C-type natriuretic peptide: a new cardiac mediator

The Natriuretic Peptide System: A Single Entity, Pleiotropic Effects

In the modern scientific landscape, natriuretic peptides are a complex and interesting network of molecules playing pleiotropic effects on many organs and tissues, ensuring the maintenance of homeostasis mainly in the cardiovascular system and regulating the water-salt balance. The characterization of their receptors, the understanding of the molecular mechanisms through which they exert their action, and the discovery of new peptides in the last period have made it possible to increasingly feature the physiological and pathophysiological role of the members of this family, also allowing to hypothesize the possible settings for using these molecules for therapeutic purposes. This literature review traces the history of the discovery and characterization of the key players among the natriuretic peptides, the scientific trials performed to ascertain their physiological role, and the applications of this knowledge in the clinical field, leaving a glimpse of new and exciting possibilities for their use in the treatment of diseases.

Therapeutic Peptides for Treatment of Lung Diseases: Infection, Fibrosis, and Cancer

Various lung diseases endanger people's health. Side effects and pharmaceutical resistance complicate the treatment of acute lung injury, pulmonary fibrosis, and lung cancer, necessitating the development of novel treatments. Antimicrobial peptides (AMPs) are considered to serve as a viable alternative to conventional antibiotics. These peptides exhibit a broad antibacterial activity spectrum as well as immunomodulatory properties. Previous studies have shown that therapeutic peptides including AMPs had remarkable impacts on animal and cell models of acute lung injury, pulmonary fibrosis, and lung cancer. The purpose of this paper is to outline the potential curative effects and mechanisms of peptides in the three types of lung diseases mentioned above, which may be used as a therapeutic strategy in the future.

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.

The natriuretic peptide system in heart failure: Diagnostic and therapeutic implications

Natriuretic peptides, which are activated in heart failure, play an important cardioprotective role. The most notable of the cardioprotective natriuretic peptides are atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), which are abundantly expressed and secreted in the atrium and ventricles, respectively, and C-type natriuretic peptide (CNP), which is expressed mainly in the vasculature, central nervous system, and bone. ANP and BNP exhibit antagonistic effects against angiotensin II via diuretic/natriuretic actions, vasodilatory actions, and inhibition of aldosterone secretion, whereas CNP is involved in the regulation of vascular tone and blood pressure, among other roles. ANP and BNP are of particular interest with respect to heart failure, as their levels, most notably BNP and N-terminal proBNP-a cleavage product produced when proBNP is processed to mature BNP-are increased in patients with heart failure. Furthermore, the identification of natriuretic peptides as sensitive markers of cardiac load has driven significant research into their physiological roles in cardiovascular homeostasis and disease, as well as their potential use as both biomarkers and therapeutics. In this review, I discuss the physiological functions of the natriuretic peptide family, with a particular focus on the basic research that has led to our current understanding of its roles in maintaining cardiovascular homeostasis, and the pathophysiological implications for the onset and progression of heart failure. The clinical significance and potential of natriuretic peptides as diagnostic and/or therapeutic agents are also discussed.

Scientific hypothesis and rational pharmacological for the use of sacubitril/valsartan in cardiac damage caused by COVID-19

On March 11, 2020 the World Health Organization (WHO) declared the state of global pandemic caused by the new SARS-CoV-2 (COVID-19). To date, no antivirals directed against SARS-CoV-2 or effective vaccines to combat the viral infection are available. Severe acute respiratory syndrome caused by SARS-CoV-2 is treated empirically with antivirals, anti-inflammatory, anticoagulants. The approval of an effective vaccine still takes time. In this state, it may be useful to find new therapeutic solutions from drugs already on the market. Recent hypotheses suggest that the use of AT-1 receptor antagonists (ARB) in combination with neprilisin inhibitors (NEPi) could indirectly provide clinical benefits to patients with SARS-CoV-2 and cardiac involvement. In this article we investigate and describe a possible innovative pharmacological approach for the treatment of the most severe stages of COVID-19 infection.

C-type natriuretic peptide plasma levels and whole blood mRNA expression show different trends in adolescents with different degree of endothelial dysfunction

C-type natriuretic peptide (CNP) is an endogenous adipogenesis regulator whose plasma levels in childhood are known, while no data are available on its expression. Our aim was to evaluate both CNP plasma levels and CNP system expression in whole blood obtained from normal-weight (N, n = 24) and obese (O, n = 16) adolescents (age:13.5 ± 0.4 years). Endothelial function was assessed measuring reactive hyperemia index (RHI). CNP plasma levels, evaluated with specific RIA, resulted significantly lower in O than in N (6.1 ± 0.8 vs.15.2 ± 1.3 pg/mL; p < 0.0001), while CNP/NPR-B/NPR-C mRNA, measured by Real-Time PCR, resulted similar in N (4.1 ± 1.7; 5.0 ± 1.6; 2.2 ± 0.9) and in O (4.3 ± 1.6; 3.5 ± 1.1; 2.3 ± 0.8). RHI was significantly lower in O than in N (1.4 ± 0.08 vs.2.1 ± 0.04, p < 0.0001). Dividing all subjects according to the RHI median value, irrespective of the presence or absence of obesity (Group 1 > 1.9, n = 23, Group 2 < 1.9, n = 17), CNP plasma concentrations resulted significantly (p = 0.014) higher in Group 1 (14.6 ± 1.6) than in Group 2 (7.5 ± 1.0), showing a significant correlation with RHI (p = 0.0026), while CNP mRNA expression was, surprisingly, higher in Group 2 (7.0 ± 2.3) than in Group 1 (1.8 ± 0.4; p = 0.02). NPR-B mRNA resulted similar in both Groups (4.3 ± 1.6; 4.7 ± 1.3) and NPR-C significantly higher in Group 2 (p = 0.02). Our data suggest different trends between CNP plasma levels and expression, assessed for the first time in whole blood, that could reflect changes occurring both at CNP transcriptional level in activated leukocytes due to inflammation, and at circulating levels, due to CNP paracrine/autocrine activities. This could represent an interesting area for new therapies able to modulate endothelial dysfunction.

C‑type natriuretic peptide prevents angiotensin II‑induced atrial connexin 40 and 43 dysregulation by activating AMP‑activated kinase signaling

C‑type natriuretic peptide (CNP), from the family of natriuretic peptides (NPs), has been shown to induce antihypertrophic and antifibrotic effects in cardiomyocytes. However, the roles of CNP in the atrial dysregulation of connexin (Cx)40 and Cx43 remain to be elucidated. The present study aimed to investigate the effects of CNP on angiotensin (Ang) II‑induced Cx40 and Cx43 dysregulation in isolated perfused beating rat left atria. A rat isolated perfused beating atrial model was used and the protein levels were determined via western blotting. Ang II significantly upregulated NF‑κB, activator protein‑1, transforming growth factor‑β1 (TGF‑β1), collagen I and matrix metalloproteinase 2, leading to atrial fibrosis, and downregulated expression of Cx40 and Cx43. The changes in Cx40 and Cx43 induced by Ang II were abolished by CNP through upregulation of phosphorylated AMP‑activated kinase a1 (AMPK) and downregulation of TGF‑β1. The effects of CNP on AMPK and TGF‑β1 levels were inhibited by KT5823 and pertussis toxin, inhibitors of protein kinase G (PKG) and NP receptor type C (NPR‑C), respectively. Thus, CNP can prevent Ang II‑induced dysregulation of Cx40 and Cx43 through activation of AMPK via the CNP‑PKG and CNP‑NPR‑C pathways in isolated beating rat atria. The present findings suggested that CNP may be therapeutically useful for clinical conditions involving cardiac dysregulation of Cx expression‑related diseases.

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.

Neprilysin Inhibitors: Filling a Gap in Heart Failure Management, Albeit Amidst Controversy and at a Significant Cost

Dual angiotensin and neprilysin inhibition using the combination drug sacubitril-valsartan has ushered in a new era in the treatment of heart failure (HF). The randomized controlled PARADIGM-HF trial, which randomized 8399 patients with HF to enalapril or sacubitril-valsartan, showed a 20% reduction in mortality and HF hospitalization with the new drug. This has been heralded as a step toward filling a crucial gap in HF management by providing strong evidence that combined inhibition of the angiotensin receptor and neprilysin is superior to inhibition of the renin-angiotensin system alone in stable patients with chronic HF as it negates the deleterious effects of angiotensin while concomitantly augmenting the beneficial effects of the endogenous natriuretic peptide system. This new therapy is costly, and other confirmatory studies have been lacking for over 2 years since its approval by major regulatory authorities. As such, controversy and heated discussions have amassed, as has detailed information from a plethora of secondary analyses of this pivotal trial about the pros and cons of this promising new therapeutic strategy in HF management. The aim of this review was to provide a critical assessment of all these aspects.

C-Type Natriuretic Peptide Dampens Fibroblast Growth Factor-23 Expression Through MAPK Signaling Pathway in Human Mesangial Cells

C-type natriuretic peptide (CNP) is believed to be produced locally in the kidneys and possess several renoprotective properties. In contrast, fibroblast growth factor (FGF) -23 elevates in the early stage of chronic kidney disease and predicts its outcomes. Currently, several studies have demonstrated that CNP and FGF-23 act through a close pathway, and moreover, FGF-23/mitogen-activated protein kinase (MAPK) can be obviously suppressed by CNP. In the present study, human mesangial cells (MCs) were incubated in serum-containing medium in the absence or presence of CNP (0, 10 and 100 pM) for 24, 48 and 72 h, respectively. CNP administration significantly suppresses MCs proliferation in a time- and dose-dependent manner. As a down-stream signaling of CNP activation, the expressions of natriuretic peptide receptor (NPR)-B, cyclic guanosine monophosphate-dependent protein kinases II and NPR-C were obviously augmented, whereas neutral endopeptidase expression was significantly decreased after CNP treatment in MCs. FGF-23, FGF receptor-1 and RAF-1 experienced a pronounced down-regulation in MCs with different doses of CNP throughout the whole observational period. CNP may dampen FGF-23 expression via MAPK signaling pathway in MCs.

C-Type Natriuretic Peptide (CNP) Inhibition of Interferon-γ-Mediated Gene Expression in Human Endothelial Cells In Vitro

Cardiovascular diseases, including atherosclerosis, now account for more deaths in the Western world than from any other cause. Atherosclerosis has a chronic inflammatory component involving Th1 pro-inflammatory cytokines such as IFN-γ, which is known to induce endothelial cell inflammatory responses. On the other hand CNP, which acts via its receptors to elevate intracellular cGMP, is produced by endothelium and endocardium and is upregulated in atherosclerosis. It is believed to be protective, however its role in vascular inflammation is not well understood. The aim of this study was to investigate the effects of CNP on human endothelial cell inflammatory responses following IFN-γ stimulation. Human umbilical vein endothelial cells were treated with either IFN-γ (10 ng/mL) or CNP (100 nm), or both in combination, followed by analysis by flow cytometry for expression of MHC class I and ICAM-1. IFN-γ significantly increased expression of both molecules, which was significantly inhibited by CNP or the cGMP donor 8-Bromoguanosine 3',5'-cyclic monophosphate (1 µm). CNP also reduced IFN-γ mediated kynurenine generation by the IFN-γ regulated enzyme indoleamine-2,3-deoxygenase (IDO). We conclude that CNP downmodulates IFN-γ induced pro-inflammatory gene expression in human endothelial cells via a cGMP-mediated pathway. Thus, CNP may have a protective role in vascular inflammation and novel therapeutic strategies for CVD based on upregulation of endothelial CNP expression could reduce chronic EC inflammation.

Molecular Mechanisms of Prophase I Meiotic Arrest Maintenance and Meiotic Resumption in Mammalian Oocytes

Mechanisms of meiotic prophase I arrest maintenance (germinal vesicle [GV] stage) and meiotic resumption (germinal vesicle breakdown [GVBD] stage) in mammalian oocytes seem to be very complicated. These processes are regulated via multiple molecular cascades at transcriptional, translational, and posttranslational levels, and many of them are interrelated. There are many molecular cascades of meiosis maintaining and meiotic resumption in oocyte which are orchestrated by multiple molecules produced by pituitary gland and follicular cells. Furthermore, many of these molecular cascades are duplicated, thus ensuring the stability of the entire system. Understanding mechanisms of oocyte maturation is essential to assess the oocyte status, develop effective protocols of oocyte in vitro maturation, and design novel contraceptive drugs. Mechanisms of meiotic arrest maintenance at prophase I and meiotic resumption in mammalian oocytes are covered in the present article.

Receptor signaling and neutral endopeptidase are involved in the resistance of C-type natriuretic peptide to human mesangial proliferation and collagen-IV expression

C-type natriuretic peptide (CNP) is regarded as a local, paracrine hormone to regulate vascular tone and cell proliferation. Although several in vivo studies have documented that CNP exerts the inhibitory effects on mesangial cells (MCs) proliferation and collagen production, a limited number of studies exist about the resistance of CNP to MCs proliferation in vitro. Besides, whether its receptor signaling and neutral endopeptidase (NEP) are involved remains unclear. In the present study, human MCs were incubated in serum-containing medium in the absence or presence of CNP (0, 10 and 100 pM) for 24, 48 and 72 hours, respectively. CNP administration significantly suppresses MCs proliferation and collagen-IV (Col-IV) expression in a time-dependent and dose-dependent manner. As a down-stream signal molecule of CNP activation, the expressions of natriuretic peptide receptor (NPR)-B, cyclic guanosine monophosphate-dependent protein kinases II and NPR-C were obviously augmented, whereas NEP expression was significantly decreased after CNP treatment. In conclusion, receptor signaling and NEP are involved in the resistance of CNP to human mesangial proliferation and Col-IV expression.

Effects of gene knockdown of CNP on ventricular remodeling after myocardial ischemia-reperfusion injury through NPRB/Cgmp signaling pathway in rats

This study aimed to explore effects of CNP on ventricular remodeling following myocardial ischemia-reperfusion (I/R) injury through the NPRB/cGMP signaling pathway. Rat cardiomyocytes were assigned into: control, I/R, I/R + CNP, and I/R + 8-Br-cGMP groups. ELISA, qRT-PCR, and Western blotting were used to detect cGMP content and expression, respectively. After model establishment of I/R rats, normal control, CNP^-/- control, I/R, and CNP^-/- groups were set. Indexes of heart were detected using echocardiography and hemodynamics. ELISA was used to measure serum CNP, cGMP, LDH, cTn I, CK-MB, TNF-α, and IL-6 levels. Myocardial infarct was identified by TTC staining, and apoptosis conditions by TUNEL staining. QRT-PCR and Western blotting were adopted to detect expressions of CNP, NPRB, cGMP, and apoptosis-related genes. Compared with control group, cGMP contents and expression in the I/R, I/R + CNP and I/R + 8-Br-cGMP groups were decreased. Levels of LVEDV, LVESV, LVDS, LVDD, IVSD, LVM, LVEDP, and LVSP were higher in the I/R, CNP^-/- control, and CNP^-/- groups than normal control group while LVEF, SV, CO, and ±dp/dtmax were lower. Compared with the normal control group, LDH, cTn I, CK-MB, TNF-α, and IL-6 were higher in the I/R, CNP^-/- control and CNP^-/- groups; pathological changes and myocardial infarction were observed in the I/R, CNP^-/- control, and CNP^-/- groups; expressions of apoptosis-related genes in those groups were higher; while CNP, NPRB, cGMP, and Bcl-2 expressions were decreased. We came to the conclusion that gene knockdown of CNP blocks the NPRB/cGMP signaling pathway, thereby aggravating myocardial I/R injury and causing ventricular remodeling in rats.

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.

Myeloprotective effects of C-type natriuretic peptide on cisplatin-induced bone marrow granulocytopenia in mice

PURPOSE

Cisplatin is an effective chemotherapeutic agent used to treat a variety of malignant tumors. The major toxicity associated with cisplatin treatment is granulocytopenia. C-type natriuretic peptide (CNP), a member of the natriuretic peptide family, protects against toxicity in many organs, including the heart, blood vessels, lung, and kidney. The objective of this study was to investigate the myeloprotective effects of CNP in a mouse model of cisplatin-induced granulocytopenia.

METHODS

The mice were divided into two groups: cisplatin with vehicle and cisplatin with CNP. CNP (2.5 μg/kg/min via osmotic pump, subcutaneously) or vehicle administration was started two day before cisplatin injection, and continued until the mice were killed. At 0, 2, 4, 8, and 14 days after cisplatin injection (16 mg/kg, intraperitoneally as a single dose), we counted total and living cells and granulocyte/macrophage colony-forming units (CFU-GM) in bone marrow. In addition, at 0, 1, 2, and 4 days after cisplatin injection, we measured mRNA levels of CXC chemokine receptor 4 (CXCR4) and chemokine CXC ligand 12 (CXCL12) in bone marrow.

RESULTS

CNP significantly attenuated the reduction in bone marrow nucleated cell count and CFU-GM in bone marrow at 4 days after cisplatin injection. Four days after cisplatin injection, CNP significantly decreased the CXCR4 mRNA level in bone marrow, but had no effect on the level of CXCL12 mRNA.

CONCLUSIONS

CNP exerts myeloprotective effects in cisplatin-induced granulocytopenia and decreases CXCR4 expression.

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.

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.

The Effects of Exercise on Natriuretic Peptides in Individuals without Heart Failure

Cardiac natriuretic peptides (NPs) play an important role in the regulation of energy expenditure in skeletal muscle and adipose tissue. A systematic review on the effects of exercise on NPs in patients with heart failure reported that aerobic and resistance training reduced NPs; however, the effects of exercise on NPs and the underlying mechanism of exercise-induced NP secretion in subjects without heart failure remain unknown. In athletes and young, healthy subjects, the NP concentration at rest is not elevated, but strenuous endurance exercise significantly increases NPs. The exercise-induced increase in NPs may be caused by transient myocardial wall stress, cardiomyocyte metabolic changes, or neuroendocrinological response, which may have cytoprotective and growth-regulating effects on the heart. On the other hand, in elderly, overweight/obese subjects, and patients with hypertension, NP concentrations also increase during exercise; however, NP secretion may be more susceptible to cardiac stress compared to young, healthy individuals. Recent studies have shown that NPs are associated with thermogenesis in fat tissue and oxidative capacity in skeletal muscles. NPs may also have a protective role for skeletal muscle in humans, although further studies are warranted to elucidate the physiological mechanism of exercise-induced NP secretion.

C-type natriuretic peptide ameliorates pulmonary fibrosis by acting on lung fibroblasts in mice

Background

Pulmonary fibrosis has high rates of mortality and morbidity; however, no effective pharmacological therapy has been established. C-type natriuretic peptide (CNP), a member of the natriuretic peptide family, selectively binds to the transmembrane guanylyl cyclase (GC)-B receptor and exerts anti-inflammatory and anti-fibrotic effects in various organs through vascular endothelial cells and fibroblasts that have a cell-surface GC-B receptor. Given the pathophysiological importance of fibroblast activation in pulmonary fibrosis, we hypothesized that the anti-fibrotic and anti-inflammatory effects of exogenous CNP against bleomycin (BLM)-induced pulmonary fibrosis were exerted in part by the effect of CNP on pulmonary fibroblasts.

Methods

C57BL/6 mice were divided into two groups, CNP-treated (2.5 μg/kg/min) and vehicle, to evaluate BLM-induced (1 mg/kg) pulmonary fibrosis and inflammation. A periostin-CNP transgenic mouse model exhibiting CNP overexpression in fibroblasts was generated and examined for the anti-inflammatory and anti-fibrotic effects of CNP via fibroblasts in vivo. Additionally, we assessed CNP attenuation of TGF-β-induced differentiation into myofibroblasts by using immortalized human lung fibroblasts stably expressing GC-B receptors. Furthermore, to investigate whether CNP acts on human lung fibroblasts in a clinical setting, we obtained primary-cultured fibroblasts from surgically resected lungs of patients with lung cancer and analyzed levels of GC-B mRNA transcription.

Results

CNP reduced mRNA levels of the profibrotic cytokines interleukin (IL)-1β and IL-6, as well as collagen deposition and the fibrotic area in lungs of mice with bleomycin-induced pulmonary fibrosis. Furthermore, similar CNP effects were observed in transgenic mice exhibiting fibroblast-specific CNP overexpression. In cultured-lung fibroblasts, CNP treatment attenuated TGF-β–induced phosphorylation of Smad2 and increased mRNA and protein expression of α-smooth muscle actin and SM22α, indicating that CNP suppresses fibroblast differentiation into myofibroblasts. Furthermore, human lung fibroblasts from patients with or without interstitial lung disease substantially expressed GC-B receptor mRNA.

Conclusions

These data suggest that CNP ameliorates bleomycin-induced pulmonary fibrosis by suppressing TGF-β signaling and myofibroblastic differentiation in lung fibroblasts. Therefore, we propose consideration of CNP for clinical application to pulmonary fibrosis treatment.

C-type natriuretic peptide in combination with sildenafil attenuates proliferation of rhabdomyosarcoma cells

Rhabdomyosarcoma (RMS) is a malignant mesenchymal tumor and the most common soft tissue sarcoma in children. Because of several complications associated with intensive multimodal therapies, including growth disturbance and secondary cancer, novel therapies with less toxicity are urgently needed. C‐type natriuretic peptide (CNP), an endogenous peptide secreted by endothelial cells, exerts antiproliferative effects in multiple types of mesenchymal cells. Therefore, we investigated whether CNP attenuates proliferation of RMS cells. We examined RMS patient samples and RMS cell lines. All RMS clinical samples expressed higher levels of guanylyl cyclase B (GC‐B), the specific receptor for CNP, than RMS cell lines. GC‐B expression in RMS cells decreased with the number of passages in vitro. Therefore, GC‐B stable expression lines were established to mimic clinical samples. CNP increased cyclic guanosine monophosphate (cGMP) levels in RMS cells in a dose‐dependent manner, demonstrating the biological activity of CNP. However, because cGMP is quickly degraded by phosphodiesterases (PDEs), the selective PDE5 inhibitor sildenafil was added to inhibit its degradation. In vitro, CNP, and sildenafil synergistically inhibited proliferation of RMS cells stably expressing GC‐B and decreased Raf‐1, Mitogen‐activated protein kinase kinase (MEK), and extracellular signal‐regulated kinase (ERK) phosphorylation. These results suggested that CNP in combination with sildenafil exerts antiproliferative effects on RMS cells by inhibiting the Raf/MEK/ERK pathway. This regimen exerted synergistic effects on tumor growth inhibition without severe adverse effects in vivo such as body weight loss. Thus, CNP in combination with sildenafil represents a promising new therapeutic approach against RMS.

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.

Cardioprotective effect of metformin against doxorubicin cardiotoxicity in rats

Objective:

The clinical use of doxorubicin, which is a strong antineoplastic agent, is limited due to its cardiotoxic side effects. Metformin is a drug with antihyperglycemic effects, and it has been shown to have a cardioprotective effect on left ventricular function in experimental animal models of myocardial ischemia. The present study investigated the cardioprotective effect of metformin in rats with doxorubicin cardiotoxicity.

Methods:

Wistar albino rats were used in the study. Forty male, 10-week-old Wistar albino rats were randomly divided four groups. The control group rats were intraperitoneally administered saline solution twice a week, four doses in total. The doxorubicin group rats received doxorubicin (4 mg/kg, twice a week, cumulative dose: 16 mg/kg) intraperitoneally. The metformin group rats received metformin (250 mg/kg/day, every day for 14 days) via gavage. The doxorubicin + metformin group rats received doxorubicin and metformin at the same dose. Left ventricular functions were evaluated by using M-mode echocardiography one day after the last dose of doxorubicin. Heart tissue samples were histopathologically examined. Cardiomyocyte apoptosis was detected using in situ terminal deoxynucleotide transferase assay (TUNEL). Serum brain natriuretic peptide and C-type natriuretic peptide levels were measured. Catalase, superoxide dismutase, glutathione peroxidase, and tumor necrosis factor alpha levels were analyzed in the heart tissue. The assumptions of equality of variances and normal distribution were checked for all variables (Shapiro-Wilk test and Q-Q graphics). To identify intergroup differences, one-way variant analysis or the Kruskal-Wallis test was used. A p<0.05 value was accepted as statistically significant.

Results:

Our results showed that doxorubicin treatment caused significant deterioration in left ventricular functions by echocardiography, histological heart tissue damage, and increase in cardiomyocyte apoptosis. Doxorubicin + metformin group showed protection in left ventricular function, elimination of histopathologic change, and reduced of cardiomyocyte apoptosis.

Conclusion:

The present study provided evidence that metformin has cardioprotective effects against doxorubicin cardiotoxicity.

Protective effects of C-type natriuretic peptide on cisplatin-induced nephrotoxicity in mice

PURPOSE

Cisplatin is a highly effective chemotherapeutic agent used to treat various malignancies, but its utility is compromised by its nephrotoxicity. C-type natriuretic peptide (CNP), a member of the natriuretic peptide family, exhibits anti-inflammatory effects by activating its specific receptor, guanylyl cyclase (GC)-B. CNP and GC-B receptor are known to be expressed in both the vascular endothelium and the kidney. The objective of this study was to investigate the renoprotective effects of CNP in a mouse model of cisplatin-induced nephrotoxicity.

METHODS

C57BL/6 mice were divided into three groups: normal control mice; cisplatin (20 mg/kg, intraperitoneal) mice treated with vehicle; and cisplatin mice treated with CNP (2.5 µg/kg/min, subcutaneous). At 72 h after cisplatin injection, urine, blood and kidney samples were collected. Urine and blood samples were examined biochemically. Histological findings and gene expression in kidney tissue were evaluated.

RESULTS

CNP reduced histological renal tubular damage and apoptosis induced by cisplatin and suppressed plasma blood urea nitrogen and creatinine levels, which were elevated by cisplatin administration. CNP treatment decreased the expression of kidney injury molecule-1 and monocyte chemoattractant protein-1, which were elevated in the kidney by cisplatin administration. CNP treatment attenuated the decrease in GC-B expression in cisplatin-induced kidney injury.

CONCLUSIONS

The present study is the first to show that CNP inhibits nephrotoxicity and kidney cell damage induced by cisplatin. The mechanism of action may involve down-regulation of inflammatory cytokine expression in cisplatin-induced kidney injury and attenuation of apoptosis in renal tubular cells.

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.

ANP-induced signaling cascade and its implications in renal pathophysiology

The balance between vasoconstrictor/sodium-retaining and vasodilator/natriuretic systems is essential for maintaining body fluid and electrolyte homeostasis. Natriuretic peptides, such as atrial natriuretic peptide (ANP), belong to the vasodilator/natriuretic system. ANP is produced by the conversion of pro-ANP into ANP, which is achieved by a proteolytical cleavage executed by corin. In the kidney, ANP binds to the natriuretic peptide receptor-A (NPR-A) and enhances its guanylyl cyclase activity, thereby increasing intracellular cyclic guanosine monophosphate production to promote natriuretic and renoprotective responses. In the glomerulus, ANP increases glomerular permeability and filtration rate and antagonizes the deleterious effects of the renin-angiotensin-aldosterone system activation. Along the nephron, natriuretic and diuretic actions of ANP are mediated by inhibiting the basolaterally expressed Na(+)-K(+)-ATPase, reducing apical sodium, potassium, and protein organic cation transporter in the proximal tubule, and decreasing Na(+)-K(+)-2Cl(-) cotransporter activity and renal concentration efficiency in the thick ascending limb. In the medullary collecting duct, ANP reduces sodium reabsorption by inhibiting the cyclic nucleotide-gated cation channels, the epithelial sodium channel, and the heteromeric channel transient receptor potential-vanilloid 4 and -polycystin 2 and diminishes vasopressin-induced water reabsorption. Long-term ANP treatment may lead to NPR-A desensitization and ANP resistance, resulting in augmented sodium and water reabsorption. In mice, corin deficiency impairs sodium excretion and causes salt-sensitive hypertension. Characteristics of ANP resistance and corin deficiency are also encountered in patients with edema-associated diseases, highlighting the importance of ANP signaling in salt-water balance and renal pathophysiology.

Corin in natriuretic peptide processing and hypertension

Corin is a serine protease originally isolated from the heart. Functional studies show that corin is the long-sought enzyme responsible for activating cardiac natriuretic peptides. In mice, lack of corin prevents natriuretic peptide processing, causing salt-sensitive hypertension. In humans, corin variants and mutations that reduce corin activity have been identified in patients with hypertension and heart failure. Decreased plasma levels of corin antigen and activity have been reported in patients with heart failure and coronary artery disease. Low levels of urinary corin also have been found in patients with chronic kidney disease. Most recent studies show that corin also acts in the uterus to promote spiral artery remodeling and prevent pregnancy-induced hypertension. Here, we review the role of corin in natriuretic peptide processing and cardiovascular diseases such as hypertension, heart disease, pre-eclampsia, and chronic kidney disease.

Guanylyl cyclase/natriuretic peptide receptor-A signaling antagonizes phosphoinositide hydrolysis, Ca(2+) release, and activation of protein kinase C

Thus far, three related natriuretic peptides (NPs) and three distinct sub-types of cognate NP receptors have been identified and characterized based on the specific ligand binding affinities, guanylyl cyclase activity, and generation of intracellular cGMP. Atrial and brain natriuretic peptides (ANP and BNP) specifically bind and activate guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA), and C-type natriuretic peptide (CNP) shows specificity to activate guanylyl cyclase/natriuretic peptide receptor-B (GC-B/NPRB). All three NPs bind to natriuretic peptide receptor-C (NPRC), which is also known as clearance or silent receptor. The NPRA is considered the principal biologically active receptor of NP family; however, the molecular signaling mechanisms of NP receptors are not well understood. The activation of NPRA and NPRB produces the intracellular second messenger cGMP, which serves as the major signaling molecule of all three NPs. The activation of NPRB in response to CNP also produces the intracellular cGMP; however, at lower magnitude than that of NPRA, which is activated by ANP and BNP. In addition to enhanced accumulation of intracellular cGMP in response to all three NPs, the levels of cAMP, Ca²⁺ and inositol triphosphate (IP₃) have also been reported to be altered in different cells and tissue types. Interestingly, ANP has been found to lower the concentrations of cAMP, Ca²⁺, and IP₃; however, NPRC has been proposed to increase the levels of these metabolic signaling molecules. The mechanistic studies of decreased and/or increased levels of cAMP, Ca²⁺, and IP₃ in response to NPs and their receptors have not yet been clearly established. This review focuses on the signaling mechanisms of ANP/NPRA and their biological effects involving an increased level of intracellular accumulation of cGMP and a decreased level of cAMP, Ca²⁺, and IP₃ in different cells and tissue systems.

Time and technology will tell: the pathophysiologic basis of neurohormonal modulation in heart failure

The central roles of neurohormonal abnormalities in the pathobiology of heart failure have been defined in recent decades. Experiments have revealed both systemic involvement and intricate subcellular regulation by circulating effectors of the sympathetic nervous system, the renin-angiotensin-aldosterone system, and others. Randomized clinical trials substantiated these findings, establishing neurohormonal antagonists as cornerstones of heart failure pharmacotherapy, and occasionally offering further insight on mode of benefit. This review discusses the use of β-blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and aldosterone receptor antagonists in the treatment of heart failure, with particular attention to the pathophysiologic basis and mechanisms of action.

Cardiovascular biomarkers pro-atrial natriuretic peptide and pro-endothelin-1 to monitor ductus arteriosus evolution in very preterm infants

BACKGROUND

The diagnostic and prognostic appraisal of patent ductus arteriosus (PDA) in preterm infants is still debatable.

AIMS

To compare plasma cardiovascular biomarkers with echocardiographic indices alongside ductus arteriosus (DA) evolution in very preterm infants within the first week of life.

METHODS

Mid-regional pro-atrial natriuretic peptide (MR-proANP) and C-terminal pro-endothelin-1 (CT-proET-1) levels were prospectively measured on the second and sixth days of life (DOL) in 52 preterm infants born before 32weeks of gestation. Echocardiographic indices to define DA patency and significance were simultaneously obtained. Logistic regression and receiver operating characteristics (ROC) analyses were used to assess and quantify the biomarkers' diagnostic capacities.

RESULTS

Thirty infants exhibited PDA on DOL 2; in 21 of these infants, DA was characterized as hemodynamically significant. Treatment failure after a first course of indomethacin was noted in 8 infants (DOL 6), whereas 7 participants underwent later surgical ligation. The diagnostic accuracy of cardiovascular biomarkers was moderate on DOL 2 but high on DOL 6. PDA was the only significant predictor of MR-proANP levels on DOL 6, independent of the effect of clinical confounders (regression coefficient 0.426, R(2) 0.60). Infants with MR-proANP ≥850pmol/l on DOL 2 had 3.9-fold higher risk (95% CI 1.01 to 14.5) of being diagnosed with significant DA, whereas infants with MR-proANP ≥700pmol/l on DOL 6 had 7.1-fold higher risk (1.9 to 27.2) for pharmaceutical treatment failure.

CONCLUSION

The cardiovascular plasma biomarker MR-proANP is a promising candidate for monitoring PDA evolution in very preterm infants.

Prediabetes: grounds of pitfall signalling alteration for cardiovascular disease

Prediabetes manifested by impaired glucose tolerance and impaired fasting glucose offers high risk of myocardial dysfunction by causing endothelial dysfunction, inflammation, oxidative stress, atherosclerosis and genetic alterations.