Sacubitril/Valsartan inhibits M1 type macrophages polarization in acute myocarditis by targeting C-type natriuretic peptide

Studies have shown that Sacubitril/valsartan (Sac/Val) can reduce myocardial inflammation in myocarditis mice, in addition to its the recommended treatment of heart failure. However, the underlying mechanisms of Sac/Val in myocarditis remain unclear. C-type natriuretic peptide (CNP), one of the targeting natriuretic peptides of Sac/Val, was recently reported to exert cardio-protective and anti-inflammatory effects in cardiovascular systems. Here, we focused on circulating levels of CNP in patients with acute myocarditis (AMC) and whether Sac/Val modulates inflammation by targeting CNP in experimental autoimmune myocarditis (EAM) mice as well as LPS-induced RAW 264.7 cells and bone marrow derived macrophages (BMDMs) models. Circulating CNP levels were higher in AMC patients compared to healthy controls, and these levels positively correlated with the elevated inflammatory cytokines IL-6 and monocyte count. In EAM mice, Sac/Val alleviated myocardial inflammation while augmenting circulating CNP levels rather than BNP and ANP, accompanied by reduction in intracardial M1 macrophage infiltration and expression of inflammatory cytokines IL-1β, TNF-α, and IL-6. Furthermore, Sac/Val inhibited CNP degradation and directly blunted M1 macrophage polarization in LPS-induced RAW 264.7 cells and BMDMs. Mechanistically, the effects might be mediated by the NPR-C/cAMP/JNK/c-Jun signaling pathway apart from NPR-B/cGMP/NF-κB pathway. In conclusion, Sac/Val exerts a protective effect in myocarditis by increasing CNP concentration and inhibiting M1 macrophages polarization.

Downregulation of natriuretic peptide receptor-C in vascular smooth muscle cells from spontaneously hypertensive rats contributes to vascular remodeling

Hypertension is associated with vascular remodeling due to hyperproliferation and hypertrophy of vascular smooth muscle cells (VSMC). VSMC from several animal models of hypertensive rats including spontaneously hypertensive rats (SHR) exhibit hyperproliferation, hypertrophy and decreased expression of natriuretic peptide receptor-C (NPR-C). In addition, angiotensin II (Ang II) and growth factors that promotes vascular remodeling have also been shown to attenuate the expression of NPR-C in VSMC. The present study investigates the relationship between the decreased expression of NPR-C and vascular remodeling in SHR and the underlying molecular mechanisms. Aortic VSMC from SHR and their control Wistar Kyoto (WKY) rats were transfected with cDNA of NPR-C and used for the vascular remodeling studies. Transfection of VSMC with cDNA of NPR-C augmented the expression of NPR-C in both VSMC from SHR and WKY rats and resulted in the attenuation of hyperproliferation and hypertrophy of VSMC from SHR. The overexpression of NPR-C also resulted in the attenuation of increased expression of epidermal growth factor receptor (EGFR), platelet derived growth factor receptor (PDGFR), cell cycle proteins, cyclin D1, cyclin-dependent kinase 4 (Cdk4), phospho-retinoblastoma (pRb) and Giα-2 proteins, all these signaling molecules implicated in the hyperproliferation/hypertrophy of VSMC from SHR. In summary, these results indicate that augmenting the decreased expression of NPR-C in VSMC from SHR improves vascular remodeling by attenuating hyperproliferation and hypertrophy through decreasing the overexpression of several signaling molecules. It may be suggested that NPR-C plays a vasculoprotective role and that the downregulation of NPR-C contributes to the vascular remodeling in SHR.

Natriuretic Peptide Clearance Receptor (NPR-C) Pathway as a Novel Therapeutic Target in Obesity-Related Heart Failure With Preserved Ejection Fraction (HFpEF)

Heart failure (HF) with preserved ejection fraction (HFpEF) is a major public health problem with cases projected to double over the next two decades. There are currently no US Food and Drug Administration–approved therapies for the health-related outcomes of HFpEF. However, considering the high prevalence of this heterogeneous syndrome, a directed therapy for HFpEF is one the greatest unmet needs in cardiovascular medicine. Additionally, there is currently a lack of mechanistic understanding about the pathobiology of HFpEF. The phenotyping of HFpEF patients into pathobiological homogenous groups may not only be the first step in understanding the molecular mechanism but may also enable the development of novel targeted therapies. As obesity is one of the most common comorbidities found in HFpEF patients and is associated with many cardiovascular effects, it is a viable candidate for phenotyping. Large outcome trials and registries reveal that being obese is one of the strongest independent risk factors for developing HFpEF and that this excess risk may not be explained by traditional cardiovascular risk factors. Recently, there has been increased interest in the intertissue communication between adipose tissue and the heart. Evidence suggests that the natriuretic peptide clearance receptor (NPR-C) pathway may play a role in the development and pathobiology of obesity-related HFpEF. Therefore, therapeutic manipulations of the NPR-C pathway may represent a new pharmacological strategy in the context of underlying molecular mechanisms.

Natriuretic peptide receptor-C releases and activates guanine nucleotide-exchange factor H1 in a ligand-dependent manner

Although natriuretic peptide receptor-C (NPR-C) is involved in the clearance of natriuretic peptides from plasma, it also possesses other physiological functions, such as inhibition of adenylyl cyclase activity through Gαi. However, the physiological roles and intracellular signaling pathways of NPR-C have yet been not fully elucidated. In this study, we identified a RhoA-specific guanine nucleotide-exchange factor, GEF-H1, as a novel binding protein of NPR-C. We demonstrated that endogenous NPR-C interacted with GEF-H1 in HeLa cells, and that the interaction between NPR-C and GEF-H1 was dependent on a 37-amino acid cytoplasmic region of NPR-C. In contrast, another natriuretic peptide receptor, NPR-A, which includes the kinase homology and guanylyl cyclase domains in the intracellular region, did not interact with GEF-H1. We also revealed that the ligands of NPR-C (i.e., ANP, CNP, and osteocrin) caused dissociation of GEF-H1 from NPR-C. Furthermore, osteocrin treatment induced phosphorylation of GEF-H1 at Ser-886, enhanced the interaction of GEF-H1 with 14-3-3, and increased the amount of activated GEF-H1. These findings strongly supported that NPR-C may be involved in diverse physiological roles by regulating GEF-H1 signaling.

Biophysical screening methods for extracellular domain peptide receptors, application to natriuretic peptide receptor C ligands

Endothelium-derived C-type natriuretic peptide possesses cytoprotective and anti-atherogenic functions that regulate vascular homeostasis. The vasoprotective effects of C-type natriuretic peptide are somewhat mediated by the natriuretic peptide receptor C, suggesting that this receptor represents a novel therapeutic target for the treatment of cardiovascular diseases. In order to facilitate our drug discovery efforts, we have optimized an array of biophysical methods including surface plasmon resonance, fluorescence polarization and thermal shift assays to aid in the design, assessment and characterization of small molecule agonist interactions with natriuretic peptide receptors. Assay conditions are investigated to explore the feasibility and dynamic range of each method, and peptide-based agonists and antagonists are used as controls to validate these conditions. Once established, each technique was compared and contrasted with respect to their drug discovery utility. We foresee that such techniques will facilitate the discovery and development of potential therapeutic agents for NPR-C and other large extracellular domain membrane receptors.

Natriuretic peptide receptor-C-mediated attenuation of vascular smooth muscle cell hypertrophy involves Gqα/PLCβ1 proteins and ROS-associated signaling

Hypertension is associated with vascular remodeling due to hyperproliferation and hypertrophy of vascular smooth muscle cells (VSMC). Recently, we showed the implication of enhanced expression of Gqα and PLCβ1 proteins in hypertrophy of VSMCs from 16‐week‐old spontaneously hypertensive rats (SHR). The aim of this study was to investigate whether C‐ANP_4‐23, a natriuretic peptide receptor‐C (NPR‐C) ligand that was shown to inhibit vasoactive peptide‐induced enhanced protein synthesis in A10 VSMC could also attenuate hypertrophy of VSMC isolated from rat model of cardiac hypertrophy and to further explore the possible involvement of Gqα/PLCβ1 proteins and ROS‐mediated signaling in this effect. The protein synthesis and cell volume, markers of hypertrophy were significantly enhanced in VSMC from 16‐week‐old SHR compared with age‐matched WKY rats and C‐ANP_4‐23 treatment attenuated both to WKY levels. In addition, C‐ANP_4‐23 treatment also attenuated the enhanced expression of AT1 receptor, Gqα, PLCβ1, Nox4, and p47^phox proteins, the enhanced activation of EGFR, PDGFR, IGF‐1R, enhanced phosphorylation of ERK1/2/AKT and c‐Src in VSMC from SHR. Furthermore, the enhanced levels of superoxide anion and NADPH oxidase activity exhibited by VSMC from SHR were also attenuated to control levels by C‐ANP_4‐23 treatment. These results indicate that C‐ANP_4‐23 via the activation of NPR‐C attenuates VSMC hypertrophy through decreasing the overexpression of Gqα/PLCβ1 proteins, enhanced oxidative stress, increased activation of growth factor receptors, and enhanced phosphorylation of MAPK/AKT signaling pathways. Thus, it can be suggested that C‐ANP_4‐23 may be used as a therapeutic agent for the treatment of vascular complications associated with hypertension and atherosclerosis.

Effect of atrial natriuretic peptide on reactive oxygen species-induced by hydrogen peroxide in THP-1 monocytes: role in cell growth, migration and cytokine release

Atrial natriuretic peptide (ANP), a cardiovascular hormone, elicits different biological actions in the immune system. The aim of the present study was to investigate in THP-1 monocytes the ANP effect on hydrogen peroxide (H2O2)-induced Reactive Oxygen Species (ROS), cell proliferation and migration. A significant increase of H2O2-dependent ROS production was induced by physiological concentration of ANP (10(-10)M). The ANP action was partially affected by cell pretreatment with PD98059, an inhibitor of mitogen activated-protein kinases (MAPK) as well as by wortmannin, an inhibitor of phosphatidylinositol 3-kinase (PI3K) and totally suppressed by diphenylene iodonium (DPI), an inhibitor of the enzyme nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. The hormone effect was mimicked by cANF and an ANP/NPR-C signaling pathway was studied using pertussis toxin (PTX). A significant increase of H2O2-induced cell migration was observed after ANP (10(-10)M) treatment, conversely a decrease of THP-1 proliferation, due to cell death, was found. Both ANP actions were partially prevented by DPI. Moreover, H2O2-induced release of IL-9, TNF-α, MIP-1α and MIP-1β was not counteracted by DPI, whereas no effect was observed in any experimental condition for both IL-6 and IL-1β. Our results support the view that ANP can play a key role during the inflammatory process.

Gestational hypertension in atrial natriuretic peptide knockout mice and the developmental origins of salt-sensitivity and cardiac hypertrophy

OBJECTIVE

To determine the effect of gestational hypertension on the developmental origins of blood pressure (BP), altered kidney gene expression, salt-sensitivity and cardiac hypertrophy (CH) in adult offspring.

METHODS

Female mice lacking atrial natriuretic peptide (ANP-/-) were used as a model of gestational hypertension. Heterozygous ANP+/- offspring was bred from crossing either ANP+/+ females with ANP-/- males yielding ANP+/-(WT) offspring, or from ANP-/- females with ANP+/+ males yielding ANP+/-(KO) offspring. Maternal BP during pregnancy was measured using radiotelemetry. At 14weeks of age, offspring BP, gene and protein expression were measured in the kidney with real-time quantitative PCR, receptor binding assay and ELISA.

RESULTS

ANP+/-(KO) offspring exhibited normal BP at 14weeks of age, but displayed significant CH (P<0.001) as compared to ANP+/-(WT) offspring. ANP+/-(KO) offspring exhibited significantly increased gene expression of natriuretic peptide receptor A (NPR-A) (P<0.001) and radioligand binding studies demonstrated significantly reduced NPR-C binding (P=0.01) in the kidney. Treatment with high salt diet increased BP (P<0.01) and caused LV hypertrophy (P<0.001) and interstitial myocardial fibrosis only in ANP+/-(WT) and not ANP+/-(KO) offspring, suggesting gestational hypertension programs the offspring to show resistance to salt-induced hypertension and LV remodeling. Our data demonstrate that altered maternal environments can determine the salt-sensitive phenotype of offspring.