Da-Bu-Yin-Wan rescues cognitive deficits in aging and Alzheimer's disease models by Wnt/β-catenin-dependent restoration of lysosomal acidification.

Alzheimer’s disease (AD) is a degenerative neurological disease that primarily affects the elderly. Drug therapy is the main strategy for AD treatment, but current treatments suffer from poor efficacy and a number of side effects. Non-drug therapy is attracting more attention and may be a better strategy for treatment of AD. Hypoxia is one of the important factors that contribute to the pathogenesis of AD. Multiple cellular processes synergistically promote hypoxia, including aging, hypertension, diabetes, hypoxia/obstructive sleep apnea, obesity, and traumatic brain injury. Increasing evidence has shown that hypoxia may affect multiple pathological aspects of AD, such as amyloid-beta metabolism, tau phosphorylation, autophagy, neuroinflammation, oxidative stress, endoplasmic reticulum stress, and mitochondrial and synaptic dysfunction. Treatments targeting hypoxia may delay or mitigate the progression of AD. Numerous studies have shown that oxygen therapy could improve the risk factors and clinical symptoms of AD. Increasing evidence also suggests that oxygen therapy may improve many pathological aspects of AD including amyloid-beta metabolism, tau phosphorylation, neuroinflammation, neuronal apoptosis, oxidative stress, neurotrophic factors, mitochondrial function, cerebral blood volume, and protein synthesis. In this review, we summarized the effects of oxygen therapy on AD pathogenesis and the mechanisms underlying these alterations. We expect that this review can benefit future clinical applications and therapy strategies on oxygen therapy for AD.

Nilotinib: from animal-based studies to clinical investigation in Alzheimer's disease patients.

Alzheimer's disease: cerebrolysin and nanotechnology as a therapeutic strategy.

Unique microglial states have been identified in Alzheimer's disease (AD) model mice and postmortem AD brains. Although it has been well documented that amyloid-β accumulation induces the alteration of microglial states, the relationship between tau pathology and microglial states remains incompletely understood because of a lack of suitable AD models. In the present study, we generated a novel AD model mouse by the intracerebral administration of tau purified from human brains with primary age-related tauopathy into App knock-in mice with humanized tau. Immunohistochemical analyses revealed that Dectin-1-positive disease-associated microglia were increased in the AD model mice after tau accumulation in the brain. We then performed single-nucleus RNA sequencing on the AD model mice to evaluate the differences in microglial states with and without tau propagation and accumulation. By taking advantage of spatial transcriptomics and existing single-cell RNA sequencing datasets, we showed for the first time that tau propagation and accumulation induce a disease-associated microglial phenotype at the expense of an age-related nonhomeostatic counterpart (namely, white matter-associated microglia) in an AD model mouse brain. Future work using spatial transcriptomics at single-cell resolution will pave the way for a more appropriate interpretation of microglial alterations in response to tau pathology in the AD brain.

PSD-95, a major scaffolding protein, requires palmitoylation to remain at synapses where it plays critical roles in synaptic structure and function. Here, we show that PSD-95 palmitoylation is specifically reduced in the hippocampus of female Alzheimer's disease (AD) model mice. Accordingly, these mice have significant memory deficits that are not observed in male AD model mice. Systemic injections of Palmostatin B, a depalmitoylating enzyme inhibitor (including the one acting on PSD-95), rescues memory deficits in female AD model mice and restores PSD-95 palmitoylation levels. Importantly, both synaptic structure and function are impaired in female AD model mice, and these deficits are normalized in Palmostatin B injected animals. This drug has no effects on amyloid plaques or GFAP levels, indicating that the rescue of behavioral and synaptic deficits is not due to effects on plaque or astrogliosis related AD pathology. Our data instead suggest that the sex-dependent rescue we observe is mediated by the stabilization of small, vulnerable dendritic spines. This study demonstrates that increasing PSD-95 palmitoylation might be an effective way to protect synapses from AD pathology and therefore a promising therapy for AD.

Objective To investigate the effect of Fructus arctii extract on Alzheimer disease (AD) model of mice and its mechanism. Methods Fifty healthy male Kunming mice were randomly divided into 5 groups, respectively, the negative control group, AD model group, Oxiracetam Capsules (400 mg/kg) and Fructus arctii extract (FAE 800 mg/kg, 400 mg/kg). The AD model was intraperitoneally injected with D-galactose 100 mg/kg and aluminum trichloride 10 mg/kg by intragastric administration every day. Since the 15th day of AD model developed, the mice in experimental groups were intragastric administrated with the corresponding dosage each day for 45 days. Behavioral testing in exposed and control mice were developed using step-down assays and water maze test, and the chemical parameters SOD, T-AOC, MDA, [Ca2+], NO and NOS of brain tissue were measured. Differences among groups were compared by SPSS statistics software using ANOVA. Results Compared with model group, the latency period in step-down assays was statistically lengthened and the whole swimming time in water maze test was reduced in the FAE groups, and the rate of errors was decreased in step-down tests (F=11.07, P=0.004. F=8.13, P=0.011, F=6.25, P=0.02). The chemical parameter showed that the levels of MDA, NO, NOS and [Ca2+] in brain tissue were significantly decreased in the FAE group (F=5.12, P=0.04 F=4.49, P=0.05, F=4.55, P=0.05, F=4.62, P=0.05) and the activity of the SOD and T-AOC (F=6.49, P=0.02. F=4.76, P=0.05) increased greatly. Conclusions The FAE can protect the deficit of learning and memory of the AD model mice. The mechanisms of effects may be related to the improvement of enzymes, reduce the formation of free radical; resulting in prevention of peroxide generation and reduction of NO-related neurological damage. Key words: Fructus arctii; Alzheimer disease; Learning and memory; Model

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder worldwide, causing dementia and affecting millions of individuals. One prominent characteristic in the brains of AD patients is glucose hypometabolism. In the context of galactose metabolism, intracellular glucose levels are heightened. Galactose mutarotase (GALM) plays a crucial role in maintaining normal galactose metabolism by catalyzing the conversion of β-D-galactose into α-D-galactose (α-D-G). The latter is then converted into glucose-6-phosphate, improving glucose metabolism levels. However, the involvement of GALM in AD progression is still unclear. In the present study, we found that the expression of GALM was significantly increased in AD patients and model mice. Genetic knockdown of GALM using adeno-associated virus did not change the expression of amyloid precursor protein (APP) and APP-cleaving enzymes including a disintegrin and metalloprotease 10 (ADAM10), β-site APP-cleaving enzyme 1 (BACE1), and presenilin-1 (PS1). Interestingly, genetic overexpression of GALM reduced APP and Aβ deposition by increasing the maturation of ADAM10, although it did not alter the expression of BACE1 and PS1. Further electrophysiological and behavioral experiments showed that GALM overexpression significantly ameliorated the deficits in hippocampal CA1 long-term potentiation (LTP) and spatial learning and memory in AD model mice. Importantly, direct α-D-G (20 mg/kg, i.p.) also inhibited Aβ deposition by increasing the maturation of ADAM10, thereby improving hippocampal CA1 LTP and spatial learning and memory in AD model mice. Taken together, our results indicate that GALM shifts APP processing towards α-cleavage, preventing Aβ generation by increasing the level of mature ADAM10. These findings indicate that GALM may be a potential therapeutic target for AD, and α-D-G has the potential to be used as a dietary supplement for the prevention and treatment of AD.

Amyloid pathology in Alzheimer’s disease (AD) is characterized by a heterogeneity of amyloid-β peptides (Aβ) variants. The N-terminally truncated Aβ4-42 peptides are among the most abundant species and were reported having an enhanced aggregation propensity and comparable toxicity to full-length Aβ peptides. Employing transgenic mouse models of AD, we aim to address the importance of this particular Aβ isoform in AD pathology. We questioned if an alteration of their degradation or generation affects the course of the pathology and how Aβ4-42 peptides and the two main neuropathological hallmarks of AD, extracellular amyloid deposits and tau pathology, are interrelated in-vivo. We showed that Aβ4-42 is a substrate of the enzyme Neprilysin (NEP) in-vitro, and that in-vivo, the absence of endogenous NEP in the Tg4-42het mouse model of AD, exclusively expressing Aβ4-42 peptides preferentially in the CA1 region of the hippocampus, led to an increased deposition of this isoform in hippocampal CA1 pyramidal neurons. The removal of ADAMTS4, a metalloprotease able to generate Aβ4-x peptides in oligodendrocytes, from the 5xFAD mouse model of familial AD, caused an improvement in the motor deficits characterizing this transgenic line, concomitant to reduced Aβ4-x levels in the spinal cord. To investigate the relationship between Aβ4-42 peptides and extracellular amyloid pathology, the FAD/Tg4-42hom line was generated crossing the Tg4-42hom transgenic model, characterized by the sole expression of the Aβ4-42 isoform and time-dependent behavioral deficits and neurodegeneration, with the plaque-bearing 5xFAD mouse model of AD, demonstrating no impairment or hippocampal loss of neurons at the age employed here. While an aggravation of deficits in motor performance and an increased loss of spinal α-motoneurons was detected in the filial line, cognitive performance was unaltered. Surprisingly, a rescue of recognition memory could even be observed in FAD/Tg4-42hom mice, accompanied by an increased number of pyramidal neurons in the distal portion of the CA1 region of the hippocampus compared to Tg4-42hom controls. Together with increased levels of insoluble Aβ4-x peptides in the hippocampus of FAD/Tg4-42hom mice, these results support the hypothesis of extracellular amyloid plaques possessing buffering properties towards soluble Aβ4-42 peptides. In the classical amyloid cascade hypothesis, Aβ is considered to act upstream of tau pathology. This hypothesis is supported by several studies on APP-overexpressing lines that have been crossed with mouse models of tauopathy. We crossed the Tg4-42hom line with the MAPT (PS19) transgenic tau model to investigate whether soluble N-truncated Aβ4-42 variants affect the phosphorylation and aggregation of tau. Although the co-expression of Aβ4-42 and transgenic human tau caused an aggravation of spatial memory deficits, neurodegeneration, and tau hyperphosphorylation remained unaltered in MAPT/Tg4-42hom mice compared to the transgenic parental lines.

Age-related vascular changes accompany or precede the development of Alzheimer's disease (AD) pathology. The comorbidity of AD and arterial stiffening suggests that vascular changes have a pathogenic role. Carotid artery mechanics and hemodynamics have been associated with age-related cognitive decline. However, the impact of hemodynamics and vascular mechanics on regional vulnerability within the brain has not been thoroughly explored. Compared with the arterial system, brain venous circulation in cognitive impairment is less understood despite the venous system's role in transport. To study vasculature impact on biochemistry in AD models, we must first establish the differences in vasculature mechanics and hemodynamics in a common AD model compared with healthy controls. With this baseline data, future studies on manipulating vasculature integrity in mice become feasible. Young and aged female 3xTg mice and age-matched controls were imaged using a combination of ultrasound and mass spectrometry. Wall shear stress varied across age and AD models. Mean velocity and pulsatility index varied across age and AD. Liquid chromatography-mass spectrometry of brain tissue revealed several lipids that were statistically different between age and AD, and matrix-assisted laser desorption/ionization MS imaging revealed region-specific differences between groups. Combining both ultrasound and mass spectrometry, we were able to detect significant changes in the vascular biomechanics of neck vasculature prior to observing significant changes in the brain biochemistry. Our work revealed significant vascular differences in the 3xTg compared with controls and, to our knowledge, is the first to study vascular biomechanics via ultrasound in the 3xTg AD mouse model.

Memory encoding is thought to proceed from durable changes in the activity of synaptic circuits, leading to the storage of patterns of electrical events in a sparsely distributed ensemble of neurons. Located at the entry level of hippocampal circuitry, the CA3 region is thought to be important for episodic memory encoding, especially at the initial stage of acquisition, by presumably developing an instant representation of a context. CA3 pyramidal cells receive a variety of inputs, among which the mossy fiber (Mf) inputs draw special attention for their peculiar structure and unique synaptic properties. However, the links between the plasticity of CA3 circuits and memory encoding are not well understood. This thesis project aimed to address the synaptic mechanisms of episodic memory encoding in physiological conditions as well as in a mouse model of Alzheimer's disease (AD). AD is characterized at an early stage by impaired episodic memory, which may involve dysregulation of the plasticity of CA3 circuits. First of all, we searched for synaptic deficits in CA3 local circuit in the early stage of AD pathology in acute slices, taking advantage of a familial AD mouse model: 6-month male APP/PS1 mice. We report that there is a reduction in spontaneous IPSC frequency in CA3 pyramidal cells (PCs) together with decreased inhibitory charges of evoked events at Mf-CA3 synapses, whereas the short-term plasticity of these synapses and intrinsic properties of CA3 PCs remain unaffected. Furthermore, there is a robust reduction in Kainate receptor (KAR) mediated currents at Mf-CA3 synapses. The same results were obtained from PSKO mice, suggesting that disturbed function of γ-secretase and N-Cadherin processing pathways may underlie the dysfunction of KARs at Mf-CA3 synapses. In the next step, we explored the changes in CA3 circuits shortly after one-trial contextual fear conditioning in adult C57Bl6j mice. We show that despite hardly any changes in filopodia number of Mf terminals, an increase in spontaneous IPSC 4 frequency can be registered, while the EPSCs and short-term plasticities of these synapses are unaltered. However, this increase cannot be seen anymore 24 hours after the contextual learning. We also tried to do simplified computational modeling of the DG-CA3 neuronal networks, to investigate if and to what extent the local interneurons in CA3 region contribute to memory encoding precision. Finally, to screen for changes at a transcriptome level, we performed RNA-seq with dissected CA3 tissue from APP/PS1 mice and identified up- and down-regulated genes at this early stage of AD. Moreover, we carried out ChIP-seq for a histone modification marker: H3K4me3, which has been shown to be directly related to one-trial contextual memory, and we report that there is a significant decrease in H3K4me3 levels at the promoter areas of various genes in CA3 PCs. However, these genes are hardly overlapping with the down-regulated genes from RNA-seq result, suggesting that other epigenetic mechanisms may play more important roles in expressing early deficits in this AD mouse model. Taken together, we show that inhibitory connections of hippocampal CA3 circuits may be important for episodic memory encoding, and in early AD mouse model with memory deficits, there is reduced GABAergic transmission and reduced KAR-mediated currents in CA3 PCs, together with many active transcriptional regulations across the genome. Our study may contribute to the understanding of early AD pathologies at a synaptic level as well as a transcriptional level, and provide novel insights into the mechanisms underlying rapid encoding of contextual memory.

Impairment of lysosomal acidification has recently been identified as a critical driver of amyloid-β and MAPT/tau pathology in Alzheimer's disease (AD). Restoring lysosomal acidification is a promising strategy for AD treatment. N-deacetylase and N-sulfotransferase 3 (NDST3) is a newly discovered tubulin deacetylase that regulates lysosomal acidification by influencing the recruitment of V-ATPase V1 subunits to lysosomes. Nevertheless, the role of NDST3 in AD remains entirely unexplored. We began by comparing the effects of NDST3 and histone deacetylase 6 (HDAC6), a well-known tubulin deacetylase with established roles in AD, on lysosomal acidification. Using HT22 cell-based models of AD, we knocked down NDST3 to examine its role in lysosomal acidification and degradative function in the context of this disease. We also evaluated the expression profile of NDST3 in both in vitro and in vivo models of AD. Finally, we investigated the consequences of NDST3 suppression on lysosomal acidity and related AD pathological features in the hippocampi of 3 × Tg-AD mice. NDST3 differs from HDAC6 in the subcellular spatial patterns of catalyzing microtubule deacetylation but parallels HDAC6 in regulating lysosomal pH. In HT22 cells with APP695Swe overexpression, knockdown of NDST3 lowered lysosomal pH by promoting the assembly of the V-ATPase holoenzyme on the lysosomal membrane and enhanced the autophagic degradation of aberrant Aβ and MAPT/tau. Notably, NDST3 levels were found to be elevated in the brains of AD models and patients. Reducing NDST3 expression in the hippocampi of 3 × Tg-AD mice facilitated lysosomal reacidification, which decreased the abnormal accumulation of amyloid plaques and MAPT/tau tangles, mitigated neuronal damage, and ameliorated cognitive deficits. Our study identified NDST3 as a key factor regulating lysosomal acidity in AD. Suppressing NDST3 restores lysosomal function in AD and protects against AD pathology, highlighting NDST3 as a promising therapeutic target for AD.

INTRODUCTIONFaulty autolysosome acidification leads to dystrophic neurites—an early event propelling Alzheimer's disease (AD) progression—yet the underlying mechanism remains elusive.METHODSTo elucidate the physiological functions of neuronal ATP citrate lyase (ACLY) expression, its impact on amyloid beta (Aβ) pathology, and molecular mechanisms, we used intracerebroventricular ACLY inhibitor administration, adeno‐associated virus–mediated ACLY modulation in the dorsal hippocampus, and N2a‐swAPP695 cell line.RESULTSInhibition or knockdown ACLY reduced microtubule stability and impaired cognition in wild‐type mice. Neuronal ACLY decreased in both AD patients and mice. ACLY knockdown in young 5×FAD mice exacerbated dystrophic neurites, aggravated Aβ deposition, and obstructed autophagic‐lysosomal flux. Conversely, enhancing ACLY improved cognition in advanced 5×FAD mice. Mechanistically, ACLY regulates lysosomal vacuolar adenosine triphosphatase assembly and acidification through α‐tubulin acetylation.DISCUSSIONNeuronal ACLY maintains microtubule stability and cognition, while critically regulating lysosomal acidification‐mediated amyloid pathology. These findings reveal novel mechanisms linking lysosomal dysfunction to AD, offering therapeutic insights.HighlightsATP citrate lyase (ACLY) as highly expressed in the processes of hippocampal neurons is essential for maintaining learning and memory through tubulin acetylation‐mediated microtubule stability.ACLY deficiency obstructed autophagic–lysosomal flux, aggravated amyloid beta deposition, and exacerbated dystrophic neurites in the early stages of Alzheimer's disease (AD).Enhanced neuronal ACLY promoted synaptic plasticity and alleviates cognitive impairment in AD mice with advanced neuropathology.ACLY regulates lysosomal vacuolar adenosine triphosphatase subunit assembly and lysosomal acidification via α‐tubulin acetylation in the AD brain.

Expression of long-lasting synaptic plasticity and long-term memory requires new protein synthesis, which can be repressed by phosphorylation of eukaryotic initiation factor 2α subunit (eIF2α). It was reported previously that eIF2α phosphorylation is elevated in the brains of Alzheimer’s disease (AD) patients and AD model mice. Therefore, we determined whether suppressing eIF2α kinases could alleviate synaptic plasticity and memory deficits in AD model mice. The genetic deletion of the eIF2α kinase PERK prevented enhanced eIF2α phosphorylation, as well as deficits in protein synthesis, synaptic plasticity, and spatial memory in APP/PS1 AD model mice. Similarly, deletion of another eIF2α kinase, GCN2, prevented impairments of synaptic plasticity and spatial memory defects displayed in the APP/PS1 mice. Our findings implicate aberrant eIF2α phosphorylation as a novel molecular mechanism underlying AD-related synaptic pathophysioloy and memory dysfunction and suggest that PERK and GCN2 are potential therapeutic targets for the treatment of individuals with AD.

P1-066: Dietary restriction delays ageing, but not neuronal pathology, in drosophila models of Alzheimer's disease

Vulnerability of calbindin, calretinin and parvalbumin in a transgenic/knock-in APPswe/PS1dE9 mouse model of Alzheimer disease together with disruption of hippocampal neurogenesis