Tau Staining Research Articles

Inhibition of EV biogenesis reduces tau propagation in Alzheimer’s Disease mouse models

AbstractBackgroundMounting evidence correlates the propagation of hyperphosphorylated tau (pTau) along synaptically connected networks in the brain with progressive cognitive decline in Alzheimer’s Disease (AD). Recent findings have highlighted extracellular vesicle (EV)s in enabling transcellular transmission of pathological tau and identified the partial inhibition of EV biogenesis via small‐molecule inhibitors of nSMase2 as a potential therapeutic avenue. However, there are no suitable compounds for clinical development so far.MethodThrough high‐throughput screening, we identified PDDC, a highly selective and potent nSMase2 inhibitor with excellent brain penetration and oral bioavailability. To evaluate PDDC’s effect on tau propagation in vivo, we chronically administered PDDC‐containing chow to PS19 transgenic mice and measured brain ceramides, nSMase2 activity, tau levels, glial activation, hippocampal neuronal cell layer thickness, and mossy fiber synaptophysin staining. In addition, neuronally‐derived EVs from plasma were isolated and characterized. To directly monitor the effect of PDDC on tau propagation, we developed a murine model where an AAV encoding for P301L/S320F double mutant human tau was stereotaxically‐injected unilaterally into the hippocampus and transfer to the contralateral dentate gyrus (DG) was monitored ± PDDC treatment.ResultPS19 mice exhibited robust elevation of multiple ceramide species and nSMase2 enzymatic activity in the brain, both of which were normalized by PDDC treatment. PS19 mice treated with PDDC had significantly reduced hippocampal total tau and Thr181 pTau, reduced glial activation, protected synapses, and improved pyramidal and granule cell layer thickness. Plasma NEVs of treated mice were fewer in number and had lower p181‐Tau levels than the untreated group; FCA confirmed the decrease of NEVs carrying p262‐Tau at the single EV level. Similarly, the AAV‐hTau‐seeded mice treated with PDDC had reduced tau staining intensity in the contralateral DG.ConclusionData in two AD models using PDDC provides strong preclinical support for using nSMase2 inhibition as a therapeutic strategy to slow tau propagation in AD.

Susceptibility Magnetic Resonance Imaging Correlates with Glial Density and Tau in the Substantia Nigra Pars Compacta.

Susceptibility magnetic resonance imaging (MRI) is sensitive to iron-related changes in the substantia nigra pars compacta (SNc), the key pathologic locus of parkinsonisms. It is unclear, however, if iron deposition in the SNc is associated with its neurodegeneration. The objective of this study was to test whether susceptibility MRI metrics in parkinsonisms are associated with SNc neuropathologic features of dopaminergic neuron loss, gliosis, and α-synuclein and tau burden. This retrospective study included 27 subjects with both in vivo MRI and postmortem data. Multigradient echo imaging was used to derive the apparent transverse relaxation rate (R2*) and quantitative susceptibility mapping (QSM) in the SNc. Archived midbrain slides that were stained with hematoxylin and eosin, anti-α-synuclein, and anti-tau were digitized to quantify neuromelanin-positive neuron density, glial density, and the percentages of area occupied by positive α-synuclein and tau staining. MRI-histology associations were examined using Pearson correlations and regression. Twenty-four subjects had postmortem parkinsonism diagnoses (Lewy body disorder, progressive supranuclear palsy, multiple system atrophy, and corticobasal degeneration), two had only Alzheimer's neuropathology, and one exhibited only mild atrophy. Among all subjects, both R2* and QSM were associated with glial density (r ≥ 0.67; P < 0.001) and log-transformed tau burden (r ≥ 0.53; P ≤ 0.007). Multiple linear regression identified glial density and log-transformed tau as determinants for both MRI metrics (R2 ≥ 0.580; P < 0.0001). Neither MRI metric was associated with neuron density or α-synuclein burden. R2* and QSM are associated with both glial density and tau burden, key neuropathologic features in the parkinsonism SNc. © 2023 International Parkinson and Movement Disorder Society.

Survey of Neuroanatomic Sampling and Staining Procedures in Alzheimer Disease Research Center Brain Banks.

The collection of post-mortem brain tissue has been a core function of the Alzheimer Disease Research Center's (ADRCs) network located within the United States since its inception. Individual brain banks and centers follow detailed protocols to record, store, and manage complex datasets that include clinical data, demographics, and when post-mortem tissue is available, a detailed neuropathological assessment. Since each institution often has specific research foci, there can be variability in tissue collection and processing workflows. While published guidelines exist for select diseases, such as those put forth by the National Institute on Aging and Alzheimer Association (NIA-AA), it is of importance to denote the current practices across institutions. To this end a survey was developed and sent to United States based brain bank leaders, collecting data on brain region sampling, including anatomic landmarks used, staining (including antibodies used), as well as whole-slide-image scanning hardware. We distributed this survey to 40 brain banks and obtained a response rate of 95% (38 / 40). Most brain banks followed guidelines defined by the NIA-AA, having H&E staining in all recommended regions and targeted region-based amyloid beta, tau, and alpha-synuclein immunohistochemical staining. However, sampling consistency varied related to key anatomic landmarks/locations in select regions, such as the striatum, periventricular white matter, and parietal cortex. This study highlights the diversity and similarities amongst brain banks and discusses considerations when amalgamating data/samples across multiple centers. This survey aids in establishing benchmarks to enhance dialogues on divergent workflows in a feasible way.

Altered localization of nucleoporin 98 in primary tauopathies.

Nucleoporin 98 is a nuclear pore complex component that is mislocalized in Alzheimer's disease and the alteration in nucleoporin 98 has been attributed to tau. In order to determine if nucleoporin 98 mislocalization is a general feature of tauopathies, we assessed the localization of nucleoporin 98 in neurons in primary tauopathies, including frontotemporal lobar degeneration-tau, corticobasal degeneration and progressive supranuclear palsy. Immunofluorescence staining was performed on frontal cortex and occipital cortex tissue from cases of primary tauopathies and controls without neurodegenerative disease using antibodies to identify nucleoporin 98, phospho-tau (Ser202, Thr205) monoclonal antibody and neuronal marker microtubule-associated protein 2. The stained tissue was imaged by fluorescence microscopy and the number of neurons with mislocalized nucleoporin 98 and phospho-tau (Ser202, Thr205) monoclonal antibody staining was quantified. In frontal cortex tissue, all primary tauopathies examined demonstrated significantly increased numbers of neurons with abnormal localization of nucleoporin 98 along the nuclear envelope compared with control tissue. Additionally, frontotemporal lobar degeneration-tau and corticobasal degeneration in the frontal cortex demonstrated significantly increased numbers of neurons with a cytoplasmic mislocalization of nucleoporin 98 compared with control tissue. The number of neurons with mislocalized nucleoporin 98 was significantly correlated with the number of neurons with phospho-tau (Ser202, Thr205) monoclonal antibody-positive tau staining. In the occipital cortex, which is relatively spared from pathological tau accumulations in these primary tauopathies, the localization of nucleoporin 98 was not significantly altered. This study demonstrates that nucleoporin 98 mislocalization is a feature of primary tauopathies and is associated with pathological tau accumulation. In the context of prior research demonstrating nucleoporin 98 mislocalization in Alzheimer's disease and an interaction between tau and nucleoporin 98, these results further support the hypothesis that pathological tau may contribute to nucleoporin 98 mislocalization. Given the critical role of the nuclear pore complex in nucleocytoplasmic transport, the identification of nucleoporin 98 mislocalization in primary tauopathies highlights a potential pathophysiological disruption in these disorders.

Differential brain expression of 3R and 4R Tau isoforms in aging wild‐type and young genetically engineered PSEN1 mutant marmosets

AbstractBackgroundThe common marmoset (Callithrix jacchus) has emerged as an important model for studying Alzheimer’s disease (AD). Several previous publications reported the natural and spontaneous accumulation of Aβ aggregates in aging marmosets. However, the presentation of tau in aging marmosets has been understudied. A recent report investigated the expression of different tau isoforms and concluded that only 4R tau is expressed throughout adulthood (Sharma et al., J. Biol. Chem. 2019). Here, we investigated the presence of amyloid and tau aggregates in aged wild‐type marmosets and in young adult individuals genetically engineered with knock‐in (KI) point mutations in the PSEN1 gene that cause early‐onset AD.MethodWe used standard IHC protocols and western blotting techniques with validated antibodies for amyloid (NAB228) and tau (RD3, 3T3, PHF‐1) to investigate the presence and localization of AD aggregates in the brains of 5 marmosets (n = 3 wild‐type and 2 PSEN1 KI mutants).ResultWe observed the natural accumulation of amyloid aggregates with the anti‐amyloid antibody NAB228 in a 10‐year male marmoset that confirms this subject’s previous in vivo evaluation with 11C‐PiB PET imaging. Interestingly, this aged marmoset showed positive 3R and 4R tau staining with the anti‐tau antibodies RD3 and 3T3, respectively (Figure 1) in the hippocampus. In agreement with Sharma et al., 2019, tau staining in the hippocampus was much more abundant for the 4R than the 3R tau isoform, with substantial phosphorylation at Ser‐396 and Ser‐404. We detected no tau staining in the entorhinal cortex of this animal and no amyloid nor tau in the brain of a one‐year‐old juvenile. We observed similar results of significant amyloid accumulation and RD3 and 3T3 labeling in the brains of two young (18 months) PSEN1 KI mutants. Separately, we confirmed by western blot 3R and 4R tau isoforms in homogenates from the hippocampus and entorhinal cortex of three individual marmosets (aged 1‐7 years).ConclusionOur genetically diverse marmoset population of aging and PSEN1 mutation carriers present both 3R and 4R isoforms across the lifespan. These data further support marmosets as an ideal species for translational studies of AD. Studies in larger sample sizes are ongoing.

Chronic FK506 treatment reduces amyloid β and tau levels in the hippocampus and cortex of 3xTg‐AD mice

AbstractBackgroundAlzheimer’s disease (AD) is the most common form of neurodegenerative dementia. While major histopathological hallmarks of AD are amyloid‐β (Aβ) plaques and neurofibrillary tau tangles, soluble oligomeric forms of Aβ and tau (TauO) have been identified as the most neurotoxic species involved in synaptic degeneration. Previous studies associate alterations of the phosphatase calcineurin (CaN) to AβO‐driven toxicity. We previously have shown that CaN mediates both the neurotoxic and cognitive effects of AβO and elevated CaN levels have been also shown in AD patients, suggesting a central role of CaN in AD onset and/or clinical progression. Our previous studies in mouse models demonstrated that an acute treatment with the CaN inhibitor FK506/Tacrolimus in Tg2576 acutely injected intracerebroventricularly with AβO restores memory function in these cognitively impaired animals. Moreover, we reported absence of AD in aging human chronically treated with KF506 following solid organ transplant. To deeper investigate the involvement of CaN in AD onset and progression, we used a 3xTgAD mouse model presenting both Aβ and Tau aggregates.Method7 month‐old 3xTg‐AD mice were chronically treated for two weeks with intraperitoneal administration of either FK506 (1mg/kg) or PBS. Using immunofluorescence and western blot analyses we analyzed the levels of CaN, total Tau and Aβ in hippocampal (dentate gyrus‐DG, CA1 and CA3) and cortical areas (frontal and parietal‐occipital cortex) in our experimental groups.ResultWe found significantly decreased levels of CaN in DG, CA1 and CA3 and cortical areas in FK506 treated 3xTg‐AD mice as compared to 3xTg‐AD mice injected with PBS. Furthermore, performing double staining for Aβ and total Tau, FK506 treated mice displayed significant lower levels of Aβ and Tau in all the considered areas as compared to PBS‐treated 3xTg‐AD mice. These data suggest that the treatment with FK506 might trigger some mechanisms involved in the elimination of Tau and Aβ, i.e. autophagy.ConclusionOur data confirm the role of CaN as a key player in AD. The reduced key AD pathology following CaN inhibition with FK506 suggests the use of an FDA approved drug as a potential treatment with rapid clinical translation to slow the progression of the disease.

Gut microbiota regulates neuroinflammation and progression of neurodegeneration in a mouse model of tauopathy

AbstractBackgroundAlthough mounting evidence supports that an unbalanced gut microbiota (GM) is linked to amyloid‐β deposition, the contribution of the GM to tau‐mediated neurodegeneration (TN) is poorly characterized. Our preliminary data have shown that the GM manipulations, using either treatment with a combination of antibiotics (ABX) or raising animals in germ‐free (GF) conditions, regulate TN (Seo, et al., AAIC 2021). However, further investigation is needed to sort out the underlying mechanisms that are involved in the interaction between GM and TN. Here, we explore neuroinflammation as a potential mediator in the interaction between GM and TN.MethodP301S tau transgenic mice were crossed with human ApoE knock‐in mice (ApoE3 or ApoE4) or ApoE knockout mice (EKO) to generate P301S::ApoE3/E3, ApoE4/E4, or P301S/EKO mice, termed TE3F, TE4F, and TEKO, respectively. Each group was gavaged with either ABX or H2O from postnatal day 16‐22, housed in a specific pathogen‐free facility, and euthanized at 9.5 months of age. A separate group of TE4F mice was housed under GF conditions. Collected brains were sectioned and used for immunohistochemistry analysis.ResultsIn agreement with brain atrophy measurements that we previously reported, TE3F mice treated with a short‐term ABX showed significantly lower phosphorylated tau (p‐tau) staining compared to the H2O‐treated group (p &lt; 0.01), but not TE4F and TEKO mice treated with ABX. GF‐TE4F mice also showed a marked decrease in p‐tau staining compared to conventionally‐raised animals (p &lt; 0.01). Further quantification of gliosis, as measured by GFAP and Iba1 immunostaining, did not reveal any ABX treatment effects. However, when we assessed the expression of clec7a+ microglia, which marks reactive microglia, ABX treated animals showed significantly lower clec7a+ staining across the different APOE isoform groups (p &lt; 0.01). Furthermore, microglial morphology analysis revealed that ABX treatment drive microglia to a more homeostatic‐like state in TE3F mice, but not in TE4F nor TEKO mice. Remarkably, GF‐TE4F mice showed a marked decrease in both GFAP and Iba1 expression compared to the control TE4F mice (p &lt; 0.05).ConclusionOur results support the hypothesis that GM manipulation modulates tau‐mediated neurodegeneration via influencing a neuroinflammatory mechanism.

NSMase2 inhibition reduces tau propagation in Alzheimer’s Disease mouse models

AbstractBackgroundAlzheimer’s Disease (AD) is the most common form of dementia worldwide and is characterized by progressive neurodegeneration and cognitive decline, putatively driven by the accumulation Amyloid‐b and hyperphosphorylated Tau. Clinical trial successes focusing on reducing Amyloid‐b plaque levels in patient brains have been modest, spurring a renewed focus on tau. Tau spreads throughout the brain along anatomical pathways, correlating strongly with the disease progression severity. Recent evidence has highlighted extracellular vesicles (EVs) in enabling transcellular transmission of pathological tau in the brain in a ‘prion‐like’ manner and identified the inhibition of EV biogenesis via small‐molecule inhibitors of nSMase2 as a potential therapeutic avenue. However, presently available tool compounds are unsuitable for clinical development.MethodTo improve upon current inhibitors, we performed high‐throughput screening followed by extensive chemistry and identified two classes of compounds. The first, PDDC, has excellent potency, oral bioavailability, and brain penetration, as well as in vitro and in vivo EV inhibition. The second, DPTIP, has higher potency, but poor oral pharmacokinetics and modest brain penetration. To circumvent these limitations, we conjugated DPTIP to a brain‐targeting hydroxyl‐dendrimer delivery system (D‐DPTIP) and demonstrated CNS target engagement following oral dosing. We then chronically administered PDDC and D‐DPTIP to PS19 transgenic mice and WT mice seeded with an AAV‐hTau vector unilaterally stereotaxically injected into the CA1 hippocampal region. After chronic dosing, we quantified the levels of phosphorylated tau in the hippocampus in the PS19s and the contralateral dentate gyrus in the AAV‐hTau seeded model. We also characterized isolated neuronally‐derived plasma EVs from these mice.ResultPS19 mice treated with PDDC had significantly reduced hippocampal tau and increased neuronal counts compared with vehicle. Additionally, PDDC treatment reduced the release of neuronally‐derived EVs into circulation with lower tau level trends. Similarly, seeded mice treated with either PDDC or D‐DPTIP had reduced tau staining intensity in the contralateral dentate gyrus. Importantly, neither compound induced significant toxicity in either model.ConclusionObserving significant reductions in tau burden in two separate AD models provides proof of concept for nSMase2 inhibition in slowing tau propagation, highlighting the promise of tested compounds as potential AD therapeutics.

Quantifying patterns of pathology: A characterization of the 3D spatial distribution of tau tangles and amyloid plaques in Alzheimer’s disease using multi‐modal image registration with a scattering transform

AbstractBackgroundVolumetric measures of MRI scans have consistently shown medial temporal lobe (MTL) atrophy in individuals across the spectrum of AD. However, these measures are not considered to be specific for AD, partly because a direct link to tau and amyloid pathology has not been demonstrated (Jack et. al, 2018). To address this limitation, we developed multi‐modal image registration and analysis tools to integrate neuropathological data from 2D histology images with 3D postmortem MRI images in the same brain region, in order to quantify the density of tangles and plaques.MethodsWe imaged tissue excised from the MTL at 0.125 mm resolution with an 11T MR scanner (fig 1a) and manually segmented it into subregions (fig 1b). We sliced the tissue into 10um thick sections, 1mm apart, and digitally imaged them with a light microscope after staining for amyloid (6E10) or tau (PHF‐1) (fig 1c). Locations of tangles and plaques on histology were estimated with a deep convolutional neural network (UNET) trained on a smaller set of annotated data (fig 1d). To align histology images with the MRI images, we first computed scattering transforms of histology to capture high resolution textural information (fig 1e). This was then used to find both optimal spatial and intensity profile transformations between the two imaging modalities (fig 1f). We rigidly aligned MRI images to the Mai Paxinos atlas for interpretability.ResultsWe localized tau tangles and amyloid plaques from histology sections of a person with severe AD, and in corresponding 3D MRI images of the brain tissue from the same individual. We quantified density of particles per region. Initial findings demonstrated the highest amount of tau in the entorhinal cortex, subiculum, and CA1 (fig 2) compared to other subregions in the MTL, consistent with Braak staging. No obvious differential distribution of amyloid was observed.ConclusionOur detailed localization of tangles and plaques in 3D offers the opportunity to study spatial distribution of pathology within brain regions among patients that span the spectrum of disease, which will foster more robust comparison with MRI atrophy, and potentially shed new light on the progression of AD.

Deep learning reveals disease-specific signatures of white matter pathology in tauopathies

Although pathology of tauopathies is characterized by abnormal tau protein aggregation in both gray and white matter regions of the brain, neuropathological investigations have generally focused on abnormalities in the cerebral cortex because the canonical aggregates that form the diagnostic criteria for these disorders predominate there. This corticocentric focus tends to deemphasize the relevance of the more complex white matter pathologies, which remain less well characterized and understood. We took a data-driven machine-learning approach to identify novel disease-specific morphologic signatures of white matter aggregates in three tauopathies: Alzheimer disease (AD), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD). We developed automated approaches using whole slide images of tau immunostained sections from 49 human autopsy brains (16 AD,13 CBD, 20 PSP) to identify cortex/white matter regions and individual tau aggregates, and compared tau-aggregate morphology across these diseases. Tau burden in the gray and white matter for individual subjects strongly correlated in a highly disease-specific fashion. We discovered previously unrecognized tau morphologies for AD, CBD and PSP that may be of importance in disease classification. Intriguingly, our models classified diseases equally well based on either white or gray matter tau staining. Our results suggest that tau pathology in white matter is informative, disease-specific, and linked to gray matter pathology. Machine learning has the potential to reveal latent information in histologic images that may represent previously unrecognized patterns of neuropathology, and additional studies of tau pathology in white matter could improve diagnostic accuracy.

Characterization of an APP/tau rat model of Alzheimer\u2019s disease by positron emission tomography and immunofluorescent labeling

BackgroundTo better understand the etiology and pathomechanisms of Alzheimer’s disease, several transgenic animal models that overexpress human tau or human amyloid-beta (Aβ) have been developed. In the present study, we generated a novel transgenic rat model by cross-breeding amyloid precursor protein (APP) rats with tau rats. We characterized this model by performing positron emission tomography scans combined with immunofluorescent labeling and cerebrospinal fluid analyses.MethodsAPP/Tau rats were generated by cross-breeding male McGill-R-Thy1-APP transgenic rats with female hTau-40/P301L transgenic rats. APP/Tau double transgenic rats and non-transgenic (ntg) littermates aged 7, 13, and 21 months were subjected to dynamic [11C] PiB scan and dynamic [18F]THK-5317 scans. For regional brain analysis, a template was generated from anatomical MR images of selected animals, which was co-registered with the PET images. Regional analysis was performed by application of the simplified reference tissue model ([11C]PiB data), whereas [18F]THK-5317 data were analyzed using a 2-tissue compartment model and Logan graphical analysis. In addition, immunofluorescent labeling (tau, amyloid) and cerebrospinal fluid analyses were performed.Results[11C]PiB binding potential (BPND) and [18F]THK-5317 volume of distribution (VT) showed an increase with age in several brain regions in the APP/Tau group but not in the ntg control group. Immunohistochemical analysis of brain slices of PET-scanned animals revealed a positive correlation between Aβ labeling and [11C]PiB regional BPND. Tau staining yielded a trend towards higher levels in the cortex and hippocampus of APP/Tau rats compared with ntg littermates, but without reaching statistical significance. No correlation was found between tau immunofluorescence labeling results and the respective [18F]THK-5317 VT values.ConclusionsWe thoroughly characterized a novel APP/Tau rat model using combined PET imaging and immunofluorescence analysis. We observed an age-related increase in [11C]PiB and [18F]THK-5317 binding in several brain regions in the APP/Tau group but not in the ntg group. Although we were able to reveal a positive correlation between amyloid labeling and [11C]PiB regional brain uptake, we observed relatively low human tau and amyloid fibril expression levels and a somewhat unstable brain pathology which questions the utility of this animal model for further studies.

Neuroprotection of cholinergic neurons with tau aggregation inhibitor and rivastigmine in L1 mice with Alzheimer’s‐like tauopathy

AbstractBackgroundBasal forebrain cholinergic dysfunction, likely linked to tau aggregation pathology, is a characteristic feature of AD. Cholinergic neurons contain choline acetyltransferase (ChAT) and high‐affinity tropomyosin‐related kinase A (TrkA) and send efferents to cortex and hippocampus where they release acetylcholine (ACh). The vesicular acetylcholine transporter (VAChT) is responsible for loading ACh into secretory vesicles and acetylcholine esterase (AChE) hydrolyses ACh in the synaptic cleft. We here aimed to evaluate the cholinergic phenotype in the Line 1 animal model of tauopathy and to determine the effect of the choline esterase inhibitor rivastigmine alone and in conjunction with the tau aggregation inhibitor hydromethylthionine on the cholinergic system.MethodLine 1 (L1) and control NMRI mice, 8‐9 months old, divided into 13 groups (n = 5 each), were treated with rivastigmine (0.1 and 0.5 mg/kg) and hydromethylthionine (5 and 15 mg/kg) and their combinations for 11 weeks. Immunohistochemical staining in brain sections was performed for ChAT, TrkA, VAChT and tau with a repeat domain monoclonal antibody (TauRx Therapeutics Ltd.). AChE activity was measured histochemically. The state of the cholinergic system was determined by stereological counting of ChAT‐ir and TrkA‐ir neurons, while Relative Optical Intensity (ROI) was used to tau immunoreactivity in basal forebrain, and cholinergic projections were evaluated using VAChT and AChE ROI.ResultNumber of ChAT‐ir, TrkA‐ir neurons and ROI value for VAChT and AChE were significantly lower while ROI value for tau was higher in vehicle‐treated L1 mice compared with wild type control. Numbers of ChAT‐ir, TrkA‐ir neurons and ROI value of VAChT and AChE in L1 mice were increased and tau ROI was decreased by hydromethylthionine treatment. Combined treatment decreased numbers of ChAT‐ir, TrkA‐ir neurons and ROI for VAChT and AChE compared to L1 groups treated with hydromethylthionine alone.ConclusionThere was a significant loss of cholinergic basal forebrain neurones, impaired cholinergic projection and increased tau staining in L1 mice. Monotherapy with hydromethylthionine improved the cholinergic neurons phenotype, enhanced their projection and reduced tau pathology. Combination therapy interacted negatively attenuating the effect of hydromethylthionine given alone.

Tau deposition in the spinal cord is not specific for CTE-ALS.

Previous studies have reported neuropathologic findings from autopsy cases in which patients had clinical diagnoses of both chronic traumatic encephalopathy (CTE) and amyotrophic lateral sclerosis (ALS).1,2 Not surprisingly, these cases demonstrated coexisting pathologic findings of both CTE and ALS. A recent study by Moszczynski et al.1 found abnormal pThr175 tau staining in the spinal cords from 3/5 CTE cases, 3/5 cases with both CTE and ALS, and 0/5 control cases with no known neurologic disease. Although this study did not examine any cases of sporadic ALS without coexisting CTE, the authors concluded that “the absence of tau deposition in the spinal cords of patients with sporadic ALS suggests that the spinal motor neuron tauopathy of CTE-ALS is not an incidental finding or secondary to the primary neuronal injury of ALS.1” When this assertion was challenged in a reader response,3 the author reply urged the respondents “to assemble their case experience and submit it for peer review as it would be an important contribution to the literature.4”

Low Dose Brain Irradiation Reduces Amyloid-β and Tau in 3xTg-AD Mice.

We have previously reported that low doses of external beam ionizing irradiation reduced amyloid-β (Aβ) plaques and improved cognition in APP/PS1 mice. In this study we investigated the effects of radiation in an age-matched series of 3xTg-AD mice. Mice were hemibrain-irradiated with 5 fractions of 2 Gy and sacrificed 8 weeks after the end of treatment. Aβ and tau were assessed using immunohistochemistry and quantified using image analysis with Definiens Tissue Studio. We observed a significant reduction in Aβ plaque burden and tau staining; these two parameters were significantly correlated. This preliminary data is further support that low doses of radiation may be beneficial in Alzheimer's disease.

Isolation and characterization of antibody fragment selective for human Alzheimer’s disease brain-derived tau variants

Reagents that can selectively recognize specific toxic tau variants associated with onset and progression of Alzheimer’s disease (AD) and other tauopathies can be effective diagnostic and therapeutic tools. We utilized a novel atomic force microscopy–based biopanning protocol to isolate antibody fragments (single chain variable fragments, scFvs) that selectively bind tau variants present in human AD but not cognitively normal age-matched brain tissue. We identified 6 scFvs [Alzheimer's disease tau (ADT)-1 through 6] that readily distinguished between AD and control tissue and sera samples. We utilized 3 of the scFvs (ADT-2, ADT-4, and ADT-6) to analyze longitudinal plasma samples from 50 human patients, 25 patients which converted to AD during the study and 25 that remained cognitively normal. All 3 scFvs could distinguish the AD from control samples with higher tau levels in apolipoprotein E3/3 AD cases compared to apolipoprotein E3/4. Immunohistochemical analyses of human AD brain slices indicated several but not all tau variants overlapping with phosphorylated tau staining. Several reagents also showed therapeutic potential, protecting neuronal cells against AD tau-induced toxicity.

The Role of mTOR and Ubiquitin in Plaque and Tangle Formation in Alzheimer's Disease Pathogenesis: A Report of Co‐localization in Two Alzheimer's Autopsy Cases

The brains from two patients that died with Alzheimer's disease were examined to determine the role of mTOR and ubiquitin in the pathogenesis of plaque and tangle formation. Conditions of ongoing stress can lead to a failure of normal homeostatic mechanisms, mTOR signaling dysregulation, and accumulation of ubiquitinated protein aggregates. Ubiquitin is known to accumulate in neuritic plaques and neurofibrillary tangles, and we hypothesized that mTOR would co-localize with ubiquitin in neurodegenerative protein aggregates. Formalin-fixed, Paraffin-embeded tissue blocks were obtained from autopsies obtained at a county hospital. Standard H&E and Sevier-Munger stained slides were reviewed, and IHC was performed mTOR and ubiquitin. The slides were double stained with antibodies (conjugated to fluorophores) to mTOR and ubiquitin, and visualized on a fluorescent microscope. Alzheimer's patients showed co-localization of mTOR and ubiquitin within cells associate with both plaques and tangles. We identified plaques and tangles in both patients in the hippocampus consistent with previous neuropathologic diagnoses of Alzheimer's dementia. For the first time, we have demonstrated that mTOR and ubiquitin co-localize to neuritic plaques and neurofibrillary tangles found in Alzheimer's disease. These findings further supports the already existing evidence that the mTOR/autophagy system is likely involved in the pathogenesis of Alzheimer's disease, and perhaps is involved in other neurodegenerative diseases as well. Support or Funding Information None Patient 1 (A) Neuritic plaque with IHC staining of B-amyloid. 436× (B) The neurofibrillary tangles in Patient 1 specimen triple-stained for DAPI (blue), Ubiquitin (red), and mTOR (green). 959× (C) Neurofibrillary tangles with IHC staining for Tau. 436× (D) Neuritic plaque (Patient 1) showing aggregation of ubiquitin (green) and mTOR (red). 959x Patient 2 (A) Neuritic plaque with IHC stain for B-amyloid. 436× (B) A neurofibrillary tangle in Patient 2 double stained for Ubiquitin (red), and mTOR (green). 959× (C) Patient 2 Sevier-Munger stain highlighting tangles. 436× (D) Cells with colocalization of mTOR (red) and ubiquitin (green) in neurons with tangle formation. 959x This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

TREM2 deficiency attenuates neuroinflammation and protects against neurodegeneration in a mouse model of tauopathy

Variants in the gene encoding the triggering receptor expressed on myeloid cells 2 (TREM2) were recently found to increase the risk for developing Alzheimer's disease (AD). In the brain, TREM2 is predominately expressed on microglia, and its association with AD adds to increasing evidence implicating a role for the innate immune system in AD initiation and progression. Thus far, studies have found TREM2 is protective in the response to amyloid pathology while variants leading to a loss of TREM2 function impair microglial signaling and are deleterious. However, the potential role of TREM2 in the context of tau pathology has not yet been characterized. In this study, we crossed Trem2+/+ (T2+/+) and Trem2-/- (T2-/-) mice to the PS19 human tau transgenic line (PS) to investigate whether loss of TREM2 function affected tau pathology, the microglial response to tau pathology, or neurodegeneration. Strikingly, by 9 mo of age, T2-/-PS mice exhibited significantly less brain atrophy as quantified by ventricular enlargement and preserved cortical volume in the entorhinal and piriform regions compared with T2+/+PS mice. However, no TREM2-dependent differences were observed for phosphorylated tau staining or insoluble tau levels. Rather, T2-/-PS mice exhibited significantly reduced microgliosis in the hippocampus and piriform cortex compared with T2+/+PS mice. Gene expression analyses and immunostaining revealed microglial activation was significantly attenuated in T2-/-PS mice, and there were lower levels of inflammatory cytokines and astrogliosis. These unexpected findings suggest that impairing microglial TREM2 signaling reduces neuroinflammation and is protective against neurodegeneration in the setting of pure tauopathy.

Neurofibrillary Tangles of Aβx-40 in Alzheimer's Disease Brains.

The two pathognomonic lesions in the brain of AD patients are senile plaques and intraneuronal neurofibrillary tangles (NFT). Previous studies have demonstrated that amyloid-β (Aβ) is a component of both senile plaques and NFTs, and have showed that intracellular accumulation of Aβ is toxic for cells and precedes the appearance of extracellular amyloid deposits. Here we report that there are numerous intraneuronal NFT and extraneuronal NFT immunoreactive for Aβx-40 in which there is no co-localization with tau staining suggesting the existence of two different neurodegenerating populations associated with the intracellular accumulation of either tau protein or Aβx-40 in AD.

Accumulation of multiple neurodegenerative disease-related proteins in familial frontotemporal lobar degeneration associated with granulin mutation

In 2006, mutations in the granulin gene were identified in patients with familial Frontotemporal Lobar Degeneration. Granulin transcript haploinsufficiency has been proposed as a disease mechanism that leads to the loss of functional progranulin protein. Granulin mutations were initially found in tau-negative patients, though recent findings indicate that these mutations are associated with other neurodegenerative disorders with tau pathology, including Alzheimer’s disease and corticobasal degeneration. Moreover, a reduction in progranulin in tau transgenic mice is associated with increasing tau accumulation. To investigate the influence of a decline in progranulin protein on other forms of neurodegenerative-related protein accumulation, human granulin mutation cases were investigated by histochemical and biochemical analyses. Results showed a neuronal and glial tau accumulation in granulin mutation cases. Tau staining revealed neuronal pretangle forms and glial tau in both astrocytes and oligodendrocytes. Furthermore, phosphorylated α-synuclein-positive structures were also found in oligodendrocytes and the neuropil. Immunoblot analysis of fresh frozen brain tissues revealed that tau was present in the sarkosyl-insoluble fraction, and composed of three- and four-repeat tau isoforms, resembling Alzheimer’s disease. Our data suggest that progranulin reduction might be the cause of multiple proteinopathies due to the accelerating accumulation of abnormal proteins including TDP-43 proteinopathy, tauopathy and α-synucleinopathy.

Comparison of phosphorylated Tau and Ki-67 staining in SCIS, SCC, and BCC

Comparison of phosphorylated Tau and Ki-67 staining in SCIS, SCC, and BCC