Alzheimer's Disease Samples Research Articles

Identification of novel risk genes for Alzheimer’s disease by integrating genetics from hippocampus

Alzheimer’s disease (AD) stands as the most prevalent neurodegenerative ailment, presently lacking a definitive cure. Given that primary medications for AD patients in the early or middle stages demonstrate optimal efficacy, it becomes crucial to delve into the identification of risk genes associated with early onset. In our study, we compiled and integrated three transcriptomics datasets (GSE48350, GSE36980, GSE5281) originating from the hippocampus of 37 AD patients and 66 healthy controls (CTR) for comprehensive bioinformatics analysis. Comparative analysis with CTR revealed 25 up-regulated genes and 291 down-regulated genes in AD. Those down-regulated genes were notably enriched in processes related to the transmission and transport of synaptic signals. Intriguingly, 27 differentially expressed genes implicated in AD were also correlated with the Braak stage, establishing a connection with various immune cell types that exhibit differences in AD, including cytotoxic T cells, neutrophils, CD4 T cells, Th1, Th2, and Tfh. Significantly, a Cox model, constructed using nine feature genes, effectively stratified AD samples (HR = 2.72, 95% CI 1.94 ~ 3.81, P = 3.6e–10), highlighting their promising potential for risk assessment. In conclusion, our investigation sheds light on novel genes intricately linked to the onset and progression of AD, offering potential biomarkers for the early detection of this debilitating condition. This study contributes valuable insights toward enhancing the strategies for preventing and treating AD.

Alterations in Zinc, Copper, and Iron Levels in the Retina and Brain of Alzheimer's Disease Patients and the APP/PS1 Mouse Model.

Transition metals like copper, iron, and zinc are vital for normal central nervous system function and are also linked to neurodegeneration, particularly in the onset and progression of Alzheimer's disease (AD). Their alterations in AD, identified prior to amyloid plaque aggregation, offer a unique target for staging pre-amyloid AD. However, analysing their levels in the brain is extremely challenging, necessitating the development of alternative approaches. Here, we utilised laser ablation-inductively coupled plasma-mass spectrometry and solution nebulisation-inductively coupled plasma-mass spectrometry to quantitatively measure Cu, Fe, and Zn concentrations in the retina and hippocampus samples obtained from human donors (i.e., AD and healthy controls), and in the APP/PS1 mouse model of AD, and Wild Type controls, aged 9 and 18 months. Our findings revealed significantly elevated Cu, Fe, and Zn levels in the retina (*p < 0.05, **p < 0.01, ***p < 0.001) and hippocampus (*p < 0.05, *p < 0.05, *p < 0.05) of human AD samples compared to healthy controls. Conversely, APP/PS1 mouse models exhibited notably lower metal levels in the same regions compared to WT mice, Cu, Fe, and Zn levels in the retina (**p < 0.01, *p < 0.05, *p < 0.05) and hippocampus (**p < 0.01, **p < 0.01, *p < 0.05). The contrasting metal profiles in human and mouse samples, yet similar patterns within each species' retina and brain, suggest the retina mirrors cerebral metal dyshomeostasis in AD. Our findings lay the groundwork for staging pre-AD pathophysiology through assessment of transition metal levels in the retina.

Heparin-enriched plasma proteome is significantly altered in Alzheimer’s disease

IntroductionHeparin binding proteins (HBPs) with roles in extracellular matrix assembly are strongly correlated to β-amyloid (Aβ) and tau pathology in Alzheimer’s disease (AD) brain and cerebrospinal fluid (CSF). However, it remains challenging to detect these proteins in plasma using standard mass spectrometry-based proteomic approaches.MethodsWe employed heparin-affinity chromatography, followed by off-line fractionation and tandem mass tag mass spectrometry (TMT-MS), to enrich HBPs from plasma obtained from AD (n = 62) and control (n = 47) samples. These profiles were then correlated to Aβ, tau and phosphorylated tau (pTau) CSF biomarkers and plasma pTau181 from the same individuals, as well as a consensus brain proteome network to assess the overlap with AD brain pathophysiology.ResultsHeparin enrichment from plasma was highly reproducible, enriched well-known HBPs like APOE and thrombin, and depleted high-abundant proteins such as albumin. A total of 2865 proteins, spanning 10 orders of magnitude in abundance, were measured across 109 samples. Compared to the consensus AD brain protein co-expression network, we observed that specific plasma proteins exhibited consistent direction of change in both brain and plasma, whereas others displayed divergent changes, highlighting the complex interplay between the two compartments. Elevated proteins in AD plasma, when compared to controls, included members of the matrisome module in brain that accumulate with Aβ deposits, such as SMOC1, SMOC2, SPON1, MDK, OLFML3, FRZB, GPNMB, and the APOE4 proteoform. Additionally, heparin-enriched proteins in plasma demonstrated significant correlations with conventional AD CSF biomarkers, including Aβ, total tau, pTau, and plasma pTau181. A panel of five plasma proteins classified AD from control individuals with an area under the curve (AUC) of 0.85. When combined with plasma pTau181, the panel significantly improved the classification performance of pTau181 alone, increasing the AUC from 0.93 to 0.98. This suggests that the heparin-enriched plasma proteome captures additional variance in cognitive dementia beyond what is explained by pTau181.ConclusionThese findings support the utility of a heparin-affinity approach coupled with TMT-MS for enriching amyloid-associated proteins, as well as a wide spectrum of plasma biomarkers that reflect pathological changes in the AD brain.

A scoping review of remote and unsupervised digital cognitive assessments in preclinical Alzheimer's disease.

Subtle cognitive changes in preclinical Alzheimer's disease (AD) are difficult to detect using traditional pen-and-paper neuropsychological assessments. Remote and unsupervised digital assessments can improve scalability, measurement reliability, and ecological validity, enabling the detection and monitoring of subtle cognitive change. Here, we evaluate such tools deployed in preclinical AD samples, defined as cognitively unimpaired individuals with abnormal levels of amyloid-β (Aβ), or Aβ and tau. In this scoping review, we screened 1,680 unique reports for studies using remote and unsupervised cognitive assessment tools in preclinical AD samples; 23 tools were found. We describe each tool's usability, validity, and reported metrics of reliability. Construct and criterion validity according to associations with established neuropsychological assessments and measures of Aβ and tau are reported. With this review, we aim to present a necessary update to a rapidly evolving field, following a previous review by Öhman and colleagues (2021; Alzheimers Dement. Diagn. Assess. Dis. Monit ) and addressing the open questions of feasibility and reliability of remote testing in the target population. We discuss future directions for using remote and unsupervised digital cognitive assessments in preclinical AD and how such tools may be used for longitudinal monitoring of cognitive function, scalable case finding, and individualized prognostics in both clinical trials and healthcare contexts.

Investigation of amyloid‑β peptide production and clearance pathways in different stages of Alzheimer's disease.

Alzheimer's disease (AD) is an age‑related, progressive decline in cognitive ability. Accumulation and deposition of amyloid‑β (Aβ) is still the best‑known cause of AD that worsens over time. It is unclear whether the increase in Aβ production or the inefficiency of the degradation system causes the accumulation of β‑fibrils during AD development. This research investigated Aβ‑producing and clearance pathways in different stages of AD. For this purpose, patients were categorized into four experimental groups: patients with mild cognitive impairment, patients with moderate cognitive decline, patients with very severe cognitive decline, and healthy patients as control. Levels of Aβ‑40, soluble amyloid precursor protein beta (sAPPβ), matrix metalloproteinase‑9 (MMP‑9), matrix metalloproteinase‑3 (MMP‑3), neprilysin (NEP), angiotensin‑converting enzyme (ACE), and insulin‑degrading enzyme (IDE) were determined by ELISA kits and immunoblotting in serum samples. According to the results, the levels of Aβ‑40 and sAPPβ increased in AD patients from an early stage, and levels were maintained in progressive AD stages. MMP‑9 also increased in the early stage, but its content decreased with disease development. MMP‑3 was significantly higher in the three stages of AD compared to the control patients. However, IDE, NEP, and ACE enzymes as clearing systems decreased in all studied AD samples, with their reductions more remarkable in the middle and late stages. The results showed that multiple Aβ‑degrading enzymes such as NEP and IDE in AD patients decline as AD progresses, while Aβ‑40 and sAPPβ increased from the early stage of the disease. Therefore, it could be concluded that detection of the dementia phase is a critical step for therapeutic strategies.

Identification of neutrophil extracellular trap-related genes in Alzheimer's disease based on comprehensive bioinformatics analysis.

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease. There are currently no effective interventions to slow down or prevent the occurrence and progression of AD. Neutrophil extracellular traps (NETs) have been proven to be tightly linked to AD. This project attempted to identify hub genes for AD based on NETs. Gene expression profiles of the training set and validation set were downloaded from the Gene Expression Omnibus (GEO) database, including non-demented (ND) controls and AD samples. NET-related genes (NETRGs) were collected from the literature. Differential analysis identified 21 AD differentially expressed NETRGs (AD-DE-NETRGs) majorly linked to functions such as defense response to bacterium as well as pathways including IL-17 signaling pathway, as evidenced by enrichment analyses of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Protein-protein interaction (PPI) network, Minutia Cylinder-Code (MCC) algorithm, and molecular complex detection (MCODE) algorithm in the CytoHubba plug-in were employed to identify five hub genes (NFKBIA, SOCS3, CCL2, TIMP1, ACTB). Their diagnostic ability was validated in the validation set using receiver operating characteristic (ROC) curves and gene differential expression analysis. A total of 16 miRNAs and 132 lncRNAs were predicted through the mirDIP and ENCORI databases, and a lncRNA-miRNA-mRNA regulatory network was constructed using Cytoscape software. Small molecular compounds such as Benzo(a)pyrene and Copper Sulfate were predicted to target hub genes using the CTD database. This project successfully identified five hub genes, which may serve as potential biomarkers for AD, proffering clues for new therapeutic targets.

Targeting Caspases 3/6 and Cathepsins L/B May Decrease Laminopathy-Induced Apoptosis in Alzheimer's Disease.

Laminopathy is a pathological manifestation observed in Alzheimer's disease (AD), leading to neuronal apoptosis. Our objective was to assess inhibitors of enzymes involved in laminopathy. The mRNA expression of the cathepsins L and B, caspases 3 and 6, lamins b1 and b2, granzymes A and B, and lamins A and C were extracted and analyzed from GSE5281 and GSE28146 datasets. A total of 145 ligands were selected for molecular docking. Subsequently, 10 ns and 100 ns atomistic molecular dynamics (MD) and Martini 3 were performed with NAMD for two selected ligands (PubChem id: 608841 and ChEMBL id: 550872). The mRNA expression level highlighted caspase 6 and lamin A/C upregulation in the hippocampus of the AD samples, in contrast to cathepsin B, lamin b2, and caspase 3. Moreover, there was a strong correlation between the expression level of cathepsin B, lamin A/C, and caspase 6 in the AD group. The MD results suggested molecule with ChEMBL id of 550872 had higher free binding energy, while in longer simulation the molecule with PubChem id of 608841 was suggested to be more stable in complex with the receptor. Our findings suggest that lamins A/C, cathepsins B/L, caspase 6, and lamin B2 are associated with laminopathy as potential factors contributing to apoptosis in AD. We propose that simultaneous inhibition of caspases 6 and cathepsins L may decrease the rate of apoptosis triggered by lamin degradation. Nevertheless, further studies are required to confirm these observations due to the lack of in vivo findings.

Convergence of Accelerated Brain Volume Decline in Normal Aging and Alzheimer's Disease Pathology.

Age represents the largest risk factor for Alzheimer's disease (AD) but is typically treated as a covariate. Still, there are similarities between brain regions affected in AD and those showing accelerated decline in normal aging, suggesting that the distinction between the two might fall on a spectrum. Our goal was to identify regions showing accelerated atrophy across the brain and investigate whether these overlapped with regions involved in AD or where related to amyloid. We used a longitudinal sample of 137 healthy older adults from the Alzheimer's Disease Neuroimaging Initiative (ADNI), who underwent magnetic resonance imaging (MRI). In addition, a total of 79 participants also had longitudinal positron emission tomography (PET) data. We computed linear-mixed effects models for brain regions declining faster than the average to investigate variability in the rate of change. 23 regions displayed a 0.5 standard deviation (SD) above average decline over 2 years. Of these, 52% overlapped with regions showing similar decline in a matched AD sample. Beyond this, the left precuneus, right superior frontal, transverse temporal, and superior temporal sulcus showed accelerated decline. Lastly, atrophy in the precuneus was associated with increased amyloid load. Accelerated decline in normal aging might contribute to the detection of early signs of AD among healthy individuals.

Elucidating the Functional Roles of Long Non-Coding RNAs in Alzheimer's Disease.

Alzheimer's disease (AD) is a multifaceted neurodegenerative disorder characterized by cognitive decline and neuronal loss, representing a most challenging health issue. We present a computational analysis of transcriptomic data of AD tissues vs. healthy controls, focused on the elucidation of functional roles played by long non-coding RNAs (lncRNAs) throughout the AD progression. We first assembled our own lncRNA transcripts from the raw RNA-Seq data generated from 527 samples of the dorsolateral prefrontal cortex, resulting in the identification of 31,574 novel lncRNA genes. Based on co-expression analyses between mRNAs and lncRNAs, a co-expression network was constructed. Maximal subnetworks with dense connections were identified as functional clusters. Pathway enrichment analyses were conducted over mRNAs and lncRNAs in each cluster, which served as the basis for the inference of functional roles played by lncRNAs involved in each of the key steps in an AD development model that we have previously built based on transcriptomic data of protein-encoding genes. Detailed information is presented about the functional roles of lncRNAs in activities related to stress response, reprogrammed metabolism, cell polarity, and development. Our analyses also revealed that lncRNAs have the discerning power to distinguish between AD samples of each stage and healthy controls. This study represents the first of its kind.

Exploring neuron-specific steroid synthesis and DHEAS therapy in Alzheimer's disease

Alzheimer's Disease (AD) is a neurodegenerative disorder characterized by cognitive decline and memory loss. Recent studies have suggested a potential role for steroid synthesis in AD pathology. This study investigated the co-localization of steroidogenic enzymes in neuronal cells, changes in enzyme expression in an AD mouse model, and steroid expressions in human AD samples. Additionally, we conducted a steroidomic metabolomics analysis and evaluated the effects of dehydroepiandrosterone sulfate (DHEAS) treatment in an AD mouse model. Immunofluorescence analysis revealed significant co-localization of cytochrome P450 family 17 subfamily A member 1 (CYP17A1) and steroidogenic acute regulatory protein (StAR) proteins with α-synuclein in presynaptic neurons, suggesting active steroid synthesis in these cells. Conversely, such co-localization was absent in astrocytes. In the AD mouse model, a marked decrease in the expression of steroidogenic enzymes (Cyp11a1, Cyp17a1, Star) was observed, especially in areas with amyloid beta plaque accumulation. Human AD and MS brain tissues showed similar reductions in StAR and CYP17A1 expressions. Steroidomic analysis indicated a downregulation of key steroids in the serum of AD patients. DHEAS treatment in AD mice resulted in improved cognitive function and reduced Aβ accumulation. Our findings indicate a neuron-specific pathway for steroid synthesis, potentially playing a crucial role in AD pathology. The reduction in steroidogenic enzymes and key steroids in AD models and human samples suggests that impaired steroid synthesis is a feature of neurodegenerative diseases. The therapeutic potential of targeting steroid synthesis pathways, as indicated by the positive effects of DHEAS treatment, warrants further investigation.

Nanoscale flow cytometry-based quantification of blood-based extracellular vesicle biomarkers distinguishes MCI and Alzheimer's disease.

Accurate testing for Alzheimer's disease (AD) represents a crucial step for therapeutic advancement. Currently, tests are expensive and require invasive sampling or radiation exposure. We developed a nanoscale flow cytometry (nFC)-based assay of extracellular vesicles (EVs) to screen biomarkers in plasma from mild cognitive impairment (MCI), AD, or controls. Circulating amyloid beta (Aβ), tau, phosphorylated tau (p-tau)181, p-tau231, p-tau217, p-tauS235, ubiquitin, and lysosomal-associated membrane protein 1-positive EVs distinguished AD samples. p-tau181, p-tau217, p-tauS235, and ubiquitin-positive EVs distinguished MCI samples. The most sensitive marker for AD distinction was p-tau231, with an area under the receiver operating characteristic curve (AUC) of 0.96 (sensitivity 0.95/specificity 1.0) improving to an AUC of 0.989 when combined with p-tauS235. This nFC-based assay accurately distinguishes MCI and AD plasma without EV isolation, offering a rapid approach requiring minute sample volumes. Incorporating nFC-based measurements in larger populations and comparison to "gold standard" biomarkers is an exciting next step for developing AD diagnostic tools. Extracellular vesicles represent promising biomarkers of Alzheimer's disease (AD) that can be measured in the peripheral circulation. This study demonstrates the utility of nanoscale flow cytometry for the measurement of circulating extracellular vesicles (EVs) in AD blood samples. Multiple markers including amyloid beta, tau, phosphorylated tau (p-tau)181, p-tau231, p-tau217, and p-tauS235 accurately distinguished AD samples from healthy controls. Future studies should expand blood and cerebrospinal fluid-based EV biomarker development using nanoflow cytometry approaches.

Identification and experimental validation of m7G-related molecular subtypes, immune signature, and feature genes in Alzheimer's disease

BackgroundStudies has shown that N7-methylguanosine (m7G) modification plays a critical role in neurological diseases. However, the exact role and association of m7G with the immune microenvironment in Alzheimer's disease (AD) remain largely unknown and unexplored. MethodsThe study datasets comprised 667 AD samples and 503 control samples selected from eight datasets in the Gene Expression Omnibus database; m7G regulator genes were obtained from previous literature. The AD subtypes were identified by consensus clustering analysis according to m7G regulator genes. The clinical characteristics, immune infiltration, and biological functions of the AD subgroups were evaluated. A combination of different types of machine-learning algorithms were used for the identification of AD genes. We also assessed and validated the diagnostic performance of the identified genes via qRT-PCR, immunofluorescence, and immunohistochemical analyses. ResultsTwo AD distinct subgroups, namely cluster A and cluster B, were identified. Cluster A had poor pathological progression and immune infiltration, representing a high-risk subgroup for AD. The differentially expressed genes of cluster A were enriched in immune and synapse-related pathways, suggesting that these genes probably contribute to AD progression by regulating immune-related pathways. Additionally, five feature genes (AEBP1, CARTPT, AK5, NPTX2, and COPG2IT1) were identified, which were used to construct a nomogram model with good ability to predict AD. The animal experiment analyses further confirmed that these feature genes were associated with AD development. ConclusionTo the best of our knowledge, this is the first study to reveal close correlations among m7G RNA modification, the immune microenvironment, and the pathogenesis of AD. We also identified five feature genes associated with AD, further contributing to our understanding of the underlying mechanisms and potential therapeutic targets for AD.

Plasma pTau181 Predicts Clinical Progression in a Phase 2 Randomized Controlled Trial of the 11β-HSD1 Inhibitor Xanamem® for Mild Alzheimer's Disease.

Blood biomarkers are proposed as a diagnostic alternative to amyloid PET or cerebrospinal fluid (CSF) analyses for the diagnosis of Alzheimer's disease (AD). Relatively little is known of the natural history of patients identified by different blood biomarkers. To identify patients with elevated plasma phosphorylated tau (pTau)181 from a prior Phase 2a trial, and explore the natural histories of their clinical progression, and potential efficacy of Xanamem, a selective inhibitor of 11beta-hydroxysteroid dehydrogenase type 1 (11β-HSD1) in these patients. A prespecified, double-blind analysis was conducted in 72 participants with clinically diagnosed AD and available plasma samples from baseline and Week 12 of the "XanADu" Phase 2a trial of Xanamem versus placebo. The analysis prespecified plasma pTau181 > median to identify patients more likely to have AD ("H", > 6.74 pg/mL, n = 34). Cohen's d (d) of≥0.2 defined potential clinical significance. In the placebo group, H patients showed greater clinical progression compared to L patients (pTau181≤median) on ADCOMS (d = 0.55, p < 0.001), CDR-SB (d = 0.63, p < 0.001), MMSE (d = 0.52, p = 0.12), and ADAS-Cog14 (d = 0.53, p = 0.19). In H patients, a potentially clinically meaningful Xanamem treatment effect compared to placebo was seen in the CDR-SB (LS mean difference 0.6 units, d = 0.41, p = 0.09) and Neuropsychological Test Battery (NTB; LS mean difference 1.8 units, d = 0.26, p = 0.48) but not ADCOMS or ADAS-Cog14. This trial demonstrates that elevated plasma pTau181 identifies participants more likely to have progressive AD and is a suitable method for enrichment in AD clinical trials. Xanamem treatment showed evidence of potential clinically meaningful benefits.

SCG5 and MITF may be novel markers of copper metabolism immunorelevance in Alzheimer’s disease

The slow-developing neurological disorder Alzheimer’s disease (AD) has no recognized etiology. A bioinformatics investigation verified copper metabolism indicators for AD development. GEO contributed AD-related datasets GSE1297 and GSE5281. Differential expression analysis and WGCNA confirmed biomarker candidate genes. Each immune cell type in AD and control samples was scored using single sample gene set enrichment analysis. Receiver Operating Characteristic (ROC) analysis, short Time-series Expression Miner (STEM) grouping, and expression analysis between control and AD samples discovered copper metabolism indicators that impacted AD progression. We test clinical samples and cellular function to ensure study correctness. Biomarker-targeting miRNAs and lncRNAs were predicted by starBase. Trust website anticipated biomarker-targeting transcription factors. In the end, Cytoscape constructed the TF/miRNA-mRNA and lncRNA-miRNA networks. The DGIdb database predicted biomarker-targeted drugs. We identified 57 differentially expressed copper metabolism-related genes (DE-CMRGs). Next, fourteen copper metabolism indicators impacting AD progression were identified: CCK, ATP6V1E1, SYT1, LDHA, PAM, HPRT1, SCG5, ATP6V1D, GOT1, NFKBIA, SPHK1, MITF, BRCA1, and CD38. A TF/miRNA-mRNA regulation network was then established with two miRNAs (hsa-miR-34a-5p and 34c-5p), six TFs (NFKB1, RELA, MYC, HIF1A, JUN, and SP1), and four biomarkers. The DGIdb database contained 171 drugs targeting ten copper metabolism-relevant biomarkers (BRCA1, MITF, NFKBIA, CD38, CCK2, HPRT1, SPHK1, LDHA, SCG5, and SYT1). Copper metabolism biomarkers CCK, ATP6V1E1, SYT1, LDHA, PAM, HPRT1, SCG5, ATP6V1D, GOT1, NFKBIA, SPHK1, MITF, BRCA1, and CD38 alter AD progression, laying the groundwork for disease pathophysiology and novel AD diagnostic and treatment.

IL-1β and CXCR4 as Potential Therapeutic Targets for Alzheimer's Disease.

Alzheimer's Disease (AD) is a highly prevalent form of age-related dementia. However, the underlying mechanisms of AD are largely unexplored. In this study, bioinformatics analysis was performed to identify the possible therapeutic targets for AD. The GEO database was used to screen the Differentially Expressed Genes (DEGs). Enrichment analysis, protein-protein interaction network, and LASSO model analyses were successfully performed. Furthermore, an ELISA assay was also conducted to determine the expression of principal genes within the AD and control samples. A total of 416 differentially expressed genes (DEGs) were recognized based on the GSE48350 and GSE28146 datasets. The IL-1β and CXCR4 levels were markedly elevated in the AD samples relative to the control. The IL-1β and CXCR4 genes were identified as principal AD-related genes that can be targeted for anti-AD therapy.

Compromised Plasma Membrane Repair Contributes to Neuronal Cell Death and Neurodegeneration During Alzheimer’s Disease

Alzheimer’s Disease (AD) is the most common neurodegenerative disease and involves accumulation of intracellular amyloid beta (Aβ) in the early stages of the disease. Aβ has been shown to compromise neuronal cell membrane integrity by increasing membrane permeability, elevating intracellular calcium concentrations, and Aβ directly penetrating and damaging the neuronal cell membrane. Damage to the cell membrane requires a rapid and effcient repair mechanism to restore the barrier function of the membrane and avoid cell death. Here, we aimed to study the effects of intracellular Aβ on neuronal cell membrane repair. To determine if membrane permeability is compromised in vivo, we stained 6-month FVB and APP/PS1 brain sections with anti-IgG. We observed a significant increase in IgG positivity in the APP/PS1 tissue as compared to the FVB brains. We repeated this with post-mortem frontal lobe tissue and observed a significant increase in IgG-positivity in the AD samples as compared to the non-AD. To assess the effect of neuronal membrane repair in AD patients, we treated mouse neuroblastomas (N2A) and primary mouse hippocampal neurons with non-AD and AD patient cerebrospinal fluid (CSF) at a 1:100 dilution or 1μM recombinant human Aβ42. We conducted laser damage assays and observed a membrane repair defect in these neuronal cell models. We explored the biochemical components of the CSF that may be contributing to this induced repair defect, we measured the Aβ42 by ELISA and stratified Aβ42 concentration by the corresponding CSF AUC. We observed a positive correlation between Aβ42 concentrations and reduced membrane repair capacity. We sought to determine the mechanism of the reduced membrane repair capacity by assessing the expression levels of membrane repair proteins and observed decreased dysferlin in cell models, 6-month APP/PS1 mouse models, and human postmortem tissues with high levels of Aβ. Overexpression of dysferlin in the AD cell models can increase dysferlin expression and restore membrane repair capacity in neurons treated with AD CSF samples or recombinant Aβ42. We have determined this reduction in repair capacity is due to reduced dysferlin expression, and future studies will determine the mechanism leading to dysferlin downregulation. This work was supported by The Ohio State University College of Medicine Dean’s Discovery Grants Program. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

MiR-519a-3p, found to regulate cellular prion protein during Alzheimer's disease pathogenesis, as a biomarker of asymptomatic stages

Clinical relevance of miRNAs as biomarkers is growing due to their stability and detection in biofluids. In this, diagnosis at asymptomatic stages of Alzheimer's disease (AD) remains a challenge since it can only be made at autopsy according to Braak NFT staging. Achieving the objective of detecting AD at early stages would allow possible therapies to be addressed before the onset of cognitive impairment. Many studies have determined that the expression pattern of some miRNAs is dysregulated in AD patients, but to date, none has been correlated with downregulated expression of cellular prion protein (PrPC) during disease progression. That is why, by means of cross studies of miRNAs up-regulated in AD with in silico identification of potential miRNAs-binding to 3′UTR of human PRNP gene, we selected miR-519a-3p for our study. Then, in vitro experiments were carried out in two ways. First, we validated miR-519a-3p target on 3′UTR-PRNP, and second, we analyzed the levels of PrPC expression after using of mimic technology on cell culture. In addition, RT-qPCR was performed to analyzed miR-519a-3p expression in human cerebral samples of AD at different stages of disease evolution. Additionally, samples of other neurodegenerative diseases such as other non-AD tauopathies and several synucleinopathies were included in the study.Our results showed that miR-519a-3p overlaps with PRNP 3′UTR in vitro and promotes downregulation of PrPC. Moreover, miR-519a-3p was found to be up-regulated exclusively in AD samples from stage I to VI, suggesting its potential use as a novel label of preclinical stages of the disease.

The role of olfactory dysfunction in mild cognitive impairment and Alzheimer's disease: A meta-analysis

PurposeThis comprehensive meta-analysis investigates the association between olfactory deficits in mild cognitive impairment (MCI) and Alzheimer's disease (AD). MethodsA thorough search across databases identified articles analyzing olfactory status in MCI or AD patients. Methodological quality assessment followed PRISMA guidelines. Hedges' g effect size statistic computed standard mean differences and 95% confidence intervals. Moderator analysis was conducted. ResultsAmong the included studies (65 for MCI and 61 for AD), odor identification exhibited larger effect sizes compared to odor threshold and discrimination, in both MCI and AD samples. Moderate effect size is found in OI scores in MCI (k = 65, SE = 0.078, CI 95% = [-1.151, -0.844]). Furthermore, compared to MCI, AD had moderate to large heterogeneous effects in olfactory identification (k = 61, g = -2.062, SE = 0.125, CI 95% = [-2.308, -1.816]). Global cognitive status is positively related to olfactory identification impairment in both MCI (k = 57, Z = 2.74, p = 0.006) and AD (k = 53, Z = 5.03, p < 0.0001) samples. ConclusionOlfactory impairments exhibit a notable and substantial presence in MCI. Among these impairments, odor identification experiences the greatest decline in MCI, mirroring the primary sensory deficit observed in AD. Consequently, the incorporation of a straightforward odor identification test is advisable in the evaluation of individuals vulnerable to the onset of AD, offering a practical screening tool for early detection.

Single-cell and spatial transcriptomics reveals that PTPRG activates the m6A methyltransferase VIRMA to block mitophagy-mediated neuronal death in Alzheimer’s disease

Neuronal death is one of the key pathologies in Alzheimer's disease (AD). How neuronal death begins in AD is far from clear, so clarifying this process may help develop effective therapies. This study collected single-cell RNA sequencing data of 85 AD samples and 83 control samples, covering the prefrontal cortex, internal olfactory cortex, superior parietal lobe, superior frontal gyrus, caudal internal olfactory cortex, somatosensory cortex, hippocampus, superior frontal cortex and peripheral blood mononuclear cells. Additionally, spatial transcriptomic data of coronal sections from 6 AppNL-G-F AD mice and 6 control C57Bl/6 J mice were acquired. The main single-cell and spatial transcriptomics results were experimentally validated in wild type and 5 × FAD mice. We found that the microglia subpopulation Mic_PTPRG can communicate with specific types of neurons (especially excitatory ExNeu_PRKN_VIRMA and inhibitory InNeu_PRKN_VIRMA neuronal subpopulations) and cause them to express PTPRG during AD progression. Within neurons, PTPRG binds and upregulates the m6A methyltransferase VIRMA, thus inhibiting translation of PRKN mRNA to prevent the clearance of damaged mitochondria in neurons through suppressing mitophagy. As the disease progresses, the energy and nutrient metabolic pathways in neurons are reprogrammed, leading to their death. Consistently, we determined that PTPTRG can physically interact with VIRMA in mouse brains and PRKN is significantly upregulated in 5 × FAD mouse brain. Altogether, our findings demonstrate that PTPRG activates the m6A methyltransferase VIRMA to block mitophagy-mediated neuronal death in AD, which is a potential pathway, through which microglia and neuronal PTPRG modify neuronal connections in the brain during AD progression.

Unraveling the Role of TREM2 and CD33 in Alzheimer’s Disease

Alzheimer's disease (AD) is a complex neurodegenerative disorder characterized by the accumulation of amyloid plaques and neurofibrillary tangles. This study investigates the role of two key genes, TREM2 and CD33, in AD pathogenesis. Gene expression profiles from human brain samples and transgenic mouse models were analyzed using data from the Gene Expression Omnibus. Differential gene expression analysis revealed significant upregulation of TREM2 and CD33 in AD samples compared to controls. Analysis of KEGG pathway, a database composed of biological pathway maps, showed TREM2 involvement in osteoclast differentiation and CD33 in hematopoietic cell lineage. String database analysis highlighted both genes' roles in regulating tumor necrosis factor production and cytokine production. Furthermore, TREM2 variants in AD patients were examined, identifying six variants (H157Y, R98W, D87N, T66M, Y38C, and Q33X) exclusive to AD samples. The R47H variant showed the strongest correlation with AD (p&lt;0.001). The following SNPs of CD33 were identified as contributors to AD development: rs3826656, rs3865444, and rs12459419. These findings suggest that TREM2 and CD33 play crucial roles in AD progression, potentially through modulation of microglial function and inflammatory responses. These genes may serve as promising targets for developing novel AD therapeutics and biomarkers.