scholarly journals Alzheimer’s disease brain-derived extracellular vesicles spread tau pathology in interneurons

Brain ◽  
2020 ◽  
Author(s):  
Zhi Ruan ◽  
Dhruba Pathak ◽  
Srinidhi Venkatesan Kalavai ◽  
Asuka Yoshii-Kitahara ◽  
Satoshi Muraoka ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Extracellular Vesicles ◽  
Cortical Neurons ◽  
Acid Decarboxylase ◽  
Gabaergic Interneurons ◽  
Phosphorylated Tau ◽  
Tau Pathology ◽  
Tau Oligomers ◽  
Prodromal Alzheimer’S Disease

Abstract Extracellular vesicles are highly transmissible and play critical roles in the propagation of tau pathology, although the underlying mechanism remains elusive. Here, for the first time, we comprehensively characterized the physicochemical structure and pathogenic function of human brain-derived extracellular vesicles isolated from Alzheimer’s disease, prodromal Alzheimer’s disease, and non-demented control cases. Alzheimer’s disease extracellular vesicles were significantly enriched in epitope-specific tau oligomers in comparison to prodromal Alzheimer’s disease or control extracellular vesicles as determined by dot blot and atomic force microscopy. Alzheimer’s disease extracellular vesicles were more efficiently internalized by murine cortical neurons, as well more efficient in transferring and misfolding tau, than prodromal Alzheimer’s disease and control extracellular vesicles in vitro. Strikingly, the inoculation of Alzheimer’s disease or prodromal Alzheimer’s disease extracellular vesicles containing only 300 pg of tau into the outer molecular layer of the dentate gyrus of 18-month-old C57BL/6 mice resulted in the accumulation of abnormally phosphorylated tau throughout the hippocampus by 4.5 months, whereas inoculation of an equal amount of tau from control extracellular vesicles, isolated tau oligomers, or fibrils from the same Alzheimer’s disease donor showed little tau pathology. Furthermore, Alzheimer’s disease extracellular vesicles induced misfolding of endogenous tau in both oligomeric and sarkosyl-insoluble forms in the hippocampal region. Unexpectedly, phosphorylated tau was primarily accumulated in glutamic acid decarboxylase 67 (GAD67) GABAergic interneurons and, to a lesser extent, glutamate receptor 2/3-positive excitatory mossy cells, showing preferential extracellular vesicle-mediated GABAergic interneuronal tau propagation. Whole-cell patch clamp recordings of CA1 pyramidal cells showed significant reduction in the amplitude of spontaneous inhibitory post-synaptic currents. This was accompanied by reductions in c-fos+ GAD67+ neurons and GAD67+ neuronal puncta surrounding pyramidal neurons in the CA1 region, confirming reduced GABAergic transmission in this region. Our study posits a novel mechanism for the spread of tau in hippocampal GABAergic interneurons via brain-derived extracellular vesicles and their subsequent neuronal dysfunction.

scholarly journals On the design of early-phase Alzheimer’s disease clinical trials with cerebrospinal fluid tau outcomes

2021 ◽  
pp. 174077452110344
Author(s):  
Michelle M Nuño ◽  
Joshua D Grill ◽  
Daniel L Gillen ◽  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Clinical Trials ◽  
Cerebrospinal Fluid ◽  
Phosphorylated Tau ◽  
Inclusion Criteria ◽  
Eligibility Criteria ◽  
Total Tau ◽  
Prodromal Alzheimer’S Disease ◽  
Study Power

Background/Aims: The focus of Alzheimer’s disease studies has shifted to earlier disease stages, including mild cognitive impairment. Biomarker inclusion criteria are often incorporated into mild cognitive impairment clinical trials to identify individuals with “prodromal Alzheimer’s disease” to ensure appropriate drug targets and enrich for participants likely to develop Alzheimer’s disease dementia. The use of these eligibility criteria may affect study power. Methods: We investigated outcome variability and study power in the setting of proof-of-concept prodromal Alzheimer’s disease trials that incorporate cerebrospinal fluid levels of total tau (t-tau) and phosphorylated (p-tau) as primary outcomes and how differing biomarker inclusion criteria affect power. We used data from the Alzheimer’s Disease Neuroimaging Initiative to model trial scenarios and to estimate the variance and within-subject correlation of total and phosphorylated tau. These estimates were then used to investigate the differences in study power for trials considering these two surrogate outcomes. Results: Patient characteristics were similar for all eligibility criteria. The lowest outcome variance and highest within-subject correlation were obtained when phosphorylated tau was used as an eligibility criterion, compared to amyloid beta or total tau, regardless of whether total tau or phosphorylated tau were used as primary outcomes. Power increased when eligibility criteria were broadened to allow for enrollment of subjects with either low amyloid beta or high phosphorylated tau. Conclusion: Specific biomarker inclusion criteria may impact statistical power in trials using total tau or phosphorylated tau as the primary outcome. In concert with other important considerations such as treatment target and population of clinical interest, these results may have implications to the integrity and efficiency of prodromal Alzheimer’s disease trial designs.

scholarly journals Alzheimer’s disease brain-derived tau-containing extracellular vesicles: Pathobiology and GABAergic neuronal transmission

2020 ◽  
Author(s):  
Zhi Ruan ◽  
Dhruba Pathak ◽  
Srinidhi Venkatesan Kalavai ◽  
Asuka Yoshii-Kitahara ◽  
Satoshi Muraoka ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Extracellular Vesicles ◽  
Cortical Neurons ◽  
Pyramidal Neurons ◽  
Molecular Layer ◽  
Pyramidal Cells ◽  
Gabaergic Neurons ◽  
Dot Blot ◽  
Patch Clamp Recording

AbstractExtracellular vesicles (EVs) propagate tau pathology for Alzheimer’s disease (AD). How EV transmission influences AD are, nonetheless, poorly understood. To these ends, the physicochemical and molecular structure-function relationships of human brain-derived EVs, from AD and prodromal AD (pAD), were compared to non-demented controls (CTRL). AD EVs were shown to be significantly enriched in epitope-specific tau oligomers versus pAD or CTRL EVs assayed by dot-blot and atomic force microscopy tests. AD EVs were efficiently internalized by murine cortical neurons and transferred tau with higher aggregation potency than pAD and CTRL EVs. Strikingly, inoculation of tau-containing AD EVs into the outer molecular layer of the dentate gyrus induced tau propagation throughout the hippocampus. This was seen in 22 months-old C57BL/6 mice at 4.5 months post-injection by semiquantitative brain-wide immunohistochemistry tests with multiple anti-phospho-tau (p-tau) antibodies. Inoculation of the equal amount of tau from CTRL EVs or as oligomer or fibril-enriched fraction from the same AD donor showed little propagation. AD EVs induced tau accumulation in the hippocampus as oligomers or sarkosyl-insoluble proteins. Unexpectedly, p-tau cells were mostly GAD67+ GABAergic neurons and to a lesser extent, GluR2/3+ excitatory mossy cells, showing preferential EV-mediated GABAergic neuronal tau propagation. Whole-cell patch clamp recording of Cornu Ammonis (CA1) pyramidal cells showed significant reduction in the amplitude of spontaneous inhibitory post-synaptic currents. This was accompanied by reductions in c-fos+ GAD67+GABAergic neurons and GAD67+ GABAergic neuronal puncta surrounding pyramidal neurons in the CA1 region confirming reduced interneuronal projections. Our study posits a novel tau-associated pathological mechanism for brain-derived EVs.

scholarly journals Differential cross-seeding properties of tau and α-synuclein in mouse models of tauopathy and synucleinopathy

2020 ◽  
Vol 2 (2) ◽  
Author(s):  
Tosha Williams ◽  
Zachary Sorrentino ◽  
Mary Weinrich ◽  
Benoit I Giasson ◽  
Paramita Chakrabarty
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Phosphorylated Tau ◽  
Tau Pathology ◽  
Whole Brain ◽  
Transmission Properties ◽  
Priming Process ◽  
Robust Transmission ◽  
Cooperative Relationship ◽  
Tau Fibrils

Abstract Co-occurrence of tau and α-synuclein pathologies in a subset of Alzheimer’s disease patients has led to the idea that mixed pathologies may play a unique characteristic role in the Alzheimer’s disease neurodegenerative cascade. To understand the aetiology of such mixed pathologies, we investigated cross-seeding by human recombinant tau and human recombinant α-synuclein fibrillar species in a mouse model of tauopathy (Line PS19) or synucleinopathy (Line M20). Unilateral hippocampal injection of tau fibrils or α-synuclein fibrils, and to a lesser extent tau + α-synuclein copolymer fibrils prepared from co-incubating individual recombinant monomers, induced robust phosphorylated tau pathology in PS19 mice relative to control mice. Though the tau + α-synuclein copolymer fibrils did not modulate induction of pathologies at the site of injection, examination of the whole brain showed that these copolymers exacerbated neuroanatomic transmission of seeded tau pathology compared to tau fibril-injected mice. Only α-synuclein fibrils, but not tau alone or tau + α-synuclein copolymers, triggered modest levels of endogenous phosphorylated α-synuclein pathology. Overall, data from the PS19 mice suggest that human α-synuclein fibrils can efficiently cross-seed human tau and have a modest priming effect on mouse α-synuclein, and the presence of tau fibrils does not exacerbate the priming process. In M20 mice, unilateral hippocampal injection of α-synuclein fibrils or tau fibrils induced robust bilateral phosphorylated α-synuclein pathology, while tau + α-synuclein copolymer injection resulted in restricted phosphorylated α-synuclein pathology predominantly in the ipsilateral cortex. This suggests that human tau fibrils can also induce human α-synuclein pathogenesis, and the presence of combinatorial seeds is not synergistic. None of these aggregates induced phosphorylated tau pathology in M20 mice, showing that mouse tau cannot be primed efficiently by human tau fibrils or human α-synuclein fibrils. Neuropathological analysis of the whole brain of M20 mice showed that tau + α-synuclein copolymer-injected mice had lower abundance of bilaterally transmitted α-synuclein pathologies relative to α-synuclein fibril-injected mice. Thus, the tau + α-synuclein copolymer fibrils show robust transmission properties preferentially in rodent model of tauopathies but not in synucleinopathy, probably signifying an enhanced cooperative relationship between tau and α-synuclein in the tau seeding process. Together, our data highlight the unique cross-seeding properties of tau and αSyn in neurodegenerative proteinopathies.

scholarly journals Alix and Syntenin-1 direct amyloid precursor protein trafficking into extracellular vesicles

2020 ◽  
Author(s):  
Allaura S. Cone ◽  
Stephanie N. Hurwitz ◽  
Glorida S. Lee ◽  
Xuegang Yuan ◽  
Yi Zhou ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Subcellular Localization ◽  
Amyloid Precursor Protein ◽  
Extracellular Vesicles ◽  
Protein Trafficking ◽  
Cortical Neurons ◽  
Molecular Mechanisms ◽  
Precursor Protein ◽  
Amyloid Precursor Protein Trafficking

Abstract Background: Endosomal trafficking and amyloidogenic cleavage of amyloid precursor protein (APP) is believed to play a role in the neurodegeneration observed in Alzheimer’s disease (AD). Recent evidence has suggested that packaging and secretion of APP and its amyloidogenic cleaved product (βAPP) into small extracellular vesicles (EVs) may facilitate uptake of these neurotoxic factors during disease progression. However, the molecular mechanisms underlying trafficking of APP into EVs are poorly understood. Results: In this study, the mechanism and impact of amyloid precursor protein trafficking into extracellular vesicles (EVs) were assessed by a series of inducible gene knockdowns. We demonstrate that vesicle-associated proteins Alix and Syntenin-1 are essential for proper subcellular localization and efficient EV secretion of APP via an endosomal sorting complexes required for transport (ESCRT)-independent pathway. The neurotoxic C-terminal fragment (CTF) of APP is similarly secreted in association with small vesicles. These mechanisms are conserved in terminally differentiated neuron-like cells. Furthermore, knockdown of Alix and Syntenin-1 alters the subcellular localization of APP, sequestering the precursor protein to endoplasmic reticulum and endolysosomal compartments, respectively. Finally, transfer of small EVs containing APP confers an increase in reactive oxygen species production and neurotoxicity to human induced pluripotent stem cell-derived cortical neurons and naïve primary neurons, an effect that is ameliorated by Alix and Syntenin-1 depletion. Conclusions: Altogether these findings elucidate a novel mechanism for understanding the intracellular trafficking of APP and βAPP into secreted extracellular vesicles, and the resultant potential impact on neurotoxicity in the context of Alzheimer’s disease amyloidopathy.

scholarly journals Aβ/Tau Oligomer Interplay at Human Synapses Supports Shifting Therapeutic Targets for Alzheimer’s Disease

2021 ◽  
Author(s):  
Michela Marcatti ◽  
Anna Fracassi ◽  
Mauro Montalbano ◽  
Chandramouli Natarajan ◽  
Balaji Krishnan ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cortical Neurons ◽  
Fluorescence Analysis ◽  
Long Term Potentiation ◽  
Immunofluorescence Assay ◽  
Proteinase K ◽  
Tau Oligomers ◽  
High Concentrations

Abstract Background. Alzheimer’s Disease (AD) is characterized by progressive cognitive decline due to accumulating synaptic insults by toxic oligomers of amyloid beta (AβO) and tau (TauO). There is growing consensus that preventing these oligomers from interacting with synapses might be an effective approach to treat AD. However, recent clinical trial failures suggest low effectiveness of targeting Aβ in late-stage AD. Researchers have redirected their attention toward TauO as the levels of this species increase later in disease pathogenesis. Here we show that AβO and TauO differentially target synapses and affect each other's binding dynamics. Methods. Binding of labeled, pre-formed Aβ and tau oligomers onto synaptosomes isolated from the hippocampus and frontal cortex of mouse and postmortem cognitively intact elderly human brains was evaluated using flow-cytometry and western blot analyses. Binding of labeled, pre-formed Aβ and tau oligomers onto mouse primary neurons was assessed using immunofluorescence assay. The synaptic dysfunction was measured by fluorescence analysis of single-synapse long-term potentiation (FASS-LTP) assay. Results. We demonstrated that higher TauO concentrations effectively outcompete AβO and become the prevailing synaptic-associated species. Conversely, high concentrations of AβO facilitate synaptic TauO recruitment. Immunofluorescence analyses of mouse primary cortical neurons confirmed differential synaptic binding dynamics of AβO and TauO. Moreover, in vivo experiments using old 3xTgAD mice ICV injected with either AβO or TauO fully supported these findings. Consistent with these observations, FASS-LTP analyses demonstrated that TauO-induced suppression of chemical LTP was exacerbated by AβO. Finally, predigestion with proteinase K abolished the ability of TauO to compete off AβO without affecting the ability of high AβO levels to increase synaptic TauO recruitment. Thus, unlike AβO, TauO effects on synaptosomes are hampered by the absence of protein substrate in the membrane.Conclusions. These results introduce the concept that TauO become the main synaptototoxic species at late AD, thus supporting the hypothesis that TauO may be the most effective therapeutic target for clinically manifest AD.

scholarly journals Alix and Syntenin-1 direct amyloid precursor protein and amyloid beta trafficking into extracellular vesicles

2020 ◽  
Author(s):  
Allaura S. Cone ◽  
Stephanie N. Hurwitz ◽  
Glorida S. Lee ◽  
Xuegang Yuan ◽  
Yi Zhou ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Subcellular Localization ◽  
Amyloid Precursor Protein ◽  
Extracellular Vesicles ◽  
Amyloid Beta ◽  
Cortical Neurons ◽  
Molecular Mechanisms ◽  
Precursor Protein ◽  
Endosomal Trafficking

Abstract Background: Endosomal trafficking and amyloidogenic cleavage of amyloid precursor protein (APP) is believed to play a role in the neurodegeneration observed in Alzheimer’s disease (AD). Recent evidence has suggested that packaging and secretion of APP and amyloid beta into small extracellular vesicles (EVs) may facilitate uptake of these neurotoxic factors during disease progression. However, the molecular mechanisms underlying trafficking of APP into EVs are poorly understood. Results: In this study, the mechanism and impact of amyloid precursor protein (APP) trafficking into extracellular vesicles (EVs) were assessed by a series of inducible gene knockdowns. We demonstrate that vesicle-associated proteins Alix and Syntenin-1 are essential for proper subcellular localization and efficient EV secretion of APP via an endosomal sorting complexes required for transport (ESCRT)-independent pathway. The neurotoxic metabolite amyloid beta (Aβ) is similarly secreted in association with small vesicles. These mechanisms are conserved in terminally differentiated neuron-like cells. Furthermore, knockdown of Alix and Syntenin-1 alters the subcellular localization of APP, sequestering the precursor protein to endoplasmic reticulum and endolysosomal compartments, respectively. Finally, transfer of small EVs containing APP confers an increase in reactive oxygen species production and neurotoxicity to human induced pluripotent stem cell-derived cortical neurons and naïve primary neurons, an effect that is ameliorated by Alix and Syntenin-1 depletion. Conclusions: Altogether these findings elucidate a novel mechanism for understanding the intracellular trafficking of APP and Aβ into secreted extracellular vesicles, and the resultant potential impact on neurotoxicity in the context of Alzheimer’s disease amyloidopathy.

scholarly journals Acetylation of Tau Induces Alzheimer's Disease-Associated Tau in Transgenic Mice

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. 966-966
Author(s):  
Addison Ali ◽  
Kristeen Pareja ◽  
Tara Tracy
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Transgenic Mice ◽  
Neurodegenerative Disorder ◽  
Mossy Fibers ◽  
Tau Proteins ◽  
Phosphorylated Tau ◽  
Tau Pathology ◽  
Ca1 Region ◽  
Tau Aggregation

Abstract Alzheimer’s disease (AD) is a neurodegenerative disorder that is characterized by neurofibrillary tangles (NFTs) and amyloid beta plaques. These NFTs are made up of aggregated tau proteins. Tau is involved in stabilizing microtubules and does not usually display aggregation. Acetylation of tau protein causes an increase in tau aggregation but its role in AD progression is still not well understood. I hypothesized that enhanced acetylated tau results in an increase in AD-like tau pathology. To test this, a murine prion promoter-tauKQ transgene was injected into the mouse fertilized oocyte. The tauKQ mutation alters lysine to glutamine to mimic acetylation of tau. Nontransgenic mice were used as controls. AT8 and GT-38 antibodies were used in immunohistochemistry (IHC) to target phosphorylated tau and AD-associated tau, respectively. GT-38 is conformation-dependent and requires 3R and 4R tau isoforms which makes it specific to AD. Through immunofluorescence, increased phosphorylated tau was observed in the hippocampus of the tauKQ mice compared to the nontransgenic mice. I focused on the dentate gyrus, CA1 region, and the mossy fibers of the CA3 region since they are involved in many memory processes. Through chromogenic IHC, the tauKQ mice exhibited more 3R+4R tau isoform pathology in the mossy fibers than the nontransgenic mice. This data suggests that an acetylation mimic is sufficient to stimulate an abundance of AD-related tau pathology in transgenic mice which is consistent with my hypothesis. The tauKQ mouse model can assist in understanding the role of tau acetylation and tau progression for AD.

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