Neuroprotective microRNA pathways

描述（由申请人提供）：调节mRNA稳定性的小的非编码microRNA（miRNA）的存在已越来越被认为是微调特定神经元蛋白质水平以介导多种脑功能的关键因素。miRNA调节对神经元生理学的这种广泛影响表明，miRNA功能的扰动涉及复杂的神经退行性疾病如阿尔茨海默病（AD）的发病机制。 然而，尽管最初的见解是miRNA在疾病进展期间有助于淀粉样蛋白病理学，但该领域仍处于起步阶段，必须扩大到专注于识别AD发作期间发生的关键的多种miRNA网络变化，这将推动新的治疗靶点。特别是，在AD的前驱期（如遗忘型轻度认知障碍（aMCI））的人的大脑中，miRNA网络是否失调，以及这些变化对AD进展的生理后果的程度仍有待研究。为此，我们初步的微阵列和定量PCR（qPCR）研究发现了两个家族的miRNAs，miR-212/132和miR-23 a/B，与对照组相比，在aMCI受试者的额叶皮质中下调。人类miRNA数据库显示，下调miR-212/132或miR-23 a/B可上调两个相互作用介导神经保护性细胞应激反应的靶点，即去乙酰化酶sirt 1和叉头转录因子foxo 3a;使用相同的额叶皮层样品的pilot qPCR研究显示，与对照相比，aMCI中sirt 1和foxo 3a mRNA水平均较高。鉴于AD发病机制中额叶皮质的参与相对延迟，以及该区域通过神经元重组对痴呆发作做出反应的能力，这些数据表明，miRNA介导的sirt 1/foxo 3a通路的上调代表了对疾病的代偿性神经保护反应。事实上，对颞叶皮层（AD进展早期受影响的区域）进行的qPCR分析显示，aMCI受试者的miR-212、miR-23 a、sirt 1或foxo 3a转录物没有变化。 此外，初步的体外机制研究表明，miR-212和miR-23 a的协同下调增加了Sirt 1和Foxo 3a蛋白的表达，并在人类神经元细胞中提供了免受淀粉样蛋白毒性的神经保护。 因此，我们的初步数据表明，我们已经发现了一种新的miRNA介导的神经保护途径激活前驱AD。该提案将使用人类组织分子，生物化学和组织化学方法以及人类神经元中的机制通路建模来验证这一假设。这些研究可能揭示基因调控途径的新见解，从而为改变AD进展提供创新的治疗途径。

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.