Neuroinflammatory responses of microglia in central nervous system trauma

Baicalin ameliorates neuroinflammation by targeting TLR4/MD2 complex on microglia via PI3K/AKT/NF-κB signaling pathway

This study aims to elucidate the target and mechanism of baicalin, a clinically utilized drug, in the treatment of neuroinflammatory diseases. Neuroinflammation, characterized by the activation of glial cells and the release of various pro-inflammatory cytokines, plays a critical role in the pathogenesis of various diseases, including spinal cord injury (SCI). The remission of such diseases is significantly dependent on the improvement of inflammatory microenvironment. Toll-like receptor 4/myeloid differentiation protein 2 (TLR4/MD2) complex plays an important role in pathogen recognition and innate immune activation. baicalin, a natural flavonoid, is renowned for its potent anti-inflammatory property. In this study, we discovered that baicalin significantly reduced the activation of glial cells and the levels of pro-inflammatory cytokines at the lesion site of SCI mice, thereby mitigating demyelination and neuronal damage. By directly occupying the active pocket of TLR4/MD2 complex on microglia, baicalin inhibited PI3K/AKT/NF-κB pathway, thereby exerting its anti-inflammatory effect. These findings were corroborated in mice induced by lipopolysaccharide, a TLR4 agonist. Furthermore, baicalin indirectly altered phenotype of astrocytes by reducing secretion of TNF-α, IL-1α, and C1q levels from microglia. Our work demonstrated that baicalin effectively alleviated neuroinflammation by directly targeting microglia and indirectly modulating astrocytes phenotype. As a natural flavonoid, baicalin holds significant potential as a therapeutic candidate for diseases characterized by neuroinflammation.

Microglial type I interferon signaling mediates chronic stress-induced synapse loss and social behavior deficits

Inflammation and synapse loss have been associated with deficits in social behavior and are involved in pathophysiology of many neuropsychiatric disorders. Synapse loss, characterized by reduction in dendritic spines can significantly disrupt synaptic connectivity and neural circuitry underlying social behavior. Chronic stress is known to induce loss of spines and dendrites in the prefrontal cortex (PFC), a brain region implicated in social behavior. However, the underlying mechanisms are not well understood. In the present study, we investigated the role of type I Interferon (IFN-I) signaling in chronic unpredictable stress (CUS)-induced synapse loss and behavior deficits in mice. We found increased expression of type I IFN receptor (IFNAR) in microglia following CUS. Conditional knockout of microglial IFNAR in adult mice rescued CUS-induced social behavior deficits and synapse loss. Bulk RNA sequencing data show that microglial IFNAR deletion attenuated CUS-mediated changes in the expression of genes such as Keratin 20 (Krt20), Claudin-5 (Cldn5) and Nuclear Receptor Subfamily 4 Group A Member 1 (Nr4a1) in the PFC. Cldn5 and Nr4a1 are known for their roles in synaptic plasticity. Krt20 is an intermediate filament protein responsible for the structural integrity of epithelial cells. The reduction in Krt20 following CUS presents a novel insight into the potential contribution of cytokeratin in stress-induced alterations in neuroplasticity. Overall, these results suggest that microglial IFNAR plays a critical role in regulating synaptic plasticity and social behavior deficits associated with chronic stress conditions.

The dynamic duo: Decoding the roles of hypoxia-inducible factors in neonatal hypoxic-ischemic brain injury

Neonatal hypoxic-ischemic encephalopathy (HIE) results in considerable mortality and neurodevelopmental disability, with a particularly high disease burden in low- and middle-income countries. Improved understanding of the pathophysiology underlying this injury could allow for improved diagnostic and therapeutic options. Specifically, hypoxia-inducible factors (HIF-1α and HIF-2α) likely play a key role, but that role is complex and remains understudied. This review analyses the recent findings seeking to uncover the impacts of HIF-1α and HIF-2α in neonatal hypoxic-ischemic brain injury (HIBI), focusing on their cell specific expression, time-dependant activities, and potential therapeutic implications. Recent findings have revealed temporal patterns of HIF-1α and HIF-2α expression following hypoxic-ischemic injury, with distinct functions for HIF-1α versus HIF-2α within the neonatal brain. Ongoing studies aimed at further revealing the relationship between HIF isoforms and developing targeted interventions offer promising avenues for therapeutic management which could improve long-term neurological outcomes in affected newborns.

Severity of Repetitive Mild Traumatic Brain Injury Depends on Microglial Heme Oxygenase-1 and Carbon Monoxide

Traumatic brain injury is one of the most common cerebral incidences worldwide. Repetitive mild traumatic brain injuries occurring, for example, in athletes or victims of abuse, can cause chronic neurodegeneration due to neuroinflammation, in which the crosstalk between reactive astrocytes and activated microglia is crucial for modulating neuronal damage. The inducible enzyme heme oxygenase-1 and its product carbon monoxide are known to be ascribed neuroprotective and anti-inflammatory properties. We caused repetitive mild traumatic brain injuries in wild-type mice compared to mice without microglial heme oxygenase-1 expression. Additionally, mice were treated daily with either air or carbon monoxide exogenously. In wild-type mice, we observed enhanced microglia activation and astrogliosis as well as vasodilation after repetitive trauma. In heme oxygenase-1 knockout mice, we observed enhanced activation of microglia and astrocytes at baseline pretrauma with a lack of an adequate inflammatory response to repetitive injury. However, the knockout led to enhanced NF-κB and IFNγ expression in the post-trauma period. Carbon monoxide exerted neuroprotection, as suggested by reduced wake-up times in mice and by beneficially altering inflammation post-traumatic brain injury. This study further underlines the crucial role of the heme oxygenase-1/carbon monoxide system in the modulation of neuronal damage and the associated neuroinflammatory response after repetitive traumatic brain injury.

The protective effects of gastrodin on neurological disorders: an update and future perspectives

Neurological disorders are characterized by high mortality and disability rates. Furthermore, the burden associated with disability and mortality resulting from neurological disorders has been increasing at an alarming rate. Botanical drugs and their bioactive components have emerged as a prominent area of research, offering a promising avenue for developing novel alternatives for treating neurological diseases. Gastrodin is the principal active component derived from the traditional Chinese medicinal plant Gastrodia elata Blume (GEB). Existing literature reveals that gastrodin exerts various pharmacological protective actions against neurological disorders. This review aimed to collate novel literature on gastrodin for treating neurological disorders from Web of Science, PubMed, Embase and CNKI. The pharmacokinetics of gastrodin, its therapeutic role in neurological disorders, the main mechanisms of action and clinical application were addressed. Furthermore, a detailed overview of gastrodin drug delivery systems and physical enhancement methods was presented, offering invaluable insights into potential research and the extensive applications of gastrodin.

Betaine improves METH-induced depressive-like behavior and cognitive impairment by alleviating neuroinflammation via NLRP3 inflammasome inhibition

Methamphetamine abuse has been associated with central nervous system damage, contributing to the development of neuropsychiatric disorders such as depressive-like behavior and cognitive impairment. With the escalating prevalence of METH abuse, there is a pressing need to explore effective therapeutic interventions. Thus, the objective of this research was to investigate whether betaine can protect against depressive-like behavior and cognitive impairment induced by METH. Following intraperitoneal injections of METH in mice, varying doses of betaine were administered. Subsequently, the behavioral responses of mice and the impact of betaine intervention on METH-induced neural damage, synaptic plasticity, microglial activation, and NLRP3 inflammatory pathway activation were assessed. Administration 30 mg/kg and 100 mg/kg of betaine ameliorated METH-induced depressive-like behaviors in the open field test, tail suspension test, forced swimming test, and sucrose preference test and cognitive impairment in the novel object recognition test and Barnes maze test. Moreover, betaine exerted protective effects against METH-induced neural damage and reversed the reduced synaptic plasticity, including the decline in dendritic spine density, as well as alterations in the expression of hippocampal PSD95 and Synapsin-1. Additionally, betaine treatment suppressed hippocampal microglial activation induced by METH. Likewise, it also inhibited the activation of the hippocampal NLRP3 inflammasome pathway and reduced IL-1β and TNF-α release. These results collectively suggest that betaine's significant role in mitigating depressive-like behavior and cognitive impairment resulting from METH abuse, presenting potential applications in the prevention and treatment of substance addiction.

Falcarindiol improves functional recovery and alleviates neuroinflammation after spinal cord injury by inhibiting STAT/MAPK signaling pathways

Spinal cord injury (SCI) is a devastating trauma in the central nervous system (CNS), leading to motor and sensory impairment. Neuroinflammation is one of the critical contributors to the progression of secondary injury. Falcarindiol has been reported to efficaciously mitigate lipopolysaccharide (LPS)-mediated inflammation in RAW 264.7 cells. The role of falcarindiol in SCI recovery remains unclear. In this present study, traumatic SCI mice models and LPS-stimulated murine microglia cell line (BV2 cells) were performed to explore the pharmacological effects and the underlying mechanisms of falcarindiol in improving SCI repair with detection of motor function recovery, morphological changes, numbers of survival neurons and protein expression levels of inflammation or apoptosis-related proteins. Our study found that falcarindiol intervention could promote motor function recovery and reduce spinal cord tissue damage in mice following SCI. Mechanistically, falcarindiol intervention suppressed apoptosis-driven neuronal cell death and mitigated inflammatory reactions following SCI. Additionally, falcarindiol inhibited the activation of signal transducer and activator of transcription (STAT) and mitogen-activated protein kinases (MAPK) signaling pathways in vivo and in vitro. This suppression of STAT and MAPK activation by falcarindiol was reversed by STAT3 agonist Colivelin TFA and MAPK agonist C16-PAF in BV2 cells, respectively. Moreover, the study further demonstrated that the anti-inflammation role of falcarindiol was obstructed by Colivelin TFA but not by C16-PAF in LPS-stimulated BV2 cells, suggesting that falcarindiol may efficaciously ameliorate neuroinflammation through inhibiting the activation of STAT signaling pathway following SCI. Collectively, our study indicates that falcarindiol may be a novel drug candidate for the treatment and management of SCI.

PTPN7 mediates macrophage-polarization and determines immunotherapy in gliomas: A single-cell sequencing analysis

BACKGROUND

Protein tyrosine phosphatase non-receptor type 7 (PTPN7) is a signaling molecule that regulates a multitude of cellular processes, spanning cell proliferation, cellular differentiation, the mitotic cycle, and oncogenic metamorphosis. However, the characteristic of PTPN7 in the glioma microenvironment has yet to be elucidated.

METHODS

The prognostic value, genomic features, immune characteristics, chemotherapy prediction, and immunotherapy prediction of PTPN7 were systematically explored at the bulk sequencing level. The cell evolution trajectory, cell communication pattern, and cell metabolic activity related to PTPN7 were systematically explored at the single-cell sequencing level. HMC3 and M0 cells were cocultured with U251 and T98G cells, and flow cytometry was carried out to investigate the polarization of HMC3 and M0. Transwell assay and CCK-8 assay were performed to explore the migration and proliferation activity of U251 and T98G.

RESULTS

The expression level of PTPN7 is significantly elevated in glioma and indicates malignant features. PTPN7 expression predicts worse prognosis of glioma patients. PTPN7 is associated with genome alteration and immune infiltration. Besides, PTPN7 plays a crucial role in modulating metabolic and immunogenic processes, particularly by influencing the activity of microglia and macrophages through multiple signaling pathways involved in cellular communication. Specifically, PTPN7 actively mediates inflammation-resolving-polarization of macrophages and microglia and protects glioma from immune attack. PTPN7 could also predict the response of immunotherapy.

CONCLUSIONS

PTPN7 is critically involved in inflammation-resolving-polarization mediated by macrophage and microglia and promotes the immune escape of glioma cells.

Quercetin ameliorates neuroinflammatory and neurodegenerative biomarkers in the brain and improves neurobehavioral parameters in a repeated intranasal amyloid-beta exposed model of Alzheimer's disease

Objectives: The aim of the present study was to study the potential therapeutic effects of quercetin in protection against repeated intranasal exposure of an amyloid-beta-induced mouse model. Methods: Mice received intranasal Aβ1-42 (5 μg/10 μL) exposure once daily for seven consecutive days. Quercetin was orally administered to them at 30 mg kg-1 and 100 mg kg-1 doses for one week starting from day five following Aβ1-42 peptide administration. Following this, the animals were evaluated for neurobehavioral parameters using a Morris water maze test and a novel object recognition test. Further to this, the biomarkers for neuroinflammation and neurodegeneration were evaluated in the hippocampus and cortex regions of the brain in these animals. Results: Multiple exposures to intranasal Aβ led to a significant decline in the learning and cognitive memory of the animals, whereas oral treatment with quercetin at dosages of 30 and 100 mg kg-1 alleviated Aβ-induced effects. Quercetin treatment significantly reduced Aβ accumulation, oxidative stress and proinflammatory cytokine biomarkers in the brain. In addition, it also alleviated the activation of astrocytic biomarkers, amyloid precursor protein and phosphorylated-tau proteins in the brain. Conclusion: Quercetin was found to be a potent antioxidant, anti-inflammatory compound with protection against neurodegenerative damage and improved learning and cognitive memory in a repeated Aβ-exposure model of AD.

Analysis of gene expression in microglial apoptotic cell clearance following spinal cord injury based on machine learning algorithms

Spinal cord injury (SCI) is a severe neurological complication following spinal fracture, which has long posed a challenge for clinicians. Microglia play a dual role in the pathophysiological process after SCI, both beneficial and detrimental. The underlying mechanisms of microglial actions following SCI require further exploration. The present study combined three different machine learning algorithms, namely weighted gene co-expression network analysis, random forest analysis and least absolute shrinkage and selection operator analysis, to screen for differentially expressed genes in the GSE96055 microglia dataset after SCI. It then used protein-protein interaction networks and gene set enrichment analysis with single genes to investigate the key genes and signaling pathways involved in microglial function following SCI. The results indicated that microglia not only participate in neuroinflammation but also serve a significant role in the clearance mechanism of apoptotic cells following SCI. Notably, bioinformatics analysis and lipopolysaccharide + UNC569 (a MerTK-specific inhibitor) stimulation of BV2 cell experiments showed that the expression levels of Anxa2, Myo1e and Spp1 in microglia were significantly upregulated following SCI, thus potentially involved in regulating the clearance mechanism of apoptotic cells. The present study suggested that Anxa2, Myo1e and Spp1 may serve as potential targets for the future treatment of SCI and provided a theoretical basis for the development of new methods and drugs for treating SCI.

NDC80/HEC1 promotes macrophage polarization and predicts glioma prognosis via single-cell RNA-seq and in vitro experiment

INTRODUCTION

Glioma is the most frequent and lethal form of primary brain tumor. The molecular mechanism of oncogenesis and progression of glioma still remains unclear, rendering the therapeutic effect of conventional radiotherapy, chemotherapy, and surgical resection insufficient. In this study, we sought to explore the function of HEC1 (highly expressed in cancer 1) in glioma; a component of the NDC80 complex in glioma is crucial in the regulation of kinetochore.

METHODS

Bulk RNA and scRNA-seq analyses were used to infer HEC1 function, and in vitro experiments validated its function.

RESULTS

HEC1 overexpression was observed in glioma and was indicative of poor prognosis and malignant clinical features, which was confirmed in human glioma tissues. High HEC1 expression was correlated with more active cell cycle, DNA-associated activities, and the formation of immunosuppressive tumor microenvironment, including interaction with immune cells, and correlated strongly with infiltrating immune cells and enhanced expression of immune checkpoints. In vitro experiments and RNA-seq further confirmed the role of HEC1 in promoting cell proliferation, and the expression of DNA replication and repair pathways in glioma. Coculture assay confirmed that HEC1 promotes microglial migration and the transformation of M1 phenotype macrophage to M2 phenotype.

CONCLUSION

Altogether, these findings demonstrate that HEC1 may be a potential prognostic marker and an immunotherapeutic target in glioma.

The Janus face of HIF-1α in ischemic stroke and the possible associated pathways

Stroke is the most devastating disease, causing paralysis and eventually death. Many clinical and experimental trials have been done in search of a new safe and efficient medicine; nevertheless, scientists have yet to discover successful remedies that are also free of adverse effects. This is owing to the variability in intensity, localization, medication routes, and each patient's immune system reaction. HIF-1α represents the modern tool employed to treat stroke diseases due to its functions: downstream genes such as glucose metabolism, angiogenesis, erythropoiesis, and cell survival. Its role can be achieved via two downstream EPO and VEGF strongly related to apoptosis and antioxidant processes. Recently, scientists paid more attention to drugs dealing with the HIF-1 pathway. This review focuses on medicines used for ischemia treatment and their potential HIF-1α pathways. Furthermore, we discussed the interaction between HIF-1α and other biological pathways such as oxidative stress; however, a spotlight has been focused on certain potential signalling contributed to the HIF-1α pathway. HIF-1α is an essential regulator of oxygen balance within cells which affects and controls the expression of thousands of genes related to sustaining homeostasis as oxygen levels fluctuate. HIF-1α's role in ischemic stroke strongly depends on the duration and severity of brain damage after onset. HIF-1α remains difficult to investigate, particularly in ischemic stroke, due to alterations in the acute and chronic phases of the disease, as well as discrepancies between the penumbra and ischemic core. This review emphasizes these contrasts and analyzes the future of this intriguing and demanding field.

Automated radiosynthesis of [18F]DPA-714 on a commercially available IBA Synthera®

The goal of this work was to develop a reliable method to produce the well-validated microglial activation PET tracer, [18F]DPA-714, routinely for clinical and preclinical research using an IBA Synthera®. Optimization of literature methods included reduced precursor mass and use of TBA HCO3 as the phase transfer agent in place of Kryptofix® 222 in a 65-min synthesis with an average activity yield of 24.6 ± 3.8% (n = 5). Successful quality control testing and process validation results are reported.

Ultrasound imaging guided precision histotripsy: Effects of pulse settings on ablation properties in rat brain

A high-frequency 6 MHz miniature handheld histotripsy device with an endoscopic form factor and co-registered high-resolution ultrasound imaging was developed. This device could allow precision histotripsy ablation during minimally invasive brain tumor surgeries with real-time image guidance. This study characterized the outcome of acute histotripsy in the normal in vivo rat brain using the device with a range of histotripsy pulse settings, including number of cycles, pulse repetition frequency, and pressure, as well as other experimental factors. The stability and shape of the bubble cloud were measured during ablations, as well as the post-histotripsy ablation shape in ultrasound B-mode and histology. The results were compared between histological images and the ultrasound imaging data to determine how well ultrasound data reflected observable damage in histology. The results indicated that while pulse settings can have some influence on ablation shape, sample-to-sample variation had a larger influence on ablation shape. This suggests that real-time ablation monitoring is essential for accurate knowledge of outcomes. Ultrasound imaging provided an accurate real-time indication of ablation shape both during ablation and post-ablation.

Research progress on the relationship between traumatic brain injury and brain-gut-microbial axis

Traumatic brain injury (TBI) is a common disease with a high rate of death and disability, which poses a serious threat to human health; thus, the effective treatment of TBI has been a high priority. The brain-gut-microbial (BGM) axis, as a bidirectional communication network for information exchange between the brain and gut, plays a crucial role in neurological diseases. This article comprehensively explores the interrelationship between the BGM axis and TBI, including its physiological effects, basic pathophysiology, and potential therapeutic strategies. It highlights how the bidirectional regulatory pathways of the BGM axis could provide new insights into clinical TBI treatment and underscores the necessity for advanced research and development of innovative clinical treatments for TBI.

Cofilactin rod formation mediates inflammation-induced neurite degeneration

Stroke, trauma, and neurodegenerative disorders cause loss of neurites (axons and dendrites) in addition to neuronal death. Neurite loss may result directly from a primary insult, secondary to parental neuron death, or secondary to a post-injury inflammatory response. Here, we use lipopolysaccharide and the alarmin S100β to selectively evaluate neurite loss caused by the inflammatory response. Activation of microglia and infiltrating macrophages by these stimuli causes neurite loss that far exceeds neuronal death, both in vitro and in vivo. Neurite loss is accompanied by the formation of cofilactin rods and aggregates (CARs), which are polymers of cofilin-1 and actin induced by oxidative stress and other factors. Mice deficient in either cofilin-1 or the superoxide-generating enzyme NADPH oxidase-2 show reduced CAR formation, neurite loss, and motor impairment. The findings identify a mechanism by which inflammation leads to neurite loss via CAR formation and highlight the relevance of neurite loss to functional impairment.

Exosomes derived from umbilical cord-mesenchymal stem cells inhibit the NF-κB/MAPK signaling pathway and reduce the inflammatory response to promote recovery from spinal cord injury

Spinal cord injury (SCI) is a serious traumatic disease of the central nervous system and leads to incomplete or complete loss of the body's autonomous motor and sensory functions, seriously endangering human health. Recently, exosomes have been proposed as important substances in cell-to-cell interactions. Mesenchymal stem cell (MSC)-derived exosomes exert good therapeutic effects and play a crucial role in neurological damage repair. However, the detailed mechanisms underlying their effects remain unknown. Herein, we found that compared to SCI rats, those subjected to umbilical cord MSC (UC-MSC)-derived exosomes injection showed an improved motor ability. Nevertheless, the transcriptome of BV2 microglia in different treatment groups indicated that the action pathway of exosomes might be the NF-κB/MAPK pathway. Additionally, exosomes from UC-MSCs could inhibit P38, JNK, ERK, and P65 phosphorylation in BV2 microglia and SCI rat tissues. Moreover, exosomes could inhibit apoptosis and inflammatory reaction and reactive oxygen species (ROS) production of BV2 microglia in vitro and in vivo. In conclusion, UC-MSCs-derived exosomes might protect SCI in rats by inhibiting inflammatory response via the NF-κB/MAPK signaling pathway, representing novel treatment targets or approaches for SCI.

Down-regulation of MKP-1 in hippocampus protects against stress-induced depression-like behaviors and neuroinflammation

Chronic stress is the primary environmental risk factor for major depressive disorder (MDD), and there is compelling evidence that neuroinflammation is the major pathomechanism linking chronic stress to MDD. Mitogen-activated protein kinase (MAPK) phosphatase-1 (MKP-1) is a negative regulator of MAPK signaling pathways involved in cellular stress responses, survival, and neuroinflammation. We examined the possible contributions of MKP-1 to stress-induced MDD by comparing depression-like behaviors (anhedonia, motor retardation, behavioral despair), neuroinflammatory marker expression, and MAPK signaling pathways among rats exposed to chronic unpredictable mild stress (CUMS), overexpressing MKP-1 in the hippocampus, and CUMS-exposed rats underexpressing MKP-1 in the hippocampus. Rats exposed to CUMS exhibited MKP-1 overexpression, greater numbers of activated microglia, and enhanced expressions of neuroinflammatory markers (interleukin [IL]-6, [IL]-1β, tumor necrosis factor [TNF]-ɑ, and decreased phosphorylation levels of ERK and p38 in the hippocampus as well as anhedonia in the sucrose preference test, motor retardation in the open field, and greater immobility (despair) in the forced swimming tests. These signs of neuroinflammation and depression-like behaviors and phosphorylation levels of ERK and p38 were also observed in rats overexpressing MKP-1 without CUMS exposure, while CUMS-induced neuroinflammation, microglial activation, phosphorylation levels of ERK and p38, and depression-like behaviors were significantly reversed by MKP-1 knockdown. Moreover, MKP-1 knockdown promoted the activation of the MAPK isoform ERK, implying that the antidepressant-like effects of MKP-1 knockdown may be mediated by the ERK pathway disinhibition. These findings suggested that hippocampal MKP-1 is an essential regulator of stress-induced neuroinflammation and a promising target for antidepressant development.

Reactive gliosis in traumatic brain injury: a comprehensive review

Traumatic brain injury (TBI) is one of the most common pathological conditions impacting the central nervous system (CNS). A neurological deficit associated with TBI results from a complex of pathogenetic mechanisms including glutamate excitotoxicity, inflammation, demyelination, programmed cell death, or the development of edema. The critical components contributing to CNS response, damage control, and regeneration after TBI are glial cells-in reaction to tissue damage, their activation, hypertrophy, and proliferation occur, followed by the formation of a glial scar. The glial scar creates a barrier in damaged tissue and helps protect the CNS in the acute phase post-injury. However, this process prevents complete tissue recovery in the late/chronic phase by producing permanent scarring, which significantly impacts brain function. Various glial cell types participate in the scar formation, but this process is mostly attributed to reactive astrocytes and microglia, which play important roles in several brain pathologies. Novel technologies including whole-genome transcriptomic and epigenomic analyses, and unbiased proteomics, show that both astrocytes and microglia represent groups of heterogenic cell subpopulations with different genomic and functional characteristics, that are responsible for their role in neurodegeneration, neuroprotection and regeneration. Depending on the representation of distinct glia subpopulations, the tissue damage as well as the regenerative processes or delayed neurodegeneration after TBI may thus differ in nearby or remote areas or in different brain structures. This review summarizes TBI as a complex process, where the resultant effect is severity-, region- and time-dependent and determined by the model of the CNS injury and the distance of the explored area from the lesion site. Here, we also discuss findings concerning intercellular signaling, long-term impacts of TBI and the possibilities of novel therapeutical approaches. We believe that a comprehensive study with an emphasis on glial cells, involved in tissue post-injury processes, may be helpful for further research of TBI and be the decisive factor when choosing a TBI model.

Regional Microglial Response in Entorhino-Hippocampal Slice Cultures to Schaffer Collateral Lesion and Metalloproteinases Modulation

Microglia and astrocytes are essential in sustaining physiological networks in the central nervous system, with their ability to remodel the extracellular matrix, being pivotal for synapse plasticity. Recent findings have challenged the traditional view of homogenous glial populations in the brain, uncovering morphological, functional, and molecular heterogeneity among glial cells. This diversity has significant implications for both physiological and pathological brain states. In the present study, we mechanically induced a Schaffer collateral lesion (SCL) in mouse entorhino-hippocampal slice cultures to investigate glial behavior, i.e., microglia and astrocytes, under metalloproteinases (MMPs) modulation in the lesioned area, CA3, and the denervated region, CA1. We observed distinct response patterns in the microglia and astrocytes 3 days after the lesion. Notably, GFAP-expressing astrocytes showed no immediate changes post-SCL. Microglia responses varied depending on their anatomical location, underscoring the complexity of the hippocampal neuroglial network post-injury. The MMPs inhibitor GM6001 did not affect microglial reactions in CA3, while increasing the number of Iba1-expressing cells in CA1, leading to a withdrawal of their primary branches. These findings highlight the importance of understanding glial regionalization following neural injury and MMPs modulation and pave the way for further research into glia-targeted therapeutic strategies for neurodegenerative disorders.

Emerging role of mesenchymal stem cells-derived extracellular vesicles in vascular dementia

Vascular dementia (VD) is a prevalent cognitive disorder among the elderly. Its pathological mechanism encompasses neuronal damage, synaptic dysfunction, vascular abnormalities, neuroinflammation, and oxidative stress, among others. In recent years, extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) have garnered significant attention as an emerging therapeutic strategy. Current research indicates that MSC-derived extracellular vesicles (MSC-EVs) play a pivotal role in both the diagnosis and treatment of VD. Thus, this article delves into the recent advancements of MSC-EVs in VD, discussing the mechanisms by which EVs influence the pathophysiological processes of VD. These mechanisms form the theoretical foundation for their neuroprotective effect in VD treatment. Additionally, the article highlights the potential applications of EVs in VD diagnosis. In conclusion, MSC-EVs present a promising innovative treatment strategy for VD. With rigorous research and ongoing innovation, this concept can transition into practical clinical treatment, providing more effective options for VD patients.

Anti-inflammatory and antioxidative actions of tacrolimus (FK506) on human microglial HMC3 cell line

Microglial cells are indispensable for the normal development and functioning of neurons in the central nervous system, where they play a crucial role in maintaining brain homeostasis by surveilling the microenvironment for signs of injury or stress and responding accordingly. However, in neurodegenerative diseases, the density and phenotypes of microglial cells undergo changes, leading to chronic activation and inflammation. Shifting the focus from neurons to microglia in drug discovery for neurodegenerative diseases has become an important therapeutic target. This study was aimed to investigate the potential of Tacrolimus (FK506) an FDA-approved calcineurin inhibitor, to modulate the pathology of neurodegenerative diseases through anti-inflammatory and antioxidative effects on microglial activation. The human microglia clone 3 (HMC3) cells were exposed to 1 μg/mL LPS in the presence and absence of doses of FK506. Survival rates of cells were determined using the 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) method. Morphological evaluation of cells showed that FK506 restored the normal morphology of activated microglia. Furthermore, FK506 treatment increases the total antioxidant capacity and reduces the total oxidative capacity, indicating its potential antioxidant effects. Data from ELISA and RT-PCR analyses showed that LPS abolished its promoting effects on the release of proinflammatory IL-1β and IL-6 cytokines in HMC3 cells, reflecting the anti-inflammatory effect of FK506. These findings support the idea that FK506 could be a promising therapeutic agent for neurodegenerative diseases by modulating microglial activation and reducing inflammation and oxidative stress.

The Multifaceted Role of Cofilin in Neurodegeneration and Stroke: Insights into Pathogenesis and Targeting as a Therapy

This comprehensive review explores the complex role of cofilin, an actin-binding protein, across various neurodegenerative diseases (Alzheimer's, Parkinson's, schizophrenia, amyotrophic lateral sclerosis (ALS), Huntington's) and stroke. Cofilin is an essential protein in cytoskeletal dynamics, and any dysregulation could lead to potentially serious complications. Cofilin's involvement is underscored by its impact on pathological hallmarks like Aβ plaques and α-synuclein aggregates, triggering synaptic dysfunction, dendritic spine loss, and impaired neuronal plasticity, leading to cognitive decline. In Parkinson's disease, cofilin collaborates with α-synuclein, exacerbating neurotoxicity and impairing mitochondrial and axonal function. ALS and frontotemporal dementia showcase cofilin's association with genetic factors like C9ORF72, affecting actin dynamics and contributing to neurotoxicity. Huntington's disease brings cofilin into focus by impairing microglial migration and influencing synaptic plasticity through AMPA receptor regulation. Alzheimer's, Parkinson's, and schizophrenia exhibit 14-3-3 proteins in cofilin dysregulation as a shared pathological mechanism. In the case of stroke, cofilin takes center stage, mediating neurotoxicity and neuronal cell death. Notably, there is a potential overlap in the pathologies and involvement of cofilin in various diseases. In this context, referencing cofilin dysfunction could provide valuable insights into the common pathologies associated with the aforementioned conditions. Moreover, this review explores promising therapeutic interventions, including cofilin inhibitors and gene therapy, demonstrating efficacy in preclinical models. Challenges in inhibitor development, brain delivery, tissue/cell specificity, and long-term safety are acknowledged, emphasizing the need for precision drug therapy. The call to action involves collaborative research, biomarker identification, and advancing translational efforts. Cofilin emerges as a pivotal player, offering potential as a therapeutic target. However, unraveling its complexities requires concerted multidisciplinary efforts for nuanced and effective interventions across the intricate landscape of neurodegenerative diseases and stroke, presenting a hopeful avenue for improved patient care.

Leveraging the ATP-P2X7 receptor signalling axis to alleviate traumatic CNS damage and related complications

The P2X7 receptor is an exceptional member of the P2X purinergic receptor family, with its activation requiring high concentrations of extracellular adenosine 5'-triphosphate (ATP) that are often associated with tissue damage and inflammation. In the central nervous system (CNS), it is highly expressed in glial cells, particularly in microglia. In this review, we discuss the role and mechanisms of the P2X7 receptor in mediating neuroinflammation and other pathogenic events in a variety of traumatic CNS damage conditions, which lead to loss of neurological and cognitive functions. We raise the perspective on the steady progress in developing CNS-penetrant P2X7 receptor-specific antagonists that leverage the ATP-P2X7 receptor signaling axis as a potential therapeutic strategy to alleviate traumatic CNS damage and related complications.

Development and validation of a differentiation-related signature based on single-cell RNA sequencing data of immune cells in spinal cord injury

Background

After spinal cord injury (SCI), the native immune surveillance function of the central nervous system is activated, resulting in a substantial infiltration of immune cells into the affected tissue. While numerous studies have explored the transcriptome data following SCI and revealed certain diagnostic biomarkers, there remains a paucity of research pertaining the identification of immune subtypes and molecular markers related to the immune system post-spinal cord injury using single-cell sequencing data of immune cells.

Methods

The researchers conducted an analysis of spinal cord samples obtained at three time points (3,10, and 21 days) following SCI using the GSE159638 dataset. The SCI subsets were delineated through pseudo-time analysis, and differentiation related genes were identified after principal component analysis (PCA), cell clustering, and annotation techniques. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were employed to assess the differentiation-related genes (DRGs) across different subsets. The molecular subtypes of SCI were determined using consensus clustering analysis. To further explore and validate the correlation between the molecular subtypes and the immune microenvironment, the CIBERSORT algorithm was employed. High-value diagnostic gene markers were identified using LASSO regression, and their diagnostic sensitivity was assessed using receiver operating characteristic curves (ROC) and quantitative real-time polymerase chain reaction (qRT-PCR).

Results

Three SCI subsets were obtained, and differentiation-related genes were characterized. Within these subsets, two distinct molecular subtypes, namely C1 and C2, were identified. These subtypes demonstrated significant variations in terms of immune cell infiltration levels and the expression of immune checkpoint genes. Through further analysis, three candidate biomarkers (C1qa, Lgals3 and Cd63) were identified and subsequently validated.

Conclusions

Our study revealed a diverse immune microenvironment in SCI samples, highlighting the potential significance of C1qa, Lgals3 and Cd63 as immune biomarkers for diagnosing SCI. Moreover, the identification of immune checkpoints corresponding to the two molecular subtypes suggests their potential as targets for immunotherapy to enhance SCI repair in future interventions.

Regulation of enolase activation to promote neural protection and regeneration in spinal cord injury

Spinal cord injury (SCI) is a debilitating condition characterized by damage to the spinal cord resulting in loss of function, mobility, and sensation with no U.S. Food and Drug Administration-approved cure. Enolase, a multifunctional glycolytic enzyme upregulated after SCI, promotes pro- and anti-inflammatory events and regulates functional recovery in SCI. Enolase is normally expressed in the cytosol, but the expression is upregulated at the cell surface following cellular injury, promoting glial cell activation and signal transduction pathway activation. SCI-induced microglia activation triggers pro-inflammatory mediators at the injury site, activating other immune cells and metabolic events, i.e., Rho-associated kinase, contributing to the neuroinflammation found in SCI. Enolase surface expression also activates cathepsin X, resulting in cleavage of the C-terminal end of neuron-specific enolase (NSE) and non-neuronal enolase (NNE). Fully functional enolase is necessary as NSE/NNE C-terminal proteins activate many neurotrophic processes, i.e., the plasminogen activation system, phosphatidylinositol-4,5-bisphosphate 3-kinase/protein kinase B, and mitogen-activated protein kinase/extracellular signal-regulated kinase. Studies here suggest an enolase inhibitor, ENOblock, attenuates the activation of Rho-associated kinase, which may decrease glial cell activation and promote functional recovery following SCI. Also, ENOblock inhibits cathepsin X, which may help prevent the cleavage of the neurotrophic C-terminal protein allowing full plasminogen activation and phosphatidylinositol-4,5-bisphosphate 3-kinase/mitogen-activated protein kinase activity. The combined NSE/cathepsin X inhibition may serve as a potential therapeutic strategy for preventing neuroinflammation/degeneration and promoting neural cell regeneration and recovery following SCI. The role of cell membrane-expressed enolase and associated metabolic events should be investigated to determine if the same strategies can be applied to other neurodegenerative diseases. Hence, this review discusses the importance of enolase activation and inhibition as a potential therapeutic target following SCI to promote neuronal survival and regeneration.

Multiple mechanisms of curcumin targeting spinal cord injury

Spinal cord injury (SCI) is an irreversible disease process with a high disability and mortality rate. After primary spinal cord injury, the secondary injury may occur in sequence, which is composed of ischemia and hypoxia, excitotoxicity, calcium overload, oxidative stress and inflammation, resulting in massive death of parenchymal cells in the injured area, followed by the formation of syringomyelia. Effectively curbing the process of secondary injury can promote nerve repair and improve functional prognosis. As the main active ingredient in turmeric, curcumin can play an important role in reducing inflammation and oxidation, protecting the neurons, and ultimately reducing spinal cord injury. This article reviews the effects of curcumin on the repair of nerve injury, with emphasis on the various mechanisms by which curcumin promotes the treatment of spinal cord injury.

The polarization of microglia and infiltrated macrophages in the injured mice spinal cords: a dynamic analysis

Background

Following spinal cord injury (SCI), a large number of peripheral monocytes infiltrate into the lesion area and differentiate into macrophages (Mø). These monocyte-derived Mø are very difficult to distinguish from the local activated microglia (MG). Therefore, the term Mø/MG are often used to define the infiltrated Mø and/or activated MG. It has been recognized that pro-inflammatory M1-type Mø/MG play "bad" roles in the SCI pathology. Our recent research showed that local M1 cells are mainly CD45^-/lowCD68⁺CD11b⁺ in the subacute stage of SCI. Thus, we speculated that the M1 cells in injured spinal cords mainly derived from MG rather than infiltrating Mø. So far, their dynamics following SCI are not yet entirely clear.

Methods

Female C57BL/6 mice were used to establish SCI model, using an Infinite Horizon impactor with a 1.3 mm diameter rod and a 50 Kdynes force. Sham-operated (sham) mice only underwent laminectomy without contusion. Flow cytometry and immunohistofluorescence were combined to analyze the dynamic changes of polarized Mø and MG in the acute (1 day), subacute (3, 7 and 14 days) and chronic (21 and 28 days) phases of SCI.

Results

The total Mø/MG gradually increased and peaked at 7 days post-injury (dpi), and maintained at high levels 14, 21 and 28 dpi. Most of the Mø/MG were activated, and the Mø increased significantly at 1 and 3 dpi. However, with the pathological process, activated MG increased nearly to 90% at 7, 14, 21 and 28 dpi. Both M1 and M2 Mø were increased significantly at 1 and 3 dpi. However, they decreased to very low levels from 7 to 28 dpi. On the contrary, the M2-type MG decreased significantly following SCI and maintained at a low level during the pathological process.

Ang-(1-7)/MasR axis promotes functional recovery after spinal cord injury by regulating microglia/macrophage polarization

BACKGROUND

Inflammatory response is an essential part of secondary injury after spinal cord injury (SCI). During this period, the injury may be exacerbated through the release of a large number of inflammatory factors and the polarization of infiltrating macrophages and microglia towards M1. Ang-(1-7), mainly generated by Ang II via angiotensin-converting enzyme 2 (ACE2), can specifically bind to the G protein-coupled receptor Mas (MasR) and plays an important role in regulating inflammation and alleviating oxidative stress.

METHODS

We aimed to investigate whether activating the Ang-(1-7)/MasR axis in rats after SCI can regulate local neuroinflammation to achieve functional recovery and obtain its potential mechanism. MasR expression of bone marrow-derived macrophages was determined by Western blot. Immunofluorescence, Western blot, Flow cytometry, and RT-qPCR were applied to evaluate the polarization of Ang-(1-7) on macrophages and the regulation of inflammatory cytokines. Previous evaluation of the spinal cord and bladder after SCI was conducted by hematoxylin-eosin staining, Basso, Beattie, and Bresnahan (BBB) score, inclined plate test, electrophysiology, and catwalk were used to evaluate the functional recovery of rats.

RESULTS

MasR expression increased in macrophages under inflammatory conditions and further elevated after Ang-(1-7) treatment. Both in vivo and in vitro results confirmed that Ang-(1-7) could regulate the expression of inflammatory cytokines by down-regulating proinflammatory cytokines and up-regulating anti-inflammatory cytokines, and bias the polarization direction of microglia/macrophages to M2 phenotypic. After SCI, Ang-(1-7) administration in situ led to better histological and functional recovery in rats, and this recovery at least partly involved the TLR4/NF-κB signaling pathway.

CONCLUSION

As shown in our data, activating Ang-(1-7)/MasR axis can effectively improve the inflammatory microenvironment after spinal cord injury, promote the polarization of microglia/macrophages towards the M2 phenotype, and finally support the recovery of motor function. Therefore, we suggest using Ang-(1-7) as a feasible treatment strategy for spinal cord injury to minimize the negative consequences of the inflammatory microenvironment after spinal cord injury.

Dopamine inhibits pyroptosis and attenuates secondary damage after spinal cord injury in female mice

BACKGROUND

An excessive inflammatory response accompanies the pathogenesis of spinal cord injury (SCI) and has been found to be promoted by inflammasomes in a variety of disease models. Dopamine is a neurotransmitter that also regulates nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) inflammasome-dependent neuroinflammation. However, little is known regarding the effects and molecular mechanisms underlying the role of dopamine in SCI.

METHODS

Functional recovery in mice was assessed with the Basso Mouse Scale (BMS). Neuronal loss was evaluated with immunochemical staining of NeuN. Pyroptosis was assessed with immunofluorescence staining, flow cytometry, western blotting, and cell viability and cytotoxicity assays.

RESULTS

Dopamine was significantly associated with enhanced locomotor recovery after SCI, and with decreased NLRP3 inflammasome activation, pyroptosis, neuronal loss and pro-inflammatory cytokine levels. In vitro data suggested that dopamine suppressed NLRP3 inflammasome activation and pyroptosis, and decreased pro-inflammatory cytokine levels.

CONCLUSIONS

Dopamine may be a novel approach for alleviating secondary damage after SCI.

Deletion of Bak1 alleviates microglial necroptosis and neuroinflammation after experimental subarachnoid hemorrhage

Microglial necroptosis exacerbates neurodegenerative diseases, central nervous system (CNS) injury, and demonstrates a proinflammatory process, but its contribution to subarachnoid hemorrhage (SAH) is poorly characterized. BCL-2 homologous antagonist-killer protein (Bak1), a critical regulatory molecule of endogenous apoptosis, can be involved in the pathologic process of necroptosis by regulating mitochondrial permeability. In this study, we revealed microglia undergo necroptosis after SAH in vivo and vitro. Western blot revealed that Bak1 was elevated at 24 h after SAH. Knocked down of Bak1 by adeno-associated virus attenuates microglial necroptosis, alleviates neuroinflammation, and improves neurologic function after SAH in mice. Furthermore, oxyhemoglobin (10 μM) induced necroptosis in BV2 microglia, increasing Bak1 expression and mediating proinflammatory phenotype transformation, exacerbating oxidative stress and neuroinflammation. Abrogating BV2 Bak1 could reduce necroptosis by down-regulating the expression of phosphorylated pseudokinase mixed lineage kinase domain-like protein (p-MLKL), then down-regulating proinflammatory phenotype gene expression. RNA-Seq showed that disrupting BV2 Bak1 down-regulates multiple immune and inflammatory pathways and ameliorates cell injury by elevating thrombospondin 1 (THBS1) expression. In summary, we identified a critical regulatory role for Bak1 in microglial necroptosis and neuroinflammation after SAH. Bak1 is expected to be a potential target for the treatment strategy of SAH.

Phagocytic microglia and macrophages in brain injury and repair

AIMS

Phagocytosis is the cellular digestion of extracellular particles, such as pathogens and dying cells, and is a key element in the evolution of central nervous system (CNS) disorders. Microglia and macrophages are the professional phagocytes of the CNS. By clearing toxic cellular debris and reshaping the extracellular matrix, microglia/macrophages help pilot the brain repair and functional recovery process. However, CNS resident and invading immune cells can also magnify tissue damage by igniting runaway inflammation and phagocytosing stressed-but viable-neurons.

DISCUSSION

Microglia/macrophages help mediate intercellular communication and react quickly to the "find-me" signals expressed by dead/dying neurons. The activated microglia/macrophages then migrate to the injury site to initiate the phagocytic process upon encountering "eat-me" signals on the surfaces of endangered cells. Thus, healthy cells attempt to avoid inappropriate engulfment by expressing "do not-eat-me" signals. Microglia/macrophages also have the capacity to phagocytose immune cells that invade the injured brain (e.g., neutrophils) and to regulate their pro-inflammatory properties. During brain recovery, microglia/macrophages engulf myelin debris, initiate synaptogenesis and neurogenesis, and sculpt a favorable extracellular matrix to support network rewiring, among other favorable roles. Here, we review the multilayered nature of phagocytotic microglia/macrophages, including the molecular and cellular mechanisms that govern microglia/macrophage-induced phagocytosis in acute brain injury, and discuss strategies that tap into the therapeutic potential of this engulfment process.

CONCLUSION

Identification of biological targets that can temper neuroinflammation after brain injury without hindering the essential phagocytic functions of microglia/macrophages will expedite better medical management of the stroke recovery stage.

NG2-glia crosstalk with microglia in health and disease

Neurodegenerative diseases are increasingly becoming a global problem. However, the pathological mechanisms underlying neurodegenerative diseases are not fully understood. NG2‐glia abnormalities and microglia activation are involved in the development and/or progression of neurodegenerative disorders, such as multiple sclerosis, Alzheimer's disease, Parkinson's disease, and cerebrovascular diseases. In this review, we summarize the present understanding of the interaction between NG2‐glia and microglia in physiological and pathological states and discuss unsolved questions concerning their fate and potential fate. First, we introduce the NG2‐glia and microglia in health and disease. Second, we formulate the interaction between NG2‐glia and microglia. NG2‐glia proliferation, migration, differentiation, and apoptosis are influenced by factors released from the microglia. On the other hand, NG2‐glia also regulate microglia actions. We conclude that NG2‐glia and microglia are important immunomodulatory cells in the brain. Understanding the interaction between NG2‐glia and microglia will help provide a novel method to modulate myelination and treat neurodegenerative disorders.

5-Fluorouracil reduces the fibrotic scar via inhibiting matrix metalloproteinase 9 and stabilizing microtubules after spinal cord injury

AIMS

Fibrotic scars composed of a dense extracellular matrix are the major obstacles for axonal regeneration. Previous studies have reported that antitumor drugs promote neurofunctional recovery.

METHODS

We investigated the effects of 5-fluorouracil (5-FU), a classical antitumor drug with a high therapeutic index, on fibrotic scar formation, axonal regeneration, and functional recovery after spinal cord injury (SCI).

RESULTS

5-FU administration after hemisection SCI improved hind limb sensorimotor function of the ipsilateral hind paws. 5-FU application also significantly reduced the fibrotic scar formation labeled with aggrecan and fibronectin-positive components, Iba1⁺ /CD11b⁺ macrophages/microglia, vimentin, chondroitin sulfate proteoglycan 4 (NG2/CSPG4), and platelet-derived growth factor receptor beta (PDGFRβ)⁺ pericytes. Moreover, 5-FU treatment promoted stromal cells apoptosis and inhibited fibroblast proliferation and migration by abrogating the polarity of these cells and reducing matrix metalloproteinase 9 expression and promoted axonal growth of spinal neurons via the neuron-specific protein doublecortin-like kinase 1 (DCLK1). Therefore, 5-FU administration impedes the formation of fibrotic scars and promotes axonal regeneration to further restore sensorimotor function after SCI.

PTX3 mediates the infiltration, migration, and inflammation-resolving-polarization of macrophages in glioblastoma

Introduction

Pentraxin 3 (PTX3) is an essential regulator of the immune system. However, the immune‐modulatory role of PTX3 in the tumor microenvironment of glioma has not been elucidated.

Methods

The RNA seq samples were obtained from The Cancer Genome Atlas (TCGA) and the China Glioma Genome Atlas (CGGA) datasets. The single‐cell sequencing data of glioblastoma (GBM) samples were obtained from the Single Cell Portal platform (http://singlecell.broadinstitute.org). Immunohistochemistry was used to assess PTX3 expression, HAVCR2, PD‐1, PD‐L1, and CD276 in glioma sections from the Xiangya cohort (n = 60). Multiplex immunofluorescence staining of PTX3, CD68, and CD163 was performed in several solid cancer types, including GBM. HMC3 was cocultured with U251 and U87, and transwell assay and flow cytometry assay were performed to explore the migration and polarization activity of HMC3.

Results

PTX3 expression is significantly increased in GBM. PTX3 expression predicts worse survival in the Xiangya cohort. PTX3 is closely related to the expression of PD‐1, PD‐L1, CD276, and HAVCR2 in the tumor microenvironment. Additionally, PTX3 is involved in tumorigenic and immunogenic processes, especially the activity of macrophages based on various signaling pathways in cellular communications and critical transcription factors. Specifically, PTX3 actively mediates macrophages' infiltration, migration, and inflammation‐resolving‐polarization. PTX3 could also predict immunotherapy response.

Conclusion

PTX3 is critically involved in macrophage infiltration, migration, and inflammation‐resolving‐polarization and modulates an immunosuppressive microenvironment.

Restorative therapy using microglial depletion and repopulation for central nervous system injuries and diseases

Microglia are important resident immune cells in the central nervous system (CNS) and play an important role in its development, homeostasis, and disease treatments. Activated microglia perform diverse functions in mouse models of CNS neurodegenerative diseases or deficits. In humans, microglia have been linked to various neurodegenerative diseases. Following brain or spinal cord injury, microglia express pro- and anti-inflammatory phenotypes at different stages of recovery. With the development of pharmacological and genetic tools for microglial depletion, studies have demonstrated that microglial depletion exerts both positive and negative effects in the treatment of CNS diseases. Notably, microglial depletion provides an empty niche that stimulates production of new microglia. Microglial depletion and repopulation can not only treat diseases by eliminating dysfunctional microglia but can also provide an indication of the molecular mechanisms of diseases. Although this approach has shown impressive results, its use is still in its infancy. In this review, we summarize the current pharmacological and genetic tools for microglial depletion and highlight recent advances in microglial repopulation therapy for the treatment and functional recovery of neurological diseases and deficits. Finally, we briefly discuss the therapeutic challenges and prospective uses of microglial repopulation therapy.

Neuroimmune Mechanisms Underlying Neuropathic Pain: The Potential Role of TNF-α-Necroptosis Pathway

The neuroimmune mechanism underlying neuropathic pain has been extensively studied. Tumor necrosis factor-alpha (TNF-α), a key pro-inflammatory cytokine that drives cytokine storm and stimulates a cascade of other cytokines in pain-related pathways, induces and modulates neuropathic pain by facilitating peripheral (primary afferents) and central (spinal cord) sensitization. Functionally, TNF-α controls the balance between cell survival and death by inducing an inflammatory response and two programmed cell death mechanisms (apoptosis and necroptosis). Necroptosis, a novel form of programmed cell death, is receiving increasing attraction and may trigger neuroinflammation to promote neuropathic pain. Chronic pain is often accompanied by adverse pain-associated emotional reactions and cognitive disorders. Overproduction of TNF-α in supraspinal structures such as the anterior cingulate cortex (ACC) and hippocampus plays an important role in pain-associated emotional disorders and memory deficits and also participates in the modulation of pain transduction. At present, studies reporting on the role of the TNF-α–necroptosis pathway in pain-related disorders are lacking. This review indicates the important research prospects of this pathway in pain modulation based on its role in anxiety, depression and memory deficits associated with other neurodegenerative diseases. In addition, we have summarized studies related to the underlying mechanisms of neuropathic pain mediated by TNF-α and discussed the role of the TNF-α–necroptosis pathway in detail, which may represent an avenue for future therapeutic intervention.

Effects of astrocytes and microglia on neuroinflammation after spinal cord injury and related immunomodulatory strategies

Spinal cord injury (SCI) is a catastrophic event which is still without adequate therapies. Neuroinflammation is the main pathogenesis of secondary damage post-SCI, leading to tissue loss and neurological dysfunction. Previous studies have shown that microglia and astrocytes are the major immune cells in the central nervous system (CNS) and play a crucial role in modulating neuroinflammatory responses. In this study, we mainly review the effects of neuroinflammation in SCI, focusing on the contributions of microglia and astrocytes and their cross-talk. Furthermore, we will also discuss therapeutic strategies on how to regulate their immunophenotype to suppress robust inflammation and facilitate injury prognosis.

Anti-Neuroinflammatory Components from Clausena lenis Drake

Clausena lenis Drake (C. lenis) is a folk medicinal herb to treat influenza, colds, bronchitis, and malaria. The 95% and 50% ethanol extract of C. lenis showed significant nitric oxide (NO) inhibition activity in BV-2 microglial cells stimulated by lipopolysaccharide (LPS). Bio-guided isolation of the active extract afforded five new compounds, including a chlorine-containing furoquinoline racemate, (±)-claulenine A (1), an amide alkaloid, claulenine B (2), a prenylated coumarin, claulenin A (3), a furocoumarin glucoside, clauleside A (4), and a multi-prenylated p-hydroxybenzaldehyde, claulenin B (5), along with 33 known ones. Their structures were determined via spectroscopic methods, and the absolute configurations of new compounds were assigned via the electronic circular dichroism (ECD) calculations and single-crystal X-ray diffraction analysis. Compounds 2, 23, 27, 28, 33, and 34 showed potent anti-neuroinflammatory effects on LPS-induced NO production in BV-2 microglial cells, with IC₅₀ values in the range of 17.6–40.9 μM. The possible mechanism was deduced to interact with iNOS through molecular docking.

A Review of Pharmacology, Toxicity and Pharmacokinetics of 2,3,5,4'-Tetrahydroxystilbene-2-O-β-D-Glucoside

Polygonum multiflorum Thunb. (He-shou-wu in Chinese), a Chinese botanical drug with a long history, is widely used to treat a variety of chronic diseases in clinic, and has been given the reputation of “rejuvenating and prolonging life” in many places. 2,3,4′,5-tetrahydroxystilbene-2-O-β-D-glucoside (TSG, C₂₀H₂₂O₉) is the main and unique active ingredient isolated from Polygonum multiflorum Thunb., which has extensive pharmacological activities. Modern pharmacological studies have confirmed that TSG exhibits significant activities in treating various diseases, including inflammatory diseases, neurodegenerative diseases, cardiovascular diseases, hepatic steatosis, osteoporosis, depression and diabetic nephropathy. Therefore, this review comprehensively summarizes the pharmacological and pharmacokinetic properties of TSG up to 2021 by searching the databases of Web of Science, PubMed, ScienceDirect and CNKI. According to the data, TSG shows remarkable anti-inflammation, antioxidation, neuroprotection, cardiovascular protection, hepatoprotection, anti-osteoporosis, enhancement of memory and anti-aging activities through regulating multiple molecular mechanisms, such as NF-κB, AMPK, PI3K-AKT, JNK, ROS-NO, Bcl-2/Bax/Caspase-3, ERK1/2, TGF-β/Smad, Nrf2, eNOS/NO and SIRT1. In addition, the toxicity and pharmacokinetics of TSG are also discussed in this review, which provided direction and basis for the further development and clinical application of TSG.

Ketogenic diet ameliorates cognitive impairment and neuroinflammation in a mouse model of Alzheimer's disease

Introduction

Alzheimer's disease (AD) is the most common neurodegenerative disorder that causes dementia and affects millions of people worldwide. Although it has devastating outcomes for patients and tremendous economic costs to society, there is currently no effective treatment available.

Aims

The high‐fat, low‐carbohydrate ketogenic diet (KD) is an established treatment for refractory epilepsy with a proven efficacy. Although the considerable interest has emerged in recent years for applying KD in AD patients, only few interventional studies in animals and humans have addressed the effects of KD on cognitive impairments, and the results were inconclusive. The aim of this study was to explore the impact of KD on cognitive functions and AD pathology in 5XFAD mice—a validated animal model of AD.

Results

Four months of a ketogenic diet improved spatial learning, spatial memory and working memory in 5XFAD mice. The improvement in cognitive functions was associated with a restored number of neurons and synapses in both the hippocampus and the cortex. Ketogenic diet treatment also reduced amyloid plaque deposition and microglial activation, resulting in reduced neuroinflammation. The positive effect of ketogenic diet on cognitive functions depended on the starting time and the duration of the diet. A shorter period (2 months) of ketogenic diet treatment had a weaker effect. Ketogenic diet initiated at late stage of AD (9 months of age) displayed no effect on cognitive improvement.

Conclusions

These findings indicate positive effects of ketogenic diet on both cognitive function and histopathology in Alzheimer's disease, which could be due to reduced microglial activation and neuroinflammation. Our findings provide new insights and therapeutic interventions for the treatment of Alzheimer's disease.

Microglial deactivation by adeno-associated virus expressing small-hairpin GCH1 has protective effects against neuropathic pain development in a spinothalamic tract-lesion model

AIMS

Neuropathic pain after spinal cord injury is one of the most difficult clinical problems after the loss of mobility, and pharmacological or neuromodulation therapy showed limited efficacy. In this study, we examine the possibility of pain modulation by a recombinant adeno-associated virus (rAAV) encoding small-hairpin RNA against GCH1 (rAAV-shGCH1) in a spinal cord injury model in which neuropathic pain was induced by a spinothalamic tract (STT) lesion.

METHODS

Micro-electric lesioning was used to damage the left STT in rats (n = 32), and either rAAV-shGCH1 (n = 19) or rAAV control (n = 6) was injected into the dorsal horn of the rats at the same time. On postoperative days 3, 7, and 14, we evaluated neuropathic pain using a behavioral test and microglial activation by immunohistochemical staining.

RESULTS

A pain modulation effect of shGCH1 was observed from postoperative days 3 to 14. The mechanical withdrawal threshold was 13.0 ± 0.95 in the shGCH1 group, 4.3 ± 1.37 in the control group, and 3.49 ± 0.85 in sham on postoperative day 3 (p < 0.0001) and continued to postoperative day 14 (shGCH1 vs. control: 11.4 ± 1.1 vs. 2.05 ± 0.60, p < 0.001 and shGCH1 vs. sham: 11.4 ± 1.1 vs. 1.43 ± 0.54, p < 0.001). Immunohistochemical staining of the spinal cord dorsal horn showed deactivation of microglia in the shGCH1 group without any change of delayed pattern of astrocyte activation as in STT model.

CONCLUSIONS

Neuropathic pain after spinal cord injury can be modulated bilaterally by deactivating microglial activation after a unilateral injection of rAAV-shGCH1 into the dorsal horn of a STT lesion spinal cord pain model. This new attempt would be another therapeutic approach for NP after SCI, which once happens; there is no clear curative options still now.

Inflammation-relevant microbiome signature of the stroke brain, gut, spleen, and thymus and the impact of exercise

Stroke remains a significant unmet need in the clinic with few therapeutic options. We, and others, have implicated the role of inflammatory microbiota in stroke secondary cell death. Elucidating this inflammation microbiome as a biomarker may improve stroke diagnosis and treatment. Here, adult Sprague-Dawley rats performed 30 minutes of exercise on a motorized treadmill for 3 consecutive days prior to transient middle cerebral artery occlusion (MCAO). Stroke animals that underwent exercise showed 1) robust behavioral improvements, 2) significantly smaller infarct sizes and increased peri-infarct cell survival and 3) decreasing trends of inflammatory microbiota BAC303, EREC482, and LAB158 coupled with significantly reduced levels of inflammatory markers ionized calcium binding adaptor molecule 1, tumor necrosis factor alpha, and mouse monoclonal MHC Class II RT1B in the brain, gut, spleen, and thymus compared to non-exercised stroke rats. These results suggest that a specific set of inflammatory microbiota exists in central and peripheral organs and can serve as a disease biomarker and a therapeutic target for stroke.

The AST-120 Recovers Uremic Toxin-Induced Cognitive Deficit via NLRP3 Inflammasome Pathway in Astrocytes and Microglia

Chronic kidney disease (CKD) is characterized by the progressive loss of renal function; moreover, CKD progression commonly leads to multiple comorbidities, including neurological dysfunction and immune disorders. CKD-triggered neuroinflammation significantly contributes to cognitive impairment. This study aimed to investigate the contribution of uremic toxins to cognitive impairment. Serum creatinine, blood urea nitrogen (BUN), indoxyl sulfate (IS), and p-cresol sulfate (PCS) levels were measured using an enzyme-linked immunosorbent assay and high-performance liquid chromatography. The creatinine, BUN, IS, and PCS levels were increased from 4 weeks after 5/6-nephrectomy in mice, which suggested that 5/6-nephrectomy could yield a CKD animal model. Further, CKD mice showed significantly increased brain and serum indoxyl sulfate levels. Immunohistochemistry analysis revealed hippocampal inflammation and NLRP3-inflammasomes in astrocytes. Further, the Y-maze and Morris water maze tests revealed learning and memory defects in CKD mice. AST-120, which is also an IS absorbent, effectively reduced serum and hippocampal IS levels as well as reversed the cognitive impairment in CKD mice. Additionally, NLRP3-knockout mice that underwent 5/6-nephrectomy showed no change in cognitive function. These findings suggested that IS is an important uremic toxin that induces NLRP3 inflammasome-mediated not only in microglia, but it also occurred in astrocytic inflammation, which subsequently causes cognitive impairment.

Transplantation of a vascularized pedicle of hemisected spinal cord to establish spinal cord continuity after removal of a segment of the thoracic spinal cord: A proof-of-principle study in dogs

Introduction

Glial scar formation impedes nerve regeneration/reinnervation after spinal cord injury (SCI); therefore, removal of scar tissue is essential for SCI treatment.

Aims

To investigate whether removing a spinal cord and transplanting a vascularized pedicle of hemisected spinal cord from the spinal cord caudal to the transection can restore motor function, to aid in the treatment of future clinical spinal cord injuries. We developed a canine model. After removal of a 1‐cm segment of the thoracic (T10–T11) spinal cord in eight beagles, a vascularized pedicle of hemisected spinal cord from the first 1.5 cm of the spinal cord caudal to the transection (cut along the posterior median sulcus of the spinal cord) was transplanted to bridge the transected spinal cord in the presence of a fusogen (polyethylene glycol, PEG) in four of the eight dogs. We used various forms of imaging, electron microscopy, and histologic data to determine that after our transplantation of a vascular pedicled hemisection to bridge the transected spinal cord, electrical continuity across the spinal bridge was restored.

Results

Motor function was restored following our transplantation, as confirmed by the re‐establishment of anatomic continuity along with interfacial axonal sprouting.

Conclusion

Taken together, our findings suggest that SCI patients—who have previously been thought to have irreversible damage and/or paralysis—may be treated effectively with similar operative techniques to re‐establish electrical and functional continuity following SCI.

Cellular and molecular pathophysiology in the progression of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder etiologically linked to the loss of substantia nigra (SN) dopaminergic neurons in the mid-brain. The etiopathology of sporadic PD is still unclear; however, the interaction of extrinsic and intrinsic factors may play a critical role in the onset and progression of the disease. Studies in animal models and human post-mortem tissue have identified distinct cellular and molecular changes in the diseased brain, suggesting complex interactions between different glial cell types and various molecular pathways. Small changes in the expression of specific genes in a single pathway or cell type possibly influence others at the cellular and system levels. These molecular and cellular signatures like neuroinflammation, oxidative stress, and autophagy have been observed in PD patients' brain tissue. While the etiopathology of PD is still poorly understood, the interplay between glial cells and molecular events may play a crucial role in disease onset and progression.

The Complexity of the cGAS-STING Pathway in CNS Pathologies

Neuroinflammation driven by type-I interferons in the CNS is well established to exacerbate the progression of many CNS pathologies both acute and chronic. The role of adaptor protein Stimulator of Interferon Genes (STING) is increasingly appreciated to instigate type-I IFN-mediated neuroinflammation. As an upstream regulator of type-I IFNs, STING modulation presents a novel therapeutic opportunity to mediate inflammation in the CNS. This review will detail the current knowledge of protective and detrimental STING activity in acute and chronic CNS pathologies and the current therapeutic avenues being explored.

Niche Cells Crosstalk In Neuroinflammation After Traumatic Brain Injury

Traumatic brain injury (TBI) is recognized as the disease with high morbidity and disability around world in spite of the work ongoing in neural protection. Due to heterogeneity among the patients, it's still hard to acquire satisfying achievements in clinic. Neuroinflammation, which exists since primary injury occurs, with elusive duality, appear to be of significance from recovery of injury to neurogenesis. In recent years, studied have revealed that communication in neurogenic niche is more than “cell to cell” communication, and study on NSCs represent it as central role in the progress of neural regeneration. Hence, the neuroinflammation-affecting crosstalk after TBI, and clarifying definitive role of NSCs in the course of regeneration is a promising subject for researchers, for its great potential in overcoming the frustrating status quo in clinic, promoting welfare of TBI patient.