Ethanol alteration of the neurogenic niche

描述(申请人提供)：酒精使用障碍仍然是美国主要的公共卫生问题之一，超过1700万美国人符合酒精滥用或依赖的诊断标准。慢性酗酒者表现出与大脑质量丧失或神经退化有关的认知障碍，这些影响可能会在戒酒后恢复。许多人认为这种恢复的机制是由于神经胶质细胞的再生，然而我们实验室最近的发现表明，酒精诱导的神经干细胞(NSCs)的调节与活跃酒精中毒(减少)和戒酒(增加)期间海马区大脑质量和认知的变化平行。神经干细胞的调节依赖于当地环境或神经源性生态位的环境。小胶质细胞是三种神经胶质细胞之一，为这一利基做出了贡献。虽然小胶质细胞事件在历史上是细胞毒性的同义词，但在神经发生中一个新的角色正在出现。一些激活的小胶质细胞分泌生长因子和抗炎细胞因子，这一作用与最近的数据一致，即某些类型的小胶质细胞促进神经干细胞的增殖和成年神经发生。因此，当我们在慢性酒精中毒模型中观察到小胶质细胞反应先于神经源性反应时，我们怀疑小胶质细胞事件与促进神经发生之间存在因果联系。因此，这一提议将检验一种假设，即酗酒会产生分级的小胶质细胞反应，促使戒酒后静止的神经干细胞重新聚集到增殖和神经发生中。针对这一假说，有三个具体的目标：(1)酗酒是否会招募更多的神经干细胞；(2)小胶质细胞是否表现出一种分级的、非吞噬的表型，可以预测神经源性微环境；(3)在慢性酒精中毒模型中，我们是否可以调节这种表型来改变神经发生。将使用多种方法，即免疫组织化学方法来评估NSCs的募集和增殖动力学，小胶质细胞的形态，以及原位杂交、受体放射自显影和酶联免疫吸附试验来确定小胶质细胞的表型和细胞因子的表达。最后，神经解剖学和行为学研究将证实小胶质细胞表型在酗酒后神经退化和再生中的作用。与公共健康相关：这项提议将通过研究激活的小胶质细胞在神经干细胞和神经发生环境中的作用来揭示戒酒后大脑再生的机制。这一结果将为我们治疗与慢性酒精中毒相关的脑损伤的长期目标带来一种新的方法：在招募神经干细胞修复受损部位的过程中，识别促进小胶质细胞保护作用的药物或行为，希望逆转或预防与酒精神经变性相关的认知缺陷。

DESCRIPTION (provided by applicant): Alcohol use disorders remain as one of the nation's major public health problems with over 17 million Americans meeting the diagnostic criteria for alcohol abuse or dependence. Chronic alcoholics demonstrate cognitive impairments that are related to a loss of brain mass or neurodegeneration, effects that may recover with abstinence. Many assumed that the mechanism of this recovery was due to glial regeneration, however recent discoveries from our laboratory show that alcohol-induced regulation of neural stem cells (NSCs) parallels the changes in brain mass and cognition during active alcoholism (decrease) versus abstinence (increase) in the hippocampus. The regulation of NSCs relies on the milieu of the local environment, or neurogenic niche. Microglial, one of three types of glia, contribute to this niche. Though microglial events historically were synonymous with cytotoxicity, a new role in neurogenesis is emerging. Some activated microglia secrete growth factors and anti-inflammatory cytokines, an effect that is consistent with recent data that certain types of microglia promote NSC proliferation and adult neurogenesis. Thus, when we observed a microglial response that precedes the neurogenic response in our model of chronic alcoholism, we suspected a causal link between microglial events and the promotion of neurogenesis. Therefore, this proposal will test the hypothesis that binge alcohol exposure produces a graded microglial response that drives the recruitment of quiescent NSCs into proliferation and neurogenesis in abstinence. Three specific aims address this hypothesis by asking: (1) whether binge alcohol exposure recruits additional NSCs, (2) whether microglia show a graded, nonphagocytic phenotype predictive of a proneurogenic microenvironment and (3) whether can we modulate this phenotype to alter neurogenesis in a model of chronic alcoholism. Multiple approaches will be used, namely immunohistochemistry to assess the recruitment and proliferative dynamics of NSCs, the morphology of microglia, as well as in situ hybridization, receptor autoradiography and Enzyme-Linked ImmunoSorbant Assays to determine microglia phenotype and cytokine expression. And finally, neuroanatomical and behavioral work will confirm the role of microglia phenotype in neurodegneration and regeneration following binge alcohol exposure. Relevance to public health: This proposal will uncover a mechanism of brain regrowth in abstinence from alcohol by investigating the role of activated microglia on neural stem cells and the neurogenic environment. The results will lead to a novel approach in our long term goal of treating brain damage associated with chronic alcoholism: Identifying agents or behaviors that promote protective actions of microglia in recruiting NSCs to repair sites of damage with the hope of reversing or preventing cognitive deficits associated with alcoholic neurodegeneration.