Neuroinflammation and regulation of glial glutamate uptake in neurological disorders

Activation of NLRP3-Caspase-1 pathway contributes to age-related impairments in cognitive function and synaptic plasticity

Aging is characterized by a progressive deterioration in physiological functions that is associated with cognitive decline as well as other physical functional impairments. Microglia activation leading to neuroinflammation has been generally recognized as playing a critical role in the development of age-related cognitive decline. NLRP3 inflammasome in microglia is fundamental for IL-1β maturation and subsequent inflammatory events. However, it remains unknown whether NLRP3 activation contributes to aging-induced cognitive decline in vivo. Here, our study demonstrated that aging rats showed declined cognitive function and impaired synaptic plasticity as well as decreased density of dendritic spines. Importantly, our data demonstrated strongly enhanced expression of NLRP3, ASC and Caspase-1 in the hippocampus of aged rats as well as decreased AMPA receptor and phosphorylated levels of CaMKII and CREB in the hippocampus of natural aging rats. Furthermore, NLRP3 inflammasome inhibitor elevated the surface expression of AMPA receptor and the phosphorylated levels of CaMKII, CREB in hippocampus, and finally contributed to the attenuation of hippocampal long-term potentiation (LTP) deficits and the improvement of cognitive decline of natural aging rats. These results revealed an important role for the NLRP3-Caspase-1 pathway in aging-induced cognitive decline and suggested that inhibition of NLRP3 inflammasome represented a novel therapeutic intervention for aging-related cognitive impairment.

Food-Origin Mycotoxin-Induced Neurotoxicity: Intend to Break the Rules of Neuroglia Cells

Mycotoxins are key risk factors in human food and animal feed. Most of food-origin mycotoxins could easily enter the organism and evoke systemic toxic effects, such as aflatoxin B1 (AFB1), ochratoxin A (OTA), T-2 toxin, deoxynivalenol (DON), zearalenone (ZEN), fumonisin B1 (FB1), and 3-nitropropionic acid (3-NPA). For the last decade, the researches have provided much evidences in vivo and in vitro that the brain is an important target organ on mycotoxin-mediated neurotoxic phenomenon and neurodegenerative diseases. As is known to all, glial cells are the best regulator and defender of neurons, and a few evaluations about the effects of mycotoxins on glial cells such as astrocytes or microglia have been conducted. The fact that mycotoxin contamination may be a key factor in neurotoxicity and glial dysfunction is exactly the reason why we reviewed the activation, oxidative stress, and mitochondrial function changes of glial cells under mycotoxin infection and summarized the mycotoxin-mediated glial cell proliferation disorders, death pathways, and inflammatory responses. The purpose of this paper is to analyze various pathways in which common food-derived mycotoxins can induce glial toxicity and provide a novel perspective for future research on the neurodegenerative diseases.

Immune treatments for alcohol use disorder: A translational framework

While the immune system is essential for survival, an excessive or prolonged inflammatory response, such as that resulting from sustained heavy alcohol use, can damage the host and contribute to psychiatric disorders. A growing body of literature indicates that the immune system plays a critical role in the development and maintenance of alcohol use disorder (AUD). As such, there is enthusiasm for treatments that can restore healthy levels of inflammation as a mechanism to reduce drinking and promote recovery. In this qualitative literature review, we provide a conceptual rationale for immune therapies and discuss progress in medications development for AUD focused on the immune system as a treatment target. This review is organized into sections based on primary signaling pathways targeted by the candidate therapies, namely: (a) toll-like receptors, (b) phosphodiesterase inhibitors, (c) peroxisome proliferator-activated receptors, (d) microglia and astrocytes, (e) other immune pharmacotherapies, and (f) behavioral therapies. As relevant within each section, we examine the basic biological mechanisms of each class of therapy and evaluate preclinical research testing the role of the therapy on mitigating alcohol-related behaviors in animal models. To the extent available, translational findings are reviewed with discussion of completed and ongoing randomized clinical trials and their findings to date. An applied and clinically focused approach is taken to identify the potential clinical applications of the various treatments reviewed. We conclude by delineating the most promising candidate treatments and discussing future directions by considering opportunities for immune treatment development and personalized medicine for AUD.

Role of glutamate excitotoxicity and glutamate transporter EAAT2 in epilepsy: Opportunities for novel therapeutics development

Epilepsy is a complex neurological syndrome characterized by seizures resulting from neuronal hyperexcitability and sudden and synchronized bursts of electrical discharges. Impaired astrocyte function that results in glutamate excitotoxicity has been recognized to play a key role in the pathogenesis of epilepsy. While there are 26 drugs marketed as anti-epileptic drugs no current treatments are disease modifying as they only suppress seizures rather than the development and progression of epilepsy. Excitatory amino acid transporters (EAATs) are critical for maintaining low extracellular glutamate concentrations and preventing excitotoxicity. When extracellular glutamate concentrations rise to abnormal levels, glutamate receptor overactivation and the subsequent excessive influx of calcium into the post-synaptic neuron can trigger cell death pathways. In this review we discuss targeting EAAT2, the predominant glutamate transporter in the CNS, as a promising approach for developing therapies for epilepsy. EAAT2 upregulation via transcriptional and translational regulation has proven successful in vivo in reducing spontaneous recurrent seizures and offering neuroprotective effects. Another approach to regulate EAAT2 activity is through positive allosteric modulation (PAM). Novel PAMs of EAAT2 have recently been identified and are under development, representing a promising approach for the advance of novel therapeutics for epilepsy.

Interweaving epilepsy and neurodegeneration: Vitamin E as a treatment approach

Epilepsy is the most common neurological disorder, affecting nearly 50 million people worldwide. The condition can be manifested either due to genetic predisposition or acquired from acute insult which leads to alteration of cellular and molecular mechanisms. Evaluating the latest and the current knowledge in regard to the mechanisms underlying molecular and cellular alteration, hyperexcitability is a consequence of an imbalanced state wherein enhance excitatory glutamatergic and reduced inhibitory GABAergic signaling is considered to be accountable for seizures associated damage. However, neurodegeneration contributing to epileptogenesis has become increasingly appreciated. The components at the helm of neurodegenerative alterations during epileptogenesis include GABAergic neuronal and receptor changes, neuroinflammation, alteration in axonal transport, oxidative stress, excitotoxicity, and other cellular as well as functional changes. Targeting neurodegeneration with vitamin E as an antioxidant, anti-inflammatory and neuroprotective may prove to be one of the therapeutic approaches useful in managing epilepsy. In this review, we discuss and converse about the seizure-induced episodes as a link for the development of neurodegenerative and pathological consequences of epilepsy. We also put forth a summary of the potential intervention with vitamin E therapy in the management of epilepsy.

Cognitive Dysfunction After Analgesia and Sedation: Out of the Operating Room and Into the Pediatric Intensive Care Unit

In the midst of concerns for potential neurodevelopmental effects after surgical anesthesia, there is a growing awareness that children who require sedation during critical illness are susceptible to neurologic dysfunctions collectively termed pediatric post-intensive care syndrome, or PICS-p. In contrast to healthy children undergoing elective surgery, critically ill children are subject to inordinate neurologic stress or injury and need to be considered separately. Despite recognition of PICS-p, inconsistency in techniques and timing of post-discharge assessments continues to be a significant barrier to understanding the specific role of sedation in later cognitive dysfunction. Nonetheless, available pediatric studies that account for analgesia and sedation consistently identify sedative and opioid analgesic exposures as risk factors for both in-hospital delirium and post-discharge neurologic sequelae. Clinical observations are supported by animal models showing neuroinflammation, increased neuronal death, dysmyelination, and altered synaptic plasticity and neurotransmission. Additionally, intensive care sedation also contributes to sleep disruption, an important and overlooked variable during acute illness and post-discharge recovery. Because analgesia and sedation are potentially modifiable, understanding the underlying mechanisms could transform sedation strategies to improve outcomes. To move the needle on this, prospective clinical studies would benefit from cohesion with regard to datasets and core outcome assessments, including sleep quality. Analyses should also account for the wide range of diagnoses, heterogeneity of this population, and the dynamic nature of neurodevelopment in age cohorts. Much of the related preclinical evidence has been studied in comparatively brief anesthetic exposures in healthy animals during infancy and is not generalizable to critically ill children. Thus, complementary animal models that more accurately "reverse translate" critical illness paradigms and the effect of analgesia and sedation on neuropathology and functional outcomes are needed. This review explores the interactive role of sedatives and the neurologic vulnerability of critically ill children as it pertains to survivorship and functional outcomes, which is the next frontier in pediatric intensive care.

Aiding and Abetting Anhedonia: Impact of Inflammation on the Brain and Pharmacological Implications

Exogenous administration of inflammatory stimuli to humans and laboratory animals and chronic endogenous inflammatory states lead to motivational deficits and ultimately anhedonia, a core and disabling symptom of depression present in multiple other psychiatric disorders. Inflammation impacts neurotransmitter systems and neurocircuits in subcortical brain regions including the ventral striatum, which serves as an integration point for reward processing and motivational decision-making. Many mechanisms contribute to these effects of inflammation, including decreased synthesis, release and reuptake of dopamine, increased synaptic and extrasynaptic glutamate, and activation of kynurenine pathway metabolites including quinolinic acid. Neuroimaging data indicate that these inflammation-induced neurotransmitter effects manifest as decreased activation of ventral striatum and decreased functional connectivity in reward circuitry involving ventral striatum and ventromedial prefrontal cortex. Neurocircuitry changes in turn mediate nuanced effects on motivation that include decreased willingness to expend effort for reward while maintaining the ability to experience reward. Taken together, the data reveal an inflammation-induced pathophysiologic phenotype that is agnostic to diagnosis. Given the many mechanisms involved, this phenotype represents an opportunity for development of novel and/or repurposed pharmacological strategies that target inflammation and associated cellular and systemic immunometabolic changes and their downstream effects on the brain. To date, clinical trials have failed to capitalize on the unique nature of this transdiagnostic phenotype, leaving the field bereft of interpretable data for meaningful clinical application. However, novel trial designs incorporating established targets in the brain and/or periphery using relevant outcome variables (e.g., anhedonia) are the future of targeted therapy in psychiatry. SIGNIFICANCE STATEMENT: Emerging understanding of mechanisms by which peripheral inflammation can affect the brain and behavior has created unprecedented opportunities for development of pharmacological strategies to treat deficits in motivation including anhedonia, a core and disabling symptom of depression well represented in multiple psychiatric disorders. Mechanisms include inflammation and cellular and systemic immunometabolism and alterations in dopamine, glutamate, and kynurenine metabolites, revealing a target-rich environment that nevertheless has yet to be fully exploited by current clinical trial designs and drugs employed.

White matter injury in infants with intraventricular haemorrhage: mechanisms and therapies

Intraventricular haemorrhage (IVH) continues to be a major complication of prematurity that can result in cerebral palsy and cognitive impairment in survivors. No optimal therapy exists to prevent IVH or to treat its consequences. IVH varies in severity and can present as a bleed confined to the germinal matrix, small-to-large IVH or periventricular haemorrhagic infarction. Moderate-to-severe haemorrhage dilates the ventricle and damages the periventricular white matter. This white matter injury results from a constellation of blood-induced pathological reactions, including oxidative stress, glutamate excitotoxicity, inflammation, perturbed signalling pathways and remodelling of the extracellular matrix. Potential therapies for IVH are currently undergoing investigation in preclinical models and evidence from clinical trials suggests that stem cell treatment and/or endoscopic removal of clots from the cerebral ventricles could transform the outcome of infants with IVH. This Review presents an integrated view of new insights into the mechanisms underlying white matter injury in premature infants with IVH and highlights the importance of early detection of disability and immediate intervention in optimizing the outcomes of IVH survivors.

Altered in vivo brain GABA and glutamate levels are associated with multiple sclerosis central fatigue

PURPOSE

Fatigue is a common symptom in patients with multiple sclerosis (MS) with unknown pathophysiology. Dysfunction of the GABAergic/glutamatergic pathways involving inhibitory and excitatory neurotransmitters such as  γ-aminobutyric acid (GABA) and glutamine + glutamate pool (Glx) have been implicated in several neurological disorders. This study is aimed to evaluate the potential role of GABA and Glx in the origin of central fatigue in relapse remitting MS (RRMS) patients.

METHODS

24 RRMS patients and 16 age- and sex-matched healthy controls (HC) were scanned using Mescher-Garwood point resolved spectroscopy (MEGA-PRESS) with a 3 T system to quantify GABA+ and Glx from prefrontal (PFC) and sensorimotor (SMC) cortices. Self-reported fatigue status was measured on all participants using the Modified Fatigue Impact Scale (MFIS).

RESULTS

RRMS patients had higher fatigue scores relative to HC (p ≤  0.05). Compared to HC, Glx levels in RRMS patients were significantly decreased in SMC (p =  0.04). Significant correlations were found between fatigue scores and GABA+ (r = -0.531, p =  0.008) and Glx (r = 0.511, p =  0.018) in PFC. Physical fatigue was negatively correlated with GABA+ in SMC and PFC (r = -0.428 and -0.472 respectively, p ≤  0.04) and positively with PFC Glx (r = 0.480, p =  0.028).

CONCLUSION

The associations between fatigue and GABA + and Glx suggest that there might be dysregulation of GABAergic/glutamatergic neurotransmission in the pathophysiological mechanism of central fatigue in MS.

Biochemical Correlations with Fatigue in Multiple Sclerosis Detected by MR 2D Localized Correlated Spectroscopy

BACKGROUND AND PURPOSE

Fatigue is the common symptom in patients with multiple sclerosis (MS), yet its pathophysiological mechanism is poorly understood. We investigated the metabolic changes in fatigue in a group of relapsing-remitting MS (RRMS) patients using MR two-dimensional localized correlated spectroscopy (2D L-COSY).

METHODS

Sixteen RRMS and 16 healthy controls were included in the study. Fatigue impact was assessed with the Modified Fatigue Impact Scale (MFIS). MR 2D L-COSY data were collected from the posterior cingulate cortex. Nonparametric statistical analysis was used to calculate the changes in creatine scaled metabolic ratios and their correlations with fatigue scores.

RESULTS

Compared to healthy controls, the RRMS group showed significantly higher fatigue and lower metabolic ratios for tyrosine, glutathione, homocarnosine (GSH+Hca), fucose-3, glutamine+glutamate (Glx), glycerophosphocholine (GPC), total choline, and N-acetylaspartate (NAA-2), while increased levels for isoleucine and glucose (P ≤ .05). Only GPC showed positive correlation with all fatigue domains (r = .537, P ≤ .05). On the other hand, Glx-upper, NAA-2, GSH+Hca, and fucose-3 showed negative correlations with all fatigue domains (r = -.345 to -.580, P ≤ .05). While tyrosine showed positive correlation with MFIS (r = .499, P ≤ .05), cognitive fatigue was negatively correlated with total GSH (r = -.530, P ≤ .05). No correlations were found between lesion load or brain volumes with fatigue score.

CONCLUSIONS

Our results suggest that fatigue in MS is strongly correlated with an imbalance in neurometabolites but not structural brain measurements.

Interactions of neuroimmune signaling and glutamate plasticity in addiction

Chronic use of drugs of abuse affects neuroimmune signaling; however, there are still many open questions regarding the interactions between neuroimmune mechanisms and substance use disorders (SUDs). Further, chronic use of drugs of abuse can induce glutamatergic changes in the brain, but the relationship between the glutamate system and neuroimmune signaling in addiction is not well understood. Therefore, the purpose of this review is to bring into focus the role of neuroimmune signaling and its interactions with the glutamate system following chronic drug use, and how this may guide pharmacotherapeutic treatment strategies for SUDs. In this review, we first describe neuroimmune mechanisms that may be linked to aberrant glutamate signaling in addiction. We focus specifically on the nuclear factor-kappa B (NF-κB) pathway, a potentially important neuroimmune mechanism that may be a key player in driving drug-seeking behavior. We highlight the importance of astroglial-microglial crosstalk, and how this interacts with known glutamatergic dysregulations in addiction. Then, we describe the importance of studying non-neuronal cells with unprecedented precision because understanding structure-function relationships in these cells is critical in understanding their role in addiction neurobiology. Here we propose a working model of neuroimmune-glutamate interactions that underlie drug use motivation, which we argue may aid strategies for small molecule drug development to treat substance use disorders. Together, the synthesis of this review shows that interactions between glutamate and neuroimmune signaling may play an important and understudied role in addiction processes and may be critical in developing more efficacious pharmacotherapies to treat SUDs.

Astrocyte-induced synapse formation and ischemic stroke

Astrocytes are closely associated with the regulation of synapse formation and function. In addition, astrocytes have been shown to block certain brain impairments, including synaptic damage from stroke and other diseases of the central nervous system (CNS). Although astrocytes do not completely prevent synaptic damage, they appear to be protective and to restore synaptic function following damage. The purpose of this study is to discuss the role of astrocytes in synaptogenesis and synaptic damage in ischemic stroke. I detail the mechanism of action of the multiple factors secreted by astrocytes that are involved in synapse formation. In particular, I describe the characteristics and role in synapse formation of each secreted molecule related to synaptic structure and function. Furthermore, I discuss the effect of astrocytes on synaptogenesis and repair in ischemic stroke and in other CNS diseases. Astrocytes release molecules such as thrombospondin, hevin, secreted protein acidic rich in cysteine, etc., due to activation by ischemia to induce synaptic structure and function, an effect associated with protection of the brain from synaptic damage in ischemic stroke. In conclusion, I show that astrocytes may regulate synaptic transmission while having the potential to block and repair synaptic dysfunction in stroke-associated brain damage.

Effects of infliximab on brain neurochemistry of adults with bipolar depression

OBJECTIVES

To explore the relationship between inflammation and neuronal metabolism in bipolar disorder (BD) by evaluating the neurochemical effects of the tumor necrosis factor-α (TNF-α) antagonist infliximab among individuals with bipolar depression METHODS: This is a post-hoc, exploratory analysis from a 12-week, randomized, double-blind, placebo-controlled trial with infliximab for adults with bipolar depression. We assessed the effects of infliximab on concentration of metabolites in the prefrontal cortex, using proton-magnetic resonance spectroscopy (¹H-MRS), as well as its association with clinical outcomes (i.e. depressive symptom severity and cognitive function).

RESULTS

Eighteen participants in the placebo and 15 in the infliximab group were included in this analysis. In the pre-specified primary outcome, there were no significant effects of treatment on prefrontal concentrations of N-acetylaspartate (NAA; p = 0.712). In the secondary analyses, there was a significant treatment by time interaction for glutamate (Glx; p = 0.018), indicating that Glx levels decreased in infliximab-treated patients, relative to placebo. Treatment group significantly moderated the association between changes in Glx levels and changes in a neurocognitive test (i.e. Digit Symbol Substitution Test; p = 0.014), indicating that in infliximab-treated participants reductions in Glx were associated with cognitive improvement.

CONCLUSIONS

Treatment with infliximab did not affect prefrontal NAA concentration in adults with BD. Exploratory analysis suggested a potential effect of treatment on the glutamate system, a finding that should be confirmed and validated by additional studies.

The effect of aged microglia on synaptic impairment and its relevance in neurodegenerative diseases

Microglia serve key functions in the central nervous system (CNS), participating in the establishment and regulation of synapses and the neuronal network, and regulating activity-dependent plastic changes. As the neuroimmune system, they respond to endogenous and exogenous signals to protect the CNS. In aging, one of the main changes is the establishment of inflamm-aging, a mild chronic inflammation that reduces microglial response to stressors. Neuroinflammation depends mainly on the increased activation of microglia. Microglia over-activation may result in a reduced capacity for performing normal functions related to migration, clearance, and the adoption of an anti-inflammatory state, contributing to an increased susceptibility for neurodegeneration. Oxidative stress contributes both to aging and to the progression of neurodegenerative diseases. Increased production of reactive oxygen species (ROS) and neuroinflammation associated with age- and disease-dependent mechanisms affect synaptic activity and neurotransmission, leading to cognitive dysfunction. Astrocytes prevent microglial cell cytotoxicity by mechanisms mediated by transforming growth factor β1 (TGFβ1). However, TGFβ1-Smad3 pathway is impaired in aging, and the age-related impairment of TGFβ signaling can reduce protective activation while facilitating cytotoxic activation of microglia. A critical analysis on the effect of aging microglia on neuronal function is relevant for the understanding of age-related changes on neuronal function. Here, we present evidence in the context of the "microglial dysregulation hypothesis", which leads to the reduction of the protective functions and increased cytotoxicity of microglia, to discuss the mechanisms involved in neurodegenerative changes and Alzheimer's disease.

Antidepressant-Like Effects of Chronic Guanosine in the Olfactory Bulbectomy Mouse Model

Major depressive disorder (MDD) leads to pervasive changes in the health of afflicted patients. Despite advances in the understanding of MDD and its treatment, profound innovation is needed to develop fast-onset antidepressants with higher effectiveness. When acutely administered, the endogenous nucleoside guanosine (GUO) shows fast-onset antidepressant-like effects in several mouse models, including the olfactory bulbectomy (OBX) rodent model. OBX is advocated to possess translational value and be suitable to assess the time course of depressive-like behavior in rodents. This study aimed at investigating the long-term behavioral and neurochemical effects of GUO in a mouse model of depression induced by bilateral bulbectomy (OBX). Mice were submitted to OBX and, after 14 days of recovery, received daily (ip) administration of 7.5 mg/kg GUO or 40 mg/kg imipramine (IMI) for 45 days. GUO and IMI reversed the OBX-induced hyperlocomotion and recognition memory impairment, hippocampal BDNF increase, and redox imbalance (ROS, NO, and GSH levels). GUO also mitigated the OBX-induced hippocampal neuroinflammation (IL-1, IL-6, TNF-α, INF-γ, and IL-10). Brain microPET imaging ([¹⁸F]FDG) shows that GUO also prevented the OBX-induced increase in hippocampal FDG metabolism. These results provide additional evidence for GUO antidepressant-like effects, associated with beneficial neurochemical outcomes relevant to counteract depression.

Dopamine and Neuroinflammation in Schizophrenia - Interpreting the Findings from Translocator Protein (18kDa) PET Imaging

Schizophrenia is a complex disease whose pathophysiology is not yet fully understood. In addition to the long prevailing dopaminergic hypothesis, the evidence suggests that neuroinflammation plays a role in the pathophysiology of the disease. Recent studies using positron emission tomography (PET) that target a 18kDa translocator protein (TSPO) in activated microglial cells in an attempt to measure neuroinflammation in patients have shown a decrease or a lack of an increase in TSPO binding. Many biological and methodological considerations have been formulated to explain these findings. Although dopamine has been described as an immunomodulatory molecule, its potential role in neuroinflammation has not been explored in the aforementioned studies. In this review, we discuss the interactions between dopamine and neuroinflammation in psychotic states. Dopamine may inhibit neuroinflammation in activated microglia. Proinflammatory molecules released from microglia may decrease dopaminergic transmission. This could potentially explain why the levels of neuroinflammation in the brain of patients with schizophrenia seem to be unchanged or decreased compared to those in healthy subjects. However, most data are indirect and are derived from animal studies or from studies performed outside the field of schizophrenia. Further studies are needed to combine TSPO and dopamine imaging to study the association between microglial activation and dopamine system function.

Tumour Necrosis Factor in Neuroplasticity, Neurogenesis and Alcohol Use Disorder

Alcohol use disorder is a pervasive and detrimental condition that involves changes in neuroplasticity and neurogenesis. Alcohol activates the neuroimmune system and alters the inflammatory status of the brain. Tumour necrosis factor (TNF) is a well characterised neuroimmune signal but its involvement in alcohol use disorder is unknown. In this review, we discuss the variable findings of TNF's effect on neuroplasticity and neurogenesis. Acute ethanol exposure reduces TNF release while chronic alcohol intake generally increases TNF levels. Evidence suggests TNF potentiates excitatory transmission, promotes anxiety during alcohol withdrawal and is involved in drug use in rodents. An association between craving for alcohol and TNF is apparent during withdrawal in humans. While anti-inflammatory therapies show efficacy in reversing neurogenic deficit after alcohol exposure, there is no evidence for TNF's essential involvement in alcohol's effect on neurogenesis. Overall, defining TNF's role in alcohol use disorder is complicated by poor understanding of its variable effects on synaptic transmission and neurogenesis. While TNF may be of relevance during withdrawal, the neuroimmune system likely acts through a larger group of inflammatory cytokines to alter neuroplasticity and neurogenesis. Understanding the individual relevance of TNF in alcohol use disorder awaits a more comprehensive understanding of TNF's effects within the brain.

Possible interplay between the theories of pharmacoresistant epilepsy

Epilepsy is one of the oldest known neurological disorders and is characterized by recurrent seizure activity. It has a high incidence rate, affecting a broad demographic in both developed and developing countries. Comorbid conditions are frequent in patients with epilepsy and have detrimental effects on their quality of life. Current management options for epilepsy include the use of anti-epileptic drugs, surgery, or a ketogenic diet. However, more than 30% of patients diagnosed with epilepsy exhibit drug resistance to anti-epileptic drugs. Further, surgery and ketogenic diets do little to alleviate the symptoms of patients with pharmacoresistant epilepsy. Thus, there is an urgent need to understand the underlying mechanisms of pharmacoresistant epilepsy to design newer and more effective anti-epileptic drugs. Several theories of pharmacoresistant epilepsy have been suggested over the years, the most common being the gene variant hypothesis, network hypothesis, multidrug transporter hypothesis, and target hypothesis. In our review, we discuss the main theories of pharmacoresistant epilepsy and highlight a possible interconnection between their mechanisms that could lead to the development of novel therapies for pharmacoresistant epilepsy.

Neuron-Astrocyte Interactions in Parkinson's Disease

Parkinson’s disease (PD) is the second most common neurodegenerative disease. PD patients exhibit motor symptoms such as akinesia/bradykinesia, tremor, rigidity, and postural instability due to a loss of nigrostriatal dopaminergic neurons. Although the pathogenesis in sporadic PD remains unknown, there is a consensus on the involvement of non-neuronal cells in the progression of PD pathology. Astrocytes are the most numerous glial cells in the central nervous system. Normally, astrocytes protect neurons by releasing neurotrophic factors, producing antioxidants, and disposing of neuronal waste products. However, in pathological situations, astrocytes are known to produce inflammatory cytokines. In addition, various studies have reported that astrocyte dysfunction also leads to neurodegeneration in PD. In this article, we summarize the interaction of astrocytes and dopaminergic neurons, review the pathogenic role of astrocytes in PD, and discuss therapeutic strategies for the prevention of dopaminergic neurodegeneration. This review highlights neuron-astrocyte interaction as a target for the development of disease-modifying drugs for PD in the future.

Sexual function and depression in polycystic ovary syndrome: Is it associated with inflammation and neuromodulators?

Numerous studies have been carried out on depression and sexual dysfunction concomitant with polycystic ovary syndrome (PCOS). Increasing evidence has revealed the importance of inflammation in the etiology of PCOS. In addition, it has been known that some neuromodulators affect depression and sexual function. However, their effects on PCOS are not known. This study aimed to evaluate the relationship of depression and sexual function with cytokines and neuromodulators in PCOS patients. The present study included 20 fertile and 30 infertile patients diagnosed with PCOS and 30 healthy volunteers. Metabolic and endocrine parameters, interleukin (IL)-1β, IL-6, TNFα, γ-aminobutyric acid (GABA), Glutamate, Brain-derived neurotrophic factor (BDNF) serum levels, Beck Depression Index (BDI) and Female Sexual Function Index (FSFI) scores of the patients were compared between the groups. TNFα, IL-1β, IL-6, glutamate, GABA, and BDI scores were found to be significantly higher (p < 0.05) in the PCOS group (p < 0.05). Glutamate, TNFα, IL-1β, and IL-6 values were higher whereas GABA and BDNF values were lower in pateints with moderate and severe depression (p < 0.05). There were no statistically significant relationships between these parameters and the FSFI scores (p > 0.05). Multivariate logistic regression analysis was conducted with potential factors that may affect sexual dysfunction. The results indicated that high waist-to-hip ratio (WHR) (> 0.80) with an odds ratio of 1.81 in PCOS patients, and body mass index (BMI) with an odds ratio of 2.3 and high WHR (> 0.80) with an odds ratio of 1.97 in all patients were found to be independent risk factors affecting sexual dysfunction. The results of the present study suggested that chronic low-dose inflammation seen in PCOS may interact with some neuromodulators, leading to the development of depression. However, no relationship was found between these parameters and sexual function.

The role of gut-immune-brain signaling in substance use disorders

Substance use disorders (SUDs) are debilitating neuropsychiatric conditions that exact enormous costs in terms of loss of life and individual suffering. While much progress has been made defining the neurocircuitry and intracellular signaling cascades that contribute to SUDs, these studies have yielded limited effective treatment options. This has prompted greater exploration of non-traditional targets in addiction. Emerging data suggest inputs from peripheral systems, such as the immune system and the gut microbiome, impact multiple neuropsychiatric diseases, including SUDs. Until recently the gut microbiome, peripheral immune system, and the CNS have been studied independently; however, current work shows the gut microbiome and immune system critically interact to modulate brain function. Additionally, the gut microbiome and immune system intimately regulate one another via extensive bidirectional communication. Accumulating evidence suggests an important role for gut-immune-brain communication in the pathogenesis of substance use disorders. Thus, a better understanding of gut-immune-brain signaling could yield important insight to addiction pathology and potential treatment options.

Post-inflammatory behavioural despair in male mice is associated with reduced cortical glutamate-glutamine ratios, and circulating lipid and energy metabolites

Post-inflammatory behaviours in rodents are widely used to model human depression and to test the efficacy of novel anti-depressants. Mice injected with lipopolysaccharide (LPS) display a depressive-like phenotype twenty-four hours after endotoxin administration. Despite the widespread use of this model, the mechanisms that underlie the persistent behavioural changes after the transient peripheral inflammatory response remain elusive. The study of the metabolome, the collection of all the small molecule metabolites in a sample, combined with multivariate statistical techniques provides a way of studying biochemical pathways influenced by an LPS challenge. Adult male CD-1 mice received an intraperitoneal injection of either LPS (0.83 mg/kg) or saline, and were assessed for depressive-like behaviour 24 h later. In a separate mouse cohort, pro-inflammatory cytokine gene expression and 1H nuclear magnetic resonance (NMR) metabolomics measurements were made in brain tissue and blood. Statistical analyses included Independent Sample t-tests for gene expression data, and supervised multi-variate analysis using orthogonal partial least squares discriminant analysis for metabolomics. Both plasma and brain metabolites in male mice were altered following a single peripheral LPS challenge that led to depressive-like behaviour in the forced swim test. The plasma metabolites altered by LPS are involved in energy metabolism, including lipoproteins, glucose, creatine, and isoleucine. In the brain, glutamate, serine, and N-acetylaspartate (NAA) were reduced after LPS, whereas glutamine was increased. Serine-modulated glutamatergic signalling and changes in bioenergetics may mediate the behavioural phenotype induced by LPS. In light of other data supporting a central imbalance of glutamate-glutamine cycling in depression, our results suggest that aberrant central glutaminergic signalling may underpin the depressive-like behaviours that result from both inflammation and non-immune pathophysiology. Normalising glutaminergic signalling, rather than seeking to increase serotonergic signalling, might prove to be a more coherent approach to the development of new treatments for mood disorder.

Neuron-Glia Interactions in Neurodevelopmental Disorders

Recent studies have revealed synaptic dysfunction to be a hallmark of various psychiatric diseases, and that glial cells participate in synapse formation, development, and plasticity. Glial cells contribute to neuroinflammation and synaptic homeostasis, the latter being essential for maintaining the physiological function of the central nervous system (CNS). In particular, glial cells undergo gliotransmission and regulate neuronal activity in tripartite synapses via ion channels (gap junction hemichannel, volume regulated anion channel, and bestrophin-1), receptors (for neurotransmitters and cytokines), or transporters (GLT-1, GLAST, and GATs) that are expressed on glial cell membranes. In this review, we propose that dysfunction in neuron-glia interactions may contribute to the pathogenesis of neurodevelopmental disorders. Understanding the mechanisms of neuron-glia interaction for synapse formation and maturation will contribute to the development of novel therapeutic targets of neurodevelopmental disorders.

Pathomechanisms of Non-Traumatic Acute Brain Injury in Critically Ill Patients

Delirium, an acute alteration in mental status characterized by confusion, inattention and a fluctuating level of arousal, is a common problem in critically ill patients. Delirium prolongs hospital stay and is associated with higher mortality. The pathophysiology of delirium has not been fully elucidated. Neuroinflammation and neurotransmitter imbalance seem to be the most important factors for delirium development. In this review, we present the most important pathomechanisms of delirium in critically ill patients, such as neuroinflammation, neurotransmitter imbalance, hypoxia and hyperoxia, tryptophan pathway disorders, and gut microbiota imbalance. A thorough understanding of delirium pathomechanisms is essential for effective prevention and treatment of this underestimated pathology in critically ill patients.

Glutamate-induced excitotoxicity in Parkinson's disease: The role of glial cells

Glutamate is the major excitatory neurotransmitter in the central nervous system. Glutamate transmission efficiency depends on the correct functionality and expression of a plethora of receptors and transporters, located both on neurons and glial cells. Of note, glutamate reuptake by dedicated transporters prevents its accumulation at the synapse as well as non-physiological spillover. Indeed, extracellular glutamate increase causes aberrant synaptic signaling leading to neuronal excitotoxicity and death. Moreover, extrasynaptic glutamate diffusion is strongly associated with glia reaction and neuroinflammation. Glutamate-induced excitotoxicity is mainly linked to an impaired ability of glial cells to reuptake and respond to glutamate, then this is considered a common hallmark in many neurodegenerative diseases, including Parkinson's disease (PD). In this review, we discuss the function of astrocytes and microglia in glutamate homeostasis, focusing on how glial dysfunction causes glutamate-induced excitotoxicity leading to neurodegeneration in PD.

Neuroimmune Mechanisms and Sex/Gender-Dependent Effects in the Pathophysiology of Mental Disorders

Innate and adaptive immune mechanisms have emerged as critical regulators of CNS homeostasis and mental health. A plethora of immunologic factors have been reported to interact with emotion- and behavior-related neuronal circuits, modulating susceptibility and resilience to mental disorders. However, it remains unclear whether immune dysregulation is a cardinal causal factor or an outcome of the pathologies associated with mental disorders. Emerging variations in immune regulatory pathways based on sex differences provide an additional framework for discussion in these psychiatric disorders. In this review, we present the current literature pertaining to the effects that disrupted immune pathways have in mental disorder pathophysiology, including immune dysregulation in CNS and periphery, microglial activation, and disturbances of the blood-brain barrier. In addition, we present the suggested origins of such immune dysregulation and discuss the gender and sex influence of the neuroimmune substrates that contribute to mental disorders. The findings challenge the conventional view of these disorders and open the window to a diverse spectrum of innovative therapeutic targets that focus on the immune-specific pathophenotypes in neuronal circuits and behavior. SIGNIFICANCE STATEMENT: The involvement of gender-dependent inflammatory mechanisms on the development of mental pathologies is gaining momentum. This review addresses these novel factors and presents the accumulating evidence introducing microglia and proinflammatory elements as critical components and potential targets for the treatment of mental disorders.

Diclofenac reduces the risk of Alzheimer's disease: a pilot analysis of NSAIDs in two US veteran populations

Background:

Our aim was to determine whether specific nonsteroidal anti-inflammatory (NSAID) agents are associated with a decreased frequency of Alzheimer’s disease (AD).

Materials and methods:

Days of drug exposure were determined for diclofenac, etodolac, and naproxen using US Department of Veterans Affairs (VA) pharmacy transaction records, combined from two separate VA sites. AD diagnosis was established by the International Classification of Diseases, ninth revision (ICD-9)/ICD-10 diagnostic codes and the use of AD medications. Cox regression survival analysis was used to evaluate the association between AD frequency and NSAID exposure over time. Age at the end of the study and the medication-based disease burden index (a comorbidity index) were used as covariates.

Results:

Frequency of AD was significantly lower in the diclofenac group (4/1431, 0.28%) compared with etodolac (328/14,646, 2.24%), and naproxen (202/12,203, 1.66%). For regression analyses, naproxen was chosen as the comparator drug, since it has been shown to have no effect on the development of AD. Compared with naproxen, etodolac had no effect on the development of AD, hazard ratio (HR) 1.00 [95% confidence interval (CI): 0.84–1.20, p = 0.95]. In contrast, diclofenac had a significantly lower HR of AD compared with naproxen, HR 0.25 (95% CI: 0.09–0.68, p <0.01). After site effects were controlled for, age at end of the study (HR = 1.08, 95% CI: 1.07–1.09, p <0.001) was also found to influence the development of AD, and the medication-based disease burden index was a strong predictor for AD, HR 5.17 (95% CI: 4.60–5.81) indicating that as comorbidities increase, the risk for AD increases very significantly.

Conclusion:

Diclofenac, which has been shown to have active transport into the central nervous system, and which has been shown to lower amyloid beta and interleukin 1 beta, is associated with a significantly lower frequency of AD compared with etodolac and naproxen. These results are compelling, and parallel animal studies of the closely related fenamate NSAID drug class.

Neuroinflammation and microglia/macrophage phenotype modulate the molecular background of post-stroke depression: A literature review

Increasing evidence hints to the central role of neuroinflammation in the development of post-stroke depression. Danger signals released in the acute phase of ischemia trigger microglial activation, along with the infiltration of neutrophils and macrophages. The increased secretion of proinflammatory cytokines interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor α (TNFα) provokes neuronal degeneration and apoptosis, whereas IL-6, interferon γ (IFNγ), and TNFα induce aberrant tryptophane degradation with the accumulation of the end-product quinolinic acid in resident glial cells. This promotes glutamate excitotoxicity via hyperexcitation of N-methyl-D-aspartate receptors and antagonizes 5-hydroxy-tryptamine, reducing synaptic plasticity and neuronal survival, thus favoring depression. In the post-stroke period, CX3CL1 and the CD200-CD200R interaction mediates the activation of glial cells, whereas CCL-2 attracts infiltrating macrophages. CD206 positive cells grant the removal of excessive danger signals; the high number of regulatory T cells, IL-4, IL-10, transforming growth factor β (TGFβ), and intracellular signaling via cAMP response element-binding protein (CREB) support the M2 type differentiation. In favorable conditions, these cells may exert efficient clearance, mediate tissue repair, and might be essential players in the downregulation of molecular pathways that promote post-stroke depression.

Leptin increases sympathetic nerve activity via induction of its own receptor in the paraventricular nucleus

Whether leptin acts in the paraventricular nucleus (PVN) to increase sympathetic nerve activity (SNA) is unclear, since PVN leptin receptors (LepR) are sparse. We show in rats that PVN leptin slowly increases SNA to muscle and brown adipose tissue, because it induces the expression of its own receptor and synergizes with local glutamatergic neurons. PVN LepR are not expressed in astroglia and rarely in microglia; instead, glutamatergic neurons express LepR, some of which project to a key presympathetic hub, the rostral ventrolateral medulla (RVLM). In PVN slices from mice expressing GCaMP6, leptin excites glutamatergic neurons. LepR are expressed mainly in thyrotropin-releasing hormone (TRH) neurons, some of which project to the RVLM. Injections of TRH into the RVLM and dorsomedial hypothalamus increase SNA, highlighting these nuclei as likely targets. We suggest that this neuropathway becomes important in obesity, in which elevated leptin maintains the hypothalamic pituitary thyroid axis, despite leptin resistance.

Inflammation as a treatment target in mood disorders: review

BACKGROUND

Mood disorders, i.e. major depressive disorder (MDD) and bipolar disorders, are leading sources of disability worldwide. Currently available treatments do not yield remission in approximately a third of patients with a mood disorder. This is in part because these treatments do not target a specific core pathology underlying these heterogeneous disorders. In recent years, abnormal inflammatory processes have been identified as putative pathophysiological mechanisms and treatment targets in mood disorders, particularly among individuals with treatment-resistant conditions.

AIMS

In this selective review, we aimed to summarise recent advances in the field of immunopsychiatry, including emerging pathophysiological models and findings from treatment ttrials of immunomodulatory agents for both MDD and bipolar disorders.

METHOD

We performed a literature review by searching Medline for clinical trials of immunomodulating agents as monotherapy or adjunctive treatments in MDD and bipolar disorders. Included studies are randomised controlled trials (RCTs), cluster RCTs or cross-over trials of immunomodulating agents that had an active comparator or a placebo-arm.

RESULTS

Current evidence shows an association between inflammation and mood symptoms. However, there is conflicting evidence on whether this link is causal.

CONCLUSIONS

Future studies should focus on identifying specific neurobiological underpinnings for the putative causal association between an activated inflammatory response and mood disorders. Results of these studies are needed before further treatment trials of immunomodulatory agents can be justified.

Platelet glutamate uptake and Th1 cells inversely correlate in relapsing/remitting and in progressive multiple sclerosis

BACKGROUND

High affinity sodium-dependent Excitatory Amino Acid Transporters (EAAT), present in glial and neuron cells, clear around 90% of the synaptic cleft released glutamate, and their impaired activity seem to be critical for many neurodegenerative disorders, including Multiple Sclerosis (MS). These transporters are also present in human platelets, and they show molecular and biochemical characteristics similar to those in the CNS.

OBJECTIVES

The aim of this study was to investigate whether EAAT-dependent uptake is present also at the peripheral level in blood of MS patients. Moreover, since platelets (plt) and peripheral blood mononuclear cells (PBMC) share the same intra-corporeal fluid, they might be reciprocally influenced, and the glutamate uptake modulation might be useful as a peripheral "trait-marker" to characterize different clinical courses of MS RESULTS: : Reduced uptake values were found in MS patients compared to healthy controls (HC), as well as significant differences were found across MS clinical courses. Representative saturation curves showed that Vmax was significantly decreased for patients compared to HC. Conversely, dissociation constant of the two reactions appeared similar for MS and HC subjects. Furthermore, clinical forms of MS with mild (benign) prognosis was not affected as fa as concern EAAT uptake. Gender, age, and drug treatments did not impact glutamate uptake efficiency. Interestingly, a negative correlation between EAAT activity and percentage of Th1 cells (CD4+IFNγ+ and CD4+TBET+IFNγ+ cells) was observed, suggesting a relationship between EAAT impairment and a pro-inflammatory environment.

CONCLUSIONS

Interestingly, as shown in the CNS, a relationship between clinical, inflammatory MS features and glutamate clearance can be also assessed in platelets. Moreover, glutamate uptake activity might be an useful biomarker to characterize patients with benign prognosis.

Systemic inflammation is associated with depressive symptoms differentially by sex and race: a longitudinal study of urban adults

Systemic inflammation may influence trajectories of depressive symptoms over time, perhaps differentially by sex and race. Inflammatory markers and the Center for Epidemiologic Studies-Depression scale [total score: CES-D_total and four distinctive domains: somatic complaints, depressed affect, positive affect and interpersonal problems] were examined among African-American (AA) and White urban adults participating in the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study [2004-2013, Age_base:30-64 y, mean ± SD follow-up time: 4.64 ± 0.93 y, N = 150 (with cytokine data) to N = 1,767 (with other inflammatory markers)]. Findings suggest that serum concentrations of high-sensitivity C-reactive protein (hsCRP), z-inflammation composite score [ICS, combining elevated hsCRP and ESR with low serum albumin and iron], and serum interleukin (IL) 1β were positively associated with ΔCES-D_total (Δ: annual rate of increase) among Whites only. IL-12 was directly related to ΔCES-D_total among men and AA. The race-specific associations of hsCRP, ICS, IL-1β and the sex-specific association of IL-12 with ΔCES-D_total were replicated for the "depressed affect" domain. Similarly, among men, lower serum albumin and higher ICS were linked with higher baseline "somatic complaints". IL-10 among AA and IL-12 among men were inversely related to Δ"positive affect", while "interpersonal problems" were cross-sectionally associated with IL-6 among AA and IL-10 among Whites. Finally, baseline ICS was positively associated with incident "elevated depressive symptoms" (EDS: CES-D_total ≥ 16) among AA (HR = 1.28, 95% CI: 1.04-1.56, P = 0.017). Overall, systemic inflammation was directly linked to increased depressive symptoms over time and at baseline, differentially across sex and race groups. More longitudinal research is needed to replicate our findings.

Protective effects of 3,4-dihydroxyphenylethanol on spinal cord injury-induced oxidative stress and inflammation

3,4-Dihydroxyphenylethanol (DOPET) is a potent antioxidant polyphenolic compound. In this study, our objective was to investigate the underlying mechanism of the neuroprotective role of DOPET in attenuating spinal cord injury (SCI). Initially, SCI was induced by performing surgical laminectomy on the rats at T10-T12 level. Then, the neurological function-dependent locomotion was measured using Basso Beattie Bresnahan score, which declined in the SCI-induced group. Increased antioxidant levels such as superoxide dismutase, glutathione peroxidase, and glutathione along with other parameters such as increased lipid peroxidation (LPO) and myeloperoxidase (MPO) activities were all observed in the SCI group. Levels of proinflammatory cytokines such as tumor necrosis factor-α and interleukin-1β were upregulated in the serum and spinal cord tissue as observed on the immunoblot. Interestingly, protein levels of apoptotic markers such as Bax, cleaved caspase 3 and RT-PCR analysis-based mRNA level of pro-inflammatory cytokine, nuclear factor- κ activated B cells (NF-κB) were significantly upregulated in the spinal cord tissue. Nonetheless, antiapoptotic factor such as B-cell lymphoma 2 (Bcl-2) protein expression was downregulated in the same group. However, on administering 10 mg/kg of DOPET, the neuronal function was rescued, antioxidants were restored back to the normal levels, LPO and MPO activities were reduced in conjunction with downregulated levels of proinflammatory cytokines and apoptotic markers in the SCI group. These findings show that DOPET could potentially target multiple signalling pathways to combat SCI.

From adolescence to late aging: A comprehensive review of social behavior, alcohol, and neuroinflammation across the lifespan

The passage of time dictates the pace at which humans and other organisms age but falls short of providing a complete portrait of how environmental, lifestyle and underlying biological processes contribute to senescence. Two fundamental features of the human experience that change dramatically across the lifespan include social interactions and, for many, patterns of alcohol consumption. Rodent models show great utility for understanding complex interactions among aging, social behavior and alcohol use and abuse, yet little is known about the neural changes in late aging that contribute to the natural decline in social behavior. Here, we posit that aging-related neuroinflammation contributes to the insipid loss of social motivation across the lifespan, an effect that is exacerbated by patterns of repeated alcohol consumption observed in many individuals. We provide a comprehensive review of (i) neural substrates crucial for the expression of social behavior under non-pathological conditions; (ii) unique developmental/lifespan vulnerabilities that may contribute to the divergent effects of low-and high-dose alcohol exposure; and (iii) aging-associated changes in neuroinflammation that may sit at the intersection between social processes and alcohol exposure. In doing so, we provide an overview of correspondence between lifespan/developmental periods between common rodent models and humans, give careful consideration to model systems used to aptly probe social behavior, identify points of coherence between human and animal models, and point toward a multitude of unresolved issues that should be addressed in future studies. Together, the combination of low-dose and high-dose alcohol effects serve to disrupt the normal development and maintenance of social relationships, which are critical for both healthy aging and quality of life across the lifespan. Thus, a more complete understanding of neural systems-including neuroinflammatory processes-which contribute to alcohol-induced changes in social behavior will provide novel opportunities and targets for promoting healthy aging.

Neuroimmune mechanisms of psychostimulant and opioid use disorders

Substance use disorders are global health problems with few effective treatment options. Unfortunately, most potential pharmacological treatments are hindered by abuse potential of their own, limited efficacy, or adverse side effects. As a consequence, there is a pressing need for the development of addiction treatments with limited abuse potential and fewer off target effects. Given the difficulties in developing new pharmacotherapies for substance use disorders, there has been growing interest in medications that act on non-traditional targets. Recent evidence suggests a role for dysregulated immune signaling in the pathophysiology of multiple psychiatric diseases. While there is evidence that immune responses in the periphery and the central nervous system are altered by exposure to drugs of abuse, the contributions of neuroimmune interactions to addictive behaviors are just beginning to be appreciated. In this review, we discuss the data on immunological changes seen in clinical populations with substance use disorders, as well as in translational animal models of addiction. Importantly, we highlight those mechanistic findings showing causal roles for central or peripheral immune mediators in substance use disorder and appropriate animal models. Based on the literature reviewed here, it is clear that brain-immune system interactions in substance use disorders are much more complex and important than previously understood. While much work remains to be done, there are tremendous potential therapeutic implications for immunomodulatory treatments in substance use disorders.

Intranasal Losartan Decreases Perivascular Beta Amyloid, Inflammation, and the Decline of Neurogenesis in Hypertensive Rats

The contribution of the local angiotensin receptor system to neuroinflammation, impaired neurogenesis, and amyloid beta (Aβ) accumulation in Alzheimer's disease (AD) and in hypertension is consistent with the remarkable neuroprotection provided by angiotensin receptor blockers (ARBs) independent of their blood pressure-lowering effect. Considering the causal relationship between hypertension and AD and that targeting cerebrovascular pathology with ARBs does not necessarily require their systemic effects, we tested intranasal losartan in the rat model of chronic hypertension (spontaneously hypertensive stroke-prone rats, SHRSP). Intranasal losartan at a subdepressor dose decreased mortality, neuroinflammation, and perivascular content of Aβ by enhancing key players in its metabolism and clearance, including insulin-degrading enzyme, neprilysin, and transthyretin. Furthermore, this treatment improved neurologic deficits and increased brain IL-10 concentration, hippocampal cell survival, neurogenesis, and choroid plexus cell proliferation in SHRSP. Losartan (1 μM) also reduced LDH release from cultured astroglial cells in response to toxic glutamate concentrations. This effect was completely blunted by IL-10 antibodies. These findings suggest that intranasal ARB treatment is a neuroprotective, neurogenesis-inducing, and Aβ-decreasing strategy for the treatment of hypertensive stroke and cerebral amyloid angiopathy acting at least partly through the IL-10 pathway.

Glutamate Transport and Preterm Brain Injury

Preterm birth complications are the leading cause of child death worldwide and a top global health priority. Among the survivors, the risk of life-long disabilities is high, including cerebral palsy and impairment of movement, cognition, and behavior. Understanding the molecular mechanisms of preterm brain injuries is at the core of future healthcare improvements. Glutamate excitotoxicity is a key mechanism in preterm brain injury, whereby the accumulation of extracellular glutamate damages the delicate immature oligodendrocytes and neurons, leading to the typical patterns of injury seen in the periventricular white matter. Glutamate excitotoxicity is thought to be induced by an interaction between environmental triggers of injury in the perinatal period, particularly cerebral hypoxia-ischemia and infection/inflammation, and developmental and genetic vulnerabilities. To avoid extracellular build-up of glutamate, the brain relies on rapid uptake by sodium-dependent glutamate transporters. Astrocytic excitatory amino acid transporter 2 (EAAT2) is responsible for up to 95% of glutamate clearance, and several lines of evidence suggest that it is essential for brain functioning. While in the adult EAAT2 is predominantly expressed by astrocytes, EAAT2 is transiently upregulated in the immature oligodendrocytes and selected neuronal populations during mid-late gestation, at the peak time for preterm brain injury. This developmental upregulation may interact with perinatal hypoxia-ischemia and infection/inflammation and contribute to the selective vulnerability of the immature oligodendrocytes and neurons in the preterm brain. Disruption of EAAT2 may involve not only altered expression but also impaired function with reversal of transport direction. Importantly, elevated EAAT2 levels have been found in the reactive astrocytes and macrophages of human infant post-mortem brains with severe white matter injury (cystic periventricular leukomalacia), potentially suggesting an adaptive mechanism against excitotoxicity. Interestingly, EAAT2 is suppressed in animal models of acute hypoxic-ischemic brain injury at term, pointing to an important and complex role in newborn brain injuries. Enhancement of EAAT2 expression and transport function is gathering attention as a potential therapeutic approach for a variety of adult disorders and awaits exploration in the context of the preterm brain injuries.

Astroglial Mechanisms of Ketamine Action Include Reduced Mobility of Kir4.1-Carrying Vesicles

The finding that ketamine, an anaesthetic, can elicit a rapid antidepressant effect at low doses that lasts for weeks in patients with depression is arguably a major achievement in psychiatry in the last decades. However, the mechanisms of action are unclear. The glutamatergic hypothesis of ketamine action posits that ketamine is a N-methyl-D-aspartate receptor (NMDAR) antagonist modulating downstream cytoplasmic events in neurons. In addition to targeting NMDARs in synaptic transmission, ketamine may modulate the function of astroglia, key homeostasis-providing cells in the central nervous system, also playing a role in many neurologic diseases including depression, which affects to 20% of the population globally. We first review studies on astroglia revealing that (sub)anaesthetic doses of ketamine attenuate stimulus-evoked calcium signalling, a process of astroglial cytoplasmic excitability, regulating the exocytotic release of gliosignalling molecules. Then we address how ketamine alters the fusion pore activity of secretory vesicles, and how ketamine affects extracellular glutamate and K⁺ homeostasis, both considered pivotal in depression. Finally, we also provide evidence indicating reduced cytoplasmic mobility of astroglial vesicles carrying the inward rectifying potassium channel (Kir4.1), which may regulate the density of Kir4.1 at the plasma membrane. These results indicate that the astroglial capacity to control extracellular K⁺ concentration may be altered by ketamine and thus indirectly affect the action potential firing of neurons, as is the case in lateral habenula in a rat disease model of depression. Hence, ketamine-altered functions of astroglia extend beyond neuronal NMDAR antagonism and provide a basis for its antidepressant action through glia.

Immunological Aspects of Depressive Disorder – The Review

Depression represents a mood disorder and is considered to be one of the most common mental disorders in general. World Health Organization estimates that depression will be the leading cause of disability-adjusted life years, until 2030. Depression is a complex heterogeneous disorder where immune system and its regulation play an important role. Innate and adaptive immunity mecha nisms are included, along with processes of immune activation and suppression. The expression of humoral factors of innate immunity, especially pro-inflammatory cytokines, is increased, whereas the intensity of cellular immune mechanisms, primarily T cells and NK cells, are impaired. The influence of pro-inflammatory cytokines on depression is reflected in their effect on certain enzymes and ensuing reduction of neurotransmitters serotonin and dopamine. They also affect the neuroendocrine function in central nervous system, resulting in increase of cortisol levels and inactivation of glucocorticoid receptors in the periphery, which leads to neurodegeneration and decrease in neurotransmitter production. Certain cytokines affect neuroplasticity through the decreasing of concentration of neurotrophic brain factor and induction of brain cell apoptosis. The results are often contradictory talking about mechanisms of adaptive immunity. On one hand, an increased activity of Tlymphocytes is observed, while on the other, there are evidence of spontaneous apoptosis and impaired function of these cells in depression. In addition, neuroprotective role of autoreactive and regulatory T cells in prevention of depression has also been demonstrated. The aim of this paper is to analyze the current knowledge on the role of immune mechanisms in the pathogenesis of depression.

Excitotoxicity, neuroinflammation and oxidant stress as molecular bases of epileptogenesis and epilepsy-derived neurodegeneration: The role of vitamin E

Glutamate-mediated excitotoxicity, neuroinflammation, and oxidative stress are common underlying events in neurodegeneration. This pathogenic "triad" characterizes the neurobiology of epilepsy, leading to seizure-induced cell death, increased susceptibility to neuronal synchronization and network alterations. Along with other maladaptive changes, these events pave the way to spontaneous recurrent seizures and progressive degeneration of the interested brain areas. In vivo models of epilepsy are available to explore such epileptogenic mechanisms, also assessing the efficacy of chemoprevention and therapy strategies at the pre-clinical level. The kainic acid model of pharmacological excitotoxicity and epileptogenesis is one of the most investigated mimicking the chronicization profile of temporal lobe epilepsy in humans. Its pathogenic cues include inflammatory and neuronal death pathway activation, mitochondrial disturbances and lipid peroxidation of several regions of the brain, the most vulnerable being the hippocampus. The importance of neuroinflammation and lipid peroxidation as underlying molecular events of brain damage was demonstrated in this model by the possibility to counteract the related maladaptive morphological and functional changes of this organ with vitamin E, the main fat-soluble cellular antioxidant and "conditional" co-factor of enzymatic pathways involved in polyunsaturated lipid metabolism and inflammatory signaling. The present review paper provides an overview of the literature supporting the potential for a timely intervention with vitamin E therapy in clinical management of seizures and epileptogenic processes associated with excitotoxicity, neuroinflammation and lipid peroxidation, i.e. the pathogenic "triad".

Neuroinflammation in addiction: A review of neuroimaging studies and potential immunotherapies

Addiction is a worldwide public health problem and this article reviews scientific advances in identifying the role of neuroinflammation in the genesis, maintenance, and treatment of substance use disorders. With an emphasis on neuroimaging techniques, this review examines human studies of addiction using positron emission tomography to identify binding of translocator protein (TSPO), which is upregulated in reactive glial cells and activated microglia during pathological states. High TSPO levels have been shown in methamphetamine use but exhibits variable patterns in cocaine use. Alcohol and nicotine use, however, are associated with lower TSPO levels. We discuss how mechanistic differences at the neurotransmitter and circuit level in the neural effects of these agents and subsequent immune response may explain these observations. Finally, we review the potential of anti-inflammatory drugs, including ibudilast, minocycline, and pioglitazone, to ameliorate the behavioral and cognitive consequences of addiction.

Anandamide Reduces the Toxic Synergism Exerted by Quinolinic Acid and Glutaric Acid in Rat Brain Neuronal Cells

The endocannabinoid system (ECS) regulates several physiological processes in the Central Nervous System, including the modulation of neuronal excitability via activation of cannabinoid receptors (CBr). Both glutaric acid (GA) and quinolinic acid (QUIN) are endogenous metabolites that, under pathological conditions, recruit common toxic mechanisms. A synergistic effect between them has already been demonstrated, supporting potential implications for glutaric acidemia type I (GA I). Here we investigated the possible involvement of a cannabinoid component in the toxic model exerted by QUIN + GA in rat cortical slices and primary neuronal cell cultures. The effects of the CB1 receptor agonist anandamide (AEA), and the fatty acid amide hydrolase inhibitor URB597, were tested on cell viability in cortical brain slices and primary neuronal cultures exposed to QUIN, GA, or QUIN + GA. As a pre-treatment to the QUIN + GA condition, AEA prevented the loss of cell viability in both preparations. URB597 only protected in a moderate manner the cultured neuronal cells against the QUIN + GA-induced damage. The use of the CB1 receptor reverse agonist AM251 in both biological preparations prevented partially the protective effects exerted by AEA, thus suggesting a partial role of CB1 receptors in this toxic model. AEA also prevented the cell damage and apoptotic death induced by the synergic model in cell cultures. Altogether, these findings demonstrate a modulatory role of the ECS on the synergic toxic actions exerted by QUIN + GA, thus providing key information for the understanding of the pathophysiological events occurring in GA I.