Mechanisms of Neuroprotection by Histone Deacetylase Inhibition

描述（由申请人提供）：肿瘤抑制因子p53被认为是急慢性神经损伤和神经退行性疾病中重要的细胞凋亡调节因子。然而，p53在神经元中激活的下游分子后果仍然不清楚。我们的蛋白质组学分析表明，DNA损伤诱导的神经元凋亡涉及组成组蛋白去乙酰化酶（HDAC）复合物的蛋白质表达的p53依赖性增加。这些数据表明p53可能通过激活组蛋白去乙酰化酶活性来促进神经元功能障碍/细胞死亡。我们的初步研究确实表明，组蛋白去乙酰化酶抑制剂可以防止p53介导的细胞死亡。相反，HDAC活性在癌细胞中普遍升高，HDAC抑制实际上诱导p53依赖性细胞死亡。在目前的应用中，基于HDAC抑制剂作用的神经元特异性模式的这一新发现，我们建议通过检查HDAC抑制剂如何阻断神经元细胞死亡来验证神经元中p53介导的细胞死亡信号依赖于组蛋白去乙酰化酶活性的假设。我们将具体地：1)确定HDAC抑制剂是否选择性地保护神经元免受p53介导的细胞死亡，2)确定HDAC抑制剂是否直接阻断p53激活和/或p53依赖性细胞死亡所需的转录活性；3)确定HDAC抑制剂是否能阻止p53依赖性线粒体完整性的改变。本研究的目的将有助于我们更好地了解HDAC抑制剂作用的分子位点和机制，从而提高这些抑制剂作为神经系统疾病和损伤治疗药物的实用性。

DESCRIPTION (provided by applicant): The tumor suppressor p53 is recognized as an important regulator of apoptosis in acute and chronic neurological insults and neurodegenerative disorders. However, the downstream molecular consequences of p53 activation in neurons still remain obscure. Our proteomic analyses have demonstrated that DNA damage-induced neuronal apoptosis involves a p53-dependent increase in the expression of proteins that comprise histone deacetylase (HDAC) complexes. This data suggests that p53 might promote neuronal dysfunction/cell death by activating histone deacetylase activity. Our preliminary studies indeed demonstrate that histone deacetylase inhibitors protect against p53-mediated cell death. In contrast HDAC activity is generally elevated in cancer cells, and HDAC inhibition actually induces p53-dependent cell death. In the present application, based on this novel finding of the neuron-specific mode of HDAC inhibitor actions, we propose to test the hypothesis that p53-mediated cell death signaling in neurons is dependent on histone deacetylase activity by examining how HDAC inhibitors block neuronal cell death. We will specifically: 1) Determine if HDAC inhibitors selectively protect neurons from p53-mediated cell death, 2) Determine if HDAC inhibitors directly block p53 activation and/or transcriptional activity required for p53-dependent cell death in neurons; and 3) Determine if HDAC inhibitors prevent p53- dependent changes in mitochondrial integrity. The aims of this proposal will help us to better understand the molecular sites and mechanism of HDAC inhibitor action, which will enhance the utility of these inhibitors as therapeutic agents for neurological diseases and injury. PUBLIC HEALTH RELEVANCE: Histone deacetylase inhibitors protect neurons from dying in several mouse models of human neurodegenerative disease. However, the mechanism by which histone deacetylase inhibitors prevent cell death is not understood. A better understanding of how these compounds work and the types of diseases or injuries that they protect against would enhance their range of action and their effectiveness. We propose to determine how histone deacetylase inhibitors block neuronal cell death which could lead to the development of new therapeutic agents for treating neurological diseases and nervous system injury.