Widespread activation of microglial cells in the hippocampus of chronic epileptic rats correlates only partially with neurodegeneration

Contrasting Disease Progression, Microglia Reactivity, Tolerance, and Resistance to Toxoplasma gondii Infection in Two Mouse Strains

Our study investigated the innate immune response to Toxoplasma gondii infection by assessing microglial phenotypic changes and sickness behavior as inflammatory response markers post-ocular tachyzoite instillation. Disease progression in Swiss albino mice was compared with the previously documented outcomes in BALB/c mice using an identical ocular route and parasite burden (2 × 105 tachyzoites), with saline as the control. Contrary to expectations, the Swiss albino mice displayed rapid, lethal disease progression, marked by pronounced sickness behaviors and mortality within 11-12 days post-infection, while the survivors exhibited no apparent signs of infection. Comparative analysis revealed the T. gondii-infected BALB/c mice exhibited reduced avoidance of feline odors, while the infected Swiss albino mice showed enhanced avoidance responses. There was an important increase in microglial cells in the dentate gyrus molecular layer of the infected Swiss albino mice compared to the BALB/c mice and their respective controls. Hierarchical cluster and discriminant analyses identified three microglial morphological clusters, differentially affected by T. gondii infection across strains. The BALB/c mice exhibited increased microglial branching and complexity, while the Swiss albino mice showed reduced shrunken microglial arbors, diminishing their morphological complexity. These findings highlight strain-specific differences in disease progression and inflammatory regulation, indicating lineage-specific mechanisms in inflammatory responses, tolerance, and resistance. Understanding these elements is critical in devising control measures for toxoplasmosis.

A high seizure burden increases several prostaglandin species in the hippocampus of a Scn1a+/- mouse model of Dravet syndrome

Dravet syndrome is an intractable epilepsy with a high seizure burden that is resistant to current anti-seizure medications. There is evidence that neuroinflammation plays a role in epilepsy and seizures, however few studies have specifically examined neuroinflammation in Dravet syndrome under conditions of a higher seizure burden. Here we used an established genetic mouse model of Dravet syndrome (Scn1a+/- mice), to examine whether a higher seizure burden impacts the number and morphology of microglia in the hippocampus. Moreover, we examined whether a high seizure burden influences classical inflammatory mediators in this brain region. Scn1a+/- mice with a high seizure burden induced by thermal priming displayed a localised reduction in microglial cell density in the granule cell layer and subgranular zone of the dentate gyrus, regions important to postnatal neurogenesis. However, microglial cell number and morphology remained unchanged in other hippocampal subfields. The high seizure burden in Scn1a+/- mice did not affect hippocampal mRNA expression of classical inflammatory mediators such as interleukin 1β and tumour necrosis factor α, but increased cyclooxygenase 2 (COX-2) expression. We then quantified hippocampal levels of prostanoids that arise from COX-2 mediated metabolism of fatty acids and found that Scn1a+/- mice with a high seizure burden displayed increased hippocampal concentrations of numerous prostaglandins, notably PGF2α, PGE2, PGD2, and 6-K-PGF1A, compared to Scn1a+/- mice with a low seizure burden. In conclusion, a high seizure burden increased hippocampal concentrations of various prostaglandin mediators in a mouse model of Dravet syndrome. Future studies could interrogate the prostaglandin pathways to further better understand their role in the pathophysiology of Dravet syndrome.

Scoping review of disease-modifying effect of drugs in experimental epilepsy

Objective

Epilepsy affects ~50 million people worldwide causing significant medical, financial, and sociologic concerns for affected patients and their families. To date, treatment of epilepsy is primarily symptomatic management because few effective preventative or disease-modifying interventions exist. However, recent research has identified neurobiological mechanisms of epileptogenesis, providing new pharmacologic targets to investigate. The current scientific evidence remains scattered across multiple studies using different model and experimental designs. The review compiles different models of anti-epileptogenic investigation and highlights specific compounds with potential epileptogenesis-modifying experimental drugs. It provides a platform for standardization of future epilepsy research to allow a more robust compound analysis of compounds with potential for epilepsy prevention.

Methods

PubMed, Ovid MEDLINE, and Web of Science were searched from 2007 to 2021. Studies with murine models of epileptogenesis and explicitly detailed experimental procedures were included in the scoping review. In total, 51 articles were selected from 14,983 and then grouped by five core variables: (1) seizure frequency, (2) seizure severity, (3) spontaneous recurrent seizures (SRS), (4) seizure duration, and (5) mossy fiber sprouting (MFS). The variables were differentiated based on experimental models including methods of seizure induction, treatment schedule and timeline of data collection. Data was categorized by the five core variables and analyzed by converting original treatment values to units of percent of its respective control.

Results

Discrepancies in current epileptogenesis models significantly complicate inter-study comparison of potential anti-epileptogenic interventions. With our analysis, many compounds showed a potential to reduce epileptogenic characteristics defined by the five core variables. WIN55,212-2, aspirin, rapamycin, 1400W, and LEV + BQ788 were identified compounds with the potential of effective anti-epileptic properties.

Significance

Our review highlights the need for consistent methodology in epilepsy research and provides a novel approach for future research. Inconsistent experimental designs hinder study comparison, slowing the progression of treatments for epilepsy. If the research community can optimize and standardize parameters such as methods of seizure induction, administration schedule, sampling time, and aniMal models, more robust meta-analysis and collaborative research would follow. Additionally, some compounds such as rapamycin, WIN 55,212-2, aspirin, 1400W, and LEV + BQ788 showed anti-epileptogenic modulation across multiple variables. We believe they warrant further study both individually and synergistically.

Identification of perioperative neurocognitive dysfunction biomarkers in cerebrospinal fluid with quantitative proteomic approach in patients undergoing transurethral resection of prostate with combined spinal and epidural analgesia

BACKGROUND

This study aimed to identify predictive biomarkers of perioperative neurocognitive dysfunction (PND) in cerebrospinal fluid of elderly male patients undergoing elective transurethral resection of prostate, using an isobaric tags for relative and absolute quantitative-based quantitative proteomic approach.

METHODS

Patients were evaluated with Mini Mental State Examination at -1 and+3 days of operation. Presence of PND was determined with Z-score method. Patients characteristics and quantitative cerebrospinal fluid proteomes detected with isobaric tags for relative and absolute quantitative-were compared between PND and non-PND patients. Gene ontology and Kyoto Encyclopedia of Genes and Genomes analysis were performed to identify pathways potentially involved in PND.

RESULT

A total of 229 patients were included in the study and 32 were diagnosed with PND (incidence 14.4%). The age, incidence of hypertension, and diabetes of PND patients were significantly higher than non-PND patients (P < .05). There were 85 differentially expressed proteins identified, among which High Mobility Group Box 1, prostaglandin D synthase, and matrix metalloproteinase inhibitor were considered to be promising candidates as they might play important roles in pathophysiology of PND.

CONCLUSION

Proteomic approach identified potential biomarkers for predicting the occurrence of PND. These findings need to be validated in further studies.

IL-37 expression reduces acute and chronic neuroinflammation and rescues cognitive impairment in an Alzheimer's disease mouse model

The anti-inflammatory cytokine interleukin-37 (IL-37) belongs to the IL-1 family but is not expressed in mice. We used a human IL-37 (hIL-37tg) expressing mouse, which has been subjected to various models of local and systemic inflammation as well as immunological challenges. Previous studies reveal an immunomodulatory role of IL-37, which can be characterized as an important suppressor of innate immunity. Here, we examined the functions of IL-37 in the central nervous system and explored the effects of IL-37 on neuronal architecture and function, microglial phenotype, cytokine production and behavior after inflammatory challenge by intraperitoneal LPS-injection. In wild-type mice, decreased spine density, activated microglial phenotype and impaired long-term potentiation (LTP) were observed after LPS injection, whereas hIL-37tg mice showed no impairment. In addition, we crossed the hIL-37tg mouse with an animal model of Alzheimer’s disease (APP/PS1) to investigate the anti-inflammatory properties of IL-37 under chronic neuroinflammatory conditions. Our results show that expression of IL-37 is able to limit inflammation in the brain after acute inflammatory events and prevent loss of cognitive abilities in a mouse model of AD.

Mapping microglia and astrocyte activation in vivo using diffusion MRI

While glia are increasingly implicated in the pathophysiology of psychiatric and neurodegenerative disorders, available methods for imaging these cells in vivo involve either invasive procedures or positron emission tomography radiotracers, which afford low resolution and specificity. Here, we present a noninvasive diffusion-weighted magnetic resonance imaging (MRI) method to image changes in glia morphology. Using rat models of neuroinflammation, degeneration, and demyelination, we demonstrate that diffusion-weighted MRI carries a fingerprint of microglia and astrocyte activation and that specific signatures from each population can be quantified noninvasively. The method is sensitive to changes in glia morphology and proliferation, providing a quantitative account of neuroinflammation, regardless of the existence of a concomitant neuronal loss or demyelinating injury. We prove the translational value of the approach showing significant associations between MRI and histological microglia markers in humans. This framework holds the potential to transform basic and clinical research by clarifying the role of inflammation in health and disease.

Microglia Activation in the Midbrain of the Human Neonate: The Effect of Perinatal Hypoxic-Ischemic Injury

Perinatal hypoxia-ischemia (PHI) is a major risk factor for the development of neuropsychiatric deficits later in life. We previously reported that after prolonged PHI, the dopaminergic neurons of the human neonate showed a dramatic reduction of tyrosine hydroxylase (TH) in the substantia nigra, without important signs of neuronal degeneration despite the significant reduction in their cell size. Since microglia activation could precede neuronal death, we now investigated 2 microglia activation markers, ionized calcium-binding adapter molecule 1 (Iba1), and the phagocytosis marker Cd68. The highest Iba1 immunoreactivity was found in neonates with neuropathological lesions of severe/abrupt PHI, while the lowest in subjects with moderate/prolonged or older PHI. Subjects with very severe/prolonged or chronic PHI showed an increased Iba1 expression and very activated microglial morphology. Heavy attachment of microglia on TH neurons and remarkable expression of Cd68 were also observed indicating phagocytosis in this group. Females appear to express more Iba1 than males, suggesting a gender difference in microglia maturation and immune reactivity after PHI insult. PHI-induced microglial "priming" during the sensitive for brain development perinatal/neonatal period, in combination with genetic or other epigenetic factors, could predispose the survivors to neuropsychiatric disorders later in life, possibly through a sexually dimorphic way.

Brain Immunoinformatics: A Symmetrical Link between Informatics, Wet Lab and the Clinic

Breakthrough advances in informatics over the last decade have thoroughly influenced the field of immunology. The intermingling of machine learning with wet lab applications and clinical results has hatched the newly defined immunoinformatics society. Immunoinformatics of the central neural system, referred to as neuroimmunoinformatics (NII), investigates symmetrical and asymmetrical interactions of the brain-immune interface. This interdisciplinary overview on NII is addressed to bioscientists and computer scientists. We delineate the dominating trajectories and field-shaping achievements and elaborate on future directions using bridging language and terminology. Computation, varying from linear modeling to complex deep learning approaches, fuels neuroimmunology through three core directions. Firstly, by providing big-data analysis software for high-throughput methods such as next-generation sequencing and genome-wide association studies. Secondly, by designing models for the prediction of protein morphology, functions, and symmetrical and asymmetrical protein–protein interactions. Finally, NII boosts the output of quantitative pathology by enabling the automatization of tedious processes such as cell counting, tracing, and arbor analysis. The new classification of microglia, the brain’s innate immune cells, was an NII achievement. Deep sequencing classifies microglia in “sensotypes” to accurately describe the versatility of immune responses to physiological and pathological challenges, as well as to experimental conditions such as xenografting and organoids. NII approaches complex tasks in the brain-immune interface, recognizes patterns and allows for hypothesis-free predictions with ultimate targeted individualized treatment strategies, and personalizes disease prognosis and treatment response.

Phosphatase and Tensin Homolog Deleted on Chromosome Ten Knockdown Attenuates Cognitive Deficits by Inhibiting Neuroinflammation in a Mouse Model of Perioperative Neurocognitive Disorder

Phosphatase and tensin homolog deleted on chromosome ten (PTEN) is a crucial regulator of neuronal development, neuronal survival, axonal regeneration, and synaptic plasticity. In this study we examined the potential role of PTEN in cognitive function in a mouse model of perioperative neurocognitive disorder (PND). Adult male C57BL/6J mice received intracerebroventricular injections of small interfering RNA (siRNA) against PTEN or control siRNA 3 days prior to exploratory laparotomy (n = 8 per group). A group of healthy mice not undergoing surgery included as additional control. Barnes maze and fear conditioning tests were conducted 7 days after surgery. Mice were then sacrificed to examine the expression of PTEN, AMP-activated protein kinase (AMPK), ionized calcium binding adaptor molecule (Iba)-1, B-cell lymphoma (Bcl)-2, Bcl2-associated X protein (Bax), interleukin (IL)-1β, and tumor necrosis factor (TNF)-α in the hippocampus. The microglial activation was examined by immunohistochemistry using Iba-1 as a microglia maker. Nissl and terminal transferase deoxyuridine triphosphate nick-end labeling (TUNEL) staining were used to measure cell death and apoptosis. In comparison to the healthy controls, surgically treated mice had longer latency to identify the target box in both training and testing sessions in the Barnes maze test and shorter freezing time in the fear conditioning test. Surgically treated mice had increased expression of PTEN, AMPK, Bax, IL-1β, and TNF-α, as well as increasing number of activated microglia and apoptosis neurons in the hippocampus. PTEN knockdown significantly attenuated the behavioral deficits in Barnes maze and fear conditioning tests, as well as over-expression of PTEN, AMPK, Bax, IL-1β, and TNF-α induced by surgery. PTEN knockdown could attenuate cognitive deficits induced by trauma, likely through inhibiting the activation of microglia.

Type I Interferon Receptor Signaling in Astrocytes Regulates Hippocampal Synaptic Plasticity and Cognitive Function of the Healthy CNS

Type I interferon receptor (IFNAR) signaling is a hallmark of viral control and host protection. Here, we show that, in the hippocampus of healthy IFNAR-deficient mice, synapse number and synaptic plasticity, as well as spatial learning, are impaired. This is also the case for IFN-β-deficient animals. Moreover, antibody-mediated IFNAR blocking acutely interferes with neuronal plasticity, whereas a low-dose application of IFN-β has a positive effect on dendritic spine structure. Interfering with IFNAR signaling in different cell types shows a role for cognitive function and synaptic plasticity specifically mediated by astrocytes. Intriguingly, levels of the astrocytic glutamate-aspartate transporter (GLAST) are reduced significantly upon IFN-β treatment and increase following inhibition of IFNAR signaling. These results indicate that, besides the prominent role for host defense, IFNAR is important for synaptic plasticity as well as cognitive function. Astrocytes are at the center stage of this so-far-unknown signaling cascade.

Long-Term Consequence of Non-neurotropic H3N2 Influenza A Virus Infection for the Progression of Alzheimer's Disease Symptoms

Influenza viruses until today are a leading cause of worldwide severe pandemics and represent a major threat to human and animal health. Although the primary target of influenza viruses is the lung, infection may manifest with acute and even chronic neurological complications (e.g., status epilepticus, encephalopathies, and encephalitis) potentially increasing the long-term risk for neurodegenerative diseases. We previously described that a peripheral influenza A virus (IAV) infection caused by non-neurotropic H3N2 (maHK68) variant leads to long-term neuroinflammation and synapse loss together with impaired memory formation in young adult mice. Processes of neuroinflammation have been associated with neurodegenerative diseases such as Alzheimer’s disease (AD) and prolonged or excessive innate immune responses are considered a risk factor for AD. Here, the role of purely peripheral IAV infection for the development and progression of AD in a transgenic mouse model (APP/PS1) was investigated. At 2 months of age, mice were infected with H3N2 IAV and the detailed analysis of microglia morphology revealed neuroinflammation in the hippocampus already of 6 months old non-infected APP/PS1 mice together with impaired spatial learning, however, microglia activation, amyloid-β plaques load and cognitive impairments were even more pronounced in APP/PS1 mice upon H3N2 infection. Moreover, CA1 hippocampal dendritic spine density was reduced even at 120 dpi compared to wild-type and also to non-infected APP/PS1 mice, whereas neuronal cells number was not altered. These findings demonstrate that non-neurotropic H3N2 IAV infection as a peripheral immune stimulation may exacerbate AD symptoms possibly by triggering microglial hyperactivation.

Epigallocatechin-3-Gallate-Loaded Liposomes Favor Anti-Inflammation of Microglia Cells and Promote Neuroprotection

Microglia-mediated neuroinflammation is recognized to mainly contribute to the progression of neurodegenerative diseases. Epigallocatechin-3-gallate (EGCG), known as a natural antioxidant in green tea, can inhibit microglia-mediated inflammation and protect neurons but has disadvantages such as high instability and low bioavailability. We developed an EGCG liposomal formulation to improve its bioavailability and evaluated the neuroprotective activity in in vitro and in vivo neuroinflammation models. EGCG-loaded liposomes have been prepared from phosphatidylcholine (PC) or phosphatidylserine (PS) coated with or without vitamin E (VE) by hydration and membrane extrusion method. The anti-inflammatory effect has been evaluated against lipopolysaccharide (LPS)-induced BV-2 microglial cells activation and the inflammation in the substantia nigra of Sprague Dawley rats. In the cellular inflammation model, murine BV-2 microglial cells changed their morphology from normal spheroid to activated spindle shape after 24 h of induction of LPS. In the in vitro free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, EGCG scavenged 80% of DPPH within 3 min. EGCG-loaded liposomes could be phagocytized by BV-2 cells after 1 h of cell culture from cell uptake experiments. EGCG-loaded liposomes improved the production of BV-2 microglia-derived nitric oxide and TNF-α following LPS. In the in vivo Parkinsonian syndrome rat model, simultaneous intra-nigral injection of EGCG-loaded liposomes attenuated LPS-induced pro-inflammatory cytokines and restored motor impairment. We demonstrated that EGCG-loaded liposomes exert a neuroprotective effect by modulating microglia activation. EGCG extracted from green tea and loaded liposomes could be a valuable candidate for disease-modifying therapy for Parkinson’s disease (PD).

Effect of adenovirus-mediated overexpression of PTEN on brain oxidative damage and neuroinflammation in a rat kindling model of epilepsy

Background:

Epilepsy is a chronic and severe neurological disorder. Phosphatase and tensin homolog deleted on chromosome ten (PTEN)-deficient mice exhibit learning and memory deficits and spontaneous epilepsy. The aim of this study was to investigate the role of PTEN in brain oxidative damage and neuroinflammation in a rat model of epilepsy.

Methods:

An adenovirus (Ad)-PTEN vector was constructed, and status epilepticus (SE) was induced in 41 model rats using lithium chloride-pilocarpine. Thirty-six SE rats were then allocated into the Ad-PTEN, Ad-LacZ, and SE groups, those were administered intracerebroventricular injections of Ad-PTEN, Ad-enhanced green fluorescent protein, and phosphate buffer saline, respectively. The normal group was comprised of healthy Sprague-Dawley rats. Nissl staining was conducted to evaluate neuronal damage, and immunohistochemistry was conducted to observe the morphology of cells in the hippocampal CA1 region and the distribution of ionized calcium-binding adaptor molecule 1 (Iba1) and ED1 (rat homologue of human CD68). Levels of apoptosis-related proteins, inflammatory-related factors, and oxidative stress-related markers (reactive oxygen species [ROS], glutathione [GSH], superoxide dismutase [SOD], and malondialdehyde [MDA]) were measured. Comparisons between multiple groups were conducted using one-way analysis of variance (ANOVA), and pairwise comparisons after ANOVA were conducted using the Tukey multiple comparisons test.

Results:

After SE induction, PTEN expression in the rat brain exhibited a four-fold decrease (P = 0.000) and the expression of both Iba1 and ED1 increased. Furthermore, significant neuronal loss, oxidative damage, and neuroinflammation were observed in the SE rat brain. After intracerebroventricular injection of Ad-PTEN, PTEN expression exhibited a three-fold increase (P = 0.003), and the expression of both Iba1 and ED1 decreased. Additionally, neurons were restored and neuronal apoptosis was inhibited. Furthermore, ROS and MDA levels decreased, GSH level and SOD activity increased, and neuroinflammation was reduced.

Conclusion:

Our study demonstrated that brain oxidative damage and neuroinflammation in SE rats were ameliorated by intracerebroventricular injection of Ad-PTEN.

Multiple Morphometric Assessment of Microglial Cells in Deafferented Spinal Trigeminal Nucleus

Microglia (MG) are the first cells to react to the abnormal incoming signals that follow an injury of sensory nerves and play a critical role in the development and maintenance of neuropathic pain, a common sequel of nerve injuries. Here we present population data on cell number, soma size, and length of processes of MG in the caudal division of the spinal trigeminal nucleus (Sp5C) in control mice and at the peak of microgliosis (7 days) following unilateral transection of the infraorbital nerve (IoN). The study is performed combining several bias- and assumption-free imaging and stereological approaches with different immunolabeling procedures, with the objective of tackling some hard problems that often hinder proper execution of MG morphometric studies. Our approach may easily be applied to low-density MG populations, but also works, with limited biases, in territories where MG cell bodies and processes form dense meshworks. In controls, and contralaterally to the deafferented side, MG cell body size and shape and branching pattern matched well the descriptions of “resting” or “surveillant” MG described elsewhere, with only moderate intersubject variability. On the superficial laminae of the deafferented side, however, MG displayed on average larger somata and remarkable diversity in shape. The number of cells and the length of MG processes per mm³ increased 5 and 2.5 times, respectively, indicating a net 50% decrease in the mean length of processes per cell. By using specific immunolabeling and cell sorting of vascular macrophages, we found only a negligible fraction of these cells in Sp5C, with no differences between controls and deafferented animals, suggesting that blood-borne monocytes play at most a very limited role in the microgliosis occurring following sensory nerve deafferentation. In sum, here we present reliable morphometric data on MG in control and deafferented trigeminal nuclei using efficient methods that we propose may equally be applied to any morphometric population analysis of these cells under different physiological or pathological conditions.

Treatment with CCR2 antagonist is neuroprotective but does not alter epileptogenesis in the pilocarpine rat model of epilepsy

Neuroinflammation role on epileptogenesis has been the subject of increasing interest. Many studies showed elevation in cytokines and chemokines expression following seizures, such as, CCL2 protein (C-C motif ligand 2 chemokine) and its specific receptor, CCR2. In addition, recent studies manipulating the CCL2/CCR2 complex verified improved seizure outcome in different seizure models. In the present study, the effects of CCR2 antagonist was investigated using the pilocarpine rat model of epilepsy. Status epilepticus (SE) was induced by pilocarpine i.p. injection in adult rats. Daily oral treatment with CCR2 antagonist or vehicle was initiated 5 h following SE and lasted 5 or 10 days. Rats were euthanized 5 days after SE to evaluate neuronal damage and glial density or 30 days after SE to investigate spontaneous seizures development and seizure susceptibility to a second hit pentylenetetrazol (PTZ) test. Rats that received CCR2 antagonist presented less degenerating cells at hippocampal CA1 region. There was also a significant decrease in CA1 volume after SE that was not observed in treated rats. On the other hand, microglia cell density increased after SE regardless of CCR2 antagonist use. Treatment with CCR2 antagonist did not alter spontaneous seizure occurrence or later seizure susceptibility to PTZ in chronic rats. Additional rats were pretreated with CCR2 antagonist prior to SE induction, but this did not change SE progression. The data show that oral treatment with CCR2 antagonist is neuroprotective, but does not alter other epileptogenic factors, such as, neuroinflammation, or seizure development, after pilocarpine-induced SE in rats.

Human Mesenchymal glioblastomas are characterized by an increased immune cell presence compared to Proneural and Classical tumors

Glioblastoma (GBM) is the most aggressive malignant primary brain tumor in adults, with a median survival of 14.6 months. Recent efforts have focused on identifying clinically relevant subgroups to improve our understanding of pathogenetic mechanisms and patient stratification. Concurrently, the role of immune cells in the tumor microenvironment has received increasing attention, especially T cells and tumor-associated macrophages (TAM). The latter are a mixed population of activated brain-resident microglia and infiltrating monocytes/monocyte-derived macrophages, both of which express ionized calcium-binding adapter molecule 1 (IBA1). This study investigated differences in immune cell subpopulations among distinct transcriptional subtypes of GBM. Human GBM samples were molecularly characterized and assigned to Proneural, Mesenchymal or Classical subtypes as defined by NanoString nCounter Technology. Subsequently, we performed and analyzed automated immunohistochemical stainings for TAM as well as specific T cell populations. The Mesenchymal subtype of GBM showed the highest presence of TAM, CD8⁺, CD3⁺ and FOXP3⁺ T cells, as compared to Proneural and Classical subtypes. High expression levels of the TAM-related gene AIF1, which encodes the TAM-specific protein IBA1, correlated with a worse prognosis in Proneural GBM, but conferred a survival benefit in Mesenchymal tumors. We used our data to construct a mathematical model that could reliably identify Mesenchymal GBM with high sensitivity using a combination of the aforementioned cell-specific IHC markers. In conclusion, we demonstrated that molecularly distinct GBM subtypes are characterized by profound differences in the composition of their immune microenvironment, which could potentially help to identify tumors amenable to immunotherapy.

Combined dipeptidyl peptidase-4 inhibitor with low-dose testosterone exerts greater efficacy than monotherapy on improving brain function in orchiectomized obese rats

Both obesity and orchiectomy lead to the development of brain pathologies and cognitive decline. Testosterone replacement therapy (2 mg/kg/day TRT) and dipeptidyl peptidase-4 inhibitor (vildagliptin) improved cognition in orchiectomized rats, and obese rats. However, both had no beneficial effects in brain of orchiectomized-obese rats. TRT (>2 mg/kg/day) is possible to attenuate brain defects in those rats, but high dose of TRT causes adverse effects. Then, combined effect of low-dose TRT (1 mg/kg/day) and vildagliptin on brain and cognitive functions in orchiectomized-obese rats should be investigated. Sixty male rats were fed with either a normal diet (ND) or a high-fat diet (HFD) for 28 weeks. At week 13, both ND and HFD-fed rats had either a sham-operation or an orchiectomy. At week 25, orchiectomized rats were treated with either: a vehicle, 2 mg/kg/day TRT, vildagliptin (3 mg/kg/day) or a combined vildagliptin with 1 mg/kg/day TRT for 4 weeks. Then, metabolic parameters, brain and cognitive functions were determined. Hippocampal oxidative stress, apoptosis, dendritic spine loss, microglial hyperactivity, and cognitive decline were found in orchiectomized ND-fed rats and sham-operated HFD-fed rats. Interestingly, orchiectomy aggravated these brain pathologies and cognitive decline in HFD-fed rats. In orchiectomized ND-fed rats, all treatments restored brain and cognitive functions. In orchiectomized HFD-fed rats, monotherapies ameliorated these brain pathologies, while the combined therapies had the greatest beneficial effect on the brains. These findings suggest the combined therapies may be the best therapeutic approach for restoring brain functions in the orchiectomized-obese condition.

Differential Microglial Morphological Response, TNFα, and Viral Load in Sedentary-like and Active Murine Models After Systemic Non-neurotropic Dengue Virus Infection

Peripheral inflammatory stimuli increase proinflammatory cytokines in the bloodstream and central nervous system and activate microglial cells. Here we tested the hypothesis that contrasting environments mimicking sedentary and active lives would be associated with differential microglial morphological responses, inflammatory cytokines concentration, and virus load in the peripheral blood. For this, mice were maintained either in standard (standard environment) or enriched cages (enriched environment) and then subjected to a single (DENV1) serotype infection. Blood samples from infected animals showed higher viral loads and higher tumor necrosis factor-α (TNFα) mRNA concentrations than control subjects. Using an unbiased stereological sampling approach, we selected 544 microglia from lateral septum for microscopic 3D reconstruction. Morphological complexity contributed most to cluster formation. Infected groups exhibited significant increase in the microglia morphological complexity and number, despite the absence of dengue virus antigens in the brain. Two microglial phenotypes (type I with lower and type II with higher morphological complexity) were found in both infected and control groups. However, microglia from infected mice maintained in enriched environment showed only one morphological phenotype. Two-way ANOVA revealed that environmental changes and infection influenced type-I and II microglial morphologies and number. Environmental enrichment and infection interactions may contribute to microglial morphological change to a point that type-I and II morphological phenotypes could no longer be distinguished in infected mice from enriched environment. Significant linear correlation was found between morphological complexity and TNFα peripheral blood. Our findings demonstrated that sedentary-like and active murine models exhibited differential microglial responses and peripheral inflammation to systemic non-neurotropic infections with DENV1 virus.

Implication of microglia activation and CSF-1/CSF-1Rpathway in lumbar disc degeneration-related back pain

Back pain is common and costly. Although lumbar disc degeneration has long been regarded as a major contributor to back pain, how disc degeneration leads to back pain remains unclear. Recent studies observed microglia activation in the spinal cord after disc degeneration, suggesting activated microglia may be involved in discogenic back pain. To determine whether microglia activation participates in disc degeneration-induced back pain, we used a modified disc puncture-induced degeneration-related back pain mouse model to examine the changes in spinal microglia and investigate the potential link between microglia activation and discogenic back pain. In this study, 46 CX3CR1^GFP/+ male mice were used in experimental and sham groups. A modified posterolateral retroperitoneal approach was used to expose the L3/L4 disc to induce the needle puncture in the experimental group. Behavioral tests, including grip force and physical function, were used to measure back pain at pre- and postsurgery. The L3 dorsal root ganglions and lumbar spinal cord were obtained at postoperative weeks 1 to 4 followed by immunofluorescence with different antibodies. Micrographs were obtained by confocal microscopy, and morphometric measurements of microglia were analyzed using Imaris. The punctured disc underwent progressive degeneration and mice with disc degeneration showed impaired grip force and physical function. Compared to the control mice, the number of microglia in the lumbar spinal cord was significantly increased in the disc-punctured animals. Moreover, accumulated microglia exhibited larger soma size and lesser ramification in the disc-injured mice. Immunofluorescence demonstrated colony-stimulating factor 1, a cytokine that promotes microglia repopulation, was significantly increased in L3 dorsal root ganglions, whereas its receptor colony-stimulating factor 1 receptor was upregulated on microglia in the disc-injured mice. In summary, lumbar disc puncture caused progressive disc degeneration which induced microglia activation and back pain in mice. Increased colony-stimulating factor 1/colony-stimulating factor 1 receptor signaling is involved in the disc degeneration-induced microglia activation and back pain.

HMGB1 mediates microglia activation via the TLR4/NF-κB pathway in coriaria lactone induced epilepsy

Epilepsy is a chronic and recurrent disease of the central nervous system, with a complex pathology. Recent studies have demonstrated that the activation of glial cells serve an important role in the development of epilepsy. The objective of the present study was to investigate the role of high‑mobility group box‑1 (HMGB1) in mediating the activation of glial cells through the toll‑like receptor 4 (TLR4)/nuclear factor (NF)‑κB signaling pathway in seizure, and the underlying mechanism. The brain tissue of post‑surgery patients with intractable epilepsy after resection and the normal control brain tissue of patients with craniocerebral trauma induced intracranial hypertension were collected. The expression level and distribution pattern of HMGB1, OX42 and NF‑κB p65 were detected by immunohistochemistry. HMGB1, TLR4, receptor for advanced glycation end products (RAGE), NF‑κB p65 and inducible nitric oxide synthase (iNOS) expression levels were detected by western blotting, and serum cytokine levels of interleukin (IL)‑1, IL‑6, tumor necrosis factor (TNF)‑α, transforming growth factor (TGF)‑β and IL‑10 in patients with epilepsy and craniocerebral trauma were detected by ELISA. And cell model of epilepsy was established by coriaria lactone (CL)‑stimulated HM cell, and the same factors were measured. The potential toxic effect of HMGB1 on HM cells was evaluated by MTT and 5‑ethynyl‑2‑deoxyuridine assays. The results demonstrated that compared with the control group, levels of HMGB1, TLR4, RAGE, NF‑κB p65 and iNOS in the brain of the epilepsy group were significantly increased, and increased cytokine levels of IL‑1, IL‑6, TNF‑α, TGF‑β and IL‑10 in patients with epilepsy were also observed. At the same time, the above results were also observed in HM cells stimulated with CL. Overexpression of HMGB1 enhanced the results, while HMGB1 small interfering RNA blocked the function of CL. There was no significant toxic effect of HMGB1 on HM cells. In conclusion, overexpression of HMGB1 potentially promoted epileptogenesis. CL‑induced activation of glial cells may act via up‑regulation of HMGB1 and TLR4/RAGE receptors, and the downstream transcription factor NF‑κB.

The Isotropic Fractionator as a Tool for Quantitative Analysis in Central Nervous System Diseases

One major aim in quantitative and translational neuroscience is to achieve a precise and fast neuronal counting method to work on high throughput scale to obtain reliable results. Here, we tested the isotropic fractionator (IF) method for evaluating neuronal and non-neuronal cell loss in different models of central nervous system (CNS) pathologies. Sprague-Dawley rats underwent: (i) ischemic brain damage; (ii) intraperitoneal injection with kainic acid (KA) to induce epileptic seizures; and (iii) monolateral striatal injection with quinolinic acid (QA) mimicking human Huntington's disease. All specimens were processed for IF method and cell loss assessed. Hippocampus from KA-treated rats and striatum from QA-treated rats were carefully dissected using a dissection microscope and a rat brain matrix. Ischemic rat brains slices were first processed for TTC staining and then for IF. In the ischemic group the cell loss corresponded to the neuronal loss suggesting that hypoxia primarily affects neurons. Combining IF with TTC staining we could correlate the volume of lesion to the neuronal loss; by IF, we could assess that neuronal loss also occurs contralaterally to the ischemic side. In the epileptic group we observed a reduction of neuronal cells in treated rats, but also evaluated the changes in the number of non-neuronal cells in response to the hippocampal damage. In the QA model, there was a robust reduction of neuronal cells on ipsilateral striatum. This neuronal cell loss was not related to a drastic change in the total number of cells, being overcome by the increase in non-neuronal cells, thus suggesting that excitotoxic damage in the striatum strongly activates inflammation and glial proliferation. We concluded that the IF method could represent a simple and reliable quantitative technique to evaluate the effects of experimental lesions mimicking human diseases, and to consider the neuroprotective/anti-inflammatory effects of different treatments in the whole brain and also in discrete regions of interest, with the potential to investigate non-neuronal alterations. Moreover, IF could be used in addition or in substitution to classical stereological techniques or TTC staining used so far, since it is fast, precise and easily combined with complex molecular analysis.

1400W, a highly selective inducible nitric oxide synthase inhibitor is a potential disease modifier in the rat kainate model of temporal lobe epilepsy

Status epilepticus (SE) initiates epileptogenesis to transform normal brain to epileptic state which is characterized by spontaneous recurrent seizures (SRS). Prior to SRS, progressive changes occur in the brain soon after SE, for example, loss of blood-brain barrier (BBB) integrity, neuronal hyper-excitability (epileptiform spiking), neuroinflammation [reactive gliosis, high levels of reactive oxygen/nitrogen species (ROS/RNS)], neurodegeneration and synaptic re-organization. Our hypothesis was that modification of early epileptogenic events will alter the course of disease development and its progression. We tested the hypothesis in the rat kainate model of chronic epilepsy using a novel disease modifying drug, 1400W, a highly selective inhibitor of inducible nitric oxide synthase (iNOS/NOS-II). In an in vitro mouse brain slice model, using a multi-electrode array system, co-application of 1400W with kainate significantly suppressed kainate-induced epileptiform spiking. In the rats, in vivo, 4h after the induction of SE with kainate, 1400W (20mg/kg, i.p.) was administered twice daily for three days to target early events of epileptogenesis. The rats were subjected to continuous (24/7) video-EEG monitoring, remotely, for six months from epidurally implanted cortical electrodes. The 1400W treatment significantly reduced the epileptiform spike rate during the first 12-74h post-SE, which resulted in >90% reduction in SRS in long-term during the six month period when compared to the vehicle-treated control group (257±113 versus 19±10 episodes). Immunohistochemistry (IHC) of brain sections at seven days and six months revealed a significant reduction in; reactive astrogliosis and microgliosis (M1 type), extravascular serum albumin (a marker for BBB leakage) and neurodegeneration in the hippocampus, amygdala and entorhinal cortex in the 1400W-treated rats when compared to the vehicle control. In the seven day group, hippocampal Western blots revealed downregulation of inwardly-rectifying potassium (Kir 4.1) channels and glutamate transporter-1 (GLT-1) levels in the vehicle group, and 1400W treatment partially reversed Kir 4.1 levels, however, GLT-1 levels were unaffected. In the six month group, a significant reduction in mossy fiber staining intensity in the inner molecular layer of the dentate gyrus was observed in the 1400W-treated group. Overall these findings demonstrate that 1400W, by reducing the epileptiform spike rate during the first three days of post-insult, potentially modifies epileptogenesis and the severity of chronic epilepsy in the rat kainate model of TLE.

Hierarchical Cluster Analysis of Three-Dimensional Reconstructions of Unbiased Sampled Microglia Shows not Continuous Morphological Changes from Stage 1 to 2 after Multiple Dengue Infections in Callithrix penicillata

It is known that microglial morphology and function are related, but few studies have explored the subtleties of microglial morphological changes in response to specific pathogens. In the present report we quantitated microglia morphological changes in a monkey model of dengue disease with virus CNS invasion. To mimic multiple infections that usually occur in endemic areas, where higher dengue infection incidence and abundant mosquito vectors carrying different serotypes coexist, subjects received once a week subcutaneous injections of DENV3 (genotype III)-infected culture supernatant followed 24 h later by an injection of anti-DENV2 antibody. Control animals received either weekly anti-DENV2 antibodies, or no injections. Brain sections were immunolabeled for DENV3 antigens and IBA-1. Random and systematic microglial samples were taken from the polymorphic layer of dentate gyrus for 3-D reconstructions, where we found intense immunostaining for TNFα and DENV3 virus antigens. We submitted all bi- or multimodal morphological parameters of microglia to hierarchical cluster analysis and found two major morphological phenotypes designated types I and II. Compared to type I (stage 1), type II microglia were more complex; displaying higher number of nodes, processes and trees and larger surface area and volumes (stage 2). Type II microglia were found only in infected monkeys, whereas type I microglia was found in both control and infected subjects. Hierarchical cluster analysis of morphological parameters of 3-D reconstructions of random and systematic selected samples in control and ADE dengue infected monkeys suggests that microglia morphological changes from stage 1 to stage 2 may not be continuous.

TLR4-activated microglia require IFN-γ to induce severe neuronal dysfunction and death in situ

Microglia (tissue-resident macrophages) represent the main cell type of the innate immune system in the CNS; however, the mechanisms that control the activation of microglia are widely unknown. We systematically explored microglial activation and functional microglia-neuron interactions in organotypic hippocampal slice cultures, i.e., postnatal cortical tissue that lacks adaptive immunity. We applied electrophysiological recordings of local field potential and extracellular K(+) concentration, immunohistochemistry, design-based stereology, morphometry, Sholl analysis, and biochemical analyses. We show that chronic activation with either bacterial lipopolysaccharide through Toll-like receptor 4 (TLR4) or leukocyte cytokine IFN-γ induces reactive phenotypes in microglia associated with morphological changes, population expansion, CD11b and CD68 up-regulation, and proinflammatory cytokine (IL-1β, TNF-α, IL-6) and nitric oxide (NO) release. Notably, these reactive phenotypes only moderately alter intrinsic neuronal excitability and gamma oscillations (30-100 Hz), which emerge from precise synaptic communication of glutamatergic pyramidal cells and fast-spiking, parvalbumin-positive GABAergic interneurons, in local hippocampal networks. Short-term synaptic plasticity and extracellular potassium homeostasis during neural excitation, also reflecting astrocyte function, are unaffected. In contrast, the coactivation of TLR4 and IFN-γ receptors results in neuronal dysfunction and death, caused mainly by enhanced microglial inducible nitric oxide synthase (iNOS) expression and NO release, because iNOS inhibition is neuroprotective. Thus, activation of TLR4 in microglia in situ requires concomitant IFN-γ receptor signaling from peripheral immune cells, such as T helper type 1 and natural killer cells, to unleash neurotoxicity and inflammation-induced neurodegeneration. Our findings provide crucial mechanistic insight into the complex process of microglia activation, with relevance to several neurologic and psychiatric disorders.

Altered morphological dynamics of activated microglia after induction of status epilepticus

BACKGROUND

Microglia cells are the resident macrophages of the central nervous system and are considered its first line of defense. In the normal brain, their ramified processes are highly motile, constantly scanning the surrounding brain tissue and rapidly moving towards sites of acute injury or danger signals. These microglial dynamics are thought to be critical for brain homeostasis. Under pathological conditions, microglial cells undergo "activation," which modifies many of their molecular and morphological properties. Investigations of the effects of activation on motility are limited and have given mixed results. In particular, little is known about how microglial motility is altered in epilepsy, which is characterized by a strong inflammatory reaction and microglial activation.

METHODS

We used a mouse model of status epilepticus induced by kainate injections and time-lapse two-photon microscopy to image GFP-labeled microglia in acute hippocampal brain slices. We studied how microglial activation affected the motility of microglial processes, including basal motility, and their responses to local triggering stimuli.

RESULTS

Our study reveals that microglial motility was largely preserved in kainate-treated animals, despite clear signs of microglial activation. In addition, whereas the velocities of microglial processes during basal scanning and towards a laser lesion were unaltered 48 h after status epilepticus, we observed an increase in the size of the territory scanned by single microglial processes during basal motility and an elevated directional velocity towards a pipette containing a purinergic agonist.

CONCLUSIONS

Microglial activation differentially impacted the dynamic scanning behavior of microglia in response to specific acute noxious stimuli, which may be an important feature of the adaptive behavior of microglia during pathophysiological conditions.

Antibody-enhanced dengue disease generates a marked CNS inflammatory response in the black-tufted marmoset Callithrix penicillata

Severe dengue disease is often associated with long-term neurological impairments, but it is unclear what mechanisms are associated with neurological sequelae. Previously, we demonstrated antibody-enhanced dengue disease (ADE) dengue in an immunocompetent mouse model with a dengue virus 2 (DENV2) antibody injection followed by DENV3 virus infection. Here we migrated this ADE model to Callithrix penicillata. To mimic human multiple infections of endemic zones where abundant vectors and multiple serotypes co-exist, three animals received weekly subcutaneous injections of DENV3 (genotype III)-infected supernatant of C6/36 cell cultures, followed 24 h later by anti-DENV2 antibody for 12 weeks. There were six control animals, two of which received weekly anti-DENV2 antibodies, and four further animals received no injections. After multiple infections, brain, liver, and spleen samples were collected and tissue was immunolabeled for DENV3 antigens, ionized calcium binding adapter molecule 1, Ki-67, TNFα. There were marked morphological changes in the microglial population of ADE monkeys characterized by more highly ramified microglial processes, higher numbers of trees and larger surface areas. These changes were associated with intense TNFα-positive immunolabeling. It is unclear why ADE should generate such microglial activation given that IgG does not cross the blood-brain barrier, but this study reveals that in ADE dengue therapy targeting the CNS host response is likely to be important.

The interneuron energy hypothesis: Implications for brain disease

Fast-spiking, inhibitory interneurons - prototype is the parvalbumin-positive (PV+) basket cell - generate action potentials at high frequency and synchronize the activity of numerous excitatory principal neurons, such as pyramidal cells, during fast network oscillations by rhythmic inhibition. For this purpose, fast-spiking, PV+ interneurons have unique electrophysiological characteristics regarding action potential kinetics and ion conductances, which are associated with high energy expenditure. This is reflected in the neural ultrastructure by enrichment with mitochondria and cytochrome c oxidase, indicating the dependence on oxidative phosphorylation for adenosine-5'-triphosphate (ATP) generation. The high energy expenditure is most likely required for membrane ion transport in dendrites and the extensive axon arbor as well as for presynaptic release of neurotransmitter, gamma-aminobutyric acid (GABA). Fast-spiking, PV+ interneurons are central for the emergence of gamma oscillations (30-100Hz) that provide a fundamental mechanism of complex information processing during sensory perception, motor behavior and memory formation in networks of the hippocampus and the neocortex. Conversely, shortage in glucose and oxygen supply (metabolic stress) and/or excessive formation of reactive oxygen and nitrogen species (oxidative stress) may render these interneurons to be a vulnerable target. Dysfunction in fast-spiking, PV+ interneurons might set a low threshold for impairment of fast network oscillations and thus higher brain functions. This pathophysiological mechanism might be highly relevant for cerebral aging as well as various acute and chronic brain diseases, such as stroke, vascular cognitive impairment, epilepsy, Alzheimer's disease and schizophrenia.

What Elements of the Inflammatory System Are Necessary for Epileptogenesis In Vitro?

The inflammatory and central nervous systems share many signaling molecules, compromising the utility of traditional pharmacological and knockout approaches in defining the role of inflammation in CNS disorders such as epilepsy. In an in vitro model of post-traumatic epileptogenesis, the development of epilepsy proceeded in the absence of the systemic inflammatory system, and was unaffected by removal of cellular mediators of inflammation, including macrophages and T-lymphocytes.

Epileptogenesis in vivo can be altered by manipulation of molecules such as cytokines and complement that subserve intercellular signaling in both the inflammatory and central nervous systems. Because of the dual roles of these signaling molecules, it has been difficult to precisely define the role of systemic inflammation in epileptogenesis. Organotypic hippocampal brain slices can be maintained in culture independently of the systemic inflammatory system, and the rapid course of epileptogenesis in these cultures supports the idea that inflammation is not necessary for epilepsy. However, this preparation still retains key cellular inflammatory mediators. Here, we found that rodent hippocampal organotypic slice cultures depleted of T lymphocytes and microglia developed epileptic activity at essentially the same rate and to similar degrees of severity as matched control slice cultures. These data support the idea that although the inflammatory system, neurons, and glia share key intercellular signaling molecules, neither systemic nor CNS-specific cellular elements of the immune and inflammatory systems are necessary components of epileptogenesis.