Natriuretic Peptide Receptor A Expression Research Articles

NPRA promotes fatty acid metabolism and proliferation of gastric cancer cells by binding to PPARα

Among cancers, gastric cancer (GC) ranks third globally in morbidity and mortality, particularly in East Asia. Natriuretic peptide receptor A (NPRA), a receptor for guanylate cyclase, plays important roles in regulating water and sodium balance. Recent studies have suggested that NPRA is involved in tumorigenesis, but its role in GC development remains unclear. Herein, we showed that the expression level of NPRA was positively correlated with gastric tumor size and clinical stage. Patients with high NPRA expression had a lower five-year survival rate than those with low expression, and NPRA was identified as an independent predictor of GC prognosis. NPRA knockdown suppressed GC cell proliferation, migration and invasion. NPRA overexpression enhanced cell malignant behavior. Immunohistochemistry of collected tumor samples showed that tumors with high NPRA expression had higher peroxisome proliferator-activated receptor α (PPARα) levels. In vivo and in vitro studies showed that NPRA promotes fatty acid oxidation and tumor cell metastasis. Co-IP showed that NPRA binds to PPARα and prevents PPARα degradation. PPARα upregulation under NPRA protection activates arnitine palmitoyl transferase 1B (CPT1B) to promote fatty acid oxidation. In this study, new mechanisms by which NPRA promotes the development of GC and new regulatory mechanisms of PPARα were identified.

Shunxin decoction improves diastolic function in rats with heart failure with preserved ejection fraction induced by abdominal aorta constriction through cyclic guanosine monophosphate-dependent protein kinase Signaling Pathway.

To determine whether Shunxin decoction improves diastolic function in rats with heart failure with preserved ejection fraction (HFpEF) by regulating the cyclic guanosine monophosphate-dependent protein kinase (cGMP-PKG) signaling pathway. Except for control group 8 and sham surgery group 8, the remaining 32 male Sprague-Dawlay rats were developed into HFpEF rat models using the abdominal aorta constriction method. These rats in the HFpEF model were randomly divided into the model group, the Shunxin high-dose group, the Shunxin low-dose group, and the Qiliqiangxin capsule group. The three groups received high-dose Shunxin decoction, low-dose Shunxin decoction, and Qiliqiangxin capsule by gavage, respectively, for 14 d. After the intervention, the diastolic function of each rat was evaluated by testing E/A, heart index, hematoxylin-eosin staining, Masson, myocardial ultrastructure, and N-terminal pro-brain natriuretic peptide (NT-proBNP). The Bioinformatics Analysis Tool for Molecular Mechanism of Traditional Chinese Medicine (BATMAN-TCM) software was used to predict targets for which Shunxin decoction acts on the cGMP-PKG pathway. Natriuretic peptide receptor A (NPRA) and guanylate cyclase (GC) were detected by immunohistochemistry, and eNOS, phosphodiesterase 5A (PDE5A), and cGMP-dependent protein kinase 1(PKG I) were determined by Western blotting. Compared to the model group, the thickness of the interventricular septum at the end of diastole (IVSd) and the thickness of the posterior wall at the end of diastole (PWd) of the Shunxin decoction high-dose group, Shunxin decoction low-dose group, and Qiliqiangxin capsule group were all significantly reduced ( < 0.01). Furthermore, Shunxin decoction high-dose group E/A value was decreased ( < 0.01). Compared to the model group, the expression of NPRA and GC increased in the Shunxin decoction low-dose group and the Qiliqiangxin capsule group ( < 0.01). Compared to the model group, the expressions of eNOS and PKG I increased ( < 0.05) in the Shunxin decoction high-dose group. The expression of PDE5A expression decreased in the myocardium of the Shunxin decoction high-dose group, Shunxin decoction low-dose group, and Qiliqiangxin capsule group compared to the model group ( < 0.01). Shunxin decoction can improve diastolic function in rats with HFpEF. It increases the expression of NPRA, GC, and eNOS in the myocardial cell cGMP-PKG signaling pathway, upregulates cGMP expression, decreases PDE5A expression to reduce the cGMP degradation. Thus, the cGMP continually stimulates PKG I, reversing myocardial hypertrophy and improving myocardial compliance in HFpEF rats.

Natriuretic peptide receptor a promotes gastric malignancy through angiogenesis process

Gastric cancer (GC) ranks the third among global cancer-related mortality, especially in East Asia. Angiogenesis plays an important role in promoting tumor progression, and clinical trials have demonstrated that anti-angiogenesis therapy is effective in GC management. Natriuretic peptide receptor A (NPRA) functions significantly in promoting GC development and progression. Whether NPRA can promote angiogenesis of GC remains unclear. Tumor samples collection and immunohistochemical experiment showed that the expression of NPRA was positively correlated with the expression of CD31 and vessel density. In vivo and in vitro analysis showed that NPRA could promote GC-associated angiogenesis and tumor metastasis. Results of Co-IP/MS showed that NPRA could prevent HIF-1α from being degraded by binding to HIF-1α. Protection of HIF-1α improved VEGF levels and thus promoted angiogenesis. In summary, NPRA protected HIF-1α from proteolysis by binding to HIF-1α, increased the expression of HIF-1α, and promoted GC angiogenesis. This study has discovered a new mechanism for NPRA to promote gastric cancer development and a new regulatory mechanism for HIF-1α.

Skeletal muscle alterations in tachycardia-induced heart failure are linked to deficient natriuretic peptide signalling and are attenuated by RAS-/NEP-inhibition.

BackgroundHeart failure induced cachexia is highly prevalent. Insights into disease progression are lacking.MethodsEarly state of left ventricular dysfunction (ELVD) and symptomatic systolic heart failure (HF) were both induced in rabbits by tachypacing. Tissue of limb muscle (LM) was subjected to histologic assessment. For unbiased characterisation of early and late myopathy, a proteomic approach followed by computational pathway-analyses was performed and combined with pathway-focused gene expression analyses. Specimen of thoracic diaphragm (TD) served as control for inactivity-induced skeletal muscle alterations. In a subsequent study, inhibition of the renin-angiotensin-system and neprilysin (RAS-/NEP) was compared to placebo.ResultsHF was accompanied by loss of protein content (8.7±0.4% vs. 7.0±0.5%, mean±SEM, control vs. HF, p<0.01) and a slow-to-fast fibre type switch, establishing hallmarks of cachexia. In ELVD, the enzymatic set-up of LM and TD shifted to a catabolic state. A disturbed malate-aspartate shuttle went well with increased enzymes of glycolysis, forming the enzymatic basis for enforced anoxic energy regeneration. The histological findings and the pathway analysis of metabolic results drew the picture of suppressed PGC-1α signalling, linked to the natriuretic peptide system. In HF, natriuretic peptide signalling was desensitised, as confirmed by an increase in the ratio of serum BNP to tissue cGMP (57.0±18.6pg/ml/nM/ml vs. 165.8±16.76pg/ml/nM/ml, p<0.05) and a reduced expression of natriuretic peptide receptor-A. In HF, combined RAS-/NEP-inhibition prevented from loss in protein content (8.7±0.3% vs. 6.0±0.6% vs. 8.3±0.9%, Baseline vs. HF-Placebo vs. HF-RAS/NEP, p<0.05 Baseline vs. HF-Placebo, p = 0.7 Baseline vs. HF-RAS/NEP).ConclusionsTachypacing-induced heart failure entails a generalised myopathy, preceding systolic dysfunction. The characterisation of “pre-cachectic” state and its progression is feasible. Early enzymatic alterations of LM depict a catabolic state, rendering LM prone to futile substrate metabolism. A combined RAS-/NEP-inhibition ameliorates cardiac-induced myopathy independent of systolic function, which could be linked to stabilised natriuretic peptide/cGMP/PGC-1α signalling.

Expression and Regulation of Brain Natriuretic Peptide and Natriuretic Peptide Receptor A (NPR-A) in L6-S1 Dorsal Root Ganglia in a Rat Model of Chronic Nonbacterial Prostatitis.

BackgroundThe study aimed to investigate the expression of brain natriuretic peptide (BNP) and natriuretic peptide receptor A (NPR-A) in L6–S1 dorsal root ganglia (DRG) in a rat model of chronic nonbacterial prostatitis (CNP).Material/MethodsOne hundred specific pathogen-free (SPF) male Sprague–Dawley rats were randomly divided into a control group (N=50) and a study group (N=50). The control group underwent prostatic injection of 0.1 ml of normal saline on days 3, 7, 10, 14, and 28. The study group, or rat model of CNP, underwent prostatic injection of 0.1 ml of complete Freund’s adjuvant on days 3, 7, 10, 14, and 28. At the end of the study, the rats were euthanized, and the prostate tissues and L6–S1 DRG were removed. Histology was performed on the prostate tissue from the rats in the study group and control group. Real-time fluorescence-based quantitative polymerase chain reaction (PCR) and Western blot were used to study the expression of BNP and NPR-A mRNA and protein in the DRG from the rats in the study group and control group.ResultsIn the rat model of CNP, the expression of BNP and NPR-A were significantly increased in L6–S1 DRG compared with the controls.ConclusionsIn a rat model of CNP, the increased expression of BNP and NPR-A in L6–S1 DRG may have a role in pain signaling pathways associated with chronic prostatitis.

Is Atrial Natriuretic Peptide (ANP) and Natriuretic Peptide Receptor-A (NPR-A) Expression in Human Placenta and Decidua Normal?

BackgroundAtrial natriuretic peptide (ANP) is a cardiac hormone that regulates blood pressure and the salt-water balance in the blood. It acts through natriuretic peptide receptors (NPR), and the major biologically active ANP receptor is natriuretic peptide receptor-A (NPR-A). Aberrant forms of ANP and its receptors have been reported in patients with preeclampsia. However, whether aberrant forms of ANP or NPR-A are present in preeclamptic placenta, and what their role is in preeclampsia pathogenesis, has not yet been elucidated clearly. The aim of this study was to assess the expression of ANP and NPR-A in the placenta and decidua and its role in preeclampsia development.Material/MethodsThe expression of ANP and NPR-A in the first-trimester villous and decidua, full-term placenta, and preeclamptic placenta was determined using immunohistochemistry and Western blot analysis. The HTR8/SVneo cell line was used to investigate the role of NPR-A in proliferation, apoptosis, and invasion using Cell Counting Kit-8 analysis, flow cytometry analysis, and a Transwell invasion assay, respectively.ResultsANP and NPR-A were localized in the syncytiotrophoblasts, cytotrophoblasts, and trophoblast columns of human first-trimester villous trophoblast cells of decidua, and in the glandular epithelium and extravillous trophoblast cells of decidua. ANP-positive and NPR-A-positive cells in the decidual stroma were clustered around and infiltrated into the vascular wall of the spiral artery undergoing remodeling. NPR-A expression was significantly reduced in preeclamptic placentas, and NPR-A knockdown significantly impaired the invasion ability of HTR8/SVneo cells, although it had no effect on cell proliferation and apoptosis.ConclusionsANP and NPR-A are involved in human placental development. Decreased levels of NPR-A may contribute to the development of preeclampsia.

Abstract P255: Differential Regulation of Blood Pressure and Renal Injury by HDAC Inhibitor Mocetinostat in Npr1 Gene-targeted Male and Female Mutant Mice

The objective of the present study was to elucidate the systolic blood pressure (SBP) lowering effect of class I histone deacetylase (HDAC) inhibitor, mocetinostat (MGCD0103) by enhanced expression of natriuretic peptide receptor-A (NPRA) in gene ( Npr1 ). Adult male and female Npr1 heterozygous (1-copy; Npr1 +/- ), wild-type (2-copy; Npr1 +/+ ), and gene-duplicated (3-copy; Npr1 ++/+ ) mice were intraperitonealy injected with MGCD (2 mg/kg) for 2-weeks. The renal NPRA protein levels were significantly increased in the treated male (1-copy, 2.1-fold; 2-copy, 2.3-fold; and 3-copy, 1.5-fold; p &lt; 0.05) and female (1-copy, 3.6-fold; 2-copy, 2.1-fold; and 3-copy, 1.7-fold; p &lt; 0.05) mice compared with untreated animals. HDAC activity was significantly higher in male (1-copy, 24.4 ± 2.8; 2-copy, 15.9 ± 1.2; and 3-copy, 6.4 ± 0.7; ng/min/mg protein) than female (1-copy, 13.7 ± 1.4; 2-copy, 8.5 ± 0.9; and 3-copy, 4.7 ± 0.9, p &lt; 0.05) mice; however, treatment with MGCD significantly attenuated HDAC activity in both male (~40%, p &lt; 0.05) and female (~50%, p &lt; 0.05) animals. Male mice exhibited significantly higher SBP than female mice and treatment with MGCD decreased SBP in both 1-copy male (106 ± 0.6 vs. control, 129 ± 1.9; mm Hg) and female (97 ± 2.2 vs. control, 110 ± 2.1, p &lt; 0.001) mice. Significantly high urinary protein to creatinine ratio was detected in male compared with female mice which was attenuated by MGCD treatment in male mice (1-copy, 3.2 ± 0.4 vs. untreated 5.5 ± 04; 2-copy 2.5 ± 0.4 vs. untreated 4.6 ± 0.2; and 3-copy, 1.6 ± 0.3 vs. untreated 3.1 ± 0.4; p &lt; 0.05). Lower creatinine clearance (μl/min) was observed in both male (1-copy, 51 ± 11 vs. 2-copy, 130 ± 14.0; p &lt; 0.05) and female (1-copy, 55 ± 2.7 vs. 2-copy, 129 ± 6.4; p &lt; 0.01) mice. However, treatment with MGCD increased creatinine clearance in male (105 ± 13; p &lt; 0.05) and female (97 ± 8.4; p &lt; 0.05) vs. control mice. The present results demonstrate that class I HDAC inhibitor, MGCD upregulates NPRA expression in vivo , lowers SBP, and repairs renal injury differentially in male vs. female mice. These findings will have important implications for treatment of hypertension and renal injury in humans in a sex-related manner.

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.

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.

Natriuretic peptide receptor A inhibition suppresses gastric cancer development through reactive oxygen species-mediated G2/M cell cycle arrest and cell death

Natriuretic peptide receptor A (NPRA), the major receptor for atrial natriuretic peptide (ANP), has been implicated in tumorigenesis; however, the role of ANP-NPRA signaling in the development of gastric cancer remains unclear. Immunohistochemical analyses indicated that NPRA expression was positively associated with gastric tumor size and cancer stage. NPRA inhibition by shRNA induced G2/M cell cycle arrest, cell death, and autophagy in gastric cancer cells, due to accumulation of reactive oxygen species (ROS). Either genetic or pharmacologic inhibition of autophagy led to caspase-dependent cell death. Therefore, autophagy induced by NPRA silencing may represent a cytoprotective mechanism. ROS accumulation activated c-Jun N-terminal kinase (JNK) and AMP-activated protein kinase (AMPK). ROS-mediated activation of JNK inhibited cell proliferation by disturbing cell cycle and decreased cell viability. In addition, AMPK activation promoted autophagy in NPRA-downregulated cancer cells. Overall, our results indicate that the inhibition of NPRA suppresses gastric cancer development and targeting NPRA may represent a promising strategy for the treatment of gastric cancer.

Angiotensin II down-regulates natriuretic peptide receptor-A expression and guanylyl cyclase activity in H9c2 (2-1) cardiac myoblast cells: Role of ROS and NF-κB.

Atrial natriuretic peptide (ANP)/natriuretic peptide receptor-A (NPR-A) system is suggested as an endogenous anti-hypertrophic protective mechanism of the heart. We have shown previously that Angiotensin II (ANG II), an effector molecule of renin-angiotensin-aldosterone system, down-regulates NPR-A expression and its activity in vivo rat heart. However, the underlying mechanism by which ANG II down-regulates NPR-A expression in the heart is not well understood. Hence, the present investigation was aimed to determine whether ANG II-stimulated reactive oxygen species (ROS) and NF-κB are involved in the down-regulation of NPR-A activity in H9c2 (2-1) cardiac myoblast cells. The H9c2 (2-1) cardiac myoblast cells were exposed to ANG II (10(-7)M for 20h) with/or without blocker treatment (losartan-10µM, N-acetyl cysteine (NAC)-10mM and pyrrolidine dithiocarbamate (PDTC)-100µM). On exposure, ANG II induced a significant decrease (P<0.001) in the expression of Npr1 (coding for NPR-A) gene and NPR-A receptor-dependent guanylyl cyclase (GC) activity. The level of expression of proto-oncogenes (c-fos, c-myc, and c-jun) and natriuretic peptides (ANP and BNP) was increased in ANG II-treated cells when compared with control cells. Interestingly, ANG II-dependent repression of Npr1 gene expression and guanylyl cyclase (GC) activity was completely restored on treatment with losartan, while only a partial reversal was observed in NAC- and PDTC-co-treated cells. In conclusion, the results of this study suggest that ROS-mediated NF-κB activation mechanism is critically involved in the ANG II-mediated down-regulation of NPR-A expression and its GC activity.

A synthetic cGMP-sensitive gene switch providing Viagra®-controlled gene expression in mammalian cells and mice

Cyclic guanosine monophosphate (cGMP) is a universal second messenger that is synthesized from guanosine triphosphate (GTP) by guanylyl cyclases (GCs) and hydrolyzed into guanosine monophosphate (GMP) by phosphodiesterases (PDEs). Small-molecule drugs that induce high cGMP levels in specialized tissues by boosting GC activity or inhibiting PDE activity have become the predominant treatment strategy for a wide range of medical conditions, including congestive heart failure, pulmonary hypertension, atherosclerosis-based claudication and erectile dysfunction. By fusing the cGMP receptor protein (CRP) of Rhodospirillum centenum to the Herpes simplex-derived transactivation domain VP16, we created a novel synthetic mammalian cGMP-sensing transcription factor (GTA) that activates synthetic promoters (PGTA) containing newly identified GTA-specific operator sites in a concentration-dependent manner. In cell lines expressing endogenous natriuretic peptide receptor A (NPR-A) (HeLa), GTA/PGTA-driven transgene expression was induced by B-type natriuretic peptide (BNP; Nesiritide®) in a concentration-dependent manner, which activated NPR-A׳s intracellular GC domain and triggered a corresponding cGMP surge. Ectopic expression of NPR-A in NPR-A-negative cell lines (HEK-293T) produced high cGMP levels and mediated maximum GTA/PGTA-driven transgene expression, which was suppressed by co-expression of PDEs (PDE-3A, PDE-5A and PDE-9A) and was re-triggered by the corresponding PDE inhibitor drugs (Pletal®, Perfan®, Primacor® (PDE-3A), Viagra®, Levitra®, Cialis® (PDE-5A) and BAY73-6691 (PDE-9A)). Mice implanted with microencapsulated designer cells co-expressing the GTA/PGTA device with NPR-A and PDE-5A showed control of blood SEAP levels through administration of sildenafil (Viagra®). Designer cells engineered for PDE inhibitor-modulated transgene expression may provide a cell-based PDE-targeting drug discovery platform and enable drug-adjusted gene- and cell-based therapies.

Effect of atrial natriuretic peptide on lipolysis in the mouse heart

Overweight is associated with triglyceride accumulation in cardiomyocytes, which can cause cardiac dysfunction. It is also associated with reduced synthesis and plasma concentration of atrial natriuretic peptide (ANP). In adipocytes, ANP stimulates lipolysis through natriuretic peptide receptor-A (NPR-A), leading to cGMP-dependent phosphorylation of hormone-sensitive lipase. Cardiac myocytes express NPR-A and hormone-sensitive lipase. In the present study, we investigated whether ANP affects triglyceride stores in the heart. Subcutaneously implanted osmotic minipumps were used to administer ANP (125 or 500 ng/kg/min) or saline to obese leptin-deficient (ob/ob) mice or lean control mice (ob/+) for a week. ANP (500 ng/kg/min) reduced blood pressure but did not affect the cardiac triglyceride stores or mRNA expression of NPR-A and NPR-C. Also, deficiency of NPR-A did not affect the cardiac triglyceride content. Finally, addition of ANP to the culture medium (10−7 mol/l) increased cellular cGMP content (P=0.009) but did not affect triglyceride stores in HL-1 cardiac myocyte cultures. Hence, ANP does not affect triglyceride stores in the murine heart.

Natriuretic peptide receptor A as a novel target for cancer.

The receptor for the cardiac hormone atrial natriuretic peptide (ANP), natriuretic peptide receptor A (NPR-A), has been reported to be expressed in lung cancer, prostate cancer and ovarian cancer. NPR-A expression and signaling is important for tumor growth; its deficiency protects C57BL/6 mice from lung, skin and ovarian cancers. This suggests that NPR-A is a new marker and a new target for cancer therapy. Recently, NPR-A has been demonstrated to be expressed in pre-implantation embryos and in embryonic stem cells, which has a novel role in the maintenance of self-renewal and pluripotency of embryonic stem cells. A nanoparticle-formulated interfering RNA for NPR-A attenuated B16 melanoma tumors in mice. Ectopic expression of a plasmid encoding NP73-102, the NH2-terminal peptide of the ANP prohormone which downregulates NPR-A expression, also suppressed lung metastasis of A549 cells in nude mice and tumorigenesis of Line 1 cells in immunocompetent BALB/c mice. These results suggest that NPR-A is involved in tumorigenesis and a new target for cancer therapy. This review focuses on structure, abnormal functions and carcinogenic mechanisms of NPR-A to investigate its role in tumorigenesis.

P-0002 - Expression and Clinical Significance of Npra in Esophageal Squamous Cell Carcinoma

Background: Esophageal cancer is a main reason of cancer related mortality, the tumor targeted therapy is a new and effective treatment. NPRA (natriuretic peptide receptor A), as a new oncogene, that promotes tumorigenesis in several cancer types, might represent a novel therapeutic target in esophageal cancer. In this study we suggested that the expression and clinical significance of NPRA in esophageal squamous cell carcinoma (ESCC).Methods: The expression of NPRA in 45 cases of ESCC tissues, 40 cases of adjacent tissues, 30 positive Lymph node tissues and 24 negative Lymph node tissues were assessed by SP immunohistochemical method. No patients received preoperative chemotherapy, radiation therapy, and immune therapy and all of patients were confirmed for ESCC by pathologist at Department of Thoracic Oncosurgery, the First Affiliated Hospital of Xi'an Jiaotong University.Results: In esophageal squamous cells, The expression of NPRA was strongly detected in cytoplasm, while undetectable or very weak in nuclear. The positive rates of NPRA in the cancer tissues was 71.1%, while that in the adjacent tissues group was 17.5%, and showed 63.32% and 24.3% in the positive Lymph node tissues and negative Lymph node tissues respectively, there was a significant difference between the two groups (P<0.05). Clinicopathological analyses revealed that increased cytoplasmic NPRA expression correlated with differentiation and TNM stage, while showed no statistically significant among the association of age, gender, and lymph node metastasis.Conclusion: Our findings demonstrate that The NPRA has high expression in ESCC tissues, and the positive rate is closely correlated with the differentiation and TNM stage, and suggest that NPRA represents a potential therapeutic target. Background: Esophageal cancer is a main reason of cancer related mortality, the tumor targeted therapy is a new and effective treatment. NPRA (natriuretic peptide receptor A), as a new oncogene, that promotes tumorigenesis in several cancer types, might represent a novel therapeutic target in esophageal cancer. In this study we suggested that the expression and clinical significance of NPRA in esophageal squamous cell carcinoma (ESCC). Methods: The expression of NPRA in 45 cases of ESCC tissues, 40 cases of adjacent tissues, 30 positive Lymph node tissues and 24 negative Lymph node tissues were assessed by SP immunohistochemical method. No patients received preoperative chemotherapy, radiation therapy, and immune therapy and all of patients were confirmed for ESCC by pathologist at Department of Thoracic Oncosurgery, the First Affiliated Hospital of Xi'an Jiaotong University. Results: In esophageal squamous cells, The expression of NPRA was strongly detected in cytoplasm, while undetectable or very weak in nuclear. The positive rates of NPRA in the cancer tissues was 71.1%, while that in the adjacent tissues group was 17.5%, and showed 63.32% and 24.3% in the positive Lymph node tissues and negative Lymph node tissues respectively, there was a significant difference between the two groups (P<0.05). Clinicopathological analyses revealed that increased cytoplasmic NPRA expression correlated with differentiation and TNM stage, while showed no statistically significant among the association of age, gender, and lymph node metastasis. Conclusion: Our findings demonstrate that The NPRA has high expression in ESCC tissues, and the positive rate is closely correlated with the differentiation and TNM stage, and suggest that NPRA represents a potential therapeutic target.

Role of NPRA in MDSC mediated suppression in cancer (P2071)

Abstract It is now evident that inadequate function of the host immune system is due to suppressive factors such as myeloid derived suppressor cells (MDSC). In our study we found that MDSCs isolated from tumor bearing mice expressed high levels of natriuretic peptide receptor A (NPRA) a receptor for atrial natriuretic peptide (ANP). Since MDSCs play a pivotal role in tumorigenesis, we addressed whether NPRA signaling may be linked with altered differentiation of myeloid cells and their suppressive function. We examined the wild type and NPRA deficient mice for MDSC differentiation, and the results showed that NPRA deficient mice exhibited restricted tumor growth and altered differentiation of MDSCs. Next we investigated the link between ANP levels and accumulation of MDSCs. Increase in ANP levels triggered expansion of MDSC. MDSCs suppressed T cells via reactive oxygen species (ROS), and increase in NPRA expression was associated with decreased miR150 as well as increased expression of Nox. NPRA KO mice showed increased expression of miR150 compared to WT mice.Our experiments suggested that activation of NPRA and was regulated by a key micro RNA, miR-150. Taken together, these results suggest a key role to NPRA signaling in myeloid cell differentiation and cancer progression.

Nanoparticle PET/CT imaging of natriuretic peptide clearance receptor in prostate cancer.

Atrial natriuretic peptide has been recently discovered to have anticancer effects via interaction with cell surface natriuretic peptide receptor A (NPRA) and natriuretic peptide clearance receptor (NPRC). In a preclinical model, NPRA expression has been identified during tumor angiogenesis and may serve as a potential prognostic marker and target for prostate cancer (PCa) therapy. However, the presence of NPRC receptor in the PCa model has not yet been assessed. Furthermore, there is still no report using nanoparticle for PCa positron emission tomography (PET) imaging. Herein, an amphiphilic comb-like nanoparticle was synthesized with controlled properties through modular construction containing C-atrial natriuretic factor (CANF) for NPRC receptor targeting and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelator for high specific activity Cu-64 radiolabeling. The pharmacokinetics of (64)Cu-CANF-Comb exhibited tuned biodistribution and optimized in vivo profile in contrast to the nontargeted (64)Cu-Comb nanoparticle. PET imaging with (64)Cu-CANF-Comb in CWR22 PCa tumor model showed high blood pool retention, low renal clearance, enhanced tumor uptake, and decreased hepatic burden relative to the nontargeted (64)Cu-Comb. Immunohistochemistry staining confirmed the presence of NPRC receptor in tumor tissue. Competitive PET receptor blocking study demonstrated the targeting specificity of (64)Cu-CANF-Comb to NPRC receptor in vivo. These results establish a new nanoagent for prostate cancer PET imaging.

Atrial natriuretic peptide attenuates agonist-induced pulmonary edema in mice with targeted disruption of the gene for natriuretic peptide receptor-A

Atrial natriuretic peptide (ANP) inhibits agonist-induced pulmonary edema formation, but the signaling pathway responsible is not well defined. To investigate the role of the particulate guanylate cyclase-linked receptor, natriuretic peptide receptor-A (NPR-A), we measured acute lung injury responses in intact mice and pulmonary microvascular endothelial cells (PMVEC) with normal and disrupted expression of NPR-A. NPR-A wild-type (NPR-A+/+), heterozygous (NPR-A+/-), and knockout (NPR-A-/-) mice were anesthetized and treated with thrombin receptor agonist peptide (TRAP) or lipopolysaccharide (LPS). Lung injury was assessed by lung wet-to-dry (W/D) weight and by protein and cell concentration of bronchoalveolar lavage (BAL) fluid. No difference in pulmonary edema formation was seen between NPR-A genotypes under baseline conditions. TRAP and LPS increased lung W/D weight and BAL fluid cell counts more in NPR-A-/- mice than in NPR-A+/- or NPR-A+/+ mice, but no genotype-related differences were seen in TRAP-induced increases in bloodless lung W/D weight or LPS-induced increases in BAL protein concentration. Pretreatment with ANP infusion completely blocked TRAP-induced increases in lung W/D weight and blunted LPS-induced increases in BAL cell counts and protein concentration in both NPR-A-/- and NPR-A+/+ mice. Thrombin decreased transmembrane electrical resistance in monolayers of PMVECs in vitro, and this effect was attenuated by ANP in PMVECs isolated from both genotypes. Administration of the NPR-C-specific ligand, cANF, also blocked TRAP-induced increases in lung W/D weight and LPS-induced increases in BAL cell count and protein concentration in NPR-A+/+ and NPR-A-/- mice. We conclude that ANP is capable of attenuating agonist-induced lung edema in the absence of NPR-A. The protective effect of ANP on agonist-induced lung injury and pulmonary barrier function may be mediated by NPR-C.

748 - Expression and Clinical Significance of NPRA in Esophageal Squamous Cell Carcinoma

ABSTRACT Background and objective Esophageal cancer is a main reason of cancer related mortality, and the tumer targeted therapy is a new and effective treatment. NPRA (natriuretic peptide receptor A), as a new oncogene, that promotes tumorigenesis in several cancer types, might represent a novel therapeutic target in esophageal cancer. In this study we suggested that the expression and clinical significance of NPRA in esophageal squamous cell carcinoma (ESCC). Methods The expression of NPRA in 45 cases of ESCC tissues, 40 cases of adjacent tissues, 30 positive Lymph node tissues and 24 negative Lymph node tissues were assessed by SP immunohistochemical method. No patients received preoperative chemotherapy, radiation therapy, and immune therapy and all of patients were confirmed for ESCC by pathologist at Department of Thoracic Oncosurgery, the First Affiliated Hospital of Xi,an Jiaotong University. Results In esophageal squamous cells, the expression of NPRA was strongly detected in cytoplasm, while undetectable or very weak in nuclear. The positive rates of NPRA in the cancer tissues was 71.1%, while that in the adjacent tissues group was 17.5%, and showed 63.32% and 24.3% in the positive Lymph node tissues and negative Lymph node tissues respectively, there was a significant difference between the two groups ( P>0.05). Clinicopathological analyses revealed that increased cytoplasmic NPRA expression correlated with differentiation and TNM stage, while showed no statistically significant among the association of age, gender, and lymph node metastasis. Conclusion Our findings demonstrate that the NPRA has high expression in ESCC tissues, and the positive rate is closely correlated with the differentiation and TNM stage, and suggest that NPRA represents a potential therapeutic target. Disclosure All authors have declared no conflicts of interest.