Brain epigenetic mechanisms in alcohol dependence

描述(申请人提供)：焦虑是酒精戒断的常见早期症状，被认为是酗酒者继续饮酒的重要因素。众所周知，酒精会产生缓解焦虑的作用。不同的表观遗传机制如何影响与酒精成瘾相关的神经可塑性的变化尚不清楚。研究表明，组蛋白通过乙酰化和去乙酰化修饰引起的染色质结构变化在基因表达调控中的作用。组蛋白乙酰化由两组酶控制，组蛋白乙酰转移酶(HATS)和组蛋白脱乙酰酶(HDACs)。已经描述了三个不同的HDAC家族，曲古抑菌素A(ISA)是I类和II类HDAC的有效抑制剂，但不是III类HDAC[沉默信息调节因子2(Sir2)蛋白家族]，后者需要辅因子烟酰胺-腺嘌呤二核苷酸(NAD)来实现酶活性。研究表明，磷酸化cAMP反应元件结合(p-CREB)通过募集与CREB结合蛋白(CBP)相关的HAT来激活基因转录，从而调节神经元的可塑性。神经肽Y(NPY)是CREB相关基因之一，是一种有效的内源性抗焦虑化合物，在酒精中毒中起重要作用。我们的建议是基于这样一种假设，即由于杏仁核乙酰化状态的改变，组蛋白修饰参与了酒精依赖的分子机制。我们已经提出了几种方法来检验这一假说，具体方法是：a)急性乙醇对组蛋白乙酰化机制的各个组成部分以及大鼠中央(CEA)、内侧(MEA)和基底外侧杏仁核(BLA)中NPY表达的影响，以及对CEA、MEA和BLA中HATS活性和Sir2活性的操纵也将考察乙醇的抗焦虑特性。2)HDACs抑制剂(曲古抑素A)激发或杏仁核内注射SIR_2抑制剂对慢性酒精暴露后戒断大鼠焦虑样行为、组蛋白乙酰化的影响以及对杏仁核NPY表达的影响。我们还将检查H3乙酰化对酒精处理及其戒断过程中杏仁核NPY mRNA水平的影响。拟议的研究将为杏仁核神经回路中可能涉及酒精依赖过程的表观遗传机制提供新的信息。

DESCRIPTION (provided by applicant): Anxiety is a common early symptom of ethanol withdrawal and is considered an important factor in the continued use of alcohol by alcoholics. It is also well known that alcohol produces anxiolytic effects. How different epigenetic mechanisms are contributing to changes in neural plasticity associated with alcohol addiction is unknown. Studies have shown the role of changes in chromatin structure due to histone covalent modifications via acetylation and deacetylation in the regulation of gene expression. Histone acetylation is controlled by two groups of enzymes known as histone acetyl-transferases (HATs) and histone deacetylases (HDACs). Three distinct families of HDACs have been described and trichostatin A (ISA) is a potent inhibitor of class I and II HDACs, but not the class III HDACs [silent information regulator 2(Sir2) protein family] which requires a cofactor, nicotinamide-adenine dinucleotide (NAD), for enzymatic activity. It has been shown that phosphorylated cAMP-responsive element binding (p-CREB) regulates neuronal plasticity via recruitment of the HAT associated with CREB binding protein (CBP) to activate gene transcription. Neuropeptide Y (NPY) is one of the CREB-related genes and acts as a potent endogenous anxiolytic compound ,and plays a role in alcoholism. Our proposal is based on the hypothesis that histone modifications, due to an altered acetylation state in the amygdala, are involved in the molecular mechanisms of alcohol dependence. We have proposed several approaches to test this hypothesis specifically by examining a) the effects of acute ethanol on various components of histone acetylation mechanisms as well as NPY expression in the central (CeA), medial (MeA) and basolateral amygdala(BLA) of rats and manipulations of activities of HATs activity and Sir2 in the CeA, MeA, and BLA will also be examined on the anxiolytic properties of ethanol. b) Effects of HDACs inhibitor (Trichostatin A) challenge or intra-amygdaloid Sir 2 inhibitor infusion on anxiety-like behaviors and also on various components of histone acetylation and on NPY expression in amygdala during withdrawal after chronic ethanol exposure. We will also examine the effects of H3 acetylation on NPY mRNA levels in the amygdala during ethanol treatment and its withdrawal. The proposed studies will provide new information on epigenetic mechanisms in the neurocircuitry of the amygdala that may be involved in the process of alcohol dependence.