

Of 79 patients, 34 had neurologic AES and 45 had systemic AES; 22 (27.8%) patients had hyponatremia. The neurologic AES as compared to systemic AES was more commonly associated with hyponatremia (38.2% vs 20%, P = .07), need longer hospitalization (25.0 vs 12.5 days, P = .003), and longer time for sodium correction (13.3 vs 8.2 days, P = .05). The hyponatremia was due to CSW in 12 patients, SIADH in 2 patients, and indeterminate in 8 patients. Thirty-six patients had poor outcome (15 died) and 43 had good outcome which was not related to hyponatremia.

CONCLUSION:

Hyponatremia occurs in one-third of patients with AES, being commoner in neurologic AES, and CSW is the commonest cause.

C-type natriuretic peptide and natriuretic peptide receptor B signalling inhibits cardiac sympathetic neurotransmission and autonomic function

Aims

B-type natriuretic peptide (BNP)–natriuretic peptide receptor A (NPR-A) receptor signalling inhibits cardiac sympathetic neurotransmission, although C-type natriuretic peptide (CNP) is the predominant neuropeptide of the nervous system with expression in the heart and vasculature. We hypothesized that CNP acts similarly to BNP, and that transgenic rats (TGRs) with neuron-specific overexpression of a dominant negative NPR-B receptor would develop heightened sympathetic drive.

Methods and results

Mean arterial pressure and heart rate (HR) were significantly (P < 0.05) elevated in freely moving TGRs (n = 9) compared with Sprague Dawley (SD) controls (n = 10). TGR had impaired left ventricular systolic function and spectral analysis of HR variability suggested a shift towards sympathoexcitation. Immunohistochemistry demonstrated co-staining of NPR-B with tyrosine hydroxylase in stellate ganglia neurons. In SD rats, CNP (250 nM, n = 8) significantly reduced the tachycardia during right stellate ganglion stimulation (1–7 Hz) in vitro whereas the response to bath-applied norepinephrine (NE, 1 μM, n = 6) remained intact. CNP (250 nM, n = 8) significantly reduced the release of ³H-NE in isolated atria and this was prevented by the NPR-B antagonist P19 (250 nM, n = 6). The neuronal Ca²⁺ current (n = 6) and intracellular Ca²⁺ transient (n = 9, using fura-2AM) were also reduced by CNP in isolated stellate neurons. Treatment of the TGR (n = 9) with the sympatholytic clonidine (125 µg/kg per day) significantly reduced mean arterial pressure and HR to levels observed in the SD (n = 9).

Conclusion

C-type natriuretic peptide reduces cardiac sympathetic neurotransmission via a reduction in neuronal calcium signalling and NE release through the NPR-B receptor. Situations impairing CNP–NPR-B signalling lead to hypertension, tachycardia, and impaired left ventricular systolic function secondary to sympatho-excitation.

Myocardial Expression Analysis of Osteopontin and Its Splice Variants in Patients Affected by End-Stage Idiopathic or Ischemic Dilated Cardiomyopathy

Osteopontin (OPN) is a phosphoglycoprotein of cardiac extracellular matrix and it is still poorly defined whether its expression changes in failing heart of different origin. The full-length OPN-a and its isoforms (OPN-b, OPN-c) transcriptomic profile were evaluated in myocardium of patients with dilated or ischemic cardiomyopathy (DCM n = 8; LVEF% = 17.5±3; ICM n = 8; LVEF% = 19.5±5.2) and in auricle of valvular patients (VLP n = 5; LVEF%≥50), by Real-time PCR analysis. OPN-a and thrombin mRNA levels resulted significantly higher in DCM compared to ICM patients (DCM:31.3±7.4, ICM:2.7±1.1, p = 0.0002; DCM:19.1±4.9, ICM:5.4±2.2, p = 0.007, respectively). Although both genes’ mRNA levels increased in patients with LVEF<50% (DCM+ICM) with respect to VLP with LVEF>50%, a significant increase in OPN (p = 0.0004) and thrombin (p = 0.001) expression was observed only in DCM. In addition, a correlation between OPN-a and thrombin was found in patients with LVEF<50% (r = 0.6; p = 0.003). The mRNA pattern was confirmed by OPN-a cardiac protein concentration (VLP:1.127±0.26; DCM:1.29±0.22; ICM:1.00±0.077 ng/ml). The OPN splice variants expression were detectable only in ICM (OPN-b: 0.357±0.273; OPN-c: 0.091±0.033) and not in DCM patients. A significant correlation was observed between collagen type I, evaluated by immunohistochemistry analysis, and both OPN-a mRNA expression (r = 0.87, p = 0.002) and OPN protein concentrations (r = 0.77, p = 0.016). Concluding, OPN-a and thrombin mRNA resulted dependent on the origin of heart failure while OPN-b and OPN-c highlighted a different expression for DCM and ICM patients, suggesting their correlation with different clinical-pathophysiological setting.

Molecular Physiology of Membrane Guanylyl Cyclase Receptors

cGMP controls many cellular functions ranging from growth, viability, and differentiation to contractility, secretion, and ion transport. The mammalian genome encodes seven transmembrane guanylyl cyclases (GCs), GC-A to GC-G, which mainly modulate submembrane cGMP microdomains. These GCs share a unique topology comprising an extracellular domain, a short transmembrane region, and an intracellular COOH-terminal catalytic (cGMP synthesizing) region. GC-A mediates the endocrine effects of atrial and B-type natriuretic peptides regulating arterial blood pressure/volume and energy balance. GC-B is activated by C-type natriuretic peptide, stimulating endochondral ossification in autocrine way. GC-C mediates the paracrine effects of guanylins on intestinal ion transport and epithelial turnover. GC-E and GC-F are expressed in photoreceptor cells of the retina, and their activation by intracellular Ca(2+)-regulated proteins is essential for vision. Finally, in the rodent system two olfactorial GCs, GC-D and GC-G, are activated by low concentrations of CO2and by peptidergic (guanylins) and nonpeptidergic odorants as well as by coolness, which has implications for social behaviors. In the past years advances in human and mouse genetics as well as the development of sensitive biosensors monitoring the spatiotemporal dynamics of cGMP in living cells have provided novel relevant information about this receptor family. This increased our understanding of the mechanisms of signal transduction, regulation, and (dys)function of the membrane GCs, clarified their relevance for genetic and acquired diseases and, importantly, has revealed novel targets for therapies. The present review aims to illustrate these different features of membrane GCs and the main open questions in this field.

A study of hyponatremia in tuberculous meningitis

SETTING

In view of paucity of studies on predictors of hyponatremia in tuberculous meningitis (TBM) and its influence on outcome, this study was undertaken.

OBJECTIVE

To study the frequency, predictors and prognosis of hyponatremia in TBM.

DESIGN

In this prospective hospital based study, 76 patients with TBM (definite 18 and probable 58) were enrolled. The severity of meningitis was graded as I-III and hyponatremia as severe (<120mEq/L), moderate (120-129mEq/L) or mild (130-134mEq/L). Hospital death was noted and functional outcome was assessed by modified Rankin Scale (mRS) on discharge.

RESULTS

34 (44.7%) TBM patients had hyponatremia (mild 3, moderate 23 and severe 8). Hyponatremia was due to cerebral salt wasting in 17, syndrome of inappropriate secretion of antidiuretic hormone in 3 and miscellaneous causes in 14 patients. Hyponatremia was related to GCS score and basal exudates. Outcome of TBM was related to duration of hospitalization, GCS score, focal deficit, mechanical ventilation, severity of TBM, age and comorbidities. Cerebral salt wasting was related to severity of TBM.

CONCLUSION

Hyponatremia occurred in 44.7% of TBM patients. Cerebral salt wasting was the commonest cause of hyponatremia and was related to the severity of TBM.

C-Type Natriuretic Peptide Improves Left Ventricular Functional Performance at Rest and Restores Normal Exercise Responses after Heart Failure

In heart failure (HF), the impaired left ventricular (LV) arterial coupling and diastolic dysfunction present at rest are exacerbated during exercise. C-type natriuretic peptide (CNP) is elevated in HF; however, its functional effects are unclear. We tested the hypotheses that CNP with vasodilating, natriuretic, and positive inotropic and lusitropic actions may prevent this abnormal exercise response after HF. We determined the effects of CNP (2 μg/kg plus 0.4 μg/kg per minute, i.v., 20 minutes) on plasma levels of cGMP before and after HF and assessed LV dynamics during exercise in 10 chronically instrumented dogs with pacing-induced HF. Compared with the levels before HF, CNP infusion caused significantly greater increases in cGMP levels after HF. After HF, at rest, CNP administration significantly reduced LV end-systolic pressure (PES), arterial elastance (EA), and end-diastolic pressure. The peak mitral flow (dV/dtmax) was also increased owing to decreased minimum LVP (LVPmin) and the time constant of LV relaxation (τ) (P < 0.05). In addition, LV contractility (EES) was increased. The LV-arterial coupling (EES/EA) was improved. The beneficial effects persisted during exercise. Compared with exercise in HF preparation, treatment with CNP caused significantly less important increases in PES but significantly decreased τ (34.2 vs. 42.6 ms) and minimum left ventricular pressure with further augmented dV/dtmax Both EES, EES/EA (0.87 vs. 0.32) were increased. LV mechanical efficiency improved from 0.38 to 0.57 (P < 0.05). After HF, exogenous CNP produces arterial vasodilatation and augments LV contraction, relaxation, diastolic filling, and LV arterial coupling, thus improving LV performance at rest and restoring normal exercise responses after HF.

NPs/NPRs Signaling Pathways May Be Involved in Depression-Induced Loss of Gastric ICC by Decreasing the Production of mSCF

It is well known that natriuretic peptides (NPs) are involved in the regulation of gastrointestinal motility. Interstitial cells of Cajal (ICC) are the pacemaker cells of gastrointestinal motility and gastrointestinal dyskinesia is one of the important digestive tract symptoms of depression. However, it is unclear whether they are involved in depression-induced loss of ICC. The aim of the present study was to investigate the relationship between the natriuretic peptide signaling pathway and depression-induced loss of gastric ICC in depressed rats. These results showed that the expression of c-kit and stem cell factor (SCF) in smooth muscle layers of stomach were down-regulated in depressed rats at the mRNA and protein levels. The expression of natriuretic peptide receptor (NPR)-A, B and C were up-regulated in the stomach of depressed rats at the mRNA and protein levels. NPR-A, B and C can significantly decrease the expression of SCF to treat cultured gastric smooth muscle cells (GSMCs) obtained from normal rats with different concentrations of C-type natriuretic peptide (CNP). Pretreatment of cultured GSMCs with 8-Brom-cGMP (8-Br-cGMP, a membrane permeable cGMP analog), cANF (a specific NPR-C agonist) and CNP (10⁻⁶ mol/L) demonstrated that 8-Br-cGMP had a similar effect as CNP, but treatment with cANF did not. The results of the methyl thiazolyl tetrazolium bromide (MTT) assay indicated that high concentrations of cANF (10⁻⁶ mol/L) restrained the proliferation of cultured GSMCs. Taken together, these results indicate that the up-regulation of the NPs/NPR-C and NPs/NPR-A, B/cGMP signaling pathways may be involved in depression-induced loss of gastric ICC.

Functional properties of bone marrow derived multipotent mesenchymal stromal cells are altered in heart failure patients, and could be corrected by adjustment of expansion strategies

BACKGROUND

Bone marrow multipotent mesenchymal stromal cells (BM-MMSC) considered as a prospective substrate for cell therapy applications, however adult stem cells could be affected by donor-specific factors: age, gender, medical history. Our aim was to investigate how HF affects the functional properties of BM-MMSC.

MATERIALS AND METHODS

BM-MMSC from 10 healthy donors (HD), and 16 donors with chronic HF were evaluated for proliferative activity, ability to differentiate, replicative senescence, expression of genes that affect regeneration and fibrosis. The effect of culturing conditions on efficiency of BM-MMSC expansion was determined.

RESULTS

HF-derived BM-MMSC demonstrated early decrease of proliferative activity and upregulation of genes that control both, regeneration and fibrosis: Tgf-β pathway, synthesis of ECM, remodeling enzymes, adhesion molecules. We assume that these effects were related to increase of frequency of myofibroblast-like CD146+/SMAα+ CFU-F in HF samples; (ii) low seeding density and hypoxia resulted in predominant purification and expansion of CD146+/SMAα- CFU-Fs. (iii) the activity of NPs system was downregulated in HF BM-MMSC;

CONCLUSIONS

downregulation of NP signaling in combination with upregulation of Tgf-β pathway in BM-MMSC would result in pro-fibrotic phenotype and make these cells non-effective for therapeutic applications; the corrections in culturing strategy resulted in 2(3)-2(7) increase of expansion efficiency.

LCZ696 : a new paradigm for the treatment of heart failure?

INTRODUCTION

Heart failure (HF) represents a significant healthcare issue because of its ever-increasing prevalence, poor prognosis and complex pathophysiology. Currently, blockade of the renin-angiotensin-aldosterone system (RAAS) is the cornerstone of treatment; however, the combination of RAAS blockade with inhibition of neprilysin (NEP), an enzyme that degrades natriuretic peptides, has recently emerged as a potentially superior treatment strategy.

AREAS COVERED

Following the results of the recent Phase III Prospective Comparison of ARNI with ACEI to Determine Impact on Global Mortality and Morbidity in Heart Failure clinical trial in patients with chronic HF with reduced ejection fraction (HF-REF), this review focuses on LCZ696 , a first-in-class angiotensin receptor NEP inhibitor. This drug consists of a supramolecular complex containing the angiotensin receptor inhibitor valsartan in combination with the NEP inhibitor prodrug, AHU377. Following oral administration, the LCZ696 complex dissociates and the NEP inhibitor component is metabolized to the active form (LBQ657). Aspects of the trial that might be relevant to clinical practice are also discussed.

EXPERT OPINION

Speculation that LCZ696 will pass the scrutiny of regulatory agencies for HF-REF appears to be justified, and it is likely to become a core therapeutic component in the near future. Replication of the eligibility criteria and titration protocol used in the PARADIGM-HF trial would be valuable in clinical practice and may minimize the risk of adverse events. Although long-term data remain to be generated, the promising results regarding hypertension are likely to expedite acceptance of the drug for HF-REF.

Altered expression of connexin 43 and related molecular partners in a pig model of left ventricular dysfunction with and without dipyrydamole therapy

Gap junctions (GJ) mediate electrical coupling between cardiac myocytes, allowing the spreading of the electrical wave responsible for synchronized contraction. GJ function can be regulated by modulation of connexon densities on membranes, connexin (Cx) phosphorylation, trafficking and degradation. Recent studies have shown that adenosine (A) involves Cx43 turnover in A1 receptor-dependent manner, and dipyridamole increases GJ coupling and amount of Cx43 in endothelial cells. As the abnormalities in GJ organization and regulation have been described in diseased myocardium, the aim of the present study was to assess the regional expression of molecules involved in GJ regulation in a model of left ventricular dysfunction (LVD). For this purpose the distribution and quantitative expression of Cx43, its phosphorylated form pS368-Cx43, PKC phosphorylated substrates, RhoA and A receptors, were investigated in experimental models of right ventricular-pacing induced LVD, undergoing concomitant dipyridamole therapy or placebo, and compared with those obtained in the myocardium from sham-operated minipigs. Results demonstrate that an altered pattern of factors involved in Cx43-made GJ regulation is present in myocardium of a dysfunctioning left ventricle. Furthermore, dipyridamole treatment, which shows a mild protective role on left ventricular function, seems to act through modulating the expression and activation of these factors as confirmed by in vitro experiments on cardiomyoblastic cell line H9c2 cells.

Adenosine receptor transcriptomic profile in cardiac tissue of a Zucker rat model

To evaluate the possible variations of adenosine receptor (AR) profile together with TNF-α and IL-6 mRNA in cardiac tissue of obese Zucker rats (OZR) during fasting conditions (fc) and during the induction of acute hyperglycemia (AH). OZR (O, n=21) and age-matched lean control rats (CO, n=18) were studied during fc (COfc, n=8; Ofc, n=13) and during the induction of AH (COAH, n=10; OAH, n=8). The histopathologic analysis performed on O and CO heart samples did not show abnormalities of myocardial structure. The AR transcriptomic profile was analyzed in O and CO by real-time polymerase chain reaction (PCR) and a significantly lower mRNA expression was observed for A2AR in O with respect to CO (p=0.047), while a significant upregulation was observed for A3R in O with respect to CO (p=0.002). No significant differences between O and CO were observed for TNF-α or IL-6. Correlations were found between glycemia and A1R (p=0.03) and A2BR (p=0.002); total cholesterol and A2BR (p=0.02) and A3R (p=0.0002), as well as between IL-6 and A1R (p=0.05) and TNF-α and A2AR (p<0.0001). The modulation of ARs in these settings could represent a promising approach to pharmacological treatment, which must be supported by diet restrictions and physical exercise.

Dipyridamole-induced C-type natriuretic peptide mRNA overexpression in a minipig model of pacing-induced left ventricular dysfunction

Dipyridamole (DP) restores ischemic tissue blood flow stimulating angiogenesis in eNOS-dependent pathways. C-type natriuretic peptide (CNP) is expected to mimic the migration-stimulatory effect of NO via a cGMP-dependent mechanism. Aim of this study was to assess the role of concomitant treatment with DP on CNP levels in blood and myocardial tissue of minipigs with left ventricular dysfunction (LVD) induced by pacing at 200bpm in the right ventricular apex. Minipigs with DP therapy (DP+, n=4) or placebo (DP-, n=4) and controls (C-SHAM, n=4) underwent 2D-EchoDoppler examination and blood collection before and after 4 weeks of pacing, when cardiac tissue was collected. Histological/immunohistochemical analyses were performed. CNP levels were determined by radioimmunoassay; cardiac CNP, BNP, natriuretic receptors expression by Real-Time PCR. After pacing, cardiac parameters resulted less impaired in DP+ compared to DP-. Histological sections presented normal morphology while the arteriolar density resulted: C-SHAM: 9.0±1.2; DP-: 4.9±0.3; DP+: 6.5±0.6number/mm(2); C-SHAM vs DP- and DP+ p=0.004, p=0.04, respectively. CNP mRNA resulted lower in DP- compared to C-SHAM and DP+ as well as NPR-B (p=0.011, DP- vs DP+). Both NPR-A/NPR-C mRNA expressions were significantly (p<0.001) lower both in DP- and DP+ compared to C-SHAM. BNP mRNA was higher in LVD. CNP plasma levels showed a similar trend with respect to gene expression (C-SHAM: 30.5±15; DP-: 18.6±5.5; DP+: 21.2±4.7pg/ml). These data suggest that DP may serve as a preconditioning agent to increase the protective CNP-mediated endocrine response in LVD. This response, mediated by its specific receptor NPR-B, may offer new insights into molecular targets for treatment of LVD.

Endothelin system mRNA variation in the heart of Zucker rats: evaluation of a possible balance with natriuretic peptides

BACKGROUND AND AIMS

The deregulation of neurohormonal systems, including the natriuretic peptide (NP) and endothelin (ET) systems, may increase the possibility of developing obesity-related risk. The aim of our paper was to evaluate ET system mRNA variation in heart of the Zucker rat model together with the simultaneous evaluation of the NP system transcriptomic profile. In order to analyze the link between the ET-1 system and the inflammatory process, the cardiac expression of interleukin (IL)-6 and tumor necrosis factor (TNF)-α was also measured.

METHODS AND RESULTS

Zucker rats of 11-13 weeks were subdivided into obese rats (O, n = 20) and controls (CO, n = 20): half of them were studied under fasting conditions (CO(fc)-O(fc)) and the remainder after the induction of acute hyperglycemia (CO(AH)-O(AH)). Cardiac mRNA expression of TNF-α, IL-6, and NP/ET-1 systems was evaluated by Real-Time polymerase chain reaction. No significant difference for pre-proET-1, ET-A, and ET-B mRNA expression was detected between O and CO, whereas significantly lower mRNA levels of the ECE-1 were observed in O (p = 0.02). Regarding NPs, only BNP mRNA expression decreased significantly in O with respect to CO (p = 0.01). A down-regulation of NPR-B and NPR-C and an up-regulation of NPR-A were observed in O. No significant difference for IL-6 and TNF-α mRNA was revealed. Subdividing into fasting and hyperglycemic rats, many of the genes studied maintained their mRNA expression pattern almost unchanged.

CONCLUSIONS

The modulation of ET-1/NP systems in obesity could be a useful starting point for future studies aimed at identifying new therapeutic strategies for the treatment of cardiometabolic syndrome.

Cardiac C-type natriuretic peptide gene expression and plasma concentrations in neonatal piglets

BACKGROUND

C-type natriuretic peptide (CNP) is a member of the natriuretic peptide family. Cardiac ANP and BNP expressions are firmly established, whereas CNP expression in the mammalian heart remains controversial. In the present report, we used a porcine model of the neonatal period with high expressions of cardiac ANP and BNP in order to elucidate the cardiac CNP expression profile.

METHODS

Plasma and cardiac tissue were obtained from newborn piglets during the first 72 h of life. The chamber-specific CNP mRNA contents were quantified by real-time PCR analysis. The proCNP concentrations in plasma and cardiac tissue extracts were quantified by a porcine-specific radioimmunoassay.

RESULTS

Cardiac CNP mRNA contents (n=24) were low compared to sites of known expression, where porcine seminal vesicle CNP mRNA contents were 200-fold higher. In addition, plasma proCNP concentrations in the newborn piglets (n=44) were exceedingly low compared to proANP concentrations (5.3 pmol/L (3.2-8.6) vs. 3438 pmol/L (2790-5418), p<0.0001). The proCNP concentrations in atrial tissue extracts were barely detectable (≤0.06 pmol/g) (n=2) compared to ventricular proANP (130 pmol/g (101-159)) and atrial proANP (12,303 pmol/g (10,623-15,412)).

CONCLUSION

Our data show that the heart is not a major source of circulating proCNP in neonatal piglets.

C-type natriuretic peptide transcriptomic profiling increases in human leukocytes of patients with chronic heart failure as a function of clinical severity

The aim of this study was to evaluate the transcriptomic profiling of C-type natriuretic peptide (CNP) and of its specific receptor, NPR-B in human leukocytes of heart failure (HF) patients as a function of clinical severity, assessing the possible changes with respect to healthy subjects (C). mRNA expression was evaluated by Real-Time PCR and total RNA was extracted from leukocytes of C (n=8) and of HF patients (NYHA I-II, n=7; NYHA III-IV, n=13) with PAXgene Blood RNA Kit. Significantly higher levels of CNP mRNA expression were found in HF patients as a function of clinical severity (C=0.23±0.058, NYHA I-II=0.47±0.18, NYHA III-IV=2.58±0.71, p=0.005 C vs NYHA III-IV, p=0.017 NYHA I-II vs NYHA III-IV) and NPR-B transcript levels resulted down-regulated in HF patients with higher NYHA class (C=2.2±0.61, NYHA I-II=2.76±0.46, NYHA III-IV=0.29±0.13, p=0.001 C vs NYHA III-IV, p<0.0001 NYHA I-II vs NYHA III-IV). A significant negative correlation between CNP and NPR-B mRNA expression (r=0.5, p=0.03) was also observed. These results suggest a co-regulation of NPR-B and CNP expression supporting the relevance of this receptor in human disease characterized by a marked inflammatory/immune component and suggesting the possibility of manipulating inflammation via pharmacological agents selective for this receptor.

Impact of obesity on the expression profile of natriuretic peptide system in a rat experimental model

Natriuretic peptides (NPs) play an important role in obesity and aim of this study was to evaluate, in cardiac tissue of obese Zucker rats (O, n = 29) their transcriptomic profile compared to controls (CO, n = 24) by Real-Time PCR study; CNP protein expression was evaluated by immunostaining and immunometric tests. Myocardial histology was performed, confirming no alteration of organ structure. While ANP and BNP are cardiac peptides, CNP is mainly an endothelial hormone; thus its expression, as well as that of NPR-B and NPR-C, was also evaluated in kidney and lung of an animal subgroup (n = 20). In heart, lower BNP mRNA levels in O vs CO (p = 0.02) as well as ANP and CNP (p = ns), were detected. NPR-B/NPR-A mRNA was similar in O and CO, while NPR-C was numerically lower (p = ns) in O than in CO. In kidney, CNP/NPR-B/NPR-C mRNA was similar in O and CO, while in lung CNP/NPR-C expression decreased and NPR-B increased (p = ns) in O vs CO. Subdividing into fasting and hyperglycemic rats, the pattern of mRNA expression for each gene analyzed remained unchanged. The trend observed in heart, kidney and lung for CNP protein concentrations and immunohistochemistry reflected the mRNA expression. TNF-α and IL-6 mRNA were measured in each tissue and no significant genotype effect was detected in any tissue. The main NP variations were observed at the cardiac level, suggesting a reduced release by cardiac cells. The understanding of mechanisms involved in the modulation of the NP system in obesity could be a useful starting point for future clinical study devoted to identifying new obesity treatment strategies.

C-type natriuretic peptide: a new cardiac mediator

Natriuretic peptides are endogenous hormones released by the heart in response to myocardial stretch and overload. While atrial and brain natriuretic peptides (ANP, BNP) were immediately considered cardiac hormones and their role was well-characterized and defined in predicting risk in cardiovascular disease, evidence indicating the role of C-type natriuretic peptide (CNP) in cardiovascular regulation was slow to emerge until about 8 years ago. Since then, considerable literature on CNP and the cardiovascular system has been published; the aim of this review is to examine current literature relating to CNP and cardiovascular disease, in particular its role in heart failure (HF) and myocardial infarction (MI). This review retraces the fundamental steps in research that led understanding the role of CNP in HF and MI; from increased CNP mRNA expression and plasmatic concentrations in humans and in animal models, to detection of CNP expression in cardiomyocytes, to its evaluation in human leukocytes. The traditional view of CNP as an endothelial peptide has been surpassed by the results of many studies published in recent years, and while its physiological role is still under investigation, information is now available regarding its contribution to cardiovascular function. Taken together, these observations suggest that CNP and its specific receptor, NPR-B, can play a very important role in regulating cardiac hypertrophy and remodeling, indicating NPR-B as a new potential drug target for the treatment of cardiovascular disease.

Differential expression of the pro-natriuretic peptide convertases corin and furin in experimental heart failure and atrial fibrosis

In heart failure (HF), the cardiac hormone natriuretic peptides (NPs) atrial (ANP), B-type (BNP), and C-type (CNP) play a key role to protect cardiac remodeling. The proprotein convertases corin and furin process their respective pro-NPs into active NPs. Here we define in a canine model of HF furin and corin gene and protein expression in normal and failing left atrium (LA) or ventricle (LV) testing the hypothesis that the NP proproteins convertases production is altered in experimental HF. Experimental canine HF was produced by rapid right ventricular pacing for 10 days. NPs, furin, and corin mRNA expression were determined by quantitative RT-PCR. Protein concentration or expression was determined by immunostaining, radioimmunoassay, or Western blot. Furin and corin proteins were present in normal canine LA and LV myocardium and vasculature and in smooth muscle cells. In normal canines, expression of NPs was dominant in the atrium compared with the ventricle. In experimental early stage HF characterized with marked atrial fibrosis, ANP, BNP, and CNP mRNA, and protein concentrations were higher in HF LA but not HF LV compared with normals. In LA, corin mRNA and protein expressions in HF were lower, whereas furin mRNA and protein expressions were higher than normals. NPs and furin expressions were augmented in the atrium in experimental early stage HF and, conversely, corin mRNA and protein expressions were decreased with atrial remodeling. Selective changes of these NP convertases may have significance in the regulation of pro-NP processing and atrial remodeling in early stage HF.

Pacing-induced regional differences in adenosine receptors mRNA expression in a swine model of dilated cardiomyopathy

The adenosinergic system is essential in the mediation of intrinsic protection and myocardial resistance to insult; it may be considered a cardioprotective molecule and adenosine receptors (ARs) represent potential therapeutic targets in the setting of heart failure (HF). The aim of the study was to test whether differences exist between mRNA expression of ARs in the anterior left ventricle (LV) wall (pacing site: PS) compared to the infero septal wall (opposite region: OS) in an experimental model of dilated cardiomyopathy. Cardiac tissue was collected from LV PS and OS of adult male minipigs with pacing-induced HF (n = 10) and from a control group (C, n = 4). ARs and TNF–α mRNA expression was measured by Real Time-PCR and the results were normalized with the three most stably expressed genes (GAPDH, HPRT1, TBP). Immunohistochemistry analysis was also performed. After 3 weeks of pacing higher levels of expression for each analyzed AR were observed in PS except for A₁R (A₁R: C = 0.6±0.2, PS = 0.1±0.04, OS = 0.04±0.01, p<0.0001 C vs. PS and OS respectively; A_2AR: C = 1.04±0.59, PS = 2.62±0.79, OS = 2.99±0.79; A_2BR: C = 1.2±0.1, PS = 5.59±2.3, OS = 1.59±0.46; A₃R: C = 0.76±0.18, PS = 8.40±3.38, OS = 4.40±0.83). Significant contractile impairment and myocardial hypoperfusion were observed at PS after three weeks of pacing as compared to OS. TNF-α mRNA expression resulted similar in PS (6.3±2.4) and in OS (5.9±2.7) although higher than in control group (3.4±1.5). ARs expression was mainly detected in cardiomyocytes. This study provided new information on ARs local changes in the setting of LV dysfunction and on the role of these receptors in relation to pacing-induced abnormalities of myocardial perfusion and contraction. These results suggest a possible therapeutic role of adenosine in patients with HF and dyssynchronous LV contraction.

Gene expression of C-type natriuretic peptide and of its specific receptor NPR-B in human leukocytes of healthy and heart failure subjects

C-type natriuretic peptide (CNP), a member of the family of natriuretic peptides, is synthesized and secreted from monocytes and macrophages that resulted to be a source of CNP at inflammatory sites. This suggests that special attention should be focused on the possible role of CNP in the immune system, in addition to its effects on the cardiovascular system. The aim of this study was to evaluate the possibility of measuring the mRNA expression of CNP and NPR-B, its specific receptor, in human whole blood samples of healthy (N; n=7) and heart failure (HF; n=7) subjects by Real-Time PCR (RT-PCR). Total RNA was extracted from leukocytes with QIAamp RNA Blood Kit and/or with PAXgene Blood RNA Kit. RT-PCR was performed and optimized for each primer. The experimental results were normalized with the three most stably expressed genes. CNP and NPR-B expression trend was similar in both fresh and frozen human whole blood. Significant higher levels of CNP and NPR-B mRNA expression were found in HF patients with respect to controls (CNP: N=1.23±0.33 vs. HF=6.54±2.09 p=0.027; NPR-B: N=0.85±0.23 vs. HF=5.31±1.98 p=0.04). A significant correlation between CNP and NPR-B (r=0.86, p<0.0001) was observed. Further studies are needed to clarify the pathophysiological properties of this peptide but the possibility to measure CNP and NPR-B mRNA expression in human leukocytes with a fast and easy procedure is a useful starting point for future investigation devoted to better understand the biomolecular processes associated to different diseases.

The natriuretic peptide time-course in end-stage heart failure patients supported by left ventricular assist device implant: focus on NT-proCNP

This study aimed to evaluate left ventricular assist device (LVAD) effects on natriuretic peptide (NP) prohormone plasma levels in end-stage heart failure (HF) patients, especially NT-proCNP, in order to better characterize the NP system during hemodynamic recovery by LVAD. HF patients (n=17, NYHA III-IV) undergoing LVAD were studied: 6 died of multi-organ failure syndrome (NS) and 11 survived (S). Total sequential organ failure assessment (t-SOFA) score and blood samples were obtained at admission (T1) and at 24, 72h and 1, 2, 4 weeks (T2-T6) after LVAD. In S, NT-proANP and NT-proCNP significantly increased at 24h after implantation, reaching a reduction to basal levels at 4 weeks following LVAD [NT-proANP: T1 vs. T2 p=0.017, NT-proCNP: T1 vs. T2 p=0.028, T1 vs. T3 p=0.043]. Elevated NT-proBNP plasma levels were observed at all times. In NS, NP plasma levels sustained higher with respect to S. No statistical variation was observed for NT-proCNP and NT-proANP in S and NS while NT-proBNP reached significant differences at T4 in NS. Considering S+NS, only NT-proCNP strongly correlated with t-SOFA score at T1 (rho=0.554, p=0.04) while subdividing patients NT-proCNP positively correlated in NS with t-SOFA score (rho=0.988, p=0.002) only at T4. In NS a correlation between NT-proCNP and NT-proBNP at T1 was observed (rho=-0.900, p=0.037). Both IL-6 and TNF-alpha sustained higher in NS patients than in S; in particular, statistical significance was observed for IL-6. The study of new peptides, such as NT-proCNP, would provide additional information for identifying patients who are more likely to recover.

Plasma C-type natriuretic peptide levels in healthy children

C-type natriuretic peptide (CNP) is assuming increasing importance in cardiovascular disease, and in adults its plasma levels are related to clinical and functional disease severity. Data are scarce regarding the reference values for CNP in infancy. Aim of this study was to assess the reference intervals for CNP in human healthy newborns and infants. Plasma CNP was measured in 121 healthy children divided into: 41 newborns (age 0-3 days), 24 newborns (4-30 days), 22 infants (1-12 months) and 32 children (1-12 years). A group of 32 healthy adult subjects (age 64 ± 1 years) was also studied. CNP was measured by a specific radioimmunoassay. Between- and within-assay variability resulted ≤ 30 and 20%, respectively and analytical sensitivity 0.77 ± 0.05 pg/tube. Plasma CNP resulted significantly higher in children than in adult subjects (13.6 ± 1.2 pg/ml vs. 7.4 ± 1.0 pg/ml, p=0.030). When the results were analyzed as a function of the age the reference intervals for plasma CNP resulted: 11.6 ± 2.1 pg/ml for newborns (0-3 days), 16.4 ± 3.7 pg/ml for newborns (4-30 days), 15.4 ± 2.7 pg/ml for infants (1-12 months), 13.6 ± 2.3 pg/ml for children (1-12 years) [p=0.01 newborns (4-30 days) vs. adults; p=0.03 infants (1-12 months) vs. adults]. CNP showed the highest concentrations after 12h of life with a peak between 4 and 5 days of life and with a progressive decline afterwards. According to these data at least five different reference intervals for CNP determinations should be used. These observations may be helpful for future clinical application of CNP in human children.

Regulation of C-type natriuretic peptide expression

C-type natriuretic peptide (CNP) is a member of the small family of natriuretic peptides that also includes atrial natriuretic peptide (ANP) and brain, or B-type natriuretic peptide (BNP). Unlike them, it performs its major functions in an autocrine or paracrine manner. Those functions, mediated through binding to the membrane guanylyl cyclase natriuretic peptide receptor B (NPR-B), or by signaling through the non-enzyme natriuretic peptide receptor C (NPR-C), include the regulation of endochondral ossification, reproduction, nervous system development, and the maintenance of cardiovascular health. To date, the regulation of CNP gene expression has not received the attention that has been paid to regulation of the ANP and BNP genes. CNP expression in vitro is regulated by TGF-β and receptor tyrosine kinase growth factors in a cell/tissue-specific and sometimes species-specific manner. Expression of CNP in vivo is altered in diseased organs and tissues, including atherosclerotic vessels, and the myocardium of failing hearts. Analysis of the human CNP gene has led to the identification of a number of regulatory sites in the proximal promoter, including a GC-rich region approximately 50 base pairs downstream of the Tata box, and shown to be a binding site for several putative regulatory proteins, including transforming growth factor clone 22 domain 1 (TSC22D1) and a serine threonine kinase (STK16). The purpose of this review is to summarize the current literature on the regulation of CNP expression, emphasizing in particular the putative regulatory elements in the CNP gene and the potential DNA-binding proteins that associate with them.