The two vasoactive hormones, angiotensin II (ANG II; vasoconstrictive) and atrial natriuretic peptide (ANP; vasodilatory) antagonize the biological actions of each other. ANP acting through natriuretic peptide receptor-A (NPRA) lowers blood pressure and blood volume. We tested hypothesis that ANG ii plays critical roles in the transcriptional repression of Npr1 (encoding NPRA) and receptor function. ANG II significantly decreased NPRA mRNA and protein levels and cGMP accumulation in cultured mesangial cells and attenuated Anp-mediated relaxation of aortic rings ex vivo. the transcription factors, cAMP-response element-binding protein (CREB) and heat-shock factor-4a (HSF-4a) facilitated the ANG II-mediated repressive effects on Npr1 transcription. Tyrosine kinase (TK) inhibitor, genistein and phosphatidylinositol 3-kinase (PI-3K) inhibitor, wortmannin reversed the ANG II-dependent repression of Npr1 transcription and receptor function. ANG II enhanced the activities of Class I histone deacetylases (HDACs 1/2), thereby decreased histone acetylation of H3K9/14ac and H4K8ac. The repressive effect of ANG II on Npr1 transcription and receptor signaling seems to be transduced by tK and PI-3K pathways and modulated by CREB, HSF-4a, HDACs, and modified histones. The current findings suggest that ANG II-mediated repressive mechanisms of Npr1 transcription and receptor function may provide new molecular targets for treatment and prevention of hypertension and cardiovascular diseases.Atrial and brain natriuretic peptides (ANP and BNP) are endogenous cardiac hormones that regulate sodium excretion, water balance, and steroidogenesis, processes that are all largely directed toward reducing blood pressure and blood volume 1-4 . Both ANP and BNP are primarily synthesized in atrial myocytes and to a much lesser extent, they are synthesized in ventricular cells and stored in dense granules 1,5 . A third peptide, C-type natriuretic peptide (CNP), which is highly homologous to ANP and BNP, is predominantly present in the endothelial cells and the central nervous system 6 . ANP and BNP exhibit their major effects in diverse organ systems, including kidneys, adrenal glands, heart, vasculature, gonads, and adipose tissues 2,7-12 . The early discovery of three related natriuretic peptides (NPs) hormones, prompted the cloning and characterization of three distinct subtypes of natriuretic peptide receptors (NPRs). These NP receptors included: natriuretic peptide receptor-A (NPRA), receptor-B (NPRB), and receptor-C (NPRC), with binding characteristics of ANP and BNP to NPRA, CNP to NPRB, and all three NPs (ANP, BNP, and CNP) to NPRC 13-17 . NPRA and NPRB, both of which contain a guanylyl cyclase (GC) domain, are also referred to, respectively, as GC-A/NPRA and GC-B/NPRB. The NPRA has generally been considered to be the primary receptor of ANP and BNP, the reason being that most of the physiological effects of these hormones are triggered by rapidly activating this receptor and the generation of its intracellular second messenger cGMP 15,[1...

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Atrial natriuretic peptide (ANP) is an endogenous cardiac hormone that binds to guanylyl‐cyclase/natriuretic peptide receptor‐A (GC‐A/NPRA) and regulates sodium excretion, water balance, and steroidogenesis; all directed toward the reduction of blood pressure and blood volume. The present study was aimed at understanding the mechanisms involved in angiotensin II (Ang II)‐mediated repression of Npr1 (coding for GC‐A/NPRA) gene transcription. The mouse mesangial cells (MMCs) were cultured in Dulbecco's modified Eagle's medium (DMEM) containing 10% fetal bovine serum and ITS (insulin, transferrin, and sodium selenite) and treated with Ang II for 24 h. The luciferase assay of the Npr1 promoter deletion constructs showed that the region approximately –1182/–916 bp upstream of the transcription start site contains the cis‐elements involved in ANG II‐mediated transcriptional repression of Npr1. Real‐time quantitative PCR and Western blot analyses revealed that Npr1 mRNA expression and NPRA protein levels were reduced by 60 – 65% in Ang II‐treated MMCs. Treatment with Ang II also significantly decreased ANP‐stimulated intracellular accumulation of cGMP as compared with ANP‐stimulated cells. Gel mobility shift assays confirmed that Ang II enhanced the binding of transcription factors cAMP‐response element‐binding protein (CREB) and heat shock factor 4a (HSF4a) to the Npr1 promoter. Increasing concentrations of Ang II also decreased the acetylation levels of histone H3 at lysine 9 and 14 and histone H4 at lysine 8. In contrast, there was significant increase in protein expression of prohypertrophic Class 1 histone deacetylase (HDAC) 1 and 2. Treatment of MMCs with Ang II increased the activity of HDAC in a dose‐dependent manner. The present findings provide a novel regulatory mechanism of Ang II‐mediated repression of Npr1 transcription and expression, which plays an important role in the control of hypertension and cardiovascular homeostasis.Support or Funding InformationThis work was supported by NIH grants (HL057531 and HL062147).

Guanylyl cyclase/natriuretic peptide receptor‐A (GC‐A/NPRA) signaling plays a well‐defined role in the regulation of blood pressure and blood volume. Mice lacking functional Npr1 gene (coding for GC‐A/NPRA) exhibit hypertension, kidney disease, and heart failure; however, the mechanisms regulating Npr1 expression are not well understood. 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 via modulation of epigenetic changes. Male and female (16–20 weeks old) Npr1 gene‐knockout 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 result showed that MGCD0103 significantly increased the renal NPRA protein levels in male and female mice compared with vehicle‐treated controls. Plasma cGMP levels were higher in female mice compared with male mice both before and after the treatment with MGCD0103. Renal HDAC activity was significantly higher (p < 0.05) in male mice than female mice; however, treatment with MGCD0103 significantly attenuated (p < 0.05) HDAC activity by 40% in male and ~50% in female animals. The histone acetyltransferase (HAT) activity was lower in untreated 1‐copy male mice compared with wild‐type mice and MGCD0103 treatment significantly increased HAT activity whereas no significant differences were observed in drug‐or vehicle‐treated female mice. Male and female mice showed differential renal acetylation levels of histone 3 at different lysine positions (H3‐K9, H3‐K18, and H3‐K27) and treatment with MGCD0103 significantly enhanced the acetylation levels of H3‐K9 and H3‐K27 in 1‐copy male mice and H3‐K18 in 1‐copy female mice. There was substantial decrease in methylation of suppressive histone marks (H3‐K9 and H3‐K27) in MGCD0103‐treated 1‐copy male and female mice. Male mice exhibited significantly higher systolic blood pressure (SBP) than female mice and treatment with MGCD0103 decreased SBP in both 1‐copy male (106 ± 0.6 vs. vehicle‐treated, 129 ± 1.9; mmHg) and female (97 ± 2.2 vs. vehicle‐treated, 110 ± 2.1 mmHg, p < 0.001) mice. The present results provide direct evidence that MGCD0103 epigenetically regulates NPRA expression in vivo in 1‐copy male and female haplotype mice, via attenuation of HDAC activity and increase in histone H3 acetylation levels. These findings will have important implications in prevention and treatment of hypertension and renal pathophysiological conditions under reduced NPRA signaling.Support or Funding InformationThis work was supported by NIH grants (HL057531 and HL062147) and a partial support from Tulane Carol Lavin Bernick grant award.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

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