A phase II trial of tideglusib in Alzheimer's disease

Protein aggregation and neurodegenerative disease: Structural outlook for the novel therapeutics

Before the controversial approval of humanized monoclonal antibody lecanemab, which binds to the soluble amyloid-β protofibrils, all the treatments available earlier, for Alzheimer's disease (AD) were symptomatic. The researchers are still struggling to find a breakthrough in AD therapeutic medicine, which is partially attributable to lack in understanding of the structural information associated with the intrinsically disordered proteins and amyloids. One of the major challenges in this area of research is to understand the structural diversity of intrinsically disordered proteins under in vitro conditions. Therefore, in this review, we have summarized the in vitro applications of biophysical methods, which are aimed to shed some light on the heterogeneity, pathogenicity, structures and mechanisms of the intrinsically disordered protein aggregates associated with proteinopathies including AD. This review will also rationalize some of the strategies in modulating disease-relevant pathogenic protein entities by small molecules using structural biology approaches and biophysical characterization. We have also highlighted tools and techniques to simulate the in vivo conditions for native and cytotoxic tau/amyloids assemblies, urge new chemical approaches to replicate tau/amyloids assemblies similar to those in vivo conditions, in addition to designing novel potential drugs.

Tau and neuroinflammation in Alzheimer's disease: interplay mechanisms and clinical translation

Alzheimer's Disease (AD) contributes to most cases of dementia. Its prominent neuropathological features are the extracellular neuritic plaques and intercellular neurofibrillary tangles composed of aggregated β-amyloid (Aβ) and hyperphosphorylated tau protein, respectively. In the past few decades, disease-modifying therapy targeting Aβ has been the focus of AD drug development. Even though it is encouraging that two of these drugs have recently received accelerated US Food and Drug Administration approval for AD treatment, their efficacy or long-term safety is controversial. Tau has received increasing attention as a potential therapeutic target, since evidence indicates that tau pathology is more associated with cognitive dysfunction. Moreover, inflammation, especially neuroinflammation, accompanies AD pathological processes and is also linked to cognitive deficits. Accumulating evidence indicates that inflammation has a complex and tight interplay with tau pathology. Here, we review recent evidence on the interaction between tau pathology, focusing on tau post-translational modification and dissemination, and neuroinflammatory responses, including glial cell activation and inflammatory signaling pathways. Then, we summarize the latest clinical trials targeting tau and neuroinflammation. Sustained and increased inflammatory responses in glial cells and neurons are pivotal cellular drivers and regulators of the exacerbation of tau pathology, which further contributes to its worsening by aggravating inflammatory responses. Unraveling the precise mechanisms underlying the relationship between tau pathology and neuroinflammation will provide new insights into the discovery and clinical translation of therapeutic targets for AD and other tau-related diseases (tauopathies). Targeting multiple pathologies and precision therapy strategies will be the crucial direction for developing drugs for AD and other tauopathies.

Tau pathology in neurodegenerative disease: disease mechanisms and therapeutic avenues

Tauopathies are disorders associated with tau protein dysfunction and insoluble tau accumulation in the brain at autopsy. Multiple lines of evidence from human disease, as well as nonclinical translational models, suggest that tau has a central pathologic role in these disorders, historically thought to be primarily related to tau gain of toxic function. However, a number of tau-targeting therapies with various mechanisms of action have shown little promise in clinical trials in different tauopathies. We review what is known about tau biology, genetics, and therapeutic mechanisms that have been tested in clinical trials to date. We discuss possible reasons for failures of these therapies, such as use of imperfect nonclinical models that do not predict human effects for drug development; heterogeneity of human tau pathologies which may lead to variable responses to therapy; and ineffective therapeutic mechanisms, such as targeting of the wrong tau species or protein epitope. Innovative approaches to human clinical trials can help address some of the difficulties that have plagued our field's development of tau-targeting therapies thus far. Despite limited clinical success to date, as we continue to refine our understanding of tau's pathogenic mechanism(s) in different neurodegenerative diseases, we remain optimistic that tau-targeting therapies will eventually play a central role in the treatment of tauopathies.

Disruption of axonal transport in neurodegeneration

Neurons are markedly compartmentalized, which makes them reliant on axonal transport to maintain their health. Axonal transport is important for anterograde delivery of newly synthesized macromolecules and organelles from the cell body to the synapse and for the retrograde delivery of signaling endosomes and autophagosomes for degradation. Dysregulation of axonal transport occurs early in neurodegenerative diseases and plays a key role in axonal degeneration. Here, we provide an overview of mechanisms for regulation of axonal transport; discuss how these mechanisms are disrupted in neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, Huntington's disease, hereditary spastic paraplegia, amyotrophic lateral sclerosis, and Charcot-Marie-Tooth disease; and discuss therapeutic approaches targeting axonal transport.

Discovery of 2-(Anilino)pyrimidine-4-carboxamides as Highly Potent, Selective, and Orally Active Glycogen Synthase Kinase-3 (GSK-3) Inhibitors

Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase that serves as an important regulator of a broad range of cellular functions. It has been linked to Alzheimer's disease as well as various other diseases, including mood disorders, type 2 diabetes, and cancer. There is considerable evidence indicating that GSK-3β in the central nervous system plays a role in the production of abnormal, hyperphosphorylated, microtubule-associated tau protein found in neurofibrillary tangles associated with Alzheimer's disease. A series of analogues containing a pyrimidine-based hinge-binding heterocycle was synthesized and evaluated, leading to the identification of highly potent GSK-3 inhibitors with excellent kinase selectivity. Further evaluation of 34 and 40 in vivo demonstrated that these compounds are orally bioavailable, brain-penetrant GSK-3 inhibitors that lowered levels of phosphorylated tau in a triple-transgenic mouse Alzheimer's disease model.

Focusing on oligomeric tau as a therapeutic target in Alzheimer's disease and other tauopathies

INTRODUCTION

Tau has commanded much attention as a potential therapeutic target in neurodegenerative diseases. Tau pathology is a hallmark of primary tauopathies, such as progressive supranuclear palsy (PSP), corticobasal syndrome (CBS), and subtypes of frontotemporal dementia (FTD), as well as secondary tauopathies, such as Alzheimer's disease (AD). The development of tau therapeutics must reconcile with the structural complexity of the tau proteome, as well as an incomplete understanding of the role of tau in both physiology and disease.

AREAS COVERED

This review offers a current perspective on tau biology, discusses key barriers to the development of effective tau-based therapeutics, and promotes the idea that pathogenic (as opposed to merely pathological) tau should be at the center of drug development efforts.

EXPERT OPINION

An efficacious tau therapeutic will exhibit several primary features: 1) selectivity for pathogenic tau versus other tau species; 2) blood-brain barrier and cell membrane permeability, enabling access to intracellular tau in disease-relevant brain regions; and 3) minimal toxicity. Oligomeric tau is proposed as a major pathogenic form of tau and a compelling drug target in tauopathies.

In Silico-Motivated Discovery of Novel Potent Glycogen Synthase-3 Inhibitors: 1-(Alkyl/arylamino)-3H-naphtho[1,2,3-de]quinoline-2,7-dione Identified as a Scaffold for Kinase Inhibitor Development

Glycogen synthase kinase-3 (GSK-3) isoforms α and β have diverse roles within cell biology, and have been linked with multiple diseases that include prominent CNS conditions such as Alzheimer's disease and several psychiatric disorders. In this study, motivated by computation, we aimed to identify novel ATP-binding site inhibitors of GSK-3 with CNS-active potential. A ligand screening (docking) protocol against GSK-3β was first optimized, employing an active/decoy benchmarking set, with the final protocol selected based on statistical performance analysis. The optimized protocol involved pre-filtering of ligands using a three-point 3D-pharmacophore, followed by Glide-SP docking applying hinge region hydrogen bonding constraints. Using this approach, the Biogenic subset of the ZINC15 compound database was screened, focused on compounds with potential for CNS-activity. Twelve compounds (generation I) were selected for experimental validation using in vitro GSK-3β binding assays. Two hit compounds, 1 and 2, with 6-amino-7H-benzo[e]perimidin-7-one and 1-(phenylamino)-3H-naphtho[1,2,3-de]quinoline-2,7-dione type scaffolds were identified with IC₅₀ values of 1.63 µM and 20.55 µM, respectively. Ten analogues of 2 (generation II) were selected for structure activity relationship (SAR) analysis and revealed four low micromolar inhibitors (<10 µM), with 19 (IC₅₀ = 4.1 µM)~five times more potent than initial hit compound 2. Selectivity screening of low micromolar inhibitors 14 and 19 (comparing aryl- and alkyl-substituents) against 10 homologous kinases revealed unique selectivity profiles, with both compounds more potent against the GSK-3α isoform (IC₅₀s~2 µM) and, additionally, inhibitors of PKBβ (IC₅₀s < 25 µM). Compound 14 also inhibited ERK2 and 19, PKCγ, but generally good selectivity for GSK-3 isoforms over the other kinases was observed. The compounds had excellent predicted oral bioavailability and CNS-activity profiles, presenting promising candidates for future testing in cellular models of disease.

GSK-3β Allosteric Inhibition: A Dead End or a New Pharmacological Frontier?

Most kinase inhibitors are designed to bind to highly homologous ATP-binding sites, which leads to promiscuity and possible off-target effects. Allostery is an alternative approach to pursuing selectivity. However, allostery is difficult to exploit due to the wide variety of underlying mechanisms and the potential involvement of long-range conformational effects that are difficult to pinpoint. GSK-3β is involved in several pathologies. This critical target has an ATP-binding site that is highly homologous with the orthosteric sites of other kinases. Unsurprisingly, there is also great similarity between the ATP-binding sites of GSK-3β and its isomer, which is not redundant and thus would benefit from selective inhibition. Allostery would also allow for a moderate and tunable inhibition, which is ideal for GSK-3β, because this target is involved in multiple pathways, some of which must be preserved. However, despite considerable research efforts, only one allosteric GSK-3β inhibitor has reached the clinic. Moreover, unlike other kinases, there are no X-ray structures of GSK-3β in complex with allosteric inhibitors in the PDB data bank. This review aims to summarize the state of the art in allosteric GSK-3β inhibitor investigations, highlighting the aspects that make this target challenging for an allosteric approach.

3-Arylidene-2-oxindoles as GSK3β inhibitors and anti-thrombotic agents

Development of novel agents that prevent thrombotic events is an urgent task considering increasing incidence of cardiovascular diseases and coagulopathies that accompany cancer and COVID-19. Enzymatic assay identified novel GSK3β inhibitors in a series of 3-arylidene-2-oxindole derivatives. Considering the putative role of GSK3β in platelet activation, the most active compounds were evaluated for antiplatelet activity and antithrombotic activity. It was found that GSK3β inhibition by 2-oxindoles correlates with inhibition of platelet activation only for compounds 1b and 5a. Albeit, in vitro antiplatelet activity matched well with in vivo anti-thrombosis activity. The most active GSK3β inhibitor 5a exceeds antiplatelet activity of acetylsalicylic acid in vitro by 10.3 times and antithrombotic activity in vivo by 18.7 times (ED₅₀ 7.3 mg/kg). These results support the promising role of GSK3β inhibitors for development of novel antithrombotic agents.

Design, Structure-Activity Relationships, and In Vivo Evaluation of Potent and Brain-Penetrant Imidazo[1,2-b]pyridazines as Glycogen Synthase Kinase-3β (GSK-3β) Inhibitors

Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase that regulates numerous cellular processes, including metabolism, proliferation, and cell survival. Due to its multifaceted role, GSK-3 has been implicated in a variety of diseases, including Alzheimer's disease, type 2 diabetes, cancer, and mood disorders. GSK-3β has been linked to the formation of the neurofibrillary tangles associated with Alzheimer's disease that arise from the hyperphosphorylation of tau protein. The design and synthesis of a series of imidazo[1,2-b]pyridazine derivatives that were evaluated as GSK-3β inhibitors are described herein. Structure-activity relationship studies led to the identification of potent GSK-3β inhibitors. In vivo studies with 47 in a triple-transgenic mouse Alzheimer's disease model showed that this compound is a brain-penetrant, orally bioavailable GSK-3β inhibitor that significantly lowered levels of phosphorylated tau.

Targeted engagement of β-catenin-Ikaros complexes in refractory B-cell malignancies

In most cell types, nuclear β-catenin functions as prominent oncogenic driver and pairs with TCF7-family factors for transcriptional activation of MYC. Surprisingly, B-lymphoid malignancies not only lacked expression and activating lesions of β-catenin but critically depended on GSK3β for effective β-catenin degradation. Our interactome studies in B-lymphoid tumors revealed that β-catenin formed repressive complexes with lymphoid-specific Ikaros factors at the expense of TCF7. Instead of MYC-activation, β-catenin was essential to enable Ikaros-mediated recruitment of nucleosome remodeling and deacetylation (NuRD) complexes for transcriptional repression of MYC. To leverage this previously unrecognized vulnerability of B-cell-specific repressive β-catenin-Ikaros-complexes in refractory B-cell malignancies, we examined GSK3β small molecule inhibitors to subvert β-catenin degradation. Clinically approved GSK3β-inhibitors that achieved favorable safety prof les at micromolar concentrations in clinical trials for neurological disorders and solid tumors were effective at low nanomolar concentrations in B-cell malignancies, induced massive accumulation of β-catenin, repression of MYC and acute cell death. Preclinical in vivo treatment experiments in patient-derived xenografts validated small molecule GSK3β-inhibitors for targeted engagement of lymphoid-specific β-catenin-Ikaros complexes as a novel strategy to overcome conventional mechanisms of drug-resistance in refractory malignancies.

HIGHLIGHTS

Unlike other cell lineages, B-cells express nuclear β-catenin protein at low baseline levels and depend on GSK3β for its degradation.In B-cells, β-catenin forms unique complexes with lymphoid-specific Ikaros factors and is required for Ikaros-mediated tumor suppression and assembly of repressive NuRD complexes. CRISPR-based knockin mutation of a single Ikaros-binding motif in a lymphoid MYC superenhancer region reversed β-catenin-dependent Myc repression and induction of cell death. The discovery of GSK3β-dependent degradation of β-catenin as unique B-lymphoid vulnerability provides a rationale to repurpose clinically approved GSK3β-inhibitors for the treatment of refractory B-cell malignancies.

GRAPHICAL ABSTRACT

Abundant nuclear β-cateninβ-catenin pairs with TCF7 factors for transcriptional activation of MYCB-cells rely on efficient degradation of β-catenin by GSK3βB-cell-specific expression of Ikaros factors Unique vulnerability in B-cell tumors: GSK3β-inhibitors induce nuclear accumulation of β-catenin.β-catenin pairs with B-cell-specific Ikaros factors for transcriptional repression of MYC.

Ketogenic Diet as a Promising Non-Drug Intervention for Alzheimer’s Disease: Mechanisms and Clinical Implications

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that is mainly characterized by cognitive deficits. Although many studies have been devoted to developing disease-modifying therapies, there has been no effective therapy until now. However, dietary interventions may be a potential strategy to treat AD. The ketogenic diet (KD) is a high-fat and low-carbohydrate diet with adequate protein. KD increases the levels of ketone bodies, providing an alternative energy source when there is not sufficient energy supply because of impaired glucose metabolism. Accumulating preclinical and clinical studies have shown that a KD is beneficial to AD. The potential underlying mechanisms include improved mitochondrial function, optimization of gut microbiota composition, and reduced neuroinflammation and oxidative stress. The review provides an update on clinical and preclinical research on the effects of KD or medium-chain triglyceride supplementation on symptoms and pathophysiology in AD. We also detail the potential mechanisms of KD, involving amyloid and tau proteins, neuroinflammation, gut microbiota, oxidative stress, and brain metabolism. We aimed to determine the function of the KD in AD and outline important aspects of the mechanism, providing a reference for the implementation of the KD as a potential therapeutic strategy for AD.

Tideglusib enhances odontogenic differentiation in human dental pulp stem cells in vitro

AIM

Tideglusib is a small molecule agonist of the canonical Wnt pathway. The present study investigated the influence of Tideglusib on human dental pulp stem cell (hDPSC) proliferation, apoptosis, migration and odonto/osteogenic differentiation.

METHODOLOGY

hDPSCs were treated with 50, 100 nM or 200 nM Tideglusib. β-catenin accumulation was detected by immunofluorescence staining. Colony-forming unit ability was assessed by staining with Coomassie blue. Cell cycle progression and cell apoptosis were investigated using flow cytometry. Cell migration was examined using an in vitro wound-healing assay. Osteogenic differentiation was examined using alkaline phosphatase (ALP) staining, alizarin red S staining and osteogenic-related gene expression. The gene expression profile was examined using a high-throughput RNA sequencing technique. All experiments were repeated using cells derived from at least four different donors (n = 4). The Mann-Whitney U-test was used to identify significant differences between two independent group comparisons. For three or more group comparisons, statistical differences were assessed using the Kruskal-Wallis test followed by pairwise comparison. The significance level was set at 5% (p < .05).

RESULTS

Tideglusib activated the Wnt signalling pathway in hDPSCs as demonstrated by an increase in cytoplasmic β-catenin accumulation and nuclear translocation. Tideglusib did not affect hDPSC proliferation, cell cycle progression, cell apoptosis or cell migration. In contrast, 50 and 100 nM Tideglusib significantly enhanced mineralization and osteogenic marker gene expression (RUNX2, ALP, BMP2 and DSPP; p < .05).

CONCLUSIONS

Tideglusib enhanced the odonto/osteogenic differentiation of hDPSCs. Therefore, incorporating this bioactive molecule in a pulp-capping material could be a promising strategy to promote dentine repair.

Small Molecule GSK-3 Inhibitors Safely Promote the Proliferation and Viability of Human Dental Pulp Stem Cells-In Vitro

Small molecules have demonstrated promising results as successful alternatives to growth factors. In this study, focus was drawn to CHIR99021 and tideglusib as GSK-3 inhibitors known for their anti-inflammatory and regenerative potential. The effect of both tideglusib and CHIR99021 on the proliferation, viability, and stemness of human dental pulp stem cells (hDPSCs) was investigated to assess their possible role in regenerative dentistry. Briefly, hDPSCs were isolated from sound premolars extracted for orthodontic purposes. Cytotoxicity and proliferation assessment were performed via cell counting kit-8 followed by flow cytometric analysis of apoptotic marker ANNEXIN V. The effect of both small molecules on the stemness of hDPSCs was analyzed by qRT-PCR. Both tideglusib and CHIR99021 were proven to be safe on hDPSCs. The tideglusib concentration that resulted in higher viable cells was 100 nM, while the concentration for CHIR99021 was 5 nM. Both small molecules successfully induced cellular proliferation and demonstrated minimal expression of ANNEXIN V, indicative of the absence of cellular apoptosis and further confirming their positive effect on proliferation. Finally, both small molecules enhanced stemness markers expression as evidenced by qRT-PCR, which, again, highlighted the positive effect of both tideglusib and CHIR99021 on safely promoting the proliferation of hDPSCs while maintaining their stemness.

How Can Insulin Resistance Cause Alzheimer's Disease?

Alzheimer's disease (AD) is a neurodegenerative disorder associated with cognitive decline. Despite worldwide efforts to find a cure, no proper treatment has been developed yet, and the only effective countermeasure is to prevent the disease progression by early diagnosis. The reason why new drug candidates fail to show therapeutic effects in clinical studies may be due to misunderstanding the cause of AD. Regarding the cause of AD, the most widely known is the amyloid cascade hypothesis, in which the deposition of amyloid beta and hyperphosphorylated tau is the cause. However, many new hypotheses were suggested. Among them, based on preclinical and clinical evidence supporting a connection between AD and diabetes, insulin resistance has been pointed out as an important factor in the development of AD. Therefore, by reviewing the pathophysiological background of brain metabolic insufficiency and insulin insufficiency leading to AD pathology, we will discuss how can insulin resistance cause AD.

Milestoning simulation of ligand dissociation from the glycogen synthase kinase 3β

As drug-binding kinetics has become an important factor to be considered in modern drug discovery, this work evaluated the ability of the Milestoning method in computing the absolute dissociation rate of a ligand from the serine-threonine kinase, glycogen synthase kinase 3β, which is a target for designing drugs to treat diseases such as neurodegenerative disorders and diabetes. We found that the Milestoning method gave good agreement with experiment with modest computational costs. Although the time scale for dissociation lasted tens of seconds, the collective molecular dynamics simulations total less than 1μs. Computing the committor function helped to identify the transition states (TSs), in which the ligand moved substantially away from the binding pocket. The glycine-rich loop with a serine residue attaching to its tips was found to undergo large movement from the bound to the TSs and might play a role in controlling drug-dissociation kinetics.

Injectable methacrylated gelatin/thiolated pectin hydrogels carrying melatonin/tideglusib-loaded core/shell PMMA/silk fibroin electrospun fibers for vital pulp regeneration

Use of injectable hydrogels attract attention in the regeneration of dental pulp due to their ability to fill non-uniform voids such as pulp cavities. Here, gelatin methacrylate/thiolated pectin hydrogels (GelMA/PecTH) carrying electrospun core/shell fibers of melatonin (Mel)-polymethylmethacrylate (PMMA)/Tideglusib (Td)-silk fibroin (SF) were designed as an injectable hydrogel for vital pulp regeneration, through prolonged release of Td and Mel to induce proliferation and odontoblastic differentiation of dental pulp stem cells (DPSC). H NMR and FTIR confirmed methacrylation of Gel and thiolation of Pec. Addition of PMMA/SF increased degradation and water retention capacities of GelMA/PecTH. Rheological analyses and syringe tests proved the injectability of the hydrogel systems. Release studies indicated that Td and Mel were released from the fibers inside the hydrogels sequentially due to their specific locations. This release pattern from the hydrogels resulted in DPSC proliferation and odontogenic differentiation in vitro. Gene expression studies showed that the upregulation of DMP1, DSPP, and Axin-2 genes was promoted by GelMA/PecTH carrying PMMA/SF loaded with Mel (50 µg/mL) and Td (200 nM), respectively. Our results suggest that this hydrogel system holds promise for use in the regeneration of pulp tissue.

Tau, tau kinases, and tauopathies: An updated overview

Tau is a macrotubule-associated protein primarily involved in the stabilization of the cytoskeleton. Under normal conditions, phosphorylation reduces the affinity of tau for tubulin, allowing the protein to detach from microtubules and ensuring the system dynamics in neuronal cells. However, hyperphosphorylated tau aggregates into paired helical filaments, the main constituents of neurofibrillary tangles found in the brains of patients with Alzheimer's disease and other tauopathies. In this review, we provide an overview of the structure of tau and the pathophysiological roles of tau phosphorylation. We also evaluate the major protein kinases involved and discuss the progress made in the development of drug therapies aimed at inhibiting tau kinases.

Strategies for Treatment of Disease-Associated Dementia Beyond Alzheimer's Disease: An Update

Memory, cognition, dementia, and neurodegeneration are complexly interlinked processes with various mechanistic pathways, leading to a range of clinical outcomes. They are strongly associated with pathological conditions like Alzheimer's disease, Parkinson's disease, schizophrenia, and stroke and are a growing concern for their timely diagnosis and management. Several cognitionenhancing interventions for management include non-pharmacological interventions like diet, exercise, and physical activity, while pharmacological interventions include medicinal agents, herbal agents, and nutritional supplements. This review critically analyzed and discussed the currently available agents under different drug development phases designed to target the molecular targets, including cholinergic receptor, glutamatergic system, GABAergic targets, glycine site, serotonergic targets, histamine receptors, etc. Understanding memory formation and pathways involved therein aids in opening the new gateways to treating cognitive disorders. However, clinical studies suggest that there is still a dearth of knowledge about the pathological mechanism involved in neurological conditions, making the dropouts of agents from the initial phases of the clinical trial. Hence, a better understanding of the disease biology, mode of drug action, and interlinked mechanistic pathways at a molecular level is required.

Virtual Screening and Testing of GSK-3 Inhibitors Using Human SH-SY5Y Cells Expressing Tau Folding Reporter and Mouse Hippocampal Primary Culture under Tau Cytotoxicity

Glycogen synthase kinase-3β (GSK-3β) is an important serine/threonine kinase that implicates in multiple cellular processes and links with the neurodegenerative diseases including Alzheimer's disease (AD). In this study, structure-based virtual screening was performed to search database for compounds targeting GSK-3β from Enamine's screening collection. Of the top-ranked compounds, 7 primary hits underwent a luminescent kinase assay and a cell assay using human neuroblastoma SH-SY5Y cells expressing Tau repeat domain (Tau_RD) with pro-aggregant mutation ΔK280. In the kinase assay for these 7 compounds, residual GSK-3β activities ranged from 36.1% to 90.0% were detected at the IC₅₀ of SB-216763. In the cell assay, only compounds VB-030 and VB-037 reduced Tau aggregation in SH-SY5Y cells expressing ΔK280 Tau_RD-DsRed folding reporter. In SH-SY5Y cells expressing ΔK280 Tau_RD, neither VB-030 nor VB-037 increased expression of GSK-3α Ser21 or GSK-3β Ser9. Among extracellular signal-regulated kinase (ERK), AKT serine/threonine kinase 1 (AKT), mitogen-activated protein kinase 14 (P38) and mitogen-activated protein kinase 8 (JNK) which modulate Tau phosphorylation, VB-037 attenuated active phosphorylation of P38 Thr180/Tyr182, whereas VB-030 had no effect on the phosphorylation status of ERK, AKT, P38 or JNK. However, both VB-030 and VB-037 reduced endogenous Tau phosphorylation at Ser202, Thr231, Ser396 and Ser404 in neuronally differentiated SH-SY5Y expressing ΔK280 Tau_RD. In addition, VB-030 and VB-037 further improved neuronal survival and/or neurite length and branch in mouse hippocampal primary culture under Tau cytotoxicity. Overall, through inhibiting GSK-3β kinase activity and/or p-P38 (Thr180/Tyr182), both compounds may serve as promising candidates to reduce Tau aggregation/cytotoxicity for AD treatment.

Probiotic supplement as a promising strategy in early tau pathology prevention: Focusing on GSK-3β?

Neurofibrillary tangles (NFT) is one of the hallmarks of Alzheimer's disease (AD). Recent research suggests that pretangle tau, the soluble precursor of NFT, is an initiator for AD pathogenesis, thus targeting pretangle tau pathology may be a promising early intervention focus. The bidirectional communications between the gut and the brain play a crucial role in health. The compromised gut-brain axis is involved in various neurodegenerative diseases including AD. However, most research on the relationship between gut microbiome and AD have focused on amyloid-β. In this mini review, we propose to target preclinical pretangle tau stages with gut microbiota interventions such as probiotic supplementation. We discuss the importance of targeting pretangle tau that starts decades before the onset of clinical symptoms, and potential intervention focusing on probiotic regulation of tau hyperphosphorylation. A particular focus is on GSK-3β, a protein kinase that is at the interface between tau phosphorylation, AD and diabetes mellitus.

Role of Nrf2 in aging, Alzheimer's and other neurodegenerative diseases

Nuclear Factor-Erythroid Factor 2 (Nrf2) is an important transcription factor that regulates the expression of large number of genes in healthy and disease states. Nrf2 is made up of 605 amino acids and contains 7 conserved regions known as Nrf2-ECH homology domains. Nrf2 regulates the expression of several key components of oxidative stress, mitochondrial biogenesis, mitophagy, autophagy and mitochondrial function in all organs of the human body, in the peripheral and central nervous systems. Mounting evidence also suggests that altered expression of Nrf2 is largely involved in aging, neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's diseases, Amyotrophic lateral sclerosis, Stroke, Multiple sclerosis and others. The purpose of this article is to detail the essential role of Nrf2 in oxidative stress, antioxidative defense, detoxification, inflammatory responses, transcription factors, proteasomal and autophagic/mitophagic degradation, and metabolism in aging and neurodegenerative diseases. This article also highlights the Nrf2 structural and functional activities in healthy and disease states, and also discusses the current status of Nrf2 research and therapeutic strategies to treat aging and neurodegenerative diseases.

Multipronged diagnostic and therapeutic strategies for Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder and a major contributor to dementia cases worldwide. AD is clinically characterized by learning, memory, and cognitive deficits. The accumulation of extracellular amyloid β (Aβ) plaques and neurofibrillary tangles (NFTs) of tau are the pathological hallmarks of AD and are explored as targets for clinical diagnosis and therapy. AD pathology is poorly understood and there are no fully approved diagnosis and treatments. Notwithstanding the gap, decades of research in understanding disease mechanisms have revealed the multifactorial nature of AD. As a result, multipronged and holistic approaches are pertinent to targeting multiple biomarkers and targets for developing effective diagnosis and therapeutics. In this perspective, recent developments in Aβ and tau targeted diagnostic and therapeutic tools are discussed. Novel indirect, combination, and circulating biomarkers as potential diagnostic targets are highlighted. We underline the importance of multiplexing and multimodal detection of multiple biomarkers to generate biomarker fingerprints as a reliable diagnostic strategy. The classical therapeutics targeting Aβ and tau aggregation pathways are described with bottlenecks in the strategy. Drug discovery efforts targeting multifaceted toxicity involving protein aggregation, metal toxicity, oxidative stress, mitochondrial damage, and neuroinflammation are highlighted. Recent efforts focused on multipronged strategies to rationally design multifunctional modulators targeting multiple pathological factors are presented as future drug development strategies to discover potential therapeutics for AD.

Role of proline-rich tyrosine kinase 2 (Pyk2) in the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD), a progressive neurodegenerative disorder, is the most common form of dementia in the elderly. Two major pathological hallmarks have been identified for AD: extracellular amyloid plaques and intracellular neurofibrillary tangles (NFT). Recently, proline-rich tyrosine kinase 2 (Pyk2), which belongs to the focal adhesion kinase (FAK) non-receptor tyrosine kinase family, was recognized to contribute significantly towards the pathogenesis of AD. Pyk2 can influence the formation of amyloid plaques as well as NFTs. The kinase can directly phosphorylate tau, which is a significant component of NFTs and enhances tau pathology. Several competitive inhibitors have been developed for Pyk2, tested in several cancer models, as Pyk2 is known to be overexpressed under those conditions. The current review article discusses the possible mechanistic pathways by which Pyk2 can influence the pathogenesis of AD. Besides, it describes various inhibitors for Pyk2 and their potential role as therapeutics for AD in the future.

The SARS-CoV-2 main protease (Mpro): Structure, function, and emerging therapies for COVID-19

The main proteases (Mpro), also termed 3-chymotrypsin-like proteases (3CLpro), are a class of highly conserved cysteine hydrolases in β-coronaviruses. Increasing evidence has demonstrated that 3CLpros play an indispensable role in viral replication and have been recognized as key targets for preventing and treating coronavirus-caused infectious diseases, including COVID-19. This review is focused on the structural features and biological function of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) main protease Mpro (also known as 3CLpro), as well as recent advances in discovering and developing SARS-CoV-2 3CLpro inhibitors. To better understand the characteristics of SARS-CoV-2 3CLpro inhibitors, the inhibition activities, inhibitory mechanisms, and key structural features of various 3CLpro inhibitors (including marketed drugs, peptidomimetic, and non-peptidomimetic synthetic compounds, as well as natural compounds and their derivatives) are summarized comprehensively. Meanwhile, the challenges in this field are highlighted, while future directions for designing and developing efficacious 3CLpro inhibitors as novel anti-coronavirus therapies are also proposed. Collectively, all information and knowledge presented here are very helpful for understanding the structural features and inhibitory mechanisms of SARS-CoV-2 3CLpro inhibitors, which offers new insights or inspiration to medicinal chemists for designing and developing more efficacious 3CLpro inhibitors as novel anti-coronavirus agents.

Novel effective small-molecule inhibitors of protein kinases related to tau pathology in Alzheimer's disease

Background: Alzheimer's disease (AD) drugs in therapy are limited to acetylcholine esterase inhibitors and memantine. Newly developed drugs against a single target structure have an insufficient effect on symptomatic AD patients. Results: Novel aromatically anellated pyridofuranes have been evaluated for inhibition of AD-relevant protein kinases cdk1, cdk2, gsk-3b and Fyn. Best activities have been found for naphthopyridofuranes with a hydroxyl function as part of the 5-substituent and a hydrogen or halogen substituent in the 8-position. Best results in nanomolar ranges were found for benzopyridofuranes with a 6-hydroxy and a 3-alkoxy substitution or an exclusive 6-alkoxy substituent. Conclusion: First lead compounds were identified inhibiting two to three kinases in nanomolar ranges to be qualified as an innovative approach for AD multitargeting.

Emerging Therapies and Novel Targets for TDP-43 Proteinopathy in ALS/FTD

Nuclear clearance and cytoplasmic mislocalization of the essential RNA binding protein, TDP-43, is a pathologic hallmark of amyotrophic lateral sclerosis, frontotemporal dementia, and related neurodegenerative disorders collectively termed "TDP-43 proteinopathies." TDP-43 mislocalization causes neurodegeneration through both loss and gain of function mechanisms. Loss of TDP-43 nuclear RNA processing function destabilizes the transcriptome by multiple mechanisms including disruption of pre-mRNA splicing, the failure of repression of cryptic exons, and retrotransposon activation. The accumulation of cytoplasmic TDP-43, which is prone to aberrant liquid-liquid phase separation and aggregation, traps TDP-43 in the cytoplasm and disrupts a host of downstream processes including the trafficking of RNA granules, local translation within axons, and mitochondrial function. In this review, we will discuss the TDP-43 therapy development pipeline, beginning with therapies in current and upcoming clinical trials, which are primarily focused on accelerating the clearance of TDP-43 aggregates. Then, we will look ahead to emerging strategies from preclinical studies, first from high-throughput genetic and pharmacologic screens, and finally from mechanistic studies focused on the upstream cause(s) of TDP-43 disruption in ALS/FTD. These include modulation of stress granule dynamics, TDP-43 nucleocytoplasmic shuttling, RNA metabolism, and correction of aberrant splicing events.

I2-Imidazoline Ligand CR4056 Improves Memory, Increases ApoE Expression and Reduces BBB Leakage in 5xFAD Mice

Recent evidence suggests that I2-imidazoline ligands have neuroprotective properties in animal models of neurodegeneration, such as Alzheimer's disease (AD). We recently demonstrated that the I2-ligand BU224 reversed memory impairments in AD transgenic mice and this effect was not because of reductions in amyloid-β (Aβ) deposition. In this study, our aim was to determine the therapeutic potential of the powerful analgesic I2-imidazoline ligand CR4056 in the 5xFAD model of AD, since this ligand has been proven to be safely tolerated in humans. Sub-chronic oral administration of CR4056 (30 mg/kg for 10 days) led to an improvement in recognition memory in 6-month-old 5xFAD mice, but not in wild-type littermates, without affecting Aβ levels or deposition. Our results also revealed a change in the profile of microglia by CR4056, resulting in a suppression of pro-inflammatory activated microglia, but increased the density of astrocytes and the expression of ApoE, which is mainly produced by these glial cells. In addition, CR4056 restored fibrinogen extravasation, affecting the distribution of markers of astrocytic end feet in blood vessels. Therefore, these results suggest that CR4056 protects against Aβ-mediated neuroinflammation and vascular damage, and offers therapeutic potential at any stage of AD.

Evaluating the Effect of Tideglusib-Loaded Bioactive Glass Nanoparticles as a Potential Dentine Regenerative Material

Dental pulp treatment is the least intrusive procedure currently available for preserving the vitality of the pulp. Several studies are underway to improve the bioactivity of pulp capping materials. Tideglusib isa potent anti-inflammatory, antioxidant, and a regenerative drug developed against Alzheimer’s disease and has been shown to be effective in the treatment of dental cavities. However, its bioactive properties encapsulated within the nanoparticles as a component of pulp capping material are largely unknown. In this study, tideglusib-loaded bioactive glass nanoparticles were synthesized (tideglusib-BgNPs) and mixed at various concentrations into the calcium silicate cement to testits physiomechanical and bioactivitiescompared with biodentine (control). The calcium silicate cement with 10wgt% tideglusib-BgNPs showed comparable physiomechanical properties to that of biodentine. Additionally, the assessment of cytotoxicity and bioactivity (cell proliferation, wound healing, and cell migration assays) showed increased bioactivity in terms of better wound healing, increased proliferation, and better migration of human dental pulp stem cells than biodentine. These findings suggest new opportunities to use tideglusib-BgNPs in pulp therapy.

New Insights into Neuroinflammation Involved in Pathogenic Mechanism of Alzheimer's Disease and Its Potential for Therapeutic Intervention

Alzheimer's disease (AD) is the most common form of dementia, affecting more than 50 million people worldwide with an estimated increase to 139 million people by 2050. The exact pathogenic mechanisms of AD remain elusive, resulting in the fact that the current therapeutics solely focus on symptomatic management instead of preventative or curative strategies. The two most widely accepted pathogenic mechanisms of AD include the amyloid and tau hypotheses. However, it is evident that these hypotheses cannot fully explain neuronal degeneration shown in AD. Substantial evidence is growing for the vital role of neuroinflammation in AD pathology. The neuroinflammatory hypothesis provides a new, exciting lead in uncovering the underlying mechanisms contributing to AD. This review aims to highlight new insights into the role of neuroinflammation in the pathogenesis of AD, mainly including the involvement of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), nucleotide-binding oligomerization domain, leucine-rich repeat-containing protein 3 (NLRP3)/caspase-1 axis, triggering receptor expressed on myeloid cells 2 (TREM2) and cGAS-STING as key influencers in augmenting AD development. The inflammasomes related to the pathways of NF-κB, NLRP3, TREM2, and cGAS-STING as biomarkers of the neuroinflammation associated with AD, as well as an overview of novel AD treatments based on these biomarkers as potential drug targets reported in the literature or under clinical trials, are explored.

Evidence for investigating GSK-3 inhibitors as potential therapeutics for severe COVID-19

A key component of severe COVID-19 is a "cytokine storm" i.e., the excessive expression of unneeded cytokines. Previous studies suggest that SARS-CoV-2 proteins can induce macrophages to secrete pro-inflammatory cytokines; a process that may involve Toll-like receptors (TLRs). Glycogen synthase kinase-3 (GSK-3) has been implicated in TLR signal transduction and a selective GSK-3 inhibitor, termed COB-187, dramatically attenuates cytokine expression induced by the TLR ligand lipopolysaccharide (LPS). In the present study, we provide evidence that the SARS-CoV-2 spike protein (S) and the S2 subunit (S2) induce production of CXCL10 (a chemokine elevated in severe COVID-19) by a human macrophage cell line. Further, we report that two clinically relevant GSK-3 inhibitors and COB-187 attenuate S and S2 protein-induced CXCL10 production. Combined, our observations provide impetus for investigating GSK-3 inhibitors as potential therapeutics for severe COVID-19.

Curcumin as a Holistic Treatment for Tau Pathology

Global forecasts for prevalence of Alzheimer’s Disease (AD) estimate that 152.8 million people will have dementia in 2050, a sharp rise from 57.4 million in 2019 (GBD 2019). This rise can be attributable to increases in population growth and aging, but in the absence of disease-modifying therapies it poses a huge societal challenge that must be addressed urgently. One way to combat this challenge is to explore the utility of holistic treatments that may protect against AD, including traditional herbs, spices and other nutraceuticals that are pharmacologically safe, inexpensive and readily available. In this light, the spice turmeric, and its active ingredient curcumin, has been investigated as a potential holistic treatment for AD over the past 2 decades; however, promising results with animal studies have not translated to success in clinical trials. One issue is that most animal models examining the effects of curcumin and curcumin derivatives in AD have been done with a focus at ameliorating amyloid pathology. Due to the limited success of Amyloid-β-based drugs in recent clinical trials, tau-focused therapeutics provide a promising alternative. In this article, we aim to provide a clearer picture of what is currently known about the effectiveness of curcumin and curcumin derivatives to ameliorate tau pathology. Tau focused studies may help inform more successful clinical studies by placing greater emphasis on the development and optimised delivery of curcumin derivatives that more effectively target tau pathology.

[Therapy Developments in Alzheimer's Disease]

The development of new therapies to treat Alzheimer's disease is a focus of global drug discovery. Research is being conducted into more potent therapies for symptomatic treatment, particularly for behavioral disturbances, but also into drugs that intervene in the pathophysiology of the disease, with the aim of halting or at least slowing the progression of the disease. To this end, the focus of identifying people with Alzheimer's disease is shifting to stages of pre-dementia such as that of Mild Cognitive Impairment (MCI), almost synonymous with prodromal AD, or even to asymptomatic stages. Currently, passive immunization using monoclonal antibodies against Aβ42 has shown the most encouraging results. However, it has not been possible to demonstrate statistically significant differences on the primary target parameters in multiple completed pivotal trials. The anti-amyloid antibody aducanumab received conditional preliminary approval in the U.S. based on amyloid reduction; approval for its use in Europe is an ongoing process. Current pharmacological treatments of Alzheimer's disease offer limited symptomatic benefit. No drugs to delay progression of the disease is yet on the market in Germany. Therefore, it is recommended that patients, especially those in pre-dementia stages or at the onset of Alzheimer's disease, be encouraged to participate in clinical trials in order to help develop new drugs that are more effective in the treatment of this disease and that can then benefit many more patients in the future.

Wnt signaling in the adult hippocampal neurogenic niche

The subgranular zone (SGZ) of the hippocampal dentate gyrus (DG) is a neurogenic niche of the adult brain that contains neural stem cells (NSCs) able to generate excitatory glutamatergic granule neurons, which integrate into the DG circuit and contribute to hippocampal plasticity, learning, and memory. Thus, endogenous NSCs could be harnessed for therapeutic purposes. In this context, it is critical to characterize the molecular mechanisms controlling the generation and functional integration of adult-born neurons. Adult hippocampal neurogenesis is tightly controlled by both cell-autonomous mechanisms and the interaction with the complex niche microenvironment, which harbors the NSCs and provides the signals to support their maintenance, activation, and differentiation. Among niche-derived factors, Wnt ligands play diverse roles. Wnts are secreted glycoproteins that bind to Frizzled receptors and co-receptors to trigger the Wnt signaling pathway. Here, we summarize the current knowledge about the roles of Wnts in the regulation of adult hippocampal neurogenesis. We discuss the possible contribution of the different niche cells to the regulation of local Wnt signaling activity, and how Wnts derived from different cell types could induce differential effects. Finally, we discuss how the effects of Wnt signaling on hippocampal network activity might contribute to neurogenesis regulation. Although the evidence supports relevant roles for Wnt signaling in adult hippocampal neurogenesis, defining the cellular source and the mechanisms controlling secretion and diffusion of Wnts will be crucial to further understand Wnt signaling regulation of adult NSCs, and eventually, to propose this pathway as a therapeutic target to promote neurogenesis.

Neuroprotective Effects of Cholinesterase Inhibitors: Current Scenario in Therapies for Alzheimer's Disease and Future Perspectives

Alzheimer's disease (AD) is a slowly progressive neurodegenerative disease conceptualized as a continuous process, ranging from mild cognitive impairment (MCI), to the mild, moderate, and severe clinical stages of AD dementia. AD is considered a complex multifactorial disease. Currently, the use of cholinesterase inhibitors (ChEI), such as tacrine, donepezil, rivastigmine, and galantamine, has been the main treatment for AD patients. Interestingly, there is evidence that ChEI also promotes neuroprotective effects, bringing some benefits to AD patients. The mechanisms by which the ChEI act have been investigated in AD. ChEI can modulate the PI3K/AKT pathway, which is an important signaling cascade that is capable of causing a significant functional impact on neurons by activating cell survival pathways to promote neuroprotective effects. However, there is still a huge challenge in the field of neuroprotection, but in the context of unravelling the details of the PI3K/AKT pathway, a new scenario has emerged for the development of more efficient drugs that act on multiple protein targets. Thus, the mechanisms by which ChEI can promote neuroprotective effects and prospects for the development of new drug candidates for the treatment of AD are discussed in this review.

Premise and peril of Wnt signaling activation through GSK-3β inhibition

Wnt signaling pathways have been extensively studied in the context of several diseases, including cancer, coronary artery disease, and age-related disorders. β-Catenin plays a central role in the most studied Wnt pathways, the Wnt/β-catenin signaling pathway, commonly referred to as the canonical Wnt signaling pathway. β-catenin is a substrate of glycogen synthase kinase 3β (GSK-3β), and the phosphorylated β-catenin by GSK-3β can be degraded by the proteasome through ubiquitination. Thus, GSK-3β inhibitors have become a widely used chemical biology tool to study the canonical Wnt signaling pathway. Among the varied GSK-3β inhibitors, a compound known as CHIR-99021 is one of the most widely used. Although these inhibitors contribute greatly to our understanding of the canonical Wnt pathway, certain pitfalls associated with such an approach may have been overlooked. In many published studies, micromolar concentrations of CHIR-99021 are used to activate the canonical Wnt pathway. Although CHIR-99021 is a specific GSK-3β inhibitor, it specifically inhibits the kinase at the nanomolar level. Therefore, caution is required when micromolar levels of CHIR-99021 are used for the purpose of activating the canonical Wnt signaling pathway.

Targeting NLRP3 Inflammasome With Nrf2 Inducers in Central Nervous System Disorders

The NLRP3 inflammasome is an intracellular multiprotein complex that plays an essential role in the innate immune system by identifying and eliminating a plethora of endogenous and exogenous threats to the host. Upon activation of the NLRP3 complex, pro-inflammatory cytokines are processed and released. Furthermore, activation of the NLRP3 inflammasome complex can induce pyroptotic cell death, thereby propagating the inflammatory response. The aberrant activity and detrimental effects of NLRP3 inflammasome activation have been associated with cardiovascular, neurodegenerative, metabolic, and inflammatory diseases. Therefore, clinical strategies targeting the inhibition of the self-propelled NLRP3 inflammasome activation are required. The transcription factor Nrf2 regulates cellular stress response, controlling the redox equilibrium, metabolic programming, and inflammation. The Nrf2 pathway participates in anti-oxidative, cytoprotective, and anti-inflammatory activities. This prominent regulator, through pharmacologic activation, could provide a therapeutic strategy for the diseases to the etiology and pathogenesis of which NLRP3 inflammasome contributes. In this review, current knowledge on NLRP3 inflammasome activation and Nrf2 pathways is presented; the relationship between NLRP3 inflammasome signaling and Nrf2 pathway, as well as the pre/clinical use of Nrf2 activators against NLRP3 inflammasome activation in disorders of the central nervous system, are thoroughly described. Cumulative evidence points out therapeutic use of Nrf2 activators against NLRP3 inflammasome activation or diseases that NLRP3 inflammasome contributes to would be advantageous to prevent inflammatory conditions; however, the side effects of these molecules should be kept in mind before applying them to clinical practice.

Aducanumab Therapy to Treat Alzheimer's Disease: A Narrative Review

Background

Aducanumab, a new monoclonal antibody that targets β-amyloid aggregates, has been granted conditional approval by the U.S. FDA for treatment of mild Alzheimer's disease (AD). The approval of this drug without a confirmed significant clinical impact has resulted in several debates.

Objective

In this narrative review, aducanumab approval-related controversy, the drug's pharmacokinetics and pharmacodynamic characteristics, evidence from the efficacy and safety trials of aducanumab, implications of the drug approval, and the future directions in the management of patients with AD are summarized.

Methods

Using relevant keywords, Google Scholar, Web of Science, and MEDLINE databases and manufacturer's website were searched.

Results

Infusion of aducanumab at a higher dose resulted in a modest slowing of cognitive decline among patients with mild cognitive impairment or early-onset AD dementia. The drug however can cause amyloid-related imaging abnormalities. Due to modest impact on cognition, the use of this drug by patients with AD will most likely be limited. The manufacturer is required to run an extended phase IIIb trial to verify the benefit of this drug. Access to therapy requires a careful selection of patients and periodic monitoring to ensure the optimal use of the drug.

Conclusion

Despite the limitations, aducanumab is the first disease-modifying therapy approved for the treatment of AD. Aducanumab addresses a part of the pathogenesis of AD; therefore, drugs that can act on multiple targets are needed. In addition, the search for preventive strategies, validated plasma-based assays, and newer drugs for AD, which are effective, safe, convenient, and affordable, is vital.

Glycogen Synthase Kinase 3β Involvement in Neuroinflammation and Neurodegenerative Diseases

BACKGROUND

GSK-3β activity has been strictly related to neuroinflammation and neurodegeneration. Alzheimer's disease is the most studied neurodegenerative disease, but GSK-3β seems to be involved in almost all neurodegenerative diseases including Parkinson's disease, amyotrophic lateral sclerosis, frontotemporal dementia, Huntington's disease and the autoimmune disease multiple sclerosis.

OBJECTIVE

The aim of this review is to help researchers both working on this research topic or not to have a comprehensive overview on GSK-3β in the context of neuroinflammation and neurodegeneration.

METHOD

Literature has been searched using PubMed and SciFinder databases by inserting specific keywords. A total of more than 500 articles have been discussed.

RESULTS

First of all, the structure and regulation of the kinase were briefly discussed and then, specific GSK-3β implications in neuroinflammation and neurodegenerative diseases were illustrated also with the help of figures, to conclude with a comprehensive overview on the most important GSK-3β and multitarget inhibitors. For all discussed compounds, the structure and IC50 values at the target kinase have been reported.

CONCLUSION

GSK-3β is involved in several signaling pathways both in neurons as well as in glial cells and immune cells. The fine regulation and interconnection of all these pathways are at the base of the rationale use of GSK-3β inhibitors in neuroinflammation and neurodegeneration. In fact, some compounds are now under clinical trials. Despite this, pharmacodynamic and ADME/Tox profiles of the compounds were often not fully characterized and this is deleterious in such a complex system.

In vitro evaluation of injectable Tideglusib-loaded hyaluronic acid hydrogels incorporated with Rg1-loaded chitosan microspheres for vital pulp regeneration

Injectable systems receive attention in endodontics due to the complicated and irregular anatomical structure of root canals. Here, injectable Tideglusib (Td)-loaded hyaluronic acid hydrogels (HAH) incorporated with Rg1-loaded chitosan microspheres (CSM) were developed for vital pulp regeneration, providing release of Td and Rg1 to trigger odontoblastic differentiation of human dental pulp stem cells (DPSC) by Td and vascularization of pulp by Rg1. The optimal concentrations were determined as 90 nM and 50 μg/mL for Td and Rg1, and loaded in HA and CSM in HAH, respectively. Odontogenic (COL1A1, ALP, OCN, Axin-2, DSPP, and DMP1) and angiogenic (VEGFA, VEGFR2, and eNOS) differentiation of DPSC cultured in the presence of hydrogels was shown at gene expression level. Our results suggest that our injectable hydrogel formulation has potential to improve strategies for vital pulp regeneration. In vivo evaluations are needed to test the feasibility and potential of these hydrogels for vital pulp regeneration.

Potential role of Drug Repositioning Strategy (DRS) for management of tauopathy

Tauopathy is a term that has been used to represent a pathological condition in which hyperphosphorylated tau protein aggregates in neurons and glia which results in neurodegeneration, synapse loss and dysfunction and cognitive impairments. Recently, drug repositioning strategy (DRS) becomes a promising field and an alternative approach to advancing new treatments from actually developed and FDA approved drugs for an indication other than the indication it was originally intended for. This paradigm provides an advantage because the safety of the candidate compound has already been established, which abolishes the need for further preclinical safety testing and thus substantially reduces the time and cost involved in progressing of clinical trials. In the present review, we focused on correlation between tauopathy and common diseases as type 2 diabetes mellitus and the global virus COVID-19 and how tau pathology can aggravate development of these diseases in addition to how these diseases can be a risk factor for development of tauopathy. Moreover, correlation between COVID-19 and type 2 diabetes mellitus was also discussed. Therefore, repositioning of a drug in the daily clinical practice of patients to manage or prevent two or more diseases at the same time with lower side effects and drug-drug interactions is a promising idea. This review concluded the results of pre-clinical and clinical studies applied on antidiabetics, COVID-19 medications, antihypertensives, antidepressants and cholesterol lowering drugs for possible drug repositioning for management of tauopathy.

High content screening and proteomic analysis identify a kinase inhibitor that rescues pathological phenotypes in a patient-derived model of Parkinson's disease

Combining high throughput screening approaches with induced pluripotent stem cell (iPSC)-based disease modeling represents a promising unbiased strategy to identify therapies for neurodegenerative disorders. Here we applied high content imaging on iPSC-derived neurons from patients with familial Parkinson’s disease bearing the G209A (p.A53T) α-synuclein (αSyn) mutation and launched a screening campaign on a small kinase inhibitor library. We thus identified the multi-kinase inhibitor BX795 that at a single dose effectively restores disease-associated neurodegenerative phenotypes. Proteomics profiling mapped the molecular pathways underlying the protective effects of BX795, comprising a cohort of 118 protein-mediators of the core biological processes of RNA metabolism, protein synthesis, modification and clearance, and stress response, all linked to the mTORC1 signaling hub. In agreement, expression of human p.A53T-αSyn in neuronal cells affected key components of the mTORC1 pathway resulting in aberrant protein synthesis that was restored in the presence of BX795 with concurrent facilitation of autophagy. Taken together, we have identified a promising small molecule with neuroprotective actions as candidate therapeutic for PD and other protein conformational disorders.

Tideglusib Ameliorates Ischemia/Reperfusion Damage by Inhibiting GSK-3β and Apoptosis in Rat Model of Ischemic Stroke

OBJECTIVES

Glycogen synthase kinase-3β (GSK-3β), a serine/threonine protein kinase, gets activated and worsen stroke outcome after ischemia/reperfusion (I/R) injury by inducing inflammation and apoptosis. In this study, tideglusib, a selective irreversible and non-ATP competitive inhibitor of GSK-3β, was explored in cerebral I/R damage using middle cerebral artery occlusion (MCAo) model in rats.

MATERIALS AND METHODS

MCAo was done for 90 min in male Wistar rats (250-280 g) using doccol suture. In pre-treatment group, tideglusib (50 mg/kg) was administered once daily for 2 days and on the day of surgery, 30 min before MCAo. Next day, rats were examined for neurobehavioral parameters and MRI was performed to assess brain damage. In post-treatment group, tideglusib was started at 30 min after MCAo and continued for the next 2 days. After 72 h of MCAo, behavioral parameters and brain damage by MRI were assessed. Further, oxidative stress markers (MDA and GSH), inflammatory cytokines (TNF-α, IL-1β and IL-10) and expression levels of pGSK-3β S9, Bcl-2 and Bax were estimated in pre-treatment group.

RESULTS

Tideglusib pre-treatment but not post-treatment significantly improved neurobehavioral parameters (p < 0.05) and reduced brain damage (p < 0.01) when compared with MCAo group. I/R induced changes in MDA (p < 0.01), TNF-α and IL-1β (p < 0.05) were significantly attenuated by pre-treatment. Further, tideglusib pre-treatment ameliorated MCAo induced altered expressions of pGSK-3β S9, Bcl-2 and Bax.

CONCLUSION

The results of our exploratory study indicated prophylactic potential of tideglusib in I/R injury by modulating pGSK-3β S9, apoptosis and neuro-inflammation.

Multi-Targets: An Unconventional Drug Development Strategy for Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that eventually leads to dementia and death of the patient. Despite the enormous amounts of resources and efforts for AD drug development during the last three decades, no effective treatments have been developed that can slow or halt the progression of the disease. Currently available drugs for treating AD can only improve clinical symptoms temporarily with moderate efficacies. In recent years, the scientific community has realized these challenges and reconsidered the future directions of AD drug development. The most significant recent changes in AD drug development strategy include shifting from amyloid-based targets to other targets, such as tau, and efforts toward better designs for clinical trials. However, most AD drug development is still focused on a single mechanism or target, which is the conventional strategy for drug development. Although multifactorial mechanisms and, on this basis, multi-target strategies have been proposed in recent years, this approach has not been widely recognized and accepted by the mainstream of AD drug development. Here, we emphasize the multifactorial mechanisms of AD and discuss the urgent need for a paradigm shift in AD drug development from a single target to multiple targets, either with the multi-target-directed ligands approach or the combination therapy approach. We hope this article will increase the recognition of the multifactorial nature of AD and promote this paradigm shift. We believe that such a shift will facilitate successful development of effective AD therapies.

Recent Advances in Small Molecule Stimulation of Regeneration and Repair

Therapeutic approaches to stimulate regeneration and repair have the potential to transform healthcare and improve outcomes for patients suffering from numerous chronic degenerative diseases. To date most approaches have involved the transplantation of therapeutic cells, and while there have been a small number of clinical approvals, major hurdles exist to the routine adoption of such therapies. In recent years humans and other mammals have been shown to possess a regenerative capacity across multiple tissues and organs, and an innate regenerative and repair response has been shown to be activated in these organs in response to injury. These realisations have inspired a transformative approach in regenerative medicine: the development of new agents to directly target these innate regeneration and repair pathways. In this article we will review the current state of the art in the discovery of small molecule modulators of regeneration and their translation towards therapeutic agents, focussing specifically on the areas of neuroregeneration and cardiac regeneration.

Glycogen Synthase Kinase-3 Inhibitors: Preclinical and Clinical Focus on CNS-A Decade Onward

The protein kinase, GSK-3, participates in diverse biological processes and is now recognized a promising drug discovery target in treating multiple pathological conditions. Over the last decade, a range of newly developed GSK-3 inhibitors of diverse chemotypes and inhibition modes has been developed. Even more conspicuous is the dramatic increase in the indications that were tested from mood and behavior disorders, autism and cognitive disabilities, to neurodegeneration, brain injury and pain. Indeed, clinical and pre-clinical studies were largely expanded uncovering new mechanisms and novel insights into the contribution of GSK-3 to neurodegeneration and central nerve system (CNS)-related disorders. In this review we summarize new developments in the field and describe the use of GSK-3 inhibitors in the variety of CNS disorders. This remarkable volume of information being generated undoubtedly reflects the great interest, as well as the intense hope, in developing potent and safe GSK-3 inhibitors in clinical practice.

N-terminal phosphorylation regulates the activity of Glycogen Synthase Kinase 3 from Plasmodium falciparum

As the decline of malaria cases stalled over the last five years, novel targets in Plasmodium falciparum are necessary for the development of new drugs. Glycogen Synthase Kinase (PfGSK3) has been identified as a potential target, since its selective inhibitors were shown to disrupt the parasitès life cycle. In the uncanonical N-terminal region of the parasite enzyme, we identified several autophosphorylation sites and probed their role in activity regulation of PfGSK3. By combining molecular modeling with experimental small-angle X-ray scattering data, we show that increased PfGSK3 activity is promoted by conformational changes in the PfGSK3 N-terminus, triggered by N-terminal phosphorylation. Our work provides novel insights into the structure and regulation of the malarial PfGSK3.

Therapeutic potential of quinazoline derivatives for Alzheimer's disease: A comprehensive review

Quinazolines are considered as a promising class of bioactive heterocyclic compounds with broad properties. Particularly, the quinazoline scaffold has an impressive role in the design and synthesis of new CNS-active drugs. The drug-like properties and pharmacological characteristics of quinazoline could lead to different drugs with various targets. Among CNS disorders, Alzheimer's disease (AD) is a progressive neurodegenerative disorder with memory loss, cognitive decline and language dysfunction. AD is a complex and multifactorial disease therefore, the need for finding multi-target drugs against this devastative disease is urgent. A literature survey revealed that quinazoline derivatives have diverse therapeutic potential for AD as modulators/inhibitors of β-amyloid, tau protein, cholinesterases, monoamine oxidases, and phosphodiesterases as well as other protective effects. Thus, we describe here the most relevant and recent studies about anti-AD agents with quinazoline structure which can further aid the development and discovery of new anti-AD agents.

Anti-Neuroinflammatory Effects of a Semi-Synthetic Isoorientin-Based Glycogen Synthase Kinase-3β Inhibitor in Lipopolysaccharide-Activated Microglial Cells

Neuroinflammation contributes to the pathogenesis of several neurodegenerative disorders. Glycogen synthase kinase-3β (GSK-3β) regulates the release of proinflammatory cytokines and promotes inflammatory responses in immune cells. Microglia are the resident mononuclear immune cells of the central nervous system. Here, we investigated the anti-neuroinflammatory effects of (2S,3S,4R,5R,6S)-6-(2-(3,4-dimethoxyphenyl)-5,7-dimethoxy-4-oxo-4H-chromen-6-yl)-3,4,5-trihydroxy-N-((S)-1,1,1-trifluoropropan-2-yl)tetrahydro-2H-pyran-2-carboxamide (TFGF-18), a semisynthetic GSK-3β inhibitor, in lipopolysaccharide (LPS) activation of spontaneously immortalized SIM-A9 microglial cells and of mouse cortical microglia. TFGF-18 at 2.5 μM concentration inhibited LPS-induced production of nitric oxide by 56.3% and the proinflammatory cytokines TNF-α and IL-1β by 28.3 and 59.2% in SIM-A9 cells, respectively, relative to the LPS treatment control group. Pretreatment of mouse primary microglial cells with TFGF-18 at 2.5 μM concentration led to a reduction of 58.7% in TNF-α+ microglial cells at 24 h post-LPS stimulation. The migration of LPS-activated SIM-A9 cells was also reduced by 26.7% with pretreatment of TFGF-18 in a scratch assay. Analyses of signaling pathways demonstrated that TFGF-18 led to the suppression of LPS-induced GSK-3β activation and p65/NF-κB activity. Furthermore, the co-culture of SIM-A9 with SH-SY5Y neuroblastoma cells showed the suppression of TFGF-18 to microglia-mediated neurotoxicity in vitro. The findings indicate strong inhibitory effects of TFGF-18 on LPS-induced microglia activation via regulation of GSK-3β and downstream p65/NF-κB signaling. The results suggest a potential role of TFGF-18 in neuroprotection via its anti-neuroinflammatory effect.