Familial Alzheimer's Disease Research Articles

The Adult Neurogenesis Theory of Alzheimer's Disease.

Alzheimer's disease starts in neural stem cells (NSCs) in the niches of adult neurogenesis. All primary factors responsible for pathological tau hyperphosphorylation are inherent to adult neurogenesis and migration. However, when amyloid pathology is present, it strongly amplifies tau pathogenesis. Indeed, the progressive accumulation of extracellular amyloid-β deposits in the brain triggers a state of chronic inflammation by microglia. Microglial activation has a significant pro-neurogenic effect that fosters the process of adult neurogenesis and supports neuronal migration. Unfortunately, this "reactive" pro-neurogenic activity ultimately perturbs homeostatic equilibrium in the niches of adult neurogenesis by amplifying tau pathogenesis in AD. This scenario involves NSCs in the subgranular zone of the hippocampal dentate gyrus in late-onset AD (LOAD) and NSCs in the ventricular-subventricular zone along the lateral ventricles in early-onset AD (EOAD), including familial AD (FAD). Neuroblasts carrying the initial seed of tau pathology travel throughout the brain via neuronal migration driven by complex signals and convey the disease from the niches of adult neurogenesis to near (LOAD) or distant (EOAD) brain regions. In these locations, or in close proximity, a focus of degeneration begins to develop. Then, tau pathology spreads from the initial foci to large neuronal networks along neural connections through neuron-to-neuron transmission.

Genetic protection from early-onset familial Alzheimer's disease.

Genetic protection from early-onset familial Alzheimer's disease.

Weak-hyperactive hippocampal CA1 neurons in the prodromal stage of Alzheimer's disease in hybrid AppNL-G-F/NL-G-F × Thy1-GCaMP6s+/− mice suggest disrupted plasticity

This study investigated the impact of familial Alzheimer's disease (AD)-linked amyloid precursor protein (App) mutations on hippocampal CA1 neuronal activity and function at an early disease stage in AppNL-G-F/NL-G-F × Thy1-GCaMP6s+/− (A-TG) mice using calcium imaging. Longitudinal assessment of spatial behavior at 12 and 18 months of age identified an early disease stage at 12 months when there was significant amyloid beta pathology with mild behavioral deficits. Hippocampal CA1 neuronal activity and event-related encoding of distance and time were therefore assessed at 12 months of age in several configurations of an air-induced running task to assess the dynamics of cellular activity. Neurons in A-TG mice displayed diminished (weaker) and more frequent (hyperactive) neuronal firing that was more pronounced during movement compared to immobility. Responsive neurons showed configuration-specific deficits in distance and time encoding with impairment in adapting their responses to changing configurations. These results suggest that at an early stage of AD in the absence of full-blown behavioral deficits, weak-hyperactive neuronal activity may induce impairments in sensory perception of changing environments.

The Cleavage-Specific Tau 12A12mAb Exerts an Anti-Amyloidogenic Action by Modulating the Endocytic and Bioenergetic Pathways in Alzheimer's Disease Mouse Model.

Beyond deficits in hippocampal-dependent episodic memory, Alzheimer's Disease (AD) features sensory impairment in visual cognition consistent with extensive neuropathology in the retina. 12A12 is a monoclonal cleavage specific antibody (mAb) that in vivo selectively neutralizes the AD-relevant, harmful N-terminal 20-22 kDa tau fragment(s) (i.e., NH2htau) without affecting the full-length normal protein. When systemically injected into the Tg2576 mouse model overexpressing a mutant form of Amyloid Precursor Protein (APP), APPK670/671L linked to early onset familial AD, this conformation-specific tau mAb successfully reduces the NH2htau accumulating both in their brain and retina and, thus, markedly alleviates the phenotype-associated signs. By means of a combined biochemical and metabolic experimental approach, we report that 12A12mAb downregulates the steady state expression levels of APP and Beta-Secretase 1 (BACE-1) and, thus, limits the Amyloid beta (Aβ) production both in the hippocampus and retina from this AD animal model. The local, antibody-mediated anti-amyloidogenic action is paralleled in vivo by coordinated modulation of the endocytic (BIN1, RIN3) and bioenergetic (glycolysis and L-Lactate) pathways. These findings indicate for the first time that similar molecular and metabolic retino-cerebral pathways are modulated in a coordinated fashion in response to 12A12mAb treatment to tackle the neurosensorial Aβ accumulation in AD neurodegeneration.

Increased white matter hyperintensity burden on MRI in autosomal dominant familial compared to young onset sporadic Alzheimer’s disease.

AbstractBackgroundWhite matter hyperintensities (WMH) on MRI may be observed in familial and sporadic AD. However, studies comparing WMH burden between these two groups are lacking. We conducted this study to evaluate the load and distribution of WMH in individuals with autosomal dominant familial Alzheimer’s disease (FAD) and young onset sporadic AD (SAD), their relationship to grey matter volumes and to neuropsychological test scores (NPT).MethodIn this cross‐sectional study, we evaluated global and local differences in WMH severity on MRI in 19 individuals with symptomatic FAD due to Presenilin 1 mutations, 20 individuals with young onset SAD and 19 healthy control subjects, controlling for age, cerebrovascular risk (CVR) and APOEε4 carrier status. Relationships between WMH, grey matter (GM) volumes and NPT were also investigated.ResultThe FAD group had higher WMH load in all the areas considered apart from juxta‐cortical and periventricular layers when compared to the SAD group. The two groups were well matched for disease duration and severity of cognitive impairment as assessed by the MMSE. APOEε4 genotype and cardiovascular risk factors acted as negative confounders in the identified differences in WMH volumes. There was no association between WMH and GM volumes or NPT in either AD group.ConclusionDespite their young age and minimal CVR, the FAD group in this study had a higher load of WMH compared to the SAD group, suggesting that WMH may reflect aspects of AD pathology that are particularly prominent in FAD. Our analysis suggests that APOEε4 genotype and cardiovascular risk factors may have a greater influence on WMH burden in SAD than in FAD. Furthermore, we did not identify a correlation between WMH load and GM volumes in either group, suggesting that WMH are not merely correlates of GM pathology in AD but may represent independent features of the disease.

Differential effects of familial Alzheimer’s disease-causing mutations on amyloid precursor protein (APP) trafficking, proteolytic conversion, and synaptogenic activity

The amyloid precursor protein (APP) is a key player in Alzheimer`s disease (AD) and the precursor of the Aβ peptide, which is generated by consecutive cleavages of β- and γ-secretases. Familial Alzheimer’s disease (FAD) describes a hereditary subgroup of AD that represents a low percentage of AD cases with an early onset of the disease. Different APP FAD mutations are thought to have qualitatively different effects on its proteolytic conversion. However, few studies have explored the pathogenic and putative physiological differences in more detail. Here, we compared different FAD mutations, located at the β- (Swedish), α- (Flemish, Arctic, Iowa) or γ-secretase (Iberian) cleavage sites. We examined heterologous expression of APP WT and FAD mutants in non-neuronal cells and their impact on presynaptic differentiation in contacting axons of co-cultured neurons. To decipher the underlying molecular mechanism, we tested the subcellular localization, the endocytosis rate and the proteolytic processing in detail by immunoprecipitation–mass spectrometry. Interestingly, we found that only the Iberian mutation showed altered synaptogenic function. Furthermore, the APP Iowa mutant shows significantly decreased α-secretase processing which is in line with our results that APP carrying the Iowa mutation was significantly increased in early endosomes. However, most interestingly, immunoprecipitation–mass spectrometry analysis revealed that the amino acid substitutions of APP FAD mutants have a decisive impact on their processing reflected in altered Aβ profiles. Importantly, N-terminally truncated Aβ peptides starting at position 5 were detected preferentially for APP Flemish, Arctic, and Iowa mutants containing amino acid substitutions around the α-secretase cleavage site. The strongest change in the ratio of Aβ40/Aβ42 was observed for the Iberian mutation while APP Swedish showed a substantial increase in Aβ1–17 peptides. Together, our data indicate that familial AD mutations located at the α-, β-, and γ-secretase cleavage sites show considerable differences in the underlying pathogenic mechanisms.

Effects of long‐term oral treatment with a novel estrogen receptor beta agonist on memory, vasomotor, and anxiety outcomes in an EFAD mouse model of Alzheimer’s disease

AbstractBackgroundThe prevalence and severity of Alzheimer’s disease (AD) are increased by female sex, apolipoprotein E (APOE) genotype, and age, such that postmenopausal female carriers of the Apoe4 allele are at greater risk of developing AD than age‐matched males. Although estrogen therapy shows promise in preventing and reducing menopause‐ and AD‐related symptoms, activation of estrogen receptor alpha (ERa) is associated with increased risk for health concerns, such as breast cancer. Therefore, treatments more selective for estrogen receptor beta (ERb) may provide estrogen‐related health benefits without the risks of activating ERa. Long‐term or acute treatment of wild‐type mice with the novel ERb agonist, EGX358, improves memory and reduces drug‐induced vasomotor alterations. However, efficacy of this compound in an AD model is unknown.MethodFemale APOE‐TR+/+/5xFAD+/− (EFAD) mice expressed five familial AD and were homozygous for human APOE3 (E3FAD) or heterozygous for APOE3 and APOE4 (E3/4FAD). Mice were ovariectomized at 5 months of age and then treated orally with vehicle (1% DMSO) or EGX358 (10 mg/kg/day) via hydrogel for 8 weeks. Mice were weighed weekly and tested for spatial and object memory in the object placement (OP) and object recognition (OR) tasks, respectively. Anxiety‐like behaviors were also tested in the open field and elevated plus maze, and vasomotor symptoms were assessed via tail temperature following injection of the tachykinin receptor 3 agonist, senktide.ResultEGX358 significantly enhanced OR memory in both E3FAD and E3/4FAD mice. However, treatment did not affect OP memory or anxiety in the open field or elevated plus maze. Interestingly, there were significant genotype differences in open field, vasomotor response, and body weight such that E3/4FADs spent more time in the center of open field, had a greater increase in tail temperature following senktide injection, and gained more weight compared to E3FADs.ConclusionOur findings indicate a potential for ERβ‐specific estrogen treatment to improve memory for the identity of objects. Unexpected genotype differences indicate the need to further study how APOE genotype affects anxiety and metabolic outcomes in AD.

Genetic mapping of APP and amyloid‐β biology modulation by trisomy 21

AbstractBackgroundIndividuals who have Down syndrome frequently develop early onset Alzheimer’s disease, a neurodegenerative condition caused by the build‐up of aggregated amyloid‐β and tau proteins in the brain. Amyloid‐β is produced by APP, a gene located on chromosome 21. People who have Down syndrome have three copies of chromosome 21 and thus also an additional copy of APP; this genetic change drives the early development of Alzheimer’s disease in these individuals.MethodsHere we use a combination of next‐generation mouse models of Down syndrome (Tc1, Dp3Tyb Dp(10)2Yey and Dp(17)3Yey) and a knockin mouse model of amyloid‐β accumulation (AppNL‐F) to determine how chromosome 21 genes other than APP modulate APP/amyloid‐β in the brain when in three copies.ResultsWe demonstrate that three copies of other chromosome 21 genes are sufficient to partially ameliorate amyloid‐β accumulation in the brain. We go on to identify a subregion of chromosome 21 that contains the gene/genes causing this decrease in amyloid‐β accumulation and investigate the role of two lead candidate genes Dyrk1a and Bace2.ConclusionThus an additional copy of chromosome 21 genes, other than APP, can modulate APP/amyloid‐β in the brain under physiological conditions. This work provides critical mechanistic insight into the development of disease and an explanation for the typically later age of onset of dementia in people who have AD‐DS compared to those who have familial AD caused by triplication of APP.

Plasma metabolomics indexes time to clinical dementia in autosomal dominant Alzheimer’s disease mutation carriers

AbstractBackgroundMetabolic dysregulation has been implicated in the pathobiology of Alzheimer’s disease (AD), including familial autosomal dominant AD (ADAD). Recent metabolic neuroimaging of preclinical ADAD mutation carriers has suggested that levels of the reactive glial marker myo‐inositol increase with proximity to expected age at dementia onset. It remains unclear, however, if similar metabolic change related to anticipated phenoconversion can be observed at network‐scale in the peripheral plasma metabolome of ADAD mutation carriers.MethodWe collected peripheral blood plasma from ADAD mutation carriers with and without objective cognitive decline (ncarrier = 55) who participated in a longitudinal kindred study. We used untargeted liquid chromatography‐ mass spectrometry (LC‐MS) metabolomics to infer putative metabolic pathway and protein disruptions associated with impending dementia diagnosis at whole‐genome scale. Spearman 𝝆 correlation coefficients were determined for each identified mass feature in relation to clinical, family‐wise estimated years to diagnosis prior to the submission of these summary statistics to metabolomic modeling.ResultA total of 91 LC‐MS mass features were significantly correlated with estimated years to dementia onset, nominal p’s < .05. Pathway‐based, genome‐scale metabolomic modeling analysis revealed a de novo plasma metabolomic activity network composed of interconnected lipid and small, polar metabolite hubs. These same correlations were also submitted to gene‐inferring, whole‐genome metabolomic modeling using PIUmet. Intriguingly, mRNA expression of prioritized genes was not limited to the brain and involved multiple peripheral tissues. In the CNS itself, however, genes prioritized by PIUMet metabolomic modeling frequently demonstrated expression in glia.ConclusionConsistent with prior metabolic findings in ADAD mutation carriers, network alterations to the peripheral plasma metabolome correspond with increasing proximity to expected age of dementia onset. Because neuroinflammation has been previously described as an immunometabolic process in pathological aging, emerging metabolic network disintegrity in ADAD may index reactive glial pathobiology previously suggested by prior metabolic investigations of this population. These perturbed networks inferred from participant blood plasma suggest targetable CNS‐peripheral metabolic dyshomeostases which otherwise precipitate pathobiological “failures of compensation” and concomitant cognitive decline in carriers of Mendelian ADAD mutations.

Human amyloid seeds induce a more profound pathology than seeds from old 3x‐Tg‐AD mice

AbstractBackgroundMost age‐associated neurodegenerative disorders involve the aggregation of specific proteins within the nervous system, as occurs in Alzheimer’s disease (AD). Recent evidence indicates that Aβ can misfold and aggregate into seeds that structurally corrupt native proteins, mimicking a prion‐like process of template protein corruption or seeding. In fact, studies in animal models show that the injection of brain homogenates from AD patients or from aged APP‐transgenic mice containing Aβ aggregates, can induce some of the neuropathological hallmarks of AD. However, it is still unknown which Aβ‐misfolded species are most efficient in triggering the aggregation process. Here, we seek to perform a comparative study to determine whether Aβ seeds from humans vs a familial AD line (the 3xTg‐AD model) is more efficient to generate amyloid aggregates.MethodWe employed histological and molecular approaches to determine amyloid level, species and aggregative capacity of brain homogenates from an AD patient (stage C for amyloid, from the Alzheimer’s Disease Research Center at UCI) vs old‐3xTg‐AD mice (25‐month‐old). Such brain homogenates were injected into the hippocampus of 7‐month‐old 3xTg‐AD mice and the mice were analyzed at 18 months of age.ResultOur findings demonstrated that amyloid seeds from the human patient induce more aggressive amyloid pathology compared to seeds from aged 3xTg‐AD mice.ConclusionThese results suggest that seeds from human patients seem to be more amyloidogenic than from aged 3xTg‐AD mice. Thus, more profound understanding these factors will provide key insight on how amyloid pathology progress in AD.

A unique transgenic model that expressing Aβ oligomers: PS1V97L mutation discovered from Chinese Alzheimer’s disease families

AbstractBackgroundTransgenic mouse models are important tools for studying the pathogenesis of Alzheimer’s Disease (AD) and drug development. Commonly used models are constructed from early‐onset AD mutations in the Caucasian population, and are usually overexpression or knock‐in of multiple pathogenic gene mutations. However, they are not consistent with the genetic characteristics in real world where single gene mutation occurs most of the time. Furthermore, AD transgenic mouse models have been mostly depending on a few institutions/companies and limited by intellectual property protection.MethodWe systematically summarized the research progress of a transgenic mouse model based on a single gene mutation (PS1V97L) found uniquely in Chinese familial AD, as well as the underling mechanisms such as Aβ oligomers (AβO) self‐replication (figure 1). We further compared them with other single‐transgene models, and summarized the preliminary findings of several drugs targeting AβO.ResultPS1V97L transgenic mice showed age‐related AD phenotypes such as Aβ accumulation, tau phosphorylation, neurofibrillary tangles, gliosis, synaptic degeneration and cognitive impairment (figure 2). The unique characteristics of this model is the aggregation of interneuronal AβO in cortex and hippocampus, but no plaques formed up to 24 months. Other mechanisms of PS1V97L model include oxidative stress, inflammation, abnormal energy metabolism, and alterations in AD‐related signaling pathways, such as PI3K/Akt and Nrf2/ARE pathways. Several drugs including sulforaphane, honokiol, tenuifolin, isoliquiritigenin, ginsenoside, butylphthalide and oxiracetam were found effective in PS1V97L mouse model as well as rat and cell models based on AβO mechanism.ConclusionAlthough carrying only one mutation, PS1V97L transgenic mouse model can mimic almost all AD pathological phenotypes, and supports AβO pathogenic hypothesis. It provides important basic and translational tool for exploring the upstream mechanisms, risk factors, and multi‐target drug development in AD.

The neuroprotective N-terminal amyloid-β core hexapeptide reverses reactive gliosis and gliotoxicity in Alzheimer’s disease pathology models

BackgroundAlzheimer’s disease (AD) is a progressive neurodegenerative disorder characterized by accumulation of extracellular amyloid beta (Aβ) and intracellular neurofibrillary tangles, leading to chronic activation of astrocytes and microglia and persistent neuroinflammation. Aβ-linked activation of microglia and astrocytes leads to increased intracellular calcium and production of proinflammatory cytokines, impacting the progression of neurodegeneration. An N-terminal Aβ fragment (Aβ1–15) and a shorter hexapeptide core sequence within the N-Aβ fragment (N-Aβcore: Aβ10–15) have previously been shown to protect against Aβ-induced mitochondrial dysfunction, oxidative stress and apoptosis in neurons and rescue synaptic and spatial memory deficits in an APP/PSEN1 mouse model. Here, we hypothesized that the N-Aβ fragment and N-Aβcore are protective against Aβ-induced gliotoxicity, promoting a neuroprotective environment and potentially alleviating the characteristically persistent neuroinflammation present in AD.MethodsWe treated ex vivo organotypic brain slice cultures from an aged familial AD mouse model, 5xFAD, with the N-Aβcore and used immunocytochemistry to assess the impact on astrogliosis and microgliosis and alterations in synaptophysin-positive puncta engulfed by microglia. Isolated neuron/glia cultures, mixed glial cultures or a microglial cell line were treated with oligomeric human Aβ at concentrations mimicking the pathogenic concentrations (μM) observed in AD in the absence or presence of the non-toxic N-terminal Aβ fragments. Resultant changes in synaptic density, gliosis, oxidative stress, mitochondrial dysfunction, apoptosis, and the expression and release of proinflammatory markers were then determined.ResultsWe demonstrate that the N-terminal Aβ fragments mitigated the phenotypic switch leading to astrogliosis and microgliosis induced by pathological concentrations of Aβ in mixed glial cultures and organotypic brain slice cultures from the transgenic 5xFAD mouse model, while protecting against Aβ-induced oxidative stress, mitochondrial dysfunction and apoptosis in isolated astrocytes and microglia. Moreover, the addition of the N-Aβcore attenuated the expression and release of proinflammatory mediators in microglial cells activated by Aβ and rescued microglia-mediated loss of synaptic elements induced by pathological levels of Aβ.ConclusionsTogether, these findings indicate the protective functions of the N-terminal Aβ fragments extend to reactive gliosis and gliotoxicity induced by Aβ, by preventing or reversing glial reactive states indicative of neuroinflammation and synaptic loss central to AD pathogenesis.

Matrix disequilibrium in Alzheimer's disease and conditions that increase Alzheimer's disease risk.

Alzheimer's Disease (AD) and related dementias are a leading cause of death globally and are predicted to increase in prevalence. Despite this expected increase in the prevalence of AD, we have yet to elucidate the causality of the neurodegeneration observed in AD and we lack effective therapeutics to combat the progressive neuronal loss. Throughout the past 30 years, several non-mutually exclusive hypotheses have arisen to explain the causative pathologies in AD: amyloid cascade, hyper-phosphorylated tau accumulation, cholinergic loss, chronic neuroinflammation, oxidative stress, and mitochondrial and cerebrovascular dysfunction. Published studies in this field have also focused on changes in neuronal extracellular matrix (ECM), which is critical to synaptic formation, function, and stability. Two of the greatest non-modifiable risk factors for development of AD (aside from autosomal dominant familial AD gene mutations) are aging and APOE status, and two of the greatest modifiable risk factors for AD and related dementias are untreated major depressive disorder (MDD) and obesity. Indeed, the risk of developing AD doubles for every 5 years after ≥ 65, and the APOE4 allele increases AD risk with the greatest risk in homozygous APOE4 carriers. In this review, we will describe mechanisms by which excess ECM accumulation may contribute to AD pathology and discuss pathological ECM alterations that occur in AD as well as conditions that increase the AD risk. We will discuss the relationship of AD risk factors to chronic central nervous system and peripheral inflammation and detail ECM changes that may follow. In addition, we will discuss recent data our lab has obtained on ECM components and effectors in APOE4/4 and APOE3/3 expressing murine brain lysates, as well as human cerebrospinal fluid (CSF) samples from APOE3 and APOE4 expressing AD individuals. We will describe the principal molecules that function in ECM turnover as well as abnormalities in these molecular systems that have been observed in AD. Finally, we will communicate therapeutic interventions that have the potential to modulate ECM deposition and turnover in vivo.

Peripheral Administration of the Kv1.3-Blocking Peptide HsTX1[R14A] Improves Cognitive Performance in Senescence Accelerated SAMP8 Mice

Increased expression of the voltage-gated potassium channel Kv1.3 in activated microglia, and the subsequent release of pro-inflammatory mediators, are closely associated with the progression of Alzheimer’s disease (AD). Studies have shown that reducing neuroinflammation through the non-selective blockade of microglial Kv1.3 has the potential to improve cognitive function in mouse models of familial AD. We have previously demonstrated that a potent and highly-selective peptide blocker of Kv1.3, HsTX1[R14A], not only entered the brain parenchyma after peripheral administration in a lipopolysaccharide (LPS)-induced mouse model of inflammation, but also significantly reduced pro-inflammatory mediator release from activated microglia. In this study, we show that microglial expression of Kv1.3 is increased in senescence accelerated mice (SAMP8), an animal model of sporadic AD, and that subcutaneous dosing of HsTX1[R14A] (1 mg/kg) every other day for 8 weeks provided a robust improvement in cognitive deficits in SAMP8 mice. The effect of HsTX1[R14A] on the whole brain was assessed using transcriptomics, which revealed that the expression of genes associated with inflammation, neuron differentiation, synapse function, learning and memory were altered by HsTX1[R14A] treatment. Further study is required to investigate whether these changes are downstream effects of microglial Kv1.3 blockade or a result of alternative mechanisms, including any potential effect of Kv1.3 blockade on other brain cell types. Nonetheless, these results collectively demonstrate the cognitive benefits of Kv1.3 blockade with HsTX1[R14A] in a mouse model of sporadic AD, demonstrating its potential as a therapeutic candidate for this neurodegenerative disease.

PSEN1 E280A Cholinergic-like Neurons and Cerebral Spheroids Derived from Mesenchymal Stromal Cells and from Induced Pluripotent Stem Cells Are Neuropathologically Equivalent.

Alzheimer's disease (AD) is a chronic neurological condition characterized by the severe loss of cholinergic neurons. Currently, the incomplete understanding of the loss of neurons has prevented curative treatments for familial AD (FAD). Therefore, modeling FAD in vitro is essential for studying cholinergic vulnerability. Moreover, to expedite the discovery of disease-modifying therapies that delay the onset and slow the progression of AD, we depend on trustworthy disease models. Although highly informative, induced pluripotent stem cell (iPSCs)-derived cholinergic neurons (ChNs) are time-consuming, not cost-effective, and labor-intensive. Other sources for AD modeling are urgently needed. Wild-type and presenilin (PSEN)1 p.E280A fibroblast-derived iPSCs, menstrual blood-derived menstrual stromal cells (MenSCs), and umbilical cord-derived Wharton Jelly's mesenchymal stromal cells (WJ-MSCs) were cultured in Cholinergic-N-Run and Fast-N-Spheres V2 medium to obtain WT and PSEN 1 E280A cholinergic-like neurons (ChLNs, 2D) and cerebroid spheroids (CSs, 3D), respectively, and to evaluate whether ChLNs/CSs can reproduce FAD pathology. We found that irrespective of tissue source, ChLNs/CSs successfully recapitulated the AD phenotype. PSEN 1 E280A ChLNs/CSs show accumulation of iAPPβ fragments, produce eAβ42, present TAU phosphorylation, display OS markers (e.g., oxDJ-1, p-JUN), show loss of ΔΨm, exhibit cell death markers (e.g., TP53, PUMA, CASP3), and demonstrate dysfunctional Ca2+ influx response to ACh stimuli. However, PSEN 1 E280A 2D and 3D cells derived from MenSCs and WJ-MSCs can reproduce FAD neuropathology more efficiently and faster (11 days) than ChLNs derived from mutant iPSCs (35 days). Mechanistically, MenSCs and WJ-MSCs are equivalent cell types to iPSCs for reproducing FAD in vitro.

The in-tissue molecular architecture of β-amyloid pathology in the mammalian brain

Amyloid plaques composed of Aβ fibrils are a hallmark of Alzheimer’s disease (AD). However, the molecular architecture of amyloid plaques in the context of fresh mammalian brain tissue is unknown. Here, using cryogenic correlated light and electron tomography we report the in situ molecular architecture of Aβ fibrils in the AppNL-G-F familial AD mouse model containing the Arctic mutation and an atomic model of ex vivo purified Arctic Aβ fibrils. We show that in-tissue Aβ fibrils are arranged in a lattice or parallel bundles, and are interdigitated by subcellular compartments, extracellular vesicles, extracellular droplets and extracellular multilamellar bodies. The Arctic Aβ fibril differs significantly from an earlier AppNL-F fibril structure, indicating a striking effect of the Arctic mutation. These structural data also revealed an ensemble of additional fibrillar species, including thin protofilament-like rods and branched fibrils. Together, these results provide a structural model for the dense network architecture that characterises β-amyloid plaque pathology.

Reactive Sulfur Species Omics Analysis in the Brain Tissue of the 5xFAD Mouse Model of Alzheimer's Disease.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder whereby oxidative stress augmentation results in mitochondrial dysfunction and cell death by apoptosis. Emerging evidence indicates that reactive sulfur species (RSS), such as glutathione hydropersulfide (GSSH), is endogenously produced, functions as potent antioxidants, and regulate redox signaling through the formation of protein polysulfides. However, the relationship between RSS and AD pathogenesis is not fully understood. In this study, we analyzed endogenous RSS production in the brain tissue of a familial AD model (5xFAD) mouse using multiple RSS-omics approaches. Memory impairment, increased amyloid plaques, and neuroinflammation have been confirmed in 5xFAD mice. Quantitative RSS omics analysis revealed that the total polysulfide content was significantly decreased in the brains of 5xFAD mice, whereas there was no significant difference in the levels of glutathione, GSSH, or hydrogen sulfide between wild-type and 5xFAD mice. In contrast, a significant decline in the protein polysulfide status was observed in the brains of 5xFAD mice, suggesting that RSS production and subsequent redox signaling might be altered during the onset and progression of AD. Our findings have important implications for understanding the significance of RSS in the development of preventive and therapeutic strategies for AD.

Loss of insulin signaling in astrocytes exacerbates Alzheimer-like phenotypes in a 5xFAD mouse model

Brain insulin signaling controls peripheral energy metabolism and plays a key role in the regulation of mood and cognition. Epidemiological studies have indicated a strong connection between type 2 diabetes (T2D) and neurodegenerative disorders, especially Alzheimer's disease (AD), linked via dysregulation of insulin signaling, i.e., insulin resistance. While most studies have focused on neurons, here, we aim to understand the role of insulin signaling in astrocytes, a glial cell type highly implicated in AD pathology and AD progression. To this end, we created a mouse model by crossing 5xFAD transgenic mice, a well-recognized AD mouse model that expresses five familial AD mutations, with mice carrying a selective, inducible insulin receptor (IR) knockout in astrocytes (iGIRKO). We show that by age 6mo, iGIRKO/5xFAD mice exhibited greater alterations in nesting, Y-maze performance, and fear response than those of mice with the 5xFAD transgenes alone. This was associated with increased Tau (T231) phosphorylation, increased Aβ plaque size, and increased association of astrocytes with plaques in the cerebral cortex as assessed using tissue CLARITY of the brain in the iGIRKO/5xFAD mice. Mechanistically, invitro knockout of IR in primary astrocytes resulted in loss of insulin signaling, reduced ATP production and glycolic capacity, and impaired Aβ uptake both in the basal and insulin-stimulated states. Thus, insulin signaling in astrocytes plays an important role in the control of Aβ uptake, thereby contributing to AD pathology, and highlighting the potential importance of targeting insulin signaling in astrocytes as a site for therapeutics for patients with T2D and AD.

Inhibition of ACAT as a Therapeutic Target for Alzheimer's Disease Is Independent of ApoE4 Lipidation.

APOE4, encoding apolipoprotein E4 (apoE4), is the greatest genetic risk factor for Alzheimer's disease (AD), compared to the common APOE3. While the mechanism(s) underlying APOE4-induced AD risk remains unclear, increasing the lipidation of apoE4 is an important therapeutic target as apoE4-lipoproteins are poorly lipidated compared to apoE3-lipoproteins. ACAT (acyl-CoA: cholesterol-acyltransferase) catalyzes the formation of intracellular cholesteryl-ester droplets, reducing the intracellular free cholesterol (FC) pool. Thus, inhibiting ACAT increases the FC pool and facilitates lipid secretion to extracellular apoE-containing lipoproteins. Previous studies using commercial ACAT inhibitors, including avasimibe (AVAS), as well as ACAT-knock out (KO) mice, exhibit reduced AD-like pathology and amyloid precursor protein (APP) processing in familial AD (FAD)-transgenic (Tg) mice. However, the effects of AVAS with human apoE4 remain unknown. In vitro, AVASinduced apoE efflux at concentrations of AVASmeasured in the brains of treated mice. AVAS treatment of male E4FAD-Tg mice (5xFAD+/-APOE4+/+) at6-8months had no effect on plasma cholesterol levels or distribution, the original mechanism forAVAS treatment of CVD. In the CNS, AVAS reduced intracellular lipid droplets, indirectly demonstrating target engagement. Surrogate efficacy was demonstrated by an increase in Morris water maze measures of memory and postsynaptic protein levels. Amyloid-beta peptide (Aβ) solubility/deposition and neuroinflammation were reduced, critical components of APOE4-modulated pathology. However, there was no increase in apoE4 levels or apoE4 lipidation, while amyloidogenic and non-amyloidogenic processing of APP were significantly reduced. This suggests that the AVAS-induced reduction in Aβ via reduced APP processing was sufficient to reduce AD pathology, as apoE4-lipoproteins remained poorly lipidated.

Differentiated Embryonic Neurospheres from Familial Alzheimer's Disease Model Show Innate Immune and Glial Cell Responses.

Proteins involved in the Alzheimer's disease (AD), such as amyloid precursor protein (APP) and presenilin-1 (PS1), play critical roles in early development of the central nervous system (CNS), as well as in innate immune and glial cell responses. Familial AD is associated with the presence of APPswe and PS1dE9 mutations. However, it is still unknown whether these mutations cause deficits in CNS development of carriers. We studied genome-wide gene expression profiles of differentiated neural progenitor cells (NPCs) from wild-type and APPswe/PS1dE9 mouse embryo telencephalon. The occurrence of strong innate immune and glial cell responses in APPswe/PS1dE9 neurospheres mainly involves microglial activation, inflammatory mediators and chemokines. APPswe/PS1dE9 neurospheres augmented up to 100-fold CCL12, CCL5, CCL3, C3, CX3CR1, TLR2 and TNF-alpha expression levels, when compared to WT neurospheres. Expression levels of the glia cell marker GFAP and microglia marker Iba-1 were up to 20-fold upregulated in APPswe/PS1dE9 neurospheres. The secretome of differentiated APPswe/PS1dE9 NPCs revealed enhanced chemoattraction of peripheral blood mononuclear cells. When evaluating the inferred protein interaction networks constructed from the array data, an improvement in astrocyte differentiation in APPswe/PS1dE9 neurosphereswas evident in view ofincreased GFAPexpression. Transgenic NPCs differentiated into neural phenotypes presented expression patterns of cytokine, glial cells, and inflammatory mediators characteristic of APPswe/PS1dE9 adult animals. Consequently, the neurogenic niche obtained from differentiation of embryonic APPswe/PS1dE9 neurospheres spontaneously presents several alterations observed in adult ADbrains. Finally, our data strengthen pathophysiological hypotheses that propose an early neurodevelopmental origin for familial AD.