Granulovacuolar Degeneration Research Articles

Inhibition of an Alzheimer's disease-associated form of necroptosis rescues neuronal death in mouse models.

Necroptosis is a regulated form of cell death that has been observed in Alzheimer's disease (AD) along with the classical pathological hallmark lesions of amyloid plaques and Tau neurofibrillary tangles. To understand the neurodegenerative process in AD, we studied the role of necroptosis in mouse models and primary mouse neurons. Using immunohistochemistry, we demonstrated activated necroptosis-related proteins in transgenic mice developing Tau pathology and in primary neurons from amyloid precursor protein (APP)-Tau double transgenic mice treated with phosphorylated Tau seeds derived from a patient with AD but not in APP transgenic mice that only exhibited β-amyloid deposits. Necroptosis proteins in granulovacuolar degeneration (GVD) bodies were associated with neuronal loss in mouse brain regions also known to be vulnerable to GVD in the human AD brain. Necroptosis inhibitors lowered the percentage of neurons showing GVD and reduced neuronal loss, both in transgenic mice and in primary mouse neurons. This suggests that a GVD-associated form of necroptosis that we refer to as "GVD-necroptosis" may represent a delayed form of necroptosis in AD. We propose that inhibition of necroptosis could rescue this type of neuronal death in AD.

Increased expression of the proapoptotic presenilin associated protein is involved in neuronal tangle formation in human brain

Presenilin-associated protein (PSAP) is a mitochondrial proapoptotic protein as established in cell biology studies. It remains unknown whether it involves in neurodegenerative diseases. Here, we explored PASP expression in adult and aged human brains and its alteration relative to Alzheimer-disease (AD)-type neuropathology. In pathology-free brains, light PASP immunoreactivity (IR) occurred among largely principal neurons in the cerebrum and subcortical structures. In the brains with AD pathology, enhanced PSAP IR occurred in neuronal and neuritic profiles with a tangle-like appearance, with PSAP and pTau protein levels elevated in neocortical lysates relative to control. Neuronal/neuritic profiles with enhanced PSAP IR partially colocalized with pTau, but invariably with Amylo-Glo labelled tangles. The neuronal somata with enhanced PASP IR also showed diminished IR for casein kinase 1 delta (Ck1δ), a marker of granulovacuolar degeneration; and diminished IR for sortilin, which is normally expressed in membrane and intracellular protein sorting/trafficking organelles. In old 3xTg-AD mice with β-amyloid and pTau pathologies developed in the brain, PSAP IR in the cerebral sections exhibited no difference relative to wildtype mice. These findings indicate that PSAP upregulation is involved in the course of tangle formation especially in the human brain during aging and in AD pathogenesis.

Hypothesis-based investigation of known AD risk variants reveals the genetic underpinnings of neuropathological lesions observed in Alzheimer’s-type dementia

Alzheimer’s disease (AD) is the leading cause of dementia worldwide. Besides neurofibrillary tangles and amyloid beta (Aβ) plaques, a wide range of co-morbid neuropathological features can be observed in AD brains. Since AD has a very strong genetic background and displays a wide phenotypic heterogeneity, this study aims at investigating the genetic underpinnings of co-morbid and hallmark neuropathological lesions. This was realized by obtaining the genotypes for 75 AD risk variants from low-coverage whole-genome sequencing data for 325 individuals from the Leuven Brain Collection. Association testing with deeply characterized neuropathological lesions revealed a strong and likely direct effect of rs117618017, a SNP in exon 1 of APH1B, with tau-related pathology. Second, a relation between APOE and granulovacuolar degeneration, a proxy for necroptosis, was also discovered in addition to replication of the well-known association of APOE with AD hallmark neuropathological lesions. Additionally, several nominal associations with AD risk genes were detected for pTDP pathology, α-synuclein lesions and pTau-related pathology. These findings were confirmed in a meta-analysis with three independent cohorts. For example, we replicated a prior association between TPCN1 (rs6489896) and LATE-NC risk. Furthermore, we identified new putative LATE-NC-linked SNPs, including rs7068231, located upstream of ANK3. We found association between BIN1 (rs6733839) and α-synuclein pathology, and replicated a prior association between USP6NL (rs7912495) and Lewy body pathology. Additionally, we also found that UMAD1 (rs6943429) was nominally associated with Lewy body pathology. Overall, these results contribute to a broader general understanding of how AD risk variants discovered in large-scale clinical genome-wide association studies are involved in the pathological mechanisms of AD and indicate the importance of downstream elimination of phenotypic heterogeneity introduced in these studies.

TDP-43 and Alzheimer's Disease Pathology in the Brain of a Harbor Porpoise Exposed to the Cyanobacterial Toxin BMAA.

Cetaceans are well-regarded as sentinels for toxin exposure. Emerging studies suggest that cetaceans can also develop neuropathological changes associated with neurodegenerative disease. The occurrence of neuropathology makes cetaceans an ideal species for examining the impact of marine toxins on the brain across the lifespan. Here, we describe TAR DNA-binding protein 43 (TDP-43) proteinopathy and Alzheimer's disease (AD) neuropathological changes in a beached harbor porpoise (Phocoena phocoena) that was exposed to a toxin produced by cyanobacteria called β-N-methylamino-L-alanine (BMAA). We found pathogenic TDP-43 cytoplasmic inclusions in neurons throughout the cerebral cortex, midbrain and brainstem. P62/sequestosome-1, responsible for the autophagy of misfolded proteins, was observed in the amygdala, hippocampus and frontal cortex. Genes implicated in AD and TDP-43 neuropathology such as APP and TARDBP were expressed in the brain. AD neuropathological changes such as amyloid-β plaques, neurofibrillary tangles, granulovacuolar degeneration and Hirano bodies were present in the hippocampus. These findings further support the development of progressive neurodegenerative disease in cetaceans and a potential causative link to cyanobacterial toxins. Climate change, nutrient pollution and industrial waste are increasing the frequency of harmful cyanobacterial blooms. Cyanotoxins like BMAA that are associated with neurodegenerative disease pose an increasing public health risk.

Ponatinib and dabrafenib reduce the accumulation of necroptosis‐related proteins and neuronal loss in APP23xTAU58 mice.

AbstractBackgroundNeuronal death is the result of the neurodegenerative process in Alzheimer’s disease (AD). Both histopathological hallmark lesions of AD, i.e., amyloid plaques and neurofibrillary tangles, are associated with reduced numbers of neurons in the brain. To model AD‐like neuronal death, mouse models with transgenic overexpression of the amyloid precursor protein (APP) and the tau protein can be used. Recently, the necroptotic cell death pathway was found to be activated in the AD brain. In this context, the activated necrosome was found in granulovacuolar degeneration (GVD) lesions in neurons. Therefore, the question arises whether inhibition of the necroptosis pathway reduces neuron loss.MethodWe analyzed APP23xTAU58 double transgenic mice for the presence of the activated necrosome in GVD lesions in association with amyloid and tau pathology. APP23xTAU58 mice at 2, 6, and 12 months of age were studied (n = 5‐10 animals/group). Neuronal densities in the subiculum and the amygdala were compared with those of wildtype littermates. To clarify whether necroptosis inhibitors can interfere with neuron death in this model, we treated APP23xTAU58 mice from 2‐6 months either with dabrafenib or ponatinib (n = 5 animals/group) and compared neuronal densities with that of vehicle‐treated mice. Neuronal densities as well as the percentage of necroptosis markers exhibiting neurons in the subiculum and amygdala were assessed.ResultSix‐ and 12‐month‐old APP23xTAU58 mice showed significantly decreased neuronal densities in the subiculum and amygdala compared to wildtype mice (p < 0.005), as well as an increased number of neurons exhibiting the necroptosis executor pMLKL in GVD lesions (p < 0.0001). Treatment with the necroptosis inhibitors ponatinib and dabrafenib reduced neuronal loss in the subiculum and the amygdala compared to vehicle treatment (p ≤ 0.0002).ConclusionThese results show that neuron loss in the APP23xTAU58 model is associated with the accumulation of necroptosis‐related proteins. This neuron loss and the expression of necrosome components can be reduced by ponatinib or dabrafenib. Thus, it is tempting to speculate that necroptosis inhibition could be a promising strategy to prolong neuron survival and, by doing so, to slow down cognitive decline in AD patients. Funding: FWO

Single nucleotide polymorphisms linked to Alzheimer’s disease are associated with distinct neuropathological phenotypes

AbstractBackgroundNeurodegenerative brain diseases (NBDs) ultimately result in neuronal loss and subsequent cognitive decline. In Alzheimer’s disease, tau neurofibrillary tangles (NFT) and amyloid plaques are considered as the hallmark lesions, but there are a number of other distinct features that are not exclusive to AD and do occur to a certain extent in other NBDs.MethodWe extracted DNA from a cohort of 382 post‐mortem brains of NBD patients and controls with detailed neuropathological characterization. Genotyping of 85 genetic loci, previously found to be associated with AD, is ongoing using an in‐house developed oxford nanopore technologies (ONT) multiplex assay, allowing simultaneous sequencing of all variants on an ONT Flongle platform. Base‐ calling, alignment to Hg38 and variant calling were performed followed by QC on the data and regression analysis.ResultAssociation testing has currently been performed for 59 of the total 85 SNPs in the assay using either linear or logistic regression. This revealed significant association for an AD risk variant in the SIGLEC11 locus and Braak NFT staging (p = 0.003) and NIA_AA score (p = 0.002). Significance was also found for a risk variant in the EPHA1 locus and Hirano body score (p = 0.008). Furthermore, we found numerous nominally significant associations between risk loci and TDP43 LATE, granulovacuolar degeneration, phases of amyloid plaque distribution and CAA severity.ConclusionThese results possibly highlight biological pathways involved in generating these additional features. Our ongoing work is currently focusing on increasing our sample size to further validate the associations we discovered and optimizing our ONT assay.

Necroptosis and Alzheimer's Disease: Pathogenic Mechanisms and Therapeutic Opportunities.

Alzheimer's disease (AD) is considered to be the most common neurodegenerative disease, with clinical symptoms encompassing progressive memory loss and cognitive impairment. Necroptosis is a form of programmed necrosis that promotes cell death and neuroinflammation, which further mediates the pathogenesis of several neurodegenerative diseases, especially AD. Current evidence has strongly suggested that necroptosis is activated in AD brains, resulting in neuronal death and cognitive impairment. We searched the PubMed database, screening all articles published before September 28, 2022 related to necroptosis in the context of AD pathology. The keywords in the search included: "necroptosis", "Alzheimer's disease", "signaling pathways", "Aβ", Aβo", "Tau", "p-Tau", "neuronal death", "BBB damage", "neuroinflammation", "microglia", "mitochondrial dysfunction", "granulovacuolar degeneration", "synaptic loss", "axonal degeneration", "Nec-1", "Nec-1s", "GSK872", "NSA", "OGA", "RIPK1", "RIPK3", and "MLKL". Results show that necroptosis has been involved in multiple pathological processes of AD, including amyloid-β aggregation, Tau accumulation, neuronal death, and blood-brain barrier damage, etc. More importantly, existing research on AD necroptosis interventions, including drug intervention and potential gene targets, as well as its current clinical development status, was discussed. Finally, the issues pertaining to necroptosis in AD were presented. Accordingly, this review may provide further insight into clinical perspectives and challenges for the future treatment of AD by targeting the necroptosis pathway.

Structurally and Morphologically Distinct Pathological Tau Assemblies Differentially Affect GVB Accumulation.

Tau aggregation is central to the pathogenesis of a large group of neurodegenerative diseases termed tauopathies, but it is still unclear in which way neurons respond to tau pathology and how tau accumulation leads to neurodegeneration. A striking neuron-specific response to tau pathology is presented by granulovacuolar degeneration bodies (GVBs), lysosomal structures that accumulate specific cargo in a dense core. Here we employed different tau aggregation models in primary neurons to investigate which properties of pathological tau assemblies affect GVB accumulation using a combination of confocal microscopy, transmission electron microscopy, and quantitative automated high-content microscopy. Employing GFP-tagged and untagged tau variants that spontaneously form intraneuronal aggregates, we induced pathological tau assemblies with a distinct subcellular localization, morphology, and ultrastructure depending on the presence or absence of the GFP tag. The quantification of the GVB load in the different models showed that an increased GVB accumulation is associated with the untagged tau aggregation model, characterized by shorter and more randomly distributed tau filaments in the neuronal soma. Our data indicate that tau aggregate structure and/or subcellular localization may be key determinants of GVB accumulation.

Neuropathology and morphometry of dentate nucleus neurons in DYT1 brains: Cerebellar abnormalities in isolated dystonia.

Brain lesions exclusive to dystonia, or specific forms of it, such as isolated dystonia, have been rarely described. While the identification of distinctive intra- or extraneuronal abnormalities in childhood-onset generalized dystonia (DYT1) brains remains lacking, recent stereology-based findings demonstrated hypertrophy of neurons in the substantia nigra (SN) of DYT1-carriers manifesting dystonia (DYT1-manif) versus DYT1-carriers nonmanifesting dystonia (DYT1-nonmanif), and age-matched control subjects (C). Because other brain regions including the cerebellum (CRB) have been implicated in the pathomechanisms of dystonia, we investigated neurons of the dentate nucleus (DN), the "door-out" nucleus of the CRB. We performed systematic neuropathologic assessments and stereology-based measurements of 7 DN from DYT1-carriers (DYT1-DN; 4 DYT1-manif and 3 DYT1-nonmanif), and 5 age-matched control (C-DN) subjects. Data demonstrated larger cell body (+14.1%), nuclear (+10.6%), and nucleolar (+48.3%) volumes of DYT1-DN versus C-DN neurons. No differences in intra- and extracellular pathological indicators (β-amyloid, pTau, α-synuclein, Torsin1A, Negri, Bunina, Hirano, Marinesco, Nissl bodies, Buscaino bodies, granulovacuolar degeneration, or cerebrovascular lesions) were detected in DYT1-DN versus C-DN. Astroglial reactivity (GFAP) and microglial activation (IBA1) were observed in some DYT1-DNs. These novel findings confirm involvement of the DN and CRB in the pathogenesis of DYT1 and perhaps of other forms of isolated dystonia.

Predicting Alzheimer’s Disease from Clinical Dementia Rating, Estimated Total Intracranial Volume, Atlas Scaling Factor: Incorporating Ensemble Approach into Automated Machine Learning (P12-6.010)

<h3>Objective:</h3> With artificial intelligence (particularly machine learning) exhibiting superior predictive and prognosticative capabilities when compared with conventional statistical techniques, for neurological as well as non-neurological conditions, we explored automated Machine Learning to predict AD using variables such as socioeconomic status, Normalized Whole Brain Volume and Atlas Scaling Factor. <h3>Background:</h3> Alzheimer’s Disease (AD) is a debilitating disease associated with the pathognomonic deposition of neurofibrillary tangles and neuritic plaques along with characteristic amyloid angiopathy-driven hippocampal granulovacuolar degeneration and Meynert’s nucleus neuronal loss. <h3>Design/Methods:</h3> The data was adopted as shared on Kaggle. The study population comprised 373 human subjects (Female subjects = 57%; Range of age = 60–98). Variables include years of education, socioeconomic status and MMSE scores. The current state of the art for aML was adopted to develop classification models using algorithms including Extreme Gradient Boosting, Random Forest and Neural Network. The models were stacked after implementation of hyperparameter tuning, via insertion of random features and boosting on errors. Ensemble approach, which is the amalgamation of two or more than two algorithmic models to develop a model better than either of its computive components, was superimposed on stacked models. The mwA-AUROC area gauged the discriminating ability of models, with the highest value of 1 indicating perfect discriminative classification ability. <h3>Results:</h3> An ensemble of CatBoost, Nearest Neighbours and Neural Network algorithmic models with incorporated K-means features and boost on errors achieved an mwA-AUROC of 0.96 with a close-to perfect AD detection score. The respective model did not perform well in classifying converted patients. The ensemble model exhibited the least log loss among all developed algorithmic models. <h3>Conclusions:</h3> Such predictive models, when deployed on cloud, would serve to improve the management of the respective patient as well as the resource allocation, ultimately translating into significant reduction of morbidity and mortality associated with this enfeebling condition. <b>Disclosure:</b> Mr. Bangash has nothing to disclose. Miss Batool has nothing to disclose.

The correlation between neuropathology levels and cognitive performance in centenarians.

Neuropathological substrates associated with neurodegeneration occur in brains of the oldest old. How does this affect cognitive performance? The 100-plus Study is an ongoing longitudinal cohort study of centenarians who self-report to be cognitively healthy; post mortem brain donation is optional. In 85 centenarian brains, we explored the correlations between the levels of 11 neuropathological substrates with ante mortem performance on 12 neuropsychological tests. Levels of neuropathological substrates varied: we observed levels up to Thal-amyloid beta phase 5, Braak-neurofibrillary tangle (NFT) stage V, Consortium to Establish a Registry for Alzheimer's Disease (CERAD)-neuritic plaque score 3, Thal-cerebral amyloid angiopathy stage 3, Tar-DNA binding protein 43 (TDP-43) stage 3, hippocampal sclerosis stage 1, Braak-Lewy bodies stage 6, atherosclerosis stage 3, cerebral infarcts stage 1, and cerebral atrophy stage 2. Granulovacuolar degeneration occurred in all centenarians. Some high performers had the highest neuropathology scores. Only Braak-NFT stage and limbic-predominant age-related TDP-43 encephalopathy (LATE) pathology associated significantly with performance across multiple cognitive domains. Of all cognitive tests, the clock-drawing test was particularly sensitive to levels of multiple neuropathologies.

Friend or foe: role of pathological tau in neuronal death.

Neuronal death is one of the most common pathological hallmarks of diverse neurological diseases, which manifest varying degrees of cognitive or motor dysfunction. Neuronal death can be classified into multiple forms with complicated and unique regulatory signaling pathways. Tau is a key microtubule-associated protein that is predominantly expressed in neurons to stabilize microtubules under physiological conditions. In contrast, pathological tau always detaches from microtubules and is implicated in a series of neurological disorders that are characterized by irreversible neuronal death, such as necrosis, apoptosis, necroptosis, pyroptosis, ferroptosis, autophagy-dependent neuronal death and phagocytosis by microglia. However, recent studies have also revealed that pathological tau can facilitate neuron escape from acute apoptosis, delay necroptosis through its action on granulovacuolar degeneration bodies (GVBs), and facilitate iron export from neurons to block ferroptosis. In this review, we briefly describe the current understanding of how pathological tau exerts dual effects on neuronal death by acting as a double-edged sword in different neurological diseases. We propose that elucidating the mechanism by which pathological tau affects neuronal death is critical for exploring novel and precise therapeutic strategies for neurological disorders.

Expression of Concern: Molecular Markers for Granulovacuolar Degeneration Are Present in Rimmed Vacuoles.

Expression of Concern: Molecular Markers for Granulovacuolar Degeneration Are Present in Rimmed Vacuoles.

Granulovacuolar degeneration bodies are independently induced by tau and α-synuclein pathology

BackgroundGranulovacuolar degeneration bodies (GVBs) are intracellular vesicular structures that commonly accompany pathological tau accumulations in neurons of patients with tauopathies. Recently, we developed the first model for GVBs in primary neurons, that requires exogenous tau seeds to elicit tau aggregation. This model allowed the identification of GVBs as proteolytically active lysosomes induced by tau pathology. GVBs selectively accumulate cargo in a dense core, that shows differential and inconsistent immunopositivity for (phosphorylated) tau epitopes. Despite the strong evidence connecting GVBs to tau pathology, these structures have been reported in neurons without apparent pathology in brain tissue of tauopathy patients. Additionally, GVBs and putative GVBs have also been reported in the brain of patients with non-tau proteinopathies. Here, we investigated the connection between pathological protein assemblies and GVBs in more detail.MethodsThis study combined newly developed primary neuron models for tau and α-synuclein pathology with observations in human brain tissue from tauopathy and Parkinson’s disease patients. Immunolabeling and imaging techniques were employed for extensive characterisation of pathological proteins and GVBs. Quantitative data were obtained by high-content automated microscopy as well as single-cell analysis of confocal images.ResultsEmploying a novel seed-independent neuronal tau/GVB model, we show that in the context of tauopathy, GVBs are inseparably associated with the presence of cytosolic pathological tau and that intracellular tau aggregation precedes GVB formation, strengthening the causal relationship between pathological accumulation of tau and GVBs. We also report that GVBs are inseparably associated with pathological tau at the single-cell level in the hippocampus of tauopathy patients. Paradoxically, we demonstrate the presence of GVBs in the substantia nigra of Parkinson’s disease patients and in a primary neuron model for α-synuclein pathology. GVBs in this newly developed α-synuclein/GVB model are induced in the absence of cytosolic pathological tau accumulations. GVBs in the context of tau or α-synuclein pathology showed similar immunoreactivity for different phosphorylated tau epitopes. The phosphorylated tau immunoreactivity signature of GVBs is therefore independent of the presence of cytosolic tau pathology.ConclusionOur data identify the emergence of GVBs as a more generalised response to cytosolic protein pathology.

LATE-NC aggravates GVD-mediated necroptosis in Alzheimer’s disease

It has become evident that Alzheimer’s Disease (AD) is not only linked to its hallmark lesions—amyloid plaques and neurofibrillary tangles (NFTs)—but also to other co-occurring pathologies. This may lead to synergistic effects of the respective cellular and molecular players, resulting in neuronal death. One of these co-pathologies is the accumulation of phosphorylated transactive-response DNA binding protein 43 (pTDP-43) as neuronal cytoplasmic inclusions, currently considered to represent limbic-predominant age-related TDP-43 encephalopathy neuropathological changes (LATE-NC), in up to 70% of symptomatic AD cases. Granulovacuolar degeneration (GVD) is another AD co-pathology, which also contains TDP-43 and other AD-related proteins. Recently, we found that all proteins required for necroptosis execution, a previously defined programmed form of neuronal cell death, are present in GVD, such as the phosphorylated necroptosis executioner mixed-lineage kinase domain-like protein (pMLKL). Accordingly, this protein is a reliable marker for GVD lesions, similar to other known GVD proteins. Importantly, it is not yet known whether the presence of LATE-NC in symptomatic AD cases is associated with necroptosis pathway activation, presumably contributing to neuron loss by cell death execution. In this study, we investigated the impact of LATE-NC on the severity of necroptosis-associated GVD lesions, phosphorylated tau (pTau) pathology and neuronal density. First, we used 230 human post-mortem cases, including 82 controls without AD neuropathological changes (non-ADNC), 81 non-demented cases with ADNC, i.e.: pathologically-defined preclinical AD (p-preAD) and 67 demented cases with ADNC. We found that Braak NFT stage and LATE-NC stage were good predictors for GVD expansion and neuronal loss in the hippocampal CA1 region. Further, we compared the impact of TDP-43 accumulation on hippocampal expression of pMLKL-positive GVD, pTau as well as on neuronal density in a subset of nine non-ADNC controls, ten symptomatic AD cases with (ADTDP+) and eight without LATE-NC (ADTDP−). Here, we observed increased levels of pMLKL-positive, GVD-exhibiting neurons in ADTDP+ cases, compared to ADTDP− and controls, which was accompanied by augmented pTau pathology. Neuronal loss in the CA1 region was increased in ADTDP+ compared to ADTDP− cases. These data suggest that co-morbid LATE-NC in AD impacts not only pTau pathology but also GVD-mediated necroptosis pathway activation, which results in an accelerated neuronal demise. This further highlights the cumulative and synergistic effects of comorbid pathologies leading to neuronal loss in AD. Accordingly, protection against necroptotic neuronal death appears to be a promising therapeutic option for AD and LATE.

Intraneuronal sortilin aggregation relative to granulovacuolar degeneration, tau pathogenesis and sorfra plaque formation in human hippocampal formation.

Extracellular β-amyloid (Aβ) deposition and intraneuronal phosphorylated-tau (pTau) accumulation are the hallmark lesions of Alzheimer’s disease (AD). Recently, “sorfra” plaques, named for the extracellular deposition of sortilin c-terminal fragments, are reported as a new AD-related proteopathy, which develop in the human cerebrum resembling the spatiotemporal trajectory of tauopathy. Here, we identified intraneuronal sortilin aggregation as a change related to the development of granulovacuolar degeneration (GVD), tauopathy, and sorfra plaques in the human hippocampal formation. Intraneuronal sortilin aggregation occurred as cytoplasmic inclusions among the pyramidal neurons, co-labeled by antibodies to the extracellular domain and intracellular C-terminal of sortilin. They existed infrequently in the brains of adults, while their density as quantified in the subiculum/CA1 areas increased in the brains from elderly lacking Aβ/pTau, with pTau (i.e., primary age-related tauopathy, PART cases), and with Aβ/pTau (probably/definitive AD, pAD/AD cases) pathologies. In PART and pAD/AD cases, the intraneuronal sortilin aggregates colocalized partially with various GVD markers including casein kinase 1 delta (Ck1δ) and charged multivesicular body protein 2B (CHMP2B). Single-cell densitometry established an inverse correlation between sortilin immunoreactivity and that of Ck1δ, CHMP2B, p62, and pTau among pyramidal neurons. In pAD/AD cases, the sortilin aggregates were reduced in density as moving from the subiculum to CA subregions, wherein sorfra plaques became fewer and absent. Taken together, we consider intraneuronal sortilin aggregation an aging/stress-related change implicating protein sorting deficit, which can activate protein clearance responses including via enhanced phosphorylation and hydrolysis, thereby promoting GVD, sorfra, and Tau pathogenesis, and ultimately, neuronal destruction and death.

Mixed Cerebrovascular And Alzheimer’s Type Pathology Mimicking Lewy Body Disease And Its Possible Contribution To the Increased Risk of Developing Cognitive Impairment In Elderly Patients with Bipolar Disorder/Schizophrenia

BackgroundIt has been recently reported that bipolar disorder (BD), as compared to other major adult psychiatric disorders, was associated with an increased risk of developing Parkinson’s disease (PD), cerebrovascular disease (CVD), and dementia in a later life (PMID: 33075191). The similar to BD increased risk of developing dementia was also observed for schizophrenia (SCZ) (PMID: 33075191). Surprisingly, the most common cause of dementia, Alzheimer’s disease (AD) (PMID: 31564456), was absent in elderly BD patients with cognitive impairment when AD was probed by its signature biomarkers in the cerebrospinal fluid (PMID: 26876913). Altogether, these data question AD contribution to the increased risk for dementia development in elderly patients with BD. Therefore, the main objective of this study was to address the above issue by probing postmortem AD related pathology in two brains of 83‐year‐old individuals. The first subject (D1) was diagnosed with BD, SCZ, and PD, whereas the second (D2) had Lewy Body Dementia (LBD). PD, PD dementia, and LBD constitute Lewy Body Disease (PMID: 30665447).ResultsParaffin embedded tissue sections from specific regions of each brain underwent H&amp;E staining, as well as immunohistochemical staining for β‐amyloid and phospho‐tau. Upon examination, Lewy bodies were not observed in D1 and D2 brains and the substantia nigra was well preserved in both brains, thereby not confirming the respective PD and LBD diagnoses. However, D1 brain displayed Alzheimer’s type pathology in the frontal, temporal, and occipital cortices as well as in the hippocampus. The respective pathological features included senile plaques and neurofibrillary tangles (NFTs) in the cortices and hippocampus as well as granulovacuolar degeneration (GVD) in pyramidal neurons of the hippocampus. Interestingly, in the same brain, a strong diffused β‐amyloid staining of potential significance was observed within the cerebellar neurons. Overall, the severity of the respective Alzheimer’s type pathology in D1 brain could be characterized by its clinical stage as mild to moderate. Importantly, there were also vascular changes in D1 brain consistent with hypertensive CVD including hyaline atherosclerosis, microbleeds, and dilated Virchow Robin spaces. Some blood vessels showed β‐amyloid deposits within the vessel wall and lumen which is indicative of amyloid angiopathy. In D2 brain, the AD pathology was also present in the form of NFTs and GVD in the hippocampus and was accompanied by mild neuronal loss in the hippocampus and cortex. Striking vascular pathology including thick‐walled blood vessels with microbleeds was also observed.Conclusionsi) AD could be present in elderly BD/SCZ patients and advance to clinical stage associated with cognitive impairment. ii) CVD in conjunction with AD could mimic Lewy Body Disease and contribute to the increased risk of dementia development in older BD/SCZ patients. iii) A proper diagnosis of dementia associated with mixed CVD/AD pathology in elderly patients with BD/SCZ would be important for their adequate treatment and care.

Cellular localization of p-tau217 in brain and its association with p-tau217 plasma levels

Recent studies highlight phosphorylated tau (p-tau) at threonine tau 217 (p-tau217) as a new promising plasma biomarker for pathological changes implicated in Alzheimer’s disease (AD), but the specific brain pathological events related to the alteration in p-tau217 plasma levels are still largely unknown. Using immunostaining techniques of postmortem AD brain tissue, we show that p-tau217 is found in neurofibrillary tangles (NFTs) and neuropil threads that are also positive for p-tau181, 202, 202/205, 231, and 369/404. The p-tau217, but not the other five p-tau variants, was also prominently seen in vesicles structure positive for markers of granulovacuolar degeneration bodies and multi-vesicular bodies. Further, individuals with a high likelihood of AD showed significantly higher p-tau217 area fraction in 4 different brain areas (entorhinal cortex, inferior temporal gyrus, and superior frontal gyrus) compared to those with Primary age related tauopathy or other non-AD tauopathies. The p-tau217 area fraction correlated strongly with total amyloid-beta (Aβ) and NFT brain load when the whole group was analyzed. Finally, the mean p-tau217 area fraction correlated significantly with p-tau217 concentrations in antemortem collected plasma specifically in individuals with amyloid plaques and not in those without amyloid plaques. These studies highlight differences in cellular localization of different p-tau variants and suggest that plasma levels of p-tau217 reflect an accumulation of p-tau217 in presence of Aβ plaque load.

Dysregulated Protein Phosphorylation as Main Contributor of Granulovacuolar Degeneration at the First Stages of Neurofibrillary Tangles Pathology

The hippocampus of cases with neurofibrillary tangles (NFT) pathology classified as stages I–II, III–IV, and V–VI without comorbidities, and middle-aged (MA) individuals with no NFT pathology, were examined to learn about the composition of granulovacuolar degeneration (GVD). Our results confirm the presence of CK1-δ, p38-P Thr180/Tyr182, SAPK/JNK-P Thr183/Thr185, GSK-3α/β-P Tyr279/Tyr216, and GSK-3β Ser9 in the cytoplasmic granules in a subset of neurons of the CA1 and CA2 subfields of the hippocampus. Also, we identify the presence of PKA α/β-P Thr197, SRC-P Tyr416, PAK1-P Ser199/Ser204, CAMK2A-P Tyr197, and PKCG-P Thr655 in cytoplasmic granules in cases with NFT pathology, but not in MA cases. Our results also confirm the presence of β-catenin-P Ser45/Thr41, IREα-P Ser274, eIF2α-P Ser51, TDP-43-P Ser403-404 (but absent TDP-43), and ubiquitin in cytoplasmic granules. Other components of the cytoplasmic granules are MAP2-P Thr1620/1623, MAP1B-P Thr1265, ADD1-P Ser726, and ADD1/ADD1-P Ser726/Ser713, in addition to several tau species including 3Rtau, 4Rtau, and tau-P Ser262. The analysis of GVD at progressive stages of NFT pathology reveals the early appearance of phosphorylated kinases and proteins in cytoplasmic granules at stages I–II, before the appearance of pre-tangles and NFTs. Most of these granules are not surrounded by LAMP1-positive membranes. Markers of impaired ubiquitin-protesome system, abnormal reticulum stress response, and altered endocytic and autophagic pathways occur in a subpopulation of neurons containing cytoplasmic granules, and they appear later. These observations suggest early phosphorylation of kinases leading to their activation, and resulting in the abnormal phosphorylation of various substrates, including tau, as a main alteration at the first stages of GVD.

Dense core vesicle markers in CSF and cortical tissues of patients with Alzheimer\u2019s disease

BackgroundNew fluid biomarkers for Alzheimer's disease (AD) that reveal synaptic and neural network dysfunctions are needed for clinical practice and therapeutic trial design. Dense core vesicle (DCV) cargos are promising cerebrospinal fluid (CSF) indicators of synaptic failure in AD patients. However, their value as biomarkers has not yet been determined.MethodsImmunoassays were performed to analyze the secretory proteins prohormone convertases PC1/3 and PC2, carboxypeptidase E (CPE), secretogranins SgIII and SgII, and Cystatin C in the cerebral cortex (n = 45, provided by Bellvitge University Hospital) and CSF samples (n = 66, provided by The Sant Pau Initiative on Neurodegeneration cohort) from AD patients (n = 56) and age-matched controls (n = 55).ResultsIn AD tissues, most DCV proteins were aberrantly accumulated in dystrophic neurites and activated astrocytes, whereas PC1/3, PC2 and CPE were also specifically accumulated in hippocampal granulovacuolar degeneration bodies. AD individuals displayed an overall decline of secretory proteins in the CSF. Interestingly, in AD patients, the CSF levels of prohormone convertases strongly correlated inversely with those of neurodegeneration markers and directly with cognitive impairment status.ConclusionsThese results demonstrate marked alterations of neuronal-specific prohormone convertases in CSF and cortical tissues of AD patients. The neuronal DCV cargos are biomarker candidates for synaptic dysfunction and neurodegeneration in AD.