Natriuretic Peptide receptor-A Research Articles

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

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

Association of fat mass profile with natriuretic peptide receptor alpha in subcutaneous adipose tissue of medication-free healthy men:A cross-sectional study.

Background: Atrial natriuretic peptide increases lipolysis in human adipocytes by binding to natriuretic peptide receptor-A (NPRA). The aim of the current study was to examine the associations of NPRA mRNA of subcutaneous adipose tissue with fat mass, fat-free mass, body mass index (BMI) and arterial blood pressure in medication-free healthy men. Method: Thirty-two volunteers [age (years): 36.06±7.36, BMI: 27.60±4.63 (kg/m 2)] underwent assessments of body height/weight, % fat mass, fat-free mass (kg), blood pressure, and a subcutaneous adipose tissue biopsy via a surgical technique. Results: We found that NPRA mRNA was negatively associated with % fat mass (r=-0.40, R 2=0.16, p=0.03) and BMI (r=-0.45, R 2=0.20, p=0.01). Cohen's f 2 effect size analyses showed a small effect size between NPRA mRNA and BMI ( f 2 =0.25). One-way analysis of variance with Bonferroni post-hoc tests showed a tendency for mean differences of NPRA mRNA across BMI categories (p=0.06). This was confirmed by Cohen's d effect size analyses revealing a large effect size of NPRA mRNA between obese individuals (BMI≥30 kg/m 2) and either normal weight (BMI=19-25 kg/m 2; d=0.94) or overweight (BMI=25-30 kg/m 2; d=1.12) individuals. Conclusions: NPRA mRNA is negatively associated with % fat mass and BMI in medication-free healthy men, suggesting a possible role of NPRA in the control of fat mass accumulation.

Association of fat mass profile with natriuretic peptide receptor alpha in subcutaneous adipose tissue of medication-free healthy men: A cross-sectional study

Background: Atrial natriuretic peptide increases lipolysis in human adipocytes by binding to natriuretic peptide receptor-A (NPRA). The aim of the current study was to examine the associations of NPRA mRNA of subcutaneous adipose tissue with fat mass, fat-free mass, body mass index (BMI) and arterial blood pressure in medication-free healthy men. Method: Thirty-two volunteers [age (years): 36.06±7.36, BMI: 27.60±4.63 (kg/m 2)] underwent assessments of body height/weight, % fat mass, fat-free mass (kg), blood pressure, and a subcutaneous adipose tissue biopsy via a surgical technique. Results: We found that NPRA mRNA was negatively associated with % fat mass (r=-0.40, R 2=0.16, p=0.03) and BMI (r=-0.45, R 2=0.20, p=0.01). Cohen’s f 2 effect size analyses showed a small effect size between NPRA mRNA and BMI ( f 2=0.25). One-way analysis of variance with Bonferroni post-hoc tests showed a tendency for mean differences of NPRA mRNA across BMI categories (p=0.06). This was confirmed by Cohen’s d effect size analyses revealing a large effect size of NPRA mRNA between obese individuals (BMI≥30 kg/m 2) and either normal weight (BMI=19-25 kg/m 2; d=0.94) or overweight (BMI=25-30 kg/m 2; d=1.12) individuals. Conclusions: NPRA mRNA is negatively associated with % fat mass and BMI in medication-free healthy men, suggesting a possible role of NPRA in the control of fat mass accumulation.

The expression of natriuretic peptide receptors in developing zebrafish embryos

There are three isoforms of natriuretic peptide (NP) specific cell surface receptor: NP receptor-A (NPRA), receptor-B (NPRB), and receptor-C (NPRC). They are also known as NPR1, NPR2 and NPR3, respectively. NPs and their receptors were revealed to involve in diverse cellular and physiological processes including renal, cardiovascular, neuronal, and immunological aspects. However, the systematic analysis of the expression of these receptors in non-mammalian vertebrates is thus far lacking. In this study, two versions of the npr1 gene (npr1a and npr1b) in zebrafish was identified. Multiple sequences alignment analysis showed that zebrafish NPRs shared high homologies with NPRs of other species and possessed a typical signature domain of NPRs. The results of whole mount in situ hybridization and reverse transcription polymerase chain reaction analysis revealed that at embryonic stages, npr1a was mainly expressed in tectal ventricle, brian, heart and retina, whereas npr1b was broadly present in anterior pronephric duct. Unlike npr1, npr2 mainly expressed in branchial arches and neural tube during embryonic development. However, npr3 was expressed in pronephric ducts and corpuscle of stannius in zebrafish embryos at 72 hpf. In adults, we demonstrated that all the three NP receptors were highly existed in brain and kidney. Overall, these findings will provide an important basis for the functional analysis of NPs and its receptor during embryonic development.

Association of fat mass profile with natriuretic peptide receptor alpha in subcutaneous adipose tissue of medication-free healthy men:A cross-sectional study.

Background: Atrial natriuretic peptide increases lipolysis in human adipocytes by binding to natriuretic peptide receptor-A (NPRA). The aim of the current study was to examine the associations of NPRA mRNA of subcutaneous adipose tissue with fat mass, fat-free mass, body mass index (BMI) and arterial blood pressure in medication-free healthy men. Method: Thirty-two volunteers [age (years): 36.06±7.36, BMI: 27.60±4.63 (kg/m 2)] underwent assessments of body height/weight, % fat mass, fat-free mass (kg), blood pressure, and a subcutaneous adipose tissue biopsy via a surgical technique. Results: We found that NPRA mRNA was negatively associated with % fat mass (r=-0.40, R 2=0.16, p=0.03) and BMI (r=-0.45, R 2=0.20, p=0.01). Cohen's f 2 effect size analyses showed a small effect size between NPRA mRNA and BMI ( f 2 =0.25). One-way analysis of variance with Bonferroni post-hoc tests showed a tendency for mean differences of NPRA mRNA across BMI categories (p=0.06). This was confirmed by Cohen's d effect size analyses revealing a large effect size of NPRA mRNA between obese individuals (BMI≥30 kg/m 2) and either normal weight (BMI=19-25 kg/m 2; d=0.94) or overweight (BMI=25-30 kg/m 2; d=1.12) individuals. Conclusions: NPRA mRNA is negatively associated with % fat mass and BMI in medication-free healthy men, suggesting a possible role of NPRA in the control of fat mass accumulation.

Cross-Talk between Distinct Receptors Shapes Itch Behavior in the Spinal Cord

Natriuretic peptide (NP) family comprises multiple peptides/receptors whose respective role in itch transmission remains unclear. We report that about 23% of Npr1 that encodes NP receptor A (NPRA) in the superficial spinal cord co-express gastrin-releasing peptide (Grp), while Npr3 that encodes NP receptor C (NPRC), partially overlaps with the neuromedin B receptor (NMBR) required for histamine-evoked itch. While Npr1 is required for chloroquine- (CQ) and histamine-evoked itch, the role of Npr3 is limited to the latter. Notably, B-type natriuretic peptide (BNP) significantly facilitated NMB-, but not GRP-, evoked scratching behavior, and Ca2 response in NMBR/NPRC cells. Consistently, BNP-saporin ablated spinal Npr1 and Npr3 neurons and impaired histamine-, but not CQ-evoked, itch. Thus, the findings identify the role of BNP-NPRC signaling in modulation of histamine-evoked itch via NPRC-NMBR cross-talk independent of GRP-GRPR signaling. Our studies reveal distinct modes of action for bombesin-related peptides and NP in itch transmission.

Discovery and in vivo effects of novel human natriuretic peptide receptor A (NPR-A) agonists with improved activity for rat NPR-A

Natriuretic peptide receptor A (NPR-A) agonists were evaluated in vivo by optimizing the structure of quinazoline derivatives to improve agonistic activity for rat NPR-A. A 1,4-Cis-aminocyclohexylurea moiety at 4-position and hydroxy group of d-alaninol at 2-position on the quinazoline ring were found to be important factors in improving rat NPR-A activity. We identified potent quinazoline and pyrido[2,3-d]pyrimidine derivatives against rat NPR-A, with double-digit nanomolar EC50 values. The in vivo results showed that compound 56b administered at 1.0 mg/kg/min significantly increased plasma cGMP concentration and urine volume in rats. We discovered novel potent NPR-A agonists that showed agonistic effects similar to those of atrial natriuretic peptide.

Discovery and SAR of a novel series of Natriuretic Peptide Receptor-A (NPR-A) agonists

Novel thienopyrimidine compounds 2 and 3 were discovered from high-throughput screening as Natriuretic Peptide Receptor A (NPR-A) agonists. Scaffold hopping of a thienopyrimidine ring to a quinazoline ring, introduction of the basic functional group and optimization of the substituent on the 6-position of the benzene ring of quinazoline led to improved agonistic activity. We discovered compound 48, which showed potent agonistic activity for NPR-A with an EC50 value of 0.073μM, indicating 350-fold potency compared to the hit compound 3.

Abstract P340: Immunomodulatory Effect of Rapamycin on the Expression of Anti-inflammatory Cytokines in Npr1 Gene-deleted Mice

Disruption of natriuretic peptide receptor-A (NPRA) gene ( Npr1 ) activates the pro-inflammatory responses, which contributes to the pathogenesis of hypertension and end-organ damage. The objective of this study was to determine the kinetic responses of pro- and anti-inflammatory cytokines in Npr1 gene-knockout (KO) mice. Npr1 0-copy ( Npr1 -/- ), 1-copy ( Npr1 +/- ), and 2-copy ( Npr1 +/+ ) mice were pre-treated with rapamycin and multiplex analyses were done to assess cytokines levels. Pro-inflammatory cytokine, IFN-γ protein levels in plasma and kidney of 0-copy and 1-copy mice were markedly higher compared with 2-copy mice (76±1; 49±2 vs 32±1.3 pg/ml; 79±2; 29±1 vs. 27±0.5 pg/mg, respectively). Similarly, IL-6 levels in plasma and kidney were significantly elevated in 0-copy and 1-copy mice than 2-copy mice (52±1; 27±0.5 vs.12±0.4 pg/ml; 49±1.5; 38±2 vs.18±1.1 pg/mg, respectively). Interestingly, anti-inflammatory cytokine IL-5 protein levels in plasma and kidneys were significantly down-regulated in 0-copy and 1-copy mice than 2-copy mice (6±0.8; 5±0.1 vs. 12±0.5 pg/ml; 6±0.6; 9±0.4 vs. 28±0.5 pg/mg). IL-10 levels in plasma and kidney of 0-copy and 1-copy mice were also significantly decreased than 2-copy mice (22±0.4; 39±1 vs. 62±3 pg/ml; 14±1.7; 36±0.2 vs. 52±3 pg/mg). Rapamycin significantly reduced the levels of IFN- γ in plasma and kidney of 0-copy (50%, 35%) and 1-copy (63%, 55%) mice and IL-6 level in 0-copy (60%, 38%) and in 1-copy (40%, 26%) mice compared with 2-copy mice. In contrast, rapamycin treatment significantly elevated IL-5 levels in plasma and kidneys of 0-copy (68%, 77%) and 1-copy (61%, 64%) mice and IL-10 levels in 0-copy (80%, 78%) and 1-copy (47%, 25%) mice than 2-copy mice. A significant decrease in blood pressure occurred in rapamycin-treated 0-copy (19±4 mmHg) and 1-copy (12±3 mmHg) mice than untreated control mice. The results demonstrate that the expression of pro-inflammatory cytokines is greatly upregulated in Npr1 KO mice compared with 2-copy mice and rapamycin serves as the immune modulator of anti-inflammatory cytokines in these animals. The present findings implicate that rapamycin might act as an anti-inflammatory drug for the treatment of pathophysiology of hypertension-associated inflammation.

Abstract P161: Inhibition of Class I HDAC Enhances the Expression of Npr1 and Repairs Renal Pathology in Gene-targeted Haplotype Mice

The objective of the present study was to determine the effect of class I histone deacetylase (HDAC) inhibitor, mocetinostat (MGCD0103) on the expression of Npr1 (coding for natriuretic peptide receptor-A; NPRA) and renal pathology in Npr1 gene-disrupted haplotype (50% of normal) mice. Adult male Npr1 haplotype (1-copy; Npr1 +/- ), wild-type (2-copy; Npr1 +/+ ), and gene-duplicated (3-copy; Npr1 ++/+ ) mice were injected intraperitonealy with MGCD0103 (2 mg/kg) at alternate days for 2-weeks. After MGCD0103 treatment, the renal Npr1 mRNA was increased in Npr1 +/- mice by 7.3-fold (p < 0.01), Npr1 +/+ mice by 4.4-fold (p < 0.05) and Npr1 ++/+ mice by 3.6-fold (p < 0.05) compared with vehicle-treated controls. The MGCD0103 also enhanced renal cGMP levels (pmol/mg protein) in Npr1 +/- (57 ± 7 vs. control, 12 ± 1; p < 0.01), Npr1 +/+ (125 ± 9 vs. control, 66 ± 5; p < 0.01), and Npr1 ++/+ (202 ± 7 vs. control, 127 ± 15; p < 0.05) mice. An increased HDAC activity (ng/min/mg protein) was observed in Npr1 +/- mice (24.4 ± 2.8; p < 0.05); however, Npr1 ++/+ mice showed lower HDAC activity (6.4 ± 0.7; p < 0.05); compared with Npr1 +/+ mice (15.9 ± 1.3). Treatment with MGCD0103 significantly attenuated HDAC activity by almost 50% (15.3 ± 1.2; p < 0.01) in Npr1 haplotype mice. A significant decrease in systolic blood pressure was observed in MGCD0103-treated Npr1 +/- mice (106 ± 0.6 vs. control, 131 ± 1.9, p < 0.001). Significantly lower creatinine clearance (μl/min) was observed in Npr1 +/- (51 ± 11; p < 0.05) vs. Npr1 +/+ mice (130 ± 14.0; p < 0.05) and treatment with MGCD0103 increased creatinine clearance in Npr1 +/- mice (105 ± 13; p < 0.05) vs. controls. Higher urinary albumin to creatinine ratio was detected in Npr1 +/- mice (0.7 ± 0.05) vs. Npr1 +/+ animals (0.5 ± 0.05; p < 0.05) and a complete reversal was observed in drug-treated Npr1 +/- mice (0.4 ± 0.04). The present results provide direct evidence that class I HDAC inhibition upregulates NPRA expression in vivo and repairs the renal pathology in Npr1 +/- haplotype mice. The present findings will have important implications in the treatment and prevention of hypertension and renal pathophysiological conditions.

DNA methylation dysregulations in valvular atrial fibrillation.

The epigenetic changes underlying the development of atrial fibrillation (AF) remain incompletely understood. Limited evidence suggests that abnormal DNA methylation might be involved in the pathogenesis of AF. In the present study, we evaluated the methylation status of genomic DNA from myocardial tissue in AF patients and sinus rhythm (SR) patients systematically. DNA methylation dysregulations will be associated with valvular AF. Right atrial myocardial tissue was obtained from rheumatic valvular patients who had undergone valve replacement surgery (SR group, n = 10; AF group, n = 10). The global DNA methylation level, the promoter methylation level of the natriuretic peptide receptor-A gene (NPRA), and its correlation with the mRNA expression level of DNA methyltransferase genes were detected. The global DNA methylation level was significantly higher in the AF group than in the SR group (P < 0.05). The NPRA mRNA expression was decreased and the NPRA gene was hypermethylated in the AF group (P < 0.05). Meanwhile, the NPRA mRNA expression level has a negative correlation with the mean methylation level in the promoter region of the NPRA gene. DNA methylation dysregulations may be relevant in the pathogenesis of AF. DNA methyltransferase 3B likely plays an essential role in the DNA methylation dysregulations in AF.

Natriuretic peptide C receptor in the developing sheep lung: role in perinatal transition

Background: At birth, the release of surfactant from alveolar type II cells (ATIIs) is stimulated by increased activity of the beta-adrenergic/adenylyl cyclase/cyclic 3'-5' adenosine monophosphate-signaling cascade. Atrial natriuretic peptide (ANP) stimulates surfactant secretion through natriuretic peptide receptor A (NPR-A). ANP inhibits adenylyl cyclase activity through its binding to NPR-C. We wished to further understand the role of the NPR-C in perinatal transition. Methods: We studied ATII expression of NPR-C in fetal and newborn sheep using immunohistochemistry, and surfactant secretion in isolated ATIIs by measuring 3[H] choline release into the media. Results: ANP induced surfactant secretion, and, at higher doses, it inhibits the stimulatory effect of the secretagogue terbutaline. ATII NPR-C expression decreased significantly after birth. Premature delivery also markedly decreased ANP and NPR-C in ATIIs. Co-incubation of terbutaline (10-4 M) with ANP (10-6 M) significantly decreased 3[H] choline release from isolated newborn ATII cells when compared with terbutaline alone; this inhibitory effect was mimicked by the specific NPR-C agonist, C-ANP (10-10 M). Conclusion: ANP may act as an important epithelial-derived inhibitor of surfactant release in the fetal lung, and downregulation of ANP and NPR-C following birth may sensitize ATII cells to the effects of circulating catecholamines, thus facilitating surfactant secretion.

Natriuretic peptide receptor A is related to the expression of vascular endothelial growth factors A and C, and is associated with the invasion potential of tongue squamous cell carcinoma

Natriuretic peptide receptor A (NPRA) is one of the natriuretic peptide receptors. NPRA has been reported to play a role in the carcinogenesis of various tumours, as well as functional roles in renal, cardiovascular, endocrine, and skeletal homeostasis. The clinicopathological significance of NPRA in tongue squamous cell carcinoma (TSCC) was examined in this study. The overexpression of NPRA was more frequent in TSCC (21/58, 36.2%) than in the normal oral epithelium (0/10, 0%) (P<0.05). It was also more frequently observed in cancers with higher grades according to the pattern of invasion (grades 1–2 vs. grades 3–4, P<0.01). Additionally, there was a tendency towards an association between the N classification and NPRA expression (N0 vs. N1–2, P=0.06). Significant correlations were also observed between the expression of NPRA and that of VEGF-A (P<0.001) and VEGF-C (P<0.001). The high-NPRA expression group had a significantly poorer prognosis, with a 5-year disease-specific survival rate of 39.7%, compared to 97.0% in the low-expression group (P<0.001). Multivariate analysis suggested that the overexpression of NPRA may also be an independent prognostic factor (P<0.05). In conclusion, NPRA is associated with VEGF expression levels, invasion, and metastasis, and may be a prognostic factor in TSCC patients.

The effects of valproic acid on the mRNA expression of Natriuretic Peptide Receptor A and KQT-like subfamily Q-1 in human colon cancer cell lines

Aim and objectivesThe histone deacetylase (HDAC) inhibitor, Valproic Acid (VPA), causes growth inhibition and apoptosis in colorectal cancer cells. HDAC inhibition is associated with the transcriptional regulation of Natriuretic Peptide Receptor-A (NPR-A). NPR-A regulates voltage-gated potassium channel, KQT-like subfamily Q, member 1 (KCNQ1). NPR-A and KCNQ1 are also involved in the initiation and propagation of cancer cells. In this study, we investigated the simultaneous expressional changes of NPR-A and KCNQ1 among VPA-treated colon cancer cells. Materials and methodsHuman colorectal cancer cells were cultured and treated with increasing concentrations of VPA at different time points. MTT viability test was conducted to evaluate the growth inhibition. Real Time RT-PCR was used to quantify differential mRNA expression of NPR-A and KCNQ1 genes. Two-way ANOVA and bonferroni post-tests were used to analyze data statistically. ResultsWe showed that VPA treatment inhibits the growth of SW-480 cells more efficiently compared to HT-29. NPR-A and KCNQ1 genes were significantly upregulated upon VPA treatment in both cell lines (P<0.0001). ConclusionThe alteration of NPR-A and KCNQ1 genes were more ordered among SW-480 cancer cells. The expressional changes of KCNQ1 and NPR-A among VPA treated human colon cancer cells follow the same pattern in similar combinations. VPA could regulate the expression of KCNQ1 through altering the mRNA expression of NPR-A.

Enhanced expression of natriuretic peptide receptor A and B in neutrophils of culprit lesions in patients with acute myocardial infarction.

Natriuretic peptides and their specific receptors have been suggested to have regulatory effects on smooth muscle cell (SMC) growth and inflammatory cell reactions. However, the roles of natriuretic peptide receptor A (NPR‑A) and B (NPR‑B) in unstable plaques remain to be studied in detail. Frozen sections from 82 coronary artery segments were used. These segments were obtained at autopsy from 13patients with acute myocardial infarction (AMI; 7 ruptured and 6 eroded plaques) and from 30patients with non‑cardiovascular diseases. Antibodies against SMCs, endothelial cells, macrophages, neutrophils, NPR‑A, NPR‑B and neutral endopeptidase (NEP) were used. Neutrophil infiltration was identified in all lesions with plaque rupture or erosion. Double immunostaining identified that the majority of NPR‑A‑ or NPR‑B‑positive cells were neutrophils in ruptured and eroded plaques. Using morphometric analysis, no significant difference was observed in the percentage of NPR‑A‑ and NPR‑B‑positive cells between ruptured and eroded plaques, while the number of NEP‑positive neutrophils in ruptured plaques was significantly higher compared with eroded plaques(P<0.0001). These results of the distinct presence of NPR‑A‑ and NPR‑B‑positive cells in unstable plaques underlying AMI suggested that natriuretic peptides serve a role in regulating plaque instability in humans.

Atrial natriuretic peptide regulates adipose tissue accumulation in adult atria

The abundance of epicardial adipose tissue (EAT) is associated with atrial fibrillation (AF), the most frequent cardiac arrhythmia. However, both the origin and the factors involved in EAT expansion are unknown. Here, we found that adult human atrial epicardial cells were highly adipogenic through an epithelial-mesenchymal transition both in vitro and in vivo. In a genetic lineage tracing the WT1CreERT2+/-RosatdT+/- mouse model subjected to a high-fat diet, adipocytes of atrial EAT derived from a subset of epicardial progenitors. Atrial myocardium secretome induces the adipogenic differentiation of adult mesenchymal epicardium-derived cells by modulating the balance between mesenchymal Wingless-type Mouse Mammary Tumor Virus integration site family, member 10B (Wnt10b)/β-catenin and adipogenic ERK/MAPK signaling pathways. The adipogenic property of the atrial secretome was enhanced in AF patients. The atrial natriuretic peptide secreted by atrial myocytes is a major adipogenic factor operating at a low concentration by binding to its natriuretic peptide receptor A (NPRA) receptor and, in turn, by activating a cGMP-dependent pathway. Hence, our data indicate cross-talk between EAT expansion and mechanical function of the atrial myocardium.

Optical control of a receptor-linked guanylyl cyclase using a photoswitchable peptidic hormone.

The optical control over biological function with small photoswitchable molecules has gathered significant attention in the last decade. Herein, we describe the design and synthesis of a small library of photoswitchable peptidomimetics based upon human atrial natriuretic peptide (ANP), in which the photochromic amino acid [3-(3-aminomethyl)phenylazo]phenylacetic acid (AMPP) is incorporated into the peptide backbone. The endogeneous hormone ANP signals via the natriuretic peptide receptor A (NPR-A) through raising intracellular cGMP concentrations, and is involved in blood pressure regulation and sodium homeostasis, as well as lipid metabolism and pancreatic function. The cis- and trans-isomers of one of our peptidomimetics, termed TOP271, exhibit a four-fold difference in NPR-A mediated cGMP synthesis in vitro. Despite this seemingly small difference, TOP271 enables large, optically-induced conformational changes ex vivo and transforms the NPR-A into an endogenous photoswitch. Thus, application of TOP271 allows the reversible generation of cGMP using light and remote control can be afforded over vasoactivity in explanted murine aortic rings, as well as pancreatic beta cell function in islets of Langerhans. This study demonstrates the broad applicability of TOP271 to enzyme-dependent signalling processes, extends the toolbox of photoswitchable molecules to all classes of transmembrane receptors and utilizes photopharmacology to deduce receptor activation on a molecular level.

Role of corin in the regulation of blood pressure.

Corin is a transmembrane protease that activates atrial natriuretic peptide (ANP), an important hormone in regulating salt-water balance and blood pressure. This review focuses on the regulation of corin function and potential roles of corin defects in hypertensive, heart, and renal diseases. Proprotein convertase subtilisin/kexin-6 has been identified as a primary enzyme that converts zymogen corin to an active protease. Genetic variants that impair corin intracellular trafficking, cell surface expression, and zymogen activation have been found in patients with hypertension, cardiac hypertrophy, and pre-eclampsia. Reduced corin expression has been detected in animal models of cardiomyopathies and in human failing hearts. Low levels of circulating soluble corin have been reported in patients with heart disease and stroke. Corin, ANP and natriuretic peptide receptor-A mRNAs, and proteins have been colocalized in human renal segments, suggesting a corin-ANP autocrine function in the kidney. Corin is a key enzyme in the natriuretic peptide system. The latest findings indicate that corin-mediated ANP production may act in a tissue-specific manner to regulate cardiovascular and renal function. Corin defects may contribute to major diseases such as hypertension, heart failure, pre-eclampsia, and kidney disease.

1 Peripheral blood natriuretic peptide is associated with myocardial fibrosis and cardiac tissue expression of natriuretic peptide and fibro-inflammatory genes in patients with normal ejection fraction

Introduction The St Vincent’s Screening TO Prevent Heart Failure (STOP-HF) study showed that preclinical left ventricular diastolic dysfunction (PCDD) is more prevalent than left ventricular systolic function, that peripheral blood natriuretic peptide (NP) can be used to identify asymptomatic myocardial disease and that NP correlates with disease severity. Methods We investigated peripheral blood biomarkers associated with PCDD and corresponding myocardial gene expression of the biomarkers in 35 consecutive, consenting stable patients with normal ejection fraction (EF > 45%) undergoing elective CABG surgery. Atrial tissue was obtained adjacent to the venous cannulation site and was stained for collagen using picosirus red and macrophage markers. Patients were categorised as PCDD or controls based on Doppler Echocardiography. Biomarkers and genes of interest included fibro-inflammatory genes, NP and its main transmembrane receptor Natriuretic Peptide Receptor A (NPRA). Results Patients were aged 67.4 ± 9.8 years, 25 (69%) were male, 18 (53%) had hypertension and 5 (14%) had diabetes. Preclinical LVDD patients (n = 10) had greater tissue collagen volume fraction, E/Eprime (12.5 ± 2.6 vs. 8.4 ± 2.0), LAVI (30.6 ± 4.2 vs. 27.8 ± 3.4) and atrial fibrillation (70% vs 8%) than controls (all p Conclusion PCDD is associated with elevated peripheral blood NP, myocardial fibrosis and altered expression of fibro-inflammatory genes in the myocardium. Unlike other markers of fibro-inflammation, peripheral blood NP was correlated with myocardial tissue expression of its corresponding gene and these data underline the value of peripheral blood NP in risk stratification in PCDD.

Brain natriuretic peptide suppresses pain induced by BmK I, a sodium channel-specific modulator, in rats

BackgroundA previous study found that brain natriuretic peptide (BNP) inhibited inflammatory pain via activating its receptor natriuretic peptide receptor A (NPRA) in nociceptive sensory neurons. A recent study found that functional NPRA is expressed in almost all the trigeminal ganglion (TG) neurons at membrane level suggesting a potentially important role for BNP in migraine pathophysiology.MethodsAn inflammatory pain model was produced by subcutaneous injection of BmK I, a sodium channel-specific modulator from venom of Chinese scorpion Buthus martensi Karsch. Quantitative PCR, Western Blot, and immunohistochemistry were used to detect mRNA and protein expression of BNP and NPRA in dorsal root ganglion (DRG) and dorsal horn of spinal cord. Whole-cell patch clamping experiments were conducted to record large-conductance Ca2+-activated K+ (BKCa) currents of membrane excitability of DRG neurons. Spontaneous and evoked pain behaviors were examined.ResultsThe mRNA and protein expression of BNP and NPRA was up-regulated in DRG and dorsal horn of spinal cord after BmK I injection. The BNP and NPRA was preferentially expressed in small-sized DRG neurons among which BNP was expressed in both CGRP-positive and IB4-positive neurons while NPRA was preferentially expressed in CGRP-positive neurons. BNP increased the open probability of BKCa channels and suppressed the membrane excitability of small-sized DRG neurons. Intrathecal injection of BNP significantly inhibited BmK-induced pain behaviors including both spontaneous and evoked pain behaviors.ConclusionsThese results suggested that BNP might play an important role as an endogenous pain reliever in BmK I-induced inflammatory pain condition. It is also suggested that BNP might play a similar role in other pathophysiological pain conditions including migraine.