(626.5) Vitamin D Regulates Natriuretic Peptide Receptor-A Gene Expression via Modulation of Histone Deacetylases and DNA Methyltransferase Activity

Poster Board Number: E678

Prerna Kumar (Tulane University Health Sciences Center, School of Medicine), Krishna Pandya (Tulane University Health Sciences Center, School of Medicine,), Christian Nguyen (Tulane University Health Sciences Center, School of Medicine), Kailash N Pandey (Tulane University Health Sciences Center, School of Medicine)

Cardiac hormones atrial and brain natriuretic peptides (ANP and BNP) activate guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) and produces the second messenger cGMP. cGMP activates downstream signaling and biological consequences of ANP/NPRA such as natriuresis, diuresis, vasorelaxation, antimitogenic responses, and cardiac and renal anti-hypertrophic effects. The activity and expression of Npr1 gene (coding for GC-A/NPRA)  assessed primarily through ANP-stimulated cGMP production, are mediated by agents, including autoregulation involving natriuretic peptides, osmotic sensors, and other external and internal stimuli, but the hormonal and epigenetic mechanisms mediating Npr1 regulation are not well understood. The objective of present study was to study the effect of Vitamin D (vitD) in the regulation of Npr1 gene transcription and expression via modulation of epigenetic factors. Our bioinformatics study with the murine Npr1 promoter has shown presence of 4 vitD response elements (VDRE) in the region -583 to -495 from the transcription start site having perfect and VDRE-like consensus sequence. Npr1 promoter activity was determined by transient transfection of Npr1 promoter deletion constructs in cultured rat thoracic aortic smooth muscle cells (RTASMCs) and mouse mesangial cells (MMCs) treated with Vitamin D₃ (1α, 25-dihydroxy; VD3) using dual luciferase assay kit. Luciferase assay demonstrated that VD3 enhances Npr1 promoter activity by more than 5-6-fold in RTASMCs and MMCs in a dose-dependent manner. Western blot and densitometry analysis showed increasing concentrations of VD3 significantly induced NPRA protein levels by 3.5-fold in MMCs and 4.5-fold in RTASMCs and maximum effect was observed at 100 nM. There was 45%-50% inhibition of histone deacetylase (HDAC) activity in presence of VD3 in both cell lines as measured by HDAC activity/inhibition ELISA kit. Moreover, treatment with VD3 reduced class I HDAC enzymes, HDAC1 and HDAC3 protein levels and dose-dependently enhanced acetylation level of histones, H3 at lysine residues 9 and 14 (H3-K9/14 ac) and H4 at lysine residue 12 (H4-K14ac). Treatment of RTASMCs and MMCs with VD3 attenuated DNA methyltransferase (DNMT) activity by 40%-55% as measured by DNMT activity/inhibition ELISA kit. The results demonstrate that VD3 regulate Npr1 gene expression by modulation of histone deacetylases and DNMT activity. The identification of epigenetic targets of vitamin D signaling as a regulator of Npr1 gene transcription and protein expression will have important implications in hypertension and cardiovascular regulation.

This work was supported by NIH grant (HL062147).