Tau Protein Research Articles

Metabolic and Immune System Dysregulation: Unraveling the Connections between Alzheimer's Disease, Diabetes, Inflammatory Bowel Diseases, and Rheumatoid Arthritis.

Alzheimer's disease (AD), diabetes mellitus (DM), inflammatory bowel diseases (IBD), and rheumatoid arthritis (RA) are chronic conditions affecting millions globally. Despite differing clinical symptoms, these diseases share pathophysiological mechanisms involving metabolic and immune system dysregulation. This paper examines the intricate connections between these disorders, focusing on shared pathways such as insulin resistance, lipid metabolism dysregulation, oxidative stress, and chronic inflammation. An important aspect is the role of amyloid-beta plaques and tau protein tangles, which are hallmark features of AD. These protein aggregates are influenced by metabolic dysfunction and inflammatory processes similar to those seen in DM, RA, and IBD. This manuscript explores how amyloid and tau pathologies may be exacerbated by shared metabolic and immune dysfunction. Additionally, this work discusses the gut-brain axis and the influence of gut microbiota in mediating disease interactions. Understanding these commonalities opens new avenues for multi-targeted therapeutic approaches that address the root causes rather than merely the symptoms of these conditions. This integrative perspective could lead to more effective interventions and improved patient outcomes, emphasizing the importance of a unified approach in managing these interconnected diseases.

DGAE(297‐391) Tau Fragment Promotes Formation of Chronic Traumatic Encephalopathy‐Like Tau Filaments

The microtubule‐associated protein tau forms disease‐specific filamentous aggregates in several different neurodegenerative diseases. In order to understand how tau undergoes misfolding into a specific filament type and to control this process for drug development purposes, it is crucial to study in vitro tau aggregation methods and investigate the structures of the obtained filaments at the atomic level. Here, we used the tau fragment dGAE, which aggregates spontaneously, to seed the formation of full‐length tau filaments. The structures of dGAE and full‐length tau filaments were investigated by magic‐angle spinning (MAS) solid‐state NMR, showing that dGAE allows propagation of a chronic traumatic encephalopathy (CTE)‐like fold to the full‐length tau. The obtained filaments efficiently seeded tau aggregation in HEK293T cells. This work demonstrates that in vitro preparation of disease‐specific types of full‐length tau filaments is feasible.

Chloride intracellular channel 4 blockade improves cognition in mice with Alzheimer's disease: CLIC4 protein expression and tau protein hyperphosphorylation

Numerous academic literature suggests that amyloid-β (Aβ) deposition, tau protein phosphorylation, and irreversible neuronal death are the three major causes of AD. The chloride intracellular channel (CLIC) protein family not only regulates the polarisation of neurons, but also has important implications for neuronal survival. Chloride intracellular channel 4 (CLIC4) can be pathologically activated by cyclin-dependent kinase 5 (Cdk5), which causes a significant increase in the expression of CLIC4 and mediates neuronal apoptosis. CLIC4 knockdown inhibits H2O2-induced neuronal apoptosis; however, the relationship between CLIC4 and AD remains unknown. In the present study, we showed that CLIC4 expression was elevated in the hippocampus of AD mice; knockdown of hippocampal CLIC4 alleviated Aβ25–35-induced cognitive impairment in mice; overexpression of hippocampal CLIC4 accelerated Aβ deposition and tau protein hyperphosphorylation in young AD mice (APP/PS1 mice at three months of age). CLIC4 overexpressing mice had a longer escape latency compared to controls in behavioural testing (Morris water maze and T-maze tests). By Co-immunoprecipitation/mass spectrometry (Co-IP/MS) of HT22 cells to identify proteins that specifically bind to CLIC4, we found interactions with CCAAT enhancer binding protein (C/EBPβ); a critical pathway involved in the development of various neurodegenerative diseases. In addition, the knockdown of hippocampal CLIC4 alleviated AD-like pathology by inhibiting the C/EBPβ/AEP signaling pathway. These data suggest an essential role for high CLIC4 expression in the pathophysiology of AD and reveal that inhibition of CLIC4 expression may provide an opportunity for treatment.

Mechanistic Approach to Immunity and Immunotherapy of Alzheimer's Disease: A Review.

Alzheimer's disease (AD) is a debilitating neurodegenerative condition characterized by progressive cognitive decline and memory loss, affecting millions of people worldwide. Traditional treatments, such as cholinesterase inhibitors and NMDA receptor antagonists, offer limited symptomatic relief without addressing the underlying disease mechanisms. These limitations have driven the development of more potent and effective therapies. Recent advances in immunotherapy present promising avenues for AD treatment. Immunotherapy strategies, including both active and passive approaches, harness the immune system to target and mitigate AD-related pathology. Active immunotherapy stimulates the patient's immune response to produce antibodies against AD-specific antigens, while passive immunotherapy involves administering preformed antibodies or immune cells that specifically target amyloid-β (Aβ) or tau proteins. Monoclonal antibodies, such as aducanumab and lecanemab, have shown potential in reducing Aβ plaques and slowing cognitive decline in clinical trials, despite challenges related to adverse immune responses and the need for precise targeting. This comprehensive review explores the role of the immune system in AD, evaluates the current successes and limitations of immunotherapeutic approaches, and discusses future directions for enhancing the treatment efficacy.

Serum and CSF biomarkers in asymptomatic patients during primary HIV infection: a randomized study.

It is debated whether central nervous system involvement begins during acute HIV infection in persons without meningitis/encephalitis and if specific antiretroviral drugs or combinations would be beneficial. Neurologically asymptomatic participants enrolled in a randomized and controlled study comparing three combination antiretroviral regimens (tenofovir alafenamide/emtricitabine plus dolutegravir, darunavir or both) during primary HIV infection were enrolled. Serum and cerebrospinal fluid (CSF) were collected at baseline, 12 and 48 (serum only) weeks after treatment initiation. Single Molecule Array was used to measure neurofilament light chain (NFL), total tau protein (Tau), Brain-Derived Neurotrophic Factor (BDNF), Glial Fibrillary Acidic Protein (GFAP), Ubiquitin C-terminal Hydrolase (UCH-L1). We assessed the longitudinal change in biomarkers over time as well as the change in the prevalence of serum NFL concentrations above previously published age-adjusted cut-offs (7 pg/mL if 5-18 years, 10 pg/mL if 18-51 years, 15 pg/mL if 51-61 years, 20 pg/mL if 61-70 years and 35 pg/mL if >70 years). Serum was available from 47 participants at all time points while CSF was in 13 and 7 participants (baseline/W12). We observed a significant direct serum-to-CSF correlation for NFL (rho = 0.692, p = 0.009), GFAP (rho = 0.659, p = 0.014) and BDNF (rho = 0.587, p = 0.045). Serum (rho = 0.560, p = 0.046) and CSF NFL (rho = 0.582, p = 0.037) concentrations were directly associated with CSF HIV RNA levels. We observed a significant decrease over time in serum NFL (p = 0.006) and GFAP (p = 0.006) but not in the other biomarkers. No significant difference was observed among the treatment arms. At baseline, serum and CSF age-adjusted NFL levels were above age-adjusted cut-offs in 23 (48.9%) and 4 participants (30.8%); considering serum NFL, this proportion was lower at weeks 12 (31.9%, p = 0.057) and 48 (27.7%, p = 0.13). A relevant proportion of neurologically asymptomatic participants had abnormal CSF and serum NFL levels during primary HIV infection. NFL and GFAP decreased in serum following combination antiretroviral therapy without significant differences among the treatment arms.

Inhibition of Calcineurin with FK506 Reduces Tau Levels and Attenuates Synaptic Impairment Driven by Tau Oligomers in the Hippocampus of Male Mouse Models.

Alzheimer's disease (AD) is the most common age-associated neurodegenerative disorder, characterized by progressive cognitive decline, memory impairment, and structural brain changes, primarily involving Aβ plaques and neurofibrillary tangles of hyperphosphorylated tau protein. Recent research highlights the significance of smaller Aβ and Tau oligomeric aggregates (AβO and TauO, respectively) in synaptic dysfunction and disease progression. Calcineurin (CaN), a key calcium/calmodulin-dependent player in regulating synaptic function in the central nervous system (CNS) is implicated in mediating detrimental effects of AβO on synapses and memory function in AD. This study aims to investigate the specific impact of CaN on both exogenous and endogenous TauO through the acute and chronic inhibition of CaN. We previously demonstrated the protective effect against AD of the immunosuppressant CaN inhibitor, FK506, but its influence on TauO remains unclear. In this study, we explored the short-term effects of acute CaN inhibition on TauO phosphorylation and TauO-induced memory deficits and synaptic dysfunction. Mice received FK506 post-TauO intracerebroventricular injection and TauO levels and phosphorylation were assessed, examining their impact on CaN and GSK-3β. The study investigated FK506 preventive/reversal effects on TauO-induced clustering of CaN and GSK-3β. Memory and synaptic function in TauO-injected mice were evaluated with/without FK506. Chronic FK506 treatment in 3xTgAD mice explored its influence on CaN, Aβ, and Tau levels. This study underscores the significant influence of CaN inhibition on TauO and associated AD pathology, suggesting therapeutic potential in targeting CaN for addressing various aspects of AD onset and progression. These findings provide valuable insights for potential interventions in AD, emphasizing the need for further exploration of CaN-targeted strategies.

MiR-137-3p mechanisms of action and blood-brain barrier penetrating and neuron-targeting lipid nanoparticles deliver miR-137-3p for the treatment of Alzheimer's disease

IntroductionThis study aimed to investigate the impact of miR-137-3p on the pathogenesis of Alzheimer's disease (AD) and develop a pioneering in vivo delivery method for its therapeutic potential. MethodsThis study was initiated by quantifying the levels of miR-137-3p in both human neuroblastoma cells and a mouse model of AD. Our focus was on elucidating its effects on microtubule (MT) stability, tau protein hyperphosphorylation, synaptic damage, and other hallmark features of AD. To circumvent the risks associated with direct brain injections, a novel drug delivery system was engineered, employing lipid nanoparticles (LNPs) functionalized with rabies virus glycoprotein to facilitate the transcytosis of miR-137-3p across the blood-brain barrier and target its delivery directly to neurons. ResultsThe results confirmed miR-137-3p deficiency in both AD cells and animal models. A protective effect of miR-137-3p on MT stability in the AD model was first observed in SH-SY5Y. We validated that the delivery system could effectively penetrate the blood-brain barrier and target neurons, resulting in a significant increase in miR-137-3p levels in the hippocampus of APP/PS1 mice. Glycogen synthase kinase-3 beta expression in the hippocampus of AD mice was inhibited, suggesting successful treatment of AD in this animal model. DiscussionThis study verified a new mechanism of action of miR-137-3p in AD pathogenesis in cells. By developing an LNPs-based miR-137-3p delivery system, this study offers a novel avenue for treating AD, highlighting miR-137-3p as a key factor in AD pathogenesis and its therapeutic application.

Brain resident microglia in Alzheimer's disease: foe or friends.

The neurobiology of Alzheimer's disease (AD) is unclear due to its multifactorial nature. Although a wide range of studies revealed several pathomechanisms of AD, dementia is yet unmanageable with current pharmacotherapies. The recent growing literature illustrates the role of microglia-mediated neuroinflammation in the pathogenesis of AD. Indeed, microglia serve as predominant sentinels of the brain, which diligently monitor the neuroimmune axis by phagocytosis and releasing soluble factors. In the case of AD, microglial cells are involved in synaptic pruning and remodeling by producing inflammatory mediators. The conditional inter-transformation of classical activation (proinflammatory) or alternative activation (anti-inflammatory) microglia is responsible for most brain disorders. In this review, we discussed the role of microglia in neuroinflammatory processes in AD following the accumulation of amyloid-β and tau proteins. We also described the prominent phenotypes of microglia, such as disease-associated microglia (DAM), dark microglia, interferon-responsive microglia (IRMs), human AD microglia (HAMs), and microglial neurodegenerative phenotype (MGnD), which are closely associated with AD incidence. Considering the key role of microglia in AD progression, microglial-based therapeutics may hold promise in mitigating cognitive deficits by addressing the neuroinflammatory responses.

Exploring the Frontier: Antisense Long Non-Coding RNAs as Key Regulators in Alzheimer's Disease.

Alzheimer's Disease (AD) is the most prevalent, costly, and fatal neurodegenerative disorder of this century. Two hallmark features of AD are the anomalous cleavage of amyloid precursor protein (APP), which leads to the accumulation of amyloid-beta (Aβ), and the hyperphosphorylation of tau protein. Despite extensive research efforts, the pathology and pathogenesis of AD remain elusive. Recent investigations have highlighted the close association between antisense long non-coding RNAs (AS-lncRNAs) and various biological and functional aspects of AD. However, many AS-lncRNAs implicated in AD have not yet been comprehensively compiled and discussed. This paper reviews the role of AS-lncRNAs in neurodegenerative diseases, outlines their association with AD, and offers novel insights into the potential applications of antisense RNAs in the diagnosis and treatment of AD.

Long Non-Coding RNA Profile in Genetic Symptomatic and Presymptomatic Frontotemporal Dementia: A GENFI Study.

Long non-coding RNAs (lncRNAs) play crucial roles in gene regulation and are implicated in neurodegenerative diseases, including frontotemporal dementia (FTD). However, their expression patterns and potential as biomarkers in genetic FTD involving Chromosome 9 Open Reading Frame (C9ORF72), Microtubule Associated Protein Tau (MAPT), and Progranulin (GRN) genes are not well understood. This study aimed to profile the expression levels of lncRNAs in peripheral blood mononuclear cells collected within the GENetic Frontotemporal dementia Initiative (GENFI). Fifty-three lncRNAs were analyzed with the OpenArray Custom panel, in 131 patients with mutations in C9ORF72, MAPT, and GRN, including 68 symptomatic mutation carriers (SMC) and 63 presymptomatic mutation carriers (PMC), compared with 40 non-carrier controls (NC). Thirty-eight lncRNAs were detectable; the relative expression of NEAT1 and NORAD was significantly higher in C9ORF72 SMC as compared with NC. GAS5 expression was instead significantly lower in the GRN group versus NC. MAPT carriers showed no significant deregulations. No significant differences were observed in PMC. Disease duration did not correlate with lncRNA expression. NEAT1 and NORAD are upregulated in C9ORF72 SMC and GAS5 levels are downregulated in GRN SMC, underlining lncRNAs' relevance in FTD and their potential for biomarker development. Further validation and mechanistic studies are crucial for clinical implications.

Effects of simulated gas of thermobaric bomb charge explosion on Tau protein phosphorylation and cognitive function in rats

Objective: To explore the effect of simulated gas of thermobaric bomb charge explosion on cognitive function and the related mechanism of damage. Methods: In January 2022, thirty-two SPF rats were selected and randomly divided into control group, exposed group 1, 2 and 3 (the exposure time of the simulated gas of the explosion of the thermobaric bomb charge was 5 min, 10 min and 15 min, respectively) according to random number table method, with 8 rats in each group. The simulated gas of the explosion of the thermobaric bomb charge were CO 0.15%, CO(2) 3%, NO 0.1%, O(2) 15%, and the rest were N(2). After 30 days of exposure, water maze was used to detect the learning and memory function of rats. Golgi staining was used to observe the number distribution and morphological structure of hippocampal neurons in rats. Western blot was used to detect the expression of Tau-5, pSer262, pSer396, pThr181 and pThr231 proteins in rats. Repeated measure ANOVA was used to compare the design data of repeated measure, one-way ANOVA was used for multi-group mean comparison, and LSD method was used for pound-wise comparison. Results: There were significant differences in the results of repeated measurement ANOVA of the water maze localization navigation test (F=80.98, P<0.001), and there was an interaction between the group and the training days (F=2.16, P=0.022). There were significant differences in escape latency of rats at the 2nd, 3rd, 4th and 5th days among all groups (P<0.05). The results of spatial exploration showed that the frequency of rats crossing the platform was significantly different among all groups (F=4.49, P=0.011). The frequency of rats crossing the platform in exposed group 2 and exposed group 3 was lower than that in control group, and the frequency of rats crossing the platform in exposed group 3 was lower than that in exposed group 1 (P<0.05). With the increase of exposure time, the number of hippocampal neurons decreased, and the dendrite spine density of neurons in CA1 region decreased (P<0.05). Compared with the control group, there was no significant difference in the relative expression level of Tau-5 protein in all exposed groups (P>0.05), but the expression level of pSer262 protein was significantly increased (P<0.05). Compared with the control group, the protein expressions of pSer396, pThr181 and pThr231 in exposed group 2 and exposed group 3 were significantly increased (P<0.05) . Conclusion: The simulated gas of the explosion of the thermobaric bomb charge may contribute to the development of cognitive dysfunction by damaging hippocampal neurons with aberrant phosphorylation of Tau proteins.

In Vivo Prevalence of Beta-Amyloid Pathology and Alzheimer's Disease Co-Pathology in Idiopathic Normal-Pressure Hydrocephalus-Association with Neuropsychological Features.

Idiopathic normal-pressure hydrocephalus (iNPH) is a clinic-radiological neurological syndrome presenting with cognitive deficits, gait disturbances and urinary incontinence. It often coexists with Alzheimer's disease (AD). Due to the reversible nature of iNPH when promptly treated, a lot of studies have focused on possible biomarkers, among which are cerebrospinal fluid (CSF) biomarkers. The aim of the present study was to determine the rate of beta-amyloid pathology and AD co-pathology by measuring AD CSF biomarkers, namely, amyloid beta with 42 and 40 amino acids (Aβ42), the Aβ42/Aβ40 ratio, total Tau protein (t-Tau) and phosphorylated Tau protein at threonine 181 (p-Tau), in a cohort of iNPH patients, as well as to investigate the possible associations among CSF biomarkers and iNPH neuropsychological profiles. Fifty-three patients with iNPH were included in the present study. CSF Aβ42, Aβ40, t-Tau and p-Tau were measured in duplicate with double-sandwich ELISA assays. The neuropsychological evaluation consisted of the Mini-Mental State Examination, Frontal Assessment Battery, Five-Word Test and CLOX drawing tests 1 and 2. After statistical analysis, we found that amyloid pathology and AD co-pathology are rather common in iNPH patients and that higher values of t-Tau and p-Tau CSF levels, as well as the existence of the AD CSF profile, are associated with more severe memory impairment in the study patients. In conclusion, our study has confirmed that amyloid pathology and AD-co-pathology are rather common in iNPH patients and that CSF markers of AD pathology and t-Tau are associated with a worse memory decline in these patients.

Dendrimers-Novel Therapeutic Approaches for Alzheimer's Disease.

Dendrimers are covalently bonded globular nanostructures that may be used in the treatment of Alzheimer's disease (AD). Nowadays, AD therapies are focused on improving cognitive functioning and not causal treatment. However, this may change with the use of dendrimers, which are being investigated as a drug-delivery system or as a drug per se. With their ability to inhibit amyloid formation and their anti-tau properties, they are a promising therapeutic option for AD patients. Studies have shown that dendrimers may inhibit amyloid formation in at least two ways: by blocking fibril growth and by breaking already existing fibrils. Neurofibrillary tangles (NFTs) are abnormal filaments built by tau proteins that can be accumulated in the cell, which leads to the loss of cytoskeletal microtubules and tubulin-associated proteins. Cationic phosphorus dendrimers, with their anti-tau properties, can induce the aggregation of tau into amorphous structures. Drug delivery to mitochondria is difficult due to poor transport across biological barriers, such as the inner mitochondrial membrane, which is highly negatively polarized. Dendrimers may be potential nanocarriers and increase mitochondria targeting. Another considered use of dendrimers in AD treatment is as a drug-delivery system, for example, carbamazepine (CBZ) or tacrine. They can also be used to transport siRNA into neuronal tissue and to carry antioxidants and anti-inflammatory drugs to act protectively on the nervous system.

Severe neurodegeneration in brains of transgenic rats producing human tau prions

Both wild-type and mutant tau proteins can misfold into prions and self-propagate in the central nervous system of animals and people. To extend the work of others, we investigated the molecular basis of tau prion–mediated neurodegeneration in transgenic (Tg) rats expressing mutant human tau (P301S); this line of Tg rats is denoted Tg12099. We used the rat Prnp promoter to drive the overexpression of mutant tau (P301S) in the human 0N4R isoform. In Tg12099(+/+) rats homozygous for the transgene, ubiquitous expression of mutant human tau resulted in the progressive accumulation of phosphorylated tau inclusions, including silver-positive tangles in the frontal cortices and limbic system. Signs of central nervous system dysfunction were found in terminal Tg12099(+/+) rats exhibiting severe neurodegeneration and profound atrophy of the amygdala and piriform cortex. The greatest increases in tau prion activity were found in the corticolimbic structures. In contrast to the homozygous Tg12099(+/+) rats, we found lower levels of mutant tau in the hemizygous rats, resulting in few neuropathologic changes up to 2 years of age. Notably, these hemizygous rats could be infected by intracerebral inoculation with recombinant tau fibrils or precipitated tau prions from the brain homogenates of sick, aged homozygous Tg12099(+/+) rats. Our studies argue that the regional propagation of tau prions and neurodegeneration in the Tg12099 rats resembles that found in human primary tauopathies. These findings seem likely to advance our understanding of human tauopathies and may lead to effective therapeutics for Alzheimer’s disease and other tau prion disorders.

A Bioinformatics-Based Study on Methylation Alterations of the FBLN1 Gene in Hippocampal Tissue of Alzheimer's Disease Model DKO and DTG Mice.

Alzheimer's disease (AD) is characterized by progressive cognitive decline and late-stage neurobehavioral issues marked by amyloid-beta plaques and Tau protein tangles. This study aims to investigate Fibulin-1(FBLN1) gene expression in the hippocampal tissue of Presenilin-1/Presenilin-2 conditional double-knockout (DKO) and double-transgenic (DTG) mice, using single-cell sequencing and experimental methods to verify abnormal methylation status and correlation with AD. Genomic DNA from DKO and DTG mice was used for genotyping. Reduced Representation Bisulfite Sequencing (RRBS) identified 10 genes with abnormal methylation changes, with protein-protein interaction (PPI) analysis highlighting five core genes, including FBLN1. Single-cell sequencing, RT-PCR, and Western blotting (WB) were used to analyze FBLN1 mRNA and protein levels in the hippocampal tissues of early-stage and mid-stage AD DKO, DTG, and CBAC57 mice. RRBS identified 10 genes with abnormal methylation, with PPI highlighting five core genes. Single-cell sequencing showed significant FBLN1 expression in AD groups. RT-PCR and WB indicated elevated FBLN1 mRNA and protein levels in mid-stage AD DKO and DTG mice compared to CBAC57 mice, with no differences in early-stage AD DKO and CBAC57 mice. RRBS revealed hypomethylation of the FBLN1 gene in mid-stage AD DKO mice. Elevated FBLN1 expression in AD models suggests an age-dependent neurodegenerative mechanism independent of amyloid-beta deposition. This study enhances our understanding of AD's epigenetic mechanisms, which will aid targeted diagnosis, treatment, and prognosis.

Iron Chelators and Alzheimer's Disease Clinical Trials.

Alzheimer's disease (AD) is a major neurodegenerative disorder impacting millions of people with cognitive impairment and affecting activities of daily living. The deposition of neurofibrillary tangles of hyperphosphorylated tau proteins and accumulation of amyloid-β (Aβ) are the main pathological characteristics of AD. However, the actual causal process of AD is not yet identified. Oxidative stress occurs prior to amyloid Aβ plaque formation and tau phosphorylation in AD. The role of master antioxidant, glutathione, and metal ions (e.g., iron) in AD are the frontline area of AD research. Iron overload in specific brain regions in AD is associated with the rate of cognitive decline. We have presented the outcome from various interventional trials involving iron chelators intended to minimize the iron overload in AD. To date, however, no significant positive outcomes have been reported using iron chelators in AD and warrant further research.

Performance of plasma p-tau217 for the detection of amyloid-β positivity in a memory clinic cohort using an electrochemiluminescence immunoassay

BackgroundPlasma p-tau217 has emerged as the most promising blood-based marker (BBM) for the detection of Alzheimer Disease (AD) pathology, yet few studies have evaluated plasma p-tau217 performance in memory clinic settings. We examined the performance of plasma p-tau217 for the detection of AD using a high-sensitivity immunoassay in individuals undergoing diagnostic lumbar puncture (LP).MethodsPaired plasma and cerebrospinal fluid (CSF) samples were analysed from the TIMC-BRAiN cohort. Amyloid (Aβ) and Tau (T) pathology were classified based on established cut-offs for CSF Aβ42 and CSF p-tau181 respectively. High-sensitivity electrochemiluminescence (ECL) immunoassays were performed on paired plasma/CSF samples for p-tau217, p-tau181, Glial Fibrillary Acidic Protein (GFAP), Neurofilament Light (NfL) and total tau (t-tau). Biomarker performance was evaluated using Receiver-Operating Curve (ROC) and Area-Under-the-Curve (AUC) analysis.ResultsOf 108 participants (age: 69 ± 6.5 years; 54.6% female) with paired samples obtained at time of LP, 64.8% (n = 70/108) had Aβ pathology detected (35 with Mild Cognitive Impairment and 35 with mild dementia). Plasma p-tau217 was over three-fold higher in Aβ + (12.4 pg/mL; 7.3—19.2 pg/mL) vs. Aβ- participants (3.7 pg/mL; 2.8—4.1 pg/mL; Mann–Whitney U = 230, p < 0.001). Plasma p-tau217 exhibited excellent performance for the detection of Aβ pathology (AUC: 0.91; 95% Confidence Interval [95% CI]: 0.86–0.97)—greater than for T pathology (AUC: 0.83; 95% CI: 0.75–0.90; z = 1.75, p = 0.04). Plasma p-tau217 outperformed plasma p-tau181 for the detection of Aβ pathology (z = 3.24, p < 0.001). Of the other BBMs, only plasma GFAP significantly differed by Aβ status which significantly correlated with plasma p-tau217 in Aβ + (but not in Aβ-) individuals. Application of a two-point threshold at 95% and 97.5% sensitivities & specificities may have enabled avoidance of LP in 58–68% of cases.ConclusionsPlasma p-tau217 measured using a high-sensitivity ECL immunoassay demonstrated excellent performance for detection of Aβ pathology in a real-world memory clinic cohort. Moving forward, clinical use of plasma p-tau217 to detect AD pathology may substantially reduce need for confirmatory diagnostic testing for AD pathology with diagnostic LP in specialist memory services.

Exploring Novel GSK-3β Inhibitors for Anti-Neuroinflammatory and Neuroprotective Effects: Synthesis, Crystallography, Computational Analysis, and Biological Evaluation.

In the pathogenesis of Alzheimer's disease, the overexpression of glycogen synthase kinase-3β (GSK-3β) stands out due to its multifaced nature, as it contributes to the promotion of amyloid β and tau protein accumulation, as well as neuroinflammatory processes. Therefore, in the present study, we have designed, synthesized, and evaluated a new series of GSK-3β inhibitors based on the N-(pyridin-2-yl)cyclopropanecarboxamide scaffold. We identified compound 36, demonstrating an IC50 of 70 nM against GSK-3β. Subsequently, through crystallography studies and quantum mechanical analysis, we elucidated its binding mode and identified the structural features crucial for interactions with the active site of GSK-3β, thereby understanding its inhibitory potency. Compound 36 was effective in the cellular model of hyperphosphorylated tau-induced neurodegeneration, where it restored cell viability after okadaic acid treatment and showed anti-inflammatory activity in the LPS model, significantly reducing NO, IL-6, and TNF-α release. In ADME-tox in vitro studies, we confirmed the beneficial profile of 36, including high permeability in PAMPA (Pe equals 9.4) and high metabolic stability in HLMs as well as lack of significant interactions with isoforms of the CYP enzymes and lack of considerable cytotoxicity on selected cell lines (IC50 > 100 μM on HT-22 cells and 89.3 μM on BV-2 cells). Based on promising pharmacological activities and favorable ADME-tox properties, compound 36 may be considered a promising candidate for in vivo research as well as constitute a reliable starting point for further studies.

Phosphoryl group wires stabilize pathological tau fibrils as revealed by multiple quantum spin counting NMR.

Hyperphosphorylation of the protein tau is one of the biomarkers of neurodegenerative diseases in the category of tauopathies. However, the molecular level, mechanistic, role of this common post-translational modification (PTM) in enhancing or reducing the aggregation propensity of tau is unclear, especially considering that combinatorial phosphorylation of multiple sites can have complex, non-additive, effects on tau protein aggregation. Since tau proteins stack in register and parallel to elongate into pathological fibrils, phosphoryl groups from adjacent tau strands with 4.8 Å separation must find an energetically favorable spatial arrangement. At first glance, this appears to be an unfavorable configuration due to the proximity of negative charges between phosphate groups from adjacent neighboring tau fibrils. However, this study tests a counterhypothesis that phosphoryl groups within the fibril core-forming segments favorably assemble into highly ordered, hydrogen-bonded, one-dimensionally extended wires under biologically relevant conditions. We selected two phosphorylation sites associated with neurodegeneration, serine 305 (S305p) and tyrosine 310 (Y310p), on a model tau peptide jR2R3-P301L (tau295-313) spanning the R2/R3 splice junction of tau, that readily aggregate into a fibril with characteristics of a seed-competent mini prion. Using multiple quantum spin counting (MQ-SC) by 31P solid-state NMR of phosphorylated jR2R3-P301L tau peptide fibrils, enhanced by dynamic nuclear polarization, we find that at least six phosphorous spins must neatly arrange in 1D within fibrils or in 2D within a protofibril to yield the experimentally observed MQ-coherence orders of four. We found that S305p stabilizes the tau fibrils and leads to more seeding-competent fibrils compared to jR2R3 P301L or Y310p. This study introduces a new concept that phosphorylation of residues within a core forming tau segment can mechanically facilitate fibril registry and stability due a hitherto unrecognized role of phosphoryl groups to form highly ordered, extended, 1D wires that stabilize pathological tau fibrils.

Proteomics of plasma-derived extracellular vesicles reveals S100A8 as a novel biomarker for Alzheimer's disease: A preliminary study

Extracellular vesicles (EVs) act as mediators for intercellular transfer of Aβ and tau proteins, promoting the propagation of these pathological misfolded proteins throughout the brain in Alzheimer's disease (AD). Levels of blood exosomal Aβ42, total Tau (t-Tau) and phosphorylated Tau (p-Tau) had a high correlation with their concentrations in cerebrospinal fluid (CSF), demonstrating that exosomal biomarkers have equal contribution as those in CSF for the diagnosis of AD. We aimed to comprehensively characterize the proteome of plasma-derived EVs to identify differentially expressed proteins (DEPs) and pathways in AD. Tandem mass tag (TMT) labeled quantitative proteomics was applied to analyze plasma-derived EV proteins in 9 AD patients and 9 healthy controls. 335 proteins were quantified, and 12 DEPs were identified including seven upregulated proteins and five down-regulated proteins. Oligomerized Aβ1–42 induced SH-SY5Y cell damage model was built to mimic the pathological changes of AD, and small interfering RNA (siRNA) against S100A8 was used to knock down S100A8 expression. Results displayed S100A8 was down regulated in plasma-derived EVs from AD patients, while enriched in EVs derived from Aβ1–42-induced SH-SY5Y cells. Furthermore, Aβ1–42-induced SH-SY5Y cells treated with S100A8 siRNA showed decreased Aβ levels in cell lysate and EVs, especially in EVs. SignificanceThe investigation aimed to comprehensively characterize the proteome of plasma-derived EVs to identify DEPs and potential biomarker of AD. S100A8 was found down regulated in plasma-derived EVs from AD patients using TMT labeled quantitative proteomics. The diagnostic value of S100A8 was also confirmed using receiver operating characteristic curve (ROC) analysis. Furthermore, Aβ1–42-induced SH-SY5Y cells treated with S100A8 siRNA showed decreased Aβ levels in cell lysate and EVs, especially in EVs. The preliminary findings suggest that suppression of S100A8 expression inhibits Aβ aggregation both in cell lysate and EVs from Aβ1–42-induced SH-SY5Y cells, and S100A8 more likely regulates Aβ aggregation via EVs. Therefore, plasma-derived EV S100A8 might be a potential biomarker of AD. Manipulation of S100A8 expression may be a novel therapeutic strategy in the treatment of AD.