Role of HMGB1 in the Interplay between NETosis and Thrombosis in Ischemic Stroke: A Review

Nets in fibrosis: Bridging innate immunity and tissue remodeling

Fibrosis, a complex pathological process characterized by excessive deposition of extracellular matrix components, leads to tissue scarring and dysfunction. Emerging evidence suggests that neutrophil extracellular traps (NETs), composed of DNA, histones, and antimicrobial proteins, significantly contribute to fibrotic diseases pathogenesis. This review summarizes the process of NETs production, molecular mechanisms, and related diseases, and outlines the cellular and molecular mechanisms associated with fibrosis. Subsequently, this review comprehensively summarizes the current understanding of the intricate interplay between NETs and fibrosis across various organs, including the lung, liver, kidney, skin, and heart. The mechanisms by which NETs contribute to fibrogenesis, including their ability to promote inflammation, induce epithelial-mesenchymal transition (EMT), activate fibroblasts, deposit extracellular matrix (ECM) components, and trigger TLR4 signaling were explored. This review aimed to provide insights into the complex relationship between NETs and fibrosis via a comprehensive analysis of existing reports, offering novel perspectives for future research and therapeutic interventions.

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.

The synergistic effect of Huangqi Gegen decoction on thrombosis relates to the astragalus polysaccharide-improved oral delivery of puerarin

ETHNO-PHARMACOLOGICAL RELEVANCE

Huangqi Gegen decoction (HGD), which comprises Astragali Radix (AR) and Puerariae Radix (PR), is widely used to treat thrombosis in China. However, the mechanism underlying its synergistic effect in thrombosis treatment remains unclear.

AIM OF THE STUDY

Following PR administration, low plasma exposure was reported for its primary ingredients. In this regard, this study examined the effect of AR on PR's antithrombotic efficacy with respect to the impact of Astragalus Polysaccharide (APS) on the oral delivery of Puerarin (PUE).

MATERIALS AND METHODS

To evaluate the synergistic effect of HGD, a thrombus mice model was established via intraperitoneal injection of carrageenan. After treatment, histopathological observations were made, and the proportion of thrombus length in the tail, as well as the plasma APTT, PT, INR, and FIB levels, were detected. Molecular docking was employed to assess the PR ingredients that could inhibit the HMGB1/NF-κB/NLRP3 pathway. The Pharmacokinetics of PR ingredients in rats were also compared between the PR and HGD groups. Moreover, the effect of APS on the solubility, intestinal absorption, and pharmacokinetics of PUE was evaluated. Furthermore, the impact of APS on the antithrombotic efficacy of PUE was assessed.

RESULTS

In mice, AR enhanced the antithrombotic effect of PR. This improved PR effect was associated with isoflavones-induced downregulation of the HMGB1/NF-κB/NLRP3 pathway. The synergistic effect resulting from the compatibility of HGD components was primarily achieved by improving the plasma exposure of PR isoflavones. Specifically, APS enhanced PUE's water solubility through the formation of self-assembly Nanoparticles, increasing its intestinal absorption and oral bioavailability, which, in turn, suppressed the HMGB1/NF-κB/NLRP3 pathway, thus improving its antithrombotic effect.

CONCLUSIONS

Our findings revealed that APS improved PUE's plasma exposure, enhancing its inhibitory effect on the HMGB1/NF-κB/NLRP3 pathway. This mechanism presents a key aspect of the synergistic effect of HGD compatibility in thrombosis treatment.

HMGB1/TLR4 axis promotes pyroptosis after ICH by activating the NLRP3 inflammasome

BACKGROUND

We previously reported that the HMGB1/TLR4 axis promoted inflammation during the acute phase of intracerebral hemorrhage. Given that this phase is known to involve neuronal pyroptosis and neuroinflammation, here we explore whether HMGB1/TLR signaling activate inflammasome and pyroptosis after intracerebral hemorrhage.

METHODS

Autologous blood was injected into Sprague-Dawley rats to induce intracerebral hemorrhage. Neurological deficits were assessed using a modified neurological severity score. These expression and localization of NLRP1 and NLRP3 inflammasomes, as well as the levels of pyroptosis and pyroptosis-associated proteins were assessed using Western blot or immunocytochemistry. These experiments were repeated in animals that received treatment with short interfering RNAs against NLRP1 or NLRP3, with HMGB1 inhibitor ethyl pyruvate or TLR4 inhibitor TAK-242.

RESULTS

Intracerebral hemorrhage upregulated NLRP1 and NLRP3 in the ipsilateral striatum and increased the proportions of these cells that were pyroptosis-positive. Additionally, the levels of caspase protein family (e.g., pro-caspase-1 and caspase-1), apoptosis-associated speck-like protein (ASC), pro-interleukin-1β (IL-1β), and IL-1β were also elevated. These effects on pyroptosis and associated neurological deficit, were partially reversed by knockdown of NLRP1 or NLRP3, or by inhibition of HMGB1 or TLR4. Inhibition of HMGB1 or TLR4 resulted in the downregulation NLRP3 but not NLRP1.

CONCLUSIONS

The HMGB1/TLR4 signaling may activate the NLRP3 inflammasome during the acute phase of intracerebral hemorrhage, resulting in the inflammatory process known as pyroptosis. These insights suggest potential therapeutic targets for the mitigation tissue injury and associated neurological deficits following hemorrhagic stroke.

Neuroinflammation in Alzheimer's disease: insights from peripheral immune cells

Alzheimer's disease (AD) is a serious brain disorder characterized by the presence of beta-amyloid plaques, tau pathology, inflammation, neurodegeneration, and cerebrovascular dysfunction. The presence of chronic neuroinflammation, breaches in the blood-brain barrier (BBB), and increased levels of inflammatory mediators are central to the pathogenesis of AD. These factors promote the penetration of immune cells into the brain, potentially exacerbating clinical symptoms and neuronal death in AD patients. While microglia, the resident immune cells of the central nervous system (CNS), play a crucial role in AD, recent evidence suggests the infiltration of cerebral vessels and parenchyma by peripheral immune cells, including neutrophils, T lymphocytes, B lymphocytes, NK cells, and monocytes in AD. These cells participate in the regulation of immunity and inflammation, which is expected to play a huge role in future immunotherapy. Given the crucial role of peripheral immune cells in AD, this article seeks to offer a comprehensive overview of their contributions to neuroinflammation in the disease. Understanding the role of these cells in the neuroinflammatory response is vital for developing new diagnostic markers and therapeutic targets to enhance the diagnosis and treatment of AD patients.

HMGB1: A New Target for Ischemic Stroke and Hemorrhagic Transformation

Stroke in China is distinguished by its high rates of morbidity, recurrence, disability, and mortality. The ultra-early administration of rtPA is essential for restoring perfusion in acute ischemic stroke, though it concurrently elevates the risk of hemorrhagic transformation. High-mobility group box 1 (HMGB1) emerges as a pivotal player in neuroinflammation after brain ischemia and ischemia-reperfusion. Released passively by necrotic cells and actively secreted, including direct secretion of HMGB1 into the extracellular space and packaging of HMGB1 into intracellular vesicles by immune cells, glial cells, platelets, and endothelial cells, HMGB1 represents a prototypical damage-associated molecular pattern (DAMP). It is intricately involved in the pathogenesis of atherosclerosis, thromboembolism, and detrimental inflammation during the early phases of ischemic stroke. Moreover, HMGB1 significantly contributes to neurovascular remodeling and functional recovery in later stages. Significantly, HMGB1 mediates hemorrhagic transformation by facilitating neuroinflammation, directly compromising the integrity of the blood-brain barrier, and enhancing MMP9 secretion through its interaction with rtPA. As a systemic inflammatory factor, HMGB1 is also implicated in post-stroke depression and an elevated risk of stroke-associated pneumonia. The role of HMGB1 extends to influencing the pathogenesis of ischemia by polarizing various subtypes of immune and glial cells. This includes mediating excitotoxicity due to excitatory amino acids, autophagy, MMP9 release, NET formation, and autocrine trophic pathways. Given its multifaceted role, HMGB1 is recognized as a crucial therapeutic target and prognostic marker for ischemic stroke and hemorrhagic transformation. In this review, we summarize the structure and redox properties, secretion and pathways, regulation of immune cell activity, the role of pathophysiological mechanisms in stroke, and hemorrhage transformation for HMGB1, which will pave the way for developing new neuroprotective drugs, reduction of post-stroke neuroinflammation, and expansion of thrombolysis time window.

The potential therapeutic effect of phosphodiesterase 5 inhibitors in the acute ischemic stroke (AIS)

Acute ischemic stroke (AIS) is a focal neurological disorder that accounts for 85% of all stroke types, due to occlusion of cerebral arteries by thrombosis and emboli. AIS is also developed due to cerebral hemodynamic abnormality. AIS is associated with the development of neuroinflammation which increases the severity of AIS. Phosphodiesterase enzyme (PDEs) inhibitors have neuro-restorative and neuroprotective effects against the development of AIS through modulation of the cerebral cyclic adenosine monophosphate (cAMP)/cyclic guanosine monophosphate (cGMP)/nitric oxide (NO) pathway. PDE5 inhibitors through mitigation of neuroinflammation may decrease the risk of long-term AIS-induced complications. PDE5 inhibitors may affect the hemodynamic properties and coagulation pathway which are associated with thrombotic complications in AIS. PDE5 inhibitors reduce activation of the pro-coagulant pathway and improve the microcirculatory level in patients with hemodynamic disturbances in AIS. PDE5 inhibitors mainly tadalafil and sildenafil improve clinical outcomes in AIS patients through the regulation of cerebral perfusion and cerebral blood flow (CBF). PDE5 inhibitors reduced thrombomodulin, P-selectin, and tissue plasminogen activator. Herein, PDE5 inhibitors may reduce activation of the pro-coagulant pathway and improve the microcirculatory level in patients with hemodynamic disturbances in AIS. In conclusion, PDE5 inhibitors may have potential roles in the management of AIS through modulation of CBF, cAMP/cGMP/NO pathway, neuroinflammation, and inflammatory signaling pathways. Preclinical and clinical studies are recommended in this regard.

Targeting Neutrophil Extracellular Traps in Gouty Arthritis: Insights into Pathogenesis and Therapeutic Potential

Gouty arthritis (GA) is an immune-mediated disorder characterized by severe inflammation due to the deposition of monosodium urate (MSU) crystals in the joints. The pathophysiological mechanisms of GA are not yet fully understood, and therefore, the identification of effective therapeutic targets is of paramount importance. Neutrophil extracellular traps (NETs), an intricate structure of DNA scaffold, encompassing myeloperoxidase, histones, and elastases - have gained significant attention as a prospective therapeutic target for gouty arthritis, due to their innate antimicrobial and immunomodulatory properties. Hence, exploring the therapeutic potential of NETs in gouty arthritis remains an enticing avenue for further investigation. During the process of gouty arthritis, the formation of NETs triggers the release of inflammatory cytokines, thereby contributing to the inflammatory response, while MSU crystals and cytokines are sequestered and degraded by the aggregation of NETs. Here, we provide a concise summary of the inflammatory processes underlying the initiation and resolution of gouty arthritis mediated by NETs. Furthermore, this review presents an overview of the current pharmacological approaches for treating gouty arthritis and summarizes the potential of natural and synthetic product-based inhibitors that target NET formation as novel therapeutic options, alongside elucidating the intrinsic challenges of these inhibitors in NETs research. Lastly, the limitations of HL-60 cell as a suitable substitute of neutrophils in NETs research are summarized and discussed. Series of recommendations are provided, strategically oriented towards guiding future investigations to effectively address these concerns. These findings will contribute to an enhanced comprehension of the interplay between NETs and GA, facilitating the proposition of innovative therapeutic strategies and novel approaches for the management of GA.

The immunologic phenotype of thrombi is associated with future vascular events after cerebral infarction

BACKGROUND

Thrombi retrieved from patients with acute ischemic stroke may contain prognostic information.

OBJECTIVE

To investigate the relationship between the immunologic phenotype of thrombi and future vascular events in patients with a stroke.

METHODS

This study included patients with acute ischemic stroke who underwent endovascular thrombectomy at Chung-Ang University Hospital in Seoul, Korea, between February 2017 and January 2020. Laboratory and histological variables were compared between patients with and without recurrent vascular events (RVEs). Kaplan-Meier analysis followed by the Cox proportional hazards model was used to identify factors related to RVE. Receiver operating characteristic (ROC) analysis was conducted to evaluate the performance of the immunologic score by combining immunohistochemical phenotypes to predict RVE.

RESULTS

A total of 46 patients were included in the study with 13 RVEs (mean±SD age, 72.8±11.3 years; 26 (56.5%) men). Thrombi with a lower percentage of programmed death ligand-1 expression (HR=11.64; 95% CI 1.60 to 84.82) and a higher number of citrullinated histone H3 positive cells (HR=4.19; 95% CI 0.81 to 21.75) were associated with RVE. The presence of high-mobility group box 1 positive cell was associated with reduced risk of RVE, but the association was lost after adjustment for stroke severity. The immunologic score, which consists of the three immunohistochemical phenotypes, showed good performance in predicting RVE (area under the ROC curve, 0.858; 95% CI 0.758 to 0.958).

CONCLUSIONS

The immunological phenotype of thrombi could provide prognostic information after stroke.

Effects of Jatrorrhizine on inflammatory response induced by H2O2 in microglia by regulating the MAPK/NF-κB/NLRP3 signaling pathway

Microglia-induced neuroinflammation is a contributing factor to neurodegenerative diseases. Jatrorrhizine (JAT), an alkaloid isolated from Huanglian, has been shown to have neuroprotective effects against various neurodegenerative diseases, but its impact on microglia-induced neuroinflammation remains unclear. In this study, we investigated the role of JAT in MAPK/NF-κB/NLRP3 signaling pathway in an H2O2-induced oxidative stress model using microglia (N9 cells). We divided cells into six groups, including control, JAT, H2O2, H2O2 + 5 μmol/L JAT, H2O2 + 10 μmol/L JAT, and H2O2 + 20 μmol/L minocycline groups. Cell viability was measured using MTT assay and TNF-α levels were detected with an ELISA Kit. Western blot was used to detect NLRP3, HMGB1, NF-κB, p-NF-κB, ERK, p-ERK, p38, p-p38, p-JNK, JNK, IL-1β, and IL-18 expressions. Our results showed that JAT intervention improved H2O2-induced cytotoxicity in N9 cells and reduced the elevated expression of TNF-α, IL-1β, IL-18, p-ERK/ERK, p-p38/p38, p-JNK/JNK, p-p65/p65, NLRP3, and HMGB1 in H2O2 group. Furthermore, treatment with ERK inhibitor SCH772984 specifically blocked ERK phosphorylation, resulting in decreased protein levels of p-NF-κB, NLRP3, IL-1β, and IL-18 in H2O2 group. These results suggest that the MAPK/NF-κB signaling pathway may regulate the protein levels of NLRP3. Overall, our study indicates that JAT may have a protective effect on H2O2-treated microglia via inhibition the MAPK/NF-κB/NLRP3 pathway and could be a potential therapeutic approach for neurodegenerative diseases.

Neutrophil extracellular traps mediate deep vein thrombosis: from mechanism to therapy

Deep venous thrombosis (DVT) is a part of venous thromboembolism (VTE) that clinically manifests as swelling and pain in the lower limbs. The most serious clinical complication of DVT is pulmonary embolism (PE), which has a high mortality rate. To date, its underlying mechanisms are not fully understood, and patients usually present with clinical symptoms only after the formation of the thrombus. Thus, it is essential to understand the underlying mechanisms of deep vein thrombosis for an early diagnosis and treatment of DVT. In recent years, many studies have concluded that Neutrophil Extracellular Traps (NETs) are closely associated with DVT. These are released by neutrophils and, in addition to trapping pathogens, can mediate the formation of deep vein thrombi, thereby blocking blood vessels and leading to the development of disease. Therefore, this paper describes the occurrence and development of NETs and discusses the mechanism of action of NETs on deep vein thrombosis. It aims to provide a direction for improved diagnosis and treatment of deep vein thrombosis in the near future.

QHRD106 ameliorates ischemic stroke injury as a long-acting tissue kallikrein preparation

Ischemic stroke is the second leading cause of death worldwide, and there are limited effective treatment strategies. QHRD106, a polyethyleneglycol (PEG)-modified long-acting tissue kallikrein preparation, has not been reported previously. In this study, we aimed to investigate the therapeutic effect of QHRD106 in ischemic stroke and its possible mechanism. We found that QHRD106 treatment alleviated brain injury after stroke via bradykinin (BK) receptor B2 (B2R) instead of BK receptor B1 (B1R). Mechanistically, QHRD106 reduced high-mobility group box 1 (HMGB1)-induced apoptosis and inflammation after ischemic stroke in vivo and in vitro. Moreover, we confirmed that QHRD106 reduced the level of acetylated HMGB1 and reduced the binding between heat shock protein 90 alpha family class A member 1 (HSP90AA1) and HMGB1, thus inhibiting the translocation and release of HMGB1. In summary, these findings indicate that QHRD106 treatment has therapeutic potential for cerebral ischemic stroke.

Different Ways to Die: Cell Death Pathways and Their Association With Spinal Cord Injury

Cell death is a systematic/nonsystematic process of cessation of normal morphology and functional properties of the cell to replace and recycle old cells with new also promoting inflammation in some cases. It is a complicated process comprising multiple pathways. Some are well-explored, and others have just begun to be. The research on appropriate control of cell death pathways after acute and chronic damage of neuronal cells is being widely researched today due to the lack of regeneration and recovering potential of a neuronal cell after sustaining damage and the inability to control the direction of neuronal growth. In the progression and onset of various neurological diseases, impairments in programmed cell death signaling processes, like necroptosis, apoptosis, ferroptosis, pyroptosis, and pathways directly or indirectly linked, like autophagy as in nonprogrammed necrosis, are observed. Spinal cord injury (SCI) involves the temporary or permanent disruption of motor activities due to the death of a neuronal and glial cell in the spinal cord accompanied by axonal degeneration. Recent years have seen a significant increase in research on the intricate biochemical interactions that occur after a SCI. Different cell death pathways may significantly impact the subsequent damage processes that lead to the eventual neurological deficiency after an injury to the spinal cord. A better knowledge of the molecular basis of the involved cell death pathways might help enhance neuronal and glial survival and neurological deficits, promoting a curative path for SCI.

Inflammatory microRNAs in cardiovascular pathology: another brick in the wall

The regulatory role of microRNAs (miRNAs) is mainly mediated by their effect on protein expression and is recognized in a multitude of pathophysiological processes. In recent decades, accumulating evidence has interest in these factors as modulatory elements of cardiovascular pathophysiology. Furthermore, additional biological processes have been identified as new components of cardiovascular disease etiology. In particular, inflammation is now considered an important cardiovascular risk factor. Thus, in the present review, we will focus on the role of a subset of miRNAs called inflamma-miRs that may regulate inflammatory status in the development of cardiovascular pathology. According to published data, the most representative candidates that play functional roles in thromboinflammation are miR-21, miR-33, miR-34a, miR-146a, miR-155, and miR-223. We will describe the functions of these miRNAs in several cardiovascular pathologies in depth, with specific emphasis on the molecular mechanisms related to atherogenesis. We will also discuss the latest findings on the role of miRNAs as regulators of neutrophil extracellular traps and their impact on cardiovascular diseases. Overall, the data suggest that the use of miRNAs as therapeutic tools or biomarkers may improve the diagnosis or prognosis of adverse cardiovascular events in inflammatory diseases. Thus, targeting or increasing the levels of adequate inflamma-miRs at different stages of disease could help mitigate or avoid the development of cardiovascular morbidities.

Crosstalk between oxidative stress and neutrophil response in early ischemic stroke: a comprehensive transcriptome analysis

Background

Ischemic stroke (IS) is the second leading cause of mortality worldwide, continuing to be a serious health concern. It is well known that oxidative stress and neutrophil response play vital roles in the pathophysiology of early IS. However, the complex interactions and critical genes associated with them have not been fully understood.

Methods

Two datasets (GSE37587 and GSE16561) from the Gene Expression Omnibus database were extracted and integrated as the discovery dataset. Subsequent GSVA and WGCNA approaches were used to investigate IS-specific oxidative stress-related genes (ISOSGS). Then, we explored IS-specific neutrophil-associated genes (ISNGS) using CIBERSORT analysis. Next, the protein-protein interaction network was established to ascertain candidate critical genes related with oxidative stress and neutrophil response. Furthermore, these candidate genes were validated using GSE58294 dataset and our clinical samples by RT-qPCR method. Finally, functional annotation, diagnostic capability evaluation and drug-gene interactions were performed by using GSEA analysis, ROC curves and DGIDB database.

Result

In our analysis of discovery dataset, 155 genes were determined as ISOSGS and 559 genes were defined as ISNGS. Afterward, 9 candidate genes were identified through the intersection of ISOSGS and ISNGS, PPI network construction, and filtration by degree algorithm. Then, six real critical genes, including STAT3, MMP9, AQP9, SELL, FPR1, and IRAK3, passed the validation using the GSE58294 dataset and our clinical samples. Further functional annotation analysis indicated these critical genes were associated with neutrophil response, especially neutrophil extracellular trap. Meanwhile, they had a good diagnostic performance. Lastly, 53 potential drugs targeting these genes were predicted by DGIDB database.

Conclusion

We identified 6 critical genes, STAT3, FPR1, AQP9, SELL, MMP9 and IRAK3, related to oxidative stress and neutrophil response in early IS, which may provide new insights into understanding the pathophysiological mechanism of IS. We hope our analysis could help develop novel diagnostic biomarkers and therapeutic strategies for IS.

QiShen YiQi and its components attenuate acute thromboembolic stroke and carotid thrombosis by inhibition of CD62P/PSGL-1-mediated platelet-leukocyte aggregate formation

BACKGROUND

QiShen YiQi (QSYQ) dropping pill, a component-based Chinese medicine consisting of benefiting Qi (YQ) and activating blood (HX) components, has been reported to exert a beneficial effect on cerebral ischemia-induced stroke. However, its efficacy and pharmacological mechanism on acute thromboembolic stroke is not clear.

PURPOSE

This study is to explore the preventative effect and pharmacological mechanism of QSYQ and its YQ/HX components on the formation of platelet-leukocyte aggregation (PLA) in acute thromboembolic stroke.

STUDY DESIGN AND METHODS

In vivo thromboembolic stroke model and FeCl₃-induced carotid arterial occlusion models were used. Immunohistochemistry, Western blot, RT-qPCR, and flow cytometry experiments were performed to reveal the pharmacological mechanisms of QSYQ and its YQ/HX components.

RESULTS

In thromboembolic stroke rats, QSYQ significantly attenuated infarct area, improved neurological recovery, reduced PLA formation, and inhibited P-selection (CD62P)/ P-selectin glycoprotein ligand-1 (PSGL-1) expressions. The YQ component preferentially down-regulated PSGL-1 expression in leukocyte, while the HX component preferentially down-regulated CD62P expression in platelet. In carotid arterial thrombosis mice, QSYQ and its YQ/HX components inhibited thrombus formation, prolonged vessel occlusion time, reduced circulating leukocytes and P-selectin expression. PLA formation and platelet/leukocyte adhesion to endothelial cell were also inhibited by QSYQ and its YQ/HX components in vitro.

CONCLUSION

QSYQ and YQ/HX components attenuated thromboembolic stroke and carotid thrombosis by decreasing PLA formation via inhibiting CD62P/PSGL-1 expressions. This study shed a new light on the prevention of thromboembolic stroke.

The protective role of HMGB1 in affecting the balance between autophagy and pyroptosis to maintain neutrophils homeostasis during β-glucan-induced mice lung inflammation

Fungal contamination is omnipresent, and inhalation of fungi-contaminated organic dust leads to hypersensitivity pneumonitis (HP), in which neutrophils played a pivotal role. Existing studies have suggested that cell homeostasis is crucial for the pathogenesis of the inflammatory disease. Although HMGB1 has been shown to contribute to suppressing HP, there is a lack of studies on its mechanisms, especially the regulation of neutrophil homeostasis. This study aims to investigate how HMGB1 regulates neutrophil function by affecting neutrophil homeostasis, and then affects lung inflammation induced by β-glucan, the exposure marker of fungi. Our results showed that deficient HMGB1 led to neutrophil death by disrupting the balance between autophagy and pyroptosis after β-glucan treatment. And HMGB1 deficiency exacerbated the β-glucan-induced lung inflammation and neutrophil dysfunction both in vivo and in vitro. Furthermore, HMGB1 contributed to remodeling neutrophil function by restricting autophagy and aggravating pyroptosis β-glucan exposure. Our funding suggested that HMGB1 deficiency could break the balance between autophagy and pyroptosis towards pyroptosis to cause neutrophil dysfunction during the exacerbated inflammatory response, which provides insights into the pathogenesis of HP and the potential biological targets for its treatment. DATA AVAILABILITY: The datasets used during the current study are available from the corresponding author on reasonable request.

Application of Nanomaterials in Stem Cell-Based Therapeutics for Cardiac Repair and Regeneration

Cardiovascular disease is a leading cause of disability and death worldwide. Although the survival rate of patients with heart diseases can be improved with contemporary pharmacological treatments and surgical procedures, none of these therapies provide a significant improvement in cardiac repair and regeneration. Stem cell-based therapies are a promising approach for functional recovery of damaged myocardium. However, the available stem cells are difficult to differentiate into cardiomyocytes, which result in the extremely low transplantation efficiency. Nanomaterials are widely used to regulate the myocardial differentiation of stem cells, and play a very important role in cardiac tissue engineering. This study discusses the current status and limitations of stem cells and cell-derived exosomes/micro RNAs based cardiac therapy, describes the cardiac repair mechanism of nanomaterials, summarizes the recent advances in nanomaterials used in cardiac repair and regeneration, and evaluates the advantages and disadvantages of the relevant nanomaterials. Besides discussing the potential clinical applications of nanomaterials in cardiac therapy, the perspectives and challenges of nanomaterials used in stem cell-based cardiac repair and regeneration are also considered. Finally, new research directions in this field are proposed, and future research trends are highlighted.

Coagulation Disorders in Sepsis and COVID-19-Two Sides of the Same Coin? A Review of Inflammation-Coagulation Crosstalk in Bacterial Sepsis and COVID-19

Sepsis is a major cause of morbidity and mortality worldwide. Sepsis-associated coagulation disorders are involved in the pathogenesis of multiorgan failure and lead to a subsequently worsening prognosis. Alongside the global impact of the COVID-19 pandemic, a great number of research papers have focused on SARS-CoV-2 pathogenesis and treatment. Significant progress has been made in this regard and coagulation disturbances were once again found to underlie some of the most serious adverse outcomes of SARS-CoV-2 infection, such as acute lung injury and multiorgan dysfunction. In the attempt of untangling the mechanisms behind COVID-19-associated coagulopathy (CAC), a series of similarities with sepsis-induced coagulopathy (SIC) became apparent. Whether they are, in fact, the same disease has not been established yet. The clinical picture of CAC shows the unique feature of an initial phase of intravascular coagulation confined to the respiratory system. Only later on, patients can develop a clinically significant form of systemic coagulopathy, possibly with a consumptive pattern, but, unlike SIC, it is not a key feature. Deepening our understanding of CAC pathogenesis has to remain a major goal for the research community, in order to design and validate accurate definitions and classification criteria.

Activation of GPR81 aggravated intestinal ischemia/reperfusion injury-induced acute lung injury via HMGB1-mediated neutrophil extracellular traps formation

INTRODUCTION

Intestinal ischemia/reperfusion (II/R) injury is a life-threatening situation accompanied by severe organ injury, especially acute lung injury (ALI). A great body of evidence indicates that II/R injury is usually associated with hyperlactatemia. G-protein-coupled receptor 81 (GPR81), a receptor of lactate, has been recognized as a regulatory factor in inflammation, but whether it was involved in II/R injury-induced ALI is still unknown.

METHODS

To establish the II/R injury model, the superior mesenteric artery of the mice was occluded gently by a microvascular clamp for 45 min to elicit intestinal ischemia and then a 90-min reperfusion was performed. Broncho-alveolar lavage fluid (BALF) and lung tissues were obtained to evaluate the lung injury after II/R. The pulmonary histopathological alteration was evaluated by H&E staining. The concentration of proteins, the number of infiltrated cells, and the level of IL-6 were measured in BALF. The formation of neutrophil extracellular traps (NETs) was evaluated by the level of double-stranded DNA (dsDNA) and myeloperoxidase- double-stranded DNA (MPO-dsDNA) complex in BALF, and the content of citrullinated histone H3 (Cit-H3) in lung tissue. The level of HMGB1 in the BALF and plasma was measured by enzyme linked immunosorbent assay (ELISA).

RESULTS

Administration of the GPR81 agonist 3,5-dihydroxybenzoic acid (DHBA) aggravated II/R injury-induced lung histological abnormalities, upregulated the concentration of proteins, the number of infiltrated cells, and the level of IL-6 in BALF. In addition, DHBA treatment increased the level of dsDNA and MPO-dsDNA complex in BALF, and promoted the elevation of Cit-H3 in lung tissue and the release of HMGB1 in BALF and plasma.

CONCLUSION

After induction of ALI by II/R, the administration of DHBA aggravated ALI through NETs formation in the lung.

NETosis as an oncologic therapeutic target: a mini review

Neutrophil Extracellular Traps (NETs) are a key form of pro-inflammatory cell death of neutrophils characterized by the extrusion of extracellular webs of DNA containing bactericidal killing enzymes. NETosis is heavily implicated as a key driver of host damage in autoimmune diseases where injurious release of proinflammatory enzymes damage surrounding tissue and releases 70 known autoantigens. Recent evidence shows that both neutrophils and NETosis have a role to play in carcinogenesis, both indirectly through triggering DNA damage through inflammation, and directly contributing to a pro-tumorigenic tumor microenvironment. In this mini-review, we summarize the current knowledge of the various mechanisms of interaction and influence between neutrophils, with particular attention to NETosis, and cancer cells. We will also highlight the potential avenues thus far explored where we can intercept these processes, with the aim of identifying promising prospective targets in cancer treatment to be explored in further studies.

Effects of the interactions between platelets with other cells in tumor growth and progression

It has been confirmed that platelets play a key role in tumorigenesis. Tumor-activated platelets can recruit blood cells and immune cells to migrate, establish an inflammatory tumor microenvironment at the sites of primary and metastatic tumors. On the other hand, they can also promote the differentiation of mesenchymal cells, which can accelerate the proliferation, genesis and migration of blood vessels. The role of platelets in tumors has been well studied. However, a growing number of studies suggest that interactions between platelets and immune cells (e.g., dendritic cells, natural killer cells, monocytes, and red blood cells) also play an important role in tumorigenesis and tumor development. In this review, we summarize the major cells that are closely associated with platelets and discuss the essential role of the interaction between platelets with these cells in tumorigenesis and tumor development.

Neutrophil Extracellular Traps in Cerebral Ischemia/Reperfusion Injury: Friend and Foe

Cerebral ischemic injury, one of the leading causes of morbidity and mortality worldwide, triggers various central nervous system (CNS) diseases, including acute ischemic stroke (AIS) and chronic ischemia-induced Alzheimer's disease (AD). Currently, targeted therapies are urgently needed to address neurological disorders caused by cerebral ischemia/reperfusion injury (CI/RI), and the emergence of neutrophil extracellular traps (NETs) may be able to relieve the pressure. Neutrophils are precursors to brain injury following ischemic stroke and exert complicated functions. NETs extracellularly release reticular complexes of neutrophils, i.e., double-stranded DNA (dsDNA), histones, and granulins. Paradoxically, NETs play a dual role, friend and foe, under different conditions, for example, physiological circumstances, infection, neurodegeneration, and ischemia/reperfusion. Increasing evidence indicates that NETs exert anti-inflammatory effects by degrading cytokines and chemokines through protease at a relatively stable and moderate level under physiological conditions, while excessive amounts of NETs release (NETosis) irritated by CI/RI exacerbate the inflammatory response and aggravate thrombosis, disrupt the blood-brain barrier (BBB), and initiates sequential neuron injury and tissue damage. This review provides a comprehensive overview of the machinery of NETs formation and the role of an abnormal cascade of NETs in CI/RI, as well as other ischemia-induced neurological diseases. Herein, we highlight the potential of NETs as a therapeutic target against ischemic stroke that may inspire translational research and innovative clinical approaches.

An intravenous anesthetic drug-propofol, influences the biological characteristics of malignant tumors and reshapes the tumor microenvironment: A narrative literature review

Malignant tumors are the second leading cause of death worldwide. This is a public health concern that negatively impacts human health and poses a threat to the safety of life. Although there are several treatment approaches for malignant tumors, surgical resection remains the primary and direct treatment for malignant solid tumors. Anesthesia is an integral part of the operation process. Different anesthesia techniques and drugs have different effects on the operation and the postoperative prognosis. Propofol is an intravenous anesthetic that is commonly used in surgery. A substantial number of studies have shown that propofol participates in the pathophysiological process related to malignant tumors and affects the occurrence and development of malignant tumors, including anti-tumor effect, pro-tumor effect, and regulation of drug resistance. Propofol can also reshape the tumor microenvironment, including anti-angiogenesis, regulation of immunity, reduction of inflammation and remodeling of the extracellular matrix. Furthermore, most clinical studies have also indicated that propofol may contribute to a better postoperative outcome in some malignant tumor surgeries. Therefore, the author reviewed the chemical properties, pharmacokinetics, clinical application and limitations, mechanism of influencing the biological characteristics of malignant tumors and reshaping the tumor microenvironment, studies of propofol in animal tumor models and its relationship with postoperative prognosis of propofol in combination with the relevant literature in recent years, to lay a foundation for further study on the correlation between propofol and malignant tumor and provide theoretical guidance for the selection of anesthetics in malignant tumor surgery.

PAD4 and Its Inhibitors in Cancer Progression and Prognosis

The systemic spread of malignancies and the risk of cancer-associated thrombosis are major clinical challenges in cancer therapy worldwide. As an important post-translational modification enzyme, peptidyl arginine deiminase 4 (PAD4) could mediate the citrullination of protein in different components (including nucleus and cytoplasm, etc.) of a variety of cells (tumor cells, neutrophils, macrophages, etc.), thus participating in gene regulation, neutrophil extracellular trap (NET) and macrophage extracellular trap (MET). Thereby, PAD4 plays an important role in enhancing the growth of primary tumors and facilitating the distant metastasis of cancer cells. In addition, it is related to the formation of cancer-associated thrombosis. Therefore, the development of PAD4-specific inhibitors may be a promising strategy for treating cancer, and it may improve patient prognosis. In this review, we describe PAD4 involvement in gene regulation, protein citrullination, and NET formation. We also discuss its potential role in cancer and cancer-associated thrombosis, and we summarize the development and application of PAD4 inhibitors.

Role of myeloid-derived suppressor cells in the formation of pre-metastatic niche

Metastasis is a complex process, which depends on the interaction between tumor cells and host organs. Driven by the primary tumor, the host organ will establish an environment suitable for the growth of tumor cells before their arrival, which is called the pre-metastasis niche. The formation of pre-metastasis niche requires the participation of a variety of cells, in which myeloid-derived suppressor cells play a very important role. They reach the host organ before the tumor cells, and promote the establishment of the pre-metastasis niche by influencing immunosuppression, vascular leakage, extracellular matrix remodeling, angiogenesis and so on. In this article, we introduced the formation of the pre-metastasis niche and discussed the important role of myeloid-derived suppressor cells. In addition, this paper also emphasized the targeting of myeloid-derived suppressor cells as a therapeutic strategy to inhibit the formation of pre-metastasis niche, which provided a research idea for curbing tumor metastasis.

Predicting the Immune Microenvironment and Prognosis with a NETosis-Related lncRNA Signature in Head and Neck Squamous Cell Carcinoma

Background. The mechanistic aspects of the involvement of long noncoding RNAs (lncRNAs) in NETosis, the process of neutrophil extracellular trap (NET) formation in head and neck squamous cell carcinoma (HNSCC), lack comprehensive elucidation. The involvement of these molecules in the immune microenvironment and plausible HNSCC prognosis remain to see the light of the day. The plausible functioning of NETosis-related lncRNAs with their plausible prognostic impact in HNSCC was probed in this work. Methods. The scrutiny of lncRNAs linked to NETosis entailed the probing of twenty-four genes associated with the process employing Pearson’s correlation analysis on HNSCC patients’ RNA sequencing data from The Cancer Genome Atlas (TCGA) database. The application of univariate, least absolute shrinkage and selection operator (LASSO), and multivariate Cox regression analyses yielded a NETosis-related lncRNA signature that was subjected to probing for its suitability in prognosis employing survival and nomogram analyses. Results. The NETosis-related lncRNA signature inclusive of five lncRNAs facilitated patients to be segregated as high-risk and low-risk groups with the former documenting a poor prognosis. Regression unearthed that the risk score was an independent factor for prognosis. The receiver operating characteristic (ROC) or receiver operating characteristic curve analysis documented a one-year area under time-dependent ROC curve (AUC) value of 0.711 that is corroborative of the accuracy of this signature. Additional probing documented an evident enriching of immune-linked pathways in the low-risk patients, while the high-risk patients documented an immunologically “cold” profile as per the infiltration of immune cells. We verified lncRNA expression from our NETosis-related lncRNA signature in vitro, which reflects the reliability of our model to a certain extent. Moreover, we also verified the function of the lncRNA. We found that LINC00426 contributes to the innate immune cGAS-STING signaling pathway, which explain to some extent the role of our prognostic model in predicting “hot” and “cold” tumors. Conclusions. The plausible prognostic relevance of the NETosis-related lncRNA signature (with five lncRNAs) emerges that is suggestive of its promise in targeting HNSCC.

Extracellular traps and the role in thrombosis

Thrombotic complications pose serious health risks worldwide. A significant change in our understanding of the pathophysiology of thrombosis has occurred since the discovery of extracellular traps (ETs) and their prothrombotic properties. As a result of immune cells decondensing chromatin into extracellular fibers, ETs promote thrombus formation by acting as a scaffold that activates platelets and coagulates them. The involvement of ETs in thrombosis has been reported in various thrombotic conditions including deep vein thrombosis (DVT), pulmonary emboli, acute myocardial infarction, aucte ischemic stroke, and abdominal aortic aneurysms. This review summarizes the existing evidence of ETs in human and animal model thrombi. The authors described studies showing the existence of ETs in venous or arterial thrombi. In addition, we studied potential novel therapeutic opportunities related to the resolution or prevention of thrombosis by targeting ETs.

Ferroptosis and its role in cardiomyopathy

Heart disease is the leading cause of death worldwide. Cardiomyopathy is a disease characterized by the heart muscle damage, resulting heart in a structurally and functionally change, as well as heart failure and sudden cardiac death. The key pathogenic factor of cardiomyopathy is the loss of cardiomyocytes, but the related molecular mechanisms remain unclear. Ferroptosis is a newly discovered regulated form of cell death, characterized by iron accumulation and lipid peroxidation during cell death. Recent studies have shown that ferroptosis plays an important regulatory roles in the occurrence and development of many heart diseases such as myocardial ischemia/reperfusion injury, cardiomyopathy and heart failure. However, the systemic association of ferroptosis and cardiomyopathy remains largely unknown and needs to be elucidated. In this review, we provide an overview of the molecular mechanisms of ferroptosis and its role in individual cardiomyopathies, highlight that targeting ferroptosis maybe a potential therapeutic strategy for cardiomyopathy therapy in the future.

Gegen Qinlian pills alleviate carrageenan-induced thrombosis in mice model by regulating the HMGB1/NF-κB/NLRP3 signaling

BACKGROUND

The high incidence of thrombotic events is one of the clinical characteristics of coronavirus disease of 2019 (COVID-19), due to a hyperinflammatory response caused by the virus. Gegen Qinlian Pills (GQP) is a Traditional Chinese Medicine that is included in the Chinese Pharmacopoeia and played an important role in the clinical fight against COVID-19. Although GQP has shown the potential to treat thrombosis, there is no relevant research on its treatment of thrombosis so far.

HYPOTHESIS

We hypothesized that GQP may be capable inhibit inflammation-induced thrombosis.

STUDY DESIGN

We tested our hypothesis in a carrageenan-induced thrombosis mouse model in vivo and lipopolysaccharide (LPS)-induced human endothelial cells (HUVECs) in vitro.

METHODS

We used a carrageenan-induced mouse thrombus model to confirm the inhibitory effect of GQP on inflammation-induced thrombus. In vitro, studies in human umbilical vein endothelial cells (HUVECs) and in silico network pharmacology analyses were performed to reveal the underlying mechanisms of GQP and determine the main components, targets, and pathways of GQP, respectively.

RESULTS

Oral administration of 227.5 mg/kg, 445 mg/kg and 910 mg/kg of GQP significantly inhibited thrombi in the lung, liver, and tail and augmented tail blood flow of carrageenan-induced mice with reduced plasma tumor necrosis factor α (TNF-α) and diminished expression of high mobility group box 1 (HMGB1) in lung tissues. GQP ethanol extract (1, 2, or 5 μg/ml) also reduced the adhesion of platelets to LPS stimulated HUVECs. The TNF-α and the expression of HMGB1, nuclear factor kappa B (NF-κB), and NLR family pyrin domain containing 3 (NLRP3) in LPS stimulated HUVECs were also attenuated. Moreover, we analyzed the components of GQP and inferred the main targets, biological processes, and pathways of GQP in the treatment of inflammation-induced thrombosis through network pharmacology.

CONCLUSION

Overall, we demonstrated that GQP could reduce inflammation-induced thrombosis by inhibiting HMGB1/NFκB/NLRP3 signaling and provided an accurate explanation for the multi-target, multi-function mechanism of GQP in the treatment of thromboinflammation, and provides a reference for the clinical usage of GQP.

Impact of Neutrophil Extracellular Traps on Thrombosis Formation: New Findings and Future Perspective

Thrombotic diseases seriously endanger human health, neutrophils and neutrophil extracellular traps (NETs) play an important role in abnormal thrombus formation. NETs are extracellular structures released by neutrophils upon stimulation by pathogens. NETs include neutrophil elastase (NE), myeloperoxidase (MPO), cathepsin G and other active substances. The network structure provided by NETs can prevent the spread of pathogens and effectively kill and eliminate pathogens. However, the components of NETs can also abnormally activate the coagulation pathway and participate in the formation of pathological thrombi. This review aims to summarize the mechanisms of NETs formation in detail; the research progress of NETs in venous thrombosis, arterial thrombosis, acquired disease-associated thrombosis, sepsis coagulation disorder; as well as the strategies to target NETs in thrombosis prevention and treatment.

A Novel Rodent Model of Hypertensive Cerebral Small Vessel Disease with White Matter Hyperintensities and Peripheral Oxidative Stress

Cerebral small vessel disease (CSVD) is the second most common cause of stroke and a major contributor to dementia. Manifestations of CSVD include cerebral microbleeds, intracerebral hemorrhages (ICH), lacunar infarcts, white matter hyperintensities (WMH) and enlarged perivascular spaces. Chronic hypertensive models have been found to reproduce most key features of the disease. Nevertheless, no animal models have been identified to reflect all different aspects of the human disease. Here, we described a novel model for CSVD using salt-sensitive ‘Sabra’ hypertension-prone rats (SBH/y), which display chronic hypertension and enhanced peripheral oxidative stress. SBH/y rats were either administered deoxycorticosteroid acetate (DOCA) (referred to as SBH/y-DOCA rats) or sham-operated and provided with 1% NaCl in drinking water. Rats underwent neurological assessment and behavioral testing, followed by ex vivo MRI and biochemical and histological analyses. SBH/y-DOCA rats show a neurological decline and cognitive impairment and present multiple cerebrovascular pathologies associated with CSVD, such as ICH, lacunes, enlarged perivascular spaces, blood vessel stenosis, BBB permeability and inflammation. Remarkably, SBH/y-DOCA rats show severe white matter pathology as well as WMH, which are rarely reported in commonly used models. Our model may serve as a novel platform for further understanding the mechanisms underlying CSVD and for testing novel therapeutics.

Neutrophil Extracellular Traps Regulate HMGB1 Translocation and Kupffer Cell M1 Polarization During Acute Liver Transplantation Rejection

Neutrophil extracellular traps (NETs) play important roles in hepatic ischemic reperfusion injury (IRI) and acute rejection (AR)-induced immune responses to inflammation. After liver transplantation, HMGB1, an inflammatory mediator, contributes to the development of AR. Even though studies have found that HMGB1 can promote NET formation, the correlation between NETs and HMGB1 in the development of AR following liver transplantation has not been elucidated. In this study, levels of serum NETs were significantly elevated in patients after liver transplantation. Moreover, we found that circulating levels of NETs were negatively correlated with liver function. In addition, liver transplantation and elevated extracellular HMGB1 promoted NET formation. The HMGB1/TLR-4/MAPK signaling pathway, which is initiated by HMGB1, participates in NET processes. Moreover, in the liver, Kupffer cells were found to be the main cells secreting HMGB1. NETs induced Kupffer cell M1 polarization and decreased the intracellular translocation of HMGB1 by inhibiting DNase-1. Additionally, co-treatment with TAK-242 (a TLR-4 inhibitor) and rapamycin more effectively alleviated the damaging effects of AR following liver transplantation than either drug alone.

Neutrophil Extracellular Trap Targeting Protects Against Ischemic Damage After Fibrin-Rich Thrombotic Stroke Despite Non-Reperfusion

Stroke is one of the most prevalent diseases worldwide caused primarily by a thrombotic vascular occlusion that leads to cell death. To date, t-PA (tissue-type plasminogen activator) is the only thrombolytic therapy approved which targets fibrin as the main component of ischemic stroke thrombi. However, due to its highly restrictive criteria, t-PA is only administrated to less than 10% of all stroke patients. Furthermore, the research in neuroprotective agents has been extensive with no translational results from medical research to clinical practice up to now. Since we first described the key role of NETs (Neutrophil Extracellular Traps) in platelet-rich thrombosis, we asked, first, whether NETs participate in fibrin-rich thrombosis and, second, if NETs modulation could prevent neurological damage after stroke. To this goal, we have used the thromboembolic in situ stroke model which produces fibrin-rich thrombotic occlusion, and the permanent occlusion of the middle cerebral artery by ligature. Our results demonstrate that NETs do not have a predominant role in fibrin-rich thrombosis and, therefore, DNase-I lacks lytic effects on fibrin-rich thrombosis. Importantly, we have also found that NETs exert a deleterious effect in the acute phase of stroke in a platelet-TLR4 dependent manner and, subsequently, that its pharmacological modulation has a neuroprotective effect. Therefore, our data strongly support that the pharmacological modulation of NETs in the acute phase of stroke, could be a promising strategy to repair the brain damage in ischemic disease, independently of the type of thrombosis involved.

Role of NETosis in Central Nervous System Injury

Central nervous system (CNS) injury is divided into brain injury and spinal cord injury and remains the most common cause of morbidity and mortality worldwide. Previous reviews have defined numerous inflammatory cells involved in this process. In the human body, neutrophils comprise the largest numbers of myeloid leukocytes. Activated neutrophils release extracellular web-like DNA amended with antimicrobial proteins called neutrophil extracellular traps (NETs). The formation of NETs was demonstrated as a new method of cell death called NETosis. As the first line of defence against injury, neutrophils mediate a variety of adverse reactions in the early stage, and we consider that NETs may be the prominent mediators of CNS injury. Therefore, exploring the specific role of NETs in CNS injury may help us shed some light on early changes in the disease. Simultaneously, we discovered that there is a link between NETosis and other cell death pathways by browsing other research, which is helpful for us to establish crossroads between known cell death pathways. Currently, there is a large amount of research concerning NETosis in various diseases, but the role of NETosis in CNS injury remains unknown. Therefore, this review will introduce the role of NETosis in CNS injury, including traumatic brain injury, cerebral ischaemia, CNS infection, Alzheimer's disease, and spinal cord injury, by describing the mechanism of NETosis, the evidence of NETosis in CNS injury, and the link between NETosis and other cell death pathways. Furthermore, we also discuss some agents that inhibit NETosis as therapies to alleviate the severity of CNS injury. NETosis may be a potential target for the treatment of CNS injury, so exploring NETosis provides a feasible therapeutic option for CNS injury in the future.

High Mobility Group Box 1: Biological Functions and Relevance in Oxidative Stress Related Chronic Diseases

In the early 1970s, a group of non-histone nuclear proteins with high electrophoretic mobility was discovered and named high-mobility group (HMG) proteins. High-mobility group box 1 (HMGB1) is the most studied HMG protein that detects and coordinates cellular stress response. The biological function of HMGB1 depends on its subcellular localization and expression. It plays a critical role in the nucleus and cytoplasm as DNA chaperone, chromosome gatekeeper, autophagy maintainer, and protector from apoptotic cell death. HMGB1 also functions as an extracellular alarmin acting as a damage-associated molecular pattern molecule (DAMP). Recent findings describe HMGB1 as a sophisticated signal of danger, with a pleiotropic function, which is useful as a clinical biomarker for several disorders. HMGB1 has emerged as a mediator in acute and chronic inflammation. Furthermore, HMGB1 targeting can induce beneficial effects on oxidative stress related diseases. This review focus on HMGB1 redox status, localization, mechanisms of release, binding with receptors, and its activities in different oxidative stress-related chronic diseases. Since a growing number of reports show the key role of HMGB1 in socially relevant pathological conditions, to our knowledge, for the first time, here we analyze the scientific literature, evaluating the number of publications focusing on HMGB1 in humans and animal models, per year, from 2006 to 2021 and the number of records published, yearly, per disease and category (studies on humans and animal models).

The mechanism of HMGB1 secretion and release

High mobility group box 1 (HMGB1) is a nonhistone nuclear protein that has multiple functions according to its subcellular location. In the nucleus, HMGB1 is a DNA chaperone that maintains the structure and function of chromosomes. In the cytoplasm, HMGB1 can promote autophagy by binding to BECN1 protein. After its active secretion or passive release, extracellular HMGB1 usually acts as a damage-associated molecular pattern (DAMP) molecule, regulating inflammation and immune responses through different receptors or direct uptake. The secretion and release of HMGB1 is fine-tuned by a variety of factors, including its posttranslational modification (e.g., acetylation, ADP-ribosylation, phosphorylation, and methylation) and the molecular machinery of cell death (e.g., apoptosis, pyroptosis, necroptosis, alkaliptosis, and ferroptosis). In this minireview, we introduce the basic structure and function of HMGB1 and focus on the regulatory mechanism of HMGB1 secretion and release. Understanding these topics may help us develop new HMGB1-targeted drugs for various conditions, especially inflammatory diseases and tissue damage.

A nuclear protein that gets released after cell death or is actively secreted by immune cells offers a promising therapeutic target for treating diseases linked to excessive inflammation. Daolin Tang from the University of Texas Southwestern Medical Center in Dallas, USA, and colleagues review how cellular stresses can trigger the accumulation of HMGB1, a type of alarm signal protein that promotes the recruitment and activation of inflammation-promoting immune cells. The researchers discuss various mechanisms that drive both passive and active release of HMGB1 into the space around cells. These processes, which include enzymatic modifications of the HMGB1 protein, cell–cell interactions and molecular pathways of cell death, could be targeted by drugs to lessen tissue damage and inflammatory disease caused by HMGB1-induced immune responses

Correlation Between Plasma High Mobility Group Protein N1 Level and the Prognosis of Patients with Acute Cerebral Infarction: Preliminary Findings

PURPOSE

To investigate the correlation between plasma levels of high mobility group protein N1 (HMGN1) and the severity of neurological deficits and prognosis in patients with acute cerebral infarction (ACI).

PATIENTS AND METHODS

The plasma HMGN1 levels of 108 patients with ACI were detected by ELISA. The National Institutes of Health Stroke Scale (NIHSS) and the modified Rankin Scale (mRS) were used to assess the neurological impairment and outcomes of these patients, respectively. The correlation between HMGN1 levels and clinical parameters was analyzed.

RESULTS

The plasma HMGN1 levels of patients with ACI were positively correlated with their NIHSS and mRS scores. Patients with the large artery atherosclerosis (LAA) subtype in the Trial of Org 10172 in Acute Stroke Treatment (TOAST) classification had higher plasma HMGN1 levels than patients with other subtypes.

CONCLUSION

HMGN1 levels are positively correlated with the severity of ACI and could be used to predict the prognosis of these patients. HMGN1 can be used as a biological marker and potential target for clinical assessment and therapy of ACI.

Complement C5a induces the formation of neutrophil extracellular traps by myeloid-derived suppressor cells to promote metastasis

Myeloid-derived suppressor cells (MDSCs) play a major role in cancer progression. In this study, we investigated the mechanisms by which complement C5a increases the capacity of polymorphonuclear MDSCs (PMN-MDSCs) to promote tumor growth and metastatic spread. Stimulation of PMN-MDSCs with C5a favored the invasion of cancer cells via a process dependent on the formation of neutrophil extracellular traps (NETs). NETosis was dependent on the production of high mobility group box 1 (HMGB1) by cancer cells. Moreover, C5a induced the surface expression of the HMGB1 receptors TLR4 and RAGE in PMN-MDSCs. In a mouse lung metastasis model, inhibition of C5a, C5a receptor-1 (C5aR1) or NETosis reduced the number of circulating-tumor cells (CTCs) and the metastatic burden. In support of the translational relevance of these findings, C5a was able to stimulate migration and NETosis in PMN-MDSCs obtained from lung cancer patients. Furthermore, myeloperoxidase (MPO)-DNA complexes, as markers of NETosis, were elevated in lung cancer patients and significantly correlated with C5a levels. In conclusion, C5a induces the formation of NETs from PMN-MDSCs in the presence of cancer cells, which may facilitate cancer cell dissemination and metastasis.

The Emerging Role of Neutrophil Extracellular Traps in Arterial, Venous and Cancer-Associated Thrombosis

Neutrophils play a vital role in the formation of arterial, venous and cancer-related thrombosis. Recent studies have shown that in a process known as NETosis, neutrophils release proteins and enzymes complexed to DNA fibers, collectively called neutrophil extracellular traps (NETs). Although NETs were originally described as a way for the host to capture and kill bacteria, current knowledge indicates that NETs also play an important role in thrombosis. According to recent studies, the destruction of vascular microenvironmental homeostasis and excessive NET formation lead to pathological thrombosis. In vitro experiments have found that NETs provide skeletal support for platelets, red blood cells and procoagulant molecules to promote thrombosis. The protein components contained in NETs activate the endogenous coagulation pathway to promote thrombosis. Therefore, NETs play an important role in the formation of arterial thrombosis, venous thrombosis and cancer-related thrombosis. This review will systematically summarize and explain the study of NETs in thrombosis in animal models and in vivo experiments to provide new targets for thrombosis prevention and treatment.

Role of the Extracellular Traps in Central Nervous System

It has been reported that several immune cells can release chromatin and granular proteins into extracellular space in response to the stimulation, forming extracellular traps (ETs). The cells involved in the extracellular trap formation are recognized including neutropils, macrophages, basophils, eosinophils, and mast cells. With the development of research related to central nervous system, the role of ETs has been valued in neuroinflammation, blood–brain barrier, and other fields. Meanwhile, it has been found that microglial cells as the resident immune cells of the central nervous system can also release ETs, updating the original understanding. This review aims to clarify the role of the ETs in the central nervous system, especially in neuroinflammation and blood–brain barrier.

NETosis in ischemic/reperfusion injuries: An organ-based review

Neutrophil extracellular trap (NETosis), the web-like structures induced by neutrophil death, is an important inflammatory mechanism of the immune system leading to reactive oxygen species production/coagulopathy, endothelial dysfunction, atherosclerosis, and ischemia. NETosis exerts its role through different mechanisms such as triggering Toll-like receptors, inflammatory cytokines, platelet aggregation, neutrophil activation/infiltration, and vascular impairment. NETosis plays a key role in the prognosis of coronary artery disease, ischemic injury of kidney, lung, gastrointestinal tract and skeletal muscles. In this review, we explored the molecular mechanisms involved in NETosis, and ischemic/reperfusion injuries in body organs.

Neutrophil Extracellular Traps Exacerbate Ischemic Brain Damage

Most acute strokes are ischemic, and subsequent neuroinflammation promotes further damage leading to cell death but also plays a beneficial role by promoting cellular repair. Neutrophils are forerunners to brain lesions after ischemic stroke and exert elaborate functions. While neutrophil extracellular traps (NETs) possess a fundamental antimicrobial function within the innate immune system under physiological circumstances, increasing evidence indicates that NETosis, the release process of NETs, occurs in the pathogenic process of stroke. In this review, we focus on the processes of NET formation and clearance, the temporal and spatial alterations of neutrophils and NETs after ischemic damage, and how NETs are involved in several stroke-related phenomena. Generally, NET formation and release processes depend on the generation of reactive oxygen species (ROS) and the activation of nuclear peptidylarginine deiminase-4 (PAD4). The acid-base environment, oxygen concentration, and iron ions around the infarct may also impact NET formation. DNase 1 has been identified as the primary degrader of NETs in serum, while reactive microglia are expected to inhibit the formation of NETs around ischemic lesions by phagocytosis of neutrophils. The neutrophils and NETs are present in the perivascular space ipsilateral to the infarct arising after ischemic damage, peaking between 1 and 3 days postischemia, but their location in the brain parenchyma remains controversial. After the ischemic injury, NETs are involved in the destruction of neurological function primarily by disrupting the blood-brain barrier and promoting thrombosis. The potential effects of NETs on various ischemic nerve cells need to be further investigated, especially in the chronic ischemic phase.

High Mobility Group Box 1 Protein in Cerebral Thromboemboli

High-mobility group box 1 protein (HMGB1) is a damage-associated molecular pattern (DAMP) involved in neutrophil extracellular trap (NET) formation and thrombosis. NETs are regularly found in cerebral thromboemboli. We here analyzed associated HMGB1 expression in human thromboemboli retrieved via mechanical thrombectomy from 37 stroke patients with large vessel occlusion. HMGB1 was detected in all thromboemboli, accounting for 1.7% (IQR 0.6–6.2%) of the total thromboemboli area and was found to be colocalized with neutrophils and NETs and in spatial proximity to platelets. Correlation analysis revealed that the detection of HMGB1 was strongly related to the number of neutrophils (r = 0.58, p = 0.0002) and platelets (r = 0.51, p = 0.001). Our results demonstrate that HMGB1 is a substantial constituent of thromboemboli causing large vessel occlusion stroke.

Anti-Phospholipid Antibodies and COVID-19 Thrombosis: A Co-Star, Not a Supporting Actor

Background: COVID-19 clinical features include a hypercoagulable state that resembles the antiphospholipid syndrome (APS), a disease characterized by thrombosis and presence of antiphospholipid antibodies (aPL). The relationship between aPL-presence and the appearance of thrombi as well as the transience or permanence of aPL in COVID-19 patients is not sufficiently clear. Methods: A group of 360 COVID-19 patients were followed-up for 6 months. Classic aPL, anti-B2GPI IgA, anti-phosphatidylserine/prothrombin IgG/M and anti-SARS-CoV-2 antibodies were determined at acute phase and >12 weeks later. The reference group included 143 healthy volunteers of the same age-range distribution. Results: aPL prevalence was similar in COVID-19 patients and the reference population. aPL presence in both determinations was significantly associated with thrombosis (OR: 2.33 and 3.71), strong agreement being found for classic aPL and anti-B2GPI IgA (Weighted kappa: 0.85–0.91). Thrombosis-associated aPL occurred a median of 17 days after hospital admission (IQR: 6–28) vs. 4 days for the rest (IQR: 3–7). Although anti-SARS-CoV-2 antibodies levels increased during convalescence, aPL hardly changed. Conclusions: Most COVID-19 patients would carry these aPL before the infection. At least two mechanisms could be behind thrombosis, early immune-dysregulation-mediated thrombosis after infection and belated-aPL-mediated thrombosis, with SARS-CoV-2 behaving as a second hit.

The Immune System Throws Its Traps: Cells and Their Extracellular Traps in Disease and Protection

The first formal description of the microbicidal activity of extracellular traps (ETs) containing DNA occurred in neutrophils in 2004. Since then, ETs have been identified in different populations of cells involved in both innate and adaptive immune responses. Much of the knowledge has been obtained from in vitro or ex vivo studies; however, in vivo evaluations in experimental models and human biological materials have corroborated some of the results obtained. Two types of ETs have been described—suicidal and vital ETs, with or without the death of the producer cell. The studies showed that the same cell type may have more than one ETs formation mechanism and that different cells may have similar ETs formation mechanisms. ETs can act by controlling or promoting the mechanisms involved in the development and evolution of various infectious and non-infectious diseases, such as autoimmune, cardiovascular, thrombotic, and neoplastic diseases, among others. This review discusses the presence of ETs in neutrophils, macrophages, mast cells, eosinophils, basophils, plasmacytoid dendritic cells, and recent evidence of the presence of ETs in B lymphocytes, CD4+ T lymphocytes, and CD8+ T lymphocytes. Moreover, due to recently collected information, the effect of ETs on COVID-19 is also discussed.

Admission serum high mobility group box 1 (HMGB1) protein predicts delayed cerebral ischemia following aneurysmal subarachnoid hemorrhage

High mobility group box 1 protein (HMGB1) is a prototypical damage associated particle and acts as a key player in aseptic inflammation. HMGB1 appears critical for the crosstalk of a prothrombotic and proinflammatory state that is implicated in mediating and exacerbating ischemic brain injury. The role of HMGB1 in aneurysmal subarachnoid hemorrhage (aSAH) remains to be elucidated. A prospective, single blinded observational study was designed to investigate the role of HMGB1 in aSAH. Serial serum HMGB1 level quantification on admission day 0, 4, 8, and 12 was performed. Primary outcome measures were delayed cerebral ischemia (DCI - new infarction on CT) and poor functional outcome (90-day modified Rankin Scale 4-6). The role of HMGB1 levels for DCI, functional outcome and radiological vasospasm prediction was analyzed. Collectively, 83 aSAH patients were enrolled. Five patients died within 48 h. In 29/78 patients (37.2%), DCI was identified. In multivariable analysis, radiological vasospasm and admission HMGB1 were independent predictors for DCI. Younger age and higher white blood cell count, but not insult burden (World Federation of Neurosurgical Societies scale, modified Fisher scale, intraparenchymal or intraventricular hematoma existence) correlated with admission HMGB1 levels. Serial HMGB1 levels did not differ between patients with or without DCI, poor functional outcome or radiological vasospasm development. Admission serum HMGB1 does not reflect initial insult burden but serves as an independent biomarker predictive of DCI. Further studies are warranted to disentangle the role of HMGB1 surrounding the sequelae of aSAH.

Neutrophil extracellular traps in inflammatory bowel diseases: Implications in pathogenesis and therapeutic targets

Crohn's disease (CD) and ulcerative colitis (UC) are the two main forms of inflammatory bowel disease (IBD). Among the various immune cells involved in IBD, neutrophils are the first to infiltrate and appear to contribute to the impairment of the epithelial barrier, destruction of tissues by oxidative and proteolytic damage, as well as to the perpetuation of inflammation by the release of cytokines and chemokines associated with pro-inflammatory effects. In addition to basic effector mechanisms, such as phagocytosis and chemotaxis, neutrophils can also form extracellular traps (NETs), which is made up of a mesh-like structure - which contains its chromatin (DNA + histones) together with granules and enzymes, such as myeloperoxidase (MPO) and neutrophilic elastase (NE) - and that acts as a trap that can result in the death of extracellular pathogens and/or can promote tissue damage. Recent evidence indicates that NETs also play an important and significant role in the pathogenesis of IBD. Previous studies have reported increased levels of NETs in tissue and serum samples from patients with IBD, as well as in experimental colitis. In this review, we discuss current knowledge about the formation of NETs and their role in the pathophysiology of IBD, pointing out potential mechanisms by which NETs promote tissue damage, as well as their involvement in complications associated with IBD. In addition, we propose potential targets for therapy to regulate the production of NETs, making it possible to expand the current spectrum of therapies for IBD.

The association between circulating neutrophil extracellular trap related biomarkers and retinal vein occlusion incidence: A case-control pilot study

Retinal vein occlusion (RVO) is the second most common retinal vascular disorders and causes visual damage in a large population. Neutrophil extracellular traps (NETs) formation (NETosis) is an important cause of vascular diseases, however, the association between NETs related biomarkers and RVO development remained unclear. In this pilot study, a total of 77 RVO cases and 48 controls were included between Jan 2020 and July 2020. Besides, the circulating levels of three NETs related markers, cell-free DNA (cfDNA), myeloperoxidase (MPO)-DNA and citrullinated histone H3 (H3Cit), were detected in all the participants and thus the association between NETosis and RVO incidence was analyzed. Advanced assays were conducted to investigate the inflammation and thrombosis related biomarkers in RVO cases with higher or lower NETs biomarkers. When the results were considered, it was found that NETs biomarkers, including cfDNA, MPO-DNA and H3Cit, were increased in the RVO cases comparing with the controls (P < 0.05). Through the receiver operating characteristic (ROC) analyses, we found that circulating NETs related biomarkers demonstrated potential diagnostic effects for RVO and the AUCs of plasma cfDNA, MPO-DNA and H3Cit were 0.859, 0.871 and 0.928, respectively (P < 0.001). Through analyzing the correlations between circulating NETs markers and RVO stages and durations, inflammatory markers as well as thrombotic indexes, it was found that NETs were related with the RVO subtypes, inflammatory status and thrombus formation. In conclusion, the plasma NETs remnants are significantly increased in RVO cases. Besides, advanced studies demonstrate that inflammation as well as thrombus formation might be involved in this association.