Aβ reduction in BACE1 heterozygous null 5XFAD mice is associated with transgenic APP level

Age- and Sex-Associated Wnt Signaling Dysregulation is Exacerbated from the Early Stages of Neuropathology in an Alzheimer's Disease Model

Emerging studies suggest that Wnt signaling is dysregulated in the brains of AD patients, suggesting that this pathway may also contribute to disease progression. However, it remains to be determined whether alterations in the Wnt pathway are the cause or consequence of this disease and which elements of Wnt signaling mainly contribute to the appearance of AD histopathological markers early in disease compared to what occurs during normal aging. The present study aimed to describe the status of several canonical Wnt pathway components and the expression of the AD marker p-tau in the hippocampi of female and male 3xTg-AD mice during disease progression compared to those during normal aging. We analyzed the levels of the canonical Wnt components Wnt7a, Dkk-1, LRP6 and GSK3β as well as the levels of p-tau and BDNF at 3, 6, 9-12 and 18 months of age. We found a gradual increase in Dkk-1 levels during aging prior to Wnt7a and LRP5/6 depletion, which was strongly exacerbated in 3xTg-AD mice even at young ages and correlated with GSK3β activation and p-tau-S202/Thr205 expression. Dkk-1 upregulation, as well as the level of p-tau, was significantly greater in females than in males. Our results suggest that Dkk-1 upregulation is involved in the expression of several features of AD at early stages, which supports the possibility of positively modulating the canonical Wnt pathway as a therapeutic tool to delay this disease at early stages.

Effects of natural reduced water on cognitive functions in older adults: A RCT study

Oxidative stress and diabetes increase the risk of cognitive decline and dementia. Natural reduced water contains active hydrogen (hydrogen radicals), eliminates reactive oxygen species, and has antidiabetic effects. However, whether natural reduced water affects human cognitive function is unknown. Therefore, we implemented a double-blind intervention experiment in which participants consumed 1 L of natural reduced water or tap water daily for 6 months. The participants were healthy older adults living in Japan. The intervention group showed significant improvements in cognitive functions of attention function (p < 0.01) and short-term memory (p < 0.05). These results indicate that the continuous intake of natural reduced water improves several cognitive functions.

Activation of the muscle-to-brain axis ameliorates neurocognitive deficits in an Alzheimer's disease mouse model via enhancing neurotrophic and synaptic signaling

Skeletal muscle regulates central nervous system (CNS) function and health, activating the muscle-to-brain axis through the secretion of skeletal muscle-originating factors ("myokines") with neuroprotective properties. However, the precise mechanisms underlying these benefits in the context of Alzheimer's disease (AD) remain poorly understood. To investigate muscle-to-brain axis signaling in response to amyloid β (Aβ)-induced toxicity, we generated 5xFAD transgenic female mice with enhanced skeletal muscle function (5xFAD;cTFEB;HSACre) at prodromal (4-months old) and late (8-months old) symptomatic stages. Skeletal muscle TFEB overexpression reduced Aβ plaque accumulation in the cortex and hippocampus at both ages and rescued behavioral neurocognitive deficits in 8-month-old 5xFAD mice. These changes were associated with transcriptional and protein remodeling of neurotrophic signaling and synaptic integrity, partially due to the CNS-targeting myokine prosaposin (PSAP). Our findings implicate the muscle-to-brain axis as a novel neuroprotective pathway against amyloid pathogenesis in AD.

Challenges and Future Perspectives in Modeling Neurodegenerative Diseases Using Organ-on-a-Chip Technology

Neurodegenerative diseases (NDDs) affect more than 50 million people worldwide, posing a significant global health challenge as well as a high socioeconomic burden. With aging constituting one of the main risk factors for some NDDs such as Alzheimer's disease (AD) and Parkinson's disease (PD), this societal toll is expected to rise considering the predicted increase in the aging population as well as the limited progress in the development of effective therapeutics. To address the high failure rates in clinical trials, legislative changes permitting the use of alternatives to traditional pre-clinical in vivo models are implemented. In this regard, microphysiological systems (MPS) such as organ-on-a-chip (OoC) platforms constitute a promising tool, due to their ability to mimic complex and human-specific tissue niches in vitro. This review summarizes the current progress in modeling NDDs using OoC technology and discusses five critical aspects still insufficiently addressed in OoC models to date. Taking these aspects into consideration in the future MPS will advance the modeling of NDDs in vitro and increase their translational value in the clinical setting.

Truncated GPNMB, a microglial transmembrane protein, serves as a scavenger receptor for oligomeric β-amyloid peptide1-42 in primary type 1 microglia

Glycoprotein non-metastatic melanoma protein B (GPNMB) is up-regulated in one subtype of microglia (MG) surrounding senile plaque depositions of amyloid-beta (Aβ) peptides. However, whether the microglial GPNMB can recognize the fibrous Aβ peptides as ligands remains unknown. In this study, we report that the truncated form of GPNMB, the antigen for 9F5, serves as a scavenger receptor for oligomeric Aβ1-42 (o-Aβ1-42) in rat primary type 1 MG. 125I-labeled o-Aβ1-42 exhibited specific and saturable endosomal/lysosomal degradation in primary-cultured type 1 MG from GPNMB-expressing wild-type mice, whereas the degradation activity was markedly reduced in cells from Gpnmb-knockout mice. The Gpnmb-siRNA significantly inhibits the degradation of 125I-o-Aβ1-42 by murine microglial MG5 cells. Therefore, GPNMB contributes to mouse MG's o-Aβ1-42 clearance. In rat primary type 1 MG, the cell surface expression of truncated GPNMB was confirmed by a flow cytometric analysis using a previously established 9F5 antibody. 125I-labeled o-Aβ1-42 underwent endosomal/lysosomal degradation by rat primary type 1 MG in a dose-dependent fashion, while the 9F5 antibody inhibited the degradation. The binding of 125I-o-Aβ1-42 to the rat primary type 1 MG was inhibited by 42% by excess unlabeled o-Aβ1-42, and by 52% by the 9F5 antibody. Interestingly, the 125I-o-Aβ1-42 degradations by MG-like cells from human-induced pluripotent stem cells was inhibited by the 9F5 antibody, suggesting that truncated GPNMB also serve as a scavenger receptor for o-Aβ1-42 in human MG. Our study demonstrates that the truncated GPNMB (the antigen for 9F5) binds to oligomeric form of Aβ1-42 and functions as a scavenger receptor on MG, and 9F5 antibody can act as a blocking antibody for the truncated GPNMB.

Dual-specificity protein phosphatase 6 (DUSP6) overexpression reduces amyloid load and improves memory deficits in male 5xFAD mice

Introduction

Dual specificity protein phosphatase 6 (DUSP6) was recently identified as a key hub gene in a causal VGF gene network that regulates late-onset Alzheimer's disease (AD). Importantly, decreased DUSP6 levels are correlated with an increased clinical dementia rating (CDR) in human subjects, and DUSP6 levels are additionally decreased in the 5xFAD amyloidopathy mouse model.

Methods

To investigate the role of DUSP6 in AD, we stereotactically injected AAV5-DUSP6 or AAV5-GFP (control) into the dorsal hippocampus (dHc) of both female and male 5xFAD or wild type mice, to induce overexpression of DUSP6 or GFP.

Results

Barnes maze testing indicated that DUSP6 overexpression in the dHc of 5xFAD mice improved memory deficits and was associated with reduced amyloid plaque load, Aß1-40 and Aß1-42 levels, and amyloid precursor protein processing enzyme BACE1, in male but not in female mice. Microglial activation, which was increased in 5xFAD mice, was significantly reduced by dHc DUSP6 overexpression in both males and females, as was the number of "microglial clusters," which correlated with reduced amyloid plaque size. Transcriptomic profiling of female 5xFAD hippocampus revealed upregulation of inflammatory and extracellular signal-regulated kinase pathways, while dHc DUSP6 overexpression in female 5xFAD mice downregulated a subset of genes in these pathways. Gene ontology analysis of DEGs (p < 0.05) identified a greater number of synaptic pathways that were regulated by DUSP6 overexpression in male compared to female 5xFAD.

Discussion

In summary, DUSP6 overexpression in dHc reduced amyloid deposition and memory deficits in male but not female 5xFAD mice, whereas reduced neuroinflammation and microglial activation were observed in both males and females, suggesting that DUSP6-induced reduction of microglial activation did not contribute to sex-dependent improvement in memory deficits. The sex-dependent regulation of synaptic pathways by DUSP6 overexpression, however, correlated with the improvement of spatial memory deficits in male but not female 5xFAD.

Effects of SPI1-mediated transcriptome remodeling on Alzheimer's disease-related phenotypes in mouse models of Aβ amyloidosis

SPI1 was recently reported as a genetic risk factor for Alzheimer's disease (AD) in large-scale genome-wide association studies. However, it is unknown whether SPI1 should be downregulated or increased to have therapeutic benefits. To investigate the effect of modulating SPI1 levels on AD pathogenesis, we performed extensive biochemical, histological, and transcriptomic analyses using both Spi1-knockdown and Spi1-overexpression mouse models. Here, we show that the knockdown of Spi1 expression significantly exacerbates insoluble amyloid-β (Aβ) levels, amyloid plaque deposition, and gliosis. Conversely, overexpression of Spi1 significantly ameliorates these phenotypes and dystrophic neurites. Further mechanistic studies using targeted and single-cell transcriptomics approaches demonstrate that altered Spi1 expression modulates several pathways, such as immune response pathways and complement system. Our data suggest that transcriptional reprogramming by targeting transcription factors, like Spi1, might hold promise as a therapeutic strategy. This approach could potentially expand the current landscape of druggable targets for AD.

Mechanisms of sex differences in Alzheimer's disease

Alzheimer's disease (AD) and the mechanisms underlying its etiology and progression are complex and multifactorial. The higher AD risk in women may serve as a clue to better understand these complicated processes. In this review, we examine aspects of AD that demonstrate sex-dependent effects and delve into the potential biological mechanisms responsible, compiling findings from advanced technologies such as single-cell RNA sequencing, metabolomics, and multi-omics analyses. We review evidence that sex hormones and sex chromosomes interact with various disease mechanisms during aging, encompassing inflammation, metabolism, and autophagy, leading to unique characteristics in disease progression between men and women.

Spatiotemporal development of the neuronal accumulation of amyloid precursor protein and the amyloid plaque formation in the brain of 3xTg-AD mice

The amyloid plaque is a hallmark of Alzheimer's disease. The accumulation of the amyloid precursor protein (APP) in the neuronal structure is assumed to lead to amyloid plaque formation through the excessive production of β-amyloid protein. To study the relationship between the neuronal accumulation of APP and amyloid plaque formation, we histologically analyzed their development in the different brain regions in 3xTg-AD mice, which express Swedish mutated APP (APPSWE) in the neurons. Observation throughout the brain revealed APPSWE-positive somata in the broad regions. Quantitative model analysis showed that the somatic accumulation of APPSWE developed firstly in the hippocampus from a very early age (<1 month) and proceeded slower in the isocortex. In line with this, the hippocampus was the first region to form amyloid plaques at the age of 9-12 months, while amyloid plaques were rarely observed in the isocortex. Females had more APPSWE-positive somata and plaques than males. Furthermore, amyloid plaques were observed in the lateral septum and pontine grey, which did not contain APPSWE-positive somata but only the APPSWE-positive fibers. These results suggested that neuronal accumulation of APPSWE, both in somatodendritic and axonal domains, is closely related to the formation of amyloid plaques.

Review on anti-alzheimer drug development: approaches, challenges and perspectives

Alzheimer is an irreversible progressive neurodegenerative disease that causes failure of cerebral neurons and disability of the affected person to practice normal daily life activities. There is no concrete evidence to identify the exact reason behind the disease, so several relevant hypotheses emerged, highlighting many possible therapeutic targets, such as acetylcholinesterase, cholinergic receptors, N-methyl d-aspartate receptors, phosphodiesterase, amyloid β protein, protein phosphatase 2A, glycogen synthase kinase-3 beta, β-secretase, γ-secretase, α-secretase, serotonergic receptors, glutaminyl cyclase, tumor necrosis factor-α, γ-aminobutyric acid receptors, and mitochondria. All of these targets have been involved in the design of new potential drugs. An extensive number of these drugs have been studied in clinical trials. However, only galantamine, donepezil, and rivastigmine (ChEIs), memantine (NMDA antagonist), and aducanumab and lecanemab (selective anti-Aβ monoclonal antibodies) have been approved for AD treatment. Many drugs failed in the clinical trials to such an extent that questions have been posed about the significance of some of the aforementioned targets. On the contrary, the data of other drugs were promising and shed light on the significance of their targets for the development of new potent anti-alzheimer drugs.

Cognitive decline, Aβ pathology, and blood-brain barrier function in aged 5xFAD mice

BACKGROUND

Patients with Alzheimer's disease (AD) develop blood-brain barrier dysfunction to varying degrees. How aging impacts Aβ pathology, blood-brain barrier function, and cognitive decline in AD remains largely unknown. In this study, we used 5xFAD mice to investigate changes in Aβ levels, barrier function, and cognitive decline over time.

METHODS

5xFAD and wild-type (WT) mice were aged between 9.5 and 15.5 months and tested for spatial learning and reference memory with the Morris Water Maze (MWM). After behavior testing, mice were implanted with acute cranial windows and intravenously injected with fluorescent-labeled dextrans to assess their in vivo distribution in the brain by two-photon microscopy. Images were processed and segmented to obtain intravascular intensity, extravascular intensity, and vessel diameters as a measure of barrier integrity. Mice were sacrificed after in vivo imaging to isolate brain and plasma for measuring Aβ levels. The effect of age and genotype were evaluated for each assay using generalized or cumulative-linked logistic mixed-level modeling and model selection by Akaike Information Criterion (AICc). Pairwise comparisons were used to identify outcome differences between the two groups.

RESULTS

5xFAD mice displayed spatial memory deficits compared to age-matched WT mice in the MWM assay, which worsened with age. Memory impairment was evident in 5xFAD mice by 2-threefold higher escape latencies, twofold greater cumulative distances until they reach the platform, and twice as frequent use of repetitive search strategies in the pool when compared with age-matched WT mice. Presence of the rd1 allele worsened MWM performance in 5xFAD mice at all ages but did not alter the rate of learning or probe trial outcomes. 9.5-month-old 15.5-month-old 5xFAD mice had twofold higher brain Aβ40 and Aβ42 levels (p < 0.001) and 2.5-fold higher (p = 0.007) plasma Aβ40 levels compared to 9.5-month-old 5xFAD mice. Image analysis showed that vessel diameters and intra- and extravascular dextran intensities were not significantly different in 9.5- and 15.5-month-old 5xFAD mice compared to age-matched WT mice.

CONCLUSION

5xFAD mice continue to develop spatial memory deficits and increased Aβ brain levels while aging. Given in vivo MP imaging limitations, further investigation with smaller molecular weight markers combined with advanced imaging techniques would be needed to reliably assess subtle differences in barrier integrity in aged mice.

Updates on mouse models of Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disease in the United States (US). Animal models, specifically mouse models have been developed to better elucidate disease mechanisms and test therapeutic strategies for AD. A large portion of effort in the field was focused on developing transgenic (Tg) mouse models through over-expression of genetic mutations associated with familial AD (FAD) patients. Newer generations of mouse models through knock-in (KI)/knock-out (KO) or CRISPR gene editing technologies, have been developed for both familial and sporadic AD risk genes with the hope to more accurately model proteinopathies without over-expression of human AD genes in mouse brains. In this review, we summarized the phenotypes of a few commonly used as well as newly developed mouse models in translational research laboratories including the presence or absence of key pathological features of AD such as amyloid and tau pathology, synaptic and neuronal degeneration as well as cognitive and behavior deficits. In addition, advantages and limitations of these AD mouse models have been elaborated along with discussions of any sex-specific features. More importantly, the omics data from available AD mouse models have been analyzed to categorize molecular signatures of each model reminiscent of human AD brain changes, with the hope to guide future selection of most suitable models for specific research questions to be addressed in the AD field.

Behavioral, metabolic, and lipidomic characterization of the 5xFADxTg30 mouse model of Alzheimer's disease

Alzheimer's disease (AD) is associated with both extracellular amyloid-β (Aβ) plaques and intracellular tau-containing neurofibrillary tangles (NFT). We characterized the behavioral, metabolic and lipidomic phenotype of the 5xFADxTg30 mouse model which contains overexpression of both Aβ and tau. Our results independently reproduce several phenotypic traits described previously for this model, while providing additional characterization. This model develops many aspects associated with AD including frailty, decreased survival, initiation of aspects of cognitive decline and alterations to specific lipid classes and molecular lipid species in the plasma and brain. Notably, some sex-specific differences exist in this model and motor impairment with aging in this model does compromise the utility of the model for some movement-based behavioral assessments of cognitive function. These findings provide a reference for individuals interested in using this model to understand the pathology associated with elevated Aβ and tau or for testing potential therapeutics for the treatment of AD.

Ginsenoside Rg1 promotes β‑amyloid peptide degradation through inhibition of the ERK/PPARγ phosphorylation pathway in an Alzheimer's disease neuronal model

β-Amyloid peptide (Aβ) deposition in the brain is an important pathological change in Alzheimer's disease (AD). Insulin-degrading enzyme (IDE), which is regulated transcriptionally by peroxisome proliferator-activated receptor γ (PPARγ), is able to proteolyze Aβ. One of the members of the MAPK family, ERK, is able to mediate the phosphorylation of PPARγ at Ser112, thereby inhibiting its transcriptional activity. Ginsenoside Rg1 is one of the active ingredients in the natural medicine ginseng and has inhibitory effects on Aβ production. The present study was designed to investigate whether ginsenoside Rg1 is able to affect the regulation of PPARγ based on the expression of its target gene, IDE, and whether it is able to promote Aβ degradation via inhibition of the ERK/PPARγ phosphorylation pathway. In the present study, primary cultured rat hippocampal neurons were treated with Aβ1-42, ginsenoside Rg1 and the ERK inhibitor PD98059, and subsequently TUNEL staining was used to detect the level of neuronal apoptosis. ELISA was subsequently employed to detect the intra- and extracellular Aβ1-42 levels, immunofluorescence staining and western blotting were used to detect the translocation of ERK from the cytoplasm to the nucleus, immunofluorescence double staining was used to detect the co-expression of ERK and PPARγ, and finally, western blotting was used to detect the phosphorylation of PPARγ at Ser112 and IDE expression. The results demonstrated that ginsenoside Rg1 or PD98059 were able to inhibit primary cultured hippocampal neuron apoptosis induced by Aβ1-42 treatment, reduce the levels of intra- and extraneuronal Aβ1-42 and inhibit the translocation of ERK from the cytoplasm to the nucleus. Furthermore, administration of ginsenoside Rg1 or PD98059 resulted in attenuated co-expression of ERK and PPARγ, inhibition of phosphorylation of PPARγ at Ser112 mediated by ERK and an increase in IDE expression. In addition, the effects when PD98059 to inhibit ERK followed by treatment with ginsenoside Rg1 were found to be more pronounced than those when using PD98059 alone. In conclusion, ginsenoside Rg1 was demonstrated to exert neuroprotective effects on AD via inhibition of the ERK/PPARγ phosphorylation pathway, which led to an increase in IDE expression, the promotion of Aβ degradation and the decrease of neuronal apoptosis. These results could provide a theoretical basis for the clinical application of ginsenoside Rg1 in AD.

ANKS1A regulates LDL receptor-related protein 1 (LRP1)-mediated cerebrovascular clearance in brain endothelial cells

Brain endothelial LDL receptor-related protein 1 (LRP1) is involved in the clearance of Aβ peptides across the blood-brain barrier (BBB). Here we show that endothelial deficiency of ankyrin repeat and SAM domain containing 1 A (ANKS1A) reduces both the cell surface levels of LRP1 and the Aβ clearance across the BBB. Association of ANKS1A with the NPXY motifs of LRP1 facilitates the transport of LRP1 from the endoplasmic reticulum toward the cell surface. ANKS1A deficiency in an Alzheimer's disease mouse model results in exacerbated Aβ pathology followed by cognitive impairments. These deficits are reversible by gene therapy with brain endothelial-specific ANKS1A. In addition, human induced pluripotent stem cell-derived BBBs (iBBBs) were generated from endothelial cells lacking ANKS1A or carrying the rs6930932 variant. Those iBBBs exhibit both reduced cell surface LRP1 and impaired Aβ clearance. Thus, our findings demonstrate that ANKS1A regulates LRP1-mediated Aβ clearance across the BBB.

Minding the Gap: Exploring Neuroinflammatory and Microglial Sex Differences in Alzheimer's Disease

Research into Alzheimer's Disease (AD) describes a link between AD and the resident immune cells of the brain, the microglia. Further, this suspected link is thought to have underlying sex effects, although the mechanisms of these effects are only just beginning to be understood. Many of these insights are the result of policies put in place by funding agencies such as the National Institutes of Health (NIH) to consider sex as a biological variable (SABV) and the move towards precision medicine due to continued lackluster therapeutic options. The purpose of this review is to provide an updated assessment of the current research that summarizes sex differences and the research pertaining to microglia and their varied responses in AD.

Decreased circulating transforming growth factor-beta (TGF-β) and kidney TGF-β immunoreactivity predict renal disease in cats with naturally occurring chronic kidney disease

OBJECTIVES

The aim of the present study was to compare the circulating transforming growth factor-beta (TGF-β) of clinically normal age-matched and naturally occurring chronic kidney disease (CKD) cats and to determine the correlation between the TGF-β expression and histopathological changes in cats with CKD.

METHODS

A total of 11 clinically normal age-matched and 27 cats with naturally occurring CKD were included in this study. Circulating TGF-β was quantified by immunoassays. Kaplan-Meier analysis was used to calculate the association between survival time and the concentration of circulating TGF-β. A general linear model was used to compare the circulating TGF-β between groups. Immunohistochemical analyses revealed TGF-β expression in renal tissues from cats with CKD that died during the study (n = 7) and in available archived renal tissue specimens taken at necropsy from cats that had previous CKD with renal lesions (n = 10). Correlations of the TGF-β expression and clinical parameters (n = 7) and histopathological changes (n = 17) were analysed using Spearman's rank correlation.

RESULTS

The median survival time of cats with a lower concentration of circulating TGF-β was shorter than that of cats with a higher concentration. The area under the curve of circulating TGF-β for predicting CKD was 0.781, indicating good differentiation. The study indicated a significant difference in circulating TGF-β concentrations between clinically normal cats and those with CKD and demonstrated that TGF-β expression is correlated with tubular atrophy.

CONCLUSIONS AND RELEVANCE

The study findings suggest that decreased serum TGF-β and tubular atrophy with TGF-β immunoreactivity may be significant in cats with CKD.

Interaction of amisulpride with GLUT1 at the blood-brain barrier. Relevance to Alzheimer's disease

Blood-brain barrier (BBB) dysfunction may be involved in the increased sensitivity of Alzheimer's disease (AD) patients to antipsychotics, including amisulpride. Studies indicate that antipsychotics interact with facilitated glucose transporters (GLUT), including GLUT1, and that GLUT1 BBB expression decreases in AD. We tested the hypotheses that amisulpride (charge: +1) interacts with GLUT1, and that BBB transport of amisulpride is compromised in AD. GLUT1 substrates, GLUT1 inhibitors and GLUT-interacting antipsychotics were identified by literature review and their physicochemical characteristics summarised. Interactions between amisulpride and GLUT1 were studied using in silico approaches and the human cerebral endothelial cell line, hCMEC/D3. Brain distribution of [3H]amisulpride was determined using in situ perfusion in wild type (WT) and 5xFamilial AD (5xFAD) mice. With transmission electron microscopy (TEM) we investigated brain capillary degeneration in WT mice, 5xFAD mice and human samples. Western blots determined BBB transporter expression in mouse and human. Literature review revealed that, although D-glucose has no charge, charged molecules can interact with GLUT1. GLUT1 substrates are smaller (184.95±6.45g/mol) than inhibitors (325.50±14.40g/mol) and GLUT-interacting antipsychotics (369.38±16.04). Molecular docking showed beta-D-glucose (free energy binding: -15.39kcal/mol) and amisulpride (-29.04kcal/mol) interact with GLUT1. Amisulpride did not affect [14C]D-glucose hCMEC/D3 accumulation. [3H]amisulpride uptake into the brain (except supernatant) of 5xFAD mice compared to WT remained unchanged. TEM revealed brain capillary degeneration in human AD. There was no difference in GLUT1 or P-glycoprotein BBB expression between WT and 5xFAD mice. In contrast, caudate P-glycoprotein, but not GLUT1, expression was decreased in human AD capillaries versus controls. This study provides new details about the BBB transport of amisulpride, evidence that amisulpride interacts with GLUT1 and that BBB transporter expression is altered in AD. This suggests that antipsychotics could potentially exacerbate the cerebral hypometabolism in AD. Further research into the mechanism of amisulpride transport by GLUT1 is important for improving antipsychotics safety.

Dual-specificity protein phosphatase 6 (DUSP6) overexpression reduces amyloid load and improves memory deficits in male 5xFAD mice

Background

Dual specificity protein phosphatase 6 (DUSP6) was recently identified as a key hub gene in a causal network that regulates late-onset Alzheimer's disease. Importantly, decreased DUSP6 levels are correlated with an increased clinical dementia rating in human subjects, and DUSP6 levels are additionally decreased in the 5xFAD amyloidopathy mouse model.

Methods

AAV5-DUSP6 or AAV5-GFP (control) were stereotactically injected into the dorsal hippocampus (dHc) of female and male 5xFAD or wild type mice to overexpress DUSP6 or GFP. Spatial learning memory of these mice was assessed in the Barnes maze, after which hippocampal tissues were isolated for downstream analysis.

Results

Barnes maze testing indicated that DUSP6 overexpression in the dHc of 5xFAD mice improved memory deficits and was associated with reduced amyloid plaque load, Aß 1-40 and Aß 1-42 levels, and amyloid precursor protein processing enzyme BACE1, in male but not in female mice. Microglial activation and microgliosis, which are increased in 5xFAD mice, were significantly reduced by dHc DUSP6 overexpression in both males and females. Transcriptomic profiling of female 5xFAD hippocampus revealed upregulated expression of genes involved in inflammatory and extracellular signal-regulated kinase (ERK) pathways, while dHc DUSP6 overexpression in female 5xFAD mice downregulated a subset of genes in these pathways. A limited number of differentially expressed genes (DEGs) (FDR<0.05) were identified in male mice; gene ontology analysis of DEGs (p<0.05) identified a greater number of synaptic pathways that were regulated by DUSP6 overexpression in male compared to female 5xFAD. Notably, the msh homeobox 3 gene, Msx3 , previously shown to regulate microglial M1/M2 polarization and reduce neuroinflammation, was one of the most robustly upregulated genes in female and male wild type and 5xFAD mice overexpressing DUSP6.

Conclusions

In summary, our data indicate that DUSP6 overexpression in dHc reduced amyloid deposition and memory deficits in male but not female 5xFAD mice, whereas reduced neuroinflammation and microglial activation were observed in both males and females. The sex-dependent regulation of synaptic pathways by DUSP6 overexpression, however, correlated with the improvement of spatial memory deficits in male but not female 5xFAD.

Extracellular vesicles improve GABAergic transmission in Huntington's disease iPSC-derived neurons

Background: Extracellular vesicles (EVs) carry bioactive molecules associated with various biological processes, including miRNAs. In both Huntington's disease (HD) models and human samples, altered expression of miRNAs involved in synapse regulation was reported. Recently, the use of EV cargo to reverse phenotypic alterations in disease models with synaptopathy as the end result of the pathophysiological cascade has become an interesting possibility. Methods: Here, we assessed the contribution of EVs to GABAergic synaptic alterations using a human HD model and studied the miRNA content of isolated EVs. Results: After differentiating human induced pluripotent stem cells into electrophysiologically active striatal-like GABAergic neurons, we found that HD-derived neurons displayed reduced density of inhibitory synapse markers and GABA receptor-mediated ionotropic signaling. Treatment with EVs secreted by control (CTR) fibroblasts reversed the deficits in GABAergic synaptic transmission and increased the density of inhibitory synapses in HD-derived neuron cultures, while EVs from HD-derived fibroblasts had the opposite effects on CTR-derived neurons. Moreover, analysis of miRNAs from purified EVs identified a set of differentially expressed miRNAs between manifest HD, premanifest, and CTR lines with predicted synaptic targets. Conclusion: The EV-mediated reversal of the abnormal GABAergic phenotype in HD-derived neurons reinforces the potential role of EV-miRNAs on synapse regulation.

Characterization of apathy-like behaviors in the 5xFAD mouse model of Alzheimer's disease

Most patients with Alzheimer's disease (AD) develop neuropsychiatric symptoms (NPS) alongside cognitive decline, and apathy is one of the most common symptoms. Few preclinical studies have investigated the biological substrates underlying NPS in AD. In this study, we used a cross-sectional design to characterize apathy-like behaviors and assess memory in 5xFAD and wildtype control mice at 6, 12, and 16 months of age. Nest building, burrowing, and marble burying were used to test representative behaviors of apathy, and a composite score of apathy-like behavior was generated from these assays. Soluble Aβ42 and plaques were quantified in the prefrontal cortex and hippocampus of the 5xFAD mice with the highest and lowest composite scores using ELISA and histology. Results suggest that 5xFAD mice develop significant apathy-like behaviors starting at 6 months of age that worsen with aging and are positively correlated with soluble Aβ42 and plaques in the prefrontal cortex and hippocampus. Our findings highlight the utility of studying NPS in mouse models of AD to uncover important relationships with underlying neuropathology.

Preliminary In Vitro and In Vivo Insights of In Silico Candidate Repurposed Drugs for Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease and is the most common type of dementia. Although a considerably large amount of money has been invested in drug development for AD, no disease modifying treatment has been detected so far. In our previous work, we developed a computational method to highlight stage-specific candidate repurposed drugs against AD. In this study, we tested the effect of the top 13 candidate repurposed drugs that we proposed in our previous work in a severity stage-specific manner using an in vitro BACE1 assay and the effect of a top-ranked drug from the list of our previous work, tetrabenazine (TBZ), in the 5XFAD as an AD mouse model. From our in vitro screening, we detected 2 compounds (clomiphene citrate and Pik-90) that showed statistically significant inhibition against the activity of the BACE1 enzyme. The administration of TBZ at the selected dose and therapeutic regimen in 5XFAD in male and female mice showed no significant effect in behavioral tests using the Y-maze and the ELISA immunoassay of Aβ40. To our knowledge, this is the first time the drug tetrabenazine has been tested in the 5XFAD mouse model of AD in a sex-stratified manner. Our results highlight 2 drugs (clomiphene citrate and Pik-90) from our previous computational work for further investigation.

In situ silver nanoparticle development for molecular-specific biological imaging via highly accessible microscopies

In biological studies and diagnoses, brightfield (BF), fluorescence, and electron microscopy (EM) are used to image biomolecules inside cells. When compared, their relative advantages and disadvantages are obvious. BF microscopy is the most accessible of the three, but its resolution is limited to a few microns. EM provides a nanoscale resolution, but sample preparation is time-consuming. In this study, we present a new imaging technique, which we termed decoration microscopy (DecoM), and quantitative investigations to address the aforementioned issues in EM and BF microscopy. For molecular-specific EM imaging, DecoM labels proteins inside cells using antibodies bearing 1.4 nm gold nanoparticles (AuNPs) and grows silver layers on the AuNPs' surfaces. The cells are then dried without buffer exchange and imaged using scanning electron microscopy (SEM). Structures labeled with silver-grown AuNPs are clearly visible on SEM, even they are covered with lipid membranes. Using stochastic optical reconstruction microscopy, we show that the drying process causes negligible distortion of structures and that less structural deformation could be achieved through simple buffer exchange to hexamethyldisilazane. Using DecoM, we visualize the nanoscale alterations in microtubules by microtubule-severing proteins that cannot be observed with diffraction-limited fluorescence microscopy. We then combine DecoM with expansion microscopy to enable sub-micron resolution BF microscopy imaging. We first show that silver-grown AuNPs strongly absorb white light, and the structures labeled with them are clearly visible on BF microscopy. We then show that the application of AuNPs and silver development must follow expansion to visualize the labeled proteins clearly with sub-micron resolution.

The bidirectional lung brain-axis of amyloid-β pathology: ozone dysregulates the peri-plaque microenvironment

The mechanisms underlying how urban air pollution affects Alzheimer's disease (AD) are largely unknown. Ozone (O3) is a reactive gas component of air pollution linked to increased AD risk, but is confined to the respiratory tract after inhalation, implicating the peripheral immune response to air pollution in AD neuropathology. Here, we demonstrate that O3 exposure impaired the ability of microglia, the brain's parenchymal immune cells, to associate with and form a protective barrier around Aβ plaques, leading to augmented dystrophic neurites and increased Aβ plaque load. Spatial proteomic profiling analysis of peri-plaque proteins revealed a microenvironment-specific signature of dysregulated disease-associated microglia protein expression and increased pathogenic molecule levels with O3 exposure. Unexpectedly, 5xFAD mice exhibited an augmented pulmonary cell and humoral immune response to O3, supporting that ongoing neuropathology may regulate the peripheral O3 response. Circulating HMGB1 was one factor upregulated in only 5xFAD mice, and peripheral HMGB1 was separately shown to regulate brain Trem2 mRNA expression. These findings demonstrate a bidirectional lung-brain axis regulating the central and peripheral AD immune response and highlight this interaction as a potential novel therapeutic target in AD.

Sex Differences between Neuronal Loss and the Early Onset of Amyloid Deposits and Behavioral Consequences in 5xFAD Transgenic Mouse as a Model for Alzheimer's Disease

A promising direction in the research on Alzheimer's Disease (AD) is the identification of biomarkers that better inform the disease progression of AD. However, the performance of amyloid-based biomarkers in predicting cognitive performance has been shown to be suboptimal. We hypothesise that neuronal loss could better inform cognitive impairment. We have utilised the 5xFAD transgenic mouse model that displays AD pathology at an early phase, already fully manifested after 6 months. We have evaluated the relationships between cognitive impairment, amyloid deposition, and neuronal loss in the hippocampus in both male and female mice. We observed the onset of disease characterized by the emergence of cognitive impairment in 6-month-old 5xFAD mice coinciding with the emergence of neuronal loss in the subiculum, but not amyloid pathology. We also showed that female mice exhibited significantly increased amyloid deposition in the hippocampus and entorhinal cortex, highlighting sex-related differences in the amyloid pathology of this model. Therefore, parameters based on neuronal loss might more accurately reflect disease onset and progression compared to amyloid-based biomarkers in AD patients. Moreover, sex-related differences should be considered in studies involving 5xFAD mouse models.

Depletion of Paraoxonase 1 (Pon1) Dysregulates mTOR, Autophagy, and Accelerates Amyloid Beta Accumulation in Mice

Paraoxonase 1 (PON1), a homocysteine (Hcy)-thiolactone detoxifying enzyme, has been associated with Alzheimer's disease (AD), suggesting that PON1 plays an important protective role in the brain. To study the involvement of PON1 in the development of AD and to elucidate the mechanism involved, we generated a new mouse model of AD, the Pon1-/-xFAD mouse, and examined how Pon1 depletion affects mTOR signaling, autophagy, and amyloid beta (Aβ) accumulation. To elucidate the mechanism involved, we examined these processes in N2a-APPswe cells. We found that Pon1 depletion significantly downregulated Phf8 and upregulated H4K20me1; mTOR, phospho-mTOR, and App were upregulated while autophagy markers Bcln1, Atg5, and Atg7 were downregulated at the protein and mRNA levels in the brains of Pon1─/─5xFAD vs. Pon1+/+5xFAD mice. Pon1 depletion in N2a-APPswe cells by RNA interference led to downregulation of Phf8 and upregulation of mTOR due to increased H4K20me1-mTOR promoter binding. This led to autophagy downregulation and significantly increased APP and Aβ levels. Phf8 depletion by RNA interference or treatments with Hcy-thiolactone or N-Hcy-protein metabolites similarly increased Aβ levels in N2a-APPswe cells. Taken together, our findings define a neuroprotective mechanism by which Pon1 prevents Aβ generation.

Search Strategy Analysis of 5xFAD Alzheimer Mice in the Morris Water Maze Reveals Sex- and Age-Specific Spatial Navigation Deficits

Spatial disorientation and navigational impairments are not only some of the first memory deficits in Alzheimer's disease, but are also very disease-specific. In rodents, the Morris Water Maze is used to investigate spatial navigation and memory. Here, we examined the spatial memory in the commonly used 5xFAD Alzheimer mouse model in a sex- and age-dependent manner. Our findings show first spatial learning deficits in 7-month-old female 5xFAD and 12-month-old male 5xFAD mice, respectively. While the assessment of spatial working memory using escape latencies provides a global picture of memory performance, it does not explain how an animal solves a spatial task. Therefore, a detailed analysis of swimming strategies was performed to better understand the behavioral differences between 5xFAD and WT mice. 5xFAD mice used a qualitatively and quantitatively different search strategy pattern than wildtype animals that used more non-spatial strategies and showed allocentric-specific memory deficits. Furthermore, a detailed analysis of swimming strategies revealed allocentric memory deficits in the probe trial in female 3-month-old and male 7-month-old 5xFAD animals before the onset of severe reference memory deficits. Overall, we could demonstrate that spatial navigation deficits in 5xFAD mice are age- and sex-dependent, with female mice being more severely affected. In addition, the implementation of a search strategy classification system allowed an earlier detection of behavioral differences and therefore could be a powerful tool for preclinical drug testing in the 5xFAD model.

Dual-Specificity Protein Phosphatase 4 (DUSP4) Overexpression Improves Learning Behavior Selectively in Female 5xFAD Mice, and Reduces β-Amyloid Load in Males and Females

Recent multiscale network analyses of banked brains from subjects who died of late-onset sporadic Alzheimer's disease converged on VGF (non-acronymic) as a key hub or driver. Within this computational VGF network, we identified the dual-specificity protein phosphatase 4 (DUSP4) [also known as mitogen-activated protein kinase (MAPK) phosphatase 2] as an important node. Importantly, DUSP4 gene expression, like that of VGF, is downregulated in postmortem Alzheimer's disease (AD) brains. We investigated the roles that this VGF/DUSP4 network plays in the development of learning behavior impairment and neuropathology in the 5xFAD amyloidopathy mouse model. We found reductions in DUSP4 expression in the hippocampi of male AD subjects, correlating with increased CDR scores, and in 4-month-old female and 12-18-month-old male 5xFAD hippocampi. Adeno-associated virus (AAV5)-mediated overexpression of DUSP4 in 5xFAD mouse dorsal hippocampi (dHc) rescued impaired Barnes maze performance in females but not in males, while amyloid loads were reduced in both females and males. Bulk RNA sequencing of the dHc from 5-month-old mice overexpressing DUSP4, and Ingenuity Pathway and Enrichr analyses of differentially expressed genes (DEGs), revealed that DUSP4 reduced gene expression in female 5xFAD mice in neuroinflammatory, interferon-gamma (IFNγ), programmed cell death protein-ligand 1/programmed cell death protein 1 (PD-L1/PD-1), and extracellular signal-regulated kinase (ERK)/MAPK pathways, via which DUSP4 may modulate AD phenotype with gender-specificity.

Isoflurane has no effect on cognitive or behavioral performance in a mouse model of early-stage Alzheimer’s disease

Background

Patients with Alzheimer’s disease show a sex-dependent decline of cognitive and behavioral performance. It is controversially discussed whether general anesthesia itself can aggravate or even cause this neurocognitive decline. Therefore, we investigated the effect of general anesthesia on neurocognitive and behavioral function and amyloidopathy in a mouse model of early-stage Alzheimer’s disease with respect to sex.

Methods

After governmental approval 10 months old Tg2576 mice and wild type (total 85 mice) either underwent general anesthesia with 1.0 minimal alveolar concentration of isoflurane for 2 h or were not exposed to isoflurane (controls). Following cognitive and behavioral testing using the modified hole board test (mHBT), brains were investigated regarding amyloidopathy, inflammation, and apoptosis. Data were analyzed using repeated measure analysis of variance (ANOVA) and univariate analysis of variance (UNIANOVA).

Results

Tg2576 mice showed a decline in memory function (p &lt; 0.001), less anxiety (p = 0.022 and p = 0.024), increased locomotor activity (p = 0.025), and impaired fine motor skills (p &lt; 0.001). Amyloid precursor protein (p &lt; 0.001), soluble amyloid-beta (p &lt; 0.001) and insoluble amyloid deposits (p &lt; 0.001) were increased in Tg2576 animals. Neither sex nor exposure to isoflurane had an effect on cognitive or behavioral testing or expression of amyloid-related biomarkers.

Discussion and conclusion

We found that 10 months old Tg2576 showed typical signs of early-stage Alzheimer’s disease and corresponding histopathological alterations. Relevant sex-specific differences or an effect of isoflurane anesthesia could not be detected at this early stage of the disease.

Acutely increased aquaporin-4 exhibits more potent protective effects in the cortex against single and repeated isoflurane-induced neurotoxicity in the developing rat brain

Damage to hippocampus, cerebellum, and cortex associated with cognitive functions due to anesthetic-induced toxicity early in life may cause cognitive decline later. Aquaporin 4 (AQP4), a key protein in waste clearance pathway of brain, is involved in synaptic plasticity and neurocognition. We investigated the effects of single and repeated isoflurane (Iso) anesthesia on AQP4 levels and brain damage. Postnatal-day (P)7 Wistar albino rats were randomly assigned to Iso or Control (C) groups. For single-exposure, pups were exposed to 1.5% Iso in 30% oxygenated-air for 3-h at P7 (Iso₁). For repeated-exposure, pups were exposed to Iso for 3 days, 3-h each day, at 1-day intervals (P7 + 9+11) starting at P7 (Iso₃). C₁ and C₃ groups received only 30% oxygenated-air. Based on HE-staining and immunoblotting (Bax/Bcl-2, cleaved-caspase3 and PARP1) analyses, Iso exposures caused a higher degree of apoptosis in hippocampus. Anesthesia increased 4HNE, oxidative stress marker; the highest ROS accumulation was determined in cerebellum. Increased inflammation (TNF-α, NF-κB) was detected. Multiple Iso-exposures caused more significant damage than single exposure. Moreover, 4HNE and TNF-α contributed synergistically to Iso-induced neurotoxicity. After anesthesia, higher expression of AQP4 was detected in cortex than hippocampus and cerebellum. There was an inverse correlation between increased AQP4 levels and apoptosis/ROS/inflammation. Correlation analysis indicated that AQP4 had a more substantial protective profile against oxidative stress than apoptosis. Remarkably, acutely increased AQP4 against Iso exhibited a more potent neuroprotective effect in cortex, especially frontal cortex. These findings promote further research to understand better the mechanisms underlying anesthesia-induced toxicity in the developing brain.

Farnesyltransferase inhibitor LNK-754 attenuates axonal dystrophy and reduces amyloid pathology in mice

BACKGROUND

Amyloid plaque deposition and axonal degeneration are early events in AD pathogenesis. Aβ disrupts microtubules in presynaptic dystrophic neurites, resulting in the accumulation of impaired endolysosomal and autophagic organelles transporting β-site amyloid precursor protein cleaving enzyme (BACE1). Consequently, dystrophic neurites generate Aβ42 and significantly contribute to plaque deposition. Farnesyltransferase inhibitors (FTIs) have recently been investigated for repositioning toward the treatment of neurodegenerative disorders and block the action of farnesyltransferase (FTase) to catalyze farnesylation, a post-translational modification that regulates proteins involved in lysosome function and microtubule stability. In postmortem AD brains, FTase and its downstream signaling are upregulated. However, the impact of FTIs on amyloid pathology and dystrophic neurites is unknown.

METHODS

We tested the effects of the FTIs LNK-754 and lonafarnib in the 5XFAD mouse model of amyloid pathology.

RESULTS

In 2-month-old 5XFAD mice treated chronically for 3 months, LNK-754 reduced amyloid plaque burden, tau hyperphosphorylation, and attenuated the accumulation of BACE1 and LAMP1 in dystrophic neurites. In 5-month-old 5XFAD mice treated acutely for 3 weeks, LNK-754 reduced dystrophic neurite size and LysoTracker-Green accumulation in the absence of effects on Aβ deposits. Acute treatment with LNK-754 improved memory and learning deficits in hAPP/PS1 amyloid mice. In contrast to LNK-754, lonafarnib treatment was less effective at reducing plaques, tau hyperphosphorylation and dystrophic neurites, which could have resulted from reduced potency against FTase compared to LNK-754. We investigated the effects of FTIs on axonal trafficking of endolysosomal organelles and found that lonafarnib and LNK-754 enhanced retrograde axonal transport in primary neurons, indicating FTIs could support the maturation of axonal late endosomes into lysosomes. Furthermore, FTI treatment increased levels of LAMP1 in mouse primary neurons and in the brains of 5XFAD mice, demonstrating that FTIs stimulated the biogenesis of endolysosomal organelles.

CONCLUSIONS

We show new data to suggest that LNK-754 promoted the axonal trafficking and function of endolysosomal compartments, which we hypothesize decreased axonal dystrophy, reduced BACE1 accumulation and inhibited amyloid deposition in 5XFAD mice. Our results agree with previous work identifying FTase as a therapeutic target for treating proteinopathies and could have important therapeutic implications in treating AD.

Transcorneal electrical stimulation enhances cognitive functions in aged and 5XFAD mouse models

Dementia is a major burden on global health for which there are no effective treatments. The use of noninvasive visual stimulation to ameliorate cognitive deficits is a novel concept that may be applicable for treating dementia. In this study, we investigated the effects of transcorneal electrical stimulation (TES) on memory enhancement using two mouse models, in aged mice and in the 5XFAD model of Alzheimer's disease. After 3 weeks of TES treatment, mice were subjected to Y-maze and Morris water maze tests to assess hippocampal-dependent learning and memory. Immunostaining of the hippocampus of 5XFAD mice was also performed to examine the effects of TES on amyloid plaque pathology. The results showed that TES improved the performance of both aged and 5XFAD mice in memory tests. TES also reduced hippocampal plaque deposition in male, but not female, 5XFAD mice. Moreover, TES significantly reversed the downregulated level of postsynaptic protein 95 in the hippocampus of male 5XFAD mice, suggesting the effects of TES involve a postsynaptic mechanism. Overall, these findings support further investigation of TES as a potential treatment for cognitive dysfunction and mechanistic studies of TES effects in other dementia models.

CRISPR/Cas9 application in cancer therapy: a pioneering genome editing tool

The progress of genetic engineering in the 1970s brought about a paradigm shift in genome editing technology. The clustered regularly interspaced short palindromic repeats/CRISPR associated protein 9 (CRISPR/Cas9) system is a flexible means to target and modify particular DNA sequences in the genome. Several applications of CRISPR/Cas9 are presently being studied in cancer biology and oncology to provide vigorous site-specific gene editing to enhance its biological and clinical uses. CRISPR's flexibility and ease of use have enabled the prompt achievement of almost any preferred alteration with greater efficiency and lower cost than preceding modalities. Also, CRISPR/Cas9 technology has recently been applied to improve the safety and efficacy of chimeric antigen receptor (CAR)-T cell therapies and defeat tumor cell resistance to conventional treatments such as chemotherapy and radiotherapy. The current review summarizes the application of CRISPR/Cas9 in cancer therapy. We also discuss the present obstacles and contemplate future possibilities in this context.

A novel process driving Alzheimer's disease validated in a mouse model: Therapeutic potential

Introduction

The neuronal mechanism driving Alzheimer's disease (AD) is incompletely understood.

Methods

Immunohistochemistry, pharmacology, biochemistry, and behavioral testing are employed in two pathological contexts-AD and a transgenic mouse model-to investigate T14, a 14mer peptide, as a key signaling molecule in the neuropathology.

Results

T14 increases in AD brains as the disease progresses and is conspicuous in 5XFAD mice, where its immunoreactivity corresponds to that seen in AD: neurons immunoreactive for T14 in proximity to T14-immunoreactive plaques. NBP14 is a cyclized version of T14, which dose-dependently displaces binding of its linear counterpart to alpha-7 nicotinic receptors in AD brains. In 5XFAD mice, intranasal NBP14 for 14 weeks decreases brain amyloid and restores novel object recognition to that in wild-types.

Discussion

These findings indicate that the T14 system, for which the signaling pathway is described here, contributes to the neuropathological process and that NBP14 warrants consideration for its therapeutic potential.

High-fat diet exacerbates cognitive and metabolic abnormalities in neuronal BACE1 knock-in mice - partial prevention by Fenretinide

Objective: The β-site APP-cleaving enzyme 1 (BACE1) is a rate-limiting step in β-amyloid (Aβ) production in Alzheimer's disease (AD) brains, but recent evidence suggests that BACE1 is also involved in metabolic regulation. Here, we aimed to assess the effects of highfat diet (HFD) on metabolic and cognitive phenotypes in the diabetic BACE1 knock-in mice (PLB4) and WT controls; we additionally examined whether these phenotypes can be normalized with a synthetic retinoid (Fenretinide, Fen) targeting weight loss.Methods: Five-month old male WT and PLB4 mice were fed either (1) control chow diet, (2) 45%-saturated fat diet (HFD), (3) HFD with 0.04% Fen (HFD + Fen) or (4) control chow diet with 0.04% Fen (Fen) for 10 weeks. We assessed basic metabolic parameters, circadian rhythmicity, spatial habituation (Phenotyper) and working memory (Y-maze). Hypothalami, forebrain and liver tissues were assessed using Western blots, qPCR and ELISAs.Results: HFD feeding drastically worsened metabolism and induced early mortality (-40%) in otherwise viable PLB4 mice. This was ameliorated by Fen, despite no effects on glucose intolerance. In HFD-fed WT mice, Fen reduced weight gain, glucose intolerance and hepatic steatosis. The physiological changes induced in WT and PLB4 mice by HFD (+/-Fen) were accompanied by enhanced cerebral astrogliosis, elevated PTP1B, phopsho-eIF2α and altered hypothalamic transcription of Bace1, Pomc and Mc4r. Behaviourally, HFD feeding exacerbated spatial memory deficits in PLB4 mice, which was prevented by Fen and linked with increased full-length APP, normalized brain Aβ*56 oligomerization and astrogliosis.Conclusions: HFD induces early mortality and worsened cognition in the Alzheimer's-like BACE1 mice- partial prevention was achieved with Fenretinide, without improvements in glucose homeostasis.

Visuo-spatial learning and memory impairments in the 5xFAD mouse model of Alzheimer's disease: Effects of age, sex, albinism, and motor impairments

The 5xFAD mouse model of Alzheimer's disease (AD) rapidly develops AD-related neuro-behavioral pathology. Learning and memory impairments in 5xFAD mice, however, are not always replicated and the size of impairments varies considerably across studies. To examine possible sources of this variability, we analyzed the effects of age, sex, albinism due to background genes (Tyrc , Oca2p ) and motor impairment on learning and memory performance of wild type and 5xFAD mice on the Morris water maze, from 3 to 15 months of age. The 5xFAD mice showed impaired learning at 6-9 months of age, but memory impairments were not detected with the test procedure used in this study. Performance of 5xFAD mice was profoundly impaired at 12-15 months of age, but was accompanied by slower swim speeds than wild-type mice and a frequent failure to locate the escape platform. Overall female mice performed worse than males, and reversal learning impairments in 5xFAD mice were more pronounced in females than males. Albino mice performed worse than pigmented mice, confirming that albinism can impair performance of 5xFAD mice independently of AD-related transgenes. Overall, these results show that 5xFAD mice have impaired learning performance at 6-9 months of age, but learning and memory performance at 12-15 months is confounded with motor impairments. Furthermore, sex and albinism should be controlled to provide an accurate assessment of AD-related transgenes on learning and memory. These results will help reduce variability across pre-clinical experiments with 5xFAD mice, and thus enhance the reliability of studies developing new therapeutics for AD.

The role of mTORC1 activation in seizure-induced exacerbation of Alzheimer's disease

The risk of seizures is 10-fold higher in patients with Alzheimer's disease than the general population, yet the mechanisms underlying this susceptibility and the effects of these seizures are poorly understood. To elucidate the proposed bidirectional relationship between Alzheimer's disease and seizures, we studied human brain samples (n = 34) from patients with Alzheimer's disease and found that those with a history of seizures (n = 14) had increased amyloid-β and tau pathology, with upregulation of the mechanistic target of rapamycin (mTOR) pathway, compared with patients without a known history of seizures (n = 20). To establish whether seizures accelerate the progression of Alzheimer's disease, we induced chronic hyperexcitability in the five times familial Alzheimer's disease mouse model by kindling with the chemoconvulsant pentylenetetrazol and observed that the mouse model exhibited more severe seizures than the wild-type. Furthermore, kindled seizures exacerbated later cognitive impairment, Alzheimer's disease neuropathology and mTOR complex 1 activation. Finally, we demonstrated that the administration of the mTOR inhibitor rapamycin following kindled seizures rescued enhanced remote and long-term memory deficits associated with earlier kindling and prevented seizure-induced increases in Alzheimer's disease neuropathology. These data demonstrated an important link between chronic hyperexcitability and progressive Alzheimer's disease pathology and suggest a mechanism whereby rapamycin may serve as an adjunct therapy to attenuate progression of the disease.

Enhanced defense against ferroptosis ameliorates cognitive impairment and reduces neurodegeneration in 5xFAD mice

Oxidative damage including lipid peroxidation is widely reported in Alzheimer's disease (AD) with the peroxidation of phospholipids in membranes being the driver of ferroptosis, an iron-dependent oxidative form of cell death. However, the importance of ferroptosis in AD remains unclear. This study tested whether ferroptosis inhibition ameliorates AD. 5xFAD mice, a widely used AD mouse model with cognitive impairment and robust neurodegeneration, exhibit markers of ferroptosis including increased lipid peroxidation, elevated lyso-phospholipids, and reduced level of Gpx4, the master defender against ferroptosis. To determine if enhanced defense against ferroptosis retards disease development, we generated 5xFAD mice that overexpress Gpx4, i.e., 5xFAD/GPX4 mice. Consistent with enhanced defense against ferroptosis, neurons from 5xFAD/GPX4 mice showed an augmented capacity to reduce lipid reactive oxygen species. In addition, compared with control 5xFAD mice, 5xFAD/GPX4 mice showed significantly improved learning and memory abilities and had reduced neurodegeneration. Moreover, 5xFAD/GPX4 mice exhibited attenuated markers of ferroptosis. Our results indicate that enhanced defense against ferroptosis is effective in ameliorating cognitive impairment and decreasing neurodegeneration of 5xFAD mice. The findings support the notion that ferroptosis is a key contributor to AD pathogenesis.

Oral nimodipine treatment has no effect on amyloid pathology or neuritic dystrophy in the 5XFAD mouse model of amyloidosis

Dysregulation of calcium homeostasis has been hypothesized to play a role in Alzheimer's disease (AD) pathogenesis. Increased calcium levels can impair axonal transport, disrupt synaptic transmission, and ultimately lead to cell death. Given the potential role of calcium dyshomeostasis in AD, there is interest in testing the ability of already approved drugs targeting various calcium channels to affect amyloid pathology and other aspects of disease. The objective of this study was to test the effects of FDA-approved L-type calcium channel antagonist nimodipine on amyloid accumulation and dystrophic neurite formation in 5XFAD mice, a mouse model of amyloid pathology. 5XFAD transgenic mice and non-transgenic littermates were treated with vehicle or nimodipine-containing chow from two to eight months of age, then brains were harvested and amyloid pathology assessed by immunoblot and immunofluorescence microscopy analyses. Nimodipine was well tolerated and crossed the blood brain barrier, as expected, but there was no effect on Aβ accumulation or on the relative amount of neuritic dystrophy, as assessed by either immunoblot, dot blot or immunofluorescence imaging of Aβ42 and dystrophic neurite marker LAMP1. While we conclude that nimodipine treatment is not likely to improve amyloid pathology or decrease neuritic dystrophy in AD, it is worth noting that nimodipine did not worsen the phenotype suggesting its use is safe in AD patients.

Systematic Phenotyping and Characterization of the 3xTg-AD Mouse Model of Alzheimer’s Disease

Animal models of disease are valuable resources for investigating pathogenic mechanisms and potential therapeutic interventions. However, for complex disorders such as Alzheimer’s disease (AD), the generation and availability of innumerous distinct animal models present unique challenges to AD researchers and hinder the success of useful therapies. Here, we conducted an in-depth analysis of the 3xTg-AD mouse model of AD across its lifespan to better inform the field of the various pathologies that appear at specific ages, and comment on drift that has occurred in the development of pathology in this line since its development 20 years ago. This modern characterization of the 3xTg-AD model includes an assessment of impairments in long-term potentiation followed by quantification of amyloid beta (Aβ) plaque burden and neurofibrillary tau tangles, biochemical levels of Aβ and tau protein, and neuropathological markers such as gliosis and accumulation of dystrophic neurites. We also present a novel comparison of the 3xTg-AD model with the 5xFAD model using the same deep-phenotyping characterization pipeline and show plasma NfL is strongly driven by plaque burden. The results from these analyses are freely available via the AD Knowledge Portal (https://modeladexplorer.org/). Our work demonstrates the utility of a characterization pipeline that generates robust and standardized information relevant to investigating and comparing disease etiologies of current and future models of AD.

Centella asiatica Alters Metabolic Pathways Associated With Alzheimer's Disease in the 5xFAD Mouse Model of ß-Amyloid Accumulation

Centella asiatica is an herb used in Ayurvedic and traditional Chinese medicine for its beneficial effects on brain health and cognition. Our group has previously shown that a water extract of Centella asiatica (CAW) elicits cognitive-enhancing effects in animal models of aging and Alzheimer's disease, including a dose-related effect of CAW on memory in the 5xFAD mouse model of ß-amyloid accumulation. Here, we endeavor to elucidate the mechanisms underlying the effects of CAW in the brain by conducting a metabolomic analysis of cortical tissue from 5xFAD mice treated with increasing concentrations of CAW. Tissue was collected from 8-month-old male and female 5xFAD mice and their wild-type littermates treated with CAW (0, 200, 500, or 1,000 mg/kg/d) dissolved in their drinking water for 5 weeks. High-performance liquid chromatography coupled to high-resolution mass spectrometry analysis was performed and relative levels of 120 annotated metabolites were assessed in the treatment groups. Metabolomic analysis revealed sex differences in the effect of the 5xFAD genotype on metabolite levels compared to wild-type mice, and variations in the metabolomic response to CAW depending on sex, genotype, and CAW dose. In at least three of the four treated groups (5xFAD or wild-type, male or female), CAW (500 mg/kg/d) significantly altered metabolic pathways related to purine metabolism, nicotinate and nicotinamide metabolism, and glycerophospholipid metabolism. The results are in line with some of our previous findings regarding specific mechanisms of action of CAW (e.g., improving mitochondrial function, reducing oxidative stress, and increasing synaptic density). Furthermore, these findings provide new information about additional, potential mechanisms for the cognitive-enhancing effect of CAW, including upregulation of nicotinamide adenine dinucleotide in the brain and modulation of brain-derived neurotrophic factor. These metabolic pathways have been implicated in the pathophysiology of Alzheimer's disease, highlighting the therapeutic potential of CAW in this neurodegenerative disease.

Quantitative Brain Positron Emission Tomography in Female 5XFAD Alzheimer Mice: Pathological Features and Sex-Specific Alterations

Successful back-translating clinical biomarkers and molecular imaging methods of Alzheimer's disease (AD), including positron emission tomography (PET), are very valuable for the evaluation of new therapeutic strategies and increase the quality of preclinical studies. ¹⁸F-Fluorodeoxyglucose (FDG)–PET and ¹⁸F-Florbetaben–PET are clinically established biomarkers capturing two key pathological features of AD. However, the suitability of ¹⁸F-FDG– and amyloid–PET in the widely used 5XFAD mouse model of AD is still unclear. Furthermore, only data on male 5XFAD mice have been published so far, whereas studies in female mice and possible sex differences in ¹⁸F-FDG and ¹⁸F-Florbetaben uptake are missing. The aim of this study was to evaluate the suitability of ¹⁸F-FDG– and ¹⁸F-Florbetaben–PET in 7-month-old female 5XFAD and to assess possible sex differences between male and female 5XFAD mice. We could demonstrate that female 5XFAD mice showed a significant reduction in brain glucose metabolism and increased cerebral amyloid deposition compared with wild type animals, in accordance with the pathology seen in AD patients. Furthermore, we showed for the first time that the hypometabolism in 5XFAD mice is gender-dependent and more pronounced in female mice. Therefore, these results support the feasibility of small animal PET imaging with ¹⁸F-FDG- and ¹⁸F-Florbetaben in 5XFAD mice in both, male and female animals. Moreover, our findings highlight the need to account for sex differences in studies working with 5XFAD mice.

Complement as a powerful "influencer" in the brain during development, adulthood and neurological disorders

The complement system was long considered as only a powerful effector arm of the immune system that, while critically protective, could lead to inflammation and cell death if overactivated, even in the central nervous system (CNS). However, in the past decade it has been recognized as playing critical roles in key physiological processes in the CNS, including neurogenesis and synaptic remodeling in the developing and adult brain. Inherent in these processes are the interactions with cells in the brain, and the cascade of interactions and functional consequences that ensue. As a result, investigations of therapeutic approaches for both suppressing excessive complement driven neurotoxicity and aberrant sculpting of neuronal circuits, require broad (and deep) knowledge of the functional activities of multiple components of this highly evolved and regulated system to avoid unintended negative consequences in the clinic. Advances in basic science are beginning to provide a roadmap for translation to therapeutics, with both small molecule and biologics. Here, we present examples of the critical roles of proper complement function in the development and sculpting of the nervous system, and in enabling rapid protection from infection and clearance of dying cells. Microglia are highlighted as important command centers that integrate signals from the complement system and other innate sensors that are programed to provide support and protection, but that direct detrimental responses to aberrant activation and/or regulation of the system. Finally, we present promising research areas that may lead to effective and precision strategies for complement targeted interventions to promote neurological health.

Sex Differences in Behavior and Molecular Pathology in the 5XFAD Model

BACKGROUND

The prevalence of Alzheimer's disease (AD) is greater in women compared to men, but the reasons for this remain unknown. This sex difference has been widely neglected in experimental studies using transgenic mouse models of AD.

OBJECTIVE

Here, we studied behavior and molecular pathology of 5-month-old 5XFAD mice, which express mutated human amyloid precursor protein and presenilin-1 on a C57BL/6J background, versus their wild-type littermate controls, to compared both sex- and genotype-dependent differences.

METHODS

A novel behavioral paradigm was utilized (OF-NO-SI), comprising activity measures (Open Field, OF) arena, followed by Novel Object exploration (NO) and Social Interaction (SI) of a sex-matched conspecific. Each segment consisted of two repeated trials to assess between-trial habituation. Subsequently, brain pathology (amyloid load, stress response and inflammation markers, synaptic integrity, trophic support) was assessed using qPCR and western blotting.

RESULTS

Female 5XFAD mice had higher levels of human APP and amyloid-β and heightened inflammation versus males. These markers correlated with hyperactivity observed in both sexes, yet only female 5XFAD mice presented with deficits in object and social exploration. Male animals had higher expression of stress markers and neurotrophic factors irrespective of genotype, this correlated with cognitive performance.

CONCLUSION

The impact of sex on AD-relevant phenotypes is in line with human data and emphasizes the necessity of appropriate study design and reporting. Differential molecular profiles observed in male versus female mice offer insights into possible protective mechanisms, and hence treatment strategies.

Deletion of Abi3 gene locus exacerbates neuropathological features of Alzheimer's disease in a mouse model of Aβ amyloidosis

Recently, large-scale human genetics studies identified a rare coding variant in the ABI3 gene that is associated with an increased risk of Alzheimer’s disease (AD). However, pathways by which ABI3 contributes to the pathogenesis of AD are unknown. To address this question, we determined whether loss of ABI3 function affects pathological features of AD in the 5XFAD mouse model. We demonstrate that the deletion of Abi3 locus significantly increases amyloid β (Aβ) accumulation and decreases microglia clustering around the plaques. Furthermore, long-term potentiation is impaired in 5XFAD;Abi3 knockout (“Abi3−/−”) mice. Moreover, we identified marked changes in the proportion of microglia subpopulations in Abi3−/− mice using a single-cell RNA sequencing approach. Mechanistic studies demonstrate that Abi3 knockdown in microglia impairs migration and phagocytosis. Together, our study provides the first in vivo functional evidence that loss of ABI3 function may increase the risk of developing AD by affecting Aβ accumulation and neuroinflammation.

The Swedish dilemma - the almost exclusive use of APPswe-based mouse models impedes adequate evaluation of alternative β-secretases

Alzheimer's disease (AD) is the most common form of dementia, however incurable so far. It is widely accepted that aggregated amyloid β (Aβ) peptides play a crucial role for the pathogenesis of AD, as they cause neurotoxicity and deposit as so-called Aβ plaques in AD patient brains. Aβ peptides derive from the amyloid precursor protein (APP) upon consecutive cleavage at the β- and γ-secretase site. Hence, mutations in the APP gene are often associated with autosomal dominant inherited AD. Almost thirty years ago, two mutations at the β-secretase site were observed in two Swedish families (termed Swedish APP (APPswe) mutations), which led to early-onset AD. Consequently, APPswe was established in almost every common AD mouse model, as it contributes to early Aβ plaque formation and cognitive impairments. Analyzing these APPswe-based mouse models, the aspartyl protease BACE1 has been evolving as the prominent β-secretase responsible for Aβ release in AD and as the most important therapeutic target for AD treatment. However, with respect to β-secretase processing, the very rare occurring APPswe variant substantially differs from wild-type APP. BACE1 dominates APPswe processing resulting in the release of Aβ1-x, whereas N-terminally truncated Aβ forms are scarcely generated. However, these N-terminally truncated Aβ species such as Aβ2-x, Aβ3-x and Aβ4-x are elevated in AD patient brains and exhibit an increased potential to aggregate compared to Aβ1-x peptides. Proteases such as meprin β, cathepsin B and ADAMTS4 were identified as alternative β-secretases being capable of generating these N-terminally truncated Aβ species from wild-type APP. However, neither meprin β nor cathepsin B are capable of generating N-terminally truncated Aβ peptides from APPswe. Hence, the role of BACE1 for the Aβ formation during AD might be overrepresented through the excessive use of APPswe mouse models. In this review we critically discuss the consideration of BACE1 as the most promising therapeutic target. Shifting the focus of AD research towards alternative β secretases might unveil promising alternatives to BACE1 inhibitors constantly failing in clinical trials due to ineffectiveness and harmful side effects.

Systematic phenotyping and characterization of the 5xFAD mouse model of Alzheimer's disease

Mouse models of human diseases are invaluable tools for studying pathogenic mechanisms and testing interventions and therapeutics. For disorders such as Alzheimer's disease in which numerous models are being generated, a challenging first step is to identify the most appropriate model and age to effectively evaluate new therapeutic approaches. Here we conducted a detailed phenotypic characterization of the 5xFAD model on a congenic C57BL/6 J strain background, across its lifespan - including a seldomly analyzed 18-month old time point to provide temporally correlated phenotyping of this model and a template for characterization of new models of LOAD as they are generated. This comprehensive analysis included quantification of plaque burden, Aβ biochemical levels, and neuropathology, neurophysiological measurements and behavioral and cognitive assessments, and evaluation of microglia, astrocytes, and neurons. Analysis of transcriptional changes was conducted using bulk-tissue generated RNA-seq data from microdissected cortices and hippocampi as a function of aging, which can be explored at the MODEL-AD Explorer and AD Knowledge Portal. This deep-phenotyping pipeline identified novel aspects of age-related pathology in the 5xFAD model.

Therapeutic Effects of Aripiprazole in the 5xFAD Alzheimer's Disease Mouse Model

Global aging has led to growing health concerns posed by Alzheimer's disease (AD), the most common type of dementia. Aripiprazole is an atypical FDA-approved anti-psychotic drug with potential against AD. To investigate its therapeutic effects on AD pathology, we administered aripiprazole to 5xFAD AD model mice and examined beta-amyloid (βA)-induced AD-like phenotypes, including βA production, neuroinflammation, and cerebral glucose metabolism. Aripiprazole administration significantly decreased βA accumulation in the brains of 5xFAD AD mice. Aripiprazole significantly modified amyloid precursor protein processing, including carboxyl-terminal fragment β and βA, a disintegrin and metalloproteinase domain-containing protein 10, and beta-site APP cleaving enzyme 1, as determined by Western blotting. Neuroinflammation, as evidenced by ionized calcium binding adapter molecule 1 and glial fibrillary acidic protein upregulation was dramatically inhibited, and the neuron cell layer of the hippocampal CA1 region was preserved following aripiprazole administration. In 18F-fluorodeoxyglucose positron emission tomography, after receiving aripiprazole, 5xFAD mice showed a significant increase in glucose uptake in the striatum, thalamus, and hippocampus compared to vehicle-treated AD mice. Thus, aripiprazole effectively alleviated βA lesions and prevented the decline of cerebral glucose metabolism in 5xFAD AD mice, suggesting its potential for βA metabolic modification and highlighting its therapeutic effect over AD progression.

Cerebrovascular phenotypes in mouse models of Alzheimer's disease

Alzheimer's disease (AD) is a devastating neurological degenerative disorder and is the most common cause of dementia in the elderly. Clinically, AD manifests with memory and cognitive decline associated with deposition of hallmark amyloid beta (Aβ) plaques and neurofibrillary tangles (NFTs). Although the mechanisms underlying AD remains unclear, two hypotheses have been proposed. The established amyloid hypothesis states that Aβ accumulation is the basis of AD and leads to formation of NFTs. In contrast, the two-hit vascular hypothesis suggests that early vascular damage leads to increased accumulation of Aβ deposits in the brain. Multiple studies have reported significant morphological changes of the cerebrovasculature which can result in severe functional deficits. In this review, we delve into known structural and functional vascular alterations in various mouse models of AD and the cellular and molecular constituents that influence these changes to further disease progression. Many studies shed light on the direct impact of Aβ on the cerebrovasculature and how it is disrupted during the progression of AD. However, more research directed towards an improved understanding of how the cerebrovasculature is modified over the time course of AD is needed prior to developing future interventional strategies.

Decreased Glucose Metabolism and Glutamine Synthesis in the Retina of a Transgenic Mouse Model of Alzheimer's Disease

Visual changes are some of the earliest symptoms that patients with Alzheimer's disease (AD) experience. Pathophysiological processes such as amyloid-β plaque formation, vascular changes, neuroinflammation, and loss of retinal ganglion cells (RGCs) have been detected in the retina of AD patients and animal models. However, little is known about the molecular processes that underlie retinal neurodegeneration in AD. The cellular architecture and constant sensory activity of the retina impose high metabolic demands. We thus hypothesized that energy metabolism might be compromised in the AD retina similarly to what has been observed in the AD brain. To address this question, we explored cellular alterations and retinal metabolic activity in the 5 × FAD mouse model of AD. We used 8-month-old female 5 × FAD mice, in which the AD-related pathology has been shown to be apparent. We observed that RGC density is selectively affected in the retina of 5 × FAD mice. To map retinal metabolic activity, we incubated isolated retinal tissue with [U-¹³C] glucose and analyzed tissue extracts by gas chromatography-mass spectrometry. We found that the retinas of 5 × FAD mice exhibit glucose hypometabolism. Moreover, we detected decreased glutamine synthesis in 5 × FAD retinas but no changes in the expression of markers of Müller glia, the main glial cell type responsible for glutamate uptake and glutamine synthesis in the retina. These findings suggest that AD presents with metabolic alterations not only in the brain but also in the retina that may be detrimental to RGC activity and survival, potentially leading to the visual impairments that AD patients suffer.