Neuroglia

The traditional neuron-centric view of the central nervous system (CNS) is shifting toward recognizing the importance of communication between the neurons and the network of glial cells. This shift is leading to a more comprehensive understanding of how glial cells contribute to CNS function. Alongside this shift, recent discoveries have illuminated the significant role of the human microbiome, comprising trillions of microorganisms, mirroring the number of human cells in an individual. This paper delves into the multifaceted functions of neuroglia, or glial cells, which extend far beyond their traditional roles of supporting and protecting neurons. Neuroglia modulate synaptic activity, insulate axons, support neurogenesis and synaptic plasticity, respond to injury and inflammation, and engage in phagocytosis. Meanwhile, the microbiome, long overlooked, emerges as a crucial player in brain functionality akin to glial cells. This review aims to underscore the importance of the interaction between glial cells and resident microorganisms in shaping the development and function of the human brain, a concept that has been less studied. Through a comprehensive examination of existing literature, we discuss the mechanisms by which glial cells interface with the microbiome, offering insights into the contribution of this relationship to neural homeostasis and health. Furthermore, we discuss the implications of dysbiosis within this interaction, highlighting its potential contribution to neurological disorders and paving the way for novel therapeutic interventions targeting both glial cells and the microbiome. Full article

Glioblastoma (GBM) is the predominant primary malignant brain tumor. Metformin, a well-known antidiabetic medication, has emerged as a potential therapeutic candidate in the treatment of GBM. We have herein investigated two aspects of the effect of MTF on GBM cells: the effect of MTF on GBM cell viability, as previous studies have shown that MTF can selectively affect human GBM tumors; and the immunomodulatory effect of MTF on GBM, as there is evidence that inflammation is associated with GBM growth and progression. The human GBM cell line (U87) was exposed to various doses of MTF (1 mM, 20 mM, and 50 mM), followed by examination of cell viability and inflammatory mediator secretion at various time points. We observed that MTF treatment exerted a dose-response effect on glioblastoma multiforme cell viability. It also had an immunomodulatory effect on GBM cells. Our study identified several mechanisms that led to the overall inhibitory effect of MTF on human GBM. Further inquiry is necessary to gain a better understanding of how these in vitro findings would translate into successful in vivo approaches. Full article

Glioblastoma is a highly aggressive brain tumor that has a poor prognosis despite various treatments like surgery, chemotherapy, and irradiation. However, a restricted ketogenic diet (RKD), which has been proven to be effective in treating drug-resistant epilepsy, could be a potential adjunct in the treatment of certain GBM cases. Our study aimed to highlight the existing knowledge, identify collaboration networks, and emphasize the ongoing research based on highly cited studies. During the literature search, we found 119 relevant articles written between 2010 and 2023. Among the top 20 most cited articles, there were seven laboratory and five clinical studies. The works of Olson LK, Chang HT, Schwartz KA, and Nikolai M from the Michigan State University, followed by Seyfried TN and Mukherjee P from Boston College, and Olieman JF, and Catsman-Berrevoets CE from the University Medical Center of Rotterdam, were significant contributions. The laboratory studies showed that RKD had a significant antitumor effect and could prolong survival in mouse glioblastoma models. The clinical studies verified the tolerability, efficacy, and safety of RKD in patients with GBM, but raised concerns about whether it could be used as a single therapy. The current research interest is focused on the efficacy of using RKD as an adjunct in selected chemotherapy regimens and demonstrates that it could provide GBM patients with better treatment options. Full article

Background: The primary co-occurrence of gonadal and extragonadal central nervous system (CNS) germ cell tumors (GCTs) has rarely been reported in the literature, and a common opinion on the underlying etiopathogenetic mechanism is lacking. Objective: We aim to investigate the pathophysiological mechanisms and genetic pathways underlying the primary co-occurrence of gonadal and CNS GCTs. Methods: We reviewed data from 29 consecutive patients with a diagnosis of CNS GCT, evaluated in our Hospital over the past 23 years, and searched for those who had at least a primary gonadal co-occurrence of GCT. A systematic review of the literature according to the PRISMA guidelines was also conducted. For a comprehensive and detailed search, PubMed, Ovid MEDLINE, and Ovid EMBASE databases have been consulted. Boolean operators and MeSH terms were used to find studies. Only articles published between 2000 and 2023 were considered. Results: Including our Institutional case report, a total of 7 patients with both testicular NGGCTs and CNS GCTs were identified (5 patients with metachronous tumors and patients with synchronous presentation). The average age at tumor diagnosis was 17 years. The cerebral histotypes reported were mixed GCTs (3 cases; 43%), pure germinomas (3 cases, 43%), and one yolk sac tumor (14%). Two out of seven cases (29%) were syndromic, one suffering from Down Syndrome and the other from Testicular Dysgenesis Syndrome. Regarding the etiology and molecular mechanism of GCT development, several gene mutations have been reported in the literature. Particularly, genetic alterations in the MAPK and/or PI3K/AKT/mTOR pathway, together with mutations of the KIT gene, have been shown to guarantee survival and transformation of mismigrated totipotent primordial germ cells, while suppressor genes allow their resistance against apoptotic death. Aberrant chromosomes have also been reported to be responsible for oncogenic transformation. It is also known that CNS and testicular GCTs share some genetic/epigenetic profiles. Conclusions: The primary co-occurrence of testicular NGGCT and extragonadal CNS GCTs is extremely rare. Genetic factors seem to play a paramount role in their etiopathogenesis. Additional research is needed to elucidate molecular mechanisms of oncogenesis in such patients. Full article

Astrocytes are the predominant glial cells that provide essential support to neurons and promote microenvironment changes in neuropathological states. Astrocyte and astrocytic-like cell culture have substantially contributed to elucidating the molecular pathways involved in key glial roles, including those relevant to neurodevelopment, brain physiology and metabolism, which are not readily accessible with traditional approaches. The in vitro methodology has also been applied to neuroinflammatory and neurodegeneration contexts, revealing cellular changes involved in brain dysfunction. Astrocytes studies in culture started with primary cell approaches using embryonic and postmortem tissue. Further developments included newborn rodent primary cells, cell lines and immortalized astrocytes, which resulted in homogeneous cell-type preparations grown on flat surfaces. To overcome some in vitro shortcomings, tridimensional bioprinted models and organoid culture enabled the mimicking of tissue cellular arrangements and, above these achievements, complex astrocyte cell culture can be generated from induced pluripotent stem cells (iPSCs) to model diseases. These unprecedented breakthroughs allowed the development of platforms to test new therapies in brain cells derived from human material noninvasively obtained from live patients. In this work, we reviewed the most studied astrocytic cell models for discussing limitations, advantages and reliable experimental readouts for neuroinflammation in neurodegeneration research. Full article

Dysfunction of the neuroglia can have profound consequences on the blood–brain barrier (BBB). Studies have shown that the disruption of astrocytic–endothelial interaction can compromise the permeability of BBB and its effectiveness in selectively regulating the exchange of substances. Microglia have recently been recognized to have a significant role in the initiation of chronic pain and in its interactions with various nerve blockers and anesthetic agents. Microglia have a role in pain resolution via a pathway that involves Cannabinoid receptor type 2 activation and MAP kinase phosphorylation. Understanding the role of these cells in the context of neuropathic pain and neurological disorders can aid in improving clinical outcomes and the challenging nature of managing pain. Advancing studies have proposed pharmacological and genetic modulation of microglia as a potential treatment option for patients with chronic pain. Full article

Extracellular vesicles (EVs), including exosomes and microvesicles, are membrane-bound particles released by cells into extracellular space. These vesicles carry various molecules, such as proteins and lipids, and can serve as mediators of intercellular communication. EVs have been implicated in the communication between different cell types in the nervous system, for instance, the neurons and glial cells of the central nervous system (CNS) and peripheral nervous system (PNS). Satellite glial cells (SGCs) surround and support neurons in the sensory ganglia of the PNS, and it has been proposed that the EVs released by SGCs may contribute to the processing of pain-related signals and features. This includes the modulation of neuronal activity, the release of pro-inflammatory signaling molecules, and sensitization. A noticeable finding is that EVs can transfer bioactive molecules, including proteins and microRNAs (miRNAs), between cells, influencing cellular functions such as gene expression regulation involved in the transmission and modulation of pain signals. Schwann cells (SCs) also release EVs. SC-derived EVs sequester TNFR1, influencing TNFα activity and regulating neuroinflammation in peripheral nerve injuries. Understanding peripheral glia’s EVs role in pain processing is an emerging area in neuroscience. Here, the latest findings, challenges, and potential are presented to encourage future research. Full article

Astrocytes (ACs) are the most abundant cells in the brain and, importantly, are the master connecting and communicating cells that provide structural and functional support for brain cells at all levels of organization. Further, they are recognized as the guardians and housekeepers of the brain. Protoplasmic perivascular astrocyte endfeet and their basal lamina form the delimiting outermost barrier (glia limitans) of the perivascular spaces in postcapillary venules and are important for the clearance of metabolic waste. They comprise the glymphatic system, which is critically dependent on proper waste removal by the pvACef polarized aquaporin-4 water channels. Also, the protoplasmic perisynaptic astrocyte endfeet (psACef) are important in cradling the neuronal synapses that serve to maintain homeostasis and serve a functional and supportive role in synaptic transmission. Enlarged perivascular spaces (EPVS) are emerging as important aberrant findings on magnetic resonance imaging (MRI), and are associated with white matter hyperintensities, lacunes, and aging, and are accepted as biomarkers for cerebral small vessel disease, increased obesity, metabolic syndrome, and type 2 diabetes. Knowledge is exponentially expanding regarding EPVS along with the glymphatic system, since EPVS are closely associated with impaired glymphatic function and waste removal from the brain to the cerebrospinal fluid and systemic circulation. This review intends to focus on how the pvACef play a crucial role in the development of EPVS. Full article

Astrocytes make up the predominant cell population among glial cells in the mammalian brain, and they play a vital role in ensuring its optimal functioning. They promote neuronal health and survival and protect neurons from glutamate-induced excitotoxicity. In the spinal cord’s dorsal horn (DH) and ventral horn (VH) regions, astrocytes serve crucial roles. Notably, VH motor neurons exhibit a heightened sensitivity to glutamate-induced damage. It is posited that this selective sensitivity could be related to their localized presence within the VH, where astrocytes possess a distinct set of mechanisms for managing glutamate. As organisms age, the risk of damage from glutamate increases, indicating a potential decline in the efficiency of astrocytic glutamate regulation. Our research involved an analysis of astrocytic structure, glutamate transporter levels, and glutamate uptake capabilities within the DH and VH through immunohistochemical methods, protein analysis via Western blot, and patch-clamp studies in electrophysiology. The investigations revealed a decrease in both the number and coverage of astroglia in the spinal cord, more so within the VH as aging progressed. Notably, levels of the excitatory amino acid transporters 1 and 2 (EAAT1 and EAAT2) also decreased with age, particularly within the VH. Patch-clamp analyses of astrocytes from both spinal regions confirmed a significant reduction in glutamate uptake activity as age advanced, indicating an age-related impairment in glutamate processing. The findings indicate aging leads to distinct changes in DH and VH astrocytes, impairing their glutamate management abilities, which could contribute significantly to the development of late-onset neurodegenerative conditions. Full article

In the present study, we compared the astrocyte-transducing potential of the relatively novel engineered AAV PHP.eB serotype and the well-examined conventional AAV5 serotype. We generated the AAV-based genetic constructs with membrane-bound fluorescent markers under the control of the astroglial promoter GfaABC1D to target astrocytes in vivo, either via local injection into the hippocampus (AAV5, AAV PHP.eB) or via systemic injection in the retro-orbital venous sinus (AAV PHP.eB). We collected new data on the transduction properties of locally injected PHP.eB and AAV5 viruses. A morphological examination and immunostainings of mouse brain slices revealed a dose-dependent shift of cellular tropism for locally injected PHP.eB from astroglial to astroglial-neuronal as the concentration increased. When the high doses of PHP.eB viruses were administered systemically, we observed strong astrocyte transduction throughout the brain, as confirmed by the morphological examination and GFAP immunostaining. AAV5 exhibited consistent astrocytic expression in all tested concentrations. The obtained results suggest that AAV5 is more suitable for astrocyte targeting in routine stereotaxic viral injection experiments. The widely used engineered PHP.eB capsid was originally designed for the transduction of both neurons and glia. Dual cellular tropism of PHP.eB viruses, observed using different doses and different delivery protocols (local vs. systemic), suggests that the usage of AAV5 is more reliable for astrocyte labeling and that intrahippocampal injection is more suitable than systemic injection for the preferential labeling of hippocampal astroglia. Full article

The activation of members of the Epidermal Growth Factor Receptor (EGFR) family (including ErbB) triggers pathways that have significant effects on cellular processes and have profound consequences both in physiological and pathological conditions. Within the nervous system, the neuregulin (NRG)/ErbB3 signaling plays a crucial role in promoting the formation and maturation of excitatory synapses. Noteworthy is ErbB3, which is actively involved in the process of cerebellar lamination and myelination. All members of the ErbB-family, in particular ErbB3, have been observed within the nuclei of various cell types, including both full-length receptors and alternative variants. One of these variants was detected in Schwann cells and in glioblastoma primary cells where it showed a neuregulin-dependent expression. It binds to promoters’ chromatin associated with genes, like ezrin, involved in the formation of Ranvier’s node. Its nucleolar localization suggests that it may play a role in ribosome biogenesis and in cell proliferation. The regulation of ErbB3 expression is a complex and dynamic process that can be influenced by different factors, including miRNAs. This mechanism appears to play a significant role in glioblastoma and is often associated with a poor prognosis. Altogether, the targeting of ErbB3 has emerged as an active area of research in glioblastoma treatment. These findings highlight the underappreciated role of ErbB3 as a significant receptor that can potentially play a pivotal role in diverse pathologies, implying the existence of a shared and intricate mechanism that warrants further investigation. Full article

Gamma-aminobutyric acid (GABA) is known as the main inhibitory transmitter in the central nervous system (CNS), where it hyperpolarizes mature neurons through activation of GABA_A receptors, pentameric complexes assembled by combination of subunits (α1–6, β1–3, γ1–3, δ, ε, θ, π and ρ1–3). GABA_A-ρ subunits were originally described in the retina where they generate non-desensitizing Cl- currents that are insensitive to bicuculline and baclofen. However, now is known that they are widely expressed throughout the brain including glial cells. For example, whole-cell patch-clamp recordings demonstrated the functional expression of GABA_A-ρ receptors in primary cultures of cerebellar astrocytes, as well as in cerebellar ependymal cells and striatal astrocytes. In these cells GABA-currents were partially blocked by TPMPA and insensitive to barbiturates. These receptors are proposed to be involved in extrasynaptic communication and dysfunction of the signaling is accompanied by reduced expression of GABA_A-ρ receptors in Huntington’s disease and autism spectrum disorders (ASD). Thus, the aim of this review is to present an overview about GABA_A-ρ receptors including their structure and function, as well as their importance in the excitatory/inhibitory (E/I) balance in neurodevelopment and in disease. Full article

Providing cellular support and modifying the glial scar around the lesion are two key strategies for promoting axonal regeneration after spinal cord injury. We showed previously that over-expressing polysialic acid (PSA) on Schwann cells (SCs) by lentiviral vector (LV)-mediated expression of polysialyltransferase (PST) facilitated their integration and migration in the injured spinal cord. We also showed that PSA over-expression in the injured spinal cord modified the glial scar and promoted the growth of ascending sensory axons. In this study, we combined the PST/SC transplantation with LV/PST injection in spinal cords after dorsal column transection and found the combined treatments led to faster and more profound locomotor functional recovery compared with animals receiving combined GFP/SC transplantation with LV/GFP injection. Histological examination showed significantly more injured corticospinal axons growing close to the lesion/transplant borders and into the caudal spinal cord in the PST group than in the GFP group. We also found over -expressing PSA around the lesion site did not cause allodynia and hyperalgesia in our injury model. These results demonstrate the promising therapeutic benefit of over-expressing PSA in transplanted SCs and spinal cord in promoting axonal growth and restoring motor function. Full article

The blood–brain barrier (BBB) is a highly intricate neurovascular structure that plays a crucial role in maintaining neural homeostasis by selectively allowing certain molecules to enter the central nervous system (CNS). However, in the context of Alzheimer’s Disease (AD), a progressive neurodegenerative disorder characterized by a gradual decline in cognitive function, the BBB’s functionality becomes impaired. This impairment leads to the breakdown of the barrier and disrupts its ability to regulate molecular transport effectively. Consequently, cellular infiltration into the CNS occurs, along with aberrant signaling and clearance of molecules, ultimately contributing to neurological deficits. One of the key factors implicated in the failure of amyloid-beta (Aβ) transport, a hallmark of AD, is the decreased expression of low-density lipoprotein receptor-related protein 1 (LRP1). LRP1 plays a crucial role in facilitating the transport of Aβ across the BBB. Additionally, the increased levels of the receptor for advanced glycation end products (RAGE) further contribute to the deregulation of the BBB in AD. These molecular imbalances significantly impact Aβ clearance and contribute to the development and progression of AD. In this review, we aimed to summarize the critical aspects of Aβ transporters in the BBB that become dysfunctional during the pathogenesis of AD. Full article

Alzheimer’s disease (AD) is one of the major causes of dementia and its incidence represents approximately 60–70% of all dementia cases worldwide. Many theories have been proposed to describe the pathological events in AD, including deterioration in cognitive function, accumulation of β-amyloid, and tau protein hyperphosphorylation. Infection as well as various cellular molecules, such as apolipoprotein, micro-RNA, calcium, ghrelin receptor, and probiotics, are associated with the disruption of β-amyloid and tau protein hemostasis. This review gives an overview on the integrative cellular and signaling molecules that could play a complementary role in the dysregulation of β-amyloid and tau proteins. Full article

Gamma-aminobutyric acid (GABA) is an essential neurotransmitter and an important regulator of neuroinflammation and disease. Microglia are important immune cells in the brain that express GABA receptors (GABAR) and respond to both GABA and GABAR agonists, yet the effect of GABA on microglial inflammatory responses is unclear. We hypothesized that GABA and GABAR agonists might modify the activation of a human microglial cell line (HMC3). We further hypothesized that Amanita muscaria extract (AME-1), which contained GABAR agonists (GABA and muscimol), would similarly stimulate HMC3. Ligand-gated GABAR (GABA_AR) and G protein-coupled GABAR (GABABR) subunit expression was analyzed by qRT-PCR, metabolic activity was determined by nicotinamide adenine dinucleotide (NADH)-dependent oxidoreductase assay (XTT), reactive oxygen species (ROS) generation was analyzed by 2′,7′-dichlorodihydrofluorescein diacetate (DCFDA), and interleukin-8 (IL-8) production was analyzed by an enzyme-linked immunosorbent assay (ELISA). HMC3 expressed several neuroreceptors such as subunits of the GABA_A receptor (GABA_AR). HMC3 constitutively produce IL-8 and ROS. Both muscimol and GABA stimulated HMC3 to produce more IL-8 but had no effect on constitutive ROS production. GABA and muscimol altered the morphology and Iba1 localization of HMC3. GABA, but not muscimol, increased HMC3 metabolic activity. Similarly, AME-1 induced HMC3 to produce more IL-8 but not ROS and altered cell morphology and Iba1 localization. GABA induction of IL-8 was blocked by bicuculline, an antagonist of GABA_AR. AME-1-induced production of IL-8 was not blocked by bicuculline, suggesting that AME-1’s effect on HMC3 was independent of GABA_AR. In conclusion, these data show that GABA and GABA agonists stimulate HMC3 to increase their production of IL-8. Mixtures that contain GABA and muscimol, such as AME-1, have similar effects on HMC3 that are independent of GABA_AR. Full article

The plasma membrane glucose transporter (GLUT)-2 is unique among GLUT family proteins in that it also functions as a glucose sensor. GLUT2 imposes sex-dimorphic control of hypothalamic astrocyte glucose storage and catabolism by unknown mechanisms. Mitogen-activated protein kinase (MAPK) signaling cascades operate within stress-sensitive signal transduction pathways. The present study employed an established primary astrocyte culture model and gene knockdown tools to investigate whether one or more of the three primary MAP kinase families are regulated by GLUT2. GLUT2 gene knockdown caused opposing adjustments in total ERK1/2 proteins in glucose-supplied male versus female astrocytes, augmenting or reducing the mean phosphorylated/total protein ratio for 44 and 42 kDa variants in these sexes. Glucose deprivation amplified this ratio for both ERK1/2 variants, albeit by a larger magnitude in males; GLUT2 siRNA exacerbated this stimulatory response in males only. Phosphorylated/total p38 MAPK protein ratios were up-regulated by GLUT2 knockdown in male, but not female astrocytes. Glucose-deprived astrocytes exhibited no change (male) or reduction (female) in this ratio after GLUT2 gene silencing. GLUT2 siRNA increased the phosphorylated/total protein ratio for 54 and 46 kDa SAPK/JNK proteins in each sex when glucose was present. However, glucose withdrawal suppressed (male) or amplified (female) these ratios, while GLUT2 knockdown attenuated these inverse responses. The results show that GLUT2 inhibits ERK1/2, p38, and SAPK/JNK MAPK activity in male astrocytes, but differentially stimulates and inhibits activity of these signaling pathways in female hypothalamic astrocytes. Glucoprivation induces divergent adjustments in astrocyte p38 MAPK and SAPK/JNK activities. The findings demonstrate a stimulatory role for GLUT2 in p38 MAPK activation in glucose-starved female astrocytes, but it can act as either an inhibitor or inducer of SAPK/JNK activation in glucose-deprived male versus female glial cells, respectively. Full article

Neuroimmunomodulation is a promising form of drug-free treatment for neurological diseases ranging from Alzheimer’s disease to depression. The evidence supporting the efficacy of focused ultrasound (FUS) neuroimmunomodulation is encouraging; however, the method has yet to be standardized, and its mechanism remains poorly understood. Methods of FUS neuroimmunomodulation can be categorized into three paradigms based on the parameters used. In the first paradigm, focused ultrasound blood–brain barrier opening (FUS-BBBO) combines FUS with microbubbles (MB) to transiently and safely induce BBB opening. In the second paradigm, focused ultrasound neuromodulation (FUS-N) harnesses the acoustic effects of FUS alone (without MB). In the third paradigm, focused ultrasound with microbubbles without BBBO (FUS + MB) combines MB with FUS below the BBBO pressure threshold—harnessing the mechanical effects of FUS without opening the barrier. Due to the recent evidence of brain macrophage modulation in response to FUS-BBBO, we provide the first direct comparison of brain macrophage modulation between all three paradigms both in the presence and absence of Alzheimer’s disease (AD) pathology. Flow cytometry and single-cell sequencing are employed to identify FUS-BBBO as the FUS paradigm, which maximizes brain macrophage modulation, including an increase in the population of neuroprotective, disease-associated microglia and direct correlation between treatment cavitation dose and brain macrophage phagocytosis. Next, we combine spatial and single-cell transcriptomics with immunohistochemical validation to provide the first characterization of brain macrophage distribution in response to FUS-BBBO. Given their relevance within neurodegeneration and perturbation response, we emphasize the analysis of three brain macrophage populations—disease- and interferon-associated microglia and central-nervous-system-associated macrophages. We find and validate the redistribution of each population with an overall trend toward increased interaction with the brain–cerebrospinal fluid barrier (BCSFB) after FUS-BBBO, an effect that is found to be more pronounced in the presence of disease pathology. This study addresses the prior lack of FUS neuroimmunomodulation paradigm optimization and mechanism characterization, identifying that FUS-BBBO best modulates brain macrophage response via complex redistribution. Full article