APP Transgenic Mice Research Articles

Combination anti-Aβ treatment maximizes cognitive recovery and rebalances mTOR signaling in APP mice.

Drug development for Alzheimer's disease has endeavored to lower amyloid β (Aβ) by either blocking production or promoting clearance. The benefit of combining these approaches has been examined in mouse models and shown to improve pathological measures of disease over single treatment; however, the impact on cellular and cognitive functions affected by Aβ has not been tested. We used a controllable APP transgenic mouse model to test whether combining genetic suppression of Aβ production with passive anti-Aβ immunization improved functional outcomes over either treatment alone. Compared with behavior before treatment, arresting further Aβ production (but not passive immunization) was sufficient to stop further decline in spatial learning, working memory, and associative memory, whereas combination treatment reversed each of these impairments. Cognitive improvement coincided with resolution of neuritic dystrophy, restoration of synaptic density surrounding deposits, and reduction of hyperactive mammalian target of rapamycin signaling. Computational modeling corroborated by in vivo microdialysis pointed to the reduction of soluble/exchangeable Aβ as the primary driver of cognitive recovery.

7-Deoxy-trans-dihydronarciclasine Reduces β-Amyloid and Ameliorates Memory Impairment in a Transgenic Model of Alzheimer's Disease.

The critical pathological feature of Alzheimer's disease (AD) is the accumulation of β-amyloid (Aβ), the main constituent of amyloid plaques. β-amyloid precursor protein (APP) undergoes amyloidogenic cleavage by β- and γ-secretase generating Aβ at endosomes or non-amyloidogenic processing by α-secretase precluding the production of Aβ at the plasma membrane. Recently, several natural products have been widely researched on the prevention of Aβ accumulation for AD treatment. We previously reported that Lycoris chejuensis K. Tae et S. Ko (CJ), which originated from Jeju Island in Korea, improved the disrupted memory functions and reduced Aβ production in vivo. Here, we further explored the effect of its active component, 7-deoxy-trans-dihydronarciclasine (coded as E144), on Aβ generation and the underlying mechanism. Our results showed that E144 reduced the level of APP, especially its mature form, in HeLa cells overexpressing human APP with the Swedish mutation. Concomitantly, E144 decreased the levels of Aβ, sAPPβ, sAPPα, and C-terminal fragment. In addition, administration of E144 normalized the behavioral deficits in Tg2576 mice, an APP transgenic mouse model of AD. E144 also decreased the Aβ and APP levels in the cerebral cortex of Tg2576 mice. Thus, we propose that E144 could be a potential drug candidate for an anti-amyloid disease-modifying AD therapy.

Hippocampal mutant APP and amyloid beta-induced cognitive decline, dendritic spine loss, defective autophagy, mitophagy and mitochondrial abnormalities in a mouse model of Alzheimer's disease.

The purpose of our study was to determine the toxic effects of hippocampal mutant APP and amyloid beta (Aβ) in 12-month-old APP transgenic mice. Using rotarod and Morris water maze tests, immunoblotting and immunofluorescence, Golgi-cox staining and transmission electron microscopy, we assessed cognitive behavior, protein levels of synaptic, autophagy, mitophagy, mitochondrial dynamics, biogenesis, dendritic protein MAP2 and quantified dendritic spines and mitochondrial number and length in 12-month-old APP mice that express Swedish mutation. Mitochondrial function was assessed by measuring the levels of hydrogen peroxide, lipid peroxidation, cytochrome c oxidase activity and mitochondrial ATP. Morris water maze and rotarod tests revealed that hippocampal learning and memory and motor learning and coordination were impaired in APP mice relative to wild-type (WT) mice. Increased levels of mitochondrial fission proteins, Drp1 and Fis1 and decreased levels of fusion (Mfn1, Mfn2 and Opa1) biogenesis (PGC1α, NRF1, NRF2 and TFAM), autophagy (ATG5 and LC3BI, LC3BII), mitophagy (PINK1 and TERT), synaptic (synaptophysin and PSD95) and dendritic (MAP2) proteins were found in 12-month-old APP mice relative to age-matched non-transgenic WT mice. Golgi-cox staining analysis revealed that dendritic spines are significantly reduced. Transmission electron microscopy revealed significantly increased mitochondrial numbers and reduced mitochondrial length in APP mice. These findings suggest that hippocampal accumulation of mutant APP and Aβ is responsible for abnormal mitochondrial dynamics and defective biogenesis, reduced MAP2, autophagy, mitophagy and synaptic proteins and reduced dendritic spines and hippocampal-based learning and memory impairments, and mitochondrial structural and functional changes in 12-month-old APP mice.

Seed‐induced Aβ deposition is modulated by microglia under environmental enrichment in a mouse model of Alzheimer's disease

Alzheimer's disease (AD) is characterized by severe neuronal loss as well as the accumulation of amyloid‐β (Aβ), which ultimately leads to plaque formation. Although there is now a general agreement that the aggregation of Aβ can be initiated by prion‐like seeding, the impact and functional consequences of induced Aβ deposits (Aβ seeding) on neurons still remain open questions. Here, we find that Aβ seeding, representing early stages of plaque formation, leads to a dramatic decrease in proliferation and neurogenesis in two APP transgenic mouse models. We further demonstrate that neuronal cell death occurs primarily in the vicinity of induced Aβ deposits culminating in electrophysiological abnormalities. Notably, environmental enrichment and voluntary exercise not only revives adult neurogenesis and reverses memory deficits but, most importantly, prevents Aβ seeding by activated, phagocytic microglia cells. Our work expands the current knowledge regarding Aβ seeding and the consequences thereof and attributes microglia an important role in diminishing Aβ seeding by environmental enrichment.

The direct role of 5-lipoxygenase on tau pathology, synaptic integrity and cognition in a mouse model of tauopathy

Neurodegenerative tauopathies are characterized by pathological accumulation of highly phosphorylated isoforms of tau protein, which leads to progressive neuronal loss. Neuroinflammation often accompanies tau-driven diseases; however, the direct role of neuroinflammation in tauopathies remains unknown. The 5-lipoxygenase (5LO) is a pro-inflammatory enzyme, which produces several bioactive metabolites and is widely expressed in the central nervous system. Previously, our group showed that 5LO influences the Alzheimer’s disease (AD) phenotype of APP transgenic mice as well as a mouse model with plaques and tangles. However, whether this protein directly modulates tau phosphorylation and subsequent neuropathology remains to be fully investigated. In the current study, we provide evidence for an age-dependent and region-specific upregulation of the 5LO pathway (protein, message and activity) in a transgenic mouse model of tauopathy, the P301S line. In addition, we demonstrate that genetic deletion of 5LO in this mouse model results in significant memory improvement, reduces tau phosphorylation at specific epitopes as well as neuroinflammation and rescues synaptic pathology. In vitro studies confirmed that 5LO directly modulates tau phosphorylation at the same epitopes as for the brain tissues. Taken together, our data reveal an active involvement of the 5LO pathway in the development of the tauopathy phenotype and provide strong support to the hypothesis that this enzymatic protein should be considered a novel and viable therapeutic target for the treatment of human tauopathy.

Near infrared light decreases synaptic vulnerability to amyloid beta oligomers

Synaptic dysfunction due to the disrupting binding of amyloid beta (Aβ) and tau oligomers is one of the earliest impairments in Alzheimer’s Disease (AD), driving initial cognitive deficits and clinical manifestation. Consequently, there is ample consensus that preventing early synaptic dysfunction would be an effective therapeutic strategy for AD. With this goal in mind, we investigated the effect of a treatment of mice with near infrared (NIR) light on synaptic vulnerability to Aβ oligomers. We found that Aβ oligomer binding to CNS synaptosomes isolated from wild type (wt) mice treated with NIR light was significantly reduced and the resulting suppression of long term potentiation (LTP) by Aβ oligomers was prevented. Similarly, APP transgenic mice treated with NIR showed a significant reduction of endogenous Aβ at CNS synapses. We further found that these phenomena were accompanied by increased synaptic mitochondrial membrane potential in both wt and Tg2576 mice. This study provides evidence that NIR light can effectively reduce synaptic vulnerability to damaging Aβ oligomers, thus furthering NIR light therapy as a viable treatment for AD.

SEN1500, a novel oral amyloid-β aggregation inhibitor, attenuates brain pathology in a mouse model of Alzheimer's disease.

Amyloid-β (Aβ) aggregation is thought to be a major pathogenic event underlying the neuropathology of Alzheimer's disease (AD). The development of new drugs inhibiting the Aβ aggregation process is, therefore, important. SEN1500, an orally bioavailable and CNS-penetrant Aβ aggregation inhibitor, has previously been shown to reduce spatial learning and memory deficits in an APP transgenic mouse model. To verify that the pharmacological properties of SEN1500 are not unique to this model, we investigated brain Aβ pathology, neuroinflammation, as well as memory in a different mouse model of AD expressing the human amyloid precursor protein with Swedish and London mutations (APPSL). APPSL transgenic mice and non-transgenic littermates were treated with SEN1500 via food pellets from three months of age for four months. At the end of the treatment, animals were tested for memory deficits using the contextual fear conditioning test and brain tissue was analyzed for soluble and insoluble amyloid-β1-38, -40, -42, β-amyloid plaques, β-sheet plaque cores, as well as for astrocytosis and activated microglia. SEN1500 treatment lowered insoluble Aβ levels and β-amyloid plaque load in the brain compared with control-treated APPSL mice. Activated microglia were significantly reduced in the cortex but not the hippocampus of SEN1500-treated APPSL mice. Memory deficits of APPSL mice could not be rescued by SEN1500. SEN1500 is not only able to reduce Aβ pathology and activated microglia but also to improve learning and memory as previously shown, making SEN1500 a potential candidate for human AD treatment. This Aβ aggregation inhibitor could be a promising therapeutic agent for the disease-modifying treatment of AD.

Intravenous treatment with human recombinant ApoA-I Milano reduces beta amyloid cerebral deposition in the APP23-transgenic mouse model of Alzheimer's disease

Beyond the crucial role of apolipoprotein A-I (ApoA-I) on peripheral cholesterol metabolism, this apolipoprotein has also been implicated in beta amyloid (Aβ)–related neuropathologies. ApoA-I-Milano (M) is a mutated variant, which showed increased vasoprotective properties compared to ApoA-I-wild type in models of atherosclerosis and cardiovascular damage. We speculated that ApoA-I-M may also protect Aβ-affected vasculature and reverse some of the pathological features associated with Alzheimer's disease (AD). For this purpose, we produced and characterized human recombinant ApoA-I-wild type and ApoA-I-M proteins. Both of them were able to avoid the aggregation of Aβ in vitro, even though recombinant ApoA-I-M was significantly more effective in protecting endothelial cells from Aβ(1–42)-toxicity. Next, we determined the effect of chronic intravenous administration of rApoA-I-M in the APP23-transgenic mouse model of AD. We found reduced cerebral Aβ levels in mice that received rApoA-I-M, which were accompanied by a lower expression of astrocyte and microglia neuroinflammatory markers. Our results suggest an applicability of this molecule as a therapeutic candidate for protecting the brain in AD.

Alleviation of Neuropathology by Inhibition of Monoacylglycerol Lipase in APP Transgenic Mice Lacking CB2 Receptors.

Inhibition of monoacylglycerol lipase (MAGL), the primary enzyme that hydrolyzes the endocannabinoid 2-arachidonoylglycerol (2-AG) in the brain, produces profound anti-inflammatory and neuroprotective effects and improves synaptic and cognitive functions in animal models of Alzheimer's disease (AD). However, the molecular mechanisms underlying the beneficial effects produced by inhibition of 2-AG metabolism are still not clear. The cannabinoid receptor type 2 (CB2R) has been thought to be a therapeutic target for AD. Here, we provide evidence, however, that CB2R does not play a role in ameliorating AD neuropathology produced by inactivation of MAGL in 5XFAD APP transgenic mice, an animal model of AD. We observed that expression of APP and β-secretase as well as production of total Aβ and Aβ42 were significantly reduced in APP transgenic mice lacking CB2R (TG-CB2-KO) treated with JZL184, a selective and potent inhibitor for MAGL. Inactivation of MAGL also alleviated neuroinflammation and neurodegeneration in TG-CB2-KO mice. Importantly, TG-CB2-KO mice treated with JZL184 still exhibited improvements in spatial learning and memory. In addition, MAGL inhibition prevented deterioration in expression of important synaptic proteins in TG-CB2-KO mice. Our results suggest that CB2R is not required in ameliorating neuropathology and preventing cognitive decline by inhibition of 2-AG metabolism in AD model animals.

IMMUNE SYSTEM GENETICS IN ALZHEIMER'S DISEASE

Our genetic analysis originally showed that trem2 was a risk gene for Alzheimer's disease. With this background, we wanted to try and understand how trem2 related to other Alzheimer genes in terms of function and gene expression. We examined transgenic APP and MAPT mice and assessed how genome expression by expression array and assessed which genes were co-regulated with trem2. Using WGCNA we found that many other genes which were co-regulated with trem2 were also AD risk loci and that this module of coexpression contained several AD loci. These data indicate that instead of thinking of individuals genes as being risk genes for the disease, rather we should consider the process of microglia reponse as central to disease pathogenesis.

Ciproxifan improves cholinergic transmission, attenuates neuroinflammation and oxidative stress but does not reduce amyloid level in transgenic mice

AimThe present study is aimed to investigate the ability of ciproxifan, a histamine H3 receptor antagonist to inhibit β-amyloid (Aβ)-induced neurotoxicity in SK-N-SH cells and APP transgenic mouse model. Materials and methodsIn vitro studies was designed to evaluate the neuroprotective effects of ciproxifan in Aβ25–35 - induced SK-N-SH cells. For the in vivo study, ciproxifan (1 and 3mg/kg, i.p.) was administrated to transgenic mice for 15days and behaviour was assessed using the radial arm maze (RAM). Brain tissues were collected to measure Aβ levels (Aβ1–40 and Aβ1–42), acetylcholine (ACh), acetylcholinesterase (AChE), nitric oxide (NO), lipid peroxidation (LPO), antioxidant activities, cyclooxygenases (COX) and cytokines (IL-1α, IL-1β and IL-6), while plasma was collected to measure TGF-1β. ResultsThe in vitro studies demonstrated neuroprotective effect of ciproxifan by increasing cell viability and inhibiting reactive oxygen species (ROS) in Aβ25–35-induced SK-N-SH cells. Ciproxifan significantly improved the behavioural parameters in RAM. Ciproxifan however, did not alter the Aβ levels in APP transgenic mice. Ciproxifan increased ACh and showed anti-oxidant properties by reducing NO and LPO levels as well as enhancing antioxidant levels. The neuroinflammatory analysis showed that ciproxifan reduced both COX-1 and COX-2 activities, decreased the level of pro-inflammatory cytokines IL-1α, IL-1β and IL-6 and increased the level of anti-inflammatory cytokine TGF-1β. ConclusionThis present study provides scientific evidence of the use of ciproxifan via antioxidant and cholinergic pathways in the management of AD.

Amelioration of amyloid-\u03b2-induced deficits by DcR3 in an Alzheimer\u2019s disease model

BackgroundMicroglia mediate amyloid-beta peptide (Aβ)-induced neuroinflammation, which is one of the key events in the pathogenesis of Alzheimer’s disease (AD). Decoy receptor 3 (DcR3)/TNFRSF6B is a pleiotropic immunomodulator that promotes macrophage differentiation toward the M2 anti-inflammatory phenotype. Based on its role as an immunosupressor, we examined whether DcR3 could alleviate neuroinflammation and AD-like deficits in the central nervous system.MethodWe crossed human APP transgenic mice (line J20) with human DcR3 transgenic mice to generate wild-type, APP, DcR3, and APP/DcR3 mice for pathological analysis. The Morris water maze, fear conditioning test, open-field, and elevated-plus maze were used to access their cognitive behavioral changes. Furthermore, the pathological and immune profiles were examined by immunostaining, ELISA, Q-PCR, and IP. In vitro assays were designed to examine DcR3-mediated innate cytokine profile alteration and the potential protective mechanism.ResultsWe reported that DcR3 ameliorates hippocampus-dependent memory deficits and reduces amyloid plaque deposition in APP transgenic mouse. The protective mechanism of DcR3 mediates through interacting with heparan sulfate proteoglycans and activating IL-4+YM1+ M2a-like microglia that reduces Aβ-induced proinflammatory cytokines and promotes phagocytosis ability of microglia.ConclusionThe neuroprotective effect of DcR3 is mediated via modulating microglia activation into anti-inflammatory M2a phenotype, and upregulating DcR3 expression in the brain may be a potential therapeutic approach for AD.

NLRP3 Inflammasome Inhibitor Ameliorates Amyloid Pathology in a Mouse Model of Alzheimer's Disease.

The activation of the NLRP3 inflammasome signaling pathway plays an important role in the neuroinflammation in Alzheimer's disease (AD). In this study, we investigated the effects of JC-124, a rationally designed NLRP3 inflammasome inhibitor, on AD-related deficits in CRND8 APP transgenic mice (TgCRND8). We first demonstrated increased formation and activation of NLRP3 inflammasome in TgCRND8 mice compared to non-transgenic littermate controls, which was inhibited by the treatment with JC-124. Importantly, JC-124 treatment led to decreased levels of Aβ deposition and decreased levels of soluble and insoluble Aβ1-42 in the brain of CRND8 mice which was accompanied by reduced β-cleavage of APP, reduced activation of microglia but enhanced astrocytosis. Oxidative stress was decreased and synaptophysin was increased in the CRND8 mice after JC-124 treatment, demonstrating a neuroprotective effect. Overall, these data demonstrated beneficial effects of JC-124 as a specific NLRP3 inflammasome inhibitor in AD mouse model and supported the further development of NLRP3 inflammasome inhibitors as a viable option for AD therapeutics.

3D printing of beta-amyloid protein deposits along capillary walls

Abnormally high levels of neocortical beta-amyloid protein (A+) reflect Alzheimer’s disease (AD) pathology in persons with clinical evidence of dementia or mild cognitive impairment (MCI). The abnormal aggregation of beta-amyloid protein in the brain neuropil may lead to either diffuse plaques and/or concentrated neuritic plaques, with the latter form of deposits often present in the vicinity of the cerebral microvasculature. The A protein, with its crystalline molecular structure, infiltrates the vessel walls and compromises the blood-brain barrier (BBB). The physical basis for this was elegantly shown by Meyer and colleagues, in a 2008 publication showing two-dimensional (2D) confocal laser scanning microscopic imaging of vascular A protein deposits in APP23 transgenic mice. These investigators showed accumulations of “tuft-life structures”, also referred to as “pompons” with protruding spikes on – and embedded within – microvessels. These pompons of beta-amyloid protein “consist of fibrillar structures, [and] can encircle and constrict capillaries, and are often associated with distortion of capillaries”.We were struck by both the heuristic value of the imaging of Meyer and colleagues, in explaining the root cause of both the amyloid-related alterations in the vascular bed, and depicting minute protein deposits that are both geometrically complex, seemingly delicate and fragile, and yet tenacious in their embedding within small vessel walls. We re-created these images with standard 3D printing technology (extruded plastic) for both educational/teaching and artistic purposes.

Liver X receptor agonist treatment significantly affects phenotype and transcriptome of APOE3 and APOE4 Abca1 haplo-deficient mice.

ATP-binding cassette transporter A1 (ABCA1) controls cholesterol and phospholipid efflux to lipid-poor apolipoprotein E (APOE) and is transcriptionally controlled by Liver X receptors (LXRs) and Retinoic X Receptors (RXRs). In APP transgenic mice, lack of Abca1 increased Aβ deposition and cognitive deficits. Abca1 haplo-deficiency in mice expressing human APOE isoforms, increased level of Aβ oligomers and worsened memory deficits, preferentially in APOE4 mice. In contrast upregulation of Abca1 by LXR/RXR agonists significantly ameliorated pathological phenotype of those mice. The goal of this study was to examine the effect of LXR agonist T0901317 (T0) on the phenotype and brain transcriptome of APP/E3 and APP/E4 Abca1 haplo-deficient (APP/E3/Abca1+/- and APP/E4/Abca1+/-) mice. Our data demonstrate that activated LXRs/RXR ameliorated APOE4-driven pathological phenotype and significantly affected brain transcriptome. We show that in mice expressing either APOE isoform, T0 treatment increased mRNA level of genes known to affect brain APOE lipidation such as Abca1 and Abcg1. In both APP/E3/Abca1+/- and APP/E4/Abca1+/- mice, the application of LXR agonist significantly increased ABCA1 protein level accompanied by an increased APOE lipidation, and was associated with restoration of APOE4 cognitive deficits, reduced levels of Aβ oligomers, but unchanged amyloid load. Finally, using Gene set enrichment analysis we show a significant APOE isoform specific response to LXR agonist treatment: Gene Ontology categories “Microtubule Based Process” and “Synapse Organization” were differentially affected in T0-treated APP/E4/Abca1+/- mice. Altogether, the results are suggesting that treatment of APP/E4/Abca1+/- mice with LXR agonist T0 ameliorates APOE4-induced AD-like pathology and therefore targeting the LXR-ABCA1-APOE regulatory axis could be effective as a potential therapeutic approach in AD patients, carriers of APOEε4.

Mitochondria-targeted small molecule SS31: a potential candidate for the treatment of Alzheimer's disease.

The objective of our study was to better understand the protective effects of the mitochondria-targeted tetra-peptide SS31 against amyloid beta (Aβ)-induced mitochondrial and synaptic toxicities in Alzheimer's disease (AD) progression. Using intraperitoneal injections, we administered SS31 to an AD mouse model (APP) over a period of 6 weeks, beginning when the APP mice were 12 months of age. We studied their cortical tissues after SS31 treatment and determined that SS31 crosses the blood brain barrier and reaches mitochondrial sites of free radical production. We also determined: (1) plasma and brain levels of SS31, (2) mRNA levels and levels of mitochondrial dynamics, biogenesis proteins and synaptic proteins, (3) soluble Aβ levels and immunoreactivity of mutant APP and Aβ levels and (4) mitochondrial function by measuring H2O2, lipid peroxidation, cytochrome c oxidase activity and mitochondrial ATP. We found reduced mRNA expression and reduced protein levels of fission genes, and increased levels of mitochondrial fusion, biogenesis and synaptic genes in SS31-treated APP mice relative to SS31-untreated APP mice. Immunofluorescence analysis revealed reduced full-length mutant APP and soluble/insoluble Aβ levels in the SS31-treated APP mice. Sandwich ELISA assays revealed significantly reduced soluble Aβ levels in the SS31-treated APP mice relative to the untreated APP mice. Mitochondrial function was maintained in the SS31-treated APP mice over the 6 weeks of SS31 treatment compared with mitochondrial function in the untreated APP mice. Our findings indicate that SS31 treatment reduces Aβ production, reduces mitochondrial dysfunction, maintains mitochondrial dynamics and enhances mitochondrial biogenesis and synaptic activity in APP mice; and that SS31 may confer protective effects against mitochondrial and synaptic toxicities in APP transgenic mice.

Reduction of Abeta amyloid pathology in APPPS1 transgenic mice in the absence of gut microbiota

Alzheimer’s disease is the most common form of dementia in the western world, however there is no cure available for this devastating neurodegenerative disorder. Despite clinical and experimental evidence implicating the intestinal microbiota in a number of brain disorders, its impact on Alzheimer’s disease is not known. To this end we sequenced bacterial 16S rRNA from fecal samples of Aβ precursor protein (APP) transgenic mouse model and found a remarkable shift in the gut microbiota as compared to non-transgenic wild-type mice. Subsequently we generated germ-free APP transgenic mice and found a drastic reduction of cerebral Aβ amyloid pathology when compared to control mice with intestinal microbiota. Importantly, colonization of germ-free APP transgenic mice with microbiota from conventionally-raised APP transgenic mice increased cerebral Aβ pathology, while colonization with microbiota from wild-type mice was less effective in increasing cerebral Aβ levels. Our results indicate a microbial involvement in the development of Abeta amyloid pathology, and suggest that microbiota may contribute to the development of neurodegenerative diseases.

APOE Genotype Differentially Modulates Effects of Anti-A\u03b2, Passive Immunization in APP Transgenic Mice

BackgroundAPOE genotype is the foremost genetic factor modulating β-amyloid (Aβ) deposition and risk of sporadic Alzheimer’s disease (AD). Here we investigated how APOE genotype influences response to anti-Aβ immunotherapy.MethodsAPPSW/PS1dE9 (APP) transgenic mice with targeted replacement of the murine Apoe gene for human APOE alleles received 10D5 anti-Aβ or TY11-15 isotype control antibodies between the ages of 12 and 15 months.ResultsAnti-Aβ immunization decreased both the load of fibrillar plaques and the load of Aβ immunopositive plaques in mice of all APOE backgrounds. Although the relative reduction in parenchymal Aβ plaque load was comparable across all APOE genotypes, APP/ε4 mice showed the greatest reduction in the absolute Aβ plaque load values, given their highest baseline. The immunization stimulated phagocytic activation of microglia, which magnitude adjusted for the post-treatment plaque load was the greatest in APP/ε4 mice implying association between the ε4 allele and impaired Aβ phagocytosis. Perivascular hemosiderin deposits reflecting ensued microhemorrhages were associated with vascular Aβ (VAβ) and ubiquitously present in control mice of all APOE genotypes, although in APP/ε3 mice their incidence was the lowest. Anti-Aβ immunization significantly reduced VAβ burden but increased the number of hemosiderin deposits across all APOE genotypes with the strongest and the weakest effect in APP/ε2 and APP/ε3 mice, respectively.ConclusionsOur studies indicate that APOE genotype differentially modulates microglia activation and Aβ plaque load reduction during anti-Aβ immunotherapy. The APOE ε3 allele shows strong protective effect against immunotherapy associated microhemorrhages; while, conversely, the APOE ε2 allele increases risk thereof.

Administrations of human adult ischemia-tolerant mesenchymal stem cells and factors reduce amyloid beta pathology in a mouse model of Alzheimer's disease

The impact of human adult ischemia-tolerant mesenchymal stem cells (hMSCs) and factors (stem cell factors) on cerebral amyloid beta (Aβ) pathology was investigated in a mouse model of Alzheimer's disease (AD). To this end, hMSCs were administered intravenously to APPPS1 transgenic mice that normally develop cerebral Aβ. Quantitative reverse transcriptase polymerase chain reaction biodistribution revealed that intravenously delivered hMSCs were readily detected in APPPS1 brains 1 hour following administration, and dropped to negligible levels after 1 week. Notably, intravenously injected hMSCs that migrated to the brain region were localized in the cerebrovasculature, but they also could be observed in the brain parenchyma particularly in the hippocampus, as revealed by immunohistochemistry. A single hMSC injection markedly reduced soluble cerebral Aβ levels in APPPS1 mice after 1 week, although increasing several Aβ-degrading enzymes and modulating a panel of cerebral cytokines, suggesting an amyloid-degrading and anti-inflammatory impact of hMSCs. Furthermore, 10 weeks of hMSC treatment significantly reduced cerebral Aβ plaques and neuroinflammation in APPPS1 mice, without increasing cerebral amyloid angiopathy or microhemorrhages. Notably, a repeated intranasal delivery of soluble factors secreted by hMSCs in culture, in the absence of intravenous hMSC injection, was also sufficient to diminish cerebral amyloidosis in the mice. In conclusion, this preclinical study strongly underlines that cerebral amyloidosis is amenable to therapeutic intervention based on peripheral applications of hMSC or hMSC factors, paving the way for a novel therapy for Aβ amyloidosis and associated pathologies observed in AD.

Mapping synaptic glutamate transporter dysfunction in vivo to regions surrounding Aβ plaques by iGluSnFR two-photon imaging.

Amyloid-β (Aβ) plaques, a hallmark of Alzheimer's disease (AD), are surrounded by regions of neuronal and glial hyperactivity. We use in vivo two-photon and wide-field imaging of the glutamate sensor iGluSnFR to determine whether pathological changes in glutamate dynamics in the immediate vicinity of Aβ deposits in APPPS1 transgenic mice could alter neuronal activity in this microenvironment. In regions close to Aβ plaques chronic states of high spontaneous glutamate fluctuations are observed and the timing of glutamate responses evoked by sensory stimulation exhibit slower decay rates in two cortical brain areas. GLT-1 expression is reduced around Aβ plaques and upregulation of GLT-1 expression and activity by ceftriaxone partially restores glutamate dynamics to values in control regions. We conclude that the toxic microenvironment surrounding Aβ plaques results, at least partially, from enhanced glutamate levels and that pharmacologically increasing GLT-1 expression and activity may be a new target for early therapeutic intervention.