Human astrocytes: structure and functions in the healthy brain

Non-neuronal brain biology and its relevance to animal welfare

Non-neuronal cells constitute a significant portion of brain tissue and are seen as having key roles in brain homeostasis and responses to challenges. This review illustrates how non-neuronal biology can bring new perspectives to animal welfare through understanding mechanisms that determine welfare outcomes and highlighting interventions to improve welfare. Most obvious in this respect is the largely unrecognised relevance of neuroinflammation to animal welfare which is increasingly found to have roles in determining how animals respond to challenges. We start by introducing non-neuronal cells and review their involvement in affective states and cognition often seen as core psychological elements of animal welfare. We find that the evidence for a causal involvement of glia in cognition is currently more advanced than the corresponding evidence for affective states. We propose that translational research on affective disorders could usefully apply welfare science derived approaches for assessing affective states. Using evidence from translational research, we illustrate the involvement of non-neuronal cells and neuroinflammatory processes as mechanisms modulating resilience to welfare challenges including disease, pain, and social stress. We review research on impoverished environments and environmental enrichment which suggests that environmental conditions which improve animal welfare also improve resilience to challenges through balancing pro- and anti-inflammatory non-neuronal processes. We speculate that non-neuronal biology has relevance to animal welfare beyond neuro-inflammation including facilitating positive affective states. We acknowledge the relevance of neuronal biology to animal welfare whilst proposing that non-neuronal biology provides additional and relevant insights to improve animals' lives.

Study on individual differences in visual working memory tasks based on spatiotemporal brain functional metrics and biological perspectives

Visual working memory (VWM) is a critical area of study in cognitive neuroscience, yet the neural and genetic foundations of individual differences in VWM remain unclear. This study investigates individual differences in VWM performance across four types of visual stimuli (Body, Face, Place, Tool) under 0-back and 2-back conditions by integrating gene expression data and spatiotemporal brain function metrics. First, multiple spatiotemporal brain function metrics were extracted, and Sequential Backward Selection (SBS) and Leave-One-Subject-Out Cross-Validation (LOSO-CV) linear regression were applied to predict behavioral performance under VWM conditions. Model performance was evaluated using RMSE. Next, the Working Memory Individual Differences Map (WMIDM) was constructed based on Pearson correlation coefficients between actual and predicted behavioral performance. Finally, WMIDM was integrated with Allen Human Brain Atlas (AHBA) gene expression data to explore its genetic underpinnings. Notably, the gene analysis is exploratory, providing a preliminary framework for future investigations into the molecular basis of working memory. The results demonstrated that under the 2 vs. 0-back condition, spatiotemporal metrics outperformed static metrics (rspa=0.40,q=8.9×10-28,RMSE=0.928 vs. rsta=0.28,q=2.7×10-14,RMSE=0.966). Brain regions contributing to the WMIDM were primarily located in the frontal lobe. Furthermore, genes associated with WMIDM were significantly enriched in pathways linked to intellectual disability and mental disorders, as well as related biological processes and cell types. This study highlights the neural and potential genetic foundations of individual differences in working memory through the lens of spatiotemporal multidimensional brain function and gene expression. These findings provide valuable insights for future neuroscience research and pave the way for personalized cognitive interventions.

The role of astrocytes in attention-deficit hyperactivity disorder: An update

Attention-deficit hyperactivity disorder (ADHD), the most prevalent neurodevelopmental disorder, is characterized by inattention, hyperactivity, and impulsivity, manifesting in distinct symptoms and varying degrees of severity among patients. While the cellular processes underlying the neurobiology of ADHD are still being explored, in vitro studies suggest the involvement of certain cellular pathways in its clinical manifestations. Neurodevelopmental disorders such as ADHD are caused by malfunctions in numerous cells in the central nervous system (CNS) throughout development; nevertheless, most of the research focuses on neuronal dysfunction. In the last decade, it has become evident that glia and astrocytes play a crucial role in neurodevelopmental processes, which, if deficient, may result in neurodevelopmental disorders. Besides contributing to homeostatic maintenance of the blood-brain barrier (BBB) and other glial cell types, astrocytes provide neurons with structural, trophic, and metabolic support, which is indispensable for their proper functionality. Emerging evidence implicates that astrocytes are involved in processes associated with the etiopathology of ADHD, including oxidative stress, aberrant synaptic formation, neuroinflammation, and excitatory/inhibitory imbalance. This review will summarize the current knowledge addressing astrocyte dysfunction in ADHD, the remaining caveats in clinical data, and the possibilities for drug therapy. Findings substantiated by in vivo, in vitro, and genetic data will be provided, along with the impact of methylphenidate on astrocyte condition.

Astrocyte-neuron metabolic crosstalk in ischaemic stroke

Ischemic stroke (IS) is caused by temporary or permanent obstruction of the brain's blood supply. The disruption in glucose and oxygen delivery that results from the drop in blood flow impairs energy metabolism. A significant pathological feature of IS impaired energy metabolism. Astrocytes, as the most prevalent glial cells in the brain, sit in between neurons and the microvasculature. By taking advantage of their special anatomical location, they play a crucial part in regulating cerebral blood flow (CBF) and metabolism. Astrocytes can withstand hypoxic and ischemic conditions better than neurons do. Additionally, astrocytes are essential for maintaining the metabolism and function of neurons. Therefore, the "neurocentric" perspective on neuroenergetics is gradually giving way to a more comprehensive perspective that takes into account metabolic interaction between astrocytes and neurons. Since neurons in the core region of the infarct are unable to undergo oxidative metabolism, the focus of attention in this review is on neurons in the peri-infarct region. We'll go over the metabolic crosstalk of astrocytes and neurons during the acute phase of IS using three different types of metabolites: lactate, fatty acids (FAs), and amino acids, as well as the mitochondria. After IS, astrocytes in the peri-infarct zone can produce lactate, ketone bodies (KBs), glutamine (Gln), and l-serine, shuttling these metabolites, along with mitochondria, to neurons. This process helps maintain the energy requirements of neurons, preserves their redox state, and regulates neurotransmitter receptor activity.

Astragalin actives autophagy and inhibits apoptosis of astrocytes in AD mice via down-regulating Fas/Fasl-VDAC1 pathway

Alzheimer's disease (AD) as a common neurodegenerative disease, which characterized by amyloid Aβ deposition and neurofibrillary tangles. Astragalin (AST), a natural flavonoid, has anti-inflammatory, antioxidant, anti-cancer, and other pharmacological effects. Astrocytes can phagocytize and degrade Aβ in their vicinity. In this study, we used the AD mice model established by injecting the mixture of Aβ1-42 and Aβ25-35 into the CA1 region of the hippocampus, and C8D1A cells injured by Aβ1-42 to explore the neuroprotective effects of AST. Our findings showed that AST enhances learning and cognitive ability of AD mice, reduces Aβ deposition and neurofibrillary tangles in the brain, and improves the structural morphology of hippocampal nerve cells. Furthermore, AST promoted autophagy and suppressed apoptosis of astrocytes in the AD model. Additionally, AST inhibited the expression of proteins associated with the Fas/Fasl-VDAC1 signaling pathway, while autophagy inhibitor chloroquine (CQ) or apoptosis agonist phenoxodiol reversed above change. Interestingly, consistent with the action of pathway Fas inhibitor KR-33493, AST could activate autophagy of Aβ1-42 injured C8D1A cells while inhibit their apoptosis. In conclusion, AST activated autophagy and inhibited apoptosis of hippocampal astrocytes in AD mice, ameliorating animal cognitive deficits by down-regulating Fas/Fasl-VDAC1 signaling pathway. Thus, this study provided a new perspective and experimental foundation for developing AD treatment drugs.

TLR7 Mediates HIV-1 Tat-Induced Cellular Senescence in Human Astrocytes

Cellular senescence contributes to accelerated aging, neuroinflammation, and the development of HIV-associated neurocognitive disorders (HAND) in the era of combined antiretroviral therapy (cART). One HIV viral factor that could lead to cellular senescence is the persistence of HIV-1 Tat in the brain. As a secreted viral protein, Tat is known to enter endolysosomes of cells through receptor-mediated endocytosis, and we have shown that Tat induces endolysosome damage and dysfunction. Significantly, endolysosome dysfunction has been strongly linked to cellular senescence. However, it is not known whether endolysosome dysfunction represents a driver or consequence of cellular senescence. Because Tat-induced endolysosome damage represents an early step in exogenous Tat-induced cellular senescence, we tested the hypothesis that Tat induces cellular senescence via an endolysosome-dependent mechanism in human astrocytes. We demonstrated that Tat interacts with an endolysosome-resident Toll-like receptor 7 (TLR7) via its arginine-rich basic domain, and such an interaction results in endolysosome damage and the development of a senescence-like phenotype including cell cycle arrest, enhanced SA-β-gal activity, and increased release of senescence-associated secretory phenotype (SASP) factors (IL-6, IL-8, and CCL2). Thus, our finding provided mechanistic insights whereby Tat induces endolysosome damage and cellular senescence in human astrocytes. We provide compelling evidence that endolysosome damage drives the development of cellular senescence. Our findings also highlight the novel role of TLR7 in the development of cellular senescence and suggest that TLR7 represents a novel therapeutic target against senescence and the development of HAND.

Functional Specificity of Astrocyte Subtypes in Alzheimer's Disease: Decoding Disease Mechanisms Through Network-based Analysis of Integrated Single-Nuclei Multi-Omic Data

Alzheimer's disease (AD) is the most common cause of dementia. Recent studies have revealed incontrovertible roles of astrocytes in the pathology of AD. Considering the conflicting behaviours of astrocytes in AD brain, they have been proposed to have subtypes. In this study, astrocytes from two publicly available single-nuclei transcriptome datasets were integrated to provide in-depth characterization of astrocyte subtypes in AD. Differentially expressed genes within each astrocyte subtype were analyzed by mapping them onto a human protein-protein interaction network to discover subnetworks with biologically relevant genes. Integrating single-nuclei datasets and using network-based analysis approach led to higher sensitivity in capturing AD-related genes compared to traditional approaches. One of the identified subtypes was highly representative of neurotoxic reactive astrocytes in AD. The results show that A1 reactive astrocytes could have an enhancing role for the amyloid beta and neurofibrillary tangle accumulation through MAPK10, MAPT, and TMED10, which were all found to be differentially expressed in this subtype during AD in our analysis. Moreover, single-nuclei ATAC-Seq data from the same tissue was re-analyzed to evaluate astrocyte subtypes at multi-omic level. It was found that astrocyte subtypes underwent epigenetic reprogramming during AD. Potential transcription factors were also identified for the regulation of the genes that exhibited alterations in both promoter accessibility and gene expression in AD. Comparative analysis of single-nuclei RNA-Seq and ATAC-Seq datasets showed that PTN gene, which was reported to be important for AD pathology, is likely regulated by ATF3 transcription factor in subtype-specific manner in astrocytes.

From structure to mechanics: exploring the role of axons and interconnections in anisotropic behavior of brain white matter

According to various experimental studies, the role of axons in the brain's white matter (WM) is still a subject of debate: Is the role of axons in brain white matter (WM) limited to their functional significance, or do they also play a pivotal mechanical role in defining its anisotropic behavior? Micromechanics and computational models provide valuable tools for scientists to comprehend the underlying mechanisms of tissue behavior, taking into account the contribution of microstructures. In this review, we delve into the consideration of strain level, strain rates, and injury threshold to determine when WM should be regarded as anisotropic, as well as when the assumption of isotropy can be deemed acceptable. Additionally, we emphasize the potential mechanical significance of interconnections between glial cells-axons and glial cells-vessels. Moreover, we elucidate the directionality of WM stiffness under various loading conditions and define the possible roles of microstructural components in each scenario. Ultimately, this review aims to shed light on the significant mechanical contributions of axons in conjunction with glial cells, paving the way for the development of future multiscale models capable of predicting injuries and facilitating the discovery of applicable treatments.

The Role of Astrocytes in the Molecular Pathophysiology of Schizophrenia: Between Neurodevelopment and Neurodegeneration

Schizophrenia is a chronic and severe psychiatric disorder affecting approximately 1% of the global population, characterized by disrupted synaptic plasticity and brain connectivity. While substantial evidence supports its classification as a neurodevelopmental disorder, non-canonical neurodegenerative features have also been reported, with increasing attention given to astrocytic dysfunction. Overall, in this study, we explore the role of astrocytes as a structural and functional link between neurodevelopment and neurodegeneration in schizophrenia. Specifically, we examine how astrocytes contribute to forming an aberrant substrate during early neurodevelopment, potentially predisposing individuals to later neurodegeneration. Astrocytes regulate neurotransmitter homeostasis and synaptic plasticity, influencing early vulnerability and disease progression through their involvement in Ca2⁺ signaling and dopamine-glutamate interaction-key pathways implicated in schizophrenia pathophysiology. Astrocytes differentiate via nuclear factor I-A, Sox9, and Notch pathways, occurring within a neuronal environment that may already be compromised in the early stages due to the genetic factors associated with the 'two-hits' model of schizophrenia. As a result, astrocytes may contribute to the development of an altered neural matrix, disrupting neuronal signaling, exacerbating the dopamine-glutamate imbalance, and causing excessive synaptic pruning and demyelination. These processes may underlie both the core symptoms of schizophrenia and the increased susceptibility to cognitive decline-clinically resembling neurodegeneration but driven by a distinct, poorly understood molecular substrate. Finally, astrocytes are emerging as potential pharmacological targets for antipsychotics such as clozapine, which may modulate their function by regulating glutamate clearance, redox balance, and synaptic remodeling.

The role of glutamate receptors and transporters in epilepsy: evidence from animal studies

Epilepsy encompasses a group of chronic brain disorders characterized by recurrent, hypersynchronous activity of neuronal clusters, with epileptic seizures being the primary manifestation of these disorders. The objective of epilepsy treatment is to prevent seizures with minimum adverse side effects. However, approximately 30 % of patients do not respond to available medications. One proposed mechanism of epileptogenesis is glutamate excitotoxicity. When released in excess or not appropriately removed from the synaptic cleft, glutamate hyperactivates receptors, causing a biochemical cascade, which culminates in seizures and cell death. The use of animal models is essential for uncovering potential epileptogenic pathways, understanding the role of receptors and transporters in excitotoxicity, and screening effective antiepileptic treatments. This review examines studies that investigate the role of glutamate transporters and receptors in excitotoxicity and epileptogenesis using animal models. For this, we searched through both PubMed/Medline and ScienceDirect databases. After applying the inclusion and exclusion criteria, 26 (twenty-six) studies were selected for analysis. The studies addressed key glutamate transporter family of excitatory amino acid transporters (EAATs) EAAT1, EAAT2, and EAAT3, responsible for glutamate clearance, as well as AMPA receptor subunits GluA1 and GluA2, NMDA receptor subunits GluN1, GluN2a, and GluN2b, and the metabotropic receptors mGluR5 and mGluR2/3. Results showed that the dysregulation of these transporters and receptors is associated to seizure induction and excitotoxic damage, pointing to their fundamental role in the mechanisms of excitotoxicity and epileptogenesis. These findings highlight the potential of targeting glutamate transporters and receptors to stabilize glutamate homeostasis as an intervention in epilepsy management.

Role of glial cells in motor neuron degeneration in hereditary spastic paraplegias

This review provides a comprehensive overview of hereditary spastic paraplegias (HSPs) and summarizes the recent progress on the role of glial cells in the pathogenesis of HSPs. HSPs are a heterogeneous group of neurogenetic diseases characterized by axonal degeneration of cortical motor neurons, leading to muscle weakness and atrophy. Though the contribution of glial cells, especially astrocytes, to the progression of other motor neuron diseases like amyotrophic lateral sclerosis (ALS) is well documented, the role of glial cells and the interaction between neurons and astrocytes in HSP remained unknown until recently. Using human pluripotent stem cell-based models of HSPs, a study reported impaired lipid metabolisms and reduced size of lipid droplets in HSP astrocytes. Moreover, targeting lipid dysfunction in astrocytes rescues axonal degeneration of HSP cortical neurons, demonstrating a non-cell-autonomous mechanism in axonal deficits of HSP neurons. In addition to astrocytes, recent studies revealed dysfunctions in HSP patient pluripotent stem cell-derived microglial cells. Increased microgliosis and pro-inflammation factors were also observed in HSP patients' samples, pointing to an exciting role of innate immunity and microglia in HSP. Building upon these recent studies, further investigation of the detailed molecular mechanism and the interplay between glial cell dysfunction and neuronal degeneration in HSP by combining human stem cell models, animal models, and patient samples will open avenues for identifying new therapeutic targets and strategies for HSP.

Electroacupuncture Serum Alleviates Ogd/R-Induced Astrocyte Damage by Regulating the AQP4 Via m6A Methylation of lncRNA MALAT1

Electroacupuncture (EA) might exert endogenous protective effects on astrocytes in ischemic stroke. Nevertheless, the biological regulatory processes involved have not been identified. The astrocytes were randomly divided into six groups: the control, oxygen-glucose deprivation/reoxygenation (OGD/R), EA serum, METTL3, lncRNA MALAT1 (MALAT1) and AQP4 groups. OGD/R was performed to establish in vitro models of ischemic stroke. EA serum was obtained from rats that were received EA treatment 3 times at "Renzhong" (GV26) and "Baihui" (GV20) acupoints. The morphological characteristics of astrocytes were identified by microscopy and immunohistochemistry. Mitochondrial ultrastructure was observed using transmission electron microscopy. Cell viability and apoptosis rate were measured with cell counting kit-8 and flow cytometry, respectively. RNA m6A levels were detected by colorimetry, and the expression levels of METTL3, MALAT1 and AQP4 were tested with Western blot and quantitative real-time PCR. 10% EA serum was found to be more effective in improving astrocyte morphology and cell viability. EA serum improved mitochondrial ultrastructure, the viability and apoptosis of astrocytes in OGD/R condition, whereas overexpression of METTL3, MALAT1 and AQP4 inhibited the protective effect of EA serum on astrocytes. Furthermore, EA serum down-regulated the level of RNA m6A and the expression levels of METTL3, MALAT1 and AQP4 in OGD/R condition, while overexpression of METTL3, MALAT1 and AQP4 reversed the down-regulatory effects of EA serum. EA serum attenuates OGD/R-induced astrocyte damage in vitro, and this protective role might be achieved by down-regulating the AQP4 via m6A methylation of MALAT1.

Can Serum GFAP and UCH-L1 Replace CT in Assessing Acute Ischemic Stroke Severity?

As acute ischemic stroke (AIS) is still a significant cause of morbidity globally, new methods of rapid diagnostics are continually being researched and improved. Still, the only definite way to diagnose AIS is radiological imaging. Lately, serum biomarkers glial fibrillary acidic protein (GFAP) and ubiquitin C-terminal hydrolase L1 (UCH-L1) have shown their usefulness in AIS as potential complementary tools in early recognition. We aimed to investigate if GFAP and UCH-L1 can correlate with comprehensive diagnostic information provided by computed tomography (CT) and several clinical parameters in AIS severity assessment and subsequently with clinical outcomes. Fifty-two patients with AIS and a potential for mechanical thrombectomy (MT) were included in our study. Thirty-seven patients underwent MT. Results showed no correlation of biomarkers with any analyzed CT parameter (thrombus length, volume, and density, clot burden score, collateral score, AIS core and penumbra volume, differences in perfusion between healthy and affected brain tissue). In addition, none of the clinical parameters, such as sex, symptom onset time, or the National Institutes of Health Stroke Scale, correlated with biomarkers. However, lower biomarker levels corresponded with a good clinical outcome, and higher levels to a poor outcome following hospital discharge, irrespective of the performed MT (p = 0.005 for GFAP, p = 0.001 for UCH-L1). In patients with successful MT, there were also differences between patients with a good clinical outcome compared with patients with a poor clinical outcome (p = 0.007 for GFAP, p = 0.004 for UCH-L1). In conclusion, these biomarkers cannot replace imaging modalities but can provide complementary diagnostic information in the setting of AIS.

SYSTEM XC- AS A MOLECULAR MECHANISM FOR EVOLUTIONARY NEW FORMS OF ADVANCED COGNITION

Human cognitive abilities are deeply rooted in evolutionary building blocks that maximize computation while maintaining efficiency. These abilities are not without evolutionary signatures; conserved processes like vision have undergone continual phylogenetic adjustments to better serve ecological niches. Conversely, more sophisticated forms of cognition may have required evolutionary innovations to transform existing neuronal processing to expand computational abilities. One such innovation is system xc- (Sxc), a cystine-glutamate antiporter predominantly localized to astrocytes that emerged in deuterostomes (e.g., vertebrates) after their divergence from protostomes over 550 million years ago. Previous evidence suggests that genetically modified rats that lack functional Sxc (MSxc) exhibit enhanced cocaine-seeking behavior. In this study, we deconstructed drug-seeking into its component behaviors, categorizing them as reliant on evolutionary conserved or newly evolved cognitive processes. Our results reveal that Sxc function is dispensable for conserved processes like visual, emotional, and hedonic processing, but critical for advanced, evolutionary new cognitive functions, particularly impulse control and decision making. Notably, we demonstrate a temporally specific reliance on Sxc during the learning phase of optimal decision-making, but not in maintaining established strategies. This is an important addition to our current understanding of astrocytes in non-homeostatic functions, indicating their critical role in computationally demanding phases of learning and memory. Unraveling evolutionary innovations like Sxc not only deepens our understanding of cognitive evolution but also paves the way for revolutionary, precision- targeted therapies in neuropsychiatric disorders, potentially transforming treatment paradigms and patient outcomes.

Uncovering Astrocyte Morphological Dynamics Using Optical Diffraction Tomography and Shape-Based Trajectory Inference

Astrocytes, integral components of the central nervous system, are increasingly recognized for their multifaceted roles beyond support cells. Despite their acknowledged importance, understanding the intricacies of astrocyte morphological dynamics remains limited. Our study marks the first exploration of astrocytes using optical diffraction tomography (ODT), establishing a label-free, quantitative method to observe morphological changes in astrocytes over a 7-day in-vitro period. ODT offers quantitative insights into cell volume, dry mass, and area through label-free, real-time measurements-capabilities that are challenging to achieve with conventional imaging techniques. Through comprehensive analysis of 3D refractive index maps and shape characterization techniques, we capture the developmental trajectory and dynamic morphological transformations of astrocytes. Specifically, our observations reveal increased area and a transition to larger, flattened shapes, with alterations in cell volume and density, indicating shifts in cellular composition. By employing unsupervised clustering and pseudotime trajectory analysis, we introduce a novel morphological trajectory inference for neural cells, tracking the morphological evolution of astrocytes from elongated to evenly spread shapes. This analysis marks the first use of trajectory inference based solely on morphology for neural cell types, laying a foundation for future studies employing ODT to examine astrocyte dynamics and neural cell interactions across diverse substrates.

Melanocortin 4 Receptor-Dependent Mechanism of ACTH in Preventing Anxiety-Like Behaviors and Normalizing Astrocyte Proteins after Early Life Seizures

Epilepsy, affecting millions globally, often leads to significant cognitive and psychiatric comorbidities, particularly in children. Anxiety and depression are particularly prevalent, with roughly a quarter of pediatric epilepsy patients having a comorbid diagnosis. Current treatments inadequately address these issues. Adrenocorticotropic hormone (ACTH), a melanocortin peptide, has shown promise in mitigating deficits after early-life seizures (ELS), potentially through mechanisms beyond its canonical action on the melanocortin 2 receptor. This study explores the hypothesis that recurrent ELS is associated with long-term anxiety and that treatment with ACTH can prevent this anxiety through a mechanism that involves the melanocortin 4 receptor (MC4R) in the brain. Our findings reveal that ACTH ameliorates anxiety-like behavior associated with ELS, without altering seizure parameters, in wild-type but not in male and female MC4R knock-out mice. Our findings also show that knocking-in MC4R in either neurons or astrocytes was able to rescue the anxiety-like behavior after ACTH treatment. Furthermore, our results show that ACTH normalizes important astrocytic proteins like glial fibrillary acidic protein and aquaporin-4 after ELS. This suggests that ACTH's beneficial effects on anxiety are mediated through MC4R activation in both neuronal and astrocytic populations. This study underscores the therapeutic potential of targeting MC4R as a treatment, highlighting its role in mitigating anxiety-like behaviors associated with ELS.

boron neutron capture therapy for glioblastoma: The delivery dilemma

This review delves into boron neutron capture therapy (BNCT), a targeted alpha-particle radiotherapy that holds promise in oncology and has the potential to address concerns of efficacy and safety associated to conventional cancer therapies. Information was gathered from literature searches that used the keywords "boron neutron capture therapy," "clinical application," "nanotechnology," and "liposome" so as to analyze the clinical applications of BNCT in cancer over time. The methodology includes a thorough literature review, analysis of preclinical studies, and clinical trials to assess the viability of BNCT in treating glioblastoma (GB), as an example of a hard-to-treat cancer type. Firstly, the fundamental principles of BNCT are outlined, followed by an extensive exploration of the respective application in oncology, particularly emphasizing its synergy with nanotechnology advancements. A key focus is placed on evaluating whether third-generation nanoparticles show superior efficacy compared to conventional boron-delivering systems used in BNCT. Additionally, attention is drawn to the critical analysis of safety concerns surrounding nanotechnology, which are crucial for clinical translation. Noteworthy is the clinical application of liposomes (LPs) in GB, highlighting their potential and limitations in clinical settings. Overall, the collected evidence sheds light on the high potential of BNCT in the research and development of new treatment (and diagnosis) modalities for GB and other cancer types.

The Frequency of a Magnetic Field Determines the Behavior of Tumor and Non-Tumor Nerve Cell Models

The involvement of magnetic fields in basic cellular processes has been studied for years. Most studies focus their results on a single frequency and intensity. Intensity has long been the central parameter in hypotheses of interaction between cells and magnetic fields; however, frequency has always played a secondary role. The main objective of this study was to obtain a specific frequency that allows a reduction in the viability and proliferation of glioblastoma (CT2A) and neuroblastoma (N2A) cell models. These were compared with an astrocyte cell model (C8D1A) (nontumor) to determine whether there is a specific frequency of response for each of the cell lines used. The CT2A, C8D1A, and N2A cell lines were exposed to a magnetic field of 100 µT and a variable frequency range between 20 and 100 Hz for 24, 48 and 72 h. The results fit a biological window model in which the viability and proliferation of N2A and CT2A cells decrease statistically significantly in a 50 Hz center of value window. In addition, the non-tumor cell model showed different behavior from tumor cell models depending on the applied frequency. These results are promising in the use of magnetic fields for therapeutic purposes.

Internalization of extracellular Tau oligomers in Alzheimer's disease

A key factor in the progression of Alzheimer's disease (AD) is internalization of extracellular Tau oligomers (ecTauOs) by neuroglial cells. Aberrant hyperphosphorylation of Tau results in their dissociation from microtubules and formation of toxic intracellular Tau oligomers (icTauOs). These are subsequently released to the extracellular space following neuronal dysfunction and death. Although receptor mediated internalization of these ecTauOs by other neurons, microglia and astrocytes can facilitate elimination, incomplete degradation thereof promotes inflammation, exacerbates pathologic spread and accelerates neurodegeneration. Targeting Tau oligomer degradation pathways, blocking internalization receptors, and mitigating neuroinflammation are proposed as therapeutic strategies to control Tau propagation and toxicity. This review highlights the urgent need for innovative approaches to prevent the spread of Tau pathology, emphasizing its implications for AD and related neurodegenerative diseases.

Mapping reactive astrogliosis in Parkinson's brain with astroglial tracers BU99008 and Deprenyl: New insights from a multi-marker postmortem study

BACKGROUND

Despite significant astrocytic involvement in Parkinson's disease (PD), the knowledge regarding the role of reactive astrogliosis is still at the surface level; largely due to lack of specific biomarkers to track these processes. Novel astroglial PET-tracers BU99008 and Deprenyl, hold immense potential for visualizing reactive astrogliosis in PD.  However, they have not been thoroughly investigated in PD.

METHODS

We employed a multi-marker approach and performed in vitro radioligand binding and autoradiography studies with 3H-BU99008 and 3H-Deprenyl together with astrocytic immunofluorescence and morphometric analyses in the frontal cortex, temporal cortex, caudate and putamen brain regions of PD (n = 4) and control (n = 7) cases.

RESULTS AND DISCUSSION

3H-BU99008 and 3H-Deprenyl showed distinct binding behavior and displayed a diverse array of binding sites (single or multiple) in PD and control brains. Importantly, 3H-BU99008 and 3H-Deprenyl autoradiography studies captured pronounced reactive astrogliosis in PD brain regions, corroborated by marked changes in astrocytic markers, morphology, and cellular processes.

HIGHLIGHTS

Astroglial tracers BU99008 and Deprenyl displayed a range of binding sites with different levels of affinity and proportions (%) in healthy control (CN) and Parkinson's disease (PD) brains. Astroglial tracers BU99008 and Deprenyl showed a highly specific (permanent) high-affinity (HA) binding site in the nanomolar range, which might be consistent across different pathologies. Astroglial tracers BU99008 and Deprenyl highlighted distinct tracer binding behavior, indicating that they might be targeting different subpopulations or specific states of astrocytes in CN and PD brains. Astroglial tracers BU99008 and Deprenyl captured prominent reactive astrogliosis at the advanced/end stages of PD, substantiated by a significant increase in intercellular adhesion molecule 1 (ICAM-1)-positive reactive astrocytes and marked changes in astrocytic morphology and processes.

The Rise of Pluripotent Stem Cell-Derived Glia Models of Neuroinflammation

Neuroinflammation is a blanket term that describes the body's complex inflammatory response in the central nervous system (CNS). It encompasses a phenotype shift to a proinflammatory state, the release of cytokines, the recruitment of peripheral immune cells, and a wide variety of other processes. Neuroinflammation has been implicated in nearly every major CNS disease ranging from Alzheimer's disease to brain cancer. Understanding and modeling neuroinflammation is critical for the identification of novel therapeutic targets in the treatment of CNS diseases. Unfortunately, the translation of findings from non-human models has left much to be desired. This review systematically discusses the role of human pluripotent stem cell (hPSC)-derived glia and supporting cells within the CNS, including astrocytes, microglia, oligodendrocyte precursor cells, pericytes, and endothelial cells, to describe the state of the field and hope for future discoveries. hPSC-derived cells offer an expanded potential to study the pathobiology of neuroinflammation and immunomodulatory cascades that impact disease progression. While much progress has been made in the development of models, there is much left to explore in the application of these models to understand the complex inflammatory response in the CNS.

Neuroligin-3 R451C induces gain-of-function gene expression in astroglia in an astroglia-enriched brain organoid model

Astroglia are integral to brain development and the emergence of neurodevelopmental disorders. However, studying the pathophysiology of human astroglia using brain organoid models has been hindered by inefficient astrogliogenesis. In this study, we introduce a robust method for generating astroglia-enriched organoids through BMP4 treatment during the neural differentiation phase of organoid development. Our RNA sequencing analysis reveals that astroglia developed within these organoids exhibit advanced developmental characteristics and enhanced synaptic functions compared to those grown under traditional two-dimensional conditions, particularly highlighted by increased neurexin (NRXN)-neuroligin (NLGN) signaling. Cell adhesion molecules, such as NRXN and NLGN, are essential in regulating interactions between astroglia and neurons. We further discovered that brain organoids derived from human embryonic stem cells (hESCs) harboring the autism-associated NLGN3 R451C mutation exhibit increased astrogliogenesis. Notably, the NLGN3 R451C astroglia demonstrate enhanced branching, indicating a more intricate morphology. Interestingly, our RNA sequencing data suggest that these mutant astroglia significantly upregulate pathways that support neural functions when compared to isogenic wild-type astroglia. Our findings establish a novel astroglia-enriched organoid model, offering a valuable platform for probing the roles of human astroglia in brain development and related disorders.

Dialogue mechanisms between astrocytic and neuronal networks: A whole-brain modelling approach

Astrocytes critically shape whole-brain structure and function by forming extensive gap junctional networks that intimately and actively interact with neurons. Despite their importance, existing computational models of whole-brain activity ignore the roles of astrocytes while primarily focusing on neurons. Addressing this oversight, we introduce a biophysical neural mass network model, designed to capture the dynamic interplay between astrocytes and neurons via glutamatergic and GABAergic transmission pathways. This network model proposes that neural dynamics are constrained by a two-layered structural network interconnecting both astrocytic and neuronal populations, allowing us to investigate astrocytes' modulatory influences on whole-brain activity and emerging functional connectivity patterns. By developing a simulation methodology, informed by bifurcation and multilayer network theories, we demonstrate that the dialogue between astrocytic and neuronal networks manifests over fast-slow fluctuation mechanisms as well as through phase-amplitude connectivity processes. The findings from our research represent a significant leap forward in the modeling of glial-neuronal collaboration, promising deeper insights into their collaborative roles across health and disease states.

Ku70 silencing aggravates oxygen-glucose deprivation/reperfusion-induced injury by activation of the p53 apoptotic pathway in rat cortical astrocytes

Oxidative stress-induced DNA damage is an important mechanism that leads to the death of neuronal cells after ischemic stroke. Our previous study found that Ku70 was highly expressed in ischemic brain tissue of rats after cerebral ischemia-reperfusion injury. However, the role of Ku70 in glucose-oxygen deprivation/reperfusion (OGD/R) in astrocytes has not been reported. Therefore, we investigated the effect and mechanism of Ku70 on OGD/R-induced astrocyte injury in rats. Rat astrocytes were cultured in vitro to establish the OGD/R-induced injury model and transfected with small interfering RNA (siRNA) to disturb Ku70 expression. Real-time quantitative polymerase chain reaction (RT-qPCR), western blotting, and immunofluorescence were performed to assay the expression of mRNA and proteins. Cell viability, apoptosis, and ROS accumulation were determined by CCK-8 assay, flow cytometry, and fluorescence microscopy, respectively. Our results showed Ku70 can be expressed in both the nucleus and cytoplasm of astrocytes, although mainly in the nucleus. Ku70 expression showed a trend of first increasing and then decreasing after OGD/R, reaching its highest change at 24 h of reoxygenation. OGD/R induced ROS production and DNA damage in rat astrocytes, and Ku70 silencing further increased ROS production and DNA lesions, which aggravated astrocyte injury and apoptosis. Furthermore, the expression of p53, Bax, and caspase 3 proteins significantly increased after OGD/R in astrocytes, and downregulation of Ku70 further enhanced expression of the above proteins. These results indicate that Ku70 silencing promotes OGD/R-induced astrocyte apoptosis, which may be associated with p53 apoptotic pathway activation. Our study suggests that Ku70 may be a novel target for cerebral ischemia-reperfusion injury therapy.

Pathology and Treatments of Alzheimer's Disease Based on Considering Changes in Brain Energy Metabolism Due to Type 2 Diabetes

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with cognitive dysfunction, memory decline, and behavioral disturbance, and it is pathologically characterized by the accumulation of amyloid plaques and neurofibrillary tangles in the brain. Although various hypotheses have been proposed to explain the pathogenesis of AD, including the amyloid beta hypothesis, oxidative stress hypothesis, and abnormal phosphorylation of tau proteins, the exact pathogenic mechanisms underlying AD remain largely undefined. Furthermore, effective curative treatments are very limited. Epidemiologic studies provide convincing evidence for a significant association between type 2 diabetes and AD. Here, we showed energy metabolism using glucose, lactate, ketone bodies, and lipids as energy substrates in a normal brain, and changes in such energy metabolism due to type 2 diabetes. We also showed the influences of such altered energy metabolism due to type 2 diabetes on the pathology of AD. Furthermore, we comprehensively searched for risk factors related with type 2 diabetes for AD and showed possible therapeutic interventions based on considering risk factors and altered brain energy metabolism due to type 2 diabetes for the development of AD.

Mitochondrial dysfunction of Astrocyte induces cell activation under high salt condition

Excess dietary sodium can accumulate in brain and adversely affect human health. We have confirmed in previous studies that high salt can induce activation of astrocyte manifested by the secretion of various inflammatory factors. In order to further explore the effect of high salt on the internal cell metabolism of astrocytes, RNA sequencing was performed on astrocytes under high salt environment, which indicated the oxidative phosphorylation and glycolysis pathways of astrocytes were downregulated. Next, we found that high salt concentrations elicited astrocyte mitochondrial morphology change, as evidenced by swelling from a short rod to a round shape through a High Intelligent and Sensitive Structured Illumination Microscope (HIS-SIM). Furthermore, we found that high salt concentrations reduced astrocyte mitochondrial oxygen consumption and membrane potential. Treatment with 18-kDa translocator protein (TSPO) ligands FGIN-1-27 improved mitochondrial networks and reversed astrocyte activation under high-salt circumstances. Our study shows that high salt can directly disrupt astrocytic mitochondrial homeostasis and function. Targeting translocator protein signaling may have therapeutic potential against high-salt neurotoxicity.

The role of astrocytes response triggered by hyperglycaemia during spinal cord injury

OBJECTIVE

This manuscript aimed to provide a comprehensive overview of the physiological, molecular, and cellular mechanisms triggered by reactive astrocytes (RA) in the context of spinal cord injury (SCI), with a particular focus on cases involving hyperglycaemia.

METHODS

The compilation of articles related to astrocyte responses in neuropathological conditions, with a specific emphasis on those related to SCI and hyperglycaemia, was conducted by searching through databases including Science Direct, Web of Science, and PubMed.

RESULTS AND CONCLUSIONS

This article explores the dual role of astrocytes in both neurophysiological and neurodegenerative conditions within the central nervous system (CNS). In the aftermath of SCI and hyperglycaemia, astrocytes undergo a transformation into RA, adopting a distinct phenotype. While there are currently no approved therapies for SCI, various therapeutic strategies have been proposed to alleviate the detrimental effects of RAs following SCI and hyperglycemia. These strategies show promising potential in the treatment of SCI and its likely comorbidities.

Role of astrocytes in Alzheimer's disease pathogenesis and the impact of exercise-induced remodeling

Alzheimer's disease (AD) is a prevalent and debilitating brain disorder that worsens progressively with age, characterized by cognitive decline and memory impairment. The accumulation of amyloid-beta (Aβ) leading to amyloid plaques and hyperphosphorylation of Tau, resulting in intracellular neurofibrillary tangles (NFTs), are primary pathological features of AD. Despite significant research investment and effort, therapies targeting Aβ and NFTs have proven limited in efficacy for treating or slowing AD progression. Consequently, there is a growing interest in non-invasive therapeutic strategies for AD prevention. Exercise, a low-cost and non-invasive intervention, has demonstrated promising neuroprotective potential in AD prevention. Astrocytes, among the most abundant glial cells in the brain, play essential roles in various physiological processes and are implicated in AD initiation and progression. Exercise delays pathological progression and mitigates cognitive dysfunction in AD by modulating astrocyte morphological and phenotypic changes and fostering crosstalk with other glial cells. This review aims to consolidate the current understanding of how exercise influences astrocyte dynamics in AD, with a focus on elucidating the molecular and cellular mechanisms underlying astrocyte remodeling. The review begins with an overview of the neuropathological changes observed in AD, followed by an examination of astrocyte dysfunction as a feature of the disease. Lastly, the review explores the potential therapeutic implications of exercise-induced astrocyte remodeling in the context of AD.

Structural and molecular characterization of astrocyte and vasculature connectivity in the mouse hippocampus and cortex

The relation of astrocytic endfeet to the vasculature plays a key functional role in the neuro-glia-vasculature unit. We characterize the spatial organization of astrocytes and the structural aspects that facilitate their involvement in molecular exchanges. Using double transgenic mice, we performed co-immunostaining, confocal microscopy, and three-dimensional digital segmentation to investigate the biophysical and molecular organization of astrocytes and their intricate endfoot network at the micrometer level in the isocortex and hippocampus. The results showed that hippocampal astrocytes had smaller territories, reduced endfoot dimensions, and fewer contacts with blood vessels compared with those in the isocortex. Additionally, we found that both connexins 43 and 30 have a higher density in the endfoot and the former is overexpressed relative to the latter. However, due to the limitations of the method, further studies are needed to determine the exact localization on the endfoot. The quantitative information obtained in this study will be useful for modeling the interactions of astrocytes with the vasculature.

Sex Differences in Astrocyte Activity

Astrocytes are essential for maintaining brain homeostasis. Alterations in their activity have been associated with various brain pathologies. Sex differences were reported to affect astrocyte development and activity, and even susceptibility to different neurodegenerative diseases. This review aims to summarize the current knowledge on the effects of sex on astrocyte activity in health and disease.

Astrocytes and microglia in the coordination of CNS development and homeostasis

Glia have emerged as important architects of central nervous system (CNS) development and maintenance. While traditionally glial contributions to CNS development and maintenance have been studied independently, there is growing evidence that either suggests or documents that glia may act in coordinated manners to effect developmental patterning and homeostatic functions in the CNS. In this review, we focus on astrocytes, the most abundant glia in the CNS, and microglia, the earliest glia to colonize the CNS highlighting research that documents either suggestive or established coordinated actions by these glial cells in various CNS processes including cell and/or debris clearance, neuronal survival and morphogenesis, synaptic maturation, and circuit function, angio-/vasculogenesis, myelination, and neurotransmission. Some molecular mechanisms underlying these processes that have been identified are also described. Throughout, we categorize the available evidence as either suggestive or established interactions between microglia and astrocytes in the regulation of the respective process and raise possible avenues for further research. We conclude indicating that a better understanding of coordinated astrocyte-microglial interactions in the developing and mature brain holds promise for developing effective therapies for brain pathologies where these processes are perturbed.

The challenges to detect, quantify, and characterize viral reservoirs in the current antiretroviral era

A major barrier to cure HIV is the early generation of viral reservoirs in tissues. These viral reservoirs can contain intact or defective proviruses, but both generates low levels of viral proteins contribute to chronic bystander damage even in the ART era. Most viral reservoir detection techniques are limited to blood-based, reactivation, and sequencing assays that lack spatial properties to examine the contribution of the host's microenvironment to latency and cure efforts. Currently, little is known about the contribution of the microenvironment to viral reservoir survival, residual viral expression, and associated inflammation. Only a few spatiotemporal techniques are available, and fewer integrate spatial genomics, transcriptomics, and proteomics into the analysis of the viral reservoir microenvironment-all essential components to cure HIV. During the development of these spatial techniques, many considerations need to be included in the analysis to avoid misinterpretation. This manuscript tries to clarify some critical concepts in viral reservoir detection by spatial techniques and the upcoming opportunities for cure efforts.

The functions of exosomes targeting astrocytes and astrocyte-derived exosomes targeting other cell types

Astrocytes are the most abundant glial cells in the central nervous system; they participate in crucial biological processes, maintain brain structure, and regulate nervous system function. Exosomes are cell-derived extracellular vesicles containing various bioactive molecules including proteins, peptides, nucleotides, and lipids secreted from their cellular sources. Increasing evidence shows that exosomes participate in a communication network in the nervous system, in which astrocyte-derived exosomes play important roles. In this review, we have summarized the effects of exosomes targeting astrocytes and the astrocyte-derived exosomes targeting other cell types in the central nervous system. We also discuss the potential research directions of the exosome-based communication network in the nervous system. The exosome-based intercellular communication focused on astrocytes is of great significance to the biological and/or pathological processes in different conditions in the brain. New strategies may be developed for the diagnosis and treatment of neurological disorders by focusing on astrocytes as the central cells and utilizing exosomes as communication mediators.

Brain stars take the lead during critical periods of early postnatal brain development: relevance of astrocytes in health and mental disorders

In the brain, astrocytes regulate shape and functions of the synaptic and vascular compartments through a variety of released factors and membrane-bound proteins. An imbalanced astrocyte activity can therefore have drastic negative impacts on brain development, leading to the onset of severe pathologies. Clinical and pre-clinical studies show alterations in astrocyte cell number, morphology, molecular makeup and astrocyte-dependent processes in different affected brain regions in neurodevelopmental (ND) and neuropsychiatric (NP) disorders. Astrocytes proliferate, differentiate and mature during the critical period of early postnatal brain development, a time window of elevated glia-dependent regulation of a proper balance between synapse formation/elimination, which is pivotal in refining synaptic connectivity. Therefore, any intrinsic and/or extrinsic factors altering these processes during the critical period may result in an aberrant synaptic remodeling and onset of mental disorders. The peculiar bridging position of astrocytes between synaptic and vascular compartments further allows them to "compute" the brain state and consequently secrete factors in the bloodstream, which may serve as diagnostic biomarkers of distinct healthy or disease conditions. Here, we collect recent advancements regarding astrogenesis and astrocyte-mediated regulation of neuronal network remodeling during early postnatal critical periods of brain development, focusing on synapse elimination. We then propose alternative hypotheses for an involvement of aberrancies in these processes in the onset of ND and NP disorders. In light of the well-known differential prevalence of certain brain disorders between males and females, we also discuss putative sex-dependent influences on these neurodevelopmental events. From a translational perspective, understanding age- and sex-dependent astrocyte-specific molecular and functional changes may help to identify biomarkers of distinct cellular (dys)functions in health and disease, favouring the development of diagnostic tools or the selection of tailored treatment options for male/female patients.

Inflammatory aspects of Alzheimer's disease

Alzheimer´s disease (AD) stands out as the most common chronic neurodegenerative disorder. AD is characterized by progressive cognitive decline and memory loss, with neurodegeneration as its primary pathological feature. The role of neuroinflammation in the disease course has become a focus of intense research. While microglia, the brain's resident macrophages, have been pivotal to study central immune inflammation, recent evidence underscores the contributions of other cellular entities to the neuroinflammatory process. In this article, we review the inflammatory role of microglia and astrocytes, focusing on their interactions with AD's core pathologies, amyloid beta deposition, and tau tangle formation. Additionally, we also discuss how different modes of regulated cell death in AD may impact the chronic neuroinflammatory environment. This review aims to highlight the evolving landscape of neuroinflammatory research in AD and underscores the importance of considering multiple cellular contributors when developing new therapeutic strategies.

Novel strategies in Parkinson's disease treatment: a review

An unprecedented extension of life expectancy observed during the past century drastically increased the number of patients diagnosed with Parkinson's diseases (PD) worldwide. Estimated costs of PD alone reached $52 billion per year, making effective neuroprotective treatments an urgent and unmet need. Current treatments of both AD and PD focus on mitigating the symptoms associated with these pathologies and are not neuroprotective. In this review, we discuss the most advanced therapeutic strategies that can be used to treat PD. We also critically review the shift of the therapeutic paradigm from a small molecule-based inhibition of protein aggregation to the utilization of natural degradation pathways and immune cells that are capable of degrading toxic amyloid deposits in the brain of PD patients.

A Novel Approach to Increase Glial Cell Populations in Brain Microphysiological Systems

Brain microphysiological systems (bMPS) recapitulate human brain cellular architecture and functionality more closely than traditional monolayer cultures and have become increasingly relevant for the study of neurological function in health and disease. Existing 3D brain models vary in reflecting the relative populations of different cell types present in the human brain. Most models consist mainly of neurons, while glial cells represent a smaller portion of the cell populations. Here, by means of a chemically defined glial-enriched medium (GEM), an improved method to expand the population of astrocytes and oligodendrocytes without compromising neuronal differentiation in bMPS, is presented. An important finding is that astrocytes also change in morphology when cultured in GEM, more closely recapitulating primary culture astrocytes. GEM bMPS are electro-chemically active and show different patterns of calcium staining and flux. Synaptic vesicles and terminals observed by electron microscopy are also present. No significant changes in neuronal differentiation are observed by gene expression, however, GEM enhanced neurite outgrowth and cell migration, and differentially modulated neuronal maturation in two different cell lines. These results have the potential to significantly improve functionality of bMPS for the study of neurological diseases and drug discovery, contributing to the unmet need for safe human models.

Region-specific and age-related differences in astrocytes in the human brain

Astrocyte heterogeneity and its relation to aging in the normal human brain remain poorly understood. We here analyzed astrocytes in gray and white matter brain tissues obtained from donors ranging in age between the neonatal period to over 100 years. We show that astrocytes are differently distributed with higher density in the white matter. This regional difference in cellular density becomes less prominent with age. Additionally, we confirm the presence of morphologically distinct astrocytes, with gray matter astrocytes being morphologically more complex. Notably, gray matter astrocytes morphologically change with age, while white matter astrocytes remain relatively consistent in morphology. Using regional mass spectrometry-based proteomics, we did, however, identify astrocyte specific proteins with regional differences in abundance, reflecting variation in cellular density or expression level. Importantly, the expression of some astrocyte specific proteins region-dependently decreases with age. Taken together, we provide insights into region- and age-related differences in astrocytes in the human brain.

The Role of Astrocytes in Migraine with Cortical Spreading Depression: Protagonists or Bystanders? A Narrative Review

Cortical spreading depression (CSD) is a slow wave of cortical depolarization closely associated with migraines with an aura. Previously, it was thought that CSD depolarization was mainly driven by neurons, with characteristic changes in neuronal swelling and increased extracellular potassium (K+) and glutamate. However, the role of astrocytes, a member of the neurovascular unit, in migraine with CSD has recently received increasing attention. In the early stages of CSD, astrocytes provide neurons with energy support and clear K+ and glutamate from synaptic gaps. However, in the late stages of CSD, astrocytes release large amounts of lactic acid to exacerbate hypoxia when the energy demand exceeds the astrocytes' compensatory capacity. Astrocyte endfoot swelling is a characteristic of CSD, and neurons are not similarly altered. It is primarily due to K+ influx and abnormally active calcium (Ca2+) signaling. Aquaporin 4 (AQP-4) only mediates K+ influx and has little role as an aquaporin. Astrocytes endfoot swelling causes perivascular space closure, slowing the glymphatic system flow and exacerbating neuroinflammation, leading to persistent CSD. Astrocytes are double-edged swords in migraine with CSD and may be potential targets for CSD interventions.

Enteric Glia and Brain Astroglia: Complex Communication in Health and Disease along the Gut-Brain Axis

Several studies have provided interesting evidence about the role of the bidirectional communication between the gut and brain in the onset and development of several pathologic conditions, including inflammatory bowel diseases (IBDs), neurodegenerative diseases, and related comorbidities. Indeed, patients with IBD can experience neurologic disorders, including depression and cognitive impairment, besides typical intestinal symptoms. In parallel, patients with neurodegenerative disease, such as Parkinson disease and Alzheimer disease, are often characterized by the occurrence of functional gastrointestinal disorders. In this context, enteric glial cells and brain astrocytes are emerging as pivotal players in the initiation/maintenance of neuroinflammatory responses, which appear to contribute to the alterations of intestinal and neurologic functions observed in patients with IBD and neurodegenerative disorders. The present review was conceived to provide a comprehensive and critical overview of the available knowledge on the morphologic, molecular, and functional changes occurring in the enteric glia and brain astroglia in IBDs and neurologic disorders. In addition, our intent is to identify whether such alterations could represent a common denominator involved in the onset of comorbidities associated with the aforementioned disorders. This might help to identify putative targets useful to develop novel pharmacologic approaches for the therapeutic management of such disturbances.

Glial cells in the mammalian olfactory bulb

The mammalian olfactory bulb (OB), an essential part of the olfactory system, plays a critical role in odor detection and neural processing. Historically, research has predominantly focused on the neuronal components of the OB, often overlooking the vital contributions of glial cells. Recent advancements, however, underscore the significant roles that glial cells play within this intricate neural structure. This review discus the diverse functions and dynamics of glial cells in the mammalian OB, mainly focused on astrocytes, microglia, oligodendrocytes, olfactory ensheathing cells, and radial glia cells. Each type of glial contributes uniquely to the OB's functionality, influencing everything from synaptic modulation and neuronal survival to immune defense and axonal guidance. The review features their roles in maintaining neural health, their involvement in neurodegenerative diseases, and their potential in therapeutic applications for neuroregeneration. By providing a comprehensive overview of glial cell types, their mechanisms, and interactions within the OB, this article aims to enhance our understanding of the olfactory system's complexity and the pivotal roles glial cells play in both health and disease.

Integrated platform for multiscale molecular imaging and phenotyping of the human brain

Understanding cellular architectures and their connectivity is essential for interrogating system function and dysfunction. However, we lack technologies for mapping the multiscale details of individual cells and their connectivity in the human organ-scale system. We developed a platform that simultaneously extracts spatial, molecular, morphological, and connectivity information of individual cells from the same human brain. The platform includes three core elements: a vibrating microtome for ultraprecision slicing of large-scale tissues without losing cellular connectivity (MEGAtome), a polymer hydrogel-based tissue processing technology for multiplexed multiscale imaging of human organ-scale tissues (mELAST), and a computational pipeline for reconstructing three-dimensional connectivity across multiple brain slabs (UNSLICE). We applied this platform for analyzing human Alzheimer's disease pathology at multiple scales and demonstrating scalable neural connectivity mapping in the human brain.

The role of glial cells in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) has traditionally been considered a neuron-centric disease. This view is now outdated, with increasing recognition of cell autonomous and non-cell autonomous contributions of central and peripheral nervous system glia to ALS pathomechanisms. With glial research rapidly accelerating, we comprehensively interrogate the roles of astrocytes, microglia, oligodendrocytes, ependymal cells, Schwann cells and satellite glia in nervous system physiology and ALS-associated pathology. Moreover, we highlight the inter-glial, glial-neuronal and inter-system polylogue which constitutes the healthy nervous system and destabilises in disease. We also propose classification based on function for complex glial reactive phenotypes and discuss the pre-requisite for integrative modelling to advance translation. Given the paucity of life-enhancing therapies currently available for ALS patients, we discuss the promising potential of harnessing glia in driving ALS therapeutic discovery.

Effect of total flavonoids of Dracocephalum moldavica L. On neuroinflammation in Alzheimer's disease model amyloid-β (Aβ1-42)-peptide-induced astrocyte activation

One of the main pathological features noted in Alzheimer's disease (AD) is the presence of plagues of aggregated β-amyloid (Aβ1-42)-peptides. Excess deposition of amyloid-β oligomers (AβO) are known to promote neuroinflammation. Sequentially, following neuroinflammation astrocytes become activated with cellular characteristics to initiate activated astrocytes. The purpose of this study was to determine whether total flavonoids derived from Dracocephalum moldavica L. (TFDM) inhibited Aβ1-42-induced damage attributed to activated C8-D1A astrocytes. Western blotting and ELISA were used to determine the expression of glial fibrillary acidic protein (GFAP), and complement C3 to establish the activation status of astrocytes following induction from exposure to Aβ1-42. Data demonstrated that stimulation of C8-D1A astrocytes by treatment with 40 μM Aβ1-42 for 24 hr produced significant elevation in protein expression and protein levels of acidic protein (GFAP) and complement C3 accompanied by increased expression and levels of inflammatory cytokines. Treatment with TFDM or the clinically employed drug donepezil in AD therapy reduced production of inflammatory cytokines, and toxicity initiated following activation of C8-D1A astrocytes following exposure to Aβ1-42. Therefore, TFDM similar to donepezil inhibited inflammatory secretion in reactive astrocytes, suggesting that TFDM may be considered as a potential compound to be utilized in AD therapy.

The deletion of AQP4 and TRPV4 affects astrocyte swelling/volume recovery in response to ischemia-mimicking pathologies

Introduction

Astrocytic Transient receptor potential vanilloid 4 (TRPV4) channels, together with Aquaporin 4 (AQP4), are suspected to be the key players in cellular volume regulation, and therefore may affect the development and severity of cerebral edema during ischemia. In this study, we examined astrocytic swelling/volume recovery in mice with TRPV4 and/or AQP4 deletion in response to in vitro ischemic conditions, to determine how the deletion of these channels can affect the development of cerebral edema.

Methods

We used three models of ischemia-related pathological conditions: hypoosmotic stress, hyperkalemia, and oxygenglucose deprivation (OGD), and observed their effect on astrocyte volume changes in acute brain slices of Aqp4-/-, Trpv4-/- and double knockouts. In addition, we employed single-cell RT-qPCR to assess the effect of TRPV4 and AQP4 deletion on the expression of other ion channels and transporters involved in the homeostatic functioning of astrocytes.

Results

Quantification of astrocyte volume changes during OGD revealed that the deletion of AQP4 reduces astrocyte swelling, while simultaneous deletion of both AQP4 and TRPV4 leads to a disruption of astrocyte volume recovery during the subsequent washout. Of note, astrocyte exposure to hypoosmotic stress or hyperkalemia revealed no differences in astrocyte swelling in the absence of AQP4, TRPV4, or both channels. Moreover, under ischemia-mimicking conditions, we identified two distinct subpopulations of astrocytes with low and high volumetric responses (LRA and HRA), and their analyses revealed that mainly HRA are affected by the deletion of AQP4, TRPV4, or both channels. Furthermore, gene expression analysis revealed reduced expression of the ion transporters KCC1 and ClC2 as well as the receptors GABAB and NMDA in Trpv4-/- mice. The deletion of AQP4 instead caused reduced expression of the serine/cysteine peptidase inhibitor Serpina3n.

Discussion

Thus, we showed that in AQP4 or TRPV4 knockouts, not only the specific function of these channels is affected, but also the expression of other proteins, which may modulate the ischemic cascade and thus influence the final impact of ischemia.

Brain energy metabolism: A roadmap for future research

Although we have learned much about how the brain fuels its functions over the last decades, there remains much still to discover in an organ that is so complex. This article lays out major gaps in our knowledge of interrelationships between brain metabolism and brain function, including biochemical, cellular, and subcellular aspects of functional metabolism and its imaging in adult brain, as well as during development, aging, and disease. The focus is on unknowns in metabolism of major brain substrates and associated transporters, the roles of insulin and of lipid droplets, the emerging role of metabolism in microglia, mysteries about the major brain cofactor and signaling molecule NAD+, as well as unsolved problems underlying brain metabolism in pathologies such as traumatic brain injury, epilepsy, and metabolic downregulation during hibernation. It describes our current level of understanding of these facets of brain energy metabolism as well as a roadmap for future research.

Identification of the abnormalities in astrocytic functions as potential drug targets for neurodegenerative disease

INTRODUCTION

Historically, astrocytes were seen primarily as a supportive cell population within the brain; with neurodegenerative disease research focusing exclusively on malfunctioning neurons. However, astrocytes perform numerous tasks that are essential for maintenance of the central nervous system`s complex processes. Disruption of these functions can have negative consequences; hence, it is unsurprising to observe a growing amount of evidence for the essential role of astrocytes in the development and progression of neurodegenerative diseases. Targeting astrocytic functions may serve as a potential disease-modifying drug therapy in the future.

AREAS COVERED

The present review emphasizes the key astrocytic functions associated with neurodegenerative diseases and explores the possibility of pharmaceutical interventions to modify these processes. In addition, the authors provide an overview of current advancement in this field by including studies of possible drug candidates.

EXPERT OPINION

Glial research has experienced a significant renaissance in the last quarter-century. Understanding how disease pathologies modify or are caused by astrocyte functions is crucial when developing treatments for brain diseases. Future research will focus on building advanced models that can more precisely correlate to the state in the human brain, with the goal of routinely testing therapies in these models.

Sex-Specific Regulation of Stress Susceptibility by the Astrocytic Gene Htra1

Major depressive disorder (MDD) is linked to impaired structural and synaptic plasticity in limbic brain regions. Astrocytes, which regulate synapses and are influenced by chronic stress, likely contribute to these changes. We analyzed astrocyte gene profiles in the nucleus accumbens (NAc) of humans with MDD and mice exposed to chronic stress. Htra1 , which encodes an astrocyte-secreted protease targeting the extracellular matrix (ECM), was significantly downregulated in the NAc of males but upregulated in females in both species. Manipulating Htra1 in mouse NAc astrocytes bidirectionally controlled stress susceptibility in a sex-specific manner. Such Htra1 manipulations also altered neuronal signaling and ECM structural integrity in NAc. These findings highlight astroglia and the brain's ECM as key mediators of sex-specific stress vulnerability, offering new approaches for MDD therapies.

Neuroprotective role of lactate in a human in vitro model of the ischemic penumbra

In patients suffering from cerebral ischemic stroke, there is an urgent need for treatments to protect stressed yet viable brain cells. Recently, treatment strategies that induce neuronal activity have been shown to be neuroprotective. Here, we hypothesized that neuronal activation might maintain or trigger the astrocyte-to-neuron lactate shuttle (ANLS), whereby lactate is released from astrocytes to support the energy requirements of ATP-starved hypoxic neurons, and this leads to the observed neuroprotection. We tested this by using a human cell based in vitro model of the ischemic penumbra and investigating whether lactate might be neuroprotective in this setting. We found that lactate transporters are involved in the neuroprotective effect mediated by neuronal activation. Furthermore, we showed that lactate exogenously administered before hypoxia correlated with neuroprotection in our cellular model. In addition, stimulation of astrocyte with consequent endogenous production of lactate resulted in neuroprotection. To conclude, here we presented evidence that lactate transport into neurons contributes to neuroprotection during hypoxia providing a potential basis for therapeutic approaches in ischemic stroke.

Alzheimer's Disease: A Review of Pathology, Current Treatments, and the Potential Therapeutic Effect of Decreasing Oxidative Stress by Combined Vitamin D and l-Cysteine Supplementation

Significance: Excess oxidative stress and neuroinflammation are risk factors in the onset and progression of Alzheimer's disease (AD) and its association with amyloid-β plaque accumulation. Oxidative stress impairs acetylcholine (ACH) and N-methyl-d-aspartate receptor signaling in brain areas that function in memory and learning. Glutathione (GSH) antioxidant depletion positively correlates with the cognitive decline in AD subjects. Treatments that upregulate GSH and ACH levels, which simultaneously decrease oxidative stress and inflammation, may be beneficial for AD. Recent Advances: Some clinical trials have shown a benefit of monotherapy with vitamin D (VD), whose deficiency is linked to AD or with l-cysteine (LC), a precursor of GSH biosynthesis, in reducing mild cognitive impairment. Animal studies have shown a simultaneous decrease in ACH esterase (AChE) and increase in GSH; combined supplementation with VD and LC results in a greater decrease in oxidative stress and inflammation, and increase in GSH levels compared with monotherapy with VD or LC. Therefore, cosupplementation with VD and LC has the potential of increasing GSH, downregulation of oxidative stress, and decreased inflammation and AChE levels. Future Directions: Clinical trials are needed to determine whether safe low-cost dietary supplements, using combined VD+LC, have the potential to alleviate elevated AChE, oxidative stress, and inflammation levels, thereby halting the onset of AD. Goal of Review: The goal of this review is to highlight the pathological hallmarks and current Food and Drug Administration-approved treatments for AD, and discuss the potential therapeutic effect that cosupplementation with VD+LC could manifest by increasing GSH levels in patients. Antioxid. Redox Signal. 40, 663-678.