Inhibition Of Tau Aggregation Research Articles

Tau-aggregation inhibitors derived from Streptomyces tendae MCCC 1A01534 protect HT22 cells against okadaic acid-induced damage

Alzheimer's disease (AD) is an age-related neurodegenerative disease characterized by tau aggregating into neurofibrillary tangles. Targeting tau aggregation is one of the most critical strategies for AD treatment and prevention. Herein, a high-throughput screening of tau-aggregation inhibitors was performed by thioflavin T (ThT) fluorescence assay and tauR3 peptides. According to bioactivity-guided isolation, homoprejadomycin (1) was obtained from the marine bacterium Streptomyces tendae MCCC 1A01534. Two new stable derivatives, 2 and 3, were yielded in a one-step reaction. By ThT assay, transmission electron microscopy, and circular dichroism, we demonstrated that the angucyclinones 2 and 3 inhibited tau aggregation and disaggregated tau fibrils. In the presence of 2, native tauR3 peptides maintained the disorder conformation, whereas the tauR3 aggregates reduced β-sheet structures. And compound 2 was confirmed to inhibit the aggregation of full-length 2N4R tau protein. Furthermore, 2 with low cytotoxicity protected HT22 cells from okadaic acid-induced damage by suppressing tau aggregates. These results indicated that 2 was a promising lead structure with tau therapeutic potency for AD treatment.

Atomistic Insights into the Inhibitory Mechanism of Tyrosine Phosphorylation against the Aggregation of Human Tau Fragment PHF6.

Abnormal aggregation of the microtubule-associated protein tau into intracellular fibrillary inclusions is characterized as the hallmark of tauopathies, including Alzheimer's disease and chronic traumatic encephalopathy. The hexapeptide 306VQIVYK311 (PHF6) of R3 plays an important role in the aggregation of tau. Recent experimental studies reported that phosphorylation of residue tyrosine 310 (Y310) could decrease the propensity of PHF6 to form fibrils and inhibit tau aggregation. However, the underlying inhibitory mechanism is not well understood. In this work, we systematically investigated the influences of phosphorylation on the conformational ensembles and oligomerization dynamics of PHF6 by performing extensive all-atom molecular dynamics (MD) simulations. Our replica exchange MD simulations demonstrate that Y310 phosphorylation could effectively suppress the formation of β-structure and shift PHF6 oligomers toward coil-rich aggregates. The interaction analyses show that hydrogen bonding and hydrophobic interactions among PHF6 peptides, as well as Y310-Y310 π-π stacking and I308-Y310 CH-π interactions, are weakened by phosphorylation. Additional microsecond MD simulations show that Y310 phosphorylation could inhibit the oligomerization of PHF6 by preventing the formation of large β-sheet oligomers and multi-layer β-sheet aggregates. This study provides mechanistic insights into the phosphorylation-inhibited tau aggregation, which may be helpful for the in-depth understanding of the pathogenesis of tauopathies.

Blocking tau transmission by biomimetic graphene nanoparticles.

Tauopathies are a class of neurodegenerative diseases resulting in cognitive dysfunction, executive dysfunction, and motor disturbance. The primary pathological feature of tauopathies is the presence of neurofibrillary tangles in the brain composed of tau protein aggregates. Moreover, tau aggregates can spread from neuron to neuron and lead to the propagation of tau pathology. Although numerous small molecules are known to inhibit tau aggregation and block tau cell-to-cell transmission, it is still challenging to use them for therapeutic applications due to poor specificity and low blood-brain barrier (BBB) penetration. Graphene nanoparticles were previously demonstrated to penetrate the BBB and are amenable to functionalization for targeted delivery. Moreover, these nanoscale biomimetic particles can self-assemble or assemble with various biomolecules including proteins. In this paper, we show that graphene quantum dots (GQDs), as graphene nanoparticles, block the seeding activity of tau fibrils by inhibiting the fibrillization of monomeric tau and triggering the disaggregation of tau filaments. This behavior is attributed to electrostatic and π-π stacking interactions of GQDs with tau. Overall, our studies indicate that GQDs with biomimetic properties can efficiently inhibit and disassemble pathological tau aggregates, and thus block tau transmission, which supports their future developments as a potential treatment for tauopathies.

Inhibition of Tau Protein Aggregation Using Small Molecule Inhibitors and Immunotherapies

AbstractBackgroundTau protein aggregation is one of the biomarkers of neurodegenerative diseases and is a viable drug target. Small molecules and immunotherapies have been tested targeting tauopathies. Understanding of the inhibitor mode‐of‐action is needed in order to develop effective drugs against neurodegeneration.MethodThe full length tau protein (2N4R, 441) was used in vitro with aggregation inducers: heparin and arachidonic acid. We have used small molecule inhibitors based of dopamine receptor agonist as inhibitors of tau aggregation in vitro. The inhibition of tau aggregation was also conducted in vitro using anti‐tau antibodies. The biophysical methods including electron microscopy and fluorescence spectroscopy were used to measure inhibitor efficiency.ResultThe anti‐tau antibodies which target epitope in R1‐R4 repeat domain were most effective in inhibition aggregation. The small molecules containing catechol groups were effective aggregation inhibitors and were in micromolar range, which was similar to the efficacy of methylene blue.ConclusionThe tau aggregation was inhibited in vitro using dual approach, with small and large molecules, indicating that both strategies are viable against tauopathies. Future work will require design of multifunctional inhibitors to improve selectivity and potency.

Visualization of tau oligomers in TauP301L‐BiFC transgenic mice exhibits the progression of tauopathy

AbstractBackgroundAccumulation of abnormal tau aggregates in the brain is a pathological hallmark of multiple neurodegenerative disorders including Alzheimer’s disease (AD). Increasing evidence suggests that soluble tau aggregates play a key role in tau pathology as neurotoxic species causing neuronal cell death and act as prion‐like seeds mediating tau propagation. Despite the pathological relevance, there is a paucity of methods to monitor tau oligomerization in the brain. Therefore, we have developed a novel tau transgenic mouse model as a tool to monitor tau self‐assembly in the brain.MethodWe introduced bimolecular fluorescence complementation (BiFC) technique to human tau containing a P301L mutation to generate a novel tau transgenic mouse, named TauP301L‐BiFC. Tau self‐assembly, represented by BiFC fluorescence was monitored and quantified in the brain of transgenic TauP301L‐BiFC mice. Behavior and biochemical differences were assessed between 3 and 12 months for the characterization of TauP301L‐BiFC mice. In vivo efficacy of methylene blue, a tau aggregation inhibitor, was evaluated for further validation of TauP301L‐BiFC mice as an in vivo model of tauopathy.ResultsTauP301L‐BiFC mice showed soluble tau oligomerization from 3 months, showing significantly enriched BiFC fluorescence in the brain. Then, massive tau fragmentation occurred at 6 months showing dramatically decreased TauP301L‐BiFC fluorescence. The fragmented tau species served as a seed for insoluble tau aggregation. In a result, insoluble TauP301L‐BiFC aggregates co‐aggregated with endogenous mouse tau accumulated in the brain, showing subsequently increased BiFC fluorescence from 9 months. Neuronal degeneration and cognitive deficits were observed from 12 months of age. Administration of methylene blue significantly reduced tau‐BiFC fluorescence in the brain of TauP301L‐BiFC mice, presenting a significant decrease in the level of matured tau‐BiFC complexes in the soluble brain lysates. TauP301L‐BiFC mouse model demonstrated that methylene blue reduced the amount of soluble tau oligomers in the brain, resulting in the prevention of cognitive impairments.ConclusionThe tau oligomerization was able to monitor and quantify in the brain of TauP301L‐BiFC mice. Thus, we assure that TauP301L‐BiFC mice are a bonafide animal tool to monitor pathological tau oligomerization in AD and other tauopathies.

Tau immunotherapy in Alzheimer's disease and progressive supranuclear palsy.

Tubulin-associated unit (tau) has been associated with more than 25 neurological disorders-the so-called tauopathies. Hence, finding a novel therapeutic agent targeting tau to halt the progression of diseases has been of interest. Alzheimer's disease (AD) and progressive supranuclear palsy (PSP) are the most studied tauopathies. AD is characterized by two cardinal pathological mechanisms: amyloid β (Aβ) plaques and neurofibrillary tangles (NFTs), leading to atrophy of the brain. Over the last few years, attention has been on NFTs composed of the hyperphosphorylated microtubule-associated protein tau. Tau contributes to the synaptic plasticity of axons; hyperphosphorylated and aggregated tau have been shown to increase the likelihood of cognitive impairments. PSP is also associated with tau accumulation in NFTs and neuropil threads, making this condition a candidate for tau-targeted therapies. Many tau-targeting therapies have been developed, and clinical trials are being conducted. Tau-targeting drugs are classified into four subgroups based on the pathological target: tau phosphorylation inhibitors, stabilizers of microtubules, enhancing tau clearance, and tau aggregation inhibitors. On the other hand, the desired specificity and sensitivity of tau immunotherapy agents without interrupting normal proteome are the fundamental point of tremendous attention. Starting with animal studies of these therapies to clinical trials, both are divided into passive and active immunotherapies, while passive immunotherapies are the method of desire. Targeting aggregation and phosphorylation sites of tau is the chief target of therapies. This article reviews the latest animal and clinical studies of tau-based immunotherapies and tau-targeted drugs for AD and PSP.

Discovery of DA‐7503 as a Novel Tau‐targeted Therapeutic Candidate for the Treatment of Alzheimer’s Disease

AbstractBackgroundAlzheimer’s disease (AD) is a late‐onset, progressive, age‐dependent neurodegenerative disorder. The load of neurofibrillary tangles correlates strongly with clinical progression of the disease. Although tauopathy has been extensively studied as a key hypothesis in AD, there are currently no clinical tau‐targeted drugs that produce a noticeable improvement. Therefore, we studied and developed novel tau‐targeted therapeutic drug candidates for the treatment of AD; in particular, tau aggregation inhibitors.MethodWe performed high‐content screening based on a Tau‐BiFC cell‐based assay platform and identified novel tau aggregation inhibitors. Lead optimization was subsequently performed to improve potency and ADME/Tox properties, resulting in the production of DA‐7503. In vivo efficacy of the candidate was validated by demonstration of memory impairment restoration in two transgenic animal models of P301L Tau‐BiFC and rTg4510. The non‐clinical GLP‐Tox studies of DA‐7503 is ongoing in order to proceed to clinical studies.ResultDA‐7503 exhibited excellent tau aggregation inhibitory activities (cell‐based IC50, 0.02 mM, in vitro IC50, 0.96 mM) with good cell viability (MTS IC50, 77.8 mM). DA‐7503 reduced tau oligomerization and protected against neuronal cell death. It restored memory impairment in P301L Tau‐BiFC and rTg4510 Tg mouse models (NOR, Open Field, and Morris Water Maze test) with reduction of tau pathology. The mode of action of DA‐7503 was confirmed by MALDI‐TOF Mass Spectrometric Analysis, 2D HSQC NMR and TR‐2 competition study to show reversible covalent inhibition of disulfide‐dependent oligomer formation.Conclusion DA‐7503, a highly potent inhibitor of tau aggregation, significantly improved memory impairment and reduced tau pathology in P301L Tau‐BiFC and rTg4510 Tg mouse models with good pharmacological properties. Currently, the GLP‐Tox safety profile of DA‐7503 as a non‐clinical candidate is being evaluated, and early results are promising enough to proceed to clinical studies.

Brain Derived Biologically Relevant Tau Oligomers

AbstractBackgroundNeurodegenerative Tauopathies, including Alzheimer’s disease (AD), are characterized by the appearance of extracellular lesions composed of aggregated and post‐translationally modified tau proteins. The resulting tau pathology is an established marker for differential disease diagnosis and staging, a surrogate marker for neurodegeneration, a potential vector for disease propagation, and a source of toxicity in biological models. In comparison to the well‐established methods for isolation/preparation and biochemical and structural characterization of stable tau filaments from tauopathy brain, the characterization of smaller and much dynamic oligomeric tau aggregates has not been investigated to the same degree. As a result, tau oligomers that may associate most closely with disease propagation and toxicity as suggested by a large body of research, are not fully established.MethodHerein, we leverage our well‐optimized brain‐derived tau oligomers (BDTOs) from well‐vetted human tauopathy cases of AD, progressive supranuclear palsy (PSP) and dementia with Lewy bodies (DLB). In addition to our rigorous biochemical characterization of the BDTOs by immunological probing, and structural characterization by proteolysis and microscopic analyses, we have optimized Fluorescent Amyloid Multi Emission Spectra (FLAMES) microscopy for cataloging and comparing tau conformational variants across a wide range of samples, from brain tissue sections and BDTOs to in vitro aggregated tau assemblies. For selective immunodetection of the BDTOs, we have used our novel four fully sequenced and epitope mapped Tau Oligomer Monoclonal Antibodies (TOMAs), which recognize non‐continuous sequences on tau. Furthermore, the bioactivity of the BDTOs was assessed by evaluating their seeding propensity in biosensor cells and primary cortical neurons from tauopathy mice and their effects on synaptic function by electrophysiological studies.ResultWe observed that the BDTOs differed in their immunological properties, morphology, and sensibility/stability to proteolysis. The BDTOs were distinguished based on FLAMES spectral signature. Distinct seeding propensity and impairment of long‐term potentiation (LTP) indicated their differences in bioactivity as well.ConclusionOur thorough investigation/characterization of biologically active disease‐relevant tau oligomers will provide new opportunities to diagnose and evaluate therapeutics beyond the current capabilities for AD and related tauopathies by developing specific tau aggregation inhibitors and/or diagnostic probes for pathological tau protein.

Discovery of Dual Aβ/Tau Inhibitors and Evaluation of Their Therapeutic Effect on a Drosophila Model of Alzheimer's Disease.

Alzheimer's disease (AD), the most common type of dementia, currently represents an extremely challenging and unmet medical need worldwide. Amyloid-β (Aβ) and Tau proteins are prototypical AD hallmarks, as well as validated drug targets. Accumulating evidence now suggests that they synergistically contribute to disease pathogenesis. This could not only help explain negative results from anti-Aβ clinical trials but also indicate that therapies solely directed at one of them may have to be reconsidered. Based on this, herein, we describe the development of a focused library of 2,4-thiazolidinedione (TZD)-based bivalent derivatives as dual Aβ and Tau aggregation inhibitors. The aggregating activity of the 24 synthesized derivatives was tested in intact Escherichia coli cells overexpressing Aβ42 and Tau proteins. We then evaluated their neuronal toxicity and ability to cross the blood-brain barrier (BBB), together with the in vitro interaction with the two isolated proteins. Finally, the most promising (most active, nontoxic, and BBB-permeable) compounds 22 and 23 were tested in vivo, in a Drosophila melanogaster model of AD. The carbazole derivative 22 (20 μM) showed extremely encouraging results, being able to improve both the lifespan and the climbing abilities of Aβ42 expressing flies and generating a better outcome than doxycycline (50 μM). Moreover, 22 proved to be able to decrease Aβ42 aggregates in the brains of the flies. We conclude that bivalent small molecules based on 22 deserve further attention as hits for dual Aβ/Tau aggregation inhibition in AD.

The inhibitory effect of Curcumin-Artemisinin co-amorphous on Tau aggregation and Tau phosphorylation

Tau is a natively unfolded microtubule-associated protein. Tau neurofibrillary tangles are one of the hallmarks of Alzheimer’s disease. The post-translational modifications of Tau lead to its pathological state. Phosphorylation is the key post-translational modification associated with Tauopathy. Curcumin is a polyphenolic compound present in the rhizomes of Curcuma longa. Curcumin has been reported to have remarkable medicinal properties in several diseases, but its poor solubility limits its therapeutic potency. Artemisinin is a sesquiterpene lactone, which has been known sience ancient times for its applications as a treatment for various diseases such as malaria, cancer, autoimmune disease, etc. In the present study, the potency of crystalline curcumin, crystalline artemisinin, and Cur-Art co-amorphous dispersion were evaluated against Tau pathology. The in-vitro ThS/ANS fluorescence and electron microscopy results suggested that curcumin and Cur-Art efficiently inhibited Tau aggregation. Furthermore, exposure to curcumin and Cur-Art co-amorphous restored the impaired nuclear transport in formaldehyde-stressed cells. Curcumin was also found to modulate the phosphorylation of Tau, which indicated the neuroprotective potency. Thus, curcumin and Cur-Art co-amorphous exhibit therapeutic potential against Tau protein in Alzheimer’s disease.

Rose Bengal inhibits β-amyloid oligomers-induced tau hyperphosphorylation via acting on Akt and CDK5 kinases.

Tau hyperphosphorylation and aggregation is considered as a main pathological mechanism underlying Alzheimer's disease (AD). Rose Bengal (RB) is a synthetic dye used for disease diagnosis, which was reported to inhibit tau toxicity via inhibiting tau aggregation in Drosophila. However, it was unknown if RB could produce anti-AD effects in rodents. The research aimed to investigate if and how RB could prevent β-amyloid (Aβ) oligomers-induced tau hyperphosphorylation in rodents. RB was tested in vitro (0.3-1μM) and prevented Aβ oligomers-induced tau hyperphosphorylation in PC12 cells. Moreover, RB (10-30mg/kg, i.p.) effectively attenuated cognitive impairments induced by Aβ oligomers in mice. Western blotting analysis demonstrated that RB significantly increased the expression of pSer473-Akt, pSer9-glycogen synthase kinase-3β (GSK3β) and reduced the expression of cyclin-dependent kinase 5 (CDK5) both in vitro and in vivo. Molecular docking analysis suggested that RB might directly interact with GSK3β and CDK5 by acting on ATP binding sites. Gene Ontology enrichment analysis indicated that RB might act on protein phosphorylation pathways to inhibit tau hyperphosphorylation. RB was shown to inhibit tau neurotoxicity at least partially via inhibiting the activity of GSK3β and CDK5, which is a novel neuroprotective mechanism besides the inhibition of tau aggregation. As tau hyperphosphorylation is an important target for AD therapy, this study also provided support for investigating the drug repurposing of RB as an anti-AD drug candidate.

A Critical Review of Role of Medhya Dravyas (Nootropic Drugs) in Brain Fog with special reference to Covid- 19

Cognitive dysfunction after COVID-19 are hypoxia, microvascular injury, immunological dysregulation, chronic inflammation, patients with mild infections also report cognitive symptoms. A recognized symptom of long COVID is “Brain Fog”, characterized by fatigue, lack of ability to concentrate and can severely affect memory and cognition. Long-term side effects of COVID-19 is Brain fog which occurs irrespective of the severity of the infection. The Medhya Dravyas (Nootropic drugs) are beneficial to improve the power of retention, grasping, discrimination and recollection thus improving the Medha (Cognition). Present clinical study is an attempt to evaluate the nootropic effect of certain drugs in Brain Fog with special reference to Covid 19. Aim: To review medicinal plants showing Medhya Karma (Nootropic activity) on signs and symptoms correlated with brain fog in Covid 19 with Ayurveda as a natural and safe remedy. Material and Methods: Materials related to Covid 19, Brain fog, Neurological symptoms cognitive impairment, Medhya Dravyas (Nootropic drugs) have been collected from different journals, Ayurveda and Modern text, Authentic websites (PubMed, Google scholar, Scopus, etc.), Observation and Results: Plants reviewed showed nootropic action by Antioxidant, Acetylcholine esterase inhibition, NMDA antagonism, Dopaminergic, Anti-amyloidogenic, Inhibition of Tau aggregation and Neuroprotection. These properties helps in the management of cognitive impairment. Conclusion-Medhya Dravyas possess nootropic and rejuvenative properties. Plants shown maximum inhibitory activities against the factors causing brain Fog by Neuroprotection and memory enhancement. It reveals the strength of the Ayurveda system as well as potential in developing new drug for memory enhancement

Effectiveness and safety of anti-tau drugs for Alzheimer's disease: Systematic review and meta-analysis.

To assess the cognitive effectiveness and safety of tau-targeting drugs for Alzheimer's disease (AD) METHODS: The MEDLINE, Embase, Cochrane Library, PsycINFO, ClinicalTrials.gov, and WHO International Clinical Trials Registry Platform databases were searched from inception to 22 November 2021. A systematic review and meta-analysis of randomized controlled trials were performed RESULTS: Thirty-four randomized controlled trials comprising 5549 participants, of which fifteen (51.7%) had a low risk of bias, were included. The meta-analysis showed no differences in the cognitive subscale of the AD: Assessment Scale (ADAS-Cog) between anti-tau drugs and placebo (mean difference [MD]: -0.77, 95% CI: -1.64 to 0.10; minimal important difference 3.1-3.8 points, moderate certainty evidence). For ADAS-Cog, the results subgroup analysis suggested a statistical effect of tau posttranslational modifications on drug inhibition (MD: -0.80, 95% CI: -1.43 to -0.17), which was not seen with tau aggregation inhibitors or immunotherapy (interaction p=0.24). A total of 11.0%, 5.2%, and 4.8% of drugs inhibiting tau aggregation, immunotherapy, and drugs targeting posttranslational modifications, respectively, had a reduced risk of dropouts due to adverse events (AEs). Current evidence suggests that anti-tau drugs are unlikely to have an important impact on slowing cognitive impairment. Although the subgroup analysis suggested that inhibition of tau posttranslational modifications is statistically effective and generally safer because of reduced dropouts due to AEs, the analysis has limited credibility. Additional large-scale and well-designed randomized and placebo-controlled trials will be necessary to explore the benefit of a certain type of anti-tau drug for AD.

Merocyanine Complexes Coupled with Plasmonic Au Nanoparticles for Inhibiting Tau Aggregation

Singlet oxygen (1O2) has been recently identified as the key mechanism for depressing β-amyloid (Aβ) accumulation and neurofibrillary tangles (NFTs). Slow cell internalization and short half-life of photosensitizing effects still impede the application of nanophotosensitizers for photodynamic therapy (PDT). The current major challenge of using spiropyran for PDT is the extremely short half-life of its ring-opened isomer, merocyanine. Merocyanine is the center of generation of 1O2. Here, we report that the complexation of spiropyran onto Au nanoparticles greatly enhances the stability of merocyanine (half-life is 91.6 h). Additionally, Au nanoparticles sharply decelerate the reversion of merocyanine back to spiropyran (a ring-closed form) by modifying the energy configuration of merocyanine, resulting in generation of a long-lived 1O2 phototherapy response (24 h) in the intracellular environment for depressing tau aggregation (a 32% reduction of NFT formation).

A Review of the pharmacological treatments of Alzheimer’s disease (AD)

Alzheimer’s disease (AD) is an irreversible, neurodegenerative disease that has haunted millions of lives globally. This article briefly reviews the diagnosis and pathophysiology behind AD while focusing on the currently approved and potential pharmacological treatments for AD. Cholinesterase inhibitors and NMDA receptor antagonists have been the most widely used drug to treat AD for decades. In 2003, Aducanumab was authorized by the US FDA for market use but not by other countries. Unfortunately, all the drugs mentioned could only ameliorate the clinical syndromes of AD instead of curing the disease and came with various side effects. Research has shown that the clinical progression of AD happens in parallel with the accumulation of amyloid β plaques and the spread of neurofibrillary tangles composed of hyperphosphorylated tau. There are many potential drugs under different stages of trials, including β‑secretase inhibitors, γ‑secretase inhibitors, monoclonal antibodies, tau aggregation inhibitors, and other therapeutic strategies. Although they are still immature to be put into clinical use, we are looking forward that a specific and efficient drug that has fewer side effects for AD will be developed in the future.

Inhibition Of Tau Protein Aggregation By a Chaperone-like β-Boswellic Acid Conjugated To Gold Nanoparticles

A potential therapeutic strategy to inhibit tau protein aggregation in neurons has substantial effects on preventing or controlling Alzheimer’s disease (AD). In this work, we designed a covalent and noncovalent conjugation of β-boswellic acid (BA) to gold nanoparticles (GNPs). We provided the opportunity to investigate the effect of the surface composition of BA-GNPs on the aggregation of the tau protein 1N/4R isoform in vitro. HR-TEM and FESEM micrographs revealed that GNPs were spherical and uniform, smaller than 25 nm. According to UV–visible and FTIR data, BA was successfully conjugated to GNPs. The finding illustrates the effect of the surface charge, size, and hydrophobicity of BA-GNPs on the kinetics of tau protein aggregation. The size and surface area of U-G-BA demonstrated that inhibited tau aggregation more effectively than covalently linked BA. The proposed method for preventing tau aggregation was monomer reduction. At the same time, a chaperone-like feature of GNP-BA while sustaining a tau native structure prevented the additional formation of fibrils. Overall, this study provides insight into the interaction of GNP-BAs with a monomer of tau protein and may suggest novel future therapies for AD.

Imipramine and olanzapine block apoE4-catalyzed polymerization of Aβ and show evidence of improving Alzheimer’s disease cognition

BackgroundThe apolipoprotein E (APOE) ε4 allele confers the strongest risk for late-onset Alzheimer’s disease (AD) besides age itself, but the mechanisms underlying this risk are debated. One hypothesis supported by evidence from multiple labs is that apoE4 binds to the amyloid-β (Aβ) peptide and catalyzes its polymerization into neurotoxic oligomers and fibrils. Inhibiting this early step in the amyloid cascade may thereby reduce or prevent neurodegeneration and AD.MethodsUsing a design of experiments (DOE) approach, we developed a high-throughput assay to identify inhibitors of apoE4-catalyzed polymerization of Aβ into oligomers and fibrils. We used it to screen the NIH Clinical Collection of small molecule drugs tested previously in human clinical trials. We then evaluated the efficacy and cytotoxicity of the hit compounds in primary neuron models of apoE4-induced Aβ and phosphorylated tau aggregation. Finally, we performed retrospective analyses of the National Alzheimer’s Coordinating Center (NACC) clinical dataset, using Cox regression and Cox proportional hazards models to determine if the use of two FDA-approved hit compounds was associated with better cognitive scores (Mini-Mental State Exam), or improved AD clinical diagnosis, when compared with other medications of the same clinical indication.ResultsOur high-throughput screen identified eight blood-brain barrier (BBB)-permeable hit compounds that reduced apoE4-catalyzed Aβ oligomer and fibril formation in a dose-dependent manner. Five hit compounds were non-toxic toward cultured neurons and also reduced apoE4-promoted Aβ and tau neuropathology in a dose-dependent manner. Three of the five compounds were determined to be specific inhibitors of apoE4, whereas the other two compounds were Aβ or tau aggregation inhibitors. When prescribed to AD patients for their normal clinical indications, two of the apoE4 inhibitors, imipramine and olanzapine, but not other (non-hit) antipsychotic or antidepressant medications, were associated with improvements in cognition and clinical diagnosis, especially among APOE4 carriers.ConclusionsThe critical test of any proposed AD mechanism is whether it leads to effective treatments. Our high-throughput screen identified two promising FDA-approved drugs, imipramine and olanzapine, which have no structural, functional, or clinical similarities other than their shared ability to inhibit apoE4-catalyzed Aβ polymerization, thus identifying this mechanism as an essential contribution of apoE4 to AD.

Oral Tau Aggregation Inhibitor for Alzheimer’s Disease: Design, Progress and Basis for Selection of the 16 mg/day Dose in a Phase 3, Randomized, Placebo-Controlled Trial of Hydromethylthionine Mesylate

BackgroundHydromethylthionine mesylate is a tau aggregation inhibitor shown to have exposure-dependent pharmacological activity on cognitive decline and brain atrophy in two completed Phase 3 trials in mild/moderate Alzheimer’s disease (AD).ObjectivesThe present report summarises the basis for selection of 16 mg/day as monotherapy as the optimal treatment regime and the design rationale of a confirmatory Phase 3 trial (LUCIDITY).DesignThe trial comprises a 12-month double-blind, placebo-controlled phase followed by a 12-month modified delayed-start open-label treatment phase.Setting76 clinical research sites in North America and Europe.Participants545 patients with probable AD or MCI-AD in the final version of the protocol.InterventionParticipants were assigned randomly to receive hydromethylthione mesylate at doses of 16 mg/day, 8 mg/day or placebo at a 4:1:4 ratio during the double-blind phase. All participants in the open-label phase receive the 16 mg/day dose.MeasurementsCo-primary clinical outcomes are the 11-item Alzheimer’s Disease Assessment Scale (ADAS-cog11) and the 23-item Alzheimer’s Disease Cooperative Study — Activities of Daily Living (ADCS-ADL23). Secondary biomarker measures include whole-brain atrophy and temporal lobe 18F-fluorodeoxyglucose positron emission tomography.Results446 participants are expected to complete the 12-month placebo-controlled phase in March 2022.ConclusionsIf the primary end points are met, the data will provide confirmatory evidence of the clinical and biomarker benefits of hydromethylthionine mesylate in minimal to moderate AD. As low-dose oral hydromethylthionine mesylate is simple to use clinically, does not cause amyloid-related imaging abnormalities and has a benign safety profile, it would likely improve AD management.

Vascular risk factors affect different brain regions in people with Alzheimer’s disease

IntroductionVascular risk factors including hypertension, diabetes and dyslipidaemia promote diverse pathological mechanisms in the brain leading to cerebral hypoperfusion and ultimately cognitive decline in people. Medial temporal, medial frontal and anterior cingulate atrophy has been closely associated with diabetes and medial temporal lobe atrophy is associated with hypertension in people with Alzheimer’s disease (AD).ObjectivesTo assess if hypertension, diabetes and dyslipidaemia have differential effects on different brain locations using brain imaging in people with AD.MethodsThe current study is based on [18F] fluorodeoxyglucose- positron emission tomography (FDG-PET) data of 970 participants from two large Phase III multi-centre clinical trials of a novel tau aggregation inhibitor drug Leuco-Methylthioninium (LMTX)meeting research criteria for mild to moderate AD. Vascular risk factor data including hypertension, diabetes and dyslipidaemia were collected and quantification of FDG PET hypo-metabolism was done by calculating Standardized Uptake Value Ratio(SUVR).ResultsHypertension, diabetes and dyslipidaemia were found to have differential effects on brain locations in people with AD. When people with hypertension, diabetes and dyslipidaemia were compared to those without, mean SUVR was increased significantly in both left and right parietal and occipital lobes and decreased in left and right anterior cingulate gyri in hypertensives. SUVR was significantly higher in both left and right temporal lobes in diabetics andlower in both left and right anterior cingulate gyri in people with dyslipidaemia.ConclusionsVascular risk factors including hypertension, diabetes and dyslipidaemia have differential effects on different brain regions, measured using SUVR analysis of FDG-PET.DisclosureThe FDG-PET data was taken from participants of two large phase III clinical trials sponsored by TauRx Therapeutics (Singapore). TauRx Therapeutics has contributed towards my studentship during my PhD but the data related to drug used in the clinical tria

In silico Analysis of Selected Phytocompounds of Cocculus hirsutus as Potent Inhibitors of Tau Aggregation in Alzheimer's Disease

In the current investigation, the selected phytocompounds of Cocculus hirsutus were screened for potent tau aggregation inhibitors for Alzheimer's disease through in silico molecular docking. Approximately 19 phytocompounds from Cocculus hirsutus were selected and assessed for their drug likeness based on rule-of-five using Swiss ADME. The phytocompounds that passed rule-of-five were subjected to in silico analysis through molecular docking on Cyclin-dependent kinase 5 (CDK5) and Glycogen synthase kinase 3 beta (GSK3B) using Molegro Virtual Docker v6.0. Molecular docking studies. The molecular interaction on CDK5 and GSK3B enzymes indicate their role in the tau protein aggregation inhibitory activity of the phytocompounds. In silico analysis showed that hirsutine and cohirsinine bind effectively at the active site of target proteins with a MolDock score of -115.08 and -107.29 respectively. The MolDock scores, ReRank scores and interaction poses of the phytocompounds were compared with the known inhibitors of CDK5 and GSK3B enzymes. The present research created a new perspective in understanding hirsutine and cohirsinine phytocompounds as effective inhibitors of tau aggregation and further research in vitro and in vivo may confirm their therapeutic potential in Alzheimer's.