Targeting Tau Hyperphosphorylation via Kinase Inhibition: Strategy to Address Alzheimer's Disease

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.

Tau pathology is associated with synaptic density and longitudinal synaptic loss in Alzheimer's disease

The associations of synaptic loss with amyloid-β (Aβ) and tau pathology measured by positron emission tomography (PET) and plasma analysis in Alzheimer's disease (AD) patients are unknown. Seventy-five participants, including 26 AD patients, 19 mild cognitive impairment (MCI) patients, and 30 normal controls (NCs), underwent [18F]SynVesT-1 PET/MR scans to assess synaptic density and [18F]florbetapir and [18F]MK6240 PET/CT scans to evaluate Aβ plaques and tau tangles. Among them, 19 AD patients, 12 MCI patients, and 29 NCs had plasma Aβ42/40 and p-tau181 levels measured by the Simoa platform. Twenty-three individuals, 6 AD patients, 4 MCI patients, and 13 NCs, underwent [18F]SynVesT-1 PET/MRI and [18F]MK6240 PET/CT scans during a one-year follow-up assessment. The associations of Aβ and tau pathology with cross-sectional and longitudinal synaptic loss were investigated using Pearson correlation analyses, generalized linear models and mediation analyses. AD patients exhibited lower synaptic density than NCs and MCI patients. In the whole cohort, global Aβ deposition was associated with synaptic loss in the medial (r = -0.431, p < 0.001) and lateral (r = -0.406, p < 0.001) temporal lobes. Synaptic density in almost all regions was related to the corresponding regional tau tangles independent of global Aβ deposition in the whole cohort and stratified groups. Synaptic density in the medial and lateral temporal lobes was correlated with plasma Aβ42/40 (r = 0.300, p = 0.020/r = 0.289, p = 0.025) and plasma p-tau 181 (r = -0.412, p = 0.001/r = -0.529, p < 0.001) levels in the whole cohort. Mediation analyses revealed that tau tangles mediated the relationship between Aβ plaques and synaptic density in the whole cohort. Baseline tau pathology was positively associated with longitudinal synaptic loss. This study suggested that tau burden is strongly linked to synaptic density independent of Aβ plaques, and also can predict longitudinal synaptic loss.

Catecholamine Derivatives: Natural Occurrence, Structural Diversity, and Biological Activity

Catecholamines (CAs) are aromatic amines containing a 3,4-dihydroxyphenyl nucleus and an amine side chain. Representative CAs included the endogenous neurotransmitters epinephrine, norepinephrine, and dopamine. CAs and their derivatives are good resources for the development of sympathomimetic or central nervous system drugs, while they also provide ligands important for G-protein coupled receptor (GPCR) research. CAs are of broad interest in the fields of chemical, biological, medical, and material sciences due to their high adhesive capacities, chemical reactivities, metal-chelating abilities, redox activities, excellent biocompatibilities, and ease of degradability. Herein, we summarize CAs derivatives isolated and identified from microorganisms, plants, insects, and marine invertebrates in recent decades, alongside their wide range of reported biological activities. The aim of this review is to provide an overview of the structural and biological diversities of CAs, the regularity of their natural occurrences, and insights toward future research and development pertinent to this important class of naturally occurring compounds.

The link between metabolic syndrome and Alzheimer disease: A mutual relationship and long rigorous investigation

It has been illustrated that metabolic syndrome (MetS) is associated with Alzheimer disease (AD) neuropathology. Components of MetS including central obesity, hypertension, insulin resistance (IR), and dyslipidemia adversely affect the pathogenesis of AD by different mechanisms including activation of renin-angiotensin system (RAS), inflammatory signaling pathways, neuroinflammation, brain IR, mitochondrial dysfunction, and oxidative stress. MetS exacerbates AD neuropathology, and targeting of molecular pathways in MetS by pharmacological approach could a novel therapeutic strategy in the management of AD in high risk group. However, the underlying mechanisms of these pathways in AD neuropathology are not completely clarified. Therefore, this review aims to elucidate the association between MetS and AD regarding the oxidative and inflammatory mechanistic pathways.

Identification of Uncaria rhynchophylla in the Potential Treatment of Alzheimer's Disease by Integrating Virtual Screening and In Vitro Validation

Uncaria rhynchophylla (Gouteng in Chinese, GT) is the main medicine in many traditional recipes in China. It is commonly used to alleviate central nervous system (CNS) disorders, although its mechanism in Alzheimer's disease is still unknown. This study was designed to predict and validate the underlying mechanism in AD treatment, thus illustrating the biological mechanisms of GT in treating AD. In this study, a PPI network was constructed, KEGG analysis and GO analysis were performed, and an "active ingredient-target-pathway" network for the treatment of Alzheimer's disease was constructed. The active ingredients of GT were screened out, and the key targets were performed by molecular docking. UHPLC-Q-Exactive Orbitrap MS was used to screen the main active ingredients and was compared with the network pharmacology results, which verified that GT did contain the above ingredients. A total of targets were found to be significantly bound up with tau, Aβ, or Aβ and tau through the network pharmacology study. Three SH-SY5Y cell models induced by okadaic acid (OA), Na2S2O4, and H2O2 were established for in vitro validation. We first found that GT can reverse the increase in the hyperphosphorylation of tau induced by OA to some extent, protecting against ROS damage. Moreover, the results also indicated that GT has significant neuroprotective effects. This study provides a basis for studying the potential mechanisms of GT in the treatment of AD.

Phosphorylation of MAP 1A regulates hyperphosphorylation of Tau in Alzheimer's disease model

BACKGROUND AND PURPOSE

Hyperphosphorylation of Tau is one of the important pathological features of Alzheimer's disease (AD). Therefore, studying the mechanisms behind Tau hyperphosphorylation is crucial in exploring the pathogenesis of neurological damage in AD.

METHODS

In this study, after the establishment of rat models of AD, quantitative phosphoproteomics and proteomics were performed to identify proteins, showing that phosphorylation of microtubule associated protein 1A (MAP 1A) was lower in the model group. Western blot confirmed the changes of MAP 1A in the SD rats, APP/PS1 transgenic mice and cell AD models. To further study the molecular mechanism of recombinant MAP 1A phosphorylation affecting Tau phosphorylation, interfering siRNA-MAP 1A and protein immunoprecipitation reaction analysis were performed in AD cell models.

RESULTS

Cyclin-dependent kinase 5 (CDK5) showed reduced binding to MAP 1A and increased binding to Tau, resulting in a decrease in phosphorylated MAP 1A (p-MAP 1A) and an increase in phosphorylated Tau (p-Tau), and MAP 1A silencing promoted binding of CDK5-Tau and increased Tau phosphorylation, thereby reducing the cell survival rate.

CONCLUSIONS

In summary, we found that p-MAP 1A downregulation associated with p-Tau upregulation was due to their altered binding forces to CDK5, and MAP 1A could enhance autophosphorylation by competitive binding to CDK5 and antagonise Tau phosphorylation. This leads to neuronal protection and reducing tissue damage levels in AD, which can help better understand the mechanisms of AD pathogenesis.

The emerging role of mixed lineage kinase 3 (MLK3) and its potential as a target for neurodegenerative diseases therapies

Selective and brain-permeable protein kinase inhibitors are in preclinical development for treating neurodegenerative diseases. Among them, MLK3 inhibitors, with a potent neuroprotective biological action have emerged as valuable agents for the treatment of pathologies such as Alzheimer's, Parkinson's disease and amyotrophic lateral sclerosis. In fact, one MLK3 inhibitor, CEP-1347, reached clinical trials for Parkinson's disease. Additionally, another compound called prostetin/12k, a potent and rather selective MLK3 inhibitor has started clinical development for ALS based on its motor neuron protection in both in vitro and in vivo models. In this review, we will focus on the role of MLK3 in neuron-related cell death processes, neurodegenerative diseases, and the potential advantages of targeting this kinase through pharmacological modulation for neuroprotective treatment.

A review on cyclin-dependent kinase 5: An emerging drug target for neurodegenerative diseases

Cyclin-dependent kinase 5 (CDK5) is the serine/threonine-directed kinase mainly found in the brain and plays a significant role in developing the central nervous system. Recent evidence suggests that CDK5 is activated by specific cyclins regulating its expression and activity. P35 and p39 activate CDK5, and their proteolytic degradation produces p25 and p29, which are stable products involved in the hyperphosphorylation of tau protein, a significant hallmark of various neurological diseases. Numerous high-affinity inhibitors of CDK5 have been designed, and some are marketed drugs. Roscovitine, like other drugs, is being used to minimize neurological symptoms. Here, we performed an extensive literature analysis to highlight the role of CDK5 in neurons, synaptic plasticity, DNA damage repair, cell cycle, etc. We have investigated the structural features of CDK5, and their binding mode with the designed inhibitors is discussed in detail to develop attractive strategies in the therapeutic targeting of CDK5 for neurodegenerative diseases. This review provides deeper mechanistic insights into the therapeutic potential of CDK5 inhibitors and their implications in the clinical management of neurodegenerative diseases.

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

RATIONALE

Tau hyperphosphorylation and aggregation is considered as a main pathological mechanism underlying Alzheimer's disease (AD). Rose Bengal (RB) is a synthetic dye used for disease diagnosis, which was reported to inhibit tau toxicity via inhibiting tau aggregation in Drosophila. However, it was unknown if RB could produce anti-AD effects in rodents.

OBJECTIVES

The research aimed to investigate if and how RB could prevent β-amyloid (Aβ) oligomers-induced tau hyperphosphorylation in rodents.

METHODS AND RESULTS

RB was tested in vitro (0.3-1 μM) and prevented Aβ oligomers-induced tau hyperphosphorylation in PC12 cells. Moreover, RB (10-30 mg/kg, i.p.) effectively attenuated cognitive impairments induced by Aβ oligomers in mice. Western blotting analysis demonstrated that RB significantly increased the expression of pSer473-Akt, pSer9-glycogen synthase kinase-3β (GSK3β) and reduced the expression of cyclin-dependent kinase 5 (CDK5) both in vitro and in vivo. Molecular docking analysis suggested that RB might directly interact with GSK3β and CDK5 by acting on ATP binding sites. Gene Ontology enrichment analysis indicated that RB might act on protein phosphorylation pathways to inhibit tau hyperphosphorylation.

CONCLUSIONS

RB was shown to inhibit tau neurotoxicity at least partially via inhibiting the activity of GSK3β and CDK5, which is a novel neuroprotective mechanism besides the inhibition of tau aggregation. As tau hyperphosphorylation is an important target for AD therapy, this study also provided support for investigating the drug repurposing of RB as an anti-AD drug candidate.

Pharmacological attributes of Bacopa monnieri extract: Current updates and clinical manifestation

Bacopa monnieri has been used for centuries in Ayurvedic medicine, alone or in combination with other herbs, as a memory and learning enhancer, sedative, and anti-epileptic. This review aimed to highlight the health benefits of B. monnieri extracts (BME), focusing on anti-cancer and neurodegenerative diseases. We examined the clinical studies on phytochemistry and pharmacological application of BME. We further highlighted the mechanism of action of these extracts in varying types of cancer and their therapeutic implications. In addition, we investigated the underlying molecular mechanism in therapeutic interventions, toxicities, safety concerns and synergistic potential in cognition and neuroprotection. Overall, this review provides deeper insights into the therapeutic implications of Brahmi as a lead formulation for treating neurological disorders and exerting cognitive-enhancing effects.

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

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

Identification of a reciprocal negative feedback loop between tau-modifying proteins MARK2 kinase and CBP acetyltransferase

The posttranslational regulation of the neuronal proteome is critical for brain homeostasis but becomes dysregulated in the aged or diseased brain, in which abnormal posttranslational modifications (PTMs) are frequently observed. While the full extent of modified substrates that comprise the "PTM-ome" are slowly emerging, how the upstream enzymes catalyzing these processes are regulated themselves is not well understood, particularly in the context of neurodegeneration. Here, we describe the reciprocal regulation of a kinase, the microtubule affinity-regulating kinase 2 (MARK2), and an acetyltransferase, CREB-binding protein (CBP), two enzymes known to extensively modify tau proteins in the progression of Alzheimer's disease. We found that MARK2 negatively regulates CBP and, conversely, CBP directly acetylates and inhibits MARK2 kinase activity. These findings highlight a reciprocal negative feedback loop between a kinase and an acetyltransferase, which has implications for how PTM interplay is coordinated on substrates including tau. Our study suggests that PTM profiles occur through the posttranslational control of the master PTM remodeling enzymes themselves.

Melatonin ameliorates tau-related pathology via the miR-504-3p and CDK5 axis in Alzheimer’s disease

Background

Intracellular accumulation of the microtubule-associated protein tau and its hyperphosphorylated forms is a key neuropathological feature of Alzheimer’s disease (AD). Melatonin has been shown to prevent tau hyperphosphorylation in cellular and animal models. However, the molecular mechanisms by which melatonin attenuates tau hyperphosphorylation and tau-related pathologies are not fully understood.

Methods

Immunofluorescence, immunoblotting analysis and thioflavin-S staining were employed to examine the effects of early and late treatment of melatonin on tau-related pathology in hTau mice, in which nonmutated human tau is overexpressed on a mouse tau knockout background. High-throughput microRNA (miRNA) sequencing, quantitative RT-PCR, luciferase reporter assay and immunoblotting analysis were performed to determine the molecular mechanism.

Results

We found that both early and late treatment of melatonin efficiently decreased the phosphorylation of soluble and insoluble tau at sites related to AD. Moreover, melatonin significantly reduced the number of neurofibrillary tangles (NFTs) and attenuated neuronal loss in the cortex and hippocampus. Furthermore, using miRNA microarray analysis, we found that miR-504-3p expression was upregulated by melatonin in the hTau mice. The administration of miR-504-3p mimics dramatically decreased tau phosphorylation by targeting p39, an activator of the well-known tau kinase cyclin-dependent kinase 5 (CDK5). Compared with miR-504-3p mimics alone, co-treatment with miR-504-3p mimics and p39 failed to reduce tau hyperphosphorylation.

Conclusions

Our results suggest for the first time that melatonin alleviates tau-related pathologies through upregulation of miR-504-3p expression by targeting the p39/CDK5 axis and provide novel insights into AD treatment strategies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40035-022-00302-4.

Recent Advances in the Treatment of Alzheimer’s Disease Using Nanoparticle-Based Drug Delivery Systems

Alzheimer’s disease (AD) is an irreversible and progressive neurodegenerative disorder. Most existing treatments only provide symptomatic solutions. Here, we introduce currently available commercial drugs and new therapeutics, including repositioned drugs, to treat AD. Despite tremendous efforts, treatments targeting the hallmarks of AD show limited efficacy. Challenges in treating AD are partly caused by difficulties in penetrating the blood–brain barrier (BBB). Recently, nanoparticle (NP)-based systems have shown promising potential as precision medicines that can effectively penetrate the BBB and enhance the targeting ability of numerous drugs. Here, we describe how NPs enter the brain by crossing, avoiding, or disrupting the BBB. In addition, we provide an overview of the action of NPs in the microenvironment of the brain for the treatment of AD. Diverse systems, including liposomes, micelles, polymeric NPs, solid-lipid NPs, and inorganic NPs, have been investigated for NP drug loading to relieve AD symptoms, target AD hallmarks, and target moieties to diagnose AD. We also highlight NP-based immunotherapy, which has recently gained special attention as a potential treatment option to disrupt AD progression. Overall, this review focuses on recently investigated NP systems that represent innovative strategies to understand AD pathogenesis and suggests treatment and diagnostic modalities to cure AD.

Natural products can be used in therapeutic management of COVID-19: Probable mechanistic insights

The unexpected emergence of the new Coronavirus disease (COVID-19) has affected more than three hundred million individuals and resulted in more than five million deaths worldwide. The ongoing pandemic has underscored the urgent need for effective preventive and therapeutic measures to develop anti-viral therapy. The natural compounds possess various pharmaceutical properties and are reported as effective anti-virals. The interest to develop an anti-viral drug against the novel severe acute respiratory syndrome Coronavirus (SARS-CoV-2) from natural compounds has increased globally. Here, we investigated the anti-viral potential of selected promising natural products. Sources of data for this paper are current literature published in the context of therapeutic uses of phytoconstituents and their mechanism of action published in various reputed peer-reviewed journals. An extensive literature survey was done and data were critically analyzed to get deeper insights into the mechanism of action of a few important phytoconstituents. The consumption of natural products such as thymoquinone, quercetin, caffeic acid, ursolic acid, ellagic acid, vanillin, thymol, and rosmarinic acid could improve our immune response and thus possesses excellent therapeutic potential. This review focuses on the anti-viral functions of various phytoconstituent and alkaloids and their potential therapeutic implications against SARS-CoV-2. Our comprehensive analysis provides mechanistic insights into phytoconstituents to restrain viral infection and provide a better solution through natural, therapeutically active agents.

1-(7-Chloroquinolin-4-yl)-N-(4-Methoxybenzyl)-5-Methyl-1H-1,2, 3-Triazole-4- carboxamide Reduces Aβ Formation and Tau Phosphorylation in Cellular Models of Alzheimer's Disease

1-(7-Chloroquinolin-4-yl)-N-(4-methoxybenzyl)-5-methyl-1H-1,2,3-triazole-4- carboxamide (QTC-4-MeOBnE) is a new multi-target directed ligand (MTDL) rationally designed to have affinity with β-secretase (BACE), Glycogen Synthase Kinase 3β (GSK3β) and acetylcholinesterase, which are considered promising targets on the development of disease-modifying therapies against Alzheimer's Disease (AD). Previously, QTC-4-MeOBnE treatment showed beneficial effects in preclinical AD-like models by influencing in vivo neurogenesis, oxidative and inflammatory pathways. However, the biological effect and mechanism of action exerted by QTC-4-MeOBnE in AD cellular models have not been elucidated yet. Hereby we investigate the acute effect of QTC-4-MeOBnE on neuronal cells overexpressing Amyloid Protein Precursor (APP) or human tau protein, the two main features of the AD pathophysiology. When compared to the control group, QTC-4-MeOBnE treatment prevented amyloid beta (Aβ) formation through the downregulation of APP and BACE levels in APPswe-expressing cells. Furthermore, in N2a cells overexpressing human tau, QTC-4-MeOBnE reduced the levels of phosphorylated forms of tau via the modulation of the GSK3β pathway. Taken together, our findings provide new insights into the mechanism of action exerted by QTC-4-MeOBnE in AD cellular models, and further support its potential as an interesting therapeutic strategy against AD.

From virtual screening hits targeting a cryptic pocket in BACE-1 to a nontoxic brain permeable multitarget anti-Alzheimer lead with disease-modifying and cognition-enhancing effects

Starting from six potential hits identified in a virtual screening campaign directed to a cryptic pocket of BACE-1, at the edge of the catalytic cleft, we have synthesized and evaluated six hybrid compounds, designed to simultaneously reach BACE-1 secondary and catalytic sites and to exert additional activities of interest for Alzheimer's disease (AD). We have identified a lead compound with potent in vitro activity towards human BACE-1 and cholinesterases, moderate Aβ42 and tau antiaggregating activity, and brain permeability, which is nontoxic in neuronal cells and zebrafish embryos at concentrations above those required for the in vitro activities. This compound completely restored short- and long-term memory in a mouse model of AD (SAMP8) relative to healthy control strain SAMR1, shifted APP processing towards the non-amyloidogenic pathway, reduced tau phosphorylation, and increased the levels of synaptic proteins PSD95 and synaptophysin, thereby emerging as a promising disease-modifying, cognition-enhancing anti-AD lead.

Therapeutic Potential of Ursolic Acid in Cancer and Diabetic Neuropathy Diseases

Ursolic acid (UA) is a pentacyclic triterpenoid frequently found in medicinal herbs and plants, having numerous pharmacological effects. UA and its analogs treat multiple diseases, including cancer, diabetic neuropathy, and inflammatory diseases. UA inhibits cancer proliferation, metastasis, angiogenesis, and induced cell death, scavenging free radicals and triggering numerous anti- and pro-apoptotic proteins. The biochemistry of UA has been examined broadly based on the literature, with alterations frequently having been prepared on positions C-3 (hydroxyl), C12-C13 (double bonds), and C-28 (carboxylic acid), leading to several UA derivatives with increased potency, bioavailability and water solubility. UA could be used as a protective agent to counter neural dysfunction via anti-oxidant and anti-inflammatory effects. It is a potential therapeutic drug implicated in the treatment of cancer and diabetic complications diseases provide novel machinery to the anti-inflammatory properties of UA. The pharmacological efficiency of UA is exhibited by the therapeutic theory of one-drug → several targets → one/multiple diseases. Hence, UA shows promising therapeutic potential for cancer and diabetic neuropathy diseases. This review aims to discuss mechanistic insights into promising beneficial effects of UA. We further explained the pharmacological aspects, clinical trials, and potential limitations of UA for the management of cancer and diabetic neuropathy diseases.

Discovery of a Potent and Selective JNK3 Inhibitor with Neuroprotective Effect Against Amyloid β-Induced Neurotoxicity in Primary Rat Neurons

As members of the MAPK family, c-Jun-N-terminal kinases (JNKs) regulate the biological processes of apoptosis. In particular, the isoform JNK3 is expressed explicitly in the brain at high levels and is involved in the pathogenesis of neurodegenerative diseases such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). In this study, we prepared a series of five 6-dihydroxy-1H-benzo[d]imidazoles as JNK3 inhibitors and found them have potential as neuroprotective agents. Following a previous lead scaffold, benzimidazole moiety was modified with various aryl groups and hydroxylation, and the resulting compounds exhibited JNK3 inhibitory activity with improved potency and selectivity. Out of 37 analogues synthesized, (S)-cyclopropyl(3-((4-(2-(2,3-dihydrobenzo[b][1,4]dioxin -6-yl)-5,6-dihydroxy-1H-benzo[d]imidazol-1-yl)pyrimidin-2-yl)amino) piperidin-1-yl)methanone (35b) demonstrated the highest JNK3 inhibition (IC₅₀ = 9.7 nM), as well as neuroprotective effects against Aβ-induced neuronal cell death. As a protein kinase inhibitor, it also showed excellent selectivity over other protein kinases including isoforms JNK1 (>1000 fold) and JNK2 (−10 fold).

The Synaptic Vesicle Protein 2A Interacts With Key Pathogenic Factors in Alzheimer's Disease: Implications for Treatment

Alzheimer’s disease (AD), a serious neurodegenerative disease, is pathologically characterized by synaptic loss and dysfunction. Synaptic vesicle protein 2A (SV2A) is an indispensable vesicular protein specifically expressed in synapses and can be used as a biomarker for synaptic density. We found that the expression of SV2A was down-regulated in the hippocampus of AD patients, yet the relation of SV2A to other hallmarks of AD pathology such as amyloid precursor protein (APP), β-amyloid (Aβ), and Tau protein is not thoroughly clear. In addition, SV2A colocalized with APP and was down-regulated at Aβ deposition. Moreover, we found that SV2A deficiency leads to a simultaneous increase in Aβ and Tau hyperphosphorylation, while SV2A overexpression was associated with downregulation of β-site APP cleaving enzyme 1 and apolipoprotein E genes. In addition, evidence gained in the study points to the phosphatidylinositol 3-kinase signaling pathway as a possible mediator in SV2A regulation influencing the incidence and development of AD. With limited effective diagnostic methods for AD, a close interplay between SV2A and AD-related proteins demonstrated in our study may provide novel and innovative diagnostic and therapeutic opportunities.

Structure-based investigation of MARK4 inhibitory potential of Naringenin for therapeutic management of cancer and neurodegenerative diseases

MAP/microtubule affinity-regulating kinase 4 (MARK4) is a member of serine/threonine kinase family and considered an attractive drug target for many diseases. Screening of Indian Medicinal Plants, Phytochemistry, and Therapeutics (IMPPAT) using virtual high-throughput screening coupled with enzyme assay suggested that Naringenin (NAG) could be a potent inhibitor of MARK4. Structure-based molecular docking analysis showed that NAG binds to the critical residues found in the active site pocket of MARK4. Furthermore, molecular dynamics (MD) simulation studies for 100 ns have delineated the binding mechanism of NAG to MARK4. Results of MD simulation suggested that binding of NAG further stabilizes the structure of MARK4 by forming a stable complex. In addition, no significant conformational change in the MARK4 structure was observed. Fluorescence binding and isothermal titration calorimetric measurements revealed an excellent binding affinity of NAG to MARK4 with a binding constant (K) = 0.13 × 10⁶ M^-1 obtained from fluorescence binding studies. Further, enzyme inhibition studies showed that NAG has an admirable IC₅₀ value of 4.11 µM for MARK4. Together, these findings suggest that NAG could be an effective MARK4 inhibitor that can potentially be used to treat cancer and neurodegenerative diseases.

Inhibition of 2-Arachidonoylglycerol Metabolism Alleviates Neuropathology and Improves Cognitive Function in a Tau Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is the most common cause of dementia, which affects more than 5 million individuals in the USA. Unfortunately, no effective therapies are currently available to prevent development of AD or to halt progression of the disease. It has been proposed that monoacylglycerol lipase (MAGL), the key enzyme degrading the endocannabinoid 2-arachidonoylglycerol (2-AG) in the brain, is a therapeutic target for AD based on the studies using the APP transgenic models of AD. While inhibition of 2-AG metabolism mitigates β-amyloid (Aβ) neuropathology, it is still not clear whether inactivation of MAGL alleviates tauopathies as accumulation and deposition of intracellular hyperphosphorylated tau protein are the neuropathological hallmark of AD. Here we show that JZL184, a potent MAGL inhibitor, significantly reduced proinflammatory cytokines, astrogliosis, phosphorylated GSK3β and tau, cleaved caspase-3, and phosphorylated NF-kB while it elevated PPARγ in P301S/PS19 mice, a tau mouse model of AD. Importantly, tau transgenic mice treated with JZL184 displayed improvements in spatial learning and memory retention. In addition, inactivation of MAGL ameliorates deteriorations in expression of synaptic proteins in P301S/PS19 mice. Our results provide further evidence that MAGL is a promising therapeutic target for AD.

Mechanistic insights into the pathogenesis of neurodegenerative diseases: towards the development of effective therapy

Neurodegeneration is a prevalent and one of the emerging reasons for morbidity, mortality, and cognitive impairment in aging. Dementia is one of such conditions of neurodegeneration, partially manageable, irreversible, and worsens over time. This review is focused on biological and psychosocial risk factors associated with Alzheimer's and Parkinson's diseases, highlighting the value of cognitive decline. We further emphasized on current therapeutic strategies from pharmacological and non-pharmacological perspectives focusing on their effects on cognitive impairment, protein aggregation, tau pathology, and improving the quality of life. Deeper mechanistic insights into the multifactorial neurodegeneration could offer the design and development of promising diagnostic and therapeutic strategies.

Potential Therapeutic Role of Phytochemicals to Mitigate Mitochondrial Dysfunctions in Alzheimer's Disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder characterized by a decline in cognitive function and neuronal damage. Although the precise pathobiology of AD remains elusive, accumulating evidence suggests that mitochondrial dysfunction is one of the underlying causes of AD. Mutations in mitochondrial or nuclear DNA that encode mitochondrial components may cause mitochondrial dysfunction. In particular, the dysfunction of electron transport chain complexes, along with the interactions of mitochondrial pathological proteins are associated with mitochondrial dysfunction in AD. Mitochondrial dysfunction causes an imbalance in the production of reactive oxygen species, leading to oxidative stress (OS) and vice versa. Neuroinflammation is another potential contributory factor that induces mitochondrial dysfunction. Phytochemicals or other natural compounds have the potential to scavenge oxygen free radicals and enhance cellular antioxidant defense systems, thereby protecting against OS-mediated cellular damage. Phytochemicals can also modulate other cellular processes, including autophagy and mitochondrial biogenesis. Therefore, pharmacological intervention via neuroprotective phytochemicals can be a potential strategy to combat mitochondrial dysfunction as well as AD. This review focuses on the role of phytochemicals in mitigating mitochondrial dysfunction in the pathogenesis of AD.

Discovery of 1-Pyrimidinyl-2-Aryl-4,6-Dihydropyrrolo [3,4-d]Imidazole-5(1H)-Carboxamide as a Novel JNK Inhibitor

We designed and synthesized 1-pyrimidinyl-2-aryl-4, 6-dihydropyrrolo [3,4-d] imidazole-5(1H)-carboxamide derivatives as selective inhibitors of c-Jun-N-terminal Kinase 3 (JNK3), a target for the treatment of neurodegenerative diseases. Based on the compounds found in previous studies, a novel scaffold was designed to improve pharmacokinetic characters and activity, and compound 18a, (R)-1-(2-((1-(cyclopropanecarbonyl)pyrrolidin-3-yl)amino)pyrimidin-4-yl)-2-(3,4-dichlorophenyl)-4,6-dihydro pyrrolo [3,4-d]imidazole-5(1H)-carboxamide, showed the highest IC₅₀ value of 2.69 nM. Kinase profiling results also showed high selectivity for JNK3 among 38 kinases, having mild activity against JNK2, RIPK3, and GSK3β, which also known to involve in neuronal apoptosis.