Aged Alzheimer's Disease Mice Research Articles

Aging-dependent loss of functional connectivity in a mouse model of Alzheimer's disease and reversal by mGluR5 modulator.

Amyloid accumulation in Alzheimer's disease (AD) is associated with synaptic damage and altered connectivity in brain networks. While measures of amyloid accumulation and biochemical changes in mouse models have utility for translational studies of certain therapeutics, preclinical analysis of altered brain connectivity using clinically relevant fMRI measures has not been well developed for agents intended to improve neural networks. Here, we conduct a longitudinal study in a double knock-in mouse model for AD (AppNL-G-F/hMapt), monitoring brain connectivity by means of resting-state fMRI. While the 4-month-old AD mice are indistinguishable from wild-type controls (WT), decreased connectivity in the default-mode network is significant for the AD mice relative to WT mice by 6 months of age and is pronounced by 9 months of age. In a second cohort of 20-month-old mice with persistent functional connectivity deficits for AD relative to WT, we assess the impact of two-months of oral treatment with a silent allosteric modulator of mGluR5 (BMS-984923/ALX001) known to rescue synaptic density. Functional connectivity deficits in the aged AD mice are reversed by the mGluR5-directed treatment. The longitudinal application of fMRI has enabled us to define the preclinical time trajectory of AD-related changes in functional connectivity, and to demonstrate a translatable metric for monitoring disease emergence, progression, and response to synapse-rescuing treatment.

Alzheimer's disease-associated genotypes differentially influence chronic evoked seizure outcomes and antiseizure medicine activity in aged mice.

Alzheimer's disease (AD) patients are at greater risk of focal seizures than similarly aged adults; these seizures, left untreated, may worsen functional decline. Older people with epilepsy generally respond well to antiseizure medications (ASMs). However, whether specific ASMs can differentially control seizures in AD is unknown. The corneal kindled mouse model of acquired chronic secondarily generalized focal seizures allows for precisely timed drug administration studies to quantify the efficacy and tolerability of ASMs in an AD-associated genetic model. Wh+e hypothesized that mechanistically distinct ASMs would exert differential anticonvulsant activity and tolerability in aged AD mice (8-15 months) to define whether rational ASM selection may benefit specific AD genotypes. Aged male and female PSEN2-N141I versus age-matched non-transgenic control (PSEN2 control) C57Bl/6J mice, and APPswe/PS1dE9 versus transgene negative (APP control) littermates underwent corneal kindling to quantify latency to fully kindled criterion. Dose-related ASM efficacy was then compared in each AD model versus matched control over 1-2 months using ASMs commonly prescribed in older adults with epilepsy: valproic acid, levetiracetam, lamotrigine, phenobarbital, and gabapentin. Sex and AD genotype differentially impacted seizure susceptibility. Male PSEN2-N141I mice required more stimulations to attain kindling criterion (X2=5.521; p<0.05). Male APP/PS1 mice did not differ in kindling rate versus APP control mice, but they did have more severe seizures. There were significant ASM class-specific differences in acute seizure control and dose-related tolerability. APP/PS1 mice were more sensitive than APP controls to valproic acid, levetiracetam, and gabapentin. PSEN2-N141I mice were more sensitive than PSEN2 controls to valproic acid and lamotrigine. AD genotypes may differentially impact ASMs activity and tolerability in vivo with advanced biological age. These findings highlight the heterogeneity of seizure risk in AD and suggest that precisely selected ASMs may beneficially control seizures in AD, thus reducing functional decline.

Cholecystokinin B receptor agonists alleviates anterograde amnesia in cholecystokinin-deficient and aged Alzheimer's disease mice

BackgroundAs one major symptom of Alzheimer’s disease (AD), anterograde amnesia describes patients with an inability in new memory formation. The crucial role of the entorhinal cortex in forming new memories has been well established, and the neuropeptide cholecystokinin (CCK) is reported to be released from the entorhinal cortex to enable neocortical associated memory and long-term potentiation. Though several studies reveal that the entorhinal cortex and CCK are related to AD, it is less well studied. It is unclear whether CCK is a good biomarker or further a great drug candidate for AD.MethodsmRNA expressions of CCK and CCK-B receptor (CCKBR) were examined in two mouse models, 3xTg AD and CCK knock-out (CCK−/−) mice. Animals’ cognition was investigated with Morris water maze, novel object recognition test and neuroplasticity with in-vitro electrophysiological recording. Drugs were given intraperitoneally to animals to investigate the rescue effects on cognitive deficits, or applied to brain slices directly to explore the influence in inducement of long-term potentiation.ResultsAged 3xTg AD mice exhibited reduced CCK mRNA expression in the entorhinal cortex but reduced CCKBR expression in the neocortex and hippocampus, and impaired cognition and neuroplasticity comparable with CCK−/− mice. Importantly, the animals displayed improved performance and enhanced long-term potentiation after the treatment of CCKBR agonists.ConclusionsHere we provide more evidence to support the role of CCK in learning and memory and its potential to treat AD. We elaborated on the rescue effect of a promising novel drug, HT-267, on aged 3xTg AD mice. Although the physiological etiology of CCK in AD still needs to be further investigated, this study sheds light on a potential pharmaceutical candidate for AD and dementia.

Aged AβPPswe/PS1ΔE9 mice as a useful animal model for studying the link between immunological senescence and diseases

The APPswe/PS1ΔE9 mouse is a double transgenic murine model that harbors two transgenes for Alzheimer's Disease (AD)-related mutant proteins. We previously discovered that this double transgenic animal had a premature immunosenescence phenotype. However, it is unclear how this phenotype progresses to a later stage. This study aimed to elucidate the changes in systemic characteristics aside from those associated with AD between elderly APPswe/PS1ΔE9 mice and littermate control wild-type mice. Tumors in all organs were considerably more frequent in AD mice aged 24 months than in the control wild-type mice. In addition, the survival rate of aged AD mice was considerably lower than that of wild-type control mice. Further, we discovered that the phenotypic difference was mainly caused by severe immunological aging, as evidenced by a high proportion of exhausted T lymphocytes in AD mice compared to wild-type mice of the same age. Based on our findings, the harm produced by normal aging is not as severe as immunological senescence. Addressing immunological aging, as opposed to anti-aging alone, may be a more crucial target for a long life free of cancer.

H3K18 lactylation of senescent microglia potentiates brain aging and Alzheimer's disease through the NFκB signaling pathway

Cellular senescence serves as a fundamental and underlying activity that drives the aging process, and it is intricately associated with numerous age-related diseases, including Alzheimer's disease (AD), a neurodegenerative aging-related disorder characterized by progressive cognitive impairment. Although increasing evidence suggests that senescent microglia play a role in the pathogenesis of AD, their exact role remains unclear. In this study, we quantified the levels of lactic acid in senescent microglia, and hippocampus tissues of naturally aged mice and AD mice models (FAD4T and APP/PS1). We found lactic acid levels were significantly elevated in these cells and tissues compared to their corresponding counterparts, which increased the level of pan histone lysine lactylation (Kla). We aslo identified all histone Kla sites in senescent microglia, and found that both the H3K18 lactylation (H3K18la) and Pan-Kla were significantly up-regulated in senescent microglia and hippocampus tissues of naturally aged mice and AD modeling mice. We demonstrated that enhanced H3K18la directly stimulates the NFκB signaling pathway by increasing binding to the promoter of Rela (p65) and NFκB1(p50), thereby upregulating senescence-associated secretory phenotype (SASP) components IL-6 and IL-8. Our study provides novel insights into the physiological function of Kla and the epigenetic regulatory mechanism that regulates brain aging and AD. Specifically, we have identified the H3K18la/NFκB axis as a critical player in this process by modulating IL-6 and IL-8. Targeting this axis may be a potential therapeutic strategy for delaying aging and AD by blunting SASP.

Abstract P2019: Diastolic Dysfunction In Alzheimer's Disease Is Associated With aβ- Amyloid Aggregate Formation And Mitochondrial Dysfunction

Background: Alzheimer's disease (AD) is a neurodegenerative disease with memory impairment caused by an accumulation of toxic protein aggregates (Aβ- amyloid plaques and tau-derived neurofibrillary tangles). Several studies reported cardiovascular abnormalities with diastolic dysfunction in AD patients; however, the direct mechanism of cardiac dysfunction in AD patients remains unexplored. Therefore, we investigated the pathophysiological mechanism of cardiac dysfunction in the mice model of AD. Hypothesis: Two most commonly used mice models of AD was thoroughly evaluated for cardiac dysfunction, histopathology, and biochemical changes over aging. Methods and Result: To determine the mechanism of AD-associated cardiac dysfunction, we used two different AD mice models: double transgenic mice expressing a chimeric mouse/human amyloid precursor protein and a mutant human presenilin 1 (APP/PS1 Tg), and transgenic mice that is homozygous for a Psen1 mutation and the co-injected APPSwe and tauP301L transgenes (3xTg-AD). Cardiac function measurement using non-invasive echocardiography in aged Ntg and AD mice models showed no difference in systolic cardiac functional parameters. However, diastolic function assessment using Doppler echocardiographic measurements showed ventricular diastolic dysfunction with reduced diastolic filling in APP/PS1 Tg and 3xTg-AD mice. Western blot analysis showed Aβ- amyloid protein expression in APP/PS1 Tg hearts. Immunohistochemical and immunofluorescence staining of the APP/PS1 Tg heart sections further confirmed the Aβ- amyloid protein expression and Aβ- amyloid aggregate formation in the cardiomyocytes. Further evaluation of APP/PS1 Tg hearts demonstrated increased collagen deposition (Picro-Sirius red staining) and increased cardiomyocyte cross-sectional area. Interestingly, APP/PS1 Tg hearts also displayed mitochondrial dysfunction with decreased mitochondrial bioenergetics and significantly reduced mitochondrial function regulatory parameters. Conclusion: Overall, we found diastolic dysfunction development with Aβ- amyloid aggregate formation, fibrotic remodeling, increased cardiomyocyte cross-sectional area, and mitochondrial dysfunction in the AD mice hearts.

Endogenous Amyloid-formed Ca2+-permeable Channels in Aged 3xTg AD Mice.

Alzheimer's disease (AD), the leading cause of dementia, is characterized by the accumulation of beta-amyloid peptides (Aβ). However, whether Aβ itself is a key toxic agent in AD pathogenesis and the precise mechanism of Aβ-elicited neurotoxicity are still debated. Emerging evidence demonstrates that the Aβ channel/pore hypothesis could explain Aβ toxicity, because Aβ oligomers are able to disrupt membranes and cause edge-conductivity pores that may disrupt cell Ca2+ homeostasis and drive neurotoxicity in AD. However, all available data to support this hypothesis have been collected from "in vitro" experiments using high concentrations of exogenous Aβ. It is still unknown whether Aβ channels can be formed by endogenous Aβ in AD animal models. Here, we report an unexpected finding of the spontaneous Ca2+ oscillations in aged 3xTg AD mice but not in age-matched wild-type mice. These spontaneous Ca2+ oscillations are sensitive to extracellular Ca2+, ZnCl2, and the Aβ channel blocker Anle138b, suggesting that these spontaneous Ca2+ oscillations in aged 3xTg AD mice are mediated by endogenous Aβ-formed channels.

Caspase-1 inhibition improves cognition without significantly altering amyloid and inflammation in aged Alzheimer disease mice

Human genetic and animal model studies indicate that brain microglial inflammation is a primary driver of cognitive impairment in Alzheimer Disease (AD). Inflammasome-activated Caspase-1 (Casp1) is associated with both AD microglial inflammation and neuronal degeneration. In mice, Casp1 genetic ablation or VX-765 small molecule inhibition of Casp1 given at onset of cognitive deficits strongly supports the association between microglial inflammation and cognitive impairment. Here, VX-765 significantly improved episodic and spatial memory impairment eight months after the onset of cognitive impairment in aged AD mice with significant amyloid beta peptide (Aβ) accumulation and microglial inflammation. Unexpectedly, while cognitive improvement was associated with dendritic spine density and hippocampal synaptophysin level recovery, VX-765 only slightly decreased Aβ deposition and did not alter biochemically-measured Aβ levels. Furthermore, increased hippocampal Iba1+-microglia, GFAP+-astrocytes, IL-1β, and TNF-α levels were unaltered by VX-765. These results support the hypothesis that neuronal degeneration, not Aβ or microglial inflammation, drives cognitive impairment in AD.

Hippocampal neural circuit connectivity alterations in an Alzheimer's disease mouse model revealed by monosynaptic rabies virus tracing

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with growing major health impacts, particularly in countries with aging populations. The examination of neural circuit mechanisms in AD mouse models is a recent focus for identifying new AD treatment strategies. We hypothesize that age-progressive changes of both long-range and local hippocampal neural circuit connectivity occur in AD. Recent advancements in viral-genetic technologies provide new opportunities for semi-quantitative mapping of cell-type-specific neural circuit connections in AD mouse models. We applied a recently developed monosynaptic rabies tracing method to hippocampal neural circuit mapping studies in AD model mice to determine how local and global circuit connectivity to hippocampal CA1 excitatory neurons may be altered in the single APP knock-in (APP-KI) AD mouse model. To determine age-related AD progression, we measured circuit connectivity in age-matched littermate control and AD model mice at two different ages (3–4 vs. 10–11 months old). We quantitatively mapped the connectivity strengths of neural circuit inputs to hippocampal CA1 excitatory neurons from brain regions including hippocampal subregions, medial septum, subiculum and entorhinal cortex, comparing different age groups and genotypes. We focused on hippocampal CA1 because of its clear relationship with learning and memory and that the hippocampal formation shows clear neuropathological changes in human AD. Our results reveal alterations in circuit connectivity of hippocampal CA1 in AD model mice. Overall, we find weaker extrinsic CA1 input connectivity strengths in AD model mice compared with control mice, including sex differences of reduced subiculum to CA1 inputs in aged female AD mice compared with aged male AD mice. Unexpectedly, we find a connectivity pattern shift with an increased proportion of inputs from the CA3 region to CA1 excitatory neurons when comparing young and old AD model mice, as well as old wild-type mice and old AD model mice. These unexpected shifts in CA3-CA1 input proportions in this AD mouse model suggest the possibility that compensatory circuit increases may occur in response to connectivity losses in other parts of the hippocampal circuits. We expect that this work provides new insights into the neural circuit mechanisms of AD pathogenesis.

Reversing pathology in a preclinical model of Alzheimer's disease by hacking cerebrovascular neoangiogenesis with advanced cancer therapeutics.

BackgroundCognitive decline leading to dementia, accompanied by the accumulation of amyloid-beta (Aβ) in neuritic plaques together with the appearance of neurofibrillary tangles (NFT) composed of hyperphosphorylated tau protein (tau), are previously noted hallmarks of Alzheimer's disease (AD). We previously discovered hypervascularity in brain specimens from AD patients and consistent with this observation, we demonstrated that overexpression of Aβ drives cerebrovascular neoangiogenesis leading to hypervascularity and coincident tight-junction disruption and blood-brain barrier (BBB) leakiness in animal models of AD. We subsequently demonstrated that amyloid plaque burden and cerebrovascular pathogenesis subside when pro-angiogenic Aβ levels are reduced. Based on these data, we propose a paradigm of AD etiology where, as a compensatory response to impaired cerebral blood flow (CBF), Aβ triggers pathogenic cerebrovascular neoangiogenesis that underlies the conventional hallmarks of AD. Consequently, here we present evidence that repurposing anti-cancer drugs to modulate cerebrovascular neoangiogenesis, rather than directly targeting the amyloid cascade, may provide an effective treatment for AD and related vascular diseases of the brain.MethodsWe explored whether the anti-cancer drug, Axitinib, a small molecule tyrosine kinase inhibitor that targets vascular endothelial growth factor receptors (VEGFR) can inhibit aberrant cerebrovascular neoangiogenic changes, reduce Aβ deposits and reverse cognitive decline in an animal model of AD. One month post-treatment with Axitinib, we employed a battery of tests to assess cognition and memory in aged Tg2576 AD mice and used molecular analysis to demonstrate reduction of amyloid plaques, BBB leakage, hypervascularity and associated disease pathology.FindingsTargeting the pro-angiogenic pathway in AD using the cancer drug, Axitinib, dramatically reduced cerebrovascular neoangiogenesis, restored BBB integrity, resolved tight-junction pathogenesis, diminishes Aβ depositions in plaques and effectively restores memory and cognitive performance in a preclinical mouse model of AD.InterpretationModulation of neoangiogenesis, in an analogous approach to those used to treat aberrant vascularization in cancer and also in the wet form of age-related macular degeneration (AMD), provides an alternative therapeutic strategy for intervention in AD that warrants clinical investigation.

Effects of Steroidal Na/K‐ATPase Inhibitor Marinobufagenin on Neurodegeneration, Neuroinflammation and Cognition in a Mouse Model of Alzheimer's Disease and Cardiovascular Amyloidosis

Background Na/K-ATPase is a keystone enzyme in all living cells. Steroidal inhibitor of Na/K-ATPase, marinobufagenin (MBG), participates in regulating cardiac function, vessel architecture, intracellular signaling transduction, and anti-neuroinflammatory response. The aged double-transgene APPswe/PS1dE9 mice, a model of Alzheimer's disease (AD), exhibit lower levels of urine MBG compared to wild-type (WT) mice, impairments in cognitive function and amyloid β (Aβ) pathologies. Compromised blood supply to the brain may contribute to AD development and Aβ pathologies. Here we examined Aβ pathology in the cerebral and central vasculature of aged AD mice and whether MBG treatment affects neuroinflammation, neurodegeneration, and cognitive function. Methods To aged male AD (n=8; 15-mo old) and age-matched WT mice (n=4) MBG (100 µg/day/kg body weight) was administered via subcutaneous ALZET minipumps for 3-mo. Age-matched control mice received saline (AD-C, n=8; WT-C, n=4). Systolic blood pressure (SBP; by tail cuff plethysmography), cognitive flexibility (reversal learning in a water T-maze), plasma (for MBG measurement), brain and tissue samples (for qPCR, 3D green light laser microscopy and immunohistochemistry analysis) were collected at 18-mo. Data was analyzed by 2-way ANOVA and presented as mean±SE. Results In aged AD mice, we observed granulated Aβ plaques and Aβ localization around small cerebral blood vessels (Fig 1B; white arrows). Aβ protein was also found in significantly larger abundance in aortae vessel wall of old AD mice vs. WT mice (Fig 2; blue stain). SBP was not affected by treatment and did not differ between AD and WT mice. Endogenous plasma MBG was lower in AD-C vs. WT-C (125±21 vs. 223±41 pmol/L; p<0.05). Plasma MBG was elevated in both WT-MBG and AD-MBG (483±116 and 657±176 pmol/L; p<0.05 vs. WT-C and AD-C, correspondently). Hippocampal mRNA expression of inflammatory marker IL6 was upregulated 1.5-fold in AD-C vs. WT-C (p<0.05); MBG reduced this expression in AD-MBG vs. AD-C (p<0.01). Hippocampal mRNA expression of amyloid precursor protein (APP) was upregulated 2.6-fold in AD-C vs. WT-C (p<0.01); MBG reduced this expression in AD-MBG vs. AD-C (p<0.01). AD mice showed normal learning for a turn-based discrimination rule but were impaired during the reversal phase vs. WT mice. MBG treatment did not affect the amount of Aβ plaque load in the brains of AD-MBG vs. AD-C. Conclusion Old AD mice exhibited lower endogenous plasma MBG, impaired cognitive flexibility, higher hippocampal IL6 and APP mRNAs, and Aβ accumulation in cerebral vessels and aortae relative to WT counterparts. MBG treatment significantly reduced hippocampal APP and inflammatory mRNA markers; however, it had no effect on existing Aβ load. In future experiments, we will examine how MBG treatment affects the formation of brain Aβ plaques in younger AD mice.

Longitudinal evaluation of a novel BChE PET tracer as an early in vivo biomarker in the brain of a mouse model for Alzheimer disease.

Purpose: The increase in butyrylcholinesterase (BChE) activity in the brain of Alzheimer disease (AD) patients and animal models of AD position this enzyme as a potential biomarker of the disease. However, the information on the ability of BChE to serve as AD biomarker is contradicting, also due to scarce longitudinal studies of BChE activity abundance. Here, we report 11C-labeling, in vivo stability, biodistribution, and longitudinal study on BChE abundance in the brains of control and 5xFAD (AD model) animals, using a potent BChE selective inhibitor, [11C]4, and positron emission tomography (PET) in combination with computerised tomography (CT). We correlate the results with in vivo amyloid beta (Aβ) deposition, longitudinally assessed by [18F]florbetaben-PET imaging.Methods: [11C]4 was radiolabelled through 11C-methylation. Metabolism studies were performed on blood and brain samples of female wild type (WT) mice. Biodistribution studies were performed in female WT mice using dynamic PET-CT imaging. Specific binding was demonstrated by ex vivo and in vivo PET imaging blocking studies in female WT and 5xFAD mice at the age of 7 months. Longitudinal PET imaging of BChE was conducted in female 5xFAD mice at 4, 6, 8, 10 and 12 months of age and compared to age-matched control animals. Additionally, Aβ plaque distribution was assessed in the same mice using [18F]florbetaben at the ages of 2, 5, 7 and 11 months. The results were validated by ex vivo staining of BChE at 4, 8, and 12 months and Aβ at 12 months on brain samples.Results: [11C]4 was produced in sufficient radiochemical yield and molar activity for the use in PET imaging. Metabolism and biodistribution studies confirmed sufficient stability in vivo, the ability of [11C]4 to cross the blood brain barrier (BBB) and rapid washout from the brain. Blocking studies confirmed specificity of the binding. Longitudinal PET studies showed increased levels of BChE in the cerebral cortex, hippocampus, striatum, thalamus, cerebellum and brain stem in aged AD mice compared to WT littermates. [18F]Florbetaben-PET imaging showed similar trend of Aβ plaques accumulation in the cerebral cortex and the hippocampus of AD animals as the one observed for BChE at ages 4 to 8 months. Contrarily to the results obtained by ex vivo staining, lower abundance of BChE was observed in vivo at 10 and 12 months than at 8 months of age.Conclusions: The BChE inhibitor [11C]4 crosses the BBB and is quickly washed out of the brain of WT mice. Comparison between AD and WT mice shows accumulation of the radiotracer in the AD-affected areas of the brain over time during the early disease progression. The results correspond well with Aβ accumulation, suggesting that BChE is a promising early biomarker for incipient AD.

Enhanced autophagic retrograde axonal transport by dynein intermediate chain upregulation improves Aβ clearance and cognitive function in APP/PS1 double transgenic mice.

Autophagosome accumulation is observed in the distal axons of Alzheimer disease (AD) patients and AD animal models, suggesting that deficient retrograde transport and impaired autophagic clearance of beta-amyloid (A β) contribute to AD pathogenesis. Expression of the retrograde axonal transport-related protein dynein intermediate chain (DIC) is also reduced in AD patients, but the contributions of DIC to AD pathology remain elusive. This study investigated the effects of DIC expression levels on cognitive function, autophagosome axonal transport, and A β clearance in the APP/PS1 double transgenic mouse model of AD. Autophagic activity was enhanced in the hippocampus of young (3-month-old) AD mice, as evidenced by greater expression of autophagosome markers, lysosome markers, axonal transport motors (including DIC), and dynein regulatory proteins. The expression levels of autophagosome markers remained elevated, whereas those of autophagic and axonal transport proteins decreased progressively with age, accompanied by spatial learning and memory deficits, axonal autophagosome accumulation, and A β deposition. Knockdown of DIC exacerbated while overexpression improved axonal transport, autophagosome maturation, Aβ clearance, and spatial learning and memory in aged AD mice. Our study provides evidence that age-dependent failure of axonal autophagic flux contributes to AD-associated neuropathology and cognitive deficits, suggesting DIC as a potential therapeutic target for AD.

Effective expression of Drebrin in hippocampus improves cognitive function and alleviates lesions of Alzheimer's disease in APP (swe)/PS1 (ΔE9) mice

Alzheimer's disease (AD), a progressive development dementia, is increasingly impacting patients' living conditions worldwide. Despite medical care and funding support, there are still no highly individualized drugs and practical strategies for clinical prevention and treatment. Developmentally regulated brain protein (abbreviated as Drebrin or Dbn, also known as Dbn1 in mouse) exists in neurons, especially in dendrites, and is an actin-binding protein that modulates synaptic morphology and long-term memory. However, the majority of previous studies have focused on its upstream proteins and neglected the impact Drebrin has on behavior and AD in vivo. Here, we tracked the behavioral performances of 4-, 8-, 12-, and 16-month-old AD mice and investigated the expression level of Drebrin in their hippocampi. A Pearson correlation analysis between Drebrin levels and behavioral data was performed. Subsequently, 2-month-old AD mice were injected with rAAV-zsGreen-Dbn1 vector, composing the APP/PS1-Dbn1 group, and sex- and age-matched AD mice were injected with rAAV-tdTomato vector to serve as the control group. All mice were conducted behavioral tests and molecular detection 6months later. (i) The expression of Drebrin is decreased in the hippocampus of aged AD mice compared with that of age-matched WT and young adult AD mice; (ii) cognitive ability of APP/PS1 mice decreases with age; (iii) Drebrin protein expression in the hippocampus correlates with behavioral performance in different aged AD mice; (iv) cognitive ability improved significantly in APP/PS1-Dbn1 mice; (v) the expression level of Drebrin in APP/PS1-Dbn1 mouse hippocampus was significantly increased; (vi) the pathological lesion of AD was alleviated in APP/PS1-Dbn1 mice; (vii) the filamentous actin (F-actin) and microtubule-associated protein 2(MAP-2) in APP/PS1-Dbn1 mice were notably more than control mice. In this study, an effective expression of Drebrin improves cognitive abilities and alleviates lesions in an AD mouse model. These results may provide some valid resources for therapy and research of AD.

EEF2K inhibition blocks Aβ42 neurotoxicity by promoting an NRF2 antioxidant response.

Soluble oligomers of amyloid-β (Aβ) impair synaptic plasticity, perturb neuronal energy homeostasis, and are implicated in Alzheimer's disease (AD) pathogenesis. Therefore, significant efforts in AD drug discovery research aim to prevent the formation of Aβ oligomers or block their neurotoxicity. The eukaryotic elongation factor-2 kinase (eEF2K) plays a critical role in synaptic plasticity, and couples neurotransmission to local dendritic mRNA translation. Recent evidence indicates that Aβ oligomers activate neuronal eEF2K, suggesting a potential link to Aβ induced synaptic dysfunction. However, a detailed understanding of the role of eEF2K in AD pathogenesis, and therapeutic potential of eEF2K inhibition in AD, remain to be determined. Here, we show that eEF2K activity is increased in postmortem AD patient cortex and hippocampus, and in the hippocampus of aged transgenic AD mice. Furthermore, eEF2K inhibition using pharmacological or genetic approaches prevented the toxic effects of Aβ42 oligomers on neuronal viability and dendrite formation in vitro. We also report that eEF2K inhibition promotes the nuclear factor erythroid 2-related factor (NRF2) antioxidant response in neuronal cells, which was crucial for the beneficial effects of eEF2K inhibition in neurons exposed to Aβ42 oligomers. Accordingly, NRF2 knockdown or overexpression of the NRF2 inhibitor, Kelch-Like ECH-Associated Protein-1 (Keap1), significantly attenuated the neuroprotection associated with eEF2K inhibition. Finally, genetic deletion of the eEF2K ortholog efk-1 reduced oxidative stress, and improved chemotaxis and serotonin sensitivity in C. elegans expressing human Aβ42 in neurons. Taken together, these findings highlight the potential utility of eEF2K inhibition to reduce Aβ-mediated oxidative stress in AD.

Review of the Evidence that Transcranial Electromagnetic Treatment will be a Safe and Effective Therapeutic Against Alzheimer's Disease.

We have demonstrated in multiple studies that daily, long-term electromagnetic field (EMF) treatment in the ultra-high frequency range not only protects Alzheimer’s disease (AD) transgenic mice from cognitive impairment, but also reverses such impairment in aged AD mice. Moreover, these beneficial cognitive effects appear to be through direct actions on the AD process. Based on a large array of pre-clinical data, we have initiated a pilot clinical trial to determine the safety and efficacy of EMF treatment to mild-moderate AD subjects. Since it is important to establish the safety of this new neuromodulatory approach, the main purpose of this review is to provide a comprehensive assessment of evidence supporting the safety of EMFs, particularly through transcranial electromagnetic treatment (TEMT). In addition to our own pre-clinical studies, a rich variety of both animal and cell culture studies performed by others have underscored the anticipated safety of TEMT in clinical AD trials. Moreover, numerous clinical studies have determined that short- or long-term human exposure to EMFs similar to those to be provided clinically by TEMT do not have deleterious effects on general health, cognitive function, or a variety of physiologic measures—to the contrary, beneficial effects on brain function/activity have been reported. Importantly, such EMF exposure has not been shown to increase the risk of any type of cancer in human epidemiologic studies, as well as animal and cell culture studies. In view of all the above, clinical trials of safety/efficacy with TEMT to AD subjects are clearly warranted and now in progress.

Hyperglycemia modulates extracellular amyloid-β concentrations and neuronal activity in vivo.

Epidemiological studies show that patients with type 2 diabetes (T2DM) and individuals with a diabetes-independent elevation in blood glucose have an increased risk for developing dementia, specifically dementia due to Alzheimer's disease (AD). These observations suggest that abnormal glucose metabolism likely plays a role in some aspects of AD pathogenesis, leading us to investigate the link between aberrant glucose metabolism, T2DM, and AD in murine models. Here, we combined two techniques – glucose clamps and in vivo microdialysis – as a means to dynamically modulate blood glucose levels in awake, freely moving mice while measuring real-time changes in amyloid-β (Aβ), glucose, and lactate within the hippocampal interstitial fluid (ISF). In a murine model of AD, induction of acute hyperglycemia in young animals increased ISF Aβ production and ISF lactate, which serves as a marker of neuronal activity. These effects were exacerbated in aged AD mice with marked Aβ plaque pathology. Inward rectifying, ATP-sensitive potassium (K(ATP)) channels mediated the response to elevated glucose levels, as pharmacological manipulation of K(ATP) channels in the hippocampus altered both ISF Aβ levels and neuronal activity. Taken together, these results suggest that K(ATP) channel activation mediates the response of hippocampal neurons to hyperglycemia by coupling metabolism with neuronal activity and ISF Aβ levels.

A mouse model of Alzheimer's disease displays increased susceptibility to kindling and seizure‐associated death

People with Alzheimer's disease (AD) are up to 10 times more likely to develop epilepsy than the age-matched general population. However, given that only a proportion of patients with AD develop epilepsy, it is likely that additional factors may be required for the epilepsy to emerge. This study aimed to better understand the relationship between AD pathology and seizure susceptibility. It also aimed to investigate a "two-hit" hypothesis for seizure susceptibility through amygdala kindling of rodent AD models. Aged AD mice (Tg2576 model) and wild-type (WT) mice underwent electrical amygdala kindling. Compared with WT mice, Tg2576 mice had significantly lower afterdischarge threshold. Significantly fewer stimulations were required for the Tg2576 mice to reach the first class V seizure. Higher death rate was observed with Tg2576 mice in the kindling group. Both sham and kindled Tg2576 animals had increased levels of sprouting in the supragranular layer of the dentate gyrus compared with the WT counterparts. These findings support the "two-hit" hypothesis and represent a potentially novel research model to help better understand the relationship between AD pathology and epilepsy.

Zileuton restores memory impairments and reverses amyloid and tau pathology in aged Alzheimer's disease mice

The enzyme 5-lipoxygenase (5LO) is upregulated in Alzheimer's disease (AD), and its pharmacologic blockade with zileuton slows down the development of the AD-like phenotype in young AD mice. However, its efficacy after the AD pathology is established is unknown. To this end, starting at 12 months of age triple transgenic mice (3xTg) received zileuton, a selective 5LO inhibitor, or placebo for 3 months, and then the effect of this treatment on behavior, amyloid, and tau pathology assessed. Although mice on placebo showed worsening of their memory, treated mice performed even better than at baseline. Compared with placebo, treated mice had significantly less Aβ deposits and tau phosphorylation secondary to reduced γ-secretase and CDK-5 activation, respectively. Our data provide novel insights into the disease-modifying action of pharmacologically inhibiting 5LO as a viable AD therapeutic approach. They represent the successful completion of preclinical studies for the development of this class of drug as clinically applicable therapy for the disease.

Suppressed Retinal Degeneration in Aged Wild Type and APPswe/PS1ΔE9 Mice by Bone Marrow Transplantation

Alzheimer's disease (AD) is an age-related condition characterized by accumulation of neurotoxic amyloid β peptides (Aβ) in brain and retina. Because bone marrow transplantation (BMT) results in decreased cerebral Aβ in experimental AD, we hypothesized that BMT would mitigate retinal neurotoxicity through decreased retinal Aβ. To test this, we performed BMT in APPswe/PS1ΔE9 double transgenic mice using green fluorescent protein expressing wild type (wt) mice as marrow donors. We first examined retinas from control, non-transplanted, aged AD mice and found a two-fold increase in microglia compared with wt mice, prominent inner retinal Aβ and paired helical filament-tau, and decreased retinal ganglion cell layer neurons. BMT resulted in near complete replacement of host retinal microglia with BMT-derived cells and normalized total AD retinal microglia to non-transplanted wt levels. Aβ and paired helical filament-tau were reduced (61.0% and 44.1% respectively) in BMT-recipient AD mice, which had 20.8% more retinal ganglion cell layer neurons than non-transplanted AD controls. Interestingly, aged wt BMT recipients also had significantly more neurons (25.4%) compared with non-transplanted aged wt controls. Quantitation of retinal ganglion cell layer neurons in young mice confirmed age-related retinal degeneration was mitigated by BMT. We found increased MHC class II expression in BMT-derived microglia and decreased oxidative damage in retinal ganglion cell layer neurons. Thus, BMT is neuroprotective in age-related as well as AD-related retinal degeneration, and may be a result of alterations in innate immune function and oxidative stress in BMT recipient mice.