Loss of Cholinergic and Monoaminergic Afferents in APPswe/PS1ΔE9 Transgenic Mouse Model of Cerebral Amyloidosis Preferentially Occurs Near Amyloid Plaques.

Alzheimer's disease (AD) is characterized by a loss of neurons in the cortex and subcortical regions. Previously, we showed that the progressive degeneration of subcortical monoaminergic (MAergic) neurons seen in human AD is recapitulated in the APPswe/PS1ΔE9 (APP/PS) transgenic mouse model. Because degeneration of cholinergic (Ach) neurons is also a prominent feature of AD, we examined the integrity of the Ach system in the APP/PS model. The overall density of Ach fibers is reduced in APP/PS1 mice at 12 and 18 months of age but not at 4 months of age. Analysis of basal forebrain Ach neurons shows no loss of Ach neurons in the APP/PS model. Thus, since MAergic systems show overt cell loss at 18 months of age, the Ach system is less vulnerable to neurodegeneration in the APP/PS1 model. We also examined whether the proximity to Aß deposition affected the degeneration of Ach and 5-HT afferents. We found that the areas closer to the edges of compact Aß deposits exhibit a more severe loss of afferents than the areas that are more distal to Aß deposits. Collectively, the results indicate that the APP/PS model recapitulates the degeneration of multiple subcortical neurotransmitter systems, including the Ach system. In addition, the results indicate that Aß deposits cause global as well as local toxicity to subcortical afferents.

Electropositive Citric Acid-Polyethyleneimine Carbon Dots Carrying the PINK1 Gene Regulate ATP-Related Metabolic Dysfunction in APP/PS1-N2a Cells.

(1) Background: Alzheimer's disease (AD) is characterized by ß-amyloid (Aß) peptide accumulation and mitochondrial dysfunction during the early stage of disease. PINK1 regulates the balance between mitochondrial homeostasis and bioenergy supply and demand via the PINK1/Parkin pathway, Na+/Ca2+ exchange, and other pathways. (2) Methods: In this study, we synthesized positively charged carbon dots (CA-PEI CDs) using citric acid (CA) and polyethyleneimine (PEI) and used them as vectors to express PINK1 genes in the APP/PS1-N2a cell line to determine mitochondrial function, electron transport chain (ETC) activity, and ATP-related metabolomics. (3) Results: Our findings showed that the CA-PEI CDs exhibit the characteristics of photoluminescence, low toxicity, and concentrated DNA. They are ideal biological carriers for gene delivery. PINK1 overexpression significantly increased the mitochondrial membrane potential in APP/PS1-N2a cells and reduced reactive-oxygen-species generation and Aß1-40 and Aß1-42 levels. An increase in the activity of NADH ubiquinone oxidoreductase (complex I, CI) and cytochrome C oxidase (complex IV, CIV) induces the oxidative phosphorylation of mitochondria, increasing ATP generation. (4) Conclusions: These findings indicate that the PINK gene can alleviate AD by increasing bioenergetic metabolism, reducing Aß1-40 and Aß1-42, and increasing ATP production.

Combination of Tramiprosate, Curcumin, and SP600125 Reduces the Neuropathological Phenotype in Familial Alzheimer Disease PSEN1 I416T Cholinergic-like Neurons.

Familial Alzheimer's disease (FAD) is a complex and multifactorial neurodegenerative disorder for which no curative therapies are yet available. Indeed, no single medication or intervention has proven fully effective thus far. Therefore, the combination of multitarget agents has been appealing as a potential therapeutic approach against FAD. Here, we investigated the potential of combining tramiprosate (TM), curcumin (CU), and the JNK inhibitor SP600125 (SP) as a treatment for FAD. The study analyzed the individual and combined effects of these two natural agents and this pharmacological inhibitor on the accumulation of intracellular amyloid beta iAß; hyperphosphorylated protein TAU at Ser202/Thr205; mitochondrial membrane potential (ΔΨm); generation of reactive oxygen species (ROS); oxidized protein DJ-1; proapoptosis proteins p-c-JUN at Ser63/Ser73, TP53, and cleaved caspase 3 (CC3); and deficiency in acetylcholine (ACh)-induced transient Ca2+ influx response in cholinergic-like neurons (ChLNs) bearing the mutation I416T in presenilin 1 (PSEN1 I416T). We found that single doses of TM (50 µM), CU (10 µM), or SP (1 µM) were efficient at reducing some, but not all, pathological markers in PSEN 1 I416T ChLNs, whereas a combination of TM, CU, and SP at a high (50, 10, 1 µM) concentration was efficient in diminishing the iAß, p-TAU Ser202/Thr205, DJ-1Cys106-SO3, and CC3 markers by -50%, -75%, -86%, and -100%, respectively, in PSEN1 I417T ChLNs. Although combinations at middle (10, 2, 0.2) and low (5, 1, 0.1) concentrations significantly diminished p-TAU Ser202/Thr205, DJ-1Cys106-SO3, and CC3 by -69% and -38%, -100% and -62%, -100% and -62%, respectively, these combinations did not alter the iAß compared to untreated mutant ChLNs. Moreover, a combination of reagents at H concentration was able to restore the dysfunctional ACh-induced Ca2+ influx response in PSEN 1 I416T. Our data suggest that the use of multitarget agents in combination with anti-amyloid (TM, CU), antioxidant (e.g., CU), and antiapoptotic (TM, CU, SP) actions might be beneficial for reducing iAß-induced ChLN damage in FAD.

Early molecular events of autosomal-dominant Alzheimer's disease in marmosets with PSEN1 mutations.

INTRODUCTION: Fundamental questions remain about the key mechanisms that initiate Alzheimer's disease (AD) and the factors that promote its progression. Here we report the successful generation of the first genetically engineered marmosets that carry knock-in (KI) point mutations in the presenilin 1 (PSEN1) gene that can be studied from birth throughout lifespan. METHODS: CRISPR/Cas9 was used to generate marmosets with C410Y or A426P point mutations in PSEN1. Founders and their germline offspring are comprehensively studied longitudinally using non-invasive measures including behavior, biomarkers, neuroimaging, and multiomics signatures. RESULTS: Prior to adulthood, increases in plasma amyloid beta were observed in PSEN1 mutation carriers relative to non-carriers. Analysis of brain revealed alterations in several enzyme-substrate interactions within the gamma secretase complex prior to adulthood. DISCUSSION: Marmosets carrying KI point mutations in PSEN1 provide the opportunity to study the earliest primate-specific mechanisms that contribute to the molecular and cellular root causes of AD onset and progression. HIGHLIGHTS: We report the successful generation of genetically engineered marmosets harboring knock-in point mutations in the PSEN1 gene. PSEN1 marmosets and their germline offspring recapitulate the early emergence of AD-related biomarkers. Studies as early in life as possible in PSEN1 marmosets will enable the identification of primate-specific mechanisms that drive disease progression.

[Age-dependent expression of HSP90 in the hippocampus of APP/PS1 mice].

The present study aims to observe the change in expression of heat shock protein 90 (HSP90) along with amyloid-ß (Aß) and phosphorylated Tau (p-Tau) protein levels in the hippocampus tissue of Alzheimer's disease (AD) transgenic animal model with age. APP/PS1 transgenic mice at age of 6-, 9- and 12-month and C57BL/6J mice of the same age were used. The cognitive abilities of these animals were evaluated using a Morris water maze. Western blot or immunohistochemistry was used to detect the expressions of HSP90 and Aß1-42, as well as the phosphorylation levels of Tau protein in the hippocampus. The hsp90 mRNA levels and the morphology and number of cells in the hippocampus were detected with real-time quantitative polymerase chain reaction (qRT-PCR) and Nissl staining, respectively. The results showed that compared with C57BL/6J mice of the same age, HSP90 and hsp90 mRNA expression were decreased (P < 0.05 or P < 0.01), while Aß1-42 and p-Tau protein levels were increased (P < 0.05 or P < 0.01) in the hippocampal tissue of APP/PS1 transgenic mice. Meanwhile, the decrease in HSP90 and hsp90 mRNA expression (P < 0.05 or P < 0.01), the increase in Aß1-42 and p-Tau levels (P < 0.01 or P < 0.05) in hippocampal tissue and the reduction in behavioral ability showed a progressive development with the advancing of age in the APP/PS1 transgenic mice. In conclusion, in the hippocampal tissue of APP/PS1 mice, the decrease in HSP90 expression and the increase in Aß1-42 and p-Tau levels together with the decline of their cognitive ability are age-dependent.

Total ginsenosides decrease Aß production through activating PPARγ.

INTRODUCTION: Total ginsenosides (TG), the major active constituents of ginseng, have been proven to be beneficial in treatment of Alzheimer's disease (AD). However, the underlying mechanism of TG remains unclear. METHODS: APP/PS1 mice and N2a/APP695 cells were used as in vivo and in vitro model, respectively. Morris water maze (MWM) was used to investigate behavioral changes of mice; neuronal pathological changes were assessed by hematoxylin and eosin (H&E) and nissl staining; immunofluorescence staining was used to examine amyloid beta (Aß) deposition; Western blotting and quantitative real-time polymerase chain reaction (qRT-PCR) were used to examine the expression of relative amyloidogenic genes and proteins. Moreover, the antagonist of PPARγ, GW9662, was used to determine whether the effects of TG on Aß production were associated with PPARγ activity. RESULTS: TG treatment increased the spatial learning and memory abilities of APP/PS1 mice while decreasing the Aß accumulation in the cortex and hippocampus. In N2a/APP695 cells, TG treatment attenuated the secretion of Aß1-40 and Aß1-42 acting as an PPARγ agonist by inhibiting the translocation of NF-κB p65. Additionally, TG treatment also decreased the expression of amyloidogenic pathway related gene BACE1, PS1 and PS2. CONCLUSIONS: TG treatment reduced the production of Aß both in vivo and in vitro. Activating PPARγ might be a potential therapeutic target of TG in facilitating Aß clearance and ameliorating cognitive deficiency in APP/PS1 mice.

METTL3-dependent m6A modification of PSEN1 mRNA regulates craniofacial development through the Wnt/ß-catenin signaling pathway.

Craniofacial malformations, often associated with syndromes, are prevalent birth defects. Emerging evidence underscores the importance of m6A modifications in various bioprocesses such as stem cell differentiation, tissue development, and tumorigenesis. Here, in vivo, experiments with zebrafish models revealed that mettl3-knockdown embryos at 144 h postfertilization exhibited aberrant craniofacial features, including altered mouth opening, jaw dimensions, ethmoid plate, tooth formation and hypoactive behavior. Similarly, low METTL3 expression inhibited the proliferation and migration of BMSCs, HEPM cells, and DPSCs. Loss of METTL3 led to reduced mRNA m6A methylation and PSEN1 expression, impacting craniofacial phenotypes. Co-injection of mettl3 or psen1 mRNA rescued the level of Sox10 fusion protein, promoted voluntary movement, and mitigated abnormal craniofacial phenotypes induced by mettl3 knockdown in zebrafish. Mechanistically, YTHDF1 enhanced the mRNA stability of m6A-modified PSEN1, while decreased METTL3-mediated m6A methylation hindered ß-catenin binding to PSEN1, suppressing Wnt/ß-catenin signaling. Pharmacological activation of the Wnt/ß-catenin pathway partially alleviated the phenotypes of mettl3 morphant and reversed the decreases in cell proliferation and migration induced by METTL3 silencing. This study elucidates the pivotal role of METTL3 in craniofacial development via the METTL3/YTHDF1/PSEN1/ß-catenin signaling axis.

Genetic modifiers of cognitive decline in PSEN1 E280A Alzheimer's disease.

INTRODUCTION: Rate of cognitive decline (RCD) in Alzheimer's disease (AD) determines the degree of impairment for patients and of burden for caretakers. We studied the association of RCD with genetic variants in AD. METHODS: RCD was evaluated in 62 familial AD (FAD) and 53 sporadic AD (SAD) cases, and analyzed by whole-exome sequencing for association with common exonic functional variants. Findings were validated in post mortem brain tissue. RESULTS: One hundred seventy-two gene variants in FAD, and 227 gene variants in SAD associated with RCD. In FAD, performance decline of the immediate recall of the Rey-Osterrieth figure test associated with 122 genetic variants. Olfactory receptor OR51B6 showed the highest number of associated variants. Its expression was detected in temporal cortex neurons. DISCUSSION: Impaired olfactory function has been associated with cognitive impairment in AD. Genetic variants in these or other genes could help to identify risk of faster memory decline in FAD and SAD patients.

Probable Novel APP Met671Leu Mutation in a Chinese Han Family with Early-Onset Alzheimer's Disease.

Familial Alzheimer's disease (AD) is a rare disease caused by autosomal-dominant mutations. APP (encoding amyloid precursor protein), PSEN1 (encoding presenilin 1), and PSEN2 (encoding presenilin 2) are the most common genes cause dominant inherited AD. This study aimed to demonstrate a Chinese early-onset AD pedigree presenting as progressive memory impairment, apraxia, visual-spatial disorders, psychobehavioral disorders, and personality changes with a novel APP gene mutation. The family contains four patients, three carries and three normal family members. The proband underwent brain magnetic resonance imaging (MRI), 18F-fludeoxyglucose positron emission tomography (18F-FDG-PET), cerebrospinal fluid amyloid detection, 18F-florbetapir (AV-45) Positron Emission Computed Tomography (PET) imaging, whole-exome sequencing and Sanger sequencing. Brain MRI images showed brain atrophy, especially in the entorhinal cortex, temporal hippocampus, and lateral ventricle dilation. The FDG-PET showed hypometabolism in the frontotemporal, parietal, and hippocampal regions. 18F-florbetapir (AV-45) PET imaging showed cerebral cortex Aß protein deposition. The cerebrospinal fluid amyloid protein test showed Aß42/Aß40 ratio decreases, pathological phosphor-tau level increases. Whole-exome sequencing detected a new missense mutation of codon 671 (M671L), which was a heterozygous A to T point mutation at position 2011 (c.2011A > T) in exon 16 of the amyloid precursor protein, resulting in the replacement of methionine to Leucine. The co-separation analysis was validated in this family. The mutation was found in 3 patients, 3 clinical normal members in the family, but not in the other 3 unaffected family members, 100 unrelated normal subjects, or 100 sporadic patients with AD. This mutation was probably pathogenic and novel in a Chinese Han family with early-onset AD.

Early amyloid-induced changes in microglia gene expression in male APP/PS1 mice.

Alzheimer's disease (AD) is a progressive neurodegenerative disease and the most common cause of dementia, characterized by deposition of extracellular amyloid-beta (Aß) aggregates and intraneuronal hyperphosphorylated Tau. Many AD risk genes, identified in genome-wide association studies (GWAS), are expressed in microglia, the innate immune cells of the central nervous system. Specific subtypes of microglia emerged in relation to AD pathology, such as disease-associated microglia (DAMs), which increased in number with age in amyloid mouse models and in human AD cases. However, the initial transcriptional changes in these microglia in response to amyloid are still unknown. Here, to determine early changes in microglia gene expression, hippocampal microglia from male APPswe/PS1dE9 (APP/PS1) mice and wild-type littermates were isolated and analyzed by RNA sequencing (RNA-seq). By bulk RNA-seq, transcriptomic changes were detected in hippocampal microglia from 6-months-old APP/PS1 mice. By performing single-cell RNA-seq of CD11c-positive and negative microglia from 6-months-old APP/PS1 mice and analysis of the transcriptional trajectory from homeostatic to CD11c-positive microglia, we identified a set of genes that potentially reflect the initial response of microglia to Aß.

Chronic pain exacerbates memory impairment and pathology of Aß and tau by upregulating IL-1ß and p-65 signaling in a mouse model of Alzheimer's disease.

BACKGROUND: Chronic pain is linked to cognitive impairment; however, the underlying mechanisms remain unclear. In the present study, we examined these mechanisms in a well-established mouse model of Alzheimer's disease (AD). METHODS: Neuropathic pain was modeled in 5-month-old transgenic APPswe/PS1dE9 (APP/PS1) mice by partial ligation of the sciatic nerve on the left side, and chronic inflammatory pain was modeled in another group of APP/PS1 mice by injecting them with complete Freund's adjuvant on the plantar surface of the left hind paw. Six weeks after molding, the animals were tested to assess pain threshold (von Frey filament), learning, memory (novel object recognition, Morris water maze, Y-maze, and passive avoidance), and depression-like symptoms (sucrose preference, tail suspension, and forced swimming). After behavioral testing, mice were sacrificed and the levels of p65, amyloid-ß (residues 1-42) and phospho-tau in the hippocampus and cerebral cortex were assayed using western blotting, while interleukin (IL)-1ß levels were measured by enzyme-linked immunosorbent assay. RESULTS: Animals subjected to either type of chronic pain showed lower pain thresholds, more severe deficits in learning and memory, and stronger depression-like symptoms than the corresponding control animals. Either type of chronic pain was associated with upregulation of p65, amyloid-ß (1-42), and IL-1ß in the hippocampus and cerebral cortex, as well as higher levels of phosphorylated tau. CONCLUSIONS: Chronic pain may exacerbate cognitive deficits and depression-like symptoms in APP/PS1 mice by worsening pathology related to amyloid-ß and tau and by upregulating signaling involving IL-1ß and p65.

Efficacy of Sailuotong on neurovascular unit in amyloid precursor protein/presenilin-1 transgenic mice with Alzheimer's disease.

OBJECTIVE: To discuss the influence of Sailuotong (, SLT) on the Neurovascular Unit (NVUs) of amyloid precursor protein (APP)/presenilin-1(PS1) mice and evaluate the role of gas supplementation in activating blood circulation during the progression of Alzheimer's disease (AD). METHODS: The mice were allocated into the following nine groups: (a) the C57 Black (C57BL) sham-operated group (control group), (b) ischaemic treatment in C57BL mice (the C57 ischaemic group), (c) the APP/PS1 sham surgery group (APP/PS1 model group), (d) ischaemic treatment in APP/PS1 mice (APP/PS1 ischaemic group), (e) C57BL mice treated with aspirin following ischaemic treatment (C57BL ischaemic + aspirin group), (f) C57BL mice treated with SLT following ischaemic treatment (C57BL ischaemic + SLT group), (g) APP/PS1 mice treated with SLT (APP/PS1 + SLT group), (h) APP/PS1 mice treated with donepezil hydrochloride following ischaemic treatment (APP/PS1 ischaemic + donepezil hydrochloride group) and (i) APP/PS1 mice treated with SLT following ischaemic treatment (APP/PS1 ischaemic + SLT group). The ischaemic model was established by operating on the bilateral common carotid arteries and creating a microembolism. The Morris water maze and step-down tests were used to detect the spatial behaviour and memory ability of mice. The hippocampus of each mouse was observed by haematoxylin and eosin (HE) and Congo red staining. The ultrastructure of NVUs in each group was observed by electron microscopy, and various biochemical indicators were detected by enzyme-linked immunosorbent assay (ELISA). The protein expression level was detected by Western blot. The mRNA expression was detected by quantitative real-time polymerase chain reaction (qRT-PCR). RESULTS: The results of the Morris water maze and step-down tests showed that ischemia reduced learning and memory in the mice, which were restored by SLT. The results of HE staining showed that SLT restored the pathological changes of the NVUs. The Congo red staining results revealed that SLT also improved the scattered orange-red sediments in the upper cortex and hippocampus of the APP/PS1 and APP/PS1 ischaemic mice. Furthermore, SLT significantly reduced the content of Aß, improved the vascular endothelium and repaired the mitochondrial structures. The ELISA detection, western blot detection and qRT-PCR showed that SLT significantly increased the vascular endothelial growth factor (VEGF), angiopoietin and basic fibroblast growth factor, as well as the levels of gene and protein expression of low-density lipoprotein receptor-related protein-1 (LRP-1) and VEGF in brain tissue. CONCLUSIONS: By increasing the expression of VEGF, SLT can promote vascular proliferation, up-regulate the expression of LRP-1, promote the clearance of Aß and improve the cognitive impairment of APP/PS1 mice. These results confirm that SLT can improve AD by promoting vascular proliferation and Aß clearance to protect the function of NVUs.

Role of GABAB receptors in cognition and EEG activity in aged APP and PS1 transgenic mice.

Alzheimer's disease (AD) is the most common cause of dementia in the elderly. Recent evidence suggests that gamma-aminobutyric acid B (GABAB) receptor-mediated inhibition is a major contributor to AD pathobiology, and GABAB receptors have been hypothesized to be a potential target for AD treatment. The aim of this study is to determine how GABAB regulation alters cognitive function and brain activity in an AD mouse model. Early, middle and late stage (8-23 months) amyloid precursor protein (APP) and presenilin 1 (PS1) transgenic mice were used for the study. The GABAB agonist baclofen (1 and 2.5 mg/kg, i. p.) and the antagonist phaclofen (0.5 mg/kg, i. p.) were used. Primarily, we found that GABAB activation was able to improve spatial and/or working memory performance in early and late stage AD animals. In addition, GABAB activation and inhibition could regulate global and local EEG oscillations in AD animals, with activation mainly regulating low-frequency activity (delta-theta bands) and inhibition mainly regulating mid- and high-frequency activity (alpha-gamma bands), although the regulated magnitude at some frequencies was reduced in AD. The cognitive improvements in AD animals may be explained by the reduced EEG activity in the theta frequency band (2-4 Hz). This study provides evidence for a potential therapeutic effect of baclofen in the elderly AD brain and for GABAB receptor-mediated inhibition as a potential therapeutic target for AD.

Insights on the Use of Transgenic Mice Models in Alzheimer's Disease Research.

Alzheimer's disease (AD), the leading cause of dementia, presents a significant global health challenge with no known cure to date. Central to our understanding of AD pathogenesis is the ß-amyloid cascade hypothesis, which underlies drug research and discovery efforts. Despite extensive studies, no animal models of AD have completely validated this hypothesis. Effective AD models are essential for accurately replicating key pathological features of the disease, notably the formation of ß-amyloid plaques and neurofibrillary tangles. These pathological markers are primarily driven by mutations in the amyloid precursor protein (APP) and presenilin 1 (PS1) genes in familial AD (FAD) and by tau protein mutations for the tangle pathology. Transgenic mice models have been instrumental in AD research, heavily relying on the overexpression of mutated APP genes to simulate disease conditions. However, these models do not entirely replicate the human condition of AD. This review aims to provide a comprehensive evaluation of the historical and ongoing research efforts in AD, particularly through the use of transgenic mice models. It is focused on the benefits gathered from these transgenic mice models in understanding ß-amyloid toxicity and the broader biological underpinnings of AD. Additionally, the review critically assesses the application of these models in the preclinical testing of new therapeutic interventions, highlighting the gap between animal models and human clinical realities. This analysis underscores the need for refinement in AD research methodologies to bridge this gap and enhance the translational value of preclinical studies.

Identification of PS1/gamma-secretase and glutamate transporter GLT-1 interaction sites.

The recently discovered interaction between Presenilin 1 (PS1), a catalytic subunit of γ-secretase responsible for generating amyloid-ß peptides, and GLT-1, a major glutamate transporter in the brain (EAAT2), provides a mechanistic link between these two key factors involved in Alzheimer's disease (AD) pathology. Modulating this interaction can be crucial to understand the consequence of such crosstalk in AD context and beyond. However, the interaction sites between these two proteins are unknown. Herein, we utilized an alanine scanning approach coupled with FRET-based fluorescence lifetime imaging microscopy to identify the interaction sites between PS1 and GLT-1 in their native environment within intact cells. We found that GLT-1 residues at position 276 to 279 (TM5) and PS1 residues at position 249 to 252 (TM6) are crucial for GLT-1-PS1 interaction. These results have been cross validated using AlphaFold Multimer prediction. To further investigate whether this interaction of endogenously expressed GLT-1 and PS1 can be prevented in primary neurons, we designed PS1/GLT-1 cell-permeable peptides (CPPs) targeting the PS1 or GLT-1 binding site. We used HIV TAT domain to allow for cell penetration which was assayed in neurons. First, we assessed the toxicity and penetration of CPPs by confocal microscopy. Next, to ensure the efficiency of CPPs, we monitored the modulation of GLT-1-PS1 interaction in intact neurons by fluorescence lifetime imaging microscopy. We saw significantly less interaction between PS1 and GLT-1 with both CPPs. Our study establishes a new tool to study the functional aspect of GLT-1-PS1 interaction and its relevance in normal physiology and AD models.

Sex- and region-specific cortical and hippocampal whole genome transcriptome profiles from control and APP/PS1 Alzheimer's disease mice.

A variety of Alzheimer's disease (AD) mouse models has been established and characterized within the last decades. To get an integrative view of the sophisticated etiopathogenesis of AD, whole genome transcriptome studies turned out to be indispensable. Here we carried out microarray data collection based on RNA extracted from the retrosplenial cortex and hippocampus of age-matched, eight months old male and female APP/PS1 AD mice and control animals to perform sex- and brain region specific analysis of transcriptome profiles. The results of our studies reveal novel, detailed insight into differentially expressed signature genes and related fold changes in the individual APP/PS1 subgroups. Gene ontology and Venn analysis unmasked that intersectional, upregulated genes were predominantly involved in, e.g., activation of microglial, astrocytic and neutrophilic cells, innate immune response/immune effector response, neuroinflammation, phagosome/proteasome activation, and synaptic transmission. The number of (intersectional) downregulated genes was substantially less in the different subgroups and related GO categories included, e.g., the synaptic vesicle docking/fusion machinery, synaptic transmission, rRNA processing, ubiquitination, proteasome degradation, histone modification and cellular senescence. Importantly, this is the first study to systematically unravel sex- and brain region-specific transcriptome fingerprints/signature genes in APP/PS1 mice. The latter will be of central relevance in future preclinical and clinical AD related studies, biomarker characterization and personalized medicinal approaches.

Gene replacement-Alzheimer's disease (GR-AD): Modeling the genetics of human dementias in mice.

INTRODUCTION: Genetic studies conducted over the past four decades have provided us with a detailed catalog of genes that play critical roles in the etiology of Alzheimer's disease (AD) and related dementias (ADRDs). Despite this progress, as a field we have had only limited success in incorporating this rich complexity of human AD/ADRD genetics findings into our animal models of these diseases. Our primary goal for the gene replacement (GR)-AD project is to develop mouse lines that model the genetics of AD/ADRD as closely as possible. METHODS: To do this, we are generating mouse lines in which the genes of interest are precisely and completely replaced in the mouse genome by their full human orthologs. RESULTS: Each model set consists of a control line with a wild-type human allele and variant lines that precisely match the human genomic sequence in the control line except for a high-impact pathogenic mutation or risk variant.

New precision medicine avenues to the prevention of Alzheimer's disease from insights into the structure and function of γ-secretases.

Two phase-III clinical trials with anti-amyloid peptide antibodies have met their primary goal, i.e. slowing of Alzheimer's disease (AD) progression. However, antibody therapy may not be the optimal therapeutic modality for AD prevention, as we will discuss in the context of the earlier small molecules described as "γ-secretase modulators" (GSM). We review here the structure, function, and pathobiology of γ-secretases, with a focus on how mutations in presenilin genes result in early-onset AD. Significant progress has been made in generating compounds that act in a manner opposite to pathogenic presenilin mutations: they stabilize the proteinase-substrate complex, thereby increasing the processivity of substrate cleavage and altering the size spectrum of Aß peptides produced. We propose the term "γ-secretase allosteric stabilizers" (GSAS) to distinguish these compounds from the rather heterogenous class of GSM. The GSAS represent, in theory, a precision medicine approach to the prevention of amyloid deposition, as they specifically target a discrete aspect in a complex cell biological signalling mechanism that initiates the pathological processes leading to Alzheimer's disease.

Targeting blood brain barrier-Remote ischemic conditioning alleviates cognitive impairment in female APP/PS1 rats.

AIMS: Alzheimer's disease (AD) is a significant global health concern, and it is crucial that we find effective methods to prevent or slow down AD progression. Recent studies have highlighted the essential role of blood vessels in clearing Aß, a protein that contributes to AD. Scientists are exploring blood biomarkers as a potential tool for future AD diagnosis. One promising method that may help prevent AD is remote ischemic conditioning (RIC). RIC involves using sub-lethal ischemic-reperfusion cycles on limbs. However, a comprehensive understanding of how RIC can prevent AD and its long-term effectiveness is still lacking. Further research is essential to fully comprehend the potential benefits of RIC in preventing AD. METHODS: Female wild-type (WT) and APP/PS1 transgenic rats, aged 12 months, underwent ovariectomy and were subsequently assigned to WT, APP/PS1, and APP/PS1 + RIC groups. RIC was conducted five times a week for 4 weeks. The rats' depressive and cognitive behaviors were evaluated using force swimming, open-field tests, novel objective recognition, elevated plus maze, and Barnes maze tests. Evaluation of the neurovascular unit (NVU), synapses, vasculature, astrocytes, and microglia was conducted using immunofluorescence staining (IF), Western blot (WB), and transmission electron microscopy (TEM). Additionally, the cerebro-vasculature was examined using micro-CT, and cerebral blood flow (CBF) was measured using Speckle Doppler. Blood-brain barrier (BBB) permeability was determined by measuring the Evans blue leakage. Finally, Aß levels in the rat frontal cortex were measured using WB, ELISA, or IF staining. RESULTS: RIC enhanced memory-related protein expression and rescued depressive-like behavior and cognitive decline in APP/PS1 transgenic rats. Additionally, the intervention protected NVU in the rat frontal cortex, as evidenced by (1) increased expression of TJ (tight junction) proteins, pericyte marker PDGFRß, and glucose transporter 1 (GLUT1), as well as decreased VCAM1; (2) mitigation of ultrastructure impairment in neuron, cerebral vascular, and astrocyte; (3) upregulation of A2 astrocyte phenotype markers and downregulation of A1 phenotype markers, indicating a shift toward a healthier phenotype. Correspondingly, RIC intervention alleviated neuroinflammation, as evidenced by the decreased Iba1 level, a microglia marker. Meanwhile, RIC intervention elevated CBF in frontal cortex of the rats. Notably, RIC intervention effectively suppressed Aß toxicity, as demonstrated by the enhancement of α-secretase and attenuation of ß-secretase (BACE1) and γ- secretase and Aß1-42 and Aß1-40 levels as well. CONCLUSION: Chronic RIC intervention exerts vascular and neuroprotective roles, suggesting that RIC could be a promising therapeutic strategy targeting the BBB and NVU during AD development.

Presenilin-1 mutation position influences amyloidosis, small vessel disease, and dementia with disease stage.

INTRODUCTION: Amyloidosis, including cerebral amyloid angiopathy, and markers of small vessel disease (SVD) vary across dominantly inherited Alzheimer's disease (DIAD) presenilin-1 (PSEN1) mutation carriers. We investigated how mutation position relative to codon 200 (pre-/postcodon 200) influences these pathologic features and dementia at different stages. METHODS: Individuals from families with known PSEN1 mutations (n = 393) underwent neuroimaging and clinical assessments. We cross-sectionally evaluated regional Pittsburgh compound B-positron emission tomography uptake, magnetic resonance imaging markers of SVD (diffusion tensor imaging-based white matter injury, white matter hyperintensity volumes, and microhemorrhages), and cognition. RESULTS: Postcodon 200 carriers had lower amyloid burden in all regions but worse markers of SVD and worse Clinical Dementia Rating® scores compared to precodon 200 carriers as a function of estimated years to symptom onset. Markers of SVD partially mediated the mutation position effects on clinical measures. DISCUSSION: We demonstrated the genotypic variability behind spatiotemporal amyloidosis, SVD, and clinical presentation in DIAD, which may inform patient prognosis and clinical trials. HIGHLIGHTS: Mutation position influences Aß burden, SVD, and dementia. PSEN1 pre-200 group had stronger associations between Aß burden and disease stage. PSEN1 post-200 group had stronger associations between SVD markers and disease stage. PSEN1 post-200 group had worse dementia score than pre-200 in late disease stage. Diffusion tensor imaging-based SVD markers mediated mutation position effects on dementia in the late stage.