Author Correction: Astrocytic Sox9 overexpression in Alzheimer's disease mouse models promotes Aβ plaque phagocytosis and preserves cognitive function.

Delivery of therapeutic substances into the brain poses a significant challenge in the treatment of neurological disorders. This is primarily due to the blood–brain barrier (BBB), which restricts access, alongside the limited stability and distribution of these agents within the brain tissue. Here we demonstrate an efficient delivery of microRNA (miRNA) and antisense RNA preferentially to neurons compared to astroglia in the brain of healthy and Alzheimer's disease mice, via disulfide-linked conjugation with poly(ß-L-malic acid-trileucine)-copolymer a biodegradable, amphiphilic, and multivalent platform. By conjugating a D-configured (D3)-peptide (vector) for specific targeting, highly efficient delivery across the BBB is achieved through the Low-Density Lipoprotein Receptor-Related Protein-1 (LRP-1) transcytosis pathway, amyloid beta (Aβ) peptides. Nanodrug distribution was determined by fluorescent labeling and analyzed by microscopy in neurons, astroglia, and in extracellular amyloid plaques typical for Alzheimer's disease. Whereas D-configured BBB-vectors can efficiently target neurons, L-configured (e.g., AP2-peptide) guided vector can only cross BBB but not seem to bind neurons. An analysis of post-injection fluorescence distribution, and RNA-seq followed by real-time PCR validation, confirmed a successful in vivo delivery of morpholino-miRNA-186 nanoconjugates into mouse brain. The size and fluorescence intensity of the intracellular nanodrug particulates were analyzed and verified by a competition with non-fluorescent conjugates. Differentially expressed genes (DEGs) from RNA-seq were identified in the nanodrug injected mice, and the changes of selected DEGs related to Alzheimer's disease were further validated by western blot and real-time PCR. Collectively, these results demonstrated that D3-peptide-conjugated nanopolymer drug is able to achieve neuron-selective delivery of miRNA and can serve as an efficient brain delivery vehicle in Alzheimer's disease (AD) mouse models.

There is an urgent need to improve the translational validity of Alzheimer's disease (AD) mouse models. Introducing genetic background diversity in AD mouse models has been proposed as a way to increase validity and enable the discovery of previously uncharacterized genetic contributions to AD susceptibility or resilience. However, the extent to which genetic background influences the mouse brain proteome and its perturbation in AD mouse models is unknown. In this study, we crossed the 5XFAD AD mouse model on a C57BL/6J (B6) inbred background with the DBA/2J (D2) inbred background and analyzed the effects of genetic background variation on the brain proteome in F1 progeny. Both genetic background and 5XFAD transgene insertion strongly affected protein variance in the hippocampus and cortex (n = 3,368 proteins). Protein co-expression network analysis identified 16 modules of highly co-expressed proteins common across the hippocampus and cortex in 5XFAD and non-transgenic mice. Among the modules strongly influenced by genetic background were those related to small molecule metabolism and ion transport. Modules strongly influenced by the 5XFAD transgene were related to lysosome/stress responses and neuronal synapse/signaling. The modules with the strongest relationship to human disease—neuronal synapse/signaling and lysosome/stress response—were not significantly influenced by genetic background. However, other modules in 5XFAD that were related to human disease, such as GABA synaptic signaling and mitochondrial membrane modules, were influenced by genetic background. Most disease-related modules were more strongly correlated with AD genotype in the hippocampus compared with the cortex. Our findings suggest that the genetic diversity introduced by crossing B6 and D2 inbred backgrounds influences proteomic changes related to disease in the 5XFAD model, and that proteomic analysis of other genetic backgrounds in transgenic and knock-in AD mouse models is warranted to capture the full range of molecular heterogeneity in genetically diverse models of AD.

Epigenetic aberration is implicated in aging and neurodegeneration. Using postmortem tissues from patients with Alzheimer's disease (AD) and AD mouse models, we have found that the permissive histone mark H3K4me3 and its catalyzing enzymes are significantly elevated in the prefrontal cortex (PFC). Inhibiting H3K4-specific methyltransferases with the compound WDR5-0103 leads to the substantial recovery of PFC synaptic function and memory-related behaviors in AD mice. Among the up-regulated genes reversed by WDR5-0103 treatment in PFC of AD mice, many have the increased H3K4me3 enrichment at their promoters. One of the identified top-ranking target genes, Sgk1, which encodes serum and glucocorticoid-regulated kinase 1, is also significantly elevated in PFC of patients with AD. Administration of a specific Sgk1 inhibitor reduces hyperphosphorylated tau protein, restores PFC glutamatergic synaptic function, and ameliorates memory deficits in AD mice. These results have found a novel epigenetic mechanism and a potential therapeutic strategy for AD and related neurodegenerative disorders.

This study investigates the role of autophagy regulation in modulating neuroinflammation and cognitive function in an Alzheimer's disease (AD) mouse model with chronic cerebral hypoperfusion (CCH). Using the APP23/PS1 mice plus CCH model, we examined the impact of autophagy regulation on cognitive function, neuroinflammation, and autophagic activity. Our results demonstrate significant cognitive impairments in AD mice, exacerbated by CCH, but mitigated by treatment with the autophagy inhibitor 3-methyladenine (3-MA). Dysregulation of autophagy-related proteins, accentuated by CCH, underscores the intricate relationship between cerebral blood flow and autophagy dysfunction in AD pathology. While 3-MA restored autophagic balance, rapamycin (RAPA) treatment did not induce significant changes, suggesting alternative therapeutic approaches are necessary. Dysregulated microglial polarization and neuroinflammation in AD+CCH were linked to cognitive decline, with 3-MA attenuating neuroinflammation. Furthermore, alterations in M2 microglial polarization and the levels of inflammatory markers NLRP3 and MCP1 were observed, with 3-MA treatment exhibiting potential anti-inflammatory effects. Our findings shed light on the crosstalk between autophagy and neuroinflammation in AD+CCH and suggest targeting autophagy as a promising strategy for mitigating neuroinflammation and cognitive decline in AD+CCH.

Inhibition of autophagy attenuates cognitive decline and mitochondrial dysfunction in an Alzheimer's disease mouse model with chronic cerebral hypoperfusion.

Our recent study has demonstrated that peripheral amylin treatment reduces the amyloid pathology in the brain of Alzheimer's disease (AD) mouse models, and improves their learning and memory. We hypothesized that the beneficial effects of amylin for AD was beyond reducing the amyloids in the brain, and have now directly tested the actions of amylin on other aspects of AD pathogenesis, especially neuroinflammation. A 10-week course of peripheral amylin treatment significantly reduced levels of cerebral inflammation markers, Cd68 and Iba1, in amyloid precursor protein (APP) transgenic mice. Mechanistic studies indicated the protective effect of amylin required interaction with its cognate receptor because silencing the amylin receptor expression blocked the amylin effect on Cd68 in microglia. Using weighted gene co-expression network analysis, we discovered that amylin treatment influenced two gene modules linked with amyloid pathology: 1) a module related to proinflammation and transport/vesicle process that included a hub gene of Cd68, and 2) a module related to mitochondria function that included a hub gene of Atp5b. Amylin treatment restored the expression of most genes in the APP cortex toward levels observed in the wild-type (WT) cortex in these two modules including Cd68 and Atp5b. Using a human dataset, we found that the expression levels of Cd68 and Atp5b were significantly correlated with the neurofibrillary tangle burden in the AD brain and with their cognition. These data suggest that amylin acts on the pathological cascade in animal models of AD, and further supports the therapeutic potential of amylin-type peptides for AD.

We recently demonstrated that activation of tyrosine receptor kinase B (TrkB) by 7, 8-dihydroxyflavone (7, 8-DHF), the selective TrkB agonist, increased surface alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors (AMPARs) AMPA receptor subunit GluR1 (GluA1) subunit expression at the synapses of Fragile X Syndrome mutant mice. This present study investigated the effects of 7, 8-DHF on both memory function and synapse structure in relation to the synapse protein level of AMPARs in the Tg2576 Alzheimer's disease (AD) mouse model. The study found that chronic oral administration of 7, 8-DHF significantly improved spatial memory and minimized dendrite loss in the hippocampus of Tg2576 mice. A key feature of 7, 8-DHF action was the increased expression of both GluA1 and GluA2 at synapses. Interestingly, 7, 8-DHF had no effect on the attenuation of amyloid precursor protein or Aβ exhibiting in the Tg2576 AD brains, yet it activated the phosphorylation of TrkB receptors and its downstream signals including CaMKII, Akt, Erk1/2, and cAMP-response element-binding protein. Importantly, cyclotraxin B (a TrkB inhibitor), U0126 (a Ras-ERK pathway inhibitor), Wortmannin (an Akt phosphorylation inhibitor), and KN-93 (a CaMKII inhibitor) counteracted the enhanced expression and phosphorylation of AMPAR subunits induced by 7, 8-DHF. Collectively, our results demonstrated that 7, 8-DHF acted on TrkB and resolved learning and memory impairments in the absence of reduced amyloid in amyloid precursor protein transgenic mice partially through improved synaptic structure and enhanced synaptic AMPARs. The findings suggest that the application of 7, 8-DHF may be a promising new approach to improve cognitive abilities in AD. We provided extensive data demonstrating that 7, 8-dihydroflavone, the TrkB agonist, improved Tg2576 mice spatial memory. This improvement is correlated with a reversion to normal values of GluA1 and GluA2 AMPA receptor subunits and dendritic spines in CA1. This work suggests that 7, 8-DHF is a suitable drug to potentiate in vivo Tropomyosin receptor kinase B (TrkB) signaling in the Alzheimer's disease mice model.

Objective To investigate the effects of Epimedium flavanoids(EF)on learning and memory ability in Alzheimer's disease(AD)mouse model induced by β-amyloid(Aβ)lateral ventricle injection. Methods ICR mice were divided into normal group, sham operation group, model group, positive control drug(Ibuprofen)group, EF low dose(0.03 g/kg),middle dose(0.1 g/kg)and high dose(0.3 g/kg)groups. The model was induced by injecting Aβ1-40 into right lateral ventricle of mice. In the treatment groups, EF was introgastrically administrated 14 d before injection and 7 d after injection. The learning and memory ability was determined by Morris water maze, step through and spontaneous locomotor activity tests. Results The function of learning-memory was signifcantly decreased in mouse model induced by Aβ lateral ventricle injection. Administration of middle and high dose EF significantly decreased the escape latency[(40.12±4.15)s,(34.99±5.49)s]and swimming distanee[(648.36±88.42)cm,(781.57±104.41)cm]than that of the model group(65.45±5.15)s,(1142.66±96.80)cm.P＜0.01)in Moms water maze test,and prolonged the latent period[(255.40±11.00)s,(257.46±19.50)s]and decreased the error times(0.80±0.14,0.77±0.17)in step-through test significantly, compared with the model mice[(196.27±25.47)s,(1.47±0.31)](P＜0.05).In the spontaneous locomotor activity experiment, no obvious difference was found among all groups(P＞0.05).Conclusion EF significantly improved the learning and memory ability in AD mouse model induced by A∞1-40 lateral ventricle injection. Key words: Learning and memory; β-amyloid; Alzheimer's disease; Epimedium flavanoids

There is emerging evidence that amyloid beta (Aβ) aggregates forming neuritic plaques lead to impairment of the lipid-rich myelin sheath and glia. In this study, we examined focal myelin lipid alterations and the disruption of the myelin sheath associated with amyloid plaques in a widely used familial Alzheimer's disease (AD) mouse model; 5xFAD. This AD mouse model has Aβ42 peptide-rich plaque deposition in the brain parenchyma. Matrix-assisted laser desorption/ionization imaging mass spectrometry of coronal brain tissue sections revealed focal Aβ plaque-associated depletion of multiple myelin-associated lipid species including sulfatides, galactosylceramides, and specific plasmalogen phopshatidylethanolamines in the hippocampus, cortex, and on the edges of corpus callosum. Certain phosphatidylcholines abundant in myelin were also depleted in amyloid plaques on the edges of corpus callosum. Further, lysophosphatidylethanolamines and lysophosphatidylcholines, implicated in neuroinflammation, were found to accumulate in amyloid plaques. Double staining of the consecutive sections with fluoromyelin and amyloid-specific antibody revealed amyloid plaque-associated myelin sheath disruption on the edges of the corpus callosum which is specifically correlated with plaque-associated myelin lipid loss only in this region. Further, apolipoprotein E, which is implicated in depletion of sulfatides in AD brain, is deposited in all the Aβ plaques which suggest apolipoprotein E might mediate sulfatide depletion as a consequence of an immune response to Aβ deposition. This high-spatial resolution matrix-assisted laser desorption/ionization imaging mass spectrometry study in combination with (immuno) fluorescence staining of 5xFAD mouse brain provides new understanding of morphological, molecular and immune signatures of Aβ plaque pathology-associated myelin lipid loss and myelin degeneration in a brain region-specific manner. Read the Editorial Highlight for this article on page 7.

Cognitive dysfunction associated with various diseases and its biomarkers have been extensively studied. However, research focusing on biomarkers related to cognitive function remains limited. This study aims to identify potential biomarkers associated with cognitive function and validate them through in vitro and in vivo experiments to address the current research gaps. We employed GWAS, PWAS, and TWAS analyses, combined with Mendelian randomization and colocalization analysis, to identify potential cognitive function-related biomarkers from European cohorts. An Alzheimer's disease (AD) cell model was established in SH-SY5Y and BV2 cells using Aβ25-35 oligomers, and an APP/PS1 (AD mouse model) was purchased. The mRNA and protein expression levels of potential biomarkers were assessed in AD cells and mouse models using RT-qPCR and western blotting. Immunofluorescence was used to evaluate the fluorescence expression of these biomarkers in the AD cells, while immunohistochemistry was employed to assess staining intensity in the dorsolateral prefrontal cortex of AD model mice. Three potential biomarkers associated with cognitive function were identified: GPX1, CSE1L, and SULT1A1. KEGG enrichment analysis indicated that GPX1, CSE1L, and SULT1A1 are involved in various metabolic pathways, including those related to amyotrophic lateral sclerosis and Huntington's disease signaling. RT-qPCR and western blotting revealed low expression of GPX1 and CSE1L, and high expression of SULT1A1 in both AD cells and mouse models. These findings were further confirmed by immunofluorescence and immunohistochemistry, which demonstrated similar expression patterns in the AD cell and mouse models. GPX1, CSE1L, and SULT1A1 serve as biomarkers of cognitive function.

Quaternary Structure Defines a Large Class of Amyloid-β Oligomers Neutralized by Sequestration

Metallothionein 3 (Mt3) is crucial for cellular homeostasis and neuroprotection, with accumulating evidence linking it to amyloid‐beta (Aβ) clearance by astrocytes. This study developed a CRISPR activator (CRISPRa) system using lipid nanoparticles to selectively upregulate Mt3 in astrocytes, aiming to enhance Aβ endocytosis in an Alzheimer's disease (AD) mouse model. To directly assess the therapeutic potential of Mt3 activation in a specific brain region, stereotaxic injection is utilized to deliver the CRISPRa lipid nanocomplexes. This approach enabled precise in vivo brain delivery and Mt3 activation. The findings reveal that CRISPRa lipid nanocomplex‐mediated Mt3 upregulation significantly boosts Aβ uptake by astrocytes, leading to a marked reduction in Aβ plaque accumulation in AD mouse brains. These results highlight CRISPRa lipid nanocomplex‐mediated Mt3 targeting as a promising strategy to enhance endogenous Aβ clearance, presenting a novel therapeutic avenue for AD.

Laminar specific detection of APP induced neurodegeneration and recovery using MEMRI in an olfactory based Alzheimer's disease mouse model

Development of chemical isotope labeling LC-MS for tissue metabolomics and its application for brain and liver metabolome profiling in Alzheimer's disease mouse model

This review explores the dual role of TREM2 (Triggered Receptor Expressed on Myeloid cells 2) in the 5xFAD Alzheimer's disease (AD) mouse model and its potential implications for targeted therapeutic strategies. TREM2, a key regulator of microglia, exhibits complex dual effects of neuroprotection and neurotoxicity in AD pathogenesis. In recent years, with deepening insights into AD pathogenesis, TREM2's roles in Aβ clearance, metabolic homeostasis maintenance, and inflammatory regulation have garnered increasing attention. However, TREM2 may exhibit diametrically opposed functions across different disease stages and activation states, posing challenges for targeted therapies. This paper systematically elucidates TREM2's protective role in the 5xFAD model (e.g., promoting Aβ clearance, maintaining neuronal function) alongside its potential harmful effects (e.g., driving pathological inflammation), and analyzes the mechanisms underlying its dual roles (e.g., disease stage dependency, activation level dependency). Based on existing research, this paper further summarizes the challenges facing TREM2-targeted therapies and explores novel strategies for precisely regulating TREM2 function, providing theoretical foundations and directions for future AD treatments.