Neutrophil extracellular traps are increased in patients with acute ischemic stroke: prognostic significance

Research trends on neutrophil extracellular traps in ischemic stroke: a scientific metrology study

Background

Ischemic stroke (IS) remains a leading global cause of mortality and chronic disability. Neutrophil extracellular traps (NETs), recently identified as neutrophil-derived structures that trap and neutralize pathogens, have increasingly drawn attention for their involvement in IS pathogenesis. Despite a surge in related research, no bibliometric analyses have yet examined the knowledge framework and trends within this emerging field. Here, we conducted a systematic bibliometric analysis to map the research landscape and identify current and potential hotspots regarding NETs in IS.

Methods

Relevant literature published between 2014 and 2024 was systematically retrieved from the Web of Science Core Collection (WoSCC) database. Multiple analytical tools, including CiteSpace, VOSviewer, R package "bibliometrix," and Python scripts, were employed to explore publication trends, academic collaborations, prominent research themes, and emerging topics.

Results

Ninety-two publications were eligible for bibliometric assessment, supplemented by an additional latent Dirichlet allocation (LDA)-based topic analysis of 4,504 documents. China (30 publications) and the United States (23 publications) emerged as leading countries in terms of research output, with global collaboration networks predominantly centering around the United States. Noteworthy contributions also arose from European institutions, particularly Katholieke Universiteit Leuven and Karolinska Institutet. The leading authors identified were Desilles, Jean-Philippe, Ho-Tin-Noé, Benoit, and Mazighi, Mikael. Journals such as Stroke, Annals of Neurology, and Nature Communications significantly influenced this domain. Three main research hotspots emerged: (1) "promoting effect of protein arginine deiminase 4 (PAD4) in NET formation," (2) "cell-free DNA as a biomarker for disease diagnosis," and (3) "influence of platelets and thrombosis on NETs-related diseases."

Conclusion

Our study offers an extensive overview of existing literature and evolving research trajectories concerning NETs in IS, providing researchers with clear insights into current trends and future investigative directions. Nevertheless, our study has limitations-including dependence on a single database (WoSCC), restriction to English-language publications, and inherent constraints of the LDA methodology-that merit consideration in interpreting these findings.

Identification of NETs-related genes as diagnostic biomarkers in ischemic stroke using RNA sequencing and single-cell analysis

Neutrophil extracellular traps (NETs) are increasingly recognized for their involvement in ischemic stroke (IS), yet their precise contribution to IS outcomes is not fully understood. This study aims to elucidate the role of NETs in IS progression and identify potential biomarkers and therapeutic targets. In this study, mice were subjected to middle cerebral artery occlusion (MCAO). RNA sequencing was conducted on brain tissue samples to identify differentially expressed genes (DEGs) using the "limma" package. The diagnostic potential of these biomarkers was assessed using receiver operating characteristic (ROC) curve analysis. Additionally, single-cell RNA sequencing data were analyzed with the Seurat package to further investigate the cellular dynamics. We identified DEGs, and NETs-related genes associated with IS progression. Specifically, Ceacam3, Tnf, Selp, and Fcgr4 were found to be upregulated in MCAO samples, exhibiting diagnostic value as biomarkers for IS. Immune infiltration analysis indicated associations between these genes and various immune cell types. Gene Set Enrichment Analysis (GSEA) revealed their involvement in IS-related pathways, including ferroptosis, IL-17 signaling, leukocyte transendothelial migration, necroptosis, and NETs formation. Single-cell data confirmed the expression of Tnf, Selp, and Fcgr4 in neutrophils. CellChat analysis uncovered key cell-cell interactions in IS, emphasizing the role of neutrophils in communicating with microglia and T cells via the JAM pathway, with Thbs1 and Cd47 as key mediators. The findings provide insights into the cellular and molecular mechanisms underlying IS and may pave the way for novel therapeutic strategies targeting NETs in IS patients.

Cell-Free Nucleic Acids for Early Diagnosis of Acute Ischemic Stroke: A Systematic Review and Meta-Analysis

Rapid identification of acute ischemic stroke (AIS) is challenging in both pre-hospital and hospital settings. We aimed to identify the most promising cell-free nucleic acids (cfNAs) as diagnostic biomarkers for IS within 72 h from symptom onset. We searched PubMed, Web of Science, EMBASE, and Cochrane Library for published articles that evaluated blood cfNAs in the early diagnosis of AIS until 10 May 2023. The diagnostic performances of individual cfNAs were pooled by random-effects meta-analysis based on the fold change of biomarkers' level between AIS and non-AIS patients. Of 2955 records, 66 articles reporting 143 different cfNAs met the inclusion criteria. The median sample size was 110, and 21.4% of the studies performed validation. Among selected high-quality studies, miR-106b-5p, miR-124, miR-155, lncRNA H19, and cfDNA showed good diagnostic performance. Data from four studies on cfDNA involving 355 AIS patients and 97 controls were pooled in the meta-analysis, which showed a significant fold change between AIS and controls (pooled ratio 1.48, 95% confidence interval 1.23-1.79, p < 0.001). This review highlights that cfDNA, miR-106b-5p, miR-124, miR-155, and lncRNA H19 are the most promising biomarkers for AIS diagnosis, and further research is needed for verification.

Research progress on the relationship between neutrophil extra-cellular traps and autogenous arteriovenous fistula thrombosis

Autogenous arteriovenous fistula (AVF) is the preferred vascular access for long-term hemodialysis, and thrombosis is one of the most common complications. In recent years, it has been found that neutrophil extra-cellular traps (NETs) play an important role in thrombosis. NETs are a kind of network structure with DNA as a skeleton and intercalated with a variety of granule proteins, proteolytic enzymes, antimicrobial peptides and histone proteins, which are released into the extracellular space by neutrophils after stimulation. In this paper, the NETs in the role of AVF thrombus formation and NETs in the value of prevention and cure of AVF thrombus complications were reviewed.

Platelet-derived HMGB1 induces NETosis, exacerbating brain damage in the photothrombotic stroke model

Following cerebral ischemia, neutrophil extracellular traps (NETs) contribute significantly to brain damage by exacerbating delayed immune cell infiltration and vascular injury. They are detected both in brain tissue and within blood vessels. Danger-associated molecular pattern (DAMP) molecules have been implicated in inducing NETosis after cerebral ischemia. This study investigated the role of High mobility group box 1 (HMGB1), a prototype DAMP molecule, in NETosis induction following photothrombotic stroke (PTS), with a particular focus on neutrophil-platelet interactions. In PTS, thrombi consist primarily of aggregated platelets and neutrophils, lacking significant fibrin content. Triphenyltetrazolium chloride (TTC) staining revealed rapid but progressive expansion of the infarct area in the PTS model, commencing within 1 h and continuing until 24 h. Concomitant with this, peripheral neutrophils isolated following PTS exhibited progressive NETosis, particularly intravascular NETosis. This was evidenced by significant increase in citrullinated histone H3 (CitH3), a marker of NETosis, as early as 1 h post-PTS. Furthermore, serum levels of free DNA gradually and significantly increased, further supporting the induction of NETosis following PTS. Intranasal administration of BBCA, a peptidylarginine deiminase (PAD) inhibitor, effectively suppressed the induction of intravascular NETosis. Importantly, BBCA administration, both 30 min before and 4 h after PTS surgery, significantly reduced infarct volumes at 24 h and improved neurological outcomes. These findings underscore the crucial role of NETosis in both the initiation and progression of ischemic brain damage in this model. Following PTS, HMGB1 rapidly accumulated in serum, detectable as early as 1 h. Immunofluorescence staining revealed initial localization of HMGB1 in neurons, followed by its accumulation within activated neutrophils and platelets within blood vessels. Functional inhibition of HMGB1 by intranasal administration of an HMGB1 A box 4 h post-PTS significantly suppressed NETosis induction, reduced infarct volume, and improved neurological deficits, confirming the pivotal role of HMGB1 in NETosis induction. Notably, we observed a rapid platelet activation and concomitant HMGB1 induction within activated platelets after PTS. Co-culture experiments using naïve PMNs-platelets isolated following PTS demonstrate that extracellular HMGB1, particularly one derived from platelets, plays a critical role in activating neutrophils and inducing intravascular NETosis via a TLR4-dependent manner. Collectively, these findings highlight the critical role of NETosis not only in the initial stages of thrombus formation but also in the subsequent progression of ischemic brain damage in the PTS animal model. HMGB1, particularly platelet-derived HMGB1, emerges as a key mediator to this process. Therefore, targeting NETosis through modulation of HMGB1 presents a promising multipotent therapeutic strategy for mitigating ischemic brain damage.

Daytime DNase-I Administration Protects Mice From Ischemic Stroke Without Inducing Bleeding or tPA-Induced Hemorrhagic Transformation, Even With Aspirin Pretreatment

BACKGROUND

Acute ischemic stroke treatment typically involves tissue-type plasminogen activator (tPA) or tenecteplase, but about 50% of patients do not achieve successful reperfusion. The causes of tPA resistance, influenced by thrombus composition and timing, are not fully clear. Neutrophil extracellular traps (NETs), associated with poor outcomes and reperfusion resistance, contribute to thrombosis. DNase-I, which degrades neutrophil extracellular traps, could improve thrombolytic efficacy. However, more studies are needed to understand the impact of DNase-I in tPA-sensitive stroke models, the safety of coadministering DNase-I and tPA regarding hemorrhagic transformation (HT), optimal timing for use, and effects on aspirin-treated animals.

METHODS

We used in situ thromboembolic stroke, a tPA-sensitive model, where late tPA administration causes HT. Middle cerebral artery occlusion was induced at different zeitgeber times (ZT) to study the optimal timing for administration. DNase-I, tPA, and aspirin were administered at various times to evaluate their effects.

RESULTS

DNase-I reduced infarct volume and improved functional outcomes 24 hours post-middle cerebral artery occlusion by decreasing plasma and cortical neutrophil extracellular trap levels. DNase-I caused no bleeding or impact on HT induced by late tPA. Its protective effect was only seen when given during the daytime (rodent inactive phase; ZT4-7), not overnight (active phase; ZT13-16). Chronic aspirin pretreatment increased tPA-induced HT but did not change the protective effects of DNase-I, with or without tPA.

CONCLUSIONS

Our study demonstrates that daytime (inactive phase) DNase-I administration is a safe and effective treatment for experimental stroke. This is particularly important given the 2 ongoing clinical trials for stroke patients.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT05203224 and NCT05880524.

Cytokine signalling in formation of neutrophil extracellular traps: Implications for health and diseases

Neutrophils, as essential component of the innate immune response, form a crucial part in the defence mechanisms through the release of extracellular traps (NETs). These web-like structures, composed of chromatin and antimicrobial proteins, are essential for the entrapment and inactivation of pathogens. However, either constitutive formation or inefficient clearance of NETs leads to adverse effects such as fibrosis, thrombosis, delayed wound healing and tissue damage in multiple diseases associated with sterile inflammation. This dichotomy casts NETs as both protective agents and harmful factors in several diseases such as autoimmune diseases, metabolic syndromes, systemic infections, and malignancies. Besides microbes and their products, variety of stimulants including pro-inflammatory cytokines induce NETs. The complex interactions and cross talk among the pro-inflammatory cytokines including IL-8, IL-6, GM-CSF, TNF-α, IFNs, and IL-1β activate neutrophils to form NETs and also contributes to a vicious circle of inflammatory cascade, leading to increased inflammation, oxidative stress, and thrombotic events. Emerging evidence indicates that the dysregulated cytokine milieus in diseases, such as diabetes mellitus, obesity, atherosclerosis, stroke, rheumatoid arthritis, and systemic lupus erythematosus, potentiate NETs release, thereby promoting disease development. Thus, neutrophils represent both critical effectors and potential therapeutic targets, underscoring their importance in the context of cytokine-mediated therapies for a spectrum of diseases. In the present review, we describe various cytokines and associated signalling pathways activating NETs formation in different human pathologies. Further, the review identifies potential strategies to pharmacologically modulate cytokine pathways to reduce NETs.

Gut dysbiosis and neutrophil extracellular traps in chronic heart failure

BACKGROUND

Chronic heart failure (HF) patients have reduced microbiota diversity. Leakage of microbes and their metabolites into the bloodstream may activate neutrophils. Neutrophil extracellular traps (NETs) consist of chromatin and proteases, and may contribute to HF pathogenesis. We assessed associations between circulating NETs and 1) cardiac function, 2) the degree of gut microbiota diversity and 3) gut leakage and microbial metabolites in HF patients.

METHODS

A cross-sectional study including 124 patients with chronic HF and left ventricular ejection fraction ≤40 %. Severe HF was defined as N-terminal pro-B-type natriuretic peptide concentrations above median. We measured citrullinated histone H3 (CitH3), myeloperoxidase- and double-stranded-DNA in the blood. Gut leakage markers included bacterial lipopolysaccharides and soluble cluster of differentiation 14. The microbial metabolites included circulating trimethylamine N-oxide and butyrate producing capacity. We used the Shannon diversity-index and a dysbiosis-index based on bacteria with altered relative abundance to characterize the gut microbiota profile.

RESULTS

Quartile 4 of CitH3 was associated with more severe HF compared to quartiles 1-3, after adjustments for age, gender and hypertension (adjusted odds ratio [95 %CI] 3.21[1.18-8.69], p = 0.022). CitH3 was moderately associated with hypertension (p = 0.04), higher CRP levels (p = 0.016) and lower Shannon diversity index, (p = 0.039). No other NET marker associated with severe HF.

CONCLUSIONS

In chronic HF patients with reduced LVEF, high levels of CitH3 were associated with disease severity, inflammation and reduced gut microbiota diversity. Our results suggest that enhanced release of NETs could be involved in progressive HF, although the contribution of the gut microbiota seems limited in this context.

Associations of NETs with inflammatory risk and clinical predictive value in large artery atherosclerosis stroke: a prospective cohort study

Background and objective

Neutrophil extracellular traps (NETs) with inflammatory risk are important contributors to cardiovascular disease, but no definitive information is available in large artery atherosclerotic (LAA) stroke. This study aims to investigate the association between NETs with related inflammatory biomarkers and prognosis of LAA stroke in the Chinese population.

Methods

A prospective study involving 145 LAA stroke cases and 121 healthy controls was conducted. Serum levels of MPO-DNA, PAD4, HMGB1, C1q, AIM2, ASC, Caspase-1, IL-1β, IL-6, and IL-8 were determined in all participants. The biomarkers were detected at three time points after stroke onset (24 hours: T1, 48 hours: T2, 7 days: T3) for LAA stroke patients and once for controls. Patients were followed up for 2 years after the ischemic event.

Results

The serum MPO-DNA, PAD4, C1q, IL-1β, IL-6 and IL-8 reach their peak at 24 hours after stroke onset and show a decreasing trend during acute phase. MPO-DNA, AIM2 and IL-1β at baseline were associated with poor outcome at 3 months, further GMDR analysis revealed that the combination of MPO-DNA, AIM2 and IL-1β exert a synergistic effect on the prognosis of LAA stroke (OR: 8.75 95%CI (2.10-32.42)). For time-to-event analysis, MPO-DNA, Caspase-1 and IL-1β at baseline were predictors of MVEs after stroke (HR:4.04 (95%CI 1.28-12.70), 2.33 (95%CI 1.06-5.12) and 4.09 (95%CI 1.39-11.99), respectively).

Conclusions

NETs and related inflammatory biomarkers at baseline predicted outcome at 3 months and late major vascular events following LAA stroke, supporting a rationale of randomized trials for targeted therapy directed at high-risk patients with elevated baseline NETs and related inflammatory biomarkers.

Prognostic Impact of Neutrophil-to-Lymphocyte Ratio in Ischemic Stroke

Background/objective: Studies suggest that the neutrophil/lymphocyte ratio (NLR) may be a prognostic marker for different diseases with inflammatory components. This study aimed to quantify the NLR in individuals affected by different subtypes and severities of ischemic stroke and associated it with risk factors and treatment, and compared the results with data from healthy individuals. Methods: Clinical and laboratory data from medical records of patients over 18 years of age, victims of ischemic stroke, were collected. Data included leukocyte count and subtype, topography, risk factors, treatment and severity of stroke. For comparison, the number of leukocytes in healthy individuals was also quantified. NLR was determined by dividing the number of neutrophils by the number of lymphocytes. Results: A total of 218 patients were included, 194 stroke patients and 24 healthy individuals. Among all stroke patients, 45% had NLR values > 4 and 35% had values between 2 and 4; otherwise, 71% of healthy individuals had NRL < 2. The data also showed that the greater the severity of the stroke, measured by the NIHSS scale, the higher the NLR, at 24 and 72 h after the stroke. Among the stroke subtypes evaluated, the one with the lowest NLR values was small vessel stroke. Finally, the risk factors for stroke, its topography and treatment were not associated with NLR values. Conclusions: NLR is associated with stroke severity but does not correlate with stroke risk factors, topography, and treatment. The NLR may serve as a marker of stroke severity.

The role of neutrophils in tPA thrombolysis after stroke: a malicious troublemaker

Acute ischemic stroke represents a critical, life-threatening condition affecting the central nervous system. Intravenous thrombolysis with tissue plasminogen activator (tPA) remains a cornerstone for achieving vascular recanalization in such patients; however, its therapeutic utility is limited, with only approximately 10% of patients benefiting due to the narrow therapeutic window and significant risk of hemorrhagic transformation. Enhancing the efficacy of tPA thrombolysis is therefore imperative. Neutrophils have been identified as key modulators of thrombolytic outcomes, interacting with tPA post-stroke to influence treatment effectiveness. The binding of tPA to low-density lipoprotein receptor-related protein 1 (LRP-1) on neutrophil surfaces induces degranulation and formation of neutrophil extracellular traps (NETs). Conversely, neutrophils impede the thrombolytic action of tPA by obstructing its interaction with fibrin and activating platelets. These findings suggest that targeting neutrophils may hold promise for improving thrombolysis outcomes. This review explores the role of neutrophils in tPA-mediated thrombolysis following acute ischemic stroke, examines neutrophil-associated biomarkers, and outlines potential strategies for enhancing tPA efficacy.

Alternating high-fat diet enhances atherosclerosis by neutrophil reprogramming

Systemic immune responses caused by chronic hypercholesterolaemia contribute to atherosclerosis initiation, progression and complications1. However, individuals often change their dietary habits over time2, and the effects of an alternating high-fat diet (HFD) on atherosclerosis remain unclear. Here, to address this relevant issue, we developed a protocol using atherosclerosis-prone mice to compare an alternating versus continuous HFD while maintaining similar overall exposure periods. We found that an alternating HFD accelerated atherosclerosis in Ldlr-/- and Apoe-/- mice compared with a continuous HFD. This pro-atherogenic effect of the alternating HFD was also observed in Apoe-/-Rag2-/- mice lacking T, B and natural killer T cells, ruling out the role of the adaptive immune system in the observed phenotype. Discontinuing the HFD in the alternating HFD group downregulated RUNX13, promoting inflammatory signalling in bone marrow myeloid progenitors. After re-exposure to an HFD, these cells produced IL-1β, leading to emergency myelopoiesis and increased neutrophil levels in blood. Neutrophils infiltrated plaques and released neutrophil extracellular traps, exacerbating atherosclerosis. Specific depletion of neutrophils or inhibition of IL-1β pathways abolished emergency myelopoiesis and reversed the pro-atherogenic effects of the alternating HFD. This study highlights the role of IL-1β-dependent neutrophil progenitor reprogramming in accelerated atherosclerosis induced by alternating HFD.

Targeting neutrophils extracellular traps, a promising anti-thrombotic therapy for natural products from traditional Chinese herbal medicine

Thrombi are the main cause of vascular occlusion and contribute significantly to cardiovascular events and death. Neutrophils extracellular traps (NETs)-induced thrombosis plays a vital role in thrombotic complications and it takes the main responsibility for the resistance of fibrinolysis. However, the conventional anti-thrombotic therapies are inadequate to treat NETs-induced thrombotic complications but carry a high risk of bleeding. Consequently, increased attention has shifted towards exploring novel anti-thrombotic treatments targeting NETs. Interestingly, accumulating evidences prove that natural products from traditional Chinese herbal medicines have a great potential to mitigate thrombosis through inhibiting generous NETs formation and degrading excessive NETs. In this review, we elaborated the formation and degradation of NETs and highlighted its pivotal role in immunothrombosis through interactions with platelets and coagulation factors. Since available anti-thrombotic drugs targeting NETs are deficient, we further summarized the natural products and compounds from traditional Chinese herbal medicines which exert effective actions on regulating NETs formation and also have anti-thrombotic effects. Our findings underscore the diverse effects of natural products in targeting NETs, including relieving inflammation and oxidative stress of neutrophils, inhibiting neutrophils activation and DNA efflux, suppressing granule proteins release, reducing histones and promoting DNA degradation. This review aims to highlight the significance of natural medicines in anti-thrombotic therapies through targeting NETs and to lay a groundwork for developing novel anti-thrombotic agents from traditional Chinese herbal medicines.

Neutrophil extracellular traps in homeostasis and disease

Neutrophil extracellular traps (NETs), crucial in immune defense mechanisms, are renowned for their propensity to expel decondensed chromatin embedded with inflammatory proteins. Our comprehension of NETs in pathogen clearance, immune regulation and disease pathogenesis, has grown significantly in recent years. NETs are not only pivotal in the context of infections but also exhibit significant involvement in sterile inflammation. Evidence suggests that excessive accumulation of NETs can result in vessel occlusion, tissue damage, and prolonged inflammatory responses, thereby contributing to the progression and exacerbation of various pathological states. Nevertheless, NETs exhibit dual functionalities in certain pathological contexts. While NETs may act as autoantigens, aggregated NET complexes can function as inflammatory mediators by degrading proinflammatory cytokines and chemokines. The delineation of molecules and signaling pathways governing NET formation aids in refining our appreciation of NETs' role in immune homeostasis, inflammation, autoimmune diseases, metabolic dysregulation, and cancer. In this comprehensive review, we delve into the multifaceted roles of NETs in both homeostasis and disease, whilst discussing their potential as therapeutic targets. Our aim is to enhance the understanding of the intricate functions of NETs across the spectrum from physiology to pathology.

Targeting NETosis in Acute Brain Injury: A Systematic Review of Preclinical and Clinical Evidence

Acute brain injury (ABI) remains one of the leading causes of death and disability world-wide. Its treatment is challenging due to the heterogeneity of the mechanisms involved and the variability among individuals. This systematic review aims at evaluating the impact of anti-histone treatments on outcomes in ABI patients and experimental animals and defining the trend of nucleosome levels in biological samples post injury. We performed a search in Pubmed/Medline and Embase databases for randomized controlled trials and cohort studies involving humans or experimental settings with various causes of ABI. We formulated the search using the PICO method, considering ABI patients or animal models as population (P), comparing pharmacological and non-pharmacological therapy targeting the nucleosome as Intervention (I) to standard of care or no treatment as Control (C). The outcome (O) was mortality or functional outcome in experimental animals and patients affected by ABI undergoing anti-NET treatments. We identified 28 studies from 1246 articles, of which 7 were experimental studies and 21 were human clinical studies. Among these studies, only four assessed the effect of anti-NET therapy on circulating markers. Three of them were preclinical and reported better outcome in the interventional arm compared to the control arm. All the studies observed a significant reduction in circulating NET-derived products. NETosis could be a target for new treatments. Monitoring NET markers in blood and cerebrospinal fluid might predict mortality and long-term outcomes. However, longitudinal studies and randomized controlled trials are warranted to fully evaluate their potential, as current evidence is limited.

Extracellular histones: a unifying mechanism driving platelet-dependent extracellular vesicle release and thrombus formation in COVID-19

BACKGROUND

COVID-19 can cause profound inflammation and coagulopathy, and while many mechanisms have been proposed, there is no known common pathway leading to a prothrombotic state.

OBJECTIVES

From the beginning of the COVID-19 pandemic, elevated levels of extracellular histones have been found in plasma of patients infected with SARS-CoV-2. We hypothesized that platelet activation triggered by extracellular histones might represent a unifying mechanism leading to increased thrombin generation and thrombosis.

METHODS

We utilized blood samples collected from an early clinical trial of hospitalized COVID-19 patients (NCT04360824) and recruited healthy subjects as controls. Using plasma samples, we measured the procoagulant and prothrombotic potential of circulating extracellular histones and extracellular vesicles (EVs). Platelet prothrombotic activity was assessed via thrombin generation potential and platelet thrombus growth. Circulating EVs were assessed for thrombin generation potential in vitro in plasma and enhancement of thrombotic susceptibility in vivo in mice.

RESULTS

Compared with controls, COVID-19 patients had elevated plasma levels of citrullinated histone H3, cell-free DNA, nucleosomes, and EVs. Plasma from COVID-19 patients promoted platelet activation, platelet-dependent thrombin generation, thrombus growth under venous shear stress, and release of platelet-derived EVs. These prothrombotic effects of COVID-19 plasma were inhibited by an RNA aptamer that neutralizes both free and DNA-bound histones. EVs isolated from COVID-19 plasma enhanced thrombin generation in vitro and potentiated venous thrombosis in mice in vivo.

CONCLUSION

We conclude that extracellular histones and procoagulant EVs drive the prothrombotic state in COVID-19 and that histone-targeted therapy may prove beneficial.

Assessment of associations between neutrophil extracellular trap biomarkers in blood and thrombi in acute ischemic stroke patients

Inflammation including immunothrombosis by neutrophil extracellular traps (NETs) has important implications in acute ischemic stroke and can affect reperfusion status, susceptibility to stroke associated infections (SAI) as well as functional clinical outcome. NETs were shown to be prevalent in stroke thrombi and NET associated markers were found in stroke patients' blood. However, little is known whether blood derived NET markers reflect the amount of NETs in thrombi. Conclusions from blood derived markers to thrombus composition might open avenues for novel strategies in diagnostic and therapeutic approaches. We prospectively recruited 166 patients with acute ischemic stroke undergoing mechanical thrombectomy between March 2018 and May 2021. Available thrombi (n = 106) were stained for NET markers DNA-histone-1 complexes and myeloperoxidase (MPO). Cell free DNA (cfDNA), deoxyribonuclease (DNase) activity, MPO-histone complexes and a cytokine-panel were measured before thrombectomy and after seven days. Clinical data, including stroke etiology, reperfusion status, SAI and functional outcome after rehabilitation, were collected of all patients. NET markers were present in all thrombi. At onset the median concentration of cfDNA in blood was 0.19 µg/ml increasing to 0.30 µg/ml at 7 days. Median DNase activity at onset was 4.33 pmol/min/ml increasing to 4.96 pmol/min/ml at 7 days. Within thrombi DNA-histone-1 complexes and MPO correlated with each other (ρ = 0.792; p < 0.001). Moreover, our study provides evidence for an association between the amount of NETs and endogenous DNase activity in blood with amounts of NETs in cerebral thrombi. However, these associations need to be confirmed in larger cohorts, to investigate the potential clinical implications for individualized therapeutic and diagnostic approaches in acute ischemic stroke.

Huanglian Jiedu decoction alleviates ischemia-induced cerebral injury in rats by mitigating NET formation and activiting GABAergic synapses

Huanglian Jiedu decoction (HLJD) has been used to treat ischemic stroke in clinic. However, the detailed protective mechanisms of HLJD on ischemic stroke have yet to be elucidated. The aim of this study is to elucidate the underlying pharmacological mechanisms of HLJD based on the inhibition of neuroinflammation and the amelioration of nerve cell damage. A middle cerebral artery occlusion reperfusion (MCAO/R) model was established in rats and received HLJD treatment. Effects of HLJD on neurological function was assessed based on Bederson's score, postural reflex test and asymmetry score. 2, 3, 5-Triphenyltetrazolium chloride (TTC) staining, Hematein and eosin (HE) and Nissl staining were used to observe the pathological changes in brain. Then, transcriptomics was used to screen the differential genes in brain tissue in MCAO/R model rats following HLJD intervention. Subsequently, the effects of HLJD on neutrophil extracellular trap (NET) formation-related neuroinflammation, gamma-aminobutyric acid (GABA)ergic synapse activation, nerve cell damage and proliferation were validated using immunofluorescence, western blot and enzyme-linked immunosorbent assay (ELISA). Our results showed that HLJD intervention reduced the Bederson's score, postural reflex test score and asymmetry score in MCAO/R model rats. Pathological staining indicated that HLJD treatment decreased the cerebral infarction area, mitigated neuronal damage and increased the numbers of Nissl bodies. Transcriptomics suggested that HLJD affected 435 genes in MCAO/R rats. Among them, several genes involving in NET formation and GABAergic synapses pathways were dysregulated. Subsequent experimental validation showed that HLJD reduced the MPO+CitH3+ positive expression area, reduced the protein expression of PAD4, p-P38/P38, p-ERK/ERK and decreased the levels of IL-1β, IL-6 and TNF-α, reversed the increase of Iba1+TLR4+, Iba1+p65+ and Iba1+NLRP3+ positive expression area in brain. Moreover, HLJD increased GABA levels, elevated the protein expression of GABRG1 and GAT3, decreased the TUNEL positive expression area and increased the Ki67 positive expression area in brain. HLJD intervention exerts a multifaceted positive impact on ischemia-induced cerebral injury in MCAO/R rats. This intervention effectively inhibits neuroinflammation by mitigating NET formation, and concurrently improves nerve cell damage and fosters nerve cell proliferation through activating GABAergic synapses.

SIRT1-Mediated HMGB1 Deacetylation Suppresses Neutrophil Extracellular Traps Related to Blood-Brain Barrier Impairment After Cerebral Venous Thrombosis

Cerebral venous thrombosis (CVT) is a neurovascular disease with recently increasing incidence. Aseptic inflammatory responses play an important role in the pathology of CVT. Recent studies report that neutrophil extracellular traps (NETs) are major triggers of thrombosis and inflammation in stroke, but their effect on brain injury in CVT requires further validation. In this study, two CVT animal models were used to simulate superior sagittal sinus thrombosis and cortical vein thrombosis. The effects of brain tissue infiltration of NETs and the molecular mechanisms associated with NET formation were deeply explored in combination with proteomics, histology, and serology. The results showed that the cortical vein thrombosis model could be combined with more severe blood-brain barrier (BBB) disruption and showed more severe cerebral hemorrhage. Decreased Sirtuin 1 (SIRT1) expression promotes high mobility group box 1 (HMGB1) acetylation, causing increased cytosolic translocation and extracellular release, and HMGB1 can promote NET formation and recruitment. In addition, corticocerebral accumulation of NETs contributes to BBB damage. This establishes a vicious cycle between BBB damage and NET accumulation. SIRT1 mediated-HMGB1 deacetylation may play a critical role in attenuating BBB damage following CVT. This study employed a combined validation using models of venous sinus thrombosis and cortical vein thrombosis to investigate the deacetylation role of SIRT1, aiming to offer new insights into the pathological mechanisms of brain injury following CVT.

Epigenetics of cerebrovascular diseases: an update review of clinical studies

Cerebrovascular diseases, especially stroke, are critical and heterogenous clinical conditions associated with high mortality and chronic disability. Genome-wide association studies reveal substantial stroke heritability, though specific genetic variants account for a minor fraction of stroke risk, suggesting an essential role for the epigenome. Epigenome-wide association studies and candidate gene approaches show that DNA methylation patterns significantly influence stroke susceptibility. Additionally, chromatin remodelers and non-coding RNA regulate gene expression in response to ischemic conditions. In this updated review, we summarized the progress of knowledge on epigenetics in the field of ischemic stroke underlying opportunities and challenges.

Ischaemic Stroke, Thromboembolism and Clot Structure

Ischaemic stroke is a major cause of morbidity and mortality worldwide. Blood clotting and thromboembolism play a central role in the pathogenesis of ischaemic stroke. An increasing number of recent studies indicate changes in blood clot structure and composition in patients with ischaemic stroke. In this review, we aim to summarise and discuss clot structure, function and composition in ischaemic stroke, including its relationships with clinical diagnosis and treatment options such as thrombolysis and thrombectomy. Studies are summarised in which clot structure and composition is analysed both in vitro from patients' plasma samples and ex vivo in thrombi obtained through interventional catheter-mediated thrombectomy. Mechanisms that drive clot composition and architecture such as neutrophil extracellular traps and clot contraction are also discussed. We find that, while in vitro clot structure in plasma samples from ischaemic stroke patients are consistently altered, showing denser clots that are more resistant to fibrinolysis, current data on the composition and architecture of ex vivo clots obtained by thrombectomy are more variable. With the potential of advances in technologies underpinning both the imaging and retrieving of clots, we expect that future studies in this area will generate new data that is of interest for the diagnosis, optimal treatment strategies and clinical management of patients with ischaemic stroke.

Ficolin-A/2 Aggravates Severe Lung Injury through Neutrophil Extracellular Traps Mediated by Gasdermin D-Induced Pyroptosis

Neutrophil extracellular traps (NETs) and pyroptosis are critical events in lung injury. This study investigated whether ficolin-A influenced NET formation through pyroptosis to exacerbate lipopolysaccharide (LPS)-induced lung injury. The expression of ficolin-A/2, NETs, and pyroptosis-related molecules was investigated in animal and cell models. Knockout and knockdown (recombinant protein) methods were used to elucidate regulatory mechanisms. The Pearson correlation coefficient was used to analyze the correlation between ficolins and pyroptosis- and NET-related markers in clinical samples. In this study, ficolin-2 (similar to ficolin-A) showed significant overexpression in patients with acute respiratory distress syndrome. In vivo, knockout of Fcna, but not Fcnb, attenuated lung inflammation and inhibited NET formation in the LPS-induced mouse model. DNase I further alleviated lung inflammation and NET formation in Fcna knockout mice. In vitro, neutrophils derived from Fcna-/- mice showed less pyroptosis and necroptosis than those from the control group after LPS stimulation. Additionally, GSDMD knockdown or Nod-like receptor protein 3 inhibitor reduced NET formation. Addition of recombinant ficolin-2 protein to human peripheral blood neutrophils promoted NET formation and pyroptosis after LPS stimulation, whereas Fcn2 knockdown had the opposite effect. Acute respiratory distress syndrome patients showed increased levels of pyroptosis- and NET-related markers, which were correlated positively with ficolin-2 levels. In conclusion, these results suggested that ficolin-A/2 exacerbated NET formation and LPS-induced lung injury via gasdermin D-mediated pyroptosis.

Bioinformatics gene analysis for potential biomarkers and therapeutic targets of Parkinson's disease based on neutrophil extracellular traps

Introduction

Neutrophil extracellular traps (NETs) provide key innate immune mechanisms, and studies have shown innate immunity and adaptive immunity are directly linked to Parkinson's disease (PD) pathology. However, limited research has been conducted on NETs in the context of PD.

Methods

A differential analysis was implemented to acquire differentially expressed genes (DEGs) between PD and control as well as between high- and low-score groups determined by a gene set variation analysis (GSVA). Then, the genes within the critical module, obtained through a weighted gene co-expression network analysis (WGCNA), were intersected with the DEGs to identify the overlapping genes. Then, five kinds of algorithms in the protein-protein interaction (PPI) were performed to identify potential biomarkers. Subsequently, a nomogram for forecasting PD probability was created. An enrichment analysis and an immune infiltration analysis were performed on the identified biomarkers. qRT-PCR was performed to validate the expression trends of three biomarkers.

Results

We revealed 798 DEGs between PD and control groups as well as 168 DEGs between high- and low-score groups obtained by differential analyses. The pink module containing 926 genes was identified as the critical module. According to the intersection of these gene sets, a total of 43 overlapping genes were screened out. Furthermore, GPR78, CADM3, and CACNA1E were confirmed as biomarkers. Moreover, we found that biomarkers mainly participated in pathways, such as the 'hydrogen peroxide catabolic process', and 'cell cycle'; five kinds of differential immune cells between PD and control groups were identified. Finally, the qRT-PCR analysis demonstrated the up-regulation of GPR78, CADM3, and CACNA1E in the PD group.

Discussion

Our study authenticated GPR78, CADM3, and CACNA1E as the biomarkers associated with PD. These findings provide an original reference for the diagnosis and treatment of PD.

Body fluids biomarkers associated with prognosis of acute ischemic stroke: progress and prospects

Acute ischemic stroke (AIS) is one of the most common strokes posing a grave threat to human life and health. Predicting the prognosis of AIS allows for an understanding of disease progress, and a better quality of life by making individualized treatment scheme. In this paper, we conducted a systematic search on PubMed, focusing on the relevant literature in the last 5 years. Summarizing the candidate prognostic biomarkers of AIS in body fluids such as blood, urine, saliva and cerebrospinal fluid is often of great significance for the management of acute ischemic stroke, which has the potential to facilitate early diagnosis, treatment, prevention and long-term outcome improvement.

Histone content, and thus DNA content, is associated with differential in vitro lysis of acute ischemic stroke clots

BACKGROUND

Fibrin, von Willebrand factor, and extracellular DNA from neutrophil extracellular traps all contribute to acute ischemic stroke thrombus integrity.

OBJECTIVES

In this study, we explored how the proteomic composition of retrieved thromboemboli relates to susceptibility to lysis with distinct thrombolytics.

METHODS

Twenty-six retrieved stroke thromboemboli were portioned into 4 segments, with each subjected to 1 hour of in vitro lysis at 37 °C in 1 of 4 solutions: tissue plasminogen activator (tPA), tPA + von Willebrand factor-cleaving ADAMTS-13, tPA + DNA-cleaving deoxyribonuclease (DNase) I, and all 3 enzymes. Lysis, characterized by the percent change in prelysis and postlysis weight, was compared across the solutions and related to the corresponding abundance of proteins identified on mass spectrometry for each of the thromboemboli used in lysis.

RESULTS

Solutions containing DNase resulted in approximately 3-fold greater thrombolysis than that with the standard-of-care tPA solution (post hoc Tukey, P < .01 for all). DNA content was directly related to lysis in solutions containing DNase (Spearman's ρ > 0.39 and P < .05 for all significant histones) and inversely related to lysis in solutions without DNase (Spearman's ρ < -0.40 and P < .05 for all significant histones). Functional analysis suggests distinct pathways associated with susceptibility to thrombolysis with tPA (platelet-mediated) or DNase (innate immune system-mediated).

CONCLUSION

This study demonstrates synergy of DNase and tPA in thrombolysis of stroke emboli and points to DNase as a potential adjunct to our currently limited selection of thrombolytics in treating acute ischemic stroke.

The Role of Neutrophils in Multiple Sclerosis and Ischemic Stroke

Inflammation plays an important role in numerous central nervous system (CNS) disorders. Its role is ambiguous-it can induce detrimental effects, as well as repair and recovery. In response to injury or infection, resident CNS cells secrete numerous factors that alter blood-brain barrier (BBB) function and recruit immune cells into the brain, like neutrophils. Their role in the pathophysiology of CNS diseases, like multiple sclerosis (MS) and stroke, is highly recognized. Neutrophils alter BBB permeability and attract other immune cells into the CNS. Previously, neutrophils were considered a homogenous population. Nowadays, it is known that various subtypes of these cells exist, which reveal proinflammatory or immunosuppressive functions. The primary goal of this review was to discuss the current knowledge regarding the important role of neutrophils in MS and stroke development and progression. As the pathogenesis of these two disorders is completely different, it gives the opportunity to get insight into diverse mechanisms of neutrophil involvement in brain pathology. Our understanding of the role of neutrophils in CNS diseases is still evolving as new aspects of their activity are being unraveled. Neutrophil plasticity adds another level to their functional complexity and their importance for CNS pathophysiology.

A promising frontier: targeting NETs for stroke treatment breakthroughs

Stroke is a prevalent global acute cerebrovascular condition, with ischaemic stroke being the most frequently occurring type. After a stroke, neutrophils accumulate in the brain and subsequently generate and release neutrophil extracellular traps (NETs). The accumulation of NETs exacerbates the impairment of the blood‒brain barrier (BBB), hampers neovascularization, induces notable neurological deficits, worsens the prognosis of stroke patients, and can facilitate the occurrence of t-PA-induced cerebral haemorrhage subsequent to ischaemic stroke. Alternative approaches to pharmacological thrombolysis or endovascular thrombectomy are being explored, and targeting NETs is a promising treatment that warrants further investigation.

Molecular subtype identification of cerebral ischemic stroke based on ferroptosis-related genes

Cerebral ischemic stroke (CIS) has the characteristics of a high incidence, disability, and mortality rate. Here, we aimed to explore the potential pathogenic mechanisms of ferroptosis-related genes (FRGs) in CIS. Three microarray datasets from the Gene Expression Omnibus (GEO) database were utilized to analyze differentially expressed genes (DEGs) between CIS and normal controls. FRGs were obtained from a literature report and the FerrDb database. Weighted gene co-expression network analysis (WGCNA) and protein-protein interaction (PPI) network were used to screen hub genes. The receiver operating characteristic (ROC) curve was adopted to evaluate the diagnostic value of key genes in CIS, followed by analysis of immune microenvironment, transcription factor (TF) regulatory network, drug prediction, and molecular docking. In total, 128 CIS samples were divided into 2 subgroups after clustering analysis. Compared with cluster A, 1560 DEGs were identified in cluster B. After the construction of the WGCNA and PPI network, 5 hub genes, including MAPK3, WAS, DNAJC5, PRKCD, and GRB2, were identified for CIS. Interestingly, MAPK3 was a FRG that differentially expressed between cluster A and cluster B. The expression levels of 5 hub genes were all specifically highly in cluster A subtype. It is noted that neutrophils were the most positively correlated with all 5 real hub genes. PRKCD was one of the target genes of FASUDIL. In conclusion, five real hub genes were identified as potential diagnostic markers, which can distinguish the two subtypes well.

Neutrophil extracellular traps correlate with severity and prognosis in patients with ischemic stroke: a systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

A correlation between neutrophil extracellular traps (NETs) and ischemic stroke (IS) has been hypothesized, but the results of relevant studies remain controversial. The purpose was to determine whether NETs have an impact on ischemic stroke.

METHODS

The studies on the correlation between NETs and IS were retrieved from CNKI, Wanfang Data, VIP, CBM, PubMed, Web of Science, Embase, and Cochrane databases by computer from the start of the database to December 2022. The study adhered to PRISMA guidelines. The PICOS model was used to create inclusion criteria. Two researchers screened the literature and extracted the relevant data. The quality of the included studies was evaluated using the NOS and the 11 items recommended by the AHRQ, and meta-analysis was completed using Stata 15.1 software.

RESULTS

The researchers included 752 patients in 7 studies (4 case-control studies and 3 cross-sectional studies). The meta-analysis found NETs are positively associated with the severity of IS at the time of onset [r(95% CI) = 0.31(0.24, 0.38), P < 0.001]. NETs are positively associated with a worse prognosis of IS [r(95% CI) = 0.34(0.13, 0.53), P = 0.003].

CONCLUSION

The presence of NETs is positively related to the severity and prognosis of IS. Higher levels of NETs indicate a more severe disease and a poorer prognosis. Because the number and quality of included studies are limited, the above results must be supported by further high-quality studies.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/PROSPERO/ , identifier: CRD42022356619.

Stroke emboli from patients with atrial fibrillation enriched with neutrophil extracellular traps

Background

Recent literature has demonstrated remarkable heterogeneity in the composition of acute ischemic stroke (AIS) emboli, which may impact susceptibility to therapy.

Objectives

In this study, we explored differences in proteomic composition of retrieved embolic material from patients with stroke with and without atrial fibrillation (AF) (AF+ and AF-, respectively).

Methods

The full proteome of retrieved thromboembolic material from 24 patients with AIS was obtained by mass spectrometry. Known marker proteins were assigned groups representing broad classes of embolus components: red blood cells, platelets, neutrophils, eosinophils, histones, complement, and other clotting-associated proteins (eg, fibrinogen). Relative protein abundances were compared between AF+ and AF- samples. Functional implications of differences were explored with gene set enrichment analysis and Gene Ontology enrichment analysis and visualization tool.

Results

One hundred sixty-six proteins were differentially expressed between AF+ and AF- specimens. Eight out of the 15 neutrophil proteins (P < .05; fold change, >2) and 4 of the 14 histone proteins were significantly enriched in AF+ emboli (P < .05; fold change, >2). Gene set enrichment analysis revealed a significant representation of proteins from published neutrophil extracellular trap (NET) proteomic gene sets. The most significantly represented functional Gene Ontology pathways in patients with AF involved neutrophil activation and degranulation (P < 1 × 10-7).

Conclusion

The present analysis suggests enrichment of NETs in emboli of patients with stroke and AF. NETs are a significant though understudied structural component of thrombi. This work suggests not only unique stroke biology in AF but also potential therapeutic targets for AIS in this population.

White blood cell subtypes and neutrophil extracellular traps content as biomarkers for stroke etiology in acute ischemic stroke clots retrieved by mechanical thrombectomy

BACKGROUND

Lymphocytes, macrophages, neutrophils, and neutrophil extracellular traps (NETs) associate with stroke risk factors and form a thrombus through different mechanisms. We investigated the total WBCs, WBC subtypes and NETs composition in acute ischemic stroke (AIS) clots to identify possible etiological differences that could help us further understand the process of thrombosis that leads to AIS.

METHODS

AIS clots from 100 cases each of atherothrombotic (AT), cardioembolic (CE) and cryptogenic stroke etiology were collected per-pass as part of the CÚRAM RESTORE registry of AIS clots. Martius Scarlet Blue stain was used to identify the main histological components of the clots. Immunohistochemical staining was used to identify neutrophils, lymphocytes, macrophages, and NETs patterns. The cellular and histological components were quantified using Orbit Image Analysis software.

RESULTS

AT clots were larger, with more red blood cells and fewer WBCs than CE clots. AT clots had more lymphocytes and cryptogenic clots had fewer macrophages than other etiologies. Most significantly, CE clots showed higher expression of neutrophils and extracellular web-like NETs compared to AT and cryptogenic clots. There was also a significantly higher distribution of web-like NETs around the periphery of the CE clots while a mixed distribution was observed in AT clots.

CONCLUSION

The difference in neutrophil and NETs expression in clots from different etiologies may provide insight into the mechanism of clot formation.

Identification of potential biological processes and key genes in diabetes-related stroke through weighted gene co-expression network analysis

BACKGROUND

Type 2 diabetes mellitus (T2DM) is an established risk factor for acute ischemic stroke (AIS). Although there are reports on the correlation of diabetes and stroke, data on its pathogenesis is limited. This study aimed to explore the underlying biological mechanisms and promising intervention targets of diabetes-related stroke.

METHODS

Diabetes-related datasets (GSE38642 and GSE44035) and stroke-related datasets (GSE16561 and GSE22255) were obtained from the Gene Expression omnibus (GEO) database. The key modules for stroke and diabetes were identified by weight gene co-expression network analysis (WGCNA). Gene Ontology (GO) and Kyoto Encyclopedia of Genes Genomes (KEGG) analyses were employed in the key module. Genes in stroke- and diabetes-related key modules were intersected to obtain common genes for T2DM-related stroke. In order to discover the key genes in T2DM-related stroke, the Cytoscape and protein-protein interaction (PPI) network were constructed. The key genes were functionally annotated in the Reactome database.

RESULTS

By intersecting the diabetes- and stroke-related crucial modules, 24 common genes for T2DM-related stroke were identified. Metascape showed that neutrophil extracellular trap formation was primarily enriched. The hub gene was granulin precursor (GRN), which had the highest connectivity among the common genes. In addition, functional enrichment analysis indicated that GRN was involved in neutrophil degranulation, thus regulating neutrophil extracellular trap formation.

CONCLUSIONS

This study firstly revealed that neutrophil extracellular trap formation may represent the common biological processes of diabetes and stroke, and GRN may be potential intervention targets for T2DM-related stroke.

Platelets and neutrophils cooperate to induce increased neutrophil extracellular trap formation in JAK2V617F myeloproliferative neoplasms

BACKGROUND

Neutrophils participate in the pathogenesis of thrombosis through the formation of neutrophil extracellular traps (NETs). Thrombosis is the main cause of morbidity and mortality in patients with myeloproliferative neoplasms (MPNs). Recent studies have shown an increase in NET formation (NETosis) both in patients with JAK2V617F neutrophils and in mouse models, and reported the participation of NETosis in the pathophysiology of thrombosis in mice.

OBJECTIVES

This study investigated whether JAK2V617F neutrophils are sufficient to promote thrombosis or whether their cooperation with other blood cell types is necessary.

METHODS

NETosis was studied in PF4iCre;Jak2V617F/WT mice expressing JAK2V617F in all hematopoietic lineages, as occurs in MPNs, and in MRP8Cre;Jak2V617F/WT mice in which JAK2V617F is expressed only in leukocytes.

RESULTS

In PF4iCre;Jak2V617F/WT mice, an increase in NETosis and spontaneous lung thrombosis abrogated by DNAse administration were observed. The absence of spontaneous NETosis or lung thrombosis in MRP8Cre;Jak2V617F/WT mice suggested that mutated neutrophils alone are not sufficient to induce thrombosis. Ex vivo experiments demonstrated that JAK2V617F-mutated platelets trigger NETosis by JAK2V617F-mutated neutrophils. Aspirin treatment in PF4iCre;Jak2V617F/WT mice reduced NETosis and reduced lung thrombosis. In cytoreductive-therapy-free patients with MPN treated with aspirin, plasma NET marker concentrations were lower than that in patients with MPN not treated with aspirin.

CONCLUSION

Our study demonstrates that JAK2V617F neutrophils alone are not sufficient to promote thrombosis; rather, platelets cooperate with neutrophils to promote NETosis in vivo. A new role for aspirin in thrombosis prevention in MPNs was also identified.

NLRP3-Induced NETosis: A Potential Therapeutic Target for Ischemic Thrombotic Diseases?

Ischemic thrombotic disease, characterized by the formation of obstructive blood clots within arteries or veins, is a condition associated with life-threatening events, such as stroke, myocardial infarction, deep vein thrombosis, and pulmonary embolism. The conventional therapeutic strategy relies on treatments with anticoagulants that unfortunately pose an inherent risk of bleeding complications. These anticoagulants primarily target clotting factors, often overlooking upstream events, including the release of neutrophil extracellular traps (NETs). Neutrophils are integral components of the innate immune system, traditionally known for their role in combating pathogens through NET formation. Emerging evidence has now revealed that NETs contribute to a prothrombotic milieu by promoting platelet activation, increasing thrombin generation, and providing a scaffold for clot formation. Additionally, NET components enhance clot stability and resistance to fibrinolysis. Clinical and preclinical studies have underscored the mechanistic involvement of NETs in the pathogenesis of thrombotic complications, since the clots obtained from patients and experimental models consistently exhibit the presence of NETs. Given these insights, the inhibition of NETs or NET formation is emerging as a promising therapeutic approach for ischemic thrombotic diseases. Recent investigations also implicate a role for the nucleotide-binding oligomerization domain (NOD)-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome as a mediator of NETosis and thrombosis, suggesting that NLRP3 inhibition may also hold potential for mitigating thrombotic events. Therefore, future preclinical and clinical studies aimed at identifying and validating NLRP3 inhibition as a novel therapeutic intervention for thrombotic disorders are imperative.

Role of Peptidylarginine Deiminase 4 in Central Nervous System Diseases

The deimination or citrullination of arginine residues in the polypeptide chain by peptidylarginine deiminase 4 alters the charge state of the polypeptide chain and affects the function of proteins. It is one of the main ways of protein post-translational modifications to regulate its function. Peptidylarginine deiminase 4 is widely expressed in multiple tissues and organs of the body, especially the central nervous system, and regulates the normal development of organisms. The abnormal expression and activation of peptidylarginine deiminase 4 is an important pathological mechanism for the occurrence and development of central nervous system diseases such as multiple sclerosis, Alzheimer's disease, cerebral ischemia reperfusion injury, and glioblastoma.

Role of Crosstalk between Glial Cells and Immune Cells in Blood-Brain Barrier Damage and Protection after Acute Ischemic Stroke

Blood-brain barrier (BBB) damage is the main pathological basis for acute ischemic stroke (AIS)-induced cerebral vasogenic edema and hemorrhagic transformation (HT). Glial cells, including microglia, astrocytes, and oligodendrocyte precursor cells (OPCs)/oligodendrocytes (OLs) play critical roles in BBB damage and protection. Recent evidence indicates that immune cells also have an important role in BBB damage, vasogenic edema and HT. Therefore, regulating the crosstalk between glial cells and immune cells would hold the promise to alleviate AIS-induced BBB damage. In this review, we first introduce the roles of glia cells, pericytes, and crosstalk between glial cells in the damage and protection of BBB after AIS, emphasizing the polarization, inflammatory response and crosstalk between microglia, astrocytes, and other glia cells. We then describe the role of glial cell-derived exosomes in the damage and protection of BBB after AIS. Next, we specifically discuss the crosstalk between glial cells and immune cells after AIS. Finally, we propose that glial cells could be a potential target for alleviating BBB damage after AIS and we discuss some molecular targets and potential strategies to alleviate BBB damage by regulating glial cells after AIS.

Immune Thrombosis: Exploring the Significance of Immune Complexes and NETosis

Neutrophil extracellular traps (NETs) are major contributors to inflammation and autoimmunity, playing a key role in the development of thrombotic disorders. NETs, composed of DNA, histones, and numerous other proteins serve as scaffolds for thrombus formation and promote platelet activation, coagulation, and endothelial dysfunction. Accumulating evidence indicates that NETs mediate thrombosis in autoimmune diseases, viral and bacterial infections, cancer, and cardiovascular disease. This article reviews the role and mechanisms of immune complexes in NETs formation and their contribution to the generation of a prothrombotic state. Immune complexes are formed by interactions between antigens and antibodies and can induce NETosis by the direct activation of neutrophils via Fc receptors, via platelet activation, and through endothelial inflammation. We discuss the mechanisms by which NETs induced by immune complexes contribute to immune thrombotic processes and consider the potential development of therapeutic strategies. Targeting immune complexes and NETosis hold promise for mitigating thrombotic events and reducing the burden of immune thrombosis.

Spatial and temporal mapping of neuron-microglia interaction modes in acute ischemic stroke

Ischemic stroke (IS) is a major cause of morbidity and mortality worldwide, accounting for 75-80% of all strokes. Under conditions of ischemia and hypoxia, neurons suffer damage or death, leading to a series of secondary immune reactions. Microglia, the earliest activated immune cells, can exert neurotoxic or neuroprotective effects on neurons through secretion of factors. There exists a complex interaction between neurons and microglia during this process. Moreover, the interaction between them becomes even more complex due to differences in the infarct area and reperfusion time. This review first elaborates on the differences in neuronal death modes between the ischemic core and penumbra, and then introduces the differences in microglial markers across different infarct areas with varying reperfusion time, indicating distinct functions. Finally, we focus on exploring the interaction modes between neurons and microglia in order to precisely target beneficial interactions and inhibit harmful ones, thus providing new therapeutic strategies for the treatment of IS.

NETosis in Acute Thrombotic Disorders

The release of extracellular traps by neutrophils (NETs) represents a novel active mechanism of cell death that has been recently implicated in the pathogenesis of thrombotic disorders. The aim of this study was to investigate the generation of NETs in different groups of patients with acute thrombotic events (ATEs) and to establish whether NETs markers can predict the risk of new cardiovascular events. We performed a case-control study of patients with ATE, including acute coronary syndrome (n = 60), cerebrovascular accident (n = 50), and venous thromboembolism (n = 55). Control subjects (n = 70) were identified among patients admitted for acute chest pain and in which a diagnosis of ATE was excluded. Serum levels of NET markers and neutrophil activation, such as myeloperoxidase (MPO)-DNA complexes, neutrophil gelatinase-associated lipocalin, polymorphonuclear neutrophil elastase, lactoferrin, and MPO, were measured in each patient. We found that circulating levels of MPO-DNA complexes were significantly increased in patients with ATE (p < 0.001) compared with controls and that this association remained significant even after fully adjustment for traditional risk factors (p = 0.001). A receiver operating characteristics analysis of circulating MPO-DNA complexes in discriminating between controls and patients with ATE showed a significant area under the curve of 0.76 (95% confidence interval: 0.69-0.82). After a median follow-up of 40.7 (± 13.8) months, 24 out of the 165 patients with ATE presented a new cardiovascular event and 18 patients died. None of the markers under investigation influenced survival or the incidence of new cardiovascular events. In conclusion, we found that increase of markers of NETosis can be observed in acute thrombotic conditions, occurring both on the arterial and venous site. Nevertheless, the level of neutrophil markers measured during the ATE is not predictive of future risk of mortality and cardiovascular events.

Alexander M, A. Campbell R, Grandhi R. Endovascular mechanical thrombectomy in a child with COVID-19: Clot analysis reveals a novel pathway in the neuroinflammatory cascade resulting in large-vessel occlusion

Large-vessel occlusion is rare in children, but its results can be devastating and may lead to recurrent strokes, persistent neurological deficits, and decreased quality of life. Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has yielded extrapulmonary effects and multiorgan diseases, many of which are neurological manifestations. There is a paucity of literature in pediatric patients about large-vessel occlusion in the setting of COVID-19 infection. We discuss a nine-year-old child who presented with a left middle cerebral artery occlusion and underwent revascularization with a Thrombolysis in Cerebral Infarction grade 3 reperfusion approximately three weeks after COVID-19 diagnosis. The patient harbored concerning signs and symptoms of multisystem inflammatory syndrome in children. This case emphasizes the importance of recognizing SARS-CoV-2 and the propensity for thrombosis in a delayed fashion, which can lead to severe stroke in young people.

The thrombus proteome in stroke reveals a key role of the innate immune system and new insights associated with its etiology, severity, and prognosis

BACKGROUND

Nowadays little is known about the molecular profile of the occluding thrombus of patients with ischemic stroke.

OBJECTIVES

To analyze the proteomic profile of thrombi in patients who experienced an ischemic stroke in order to gain insights into disease pathogenesis.

METHODS

Thrombi from an exploratory cohort of patients who experienced a stroke were obtained by thrombectomy and analyzed by sequential window acquisition of all theoretical spectra-mass spectrometry. Unsupervised k-means clustering analysis was performed to stratify patients who experienced a stroke. The proteomic profile was associated with both the neurological function (National Institute of Health Stroke Scale [NIHSS]) and the cerebral involvement (Alberta Stroke Program Early CT Score [ASPECTS]) prior to thrombectomy and the clinical status of patients at 3 months using the modified Rankin Scale. In an independent cohort of 210 patients who experienced a stroke, the potential role of neutrophils in stroke severity was interrogated.

RESULTS

Proteomic analysis identified 580 proteins in thrombi, which were stratified into 4 groups: hemostasis, proteasome and neurological diseases, structural proteins, and innate immune system and neutrophils. The thrombus proteome identified 3 clusters of patients with distinctive severity, prognosis, and etiology of the stroke. A protein signature clearly distinguished atherothrombotic and cardioembolic strokes. Several proteins were significantly correlated with the severity of the stroke (NIHSS and ASPECTS). Functional proteomic analysis highlighted the prominent role of neutrophils in stroke severity. This was in line with the association of neutrophil activation markers and count with NIHSS, ASPECTS, and the modified Rankin Scale score 90 days after the event.

CONCLUSION

The use of sequential window acquisition of all theoretical spectra-mass spectrometry in thrombi from patients who experienced an ischemic stroke has provided new insights into pathways and players involved in its etiology, severity, and prognosis. The prominent role of the innate immune system identified might pave the way for the development of new biomarkers and therapeutic approaches in this disease.

Targeting Neutrophil Extracellular Traps for Stroke Prognosis: A Promising Path

Stroke has become the first cause of functional disability and one of the leading causes of mortality worldwide. Therefore, it is of crucial importance to develop accurate biomarkers to assess stroke risk and prognosis. Emerging evidence suggests that neutrophil extracellular trap (NET) levels may serve as a valuable biomarker to predict stroke occurrence and functional outcome. NETs are known to create a procoagulant state by serving as a scaffold for tissue factor (TF) and platelets inducing thrombosis by activating coagulation pathways and endothelium. A literature search was conducted in two databases (MEDLINE and Scopus) to trace all relevant studies published between 1 January 2016 and 31 December 2022, addressing the potential utility of NETs as a stroke biomarker. Only full-text articles in English were included. The current review includes thirty-three papers. Elevated NET levels in plasma and thrombi seem to be associated with increased mortality and worse functional outcomes in stroke, with all acute ischemic stroke, intracerebral hemorrhage, and subarachnoid hemorrhage included. Additionally, higher NET levels seem to correlate with worse outcomes after recanalization therapies and are more frequently found in strokes of cardioembolic or cryptogenic origin. Additionally, total neutrophil count in plasma seems also to correlate with stroke severity. Overall, NETs may be a promising predictive tool to assess stroke severity, functional outcome, and response to recanalization therapies.

Targeting Neutrophil α9 Improves Functional Outcomes After Stroke in Mice With Obesity-Induced Hyperglycemia

BACKGROUND

Obesity-induced hyperglycemia is a significant risk factor for stroke. Integrin α9β1 is expressed on neutrophils and stabilizes adhesion to the endothelium via ligands, including Fn-EDA (fibronectin containing extra domain A) and tenascin C. Although myeloid deletion of α9 reduces susceptibility to ischemic stroke, it is unclear whether this is mediated by neutrophil-derived α9. We determined the role of neutrophil-specific α9 in stroke outcomes in a mice model with obesity-induced hyperglycemia.

METHODS

α9Neu-KO (α9fl/flMRP8Cre+) and littermate control α9WT (α9fl/flMRP8Cre-) mice were fed on a 60% high-fat diet for 20 weeks to induce obesity-induced hyperglycemia. Functional outcomes were evaluated up to 28 days after stroke onset in mice of both sexes using a transient (30 minutes) middle cerebral artery ischemia. Infarct volume (magnetic resonance imaging) and postreperfusion thrombo-inflammation (thrombi, fibrin, neutrophil, phospho-nuclear factor kappa B [p-NFκB], TNF [tumor necrosis factor]-α, and IL [interleukin]-1β levels, markers of neutrophil extracellular traps) were measured post 6 or 48 hours of reperfusion. In addition, functional outcomes (modified Neurological Severity Score, rota-rod, corner, and wire-hanging test) were measured for up to 4 weeks.

RESULTS

Stroke upregulated neutrophil α9 expression more in obese mice (P<0.05 versus lean mice). Irrespective of sex, deletion of neutrophil α9 improved functional outcomes up to 4 weeks, concomitant with reduced infarct, improved cerebral blood flow, decreased postreperfusion thrombo-inflammation, and neutrophil extracellular traps formation (NETosis) (P<0.05 versus α9WT obese mice). Obese α9Neu-KO mice were less susceptible to thrombosis in FeCl3 injury-induced carotid thrombosis model. Mechanistically, we found that α9/cellular fibronectin axis contributes to NETosis via ERK (extracellular signal-regulated kinase) and PAD4 (peptidyl arginine deiminase 4), and neutrophil α9 worsens stroke outcomes via cellular fibronectin-EDA but not tenascin C. Obese wild-type mice infused with anti-integrin α9 exhibited improved functional outcomes up to 4 weeks (P<0.05 versus vehicle).

CONCLUSIONS

Genetic ablation of neutrophil-specific α9 or pharmacological inhibition improves long-term functional outcomes after stroke in mice with obesity-induced hyperglycemia, most likely by limiting thrombo-inflammation.

Endothelial Damage, Neutrophil Extracellular Traps and Platelet Activation in COVID-19 vs. Community-Acquired Pneumonia: A Case-Control Study

COVID-19 has been a diagnostic and therapeutic challenge. It has marked a paradigm shift when considering other types of pneumonia etiology. We analyzed the biomarkers related to endothelial damage and immunothrombosis in COVID-19 in comparison to community-acquired pneumonia (CAP) through a case-control study of 358 patients with pneumonia (179 hospitalized with COVID-19 vs. 179 matched hospitalized with CAP). Endothelial damage markers (endothelin and proadrenomedullin), neutrophil extracellular traps (NETs) (citrullinated-3 histone, cell-free DNA), and platelet activation (soluble P-selectin) were measured. In-hospital and 1-year follow-up outcomes were evaluated. Endothelial damage, platelet activation, and NET biomarkers are significantly higher in CAP compared to COVID-19. In-hospital mortality in COVID-19 was higher compared to CAP whereas 1-year mortality and cardiovascular complications were higher in CAP. In the univariate analysis (OR 95% CIs), proADM and endothelin were associated with in-hospital mortality (proADM: CAP 3.210 [1.698-6.070], COVID-19 8.977 [3.413-23.609]; endothelin: CAP 1.014 [1.006-1.022], COVID-19 1.024 [1.014-1.034]), in-hospital CVE (proADM: CAP 1.623 [1.080-2.439], COVID-19 2.146 [1.186-3.882]; endothelin: CAP 1.005 [1.000-1.010], COVID-19 1.010 [1.003-1.018]), and 1-year mortality (proADM: CAP 2.590 [1.644-4.080], COVID-19 13.562 [4.872-37.751]; endothelin: CAP 1.008 [1.003-1.013], COVID-19 1.026 [1.016-1.037]). In conclusion, COVID-19 and CAP showed different expressions of endothelial damage and NETs. ProADM and endothelin are associated with short- and long-term mortality.

Association between Citrullinated Histone H3 and White Matter Lesions Burden in Patients with Ischemic Stroke

INTRODUCTION

Neutrophil extracellular traps play a role in the pathophysiology of stroke and are associated with severity and mortality. We aimed to investigate whether the citrullinated histone H3 (CitH3), a biomarker for neutrophil extracellular traps formation, is associated with the white matter lesion (WML) burden in ischemic stroke patients.

METHODS

Between September 2021 and April 2022, 322 patients were enrolled in this prospective observational cohort study. Serum CitH3 levels were measured after admission using an enzyme-linked immunosorbent assay. WMLs severity was graded according to the Fazekas scale and conceptually defined as mild (total Fazekas score 0-2) and severe (total Fazekas score 3-6). We used multivariable regression models to determine the relationship between CitH3 concentrations and the severity of WMLs burden.

RESULTS

One-hundred and forty-eight (46.0%) patients were diagnosed with severe WMLs burden after admission. Increased CitH3 levels (first quartile vs. fourth quartile of H3Cit, odds ratio, 3.311, 95% confidence interval, 1.336-8.027; p = 0.011) were independently associated with a greater WML burden in the fully adjusted multivariable model. Similar results were found when the H3Cit was analyzed as a continuous variable. Furthermore, the multiple-adjusted spline regression model showed a linear association between H3Cit levels and severe WMLs (P = 0.001 for linearity).

CONCLUSIONS

In the present study, increased CitH3 levels were positively associated with extensive WMLs in ischemic stroke patients, indicating a role of neutrophil extracellular traps formation in the pathogenesis of WMLs.

The role of circulating cell-free DNA as an inflammatory mediator after stroke

Stroke is the second leading cause of death worldwide and a leading cause of disability. Clinical and experimental studies highlighted the complex role of the immune system in the pathophysiology of stroke. Ischemic brain injury leads to the release of cell-free DNA, a damage-associated molecular pattern, which binds to pattern recognition receptors on immune cells such as toll-like receptors and cytosolic inflammasome sensors. The downstream signaling cascade then induces a rapid inflammatory response. In this review, we are highlighting the characteristics of cell-free DNA and how these can affect a local as well as a systemic response after stroke. For this purpose, we screened literature on clinical studies investigating cell-free DNA concentration and properties after brain ischemia. We report the current understanding for mechanisms of DNA uptake and sensing in the context of post-stroke inflammation. Moreover, we compare possible treatment options targeting cell-free DNA, DNA-sensing pathways, and the downstream mediators. Finally, we describe clinical implications of this inflammatory pathway for stroke patients, open questions, and potential future research directions.

Coagulation biomarkers for ischemic stroke

A State of the Art lecture titled "coagulation biomarkers for ischemic stroke" was presented at the International Society on Thrombosis and Haemostasis (ISTH) Congress in 2022. Ischemic stroke (IS) is a common disease with major morbidity and mortality. It is a challenge to determine which patients are at risk for IS or have poor clinical outcome after IS. An imbalance of coagulation markers may contribute to the progression and prognosis of IS. Therefore, we now discuss studies on the association of selected coagulation biomarkers from the hemostasis, inflammation, and immunothrombosis systems with the risk of IS, stroke severity at the acute phase, and clinical outcome after treatment. We report on coagulation biomarker-induced risk of IS, stroke severity, and outcomes following IS derived from prospective population studies, case-control studies, and acute-phase IS studies. We found indications that many coagulation and inflammation biomarkers are associated with IS, but it is early to conclude that any of these biomarkers can be applied in a therapeutic setting to predict patients at risk of IS, stroke severity at the acute phase, and clinical outcome after treatment. The strongest evidence for a role in IS was found for beta-thromboglobulin, von Willebrand factor, factor VIII, fibrinogen, thrombin-activatable fibrinolysis inhibitor, D-dimer, and neutrophil extracellular traps, and therefore, they are promising candidates. Further research and validation in large-size populations using well-defined study designs are warranted. Finally, we provide a selection of recent data relevant to this subject that was presented at the 2022 ISTH Congress.

Sex differences in the inflammatory response to stroke

Ischemic stroke is a leading cause of morbidity and mortality and disproportionally affects women, in part due to their higher longevity. Older women have poorer outcomes after stroke with high rates of cognitive deficits, depression, and reduced quality of life. Post-stroke inflammatory responses are also sexually dimorphic and drive differences in infarct size and recovery. Factors that influence sex-specific immune responses can be both intrinsic and extrinsic. Differences in gonadal hormone exposure, sex chromosome compliment, and environmental/social factors can drive changes in transcriptional and metabolic profiles. In addition, how these variables interact, changes across the lifespan. After the onset of ischemic injury, necrosis and apoptosis occur, which activate microglia and other glial cells within the central nervous system, promoting the release of cytokines and chemokines and neuroinflammation. Cells involved in innate and adaptive immune responses also have dual functions after stroke as they can enhance inflammation acutely, but also contribute to suppression of the inflammatory cascade and later repair. In this review, we provide an overview of the current literature on sex-specific inflammatory responses to ischemic stroke. Understanding these differences is critical to identifying therapeutic options for both men and women.

NETs-Induced Thrombosis Impacts on Cardiovascular and Chronic Kidney Disease

Arterial and venous thrombosis constitute a major source of morbidity and mortality worldwide. Association between thrombotic complications and cardiovascular and other chronic inflammatory diseases are well described. Inflammation and subsequent initiation of thrombotic events, termed immunothrombosis, also receive growing attention but are still incompletely understood. Nevertheless, the clinical relevance of aberrant immunothrombosis, referred to as thromboinflammation, is evident by an increased risk of thrombosis and cardiovascular events in patients with inflammatory or infectious diseases. Proinflammatory mediators released from platelets, complement activation, and the formation of NETs (neutrophil extracellular traps) initiate and foster immunothrombosis. In this review, we highlight and discuss prominent and emerging interrelationships and functions between NETs and other mediators in immunothrombosis in cardiovascular disease. Also, with patients with chronic kidney disease suffering from increased cardiovascular and thrombotic risk, we summarize current knowledge on neutrophil phenotype, function, and NET formation in chronic kidney disease. In addition, we elaborate on therapeutic targeting of NETs-induced immunothrombosis. A better understanding of the functional relevance of antithrombotic mediators which do not increase bleeding risk may provide opportunities for successful therapeutic interventions to reduce thrombotic risk beyond current treatment options.