Natriuretic Peptide Receptor Type Research Articles

C-type natriuretic peptide (CNP) in the paraventricular nucleus-mediated renal sympatho-inhibition.

Volume reflex produces sympatho-inhibition that is mediated by the hypothalamic paraventricular nucleus (PVN). However, the mechanisms for the sympatho-inhibitory role of the PVN and the neurochemical factors involved remain to be identified. In this study, we proposed C-type natriuretic peptide (CNP) as a potential mediator of this sympatho-inhibition within the PVN. Microinjection of CNP (1.0μg) into the PVN significantly decreased renal sympathetic nerve activity (RSNA) (-25.8% ± 1.8% vs. -3.6% ± 1.5%), mean arterial pressure (-15.0 ± 1.9 vs. -0.1 ± 0.9mmHg) and heart rate (-23.6 ± 3.5 vs. -0.3 ± 0.9 beats/min) compared with microinjection of vehicle. Picoinjection of CNP significantly decreased the basal discharge of extracellular single-unit recordings in 5/6 (83%) rostral ventrolateral medulla (RVLM)-projecting PVN neurons and in 6/13 (46%) of the neurons that were not antidromically activated from the RVLM. We also observed that natriuretic peptide receptor type C (NPR-C) was present on the RVLM projecting PVN neurons detected by dual-labeling with retrograde tracer. Prior NPR-C siRNA microinjection into the PVN significantly blunted the decrease in RSNA to CNP microinjections into the PVN. Volume expansion-mediated reduction in RSNA was significantly blunted by prior administration of NPR-C siRNA into the PVN. These results suggest a potential role for CNP within the PVN in regulating RSNA, specifically under physiological conditions of alterations in fluid balance.

VDR Regulates BNP Promoting Neurite Growth and Survival of Cochlear Spiral Ganglion Neurons through cGMP-PKG Signaling Pathway

Spiral ganglion neurons (SGNs) are important for hearing, and their peripheral and central processes connect sensory cells of the Corti organ to the central nervous system. The resulting network forms a point-to-point auditory conduction. As a cardiac hormone, brain natriuretic peptide (BNP) binds to natriuretic peptide receptor type A leading to diuresis, vasodilatation, inhibition of renin and aldosterone production, and cardiac and vascular myocyte growth. This study primarily aimed to explore the expression and function of BNP in the rat's inner ear and elucidate its regulatory mechanism. We determined the expression and function of BNP and found that the vitamin D receptor (VDR) could upregulate the expression of BNP and enhance its function. In SGNs of the rat inner ear, BNP promotes neuron survival and prolongs neurite length through the cGMP-PKG signaling pathway, which could be regulated by VDR and provide a novel approach for neuronal regeneration therapy. To the best of our knowledge, this is the first study to report this potential transcriptional regulatory relationship and will act as a reference for research on neuronal regeneration therapy for SGNs injury.

Effects of bisphenol A on human umbilical arteries.

Bisphenol A (BPA) is an endocrine-disrupting chemical widely used in the plastics industry, including food container, toys, and medical equipment. We analyzed the effect of BPA in human umbilical artery contractility and expression of some proteins modulating this function, such as ionic channels and proteins involved in the cGMP pathway. Using standard organ bath technique, rings of human umbilical arteries without endothelium were contracted by 5-HT (1μM) and histamine (10μM) and the effect of different concentrations of BPA (1nM-100μM) was analyzed. The results showed that BPA is a vasodilator of these arteries in a concentration-dependent way. Besides, qPCR studies on human umbilical smooth muscle cells (HUSMC) allowed to analyze the effects of BPA on gene expression. Thus, 12-h exposition to BPA induced reduction of expression of L-type calcium channels (LTCC), alpha subunit of BKCa channels, and Kvβ1 and Kvβ3 from Kv channels. BPA also decreased the expression of soluble guanylate cyclase (sGC) and natriuretic peptide receptor type A (NPRA), meanwhile increasing that of PKG, proteins involved in vasodilation of human umbilical arteries (HUA) by cGMP. Further studies will be necessary to increase knowledge about the implications of these changes induced by BPA exposure.

NPR2 Variants are frequent among children with familial short stature and respond well to growth hormone therapy

This study aimed to assess the frequency of natriuretic peptide receptor type B gene (NPR2 ) variants in 87 children with familial short stature (FSS) and evaluate their response to GH therapy. By applying whole-exome or custom-targeted NGS panel sequencing, NPR2 variants were found in 5 children (5.7%) belonging to 4 families. These variants were classified as pathogenic (n =2) or likely pathogenic (n =3) according to the American College of Medical Genetics and Genomics guidelines. Three children were born SGA and 3 were classified as GH deficient (GHD). Two children had disproportionate short stature with short limbs and one had a dysplastic middle phalanx of the fifth finger. All parents with short stature carried the same NPR2 variant as the probands. GH therapy improved growth velocity after the first year of treatment (from 3.6 to 4.2 cm/year) and the gain in height ranged from 0.33 to 0.79 S.D. after 1 year of GH therapy, 0.43 to 1.34 S.D. at 2 years, and 1.2 to 1.8 S.D. after 5 years.

Functional modulation of sarcolemmal KATP channels by atrial natriuretic peptide-elicited intracellular signaling in adult rabbit ventricular cardiomyocytes.

ATP-sensitive potassium (KATP) channels couple cell metabolic status to membrane excitability and are crucial for stress adaptation and cytoprotection in the heart. Atrial natriuretic peptide (ANP), a cardiac peptide important for cardiovascular homeostasis, also exhibits cytoprotective features including protection against myocardial ischemia-reperfusion injuries. However, how ANP modulates cardiac KATP channels is largely unknown. In the present study we sought to address this issue by investigating the role of ANP signaling in functional modulation of sarcolemmal KATP (sarcKATP) channels in ventricular myocytes freshly isolated from adult rabbit hearts. Single-channel recordings were performed in combination with pharmacological approaches in the cell-attached patch configuration. Bath application of ANP markedly potentiated sarcKATP channel activities induced by metabolic inhibition with sodium azide, whereas the KATP-stimulating effect of ANP was abrogated by selective inhibition of the natriuretic peptide receptor type A (NPR-A), cGMP-dependent protein kinase (PKG), reactive oxygen species (ROS), extracellular signal-regulated protein kinase (ERK)1/2, Ca2+/calmodulin-dependent protein kinase II (CaMKII), or the ryanodine receptor (RyR). Blockade of RyRs also nullified hydrogen peroxide (H2O2)-induced stimulation of sarcKATP channels in intact cells. Furthermore, single-channel kinetic analyses revealed that ANP enhanced the function of ventricular sarcKATP channels through destabilizing the long closures and facilitating the opening transitions, without affecting the single-channel conductance. In conclusion, here we report that ANP positively modulates the activity of ventricular sarcKATP channels via an intracellular signaling mechanism consisting of NPR-A, PKG, ROS, ERK1/2, CaMKII, and RyR2. This novel mechanism may regulate cardiac excitability and contribute to cytoprotection, in part, by opening myocardial KATP channels.

The exocrine pancreas is an extracardiac source of atrial natriuretic peptide.

Previous studies have shown that atrial natriuretic peptide (ANP) regulates exocrine pancreatic function in health and disease. As extracardiac sources of ANP have been identified and ANP-like immunoreactivity has been reported in the exocrine pancreas, in the present work we sought to establish whether ANP was produced in the rat exocrine pancreas and if conditions like fasting/feeding or acute pancreatitis were reflected on ANP expression. By using RT-PCR, immunoblotting, and immunofluorescence microscopy assays, it was found that both mRNA and protein ANP were present in the acinar cells of the exocrine pancreas. The amount of ANP in the pancreas was lower in than the atrium but similar to other tissues like the kidney and liver. Immunogold labeling electron microscopy studies revealed that ANP was localized in zymogen granules and the endoplasmic reticulum suggesting local synthesis and package into granules. ANP protein expression was significantly increased not only in fasting but also in acute pancreatitis, the latter probably related to impaired secretion. Natriuretic peptide receptor type C which mediates ANP biological effects in the exocrine pancreas was also present in acinar cells and its expression did not change with either fasting or acute pancreatitis. Present findings show that the exocrine pancreas is a relatively important extracardiac source of ANP and further support previous studies strongly suggesting the active role of the peptide in pancreatic physiology and pathophysiology.

The effects of exercise training and caloric restriction on the cardiac oxytocin natriuretic peptide system in the diabetic mouse.

BackgroundRegular exercise training (ET) and caloric restriction (CR) are the frontline strategies in the treatment of type 2 diabetes mellitus with the aim at reducing cardiometabolic risk. ET and CR improve body weight and glycemic control, and experimental studies indicate that these paradigms afford cardioprotection. In this study, the effects of combined ET and CR on the cardioprotective oxytocin (OT)–natriuretic peptide (NP) system were determined in the db/db mouse, a model of type 2 diabetes associated with insulin resistance, hyperglycemia, and obesity.MethodsFive-week-old male db/db mice were assigned to the following groups: sedentary, ET, and ET + CR. Nonobese heterozygote littermates served as controls. ET was performed on a treadmill at moderate intensity, and CR was induced by reducing food intake by 30% of that consumed by sedentary db/db mice for a period of 8 weeks.ResultsAfter 8 weeks, only ET + CR, but not ET, slightly improved body weight compared to sedentary db/db mice. Regardless of the treatment, db/db mice remained hyperglycemic. Hearts from db/db mice demonstrated reduced expression of genes linked to the cardiac OT–NP system. In fact, compared to control mice, mRNA expression of GATA binding protein 4 (GATA4), OT receptor, OT, brain NP, NP receptor type C, and endothelial nitric oxide synthase (eNOS) was decreased in hearts from sedentary db/db mice. Both ET alone and ET + CR increased the mRNA expression of GATA4 compared to sedentary db/db mice. Only ET combined with CR produced increased eNOS mRNA and protein expression.ConclusionOur data indicate that enhancement of eNOS by combined ET and CR may improve coronary endothelial vasodilator dysfunction in type 2 diabetes but did not prevent the downregulation of cardiac expression in the OT–NP system, possibly resulting from the sustained hyperglycemia and obesity in diabetic mice.

In Vivo Treatment with Natriuretic Peptide Receptor Type C Agonist Attenuates Overexpression of Cell Cycles Proteins and Hyperproliferation of Vascular Smooth Muscle Cells from SHR : Molecular Mechanisms

Vascular remodeling due to hyper‐proliferation of vascular smooth muscle cells (VSMCs) is associated with hypertension. We previously showed that in vivo treatment of spontaneously hypertensive rats (SHR) with NPR‐C specific agonist C‐ANP4–23 attenuates the hyper‐proliferation of VSMC. We undertook the present study to investigate if the anti‐proliferative effect of C‐ANP4–23 treatment is mediated through the inhibition of the over‐expression of cell cycle proteins and explore the signaling molecules contributing to this effect. For this study, one‐week‐old SHR and age‐matched WKY rats were injected intraperitoneally with C‐ANP4–23 twice per week for 6 weeks and sacrificed at the end of the 8th week, blood pressure measurements were done by tail cuff method, proliferation of VSMC was determined by thymidine incorporation and MTT assay, and Western blotting was used to measure the levels of proteins. VSMC from SHR exhibited enhanced proliferation as compared to Wistar Kyoto rats (WKY) and C‐ANP4–23 treatment attenuated the hyper‐proliferation to control levels. In addition the overexpression of cyclin D1, cyclin A, cyclin E, cyclin dependent kinase 2 and 4 (cdk2, cdk4), phosphorylated retinoblastoma protein (pRb) and Giα proteins exhibited by VSMC from SHR was attenuated to control levels. Furthermore, the enhanced phosphorylation of ERK1/2, AKT, EGF‐R, PDGF‐R, IGF‐R and c‐Src was significantly decreased by C‐ANP4–23 treatment. Moreover, the enhanced levels of superoxide anion (O2 −), NADPH oxydase activity, and the enhanced expression of NOX4 and P47phox in SHRs were attenuated by C‐ANP4–23. These results indicate that in vivo NPR‐C activation attenuates the over‐expression of cell cycle proteins through the inhibition of the enhanced oxidative stress, c‐Src and EGF‐R, PDGF‐R, IGF‐R activation, MAPK signaling and over‐expression of Giα proteins resulting in the inhibition of the hyper‐proliferation of VSMC from SHR. Thus, it can be suggested that C‐ANP4–23 may be used as a therapeutic agent for the treatment of vascular complications associated with hypertension and atherosclerosis.Support or Funding InformationSupported by grants from Canadian Institutes of Health Research (CIHR) and Heart and Stroke Foundation of Canada (HSFC).

Heart Failure With Preserved Ejection Fraction Induces Beiging in Adipose Tissue

Despite the increasing prevalence of heart failure with preserved ejection fraction (HFpEF) in humans, there are no evidence-based therapies for HFpEF. Clinical studies suggest a relationship between obesity-associated dysfunctional adipose tissue (AT) and HFpEF. However, an apparent obesity paradox exists in some HF populations with a higher body mass index. We sought to determine whether HFpEF exerted effects on AT and investigated the involved mechanisms. Mice underwent d-aldosterone infusion, uninephrectomy, and were given 1% saline for 4 weeks. HFpEF mice developed hypertension, left ventricular hypertrophy, and diastolic dysfunction and had higher myocardial natriuretic peptide expression. Although body weights were similar in HFpEF and sham-operated mice, white AT was significantly smaller in HFpEF than in sham (epididymal AT, 7.59 versus 10.67 mg/g; inguinal AT, 6.34 versus 8.38 mg/g). These changes were associated with smaller adipocyte size and increased beiging markers (ucp-1, cidea, and eva) in white AT. Similar findings were seen in HFpEF induced by transverse aortic constriction. Increased activation of natriuretic peptide signaling was seen in white AT of HFpEF mice. The ratio of the signaling receptor, natriuretic peptide receptor type A, to the clearance receptor, nprc, was increased as was p38 mitogen-activated protein kinase activation. However, HFpEF mice failed to regulate body temperature during cold temperature exposure. In HFpEF, despite a larger brown AT mass (5.96 versus 4.50 mg/g), brown AT showed reduced activity with decreased uncoupling protein 1 (ucp-1), cell death-inducing DFFA-like effector a (cidea), and epithelial V-like antigen (eva) expression and decreased expression of lipolytic enzymes (hormone-sensitive lipase, lipoprotein lipase, and fatty acid binding protein 4) versus sham. These findings show that HFpEF is associated with beiging in white AT and with dysfunctional brown AT.

Nesfatin-1 and the Cardiovascular System: Central and Pheripheral Actions and Cardioprotection.

Recently, the hypothalamic 82-aa peptide Nesfatin-1 received notable attention for its anorexigenic and anti-hyperglycemic properties. In mammalian hypothalamus, Nesfatin-1 is expressed, together with the precursor Nucleobindin 2 (NUCB2), in regions controlling water-food intake, body weight, and glucose homeostasis. The peptide is also peripherally expressed, as shown in the rat heart, in which it is present together with NUCB2. In addition to a central modulation of nutrition and energy balance, and of the nervous circuits responsible for blood pressure and heart rate control, Nesfatin-1 also acts peripherally on several districts, including the cardiovascular (CV) system. Accordingly, the peptide is regarded with interest as a multifunctional hormone not only linked to alimentary homeostasis. This review aims to analyze the literature on Nesfatin-1, with focus on its emerging CV activity. Few available studies show that the peptide affects energy metabolism of murine and human cardiomyocytes, by eliciting insulin-like effects. On the ex vivo rat heart, it directly depresses contractility and relaxation via cGMP, PKG and ERK1/2, and limits ischemia/reperfusion (I/R) damage, acting in post-conditioning protection. Nesfatin-1 actions are proposed to involve an unknown G-protein coupled receptor. However, in the rat heart, functional studies, co-immunoprecipitation and local sequence alignment analyses suggest an interaction with the Natriuretic Peptide Receptor-type A (NPR-A). These data open up novel perspectives to clarify not only the biological significance of the peptide, but also its putative biomedical potential in the presence of nutrition-dependent cardiovascular diseases.

Differential response of the natriuretic peptide system to weight loss and exercise in overweight or obese patients.

Relative atrial natriuretic peptide (ANP) deficiency has been implicated in the pathogenesis of obesity-associated cardiovascular and metabolic disease. We tested the hypothesis that more than 5% body weight reduction through 6 months hypocaloric dieting alters ANP release at rest and more so during exercise in overweight or obese patients. Venous mid-regional pro-ANP concentration was assessed at rest and after incremental exhaustive exercise testing before and after weight reduction. We also measured natriuretic peptide receptor A and C mRNA expression in subcutaneous adipose tissue to gauge both ANP responsiveness and clearance mechanisms. The average weight reduction of 9.1 ± 3.8 kg was associated with reductions in visceral and subcutaneous abdominal fat mass, liver fat content, insulin resistance, and ambulatory blood pressure. However, mid-regional pro-ANP plasma concentrations were unchanged with weight loss (51 ± 24 vs. 53 ± 24 pmol/l). Exercise elicited similar acute mid-regional pro-ANP increases before and after weight loss. Adipose tissue natriuretic peptide receptor type A mRNA expression remained unchanged, whereas natriuretic peptide receptor type C mRNA decreased with weight loss. We conclude that physical exercise acutely increases ANP release in obese patients, whereas modest diet-induced weight loss primarily affects ANP clearance mechanisms. Interventions combining weight loss and regular physical exercise may be particularly efficacious in reversing obesity-associated relative natriuretic peptide deficiency.

Atrial natriuretic peptide and regulation of vascular function in hypertension and heart failure

Atrial natriuretic peptide (ANP) plays a pivotal role in modulation of vascular function and it is also involved in the pathophysiology of several cardiovascular diseases. We provide an updated overview of the current appraisal of ANP vascular effects in both animal models and humans. We describe the physiological implications of ANP vasomodulatory properties as well as the involvement of ANP, through its control of vascular function, in hypertension and heart failure. The principal molecular mechanisms underlying regulation of vascular tone, that is natriuretic peptide receptor type A/cyclic guanylate monophosphate, natriuretic peptide receptor type C, nitric oxide system, are discussed. We review the literature on therapeutic implications of ANP in hypertension and heart failure, examining the potential use of ANP analogues, neutral endopeptidase (NEP) inhibitors, ACE/NEP inhibitors, angiotensin receptor blocker (ARB)/NEP inhibitors, the new dual endothelin-converting enzyme (ECE)/NEP inhibitors and ANP-based gene therapy. The data discussed support the role of ANP in different pathological conditions through its vasomodulatory properties. They also indicate that ANP may represent an optimal therapeutic agent in cardiovascular diseases.

A novel loss-of-function mutation in Npr2 clarifies primary role in female reproduction and reveals a potential therapy for acromesomelic dysplasia, Maroteaux type

We discovered a new spontaneous mutant allele of Npr2 named peewee (pwe) that exhibits severe disproportionate dwarfism and female infertility. The pwe phenotype is caused by a four base-pair deletion in exon 3 that generates a premature stop codon at codon 313 (L313X). The Npr2(pwe/pwe) mouse is a model for the human skeletal dysplasia acromesomelic dysplasia, Maroteaux type (AMDM). We conducted a thorough analysis of the female reproductive tract and report that the primary cause of Npr2(pwe/pwe) female infertility is premature oocyte meiotic resumption, while the pituitary and uterus appear to be normal. Npr2 is expressed in chondrocytes and osteoblasts. We determined that the loss of Npr2 causes a reduction in the hypertrophic and proliferative zones of the growth plate, but mineralization of skeletal elements is normal. Mutant tibiae have increased levels of the activated form of ERK1/2, consistent with the idea that natriuretic peptide receptor type 2 (NPR2) signaling inhibits the activation of the MEK/ERK mitogen activated protein kinase pathway. Treatment of fetal tibiae explants with mitogen activated protein kinase 1 and 2 inhibitors U0126 and PD325901 rescues the Npr2(pwe/pwe) growth defect, providing a promising foundation for skeletal dysplasia therapeutics.

Association of a single nucleotide polymorphism of the NPR3 gene promoter with early onset ischemic stroke in an Italian cohort

BackgroundNPR3, located on human chromosome 5 (5p14–p13), encodes the natriuretic peptide receptor type C (NPR-C) that is mainly known as the natriuretic peptide clearance receptor. Involvement of NPR3 in susceptibility to cardiovascular diseases, i.e. hypertension, has been previously shown. With regard to stroke predisposition, evidence for a potential role of genetic variation within or nearby NPR3 has been suggested by a previous genome wide association study. MethodsWe investigated the contribution to early-onset ischemic stroke susceptibility of the NPR3 −55 C>A transition by genotyping this variant in an Italian cohort of 368 cases and 335 controls. ResultsIn a multivariable logistic regression analysis adjusting for age, gender, hypertension, hypercholesterolemia, smoking habit and diabetes, a significant association of the −55 AA genotype with stroke was observed (OR=3.2, 95% CI 1.2–8.3, p=0.016). Remarkably, the polymorphism remained associated with stroke after adjusting for hypertensive status. ConclusionOur observation obtained in an Italian cohort of early onset ischemic strokes suggests that a NPR3 promoter gene variant could have a role on cerebrovascular disease susceptibility.

Novel mutations in natriuretic peptide receptor-2 gene underlie acromesomelic dysplasia, type maroteaux

BackgroundNatriuretic peptides (NPs) are peptide hormones that exert their biological actions by binding to three types of cell surface natriuretic peptide receptors (NPRs). The receptor NPR-B binding C-type natriuretic peptide (CNP) acts locally as a paracrine and/or autocrine regulator in a wide variety of tissues. Mutations in the gene NPR2 have been shown to cause acromesomelic dysplasia-type Maroteaux (AMDM), an autosomal recessive skeletal disproportionate dwarfism disorder in humans.MethodsIn the study, presented here, genotyping of six consanguineous families of Pakistani origin with AMDM was carried out using polymorphic microsatellite markers, which are closely linked to the gene NPR2 on chromosome 9p21-p12. To screen for mutations in the gene NPR2, all of its coding exons and splice junction sites were PCR amplified from genomic DNA of affected and unaffected individuals of the families and sequenced.ResultsSequence analysis of the gene NPR2 identified a novel missence mutation (p.T907M) in five families, and a splice donor site mutation c.2986 + 2 T > G in the other family.ConclusionWe have described two novel mutations in the gene NPR2. The presence of the same mutation (p.T907M) and haplotype in five families (A, B, C, D, E) is suggestive of a founder effect.

Protein kinase G type I in cardiac myocytes: unmasked at last?

This editorial refers to ‘Stress-dependent dilated cardiomyopathy in mice with cardiomyocyte-restricted inactivation of cyclic GMP-dependent protein kinase I’[†][1], by S. Frantz et al. , on page 1233 Increasing evidence over the past decade has suggested that elevations in myocardial cGMP may protect against adverse ventricular remodelling. cGMP is produced in different cell types comprising cardiac muscle, including vascular smooth muscle and endothelial cells, fibroblasts, monocytes/macrophages, and cardiac myocytes (CMs) themselves, all of which participate in remodelling. In the latter, cGMP is produced either from particulate guanylate cyclase (pGC) contained within GC-A [natriuretic peptide receptor type A (NPRA) activated by atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP)] and GC-B [(NPRB) activated by C-type natriuretic peptide (CNP)], or from soluble GC (sGC) activated by NO and CO. Given the diffusible nature of NO, CM sGC can theoretically be activated by NO from autocrine sources [endogenously expressed nitric oxide synthases (NOS)], paracrine sources (i.e. mainly from endothelial and inflammatory cells), and, possibly, exogenous NO. cGMP-dependent protein kinase type I (cGKI) is part of a family of cGMP-activated protein kinases (PKs) encoded by two different genes; one encoding cGKIα and cGKIβ (through alternative splicing), and the other encoding cGKII, a membrane-bound PK classically detected in the intestinal brush border.1 Together with cGMP-modulated phosphodiesterases (PDEs), cGKs represent the main effectors of cGMP signalling in cardiovascular (and other) tissues. As such they modulate the function of key proteins involved in excitation–contraction (EC) coupling ( Figure 1 ), contractility, cell survival, metabolism, and CM hypertrophic remodelling ( Figure 2 ). Recent studies have highlighted the functional compartmentation of cGMP pools within CM, each susceptible to activate a specific subset of cGK and effectors; this would be in line with the identification of cGK anchoring proteins2 (akin to the PKA-associated A kinase anchoring proteins family) that … [1]: #fn-2

Heart failure mice exhibit decreased gastric emptying and intestinal absorption

Our recent study showed that intravenously administered B-type natriuretic peptide (BNP) decreases gastric emptying and intestinal absorption in mice. We aimed to test whether acute myocardial injury and heart failure have similar effects. Wild-type (WT) and natriuretic peptide receptor type A (NPR-A) knockout (KO) mice underwent cryoinfarction (myocardial infarction [MI]) of the left ventricle (LV) versus sham. LV dysfunction was confirmed by echocardiography. Percent gastric emptying and intestinal absorption were measured and analyzed one and two weeks after infarction, by gavage feeding the mice with fluorescein-isothiocyanate-dextran. Ejection fraction was 48 ± 3% versus 64 ± 2% (P < 0.05) and fractional shortening was 24 ± 2% versus 35 ± 2% (P < 0.01), MI versus sham, respectively. BNP levels (pg/mL) were 4292 ± 276 one week after MI versus 105 ± 11 in sham (n = 5, P < 0.05) and 1964 ± 755 two weeks after MI (n = 5, P < 0.05). Gastric emptying was significantly decreased, 68 ± 6% in MI versus 89 ± 3% in sham (n = 5, P < 0.05) one week after MI and 82 ± 0.5% versus 98 ± 0.4%, MI versus sham (n = 5, P < 0.05), two weeks post-MI. Absorption, measured in relative plasma fluorescence units in WT mice, was 350 ± 79 in MI versus 632 ± 121 in sham (n = 6, P < 0.05). KO mice did not show a significant difference in emptying or absorption compared with sham. These findings suggest that MI and LV dysfunction decrease gastric emptying and absorption in mice through a mechanism that involves NPR-A.

Molecular mechanisms underlying cardiac antihypertrophic and antifibrotic effects of natriuretic peptides

Natriuretic peptides (NPs) exert well-characterized protective effects on the cardiovascular system, such as vasorelaxation, natri- and diuresis, increase of endothelial permeability, and inhibition of renin-angiotensin-aldosterone system. It has been reported that they also possess antihypertrophic and antifibrotic properties and contribute actively to cardiac remodeling. As a consequence, they are involved in several aspects of cardiovascular diseases. Antihypertrophic and antifibrotic actions of NPs appear to be mediated by specific signaling pathways within a more complex cellular network. Elucidation of the molecular mechanisms underlying the effects of NPs on cardiac remodeling represents an important research objective in order to gain more insights on the complex network leading to cardiac hypertrophy, ventricular dysfunction, and transition to heart failure, and in the attempt to develop novel therapeutic agents. The aim of the present article is to review well-characterized molecular mechanisms underlying the antihypertrophic and antifibrotic effects of NPs in the heart that appear to be mainly mediated by guanylyl cyclase type A receptor. In particular, we discuss the calcineurin/NFAT, the sodium exchanger NHE-1, and the TGFβ1/Smad signaling pathways. The role of guanylyl cyclase type B receptor, along with the emerging functional significance of natriuretic peptide receptor type C as mediators of CNP antihypertrophic and antifibrotic actions in the heart are also considered.

Interaction between bradykinin and urodilatin - a possible mechanism of clinical relevance

Background Bradykinin (BK) plays a significant role in pathophysiology of different diseases from angioedema to brain stroke and heart attack by inducing vasodilatation and increasing capillary permeability. We investigate the potential effects of natriuretic peptides on BK signaling by measuring membrane potential (Vm) of HEK293 cells using the whole cell patch clamp technique. HEK293cells are an excellent model since they display the natriuretic peptide receptor type A as well as both BK receptors (BR1 and BR2).

Endogenous Vasoactive Peptides and the Human Vagina—A Molecular Biology and Functional Study

Endogenous peptides, such as vasoactive intestinal polypeptide (VIP), C-type natriuretic peptide (CNP), and bradykinin (BK), have been proposed to play a role in the female sexual arousal response by exerting relaxation of clitoral, labial, and vaginal smooth muscle. While the effects of endogenous peptides on the human male erectile tissue have already been described, only very few studies have been conducted to investigate the peptidergic control of female genital tissues, including the vagina. To elucidate the expression of mRNA specifically encoding for peptide receptors in the human vagina and the effects of VIP, CNP, and BK on the tension induced by endothelin-1 (ET-1) of isolated human vaginal wall smooth muscle. The production of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) in response to exposure of the tissue to the peptides was also measured. The expression of mRNA encoding for receptor proteins specific for VIP, CNP, and BK were investigated by means of molecular biology (reverse transcriptase polymerase chain reaction [RT-PCR] analysis). Using the organ bath technique, the effects of VIP, CNP, and BK (0.1 nM to 1 µM) on the tension induced by 0.1 µM ET-1 of human vaginal strips were investigated. The tissue was also exposed to three different concentrations of VIP, CNP, and BK (0.01 µM, 0.1 µM, 1 µM) and the production of cAMP and cGMP determined by means of radioimmunoassays. Characterize the expression of peptide receptors in the human vagina and measure the relaxation exerted by BK, CNP, and VIP on the contraction induced by ET-1 of isolated human vaginal tissue. In addition, the effects of the peptides on the production of cAMP and cGMP were also elucidated. RT-PCR analysis revealed the expression of mRNA transcripts encoding for the VIP receptors VIP1R/vasoactive intestinal polypeptide receptor type 1 (VPAC1) and VIP2R/VPAC2, CNP receptors natriuretic peptide receptor type A (NPRA), natriuretic peptide receptor type B (NPRB) and natriuretic peptide receptor type C (NPRC), and BK receptor B2R. The tension induced by ET-1 was reversed by the peptides with the following rank order of efficacy: BK (21.7%) > VIP (20.9%) > CNP (13.3%). The relaxing effects of VIP and BK were paralleled by a 4.8-fold and fivefold increase in cAMP, while the production of cGMP was stimulated 38-fold and 119-fold in the presence of CNP or BK, respectively. Our results are in support of the hypothesis that endogenous peptides may contribute to the control of human vaginal smooth muscle tone through the involvement of the cyclic nucleotide-dependent pathways.