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Detection of Amyloid β Oligomers with RNA Aptamers in App^{NL-G-F/NL-G-F} Mice: A Model of Arctic Alzheimer's Disease.

ABSTRACT: RNA aptamers have garnered attention for diagnostic applications due to their ability to recognize diverse targets. Oligomers of 42-mer amyloid β-protein (Aβ42), whose accumulation is relevant to the pathology of Alzheimer's disease (AD), are among the most difficult molecules for aptamer recognition because they are prone to aggregate in heterogeneous forms. In addition to designing haptens for in vitro selection of aptamers, the difficulties involved in determining their effect on Aβ42 oligomerization impede aptamer research. We previously developed three RNA aptamers (E22P-AbD4, -AbD31, and -AbD43) with high affinity for protofibrils (PFs) derived from a toxic Aβ42 dimer. Notably, these aptamers recognized diffuse staining, which likely originated from PFs or higher-order oligomers with curvilinear structures in a knock-in App^{NL-G-F/NL-G-F} mouse, carrying the Arctic mutation that preferentially induced the formation of PFs, in addition to a PS2Tg2576 mouse. To determine which oligomeric sizes were mainly altered by the aptamer, ion mobility-mass spectrometry (IM-MS) was carried out. One aptamer, E22P-AbD43, formed adducts with the Aβ42 monomer and dimer, leading to suppression of further oligomerization. These findings support the utility of these aptamers as diagnostics for AD.

SUBMITTER: Obata Y

PROVIDER: S-EPMC7469371 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Detection of Amyloid β Oligomers with RNA Aptamers in App<sup>NL-G-F/NL-G-F</sup> Mice: A Model of Arctic Alzheimer's Disease.

Obata Yayoi Y Murakami Kazuma K Kawase Taiji T Hirose Kenji K Izuo Naotaka N Shimizu Takahiko T Irie Kazuhiro K

ACS omega 20200817 34

RNA aptamers have garnered attention for diagnostic applications due to their ability to recognize diverse targets. Oligomers of 42-mer amyloid β-protein (Aβ42), whose accumulation is relevant to the pathology of Alzheimer's disease (AD), are among the most difficult molecules for aptamer recognition because they are prone to aggregate in heterogeneous forms. In addition to designing haptens for in vitro selection of aptamers, the difficulties involved in determining their effect on Aβ42 oligome ...[more]

PMID: 32905362

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Project description:IntroductionThe study of the pathophysiology study of Alzheimer's disease (AD) has been hampered by lack animal models that recapitulate the major AD pathologies, including extracellular -amyloid (A) deposition, intracellular aggregation of microtubule associated protein tau (MAPT), inflammation and neurodegeneration.MethodsThe humanized APPNL-G-F knock-in mouse line was crossed to the PS19 MAPTP301S, over-expression mouse line to create the dual APPNL-G-F/PS19 MAPTP301S line. The resulting pathologies were characterized by immunochemical methods and PCR.ResultsWe now report on a double transgenic APPNL-G-F/PS19 MAPTP301S mouse that at 6 months of age exhibits robust A plaque accumulation, intense MAPT pathology, strong inflammation and extensive neurodegeneration. The presence of A pathology potentiated the other major pathologies, including MAPT pathology, inflammation and neurodegeneration. MAPT pathology neither changed levels of amyloid precursor protein nor potentiated A accumulation. Interestingly, study of immunofluorescence in cleared brains indicates that microglial inflammation was generally stronger in the hippocampus, dentate gyrus and entorhinal cortex, which are regions with predominant MAPT pathology. The APPNL-G-F/MAPTP301S mouse model also showed strong accumulation of N6-methyladenosine (m6A), which was recently shown to be elevated in the AD brain. m6A primarily accumulated in neuronal soma, but also co-localized with a subset of astrocytes and microglia. The accumulation of m6A corresponded with increases in METTL3 and decreases in ALKBH5, which are enzymes that add or remove m6A from mRNA, respectively.DiscussionOur understanding of the pathophysiology of Alzheimer's disease (AD) has been hampered by lack animal models that recapitulate the major AD pathologies, including extracellular -amyloid (A) deposition, intracellular aggregation of microtubule associated protein tau (MAPT), inflammation and neurodegeneration. The APPNL-G-F/MAPTP301S mouse recapitulates many features of AD pathology beginning at 6 months of aging, and thus represents a useful new mouse model for the field.

Project description:BackgroundIn spite of many years of research, our understanding of the molecular bases of Alzheimer's disease (AD) is still incomplete, and the medical treatments available mainly target the disease symptoms and are hardly effective. Indeed, the modulation of a single target (e.g., β-secretase) has proven to be insufficient to significantly alter the physiopathology of the disease, and we should therefore move from gene-centric to systemic therapeutic strategies, where AD-related changes are modulated globally.MethodsHere we present the complete characterization of three murine models of AD at different stages of the disease (i.e., onset, progression and advanced). We combined the cognitive assessment of these mice with histological analyses and full transcriptional and protein quantification profiling of the hippocampus. Additionally, we derived specific Aβ-related molecular AD signatures and looked for drugs able to globally revert them.ResultsWe found that AD models show accelerated aging and that factors specifically associated with Aβ pathology are involved. We discovered a few proteins whose abundance increases with AD progression, while the corresponding transcript levels remain stable, and showed that at least two of them (i.e., lfit3 and Syt11) co-localize with Aβ plaques in the brain. Finally, we found two NSAIDs (dexketoprofen and etodolac) and two anti-hypertensives (penbutolol and bendroflumethiazide) that overturn the cognitive impairment in AD mice while reducing Aβ plaques in the hippocampus and partially restoring the physiological levels of AD signature genes to wild-type levels.ConclusionsThe characterization of three AD mouse models at different disease stages provides an unprecedented view of AD pathology and how this differs from physiological aging. Moreover, our computational strategy to chemically revert AD signatures has shown that NSAID and anti-hypertensive drugs may still have an opportunity as anti-AD agents, challenging previous reports.

Project description:Alzheimer's disease begins about two decades before the onset of symptoms or neuron death, and is believed to be caused by pathogenic amyloid-β aggregates that initiate a cascade of molecular events culminating in widespread neurodegeneration. The microtubule binding protein tau may mediate the effects of amyloid-β in this cascade. Amyloid plaques comprised of insoluble, fibrillar amyloid-β aggregates are the most characteristic feature of Alzheimer's disease. However, the correspondence between the distribution of plaques and the pattern of neurodegeneration is tenuous. This discrepancy has stimulated the investigation of other amyloid-β aggregates, including soluble amyloid-β oligomers. Different soluble amyloid-β oligomers have been studied in several mouse models, but not systematically in humans. Here, we measured three amyloid-β oligomers previously described in mouse models-amyloid-β trimers, Aβ*56 and amyloid-β dimers-in brain tissue from 75 cognitively intact individuals, ranging from young children to the elderly, and 58 impaired subjects with mild cognitive impairment or probable Alzheimer's disease. As in mouse models, where amyloid-β trimers appear to be the fundamental amyloid-β assembly unit of Aβ*56 and are present in young mice prior to memory decline, amyloid-β trimers in humans were present in children and adolescents; their levels rose gradually with age and were significantly above baseline in subjects in their 70s. Aβ*56 levels were negligible in children and young adults, rose significantly above baseline in subjects in their 40s and increased steadily thereafter. Amyloid-β dimers were undetectable until subjects were in their 60s; their levels then increased sharply and correlated with plaque load. Remarkably, in cognitively intact individuals we found strong positive correlations between Aβ*56 and two pathological forms of soluble tau (tau-CP13 and tau-Alz50), and negative correlations between Aβ*56 and two postsynaptic proteins (drebrin and fyn kinase), but none between amyloid-β dimers or amyloid-β trimers and tau or synaptic proteins. Comparing impaired with age-matched unimpaired subjects, we found the highest levels of amyloid-β dimers, but the lowest levels of Aβ*56 and amyloid-β trimers, in subjects with probable Alzheimer's disease. In conclusion, in cognitively normal adults Aβ*56 increased ahead of amyloid-β dimers or amyloid-β trimers, and pathological tau proteins and postsynaptic proteins correlated with Aβ*56, but not amyloid-β dimers or amyloid-β trimers. We propose that Aβ*56 may play a pathogenic role very early in the pathogenesis of Alzheimer's disease.

Project description:Protein aggregation is common to dozens of diseases including prionoses, diabetes, Parkinson's and Alzheimer's. Over the past 15 years, there has been a paradigm shift in understanding the structural basis for these proteinopathies. Precedent for this shift has come from investigation of soluble Aβ oligomers (AβOs), toxins now widely regarded as instigating neuron damage leading to Alzheimer's dementia. Toxic AβOs accumulate in AD brain and constitute long-lived alternatives to the disease-defining Aβ fibrils deposited in amyloid plaques. Key experiments using fibril-free AβO solutions demonstrated that while Aβ is essential for memory loss, the fibrillar Aβ in amyloid deposits is not the agent. The AD-like cellular pathologies induced by AβOs suggest their impact provides a unifying mechanism for AD pathogenesis, explaining why early stage disease is specific for memory and accounting for major facets of AD neuropathology. Alternative ideas for triggering mechanisms are being actively investigated. Some research favors insertion of AβOs into membrane, while other evidence supports ligand-like accumulation at particular synapses. Over a dozen candidate toxin receptors have been proposed. AβO binding triggers a redistribution of critical synaptic proteins and induces hyperactivity in metabotropic and ionotropic glutamate receptors. This leads to Ca(2+) overload and instigates major facets of AD neuropathology, including tau hyperphosphorylation, insulin resistance, oxidative stress, and synapse loss. Because different species of AβOs have been identified, a remaining question is which oligomer is the major pathogenic culprit. The possibility has been raised that more than one species plays a role. Despite some key unknowns, the clinical relevance of AβOs has been established, and new studies are beginning to point to co-morbidities such as diabetes and hypercholesterolemia as etiological factors. Because pathogenic AβOs appear early in the disease, they offer appealing targets for therapeutics and diagnostics. Promising therapeutic strategies include use of CNS insulin signaling enhancers to protect against the presence of toxins and elimination of the toxins through use of highly specific AβO antibodies. An AD-dependent accumulation of AβOs in CSF suggests their potential use as biomarkers and new AβO probes are opening the door to brain imaging. Overall, current evidence indicates that Aβ oligomers provide a substantive molecular basis for the cause, treatment and diagnosis of Alzheimer's disease.

Dataset Information

Detection of Amyloid β Oligomers with RNA Aptamers in App^{NL-G-F/NL-G-F} Mice: A Model of Arctic Alzheimer's Disease.

Publications

Detection of Amyloid β Oligomers with RNA Aptamers in App<sup>NL-G-F/NL-G-F</sup> Mice: A Model of Arctic Alzheimer's Disease.

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Dataset Information

Detection of Amyloid β Oligomers with RNA Aptamers in AppNL-G-F/NL-G-F Mice: A Model of Arctic Alzheimer's Disease.

Publications

Detection of Amyloid β Oligomers with RNA Aptamers in App<sup>NL-G-F/NL-G-F</sup> Mice: A Model of Arctic Alzheimer's Disease.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Detection of Amyloid β Oligomers with RNA Aptamers in App^{NL-G-F/NL-G-F} Mice: A Model of Arctic Alzheimer's Disease.