Inhibition of c-Jun kinase provides neuroprotection in a model of Alzheimer's disease

Evaluation of a Covalent Library of Diverse Warheads (CovLib) Binding to JNK3, USP7, or p53

Purpose

Over the last few years, covalent fragment-based drug discovery has gained significant importance. Thus, striving for more warhead diversity, we conceived a library consisting of 20 covalently reacting compounds. Our covalent fragment library (CovLib) contains four different warhead classes, including five α-cyanoacacrylamides/acrylates (CA), three epoxides (EO), four vinyl sulfones (VS), and eight electron-deficient heteroarenes with a leaving group (SNAr/SN).

Methods

After predicting the theoretical solubility of the fragments by LogP and LogS during the selection process, we determined their experimental solubility using a turbidimetric solubility assay. The reactivities of the different compounds were measured in a high-throughput 5,5'-dithiobis-(2-nitrobenzoic acid) DTNB assay, followed by a (glutathione) GSH stability assay. We employed the CovLib in a (differential scanning fluorimetry) DSF-based screening against different targets: c-Jun N-terminal kinase 3 (JNK3), ubiquitin-specific protease 7 (USP7), and the tumor suppressor p53. Finally, the covalent binding was confirmed by intact protein mass spectrometry (MS).

Results

In general, the purchased fragments turned out to be sufficiently soluble. Additionally, they covered a broad spectrum of reactivity. All investigated α-cyanoacrylamides/acrylates and all structurally confirmed epoxides turned out to be less reactive compounds, possibly due to steric hindrance and reversibility (for α-cyanoacrylamides/acrylates). The SNAr and vinyl sulfone fragments are either highly reactive or stable. DSF measurements with the different targets JNK3, USP7, and p53 identified reactive fragment hits causing a shift in the melting temperatures of the proteins. MS confirmed the covalent binding mode of all these fragments to USP7 and p53, while additionally identifying the SNAr-type electrophile SN002 as a mildly reactive covalent hit for p53.

Conclusion

The screening and target evaluation of the CovLib revealed first interesting hits. The highly cysteine-reactive fragments VS004, SN001, SN006, and SN007 covalently modify several target proteins and showed distinct shifts in the melting temperatures up to +5.1 °C and -9.1 °C.

A Combination of Heavy Metals and Intracellular Pathway Modulators Induces Alzheimer Disease-like Pathologies in Organotypic Brain Slices

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that is characterized by amyloid-beta (Aβ) plaques and tau neurofibrillary tangles (NFT). Modelling aspects of AD is challenging due to its complex multifactorial etiology and pathology. The present study aims to establish a cost-effective and rapid method to model the two primary pathologies in organotypic brain slices. Coronal hippocampal brain slices (150 µm) were generated from postnatal (day 8-10) C57BL6 wild-type mice and cultured for 9 weeks. Collagen hydrogels containing either an empty load or a mixture of human Aβ42 and P301S aggregated tau were applied to the slices. The media was further supplemented with various intracellular pathway modulators or heavy metals to augment the appearance of Aβ plaques and tau NFTs, as assessed by immunohistochemistry. Immunoreactivity for Aβ and tau was significantly increased in the ventral areas in slices with a mixture of human Aβ42 and P301S aggregated tau compared to slices with empty hydrogels. Aβ plaque- and tau NFT-like pathologies could be induced independently in slices. Heavy metals (aluminum, lead, cadmium) potently augmented Aβ plaque-like pathology, which developed intracellularly prior to cell death. Intracellular pathway modulators (scopolamine, wortmannin, MHY1485) significantly boosted tau NFT-like pathologies. A combination of nanomolar concentrations of scopolamine, wortmannin, MHY1485, lead, and cadmium in the media strongly increased Aβ plaque- and tau NFT-like immunoreactivity in ventral areas compared to the slices with non-supplemented media. The results highlight that we could harness the potential of the collagen hydrogel-based spreading of human Aβ42 and P301S aggregated tau, along with pharmacological manipulation, to produce pathologies relevant to AD. The results offer a novel ex vivo organotypic slice model to investigate AD pathologies with potential applications for screening drugs or therapies in the future.

JNK3 Overexpression in the Entorhinal Cortex Impacts on the Hippocampus and Induces Cognitive Deficiencies and Tau Misfolding

c-Jun N-terminal kinases (JNKs) are a family of protein kinases activated by a myriad of stimuli consequently modulating a vast range of biological processes. In human postmortem brain samples affected with Alzheimer's disease (AD), JNK overactivation has been described; however, its role in AD onset and progression is still under debate. One of the earliest affected areas in the pathology is the entorhinal cortex (EC). Noteworthy, the deterioration of the projection from EC to hippocampus (Hp) point toward the idea that the connection between EC and Hp is lost in AD. Thus, the main objective of the present work is to address if JNK3 overexpression in the EC could impact on the hippocampus, inducing cognitive deficits. Data obtained in the present work suggest that JNK3 overexpression in the EC influences the Hp leading to cognitive impairment. Moreover, proinflammatory cytokine expression and Tau immunoreactivity were increased both in the EC and in the Hp. Therefore, activation of inflammatory signaling and induction of Tau aberrant misfolding caused by JNK3 could be responsible for the observed cognitive impairment. Altogether, JNK3 overexpression in the EC may impact on the Hp inducing cognitive dysfunction and underlie the alterations observed in AD.

Photocaging of Pyridinylimidazole-Based Covalent JNK3 Inhibitors Affords Spatiotemporal Control of the Binding Affinity in Live Cells

The concept of photocaging represents a promising approach to acquire spatiotemporal control over molecular bioactivity. To apply this strategy to pyridinylimidazole-based covalent JNK3 inhibitors, we used acrylamido-N-(4-((4-(4-(4-fluorophenyl)-1-methyl-2-(methylthio)-1H-imidazol-5-yl)pyridin-2-yl)amino)phenyl)benzamide (1) as a lead compound to design novel covalent inhibitors of JNK3 by modifying the amide bond moiety in the linker. The newly synthesized inhibitors demonstrated IC50 values in the low double-digit nanomolar range in a radiometric kinase assay. They were further characterized in a NanoBRETTM intracellular JNK3 assay, where covalent engagement of the target enzyme was confirmed by compound washout experiments and a loss in binding affinity for a newly generated JNK3(C154A)-NLuc mutant. The most potent compound of the series, N-(3-acrylamidophenyl)-4-((4-(4-(4-fluorophenyl)-1-methyl-2-(methylthio)-1H-imidazol-5-yl)pyridin-2-yl)amino)benzamide (13), was equipped with a photolabile protecting group leading to a nearly 10-fold decrease in intracellular JNK3 binding affinity, which was fully recovered by UV irradiation at a wavelength of 365 nm within 8 min. Our results highlight that photocaged covalent inhibitors can serve as a pharmacological tool to control JNK3 activity in live cells with light.

Protective effects of apigenin on methylmercury-induced behavioral/neurochemical abnormalities and neurotoxicity in rats

Methylmercury (MeHg) is a neurotoxin that induces neurotoxicity and cell death in neurons. MeHg increases oligodendrocyte death, glial cell activation, and motor neuron demyelination in the motor cortex and spinal cord. As a result, MeHg plays an important role in developing neurocomplications similar to amyotrophic lateral sclerosis (ALS). Recent research has implicated c-JNK and p38MAPK overactivation in the pathogenesis of ALS. Apigenin (APG) is a flavonoid having anti-inflammatory, antioxidant, and c-JNK/p38MAPK inhibitory activities. The purpose of this study is to determine whether APG possesses neuroprotective effects in MeHg-induced neurotoxicity in adult rats associated with ALS-like neuropathological alterations. In the current study, the neurotoxin MeHg causes an ALS-like phenotype in Wistar rats after 21 days of oral administration at a dose of 5 mg/kg. Prolonged administration of APG (40 and 80 mg/kg) improved neurobehavioral parameters such as learning memory, cognition, motor coordination, and grip strength. This is mainly associated with the downregulation of c-JNK and p38MAPK signaling as well as the restoration of myelin basic protein within the brain. Furthermore, APG inhibited neuronal apoptotic markers (Bax, Bcl-2, and caspase-3), restored neurotransmitter imbalance, decreased inflammatory markers (TNF- and IL-1), and alleviated oxidative damage. As a result, the current study shows that APG has neuroprotective potential as a c-JNK and p38MAPK signaling inhibitor against MeHg-induced neurotoxicity in adult rats. Based on these promising findings, we suggested that APG could be a potential new therapeutic approach over other conventional therapeutic approaches for MeHg-induced neurotoxicity in neurobehavioral, molecular, and neurochemical abnormalities.

Cell competition from development to neurodegeneration

Cell competition is a process by which suboptimal cells are eliminated to the benefit of cells with higher fitness. It is a surveillance mechanism that senses differences in the fitness status by several modes, such as expression of fitness fingerprints, survival factor uptake rate and resistance to mechanical stress. Fitness fingerprints-mediated cell competition recognizes isoforms of the transmembrane protein Flower, and translates the relative fitness of cells into distinct fates through the Flower code. Impairments in cell competition potentiate the development of diseases like cancer and ageing-related pathologies. In cancer, malignant cells acquire a supercompetitor behaviour, killing the neighbouring cells and overtaking the tissue, thus avoiding elimination. Neurodegenerative disorders affect millions of people and are characterized by cognitive decline and locomotor deficits. Alzheimer's disease is the most common form of dementia, and one of the largely studied diseases. However, the cellular processes taking place remain unclear. Drosophila melanogaster is an emerging neurodegeneration model due to its versatility as a tool for genetic studies. Research in a Drosophila Alzheimer's disease model detected fitness markers in the suboptimal and hyperactive neurons, thus establishing a link between cell competition and Alzheimer's disease. In this Review, we overview cell competition and the new insights related to neurodegenerative disorders, and discuss how research in the field might contribute to the development of new therapeutic targets for these diseases.

The Tetramethylpyrazine Analogue T-006 Alleviates Cognitive Deficits by Inhibition of Tau Expression and Phosphorylation in Transgenic Mice Modeling Alzheimer's Disease

T-006, a small-molecule compound derived from tetramethylpyrazine (TMP), has potential for the treatment of neurological diseases. In order to investigate the effect of T-006 prophylactic treatment on an Alzheimer's disease (AD) model and identify the target of T-006, we intragastrically administered T-006 (3 mg/kg) to Alzheimer's disease (AD) transgenic mice (APP/PS1-2xTg and APP/PS1/Tau-3xTg) for 6 and 8 months, respectively. T-006 improved cognitive ability after long-term administration in two AD mouse models and targeted mitochondrial-related protein alpha-F1-ATP synthase (ATP5A). T-006 significantly reduced the expression of phosphorylated-tau, total tau, and APP while increasing the expression of synapse-associated proteins in 3xTg mice. In addition, T-006 modulated the JNK and mTOR-ULK1 pathways to reduce both p-tau and total tau levels. Our data suggested that T-006 mitigated cognitive decline primarily by reducing the p-tau and total tau levels in 3xTg mice, supporting further investigation into its development as a candidate drug for AD treatment.

Photobiomodulation suppresses JNK3 by activation of ERK/MKP7 to attenuate AMPA receptor endocytosis in Alzheimer's disease

Alzheimer's disease (AD), a severe age‐related neurodegenerative disorder, lacks effective therapeutic methods at present. Physical approaches such as gamma frequency light flicker that can effectively reduce amyloid load have been reported recently. Our previous research showed that a physical method named photobiomodulation (PBM) therapy rescues Aβ‐induced dendritic atrophy in vitro. However, it remains to be further investigated the mechanism by which PBM affects AD‐related multiple pathological features to improve learning and memory deficits. Here, we found that PBM attenuated Aβ‐induced synaptic dysfunction and neuronal death through MKP7‐dependent suppression of JNK3, a brain‐specific JNK isoform related to neurodegeneration. The results showed PBM‐attenuated amyloid load, AMPA receptor endocytosis, dendrite injury, and inflammatory responses, thereby rescuing memory deficits in APP/PS1 mice. We noted JNK3 phosphorylation was dramatically decreased after PBM treatment in vivo and in vitro. Mechanistically, PBM activated ERK, which subsequently phosphorylated and stabilized MKP7, resulting in JNK3 inactivation. Furthermore, activation of ERK/MKP7 signaling by PBM increased the level of AMPA receptor subunit GluR 1 phosphorylation and attenuated AMPA receptor endocytosis in an AD pathological model. Collectively, these data demonstrated that PBM has potential therapeutic value in reducing multiple pathological features associated with AD, which is achieved by regulating JNK3, thus providing a noninvasive, and drug‐free therapeutic strategy to impede AD progression.

Protein Phosphatase 2A as a Drug Target in the Treatment of Cancer and Alzheimer's Disease

Protein phosphatase 2A (PP2A) is a major serine/threonine phosphatase which participates in the regulation of multiple cellular processes. As a confirmed tumor suppressor, PP2A activity is downregulated in tumors and its re-activation can induce apoptosis of cancer cells. In the brains of Alzheimer's disease (AD) patients, decreased PP2A activity also plays a key role in promoting tau hyperphosphorylation and Aβ generation. In this review, we discussed compounds aiming at modulating PP2A activity in the treatment of cancer or AD. The upstream factors that inactivate PP2A in diseases have not been fully elucidated and further studies are needed. It will help for the refinement and development of novel and clinically tractable PP2A-targeted compounds or therapies for the treatment of tumor and AD.

Oral Administration of Alpha Linoleic Acid Rescues Aβ-Induced Glia-Mediated Neuroinflammation and Cognitive Dysfunction in C57BL/6N Mice

In this work, we evaluated the effects of alpha linoleic acid (ALA), an omega-3 polyunsaturated fatty acid, on amyloid-beta-induced glial-cell-mediated neuroinflammation, amyloidogenesis, and cognitive dysfunction in mice. After an infusion of Aβ_1-42 (Aβ_1-42, 5 μL/5 min/mouse, intracerebroventricular injection (i.c.v), and respective treatments of ALA (60 mg/kg per oral for six weeks), neuroinflammation, apoptotic markers, and synaptic markers were evaluated by Western blot and immunofluorescence analyses. According to our findings, the infusion of Aβ_1-42 activated Toll-like receptor 4 (TLR4), glial fibrillary acidic protein (GFAP), and ionized calcium adaptor molecule 1 (Iba-1) in the frontal cortices and hippocampi of the Aβ_1-42-injected mice to a greater extent than the Aβ_1-42 + ALA-cotreated mice. Similarly, there was an elevated expression of phospho-c-Jun-N-terminal kinase (p-JNK), phospho-nuclear factor-kB p65 (p-NF-kB p65 (Ser536)), and tissue necrosis factor (TNF) in the Aβ_1-42 infused mouse brains; interestingly, these markers were significantly reduced in the Aβ + ALA-cotreated group. The elevated expression of pro-apoptotic markers was observed during apoptotic cell death in the Aβ_1-42-treated mouse brains, whereas these markers were markedly reduced in the Aβ + ALA-cotreated group. Moreover, Aβ_1-42 infusion significantly increased amyloidogenesis, as assessed by the enhanced expression of the amyloid precursor proteins (APP) beta-amyloid cleaving enzyme-1 (BACE-1) and amyloid-beta (Aβ_1-42) in the mouse brains, whereas these proteins were markedly reduced in the Aβ + ALA-cotreated group. We also checked the effects of ALA against Aβ-triggered synaptic dysfunction and memory dysfunction, showing that ALA significantly improved memory and synaptic functions in Aβ-treated mouse brains. These results indicated that ALA could be an applicable intervention in neuroinflammation, apoptotic cell loss, amyloidogenesis, and memory dysfunction via the inhibition of TLR4 and its downstream targets in Aβ + ALA-cotreated mouse brains.

Organotypic brain slice cultures to model neurodegenerative proteinopathies

Organotypic slice cultures of brain or spinal cord have been a longstanding tool in neuroscience research but their utility for understanding Alzheimer's disease (AD) and other neurodegenerative proteinopathies has only recently begun to be evaluated. Organotypic brain slice cultures (BSCs) represent a physiologically relevant three-dimensional model of the brain. BSCs support all the central nervous system (CNS) cell types and can be produced from brain areas involved in neurodegenerative disease. BSCs can be used to better understand the induction and significance of proteinopathies underlying the development and progression of AD and other neurodegenerative disorders, and in the future may serve as bridging technologies between cell culture and in vivo experiments for the development and evaluation of novel therapeutic targets and strategies. We review the initial development and general use of BSCs in neuroscience research and highlight the advantages of these cultures as an ex vivo model. Subsequently we focus on i) BSC-based modeling of AD and other neurodegenerative proteinopathies ii) use of BSCs to understand mechanisms underlying these diseases and iii) how BSCs can serve as tools to screen for suitable therapeutics prior to in vivo investigations. Finally, we will examine i) open questions regarding the use of such cultures and ii) how emerging technologies such as recombinant adeno-associated viruses (rAAV) may be combined with these models to advance translational research relevant to neurodegenerative disorders.

Isorhynchophylline ameliorates cognitive impairment via modulating amyloid pathology, tau hyperphosphorylation and neuroinflammation: Studies in a transgenic mouse model of Alzheimer's disease

Isorhynchophylline (IRN) has been demonstrated to have distinct anti-Alzheimer's disease (AD) activity in several animal models of AD. In this study, we aimed at evaluating the preventive effect of IRN on the cognitive deficits and amyloid pathology in TgCRND8 mice. Male TgCRND8 mice were administered with IRN (20 or 40 mg/kg) by oral gavage daily for 4 months, followed by assessing the spatial learning and memory functions with the Radial Arm Maze (RAM) test. Brain tissues were determined immunohistochemically or biochemically for changes in amyloid pathology, tau hyperphosphorylation and neuroinflammation. Our results revealed that IRN (40 mg/kg) significantly ameliorated cognitive deficits in TgCRND8 mice. In addition, IRN (40 mg/kg) markedly reduced the levels of Aβ₄₀, Aβ₄₂ and tumor necrosis factor (TNF-α), interleukin 6 (IL-6) and IL-1β, and modulated the amyloid precursor protein (APP) processing and phosphorylation by altering the protein expressions of β-site APP cleaving enzyme-1 (BACE-1), phosphorylated APP (Thr668), presenilin-1 (PS-1) and anterior pharynx-defective-1 (APH-1), as well as insulin degrading enzyme (IDE), a major Aβ-degrading enzyme. IRN was also found to inhibit the phosphorylation of tau at the sites of Thr205 and Ser396. Immunofluorescence showed that IRN reduced the Aβ deposition, and suppressed the activation of microglia (Iba-1) and astrocytes (GFAP) in the cerebral cortex and hippocampus of TgCRND8 mice. Furthermore, IRN was able to attenuate the ratios of p-c-Jun/c-Jun and p-JNK/JNK in the brains of TgCRND8 mice. IRN also showed marked inhibitory effect on JNK signaling pathway in the Aβ-treated rat primary hippocampus neurons. We conclude that IRN improves cognitive impairment in TgCRND8 transgenic mice via reducing Aβ generation and deposition, tau hyperphosphorylation and neuroinflammation through inhibiting the activation of JNK signaling pathway, and has good potential for further development into pharmacological treatment for AD.

MicroRNA-326 decreases tau phosphorylation and neuron apoptosis through inhibition of the JNK signaling pathway by targeting VAV1 in Alzheimer's disease

Alzheimer's disease (AD) is a progressive and age-related neurological dysfunction. Abundant data have profiled microRNA (miR) patterns in healthy, aging brain, and in the moderate and late-stages of AD. Herein, this study aimed to explore whether miR-326 could influence neuron apoptosis in AD mice and how miR-326 functions in this process. The candidate differentially expressed gene VAV1 was obtained by microarray analysis, and miRNAs that could regulate VAV1 candidate gene were predicted. Luciferase activity determination confirmed VAV1 as a target gene of miR-326. AD mice models were established for investigating the effect of miR-326 on AD mice. The overexpression of miR-326 contributed to decreased time of the mice to find the platform and the escape latency and increased residence time on the target area. Besides, elevation of miR-326 decreased Aβ deposition and contents of Aβ_1-40 and Aβ_1-42 . Moreover, miR-326 overexpression increased neuron cell ability, mediated cell entry, and inhibited neuron apoptosis via JNK signaling pathway. Of crucial importance, miR-326 negatively regulated the expression of VAV1, inhibited tau phosphorylation, and blocked the activation of the JNK signaling pathway. Taken together these observations, we demonstrate that miR-326 improves cognitive function of AD mice and inhibits neuron apoptosis in AD mice through inactivation of the JNK signaling pathway by targeting VAV1. Based on those findings, miR-326 might exert promise as target for the treatment of AD.

To be or not to be: PP2A as a dual player in CNS functions, its role in neurodegeneration, and its interaction with brain insulin signaling

Accumulating evidence has reached the consensus that the balance of phosphorylation state of signaling molecules is a pivotal point in the regulation of cell signaling. Therefore, characterizing elements (kinases-phosphatases) in the phosphorylation balance are at great importance. However, the role of phosphatase enzymes is less investigated than kinase enzymes. PP2A is a member of serine/threonine protein phosphatase that its imbalance has been reported in neurodegenerative diseases. Therefore, we reviewed the superfamily of phosphatases and more specifically PP2A, its regulation, and physiological functions participate in CNS. Thereafter, we discussed the latest findings about PP2A dysregulation in Alzheimer and Parkinson diseases and possible interplay between this phosphatase and insulin signaling pathways. Finally, activating/inhibitory modulators for PP2A activity as well as experimental methods for PP2A study have been reviewed.

New insights into the structural dynamics of the kinase JNK3

In this work, we study the dynamics and the energetics of the all-atom structure of a neuronal-specific serine/threonine kinase c-Jun N-terminal kinase 3 (JNK3) in three states: unphosphorylated, phosphorylated, and ATP-bound phosphorylated. A series of 2 µs atomistic simulations followed by a conformational landscape mapping and a principal component analysis supports the mechanistic understanding of the JNK3 inactivation/activation process and also indicates key structural intermediates. Our analysis reveals that the unphosphorylated JNK3 undergoes the ‘open-to-closed’ movement via a two-step mechanism. Furthermore, the phosphorylation and ATP-binding allow the JNK3 kinase to attain a fully active conformation. JNK3 is a widely studied target for small-drugs used to treat a variety of neurological disorders. We believe that the mechanistic understanding of the large-conformational changes upon the activation of JNK3 will aid the development of novel targeted therapeutics.

β-amyloid cytotoxicity is prevented by natural achillolide A

Alzheimer's disease (AD) is the most prevalent cause of dementia in adults. Current available drugs for AD transiently alleviate some of the symptoms, but do not modify the disease mechanism or cure it. Therefore, new drugs are desperately needed. Key contributors to AD are amyloid beta (Aβ)- and reactive oxygen species (ROS)-induced cytotoxicities. Plant-derived substances have been shown to affect various potential targets in various diseases including AD. Therefore, phytochemicals which can protect neuronal cells against these insults might help in preventing and treating this disease. In the following research, we have isolated the sesquiterpene lactone achillolide A from the plant Achillea fragrantissima and, for the first time, characterized its effects on Aβ-treated neuroblastoma cells. Aβ is a peptide derived from the sequential cleavage of amyloid precursor protein, and is part of the pathogenesis of AD. Our current study aimed to determine whether achillolide A can interfere with Aβ-induced processes in Neuro2a cells, and protect them from its toxicity. Our results show that achillolide A decreased Aβ-induced death and enhanced the viability of Neuro2a cells. In addition, achillolide A reduced the accumulation of Aβ-induced ROS and inhibited the phosphorylation of stress-activated protein kinase/c-Jun N-terminal kinase and p44/42 mitogen-activated protein kinase in these cells. We therefore suggest that achillolide A may have therapeutic potential for the treatment of AD.

Modulation of AβPP and GSK3β by Endoplasmic Reticulum Stress and Involvement in Alzheimer's Disease

Alzheimer's disease (AD) is a dementia disease with neuronal loss and synaptic impairment. This impairment is caused, at least partly, by the generation of two main AD hallmarks, namely the hyperphosphorylated tau protein comprising neurofibrillary tangles and senile plaques containing amyloid-β (Aβ) peptides. The amyloid-β protein precursor (AβPP) and glycogen synthase kinase-3β (GSK3β) are two main proteins associated with AD and are closely correlated with these hallmarks. Recently, both of the proteins were reported to be modulated by endoplasmic reticulum stress (ERS) and are involved in the pathogenesis of AD. The mechanism of ERS plus the modulation of AβPP processing and GSK3β activity by ERS in AD are summarized and explored in this review.

3,5,4'-trihydroxy-6,7,3'-trimethoxyflavone protects against beta amyloid-induced neurotoxicity through antioxidative activity and interference with cell signaling

Background

Alzheimer’s disease is a neurodegenerative disease, characterized by progressive decline in memory and cognitive functions, that results from loss of neurons in the brain. Amyloid beta (Aβ) protein and oxidative stress are major contributors to Alzheimer’s disease, therefore, protecting neuronal cells against Aβ-induced toxicity and oxidative stress might form an effective approach for treatment of this disease. 3,5,4′-trihydroxy-6,7,3′-trimethoxyflavone (TTF) is a flavonoid we have purified from the plant Achillea fragrantissima; and the present study examined, for the first time, the effects of this compound on Aβ-toxicity to neuronal cells.

Methods

Various chromatographic techniques were used to isolate TTF from the plant Achillea fragrantissima, and an N2a neuroblastoma cell line was used to study its activities. The cellular levels of total and phosphorylated stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) and of total and phosphorylated extracellular signal-regulated kinase (ERK 1/2) were determined by enzyme-linked immunosorbent assay (ELISA). Intracellular reactive oxygen species (ROS) levels were measured by using 2′,7′-dichlorofluorescein diacetate (DCF-DA). Cytotoxicity and cell viability were assessed by using lactate dehydrogenase (LDH) activity in cell-conditioned media, or by crystal violet cell staining, respectively.

Results

TTF prevented the Aβ-induced death of neurons and attenuated the intracellular accumulation of ROS following treatment of these cells with Aβ. TTF also inhibited the Aβ-induced phosphorylation of the signaling proteins SAPK/JNK and ERK 1/2, which belong to the mitogen-activated protein kinase (MAPK) family.

Conclusion

TTF should be studied further as a potential therapeutic means for the treatment of Alzheimer’s disease.

Nicotinamide mononucleotide inhibits JNK activation to reverse Alzheimer disease

Amyloid-β (Aβ) oligomers have been accepted as major neurotoxic agents in the therapy of Alzheimer's disease (AD). It has been shown that the activity of nicotinamide adenine dinucleotide (NAD+) is related with the decline of Aβ toxicity in AD. Nicotinamide mononucleotide (NMN), the important precursor of NAD+, is produced during the reaction of nicotinamide phosphoribosyl transferase (Nampt). This study aimed to figure out the potential therapeutic effects of NMN and its underlying mechanisms in APPswe/PS1dE9 (AD-Tg) mice. We found that NMN gave rise to a substantial improvement in behavioral measures of cognitive impairments compared to control AD-Tg mice. In addition, NMN treatment significantly decreased β-amyloid production, amyloid plaque burden, synaptic loss, and inflammatory responses in transgenic animals. Mechanistically, NMN effectively controlled JNK activation. Furthermore, NMN potently progressed nonamyloidogenic amyloid precursor protein (APP) and suppressed amyloidogenic APP by mediating the expression of APP cleavage secretase in AD-Tg mice. Based on our findings, it was suggested that NMN substantially decreases multiple AD-associated pathological characteristically at least partially by the inhibition of JNK activation.

Evidence of Presynaptic Localization and Function of the c-Jun N-Terminal Kinase

The c-Jun N-terminal kinase (JNK) is part of a stress signalling pathway strongly activated by NMDA-stimulation and involved in synaptic plasticity. Many studies have been focused on the post-synaptic mechanism of JNK action, and less is known about JNK presynaptic localization and its physiological role at this site. Here we examined whether JNK is present at the presynaptic site and its activity after presynaptic NMDA receptors stimulation. By using N-SIM Structured Super Resolution Microscopy as well as biochemical approaches, we demonstrated that presynaptic fractions contained significant amount of JNK protein and its activated form. By means of modelling design, we found that JNK, via the JBD domain, acts as a physiological effector on T-SNARE proteins; then using biochemical approaches we demonstrated the interaction between Syntaxin-1-JNK, Syntaxin-2-JNK, and Snap25-JNK. In addition, taking advance of the specific JNK inhibitor peptide, D-JNKI1, we defined JNK action on the SNARE complex formation. Finally, electrophysiological recordings confirmed the role of JNK in the presynaptic modulation of vesicle release. These data suggest that JNK-dependent phosphorylation of T-SNARE proteins may have an important functional role in synaptic plasticity.

Coriandrum sativum Suppresses Aβ42-Induced ROS Increases, Glial Cell Proliferation, and ERK Activation

Alzheimer's disease (AD), the most common neurodegenerative disease, has a complex and widespread pathology that is characterized by the accumulation of amyloid [Formula: see text]-peptide (A[Formula: see text]) in the brain and various cellular abnormalities, including increased oxidative damage, an amplified inflammatory response, and altered mitogen-activated protein kinase signaling. Based on the complex etiology of AD, traditional medicinal plants with multiple effective components are alternative treatments for patients with AD. In the present study, we investigated the neuroprotective effects of an ethanol extract of Coriandrum sativum (C. sativum) leaves on A[Formula: see text] cytotoxicity and examined the molecular mechanisms underlying the beneficial effects. Although recent studies have shown the benefits of the inhalation of C. sativum oil in an animal model of AD, the detailed molecular mechanisms by which C. sativum exerts its neuroprotective effects are unclear. Here, we found that treatment with C. sativum extract increased the survival of both A[Formula: see text]-treated mammalian cells and [Formula: see text]42-expressing flies. Moreover, C. sativum extract intake suppressed [Formula: see text]-induced cell death in the larval imaginal disc and brain without affecting A[Formula: see text]42 expression and accumulation. Interestingly, the increases in reactive oxygen species levels and glial cell number in AD model flies were reduced by C. sativum extract intake. Additionally, C. sativum extract inhibited the epidermal growth factor receptor- and A[Formula: see text]-induced phosphorylation of extracellular signal-regulated kinase (ERK). The constitutively active form of ERK abolished the protective function of C. sativum extract against the [Formula: see text]-induced eye defect phenotype in Drosophila. Taken together, these results suggest that C. sativum leaves have antioxidant, anti-inflammatory, and ERK signaling inhibitory properties that are beneficial for patients with AD.

Neuroprotection of Cilostazol against ischemia/reperfusion-induced cognitive deficits through inhibiting JNK3/caspase-3 by enhancing Akt1

Cilostazol(CTL) is a phosphodiesterase inhibitor, which has been widely used as anti-platelet agent. It also has preventive effects on various central nervous system (CNS) diseases, including ischemic stroke, Parkinson's disease and Alzheimer disease. However, the molecular mechanism underlying the protective effects of CTL is still unclear, and whether CTL can prevent I/R induced cognitive deficit has not been reported. Transient global brain ischemia was induced by 4-vessel occlusion in adult male Sprague-Dawley rats. The open field tasks and Morris water maze were used to assess the effect of CTL on anxiety-like behavioral and cognitive impairment after I/R. Western blotting were performed to examine the expression of related proteins, and HE-staining was used to detect the percentage of neuronal death in the hippocampal CA1 region. Here we found that CTL significantly improved cognitive deficits and the behavior of rats in Morris water maze and open field tasks (P<0.05). HE staining results showed that CTL could significantly protect CA1 neurons against cerebral I/R (P<0.05). Additionally, Akt1 phosphorylation levels were evidently up-regulated (P<0.05), while the activation of JNK3, which is an important contributor to I/R-induced neuron apoptosis, was reduced by CTL after I/R (P<0.05), and caspase-3 levels were also decreased by CTL treatment. Furthermore, all of CTL's protective effects were reversed by LY294002, which is a PI3K/Akt1 inhibitor. Taken together, our results suggest that CTL could protect hippocampal neurons and ameliorate the impairment of learning/memory abilities and locomotor/ exploratory activities in ischemic stroke via a PI3K-Akt1/JNK3/caspase-3 dependent mechanism.

Aberrant Axonal Arborization of PDF Neurons Induced by Aβ42-Mediated JNK Activation Underlies Sleep Disturbance in an Alzheimer's Model

Impaired sleep patterns are common symptoms of Alzheimer's disease (AD). Cellular mechanisms underlying sleep disturbance in AD remain largely unknown. Here, using a Drosophila Aβ42 AD model, we show that Aβ42 markedly decreases sleep in a large population, which is accompanied with postdevelopmental axonal arborization of wake-promoting pigment-dispersing factor (PDF) neurons. The arborization is mediated in part via JNK activation and can be reversed by decreasing JNK signaling activity. Axonal arborization and impaired sleep are correlated in Aβ42 and JNK kinase hemipterous mutant flies. Image reconstruction revealed that these aberrant fibers preferentially project to pars intercerebralis (PI), a fly brain region analogous to the mammalian hypothalamus. Moreover, PDF signaling in PI neurons was found to modulate sleep/wake activities, suggesting that excessive release of PDF by these aberrant fibers may lead to the impaired sleep in Aβ42 flies. Finally, inhibition of JNK activation in Aβ42 flies restores nighttime sleep loss, decreases Aβ42 accumulation, and attenuates neurodegeneration. These data provide a new mechanism by which sleep disturbance could be induced by Aβ42 burden, a key initiator of a complex pathogenic cascade in AD.

Dual activities of the anti-cancer drug candidate PBI-05204 provide neuroprotection in brain slice models for neurodegenerative diseases and stroke

We previously reported neuroprotective activity of the botanical anti-cancer drug candidate PBI-05204, a supercritical CO₂ extract of Nerium oleander, in brain slice and in vivo models of ischemic stroke. We showed that one component of this neuroprotective activity is mediated through its principal cardiac glycoside constituent, oleandrin, via induction of the potent neurotrophic factor brain-derived neurotrophic factor (BDNF). However, we also noted that the concentration-relation for PBI-05204 in the brain slice oxygen-glucose deprivation (OGD) model is considerably broader than that for oleandrin as a single agent. We thus surmised that PBI-05204 contains an additional neuroprotective component(s), distinct from oleandrin. We report here that neuroprotective activity is also provided by the triterpenoid constituents of PBI-05204, notably oleanolic acid. We demonstrate that a sub-fraction of PBI-05204 (Fraction 0–4) containing oleanolic and other triterpenoids, but without cardiac glycosides, induces the expression of cellular antioxidant gene transcription programs regulated through antioxidant transcriptional response elements (AREs). Finally, we show that Fraction 0–4 provides broad neuroprotection in organotypic brain slice models for neurodegeneration driven by amyloid precursor protein (APP) and tau implicated in Alzheimer’s disease and frontotemporal dementias, respectively, in addition to ischemic injury modeled by OGD.

Reduction of autophagy markers mediated protective effects of JNK inhibitor and bucladesine on memory deficit induced by Aβ in rats

Autophagy, the process of self-degradation of cellular components, has an important role in neurodegenerative diseases, such as Alzheimer's disease. In this study, we investigated the effects of SP600125 as c-Jun N-terminal kinase (JNK) inhibitor and bucladesine as a cyclic adenosine 3',5'-monophosphate (cAMP) analog on spatial memory and expression of autophagic factors in Aβ-injected rats. Male Wistar rats were used. Rats were randomly allocated into five groups as following: amyloid beta (Aβ)-only group, Aβ + SP600125 (30 μg/1 μ/side, n = 7) and/or bucladesine (100 μM/1 μl/side, n = 7), and the normal control (vehicle only) group. The treatments were administered bilaterally to the CA1 sub-region of the hippocampus stereotaxically. Spatial reference memory was performed using Morris Water Maze 21 days later. The expression of authophagy markers (beclin1, Atg7, Atg12, and LC3 II/LC3 I) in the hippocampus was evaluated using western blotting. Compared to the vehicle group, Aβ administration reduced spatial reference learning (P < 0.001) and memory (P < 0.01) and upregulated the expression of beclin1, Atg7, Atg12, and LC3 II/I (P < 0.0001). Compare to Aβ-only group, the administration of SP600125 and/or bucladesine improved spatial reference learning (P < 0.001) and memory (P < 0.01). Compared to the Aβ-only group, the treatment with SP600125 and/or bucladesine also reduced beclin1, Atg7, Atg12, and LC3 II/I (P < 0.0001) which was similar to amount of normal rats. In summary, it seems that the improvement of spatial memory by SP600125 and/or bucladesine in Aβ-injected rats is in relation with normalizing of autophagy to the physiologic level, possibly through neuroprotection and/or neuroplasticity.

Molecular Targets in Alzheimer's Disease: From Pathogenesis to Therapeutics

Alzheimer's disease (AD) is characterized by progressive cognitive decline usually beginning with impairment in the ability to form recent memories. Nonavailability of definitive therapeutic strategy urges developing pharmacological targets based on cell signaling pathways. A great revival of interest in nutraceuticals and adjuvant therapy has been put forward. Tea polyphenols for their multiple health benefits have also attracted the attention of researchers. Tea catechins showed enough potentiality to be used in future as therapeutic targets to provide neuroprotection against AD. This review attempts to present a concise map of different receptor signaling pathways associated with AD with an insight into drug designing based on the proposed signaling pathways, molecular mechanistic details of AD pathogenesis, and a scientific rationale for using tea polyphenols as proposed therapeutic agents in AD.

JNK pathway signaling: a novel and smarter therapeutic targets for various biological diseases

JNK pathway regulates various physiological processes including inflammatory responses, cell differentiation, cell proliferation, cell death, cell survival and expression of proteins. Deregulation of JNK is linked with various diseases including neurodegenerative disease, autoimmune disease, diabetes, cancer, cardiac hypertrophy and asthma. Three distinct genes JNK1, JNK2 and JNK3 have been identified as regulator of JNK pathway. JNK1 and JNK2 have broad tissue distribution and play a potential role in insulin resistance, inflammation and cell signaling. JNK3 is predominantly found in the CNS neurons, making it an attractive target for neurodegenerative disorders. In this review, we summarize the evidence supporting JNK as a potent therapeutic target, and small molecules from various chemical classes as JNK inhibitors.

In Vivo Screening of Traditional Medicinal Plants for Neuroprotective Activity against Aβ42 Cytotoxicity by Using Drosophila Models of Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder, characterized by progressive neuronal loss with amyloid β-peptide (Aβ) plaques. Despite several drugs currently used to treat AD, their beneficial effects on AD progress remains under debate. Here, we established a rapid in vivo screening system using Drosophila AD models to assess the neuroprotective activities of medicinal plants that have been used in traditional Chinese medicine. Among 23 medicinal plants tested, the extracts from five plants, Coriandrum sativum, Nardostachys jatamansi, Polygonum multiflorum (P. multiflorum), Rehmannia glutinosa, and Sorbus commixta (S. commixta), showed protective effects against the Aβ42 neurotoxicity. We further characterized the neuroprotective activity of ethanol extracts from P. multiflorum and S. commixta. Aβ42-expressing flies that we used showed AD neurological phenotypes, such as decreased survival and motility and increased cell death and reactive oxygen species level. However, feeding these flies extracts from P. multiflorum or S. commixta showed strong suppression of such phenotypes. Similar results were observed in human cells, so that the treatment of P. multiflorum and S. commixta extracts increased the viability of Aβ-treated SH-SY5Y cells. Moreover, 2,3,5,4'-tetrahydroxystilbene-2-O-β-D-glucoside, one of the main constituents of P. multiflorum, also showed similar protective activity against Aβ42 cytotoxicity in both Drosophila and human cells. Taken together, our results suggest that both P. multiflorum and S. commixta have therapeutic potential for the treatment of neurodegenerative diseases, such as AD.

Forebrain microglia from wild-type but not adult 5xFAD mice prevent amyloid-β plaque formation in organotypic hippocampal slice cultures

The role of microglia in amyloid-β (Aβ) deposition is controversial. In the present study, an organotypic hippocampal slice culture (OHSC) system with an in vivo-like microglial-neuronal environment was used to investigate the potential contribution of microglia to Aβ plaque formation. We found that microglia ingested Aβ, thereby preventing plaque formation in OHSCs. Conversely, Aβ deposits formed rapidly in microglia-free wild-type slices. The capacity to prevent Aβ plaque formation was absent in forebrain microglia from young adult but not juvenile 5xFamilial Alzheimer's disease (FAD) mice. Since no loss of Aβ clearance capacity was observed in both wild-type and cerebellar microglia from 5xFAD animals, the high Aβ1-42 burden in the forebrain of 5xFAD animals likely underlies the exhaustion of microglial Aβ clearance capacity. These data may therefore explain why Aβ plaque formation has never been described in wild-type mice, and point to a beneficial role of microglia in AD pathology. We also describe a new method to study Aβ plaque formation in a cell culture setting.

Drosophila Eye Model to Study Neuroprotective Role of CREB Binding Protein (CBP) in Alzheimer's Disease

BACKGROUND

The progressive neurodegenerative disorder Alzheimer's disease (AD) manifests as loss of cognitive functions, and finally leads to death of the affected individual. AD may result from accumulation of amyloid plaques. These amyloid plaques comprising of amyloid-beta 42 (Aβ42) polypeptides results from the improper cleavage of amyloid precursor protein (APP) in the brain. The Aβ42 plaques have been shown to disrupt the normal cellular processes and thereby trigger abnormal signaling which results in the death of neurons. However, the molecular-genetic mechanism(s) responsible for Aβ42 mediated neurodegeneration is yet to be fully understood.

METHODOLOGY/PRINCIPAL FINDINGS

We have utilized Gal4/UAS system to develop a transgenic fruit fly model for Aβ42 mediated neurodegeneration. Targeted misexpression of human Aβ42 in the differentiating photoreceptor neurons of the developing eye of transgenic fly triggers neurodegeneration. This progressive neurodegenerative phenotype resembles Alzheimer's like neuropathology. We identified a histone acetylase, CREB Binding Protein (CBP), as a genetic modifier of Aβ42 mediated neurodegeneration. Targeted misexpression of CBP along with Aβ42 in the differentiating retina can significantly rescue neurodegeneration. We found that gain-of-function of CBP rescues Aβ42 mediated neurodegeneration by blocking cell death. Misexpression of Aβ42 affects the targeting of axons from retina to the brain but misexpression of full length CBP along with Aβ42 can restore this defect. The CBP protein has multiple domains and is known to interact with many different proteins. Our structure function analysis using truncated constructs lacking one or more domains of CBP protein, in transgenic flies revealed that Bromo, HAT and polyglutamine (BHQ) domains together are required for the neuroprotective function of CBP. This BHQ domain of CBP has not been attributed to promote survival in any other neurodegenerative disorders.

CONCLUSIONS/SIGNIFICANCE

We have identified CBP as a genetic modifier of Aβ42 mediated neurodegeneration. Furthermore, we have identified BHQ domain of CBP is responsible for its neuroprotective function. These studies may have significant bearing on our understanding of genetic basis of AD.

Nicotinic Acetylcholine Receptors Sensitize a MAPK-linked Toxicity Pathway on Prolonged Exposure to β-Amyloid

Among putative downstream synaptic targets of β-amyloid (Aβ) are signaling molecules involved in synaptic function, memory formation and cognition, such as the MAP kinases, MKPs, CaMKII, CREB, Fyn, and Tau. Here, we assessed the activation and interaction of signaling pathways upon prolonged exposure to Aβ in model nerve cells expressing nicotinic acetylcholine receptors (nAChRs). Our goal was to characterize the steps underlying sensitization of the nerve cells to neurotoxicity when Aβ-target receptors are present. Of particular focus was the connection of the activated signaling molecules to oxidative stress. Differentiated neuroblastoma cells expressing mouse α4β2-nAChRs were exposed to Aβ1-42 for intervals from 30 min to 3 days. The cells and cell-derived protein extracts were then probed for activation of signaling pathway molecules (ERK, JNK, CaMKII, CREB, MARCKS, Fyn, tau). Our results show substantial, progressive activation of ERK in response to nanomolar Aβ exposure, starting at the earliest time point. Increased ERK activation was followed by JNK activation as well as an increased expression of PHF-tau, paralleled by increased levels of reactive oxygen species (ROS). The impact of prolonged Aβ on the levels of pERK, pJNK, and ROS was attenuated by MEK-selective and JNK-selective inhibitors. In addition, the MEK inhibitor as well as a JNK inhibitor attenuated Aβ-induced nuclear fragmentation, which followed the changes in ROS levels. These results demonstrate that the presence of nAChRs sensitizes neurons to the neurotoxic action of Aβ through the timed activation of discrete intracellular signaling molecules, suggesting pathways involved in the early stages of Alzheimer disease.

Induction of GADD34 Regulates the Neurotoxicity of Amyloid β

The possible roles played by growth arrest and DNA damage-inducible gene 34 (GADD34) in Alzheimer's disease (AD) are so far less understood. In this study, we found that GADD34 was increased in the brains of AD transgenic J20 mice. The deposition of β-amyloid (Aβ) peptide is the main component of neurotic plaques in AD brain. Thus, we examined the effect of Aβ in the expression of GADD34 in human SH-SY5Y cells in vitro. Amyloid β (Aβ1-42) treatment led to increased expression of GADD34. Pretreatment with 50 nmol/L of c-Jun N-terminal kinases (JNK) inhibitor SP600125 abolished the upregulation of GADD34. c-Jun silencing by transfection with c-Jun small-interfering RNA abolished the effects of Aβ1-42 on the expression of GADD34. Importantly, chromatin immunoprecipitation studies verified the ability of c-Jun to bind to the GADD34 promoter, and this ability was increased more than 3-fold by Aβ1-42. These data suggest that the induction of GADD34 by Aβ is mediated by JNK/c-Jun pathway. Finally, depletion of GADD34 significantly rescued Aβ-induced cell apoptosis as evidenced by a marked decrease in the number of terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling (TUNEL)-positive cells. Consistently, knockdown of GADD34 attenuated caspase 3 activation induced by Aβ1-42.

Inhibition of c-Jun N-terminal kinase activation reverses Alzheimer disease phenotypes in APPswe/PS1dE9 mice

OBJECTIVE

Growing evidence indicates that the activation of c-Jun N-terminal kinase (JNK) is implicated in the multiple major pathological features of Alzheimer disease (AD). However, whether specific inhibition of JNK activation could prevent disease progression in adult transgenic AD models at moderate stage remains unknown. Here we first investigated the potential disease-modifying therapeutic effect of systemic administration of SP600125, a small-molecule JNK-specific inhibitor, in middle-aged APPswe/PS1dE9 mice.

METHODS

Using behavioral, histological, and biochemical methods, outcomes of SP600125 treatment on neuropathology and cognitive deficits were studied in APPswe/PS1dE9 mice.

RESULTS

Compared with vehicle-treated APPswe/PS1dE9 mice, chronic treatment of SP600125 for 12 weeks potently inhibited JNK activation, which resulted in a marked improvement of behavioral measures of cognitive deficits and a dramatic reduction in amyloid plaque burden, β-amyloid production, tau hyperphosphorylation, inflammatory responses, and synaptic loss in these transgenic animals. In particular, we found that SP600125 treatment strongly promoted nonamyloidogenic amyloid precursor protein (APP) processing and inhibited amyloidogenic APP processing via regulating APP-cleavage secretase expression (ie, ADAM10, BACE1, and PS1) in APPswe/PS1dE9 mice.

INTERPRETATION

Our findings demonstrate that chronic SP600125 treatment is powerfully effective in slowing down disease progression by markedly reducing multiple pathological features and ameliorating cognitive deficits associated with AD. This study highlights the concept that active JNK actually contributes to the development of the disease, and provides critical preclinical evidence that specific inhibition of JNK activation by SP600125 treatment may be a novel promising disease-modifying therapeutic strategy for the treatment of AD.

Structural basis and biological consequences for JNK2/3 isoform selective aminopyrazoles

Three JNK isoforms, JNK1, JNK2, and JNK3 have been reported and unique biological function has been ascribed to each. It is unknown if selective inhibition of these isoforms would confer therapeutic or safety benefit. To probe JNK isoform function we designed JNK2/3 inhibitors that have >30-fold selectivity over JNK1. Utilizing site-directed mutagenesis and x-ray crystallography we identified L144 in JNK3 as a key residue for selectivity. To test whether JNK2/3 selective inhibitors protect human dopaminergic neurons against neurotoxin-induced mitochondrial dysfunction, we monitored reactive oxygen species (ROS) generation and mitochondrial membrane potential (MMP). The results showed that JNK2/3 selective inhibitors protected against 6-hydroxydopamine-induced ROS generation and MMP depolarization. These results suggest that it was possible to develop JNK2/3 selective inhibitors and that residues in hydrophobic pocket I were responsible for selectivity. Moreover, the findings also suggest that inhibition of JNK2/3 likely contributed to protecting mitochondrial function and prevented ultimate cell death.

Subconjunctival injection of XG-102, a JNK inhibitor peptide, in patients with intraocular inflammation: a safety and tolerability study

PURPOSE

We aimed to investigate the safety, tolerability, and systemic diffusion of a single escalating dose of XG-102 (a 31-D-amino-acid peptide inhibiting JNK pathway activation), administered subconjunctivally in the treatment of post-surgery or post-trauma intraocular inflammation.

METHODS

This is a dose-escalating, tolerance Phase Ib study. Twenty patients with post-surgery or post-traumatic intraocular inflammation were assigned to 1 of the 4 dose escalating (45, 90, 450, or 900 μg XG-102) groups of 5 patients each. Patients were evaluated at 24, 48 h, 8, and 28 days following the administration of XG-102, including laboratory tests, standard eye examinations, vital signs, and occurrence of adverse events. A single plasma quantification of XG-102 was performed 30 min after administration, according to previous pharmacokinetics studies performed on volunteers.

RESULTS

A total of 17 non-serious adverse events, considered unrelated to the study treatment, were reported for 10 patients. The adverse event incidence was not related to the drug dose. All patients experienced a decrease in intraocular inflammation as of 24 h post-administration and this decrease was sustained up to 28 days thereafter. No patient required local injection or systemic administration of corticoids following the administration of XG-102. XG-102 was undetectable in the first 3 dose groups. In the fourth-dose group (900 μg) the XG-102 plasma levels were above the limit of detection for 3 patients and above the limit of quantification for 1 patient.

CONCLUSIONS

In this first clinical trial using XG-102, administered as a single subconjunctival injection as adjunct therapy, in patients with recent post-surgery or post-trauma intraocular inflammation is safe and well tolerated. Further studies are required to evaluate its efficacy.

AlphaLISA-based high-throughput screening assay to measure levels of soluble amyloid precursor protein α

Activation of nonamyloidogenic processing of amyloid precursor protein (APP) has been hypothesized to be a viable approach for Alzheimer's disease drug discovery. However, until recently, the lack of HTS-compatible assay technologies precluded large scale screening efforts to discover molecules that potentiate nonamyloidogenic pathways. We have developed an HTS-compatible assay based on AlphaLISA technology that quantitatively detects soluble APPα (sAPPα), a marker of nonamyloidogenic processing of APP, released from live cells in low volume, 384-well plates. The assay exhibited good QC parameters (Z'>0.5, S/B>2). A pilot screen of 801 compounds yielded a novel chemotype that increased the release of sAPPα 2-fold at 5μM. These results suggest that the AlphaLISA-based HTS assay is robust and sensitive and can be used to screen large compound collections to discover molecules that potentiate the release of sAPPα. Additionally, we demonstrated that increase of APP processing by nonamyloidogenic pathways will result in decrease of release of amyloidogenic Aβ40 fragments.

Attenuated neuroprotective effect of riboflavin under UV-B irradiation via miR-203/c-Jun signaling pathway in vivo and in vitro

Background

Riboflavin (RF) or vitamin B2 is known to have neuroprotective effects. In the present study, we report the attenuation of the neuroprotective effects of RF under UV-B irradiation. Preconditioning of UV-B irradiated riboflavin (UV-B-RF) showed attenuated neuroprotective effects compared to that of RF in SH-SY5Y neuroblostoma cell line and primary cortical neurons in vitro and a rat model of cerebral ischemia in vivo.

Results

Results indicated that RF pretreatment significantly inhibited cell death and reduced LDH secretion compared to that of the UV-B-RF pretreatment in primary cortical neuron cultures subjected to oxygen glucose deprivation in vitro and cortical brain tissue subjected to ischemic injury in vivo. Further mechanistic studies using cortical neuron cultures revealed that RF treatment induced increased miR-203 expression which in turn inhibited c-Jun expression and increased neuronal cell survival. Functional assays clearly demonstrated that the UV-B-RF preconditioning failed to sustain the increased expression of miR-203 and the decreased levels of c-Jun, mediating the neuroprotective effects of RF. UV-B irradiation attenuated the neuroprotective effects of RF through modulation of the miR-203/c-Jun signaling pathway.

Conclusion

Thus, the ability of UV-B to serve as a modulator of this neuroprotective signaling pathway warrants further studies into its role as a regulator of other cytoprotective/neuroprotective signaling pathways.

BDNF mediates neuroprotection against oxygen-glucose deprivation by the cardiac glycoside oleandrin

We have previously shown that the botanical drug candidate PBI-05204, a supercritical CO2 extract of Nerium oleander, provides neuroprotection in both in vitro and in vivo brain slice-based models for focal ischemia (Dunn et al., 2011). Intriguingly, plasma levels of the neurotrophin BDNF were increased in patients treated with PBI-05204 in a phase I clinical trial (Bidyasar et al., 2009). We thus tested the hypothesis that neuroprotection provided by PBI-05204 to rat brain slices damaged by oxygen-glucose deprivation (OGD) is mediated by BDNF. We found, in fact, that exogenous BDNF protein itself is sufficient to protect brain slices against OGD, whereas downstream activation of TrkB receptors for BDNF is necessary for neuroprotection provided by PBI-05204, using three independent methods. Finally, we provide evidence that oleandrin, the principal cardiac glycoside component of PBI-05204, can quantitatively account for regulation of BDNF at both the protein and transcriptional levels. Together, these findings support further investigation of cardiac glycosides in providing neuroprotection in the context of ischemic stroke.

XG-102 administered to healthy male volunteers as a single intravenous infusion: a randomized, double-blind, placebo-controlled, dose-escalating study

The aim of the study is to evaluate the safety, tolerability and pharmacokinetics (PK) of the JNK inhibitor XG-102 in a randomized, double blind, placebo controlled, sequential ascending dose parallel group Phase 1 Study. Three groups of male subjects received as randomly assigned ascending single XG-102 doses (10, 40, and 80 μg/kg; 6 subjects per dose) or placebo (2 subjects per dose) as an intravenous (IV) infusion over 60 min. Safety and tolerability were assessed by physical examination, vital signs, electrocardiography, eye examination, clinical laboratory tests and adverse events (AEs). PK was analyzed using noncompartmental methods. All reported AEs were mild to moderate and neither their number nor their distribution by System Organ Class suggest a dose relationship. Only headache and fatigue were considered probably or possibly study drug related. Headache frequency was similar for active and placebo, consequently this was not considered to be drug related but probably to study conditions. The other examinations did not show clinically relevant deviations or trends suggesting a XG-102 relationship. Geometric mean half-life was similar among doses, ranging from 0.36 to 0.65 h. Geometric mean XG-102 AUC_0–last increased more than linearly with dose, 90% confidence intervals (CIs) did not overlap for the two highest doses. Geometric mean dose normalized C_max values suggest a more than linear increase with dose but 90% CIs overlap. It may be concluded that XG-102 single IV doses of 10–80 μg/kg administered over 1 h to healthy male subjects were safe and well tolerated.

Amyloid β suppresses protein C activation through inhibition of the endothelial protein C receptor (EPCR)

Alzheimer's disease (AD) is known to be associated with microcirculatory injury, capillary blockage, and disruption of the blood-brain barrier. Endothelial dysfunction has also been reported to be associated with AD, but the underlying mechanisms remain to be elucidated. Endothelial protein C receptor (EPCR) is an N-glycosylated type I membrane protein that enhances the activation of protein C. However, the effects of EPCR and protein C in AD are still unknown. In this study, we found that the expression of EPCR was reduced in the brains of β-amyloid precursor protein overexpressing Tg2576 transgenic mice at both the mRNA level and the protein level. However, levels of thrombomodulin (TM) did not undergo any changes. An in vitro study displayed that β-amyloid (Aβ) treatment led to suppression of EPCR along with reduction of protein C activation in mouse primary endothelial cells. Further study revealed that the induction of the c-Jun N-terminal kinase (JNK)/c-Jun pathway plays a causal role in the inhibitory effects of Aβ1-42 on the expression of EPCR. As a transcriptional factor, c-Jun was able to transinactivate the EPCR promoter. Finally, we found that c-Jun silencing or the use of a JNK inhibitor could attenuate the effects of Aβ1-42 in the activation of protein C.

JNK inhibitors as anti-inflammatory and neuroprotective agents

JNK is involved in a broad range of physiological processes. Several inflammatory and neurodegenerative diseases, such as multiple sclerosis, Alzheimer's and Parkinson's disease have been linked with the dysregulated JNK pathway. Research on disease models using the relevant knockout mice has highlighted the importance of specific JNK isoformsin-particular disorders and has stimulated further efforts in the drug-discovery area. However, most of the experimental evidence for the efficacy of JNK inhibition in animal models is from studies using JNK inhibitors, which are not isoform selective. Some of the more recent compounds exhibit good oral bioavailability, CNS penetration and selectivity against the rest of the kinome. Efforts to design isoform-selective inhibitors have produced a number of examples with various selectivity profiles. This article presents recent progress in this area and comment on the role of isoform selectivity for efficacy.

Neuroprotective role of γ-enolase in microglia in a mouse model of Alzheimer's disease is regulated by cathepsin X

γ-Enolase is a neurotrophic-like factor promoting growth, differentiation, survival and regeneration of neurons. Its neurotrophic activity is regulated by cysteine protease cathepsin X which cleaves the C-terminal end of the molecule. We have investigated the expression and colocalization of γ-enolase and cathepsin X in brains of Tg2576 mice overexpressing amyloid precursor protein. In situ hybridization of γ-enolase and cathepsin X revealed that mRNAs for both enzymes were expressed abundantly around amyloid plaques. Immunostaining demonstrated that the C-terminally cleaved form of γ-enolase was present in the immediate plaque vicinity, whereas the intact form, exhibiting neurotrophic activity, was observed in microglia cells in close proximity to senile plaque. The upregulation of γ-enolase in microglial cells in response to amyloid-β peptide (Aβ) was confirmed in mouse microglial cell line EOC 13.31 and primary microglia and medium enriched with γ-enolase proved to be neuroprotective against Aβ toxicity; however, the effect was reversed by cathepsin X proteolytic activity. These results demonstrate an upregulation of γ-enolase in microglia cells surrounding amyloid plaques in Tg2576 transgenic mice and demonstrate its neuroprotective role in amyloid-β-related neurodegeneration.

Toll-like receptor 3 activation in retinal pigment epithelium cells - Mitogen-activated protein kinase pathways of cell death and vascular endothelial growth factor secretion

PURPOSE

Toll-like receptor 3 (TLR3) is a receptor of the innate immune system, recognizing double-stranded RNA. TLR3 can lead to cytokine release or apoptosis and has recently been associated with the development of geographical atrophy via cytotoxic effects on the retinal pigment epithelium (RPE). The current study was conducted to elucidate the underlying pathways of TLR3 effects in the RPE.

METHODS

TLR3 activation via polyinosinic acid/polycytidylic acid (Poly I:C) was investigated in primary porcine RPE cells, focussing on cell death and vascular endothelial growth factor (VEGF) secretion. Primary cells were stimulated with different concentrations of Poly I:C. Cell death was investigated in trypan blue exclusion assay and cell death detection ELISA. VEGF and IFN-ß secretion were also detected in ELISA. As Mitogen-activated protein kinases (MAPK) play an important part in TLR3-mediated signal transduction, we investigated the influence of JNK, ERK1/2 and p38 on cell death and VEGF secretion, using commercially available inhibitors.

RESULTS

Activation of TLR3 by Poly I:C induced concentration-dependent cell death, partly mediated by JNK. ERK1/2 was activated and exerted some protection. Furthermore, higher concentrations of Poly I:C increased VEGF secretion after 4 and 24 hr, which was independent of MAPK.

CONCLUSION

The induction of cell death in RPE cells by TLR3 activation confirms possible involvement of TLR3 activation in GA. As cell death is partly mediated by JNK, more studies should be conducted investigating the role of JNK in RPE cell death to evaluate whether its inhibition might be a new therapeutic opportunity for the treatment of geographical atrophy. Additionally, effects on VEGF secretion can be found.