Alzheimer Disease: An Update on Pathobiology and Treatment Strategies

Brain interleukins and Alzheimer's disease

The central nervous system (CNS) is immune-privileged by several immuno-modulators as interleukins (ILs). ILs are cytokines secreted by immune cells for cell-cell signaling communications and affect the functions of the CNS. ILs were reported to orchestrate different molecular and cellular mechanisms of both physiological and pathological events, through overproduction or over-expression of their receptors. They interact with numerous receptors mediating pro-inflammatory and/or anti-inflammatory actions. Interleukins have been implicated to participate in neurodegenerative diseases. They play a critical role in Alzheimer's disease (AD) pathology which is characterized by the over-production of pro-inflammatory ILs. These may aggravate neurodegeneration, in addition to their contribution to detrimental mechanisms as oxidative stress, and excitotoxicity. However, recent research on the relation between ILs and AD revealed major discrepancies. Most of the major ILs were shown to play both pro- and anti-inflammatory roles in different experimental settings and models. The interactions between different ILs through shared pathways also add to the difficulty of drawing solid conclusions. In addition, targeting the different ILs has not yielded consistent results. The repeated failures of therapeutic drugs in treating AD necessitate the search for novel agents targeting multiple mechanisms of the disease pathology. In this context, the understanding of interleukins and their roles throughout the disease progression and interaction with other systems in the brain may provide promising therapeutic targets for the prevention or treatment of AD.

Multi-omics analyses identify gut microbiota-fecal metabolites-brain-cognition pathways in the Alzheimer's disease continuum

BACKGROUND

Gut microbiota dysbiosis is linked to Alzheimer's disease (AD), but our understanding of the molecular and neuropathological bases underlying such association remains fragmentary.

METHODS

Using 16S rDNA amplicon sequencing, untargeted metabolomics, and multi-modal magnetic resonance imaging, we examined group differences in gut microbiome, fecal metabolome, neuroimaging measures, and cognitive variables across 30 patients with AD, 75 individuals with mild cognitive impairment (MCI), and 61 healthy controls (HC). Furthermore, we assessed the associations between these multi-omics changes using correlation and mediation analyses.

RESULTS

There were significant group differences in gut microbial composition, which were driven by 8 microbial taxa (e.g., Staphylococcus and Bacillus) exhibiting a progressive increase in relative abundance from HC to MCI to AD, and 2 taxa (e.g., Anaerostipes) showing a gradual decrease. 26 fecal metabolites (e.g., Arachidonic, Adrenic, and Lithocholic acids) exhibited a progressive increase from HC to MCI to AD. We also observed progressive gray matter atrophy in broadly distributed gray matter regions and gradual micro-structural integrity damage in widespread white matter tracts along the AD continuum. Integration of these multi-omics changes revealed significant associations between microbiota, metabolites, neuroimaging, and cognition. More importantly, we identified two potential mediation pathways: (1) microbiota → metabolites → neuroimaging → cognition, and (2) microbiota → metabolites → cognition.

CONCLUSION

Aside from elucidating the underlying mechanism whereby gut microbiota dysbiosis is linked to AD, our findings may contribute to groundwork for future interventions targeting the microbiota-metabolites-brain-cognition pathways as a therapeutic strategy in the AD continuum.

An overview on the impact of viral pathogens on Alzheimer's disease

Alzheimer's disease (AD) is the most common type of dementia which affects over than 60 million cases worldwide with higher incidence in low and middle-income countries by 2030. Based on the multifactorial nature of AD different risk factors are linked to the condition considering the brain's β-amyloid plaques (Aβ) and neurofibrillary tangles (NFTs) as its primary hallmarks. Lately, viral photogenes specially after recent SARS-CoV-2 pandemic has gained a lot of attention in promoting the neurodegenerative disorder such as AD based on their capacity to increase the permeability of the blood-brain barrier, dysregulation of immune responses, and the impact on Aβ processing and phosphorylation of tau proteins. Therefore, in this review, we summarized the important association of viral pathogens and their mechanism by which they contribute with AD formation and development. AN OVERVIEW OF THE ROLES OF VIRAL PATHOGENS IN AD: According to this figure, viruses can infect neurons directly by modulating the BBB, transferring from endothelial cells to glial cells and then to neurons, increasing the Aβ deposition, and affecting the tau protein phosphorylation or indirectly through the virus's entrance and pathogenicity that can be accelerated by genetic and epigenetic factors, as well as chronic neuroinflammation caused by activated microglia and astrocytes.

Hippocampal Subfield Volume in Relation to Cerebrospinal Fluid Amyloid-ß in Early Alzheimer's Disease: Diagnostic Utility of 7T MRI

INTRODUCTION

Alzheimer's disease (AD) is a neurodegenerative condition characterised by amyloid plaque accumulation and neurofibrillary tangles. Early detection is essential for effective intervention, but current diagnostic methods that enable early diagnosis in clinical practice rely on invasive or costly biomarker scanning. This study aimed to explore the utility of 7T MRI in assessing hippocampal subfield volumes and their correlation with cerebrospinal fluid (CSF) biomarkers in prodromal AD.

METHODS

Fifty-six participants, including AD patients and healthy controls, underwent 7T MRI scanning. Automated segmentation delineated hippocampal subfield volumes, with subsequent normalisation to whole brain volume.

RESULTS

Significant differences in hippocampal and subfield volumes were observed in prodromal AD patients, even when they did not exhibit high MTA scores on 3T MRI or show any whole brain volume loss. Additionally, the volume of the entorhinal cortex (ERC) correlated significantly with CSF amyloid-β levels, suggesting ERC's potential as a proxy CSF amyloid-ß measurement. Conversely, no significant associations were found between CSF 181-Phosphorylated-tau or total tau levels and any hippocampal subfield volumes.

DISCUSSION

These findings show the potential use of 7T MRI, particularly in ERC assessment, as a biomarker for early AD identification. Further validation studies are warranted to confirm these results and elucidate the relationship of ERC volume with CSF biomarkers.

Self-Assembled BODIPY@Au Core-Shell Structures for Durable Neuroprotective Phototherapy

BODIPY analogs are promising photosensitizers for molecular phototherapy; however, they exhibit high dark cytotoxicity and limited singlet oxygen generation capacity. In this study, we developed self-assembled core-shell nanophotosensitizers by linking a bipyridine group to BODIPY (Bpy-BODIPY) and promoting J-aggregation on gold nanourchins. This design enhances photostability and reduces the energy gap between the lowest singlet excited state and the lower triplet state, facilitating efficient singlet oxygen production. We characterized these nanophotosensitizers using UV-visible spectroscopy, transmission electron microscopy (TEM), surface-enhanced Raman spectroscopy (SERS) and dynamic light scattering (DLS), which confirmed the formation of the desired core-shell structure and J-aggregates. Notably, Bpy-BODIPY@Au significantly suppresses tau protein aggregation and enhances neuroprotective action, even in the presence of a phosphatase inhibitor. This work broadens the application of BODIPY chemistry to nanoagents for neuroprotective therapy.

Polyphenols as Wnt/β-catenin pathway modulators: A promising strategy in clinical neurodegeneration

Polyphenols, a diverse group of naturally occurring compounds found in plants, have garnered significant attention for their potential therapeutic properties in treating neurodegenerative diseases (NDs). The Wnt/β-catenin (WβC) signaling pathway, a crucial player in neurogenesis, neuronal survival, and synaptic plasticity, is involved in several cellular mechanisms related to NDs. Dysregulation of this pathway is a hallmark in the development of various NDs. This study explores multiple polyphenolic compounds, such as flavonoids, stilbenes, lignans, and phenolic acids, and their potential to protect the nervous system. It provides a comprehensive analysis of their effects on the WβC pathway, elucidating their modes of action. The study highlights the dual function of polyphenols in regulating and protecting the nervous system, providing reassurance about the research benefits. This review provides a comprehensive analysis of the results obtained from both in vitro studies and in vivo research, shedding light on how these substances influence the various components of the pathway. The focus is mainly on the molecular mechanisms that allow polyphenols to reduce oxidative stress, inflammation, and apoptotic processes, ultimately improving the function and survival of neurons. This study aims to offer a thorough understanding of the potential of polyphenols in targeting the WβC signaling pathway, which could lead to the development of innovative therapeutic options for NDs.

Plasma p-tau217 and p-tau217/Aβ1-42 are effective biomarkers for identifying CSF- and PET imaging-diagnosed Alzheimer's disease: Insights for research and clinical practice

INTRODUCTION

With the advancement of disease-modifying therapies for Alzheimer's disease (AD), validating plasma biomarkers against cerebrospinal fluid (CSF) and positron emission tomography (PET) standards is crucial in both research and real-world settings.

METHODS

We measured plasma phosphorylated tau (p-tau)217, p-tau181, amyloid beta (Aβ)1-40, Aβ1-42, and neurofilament light chain in research and real-world cohorts. Participants were categorized by brain amyloid status using US Food and Drug Administration/European Medicines Agency-approved CSF or PET methods.

RESULTS

Plasma p-tau217 and p-tau217/Aβ1-42 demonstrated superior accuracy in detecting brain amyloid pathologies, with area under the curve from 0.94 to 0.97 in all cohorts. Specificity was lower in the real-world cohort but improved significantly by integrating demographic and clinical factors, aligning performance with research cohorts. Additionally, plasma biomarkers exhibited strong correlations with their CSF counterparts and PET standardized uptake value ratios, with significant associations in amyloid-positive participants.

DISCUSSION

Plasma p-tau217 and p-tau217/Aβ1-42 are effective diagnostic tools. However, patient demographics, apolipoprotein E ε4 status, and cognitive condition must be considered to improve specificity in the clinical practice.

HIGHLIGHTS

Plasma phosphorylated tau (p-tau)217 and p-tau217/amyloid beta (Aβ)1-42 demonstrated exceptional accuracy (area under the curve: 0.94-0.97) in detecting brain amyloid pathologies across both research (Southern China Aging Brain Initiative [SCABI]-1, SCABI-2) and real-world clinical practice (RCP) cohorts. Incorporating patient-specific factors (sex, age, apolipoprotein E ε4, cognitive status) improved diagnostic specificity in the clinical RCP cohort, aligning its performance with that of research cohorts. Plasma biomarkers, particularly p-tau217 and their ratios, showed robust correlations with cerebrospinal fluid biomarkers and positron emission tomography amyloid standardized uptake value ratios, underscoring their value as non-invasive diagnostic alternatives. Plasma p-tau217 and p-tau217/Aβ1-42 proved highly effective in diagnosing amyloid burden, offering a practical solution to bridge research advancements with real-world clinical practice.

Pathological angiogenesis was associated with cerebrovascular lesion and neurodegeneration in Alzheimer's disease

INTRODUCTION

We investigated the specific factors driving abnormal angiogenesis in Alzheimer's disease (AD) and its role in cerebrovascular lesions and neurodegeneration.

METHODS

We assessed cerebrovascular pathologies, amyloid-beta (Aβ), and tau pathologies in post mortem human brains and detected 12 angiogenic factors in cerebrospinal fluid (CSF) from the China Aging and Neurodegenerative Disease Initiative (CANDI) cohort.

RESULTS

We observed severe blood-brain barrier damage and elevated levels of the vascular marker CD31 in human AD brains, which had a stronger correlation with tau pathology than Aβ pathology. Consistently, only CSF pTau181 showed positive associations with CSF angiogenesis factors (soluble vascular endothelial growth factor receptor 2 [sVEGFR2], VEGF-C, VEGF-D, placental growth factor [PLGF], Angiopoietin2, and Serpin E1), but not CSF Aβ42/40. Additionally, higher levels of CSF sVEGFR1, soluble Tyrosine-protein kinase receptor 2 [sTIE2], PLGF, and interleukin 8 [IL8], as well as lower levels of CSF urokinase-type plasminogen activator [uPA], were associated with worsen cerebrovascular pathologies and neurodegeneration.

DISCUSSION

Our findings indicate that tau pathology may play a critical role in pathological angiogenesis, contributing to cerebrovascular lesions and neurodegeneration in AD.

HIGHLIGHTS

BBB damage and elevated vascular marker CD31 in human AD brains had a stronger correlation with tau pathology than Aβ pathology. CSF pTau181 mediated the effect of CSF Aβ42/40 on CSF sVEGFR1 and sTIE2. Only CSF pTau181 showed positive associations with sVEGFR2, VEGF-C, VEGF-D, PLGF, Angiopoietin2, and Serpin E1. Higher sVEGFR1, sTIE2, PLGF, and IL8, and lower uPA in CSF, were associated with cerebrovascular pathologies and neurodegeneration.

The role of kynurenine pathway metabolism mediated by exercise in the microbial-gut-brain axis in Alzheimer's disease

In recent years, the role of the microbiome-gut-brain axis in the pathogenesis of Alzheimer's disease (AD) has garnered increasing attention. Specifically, tryptophan metabolism via the kynurenine pathway (KP) plays a crucial regulatory role in this axis. This study reviews how exercise regulates the microbiome-gut-brain axis by influencing kynurenine pathway metabolism, thereby exerting resistance against AD. This paper also discusses how exercise positively impacts AD via the microbiome-gut-brain axis by modulating the endocrine, autonomic nervous, and immune systems. Although the specific mechanisms are not fully understood, research indicates that exercise may optimize tryptophan metabolism by promoting the growth of beneficial microbiota and inhibiting harmful microbiota, producing substances that are beneficial to the nervous system and combating AD. The aim of this review is to provide new perspectives and potential intervention strategies for the prevention and treatment of AD by exploring the links between exercise, KP and the gut-brain axis.

C/EBPβ in Alzheimer's disease: An integrative regulator of pathological mechanisms

Alzheimer's disease (AD) stands as one of the most prevalent neurodegenerative disorders, characterized by a progressive decline in cognitive function, neuroinflammation, amyloid-beta (Aβ) plaques, and neurofibrillary tangles (NFTs). With the global aging population, the incidence of AD continues to rise, yet current therapeutic strategies remain limited in their ability to significantly alleviate cognitive impairments. Therefore, a deeper understanding of the molecular mechanisms underlying AD is imperative for the development of more effective treatments. In recent years, the transcription factor C/EBPβ has emerged as a pivotal regulator in several pathological processes of AD, including neuroinflammation, lipid metabolism, Aβ processing, and tau phosphorylation. Through intricate post-translational modifications, C/EBPβ modulates these processes and may influence the progression of AD on multiple fronts. This review systematically explores the multifaceted roles of C/EBPβ in the pathogenesis of AD, delving into its crucial involvement in neuroinflammation, Aβ production, tau pathology, and lipid metabolism dysregulation. Furthermore, we critically assess therapeutic strategies targeting C/EBPβ, examining the challenges and opportunities in regulating this factor. By synthesizing the latest research findings, we offer a more comprehensive understanding of the role of C/EBPβ in AD and discuss its potential as a therapeutic intervention target.

Essential role of sulfide oxidation in brain health and neurological disorders

Hydrogen sulfide (H2S) is an environmental hazard well known for its neurotoxicity. In mammalian cells, H2S is predominantly generated by transsulfuration pathway enzymes. In addition, H2S produced by gut microbiome significantly contributes to the total sulfide burden in the body. Although low levels of H2S is believed to exert various physiological functions such as neurotransmission and vasomotor control, elevated levels of H2S inhibit the activity of cytochrome c oxidase (i.e., mitochondrial complex IV), thereby impairing oxidative phosphorylation. To protect the electron transport chain from respiratory poisoning by H2S, the compound is actively oxidized to form persulfides and polysulfides by a mitochondrial resident sulfide oxidation pathway. The reaction, catalyzed by sulfide:quinone oxidoreductase (SQOR), is the initial and critical step in sulfide oxidation. The persulfide species are subsequently oxidized to sulfite, thiosulfate, and sulfate by persulfide dioxygenase (ETHE1 or SDO), thiosulfate sulfurtransferase (TST), and sulfite oxidase (SUOX). While SQOR is abundantly expressed in the colon, liver, lung, and skeletal muscle, its expression is notably low in the brains of most mammals. Consequently, the brain's limited capacity to oxidize H2S renders it particularly sensitive to the deleterious effects of H2S accumulation. Impaired sulfide oxidation can lead to fatal encephalopathy, and the overproduction of H2S has been implicated in the developmental delays observed in Down syndrome. Our recent findings indicate that the brain's limited capacity to oxidize sulfide exacerbates its sensitivity to oxygen deprivation. The beneficial effects of sulfide oxidation are likely to be mediated not only by the detoxification of H2S but also by the formation of persulfide, which exerts cytoprotective effects through multiple mechanisms. Therefore, pharmacological agents designed to scavenge H2S and/or enhance persulfide levels may offer therapeutic potential against neurological disorders characterized by impaired or insufficient sulfide oxidation or excessive H2S production.

Conformation pattern changes in R1-pS262 tau peptide induced endogenous tau aggregation, synaptic damage, and cognitive impairments

BACKGROUND

To date, the effect of tau phosphorylation at different amino acid sites on the conformation and function of tau is still unclear in Alzheimer's disease (AD). Protein fingerprinting, also known as the protein folding shape code (PFSC) method, is a protein structure prediction technique based on protein sequence, which can reveal proteins' most likely spatial conformation.

OBJECTIVE

To investigate the effect of phosphorylation on tau protein conformation using PFSC technology and further analyze the differences in the effect of phosphorylation on tau aggregation at specific sites.

METHODS

We performed a conformational analysis of wild-type and simulated mutant hTau441 using the PFSC method and synthesized the phosphorylated and non-phosphorylated tau fragments by the chemical solid phase method.

RESULTS

We found that the number of Ser262 protein fingerprints increased from six in tau S262A to nine in tau S262E, together with increased conformational changes and enhanced flexibility. The in vitro Thioflavin S assay showed that phosphorylated tau fragments R1-pS262 possessed a stronger activity of inducing tau aggregation. In contrast to the non-phosphorylated tau fragment R1-nS262, R1-pS262 promoted endogenous tau aggregation and decreased synaptic proteins. In rats, R1-pS262 caused cognitive impairments and neuronal loss in addition to endogenous tau aggregation and synaptic damage.

CONCLUSIONS

Our study firstly reports that tau phosphorylation at Ser262 induces tau aggregation, and phosphorylated tau fragments R1-pS262 directly result in neuropathological changes. These provide new clues to the pathogenesis of tauopathy, such as AD, and a new molecular target for possible intervention.

Elevated serum sodium is linked to increased amyloid-dependent tau pathology, neurodegeneration, and cognitive impairment in Alzheimer's disease

Vascular dysfunction is implicated in the pathophysiology of Alzheimer's disease (AD). While sodium is essential for maintaining vascular function, its role in AD pathology remains unclear. We included 353 participants from the Alzheimer's Disease Neuroimaging Initiative (ADNI), assessing serum sodium levels, cerebrospinal fluid (CSF) and positron emission tomography (PET) biomarkers, magnetic resonance imaging (MRI), and cognitive function. An independent sample (N = 471) with available CSF sodium-related proteins and AD biomarkers was also included. Associations between serum sodium levels and AD pathology, neurodegeneration, and cognition were evaluated using linear regression models. Spearman's correlation analyses assessed the relationships between CSF sodium-related proteins and AD biomarkers. Higher serum sodium levels were associated with increased AD pathology, reduced hippocampal volume, and greater cognitive decline (all p < 0.05). The relationship between serum sodium and amyloid PET was evident in several AD-susceptible brain regions, including the neocortex and limbic system. Individuals with high serum sodium exhibited higher tau pathology, lower hippocampal volume, and more severe cognitive decline per unit increase in amyloid PET compared to those with low serum sodium (all p < 0.05). Among the 14 CSF sodium-related proteins, which were inter-correlated, six were significantly correlated with CSF AD pathology and amyloid PET, while two were correlated with hippocampal volume and cognitive function, with sodium channel subunit beta-2 (SCN2B) and sodium channel subunit beta-3 (SCN3B) showing the strongest correlations. These findings underscore the crucial role of serum sodium in AD progression, highlighting a potential network of sodium dysregulation involved in AD pathology. Targeting sodium may offer a novel therapeutic approach to slowing AD progression, particularly by impeding the progression of amyloid-related downstream events.

A novel phosphodiesterase 5 inhibitor, RF26, improves memory impairment and ameliorates tau aggregation and neuroinflammation in the P301S tauopathy mouse model of Alzheimer's disease

Phosphodiesterase-5 (PDE5) inhibitors are primarily used in the treatment of erectile dysfunction and pulmonary hypertension, but have also been reported to have a potential therapeutic effect for the treatment of Alzheimer's disease (AD). This is likely to be through stimulation of nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) signaling by elevating cGMP, a secondary messenger involved in processes of neuroplasticity. In the present study, we evaluated the efficacy of a novel PDE5 inhibitor, RF26, using P301S tauopathy mice model. A body of experimental evidence suggests that the development of tau inclusions leads to the neurodegeneration observed in tauopathies, including AD, Frontotemporal dementia (FTD), Supranuclear palsy and others. RF26 successfully targeted NO/cGMP signaling pathway and showed a significant improvement of spatial memory task performance of P301S mice using Morris Water Maze and T-maze. Furthermore, RF26 -treated mice showed a significant reduction of phosphorylated tau load, gliosis and downregulated pro-inflammatory cytokines. The presented data support the efficacy of RF26 as a potent PDE5 inhibitor and calls for further investigation as a potential therapeutic drug for Alzheimer's and other tauopathy related neurological disorders.

Alzheimer's disease: insights into pathology, molecular mechanisms, and therapy

Alzheimer's disease (AD), the leading cause of dementia, is characterized by the accumulation of amyloid plaques and neurofibrillary tangles in the brain. This condition casts a significant shadow on global health due to its complex and multifactorial nature. In addition to genetic predispositions, the development of AD is influenced by a myriad of risk factors, including aging, systemic inflammation, chronic health conditions, lifestyle, and environmental exposures. Recent advancements in understanding the complex pathophysiology of AD are paving the way for enhanced diagnostic techniques, improved risk assessment, and potentially effective prevention strategies. These discoveries are crucial in the quest to unravel the complexities of AD, offering a beacon of hope for improved management and treatment options for the millions affected by this debilitating disease.

Cholinergic neurotransmission in the brain of streptozotocin-induced rat model of sporadic Alzheimer's disease: long-term follow up

Rats treated intracerebroventricularly with streptozotocin (STZ-icv) develop pathologic features, which resemble those in Alzheimer's disease and have been proposed as a non-transgenic model for sporadic type of the disease (sAD). We aimed to characterize cholinergic transmission in the rat brain as a function of STZ-icv dose and time after the treatment. Acetylcholinesterase (AChE) activity and expression of muscarinic (M1, M4) and nicotinic (α7) receptors, cholin acetyltransferase (ChAT) and glial fibrillary acidic protein (GFAP) were measured in hippocampus (HPC) and parietotemporal cortex (CTX) of STZ-icv and age-matched control rats one week, and one, three, six and nine months after the icv administration of STZ (0.3, 1 and 3 mg/kg), respectively. Cholinergic and astroglial changes were found most pronounced with a highest STZ dose in time-dependent manner. The cortex and hippocampus exhibited specific alterations in cholinergic transmission following STZ-icv administration, with either similar or distinct patterns depending on the parameter observed: increased AChE activity in HPC and invariable in CTX; increased M4 and ChAT levels in both regions; substantial cortical M1 level increment and moderate hippocampal M1 decrement; and decreased α7 levels in both regions, with subsequent increase observed only in HPC. Alterations in cerebral cholinergic neurotransmission in STZ-icv rat model were mostly following a threephasic time pattern: acute response (Phase I), complete/partial compensation (Phase II), and reappearance/progression of changes (Phase III). Staging structure of cholinergic changes in STZ-icv rat model might be speculated to partly correlate with cholinergic pathology in clinical AD stages.

Enhanced Multimodal Low-Rank Embedding-Based Feature Selection Model for Multimodal Alzheimer's Disease Diagnosis

Identification of Alzheimer's disease (AD) with multimodal neuroimaging data has been receiving increasing attention. However, the presence of numerous redundant features and corrupted neuroimages within multimodal datasets poses significant challenges for existing methods. In this paper, we propose a feature selection method named Enhanced Multimodal Low-rank Embedding (EMLE) for multimodal AD diagnosis. Unlike previous methods utilizing convex relaxations of the -norm, EMLE exploits an -norm regularized projection matrix to obtain an embedding representation and select informative features jointly for each modality. The -norm, employing an upper-bounded nonconvex Minimax Concave Penalty (MCP) function to characterize sparsity, offers a superior approximation for the -norm compared to other convex relaxations. Next, a similarity graph is learned based on the self-expressiveness property to increase the robustness to corrupted data. As the approximation coefficient vectors of samples from the same class should be highly correlated, an MCP function introduced norm, i.e., matrix -norm, is applied to constrain the rank of the graph. Furthermore, recognizing that diverse modalities should share an underlying structure related to AD, we establish a consensus graph for all modalities to unveil intrinsic structures across multiple modalities. Finally, we fuse the embedding representations of all modalities into the label space to incorporate supervisory information. The results of extensive experiments on the Alzheimer's Disease Neuroimaging Initiative datasets verify the discriminability of the features selected by EMLE.

A review on gut microbiota and miRNA crosstalk: implications for Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by cognitive decline and progressive neuronal damage. Recent research has highlighted the significant roles of the gut microbiota and microRNAs (miRNAs) in the pathogenesis of AD. This review explores the intricate interaction between gut microbiota and miRNAs, emphasizing their combined impact on Alzheimer's progression. First, we discuss the bidirectional communication within the gut-brain axis and how gut dysbiosis contributes to neuroinflammation and neurodegeneration in AD. Changes in gut microbiota composition in Alzheimer's patients have been linked to inflammation, which exacerbates disease progression. Next, we delve into the biology of miRNAs, focusing on their roles in gene regulation, neurodevelopment, and neurodegeneration. Dysregulated miRNAs are implicated in AD pathogenesis, influencing key processes like inflammation, tau pathology, and amyloid deposition. We then examine how the gut microbiota modulates miRNA expression, particularly in the brain, potentially altering neuroinflammatory responses and synaptic plasticity. The interplay between gut microbiota and miRNAs also affects blood-brain barrier integrity, further contributing to Alzheimer's pathology. Lastly, we explore therapeutic strategies targeting this gut microbiota-miRNA axis, including probiotics, prebiotics, and dietary interventions, aiming to modulate miRNA expression and improve AD outcomes. While promising, challenges remain in fully elucidating these interactions and translating them into effective therapies. This review highlights the importance of understanding the gut microbiota-miRNA relationship in AD, offering potential pathways for novel therapeutic approaches aimed at mitigating the disease's progression.

Improving cognitive impairment through chronic consumption of natural compounds/extracts: a systematic review and meta-analysis of randomized controlled trials

Introduction

This systematic review and meta-analysis aimed to compare the efficacy of extended supplementation (≥6 weeks) with natural compounds or extracts in improving cognitive function in patients with mild cognitive impairment (MCI) or Alzheimer's disease (AD).

Methods

A comprehensive literature search was conducted across Cochrane, PubMed, PsycARTICLES, Scopus, and Web of Science databases from inception to April 10, 2024. Eligible studies were randomized controlled trials evaluating cognitive outcomes in patients with MCI or AD using the Mini-Mental State Examination (MMSE) and the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog).

Results

From an initial pool of 6,687 articles, 45 were deemed relevant for qualitative analysis. Of these, 37 studies demonstrated improvements or positive trends in cognitive outcomes with natural compound or extract supplementation. A total of 35 studies met the criteria for meta-analysis. The meta-analysis, involving 4,974 participants, revealed significant improvements in ADAS-Cog scores (pooled standardized mean difference = -2.88, 95% confidence interval [CI]: -4.26 to -1.50; t24 = -4.31, p < 0.01) following supplementation. Additionally, a suggestive trend toward improvement in MMSE scores was observed in a subgroup analysis of 1,717 participants (pooled standardized mean difference = 0.76, 95% CI: 0.06 to 1.46, t18 = 2.27, p = 0.04).

Conclusion

These findings support the potential cognitive benefits of extended (≥6 weeks) supplementation with natural compounds or extracts in individuals with MCI or AD. Further research is warranted to confirm these results and elucidate the underlying mechanisms.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/.

Genetically-encoded targeted protein degradation technology to remove endogenous condensation-prone proteins and improve crop performance

Effective modulation of gene expression in plants is achievable through tools like CRISPR and RNA interference, yet methods for directly modifying endogenous proteins remain lacking. Here, we identify the E3 ubiquitin ligase E3TCD1 and develope a Targeted Condensation-prone-protein Degradation (TCD) strategy. The X-E3TCD1 fusion protein acts as a genetically engineered degrader, selectively targeting endogenous proteins prone to condensation. For example, a transgenic E3TCD1 fusion with Teosinte branched 1 (TB1) degrades the native TB1 protein, resulting in increased tiller numbers in rice. Additionally, conditional degradation of the negative defense regulator Early Flowering 3 via a pathogen-responsive ProTBF1-uORFsTBF1 cassette enhances rice blast resistance without affecting flowering time in the absence of pathogen. Unlike prevailing targeted protein degradation strategies, the TCD system does not rely on small molecules, antibodies, or genetic knock-in fusion tags, demonstrating its promise as a transgene-based approach for optimizing crop performance.

Divergent Effects of APOE3 and APOE4 Human Astrocytes on Key Alzheimer's Disease Hallmarks in Chimeric Mice

Despite strong evidence supporting that both astrocytes and apolipoprotein E (APOE) play crucial roles in the pathogenesis and progression of Alzheimer's disease (AD), the impact of astrocytes carrying different APOE variants on key AD pathological hallmarks remains largely unknown. To explore such effects in a human relevant context, we generated a chimeric model of AD. We transplanted isogenic APOE3 or APOE4 human induced pluripotent stem cell (hiPSC)-derived astrocyte progenitors into neonatal brains of AD model mice. We show that at five to six months after transplantation, transplanted cells have differentiated into mature astrocytes (h-astrocytes) that often integrate in upper layers of one cortical hemisphere. APOE3 and APOE4 h-astrocytes differentially express and secrete the APOE protein, which binds to Aβ plaques with an isoform-dependent affinity. Remarkably, APOE3 h-astrocytes ameliorate Aβ pathology, Tau pathology and neuritic dystrophy. In contrast, APOE4 h-astrocytes aggravate these AD processes. Moreover, APOE3 and APOE4 h-astrocytes modulate microglia responses to Aβ pathology in opposite ways. APOE4 h-astrocytes enhance microglia clustering around Aβ plaques and exacerbate DAM state whereas APOE3 h-astrocytes reduce microglia clustering and induce a more homeostatic state on plaque-associated microglia. These findings highlight a critical contribution of h-astrocytes not only to Aβ pathology but also to other key AD hallmarks in chimeric mice. In addition, our findings reveal that h-astrocytes with different APOE variants and the different forms of APOE they secrete have a crucial role in AD progression.

Skull bone marrow and skull meninges channels: redefining the landscape of central nervous system immune surveillance

The understanding of neuroimmune function has evolved from concepts of immune privilege and protection to a new stage of immune interaction. The discovery of skull meninges channels (SMCs) has opened new avenues for understanding central nervous system (CNS) immunity. Here, we characterize skull bone marrow and SMCs by detailing the anatomical structures adjacent to the skull, the differences between skull and peripheral bone marrow, mainstream animal processing methods, and the role of skull bone marrow in monitoring various CNS diseases. Additionally, we highlight several unresolved issues based on current research findings, aiming to guide future research directions.

A review of the application of exercise intervention on improving cognition in patients with Alzheimer's disease: mechanisms and clinical studies

Alzheimer's disease (AD) is the most common form of dementia, leading to sustained cognitive decline. An increasing number of studies suggest that exercise is an effective strategy to promote the improvement of cognition in AD. Mechanisms of the benefits of exercise intervention on cognitive function may include modulation of vascular factors by affecting cardiovascular risk factors, regulating cardiorespiratory health, and enhancing cerebral blood flow. Exercise also promotes neurogenesis by stimulating neurotrophic factors, affecting neuroplasticity in the brain. Additionally, regular exercise improves the neuropathological characteristics of AD by improving mitochondrial function, and the brain redox status. More and more attention has been paid to the effect of Aβ and tau pathology as well as sleep disorders on cognitive function in persons diagnosed with AD. Besides, there are various forms of exercise intervention in cognitive improvement in patients with AD, including aerobic exercise, resistance exercise, and multi-component exercise. Consequently, the purpose of this review is to summarize the findings of the mechanisms of exercise intervention on cognitive function in patients with AD, and also discuss the application of different exercise interventions in cognitive impairment in AD to provide a theoretical basis and reference for the selection of exercise intervention in cognitive rehabilitation in AD.

Polygenic burden of short tandem repeat expansions promotes risk for Alzheimer's disease

Studies of the genetics of Alzheimer's disease (AD) have largely focused on single nucleotide variants and short insertions/deletions. However, most of the disease heritability has yet to be uncovered, suggesting that there is substantial genetic risk conferred by other forms of genetic variation. There are over one million short tandem repeats (STRs) in the genome, and their link to AD risk has not been assessed. As pathogenic expansions of STR cause over 30 neurologic diseases, it is important to ascertain whether STRs may also be implicated in AD risk. Here, we genotype 312,731 polymorphic STR tracts genome-wide using PCR-free whole genome sequencing data from 2981 individuals (1489 AD case and 1492 control individuals). We implement an approach to identify STR expansions as STRs with tract lengths that are outliers from the population. We then test for differences in aggregate burden of expansions in case versus control individuals. AD patients harbor a 1.19-fold increase of STR expansions compared to healthy elderly controls (p = 8.27×10-3, two-sided Mann-Whitney test). Individuals carrying >30 STR expansions have a 3.69-fold higher odds of having AD and have more severe AD neuropathology. AD STR expansions are highly enriched within active promoters in post-mortem hippocampal brain tissues and particularly within SINE-VNTR-Alu (SVA) retrotransposons. Together, these results demonstrate that expanded STRs within active promoter regions of the genome associate with risk of AD.

Lycopodiaceae herb from Vietnam as a promising medicinal source of natural hupezine and novel huperzine-producing endophytic fungi

OBJECTIVES

(1) To evaluate the potential of producing huperzine (Hup) and anticholinesterase (AChE) activities of nine native Lycopodiaceae species collected in Vietnam; (2) Isolation, identification and characterization of a novel fungus producing both HupA and HupB isolated from Lycopodium casuarinoides Spring.

RESULTS

All methanolic extracts of nine plants showed AChE inhibition from 8.55 to 71.81%. Of note, Huperzia serrata (Thunb.) Trevis, L. casuarinoides, Lycopodium clavatum L., Phlegmariurus squarrosus (G. Forst.), and P. phlegmaria (L.) T. Sen & U. Sen were shown to biosynthesize both HupA and HupB by high-performance liquid chromatography (HPLC). Plants H. serrata, L. casuarinoides and L. clavatum showed the most potent AchE IC50 inhibition. HupA and HupB concentrations from six plants were greater than those of previously reported Lycopodiaceae species. Sixty-four endophytic fungi were isolated from tissue of natural L. casuarinoides and then screened for HupA- and HupB-production by HPLC. Out of 64 fungal strains, only TTD2-2.7 extract could produce both HupA and HupB with the yields of 0.034 and 0.028 µg gdcw-1, respectively. Moreover, TTD2-2.7 extract also had inhibitory effects on AChE with the IC50 of 129.76 ± 4.13 µg ml-1, which was lower than the extract of host plant L. casuarinoides (94.03 ± 4.13 µg ml-1). The fungus was identified as Aspergillus sp. TTD2-2.7 by morphological characteristics and Internal Transcribed Spacer sequence analysis.

CONCLUSIONS

These are the first reports of (1) two species L. clavatum and L. casuarinoides producing both HupA and HupB, and (2) L. casuarinoides as novel sources of Hup-producing endophytic fungi as well as (3) fungus Aspergillus as a novel HupA- and HupB-producing endophyte isolated from L. casuarinoides.

Isotope Encoded Spatial Biology Identifies Amyloid Plaque-Age-Dependent Structural Maturation, Synaptic Loss, and Increased Toxicity

Understanding how amyloid beta (Aβ) plaques form and progress to neurotoxicity in Alzheimer's disease remains a significant challenge. This study aims to elucidate the processes involved in Aβ plaque formation and maturation using a knock-in Aβ mouse model (App NL-F/NL-F ). By employing mass spectrometry imaging and stable isotope labeling, we timestamped Aβ plaques from their initial deposition, enabling the spatial tracking of plaque aging. Correlating single-plaque spatial transcriptomics with time since seeding, allowed us to track gene-expression changes specifically associated with plaque age, independent of chronological age of the mouse or disease severity. We found that plaque age, within sections from individual mice aged from 10 to 18 months, negatively correlates with synaptic gene expression. Further, correlation with hyperspectral confocal microscopy using structure-specific dyes revealed a positive link between plaque age and structural maturity, with older plaques identified as more compact and associated with significantly greater synapse loss and toxicity.

Machine learning models for dementia screening to classify brain amyloid positivity on positron emission tomography using blood markers and demographic characteristics: a retrospective observational study

BACKGROUND

Intracerebral amyloid β (Aβ) accumulation is considered the initial observable event in the pathological process of Alzheimer's disease (AD). Efficient screening for amyloid pathology is critical for identifying patients for early treatment. This study developed machine learning models to classify positron emission tomography (PET) Aβ-positivity in participants with preclinical and prodromal AD using data accessible to primary care physicians.

METHODS

This retrospective observational study assessed the classification performance of combinations of demographic characteristics, routine blood test results, and cognitive test scores to classify PET Aβ-positivity using machine learning. Participants with mild cognitive impairment (MCI) or normal cognitive function who visited Oita University Hospital or had participated in the USUKI study and met the study eligibility criteria were included. The primary endpoint was assessment of the classification performance of the presence or absence of intracerebral Aβ accumulation using five machine learning models (i.e., five combinations of variables), each constructed with three classification algorithms, resulting in a total of 15 patterns. L2-regularized logistic regression, and kernel Support Vector Machine (SVM) and Elastic Net algorithms were used to construct the classification models using 34 pre-selected variables (12 demographic characteristics, 11 blood test results, 11 cognitive test results).

RESULTS

Data from 262 records (260 unique participants) were analyzed. The mean (standard deviation [SD]) participant age was 73.8 (7.8) years. Using L2-regularized logistic regression, the mean receiver operating characteristic (ROC) area under the curve (AUC) (SD) in Model 0 (basic demographic characteristics) was 0.67 (0.01). Classification performance was similar in Model 1 (basic demographic characteristics and Mini Mental State Examination [MMSE] subscores) and Model 2 (demographic characteristics and blood test results) with a cross-validated mean ROC AUC (SD) of 0.70 (0.01) for both. Model 3 (demographic characteristics, blood test results, MMSE subscores) and Model 4 (Model 3 and ApoE4 phenotype) showed improved performance with a mean ROC AUC (SD) of 0.73 (0.01) and 0.76 (0.01), respectively. In models using blood test results, thyroid-stimulating hormone and mean corpuscular volume tended to be the largest contributors to classification. Classification performances were similar using the SVM and Elastic Net algorithms.

CONCLUSIONS

The machine learning models used in this study were useful for classifying PET Aβ-positivity using data from routine physician visits.

TRIAL REGISTRATION

UMIN Clinical Trials Registry (UMIN000051776, registered on 31/08/2023).

Targeting early tau pathology: probiotic diet enhances cognitive function and reduces inflammation in a preclinical Alzheimer's model

BACKGROUND

Alzheimer's disease (AD) remains incurable, yet its long prodromal phase offers a crucial window for early intervention. Pretangle tau, a precursor to neurofibrillary tangles, plays a key role in early AD pathogenesis. Intervening in pretangle tau pathology could significantly delay the progression of AD. The gut-brain axis, increasingly recognized as a contributor to AD, represents a promising therapeutic target due to its role in regulating neuroinflammation and neurodegeneration. While probiotics have shown cognitive benefits in amyloid-centered AD models, their effect on pretangle tau pathology remains elusive.

METHODS

This study evaluates the effects of probiotics in a rat model of preclinical AD, specifically targeting hyperphosphorylated pretangle tau in the locus coeruleus. TH-CRE rats (N = 47; 24 females and 23 males) received either AAV carrying pseudophosphorylated human tau (htauE14) or a control virus at 3 months of age. Probiotic or control diets were administered at 9-12 months, with blood and fecal samples collected for ELISA and 16S rRNA gene sequencing. Behavioral assessments were conducted at 13-14 months, followed by analysis of brain inflammation, blood-brain barrier integrity, and GSK-3β activation.

RESULTS

Rats expressing pseudophosphorylated tau displayed impairment in spatial Y-maze (F1,39 = 4.228, p = 0.046), spontaneous object location (F1,39 = 6.240, p = 0.017), and olfactory discrimination (F1,39 = 7.521, p = 0.009) tests. Phosphorylation of tau at S262 (t3 = -4.834) and S356 (t3 = -3.258) in the locus coeruleus was parallelled by GSK-3β activation in the hippocampus (F1,24 = 10.530, p = 0.003). Probiotic supplementation increased gut microbiome diversity (F1,31 = 8.065, p = 0.007) and improved bacterial composition (F1,31 = 3.4867, p = 0.001). The enhancement in gut microbiomes was associated with enhanced spatial learning (p < 0.05), reduced inflammation indexed by Iba-1 (F1,25 = 5.284, p = 0.030) and CD-68 (F1,26 = 8.441, p = 0.007) expression, and inhibited GSK-3β in female rats (p < 0.01 compared to control females).

CONCLUSIONS

This study underscores the potential of probiotics to modulate the gut-brain axis and mitigate pretangle tau-related pathology in preclinical AD. Probiotic supplementation could offer a novel early intervention strategy for AD, highlighting the pivotal role of gut health in neurodegeneration.

Investigating the Therapeutic Mechanisms of Total Saikosaponins in Alzheimer's Disease: A Metabolomic and Proteomic Approach

Alzheimer's disease (AD) is the leading cause of dementia among the elderly, yet effective treatments remain elusive. Total saikosaponins (TSS), the primary bioactive components in Bupleurum chinense, have shown promising therapeutic effects against AD in previous studies. Methods: To delve deeper into the mechanisms underlying the therapeutic role of TSS in AD, we investigated its neuroprotective effects and associated molecular mechanisms in APP/PS1 mice. Further, we employed metabolomic and proteomic analyses, with a focus on the potential protein-level changes induced by TSS, particularly those related to metabolite accumulation in the brain. Results: Our results showed that lysophosphatidylcholine, adenosine, and sphingomyelin in plasma might serve as potential biomarkers. Compared to the control group, AD mice exhibited significantly increased expression of proteins related to neuroinflammatory pathways, whereas proteins involved in cAMP signaling, cGMP-PKG signaling, and synaptic plasticity pathways were significantly downregulated. Notably, these signaling pathways were partially reversed in APP/PS1 mice following TSS administration. Behavioral tests demonstrated that TSS effectively improved the learning and memory functions of mice. Conclusions: Our findings suggest that TSS ameliorate cognitive decline through regulating neuroinflammatory pathways, cAMP and cGMP signaling, and synaptic plasticity pathways, providing insights into its therapeutic potential in AD.

Phytomedicine Potential of Oroxylum indicum Root and Its Constituents: Targeting Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative condition characterized by a gradual decline in cognitive function, for which few effective treatments exist. This study investigated the neuroprotective potential of Oroxylum indicum root extract and its key constituents (baicalein, chrysin, oroxylin A) against AD hallmarks. The extract and its constituents exhibited antioxidant activity in the DPPH assay. They inhibited β-amyloid aggregation as measured by the thioflavin T assay and acetylcholinesterase activity using the Ellman method. In cell culture models, O. indicum extract showed an ability to protect neurons from the toxic effects of H2O2. Western blot analysis revealed the extract and its major active component, baicalein, downregulated pro-apoptotic markers (cleaved caspase-3, and BAX) upon H2O2 exposure. Furthermore, they reduced the expression of amyloidogenic proteins (BACE1) and phosphorylated tau. These findings suggest that O. indicum root extract, particularly baicalein, possesses multifaceted neuroprotective properties, targeting various aspects of AD pathogenesis, including oxidative stress, cholinergic dysfunction, β-amyloid formation, aggregation, and apoptosis. O. indicum root thus warrants further investigation as a promising source of therapeutic agents for AD.

Microglial lipid phosphatase SHIP1 limits complement-mediated synaptic pruning in the healthy developing hippocampus

The gene inositol polyphosphate-5-phosphatase D (INPP5D), which encodes the lipid phosphatase SH2-containing inositol polyphosphate 5-phosphatase 1 (SHIP1), is associated with the risk of Alzheimer's disease (AD). How it influences microglial function and brain physiology is unclear. Here, we showed that SHIP1 was enriched in early stages of healthy brain development. By combining in vivo loss-of-function approaches and proteomics, we discovered that mice conditionally lacking microglial SHIP1 displayed increased complement and synapse loss in the early postnatal brain. SHIP1-deficient microglia showed altered transcriptional signatures and abnormal synaptic pruning that was dependent on the complement system. Mice exhibited cognitive defects in adulthood only when microglial SHIP1 was depleted early postnatally but not at later stages. Induced pluripotent stem cell (iPSC)-derived microglia lacking SHIP1 also showed increased engulfment of synaptic structures. These findings suggest that SHIP1 is essential for proper microglia-mediated synapse remodeling in the healthy developing brain. Disrupting this process has lasting behavioral effects and may be linked to vulnerability to neurodegeneration.

Lipid droplets in central nervous system and functional profiles of brain cells containing lipid droplets in various diseases

Lipid droplets (LDs), serving as the convergence point of energy metabolism and multiple signaling pathways, have garnered increasing attention in recent years. Different cell types within the central nervous system (CNS) can regulate energy metabolism to generate or degrade LDs in response to diverse pathological stimuli. This article provides a comprehensive review on the composition of LDs in CNS, their generation and degradation processes, their interaction mechanisms with mitochondria, the distribution among different cell types, and the roles played by these cells-particularly microglia and astrocytes-in various prevalent neurological disorders. Additionally, we also emphasize the paradoxical role of LDs in post-cerebral ischemia inflammation and explore potential underlying mechanisms, aiming to identify novel therapeutic targets for this disease.

CEST imaging combined with 1H-MRS reveal the neuroprotective effects of riluzole by improving neurotransmitter imbalances in Alzheimer's disease mice

BACKGROUND

The imbalance of glutamate (Glu) and gamma-aminobutyric acid (GABA) neurotransmitter system plays a crucial role in the pathogenesis of Alzheimer's disease (AD). Riluzole is a Glu modulator originally approved for amyotrophic lateral sclerosis that has shown potential neuroprotective effects in various neurodegenerative disorders. However, whether riluzole can improve Glu and GABA homeostasis in AD brain and its related mechanism of action remain unknown. This study utilized chemical exchange saturation transfer (CEST) imaging combined with proton magnetic resonance spectroscopy (1H-MRS) to monitor the dynamic changes of Glu and GABA in riluzole-treated AD mice, aiming to evaluate the efficacy and mechanism of riluzole in AD treatment.

METHODS

GluCEST, GABACEST and 1H-MRS were used to longitudinally monitor Glu and GABA levels in 3xTg AD mice treated with riluzole (12.5 mg/kg/day) or vehicle for 20 weeks. Magnetic resonance measurements were performed at baseline, 6, 12, and 20 weeks post-treatment. Cognitive performance was assessed using the Morris Water Maze (MWM) at baseline, 10, and 20 weeks. At the study endpoint, immunohistochemistry, Nissl staining, and Western blot were used to evaluate the brain pathology, neuronal survival, and protein expression.

RESULTS

GluCEST, GABACEST and 1H-MRS consistently revealed higher levels of Glu and GABA in the brain of riluzole-treated AD mice compared to untreated controls, which were associated with improvements in spatial learning and memory. The cognitive improvements significantly correlated with the increased GluCEST signals and Glu levels. Immunohistochemistry and Nissl staining demonstrated that riluzole treatment reduced amyloid-beta (Aβ) deposition, tau hyperphosphorylation, GFAP-positive astrocyte activation, and prevented neuronal loss. Moreover, riluzole upregulated the expression of excitatory amino acid transporter 2 (EAAT2), glutamic acid decarboxylase 65/67 (GAD65/67), and glutamine synthetase (GS), suggesting enhanced neurotransmitter metabolism.

CONCLUSIONS

CEST imaging combined with 1H-MRS demonstrated the effectiveness of riluzole in modulating Glu- and GABA-related changes and improving cognitive function in 3xTg AD mice, potentially through regulating key proteins involved in neurotransmitter metabolism. These findings suggest riluzole as a therapeutic agent for Alzheimer's disease and highlight the utility of multimodal MR imaging in monitoring treatment response and exploring disease mechanisms.

Waste clearance shapes aging brain health

Brain health is intimately connected to fluid flow dynamics that cleanse the brain of potentially harmful waste material. This system is regulated by vascular dynamics, the maintenance of perivascular spaces, neural activity during sleep, and lymphatic drainage in the meningeal layers. However, aging can impinge on each of these layers of regulation, leading to impaired brain cleansing and the emergence of various age-associated neurological disorders, including Alzheimer's and Parkinson's diseases. Understanding the intricacies of fluid flow regulation in the brain and how this becomes altered with age could reveal new targets and therapeutic strategies to tackle age-associated neurological decline.

Proteostasis as a fundamental principle of Tau immunotherapy

The microtubule-associated protein Tau is a driver of neuronal dysfunction in Alzheimer's disease and other tauopathies. In this process, Tau initially undergoes subtle changes to its abundance, subcellular localization and a vast array of post-translational modifications including phosphorylation that progressively result in the protein's somatodendritic accumulation and dysregulation of multiple Tau-dependent cellular processes. Given the various loss- and gain-of-functions of Tau in disease and the brain-wide changes in the proteome that characterize tauopathies, we asked whether targeting Tau would restore the alterations in proteostasis observed in disease. Therefore, by phage display, we generated a novel pan-Tau antibody, RNJ1, that preferentially binds human Tau and neutralizes proteopathic seeding activity in multiple cell lines and benchmarked it against a clinically tested pan-Tau antibody, HJ8.5 (murine version of tilavonemab). We then evaluated both antibodies, alone and in combination, in the K3 tauopathy mouse model, showing reduced Tau pathology and improvements in neuronal function following 14 weekly treatments, without obtaining synergy for the combination. These effects were more pronounced in female mice. To investigate the molecular mechanisms contributing to improvements in neuronal function, we employed quantitative proteomics, phosphoproteomics and kinase prediction analysis to first establish alterations in K3 mice relative to wild-type controls at the proteome level. In female K3 mice, we found 342 differentially abundant proteins, which are predominantly involved in metabolic and microtubule-associated processes, strengthening previously reported findings of defects in several functional domains in multiple tauopathy models. We next asked whether antibody-mediated Tau target engagement indirectly affects levels of deregulated proteins in the K3 model. Importantly, both immunotherapies, in particular RNJ1, induced abundance shifts towards a restoration to wild-type levels (proteostasis). A total of 257 of 342 (∼75%) proteins altered in K3 were closer in abundance to wild-type levels after RNJ1 treatment, and 73% after HJ8.5 treatment. However, the magnitude of these changes was less pronounced than that observed with RNJ1. Furthermore, analysis of the phosphoproteome showed an even stronger restoration effect with RNJ1, with ∼82% of altered phosphopeptides in K3 showing a shift to wild-type levels, and 75% with HJ8.5. Gene set over-representation analysis further confirmed that proteins undergoing restoration are involved in biological pathways affected in K3 mice. Together, our study suggests that a Tau immunotherapy-induced restoration of proteostasis links target engagement and treatment efficacy.

Microbiota-derived lysophosphatidylcholine alleviates Alzheimer's disease pathology via suppressing ferroptosis

Alzheimer's disease (AD) is a pervasive neurodegenerative disorder, and new approaches for its prevention and therapy are critically needed. Here, we elucidate a gut-microbiome-brain axis that offers actionable perspectives for achieving this objective. Using the 5xFAD mouse model, we identify increased Clostridium abundance and decreased Bacteroides abundance as key features associated with β-amyloid (Aβ) burden. Treatment with Bacteroides ovatus, or its associated metabolite lysophosphatidylcholine (LPC), significantly reduces Aβ load and ameliorates cognitive impairment. Mechanistically, LPC acts through the orphan receptor GPR119, inhibiting ACSL4 expression, thereby suppressing ferroptosis and ameliorating AD pathologies. Analysis of fecal and serum samples from individuals with AD also reveals diminished levels of Bacteroides and LPC. This study thus identifies a B.ovatus-triggered pathway regulating AD pathologies and indicates that the use of single gut microbiota, metabolite, or small molecule compound may complement current prevention and treatment approaches for AD.

Penetratin and Mannose-Functionalized Cannabidiol Lipid Nanoparticles Encapsulating the BDNF Gene Reduce Amyloid-Induced Inflammation

Inflammation is emerging as a critical player in the disease progression of Alzheimer's disease (AD) by its interaction with amyloid beta plaques in a feed-forward loop. There is also a decline in the nourishment and enriching neurotrophic factor, brain-derived neurotrophic factor (BDNF), in the brain. Therefore, supplementing the brain with BDNF by gene delivery and delivering the anti-inflammatory agent, cannabidiol (CBD) in this case, to mitigate inflammation-induced disease cascade offers an attractive treatment strategy. To achieve the brain localization of CBD and pBDNF, lipid nanoparticles (LNPs) functionalized with mannose and penetratin were utilized. CBD and pBDNF were successfully encapsulated in the LNPs (more than 80%) with a size less than 180 nm, polydispersity index less than 0.25, and zeta potential of 23 mV. CBD was released from the formulation over a period of a week. The dual-functionalized LNPs demonstrated higher cellular uptake of CBD and expressed a significantly higher amount of BDNF (p-value <0.05) after transfection than their nonmodified counterparts in four brain cell lines, i.e., brain endothelial cells (b.END3), immortalized microglia cells (IMGs), primary astrocytes, and primary neurons. Similarly, the permeation of CBD through the dual-modified LNPs across the in vitro coculture blood-brain barrier model was significantly higher (p-value <0.05) compared to free CBD or nonfunctionalized nanoparticles. The LNPs demonstrated anti-inflammatory activity against lipopolysaccharides and human amyloid beta1-42 oligomer induction as they reduced the protein and mRNA expression of pro-inflammatory cytokines TNF-α (p < 0.05) and IL-1β (p < 0.05) in IMG cells. In summary, the penetratin and mannose-functionalized LNPs encapsulating CBD and pBDNF could serve as a promising therapy in AD, requiring further validation in animal models.

Synthesis and preclinical evaluation of diarylamine derivative as Tau-PET radiotracer for Alzheimer's Disease

The presence of aggregated Tau in the brain is a dominant pathological hallmark of Tauopathies, particularly in Alzheimer's disease (AD). Therefore, developing ligands that can specifically and sensitively bind to Tau aggregates is essential for diagnosing and monitoring therapeutic interventions. In this study, we further investigated the structural optimization of the diarylamine skeleton, which exhibited promising binding characteristics and biological properties. We supplementarily explored the effects of the number and position of nitrogen atoms, types of heteroatoms and aromatic moieties, and radioactive positions on affinity for Tau. Through a structure-activity relationship (SAR) analysis based on 125I-labeled diarylamine derivatives, [125I]A6 was identified as a lead compound due to its desirable binding properties and ability to penetrate the brain, making it suitable for conversion into a18F-labeled PET tracer. Satisfactorily, [18F]FA1 fulfilled critical requirements as a Tau radiotracer, demonstrating high specificity and selectivity for Tau, a clean off-target profile against Aβ plaques and monoamine oxidase B (MAO-B), and favorable in vivo brain kinetics, as confirmed by dynamic PET studies in rodents and non-human primates.

Roles of the Receptor for Advanced Glycation End Products and Its Ligands in the Pathogenesis of Alzheimer's Disease

The Receptor for Advanced Glycation End Products (RAGE), part of the immunoglobulin superfamily, plays a significant role in various essential functions under both normal and pathological conditions, especially in the progression of Alzheimer's disease (AD). RAGE engages with several damage-associated molecular patterns (DAMPs), including advanced glycation end products (AGEs), beta-amyloid peptide (Aβ), high mobility group box 1 (HMGB1), and S100 calcium-binding proteins. This interaction impairs the brain's ability to clear Aβ, resulting in increased Aβ accumulation, neuronal injury, and mitochondrial dysfunction. This further promotes inflammatory responses and oxidative stress, ultimately leading to a range of age-related diseases. Given RAGE's significant role in AD, inhibitors that target RAGE and its ligands hold promise as new strategies for treating AD, offering new possibilities for alleviating and treating this serious neurodegenerative disease. This article reviews the various pathogenic mechanisms of AD and summarizes the literature on the interaction between RAGE and its ligands in various AD-related pathological processes, with a particular focus on the evidence and mechanisms by which RAGE interactions with AGEs, HMGB1, Aβ, and S100 proteins induce cognitive impairment in AD. Furthermore, the article discusses the principles of action of RAGE inhibitors and inhibitors targeting RAGE-ligand interactions, along with relevant clinical trials.

Microglia depletion reduces human neuronal APOE4-related pathologies in a chimeric Alzheimer's disease model

Despite strong evidence supporting the important roles of both apolipoprotein E4 (APOE4) and microglia in Alzheimer's disease (AD) pathogenesis, the effects of microglia on neuronal APOE4-related AD pathogenesis remain elusive. To examine such effects, we utilized microglial depletion in a chimeric model with induced pluripotent stem cell (iPSC)-derived human neurons in mouse hippocampus. Specifically, we transplanted homozygous APOE4, isogenic APOE3, and APOE-knockout (APOE-KO) iPSC-derived human neurons into the hippocampus of human APOE3 or APOE4 knockin mice and then depleted microglia in half of the chimeric mice. We found that both neuronal APOE and microglial presence were important for the formation of Aβ and tau pathologies in an APOE isoform-dependent manner (APOE4 > APOE3). Single-cell RNA sequencing analysis identified two pro-inflammatory microglial subtypes with elevated MHC-II gene expression enriched in chimeric mice with human APOE4 neuron transplants. These findings highlight the concerted roles of neuronal APOE, especially APOE4, and microglia in AD pathogenesis.

Linking activation of synaptic NMDA receptors-induced CREB signaling to brief exposure of cortical neurons to oligomeric amyloid-beta peptide

Amyloid-beta peptide oligomers (AβO) have been considered "primum movens" for a cascade of events that ultimately cause selective neuronal death in Alzheimer's disease (AD). However, initial events triggered by AβO have not been clearly defined. Synaptic (Syn) N-methyl-d-aspartate receptors (NMDAR) are known to activate cAMP response element-binding protein (CREB), a transcriptional factor involved in gene expression related to cell survival, memory formation and synaptic plasticity, whereas activation of extrasynaptic (ESyn) NMDARs was linked to excitotoxic events. In AD brain, CREB phosphorylation/activation was shown to be altered, along with dyshomeostasis of intracellular Ca2+ (Ca2+ i). Thus, in this work, we analyze acute/early and long-term AβO-mediated changes in CREB activation involving Syn or ESyn NMDARs in mature rat cortical neurons. Our findings show that acute AβO exposure produce early increase in phosphorylated CREB, reflecting CREB activity, in a process occurring through Syn NMDAR-mediated Ca2+ influx. Data also demonstrate that AβO long-term (24 h) exposure compromises synaptic function related to Ca2+-dependent CREB phosphorylation/activation and nuclear CREB levels and related target genes, namely Bdnf, Gadd45γ, and Btg2. Data suggest a dual effect of AβO following early or prolonged exposure in mature cortical neurons through the activation of the CREB signaling pathway, linked to the activation of Syn NMDARs.

Imino and Thioureidic Derivatives as New Tools for Alzheimer's Disease: Preliminary Studies

Alzheimer's disease is a neurodegenerative chronic disease with a severe social and economic impact in the societies, which still lacks an efficient therapy. Several pathophysiological events (β-amyloid [Aβ] deposits, τ-protein aggregation, loss of cholinergic activity, and oxidative stress) occurs in the progression of the disease. Therefore, the search for efficient multi-targeted agents for the treatment of Alzheimer's disease becomes indispensable. In this paper we evaluated the AChE inhibition by Ellman's method and antioxidant activity by DPPH assay of nine synthetic compounds: two hydroxy-benzene derivatives (1 and 2), three bis-thioureidic derivatives (3-5), two imidazole derivatives (6 and 7), and two phenylacetamide derivatives (8 and 9). The compound 2, (3s,5s,7s)-adamantan-1-yl 4-(((E)-2,5-dihydroxybenzylidene)amino)benzoate, exhibited the best antioxidant activity (30.00 ± 1.05 μM eq Trolox) and compound 4 showed the highest AChE inhibition value (IC50 [μM] 8.40 ± 0.32). In the search for a compound showing combined activities (antioxidant and AChE inhibition), the compound 4, octane-1,8-diyl-bis-S-amidinothiourea dihydrobromide, (19.02 ± 1.52 μM eq Trolox; IC50 [μM] 8.40 ± 0.32) was chosen to carry out a molecular docking study. The results showed that compound 4 has the ability to bind the active site of acetylcholinesterase with considerable affinity (estimated binding energies of -8.5 kcal/mol). All data indicate that compound 4 has the potential to be further investigated as a possible candidate in the Alzheimer's disease treatment.

Clinical-grade human dental pulp stem cells improve adult hippocampal neural regeneration and cognitive deficits in Alzheimer's disease

Background: Disrupted hippocampal functions and progressive neuronal loss represent significant challenges in the treatment of Alzheimer's disease (AD). How to achieve the improvement of pathological progression and effective neural regeneration to ameliorate the intracerebral dysfunctional environment and cognitive impairment is the goal of the current AD therapy. Methods: We examined the therapeutic potential of clinical-grade human derived dental pulp stem cells (hDPSCs) in cognitive function and neuropathology in AD. Specifically, we investigated the effect of neural crest-specific derived hDPSCs on endogenous neural regeneration and long-term efficacy following a single transplantation in the triple-transgenic mouse model (3xTg-AD). Results: Our research demonstrated that a single administration of clinical-grade hDPSCs yielded dramatic short-term therapeutic benefits (5 weeks) and sustained partial efficacy (6 months) with respect to improving cognitive impairment and delaying typical pathological progression in 3xTg-AD mice. Intriguingly, exogenous hDPSCs were robustly self-differentiated into newborn functional neurons in the hippocampus of 3xTg-AD mice. The foremost evidence is provided that hDPSCs promote endogenic neural regeneration by enhancing the activation of the Wnt/β-catenin pathway, which may contribute to stabilizing the hippocampal neural network to reverse memory deficits. Conclusion: These findings highlight the multifunctional potential of hDPSCs in AD treatment, which enhances cognition through alleviating neuropathology and providing neural regenerative driving force. Understanding these multiplicity effects is critical to advancing the clinical translation of stem cell-based therapies for AD.

Novel donepezil-tacrine hybrid (TAHB3) induces neurodifferentiation, neuroprotective effects, and activates the PI3K/AKT pathway on PC12 cells

Background

Alzheimer's disease (AD) is a neurodegenerative disease characterized by the impairment of cognitive functions and neuronal loss. AD has no cure; current treatments like acetylcholinesterase inhibitors (AChEI) alleviate symptoms but do not halt disease progression.

Objective

We aimed to evaluate the effects and mechanisms of two novel AChEI hybrid compounds (TAHB3 and TA8Amino), regarding cytotoxicity, neuroprotection and neurodifferentiation in PC12 cells.

Methods

The effects of TAHB3 and TA8Amino on neurodifferentiation were analyzed on PC12 cells which were treated with AChEI compounds for seven days, following morphological, and quantitative analyses to calculate the differentiation percentages, neurite length, and protein expression. Regarding cytotoxicity and neuroprotection assays, PC12 cells were differentiated into mature neurons, then treated with TAHB3 or TA8Amino, following a posttreatment with H2O2 (an inducer of oxidative damage); the analyses were performed using the XTT assay and flow cytometry.

Results

The hybrid compound TAHB3 induced differentiation of PC12 cells, but TA8Amino did not cause the same effect. Both compounds did not show cytotoxic effects to PC12 cells and did not change the cell cycle progression, nor induce cell death. Only TAHB3 showed neuroprotective potential against induced-oxidative damage, and TAHB3 increased the levels of p-AKT, suggesting its action through the activation of the PI3K/AKT pathway.

Conclusions

Our results showed that TAHB3 can induce neurodifferentiation, besides a neuroprotective activity, indicating the potential of AChEI hybrid compounds as novel candidates to be explored for the establishment of novel therapeutic strategies for patients with AD.

Transethnic analysis identifies SORL1 variants and haplotypes protective against Alzheimer's disease

INTRODUCTION

The SORL1 locus exhibits protective effects against Alzheimer's disease (AD) across ancestries, yet systematic studies in diverse populations are sparse.

METHODS

Logistic regression identified AD-associated SORL1 haplotypes in East Asian (N = 5249) and European (N = 8588) populations. Association analysis between SORL1 haplotypes and AD-associated traits or plasma biomarkers was conducted. The effects of non-synonymous mutations were assessed in cell-based systems.

RESULTS

Protective SORL1 variants/haplotypes were identified in the East Asian and European populations. Haplotype Hap_A showed a strong protective effect against AD in East Asians, linked to less severe AD phenotypes, higher SORL1 transcript levels, and plasma proteomic changes. A missense variant within Hap_A, rs2282647-C allele, was linked to a lower risk of AD and decreased expression of a truncated SORL1 protein isoform.

DISCUSSION

Our transethnic analysis revealed key SORL1 haplotypes that exert protective effects against AD, suggesting mechanisms of the protective role of SORL1 in AD.

HIGHLIGHTS

We examined the AD-protective mechanisms of SORL1 in the general population across diverse ancestral backgrounds by jointly analyzing data from three East Asian cohorts (ie, mainland China, Hong Kong, and Japan) and a European cohort. Comparative analysis unveiled key ethnic-specific SORL1 genetic variants and haplotypes. Among these, the SORL1 minor haplotype, Hap_A, emerged as the primary AD-protective factor in East Asians. Hap_A exerts significant AD-protective effects in both APOE ε4 carriers and non-carriers. SORL1 haplotype Hap_A is associated with cognitive function, brain volume, and the activity of specific neuronal and immune-related pathways closely connected to AD risk. Protective variants within Hap_A are linked to increased SORL1 expression in human tissues. We identified an isoform-specific missense variant in Hap_A that modifies the function and levels of a truncated SORL1 protein isoform that is poorly investigated.

Adverse outcome pathway of Alzheimer's disease-like changes resulting from autophagy flux blockade after MC-LR exposure

Microcystins (MCs) pollution is a worldwide environmental issue concerning about human health. Microcystin-leucine-arginine (MC-LR), the most common type of MCs produced by cyanobacteria, could enter the brain and bring about damage to the nervous system. Up to date, it is not clear about the mechanism of MC-LR-induced neurotoxicity. Amyloid-β (Aβ) deposits are hallmark of Alzheimer's disease (AD). In this study, we revealed that MC-LR exposure at environment-related doses (1, 7.5, 15 μg/L) could promote Aβ accumulation in mouse brain. Mechanically, we firstly found that Aβ accumulation is closely associated with abnormal Aβ degradation due to autophagy flux blockade and lysosome dysfunctions in neurons after MC-LR exposure. Moreover, an adverse outcome pathway (AOP) framework oriented to neurotoxicity of MC-LR was conducted in this study. MC-LR inhibited the activity of protein phosphatase 2A (PP2A) in neurons, which is regarded as a molecular initiating event (MIE). In addition, the abnormalities in autophagy were observed after MC-LR exposure. The hindered autophagosome-lysosome fusion and disrupted lysosomal function were key events (KEs) after MC-LR exposure, which contributed to proteostasis dysregulation, ultimately leading to Aβ abnormal degradation and learning deficits as adverse outcomes (AO) of neurotoxicity. This study provided novel information about MC-LR neurotoxicity and new insights into understanding the mechanisms underlying the environmental chemicals-induced neurodegeneration diseases, which has deep implications for public health.

Melatonin: A potential nighttime guardian against Alzheimer's

In the context of the escalating global health challenge posed by Alzheimer's disease (AD), this comprehensive review considers the potential of melatonin in both preventive and therapeutic capacities. As a naturally occurring hormone and robust antioxidant, accumulating evidence suggests melatonin is a compelling candidate to consider in the context of AD-related pathologies. The review considers several mechanisms, including potential effects on amyloid-beta and pathologic tau burden, antioxidant defense, immune modulation, and regulation of circadian rhythms. Despite its promise, several gaps need to be addressed prior to clinical translation. These include conducting additional randomized clinical trials in patients with or at risk for AD dementia, determining optimal dosage and timing, and further determining potential side effects, particularly of long-term use. This review consolidates existing knowledge, identifies gaps, and suggests directions for future research to better understand the potential of melatonin for neuroprotection and disease mitigation within the landscape of AD.

Recent advances in discovery and functional analysis of the small proteins and microRNA expressed by polyomaviruses

The polyomavirus family consists of a highly diverse group of small DNA viruses isolated from various species, including humans. Some family members have been used as model systems to understand the fundamentals of modern biology. After the discovery of the first two human polyomaviruses (JC virus and BK virus) during the early 1970s, their current number reached 14 today. Some family members cause considerably severe human diseases, including polyomavirus-associated nephropathy (PVAN), progressive multifocal leukoencephalopathy (PML), trichodysplasia spinulosa (TS) and Merkel cell carcinoma (MCC). Polyomaviruses encode universal regulatory and structural proteins, but some members express additional virus-specific proteins and microRNA, which significantly contribute to the viral biology, cell transformation, and perhaps progression of the disease that they are associated with. In the current review, we summarized the recent advances in discovery, and functional and structural analysis of those viral proteins and microRNA.

Excessive Alcohol Use as a Risk Factor for Alzheimer's Disease: Epidemiological and Preclinical Evidence

Alcohol use has recently emerged as a modifiable risk factor for Alzheimer's disease (AD). However, the neurobiological mechanisms by which alcohol interacts with AD pathogenesis remain poorly understood. In this chapter, we review the epidemiological and preclinical support for the interaction between alcohol use and AD. We hypothesize that alcohol use increases the rate of accumulation of specific AD-relevant pathologies during the prodromal phase and exacerbates dementia onset and progression. We find that alcohol consumption rates are increasing in adolescence, middle age, and aging populations. In tandem, rates of AD are also on the rise, potentially as a result of this increased alcohol use throughout the lifespan. We then review the biological processes in common between alcohol use disorder and AD as a means to uncover potential mechanisms by which they interact; these include oxidative stress, neuroimmune function, metabolism, pathogenic tauopathy development and spread, and neuronal excitatory/inhibitory balance (EIB). Finally, we provide some forward-thinking suggestions we believe this field should consider. In particular, the inclusion of alcohol use assessments in longitudinal studies of AD and more preclinical studies on alcohol's impacts using better animal models of late-onset Alzheimer's disease (LOAD).

Therapeutic Potential of Polyphenols in Cellular Reversal of Patho-Mechanisms of Alzheimer's Disease Using In Vitro and In Vivo Models: A Comprehensive Review

Alzheimer's disease (AD) is considered one of the most common neurological conditions associated with memory and cognitive impairment and mainly affects people aged 65 or above. Even with tremendous progress in modern neuroscience, a permanent remedy or cure for this crippling disease is still unattainable. Polyphenols are a group of naturally occurring potent compounds that can modulate the neurodegenerative processes typical of AD. The present comprehensive study has been conducted to find out the preclinical and clinical potential of polyphenols and elucidate their possible mechanisms in managing AD. Additionally, we have reviewed different clinical studies investigating polyphenols as single compounds or cotherapies, including those currently recruiting, completed, terminated, withdrawn, or suspended in AD treatment. Natural polyphenols were systematically screened and identified through electronic databases including Google Scholar, PubMed, and Scopus based on in vitro cell line studies and preclinical data demonstrating their potential for neuroprotection. A total of 63 significant polyphenols were identified. A multimechanistic pathway for polyphenol's mode of action has been proposed in the study. Out of 63, four potent polyphenols have been identified as promising potential candidates, based on their reported clinical efficacy. Polyphenols hold tremendous scope for the development of a future drug molecule as a phytopharmaceutical that may be incorporated as an adjuvant to the therapeutic regime. However, more high-quality studies with novel delivery methods and combinatorial approaches are required to overcome obstacles such as bioavailability and blood-brain barrier crossing to underscore the therapeutic potential of these compounds in AD management.