Identification of intracellular signaling molecules that bind to cardiac p300 during the development of heart failure and its application to pharmacological therapy

高血压等肥大刺激启动多条亚细胞信号通路，最终到达心肌细胞核，改变基因表达模式。在从代偿性肥厚向失代偿性心力衰竭转变过程中，压力超负荷可显著诱导心肌细胞内皮素-1的表达。识别导致这种诱导的核通路将为心力衰竭提供新的药理靶点。作为E1a相关蛋白之一，p300在诱导心肌细胞内皮素-1的表达中起着关键作用，并且是肥大反应转录因子如MEF-2和GATA-4的共激活因子。P300蛋白还具有组蛋白乙酰转移酶(HAT)活性，参与肥大刺激诱导的心肌细胞GATA-4乙酰化和DNA结合。我们已经建立了心脏特异性过表达野生型p300或突变型p300的转基因小鼠，这些小鼠失去了HAT活性，并发现p300介导的GATA-4乙酰化是失代偿性心力衰竭患者体内病理性心肌细胞生长所必需的。最近，几种化合物在体外和培养中抑制p300-HAT活性已有报道。其中之一是一种天然化合物，姜黄素，它抑制培养的HeLa细胞中的组蛋白乙酰化，并抑制p300介导的染色质转录。该化合物抑制了PE诱导的肥大反应，如肌原纤维组织化和细胞大小增加，PE诱导的心脏胎儿基因的反式激活，以及PE诱导的GATA-4 DNA结合活性的增加。因此，我们确定了一种针对心肌细胞内压力超负荷信号转导的核通路的药物，并可用于体内治疗高血压引起的心力衰竭。

Hypertrophic stimuli such as hypertension initiates a number of subcellular signaling pathways, which finally reach the nuclei of cardiac myocytes and change the pattern of gene expression. The expression of endothelin-1 in cardiac myocytes is markedly induced following pressure overload during the transition from compensated hypertrophy to decompensated heart failure. Identification of nuclear pathways that lead to this induction will provide novel pharmacological targets for heart failure. One of E1A-associated proteins, p300 plays a critical role for the induction of endothelin-1 expression in cardiac myoytes, and serves as a coactivator of hypertrophy-responsive transcriptional factors such as MEF-2 and GATA-4. A p300 protein also possesses histone acetyltransferase (HAT) activity, and is involved in hypertrophic stimuli-induced acetylation and DNA binding of GATA-4 in cardiac myocytes. We have generated transgenic mice with cardiac-specific overexpression of either wild-type p300 or mutant p300 that lose its HAT activity, and found that p300-mediated acetylation of GATA-4 is required for pathological myocyte growth with decompensated heart failure in vivo. Recently, several compounds that inhibit p300-HAT activity in vitro and in culture have been reported. One of these is a natural compound, currcumin, which inhibits histone acetylation in cultured HeLa cells and repress p300-mediated chromatin transcription. This compound repressed PE-induced hypertrophic responses such as myofibrilar organization and increase in cell size, PE-induced transactivation of the cardiac fetal genes, and PE-induced increase in the DNA binding activity of GATA-4. Thus, we identified a pharmacological agent that targets nuclear pathways for pressure overload-signaling in cardiac myocytes, and could be applied for the treatment of hypertension-induced heart failure in vivo.