Micro RNA-146a (miRNA-146a) signaling in Alzheimers disease (AD)

描述（由申请人提供）：大量证据支持复杂促炎信号的进行性上调、A¿42肽的进化和神经营养支持的丧失是阿尔茨海默病（AD）发生和传播的基础。微RNA （miRNA）介导的信使RNA （mRNA）干扰是一种新发现的参与转录后水平基因表达调控的遗传机制。miRNA的主要作用方式是靶向并结合特定mRNA的3'非翻译区，从而抑制该mRNA的表达，从而起到基因表达的负调控作用。阿尔茨海默病仅影响大脑的特定区域，而miRNA表达失调与这些区域内基因表达的改变密切相关。在AD模型中，这些相同的富含AD的mirna诱导了与AD大脑中观察到的非常相似的特异性病理变化。越来越多的证据有力地表明，mirna介导的特定mRNA群体加工的改变触发了驱动AD过程的基因的致病性表达。该项目的总体目标是通过定义特异性mirna如何诱导导致AD类型变化的分子遗传机制，显著推动mirna - AD领域向前发展，并影响对AD的科学理解。人类大脑只利用了所有已知miRNA物种的一小部分；其中只有一小部分在AD大脑中发生了改变。一种特定的NF-？b敏感的miRNA-146a下调至少三个主要mRNA靶点的丰度，补体因子H (CFH)，白细胞介素-1受体相关激酶（IRAK）和四种蛋白12 (TSPAN12)，它们编码大脑先天免疫系统，炎症反应和神经营养或神经毒性淀粉样肽的产生的关键调节剂。下调的TSPAN12限制ADAM10 （a-分泌酶）依赖的β -淀粉样蛋白前体蛋白（¿APP）的切割。应激的人脑细胞上调miRNA-146a，同时增加淀粉样蛋白的形成和A¿42肽的脱落。假设：上调miRNA-146a有助于改变先天免疫和炎症反应，增加A¿42肽的产生和减少神经营养支持。Three Specific Aims测试基于这一假设预测了阿尔茨海默病、应激的人脑原代细胞和特定的阿尔茨海默病转基因模型的结果。这些特定目标包括(1)确定AD大脑中miRNA-146a丰度的变化；(2)检测应激的人类神经元、星形胶质细胞或小胶质细胞是否表现出类似于AD组织中炎性神经变性和A¿42肽生成的miRNA变化，并检测添加外源性miRNA-146a或抗miRNA-146a寡核苷酸是否会促进或中和这些变化；(3)检测miRNA-146a、抗miRNA-146a以及CFH、IRAK或TSPAN12表达的调节是否是淀粉样蛋白过表达Tg2576小鼠炎症反应和淀粉样蛋白形成的关键调节因子。

DESCRIPTION (provided by applicant): Abundant evidence supports the idea that progressive up-regulation of complex pro-inflammatory signaling, A¿42 peptide evolution, and loss of neurotrophic support underlie the initiation and propagation of Alzheimer's disease (AD). Micro RNA (miRNA)-mediated messenger RNA (mRNA) interference is a newly discovered genetic mechanism involved in the regulation of gene expression at the post-transcriptional level. The major mode of miRNA action is to target and bind to the 3' un-translated region of specific mRNAs and in doing so, quench expression of that mRNA, thereby acting as a negative regulator of gene expression. AD affects only specific areas of the brain, and mis-regulated miRNA expression is strongly linked to altered gene expression within these regions. In AD models, these same AD-enriched miRNAs induce specific pathological changes that are strikingly similar to those observed in AD brain. Accumulating evidence strongly suggests that altered miRNA-mediated processing of specific mRNA populations triggers the pathogenic expression of genes that drive the AD process. The overall goal of this project is to significantly move the miRNAin- AD field forward, and impact the scientific understanding of AD, by defining mechanistically how specific miRNAs induce molecular-genetic mechanisms that result in AD-type change. Human brains utilize only a fraction of all known miRNA species; and only a subset of these are altered in AD brain. Increases in the expression of a specific NF-?B-sensitive miRNA-146a down-regulates the abundance of at least three major mRNA targets, complement factor H (CFH), interleukin-1 receptor associated kinase (IRAK) and tetraspanin 12 (TSPAN12), that encode key modulators of the brain's innate immune system, inflammatory response and the generation of neurotrophic or neurotoxic amyloid peptides. Down-regulated TSPAN12 restricts ADAM10 (a-secretase) dependent cleavage of beta-amyloid precursor protein (¿APP). Stressed human brain cells up-regulate miRNA-146a in parallel with increased amyloidogenesis and shedding of A¿42 peptides. Hypothesis: up-regulated miRNA-146a contributes to altered innate immune and inflammatory responses, increased A¿42 peptide generation and decreased neurotrophic support. Three Specific Aims test predicted outcomes based on this hypothesis in AD, in stressed human brain primary cells, and in specific transgenic models of AD. These Specific Aims include (1) identification of alterations in miRNA-146a abundance in AD brain; (2) testing whether stressed human neuronal, astrocyte or microglial cells exhibit miRNA changes similar to those conducive to inflammatory neurodegeneration and A¿42 peptide generation in AD tissues, and testing if added exogenous miRNA-146a or anti-miRNA-146a oligonucleotides will promote or neutralize these changes; and (3) testing whether miRNA-146a, anti-miRNA-146a and modulation of CFH, IRAK or TSPAN12 expression are key regulators of the inflammatory response and amyloidogenesis in amyloid over-expressing Tg2576 mice.