5XFAD Mouse Model Research Articles

Ketamine does not rescue plaque load or gap detection in the 5XFAD mouse model of Alzheimer's disease

Ketamine has received growing attention for its effects on neuroplasticity and neuroinflammation, and as a treatment for depression and other mental health disorders. Recent evidence suggests that early sensory and behavioral deficits in Alzheimer's disease could be caused by synaptic disruption that occurs before irreversible neuropathology. This raises the possibility that ketamine could slow down or prevent network disruption and the ensuing sensory and behavioral deficits in Alzheimer's. Here we tested this idea in the 5XFAD mouse model of Alzheimer's, using either an acute single injection of ketamine, or chronic daily injections over 15 weeks. We tested the effects of ketamine on both amyloid plaque load and on a behavioral auditory gap detection task that is an early Alzheimer's biomarker in both mice and humans. We found that ketamine had no effect on plaque load, nor any effect on gap detection, for either acute or chronic dosing. Chronic ketamine facilitated startle responses specifically in 5XFAD mice, but this could simply be related to experience-dependent effects on stress or habituation rather than any rescue effect of ketamine on Alzheimer's-related deficits. We did find robust correlations between gap detection deficits and plaque load in auditory cortex and in the caudal pontine reticular nucleus, demonstrating that the behavioral deficits seen in 5XFAD mice are directly related to amyloid accumulation in these brain regions, and confirming the validity of gap detection as an early biomarker of Alzheimer's. Ketamine, however, had no effect on the strength of these correlations. We conclude that ketamine has no beneficial effect on the development of behavioral gap detection deficits or plaque load in the 5XFAD Alzheimer's mouse model, following either an acute single dose or a chronic daily dose regimen.

FOXP1 is a Transcription Factor for the Alzheimer's Disease Risk Gene SORL1.

Sortilin-related receptor 1 (SORL1) is a risk gene of Alzheimer's disease (AD), and some protein-truncating (PTV) and rare missense variants causing the loss of function of SORL1 contribute to AD pathogenesis. SORL1 is an endosomal receptor that interacts with multiple protein sorting complexes to facilitate the transport of various cargoes through the endolysosomal network (ELN). However, the regulatory mechanisms governing SORL1 expression remain unknown. Through biochemical methods, we identified Forkhead Box P1 (FOXP1) as a binding protein to the minimal promoter region of SORL1 gene. Silencing FOXP1 using siRNA significantly decreased the activity of the SORL1 minimal promoter and reduced SORL1 protein and mRNA levels in the neuroblastoma cell line SH-SY5Y. Additionally, using 5xFAD mouse models of AD, we observed significantly decreased FOXP1 and SORL1 expression in neurons within the prefrontal cortex. Disruption of ELN and the autophagy degradation system by bafilomycin A1 (BafA1) appeared to be a specific condition to suppress FOXP1 and hence SORL1 in SH-SY5Y cells. These findings highlight the critical role of FOXP1 in regulating SORL1 expression and suggest that FOXP1 could be a potential target to maintain SORL1 expression for AD prevention and therapy.

Parental origin of transgene modulates amyloid-β plaque burden in the 5xFAD mouse model of Alzheimer's disease.

In Alzheimer's disease (AD) research, the 5xFAD mouse model is commonly used as a heterozygote crossed with other genetic models to study AD pathology. We investigated whether the parental origin of the 5xFAD transgene affects plaque deposition. Using quantitative light-sheet microscopy, we found that paternal inheritance of the transgene led to a 2-fold higher plaque burden compared with maternal inheritance, a finding consistent across multiple 5xFAD colonies. This effect was not due to gestation in or rearing by 5xFAD females. Immunoblotting suggested that transgenic inheritance modulates transgenic protein expression, potentially due to genomic imprinting of the Thy1.2 promoter. Surprisingly, fewer than 20% of 5xFAD studies report breeding schemes, suggesting that this factor might confound previous findings. Our data highlight a significant determinant of plaque burden in 5xFAD mice and underscore the importance of reporting the parental origin of the transgene to improve scientific rigor and reproducibility in AD research.

Inhaled xenon modulates microglia and ameliorates disease in mouse models of amyloidosis and tauopathy.

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder. Antiamyloid antibody treatments modestly slow disease progression in mild dementia due to AD. Emerging evidence shows that homeostatic dysregulation of the brain immune system, especially that orchestrated by microglia, plays an important role in disease onset and progression. Thus, a major question is how to modulate the phenotype and function of microglia to treat AD. Xenon (Xe) gas is a noble gas used in human patients as an anesthetic and a neuroprotectant used for treating brain injuries. Xe penetrates the blood-brain barrier, which could make it an effective therapeutic. To assess the effect of Xe on microglia and AD pathology, we designed a custom Xe inhalation chamber and treated several mouse models of AD with Xe gas. Xe treatment induced mouse microglia to adopt an intermediate activation state that we have termed pre-neurodegenerative microglia (pre-MGnD). This microglial phenotypic transition was observed in mouse models of acute neurodegeneration and amyloidosis (APP/PS1 and 5xFAD mice) and tauopathy (P301S mice). This microglial state enhanced amyloid plaque compaction and reduced dystrophic neurites in the APP/PS1 and 5xFAD mouse models. Moreover, Xe inhalation reduced brain atrophy and neuroinflammation and improved nest-building behavior in P301S mice. Mechanistically, Xe inhalation induced homeostatic brain microglia toward a pre-MGnD state through IFN-γ signaling that maintained the microglial phagocytic response in APP/PS1 and 5xFAD mice while suppressing the microglial proinflammatory phenotype in P301S mice. These results support the translation of Xe inhalation as an approach for treating AD.

Elevated BACE1 and IFNγ+ T Cells in Patients with Cognitive Impairment and the 5xFAD Mouse Model.

The dysregulation of T cell differentiation was associated with cognitive impairment. Recently, the peripheric β-secretase (BACE1) has been suggested as a regulator of T cell differentiation, which was increased in both cognitive impairment (CI) and type 2 diabetes mellitus (T2DM) in CI patients. However, the relationship between T cell dysfunction and CI remains unclear. To address this question, we measured T cell subtypes and BACE1 enzyme activity in a clinical cohort and 5xFAD mice. We found that both IFNγ+ Th1 and Tc1 cells were increased in the CI and T2DM-CI groups, which were associated with worsening cognitive function. The elevated IFNγ + Th1 and Tc1 cells were also observed in 8-month-old 5xFAD mice. The elevated BACE1-mediated INSR cleavage was associated with increased IFNγ + Th1 and Tc1 cells. These findings demonstrate the potential role of elevated BACE1 in IFNγ+ T cells and CI.

The CD74 inhibitor DRhQ improves short-term memory and mitochondrial function in 5xFAD mouse model of Aβ accumulation.

Neuroinflammation and mitochondrial dysfunction are early events in Alzheimer's disease (AD) and contribute to neurodegeneration and cognitive impairment. Evidence suggests that the inflammatory axis mediated by macrophage migration inhibitory factor (MIF) binding to its receptor, CD74, plays an important role in many central nervous system (CNS) disorders such as AD. Our group has developed DRhQ, a novel CD74 binding construct which competitively inhibits MIF binding, blocks macrophage activation and migration into the CNS, enhances anti-inflammatory microglia cell numbers and reduces pro-inflammatory gene expression. Here, we evaluate its effects in amyloid-β (Aβ) overexpressing mice. 5xFAD mice and their wild type littermates were treated with DRhQ (100µg) or vehicle for 4 weeks. DRhQ improved cognition and cortical mitochondrial function in both male and female 5xFAD mice. Aβ plaque burden in 5xFAD animals was not robustly impacted by DRhQ treatment in either the hippocampus or the cortex. Cortical microglial activation was similarly not apparently affected by DRhQ treatment, although in the hippocampus there was evidence of a reduction in activated microglia for female 5xFAD mice. Future studies are needed to confirm this possible sex-dependent response on microglial activation, as well as to optimize the dose and timing of DRhQ treatment and gain a better understanding of its mechanism of action in AD.

Regulation of Microglial Polarization through the NF-kB Pathway by activating Rho/ROCK Pathway induced by LPS Priming in the 5xFAD Mouse Model of AD

The symptoms of Alzheimer's disease (AD) are the deposition of beta-amyloid plaques and chronic neuroinflammation caused by microglia. Its pathological process is closely related to microglia. Microglia have innated immune memory (IIM) and have different roles that vary with animal models of neurodegenerative diseases such as AD. However, how IIM-mediated microglia function is well validated in the 5*FAD model. We want to know if lipopolysaccharide (LPS)-induced IIM in the preclinical period of AD alters microglia polarization. We did this by injecting LPS into 5*FAD mice at 6 weeks (before plaque formation). After 140 days, we assessed microglia polarization and activation of the Rho/ROCK pathway and NF-B pathway in 5*FAD-initiated and non-initiated mice. Furthermore, the activation of them in microglia was also evaluated. ROCK2 was overexpressed in primary microglia by lentivirus transfection. Then, ROCK2 overexpression model was constructed by CRISPR/Cas9 based on 5*FAD mice. Cross with Tmem119-CreERT2 mice to obtain microglia overexpressing ROCK2 mice. The activation of microglia, and these two pathways were evaluated after LPS-induced IIM. Our expected result is that LPS-induced IIM changes microglial polarization from M1 to M2 by the inhibition of them. The paper only provides theoretical experiment design and possible results about alterations in microglia polarization and their mechanisms after LPS priming stimulates innate immune memory, which needs further research in its mechanisms. Suggestions for more long-term effects and potential therapeutic applications in humans also has been listed for reference

Ultrastructural analysis of retinal pigment epithelial cells in 5XFAD mouse model

Aims/Purpose: The 5xFAD mouse model of Alzheimer's disease overexpresses 42 amino acids long amyloid beta (Aβ42) found also from the drusen of age‐related macular degeneration (AMD) patients. In this model, Aβ42 is produced in all tissues expressing amyloid precursor protein, including retinal pigment epithelial (RPE) cells, making it an interesting candidate model for AMD. Ultrastructural changes in RPE cells of 5XFAD were examined.Methods: Six‐ and twelve‐months old 5xFAD mice and wild type (WT) littermates (n = 6) were sacrificed and eyes were enucleated. The eyes were sectioned for TEM imaging (JEM‐2100F, Jeol CO, Tokyo, Japan). The TEM images were analyzed for RPE morphology, cell organelle morphology, and autophagic structures.Results: The 5xFAD RPE showed gradual loss of basal infoldings, accumulation of drusen‐like structures beneath the RPE cells and Bruch's membrane, abnormal RPE cell size, changes in melanosome shape and localization, accumulation of lipofuscin‐like structures, and accumulation of autophagic structures. Closer inspection on autophagic structures revealed change in autophagosome/autolysosome ratio towards higher number of autolysosomes.Conclusions: The overexpression of Aβ42 was shown to induce changes in the RPE resembling pathology of AMD. Accumulation of lipofuscin‐like structures and autolysosomes suggests dysfunctional autophagic clearance system hampering the cellular homeostasis. Therefore, the RPE cells loose gradually their functioning and polarization which can be seen as a loss of basal infoldings and abnormal size. The change in melanosome shape and localization suggests high oxidative stress resulting malfunction of these organelles. Finally, the appearance of drusen‐like structures beneath the RPE cells can be considered as impaired proteostasis.

Ginkgo biloba extract EGb 761® ameliorates cognitive impairment and alleviates TNFα response in 5xFAD Alzheimer's disease model mice.

Ginkgo biloba leaf extract EGb 761® has shown clinical efficacy in patients with mild cognitive impairment and dementia. However, the pharmacological action of EGb 761® in Alzheimer's disease (AD) remains unclear and molecular mechanisms targeted in the brain are not completely understood. We aimed to investigate 1) the potential sex-dependent effects of oral administration of EGb 761® in 5xFAD mice, an AD mouse model, and 2) the underlying microglial subtype responsible for the observed anti-inflammatory effects in the brain. Eight-week old 5xFAD and wild type mice received EGb 761®-supplemented diet or control diet for eight weeks. The study investigated changes in cognitive function as well as amyloid plaque load, expression of AD-related genes, and anti-inflammatory effects. Moreover, we used organotypic brain slices for confirmation and assessment of concentration-dependency of the observed EGb 761® effects and performed single cell RNA sequencing on the prefrontal cortex of male mice with focus on microglia. We demonstrate that EGb 761® treatment improves cognitive function in 5xFAD mice in several behavioral tests. Analysis of the brain tissue from these animals indicated a reduction in amyloid plaque load in the prefrontal cortex (PFC). This brain area was further investigated to assess the molecular changes that occurred following EGb 761® intake. Alterations in the expression of genes related to AD were highly sex-specific with effects on the cholinergic system, the γ-secretase complex, and neuroinflammation. Anti-inflammatory effects of EGb 761® with a particularly pronounced reduction of the TNFα-response could be shown for the PFC but also peripherally in the serum of 5xFAD mice of both sexes. Single-cell RNA sequencing revealed that EGb761® mainly affected disease-associated microglia stage 2 (DAM2), which are thought to have a detrimental role in AD. EGb 761® shows efficacy in the treatment of cognitive deficits in the 5xFAD mouse model via multimodal activity, including sex-specific and sex-unrelated mechanisms including the normalization of neuroinflammatory parameters.

Early intervention using long-term rhythmic pulsed magnetic stimulation alleviates cognitive decline in a 5xFAD mouse model of Alzheimer's disease

BackgroundAlzheimer's disease (AD) is the most prevalent form of dementia, but no effective therapeutic strategy is available to date. Rhythmic magnetic stimulation is an attractive means of neuron modulation that could be beneficial for restoring learning and memory abilities. ObjectiveTo assess the effect of a compound pulsed rhythmic magnetic field (cPMF) on cognition during AD progression and to explore the appropriate cPMF intervention period. MethodsFemale 5xFAD mice aged 10 weeks and 18 weeks were exposed to cPMF with a carrier frequency of 40 Hz, repeated at 5 Hz for 1 h/d for 8 consecutive weeks. The Morris water maze (MWM) test was used for cognitive behavioral assessment. Furthermore, changes in molecular pathology within the brain were detected using immunofluorescence staining and real-time PCR. Results10-week-old AD mice treated with cPMF explored the target quadrant more frequently than sham-exposed AD mice in MWM test, exhibiting improved learning and memory abilities. Additionally, cPMF exposure alleviated Aβ plaque deposition and astrogliosis in the AD brain. Moreover, neurotrophic factor fibroblast growth factor 1 (FGF1) in the AD brain was upregulated by cPMF treatment. However, in 18-week-old AD mice treated with cPMF, cognitive performance and Fgf1 gene expression were not significantly improved, although Aβ plaque deposition and astrogliosis were alleviated. ConclusionEarly intervention via long-term rhythmic cPMF stimulation may alleviate the histopathological features and enhance neuroprotective gene Fgf1 expression, thereby improving the cognitive performance of 5xFAD mice, which should provide promising insight for the clinical treatment of patients with AD.

Maresin-like 1 Ameliorates Neuropathology of Alzheimer's Disease in Brains of a Transgenic Mouse Model.

(1) Background: Impeded resolution of inflammation contributes substantially to the pathogenesis of Alzheimer's disease (AD); consequently, resolving inflammation is pivotal to the amelioration of AD pathology. This can potentially be achieved by the treatment with specialized pro-resolving lipid mediators (SPMs), which should resolve neuroinflammation in brains. (2) Methods: Here, we report the histological effects of long-term treatment with an SPM, maresin-like 1 (MarL1), on AD pathogenesis in a transgenic 5xFAD mouse model. (3) Results: MarL1 treatment reduced Aβ overload, curbed the loss of neurons in brains especially cholinergic neurons associated with cleaved-caspase-3-associated apoptotic degeneration, reduced microgliosis and the pro-inflammatory M1 polarization of microglia, curbed the AD-associated decline in anti-inflammatory Iba1+Arg-1+-M2 microglia, inhibited phenotypic switching to pro-inflammatory N1 neutrophils, promoted the blood-brain barrier-associated tight-junction protein claudin-5 and decreased neutrophil leakage in 5xFAD brains, and induced the switch of neutrophils toward the inflammation-resolving N2 phenotype. (4) Conclusions: Long-term administration of MarL1 mitigates AD-related neuropathogenesis in brains by curbing neuroinflammation and neurodegeneration, based on the histological results. These findings provide preclinical leads and mechanistic insights for the development of MarL1 into an effective modality to ameliorate AD pathogenesis.

Targeting Neuroinflammation and Apoptosis: Cardamonin's Cognitive Benefits in Alzheimer's 5XFAD Mice.

This study aimed to evaluate the cognitive-enhancing and neuroprotective effects of cardamonin in the 5XFAD transgenic mouse model of Alzheimer's disease (AD). We treated six-month-old female 5XFAD mice with cardamonin at 5mg/kg, 10mg/kg, and 20mg/kg. Cognitive function was assessed using the Morris Water Maze (MWM) and Novel Object Recognition (NOR) tests. ELISA, western blot, and PCR analyses evaluated amyloid-beta (Aβ) levels, neuroinflammation markers, and apoptosis-related factor expression. All animals survived without toxicity. Cardamonin treatment significantly improved spatial learning and memory retention in MWM and NOR tests, with the 20mg/kg dose showing the most pronounced effects. Additionally, cardamonin reduced soluble and insoluble Aβ levels in the frontal cortex and hippocampus. The treatment also significantly decreased neuroinflammatory markers, with IL-1β, IL-6, and TNF-α levels dropping substantially at higher doses. Cardamom treatment also normalizes cleaved caspase 3, GFAP, Iba-1, PSD-95, and synaptophysin, which aids in restoring synaptic integrity. Furthermore, cardamonin led to a marked reduction in apoptosis-related gene expression, indicating its potential to mitigate neurodegeneration. Cardamonin demonstrates significant cognitive-enhancing and neuroprotective properties in the 5XFAD mouse model, suggesting its potential as a therapeutic agent for AD. These findings support further investigation into cardamonin's mechanisms and applicability in treating neurodegenerative disorders.

Mitochondrial Alterations in Alzheimer's Disease: Insight from the 5xFAD Mouse Model.

Mitochondrial dysfunction is increasingly recognized as a key factor in Alzheimer's disease (AD) pathogenesis, but the precise relationship between mitochondrial dynamics and proteinopathies in AD remains unclear. This study investigates the role of mitochondrial dynamics and function in the hippocampal tissue and peripheral blood mononuclear cells (PBMCs) of 5xFAD transgenic mice, as a model of AD. The levels of mitochondrial fusion proteins OPA1 and MFN2 and fission proteins DRP1 and phospho-DRP1 (S616) at 3, 6, and 9months of age were assessed. Western blot analysis revealed significantly lower levels of OPA1 and MFN2 in the hippocampus of 6- and 9-month-old transgenic (TG) 5xFAD mice compared to controls (CTR), while DRP1 and pDRP1 levels were increased in 9-month-old TG mice. Additionally, MFN2 were decreased inthe PBMCs of 9-month-old TGmice,indicatingsystemic mitochondrial alterations. Ultrastructural analysis of hippocampal tissues showed substantial alterations in mitochondrial morphology, including abnormalities in size and shape, a preponderance of teardrop-shaped mitochondria, and alterations in the somatic mitochondria-ER complex. Notably,mitochondria-associated ER contact sites were more distant in TG mice, suggesting functional impairments. Flow cytometric measurements demonstrated decreased mitochondrial membrane potential and mass, along with increased superoxide production, in the PBMCs of TG mice, particularly at 9months, highlighting compromised mitochondrial function. Levels of keymitochondrial proteins including VDAC, TOM2O, and mitophagy-related protein PINK1 levels altered in both central andperipheral tissue of TG mice. These findings suggest that mitochondrial dysfunction and altered dynamics are early events in AD development in 5xFAD mice, manifesting in both central and peripheral tissues, and support the notion that mitochondrial abnormalities are an integral component of AD pathology. These insights might lead to the development of targeted therapies that modulate mitochondrial dynamics and function to mitigate AD progression.

Mitigation of Atherosclerotic Vascular Damage and Cognitive Improvement Through Mesenchymal Stem Cells in an Alzheimer's Disease Mouse Model.

Alzheimer's disease (AD) is a neurodegenerative condition characterized by progressive memory loss and other cognitive disturbances. Patients with AD can be vulnerable to vascular damage, and damaged vessels can lead to cognitive impairment. Mesenchymal stem cell (MSC) treatment has shown potential in ameliorating AD pathogenesis, but its effect on vascular function remains unclear. This study aimed to improve cognitive function by alleviating atherosclerosis-induced vessel damage using MSCs in mice with a genetic AD background. In this study, a 5xFAD mouse model of AD was used, and atherosclerotic vessel damage was induced by high-fat diets (HFDs). MSCs were injected into the tail vein along with mannitol in 5xFAD mice on an HFD. MSCs were detected in the brain, and vascular damage was improved following MSC treatment. Behavioral tests showed that MSCs enhanced cognitive function, as measured by the Y-maze and passive avoidance tests. Additionally, muscle strength measured by the rotarod test was also increased by MSCs in AD mice with vessel damage induced by HFDs. Overall, our results suggest that stem cells can alleviate vascular damage caused by metabolic diseases, including HFDs, and vascular disease in individuals carrying the AD gene. Consequently, this alleviates cognitive decline related to vascular dementia symptoms.

Sildenafil is a candidate drug for Alzheimer’s disease: Real‐world patient data observation and functional validation in patient iPSC‐derived neurons and the 5xFAD mouse model

Sildenafil is a candidate drug for Alzheimer’s disease: Real‐world patient data observation and functional validation in patient iPSC‐derived neurons and the 5xFAD mouse model

Seizure‐activated neurons facilitate tau spread in 5XFAD mice

AbstractBackgroundSeizures are highly comorbid with Alzheimer’s disease (AD). We and others have demonstrated worsened pathological and cognitive outcomes in AD patients with seizure history and after seizure induction in AD mouse models. Central to AD progression is the spread of tau along neuronal connections, which can be modelled by intracerebral injection of human AD brain derived tau lysate (AD‐tau), but whether seizures impact the spread of tau is unknown. We hypothesized that seizures would worsen tau spread and that neurons activated during seizures would have increased susceptibility to develop and possibly transmit tau pathology.MethodsTo investigate seizure‐tau interactions, we crossed the 5XFAD mouse model with targeted recombination in active populations mice (TRAP; 5X‐/WT‐TRAP) to permanently label seizure‐activated neurons. We injected AD‐tau unilaterally into the hippocampus and overlying cortex (1 µg/site) at three months of age in 5X‐TRAP and WT‐TRAP littermates. Seizures were then induced with pentylenetetrazol (PTZ) kindling 2‐3 weeks following surgery and seizure‐activated neurons were induced to express tdTomato on the final day of kindling via 4‐hydroxytamoxifen administration. Three months following AD‐tau seeding, 5X‐/WT‐TRAP brains were serially sectioned and underwent immunofluorescent slide scanning. Scanned brain images were then registered to the Allen Brain Atlas and mapped for seizure‐activated neurons (tdTomato+) and tau pathology (phospho‐tau Ser202/Ser205; AT8).ResultsWe found that 5X‐TRAP mice had increased tau pathology compared to WT‐TRAP in hippocampal subregions ipsilateral to AD‐tau injection, including the dentate gyrus (p<0.05, n = 5‐10/group) and subiculum (p<0.01, n = 5‐9/group), regardless of seizure kindling, without changes in the contralateral hippocampus. Seizure induction resulted in increased tau spread in remote interconnected brain regions, including the ipsilateral and contralateral thalamo‐cortical regions (p<0.05, n = 5‐9/group). In addition, we found that, compared to neurons from a saline‐treated 5XFAD mouse, thalamic seizure‐activated (tdTomato+) neurons showed significantly increased somatic AT8 levels (p<0.05, n = 8‐11), while surrounding (tdTomato‐) neurons from 5XFAD mice did not, suggesting that these thalamic, seizure‐activated neurons preferentially facilitate tau spread.ConclusionTogether, our data demonstrate that seizures increase tau spread in mouse models and identify seizures and seizure‐activated neurons as therapeutic targets to slow pathological AD progression.

Defining the role of perineuronal nets in Alzheimer’s disease pathology

AbstractBackgroundCondensed extracellular matrix structures called perineuronal nets (PNNs) preferentially enwrap the soma and stabilize proximal synapses of parvalbumin‐expressing inhibitory neurons in the cortex, serving as a protective barrier against neurotoxins. While PNN structural integrity declines in the healthy aging brain, this reduction is exacerbated in Alzheimer’s disease (AD). In the 5xFAD mouse model of amyloidosis, the elimination of microglia prevents reductions in PNN, suggesting microglia are responsible for the over‐degradation of PNNs observed in AD. Additionally, microglial elimination before plaque onset impairs plaque formation, suggesting microglia are critical for plaque development. We observe that plaque formation is inhibited in areas of PNN deposition, and therefore postulate that PNNs are protective against plaque accumulation and synaptic/neuronal damage.MethodsExpression of aggrecan protein (ACAN) is required for PNN formation, therefore we crossed ACAN floxed mice with Nestin‐Cre and 5xFAD to selectively prevent PNN production from all neurons. Mouse brains were harvested for the following 4 groups: wild‐type (WT) control, WT PNN knockout (KO), 5xFAD control, and 5xFAD PNN KO at 4 months and 8 months of age with n = 4‐6 per sex per group. One hemisphere was processed for immunohistochemistry and the other hemisphere for spatial transcriptomics.ResultsAt the 8‐month timepoint, immunohistochemical quantification of AmyloGlo+ plaques shows a significant increase in both total plaque volume and total plaque number in the cortex of the 5xFAD PNN KO group compared to the 5xFAD control group. Notably, plaque pathology spread to the upper cortical layers normally occupied by PNNs. Additionally, we know that the microglial response to plaques is important for protecting against dystrophic neurites and preventing the spread of tau pathology. Therefore, we investigated the microglia and plaque interaction and found that the absence of PNNs impairs the microglial response to plaques, suggesting that the ECM composition is integral to proper microglial sensing and responses.ConclusionsIncreases in plaque load and an impaired microglial response to plaques by 8 months in the PNN KO group suggest PNNs protect against plaque accumulation and appear to be essential for proper microglial response to plaques.

Exploring Protective Alleles in the Pathogenesis of Alzheimer’s Disease Using Mouse Models

AbstractBackgroundSeveral variants have been identified that protect against the development of Alzheimer’s disease (AD). Understanding how these alleles convey protection inform us not only about the disease pathogenesis, but also guide therapeutic strategies. The UCI MODEL‐AD consortium has developed several protective alleles including a putative gain of function variant of ABCA7, and the APOE Christchurch variant. Here we have explored the impacts on these variants in animal models of AD to elucidate their mechanisms of protection.MethodCRISPR‐Cas9 was used to introduce either murine equivalent of ABCA7 V1613M, or APOE R136S (Christchurch) into the murine genome. Mice were then bred to homozygosity with either the 5xFAD mouse model of amyloidosis (Abca7 and Apoe), or the PS19 mouse model of tauopathy (Apoe), and then phenotyped across multiple ages using histology, biochemistry, and single cell spatial transcriptomics and proteomics.ResultAbca7V1613M variant dramatically reduced Ab production, protected against the formation of parenchymal plaques, and against increases in cortical and plasma neurofilament light chain. ApoeR136S produced divergent effects in glial populations depending on the stimulus. In 5xFAD mice it decreased plaque number and size, and increased the microglial response to the plaques, as evidenced by upregulated disease associated gene expression and protein expression. In PS19 mice tau pathology was mildly increased, but the glia response was markedly suppressed with ApoeR136S. Plasma neurofilament light chain was reduced by ApoeR136S in 5xFAD mice but not PS19 mice.ConclusionWe highlight that the primary mechanism of ABCA7 appears to be via the production of Ab and plaques. On the other hand, APOE Christchurch dramatically effects glial responses to pathology, notably increasing microglial reactivity to plaques, but markedly suppressing their response to tauopathy.

Specific expression of APOE in astrocytes reduces Aβ accumulation and plaque‐related pathology in a mouse model of amyloidosis

AbstractBackgroundAccumulation of the amyloid‐β (Aβ) peptide into amyloid plaque is one of the key pathological markers of Alzheimer’s disease (AD). Apolipoprotein E (APOE) is known to modify AD risk and has been reported to influence Aβ accumulation in the brain in an isoform‐dependent manner. ApoE can be produced by various cell types in the brain, with astrocytes being the main producer. Increasing studies show that altering apoE levels can influence Aβ plaque pathology. However, it is not fully understood how apoE produced by specific cell types, such as astrocytes, contributes to amyloid pathology.MethodWe utilized mouse models expressing APOE isoforms in astrocytes and crossed them with 5xFAD mouse models of amyloidosis. We analyzed the changes to amyloid plaques and assessed the impact on cellular responses to amyloid plaques in condition of astrocytic APOE expression.ResultSpecific expression of APOE3 in astrocytes resulted in compact amyloid plaques and a large increase in plaque deposition, while the total plaque burden was reduced. Astrocytic APOE2 expression led to similar changes to amyloid plaques, but the fold change is lower comparing to that in astrocytic APOE3 models. Intriguingly, the total microglial response increased dramatically in condition of astrocytic APOE3 expression but not in condition of astrocytic APOE2 expression. Further, the ratio of plaque associated Lgals3/Iba1 is higher in condition of astrocytic APOE3 expression, indicating increased microglial activation. Additionally, astrocyte GFAP levels only increased in astrocytic APOE3 models, but not in astrocytic APOE2 models. Finally, APOE isoform effect on dystrophic neurites amount was also observed.ConclusionTogether, our study reveals an important role of astrocytic APOE on the deposition and accumulation of Aβ plaques as well as on Aβ‐associated downstream effects.

Can Butyrate offer a novel approach to mitigate the pathology of AD?

AbstractBackgroundOur research group is currently exploring the potential of Butyric acid (NaB), a Short Chain Fatty Acid (SCFA), as a novel therapeutic agent for Alzheimer’s disease (AD).MethodsIn our investigation using the 5xFAD mouse model of AD, we observed that NaB had significant effects on Aβ levels, as well as on associative learning and cognitive functioning. Notably, we recorded a 40% reduction in brain Aβ and a 25% increase in fear response during both cued and contextual testing. Our studies employing M17 cell models demonstrated that butyrate provides a degree of protection against Aβ‐induced toxicity. Additionally, nanoindentation studies confirmed that butyrate induces changes in cell physiology. Building on these findings, we explored the impact of butyrate on astrocytes and microglial cells concerning amyloid beta toxicity.ResultsCurrent studies with stem cells have exhibited promising outcomes, indicating that butyrate significantly alleviates amyloid beta.ConclusionsThis investigation represents the initial confirmation of butyrate as an amyloid beta inhibitor across various Alzheimer’s disease (AD) models. The subsequent steps involve determining the levels of butyrate at different stages of AD by analyzing fecal samples and conducting tests to assess its therapeutic efficacy.