Verbenalin alleviates acute lung injury induced by sepsis and IgG immune complex through GPR18 receptor.

Acute lung injury is significantly associated with the aberrant activation and pyroptosis of alveolar macrophages. Targeting the GPR18 receptor presents a potential therapeutic approach to mitigate inflammation. Verbenalin, a prominent component of Verbena in Xuanfeibaidu (XFBD) granules, is recommended for treating COVID-19. In this study, we demonstrate the therapeutic effect of verbenalin on lung injury through direct binding to the GPR18 receptor. Verbenalin inhibits the activation of inflammatory signaling pathways induced by lipopolysaccharide (LPS) and IgG immune complex (IgG IC) via GPR18 receptor activation. The structural basis for verbenalin's effect on GPR18 activation is elucidated through molecular docking and molecular dynamics simulations. Furthermore, we establish that IgG IC induces macrophage pyroptosis by upregulating the expression of GSDME and GSDMD through CEBP-δ activation, while verbenalin inhibits this process. Additionally, we provide the first evidence that IgG IC promotes the formation of neutrophil extracellular traps (NETs), and verbenalin suppresses NETs formation. Collectively, our findings indicate that verbenalin functions as a "phytoresolvin" to promote inflammation regression and suggests that targeting the C/EBP-δ/GSDMD/GSDME axis to inhibit macrophage pyroptosis may represent a novel strategy for treating acute lung injury and sepsis.

Platelet-neutrophil interaction in COVID-19 and vaccine-induced thrombotic thrombocytopenia.

Coronavirus disease 2019 (COVID-19) is known to commonly induce a thrombotic diathesis, particularly in severely affected individuals. So far, this COVID-19-associated coagulopathy (CAC) has been partially explained by hyperactivated platelets as well as by the prothrombotic effects of neutrophil extracellular traps (NETs) released from neutrophils. However, precise insight into the bidirectional relationship between platelets and neutrophils in the pathophysiology of CAC still lags behind. Vaccine-induced thrombotic thrombocytopenia (VITT) is a rare autoimmune disorder caused by auto-antibody formation in response to immunization with adenoviral vector vaccines. VITT is associated with life-threatening thromboembolic events and thus, high fatality rates. Our concept of the thrombophilia observed in VITT is relatively new, hence a better understanding could help in the management of such patients with the potential to also prevent VITT. In this review we aim to summarize the current knowledge on platelet-neutrophil interplay in COVID-19 and VITT.

THE ROLE OF NEUTROPHIL EXTRACELLULAR TRAPS (NETs) IN THE IMMUNOPATHOGENESIS OF SEVERE COVID-19: POTENTIAL IMMUNOTHERAPEUTIC STRATEGIES REGULATING NET FORMATION AND ACTIVITY.

The role of neutrophil granulocytes (NG) in the pathogenesis of COVID-19 is associated with the NG recruitment into inflammatory foci, activation of their functions and enhanced formation of neutrophil extracellular networks (NETs). In this review, we analyzed a large body of scientific literature devoted to the features of developing NETs, their role in the COVID-19 pathogenesis, a role in emerging immunothrombosis, vasculitis, acute respiratory distress syndrome, cytokine storm syndrome, and multi-organ lesions. Convincing data are presented clearly indicating about a profound role of NETs in the COVID-19 immunopathogenesis and associated severe complications resulting from intensified inflammation process, which is a key for the course of SARS-CoV-2 virus infection. The presented role of NGs and NETs, along with that of other immune system cells and pro-inflammatory cytokines, is extremely important in understanding development of overactive immune response in severe COVID-19. The scientific results obtained available now allow to identify an opportunity of regulatory effects on hyperactivated NGs, NETosis at various stages and on limiting a negative impact of pre-formed NETs on various tissues and organs. All the aforementioned data should help in creating new, specialized immunotherapy strategies designed to increase the odds of survival, reduce severity of clinical manifestations in COVID-19 patients as well as markedly reduce mortality rates. Currently, it is possible to use existing drugs, while a number of new drugs are being developed, the action of which can regulate NG quantity, positively affect NG functions and limit intensity of NETosis. Continuing research on the role of hyperactive NG and NETosis as well as understanding the mechanisms of regulating NET formation and restriction in severe COVID-19, apparently, are of high priority, because in the future the new data obtained could pave the basis for development of targeted approaches not only for immunotherapy aimed at limiting education and blocking negative effects already formed NETs in severe COVID-19, but also for immunotherapy, which could be used in combination treatment of other netopathies, primarily autoimmune diseases, auto-inflammatory syndromes, severe purulent-inflammatory processes, including bacterial sepsis and hematogenous osteomyelitis.Copyright © 2023 Saint Petersburg Pasteur Institute. All rights reserved.

Corrigendum: Phenotypic alteration of low-density granulocytes in people with pulmonary post-acute sequelae of SARS-CoV-2 infection.

[This corrects the article DOI: 10.3389/fimmu.2022.1076724.].

IgG Stimulates the Formation of Neutrophil Extracellular Traps and Modifies Their Structure.

We studied the neutrophils and monocytes obtained from 37 patients with various inflammatory diseases such as psoriasis, acute infectious process in the abdominal cavity (acute appendicitis/abscess of the abdominal cavity, and acute cholecystitis), acute pancreatitis, and post-COVID syndrome after mild COVID infection. The number and the morphological structure of neutrophil extracellular traps (NET) as well as the effect of IgG on NET were examined. NET were visualized and counted by fluorescence microscopy with fluorescent dye SYBR Green. All the studied types of inflammation were accompanied by spontaneous formation of NET. After application of IgG, the number of NET doubled, their size increased, and transformation of net-like traps into the cloud forms was observed. The clouds form structure of the network is not capable of capturing pathogens with subsequent retraction, the products of its enzymatic degradation can be the factors of secondary alteration. The study results demonstrate a previously unknown mechanism of infection resistance.

Neutrophil and Monocyte Extracellular Traps in the Diagnosis of Post-Covid Syndrome

Post-COVID syndrome (long covid, post COVID-19 condition) is characterized by cognitive and mental disorders, chest and joint pain, impaired sense of smell and taste, as well as by gastrointestinal and cardiac disorders. The diagnosis of post-COVID syndrome is based mainly on the patients' complaints. To date, no optimal diagnostic method has been proposed. The study was aimed to compare the informative value of the indicators obtained during conventional assessment of patients with post-COVID syndrome and the blood levels of neutrophil (NETs) and monocyte (METs) extracellular traps. The study involved neutropils and monocytes collected from 21 patients with post-COVID syndrome aged 18-59. Fluorescence microscopy and the SYBR Green (Evrogen) fluorescent dye for double-stranded DNA were used for enumeration and imaging of extracellular traps. Clinical and laboratory indicators make it impossible to identify the changes specific for post-COVID syndrome. At the same time, post-COVID syndrome is characterized by inflammation in the vascular endothelium. The filamentous forms of NETs found in blood are a laboratory feature of such aseptic inflammation. The filamentous forms of NETs have been detected only in those patients who have a history of mild to severe COVID-19, while the filamentous forms of METs have been found in patients having a history of severe infection. The findings show that the detection of the filamentous forms of NETs and METs in blood is the most informative diagnostic feature of post-COVID syndrome.

Neutrophil Extracellular Traps in Airway Diseases: Pathological Roles and Therapeutic Implications.

Neutrophils are important effector cells of the innate immune response that fight pathogens by phagocytosis and degranulation. Neutrophil extracellular traps (NETs) are released into the extracellular space to defend against invading pathogens. Although NETs play a defensive role against pathogens, excessive NETs can contribute to the pathogenesis of airway diseases. NETs are known to be directly cytotoxic to the lung epithelium and endothelium, highly involved in acute lung injury, and implicated in disease severity and exacerbation. This review describes the role of NET formation in airway diseases, including chronic rhinosinusitis, and suggests that targeting NETs could be a therapeutic strategy for airway diseases.

Role of increased neutrophil extracellular trap formation on acute kidney injury in COVID-19 patients.

Background: A strong association between elevated neutrophil extracellular trap (NET) levels and poor clinical outcomes in patients with coronavirus infection 2019 (COVID-19) has been reported. However, while acute kidney injury (AKI) is a common complication of COVID-19, the role of NETs in COVID-19-associated AKI is unclear. We investigated the association between elevated NETs and AKI and the prognostic role of NETs in COVID-19 patients. Methods: Two representative markers of NETs, circulating nucleosomes and myeloperoxidase-DNA, were measured in 115 hospitalized patients. Serum levels of interleukin [IL]-6, monocyte chemotactic protein-1 [MCP-1], plasma von Willebrand factor (vWF) and urinary biomarkers of renal tubular damage (ß2-microglobulin [ß2M] and kidney injury molecule 1 [KIM-1]) were measured. Results: AKI was found in 43 patients (37.4%), and pre-existing chronic kidney disease (CKD) was a strong risk factor for AKI. Higher circulating NET levels were a significant predictor of increased risk of initial ICU admission, in-hospital mortality (adjusted HR 3.21, 95% CI 1.08-9.19) and AKI (OR 3.67, 95% CI 1.30-10.41), independent of age, diabetes, pre-existing CKD and IL-6 levels. There were strong correlations between circulating nucleosome levels and urinary KIM-1/creatinine (r=0.368, p=0.001) and ß2M (r=0.218, p=0.049) levels. NETs were also strongly closely associated with serum vWF (r = 0.356, p<0.001), but not with IL-6 or MCP-1 levels. Conclusions: Elevated NETs were closely associated with AKI, which was a strong predictor of mortality. The close association between NETs and vWF may suggest a role for NETs in COVID-19-associated vasculopathy leading to AKI.

Neutrophil Extracellular Traps and Platelet Activation for Identifying Severe Episodes and Clinical Trajectories in COVID-19.

The role of NETs and platelet activation in COVID-19 is scarcely known. We aimed to evaluate the role of NETs (citrullinated histone H3 [CitH3], cell-free DNA [cfDNA]) and platelet activation markers (soluble CD40 ligand [CD40L] and P-selectin) in estimating the hazard of different clinical trajectories in patients with COVID-19. We performed a prospective study of 204 patients, categorized as outpatient, hospitalized and ICU-admitted. A multistate model was designed to estimate probabilities of clinical transitions across varying states, such as emergency department (ED) visit, discharge (outpatient), ward admission, ICU admission and death. Levels of cfDNA, CitH3 and P-selectin were associated with the severity of presentation and analytical parameters. The model showed an increased risk of higher levels of CitH3 and P-selectin for ED-to-ICU transitions (Hazard Ratio [HR]: 1.35 and 1.31, respectively), as well as an elevated risk of higher levels of P-selectin for ward-to-death transitions (HR: 1.09). Elevated levels of CitH3 (HR: 0.90), cfDNA (HR: 0.84) and P-selectin (HR: 0.91) decreased the probability of ward-to-discharge transitions. A similar trend existed for elevated levels of P-selectin and ICU-to-ward transitions (HR 0.40); In conclusion, increased NET and P-selectin levels are associated with more severe episodes and can prove useful in estimating different clinical trajectories.

COVID-19, Blood Lipid Changes, and Thrombosis.

Although there is increasing evidence that oxidative stress and inflammation induced by COVID-19 may contribute to increased risk and severity of thromboses, the underlying mechanism(s) remain to be understood. The purpose of this review is to highlight the role of blood lipids in association with thrombosis events observed in COVID-19 patients. Among different types of phospholipases A2 that target cell membrane phospholipids, there is increasing focus on the inflammatory secretory phospholipase A2 IIA (sPLA2-IIA), which is associated with the severity of COVID-19. Analysis indicates increased sPLA2-IIA levels together with eicosanoids in the sera of COVID patients. sPLA2 could metabolise phospholipids in platelets, erythrocytes, and endothelial cells to produce arachidonic acid (ARA) and lysophospholipids. Arachidonic acid in platelets is metabolised to prostaglandin H2 and thromboxane A2, known for their pro-coagulation and vasoconstrictive properties. Lysophospholipids, such as lysophosphatidylcholine, could be metabolised by autotaxin (ATX) and further converted to lysophosphatidic acid (LPA). Increased ATX has been found in the serum of patients with COVID-19, and LPA has recently been found to induce NETosis, a clotting mechanism triggered by the release of extracellular fibres from neutrophils and a key feature of the COVID-19 hypercoagulable state. PLA2 could also catalyse the formation of platelet activating factor (PAF) from membrane ether phospholipids. Many of the above lipid mediators are increased in the blood of patients with COVID-19. Together, findings from analyses of blood lipids in COVID-19 patients suggest an important role for metabolites of sPLA2-IIA in COVID-19-associated coagulopathy (CAC).

Pathophysiology of SARS-CoV-2 Infection and COVID-19

A detailed understanding of the pathophysiologic mechanisms of severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2) infection and Coronavirus disease 2019 (COVID-19) is vital for improving patient management - to facilitate prompt recognition of progression to severe disease and effective therapeutic strategies. This chapter summarizes the underlyingpathophysiology in the lungs and other organs of COVID- 19 patients. The roles of the cytokine storm culminating in exaggerated inflammatory responses and formation of neutrophil extracellular traps (NETs) are discussed. Pathological features of the various stages from the onset of COVID-19 are outlined - progressing from early mild infection to severe clinical illness to the critically ill phase. © 2023 by World Scientific Publishing Co. Pte. Ltd.

Humoral immunity and thrombosis in COVID-19

Coronavirus disease 2019 (COVID-19) is due to the infection of the upper and lower airways by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). COVID-19 is characterized by different clinical manifestations ranging from paucisymptomatic conditions to life-threatening acute respiratory distress syndrome and may present multisystem involvement. A hyperinflammatory response to the virus and the associated prothrombotic state (immunothrombosis) are the major causes of tissue/organ damage. Several humoral mediators have been described to mediate the immunothrombosis in COVID-19;among them, a lot of attention has been paid to the synthesis of nonorgan specific procoagulant autoantibodies, the hyperproduction of proinflammatory cytokines, and to the activation of the complement cascade. All the above-mentioned pathogenic pathways are affecting the endothelium as one of the main targets of the disease and contribute to the clinical manifestations. © 2023 Elsevier Inc. All rights reserved.

In silico study of molecular mimicry between SARS-CoV-2 and neutrophil extracellular traps composition in granulocyte-rich supernatants of patients with systemic lupus erythematosus and lupus nephritis

Neutrophil extracellular traps (NETs) are detected in both COVID-19 and autoimmune disorders. Molecular mimicry between NETs-related proteins and SARS-CoV-2 proteins may be the mechanism that can lead to an autoimmune response. Accordingly, similar sequences were searched with blastp, between SARS-CoV-2 proteins and 148 proteins that were reported in the NETs composition induced in neutrophils of supernatants from patients with systemic lupus erythematosus and lupus nephritis. Query-subject epitope pairs with strong-binding affinities to 12 HLA supertype representative alleles were predicted for the aligned sequences with at least 50% identities. According to the prediction results, all HLA alleles under study have affinities to the similar SARS-CoV-2 and NETs' proteins. These affinities can bring molecular mimicry-based autoimmunity risk with NETs-pathology, in susceptible individuals, upon infection with SARS-CoV-2. However, HLA-A∗01:01 carriers can be at a higher risk due to the association of this allele with the highest number of NETs-related human proteins, and similar (unique) query-subject epitope pairs of those proteins and SARS-CoV-2. Additionally, HLA-A∗02:01 carriers may specifically be prone to higher risk than expected, if infected with SARS-CoV-2. Furthermore, HLA-A∗24:02 was predicted to bind strongly to an elevated number of unique SARS-CoV-2 subject sequences while the number of both associated human proteins, and unique queries of those, are rather low. It may be indicative of a pertaining pathology despite viral evolution. © 2023 Elsevier Inc. All rights reserved.

Chemokines and chemokine receptors during COVID-19 infection.

Chemokines are crucial inflammatory mediators needed during an immune response to clear pathogens. However, their excessive release is the main cause of hyperinflammation. In the recent COVID-19 outbreak, chemokines may be the direct cause of acute respiratory disease syndrome, a major complication leading to death in about 40% of severe cases. Several clinical investigations revealed that chemokines are directly involved in the different stages of SARS-CoV-2 infection. Here, we review the role of chemokines and their receptors in COVID-19 pathogenesis to better understand the disease immunopathology which may aid in developing possible therapeutic targets for the infection.

NETs Promote Inflammatory Injury by Activating cGAS-STING Pathway in Acute Lung Injury.

Acute respiratory distress syndrome (ARDS) threatens the survival of critically ill patients, the mechanisms of which are still unclear. Neutrophil extracellular traps (NETs) released by activated neutrophils play a critical role in inflammatory injury. We investigated the role of NETs and the underlying mechanism involved in acute lung injury (ALI). We found a higher expression of NETs and cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) in the airways, which was reduced by Deoxyribonuclease I (DNase I) in ALI. The administration of the STING inhibitor H-151 also significantly relieved inflammatory lung injury, but failed to affect the high expression of NETs in ALI. We isolated murine neutrophils from bone marrow and acquired human neutrophils by inducing HL-60 to differentiate. After the PMA interventions, exogenous NETs were obtained from such extracted neutrophils. Exogenous NETs intervention in vitro and in vivo resulted in airway injury, and such inflammatory lung injury was reversed upon degrading NETs with or inhibiting cGAS-STING with H-151 as well as siRNA STING. In conclusion, cGAS-STING participates in regulating NETs-mediated inflammatory pulmonary injury, which is expected to be a new therapeutic target for ARDS/ALI.

Molecular Mechanisms of Neutrophil Extracellular Trap (NETs) Degradation.

Although many studies have been exploring the mechanisms driving NETs formation, much less attention has been paid to the degradation and elimination of these structures. The NETs clearance and the effective removal of extracellular DNA, enzymatic proteins (neutrophil elastase, proteinase 3, myeloperoxidase) or histones are necessary to maintain tissue homeostasis, to prevent inflammation and to avoid the presentation of self-antigens. The persistence and overabundance of DNA fibers in the circulation and tissues may have dramatic consequences for a host leading to the development of various systemic and local damage. NETs are cleaved by a concerted action of extracellular and secreted deoxyribonucleases (DNases) followed by intracellular degradation by macrophages. NETs accumulation depends on the ability of DNase I and DNAse II to hydrolyze DNA. Furthermore, the macrophages actively engulf NETs and this event is facilitated by the preprocessing of NETs by DNase I. The purpose of this review is to present and discuss the current knowledge about the mechanisms of NETs degradation and its role in the pathogenesis of thrombosis, autoimmune diseases, cancer and severe infections, as well as to discuss the possibilities for potential therapeutic interventions. Several anti-NETs approaches had therapeutic effects in animal models of cancer and autoimmune diseases; nevertheless, the development of new drugs for patients needs further study for an effective development of clinical compounds that are able to target NETs.

Neutrophil extracellular traps primed intercellular communication in cancer progression as a promising therapeutic target.

In addition to the anti-infection response, neutrophils are linked to tumor progression through the secretion of inflammation components and neutrophil extracellular traps (NETs) formation. NET is a web-like structure constituted by a chromatin scaffold coated with specific nuclear and cytoplasmic proteins, such as histone and granule peptides. Increasing evidence has demonstrated that NETs are favorable factors to promote tumor growth, invasion, migration, and immunosuppression. However, the cell-cell interaction between NETs and other cells (tumor cells and immune cells) is complicated and poorly studied. This work is the first review to focus on the intercellular communication mediated by NETs in cancer. We summarized the complex cell-cell interaction between NETs and other cells in the tumor microenvironment. We also address the significance of NETs as both prognostic/predictive biomarkers and molecular targets for cancer therapy. Moreover, we presented a comprehensive landscape of cancer immunity, improving the therapeutic efficacy for advanced cancer in the future.

Xuebijing injection inhibited neutrophil extracellular traps to reverse lung injury in sepsis mice via reducing Gasdermin D.

The mortality of sepsis and septic shock remains high worldwide. Neutrophil extracellular traps (NETs) release is a major cause of organ failure and mortality in sepsis. Targeting Gasdermin D (GSDMD) can restrain NETs formation, which is promising for sepsis management. However, no medicine is identified without severe safety concerns for this purpose. Xuebijing injection (XBJ) has been demonstrated to alleviate the clinical symptoms of COVID-19 and sepsis patients, but there are not enough animal studies to reveal its mechanisms in depth. Therefore, we wondered whether XBJ relieved pulmonary damage in sepsis by suppressing NETs formation and adopted a clinically relevant polymicrobial infection model to test this hypothesis. Firstly, XBJ effectively reversed lung injury caused by sepsis and restrained neutrophils recruitment to lung by down-regulating proinflammatory chemokines, such as CSF-3, CXCL-2, and CXCR-2. Strikingly, we found that XBJ significantly reduced the expressions of NETs component proteins, including citrullinated histone H3 (CitH3), myeloperoxidase (MPO), and neutrophil elastase (NE). GSDMD contributes to the production of NETs in sepsis. Notably, XBJ exhibited a reduced effect on the expressions of GSDMD and its upstream regulators. Besides, we also revealed that XBJ reversed NETs formation by inhibiting the expressions of GSDMD-related genes. Collectively, we demonstrated XBJ protected against sepsis-induced lung injury by reversing GSDMD-related pathway to inhibit NETs formation.

The Impact of COVID-19 on Cancer Recurrence: A Narrative Review.

Severe acute respiratory syndrome coronavirus 2 (SARSCoV-2) continues to be a worldwide healthcare problem. While our knowledge of the interaction of cancer and its management with COVID-19 mortality is gradually evolving, there are still many unanswered questions regarding the impact of COVID-19 on cancer and its prognosis. Several factors activated during COVID-19 have been implicated in tumorigenesis and the development of metastasis. Inflammation, hypoxia, reduced levels of angiotensin converting enzyme 2, elevated levels of Interleukin 6 and some other cytokines that are hallmarks of COVID-19 are capable of inducing tumor relapse and metastasis. On the other hand, there are reports that COVID-19 has been associated with cancer cure. Understanding the interaction between COVID-19 and tumor cells is essential for evaluating the potential long-term risks of COVID-19 in cancer patients, and for scheduling necessary preventive and therapeutic interventions. In this review, we briefly overview the potential impacts that COVID-19 might have on tumorigenesis and cancer relapse, as well as the role that COVID-19 might play in cancer remission and cure.