Abstract 654: Overexpression Of Class I Histone Deacetylases Repress Npr1 Gene Transcription In Mouse Mesangial Cells

Abstract

Activation of guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) by cardiac hormones atrial and brain natriuretic peptides (ANP and BNP) produces the second messenger cGMP, which plays a pivotal role in maintaining blood pressure and cardiovascular homeostasis. The objective of the present study was to gain insight into the epigenetic signaling mechanism in the regulation of Npr1 (coding for GC-A/NPRA) gene transcription and expression. The mouse mesangial cells were cultured in Dulbecco’s modified Eagles medium containing 10% fetal bovine serum and ITS (insulin, transferrin, and sodium selenite). The results showed that class I and II histone deacetylase (HDAC) inhibitors trichostatin A (TSA) and sodium butyrate (NaBu) significantly induced Npr1 promoter activity by 5- and 7-fold (TSA-treated, 2160.3 ± 32.4 and NaBu-treated, 3024.89 ± 25.03 vs. untreated control 432.2 ± 23.2, p < 0.001). TSA induced Npr1 mRNA levels by 3.5-fold and NaBu by 5-fold (TSA-treated, 9.7 ± 0.89 and NaBu-treated, 13.8 ± 1.9 vs. control 2.68 ± 0.5; p < 0.001). NaBu significantly reduced HDAC activity by 50% (5.15 ± 0.11 vs. control 1.94 ± 0.26) and stimulated histone acetyltransferase activity by 3-fold (48.93 ± 7.32 vs. control 15.98 ± 2.1). Furthermore, class I specific HDAC inhibitor mocetinostat (MGCD0103) significantly enhanced Npr1 promoter activity by 6-fold (1955.4 ± 47.32 vs. control 325.9 ± 23.4, p < 0.001) whereas class II HDAC inhibitor MC 1568 showed no significant effect on the promoter activity. MGCD0103 increased the acetylation of histones H3 by 2.5-fold (8850 ± 90.4 vs. control 3421 ± 68.5) and H4 by 4-fold (27320 ± 213 vs. control 6919 ± 78.5), respectively. Overexpression of class I HDACs (HDAC1 and HDAC2) repressed Npr1 promoter activity by 50% (234.8 ± 9.5 and 265.4 ± 10.32, respectively vs. control 543.23 ± 7.8, p < 0.001) and knockdown of HDAC1 and HDAC2 expression by siRNA abolished this repression. Collectively, the present results demonstrate that class I HDAC inhibitor upregulates Npr1 gene transcription via inhibition of HDAC activity and histone acetylation. The identification of epigenetic signaling as a regulator of Npr1 gene expression will have important implications in prevention of hypertension and cardiac remodeling.