Tau Protein Hyperphosphorylation and Aggregation in Alzheimer's Disease and Other Tauopathies, and Possible Neuroprotective Strategies

Mutant β1-adrenergic receptor improves REM sleep and ameliorates tau accumulation in a mouse model of tauopathy

Sleep is essential for our well-being, and chronic sleep deprivation has unfavorable health consequences. We recently demonstrated that two familial natural short sleep (FNSS) mutations, DEC2-P384R and Npsr1-Y206H, are strong genetic modifiers of tauopathy in PS19 mice, a model of tauopathy. To gain more insight into how FNSS variants modify the tau phenotype, we tested the effect of another FNSS gene variant, Adrb1-A187V, by crossing mice with this mutation onto the PS19 background. We found that the Adrb1-A187V mutation helped restore rapid eye movement (REM) sleep and alleviated tau aggregation in a sleep-wake center, the locus coeruleus (LC), in PS19 mice. We found that ADRB1+ neurons in the central amygdala (CeA) sent projections to the LC, and stimulating CeAADRB1+ neuron activity increased REM sleep. Furthermore, the mutant Adrb1 attenuated tau spreading from the CeA to the LC. Our findings suggest that the Adrb1-A187V mutation protects against tauopathy by both mitigating tau accumulation and attenuating tau spreading.

Magnetic Ti3C2 MXene Nanosheets Prepared for Enrichment of Phosphopeptides

MXenes have received lots of attention since discovered and have been applied in various fields. In this work, Ti₃C₂-Fe₃O₄ composites with exposed non-modified Ti₃C₂ MXene nanosheets were designed and prepared by an in situ growth strategy and then applied in the enrichment of phosphopeptides. The two-dimensional composites could interact with the phosphopeptides through a metal oxide affinity chromatography mechanism provided by Ti-O and Fe-O bonds and a hydrophilic interaction chromatography mechanism by surface hydroxyl groups. This magnetic nanomaterial with a specific surface area of 66.1 m²·g^-1 had high sensitivity to phosphopeptides (0.5 nmol·L^-1) and high selectivity (1:1000 of the molar ratio of β-casein to bovine serum albumin). Non-fat milk was adopted as a real sample to preliminarily examine the applicability of the Ti₃C₂-Fe₃O₄-based protocol. Subsequently, Qingkailing injection, a kind of traditional Chinese medicine injection, was introduced to further explore the suitability of the nanocomposites for phosphopeptide enrichment from more complex matrices and satisfactory results were obtained.

Identification of gene networks mediating regional resistance to tauopathy in late-onset Alzheimer’s disease

Neurofibrillary lesions composed of tau protein aggregates are defining hallmarks of Alzheimer’s Disease. Despite tau filaments appearing to spread between networked brain regions in a prion-like manner, certain areas including cerebellum resist trans-synaptic spread of tauopathy and degeneration of their constituent neuronal cell bodies. To identify molecular correlates of resistance, we derived and implemented a ratio of ratios approach for disaggregating gene expression data on the basis of regional vulnerability to tauopathic neurodegeneration. When applied to vulnerable pre-frontal cortex as an internal reference for resistant cerebellum, the approach segregated adaptive changes in expression into two components. The first was enriched for neuron-derived transcripts associated with proteostasis including specific members of the molecular chaperone family and was unique to resistant cerebellum. When produced as purified proteins, each of the identified chaperones depressed aggregation of 2N4R tau in vitro at sub-stoichiometric concentrations, consistent with the expression polarity deduced from ratio of ratios testing. In contrast, the second component enriched for glia- and microglia-derived transcripts associated with neuroinflammation, segregating these pathways from susceptibility to tauopathy. These data support the utility of ratio of ratios testing for establishing the polarity of gene expression changes with respect to selective vulnerability. The approach has the potential to identify new targets for drug discovery predicated on their ability to promote resistance to disease in vulnerable neuron populations.

Anterograde and Retrograde Propagation of Inoculated Human Tau Fibrils and Tau Oligomers in a Non-Transgenic Rat Tauopathy Model

The tauopathy of Alzheimer's disease (AD) is first observed in the brainstem and entorhinal cortex, spreading trans-synaptically along specific pathways to other brain regions with recognizable patterns. Tau propagation occurs retrogradely and anterogradely (trans-synaptically) along a given pathway and through exosomes and microglial cells. Some aspects of in vivo tau spreading have been replicated in transgenic mice models expressing a mutated human MAPT (tau) gene and in wild-type mice. In this study, we aimed to characterize the propagation of different forms of tau species in non-transgenic 3-4 months old wild-type rats after a single unilateral injection of human tau oligomers and tau fibrils into the medial entorhinal cortex (mEC). We determined whether different variants of the inoculated human tau protein, tau fibrils, and tau oligomers, would induce similar neurofibrillary changes and propagate in an AD-related pattern, and how tau-related pathological changes would correlate with presumed cognitive impairment. We injected human tau fibrils and tau oligomers stereotaxically into the mEC and examined the distribution of tau-related changes at 3 days and 4, 8, and 11 months post-injection using antibodies AT8 and MC1, which reveal early phosphorylation and aberrant conformation of tau, respectively, HT7, anti-synaptophysin, and the Gallyas silver staining method. Human tau oligomers and tau fibrils exhibited some similarities and some differences in their ability to seed and propagate tau-related changes. Both human tau fibrils and tau oligomers rapidly propagated from the mEC anterogradely into the hippocampus and various parts of the neocortex. However, using a human tau-specific HT7 antibody, 3 days post-injection we found inoculated human tau oligomers in the red nucleus, primary motor, and primary somatosensory cortex, a finding not seen in animals inoculated with human tau fibrils. In animals inoculated with human tau fibrils, 3 days post-injection the HT7 antibody showed fibrils in the pontine reticular nucleus, a finding explained only by uptake of human tau fibrils by incoming presynaptic fibers to the mEC and retrograde transport of inoculated human tau fibrils to the brainstem. Rats inoculated with human tau fibrils showed as early as 4 months after inoculation a spread of phosphorylated tau protein at the AT8 epitopes throughout the brain, dramatically faster propagation of neurofibrillary changes than with human tau oligomers. The overall severity of tau protein changes 4, 8, and 11 months after inoculation of human tau oligomers and tau fibrils correlated well with spatial working memory and cognition impairments, as measured by the T-maze spontaneous alternation, novel object recognition, and object location tests. We concluded that this non-trangenic rat model of tauopathy, especially when using human tau fibrils, demonstrates rapidly developing pathologic alterations in neurons, synapses, and identifiable pathways together with cognitive and behavioral changes, through the anterograde and retrograde spreading of neurofibrillary degeneration. Therefore, it represents a promising model for future experimental studies of primary and secondary tauopathies, especially AD.

The Involvement of Post-Translational Modifications in Regulating the Development and Progression of Alzheimer's Disease

Post-translational modifications (PTMs) have been recently reported to be involved in the development and progression of Alzheimer's disease (AD). In detail, PTMs include phosphorylation, glycation, acetylation, sumoylation, ubiquitination, methylation, nitration, and truncation, which are associated with pathological functions of AD-related proteins, such as β-amyloid (Aβ), β-site APP-cleavage enzyme 1 (BACE1), and tau protein. In particular, the roles of aberrant PTMs in the trafficking, cleavage, and degradation of AD-associated proteins, leading to the cognitive decline of the disease, are summarized under AD conditions. By summarizing these research progress, the gaps will be filled between PMTs and AD, which will facilitate the discovery of potential biomarkers, leading to the establishment of novel clinical intervention methods against AD.

Acetylation and phosphorylation processes modulate Tau's binding to microtubules: A molecular dynamics study

The microtubule-associated protein Tau has its normal function impaired when undergoing post-translational modifications. In this work, molecular modelling techniques were used to infer the effects of acetylation and phosphorylation in Tau's overall conformation, electrostatics, and interactions, but mostly in Tau's ability to bind microtubules. Reported harmful Lys sites were mutated by its acetylated form, generating eight different acetylated Tau (aTau) analogues. Similarly, phosphorylation sites found in normal brains and in Alzheimer's lesioned brains were considered to design phosphorylated Tau (pTau) analogues. All these designed variants were evaluated in intracellular fluid and near a microtubule (MT) model. Our in silico findings demonstrated that the electrostatic changes, due to the absence of positive Lys' charges in acetylation cases, or the increasingly negative charge in the phosphorylated forms, hamper the association to the MT tubulins in most cases. Post-translational modifications also pose very distinct conformations to the ones described for native Tau, which hinders the microtubule-binding region (MTBR) and turns difficult the expected binding. Our study elucidates important molecular processes behind Tau abnormal function which can inspire novel therapeutics to address Alzheimer's disease.

Destabilization of Aβ fibrils by omega-3 polyunsaturated fatty acids: a molecular dynamics study

The senile plaques of neurotoxic aggregates of Aβ protein, deposited extraneuronally, mark the pathological hallmark of Alzheimer's disease (AD). The natural compounds such as omega-3 (ω-3) polyunsaturated fatty acids (PUFAs), which can access blood-brain barrier, are believed to be potential disruptors of preformed Aβ fibrils to cure AD with unknown mechanism. Herein, we present the destabilization potential of three ω-3 PUFAs, viz. Eicosapentaenoic acid (EPA), Docosahexaenoic acid (HXA), and α-linolenic acid (LNL) by molecular dynamics simulation. After an initial testing of 300 ns, EPA and HXA have been considered further for extended production run time, 500 ns. The increased value of root mean square deviation (RMSD), radius of gyration, and solvent-accessible surface area (SASA), the reduced number of H-bonds and β-sheet content, and disruption of salt bridges and hydrophobic contacts establish the binding of these ligands to Aβ fibril leading to destabilization. The polar head was found to interact with positively charged lysine (K28) residue in the fibril. However, the hydrophobicity of the long aliphatic tail competes with the intrinsic hydrophobic interactions of Aβ fibril. This amphiphilic nature of EPA and HXA led to the breaking of inherent hydrophobic contacts and formation of new bonds between the tail of PUFA and hydrophobic residues of Aβ fibril, leading to the destabilization of fibril. The Molecular Mechanics Poisson-Boltzmann Surface Area (MM-PBSA) results explain the binding of EPA and HXA to Aβ fibril by interacting with different residues. The destabilization potential of EPA and HXA establishes them as promising drug leads to cure AD, and encourages prospecting of other fatty acids for therapeutic intervention in AD.Communicated by Ramaswamy H. Sarma.

String/Cdc25 phosphatase is a suppressor of Tau-associated neurodegeneration

Tau pathology is defined by the intracellular accumulation of abnormally phosphorylated Tau (MAPT) and is prevalent in several neurodegenerative disorders. The identification of modulators of Tau abnormal phosphorylation and aggregation is key to understanding disease progression and developing targeted therapeutic approaches. In this study, we identified String (Stg)/Cdc25 phosphatase as a suppressor of abnormal Tau phosphorylation and associated toxicity. Using a Drosophila model of tauopathy, we showed that Tau dephosphorylation by Stg/Cdc25 correlates with reduced Tau oligomerization, brain vacuolization and locomotor deficits in flies. Moreover, using a disease mimetic model, we provided evidence that Stg/Cdc25 reduces Tau phosphorylation levels independently of Tau aggregation status and delays neurodegeneration progression in the fly. These findings uncover a role for Stg/Cdc25 phosphatases as regulators of Tau biology that extends beyond their well-characterized function as cell-cycle regulators during cell proliferation, and indicate Stg/Cdc25-based approaches as promising entry points to target abnormal Tau phosphorylation.

Alzheimer's disease biomarkers in patients with obstructive sleep apnea hypopnea syndrome and effects of surgery: A prospective cohort study

Background

Obstructive sleep apnea hypopnea syndrome (OSAHS) may cause Alzheimer's disease (AD), t-tau, p-tau, Aβ42, and Aβ40 are important elements in the process of AD, and changes in the levels of these biomarkers may affect the cognitive functioning of patients. Our objective was to investigate whether uvulopalatopharyngoplasty could reduce the plasma levels of AD biomarkers in OSAHS patients and the potential correlations of AD biomarkers with cognitive impairment and sleepiness, and explore the independent influencing factors of cognitive function.

Methods

Alzheimer's disease biomarkers were measured in the plasma of 35 patients with severe OSAHS requiring surgical treatment and 16 healthy controls without OSAHS. The cognitive function and sleepiness of OSAHS patients was also evaluated. The case group was given uvulopalatopharyngoplasty and followed at the postoperative sixth month, the follow-up cases were 27, and plasma AD biomarker levels, cognitive function, and sleepiness were re-evaluated. The preoperative and postoperative AD biomarker levels OSAHS patients were compared with each other and those of the control group. Linear stepwise regression and lasso regression were used to explore the relationships of AD biomarkers with cognitive impairment and sleepiness.

Results

Significantly higher Aβ40, t-tau, p-tau in plasma were observed preoperatively in OSAHS patients comparing to controls (29.24 ± 32.52 vs. 13.18 ± 10.78, p = 0.049; 11.88 ± 7.05 vs. 7.64 ± 4.17, p = 0.037; 26.31 ± 14.41 vs. 17.34 ± 9.12, p = 0.027). The sixth month of postoperation, the plasma AD biomarkers (Aβ42, Aβ40, t-tau, p-tau) in plasma levels decreased significantly (0.23 ± 0.17 vs. 0.20 ± 0.16, p = 0.0001; 29.24 ± 32.52 vs. 23.52 ± 24.46, p = 0.0046; 11.88 ± 7.05 vs. 8.88 ± 6.21, p = 0.0001;26.31 ± 14.41 vs. 20.43 ± 10.50, p = 0.0001). A comparison of MMSE and ESS scores from before to after surgery revealed obvious differences (27.14 ± 1.65 vs. 29.07 ± 1.78, p = 0.0001; 11.91 ± 4.84 vs. 5.89 ± 2.83, p = 0.0001). Changes in cognitive function and sleepiness scores from before to after uvulopalatopharyngoplasty were significantly correlated with AD biomarkers. Body mass index and t-tau were potential influencing factors cognitive function.

Conclusion

Obstructive sleep apnea hypopnea syndrome can increase plasma AD biomarkers levels. Uvulopalatopharyngoplasty can improve patients' cognition and sleepiness, and the mechanism may be related to changes in plasma AD biomarkers. Higher AHI and higher t-tau level were identified as independent risk factors for cognitive decline.

HMGCS2-Induced Autophagic Degradation of Tau Involves Ketone Body and ANKRD24

BACKGROUND

Accumulation of hyperphosphorylated Tau (pTau) contributes to the formation of neurofibrillary tangles in Alzheimer's disease (AD), and targeting Tau/pTau metabolism has emerged as a therapeutic approach. We have previously reported that mitochondrial 3-hydroxy-3-methylglutaryl-COA synthase 2 (HMGCS2) is involved in AD by promoting autophagic clearance of amyloid-β protein precursor via ketone body-associated mechanism, whether HMGCS2 may also regulate Tau metabolism remains elusive.

OBJECTIVE

The present study was to investigate the role of HMGCS2 in Tau/p degradation.

METHODS

The protein levels of Tau and pTau including pT217 and pT181, as well as autophagic markers LAMP1 and LC3-II were assessed by western blotting. The differentially regulated genes by HMGCS2 were analyzed by RNA sequencing. Autophagosomes were assessed by transmission electron microscopy.

RESULTS

HMGCS2 significantly decreased Tau/pTau levels, which was paralleled by enhanced formation of autophagic vacuoles and prevented by autophagic regulators chloroquine, bafilomycin A1, 3-methyladenine, and rapamycin. Moreover, HMGCS2-induced alterations of LAMP1/LC3-II and Tau/pTau levels were mimicked by ketone body acetoacetate or β-hydroxybutyrate. Further RNA-sequencing identified ankyrin repeat domain 24 (ANKRD24) as a target gene of HMGCS2, and silencing of ANKRD24 reduced LAMP1/LC3-II levels, which was accompanied by the altered formation of autophagic vacuoles, and diminished the effect of HMGCS2 on Tau/pTau.

CONCLUSION

HMGCS2 promoted autophagic clearance of Tau/pTau, in which ketone body and ANKRD24 played an important role.

Review: Emerging Eye-Based Diagnostic Technologies for Traumatic Brain Injury

The study of ocular manifestations of neurodegenerative disorders, Oculomics, is a growing field of investigation for early diagnostics, enabling structural and chemical biomarkers to be monitored overtime to predict prognosis. Traumatic brain injury (TBI) triggers a cascade of events harmful to the brain, which can lead to neurodegeneration. TBI, termed the "silent epidemic" is becoming a leading cause of death and disability worldwide. There is currently no effective diagnostic tool for TBI, and yet, early-intervention is known to considerably shorten hospital stays, improve outcomes, fasten neurological recovery and lower mortality rates, highlighting the unmet need for techniques capable of rapid and accurate point-of-care diagnostics, implemented in the earliest stages. This review focuses on the latest advances in the main neuropathophysiological responses and the achievements and shortfalls of TBI diagnostic methods. Validated and emerging TBI-indicative biomarkers are outlined and linked to ocular neuro-disorders. Methods detecting structural and chemical ocular responses to TBI are categorised along with prospective chemical and physical sensing techniques. Particular attention is drawn to the potential of Raman spectroscopy as a non-invasive sensing of neurological molecular signatures in the ocular projections of the brain, laying the platform for the first tangible path towards alternative point-of-care diagnostic technologies for TBI.

Mitochondrial dysfunctions, oxidative stress and neuroinflammation as therapeutic targets for neurodegenerative diseases: An update on current advances and impediments

Neurodegenerative diseases (NDs) such as Alzheimer disease (AD), Parkinson disease (PD), and Huntington disease (HD) represent a major socio-economic challenge in view of their high prevalence yet poor treatment outcomes affecting quality of life. The major challenge in drug development for these NDs is insufficient clarity about the mechanisms involved in pathogenesis and pathophysiology. Mitochondrial dysfunction, oxidative stress and inflammation are common pathways that are linked to neuronal abnormalities and initiation of these diseases. Thus, elucidating the shared initial molecular and cellular mechanisms is crucial for recognizing novel remedial targets, and developing therapeutics to impede or stop disease progression. In this context, use of multifunctional compounds at early stages of disease development unclogs new avenues as it acts on act on multiple targets in comparison to single target concept. In this review, we summarize overview of the major findings and advancements in recent years focusing on shared mechanisms for better understanding might become beneficial in searching more potent pharmacological interventions thereby reducing the onset or severity of various NDs.

Effects of Current Psychotropic Drugs on Inflammation and Immune System

The immune system and inflammation are involved in the pathological progression of various psychiatric disorders such as depression or major depressive disorder (MDD), generalized anxiety disorder (GAD) or anxiety, schizophrenia, Alzheimer's disease (AD), and Huntington's disease. It is observed that levels of inflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and other markers are highly increased in the abovementioned disorders. The inflammation and immune component also lead to enhance the oxidative stress. The oxidative stress and increased production of reactive oxygen species (ROS) are considered as important factors that are involved in pathological progression of psychiatric disorders. Increase production of ROS is associated with excessive inflammation followed by cell necrosis and death. The psychotropic drugs are mainly work through modulations of neurotransmitter system. However, it is evident that inflammation and immune modulation are also having important role in the progression of psychiatric disorders. Rationale of the use of current psychotropic drugs is modulation of immune system by them. However, the effects of psychotropic drugs on the immune system and how these might contribute to their efficacy remain largely unclear. The drugs may act through modification of inflammation and related markers. The main purpose of this book chapter is to address the role of current psychotropic drugs on inflammation and immune system. Moreover, it will also address the role of inflammation in the progression of psychiatric disorders.

A Systematic Review of Dietary Supplements in Alzheimer's Disease

Alzheimer's is the most common neurodegenerative disease among the aging population, which has been a major global challenge. The pathogenesis of the disease is still undetermined but postulated to be involved in various mechanisms including oxidative stress, excitotoxicity, inflammation, cell death, genetic factors, protein accumulation, and degradation. There are few Food and Drug Administration (FDA)-approved drugs available for the treatment of Alzheimer's disease (AD) that have limited benefits along with associated adverse effects. A retrospective review of randomized double-blind controlled trials of various supplements used in AD patients was performed on a PubMed search from January 1983 to March 2022. We found 10 articles that have shown positive outcomes in various cognitive domains. We conclude that there should be a global standard to endorse the quality and safety of these supplements.

Tau Isoforms: Gaining Insight into MAPT Alternative Splicing

Tau microtubule-associated proteins, encoded by the MAPT gene, are mainly expressed in neurons participating in axonal transport and synaptic plasticity. Six major isoforms differentially expressed during cell development and differentiation are translated by alternative splicing of MAPT transcripts. Alterations in the expression of human Tau isoforms and their aggregation have been linked to several neurodegenerative diseases called tauopathies, including Alzheimer's disease, progressive supranuclear palsy, Pick's disease, and frontotemporal dementia with parkinsonism linked to chromosome 17. Great efforts have been dedicated in recent years to shed light on the complex regulatory mechanism of Tau splicing, with a perspective to developing new RNA-based therapies. This review summarizes the most recent contributions to the knowledge of Tau isoform expression and experimental models, highlighting the role of cis-elements and ribonucleoproteins that regulate the alternative splicing of Tau exons.

Amyloids on Membrane Interfaces: Implications for Neurodegeneration

Membrane interfaces are vital for various cellular processes, and their involvement in neurodegenerative disorders such as Alzheimer's and Parkinson's disease has taken precedence in recent years. The amyloidogenic proteins associated with neurodegenerative diseases interact with the neuronal membrane through various means, which has implications for both the onset and progression of the disease. The parameters that regulate the interaction between the membrane and the amyloids remain poorly understood. The review focuses on the various aspects of membrane interactions of amyloids, particularly amyloid-β (Aβ) peptides and Tau involved in Alzheimer's and α-synuclein involved in Parkinson's disease. The genetic, cell biological, biochemical, and biophysical studies that form the basis for our current understanding of the membrane interactions of Aβ peptides, Tau, and α-synuclein are discussed.

Progress in the development of naturally derived active metabolites-based drugs: Potential therapeutics for Alzheimer's disease

Alzheimer's disease (AD) is an extensive age-associated neurodegenerative disorder. In spite of wide-ranging progress in understanding the AD pathology for the past 50 years, clinical trials based on the hypothesis of amyloid-beta (Aβ) have reserved worsening particularly at late-stage human trials. Consequently, very few old drugs are presently used for AD with inadequate clinical consequences and various side effects. We focus on widespread pharmacological and beneficial principles for existing as well as future drugs. Multitargeting approaches by means of general antioxidant and anti-inflammatory mechanisms allied with particular receptor and/or enzyme-mediated actions in neuroprotection and neurodegeneration. The plant kingdom comprises a vast range of species with an incredible diversity of bioactive metabolites with diverse chemical scaffolds. In recent times, an increasing body of facts recommended the use of phytochemicals to decelerate AD's onset and progression. The definitive goal of AD investigation is to avert the onset of neurodegeneration, thereby allowing successful aging devoid of cognitive decline. At this point, we discussed the neurological protective role of natural products and naturally derived therapeutic agents for AD from various natural polyphenolic compounds and medicinal plants. In conclusion, medicinal plants act as a chief source of different bioactive constituents.

How phosphorylation impacts intrinsically disordered proteins and their function

Phosphorylation is the most common post-translational modification (PTM) in eukaryotes, occurring particularly frequently in intrinsically disordered proteins (IDPs). These proteins are highly flexible and dynamic by nature. Thus, it is intriguing that the addition of a single phosphoryl group to a disordered chain can impact its function so dramatically. Furthermore, as many IDPs carry multiple phosphorylation sites, the number of possible states increases, enabling larger complexities and novel mechanisms. Although a chemically simple and well-understood process, the impact of phosphorylation on the conformational ensemble and molecular function of IDPs, not to mention biological output, is highly complex and diverse. Since the discovery of the first phosphorylation site in proteins 75 years ago, we have come to a much better understanding of how this PTM works, but with the diversity of IDPs and their capacity for carrying multiple phosphoryl groups, the complexity grows. In this Essay, we highlight some of the basic effects of IDP phosphorylation, allowing it to serve as starting point when embarking on studies into this topic. We further describe how recent complex cases of multisite phosphorylation of IDPs have been instrumental in widening our view on the effect of protein phosphorylation. Finally, we put forward perspectives on the phosphorylation of IDPs, both in relation to disease and in context of other PTMs; areas where deep insight remains to be uncovered.

Circadian dysregulation and Alzheimer’s disease: A comprehensive review

Alzheimer’s disease (AD), the foremost variant of dementia, has been associated with a menagerie of risk factors, many of which are considered to be modifiable. Among these modifiable risk factors is circadian rhythm, the chronobiological system that regulates sleep‐wake cycles, food consumption timing, hydration timing, and immune responses amongst many other necessary physiological processes. Circadian rhythm at the level of the suprachiasmatic nucleus (SCN), is tightly regulated in the human body by a host of biomolecular substances, principally the hormones melatonin, cortisol, and serotonin. In addition, photic information projected along afferent pathways to the SCN and peripheral oscillators regulates the synthesis of these hormones and mediates the manner in which they act on the SCN and its substructures. Dysregulation of this cycle, whether induced by environmental changes involving irregular exposure to light, or through endogenous pathology, will have a negative impact on immune system optimization and will heighten the deposition of Aβ and the hyperphosphorylation of the tau protein. Given these correlations, it appears that there is a physiologic association between circadian rhythm dysregulation and AD. This review will explore the physiology of circadian dysregulation in the AD brain, and will propose a basic model for its role in AD‐typical pathology, derived from the literature compiled and referenced throughout.

Do tau-synaptic long-term depression interactions in the hippocampus play a pivotal role in the progression of Alzheimer's disease?

Cognitive decline in Alzheimer's disease correlates with the extent of tau pathology, in particular tau hyperphosphorylation that initially appears in the transentorhinal and related regions of the brain including the hippocampus. Recent evidence indicates that tau hyperphosphorylation caused by either amyloid-β or long-term depression, a form of synaptic weakening involved in learning and memory, share similar mechanisms. Studies from our group and others demonstrate that long-term depression-inducing low-frequency stimulation triggers tau phosphorylation at different residues in the hippocampus under different experimental conditions including aging. Conversely, certain forms of long-term depression at hippocampal glutamatergic synapses require endogenous tau, in particular, phosphorylation at residue Ser396. Elucidating the exact mechanisms of interaction between tau and long-term depression may help our understanding of the physiological and pathological functions of tau/tau (hyper)phosphorylation. We first summarize experimental evidence regarding tau-long-term depression interactions, followed by a discussion of possible mechanisms by which this interplay may influence the pathogenesis of Alzheimer's disease. Finally, we conclude with some thoughts and perspectives on future research about these interactions.

Preparation and Multitarget Anti-AD Activity Study of Chondroitin Sulfate Lithium in AD Mice Induced by Combination of D-Gal/AlCl3

Previous studies have demonstrated that both CS and LiCl possess anti-Alzheimer's disease (AD) activities. We prepared chondroitin sulfate-Li (CS-Li) and investigated its effect on AD and explored the possible mechanisms both in vitro and in vivo. We found that CS-Li could inhibit amyloid β (Aβ) aggregation and protect SH-SY5Y cells from Aβ 1-42-induced cytotoxicity in vitro. In D-gal and AlCl3-induced AD mouse model, CS-Li improves the spatial learning and memory abilities of AD mice, reverses the nuclear pyknosis and cell edema, and increases the survival rate of neurons in hippocampus of mice. Moreover, CS-Li significantly increased the levels of GSH-Px, Na+/K+-ATPase, and ChAT and decreased the levels of MDA and AchE in AD mice. Western blot results demonstrated that CS-Li could decrease the hyperphosphorylation of tau (Ser396/Ser404) by regulating the expression of p-GSK-3β (Ser9) and PP2A and inhibit the expression of proinflammatory factors through inhibiting NF-κB nuclear translocation by activating the MAPK signaling pathways. In a word, CS-Li can delay AD development through multitarget processes, including Aβ aggregation inhibition, oxidative stress damage, tau hyperphosphorylation, and inflammatory response, thereby improves learning and memory abilities.

Astrocytes as a Therapeutic Target in Alzheimer's Disease-Comprehensive Review and Recent Developments

Alzheimer's disease (AD) is a frequent and disabling neurodegenerative disorder, in which astrocytes participate in several pathophysiological processes including neuroinflammation, excitotoxicity, oxidative stress and lipid metabolism (along with a critical role in apolipoprotein E function). Current evidence shows that astrocytes have both neuroprotective and neurotoxic effects depending on the disease stage and microenvironmental factors. Furthermore, astrocytes appear to be affected by the presence of amyloid-beta (Aβ), with alterations in calcium levels, gliotransmission and proinflammatory activity via RAGE-NF-κB pathway. In addition, astrocytes play an important role in the metabolism of tau and clearance of Aβ through the glymphatic system. In this review, we will discuss novel pharmacological and non-pharmacological treatments focused on astrocytes as therapeutic targets for AD. These interventions include effects on anti-inflammatory/antioxidant systems, glutamate activity, lipid metabolism, neurovascular coupling and glymphatic system, calcium dysregulation, and in the release of peptides which affects glial and neuronal function. According to the AD stage, these therapies may be of benefit in either preventing or delaying the progression of the disease.

Extracellular vesicles: A new paradigm in understanding, diagnosing and treating neurodegenerative disease

Neurodegenerative disorders (NDs) are becoming one of the leading causes of disability and death across the globe due to lack of timely preventions and treatments. Concurrently, intensive research efforts are being carried out to understand the etiology of these age-dependent disorders. Extracellular vesicles (EVs)-biological nanoparticles released by cells-are gaining tremendous attention in understanding their role in pathogenesis and progression of NDs. EVs have been found to transmit pathogenic proteins of NDs between neurons. Moreover, the ability of EVs to exquisitely surmount natural biological barriers, including blood-brain barrier and in vivo safety has generated interest in exploring them as potential biomarkers and function as natural delivery vehicles of drugs to the central nervous system. However, limited knowledge of EV biogenesis, their heterogeneity and lack of adequate isolation and analysis tools have hampered their therapeutic potential. In this review, we cover the recent advances in understanding the role of EVs in neurodegeneration and address their role as biomarkers and delivery vehicles to the brain.

Single cell transcriptomic profiling of a neuron-astrocyte assembloid tauopathy model

The use of iPSC derived brain organoid models to study neurodegenerative disease has been hampered by a lack of systems that accurately and expeditiously recapitulate pathogenesis in the context of neuron-glial interactions. Here we report development of a system, termed AstTau, which propagates toxic human tau oligomers in iPSC derived neuron-astrocyte assembloids. The AstTau system develops much of the neuronal and astrocytic pathology observed in tauopathies including misfolded, phosphorylated, oligomeric, and fibrillar tau, strong neurodegeneration, and reactive astrogliosis. Single cell transcriptomic profiling combined with immunochemistry characterizes a model system that can more closely recapitulate late-stage changes in adult neurodegeneration. The transcriptomic studies demonstrate striking changes in neuroinflammatory and heat shock protein (HSP) chaperone systems in the disease process. Treatment with the HSP90 inhibitor PU-H71 is used to address the putative dysfunctional HSP chaperone system and produces a strong reduction of pathology and neurodegeneration, highlighting the potential of AstTau as a rapid and reproducible tool for drug discovery.

The emerging role of autophagy and mitophagy in tauopathies: From pathogenesis to translational implications in Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease, affecting more than 55 million individuals worldwide in 2021. In addition to the "amyloid hypothesis," an increasing number of studies have demonstrated that phosphorylated tau plays an important role in AD pathogenesis. Both soluble tau oligomers and insoluble tau aggregates in the brain can induce structural and functional neuronal damage through multiple pathways, eventually leading to memory deficits and neurodegeneration. Autophagy is an important cellular response to various stress stimuli and can generally be categorized into non-selective and selective autophagy. Recent studies have indicated that both types of autophagy are involved in AD pathology. Among the several subtypes of selective autophagy, mitophagy, which mediates the selective removal of mitochondria, has attracted increasing attention because dysfunctional mitochondria have been suggested to contribute to tauopathies. In this review, we summarize the latest findings on the bidirectional association between abnormal tau proteins and defective autophagy, as well as mitophagy, which might constitute a vicious cycle in the induction of neurodegeneration. Neuroinflammation, another important feature in the pathogenesis and progression of AD, has been shown to crosstalk with autophagy and mitophagy. Additionally, we comprehensively discuss the relationship between neuroinflammation, autophagy, and mitophagy. By elucidating the underlying molecular mechanisms governing these pathologies, we highlight novel therapeutic strategies targeting autophagy, mitophagy and neuroinflammation, such as those using rapamycin, urolithin, spermidine, curcumin, nicotinamide, and actinonin, for the prevention and treatment of AD.

Earlier Detection of Alzheimer's Disease Based on a Novel Biomarker cis P-tau by a Label-Free Electrochemical Immunosensor

Early detection of cis phosphorylated tau (cis P-tau) may help as an effective treatment to control the progression of Alzheimer's disease (AD). Recently, we introduced for the first time a monoclonal antibody (mAb) with high affinity against cis P-tau. In this study, the cis P-tau mAb was utilized to develop a label-free immunosensor. The antibody was immobilized onto a gold electrode and the electrochemical responses to the analyte were acquired by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV). The immunosensor was capable of selective detection of cis P-tau among non-specific targets like trans P-tau and major plasma proteins. A wide concentration range (10 × 10^-14 M-3.0 × 10^-9 M) of cis P-tau was measured in PBS and human serum matrices with a limit of detection of 0.02 and 0.05 pM, respectively. Clinical applicability of the immunosensor was suggested by its long-term storage stability and successful detection of cis P-tau in real samples of cerebrospinal fluid (CSF) and blood serum collected from human patients at different stages of AD. These results suggest that this simple immunosensor may find great application in clinical settings for early detection of AD which is an unmet urgent need in today's healthcare services.

Novel molecular mechanisms in Alzheimer’s disease: The potential role of DEK in disease pathogenesis

Alzheimer’s disease and age-related dementias (AD/ADRD) are debilitating diseases that exact a significant physical, emotional, cognitive, and financial toll on the individual and their social network. While genetic risk factors for early-onset AD have been identified, the molecular and genetic drivers of late-onset AD, the most common subtype, remain a mystery. Current treatment options are limited for the 35 million people in the United States with AD/ADRD. Thus, it is critically important to identify novel molecular mechanisms of dementia-related pathology that may be targets for the development of new interventions. Here, we summarize the overarching concepts regarding AD/ADRD pathogenesis. Then, we highlight one potential molecular driver of AD/ADRD, the chromatin remodeling protein DEK. We discuss in vitro, in vivo, and ex vivo findings, from our group and others, that link DEK loss with the cellular, molecular, and behavioral signatures of AD/ADRD. These include associations between DEK loss and cellular and molecular hallmarks of AD/ADRD, including apoptosis, Tau expression, and Tau hyperphosphorylation. We also briefly discuss work that suggests sex-specific differences in the role of DEK in AD/ADRD pathogenesis. Finally, we discuss future directions for exploiting the DEK protein as a novel player and potential therapeutic target for the treatment of AD/ADRD.

The Interplay between GSK3β and Tau Ser262 Phosphorylation during the Progression of Tau Pathology

Tau hyperphosphorylation has been linked directly to the formation of toxic neurofibrillary tangles (NFTs) in tauopathies, however, prior to NFT formation, the sequence of pathological events involving tau phosphorylation remains unclear. Here, the effect of glycogen synthase kinase 3β (GSK3β) on tau pathology was examined independently for each step of transcellular propagation; namely, tau intracellular aggregation, release, cellular uptake and seeding activity. We find that overexpression of GSK3β-induced phosphorylated 0N4R tau led to a higher level of tau oligomerization in SH-SY5Y neuroblastoma cells than wild type 0N4R, as determined by several orthogonal assays. Interestingly, the presence of GSK3β also enhanced tau release. Further, we demonstrated that cells endocytosed more monomeric tau protein when pre-phosphorylated by GSK3β. Using an extracellular vesicle (EVs)-assisted tau neuronal delivery system, we show that exosomal GSK3β-phosphorylated tau, when added to differentiated SH-SY5Y cells, induced more efficient tau transfer, showing much higher total tau levels and increased tau aggregate formation as compared to wild type exosomal tau. The role of a primary tau phosphorylation site targeted by microtubule-affinity regulating kinases (MARKs), Ser262, was tested by pseudo-phosphorylation using site-directed mutagenesis to aspartate (S262D). S262D tau overexpression significantly enhanced tau release and intracellular tau accumulation, which were concurrent with the increase of pathological states of tau, as determined by immunodetection. Importantly, phosphorylation-induced tau accumulation was augmented by co-transfecting S262D tau with GSK3β, suggesting a possible interplay between Ser262 phosphorylation and GSK3β activity in tau pathology. Lastly, we found that pre-treatment of cells with amyloid-β (Aβ) further tau phosphorylation and accumulation when Ser262 pre-phosphorylation was present, suggesting that S262 may be a primary mediator of Aβ-induced tau toxicity. These findings provide a potential therapeutic target for treating tau-related disorders by targeting specific phospho-tau isoforms and further elucidate the GSK3β-mediated pathological seeding mechanisms.

From Small Peptides to Large Proteins against Alzheimer’sDisease

Alzheimer’s disease (AD) is the most common neurodegenerative disorder in the elderly. The two cardinal neuropathological hallmarks of AD are the senile plaques, which are extracellular deposits mainly constituted by beta-amyloids, and neurofibrillary tangles formed by abnormally phosphorylated Tau (p-Tau) located in the cytoplasm of neurons. Although the research has made relevant progress in the management of the disease, the treatment is still lacking. Only symptomatic medications exist for the disease, and, in the meantime, laboratories worldwide are investigating disease-modifying treatments for AD. In the present review, results centered on the use of peptides of different sizes involved in AD are presented.

Somatic Mutations and Alzheimer’s Disease

Alzheimer’s disease (AD) represents a global health challenge, with an estimated 55 million people suffering from the non-curable disease across the world. While amyloid-β plaques and tau neurofibrillary tangles in the brain define AD proteinopathy, it has become evident that diverse coding and non-coding regions of the genome may significantly contribute to AD neurodegeneration. The diversity of factors associated with AD pathogenesis, coupled with age-associated damage, suggests that a series of triggering events may be required to initiate AD. Since somatic mutations accumulate with aging, and aging is a major risk factor for AD, there is a great potential for somatic mutational events to drive disease. Indeed, recent data from the Gozes team/laboratories as well as other leading laboratories correlated the accumulation of somatic brain mutations with the progression of tauopathy. In this review, we lay the current perspectives on the principal genetic factors associated with AD and the potential causes, highlighting the contribution of somatic mutations to the pathogenesis of late onset Alzheimer’s disease. The roles that artificial intelligence and big data can play in accelerating the progress of causal somatic mutation markers/biomarkers identification, and the associated drug discovery/repurposing, have been highlighted for future AD and other neurodegenerative studies, with the aim to bring hope for the vulnerable aging population.

Immunotherapies for Alzheimer’s Disease—A Review

Alzheimer’s disease (AD) is a chronic neurodegenerative disorder that falls under the umbrella of dementia and is characterised by the presence of highly neurotoxic amyloid-beta (Aβ) plaques and neurofibrillary tangles (NFTs) of tau protein within the brain. Historically, treatments for AD have consisted of medications that can slow the progression of symptoms but not halt or reverse them. The shortcomings of conventional drugs have led to a growing need for novel, effective approaches to the treatment of AD. In recent years, immunotherapies have been at the forefront of these efforts. Briefly, immunotherapies utilise the immune system of the patient to treat a condition, with common immunotherapies for AD consisting of the use of monoclonal antibodies or vaccines. Most of these treatments target the production and deposition of Aβ due to its neurotoxicity, but treatments specifically targeting tau protein are being researched as well. These treatments have had great variance in their efficacy and safety, leading to a constant need for the research and development of new safe and effective treatments.

Toluidine blue O attenuates tau phosphorylation in N2a-APPSwe cells

Alzheimer's disease (AD) is characterized by extracellular amyloid plaques composed of amyloid-β peptide (Aβ), intracellular neurofibrillary tangles containing hyperphosphorylated tau protein and neuronal loss. Most of the FDA-approved AD drugs currently on the market are cholinesterase inhibitors, which are only effective in relieving the symptoms of AD. However, recent studies in AD drug discovery focus on multi-targeted strategies, including anti-amyloid and anti-tau therapy. In the current study, we have investigated the effects of toluidine blue O (TBO), a cholinesterase inhibitor, on amyloid precursor protein (APP) processing, tau phosphorylation, and tau kinases/phosphatase in N2a mouse neuroblastoma cells stably expressing the Swedish mutation of human APP695 (N2a-APPSwe). The results demonstrated that TBO reduces Aβ40/42 levels by decreasing expression levels of β-secretase 1 (BACE1), presenilin 1 (PS1) and total APP without causing cytotoxic effects in N2a-APPSwe cells. TBO also decreased the levels of both total tau and phosphorylated tau at residues Ser202/Thr205, Thr181, Ser396 and Ser 396/Ser404. Moreover, when the possible mechanisms underlying its effects on tau pathology were explored, TBO was found to decrease tau phosphorylation at those sites by reducing the expression levels of Akt, GSK-3β, Cdk5, inactive p-PP2A and increasing the expression levels of p-Akt Ser473 and inactive p-GSK-3β Ser9. Our new data support the idea that TBO may be a promising multi-target drug candidate for the treatment of AD.

Disruption of nuclear envelope integrity as a possible initiating event in tauopathies

The microtubule-associated protein tau is an abundant component of neurons of the central nervous system. In Alzheimer's disease and other neurodegenerative tauopathies, tau is found hyperphosphorylated and aggregated in neurofibrillary tangles. To obtain a better understanding of the cellular perturbations that initiate tau pathogenesis, we performed a CRISPR-Cas9 screen for genetic modifiers that enhance tau aggregation. This initial screen yielded three genes, BANF1, ANKLE2, and PPP2CA, whose inactivation promotes the accumulation of tau in a phosphorylated and insoluble form. In a complementary screen, we identified three additional genes, LEMD2, LEMD3, and CHMP7, that, when overexpressed, provide protection against tau aggregation. The proteins encoded by the identified genes are mechanistically linked and recognized for their roles in the maintenance and repair of the nuclear envelope. These results implicate the disruption of nuclear envelope integrity as a possible initiating event in tauopathies and reveal targets for therapeutic intervention.

Research advances in the study of sleep disorders, circadian rhythm disturbances and Alzheimer’s disease

Although there are still no satisfactory answers to the question of why we need to sleep, a better understanding of its function will help to improve societal attitudes toward sleep. Sleep disorders are very common in neurodegenerative diseases and are a key factor in the quality of life of patients and their families. Alzheimer’s disease (AD) is an insidious and irreversible neurodegenerative disease. Along with progressive cognitive impairment, sleep disorders and disturbances in circadian rhythms play a key role in the progression of AD. Sleep and circadian rhythm disturbances are more common in patients with AD than in the general population and can appear early in the course of the disease. Therefore, this review discusses the bidirectional relationships among circadian rhythm disturbances, sleep disorders, and AD. In addition, pharmacological and non-pharmacological treatment options for patients with AD and sleep disorders are outlined.

Deciphering the enigmatic crosstalk between prostate cancer and Alzheimer's disease: A current update on molecular mechanisms and combination therapy

Alzheimer's disease (AD) and prostate cancer (PCa) are considered the leading causes of death in elderly people worldwide. Although both these diseases have striking differences in their pathologies, a few underlying mechanisms are similar when cell survival is considered. In the current study, we employed an in-silico approach to decipher the possible role of bacterial proteins in the initiation and progression of AD and PCa. We further analyzed the molecular connections between these two life-threatening diseases. The androgen deprivation therapy used against PCa has been shown to promote castrate resistant PCa as well as AD. In addition, cell signaling pathways, such as Akt, IGF, and Wnt contribute to the progression of both AD and PCa. Besides, various proteins and genes are also common in disease progression. One such similarity is mTOR signaling. mTOR is the common downstream target for many signaling pathways and plays a vital role in both PCa and AD. Targeting mTOR can be a favorable line of treatment for both AD and PCa. However, drug resistance is one of the challenges in effective drug therapy. A few drugs that target mTOR have now become ineffective due to the development of resistance. In that regard, phytochemicals can be a rich source of novel drug candidates as they can act via multiple mechanisms. This review also presents mTOR targeting phytochemicals with promising anti-PCa, anti-AD activities, and approaches to overcome the issues associated with phytochemical-based therapies in clinical trials.

Forest Biomass as a Promising Source of Bioactive Essential Oil and Phenolic Compounds for Alzheimer's Disease Therapy

Alzheimer’s disease (AD) is the most common neurodegenerative disorder affecting elderly people worldwide. Currently, there are no effective treatments for AD able to prevent disease progression, highlighting the urgency of finding new therapeutic strategies to stop or delay this pathology. Several plants exhibit potential as source of safe and multi-target new therapeutic molecules for AD treatment. Meanwhile, Eucalyptus globulus extracts revealed important pharmacological activities, namely antioxidant and anti-inflammatory properties, which can contribute to the reported neuroprotective effects. This review summarizes the chemical composition of essential oil (EO) and phenolic extracts obtained from Eucalyptus globulus leaves, disclosing major compounds and their effects on AD-relevant pathological features, including deposition of amyloid-β (Aβ) in senile plaques and hyperphosphorylated tau in neurofibrillary tangles (NFTs), abnormalities in GABAergic, cholinergic and glutamatergic neurotransmission, inflammation, and oxidative stress. In general, 1,8-cineole is the major compound identified in EO, and ellagic acid, quercetin, and rutin were described as main compounds in phenolic extracts from Eucalyptus globulus leaves. EO and phenolic extracts, and especially their major compounds, were found to prevent several pathological cellular processes and to improve cognitive function in AD animal models. Therefore, Eucalyptus globulus leaves are a relevant source of biological active and safe molecules that could be used as raw material for nutraceuticals and plant-based medicinal products useful for AD prevention and treatment.

Targeting the Pathological Hallmarks of Alzheimer's Disease Through Nanovesicleaided Drug Delivery Approach

INTRODUCTION

Nanovesicle technology is making a huge contribution to the progress of treatment studies for various diseases, including Alzheimer's disease (AD). AD is the leading neurodegenerative disorder characterized by severe cognitive impairment. Despite the prevalence of several forms of anti-AD drugs, the accelerating pace of AD incidence cannot becurbed, and for rescue, nanovesicle technology has grabbed much attention.

METHODOLOGY

Comprehensive literature search was carried out using relevant keywords and online database platforms. The main concepts that have been covered included a complex pathomechanism underlying increased acetylcholinesterase (AchE) activity, β-amyloid aggregation, and tau-hyperphosphorylation forming neurofibrillary tangles (NFTs) in the brain, which are amongst the major hallmarks of AD pathology. Therapeutic recommendations exist in the form of AchE inhibitors, along with anti-amyloid and anti-tau therapeutics, which are being explored at a high pace. The degree of the therapeutic outcome, however, gets restricted by the pharmacological limitations. Susceptibility to peripheral metabolism and rapid elimination, inefficiency to cross the blood-brain barrier (BBB) and reach the target brain site are the factors that lower the biostability and bioavailability of anti-AD drugs. The nanovesicle technology has emerged as a route to preserve the therapeutic efficiency of the anti-AD drugs and promote AD treatment. The review hereby aims to summarize the developments made by the nanovesicle technology in aiding the delivery of synthetic and plant-based therapeutics targeting the molecular mechanism of AD pathology.

CONCLUSION

Nanovesicles appear to efficiently aid in target-specific delivery of anti-AD therapeutics and nullify the drawbacks posed by free drugs, besides reducing the dosage requirement and the adversities associated. In addition, the nanovesicle technology also appears to uplift the therapeutic potential of several phyto-compounds with immense anti-AD properties. Furthermore, the review also sheds light on future perspectives to mend the gaps that prevail in the nanovesicle-mediated drug delivery in AD treatment strategies.

Synthesis and biological evaluation of 4-hydroxy-methylpiperidinyl-N-benzyl-acylarylhydrazone hybrids designed as novel multifunctional drug candidates for Alzheimer's disease

The search for new drug candidates against Alzheimer's disease (AD) remains a complex challenge for medicinal chemists due to its multifactorial pathogenesis and incompletely understood physiopathology. In this context, we have explored the molecular hybridization of pharmacophore structural fragments from known bioactive molecules, aiming to obtain a novel molecular architecture in new chemical entities capable of concomitantly interacting with multiple targets in a so-called multi-target directed ligands (MTDLs) approach. This work describes the synthesis of 4-hydroxymethyl)piperidine-N-benzyl-acyl-hydrazone derivatives 5a-l, designed as novel MTDLs, showing improved multifunctional properties compared to the previously reported parent series of N-benzyl-(3-hydroxy)piperidine-acyl-hydrazone derivatives 4. The new improved derivatives were studied in silico, regarding their mode of interaction with AChE enzyme, and in vitro, for evaluation of their effects on the selective inhibition of cholinesterases, cellular antioxidant, and neuroprotective activities as their cytotoxicity in human neuroblastoma (SH-SY5Y) cells. Overall, compound PQM-181 (5 k) showed the best balanced selective and non-competitive inhibition of AChE (IC₅₀ = 5.9 μM, SI > 5.1), with an additional antioxidant activity (IC₅₀ = 7.45 µM) against neuronal t-BOOH-induced oxidative stress and neuroprotective ability against neurotoxicity elicited by both t-BOOH and OAβ_1-42, and a moderate ability to interfere in Aβ_1-42 aggregates, with low cytotoxicity and good predictive druggability properties, suggesting a multifunctional pharmacological profile suitable for further drug development against AD.

Tau phosphorylation sites serine202 and serine396 are differently altered in chronic traumatic encephalopathy and Alzheimer's disease

INTRODUCTION

Chronic traumatic encephalopathy (CTE) is a neurodegenerative tauopathy associated with repetitive head impacts (RHI) typically sustained by contact sport athletes. Post-translation modifications to tau in CTE have not been well delineated or compared to Alzheimer's disease (AD).

METHODS

We measured phosphorylated tau epitopes within dorsolateral frontal cortex from post mortem brains with neither CTE nor AD (n = 108), CTE (n = 109), AD (n = 223), and both CTE and AD (n = 33).

RESULTS

Levels of hyperphosphorylated tau (p-tau)202 , p-tau231 , and p-tau396 were significantly increased in CTE. Total years of RHI exposure was significantly associated with increased p-tau202 levels (P = .001), but not p-tau396 . Instead, p-tau396 was most closely related to amyloid beta (Aβ)1-42 levels (P < .001). The p-tau202 :p-tau396 ratio was significantly increased in early and late CTE compared to AD.

DISCUSSION

In frontal cortex, p-tau202 is the most upregulated p-tau species in CTE, while p-tau396 is most increased in AD. p-tau202 and p-tau396 measurements may aid in developing biomarkers for disease.

Plasma tau proteins for the diagnosis of mild cognitive impairment and Alzheimer's disease: A systematic review and meta-analysis

Objective

Detecting plasma tau biomarkers used to be impossible due to their low concentrations in blood samples. Currently, new high-sensitivity assays made it a reality. We performed a systematic review and meta-analysis in order to test the accuracy of plasma tau protein in diagnosing Alzheimer's disease (AD) or mild cognitive impairment (MCI).

Methods

We searched PubMed, Cochrane, Embase and Web of Science databases, and conducted correlation subgroup analysis, sensitivity analysis and publication bias analysis using R Programming Language.

Results

A total of 56 studies were included. Blood t-tau and p-tau levels increased from controls to MCI to AD patients, and showed significant changes in pairwise comparisons of AD, MCI and normal cognition. P-tau217 was more sensitive than p-tau181 and p-tau231 in different cognition periods. In addition, ultrasensitive analytical platforms, immunomagnetic reduction (IMR), increased the diagnostic value of tau proteins, especially the diagnostic value of t-tau.

Conclusion

Both t-tau and p-tau are suitable AD blood biomarkers, and p-tau217 is more sensitive than other tau biomarkers to differentiate MCI and AD. Detection techniques also have an impact on biomarkers' results. New ultrasensitive analytical platforms of IMR increase the diagnostic value of both t-tau and p-tau biomarkers.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/, registration number: CRD42021264701.

NLRP1 Inflammasome Activation in the Hippocampal Formation in Alzheimer's Disease: Correlation with Neuropathological Changes and Unbiasedly Estimated Neuronal Loss

Neuroinflammation is one of the core pathological features of Alzheimer's disease (AD) as both amyloid β (Aβ) and tau monomers and oligomers can trigger the long-term pro-inflammatory phenotype of microglial cells with consequent overactivation of the inflammasomes. To investigate the NLRP1 inflammasome activation in AD, we analyzed the expression of NLRP1, ASC, cleaved gasdermin (cGSDMD), and active caspase-6 (CASP-6) proteins in each hippocampal subdivision (hilar part of CA3, CA2/3, CA1, subiculum) of postmortem tissue of 9 cognitively healthy controls (HC) and 11 AD patients whose disease duration varied from 3 to 7 years after the clinical diagnosis. The total number of neurons, along with the total number of neurofibrillary tangles (NFTs), were estimated in Nissl- and adjacent modified Bielschowsky-stained sections, respectively, using the optical disector method. The same 9 HC and 11 AD cases were additionally semiquantitatively analyzed for expression of IBA1, HLA-DR, and CD68 microglial markers. Our results show that the expression of NLRP1, ASC, and CASP-6 is present in a significantly greater number of hippocampal formation neurons in AD brains compared to controls, suggesting that the NLRP1 inflammasome is more active in the AD brain. None of the investigated inflammasome and microglial markers were found to correlate with the age of the subjects or the duration of AD. However, besides positive correlations with microglial IBA1 expression in the subiculum and with microglial CD68 expression in the CA1 field and subiculum in the AD group, the overall NLRP1 expression in the hippocampal formation was positively correlated with the number of NFTs, thus providing a causal link between neuroinflammation and neurofibrillary degeneration. The accumulation of AT8-immunoreactive phosphorylated tau proteins that we observed at nuclear pores of large pyramidal neurons of the Ammon's horn further supports their role in the extent of neuronal dysfunction and degeneration in AD. This is important because unlike fibrillar amyloid-β deposits that are not related to dementia severity, total NFTs and neuron numbers in the hippocampal formation, especially in the CA1 field, are the best correlates of cognitive deterioration in both human brain aging and AD. Our findings also support the notion that the CA2 field vulnerability is strongly linked to specific susceptibilities to different tauopathies, including primary age-related tauopathy. Altogether, these findings contrast with reports of nonsignificant microglial activation in aged nonhuman primates and indicate that susceptibility to inflammasome activation may render the human brain comparatively more vulnerable to neurodegenerative changes and AD. In conclusion, our results confirm a key role of NLRP1 inflammasome in AD pathogenesis and suggest NLRP1 as a potential diagnostic marker and therapeutic target to slow or prevent AD progression.

Amylin and Secretases in the Pathology and Treatment of Alzheimer's Disease

Alzheimer’s disease remains a prevailing neurodegenerative condition which has an array physical, emotional, and financial consequences to patients and society. In the past decade, there has been a greater degree of investigation on therapeutic small peptides. This group of biomolecules have a profile of fundamentally sound characteristics which make them an intriguing area for drug development. Among these biomolecules, there are four modulatory mechanisms of interest in this review: alpha-, beta-, gamma-secretases, and amylin. These protease-based biomolecules all have a contributory role in the amyloid cascade hypothesis. Moreover, the involvement of various biochemical pathways intertwines these peptides to have shared regulators (i.e., retinoids). Further clinical and translational investigation must occur to gain a greater understanding of its potential application in patient care. The aim of this narrative review is to evaluate the contemporary literature on these protease biomolecule modulators and determine its utility in the treatment of Alzheimer’s disease.

The Locus Coeruleus - Noradrenaline system: Looking into Alzheimer's therapeutics with rose coloured glasses

Owing to the challenging ethos of global healthcare system, the Alzheimer's Disease (AD) researchers are consistently striving for a suitable target for disease amelioration. Besides the neurotransmitter release by neurons, the cells release tau proteins and amyloid peptides, within the extracellular vacancies, aggregating into tangles and plaques (AD pathological hallmarks). During neuro-stimulation, release of neuromodulator noradrenaline (NA), contained in the locus coeruleus (LC), exerts a significant impact on the neurons and microglia. The production of amyloid-β (Aβ) and hyperphosphorylation of tau proteins are affected by the α2A and β adrenoreceptors, parallel to influencing their clearance. The manuscript entails a detailed understanding of the LC-NA system, as a possible avenue in AD management. The authors provide a comprehensive data on AD pathology and its link with LC neuroanatomical projections, followed by the pathogenic implications of LC-NA system in AD. The data also integrates numerous studies from online databases, evidently supporting the loss of the system integrity in AD patients, and the impact of the sympathetic system on specific AD hallmarks. Thus, the objective of this review is to compile a wide compendium of studies, for the convenience of the neuro-researchers, aiding in the establishment of a suitable therapeutic regimen for AD treatment.

Current Progress on Neuroprotection Induced by Artemisia, Ginseng, Astragalus, and Ginkgo Traditional Chinese Medicines for the Therapy of Alzheimer's Disease

Aging is associated with the occurrence of diverse degenerative changes in various tissues and organs and with an increased incidence of neurological disorders, especially neurodegenerative diseases such as Alzheimer's disease (AD). In recent years, the search for effective components derived from medicinal plants in delaying aging and preventing and treating neurodegenerative diseases has been increasing and the number of related publications shows a rising trend. Here, we present a concise, updated review on the preclinical and clinical research progress in the assessment of the therapeutic potential of different traditional Chinese medicines and derived active ingredients and their effect on the signaling pathways involved in AD neuroprotection. Recognized by their multitargeting ability, these natural compounds hold great potential in developing novel drugs for AD.

Proteomics for comprehensive characterization of extracellular vesicles in neurodegenerative disease

Extracellular vesicles (EVs) are small lipid bilayer particles ubiquitously released by almost every cell type. A specific and selective constituents of EVs loaded with variety of proteins, lipids, small noncoding RNAs, and long non-coding RNAs are reflective of cellular events, type, and physiologic/pathophysiologic status of the cell of origin. Moreover, these molecular contents carry information from the cell of origin to recipient cells, modulating intercellular communication. Recent studies demonstrated that EVs not only play a neuroprotective role by mediating the removal of toxic proteins, but also emerge as an important player in various neurodegenerative disease onset and progression through facilitating of misfolded proteins propagation. For this reason, neurodegenerative disease-associated differences in EV proteome relative to normal EVs can be used to fulfil diagnostic, prognostic, and therapeutic purposes. Nonetheless, characterizing EV proteome obtained from biological samples (brain tissue and body fluids, including urea, blood, saliva, and CSF) is a challenging task. Herein, we review the status of EV proteome profiling and the updated discovery of potential biomarkers for the diagnosis of neurodegenerative disease with an emphasis on the integration of high-throughput advanced mass spectrometry (MS) technologies for both qualitative and quantitative analysis of EVs in different clinical tissue/body fluid samples in past five years.

Probiotic Bifidobacterium breve MCC1274 Mitigates Alzheimer's Disease-Related Pathologies in Wild-Type Mice

Probiotics improve brain function, including memory and cognition, via the microbiome–gut–brain axis. Oral administration of Bifidobacterium breve MCC1274 (B. breve MCC1274) improves cognitive function in App^NL-G-F mice and mild cognitive impairment (MCI) subjects, and mitigates Alzheimer’s disease (AD)-like pathologies. However, its effects on wild-type (WT) mice have not yet been explored. Thus, the effects of B. breve MCC1274 on AD-like pathologies in two-month-old WT mice were investigated, which were orally administered B. breve MCC1274 for four months. Aβ levels, amyloid precursor protein (APP), APP processing enzymes, phosphorylated tau, synaptic protein levels, glial activity, and cell proliferation in the subgranular zone of the dentate gyrus were evaluated. Data analysis was performed using Student’s t-test, and normality was tested using the Shapiro–Wilk test. Oral administration of B. breve MCC1274 in WT mice decreased soluble hippocampal Aβ42 levels by reducing presenilin1 protein levels, and reduced phosphorylated tau levels. It also activated the protein kinase B (Akt)/glycogen synthase kinase-3β (GSK-3β) pathway, which may be responsible for the reduction in presenilin1 levels and inhibition of tau phosphorylation. B. breve MCC1274 supplementation attenuated microglial activation and elevated synaptic protein levels in the hippocampus. These findings suggest that B. breve MCC1274 may mitigate AD-like pathologies in WT mice by decreasing Aβ42 levels, inhibiting tau phosphorylation, attenuating neuroinflammation, and improving synaptic protein levels.

HIV and FIV glycoproteins increase cellular tau pathology via cGMP-dependent kinase II activation

As the development of combination antiretroviral therapy (cART) against human immunodeficiency virus (HIV) drastically improves the lifespan of individuals with HIV, many are now entering the prime age when Alzheimer's disease (AD)-like symptoms begin to manifest. It has been shown that hyperphosphorylated tau, a known AD pathological characteristic, is prematurely increased in the brains of HIV-infected individuals as early as in their 30s and that its levels increase with age. This suggests that HIV infection might lead to accelerated AD phenotypes. However, whether HIV infection causes AD to develop more quickly in the brain is not yet fully determined. Interestingly, we have previously revealed that the viral glycoproteins HIV gp120 and feline immunodeficiency virus (FIV) gp95 induce neuronal hyperexcitation via cGMP-dependent kinase II (cGKII; also known as PRKG2) activation in cultured hippocampal neurons. Here, we use cultured mouse cortical neurons to demonstrate that the presence of HIV gp120 and FIV gp95 are sufficient to increase cellular tau pathology, including intracellular tau hyperphosphorylation and tau release to the extracellular space. We further reveal that viral glycoprotein-induced cellular tau pathology requires cGKII activation. Taken together, HIV infection likely accelerates AD-related tau pathology via cGKII activation.

Comprehensive binary interaction mapping of τ phosphotyrosine sites with SH2 domains in the human genome: Implications for the rational design of self-inhibitory phosphopeptides to target τ hyperphosphorylation signaling in Alzheimer's Disease

Human microtubule-associated protein Tau (τ) is abundant in the axons of neurons where it stabilizes microtubule bundles; abnormally hyperphosphorylated τ is a hallmark of Alzheimer's disease (AD) and related tauopathies. The hyperphosphorylation events can be recognized by phosphotyrosine-recognition domain SH2 (Src homology 2) to elicit downstream τ signaling in AD pathology. In this study, a comprehensive binary interaction map (CBIM) of all the 6 τ phosphotyrosine sites with 120 SH2 domains in the human genome was systematically created at structural level using computational analyses and binding assays, from which we were able to identify those of strong and moderate binding pairs of sites to domains. It is found that the SH2-recognition specificity of different τ phosphotyrosine sites has been evolutionally optimized to become roughly orthogonal to each other, and thus these site phosphorylations would regulate different but probably partially overlapped biological functions in τ signaling. Some SH2 groups such as SRC, RIN, PLCG, SOCS and SH2D were revealed to have effective binding potency as compared to others; they could be regarded as potential τ-associated proteins to transduce the downstream signaling. We further determined the systematic binding affinities of 6 τ-phosphopeptides to the 11 SH2 domains in SRC group, from which the FYN-τ¹⁸ and YES-τ²⁹ pairs were identified as strong binders. Subsequently, rational molecular design was performed on τ¹⁸ and τ²⁹ to derive a number of τ-phosphopeptide mutants with increased affinity; they are self-inhibitory candidates to competitively target τ hyperphosphorylation events in AD. In addition, it is revealed that the primary anchor pY₀ and secondary anchor X₊₃ of τ-phosphopeptides play an important role in SRC-group SH2 recognition, which confer stability and specificity to the SH2-phosphopeptide binding, respectively.