Astrocytes and brain injury

Lessons from the physiological role of guanosine in neurodegeneration and cancer: Toward a multimodal mechanism of action?

Neurodegenerative diseases and brain tumours represent important health challenges due to their severe nature and debilitating consequences that require substantial medical care. Interestingly, these conditions share common physiological characteristics, namely increased glutamate, and adenosine transmission, which are often associated with cellular dysregulation and damage. Guanosine, an endogenous nucleoside, is safe and exerts neuroprotective effects in preclinical models of excitotoxicity, along with cytotoxic effects on tumour cells. However, the lack of well-defined mechanisms of action for guanosine hinders a comprehensive understanding of its physiological effects. In fact, the absence of specific receptors for guanosine impedes the development of structure-activity research programs to develop guanosine derivatives for therapeutic purposes. Alternatively, given its apparent interaction with the adenosinergic system, it is plausible that guanosine exerts its neuroprotective and anti-tumorigenic effects by modulating adenosine transmission through undisclosed mechanisms involving adenosine receptors, transporters, and purinergic metabolism. Here, several potential molecular mechanisms behind the protective actions of guanosine will be discussed. First, we explore its potential interaction with adenosine receptors (A1R and A2AR), including the A1R-A2AR heteromer. In addition, we consider the impact of guanosine on extracellular adenosine levels and the role of guanine-based purine-converting enzymes. Collectively, the diverse cellular functions of guanosine as neuroprotective and antiproliferative agent suggest a multimodal and complementary mechanism of action.

Bibliometric analysis of research progress on tetramethylpyrazine and its effects on ischemia-reperfusion injury

In recent decades, natural products have attracted worldwide attention and become one of the most important resources for pharmacological industries and medical sciences to identify novel drug candidates for disease treatment. Tetramethylpyrazine (TMP) is an alkaloid extracted from Ligusticum chuanxiong Hort., which has shown great therapeutic potential in cardiovascular and cerebrovascular diseases, liver and renal injury, as well as cancer. In this review, we analyzed 1270 papers published on the Web of Science Core Collection from 2002 to 2022 and found that TMP exerted significant protective effects on ischemia-reperfusion (I/R) injury that is the cause of pathological damages in a variety of conditions, such as ischemic stroke, myocardial infarction, acute kidney injury, and liver transplantation. TMP is limited in clinical applications to some extent due to its rapid metabolism, a short biological half-life and poor bioavailability. Obviously, the structural modification, administration methods and dosage forms of TMP need to be further investigated in order to improve its bioavailability. This review summarizes the clinical applications of TMP, elucidates its potential mechanisms in protecting I/R injury, provides strategies to improve bioavailability, which presents a comprehensive understanding of the important compound. Hopefully, the information and knowledge from this review can help researchers and physicians to better improve the applications of TMP in the clinic.

Therapeutic efficacy of cinnamein, a component of balsam of Tolu/Peru, in controlled cortical impact mouse model of TBI

Traumatic brain injury (TBI) remains a major health concern which causes long-term neurological disability particularly in war veterans, athletes and young adults. In spite of intense clinical and research investigations, there is no effective therapy to cease the pathogenesis of the disease. It is believed that axonal injury during TBI is potentiated by neuroinflammation and demyelination and/or failure to remyelination. This study highlights the use of naturally available cinnamein, also chemically known as benzyl cinnamate, in inhibiting neuroinflammation, promoting remyelination and combating the disease process of controlled cortical impact (CCI)-induced TBI in mice. Oral delivery of cinnamein through gavage brought down the activation of microglia and astrocytes to decrease the expression of inducible nitric oxide synthase (iNOS), glial fibrillary acidic protein (GFAP) and ionized calcium binding adaptor molecule 1 (Iba1) in hippocampus and cortex of TBI mice. Cinnamein treatment also stimulated remyelination in TBI mice as revealed by PLP and A2B5 double-labeling, luxol fast blue (LFB) staining and axonal double-labeling for neurofilament and MBP. Furthermore, oral cinnamein reduced the size of lesion cavity in the brain, improved locomotor functions and restored memory and learning in TBI mice. These results suggest a new neuroprotective property of cinnamein that may be valuable in the treatment of TBI.

Expression of G2019S LRRK2 in Rat Primary Astrocytes Mediates Neurotoxicity and Alters the Dopamine Synthesis Pathway in N27 Cells via Astrocytic Proinflammatory Cytokines and Neurotrophic Factors

Astrocytes in the brain contribute to various essential functions, including maintenance of the neuronal framework, survival, communication, metabolic processes, and neurotransmitter levels. Leucine-rich repeat kinase 2 (LRRK2) is associated with the pathogenesis of Parkinson's disease (PD). LRRK2 is expressed in neurons, microglia, and astrocytes and plays diverse roles in these cell types. We aimed to determine the effects of mutant human G2019S-LRRK2 (GS-hLRRK2) in rat primary astrocytes (rASTROs). Transfection with GS-hLRRK2 significantly decreased cell viability compared to transfection with the vector and wild-type human LRRK2 (WT-hLRRK2). GS-hLRRK2 expression significantly reduced the levels of nerve growth factor and increased the levels of proinflammatory cytokines (interleukin-1β and tumor necrosis factor α) compared to the vector and WT-hLRRK2 expression. Furthermore, GS-hLRRK2 expression in rASTROs promoted astrogliosis, which was characterized by increased expression of glial fibrillary acidic protein and vimentin. Treatment with the conditioned medium of G2019S LRRK2-expressing rASTROs decreased N27 cell viability compared to treatment with that of WT-hLRRK2-expressing rASTROs. Consequently, the regulation of the dopamine synthesis pathway was affected in N27 cells, thereby leading to altered levels of tyrosine hydroxylase, dopamine transporter, Nurr1, and dopamine release. Overall, the G2019S LRRK2 mutation disrupted astrocyte function, thereby aggravating PD progression.

Evaluation of canine adipose-derived mesenchymal stem cells for neurological functional recovery in a rat model of traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is a common condition in veterinary medicine that is difficult to manage.Veterinary regenerative therapy based on adipose mesenchymal stem cells seem to be an effective strategy for the treatment of traumatic brain injury. In this study, we evaluated therapeutic efficacy of canine Adipose-derived mesenchymal stem cells (AD-MSCs)in a rat TBI model, in terms of improved nerve function and anti-neuroinflammation.

RESULTS

Canine AD-MSCs promoted neural functional recovery, reduced neuronal apoptosis, and inhibited the activation of microglia and astrocytes in TBI rats. According to the results in vivo, we further investigated the regulatory mechanism of AD-MSCs on activated microglia by co-culture in vitro. Finally, we found that canine AD-MSCs promoted their polarization to the M2 phenotype, and inhibited their polarization to the M1 phenotype. What's more, AD-MSCs could reduce the migration, proliferation and Inflammatory cytokines of activated microglia, which is able to inhibit inflammation in the central system.

CONCLUSIONS

Collectively, the present study demonstrates that transplantation of canine AD-MSCs can promote functional recovery in TBI rats via inhibition of neuronal apoptosis, glial cell activation and central system inflammation, thus providing a theoretical basis for canine AD-MSCs therapy for TBI in veterinary clinic.

Non-stem cell-derived exosomes: a novel therapeutics for neurotrauma

Neurotrauma, encompassing traumatic brain injuries (TBI) and spinal cord injuries (SCI) impacts a significant portion of the global population. While spontaneous recovery post-TBI or SCI is possible, recent advancements in cell-based therapies aim to bolster these natural reparative mechanisms. Emerging research indicates that the beneficial outcomes of such therapies might be largely mediated by exosomes secreted from the administered cells. While stem cells have garnered much attention, exosomes derived from non-stem cells, including neurons, Schwann cells, microglia, and vascular endothelial cells, have shown notable therapeutic potential. These exosomes contribute to angiogenesis, neurogenesis, and axon remodeling, and display anti-inflammatory properties, marking them as promising agents for neurorestorative treatments. This review provides an in-depth exploration of the current methodologies, challenges, and future directions regarding the therapeutic role of non-stem cell-derived exosomes in neurotrauma.

Functionalized ZnO-Based Nanocomposites for Diverse Biological Applications: Current Trends and Future Perspectives

The wide array of structures and characteristics found in ZnO-based nanostructures offers them a versatile range of uses. Over the past decade, significant attention has been drawn to the possible applications of these materials in the biomedical field, owing to their distinctive electronic, optical, catalytic, and antimicrobial attributes, alongside their exceptional biocompatibility and surface chemistry. With environmental degradation and an aging population contributing to escalating healthcare needs and costs, particularly in developing nations, there's a growing demand for more effective and affordable biomedical devices with innovative functionalities. This review delves into particular essential facets of different synthetic approaches (chemical and green) that contribute to the production of effective multifunctional nano-ZnO particles for biomedical applications. Outlining the conjugation of ZnO nanoparticles highlights the enhancement of biomedical capacity while lowering toxicity. Additionally, recent progress in the study of ZnO-based nano-biomaterials tailored for biomedical purposes is explored, including biosensing, bioimaging, tissue regeneration, drug delivery, as well as vaccines and immunotherapy. The final section focuses on nano-ZnO particles' toxicity mechanism with special emphasis to their neurotoxic potential, as well as the primary toxicity pathways, providing an overall review of the up-to-date development and future perspectives of nano-ZnO particles in the biomedicine field.

Astrocytic GABAergic Regulation in Alcohol Use and Major Depressive Disorders

Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the central nervous system (CNS). Most GABAergic neurons synthesize GABA from glutamate and release it in the synaptic cleft in the CNS. However, astrocytes can also synthesize and release GABA, activating GABA receptors in the neighboring neurons in physiological and pathological conditions. As the primary homeostatic glial cells in the brain, astrocytes play a crucial role in regulating GABA homeostasis and synaptic neurotransmission. Accumulating evidence demonstrates that astrocytic GABA dysregulation is implicated in psychiatric disorders, including alcohol use disorder (AUD) and major depressive disorder (MDD), the most prevalent co-occurring psychiatric disorders. Several current medications and emerging pharmacological agents targeting GABA levels are in clinical trials for treating AUD and MDD. This review offers a concise summary of the role of astrocytic GABA regulation in AUD and MDD. We also provide an overview of the current understanding and areas of debate regarding the mechanisms by which astrocytes regulate GABA in the CNS and their potential significance in the molecular basis of AUD and MDD, paving the way toward future research directions and potential therapeutic target areas within this field.

Protective effect of Tat fused HPCA protein on neuronal cell death caused by ischemic injury

Background

Bain ischemia is a disease that occurs for various reasons, induces reactive oxygen species (ROS), and causes fatal damage to the nervous system. Protective effect of HPCA on ischemic injury has not been extensively studied despite its significance in regulating calcium homeostasis and promoting neuronal survival in CA1 region of the brain.

Objective

We investigate the role of HPCA in ischemic injury using a cell-permeable Tat peptide fused HPCA protein (Tat-HPCA).

Methods

Western blot analysis determined the penetration of Tat-HPCA into HT-22 cells and apoptotic signaling pathways. 5-CFDA, AM, DCF-DA, and TUNEL staining confirmed intracellular ROS production and DNA damage. The intracellular Ca2+ was measured in primary cultured neurons treated with H2O2. Protective effects were examined using immunohistochemistry and cognitive function tests by passive avoidance test and 8-arm radial maze test.

Results

Tat-HPCA effectively penetrated into HT-22 cells and inhibited H2O2-induced apoptosis, oxidative stress, and DNA fragmentation. It also effectively inhibited phosphorylation of JNK and regulated the activation of Caspase, Bax, Bcl-2, and PARP, leading to inhibition of apoptosis. Moreover, Ca2+ concentration decreased in cells treated with Tat-HPCA in primary cultured neurons. In an animal model of ischemia, Tat-HPCA effectively penetrated the hippocampus, inhibited cell death, and regulated activities of astrocytes and microglia. Additionally, Cognitive function tests show that Tat-HPCA improves neurobehavioral outcomes after cerebral ischemic injury.

Conclusion

These results suggest that Tat-HPCA might have potential as a therapeutic agent for treating oxidative stress-related diseases induced by ischemic injury, including ischemia.

Biomaterials in Traumatic Brain Injury: Perspectives and Challenges

Traumatic brain injury (TBI) is a leading cause of mortality and long-term impairment globally. TBI has a dynamic pathology, encompassing a variety of metabolic and molecular events that occur in two phases: primary and secondary. A forceful external blow to the brain initiates the primary phase, followed by a secondary phase that involves the release of calcium ions (Ca2+) and the initiation of a cascade of inflammatory processes, including mitochondrial dysfunction, a rise in oxidative stress, activation of glial cells, and damage to the blood-brain barrier (BBB), resulting in paracellular leakage. Currently, there are no FDA-approved drugs for TBI, but existing approaches rely on delivering micro- and macromolecular treatments, which are constrained by the BBB, poor retention, off-target toxicity, and the complex pathology of TBI. Therefore, there is a demand for innovative and alternative therapeutics with effective delivery tactics for the diagnosis and treatment of TBI. Tissue engineering, which includes the use of biomaterials, is one such alternative approach. Biomaterials, such as hydrogels, including self-assembling peptides and electrospun nanofibers, can be used alone or in combination with neuronal stem cells to induce neurite outgrowth, the differentiation of human neural stem cells, and nerve gap bridging in TBI. This review examines the inclusion of biomaterials as potential treatments for TBI, including their types, synthesis, and mechanisms of action. This review also discusses the challenges faced by the use of biomaterials in TBI, including the development of biodegradable, biocompatible, and mechanically flexible biomaterials and, if combined with stem cells, the survival rate of the transplanted stem cells. A better understanding of the mechanisms and drawbacks of these novel therapeutic approaches will help to guide the design of future TBI therapies.

Pericyte dysfunction is a key mediator of the risk of cerebral ischemia

Pericytes are critical yet understudied cells that are a central component of the neurovascular unit. They are connected to the cerebrovascular endothelium and help control vascular contractility and maintain the blood-brain barrier. Pericyte dysfunction has the potential to mediate many of the deleterious vascular consequences of ischemic stroke. Current therapeutics are designed to be administered after stroke onset and limit damage, but there are few options to target vascular risk factors pre-ischemia which likely contribute to stroke outcomes. Here, we focus on the role of pericytes in health and disease, and discuss how pericyte dysfunction can increase the risk of ischemic injury. Additionally, we note that despite the importance of pericytes in cerebrovascular disease, there are relatively few current therapeutic options that target pericyte function.

Astrocytes in human central nervous system diseases: a frontier for new therapies

Astroglia are a broad class of neural parenchymal cells primarily dedicated to homoeostasis and defence of the central nervous system (CNS). Astroglia contribute to the pathophysiology of all neurological and neuropsychiatric disorders in ways that can be either beneficial or detrimental to disorder outcome. Pathophysiological changes in astroglia can be primary or secondary and can result in gain or loss of functions. Astroglia respond to external, non-cell autonomous signals associated with any form of CNS pathology by undergoing complex and variable changes in their structure, molecular expression, and function. In addition, internally driven, cell autonomous changes of astroglial innate properties can lead to CNS pathologies. Astroglial pathophysiology is complex, with different pathophysiological cell states and cell phenotypes that are context-specific and vary with disorder, disorder-stage, comorbidities, age, and sex. Here, we classify astroglial pathophysiology into (i) reactive astrogliosis, (ii) astroglial atrophy with loss of function, (iii) astroglial degeneration and death, and (iv) astrocytopathies characterised by aberrant forms that drive disease. We review astroglial pathophysiology across the spectrum of human CNS diseases and disorders, including neurotrauma, stroke, neuroinfection, autoimmune attack and epilepsy, as well as neurodevelopmental, neurodegenerative, metabolic and neuropsychiatric disorders. Characterising cellular and molecular mechanisms of astroglial pathophysiology represents a new frontier to identify novel therapeutic strategies.

Porcine Astrocytes and Their Relevance for Translational Neurotrauma Research

Astrocytes are essential to virtually all brain processes, from ion homeostasis to neurovascular coupling to metabolism, and even play an active role in signaling and plasticity. Astrocytic dysfunction can be devastating to neighboring neurons made inherently vulnerable by their polarized, excitable membranes. Therefore, correcting astrocyte dysfunction is an attractive therapeutic target to enhance neuroprotection and recovery following acquired brain injury. However, the translation of such therapeutic strategies is hindered by a knowledge base dependent almost entirely on rodent data. To facilitate additional astrocytic research in the translatable pig model, we present a review of astrocyte findings from pig studies of health and disease. We hope that this review can serve as a road map for intrepid pig researchers interested in studying astrocyte biology.

Mitochondria dysregulation contributes to secondary neurodegeneration progression post-contusion injury in human 3D in vitro triculture brain tissue model

Traumatic Brain injury-induced disturbances in mitochondrial fission-and-fusion dynamics have been linked to the onset and propagation of neuroinflammation and neurodegeneration. However, cell-type-specific contributions and crosstalk between neurons, microglia, and astrocytes in mitochondria-driven neurodegeneration after brain injury remain undefined. We developed a human three-dimensional in vitro triculture tissue model of a contusion injury composed of neurons, microglia, and astrocytes and examined the contributions of mitochondrial dysregulation to neuroinflammation and progression of injury-induced neurodegeneration. Pharmacological studies presented here suggest that fragmented mitochondria released by microglia are a key contributor to secondary neuronal damage progression after contusion injury, a pathway that requires astrocyte-microglia crosstalk. Controlling mitochondrial dysfunction thus offers an exciting option for developing therapies for TBI patients.

The Central Fluid Percussion Brain Injury in a Gyrencephalic Pig Brain: Scalable Diffuse Injury and Tissue Viability for Glial Cell Immunolabeling following Long-Term Refrigerated Storage

Traumatic brain injury (TBI) affects millions of people annually; however, our knowledge of the diffuse pathologies associated with TBI is limited. As diffuse pathologies, including axonal injury and neuroinflammatory changes, are difficult to visualize in the clinical population, animal models are used. In the current study, we used the central fluid percussion injury (CFPI) model in a micro pig to study the potential scalability of these diffuse pathologies in a gyrencephalic brain of a species with inflammatory systems very similar to humans. We found that both axonal injury and microglia activation within the thalamus and corpus callosum are positively correlated with the weight-normalized pressure pulse, while subtle changes in blood gas and mean arterial blood pressure are not. We also found that the majority of tissue generated up to 10 years previously is viable for immunofluorescent labeling after long-term refrigeration storage. This study indicates that a micro pig CFPI model could allow for specific investigations of various degrees of diffuse pathological burdens following TBI.

The Adult Neurogenesis Theory of Alzheimer's Disease

Alzheimer's disease starts in neural stem cells (NSCs) in the niches of adult neurogenesis. All primary factors responsible for pathological tau hyperphosphorylation are inherent to adult neurogenesis and migration. However, when amyloid pathology is present, it strongly amplifies tau pathogenesis. Indeed, the progressive accumulation of extracellular amyloid-β deposits in the brain triggers a state of chronic inflammation by microglia. Microglial activation has a significant pro-neurogenic effect that fosters the process of adult neurogenesis and supports neuronal migration. Unfortunately, this "reactive" pro-neurogenic activity ultimately perturbs homeostatic equilibrium in the niches of adult neurogenesis by amplifying tau pathogenesis in AD. This scenario involves NSCs in the subgranular zone of the hippocampal dentate gyrus in late-onset AD (LOAD) and NSCs in the ventricular-subventricular zone along the lateral ventricles in early-onset AD (EOAD), including familial AD (FAD). Neuroblasts carrying the initial seed of tau pathology travel throughout the brain via neuronal migration driven by complex signals and convey the disease from the niches of adult neurogenesis to near (LOAD) or distant (EOAD) brain regions. In these locations, or in close proximity, a focus of degeneration begins to develop. Then, tau pathology spreads from the initial foci to large neuronal networks along neural connections through neuron-to-neuron transmission.

Tetramethylpyrazine promotes stroke recovery by inducing the restoration of neurovascular unit and transformation of A1/A2 reactive astrocytes

2,3,5,6-Tetramethylpyrazine (TMP) as an active ingredient extracted from a traditional Chinese herbal medicine Ligusticum chuanxiong Hort. has been proved to penetrate blood-brain barrier (BBB) and show neuroprotective effects on cerebral ischemia. However, whether TMP could regulate astrocytic reactivity to facilitate neurovascular restoration in the subacute ischemic stroke needs to be urgently verified. In this research, permanent occlusion of the middle cerebral artery (MCAO) model was conducted and TMP (10, 20, 40 mg/kg) was intraperitoneally administrated to rats once daily for 2 weeks. Neurological function was evaluated by motor deficit score (MDS). Magnetic resonance imaging (MRI) was implemented to analyze tissue injury and cerebral blood flow (CBF). Magnetic resonance angiography (MRA) was applied to exhibit vascular signals. Transmission electron microscopy (TEM) was performed to detect the neurovascular unit (NVU) ultrastructure. Haematoxylin and eosin (HE) staining was utilized to evaluate cerebral histopathological lesions. The neurogenesis, angiogenesis, A1/A2 reactivity, aquaporin 4 (AQP4) and connexin 43 (Cx43) of astrocytes were observed with immunofluorescent staining. Then FGF2/PI3K/AKT signals were measured by western blot. Findings revealed TMP ameliorated neurological functional recovery, preserved NVU integrity, and enhanced endogenous neurogenesis and angiogenesis of rats with subacute ischemia. Shifting A1 to A2 reactivity, suppressing excessive AQP4 and Cx43 expression of astrocytes, and activating FGF2/PI3K/AKT pathway might be potential mechanisms of promoting neurovascular restoration with TMP after ischemic stroke.

Far from home: the role of glial mRNA localization in synaptic plasticity

Neurons and glia are highly polarized cells, whose distal cytoplasmic functional subdomains require specific proteins. Neurons have axonal and dendritic cytoplasmic extensions containing synapses whose plasticity is regulated efficiently by mRNA transport and localized translation. The principles behind these mechanisms are equally attractive for explaining rapid local regulation of distal glial cytoplasmic projections, independent of their cell nucleus. However, in contrast to neurons, mRNA localization has received little experimental attention in glia. Nevertheless, there are many functionally diverse glial subtypes containing extensive networks of long cytoplasmic projections with likely localized regulation that influence neurons and their synapses. Moreover, glia have many other neuron-like properties, including electrical activity, secretion of gliotransmitters and calcium signaling, influencing, for example, synaptic transmission, plasticity and axon pruning. Here, we review previous studies concerning glial transcripts with important roles in influencing synaptic plasticity, focusing on a few cases involving localized translation. We discuss a variety of important questions about mRNA transport and localized translation in glia that remain to be addressed, using cutting-edge tools already available for neurons.

Protective Effects of PEP-1-GSTA2 Protein in Hippocampal Neuronal Cell Damage Induced by Oxidative Stress

Glutathione S-transferase alpha 2 (GSTA2), a member of the glutathione S-transferase family, plays the role of cellular detoxification against oxidative stress. Although oxidative stress is related to ischemic injury, the role of GSTA2 against ischemia has not been elucidated. Thus, we studied whether GSTA2 prevents ischemic injury by using the PEP-1-GSTA2 protein which has a cell-permeable protein transduction domain. We revealed that cell-permeable PEP-1-GSTA2 transduced into HT-22 cells and markedly protected cell death via the inhibition of reactive oxygen species (ROS) production and DNA damage induced by oxidative stress. Additionally, transduced PEP-1-GSTA2 promoted mitogen-activated protein kinase (MAPK), and nuclear factor-kappaB (NF-κB) activation. Furthermore, PEP-1-GSTA2 regulated Bcl-2, Bax, cleaved Caspase-3 and -9 expression protein levels. An in vivo ischemic animal model, PEP-1-GSTA2, markedly prevented the loss of hippocampal neurons and reduced the activation of microglia and astrocytes. These findings indicate that PEP-1-GSTA2 suppresses hippocampal cell death by regulating the MAPK and apoptotic signaling pathways. Therefore, we suggest that PEP-1-GSTA2 will help to develop the therapies for oxidative-stress-induced ischemic injury.

Peroxiredoxin 6 Regulates Glutathione Peroxidase 1-Medited Glutamine Synthase Preservation in the Hippocampus of Chronic Epilepsy Rats

Clasmatodendrosis (an autophagic astroglial degeneration) plays an important role in the regulation of spontaneous seizure duration but not seizure frequency or behavioral seizure severity in chronic epilepsy rats. Recently, it has been reported that N-acetylcysteine (NAC), a precursor to glutathione (GSH), attenuates clasmatodendritic degeneration and shortens spontaneous seizure duration in chronic epilepsy rats, although the underlying mechanisms of its anti-convulsive effects are not fully understood. To elucidate this, the present study was designed to investigate whether NAC affects astroglial glutamine synthase (GS) expression mediated by GSH peroxidase 1 (GPx1) and/or peroxiredoxin 6 (Prdx6) in the epileptic hippocampus. As compared to control animals, GS and GPx1 expressions were upregulated in reactive CA1 astrocytes of chronic epilepsy rats, while their expressions were significantly decreased in clasmatodendritic CA1 astrocytes and reactive astrocytes within the molecular layer of the dentate gyrus. Prdx6 expression was increased in reactive CA1 astrocytes as well as clasmatodendritic CA1 astrocytes. In the molecular layer of the dentate gyrus, Prdx6 expression levels were similar to those in control animals. NAC ameliorated clasmatodendrosis through the increment of GS and GPx1 expressions, while it abolished Prdx6 upregulation. 1-hexadecyl-3-(trifluoroethgl)-sn-glycerol-2 phosphomethanol (MJ33, a selective inhibitor of aiPLA2 activity of Prdx6) alleviated clasmatodendrosis by enhancing GPx1 and GS expressions in clasmatodendritic CA1 astrocytes without changing the Prdx6 level. NAC or MJ33 did not affect GS, GPx1 and Prdx6 expression in astrocytes within the molecular layer of the dentate gyrus. These findings indicate that upregulated aiPLA2 activity of Prdx6 may abolish GPx1-mediated GS preservation and lead to clasmatodendrosis in CA1 astrocytes, which would extend spontaneous seizure duration due to impaired glutamate-glutamine conversion regulated by GS. Therefore, the present data suggest that aiPLA2 activity of Prdx6 in astrocytes may be one of the upstream effectors of seizure duration in the epileptic hippocampus.

Amino acid abundance and composition in cell culture medium affects trace metal tolerance and cholesterol synthesis

Amino acid compositions of cell culture media are empirically designed to enhance cell growth and productivity and vary both across media formulations and over the course of culture due to imbalance in supply and consumption. The interconnected nature of the amino acid transporters and metabolism suggests that changes in amino acid composition can affect cell physiology. In this study, we explore the effect of a step change in amino acid composition from a DMEM: F12-based medium to a formulation varying in relative abundances of all amino acids, evaluated at two amino acid concentrations (lean LAA vs. rich HAA). Cell growth was inhibited in LAA but not HAA. In addition to the expected effects on expression of the cell cycle, amino acid response and mTOR pathway genes in LAA, we observed an unanticipated effect on zinc uptake and efflux genes. This was accompanied by a lower tolerance to zinc supplementation in LAA but not in the other formulations. Histidine was sufficient but not necessary to prevent such zinc toxicity. Additionally, an unanticipated downregulation of genes in the cholesterol synthesis pathway was observed in HAA, accompanied by an increase in cellular cholesterol content, which may depend on the relative abundances of glutamine and other amino acids. This study shows that changes in the amino acid composition without any evident effect on growth may have profound effects on metabolism. Such analyses can help rationalize the designing of medium and feed formulations for bioprocess applications beyond replenishment of consumed components.

A dual tracer [11C]PBR28 and [18F]FDG microPET evaluation of neuroinflammation and brain energy metabolism in murine endotoxemia

BACKGROUND

Brain metabolic alterations and neuroinflammation have been reported in several peripheral inflammatory conditions and present significant potential for targeting with new diagnostic approaches and treatments. However, non-invasive evaluation of these alterations remains a challenge.

METHODS

Here, we studied the utility of a micro positron emission tomography (microPET) dual tracer ([11C]PBR28 - for microglial activation and [18F]FDG for energy metabolism) approach to assess brain dysfunction, including neuroinflammation in murine endotoxemia. MicroPET imaging data were subjected to advanced conjunction and individual analyses, followed by post-hoc analysis.

RESULTS

There were significant increases in [11C]PBR28 and [18F]FDG uptake in the hippocampus of C57BL/6 J mice 6 h following LPS (2 mg/kg) intraperitoneal (i.p.) administration compared with saline administration. These results confirmed previous postmortem observations. In addition, patterns of significant simultaneous activation were demonstrated in the hippocampus, the thalamus, and the hypothalamus in parallel with other tracer-specific and region-specific alterations. These changes were observed in the presence of robust systemic inflammatory responses manifested by significantly increased serum cytokine levels.

CONCLUSIONS

Together, these findings demonstrate the applicability of [11C]PBR28 - [18F]FDG dual tracer microPET imaging for assessing neuroinflammation and brain metabolic alterations in conditions "classically" characterized by peripheral inflammatory and metabolic pathogenesis.

A Focus on Astrocyte Contribution to Parkinson's Disease Etiology

Parkinson's disease (PD) is an incurable neurodegenerative disease of high prevalence, characterized by the prominent death of dopaminergic neurons in the substantia nigra pars compacta, which produces dopamine deficiency, leading to classic motor symptoms. Although PD has traditionally been considered as a neuronal cell autonomous pathology, in which the damage of vulnerable neurons is responsible for the disease, growing evidence strongly suggests that astrocytes might have an active role in the neurodegeneration observed. In the present review, we discuss several studies evidencing astrocyte implications in PD, highlighting the consequences of both the loss of normal homeostatic functions and the gain in toxic functions for the wellbeing of dopaminergic neurons. The revised information provides significant evidence that allows astrocytes to be positioned as crucial players in PD etiology, a factor that needs to be taken into account when considering therapeutic targets for the treatment of the disease.

Methotrexate Induces an Antioxidant Hormetic Response in Primary Rat Astrocytes

Neurodegenerative diseases have increased worldwide in recent years. Their relationship with oxidative stress has motivated the research to find therapies and medications capable of suppressing oxidative damage and therefore slowing the progression of these diseases. Glutathione (GSH) is the most important cellular antioxidant in living beings and is responsible for regulating the cellular redox state. However, GSH cannot be administered by any route of administration, so molecules that increase its levels by activating Nrf2-ARE signaling pathway are explored; since Nrf2 regulates the main genes involved in GSH de novo synthesis and recycling. Astrocytes are the most important cell-type in the antioxidant cell response and are responsible for providing GSH and other substrates for neurons to have an efficient antioxidant response. Methotrexate (MTX) is an anti-inflammatory agent that has different cellular effects when administered at low or high concentrations. So in this study, we used MTX different concentrations and exposure times to induce a hormetic antioxidant response in rat primary astrocytes. Our results showed that 20 nM MTX pre-conditioning for 12 h augmented the GSH/GSSG ratio and protected cellular viability against a toxic MTX and H₂O₂ insult, which was abrogated when Nrf2 was inhibited by brusatol. Hence, MTX subsequent studies as a drug to counteract the progression of some stress-associated neurodegenerative diseases are suggested.

Antigenicity is preserved with fixative solutions used in human gross anatomy: A mice brain immunohistochemistry study

Background

Histology remains the gold-standard to assess human brain biology, so ex vivo studies using tissue from brain banks are standard practice in neuroscientific research. However, a larger number of specimens could be obtained from gross anatomy laboratories. These specimens are fixed with solutions appropriate for dissections, but whether they also preserve brain tissue antigenicity is unclear. Therefore, we perfused mice brains with solutions used for human body preservation to assess and compare the tissue quality and antigenicity of the main cell populations.

Materials and methods

Twenty-eight C57BL/6J mice were perfused with 4% formaldehyde (FAS, N = 9), salt-saturated solution (SSS, N = 9), and alcohol solution (AS, N = 10). The brains were cut into 40 μm sections for antigenicity analysis and were assessed by immunohistochemistry of four antigens: neuronal nuclei (NeuN), glial fibrillary acidic protein (GFAP astrocytes), ionized calcium-binding adaptor molecule 1 (Iba1-microglia), and myelin proteolipid protein (PLP). We compared the fixatives according to multiple variables: perfusion quality, ease of manipulation, tissue quality, immunohistochemistry quality, and antigenicity preservation.

Results

The perfusion quality was better using FAS and worse using AS. The manipulation was very poor in SSS brains. FAS- and AS-fixed brains showed higher tissue and immunohistochemistry quality than the SSS brains. All antigens were readily observed in every specimen, regardless of the fixative solution.

Conclusion

Solutions designed to preserve specimens for human gross anatomy dissections also preserve tissue antigenicity in different brain cells. This offers opportunities for the use of human brains fixed in gross anatomy laboratories to assess normal or pathological conditions.

Interference of Interleukin-1β Mediated by Lentivirus Promotes Functional Recovery of Spinal Cord Contusion Injury in Rats via the PI3K/AKT1 Signaling Pathway

Purpose. Inflammation and apoptosis after spinal cord contusion (SCC) are important causes of irreversible spinal cord injury. Interleukin-1β (IL-1β) is a key inflammatory factor that promotes the aggravation of spinal cord contusion. However, the specific role and regulatory mechanism of IL-1β in spinal cord contusion is still unclear. Therefore, this study applied bioinformatics to analyze and mine potential gene targets interlinked with IL-1β, animal experiments and lentiviral interference technology were used to explore whether IL-1β affected the recovery of motor function in spinal cord contusion by interfering with PI3K/AKT1 signaling pathway. Method. This study used bioinformatics to screen and analyze gene targets related to IL-1β. The rat SCC animal model was established by the Allen method, and the Basso Beattie Bresnahan (BBB) score was used to evaluate the motor function of the spinal cord-injured rats. Immunohistochemistry and immunofluorescence were used to localize the expression of IL-1β and AKT1 proteins in spinal cord tissue. Quantitative polymerase chain reaction and Western blot were used to detect the gene and protein expressions of IL-1β, PI3K, and AKT1. RNAi technology was used to construct lentivirus to inhibit the expression of IL-1β, lentiviral interference with IL-1β was used to investigate the effect of IL-1β and AKT1 on the function of spinal cord contusion and the relationship among IL-1β, AKT1, and downstream signaling pathways. Results. Bioinformatics analysis suggested a close relationship between IL-1β and AKT1. Animal experiments have confirmed that IL-1β is closely related to the functional recovery of spinal cord contusion. Firstly, from the phenomenological level, the BBB score decreased after SCC, IL-1β and AKT1 were located in the cytoplasm of neurons in the anterior horn of the spinal cord, and the expression levels of IL-1β gene and protein in the experimental group were higher than those in the sham operation group. At the same time, the expression of AKT1 gene decreased, the results suggested that the increase of IL-1β affected the functional recovery of spinal cord contusion. Secondly, from the functional level, after inhibiting the expression of IL-1β with a lentivirus-mediated method, the BBB score was significantly increased, and the motor function of the spinal cord was improved. Thirdly, from the mechanistic level, bioinformatics analysis revealed the relationship between IL-1β and AKT1. In addition, the experiment further verified that in the PI3K/AKT1 signaling pathway, inhibition of IL-1β expression upregulated AKT1 gene expression, but PI3K expression was unchanged. Conclusion. Inhibition of IL-1β promotes recovery of motor function after spinal cord injury in rats through upregulation of AKT1 expression in the PI3K/AKT1 signaling pathway. Bioinformatics analysis suggested that IL-1β may affect apoptosis and regeneration by inhibiting the expression of AKT1 in the PI3K/AKT1 signaling pathway to regulate the downstream FOXO, mTOR, and GSK3 signaling pathways; thereby hindering the recovery of motor function in rats after spinal cord contusion. It provided a new perspective for clinical treatment of spinal cord contusion in the future.

Sp1-Mediated Prdx6 Upregulation Leads to Clasmatodendrosis by Increasing Its aiPLA2 Activity in the CA1 Astrocytes in Chronic Epilepsy Rats

Clasmatodendrosis is an autophagic astroglial degeneration (a non-apoptotic (type II) programmed cell death) whose underlying mechanisms are fully understood. Peroxiredoxin-6 (Prdx6), the “non-selenium glutathione peroxidase (NSGPx)”, is the only member of the 1-cysteine peroxiredoxin family. Unlike the other Prdx family, Prdx6 has multiple functions as glutathione peroxidase (GPx) and acidic calcium-independent phospholipase (aiPLA2). The present study shows that Prdx6 was upregulated in CA1 astrocytes in chronic epilepsy rats. 2-Cyano-3,12-dioxo-oleana-1,9(11)-dien-28-oic acid methyl ester (CDDO-Me) and N-acetylcysteine (NAC, a precursor of glutathione) ameliorated clasmatodendrosis accompanied by reduced Prdx6 level in CA1 astrocytes. Specificity protein 1 (Sp1) expression was upregulated in CA1 astrocyte, which was inhibited by mithramycin A (MMA). MMA alleviated clasmatodendrosis and Prdx6 upregulation. Sp1 expression was also downregulated by CDDO-Me and NAC. Furthermore, 1-hexadecyl-3-(trifluoroethgl)-sn-glycerol-2 phosphomethanol (MJ33, a selective inhibitor of aiPLA2 activity of Prdx6) attenuated clasmatodendrosis without affecting Prdx6 expression. All chemicals shortened spontaneous seizure duration but not seizure frequency and behavioral seizure severity in chronic epilepsy rats. Therefore, our findings suggest that Sp1 activation may upregulate Prdx6, whose aiPLA2 activity would dominate over GPx activity in CA1 astrocytes and may lead to prolonged seizure activity due to autophagic astroglial degeneration.

Remodeling of the Neurovascular Unit Following Cerebral Ischemia and Hemorrhage

Formulated as a group effort of the stroke community, the transforming concept of the neurovascular unit (NVU) depicts the structural and functional relationship between brain cells and the vascular structure. Composed of both neural and vascular elements, the NVU forms the blood-brain barrier that regulates cerebral blood flow to meet the oxygen demand of the brain in normal physiology and maintain brain homeostasis. Conversely, the dysregulation and dysfunction of the NVU is an essential pathological feature that underlies neurological disorders spanning from chronic neurodegeneration to acute cerebrovascular events such as ischemic stroke and cerebral hemorrhage, which were the focus of this review. We also discussed how common vascular risk factors of stroke predispose the NVU to pathological changes. We synthesized existing literature and first provided an overview of the basic structure and function of NVU, followed by knowledge of how these components remodel in response to ischemic stroke and brain hemorrhage. A greater understanding of the NVU dysfunction and remodeling will enable the design of targeted therapies and provide a valuable foundation for relevant research in this area.

Physical memory of astrocytes

Traumatic brain injury (TBI) is a major risk factor for development of neurodegenerative disorders later in life. Short, repetitive, mechanical impacts can lead to pathology that appears days or months later. The cells have a physical "memory" of mechanical events. The origin of this memory is not known. To examine the properties of this memory, we used a microfluidic chip to apply programmed fluid shear pulses to adherent adult rat astrocytes. These caused a transient rise in intracellular Ca²⁺. In response to repeated stimuli, 6 to 24 hrs apart, the Ca²⁺ response increased. This effect lasted longer than 24 hrs. The Ca²⁺ responses were more sensitive to the number of repetitions than to the rest time between stimuli. We found that inhibiting the Ca²⁺ influx during conditioning stimulus did not eliminate the stress potentiation, suggesting that mechanical deformation during the primary injury is accountable for the later response. The mechanical mechanism that triggers this long term "memory" may act by plastic deformation of the cytoskeleton.

AT2 activation does not influence brain damage in the early phase after experimental traumatic brain injury in male mice

Antagonism of the angiotensin II type 1 receptor (AT1) improves neurological function and reduces brain damage after experimental traumatic brain injury (TBI), which may be partly a result of enhanced indirect angiotensin II type 2 receptor (AT2) stimulation. AT2 stimulation was demonstrated to be neuroprotective via anti-inflammatory, vasodilatory, and neuroregenerative mechanisms in experimental cerebral pathology models. We recently demonstrated an upregulation of AT2 after TBI suggesting a protective mechanism. The present study investigated the effect of post-traumatic (5 days after TBI) AT2 activation via high and low doses of a selective AT2 agonist, compound 21 (C21), compared to vehicle-treated controls. No differences in the extent of the TBI-induced lesions were found between both doses of C21 and the controls. We then tested AT2-knockdown animals for secondary brain damage after experimental TBI. Lesion volume and neurological outcomes in AT2-deficient mice were similar to those in wild-type control mice at both 24 h and 5 days post-trauma. Thus, in contrast to AT1 antagonism, AT2 modulation does not influence the initial pathophysiological mechanisms of TBI in the first 5 days after the insult, indicating that AT2 plays only a minor role in the early phase following trauma-induced brain damage.

Motor Cortex Plasticity During Functional Recovery Following Brain Damage

Although brain damage causes functional impairment, it is often followed by partial or total recovery of function. Recovery is believed to occur primarily because of brain plasticity. Both human and animal studies have significantly contributed to uncovering the neuronal basis of plasticity. Recent advances in brain imaging technology have enabled the investigation of plastic changes in living human brains. In addition, animal experiments have revealed detailed changes at the neural and genetic levels. In this review, plasticity in motor-related areas of the cerebral cortex, which is one of the most well-studied areas of the neocortex in terms of plasticity, is reviewed. In addition, the potential of technological interventions to enhance plasticity and promote functional recovery following brain damage is discussed. Novel neurorehabilitation technologies are expected to be established based on the emerging research on plasticity from the last several decades.

Brain Energy Metabolism in Ischemic Stroke: Effects of Smoking and Diabetes

Proper regulation of energy metabolism in the brain is crucial for maintaining brain activity in physiological and different pathophysiological conditions. Ischemic stroke has a complex pathophysiology which includes perturbations in the brain energy metabolism processes which can contribute to worsening of brain injury and stroke outcome. Smoking and diabetes are common risk factors and comorbid conditions for ischemic stroke which have also been associated with disruptions in brain energy metabolism. Simultaneous presence of these conditions may further alter energy metabolism in the brain leading to a poor clinical prognosis after an ischemic stroke event. In this review, we discuss the possible effects of smoking and/or diabetes on brain glucose utilization and mitochondrial energy metabolism which, when present concurrently, may exacerbate energy metabolism in the ischemic brain. More research is needed to investigate brain glucose utilization and mitochondrial oxidative metabolism in ischemic stroke in the presence of smoking and/or diabetes, which would provide further insights on the pathophysiology of these comorbid conditions and facilitate the development of therapeutic interventions.

Insights Into the Role of Platelet-Derived Growth Factors: Implications for Parkinson’s Disease Pathogenesis and Treatment

Parkinson’s disease (PD), the second most common neurodegenerative disease after Alzheimer’s disease, commonly occurs in the elderly population, causing a significant medical and economic burden to the aging society worldwide. At present, there are few effective methods that achieve satisfactory clinical results in the treatment of PD. Platelet-derived growth factors (PDGFs) and platelet-derived growth factor receptors (PDGFRs) are important neurotrophic factors that are expressed in various cell types. Their unique structures allow for specific binding that can effectively regulate vital functions in the nervous system. In this review, we summarized the possible mechanisms by which PDGFs/PDGFRs regulate the occurrence and development of PD by affecting oxidative stress, mitochondrial function, protein folding and aggregation, Ca2+ homeostasis, and cell neuroinflammation. These modes of action mainly depend on the type and distribution of PDGFs in different nerve cells. We also summarized the possible clinical applications and prospects for PDGF in the treatment of PD, especially in genetic treatment. Recent advances have shown that PDGFs have contradictory roles within the central nervous system (CNS). Although they exert neuroprotective effects through multiple pathways, they are also associated with the disruption of the blood–brain barrier (BBB). Our recommendations based on our findings include further investigation of the contradictory neurotrophic and neurotoxic effects of the PDGFs acting on the CNS.

2, 3, 5, 4'-tetrahydroxystilbene-2-O-beta-D-glucoside protects against neuronal cell death and traumatic brain injury-induced pathophysiology

Traumatic brain injury (TBI) is a global health issue that affects at least 10 million people per year. Neuronal cell death and brain injury after TBI, including apoptosis, inflammation, and excitotoxicity, have led to detrimental effects in TBI. 2, 3, 5, 4’-tetrahydroxystilbene-2-O-beta-D-glucoside (THSG), a water-soluble compound extracted from the Chinese herb Polygonum multiflorum, has been shown to exert various biological functions. However, the effects of THSG on TBI is still poorly understood. THSG reduced L-glutamate-induced DNA fragmentation and protected glial and neuronal cell death after L-glutamate stimulation. Our results also showed that TBI caused significant behavioral deficits in the performance of beam walking, mNSS, and Morris water maze tasks in a mouse model. Importantly, daily administration of THSG (60 mg/kg/day) after TBI for 21 days attenuated the injury severity score, promoted motor coordination, and improved cognitive performance post-TBI. Moreover, administration of THSG also dramatically decreased the brain lesion volume. THSG reduced TBI-induced neuronal apoptosis in the brain cortex 24 h after TBI. Furthermore, THSG increased the number of immature neurons in the subgranular zone (SGZ) of the dentate gyrus (DG) of the hippocampus. Our results demonstrate that THSG exerts neuroprotective effects on glutamate-induced excitotoxicity and glial and neuronal cell death. The present study also demonstrated that THSG effectively protects against TBI-associated motor and cognitive impairment, at least in part, by inhibiting TBI-induced apoptosis and promoting neurogenesis.

N-acetyl-L-cysteine ameliorates mitochondrial dysfunction in ischemia/reperfusion injury via attenuating Drp-1 mediated mitochondrial autophagy

BACKGROUND AND PURPOSE

Ischemic reperfusion (I/R) injury causes a wide array of functional and structure alternations of mitochondria, associated with oxidative stress and increased the severity of injury. Despite the previous evidence for N-acetyl-L-cysteine (NAC) provide neuroprotection after I/R injury, it is unknown to evaluate the effect of NAC on altered mitochondrial autophagy forms an essential axis to impaired mitochondrial quality control in cerebral I/R injury.

METHODS

Male wistar rats subjected to I/R injury were used as transient Middle Cerebral Artery Occlusion (tMCAO) model. After I/R injury, the degree of cerebral tissue injury was detected by infarct volume, H&E staining and behavioral assessment. We also performed mitochondrial reactive oxygen species and mitochondrial membrane potential by flow cytometry and mitochondrial respiratory complexes to evaluate the mitochondrial dysfunction. Finally, we performed the western blotting analysis to measure the apoptotic and autophagic marker.

RESULTS

We found that NAC administration significantly ameliorates brain injury, improves neurobehavioral outcome, decreases neuroinflammation and mitochondrial mediated oxidative stress. We evaluated the neuroprotective effect of NAC against neuronal apoptosis by assessing its ability to sustained mitochondrial integrity and function. Further studies revealed that beneficial effects of NAC is through targeting the mitochondrial autophagy via regulating the GSK-3β/Drp1mediated mitochondrial fission and inhibiting the expression of beclin-1 and conversion of LC3, as well as activating the p-Akt pro-survival pathway.

CONCLUSION

Our results suggest that NAC exerts neuroprotective effects to inhibit the altered mitochondrial changes and cell death in I/R injury via regulation of p-GSK-3β mediated Drp-1 translocation to the mitochondria.

Glial Fibrillary Acidic Protein (GFAP): Neuroinflammation Biomarker in Acute Ischemic Stroke

Introduction

Blockage of the cerebral arteries due to thrombosis and embolism resulting in decreased blood flow to the brain, reduced oxygen supply to the brain, resulting in neuronal damage and causes astrocyte cells to secrete glial fibrillary acidic protein (GFAP). The objective of this study was to determine the correlation between GFAP levels serum and clinical outcome in patients with acute ischemic stroke.

Methods

This was observational with a cross-sectional design on acute ischemic stroke patients confirmed by CT scans and divided into large vessel occlusion and small-vessel occlusion. Clinical outcome was measured using the National Institutional Health Stroke Scale (NIHSS) tool. Statistical analysis uses Spearman’s rank correlation test and Mann Whitney’s test, significant if p < 0.05.

Results

After collecting 33 research subjects, we found 16 people with large vessel occlusion and 17 people with small vessel occlusion. Serum GFAP levels were 0.2–1.9 ng/mL, 9.1% with a mild neurological deficit, 45.45% were moderate neurological deficits, and 45.45% were severe neurological deficits. There was a significant positive correlation (r = 0.522; p = 0.002) between serum GFAP levels and the degree of neurological deficit in ischemic stroke patients. There was a statistically significant difference between serum GFAP levels in ischemic stroke patients with CT scan results of large artery occlusion compared to small artery occlusion (0.7 vs 0.4ng/mL; p = 0.001).

Conclusion

There was a positive correlation between GFAP level serum and NIHSS score on acute ischemic stroke. The higher the value of GFAP serum level, the higher the value for NIHSS and correlated with stroke severity and the extent of brain damage in ischemic stroke patients.

Temporal and spatial changes in reactive astrogliosis examined by 18F-THK5351 positron emission tomography in a patient with severe traumatic brain injury

Background

The positron emission tomography (PET) radioligand ¹⁸F-THK5351 is now used to evaluate monoamine oxidase B expression in the reactive astrogliosis seen in various central nervous diseases. Traumatic brain injury (TBI) is known to induce reactive astrogliosis in the lesion site. This is a first report to examine the spatial and temporal changes in reactive astrogliosis as evaluated by ¹⁸F-THK5351 after a severe TBI.

Case presentation

A 27-year-old man suffering from a severe TBI with multiple brain contusions was examined using ¹⁸F-THK5351 PET/CT in the subacute and chronic phases after the injury. The first PET scan, performed 46 days after the TBI, showed intense uptake of ¹⁸F-THK5351 in and around the brain contusions. The second PET scan, performed 271 days after the TBI, showed reduced uptake of ¹⁸F-THK5351 at the original sites of the brain contusions and increased uptakes in the white matter surrounding the contusions and the corpus callosum. The patient exhibited sustained improvement of neuropsychological impairment between the two PET examinations and remarkable recovery from the severe TBI.

Conclusions

There were evident temporal and spatial changes in ¹⁸F-THK5351 uptake in the traumatized brain between the two PET examinations. These changes may have been related to the remarkable neurological recovery in this patient. The degree and distribution of reactive astrogliosis detected by ¹⁸F-THK5351 PET may be useful in assessing pathophysiology and predicting prognosis in TBI patients.

Brain Volume Loss, Astrocyte Reduction, and Inflammation in Anorexia Nervosa

Anorexia nervosa is the third most common chronic disease in adolescence and is characterized by low body weight, body image distortion, weight phobia, and severe somatic consequences. Among the latter, marked brain volume reduction has been linked to astrocyte cell count reduction of about 50% in gray and white matter, while neuronal and other glial cell counts remain normal. Exact underlying mechanisms remain elusive; however, first results point to important roles of the catabolic state and the very low gonadal steroid hormones in these patients. They also appear to involve inflammatory states of "hungry astrocytes" and interactions with the gut microbiota. Functional impairments could affect the role of astrocytes in supporting neurons metabolically, neurotransmitter reuptake, and synapse formation, among others. These could be implicated in reduced learning, mood alterations, and sleep disturbances often seen in patients with AN and help explain their rigidity and difficulties in relearning processes in psychotherapy during starvation.

Inflammatory Molecules Released by Mechanically Injured Astrocytes Trigger Presynaptic Loss in Cortical Neuronal Networks

Deformation, compression, or stretching of brain tissues cause diffuse axonal injury (DAI) and induce structural and functional alterations of astrocytes, the most abundant cell type in the brain. To gain further insight into the role of mechanically activated astrocytes on neuronal networks, this study was designed to investigate whether cytokines released by mechanically activated astrocytes can affect the growth and synaptic connections of cortical neuronal networks. Astrocytes were cultivated on elastic membranes and subjected to repetitive mechanical insults, whereas well-defined protein micropatterns were used to form standardized neuronal networks. GFAP staining showed that astrocytes were mechanically activated after two cycles of stretch and mesoscale discovery assays indicated that injured astrocytes released four major cytokines. To understand the role of these cytokines, neuronal networks were cultured with the supernatant of healthy or mechanically activated astrocytes, and the individual contribution of the proinflammatory cytokine tumor necrosis factor-α (TNF-α) was studied. We found that the supernatant of two-cycle stretched astrocytes decreased presynaptic terminals and indicated that TNF-α must be considered a key player of the synaptic loss. Furthermore, our results indicate that cytokines released by injured astrocytes significantly modulate the balance between TNFR1 and TNFR2 receptors by enhancing R2 receptors. We demonstrated that TNF-α is not involved in this process, suggesting a predominant role of other secreted cytokines. Together, these results contribute to a better understanding of the consequences of repetitive astrocyte deformations and highlight the role of inflammatory signaling pathways in synaptic plasticity and modulation of TNFR1 and TNFR2 receptors.

The Many Faces of Astrocytes in Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease and is the most common cause of dementia in an aging population. The majority of research effort has focused on the role of neurons in neurodegeneration and current therapies have limited ability to slow disease progression. Recently more attention has been given to the role of astrocytes in the process of neurodegeneration. Specifically, reactive astrocytes have both advantageous and adverse effects during neurodegeneration. The ability to isolate and depict astrocyte phenotype has been challenging. However, with the recent development of single-cell sequencing technologies researchers are provided with the resource to delineate specific biomarkers associated with reactive astrocytes in AD. In this review, we will focus on the role of astrocytes in normal conditions and the pathological development of AD. We will further review recent developments in the understanding of astrocyte heterogeneity and associated biomarkers. A better understanding of astrocyte contributions and phenotypic changes in AD can ultimately lead to more effective therapeutic targets.

Advanced Metallic and Polymeric Coatings for Neural Interfacing: Structures, Properties and Tissue Responses

Neural electrodes are essential for nerve signal recording, neurostimulation, neuroprosthetics and neuroregeneration, which are critical for the advancement of brain science and the establishment of the next-generation brain-electronic interface, central nerve system therapeutics and artificial intelligence. However, the existing neural electrodes suffer from drawbacks such as foreign body responses, low sensitivity and limited functionalities. In order to overcome the drawbacks, efforts have been made to create new constructions and configurations of neural electrodes from soft materials, but it is also more practical and economic to improve the functionalities of the existing neural electrodes via surface coatings. In this article, recently reported surface coatings for neural electrodes are carefully categorized and analyzed. The coatings are classified into different categories based on their chemical compositions, i.e., metals, metal oxides, carbons, conducting polymers and hydrogels. The characteristic microstructures, electrochemical properties and fabrication methods of the coatings are comprehensively presented, and their structure-property correlations are discussed. Special focus is given to the biocompatibilities of the coatings, including their foreign-body response, cell affinity, and long-term stability during implantation. This review article can provide useful and sophisticated insights into the functional design, material selection and structural configuration for the next-generation multifunctional coatings of neural electrodes.

Weekly methotrexate may reduce valproate levels causing relapse of genetic generalized epilepsy

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Seizures have been observed in epilepsy patients receiving high dose intravenous or intrathecal Methotrexate (Mtx) therapy for the treatment of leukemias, due to reduction in valproic acid (VPA) levels.

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Prolonged low dose weekly Mtx exposure can also produce reduction in VPA levels causing seizure relapse as reported in this case.

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Mtx competes with VPA for binding to albumin as a result of which a larger proportion of VPA become unbound and is rapidly metabolized by the liver causing decline in VPA levels.

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Awareness about pharmacological interactions of anti-epileptic drugs (AEDs) is essential in epilepsy management.

Design and Evaluation of an In Vitro Mild Traumatic Brain Injury Modeling System Using 3D Printed Mini Impact Device on the 3D Cultured Human iPSC Derived Neural Progenitor Cells

Despite significant progress in understanding the disease mechanism of traumatic brain injury (TBI), promising preclinical therapeutics have seldom been translated into successful clinical outcomes, partially because the model animals have physiological and functional differences in the central nervous system (CNS) compared to humans. Human relevant models are thus urgently required. Here, an in vitro mild TBI (mTBI) modeling system is reported based on 3D cultured human induced pluripotent stem cells (iPSC) derived neural progenitor cells (iPSC-NPCs) to evaluate consequences of single and repetitive mTBI using a 3D printed mini weight-drop impact device. Computational simulation is performed to understand the single/cumulative effects of weight-drop impact on the NPC differentiated neurospheres. Experimental results reveal that neurospheres show reactive astrogliosis and glial scar formation after repetitive (10 hits) mild impacts, while no astrocyte activation is found after one or two mild impacts. A 3D co-culture model of human microglia cells with neurospheres is further developed. It is found that astrocyte response is promoted even after two mild impacts, possibly caused by the chronic neuroinflammation after microglia activation. The in vitro mTBI modeling system recapitulates several hallmarks of the brain impact injury and might serve as a good platform for future drug screening.

The involvement of nuclear factor-κB in astroprotection against ischemia-reperfusion injury by ischemia-preconditioned neurons

Ischemic preconditioned (IP) neurons protect astrocytes against ischemia/reperfusion (I/R)-induced injury by inhibiting oxidative stress. However, the relevant mechanisms are unknown. Based on the role of nuclear factor-κB (NF-κB) in cell survival and adaption to oxidative stress, we hypothesized that NF-κB might be associated with astroprotection induced by IP neurons via upregulation of antioxidant enzymes. Here, we investigated the effects of IP neurons on NF-κB activation, cell viability, reactive oxygen species (ROS), expression of antioxidant enzymes, erythropoietin (EPO), and tumor necrosis factor α (TNF-α), in the presence or absence of BAY11-7082 (an NF-κB inhibitor), anti-EPO, and anti-TNF-α antibodies, in astrocytes treated with or without I/R. We found that IP neurons could keep NF-κB activation at a relatively higher but beneficial level, and in turn, upregulated the activity of antioxidant enzymes and hence enhanced cell viability and reduced ROS in I/R treated astrocytes. The results collectively indicated that IP neurons are able to significantly inhibit the I/R-induced NF-κB overactivation, probably via EPO and TNF-α, being essential for IP neuron-induced astroprotection under the conditions of I/R. We concluded that NF-κB-mediated antioxidative stress is one of the mechanisms by which IP neurons protect astrocytes against I/R injury.

Dysregulation of Astrocyte Ion Homeostasis and Its Relevance for Stroke-Induced Brain Damage

Ischemic stroke is a leading cause of mortality and chronic disability. Either recovery or progression towards irreversible failure of neurons and astrocytes occurs within minutes to days, depending on remaining perfusion levels. Initial damage arises from energy depletion resulting in a failure to maintain homeostasis and ion gradients between extra- and intracellular spaces. Astrocytes play a key role in these processes and are thus central players in the dynamics towards recovery or progression of stroke-induced brain damage. Here, we present a synopsis of the pivotal functions of astrocytes at the tripartite synapse, which form the basis of physiological brain functioning. We summarize the evidence of astrocytic failure and its consequences under ischemic conditions. Special emphasis is put on the homeostasis and stroke-induced dysregulation of the major monovalent ions, namely Na+, K+, H+, and Cl-, and their involvement in maintenance of cellular volume and generation of cerebral edema.

Running Promotes Transformation of Brain Astrocytes Into Neuroprotective Reactive Astrocytes and Synaptic Formation by Targeting Gpc6 Through the STAT3 Pathway

Ischemic stroke is caused by cerebral ischemia upon the blockage of an artery, which results in a high disability rate. Little is known regarding the mechanism of astrocyte function in cerebral ischemia. We aimed to determine the effects of running on the transformation of astrocytes, and subsequent synapse formation. A study of middle cerebral artery occlusion (MCAO) after running in vivo showed that running can promote the transformation of astrocytes toward the neuroprotective phenotype. Our findings of oxygen-glucose deprived astrocytes in vitro after running revealed that these astrocytes transformed into the neuroprotective phenotype, and that the expression of STAT3 and Gpc6 was increased. We confirmed that mechanistically, running can target Gpc6 through the STAT3 pathway and then regulate the number of synapses. We concluded that running promotes synapse proliferation by polarizing astrocytes toward the neuroprotective phenotype and ultimately leads to nerve regeneration.

Exposure to 2.45 GHz Radiation Triggers Changes in HSP-70, Glucocorticoid Receptors and GFAP Biomarkers in Rat Brain

Brain tissue may be especially sensitive to electromagnetic phenomena provoking signs of neural stress in cerebral activity. Fifty-four adult female Sprague-Dawley rats underwent ELISA and immunohistochemistry testing of four relevant anatomical areas of the cerebrum to measure biomarkers indicating induction of heat shock protein 70 (HSP-70), glucocorticoid receptors (GCR) or glial fibrillary acidic protein (GFAP) after single or repeated exposure to 2.45 GHz radiation in the experimental set-up. Neither radiation regime caused tissue heating, so thermal effects can be ruled out. A progressive decrease in GCR and HSP-70 was observed after acute or repeated irradiation in the somatosensory cortex, hypothalamus and hippocampus. In the limbic cortex; however, values for both biomarkers were significantly higher after repeated exposure to irradiation when compared to control animals. GFAP values in brain tissue after irradiation were not significantly different or were even lower than those of nonirradiated animals in all brain regions studied. Our results suggest that repeated exposure to 2.45 GHz elicited GCR/HSP-70 dysregulation in the brain, triggering a state of stress that could decrease tissue anti-inflammatory action without favoring glial proliferation and make the nervous system more vulnerable.

Glutathione in the Brain

Glutathione (GSH) is the most abundant non-protein thiol, and plays crucial roles in the antioxidant defense system and the maintenance of redox homeostasis in neurons. GSH depletion in the brain is a common finding in patients with neurodegenerative diseases, such as Alzheimer’s disease and Parkinson’s disease, and can cause neurodegeneration prior to disease onset. Excitatory amino acid carrier 1 (EAAC1), a sodium-dependent glutamate/cysteine transporter that is selectively present in neurons, plays a central role in the regulation of neuronal GSH production. The expression of EAAC1 is posttranslationally controlled by the glutamate transporter-associated protein 3–18 (GTRAP3-18) or miR-96-5p in neurons. The regulatory mechanism of neuronal GSH production mediated by EAAC1 may be a new target in therapeutic strategies for these neurodegenerative diseases. This review describes the regulatory mechanism of neuronal GSH production and its potential therapeutic application in the treatment of neurodegenerative diseases.