Department of Pharmacology and Medical Research Center for Gene Regulation, Chonnam National University Medical School, Heart Research Center of Chonnam National University Hospital, Gwangju 501-746, South Korea.
J Mol Cell Cardiol. 2009 Dec;47(6):770-80. doi: 10.1016/j.yjmcc.2009.08.022. Epub 2009 Aug 31.
Recently, we reported that histone deacetylase (HDAC) inhibitors block cardiac hypertrophy and that activation of HDAC2, one of the class I HDACs, is required for hypertrophy. In the present study, we tried to find the downstream target of HDAC inhibitor by utilizing cardiomyocytes and H9c2 cells. Both trichostatin A (TSA, class I and II HDAC inhibitor) and SK7041 (SK, class I HDAC blocker) attenuated the expression level and promoter activity of Nppa (natriuretic polypeptide precursor type A) and Myh7 (myosin heavy polypeptide 7), which are fetal genes associated with hypertrophy. Promoter-mapping revealed that the Nppa promoter region from -130 to approximately -105, which contains binding sites for Krüppel-like factor 4 (KLF4), is responsible for the HDAC inhibitor-mediated inhibition. SK-induced repression of Nppa promoter activity was attenuated when the KLF4-binding element was deleted or disrupted. Klf4 was upregulated by HDAC inhibitors, whereas it was down-regulated by phenylephrine in cardiomyocytes or by partial aortic constriction in mice. Klf4 successfully recruited the proximal Nppa promoter region flanking the KLF4-binding element in cardiomyocytes, and the recruitment was reduced by treatment with phenylephrine, which was recovered by SK. Overexpression of Klf4 blocked the agonist-induced increase in cardiomyocyte size, [(3)H]-leucine incorporation, and Nppa promoter activation. However, promoter activity was not prominently inhibited when the KLF4-binding element was disrupted or when a small inhibitory RNA to KLF4 was transfected into cells. Hypertrophic phenotypes were enhanced in Klf4-knockdown cells. These results suggest that KLF4, a novel anti-hypertrophic transcriptional regulator, mediates the HDAC inhibitor-induced prevention of cardiac hypertrophy.
最近，我们报道组蛋白去乙酰化酶（HDAC）抑制剂可阻断心肌肥厚，且激活 HDAC2（I 类 HDAC 之一）是心肌肥厚所必需的。在本研究中，我们尝试利用心肌细胞和 H9c2 细胞寻找 HDAC 抑制剂的下游靶标。曲古抑菌素 A（TSA，I 类和 II 类 HDAC 抑制剂）和 SK7041（SK，I 类 HDAC 阻滞剂）均可减弱与肥厚相关的胎儿基因 Nppa（利钠肽前体 A）和 Myh7（肌球蛋白重链 7）的表达水平和启动子活性。启动子作图表明，包含 Krüppel 样因子 4（KLF4）结合位点的 Nppa 启动子区域-130 至约-105 负责 HDAC 抑制剂介导的抑制作用。当删除或破坏 KLF4 结合元件时，SK 诱导的 Nppa 启动子活性抑制减弱。HDAC 抑制剂上调 Klf4，而在心肌细胞中苯肾上腺素或小鼠部分主动脉缩窄时下调 Klf4。Klf4 成功招募了心肌细胞中紧邻 KLF4 结合元件的近端 Nppa 启动子区域，而用苯肾上腺素处理则减少了募集，SK 则恢复了募集。Klf4 的过表达阻断了激动剂诱导的心肌细胞大小增加、[(3)H]-亮氨酸掺入和 Nppa 启动子激活。然而，当破坏 KLF4 结合元件或转染 KLF4 的小干扰 RNA 时，启动子活性并未明显受到抑制。Klf4 敲低细胞的肥厚表型增强。这些结果表明，KLF4 作为一种新型抗肥厚转录调节因子，介导了 HDAC 抑制剂诱导的心脏肥厚预防作用。
