Abstract 182: Class I Histone Deacetylase Inhibition Represses the Upregulation of Sodium-Calcium Exchanger Expression in Cardiac Hypertrophy
Background: Histone deacetylases (HDACs) play an important role in the alteration of gene expression during cardiac hypertrophy and failure. Our previous study demonstrated that acetylated Nkx2.5 is associated with the Class I/II HDAC complex, HDAC5/1/2 at the Ncx1 promoter, and deacetylated Nkx2.5 is associated with the transcriptional activator and histone acetylase, p300 in a mutually exclusive manner. Inhibition of HDACs by the Class I/II inhibitor, trichostatin A (TSA) prevents deacetylation of Nkx2.5 and recruitment of p300 to the Ncx1 promoter, thereby repressing its upregulation.
Objective: To assess the specific roles of HDAC1, 2 and 5 in the regulation of Ncx1 gene expression and determine the specific Nkx2.5 lysine(s) undergoing acetylation or deacetylation, which mediates Ncx1 upregulation.
Results: Treatment of isolated adult cardiomyocytes with the selective class I HDAC inhibitor, BML210, prevented alpha- and beta-adrenergic stimulated upregulation of Ncx1 expression, whereas treatment with the specific class II HDAC inhibitor, dPAHA did not. Interestingly, the HDAC5 knockout prevented NCX1 upregulation after 72 hr trans-aortic constriction (TAC) in mice. In order to determine which Nkx2.5 lysine(s) is deacetylated by HDAC1/2, we performed mass spectrometry analysis. The Nkx2.5 gene contains 15 lysine moieties, and LC-MS/MS analysis demonstrates that Nkx2.5 is acetylated on two conserved lysine residues.
Conclusion: Class I HDAC activity is required for Ncx1 expression but not class II HDAC activity (HDAC5). However, the loss of HDAC5 prevents Ncx1 upregulation because it may act as a scaffold to recruit the factors required for Ncx1 promoter activation. These results suggest that HDAC inhibition may represent a novel therapeutic modality for hypertrophy and heart failure.
- © 2012 by American Heart Association, Inc.