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CD45 deficiency drives amyloid-? peptide oligomers and neuronal loss in Alzheimer's disease mice.

ABSTRACT: Converging lines of evidence indicate dysregulation of the key immunoregulatory molecule CD45 (also known as leukocyte common antigen) in Alzheimer's disease (AD). We report that transgenic mice overproducing amyloid-? peptide (A?) but deficient in CD45 (PSAPP/CD45(-/-) mice) faithfully recapitulate AD neuropathology. Specifically, we find increased abundance of cerebral intracellular and extracellular soluble oligomeric and insoluble A?, decreased plasma soluble A?, increased abundance of microglial neurotoxic cytokines tumor necrosis factor-? and interleukin-1?, and neuronal loss in PSAPP/CD45(-/-) mice compared with CD45-sufficient PSAPP littermates (bearing mutant human amyloid precursor protein and mutant human presenilin-1 transgenes). After CD45 ablation, in vitro and in vivo studies demonstrate an anti-A? phagocytic but proinflammatory microglial phenotype. This form of microglial activation occurs with elevated A? oligomers and neural injury and loss as determined by decreased ratio of anti-apoptotic Bcl-xL to proapoptotic Bax, increased activated caspase-3, mitochondrial dysfunction, and loss of cortical neurons in PSAPP/CD45(-/-) mice. These data show that deficiency in CD45 activity leads to brain accumulation of neurotoxic A? oligomers and validate CD45-mediated microglial clearance of oligomeric A? as a novel AD therapeutic target.

SUBMITTER: Zhu Y

PROVIDER: S-EPMC3068193 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature

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CD45 deficiency drives amyloid-β peptide oligomers and neuronal loss in Alzheimer's disease mice.

Zhu Yuyan Y Hou Huayan H Rezai-Zadeh Kavon K Giunta Brian B Ruscin Amanda A Gemma Carmelina C Jin Jingji J Dragicevic Natasa N Bradshaw Patrick P Rasool Suhail S Glabe Charles G CG Ehrhart Jared J Bickford Paula P Mori Takashi T Obregon Demian D Town Terrence T Tan Jun J

The Journal of neuroscience : the official journal of the Society for Neuroscience 20110101 4

Converging lines of evidence indicate dysregulation of the key immunoregulatory molecule CD45 (also known as leukocyte common antigen) in Alzheimer's disease (AD). We report that transgenic mice overproducing amyloid-β peptide (Aβ) but deficient in CD45 (PSAPP/CD45(-/-) mice) faithfully recapitulate AD neuropathology. Specifically, we find increased abundance of cerebral intracellular and extracellular soluble oligomeric and insoluble Aβ, decreased plasma soluble Aβ, increased abundance of micro ...[more]

PMID: 21273420

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Project description:Introduction: β-Amyloid protein (Aβ) putatively plays a seminal role in synaptic loss in Alzheimer's disease (AD). While there is no consensus regarding the synaptic-relevant species of Aβ, it is known that Aβ oligomers (AβOs) are noticeably increased in the early stages of AD, localizing at or within the synapse. In cell and animal models, AβOs have been shown to attach to synapses and instigate synapse dysfunction and deterioration. To establish the pathological mechanism of synaptic loss in AD, it will be important to identify the synaptic targets to which AβOs attach. Methods: An unbiased approach using far western ligand blots has identified three synaptic proteins to which AβOs specifically attach. These proteins (p100, p140, and p260) were subsequently enriched by detergent extraction, ultracentrifugation, and CHT-HPLC column separation, and sequenced by LC-MS/MS. P100, p140, and p260 were identified. These levels of AβOs targets in human AD and aging frontal cortexes were analyzed by quantitative proteomics and western-blot. The polyclonal antibody to AβOs was developed and used to block the toxicity of AβOs. The data were analyzed with one-way analysis of variance. Results: AβOs binding proteins p100, p140, and p260 were identified as Na/K-ATPase, synGap, and Shank3, respectively. α3-Na/K-ATPase, synGap, and Shank3 proteins showed loss in the postsynaptic density (PSD) of human AD frontal cortex. In short term experiments, oligomers of Aβ inhibited Na/K-ATPase at the synapse. Na/K-ATPase activity was restored by an antibody specific for soluble forms of Aβ. α3-Na/K-ATPase protein and synaptic β-amyloid peptides were pulled down from human AD synapses by co-immunoprecipitation. Results suggest synaptic dysfunction in early stages of AD may stem from inhibition of Na/K-ATPase activity by Aβ oligomers, while later stages could hypothetically result from disrupted synapse structure involving the PSD proteins synGap and Shank3. Conclusion: We identified three AβO binding proteins as α3-Na/K-ATPase, synGap, and Shank3. Soluble Aβ oligomers appear capable of attacking neurons via specific extracellular as well as intracellular synaptic proteins. Impact on these proteins hypothetically could lead to synaptic dysfunction and loss, and could serve as novel therapeutic targets for AD treatment by antibodies or other agents.

Project description:BackgroundDespite its identification as a key checkpoint regulator of microglial activation in Alzheimer's disease, the overarching role of CX3CR1 signaling in modulating mechanisms of Aβ driven neurodegeneration, including accumulation of hyperphosphorylated tau is not well understood.MethodologyAccumulation of soluble and insoluble Aβ species, microglial activation, synaptic dysregulation, and neurodegeneration is investigated in 4- and 6-month old 5xFAD;Cx3cr1+/+ and 5xFAD;Cx3cr1-/- mice using immunohistochemistry, western blotting, transcriptomic and quantitative real time PCR analyses of purified microglia. Flow cytometry based, in-vivo Aβ uptake assays are used for characterization of the effects of CX3CR1-signaling on microglial phagocytosis and lysosomal acidification as indicators of clearance of methoxy-X-04+ fibrillar Aβ. Lastly, we use Y-maze testing to analyze the effects of Cx3cr1 deficiency on working memory.ResultsDisease progression in 5xFAD;Cx3cr1-/- mice is characterized by increased deposition of filamentous plaques that display defective microglial plaque engagement. Microglial Aβ phagocytosis and lysosomal acidification in 5xFAD;Cx3cr1-/- mice is impaired in-vivo. Interestingly, Cx3cr1 deficiency results in heighted accumulation of neurotoxic, oligomeric Aβ, along with severe neuritic dystrophy, preferential loss of post-synaptic densities, exacerbated tau pathology, neuronal loss and cognitive impairment. Transcriptomic analyses using cortical RNA, coupled with qRT-PCR using purified microglia from 6 month-old mice indicate dysregulated TGFβ-signaling and heightened ROS metabolism in 5xFAD;Cx3cr1-/- mice. Lastly, microglia in 6 month-old 5xFAD;Cx3cr1-/- mice express a 'degenerative' phenotype characterized by increased levels of Ccl2, Ccl5, Il-1β, Pten and Cybb along with reduced Tnf, Il-6 and Tgfβ1 mRNA.ConclusionsCx3cr1 deficiency impairs microglial uptake and degradation of fibrillar Aβ, thereby triggering increased accumulation of neurotoxic Aβ species. Furthermore, loss of Cx3cr1 results in microglial dysfunction typified by dampened TGFβ-signaling, increased oxidative stress responses and dysregulated pro-inflammatory activation. Our results indicate that Aβ-driven microglial dysfunction in Cx3cr1-/- mice aggravates tau hyperphosphorylation, neurodegeneration, synaptic dysregulation and impairs working memory.

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-? aggregates that initiate a cascade of molecular events culminating in widespread neurodegeneration. The microtubule binding protein tau may mediate the effects of amyloid-? in this cascade. Amyloid plaques comprised of insoluble, fibrillar amyloid-? 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-? aggregates, including soluble amyloid-? oligomers. Different soluble amyloid-? oligomers have been studied in several mouse models, but not systematically in humans. Here, we measured three amyloid-? oligomers previously described in mouse models-amyloid-? trimers, A?*56 and amyloid-? 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-? trimers appear to be the fundamental amyloid-? assembly unit of A?*56 and are present in young mice prior to memory decline, amyloid-? 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. A?*56 levels were negligible in children and young adults, rose significantly above baseline in subjects in their 40s and increased steadily thereafter. Amyloid-? 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 A?*56 and two pathological forms of soluble tau (tau-CP13 and tau-Alz50), and negative correlations between A?*56 and two postsynaptic proteins (drebrin and fyn kinase), but none between amyloid-? dimers or amyloid-? trimers and tau or synaptic proteins. Comparing impaired with age-matched unimpaired subjects, we found the highest levels of amyloid-? dimers, but the lowest levels of A?*56 and amyloid-? trimers, in subjects with probable Alzheimer's disease. In conclusion, in cognitively normal adults A?*56 increased ahead of amyloid-? dimers or amyloid-? trimers, and pathological tau proteins and postsynaptic proteins correlated with A?*56, but not amyloid-? dimers or amyloid-? trimers. We propose that A?*56 may play a pathogenic role very early in the pathogenesis of Alzheimer's disease.

Project description:OBJECTIVE:The objectives of this study were to investigate whether the plasma levels of oligomeric amyloid-β (OAβ) were affected in Alzheimer's disease (AD) and to examine the associations (or possible correlations) between plasma OAβ levels and memory performance. METHOD:Thirty subjects with AD and 28 cognitively normal controls were recruited in the study. The multimer detection system (MDS) was used to measure the levels of OAβ in the plasma. In addition to assessing the general cognitive function with the Mini-Mental State Examination (MMSE), Cognitive Abilities Screening Instrument (CASI), and Alzheimer's Disease Assessment Scale-cognitive portion (ADAS-Cog), the common objects memory test (COMT) was used to examine the episodic memory performance. Pearson's and partial correlation analyses were conducted to explore the associations between cognitive performance and OAβ levels in the plasma. A receiving operating curve (ROC) analysis was used to discriminate between the AD and control groups. RESULTS:The plasma OAβ levels in the AD group were significantly higher than those in the control group [1.88 (0.38) ng/ml vs 1.20 (0.40) ng/ml, p < 0.001]. The elevated levels of plasma OAβ showed a strong correlation with cognitive performance in patients with AD, including an inverse correlation with scores on the MMSE (r = - 0.43, p = 0.02), CASI (r = - 0.56, p < 0.01), and the immediate recall (r = - 0.45, p = 0.01), 5-min delayed recall (r = - 0.56, p < 0.01), and 30-min delayed recall (r = - 0.71, p < 0.001) tests of the COMT, and a positive correlation with the ADAS-Cog scores (r = 0.59, p < 0.001). The EDTA plasma Aβ oligomer optical density (OD) value measured using the MDS could discriminate between the AD and control groups with an area under the curve (AUC) of 0.89. The optimal sensitivity and specificity were 82.1% and 90.0%, respectively. CONCLUSION:The elevated levels of OAβ in the plasma distinguished the AD and control groups and were associated with the severity of symptoms, especially memory performance, in patients with AD. Our results suggested that plasma OAβ could potentially be a simple and non-invasive blood-based biomarker for AD diagnosis. Furthermore, longitudinal studies are warranted to explore the application of plasma OAβ levels as a valid diagnostic biomarker in patients with AD.

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CD45 deficiency drives amyloid-? peptide oligomers and neuronal loss in Alzheimer's disease mice.

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CD45 deficiency drives amyloid-β peptide oligomers and neuronal loss in Alzheimer's disease mice.

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