Pivotal role of glycogen synthase kinase-3: A therapeutic target for Alzheimer's disease

Allosteric Modulators of Potential Targets Related to Alzheimer's Disease: a Review

Among neurodegenerative disorders, Alzheimer's disease (AD) is the most common type of dementia, and there is an urgent need to discover new and efficacious forms of treatment for it. Pathological patterns of AD include cholinergic dysfunction, increased β-amyloid (Aβ) peptide concentration, the appearance of neurofibrillary tangles, among others, all of which are strongly associated with specific biological targets. Interactions observed between these targets and potential drug candidates in AD most often occur by competitive mechanisms driven by orthosteric ligands that sometimes result in the production of side effects. In this context, the allosteric mechanism represents a key strategy; this can be regarded as the selective modulation of such targets by allosteric modulators in an advantageous manner, as this may decrease the likelihood of side effects. The purpose of this review is to present an overview of compounds that act as allosteric modulators of the main biological targets related to AD.

BACE1 inhibitors: Current status and future directions in treating Alzheimer's disease

Alzheimer's disease (AD) is an irreversible, progressive neurodegenerative brain disorder with no current cure. One of the important therapeutic approaches of AD is the inhibition of β-site APP cleaving enzyme-1 (BACE1), which is involved in the rate-limiting step of the cleavage process of the amyloid precursor protein (APP) leading to the generation of the neurotoxic amyloid β (Aβ) protein after the γ-secretase completes its function. The produced insoluble Aβ aggregates lead to plaques deposition and neurodegeneration. BACE1 is, therefore, one of the attractive targets for the treatment of AD. This approach led to the development of potent BACE1 inhibitors, many of which were advanced to late stages in clinical trials. Nonetheless, the high failure rate of lead drug candidates targeting BACE1 brought to the forefront the need for finding new targets to uncover the mystery behind AD. In this review, we aim to discuss the most promising classes of BACE1 inhibitors with a description and analysis of their pharmacodynamic and pharmacokinetic parameters, with more focus on the lead drug candidates that reached late stages of clinical trials, such as MK8931, AZD-3293, JNJ-54861911, E2609, and CNP520. In addition, the manuscript discusses the safety concerns and insignificant physiological effects, which were highlighted for the most successful BACE1 inhibitors. Furthermore, the review demonstrates with increasing evidence that despite tremendous efforts and promising results conceived with BACE1 inhibitors, the latest studies suggest that their clinical use for treating Alzheimer's disease should be reconsidered. Finally, the review sheds light on alternative therapeutic options for targeting AD.

Developments with multi-target drugs for Alzheimer's disease: an overview of the current discovery approaches

Introduction: Alzheimer's disease (AD), the most common type of dementia among older adults, is a chronic neurodegenerative pathology that causes a progressive loss of cognitive functioning with a decline of rational skills. It is well known that AD is multifactorial, so there are many different pharmacological targets that can be pursued. Areas covered: The authors highlight the strategic value of privileged scaffolds in a multi-target lead compound generation against AD, exploring the concept of multi-target design, with a special emphasis on hybrid compounds. Hence, the most promising building blocks for designing and synthesizing hybrid anti-AD drugs are shown, while also presenting the more advanced hybrid compounds. Expert opinion: The available therapeutic arsenal for AD, designed under the traditional paradigm of 'one-drug/one target/one-disease', is based on the inhibition of brain acetylcholinesterase (AChE) to increase acetylcholine (ACh) levels. However, this classical approach has not been sufficiently effective when used to treat any multifactor-depending pathology (cancer, diabetes or AD). The multi-target drug concept has been quickly adopted by medicinal chemists. The basic research developments reported in recent years are a solid foundation that will pave the way for the construction of future AD therapeutics.

Small-Molecule SB216763-Loaded Microspheres Repair Peripheral Nerve Injury in Small Gap Tubulization

Peripheral nerve injury has yet to be fully resolved because of its complicated pathological process. SB216763 is a small molecular compound that can enhance the remyelination of peripheral nerves by inhibiting glycogen synthase kinase-3β (GSK3β). GSK-3β inhibitor stimulates myelin gene expression and restores the myelin structure. Herein, we presented the effect of integrating small gap tubulization with SB216763-loaded microspheres by using a chitosan conduit. In vitro, SB216763 could promote neurite growth of dorsal root ganglia. In vivo studies showed that SB216763 increased the number of myelinated axons and the thickness of myelin sheaths. Electrophysiological examination and sciatic functional index results also indirectly indicated the role of SB216763 in repairing peripheral nerve injury. SB216763 promoted the recovery of muscle function. Therefore, combining SB216763-loaded PLGA microspheres with conduit small gap tubulization shows potential for applications in repairing peripheral nerve injury.

Recent Advances in Protein Kinase Activity Analysis Based on Nanomaterials

Protein phosphorylation regulated by protein kinases, as well as their dephosphorylation, is one of the most common post-translational modifications, and plays important roles in physiological activities, such as intracellular signal communications, gene transcription, cell proliferation and apoptosis. Over-expression of protein kinases is closely associated with various diseases. Consequently, accurate detection of protein kinases activities and their relevant inhibitors screening is critically important, not only to the biochemical research, but also to the clinical diagnosis and therapy. Nanomaterials, taking advantage of large surface areas, as well as excellent electrical, catalytic, magnetic and optical properties, have been utilized as target concentrators, recognition components, signal transducer or amplification elements in protein kinase related assays. This review summarizes the recent representative works to highlight the applications of nanomaterials in different biosensor technologies for protein kinases activities detection and their inhibitors screening. First, different nanomaterials developed for phosphoprotein/phosphopeptide enrichment and phosphate recognition are introduced. Next, representative works are selected that mainly focus on the utilization of nanomaterials as signal transducer or amplification elements in various protein kinases sensing platforms, such as electrochemical, colorimetric, fluorescent, and mass spectroscopy-based approaches. Finally, the major challenges and perspectives of nanomaterials being applied in protein kinases related assays are discussed.

Stereoisomers of Schisandrin B Are Potent ATP Competitive GSK-3β Inhibitors with Neuroprotective Effects against Alzheimer's Disease: Stereochemistry and Biological Activity

Glycogen synthase kinase-3β (GSK-3β) is a key enzyme in hyperphosphorylation of tau proteins and is a promising therapeutic target in Alzheimer's disease (AD). Here, we reported, for the first time, that the stereoisomers of Schisandrin B (Sch B), (+)-1, (-)-1, (+)-2, and (-)-2, were potent GSK-3β inhibitors. They were demonstrated to selectively target GSK-3β in an orthosteric binding mode, with IC₅₀ values of 340, 290, 80, and 70 nM, respectively. Further study showed that these stereoisomers can significantly increase the expression of p-GSK-3β (Ser9) and decrease the expressions of p-GSK-3β (Tyr216) and p-GSK-3β (Tyr279). Finally, these compounds can alleviate the cell injury induced by Aβ, and the cognitive disorders in AD mice, especially (+)-2 and (-)-2. Collectively, the stereoisomers of Sch B, especially (+)-2 and (-)-2, were found to be potential selective ATP-competitive GSK-3β inhibitors, which further affected their anti-AD effects. These promising findings explained the biological target of Sch B in AD, and bring a new understanding in the stereochemistry and bioactivities of Sch B.

Glycogen synthase kinase-3 inhibitor as a multi-targeting anti-rheumatoid drug

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease that causes swelling, bone erosion, and joint disorder. Patients with RA therefore suffer from pain and physiological disability, and have a decreased quality of life. During the progression of RA, many different types of cells and inflammatory factors influence each other with an important role. A better understanding of the pathology of RA should therefore lead to the development of effective anti-rheumatoid drugs, such as the anti-TNFα antibody. Glycogen synthase kinase-3 (GSK-3) is a cytoplasmic serine/threonine protein kinase that is involved in a large number of key cellular processes and is dysregulated in a wide variety of diseases, including inflammation and osteoporosis. The accumulated evidence has suggested that GSK-3 could be involved in multiple steps in the progression of RA. In the present review, the mechanisms of the pathogenesis of RA are summarized, and recent developments and potential new drugs targeting GSK-3 are discussed.

A walk through tau therapeutic strategies

Tau neuronal and glial pathologies drive the clinical presentation of Alzheimer's disease and related human tauopathies. There is a growing body of evidence indicating that pathological tau species can travel from cell to cell and spread the pathology through the brain. Throughout the last decade, physiological and pathological tau have become attractive targets for AD therapies. Several therapeutic approaches have been proposed, including the inhibition of protein kinases or protein-3-O-(N-acetyl-beta-D-glucosaminyl)-L-serine/threonine Nacetylglucosaminyl hydrolase, the inhibition of tau aggregation, active and passive immunotherapies, and tau silencing by antisense oligonucleotides. New tau therapeutics, across the board, have demonstrated the ability to prevent or reduce tau lesions and improve either cognitive or motor impairment in a variety of animal models developing neurofibrillary pathology. The most advanced strategy for the treatment of human tauopathies remains immunotherapy, which has already reached the clinical stage of drug development. Tau vaccines or humanised antibodies target a variety of tau species either in the intracellular or extracellular spaces. Some of them recognise the amino-terminus or carboxy-terminus, while others display binding abilities to the proline-rich area or microtubule binding domains. The main therapeutic foci in existing clinical trials are on Alzheimer's disease, progressive supranuclear palsy and non-fluent primary progressive aphasia. Tau therapy offers a new hope for the treatment of many fatal brain disorders. First efficacy data from clinical trials will be available by the end of this decade.

Mechanisms Associated with Type 2 Diabetes as a Risk Factor for Alzheimer-Related Pathology

Current evidence suggests dementia and pathology in Alzheimer's Disease (AD) are both dependent and independent of amyloid processing and can be induced by multiple 'hits' on vital neuronal functions. Type 2 diabetes (T2D) poses the most important risk factor for developing AD after ageing and dysfunctional IR/PI3K/Akt signalling is a major contributor in both diseases. We developed a model of T2D, coupling subdiabetogenic doses of streptozotocin (STZ) with a human junk food (HJF) diet to more closely mimic the human condition. Over 35 weeks, this induced classic signs of T2D (hyperglycemia and insulin dysfunction) and a modest, but stable deficit in spatial recognition memory, with very little long-term modification of proteins in or associated with IR/PI3K/Akt signalling in CA1 of the hippocampus. Intracerebroventricular infusion of soluble amyloid beta 42 (Aβ42) to mimic the early preclinical rise in Aβ alone induced a more severe, but short-lasting deficits in memory and deregulation of proteins. Infusion of Aβ on the T2D phenotype exacerbated and prolonged the memory deficits over approximately 4 months, and induced more severe aberrant regulation of proteins associated with autophagy, inflammation and glucose uptake from the periphery. A mild form of environmental enrichment transiently rescued memory deficits and could reverse the regulation of some, but not all protein changes. Together, these data identify mechanisms by which T2D could create a modest dysfunctional neuronal milieu via multiple and parallel inputs that permits the development of pathological events identified in AD and memory deficits when Aβ levels are transiently effective in the brain.

How to design potent and selective DYRK1B inhibitors? Molecular modeling study

DYRK1B protein kinase is an emerging anticancer target due to its overexpression in a variety of cancers and its role in cancer chemoresistance through maintaining cancer cells in the G0 (quiescent) state. Consequently, there is a growing interest in the development of potent and selective DYRK1B inhibitors for anticancer therapy. One of the major off-targets is another protein kinase, GSK3β, which phosphorylates an important regulator of cell cycle progression on the same residue as DYRK1B and is involved in multiple signaling pathways. In the current work, we performed a detailed comparative structural analysis of DYRK1B and GSK3β ATP-binding sites and identified key regions responsible for selectivity. As the crystal structure of DYRK1B has never been reported, we built and optimized a homology model by comparative modeling and metadynamics simulations. Calculation of interaction energies between docked ligands in the ATP-binding sites of both kinases allowed us to pinpoint key residues responsible for potency and selectivity. Specifically, the role of the gatekeeper residues in DYRK1B and GSK3β is discussed in detail, and two other residues are identified as key to selectivity of DYRK1B inhibition versus GSK3β. The analysis presented in this work was used to support the design of potent and selective azaindole-quinoline-based DYRK1B inhibitors and can facilitate development of more selective inhibitors for DYRK kinases.

Melatonin receptor stimulation by agomelatine prevents Aβ-induced tau phosphorylation and oxidative damage in PC12 cells

Purpose

As a novel antidepressant drug, agomelatine has good therapeutic effect on the mood disorder and insomnia in Alzheimer's disease (AD). Recent studies have shown the neuroprotective function of agomelatine, including anti-oxidative and anti-apoptosis effect. However, it remains unclear whether agomelatine exerts neuroprotection in AD. Thus, the neuroprotective effect of agomelatine against amyloid beta _25-35 (Aβ_25-35)-induced toxicity in PC12 cells was evaluated in this study.

Methods

The concentration of malondialdehyde (MDA), LDH, and ROS was investigated to evaluate oxidative damage. The expression of P-tau, tau, PTEN, P-Akt, Akt, P-GSK3β, and GSK3β proteins was assessed by Western blotting. Our results demonstrated that Aβ_25-35 significantly increased the content of MDA, LDH, and ROS. Meanwhile, Aβ_25-35 upregulated the expression of P-tau and PTEN as well as downregulated P-Akt and P-GSK3β expression. These effects could be blocked by agomelatine pretreatment. Furthermore, luzindole, the melatonin receptor (MT) antagonist, could reverse the neuroprotective effect of agomelatine.

Conclusion

The results demonstrated that antidepressant agomelatine might prevent the tau protein phosphorylation and oxidative damage induced by Aβ_25-35 in PC12 cells by activating MT-PTEN/Akt/GSK3β signaling. This study provided a novel therapeutic target for AD in the future.

Current and Emerging Pharmacological Targets for the Treatment of Alzheimer's Disease

No cure or disease-modifying therapy for Alzheimer's disease (AD) has yet been realized. However, a multitude of pharmacological targets have been identified for possible engagement to enable drug discovery efforts for AD. Herein, we review these targets comprised around three main therapeutic strategies. First is an approach that targets the main pathological hallmarks of AD: amyloid-β (Aβ) oligomers and hyperphosphorylated tau tangles which primarily focuses on reducing formation and aggregation, and/or inducing their clearance. Second is a strategy that modulates neurotransmitter signaling. Comprising this strategy are the cholinesterase inhibitors and N-methyl-D-aspartate receptor blockade treatments that are clinically approved for the symptomatic treatment of AD. Additional targets that aim to stabilize neuron signaling through modulation of neurotransmitters and their receptors are also discussed. Finally, the third approach comprises a collection of 'sensitive targets' that indirectly influence Aβ or tau accumulation. These targets are proteins that upon Aβ accumulation in the brain or direct Aβ-target interaction, a modification in the target's function is induced. The process occurs early in disease progression, ultimately causing neuronal dysfunction. This strategy aims to restore normal target function to alleviate Aβ-induced toxicity in neurons. Overall, we generally limit our analysis to targets that have emerged in the last decade and targets that have been validated using small molecules in in vitro and/or in vivo models. This review is not an exhaustive list of all possible targets for AD but serves to highlight the most promising and critical targets suitable for small molecule drug intervention.

A numerical study of sensitivity coefficients for a model of amyloid precursor protein and tau protein transport and agglomeration in neurons at the onset of Alzheimer's disease

Modeling of intracellular processes occurring during the development of Alzheimer's disease (AD) can be instrumental in understanding the disease and can potentially contribute to finding treatments for the disease. The model of intracellular processes in AD, which we previously developed, contains a large number of parameters. To distinguish between more important and less important parameters we performed a local sensitivity analysis of this model around the values of parameters that give the best fit with published experimental results. We show that the effect of model parameters on the total concentration of amyloid precursor protein (APP) and tau protein in the axon, respectively, is reciprocal to the effect of the same parameters on the average velocities of the same proteins during their transport in the axon. The results of our analysis also suggest that in the beginning of AD the aggregation of amyloid-ß and misfolded tau protein have little effect on transport of APP and tau in the axon, which suggests that early effects of AD may be reversible.

The TRAX, DISC1, and GSK3 complex in mental disorders and therapeutic interventions

Psychiatric disorders (such as bipolar disorder, depression, and schizophrenia) affect the lives of millions of individuals worldwide. Despite the tremendous efforts devoted to various types of psychiatric studies and rapidly accumulating genetic information, the molecular mechanisms underlying psychiatric disorder development remain elusive. Among the genes that have been implicated in schizophrenia and other mental disorders, disrupted in schizophrenia 1 (DISC1) and glycogen synthase kinase 3 (GSK3) have been intensively investigated. DISC1 binds directly to GSK3 and modulates many cellular functions by negatively inhibiting GSK3 activity. The human DISC1 gene is located on chromosome 1 and is highly associated with schizophrenia and other mental disorders. A recent study demonstrated that a neighboring gene of DISC1, translin-associated factor X (TRAX), binds to the DISC1/GSK3β complex and at least partly mediates the actions of the DISC1/GSK3β complex. Previous studies also demonstrate that TRAX and most of its interacting proteins that have been identified so far are risk genes and/or markers of mental disorders. In the present review, we will focus on the emerging roles of TRAX and its interacting proteins (including DISC1 and GSK3β) in psychiatric disorders and the potential implications for developing therapeutic interventions.

Targeting GSK3 signaling as a potential therapy of neurodegenerative diseases and aging

INTRODUCTION

Glycogen synthase kinase 3 (GSK3) is at the center of cellular signaling and controls various aspects of brain functions, including development of the nervous system, neuronal plasticity and onset of neurodegenerative disorders. Areas covered: In this review, recent efforts in elucidating the roles of GSK3 in neuronal plasticity and development of brain pathologies; Alzheimer's and Parkinson's disease, schizophrenia, and age-related neurodegeneration are described. The effect of microglia and astrocytes on development of the pathological states is also discussed. Expert opinion: GSK3β and its signaling pathway partners hold great promise as therapeutic target(s) for a multitude of neurological disorders. Activity of the kinase is often elevated in brain disorders. However, due to the wide range of GSK3 cellular targets, global inhibition of the kinase leads to severe side-effects and GSK3 inhibitors rarely reach Phase-2 clinical trials. Thus, a selective modulation of a specific cellular pool of GSK3 or specific down- or upstream partners of the kinase might provide more efficient anti-neurodegenerative therapies.

Novel Protein Kinase Inhibitors Related to Tau Pathology Modulate Tau Protein-Self Interaction Using a Luciferase Complementation Assay

The current number of drugs available for the treatment of Alzheimer’s disease (AD) is strongly limited and their benefit for therapy is given only in the early state of the disease. An effective therapy should affect those processes which mainly contribute to the neuronal decay. There have been many approaches for a reduction of toxic Aβ peptides which mostly failed to halt cognitive deterioration in patients. The formation of neurofibrillary tangles (NFT) and its precursor tau oligomers have been suggested as main cause of neuronal degeneration because of a direct correlation of their density to the degree of dementia. Reducing of tau aggregation may be a viable approach for the treatment of AD. NFT consist of hyperphosphorylated tau protein and tau hyperphosphorylation reduces microtubule binding. Several protein kinases are discussed to be involved in tau hyperphosphorylation. We developed novel inhibitors of three protein kinases (gsk-3β, cdk5, and cdk1) and discussed their activity in relation to tau phosphorylation and on tau–tau interaction as a nucleation stage of a tau aggregation in cells. Strongest effects were observed for those inhibitors with effects on all the three kinases with emphasis on gsk-3β in nanomolar ranges.

Investigation of the Lipid-Lowering Effect of Vitamin C Through GSK-3β/β-Catenin Signaling in Zebrafish

Vitamin C (VC) is an essential nutrient for most fish species because of the absence of L-gulonolactone oxidase in the bodies of fish. VC plays a significant role in maintaining the physiological functions and in improving the growth performance, immunity, and survival of fish. In this study, zebrafish (Danio rerio) were treated with 8.2, 509.6, and 1007.5 mg/kg VC diets for 2 weeks, and the muscle samples were collected for gene expression analysis and biochemical index analysis. The results indicated that 509.6 and 1007.5 mg/kg VC diets inhibited glycogen synthase kinase-3β (GSK-3β) expression and induced the expression of β-catenin in the muscle of zebrafish. The mRNA expression of CCAAT/enhancer-binding protein α (C/EBPα) and fatty acid synthase (FAS), FAS activity, and the content of glycerol and triglyceride (TG) were decreased in the muscle by 509.6 and 1007.5 mg/kg VC diets. In addition, GSK-3β RNA interference was observed in zebrafish fed with 8.2 and 1007.5 mg/kg VC diets. It was found that GSK-3β RNA interference induced the mRNA expression of β-catenin but decreased the mRNA expression of C/EBPα and FAS, FAS activity, as well as the content of glycerol and TG in the muscle of zebrafish. In ZF4 cells, the mRNA expression of GSK-3β, C/EBPα, and FAS was decreased, but β-catenin expression was increased by 0.1 and 0.5 mmol/L VC treatments in vitro. The glycerol and TG content, and FAS activity in ZF4 cells were decreased by 0.1 and 0.5 mmol/L VC treatments. Moreover, the result of western blot indicated that the protein expression level of GSK-3β was significantly decreased and that of β-catenin was significantly increased in ZF4 cells treated with 0.1 and 0.5 mmol/L VC. The results from in vivo and in vitro studies corroborated that VC exerted the lipid-lowering effect through GSK-3β/β-catenin signaling in zebrafish.

Dihydromyricetin Inhibits Lead-Induced Cognitive Impairments and Inflammation by the Adenosine 5'-Monophosphate-Activated Protein Kinase Pathway in Mice

Dihydromyricetin (DHM), a natural flavonoid derived from the medicinal and edible plant Ampelopsis grossedentata, exhibits antioxidant, antiapoptosis, antitumor, and anti-inflammatory bioactivities. This study evaluated the effects of DHM on Pb-induced neurotoxicity and explored the underlying mechanisms. DHM significantly ameliorated behavioral impairments of Pb-induced mice. It decreased the levels of lipid peroxidation and protein carbonyl and increased the activities of superoxide dismutase and catalase in the brains. DHM suppressed Pb-induced apoptosis, as indicated by the decreased levels of Bax and cleaved caspase-3. DHM also decreased inflammatory cytokines in the brains of Pb-treated mice. DHM decreased amyloid-beta (Aβ) level and nuclear factor-κB nuclear translocation. Moreover, DHM induced the adenosine 5'-monophosphate-activated protein kinase (AMPK) phosphorylation and inhibited the activation of p38, Toll-like receptor 4, myeloid differentiation factor 88, and glycogen synthase kinase-3. Collectively, this is the first report indicating that DHM could improve Pb-induced cognitive functional impairment by preventing oxidative stress, apoptosis, and inflammation and that the protective effect was mediated partly through the AMPK pathway.

Protective Effects of 6-(Methylsulfinyl)hexyl Isothiocyanate on Aβ1-42-Induced Cognitive Deficit, Oxidative Stress, Inflammation, and Apoptosis in Mice

Alzheimer's disease (AD) is the most common form of dementia among older people. Although soluble amyloid species are recognized triggers of the disease, no therapeutic approach is able to stop it. 6-(Methylsulfinyl)hexyl isothiocyanate (6-MSITC) is a major bioactive compound in Wasabia japonica, which is a typical Japanese pungent spice. Recently, in vivo and in vitro studies demonstrated that 6-MSITC has several biological properties. The aim of the present study was to investigate the neuroprotective activity of 6-MSITC in a murine AD model, induced by intracerebroventricular injection of β-amyloid oligomers (Aβ1-42O). The treatment with 6-MSITC started 1 h after the surgery for the next 10 days. Behavioral analysis showed that 6-MSITC ameliorated Aβ1-42O-induced memory impairments. The decrease of glutathione levels and increase of reactive oxygen species in hippocampal tissues following Aβ1-42O injection were reduced by 6-MSITC. Moreover, activation of caspases, increase of inflammatory factors, and phosphorylation of ERK and GSK3 were inhibited by 6-MSITC. These results highlighted an interesting neuroprotective activity of 6-MSITC, which was able to restore a physiological oxidative status, interfere positively with Nrf2-pathway, decrease apoptosis and neuroinflammation and contribute to behavioral recovery. Taken together, these findings demonstrated that 6-MSITC could be a promising complement for AD therapy.

MiR-124-3p attenuates hyperphosphorylation of Tau protein-induced apoptosis via caveolin-1-PI3K/Akt/GSK3β pathway in N2a/APP695swe cells

Hyperphosphorylation of Tau forming neurofibrillary tangles has been considered as a crucial event in the pathogenesis of Alzheimer's disease (AD). MiR-124-3p belongs to microRNA (miRNA) family and was markedly decreased in AD, however, the functions of miR-124-3p in the pathogenesis of AD remain unknown. We observed that the expression of miR-124-3p was significantly decreased in N2a/APP695swe cells; and transfection of miR-124-3p mimics not only attenuated cell apoptosis and abnormal hyperphosphorylation of Tau protein without any changes of total Tau protein, but also increased expression levels of Caveolin-1, phosphoinositide 3-kinase (PI3K), phospho-Akt (Akt-Ser473)/Akt, phospho-glycogen synthase kinase-3 beta (GSK-3β-Ser9)/GSK-3β in N2a/APP695swe cells. We further found that miR-12-3p directly targeted Caveolin-1; miR-124-3p inhibited abnormal hyperphosphorylation of Tau by regulating Caveolin-1-PI3K/Akt/GSK3β pathway in AD. This study reveals that miR-124-3p may play a neuroprotective role in AD, which may provide new ideas and therapeutic targets for AD.

Amaryllidaceae Alkaloids as Potential Glycogen Synthase Kinase-3β Inhibitors

Glycogen synthase kinase-3β (GSK-3β) is a multifunctional serine/threonine protein kinase that was originally identified as an enzyme involved in the control of glycogen metabolism. It plays a key role in diverse physiological processes including metabolism, the cell cycle, and gene expression by regulating a wide variety of well-known substances like glycogen synthase, tau-protein, and β-catenin. Recent studies have identified GSK-3β as a potential therapeutic target in Alzheimer´s disease, bipolar disorder, stroke, more than 15 types of cancer, and diabetes. GSK-3β is one of the most attractive targets for medicinal chemists in the discovery, design, and synthesis of new selective potent inhibitors. In the current study, twenty-eight Amaryllidaceae alkaloids of various structural types were studied for their potency to inhibit GSK-3β. Promising results have been demonstrated by alkaloids of the homolycorine-{9-O-demethylhomolycorine (IC₅₀ = 30.00 ± 0.71 µM), masonine (IC₅₀ = 27.81 ± 0.01 μM)}, and lycorine-types {caranine (IC₅₀ = 30.75 ± 0.04 μM)}.

Multi-Target Anti-Alzheimer Activities of Four Prenylated Compounds from Psoralea Fructus

Alzheimer’s disease (AD) is an age-related neurodegenerative disease that is mediated by multiple signaling pathways. In recent years, the components of Psoralea Fructus (PF) have demonstrated some anti-Alzheimer effects both in vitro and in vivo. To further reveal the active compounds of PF and their mechanisms regulating key targets of AD, in this study, we identified four prenylated compounds from the 70% ethanolic aqueous extract of PF, namely bavachin, bavachinin, bavachalcone, and isobavachalcone. Multi-target bioactivity analysis showed that these compounds could differentially inhibit neuroinflammation, oxidative damage, and key AD-related protein targets, such as amyloid β-peptide 42, β-secretase, glycogen synthase kinase 3β, and acetylcholinesterase. These compounds may generate beneficial effects in AD prevention and treatment.

Dual GSK-3β/AChE Inhibitors as a New Strategy for Multitargeting Anti-Alzheimer's Disease Drug Discovery

Designing multitarget-directed ligands (MTDLs) is considered to be a promising approach to address complex and multifactorial maladies such as Alzheimer's disease (AD). The concurrent inhibition of the two crucial AD targets, glycogen synthase kinase-3β (GSK-3β) and human acetylcholinesterase (hAChE), might represent a breakthrough in the quest for clinical efficacy. Thus, a novel family of GSK-3β/AChE dual-target inhibitors was designed and synthesized. Among these hybrids, 2f showed the most promising profile as a nanomolar inhibitor on both hAChE (IC₅₀ = 6.5 nM) and hGSK-3β kinase activity (IC₅₀ = 66 nM). It also showed good inhibitory effect on β-amyloid self-aggregation (inhibitory rate = 46%) at 20 μM. Western blot analysis revealed that compound 2f inhibited hyperphosphorylation of tau protein in mouse neuroblastoma N2a-Tau cells. In vivo studies confirmed that 2f significantly ameliorated the cognitive disorders in scopolamine-treated ICR mice and less hepatotoxicity than tacrine. This study provides new leads for assessment of GSK-3β and AChE pathway dual inhibition as a promising strategy for AD treatment.

Binge Alcohol Exposure Causes Neurobehavioral Deficits and GSK3β Activation in the Hippocampus of Adolescent Rats

Heavy alcohol exposure causes profound damage to the adolescent brain, particularly the hippocampus, which underlie some behavioral deficits. However, the underlying molecular mechanisms remain inconclusive. The current study sought to determine whether binge alcohol exposure affects the hippocampus-related behaviors and key signaling proteins that may mediate alcohol neurotoxicity in adolescent rats. Alcohol exposure reduced the number of both NeuN-positive and doublecortin-positive cells in the hippocampus. Alcohol also induced neurodegeneration which was confirmed by ultrastructural analysis by electronic microscopy and was accompanied with the activation of microglia. Binge alcohol exposure impaired spatial learning and memory which was evaluated by the Morris water maze. However, alcohol did not alter the spontaneous locomotor activity which was determined by the open field test. GSK3β is a multi-function serine/threonine protein kinase regulating both neuronal survival and neurogenesis and plays an important role in various neurodegenerative disorders. We have previously shown that GSK3β is a key mediator of alcohol-induced neuron apoptosis in the developing brain. We showed here binge alcohol exposure caused GSK3β activation by inducing dephosphorylation at Ser9 without affecting the phosphorylation of Tyr216 in the hippocampus. Thus, GSK3β may be involved in binge alcohol exposure-induced neuronal damage to the adolescent hippocampus.

Heme Oxygenase-1 Activity as a Correlate to Exercise-Mediated Amelioration of Cognitive Decline and Neuropathological Alterations in an Aging Rat Model of Dementia

Alzheimer's disease (AD) is a neurodegenerative disorder with cognitive impairment. Physical exercise has long been proven to be beneficial in the disorder. The present study was designed to examine the effect of voluntary exercise on spatial memory, imaging, and pathological abnormalities. Particular focus has been given to the role of heme oxygenase-1 (HO-1)—an important cellular cytoprotectant in preserving mental acuity—using an aging rat model of dementia. Male and female Wistar rats were segregated into six groups—namely, (i) aged sedentary (control) females (ASF, n = 8); (ii) aged sedentary (control) males (ASM, n = 8); (iii) aged running females (ARF, n = 8); (iv) aged running males (ARM, n = 8); (v) young control females (YCF, n = 8); and (vi) young control males (YCM, n = 8). Rats in the ARF and ARM groups had free access to a standardized inbuilt running wheel during the 3-month evaluation period. Spatial memory was investigated using the Morris Water Test, imaging and pathological alterations were assessed using positron emission tomography (PET) imaging and histopathological examinations (H&E, Congo red staining), respectively, and HO-1 enzyme activity assays were also conducted. The outcomes suggest that voluntary physical exercise mitigates impaired spatial memory and neuropathological changes exhibited by the aging sedentary group, via elevated HO-1 activity, contributing to the antioxidant capacity in the aging brain.

An 18-mer Peptide Derived from Prosaposin Ameliorates the Effects of Aβ1-42 Neurotoxicity on Hippocampal Neurogenesis and Memory Deficit in Mice

The pathological hallmarks of Alzheimer's disease (AD) include amyloid-β (Aβ) accumulation, neurofibrillary tangle formation, synaptic dysfunction, and neuronal loss. The present study was performed to investigate the protective effects and mechanism of action of a prosaposin-derived 18-mer peptide (PS18: LSELIINNATEELLIKGL) on mice hippocampal progenitor cell proliferation, neurogenesis, and memory tasks after intracerebroventricular injection of Aβ1-42 peptide. Seven days after Aβ1-42 injection, significant proliferation of hippocampal progenitor cells and memory impairment were evident. Two weeks after Aβ1-42 peptide injection, elevated numbers of surviving 5-bromo-2-deoxyuridine cells and newly formed neurons were detected. Treatment with PS18 attenuated these effects evoked by Aβ1-42. Our data indicate that treatment with PS18 partially attenuated the increase in hippocampal neurogenesis caused by Aβ1-42-induced neuroinflammation and prevented memory deficits associated with increased numbers of activated glial cells. We observed an increase in ADAM10 and decreases in BACE1, PS1/2, and AβPP protein levels, suggesting that PS18 enhances the nonamyloidogenic AβPP cleavage pathway. Importantly, our results further showed that PS18 activated the PI3K/Akt pathway, phosphorylated GSK-3α/β, and, as a consequence, exerted a neuroprotective effect. In addition, PS18 showed a protective effect against Aβ1-42-induced neurotoxicity via suppression of the caspase pathway; upregulation of Bcl-2; downregulation of BAX, attenuating mitochondrial damage; and inhibition of caspase-3. These findings suggest that PS18 may provide a valuable therapeutic strategy for the treatment of progressive neurodegenerative diseases, such as AD.

Dietary Total Prenylflavonoids from the Fruits of Psoralea corylifolia L. Prevents Age-Related Cognitive Deficits and Down-Regulates Alzheimer's Markers in SAMP8 Mice

Alzheimer's disease (AD) is a serious threat for the aging society. In this study, we examined the preventive effect of the total prenylflavonoids (TPFB) prepared from the dried fruits of Psoralea corylifolia L., using an age-related AD mouse model SAMP8. We found that long-term dietary TPFB at 50 mg/kg·day significantly improved cognitive performance of the SAMP8 mice in Morris water maze tests, similar to 150 mg/kg·day of resveratrol, a popular neuro-protective compound. Furthermore, TPFB treatment showed significant improvements in various AD markers in SAMP8 brains, which were restored to near control levels of the normal mice, SAMR1. TPFB significantly reduced the level of amyloid β-peptide 42 (Aβ42), inhibited hyperphosphorylation of the microtubule-associated protein Tau, induced phosphorylation of Ser9 of the glycogen synthase kinase 3β (GSK-3β), and decreased the expression of the proinflammatory cytokines TNFα, IL-6, and IL-1β. Finally, TPFB also markedly reduced the level of serum derivatives of reactive oxygen metabolites (d-ROMs), a biomarker of oxidative stress in vivo. These results showed that dietary TPFB could effectively prevent age-related cognitive deficits and AD-like neurobiochemical changes, and may have a potential role in the prevention of Alzheimer's disease.

Disparate Effects of Lithium and a GSK-3 Inhibitor on Neuronal Oscillatory Activity in Prefrontal Cortex and Hippocampus

Glycogen synthase kinase-3 (GSK-3) plays a critical role in cognitive dysfunction associated with Alzheimer’s disease (AD), yet the mechanism by which GSK-3 alters cognitive processes in other disorders, such as schizophrenia, remains unknown. In the present study, we demonstrated a role for GSK-3 in the direct regulation of neuronal oscillations in hippocampus (HIP) and prelimbic cortex (PL). A comparison of the GSK-3 inhibitors SB 216763 and lithium demonstrated disparate effects of the drugs on spatial memory and neural oscillatory activity in HIP and PL. SB 216763 administration improved spatial memory whereas lithium treatment had no effect. Analysis of neuronal local field potentials in anesthetized animals revealed that whereas both repeated SB 216763 (2.5 mg/kg) and lithium (100 mg/kg) induced a theta frequency spike in HIP at approximately 10 Hz, only SB 216763 treatment induced an overall increase in theta power (4–12 Hz) compared to vehicle. Acute administration of either drug suppressed slow (32–59 Hz) and fast (61–100 Hz) gamma power. In PL, both drugs induced an increase in theta power. Repeated SB 216763 increased HIP–PL coherence across all frequencies except delta, whereas lithium selectively suppressed delta coherence. These findings demonstrate that GSK-3 plays a direct role in the regulation of theta oscillations in regions critically involved in cognition, and highlight a potential mechanism by which GSK-3 may contribute to cognitive decline in disorders of cognitive dysfunction.

Alzheimer's disease pathology and the unfolded protein response: prospective pathways and therapeutic targets

Many vital interdependent cellular functions including proteostasis, lipogenesis and Ca homeostasis are executed by the endoplasmic reticulum (ER). Exogenous insults can impair ER performance: this must be rapidly corrected or cell death will ensue. Protective adaptations can boost the functional capacity of the ER and form the basis of the unfolded protein response (UPR). Activated in response to the accumulation of misfolded proteins, the UPR can halt protein translation while increasing protein-handling chaperones and the degradation of erroneous proteins through a conserved three-tier molecular cascade. However, prolonged activation of the UPR can result in the maladaptation of the system, resulting in the activation of inflammatory and apoptotic effectors. Recently, UPR and its involvement in neurodegenerative disease has attracted much interest and numerous potentially 'drugable' points of crosstalk are now emerging. Here, we summarize the functions of the ER and UPR, and highlight evidence for its potential role in the pathogenesis of Alzheimer's disease, before discussing several key targets with therapeutic potential.

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.

Kinase-loaded magnetic beads for sequentialin vitrophosphorylation of peptides and proteins

Kinases ERK2 and GSK-3β loaded magnetic beads for sequentialin vitrophosphorylation of peptides and proteins.

Memantine for the Treatment of Dementia: A Review on its Current and Future Applications

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the presence in the brain of extracellular amyloid-β protein (Aβ) and intracellular neurofibrillary tangles composed of hyperphosphorylated tau protein. The N-Methyl-D-aspartate receptors (NMDAR), ionotropic glutamate receptor, are essential for processes like learning and memory. An excessive activation of NMDARs has been associated with neuronal loss. The discovery of extrasynaptic NMDARs provided a rational and physiological explanation between physiological and excitotoxic actions of glutamate. Memantine (MEM), an antagonist of extrasynaptic NMDAR, is currently used for the treatment of AD jointly with acetylcholinesterase inhibitors. It has been demonstrated that MEM preferentially prevents the excessive continuous extrasynaptic NMDAR disease activation and therefore prevents neuronal cell death induced by excitotoxicity without disrupting physiological synaptic activity. The problem is that MEM has shown no clear positive effects in clinical applications while, in preclinical stages, had very promising results. The data in preclinical studies suggests that MEM has a positive impact on improving AD brain neuropathology, as well as in preventing Aβ production, aggregation, or downstream neurotoxic consequences, in part through the blockade of extrasynaptic NMDAR. Thus, the focus of this review is primarily to discuss the efficacy of MEM in preclinical models of AD, consider possible combinations of this drug with others, and then evaluate possible reasons for its lack of efficacy in clinical trials. Finally, applications in other pathologies are also considered.

High-frequency (50 Hz) electroacupuncture ameliorates cognitive impairment in rats with amyloid beta 1-42-induced Alzheimer's disease

Acupuncture has been shown to ameliorate cognitive impairment of Alzheimer's disease. Acupoints and stimulation frequency influence the therapeutic effect of electroacupuncture. Rat models of Alzheimer's disease were established by injecting amyloid beta 1–42 (Aβ_1–42) into the bilateral lateral ventricles. Electroacupuncture at 2, 30, and 50 Hz was carried out at Baihui (GV20; 15° obliquely to a depth of 2 mm) and Shenshu (BL23; perpendicularly to 4–6 mm depth), once a day for 20 minutes (each), for 15 days, taking a break every 7 days. The Morris water maze test was conducted to assess the learning and memory. The expression levels of glycogen synthase kinase-3β (GSK-3β), pSer9-GSK-3β, pTyr216-GSK-3β, amyloid precursor protein and Aβ_1–40 in the hippocampus were determined by western blot assay. Results demonstrated that electroacupuncture treatment at different frequencies markedly improved learning and memory ability, increased synaptic curvatures, decreased the width of synaptic clefts, thickened postsynaptic densities, and downregulated the expression of GSK-3β, amyloid precursor protein, and Aβ_1–40. pSer9-GSK-3β expression markedly decreased, while pTyr216-GSK-3β expression increased. High-frequency (50 Hz) electroacupuncture was more effective than low (2 Hz) or medium-frequency (30 Hz) electroacupuncture. In conclusion, electroacupuncture treatment exerts a protective effect against Aβ_1–42-induced learning and memory deficits and synapse-ultrastructure impairment via inhibition of GSK-3β activity. Moreover, high-frequency electroacupuncture was the most effective therapy.

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.

Indirubin Derivative 7-Bromoindirubin-3-Oxime (7Bio) Attenuates Aβ Oligomer-Induced Cognitive Impairments in Mice

Indirubins are natural occurring alkaloids extracted from indigo dye-containing plants. Indirubins could inhibit various kinases, and might be used to treat chronic myelocytic leukemia, cancer and neurodegenerative disorders. 7-bromoindirubin-3-oxime (7Bio), an indirubin derivative derived from indirubin-3-oxime, possesses inhibitory effects against cyclin-dependent kinase-5 (CDK5) and glycogen synthase kinase-3β (GSK3β), two pharmacological targets of Alzheimer's disease (AD). In this study, we have discovered that 2.3–23.3 μg/kg 7Bio effectively prevented β-amyloid (Aβ) oligomer-induced impairments of spatial cognition and recognition without affecting bodyweight and motor functions in mice. Moreover, 7Bio potently inhibited Aβ oligomer-induced expression of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Furthermore, 7Bio significantly prevented the decreased expression of synapsin-1 and PSD-95, biomarkers of pre-synaptic and post-synaptic proteins in Aβ oligomer-treated mice. The mean optical density (OD) with hyper-phosphorylated tau (pTau), glial fibrillary acidic protein (GFAP) and CD45 positive staining in the hippocampus of 7Bio-treated mice were significantly decreased compared to those of Aβ oligomer-treated mice. In addition, Western blotting analysis showed that 7Bio attenuated Aβ oligomer-decreased expression of pSer9-GSK3β. Those results suggested that 7Bio could potently inhibit Aβ oligomer-induced neuroinflammation, synaptic impairments, tau hyper-phosphorylation, and activation of astrocytes and microglia, which may contribute to the neuroprotective effects of 7Bio. Based on these findings, we expected that 7Bio might be developed as a novel anti-AD lead compound.

Neuroprotective Functions for the Histone Deacetylase SIRT6

The histone deacetylase SIRT6 promotes DNA repair, but its activity declines with age with a concomitant accumulation of DNA damage. Furthermore, SIRT6 knockout mice exhibit an accelerated aging phenotype and die prematurely. Here, we report that brain-specific SIRT6-deficient mice survive but present behavioral defects with major learning impairments by 4 months of age. Moreover, the brains of these mice show increased signs of DNA damage, cell death, and hyperphosphorylated Tau-a critical mark in several neurodegenerative diseases. Mechanistically, SIRT6 regulates Tau protein stability and phosphorylation through increased activation of the kinase GSK3α/β. Finally, SIRT6 mRNA and protein levels are reduced in patients with Alzheimer's disease. Taken together, our results suggest that SIRT6 is critical to maintain genomic stability in the brain and that its loss leads to toxic Tau stability and phosphorylation. Therefore, SIRT6 and its downstream signaling could be targeted in Alzheimer's disease and age-related neurodegeneration.

Targets for Drug Therapy for Autism Spectrum Disorder: Challenges and Future Directions

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by persistent deficits in social communication and interaction and restricted, repetitive patterns of behavior, interests, and activities. Various factors are involved in the etiopathogenesis of ASD, including genetic factors, environmental toxins and stressors, impaired immune responses, mitochondrial dysfunction, and neuroinflammation. The heterogeneity in the phenotype among ASD patients and the complex etiology of the condition have long impeded the advancement of the development of pharmacological therapies. In the recent years, the integration of findings from mouse models to human genetics resulted in considerable progress toward the understanding of ASD pathophysiology. Currently, strategies to treat core symptoms of ASD are directed to correct synaptic dysfunctions, abnormalities in central oxytocin, vasopressin, and serotonin neurotransmission, and neuroinflammation. Here, we present a survey of the studies that have suggested molecular targets for drug development for ASD and the state-of-the-art of medicinal chemistry efforts in related areas.

Nimodipine attenuates tau phosphorylation at Ser396 via miR-132/GSK-3β pathway in chronic cerebral hypoperfusion rats

Chronic cerebral hypofusion (CCH) promotes hyperphosphorylation of tau proteins, a key neuropathological trait that reflects neurodegenerative disorders. Nimodipine, an L-type calcium channel antagonist, has been reported to show neuroprotective effects. In this study, we investigated the potential mechanism of nimodipine in tauopathies induced by CCH. MiR-132 is downregulated in tauopathies such as AD and directly targets tau mRNA to regulate its expression. Here, we report that CCH induced miR-132 deficiency and increased tau phosphorylation at Ser396 while tau expression was not influenced. Nimodipine treatment attenuated CCH induced tau phosphorylation by up-regulating expression of miR-132. Furthermore, nimodipine inhibited activation of GSK-3β and neuronal apoptosis induced by CCH. Interestingly, GSK-3βmRNA level negatively correlated with the expression of miR-132. These findings support a role for nimodipine inhibiting tau phosphorylation at Ser396 via miR-132/GSK-3β. Therefore, nimodipine may be a candidate for the treatment of tauopathy present in CCH.

Search for Alzheimer's disease biomarkers in blood cells: hypotheses-driven approach

Current Alzheimer's disease (AD) diagnostics is based on cognitive testing, and detecting amyloid Aβ and τ pathology by brain imaging and assays of cerebrospinal fluid. However, biomarkers identifying complex pathways contributing to pathology are lacking, especially for early AD. Preferably, such biomarkers should be more cost-effective and present in easily available diagnostic tissues, such as blood. Here, we summarize the recent findings of potential early AD molecular diagnostic biomarkers in blood platelets, lymphocytes and erythrocytes. We review molecular alterations which refer to such main hypotheses of AD pathogenesis as amyloid cascade, oxidative and mitochondrial stress, inflammation and alterations in cell cycle regulatory molecules. The major advantage of such biomarkers is the potential ability to indicate individualized therapies in AD patients.

Progranulin gene delivery reduces plaque burden and synaptic atrophy in a mouse model of Alzheimer's disease

Progranulin (PGRN) is a multifunctional protein that is widely expressed throughout the brain, where it has been shown to act as a critical regulator of CNS inflammation and also functions as an autocrine neuronal growth factor, important for long-term neuronal survival. PGRN has been shown to activate cell signaling pathways regulating excitoxicity, oxidative stress, and synaptogenesis, as well as amyloidogenesis. Together, these critical roles in the CNS suggest that PGRN has the potential to be an important therapeutic target for the treatment of various neurodegenerative disorders, particularly Alzheimer’s disease (AD). AD is the leading cause of dementia and is marked by the appearance of extracellular plaques consisting of aggregates of amyloid-β (Aβ), as well as neuroinflammation, oxidative stress, neuronal loss and synaptic atrophy. The ability of PGRN to target multiple key features of AD pathophysiology suggests that enhancing its expression may benefit this disease. Here, we describe the application of PGRN gene transfer using in vivo delivery of lentiviral expression vectors in a transgenic mouse model of AD. Viral vector delivery of the PGRN gene effectively enhanced PGRN expression in the hippocampus of Tg2576 mice. This elevated PGRN expression significantly reduced amyloid plaque burden in these mice, accompanied by reductions in markers of inflammation and synaptic atrophy. The overexpression of PGRN was also found to increase activity of neprilysin, a key amyloid beta degrading enzyme. PGRN regulation of neprilysin activity could play a major role in the observed alterations in plaque burden. Thus, PGRN may be an effective therapeutic target for the treatment of AD.

Developmental neurotoxicity of the hippocampus following in utero exposure to methylmercury: impairment in cell signaling

In this study, we assessed some hippocampal signaling cascades and behavioral impairments in 30-day-old rat pups prenatally exposed to methylmercury (MeHg). Pregnant rats were exposed to 1.0 or 2.0 mg/kg MeHg by gavage in alternated days from gestational day 5 until parturition. We found increased anxiety-like and decreased exploration behavior evaluated by open field test and deficit of both short- and long-term memories by novel object recognition task, respectively, in MeHg-treated pups. Downregulated PI3K/Akt/mTOR pathway and activated/hypophosphorylated (Ser9) GSK3β in MeHg-treated pups could be upstream of hyperphosphorylated Tau (Ser396) destabilizing microtubules and contributing to neural dysfunction in the hippocampus of these rats. Hyperphosphorylated/activated p38MAPK and downregulated phosphoErk1/2 support a role for mitogen-activated protein kinase (MAPK) cascade on MeHg neurotoxicity. Decreased receptor of advanced glycation end products (RAGE) immunocontent supports the assumption that downregulated RAGE/Erk1/2 pathway could be involved in hypophosphorylated lysine/serine/proline (KSP) repeats on neurofilament subunits and disturbed axonal transport. Downregulated myelin basic protein (MBP), the major myelin protein, is compatible with dysmyelination and neurofilament hypophosphorylation. Increased glial fibrillary acidic protein (GFAP) levels suggest reactive astrocytes, and active apoptotic pathways BAD/BCL-2, BAX/BCL-XL, and caspase 3 suggest cell death. Taken together, our findings get light on important signaling mechanisms that could underlie the behavioral deficits in 30-day-old pups prenatally exposed to MeHg.

Radiosynthesis and in Vivo Evaluation of [11C]A1070722, a High Affinity GSK-3 PET Tracer in Primate Brain

Dysfunction of glycogen synthase kinase 3 (GSK-3) is implicated in the etiology of Alzheimer's disease, Parkinson's disease, diabetes, pain, and cancer. A radiotracer for functional positron emission tomography (PET) imaging could be used to study the kinase in brain disorders and to facilitate the development of small molecule inhibitors of GSK-3 for treatment. At present, there is no target-specific or validated PET tracer available for the in vivo monitoring of GSK-3. We radiolabeled the small molecule inhibitor [11C]1-(7-methoxy- quinolin-4-yl)-3-(6-(trifluoromethyl)pyridin-2-yl)urea ([11C]A1070722) with high affinity to GSK-3 (Ki = 0.6 nM) in excellent radiochemical yield. PET imaging experiments in anesthetized vervet/African green monkey exhibited that [11C]A1070722 penetrated the blood-brain barrier (BBB) and accumulated in brain regions, with highest radioactivity binding in frontal cortex followed by parietal cortex and anterior cingulate, and with the lowest bindings found in caudate, putamen, and thalamus, similarly to the known distribution of GSK-3 in human brain. Our studies suggest that [11C]A1070722 can be a potential PET radiotracer for the in vivo quantification of GSK-3 in brain.

The Role of MicroRNAs in Aβ Deposition and Tau Phosphorylation in Alzheimer's Disease

Alzheimer’s disease (AD), with main clinical features of progressive impairment in cognitive and behavioral functions, is the most common degenerative disease of the central nervous system. Recent evidence showed that microRNAs (miRNAs) played important roles in the pathological progression of AD. In this article, we reviewed the promising role of miRNAs in both Aβ deposition and Tau phosphorylation, two key pathological characters in the pathological progression of AD, which might be helpful for the understanding of pathogenesis and the development of new strategies of clinical diagnosis and treatment of AD.