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

描述(由申请人提供)：大量证据支持这一观点，即复杂的促炎信号的逐渐上调、A42肽的进化以及神经营养支持的丧失是阿尔茨海默病(AD)的启动和传播的基础。微小RNA(MiRNA)介导的信使RNA(MRNA)干扰是一种新发现的在转录后水平调控基因表达的遗传机制。MiRNA作用的主要方式是靶向并结合特定mRNAs的3‘非翻译区，从而抑制该mRNAs的表达，从而作为基因表达的负调控因子。AD只影响大脑的特定区域，错误调节的miRNA表达与这些区域内基因表达的变化密切相关。在AD模型中，这些相同的AD丰富的miRNAs会引起与AD大脑中观察到的惊人相似的特定病理变化。越来越多的证据有力地表明，改变的miRNA介导的特定mRNA群体的处理触发了驱动AD过程的基因的病理性表达。该项目的总体目标是通过从机械上定义特定的miRNAs如何诱导导致AD类型变化的分子遗传机制，显著推动miRNAin-AD领域的发展，并影响对AD的科学理解。人类大脑只利用了所有已知miRNA物种中的一小部分；在AD大脑中，只有其中的一部分发生了改变。特定的对核因子B敏感的miRNA-146a表达的增加下调了至少三个主要mRNA靶标的丰度，即补体因子H(CFH)、白细胞介素1受体相关激酶(IRAK)和TSPAN12(TSPAN12)，这三个靶标编码大脑固有免疫系统、炎症反应和神经营养或神经毒性淀粉样多肽的关键调节因子。下调的TSPAN12限制依赖于ADAM10(a-分泌酶)的β-淀粉样前体蛋白(β-APP)的切割。紧张的人脑细胞上调miRNA-146a，同时增加淀粉样蛋白的生成和A？42肽的脱落。假设：上调的miRNA-146a有助于改变先天免疫和炎症反应，增加A42肽的生成，并减少神经营养支持。在AD、应激状态下的人脑原代细胞和特定的AD转基因模型中，有三个特定的目标测试了基于这一假设的预测结果。这些特定目标包括(1)确定AD大脑中miRNA-146a丰度的变化；(2)检测应激状态下的人类神经元、星形胶质细胞或小胶质细胞是否表现出与那些促进AD组织炎性神经变性和Aé42肽生成相似的miRNA变化，并且测试添加外源miRNA-146a或抗miRNA-146a寡核苷酸是否会促进或中和这些变化；以及(3)测试miRNA-146a、抗miRNA-146a以及CFH、IRAK或TSPAN12的表达是否是过度表达Tg2576小鼠炎症反应和淀粉样蛋白形成的关键调节因素。

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.