Design, synthesis and evaluation of 7-azaindazolyl-indolyl-maleimides as glycogen synthase kinase-3β (GSK-3β) inhibitors

Impact of GSK-3β and CK-1δ on Wnt signaling pathway in alzheimer disease: A dual target approach

Alzheimer's disease (AD) is an enigmatic neurological illness that offers few treatment options. Recent exploration has highlighted the crucial connection of the Wnt signaling pathway in AD pathogenesis, shedding light on potential therapeutic targets. The present study focuses on the dual targeting of glycogen synthase kinase-3β (GSK-3β) and casein kinase-1δ (CK-1δ) within the framework of the Wnt signaling pathway as a possible technique for AD intervention. GSK-3β and CK-1δ are multifunctional kinases known for their roles in tau hyperphosphorylation, amyloid processing, and synaptic dysfunction, all of which are major hallmarks of Alzheimer's disease. They are intricately linked to Wnt signaling, which plays a pivotal part in sustaining neuronal function and synaptic plasticity. Dysregulation of the Wnt pathway in AD contributes to cognitive decline and neurodegeneration. This review delves into the molecular mechanisms by which GSK-3β and CK-1δ impact the Wnt signaling pathway, elucidating their roles in AD pathogenesis. We discuss the potential of small-molecule inhibitors along with their SAR studies along with the multi-targetd approach targeting GSK-3β and CK-1δ to modulate Wnt signaling and mitigate AD-related pathology. In summary, the dual targeting of GSK-3β and CK-1δ within the framework of the Wnt signaling pathway presents an innovative and promising avenue for future AD therapies, offering new hope for patients and caregivers in the quest to combat this challenging condition.

Small molecule inhibitors of NLRP3 inflammasome and GSK-3β in the management of traumatic brain injury: A review

Traumatic brain injury (TBI) is a debilitating mental condition which causes physical disability and morbidity worldwide. TBI may damage the brain by direct injury that subsequently triggers a series of neuroinflammatory events. The activation of NLRP3 inflammasome and dysregulated host immune system has been documented in various neurological disorders such as TBI, ischemic stroke and multiple sclerosis. The activation of NLRP3 post-TBI increases the production of pro-inflammatory cytokines and caspase-1, which are major drivers of neuroinflammation and apoptosis. Similarly, GSK-3β regulates apoptosis through tyrosine kinase and canonical Wnt signalling pathways. Thus, therapeutic targeting of NLRP3 inflammasome and GSK-3β has emerged as promising strategies for regulating the post-TBI neuroinflammation and neurobehavioral disturbances. In this review, we discuss the identification & development of several structurally diverse and pharmacologically interesting small molecule inhibitors for targeting the NLRP3 inflammasome and GSK-3β in the management of TBI.

Synthesis and biological evaluation of thieno[3,2-c]pyrazol-3-amine derivatives as potent glycogen synthase kinase 3β inhibitors for Alzheimer's disease

Glycogen synthase kinase 3β (GSK-3β) is a potential target for anti-Alzheimer's disease (AD) drug development. In this study, a series of novel thieno[3,2-c]pyrazol-3-amine derivatives was synthesized and evaluated as potential GSK-3β inhibitors by structure-based drug design. The thieno[3,2-c]pyrazol-3-amine derivative 54 with a 4-methylpyrazole moiety which interacted with Arg141 by π-cation interaction was identified as a potent GSK-3β inhibitor with an IC50 of 3.4 nM and an acceptable kinase selectivity profile. In the rat primary cortical neurons, compound 54 showed neuroprotective effects on Aβ-induced neurotoxicity. Western blot analysis indicated that 54 inhibited GSK-3β by up-regulating the expression of phosphorylated GSK-3β at Ser9 and down-regulating the expression of phosphorylated GSK-3β at Tyr216. Meanwhile, 54 decreased tau phosphorylation at Ser396 in a dose-dependent way. In astrocytes and microglia cells, 54 inhibited the expression of inducible nitric oxide synthase (iNOS), indicating that 54 showed an anti-neuroinflammatory effect. In the AlCl3-induced zebrafish AD model, 54 significantly ameliorated the AlCl3-induced dyskinesia, demonstrating its anti-AD activity in vivo.

Development of inhibitors targeting glycogen synthase kinase-3β for human diseases: Strategies to improve selectivity

Glycogen synthase kinase-3β (GSK-3β) is a conserved serine/threonine kinase that participates in the transmission of multiple signaling pathways and plays an important role in the occurrence and development of human diseases, such as metabolic diseases, neurological diseases and cancer, making it to be a potential and promising drug target. To date, copious GSK-3β inhibitors have been synthesized, but only few have entered clinical trials. Most of them exerts poor selectivity, concomitant off-target effects and side effects. This review summarizes the structural characteristics, biological functions and relationship with diseases of GSK-3β, as well as the selectivity profile and therapeutic potential of different categories of GSK-3β inhibitors. Strategies for increasing selectivity and reducing adverse effects are proposed for the future design of GSK-3β inhibitors.

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.

Design and synthesis of 3-(4-pyridyl)-5-(4-sulfamido-phenyl)-1,2,4-oxadiazole derivatives as novel GSK-3β inhibitors and evaluation of their potential as multifunctional anti-Alzheimer agents

Pleiotropic intervention has prominent advantages for complex pathomechanisms, such as Alzheimer's disease (AD). In this study, a series of novel 3-(4-pyridyl)-5-(4- sulfamido-phenyl)-1,2,4-oxadiazole derivatives were designed and synthesized following the multitarget-directed ligand-based strategy. All compounds were evaluated for glycogen synthase kinase 3β (GSK-3β) inhibition and antineuroinflammatory and neuroprotective activities. Given that abnormal glucose metabolism plays an important role in AD occurrence and development, the effects of all compounds on glucose consumption in HepG2 cells was evaluated. Compounds 5e and 10b showed good dual potency in GSK-3β inhibition (IC50: 5e = 1.52 μM, 10b = 0.19 μM) and antineuroinflammatory potency (IC50: 5e = 0.47 ± 0.64 μM, 10b = 6.94 ± 2.33 μM). The effect of compound 10b on glucose consumption was higher than that of positive drug metformin. These compounds exerted a certain neuroprotective effect. Compound 10b dramatically reduced Aβ-induced Tau hyperphosphorylation, thus inhibiting GSK-3β at the cellular level. Notably, compounds 5e and 10b exhibited good inhibitory effects on the formation of intracellular reactive oxygen species (ROS). Moreover, these compounds displayed proper blood-brain barrier permeability and lacked neurotoxicity up to 50 μM concentration. Finally, in vivo experiments revealed that compound 10b improved cognitive impairment in scopolamine-induced mouse models. Results indicated that compound 10b deserves further study as a multifunctional lead compound.

Structure-activity relationship (SAR) studies of synthetic glycogen synthase kinase-3β inhibitors: A critical review

Glycogen Synthase Kinase-3 (GSK-3) is a constitutively dynamic, omnipresent serine/threonine protein kinase regularly called as a "multitasking kinase" due to its pliable function in diverse signaling pathways. It exists in two isoforms i.e., GSK-3α and GSK-3β. Inhibition of GSK-3 may be useful in curing various diseases such as Alzheimer's disease, type II diabetes, mood disorders, cancers, chronic inflammatory agents, stroke, bipolar disorders and so on, but the approach poses significant challenges. Lithium was the first GSK-3β inhibitor to be used for therapeutic outcome and has been effectively used for many years. In recent years, a large number of structurally diverse potent GSK-3β inhibitors are reported. The present review focuses on the recent developments in the area of medicinal chemistry to explore the diverse chemical structures of potent GSK-3β inhibitors and also describes its structure-activity relationships (SAR) and molecular binding interactions of favorable applicability in various diseases.

Synthesis and biological evaluation of 3-aryl-4-indolyl-maleimides as potent mutant isocitrate dehydrogenase-1 inhibitors

A series of 3-aryl-4-indolylmaleimide IDH1/R132H inhibitors with a novel structure was obtained by high-throughput screening and structure-based optimization. Most compounds such as 7a, 7d, 7h, 7i, 7k and 7o showed high inhibitory effects on IDH1/R132H and were highly selective against IDH1/WT, IDH2/WT, GDH, GK, and FBP. Evaluation of the biological activities and function at cellular level showed that compounds 7h, 7i and 7k could effectively suppress the production of 2-hydroxyglutaric acid in U87MG cells expressing IDH1/R132H. Additionally, 7h could reversed the differentiation block of the myeloid leukemic cell line, TF-1, caused by the overexpression of IDH1/R132H. We also explore the structure-activity relationship based on the experimental data, with an attempt to pave the way for future studies.

Design, synthesis and biological evaluation of LX2343 derivatives as neuroprotective agents for the treatment of Alzheimer's disease

A series of LX2343 derivatives were designed, synthesized and evaluated as neuroprotective agents for Alzheimer's disease (AD) in vitro. Most of the compounds displayed potent neuroprotective activities. Especially for compound A6, exhibited a remarkable EC₅₀ value of 0.22 μM. Further investigation demonstrated that compound A6 can significantly reduce Aβ production and increase Aβ clearance, and alleviate Tau hyperphosphorylation. Most importantly, compound A6 could ameliorate learning and memory impairments in APP/PS1 transgenic mice. The present study evidently showed that compound A6 is a potent neuroprotective agent and might serve as a promising lead candidate for the treatment of Alzheimer's disease.

Design and synthesis of (aza)indolyl maleimide-based covalent inhibitors of glycogen synthase kinase 3β

The optimization of both non-covalent interactions and reactive groups led to azaindolyl maleimide compound 38b as a selective and covalent inhibitor against GSK3β.

Glycogen synthase kinase-3 and its inhibitors: Potential target for various therapeutic conditions

Glycogen Synthase Kinase-3 (GSK-3) is a serine/threonine kinase which is ubiquitously expressed and is regarded as a regulator for various cellular events and signalling pathways. It exists in two isoforms, GSK-3α and GSK-3β and can phosphorylate a wide range of substrates. Aberrancy in the GSK-3 activity can lead to various diseases like Alzheimer's, diabetes, cancer, neurodegeneration etc., rendering it an attractive target to develop potent and specific inhibitors. The present review focuses on the recent developments in the area of GSK-3 inhibitors and also enlightens its therapeutic applicability in various disease conditions.

Investigation of the bindings of a class of inhibitors with GSK3β kinase using thermodynamic integration MD simulation and kinase assay

GSK3β kinase is a noteworthy target for discovery of the drugs that will be used to treat several diseases. In the effort to identify a new inhibitor lead compound, we utilized thermodynamic integration (TI)-molecular dynamics (MD) simulation and kinase assay to investigate the bindings between GSK3β kinase and five compounds that were analogous to a known inhibitor with an available crystal structure. TI-MD simulations of the first two compounds (analogs 1 and 2) were used for calibration. The computed binding affinities of analogs 1 and 2 agreed well with the experimental results. The rest three compounds (analogs 3-5) were newly obtained from a database search, and their affinity data were newly measured in our labs. TI-MD simulations predicted the binding modes and the computed ΔΔG values have a reasonably good correlation with the experimental affinity data. These newly identified inhibitors appear to be new leads according to our survey of GSK3β inhibitors listed in recent review articles. The predicted binding modes of these compounds should aid in designing new derivatives of these compounds in the future.

Personalized Medicine and Resurrected Hopes for the Management of Alzheimer's Disease: A Modular Approach Based on GSK-3β Inhibitors

Alzheimer's disease (AD) is one of the most common neurological disorders with vast reaching worldwide prevalence. Research attempts to decipher what's happening to the human mind have shown that pathogenesis of AD is associated with misfolded protein intermediates displaying tertiary structure conformational changes eventually leading to forming large polymers of unwanted aggregates. The two hallmarks of AD pathological protein aggregates are extraneuronal β-amyloid (Aβ) based senile plaques and intraneuronal neurofibrillary tangles (NFTs). As such, AD is categorized as a protein misfolding neurodegenerative disease (PMND) . Therapeutic interventions interfering with the formation of these protein aggregates have been widely explored as potential pathways for thwarting AD progression. One such tactic is modulating the function of enzymes involved in the metabolic pathways leading to formation of these misfolded protein aggregates. Much evidence has shown that glycogen synthase kinase-3β (GSK-3β) plays a key role in hyperphosphorylation of tau protein leading eventually to its aggregation to form NFTs. Data presented hereby will display a plethora of information as to how to interfere with progression of AD through the route of GSK-3β activity control.

Natural and synthetic bioactive inhibitors of glycogen synthase kinase

Glycogen synthase kinase-3 is a multi-functional serine-threonine kinase and is involved in diverse physiological processes, including metabolism, cell cycle, and gene expression by regulating a wide variety of known substrates like glycogen synthase, tau-protein and β-catenin. Aberrant GSK-3 has been involved in diabetes, inflammation, cancer, Alzheimer's and bipolar disorder. In this review, we present an overview of the involvement of GSK-3 in various signalling pathways, resulting in a number of adverse pathologies due to its dysregulation. In addition, a detailed description of the small molecule inhibitors of GSK-3 with different mode of action discovered or specifically developed for GSK-3 has been presented. Furthermore, some clues for the future optimization of these promising molecules to develop specific drugs inhibiting GSK-3, for the treatment of associated disease conditions have also been discussed.

The effect of Scutellaria baicalensis stem-leaf flavonoids on spatial learning and memory in chronic cerebral ischemia-induced vascular dementia of rats

Flavonoids have been shown to improve cognitive function and delay the dementia progression. However, the underlying mechanisms remain elusive. In the present study, we examined the effect of Scutellaria baicalensis stem-leaf total flavonoids (SSTFs) extracted from S. baicalensis Georgi on spatial learning and memory in a vascular dementia (VaD) rat model and explored its molecular mechanisms. The VaD rats were developed by permanent bilateral occlusion of the common carotid artery. Seven days after recovery, the VaD rats were treated with either 50 or 100 mg/kg of SSTF for 60 days. The spatial learning and memory was evaluated in the Morris water maze (MWM) test. The tau hyperphosphorylation and the levels of the related protein kinases or phosphatases were examined by western blot analysis. In VaD rats, SSTF treatment at 100 mg/kg significantly reduced the escape latency in training trial in MWM test. In the probe trial, SSTF treatment increased the searching time and travel distance in the target quadrant. SSTF treatment inhibited the tau phosphorylation in both cortex and hippocampus in VaD rats. Meanwhile, SSTF reduced the activity of glycogen synthase kinase 3β and cyclin-dependent kinase 5 in VaD rats. In contrast, SSTF treatment increased the level of the protein phosphatase 2A subunit B in VaD rats. SSTF treatment significantly improved the spatial cognition in VaD rats. Our results suggest that SSTF may alleviate tau-hyperphosphorylation-induced neurotoxicity through coordinating the activity of kinases and phosphatase after a stroke. SSTF may be developed into promising novel therapeutics for VaD.

A high-throughput screen reveals new small-molecule activators and inhibitors of pantothenate kinases

Pantothenate kinase (PanK) is a regulatory enzyme that controls coenzyme A (CoA) biosynthesis. The association of PanK with neurodegeneration and diabetes suggests that chemical modifiers of PanK activity may be useful therapeutics. We performed a high throughput screen of >520000 compounds from the St. Jude compound library and identified new potent PanK inhibitors and activators with chemically tractable scaffolds. The HTS identified PanK inhibitors exemplified by the detailed characterization of a tricyclic compound (7) and a preliminary SAR. Biophysical studies reveal that the PanK inhibitor acts by binding to the ATP–enzyme complex.

Synthesis and biological evaluation of 3-([1,2,4]triazolo[4,3-a]pyridin-3-yl)-4-(indol-3-yl)-maleimides as potent, selective GSK-3β inhibitors and neuroprotective agents

A series of novel 3-([1,2,4]triazolo[4,3-a]pyridin-3-yl)-4-(indol-3-yl)-maleimides were designed, prepared and evaluated for their GSK-3β inhibitory activities. Most compounds showed high potency to GSK-3β inhibition with high selectivity. Among them, compounds 7c, 7f, 7h, 7l and 7m significantly reduced GSK-3β substrate Tau phosphorylation at Ser396 in primary neurons, showing the inhibition of cellular GSK-3β. In the in vitro neuronal injury models, compounds 7c, 7f, 7h, 7l and 7m prevented neuronal death against glutamate, oxygen-glucose deprivation and nutrient serum deprivation which are associated with cerebral ischemic stroke. In the in vivo cerebral ischemia animal model, compound 7f reduced infarct size by 15% and improved the neurological deficit following focal cerebral ischemia. These findings may provide new insights into the development of novel GSK-3β inhibitors with potential neuroprotective activity.

Protein phosphorylation in neurodegeneration: friend or foe?

Protein misfolding and aggregation is a common hallmark in neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), and fronto-temporal dementia (FTD). In these disorders, the misfolding and aggregation of specific proteins occurs alongside neuronal degeneration in somewhat specific brain areas, depending on the disorder and the stage of the disease. However, we still do not fully understand the mechanisms governing protein aggregation, and whether this constitutes a protective or detrimental process. In PD, alpha-synuclein (aSyn) forms protein aggregates, known as Lewy bodies, and is phosphorylated at serine 129. Other residues have also been shown to be phosphorylated, but the significance of phosphorylation in the biology and pathophysiology of the protein is still controversial. In AD and in FTD, hyperphosphorylation of tau protein causes its misfolding and aggregation. Again, our understanding of the precise consequences of tau phosphorylation in the biology and pathophysiology of the protein is still limited. Through the use of a variety of model organisms and technical approaches, we are now gaining stronger insight into the effects of phosphorylation in the behavior of these proteins. In this review, we cover recent findings in the field and discuss how targeting phosphorylation events might be used for therapeutic intervention in these devastating diseases of the nervous system.