Neutrophil extracellular traps in central nervous system pathologies: A mini review

NETosis: A key player in autoimmunity, COVID-19, and long COVID

NETosis, the process through which neutrophils release neutrophil extracellular traps (NETs), has emerged as a crucial mechanism in host defense and the pathogenesis of autoimmune responses. During the SARS-CoV-2 pandemic, this process received significant attention due to the central role of neutrophil recruitment and activation in infection control. However, elevated neutrophil levels and dysregulated NET formation have been linked to coagulopathy and endothelial damage, correlating with disease severity and poor prognosis in COVID-19. Moreover, it is known that SARS-CoV-2 can induce persistent low-grade systemic inflammation, known as long COVID, although the underlying causes remain unclear. It has been increasingly acknowledged that excessive NETosis and NET generation contribute to further pathophysiological abnormalities following SARS-CoV-2 infection. This review provides an updated overview of the role of NETosis in autoimmune diseases, but also the relationship between COVID-19 and long COVID with autoimmunity (e.g., latent and overt autoimmunity, molecular mimicry, epitope spreading) and NETosis (e.g., immune responses, NET markers). Finally, we discuss potential therapeutic strategies targeting dysregulated NETosis to mitigate the severe complications of COVID-19 and long COVID.

Extracellular DNA and Deoxyribonuclease Activity as Potential Biomarkers of Inflammation in Multiple Sclerosis

Neuroinflammation plays a critical role in the pathophysiology of multiple sclerosis (MS), involving complex interactions between reactive oxygen species (ROS), cytokines, chemokines, and immune cells. Among these, neutrophils contribute to sustained inflammation through degranulation, ROS production, and the release of neutrophil extracellular traps (NETs). Extracellular DNA (ecDNA), a key component of NETs, may act as an autoantigen, promoting chronic inflammation and tissue damage. Additionally, impaired NETs and ecDNA degradation by deoxyribonucleases (DNases) may contribute to persistence of inflammation. The aim of the present study was to determine the levels of ecDNA and DNase activity in both blood plasma and cerebrospinal fluid (CSF) in newly diagnosed, treatment-naïve adult patients with relapsing-remitting MS and whether it correlates with disease severity and inflammatory activity in MS. Fifty-one treatment-naïve relapsing-remitting MS patients without disease-modifying therapy and 16 healthy controls (HC) were included in our study. Blood and CSF samples were analyzed for ecDNA, mitochondrial DNA (mtDNA) levels, and DNase activity. Correlations with inflammatory cytokines, oxidative stress, MRI lesion burden, and the expanded disability status scale (EDSS) were analyzed. MS patients exhibited significantly elevated ecDNA levels and reduced DNase activity in blood plasma compared to HC. EcDNA levels positively correlated with inflammatory cytokines, oxidative stress, and disease severity (EDSS). Furthermore, ecDNA and mtDNA levels in CSF positively correlated with inflammatory gadolinium-enhancing MRI lesions. Interestingly, no DNase activity was detected in CSF in both MS patients and HC. Our findings demonstrate that MS patients exhibit significantly elevated ecDNA levels and reduced DNase activity in blood plasma, which correlate with inflammatory cytokines, oxidative stress, and disease severity (EDSS). Additionally, increased ecDNA and mtDNA levels in CSF are associated with higher inflammatory activity, as reflected by gadolinium-enhancing MRI lesions. Considering the pro-inflammatory nature of ecDNA in perpetuating sterile inflammation, these results suggest a potential role of circulating nucleic acids in MS pathogenesis. Furthermore, impaired DNase activity may contribute to the persistence of ecDNA, potentially sustaining pro-inflammatory state in MS. Nevertheless, it remains unclear whether elevated ecDNA actively contributes to neuroinflammation or simply reflects ongoing immune activation. Further research is needed to elucidate the mechanisms underlying ecDNA release and degradation and its implications in MS progression.

Pre-treated mesenchymal stem cell-derived exosomes: A new perspective for accelerating spinal cord injury repair

Spinal cord injury (SCI) is a devastating event for the central nervous system (CNS), often resulting in the loss of sensory and motor functions. It profoundly affects both the physiological and psychological well-being of patients, reducing their quality of life while also imposing significant economic pressure on families and the healthcare system. Due to the complex pathophysiology of SCI, effective treatments for promoting recovery remain scarce. Mesenchymal stem cell-derived exosomes (MSC-Exos) offer advantages such as low immunogenicity, good biocompatibility, and the ability to cross the blood-spinal cord barrier (BSCB). In preclinical studies, they have progressively shown efficacy in promoting SCI repair and functional recovery. However, the low yield and insufficient targeting of MSC-Exos limit their therapeutic efficacy. Currently, genetic engineering and other preprocessing techniques are being employed to optimize both the yield and functional properties of exosomes, thereby enhancing their therapeutic potential. Therefore, this paper provides an overview of the pathophysiology of SCI and the biogenesis of exosomes. It also summarizes current approaches to optimizing exosome performance. Additionally, it details the mechanisms through which optimized exosomes provide neuroprotection and explores the potential of combined treatments involving MSC-Exos and hydrogels.

Neutrophil extracellular traps (NETs) and NETosis in alcohol-associated diseases: A systematic review

Heavy alcohol consumption is implicated in the alteration of the antimicrobial function of neutrophils, such as phagocytosis, chemotaxis, the formation of neutrophil extracellular traps (NETs), and the occurrence of NETosis. NETosis is an endogenous process of elimination of invading microbes, autoantibodies, and inflammatory elements such as danger-associated molecular patterns (DAMPs) and pathogen-associated patterns (PAMPs). However, both exaggeration and suppression of NETosis modulate normal physiological and metabolic processes by influencing events at the molecular and cellular levels. Recent research shows that binge alcohol consumption induces NETosis, leading to tissue damage and inflammation. Binge alcohol consumption, chronic alcohol intake, and alcohol use disorder (AUD) can affect immunity and often lead to alcohol-associated liver disease (ALD) and/or other organ damage. Alcohol can lead to detrimental consequences in multiple organs, including the brain, liver, pancreas, and gut. Gut-derived microbial substances, such as endotoxins in the circulation, induce systemic inflammation. Sterile danger signals from damaged cells, cytokines, and prostaglandins act as proinflammatory stimuli and are involved in multiple signaling pathways. The alcohol-induced proinflammatory cytokines chemoattract neutrophils, which interact and coordinate with other immune cells to exaggerate or suppress inflammation within the inflammatory milieu, depending on the alcohol effects. Several proteins, including different receptors, play important roles in the activation and formation of NETs as well as the initiation and execution of NETosis. This review article specifically gathers the current information on NETosis, its biological components, and signaling pathways relating to the formation of NETs and the occurrence of NETosis associated with ALD and AUD in multiorgans, specifically in the brain, liver, and gut. We also briefly describe various therapeutic strategies against AUD-associated NETosis in experimental models and human disease states.

Inhibition of neutrophil extracellular traps alleviates blood-brain barrier disruption and cognitive dysfunction via Wnt3/β-catenin/TCF4 signaling in sepsis-associated encephalopathy

BACKGROUND

Neutrophils and neutrophil extracellular traps (NETs) have been identified as crucial contributors in several neuroinflammatory models, such as stroke and traumatic brain injury, but their role in sepsis-associated encephalopathy (SAE) has not been thoroughly investigated.

METHODS

In this study, we established an SAE model using cecal ligation puncture (CLP) surgery to examine neutrophil infiltration and NETs formation. A protein arginine deiminase 4 (PAD4) inhibitor, GSK484, was employed to suppress NETs release. To assess changes in hippocampal gene expression induced by GSK484 treatment in CLP mice, we utilized RNA sequencing (RNA-Seq) combined with bioinformatics analysis. Additionally, the Elisa, cognitive function test, western bolt and immunofluorescence staining were used to measured hippocampal inflammatory cytokine, cognitive function, and the protein levels of tight junctions (TJs) and adherens junctions (AJs) in SAE mice. We also established a Transwell™ co-culture system using bEnd.3 cells and bone marrow-derived neutrophils to examine the effects of GSK484 on endothelial cell function. This comprehensive approach allowed us to evaluate the impact of NETs inhibition on neuroinflammation, cognitive function, and the underlying molecular mechanisms in the CLP-induced SAE model.

RESULTS

Our findings revealed that neutrophils were significantly overactivated, releasing abundant NETs in the hippocampus of CLP-induced SAE mice. Inhibition of NET formation using GSK484 led to reduced neuroinflammatory responses, improved blood-brain barrier (BBB) integrity, and enhanced survival rates and cognitive function in SAE mice. RNA-Seq and bioinformatics analyses identified the Wnt signaling pathway as the most significant pathway affected. Subsequent experiments demonstrated that NETs inhibition alleviated BBB damage primarily by increasing the expression of Occludin, a TJs protein, and promoting the formation of the VCL/β-catenin/VE-cadherin complex at AJs, mediated by the Wnt3/β-catenin/TCF4 signaling pathway.

CONCLUSIONS

Our results suggest that inhibition of NETs may protect BBB permeability and cognitive function through the Wnt3/β-catenin/TCF4 signaling pathway in the context of CLP-induced SAE, which provides a promising strategy for SAE therapy.

Hypothesis on the role of cholesterol crystals in spontaneously ruptured aortic plaques: Potential triggers for inflammation and systemic effects

Cholesterol crystals (CCs) are a key component of atherosclerotic plaques and play a pivotal role in plaque progression, rupture, and the resulting inflammatory responses. CCs emboli trigger proinflammatory cytokines which can potentially lead to organ damage. Spontaneously ruptured aortic plaques (SRAPs) are frequently observed via non-obstructive general angioscopy (NOGA) in patients with or suspected coronary artery disease. The release of CCs from SRAPs can activate the innate immune system and induce neutrophil extracellular trap (NET) formation, further exacerbating inflammation. Inflammation levels in SRAPs vary, and the interleukin (IL)-6 ratio may reflect the degree of inflammation. Systemic inflammation induced by CCs may contribute to conditions that may lead to cerebral infarction, and chronic kidney disease. The effects of anti-inflammatory drugs, including IL-6 inhibitors, IL-1β inhibitors, and colchicine, may be evaluated by measuring the IL-6 ratio in SRAPs. This review examined innate immunity mechanisms associated with CCs in SRAPs sampled via NOGA and discussed their systemic impact and potential therapeutic strategies.

The activation of complement C5a-C5aR1 axis in astrocytes facilitates the neuropathogenesis due to EV-A71 infection by upregulating CXCL1

Enterovirus A71 (EV-A71) is a common small RNA virus that is highly neuroinvasive. Emerging evidence indicates that the complement fragment C5a and its receptor C5aR1 are important drivers of neuroinflammation. However, the potential role of the C5a-C5aR1 axis in EV-A71 encephalitis remains largely elusive. Our previous studies revealed that EV-A71 can infect astrocytes and result in complement activation in vivo. Here, we investigated how complement factors interact with astrocytes to promote a severe inflammatory response upon EV-A71 infection. Our data revealed that EV-A71 infected mainly astrocytes and caused astrocyte activation in the mouse brain, which was further verified in patients with EV-A71 infection and U87-MG cells. Notably, EV-A71 infection led to activation of the C5a-C5aR1 axis in U87-MG cells, and knockdown (siC5aR1) or blockade (PMX53) of C5aR1 significantly suppressed EV-A71-induced astrocyte activation and proinflammatory cytokine (e.g., CXCL1) production. Next, the activation of the C5a-C5aR1 axis in mouse astrocytes was confirmed. Compared with C5aR1 knockout mice, wild-type mice presented more severe symptoms and lower survival rates after EV-A71 infection. C5aR1 deficiency or blockade significantly reduced EV-A71-induced pathological damage and proinflammatory cytokine production in the mouse brain. Importantly, an increased level of soluble C5a was strongly correlated with the severity of symptoms in patients with EV-A71 infection. By using confocal microscopy, primary astrocytes, and human specimens, we observed that the increase in CXCL1 levels resulted mainly from astrocytes. Neutralizing CXCL1 significantly alleviated the neuropathological changes caused by EV-A71 infection, and the production of CXCL1 in astrocytes was regulated by p38 MAPK signaling. Taken together, our findings indicate that the activation of the C5a-C5aR1 axis in astrocytes facilitates the neuropathological changes resulting from EV-A71 infection, emphasizing the potential role of p38 MAPK-mediated CXCL1 production in these alterations.

IMPORTANCE

Enterovirus A71 (EV-A71) is a common small RNA virus with highly neuroinvasive tendencies. Our previous studies took the view that EV-A71 could infect astrocytes and result in complement activation in vivo. We investigated how complement interacts with astrocytes to promote a severe inflammatory response upon EV-A71 infection in the study. As expected, our data demonstrate that EV-A71 triggers robust activation of the C5a-C5aR1 axis in astrocytes and that knockout or blockade of C5aR1 in animals exposed to lethal doses of EV-A71 significantly enhances survival by diminishing the production of the chemokines CXCL1 and IL-6. In addition, neutralizing CXCL1 significantly alleviates the neuropathogenesis caused by EV-A71 infection. Thus, inhibiting the C5a-C5aR1 axis has emerged as a potential therapeutic strategy to mitigate neural damage caused by EV-A71 infection.

Preliminary evidence of immune infiltration and neutrophil degranulation in peripheral blood of non-obese OSA patients related to cognitive decline

Obstructive sleep apnea (OSA) patients have varying degrees of cognitive impairment, but the specific pathogenic mechanism is still unclear. Meanwhile, poor compliance with continuous positive airway pressure (CPAP) in OSA prompts better solutions. This study aimed to identify differentially expressed genes between the non-obese OSA patients and healthy controls, and to explore potential biomarkers associated with cognitive impairment. Cohorts of healthy control (n = 20) and non-obese, treatment-naïve OSA patients (n = 20) were recruited. We collected their peripheral blood mononuclear cells and neutrophils, and their cognitive performances were evaluated by the Montreal Cognitive Assessment (MoCA). The differentially expressed genes were identified by bioinformatic analysis and confirmed by PCR. Imbalanced immune cell proportions were assessed by Cibersort. Biomarkers related to enriched cellular pathways were measured by ELISA. OSA patients showed a significant decline in overall cognitive function and were associated with higher daytime sleepiness scores. Multiple signaling pathways were enriched in the non-obese OSA cohort, including upregulation of neutrophil-degranulation. Increased monocyte proportion and decreased NK cell proportion were figured out. The relevant genes, including upregulated defensin alpha 4 (DEFA4), haptoglobin (HP), survivin (BIRC5), and suppressed interferon gamma (IFNG) expression were detected. The relative expression of DEFA4 was significantly correlated with the MoCA score and sleep parameters. Biomarkers such as myeloperoxidase (MPO), H2O2, and lipocalin-2, as representatives of neutrophils' activation, elevated significantly in the OSA group. The data demonstrated a positive correlation between MPO and oxygen desaturation index (ODI) and a negative correlation between MPO and lowest oxygen saturation (LSaO2). The level of Lipocalin-2 was positively correlated with apnea-hypopnea index (AHI) and ODI and negatively correlated with LSaO2 and MoCA score. We also observed a negative correlation between H2O2 and mean oxygen saturation (MSaO2). Degranulation of neutrophils was activated in non-obese OSA patients without other complications. The process is related to OSA severity and cognitive impairment, implying its role in pathogenesis.

The Diagnostic Value of Plasma NETs Levels and iCEB in Silent Myocardial Ischemia in Maintenance Hemodialysis Patients

Objective

This study evaluated the diagnostic value of plasma Neutrophil extracellular traps (NETs) levels and the index of cardiac electrophysiological balance (iCEB) in identifying silent myocardial ischemia (SMI) in maintenance hemodialysis (MHD) patients.

Methods

This cross-sectional observational study involved patients receiving MHD treatment. Data were collected on coronary angiography performed in our hospital from February 2023 to February 2024. Patients diagnosed with myocardial ischemia via coronary angiography but without obvious symptoms were grouped as the SMI group, while those without SMI were grouped as the control group. Plasma NETs levels were assessed using markers indicative of NETs components including double-stranded DNA (dsDNA), circulating free DNA (cfDNA) and myeloperoxidase, while iCEB (QT/QRS) and electrocardiographic findings were obtained. Additionally, echocardiographic parameters, inflammatory markers, and cardiac biomarkers were analyzed. Receiver operating characteristic (ROC) analysis were employed to evaluate the diagnostic accuracy of plasma NETs levels and iCEB in identifying SMI.

Results

A total of 114 patients were included, with 79 participants in the control group and 35 participants in the SMI group. The SMI group exhibited significantly elevated levels of NETs associated components (dsDNA(37.89±4.55 vs 31.64±5.32, P<0.001), cfDNA(11.27±2.03 vs 8.91±1.84, P<0.001), MPO-DNA(23.69±4.01 vs 17.52±3.41, P<0.001)), as well as higher iCEB compared to the control group(56.45±7.67 vs 45.89±6.23, P<0.001). Furthermore, electrocardiography findings, echocardiographic parameters, inflammatory markers, and cardiac biomarkers showed significant differences between the two groups. The ROC analysis demonstrated the potential diagnostic accuracies of NETs levels and iCEB, with an area under the curve (AUC) of 0.908, sensitivity of 0.987, and specificity of 0.829 for identifying SMI.

Conclusion

The study highlights the combined diagnostic value of plasma NETs levels and iCEB in identifying SMI in MHD patients, providing valuable insights into potential early detection and risk stratification strategies for this population.

Cathelicidin antimicrobial peptide expression in neutrophils and neurons antagonistically modulates neuroinflammation

Multiple sclerosis (MS) is an autoimmune disease that affects the CNS, the pathophysiology of which remains unclear and for which there is no definitive cure. Antimicrobial peptides (AMPs) are immunomodulatory molecules expressed in various tissues, including the CNS. Here, we investigated whether the cathelicidin-related AMP (CRAMP) modulated the development of experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. We showed that, at an early stage, CNS-recruited neutrophils produced neutrophil extracellular traps (NETs) rich in CRAMP that were required for EAE initiation. NET-associated CRAMP stimulated IL-6 production by dendritic cells via the cGAS/STING pathway, thereby promoting encephalitogenic Th17 response. However, at a later disease stage, neurons also expressed CRAMP that reduced EAE severity. Camp knockdown in neurons led to disease exacerbation, while local injection of CRAMP1-39 at the peak of EAE promoted disease remission. In vitro, CRAMP1-39 regulated the activation of microglia and astrocytes through the formyl peptide receptor (FPR) 2. Finally, administration of butyrate, a gut microbiota-derived metabolite, stimulated the expression of neural CRAMP via the free fatty acids receptors 2/3 (FFAR2/3), and prevented EAE. This study shows that CRAMP produced by different cell types has opposing effects on neuroinflammation, offering therapeutic opportunities for MS and other neuroinflammatory disorders.

A biomimic anti-neuroinflammatory nanoplatform for active neutrophil extracellular traps targeting and spinal cord injury therapy

Traumatic spinal cord injury (SCI) always leads to severe neurological deficits and permanent damage. Neuroinflammation is a vital process of SCI and have become a promising target for SCI treatment. However, the neuroinflammation-targeted therapy would hinder the functional recovery of spinal cord and lead to the treatment failure. Herein, a biomimic anti-neuroinflammatory nanoplatform (DHCNPs) was developed for active neutrophil extracellular traps (NETs) targeting and SCI treatment. The curcumin-loaded liposome with the anti-inflammatory property acted as the core of the DHCNPs. Platelet membrane and neutrophil membrane were fused to form the biomimic hybrid membrane of the DHCNPs for hijacking neutrophils and neutralizing the elevated neutrophil-related proinflammatory cytokines, respectively. DNAse I modification on the hybrid membrane could achieve NETs degradation, blood spinal cord barrier, and neuron repair. Further studies proved that the DHCNPs could reprogram the multifaceted neuroinflammation and reverse the SCI process via nuclear factor kappa-B (NF-κB) pathway. We believe that the current study provides a new perspective for neuroinflammation inhibition and may shed new light on the treatment of SCI.

Identification of neutrophil extracellular trap-related genes in Alzheimer's disease based on comprehensive bioinformatics analysis

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease. There are currently no effective interventions to slow down or prevent the occurrence and progression of AD. Neutrophil extracellular traps (NETs) have been proven to be tightly linked to AD. This project attempted to identify hub genes for AD based on NETs. Gene expression profiles of the training set and validation set were downloaded from the Gene Expression Omnibus (GEO) database, including non-demented (ND) controls and AD samples. NET-related genes (NETRGs) were collected from the literature. Differential analysis identified 21 AD differentially expressed NETRGs (AD-DE-NETRGs) majorly linked to functions such as defense response to bacterium as well as pathways including IL-17 signaling pathway, as evidenced by enrichment analyses of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Protein-protein interaction (PPI) network, Minutia Cylinder-Code (MCC) algorithm, and molecular complex detection (MCODE) algorithm in the CytoHubba plug-in were employed to identify five hub genes (NFKBIA, SOCS3, CCL2, TIMP1, ACTB). Their diagnostic ability was validated in the validation set using receiver operating characteristic (ROC) curves and gene differential expression analysis. A total of 16 miRNAs and 132 lncRNAs were predicted through the mirDIP and ENCORI databases, and a lncRNA-miRNA-mRNA regulatory network was constructed using Cytoscape software. Small molecular compounds such as Benzo(a)pyrene and Copper Sulfate were predicted to target hub genes using the CTD database. This project successfully identified five hub genes, which may serve as potential biomarkers for AD, proffering clues for new therapeutic targets.

Microenvironmental regulation of tumor-associated neutrophils in malignant glioma: from mechanism to therapy

Glioma is the most common primary intracranial tumor in adults, with high incidence, recurrence, and mortality rates. Tumor-associated neutrophils (TANs) are essential components of the tumor microenvironment (TME) in glioma and play a crucial role in glioma cell proliferation, invasion and proneural-mesenchymal transition. Besides the interactions between TANs and tumor cells, the multi-dimensional crosstalk between TANs and other components within TME have been reported to participate in glioma progression. More importantly, several therapies targeting TANs have been developed and relevant preclinical and clinical studies have been conducted in cancer therapy. In this review, we introduce the origin of TANs and the functions of TANs in malignant behaviors of glioma, highlighting the microenvironmental regulation of TANs. Moreover, we focus on summarizing the TANs-targeted methods in cancer therapy, aiming to provide insights into the mechanisms and therapeutic opportunities of TANs in the malignant glioma microenvironment.

Targeted Delivery of Nanoparticle-Conveyed Neutrophils to the Glioblastoma Site for Efficient Therapy

Glioblastoma is a common brain tumor that poses considerable challenges in drug delivery. In this study, we investigated the potential of cell-based nanoparticles for targeted drug delivery to the glioblastoma sites. The anticancer drug of temozolomide (TMZ)-loaded T7-cholesterol nanoparticle micelles efficiently delivered nanoparticles to neutrophils and, subsequently, to the tumors. T7 is a cell-penetrating peptide that enhances the delivery of T7/TMZ to the target cells. T7 also serves as a transferrin target peptide, enabling targeted delivery to tumors. T7-conjugated cholesterol can self-assemble into micelles in aqueous solution and attach to the membrane of neutrophils. We confirmed that T7/TMZ nanoparticle micelles were efficiently located inside the neutrophils. Thereafter, T7/TMZ-conveyed neutrophils were administered to a glioblastoma mouse model, enabling neutrophils to penetrate the blood-brain barrier and deliver drugs directly to the tumor site. We evaluated the drug delivery efficiency and therapeutic effects of intravenous injection of T7/TMZ-conveyed neutrophils to a glioblastoma mouse model. These results demonstrate the promising role of neutrophil-based nanoparticle delivery systems in the targeted therapy of glioblastoma.

Insights of immune cell heterogeneity, tumor-initiated subtype transformation, drug resistance, treatment and detecting technologies in glioma microenvironment

BACKGROUND

With the gradual understanding of glioma development and the immune microenvironment, many immune cells have been discovered. Despite the growing comprehension of immune cell functions and the clinical application of immunotherapy, the precise roles and characteristics of immune cell subtypes, how glioma induces subtype transformation of immune cells and its impact on glioma progression have yet to be understood.

AIM OF THE REVIEW

In this review, we comprehensively center on the four major immune cells within the glioma microenvironment, particularly neutrophils, macrophages, lymphocytes, myeloid-derived suppressor cells (MDSCs), and other significant immune cells. We discuss (1) immune cell subtype markers, (2) glioma-induced immune cell subtype transformation, (3) the mechanisms of each subtype influencing chemotherapy resistance, (4) therapies targeting immune cells, and (5) immune cell-associated single-cell sequencing. Eventually, we identified the characteristics of immune cell subtypes in glioma, comprehensively summarized the exact mechanism of glioma-induced immune cell subtype transformation, and concluded the progress of single-cell sequencing in exploring immune cell subtypes in glioma.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In conclusion, we have analyzed the mechanism of chemotherapy resistance detailly, and have discovered prospective immunotherapy targets, excavating the potential of novel immunotherapies approach that synergistically combines radiotherapy, chemotherapy, and surgery, thereby paving the way for improved immunotherapeutic strategies against glioma and enhanced patient outcomes.

Neutrophil extracellular traps mediate neuro-immunothrombosis

Neutrophil extracellular traps are primarily composed of DNA and histones and are released by neutrophils to promote inflammation and thrombosis when stimulated by various inflammatory reactions. Neutrophil extracellular trap formation occurs through lytic and non-lytic pathways that can be further classified by formation mechanisms. Histones, von Willebrand factor, fibrin, and many other factors participate in the interplay between inflammation and thrombosis. Neuro-immunothrombosis summarizes the intricate interplay between inflammation and thrombosis during neural development and the pathogenesis of neurological diseases, providing cutting-edge insights into post-neurotrauma thrombotic events. The blood-brain barrier defends the brain and spinal cord against external assaults, and neutrophil extracellular trap involvement in blood-brain barrier disruption and immunothrombosis contributes substantially to secondary injuries in neurological diseases. Further research is needed to understand how neutrophil extracellular traps promote blood-brain barrier disruption and immunothrombosis, but recent studies have demonstrated that neutrophil extracellular traps play a crucial role in immunothrombosis, and identified modulators of neuro-immunothrombosis. However, these neurological diseases occur in blood vessels, and the mechanisms are unclear by which neutrophil extracellular traps penetrate the blood-brain barrier to participate in immunothrombosis in traumatic brain injury. This review discusses the role of neutrophil extracellular traps in neuro-immunothrombosis and explores potential therapeutic interventions to modulate neutrophil extracellular traps that may reduce immunothrombosis and improve traumatic brain injury outcomes.

Neutrophils in Ocular Diseases

Neutrophils, traditionally viewed as first responders to infection or tissue damage, exhibit dynamic and diverse roles in ocular health and disease. This review elaborates on previous findings that showed how neutrophils contribute to ocular diseases. In ocular infections, neutrophils play a pivotal role in host defense by orchestrating inflammatory responses to combat pathogens. Furthermore, in optic nerve neuropathies and retinal degenerative diseases like age-related macular degeneration (AMD) and diabetic retinopathy (DR), neutrophils are implicated in neuroinflammation and tissue damage owing to their ability to undergo neutrophil extracellular trap formation (NETosis) and secretion of inflammatory molecules. Targeting neutrophil-dependent processes holds promise as a therapeutic strategy, offering potential avenues for intervention in ocular infections, cancers, and retinal degenerative diseases. Understanding the multifaceted roles of neutrophils in ocular diseases is crucial for developing targeted therapies to improve patient outcomes.

Biomaterial strategies for regulating the neuroinflammatory response

Injury and disease in the central nervous system (CNS) can result in a dysregulated inflammatory environment that inhibits the repair of functional tissue. Biomaterials present a promising approach to tackle this complex inhibitory environment and modulate the mechanisms involved in neuroinflammation to halt the progression of secondary injury and promote the repair of functional tissue. In this review, we will cover recent advances in biomaterial strategies, including nanoparticles, hydrogels, implantable scaffolds, and neural probe coatings, that have been used to modulate the innate immune response to injury and disease within the CNS. The stages of inflammation following CNS injury and the main inflammatory contributors involved in common neurodegenerative diseases will be discussed, as understanding the inflammatory response to injury and disease is critical for identifying therapeutic targets and designing effective biomaterial-based treatment strategies. Biomaterials and novel composites will then be discussed with an emphasis on strategies that deliver immunomodulatory agents or utilize cell-material interactions to modulate inflammation and promote functional tissue repair. We will explore the application of these biomaterial-based strategies in the context of nanoparticle- and hydrogel-mediated delivery of small molecule drugs and therapeutic proteins to inflamed nervous tissue, implantation of hydrogels and scaffolds to modulate immune cell behavior and guide axon elongation, and neural probe coatings to mitigate glial scarring and enhance signaling at the tissue-device interface. Finally, we will present a future outlook on the growing role of biomaterial-based strategies for immunomodulation in regenerative medicine and neuroengineering applications in the CNS.

Neutrophils in glioma microenvironment: from immune function to immunotherapy

Glioma is a malignant tumor of the central nervous system (CNS). Currently, effective treatment options for gliomas are still lacking. Neutrophils, as an important member of the tumor microenvironment (TME), are widely distributed in circulation. Recently, the discovery of cranial-meningeal channels and intracranial lymphatic vessels has provided new insights into the origins of neutrophils in the CNS. Neutrophils in the brain may originate more from the skull and adjacent vertebral bone marrow. They cross the blood-brain barrier (BBB) under the action of chemokines and enter the brain parenchyma, subsequently migrating to the glioma TME and undergoing phenotypic changes upon contact with tumor cells. Under glycolytic metabolism model, neutrophils show complex and dual functions in different stages of cancer progression, including participation in the malignant progression, immune suppression, and anti-tumor effects of gliomas. Additionally, neutrophils in the TME interact with other immune cells, playing a crucial role in cancer immunotherapy. Targeting neutrophils may be a novel generation of immunotherapy and improve the efficacy of cancer treatments. This article reviews the molecular mechanisms of neutrophils infiltrating the central nervous system from the external environment, detailing the origin, functions, classifications, and targeted therapies of neutrophils in the context of glioma.

Blood-brain barrier permeability for the first 24 hours in hypoxic-ischemic brain injury following cardiac arrest

BACKGROUND

This study aimed to explore the changes in blood-brain barrier (BBB) permeability and intracranial pressure (ICP) for the first 24 h after the return of spontaneous circulation (ROSC) and their association with injury severity of cardiac arrest.

METHODS

This prospective study analysed the BBB permeability assessed using the albumin quotient (Qa) and ICP every 2 h for the first 24 h after ROSC. The injury severity of cardiac arrest was assessed using Pittsburgh Cardiac Arrest Category (PCAC) scores. The primary outcome was the time course of changes in the BBB permeability and ICP for the first 24 h after ROSC and their association with injury severity (PCAC scores of 1-4).

RESULTS

Qa and ICP were measured 274 and 197 times, respectively, in 32 enrolled patients. Overall, the BBB permeability increased progressively over time after ROSC, and then it increased significantly at 18 h after ROSC compared with the baseline. In contrast, the ICP revealed non-significant changes for the first 24 h after ROSC. The Qa in the PCAC 2 group was < 0.01, indicating normal or mild BBB disruption at all time points, whereas the PCAC 3 and 4 groups showed a significant increase in BBB permeability at 14 and 22 h, and 12 and 14 h after ROSC, respectively.

CONCLUSION

BBB permeability increased progressively over time for the first 24 h after ROSC despite post-resuscitation care, whereas ICP did not change over time. BBB permeability has an individual pattern when stratified by injury severity.

The characteristic and prognostic role of blood inflammatory markers in patients with Huntington's disease from China

Objectives

This study aims to elucidate the role of peripheral inflammation in Huntington's disease (HD) by examining the correlation of peripheral inflammatory markers with clinical manifestations and disease prognosis.

Methods

This investigation involved 92 HD patients and 92 matched healthy controls (HCs). We quantified various peripheral inflammatory markers and calculated their derived metrics including neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), lymphocyte-to-monocyte ratio (LMR), and systemic immune-inflammation index (SII). Clinical assessments spanning cognitive, motor, and disease severity were administered. Comparative analysis of inflammatory markers and clinical correlations between HD and controls was performed. Kaplan-Meier survival analysis and Cox regression model were used to assess the effect of inflammatory markers on survival.

Results

The study revealed that HD patients had significantly reduced lymphocyte counts, and LMR. Conversely, NLR, PLR, and SII were elevated compared to HCs. Lymphocyte levels inversely correlated with the age of onset and monocyte levels inversely correlated with the UHDRS-total functional capacity (TFC) scores. After adjusting for age, sex, and CAG repeat length, lymphocyte count, NLR, PLR, and SII were significantly correlated with the progression rate of TFC scores. Elevated levels of white blood cells and monocytes were associated with an increased risk of disability and mortality in the HD cohort.

Conclusion

Our findings indicate that HD patients display a distinct peripheral inflammatory profile with increased NLR, PLR, and SII levels compared to HCs. The peripheral inflammation appears to be linked with accelerated disease progression and decreased survival in HD.

Macrophages coordinate immune response to laser-induced injury via extracellular traps

BACKGROUND

Retinal degeneration results from disruptions in retinal homeostasis due to injury, disease, or aging and triggers peripheral leukocyte infiltration. Effective immune responses rely on coordinated actions of resident microglia and recruited macrophages, critical for tissue remodeling and repair. However, these phagocytes also contribute to chronic inflammation in degenerated retinas, yet the precise coordination of immune response to retinal damage remains elusive. Recent investigations have demonstrated that phagocytic cells can produce extracellular traps (ETs), which are a source of self-antigens that alter the immune response, which can potentially lead to tissue injury.

METHODS

Innovations in experimental systems facilitate real-time exploration of immune cell interactions and dynamic responses. We integrated in vivo imaging with ultrastructural analysis, transcriptomics, pharmacological treatments, and knockout mice to elucidate the role of phagocytes and their modulation of the local inflammatory response through extracellular traps (ETs). Deciphering these mechanisms is essential for developing novel and enhanced immunotherapeutic approaches that can redirect a specific maladaptive immune response towards favorable wound healing in the retina.

RESULTS

Our findings underscore the pivotal role of innate immune cells, especially macrophages/monocytes, in regulating retinal repair and inflammation. The absence of neutrophil and macrophage infiltration aids parenchymal integrity restoration, while their depletion, particularly macrophages/monocytes, impedes vascular recovery. We demonstrate that macrophages/monocytes, when recruited in the retina, release chromatin and granular proteins, forming ETs. Furthermore, the pharmacological inhibition of ETosis support retinal and vascular repair, surpassing the effects of blocking innate immune cell recruitment. Simultaneously, the absence of ETosis reshapes the inflammatory response, causing neutrophils, helper, and cytotoxic T-cells to be restricted primarily in the superficial capillary plexus instead of reaching the damaged photoreceptor layer.

CONCLUSIONS

Our data offer novel insights into innate immunity's role in responding to retinal damage and potentially help developing innovative immunotherapeutic approaches that can shift the immune response from maladaptive to beneficial for retinal regeneration.

Intravenous Administration of Mesenchymal Stem Cell-Derived Exosome Alleviates Spinal Cord Injury by Regulating Neutrophil Extracellular Trap Formation through Exosomal miR-125a-3p

Spinal cord injury (SCI) leads to devastating sequelae, demanding effective treatments. Recent advancements have unveiled the role of neutrophil extracellular traps (NETs) produced by infiltrated neutrophils in exacerbating secondary inflammation after SCI, making it a potential target for treatment intervention. Previous research has established that intravenous administration of stem cell-derived exosomes can mitigate injuries. While stem cell-derived exosomes have demonstrated the ability to modulate microglial reactions and enhance blood-brain barrier integrity, their impact on neutrophil deactivation, especially in the context of NETs, remains poorly understood. This study aims to investigate the effects of intravenous administration of MSC-derived exosomes, with a specific focus on NET formation, and to elucidate the associated molecular mechanisms. Exosomes were isolated from the cell supernatants of amnion-derived mesenchymal stem cells using the ultracentrifugation method. Spinal cord injuries were induced in Sprague-Dawley rats (9 weeks old) using a clip injury model, and 100 μg of exosomes in 1 mL of PBS or PBS alone were intravenously administered 24 h post-injury. Motor function was assessed serially for up to 28 days following the injury. On Day 3 and Day 28, spinal cord specimens were analyzed to evaluate the extent of injury and the formation of NETs. Flow cytometry was employed to examine the formation of circulating neutrophil NETs. Exogenous miRNA was electroporated into neutrophil to evaluate the effect of inflammatory NET formation. Finally, the biodistribution of exosomes was assessed using 64Cu-labeled exosomes in animal positron emission tomography (PET). Rats treated with exosomes exhibited a substantial improvement in motor function recovery and a reduction in injury size. Notably, there was a significant decrease in neutrophil infiltration and NET formation within the spinal cord, as well as a reduction in neutrophils forming NETs in the circulation. In vitro investigations indicated that exosomes accumulated in the vicinity of the nuclei of activated neutrophils, and neutrophils electroporated with the miR-125a-3p mimic exhibited a significantly diminished NET formation, while miR-125a-3p inhibitor reversed the effect. PET studies revealed that, although the majority of the transplanted exosomes were sequestered in the liver and spleen, a notably high quantity of exosomes was detected in the damaged spinal cord when compared to normal rats. MSC-derived exosomes play a pivotal role in alleviating spinal cord injury, in part through the deactivation of NET formation via miR-125a-3p.

G-CSF increases calprotectin expression, liver damage and neuroinflammation in a murine model of alcohol-induced ACLF

Background and aims: Granulocyte colony-stimulating factor (G-CSF) has been proposed as a therapeutic option for patients with ACLF, however clinical outcomes are controversial. We aimed at dissecting the role of G-CSF in an alcohol-induced murine model of ACLF. Methods: ACLF was triggered by a single alcohol binge (5 g/kg) in a bile duct ligation (BDL) liver fibrosis model. A subgroup of mice received two G-CSF (200 μg/kg) or vehicle injections prior to acute decompensation with alcohol. Liver, blood and brain tissues were assessed. Results: Alcohol binge administered to BDL-fibrotic mice resulted in features of ACLF indicated by a significant increase in liver damage and systemic inflammation compared to BDL alone. G-CSF treatment in ACLF mice induced an increase in liver regeneration and neutrophil infiltration in the liver compared to vehicle-treated ACLF mice. Moreover, liver-infiltrating neutrophils in G-CSF-treated mice exhibited an activated phenotype indicated by increased expression of CXC motif chemokine receptor 2, leukotriene B4 receptor 1, and calprotectin. In the liver, G-CSF triggered increased oxidative stress, type I interferon response, extracellular matrix remodeling and inflammasome activation. Circulating IL-1β was also increased after G-CSF treatment. In the cerebellum, G-CSF increased neutrophil infiltration and S100a8/9 expression, induced microglia proliferation and reactive astrocytes, which was accompanied by oxidative stress, and inflammasome activation compared to vehicle-treated ACLF mice. Conclusion: In our novel ACLF model triggered by alcohol binge that mimics ACLF pathophysiology, neutrophil infiltration and S100a8/9 expression in the liver and brain indicate increased tissue damage, accompanied by oxidative stress and inflammasome activation after G-CSF treatment.

How Neutrophils Shape the Immune Response: Reassessing Their Multifaceted Role in Health and Disease

Neutrophils are the most abundant of the circulating immune cells and are the first to be recruited to sites of inflammation. Neutrophils are a heterogeneous group of immune cells from which are derived extracellular traps (NETs), reactive oxygen species, cytokines, chemokines, immunomodulatory factors, and alarmins that regulate the recruitment and phenotypes of neutrophils, macrophages, dendritic cells, T cells, and B cells. In addition, cytokine-stimulated neutrophils can express class II major histocompatibility complex and the internal machinery necessary for successful antigen presentation to memory CD4+ T cells. This may be relevant in the context of vaccine memory. Neutrophils thus emerge as orchestrators of immune responses that play a key role in determining the outcome of infections, vaccine efficacy, and chronic diseases like autoimmunity and cancer. This review aims to provide a synthesis of current evidence as regards the role of these functions of neutrophils in homeostasis and disease.

Neutrophil extracellular traps and long COVID

Post-acute COVID-19 sequelae, commonly known as long COVID, encompasses a range of systemic symptoms experienced by a significant number of COVID-19 survivors. The underlying pathophysiology of long COVID has become a topic of intense research discussion. While chronic inflammation in long COVID has received considerable attention, the role of neutrophils, which are the most abundant of all immune cells and primary responders to inflammation, has been unfortunately overlooked, perhaps due to their short lifespan. In this review, we discuss the emerging role of neutrophil extracellular traps (NETs) in the persistent inflammatory response observed in long COVID patients. We present early evidence linking the persistence of NETs to pulmonary fibrosis, cardiovascular abnormalities, and neurological dysfunction in long COVID. Several uncertainties require investigation in future studies. These include the mechanisms by which SARS-CoV-2 brings about sustained neutrophil activation phenotypes after infection resolution; whether the heterogeneity of neutrophils seen in acute SARS-CoV-2 infection persists into the chronic phase; whether the presence of autoantibodies in long COVID can induce NETs and protect them from degradation; whether NETs exert differential, organ-specific effects; specifically which NET components contribute to organ-specific pathologies, such as pulmonary fibrosis; and whether senescent cells can drive NET formation through their pro-inflammatory secretome in long COVID. Answering these questions may pave the way for the development of clinically applicable strategies targeting NETs, providing relief for this emerging health crisis.