Familial Alzheimer's Disease Mutations Research Articles

The novel estrogen receptor beta agonist EGX358 and APOE genotype influence memory, vasomotor, and anxiety outcomes in an Alzheimer’s mouse model

IntroductionAlzheimer’s disease (AD) prevalence and severity are associated with increased age, female sex, and apolipoprotein E4 (APOE4) genotype. Although estrogen therapy (ET) effectively reduces symptoms of menopause including hot flashes and anxiety, and can reduce dementia risk, it is associated with increased risks of breast and uterine cancer due to estrogen receptor alpha (ERβ)-mediated increases in cancer cell proliferation. Because ERβ activation reduces this cell proliferation, selective targeting of ERβ may provide a safer method of improving memory and reducing hot flashes in menopausal women, including those with AD. APOE genotype influences the response to ET, although it is unknown whether effects of ERβ activation vary by genotype.MethodsHere, we tested the ability of long-term oral treatment with a novel highly selective ERβ agonist, EGX358, to enhance object recognition and spatial recognition memory, reduce drug-induced hot flashes, and influence anxiety-like behaviors in female mice expressing 5 familial AD mutations (5xFAD-Tg) and human APOE3 (E3FAD) or APOE3 and APOE4 (E3/4FAD). Mice were ovariectomized at 5 months of age and were then treated orally with vehicle (DMSO) or EGX358 (10 mg/kg/day) via hydrogel for 8 weeks. Spatial and object recognition memory were tested in object placement (OP) and object recognition (OR) tasks, respectively, and anxiety-like behaviors were tested in the open field (OF) and elevated plus maze (EPM). Hot flash-like symptoms (change in tail skin temperature) were measured following injection of the neurokinin receptor agonist senktide (0.5 mg/kg).ResultsEGX358 enhanced object recognition memory in E3FAD and E3/4FAD mice but did not affect spatial recognition memory. EGX358 also reduced senktide-induced tail temperature elevations in E3FAD, but not E3/4FAD, females. EGX358 did not influence anxiety-like behaviors or body weight.DiscussionThese data indicate that highly selective ERβ agonism can facilitate object recognition memory in both APOE3 homozygotes and APOE3/4 heterozygotes, but only reduce the magnitude of a drug-induced hot flash in APOE3 homozygotes, suggesting that APOE4 genotype may blunt the beneficial effects of ET on hot flashes. Collectively, these data suggest a potentially beneficial effect of selective ERβ agonism for memory and hot flashes in females with AD-like pathology, but that APOE genotype plays an important role in responsiveness.

Epileptic seizures induced by pentylenetetrazole kindling accelerate Alzheimer-like neuropathology in 5×FAD mice.

Clinical studies have shown that epileptic seizures worsen Alzheimer's disease (AD) pathology and related cognitive deficits; however, the underlying mechanism is unclear. To assess the effects of seizures on the progression of AD, chronic temporal lobe epilepsy was induced in five familial AD mutation (5×FAD) mice by kindling with the chemoconvulsant pentylenetetrazole (PTZ) at 3-3.5 months of age. The amyloidogenic pathway, tauopathy, synaptic damage, neuronal death, neurological inflammatory response and associated kinase signaling pathway dysregulation were examined at 9 months of age. We found that APP, p-APP, BACE1, Aβ and kinase-associated p-tau levels were elevated after PTZ kindling in 5×FAD mice. In addition, PTZ kindling exacerbated hippocampal synaptic damage and neuronal cell death, as determined by scanning electron microscopy and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) staining, respectively. Finally, the levels of the neuroinflammation markers GFAP and Iba1, as well as the inflammatory cytokine IL-1β, were increased after PTZ insult. PTZ kindling profoundly exacerbated extracellular regulated kinase (ERK)-death-associated protein kinase (DAPK) signaling pathway overactivation, and acute ERK inhibitor treatment downregulated Aβ production and p-APP and p-tau levels in epileptic 5×FAD mice. In addition, long-term use of the antiseizure drug carbamazepine (CBZ) alleviated seizure-induced accelerated amyloid and tau pathology and ERK-DAPK overactivation in 5×FAD mice. Collectively, these results demonstrate that seizure-induced increases in AD-like neuropathology in 5×FAD mice are partially regulated by the ERK-DAPK pathway, suggesting that the ERK-DAPK axis could be a new therapeutic target for the treatment of AD patients with comorbid seizures.

Amyloid pathology and cognitive impairment in hAβ-KI and APPSAA-KI mouse models of Alzheimer's disease

The hAβ-KI and APPSAA-KI are two amyloid models that harbor mutations in the endogenous mouse App gene. Both hAβ-KI and APPSAA-KI mice contain a humanized Aβ sequence, and APPSAA-KI mice carry three additional familial AD mutations. We herein report that the Aβ levels and Aβ42/Aβ40 ratio in APPSAA-KI homozygotes are dramatically higher than those in hAβ-KI homozygotes at 14 months of age. In addition, APPSAA-KI mice display a widespread distribution of amyloid plaques in the brain, whereas the plaques are undetectable in hAβ-KI mice. Moreover, there are no sex differences in amyloid pathology in APPSAA-KI mice. Both APPSAA-KI and hAβ-KI mice exhibit cognitive impairments, wherein no significant differences are found between these two models, although APPSAA KI mice show a trend towards worse cognitive function. Notably, female hAβ-KI and APPSAA-KI mice have a more pronounced cognitive impairments compared to their respective males. Our findings suggest that Aβ humanization contributes to cognitive deficits in APPSAA-KI mice, and that amyloid deposition might not be closely associated with cognitive impairments in APPSAA-KI mice.

Alterations in the axon initial segment plasticity is involved in early pathogenesis in Alzheimer's disease.

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder, characterized by the early presence of amyloid-β (Aβ) and hyperphosphorylated tau. Identifying the neuropathological changes preceding cognitive decline is crucial for early intervention. Axon initial segment (AIS) maintains the orderly structure of the axon and is responsible for initiating action potentials (APs). To investigate the role of AIS in early stages of AD pathogenesis, we focused on alterations in the AIS of neurons from APP/PS1 mouse models harboring familial AD mutations. AIS length and electrophysiological properties were assessed in neurons using immunostaining and patch-clamp techniques. The expression and function of ankyrin G (AnkG) isoforms were evaluated by western blot and rescue experiments. We observed a significant shortening of AIS in APP/PS1 mice, which correlated with impaired action potential propagation. Furthermore, a decrease in the 480kDa isoform of AnkG was observed. Rescue of this isoform restored AIS plasticity and improved long-term potentiation in APP/PS1 neurons. Our study implicates AIS plasticity alterations and AnkG dysregulation as early events in AD. The restoration of AIS integrity by the 480kDa AnkG isoform presents a potential therapeutic strategy for AD, underscoring the importance of targeting AIS stability in neurodegenerative diseases.

Advances in the cell biology of the trafficking and processing of amyloid precursor protein: impact of familial Alzheimer's disease mutations.

The production of neurotoxic amyloid-β peptides (Aβ) is central to the initiation and progression of Alzheimer's disease (AD) and involves sequential cleavage of the amyloid precursor protein (APP) by β- and γ-secretases. APP and the secretases are transmembrane proteins and their co-localisation in the same membrane-bound sub-compartment is necessary for APP cleavage. The intracellular trafficking of APP and the β-secretase, BACE1, is critical in regulating APP processing and Aβ production and has been studied in several cellular systems. Here, we summarise the intracellular distribution and transport of APP and its secretases, and the intracellular location for APP cleavage in non-polarised cells and neuronal models. In addition, we review recent advances on the potential impact of familial AD mutations on APP trafficking and processing. This is critical information in understanding the molecular mechanisms of AD progression and in supporting the development of novel strategies for clinical treatment.

Engineered 3D human neurovascular model of Alzheimer's disease to study vascular dysfunction

The blood–brain barrier (BBB) serves as a selective filter that prevents harmful substances from entering the healthy brain. Dysfunction of this barrier is implicated in several neurological diseases. In the context of Alzheimer's disease (AD), BBB breakdown plays a significant role in both the initiation and progression of the disease. This study introduces a three-dimensional (3D) self-assembled in vitro model of the human neurovascular unit to recapitulate some of the complex interactions between the BBB and AD pathologies. It incorporates primary human brain endothelial cells, pericytes and astrocytes, and stem cell-derived neurons and astrocytes harboring Familial AD (FAD) mutations. Over an extended co-culture period, the model demonstrates increased BBB permeability, dysregulation of key endothelial and pericyte markers, and morphological alterations mirroring AD pathologies. The model enables visualization of amyloid-beta (Aβ) accumulation in both neuronal and vascular compartments. This model may serve as a versatile tool for neuroscience research and drug development to provide insights into the dynamic relationship between vascular dysfunction and AD pathogenesis.

Alzheimer-mutant γ-secretase complexes stall amyloid β-peptide production.

Missense mutations in the amyloid precursor protein (APP) and presenilin-1 (PSEN1) cause early-onset familial Alzheimer's disease (FAD) and alter proteolytic production of secreted 38-to-43-residue amyloid β-peptides (Aβ) by the PSEN1-containing γ-secretase complex, ostensibly supporting the amyloid hypothesis of pathogenesis. However, proteolysis of APP substrate by γ-secretase is processive, involving initial endoproteolysis to produce long Aβ peptides of 48 or 49 residues followed by carboxypeptidase trimming in mostly tripeptide increments. We recently reported evidence that FAD mutations in APP and PSEN1 cause deficiencies in early steps in processive proteolysis of APP substrate C99 and that this results from stalled γ-secretase enzyme-substrate and/or enzyme-intermediate complexes. These stalled complexes triggered synaptic degeneration in a C. elegans model of FAD independently of Aβ production. Here we conducted full quantitative analysis of all proteolytic events on APP substrate by γ-secretase with six additional PSEN1 FAD mutations and found that all six are deficient in multiple processing steps. However, only one of these (F386S) was deficient in certain trimming steps but not in endoproteolysis. Fluorescence lifetime imaging microscopy in intact cells revealed that all six PSEN1 FAD mutations lead to stalled γ-secretase enzyme-substrate/intermediate complexes. The F386S mutation, however, does so only in Aβ-rich regions of the cells, not in C99-rich regions, consistent with the deficiencies of this mutant enzyme only in trimming of Aβ intermediates. These findings provide further evidence that FAD mutations lead stalled and stabilized γ-secretase enzyme-substrate and/or enzyme-intermediate complexes and are consistent with the stalled process rather than the products of γ-secretase proteolysis as the pathogenic trigger.

Simple modeling of familial Alzheimer’s disease using human pluripotent stem cell-derived cerebral organoid technology

BackgroundCerebral organoids (COs) are the most advanced in vitro models that resemble the human brain. The use of COs as a model for Alzheimer’s disease (AD), as well as other brain diseases, has recently gained attention. This study aimed to develop a human AD CO model using normal human pluripotent stem cells (hPSCs) that recapitulates the pathological phenotypes of AD and to determine the usefulness of this model for drug screening.MethodsWe established AD hPSC lines from normal hPSCs by introducing genes that harbor familial AD mutations, and the COs were generated using these hPSC lines. The pathological features of AD, including extensive amyloid-β (Aβ) accumulation, tauopathy, and neurodegeneration, were analyzed using enzyme-linked immunosorbent assay, Amylo-Glo staining, thioflavin-S staining, immunohistochemistry, Bielschowsky’s staining, and western blot analysis.ResultsThe AD COs exhibited extensive Aβ accumulation. The levels of paired helical filament tau and neurofibrillary tangle-like silver deposits were highly increased in the AD COs. The number of cells immunoreactive for cleaved caspase-3 was significantly increased in the AD COs. In addition, treatment of AD COs with BACE1 inhibitor IV, a β-secretase inhibitor, and compound E, a γ-secretase inhibitor, significantly attenuated the AD pathological features.ConclusionOur model effectively recapitulates AD pathology. Hence, it is a valuable platform for understanding the mechanisms underlying AD pathogenesis and can be used to test the efficacy of anti-AD drugs.

Swedish Alzheimer’s disease variant perturbs activity of retrograde molecular motors and causes widespread derangement of axonal transport pathways

Experimental studies in flies, mice, and humans suggest a significant role of impaired axonal transport in the pathogenesis of Alzheimer's disease (AD). The mechanisms underlying these impairments in axonal transport, however, remain poorly understood. Here we report that the Swedish familial AD mutation causes a standstill of the amyloid precursor protein (APP) in the axons at the expense of its reduced anterograde transport. The standstill reflects the perturbed directionality of the axonal transport of APP, which spends significantly more time traveling in the retrograde direction. This ineffective movement is accompanied by an enhanced association of dynactin-1 with APP, which suggests that reduced anterograde transport of APP is the result of enhanced activation of the retrograde molecular motor dynein by dynactin-1. The impact of the Swedish mutation on axonal transport is not limited to the APP vesicles since it also reverses the directionality of a subset of early endosomes, which become enlarged and aberrantly accumulate in distal locations. In addition, it also reduces the trafficking of lysosomes due to their less effective retrograde movement. Altogether, our experiments suggest a pivotal involvement of retrograde molecular motors and transport in the mechanisms underlying impaired axonal transport in AD and reveal significantly more widespread derangement of axonal transport pathways in the pathogenesis of AD.

Emerging structures and dynamic mechanisms of γ-secretase for Alzheimer's disease.

γ-Secretase, called "the proteasome of the membrane," is a membrane-embedded protease complex that cleaves 150+ peptide substrates with central roles in biology and medicine, including amyloid precursor protein and the Notch family of cell-surface receptors. Mutations in γ-secretase and amyloid precursor protein lead to early-onset familial Alzheimer's disease. γ-Secretase has thus served as a critical drug target for treating familial Alzheimer's disease and the more common late-onset Alzheimer's disease as well. However, critical gaps remain in understanding the mechanisms of processive proteolysis of substrates, the effects of familial Alzheimer's disease mutations, and allosteric modulation of substrate cleavage by γ-secretase. In this review, we focus on recent studies of structural dynamic mechanisms of γ-secretase. Different mechanisms, including the "Fit-Stay-Trim," "Sliding-Unwinding," and "Tilting-Unwinding," have been proposed for substrate proteolysis of amyloid precursor protein by γ-secretase based on all-atom molecular dynamics simulations. While an incorrect registry of the Notch1 substrate was identified in the cryo-electron microscopy structure of Notch1-bound γ-secretase, molecular dynamics simulations on a resolved model of Notch1-bound γ-secretase that was reconstructed using the amyloid precursor protein-bound γ-secretase as a template successfully captured γ-secretase activation for proper cleavages of both wildtype and mutant Notch, being consistent with biochemical experimental findings. The approach could be potentially applied to decipher the processing mechanisms of various substrates by γ-secretase. In addition, controversy over the effects of familial Alzheimer's disease mutations, particularly the issue of whether they stabilize or destabilize γ-secretase-substrate complexes, is discussed. Finally, an outlook is provided for future studies of γ-secretase, including pathways of substrate binding and product release, effects of modulators on familial Alzheimer's disease mutations of the γ-secretase-substrate complexes. Comprehensive understanding of the functional mechanisms of γ-secretase will greatly facilitate the rational design of effective drug molecules for treating familial Alzheimer's disease and perhaps Alzheimer's disease in general.

Single-Cell RNA-seq reveals transcriptomic modulation of Alzheimer's disease by activated protein C.

Single-Cell RNA sequencing reveals changes in cell population in Alzheimer's disease (AD) model 5xFAD (5x Familial AD mutation) versus wild type (WT) mice. The returned sequencing data was processed through the 10x Genomics CellRanger platform to perform alignment and form corresponding matrix to perform bioinformatic analysis. Alterations in glial cells occurred in 5xFAD versus WT, especially increases in microglia proliferation were profound in 5xFAD. Differential expression testing of glial cells in 5xFAD versus WT revealed gene regulation. Globally, the critical genes implicated in AD progression are upregulated such as Apoe, Ctsb, Trem2, and Tyrobp. Using this differential expression data, GO term enrichment was completed to observe possible biological processes impacted by AD progression. Utilizing anti-inflammatory and cyto-protective recombinant Activated Protein C (APC), we uncover inflammatory processes to be downregulated by APC treatment in addition to recuperation of nervous system processes. Moreover, animal studies demonstrated that administration of recombinant APC significantly attenuated Aβ burden and improved cognitive function of 5xFAD mice. The downregulation of highly expressed AD biomarkers in 5xFAD could provide insight into the mechanisms by which APC administration benefits AD.

Temporal Alterations in White Matter in An App Knock-In Mouse Model of Alzheimer's Disease.

Alzheimer's disease (AD) is the most common form of dementia and results in neurodegeneration and cognitive impairment. White matter (WM) is affected in AD and has implications for neural circuitry and cognitive function. The trajectory of these changes across age, however, is still not well understood, especially at earlier stages in life. To address this, we used the AppNL-G-F/NL-G-F knock-in (APPKI) mouse model that harbors a single copy knock-in of the human amyloid precursor protein (APP) gene with three familial AD mutations. We performed in vivo diffusion tensor imaging (DTI) to study how the structural properties of the brain change across age in the context of AD. In late age APPKI mice, we observed reduced fractional anisotropy (FA), a proxy of WM integrity, in multiple brain regions, including the hippocampus, anterior commissure (AC), neocortex, and hypothalamus. At the cellular level, we observed greater numbers of oligodendrocytes in middle age (prior to observations in DTI) in both the AC, a major interhemispheric WM tract, and the hippocampus, which is involved in memory and heavily affected in AD, prior to observations in DTI. Proteomics analysis of the hippocampus also revealed altered expression of oligodendrocyte-related proteins with age and in APPKI mice. Together, these results help to improve our understanding of the development of AD pathology with age, and imply that middle age may be an important temporal window for potential therapeutic intervention.

Familial Alzheimer’s Disease Mutation PSEN2 Exacerbates Toxoplasma gondii-mediated Human Blood-Brain Barrier Damage

Background and Hypothesis
 Toxoplasma gondii is an obligate intracellular parasite that infects one-third of the global population. T. gondii transmission to humans primarily occurs from the consumption of contaminated meats, water, or produce. Unfortunately, T. gondii will evade the host clearance, allowing it to cross the blood-brain barrier (BBB), infecting neurons where it transitions into slow-growing cysts, leading to a life-long chronic infection. Recently, studies have suggested that T. gondii infection may exacerbate the decline of cognitive function. The BBB is critical for restricting neurotoxic blood-derived products, leukocytes, and pathogens from entering the brain. Studies have shown that BBB dysfunction and damage to the barrier integrity may also contribute to cognitive impairment. Alzheimer’s disease (AD), the most common form of dementia, is a progressive neurodegenerative disease and its neuropathology is associated with b-amyloid plaques. Familial Alzheimer’s Disease is associated with the proteins, presenilin-1 and presenilin-2, encoded by PSEN1 and PSEN2. Mutations in these two genes contribute to early onset AD. Furthermore, dementia has been linked with an increased breakdown of the BBB. Therefore, we hypothesized that T. gondii infection will exacerbate barrier damage and dysfunction in brain microvascular endothelial cells (BMECs) containing familial AD mutations compared to healthy controls.
 Experimental Design
 To test our hypothesis, we infected human induced pluripotent stem cell (iPSC)-derived BMECs, which display near in vivo like BBB properties, containing the familial AD PSEN2 mutation or healthy controls with T. gondii. 
 Results
 Using immunofluorescence and transendothelial electrical resistance, our results show that BMECs containing the PSEN2 mutation have a quicker onset of barrier damage, but we observed no difference in the loss of tight junctions ZO-1, Occludin, and Claudin-5 compared to healthy controls after infection.
 Potential Impact
 These data suggest that a T. gondii infection can exacerbate the breakdown of the BBB in patients with the PSEN2 mutation, worsening the prognosis of familial AD patients.

Diffusion Tensor Imaging in Alzheimer's Studies.

In this chapter, we describe the use of quantitative metrics of white matter obtained from the diffusion tensor model based on diffusion-weighted imaging in Alzheimer's disease (AD). Our description synthesizes insights not only frompatient populations with AD dementia but also from participants at risk for AD dementia (e.g., amnestic mild cognitive impairment, subjective cognitive decline, or familial AD mutation carriers). A reference to studies examining correlations with behavioral variables is also included. Our main message is to caution against the overinterpretation of diffusion metrics and to favor analyses that focus on regions of interest or major white matter tracts for biomarker studies in AD.

Electroacupuncture promotes neurogenesis in the dentate gyrus and improves pattern separation in an early Alzheimer's disease mouse model

BackgroundImpaired pattern separation occurs in the early stage of Alzheimer’s disease (AD), and hippocampal dentate gyrus (DG) neurogenesis participates in pattern separation. Here, we investigated whether spatial memory discrimination impairment can be improved by promoting the hippocampal DG granule cell neogenesis-mediated pattern separation in the early stage of AD by electroacupuncture (EA).MethodsFive familial AD mutations (5 × FAD) mice received EA treatment at Baihui and Shenting points for 4 weeks. During EA, mice were intraperitoneally injected with BrdU (50 mg/kg) twice a day. rAAV containing Wnt5a shRNA was injected into the bilateral DG region, and the viral efficiency was evaluated by detecting Wnt5a mRNA levels. Cognitive behavior tests were conducted to assess the impact of EA treatment on cognitive function. The hippocampal DG area Aβ deposition level was detected by immunohistochemistry after the intervention; The number of BrdU+/CaR+ cells and the gene expression level of calretinin (CaR) and prospero homeobox 1(Prox1) in the DG area of the hippocampus was detected to assess neurogenesis by immunofluorescence and western blotting after the intervention; The gene expression levels of FZD2, Wnt5a, DVL2, p-DVL2, CaMKII, and p-CaMKII in the Wnt signaling pathway were detected by Western blotting after the intervention.ResultsCognitive behavioral tests showed that 5 × FAD mice had impaired pattern separation (P < 0.001), which could be improved by EA (P < 0.01). Immunofluorescence and Western blot showed that the expression of Wnt5a in the hippocampus was decreased (P < 0.001), and the neurogenesis in the DG was impaired (P < 0.001) in 5 × FAD mice. EA could increase the expression level of Wnt5a (P < 0.05) and promote the neurogenesis of immature granule cells (P < 0.05) and the development of neuronal dendritic spines (P < 0.05). Interference of Wnt5a expression aggravated the damage of neurogenesis (P < 0.05), weakened the memory discrimination ability (P < 0.05), and inhibited the beneficial effect of EA (P < 0.05) in AD mice. The expression level of Wnt pathway related proteins such as FZD2, DVL2, p-DVL2, CAMKII, p-CAMKII increased after EA, but the effect of EA was inhibited after Wnt5a was knocked down. In addition, EA could reduce the deposition of Aβ plaques in the DG without any impact on Wnt5a.ConclusionEA can promote hippocampal DG immature granule cell neogenesis-mediated pattern separation to improve spatial memory discrimination impairment by regulating Wnt5a in 5 × FAD mice.

APOE genotype and sex modulate Alzheimer's disease pathology in aged EFAD transgenic mice.

Increasing evidence supports that age, APOE and sex interact to modulate Alzheimer's disease (AD) risk, however the underlying pathways are unclear. One way that AD risk factors may modulate cognition is by impacting amyloid beta (Aβ) accumulation as plaques, and/or neuroinflammation Therefore, the goal of the present study was to evaluate the extent to which age, APOE and sex modulate Aβ pathology, neuroinflammation and behavior in vivo. To achieve this goal, we utilized the EFAD mice, which express human APOE3 or APOE4 and have five familial AD mutations (FAD) that result in Aβ42 overproduction. We assessed Aβ levels, reactive glia and Morris water maze performance in 6-, 10-, 14-, and 18-month-old EFAD mice. Female APOE4 mice had the highest Aβ deposition, fibrillar amyloid deposits and neuroinflammation as well as earlier behavior deficits. Interestingly, we found that female APOE3 mice and male APOE4 mice had similar levels of pathology. Collectively our data support that the combination of APOE4 and female sex is the most detrimental combination for AD, and that at older ages, female sex may be equivalent to APOE4 genotype.

Development of an accelerated cellular model for early changes in Alzheimer’s disease

Alzheimer’s Disease (AD) is a leading cause of dementia characterized by amyloid plaques and neurofibrillary tangles, and its pathogenesis remains unclear. Current cellular models for AD often require several months to exhibit phenotypic features due to the lack of an aging environment in vitro. Lamin A is a key component of the nuclear lamina. Progerin, a truncated protein resulting from specific lamin A mutations, causes Hutchinson–Gilford Progeria Syndrome (HGPS), a disease that prematurely ages individuals. Studies have reported that lamin A expression is induced in the brains of AD patients, and overlapping cellular phenotypes have been observed between HGPS and AD cells. In this study, we investigated the effects of exogenous progerin expression on neural progenitor cells carrying familial AD mutations (FAD). Within three to four weeks of differentiation, these cells exhibited robust AD phenotypes, including increased tau phosphorylation, amyloid plaque accumulation, and an elevated Aβ42 to Aβ40 ratio. Additionally, progerin expression significantly increased AD cellular phenotypes such as cell death and cell cycle re-entry. Our results suggest that progerin expression could be used to create an accelerated model for AD development and drug screening.

An Alternative View of Familial Alzheimer's Disease Genetics.

Probabilistic and parsimony-based arguments regarding available genetics data are used to propose that Hardy and Higgin's amyloid cascade hypothesis is valid but is commonly interpreted too narrowly to support, incorrectly, the primacy of the amyloid-β peptide (Aβ) in driving Alzheimer's disease pathogenesis. Instead, increased activity of the βCTF (C99) fragment of AβPP is the critical pathogenic determinant altered by mutations in the APP gene. This model is consistent with the regulation of APP mRNA translation via its 5' iron responsive element. Similar arguments support that the pathological effects of familial Alzheimer's disease mutations in the genes PSEN1 and PSEN2 are not exerted directly via changes in AβPP cleavage to produce different ratios of Aβ length. Rather, these mutations likely act through effects on presenilin holoprotein conformation and function, and possibly the formation and stability of multimers of presenilin holoprotein and/or of the γ-secretase complex. All fAD mutations in APP, PSEN1, and PSEN2 likely find unity of pathological mechanism in their actions on endolysosomal acidification and mitochondrial function, with detrimental effects on iron homeostasis and promotion of "pseudo-hypoxia" being of central importance. Aβ production is enhanced and distorted by oxidative stress and accumulates due to decreased lysosomal function. It may act as a disease-associated molecular pattern enhancing oxidative stress-driven neuroinflammation during the cognitive phase of the disease.

Iron Responsiveness to Lysosomal Disruption: A Novel Pathway to Alzheimer's Disease.

Familial Alzheimer's disease (fAD) mutations in the amyloid-β protein precursor (AβPP) enhance brain AβPP C-Terminal Fragment (CTF) levels to inhibit lysosomal v-ATPase. Consequent disrupted acidification of the endolysosomal pathway may trigger brain iron deficiencies and mitochondrial dysfunction. The iron responsive element (IRE) in the 5'Untranslated-region of AβPP mRNA should be factored into this cycle where reduced bioavailable Fe-II would decrease IRE-dependent AβPP translation and levels APP-CTFβ in a cycle to adaptively restore iron homeostasis while increases of transferrin-receptors is evident. In healthy younger individuals, Fe-dependent translational modulation of AβPP is part of the neuroprotective function of sAβPPα with its role in iron transport.

A small-molecule TLR4 antagonist reduced neuroinflammation in female E4FAD mice

BackgroundAPOE genotype is the greatest genetic risk factor for sporadic Alzheimer’s disease (AD). APOE4 increases AD risk up to 12-fold compared to APOE3, an effect that is greater in females. Evidence suggests that one-way APOE could modulate AD risk and progression through neuroinflammation. Indeed, APOE4 is associated with higher glial activation and cytokine levels in AD patients and mice. Therefore, identifying pathways that contribute to APOE4-associated neuroinflammation is an important approach for understanding and treating AD. Human and in vivo evidence suggests that TLR4, one of the key receptors involved in the innate immune system, could be involved in APOE-modulated neuroinflammation. Consistent with that idea, we previously demonstrated that the TLR4 antagonist IAXO-101 can reduce LPS- and Aβ-induced cytokine secretion in APOE4 glial cultures. Therefore, the goal of this study was to advance these findings and determine whether IAXO-101 can modulate neuroinflammation, Aβ pathology, and behavior in mice that express APOE4.MethodsWe used mice that express five familial AD mutations and human APOE3 (E3FAD) or APOE4 (E4FAD). Female and male E4FAD mice and female E3FAD mice were treated with vehicle or IAXO-101 in two treatment paradigms: prevention from 4 to 6 months of age or reversal from 6 to 7 months of age. Learning and memory were assessed by modified Morris water maze. Aβ deposition, fibrillar amyloid deposition, astrogliosis, and microgliosis were assessed by immunohistochemistry. Soluble levels of Aβ and apoE, insoluble levels of apoE and Aβ, and IL-1β were measured by ELISA.ResultsIAXO-101 treatment resulted in lower Iba-1 coverage, lower number of reactive microglia, and improved memory in female E4FAD mice in both prevention and reversal paradigms. IAXO-101-treated male E4FAD mice also had lower Iba-1 coverage and reactivity in the RVS paradigm, but there was no effect on behavior. There was also no effect of IAXO-101 treatment on neuroinflammation and behavior in female E3FAD mice.ConclusionOur data supports that TLR4 is a potential mechanistic therapeutic target for modulating neuroinflammation and cognition in APOE4 females.