Reducing Endogenous Tau Ameliorates Amyloid -Induced Deficits in an Alzheimer's Disease Mouse Model

Gladstone Institute of Neurological Disease, San Francisco, CA 94158, USA.
Science (Impact Factor: 33.61). 06/2007; 316(5825):750-4. DOI: 10.1126/science.1141736
Source: PubMed


Many potential treatments for Alzheimer's disease target amyloid-beta peptides (Abeta), which are widely presumed to cause the disease. The microtubule-associated protein tau is also involved in the disease, but it is unclear whether treatments aimed at tau could block Abeta-induced cognitive impairments. Here, we found that reducing endogenous tau levels prevented behavioral deficits in transgenic mice expressing human amyloid precursor protein, without altering their high Abeta levels. Tau reduction also protected both transgenic and nontransgenic mice against excitotoxicity. Thus, tau reduction can block Abeta- and excitotoxin-induced neuronal dysfunction and may represent an effective strategy for treating Alzheimer's disease and related conditions.

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    • "Taken together, these findings suggest that caspases play a pivotal role in appoptosininduced neurodegeneration and that caspase inhibition may be a potential target in the treatment of neurodegenerative disorders in instances where interference with caspase-dependent synaptic function is less consequential in comparison to overall ameliorative effects in disease onset with caspase inhibition. It was previously shown that tau plays an essential role in Ab-induced behavioral deficits, dendritic and axonal abnormalities in AD mouse models, and neuronal cultures (Ittner et al., 2010; Roberson et al., 2007; Stancu et al., 2014; Vossel et al., 2010). "
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    ABSTRACT: Progressive supranuclear palsy (PSP) is a movement disorder characterized by tau neuropathology where the underlying mechanism is unknown. An SNP (rs1768208 C/T) has been identified as a strong risk factor for PSP. Here, we identified a much higher T-allele occurrence and increased levels of the pro-apoptotic protein appoptosin in PSP patients. Elevations in appoptosin correlate with activated caspase-3 and caspase-cleaved tau levels. Appoptosin overexpression increased caspase-mediated tau cleavage, tau aggregation, and synaptic dysfunction, whereas appoptosin deficiency reduced tau cleavage and aggregation. Appoptosin transduction impaired multiple motor functions and exacerbated neuropathology in tau-transgenic mice in a manner dependent on caspase-3 and tau. Increased appoptosin and caspase-3-cleaved tau were also observed in brain samples of patients with Alzheimer's disease and frontotemporal dementia with tau inclusions. Our findings reveal a novel role for appoptosin in neurological disorders with tau neuropathology, linking caspase-3-mediated tau cleavage to synaptic dysfunction and behavioral/motor defects. Copyright © 2015 Elsevier Inc. All rights reserved.
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    • "The derivation and characterization of PDAPP-J20 [hAPP(J20)] mice has been described elsewhere (Hsia et al., 1999; Mucke et al., 2000; Selkoe, 2000; Galvan et al., 2006; Roberson et al., 2007; Beauquis et al., 2014). This strain, a recognized model of AD, carries the hAPP gene with the familial AD Swedish and Indiana mutations, develops amyloid pathology and behavioral alterations in a progressive fashion (Galvan et al., 2006), and also shows evidence of Tau hyperphosphorylation (Simon et al., 2009). "
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    ABSTRACT: Alzheimer's disease (AD) is a progressive neurodegenerative disease without effective therapy. Brain amyloid deposits are classical histopathological hallmarks that generate an inflammatory reaction affecting neuronal and glial function. The identification of early cell responses and of brain areas involved could help to design new successful treatments. Hence, we studied early alterations of hippocampal glia and their progression during the neuropathology in PDAPP-J20 transgenic mice, AD model, at 3, 9 and 15 months (m) of age. At 3 m, before deposits formation, microglial Iba1+ cells from transgenic mice already exhibited signs of activation and larger soma size in the hilus, alterations appearing later on stratum radiatum. Iba1 immunohistochemistry revealed increased cell density and immunoreactive area in PDAPP mice from 9 m onwards selectively in the hilus, in coincidence with prominent amyloid Congo red + deposition. At pre-plaque stages, GFAP+ astroglia showed density alterations while, at an advanced age, the presence of deposits was associated with important glial volume changes and apparently being intimately involved in amyloid degradation. Astrocytes around plaques were strongly labeled for LC3 until 15 m in Tg mice, suggestive of increased autophagic flux. Moreover, β-Amyloid fibrils internalization by astrocytes in in vitro conditions was dependent on autophagy. Co-localization of Iba1 with ubiquitin or p62 was exclusively found in microglia contacting deposits from 9 m onwards, suggesting torpid autophagy. Our work characterizes glial changes at early stages of the disease in PDAPP-J20 mice, focusing on the hilus as an especially susceptible hippocampal subfield, and provides evidence that glial autophagy could play a role in amyloid processing at advanced stages. This article is protected by copyright. All rights reserved. © 2015 Wiley Periodicals, Inc.
    Full-text · Article · Aug 2015 · Hippocampus
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    • "First, tau-deficient neurons have been shown to be resistant to Aβ-mediated neurotoxicity (Rapoport et al., 2002). Second, genetic deficiency of tau in an AD mouse model improved cognitive function and reduced excitotoxic injury (Roberson et al., 2007; Ittner et al., 2010). Third, Shipton and colleagues recently showed that deficiency of tau protected against Aβ-induced impairment of long-term potentiation in hippocampal slices of wild type mice (Shipton et al., 2011). "
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    ABSTRACT: Neuroinflammation is one of the neuropathological hallmarks of Alzheimer’s disease (AD) and related tauopathies. Activated microglia spatially coexist with microtubule-associated protein tau (Mapt or tau)-burdened neurons in the brains of human AD and non-AD tauopathies. Numerous studies have suggested that neuroinflammation precedes tau pathology and that induction or blockage of neuroinflammation via lipopolysaccharide (LPS) or anti-inflammatory compounds (such as FK506) accelerate or block tau pathology, respectively in several animal models of tauopathy. We have previously demonstrated that microglia-mediated neuroinflammation via deficiency of the microglia-specific chemokine (fractalkine) receptor, CX3CR1, promotes tau pathology and neurodegeneration in a mouse model of LPS-induced systemic inflammation. Here, we demonstrate that tau mediates the neurotoxic effects of LPS in Cx3cr1-/- mice. First, Mapt+/+ neurons displayed elevated levels of Annexin V (A5) and TUNEL (markers of neurodegeneration) when co-cultured with LPS-treated Cx3cr1-/-microglia, which is rescued in Mapt-/- neurons. Second, a neuronal population positive for phospho-S199 (AT8) tau in the dentate gyrus is also positive for activated or cleaved caspase (CC3) in the LPS-treated Cx3cr1-/- mice. Third, genetic deficiency for tau in Cx3cr1-/- mice resulted in reduced microglial activation, altered expression of inflammatory genes and a significant reduction in the number of neurons positive for CC3 compared to Cx3cr1-/- mice. Finally, Cx3cr1-/- mice exposed to LPS displayed a lack of inhibition in an open field exploratory behavioral test, which is rescued by tau deficiency. Taken together, our results suggest that pathological alterations in tau mediate inflammation-induced neurotoxicity and that deficiency of Mapt is neuroprotective. Thus, therapeutic approaches towards either reducing tau levels or blocking neuroinflammatory pathways may serve as a potential strategy in treating tauopathies.
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