Human PS1 Research Articles

Deficiency of NLRP3 protects cerebral pericytes and attenuates Alzheimer’s pathology in tau-transgenic mice

IntroductionActivation of NLRP3-containing inflammasome, which is responsible for IL-1β maturation, has been shown to contribute to Alzheimer’s disease (AD)-associated pathogenesis in both APP- and tau-transgenic mice. However, effects of NLRP3 on pericytes and subsequent cerebrovascular pathology in AD remain unknown.MethodsNLRP3-deficient and wild-type AD animal models were generated by crossing human P301S tau-transgenic mice and Nlrp3 knockout mice. AD-associated neuroinflammation, tauopathy, vasculature and pericyte coverage in the brain were investigated using immunohistological and molecular biological methods. To investigate how NLRP3 regulates pericyte activation and survival, pericytes from the brains of Nlrp3 knockout and wild-type mice were cultured, treated with IL-1β and H2O2 at different concentrations and analyzed by confocal microscopy and flow cytometry after staining with fluorescently labelled phalloidin, annexin-V and PDGFRβ antibody.ResultsDeficiency of NLRP3 (1) reduced Iba-1, GFAP and AT8 antibody-immunoreactive phosphorylated tau-positive cells, without significantly altering transcription of inflammatory genes, (2) preserved cerebral vasculature and pericyte coverage and up-regulated Osteopontin gene transcription, and (3) improved cognitive function in tau-transgenic mice. In cell culture, NLRP3 deficiency prevented pericyte apoptosis. Treatment with IL-1β or H2O2 increased the expression of PDGFRβ in NLRP3-deficient pericytes, but decreased it in NLRP3 wild-type pericytes in a dose-dependent manner.DiscussionInhibition of NLRP3 can promote pericyte survival, improve cerebrovascular function, and attenuate AD pathology in the brain of tau-transgenic mice. Our study supports NLRP3 as a novel therapeutic target for Alzheimer’s patients.

Artificial intelligence and real decisions: predictive systems and generative AI vs. emotive-cognitive legal deliberations

IntroductionActivation of NLRP3-containing inflammasome, which is responsible for IL-1β maturation, has been shown to contribute to Alzheimer’s disease (AD)-associated pathogenesis in both APP- and tau-transgenic mice. However, effects of NLRP3 on pericytes and subsequent cerebrovascular pathology in AD remain unknown.MethodsNLRP3-deficient and wild-type AD animal models were generated by crossing human P301S tau-transgenic mice and Nlrp3 knockout mice. AD-associated neuroinflammation, tauopathy, vasculature and pericyte coverage in the brain were investigated using immunohistological and molecular biological methods. To investigate how NLRP3 regulates pericyte activation and survival, pericytes from the brains of Nlrp3 knockout and wild-type mice were cultured, treated with IL-1β and H2O2 at different concentrations and analyzed by confocal microscopy and flow cytometry after staining with fluorescently labelled phalloidin, annexin-V and PDGFRβ antibody.ResultsDeficiency of NLRP3 (1) reduced Iba-1, GFAP and AT8 antibody-immunoreactive phosphorylated tau-positive cells, without significantly altering transcription of inflammatory genes, (2) preserved cerebral vasculature and pericyte coverage and up-regulated Osteopontin gene transcription, and (3) improved cognitive function in tau-transgenic mice. In cell culture, NLRP3 deficiency prevented pericyte apoptosis. Treatment with IL-1β or H2O2 increased the expression of PDGFRβ in NLRP3-deficient pericytes, but decreased it in NLRP3 wild-type pericytes in a dose-dependent manner.DiscussionInhibition of NLRP3 can promote pericyte survival, improve cerebrovascular function, and attenuate AD pathology in the brain of tau-transgenic mice. Our study supports NLRP3 as a novel therapeutic target for Alzheimer’s patients.

Impairment of Nrf2 signaling in the hippocampus of P301S tauopathy mice model aligns with the cognitive impairment and the associated neuroinflammation

Mice transgenic for human P301S tau protein exhibit many characteristics of the human tauopathies, including the formation of abundant hyperphoshorylated tau filaments, the associated neuroinflammation and disease phenotype. However, the exact underpinning mechanisms are still not fully addressed that hinder our understanding of the tauopathy diseases and the development of possible therapeutic targets.Methods: In the current study, hippocampus from three disease time points (2, 4 and 6 months) of P301S mice were further characterized in comparison to the age and sex matched control wild type mice (WT) that do not express the transgene. Different spectrum of hippocampal dependent cognitive tests, biochemical and pathological analysis were conducted to understand the disease progression and the associated changes in each stage. Results: Cognitive impairment was manifested as early as 2 months age, prior to the identification of tau aggregation and phosphorylation by immunostaining. P301S mice manifested an increased pro-inflammatory related changes at mRNA transcription level (IL-1b and IL17A) with the progression of the disease and when compared to the WT mice of the same age. Among the identified genes in the current study, the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) genes expression that is considered as the master regulator of an endogenous inducible defense system was significantly impaired in P301S mice by 4 and 6 months when compared to healthy WT controls. A data that was also supported by the immunostaining of the serial brain sections including the both brain stem and hippocampus. The current result is suggesting that the downregulation of Nrf2 gene and the impaired Nrf2 dependent anti-inflammatory mechanisms in P301S mice brain is possibly contributing -among other factors- in the neuroinflammation and tauopathy, and that modulation of Nrf2 signaling impairments can be further investigated as a promising potential therapeutic target for tauopathy.

Effects of an OX2R agonist on migration and removal of tau from mouse brain

Pathological proteins including tau are produced in neurons and released into interstitial fluid (ISF) in a neural activity-dependent manner during wakefulness. Pathological proteins in ISF can be removed from the brain via the glymphatic pathway during nighttime. Thus, in individuals with Alzheimer’s disease (AD) that have dysregulated sleep/wake rhythm, application of orexin receptor 2 (OX2R) agonists during daytime could recover the efflux of pathological proteins to ISF and indirectly promote the glymphatic pathway by improving the quality of nighttime sleep after proper daytime arousal, resulting in increased removal of these proteins from the brain. We investigated this hypothesis using OX-201, a novel OX2R-selective agonist with a 50% effective concentration of 8.0 nM. Diurnal rhythm of tau release into hippocampal ISF correlated well with neuronal activity and wakefulness in wild-type mice. In both wild-type and human P301S tau transgenic mice, OX-201 induced wakefulness and promoted tau release into hippocampal ISF. Human P301S tau transgenic mice, tested under our conditions, showed longer wakefulness time, which differs from individuals with AD. OX-201 treatment over 2 months did not alter hippocampal tau levels. Although further studies are required, at a minimum OX2R agonists may not exacerbate tau accumulation in individuals with tauopathy, including AD.

Presenilin deficiency enhances tau phosphorylation and its secretion.

Alzheimer's disease (AD) is characterized by the accumulation of abnormally folded amyloid β-protein (Aβ) in the brain parenchyma and phosphorylated tau in neurons. Presenilin (PS, PSEN) 1 and PS2 are essential components of γ-secretase, which is responsible for the cleavage of amyloid precursor protein (APP) to generate Aβ. PSEN mutations are associated with tau aggregation in frontotemporal dementia, regardless of the presence or absence of Aβ pathology. However, the mechanism by which PS regulates tau aggregation is still unknown. Here, we found that tau phosphorylation and secretion were significantly increased in PS double-knock-out (PS1/2-/-) fibroblasts compared with wild-type fibroblasts. Tau-positive vesicles in the cytoplasm were significantly increased in PS1/2-/- fibroblasts. Active GSK-3β was increased in PS1/2-/- fibroblasts, and inhibiting GSK3β activity in PS1/2-/- fibroblasts resulted in decreased tau phosphorylation and secretion. Transfection of WT human PS1 and PS2 reduced the secretion of phosphorylated tau and active GSK-3β in PS1/2-/- fibroblasts. However, PS1D257A without γ-secretase activity did not decrease the secretion of phosphorylated tau. Furthermore, nicastrin deficiency also increased tau phosphorylation and secretion. These results suggest that deficient PS complex maturation may increase tau phosphorylation and secretion. Thus, our studies discover a new pathway by which PS regulates tau phosphorylation/secretion and pathology independent of Aβ and suggest that PS serves as a potential therapeutic target for treating neurodegenerative diseases involving tau aggregation.

Brain Slice Derived Nerve Fibers Grow along Microcontact Prints and are Stimulated by Beta-Amyloid(42).

Alzheimer's disease is characterized by extracellular beta-amyloid plaques, intraneuronal tau neurofibrillary tangles and excessive neurodegeneration. The mechanisms of neuron degeneration and the potential of these neurons to form new nerve fibers for compensation remain elusive. The present study aimed to evaluate the impact of beta-amyloid and tau on new formations of nerve fibers from mouse organotypic brain slices connected to collagen-based microcontact prints. Organotypic brain slices of postnatal day 8-10 wild-type mice were connected to established collagen-based microcontact prints loaded with polyornithine to enhance nerve fiber outgrowth. Human beta-amyloid(42) or P301S mutated aggregated tau was co-loaded to the prints. Nerve fibers were immunohistochemically stained with neurofilament antibodies. The physiological activity of outgrown neurites was tested with neurotracer MiniRuby, voltage-sensitive dye FluoVolt, and calcium-sensitive dye Rhod-4. Immunohistochemical staining revealed newly formed nerve fibers extending along the prints derived from the brain slices. While collagen-only microcontact prints stimulated nerve fiber growth, those loaded with polyornithine significantly enhanced nerve fiber outgrowth. Beta-amyloid(42) significantly increased the neurofilament-positive nerve fibers, while tau had only a weak effect. MiniRuby crystals, retrogradely transported along these newly formed nerve fibers, reached the hippocampus, while FluoVolt and Rhod-4 monitored electrical activity in newly formed nerve fibers. Our data provide evidence that intact nerve fibers can form along collagen-based microcontact prints from mouse brain slices. The Alzheimer's peptide beta-amyloid(42) stimulates this growth, hinting at a neuroprotective function when physiologically active. This "brain-on-chip" model may offer a platform for screening bioactive factors or testing drug effects on nerve fiber growth.

Chromogranin A (CgA) Deficiency Attenuates Tauopathy by Altering Epinephrine-Alpha-Adrenergic Receptor Signaling.

Our previous studies have indicated that insulin resistance, hyperglycemia, and hypertension in aged wild-type (WT) mice can be reversed in mice lacking chromogranin-A (CgA-KO mice). These health conditions are associated with a higher risk of Alzheimer's disease (AD). CgA, a neuroendocrine secretory protein has been detected in protein aggregates in the brains of AD patients. Here, we determined the role of CgA in tauopathies, including AD (secondary tauopathy) and corticobasal degeneration (CBD, primary tauopathy). We found elevated levels of CgA in both AD and CBD brains, which were positively correlated with increased phosphorylated tau in the frontal cortex. Furthermore, CgA ablation in a human P301S tau (hTau) transgenic mice (CgA-KO/hTau) exhibited reduced tau aggregation, resistance to tau spreading, and an extended lifespan, coupled with improved cognitive function. Transcriptomic analysis of mice cortices highlighted altered levels of alpha-adrenergic receptors (Adra) in hTau mice compared to WT mice, akin to AD patients. Since CgA regulates the release of the Adra ligands epinephrine (EPI) and norepinephrine (NE), we determined their levels and found elevated EPI levels in the cortices of hTau mice, AD and CBD patients. CgA-KO/hTau mice exhibited reversal of EPI levels in the cortex and the expression of several affected genes, including Adra1 and 2, nearly returning them to WT levels. Treatment of hippocampal slice cultures with EPI or an Adra1 agonist intensified, while an Adra1 antagonist inhibited, tau hyperphosphorylation and aggregation. These findings reveal a critical role of CgA in regulation of tau pathogenesis via the EPI-Adra signaling axis.

Accelerated sarcopenia precedes learning and memory impairments in the P301S mouse model of tauopathies and Alzheimer's disease.

Alzheimer's disease (AD) impairs cognitive functions and peripheral systems, including skeletal muscles. The PS19 mouse, expressing the human tau P301S mutation, shows cognitive and muscular pathologies, reflecting the central and peripheral atrophy seen in AD. We analysed skeletal muscle morphology and neuromuscular junction (NMJ) through immunohistochemistry and advanced image quantification. A factorial Analysis of Variance assessed muscle weight, NCAM expression, NMJ, myofibre type distribution, cross-sectional areas, expression of single or multiple myosin heavy-chain isoforms, and myofibre grouping in PS19 and wild type (WT) mice over their lifespan (1-12months). Significant weight differences in extensor digitorum longus (EDL) and soleus muscles between WT and PS19 mice were noted by 7-8months. For EDL muscle in females, WT weighed 0.0113±0.0005 compared with PS19's 0.0071±0.0008 (P<0.05), and in males, WT was 0.0137±0.0001 versus PS19's 0.0069±0.0006 (P<0.005). Similarly, soleus muscle showed significant differences; females (WT: 0.0084±0.0004; PS19: 0.0057±0.0005, P<0.005) and males (WT: 0.0088±0.0003; PS19: 0.0047±0.0004, P<0.0001). Analysis of the NMJ in PS19 mice revealed a marked reduction in myofibre innervation at 5months, with further decline by 10months. NMJ pre-terminals in PS19 mice became shorter and simpler by 5months, showing a steep decline by 10months. Genotype and age strongly influenced muscle NCAM immunoreactivity, denoting denervation as early as 5-6months in EDL muscle Type II fibres, with earlier effects in soleus muscle Type I and II fibres at 3-4months. Muscle denervation and subsequent myofibre atrophy were linked to a reduction in Type IIB fibres in the EDL muscle and Type IIA fibres in the soleus muscle, accompanied by an increase in hybrid fibres. The EDL muscle showed Type IIB fibre atrophy with WT females at 1505±110μm2 versus PS19's 1208±94μm2, and WT males at 1731±185μm2 versus PS19's 1227±116μm2. Similarly, the soleus muscle demonstrated Type IIA fibre atrophy from 5 to 6months, with WT females at 1194±52μm2 versus PS19's 858±62μm2, and WT males at 1257±43μm2 versus PS19's 1030±55μm2. Atrophy also affected Type IIX, I+IIA, and IIA+IIX fibres in both muscles. The timeline for both myofibre and overall muscle atrophy in PS19 mice was consistent, indicating a simultaneous decline. Progressive and accelerated neurogenic sarcopenia may precede and potentially predict cognitive deficits observed in AD.

A Combination of Heavy Metals and Intracellular Pathway Modulators Induces Alzheimer Disease-like Pathologies in Organotypic Brain Slices.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that is characterized by amyloid-beta (Aβ) plaques and tau neurofibrillary tangles (NFT). Modelling aspects of AD is challenging due to its complex multifactorial etiology and pathology. The present study aims to establish a cost-effective and rapid method to model the two primary pathologies in organotypic brain slices. Coronal hippocampal brain slices (150 µm) were generated from postnatal (day 8-10) C57BL6 wild-type mice and cultured for 9 weeks. Collagen hydrogels containing either an empty load or a mixture of human Aβ42 and P301S aggregated tau were applied to the slices. The media was further supplemented with various intracellular pathway modulators or heavy metals to augment the appearance of Aβ plaques and tau NFTs, as assessed by immunohistochemistry. Immunoreactivity for Aβ and tau was significantly increased in the ventral areas in slices with a mixture of human Aβ42 and P301S aggregated tau compared to slices with empty hydrogels. Aβ plaque- and tau NFT-like pathologies could be induced independently in slices. Heavy metals (aluminum, lead, cadmium) potently augmented Aβ plaque-like pathology, which developed intracellularly prior to cell death. Intracellular pathway modulators (scopolamine, wortmannin, MHY1485) significantly boosted tau NFT-like pathologies. A combination of nanomolar concentrations of scopolamine, wortmannin, MHY1485, lead, and cadmium in the media strongly increased Aβ plaque- and tau NFT-like immunoreactivity in ventral areas compared to the slices with non-supplemented media. The results highlight that we could harness the potential of the collagen hydrogel-based spreading of human Aβ42 and P301S aggregated tau, along with pharmacological manipulation, to produce pathologies relevant to AD. The results offer a novel ex vivo organotypic slice model to investigate AD pathologies with potential applications for screening drugs or therapies in the future.

Interaction Between a High-Fat Diet and Tau Pathology in Mice: Implications for Alzheimer's Disease.

Obesity is a modifiable risk factor for Alzheimer's disease (AD). However, its relation with tau pathology (i.e., aberrant tau protein behavior in tauopathies such as AD) has been inconclusive. This study investigated the interaction between a high-fat diet (HFD) and tau pathology in adult male mice. Transgenic mice overexpressing human P301S Tau (those with the pathology) and wild-type (WT) littermates were subjected to behavioral tests, functional magnetic resonance imaging (fMRI), diffusion tensor imaging (DTI), and western blotting analysis to investigate the effects of prolonged HFD versus regular diet during adulthood. HFD increased body weight in both WT and P301S mice but had minimal effect on blood glucose levels. The brain response to HFD was tau genotype-specific. WT mice exhibited decreased recognition memory and enhanced network connectivity in fMRI, while P301S mice exhibited white matter tract disorganization in DTI as the sole significant finding. The reduction of insulin receptor β, insulin downstream signaling, neuronal nuclear protein, CD68-positive phagocytic activity, and myelin basic protein level were confined to the cortex of WT mice. In contrast to P301S mice, WT mice showed significant changes in the tau protein and its phosphorylation levels along with increased soluble neurofilament light levels in the hippocampus. HFD-induced brain dysfunction and pathological changes were blunted in mice with the pathology and more profound in healthy mice. Our findings highlight the need to consider this interaction between obesity and tau pathology when tailoring treatment strategies for AD and other tauopathies.

Consequences of Pathogenic Tau Expression in Mouse Locus Coeruleus

AbstractBackgroundDuring the early stages of Alzheimer’s disease (AD), patients often suffer from prodromal symptoms such as anxiety, impulsivity, depression, agitation, and sleep disturbances prior to the onset of cognitive impairment. Incidentally, the brainstem noradrenergic locus coeruleus (LC) is the first structure to develop hyperphosphorylated ‘pretangle’ tau pathology in the human brain. Furthermore, norepinephrine (NE) influences several physiological processes such as sleep/wake cycle, arousal, stress, mood, and attention which have been implicated in the prodromal behavioral abnormalities. While clinical studies show significant correlations between LC dysfunction and neuropsychiatric symptoms, a causal relationship between early tau accumulation in the LC and the manifestations of prodromal behaviors remains to be resolved. To explore this, we developed a translationally‐relevant tau mouse model that recapitulates the ‘LC first’ phenomena commonly observed in humans.MethodAdult male and female tyrosine hydroxylase (TH)‐Cre mice aged 4 months underwent intra‐LC infusions with a Cre‐dependent adeno‐associated virus (AAV) expressing mCherry, wild‐type (WT) human tau or P301S mutant human tau (n = 3/group). 3 months post‐infusion, mice underwent a panel of behavioral tests to assess sleep latency, locomotor activity, compulsivity, stress‐induced anxiety‐like behavior, association memory deficits, impulsivity, and attentional impairments. Following behavioral tests, brain sections comprising the LC, hippocampus and prefrontal cortex (PFC) were immunostained with TH to assess for LC integrity, AT8 to detect pretangle tau, NE transporter (NET) to evaluate NE fiber intensity in projection regions, and GFAP and IBA1 to identify neuroinflammatory markers. Immunoreactivity (IR) will be calculated as a measure of fluorescence via ImageJ.ResultIt has been proposed that tau accumulation in the LC may provoke mild to moderate damage in LC neurons, triggering compensatory mechanisms such as LC hyperactivity. It is hypothesized that at 3 months, LC‐specific tau pathology will result in hyperarousal, compulsivity, anxiety‐like behavior, and impulsivity. In tandem, human tau‐expressing mice are expected to display increased TH, reflecting LC hyperactivity, neuroinflammatory markers and reductions in NE fibers in LC‐projecting regions. These findings will be presented in July 2023.ConclusionThis research will elucidate the role of LC in governing prodromal symptoms. Further studies will be needed to assess molecular mechanisms underlying tau‐mediated LC dysfunction in early AD.

SUMOylation impact on synaptotoxicity of tau oligomers

AbstractBackgroundTau oligomers (oTau) secreted by neurons and astrocytes are linked to the propagation of pathology and negatively affect neuronal activity and viability. oTau‐mediated synaptic loss leads to cognitive deficits and manifests the clinical outcomes of Alzheimer’s disease and related tauopathies. Small Ubiquitin‐like MOdifier (SUMO) proteins regulate multiple cellular events and SUMOylation plays pivotal roles in synaptic biology. Changes in SUMO conjugation and function are also linked to AD and related neurodegenerative disorders such as Huntington’s and Parkinson’s disease. The goal of this investigation is to determine the impact of the two main SUMO isoforms, SUMO1 and SUMO2, on oTau related synaptotoxicity.MethodSUMO1 and SUMO2 transgenic mice were generated with expression regulated by the neuron‐specific prion cos‐tet promoter. These in vivo models were used to generate double transgenic mice expressing human SUMO proteins and P301S mutant Tau. Changes in synaptic density and activity and the effects of oTau pathology were investigated with respect to cognitive deficits and long term potentiation (LTP).ResultElevated expression of human SUMO1 lead to impaired synaptic development and increased tau aggregation. SUMO1 transgenics crossed to Tau mutant mice resulted in an accelerated synaptic loss and a more severe disease phenotype as evidenced by LTP impairments and rapid cognitive decline. Conversely, SUMO2 conjugation levels were decreased in the presence of oTau and phospho‐tau pathology indicating a down‐regulation of its function. Enhanced SUMO2 expression in a mouse model of Tau pathology reversed this process and resulted in a significant reduction in oTau‐mediated synaptotoxicity and the associated LTP and cognitive impairments.ConclusionCumulatively, our findings indicate that SUMO1 negative impacts and exacerbates oTau‐related synaptic dysfunction. In contrast, SUMO2 confers substantial neuroprotection and represents a potential therapeutic avenue to counteract oTau‐induced synaptotoxicity in AD.

Multimodal Gamma Stimulation Improves Activity but not Memory in Aged Tgf344-AD Rats.

Multimodal sensory gamma stimulation is a treatment approach for Alzheimers disease that has been shown to improve pathology and memory in transgenic mouse models of Alzheimer's. Because rats are closer to humans in evolution, we tested the hypothesis that the transgenic rat line bearing human APP and PS1, line TgF344-AD, would be a good supplemental candidate to test the efficacy of this treatment. Current therapy approaches under investigation seek to utilize the immune response to minimize or degrade the accumulation of β-amyloid plaque load in mouse models designed to overexpress Aβ. However, many of these models lack some of the hallmarks of Alzheimer's disease, such as hyperphosphorylated tau and neuronal cell loss. The TgF344-AD transgenic rat model is a good candidate to bridge the gap between mouse models and clinical efficacy in humans. The objective of this study was to use multimodal gamma stimulation at light and auditory modalities simultaneously to test whether this enhances memory performance as measured by the object location task and the spontaneous alternation task. In our study, we designed and built a low-cost, easy-to-construct multimodal light and sound gamma stimulator. Our gamma stimulation device was built using an Arduino microcontroller, which drives lights and a speaker at the gamma frequency. We have included in this paper our device's parts, hardware design, and software architecture for easy reproducibility. We then performed an experiment to test the effect of multimodal gamma stimulation on the cognitive performance of fourteen-month-old TgF344-AD rats. Rats were randomly assigned to either an experimental group that received gamma stimulation or a control group that did not. Performance in a Novel Object Location (NOL) task and spontaneous alternation task was evaluated in both groups before and after the treatment. Multimodal gamma stimulation did not improve memory compared to unstimulated TgF344-AD rats. However, the gamma-stimulated rats did spend significantly more time exploring objects in the novel location task than the unstimulated rats. In the spontaneous alternation task, gamma-stimulated rats exhibited significantly greater exploratory activity than unstimulated controls. Multimodal gamma stimulation did not enhance memory performance in the object location task or the spontaneous alternation task. However, in both tasks, the treatment group had improved measures of exploratory activity relative to the untreated group. We conclude that several limitations could have contributed to this mixed effect, including aging complications, different animal models, or light cycle effects.

Human Presenilin-1 delivered by AAV9 rescues impaired γ-secretase activity, memory deficits, and neurodegeneration in Psen mutant mice

Mutations in the Presenilin (PSEN1 and PSEN2) genes are the major cause of early-onset familial Alzheimer's disease (FAD). Presenilin (PS) is the catalytic subunit of the γ-secretase complex, which cleaves type I transmembrane proteins, such as Notch and the amyloid precursor protein (APP), and plays an evolutionarily conserved role in the protection of neuronal survival during aging. FAD PSEN1 mutations exhibit impaired γ-secretase activity in cell culture, in vitro, and knockin (KI) mouse brains, and the L435F mutation is the most severe in reducing γ-secretase activity and is located closest to the active site of γ-secretase. Here, we report that introduction of the codon-optimized wild-type human PSEN1 cDNA by adeno-associated virus 9 (AAV9) results in broadly distributed, sustained, low to moderate levels of human PS1 (hPS1) expression and rescues impaired γ-secretase activity in the cerebral cortex of Psen mutant mice either lacking PS or expressing the Psen1 L435F KI allele, as evaluated by endogenous γ-secretase substrates of APP and recombinant γ-secretase products of Notch intracellular domain and Aβ peptides. Furthermore, introduction of hPS1 by AAV9 alleviates impairments of synaptic plasticity and learning and memory in Psen mutant mice. Importantly, AAV9 delivery of hPS1 ameliorates neurodegeneration in the cerebral cortex of aged Psen mutant mice, as shown by the reversal of age-dependent loss of cortical neurons and elevated microgliosis and astrogliosis. These results together show that moderate hPS1 expression by AAV9 is sufficient to rescue impaired γ-secretase activity, synaptic and memory deficits, and neurodegeneration caused by Psen mutations in mouse models.

Cryo-EM structures of tau filaments from the brains of mice transgenic for human mutant P301S Tau

Mice transgenic for human mutant P301S tau are widely used as models for human tauopathies. They develop neurodegeneration and abundant filamentous inclusions made of human mutant four-repeat tau. Here we used electron cryo-microscopy (cryo-EM) to determine the structures of tau filaments from the brains of Tg2541 and PS19 mice. Both lines express human P301S tau (0N4R for Tg2541 and 1N4R for PS19) on mixed genetic backgrounds and downstream of different promoters (murine Thy1 for Tg2541 and murine Prnp for PS19). The structures of tau filaments from Tg2541 and PS19 mice differ from each other and those of wild-type tau filaments from human brains. The structures of tau filaments from the brains of humans with mutations P301L, P301S or P301T in MAPT are not known. Filaments from the brains of Tg2541 and PS19 mice share a substructure at the junction of repeats 2 and 3, which comprises residues I297-V312 of tau and includes the P301S mutation. The filament core from the brainstem of Tg2541 mice consists of residues K274-H329 of tau and two disconnected protein densities. Two non-proteinaceous densities are also in evidence. The filament core from the cerebral cortex of line PS19 extends from residues G271-P364 of tau. One strong non-proteinaceous density is also present. Unlike the tau filaments from human brains, the sequences following repeat 4 are missing from the cores of tau filaments from the brains of Tg2541 and PS19 mice.

Progressive human-like tauopathy with downstream neurodegeneration and neurovascular compromise in a transgenic rat model

Tauopathies, including frontotemporal dementia (FTD) and Alzheimer’s disease (AD), clinically present with progressive cognitive decline and the deposition of neurofibrillary tangles (NFTs) in the brain. Neurovascular compromise is also prevalent in AD and FTD however the relationship between tau and the neurovascular unit is less understood relative to other degenerative phenotypes. Current animal models confer the ability to recapitulate aspects of the CNS tauopathies, however, existing models either display overaggressive phenotypes, or do not develop neuronal loss or genuine neurofibrillary lesions. In this report, we communicate the longitudinal characterization of brain tauopathy in a novel transgenic rat model, coded McGill-R955-hTau. The model expresses the longest isoform of human P301S tau. Homozygous R955-hTau rats displayed a robust, progressive accumulation of mutated human tau leading to the detection of tau hyperphosphorylation and cognitive deficits accelerating from 14 months of age. This model features extensive tau hyperphosphorylation with endogenous tau recruitment, authentic neurofibrillary lesions, and tau-associated neuronal loss, ventricular dilation, decreased brain volume, and gliosis in aged rats. Further, we demonstrate how neurovascular integrity becomes compromised at aged life stages using a combination of electron microscopy, injection of the tracer horseradish peroxidase and immunohistochemical approaches.

Humanized APOE genotypes influence lifespan independently of tau aggregation in the P301S mouse model of tauopathy

Apolipoprotein (APOE) E4 isoform is a major risk factor of Alzheimer’s disease and contributes to metabolic and neuropathological abnormalities during brain aging. To provide insights into whether APOE4 genotype is related to tau-associated neurodegeneration, we have generated human P301S mutant tau transgenic mice (PS19) that carry humanized APOE alleles (APOE2, APOE3 or APOE4). In aging mice that succumbed to paralysis, PS19 mice homozygous for APOE3 had the longest lifespan when compared to APOE4 and APOE2 homozygous mice (APOE3 > APOE4 ~ APOE2). Heterozygous mice with one human APOE and one mouse Apoe allele did not show any variations in lifespan. At end-stage, PS19 mice homozygous for APOE3 and APOE4 showed equivalent levels of phosphorylated tau burden, inflammation levels and ventricular volumes. Compared to these cohorts, PS19 mice homozygous for APOE2 showed lower induction of phosphorylation on selective epitopes, though the effect sizes were small and variable. In spite of this, the APOE2 cohort showed shorter lifespan relative to APOE3 homozygous mice. None of the cohorts accumulated appreciable levels of phosphorylated tau compartmentalized in the insoluble cell fraction. RNAseq analysis showed that the induction of immune gene expression was comparable across all the APOE genotypes in PS19 mice. Notably, the APOE4 homozygous mice showed additional induction of transcripts corresponding to the Alzheimer’s disease-related plaque-induced gene signature. In human Alzheimer’s disease brain tissues, we found no direct correlation between higher burden of phosphorylated tau and APOE4 genotype. As expected, there was a strong correlation between phosphorylated tau burden with amyloid deposition in APOE4-positive Alzheimer’s disease cases. Overall, our results indicate that APOE3 genotype may confer some resilience to tauopathy, while APOE4 and APOE2 may act through multiple pathways to increase the pathogenicity in the context of tauopathy.

P2X7 receptor inhibition ameliorates ubiquitin–proteasome system dysfunction associated with Alzheimer’s disease

BackgroundOver recent years, increasing evidence suggests a causal relationship between neurofibrillary tangles (NFTs) formation, the main histopathological hallmark of tauopathies, including Alzheimer’s disease (AD), and the ubiquitin–proteasome system (UPS) dysfunction detected in these patients. Nevertheless, the mechanisms underlying UPS failure and the factors involved remain poorly understood. Given that AD and tauopathies are associated with chronic neuroinflammation, here, we explore if ATP, one of the danger-associated molecules patterns (DAMPs) associated with neuroinflammation, impacts on AD-associated UPS dysfunction.MethodsTo evaluate if ATP may modulate the UPS via its selective P2X7 receptor, we combined in vitro and in vivo approaches using both pharmacological and genetic tools. We analyze postmortem samples from human AD patients and P301S mice, a mouse model that mimics pathology observed in AD patients, and those from the new transgenic mouse lines generated, such as P301S mice expressing the UPS reporter UbG76V-YFP or P301S deficient of P2X7R.ResultsWe describe for the first time that extracellular ATP-induced activation of the purinergic P2X7 receptor (P2X7R) downregulates the transcription of β5 and β1 proteasomal catalytic subunits via the PI3K/Akt/GSK3/Nfr2 pathway, leading to their deficient assembly into the 20S core proteasomal complex, resulting in a reduced proteasomal chymotrypsin-like and postglutamyl-like activities. Using UPS-reported mice (UbGFP mice), we identified neurons and microglial cells as the most sensitive cell linages to a P2X7R-mediated UPS regulation. In vivo pharmacological or genetic P2X7R blockade reverted the proteasomal impairment developed by P301S mice, which mimics that were detected in AD patients. Finally, the generation of P301S;UbGFP mice allowed us to identify those hippocampal cells more sensitive to UPS impairment and demonstrate that the pharmacological or genetic blockade of P2X7R promotes their survival.ConclusionsOur work demonstrates the sustained and aberrant activation of P2X7R caused by Tau-induced neuroinflammation contributes to the UPS dysfunction and subsequent neuronal death associated with AD, especially in the hippocampus.

E2511, a novel small compound TrkA biased positive allosteric modulator, reinnervates cholinergic neuron and activates cholinergic functions in non‐clinical studies

AbstractBackgroundCholinergic innervation is particularly vulnerable in many neurodegenerative diseases associated with cognitive dysfunction, and loss of cholinergic neurons in Alzheimer’s disease (AD) is pathogenic event observed from early stage correlated with cognitive impairment. Nerve growth factor (NGF) plays a major role in the maintenance and function of cholinergic neurons, and a decrease in trophic signalling by NGF‐Tropomyosin receptor kinase A (TrkA) contributes to cholinergic neurodegeneration and cognitive decline during the course of AD. The activation of NGF‐induced trophic signal could be a promising therapy for the neurodegenerative diseases including AD, reinnervating and maintaining cholinergic neurons to functional status. E2511 was identified as a novel small compound TrkA biased positive allosteric modulator that can enhance specific trophic signal of NGF signal without induction of NGF‐like adverse effect via direct binding to TrkA in primary neuron culture and animal model. We present evidence that E2511 induced functional restoration of cholinergic neuron in animal model and rats.MethodThe trophic effect of E2511 on cholinergic neurons was assessed by biochemical studies such as western blotting and immunohistochemistry in human Tau P301S transgenic mice (Tau tg mice) following once‐daily oral administrations of E2511 for 3 months. E2511 TrkA downstream trophic effects on acetylcholine (ACh) were evaluated in cerebrospinal fluid (CSF) collected from cisterna magna in normal SD rats treated with once‐daily oral E2511 for 14 days, using an original LCMS method.ResultChronic administration of E2511 demonstrated reinnervative effects on cholinergic presynapses as well as a correlation with improvement of the number of cholinergic neurons in Tau tg mice. In SD rats, CSF ACh increased in a dose‐dependent manner at exposures associated with cholinergic reinnervation, with changes also correlating with increases in choline acetyltransferase mRNA level. These results suggest that CSF ACh may be a useful marker to establish the E2511 effective dose in humans.ConclusionE2511 functionally reinnervates cholinergic neuronal network in the Tau tg mice. CSF ACh increased in a dose‐related manner in SD rats. CSF ACh may be used as a pharmacodynamic marker to establish the dose showing the reinnervative effect of E2511 in clinical studies.

Aβ1-6A2V(D) peptide, effective on Aβ aggregation, inhibits tau misfolding and protects the brain after traumatic brain injury

Alzheimer’s disease (AD), the leading cause of dementia in older adults, is a double proteinopathy characterized by amyloid-β (Aβ) and tau pathology. Despite enormous efforts that have been spent in the last decades to find effective therapies, late pharmacological interventions along the course of the disease, inaccurate clinical methodologies in the enrollment of patients, and inadequate biomarkers for evaluating drug efficacy have not allowed the development of an effective therapeutic strategy. The approaches followed so far for developing drugs or antibodies focused solely on targeting Aβ or tau protein. This paper explores the potential therapeutic capacity of an all-D-isomer synthetic peptide limited to the first six amino acids of the N-terminal sequence of the A2V-mutated Aβ, Aβ1-6A2V(D), that was developed following the observation of a clinical case that provided the background for its development. We first performed an in-depth biochemical characterization documenting the capacity of Aβ1-6A2V(D) to interfere with the aggregation and stability of tau protein. To tackle Aβ1-6A2V(D) in vivo effects against a neurological decline in genetically predisposed or acquired high AD risk mice, we tested its effects in triple transgenic animals harboring human PS1(M146 V), APP(SW), and MAPT(P301L) transgenes and aged wild-type mice exposed to experimental traumatic brain injury (TBI), a recognized risk factor for AD. We found that Aβ1-6A2V(D) treatment in TBI mice improved neurological outcomes and reduced blood markers of axonal damage. Exploiting the C. elegans model as a biosensor of amyloidogenic proteins’ toxicity, we observed a rescue of locomotor defects in nematodes exposed to the brain homogenates from TBI mice treated with Aβ1-6A2V(D) compared to TBI controls. By this integrated approach, we demonstrate that Aβ1-6A2V(D) not only impedes tau aggregation but also favors its degradation by tissue proteases, confirming that this peptide interferes with both Aβ and tau aggregation propensity and proteotoxicity.