Angiotensin II induces cardiomyocyte hypertrophy probably through histone deacetylases

Abstract

Angiotensin II (Ang II) plays a pathophysiological role in the genesis of cardiac hypertrophy as a hypertrophic stimulus. But little is known about the terminal steps, in which Ang II reprograms cardiac gene expression. Histone deacetyltransferases (HDACs) are considered as the integrators of divergent stress-response pathways during heart remodeling. However, the exact role of HDACs in the hypertrophic process is not clear yet. Therefore, we studied the expression of HDAC2, one of Class I HDACs, and the effect of valproic acid (VPA), a nonspecific HDAC inhibitor, in the Ang II-induced cardiomyocyte hypertrophy. Primary cultures of neonatal rat cardiomyocytes were prepared from 1-day-old Wistar rats and treated with Ang II. The mRNA levels of HDAC2 and β-myosin heavy chain (β-MHC), a hypertrophic marker gene, were determined by reverse transcription-polymerase chain reaction (RT-PCR). The protein expression of HDAC2 and c-fos, an immediate early response gene, was evaluated by immunohistochemistry, and the surface areas of cardiomyocytes were measured using Motic Images software. The expression levels of HDAC2 mRNA and protein were increased in a time-dependent manner during the hypertrophic process, accompanied with the increment of β-MHC and c-fos proteins. Ang II also increased the surface area of cardiomyocytes by more than twofold. VPA significantly reversed these changes. These results suggest that Ang II may induce cardiomyocyte hypertrophy through HDACs in combination with c-fos and that VPA has the protective effect on cardiomyocyte hypertrophy. Thus, HDAC inhibition is a feasible therapeutic strategy that holds promise in the treatment of cardiac hypertrophy. © 2009 Tohoku University Medical Press.