Neuroprotective microRNA pathways

描述(申请人提供)：调节mRNA稳定性的小非编码microRNAs(MiRNAs)的存在已越来越被认为是微调特定神经元蛋白质水平以调节不同大脑功能的关键因素。MiRNA调控对神经生理学的广泛影响表明，miRNA功能的紊乱参与了阿尔茨海默病(AD)等复杂神经退行性疾病的发病机制。然而，尽管最初的见解表明miRNAs在疾病进展过程中对淀粉样蛋白病理有贡献，但该领域仍处于起步阶段，必须扩大到专注于识别AD发病期间发生的各种关键的miRNA网络变化，这将推动新的治疗靶点。特别是，在AD的前驱阶段，如遗忘性轻度认知损害(AMCI)，miRNA网络是否在大脑中调节失调，以及这些变化在多大程度上对AD进展产生生理影响仍未得到充分研究。为此，我们的初步微阵列和定量PCR(QPCR)研究发现，与对照组相比，两个miRNAs家族miR-212/132和miR-23a/b在aMCI受试者的额叶皮质中下调。人类miRNA数据库显示，miR-212/132或miR-23a/b的下调被预测为上调两个相互作用的介导神经保护细胞应激反应的靶标，脱乙酰酶sirtuin 1(SIRT1)和叉头转录因子FOXO3a；使用相同的额叶皮质样本的初步qPCR研究显示，与对照组相比，aMCI的SIRT1和FOXO3a mRNA水平更高。鉴于额叶皮质在AD发病机制中的相对延迟参与，以及该区域通过神经元重组对痴呆的发生做出反应的能力，这些数据表明，miRNA介导的SIRT1/FOXO3a通路的上调代表了对不断增加的疾病的代偿性神经保护反应。事实上，对阿尔茨海默病早期受累的颞叶皮质进行的qPCR分析显示，在aMCI受试者中，miR-212、miR-23a、SIRT1或FOXO3a转录本没有变化。此外，初步的体外机制研究表明，miR-212和miR-23a的协同下调增加了Sirt1和Foxo3a的蛋白表达，并提供了对淀粉样蛋白毒性的神经保护作用。因此，我们的初步数据表明，我们已经发现了在前驱AD期间激活的一种新的miRNA介导的神经保护途径。这项提议将使用人类组织分子、生化和组织化学方法以及人类神经元中的机制途径模型来验证这一假说。这些研究可能揭示出对基因调控途径的新见解，从而为改变AD的进展开辟创新的治疗途径。 与公共卫生相关：microRNA(MiRNA)对神经基因网络的调节影响到各种复杂的细胞过程；因此，各种miRNA功能可能会影响阿尔茨海默病(AD)等神经退行性疾病的进展。基于我们激动人心的初步研究，这一建议将测试在AD前驱阶段，两个相关miRNA家族的协同下调激活神经保护途径的程度。我们的发现将验证这一新的命题，即先天代偿miRNA介导的通路在AD进展的早期被激活。在AD发病期间更好地了解这些miRNA通路将揭示药物发现、生物标记物开发和疾病修改的创新靶点。

DESCRIPTION (provided by applicant): The presence of small non-coding microRNAs (miRNAs) which regulate mRNA stability has become increasingly appreciated as a critical factor in fine-tuning specific neuronal protein levels to mediate diverse brain functions. This widespread influence of miRNA regulation on neuronal physiology suggests that perturbations in miRNA function are involved in the pathogenesis of complex neurodegenerative disorders such as Alzheimer's disease (AD). However, despite initial insights that miRNAs contribute to amyloid pathology during disease progression, the field remains in its infancy and must expand to focus on identifying key multifarious miRNA network changes occurring during the onset of AD which will drive novel therapeutic targets. In particular, whether miRNA networks are dysregulated in the brains of people in the prodromal stages of AD such as amnestic mild cognitive impairment (aMCI) and the extent to which these changes have physiologic consequences for AD progression remain underexplored. To this end, our preliminary microarray and quantitative PCR (qPCR) studies discovered two families of miRNAs, miR-212/132 and miR-23a/b, that were down-regulated in the frontal cortex of aMCI subjects compared to controls. Human miRNA databases revealed that the down-regulation of either miR-212/132 or miR-23a/b was predicted to up-regulate two targets that interact to mediate neuroprotective cell stress responses, the deacetylase sirtuin 1 (sirt1) and the forkhead transcription factor foxo3a; pilot qPCR studies using the same frontal cortex samples revealed that both sirt1 and foxo3a mRNA levels were higher in aMCI compared to controls. Given the relatively delayed involvement of frontal cortex in AD pathogenesis and the ability of this region to respond to the onset of dementia by neuronal reorganization, these data suggest that miRNA-mediated up-regulation of the sirt1/foxo3a pathway represents a compensatory neuroprotective response to mounting disease. In fact, qPCR analysis performed on temporal cortex, an area affected early in the progression of AD, showed no changes in miR-212, miR-23a, sirt1, or foxo3a transcripts in the aMCI subjects. Moreover, pilot in vitro mechanistic studies showed that the coordinated down-regulation of miR-212 and miR-23a increased Sirt1 and Foxo3a protein expression and provided neuroprotection from ¿-amyloid toxicity in human neuronal cells. Hence, our preliminary data suggest that we have uncovered a novel miRNA-mediated neuroprotective pathway activated during prodromal AD. This proposal will test this hypothesis using human tissue molecular, biochemical, and histochemical approaches as well as mechanistic pathway modeling in human neurons. These studies may reveal new insights into gene regulation pathways leading to innovative therapeutic avenues for modifying AD progression. PUBLIC HEALTH RELEVANCE: MicroRNA (miRNA) regulation of neuronal gene networks affects a wide variety of complex cellular processes; hence, multifarious miRNA function could influence the progression of neurodegenerative disorders such as Alzheimer's disease (AD). Based on our exciting pilot studies, this proposal will test the extent to which coordinated down-regulation of two related miRNA families activates a neuroprotective pathway during the prodromal stages of AD. Our findings will validate the novel proposition that innate compensatory miRNA-mediated pathways are activated early in AD progression. A greater understanding of these miRNA pathways during the onset of AD will reveal innovative targets for drug discovery, biomarker development, and disease modification.