Lucanthone, a Potential PPT1 Inhibitor, Perturbs Stemness, Reduces Tumor Microtube Formation, and Slows the Growth of Temozolomide-Resistant Gliomas In Vivo

Glioblastoma (GBM) is the most frequently diagnosed primary central nervous system tumor in adults. Despite the standard of care therapy, which includes surgical resection, temozolomide chemotherapy, radiation and the newly added tumor-treating fields, median survival remains only ∼20 months. Unfortunately, GBM has a ∼100% recurrence rate, but after recurrence there are no Food and Drug Administration-approved therapies to limit tumor growth and enhance patient survival, as these tumors are resistant to temozolomide (TMZ). Recently, our laboratory reported that lucanthone slows GBM by inhibiting autophagic flux through lysosome targeting and decreases the number of Olig2+ glioma stem-like cells (GSC) in vitro and in vivo. We now additionally report that lucanthone efficiently abates stemness in patient-derived GSC and reduces tumor microtube formation in GSC, an emerging hallmark of treatment resistance in GBM. In glioma tumors derived from cells with acquired resistance to TMZ, lucanthone retains the ability to perturb tumor growth, inhibits autophagy by targeting lysosomes, and reduces Olig2 positivity. We also find that lucanthone may act as an inhibitor of palmitoyl protein thioesterase 1. Our results suggest that lucanthone may function as a potential treatment option for GBM tumors that are not amenable to TMZ treatment. SIGNIFICANCE STATEMENT: We report that the antischistosome agent lucanthone impedes tumor growth in a preclinical model of temozolomide-resistant glioblastoma and reduces the numbers of stem-like glioma cells. In addition, it acts as an autophagy inhibitor, and its mechanism of action may be via inhibition of palmitoyl protein thioesterase 1. As there are no defined therapies approved for recurrent, TMZ-resistant tumor, lucanthone could emerge as a treatment for glioblastoma tumors that may not be amenable to TMZ both in the newly diagnosed and recurrent settings.

Chronic psychosocial stress triggers microglial-/macrophage-induced inflammatory responses leading to neuronal dysfunction and depressive-related behavior

Chronic environmental stress and traumatic social experiences induce maladaptive behavioral changes and is a risk factor for major depressive disorder (MDD) and various anxiety-related psychiatric disorders. Clinical studies and animal models of chronic stress have reported that symptom severity is correlated with innate immune responses and upregulation of neuroinflammatory cytokine signaling in brain areas implicated in mood regulation (mPFC; medial Prefrontal Cortex). Despite increasing evidence implicating impairments of neuroplasticity and synaptic signaling deficits into the pathophysiology of stress-related mental disorders, how microglia may modulate neuronal homeostasis in response to chronic stress has not been defined. Here, using the repeated social defeat stress (RSDS) mouse model we demonstrate that microglial-induced inflammatory responses are regulating neuronal plasticity associated with psychosocial stress. Specifically, we show that chronic stress induces a rapid activation and proliferation of microglia as well as macrophage infiltration in the mPFC, and these processes are spatially related to neuronal activation. Moreover, we report a significant association of microglial inflammatory responses with susceptibility or resilience to chronic stress. In addition, we find that exposure to chronic stress exacerbates phagocytosis of synaptic elements and deficits in neuronal plasticity. Importantly, by utilizing two different CSF1R inhibitors (the brain penetrant PLX5622 and the non-penetrant PLX73086) we highlight a crucial role for microglia (and secondarily macrophages) in catalyzing the pathological manifestations linked to psychosocial stress in the mPFC and the resulting behavioral deficits usually associated with depression.

Evolving Clinical-Translational Investigations of Cerebroprotection in Ischemic Stroke

Ischemic stroke is a highly morbid disease, with over 50% of large vessel stroke (middle cerebral artery or internal carotid artery terminus occlusion) patients suffering disability despite maximal acute reperfusion therapy with thrombolysis and thrombectomy. The discovery of the ischemic penumbra in the 1980s laid the foundation for a salvageable territory in ischemic stroke. Since then, the concept of neuroprotection has been a focus of post-stroke care to (1) minimize the conversion from penumbra to core irreversible infarct, (2) limit secondary damage from ischemia-reperfusion injury, inflammation, and excitotoxicity and (3) to encourage tissue repair. However, despite multiple studies, the preclinical-clinical research enterprise has not yet created an agent that mitigates post-stroke outcomes beyond thrombolysis and mechanical clot retrieval. These translational gaps have not deterred the scientific community as agents are under continuous investigation. The NIH has recently promoted the concept of cerebroprotection to consider the whole brain post-stroke rather than just the neurons. This review will briefly outline the translational science of past, current, and emerging breakthroughs in cerebroprotection and use of these foundational ideas to develop a novel paradigm for optimizing stroke outcomes.

Intersection of Sex and Depression: Pathogenesis, Presentation, and Treatments

Major Depressive Disorder (MDD) is a highly prevalent, debilitating disorder. According to the World Health Organization, approximately 5% of adults suffer from depression worldwide and more women than men are affected. Yet, we have a very limited understanding of the pathogenesis of the disease, how sex and genetics influence the pathophenotype of MDD, and how they contribute to the responses to pharmacological treatment. This chapter addresses key theories about the etiology of depression, the variations in epidemiology and presentation, and the treatment options with respect to sex and gender. Additionally, we discuss the emerging wave of treatment modalities, diagnosis, and research focusing on MDD.

Investigation of the photoluminescent properties, scintillation behaviour and toxicological profile of various magnesium tungstate nanoscale motifs

We have synthesized several morphologies and crystal structures of MgWO₄ using a one-pot hydrothermal method, producing not only monoclinic stars and large nanoparticles but also triclinic wool balls and sub-10 nm nanoparticles. Herein we describe the importance of reaction parameters in demonstrating morphology control of as-prepared MgWO₄. Moreover, we correlate structure and composition with the resulting photoluminescence and radioluminescence properties. Specifically, triclinic-phase samples yielded a photoluminescence emission of 421 nm, whereas monoclinic-phase materials gave rise to an emission maximum of 515 nm. The corresponding radioluminescence data were characterized by a broad emission peak, located at 500 nm for all samples. Annealing the wool balls and sub-10 nm particles to transform the crystal structure from a triclinic to a monoclinic phase yielded a radioluminescence (RL) emission signal that was two orders of magnitude greater than that of their unannealed counterparts. Finally, to confirm the practical utility of these materials for biomedical applications, a series of sub-10 nm particles, including as-prepared and annealed samples, were functionalized with biocompatible PEG molecules, and subsequently were found to be readily taken up by various cell lines as well as primary cultured hippocampal neurons with low levels of toxicity, thereby highlighting for the first time the potential of this particular class of metal oxides as viable and readily generated platforms for a range of biomedical applications.

ADAM10 facilitates rapid neural stem cell cycling and proper positioning within the subventricular zone niche via JAMC/RAP1Gap signaling

The mechanisms that regulate neural stem cell (NSC) lineage progression and maintain NSCs within different domains of the adult neural stem cell niche, the subventricular zone are not well defined. Quiescent NSCs are arranged at the apical ventricular wall, while mitotically activated NSCs are found in the basal, vascular region of the subventricular zone. Here, we found that ADAM10 (a disintegrin and metalloproteinase 10) is essential in NSC association with the ventricular wall, and via this adhesion to the apical domain, ADAM10 regulates the switch from quiescent and undifferentiated NSC to an actively proliferative and differentiating cell state. Processing of JAMC (junctional adhesion molecule C) by ADAM10 increases Rap1GAP activity. This molecular machinery promotes NSC transit from the apical to the basal compartment and subsequent lineage progression. Understanding the molecular mechanisms responsible for regulating the proper positioning of NSCs within the subventricular zone niche and lineage progression of NSCs could provide new targets for drug development to enhance the regenerative properties of neural tissue.

From protein-protein interactions to immune modulation: Therapeutic prospects of targeting Neuropilin-1 in high-grade glioma

In the past several years there has been a marked increase in our understanding of the pathophysiological hallmarks of glioblastoma development and progression, with specific respect to the contribution of the glioma tumor microenvironment to the rapid progression and treatment resistance of high-grade gliomas. Despite these strides, standard of care therapy still only targets rapidly dividing tumor cells in the glioma, and does little to curb the pro-tumorigenic functions of non-cancerous cells entrenched in the glioma microenvironment. This tumor promoting environment as well as the heterogeneity of high-grade gliomas contribute to the poor prognosis of this malignancy. The interaction of non-malignant cells in the microenvironment with the tumor cells accentuate phenotypes such as rapid proliferation or immunosuppression, so therapeutically modulating one target expressed on one cell type may be insufficient to restrain these rapidly developing neoplasias. With this in mind, identifying a target expressed on multiple cell types and understanding how it governs tumor-promoting functions in each cell type may have great utility in better managing this disease. Herein, we review the physiology and pathological effects of Neuropilin-1, a transmembrane co-receptor which mediates signal transduction pathways when associated with multiple other receptors. We discuss its effects on the properties of endothelial cells and on immune cell types within gliomas including glioma-associated macrophages, microglia, cytotoxic T cells and T regulatory cells. We also consider its effects when elaborated on the surface of tumor cells with respect to proliferation, stemness and treatment resistance, and review attempts to target Neuroplin-1 in the clinical setting.

Chronic delta-9-tetrahydrocannabinol (THC) treatment counteracts SIV-induced modulation of proinflammatory microRNA cargo in basal ganglia-derived extracellular vesicles

BACKGROUND

Early invasion of the central nervous system (CNS) by human immunodeficiency virus (HIV) (Gray et al. in Brain Pathol 6:1-15, 1996; An et al. in Ann Neurol 40:611-6172, 1996), results in neuroinflammation, potentially through extracellular vesicles (EVs) and their micro RNAs (miRNA) cargoes (Sharma et al. in FASEB J 32:5174-5185, 2018; Hu et al. in Cell Death Dis 3:e381, 2012). Although the basal ganglia (BG) is a major target and reservoir of HIV in the CNS (Chaganti et al. in Aids 33:1843-1852, 2019; Mintzopoulos et al. in Magn Reson Med 81:2896-2904, 2019), whether BG produces EVs and the effect of HIV and/or the phytocannabinoid-delta-9-tetrahydrocannabinol (THC) on BG-EVs and HIV neuropathogenesis remain unknown.

METHODS

We used the simian immunodeficiency virus (SIV) model of HIV and THC treatment in rhesus macaques (Molina et al. in AIDS Res Hum Retroviruses 27:585-592, 2011) to demonstrate for the first time that BG contains EVs (BG-EVs), and that BG-EVs cargo and function are modulated by SIV and THC. We also used primary astrocytes from the brains of wild type (WT) and CX3CR1+/GFP mice to investigate the significance of BG-EVs in CNS cells.

RESULTS

Significant changes in BG-EV-associated miRNA specific to SIV infection and THC treatment were observed. BG-EVs from SIV-infected rhesus macaques (SIV EVs) contained 11 significantly downregulated miRNAs. Remarkably, intervention with THC led to significant upregulation of 37 miRNAs in BG-EVs (SIV-THC EVs). Most of these miRNAs are predicted to regulate pathways related to inflammation/immune regulation, TLR signaling, Neurotrophin TRK receptor signaling, and cell death/response. BG-EVs activated WT and CX3CR1+/GFP astrocytes and altered the expression of CD40, TNFα, MMP-2, and MMP-2 gene products in primary mouse astrocytes in an EV and CX3CR1 dependent manners.

CONCLUSIONS

Our findings reveal a role for BG-EVs as a vehicle with potential to disseminate HIV- and THC-induced changes within the CNS.

Prophylactic administration of cannabidiol reduces microglial inflammatory response to kainate-induced seizures and neurogenesis

Microglia, the dynamic innate immune cells of the central nervous system, become activated in epilepsy. The process of microglial activation in epilepsy results in the creation of an inflammatory environment around the site of seizure onset, which contributes to the epileptogenic process and epilepsy progression. Cannabidiol (CBD) has been effective for use as an adjunctive treatment for two severe pediatric seizure disorders. Newly recognized as an Food and Drug Administration (FDA)-approved drug treatment in epilepsy, it has gained in popularity primarily for pain management. Although CBD is readily available in stores and online retailers, its mechanism of action and specifically its effects on microglia and their functions are yet fully understood. In this study, we examine the effects of commercially available CBD on microglia inflammatory activation and neurogenic response, in the presence and absence of seizures. We use systemic administration of kainate to elicit seizures in mice, which are assessed behaviorally. Artisanal CBD is given in different modes of administration and timing to dissect its effect on seizure intensity, microglial activation and aberrant seizure-related neurogenesis. CBD significantly dampens microglial migration and accumulation to the hippocampus. While long term artisanal CBD use does not prevent or lessen seizure severity, CBD is a promising adjunctive partner for its ability to depress epileptogenic processes. These studies indicate that artisanal CBD is beneficial as it both decreases inflammation in the CNS and reduces the number of ectopic neurons deposited in the hippocampal area post seizure.

Chronic stress disrupts the homeostasis and progeny progression of oligodendroglial lineage cells, associating immune oligodendrocytes with prefrontal cortex hypomyelination

Major depressive disorder (MDD) is a chronic debilitating illness affecting yearly 300 million people worldwide. Oligodendrocyte-lineage cells have emerged as important neuromodulators in synaptic plasticity and crucial components of MDD pathophysiology. Using the repeated social defeat (RSDS) mouse model, we demonstrate that chronic psychosocial stress induces long-lasting losses and transient proliferation of oligodendrocyte-precursor cells (OPCs), aberrant differentiation into oligodendrocytes, and severe hypomyelination in the prefrontal cortex. Exposure to chronic stress results in OPC morphological impairments, excessive oxidative stress, and oligodendroglial apoptosis, implicating integrative-stress responses in depression. Analysis of single-nucleus transcriptomic data from MDD patients revealed oligodendroglial-lineage dysregulation and the presence of immune-oligodendrocytes (Im-OL), a novel population of cells with immune properties and myelination deficits. Im-OL were also identified in mice after RSDS, where oligodendrocyte-lineage cells expressed immune-related markers. Our findings demonstrate cellular and molecular changes in the oligodendroglial lineage in response to chronic stress and associate hypomyelination with Im-OL emergence during depression.

Beyond Myelination: Possible Roles of the Immune Proteasome in Oligodendroglial Homeostasis and Dysfunction

Oligodendroglia play a critical role in CNS homeostasis by myelinating neuronal axons in their mature stages. Dysfunction in this lineage occurs when early stage OPCs are not able to differentiate to replace dying Mature Myelinating Oligodendrocytes. Many hypotheses exist as to why de- and hypo-myelinating disorders and diseases occur. In this review, we present data to show that oligodendroglia can adopt components of the immune proteasome under inflammatory conditions. The works reviewed further reflect that these immune-component expressing oligodendroglia can in fact function as antigen presenting cells, phagocytosing foreign entities and presenting them via MHC II to activate CD4+ T cells. Additionally, we hypothesize, based on the limited literature, that the adoption of immune components by oligodendroglia may contribute to their stalled differentiation in the context of these disorders and diseases. The present review will underline: (1) Mechanisms of neuroinflammation in diseases associated with Immune Oligodendroglia; (2) the first associations between the immune proteasome and oligodendroglia and the subtle distinctions between these works; (3) the suggested functionality of these cells as it is described by current literature; and (4) the hypothesized consequences on metabolism. In doing so we aim to shed light on this fairly under-explored cell type in hopes that study of their functionality may lead to further mechanistic understanding of hypo- and de-myelinating neuroinflammatory disorders and diseases.

Lucanthone Targets Lysosomes to Perturb Glioma Proliferation, Chemoresistance and Stemness, and Slows Tumor Growth In Vivo

Glioblastoma is the most common and aggressive primary brain tumor in adults. Median survival time remains at 16-20 months despite multimodal treatment with surgical resection, radiation, temozolomide and tumor-treating fields therapy. After genotoxic stress glioma cells initiate cytoprotective autophagy, which contributes to treatment resistance, limiting the efficacy of these therapies and providing an avenue for glioma recurrence. Antagonism of autophagy steps has recently gained attention as it may enhance the efficacy of classical chemotherapies and newer immune-stimulating therapies. The modulation of autophagy in the clinic is limited by the low potency of common autophagy inhibitors and the inability of newer ones to cross the blood-brain barrier. Herein, we leverage lucanthone, an anti-schistosomal agent which crosses the blood-brain barrier and was recently reported to act as an autophagy inhibitor in breast cancer cells. Our studies show that lucanthone was toxic to glioma cells by inhibiting autophagy. It enhanced anti-glioma temozolomide (TMZ) efficacy at sub-cytotoxic concentrations, and suppressed the growth of stem-like glioma cells and temozolomide-resistant glioma stem cells. In vivo lucanthone slowed tumor growth: reduced numbers of Olig2+ glioma cells, normalized tumor vasculature, and reduced tumor hypoxia. We propose that lucanthone may serve to perturb a mechanism of temozolomide resistance and allow for successful treatment of TMZ-resistant glioblastoma.

Extracellular histones, a new class of inhibitory molecules of CNS axonal regeneration

Axonal regeneration in the mature CNS is limited by extracellular inhibitory factors. Triple knockout mice lacking the major myelin-associated inhibitors do not display spontaneous regeneration after injury, indicating the presence of other inhibitors. Searching for such inhibitors, we have detected elevated levels of histone H3 in human CSF 24 h after spinal cord injury. Following dorsal column lesions in mice and optic nerve crushes in rats, elevated levels of extracellular histone H3 were detected at the injury site. Similar to myelin-associated inhibitors, these extracellular histones induced growth cone collapse and inhibited neurite outgrowth. Histones mediate inhibition through the transcription factor Y-box-binding protein 1 and Toll-like receptor 2, and these effects are independent of the Nogo receptor. Histone-mediated inhibition can be reversed by the addition of activated protein C in vitro, and activated protein C treatment promotes axonal regeneration in the crushed optic nerve in vivo. These findings identify extracellular histones as a new class of nerve regeneration-inhibiting molecules within the injured CNS.

Immunosuppression in Multiple Sclerosis and Other Neurologic Disorders

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) characterized by peripheral immune cell infiltration into the brain and spinal cord, demyelination, glial cell activation, and neuronal damage. Currently there is no cure for MS, however, available disease-modifying agents minimize inflammation in the CNS by various mechanisms. Approved drugs lessen severity of the disease and delay disease progression, however, they are still suboptimal as patients experience adverse effects and varying efficacies. Additionally, there is only one disease-modifying therapy available for the more debilitating, progressive form of MS. This chapter focuses on the presently-available therapeutics and, importantly, the future directions of MS therapy based on preclinical studies and early clinical trials. Immunosuppression in other neurological disorders including neuromyelitis optica spectrum disorders, myasthenia gravis, and Guillain-Barré syndrome is also discussed.

Microglia modulate stable wakefulness via the thalamic reticular nucleus in mice

Microglia are important for brain homeostasis and immunity, but their role in regulating vigilance remains unclear. We employed genetic, physiological, and metabolomic methods to examine microglial involvement in the regulation of wakefulness and sleep. Microglial depletion decreased stable nighttime wakefulness in mice by increasing transitions between wakefulness and non-rapid eye movement (NREM) sleep. Metabolomic analysis revealed that the sleep-wake behavior closely correlated with diurnal variation of the brain ceramide, which disappeared in microglia-depleted mice. Ceramide preferentially influenced microglia in the thalamic reticular nucleus (TRN), and local depletion of TRN microglia produced similar impaired wakefulness. Chemogenetic manipulations of anterior TRN neurons showed that they regulated transitions between wakefulness and NREM sleep. Their firing capacity was suppressed by both microglial depletion and added ceramide. In microglia-depleted mice, activating anterior TRN neurons or inhibiting ceramide production both restored stable wakefulness. These findings demonstrate that microglia can modulate stable wakefulness through anterior TRN neurons via ceramide signaling.

A distinct microglial subset at the tumor-stroma interface of glioma

The characterization of the tumor microenvironment (TME) in high grade gliomas (HGG) has generated significant interest in an effort to understand how neoplastic lesions in the central nervous system (CNS) are supported and to devise novel therapeutic targets. The TME of the CNS contains unique and specialized cells, including the resident myeloid cells, microglia. Myeloid involvement in HGG, such as glioblastoma, is associated with poor outcomes. Glioma-associated microglia and infiltrating monocytes/macrophages (GAM) accumulate within the neoplastic lesion where they facilitate tumor growth and drive immunosuppression. However, it has been difficult to differentiate whether microglia and macrophages have similar or distinct roles in pathology, and if the spatial organization of these cells informs outcomes. Here, we characterize the tumor-stroma border and identify peritumoral GAM (PGAM) as a unique subpopulation of GAM. Using data mining and analyses of samples derived from both murine and human sources we show that PGAM exhibit a pro-inflammatory and chemotactic phenotype that is associated with peripheral monocyte recruitment, and decreased overall survival. PGAM act as a unique subset of GAM at the tumor-stroma interface. We define a novel gene signature to identify these cells and suggest that PGAM constitute a cellular target of the TME.

Interactions between Tumor Cells, Neurons, and Microglia in the Glioma Microenvironment

Despite significant strides made in understanding the pathophysiology of high-grade gliomas over the past two decades, most patients succumb to these neoplasias within two years of diagnosis. Furthermore, there are various co-morbidities associated with glioma and standard of care treatments. Emerging evidence suggests that aberrant glutamate secretion in the glioma microenvironment promotes tumor progression and contributes to the development of co-morbidities, such as cognitive defects, epilepsy, and widespread neurodegeneration. Recent data clearly illustrate that neurons directly synapse onto glioma cells and drive their proliferation and spread via glutamatergic action. Microglia are central nervous system-resident myeloid cells, modulate glioma growth, and possess the capacity to prune synapses and encourage synapse formation. However, current literature has yet to investigate the potential role of microglia in shaping synapse formation between neurons and glioma cells. Herein, we present the literature concerning glutamate's role in glioma progression, involving hyperexcitability and excitotoxic cell death of peritumoral neurons and stimulation of glioma proliferation and invasion. Furthermore, we discuss instances in which microglia are more likely to sculpt or encourage synapse formation during glioma treatment and propose studies to delineate the role of microglia in synapse formation between neurons and glioma cells. The sex-dependent oncogenic or oncolytic actions of microglia and myeloid cells, in general, are considered in addition to the functional differences between microglia and macrophages in tumor progression. We also put forth tractable methods to safely perturb aberrant glutamatergic action in the tumor microenvironment without significantly increasing the toxicities of the standard of care therapies for glioma therapy.

Guanabenz modulates microglia and macrophages during demyelination

Multiple sclerosis (MS) is an autoimmune disease characterized by infiltration of peripheral immune cells into the central nervous system, demyelination, and neuronal damage. There is no cure for MS, but available disease-modifying therapies can lessen severity and delay progression. However, current therapies are suboptimal due to adverse effects. Here, we investigate how the FDA-approved antihypertensive drug, guanabenz, which has a favorable safety profile and was recently reported to enhance oligodendrocyte survival, exerts effects on immune cells, specifically microglia and macrophages. We first employed the experimental autoimmune encephalomyelitis (EAE) model and observed pronounced immunomodulation evident by a reduction in pro-inflammatory microglia and macrophages. When guanabenz was administered in the cuprizone model, in which demyelination is less dependent upon immune cells, we did not observe improvements in remyelination, oligodendrocyte numbers, and effects on microglial activation were less dramatic. Thus, guanabenz may be a promising therapeutic to minimize inflammation without exerting severe off-target effects.

Sexual Dimorphism of Neuroimmune Cells and Its Impact on the Central Nervous System: a Special Issue

Neuroimmune-related sex differences contribute to the complexity of neurologic disorders, such as drug abuse, depression, and chronic pain. The collection of articles presented in this issue add to our understanding of sex as a critical biologic variable in the study of psychiatric and neurologic diseases. SIGNIFICANCE STATEMENT: Consideration of sex in the design and interpretation of study results is critical. Sex differences may warrant different treatment approaches for diseases in which sex or gender influences disease outcomes. The studies and reviews presented here examine the contribution of sexual dimorphism in the physiologic responses and pharmacological treatments of neurological and psychiatric disorders.

A Rigorous Quantitative Approach to Analyzing Phagocytosis Assays

Studying monocytic cells in isolated systems in vitro contributes significantly to the understanding of innate immune physiology. Functional assays produce read outs which can be used to measure responses to selected stimuli, such as pathogen exposure, antigen loading, and cytokine stimulation. Integration of these results with high quality in vivo models allows for the development of therapeutics which target these cell populations. Current methodologies to quantify phagocytic function of monocytic cells in vitro either measure phagocytic activity of individual cells (average number of beads or particles/cell), or a population outcome (% cells that contain phagocytosed material). Here we address technical challenges and shortcomings of these methods and present a protocol for collecting and analyzing data derived from a functional assay which measures phagocytic activity of macrophage and macrophage-like cells. We apply this method to two different experimental conditions, and compare to existing work flows. We also provide an online tool for users to upload and analyze data using this method.

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

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

Microglial contributions to aberrant neurogenesis and pathophysiology of epilepsy

Microglia are dynamic cells that constitute the brain's innate immune system. Recently, research has demonstrated microglial roles beyond immunity, which include homeostatic roles in the central nervous system. The function of microglia is an active area of study, with insights into changes in neurogenesis and synaptic pruning being discovered in both health and disease. In epilepsy, activated microglia contribute to several changes that occur during epileptogenesis. In this review, we focus on the effects of microglia on neurogenesis and synaptic pruning, and discuss the current state of anti-seizure drugs and how they affect microglia during these processes. Our understanding of the role of microglia post-seizure is still limited and may be pivotal in recognizing new therapeutic targets for seizure intervention.

Increased Behavioral Deficits and Inflammation in a Mouse Model of Co-Morbid Traumatic Brain Injury and Post-Traumatic Stress Disorder

Comorbid post-traumatic stress disorder with traumatic brain injury (TBI) produce more severe affective and cognitive deficits than PTSD or TBI alone. Both PTSD and TBI produce long-lasting neuroinflammation, which may be a key underlying mechanism of the deficits observed in co-morbid TBI/PTSD. We developed a model of co-morbid TBI/PTSD by combining the closed head (CHI) model of TBI with the chronic variable stress (CVS) model of PTSD and examined multiple behavioral and neuroinflammatory outcomes. Male C57/Bl6 mice received sham treatment, CHI, CVS, CHI then CVS (CHI → CVS) or CVS then CHI (CVS → CHI). The CVS → CHI group had deficits in Barnes maze or active place avoidance not seen in the other groups. The CVS → CHI, CVS and CHI → CVS groups displayed increased basal anxiety level, based on performance on elevated plus maze. The CVS → CHI had impaired performance on Barnes Maze, and Active Place Avoidance. These performance deficits were strongly correlated with increased hippocampal Iba-1 level an indication of activated MP/MG. These data suggest that greater cognitive deficits in the CVS → CHI group were due to increased inflammation. The increased deficits and neuroinflammation in the CVS → CHI group suggest that the order by which a subject experiences TBI and PTSD is a major determinant of the outcome of brain injury in co-morbid TBI/PTSD.

Lunar soil simulants alter macrophage survival and function

Lunar regolith samples collected during previous Apollo missions were found to contain components that were established to be toxic to humans; however, the health effects due to inhalation of lunar soil as a whole are still unknown. Macrophages residing in the alveolar sacs of the lungs constitute one of the last lines of defense against inhaled particulates before entry into the bloodstream. Here, we examine the macrophage response to lunar simulants that are similar in chemical composition to the lunar regolith. We assess cytotoxicity, cellular morphology, phagocytosis of simulants and expression of inflammatory markers. Overall, the exposure of macrophages to lunar simulants results in moderate cytotoxicity and marked alteration of cell morphology and uptake of the simulants. Interestingly, simulant exposure decreased proinflammatory gene expression, but may induce an anti-inflammatory phenotype in the cells. These results illustrate that although macrophages phagocytose lunar simulants as a protective response, the simulants do induce a degree of macrophage cell death. Our study reveals some toxicity associated with lunar simulants and supports further evaluation of the inhalation of lunar regolith to understand the risks of exposure fully.

Abstract 1085: Neuropilin-1 deficient macrophages as a treatment strategy for glioblastoma

Post-diagnosis survival of grade IV glioblastoma (GB) is a dismal 14 months in patients receiving standard of care therapy. With the development of immunotherapeutic strategies targeting non-cancerous, stromal cells of the tumor microenvironment (TME), new avenues are being pursued in clinical trials and pre-clinical animal models of advanced GB. Glioma-associated microglia/macrophages (GAMs) of the TME promote chemoattraction, immune suppression, neoangiogenesis, and tumor cell survival, which parallels tumor-infiltrating macrophage behavior of other solid malignancies. GAMs are now recognized as a potentially practical immunotherapeutic target in GB. Previously in our lab, we have shown that GAM-specific deletion of the cell surface co-receptor Neuropilin-1 (NRP1) drastically reduces pro-tumorigenic behavior of infiltrating microglia and/or macrophages in murine glioma by reducing immunosuppressive tendencies and neoangiogenesis. As an extension to our genetically-ablated mouse model, we present here a platform by which these NRP1-deficient monocytic cells can be harvested ex vivo and locally delivered into the TME of the bulk glioma lesion, to exert anti-tumorigenic effects. To our knowledge, this is the first attempt to deliver cells of monocytic origin intratumorally as a therapeutic option.

Citation Format: Michael D. Caponegro, Stella E. Tsirka. Neuropilin-1 deficient macrophages as a treatment strategy for glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1085.

BSSE: An open-source image processing tool for miniaturized microscopy

Single-photon-excitation-based miniaturized microscope, or miniscope, has recently emerged as a powerful tool for imaging neural ensemble activities in freely moving animals. In the meanwhile, this highly flexible and implantable technology promises great potential for studying a broad range of cells, tissues and organs. To date, however, applications have been largely limited by the properties of the imaging modality. It is therefore highly desirable for a method generally applicable for processing miniscopy images, enabling and extending the applications to diverse anatomical and functional traits, spanning various cell types in the brain and other organs. We report an image processing approach, termed BSSE, for background suppression and signal enhancement for miniscope image processing. The BSSE method provides a simple, automatic solution to the intrinsic challenges of overlapping signals, high background and artifacts in miniscopy images. We validated the method by imaging synthetic structures and various biological samples of brain, tumor, and kidney tissues. The work represents a generally applicable tool for miniscopy technology, suggesting broader applications of the miniaturized, implantable and flexible technology for biomedical research.

Proliferation and Differentiation in the Adult Subventricular Zone Are Not Affected by CSF1R Inhibition

Microglia are reported to have significant roles in regulating normal mammalian adult neurogenesis. There are two neurogenic niches in the adult mammal brain: the subgranular zone (SGZ) in the hippocampus, and the subventricular zone (SVZ), which makes up the lining of the lateral ventricles. While the microglia interactions on adult neurogenesis in the hippocampus have been characterized, the SVZ niche is not as well investigated. The SVZ niche is unique in that the newborn neurons migrate a much longer distance through multiple brain structures compared to newborn neurons in the hippocampus, making it more difficult to fully characterize how microglia influence this process. To examine the SVZ niche and migration pathway, we used the colony stimulating factor 1 receptor (CSF1R) antagonist PLX5622, which promotes brain wide microglia ablation. Microglia ablation resulted in no changes in the numbers of neural stem cells (NSCs), transient amplifying cells, and neuroblasts. Microglia ablation in the olfactory bulb (OB) was decreased compared to the SVZ. CSF1R inhibition had no effect on the ability of microglia to proliferate. Thus, our data suggest that microglia are not required for normal functioning SVZ adult neurogenesis.

Emerging small-molecule treatments for multiple sclerosis: focus on B cells

Multiple sclerosis (MS) is a major cause of disability in young adults. Following an unknown trigger (or triggers), the immune system attacks the myelin sheath surrounding axons, leading to progressive nerve cell death. Antibodies and small-molecule drugs directed against B cells have demonstrated good efficacy in slowing progression of the disease. This review focusses on small-molecule drugs that can affect B-cell biology and may have utility in disease management. The risk genes for MS are examined from the drug target perspective. Existing small-molecule therapies for MS with B-cell actions together with new drugs in development are described. The potential for experimental molecules with B-cell effects is also considered. Small molecules can have diverse actions on B cells and be cytotoxic, anti-inflammatory and anti-viral. The current B cell-directed therapies often kill B-cell subsets, which can be effective but lead to side effects and toxicity. A deeper understanding of B-cell biology and the effect on MS disease should lead to new drugs with better selectivity, efficacy, and an improved safety profile. Small-molecule drugs, once the patent term has expired, provide a uniquely sustainable form of healthcare.

Tuftsin Combines With Remyelinating Therapy and Improves Outcomes in Models of CNS Demyelinating Disease

Though promoting remyelination in multiple sclerosis (MS) has emerged as a promising therapeutic strategy, it does not address inflammatory signals that continue to induce neuronal damage and inhibit effectiveness of repair mechanisms. Our lab has previously characterized the immunomodulatory tetrapeptide, tuftsin, which induces an anti-inflammatory shift in microglia and macrophages. This targeted anti-inflammatory agent improves physical deficits in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Here, we sought to determine whether tuftsin is also effective in combination with benztropine, an FDA-approved drug that stimulates remyelination, in both EAE and in the cuprizone model of demyelination. We show that combining these two agents to promote anti-inflammatory and remyelinating mechanisms alleviates symptoms in EAE and lessens pathological hallmarks in both MS models. Importantly, tuftsin is required to transform the inflammatory CNS environment normally present in EAE/MS into one of an anti-inflammatory nature, and benztropine is required in the cuprizone model to improve remyelination. Our data further support tuftsin's beneficial immunomodulatory activity in the context of EAE, and show that when studying remyelination in the absence of an autoimmune insult, tuftsin still activated microglia toward an anti-inflammatory fate, but benztropine was necessary for significant repair of the damaged myelin. Overall, tuftsin effectively combined with benztropine to significantly improve MS-like pathologies in both models.

Expression of neuropilin-1 is linked to glioma associated microglia and macrophages and correlates with unfavorable prognosis in high grade gliomas

High grade gliomas, including glioblastoma (GB), are devastating malignancies with very poor prognosis. Over the course of the last decade, there has been a failure to develop new treatments for GB. Reasons for this failure include the lack of validation of novel molecular targets, which are often characterized in animal models and directly transposed to human trials. Here we build on our previous findings, which describe how the multi-functional co-receptor Neuropilin-1 (NRP1) signals through glioma associated microglia/macrophages (GAMS) to promote murine glioma, and investigate NRP1 expression in human glioma. Clinical and gene expression data were obtained via The Cancer Genome Atlas (TCGA), and analyzed using R statistical software. Additionally, CIBERSORT in silico deconvolution was used to determine fractions of immune cell sub-populations within the gene expression datasets. We find that NRP1 expression is correlated with poor prognosis, glioma grade, and associates with the mesenchymal GB subtype. In human GB, NRP1 expression is highly correlated with markers of monocytes/macrophages, as well as genes that contribute to the pro-tumorigenic phenotype of these cells.

Pifithrin-μ modulates microglial activation and promotes histological recovery following spinal cord injury

BACKGROUND

Treatments immediately after spinal cord injury (SCI) are anticipated to decrease neuronal death, disruption of neuronal connections, demyelination, and inflammation, and to improve repair and functional recovery. Currently, little can be done to modify the acute phase, which extends to the first 48 hours post-injury. Efforts to intervene have focused on the subsequent phases - secondary (days to weeks) and chronic (months to years) - to both promote healing, prevent further damage, and support patients suffering from SCI.

METHODS

We used a contusion model of SCI in female mice, and delivered a small molecule reagent during the early phase of injury. Histological and behavioral outcomes were assessed and compared.

RESULTS

We find that the reagent Pifithrin-μ (PFT-μ) acts early and directly on microglia in vitro, attenuating their activation. When administered during the acute phase of SCI, PFT-μ resulted in reduced lesion size during the initial inflammatory phase, and reduced the numbers of pro-inflammatory microglia and macrophages. Treatment with PFT-μ during the early stage of injury maintained a stable anti-inflammatory environment.

CONCLUSIONS

Our results indicate that a small molecule reagent PFT-μ has sustained immunomodulatory effects following a single dose after injury.

Visualizing the Brain's Astrocytes with Diverse Chemical Scaffolds

Astrocytes are the most abundant cells in the brain. They support neurons, adjust synaptic strength, and modulate neuronal signaling, yet the full extent of their functions is obscured by the dearth of methods for their visualization and analysis. Here, we report a chemical reporter that targets small molecules specifically to astrocytes both in vitro and in vivo. Fluorescent versions of this tag are imported through an organic cation transporter to label glia across species. The structural modularity of this approach will enable wide-ranging applications for understanding astrocyte biology.

Mitigation of radiation myelopathy and reduction of microglial infiltration by Ramipril, ACE inhibitor

STUDY DESIGN

Experimental study.

OBJECTIVES

To evaluate the efficacy of Angiotensin-converting enzyme inhibitor Ramipril, as a mitigator of radiation-induced spinal cord injury.

SETTING

Stony Brook University, Stony Brook, NY, USA.

METHODS

Total of 22 rats were irradiated with single doses of 23.6-33 Gy at the C4-T2 spinal levels. After irradiation, the rats were randomized to the radiation only control group and the Ramipril-treated (radiation + Ramipril) experimental group. Ramipril 1.5 mg/kg/day was given in the drinking water starting 1 week after radiation through the study duration.

RESULTS

All the rats irradiated with 28.5-33 Gy became paralyzed at 125 ± 4 days, whereas no rats became paralyzed after 23.6 Gy. The time to develop paralysis was delayed to 135 ± 4 days in Ramipril-treated group (P < 0.001). H&E and LFB showed microscopic structural restoration and remyelination with Ramipril treatment. VEGF expression was increased in the irradiated spinal cord, and the number of VEGF-positive cells was significantly decreased by Ramipril treatment (P < 0.001). Immunohistochemical stain with Iba-1 showed increased microglial infiltration in the irradiated spinal cords. The number of Iba-1-positive microglia was significantly reduced by Ramipril treatment (P < 0.05).

CONCLUSION

Ramipril reduced the rate of paralysis even at the paralysis-inducing radiation doses. It also significantly delayed the onset of paralysis. Neuroinflammation and endothelial cell damage may be the key mediators of radiation injury. Ramipril can be readily translatable to clinical application as a mitigatory of radiotherapeutic toxicity.

Csf1R inhibition attenuates experimental autoimmune encephalomyelitis and promotes recovery

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS) characterized by progressive neuronal demyelination and degeneration. Much of this damage can be attributed to microglia, the resident innate immune cells of the CNS, as well as monocyte-derived macrophages, which breach the blood-brain barrier in this inflammatory state. Upon activation, both microglia and macrophages release a variety of factors that greatly contribute to disease progression, and thus therapeutic approaches in MS focus on diminishing their activity. We use the CSF1R inhibitor PLX5622, administered in mouse chow, to ablate microglia and macrophages during the course of experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Here, we show that ablation of these cells significantly improves animal mobility and weight gain in EAE. Further, we show that this treatment addresses the pathological hallmarks of MS, as it reduces demyelination and immune activation. White matter lesion areas in microglia/macrophage-depleted animals show substantial preservation of mature, myelinating oligodendrocytes in comparison to control animals. Taken together, these findings suggest that ablation of microglia/macrophages during the symptomatic phase of EAE reduces CNS inflammation and may also promote a more permissive environment for remyelination and recovery. This microglia and macrophage-targeted therapy could be a promising avenue for treatment of MS.

Small Molecule Neuropilin-1 Antagonists Combine Antiangiogenic and Antitumor Activity with Immune Modulation through Reduction of Transforming Growth Factor Beta (TGFβ) Production in Regulatory T-Cells

We report the design, synthesis, and biological evaluation of some potent small-molecule neuropilin-1 (NRP1) antagonists. NRP1 is implicated in the immune response to tumors, particularly in Treg cell fragility, required for PD1 checkpoint blockade. The design of these compounds was based on a previously identified compound EG00229. The design of these molecules was informed and supported by X-ray crystal structures. Compound 1 (EG01377) was identified as having properties suitable for further investigation. Compound 1 was then tested in several in vitro assays and was shown to have antiangiogenic, antimigratory, and antitumor effects. Remarkably, 1 was shown to be selective for NRP1 over the closely related protein NRP2. In purified Nrp1⁺, FoxP3⁺, and CD25⁺ populations of Tregs from mice, 1 was able to block a glioma-conditioned medium-induced increase in TGFβ production. This comprehensive characterization of a small-molecule NRP1 antagonist provides the basis for future in vivo studies.

Contributions of immune cell populations in the maintenance, progression, and therapeutic modalities of glioma

Immunotherapies are becoming a promising strategy for malignant disease. Selectively directing host immune responses to target cancerous tissue is a milestone of human health care. The roles of the innate and adaptive immune systems in both cancer progression and elimination are now being realized. Defining the immune cell environment and identifying the contributions of each sub-population of these cells has lead to an understanding of the immunotherapeutic processes, and demonstrated the potential of the immune system to drive cancer shrinkage and sustained immunity against disease. Poorly treated diseases, such as high-grade glioma, suffer from lack of therapeutic efficacy and rapid progression. Immunotherapeutic success in other solid malignancies, such as melanoma, now provides the principals for which this treatment paradigm can be adapted for primary brain cancers. The central nervous system is complex, and relative contributions of immune sub-populations to high grade glioma progression are not fully characterized. Here, we summarize recent research in both animal and humans which add to the knowledge base of how innate and adaptive immune cells contribute to glioma progression, and outline work which has demonstrated their potential to elicit anti-tumorigenic responses. Additionally, we highlight Neuropilin 1, a cell surface receptor protein, describe its signaling functions in the context of immunity, and point to its potential to slow glioma progression.

Deletion of Neuropilin 1 from Microglia or Bone Marrow-Derived Macrophages Slows Glioma Progression

Glioma-associated microglia and macrophages (GAM), which infiltrate high-grade gilomas, constitute a major cellular component of these lesions. GAM behavior is influenced by tumor-derived cytokines that suppress initial antitumorigenic properties, causing them to support tumor growth and to convert and suppress adaptive immune responses to the tumor. Mice that lack the transmembrane receptor neuropilin-1 (Nrp1), which modulates GAM immune polarization, exhibit a decrease in glioma volumes and neoangiogenesis and an increase in antitumorigenic GAM infiltrate. Here we show that replacing the peripheral macrophage populations of wild-type mice with Nrp1-depleted bone marrow-derived macrophages (BMDM) confers resistance to the development of glioma. This resistance occurred in a similar fashion seen in mice in which all macrophages lacked Nrp1 expression. Tumors had decreased volumes, decreased vascularity, increased CTL infiltrate, and Nrp1-depleted BMDM adopted a more antitumorigenic phenotype relative to wild-type GAMs within the tumors. Mice with Nrp1-deficient microglia and wild-type peripheral macrophages showed resistance to glioma development and had higher microglial infiltrate than mice with wild-type GAMs. Our findings show how manipulating Nrp1 in either peripheral macrophages or microglia reprograms their phenotype and their pathogenic roles in tumor neovascularization and immunosuppression.Significance: This study highlights the proangiogenic receptor neuropilin 1 in macrophages and microglial cells in gliomas as a pivotal modifier of tumor neovascularization and immunosuppression, strengthening emerging evidence of the functional coordination of these two fundamental traits of cancer. Cancer Res; 78(3); 685-94. ©2017 AACR.

Abstract 4919: Ablation of neuropilin 1 from glioma-associated microglia and macrophages slows tumor progression

Gliomas are the most commonly diagnosed primary tumors of the central nervous system (CNS). Median times of survival are dismal regardless of the treatment approach, underlying the need to develop more effective therapies. Modulation of the immune system is a promising strategy as innate and adaptive immunity play important roles in cancer progression. Glioma associated microglia and macrophages (GAMs) can comprise over 30% of the cells in glioma biopsies. Gliomas secrete cytokines that suppress the anti-tumorigenic properties of GAMs, causing them to secrete factors that support the tumor’s spread and growth. Neuropilin 1 (Nrp1) is a transmembrane receptor that in mice both amplifies pro-angiogenic signaling in the tumor microenvironment and affects behavior of innate immune cells. Using a Cre-lox system, we generated mice that lack expression of Nrp1 in GAMs. We demonstrate, using an in vivo orthotopic glioma model, that tumors in mice with Nrp1-deficient GAMs exhibit less vascularity, grow at a slower pace, and are populated by increased numbers of anti-tumorigenic GAMs. Moreover, glioma survival times in mice with Nrp1-deficient GAMs were significantly longer. Treating wild-type mice with a small molecule inhibitor of Nrp1’s b1 domain, EG00229, which we show here is selective for Nrp1 over Nrp2, yielded an identical outcome. Moreover, transplanting bone marrow from mice with Nrp1-deficient macrophages to wild type recipient mice led to reductions in tumor growth, al-be-it not to the extent seen in knockout mice. Nrp1-deficient or EG00229-treated wild-type microglia exhibited a shift towards anti-tumorigenicity as evident by altered inflammatory marker profiles in vivo and decreased SMAD2/3 activation when conditioned in the presence of glioma-derived factors. These results provide support for the proposal that pharmacological inhibition of Nrp1 constitutes a potential strategy for suppressing glioma progression.

Citation Format: Jeremy T. Miyauchi, Danling Chen, Matthew K. Choi, Kenneth Shroyer, David Selwood, Stella E. Tsirka. Ablation of neuropilin 1 from glioma-associated microglia and macrophages slows tumor progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4919. doi:10.1158/1538-7445.AM2017-4919

The Role of Iraqi Dust in Inducing Lung Injury in United States Soldiers-An Interdisciplinary Study

United States soldiers are returning from the Greater Middle East with respiratory illnesses ranging from new onset asthma to constrictive bronchiolitis. The etiology of the diseases is unknown. A study was conducted to determine the possible role of local mineral dust in the development of abnormal respiratory illnesses in soldiers during and after deployment in Iraq. A dust sample obtained in proximity to a burn pit in Camp Victory, Iraq, (CVD) was characterized both chemically and mineralogically. For comparison, a dust sample from Fort Irwin, California, (FID) was also collected. The ability of the dust samples to generate reactive oxygen species (ROS) was quantified, as well as their ability to generate an inflammatory stress response (ISR) in human lung epithelial cells. Both samples are comprised of common silicate and carbonate minerals and contain heavy metals with concentration ranges expected for mineral dust. The ISR generated by each sample was within the range of inert material with the minimal stress generated associated with the carbonate phases. The findings based on this one sample suggest that the origin of the disease is not driven by the particles ability to generate ROS. However it is likely that particle overload, and associated complications, or endotoxin contribute extensively to pathogenesis.

Neurogenic to Gliogenic Fate Transition Perturbed by Loss of HMGB2

Mouse cortical development relies heavily on a delicate balance between neurogenesis and gliogenesis. The lateral ventricular zone produces different classes of excitatory pyramidal cells until just before birth, when the production of astroglia begins to prevail. Epigenetic control of this fate shift is of critical importance and chromatin regulatory elements driving neuronal or astroglial development play an vital role. Different classes of chromatin binding proteins orchestrate the transcriptional repression of neuronal-specific genes, while allowing for the activation of astrocyte-specific genes. Through proteomic analysis of embryonic neural progenitor cells (NPCs) our group had previously identified high mobility group B2 (HMGB2), a chromatin protein dynamically expressed throughout embryonic development. In the current study using cultures of perinatal NPCs from HMGB2^+/+ and HMGB2^-/- mice we discovered that vital elements of the polycomb group (PcG) epigenetic complexes polycomb repressive complexes 1 and 2 (PRC1/2) were downregulated during the differentiation process of HMGB2-null NPCs. These epigenetic changes led to downstream changes in specific histone modification levels, specifically the trimethylation of H3K27, and a subsequent shift in the perinatal neurogenesis to gliogenesis fate transition. Collectively these results demonstrate that chromatin binding proteins, such as HMGB2, can have significant effects on the epigenetic landscape of perinatal neural stem/progenitor cells.