The Role of Glycogen Synthase Kinase 3 Beta in Neuroinflammation and Pain

Normal Mode Analysis Elicits Conformational Shifts in Proteins at Both Proximal and Distal Regions to the Phosphosite Stemming from Single-Site Phosphorylation

Phosphorylation, a fundamental biochemical switch, intricately regulates protein function and signaling pathways. Our study employs extensive computational structural analyses on a curated data set of phosphorylated and unphosphorylated protein pairs to explore the multifaceted impact of phosphorylation on protein conformation. Using normal mode analysis (NMA), we investigated changes in protein flexibility post-phosphorylation, highlighting an enhanced level of structural dynamism. Our findings reveal that phosphorylation induces not only local changes at the phosphorylation site but also extensive alterations in distant regions, showcasing its far-reaching influence on protein structure-dynamics. Through in-depth case studies on polyubiquitin B and glycogen synthase kinase-3 beta, we elucidate how phosphorylation at distinct sites leads to variable structural and dynamic modifications, potentially dictating functional outcomes. While phosphorylation largely preserves the residue motion correlation, it significantly disrupts low-frequency global modes, presenting a dualistic impact on protein dynamics. We also explored alterations in the total accessible surface area (ASA), emphasizing region-specific changes around phosphorylation sites. This study sheds light on phosphorylation-induced conformational changes, dynamic modulation, and surface accessibility alterations, leveraging an integrated computational approach with RMSD, NMA, and ASA, thereby contributing to a comprehensive understanding of cellular regulation and suggesting promising avenues for therapeutic interventions.

Systematic review of melatonin in cerebral ischemia-reperfusion injury: critical role and therapeutic opportunities

Cerebral ischemia-reperfusion (I/R) injury is the predominant causes for the poor prognosis of ischemic stroke patients after reperfusion therapy. Currently, potent therapeutic interventions for cerebral I/R injury are still very limited. Melatonin, an endogenous hormone, was found to be valid in preventing I/R injury in a variety of organs. However, a systematic review covering all neuroprotective effects of melatonin in cerebral I/R injury has not been reported yet. Thus, we perform a comprehensive overview of the influence of melatonin on cerebral I/R injury by collecting all available literature exploring the latent effect of melatonin on cerebral I/R injury as well as ischemic stroke. In this systematic review, we outline the extensive scientific studies and summarize the beneficial functions of melatonin, including reducing infarct volume, decreasing brain edema, improving neurological functions and attenuating blood-brain barrier breakdown, as well as its key protective mechanisms on almost every aspect of cerebral I/R injury, including inhibiting oxidative stress, neuroinflammation, apoptosis, excessive autophagy, glutamate excitotoxicity and mitochondrial dysfunction. Subsequently, we also review the predictive and therapeutic implications of melatonin on ischemic stroke reported in clinical studies. We hope that our systematic review can provide the most comprehensive introduction of current advancements on melatonin in cerebral I/R injury and new insights into personalized diagnosis and treatment of ischemic stroke.

P2X4 signalling contributes to hyperactivity but not pain sensitization comorbidity in a mouse model of attention deficit/hyperactivity disorder

Introduction: Attention deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder characterized by hyperactivity, inattention, and impulsivity that often persist until adulthood. Frequent comorbid disorders accompany ADHD and two thirds of children diagnosed with ADHD also suffer from behavioural disorders and from alteration of sensory processing. We recently characterized the comorbidity between ADHD-like symptoms and pain sensitisation in a pharmacological mouse model of ADHD, and we demonstrated the implication of the anterior cingulate cortex and posterior insula. However, few studies have explored the causal mechanisms underlying the interactions between ADHD and pain. The implication of inflammatory mechanisms has been suggested but the signalling pathways involved have not been explored. Methods: We investigated the roles of purinergic signalling, at the crossroad of pain and neuroinflammatory pathways, by using a transgenic mouse line that carries a total deletion of the P2X4 receptor. Results: We demonstrated that P2X4 deletion prevents hyperactivity in the mouse model of ADHD. In contrast, the absence of P2X4 lowered thermal pain thresholds in sham conditions and did not affect pain sensitization in ADHD-like conditions. We further analysed microglia reactivity and the expression of inflammatory markers in wild type and P2X4KO mice. Our results revealed that P2X4 deletion limits microglia reactivity but at the same time exerts proinflammatory effects in the anterior cingulate cortex and posterior insula. Conclusion: This dual role of P2X4 could be responsible for the differential effects noted on ADHD-like symptoms and pain sensitization and calls for further studies to investigate the therapeutic benefit of targeting the P2X4 receptor in ADHD patients.

Molecular docking and dynamics simulations revealed the potential inhibitory activity of honey-iQfood ingredients against GSK-3β and CDK5 protein targets for brain health

Honey-iQfood is an herbal supplement made of a mixture of polyherbal extracts and wild honey. The mixture is traditionally claimed to improve various conditions related to brain cells and functions including dementia and Alzheimer's disease. Glycogen synthase kinase-3 beta (GSK-3β) and cyclin-dependent kinase 5 (CDK5) have been identified as being involved in the pathological hyperphosphorylation of tau proteins, which leads to the formation of neurofibrillary tangles and causes Alzheimer's disease. Therefore, this study was conducted to confirm the traditional claims by detection of active compounds, namely curcumin, gallic acid, catechin, rosmarinic acid, and andrographolide in the raw materials of Honey-iQfood through HPLC analysis, molecular docking, and dynamic simulations. Two potential compounds, andrographolide, and rosmarinic acid, produced the best binding affinities following the molecular docking of the active compounds against the GSK-3β and CDK5 targets. Andrographolide binds with GSK-3β at -8.2 kcal/mol, whereas rosmarinic acid binds to CDK5 targets at -8.6 kcal/mol. Molecular dynamics was further carried out to confirm the docking results and clarify their dynamic properties such as RMSD, RMSF, rGyr, SASA, PSA, and binding free energy. CDK5-andrographolide complexes had the best MM-GBSA score (-83.63 kcal/mol) compared to other complexes, indicating the better interaction profile and stability of the complex. These findings warrant further research into andrographolide and rosmarinic acid as efficient inhibitors of tau protein hyperphosphorylation to verify their therapeutic potential in brain-related illnesses.Communicated by Ramaswamy H. Sarma.

Circulating microRNAs as diagnostic biomarkers for ischemic stroke: evidence from comprehensive analysis and real-world validation

Ischemic stroke (IS) is the majority of strokes which remain the second leading cause of deaths in the last two decades. Circulating microRNAs (miRNAs) have been suggested as potential diagnostic and therapeutic tools for IS by previous studies analyzing their differential expression. However, inconclusive and controversial conclusions of these results have to be addressed. In this study, comprehensive analysis and real-world validation were performed to assess the associations between circulating miRNAs and IS. 29 studies with 112 miRNAs were extracted after manual selection and filtering, 12 differentially expressed miRNAs were obtained from our results of meta-analysis. These miRNAs were evaluated in 20 IS patients, compared to 20 healthy subjects. 4 miRNAs (hsa-let-7e-5p, hsa-miR-124-3p, hsa-miR-17-5p, hsa-miR-185-5p) exhibited the significant expression level in IS patient plasma samples. Pathway and biological process enrichment analysis for the target genes of the 4 validated miRNAs identified cellular senescence and neuroinflammation as key post-IS response pathways. The results of our analyses closely correlated with the pathogenesis and implicated pathways observed in IS subjects suggested by the literature, which may provide aid in the development of circulating diagnostic or therapeutic targets for IS patients.

Effects of glycogen synthase kinase-3β activity inhibition on cognitive, behavioral, and hippocampal ultrastructural deficits in adulthood associated with adolescent methamphetamine exposure

Objective

Glycogen synthase kinase-3β (GSK3β) has been implicated in the maintenance of synaptic plasticity, memory process, and psychostimulant-induced behavioral effects. Hyperactive GSK3β in the Cornu Ammonis 1 (CA1) subregion of the dorsal hippocampus (DHP) was associated with adolescent methamphetamine (METH) exposure-induced behavioral and cognitive deficits in adulthood. This study aimed to evaluate the possible therapeutic effects of GSK3β inhibition in adulthood on adolescent METH exposure-induced long-term neurobiological deficits.

Methods

Adolescent male mice were treated with METH from postnatal day (PND) 45-51. In adulthood, three intervention protocols (acute lithium chloride systemic administration, chronic lithium chloride systemic administration, and chronic SB216763 administration within CA1) were used for GSK3β activity inhibition. The effect of GSK3β intervention on cognition, behavior, and GSK3β activity and synaptic ultrastructure in the DHP CA1 subregion were detected in adulthood.

Results

In adulthood, all three interventions reduced adolescent METH exposure-induced hyperactivity (PND97), while only chronic systemic and chronic within CA1 administration ameliorated the induced impairments in spatial (PND99), social (PND101) and object (PND103) recognition memory. In addition, although three interventions reversed the aberrant GSK3β activity in the DHP CA1 subregion (PND104), only chronic systemic and chronic within CA1 administration rescued adolescent METH exposure-induced synaptic ultrastructure changes in the DHP CA1 subregion (PND104) in adulthood.

Conclusion

Rescuing synaptic ultrastructural abnormalities in the dHIP CA1 subregion by chronic administration of a GSK3β inhibitor may be a suitable therapeutic strategy for the treatment of behavioral and cognitive deficits in adulthood associated with adolescent METH abuse.

Triiodothyronine Treatment reverses Depression-Like Behavior in a triple-transgenic animal model of Alzheimer's Disease

Alzheimer disease's (AD) is a neurodegenerative disorder characterized by cognitive and behavioral impairment. The central nervous system is an important target of thyroid hormones (TH). An inverse association between serum triiodothyronine (T3) levels and the risk of AD symptoms and progression has been reported. We investigated the effects of T3 treatment on the depression-like behavior in male transgenic 3xTg-AD mice. Animals were divided into 2 groups treated with daily intraperitoneal injections of 20 ng/g of body weight (b.w.) L-T3 (T3 group) or saline (vehicle, control group). The experimental protocol lasted 21 days, and behavioral tests were conducted on days 18-20. At the end of the experiment, the TH profile and hippocampal gene expression were evaluated. The T3-treated group significantly increased serum T3 and decreased thyroxine (T4) levels. When compared to control hippocampal samples, the T3 group exhibited attenuated glycogen synthase kinase-3 (GSK3), metalloproteinase 10 (ADAM10), amyloid-beta precursor-protein (APP), serotonin transporter (SERT), 5HT1A receptor, monocarboxylate transporter 8 (MCT8) and bone morphogenetic protein 7 (BMP-7) gene expression, whereas augmented superoxide dismutase 2 (SOD2) and Hairless gene expression. T3-treated animals also displayed reduced immobility time in both the tail suspension and forced swim tests, and in the latter presented a higher latency time compared to the control group. Therefore, our findings suggest that in an AD mouse model, T3 supplementation promotes improvements in depression-like behavior, through the modulation of the serotonergic related genes involved in the transmission mediated by 5HT1A receptors and serotonin reuptake, and attenuated disease progression.

Inhibition of glycogen synthase kinase 3 by lithium, a mechanism in search of specificity

Inhibition of Glycogen synthase kinase 3 (GSK3) is a popular explanation for the effects of lithium ions on mood regulation in bipolar disorder and other mental illnesses, including major depression, cyclothymia, and schizophrenia. Contribution of GSK3 is supported by evidence obtained from animal and patient derived model systems. However, the two GSK3 enzymes, GSK3α and GSK3β, have more than 100 validated substrates. They are thus central hubs for major biological functions, such as dopamine-glutamate neurotransmission, synaptic plasticity (Hebbian and homeostatic), inflammation, circadian regulation, protein synthesis, metabolism, inflammation, and mitochondrial functions. The intricate contributions of GSK3 to several biological processes make it difficult to identify specific mechanisms of mood stabilization for therapeutic development. Identification of GSK3 substrates involved in lithium therapeutic action is thus critical. We provide an overview of GSK3 biological functions and substrates for which there is evidence for a contribution to lithium effects. A particular focus is given to four of these: the transcription factor cAMP response element-binding protein (CREB), the RNA-binding protein FXR1, kinesin subunits, and the cytoskeletal regulator CRMP2. An overview of how co-regulation of these substrates may result in shared outcomes is also presented. Better understanding of how inhibition of GSK3 contributes to the therapeutic effects of lithium should allow for identification of more specific targets for future drug development. It may also provide a framework for the understanding of how lithium effects overlap with those of other drugs such as ketamine and antipsychotics, which also inhibit brain GSK3.

miR-27a-3p regulates expression of intercellular junctions at the brain endothelium and controls the endothelial barrier permeability

Background

The brain endothelial barrier permeability is governed by tight and adherens junction protein complexes that restrict paracellular permeability at the blood-brain barrier (BBB). Dysfunction of the inter-endothelial junctions has been implicated in neurological disorders such as multiple sclerosis, stroke and Alzheimer’s disease. The molecular mechanisms underlying junctional dysfunction during BBB impairment remain elusive. MicroRNAs (miRNAs) have emerged as versatile regulators of the BBB function under physiological and pathological conditions, and altered levels of BBB-associated microRNAs were demonstrated in a number of brain pathologies including neurodegeneration and neuroinflammatory diseases. Among the altered micro-RNAs, miR-27a-3p was found to be downregulated in a number of neurological diseases characterized by loss of inter-endothelial junctions and disruption of the barrier integrity. However, the relationship between miR-27a-3p and tight and adherens junctions at the brain endothelium remains unexplored. Whether miR-27a-3p is involved in regulation of the junctions at the brain endothelium remains to be determined.

Methods

Using a gain-and-loss of function approach, we modulated levels of miR-27a-3p in an in-vitro model of the brain endothelium, key component of the BBB, and examined the resultant effect on the barrier paracellular permeability and on the expression of essential tight and adherens junctions. The mechanisms governing the regulation of junctional proteins by miR-27a-3p were also explored.

Results

Our results showed that miR-27a-3p inhibitor increases the barrier permeability and causes reduction of claudin-5 and occludin, two proteins highly enriched at the tight junction, while miR-27a-3p mimic reduced the paracellular leakage and increased claudin-5 and occludin protein levels. Interestingly, we found that miR-27-3p induces expression of claudin-5 and occludin by downregulating Glycogen Synthase Kinase 3 beta (GSK3ß) and activating Wnt/ß-catenin signaling, a key pathway required for the BBB maintenance.

Conclusion

For the first time, we showed that miR-27a-3p is a positive regulator of key tight junction proteins, claudin-5 and occludin, at the brain endothelium through targeting GSK3ß gene and activating Wnt/ß-catenin signaling. Thus, miR-27a-3p may constitute a novel therapeutic target that could be exploited to prevent BBB dysfunction and preserves its integrity in neurological disorders characterized by impairment of the barrier’s function.

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

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

The Identification of Blood Biomarkers of Chronic Neuropathic Pain by Comparative Transcriptomics

In this study, we recruited 50 chronic pain (neuropathic and nociceptive) and 43 pain-free controls to identify specific blood biomarkers of chronic neuropathic pain (CNP). Affymetrix microarray was carried out on a subset of samples selected 10 CNP and 10 pain-free control participants. The most significant genes were cross-validated using the entire dataset by quantitative real-time PCR (qRT-PCR). In comparative analysis of controls and CNP patients, WLS (P = 4.80 × 10^–7), CHPT1 (P = 7.74 × 10^–7) and CASP5 (P = 2.30 × 10^–5) were highly significant, whilst FGFBP2 (P = 0.00162), STAT1 (P = 0.00223), FCRL6 (P = 0.00335), MYC (P = 0.00335), XCL2 (P = 0.0144) and GZMA (P = 0.0168) were significant in all CNP patients. A three-arm comparative analysis was also carried out with control as the reference group and CNP samples differentiated into two groups of high and low S-LANSS score using a cut-off of 12. STAT1, XCL2 and GZMA were not significant but KIR3DL2 (P = 0.00838), SH2D1B (P = 0.00295) and CXCR31 (P = 0.0136) were significant in CNP high S-LANSS group (S-LANSS score > 12), along with WLS (P = 8.40 × 10^–5), CHPT1 (P = 7.89 × 10^–4), CASP5 (P = 0.00393), FGFBP2 (P = 8.70 × 10^–4) and FCRL6 (P = 0.00199), suggesting involvement of immune pathways in CNP mechanisms. None of the genes was significant in CNP samples with low (< 12) S-LANSS score. The area under the receiver operating characteristic (AUROC) analysis showed that combination of MYC, STAT1, TLR4, CASP5 and WLS gene expression could be potentially used as a biomarker signature of CNP (AUROC − 0.852, (0.773, 0.931 95% CI)).

Recent Advances in Pain Management: Relevant Protein Kinases and Their Inhibitors

The purpose of this review is to underline the protein kinases that have been established, either in fundamental approach or clinical trials, as potential biological targets in pain management. Protein kinases are presented according to their group in the human kinome: TK (Trk, RET, EGFR, JAK, VEGFR, SFK, BCR-Abl), CMGC (p38 MAPK, MEK, ERK, JNK, ASK1, CDK, CLK2, DYRK1A, GSK3, CK2), AGC (PKA, PKB, PKC, PKMζ, PKG, ROCK), CAMK, CK1 and atypical/other protein kinases (IKK, mTOR). Examples of small molecule inhibitors of these biological targets, demonstrating an analgesic effect, are described. Altogether, this review demonstrates the fundamental role that protein kinase inhibitors could play in the development of new pain treatments.

Critical Effects on Akt Signaling in Adult Zebrafish Brain Following Alterations in Light Exposure

Evidence from human and animal studies indicate that disrupted light cycles leads to alterations of the sleep state, poor cognition, and the risk of developing neuroinflammatory and generalized health disorders. Zebrafish exhibit a diurnal circadian rhythm and are an increasingly popular model in studies of neurophysiology and neuropathophysiology. Here, we investigate the effect of alterations in light cycle on the adult zebrafish brain: we measured the effect of altered, unpredictable light exposure in adult zebrafish telencephalon, homologous to mammalian hippocampus, and the optic tectum, a significant visual processing center with extensive telencephalon connections. The expression of heat shock protein-70 (HSP70), an important cell stress mediator, was significantly decreased in optic tectum of adult zebrafish brain following four days of altered light exposure. Further, pSer473-Akt (protein kinase B) was significantly reduced in telencephalon following light cycle alteration, and pSer9-GSK3β (glycogen synthase kinase-3β) was significantly reduced in both the telencephalon and optic tectum of light-altered fish. Animals exposed to five minutes of environmental enrichment showed significant increase in pSer473Akt, which was significantly attenuated by four days of altered light exposure. These data show for the first time that unpredictable light exposure alters HSP70 expression and dysregulates Akt-GSK3β signaling in the adult zebrafish brain.

Novel 18F-Labeled Isonicotinamide-Based Radioligands for Positron Emission Tomography Imaging of Glycogen Synthase Kinase-3β

Glycogen synthase kinase-3β (GSK-3β), a cytoplasmic serine/threonine protein kinase, is involved in several human pathologies including Alzheimer's disease, bipolar disorder, diabetes, and cancer. Positron emission tomography (PET) imaging of GSK-3β could aid in investigating GSK-3β levels under normal and pathological conditions. In this study, we designed and synthesized fluorinated PET radioligands starting with recently identified isonicotinamide derivatives that showed potent affinity to GSK-3β. After extensive in vitro inhibitory activity assays and analyzing U87 cell uptake, we identified [¹⁸F]10a-d as potential tracers with good specificity and high affinity. They were then subjected to further in vivo evaluation in rodent brain comprising PET imaging and metabolism studies. The radioligands [¹⁸F]10b-d penetrated the blood-brain barrier and accumulated in GSK-3β-rich regions, including amygdala, cerebellum, and hippocampus. Also, it could be specifically blocked using the corresponding standard compounds. With these results, this work sets the basis for further development of novel ¹⁸F-labeled GSK-3β PET probes.

Quinpirole-Mediated Regulation of Dopamine D2 Receptors Inhibits Glial Cell-Induced Neuroinflammation in Cortex and Striatum after Brain Injury

Brain injury is a significant risk factor for chronic gliosis and neurodegenerative diseases. Currently, no treatment is available for neuroinflammation caused by the action of glial cells following brain injury. In this study, we investigated the quinpirole-mediated activation of dopamine D2 receptors (D2R) in a mouse model of traumatic brain injury (TBI). We also investigated the neuroprotective effects of quinpirole (a D2R agonist) against glial cell-induced neuroinflammation secondary to TBI in adult mice. After the brain injury, we injected quinpirole into the TBI mice at a dose of 1 mg/kg daily intraperitoneally for 7 days. Our results showed suppression of D2R expression and deregulation of downstream signaling molecules in ipsilateral cortex and striatum after TBI on day 7. Quinpirole administration regulated D2R expression and significantly reduced glial cell-induced neuroinflammation via the D2R/Akt/glycogen synthase kinase 3 beta (GSK3-β) signaling pathway after TBI. Quinpirole treatment concomitantly attenuated increase in glial cells, neuronal apoptosis, synaptic dysfunction, and regulated proteins associated with the blood–brain barrier, together with the recovery of lesion volume in the TBI mouse model. Additionally, our in vitro results confirmed that quinpirole reversed the microglial condition media complex-mediated deleterious effects and regulated D2R levels in HT22 cells. This study showed that quinpirole administration after TBI reduced secondary brain injury-induced glial cell activation and neuroinflammation via regulation of the D2R/Akt/GSK3-β signaling pathways. Our study suggests that quinpirole may be a safe therapeutic agent against TBI-induced neurodegeneration.

NO up-regulates migraine-related CGRP via activation of an Akt/GSK-3β/NF-κB signaling cascade in trigeminal ganglion neurons

The release of the neuropeptide CGRP from the trigeminal ganglion neurons (TGNs) plays a central role in migraine. Whereas CGRP can activate NO release from ganglionic glial cells, NO in turn enhances CGRP release. However, it remains unclear how NO promotes CGRP release. Here, we report that the NO donor SNAP triggered CGRP release from cultured primary TGNs. This event was associated with GSK-3β activation and Akt inactivation. Immunofluorescent staining revealed that GSK-3β primarily located in neurons. Furthermore, GSK-3β inhibition resulted in a marked reduction in expression of CGRP as well as other migraine-related factors, including substance P, cholecystokinin, and prostaglandin E2. Last, exposure to SNAP also activated NF-κB, while NF-κB inhibition prevented the induction of CGRP by SNAP. Interestingly, this event was blocked by GSK-3β inhibition, in association with inhibition of NF-κB/p65 expression and nuclear translocation. Together, these findings argue that NO could stimulate TGNs to release of CGRP as well as other migraine-related factors, likely by activating GSK-3β, providing a novel mechanism underlying a potential feed-forward loop between NO and CGRP in migraine. They also raise a possibility that GSK-3β might act to trigger migraine through activation of NF-κB, suggesting a link between neuroinflammation and migraine.

Exercise-Induced Neuroprotection and Recovery of Motor Function in Animal Models of Parkinson's Disease

Parkinson's disease (PD) is manifested by progressive motor, autonomic, and cognitive disturbances. Dopamine (DA) synthesizing neurons in the substantia nigra (SN) degenerate, causing a decline in DA level in the striatum that leads to the characteristic movement disorders. A disease-modifying therapy to arrest PD progression remains unattainable with current pharmacotherapies, most of which cause severe side effects and lose their efficacy with time. For this reason, there is a need to seek new therapies supporting the pharmacological treatment of PD. Motor therapy is recommended for pharmacologically treated PD patients as it alleviates the symptoms. Molecular mechanisms behind the beneficial effects of motor therapy are unknown, nor is it known whether such therapy may be neuroprotective in PD patients. Due to obvious limitations, human studies are unlikely to answer these questions; therefore, the use of animal models of PD seems indispensable. Motor therapy in animal models of PD characterized by the loss of dopaminergic neurons has neuroprotective and neuroregenerative effects, and the completeness of neuronal protection may depend on (i) degree of neuronal loss, (ii) duration and intensity of exercise, and (iii) time elapsed between insult and commencing of training. As the physical activity is neuroprotective for dopaminergic neurons, the question arises what is the mechanism of this protective action. A current hypothesis assumes a central role of neurotrophic factors in the neuroprotection of dopaminergic neurons, even though it is still not clear whether increased DA level in the nigrostriatal axis results from neurogenesis of dopaminergic neurons in the SN, recovery of the phenotype of dopaminergic neurons, increased sprouting of the residual dopaminergic axons in the striatum, or generation of local striatal neurons from inhibitory interneurons. In the present review, we discuss studies describing the influence of physical exercise on the PD-like changes manifested in animal models of the disease and focus our interest on the current state of knowledge on the mechanism of neuroprotection induced by physical activity as a supportive therapy in PD.

Minocycline attenuates ethanol-induced cell death and microglial activation in the developing spinal cord

Developmental exposure to ethanol may cause fetal alcohol spectrum disorders (FASD), and the immature central nervous system (CNS) is particularly vulnerable to ethanol. In addition to vulnerability in the developing brain, we previously showed that ethanol also caused neuroapoptosis, microglial activation, and neuroinflammation in the spinal cord. Minocycline is an antibiotic that inhibits microglial activation and alleviates neuroinflammation. We sought to determine whether minocycline could protect spinal cord neurons against ethanol-induced damage. In this study, we showed that minocycline significantly inhibited ethanol-induced caspase-3 activation, microglial activation, and the expression of pro-inflammatory cytokines in the developing spinal cord. Moreover, minocycline blocked ethanol-induced activation of glycogen synthase kinase 3 beta (GSK3β), a key regulator of microglial activation. Meanwhile, minocycline significantly restored ethanol-induced inhibition of protein kinase B (AKT), mammalian target of the rapamycin (mTOR), and ERK1/2 signaling pathways, which were important pro-survival signaling pathways for neurons. Together, minocycline may attenuate ethanol-induced damage to the developing spinal cord by inhibiting microglial activation/neuroinflammation and by restoring the pro-survival signaling.

Constitutively active GSK3β as a means to bolster dendritic cell functionality in the face of tumour-mediated immune suppression

In patients with cancer, the functionality of Dendritic Cells (DC) is hampered by high levels of tumor-derived suppressive cytokines, which interfere with DC development and maturation. Poor DC development can limit the efficacy of immune checkpoint blockade and in vivo vaccination approaches. Interference in intracellular signaling cascades downstream from the receptors of major tumor-associated suppressive cytokines like IL-10 and IL-6, might improve DC development and activation, and thus enhance immunotherapy efficacy. We performed exploratory functional screens on arrays consisting of >1000 human kinase peptide substrates to identify pathways involved in DC development and its inhibition by IL-10 or IL-6. The resulting alterations in phosphorylation of the kinome substrate profile pointed to glycogen-synthase kinase-3β (GSK3β) as a pivotal kinase in both DC development and suppression. GSK3β inhibition blocked human DC differentiation in vitro, which was accompanied by decreased levels of IL-12p70 secretion, and a reduced capacity for T cell priming. More importantly, adenoviral transduction of monocytes with a constitutively active form of GSK3β induced resistance to the suppressive effects of IL-10 and melanoma-derived supernatants alike, resulting in improved DC development, accompanied by up-regulation of co-stimulatory markers, an increase in CD83 expression levels in mature DC, and diminished release of IL-10. Moreover, adenovirus-mediated intratumoral manipulation of this pathway in an in vivo melanoma model resulted in DC activation and recruitment, and in improved immune surveillance and tumor control. We propose the induction of constitutive GSK3β activity as a novel therapeutic means to bolster DC functionality in the tumor microenvironment.

Histamine, histamine receptors, and neuropathic pain relief

Histamine, acting via distinct histamine H₁, H₂, H₃, and H₄ receptors, regulates various physiological and pathological processes, including pain. In the last two decades, there has been a particular increase in evidence to support the involvement of H₃ receptor and H₄ receptor in the modulation of neuropathic pain, which remains challenging in terms of management. However, recent data show contrasting effects on neuropathic pain due to multiple factors that determine the pharmacological responses of histamine receptors and their underlying signal transduction properties (e.g., localization on either the presynaptic or postsynaptic neuronal membranes). This review summarizes the most recent findings on the role of histamine and the effects mediated by the four histamine receptors in response to the various stimuli associated with and promoting neuropathic pain. We particularly focus on mechanisms underlying histamine‐mediated analgesia, as we aim to clarify the analgesic potential of histamine receptor ligands in neuropathic pain.

Linked Articles

This article is part of a themed section on New Uses for 21st Century. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.3/issuetoc

Desoxo-narchinol A and Narchinol B Isolated from Nardostachys jatamansi Exert Anti-neuroinflammatory Effects by Up-regulating of Nuclear Transcription Factor Erythroid-2-Related Factor 2/Heme Oxygenase-1 Signaling

We previously reported that desoxo-narchinol A and narchinol B from Nardostachys jatamansi DC (Valerianaceae) inhibited the production of nitric oxide (NO) and prostaglandin E₂ (PGE₂), and the expression of inducible NO synthase (iNOS) and cyclooxygenase (COX)-2 protein in lipopolysaccharide (LPS)-stimulated BV2 and primary microglial cells. In this study, we aimed to elucidate the molecular mechanism underlying the anti-neuroinflammatory effects of desoxo-narchinol A and narchinol B. These two compounds inhibited the nuclear factor (NF)-κB pathway, by repressing the phosphorylation and degradation of inhibitor kappa B (IκB)-α, nuclear translocation of the p65/p50 heterodimer, and DNA-binding activity of the p65 subunit. Furthermore, both compounds induced heme oxygenase-1 (HO-1) protein expression, which was mediated by the activation of nuclear transcription factor erythroid-2-related factor 2 (Nrf2). Activation of the Nrf2/HO-1 pathway by desoxo-narchinol A was shown to be regulated by increased phosphorylation of p38 and extracellular signal-regulated kinase (ERK), whereas only p38 was involved in narchinol B-induced activation of the Nrf2/HO-1 pathway. In addition, phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling was also involved in the activation of HO-1 by desoxo-narchinol A and narchinol B. These compounds also increased the phosphorylation of glycogen synthase kinase 3 beta (GSK3β) at serine-9 residue, following phosphorylation of Akt. The anti-neuroinflammatory effect of desoxo-narchinol A and narchinol B was partially blocked by a selective HO-1 inhibitor, suggesting that this effect is partly mediated by HO-1 induction. In addition, both compounds also induced HO-1 protein expression in rat-derived primary microglial cells, which was correlated with their anti-neuroinflammatory effects in LPS-stimulated primary microglial cells. In conclusion, desoxo-narchinol A and narchinol B are potential candidates for the development of preventive agents for the regulation of neuroinflammation in neurodegenerative diseases.

Tau in Oligodendrocytes Takes Neurons in Sickness and in Health

Oligodendrocytes (OLGs), the myelin-forming cells of the central nervous system (CNS), are lifelong partners of neurons. They adjust to the functional demands of neurons over the course of a lifetime to meet the functional needs of a healthy CNS. When this functional interplay breaks down, CNS degeneration follows. OLG processes are essential features for OLGs being able to connect with the neurons. As many as fifty cellular processes from a single OLG reach and wrap an equal number of axonal segments. The cellular processes extend to meet and wrap axonal segments with myelin. Further, transport regulation, which is critical for myelination, takes place within the cellular processes. Because the microtubule-associated protein tau plays a crucial role in cellular process extension and myelination, alterations of tau in OLGs have deleterious effects, resulting in neuronal malfunction and CNS degeneration. Here, we review current concepts on the lifelong role of OLGs and myelin for brain health and plasticity. We present key studies of tau in OLGs and select important studies of tau in neurons. The extensive work on tau in neurons has considerably advanced our understanding of how tau promotes either health or disease. Because OLGs are crucial to neuronal health at any age, an understanding of the functions and regulation of tau in OLGs could uncover new therapeutics for selective CNS neurodegenerative diseases.

Leonurine protects cardiac function following acute myocardial infarction through anti‑apoptosis by the PI3K/AKT/GSK3β signaling pathway

Leonurine is a compound derived from Herba leonuri, which has been reported to protect cardiac tissue against ischemic injury via antioxidant and anti‑apoptosis effects. The present study investigated whether these effects may be applied to acute myocardial infarction (MI) and examined the underlying mechanisms of leonurine treatment. A rat model of MI was induced by coronary artery ligation. Leonurine was administered at 15 mg/kg/day by oral gavage following the onset of MI. Rats in the sham group and the saline group were administered with an equal volume of saline. Echocardiography, Masson's trichrome staining, and terminal‑deoxynucleotidyl transferase‑mediated dUTP nick end labeling assays were performed 28 days post MI. The expression of B‑cell lymphoma‑2 and Bax were assessed by western blot analysis and reverse transcription‑quantitative polymerase chain reaction. Phosphoinositide 3‑kinase (PI3K), protein kinase B and glycogen synthase kinase‑3β (GSK3β) protein expression were investigated by western blot analysis. Leonurine significantly alleviated collagen deposition and MI size, inhibited cell apoptosis and improved myocardial function. This was accompanied by significantly increased levels of phosphorylated (p)‑PI3K, p‑AKT, p‑GSK3β and Bcl‑2, as well as significantly decreased levels of caspase3, cleaved‑caspase3 and Bax following MI. The results demonstrated that leonurine exerts potent cardio‑protective effects in a rat model of MI by inducing anti‑apoptotic effects by activating the PI3K/AKT/GSK3β signaling pathway.

Role of MCP-1 and CCR2 in ethanol-induced neuroinflammation and neurodegeneration in the developing brain

Background

Neuroinflammation and microglial activation have been implicated in both alcohol use disorders (AUD) and fetal alcohol spectrum disorders (FASD). Chemokine monocyte chemoattractant protein 1 (MCP-1) and its receptor C-C chemokine receptor type 2 (CCR2) are critical mediators of neuroinflammation and microglial activation. FASD is the leading cause of mental retardation, and one of the most devastating outcomes of FASD is the loss of neurons in the central nervous system (CNS). The underlying molecular mechanisms, however, remain unclear. We hypothesize that MCP-1/CCR2 signaling mediates ethanol-induced neuroinflammation and microglial activation, which exacerbates neurodegeneration in the developing brain.

Methods

C57BL/6 mice and mice deficient of MCP-1 (MCP-1^−/−) and CCR2 (CCR2^−/−) were exposed to ethanol on postnatal day 4 (PD4). Neuroinflammation, and microglial activation, and neurodegeneration in the brain were evaluated by immunohistochemistry and immunoblotting. A neuronal and microglial co-culture system was used to evaluate the role of microglia and MCP-1/CCR2 signaling in ethanol-induced neurodegeneration. Specific inhibitors were employed to delineate the involved signaling pathways.

Results

Ethanol-induced microglial activation, neuroinflammation, and a drastic increase in the mRNA and protein levels of MCP-1. Treatment of Bindarit (MCP-1 synthesis inhibitor) and RS504393 (CCR2 antagonist) significantly reduced ethanol-induced microglia activation/neuroinflammation, and neuroapoptosis in the developing brain. MCP-1^−/− and CCR2^−/− mice were more resistant to ethanol-induced neuroapoptosis. Moreover, ethanol plus MCP-1 caused more neuronal death in a neuron/microglia co-culture system than neuronal culture alone, and Bindarit and RS504393 attenuated ethanol-induced neuronal death in the co-culture system. Ethanol activated TLR4 and GSK3β, two key mediators of microglial activation in the brain and cultured microglial cells (SIM-A9). Blocking MCP-1/CCR2 signaling attenuated ethanol-induced activation of TLR4 and GSK3β.

Conclusion

MCP-1/CCR2 signaling played an important role in ethanol-induced microglial activation/neuroinflammation and neurodegeneration in the developing brain. The effects may be mediated by the interaction among MCP-1/CCR2 signaling, TLR4, and GSK3β.

Quercetin attenuates AZT-induced neuroinflammation in the CNS

Highly active anti-retroviral therapy (HAART) is very effective in suppressing HIV-1 replication in patients. However, continuous HAART is required to prevent viral rebound, which may have detrimental effects in various tissues, including persistent neuroinflammation in the central nervous system (CNS). Here, we show that quercetin (3,5,7,3’,4’-pentahydroxy flavones), a natural antioxidant used in Chinese traditional medicines, suppresses the neuroinflammation that is induced by chronic exposure to Zidovudine (azidothymidine, AZT), a nucleoside reverse transcriptase inhibitor (NRTI) that is commonly part of HAART regimens. We found that the up-regulation of pro-inflammatory cytokines and microglial and astrocytic markers induced by AZT (100 mg/kg/day; 8 days) was significantly inhibited by co-administration of quercetin (50 mg/kg/day) in the mouse cortex, hippocampus and spinal cord. We further showed that quercetin attenuated AZT-induced up-regulation of Wnt5a, a key regulator of neuroinflammation. These results suggest that quercetin has an inhibitory effect on AZT-induced neuroinflammation in the CNS, and Wnt5a signaling may play an important role in this process. Our results may further our understanding of the mechanisms of HAART-related neurotoxicity and help in the development of effective adjuvant therapy.

Neuroimmune Tau Mechanisms: Their Role in the Progression of Neuronal Degeneration

Progressive neurodegenerative pathologies in aged populations are an issue of major concern worldwide. The microtubule-associated protein tau is able to self-aggregate to form abnormal supramolecular structures that include small oligomers up to complex polymers. Tauopathies correspond to a group of diseases that share tau pathology as a common etiological agent. Since microglial cells play a preponderant role in innate immunity and are the main source of proinflammatory factors in the central nervous system (CNS), the alterations in the cross-talks between microglia and neuronal cells are the main focus of studies concerning the origins of tauopathies. According to evidence from a series of studies, these changes generate a feedback mechanism reactivating microglia and provoking constant cellular damage. Thus, the previously summarized mechanisms could explain the onset and progression of different tauopathies and their functional/behavioral effects, opening the window towards an understanding of the molecular basis of anomalous tau interactions. Despite clinical and pathological differences, increasing experimental evidence indicates an overlap between tauopathies and synucleinopathies, considering that neuroinflammatory events are involved and the existence of protein misfolding. Neurofibrillary tangles of pathological tau (NFT) and Lewy bodies appear to coexist in certain brain areas. Thus, the co-occurrence of synucleinopathies with tauopathies is evidenced by several investigations, in which NFT were found in the substantia nigra of patients with Parkinson’s disease, suggesting that the pathologies share some common features at the level of neuroinflammatory events.

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.

Minocycline protects developing brain against ethanol-induced damage

Fetal alcohol spectrum disorders (FASD) are caused by ethanol exposure during the pregnancy and is the leading cause of mental retardation. Ethanol exposure during the development results in the loss of neurons in the developing brain, which may underlie many neurobehavioral deficits associated with FASD. It is important to understand the mechanisms underlying ethanol-induced neuronal loss and develop appropriate therapeutic strategies. One of the potential mechanisms involves neuroimmune activation. Using a third trimester equivalent mouse model of ethanol exposure, we demonstrated that ethanol induced a wide-spread neuroapoptosis, microglial activation, and neuroinflammation in C57BL/6 mice. Minocycline is an antibiotic that inhibits microglial activation and alleviates neuroinflammation. We tested the hypothesis that minocycline may protect neurons ethanol-induced neuron death by inhibiting microglial activation and neuroinflammation. We showed that minocycline significantly inhibited ethanol-induced caspase-3 activation, microglial activation, and the expression of pro-inflammatory cytokines. In contrast, minocycline reversed ethanol inhibition of anti-inflammatory cytokines. Minocycline blocked ethanol-induced activation of GSK3β, a key mediator of neuroinflammation and microglial activation in the developing brain. Consistent with the in vivo observations, minocycline inhibited ethanol-induced the expression of pro-inflammatory cytokines and activation of GSK3β in a microglia cell line (SIM-9). GSK3β inhibitor eliminated ethanol activation of pro-inflammatory cytokines in SIM-9 cells. Co-cultures of cortical neurons and SIM-9 microglia cells sensitized neurons to alcohol-induced neuronal death. Minocycline protected neurons against ethanol-induced neuronal death in neurons/microglia co-cultures. Together, these results suggest that minocycline may ameliorate ethanol neurotoxicity in the developing by alleviating GSK3β-mediated neuroinflammation.

Crosstalk between endoplasmic reticulum stress and brain inflammation in Alzheimer's disease

While most often noted for its cognitive symptoms, Alzheimer's disease (AD) is, at its core, a disease of protein misfolding/aggregation, with an intriguing inflammatory component. Defective clearance and/or abnormal production of the amyloid-β peptide (Aβ), and its ensuing accumulation and aggregation, underlie two hallmark features of AD: brain accumulation of insoluble protein deposits known as amyloid or senile plaques, and buildup of soluble Aβ oligomers (AβOs), diffusible toxins linked to synapse dysfunction and memory impairment. In neurons, as in typical eukaryotic cells, the endoplasmic reticulum (ER) serves as a main compartment for the folding, maturation, trafficking and quality control of newly synthesized proteins. The ER lumen, a calcium-rich, oxidizing environment, provides favorable conditions for these physiological functions to occur. These conditions, however, also favor protein aggregation. Several stressors, including metabolic/nutrient stress and certain pathologies, may upset the ER homeostasis, e.g., by affecting calcium levels or by causing the accumulation of unfolded or misfolded proteins. Whatever the underlying cause, the result is what is commonly known as "ER stress". This, in turn, triggers a conserved cellular response mechanism known as the "unfolded protein response" (UPR). The UPR comprises three pathways involving transcriptional or translational regulators aimed at normalizing ER function, and each of them results in pro-inflammatory signaling. A positive feedback loop exists between ER stress and inflammation, with clear implications for neurodegeneration and AD. Here, we explore recent findings on the role of ER stress and the UPR in inflammatory processes leading to synapse failure and memory impairment in AD. This article is part of the Special Issue entitled 'Metabolic Impairment as Risk Factors for Neurodegenerative Disorders.'

Production of proinflammatory mediators in activated microglia is synergistically regulated by Notch-1, glycogen synthase kinase (GSK-3β) and NF-κB/p65 signalling

Microglia activation and associated inflammatory response are involved in the pathogenesis of different neurodegenerative diseases. We have reported that Notch-1 and NF-κB/p65 signalling pathways operate in synergy in regulating the production of proinflammatory mediators in activated microglia. In the latter, there is also evidence by others that glycogen synthase kinase 3β (GSK-3β) mediates the release of proinflammatory cytokines but the interrelationships between the three signalling pathways have not been fully clarified. This is an important issue as activated microglia are potential therapeutic target for amelioration of microglia mediated neuroinflammation. Here we show that blocking of Notch-1 with N-[(3,5-Difluorophenyl) acetyl]-L-alanyl-2-phenylglycine-1,1-dimethylethyl ester (DAPT) in LPS activated BV-2 microglia not only suppressed Notch intracellular domain (NICD) and Hes-1 protein expression, but also that of GSK-3β. Conversely, blocking of the latter with lithium chloride (LiCl) decreased NICD expression in a dose-dependent manner; moreover, Hes-1 immunofluorescence was attenuated. Along with this, the protein expression level of p-GSK-3β and p-AKT protein expression was significantly increased. Furthermore, DAPT and LiCl decreased production of IL-1β, TNF-α, IL-6, iNOS, Cox2 and MCP-1; however, IL-10 expression was increased notably in LiCl treated cells. The effects of DAPT and LiCl on changes of the above-mentioned biomarkers were confirmed by immunofluorescence in both BV-2 and primary microglia. Additionally, NF-κB/p65 immunofluorescence was attenuated by DAPT and LiCl; as opposed to this, IκBα protein expression was increased. Taken together, it is suggested that Notch-1, NF-κB/p65 and GSK-3β operate in synergy to inhibit microglia activation. This may be effected via increased expression of phospho-GSK-3β (p-GSK-3β), phospho-protein kinase B (PKB) (p-AKT) and IκBα. It is concluded that the three signalling pathways are functionally interlinked in regulating microglia activation.

Potential involvement of glycogen synthase kinase (GSK)-3β in a rat model of multiple sclerosis: evidenced by lithium treatment

Glycogen synthase kinase (GSK)-3β has been known as a pro-inflammatory molecule in neuroinflammation. The involvement of GSK-3β remains unsolved in acute monophasic rat experimental autoimmune encephalomyelitis (EAE). The aim of this study was to evaluate a potential role of GSK-3β in central nervous system (CNS) autoimmunity through its inhibition by lithium. Lithium treatment significantly delayed the onset of EAE paralysis and ameliorated its severity. Lithium treatment reduced the serum level of pro-inflammatory tumor necrosis factor a but not that of interleukin 10. Western blot analysis showed that the phosphorylation of GSK-3β (p-GSK-3β) and its upstream factor Akt was significantly increased in the lithium-treated group. Immunohistochemical examination revealed that lithium treatment also suppressed the activation of ionized calcium binding protein-1-positive microglial cells and vascular cell adhesion molecule-1 expression in the spinal cords of lithium-treated EAE rats. These results demonstrate that lithium ameliorates clinical symptom of acute monophasic rat EAE, and GSK-3 is a target for the suppression of acute neuroinflammation as far as rat model of human CNS disease is involved.

Development of [18F]Maleimide-Based Glycogen Synthase Kinase-3β Ligands for Positron Emission Tomography Imaging

Dysregulation of glycogen synthase kinase-3β (GSK-3β) is implicated in the pathogenesis of neurodegenerative and psychiatric disorders. Thus, development of GSK-3β radiotracers for positron emission tomography (PET) imaging is of paramount importance, because such a noninvasive imaging technique would allow better understanding of the link between the activity of GSK-3β and central nervous system disorders in living organisms, and it would enable early detection of the enzyme's aberrant activity. Herein, we report the synthesis and biological evaluation of a series of fluorine-substituted maleimide derivatives that are high-affinity GSK-3β inhibitors. Radiosynthesis of a potential GSK-3β tracer [¹⁸F]10a is achieved. Preliminary in vivo PET imaging studies in rodents show moderate brain uptake, although no saturable binding was observed in the brain. Further refinement of the lead scaffold to develop potent [¹⁸F]-labeled GSK-3 radiotracers for PET imaging of the central nervous system is warranted.

Neuroprotective Effects of Exercise Treatments After Injury: The Dual Role of Neurotrophic Factors

BACKGROUND

Shared connections between physical activity and neuroprotection have been studied for decades, but the mechanisms underlying this effect of specific exercise were only recently brought to light. Several evidences suggest that physical activity may be a reasonable and beneficial method to improve functional recovery in both peripheral and central nerve injuries and to delay functional decay in neurodegenerative diseases. In addition to improving cardiac and immune functions, physical activity may represent a multifunctional approach not only to improve cardiocirculatory and immune functions, but potentially modulating trophic factors signaling and, in turn, neuronal function and structure at times that may be critical for neurodegeneration and regeneration.

METHODS

Research content related to the effects of physical activity and specific exercise programs in normal and injured nervous system have been reviewed.

RESULTS

Sustained exercise, particularly if applied at moderate intensity and early after injury, exerts anti-inflammatory and pro-regenerative effects, and may boost cognitive and motor functions in aging and neurological disorders. However, newest studies show that exercise modalities can differently affect the production and function of brain-derived neurotrophic factor and other neurotrophins involved in the generation of neuropathic conditions. These findings suggest the possibility that new exercise strategies can be directed to nerve injuries with therapeutical benefits.

CONCLUSION

Considering the growing burden of illness worldwide, understanding of how modulation of neurotrophic factors contributes to exercise-induced neuroprotection and regeneration after peripheral nerve and spinal cord injuries is a relevant topic for research, and represents the beginning of a new non-pharmacological therapeutic approach for better rehabilitation of neural disorders.

Age-related neuroinflammation and changes in AKT-GSK-3β and WNT/ β-CATENIN signaling in rat hippocampus

Aging is a multifactorial process associated with an increased susceptibility to neurodegenerative disorders which can be related to chronic inflammation. Chronic inflammation, however, can be characterized by the persistent elevated glucocorticoid (GCs) levels, activation of the proinflammatory transcription factor NF-кB, as well as an increase in cytokines. Interestingly, both NF-кB and cytokines can be even modulated by Glycogen Synthase Kinase 3 beta (GSK-3β) activity, which is a key protein that can intermediate inflammation and metabolism, once it has a critical role in AKT signaling pathway, and can also intermediate WNT/β-CATENIN signaling pathway. The aim of this study was to verify age-related changes in inflammatory status, as well as in the AKT and WNT signaling pathways. Results showed an age-related increase in neuroinflammation as indicated by NF-кB activation, TNF-α and GCs increased levels, a decrease in AKT activation and an increase in GSK-3β activity in both 12- and 24- month old animals. Aging also seems to induce a progressive decrease in canonical WNT/β-CATENIN signaling pathway once there is a decrease in DVL-2 levels and in the transcription of Axin2 gene. Little is known about the DVL-2 regulation as well as its roles in WNT signaling pathway, but for the first time it was suggested that DVL-2 expression can be changed along aging.

The glucagon-like peptide-1 receptor agonist exendin-4 ameliorates warfarin-associated hemorrhagic transformation after cerebral ischemia

Background

As the number of patients with cardioembolic ischemic stroke is predicted to be double by 2030, increased burden of warfarin-associated hemorrhagic transformation (HT) after cerebral ischemia is an expected consequence. However, thus far, no effective treatment strategy is available for HT prevention in routine clinical practice. While the glucagon-like peptide-1 receptor (GLP-1R) agonist exendin-4 (Ex-4) is known to protect against oxidative stress and neuronal cell death caused by ischemic brain damage, its effect on preventing warfarin-associated HT after cerebral ischemia is yet unknown. Therefore, we hypothesized that Ex-4 would stabilize the blood-brain barrier (BBB) and suppress neuroinflammation through PI3K-Akt-induced inhibition of glycogen synthase kinase-3β (GSK-3β) after warfarin-associated HT post-cerebral ischemia.

Methods

We used male C57BL/6 mice for all experiments. A 5-mg warfarin sodium tablet was dissolved in animals’ drinking water (effective warfarin uptake 0.04 mg (2 mg/kg) per mouse). The mice were fed for 0, 6, 12, and 24 h with ad libitum access to the treated water. To study the effects of Ex-4, temporary middle cerebral artery occlusion (MCAO) was performed. Then, either Ex-4 (10 mg/kg) or saline was injected through the tail vein, and in the Ex-4 + wortmannin group, PI3K inhibitor wortmannin was intravenously injected, after reperfusion. The infarct volume, neurological deficits, and integrity of the BBB were assessed 72 h post MCAO. One- or two-way ANOVA was used to test the difference between means followed by Newman–Keuls post hoc testing for pair-wise comparison.

Results

We observed that Ex-4 ameliorated warfarin-associated HT and preserved the integrity of the BBB after cerebral ischemia through the PI3K/Akt/GSK-3β pathway. Furthermore, Ex-4 suppressed oxidative DNA damage and lipid peroxidation, attenuated pro-inflammatory cytokine expression levels, and suppressed microglial activation and neutrophil infiltration in warfarin-associated HT post-cerebral ischemia. However, these effects were totally abolished in the mice treated with Ex-4 + the PI3K inhibitor—wortmannin. The PI3K/Akt-GSK-3β signaling pathway appeared to contribute to the protection afforded by Ex-4 in the warfarin-associated HT model.

Conclusions

GLP-1 administration could reduce warfarin-associated HT in mice. This beneficial effect of GLP-1 is associated with attenuating neuroinflammation and BBB disruption by inactivating GSK-3β through the PI3K/Akt pathway.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0661-0) contains supplementary material, which is available to authorized users.

Isoflurane Is More Deleterious to Developing Brain Than Desflurane: The Role of the Akt/GSK3β Signaling Pathway

Demand is increasing for safer inhalational anesthetics for use in pediatric anesthesia. In this regard, researchers have debated whether isoflurane is more toxic to the developing brain than desflurane. In the present study, we compared the effects of postnatal exposure to isoflurane with those of desflurane on long-term cognitive performance and investigated the role of the Akt/GSK3β signaling pathway. Postnatal day 6 (P6) mice were exposed to either isoflurane or desflurane, after which the phosphorylation levels of Akt/GSK3β and learning and memory were assessed at P8 or P31. The phosphorylation levels of Akt/GSK3β and learning and memory were examined after intervention with lithium. We found that isoflurane, but not desflurane, impaired spatial learning and memory at P31. Accompanied by behavioral change, only isoflurane decreased p-Akt (ser473) and p-GSK3β (ser9) expressions, which led to GSK3β overactivation. Lithium prevented GSK3β overactivation and alleviated isoflurane-induced cognitive deficits. These results suggest that isoflurane is more likely to induce developmental neurotoxicity than desflurane in context of multiple exposures and that the Akt/GSK3β signaling pathway partly participates in this process. GSK3β inhibition might be an effective way to protect against developmental neurotoxicity.

GSK3β inhibition protects the immature brain from hypoxic-ischaemic insult via reduced STAT3 signalling

Hypoxic-ischaemic (HI) injury is an important cause of neurological morbidity in neonates. HI leads to pathophysiological responses, including inflammation and oxidative stress that culminate in cell death. Activation of glycogen synthase kinase 3β (GSK3β) and the signal transducer and activator of transcription (STAT3) promotes brain inflammation. The purpose of this study was to test whether inhibition of GSK3β signalling protects against neonatal HI brain injury. Mice were subjected to HI at postnatal day (PND) 9 and treated with a selective GSK3β inhibitor, SB216763. Brain injury and caspase-3 activation, anti-oxidant and inflammatory mRNA responses and activation of STAT3 were analysed. Our results show that HI reduced phosphorylation of GSK3β, thus promoting its kinase activity. The GSK3β inhibitor reduced caspase-3 activation and neuronal cell death elicited by HI and reverted the effects of HI on gene expression of the anti-oxidant enzyme sod2 and mitochondrial factor pgc1α. The HI insult activated STAT3 in glial cells and GSK3β inhibition attenuated STAT3 phosphorylation and its nuclear translocation following HI. Further, GSK3β inhibition reduced HI-induced gene expression of pro-inflammatory cytokines tnfα and Il-6, while promoted the anti-inflammatory factor Il-10. In summary, data show that GSK3β inhibition is neuroprotective in neonatal HI brain injury likely via reduced pro-inflammatory responses by blocking STAT3 signalling. Our study suggests that pharmacological interventions built upon GSK3β silencing strategies could represent a novel therapy in neonatal brain injury.

Adenosine Monophosphate-activated Protein Kinase Regulates Interleukin-1β Expression and Glial Glutamate Transporter Function in Rodents with Neuropathic Pain

BACKGROUND

Neuroinflammation and dysfunctional glial glutamate transporters (GTs) in the spinal dorsal horn are implicated in the genesis of neuropathic pain. The authors determined whether adenosine monophosphate-activated protein kinase (AMPK) in the spinal dorsal horn regulates these processes in rodents with neuropathic pain.

METHODS

Hind paw withdrawal responses to radiant heat and mechanical stimuli were used to assess nociceptive behaviors. Spinal markers related to neuroinflammation and glial GTs were determined by Western blotting. AMPK activities were manipulated pharmacologically and genetically. Regulation of glial GTs was determined by measuring protein expression and activities of glial GTs.

RESULTS

AMPK activities were reduced in the spinal dorsal horn of rats (n = 5) with thermal hyperalgesia induced by nerve injury, which were accompanied with the activation of astrocytes, increased production of interleukin-1β and activities of glycogen synthase kinase 3β, and suppressed protein expression of glial glutamate transporter-1. Thermal hyperalgesia was reversed by spinal activation of AMPK in neuropathic rats (n = 10) and induced by inhibiting spinal AMPK in naive rats (n = 7 to 8). Spinal AMPKα knockdown (n = 6) and AMPKα1 conditional knockout (n = 6) induced thermal hyperalgesia and mechanical allodynia. These genetic alterations mimicked the changes of molecular markers induced by nerve injury. Pharmacological activation of AMPK enhanced glial GT activity in mice with neuropathic pain (n = 8) and attenuated glial glutamate transporter-1 internalization induced by interleukin-1β (n = 4).

CONCLUSIONS

These findings suggest that enhancing spinal AMPK activities could be an effective approach for the treatment of neuropathic pain.

Synthesis and Initial in Vivo Studies with [(11)C]SB-216763: The First Radiolabeled Brain Penetrative Inhibitor of GSK-3

Quantifying glycogen synthase kinase-3 (GSK-3) activity in vivo using positron emission tomography (PET) imaging is of interest because dysregulation of GSK-3 is implicated in numerous diseases and neurological disorders for which GSK-3 inhibitors are being considered as therapeutic strategies. Previous PET radiotracers for GSK-3 have been reported, but none of the published examples cross the blood-brain barrier. Therefore, we have an ongoing interest in developing a brain penetrating radiotracer for GSK-3. To this end, we were interested in synthesis and preclinical evaluation of [(11)C]SB-216763, a high-affinity inhibitor of GSK-3 (K i = 9 nM; IC50 = 34 nM). Initial radiosyntheses of [(11)C]SB-216763 proved ineffective in our hands because of competing [3 + 3] sigmatropic shifts. Therefore, we have developed a novel one-pot two-step synthesis of [(11)C]SB-216763 from a 2,4-dimethoxybenzyl-protected maleimide precursor, which provided high specific activity [(11)C]SB-216763 in 1% noncorrected radiochemical yield (based upon [(11)C]CH3I) and 97-100% radiochemical purity (n = 7). Initial preclinical evaluation in rodent and nonhuman primate PET imaging studies revealed high initial brain uptake (peak rodent SUV = 2.5 @ 3 min postinjection; peak nonhuman primate SUV = 1.9 @ 5 min postinjection) followed by washout. Brain uptake was highest in thalamus, striatum, cortex, and cerebellum, areas known to be rich in GSK-3. These results make the arylindolemaleimide skeleton our lead scaffold for developing a PET radiotracer for quantification of GSK-3 density in vivo and ultimately translating it into clinical use.

Synthesis and evaluation of [(11)C]PyrATP-1, a novel radiotracer for PET imaging of glycogen synthase kinase-3β (GSK-3β)

INTRODUCTION

The dysfunction of glycogen synthase kinase-3β (GSK-3β) has been implicated in a number of diseases, including Alzheimer's disease. The ability to non-invasively quantify GSK-3β activity in vivo is therefore of critical importance, and this work is focused upon development of inhibitors of GSK-3β radiolabeled with carbon-11 to examine quantification of the enzyme using positron emission tomography (PET) imaging.

METHODS

(11)C PyrATP-1 was prepared from the corresponding desmethyl-piperazine precursor in an automated synthesis module. In vivo rodent and primate imaging studies were conducted on a Concorde MicroPET P4 scanner to evaluate imaging properties and in vitro autoradiography studies with rat brain samples were carried out to examine specific binding.

RESULTS

2035±518MBq (55±14mCi) of [(11)C]PyrATP-1 was obtained (1%-2% non-corrected radiochemical yield at end-of-synthesis based upon [(11)C]CO2) with high chemical (>95%) and radiochemical (>99%) purities, and good specific activities (143±52GBq/μmol (3874±1424Ci/mmol)), n=5. In vivo microPET imaging studies revealed poor brain uptake in rodents and non-human primates. Pretreatment of rodents with cyclosporin A resulted in moderately increased brain uptake suggesting Pgp transporter involvement. Autoradiography demonstrated high levels of specific binding in areas of the rodent brain known to be rich in GSK-3β.

CONCLUSION

(11)C PyrATP-1 is readily synthesized using standard carbon-11 radiochemistry. However the poor brain uptake in rodents and non-human primates indicates that the radiotracer is not suitable for the purposes of quantifying GSK-3β in neurological and psychiatric disorders.

Benefits of exercise intervention in reducing neuropathic pain

Peripheral neuropathy is a widespread and potentially incapacitating pathological condition that encompasses more than 100 different forms and manifestations of nerve damage. The diverse pathogenesis of peripheral neuropathy affects autonomic, motor and/or sensory neurons, and the symptoms that typify the condition are abnormal cutaneous sensation, muscle dysfunction and, most notably, chronic pain. Chronic neuropathic pain is difficult to treat and is often characterized by either exaggerated responses to painful stimuli (hyperalgesia) or pain resulting from stimuli that would not normally provoke pain (allodynia). The objective of this review is to provide an overview of some pathways associated with the development of peripheral neuropathy and then discuss the benefits of exercise interventions. The development of neuropathic pain is a highly complex and multifactorial process, but recent evidence indicates that the activation of spinal glial cells via the enzyme glycogen synthase kinase 3 and increases in the production of both pro-inflammatory cytokines and brain derived neurotropic factor are crucial steps. Since many of the most common causes of peripheral neuropathy cannot be fully treated, it is critical to understand that routine exercise may not only help prevent some of those causes, but that it has also proven to be an effective means of alleviating some of the condition’s most distressing symptoms. More research is required to elucidate the typical mechanisms of injury associated with peripheral neuropathy and the exercise-induced benefits to those mechanisms.