Mutant presenilins specifically elevate the levels of the 42 residue beta-amyloid peptide in vivo: evidence for augmentation of a 42-specific gamma secretase

Effects of resistance exercise on behavioral and molecular changes in transgenic female mice for Alzheimer's disease in early and advanced stages

Alzheimer's disease (AD) is a neurodegenerative condition that affects memory and cognition, with a higher prevalence in women. Given the lack of effective treatment, physical activity stands out as a complementary approach to prevent or delay disease progression. While numerous studies on humans and animals indicate that aerobic exercise induces brain changes, the impact of resistance exercise (RE) on AD is not fully understood.

OBJECTIVE

This study aimed to investigate the behavioral and molecular changes induced by RE in female transgenic mice with AD at the early and advanced stages of the disease.

MATERIALS AND METHODS

Adult (initial phase - 7 to 8 months of age, n = 32) and adult/elderly (advanced phase - 22 to 23 months of age, n = 32) female mice (2xTg-AD) for the APPSWE/PS1dE9 mutation were subjected to a four-week RE protocol. Mobility, anxiety-like behavior, long-term memory (LTM), and depressive-like behavior were assessed. Beta-amyloid (βA) and cytokines were quantified using the ELISA technique.

RESULTS

There was a progressive increase in strength in both trained groups at different ages. RE reversed memory deficits only in adult AD animals and the anxiety-like behavior only in adult/elderly AD animals. RE reversed depressive-like behavior in adult and adult/elderly AD animals. RE reduced βA only in adult AD animals. RE modified the expression of several cytokines in animals in the early and advanced stage of AD.

CONCLUSION

RE can be a promising strategy to minimize the deleterious effects of AD; however, its effectiveness may be more limited to the early stages of the disease.

A single-cell transcriptomic atlas of all cell types in the brain of 5xFAD Alzheimer mice in response to dietary inulin supplementation

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disease that is a major threat to the aging population. Due to lack of effective therapy, preventive treatments are important strategies to limit AD onset and progression, of which dietary regimes have been implicated as a key factor. Diet with high fiber content is known to have beneficial effects on cognitive decline in AD. However, a global survey on microbiome and brain cell dynamics in response to high fiber intake at single-cell resolution in AD mouse models is still missing.

RESULTS

Here, we show that dietary inulin supplementation synergized with AD progression to specifically increase the abundance of Akkermansia muciniphila in gut microbiome of 5 × Familial AD (FAD) mice. By performing single-nucleus RNA sequencing on different regions of the whole brain with three independent biological replicates, we reveal region-specific changes in the proportion of neuron, astrocyte, and granule cell subpopulations upon inulin supplementation in 5xFAD mice. In addition, we find that astrocytes have more pronounced region-specific diversity than microglia. Intriguingly, such dietary change reduces amyloid-β plaque burden and alleviates microgliosis in the forebrain region, without affecting the spatial learning and memory.

CONCLUSIONS

These results provide a comprehensive overview on the transcriptomic changes in individual cells of the entire mouse brain in response to high fiber intake and a resourceful foundation for future mechanistic studies on the influence of diet and gut microbiome on the brain during neurodegeneration.

Selectively vulnerable deep cortical layer 5/6 fast-spiking interneurons in Alzheimer's disease models in vivo

Alzheimer's disease (AD) is initiated by amyloid-beta (Aβ) accumulation in the neocortex; however, the cortical layers and neuronal cell types first susceptible to Aβ remain unknown. Using in vivo two-photon Ca2+ imaging in the visual cortex of AD mouse models, we found that cortical layer 5 neurons displayed abnormally prolonged Ca2+ transients before substantial plaque formation. Neuropixels recordings revealed that these abnormal transients were associated with reduced spiking and impaired visual tuning of parvalbumin (PV)-positive fast-spiking interneurons (FSIs) in layers 5/6, whereas PV-FSIs in superficial layers remained unaffected. These dysfunctions occurred alongside a deep-layer-specific reduction in neuronal pentraxin 2 (NPTX2) within excitatory neurons, decreased GluA4 in PV-FSIs, and fewer excitatory synapses onto PV-FSIs. Notably, NPTX2 overexpression increased excitatory input onto layers 5/6 PV-FSIs and rectified their spiking activity. Thus, our findings reveal an early selective impairment of deep cortical layers 5/6 in AD models and identify deep-layer PV-FSIs as therapeutic targets.

Sex-Specific Effects of Anxiety on Cognition and Activity-Dependent Neural Networks: Insights From (Female) Mice and (Wo)men

BACKGROUND

Neuropsychiatric symptoms, such as depression and anxiety, are observed in 90% of patients with Alzheimer's disease (AD), two-thirds of whom are women. Neuropsychiatric symptoms usually manifest long before AD onset creating a therapeutic opportunity. Here, we examined the impact of anxiety on AD progression and the underlying brainwide neuronal mechanisms.

METHODS

To gain mechanistic insight into how anxiety affects AD progression, we performed a cross-sectional analysis on mood, cognition, and neural activity using the ArcCreERT2 x eYFP (enhanced yellow fluorescent protein) x amyloid precursor protein/presenilin 1 (APP/PS1) (AD) mice. The Alzheimer's Disease Neuroimaging Initiative dataset was used to determine the impact of anxiety on AD progression in humans.

RESULTS

Female APP/PS1 mice exhibited anxiety-like behavior and cognitive decline at an earlier age than control mice and male mice. Brainwide analysis of c-Fos+ revealed changes in regional correlations and overall network connectivity in APP/PS1 mice. Sex-specific eYFP+/c-Fos+ changes were observed; female APP/PS1 mice exhibited less eYFP+/c-Fos+ cells in dorsal CA3, whereas male APP/PS1 mice exhibited less eYFP+/c-Fos+ cells in the dorsal dentate gyrus. In the Alzheimer's Disease Neuroimaging Initiative dataset, anxiety predicted transition to dementia. Female participants positive for anxiety and amyloid transitioned more quickly to dementia than male participants.

CONCLUSIONS

While future studies are needed to understand whether anxiety is a predictor, a neuropsychiatric biomarker, or a comorbid symptom that occurs during disease onset, these results suggest that there are sex differences in AD network dysfunction and that personalized medicine may benefit male and female patients with AD rather than a one-size-fits-all approach.

Spectral Heterogeneity of Thioflavin T Binding to Aβ42:Aβ40 Mixed Fibrils: Implications for Alzheimer's Disease Screening

In Alzheimer's disease (AD), the amyloid β (Aβ) protein self-assembles, whereby Aβ40 and Aβ42 peptides interact, forming a mixed fibrillar assembly. Evaluating local Aβ40:Aβ42 mixed fibril conformations remains challenging, requiring a simple method to compare microscopic (molecular-scale) and macroscopic (plaque-scale) findings. The aim of the current study was to design a method to analyze Aβ fibril formation in a single sample without drying via fluorescent thioflavin T (ThT) labeling. The analysis revealed spectral heterogeneity associated with the ThT-binding mixed fibrils. Although the fluorescence wavelength associated with higher Aβ42:Aβ40 fibril ratios remained relatively unchanged, those associated with lower Aβ42:Aβ40 fibril ratios exhibited significant heterogeneity. This suggests that the local β-sheet structure exhibits significant variability at lower Aβ42:Aβ40 ratios. This specific feature can be attributed to differences in the shape of the "funnel" in the energy landscape during Aβ assembly. Thus, our protocol facilitates rapid and efficient screening of fibril conformational alterations compared to conventional techniques. Cumulatively, our results demonstrate that comparing the spectral features of ThT with the kinetic and morphological characteristics of a single sample provides specific molecular insights related to the origin of Aβ42:Aβ40 ratio-dependent molecular mechanism-insights that cannot be detected through conventional kinetic and morphological analyses alone.

Early involvement of D-serine in β-amyloid-dependent pathophysiology

The N-methyl-D-aspartate subtype of glutamate receptors (NMDAR) is a key regulator of brain plasticity encoding learning and memory. In addition to glutamate, NMDAR activation requires the binding of the co-agonist D-serine. The beta-amyloid (Aß) peptide which accumulates in Alzheimer's disease (AD), affects the D-serine-dependent NMDAR activation in vitro, but whether this alteration would significantly contribute to AD-related pathophysiology and memory deficits remains unclear. Herein, we report a decrease in the maximal pool of recruitable NMDAR and in the expression of NMDAR-dependent long-term potentiation together with impaired basal neurotransmission at CA3/CA1 synapses from hippocampal slices of 5xFAD mouse, an AD-related model with elevated Aß levels. The NMDAR synaptic impairments develop from 1.5 to 2 months of age with the initial rise of Aß and is correlated to a transient increase in D-serine levels. Deficits in working and spatial memories as well as cognitive flexibility then occurred in 10-12 months-old animals. Importantly, the NMDA-related synaptic deregulations (but not the altered basal neurotransmission) and behavioral impairments (working and cognitive flexibility) are prevented or reduced (spatial memory) in 5xFAD mice devoid of D-serine after genetic deletion of its synthesis enzyme serine racemase. Altogether, these results therefore provide in vivo evidence for the implication of D-serine at least in the early pathogenic signatures of AD driven by the increase in amyloid load suggesting that the recent proposal of preventive therapy of AD by administration of the precursor L-serine remains questionable.

Long-term fucoxanthin treatment prevents cognitive impairments and neuroinflammation via the inhibition of Nogo-A in APP/PS1 transgenic mice

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by neuroinflammation and cognitive impairments. Although short-term treatment with fucoxanthin, a marine carotenoid with anti-neuroinflammatory activity, has been reported to prevent cognitive impairments in scopolamine- and β-amyloid (Aβ)-treated mice, it remains uncertain whether long-term fucoxanthin treatment could produce similar effects in transgenic AD models. Moreover, the anti-neuroinflammatory mechanism of fucoxanthin is still unclear. In this study, long-term treatment with fucoxanthin (15-150 mg kg-1, twice a week for 20 weeks) significantly prevented cognitive deficits and Aβ-related neuroinflammation in APP/PS1 transgenic mice. In addition, fucoxanthin largely prevented Aβ oligomer-induced secretion of pro-inflammatory cytokines and the activation of BV2 microglial cells. Furthermore, fucoxanthin reduced the increased expression of Nogo-A, a central player in AD pathophysiology, as well as the activation of downstream Rho-associated protein kinase 2 (ROCK2) and nuclear factor kappa-B (NF-κB) pathways in AD models. Most importantly, the inhibition of neuroinflammation by fucoxanthin was not reduced by shRNA-mediated knockdown of Nogo-A, suggesting that fucoxanthin significantly prevented cognitive impairments and neuroinflammation via the inhibition of Nogo-A. These results not only elucidate an anti-neuroinflammatory mechanism of fucoxanthin, but also provide strong support for the development of fucoxanthin as a novel food ingredient or drug for the treatment of AD.

A novel finding relates to the involvement of ATF3/DOCK8 in Alzheimer's disease pathogenesis

BackgroundThe involvement of microglia is likely to be pivotal in the pathogenesis of Alzheimer's disease (AD) by modulating the deposition of amyloid-β (Aβ) plaques. The deletion of Dedicator of cytokinesis 8 (DOCK8) has a protective effect in mouse with neurodegenerative diseases.ObjectiveTo explore the underlying mechanism of DOCK8 in AD.MethodsIn present study, we first the detected the expression of DOCK8 in the hippocampal tissue of APP/PS1 mice. Then, the expression of DOCK8 was knocked down in the hippocampal tissue of APP/PS1 mice, and the effects of DOCK8 down-regulation on cognitive function, the microglia migration around Aβ plaques, and the cell division cycle 42 (Cdc42)/p38 mitogen-activated protein kinase (MAPK) signaling pathway were detected. Next, the effects of DOCK8 knockdown on Aβ-induced migration and activation of BV-2 cells as well as the MAPK signaling pathway were detected. Finally, the transcriptional regulation of DOCK by transcription factor 3 (ATF3) was detected by a dual luciferase reporter assay.ResultsDOCK8 expression exerts a significant upregulation in the hippocampus of APP/PS1 mice. However, following the DOCK8 knockdown, there was a significant recovery in the results of the behavioral tests and a notable reduction in microglial expression. Moreover, the high expression of DOCK8 mediated by ATF3 successfully triggered the Cdc42/p38 MAPK signaling pathway, thereby enhancing the migration and recruitment of microglia towards senile plaques, accelerating the production of Aβ plaques.ConclusionsATF3-mediated high expression of DOCK8 accelerates the production of Aβ plaques, and participates in the pathogenesis of AD.

Particulate matter and co-occurring genetic risk induce oxidative stress and cardiac and brain Alzheimer's pathology

Amyloid-beta (Aβ) aggregates, an Alzheimer's disease (AD) pathological hallmark, extend beyond the brain to the heart of heart failure (HF) and AD patients. Being diseases of the elderly, increased prevalence is expected as the population ages. However, changes in the incidence and prevalence of dementia over the past decades, and the independent association of exposure to air particulate matter (PM) with poor cognitive function, adverse cardiovascular effects, and oxidative stress hint to the contribution of other factors beyond senescence. Therefore we evaluate whether, and by which mechanism(s), PM exposure affects heart and brain proteinopathy with/without genetic predisposition.AD-prone and control mice are exposed for three months to filtered air (FA) or concentrated ambient PM < 2.5μm in diameter (PM2.5), and evaluated for Aβ pathology, cognitive and cardiac function, and markers of oxidative stress. Aβ pathology become noticeable in AD hearts and worsens with PM2.5 in AD brains. Functionally, PM2.5 lead to anxiety and memory deficits and worsens diastolic function. Redox homeostasis is negatively impacted by genotype and PM2.5. This study identifies environmental pollution as a potential key contributor to early progression of heart and brain proteinopathy, delineating a crucial timepoint for early interventions to limit multiorgan damage in vulnerable patients.

In Vivo Seeding of Amyloid-β Protein and Implications in Modeling Alzheimer's Disease Pathology

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by extracellular plaques containing amyloid β-protein (Aβ) and intracellular neurofibrillary tangles formed by tau. Cerebral Aβ accumulation initiates a noxious cascade that leads to irreversible neuronal degeneration and memory impairment in older adults. Recent advances in Aβ seeding studies offer a promising avenue for exploring the mechanisms underlying amyloid deposition and the complex pathological features of AD. However, the extent to which inoculated Aβ seeds can induce reproducible and reliable pathological manifestations remains unclear due to significant variability across studies. In this review, we will discuss several factors that contribute to the induction or acceleration of amyloid deposition and consequent pathologies. Specifically, we focus on the diversity of host animals, sources and recipe of Aβ seeds, and inoculating strategies. By integrating these key aspects, this review aims to offer a comprehensive perspective on Aβ seeding in AD and provide guidance for modeling AD pathogenesis through the exogenous introduction of Aβ seeds.

Target Validation Studies of PS48, a PDK-1 Allosteric Agonist, for the Treatment of Alzheimer's Disease Phenotype in APP/PS1 Transgenic Mice

The Alzheimer's disease (AD)-affected brain is known to be deficient in the utilization of glucose, its main energy substrate, and systemic diabetes is a significant risk factor for AD. In the course of biochemical and molecular investigations into this puzzling relationship, it has been shown that resistance to insulin action is a prominent feature of early stages of AD in the brain, thereby contributing to an energy failure state and a decline in synaptic function. In one AD-like cellular model, we found that β-amyloid (Aβ) accumulation inhibited insulin signaling and cell viability through an alteration of the PI3K/PDK-1/Akt signal pathway, an effect overcome by mTORC2 stimulation. A PDK-1 allosteric agonist, PS48, as well as newly synthesized analogs, were also found to reverse the metabolic defects caused by intracellular Aβ42 accumulation. In vivo, we previously showed that oral dosing of PS48 significantly improves learning and memory in APP/PS1 transgenic mice. Herein, we present evidence using unbiased immunohistological quantification and Western blot analyses demonstrating that ingested PS48 crosses into brain tissue where it targeted Akt and GSK3-β activities. Beneficial effects on neuronal number and Tau phosphorylation were found. Not unexpectedly, Aβ levels remained unchanged. These results support a path toward a future therapeutic trial of this untested strategy and agent in humans.

An update on mammalian and non-mammalian animal models for biomarker development in neurodegenerative disorders

Neurodegeneration is one of the leading factor for death globally, affecting millions of people. Developing animal models are critical to understand biological processes and comprehend pathological hallmarks of neurodegenerative diseases. For decades, many animal models have served as excellent tools to determine the disease progression, develop diagnostic methods and design novel therapies against distinct pathologies. Here, we provide a comprehensive overview of both, mammalian and non-mammalian animal models, with a focus on three most common and aggressive neurodegenerative disorders: Alzheimer's disease, Parkinson's disease and Spinocerebellar ataxia-1. We highlight various approaches including transgene, gene transfer, and chemically-induced methods used to develop disease models. In particular, we discuss applications of both non-mammalian and mammalian contributions in research on neurodegeneration. It is exciting to learn the roles of animal models in disease pathomechanisms, identifying biomarkers and hence devising novel interventions to treat neuropathological conditions.

Whole Transcriptome RNA-Seq Reveals Drivers of Pathological Dysfunction in a Transgenic Model of Alzheimer's Disease

Alzheimer's disease (AD) affects more than 55 million people worldwide, yet current theories cannot fully explain its aetiology. Accordingly, gene expression profiling has been used to provide a holistic view of the biology underpinning AD. Focusing primarily on protein-coding genes, such approaches have highlighted a critical involvement of microglia-related inflammatory processes. Simultaneous investigation of transcriptional regulators and noncoding RNA (ncRNA) can offer further insight into AD biology and inform the development of disease-modifying therapies. We previously described a method for whole transcriptome sampling to simultaneously investigate protein-coding genes and ncRNA. Here, we use this technique to explore transcriptional changes in a murine model of AD (15-month-old APP/PS1 mice). We confirmed the extensive involvement of microglia-associated genes and gene networks, consistent with literature. We also report a wealth of differentially-expressed non-coding RNA - including microRNA, long non-coding RNA, small nuclear and small nucleolar RNA, and pseudogenes - many of which have been overlooked previously. Transcription factor analysis determined that six transcription factors likely regulate gene expression changes in this model (Irf8, Junb, c-Fos, Lmo2, Runx1, and Nfe2l2). We then utilised validated miRNA-target interactions, finding 60 interactions between 15 miRNA and 42 mRNA (messenger RNA) with largely consistent directionality. Furthermore, we found that eight transcription factors (Clock, Lmo2, Runx1, Nfe2l2, Egr2, c-Fos, Junb, and Nr4a1) are likely responsible for the regulation of miRNA expression. Taken together, these data indicate a complex interplay of coding and non-coding RNA, driven by a small number of specific transcription factors, contributing to transcriptional changes in 15-month-old APP/PS1 mice.

Shallow-angle intracranial cannula for repeated infusion and in vivo imaging with multiphoton microscopy

Significance

Multiphoton microscopy serves as an essential tool for high-resolution imaging of the living mouse brain. To facilitate optical access to the brain during imaging, cranial window surgery is commonly used. However, this procedure restricts physical access above the imaging area and hinders the direct delivery of imaging agents and chemical compounds to the brain.

Aim

We aim to develop a method that allows the repeated administration of imaging agents and compounds to the mouse brain while performing in vivo imaging with multiphoton microscopy.

Approach

We have developed a cannula delivery system that enables the implantation of a low-profile cannula nearly parallel to the brain surface at angles as shallow as 8 deg while maintaining compatibility with multiphoton microscopy.

Results

To validate our shallow-angle cannula approach, we performed direct infusion and imaging of various fluorescent cell markers in the brain. In addition, we successfully demonstrated tracking of degenerating neurons over time in Alzheimer's disease mice using Fluoro-Jade C. Furthermore, we showed longitudinal imaging of the partial pressure of oxygen in brain tissue using a phosphorescent oxygen sensor.

Conclusions

Our developed technique should enable a wide range of longitudinal imaging studies in the mouse brain.

The protective PLCγ2-P522R variant mitigates Alzheimer's disease-associated pathologies by enhancing beneficial microglial functions

BACKGROUND

Phospholipase C gamma 2, proline 522 to arginine (PLCγ2-P522R) is a protective variant that reduces the risk of Alzheimer's disease (AD). Recently, it was shown to mitigate β-amyloid pathology in a 5XFAD mouse model of AD. Here, we investigated the protective functions of the PLCγ2-P522R variant in a less aggressive APP/PS1 mouse model of AD and assessed the underlying cellular mechanisms using mouse and human microglial models.

METHODS

The effects of the protective PLCγ2-P522R variant on microglial activation, AD-associated β-amyloid and neuronal pathologies, and behavioral changes were investigated in PLCγ2-P522R knock-in variant mice crossbred with APP/PS1 mice. Transcriptomic, proteomic, and functional studies were carried out using microglia isolated from mice carrying the PLCγ2-P522R variant. Finally, microglia-like cell models generated from human blood and skin biopsy samples of PLCγ2-P522R variant carriers were employed.

RESULTS

The PLCγ2-P522R variant decreased β-amyloid plaque count and coverage in female APP/PS1 mice. Moreover, the PLCγ2-P522R variant promoted anxiety in these mice. The area of the microglia around β-amyloid plaques was also increased in mice carrying the PLCγ2-P522R variant, while β-amyloid plaque-associated neuronal dystrophy and the levels of certain cytokines, including IL-6 and IL-1β, were reduced. These alterations were revealed through [18F]FEPPA PET imaging and behavioral studies, as well as various cytokine immunoassays, transcriptomic and proteomic analyses, and immunohistochemical analyses using mouse brain tissues. In cultured mouse primary microglia, the PLCγ2-P522R variant reduced the size of lipid droplets. Furthermore, transcriptomic and proteomic analyses revealed that the PLCγ2-P522R variant regulated key targets and pathways involved in lipid metabolism, mitochondrial fatty acid oxidation, and inflammatory/interferon signaling in acutely isolated adult mouse microglia and human monocyte-derived microglia-like cells. Finally, the PLCγ2-P522R variant also increased mitochondrial respiration in human iPSC-derived microglia.

CONCLUSIONS

These findings suggest that the PLCγ2-P522R variant exerts protective effects against β-amyloid and neuronal pathologies by increasing microglial responsiveness to β-amyloid plaques in APP/PS1 mice. The changes observed in lipid/fatty acid and mitochondrial metabolism revealed by the omics and metabolic assessments of mouse and human microglial models suggest that the protective effects of the PLCγ2-P522R variant are potentially associated with increased metabolic capacity of microglia.

New low-dose curcumin derivative with therapeutic potential in Alzheimer's disease: Results from an in vitro and in vivo study in mice

Curcumin has been proposed as a potential treatment for Alzheimer's disease (AD) due to its ability to inhibit amyloid-β (Aβ) peptide aggregates and to destabilise pre-formed ones. Derivative 27 was synthesized to improve low-dose efficacy in the context of AD. Its anti-inflammatory, antioxidant and anti-amyloidogenic activities were evaluated in chemico, in vitro using AD and neuroinflammation cell models, and in vivo using the double-transgenic APP/PS1 mice. In vitro, this curcumin derivative significantly reduced nitric oxide (NO) production and levels of pro-inflammatory proteins, inducible NO synthase, pro-interleukin-1β (Pro-IL-1β) and cyclooxygenase-2. Furthermore, Derivative 27 activated nuclear factor erythroid 2-related factor 2 transcription factor (Nrf2) and significantly increased Nrf2 and heme-oxygenase-1 protein levels in the nucleus and in the cytoplasm, respectively. In one-year-old APP/PS1 mice, orally administered-Derivative 27 (50 mg/Kg/day) for 28 days improved spatial short-term memory and significantly decreased hippocampal Pro-IL-1β and amyloid precursor protein levels, as well as Aβ levels in the hippocampus and plasma. This study supports developing new chemical approaches to alter curcumin molecule, enabling lower doses, while increasing the effectiveness in AD treatment.

Nanoarchitecture of CaV2.1 channels and GABAB receptors in the mouse hippocampus: Impact of APP/PS1 pathology

Voltage-gated CaV2.1 (P/Q-type) Ca2+ channels play a crucial role in regulating neurotransmitter release, thus contributing to synaptic plasticity and to processes such as learning and memory. Despite their recognized importance in neural function, there is limited information on their potential involvement in neurodegenerative conditions such as Alzheimer's disease (AD). Here, we aimed to explore the impact of AD pathology on the density and nanoscale compartmentalization of CaV2.1 channels in the hippocampus in association with GABAB receptors. Histoblotting experiments showed that the density of CaV2.1 channel was significantly reduced in the hippocampus of APP/PS1 mice in a laminar-dependent manner. CaV2.1 channel was enriched in the active zone of the axon terminals and was present at a very low density over the surface of dendritic tree of the CA1 pyramidal cells, as shown by quantitative SDS-digested freeze-fracture replica labelling (SDS-FRL). In APP/PS1 mice, the density of CaV2.1 channel in the active zone was significantly reduced in the strata radiatum and lacunosum-moleculare, while it remained unaltered in the stratum oriens. The decline in Cav2.1 channel density was found to be associated with a corresponding impairment in the GABAergic synaptic function, as evidenced by electrophysiological experiments carried out in the hippocampus of APP/PS1 mice. Remarkably, double SDS-FRL showed a co-clustering of CaV2.1 channel and GABAB1 receptor in nanodomains (~40-50 nm) in wild type mice, while in APP/PS1 mice this nanoarchitecture was absent. Together, these findings suggest that the AD pathology-induced reduction in CaV2.1 channel density and CaV2.1-GABAB1 de-clustering may play a role in the synaptic transmission alterations shown in the AD hippocampus. Therefore, uncovering these layer-dependent changes in P/Q calcium currents associated with AD pathology can benefit the development of future strategies for AD management.

Exercise-Induced Reduction of IGF1R Sumoylation Attenuates Neuroinflammation in APP/PS1 Transgenic Mice

INTRODUCTION

Alzheimer's Disease (AD), a progressive neurodegenerative disorder, is marked by cognitive deterioration and heightened neuroinflammation. The influence of Insulin-like Growth Factor 1 Receptor (IGF1R) and its post-translational modifications, especially sumoylation, is crucial in understanding the progression of AD and exploring novel therapeutic avenues.

OBJECTIVES

This study investigates the impact of exercise on the sumoylation of IGF1R and its role in ameliorating AD symptoms in APP/PS1 mice, with a specific focus on neuroinflammation and innovative therapeutic strategies.

METHODS

APP/PS1 mice were subjected to a regimen of moderate-intensity exercise. The investigation encompassed assessments of cognitive functions, alterations in hippocampal protein expressions, neuroinflammatory markers, and the effects of exercise on IGF1R and SUMO1 nuclear translocation. Additionally, the study evaluated the efficacy of KPT-330, a nuclear export inhibitor, as an alternative to exercise.

RESULTS

Exercise notably enhanced cognitive functions in AD mice, possibly through modulations in hippocampal proteins, including Bcl-2 and BACE1. A decrease in neuroinflammatory markers such as IL-1β, IL-6, and TNF-α was observed, indicative of reduced neuroinflammation. Exercise modulated the nuclear translocation of SUMO1 and IGF1R in the hippocampus, thereby facilitating neuronal regeneration. Mutant IGF1R (MT IGF1R), lacking SUMO1 modification sites, showed reduced SUMOylation, leading to diminished expression of pro-inflammatory cytokines and apoptosis. KPT-330 impeded the formation of the IGF1R/RanBP2/SUMO1 complex, thereby limiting IGF1R nuclear translocation, inflammation, and neuronal apoptosis, while enhancing cognitive functions and neuron proliferation.

CONCLUSION

Moderate-intensity exercise effectively mitigates AD symptoms in mice, primarily by diminishing neuroinflammation, through the reduction of IGF1R Sumoylation. KPT-330, as a potential alternative to physical exercise, enhances the neuroprotective role of IGF1R by inhibiting SUMOylation through targeting XPO1, presenting a promising therapeutic strategy for AD.

Microglial Responses to Alzheimer's Disease Pathology: Insights From "Omics" Studies

Human genetics studies lent firm evidence that microglia are key to Alzheimer's disease (AD) pathogenesis over a decade ago following the identification of AD-associated genes that are expressed in a microglia-specific manner. However, while alterations in microglial morphology and gene expression are observed in human postmortem brain tissue, the mechanisms by which microglia drive and contribute to AD pathology remain ill-defined. Numerous mouse models have been developed to facilitate the disambiguation of the biological mechanisms underlying AD, incorporating amyloidosis, phosphorylated tau, or both. Over time, the use of multiple technologies including bulk tissue and single cell transcriptomics, epigenomics, spatial transcriptomics, proteomics, lipidomics, and metabolomics have shed light on the heterogeneity of microglial phenotypes and molecular patterns altered in AD mouse models. Each of these 'omics technologies provide unique information and biological insight. Here, we review the literature on the approaches and findings of these methods and provide a synthesis of the knowledge generated by applying these technologies to mouse models of AD.

Engrams across diseases: Different pathologies - unifying mechanisms?

Memories are our reservoir of knowledge and thus, are crucial for guiding decisions and defining our self. The physical correlate of a memory in the brain is termed an engram and since decades helps researchers to elucidate the intricate nature of our imprinted experiences and knowledge. Given the importance that memories have for our lives, their impairment can present a tremendous burden. In this review we aim to discuss engram malfunctioning across diseases, covering dementia-associated pathologies, epilepsy, chronic pain and psychiatric disorders. Current neuroscientific tools allow to witness the emergence and fate of engram cells and enable their manipulation. We further suggest that specific mechanisms of mnemonic malfunction can be derived from engram cell readouts. While depicting the way diseases act on the mnemonic component - specifically, on the cellular engram - we emphasize a differentiation between forms of amnesia and hypermnesia. Finally, we highlight commonalities and distinctions of engram impairments on the cellular level across diseases independent of their pathogenic origins and discuss prospective therapeutic measures.

Extracellular vesicles contribute to the beneficial effects of exercise training in APP/PS1 mice

Exercise improves cognitive function in Alzheimer's disease (AD) via mechanism that are not fully clear. Here, we first examined the effect of voluntary exercise training (VET) on energy metabolism and cognitive function in the APP/PS1 transgenic mouse (Tg) model of familial AD. Next, we profiled extracellular vesicles (EVs) and examined whether they may play a role in the protective effects of VET via intranasal administration of EVs, purified from the blood of sedentary (sEV) and/or acutely exercised (eEV) donor wild-type mice into APP/PS1Tg mice. We show that VET reduced resting energy expenditure (REE) and improved cognition in APP/PS1 Tg mice. Administration of eEV, but not sEV, also reduced REE, but had no effect on cognition. Taken together, these data show that exercise is effective intervention to improve symptoms of AD in APP/PS1Tg mice. In addition, eEVs mediate some of these effects, implicating EVs in the treatment of age-related neurodegenerative diseases.

The WAVE complex in developmental and adulthood brain disorders

Actin polymerization and depolymerization are fundamental cellular processes required not only for the embryonic and postnatal development of the brain but also for the maintenance of neuronal plasticity and survival in the adult and aging brain. The orchestrated organization of actin filaments is controlled by various actin regulatory proteins. Wiskott‒Aldrich syndrome protein-family verprolin-homologous protein (WAVE) members are key activators of ARP2/3 complex-mediated actin polymerization. WAVE proteins exist as heteropentameric complexes together with regulatory proteins, including CYFIP, NCKAP, ABI and BRK1. The activity of the WAVE complex is tightly regulated by extracellular cues and intracellular signaling to execute its roles in specific intracellular events in brain cells. Notably, dysregulation of the WAVE complex and WAVE complex-mediated cellular processes confers vulnerability to a variety of brain disorders. De novo mutations in WAVE genes and other components of the WAVE complex have been identified in patients with developmental disorders such as intellectual disability, epileptic seizures, schizophrenia, and/or autism spectrum disorder. In addition, alterations in the WAVE complex are implicated in the pathophysiology of Alzheimer's disease and Parkinson's disease, as well as in behavioral adaptations to psychostimulants or maladaptive feeding.

IL-33/ST2 axis in diverse diseases: regulatory mechanisms and therapeutic potential

Interleukin-33 (IL-33) is a nuclear factor and member of the IL-1 cytokine family. IL-33 is mainly expressed by epithelial and endothelial cells and exerts its function through interaction with various immune cells, and binding to its receptor can form the IL-33/Suppression of tumorigenicity 2 (ST2) signaling pathway. While most cytokines are actively synthesized within cells, IL-33 is produced passively in response to tissue damage or cell necrosis, indicating its role as a signaling molecule following cellular infection, stress, or trauma. IL-33/ST2 signaling pathway has been proved to play diverse role in the pathological process of central nervous system disorders, cancer, fibrosis, autoimmune diseases, etc. Although research on the IL-33/ST2 signaling pathway has deepened recently, relevant treatment strategies have been proposed, and even targeted drugs are in the preclinical stage; further research on the effect of the IL-33/ST2 signaling pathway in different diseases is still necessary, to provide a clearer understanding of the different roles of IL-33/ST2 in disease progression and to develop new drugs and treatment strategies. Because IL-33/ST2 plays an important role in the occurrence and progression of diseases, the study of therapeutic drugs targeting this pathway is also necessary. This review focused on recent studies on the positive or negative role of IL-33/ST2 in different diseases, as well as the current related drugs targeting IL-33/ST2 in the preclinical and clinical stage. The mechanism of IL-33/ST2 in different diseases and its mediating effect on different immune cells have been summarized, as well as the antibody drugs targeting IL-33 or ST2, natural compounds with a mediating effect, and small molecule substances targeting relative pathway. We aim to provide new ideas and treatment strategies for IL-33/ST2-related drugs to treat different diseases.

Shallow-angle intracranial cannula for repeated infusion and in vivo imaging with multiphoton microscopy

Multiphoton microscopy serves as an essential tool for high-resolution imaging of the living mouse brain. To facilitate optical access to the brain during imaging, the cranial window surgery is commonly used. However, this procedure restricts physical access above the imaging area and hinders the direct delivery of imaging agents and drugs. To overcome this limitation, we have developed a cannula delivery system that enables the implantation of a low-profile cannula nearly parallel to the brain surface at angles as shallow as 8 degrees, while maintaining compatibility with multiphoton microscopy. To validate this approach, we perform direct infusion and imaging of various fluorescent cell markers in the brain. Additionally, we successfully demonstrate tracking of degenerating neurons over time in Alzheimer's disease mice using Fluoro-Jade C. Furthermore, we show longitudinal imaging of brain tissue partial pressure of oxygen using a phosphorescent oxygen sensor. Our developed technique should enable a wide range of new longitudinal imaging studies in the mouse brain.

Rescue of hippocampal synaptic plasticity and memory performance by Fingolimod (FTY720) in APP/PS1 model of Alzheimer's disease is accompanied by correction in metabolism of sphingolipids, polyamines, and phospholipid saturation composition

Previously, our metabolomic, transcriptomic, and genomic studies characterized the ceramide/sphingomyelin pathway as a therapeutic target in Alzheimer's disease, and we demonstrated that FTY720, a sphingosine-1-phospahate receptor modulator approved for treatment of multiple sclerosis, recovers synaptic plasticity and memory in APP/PS1 mice. To further investigate how FTY720 rescues the pathology, we performed metabolomic analysis in brain, plasma, and liver of trained APP/PS1 and wild-type mice. APP/PS1 mice showed area-specific brain disturbances in polyamines, phospholipids, and sphingolipids. Most changes were completely or partially normalized in FTY720-treated subjects, indicating rebalancing the "sphingolipid rheostat", reactivating phosphatidylethanolamine synthesis via mitochondrial phosphatidylserine decarboxylase pathway, and normalizing polyamine levels that support mitochondrial activity. Synaptic plasticity and memory were rescued, with spermidine synthesis in temporal cortex best corresponding to hippocampal CA3-CA1 plasticity normalization. FTY720 effects, also reflected in other pathways, are consistent with promotion of mitochondrial function, synaptic plasticity, and anti-inflammatory environment, while reducing pro-apoptotic and pro-inflammatory signals.

Evolution of Alzheimer's Disease Therapeutics: From Conventional Drugs to Medicinal Plants, Immunotherapy, Microbiotherapy and Nanotherapy

Alzheimer's disease (AD) represents an escalating global health crisis, constituting the leading cause of dementia among the elderly and profoundly impairing their quality of life. Current FDA-approved drugs, such as rivastigmine, donepezil, galantamine, and memantine, offer only modest symptomatic relief and are frequently associated with significant adverse effects. Faced with this challenge and in line with advances in the understanding of the pathophysiology of this neurodegenerative condition, various innovative therapeutic strategies have been explored. Here, we review novel approaches inspired by advanced knowledge of the underlying pathophysiological mechanisms of the disease. Among the therapeutic alternatives, immunotherapy stands out, employing monoclonal antibodies to specifically target and eliminate toxic proteins implicated in AD. Additionally, the use of medicinal plants is examined, as their synergistic effects among components may confer neuroprotective properties. The modulation of the gut microbiota is also addressed as a peripheral strategy that could influence neuroinflammatory and degenerative processes in the brain. Furthermore, the therapeutic potential of emerging approaches, such as the use of microRNAs to regulate key cellular processes and nanotherapy, which enables precise drug delivery to the central nervous system, is analyzed. Despite promising advances in these strategies, the incidence of Alzheimer's disease continues to rise. Therefore, it is proposed that achieving effective treatment in the future may require the integration of combined approaches, maximizing the synergistic effects of different therapeutic interventions.

Age- and Sex-Specific Regulation of Serine Racemase in the Retina of an Alzheimer's Disease Mouse

Purpose

Changes associated with Alzheimer's disease (AD) may have measurable effects on the retina, which may facilitate early detection due to the eye's accessibility. Retinal pathology and the regulation of serine racemase (SR) were investigated in the retinas of APP(SW)/PS1(∆E9) mice.

Methods

SR in the retinas and the content of D-serine in the aqueous humor were analyzed. The structure and function of the retina were assessed. Additionally, the regulation of SR in primary Müller cell cultures was investigated.

Results

SR levels were significantly higher in the retinas of 18- and 24-month-old male APP/PS1 mice, whereas aqueous humor D-serine was lower in 24-month-old APP/PS1 male mice compared to wild-type (WT) mice. Neither Aβ nor 17β-estradiol increased SR, but the combination of both did in Müller cell cultures. In contrast, 17β-estradiol increased Srr mRNA in the cultures. At 8 months of age, male APP/PS1 mice began to display reduced b-wave amplitude in scotopic and photopic electroretinography (ERG) recordings, unlike female APP/PS1 mice. Although the retinal layer thickness in APP/PS1 mice did not differ from WT mice, there was overt apoptosis in the inner and outer nuclear layers of the APP/PS1 mice retinas.

Conclusions

The age- and sex-specific regulation of SR is correlated with the pathology of an AD retina. Because the time window for SR regulation and D-serine alteration occurs after photoreceptor dysfunction in the AD retinas, it has limited value as a detection biomarker but may be useful as a topographic biomarker for staging severity and monitoring drug interventions in the eye or central nervous system.

Three-dimensional view of microglia-amyloid plaque interactions

Recent gene expression studies have revealed about 10 different states of microglia, some of which are characteristic for Alzheimer-like amyloid plaque pathology. However, it is not presently known how these translate into morphological features that would reflect microglia interaction with amyloid plaques. With optimized conditions for confocal microscopy in amyloid plaque forming APP/PS1 transgenic mice we reveal new details of how microglia processes interact with amyloid plaques. The microglia contacts differed drastically between purely diffuse plaque and those with a fibrillar core. We identified microglia that extend their enlarged processes through the diffuse shell of the amyloid plaques and cover the fibrillar plaque core with snowplow-like expanded end-feet. These end-feet were filled with the lysosomal marker CD68, while both non-fibrillar and fibrillar amyloid was found in perinuclear vesicles of some "snowplower" microglia. In the organized dense-core plaques, we consistently saw a layer of Apolipoprotein E (ApoE) between the fibrillar core and the microglial end-feet. ApoE covered also loose fibrillar amyloid and diffuse amyloid plaques that were about 10 μm or larger in diameter. These findings are compatible with both amyloid plaque phagocytosis and compaction by microglia. Further, they support a chemotactic role of ApoE for microglia contacts with amyloid plaques.

Adolescent Alcohol and the Spectrum of Cognitive Dysfunction in Aging

Among the many changes associated with aging, inflammation in the central nervous system (CNS) and throughout the body likely contributes to the constellation of health-related maladies associated with aging. Genetics, lifestyle factors, and environmental experiences shape the trajectory of aging-associated inflammation, including the developmental timing, frequency, and intensity of alcohol consumption. This chapter posits that neuroinflammatory processes form a critical link between alcohol exposure and the trajectory of healthy aging, at least in part through direct or indirect interactions with cholinergic circuits that are crucial to cognitive integrity. In this chapter, we begin with a discussion of how inflammation changes from early development through late aging; discuss the role of inflammation and alcohol in the emergence of mild cognitive impairment (MCI); elaborate on critical findings on the contribution of alcohol-related thiamine deficiency to the loss of cholinergic function and subsequent development of Wernicke-Korsakoff syndrome (WKS); and present emerging findings at the intersection of alcohol and Alzheimer's disease and related dementias (ADRD). In doing so, our analysis points toward inflammation-mediated compromise of basal forebrain cholinergic function as a key culprit in cognitive dysfunction associated with chronic alcohol exposure, effects that may be rescuable through either pharmacological or behavioral approaches. Furthermore, our chapter reveals an interesting dichotomy in the effects of alcohol on neuropathological markers of ADRD that depend upon both biological sex and genetic vulnerability.

Long-Term Treatment with Fluoroethylnormemantine (FENM) Alleviated Memory Deficits, Amyloid Pathology, and Microglial Reaction in APP/PS1 Mice

Fluoroethylnormemantine (FENM, RST-01) shows different pharmacological properties from Memantine. The drug is neuroprotective in pharmacological and transgenic mouse models of Alzheimer's disease (AD), particularly limiting the neuroinflammatory response to amyloid-β (Aβ) accumulation. In order to define early therapeutic intervention aimed at preventing AD and targeting the early activation of proinflammatory pathways, we examined the impact of chronic FENM treatment starting presymptomatically in APPswe/PSEN1∂E9 (APP/PS1) mice. APP/PS1 (32 males and 36 females) and wild-type (WT, 23 males and 36 females) mice received FENM (0, 1, and 5 mg/kg/day) in the drinking bottle between 3 and 12 months of age. They were tested once a month for spontaneous alternation and, at the end of the treatment, for object recognition, water-maze learning, and passive avoidance. Amyloid plaques, astrocytes, and microglia were assessed by immunofluorescence, and guanidine-soluble and insoluble Aβ1-40/42 levels were determined in the hippocampal formation. Spontaneous alternation performances regularly decreased in APP/PS1, but not in WT mice. The FENM treatments (1 and 5 mg/kg) prevented the deficit. At 12 months of age, APP/PS1 treated with 1 mg/kg FENM showed significant improvements in all behavioral procedures tested. The astroglial reaction was not significantly attenuated by FENM in the stratum radiatum, stratum moleculare, and polymorph layer of the dentate gyrus. The microglial reaction was significantly decreased in the two latter areas. In the polymorph layer, a significant effect on amyloid plaques was measured. Global analyses of amyloid load showed attenuations of soluble and insoluble Aβ1-40 levels and a significant decrease in the level of insoluble Aβ1-42. Moreover, significant negative correlations were observed for FENM impacts on amyloid load or microglial activation and the alternation score. FENM confirmed, under a chronic presymptomatic treatment, its neuroprotective efficacy in AD. Our data particularly suggested that an impact on Aβ and microglia could be related to the preservation of cognitive functions.

The effects of a bioavailable curcumin formulation on Alzheimer's disease pathologies: A potential risk for neuroinflammation

Alzheimer's disease (AD) is a common cause of dementia characterized by the presence of two proteinaceous deposits in the brain. These pathologies may be a consequence of complex interactions between neurons and glia before the onset of cognitive impairments. Curcumin, a bioactive compound found in turmeric, is a promising candidate for AD because it alleviates neuropathologies in mouse models of the disease. Although its clinical efficacy has been hindered by low oral bioavailability, the development of new formulations may overcome this limitation. The purpose of this study was to determine the effects of a bioavailable curcumin formulation in a mouse model of AD. The formulation was administered to mice in drinking water after encapsulation into micelles using a previously validated method. A neuropathological assessment was performed to determine if it slows or alters the course of the disease. Cognitive performance was not included because it had already been assessed by a previous study. The bioavailable curcumin formulation was unable to alter the size or number of amyloid plaques in a transgenic mouse model. In addition, mechanisms that regulate amyloid beta production were unchanged, suggesting that the disease had not been altered. The number of reactive astrocytes in the hippocampus and dentate gyrus was not altered by curcumin. However, protein levels of glial fibrillary acidic protein were increased overall in the brain, suggesting that it may have aggravated neuroinflammation. Therefore, a higher dosage, despite its enhanced oral bioavailability, may have a potential risk for neuroinflammation.

Transmissible long-term neuroprotective and pro-cognitive effects of 1-42 beta-amyloid with A2T icelandic mutation in an Alzheimer's disease mouse model

The amyloid cascade hypothesis assumes that the development of Alzheimer's disease (AD) is driven by a self-perpetuating cycle, in which β-amyloid (Aβ) accumulation leads to Tau pathology and neuronal damages. A particular mutation (A673T) of the amyloid precursor protein (APP) was identified among Icelandic population. It provides a protective effect against Alzheimer- and age-related cognitive decline. This APP mutation leads to the reduced production of Aβ with A2T (position in peptide sequence) change (Aβice). In addition, Aβice has the capacity to form protective heterodimers in association with wild-type Aβ. Despite the emerging interest in Aβice during the last decade, the impact of Aβice on events associated with the amyloid cascade has never been reported. First, the effects of Aβice were evaluated in vitro by electrophysiology on hippocampal slices and by studying synapse morphology in cortical neurons. We showed that Aβice protects against endogenous Aβ-mediated synaptotoxicity. Second, as several studies have outlined that a single intracerebral administration of Aβ can worsen Aβ deposition and cognitive functions several months after the inoculation, we evaluated in vivo the long-term effects of a single inoculation of Aβice or Aβ-wild-type (Aβwt) in the hippocampus of transgenic mice (APPswe/PS1dE9) over-expressing Aβ1-42 peptide. Interestingly, we found that the single intra-hippocampal inoculation of Aβice to mice rescued synaptic density and spatial memory losses four months post-inoculation, compared with Aβwt inoculation. Although Aβ load was not modulated by Aβice infusion, the amount of Tau-positive neuritic plaques was significantly reduced. Finally, a lower phagocytosis by microglia of post-synaptic compounds was detected in Aβice-inoculated animals, which can partly explain the increased density of synapses in the Aβice animals. Thus, a single event as Aβice inoculation can improve the fate of AD-associated pathology and phenotype in mice several months after the event. These results open unexpected fields to develop innovative therapeutic strategies against AD.

Exploring the Synergistic Effects of Erinacines on Microglial Regulation and Alzheimer's Pathology Under Metabolic Stress

BACKGROUND

Hericium erinaceus mycelium and its constituents, erinacines A and S, have shown neuroprotective effects in APP/PS1 transgenic mice; however, the precise mechanisms by which they modulate microglial phenotypes remain unclear. Our study is the first to explore the effect of erinacines on microglia morphology and the underlying mechanisms using a novel primary mixed glia cell model and advanced bioinformatic tools. Furthermore, we emphasize the clinical relevance by evaluating erinacines in a metabolically stressed APP/PS1 mouse model, which more accurately reflects the complexities of human Alzheimer's disease (AD), where metabolic syndrome is a common comorbidity.

METHODS

Rat primary mixed glial cultures were used to simulate the spectrum of microglial phenotypes, particularly the transition from immature to mature states. Microarray sequencing, along with Connectivity Map, ConsensusPathDB, and Gene Set Enrichment Analysis, identified pathways influenced by erinacines. The therapeutic efficacy was further evaluated in metabolically stressed APP/PS1 mice.

RESULTS

Erinacines significantly promoted the development of a ramified, neuroprotective microglial phenotype. Bioinformatics revealed potential modulation of microglia via histone deacetylase inhibition, actin filament dynamics, and synaptic structure modification-pathways not previously linked to erinacines in AD. Importantly, erinacines significantly lower fasting blood glucose and insulin levels while reducing amyloid-beta plaque burden, suppressing hyperactivated glial responses, and enhancing neurogenesis in the metabolically stressed APP/PS1 mice.

CONCLUSION

Our findings demonstrate the dual action of erinacines in modulating microglia morphology and phenotype while providing neuroprotection in a model that closely mimic the complexities of human Alzheimer's disease. Additionally, this study provides the foundation for understanding the potential mechanisms of action of erinacines, highlighting their promise as a novel treatment approach for Alzheimer's, particularly in cases complicated by metabolic dysfunction.

A promising drug repurposing approach for Alzheimer's treatment: Givinostat improves cognitive behavior and pathological features in APP/PS1 mice

Alzheimer's disease (AD) is the most common neurodegenerative disease, characterized by memory loss, speech and motor defects, personality changes, and psychological disorders. The exact cause of AD remains unclear. Current treatments focus on maintaining neurotransmitter levels or targeting β-amyloid (Aβ) protein, but these only alleviate symptoms and do not reverse the disease. Developing new drugs is time-consuming, costly, and has a high failure rate. Utilizing multi-omics for drug repositioning has emerged as a new strategy. Based on transcriptomic perturbation data of over 40,000 drugs in human cells from the LINCS-L1000 database, our study employed the Jaccard index and hypergeometric distribution test for reverse transcriptional feature matching analysis, identifying Givinostat as a potential treatment for AD. Our research found that Givinostat improved cognitive behavior and brain pathology in models and enhanced hippocampal synaptic plasticity. Transcriptome sequencing revealed increased expression of mitochondrial respiratory chain complex proteins in the brains of APP/PS1 mice after Givinostat treatment. Functionally, Givinostat restored mitochondrial membrane potential, reduced reactive oxygen species, and increased ATP content in Aβ-induced HT22 cells. Additionally, it improved mitochondrial morphology and quantity in the hippocampus of APP/PS1 mice and enhanced brain glucose metabolic activity. These effects are linked to Givinostat promoting mitochondrial biogenesis and improving mitochondrial function. In summary, Givinostat offers a promising new strategy for AD treatment by targeting mitochondrial dysfunction.

Astrocytic centrin-2 expression in entorhinal cortex correlates with Alzheimer's disease severity

Astrogliosis is a condition shared by acute and chronic neurological diseases and includes morphological, proteomic, and functional rearrangements of astroglia. In Alzheimer's disease (AD), reactive astrocytes frame amyloid deposits and exhibit structural changes associated with the overexpression of specific proteins, mostly belonging to intermediate filaments. At a functional level, amyloid beta triggers dysfunctional calcium signaling in astrocytes, which contributes to the maintenance of chronic neuroinflammation. Therefore, the identification of intracellular players that participate in astrocyte calcium signaling can help unveil the mechanisms underlying astrocyte reactivity and loss of function in AD. We have recently identified the calcium-binding protein centrin-2 (CETN2) as a novel astrocyte marker in the human brain and, in order to determine whether astrocytic CETN2 expression and distribution could be affected by neurodegenerative conditions, we examined its pattern in control and sporadic AD patients. By immunoblot, immunohistochemistry, and targeted-mass spectrometry, we report a positive correlation between entorhinal CETN2 immunoreactivity and neurocognitive impairment, along with the abundance of amyloid depositions and neurofibrillary tangles, thus highlighting a linear relationship between CETN2 expression and AD progression. CETN2-positive astrocytes were dispersed in the entorhinal cortex with a clustered pattern and colocalized with reactive glia markers STAT3, NFATc3, and YKL-40, indicating a human-specific role in AD-induced astrogliosis. Collectively, our data provide the first evidence that CETN2 is part of the astrocytic calcium toolkit undergoing rearrangements in AD and adds CETN2 to the list of proteins that could play a role in disease evolution.

Vascular dysfunction occurs prior to the onset of amyloid pathology and Aβ plaque deposits colocalize with endothelial cells in the hippocampus of female APPswe/PSEN1dE9 mice

Increasing evidence shows that cardiovascular diseases (CVDs) are associated with an increased risk of cognitive impairment and Alzheimer's diseases (AD). It is unknown whether systemic vascular dysfunction occurs prior to the development of AD, if this occurs in a sex-dependent manner, and whether endothelial cells play a role in the deposition of amyloid beta (Aβ) peptides. We hypothesized that vascular dysfunction occurs prior to the onset of amyloid pathology, thus escalating its progression. Furthermore, endothelial cells from female mice will present with an exacerbated formation of Aβ peptides due to an exacerbated pressure pulsatility. To test this hypothesis, we used a double transgenic mouse model of early-onset AD (APPswe/PSEN1dE9). We evaluated hippocampus-dependent recognition memory and the cardiovascular function by echocardiography and direct measurements of blood pressure through carotid artery catheterization. Vascular function was evaluated in resistance arteries, morphometric parameters in the aortas, and immunofluorescence in the hippocampus and aortas. We observed that endothelial dysfunction occurred prior to the onset of amyloid pathology irrespective of sex. However, during the onset of amyloid pathology, only female APP/PS1 mice had vascular stiffness in the aorta. There was elevated Aβ deposition which colocalized with endothelial cells in the hippocampus from female APP/PS1 mice. Overall, these data showed that vascular abnormalities may be an early marker, and potential mediator of AD, but exacerbated aortic stiffness and pressure pulsatility after the onset of amyloid pathology may be associated with a greater burden of Aβ formation in hippocampal endothelial cells from female but not male APP/PS1 mice.

Synaptic and extrasynaptic distribution of NMDA receptors in the cortex of Alzheimer's disease patients

BACKGROUND

Synaptic and extrasynaptic distribution of N-methyl-D-aspartate receptors (NMDARs) has not been addressed in the brain from Alzheimer´s disease (AD) subjects, despite their contribution to neurodegeneration.

METHODS

We have developed a protocol to isolate synaptic and extrasynaptic membranes from controls and AD frontal cortex. We characterized the distribution of the NMDAR subunits GluN2B, GluN2A, GluN1, and GluN3A, as well as post-translational modifications, such as phosphorylation and glycosylation.

RESULTS

Lower levels of synaptic GluN2B and GluN2A were found in AD fractions, while extrasynaptic GluN2B and GluN1 levels were significantly higher; GluN3A distribution remained unaffected in AD. We also identified different glycoforms of GluN2B and GluN2A in extrasynaptic membranes. Synaptic Tyr1472 GluN2B phosphorylation was significantly lower in AD fractions.

DISCUSSION

Reduction of synaptic NMDAR subunits, particularly for GluN2B, is likely to contribute to synaptic transmission failure in AD. Additionally, the increment of extrasynaptic NMDAR subunits could favor the activation of excitotoxicity in AD.

HIGHLIGHTS

New protocol to isolate synaptic and extrasynaptic membranes from the human cortex. Low GluN2B and GluN2A levels in Alzheimer´s disease (AD) synaptic membranes. High GluN2B and GluN1 levels in AD extrasynaptic membranes. Specific glycoforms of extrasynaptic GluN2B and GluN2A. Low phosphorylation at Tyr1472 in synaptic GluN2B in AD.

Thermotherapy has sexually dimorphic responses in APP/PS1 mice

A thermoregulatory decline occurs with age due to changes in muscle mass, vasoconstriction, and metabolism that lowers core body temperature (Tc). Although lower Tc is a biomarker of successful aging, we have previously shown this worsens cognitive performance in the APP/PS1 mouse model of Alzheimer's disease (AD). We hypothesized that elevating Tc with thermotherapy would improve metabolism and cognition in APP/PS1 mice. From 6-12 months of age, male and female APP/PS1 and C57BL/6 mice were chronically housed at 23 or 30°C. At 12 months of age, mice were assayed for insulin sensitivity, glucose tolerance, and spatial cognition. Plasma, hippocampal, and peripheral (adipose, hepatic, and skeletal muscle) samples were procured postmortem and tissue-specific markers of amyloid accumulation, metabolism, and inflammation were assayed. Chronic 30°C exposure increased Tc in all groups except female APP/PS1 mice. All mice receiving thermotherapy had either improved glucose tolerance or insulin sensitivity, but the underlying processes responsible for these effects varied across sexes. In males, glucose regulation was influenced predominantly by hormonal signaling in plasma and skeletal muscle glucose transporter 4 expression, whereas in females, this was modulated at the tissue level. Thermotherapy improved spatial navigation in male C57BL/6 and APP/PS1 mice, with the later attributed to reduced hippocampal soluble amyloid-β (Aβ)42. Female APP/PS1 mice exhibited worse spatial memory recall after chronic thermotherapy. Together, the data highlights the metabolic benefits of passive thermotherapy, but future studies are needed to determine therapeutic benefits for those with AD.

Sleep deprivation leads to non-adaptive alterations in sleep microarchitecture and amyloid-β accumulation in a murine Alzheimer model

Impaired sleep is a common aspect of aging and often precedes the onset of Alzheimer's disease. Here, we compare the effects of sleep deprivation in young wild-type mice and their APP/PS1 littermates, a murine model of Alzheimer's disease. After 7 h of sleep deprivation, both genotypes exhibit an increase in EEG slow-wave activity. However, only the wild-type mice demonstrate an increase in the power of infraslow norepinephrine oscillations, which are characteristic of healthy non-rapid eye movement sleep. Notably, the APP/PS1 mice fail to enhance norepinephrine oscillations 24 h after sleep deprivation, coinciding with an accumulation of cerebral amyloid-β protein. Proteome analysis of cerebrospinal fluid and extracellular fluid further supports these findings by showing altered protein clearance in APP/PS1 mice. We propose that the suppression of infraslow norepinephrine oscillations following sleep deprivation contributes to increased vulnerability to sleep loss and heightens the risk of developing amyloid pathology in early stages of Alzheimer's disease.

Navigating Alzheimer's Disease Mouse Models: Age-Related Pathology and Cognitive Deficits

Since the mid-1990s, scientists have been generating mouse models of Alzheimer's disease to elucidate key mechanisms underlying the onset and progression of the disease and aid in developing potential therapeutic approaches. The first successful mouse model of Alzheimer's disease was reported in 1995 with the generation of the PDAPP mice, which were obtained by the overexpression of gene coding for the amyloid precursor protein (APP). Since then, scientists have used different approaches to develop other APP overexpression mice, mice overexpressing tau, or a combination of them. More recently, Saito and colleagues generated a mouse model by knocking in mutations associated with familial Alzheimer's disease into the APP gene. In this review, we will describe the most used animal models and provide a practical guide for the disease's age of onset and progression. We believe that this guide will be valuable for the planning and experimental design of studies utilizing these mouse models.

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

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

Deletion of miR-33, a regulator of the ABCA1-APOE pathway, ameliorates neuropathological phenotypes in APP/PS1 mice

INTRODUCTION

Rare variants in ABCA1 increase the risk of developing Alzheimer's disease (AD). ABCA1 facilitates the lipidation of apolipoprotein E (apoE). This study investigated whether microRNA-33 (miR-33)-mediated regulation of this ABCA1-APOE pathway affects phenotypes of an amyloid mouse model.

METHODS

We generated mir-33+/+;APP/PS1 and mir-33-/-;APP/PS1 mice to determine changes in amyloid pathology using biochemical and histological analyses. We used RNA sequencing and mass spectrometry to identify the transcriptomic and proteomic changes between our genotypes. We also performed mechanistic experiments by determining the role of miR-33 in microglial migration and amyloid beta (Aβ) phagocytosis.

RESULTS

Mir-33 deletion increases ABCA1 levels and reduces Aβ accumulation and glial activation. Multi-omics studies suggested miR-33 regulates the activation and migration of microglia. We confirm that the inhibition of miR-33 significantly increases microglial migration and Aβ phagocytosis.

DISCUSSION

These results suggest that miR-33 might be a potential drug target by modulating ABCA1 level, apoE lipidation, Aβ level, and microglial function.

HIGHLIGHTS

Loss of microRNA-33 (miR-33) increased ABCA1 protein levels and the lipidation of apolipoprotein E. Loss of miR-33 reduced amyloid beta (Aβ) levels, plaque deposition, and gliosis. mRNAs and proteins dysregulated by miR-33 loss relate to microglia and Alzheimer's disease. Inhibition of miR-33 increased microglial migration and Aβ phagocytosis in vitro.

Demyelination and impaired oligodendrogenesis in the corpus callosum following lead exposure

The corpus callosum is an oligodendrocyte-enriched brain region, replenished by newborn oligodendrocytes from oligodendrocyte progenitor cells (OPCs) in subventricular zone (SVZ). Lead (Pb) exposure has been associated with multiple sclerosis, a disease characterized by the loss of oligodendrocytes. This study aimed to investigate the effects of Pb exposure on oligodendrogenesis in SVZ and myelination in the corpus callosum. Adult female mice were used for a disproportionately higher prevalence of multiple sclerosis in females. Acute Pb exposure (one ip-injection of 27 mg Pb/kg as PbAc2 24 hr before sampling) caused mild Pb accumulation in the corpus callosum. Ex vivo assay using isolated SVZ tissues collected from acute Pb-exposed brains showed a diminished oligodendrogenesis in SVZ-derived neurospheres compared with controls. In vivo subchronic Pb exposure (13.5 mg Pb/kg by daily oral gavage 4 wk) revealed significantly decreased newborn BrdU+/MBP+ oligodendrocytes in the corpus callosum, suggesting demyelination. Mechanistic investigations indicated decreased Rictor in SVZ OPCs, defective self-defense pathways, and reactive gliosis in the corpus callosum. Given the interwined pathologies between multiple sclerosis and Alzheimer's disease, the effect of Pb on myelination was evaluated in AD-modeled APP/PS1 mice. Myelin MRI on mice following chronic exposure (1,000 ppm Pb in drinking water as PbAc2 for 20 wk) revealed a profound demyelination in the corpus callosum compared with controls. Immunostaining of the choroid plexus showed diminished signaling molecule (Klotho, OTX2) expressions in Pb-treated animals. These observations suggest that Pb caused demyelination in the corpus callosum, likely by disrupting oligodendrogenesis from SVZ OPCs. Pb-induced demyelination represents a crucial pathogenic pathway in Pb neurotoxicity, including multiple sclerosis.

CD8+ T cells exacerbate AD-like symptoms in mouse model of amyloidosis

Alzheimer's disease (AD) is linked to toxic Aβ plaques in the brain and activation of innate responses. Recent findings however suggest that the disease may also depend on the adaptive immunity, as B cells exacerbate and CD8+ T cells limit AD-like pathology in mouse models of amyloidosis. Here, by artificially blocking or augmenting CD8+ T cells in the brain of 5xFAD mice, we provide evidence that AD-like pathology is promoted by pathogenic, proinflammatory cytokines and exhaustion markers expressing CXCR6+ CD39+CD73+/- CD8+ TRM-like cells. The CD8+ T cells appear to act by targeting disease associated microglia (DAM), as we find them in tight complexes with microglia around Aβ plaques in the brain of mice and humans with AD. We also report that these CD8+ T cells are induced by B cells in the periphery, further underscoring the pathogenic importance of the adaptive immunity in AD. We propose that CD8+ T cells and B cells should be considered as therapeutic targets for control of AD, as their ablation at the onset of AD is sufficient to decrease CD8+ T cells in the brain and block the amyloidosis-linked neurodegeneration.

Pharmacological inhibition of PLK2 kinase activity mitigates cognitive decline but aggravates APP pathology in a sex-dependent manner in APP/PS1 mouse model of Alzheimer's disease

Converging evidence from clinical and experimental studies suggest the potential significance of Polo-like kinase 2 (PLK2) in regulating the phosphorylation and toxicity of the Alzheimer's disease (AD)-related protein, amyloid precursor protein (APP). These findings have prompted various experimental trials aimed at inhibiting PLK2 kinase activity in different transgenic mouse models of AD. While positive impacts on cognitive decline were reported in these studies, the cellular effects remained controversial. In the present study, we sought to assess the cognitive and cellular consequences of chronic PLK2 inhibitor treatment in the APP/PS1 transgenic mouse model of AD. First, we confirmed that inhibiting PLK2 prevented cognitive decline in a sex-dependent manner, particularly by enhancing working memory in male APP/PS1 mice. Surprisingly, cellular analysis revealed that treatment with PLK2 inhibitor increased the load of amyloid plaques and elevated levels of soluble amyloid β (Aβ) 40 and Aβ42 in the cortex, as well as insoluble Aβ42 in the hippocampus of female mice, without affecting APP pathology in males. These results underscore the potential of PLK2 inhibition to mitigate cognitive symptoms in males. However, paradoxically, it intensifies amyloid pathology in females by enhancing APP amyloidogenic processing, creating a controversial aspect to its therapeutic impact. Overall, these data highlight the sex-dependent nature of the effects of PLK2 inhibition, which may also be influenced by the genetic background of the transgenic mouse model utilized.

Insights on the Characteristics and Therapeutic Potential of Mesenchymal Stem Cell-derived Exosomes for Mitigation of Alzheimer's Disease's Pathogenicity: A Systematic Review

Alzheimer's disease (AD) remains a progressive neurodegenerative disease with no cure. Treatment of AD relies on administering drugs that only subside the symptoms. In recent studies, mesenchymal stem cell (MSC)-exosomes have been marked to possess therapeutic potential for treating AD. This study aims to systematically review and analyse findings that focus on the isolation, characterisation, and sources of MSC-derived exosomes used to unravel the therapeutic potential of these exosomes targeting AD using in vitro and in vivo models. It is hypothesised that MSC-exosomes exhibit high therapeutic potential for AD treatment by exerting various modes of action. PubMed, Scopus, and Medline were used to find relevant published works from January 2016 until December 2020, using assigned keywords including "Alzheimer's disease", "secretome", and "exosomes". Only research articles meeting the predefined inclusion/exclusion criteria were selected and analysed. The risk of bias was assessed using the Office of Health Assessment and Translation tool (OHAT). A total of 17 eligible in vivo and in vitro studies were included in this review. Bone marrow-derived stem cells (BMSCs) were the most used source for exosome isolation, even though studies on exosomes from adipose-derived stem cells (ADSCs) and human umbilical cord stem cells (HUCSCs) provide more information on the characteristics. When the risk of bias was assessed, the studies presented various levels of biases. Notably, the in vitro and in vivo studies revealed neuroprotective properties of MSC-exosomes through different modes of action to alleviate AD pathology. Our review discovered that most MSC exosomes could degrade Aβ plaques, enhance neurogenesis, extenuate neuroinflammatory response through microglial activation, regulate apoptosis and reduce oxidative stress. Delivery of exosomal micro-RNAs was also found to reduce neuroinflammation. Findings from this review provided convincing systematic evidence highlighting the therapeutic properties of MSC-derived exosomes as a prospective source for cell-free (acellular) therapy in treating AD.

Impaired hippocampal functions underlying memory encoding and consolidation precede robust Aβ deposition in a mouse model of Alzheimer's disease

Current therapeutic strategies for Alzheimer's disease (AD) target amyloid-beta (Aβ) fibrils and high molecular weight protofibrils associated with plaques, but molecular cascades associated with AD may drive neural systems failure before Aβ plaque deposition in AD. Employing hippocampal electrophysiological recordings and dynamic calcium imaging across the sleep-wake cycle in the APP/PS1 mouse model of AD before Aβ plaques accumulated, we detected marked impairments of hippocampal systems function: In a spatial behavioral task, but not REM sleep, phase-amplitude coupling (PAC) of the hippocampal theta and gamma oscillations was impaired and place cell calcium fluctuations were hyper-synchronized with the theta oscillation. In subsequent slow wave sleep (SWS), place cell reactivation was reduced. These degraded neural functions underlying memory encoding and consolidation support targeting pathological processes of the pre-plaque phase of AD to treat and prevent hippocampal impairments.

The Role of CXCR3 in Nervous System-Related Diseases

Inflammatory chemokines are a group of G-protein receptor ligands characterized by conserved cysteine residues, which can be divided into four main subfamilies: CC, CXC, XC, and CX3C. The C-X-C chemokine receptor (CXCR) 3 and its ligands, C-X-C chemokine ligands (CXCLs), are widely expressed in both the peripheral nervous system (PNS) and central nervous system (CNS). This comprehensive literature review aims to examine the functions and pathways of CXCR3 and its ligands in nervous system-related diseases. In summary, while the related pathways and the expression levels of CXCR3 and its ligands are varied among different cells in PNS and CNS, the MPAK pathway is the core via which CXCR3 exerts physiological functions. It is not only the core pathway of CXCR3 after activation but also participates in the expression of CXCR3 ligands in the nervous system. In addition, despite CXCR3 being a common inflammatory chemokine receptor, there is no consensus on its precise roles in various diseases. This uncertainty may be attributable to distinct inflammatory characteristics, that inflammation simultaneously possesses the dual properties of damage induction and repair facilitation.

Optogenetic targeting of cortical astrocytes selectively improves NREM sleep in an Alzheimer's disease mouse model

Alzheimer's disease (AD) is a progressive neurodegenerative condition marked by memory impairments and distinct histopathological features such as amyloid-beta (Aβ) accumulations. Alzheimer's patients experience sleep disturbances at early stages of the disease. APPswe/PS1dE9 (APP) mice exhibit sleep disruptions, including reductions in non-rapid eye movement (NREM) sleep, that contribute to their disease progression. In addition, astrocytic calcium transients associated with a sleep-dependent brain rhythm, slow oscillations prevalent during NREM sleep, are disrupted in APP mice. However, at present it is unclear whether restoration of circuit function by targeting astrocytic activity could improve sleep in APP mice. To that end, APP mice expressing channelrhodopsin-2 (ChR2) targeted to astrocytes underwent optogenetic stimulation at the slow oscillation frequency. Optogenetic stimulation of astrocytes significantly increased NREM sleep duration but not duration of rapid eye movement (REM) sleep. Optogenetic treatment increased delta power and reduced sleep fragmentation in APP mice. Thus, optogenetic activation of astrocytes increased sleep quantity and improved sleep quality in an AD mouse model. Astrocytic activity provides a novel therapeutic avenue to pursue for enhancing sleep and slowing AD progression.

Relationship Between Reactive Astrocytes, by [18F]SMBT-1 Imaging, with Amyloid-Beta, Tau, Glucose Metabolism, and TSPO in Mouse Models of Alzheimer's Disease

Reactive astrocytes play an important role in the development of Alzheimer's disease (AD). Here, we aimed to investigate the temporospatial relationships among monoamine oxidase-B, tau and amyloid-β (Aβ), translocator protein, and glucose metabolism by using multitracer imaging in AD transgenic mouse models. Positron emission tomography (PET) imaging with [18F]SMBT-1 (monoamine oxidase-B), [18F]florbetapir (Aβ), [18F]PM-PBB3 (tau), [18F]fluorodeoxyglucose (FDG), and [18F]DPA-714 (translocator protein) was carried out in 5- and 10-month-old APP/PS1, 11-month-old 3×Tg mice, and aged-matched wild-type mice. The brain regional referenced standard uptake value (SUVR) was computed with the cerebellum as the reference region. Immunofluorescence staining was performed on mouse brain tissue slices. [18F]SMBT-1 and [18F]florbetapir SUVRs were greater in the cortex and hippocampus of 10-month-old APP/PS1 mice than in those of 5-month-old APP/PS1 mice and wild-type mice. No significant difference in the regional [18F]FDG or [18F]DPA-714 SUVRs was observed in the brains of 5- or 10-month-old APP/PS1 mice or wild-type mice. No significant difference in the SUVRs of any tracer was observed between 11-month-old 3×Tg mice and age-matched wild-type mice. A positive correlation between the SUVRs of [18F]florbetapir and [18F]DPA-714 in the cortex and hippocampus was observed among the transgenic mice. Immunostaining validated the distribution of MAO-B and limited Aβ and tau pathology in 11-month-old 3×Tg mice; and Aβ deposits in brain tissue from 10-month-old APP/PS1 mice. In summary, these findings provide in vivo evidence that an increase in astrocyte [18F]SMBT-1 accompanies Aβ accumulation in APP/PS1 models of AD amyloidosis.