Microglial Cell Proliferation Research Articles

Microglial cell proliferation is regulated, in part, by reactive astrocyte ETBR signaling after ischemic stroke.

Reciprocal communication between reactive astrocytes and microglial cells provides local, coordinated control over critical processes such as neuroinflammation, neuroprotection, and scar formation after CNS injury, but is poorly understood. The vasoactive peptide hormone endothelin (ET) is released and/or secreted by endothelial cells, microglial cells and astrocytes early after ischemic stroke and other forms of brain injury. To better understand glial cell communication after stroke, we sought to identify paracrine effectors produced and secreted downstream of astroglial endothelin receptor B (ETBR) signaling. Using a genetic loss-of-function screen, we identified angiopoietin-2 (Ang-2) as a factor produced by reactive astrocytes in response to ET. In experiments with primary adult astrocytes stimulated by IRL1620, a specific ETBR agonist, we found that ERK1/2 and NFkB mediated the effects of ET on Ang-2 production. To determine astroglial Ang-2 levels in vivo, reactive astrocytes expressing the high affinity glutamate transporter (GLAST, EAAT1) were isolated by magnetic-activated cell sorting 3days after stroke. Astrocytes obtained from the ipsilateral hemisphere expressed significantly more Ang-2 compared with astrocytes isolated from the contralateral hemisphere, or from cortices of sham-operated (control) mice. Notably, analysis of microglia sorted from CX3CR1-eGFP mice demonstrated increased cell surface expression of Tie-2, the Ang-2 receptor, on cells obtained from ipsilateral versus contralateral tissue. Addition of recombinant Ang-2 to astrocyte-conditioned medium significantly increased the number of SIM-A9 murine microglial cells cultured under hypoxic conditions (1% oxygen for 48h). In transgenic GFAP-CreER™-EDNRB-fl/fl mice with stroke, conditional knockout of astroglial ETBR significantly decreased the number of proliferating cells in the peri-infarct area with a microglial phenotype (Ki67+/CD11b+). Our results indicate that Ang-2, and possibly other paracrine effectors functioning downstream of astroglial ETBR signaling, are important mediators of microglial cell dynamics after stroke.

334 Identification of novel plasma protein biomarkers for diagnosis and prediction of Alzheimer’s disease in African Americans

OBJECTIVES/GOALS: To identify novel panel of plasma protein biomarkers to improve prediction and diagnosis of Alzheimer’s disease (AD) for African Americans (AA), who are at greater risk of developing AD compared to non-Hispanic White individuals but are underrepresented in AD research. METHODS/STUDY POPULATION: Pre-existing plasma samples from 460 AA individuals with clinical diagnoses of AD, cognitively unimpaired (CU), mild cognitive impairment (MCI), or dementia with Lewy bodies (DLB) will undergo untargeted proteomics using the SomaScan assay, where modified single stranded DNA aptamers bind to protein targets which are quantified by DNA microarray. Protein expression levels will be compared between diagnostic groups to identify differentially expressed proteins. Additional clinical, genetic, and lifestyle factors will be compared with protein expression when available. Proteins of interest, identified by differential protein expression analysis results, will be included in receiver operating characteristic analyses to identify the optimal set of proteins for diagnostic classification. RESULTS/ANTICIPATED RESULTS: A pilot experiment utilizing plasma from 40 individuals identified multiple differentially expressed proteins (DEPs) between AD and non-AD groups. Eight proteins were nominated from the differential protein analysis into a receiver operating characteristic (ROC) analysis based on pvalue and previous implication in AD genome wide association studies. Proteins involved in microglial activation, neuronal adhesion, cell proliferation, and innate immunity were nominated. The ROC model achieved 100% classification accuracy of AD and CU groups using age, sex, and the eight nominated proteins. It is expected that there will be more significant associations when utilizing the full cohort of 460 AA and that DEPs between AD, CU, MCI, and DLB will be identified. DISCUSSION/SIGNIFICANCE: The nomination of a novel panel of plasma biomarkers developed from an AA cohort will directly serve the AA community by improving access to an early and accurate diagnosis of AD. Access to improved prediction and diagnosis will likely improve disease management, thus improving patient outcomes and decreasing burden on families and caregivers.

Secretory products of DPSC mitigate inflammatory effects in microglial cells by targeting MAPK pathway

Activated microglial cells in the central nervous system (CNS) are the main contributors to neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. Inhibiting their activation will help in reducing inflammation and oxidative stress during pathogenesis, potentially limiting the progression of the diseases. The immunomodulation properties of dental pulp-derived stem cells (DPSC) make it a promising therapy for neurodegenerative disorders. This study aims to determine whether secretory factors of DPSC (DPSC℗) inhibit inflammation and proliferation of microglial cells and define the molecular mechanisms. Our quantitative RT-PCR analysis showed that the DPSC℗ reduced the markers of the inflammation and induced anti-inflammatory molecules in microglial cells. DPSC ℗ reduced the intracellular and mitochondrial reactive oxygen species (ROS) production and mitochondrial membrane potential in microglial cells. In addition, DPSC ℗ decreased the cellular bioenergetics parameters related to oxygen consumption rate (OCAR) and extracellular acidification rate (ECAR). We found that DPSC℗ inhibited microglial cell proliferation by activating a checkpoint molecule, Chk1 leading an arrest at the G1 phase of the cell cycle. To define the mechanism, we performed the western blot analysis and observed that the MAPK P38 pathway was inhibited by DPSC℗. Furthermore, a System biology analysis revealed that the BDNF and GDNF, secretory factors of DPSC, blocked at the phosphorylation site (Tyr 182) of the P38 molecule resulting in the inhibition of downstream signaling of inflammation. These data suggest that the DPSC℗ may be a potential therapeutic agent for neurodegenerative diseases.

Genome-wide association study of hippocampal blood-oxygen-level-dependent-cerebral blood flow correlation in Chinese Han population

Correlation between blood-oxygen-level-dependent (BOLD) and cerebral blood flow (CBF) has been used as an index of neurovascular coupling. Hippocampal BOLD-CBF correlation is associated with neurocognition, and the reduced correlation is associated with neuropsychiatric disorders. We conducted the first genome-wide association study of the hippocampal BOLD-CBF correlation in 4,832 Chinese Han subjects. The hippocampal BOLD-CBF correlation had an estimated heritability of 16.2-23.9% and showed reliable genome-wide significant association with a locus at 3q28, in which many variants have been linked to neuroimaging and cerebrospinal fluid markers of Alzheimer's disease. Gene-based association analyses showed four significant genes (GMNC, CRTC2, DENND4B, and GATAD2B) and revealed enrichment for mast cell calcium mobilization, microglial cell proliferation, and ubiquitin-related proteolysis pathways that regulate different cellular components of the neurovascular unit. This is the first unbiased identification of the association of hippocampal BOLD-CBF correlation, providing fresh insights into the genetic architecture of hippocampal neurovascular coupling.

LncRNA Gm44206 Promotes Microglial Pyroptosis Through NLRP3/Caspase-1/GSDMD Axis and Aggravate Cerebral Ischemia-Reperfusion Injury.

Inhibition of the inflammatory response triggered by microglial pyroptosis inflammatory activation may be one of the effective ways to alleviate cerebral ischemia-reperfusion injury, the specific mechanism of which remains unclear. In this study, BV-2 microglia with or without oxygen-glucose deprivation/reoxygenation (OGD/R) or long noncoding RNA (lncRNA) Gm44206 knockdown were used as cell models to conduct an in vitro study. Detection of lactate dehydrogenase release and pyroptosis-related protein levels was performed using a corresponding kit and western blotting, respectively. Proliferation of microglia was evaluated by CCK8 assay. Enzyme-linked immunosorbent assay was applied for measuring levels of proinflammatory cytokines. This study verified the involvement of microglial pyroptosis as well as upregulation of NLRP3, Caspase-1, GSDMD, and Apoptosis-associated Speck-like protein containing a C-terminal caspase-recruitment domain (ASC) in cerebral ischemia-reperfusion injury. Moreover, knockdown of lncRNA Gm44206 could alleviate OGD/R-induced microglial pyroptosis and cell proliferation inhibition through the NLRP3/Caspase-1/GSDMD pathway, thus decreasing the release of proinflammatory cytokines, including interleukin (IL)-1β, IL-6, IL-18, and tumor necrosis factor-alpha. In conclusion, this study established a correlation between microglial pyroptosis and cerebral ischemia-reperfusion injury and identified lncRNA Gm44206 as a potential regulator of NLRP3/Caspase-1/GSDMD axis-mediated microglial pyroptosis, which could be considered a promising therapeutic target.

Understanding the role of microglia in the onset of photoreceptor degeneration

AbstractPhotoreceptor degenerative diseases are currently the leading cause of irreversible blindness in developed countries and a major cause of irreversible blindness in the world. The most common forms of these diseases are age‐related macular degeneration and retinitis pigmentosa, both diseases cause a profound visual impairment due to photoreceptor loss. In the early stages of photoreceptor degeneration, glial cells have a major role to play, presumably leading to extensive retinal remodelling. The mammalian retina contains three types of glial cells. Two types of macroglial cells: astrocytes and Müller cells, and microglial cells. Microglial cells are the major resident immune cells in the retina and, although these cells and neuroinflammation have been implicated in the pathology of many neurodegenerative diseases, their role and function in photoreceptor degenerations are not yet fully understood. During retinal degeneration, microglial cells change their morphology, become activated and travel from the inner to the outer layers of the retina to phagocytose the dying photoreceptors, while astrocytes and Müller cells become hypertrophic, and overexpress glial fibrillary acidic protein (GFAP) filling the space left by dead photoreceptors to form a glial seal. It is known that activated microglial cells can be either neuroprotective or neurodestructive during photoreceptor degenerations, and therefore it is not yet clear whether activated microglial cells may increase or decrease photoreceptor loss. Microglial cell activation, migration and proliferation occur simultaneously with the onset of photoreceptor degeneration, prior to the loss of the vast majority of photoreceptors. During photoreceptor loss, microglial cells reach the outer nuclear and outer segment layers. These events suggest that photoreceptor death is the trigger for the activation and migration of microglia to the outer retinal layers, where they phagocytose the dying photoreceptors and remove cellular debris. By carrying out these functions, microglial cells in the retina may affect photoreceptor survival or death, eventually phagocytizing stressed but still viable photoreceptors. Interestingly, inhibition of microglial cell activation and migration during photoreceptor degeneration results in improved cone outer segment morphology and increased photoreceptor survival, which suggest that the role of activated microglial cells may be more neurodestructive than neuroprotective and that treatments with anti‐inflammatory drugs that modulate microglial reactivity may be considered in the early stages of photoreceptor degenerations.

Molecular interaction of stress granules with Tau and autophagy in Alzheimer's disease

Stress Granules (SGs) are RNA granules composed of untranslated mRNA and associated proteins, which are related to the cytoplasmic metabolism of mRNA in response to cellular stress and certain drug stimuli. Physiological SGs are dynamic structures that protect cells from the effects of stress, and continuous stress ripens the SGs into more stable complexes. Numerous studies have found that dysregulation of RNA metabolism in stress response led to misfolded protein aggregation in the pathophysiology of neurodegenerative diseases. For example, in neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), Alzheimer's disease (AD), and Parkinson's disease (PD), SGs aggregation is mainly due to up-regulation of SGs formation and down-regulation of SGs clearance. Recent studies have revealed the role of SGs in the pathogenesis and pathology of AD, especially the interaction of SGs and RNA-binding proteins with Tau and autophagy. Aggregation of SGs and increased RNA-binding proteins, especially TIA1, can facilitate Tau misfolding and propagation, and vice versa. Autophagy dysfunction disrupts the normal pathway of SGs clearance. In this review, we summarized the regulation of SGs and their relationship with Tau protein and autophagy, as well as the pathological mechanisms of AD such as RNA splicing, microglial cell proliferation and phagocytosis.

Unraveling the Cytoprotective Effects of Valproic Acid: A Transcriptomics Meta-Analysis of Transfusion Strategies for Hemorrhagic Shock and Traumatic Brain Injury

Introduction: Traumatic brain injury (TBI) results in widespread impairment of hemostasis, fibrinolysis, coagulation, endothelial function, and immune function. While damage control resuscitation (DCR) is a well-established treatment strategy for life-threatening hemorrhage, alternative treatment strategies should be applied to patients with concurrent TBI. Commonly used resuscitation fluids such as crystalloids or colloids have several disadvantages and may even be harmful when administered in large quantities. In contrast, pharmacologic agents, such as the histone deacetylase inhibitor valproic acid (VPA), have shown promising results in animal studies of TBI and hemorrhagic shock (HS). We previously showed that VPA not only decreases platelet hyper-activation and improves clot dynamics in in-vitro experiments, but also decreases transfusion requirements and improves survival in a porcine DCR model. In those animal models, VPA was administered in conjunction with fluid resuscitation such as fresh frozen plasma (FFP) or hextend (HEX). However, we wondered whether VPA itself induces cytoprotective properties that may underlie the restoration of hemostasis, endothelial function, and immune function that we observed in our models. This meta-analysis used computational biology to identify changes in the brain transcriptome due to VPA treatment that occurred independent of the chosen transfusion fluid.Methods: Swine underwent TBI+HS, kept in shock for 2 hours, and resuscitated with normal saline (control), FFP, FFP+VPA, HEX, or HEX+VPA (n=5/group; all VPA doses 300 mg/kg). After 6 hours of observation, brain RNA was isolated and gene expression was analyzed using a microarray. Gene expression data were normalized to a normal saline control group. Transcriptomic data were imported into iPathwayGuide to identify significantly enriched genes and Gene Ontology (GO) terms. Genes were considered to be differentially expressed if they exhibited a log-fold change (logFC) > 1.0 (fold change > 2) and a p-value < 0.05. The differences in gene expression where then summarized in a Venn-diagram. GO terms identified the Biological Processes with the greatest modulation based on both significance and number of DE genes. GO term P-values were corrected using Elim-pruning.Results: A total of 673 differentially expressed genes were identified. The FFP+VPA group exhibited 206 uniquely expressed genes and the HEX+VPA group 121. We found a total of 113 genes that were expressed in both the FFP+VPA and HEX+VPA groups, but not in the FFP and HEX only groups (Figure). Table 1 summarizes the 10 most up- and down-regulated genes that are only expressed in VPA groups (i.e. FFP+VPA and HEX+VPA). Unregulated genes specifically associated with VPA were involved in promotion of cell division, neurogenesis, cytoskeleton, and ion-channels, while down-regulated genes were involved in metalloproteins, neurodegenerative diseases, and cell cycle arrest. Significantly modulated Biological Processes identified by GO terms include: erythrocyte maturation, macrophage activation, microglial cell proliferation, signal transduction by P53, fibrinolysis and plasminogen activation, fibroblast migration, and neurogenesis.Conclusion: Overall, this meta-analysis suggests that VPA altered the expression of approximately 1/6 th of all genes that were differentially expressed in our cohort. These genes are involved in a variety of biological processes such as cell division, neurogenesis, coagulation, cytoskeleton, and inflammation. These results suggest that VPA treatment may promote an environment that favors the restoration of hemostasis, production of new neurons, removal of damaged cells, and attenuation of inflammation. Such findings suggest that VPA treatment alone may be a promising therapeutic for the treatment of life-threatening hemorrhage and TBI. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Astrocytes Stimulate Microglial Proliferation and M2 Polarization In Vitro through Crosstalk between Astrocytes and Microglia.

Microglia are resident immune cells of the central nervous system that act as brain-specific macrophages and are also known to regulate the innate immune functions of astrocytes through secretory molecules. This communication plays an important role in brain functions and homeostasis as well as in neuropathologic disease. In this study, we aimed to elucidate whether astrocytes and microglia could crosstalk to induce microglial polarization and proliferation, which can be further regulated under a microenvironment mimicking that of brain stroke. Microglia in a mixed glial culture showed increased survival and proliferation and were altered to M2 microglia; CD11b−GFAP+ astrocytes resulted in an approximately tenfold increase in microglial cell proliferation after the reconstitution of astrocytes. Furthermore, GM-CSF stimulated microglial proliferation approximately tenfold and induced them to become CCR7+ M1 microglia, which have a phenotype that could be suppressed by anti-inflammatory cytokines such as IL-4, IL-10, and substance P. In addition, the astrocytes in the microglial co-culture showed an A2 phenotype; they could be activated to A1 astrocytes by TNF-α and IFN-γ under the stroke-mimicking condition. Altogether, astrocytes in the mixed glial culture stimulated the proliferation of the microglia and M2 polarization, possibly through the acquisition of the A2 phenotype; both could be converted to M1 microglia and A1 astrocytes under the inflammatory stroke-mimicking environment. This study demonstrated that microglia and astrocytes could be polarized to M2 microglia and A2 astrocytes, respectively, through crosstalk in vitro and provides a system with which to explore how microglia and astrocytes may behave in the inflammatory disease milieu after in vivo transplantation.

Dysregulated Microglial Cell Activation and Proliferation Following Repeated Antigen Stimulation.

Upon reactivation of quiescent neurotropic viruses antigen (Ag)-specific brain resident-memory CD8+ T-cells (bTRM) may respond to de novo-produced viral Ag through the rapid release of IFN-γ, which drives subsequent interferon-stimulated gene expression in surrounding microglia. Through this mechanism, a small number of adaptive bTRM may amplify responses to viral reactivation leading to an organ-wide innate protective state. Over time, this brain-wide innate immune activation likely has cumulative neurotoxic and neurocognitive consequences. We have previously shown that HIV-1 p24 Ag-specific bTRM persist within the murine brain using a heterologous prime-CNS boost strategy. In response to Ag restimulation, these bTRM display rapid and robust recall responses, which subsequently activate glial cells. In this study, we hypothesized that repeated challenges to viral antigen (Ag) (modeling repeated episodes of viral reactivation) culminate in prolonged reactive gliosis and exacerbated neurotoxicity. To address this question, mice were first immunized with adenovirus vectors expressing the HIV p24 capsid protein, followed by a CNS-boost using Pr55Gag/Env virus-like particles (HIV-VLPs). Following the establishment of the bTRM population [>30 days (d)], prime-CNS boost animals were then subjected to in vivo challenge, as well as re-challenge (at 14 d post-challenge), using the immunodominant HIV-1 AI9 CD8+ T-cell epitope peptide. In these studies, Ag re-challenge resulted in prolonged expression of microglial activation markers and an increased proliferative response, longer than the challenge group. This continued expression of MHCII and PD-L1 (activation markers), as well as Ki67 (proliferative marker), was observed at 7, 14, and 30 days post-AI9 re-challenge. Additionally, in vivo re-challenge resulted in continued production of inducible nitric oxide synthase (iNOS) with elevated levels observed at 7, 14 and 30 days post re-challenge. Interestingly, iNOS expression was significantly lower among challenged animals when compared to re-challenged groups. Furthermore, in vivo specific Ag re-challenge produced lower levels of arginase (Arg)-1 when compared with the challenged group. Taken together, these results indicate that repeated Ag-specific stimulation of adaptive immune responses leads to cumulative dysregulated microglial cell activation.

Paeoniflorin improves functional recovery through repressing neuroinflammation and facilitating neurogenesis in rat stroke model.

BackgroundMicroglia, neuron, and vascular cells constitute a dynamic functional neurovascular unit, which exerts the crucial role in functional recovery after ischemic stroke. Paeoniflorin, the principal active component of Paeoniae Radix, has been verified to exhibit neuroprotective roles in cerebralischemic injury. However, the mechanisms underlying the regulatory function of Paeoniflorin on neurovascular unit after cerebral ischemia are still unclear.MethodsIn this study, adult male rats were treated with Paeoniflorin following transient middle cerebral artery occlusion (tMCAO), and then the functional behavioral tests (Foot-fault test and modified improved neurological function score, mNSS), microglial activation, neurogenesis and vasculogenesis were assessed.ResultsThe current study showed that Paeoniflorin treatment exhibited a sensorimotor functional recovery as suggested via the Foot-fault test and the enhancement of spatial learning as suggested by the mNSS in rat stroke model. Paeoniflorin treatment repressed microglial cell proliferation and thus resulted in a significant decrease in proinflammatory cytokines IL-1β, IL-6 and TNF-α. Compared with control, Paeoniflorin administration facilitated von Willebrand factor (an endothelia cell marker) and doublecortin (a neuroblasts marker) expression, indicating that Paeoniflorin contributed to neurogenesis and vasculogenesis in rat stroke model. Mechanistically, we verified that Paeoniflorin repressed JNK and NF-κB signaling activation.ConclusionsThese results demonstrate that Paeoniflorin represses neuroinflammation and facilitates neurogenesis in rat stroke model and might be a potential drug for the therapy of ischemic stroke.

Glial cell responses on tetrapod-shaped graphene oxide and reduced graphene oxide 3D scaffolds in brain in vitro and ex vivo models of indirect contact

Brain implants are promising instruments for a broad variety of nervous tissue diseases with a wide range of applications, e.g. for stimulation, signal recording or local drug delivery. Recently, graphene-based scaffold materials have emerged as attractive candidates as neural interfaces, 3D scaffolds, or drug delivery systems due to their excellent properties like flexibility, high surface area, conductivity, and lightweight. To date, however, there is a lack of appropriate studies of the foreign body response, especially by glial cells, towards graphene-based materials. In this work, we investigated the effects of macroscopic, highly porous (>99.9%) graphene oxide (GO) and reduced graphene oxide (rGO) (conductivity ∼1 S m−1) scaffolds with tailorable macro- and microstructure on human astrocyte and microglial cell viability and proliferation as well as expression of neuroinflammation and astrogliosis associated genes in an indirect contact approach. In this in vitro model, as well as ex vivo in organotypic murine brain slices, we could demonstrate that both GO and rGO based 3D scaffolds exert slight effects on the glial cell populations which are the key players of glial scar formation. These effects were in most cases completely abolished by curcumin, a known anti-inflammatory and anti-fibrotic drug that could in perspective be applied to brain implants as a protectant.

Determining the long term consequences of diabetes on hippocampal function

Type 2 diabetes mellitus (T2DM) is the most prevalent subtype of diabetes. T2DM is a chronic metabolic disorder that is characterized by hyperglycemia, hyperinsulimia, and insulin resistance. Diabetes is a major risk factor for Alzheimer’s Disease (AD). While the cause of AD remains unknown, several risk factors have been linked to the pathogenesis of AD, including T2DM. At the cellular and molecular level, both AD and T2DM share similar mechanistic abnormalities. Changes in brain structure in insulin‐resistant diabetes occur within temporal lobe circuits that are also sensitive to aging and AD, and individuals with insulin‐resistant diabetes exhibit hippocampal atrophy. While these studies demonstrate a clear link between AD and T2DM the exact mechanisms through which T2DM contributes to cognitive decline in AD remains unexplored. As such, there is a need for further understanding the mechanisms and establish potential therapeutic targets to the T2DM‐mediated development of AD pathology. Our laboratory investigated the effects of T2DM on AD‐like pathology using the db/db mouse model of leptin receptor deficiency. This model has a mutation in the gene encoding the leptin receptor, and thus induced leptin dysfunction confers susceptibility to obesity, insulin resistance and subsequently T2DM development. Our findings demonstrate that aged db/db mice present increased microglial cell activation and proliferation in the hippocampus, a region selectively vulnerable to AD, compared to controls. We next assessed the inflammatory profile of the hippocampus of aged db/db mice compared to controls at the molecular level using a cytokine array. We found that diabetic mice have a chronic inflammatory profile. Notably, we observed elevated levels of key proinflammatory cytokines (IL‐1α and IL‐1β), as well as anti‐inflammatory cytokines (IL‐10 and IL‐13) in aged db/db mice compared to controls. Furthermore, our profiling experiments showed a decreased expression of CX3CL1, indicating a possible dysregulation of fractalkine signaling in the hippocampus. To assess hippocampal synaptic integrity in these animals we assessed the protein expression of synaptic markers in an age‐dependent manner. We showed an age‐dependent decrease in the protein levels of PSD95 and synaptophysin in the hippocampi of db/db mice. These findings demonstrate a clear link between T2DM development and neuroinflammation and synaptic dysfunction. To evaluate the functional consequence of the neuroinflammatory profile and synaptic dysfunctioon observed in the hippocampi of diabetic mice, db/db mice and lean control mice were tested on the Morris Water Maze (MWM) task. In the MWM learning and relearning session test, diabetic animals group spent significantly more time to find the platform compared to their lean counterparts. In the memory retention tests, entry latency into the platform quadrant of the T2DM mice was significantly higher, and distance traveled in the platform quadrant was significantly lower compared to controls. The findings suggest that db/db mice have impaired spatial navigation. Our data suggest that neuroinflammation is a potential mechanism through which AD pathology and cognitive dysfunction is triggered in the diabetic state.Support or Funding InformationThis work was funded by Kuwait Univerisy grant number: ZM03/16

The mitochondria-targeted antioxidant MitoQ inhibits memory loss, neuropathology, and extends lifespan in aged 3xTg-AD mice

Oxidative stress, likely stemming from dysfunctional mitochondria, occurs before major cognitive deficits and neuropathologies become apparent in Alzheimer's disease (AD) patients and in mouse models of the disease. We previously reported that treating 2- to 7-month-old 3xTg-AD mice with the mitochondria-targeted antioxidant MitoQ (mitoquinone mesylate: [10-(4,5-Dimethoxy-2-methyl-3,6-dioxo-1,4-cyclohexadien-1-yl)decyl](triphenyl)phosphonium methanesulfonate), a period when AD-like pathologies first manifest in them, prevents AD-like symptoms from developing. To elucidate further a role for mitochondria-derived oxidative stress in AD progression, we examined the ability of MitoQ to inhibit AD-like pathologies in these mice at an age in which cognitive and neuropathological symptoms have fully developed. 3xTg-AD female mice received MitoQ in their drinking water for five months beginning at twelve months after birth. Untreated 18-month-old 3xTg-AD mice exhibited significant learning deficits and extensive AD-like neuropathologies. MitoQ-treated mice showed improved memory retention compared to untreated 3xTg-AD mice as well as reduced brain oxidative stress, synapse loss, astrogliosis, microglial cell proliferation, Aβ accumulation, caspase activation, and tau hyperphosphorylation. Additionally, MitoQ treatment significantly increased the abbreviated lifespan of the 3xTg-AD mice. These findings support a role for the involvement of mitochondria-derived oxidative stress in the etiology of AD and suggest that mitochondria-targeted antioxidants may lessen symptoms in AD patients.

Xenon improves long-term cognitive function, reduces neuronal loss and chronic neuroinflammation, and improves survival after traumatic brain injury in mice

BackgroundXenon is a noble gas with neuroprotective properties that can improve short and long-term outcomes in young adult mice after controlled cortical impact. This follow-up study investigates the effects of xenon on very long-term outcomes and survival. MethodsC57BL/6N young adult male mice (n=72) received single controlled cortical impact or sham surgery and were treated with either xenon (75% Xe:25% O2) or control gas (75% N2:25% O2). Outcomes measured were: (i) 24 h lesion volume and neurological outcome score; (ii) contextual fear conditioning at 2 weeks and 20 months; (iii) corpus callosum white matter quantification; (iv) immunohistological assessment of neuroinflammation and neuronal loss; and (v) long-term survival. ResultsXenon treatment significantly reduced secondary injury (P<0.05), improved short-term vestibulomotor function (P<0.01), and prevented development of very late-onset traumatic brain injury (TBI)-related memory deficits. Xenon treatment reduced white matter loss in the contralateral corpus callosum and neuronal loss in the contralateral hippocampal CA1 and dentate gyrus areas at 20 months. Xenon's long-term neuroprotective effects were associated with a significant (P<0.05) reduction in neuroinflammation in multiple brain areas involved in associative memory, including reduction in reactive astrogliosis and microglial cell proliferation. Survival was improved significantly (P<0.05) in xenon-treated animals compared with untreated animals up to 12 months after injury. ConclusionsXenon treatment after TBI results in very long-term improvements in clinically relevant outcomes and survival. Our findings support the idea that xenon treatment shortly after TBI may have long-term benefits in the treatment of brain trauma patients.

Excitotoxicity Alters Endogenous Secretoneurin Plasma Levels, but Supplementation with Secretoneurin Does Not Protect Against Excitotoxic Neonatal Brain Injury

Excitotoxicity plays an important role in the pathogenesis of developing brain injury. The neuropeptide secretoneurin (SN) has neuroprotective potential. The aim of this study was to investigate SN plasma concentrations following excitotoxicity and to evaluate the effect of SN as therapeutic strategy in excitotoxic newborn brain injury. Baseline SN plasma concentrations were established in healthy animals. To evaluate the effect of an excitotoxic insult on SN levels, mice pups were subjected to an intracranial injection of ibotenic acid and SN plasma concentrations were measured thereafter. To assess SN's neuroprotective potential, a subgroup of animals was randomly assigned to the following groups: i) “single treatment”: vehicle 1× phosphate-buffered saline (PBS), SN 0.25 μg/g body weight (bw), SN 2.5 μg/g bw or SN 12.5 μg/g bw in a single dose 1 h after insult; ii) “acute repetitive treatment”: vehicle 1× PBS or SN 0.25 μg/g bw every 24 h starting 1 h after insult; iii) “delayed repetitive treatment”: vehicle 1× PBS or SN 0.25 μg/g bw every 24 h starting 60 h after insult. Animals subjected to excitotoxic injury showed significantly lower SN plasma concentrations 6 and 120 h after insult in comparison to healthy controls. Administration of SN did not positively affect lesion size, apoptotic cell death, microglial cell activation or cell proliferation. To conclude, endogenous SN plasma levels are lower in newborn mice subjected to an excitotoxic insult than in healthy controls. Supplementation with SN in various treatment regimens is not neuroprotective in the experimental animal model of excitotoxic newborn brain injury.

Spatiotemporal expression and inhibition of prolyl oligopeptidase contradict its involvement in key pathologic mechanisms of kainic acid-induced temporal lobe epilepsy in rats.

SummaryObjectiveProlyl oligopeptidase (PREP) has been implicated in neuroinflammatory processes and neuroplasticity and has been suggested as a target for the treatment of neurodegenerative disease. The aim of this investigation was to explore the involvement of PREP in the neuropathologic mechanisms relevant to temporal lobe epilepsy (TLE) using a PREP inhibitor in a well‐established rat model.Methods PREP activity and expression was studied in Sprague‐Dawley rats 2 and 12 weeks following kainic acid–induced status epilepticus (KASE). Continuous video‐electroencephalography monitoring was performed for 2 weeks in the 12‐week cohort to identify a relationship of PREP expression/activity with epileptic seizures. In addition, the animals included in the 2‐week time point were treated with a specific inhibitor of PREP, KYP‐2047, or saline continuously, starting immediately after SE. PREP activity and its expression were analyzed in rat brain by using enzyme kinetics and western blot. In addition, markers for microglial activation, astrogliosis, cell loss, and cell proliferation were evaluated.ResultsEnzymatic activity of PREP was unchanged following induction of SE after 2 and 12 weeks in rats. PREP activity in epileptic rats did not relate to the number of seizures/day at the 12‐week time point. Moreover, continuous inhibition of PREP for 2 weeks after KASE did not alter the SE‐mediated neuroinflammatory response, cell loss, or cell proliferation in the hippocampal subgranule zone measured at the 2‐week time point.Significance PREP inhibition does not affect key pathologic mechanisms, including activation of glial cells, cell loss, and neural progenitor cell proliferation, in this KASE model of TLE. The results do not support a direct role of PREP in seizure burden during the chronic epilepsy period in this model.

Ketamine Alters Hippocampal Cell Proliferation and Improves Learning in Mice after Traumatic Brain Injury.

WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Traumatic brain injury induces cellular proliferation in the hippocampus, which generates new neurons and glial cells during recovery. This process is regulated by N-methyl-D-aspartate-type glutamate receptors, which are inhibited by ketamine. The authors hypothesized that ketamine treatment after traumatic brain injury would reduce hippocampal cell proliferation, leading to worse behavioral outcomes in mice. Traumatic brain injury was induced in mice using a controlled cortical impact injury, after which mice (N = 118) received either ketamine or vehicle systemically for 1 week. The authors utilized immunohistochemical assays to evaluate neuronal, astroglial, and microglial cell proliferation and survival 3 days, 2 weeks, and 6 weeks postintervention. The Morris water maze reversal task was used to assess cognitive recovery. Ketamine dramatically increased microglial proliferation in the granule cell layer of the hippocampus 3 days after injury (injury + vehicle, 2,800 ± 2,700 cells/mm, n = 4; injury + ketamine, 11,200 ± 6,600 cells/mm, n = 6; P = 0.012). Ketamine treatment also prevented the production of astrocytes 2 weeks after injury (sham + vehicle, 2,400 ± 3,200 cells/mm, n = 13; injury + vehicle, 10,500 ± 11,300 cells/mm, n = 12; P = 0.013 vs. sham + vehicle; sham + ketamine, 3,500 ± 4,900 cells/mm, n = 14; injury + ketamine, 4,800 ± 3,000 cells/mm, n = 13; P = 0.955 vs. sham + ketamine). Independent of injury, ketamine temporarily reduced neurogenesis (vehicle-exposed, 105,100 ± 66,700, cells/mm, n = 25; ketamine-exposed, 74,300 ± 29,200 cells/mm, n = 27; P = 0.031). Ketamine administration improved performance in the Morris water maze reversal test after injury, but had no effect on performance in sham-treated mice. Ketamine alters hippocampal cell proliferation after traumatic brain injury. Surprisingly, these changes were associated with improvement in a neurogenesis-related behavioral recall task, suggesting a possible benefit from ketamine administration after traumatic brain injury in mice. Future studies are needed to determine generalizability and mechanism.

Effect of Progesterone on Cerebral Vasospasm and Neurobehavioral Outcomes in a Rodent Model of Subarachnoid Hemorrhage.

Subarachnoid hemorrhage (SAH) induces widespread inflammation leading to cellular injury, vasospasm, and ischemia. Evidence suggests that progesterone (PROG) can improve functional recovery in acute brain injury owing to its anti-inflammatory and neuroprotective properties, which could also be beneficial in SAH. We hypothesized that PROG treatment attenuates inflammation-mediated cerebral vasospasm and microglial activation, improves synaptic connectivity, and ameliorates functional recovery after SAH. We investigated the effect of PROG in a cisternal SAH model in adult male C57BL/6 mice. Neurobehavioral outcomes were evaluated using rotarod latency and grip strength tests. Basilar artery perimeter, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid glutamate receptor 1 (GluR1)/synaptophysin colocalization, and Iba-1 immunoreactivity were quantified histologically. PROG (8 mg/kg) significantly improved rotarod latency at day 6 and grip strength at day 9. PROG-treated mice had significantly reduced basilar artery vasospasm at 24 hours. GluR1/synaptophysin colocalization, indicative of synaptic GluR1, was significantly reduced in the SAH+Vehicle group at 24 hours, and PROG treatment significantly attenuated this reduction. PROG treatment significantly reduced microglial cell activation and proliferation in cerebellum and cortex but not in the brainstem at 10 days. PROG treatment ameliorated cerebral vasospasm, reduced microglial activation, restored synaptic GluR1 localization, and improved neurobehavioral performance in a murine model of SAH. These results provide a rationale for further translational testing of PROG therapy in SAH.

Ion-shedding zinc oxide nanoparticles induce microglial BV2 cell proliferation via the ERK and Akt signaling pathways.

Given the wide application of zinc oxide nanoparticles (ZnO NPs), the health hazards of these particles have attracted extensive worldwide attention. Many more studies on the biological interactions of ZnO NPs have been performed in recent years. In this study, we focused on the biological effects on BV2 microglial cells induced by ZnO NPs at non- or sub-toxic concentrations. We found that ZnO NPs at a concentration of 5 μg/ml could significantly activate cell proliferation, while ZnO NPs at other concentrations did not. We also found that ZnO NPs induced microglial cell activation in a time-dependent manner. Moreover, a potent increase in the ratio of cells in S phase at all ZnO NPs concentrations was observed in a cell cycle analysis. Using inductively coupled plasma mass spectrometry (ICP-MS) and immunocytochemistry techniques, we demonstrated that ZnO dissolution could occur in the culture medium and in the lysosomes of BV2 cells. ZnO NPs significantly induced the phosphorylation of ERK and Akt, which might be involved in promoting cell proliferation. In conclusion, our results demonstrated that ZnO NPs induced BV2 microglial cell proliferation probably via the release of zinc ions from ZnO, which could then activate the ERK and Akt signaling pathways.