SAT-046 Modulation of Histone 3 Acetylation and Methylation Enhances the Expression and Function of Npr1 in Haplotype Mice

Atrial and brain natriuretic peptides (ANP, BNP) activate guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA), which plays a critical role in the regulation of blood pressure and fluid volume homeostasis, and inhibits the cell proliferation and fibrosis. Mice lacking functional Npr1 (coding for GC-A/NPRA) gene exhibit hypertension and renal disorders; however, the mechanisms regulating Npr1 expression and function are not well understood. The objective of the present study was to gain insight into the epigenetic regulatory mechanisms involved in Npr1 gene expression modulated by class I specific histone deacetylase (HDAC) inhibitor, mocetinostat (MGCD0103). We utilized 16- to 20-weeks old male and female Npr1 gene-knockout haplotype (1-copy; Npr1(+/-)), wild-type (2-copy; Npr1(+/+)) and gene-duplicated heterozygous (3-copy; Npr1(++/+)) mice. Mice were injected intraperitoneally with MGCD0103 (2 mg/kg) at an alternate days for 2-weeks. The Western blot analysis revealed that MGCD0103 significantly increased the renal NPRA protein levels in all male and female mice groups compared with vehicle-treated controls. After MGCD0103 treatment, the renal Npr1 mRNA expression increased in Npr1 haplotype male and female mice. Renal HDAC activity was significantly higher (p < 0.05) in all genotypes of male mice than female mice; however, treatment with MGCD0103 markedly attenuated HDAC activity in both male (~40%, p < 0.05) and female (~50%, p < 0.05) animals. The histone acetyltransferase (HAT) activity was lower in untreated 1-copy male mice compared with wild type mice and MGCD0103 treatment significantly increased the HAT activity whereas no significant differences were observed in drug- or vehicle-treated female mice. The drug treatment 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 increase in protein levels of active gene transcription mark H3-K4 tri-methylation and decrease in suppressive marks H3-K9 and H3-K27 methylation in MGCD0103-treated 1-copy male and female mice. The present results suggest that MGCD0103 epigenetically regulates Npr1 expression in vivo in 1-copy haplotype male and female mice, via inhibition of HDAC activity, upregulation of the H3 acetylation and attenuation of H3 methylation levels. These present findings will have important implications in prevention and treatment of hypertension-related renal pathophysiological conditions under reduced NPRA signaling. This work was supported by NIH grants (HL057531 and HL062147) and a partial support from Tulane Carol Lavin Bernick grant award.