Dendritic and mitochondrial changes during glutamate excitotoxicity

Purkinje Cell Dendritic Swellings: A Postmortem Study of Essential Tremor and Other Cerebellar Degenerative Disorders

Under stress, Purkinje cells (PCs) undergo a variety of reactive morphological changes. These can include swellings of neuronal processes. While axonal swellings, "torpedoes", have been well-studied, dendritic swellings (DS) have not been the centerpiece of study. Surprisingly little is known about their frequency or relationship to other morphological changes in degenerating PCs. Leveraging a large brain bank, we (1) examined the morphology of DS, (2) quantified DS, and (2) examined correlations between counts of DS versus 16 other PC morphological changes in a broad range of cerebellar degenerative disorders. There were 159 brains - 100 essential tremor (ET), 13 Friedreich's ataxia, and 46 spinocerebellar ataxia (SCA) (14 SCA1, 7 SCA2, 13 SCA3, 5 SCA6, 5 SCA7, and 2 SCA8). DS were a feature of PCs across all these disorders, with varying morphologies and changes elsewhere in the dendritic arbor. On Luxol fast blue/hematoxylin and eosin-stained sections, the median number of DS per PC ranged from 0.001 in ET to 0.025 in SCA8. Bielschowsky-stained sections yielded higher counts, from 0.003 in ET to 0.042 in SCA6. Torpedo counts exceeded DS counts by one order of magnitude. DS counts were more robustly correlated with torpedo counts than with counts for any of the other PC morphological changes. In summary, DS ranged in prevalence across cerebellar degenerative disorders, from 1/1,000 to 42/1,000 PCs. Across disorders of cerebellar degeneration, these swellings of the dendritic compartment were most robustly correlated with swellings of the axonal compartment, suggesting a similar type of cellular response to duress.

Norlignans and Phenolics from Curculigo capitulata and Their Neuroprotection Against Glutamate-Induced Oxidative Injury in SH-SY5Y Cells

The herb Curculigo capitulata (Lour.) Ktze is widely distributed in southern and southwestern China. The Curculigo genus and its primary chemical constituents exhibit remarkable antidepressant activities. To investigate the chemical constituents and potential health benefits of C. capitulata, a phytochemical study was conducted. In this study, seven new compounds (capitugenin A-G), including three new norlignans (1-3), a new chalcone dimer (4), a new hemiacetal (5), two novel pyrrolidine-based compounds (6 and 7), including one identified as a natural product (7), and nineteen known compounds (8-26), were isolated from C. capitulata. The chemical structures and absolute configurations of Compounds 1-7 were elucidated via comprehensive spectroscopic data analyses. The neuroprotective effects of Compounds 1-26 against glutamate-induced cell death were tested in the human neuroblastoma cell line SH-SY5Y. Compounds 1, 3, 6, 8, 11, and 17 showed significant neuroprotective effects, with protection rates ranging from 29.4 to 52.8% at concentrations ranging from 5 to 40 μM. Western blot analysis indicated that Compound 3 exerted a protective effect by regulating the expression of Nrf2/HO-1.

Methylphenidate Exposing During Neurodevelopment Alters Amino Acid Profile, Astrocyte Marker and Glutamatergic Excitotoxicity in the Rat Striatum

There is a public health concern about the use of methylphenidate (MPH) since the higher prescription for young individuals and non-clinical purposes is addressed to the limited understanding of its neurochemical and psychiatric consequences. This study aimed to evaluate the impact of early and chronic MPH treatment on the striatum focusing on amino acid profile, glutamatergic excitotoxicity, redox status, neuroinflammation and glial cell responses. Male Wistar rats were treated with MPH (2.0 mg/kg) or saline solution from the 15th to the 44th postnatal day. Biochemical and histological analyses were conducted after the last administration. MPH altered the amino acid profile in the striatum, increasing glutamate and ornithine levels, while decreasing the levels of serine, phenylalanine, and branched-chain amino acids (leucine, valine, and isoleucine). Glutamate uptake and Na+,K+-ATPase activity were decreased in the striatum of MPH-treated rats as well as increased ATP levels, as indicator of glutamatergic excitotoxicity. Moreover, MPH caused lipid peroxidation and nitrative stress, increased TNF alpha expression, and induced high levels of astrocytes, and led to a decrease in BDNF levels. In summary, our results suggest that chronic early-age treatment with MPH induces parallel activation of damage-associated pathways in the striatum and increases its vulnerability during the juvenile period. In addition, data presented here contribute to shedding light on the mechanisms underlying MPH-induced striatal damage and its potential implications for neurodevelopmental disorders.

GC/MS-Based Metabolomic Analysis of A549 Cells Exposed to Emerging Organophosphate Flame Retardants

Emerging organophosphate flame retardants (eOPFRs) have attracted attention in recent times and are expected to gain extensive usage in the coming years. However, they may have adverse effects on organisms. Due to their novel nature, there are few relevant articles dealing with toxicological studies of the above eOPFRs, especially their information on the perturbation of cellular metabolism, which is, thus far, marginally understood. Our research initially assessed the cytotoxicity of eOPFRs, which include compounds like cresyl diphenyl phosphate (CDP), resorcinol bis(diphenyl phosphate) (RDP), triallyl phosphate (TAP), and pentaerythritol phosphate alcohol (PEPA). This evaluation was conducted using the methyl thiazolyl tetrazolium (MTT) assay. Subsequently, we utilized a gas chromatography/mass spectrometry (GC/MS)-based metabolomic approach to investigate the metabolic disruptions induced by these four eOPFRs in A549 cells. The MTT results showed that, at high concentrations of 1 mM, their cytotoxicity was ranked as CDP > TAP > RDP > PEPA. In addition, metabolic studies at low concentrations of 10 μM showed that the metabolic interference of CDP, TAP, and PEPA focuses on oxidative stress, amino acid metabolism, and energy metabolism, while RDP mainly affects energy metabolism-galactose metabolism and gluconeogenesis. Therefore, from the perspective of cytotoxicity and metabolic analysis, RDP may be a more promising alternative. Our experiments provide important insights into the possible metabolic effects of potential toxic substances and complement the evidence on the human health risks of eOPFRs.

Microglia in Ischemic Stroke: Pathogenesis Insights and Therapeutic Challenges

Ischemic stroke is the most common type of stroke, which is the main cause of death and disability on a global scale. As the primary immune cells in the brain that are crucial for preserving homeostasis of the central nervous system microenvironment, microglia have been found to exhibit dual or even multiple effects at different stages of ischemic stroke. The anti-inflammatory polarization of microglia and release of neurotrophic factors may provide benefits by promoting neurological recovery at the lesion in the early phase after ischemic stroke. However, the pro-inflammatory polarization of microglia and secretion of inflammatory factors in the later phase of injury may exacerbate the ischemic lesion, suggesting the therapeutic potential of modulating the balance of microglial polarization to predispose them to anti-inflammatory transformation in ischemic stroke. Microglia-mediated signaling crosstalk with other cells may also be key to improving functional outcomes following ischemic stroke. Thus, this review provides an overview of microglial functions and responses under physiological and ischemic stroke conditions, including microglial activation, polarization, and interactions with other cells. We focus on approaches that promote anti-inflammatory polarization of microglia, inhibit microglial activation, and enhance beneficial cell-to-cell interactions. These targets may hold promise for the creation of innovative therapeutic strategies.

Microglia-neuron interactions in prefrontal gray matter in schizophrenia: a postmortem ultrastructural morphometric study

This study addressed the question of whether the interaction between neurons and satellite microglia (SatMg) is abnormal in schizophrenia. SatMg-neuron communication at direct contacts between neuronal soma is essential for neuroplasticity as SatMg can regulate neuronal activity. A postmortem ultrastructural morphometric study was performed to investigate SatMg and adjacent neurons in layer 5 of the prefrontal cortex in 21 cases of schizophrenia and 20 healthy controls. Density of SatMg was significantly higher in the young schizophrenia group and in the group with illness duration ≤ 26 years as compared to controls. We found lower volume fraction (Vv) and the number (N) of mitochondria and higher Vv and N of lipofuscin granules and vacuoles in endoplasmic reticulum in SatMg in the schizophrenia compared to the control brain. These changes progressed with age and illness duration. A significantly higher soma area and Vv of vacuoles of endoplasmic reticulum were revealed in neurons in schizophrenia as compared to controls. Negative significant correlations between N of vacuoles in neurons and N of mitochondria in SatMg were found in the control group but not in the schizophrenia group. Area of vacuole in neurons was significantly positively correlated with Vv and area of mitochondria in SatMg in the control group and negatively in the schizophrenia group. Correlation coefficients between these parameters differed significantly between the groups. These results indicate disturbed SatMg-neuron interactions in the schizophrenia brain and suggest a key role of mitochondrial abnormalities in SatMg in these disturbances.

Polyherbal and Multimodal Treatments: Kaempferol- and Quercetin-Rich Herbs Alleviate Symptoms of Alzheimer's Disease

Alzheimer's Disease (AD) is a progressive neurodegenerative disorder impairing cognition and memory in the elderly. This disorder has a complex etiology, including senile plaque and neurofibrillary tangle formation, neuroinflammation, oxidative stress, and damaged neuroplasticity. Current treatment options are limited, so alternative treatments such as herbal medicine could suppress symptoms while slowing cognitive decline. We followed PRISMA guidelines to identify potential herbal treatments, their associated medicinal phytochemicals, and the potential mechanisms of these treatments. Common herbs, including Ginkgo biloba, Camellia sinensis, Glycyrrhiza uralensis, Cyperus rotundus, and Buplerum falcatum, produced promising pre-clinical results. These herbs are rich in kaempferol and quercetin, flavonoids with a polyphenolic structure that facilitate multiple mechanisms of action. These mechanisms include the inhibition of Aβ plaque formation, a reduction in tau hyperphosphorylation, the suppression of oxidative stress, and the modulation of BDNF and PI3K/AKT pathways. Using pre-clinical findings from quercetin research and the comparatively limited data on kaempferol, we proposed that kaempferol ameliorates the neuroinflammatory state, maintains proper cellular function, and restores pro-neuroplastic signaling. In this review, we discuss the anti-AD mechanisms of quercetin and kaempferol and their limitations, and we suggest a potential alternative treatment for AD. Our findings lead us to conclude that a polyherbal kaempferol- and quercetin-rich cocktail could treat AD-related brain damage.

Multiple mechanisms of curcumin targeting spinal cord injury

Spinal cord injury (SCI) is an irreversible disease process with a high disability and mortality rate. After primary spinal cord injury, the secondary injury may occur in sequence, which is composed of ischemia and hypoxia, excitotoxicity, calcium overload, oxidative stress and inflammation, resulting in massive death of parenchymal cells in the injured area, followed by the formation of syringomyelia. Effectively curbing the process of secondary injury can promote nerve repair and improve functional prognosis. As the main active ingredient in turmeric, curcumin can play an important role in reducing inflammation and oxidation, protecting the neurons, and ultimately reducing spinal cord injury. This article reviews the effects of curcumin on the repair of nerve injury, with emphasis on the various mechanisms by which curcumin promotes the treatment of spinal cord injury.

Isoliquiritigenin Protects Neuronal Cells against Glutamate Excitotoxicity

It is considered that glutamate excitotoxicity may be a major factor in the pathological death of neurons and mediate the development of neurodegenerative diseases in humans. Here, we show that isoliquiritigenin (ILG) at a concentration of 0.5-5 µM protects primary neuroglial cell culture from glutamate-induced death (glutamate 100 µM). ILG (1 µM) prevented a sharp increase in [Ca²⁺]_i and a decrease in mitochondrial potential (ΔΨm). With the background action of ILG (1-5 µM), there was an increase in oxygen consumption rate (OCR) in response to glutamate, as well as in reserve respiration. The neuroprotective effect of ILG (5 µM) was accompanied by an increase in non-mitochondrial respiration. The results show that ILG can protect cortical neurons from death by preventing the development of calcium deregulation and limiting mitochondrial dysfunction caused by a high dose of glutamate. We hypothesize that ILG will be useful in drug development for the prevention or treatment of neurodegenerative diseases accompanied by glutamate excitotoxicity.

Unilateral cerebral ischemia induces morphological changes in the layer V projection neurons of the contralateral hemisphere

Decreased blood flow to the brain causes stroke and damage to neuronal networks. Neuronal damage occurs not only in the infarct core but also in areas away from the infarcts. This study was aimed to assess alterations of the cortical projection neurons that were distantly connected with the infarcts. Unilateral cortical ischemia was generated by middle cerebral artery occlusion in the right somatosensory cortex. Pre-labeled thalamocortical neurons disappeared, whereas contralateral callosal projection neurons survived 48 h post-ischemia. The unilateral ischemia increased the total length, segment length and the spine volume of dendrites from layer V callosal neurons in the homotopic cortex of the contralateral hemisphere. The morphological remolding of the contralateral cortical neurons cannot be reproduced by the spinal cord hemisection that cuts axons of corticospinal projection neurons of layer V. The data suggest that the retrograde degeneration of axons may not account for the early morphological changes in the contralateral cortex. We hypothesize that the loss of innervations from the ischemic cortex may bring in adaptive changes to the connected neurons, and adult cortical neurons can adjust their morphology to meet the reduction of synaptic inputs. This study may improve our understanding of the re-organization of cortical circuits following focal cerebral ischemia and help the development of new treatments designed to minimize the disability associated with stroke.

Dissecting the neurobiology of linguistic disorganisation and impoverishment in schizophrenia

Schizophrenia provides a quintessential disease model of how disturbances in the molecular mechanisms of neurodevelopment lead to disruptions in the emergence of cognition. The central and often persistent feature of this illness is the disorganisation and impoverishment of language and related expressive behaviours. Though clinically more prominent, the periodic perceptual distortions characterised as psychosis are non-specific and often episodic. While several insights into psychosis have been gained based on study of the dopaminergic system, the mechanistic basis of linguistic disorganisation and impoverishment is still elusive. Key findings from cellular to systems-level studies highlight the role of ubiquitous, inhibitory processes in language production. Dysregulation of these processes at critical time periods, in key brain areas, provides a surprisingly parsimonious account of linguistic disorganisation and impoverishment in schizophrenia. This review links the notion of excitatory/inhibitory (E/I) imbalance at cortical microcircuits to the expression of language behaviour characteristic of schizophrenia, through the building blocks of neurochemistry, neurophysiology, and neurocognition.

Emerging role of glutamate in the pathophysiology and therapeutics of Gulf War illness

Gulf War illness (GWI) is a chronic and multi-symptomatic disorder affecting veterans who served in the Gulf War. The commonly reported symptoms in GWI veterans include mood problems, cognitive impairment, muscle and joint pain, migraine/headache, chronic fatigue, gastrointestinal complaints, skin rashes, and respiratory problems. Neuroimaging studies have revealed significant brain structure alterations in GWI veterans, including subcortical atrophy, decreased volume of the hippocampus, reduced total grey and white matter, and increased brain white matter axial diffusivity. These brain changes may contribute to or increase the severities of the GWI-related symptoms. Epidemiological studies have revealed that neurotoxic exposures and stress may be significant contributors to the development of GWI. However, the mechanism underlying how the exposure and stress could contribute to the multi-symptomatic disorder of GWI remains unclear. We and others have demonstrated that rodent models exposed to GW-related agents and stress exhibited higher extracellular glutamate levels, as well as impaired structure and function of glutamatergic synapses. Restoration of the glutamatergic synapses ameliorated the GWI-related pathological and behavioral deficits. Moreover, recent studies showed that a low-glutamate diet reduced multiple symptoms in GWI veterans, suggesting an important role of the glutamatergic system in GWI. Currently, growing evidence has indicated that abnormal glutamate neurotransmission may contribute to the GWI symptoms. This review summarizes the potential roles of glutamate dyshomeostasis and dysfunction of the glutamatergic system in linking the initial cause to the multi-symptomatic outcomes in GWI and suggests the glutamatergic system as a therapeutic target for GWI.

Neuroprotective Effect of Gallocatechin Gallate on Glutamate-Induced Oxidative Stress in Hippocampal HT22 Cells

Oxidative stress leads to protein degeneration or mitochondrial dysfunction, causing neuronal cell death. Glutamate is a neurotransmitter that nerve cells use to send signals. However, the excess accumulation of glutamate can cause excitotoxicity in the central nervous system. In this study, we deciphered the molecular mechanism of catechin-mediated neuroprotective effect on glutamate-induced oxidative stress in mouse hippocampal neuronal HT22 cells. Cellular antioxidant activity was determined using the 1,1-diphenyl-picryl hydrazyl (DPPH) assay and 2',7'-dichlorodihydrofluorescein diacetate (DCFDA) staining. Furthermore, the levels of intracellular calcium (Ca²⁺) as well as nuclear condensation and protein expression related to neuronal damage were assessed. All five catechins (epigallocatechin gallate, gallocatechin gallate (GCG), gallocatechin, epicatechin gallate, and epicatechin) showed strong antioxidant effects. Among them, GCG exhibited the highest neuroprotective effect against glutamate excitotoxicity and was used for further mechanistic studies. The glutamate-induced increase in intracellular Ca²⁺ was reduced after GCG treatment. Moreover, GCG reduced nuclear condensation and the phosphorylation of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinases (JNK) involved in cell death. The neuroprotective effect of GCG against glutamate-induced oxidative stress in HT22 cells was attributed to the reduction in intracellular free radicals and Ca²⁺ influx and also the inhibition of phosphorylation of ERK and JNK. Furthermore, the antioxidant effect of GCG was found to be likely due to the inhibition of phosphorylation of ERK and JNK that led to the effective suppression of neurocytotoxicity caused by glutamate in HT22 cells.

A Dendrite-Focused Framework for Understanding the Actions of Ketamine and Psychedelics

Pilot studies have hinted that serotonergic psychedelics such as psilocybin may relieve depression, and could possibly do so by promoting neural plasticity. Intriguingly, another psychotomimetic compound, ketamine, is a fast-acting antidepressant and induces synapse formation. The similarities in behavioral and neural effects have been puzzling because the compounds target distinct molecular receptors in the brain. In this opinion article, we develop a conceptual framework that suggests the actions of ketamine and serotonergic psychedelics may converge at the dendrites, to both enhance and suppress membrane excitability. We speculate that mismatches in the opposing actions on dendritic excitability may relate to these compounds' cell-type and region selectivity, their moderate range of effects and toxicity, and their plasticity-promoting capacities.

Neuroprotective effects of natural compounds on neurotoxin-induced oxidative stress and cell apoptosis

OBJECTIVES

Overproduction of reactive species, notably reactive oxygen (ROS) and nitrogen (RNS) species, along with the failure of balancing effects of endogenous antioxidant defenses result in destruction of cellular structures, lipids, proteins, and genetic material, which lead to oxidative stress. Oxidative stress-induced neuronal apoptosis plays a pivotal role in pathogenesis of neurodegeneration. Antioxidants represent one of the medical choice strategies for protecting against this unbalanced oxidation-antioxidation status. Recently, natural compounds with neuroprotective potential that can scavenge free radicals and protect cells from oxidative damage have received extensive attention.

METHODS

In this review, we summarized the detailed research progress on the medicinal plants-derived natural compounds with potential anti-oxidation effects and their molecular mechanisms on modulating the neurotoxin (6-OHDA, H₂O₂, glutamate, Aβ)-induced oxidative stress and cell apoptosis.

RESULTS

The natural compounds that efficacious in modulating reactive species production and mitochondrial function include flavonoids, glucosides, alkaloids, polyphenols, lignans, coumarins, terpenoids, quinones and others. They decreased the neurotoxin-induced oxidative damage and apoptosis by (1) decreasing ROS/RNS generation, lipid peroxidation, caspase-3 and caspase-9 activities, LDH release, the ratio of Bax/Bcl-2, Ca²⁺ influx and cytochrome c release, (2) elevating MMP, and (3) restoring endogenous antioxidant enzymatic activities (CAT, GSH-Px, GSR, SOD). And they exerted neuroprotective effects against cell damages and apoptosis by modulating the oxidative cascades of different signaling pathways (Nrf2/HO-1, NF-κB, MAPKs, PI3K/Akt, GSK-3β) and preventing mitochondria-dependent apoptosis pathways.

DISCUSSION

The present work reviews the role of oxidative stress in neurodegeneration, highlighting the potential anti-oxidation effects of natural compounds as a promising approach to develop innovative neuroprotective strategy.

CDK5 Targeting as a Therapy for Recovering Neurovascular Unit Integrity in Alzheimer's Disease

The neurovascular unit (NVU) is responsible for synchronizing the energetic demand, vasodynamic changes, and neurochemical and electrical function of the brain through a closed and interdependent interaction of cell components conforming to brain tissue. In this review, we will focus on cyclin-dependent kinase 5 (CDK5) as a molecular pivot, which plays a crucial role in the healthy function of neurons, astrocytes, and the endothelium and is implicated in the cross-talk of cellular adhesion signaling, ion transmission, and cytoskeletal remodeling, thus allowing the individual and interconnected homeostasis of cerebral parenchyma. Then, we discuss how CDK5 overactivation affects the integrity of the NVU in Alzheimer's disease (AD) and cognitive impairment; we emphasize how CDK5 is involved in the excitotoxicity spreading of glutamate and Ca2+ imbalance under acute and chronic injury. Additionally, we present pharmacological and gene therapy strategies for producing partial depletion of CDK5 activity on neurons, astrocytes, or endothelium to recover neuroplasticity and neurotransmission, suggesting that the NVU should be the targeted tissue unit in protective strategies. Finally, we conclude that CDK5 could be effective due to its intervention on astrocytes by its end feet on the endothelium and neurons, acting as an intermediary cell between systemic and central communication in the brain. This review provides integrated guidance regarding the pathogenesis of and potential repair strategies for AD.

Neuroprotective Effects of Triterpenoids from Camellia japonica against Amyloid β-Induced Neuronal Damage

Alzheimer's disease (AD), a neurocognitive impairment affecting human mental capacity, is related to the accumulation of amyloid-β peptide (Aβ) and the hyperphosphorylation of tau protein. In addition to modern therapies approved for AD treatment, natural products with antioxidant and anti-inflammatory properties have been studied for their potential to prevent AD pathogenesis. Six new noroleanane triterpenoids from the fruit peels of Camellia japonica were isolated, and their structures were determined by diverse spectroscopic methods. The neuroprotective effects of the six new compounds were tested against Aβ-induced neurotoxicity and neuroinflammation in mouse hippocampal and microglial cells. In the model of HT22-transfected cells, compounds 1-4 showed strongly neuroprotective effects via antioxidant response element gene activation and decreased the level of glutamate uptake. Compounds 1-4 also appeared to have strong inhibitory effects on NO production in Aβ_1-42-transfected BV2 microglial cells. A docking simulation study was used to explain the inhibitory effects of compounds 1-4 on β-secretase 1 (BACE1). Noroleanane triterpenoids 1-4 had potential neuroprotective and anti-inflammatory effects against Aβ-induced neuronal damage. The structure-activity relationships of the 30 oleanane triterpenoids from C. japonica were assessed in a model of Aβ_1-42-transfected HT22 cells.

Neuroprotective Activity of Methanolic Extract of Lysimachia christinae against Glutamate Toxicity in HT22 Cell and Its Protective Mechanisms

Purpose

Excessive glutamate amount can give oxidative stress to neuronal cells, and the accumulation of cell death can trigger the neurodegenerative disorders. In this study, we discovered the neuroprotective effect of Lysimachia christinae Hance in the mouse hippocampal HT22 cell line.

Method

Overnight incubated HT22 cells were pretreated with L. christinae extract dose dependently (1, 10, and 100 μg/ml). Followed by then, glutamate was treated. These treated cells were incubated several times again, and cell viability, accumulation of reactive oxygen species (ROS) and Ca²⁺, mitochondrial membrane potential (MMP), and glutathione-related enzyme amount were measured.

Results

As a result, L. christinae increases the cell viability by inhibiting the ROS and Ca²⁺ formation, recovering the level of MMP and enhancing the activity of glutathione production compared with only vehicle-treated groups.

Conclusion

These draw that L. christinae may remarkably decelerate the neurodegeneration by minimizing neuronal cell damage via oxidative stress.

Cerebrospinal Fluid Neurofilament Light Chain Is Associated with Kynurenine Pathway Metabolite Changes in Multiple Sclerosis

Neurofilament light (NFL) has proved to be a good prognostic factor in multiple sclerosis (MS), as its level is proportionally elevated with extended neuraxonal damage. The involvement of the kynurenine pathway in neuroinflammation has been proved. The precursor of this pathway is the essential amino acid tryptophan, which is catabolized 95% towards kynurenine metabolites. Quinolinic acid (QUIN) within the brain is only produced in activated microglia and macrophages, leading to axonal degeneration via the activation of N-Methyl-D-aspartate receptors. Neopterin is a biomarker for inflammation produced by macrophages. The association of these biomarkers has not previously been investigated. Our aim was to assess whether there is an association of the neurodegenerative biomarker NFL with the markers of neuroinflammation, e.g., kynurenine metabolites and neopterin, in the cerebrospinal fluid (CSF). CSF samples of patients with MS (pwMS; n = 37) and age-matched controls (n = 22) were compared for NFL levels by ELISA, while the kynurenine pathway metabolites tryptophan and neopterin were detected with mass spectrometry. Spearman’s correlation showed that NFL is an independent predictor of neurological disability in the MS group. Significant correlations were found between NFL, neopterin, and QUIN, and between kynurenine and neopterin. Receiver operating characteristic (ROC) curve analysis was used to plot the top three best predictors of MS-related disability that yielded the best specificity and sensitivity. Normalized NFL (AUC: 0.923), QUIN (AUC: 0.803), and neopterin (AUC: 0.843) were the best independent predictors of neurological disability in pwMS. The CSF NFL and CSF QUIN, together with neopterin, were elevated in the CSF of pwMS compared to controls. The combination of the neurodegenerative biomarkers together with biomarkers of neuroinflammation could provide additional information on the underlying pathomechanism of disease activity, which is essential for the identification of patients at risk of developing cumulative disabilities.

Biolistic transfection and expression analysis of acute cortical slices

BACKGROUND

Biolistic gene gun transfection has been used to transfect organotypic cultures (OTCs) or dissociated cultures in vitro. Here, we modified this technique to allow successful transfection of acute brain slices, followed by measurement of neuronal activity within a few hours.

NEW METHOD

We established biolistic transfection of murine acute cortical slices to measure calcium signals. Acute slices are mounted on plasma/thrombin coagulate and transfected with a calcium sensor. Imaging can be performed within 4 h post transfection without affecting cell viability.

RESULTS

Four hours after GCaMP6s transfection, acute slices display remarkable fluorescent protein expression level allowing to study spontaneous activity and receptor pharmacology. While optimal gas pressure (150 psi) and gold particle size used (1 μm) confirm previously published protocols, the amount of 5 μg DNA was found to be optimal for particle coating.

COMPARISON WITH EXISTING METHODS

The major advantage of this technique is the rapid disposition of acute slices for calcium imaging. No transgenic GECI expressing animals or OTC for long periods are required. In acute slices, network interaction and connectivity are preserved. The method allows to obtain physiological readouts within 4 h, before functional tissue modifications might come into effect. Limitations of this technique are random transfection, low expression efficiency when using specific promotors, and preclusion or genetic manipulations that require a prolonged time before physiological changes become measurable, such as expression of recombinant proteins that require transport to distant subcellular localizations.

CONCLUSION

The method is optimal for short-time investigation of calcium signals in acute slices.

Cyanidin-3-glucoside activates Nrf2-antioxidant response element and protects against glutamate-induced oxidative and endoplasmic reticulum stress in HT22 hippocampal neuronal cells

BACKGROUND

Cyanidin-3-glucoside (C3G), a major anthocyanin present in berries, exhibits a strong antioxidant and has been shown to possess a neuroprotection. Prolonged exposure to glutamate will lead to oxidative damage and endoplasmic reticulum stress which could play a key detrimental role in the development of neurodegenerative disorders (NDs). In the present study, we investigated the neuroprotective effect and underlying mechanisms of C3G on the reduction of oxidative/ER stress-induced apoptosis by glutamate in HT22 mouse hippocampal neuronal cells.

METHOD

Cells were pre-treated with C3G in various concentrations, followed by glutamate. Cell viability and toxicity were examined using MTT and LDH assays. The apoptotic and necrotic cell death were carried out by Annexin V-FITC/propidium iodide co-staining assays. Generation of intracellular reactive oxygen species (ROS) in cells was measured by flow cytometry using DCFH-DA probe. Expression of antioxidant genes was evaluated by Real-time polymerase chain reaction analysis. The possible signaling pathways and proteins involved were subsequently demonstrated by Western blot analysis.

RESULT

The pretreatment of the HT22 cells with C3G protected cell death from oxidative toxicity induced by glutamate. We demonstrated that treatment cells with glutamate caused several radical forms of ROS formation, and they were abolished by specific ROS inhibitors. Interestingly, C3G directly scavenged radical activity and inhibited intracellular ROS generation in our cell-based system. In addition, C3G pretreatment suppressed the up-regulation of specific ER proteins namely calpain, caspase-12 and C/EBP homologous proteins (CHOP) induced by glutamate-mediated oxidative and ER stress signal by up-regulating the expressions of survival proteins, including extracellular regulated protein kinase (ERK) and nuclear factor E2-related factor 2 (Nrf2). Furthermore, dramatically activated gene expression of endogenous antioxidant enzymes (i.e. superoxide dismutases (SODs), catalase (CAT) and glutathione peroxidase (GPx)), and phase II enzymes (glutathione-S-transferases (GSTs)) was found in C3G-treated with cells.

CONCLUSIONS

Our finding suggest that C3G could be a promising neuroprotectant via inhibition of glutamate-induced oxidative and ER stress signal and activation of ERK/Nrf2 antioxidant mechanism pathways.

Neuroprotective effects of myristargenol A against glutamate-induced apoptotic HT22 cell death

Glutamate is an important neurotransmitter in the central nervous system; however, at high concentrations, it causes excitotoxicity and many neurological disorders. Excitotoxicity induces cell death by apoptosis. Thus, factors that can inhibit the apoptotic pathways are a target of drug development for the treatment and prevention of neurodegenerative diseases. Herein, the antioxidative and neuroprotective effects of myristargenol A were examined in glutamate-induced mouse hippocampal neuronal HT22 cells. When the HT22 cells were stressed with glutamate, cell viability decreased to 44.4 ± 5.6% when compared with the case of the control cells (100 ± 4.8%); however, when these cells were treated with myristargenol A (10 μM), the cell viability was increased by 113.6 ± 2.3%. The protective effect of myristargenol A against the apoptosis of glutamate-induced HT22 cells was also confirmed using FITC-annexin V/propidium iodide double staining. In addition, myristargenol A protected the mitochondrial membrane potential (ΔΨ m). Subsequently, the expression levels of proteins in the caspase pathway related with the induction of apoptosis were decreased. Moreover, the expression levels of mitochondrial-related proteins, such as Bcl-2 and Bax, were examined, and it was found that the expression ratio of Bax/Bcl-2 decreased. In addition, myristargenol A inhibited the activity of mitogen-activated protein kinases, including p38 and c-Jun N-terminal kinase, for an oxidative stress protection effect but increased the activity of the extracellular signal-regulated kinases 1 and 2 for cell proliferation. These results reveal that myristargenol A possesses a neuroprotective effect against the neuronal cell damage caused by glutamate.

Levetiracetam – a drug that can be used not only in the treatment of epilepsy

Levetiracetam, which belongs to the new generation of antiepileptic drugs, has a unique and not well-known mechanism of action. The drug affects the release of neurotransmitters through the binding to the synaptic vesicle protein SV2A. Moreover, it acts on calcium channels, inhibits glutamatergic neurotransmission and affects GABA-ergic neurotransmission through e.g. the Zn²⁺-induced suppression of GABAA-mediated presynaptic inhibition and the modulation of the action of GABAA antagonists. Levetiracetam has also neuroprotective activity which is associated with the influence on transcription processes, neurotransmission, antioxidant and anti-inflammatory activity. The results of recent research indicate that this complex action creates the prospect of using it in the alleviation of epileptogenesis, poststroke seizuires, seizure prophylaxis in brain injured patients and diabetic neuropathy. Furthermore, the drug may also have a beneficial effect in the treatment of Alzheimer patients with epileptic seizures and levodopa-induced dyskinesias in Parkinson’s disease.

NeuroEPO Preserves Neurons from Glutamate-Induced Excitotoxicity

Many experimental studies show that erythropoietin (EPO) has a neuroprotective action in the brain. EPO in acute and chronic neurological disorders, particularly in stroke, traumatic brain injury, Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, has neuroprotective effects. We previously reported the neuroprotective effect of NeuroEPO, a low sialic form of EPO, against oxidative stress induced by glutamate excitotoxicity. In this paper, we analyze the effect of NeuroEPO against apoptosis induced by glutamate excitotoxicity in primary neuronal cultures obtained from the forebrains of Wistar rat embryos after 17 days of gestation. Excitotoxicity was induced after nine days of in vitro culture by treatment with a culture medium containing 100μM glutamate for 15 min. To withdraw glutamate, a new medium containing 100 ng NeuroEPO/mL was added. Apoptosis was analyzed after 24 h. Images obtained by phase contrast microscopy show that neurons treated with glutamate exhibit cell body shrinkage, loss of dendrites that do not make contact with neighboring cells, and that NeuroEPO was able to preserve the morphological characteristics of the control. Immunocytochemistry images show that the culture is essentially pure in neurons; that glutamate causes cell mortality, and that this is partially avoided when the culture medium is supplemented with NeuroEPO. Activation of intrinsic apoptotic pathways was analyzed. The decreases in Bcl-2/Bax ratio, increase in the release of cytochrome c, and in the expression and activity of caspase-3 observed in cells treated with glutamate, were restored by NeuroEPO. The results from this study show that NeuroEPO protects cortical neurons from glutamate-induced apoptosis via upregulation of Bcl-2 and inhibit glutamate-induced activation of caspase-3.

Adiponectin Protects Against Cerebral Ischemic Injury Through AdipoR1/AMPK Pathways

Excitotoxicity induced by excessive N-methyl-D-aspartate (NMDA) receptor activation underlies the pathology of ischemic injury. Adiponectin (APN) is an adipocyte-derived protein hormone that modulates a number of metabolic processes. APN exerts a wide range of biological functions in the central nervous system. However, the role of APN and its receptors in cerebral ischemia/reperfusion (I/R)-induced injury and the related mechanisms remain to be clarified. Here, we found that APN and APN receptor agonist AdipoRon (APR) were protective against excitotoxicity induced by oxygen and glucose deprivation/reperfusion (OGD/R) and NMDA in primary neurons. Adiponectin receptor 1 (AdipoR1) knockdown reversed the protection conferred by either APN or APR. Moreover, the protective effects offered by both APN and APR were compromised by compound C, an inhibitor of amp-activated protein kinase (AMPK) phosphorylation. Both APN and APR protected the dissipation of the ΔΨm caused by OGD/R. They also up-regulated the PGC-1α expression, which was reversed by compound C. Furthermore, both APN and APR ameliorated but APN knockout aggravated the infarct volume and neurological deficient induced by transient middle cerebral artery occlusion (tMCAO) in vivo. Taken together, these findings show that APN and APR protect against ischemic injury in vitro and in vivo. The protective mechanism is mainly related to AdipoR1-dependent AMPK phosphorylation and PGC-1α up-regulation.

Protective Effects of Alpha-Lipoic Acid on Glutamate-Induced Cytotoxicity in C6 Glioma Cells

Glutamate-mediated cytotoxicity has been implicated in the pathogenesis of neurological diseases, including Parkinson's disease, Alzheimer's disease, and stroke. In this study, we investigated the protective effects of alpha-lipoic acid (ALA), a naturally occurring thiol antioxidant, on glutamate-induced cytotoxicity in cultured C6 astroglial cells. Exposure to high-dose glutamate (10 mM) caused oxidative stress and mitochondrial dysfunction through the elevation of reactive oxygen species, depletion of glutathione, and loss of the mitochondrial membrane potential (ΔΨ_m). Pretreatment with ALA (200 µM), however, significantly inhibited the glutamate-induced oxidative stress and mitochondrial dysfunction. ALA pretreatment dose-dependently suppressed glutamate-induced apoptotic events including altered nuclear morphology and activation of caspase-3. In addition, ALA significantly attenuated glutamate-induced endoplasmic reticulum (ER) stress markers; namely, glucose-regulated protein 78 (GRP78), activating transcription factor 6 (ATF6), protein kinase regulated by RNA (PKR)-like ER-associated kinase (PERK), eukaryotic translation initiation factor 2 alpha (eIF2α), inositol-requiring enzyme 1 (IRE1), CCAAT/enhancer binding protein homologous protein (CHOP), and caspase-12. We confirmed that CHOP and caspase-12 are key mediators of glutamate-induced ER stress. Furthermore, exposure of the cells to a caspase-12-specific inhibitor and CHOP small interfering RNAs (siRNAs) led to restoration of the ΔΨ_m that was damaged by glutamate treatment. These results suggest that ALA can effectively suppress oxidative stress, mitochondrial dysfunction, and ER stress in astroglial cells.

Cell Volume Control in Healthy Brain and Neuropathologies

Regulation of cellular volume is a critical homeostatic process that is intimately linked to ionic and osmotic balance in the brain tissue. Because the brain is encased in the rigid skull and has a very complex cellular architecture, even minute changes in the volume of extracellular and intracellular compartments have a very strong impact on tissue excitability and function. The failure of cell volume control is a major feature of several neuropathologies, such as hyponatremia, stroke, epilepsy, hyperammonemia, and others. There is strong evidence that such dysregulation, especially uncontrolled cell swelling, plays a major role in adverse pathological outcomes. To protect themselves, brain cells utilize a variety of mechanisms to maintain their optimal volume, primarily by releasing or taking in ions and small organic molecules through diverse volume-sensitive ion channels and transporters. In principle, the mechanisms of cell volume regulation are not unique to the brain and share many commonalities with other tissues. However, because ions and some organic osmolytes (e.g., major amino acid neurotransmitters) have a strong impact on neuronal excitability, cell volume regulation in the brain is a surprisingly treacherous process, which may cause more harm than good. This topical review covers the established and emerging information in this rapidly developing area of physiology.

Neuroprotective Effects of neuroEPO Using an In Vitro Model of Stroke

Erythropoietin (EPO) is a glycoprotein initially identified as a hormone synthesized and secreted by the kidney that regulates erythropoiesis. EPO, and a group of its derivatives, are being evaluated as possible neuroprotective agents in cerebral ischemia. The objective of this study, using an in vitro model, was to determine how neuroEPO—which is a variant of EPO with a low sialic acid content—protects neurons from the toxic action of glutamate. Primary neuronal cultures were obtained from the forebrains of Wistar rat embryos after 17 days of gestation. Excitotoxicity was induced after nine days of in vitro culture by treatment with a medium containing 100 µM glutamate for 15 min. After this time, a new medium containing 100 ng of neuroEPO/mL was added. Morphological cell change was assessed by phase-contrast microscopy. Oxidative stress was analysed by measuring antioxidant and oxidant activity. After 24 h, the treatment with 100 ng of neuroEPO/mL showed a significant (p < 0.01) decrease in mortality, compared to cells treated with glutamate alone. neuroEPO treatment decreased mortality and tended to reproduce the morphological characteristics of the control. The oxidative stress induced by glutamate is reduced after neuroEPO treatment. These results confirm that neuroEPO has a protective effect against neuronal damage induced by excitotoxicity, improving antioxidant activity in the neuron, and protecting it from oxidative stress.

Polyphenols journey through blood-brain barrier towards neuronal protection

Age-related complications such as neurodegenerative disorders are increasing and remain cureless. The possibility of altering the progression or the development of these multifactorial diseases through diet is an emerging and attractive approach with increasing experimental support. We examined the potential of known bioavailable phenolic sulfates, arising from colonic metabolism of berries, to influence hallmarks of neurodegenerative processes. In silico predictions and in vitro transport studies across blood-brain barrier (BBB) endothelial cells, at circulating concentrations, provided evidence for differential transport, likely related to chemical structure. Moreover, endothelial metabolism of these phenolic sulfates produced a plethora of novel chemical entities with further potential bioactivies. Pre-conditioning with phenolic sulfates improved cellular responses to oxidative, excitotoxicity and inflammatory injuries and this attenuation of neuroinflammation was achieved via modulation of NF-κB pathway. Our results support the hypothesis that these small molecules, derived from dietary (poly)phenols may cross the BBB, reach brain cells, modulate microglia-mediated inflammation and exert neuroprotective effects, with potential for alleviation of neurodegenerative diseases.

Neuroprotective compounds from Reynoutria sachalinensis

Glutamate is a neurotransmitter in central nervous system. Overexpression of glutamate leads to oxidative stress, resulting in several neurodegenerative disorders that include Alzheimer's disease. The n-hexane fraction of stems and ethyl acetate (EtOAc) fraction of flowers of Reynoutria sachalinensis provide neuroprotection against glutamate-induced oxidative toxicity in HT22 cells. In this study, 1-decanol (1), β-amyrin (2), dammaran-3β-ol (3), campesterol (4), daucosterol (5), ergosterol peroxide (6), emodin 8-O-β-D-glucopyranoside (7), quercetin (8) and isoquercitrin (9) were isolated from n-hexane fractions of stems and EtOAc fractions of flowers of R. sachalinensis. Their neuroprotective activity was evaluated by MTT assay. 1-Decanol, campesterol, ergosterol peroxide, quercetin and isoquercitrin exhibited neuroprotective activity. These compounds decreased reactive oxygen species level, showed anti-oxidant activity with DPPH radical and in a H₂O₂ scavenging assay. Therefore, the neuroprotective activity of 1-decanol, campesterol, ergosterol peroxide, quercetin and isoquercitrin are associated with antioxidant activity.

Sodium para-aminosalicylate protected cultured basal ganglia astrocytes from manganese-induced DNA damages and alteration of amino acid neurotransmitter levels

Sodium para-aminosalicylate (PAS-Na) was first applied successfully in clinical treatment of two manganism patients with good prognosis. However, the mechanism of how PAS-Na protects against Mn-induced neurotoxicity is still elusive. The current study was conducted to explore the effects of PAS-Na on Mn-induced basal ganglia astrocyte injury, and the involvement of amino acid neurotransmitter in vitro. Basal ganglia astrocytes were exposed to 500 μM manganese chloride (MnCl2) for 24 hr, following by 50, 150, or 450 μM PAS-Na treatment for another 24 hr. MnCl2 significantly decreased viability of astrocytes and induced DNA damages via increasing the percentage of tail DNA and Olive tail moment of DNA. Moreover, Mn interrupted amino acid neurotransmitters by decreasing Gln levels and increasing Glu, Gly levels. In contrast, PAS-Na treatment reversed the aforementioned Mn-induced toxic effects on basal ganglia astrocytes. Taken together, our results demonstrated that excessive Mn exposure may induce toxic effects on basal ganglia astrocytes, while PAS-Na could protect basal ganglia astrocytes from Mn-induced neurotoxicity.

Cleistocalyx nervosum var. paniala berry fruit protects neurotoxicity against endoplasmic reticulum stress-induced apoptosis

Oxidative and endoplasmic reticulum (ER) stresses cause neuronal damage leading to neurodegenerative disorders. Cleistocalyx nervosum var. paniala (CNP) berry fruit has been shown to possess powerful antioxidant properties. Here, we investigated the neuroprotective effect of CNP extract against glutamate-mediated oxidative/ER stress-induced cell death in mouse hippocampal neuronal HT22 cells. CNP extract was clarified for its radical scavenging activities, total phenolic and anthocyanin contents. The key anthocyanin cyanidin-3-glucoside was used as a marker to standardize the extract used in the study. We found that pretreated cells with CNP extract (0.05-1 μg/ml) prevented neuronal cell death in response to 5 mM glutamate evaluated by cell viability MTT, LDH and apoptosis/necrosis Annexin V/propidium iodide co-staining assays. For mechanistic approach, glutamate-induced cell death through reactive oxygen species (ROS)-mediated ER stress pathways, indicating the increase of ROS and ER stress signature molecules including calpain, caspases-12 and C/EBP homologous proteins (CHOP). CNP extract inhibited ROS production. Moreover, the extract also suppressed the specific-ER stress apoptotic proteins level in glutamate-induced cells by upregulating the gene expression of cellular antioxidant enzymes (SODs, CAT, GPx and GSTs). Taken together, our results provide information about and the molecular mechanism of CNP extract as a promising neuroprotectant and antioxidant.

The cellular basis of dendrite pathology in neurodegenerative diseases

One of the characteristics of the neurons that distinguishes them from other cells is their complex and polarized structure consisting of dendrites, cell body, and axon. The complexity and diversity of dendrites are particularly well recognized, and accumulating evidences suggest that the alterations in the dendrite structure are associated with many neurodegenerative diseases. Given the importance of the proper dendritic structures for neuronal functions, the dendrite pathology appears to have crucial contribution to the pathogenesis of neurodegenerative diseases. Nonetheless, the cellular and molecular basis of dendritic changes in the neurodegenerative diseases remains largely elusive. Previous studies in normal condition have revealed that several cellular components, such as local cytoskeletal structures and organelles located locally in dendrites, play crucial roles in dendrite growth. By reviewing what has been unveiled to date regarding dendrite growth in terms of these local cellular components, we aim to provide an insight to categorize the potential cellular basis that can be applied to the dendrite pathology manifested in many neurodegenerative diseases. [BMB Reports 2017; 50(1): 5-11].

Deletion of the Fractalkine Receptor, CX3CR1, Improves Endogenous Repair, Axon Sprouting, and Synaptogenesis after Spinal Cord Injury in Mice

Impaired signaling via CX3CR1, the fractalkine receptor, promotes recovery after traumatic spinal contusion injury in mice, a benefit achieved in part by reducing macrophage-mediated injury at the lesion epicenter. Here, we tested the hypothesis that CX3CR1-dependent changes in microglia and macrophage functions also will enhance neuroplasticity, at and several segments below the injury epicenter. New data show that in the presence of inflammatory stimuli, CX3CR1-deficient (CX3CR1^-/-) microglia and macrophages adopt a reparative phenotype and increase expression of genes that encode neurotrophic and gliogenic proteins. At the lesion epicenter (mid-thoracic spinal cord), the microenvironment created by CX3CR1^-/- microglia/macrophages enhances NG2 cell responses, axon sparing, and sprouting of serotonergic axons. In lumbar spinal cord, inflammatory signaling is reduced in CX3CR1^-/- microglia. This is associated with reduced dendritic pathology and improved axonal and synaptic plasticity on ventral horn motor neurons. Together, these data indicate that CX3CR1, a microglia-specific chemokine receptor, is a novel therapeutic target for enhancing neuroplasticity and recovery after SCI. Interventions that specifically target CX3CR1 could reduce the adverse effects of inflammation and augment activity-dependent plasticity and restoration of function. Indeed, limiting CX3CR1-dependent signaling could improve rehabilitation and spinal learning.SIGNIFICANCE STATEMENT Published data show that genetic deletion of CX3CR1, a microglia-specific chemokine receptor, promotes recovery after traumatic spinal cord injury in mice, a benefit achieved in part by reducing macrophage-mediated injury at the lesion epicenter. Data in the current manuscript indicate that CX3CR1 deletion changes microglia and macrophage function, creating a tissue microenvironment that enhances endogenous repair and indices of neuroplasticity, at and several segments below the injury epicenter. Interventions that specifically target CX3CR1 might be used in the future to reduce the adverse effects of intraspinal inflammation and augment activity-dependent plasticity (e.g., rehabilitation) and restoration of function.

Distinct Neurotoxicity Profile of Listeriolysin O from Listeria monocytogenes

Cholesterol-dependent cytolysins (CDCs) are protein toxins that originate from Gram-positive bacteria and contribute substantially to their pathogenicity. CDCs bind membrane cholesterol and build prepores and lytic pores. Some effects of the toxins are observed in non-lytic concentrations. Two pathogens, Streptococcus pneumoniae and Listeria monocytogenes, cause fatal bacterial meningitis, and both produce toxins of the CDC family-pneumolysin and listeriolysin O, respectively. It has been demonstrated that pneumolysin produces dendritic varicosities (dendrite swellings) and dendritic spine collapse in the mouse neocortex, followed by synaptic loss and astrocyte cell shape remodeling without elevated cell death. We utilized primary glial cultures and acute mouse brain slices to examine the neuropathological effects of listeriolysin O and to compare it to pneumolysin with identical hemolytic activity. In cultures, listeriolysin O permeabilized cells slower than pneumolysin did but still initiated non-lytic astrocytic cell shape changes, just as pneumolysin did. In an acute brain slice culture system, listeriolysin O produced dendritic varicosities in an NMDA-dependent manner but failed to cause dendritic spine collapse and cortical astrocyte reorganization. Thus, listeriolysin O demonstrated slower cell permeabilization and milder glial cell remodeling ability than did pneumolysin and lacked dendritic spine collapse capacity but exhibited equivalent dendritic pathology.

Multimodal Imaging of Neurometabolic Pathology due to Traumatic Brain Injury

The impact of traumatic brain injury (TBI) involves a combination of complex biochemical processes beginning with the initial insult and lasting for days, months and even years post-trauma. These changes range from neuronal integrity losses to neurotransmitter imbalance and metabolite dysregulation, leading to the release of pro- or anti-apoptotic factors which mediate cell survival or death. Such dynamic processes affecting the brain's neurochemistry can be monitored using a variety of neuroimaging techniques, whose combined use can be particularly useful for understanding patient-specific clinical trajectories. Here, we describe how TBI changes the metabolism of essential neurochemical compounds, summarize how neuroimaging approaches facilitate the study of such alterations, and highlight promising ways in which neuroimaging can be used to investigate post-TBI changes in neurometabolism.

Methylphenidate Decreases ATP Levels and Impairs Glutamate Uptake and Na+,K+-ATPase Activity in Juvenile Rat Hippocampus

The study of the long-term neurological consequences of early exposure with methylphenidate (MPH) is very important since this psychostimulant has been widely misused by children and adolescents who do not meet full diagnostic criteria for ADHD. The aim of this study was to examine the effect of early chronic exposure with MPH on amino acids profile, glutamatergic and Na⁺,K⁺-ATPase homeostasis, as well as redox and energy status in the hippocampus of juvenile rats. Wistar male rats received intraperitoneal injections of MPH (2.0 mg/kg) or saline solution (controls), once a day, from the 15th to the 45th day of age. Results showed that MPH altered amino acid profile in the hippocampus, decreasing glutamine levels. Glutamate uptake and Na⁺,K⁺-ATPase activity were decreased after chronic MPH exposure in the hippocampus of rats. No changes were observed in the immunocontents of glutamate transporters (GLAST and GLT-1), and catalytic subunits of Na⁺,K⁺-ATPase (α₁, α₂, and α₃), as well as redox status. Moreover, MPH provoked a decrease in ATP levels in the hippocampus of chronically exposed rats, while citrate synthase, succinate dehydrogenase, respiratory chain complexes activities (II, II-III, and IV), as well as mitochondrial mass and mitochondrial membrane potential were not altered. Taken together, our results suggest that chronic MPH exposure at early age impairs glutamate uptake and Na⁺,K⁺-ATPase activity probably by decreasing in ATP levels observed in rat hippocampus.

5α-reduced progestogens ameliorate mood-related behavioral pathology, neurotoxicity, and microgliosis associated with exposure to HIV-1 Tat

Human immunodeficiency virus (HIV) is associated with motor and mood disorders, likely influenced by reactive microgliosis and subsequent neural damage. We have recapitulated aspects of this pathology in mice that conditionally express the neurotoxic HIV-1 regulatory protein, trans-activator of transcription (Tat). Progestogens may attenuate Tat-related behavioral impairments and reduce neurotoxicity in vitro, perhaps via progesterone's 5α-reductase-dependent metabolism to the neuroprotective steroid, allopregnanolone. To test this, ovariectomized female mice that conditionally expressed (or did not express) central HIV-1 Tat were administered vehicle or progesterone (4mg/kg), with or without pretreatment of a 5α-reductase inhibitor (finasteride, 50mg/kg). Tat induction significantly increased anxiety-like behavior in an open field, elevated plus maze and a marble burying task concomitant with elevated protein oxidation in striatum. Progesterone administration attenuated anxiety-like effects in the open field and elevated plus maze, but not in conjunction with finasteride pretreatment. Progesterone also attenuated Tat-promoted protein oxidation in striatum, independent of finasteride pretreatment. Concurrent experiments in vitro revealed Tat (50nM)-mediated reductions in neuronal cell survival over 60h, as well as increased neuronal and microglial intracellular calcium, as assessed via fura-2 AM fluorescence. Co-treatment with allopregnanolone (100nM) attenuated neuronal death in time-lapse imaging and blocked the Tat-induced exacerbation of intracellular calcium in neurons and microglia. Lastly, neuronal-glial co-cultures were labeled for Iba-1 to reveal that Tat increased microglial numbers in vitro and co-treatment with allopregnanolone attenuated this effect. Together, these data support the notion that 5α-reduced pregnane steroids exert protection over the neurotoxic effects of HIV-1 Tat.

Computational Pipeline for NIRS-EEG Joint Imaging of tDCS-Evoked Cerebral Responses-An Application in Ischemic Stroke

Transcranial direct current stimulation (tDCS) modulates cortical neural activity and hemodynamics. Electrophysiological methods (electroencephalography-EEG) measure neural activity while optical methods (near-infrared spectroscopy-NIRS) measure hemodynamics coupled through neurovascular coupling (NVC). Assessment of NVC requires development of NIRS-EEG joint-imaging sensor montages that are sensitive to the tDCS affected brain areas. In this methods paper, we present a software pipeline incorporating freely available software tools that can be used to target vascular territories with tDCS and develop a NIRS-EEG probe for joint imaging of tDCS-evoked responses. We apply this software pipeline to target primarily the outer convexity of the brain territory (superficial divisions) of the middle cerebral artery (MCA). We then present a computational method based on Empirical Mode Decomposition of NIRS and EEG time series into a set of intrinsic mode functions (IMFs), and then perform a cross-correlation analysis on those IMFs from NIRS and EEG signals to model NVC at the lesional and contralesional hemispheres of an ischemic stroke patient. For the contralesional hemisphere, a strong positive correlation between IMFs of regional cerebral hemoglobin oxygen saturation and the log-transformed mean-power time-series of IMFs for EEG with a lag of about -15 s was found after a cumulative 550 s stimulation of anodal tDCS. It is postulated that system identification, for example using a continuous-time autoregressive model, of this coupling relation under tDCS perturbation may provide spatiotemporal discriminatory features for the identification of ischemia. Furthermore, portable NIRS-EEG joint imaging can be incorporated into brain computer interfaces to monitor tDCS-facilitated neurointervention as well as cortical reorganization.

Inhibition of cyclooxygenase-2 by NS398 attenuates noise-induced hearing loss in mice

Noise-induced hearing loss (NIHL) is an important occupational disorder. However, the molecular mechanisms underlying NIHL have not been fully clarified; therefore, the condition lacks effective therapeutic methods. Cyclooxygenase-2 (Cox-2) is an inducible enzyme involved in the synthesis of prostaglandins, and has been implicated in many pathophysiological events, such as oxidative stress and inflammation. In this study, we investigated the possible role of Cox-2 in the mechanisms of NIHL and the therapeutic effect of the Cox-2 inhibitor NS398 on NIHL using a mouse model. We demonstrated that Cox-2 is constitutively expressed in the mouse cochlea, and its expression could be dramatically up-regulated by high levels of noise exposure. Furthermore, we demonstrated that pre-treatment with the Cox-2 inhibitor NS398 could inhibit Cox-2 expression during noise overstimulation; and could attenuate noise-induced hearing loss and hair cell damage. Our results suggest that Cox-2 is involved in the pathogenesis of NIHL; and pharmacological inhibition of Cox-2 has considerable therapeutic potential in NIHL.

β-Secretase (BACE1) inhibitory and neuroprotective effects of p-terphenyls from Polyozellus multiplex

Polyozellin, thelephoric acid, and polyozellic acid might be useful in the development of lead compounds for the prevention of neurodegenerative disorders, especially Alzheimer's disease (AD).

Polyozellin, a key constituent of the edible mushroom Polyozellus multiplex, attenuates glutamate-induced mouse hippocampal neuronal HT22 cell death

Polyozellus multiplex (PM), a Korean edible mushroom, has biological activities such as chemoprevention of stomach cancer, inhibition of lipid peroxidation, and reduction of prolyl endopeptidase activity. However, there are little reports on the protective effects of PM or its constituents against glutamate-induced mouse hippocampal neuronal cell (HT22) death. In this study, polyozellin (PZ), a key constituent of PM, was applied to glutamate-treated HT22 cells to evaluate its neuroprotective mechanisms. PZ (25 μM) dramatically increased the HT22 cell viability when the cell death was induced by 5 mM glutamate for 12 h, which was mediated by inhibition of Ca(2+) influx, intracellular reactive oxygen species (ROS) production, and lipid peroxidation. PZ also regulated expression of Bid, Bcl-2, and apoptosis-inducing factor (AIF), as well as phosphorylation of mitogen-activated protein kinases (MAPKs). These data suggest that PM and its constituent PZ might be useful for prevention and treatment of neurodegenerative disorders.

Fixation strategies for retinal immunohistochemistry

Immunohistochemical and ex vivo anatomical studies have provided many glimpses of the variety, distribution, and signaling components of vertebrate retinal neurons. The beauty of numerous images published to date, and the qualitative and quantitative information they provide, indicate that these approaches are fundamentally useful. However, obtaining these images entailed tissue handling and exposure to chemical solutions that differ from normal extracellular fluid in composition, temperature, and osmolarity. Because the differences are large enough to alter intercellular and intracellular signaling in neurons, and because retinae are susceptible to crush, shear, and fray, it is natural to wonder if immunohistochemical and anatomical methods disturb or damage the cells they are designed to examine. Tissue fixation is typically incorporated to guard against this damage and is therefore critically important to the quality and significance of the harvested data. Here, we describe mechanisms of fixation; advantages and disadvantages of using formaldehyde and glutaraldehyde as fixatives during immunohistochemistry; and modifications of widely used protocols that have recently been found to improve cell shape preservation and immunostaining patterns, especially in proximal retinal neurons.

Excitotoxic insult results in a long-lasting activation of CaMKIIα and mitochondrial damage in living hippocampal neurons

Over-activation of excitatory NMDA receptors and the resulting Ca2+ overload is the main cause of neuronal toxicity during stroke. CaMKII becomes misregulated during such events. Biochemical studies show either a dramatic loss of CaMKII activity or its persistent autonomous activation after stroke, with both of these processes being implicated in cell toxicity. To complement the biochemical data, we monitored CaMKII activation in living hippocampal neurons in slice cultures using high spatial/temporal resolution two-photon imaging of the CaMKIIα FRET sensor, Camui. CaMKII activation state was estimated by measuring Camui fluorescence lifetime. Short NMDA insult resulted in Camui activation followed by a redistribution of its protein localization: an increase in spines, a decrease in dendritic shafts, and concentration into numerous clusters in the cell soma. Camui activation was either persistent (> 1-3 hours) or transient (~20 min) and, in general, correlated with its protein redistribution. After longer NMDA insult, however, Camui redistribution persisted longer than its activation, suggesting distinct regulation/phases of these processes. Mutational and pharmacological analysis suggested that persistent Camui activation was due to prolonged Ca2+ elevation, with little impact of autonomous states produced by T286 autophosphorylation and/or by C280/M281 oxidation. Cell injury was monitored using expressible mitochondrial marker mito-dsRed. Shortly after Camui activation and clustering, NMDA treatment resulted in mitochondrial swelling, with persistence of the swelling temporarily linked to the persistence of Camui activation. The results suggest that in living neurons excitotoxic insult produces long-lasting Ca2+-dependent active state of CaMKII temporarily linked to cell injury. CaMKII function, however, is to be restricted due to strong clustering. The study provides the first characterization of CaMKII activation dynamics in living neurons during excitotoxic insults.