Intraneuronal beta-amyloid aggregates, neurodegeneration, and neuron loss in transgenic mice with five familial Alzheimer's disease mutations: potential factors in amyloid plaque formation

Potentials of peroxisome proliferator-activated receptor (PPAR) α, β/δ, and γ: An in-depth and comprehensive review of their molecular mechanisms, cellular Signalling, immune responses and therapeutic implications in multiple diseases

Peroxisome proliferator-activated receptors (PPARs), ligand-activated transcription factors, have emerged as a key regulator of various biological processes, underscoring their relevance in the pathophysiology and treatment of numerous diseases. PPARs are primarily recognized for their critical role in lipid and glucose metabolism, which underpins their therapeutic applications in managing type 2 diabetes mellitus. Beyond metabolic disorders, they have gained attention for their involvement in immune modulation, making them potential targets for autoimmune-related inflammatory diseases. Furthermore, PPAR's ability to regulate proliferation, differentiation, and apoptosis has positioned them as promising candidates in oncology. Their anti-inflammatory and anti-fibrotic properties further highlight their potential in dermatological and cardiovascular conditions, where dysregulated inflammatory responses contribute to disease progression. Recent advancements have elucidated the molecular mechanisms of different PPAR isoforms, including their regulation of key signalling pathways such as NF-κB and MAPK, which are crucial in inflammation and cellular stress responses. Additionally, their interactions with co-factors and post-translational modifications further diversify their functional roles. The therapeutic potential of various PPAR agonists has been extensively explored, although challenges related to side effects and target specificity remain. This growing body of evidence underscores the significance of PPARs in understanding the molecular basis of diseases and advancing therapeutic interventions, paving way for targeted treatment approach across a wide spectrum of medical conditions. Here, we provide a comprehensive and detailed perspective of PPARs and their potential across different health conditions to advance our understanding, elucidate underlying mechanisms, and facilitate the development of potential treatment strategies.

A novel dual CCK/ GLP-1 receptor agonist ameliorates cognitive impairment in 5 × FAD mice by modulating mitophagy via the PINK1/Parkin pathway

To date, no therapeutic drugs available on the market can effectively reverse the progression of Alzheimer's disease (AD). Although Glucagon-like peptide-1 (GLP-1) receptor agonists (RAs) and Cholecystokinin (CCK) RAs have shown some promise in AD research, little is known about the neuroprotective effects of a novel dual CCK/GLP-1 RA in AD. This study sought to examine the effects of the novel dual CCK/GLP-1 RA on cognitive performance in an AD mouse model and to explore the associated mechanisms. Our findings indicate that dual CCK/GLP-1 RA improved cognitive deficits, reduced amyloid-beta (Aβ) accumulation, and alleviated mitochondrial damage in 5 × FAD mice by inducing mitophagy. In an in vitro model of AD cells induced by Aβ, CCK/GLP-1 RA could exert neuroprotective effects by regulating PINK1/Parkin-mediated mitophagy. These data reveal for the first time that the new CCK/GLP-1 RA modulates mitophagy via PINK1/Parkin pathway and enhances cognitive function in the 5 × FAD animal model. Moreover, the performance of the CCK/GLP-1 RA in certain indicators was superior to that of GLP-1 analogue liraglutide, suggesting that it may represent a more promising therapeutic option for AD.

Early social deficits in TgF344-AD rats are accompanied by sex-specific parvalbumin-positive interneuron reduction and altered brain oscillations in the hippocampal CA2

Social withdrawal and deficits in social cognition are hallmarks of Alzheimer's disease (AD). While early deficits in social behavior and memory have been documented in mouse AD models, they remain understudied in rat models. Early-stage AD is accompanied by dysfunction of parvalbumin-positive (PV+) interneurons, implicating their potential connection to early symptoms. In this study, we employed a 5-trial social memory task to investigate early deficits in social cognition in 6-month-old TgF344-AD male and female rats. We counted the number of PV+ interneurons and recorded local field potentials during social interactions in the hippocampal CA2 - a region critical for social information processing. Our results show decreased social interest and novelty preference in TgF344-AD male and female rats. However, reduced PV+ interneuron numbers were observed only in female rats and specific to the CA2 area. The electrophysiological recordings revealed reduced theta-gamma phase-amplitude coupling in the CA2 during direct social interactions. We conclude that deficits in social cognition accompany early-stage AD in TgF344-AD rats and are potentially linked to PV+ interneuron and brain oscillatory dysfunction in the CA2 region of the hippocampus.

MET receptor tyrosine kinase promotes the generation of functional synapses in adult cortical circuits

JOURNAL/nrgr/04.03/01300535-202505000-00026/figure1/v/2024-07-28T173839Z/r/image-tiff Loss of synapse and functional connectivity in brain circuits is associated with aging and neurodegeneration, however, few molecular mechanisms are known to intrinsically promote synaptogenesis or enhance synapse function. We have previously shown that MET receptor tyrosine kinase in the developing cortical circuits promotes dendritic growth and dendritic spine morphogenesis. To investigate whether enhancing MET in adult cortex has synapse regenerating potential, we created a knockin mouse line, in which the human MET gene expression and signaling can be turned on in adult (10-12 months) cortical neurons through doxycycline-containing chow. We found that similar to the developing brain, turning on MET signaling in the adult cortex activates small GTPases and increases spine density in prefrontal projection neurons. These findings are further corroborated by increased synaptic activity and transient generation of immature silent synapses. Prolonged MET signaling resulted in an increased α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/N-methyl-D-aspartate (AMPA/NMDA) receptor current ratio, indicative of enhanced synaptic function and connectivity. Our data reveal that enhancing MET signaling could be an interventional approach to promote synaptogenesis and preserve functional connectivity in the adult brain. These findings may have implications for regenerative therapy in aging and neurodegeneration conditions.

Advancing Alzheimer's disease pharmacotherapy: efficacy of glucocorticoid modulation with dazucorilant (CORT113176) in preclinical mouse models

BACKGROUND AND PURPOSE

Exposure to chronic stress and high levels of glucocorticoid hormones in adulthood has been associated with cognitive deficits and increased risk of Alzheimer's disease (AD). Dazucorilant has recently emerged as a selective glucocorticoid receptor (NR3C1) modulator, exhibiting efficacy in counteracting amyloid-β toxicity in an acute model of AD. We aim to assess the therapeutic potential of dazucorilant in reversing amyloid and tau pathologies through the inhibition of glucocorticoid receptor pathological activity, and providing additional evidence for its consideration in AD treatment.

EXPERIMENTAL APPROACH

The efficacy of dazucorilant was evaluated in two transgenic mouse models of amyloid pathology. The slowly progressing J20 and the aggressively pathological 5xFAD mice. Behavioural analysis was conducted to evaluate welfare, cognitive performances and anxiety levels. The activity of the glucocorticoid receptor system, neuroinflammation, amyloid burden and tau phosphorylation were examined in hippocampi.

KEY RESULTS

In both AD models, chronic treatment with dazucorilant improved working and long-term spatial memories along with the inhibition of glucocorticoid receptor-dependent pathogenic processes and the normalization of plasma glucocorticoid levels. Dazucorilant treatment also resulted in a reduction in tau hyperphosphorylation and amyloid production and aggregation. Additionally, dazucorilant seemed to mediate a specific re-localization of activated glial cells onto amyloid plaques in J20 mice, suggesting a restoration of physiological neuroinflammatory processes.

CONCLUSION AND IMPLICATIONS

Dazucorilant exhibited sustained disease-modifying effects in two AD models. Given that this compound has demonstrated safety and tolerability in human subjects, our results provide pre-clinical support for conducting clinical trials to evaluate its potential in AD.

Gastrointestinal Dysfunction and Low-Grade Inflammation Associate With Enteric Neuronal Amyloid-β in a Model for Amyloid Pathology

BACKGROUND

Patients suffering from Alzheimer's disease, a progressive neurodegenerative disorder involving cognitive decline and memory impairment, often present with gastrointestinal comorbidities. Accumulating data also indicate that alterations in the gut can modulate Alzheimer's disease pathology, highlighting the need to better understand the link between gastrointestinal abnormalities and neurodegeneration in the brain.

METHODS

To disentangle the pathophysiology of gastrointestinal dysfunction in Alzheimer's disease, we conducted a detailed pathological characterization of the gastrointestinal tract of 5xFAD mice by performing histological analyses, gene expression studies, immunofluorescence labeling and gut function assays.

RESULTS

We found that 5xFAD mice have elevated levels of intestinal amyloid precursor protein and accumulate amyloid-β in enteric neurons. Histopathology revealed that this is associated with mild intestinal inflammation and fibrosis and accompanied by increased expression of proinflammatory cytokines. While overall enteric nervous system composition and organization appeared unaffected, 5xFAD mice have faster gastrointestinal transit.

CONCLUSION

Our findings indicate that amyloid-β accumulation in enteric neurons is associated with low-grade intestinal inflammation and altered motility and suggest that peripheral pathology may cause gastrointestinal dysfunction in Alzheimer's disease patients.

Machine Learning Interpretation of Optical Spectroscopy Using Peak-Sensitive Logistic Regression

Optical spectroscopy, a noninvasive molecular sensing technique, offers valuable insights into material characterization, molecule identification, and biosample analysis. Despite the informativeness of high-dimensional optical spectra, their interpretation remains a challenge. Machine learning methods have gained prominence in spectral analyses, efficiently unveiling analyte compositions. However, these methods still face challenges in interpretability, particularly in generating clear feature importance maps that highlight the spectral features specific to each class of data. These limitations arise from feature noise, model complexity, and the lack of optimization for spectroscopy. In this work, we introduce a machine learning algorithm─logistic regression with peak-sensitive elastic-net regularization (PSE-LR)─tailored for spectral analysis. PSE-LR enables classification and interpretability by producing a peak-sensitive feature importance map, achieving an F1-score of 0.93 and a feature sensitivity of 1.0. Its performance is compared with other methods, including k-nearest neighbors (KNN), elastic-net logistic regression (E-LR), support vector machine (SVM), principal component analysis followed by linear discriminant analysis (PCA-LDA), XGBoost, and neural network (NN). Applying PSE-LR to Raman and photoluminescence (PL) spectra, we detected the receptor-binding domain (RBD) of SARS-CoV-2 spike protein in ultralow concentrations, identified neuroprotective solution (NPS) in brain samples, recognized WS2 monolayer and WSe2/WS2 heterobilayer, analyzed Alzheimer's disease (AD) brains, and suggested potential disease biomarkers. Our findings demonstrate PSE-LR's utility in detecting subtle spectral features and generating interpretable feature importance maps. It is beneficial for the spectral characterization of materials, molecules, and biosamples and applicable to other spectroscopic methods. This work also facilitates the development of nanodevices such as nanosensors and miniaturized spectrometers based on nanomaterials.

40 Hz sensory stimulation enhances CA3-CA1 coordination and prospective coding during navigation in a mouse model of Alzheimer's disease

40 Hz sensory stimulation ("flicker") has emerged as a new technique to potentially mitigate pathology and improve cognition in mouse models of Alzheimer's disease (AD) pathology. However, it remains unknown how 40 Hz flicker affects neural codes essential for memory. Accordingly, we investigate the effects of 40 Hz flicker on neural representations of experience in the hippocampus of the 5XFAD mouse model of AD by recording 1,000s of neurons during a goal-directed spatial navigation task. We find that an hour of daily exposure to 40 Hz audio-visual stimulation over 8 d leads to higher coordination between hippocampal subregions CA3 and CA1 during navigation. Consistent with CA3's role in generating sequential activity that represents future positions, 40 Hz flicker exposure increased prospective coding of future positions. In turn, prospective coding was more prominent during efficient navigation behavior. Our findings show how 40 Hz flicker enhances key hippocampal activity during behavior that is important for memory.

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

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

APP β-CTF triggers cell-autonomous synaptic toxicity independent of Aβ

Aβ is believed to play a significant role in synaptic degeneration observed in Alzheimer's disease and is primarily investigated as a secreted peptide. However, the contribution of intracellular Aβ or other cleavage products of its precursor protein (APP) to synaptic loss remains uncertain. In this study, we conducted a systematic examination of their cell-autonomous impact using a sparse expression system in rat hippocampal slice culture. Here, these proteins/peptides were overexpressed in a single neuron, surrounded by thousands of untransfected neurons. Surprisingly, we found that APP induced dendritic spine loss only when co-expressed with BACE1. This effect was mediated by β-CTF, a β-cleavage product of APP, through an endosome-related pathway independent of Aβ. Neuronal expression of β-CTF in mouse brains resulted in defective synaptic transmission and cognitive impairments, even in the absence of amyloid plaques. These findings unveil a β-CTF-initiated mechanism driving synaptic toxicity irrespective of amyloid plaque formation and suggest a potential intervention by inhibiting the endosomal GTPase Rab5.

Research models to study lewy body dementia

Lewy body dementia (LBD) encompasses neurodegenerative dementias characterized by cognitive fluctuations, visual hallucinations, and parkinsonism. Clinical differentiation of LBD from Alzheimer's disease (AD) remains complex due to symptom overlap, yet approximately 25% of dementia cases are diagnosed as LBD postmortem, primarily identified by the presence of α-synuclein aggregates, tau tangles, and amyloid plaques. These pathological features position LBD as a comorbid condition of both Parkinson's disease (PD) and AD, with over 50% of LBD cases exhibiting co-pathologies. LBD's mixed pathology complicates the development of comprehensive models that reflect the full spectrum of LBD's etiological, clinical, and pathological features. While existing animal and cellular models have facilitated significant discoveries in PD and AD research, they lack specificity in capturing LBD's unique pathogenic mechanisms, limiting the exploration of therapeutic avenues for LBD specifically. This review assesses widely used PD and AD models in terms of their relevance to LBD, particularly focusing on their ability to replicate human disease pathology and assess treatment efficacy. Furthermore, we discuss potential modifications to these models to advance the understanding of LBD mechanisms and propose innovative research directions aimed at developing models with enhanced etiological, face, predictive, and construct validity.

Liganded magnetic nanoparticles for magnetic resonance imaging of α-synuclein

Aggregation of the protein α-synuclein (α-syn) is the histopathological hallmark of neurodegenerative diseases such as Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA), which are collectively known as synucleinopathies. Currently, patients with synucleinopathies are diagnosed by physical examination and medical history, often at advanced stages of disease. Because synucleinopathies are associated with α-syn aggregates, and α-syn aggregation often precedes onset of symptoms, detecting α-syn aggregates would be a valuable early diagnostic for patients with synucleinopathies. Here, we design a liganded magnetic nanoparticle (LMNP) functionalized with an α-syn-targeting peptide to be used as a magnetic resonance imaging (MRI)-based biomarker for α-syn. Our LMNPs bind to aggregates of α-syn in vitro, cross the blood-brain barrier in mice with mannitol adjuvant, and can be used as an MRI contrast agent to distinguish mice with α-synucleinopathy from age-matched, wild-type control mice in vivo. These results provide evidence for the potential of magnetic nanoparticles that target α-syn for diagnosis of synucleinopathies.

Targeting CD38 immunometabolic checkpoint improves metabolic fitness and cognition in a mouse model of Alzheimer's disease

Protective immunity, essential for brain maintenance and repair, may be compromised in Alzheimer's disease (AD). Here, using high-dimensional single-cell mass cytometry, we find a unique immunometabolic signature in circulating CD4+ T cells preceding symptom onset in individuals with familial AD, featured by the elevation of CD38 expression. Using female 5xFAD mice, a mouse model of AD, we show that treatment with an antibody directed to CD38 leads to restored metabolic fitness, improved cognitive performance, and attenuated local neuroinflammation. Comprehensive profiling across distinct immunological niches in 5xFAD mice, reveals a high level of disease-associated CD4+ T cells that produce IL-17A in the dural meninges, previously linked to cognitive decline. Targeting CD38 leads to abrogation of meningeal TH17 immunity and cortical IL-1β, breaking the negative feedback loop between these two compartments. Taken together, the present findings suggest CD38 as an immunometabolic checkpoint that could be adopted as a pre-symptomatic biomarker for early diagnosis of AD, and might also be therapeutically targeted alone or in combination with other immunotherapies for disease modification.

Dietary methionine restriction started late in life promotes healthy aging in a sex-specific manner

Aging is associated with dysregulated methionine metabolism and increased levels of enzymes in the tyrosine degradation pathway (TDP). To investigate the efficacy of targeting either methionine metabolism or the TDP for healthspan improvement in advanced age, we initiated dietary MetR or TDP inhibition in 18-month-old C57BL/6J mice. MetR significantly improved neuromuscular function, metabolic health, lung function, and frailty. In addition, we confirmed improved neuromuscular function from dietary MetR in 5XFAD mice, whose weight was not affected by MetR. We did not observe benefits with TDP inhibition. Single-nucleus RNA and ATAC sequencing of muscle revealed cell type-specific responses to MetR, although MetR did not significantly affect mouse aging epigenetic clock markers. Similarly, an 8-week MetR intervention in a human trial (NCT04701346) showed no significant impact on epigenetic clocks. The observed benefits from late-life MetR provide translational rationale to develop MetR mimetics as an antiaging intervention.

The same but different: impact of animal facility sanitary status on a transgenic mouse model of Alzheimer's disease

The gut-brain axis has emerged as a key player in the regulation of brain function and cognitive health. Gut microbiota dysbiosis has been observed in preclinical models of Alzheimer's disease and patients. Manipulating the composition of the gut microbiota enhances or delays neuropathology and cognitive deficits in mouse models. Accordingly, the health status of the animal facility may strongly influence these outcomes. In the present study, we longitudinally analyzed the fecal microbiota composition and amyloid pathology of 5XFAD mice housed in a specific opportunistic pathogen-free (SOPF) and a conventional facility. The composition of the microbiota of 5XFAD mice after aging in conventional facility showed marked differences compared to WT littermates that were not observed when the mice were bred in SOPF facility. The development of amyloid pathology was also enhanced by conventional housing. We then transplanted fecal microbiota (FMT) from both sources into wild-type (WT) mice and measured memory performance, assessed in the novel object recognition test, in transplanted animals. Mice transplanted with microbiota from conventionally bred 5XFAD mice showed impaired memory performance, whereas FMT from mice housed in SOPF facility did not induce memory deficits in transplanted mice. Finally, 18 weeks of housing SOPF-born animals in a conventional facility resulted in the reappearance of specific microbiota compositions in 5XFAD vs WT mice. In conclusion, these results show a strong impact of housing conditions on microbiota-associated phenotypes and question the relevance of breeding preclinical models in specific pathogen-free (SPF) facilities.

IMPORTANCE

Housing conditions affect the composition of the gut microbiota. Gut microbiota of 6-month-old conventionally bred Alzheimer's mice is dysbiotic. Gut dysbiosis is absent in Alzheimer's mice housed in highly sanitized facilities. Transfer of fecal microbiota from conventionally bred mice affects cognition. Microbiota of mice housed in highly sanitized facilities has no effect on cognition.

Reshaping the gut microbiota: A novel oppinion of Eucommiae cortex polysaccharide alleviate learning and memory impairments in Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD), which is a chronic neurodegenerative disorder, is marked by the progressive deteriorations in learning and memory capabilities. The microbiota-gut-brain axis has come to be regarded as a crucial element in relation to the pathogenesis as well as the treatment of AD. Eucommiae cortex polysaccharides (EPs), being among the most plentiful substances present in the Eucommiae cortex, show the potential to exert immunomodulatory and neuroprotective function. However, whether EPs are protective against AD and their mechanism of action remain to be investigated OBJECTIVES: We hypothesize that EPs can regulate brain glutamine metabolism through gut microbiota and the butyric acid metabolized by them, improve oxidative stress and autophagy in the brain, and thus alleviate AD.

METHODS

In the present study, we used EPs (0.25 % w/w in food) and fecal microbiota transplantation, as well as butyrate supplementation (0.1 M in water), to intervene in AD mice. Multi-omics were used to determine the mechanism by which EPs improve AD-related learning and memory impairments.

RESULTS

Our results suggest that EPs, functioning as a prebiotic, alleviated learning and memory impairments in AD mice. Mechanistically, EPs are able to reshape the gut microbiota, promote the growth of gut microbiota involved in short-chain fatty acid metabolism, particularly butyrate-producing microbes. The butyrate produced by these microbes improves the brain microenvironment by modulating oxidative stress and autophagy mediated by brain glutamate metabolism, improving learning and memory impairments in AD mice, and inhibiting the formation and deposition of beta-amyloid proteins. Fecal microbiota transplantation (FMT) and butyrate supplementation further confirm this conclusion.

CONCLUSIONS

Our results highlighted that EPs can alleviate learning and memory impairments in AD with a gut microbiota-dependent manner and that butyric acid metabolized by butyric acid-metabolizing bacteria in the gut plays a central role in regulating brain glutamine metabolism to improve brain microenvironmental homeostasis. Meanwhile, the present study provides new insights into the treatment of AD with natural products.

Early plasma ceramide and sphingomyelin levels reflect APOE genotype but not familial Alzheimer's disease gene mutations in female 5xFAD mice, with brain-region specific sphingolipid alterations

Pathophysiological changes associated with Alzheimer's disease (AD) begin decades before dementia onset, with age and APOE ε4 genotype as major risk factors [1-4]. Primary risk factors for developing AD include aging and number of copies of the apolipoprotein E (APOE) ε4 allele. Altered sphingolipid metabolism is increasingly implicated in early AD. However, the relationship between early plasma and brain sphingolipid changes-particularly in the context of APOE genotype-remains poorly defined. In this study, we analyzed plasma and brain sphingolipid profiles in transgenic AD mice carrying human APOE3 or APOE4 variants, with or without familial AD mutations (E3FAD and E4FAD). Using liquid chromatography-tandem mass spectrometry (LC-MS/MS), we assessed 110 sphingolipid species across four major classes (ceramides (Cers), hexosylceramides (HexCers), lactosylceramides (LacCers), and sphingomyelins (SMs)) at 2, 4, and 6 months in plasma and at 6 months in brain tissue in the cortex, hippocampus, striatum, and cerebellum. Our results demonstrate that early plasma sphingolipid alterations are largely driven by APOE genotype rather than AD pathology. Specifically, APOE4 carriers showed significant increases in SM species and reductions in Cer species compared to APOE3 carriers, independent of age or AD genotype. Brain lipid profiles showed minimal changes across genotypes after region correction. However, combined p-value analyses revealed APOE- and EFAD-dependent differences in the composition of primarily cortical sphingolipids. ROC analyses demonstrated high discriminative power of plasma sphingolipids for APOE, but not for AD genotype. These findings suggest that early plasma lipid profiles in female 5xFAD mice are more strongly influenced by APOE genotype than by overt AD pathology, potentially reflecting systemic pathways linked to APOE4-associated AD risk, while early disease-associated changes in the brain appear to be subtle and region-specific. These results underscore the importance of accounting for APOE genotype in early-stage AD lipidomic studies and in the interpretation of peripheral lipid biomarkers.

Sugar utilization by microglia in Alzheimer's disease

Diabetes is a major risk factor for Alzheimer's disease (AD), yet the effect of specific carbohydrate sources in the diet on AD pathology remains unclear. The primary neuroimmune cell, microglia, undergo a metabolic shift during neuroinflammation associated with AD pathology. We utilized existing gene expression data and identified changes in sugar transporters (increased Slc2a1 (glucose) and decreased Slc2a5 (fructose) expression). To examine gene expression with respect to primary sugar source, N9 cells, a mouse microglia cell line, were cultured in glucose or fructose supplemented media and stimulated with lipopolysaccharide (LPS). RNA-sequencing analyses indicated significant changes between control and sugar supplemented media and several differentially expressed genes between glucose and fructose media. Concurrently, 5XFAD mice received equicaloric diets with specific carbohydrate sources: dextrose or fructose. Regardless of diet, sex, or genotype, all mice developed high blood sugar levels; confocal microscopy analyses indicated similar amyloid plaque burden and microglial response relative to the control diet, but there was a change in the microglial response between dextrose and fructose fed mice. Overall, these data indicate microglia preferentially express sugar transporters and sugar source may influence microglial reactivity in response to plaque pathology.

Huang-Lian-Jie-Du decoction alleviates cognitive deficits in Alzheimer's disease model 5xFAD mice by inhibiting Trem2/Dap12 signaling pathway

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disorder predominantly affecting the elderly population. It is characterized by cognitive deficits associated with the accumulation of amyloid-beta plaques and neurofibrillary tangles. Huang-Lian-Jie-Du (HLJD) decoction, recognized as a representative formulation with heat-clearing and detoxification effects, has been demonstrated to be effective in treating AD. However, the underlying mechanisms require further investigation.

METHODS

5xFAD mice were administrated low and high doses of HLJD. The Morris water maze test was conducted to assess the effects of HLJD. Aβ42 and total tau protein levels were evaluated. Additionally, network pharmacology analysis was performed to identify therapeutic targets of HLJD's active components and their relevance to AD. ELISA, qPCR, Western Blot, and immunofluorescence assays were employed to confirm the identified pathways. Finally, primary microglia isolated from 5xFAD mice were used to validate the candidate targets of HLJD.

RESULTS

HLJD improved cognitive deficits in 5xFAD mice and reduced amyloid plaque deposition and tau protein levels. Network pharmacology analysis indicated that HLJD influences the neuroinflammatory response, particularly through the Dap12 signaling pathway. This was confirmed by reduced levels of neuroinflammation markers, including TNF-α, IL-1β, IL-6, and indicators of microglial activation and polarization. The expression of Trem2 and Dap12 in the hippocampus (HIP) of 5xFAD mice, as well as in the isolated primary microglia, were downregulated following HLJD treatment.

CONCLUSION

Our study indicates that HLJD alleviates cognitive deficits in AD by suppressing the Trem2/Dap12 signaling pathway in the HIP of 5xFAD mice, thereby inhibiting microglial neuroinflammation.

Noradrenergic signaling controls Alzheimer's disease pathology via activation of microglial β2 adrenergic receptors

Norepinephrine (NE) is a potent anti-inflammatory agent in the brain. In Alzheimer's disease (AD), the loss of NE signaling heightens neuroinflammation and exacerbates amyloid pathology. NE inhibits surveillance activity of microglia, the brain's resident immune cells, via their β2 adrenergic receptors (β2ARs). Here, we investigate the role of microglial β2AR signaling in AD pathology in the 5xFAD mouse model of AD. We found that loss of cortical NE projections preceded the degeneration of NE-producing neurons and that microglia in 5xFAD mice, especially those microglia that were associated with plaques, significantly downregulated β2AR expression early in amyloid pathology. Importantly, dampening microglial β2AR signaling worsened plaque load and the associated neuritic damage, while stimulating microglial β2AR signaling attenuated amyloid pathology. Our results suggest that microglial β2AR could be explored as a potential therapeutic target to modify AD pathology.

Dysregulated ac4C modification of mRNA in a mouse model of early-stage Alzheimer's disease

BACKGROUND

The identification and intervention of Alzheimer's Disease (AD) in its early-stage allows for the timely implementation of lifestyle modifications and therapeutic strategies. Although dysregulation of protein expression has been reported in the brain from AD patients and AD animal models, the underlying mechanisms remain poorly understood. N4-acetylcytidine (ac4C), the only known form of RNA acetylation in eukaryotes, has recently been shown to regulate mRNA stability and translation efficiency. However, the dysregulation of ac4C associated with abnormal protein expression levels in the brain of early-stage mouse models of AD remains to be elucidated.

METHODS

This study investigated ac4C modifications, mRNA and protein expression in the hippocampus of 3 and 6-month-old 5×FAD mice, a mouse model of AD, and wild-type (WT) littermates. The multi-omics analysis was performed: acetylated RNA immunoprecipitation followed by next-generation sequencing (acRIP-seq) to identify ac4C mRNAs, deep RNA sequencing (RNA-seq) to quantify mRNA abundance, and label-free quantitative proteomics to assess protein expression levels. In addition, we used acRIP-qPCR, regular qPCR and western blots to verify the ac4C, mRNA and protein levels of some key genes that were identified by the high-throughput assays.

RESULTS

Proteomic analysis revealed significant change of protein expression in the hippocampus of 3-months-old 5×FAD mice, compared with WT littermates. In contrast, RNA-seq analysis indicated that there were no substantial alterations in mRNA expression levels in the hippocampus of 3-months-old 5×FAD mice, compared to WT littermates. Strikingly, acRIP-seq revealed notable variations in ac4C modification on mRNAs, particularly those associated with synaptic structure and function, in the hippocampus of 3-months-old 5×FAD mice, compared with WT littermates. The ac4C modifications were found to be correlated with protein expression changes. Genes that are essential for synaptic function and cognition, including GRIN1, MAP2, and DNAJC6, exhibited reduced ac4C and protein levels in 3-months-old 5×FAD mice, without any corresponding changes in the mRNA levels, compared with WT littermates. Moreover, only a small part of dysregulated ac4C mRNAs identified in the 3-month-old 5×FAD mice were found in the 6-month-old 5×FAD mice.

CONCLUSIONS

Altogether these results identified abnormal ac4C modification of mRNAs that may contribute to the dysregulation of protein synthesis in the hippocampus from an early-stage mouse model of AD.

Immune checkpoint TIM-3 regulates microglia and Alzheimer's disease

Microglia are the resident immune cells in the brain and have pivotal roles in neurodevelopment and neuroinflammation1,2. This study investigates the function of the immune-checkpoint molecule TIM-3 (encoded by HAVCR2) in microglia. TIM-3 was recently identified as a genetic risk factor for late-onset Alzheimer's disease3, and it can induce T cell exhaustion4. However, its specific function in brain microglia remains unclear. We demonstrate in mouse models that TGFβ signalling induces TIM-3 expression in microglia. In turn, TIM-3 interacts with SMAD2 and TGFBR2 through its carboxy-terminal tail, which enhances TGFβ signalling by promoting TGFBR-mediated SMAD2 phosphorylation, and this process maintains microglial homeostasis. Genetic deletion of Havcr2 in microglia leads to increased phagocytic activity and a gene-expression profile consistent with the neurodegenerative microglial phenotype (MGnD), also referred to as disease-associated microglia (DAM). Furthermore, microglia-targeted deletion of Havcr2 ameliorates cognitive impairment and reduces amyloid-β pathology in 5×FAD mice (a transgenic model of Alzheimer's disease). Single-nucleus RNA sequencing revealed a subpopulation of MGnD microglia in Havcr2-deficient 5×FAD mice characterized by increased pro-phagocytic and anti-inflammatory gene expression alongside reduced pro-inflammatory gene expression. These transcriptomic changes were corroborated by single-cell RNA sequencing data across most microglial clusters in Havcr2-deficient 5×FAD mice. Our findings reveal that TIM-3 mediates microglia homeostasis through TGFβ signalling and highlight the therapeutic potential of targeting microglial TIM-3 in Alzheimer's disease.

Harnessing human iPSC-microglia for CNS-wide delivery of disease-modifying proteins

Widespread delivery of therapeutic proteins to the brain remains challenging. To determine whether human induced pluripotent stem cell (iPSC)-microglia (iMG) could enable brain-wide and pathology-responsive delivery of therapeutic cargo, we utilized CRISPR gene editing to engineer iMG to express the Aβ-degrading enzyme neprilysin under control of the plaque-responsive promoter, CD9. To further determine whether increased engraftment enhances efficacy, we utilized a CSF1R-inhibitor resistance approach. Interestingly, both localized and brain-wide engraftment in Alzheimer's disease (AD) mice reduced multiple biochemical measures of pathology. However, within the plaque-dense subiculum, reductions in plaque load, dystrophic neurites, and astrogliosis and preservation of neuronal density were only achieved following widespread microglial engraftment. Lastly, we examined chimeric models of breast cancer brain metastases and demyelination, demonstrating that iMG adopt diverse transcriptional responses to differing neuropathologies, which could be harnessed to enable widespread and pathology-responsive delivery of therapeutics to the CNS.

Molecular signature and functional properties of human pluripotent stem cell-derived brain pericytes

Brain pericytes maintain the blood-brain barrier (BBB), secrete neurotrophic factors and clear toxic proteins. Their loss in neurological disorders leads to BBB breakdown, neuronal dysfunction, and cognitive decline. Therefore, cell therapy to replace lost pericytes holds potential to restore impaired cerebrovascular and brain functions. However, the molecular composition and function of human iPSC-derived brain pericytes (iPSC-PC) remains poorly characterized. Here, we show by a quantitative analysis of 8,344 proteins and 20,572 phosphopeptides that iPSC-PC share 96% of total proteins and 98% of protein phosphorylation sites with primary human brain pericytes. This includes cell adhesion and tight junction proteins, transcription factors, and different protein kinase families of the human kinome. In pericyte-deficient mice, iPSC-PC home to host brain capillaries to form hybrid human-mouse microvessels with ligand-receptor associations. They repair BBB leaks and protect against neuron loss, which we show requires PDGRFB and pleiotrophin. They also clear Alzheimer's amyloid-β and tau neurotoxins via lipoprotein receptor. Thus, iPSC-PC may have potential as a replacement therapy for pericyte-deficient neurological disorders.

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

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

Loss of ATG7 in microglia impairs UPR, triggers ferroptosis, and weakens amyloid pathology control

Microglia impact brain development, homeostasis, and pathology. One important microglial function in Alzheimer's disease (AD) is to contain proteotoxic amyloid-β (Aβ) plaques. Recent studies reported the involvement of autophagy-related (ATG) proteins in this process. Here, we found that microglia-specific deletion of Atg7 in an AD mouse model impaired microglia coverage of Aβ plaques, increasing plaque diffusion and neurotoxicity. Single-cell RNA sequencing, biochemical, and immunofluorescence analyses revealed that Atg7 deficiency reduces unfolded protein response (UPR) while increasing oxidative stress. Cellular assays demonstrated that these changes lead to lipoperoxidation and ferroptosis of microglia. In aged mice without Aβ buildup, UPR reduction and increased oxidative damage induced by Atg7 deletion did not impact microglia numbers. We conclude that reduced UPR and increased oxidative stress in Atg7-deficient microglia lead to ferroptosis when exposed to proteotoxic stress from Aβ plaques. However, these microglia can still manage misfolded protein accumulation and oxidative stress as they age.

Novel Approaches to Track Neurodegeneration in Murine Models of Alzheimer's Disease Reveal Previously Unknown Aspects of Extracellular Aggregate Deposition

This paper describes a novel transgenic-based platform to track degeneration of specific populations of neurons in 5xFAD mice, a murine model of Alzheimer's disease. We created a new double transgenic model by crossing 5xFAD mice with Rosa tdT reporter mice. 5xFAD +/- /Rosa tdT mice received intra-spinal cord injections of AAV-retrograde (rg)/Cre at 2-3 months of age to permanently label corticospinal neurons (CSNs). Brains and spinal cords were retrieved 2-3 weeks post-injection or at 12-14 months of age. Immunohistochemical studies of transgene expression throughout the brain and spinal cord, using an antibody selective for hAPP, revealed age-dependent accumulation of hAPP in extracellular aggregates in regions containing hAPP expressing neuronal cell bodies and in regions containing axons and synaptic terminals from hAPP expressing neurons. Permanent labeling of CSNs with tdT confirmed extensive loss of CSNs in old mice. Surprisingly, we discovered that tdT expressed by CSNs accumulated in extracellular aggregates that persisted after the neurons that expressed tdT degenerated. Extracellular aggregates of tdT also contained hAPP and co-localized with other markers of AD pathology. Overall, deposition of hAPP in extracellular aggregates in areas containing axons and synaptic terminals from hAPP expressing neurons is a prominent feature of AD pathophysiology in 5xFAD mice. In addition, accumulation of hAPP and reporter proteins in extracellular aggregates provides a secondary measure to track neurodegeneration of identified populations of neurons in these mice.

Highlights

Characterization of a new double transgenic strain allowing Cre-dependent labeling of populations of neurons that degenerate in 5xFAD mice.Selective labeling of layer V corticospinal neurons (CSNs) via retrograde transduction with AAV-rg allows quantification of previously un-recognized aspects of age-dependent CSN degeneration.Age-dependent deposition of extracellular hAPP by axons and synaptic terminals revealed by immunohistochemistry for mutant human APP in 5xFAD micePetal-shaped clusters of hAPP originate mainly due to axonal degeneration and fragmentation.Surprisingly, tdTomato expressed by neurons that degenerate, persists in extracellular deposits that co-localize with extracellular deposits of hAPP.

Pitolisant alleviates brain network dysfunction and cognitive deficits in a mouse model of Alzheimer's disease

Histamine H3 receptor (H3R) antagonists regulate histamine release that modulates neuronal activity and cognitive function. Although H3R is elevated in Alzheimer's disease (AD) patients, whether H3R antagonists can rescue AD-associated neural impairments and cognitive deficits remains unknown. Pitolisant is a clinically approved H3R antagonist/inverse agonist that treats narcolepsy. Here, we find that pitolisant reverses AD-like pathophysiology and cognitive impairments in an AD mouse model. Behavioral assays and in vivo wide-field Ca2+ imaging revealed that recognition memory, learning flexibility, and slow-wave impairment were all improved following the 15-day pitolisant treatment. Improved recognition memory was tightly correlated with slow-wave coherence, suggesting slow waves serve as a biomarker for treatment response and for AD drug screening. Furthermore, pitolisant reduced amyloid-β deposition and dystrophic neurites surrounding plaques, and enhanced neuronal lysosomal activity, inhibiting which blocked cognitive and slow-wave restoration. Our findings identify pitolisant as a potential therapeutic agent for AD treatments.

Circadian rhythms and the light-dark cycle interact to regulate amyloid plaque accumulation and tau phosphorylation in 5xFAD mice

Background

Circadian disruption has long been appreciated as a downstream consequence of Alzheimer's Disease in humans. However, an upstream role for behavioral circadian disruption in regulating AD pathology remains an open question.

Methods

To determine the role of the central circadian clock in the suprachiasmatic nucleus (SCN) in regulating amyloid pathology, we crossed the 5xFAD amyloid mouse model with mice harboring deletion of the critical clock gene Bmal1 in GABAergic neurons using VGAT-iCre, which is expressed in >95% of SCN cells. To examine the role the light-dark cycle in this process, we aged these mice in either regular 12:12 light-dark (LD) or constant darkness (DD) conditions. Transcriptional, behavioral, and physiological rhythms were examined in VGAT-iCre; 5xFAD; Bmal1 fl/fl (VGAT-BMAL1KO;5xFAD) mice under varying light conditions. Amyloid plaque deposition, peri-plaque tau phosphorylation, and other pathology was examined by immunohistochemistry, and transcriptomic changes were examined by high-throughput qPCR.

Results

VGAT-BMAL1KO;5xFAD mice showed loss of SCN BMAL1 expression and severe disruption of behavioral rhythms in both LD and DD, with loss of day-night rhythms in consolidated sleep and blunting of rhythmic clock gene expression in the brain. Surprisingly, VGAT-BMAL1KO;5xFAD mice kept under LD showed reduced total plaque accumulation and peri-plaque tau phosphorylation, compared to Cre-negative controls. These changes were gated by the light-dark cycle, as they were absent in VGAT-BMAL1KO;5xFAD mice kept in DD conditions. Total plaque accumulation was also reduced in control 5xFAD mice kept in DD as compared to LD, suggesting a general effect of light-dark cycle on amyloid aggregation. Expression of murine presenilin 1 (Psen1) -- which catalyzes the processing of sAPPβ into Aβ -- as well as APP cleavage to C-terminal fragments, were suppressed in VGAT-BMAL1KO;5xFAD under LD conditions.

Conclusions

These studies elucidated an interaction between the circadian clock in GABAergic neurons and the light-dark cycle in regulating amyloid pathology and suggest that decoupling the central clock form the light-dark cycle may reduce APP cleavage and plaque formation. These results call into question the proposed simple positive feedback loop between circadian rhythm disruption and Alzheimer's Disease pathology.

Glycolysis-enhancing α1-adrenergic antagonists are neuroprotective in Alzheimer's disease

Terazosin (TZ) is an α 1 -adrenergic receptor antagonist that enhances glycolysis by activating the enzyme phosphoglycerate kinase 1 (PGK1). Epidemiological data suggest that TZ may be neuroprotective in Parkinson's disease and in dementia with Lewy bodies and that glycolysis-enhancing drugs might be protective in other neurodegenerative diseases involving protein aggregation, such as Alzheimer's disease (AD). We investigated TZ in AD and report four main results. First, we found that TZ increased ATP levels in a Saccharomyces cerevisiae mutant with impaired energy homeostasis and reduced the aggregation of the AD-associated protein, amyloid beta (Aβ) 42. Second, in an AD transgenic mouse model (5xFAD) we found that TZ attenuated amyloid pathology in the hippocampus and rescued cognitive impairments in spatial memory and interval timing behavioral assays. Third, using the Alzheimer's Disease Neuroimaging Initiative (ADNI) database, we found that AD patients newly started on TZ or related glycolysis-enhancing drugs had a slower progression of both cognitive dysfunction and neuroimaging biomarkers, such as 18 F-fluorodeoxyglucose positron emission tomography (FDG-PET), a measure of brain metabolism. Finally, in a large human administrative dataset, we found that patients taking TZ or related glycolysis-enhancing drugs had a lower hazard of being diagnosed with AD compared to those taking tamsulosin or 5-alpha reductase inhibitors. These data further implicate metabolism in neurodegenerative diseases and suggest that glycolysis-enhancing drugs may be neuroprotective in AD.

Homeostatic Activation of 26S Proteasomes by Protein Kinase A Protects against Cardiac and Neurobehavior Malfunction in Alzheimer's Disease Mice

Alzheimer's Disease (AD) patients often show brain and cardiac malfunction. AD represents a leading cause of morbidity and mortality worldwide, but the demand for effective treatment for AD is far from being met. This is primarily because AD pathogenesis, including brain-heart interaction, is poorly understood. Proteasome functional insufficiency is implicated in AD; as such, proteasome enhancement promises a potentially new strategy to treat AD. The proteasome can be activated by protein kinase A (PKA) via selectively phosphorylating Ser14-RPN6/PSMD11 (p-S14-RPN6); however, whether p-S14-RPN6 is altered and what role p-S14-RPN6 plays in AD remain unclear. Hence, this study was conducted to address these critical gaps. We found that genetic blockade of the homeostatic p-S14-Rpn6 via germline knock-in of Rpn6 S14A (referred to as S14A) significantly reduced proteasome activities in the cerebral cortex but did not discernibly impair learning and memory function in 4-month-old mice or cause cardiac dysfunction before 12 months of age. Increases in Ser14-phosphorylated Rpn6 in the cerebral cortex and markedly elevated Aβ proteins in the myocardium were observed in young 5XFAD mice, a commonly used AD model. When introduced into the 5XFAD mice, S14A significantly aggravated the learning and memory deficits as revealed by the radial arm water maze tests and accelerated cardiac malfunction as measured by serial echocardiography in the same cohort of 5XFAD mice. Thus, the present study establishes for the first time that homeostatic activation of 26S proteasomes by basal p-S14-RPN6 or PKA activity protects against both the brain and heart malfunction in the 5XFAD mice.

S-9-PAHSA Attenuates Aβ Accumulation and Improves Cognitive Deficits by Promoting Mitochondrial Autophagy in 5xFAD Mice

Alzheimer's disease (AD) is a prevalent neurodegenerative disorder characterized by significant cognitive impairment and predominantly affects the elderly. With no effective cure available, research continues to explore novel therapeutic and preventive strategies. Recently, palmitic acid-hydroxystearic acids (PAHSAs), especially their stereochemistry S-configuration, have shown potential as a dietary supplement with anti-inflammatory and anti-diabetic properties. We previously found that one of the PAHSAs, 9-PAHSA, could improve cognitive impairment in the high-fat-diet mice, however, whether it has an equal effect on AD-like mice remains unclear. Since mitochondrial dysfunction is recognized as a significant pathological feature of AD, with impaired mitophagy leading to the accumulation of dysfunctional mitochondria, thus exacerbating disease progression, in this study, we evaluated the effects of the chiral isomer of 9-PAHSA, S-9-PAHSA, on cognitive dysfunction and mitochondrial dysfunction in 5xFAD mice. Three-month-old mice were treated with S-9-PAHSA 30 mg/kg in their drinking water for 3 months. Behavioral studies were conducted using the Morris Water Maze (MWM) and Y-maze tests, followed by assessments of amyloid-beta (Aβ) plaque deposition, neuronal apoptosis, and mitochondrial function. We found that S-9-PAHSA significantly enhanced spatial learning and memory abilities, reduced amyloid plaque deposition, decreased neuronal apoptosis, and improved mitochondrial homeostasis and autophagy in 5xFAD mice. These findings suggest that S-9-PAHSA holds promise as a supplementary preventive and therapeutic strategy for AD treatment.

Spotiphy enables single-cell spatial whole transcriptomics across an entire section

Spatial transcriptomics (ST) has advanced our understanding of tissue regionalization by enabling the visualization of gene expression within whole-tissue sections, but current approaches remain plagued by the challenge of achieving single-cell resolution without sacrificing whole-genome coverage. Here we present Spotiphy (spot imager with pseudo-single-cell-resolution histology), a computational toolkit that transforms sequencing-based ST data into single-cell-resolved whole-transcriptome images. Spotiphy delivers the most precise cellular proportions in extensive benchmarking evaluations. Spotiphy-derived inferred single-cell profiles reveal astrocyte and disease-associated microglia regional specifications in Alzheimer's disease and healthy mouse brains. Spotiphy identifies multiple spatial domains and alterations in tumor-tumor microenvironment interactions in human breast ST data. Spotiphy bridges the information gap and enables visualization of cell localization and transcriptomic profiles throughout entire sections, offering highly informative outputs and an innovative spatial analysis pipeline for exploring complex biological systems.

Astrocyte and oligodendrocyte pathology in Alzheimer's disease

Astrocytes and oligodendrocytes, once considered passive support cells, are now recognized as active participants in the pathogenesis of Alzheimer's disease. Emerging evidence highlights the critical role that these glial cells play in the pathological features of Alzheimer's, including neuroinflammation, excitotoxicity, synaptic dysfunction, and myelin degeneration, which contribute to neurodegeneration and cognitive decline. Here, we review the current understanding of astrocyte and oligodendrocyte pathology in Alzheimer's disease and highlight research that supports the therapeutic potential of modulating astrocyte and oligodendrocyte functions to treat Alzheimer's disease.

Amyloid precursor protein and presenilin-1 knock-in immunodeficient mice exhibit intraneuronal Aβ pathology, microgliosis, and extensive neuronal loss

INTRODUCTION

Transgenic mice overexpressing familial Alzheimer's disease (AD) mutations (FAD) show non-physiological traits, and their immunocompetent backgrounds limit their use in AD immunotherapy research. Preclinical models that reflect human immune responses in AD are needed.

METHODS

Using CRISPR-Cas9, we developed single (NA) and double (NAPS) knock-in (KI) amyloid precursor protein (APP)KM670,671NL (Swedish) and presenilin 1 (PS 1)M146VFAD mutations on an immunodeficient NOG (NOD.Cg-PrkdcscidIl2rgtm1Sug/JicTac) background. The models were confirmed by Sanger sequencing and evaluated for AD-like pathology.

RESULTS

Both NA and NAPS mice developed pathology without overexpression artifacts. Mutation-induced upregulation of APP-CTF-β led to intraneuronal human amyloid beta (Aβ) (6E10) deposits and amyloid-associated microgliosis as early as 3 months, which increased with age. The addition of the PS 1M146V mutation doubled the amyloid load. The models displayed broad neuronal loss, resulting in brain atrophy in older mice.

DISCUSSION

These models replicate intraneuronal amyloid pathology and, with human immune reconstitution potential, enable novel studies of human immune responses in AD.

HIGHLIGHTS

A novel Alzheimer's disease (AD) knock-in (KI) mouse was developed and characterized on an immunodeficient NOG background. The model provides a platform for human immune studies and the evaluation of immunotherapies for AD. The KI mice demonstrate intraneuronal Aβ deposits and amyloid-associated microglial reactions. KI mice demonstrate extensive neuronal loss. Human immune reconstitution enables studies of infectious AD co-morbidities, such as the human immunodeficiency and herpes simplex viruses.

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.

Central Nervous System Macrophages in Health and Disease

The central nervous system (CNS) has a unique set of macrophages that seed the tissue early during embryonic development. Microglia reside in the parenchyma, and border-associated macrophages are present in border regions, including the meninges, perivascular spaces, and choroid plexus. CNS-resident macrophages support brain homeostasis during development and steady state. In the diseased brain, however, the immune landscape is altered, with phenotypic and transcriptional changes in resident macrophages and the invasion of blood-borne monocytes, which differentiate into monocyte-derived macrophages upon entering the CNS. In this review, we focus on the fate and function of the macrophage compartment in health, neurodegenerative conditions such as amyloidosis, and neuroinflammation as observed in multiple sclerosis and infection. We discuss our current understanding that monocyte-derived macrophages contribute to neuropathology whereas native macrophages play a neuroprotective role in disease.

A new near-infrared fluorescence probe for highly selective and sensitive detection and imaging of Butyrylcholinesterase in Alzheimer's disease mice

Butylcholinesterase (BChE) is a key enzyme in living system, closely related to liver and neurological diseases. It is very challenge to develop near-infrared (NIR) fluorescence probe methods for highly selective and sensitive detection of BChE in vivo. Based on the differences in active sites and spatial pockets between acetylcholinesterase (AChE) and BChE, a new NIR BChE-responsive fluorescence probe Probe-BChE (λex/λem = 600 nm/676 nm) was designed and synthesized by introducing dimethyl carbamate group as recognizing moiety to a NIR fluorophore hemicyanine skeleton. It was found that Probe-BChE specifically binds with BChE, rather than AChE, since BChE has a big cavity and strong intermolecular forces with Probe-BChE, which was supported by the molecular docking scores. The fluorescence method for the determination of BChE was developed with a detection limit of 0.14 U/mL BChE and high selectivity as well as short reaction time (∼3 s). The fluorescence imaging method using Probe-BChE efficiently image the levels of endogenous BChE in brains and main organs (heart, liver, spleen, lung and kidney) of Alzheimer's disease (AD) mice. The results reveal that the levels of endogenous BChE in old AD mice is higher than that in young AD mice, and endogenous BChE is enriched in the liver of AD mice. This work demonstrates that Probe-BChE is a promising fluorescence probe for imaging of endogenous BChE in AD mice. The design of NIR fluorescence probes for endogenous BChE in this work will promote to design NIR fluorescence probes for endogenous cholinesterase.

Artemisiae Iwayomogii Herba mitigates excessive neuroinflammation and Aβ accumulation by regulating the pro-inflammatory response and autophagy-lysosomal pathway in microglia in 5xFAD mouse model of Alzheimer's disease

Alzheimer's disease (AD) presents a growing societal challenge, driven by an aging population. It is characterized by neurodegeneration linked to β-amyloid (Aβ) and tau protein aggregation. Reactive glial cell-mediated neuroinflammation exacerbates disease progression by facilitating the accumulation of Aβ and impairing its clearance, thus highlighting potential therapeutic targets. Aerial parts of Artemisia iwayomogi (AIH), a kind of mugwort, has been consumed as a medicinal herb in East Asia for relieving inflammation-related diseases. Previously, AIH was found to exert potent inhibitory effects on neuroinflammation. This study aimed to examine whether AIH mitigates AD pathogenesis by regulating neuroinflammation and reducing Aβ deposition. AIH treatment to primary mixed glial cultures attenuated the pro-inflammatory responses evoked by Aβ stimulation. When treated to 5 × familial AD (5xFAD) mice, AIH improved learning and cognitive ability and reduced Aβ burden in the brain. AIH suppressed glial overactivation, as well as inhibited the expressions of pro-inflammatory mediators in the brain. Moreover, AIH regulated AKT signaling and elevated the expression of autophagy-lysosomal mediators in vitro. It was confirmed that lysosome-associated membrane protein 1 (LAMP1) was increased in the Aβ-associated microglia in the mouse hippocampus. Finally, it was observed that tau phosphorylation was alleviated, and synaptic protein expression was increased in AIH-treated 5xFAD mice. Overall, this study demonstrated that AIH ameliorated excessive neuroinflammation and Aβ accumulation by regulating microglial activation and autophagy-lysosomal pathway, thereby suggesting AIH as a promising therapeutic candidate for AD treatment.

Detecting the Undetectable: Advances in Methods for Identifying Small Tau Aggregates in Neurodegenerative Diseases

Tau, a microtubule-associated protein, plays a critical role in maintaining neuronal structure and function. However, in neurodegenerative diseases such as Alzheimer's disease and other tauopathies, tau misfolds and aggregates into oligomers and fibrils, leading to neuronal damage. Tau oligomers are increasingly recognised as the most neurotoxic species, inducing synaptic dysfunction and contributing to disease progression. Detecting these early-stage aggregates is challenging due to their low concentration and high heterogeneity in biological samples. Traditional methods such as immunostaining and enzyme-linked immunosorbent assay (ELISA) lack the sensitivity and specificity to reliably detect small tau aggregates. Advanced single-molecule approaches, including single-molecule fluorescence resonance energy transfer (smFRET) and single-molecule pull-down (SiMPull), offer improved sensitivity for studying tau aggregation at the molecular level. These emerging tools provide critical insights into tau pathology, enabling earlier detection and characterisation of disease-relevant aggregates, thereby offering potential for the development of targeted therapies and diagnostic approaches for tauopathies.

The choroid plexus: a command center for brain-body communication during inflammation

During brain inflammation, rigorous regulation of brain-body communication is required for sufficient, but not excessive, immune activation. As a crucial neuroimmune interface, the choroid plexus (ChP) epithelium serves as both a physical barrier between blood and cerebrospinal fluid (CSF) and a gateway allowing peripheral immune cell entry into the central nervous system (CNS). Recent years have witnessed increasing investigations of ChP events during brain inflammation. Here, we contextualize new findings with established ChP core functions, including CSF secretion and blood-CSF barrier regulation. We reason that the ChP is an organ where immune and nonimmune cells collaborate to defend the CNS. We discuss the pertinent mechanisms and the implications for neurologic disease etiology and treatment. Finally, we discuss outstanding questions for this rapidly expanding field and suggest key technologies and experimental steps to elucidate the full range of ChP functions during neuroinflammatory conditions, such as infection, injury, and aging.

The Auditory Brainstem Response Diagnoses Alzheimer-Like Disease in the 5xFAD Mouse Model

Early and accurate diagnosis of Alzheimer's disease (AD) will be key for effective personalized treatment plans ( Cummings, 2023). Significant difficulties in auditory processing have been frequently reported in many patients with mild cognitive impairment, the prodromal form of AD ( Tarawneh et al., 2022), making it an outstanding candidate as AD diagnostic biomarker. However, the efficiency of diagnosis with this parameter has not been explored. Here we show that when male mice with amyloidosis begin to show memory decline, changes in the auditory brainstem response (ABR) to clicks enable the reliable diagnosis of disease using a machine learning algorithm. Interpretation of the machine learning diagnosis revealed that the upper levels of the auditory pathway, including the inferior colliculus, were the probable sources of the defects. Histological analyses show that in these locations, neuroinflammation and plaque deposition temporally correlate with behavioral changes consistent with memory loss. While these findings are tempered by the caveat that they derive from amyloidosis mice, we propose that ABR measurements be evaluated as an additional rapid, low-cost, noninvasive biomarker to assist the diagnostic testing of early-stage AD.

Circular RNA aptamers targeting neuroinflammation ameliorate Alzheimer disease phenotypes in mouse models

Alzheimer disease (AD) therapy may benefit from optimized approaches to inhibit neuroinflammation. Small-molecule inhibitors of the proinflammatory molecule double-stranded RNA (dsRNA)-activated protein kinase R (PKR) have efficacy in AD models but their utility is compromised by adverse side effects. Here, we target PKR in two mouse models of AD using circular RNAs containing short double-stranded regions (ds-cRNAs), which are structurally similar to what we used previously to target PKR in psoriasis models. We show that the intrahippocampal injection of ds-cRNAs to neurons and microglia by adeno-associated virus (AAV) effectively dampens excessive PKR activity with minimal toxicity, accompanied by reduced neuroinflammation and amyloid-β plaques. We also deliver ds-cRNAs to the whole brain through intravenous injection of AAV-PHP.eB, which crosses the blood-brain barrier, resulting in neuroprotection and enhanced capability of spatial learning and memory in AD mouse models. The delivery of ds-cRNAs at different progressive stages of AD alleviates disease phenotypes, with therapeutic effects sustained for at least 6 months after a single administration.

Impairment of theta oscillations in the hippocampal CA1 region may mediate age-dependent movement alternations in the 5xFAD mouse model of Alzheimer's disease

Clinical evidences indicate that multifaceted gait abnormalities may manifest in Alzheimer's disease (AD) patients, which are associated with cognitive decline. Although the correlation between hippocampal theta power and locomotion has been known for a long time, the mechanisms by how hippocampal impairment participates in the altered gait seen in AD is not fully understood. To explore the manifestations of gait disorders in AD, we characterized gait performance in 3-, 6-, and 9-month-old male 5xFAD and control mice in the semi-automated, highly sensitive, Catwalk XT system. The 5xFAD mice displayed a decrease in kinetic parameters (average speed and cadence), and spatial parameters (paw area), while the temporal parameters (stance and swing time) were significantly increased. The parameters of interlimb coordination also displayed deficits. The majority of impairment variables related to the slow speed in 5xFAD mice at 9-month-old. We further explored the theta oscillations in the brain by in vivo tetrode recording of the hippocampal CA1. The results showed that the theta oscillations reduced in the hippocampal CA1 of 5xFAD mice, which related to the gait impairments. In conclusion, gait impairments started at 6 months of age, manifested at 9 months of age in 5xFAD mice. A reduction in theta oscillation power of the hippocampal CA1 may be responsible for the gait impairments.

An improved method for sampling and quantitative protein analytics of cerebrospinal fluid of individual mice

The mouse is the species most commonly used in preclinical research, but protein analytics of murine cerebrospinal fluid (CSF) remains challenging because of low sample volumes (often <10 μl) and frequent contaminations with blood. We developed an improved CSF sampling method that allows routine collection of larger volumes (20-30 μl) of pure CSF from individual mice, enabling multiple protein analytical assays from a single sample. Based on cell counts and hemoglobin ELISAs, we provide an easy quality control workflow for obtaining cell- and blood-free murine CSF. Through mass spectrometry-based proteomics using an absolutely quantified external standard, we estimated concentrations for hundreds of mouse CSF proteins. While repeated CSF sampling from the same mouse was possible, it induced CSF proteome changes. Applying the improved method, we found that the mouse CSF proteome remains largely stable over time in wild-type mice, but that amyloid pathology in the 5xFAD mouse model of Alzheimer's disease massively changes the CSF proteome. Neurofilament light chain and TREM2, markers of neurodegeneration and activated microglia, respectively, were strongly upregulated and validated using immunoassays. In conclusion, our refined murine CSF collection method overcomes previous limitations, allowing multiple quantitative protein analyses for applications in biomedicine.

Shared early molecular mechanisms revealed in P301S and 5xFAD Alzheimer's disease mouse models

Alzheimer's disease (AD) is the most common neurodegenerative disorder characterized by early molecular events that influence disease progression. Still, the molecular mechanisms caused by different mutations of AD are not understood. We have performed a multidisciplinary study to investigate and compare the early stages of the pathology in two transgenic AD mouse models: P301S and 5xFAD. Using SNOTRAP-based mass spectrometry, we assessed changes in S-nitrosylation, a nitric oxide-mediated post-translational modification, of proteins in both models during their juvenile age. The increased levels of 3-nitrotyrosine confirmed nitrosative stress in the mutant mice. Systems biology analysis revealed shared processes between the models, particularly in the γ-aminobutyric acid (GABA)ergic and glutamatergic neurotransmission processes. In the P301S model, we identified 273 S-nitrosylated (SNOed) proteins in the cortex, with 244 proteins uniquely SNOed in the diseased mice. In the 5xFAD model, 309 SNOed proteins were identified. We have found altered proteins expression of different glutamate/GABA-related markers in the cortex and hippocampus of both AD mouse models. Additionally, the phosphorylation levels of the mTOR signaling components revealed hyperactivation of this pathway in P301S mice. Conversely, 5xFAD mice showed no significant changes in mTOR signaling except for elevated phosphorylation of the ribosomal protein S6 in the cortex. Our findings revealed key molecular mechanisms in the two AD mouse models during their early stages. These mechanisms could serve as potential biomarkers and therapeutic targets for early-stage AD.

Mitochondrial Small RNA Alterations Associated with Increased Lysosome Activity in an Alzheimer's Disease Mouse Model Uncovered by PANDORA-seq

Emerging small non-coding RNAs (sncRNAs), including tRNA-derived small RNAs (tsRNAs) and rRNA-derived small RNAs (rsRNAs), are critical in various biological processes, such as neurological diseases. Traditional sncRNA-sequencing (seq) protocols often miss these sncRNAs due to their modifications, such as internal and terminal modifications, that can interfere with sequencing. We recently developed panoramic RNA display by overcoming RNA modification aborted sequencing (PANDORA-seq), a method enabling comprehensive detection of modified sncRNAs by overcoming the RNA modifications. Using PANDORA-seq, we revealed a previously unrecognized sncRNA profile enriched by tsRNAs/rsRNAs in the mouse prefrontal cortex and found a significant downregulation of mitochondrial tsRNAs and rsRNAs in an Alzheimer's disease (AD) mouse model compared to wild-type controls, while this pattern is not present in the genomic tsRNAs and rsRNAs. Moreover, our integrated analysis of gene expression and sncRNA profiles reveals that those downregulated mitochondrial sncRNAs negatively correlate with enhanced lysosomal activity, suggesting a crucial interplay between mitochondrial RNA dynamics and lysosomal function in AD. Given the versatile tsRNA/tsRNA molecular actions in cellular regulation, our data provide insights for future mechanistic study of AD with potential therapeutic strategies.

Herpes simplex virus-1 infection alters microtubule-associated protein Tau splicing and promotes Tau pathology in neural models of Alzheimer's disease

Herpes simplex virus 1 (HSV-1) infection alters critical markers of Alzheimer's disease (AD) in neurons. One key marker of AD is the hyperphosphorylation of Tau, accompanied by altered levels of Tau isoforms. However, an imbalance in these Tau splice variants, specifically resulting from altered 3R to 4R MAPT splicing of exon 10, has yet to be directly associated with HSV-1 infection. To this end, we infected 2D and 3D human neural models with HSV-1 and monitored MAPT splicing and Tau phosphorylation. Further, we transduced SH-SY5Y neurons with HSV-1 ICP27, which alters RNA splicing, to analyze if ICP27 alone is sufficient to induce altered MAPT exon 10 splicing. We show that HSV-1 infection induces altered splicing of MAPT exon 10, increasing 4R-Tau protein levels, Tau hyperphosphorylation, and Tau oligomerization. Our experiments reveal a novel link between HSV-1 infection and the development of cytopathic phenotypes linked with AD progression.

HDAC3 as an Emerging Therapeutic Target for Alzheimer's Disease and other Neurological Disorders

Alzheimer's disease (AD) is the most common cause of dementia in the aged population. Histone acetylation is a major epigenetic mechanism linked to memory formation and cognitive function. Histone deacetylases (HDACs) are responsible for the deacetylation of lysine residues in histone proteins. Although pan-HDAC inhibitors are effective in ameliorating AD phenotypes in preclinical models, they are associated with potential unfavorable adverse effects and barely translated into clinical trials. Therefore, the development of novel HDAC inhibitors with a well isoform-selectivity has been desired in AD drug discovery. Among various HDAC isoforms, HDAC3 is highly expressed in neurons and exhibits detrimental effects on synaptic plasticity and cognitive function. Moreover, HDAC3 provokes neuroinflammation and neurotoxicity and contributes to AD pathogenesis. In this review, we highlight HDAC3 as an attractive therapeutic target for disease-modifying therapy in AD. In addition, we discuss the therapeutic potential of HDAC3 inhibitors in other neurological disorders.