Tau protein kinases: involvement in Alzheimer's disease

Identification of a novel pyrrolo[2,3-b]pyridine compound as a potent glycogen synthase kinase 3β inhibitor for treating Alzheimer's disease

Herein, a novel pyrrolo[2,3-b]pyridine-based glycogen synthase kinase 3β (GSK-3β) inhibitor, S01, was rationally designed and synthesised to target Alzheimer's disease (AD). S01 inhibited GSK-3β, with an IC50 of 0.35 ± 0.06 nM, and had an acceptable kinase selectivity for 24 structurally similar kinases. Western blotting assays indicated that S01 efficiently increased the expression of p-GSK-3β-Ser9 and decreased p-tau-Ser396 levels in a dose-dependent manner. In vitro cell experiments, S01 showed low cytotoxicity to SH-SY5Y cells, significantly upregulated the expression of β-catenin and neurogenesis-related biomarkers, and effectively promoted the outgrowth of differentiated neuronal neurites. Moreover, S01 substantially ameliorated dyskinesia in AlCl3-induced zebrafish AD models at a concentration of 0.12 μM, which was more potent than Donepezil (8 μM) under identical conditions. Acute toxicity experiments further confirmed the safety of S01 in vivo. Our findings suggested that S01 is a prospective GSK-3β inhibitor and can be tested as a candidate for treating AD.

Differential roles of human tau isoforms in the modulation of inflammation and development of neuropathology

Alzheimer's disease (AD) is the most common tauopathy characterized by progressive accumulation of Aß and tau neuropathology. Tau is expressed in two major isoforms containing either 3 or 4C-terminal repeats, 3R and 4R. Despite tau isoforms occurring in roughly equimolar ratios in AD, the majority of research focus in developed mouse and in vitro models focus only on 4Rtau. To generate a more complete model of AD tauopathy and understand specific tau isoform-mediated neuropathology and neurodegeneration, we generated a transgenic mouse line expressing both 3Rtau and 4Rtau and determined how this impacted the timing and severity of neuropathological and behavioral changes.

METHODS

3Rtau-tg and 4Rtau-tg mice were crossed to generate 3R/4Rtau-tg bigenic mice. At 3, 6, and 9 months of age, mice were assessed for behavior, neuropathology and RNA expression.

RESULTS

3R/4Rtau bigenic mice expressed increased tau and phosphorylated tau in the hippocampus and cortex compared to single (3R or 4R) transgenic cohorts as early as 3-months of age and this was accompanied with increased astrogliosis and microglial activation. Bigenic mice had significantly greater behavioral deficits compared to either single transgenic littermates in spatial learning and memory as well as nest building, indicative of depression and/or cognitive deficits.

CONCLUSION

This new mouse model of tauopathy more completely recapitulates the pattern, severity and accumulation of tau and associated neuropathology and behavioral changes observed in human tauopathies such as AD. 3R/4Rtau-tg bigenic mice should supplant existing single transgenic tau models for general validation of therapeutic targets and investigations of novel therapies on tauopathy endpoints.

Contributions of major tau kinase activation and phospho-tau accumulation to cortical and hippocampal tangle formation and cognition in older adults

Aberrant activation of tau kinases (tauK) has been proposed as a major step in tau hyperphosphorylation and misfolding, and subsequent formation of neurofibrillary tangles (NFT) in Alzheimer's disease (AD). However, evidence of tauK hyperactivation in actual AD brains is scarce and inconsistent, and their role in age-related cognitive decline remains undocumented. We evaluated activated/inhibited species of CDK5/p35/p25, GSK3α/β, and ERK1/2 as well as ten tau/phospho-tau (ptau) peptides (mapping Ser202, Thr217, Ser262, Ser305, and Ser404 phospho-residues) by Western blot or selected reaction monitoring proteomics, respectively, in postmortem dorsolateral prefrontal cortex (DLPFC) and hippocampal samples of 150 participants from the Rush Memory and Aging Project (MAP). Regression models and mediation analyses assessed the contributions of these variables to tau phosphorylation, NFT deposition and antemortem cognitive status of MAP participants. Surprisingly, greater p25 and p35 (indices for CDK5 activation) and lower pSer21/9-GSK3α/β (inhibited species) immunodensities were associated with lower ptau peptide amounts. Individuals with higher p25 cortical densities displayed better cognitive outcomes, particularly working memory. Statistical mediation analyses indicated that the beneficial effect of CDK5/p25 on cognition was mediated by lower densities of phospho-Thr217-tau and NFT deposition in DLPFC, and also identified Thr217 and Ser262 as the ptau sites with greatest influence in both NFT accumulation and cognitive impairment. The present data suggest that tau hyperphosphorylation, tangle deposition, and the subsequent cognitive impairment do not rely on aberrant activation of major tauKs. Additionally, novel evidence was provided for the beneficial contribution of cortical CDK5/p25 to the maintenance of working memory.

Hyperphosphorylated tau-based Alzheimer's Disease drug discovery: Identification of inhibitors of tau aggregation and cytotoxicity

Alzheimer's disease (AD) is a neurodegenerative disorder that affects more than 30 million people worldwide. Underlying the progressive decline of cognitive functions are the neurofibrillary tangles (NFTs) in neurons of the brain. The spatiotemporal distribution of NFTs predicts the progression of cognitive symptoms. In contrast, the senile plaques of amyloid-β aggregates, another major biomarker for AD, do not correlate with the clinical symptom development, consistent with the negligible benefits to cognitive functions in patients receiving anti-Aβ immunotherapies. A new drug discovery avenue targeting tau pathologies is therefore urgently needed. Using a recombinant hyperphosphorylated tau (p-tau) that presents characters key to the disease, e.g., formation of neurotoxic aggregates, we conducted a fluorescence p-tau aggregation assay and completed a 100K-compound high-throughput screen (HTS) and identified inhibitors of p-tau aggregation and cytotoxicity. This dual functional screen resulted in several potent compounds that effectively curbed both p-tau aggregation and cytotoxicity. Results presented in this work are the first HTS for small-molecule compounds that target the cellular toxicity of hyperphosphorylated tau. Top hits found in this screen and their analogues to be developed in the near future may lead to breakthroughs in the therapeutic development for Alzheimer's disease and other neurodegenerative tauopathies.

Glucose starvation induces tau phosphorylation leading to cellular stress response in fission yeast

Misfolded tau proteins and their accumulation cause many neurodegenerative diseases named tauopathies. While phosphorylation is required for tau protein activity, hyperphosphorylation leads to pathological conditions. Previous reports have shown that glucose deprivation might influence tau protein formation and phosphorylation in vivo, though its effect on cellular stress pathways in a yeast model has not been documented. In this study, we examined the various cellular processes, including oxidative and ER stress responses, glucose metabolism, autophagy, 20 S proteasomal activity, and glucose consumption in Schizosaccharomyces pombe cells heterologously expressing the human MAPT gene, which we obtained in our previous study. We observed increased levels of MAPT gene expression, phosphorylated tau protein (sites at Thr181, Thr231, and Ser396), and phosphorylated GSK-3β (site at Tyr216; contributes to tau phosphorylation) under glucose starvation conditions. The presence of tau protein led to increased expression levels of genes related to oxidative stress response and ER stress in fission yeast. Glucose-starved yeast expressing tau showed higher proteasomal activity and autophagy than control cells in normal glucose conditions. Additionally, cells containing tau protein exhibited higher glucose consumption under nutrient starvation conditions than those lacking tau. These findings indicate a possible relationship between increased tau protein phosphorylation and glucose metabolism, supporting the connection among tauopathies, poorly regulated blood sugar, and diabetes; thus, this provides initial evidence that S. pombe yeast can serve as a model for research in this area.

Cellular and molecular mechanisms of pathological tau phosphorylation in traumatic brain injury: implications for chronic traumatic encephalopathy

Tau protein plays a critical role in the physiological functioning of the central nervous system by providing structural integrity to the cytoskeletal architecture of neurons and glia through microtubule assembly and stabilization. Under certain pathological conditions, tau is aberrantly phosphorylated and aggregates into neurotoxic fibrillary tangles. The aggregation and cell-to-cell propagation of pathological tau leads to the progressive deterioration of the nervous system. The clinical entity of traumatic brain injury (TBI) ranges from mild to severe and can promote tau aggregation by inducing cellular mechanisms and signalling pathways that increase tau phosphorylation and aggregation. Chronic traumatic encephalopathy (CTE), which is a consequence of repetitive TBI, is a unique tauopathy characterized by pathological tau aggregates located at the depths of the sulci and surrounding blood vessels. The mechanisms leading to increased tau phosphorylation and aggregation in CTE remain to be fully defined but are likely the result of the primary and secondary injury sequelae associated with TBI. The primary injury includes physical and mechanical damage resulting from the head impact and accompanying forces that cause blood-brain barrier disruption and axonal shearing, which primes the central nervous system to be more vulnerable to the subsequent secondary injury mechanisms. A complex interplay of neuroinflammation, oxidative stress, excitotoxicity, and mitochondrial dysfunction activate kinase and cell death pathways, increasing tau phosphorylation, aggregation and neurodegeneration. In this review, we explore the most recent insights into the mechanisms of tau phosphorylation associated with TBI and propose how multiple cellular pathways converge on tau phosphorylation, which may contribute to CTE progression.

Diverse influences on tau aggregation and implications for disease progression

Tau is an intrinsically disordered protein that accumulates in fibrillar aggregates in neurodegenerative diseases. The misfolding of tau can be understood as an equilibrium between different states and their propensity to form higher-order fibers, which is affected by several factors. First, modulation of the biochemical state of tau due to ionic conditions, post-translational modifications, cofactors, and interacting molecules or assemblies can affect the formation and structure of tau fibrils. Second, cellular processes impact tau aggregation through modulating stability, clearance, disaggregation, and transport. Third, through interactions with glial cells, the neuronal microenvironment can affect intraneuronal conditions with impacts on tau fibrilization and toxicity. Importantly, tau fibrils propagate through the brain via a "prion-like" manner, contributing to disease progression. This review highlights the biochemical and cellular pathways that modulate tau aggregation and discusses implications for pathobiology and tau-directed therapeutic approaches.

Discovery of effective GSK-3β inhibitors as therapeutic potential against Alzheimer's disease: A computational drug design insight

Alzheimer's disease (AD) is mostly thought to be caused by overactivity of glycogen synthase kinase 3-beta (GSK3-β). Therefore, a GSK-3β inhibitor may be a suggested medicine for Alzheimer's therapy. Nowadays, computational techniques are thought to be among the quickest and most affordable options for therapeutic design and drug discovery. Following a preliminary screening of flavonoids for possible protection against cognitive illnesses such as Alzheimer's, Amentoflavone, Curcumin, and Notopterol were shown to be promising candidates. Using molecular docking, the ligand orientation and binding energy in the ATP-binding pocket of GSK-3β were ascertained. Amentoflavone formed a hydrogen bond with the GSK-3β protein's ATP binding site during the molecular docking phase, obtaining the highest negative binding energy. However, when the results moved closer to a molecular dynamics simulation, the findings changed, and Curcumin was shown to be the most potent inhibitor. All structures remained stable during the MD simulation of the GSK-3β protein and its ligands. Moreover, compared to other natural compounds, Curcumin showed higher binding free energy. Therefore, Curcumin may be useful as a polyphenolic flavonoid in the prevention and treatment of AD. Hence, additional research in vitro and in vivo can focus on these flavonoid compounds as an alternative treatment.

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

BACKGROUND AND PURPOSE

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

EXPERIMENTAL APPROACH

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

KEY RESULTS

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

CONCLUSION AND IMPLICATIONS

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

Going beyond ATP binding site as a novel inhibitor design strategy for tau protein kinases in the treatment of Alzheimer's disease: A review

Alzheimer's disease (AD) is among the top mortality causing diseases worldwide. The presence of extracellular β-amyloidosis, as well as intraneuronal neurofibrillary aggregates of the abnormally hyperphosphorylated tau protein are two major characteristics of AD. Targeting protein kinases that are involved in the disease pathways has been a common approach in the fight against AD. Unfortunately, most kinase inhibitors currently available target the adenosine triphosphate (ATP)- binding site, which has proven unsuccessful due to issues with selectivity and resistance. As a result, a pressing need to find other alternative sites beyond the ATP- binding site has profoundly evolved. In this review, we will showcase some case studies of inhibitors of tau protein kinases acting beyond ATP binding site which have shown promising results in alleviating AD.

Advancing Nanomaterial-Based Strategies for Alzheimer's Disease: A Perspective

Alzheimer's disease (AD) is a complex neurodegenerative disorder and the most common cause of dementia. By 2050, the number of AD cases is projected to exceed 131 million, placing significant strain on healthcare systems and economies worldwide. The pathogenesis of AD is multifactorial, involving hypotheses/mechanisms, such as amyloid-β (Aβ) plaques, tau protein hyperphosphorylation, cholinergic neuron damage, oxidative stress, and inflammation. Despite extensive research, the complexity of these potentially entangled mechanisms has hindered the development of treatments that can reverse disease progression. Nanotechnology, leveraging the unique physical, electrical, magnetic, and optical properties of nanomaterials, has emerged as a promising approach for AD treatment. In this Perspective, we first outlined the major current pathogenic hypotheses of AD and then reviewed recent advances in nanomaterials in addressing these hypotheses. We have also discussed the challenges in translating nanomaterials into clinical applications and proposed future directions, particularly the development of multifunctional and multitarget nanomaterials, to enhance their therapeutic efficacy and clinical applicability in AD treatment.

Role of saturated fatty acid metabolism in posttranslational modifications of the Tau protein

The relationship between metabolic alterations induced by the consumption of a high-fat diet (HFD) and the risk of developing neurodegenerative diseases such as Alzheimer's disease (AD) has been extensively studied. In particular, the induction of neuronal insulin resistance, endoplasmic reticulum stress, and the production of reactive oxygen species by chronic exposure to high concentrations of saturated fatty acids (sFAs), such as palmitic acid (PA), have been proposed as the cellular and molecular mechanisms underlying cognitive decline. Lipid metabolism affects many processes critical for cellular homeostasis. However, questions remain as to whether neuronal exposure to high sFA levels contributes to the onset and progression of AD features, and how their metabolism plays a role in this process. Therefore, the aim of this work is to review the accumulated evidence for the potential mechanisms by which the neuronal metabolism of sFAs affects signaling pathways that may induce biochemical changes in the AD hallmark protein Tau, ultimately promoting its aggregation and the subsequent generation of neurofibrillary tangles. In particular, the data presented here provide evidence that PA-dependent metabolic stress results in an imbalance in the activities of protein kinases and deacetylases that potentially contribute to the post-translational modifications (PTMs) of Tau.

Review on pathogenesis and treatment of Alzheimer's disease

The rising incidence of Alzheimer's disease (AD) and the associated economic impacts has prompted a global focus in the field. In recent years, there has been a growing understanding of the pathogenic mechanisms of AD, including the aggregation of β-amyloid, hyperphosphorylated tau, and neuroinflammation. These processes collectively lead to neurodegeneration and cognitive decline, which ultimately results in the loss of autonomy in patients. Currently, there are three main types of AD treatments: clinical tools, pharmacological treatment, and material interventions. This review provides a comprehensive analysis of the underlying etiology and pathogenesis of AD, as well as an overview of the current prevalence of AD treatments. We believe this article can help deepen our understanding of the AD mechanism, and facilitate the clinical translation of scientific research or therapies, to address this global problem of AD.

Molecular Motors in Myelination and Their Misregulation in Disease

Molecular motors are cellular components involved in the intracellular transport of organelles and materials to ensure cell homeostasis. This is particularly relevant in neurons, where the synaptic components synthesized in the soma need to travel over long distances to their destination. They can walk on microtubules (kinesins and dyneins) or actin filaments (myosins), the major components of cell cytoskeleton. While kinesins mostly perform the anterograde transport of intracellular components toward the plus ends of microtubules located distally in cell processes, cytoplasmic dyneins allow the retrograde flux of intracellular cargo toward the minus ends of microtubules located at the cell soma. Axon myelination represents a major aspect of neuronal maturation and is essential for neuronal function, as it speeds up the transmission of electrical signals. Increasing evidence supports a role for molecular motors in the homeostatic control of myelination. This role includes the trafficking of myelin components along the processes of myelinating cells and local regulation of pathways that ensure axon wrapping. Dysfunctional control of the intracellular transport machinery has therefore been linked to several brain pathologies, including demyelinating diseases. These disorders include a broad spectrum of conditions characterized by pathological demyelination of axons within the nervous system, ultimately leading to axonal degeneration and neuronal death, with multiple sclerosis representing the most prevalent and studied condition. This review highlights the involvement of molecular motors in the homeostatic control of myelination. It also discusses studies that have yielded insights into the dysfunctional activity of molecular motors in the pathophysiology of multiple sclerosis.

Androgens Regulate Tau Phosphorylation Through Phosphatidylinositol 3-Kinase-Protein Kinase B-Glycogen Synthase Kinase 3β Signaling

Age-related testosterone depletion in men is a risk factor for Alzheimer's disease (AD). How testosterone modulates AD risk remains to be fully elucidated, although regulation of tau phosphorylation has been suggested as a contributing protective action. To investigate the relationship between testosterone and tau phosphorylation, we first evaluated the effect of androgen status on tau phosphorylation in 3xTg-AD mice. Depletion of endogenous androgens via gonadectomy resulted in increased tau phosphorylation that was prevented by acute testosterone treatment. Parallel alterations in the phosphorylation of both glycogen synthase kinase 3β (GSK3β) and protein kinase B (Akt) suggest possible components of the underlying signaling pathway. To further explore mechanism, primary cultured neurons were treated with a physiological concentration of testosterone or its active metabolite dihydrotestosterone (DHT). Results showed that testosterone and DHT induced significant decreases in phosphorylated tau and significant increases in phosphorylation of Akt and GSK3β. Pharmacological inhibition of phosphatidylinositol 3-kinase (PI3K) effectively inhibited androgen-induced increases in Akt and GSK3β phosphorylation, and decreases in tau phosphorylation. In addition, androgen receptor (AR) knock-down by small interfering RNA prevented androgen-induced changes in the phosphorylation of Akt, GSK3β and tau, suggesting an AR-dependent mechanism. Additional experiments demonstrated androgen-induced changes in Akt, GSK3β and tau phosphorylation in AR-expressing PC12 cells but not in AR-negative PC12 cells. Together, these results suggest an AR-dependent pathway involving PI3K-Akt-GSK3β signaling through which androgens can reduce tau phosphorylation. These findings identify an additional protective mechanism of androgens that can improve neural health and inhibit development of AD.

Improving vulnerable Calbindin1- neurons in the ventral hippocampus rescues tau-induced impairment of episodic memory

BACKGROUND

Intraneuronal accumulation of hyperphosphorylated tau is a hallmark of Alzheimer's disease (AD). Given the significant correlation between tau pathology and memory loss in AD patients, identifying vulnerable brain regions, particularly susceptible neuron types in these regions, will advance our understanding of AD onset and shed light on therapeutic strategies to manage its progression.

METHODS

Immunofluorescent staining was employed to identify the brain regions and neuron types vulnerable to tau pathology in AD. A combination of chemogenetics, electrophysiological recording, in vivo Ca2+ recording, and a modified temporal-order discrimination behavior test was utilized to investigate the toxicity of tau accumulation to susceptible neurons in the dorsal part of the ventral hippocampus. Proteomics, phosphoproteomics, and molecular targeting were used to explore the underlying mechanisms of neuron susceptibility to tau accumulation in AD. The beneficial effects of microtubule affinity regulating kinase 4 (MARK4) knockdown and administration of DEPhosphorylation TArgeting Chimera (DEPTAC) were evaluated in AD mice with tau pathology.

RESULTS

In postmortem brains of AD patients, we observed robust accumulation of hyperphosphorylated tau in the anterior hippocampal CA1 region, particularly in its Calbindin1- (Calb1-) neurons, as opposed to the posterior hippocampal CA1 region and Calb1+ neurons. The susceptibility of Calb1- neurons to phospho-tau accumulation was also observed in P301L mice, especially in the dorsal part of ventral (anterior in human) hippocampal CA1 (dvCA1). In P301L mice, dvCA1 displayed distinct protein and phosphorylated protein networks compared with dorsal CA1, accompanied by overactivation of MARK4. Overexpressing human tau in Calb1- neurons in the dvCA1 (dvCA1Calb1- neurons) specifically impairs the temporal-order discrimination of objects. Meanwhile, tau accumulation significantly inhibited the excitability and firing patterns of dvCA1Calb1- neurons associated with temporal-order discrimination. Knocking down MARK4 or reducing hyperphosporylated tau via DEPTAC in P301L mice significantly ameliorated AD-like tau pathology in dvCA1Calb1- neurons and improved temporal-order discrimination of objects.

CONCLUSION

These findings highlight the crucial role of dvCA1Calb1- neurons in the early stage of tau pathology and demonstrate the potential of targeting phosphorylated tau through MARK4 knockdown or DEPTAC administration to counter the vulnerability of dvCA1Calb1- neurons and, consequently, ameliorate episodic memory deficits in AD.

Long-term exposure to excessive norepinephrine in the brain induces tau aggregation, neuronal death, and cognitive deficits in early tau transgenic mice

Alzheimer's disease (AD) is marked by the presence of intraneuronal neurofibrillary tangles (NFTs), which are primarily composed of hyperphosphorylated tau protein. The locus coeruleus (LC), the brain's main source of norepinephrine (NE), is one of the earliest regions to develop NFTs and experience neurodegeneration in AD. While LC-derived NE plays beneficial roles in cognition, emotion, locomotion, and the sleep-wake cycle, its impact on tau pathology is unclear. To explore this relationship, we administered intraperitoneal injections of either N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP4), a selective neurotoxin for noradrenergic neurons, or reboxetine (RBX), a norepinephrine reuptake inhibitor, to decrease or increase NE levels, respectively, in early tau transgenic mice expressing mutant human P301L tau (ADLPTau) for two months. Only the RBX-treated mice exhibited cognitive deficits, as evidenced by their performance in the Y-maze, novel object recognition, and contextual fear conditioning tests. Immunohistochemical analysis revealed increased hyperphosphorylated tau aggregates in the LC and hippocampus of the RBX-treated mice. Furthermore, neuronal apoptosis was observed in the hippocampal CA1 region of these mice. Western blotting showed that RBX injections led to the overactivation of tau kinases PKA and GSK3β, resulting in hyperphosphorylated tau, neuronal loss, and cognitive impairments. Consistent with these findings, human brain organoids exposed to higher NE concentrations also displayed elevated hyperphosphorylated tau and increased activity of the same tau kinases. These findings suggest that excessive NE exposure accelerates tau pathology by overactivating the tau kinases. Thus, modulating NE levels in the brain via the LC-NE system could be a potential therapeutic strategy for tau-related AD.

Harnessing the potential of long non-coding RNAs in the pathophysiology of Alzheimer's disease

Alzheimer's disease (AD), a diverse neurodegenerative disease, is the leading cause of dementia, accounting for 60-80 % of all cases. The pathophysiology of Alzheimer's disease is unknown, and there is no cure at this time. Recent developments in transcriptome-wide profiling have led to the identification of a number of non-coding RNAs (ncRNAs). Among these, long non-coding RNAs (lncRNAs)-long transcripts that don't seem to be able to code for proteins-have drawn attention because they function as regulatory agents in a variety of biological processes. Recent research suggests that lncRNAs play a role in the pathogenesis of Alzheimer's disease by modulating tau hyperphosphorylation, amyloid production, synaptic impairment, neuroinflammation, mitochondrial dysfunction, and oxidative stress, though their precise effects on the disorder are unknown. The biology and modes of action of the best-characterized lncRNAs in AD will be outlined here, with an emphasis on their possible involvement in the pathophysiology of the disease. As lncRNAs may offer prospective prognostic/diagnostic biomarkers and therapeutic targets for the treatment of AD, a greater comprehension of the molecular processes and the intricate network of interactions in which they are implicated could pave the way for future research.

Comprehensive investigation of multiple targets in the development of newer drugs for the Alzheimer's disease

Alzheimer's disease, a significant contributor to dementia, is rapidly becoming a serious healthcare concern in the 21st century. The alarming number of patients with Alzheimer's disease is steadily increasing, which is contributed by the dearth of treatment options. The current treatment for Alzheimer's disease is heavily dependent on symptomatic treatment that has failed to cure the disease despite huge investments in the development of drugs. The clinical treatment of Alzheimer's disease with limited drugs is generally targeted towards the inhibition of N-methyl-d-aspartate receptor and acetylcholine esterase, which only elevate cognition levels for a limited period. Beyond the aforementioned molecular targets, β-amyloid was much explored with little success and thus created a feel and palpable growing emphasis on discovering new putative and novel targets for AD. This has inspired medicinal chemists to explore new targets, including microglia, triggering receptors expressed on myeloid cells 2 (Trem-2), and notum carboxylesterase, to discover new lead compounds. This review explores the functions, pathophysiological roles, and importance of all AD-related targets that address therapeutic and preventive approaches for the treatment and protection of Alzheimer's disease.

Brain phosphoproteomic analysis identifies diabetes-related substrates in Alzheimer's disease pathology in older adults

INTRODUCTION

Type 2 diabetes increases the risk of Alzheimer's disease (AD) dementia. Insulin signaling dysfunction exacerbates tau protein phosphorylation, a hallmark of AD pathology. However, the comprehensive impact of diabetes on patterns of AD-related phosphoprotein in the human brain remains underexplored.

METHODS

We performed tandem mass tag-based phosphoproteome profiling in post mortem human brain prefrontal cortex samples from 191 deceased older adults with and without diabetes and pathologic AD.

RESULTS

Among 7874 quantified phosphosites, microtubule-associated protein tau (MAPT) phosphorylated at T529 and T534 (isoform 8 T212 and T217) were more abundant in AD and showed differential associations with diabetes. Network analysis of co-abundance patterns uncovered synergistic interactions between AD and diabetes, with one module exhibiting higher MAPT phosphorylation (15 MAPT phosphosites) and another displaying lower MAP1B phosphorylation (22 MAP1B phosphosites).

DISCUSSION

This study offers phosphoproteomics insights into AD in diabetes, shedding light on mechanisms that can inform the development of therapeutics for dementia.

HIGHLIGHTS

The risk of Alzheimer's disease (AD) dementia is increased among older adults living with diabetes. The patterns of AD-related phosphoprotein in the human brain in older adults are differential among older adults living with diabetes. Microtubule-associated protein tau phosphorylated at T529 and T534 (isoform 8 T212 and T217) showed differential associations with diabetes. Phosphosite co-abundance networks of synergistic interactions between AD and diabetes were identified.

Targeting tau in Alzheimer's and beyond: Insights into pathology and therapeutic strategies

Tauopathies encompass a group of approximately 20 neurodegenerative diseases characterized by the accumulation of the microtubule-associated protein tau in brain neurons. The pathogenesis of intracellular neurofibrillary tangles, a hallmark of tauopathies, is initiated by hyperphosphorylated tau protein isoforms that cause neuronal death and lead to diseases like Alzheimer's, Parkinson's disease, frontotemporal dementia, and other complex neurodegenerative diseases. Current applications of tau biomarkers, including imaging, cerebrospinal fluid, and blood-based assays, assist in the evaluation and diagnosis of tauopathies. Emerging research is providing various potential strategies to prevent cellular toxicity caused by tau aggregation such as: 1) suppressing toxic tau aggregation, 2) preventing post-translational modifications of tau, 3) stabilizing microtubules and 4) designing tau-directed immunogens. This review aims to discuss the role of tau in tauopathies along with neuropathological features of the different tauopathies and the new developments in treating tau aggregation with the therapeutics for treating and possibly preventing tauopathies.

Synaptic and synchronic impairments in subcortical brain regions associated with early non-cognitive dysfunction in Alzheimer's disease

ABSTRACT

For many decades, Alzheimer's disease research has primarily focused on impairments within cortical and hippocampal regions, which are thought to be related to cognitive dysfunctions such as memory and language deficits. The exact cause of Alzheimer's disease is still under debate, making it challenging to establish an effective therapy or early diagnosis. It is widely accepted that the accumulation of amyloid-beta peptide in the brain parenchyma leads to synaptic dysfunction, a critical step in Alzheimer's disease development. The traditional amyloid cascade model is initiated by accumulating extracellular amyloid-beta in brain areas essential for memory and language. However, while it is possible to reduce the presence of amyloid-beta plaques in the brain with newer immunotherapies, cognitive symptoms do not necessarily improve. Interestingly, recent studies support the notion that early alterations in subcortical brain regions also contribute to brain damage and precognitive decline in Alzheimer's disease. A body of recent evidence suggests that early Alzheimer's disease is associated with alterations (e.g., motivation, anxiety, and motor impairment) in subcortical areas, such as the striatum and amygdala, in both human and animal models. Also, recent data indicate that intracellular amyloid-beta appears early in subcortical regions such as the nucleus accumbens, locus coeruleus, and raphe nucleus, even without extracellular amyloid plaques. The reported effects are mainly excitatory, increasing glutamatergic transmission and neuronal excitability. In agreement, data in Alzheimer's disease patients and animal models show an increase in neuronal synchronization that leads to electroencephalogram disturbances and epilepsy. The data indicate that early subcortical brain dysfunctions might be associated with non-cognitive symptoms such as anxiety, irritability, and motivation deficits, which precede memory loss and language alterations. Overall, the evidence reviewed suggests that subcortical brain regions could explain early dysfunctions and perhaps be targets for therapies to slow disease progression. Future research should focus on these non-traditional brain regions to reveal early pathological alterations and underlying mechanisms to advance our understanding of Alzheimer's disease beyond the traditionally studied hippocampal and cortical circuits.

Anti-herpetic tau preserves neurons via the cGAS-STING-TBK1 pathway in Alzheimer's disease

Alzheimer's disease (AD) diagnosis relies on the presence of extracellular β-amyloid (Aβ) and intracellular hyperphosphorylated tau (p-tau). Emerging evidence suggests a potential link between AD pathologies and infectious agents, with herpes simplex virus 1 (HSV-1) being a leading candidate. Our investigation, using metagenomics, mass spectrometry, western blotting, and decrowding expansion pathology, detects HSV-1-associated proteins in human brain samples. Expression of the herpesvirus protein ICP27 increases with AD severity and strongly colocalizes with p-tau but not with Aβ. Modeling in human brain organoids shows that HSV-1 infection elevates tau phosphorylation. Notably, p-tau reduces ICP27 expression and markedly decreases post-infection neuronal death from 64% to 7%. This modeling prompts investigation into the cGAS-STING-TBK1 pathway products, nuclear factor (NF)-κB and IRF-3, which colocalizes with ICP27 and p-tau in AD. Furthermore, experimental activation of STING enhances tau phosphorylation, while TBK1 inhibition prevents it. Together, these findings suggest that tau phosphorylation acts as an innate immune response in AD, driven by cGAS-STING.

Molecular Mechanisms of Alzheimer's Disease Induced by Amyloid-β and Tau Phosphorylation Along with RhoA Activity: Perspective of RhoA/Rho-Associated Protein Kinase Inhibitors for Neuronal Therapy

Amyloid-β peptide (Aβ) is a critical cause of Alzheimer's disease (AD). It is generated from amyloid precursor protein (APP) through cleavages by β-secretase and γ-secretase. γ-Secretase, which includes presenilin, is regulated by several stimuli. Tau protein has also been identified as a significant factor in AD. In particular, Tau phosphorylation is crucial for neuronal impairment, as phosphorylated Tau detaches from microtubules, leading to the formation of neurofibrillary tangles and the destabilization of the microtubule structure. This instability in microtubules damages axons and dendrites, resulting in neuronal impairment. Notably, Aβ is linked to Tau phosphorylation. Another crucial factor in AD is neuroinflammation, primarily occurring in the microglia. Microglia possess several receptors that bind with Aβ, triggering the expression and release of an inflammatory factor, although their main physiological function is to phagocytose debris and pathogens in the brain. NF-κB activation plays a major role in neuroinflammation. Additionally, the production of reactive oxygen species (ROS) in the microglia contributes to this neuroinflammation. In microglia, superoxide is produced through NADPH oxidase, specifically NOX2. Rho GTPases play an essential role in regulating various cellular processes, including cytoskeletal rearrangement, morphology changes, migration, and transcription. The typical function of Rho GTPases involves regulating actin filament formation. Neurons, with their complex processes and synapse connections, rely on cytoskeletal dynamics for structural support. Other brain cells, such as astrocytes, microglia, and oligodendrocytes, also depend on specific cytoskeletal structures to maintain their unique cellular architectures. Thus, the aberrant regulation of Rho GTPases activity can disrupt actin filaments, leading to altered cell morphology, including changes in neuronal processes and synapses, and potentially contributing to brain diseases such as AD.

Exploring New Structures of Kinase Inhibitors and Multitarget Strategies in Alzheimer's Disease Treatment

Alzheimer's disease (AD) treatments currently available have ineffective results. Previously employed Acetylcholine esterase inhibitors and memantine, an NMDA receptor antagonist, target a single target structure that plays a complex role in the multifactorial progression of disease. Memantine moderates the toxic effects of excessive glutamate activity by blocking NMDA receptors, which decreases neurotoxicity in AD, while acetylcholine esterase inhibitors function by blocking cholinergic receptors (muscarinic and nicotinic), preventing the breakdown of acetylcholine, thereby enhancing cholinergic transmission, thus improving cognitive functions in mild to moderate stages of AD. Every drug class targets a distinct facet of the intricate pathophysiology of AD, indicating the diverse strategy required to counteract the advancement of this neurodegenerative disorder. Thus, patients are currently not getting much benefit from current drugs. A closer look at the course of AD revealed several potential target structures for future drug discovery. AD drug development strategies focus on developing new target structures in addition to well-established ones for combination treatment regimens, ideally with a single drug that can target two different target structures. Because of their roles in AD progression pathways like pathologic tau protein phosphorylations as well as amyloid β toxicity, protein kinases have been identified as potential targets. This review will give a quick rundown of the first inhibitors of single protein kinases, such as glycogen synthase kinase (gsk3) β, along with cyclin-dependent kinase 5. We will also look into novel inhibitors that target recently identified protein kinases in Alzheimer's disease, such as dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A). Additionally, multitargeting inhibitors, which target multiple protein kinases as well as those thought to be involved in other processes related to AD will be discussed. This kind of multitargeting offers prospective hope for improved patient outcomes down the road since it is the most effective way to impede multifactorial disease development.

Microglial activation states and their implications for Alzheimer's Disease

Alzheimer's Disease (AD) is a chronic neurodegenerative disorder characterized by the accumulation of toxic amyloid-beta (Aβ) plaques and neurofibrillary tangles (NFTs) of tau protein in the brain. Microglia, key immune cells of the central nervous system, play an important role in AD development and progression, primarily through their responses to Aβ and NFTs. Initially, microglia can clear Aβ, but in AD, chronic activation overwhelms protective mechanisms, leading to sustained neuroinflammation that enhances plaque toxicity, setting off a damaging cycle that affects neurons, astrocytes, cerebral vasculature, and other microglia. Current AD treatments have been largely ineffective, though emerging immunotherapies focusing on plaque removal show promise, but often overlook the role of neuroinflammation. Activated microglia display a complex range of phenotypes that can be broadly broken into pro- or anti-inflammatory states, although this dichotomy does not describe the significant overlap between states. Aβ can strongly induce inflammatory activity, triggering the production of reactive oxygen species, inflammatory cytokines (e.g., TNF-α, IL-1β, IL-6), synapse engulfment, blood-brain barrier compromise, and impaired Aβ clearance. These processes contribute to neural tissue loss, manifesting as cognitive decline such as impaired executive function and memory. Conversely, anti-inflammatory activation exerts neuroprotective effects by suppressing inflammatory pathways and releasing neurotrophic factors that aid neuron repair and protection. Induction of anti-inflammatory states may offer a dual therapeutic approach to address both neuroinflammation and plaque accumulation in AD. This approach suggests potential strategies to modulate microglial phenotypes, aiming to restore neuroprotective functions and mitigate disease progression by simultaneously targeting inflammation and plaque pathology.

Accurate Spatial Heterogeneity Dissection and Gene Regulation Interpretation for Spatial Transcriptomics using Dual Graph Contrastive Learning

Recent advances in spatial transcriptomics have enabled simultaneous preservation of high-throughput gene expression profiles and the spatial context, enabling high-resolution exploration of distinct regional characterization in tissue. To effectively understand the underlying biological mechanisms within tissue microenvironments, there is a requisite for methods that can accurately capture external spatial heterogeneity and interpret internal gene regulation from spatial transcriptomics data. However, current methods for region identification often lack the simultaneous characterizing of spatial structure and gene regulation, thereby limiting the ability of spatial dissection and gene interpretation. Here, stDCL is developed, a dual graph contrastive learning method to identify spatial domains and interpret gene regulation in spatial transcriptomics data. stDCL adaptively incorporates gene expression data and spatial information via a graph embedding autoencoder, thereby preserving critical information within the latent embedding representations. In addition, dual graph contrastive learning is proposed to train the model, ensuring that the latent embedding representation closely resembles the actual spatial distribution and exhibits cluster similarity. Benchmarking stDCL against other state-of-the-art clustering methods using complex cortex datasets demonstrates its superior accuracy and effectiveness in identifying spatial domains. Our analysis of the imputation matrices generated by stDCL reveals its capability to reconstruct spatial hierarchical structures and refine differential expression assessment. Furthermore, it is demonstrated that the versatility of stDCL in interpretability of gene regulation, spatial heterogeneity at high resolution, and embryonic developmental patterns. In addition, it is also showed that stDCL can successfully annotate disease-associated astrocyte subtypes in Alzheimer's disease and unravel multiple relevant pathways and regulatory mechanisms.

Natural products against tau hyperphosphorylation-induced aggregates: Potential therapies for Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline and memory impairments and is considered the most prevalent form of dementia. Among the contributing factors to AD lies the hyperphosphorylation of the microtubule-associated protein tau. Phosphorylated tau reduces its affinity for microtubules and triggers other posttranslational modifications that result in its aggregation and assembly into filaments. These structures progressively accumulate within neurons leading to neurodegeneration. While current AD medications often involve undesirable side effects, the exploration of natural products as a potential therapeutic alternative has gained considerable attention. Numerous compounds have shown potential capacity for reducing tau pathology through different mechanisms, such as inhibiting kinases to reduce tau hyperphosphorylation, enhancing phosphatase activity, and blocking fibril formation. Since tau hyperphosphorylation-induced aggregation is pivotal in AD onset, this review aims to elucidate the potential of natural products in modulating this crucial molecular mechanism.

Dietary supplementation and the role of phytochemicals against the Alzheimer's disease: Focus on polyphenolic compounds

Alzheimer's disease is a complicated, multifaceted, neurodegenerative illness that places an increasing strain on healthcare systems. Due to increasing malfunction and death of nerve cells, the person suffering from Alzheimer's disease (AD) slowly and steadily loses their memories, cognitive functions and even their personality. Although medications may temporarily enhance memory, there are currently no permanent therapies that can halt or cure this irreversible neurodegenerative process. Nonetheless, fast progress in comprehending the cellular and molecular abnormalities responsible for neuronal degeneration has increased confidence in the development of viable prevention and treatments. All FDA-approved anti-AD medications have merely symptomatic effects and cannot cure the illness. This necessitates the pursuit of alternate treatments. Accumulating data shows that systemic neuroinflammation, oxidative stress and associated mitochondrial dysfunction play crucial roles in the etiology of AD and precede its clinical presentation. Therefore, innovative therapeutic approaches targeting these pathophysiological components of Alzheimer's disease are being explored aggressively in the present scenario. Phytochemicals such as resveratrol, curcumin, quercetin, genistein and catechins are prospective therapies owing to their capacity to alter key AD pathogenetic pathways, such as oxidative stress, neuroinflammation, and mitochondrial dysfunction. The use of new phytochemical delivery strategies would certainly provide the possibility to solve several issues with standard anti-AD medicines. In this review, the roles of phytophenolic compound-based treatment strategies for AD are discussed.

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.

Small molecule-mediated therapeutic approaches to target Tau and Alzheimer's disease

Neurodegeneration is marked by the altered proteostasis and protein degradation mechanism. This is caused due to the accumulation of aberrant proteins. Alzheimer's disease is one of the leading causes of neurodegeneration characterized by the aggregation of Tau and Amyloid-β proteins intracellularly and extracellularly, respectively. The intracellular aggregation of Tau triggers accumulation of oxidative stress, loss of ER and mitochondrial function, leading to the aggravation of aggregates formation. Thus, increasing the load of aberrant proteins on chaperones and degradative mechanism, such as autophagy and ubiquitin-proteasome system. Although several small molecules are known to target and prevent Tau aggregation, the detrimental effects in the cell due to aggregates accumulation shall not be overlooked. In such instance, small molecules that effectively target Tau aggregates and the cellular aberrations would be of great importance. Here we have discussed the efficacy of natural molecule, Limonoid, isolated from Azadirachta indica that prevents Tau aggregation and also activates the heat shock protein system. The activated heat shock protein system elevates the levels of Hsp70 that is known to interact with aberrantly folded Tau. Further, the role of Hsp70 in directing Tau clearance by macroautophagy or chaperone-mediated autophagy elucidates the effect of limonoids in overcoming AD pathology due to Tau aggregation.

Molecular mechanisms of neurofilament alterations and its application in assessing neurodegenerative disorders

Neurofilaments are intermediate filaments present in neurons. These provide structural support and maintain the size and shape of the neurons. Dysregulation, mutation, and aggregation of neurofilaments raise the levels of these proteins in the blood and cerebrospinal fluid (CSF), which are characteristic features of axonal damage and certain rare neurological diseases, such as Giant Axonal Neuropathy and Charcot-Mare-Tooth disease. Understanding the structure, dynamics, and function of neurofilaments has been greatly enhanced by a diverse range of biochemical and preclinical investigations conducted over more than four decades. Recently, there has been a resurgence of interest in post-translational modifications of neurofilaments, such as phosphorylation, aggregation, mutation, oxidation, etc. Over the past twenty years, several rare disorders have been studied from structural alterations of neurofilaments. These disorders are monitored by fluid biomarkers such as neurofilament light chains. Currently, there are many tools, such as Enzyme-Linked Immunosorbent Assay, Electrochemiluminescence Assay, Single-Molecule Array, Western/immunoblotting, etc., in use to assess the neurofilament proteins in Blood and CSF. However, all these techniques utilize expensive, non-specific, or antibody-based methods, which make them unsuitable for routine screening of neurodegenerative disorders. This provides room to search for newer sensitive, cost-effective, point-of-care tools for rapid screening of the disease. For a long time, the molecular mechanisms of neurofilaments have been poorly understood due to insufficient research attempts, and a deeper understanding of them remains elusive. Therefore, this review aims to highlight the available literature on molecular mechanisms of neurofilaments and the function of neurofilaments in axonal transport, axonal conduction, axonal growth, and neurofilament aggregation, respectively. Further, this review discusses the role of neurofilaments as potential biomarkers for the identification of several neurodegenerative diseases in clinical laboratory practice.

TYK2 regulates tau levels, phosphorylation and aggregation in a tauopathy mouse model

Alzheimer's disease is one of at least 26 diseases characterized by tau-positive accumulation in neurons, glia or both. However, it is still unclear what modifications cause soluble tau to transform into insoluble aggregates. We previously performed genetic screens that identified tyrosine kinase 2 (TYK2) as a candidate regulator of tau levels. Here we verified this finding and found that TYK2 phosphorylates tau at tyrosine 29 (Tyr29) leading to its stabilization and promoting its aggregation in human cells. We discovered that TYK2-mediated Tyr29 phosphorylation interferes with autophagic clearance of tau. We also show that TYK2-mediated phosphorylation of Tyr29 facilitates pathological tau accumulation in P301S tau-transgenic mice. Furthermore, knockdown of Tyk2 reduced total tau and pathogenic tau levels and rescued gliosis in a tauopathy mouse model. Collectively, these data suggest that partial inhibition of TYK2 could thus be a strategy to reduce tau levels and toxicity.

MicroRNA-219 in the central nervous system: a potential theranostic approach

Despite the recent therapeutic advances in neurological disorders, curative therapy remains a serious challenge in many cases. Even though recent years have witnessed the development of gene therapy from among the different therapeutic approaches affecting pathophysiological mechanisms, intriguing aspects exist regarding the effectiveness, safety, and mechanism of action of gene therapies. Micro ribonucleic acid (microRNA-miRNA), as a fundamental gene regulator, regulates messenger ribonucleic acid (mRNA) by directly binding through the 3'-untranslated region (3'-UTR). MicroRNA-219 is a specific brain-enriched miRNA associated with neurodevelopmental disorders that play crucial roles in the differentiation of oligodendrocyte progenitorcells, promotion of oligodendrocyte maturation, remyelination, and cognitive functions to the extent that it can be considered a potential therapeutic option for demyelination in multiple sclerosis and spinal cord injury and reverse chronic inflammation pains. Additionally, miR-219 regulates the circadian clock, influencing the duration of the circadian clock period. This regulation can impact mood stability and is associated with phase fluctuations in bipolar patients. Furthermore, miR-219 also plays a role in modulating tau toxicity, which is relevant to the pathophysiology of Alzheimer's disease and schizophrenia. Finally, it reportedly has protective effects against seizures and Parkinson's disease, as well as neoplasms, by inhibiting proliferation, suppressing invasion, and inducing cell death in tumor cells. Exploring the miR-219 molecular pathways and their therapeutic effects on central nervous system disorders and the mechanisms involved, the present review study aims to illustrate how this information may change the future of gene therapy.

A review on synthetic inhibitors of dual-specific tyrosine phosphorylation-regulated kinase 1A (DYRK1A) for the treatment of Alzheimer's disease (AD)

Alzheimer's disease (AD) is a complex disorder that is influenced by a number of variables, such as age, gender, environmental factors, disease, lifestyle, infections, and many more. The main characteristic of AD is the formation of amyloid plaque and neurofibrillary tangles (NFT), which are caused by various reasons such as inflammation, impairment of neurotransmitters, hyperphosphorylation of tau protein, generation of toxic amyloid beta (Aβ) 40/42, oxidative stress, etc. Protein kinases located in chromosome 21, namely dual-specific tyrosine phosphorylation-regulated kinase 1A (DYRK1A), play an essential role in the pathogenesis of AD. DYRK1A stimulates the Aβ peptide aggregation and phosphorylation of tau protein to generate the NFT formation that causes neurodegeneration. Thus, DYRK1A is associated with AD, and inhibition of DYRK1A has the potential to treat AD. In this review, we discussed the pathophysiology of AD, various factors responsible for AD, and the role of DYRK1A in AD. We have also discussed the latest therapeutic potential of DYRK1A inhibitors for neurogenerative disease, along with their structure-activity relationship (SAR) studies. This article provides valuable information for guiding the future discovery of novel and target-specific DYRK1A inhibitors over other kinases and their structural optimization to treat AD.

Early intervention using long-term rhythmic pulsed magnetic stimulation alleviates cognitive decline in a 5xFAD mouse model of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the most prevalent form of dementia, but no effective therapeutic strategy is available to date. Rhythmic magnetic stimulation is an attractive means of neuron modulation that could be beneficial for restoring learning and memory abilities.

OBJECTIVE

To assess the effect of a compound pulsed rhythmic magnetic field (cPMF) on cognition during AD progression and to explore the appropriate cPMF intervention period.

METHODS

Female 5xFAD mice aged 10 weeks and 18 weeks were exposed to cPMF with a carrier frequency of 40 Hz, repeated at 5 Hz for 1 h/d for 8 consecutive weeks. The Morris water maze (MWM) test was used for cognitive behavioral assessment. Furthermore, changes in molecular pathology within the brain were detected using immunofluorescence staining and real-time PCR.

RESULTS

10-week-old AD mice treated with cPMF explored the target quadrant more frequently than sham-exposed AD mice in MWM test, exhibiting improved learning and memory abilities. Additionally, cPMF exposure alleviated Aβ plaque deposition and astrogliosis in the AD brain. Moreover, neurotrophic factor fibroblast growth factor 1 (FGF1) in the AD brain was upregulated by cPMF treatment. However, in 18-week-old AD mice treated with cPMF, cognitive performance and Fgf1 gene expression were not significantly improved, although Aβ plaque deposition and astrogliosis were alleviated.

CONCLUSION

Early intervention via long-term rhythmic cPMF stimulation may alleviate the histopathological features and enhance neuroprotective gene Fgf1 expression, thereby improving the cognitive performance of 5xFAD mice, which should provide promising insight for the clinical treatment of patients with AD.

Radiosynthesis and evaluation of a novel 18F-labeled tracer for PET imaging of glycogen synthase kinase 3

Glycogen synthase kinase 3 (GSK3) is a multifunctional serine/threonine kinase family that regulates diverse biological processes including glucose metabolism, insulin activity and energy homeostasis. Dysregulation of GSK3 is implicated in the development of several diseases such as type 2 diabetes mellitus, Alzheimer's disease (AD), and various cancer types. In this study, we report the synthesis and evaluation of a novel positron emission tomography (PET) ligand compound 28 (codenamed [18F]GSK3-2209). The PET ligand [18F]28 was obtained via copper-mediated radiofluorination in more than 32% radiochemical yields, with high radiochemical purity and high molar activity. In vitro autoradiography studies in rodents demonstrated that this tracer exhibited a high specific binding to GSK3. Furthermore, PET imaging studies of [18F]28 revealed its ability to penetrate the blood-brain barrier (BBB).

Evolving significance of kinase inhibitors in the management of Alzheimer's disease

Alzheimer's disease is a neurodegenerative problem with progressive loss of memory and other cognitive function disorders resulting in the imbalance of neurotransmitter activity and signaling progression, which poses the need of the potential therapeutic target to improve the intracellular signaling cascade brought by kinases. Protein kinase plays a significant and multifaceted role in the treatment of Alzheimer's disease, by targeting pathological mechanisms like tau hyperphosphorylation, neuroinflammation, amyloid-beta production and synaptic dysfunction. In this review, we thoroughly explore the essential protein kinases involved in Alzheimer's disease, detailing their physiological roles, regulatory impacts, and the newest inhibitors and compounds that are progressing into clinical trials. All the findings of studies exhibited the promising role of kinase inhibitors in the management of Alzheimer's disease. However, it still poses the need of addressing current challenges and opportunities involved with this disorder for the future perspective of kinase inhibitors in the management of Alzheimer's disease. Further study includes the development of biomarkers, combination therapy, and next-generation kinase inhibitors with increased potency and selectivity for its future prospects.

Updates in Alzheimer's disease: from basic research to diagnosis and therapies

Alzheimer's disease (AD) is the most common neurodegenerative disorder, characterized pathologically by extracellular deposition of β-amyloid (Aβ) into senile plaques and intracellular accumulation of hyperphosphorylated tau (pTau) as neurofibrillary tangles. Clinically, AD patients show memory deterioration with varying cognitive dysfunctions. The exact molecular mechanisms underlying AD are still not fully understood, and there are no efficient drugs to stop or reverse the disease progression. In this review, we first provide an update on how the risk factors, including APOE variants, infections and inflammation, contribute to AD; how Aβ and tau become abnormally accumulated and how this accumulation plays a role in AD neurodegeneration. Then we summarize the commonly used experimental models, diagnostic and prediction strategies, and advances in periphery biomarkers from high-risk populations for AD. Finally, we introduce current status of development of disease-modifying drugs, including the newly officially approved Aβ vaccines, as well as novel and promising strategies to target the abnormal pTau. Together, this paper was aimed to update AD research progress from fundamental mechanisms to the clinical diagnosis and therapies.

Biomarkers and Target-Specific Small-Molecule Drugs in Alzheimer's Diagnostic and Therapeutic Research: From Amyloidosis to Tauopathy

Alzheimer's disease (AD) is the most common type of human dementia and is responsible for over 60% of diagnosed dementia cases worldwide. Abnormal deposition of β-amyloid and the accumulation of neurofibrillary tangles have been recognised as the two pathological hallmarks targeted by AD diagnostic imaging as well as therapeutics. With the progression of pathological studies, the two hallmarks and their related pathways have remained the focus of researchers who seek for AD diagnostic and therapeutic strategies in the past decades. In this work, we reviewed the development of the AD biomarkers and their corresponding target-specific small molecule drugs for both diagnostic and therapeutic applications, underlining their success, failure, and future possibilities.

Alzheimer's disease approaches - Focusing on pathology, biomarkers and clinical trial candidates

The strategy for the development of new drugs for Alzheimer's disease (AD) recognizes that an effective therapy requires early therapeutic intervention and a multifactorial approach that considers the individual initiators of AD development. Current knowledge of AD includes the understanding of pathophysiology, risk factors, biomarkers, and the evolving patterns of biomarker abnormalities. This knowledge is essential in identifying potential molecular targets for new drug development. This review summarizes promising AD drug candidates, many of which are currently in phase 2 or 3 clinical trials. New agents are classified according to the Common Alzheimer's Disease Research Ontology (CADRO). The main targets of new drugs for AD are processes related to amyloid beta and tau neurotoxicity, neurotransmission, inflammation, metabolism and bioenergetics, synaptic plasticity, and oxidative stress. These interventions are aimed at preventing disease onset and slowing or eliminating disease progression. The efficacy of pharmacotherapy may be enhanced by combining these drugs with other treatments, antioxidants, and dietary supplements. Ongoing research into AD pathophysiology, risk factors, biomarkers, and the dynamics of biomarker abnormalities may contribute to the understanding of AD and offer hope for effective therapeutic strategies in the near future.

Influence of Tau on Neurotoxicity and Cerebral Vasculature Impairment Associated with Alzheimer's Disease

Alzheimer's disease is a fatal chronic neurodegenerative condition marked by a gradual decline in cognitive abilities and impaired vascular function within the central nervous system. This affliction initiates its insidious progression with the accumulation of two aberrant protein entities including Aβ plaques and neurofibrillary tangles. These chronic elements target distinct brain regions, steadily erasing the functionality of the hippocampus and triggering the erosion of memory and neuronal integrity. Several assumptions are anticipated for AD as genetic alterations, the occurrence of Aβ plaques, altered processing of amyloid precursor protein, mitochondrial damage, and discrepancy of neurotropic factors. In addition to Aβ oligomers, the deposition of tau hyper-phosphorylates also plays an indispensable part in AD etiology. The brain comprises a complex network of capillaries that is crucial for maintaining proper function. Tau is expressed in cerebral blood vessels, where it helps to regulate blood flow and sustain the blood-brain barrier's integrity. In AD, tau pathology can disrupt cerebral blood supply and deteriorate the BBB, leading to neuronal neurodegeneration. Neuroinflammation, deficits in the microvasculature and endothelial functions, and Aβ deposition are characteristically detected in the initial phases of AD. These variations trigger neuronal malfunction and cognitive impairment. Intracellular tau accumulation in microglia and astrocytes triggers deleterious effects on the integrity of endothelium and cerebral blood supply resulting in further advancement of the ailment and cerebral instability. In this review, we will discuss the impact of tau on neurovascular impairment, mitochondrial dysfunction, oxidative stress, and the role of hyperphosphorylated tau in neuron excitotoxicity and inflammation.

The Kv7 channel opener Retigabine reduces neuropathology and alleviates behavioral deficits in APP/PS1 transgenic mice

Hyperexcitability of neuronal networks is central to the pathogenesis of Alzheimer's disease (AD). Pharmacological activation of Kv7 channels is an effective way to reduce neuronal firing. Our results showed that that pharmacologically activating the Kv7 channel with Retigabine (RTG) can alleviate cognitive impairment in mice without affecting spontaneous activity. RTG could also ameliorate damage to the Nissl bodies in cortex and hippocampal CA and DG regions in 9-month-old APP/PS1 mice. Additionally, RTG could reduce the Aβ plaque number in the hippocampus and cortex of both 6-month-old and 9-month-old mice. By recordings of electroencephalogram, we showed that a decrease in the number of abnormal discharges in the brains of the AD model mice when the Kv7 channel was opened. Moreover, Western blot analysis revealed a reduction in the expression of the p-Tau protein in both the hippocampus and cortex upon Kv7 channel opening. These findings suggest that Kv7 channel opener RTG may ameliorate cognitive impairment in AD, most likely by reducing brain excitability.

Beneficial Effects of Echinacoside on Cognitive Impairment and Diabetes in Type 2 Diabetic db/db Mice

INTRODUCTION

Cognitive dysfunction is an important comorbidity of diabetes. Insulin resistance may play a critical role in diabetes-related cognitive impairment. Echinacoside (ECH), a natural phenylethanoid glycoside, is the active component of anti-diabetes prescriptions in traditional Chinese medicine. Its effect on modulating insulin resistance has been confirmed but modulating neurodegenerative disease remains unclear.

METHODS

Db/db mice, a spontaneous type 2 diabetes mode, were intragastrically administered ECH by 300 mg/kg or an equivalent volume of saline. Weight, blood glucose, and insulin resistance index were measured. Morris water maze test was performed to observe the compound effects on cognition. Hippocampal lesions were observed by histochemical analysis.

RESULTS

In db/db mice, ECH alleviated diabetes symptoms, memory loss, and hippocampal neuronal damage. Next, the expression of CD44 and phosphorylated tau was upregulated in diabetic mice. In addition, the insulin receptor substrate-1/phosphatidylinositol 3-kinase /protein kinase B signaling pathway was dysregulated in diabetic mice. All these dysregulations could be reversed by ECH.

DISCUSSION

This study provides theoretical support and experimental evidence for the future application of ECH in diabetic cognition dysfunction treatment, promoting the development of traditional medicines.

Revolutionizing Alzheimer's treatment: Harnessing human serum albumin for targeted drug delivery and therapy advancements

Alzheimer's disease (AD) is a neurodegenerative disorder initiated by amyloid-beta (Aβ) accumulation, leading to impaired cognitive function. Several delivery approaches have been improved for AD management. Among them, human serum albumin (HSA) is broadly employed for drug delivery and targeting the Aβ in AD owing to its biocompatibility, Aβ inhibitory effect, and nanoform, which showed blood-brain barrier (BBB) crossing ability via glycoprotein 60 (gp60) receptor and secreted protein acidic and rich in cysteine (SPARC) protein to transfer the drug molecules in the brain. Thus far, there is no previous review focusing on HSA and its drug delivery system in AD. Hence, the reviewed article aimed to critically compile the HSA therapeutic as well as drug delivery role in AD management. It also delivers information on how HSA-incorporated nanoparticles with surfaced embedded ligands such as TAT, GM1, and so on, not only improve BBB permeability but also increase neuron cell targetability in AD brain. Additionally, Aβ and tau pathology, including various metabolic markers likely BACE1 and BACE2, etc., are discussed. Besides, the molecular interaction of HSA with Aβ and its distinctive forms are critically reviewed that HSA can segregate Zn(II) and Cu(II) metal ions from Aβ owing to high affinity. Furthermore, the BBB drug delivery challenges in AD are addressed. Finally, the clinical formulation of HSA for the management of AD is critically discussed on how the HSA inhibits Aβ oligomer and fibril, while glycated HSA participates in amyloid plaque formation, i.e., β-structure sheet formation. This review report provides theoretical background on HSA-based AD drug delivery and makes suggestions for future prospect-related work.

Palmitic Acid Induces Posttranslational Modifications of Tau Protein in Alzheimer's Disease-Related Epitopes and Increases Intraneuronal Tau Levels

Metabolic diseases derived from an unhealthy lifestyle have been linked with an increased risk for developing cognitive impairment and even Alzheimer's disease (AD). Although high consumption of saturated fatty acids such as palmitic acid (PA) has been associated with the development of obesity and type II diabetes, the mechanisms connecting elevated neuronal PA levels and increased AD marker expression remain unclear. Among other effects, PA induces insulin resistance, increases intracellular calcium and reactive oxygen species (ROS) production, and reduces the NAD+/NADH ratio, resulting in decreased activity of the deacetylase Sirtuin1 (SIRT1) in neurons. These mechanisms may affect signaling pathways that impact the posttranslational modifications (PTMs) of the tau protein. To analyze the role played by PA in inducing the phosphorylation and acetylation of tau, we examined PTM changes in human tau in differentiated neurons from human neuroblastoma cells. We found changes in the phosphorylation state of several AD-related sites, namely, S199/202 and S214, that were mediated by a mechanism associated with the dysregulated activity of the kinases GSK3β and mTOR. PA also increased the acetylation of residue K280 and elevated total tau level after long exposure time. These findings provide information about the mechanisms by which saturated fatty acids cause tau PTMs that are similar to those observed in association with AD biochemical changes.

Age-dependent impact of streptozotocin on metabolic endpoints and Alzheimer's disease pathologies in 3xTg-AD mice

Alzheimer's disease (AD) is a multifactorial neurodegenerative disease with a complex origin, thought to involve a combination of genetic, biological and environmental factors. Insulin dysfunction has emerged as a potential factor contributing to AD pathogenesis, particularly in individuals with diabetes, and among those with insulin deficiency or undergoing insulin therapy. The intraperitoneal administration of streptozotocin (STZ) is widely used in rodent models to explore the impact of insulin deficiency on AD pathology, although prior research predominantly focused on young animals, with no comparative analysis across different age groups. Our study aimed to fill this gap by analyzing the impact of insulin dysfunction in 7 and 23 months 3xTg-AD mice, that exhibit both amyloid and tau pathologies. Our objective was to elucidate the age-specific consequences of insulin deficiency on AD pathology. STZ administration led to insulin deficiency in the younger mice, resulting in an increase in cortical amyloid-β (Aβ) and tau aggregation, while tau phosphorylation was not significantly affected. Conversely, older mice displayed an unexpected resilience to the peripheral metabolic impact of STZ, while exhibiting an increase in both tau phosphorylation and aggregation without significantly affecting amyloid pathology. These changes were paralleled with alterations in signaling pathways involving tau kinases and phosphatases. Several markers of blood-brain barrier (BBB) integrity declined with age in 3xTg-AD mice, which might have facilitated a direct neurotoxic effect of STZ in older mice. Overall, our research confirms the influence of insulin signaling dysfunction on AD pathology, but also advises careful interpretation of data related to STZ-induced effects in older animals.

Molecular mechanisms and therapeutic potential of lithium in Alzheimer's disease: repurposing an old class of drugs

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline and memory loss. Despite advances in understanding the pathophysiological mechanisms of AD, effective treatments remain scarce. Lithium salts, recognized as mood stabilizers in bipolar disorder, have been extensively studied for their neuroprotective effects. Several studies indicate that lithium may be a disease-modifying agent in the treatment of AD. Lithium's neuroprotective properties in AD by acting on multiple neuropathological targets, such as reducing amyloid deposition and tau phosphorylation, enhancing autophagy, neurogenesis, and synaptic plasticity, regulating cholinergic and glucose metabolism, inhibiting neuroinflammation, oxidative stress, and apoptosis, while preserving mitochondrial function. Clinical trials have demonstrated that lithium therapy can improve cognitive function in patients with AD. In particular, meta-analyses have shown that lithium may be a more effective and safer treatment than the recently FDA-approved aducanumab for improving cognitive function in patients with AD. The affordability and therapeutic efficacy of lithium have prompted a reassessment of its use. However, the use of lithium may lead to potential side effects and safety issues, which may limit its clinical application. Currently, several new lithium formulations are undergoing clinical trials to improve safety and efficacy. This review focuses on lithium's mechanism of action in treating AD, highlighting the latest advances in preclinical studies and clinical trials. It also explores the side effects of lithium therapy and coping strategies, offering a potential therapeutic strategy for patients with AD.