Natriuretic Peptide Receptor A Signaling Research Articles

Triiodo-L-thyronine (T3) downregulates Npr1 gene (coding for natriuretic peptide receptor-A) transcription in H9c2 cells: involvement of β-AR-ROS signaling.

Natriuretic peptide receptor-A (NPR-A) signaling system is considered as an intrinsic productive mechanism of the heart that opposes abnormal cardiac remodeling and hypertrophic growth. NPR-A is coded by Npr1 gene, and its expression is downregulated in the hypertrophied heart. We sought to examine the levels of Npr1 gene transcription in triiodo-L-thyronine (T3) treated hypertrophied cardiomyocyte (H9c2) cells, in vitro, and also the involvement of β-adrenergic receptor (β-AR) - Reactive oxygen species (ROS) signaling system in the down-regulation of Npr1 transcription also studied. Anti-hypertrophic Npr1 gene transcription was monitored in control and T3-treated (dose and time dependent) H9c2 cells, using a real time PCR method. Further, cell size, intracellular cGMP, ROS, hypertrophy markers (ANP, BNP, α-sk, α-MHC and β-MHC), β-AR, and protein kinase cGMP-dependent 1 (PKG-I) genes expression were also determined. The intracellular cGMP and ROS levels were determined by ELISA and DCF dye method, respectively. In addition, to neutralize T3 mediated ROS generation, H9c2 cells were treated with T3 in the presence and absence of antioxidants [curcumin (CU) or N-acetyl-L-cysteine (NAC)]. A dose dependent (10 pM, 100 pM, 1 nM and 10 nM) and time dependent (12 h, 24 h and 48 h) down-regulation of Npr1 gene transcription (20, 39, 60, and 74% respectively; 18, 55, and 85%, respectively) were observed in T3-treated H9c2 cells as compared with control cells. Immunofluorescence analysis also revealed that a marked down regulation of NPR- A protein in T3-treated cells as compared with control cells. Further, a parallel downregulation of cGMP and PKG-I (2.4 fold) were noticed in the T3-treated cells. In contrast, a time dependent increased expression of β-AR (60, 72, and 80% respectively) and ROS (26, 48, and 74%, respectively) levels were noticed in T3-treated H9c2 cells as compared with control cells. Interestingly, antioxidants, CU or NAC co-treated T3 cells displayed a significant reduction in ROS (69 and 81%, respectively) generation and to increased Npr1 gene transcription (81 and 88%, respectively) as compared with T3 alone treated cells. Our result suggest that down regulation of Npr1 gene transcription is critically involved in T3- induced hypertrophic growth in H9c2 cells, and identifies the cross-talk between T3-β-AR-ROS and NPR-A signaling.

Brain natriuretic peptide constitutively downregulates P2X3 receptors by controlling their phosphorylation state and membrane localization.

BackgroundATP-gated P2X3 receptors are important transducers of nociceptive stimuli and are almost exclusively expressed by sensory ganglion neurons. In mouse trigeminal ganglion (TG), P2X3 receptor function is unexpectedly enhanced by pharmacological block of natriuretic peptide receptor-A (NPR-A), outlining a potential inhibitory role of endogenous natriuretic peptides in nociception mediated by P2X3 receptors. Lack of change in P2X3 protein expression indicates a complex modulation whose mechanisms for downregulating P2X3 receptor function remain unclear.ResultsTo clarify this process in mouse TG cultures, we suppressed NPR-A signaling with either siRNA of the endogenous agonist BNP, or the NPR-A blocker anantin. Thus, we investigated changes in P2X3 receptor distribution in the lipid raft membrane compartment, their phosphorylation state, as well as their function with patch clamping. Delayed onset of P2X3 desensitization was one mechanism for the anantin-induced enhancement of P2X3 activity. Anantin application caused preferential P2X3 receptor redistribution to the lipid raft compartment and decreased P2X3 serine phosphorylation, two phenomena that were not interdependent. An inhibitor of cGMP-dependent protein kinase and siRNA-mediated knockdown of BNP mimicked the effect of anantin.ConclusionsWe demonstrated that in mouse trigeminal neurons endogenous BNP acts on NPR-A receptors to determine constitutive depression of P2X3 receptor function. Tonic inhibition of P2X3 receptor activity by BNP/NPR-A/PKG pathways occurs via two distinct mechanisms: P2X3 serine phosphorylation and receptor redistribution to non-raft membrane compartments. This novel mechanism of receptor control might be a target for future studies aiming at decreasing dysregulated P2X3 receptor activity in chronic pain.

Glipizide suppresses embryonic vasculogenesis and angiogenesis through targeting natriuretic peptide receptor A

Glipizide, a second-generation sulfonylurea, has been widely used for the treatment of type 2 diabetes. However, it is controversial whether or not glipizide would affect angiogenesis or vasculogenesis. In the present study, we used early chick embryo model to investigate the effect of glipizide on angiogenesis and vasculogenesis, which are the two major processes for embryonic vasculature formation as well as tumor neovascularization. We found that Glipizide suppressed both angiogenesis in yolk-sac membrane (YSM) and blood island formation during developmental vasculogenesis. Glipizide did not affect either the process of epithelial to mesenchymal transition (EMT) or mesoderm cell migration. In addition, it did not interfere with separation of smooth muscle cell progenitors from hemangioblasts. Moreover, natriuretic peptide receptor A (NPRA) has been identified as the putative target for glipizide׳s inhibitory effect on vasculogenesis. When NPRA was overexpressed or activated, blood island formation was reduced. NPRA signaling may play a crucial role in the effect of glipizide on vasculogenesis during early embryonic development.

NPR-A: A Therapeutic Target in Inflammation and Cancer.

Natriuretic peptide receptor A (NPR-A) is the receptor for atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP). NPR-A plays critical physiological and pathophysiological roles in several target cell and tissue system processes, such as cell growth, apoptosis, proliferation, and inflammation. Accumulating data demonstrate that NPR-A is involved in immune and inflammatory reactions and is a potential target in inflammation treatment. It is expressed in various cancer cells and is important for tumor growth. A recent study indicated that NPR-A signaling can regulate stem cell recruitment and angiogenesis. This signaling can serve as a model for studying the linkage between inflammation and tumorigenesis. In this review we highlight the mechanisms by which NPR-A affects signaling pathways involved in inflammation and cancer, and we discuss its potential as a novel target in inflammation, cancer, and cancer-related inflammation.

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.

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.

P-0033 Natriuretic Peptide Receptor a as a Novel Target for Gastric Cancer

IntroductionThe receptor for the cardiac hormone atrial natriuretic peptide (ANP), natriuretic peptide receptor A (NPRA), have been reported to express on lung cancer, prostate cancer, ovarian cancer, NPRA expression and signaling is important for tumor growth, its deficiency protect C57BL/6 mice from lung, skin, and ovarian cancers, and these result suggest that NPRA is a new target for cancer therapy. Recently, NPRA has been demonstrated express in pre-implantation embryos and in ES cells, it has a novel role in the maintenance of self-renewal and pluripotency of ES cells. However, the direct role of NPRA signaling in gastric cancer remains unclear. MethodsNPRA expression was examined by western blotting, immunofluorescence and immunohistochemistry. NPRA was downregulated by transfection of siRNA and shRNA. Resultswe demonstrated that NPRA is abundantly expressed on human gastric cancer AGS cells, but not in nontumorigenic epithelial cells. NPRA expression showed positive correlation with clinical staging and prognosis in gastric cancer patient. Down-regulation of NPRA by siNPRA induced apoptosis in AGS cells. The mechanism of siNPRA-induced anti-AGS effects was linked to NPRA-induced expression of KCNQ1, a K+ channel overexpressed in AGS and significantly reduced by siNPRA. ConclusionCollectively, these results suggest that NPRA promotes gastric cancer development in part by regulating KCNQ1. Our findings also suggest that NPRA is a potential prognostic marker and a target for gastric cancer therapy.

Preparation and Characterization of Molecularly Imprinted Polymeric Nanoparticles for Atrial Natriuretic Peptide (ANP).

Natriuretic peptide receptor A (NPRA), the receptor for the cardiac hormone atrial natriuretic peptide (ANP), is expressed abundantly on cancer cells and disruption of ANP-NPRA signaling inhibits tumor burden and metastasis. Since antagonists of NPRA signaling have not provided reproducible results, we reasoned that a synthetic neutralizing antibody to ANP, which has high selectivity and affinity for ANP, could be used to regulate ANP levels and attenuate NPRA signaling. In this study, we prepared molecularly imprinted polymer nanoparticles (MIPNPs) for ANP using a short peptide of ANP as the template and determined their binding affinity and selectivity. The MIPNPs were prepared by precipitation polymerization using NH2-SLRRSS-CONH2, which is a short peptide from ANP as template, methacrylic acid (MAA) and N-isopropylacrylamide (NIPAm) as functional monomers, bis-acrylamide (BIS) as crosslinker. The average diameter of MIPNPs and non-imprinted nanoparticles (NIPNPs) in water is 215.8 ±4.6 nm and 197.7±3.1 nm respectively. The binding isotherm analysis showed that MIPNPs have a much higher binding affinity for template peptide and ANP than NIPNPs. Scatchard analysis gave an equilibrium dissociation constant, Kd of 7.3 μM with a binding capacity 106.7 μmol/g for template peptide and Kd of 7.9 μM with a binding capacity of 36.0 μmol/g for ANP. Measurements of binding kinetics revealed that MIPNPs reach protein adsorption equilibrium in 30 min. MIPNPs found to have high specificity for ANP with little affinity for BSA or scrambled ANP peptide. MIPNPs also recognized and adsorbed ANP in cell culture media spiked with ANP and human plasma. Taken together, these results indicate that MIPNPs have high affinity and selectivity for ANP and can be used as a synthetic antibody for modulating ANP-NPRA signaling in cancers.

Natriuretic Peptide Receptor A as a Novel Target for Prostate Cancer

BackgroundThe receptor for the cardiac hormone atrial natriuretic peptide (ANP), natriuretic peptide receptor A (NPRA), is expressed in cancer cells, and natriuretic peptides have been implicated in cancers. However, the direct role of NPRA signaling in prostate cancer remains unclear.ResultsNPRA expression was examined by western blotting, RT-PCR and immunohistochemistry. NPRA was downregulated by transfection of siRNA, shRNA and NPRA inhibitor (iNPRA). Antitumor efficacy of iNPRA was tested in mice using a TRAMP-C1 xenograft. Here, we demonstrated that NPRA is abundantly expressed on tumorigenic mouse and human prostate cells, but not in nontumorigenic prostate epithelial cells. NPRA expression showed positive correlation with clinical staging in a human PCa tissue microarray. Down-regulation of NPRA by siNPRA or iNPRA induced apoptosis in PCa cells. The mechanism of iNPRA-induced anti-PCa effects was linked to NPRA-induced expression of macrophage migration inhibitory factor (MIF), a proinflammatory cytokine over-expressed in PCa and significantly reduced by siNPRA. Prostate tumor cells implanted in mice deficient in atrial natriuretic peptide receptor A (NPRA-KO) failed to grow, and treatment of TRAMP-C1 xenografts with iNPRA reduced tumor burden and MIF expression. Using the TRAMP spontaneous PCa model, we found that NPRA expression correlated with MIF expression during PCa progression.ConclusionsCollectively, these results suggest that NPRA promotes PCa development in part by regulating MIF. Our findings also suggest that NPRA is a potential prognostic marker and a target for PCa therapy.

Natriuretic peptide receptor A knock out restricts tumorigenesis through ablation of myeloid derived suppressor cells expansion (66.3)

Abstract Recent data from our group and a number of others have demonstrated that expansion and activation of Myeloid Derived Suppressor Cells(MDSC) play a pivotal role in tumorigenesis. The receptor for atrial natriuretic peptide, natriuretic peptide receptor A (NPRA) has been implicated in cancers. We have shown that NPRA expression and signaling is important for tumor growth. We hypothesize a novel link between NPRA expression, altered differentiation of myeloid cells and tumor formation. MDSC population consists of two major subsets of Ly6G+ granulocytic and Ly6C+ monocytic cells. Almost all tumor models demonstrated a preferential expansion of granulocytic subset of MDSC. MDSC isolated from tumor bearing mice expressed high levels of NPRA. Next we hypothesized that NPRA knock out would result in restricted tumor growth. Using NPRA deficient mice, we report that these mice have altered differentiation of myeloid cells. As a consequence tumor cells injected subcutaneously to NPRA KO mice failed to grow. We investigated the nature of cells responsible for tumorigenesis and proved that ablation of a subset of MDSC cells restricts tumor formation. This work may indicate key roles for NPRA in myeloid cell differentiation and cancer formation.

NPR-A regulates self-renewal and pluripotency of embryonic stem cells

Self-renewal and pluripotency of embryonic stem (ES) cells are maintained by several signaling cascades and by expression of intrinsic factors, such as Oct4, Nanog and Sox2. The mechanism regulating these signaling cascades in ES cells is of great interest. Recently, we have demonstrated that natriuretic peptide receptor A (NPR-A), a specific receptor for atrial and brain natriuretic peptides (ANP and BNP, respectively), is expressed in pre-implantation embryos and in ES cells. Here, we examined whether NPR-A is involved in the maintenance of ES cell pluripotency. RNA interference-mediated knockdown of NPR-A resulted in phenotypic changes, indicative of differentiation, downregulation of pluripotency factors (such as Oct4, Nanog and Sox2) and upregulation of differentiation genes. NPR-A knockdown also resulted in a marked downregulation of phosphorylated Akt. Furthermore, NPR-A knockdown induced accumulation of ES cells in the G1 phase of the cell cycle. Interestingly, we found that ANP was expressed in self-renewing ES cells, whereas its level was reduced after ES cell differentiation. Treatment of ES cells with ANP upregulated the expression of Oct4, Nanog and phosphorylated Akt, and this upregulation depended on NPR-A signaling, because it was completely reversed by pretreatment with either an NPR-A antagonist or a cGMP-dependent protein kinase inhibitor. These findings provide a novel role for NPR-A in the maintenance of self-renewal and pluripotency of ES cells.

P47. NPR-A is essential for embryonic stem cell self-renewal and pluripotency

The self-renewal and pluripotency of embryonic stem (ES) cells are maintained by several signaling cascades and by expression of intrinsic factors, such as Oct4, Nanog and Sox2. The mechanism that regulates these signaling cascades in ES cells is of great interest. We have recently showed that natriuretic peptide receptor A (NPR-A), which is a specific receptor for atrial and brain natriuretic peptide (ANP and BNP), is expressed in preimplantation embryos and in murine ES cells. In this study, we examined whether NPR-A is involved in the maintenance of ES cell pluripotency. Targeting of NPR-A with short interfering RNA (siRNA) resulted in phenotypic changes indicative of differentiation, downregulation of self-renewal and pluripotency factors (Oct4, Nanog and Sox2), and upregulation of differentiation genes. NPR-A knockdown also resulted in a marked downregulation of phosphorylated Akt, which is essential for ES cell self-renewal. Furthermore, NPR-A knockdown induced accumulation of ES cells in the G1-phase of the cell cycle. Interestingly, we found that ANP was expressed in self-renewing ES cells, whereas its level was reduced after ES cell differentiation by the withdrawal of leukemia inhibitory factor. Treatment of ES cells with exogenous ANP upregulated the expression of Oct4 and Nanog, and this upregulation depended on NPR-A signaling, because it was completely reversed by pretreatment with NPR-A antagonist or cGMP-dependent protein kinase inhibitor. Also, ANP increased the expression level of phosphorylated Akt. These findings provide a novel role for NPR-A in the maintenance of self-renewal and pluripotency of ES cells.

The role of natriuretic peptide receptor-A signaling in unilateral lung ischemia-reperfusion injury in the intact mouse

Ischemia-reperfusion (IR) causes human lung injury in association with the release of atrial and brain natriuretic peptides (ANP and BNP), but the role of ANP/BNP in IR lung injury is unknown. ANP and BNP bind to natriuretic peptide receptor-A (NPR-A) generating cGMP and to NPR-C, a clearance receptor that can decrease intracellular cAMP. To determine the role of NPR-A signaling in IR lung injury, we administered the NPR-A blocker anantin in an in vivo SWR mouse preparation of unilateral lung IR. With uninterrupted ventilation, the left pulmonary artery was occluded for 30 min and then reperfused for 60 or 150 min. Anantin administration decreased IR-induced Evans blue dye extravasation and wet weight in the reperfused left lung, suggesting an injurious role for NPR-A signaling in lung IR. In isolated mouse lungs, exogenous ANP (2.5 nM) added to the perfusate significantly increased the filtration coefficient sevenfold only if lungs were subjected to IR. This effect of ANP was also blocked by anantin. Unilateral in vivo IR increased endogenous plasma ANP, lung cGMP concentration, and lung protein kinase G (PKG(I)) activation. Anantin enhanced plasma ANP concentrations and attenuated the increase in cGMP and PKG(I) activation but had no effect on lung cAMP. These data suggest that lung IR triggered ANP release and altered endothelial signaling so that NPR-A activation caused increased pulmonary endothelial permeability.

Natriuretic Peptide Receptor A as a Novel Anticancer Target

The receptor for atrial natriuretic peptide (ANP), natriuretic peptide receptor A (NPRA), is expressed in cancer cells, and natriuretic peptides have been implicated in cancers. However, the direct role of NPRA signaling in tumorigenesis remains elusive. Here, we report that NPRA expression and signaling is important for tumor growth. NPRA-deficient mice showed significantly reduced antigen-induced pulmonary inflammation. NPRA deficiency also substantially protected C57BL/6 mice from lung, skin, and ovarian cancers. Furthermore, a nanoparticle-formulated interfering RNA for NPRA attenuated B16 melanoma tumors in mice. Ectopic expression of a plasmid encoding NP73-102, the NH(2)-terminal peptide of the ANP prohormone, which down-regulates NPRA expression, also suppressed lung metastasis of A549 cells in nude mice and tumorigenesis of Line 1 cells in immunocompetent BALB/c mice. The antitumor activity of NP73-102 was in part attributed to apoptosis of tumor cells. Western blot and immunohistochemistry staining indicated that the transcription factor, nuclear factor-kappaB, was inactivated, whereas the level of tumor suppressor retinoblastoma protein was up-regulated in the lungs of NPRA-deficient mice. Furthermore, expression of vascular endothelial growth factor was down-regulated in the lungs of NPRA-deficient mice compared with that in wild-type mice. These results suggest that NPRA is involved in tumor angiogenesis and represents a new target for cancer therapy.

Mice Deficient in Atrial Natriuretic Peptide Receptor A (NPRA) Exhibit Decreased Lung Inflammation: Implication of NPRA Signaling in Asthma Pathogenesis

Mice Deficient in Atrial Natriuretic Peptide Receptor A (NPRA) Exhibit Decreased Lung Inflammation: Implication of NPRA Signaling in Asthma Pathogenesis

Enhanced activation of pro-inflammatory cytokines in mice lacking natriuretic peptide receptor-A

Natriuretic peptide receptor-A (NPRA) is the principal receptor for the cardiac hormones ANP and BNP. Mice lacking NPRA develop progressive cardiac hypertrophy and congestive heart failure. However, the mechanisms responsible for hypertrophic growth in the absence of NPRA signaling are not yet known. In the present study, we determined whether deficiency of NPRA/cGMP signaling alters the cardiac pro-inflammatory cytokines gene expression in Npr1 (coding for NPRA) gene-knockout ( Npr1 −/−) mice exhibiting cardiac hypertrophy and fibrosis as compared with control wild-type ( Npr1 +/+) mice. A significant up-regulation of cytokine genes such as TNF-α (five-fold), IL-6 (three-fold) and TGF-β1 (four-fold) were observed in mutant mice hearts lacking NPRA as compared with the age-matched wild-type mice. In parallel, NF-κB binding activity was almost five-fold greater in the nuclear extract of Npr1 −/− mutant mice hearts as compared with wild-type Npr1 +/+ mice hearts. Guanylyl cyclase (GC) activity and cGMP levels were drastically reduced by 10- and 5-fold, respectively, in ventricular tissues of mutant mice hearts relative to wild-type controls. The present findings provide direct evidence that ablation of NPRA/cGMP signaling activates inflammatory cytokines, probably via NF-κB mediated signaling pathway, and is associated with hypertrophic growth of null mutant mice hearts.

Increased susceptibility to heart failure in response to volume overload in mice lacking natriuretic peptide receptor-A gene

Contribution of the natriuretic peptide system to the development of heart failure (HF) in vivo was examined using mice lacking or having decreased natriuretic peptide receptor-A (NPRA), a guanylyl cyclase-linked receptor. Volume-overloaded HF was produced by aortocaval fistula in mice with wild-type (+/+), heterozygous (+/-), and homozygous null mutants (-/-) of the NPRA gene. Severity of HF was assessed 4 weeks after operation on the basis of organ weight, hemodynamics, echocardiographic indices, urinary variables, neurohumoral factors, and myocardial gene expression. There were no significant differences in lung weight, kidney weight, left ventricular end-diastolic pressure (LVEDP), left ventricular systolic function, or urinary variables among the three sham-operated groups; however, sham-operated (-/-) mice had higher blood pressure and individual cardiac chamber weights than did (+/+) mice. In contrast, (-/-) mice with aortocaval fistula had higher LVEDP, left and right ventricular weights, lung weight, and left ventricular dimension, as well as lower fractional shortening and urinary sodium and cyclic guanosine monophosphate (cGMP) excretion than did (+/+) mice with aortocaval fistula. In addition, ventricular mRNA expression of natriuretic peptides and beta-myosin heavy chain increased markedly only in (-/-) mice. Plasma atrial natriuretic peptide, renin, and aldosterone, but not cGMP, showed greater responses to aortocaval fistula in (-/-) mice than in (+/+) mice. Both sham-operated and aortocaval fistula NPRA (+/-) mice almost consistently showed a phenotype intermediate between those of NPRA (-/-) and NPRA (+/+) mice. These results provide genetic evidence that NPRA signaling protects against HF induced by volume overload in mice.

Reduced cGMP signaling activates NF-κB in hypertrophied hearts of mice lacking natriuretic peptide receptor-A

Mice lacking natriuretic peptide receptor-A (NPRA) develop progressive cardiac hypertrophy and congestive heart failure. However, the mechanisms responsible for cardiac hypertrophic growth in the absence of NPRA signaling are not yet known. We sought to determine the activation of nuclear factor-κB (NF-κB) in Npr1 (coding for NPRA) gene-knockout (Npr1 −/−) mice exhibiting cardiac hypertrophy and fibrosis. NF-κB binding activity was 4-fold greater in the nuclear extract of Npr1 −/− mutant mice hearts as compared with wild-type (Npr1 +/+) mice hearts. In parallel, inhibitory κB kinase-β activity and IκB-α protein phosphorylation were also increased 3- and 4-fold, respectively, in hypertrophied hearts of mutant mice. cGMP levels were significantly reduced 5-fold in plasma and 10-fold in ventricular tissues of mutant mice hearts relative to wild-type controls. The present findings provide direct evidence that ablation of NPRA/cGMP signaling activates NF-κB binding activity associated with hypertrophic growth of mutant mice hearts.