Wild-type Npr1 Research Articles

Inhibition of HDAC1 and 2 Modulates the Expression and Signaling of Natriuretic Peptide Receptor A in Male and Female Gene‐targeted Mutant Mice

Guanylyl cyclase/natriuretic peptide receptor‐A (GC‐A/NPRA) signaling activates natriuresis, diuresis, and vasodilatation, and inhibits the cell proliferation and fibrosis. Mice lacking functional Npr1 gene (coding for GC‐A/NPRA) exhibit hypertension and kidney disorders, however, the mechanisms regulating Npr1 expression and function are not well understood. The objective of the present study was to elucidate the mechanisms of Npr1 expression and receptor function involving epigenetic regulatory mechanisms activated by class I histone deacetylase (HDAC) inhibitor, Mocetinostat (MGCD0103). Male and female (16–20 weeks old) Npr1 gene‐disrupted heterozygous (1‐copy; Npr1+/−), wild‐type (2‐copy; Npr1+/+) and gene‐duplicated heterozygous (3‐copy; Npr1++/+) mice were injected intraperitoneally with MGCD0103 (2 mg/kg) at alternate days for 2‐weeks. The Western blot analysis showed that MGCD0103 significantly increased the renal NPRA protein levels in Npr1+/−, Npr1+/+, and Npr1++/+ mice groups compared with vehicle‐treated controls. Female mice showed increased levels of plasma cGMP compared with male mice and treatment with MGCD0103 significantly induced cGMP levels in the drug‐treated mice groups. The renal HDAC activity and HDAC1 and 2 protein levels in male mice were higher than the corresponding female mice in all the three genotypes. MGCD0103 treatment attenuated HDAC activity by 30%‐40% and HDAC1/2 protein levels in the treated mice groups. Male and female mice showed differential acetylation levels of H3‐K9 and H3‐K27 in the renal tissues and treatment with MGCD0103 significantly enhanced the acetylation levels in the treated mice groups. Both male and female Npr1+/− mice exhibited higher systolic blood pressure (SBP) compared with the corresponding wild type Npr1+/+ mice, whereas female Npr1+/− mice exhibited significantly lower SBP than male Npr1+/− mice. A significant decrease in SBP was observed in MGCD0103‐treated male and female Npr1+/− mice. The present results suggest that MGCD0103 epigenetically regulates NPRA expression in vivo in male and female Npr1+/− mice, via inhibition of HDAC1 and 2 protein expression and histone modifications, which will have important implications in the hypertension and renal disease states.Support or Funding InformationThis work was supported by NIH grants (HL057531 and HL062147) and by an Institutional Development Award (IDeA) from the NIGMS.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Genetic disruption of guanylyl cyclase/natriuretic peptide receptor-A upregulates ACE and AT1 receptor gene expression and signaling: role in cardiac hypertrophy

Guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) signaling antagonizes the physiological effects mediated by the renin-angiotensin system (RAS). The objective of this study was to determine whether the targeted-disruption of Npr1 gene (coding for GC-A/NPRA) leads to the activation of cardiac RAS genes involved on the hypertrophic remodeling process. The Npr1 gene-knockout (Npr1(-/-)) mice showed 30-35 mmHg higher systolic blood pressure (SBP) and a 63% greater heart weight-to-body weight (HW/BW) ratio compared with wild-type (Npr1(+/+)) mice. The mRNA levels of both angiotensin-converting enzyme and angiotensin II type 1a receptor were increased by three- and fourfold, respectively, in Npr1(-/-) null mutant mice hearts compared with the wild-type Npr1(+/+) mice hearts. In parallel, the expression levels of interleukin-6 and tumor necrosis factor-alpha were increased by four- to fivefold, in Npr1(-/-) mice hearts compared with control animals. The NF-kappaB binding activity in nuclear extracts of Npr1(-/-) mice hearts was increased by fourfold compared with wild-type Npr1(+/+) mice hearts. Treatments with captopril or hydralazine equally attenuated SBP; however, only captopril significantly decreased the HW/BW ratio and suppressed cytokine gene expression in Npr1(-/-) mice hearts. The ventricular cGMP level was reduced by almost sixfold in Npr1(-/-) mice compared with wild-type control mice. The results of the present study indicate that disruption of NPRA/cGMP signaling leads to the augmented expression of cardiac RAS pathways that promote the development of cardiac hypertrophy and remodeling.

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.

The Arabidopsis NPR1 Gene That Controls Systemic Acquired Resistance Encodes a Novel Protein Containing Ankyrin Repeats

The Arabidopsis NPR1 gene controls the onset of systemic acquired resistance (SAR), a plant immunity, to a broad spectrum of pathogens that is normally established after a primary exposure to avirulent pathogens. Mutants with defects in NPR1 fail to respond to various SAR-inducing treatments, displaying little expression of pathogenesis-related (PR) genes and exhibiting increased susceptibility to infections. NPR1 was cloned using a map-based approach and was found to encode a novel protein containing ankyrin repeats. The lesion in one npr1 mutant allele disrupted the ankyrin consensus sequence, suggesting that these repeats are important for NPR1 function. Furthermore, transformation of the cloned wild-type NPR1 gene into npr1 mutants not only complemented the mutations, restoring the responsiveness to SAR induction with respect to PR-gene expression and resistance to infections, but also rendered the transgenic plants more resistant to infection by P. syringae in the absence of SAR induction.