Glia as architects of central nervous system formation and function

Spatial transcriptomics combined with single-nucleus RNA sequencing reveals glial cell heterogeneity in the human spinal cord

JOURNAL/nrgr/04.03/01300535-202511000-00032/figure1/v/2024-12-20T164640Z/r/image-tiff Glial cells play crucial roles in regulating physiological and pathological functions, including sensation, the response to infection and acute injury, and chronic neurodegenerative disorders. Glial cells include astrocytes, microglia, and oligodendrocytes in the central nervous system, and satellite glial cells and Schwann cells in the peripheral nervous system. Despite the greater understanding of glial cell types and functional heterogeneity achieved through single-cell and single-nucleus RNA sequencing in animal models, few studies have investigated the transcriptomic profiles of glial cells in the human spinal cord. Here, we used high-throughput single-nucleus RNA sequencing and spatial transcriptomics to map the cellular and molecular heterogeneity of astrocytes, microglia, and oligodendrocytes in the human spinal cord. To explore the conservation and divergence across species, we compared these findings with those from mice. In the human spinal cord, astrocytes, microglia, and oligodendrocytes were each divided into six distinct transcriptomic subclusters. In the mouse spinal cord, astrocytes, microglia, and oligodendrocytes were divided into five, four, and five distinct transcriptomic subclusters, respectively. The comparative results revealed substantial heterogeneity in all glial cell types between humans and mice. Additionally, we detected sex differences in gene expression in human spinal cord glial cells. Specifically, in all astrocyte subtypes, the levels of NEAT1 and CHI3L1 were higher in males than in females, whereas the levels of CST3 were lower in males than in females. In all microglial subtypes, all differentially expressed genes were located on the sex chromosomes. In addition to sex-specific gene differences, the levels of MT-ND4 , MT2A , MT-ATP6 , MT-CO3 , MT-ND2 , MT-ND3 , and MT-CO2 in all spinal cord oligodendrocyte subtypes were higher in females than in males. Collectively, the present dataset extensively characterizes glial cell heterogeneity and offers a valuable resource for exploring the cellular basis of spinal cord-related illnesses, including chronic pain, amyotrophic lateral sclerosis, and multiple sclerosis.

Linking depression and neuroinflammation: Crosstalk between glial cells

The inflammatory hypothesis is one of the more widely accepted pathogenesis of depression. Glia plays an important immunomodulatory role in neuroinflammation, mediating interactions between the immune system and the central nervous system (CNS). Glial cell-driven neuroinflammation is not only an important pathological change in depression, but also a potential therapeutic target. This review discusses the association between depression and glial cell-induced neuroinflammation and elucidates the role of glial cell crosstalk in neuroinflammation. Firstly, we focus on the role of glial cells in neuroinflammation in depression and glial cell interactions; secondly, we categorize changes in different glial cells in animal models of depression and depressed patients, focusing on how glial cells mediate inflammatory responses and exacerbate depressive symptoms; Thirdly, we review how conventional and novel antidepressants affect the phenotype and function of glial cells, thereby exerting anti-inflammatory activity; finally, we discuss the role of the gut-brain axis in glial cell function and depression, and objectively analyze the problems that remain in current antidepressant therapy. This review aims to provide an objective analysis of how glial cell cross-talk may mediate neuroinflammation and thereby influence pathologic progression of depression. It is concluded that a novel therapeutic strategy may be to ameliorate glial cell-mediated inflammatory responses.

Refining the interactions between microglia and astrocytes in Alzheimer's disease pathology

Microglia and astrocytes are central to the pathogenesis and progression of Alzheimer's Disease (AD), working both independently and collaboratively to regulate key pathological processes such as β-amyloid protein (Aβ) deposition, tau aggregation, neuroinflammation, and synapse loss. These glial cells interact through complex molecular pathways, including IL-3/IL-3Ra and C3/C3aR, which influence disease progression and cognitive decline. Emerging research suggests that modulating these pathways could offer therapeutic benefits. For instance, recombinant IL-3 administration in mice reduced Aβ plaques and improved cognitive functions, while C3aR inhibition alleviated Aβ and tau pathologies, restored synaptic function, and corrected immune dysregulation. However, the effects of these interactions are context-dependent. Acute C3/C3aR activation enhances microglial Aβ clearance, whereas chronic activation impairs it, highlighting the dual roles of glial signaling in AD. Furthermore, C3/C3aR signaling not only impacts Aβ clearance but also modulates tau pathology and synaptic integrity. Given AD's multifactorial nature, understanding the specific pathological environment is crucial when investigating glial cell contributions. The interplay between microglia and astrocytes can be both neuroprotective and neurotoxic, depending on the disease stage and brain region. This complexity underscores the need for targeted therapies that modulate glial cell activity in a context-specific manner. By elucidating the molecular mechanisms underlying microglia-astrocyte interactions, this research advances our understanding of AD and paves the way for novel therapeutic strategies aimed at mitigating neurodegeneration and cognitive decline in AD and related disorders.

Astrocyte activation in the cat dLGN following monocular retinal inactivation

Monocular deprivation obstructs the development of visual neural circuits and can impair vision for a lifetime. Effective treatment of this visual disorder, amblyopia, with patching therapy is limited by a short and early critical period, as well as by poor compliance with prescribed treatment. Temporary pharmacological inactivation of the dominant eye has emerged as a means to rapidly correct the effects of monocular deprivation in animal models. Recovery occurs at older ages, and inactivation causes no apparent damage to neural connections within the primary visual pathway. It is unclear what mechanisms protect synaptic connections serving the inactivated eye. Astrocytes are important for the development and maintenance of synapses throughout the nervous system, and can compensate for a prolonged decrease in neural activity. The aim of the current study was to investigate a possible role for astrocytes in mediating the protection of neural connections following monocular inactivation. A significant increase in immunolabeling for glial fibrillary acidic protein (GFAP), a marker for astrocyte activation, was measured within inactivated-eye layers of the dorsal lateral geniculate nucleus from otherwise normal animals. Elevated levels of GFAP persisted even after the period of inactivation wore off, and GFAP was not significantly elevated following monocular deprivation by lid closure. These results implicate astrocyte activation as a possible mechanism that mediates the safeguarding of neural connections during monocular retinal inactivation. The viability of retinal inactivation as a safe and effective treatment for human amblyopia is facilitated by advancing the understanding of its effects within the visual system.

How microglia contribute to the induction and maintenance of neuropathic pain

Neuropathic pain is a debilitating condition caused by damage to the nervous system that results in changes along the pain pathway that lead to persistence of the pain sensation. Unremitting pain conditions are associated with maladaptive plasticity, disruption of neuronal activity that favours excitation over inhibition, and engagement of immune cells. The substantial progress made over the last two decades in the neuroimmune interaction research area points to a mechanistic role of spinal cord microglia, which are resident immune cells of the CNS. Microglia respond to and modulate neuronal activity during establishment and persistence of neuropathic pain states, and microglia-neuron pathways provide targets that can be exploited to attenuate abnormal neuronal activity and provide pain relief.

Temperature Regulates Astroglia Morphogenesis Through Thermosensory Circuitry in Caenorhabditis elegans

Astrocytes are the most abundant type of macroglia in the brain and play crucial roles in regulating neural development and functions. The diverse functions of astrocytes are largely determined by their morphology, which is regulated by genetic and environmental factors. However, whether and how the astrocyte morphology is affected by temperature remains largely unknown. Here we discovered that elevated cultivation temperature (26°C) stimulates Caenorhabditis elegans ventral CEPsh glia endfoot extension during early developmental stages. This extension depends on the activation of glutamate AWC neurons, which inhibit the postsynaptic cholinergic AIY interneurons through glutamate-gated chloride channels, GLC-3 and GLC-4. In responding to the thermosensory signal, the guanyl-nucleotide exchange factor EPHX-1 and Rho GTPase CDC-42/Cdc42 in the glia facilitate the endfoot extension via F-actin assembly. This study elucidates the significant role of thermosensory circuitry in glia morphogenesis and the underlying molecular mechanism.

Microfabricated Organ-Specific Models of Tumor Microenvironments

Despite the advances in detection, diagnosis, and treatments, cancer remains a lethal disease, claiming the lives of more than 600,000 people in the United States alone in 2024. To accelerate the development of new therapeutic strategies with improved responses, significant efforts have been made to develop microfabricated in vitro models of tumor microenvironments (TMEs) that address the limitations of animal-based cancer models. These models incorporate several advanced tissue engineering techniques to better reflect the organ- and patient-specific TMEs. Additionally, microfabricated models integrated with next-generation single-cell omics technologies provide unprecedented insights into patient's cellular and molecular heterogeneity and complexity. This review provides an overview of the recent understanding of cancer development and outlines the key TME elements that can be captured in microfabricated models to enhance their physiological relevance. We highlight the recent advances in microfabricated cancer models that reflect the unique characteristics of their organs of origin or sites of dissemination.

Ganglioside GT1b prevents selective spinal synapse removal following peripheral nerve injury

After peripheral nerve injury, the structure of the spinal cord is actively regulated by glial cells, contributing to the chronicity of neuropathic pain. However, the mechanism by which peripheral nerve injury leads to synaptic imbalance remains elusive. Here, we use a pH-reporter system and find that nerve injury triggers a reorganization of excitatory synapses that is influenced by the accumulation of the ganglioside GT1b at afferent terminals. GT1b acts as a protective signal against nerve injury-induced spinal synapse elimination. Inhibition of GT1b-synthesis increases glial phagocytosis of excitatory pre-synapses and reduces excitatory synapses post-injury. In vitro analyses reveal a positive correlation between GT1b accumulation and the frequency of pre-synaptic calcium activity, with GT1b-mediated suppression of glial phagocytosis occurring through SYK dephosphorylation. Our study highlights GT1b's pivotal role in preventing synapse elimination after nerve injury and offers new insight into the molecular underpinning of activity-dependent synaptic stability and glial phagocytosis.

Stellate Ganglia: A Key Therapeutic Target for Malignant Ventricular Arrhythmia in Heart Disease

Malignant ventricular arrhythmias (VAs), such as ventricular tachycardia and ventricular fibrillation, are the cause of approximately half a million deaths per year in the United States, which is a common lethal event in heart disease, such as hypertension, catecholaminergic polymorphic ventricular tachycardia, takotsubo cardiomyopathy, long-QT syndrome, and progressing into advanced heart failure. A common characteristic of these heart diseases, and the subsequent development of VAs, is the overactivation of the sympathetic nervous system. Current treatments for VAs in these heart diseases, such as β-adrenergic receptor blockers and cardiac sympathetic ablation, aim at inhibiting cardiac sympathetic overactivation. However, these treatments do not translate into becoming efficacious as long-term suppressors of ventricular tachycardia/ventricular fibrillation events. As a key regulatory component in the heart, cardiac postganglionic sympathetic neurons residing in the stellate ganglia (SGs) release neurotransmitters (such as norepinephrine and NPY [neuropeptide Y]) to perform their regulatory role in dictating cardiac function. Growing evidence from animal experiments and clinical studies has demonstrated that the remodeling of the SG may be intimately involved in malignant arrhythmogenesis. This identifies the SG as a key potential therapeutic target for the treatment of malignant VAs in heart disease. Therefore, this review summarizes the role of SG in ventricular arrhythmogenesis and updates the novel targeting of SG for clinical treatment of VAs in heart disease.

Age-dependent glial heterogeneity and traumatic injury responses in a vertebrate brain structure

The progression of traumatic brain injury (TBI) pathology is significantly influenced by age and involves a complex interplay of glial cells. However, the influence of age on the glial dynamics and their TBI responses remains mostly unexplored. Here, we obtain a comprehensive single-cell transcriptome atlas of three major glial types under the physiological and TBI conditions across four post-embryonic life stages in the zebrafish midbrain optic tectum. We identify a library of glial subtypes and states with specific age-dependent patterns that respond distinctly to TBI. Combining the glial interactome analysis and CRISPR-Cas9-mediated gene disruption, we reveal the essential roles of dla-notch3 and cxcl12a-cxcr4b interactions in the early-larval-stage-specific unresponsiveness of radial astrocytes to TBI and the TBI-induced age-independent recruitment of microglia to injury sites, respectively. Overall, our findings provide the molecular and cellular framework of TBI-induced age-related glial dynamics in vertebrate brains.

Glia phagocytose neuronal sphingolipids to infiltrate developing synapses

The complex morphologies of mature neurons and glia emerge through profound rearrangements of cell membranes during development. Despite being integral components of these membranes, it is unclear whether lipids might actively sculpt these morphogenic processes. By analyzing lipid levels in the developing fruit fly brain, we discover dramatic increases in specific sphingolipids coinciding with neural circuit establishment. Disrupting this sphingolipid bolus via genetic perturbations of sphingolipid biosynthesis and catabolism leads to impaired glial autophagy. Remarkably, glia can obtain sphingolipid precursors needed for autophagy by phagocytosing neurons. These precursors are then converted into specific long-chain ceramide phosphoethanolamines (CPEs), invertebrate analogs of sphingomyelin. These lipids are essential for glia to arborize and infiltrate the brain, a critical step in circuit maturation that when disrupted leads to reduced synapse numbers. Taken together, our results demonstrate how spatiotemporal tuning of sphingolipid metabolism during development plays an instructive role in programming brain architecture.

Highlights

Brain sphingolipids (SLs) remodel to very long-chain species during circuit maturation Glial autophagy requires de novo SL biosynthesis coordinated across neurons and glia Glia evade a biosynthetic blockade by phagolysosomal salvage of neuronal SLsCeramide Phosphoethanolamine is critical for glial infiltration and synapse density.

Luteolin attenuates cadmium neurotoxicity by suppressing glial inflammation and supporting neuronal survival

Cadmium (Cd), a neurotoxic metal, is associated with the development of neurological disorders. This study investigated the neuroprotective effects of Luteolin against Cd-induced toxicity in cultured cells and mouse models. Our findings demonstrate that Luteolin protects hippocampal neurons from Cd toxicity and mitigates Cd-triggered inflammatory responses in microglial BV2 cells. In Cd-exposed mice, symptoms such as weight loss, motor retardation, multi-organ damage, and cognitive deficits were observed. Remarkably, Luteolin treatment reversed these effects, repaired organ damage, and restored learning and memory abilities. Mechanistically, Cd toxicity induced significant upregulation of pro-inflammatory factors and neuroinflammation in the hippocampus and prefrontal cortex, including elevated glial cell markers (IBA1, GFAP, and CD68) and reduced neuronal marker MAP2. Luteolin counteracted these adverse effects by inhibiting the Notch1/Hes1 inflammatory signaling axis and restoring the BDNF-TrkB/AKT1 signaling axis, thereby promoting neuronal survival. These results highlight the potential of Luteolin as a natural neuroprotective agent against Cd-induced neurotoxicity, offering a promising therapeutic strategy for mitigating Cd-related neurological damage.

Neuroplasticity and Nervous System Recovery: Cellular Mechanisms, Therapeutic Advances, and Future Prospects

Neuroplasticity, the ability of the nervous system to adapt structurally and functionally in response to environmental interactions and injuries, is a cornerstone of recovery in the central (CNS) and peripheral nervous systems (PNS). This review explores the mechanisms underlying neuroplasticity, focusing on the dynamic roles of cellular and molecular processes in recovery from nervous system injuries. Key cellular players, including Schwann cells, oligodendrocytes, and neural stem cells, are highlighted for their contributions to nerve repair, myelination, and regeneration. Advances in therapeutic interventions, such as electrical stimulation, bioluminescent optogenetics, and innovative nerve grafting techniques, are discussed alongside their potential to enhance recovery and functional outcomes. The molecular underpinnings of plasticity, involving synaptic remodeling, homeostatic mechanisms, and activity-dependent regulation of gene expression, are elucidated to illustrate their role in learning, memory, and injury repair. Integrating emerging technologies and therapeutic approaches with a foundational understanding of neuroplasticity offers a pathway toward more effective strategies for restoring nervous system functionality after injury.

Scutellarin Modulates Astrocyte-Microglia-Neuron Crosstalk to Mitigate Neuroinflammation and Apoptosis in Cerebral Ischemia

This study investigates whether scutellarin promotes astrocyte polarization in MCAO and OGD models, and its effects on astrocyte-microglia, astrocyte-neuron interactions, and the PI3K-Akt pathway in neuroprotection. We used an experimentally induced cerebral ischemia rat model and OGD-stimulated TNC1 cell model. Using western blot, RT-qPCR and immunofluorescence, we show a noticeable increase in the expression of A2 astrocyte markers and a downregulation of A1 astrocyte markers in activated astrocytes, both in vivo and in vitro. Remarkably, after the treatment of scutellarin, OGD-stimulated TNC1 cells markedly downregulated M1 microglia markers and apoptosis factors in PC12 cells, while upregulating M2 microglia markers and anti-apoptosis factor Bcl2. Therefore, it is suggested that scutellarin can promote the polarization of activated astrocyte from the A1 to the A2 phenotype. Meanwhile, there is indeed a crosstalk between astrocytes-microglia and astrocytes-neurons, and astrocytes treated with scutellarin can promote M2 polarization of microglia and neuronal apoptosis. More importantly, based on the results of transcriptome sequencing, we used TNC1-pik3r1-siRNA cell model and pcDNA3.1 ( +)-pik3r1-TNC1 cell model to investigate the effect of the PI3K-Akt signaling pathway on the polarization of astrocyte and their crosstalk. Scutellarin promotes the A2 polarization, M2 polarization, and anti-apoptosis in astrocyte crosstalk by concomitantly enhancing the PI3K-Akt signaling pathway. This is strongly supported by observations in TNC1 astrocyte in TNC1-pik3r1-siRNA cell model, where the expression of A2 markers was decreased. Conversely, in the pcDNA3.1 ( +)-pik3r1-TNC1 cell model, expression was increased. In light of the above, the PI3K-Akt signaling pathway is considered a potential therapeutic target.

Development and Preliminary Evaluation of a 125I-Labeled Radioligand ([125I]iodotrazoline) for In Vitro Detection of Imidazoline-2 Binding Site in the Brain

Astrocytes exert multiple functions within the brain, including regulating neuroinflammation and maintaining homeostasis, and the reactive astrocytes are implicated in many neurodegenerative disorders. Imidazoline-2 binding site (I2BS) has been established as a reliable biomarker for precisely quantifying reactive astrocytes. Here, we reported the development of [125I]iodotrazoline ([125I]8), a novel I2BS radioligand with high affinity (Ki = 6.8 nM) and exceptional selectivity over α2-adrenoceptors (>1400 folds). In vitro autoradiography (ARG) using rat brain sections revealed a heterogeneous distribution of [125I]8, with high signals in the medulla, midbrain, pons, and hypothalamus. Pretreatment with unlabeled I2BS-selective ligands, BU224 and FTIMD, reduced the binding by >30%, indicating high in vitro specificity for I2BS. Ex vivo ARG results confirmed this distribution pattern in the rat brain. Biodistribution results in mice demonstrated a rapid brain uptake of [125I]8 (3.35% ID/g at 2 min postinjection) with slow washout. Metabolite analysis exhibited the desirable biostability of [125I]8 in the rat brain. Altogether, this work provides a new 125I-labeled radioligand featuring a novel 2-trans-styryl-imidazoline scaffold, which shows significant specificity binding for I2BS in vitro, serving as a valuable tool for I2BS detection and astrocyte-related pathology research.

Physiological roles of embryonic microglia and their perturbation by maternal inflammation

The interplay between the nervous and immune systems is well documented in the context of adult physiology and disease. Recent advances in understanding immune cell development have highlighted a significant interaction between neural lineage cells and microglia, the resident brain macrophages, during developmental stages. Throughout development, particularly from the embryonic to postnatal stages, diverse neural lineage cells are sequentially generated, undergo fate determination, migrate dynamically to their appropriate locations while maturing, and establish connections with their surroundings to form neural circuits. Previous studies have demonstrated that microglia contribute to this highly orchestrated process, ensuring the proper organization of brain structure. These findings underscore the need to further investigate how microglia behave and function within a broader framework of neurodevelopment. Importantly, recent epidemiological studies have suggested that maternal immune activation (MIA), triggered by various factors, such as viral or bacterial infections, environmental stressors, or other external influences, can affect neurogenesis and neural circuit formation, increasing the risk of neurodevelopmental disorders (NDDs) in offspring. Notably, many studies have revealed that fetal microglia undergo significant changes in response to MIA. Given their essential roles in neurogenesis and vascular development, inappropriate activation or disruption of microglial function may impair these critical processes, potentially leading to abnormal neurodevelopment. This review highlights recent advances in rodent models and human studies that have shed light on the behaviors and multifaceted roles of microglia during brain development, with a particular focus on the embryonic stage. Furthermore, drawing on insights from rodent MIA models, this review explores how MIA disrupts microglial function and how such disturbances may impair brain development, ultimately contributing to the onset of NDDs.

Transcriptional conservation and evolutionary divergence of cell types across mammalian hypothalamus development

The hypothalamus, an "ancient" subcortical brain structure, maintains physiological homeostasis and controls native behaviors. The evolution of homeostatic regulation and behavioral control in mammals may rely on adaptable neuronal identity establishment but conserved neural patterning mechanisms during neurodevelopment. Here, we combined single-cell, single-nucleus, and spatial transcriptomic datasets to map the spatial patterning of diverse progenitor domains and reconstruct their neurogenic lineages in the developing human and mouse hypothalamus. While the regional organizers orchestrating neural patterning are conserved between primates and rodents, we identified a human-enriched neuronal subtype and found a substantial increase in neuromodulatory gene expression among human neurons. Furthermore, cross-species comparison demonstrated a potential redistribution of two neuroendocrine neuronal subtypes and a shift in inter-transmitter and transmitter-peptide coupling within hypothalamic dopamine neurons. Together, our study lays a critical foundation for understanding cellular development and evolution of the mammalian hypothalamus.

Glial-immune interactions in barrier organs

Neuro-immune interactions within barrier organs, such as lung, gut, and skin, are crucial in regulating tissue homeostasis, inflammatory responses, and host defence. Our rapidly advancing understanding of peripheral neuroimmunology is transforming the field of barrier tissue immunology, offering a fresh perspective for developing therapies for complex chronic inflammatory disorders affecting barrier organs. However, most studies have primarily examined interactions between the peripheral nervous system and the immune system from a neuron-focused perspective, while glial cells, the nonneuronal cells of the nervous system, have received less attention. Glial cells were long considered as mere bystanders, only supporting their neuronal neighbours, but recent discoveries mainly on enteric glial cells in the intestine have implicated these cells in immune-regulation and inflammatory disease pathogenesis. In this review, we will highlight the bi-directional interactions between peripheral glial cells and the immune system and discuss the emerging immune regulatory functions of glial cells in barrier organs.

Computational detection, characterization, and clustering of microglial cells in a mouse model of fat-induced postprandial hypothalamic inflammation

Obesity is associated with brain inflammation, glial reactivity, and immune cells infiltration. Studies in rodents have shown that glial reactivity occurs within 24 h of high-fat diet (HFD) consumption, long before obesity development, and takes place mainly in the hypothalamus (HT), a crucial brain structure for controlling body weight. Understanding more precisely the kinetics of glial activation of two major brain cells (astrocytes and microglia) and their impact on eating behavior could prevent obesity and offer new prospects for therapeutic treatments. To understand the mechanisms pertaining to obesity-related neuroinflammation, we developed a fully automated algorithm, NutriMorph. Although some algorithms were developed in the past decade to detect and segment cells, they are highly specific, not fully automatic, and do not provide the desired morphological analysis. Our algorithm copes with these issues and performs the analysis of cells images (here, microglia of the hypothalamic arcuate nucleus), and the morphological clustering of these cells through statistical analysis and machine learning. Using the k-Means algorithm, it clusters the microglia of the control condition (healthy mice) and the different states of neuroinflammation induced by high-fat diets (obese mice) into subpopulations. This paper is an extension and re-analysis of a first published paper showing that microglial reactivity can already be seen after few hours of high-fat diet (Cansell et al., 2021 [5]). Thanks to NutriMorph algorithm, we unravel the presence of different hypothalamic microglial subpopulations (based on morphology) subject to proportion changes in response to already few hours of high-fat diet in mice.

Glial cells diverge in fly brain evolution

How animal brains evolve to support ecological specialization is poorly understood. A recent PLOS Biology study reveals that glial cells show the most dramatic molecular and cellular changes in the brains of fruit flies adapted to a toxic niche, highlighting their underappreciated role in brain evolution.

Impacts of PI3K/protein kinase B pathway activation in reactive astrocytes: from detrimental effects to protective functions

Astrocytes are the most abundant type of glial cell in the central nervous system. Upon injury and inflammation, astrocytes become reactive and undergo morphological and functional changes. Depending on their phenotypic classification as A1 or A2, reactive astrocytes contribute to both neurotoxic and neuroprotective responses, respectively. However, this binary classification does not fully capture the diversity of astrocyte responses observed across different diseases and injuries. Transcriptomic analysis has revealed that reactive astrocytes have a complex landscape of gene expression profiles, which emphasizes the heterogeneous nature of their reactivity. Astrocytes actively participate in regulating central nervous system inflammation by interacting with microglia and other cell types, releasing cytokines, and influencing the immune response. The phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway is a central player in astrocyte reactivity and impacts various aspects of astrocyte behavior, as evidenced by in silico , in vitro , and in vivo results. In astrocytes, inflammatory cues trigger a cascade of molecular events, where nuclear factor-κB serves as a central mediator of the pro-inflammatory responses. Here, we review the heterogeneity of reactive astrocytes and the molecular mechanisms underlying their activation. We highlight the involvement of various signaling pathways that regulate astrocyte reactivity, including the PI3K/AKT/mammalian target of rapamycin (mTOR), α v β 3 integrin/PI3K/AKT/connexin 43, and Notch/PI3K/AKT pathways. While targeting the inactivation of the PI3K/AKT cellular signaling pathway to control reactive astrocytes and prevent central nervous system damage, evidence suggests that activating this pathway could also yield beneficial outcomes. This dual function of the PI3K/AKT pathway underscores its complexity in astrocyte reactivity and brain function modulation. The review emphasizes the importance of employing astrocyte-exclusive models to understand their functions accurately and these models are essential for clarifying astrocyte behavior. The findings should then be validated using in vivo models to ensure real-life relevance. The review also highlights the significance of PI3K/AKT pathway modulation in preventing central nervous system damage, although further studies are required to fully comprehend its role due to varying factors such as different cell types, astrocyte responses to inflammation, and disease contexts. Specific strategies are clearly necessary to address these variables effectively.

FGF21 Alleviates Hypoxic-Ischemic White Matter Injury in Neonatal Mice by Mediating Inflammation and Oxidative Stress Through PPAR-γ Signaling Pathway

White matter injury (WMI), the most common type of brain damage in infants born preterm, is characterized by failure in oligodendrocyte progenitor cell maturation and myelination, thereby contributing to long-term neurological impairments. Regrettably, effective therapies for promoting remyelination and improving function are currently lacking for this growing population affected by WMI. Recombinant human fibroblast growth factor (rhFGF) 21 modulated microglial activation and then ameliorated brain damage and improved neurological deficits in several central nervous system diseases. However, the effects of rhFGF21 treatment on WMI in preterm infants remain uncertain. In this study, we established an in vivo mouse model of cerebral hypoxia-ischemia (HI)-induced brain WMI and an in vitro model using oxygen-glucose deprivation (OGD)-treated HMC3 cells to investigate the neuroprotective effects of rhFGF21 against WMI and elucidated the potential mechanism. Our findings demonstrated that administration of rhFGF21 significantly ameliorated the retardation of oligodendrocyte differentiation, promoted myelination, and mitigated axonal deficits, synaptic loss, and GFAP scarring, thereby improving lifelong cognitive and neurobehavioral dysfunction associated with WMI. Moreover, rhFGF21 modulated microglial polarization, promoted a shift from the M1 to the M2 microglial phenotype, and suppressed microglial activation, thus ameliorating inflammatory response and oxidative stress. Additionally, rhFGF21 treatment significantly inhibited the HMGB1/NF-κB pathway linked to inflammation, and activated the NRF2 pathway associated with oxidative stress through the upregulation of PPAR-γ. Importantly, the beneficial effects of rhFGF21 on HI-induced WMI and microglial activation were dramatically inhibited by PPAR-γ antagonist and its siRNA. Our findings provide compelling evidence that rhFGF21 treatment mitigated the inflammatory response and oxidative stress through the modulation of microglial polarization via the PPAR-γ-mediated HMGB1/NF-κB pathway and the NRF2 pathway, respectively, contributes to neuroprotection and the amelioration of WMI in neonatal mice. Thus, rhFGF21 represents a promising therapeutic agent for the treatment of neonatal WMI.

Modification of Neural Circuit Functions by Microglial P2Y6 Receptors in Health and Neurodegeneration

Neural circuits consisting of neurons and glial cells help to establish all functions of the CNS. Microglia, the resident immunocytes of the CNS, are endowed with UDP-sensitive P2Y6 receptors (P2Y6Rs) which regulate phagocytosis/pruning of excessive synapses during individual development and refine synapses in an activity-dependent manner during adulthood. In addition, this type of receptor plays a decisive role in primary (Alzheimer's disease, Parkinson's disease, neuropathic pain) and secondary (epilepsy, ischemic-, mechanical-, or irradiation-induced) neurodegeneration. A whole range of microglial cytokines controlled by P2Y6Rs, such as the interleukins IL-1β, IL-6, IL-8, and tumor necrosis factor-α (TNF-α), leads to neuroinflammation, resulting in neurodegeneration. Hence, small molecular antagonists of P2Y6Rs and genetic knockdown of this receptor provide feasible ways to alleviate inflammation-induced neurological disorders but might also interfere with the regulation of the synaptic circuitry. The present review aims at investigating this dual role of P2Y6Rs in microglia, both in shaping neural circuits by targeted phagocytosis and promoting neurodegenerative illnesses by fostering neuroinflammation through multiple transduction mechanisms.

Crosstalk between endothelial cells and dermal papilla entails hair regeneration and angiogenesis during aging

INTRODUCTION

Tissues maintain their function through interaction with microenvironment. During aging, both hair follicles and blood vessels (BV) in skin undergo degenerative changes. However, it is elusive whether the changes are due to intrinsic aging changes in hair follicles or blood vessels respectively, or their interactions.

OBJECTIVE

To explore how hair follicles and blood vessels interact to regulate angiogenesis and hair regeneration during aging.

METHODS

Single-cell RNA-sequencing (scRNA-seq) analyses were used to identify the declined ability of dermal papilla (DP) and endothelial cells (ECs) during aging. CellChat and CellCall were performed to investigate interaction between DP and ECs. Single-cell metabolism (scMetabolism) analysis and iPATH were applied to analyze downstream metabolites in DP and ECs. Hair-plucking model and mouse cell organoid model were used for functional studies.

RESULTS

During aging, distance and interaction between DP and ECs are decreased. DP interacts with ECs, with decreased EDN1-EDNRA signaling from ECs to DP and CTF1-IL6ST signaling from DP to ECs during aging. ECs-secreted EDN1 binds to DP-expressed EDNRA which enhances Taurine (TA) metabolism to promote hair regeneration. DP-emitted CTF1 binds to ECs-expressed IL6ST which activates alpha-linolenic acid (ALA) metabolism to promote angiogenesis. Activated EDN1-EDNRA-TA signaling promotes hair regeneration in aged mouse skin and in organoid cultures, and increased CTF1-IL6ST-ALA signaling also promotes angiogenesis in aged mouse skin and organoid cultures.

CONCLUSIONS

Our finding reveals reciprocal interactions between ECs and DP. ECs releases EDN1 sensed by DP to activate TA metabolism which induces hair regeneration, while DP emits CTF1 signal received by ECs to enhance ALA metabolism which promotes angiogenesis. Our study provides new insights into mutualistic cellular crosstalk between hair follicles and blood vessels, and identifies novel signaling contributing to the interactions of hair follicles and blood vessels in normal and aged skin.

PD-L1/PD-1 checkpoint pathway regulates astrocyte morphogenesis and myelination during brain development

Programmed cell death protein 1 (PD-1) and its primary ligand PD-L1 are integral components of a significant immune checkpoint pathway, widely recognized for its central role in cancer immunotherapy. However, emerging evidence highlights their broader involvement in both the central and peripheral nervous systems. In this study, we demonstrate that PD-L1/PD-1 signaling in astrocytes during mouse brain development regulates astrocyte maturation and morphogenesis via the MEK/ERK pathway by targeting the downstream effector cysteine and glycine rich protein 1 (CSRP1). This enhanced astrocyte morphological complexity results in increased end-foot coverage of blood vessels. Additionally, aberrant secretion of CSRP1 by astrocytes interacts with oligodendrocyte precursor cells (OPCs) membrane proteins annexin A1 (ANXA1) and annexin A2 (ANXA2), leading to the exclusion of migrating OPCs from blood vessels. This disruption in OPC migration and differentiation results in abnormal myelination and is associated with cognitive deficits in the mice. Our results provide critical insights into the function of PD-L1/PD-1 signaling in astrocyte-OPC interactions and underscore its relevance to glial cell development and pathogenesis in neurodevelopmental disorders.

GPNMB and ATP6V1A interact to mediate microglia phagocytosis of multiple types of pathological particles

Pronounced elevation of glycoprotein non-metastatic melanoma B (GPNMB) is a common phenomenon in a variety of brain diseases, but the expression patterns, functions, and molecular signaling of GPNMB have not been well studied. Here, we showed that pathological factors, including neuronal degeneration caused by seizures, caspase-3-induced neuronal apoptosis, neuronal debris, and β-amyloid, induced "on-demand" GPNMB expression in hippocampal microglia. Genetic ablation of GPNMB did not affect acute seizures but worsened chronic epileptogenesis. We found that GPNMB functioned in phagocytosis, deficiency of which resulted in defects in both phagocytic engulfment and degradation. GPNMB could be internalized into cells, where it wrapped engulfed pathogenic particles and presented them to lysosomes through interaction with lysosomal vacuolar-type proton ATPase catalytic subunit A (ATP6V1A). Activating ATP6V1A was able to rescue GPNMB-deficiency-caused phagocytosis impairment. Thus, microglial GPNMB-ATP6V1A might be a common treatment target of a batch of chronic neurological disorders, and clearing the degenerative neurons might be more valuable than reserving them to protect the brain.

Astrocytic LRRK2 Controls Synaptic Connectivity via Regulation of ERM Phosphorylation

Astrocytes regulate synaptic connectivity. However, whether astrocyte dysfunction causes synaptic pathologies in disorders such as Parkinson's Disease (PD) is unknown. Here, we investigated how the most common Parkinsonism gene mutation, LRRK2 G2019S, impacts structure and synaptogenic function of cortical astrocytes. In human and mouse cortex, the LRRK2 G2019S mutation caused astrocyte morphology deficits and enhanced the phosphorylation of the ERM proteins (Ezrin, Radixin, and Moesin), components of the perisynaptic astrocyte processes. Reducing ERM phosphorylation in LRRK2 G2019S mouse astrocytes restored astrocyte morphology and corrected excitatory synaptic deficits. Using an in vivo BioID proteomic approach, we found astrocytic Ezrin interacts with Atg7, a master regulator of autophagy. The Ezrin/Atg7 interaction is inhibited by Ezrin phosphorylation and thus diminished in LRRK2 G2019S astrocytes. Importantly, Atg7 function is required to maintain proper astrocyte morphology. These studies reveal an astrocytic molecular mechanism that could serve as a therapeutic target for synaptic pathologies seen in PD.

Immunotherapy and the Tumor Microenvironment in Brain Metastases from Non-Small Cell Lung Cancer: Challenges and Future Directions

Brain metastases (BMs) are a relatively common and severe complication in advanced non-small cell lung cancer (NSCLC), significantly affecting patient prognosis. Metastatic tumor cells can alter the brain tumor microenvironment (TME) to promote an immunosuppressive state, characterized by reduced infiltration of tumor-infiltrating lymphocytes (TILs), diminished expression of programmed death-ligand 1 (PD-L1), and changes in other proinflammatory factors and immune cell populations. Microglia, the resident macrophages of the brain, play a pivotal role in modulating the central nervous system (CNS) microenvironment through interactions with metastatic cancer cells, astrocytes, and infiltrating T cells. The M2 phenotype of microglia contributes to immunosuppression in BM via the activation of signaling pathways such as STAT3 and PI3K-AKT-mTOR. Recent advances have enhanced our understanding of the immune landscape of BMs in NSCLC, particularly regarding immune evasion within the CNS. Current immunotherapeutic strategies, including immune checkpoint inhibitors, have shown promise for NSCLC patients with BM, demonstrating intracranial activity and manageable safety profiles. Future research is warranted to further explore the molecular and immune mechanisms underlying BM, aiming to develop more effective treatments.

Glial Cells in Spinal Muscular Atrophy: Speculations on Non-Cell-Autonomous Mechanisms and Therapeutic Implications

Spinal muscular atrophy (SMA) is a neuromuscular disorder caused by homozygous deletions or mutations in the SMN1 gene, leading to progressive motor neuron degeneration. While SMA has been classically viewed as a motor neuron-autonomous disease, increasing evidence indicates a significant role of glial cells-astrocytes, microglia, oligodendrocytes, and Schwann cells-in the disease pathophysiology. Astrocytic dysfunction contributes to motor neuron vulnerability through impaired calcium homeostasis, disrupted synaptic integrity, and neurotrophic factor deficits. Microglia, through reactive gliosis and complement-mediated synaptic stripping, exacerbate neurodegeneration and neuroinflammation. Oligodendrocytes exhibit impaired differentiation and metabolic support, while Schwann cells display abnormalities in myelination, extracellular matrix composition, and neuromuscular junction maintenance, further compromising motor function. Dysregulation of pathways such as NF-κB, Notch, and JAK/STAT, alongside the upregulation of complement proteins and microRNAs, reinforces the non-cell-autonomous nature of SMA. Despite the advances in SMN-restorative therapies, they do not fully mitigate glial dysfunction. Targeting glial pathology, including modulation of reactive astrogliosis, microglial polarization, and myelination deficits, represents a critical avenue for therapeutic intervention. This review comprehensively examines the multifaceted roles of glial cells in SMA and highlights emerging glia-targeted strategies to enhance treatment efficacy and improve patient outcomes.

Clinical neurocardiology: defining the value of neuroscience-based cardiovascular therapeutics - 2024 update

The intricate role of the autonomic nervous system (ANS) in regulating cardiac physiology has long been recognized. Aberrant function of the ANS is central to the pathophysiology of cardiovascular diseases. It stands to reason, therefore, that neuroscience-based cardiovascular therapeutics hold great promise in the treatment of cardiovascular diseases in humans. A decade after the inaugural edition, this White Paper reviews the current state of understanding of human cardiac neuroanatomy, neurophysiology and pathophysiology in specific disease conditions, autonomic testing, risk stratification, and neuromodulatory strategies to mitigate the progression of cardiovascular diseases.

Uncovering convergence and divergence between autism and schizophrenia using genomic tools and patients' neurons

Autism spectrum disorders (ASDs) are highly heritable and result in abnormal repetitive behaviors and impairment in communication and cognitive skills. Previous studies have focused on the genetic correlation between ASDs and other neuropsychiatric disorders, but an in-depth understanding of the correlation to other disorders is required. We conducted an extensive meta-analysis of common variants identified in ASDs by genome-wide association studies (GWAS) and compared it to the consensus genes and single nucleotide polymorphisms (SNPs) of Schizophrenia (SCZ). We found approximately 75% of the GWAS genes that are associated with ASD are also associated with SCZ. We further investigated the cellular phenotypes of neurons derived from induced pluripotent stem cell (iPSC) models in ASD and SCZ. Our findings revealed that ASD and SCZ neurons initially follow divergent developmental trajectories compared to control neurons. However, despite these early diametrical differences, both ASD and SCZ neurons ultimately display similar deficits in synaptic activity as they mature. This significant genetic overlap between ASD and SCZ, coupled with the convergence towards similar synaptic deficits, highlights the intricate interplay of genetic and developmental factors in shaping the shared underlying mechanisms of these complex neurodevelopmental and neuropsychiatric disorders.

YAP Signaling in Glia: Pivotal Roles in Neurological Development, Regeneration and Diseases

Yes-associated protein (YAP), the key transcriptional co-factor and downstream effector of the Hippo pathway, has emerged as one of the primary regulators of neural as well as glial cells. It has been detected in various glial cell types, including Schwann cells and olfactory ensheathing cells in the peripheral nervous system, as well as radial glial cells, ependymal cells, Bergmann glia, retinal Müller cells, astrocytes, oligodendrocytes, and microglia in the central nervous system. With the development of neuroscience, understanding the functions of YAP in the physiological or pathological processes of glia is advancing. In this review, we aim to summarize the roles and underlying mechanisms of YAP in glia and glia-related neurological diseases in an integrated perspective.

The Role of Complexity Theory in Understanding Brain's Neuron-Glia Interactions

Brain information processing complexity is conventionally recognized as derived from neuronal activity, with neurons and their dynamic signalling responsible for the transfer and processing of information. However, the brain also contains other non-neuronal cells, glial cells, which exceed the number of neurons and are involved in the processes related with information coding by neural networks and underlying brain functions. Decisive advances in the characterization of the molecular and physiological properties of glial cells shed light on their active roles in neurotransmission and neuronal physiopathology. This expanded relationship between neurons and glia challenges traditional neurobiology by highlighting their reciprocal influence, where it is difficult to determine whether neuronal or glial processes initiate and drive the interactions. This interplay creates a dilemma, where the causal hierarchy between these two cell types remains unresolved. A philosophical tool, the 'Theory of Complexity' of Edgard Morin can help to better explain and study the complexity of neuron-glia interactions. Morin's proposal on complexity is useful to transform brain knowledge, in order to review the brain molecular functions in antireductionist pattern. In this manuscript, we will discuss how to use the 'retroactive loop' principle from Morin's 'Theory of Complexity' at the brain molecular level, proposing a new philosophical-experimental grid that can help neuroscientists for a better understanding of the glia-neuron interactions in the brain.

The meninges host a distinct compartment of regulatory T cells that preserves brain homeostasis

Our understanding of the meningeal immune system has recently burgeoned, particularly regarding how innate and adaptive effector cells are mobilized to meet brain challenges. However, information on how meningeal immunocytes guard brain homeostasis in healthy individuals remains limited. This study highlights the heterogeneous, polyfunctional regulatory T cell (Treg) compartment in the meninges. A Treg subtype specialized in controlling interferon-γ (IFN-γ) responses and another dedicated to regulating follicular B cell responses were substantial components of this compartment. Accordingly, punctual Treg ablation rapidly unleashed IFN-γ production by meningeal lymphocytes, unlocked access to the brain parenchyma, and altered meningeal B cell profiles. Distally, the hippocampus assumed a reactive state, with morphological and transcriptional changes in multiple glial cell types. Within the dentate gyrus, neural stem cells underwent more death and were blocked from further differentiation, which coincided with impairments in short-term spatial-reference memory. Thus, meningeal Tregs are a multifaceted safeguard of brain homeostasis at steady state.

The Role of TIM-3 in Glioblastoma Progression

Several immunoregulatory or immune checkpoint receptors including T cell immunoglobulin and mucin domain 3 (TIM-3) have been implicated in glioblastoma progression. Rigorous investigation over the last decade has elucidated TIM-3 as a key player in inhibiting immune cell activation and several key associated molecules have been identified both upstream and downstream that mediate immune cell dysfunction mechanistically. However, despite several reviews being published on other immune checkpoint molecules such as PD-1 and CTLA-4 in the glioblastoma setting, no such extensive review exists that specifically focuses on the role of TIM-3 in glioblastoma progression and immunosuppression. Here, we critically summarize the current literature regarding TIM-3 expression as a prognostic marker for glioblastoma, its expression profile on immune cells in glioblastoma patients and the exploration of anti-TIM-3 agents in glioblastoma pre-clinical models for potential clinical application.

Evolving Insights into Prickle2 in Neurodevelopment and Neurological Disorders

The development of neural circuits is a complex, highly coordinated process crucial for the proper functioning of the nervous system. This process involves the intricate interplay of numerous genes and signaling pathways. Prickle2, a protein encoded by the planar cell polarity (PCP) genes, is a key component of the noncanonical Wnt/PCP signaling pathway and plays a critical role in neural circuit development. Recent studies have highlighted the essential functions of Prickle2 in various stages of neural circuit formation, including the development of the initial segment of neuronal axons, axon elongation and regeneration, dendrite formation, synapse formation, and vesicle transport. The normal expression and spatial distribution of Prickle2 are vital for these processes, and its dysregulation has been associated with several neurological disorders, including congenital neural tube defects, Alzheimer's disease, epilepsy, and autism spectrum disorders. This review aims to systematically summarize the upstream and downstream signaling pathways and regulatory interactions involving Prickle2 in neurodevelopment and neural circuit formation. By discussing the expression patterns of Prickle2 in neurodevelopment and its associations with neurological diseases, we provide insights into the mechanisms through which Prickle2 influences neurodevelopment and its potential implications in neurological disorders.

Mogroside V ameliorates astrocyte inflammation induced by cerebral ischemia through suppressing TLR4/TRADD pathway

Inflammation and oxidative stress are pivotal factors in the onset and progression of secondary injury following cerebral ischemia-reperfusion (I/R). Mogroside V (MV), a primary active compound of Siraitia grosvenorii, exhibits significant anti-inflammatory and antioxidant properties. However, its specific effects in cerebral ischemia remain unclear. In this study, we evaluated the neuroprotective effects of MV in a model of focal cerebral ischemia. Male C57BL/6J mice were subjected to middle cerebral artery occlusion/reperfusion (MCAO/R) as an in vivo model of cerebral ischemia-reperfusion injury (CIRI), while U87 cells were subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) to simulate CIRI in vitro. MV administration was found to reduce mortality, infarct volume, cerebral edema, and alleviate neurological deficits in these I/R mice. Furthermore, MV mitigated cerebral I/R injury by decreasing oxidative stress markers, such as reactive oxygen species (ROS) and malondialdehyde (MDA), while enhancing superoxide dismutase (SOD) levels. Gene Set Enrichment Analysis (GSEA) of the KEGG pathway revealed that most differentially expressed genes (DEGs) were involved in the Toll-like receptor/NF-κB/TNF/apoptosis signaling pathway. These findings were confirmed by real-time PCR, western blotting, immunohistochemistry, and immunofluorescence co-localization which demonstrated that MV reduced astrocyte inflammatory responses by inhibiting cytokine secretion associated with the TLR4/TRADD pathway. Additionally, MV protected neurons from apoptosis, as supported by TUNEL, Nissl, and HE staining. In conclusion, MV attenuates astrocyte inflammation and exerts neuroprotective effects following cerebral I/R injury, likely through suppression of the TLR4/TRADD signaling pathway.

Neuron-to-glia and glia-to-glia signaling directs critical period experience-dependent synapse pruning

Experience-dependent glial synapse pruning plays a pivotal role in sculpting brain circuit connectivity during early-life critical periods of development. Recent advances suggest a layered cascade of intercellular communication between neurons and glial phagocytes orchestrates this precise, targeted synapse elimination. We focus here on studies from the powerful Drosophila forward genetic model, with reference to complementary findings from mouse work. We present both neuron-to-glia and glia-to-glia intercellular signaling pathways directing experience-dependent glial synapse pruning. We discuss a putative hierarchy of secreted long-distance cues and cell surface short-distance cues that act to sequentially orchestrate glia activation, infiltration, target recognition, engulfment, and then phagocytosis for synapse pruning. Ligand-receptor partners mediating these stages in different contexts are discussed from recent Drosophila and mouse studies. Signaling cues include phospholipids, small neurotransmitters, insulin-like peptides, and proteins. Conserved receptors for these ligands are discussed, together with mechanisms where the receptor identity remains unknown. Potential mechanisms are proposed for the tight temporal-restriction of heightened experience-dependent glial synapse elimination during early-life critical periods, as well as potential means to re-open such plasticity at maturity.

Mitochondria and astrocyte reactivity: Key mechanism behind neuronal injury

In this special issue to celebrate the 30th anniversary of the Uruguayan Society for Neuroscience (SNU), we find it pertinent to highlight that research on glial cells in Uruguay began almost alongside the history of SNU and contributed to the understanding of neuron-glia interactions within the international scientific community. Glial cells, particularly astrocytes, traditionally regarded as supportive components in the central nervous system (CNS), undergo notable morphological and functional alterations in response to neuronal damage, a phenomenon referred to as glial reactivity. Among the myriad functions of astrocytes, metabolic support holds significant relevance for neuronal function, given the high energy demand of the nervous system. Although astrocytes are typically considered to exhibit low mitochondrial respiratory chain activity, they possess a noteworthy mitochondrial network. Interestingly, both the morphology and activity of these organelles change following glial reactivity. Despite receiving less attention compared to studies on neuronal mitochondria, recent studies indicate that mitochondria play a crucial role in driving the transition of astrocytes from a quiescent to a reactive state in various neurological disorders. Notably, stimulating mitochondria in astrocytes has been shown to reduce damage associated with the neurodegenerative disease amyotrophic lateral sclerosis. Here, we focus on studies supporting the emerging paradigm that metabolic reprogramming occurs in astrocytes following damage, which is associated with their phenotypic shift to a new functional state that significantly influences the progression of pathology. Thus, exploring mitochondrial activity and metabolic reprogramming within glial cells may provide valuable insights for developing innovative therapeutic approaches to mitigate neuronal damage. In this review, we focus on studies supporting the emerging paradigm that metabolic reprogramming occurs in astrocytes following damage, which is associated with their phenotypic shift to a new functional state that significantly influences the progression of pathology. Thus, exploring mitochondrial activity and metabolic reprogramming within glial cells may provide valuable insights for developing innovative therapeutic approaches to mitigate neuronal damage.

Metal nanoparticles in neuroinflammation: impact on microglial dynamics and CNS function

Microglia, the primary immune cells of the central nervous system (CNS), are crucial in maintaining brain homeostasis and responding to pathological changes. While they play protective roles, their activation can lead to neuroinflammation and the progression of neurodegenerative diseases. Metal nanoparticles (NPs), due to their unique ability to cross the blood-brain barrier (BBB), have emerged as promising agents for drug delivery to the CNS. In this way, we aim to review the dual role of metal-containing NPs, gold (AuNPs), silver (AgNPs), iron oxide (IONPs), zinc oxide (ZnONPs), cobalt (CoNPs), titanium dioxide (TiO2NPs), and silica (SiO2NPs) in modulating microglial activity. Some NPs promote anti-inflammatory effects, while others exacerbate neuroinflammation. We examine how these NPs influence microglial activation, focusing on their potential therapeutic benefits and risks. A deeper understanding of NP-microglia interactions is crucial for developing safe and efficient treatments for neuroinflammatory and neurodegenerative disorders.

Cross-Species Insights from Single-Nucleus Sequencing Highlight Aging-Related Hippocampal Features in Tree Shrew

The tree shrew brain has garnered considerable attention due to its remarkable similarities to human brain. However, the cellular composition and genetic signatures of tree shrew hippocampus across postnatal life remain poorly characterized. Here, we establish the first single-nucleus transcriptomic atlas of tree shrew hippocampus spanning postnatal life, detailing the dynamics and diversity of the neurogenic lineage, oligodendrocytes, microglia, and endothelial cells. Notably, cross-species transcriptomic comparison among humans, macaques, tree shrews, and mice reveals that the tree shrew transcriptome resembles that of macaques, making it a promising model for simulating human neurological diseases. More interestingly, we identified a unique class of tree shrew-specific neural stem cells and established SOX6, ADAMTS19, and MAP2 as their markers. Furthermore, aberrant gene expression and cellular dysfunction in the tree shrew hippocampus are linked to neuroinflammation and cognitive impairment during tree shrew aging. Our study provides extensive resources on cell composition and transcriptomic profiles, serving as a foundation for future research on neurodevelopmental and neurological disorders in tree shrews.

Glial polarization in neurological diseases: Molecular mechanisms and therapeutic opportunities

Glial cell polarization plays a pivotal role in various neurological disorders. In response to distinct stimuli, glial cells undergo polarization to either mitigate neurotoxicity or facilitate neural repair following injury, underscoring the importance of glial phenotypic polarization in modulating central nervous system function. This review presents an overview of glial cell polarization, focusing on astrocytes and microglia. It explores the involvement of glial polarization in neurological diseases such as Alzheimer's disease, Parkinson's disease, stroke, epilepsy, traumatic brain injury, amyotrophic lateral sclerosis, multiple sclerosis and meningoencephalitis. Specifically, it emphasizes the role of glial cell polarization in disease pathogenesis through mechanisms including neuroinflammation, neurodegeneration, calcium signaling dysregulation, synaptic dysfunction and immune response. Additionally, it summarizes various therapeutic strategies including pharmacological treatments, dietary supplements and cell-based therapies, aimed at modulating glial cell polarization to ameliorate brain dysfunction. Future research focused on the spatio-temporal manipulation of glial polarization holds promise for advancing precision diagnosis and treatment of neurological diseases.

Cerebellar Bergmann glia integrate noxious information and modulate nocifensive behaviors

The cerebellum is activated by noxious stimuli and pathological pain but its role in noxious information processing remains unknown. Here, we show that in mice, cutaneous noxious electrical stimuli induced noradrenaline (NA) release from locus coeruleus (LC) terminals in the cerebellar cortex. Bergmann glia (BG) accumulated these LC-NA signals by increasing intracellular calcium in an integrative manner ('flares'). BG flares were also elicited in response to an intraplantar capsaicin injection. Chemogenetic inactivation of LC terminals or BG in the cerebellar cortex or BG-specific knockdown of α1-adrenergic receptors suppressed BG flares, reduced nocifensive licking and had analgesic effects in nerve injury-induced chronic neuropathic pain. Moreover, chemogenetic activation of BG or an intraplantar capsaicin injection reduced Purkinje cell firing, which may disinhibit the output activity of the deep cerebellar nuclei. These results suggest a role for BG in computing noxious information from the LC and in modulating pain-related behaviors by regulating cerebellar output.

Gene module-trait network analysis uncovers cell type specific systems and genes relevant to Alzheimer's Disease

Alzheimer's Disease (AD) is marked by the accumulation of pathology, neuronal loss, and gliosis and frequently accompanied by cognitive decline. Understanding brain cell interactions is key to identifying new therapeutic targets to slow its progression. Here, we used systems biology methods to analyze single-nucleus RNA sequencing (snRNASeq) data generated from dorsolateral prefrontal cortex (DLPFC) tissues of 424 participants in the Religious Orders Study or the Rush Memory and Aging Project (ROSMAP). We identified modules of co-regulated genes in seven major cell types, assigned them to coherent cellular processes, and assessed which modules were associated with AD traits such as cognitive decline, tangle density, and amyloid-β deposition. Coexpression network structure was conserved in the majority of modules across cell types, but we also found distinct communities with altered connectivity, especially when compared to bulk RNASeq, suggesting cell-specific gene co-regulation. These coexpression modules can also capture signatures of cell subpopulations and be influenced by cell proportions. Using a Bayesian network framework, we modeled the direction of relationships between the modules and AD progression. We highlight two key modules, a microglia module (mic_M46), associated with tangles; and an astrocyte module (ast_M19), associated with cognitive decline. Our work provides cell-specific molecular networks modeling the molecular events leading to AD.

Ezrin-mediated astrocyte-synapse signaling regulates cognitive function via astrocyte morphological changes in fine processes in male mice

Astrocytes, which actively participate in cognitive processes, have a complex spongiform morphology, highlighted by extensive ramified fine processes that closely enwrap the pre- and post-synaptic compartments, forming tripartite synapses. However, the role of astrocyte morphology in cognitive processes remains incompletely understood and even controversial. The actin-binding protein Ezrin is highly expressed in astrocytes and is a key structural determinant of astrocyte morphology. Here, we found that Ezrin expression and astrocyte fine process volume in the hippocampus of male mice increased after learning but decreased after lipopolysaccharide injection and in a mouse model of postoperative cognitive dysfunction, both of which involved models with impaired cognitive function. Additionally, astrocytic Ezrin knock-out led to significantly decreased astrocytic fine process volumes, decreased astrocyte-neuron proximity, and induced anxiety-like behaviors and cognitive dysfunction. Astrocytic Ezrin deficiency in the hippocampus was achieved by using a microRNA silencing technique delivered by adeno-associated viruses. Down-regulation of Ezrin in hippocampal astrocytes led to disrupted astrocyte-synapse interactions and impaired synaptic functions, including synaptic transmission and synaptic plasticity, which could be rescued by exogenous administration of D-serine. Remarkably, decreased Ezrin expression and reduced astrocyte fine processes volumes were also observed in aged mice with decreased cognitive function. Moreover, overexpression of astrocytic Ezrin increased astrocyte fine process volumes and improved cognitive function in aged mice. Overall, our results indicate Ezrin-mediated astrocyte fine processes integrity shapes astrocyte-synapse signaling contributing to cognitive function.

Glia-glia crosstalk via semaphorins: Emerging implications in neurodegeneration

The central nervous system (CNS) is wired by a complex network of integrated glial and neuronal signals, which is critical for its development and homeostasis. In this context, glia-glia communication is a complex and dynamic process that is essential for ensuring optimal CNS function. Semaphorins, which include secreted and transmembrane molecules, and their receptors, mainly found in the plexin and neuropilin families, are expressed in a wide range of cell types, including glia. In the CNS, semaphorin signalling is involved in a spectrum of processes, including neurogenesis, neuronal migration and wiring, and glial cell recruitment. Recently, semaphorins and plexins have attracted intense research aimed at elucidating their roles in instructing glial cell behavior during development or in response to inflammatory stimuli. In this review, we provide an overview of the multifaceted role of semaphorins in glia-glia communication, highlighting recent discoveries about semaphoring-dependent regulation of glia functions in healthy conditions. We also discuss the mechanisms of gliaglia crosstalk mediated by semaphorins under pathological conditions, and how these interactions may provide potential avenues for therapeutic intervention in neuroinflammation-mediated neurodegeneration.

Psychedelics in neuroinflammation: Mechanisms and therapeutic potential

Neuroinflammation is a critical factor in the pathogenesis of various neurodegenerative and psychiatric disorders, including Alzheimer's disease, Parkinson's disease, and major depressive disorder. Psychedelics, such as psilocybin, lysergic acid diethylamide (LSD), and dimethyltryptamine (DMT), have demonstrated promising therapeutic effects on neuroinflammation, primarily through interactions with serotonin (5-HT) receptors, particularly the 5-HT2A receptor. Activation of these receptors by psychedelics modulates the production of pro-inflammatory cytokines, regulates microglial activity, and shifts the balance between neurotoxic and neuroprotective metabolites. Additionally, psychedelics affect critical signaling pathways, including the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt), and mechanistic target of rapamycin (mTOR) pathways, promoting neuroplasticity and exerting anti-inflammatory effects. Beyond the serotonergic system, other neurotransmitter systems-including the glutamatergic, dopaminergic, noradrenergic, gamma-aminobutyric acid (GABAergic), and cholinergic systems-also play significant roles in mediating the effects of psychedelics. This review examines the intricate mechanisms by which psychedelics modulate neuroinflammation and underscores their potential as innovative therapeutic agents for treating neuroinflammatory and neuropsychiatric disorders.

Exploring the Effects of Sleep Deprivation on Physical Performance: An EEG Study in the Context of High-Intensity Endurance

BACKGROUND

While the effects of sleep deprivation on cognitive function are well-documented, its impact on high-intensity endurance performance and underlying neural mechanisms remains underexplored, especially in the context of search and rescue operations where both physical and mental performance are essential. This study examines the neurophysiological basis of sleep deprivation on high-intensity endurance using electroencephalography (EEG). In this crossover study, twenty firefighters were subjected to both sleep deprivation (SD) and normal sleep conditions, with each participant performing endurance treadmill exercise the following morning after each condition. EEG signals were recorded before and after high-intensity endurance exercise, and power spectrum analysis and functional connectivity analysis were performed on sleep related frequency bands rhythm: δ (0.5-4 Hz) and θ (4-8 Hz). The EEG power spectral and functional connectivity were measured by repeated measure analysis of variance.

RESULTS

The SD condition had an average sleep duration of 3.78 ± 0.69 h, while the duration for normal sleep was 7.63 ± 0.52 h. After high-intensity endurance exercise, the SD condition had a higher maximum heart rate (p < 0.05) and shorter exercise time (p < 0.05) than normal sleep. Compared with before exercise, the δ band in the left parietal lobe P7 channel increased significantly (p < 0.01), and the θ band in the central Cz channel and the left and right parietal lobe P7 and P8 channel increased significantly (p < 0.01 & p < 0 0.05) in SD and normal sleep conditions after exercise. After exercise, compared with normal sleep, the δ band power in occipital O1 and Oz channels and parietal P7 and TP7 channels in SD significantly decreased (p < 0.05 & p < 0.01); the power of the θ band decreased significantly in the occipital O1 channel, central CZ channel and the left and right parietal P7 and P8 channel (p < 0.05 & p < 0.01). Whole connectivity showed a significant increase (p = 0.001) in the δ band for the SD condition at post-exhaustion. Local connectivity analysis identified a localized network in the δ band with reduced (p < 0.001) post-exhaustion in the SD condition displaying inter-hemispheric differences in certain connections (FP1-CP4, T7-C4, T7-TP8, and O1-FT8) and intra-hemispheric (C3-CPz and Pz-P4) variations.

CONCLUSIONS

Sleep deprivation significantly reduced maximum endurance performance, indicating decreased neural activity in the central and parietal brain regions. Alterations in δ and θ frequency band power, along with disrupted connectivity, may highlight the neurophysiological basis underlying this decline.

Altered GnRH neuron-glia networks close to interface of polycystic ovary syndrome: Molecular mechanism and clinical perspectives

Polycystic ovary syndrome (PCOS) has been noticed as a neuroendocrine syndrome manifested by reproductive hormone dysregulation involving increased luteinizing hormone (LH) pulse frequency and an increased LH to follicle-stimulating hormone ratio, yet theory is just beginning to be established. Neuroglia located in the arcuate nucleus and median eminence (ARC-ME) that are close to gonadotropin-releasing hormone (GnRH) axon terminals, comprise the blood-brain barrier and fenestrated vessels implying their putative roles in the modulation of the abnormal GnRH pulse in PCOS. This review outlines the disturbances of neuron-glia networks that underlie hypothetically the deregulation of GnRH-LH release and impaired sex hormone negative feedback in PCOS. We then discuss chronic and low-grade inflammatory status together with gut dysbiosis and how the detriments may intrude the hypothalamus by virtue of violating interfaces between the brain and periphery, which might contribute to the etiology of the impaired neural circuits in the ARC-ME to induce PCOS.

The Role of Glial Cells in the Pathophysiology of Epilepsy

Epilepsy is a chronic neurological disorder marked by recurrent seizures, significantly impacting individuals worldwide. Current treatments are often ineffective for a third of patients and can cause severe side effects, necessitating new therapeutic approaches. Glial cells, particularly astrocytes, microglia, and oligodendrocytes, are emerging as crucial targets in epilepsy management. Astrocytes regulate neuronal homeostasis, excitability, and synaptic plasticity, playing key roles in maintaining the blood-brain barrier (BBB) and mediating neuroinflammatory responses. Dysregulated astrocyte functions, such as reactive astrogliosis, can lead to abnormal neuronal activity and seizure generation. They release gliotransmitters, cytokines, and chemokines that may exacerbate or mitigate seizures. Microglia, the innate immune cells of the CNS, contribute to neuroinflammation, glutamate excitotoxicity, and the balance between excitatory and inhibitory neurotransmission, underscoring their dual role in seizure promotion and protection. Meanwhile, oligodendrocytes, primarily involved in myelination, also modulate axonal excitability and contribute to the neuron-glia network underlying seizure pathogenesis. Understanding the dynamic interactions of glial cells with neurons provides promising avenues for novel epilepsy therapies. Targeting these cells may lead to improved seizure control and better clinical outcomes, offering hope for patients with refractory epilepsy.