Neutrophil extracellular traps in COVID-19

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

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

Pediatric autoimmune diseases in the light of COVID-19 pandemic, A retrospective observational big data study

Background

The COVID-19 pandemic has raised concerns about potential links between SARS-CoV-2 infection and autoimmune diseases. This study investigated changes in the incidence rate (IR) of autoimmune diseases among children following the pandemic's onset.

Methods

A retrospective cross-sectional study analyzed data from Clalit Health Services, Israel's largest healthcare provider, examining the IR of different autoimmune diseases in children aged 0-18. The study compared pre-pandemic (2019) with pandemic/post-pandemic periods (2020-2023), encompassing a cohort of over 1.5 million children.

Results

Significant IR increases were observed across multiple autoimmune diseases. Rheumatic diseases (Juvenile Idiopathic Arthritis, Systemic Lupus Erythematosus, Henoch Schoenlein Purpura (HSP)) showed consistent increases, with HSP demonstrating the most pronounced trend. Endocrine disorders exhibited diverse patterns, with autoimmune thyroid diseases and Type 1 diabetes showing overall increases, while diabetic ketoacidosis exhibited an initial spike followed by a decline. Gastrointestinal diseases displayed heterogeneous patterns; Celiac disease and Ulcerative colitis showed general increases, Crohn's disease showed a downward trend, and autoimmune hepatitis exhibited an initial significant decrease followed by a significant increase. Dermatological conditions, including Psoriasis and Vitiligo, demonstrated consistent elevations throughout 2020-2023. Immune Thrombocytopenia Purpura showed initial decreases followed by significant increases in 2022-2023.

Conclusions

This comprehensive analysis reveals significant changes in pediatric autoimmune disease incidence following the COVID-19 pandemic, suggesting potential associations between SARS-CoV-2 infection and autoimmune dysregulation. The diverse patterns observed across different conditions highlight the complex interplay between viral infection and autoimmunity, emphasizing the need for continued surveillance and investigation of long-term immunological consequences of COVID-19 in pediatric populations.

Multi-omics driven biomarker discovery and pathological insights into Pseudomonas aeruginosa pneumonia

BACKGROUND

Pseudomonas aeruginosa (P. aeruginosa) is a leading cause of hospital-acquired pneumonia, contributing significantly to morbidity and mortality, especially in immunocompromised patients. Understanding the molecular mechanisms underlying this infection is crucial for developing targeted therapeutic strategies. This study aims to elucidate the local and systemic pathways and biomarkers involved in the pathogenesis of P. aeruginosa pneumonia through an integrated multi-omics approach.

METHODS

We performed a comprehensive proteomic and metabolomic analysis on clinical samples from patients diagnosed with P. aeruginosa pneumonia, including both bronchoalveolar lavage fluid (BALF) and serum to capture local and systemic host responses. Data were analyzed using advanced statistical techniques to identify differentially expressed proteins and metabolites. Pathway enrichment analysis was performed to highlight significant biological processes associated with the infection.

RESULTS

Our findings revealed a significant upregulation of biomarkers associated with neutrophil extracellular traps (NETs) and oxidative stress, underscoring their pivotal roles in immune response and inflammatory pathology. Key proteins such as LCN2, CALR, and TPI1 were identified as central players in NET formation and oxidative stress pathways. Our integrated approach uniquely highlights the simultaneous local and systemic impact of NETs and oxidative stress. Additionally, by analyzing both BALF and serum, we observed distinct disruptions in metabolic pathways, particularly those related to amino acid metabolism and energy production, suggesting a bioenergetic crisis in response to infection. The combined analysis revealed key interactions between local and systemic immune responses, indicating a reprogramming of host energy pathways to meet the heightened immune demands, contributing to disease progression.

CONCLUSION

This study provides a comprehensive understanding of the molecular mechanisms driving P. aeruginosa pneumonia by uniquely integrating BALF and serum analyses to explore both local and systemic host responses. Our findings highlight the dual role of NETs in both pathogen containment and tissue damage, as well as the metabolic reprogramming required to sustain immune activity. The identification of key biomarkers and disrupted pathways presents promising targets for therapeutic intervention, with the potential to refine diagnostic precision and improve patient outcomes.

CLINICAL TRIAL NUMBER

Not applicable.

The immune system in cardiovascular diseases: from basic mechanisms to therapeutic implications

Immune system plays a crucial role in the physiological and pathological regulation of the cardiovascular system. The exploration history and milestones of immune system in cardiovascular diseases (CVDs) have evolved from the initial discovery of chronic inflammation in atherosclerosis to large-scale clinical studies confirming the importance of anti-inflammatory therapy in treating CVDs. This progress has been facilitated by advancements in various technological approaches, including multi-omics analysis (single-cell sequencing, spatial transcriptome et al.) and significant improvements in immunotherapy techniques such as chimeric antigen receptor (CAR)-T cell therapy. Both innate and adaptive immunity holds a pivotal role in CVDs, involving Toll-like receptor (TLR) signaling pathway, nucleotide-binding oligomerization domain-containing proteins 1 and 2 (NOD1/2) signaling pathway, inflammasome signaling pathway, RNA and DNA sensing signaling pathway, as well as antibody-mediated and complement-dependent systems. Meanwhile, immune responses are simultaneously regulated by multi-level regulations in CVDs, including epigenetics (DNA, RNA, protein) and other key signaling pathways in CVDs, interactions among immune cells, and interactions between immune and cardiac or vascular cells. Remarkably, based on the progress in basic research on immune responses in the cardiovascular system, significant advancements have also been made in pre-clinical and clinical studies of immunotherapy. This review provides an overview of the role of immune system in the cardiovascular system, providing in-depth insights into the physiological and pathological regulation of immune responses in various CVDs, highlighting the impact of multi-level regulation of immune responses in CVDs. Finally, we also discuss pre-clinical and clinical strategies targeting the immune system and translational implications in CVDs.

Neutrophil Extracellular Traps Capturing SARS-CoV-2 in the Lung Tissue (Alveoli and Parenchyma) Cause Microthrombi - A Strategy to Eliminate SARS-CoV-2 From the Circulation as Degraded Fibrin Clots

Background

It has been thought that neutrophil extracellular traps (NETs) and thrombosis exacerbate COVID-19, but, on the other hand, NETs are an important player in innate immunity. The precise roles of NETs and thrombosis in the course of COVID-19 have not been fully elucidated.

Methods and Results

The roles were investigated in the literature and a new theory was formulated. When neutrophils encounter SARS-CoV-2 in the lung tissue, they undergo NETosis and capture the virus. This capture is triggered by electrostatic interaction between histones in NETs and SARS-CoV-2; histones are highly positively charged, and viruses, including SARS-CoV-2, have a net negative charge under physiological pH. NETs that capture SARS-CoV-2 fall into alveolar capillaries through the collapsed endothelium to spare the lung tissue from the toxicity of NETs. NETs in the microvessels cause microthrombosis; positively charged histones induce the aggregation of negatively charged platelets, which leads to microthrombi. Microthrombi engulfing SARS-CoV-2 are consolidated into fibrin clots, which are eventually degraded by increased fibrinolysis and eliminated from the circulation.

Conclusions

This novel theory suggests that NETosis and microthrombosis are phenomena inevitably elicited in COVID-19, and in combination they are a system newly termed "NETombosis". Undegraded fibrin clots remaining in the microcirculation may be the cause of the sequelae, because they cause long-lasting circulatory failure in various organs.

Soluble CD13 is a potential mediator of neutrophil-induced thrombogenic inflammation in SARS-CoV-2 infection

The soluble variant of the ectopeptidase CD13 (sCD13), released from the cell surface by matrix metalloproteinase 14 (MMP14), is a potent pro-inflammatory mediator, displaying chemotactic, angiogenic, and arthritogenic properties through bradykinin receptor B1 (B1R). We revealed a link between sCD13 and amplified neutrophil-mediated inflammatory responses in SARS-CoV-2 infection. sCD13 was markedly elevated in patients with COVID-19 and correlated with disease severity and variants, ethnicity, inflammation markers, and neutrophil extracellular trap formation (NETosis). Neutrophils treated with sCD13 showed heightened NETosis and chemotaxis, which were inhibited by sCD13 receptor blockade. Meanwhile sCD13 did not induce platelet aggregation. Single-cell analysis of COVID-19 lungs revealed coexpression of CD13 and MMP14 by various cell types, and higher CD13 expression compared with controls. Neutrophils with high CD13 mRNA were enriched for genes associated with immaturity, though CD13 protein expression was lower. Histological examination of COVID-19 lungs revealed CD13-positive leukocytes trapped in vessels with fibrin thrombi. Flow cytometry verified the presence of B1R and a second sCD13 receptor, protease-activated receptor 4, on monocytes and neutrophils. These findings identify sCD13 as a potential instigator of COVID-19-associated NETosis, potentiating vascular stress and thromboembolic complications. The potent pro-inflammatory effects of sCD13 may contribute to severe COVID-19, suggesting that sCD13 and its receptors might be therapeutic targets.

Toll-like receptor 8 activation induces a neutrophil inflammatory phenotype: therapeutic implications for the utility of toll-like receptor 8 inhibition

Excessive activation of toll-like receptor 7 and 8 (TLR7/8) plays a role in the pathogenesis of autoimmune diseases and is associated with negative outcomes from viral infections. Neutrophil activation is highly inflammatory and mediates tissue damage. We explored the effects of TLR7/8 activation in neutrophils to better understand neutrophil biology and evaluate the therapeutic utility of TLR7/8 inhibitors in indications where neutrophils contribute to disease pathogenesis. We found that TLR8, but not TLR7, is active in human neutrophils. TLR8 activation led to increased interleukin-8 (IL-8) secretion and resulted in significant changes in gene expression, as determined by RNA sequencing, with increased expression of genes encoding cytokines and other inflammatory mediators. Type I interferon (IFN) also induced gene expression changes distinct from those induced by TLR8. Additionally, neutrophil extracellular traps (NET) formation and DNA release, or NETosis, was induced by TLR8 activation in IFN-primed neutrophils. Treatment with a TLR7/8 inhibitor (CMPD2) effectively blocked IL-8 secretion and NETosis. In a Phase II clinical trial in COVID-19 pneumonia, TLR7/8 inhibition with enpatoran affected neutrophil counts. Expression of NFKBIZ was induced by TLR8 in neutrophils in vitro and found to also be reduced by enpatoran in patients with COVID-19, suggesting it may be useful as a marker for TLR8-activated neutrophils and for identifying candidate diseases and patients that may benefit from treatment with a TLR7/8 inhibitor. Overall, our findings provide new insights into TLR8 and neutrophil biology that have therapeutic implications in autoimmune diseases and immune-mediated inflammation.

Challenges and insights in detecting early inflammation in DSS-induced colitis using chemiluminescence

BACKGROUND

Ulcerative colitis (UC) is a complex inflammatory condition with limited non-invasive tools to monitor early-stage inflammation. This study aimed to investigate the early stages of inflammation in acute and chronic murine models of dextran sulfate sodium (DSS)-induced colitis using in vivo and ex vivo chemiluminescence imaging.

METHODS

Two DSS-induced colitis models were used: an acute model over 7 days and a chronic model over 6 weeks. Body weight, stool consistency, and fecal occult blood (FOB) tests were monitored. Chemiluminescence imaging was used to assess inflammation in vivo and ex vivo, complemented by colonoscopy in the chronic model.

RESULTS

In the acute model, DSS-treated mice exhibited weight loss, colon shortening, and positive FOB tests by day 7. Ex vivo chemiluminescence signals exhibited a significant increase as early as day 5 (p < 0.001), while in vivo imaging showed minimal changes. In the chronic model, periodic DSS exposure resulted in recurrent inflammation, with positive FOB tests and significantly elevated ex vivo and in vivo chemiluminescence signals during the final DSS cycle (p < 0.05). Colonoscopy confirmed inflammation progression.

DISCUSSION

This study demonstrates the progression of inflammation in acute and chronic colitis models. However, in vivo chemiluminescence imaging did not reliably detect the onset of inflammation, limiting its application for early-stage disease detection. Ex vivo chemiluminescence and FOB tests provided more consistent insights into inflammation dynamics, addressing the need for improved non-invasive monitoring tools in UC research.

Inhalable nanocatalytic therapeutics for viral pneumonia

Pneumonia is a ubiquitous disease caused by viral and bacterial infections, characterized by high levels of reactive oxygen species in inflamed areas. Therapeutic strategies targeting reactive oxygen species levels in pneumonia have limited success due to the intricate nature of lung tissues and lung inflammatory responses. Here we describe an inhalable, non-invasive therapeutic platform composed of engineered cerium-based tannic acid nanozymes bound to a self-assembling peptide. In vitro and in vivo studies show that the nanozyme is internalized mostly by activated macrophages and epithelial cells in the inflamed sites. In the oxidative environments of a mouse model of viral pneumonia, nanozyme aggregates into catalytically active structures that reduce reactive oxygen species levels and inflammatory cytokine production and promote macrophage polarization to the prohealing (M2) phenotype. Moreover, the nanozyme attenuates bacterial inflammation and reduces tissue damage in a mouse viral pneumonia model with secondary bacterial infection. Overall, this nanozyme platform is a promising strategy for treating pneumonia and its associated conditions.

Blood-perfused Vessels-on-Chips stimulated with patient plasma recapitulate endothelial activation and microthrombosis in COVID-19

A subset of coronavirus disease 2019 (COVID-19) patients develops severe symptoms, characterized by acute lung injury, endothelial dysfunction and microthrombosis. Viral infection and immune cell activation contribute to this phenotype. It is known that systemic inflammation, evidenced by circulating inflammatory factors in patient plasma, is also likely to be involved in the pathophysiology of severe COVID-19. Here, we evaluate whether systemic inflammatory factors can induce endothelial dysfunction and subsequent thromboinflammation. We use a microfluidic Vessel-on-Chip model lined by human induced pluripotent stem cell-derived endothelial cells (hiPSC-ECs), stimulate it with plasma from hospitalized COVID-19 patients and perfuse it with human whole blood. COVID-19 plasma exhibited elevated levels of inflammatory cytokines compared to plasma from healthy controls. Incubation of hiPSC-ECs with COVID-19 plasma showed an activated endothelial phenotype, characterized by upregulation of inflammatory markers and transcriptomic patterns of host defense against viral infection. Treatment with COVID-19 plasma induced increased platelet aggregation in the Vessel-on-Chip, which was associated partially with formation of neutrophil extracellular traps (NETosis). Our study demonstrates that factors in the plasma play a causative role in thromboinflammation in the context of COVID-19. The presented Vessel-on-Chip can enable future studies on diagnosis, prevention and treatment of severe COVID-19.

Cytosolic nucleic acid sensing as driver of critical illness: mechanisms and advances in therapy

Nucleic acids from both self- and non-self-sources act as vital danger signals that trigger immune responses. Critical illnesses such as acute respiratory distress syndrome, sepsis, trauma and ischemia lead to the aberrant cytosolic accumulation and massive release of nucleic acids that are detected by antiviral innate immune receptors in the endosome or cytosol. Activation of receptors for deoxyribonucleic acids and ribonucleic acids triggers inflammation, a major contributor to morbidity and mortality in critically ill patients. In the past decade, there has been growing recognition of the therapeutic potential of targeting nucleic acid sensing in critical care. This review summarizes current knowledge of nucleic acid sensing in acute respiratory distress syndrome, sepsis, trauma and ischemia. Given the extensive research on nucleic acid sensing in common pathological conditions like cancer, autoimmune disorders, metabolic disorders and aging, we provide a comprehensive summary of nucleic acid sensing beyond critical illness to offer insights that may inform its role in critical conditions. Additionally, we discuss potential therapeutic strategies that specifically target nucleic acid sensing. By examining nucleic acid sources, sensor activation and function, as well as the impact of regulating these pathways across various acute diseases, we highlight the driving role of nucleic acid sensing in critical illness.

Thromboembolic Events in the Era of COVID-19: A Detailed Narrative Review

COVID-19, caused by the SARS-CoV-2 virus, is not only characterized by respiratory symptoms but is also associated with a wide range of systemic complications, including significant hematologic abnormalities. This is a comprehensive review of the current literature, using PubMed and Google Scholar, on the pathophysiology and incidence of thromboembolic events in COVID-19 patients and thromboprophylaxis. COVID-19 infection induces a prothrombotic state in patients through the dysregulation of the renin-angiotensin-aldosterone system (RAAS), endothelial dysfunction, elevated von Willebrand factor (vWF), and a dysregulated immune response involving the complement system and neutrophil extracellular traps (NETs). As a result, thromboembolic complications have emerged in COVID-19 cases, occurring more frequently in severe cases and hospitalized patients. These thrombotic events affect both venous and arterial circulation, with increased incidences of deep venous thrombosis (DVT), pulmonary embolism (PE), systemic arterial thrombosis, and myocardial infarction (MI). While DVT and PE are more common, the literature highlights the potential lethal consequences of arterial thromboembolism (ATE). This review also briefly examines the ongoing discussions regarding the use of anticoagulants for the prevention of thrombotic events in COVID-19 patients. While theoretically promising, current studies have yielded varied outcomes: Some suggest potential benefits, whereas others report an increased risk of bleeding events among hospitalized patients. Therefore, further large-scale studies are needed to assess the efficacy and safety of anticoagulants for thromboprophylaxis in COVID-19 patients.

Neutrophil extracellular traps and macrophage activation contibute to thrombosis and post-covid syndrome in SARS-CoV-2 infection

Background

SARS-CoV-2 infection activates macrophages and induces the release of neutrophil extracellular traps (NETs). Excess NETs is linked to inflammatory and thrombotic complications observed in COVID-19.

Aim

To explore the impact of NETs and macrophage activation on SARS-CoV-2-infected patients who developed complications.

Methods

We included 30 patients from the first (March 2020) and 30 from the second wave (July 2021), collecting two plasma samples at diagnosis and seven days later. Data on demographics, comorbidities, and basic analytical data were compiled. NETs markers (myeloperoxidase (MPO), neutrophil elastase (NE), p-selectin (P-SEL) and S100A8/S100A9 heterodimer (MRP)) and macrophage activation markers (Chitotriosidase activity (ChT), CCL18/PARC and YKL-40) were measured.

Results

The first wave had higher incidences of post-COVID syndrome, ICU admissions, and mortality. Patients of each wave showed elevated blood cells, liver enzymes, and coagulation markers at the time of diagnosis, with fibrinogen and D-Dimer differing between waves. NET and macrophage markers, NE, MPO, MRP, DNAse, ChT, and CCL18 were elevated, while P-SEL, cfDNA, and YKL-40 were decreased if compared to controls. A decrease in NE and DNAse is a link to lower levels of these two markers in complications versus without complications.

Conclusions

This study emonstrates alterations in NETs and macrophage activation markers in COVID-19 patients, indicating an imbalance in inflammatory response regulation.

COVID-19 and acute limb ischemia: latest hypotheses of pathophysiology and molecular mechanisms

Coronavirus disease 2019 (COVID-19) is a multi-system disease that can lead to various severe complications. Acute limb ischemia (ALI) has been increasingly recognized as a COVID-19-associated complication that often predicts a poor prognosis. However, the pathophysiology and molecular mechanisms underlying COVID-19-associated ALI remain poorly understood. Hypercoagulability and thrombosis are considered important mechanisms, but we also emphasize the roles of vasospasm, hypoxia, and acidosis in the pathogenesis of the disease. The angiotensin-converting enzyme 2 (ACE2) pathway, inflammation, and platelet activation may be important molecular mechanisms underlying these pathological changes induced by COVID-19. Furthermore, we discuss the hypotheses of risk factors for COVID-19-associated ALI from genetic, age, and gender perspectives based on our analysis of molecular mechanisms. Additionally, we summarize therapeutic approaches such as use of the interleukin-6 (IL-6) blocker tocilizumab, calcium channel blockers, and angiotensin-converting enzyme inhibitors, providing insights for the future treatment of coronavirus-associated limb ischemic diseases.

COVID-19 patient serum-derived extracellular vesicles deliver miR-20b-5p induces neutrophil extracellular traps

BACKGROUND

Severe cases of COVID-19 are characterized by an excessive presence of neutrophils. Neutrophil extracellular traps (NETs), released by activated neutrophils due to SARS-CoV-2 infection, contribute to lung epithelial cell death and are key drivers in COVID-19-associated immunothrombosis. However, the mechanism underlying NET formation in COVID-19 remain unclear.

METHODS

Extracellular vesicles (EVs) were isolated from the serum of COVID-19 patients and healthy volunteers, while neutrophils were isolated from blood samples of healthy volunteers. Neutrophils were treated with EVs, and the formation of NETs was observed. To identify the components responsible for the COVID-19-EVs-induced NET formation, we analyzed the expression profiles of microRNA (miRNAs) in COVID-19-EVs. We identified eight highly expressed miRNAs in COVID-19-EVs and explored their potential roles in COVID-19-EVs-mediated NET formation. Additionally, we explored the role of miR-20b-5p in COVID-19-EVs-induced NET formation.

RESULTS

In this study, we demonstrate that patients with COVID-19 have a higher concentration of serum EVs (COVID-19-EVs) than healthy controls (Normal-EVs). We also found that COVID-19-EVs are internalized by neutrophils to induced NET formation. Through comprehensive miRNA profiling of COVID-19-EVs versus Normal-EVs, we identified 78 differentially expressed miRNAs, with 27 of these being upregulated and 51 being downregulated. Subsequently, we discovered that COVID-19-EVs that were highly abundant with certain miRNAs promote NET formation. Specifically, miR-20b-5p was found to be the strongest inducer of NET formation of the identified miRNAs. Inhibition of miR-20b-5p resulted in a significant decrease in COVID-19-EVs-mediated induction of NET formation.

CONCLUSION

Herein, we reveal a previously unknown role of COVID-19-EVs in NET formation, which contributes to COVID-19 progression. This study suggests that miR-20b-5p may serve as a potential therapeutic target for COVID-19 treatment.

Prothrombotic antibodies targeting the spike protein's receptor-binding domain in severe COVID-19

ABSTRACT

Thromboembolic complication is common in severe coronavirus disease 2019 (COVID-19), leading to an investigation into the presence of prothrombotic antibodies akin to those found in heparin-induced thrombocytopenia (HIT). In a study of samples from 130 hospitalized patients, collected 3.6 days after COVID-19 diagnosis, 80% had immunoglobulin G (IgG) antibodies recognizing complexes of heparin and platelet factor 4 (PF4; PF4/H), and 41% had antibodies inducing PF4-dependent P-selectin expression in CpG oligodeoxynucleotide-treated normal platelets. Unlike HIT, both PF4/H-reactive and platelet-activating antibodies were found in patients with COVID-19 regardless of recent heparin exposure. Notably, PF4/H-reactive IgG antibodies correlated with those targeting the receptor-binding domain (RBD) of the severe acute respiratory syndrome coronavirus 2 spike protein. Moreover, introducing exogenous RBD to or removing RBD-reactive IgG from COVID-19 plasma or IgG purified from COVID-19 plasma significantly reduced their ability to activate platelets. RBD-specific antibodies capable of platelet activation were cloned from peripheral blood B cells of patients with COVID-19. These antibodies possessed sequence motifs in the heavy-chain complementarity-determining region 3 (HCDR3), resembling those identified in pathogenic HIT antibodies. Furthermore, IgG+ B cells having these HCDR3 signatures were markedly expanded in patients with severe COVID-19. Importantly, platelet-activating antibodies present in patients with COVID-19 were associated with a specific elevation of platelet α-granule proteins in the plasma and showed a positive correlation with markers for inflammation and tissue damage, suggesting a functionality of these antibodies in patients. The demonstration of functional and structural similarities between certain RBD-specific antibodies in patients with COVID-19 and pathogenic antibodies typical of HIT suggests a novel mechanism by which RBD-specific antibodies might contribute to thrombosis in COVID-19.

Impact of antiplatelets, anticoagulants and cyclic nucleotide stimulators on neutrophil extracellular traps (NETs) and inflammatory markers during COVID-19

While the association between coronavirus disease-19 (COVID-19) and neutrophils extracellular traps (NETs) is recognized, uncertainties remain regarding its precise onset, timing of resolution and target therapy. To assess changes in inflammatory and NET markers during the first week of COVID-19 hospitalization, and the association with disease severity. "In vitro" experiments investigated the effect of antiplatelets, anticoagulants, and cyclic nucleotide stimulators on NETs release. Prospective cohort study, changes in interleukin (IL)-6, IL-8, IL-17, TNF-α, RANTES, PF4, and citrullinated-H3 (citH3) levels within each outcome group was evaluated using ANOVA. Differences between moderately ill, critically ill, and non-survivors were determined using Kruskal-Wallis and logistic regression. Healthy neutrophils were stimulated with phorbol-12-myristate-13-acetate (PMA) or COVID-19 sera and treated with unfractionated heparin (UFH), low molecular weight heparin (LMWH), aspirin (ASA), ticagrelor, cinaciguat, sildenafil, and milrinone. The proportion of NETosis was assessed using IncuCyte Cell Imager. Of the 125 patients, 40.8% had moderate COVID-19, 40.8% had critical COVID-19 but recovered, and 18.4% died. From admission to hospitalization day 8, IL-6 levels decreased in moderately and critically ill, but not in non-survivors, while citH3 levels increased in critically ill and non-survivors. IL-6, IL-8, and TNF-α levels were associated with critical and fatal COVID-19. The release of NETs by neutrophils stimulated with PMA or COVID-19 sera was decreased in the presence of ASA, UFH, LMWH and cyclic nucleotide stimulators in a dose-dependent manner. In the first week of hospitalization, NET markers rose later than inflammatory markers in severe COVID-19 cases. Cyclic nucleotide stimulators, ASA and heparin may emerge as treatment approaches as they may modulate NETosis.

Myocardial ischaemia following COVID-19: a cardiovascular magnetic resonance study

The pathophysiology of myocardial injury following COVID-19 remains uncertain. COVID-HEART was a prospective, multicentre study utilising cardiovascular magnetic resonance (CMR) to characterise COVID-related myocardial injury. In this pre-specified analysis, the objectives were to examine (1) the frequency of myocardial ischaemia following COVID-19, and (2) the association between ischaemia and myocardial injury. We studied 59 patients hospitalised with COVID-19 and elevated serum troponin (COVID + /troponin + , age 61 ± 11 years) and 37 control subjects without COVID-19 or elevated troponin and similar by age and cardiovascular comorbidities (COVID -/comorbidity + , 64 ± 10 years). Subjects underwent multi-parametric CMR (comprising assessment of ventricular volumes, stress perfusion, T1/T2 mapping and scar). The primary endpoint was the frequency of inducible myocardial ischaemia. Inducible ischaemia was evident in 11 (19%) COVID + /troponin + patients and in 8 (22%) control subjects (p = 0.72). In COVID + /troponin + patients with ischaemia, epicardial coronary disease pattern ischaemia was present in eight patients and microvascular disease pattern, in three patients. There was no significant difference in the frequency of inducible ischaemia in COVID + /troponin + patients with previous myocardial infarction and/or revascularisation compared to those without (2/12 [17%] vs. 9/47 [19%] respectively, p = 0.84), or in those with and without scar (7/27 [26%] vs. 4/32 [13%] respectively, p = 0.19). Myocardial ischaemia was present in ~ 20% of patients recently hospitalised with COVID-19 and with elevated cardiac troponin, but this was not different to matched comorbid controls. This finding coupled with the lack of an association between ischaemia and myocardial scar suggests that coronary artery abnormalities are unlikely to be the predominant mechanism underlying COVID-19 induced myocardial injury.

A conformational change of C-reactive protein drives neutrophil extracellular trap formation in inflammation

BACKGROUND

C-reactive protein (CRP) represents a routine diagnostic marker of inflammation. Dissociation of native pentameric CRP (pCRP) into the monomeric structure (mCRP) liberates proinflammatory features, presumably contributing to excessive immune cell activation via unknown molecular mechanisms.

RESULTS

In a multi-translational study of systemic inflammation, we found a time- and inflammation-dependent pCRP dissociation into mCRP. We were able to confirm that mCRP co-localizes with leukocytes at the site of injury after polytrauma and therefore assessed whether the CRP conformation potentiates neutrophil activation. We found mCRP-induced neutrophil-extracellular trap formation in vitro and ex vivo involving nicotinamide adenine dinucleotide phosphate oxidase activation, p38/mitogen-activated protein kinase signaling, and histone H3 citrullination. Mimicking the trauma milieu in a human ex vivo whole blood model, we found significant mCRP generation as well as NET formation, prevented by blocking pCRP conformational changes.

CONCLUSIONS

Our data provide novel molecular insights how CRP dissociation contributes to neutrophil activation as driver of various inflammatory disorders.

The β Common Cytokine Receptor Family Reveals New Functional Paradigms From Structural Complexities

Cytokines are small proteins that are critical for controlling the growth and activity of hematopoietic cells by binding to cell surface receptors and transmitting signals across membranes. The β common (βc) cytokine receptor family, consisting of the granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-3, and IL-5 cytokine receptors, is an architype of the heterodimeric cytokine receptor systems. We now know that signaling by cytokine receptors is not always an "all or none" phenomenon. Subtle alterations of the cytokine:receptor complex can result in differential or selective signaling and underpin a variety of diseases including chronic inflammatory conditions and cancers. Structural biology techniques, such as X-ray crystallography and cryo-electron microscopy alongside cell biology studies, are providing detailed insights into cytokine receptor signaling. Recently, we found that the IL-3 receptor ternary complex forms higher-order assemblies, like those found earlier for the GM-CSF receptor, and demonstrated that functionally distinct biological signals arise from different IL-3 receptor oligomeric assemblies. As we enhance our understanding of the structural nuances of cytokine-receptor interactions, we foresee a new era of theranostics whereby structurally guided mechanism-based manipulation of cytokine signaling through rational/targeted protein engineering will harness the full potential of cytokine biology for precision medicine.

Lessons Learned From Clinical Trials of Immunotherapeutics for COVID-19

The COVID-19 pandemic caused by the SARS-CoV-2 virus was arguably one of the worst public health disasters of the last 100 years. As many infectious disease experts were focused on influenza, MERS, ZIKA, or Ebola as potential pandemic-causing agents, SARS-CoV-2 appeared to come from nowhere and spread rapidly. As with any zoonotic agent, the initial pathogen was able to transmit to a new host (humans), but it was poorly adapted to the immune environment of the new host and resulted in a maladapted immune response. As the host-pathogen interaction evolved, subsequent variants of SARS-CoV-2 became less pathogenic and acquired immunity in the host provided protection, at least partial protection, to new variants. As the host-pathogen interaction has changed since the beginning of the pandemic, it is possible the clinical results discussed here may not be applicable today as they were at the start of the pandemic. With this caveat in mind, we present an overview of the immune response of severe COVID-19 from a clinical research perspective and examine clinical trials utilizing immunomodulating agents to further elucidate the importance of hyperinflammation as a factor contributing to severe COVID-19 disease.

Neutrophil Extracellular Traps Participate in the Pathogenesis of Lupus Through S100A10-Mediated Regulatory T-Cell Differentiation and Functional Abnormalities

In systemic lupus erythematosus (SLE), neutrophil dysregulation and neutrophil extracellular traps (NETs) formation contribute to disease pathogenesis, potentially worsening the autoimmune response. Although research indicates NETs' involvement in various autoimmune conditions, their relationship with regulatory T cells (Tregs) in SLE remains elusive. In this study, in vivo experiments were involved in administering NET injections to C57BL/6 and MRL/Ipr mice. In vitro, a co-culture system facilitated interaction between Tregs and NETs. Proteomic analysis elucidated NET composition, while RNA sequencing delineated their impact on Treg differentiation. We demonstrated that increased NET levels correlate inversely with Treg abundance in SLE patients, influencing both their proportion and functionality. NET administration reduced Treg levels and induced lupus-like symptoms in C57BL/6 mice, exacerbating symptoms in MRL/Ipr mice. DNase I treatment mitigated NET effects, restoring Treg levels and alleviating symptoms. RNA sequencing revealed altered gene expression in naïve CD4+ T cells exposed to NETs. Additionally, proteomic analysis showed S100A10 protein changes between SLE patients and healthy controls, hindering Treg differentiation. NETs influence TLR-4 of naïve CD4+ T cells via S100A10, thereby modulating Treg proportion and functionality. These findings highlight the critical role of NETs in Treg differentiation in SLE, suggesting that targeting NETs may provide a novel therapeutic approach.

How Electricity Prevents Us from Bleeding to Death

Rapid tissue repair is also needed in the event of damage to blood vessels. Most of the essential steps that prevent us from bleeding to death involve the functions of Von Willebrand factor (VWF) and many of these are dependent on electrical forces.

Neutrophil phenotype, effector functions, and microbicidal activity in patients with SARS-CoV-2-associated ARDS

Critically ill patients admitted to the intensive care unit (ICU) for SARS-CoV-2-induced acute respiratory distress syndrome (ARDS) are at increased risk of bacterial and fungal secondary pulmonary infections due to acquired immune dysfunction. Given that the activity of neutrophils has not been described in these patients, we aimed to investigate the function of neutrophils at ICU admission and on day 7 (D7) postadmission. Neutrophil maturation and several functional indicators were investigated. We detected a significant decrease in reactive oxygen species production at D7, but we did not observe any other significant alterations in neutrophil function. Furthermore, bronchoalveolar lavage obtained from patients displayed no inhibitory effect on the function of neutrophils from healthy donors. These findings indicate that patients admitted to the ICU for SARS-CoV-2-induced ARDS do not acquire neutrophil dysfunction within the first week of their stay, which suggests that nosocomial infections among these patients are not due to acquired neutrophil dysfunctions.

A novel biomarker of COVI-19: MMP8 emerged by integrated bulk RNAseq and single-cell sequencing

COVID-19 has been emerging as the most influential illness which has caused great costs to the heath of population and social economy. Sivelestat sodium (SS) is indicated as an effective cure for lung dysfunction, a characteristic symptom of COVID-19 infection, but its pharmacological target is still unclear. Therefore, a deep understanding of the pathological progression and molecular alteration is an urgent issue for settling the diagnosis and therapy problems of COVID-19. In this study, the bulk ribonucleic acid sequencing (RNA-seq) data of healthy donors and non-severe and severe COVID-19 patients were collected. Then, target differentially expressed genes (DEGs) were screened through integrating sequencing data and the pharmacological database. Besides, with the help of functional and molecular interaction analyses, the potential effect of target gene alteration on COVID-19 progression was investigated. Single-cell sequencing was performed to evaluate the cell distribution of target genes, and the possible interaction of gene-positive cells with other cells was explored by intercellular ligand-receptor pattern analysis. The results showed that matrix metalloproteinase 8 (MMP8) was upregulated in severe COVID-19 patients, which was also identified as a targeting site to SS. Additionally, MMP8 took a core part in the regulatory interaction network of the screened DEGs in COVID-19 and was dramatically correlated with the inflammatory signaling pathway. The further investigations indicated that MMP8 was mainly expressed in myelocytes with a high degree of heterogeneity. MMP8-positive myelocytes interacted with other cell types through RETN-TLR4 and RETN-CAP1 ligand-receptor patterns. These findings emphasize the important role of MMP8 in COVID-19 progression and provide a potential therapeutic target for COVID-19 patients.

Viral sepsis: diagnosis, clinical features, pathogenesis, and clinical considerations

Sepsis, characterized as life-threatening organ dysfunction resulting from dysregulated host responses to infection, remains a significant challenge in clinical practice. Despite advancements in understanding host-bacterial interactions, molecular responses, and therapeutic approaches, the mortality rate associated with sepsis has consistently ranged between 10 and 16%. This elevated mortality highlights critical gaps in our comprehension of sepsis etiology. Traditionally linked to bacterial and fungal pathogens, recent outbreaks of acute viral infections, including Middle East respiratory syndrome coronavirus (MERS-CoV), influenza virus, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), among other regional epidemics, have underscored the role of viral pathogenesis in sepsis, particularly when critically ill patients exhibit classic symptoms indicative of sepsis. However, many cases of viral-induced sepsis are frequently underdiagnosed because standard evaluations typically exclude viral panels. Moreover, these viruses not only activate conventional pattern recognition receptors (PRRs) and retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs) but also initiate primary antiviral pathways such as cyclic guanosine monophosphate adenosine monophosphate (GMP-AMP) synthase (cGAS)-stimulator of interferon genes (STING) signaling and interferon response mechanisms. Such activations lead to cellular stress, metabolic disturbances, and extensive cell damage that exacerbate tissue injury while leading to a spectrum of clinical manifestations. This complexity poses substantial challenges for the clinical management of affected cases. In this review, we elucidate the definition and diagnosis criteria for viral sepsis while synthesizing current knowledge regarding its etiology, epidemiology, and pathophysiology, molecular mechanisms involved therein as well as their impact on immune-mediated organ damage. Additionally, we discuss clinical considerations related to both existing therapies and advanced treatment interventions, aiming to enhance the comprehensive understanding surrounding viral sepsis.

Pharmacological blocking of neutrophil extracellular traps attenuates immunothrombosis and neuroinflammation in cerebral cavernous malformation

Cerebral cavernous malformation (CCM) is a neurovascular disease with symptoms such as strokes, hemorrhages and neurological deficits. With surgery being the only treatment strategy, understanding the molecular mechanisms of CCM is crucial in finding alternative therapeutic options for CCM. Neutrophil extracellular traps (NETs) were recently reported in CCM, and NETs were shown to have positive or negative effects in different disease contexts. In this study, we investigated the roles of NETs in CCM by pharmacologically inhibiting NET formation using Cl-amidine (a peptidyl arginine deiminase inhibitor). We show here that Cl-amidine treatment reduced lesion burden, coagulation and endothelial-to-mesenchymal transition. Furthermore, NETs promoted the activation of microglia and fibroblasts, leading to increased neuroinflammation and a chronic wound microenvironment in CCM. The inhibition of NET formation caused endothelial quiescence and promoted a healthier microenvironment. Our study suggests the inhibition of NETs as a potential therapeutic strategy in CCM.

Bioinformatics and systems-biology approach to identify common pathogenic mechanisms for COVID-19 and systemic lupus erythematosus

BACKGROUND

The Coronavirus disease 2019 (COVID-19) pandemic has brought a heavy burden to the world, interestingly, it shares many clinical symptoms with systemic lupus erythematosus (SLE). It is unclear whether there is a similar pathological process between COVID-9 and SLE. In addition, we don't know how to treat SLE patients with COVID-19. In this study, we analyse the potential similar pathogenesis between SLE and COVID-19 and explore their possible drug regimens using bioinformatics and systems biology approaches.

METHODS

The common differentially expressed genes (DEGs) were extracted from the COVID-19 datasets and the SLE datasets for functional enrichment, pathway analysis and candidate drug analysis.

RESULT

Based on the two transcriptome datasets between COVID-19 and SLE, 325 common DEGs were selected. Hub genes were identified by protein-protein interaction (PPI) analysis. few found a variety of similar functional changes between COVID-19 and SLE, which may be related to the pathogenesis of COVID-19. Besides, we explored the related regulatory networks. Then, through drug target matching, we found many candidate drugs for patients with COVID-19 only or COVID-19 combined with SLE.

CONCLUSION

COVID-19 and SLE patients share many common hub genes, related pathways and regulatory networks. Based on these common targets, we found many potential drugs that could be used in treating patient with COVID-19 or COVID-19 combined with SLE.

Association of COVID-19 with thyroid dysfunction and autoimmune thyroid disease: A retrospective cohort study

Background

Since the end of the COVID-19 pandemic, the potential roles of thyroid-inflammatory derangements in driving or being associated with the prognosis of COVID-19 remain controversial. We aimed to clarify the association between COVID-19 infection and thyroid dysfunction, and highlight the impacts of subsequent autoimmune thyroid disease (AITD) on the prognosis of COVID-19.

Methods

The retrospective, multicenter, cohort study enrolled 2,339 participants with COVID-19 from three hospitals located in the north, middle, and south regions of Shaan Xi Province, China, between December 2022 and July 2023. 464 non-COVID-19 patients within the same period were supplemented, divided into groups with and without AITD. At hospital admission (baseline), 3- and 6-month follow-ups, we presented a dynamic description and correlation analysis of thyroid-inflammatory-autoimmune derangements in patients with AITD.

Results

A total of 2,082 COVID-19 patients diagnosed with AITD and 257 cases without AITD were included in the study, and 464 non-COVID-19 patients were supplemented, dividing into 14 AITD and 450 non-AITD cases. We found that COVID-19 infection was closely associated with thyroid dysfunction (χ 2  = 1518.129, p = 0.000). AITD patients with COVID-19 showed a higher prevalence of symptoms and comorbidities and longer hospital stays at baseline than non-AITD patients with COVID-19 (p = 0.000, p = 0.000, and p = 0.000). The baseline free triiodothyronine (FT3), free thyroxine, and radioactive iodine uptake at 24 h in AITD cases significantly decreased (p = 0.000, p = 0.000, and p = 0.000), while thyroid stimulating hormone, thyroglobulin, reverse triiodothyronine (rT3), and thyroid antibodies varying elevated from the baseline to the follow-up (baseline: p = 0.000, p = 0.000, p = 0.000, p = 0.000, p = 0.000, and p = 0.000; 3-month follow-up: p = 0.000, p = 0.000, p = 0.000, p = 0.000, p = 0.030, and p = 0.000). C-reactive protein, calcitonin, interleukin-6, -8, -10, and tumor necrosis factor-α rose significantly at baseline (p = 0.000, p = 0.000, p = 0.000, p = 0.000, p = 0.000, and p = 0.000) in AITD. Interferon-α and interferon-γ at baseline showed a significant decrease (p = 0.000 and p = 0.000), and remained at low levels after 6 months (p = 0.000 and p = 0.000). FT3 and rT3 were positively and negatively correlated with hospitalization, respectively (r = -0.208 and 0.231; p = 0.000 and p = 0.000). ROC curves showed that FT3 and rT3 had better robustness in predicting severe COVID-19 prognosis (AUC = 0.801 and 0.705). Ordered logistic regression revealed that ORs were 0.370, 0.048, and 0.021 for AITD [(subacute thyroiditis, Grave's disease, and Hashimoto's thyroiditis compared to non-thyroidal illness syndrome (NTIS)] with COVID-19 risk, indicating that NTIS was the predominant risk factor for the severity of COVID-19.

Conclusions

A robust association has been identified, wherein COVID-19 infection is closely associated with thyroid dysfunction, and the subsequent AITD may aggravate the poor prognosis of COVID-19.

Diversity in the Clinical Course and Outcome of COVID-19 in Patients with Different Inborn Errors of Immunity can be Associated with the Type of Error

Background

The relationship between inborn errors of immunity (IEIs) and COVID-19 severity and incidence rates remains unclear due to limited and diverse data. This study aimed to address this gap by identifying specific IEIs associated with an increased risk of severe COVID-19 or a predisposition to severe disease before vaccination.

Materials and Methods

Data were collected from the medical records of 15 patients with various IEIs, supplemented by interviews with individuals from an IEIs registry who had experienced COVID-19 before vaccination.

Results

Among the participants, only three patients (20%) experienced severe-prolonged COVID-19. Notably, this severity was predominantly observed in two male patients with Bruton's disease (BD) and one female patient with autosomal recessive hypogammaglobinemia. Moderate and severe COVID-19 cases were equally distributed (13.33%). In the female subgroup, one patient with common variable immunodeficiency and another with combined immunodeficiency experienced moderate and severe COVID-19, respectively. Conversely, both male patients with moderate and severe COVID-19 had BD.

Conclusion

Despite the limited number of severe cases, the absence of cytokine storm manifestation suggests potential protective mechanisms, possibly due to intravenous immunoglobulin therapy and inherent deficiencies within cytokine-producing cells (B and T cells). While IEIs may not be significant risk factors for COVID-19, they offer promising avenues for further research into therapeutic strategies targeting specific immune system components to mitigate severe COVID-19.

TRIM7 ubiquitinates SARS-CoV-2 membrane protein to limit apoptosis and viral replication

SARS-CoV-2 is a highly transmissible virus that causes COVID-19 disease. Mechanisms of viral pathogenesis include excessive inflammation and viral-induced cell death, resulting in tissue damage. Here we show that the host E3-ubiquitin ligase TRIM7 acts as an inhibitor of apoptosis and SARS-CoV-2 replication via ubiquitination of the viral membrane (M) protein. Trim7-/- mice exhibit increased pathology and virus titers associated with epithelial apoptosis and dysregulated immune responses. Mechanistically, TRIM7 ubiquitinates M on K14, which protects cells from cell death. Longitudinal SARS-CoV-2 sequence analysis from infected patients reveal that mutations on M-K14 appeared in circulating variants during the pandemic. The relevance of these mutations was tested in a mouse model. A recombinant M-K14/K15R virus shows reduced viral replication, consistent with the role of K15 in virus assembly, and increased levels of apoptosis associated with the loss of ubiquitination on K14. TRIM7 antiviral activity requires caspase-6 inhibition, linking apoptosis with viral replication and pathology.

Prothrombotic state and thrombotic events in COVID-19 pandemic period, including portal vein and splenic artery thromboses

This editorial article is intended to perform a discussion on the manuscript entitled "Simultaneous portal vein thrombosis and splenic vein thrombosis in a COVID-19 patient: A case report and review of literature" written by Abramowitz et al. The article focuses on the diagnostic processes in a 77-year-old-male patient with a simultaneous portal vein and splenic artery thrombosis accompanying coronavirus disease 2019 (COVID-19). The authors postulated that splanchnic thrombosis should be on the list of differential diagnoses in a patient presenting with abdominal pain in presence of a COVID-19 infection. The tendency for venous and arterial thrombosis in COVID-19 patients is encountered, largely attributed to hypercoagulopathy. In general, venous thromboembolism mostly manifest as deep vein thrombosis (DVT), pulmonary embolism (PE) or catheter-related thromboembolic events. Acute PE, DVT, cerebrovascular events and myocardial infarction are seen as the most common thromboembolic complications in COVID-19 patients. COVID-19-associated hemostatic abnormalities include mild thrombocytopenia and increased D-dimer level. Similar to other coagulopathies, the treatment of the underlying condition is the mainstay. Addition of antiplatelet agents can be considered in critically ill patients at low bleeding risk, not on therapeutic anticoagulation, and receiving gastric acid suppression Early administration of antithrombotic drugs will have a beneficial effect in both the prevention and treatment of thrombotic events, especially in non-ambulatory patients. Low molecular weight heparin (LMWH) should be started if there is no contraindication, including in non-critical patients who are at risk of hospitalization LMWH (enoxaparin) is preferred to standard heparin.

The neutrophil extracellular traps in neurological diseases: an update

Neutrophil extracellular traps (NETs) released by neutrophils are web-like DNA structures adhered to granulin proteins with bactericidal activity and can be an important mechanism for preventing pathogen dissemination or eliminating microorganisms. However, they also play important roles in diseases of other systems, such as the central nervous system. We tracked the latest advances and performed a review based on published original and review articles related to NETs and neurological diseases. Generally, neutrophils barely penetrate the blood-brain barrier into the brain parenchyma, but when pathological changes such as infection, trauma, or neurodegeneration occur, neutrophils rapidly infiltrate the central nervous system to exert their defensive effects. However, neutrophils may adversely affect the host when they uncontrollably release NETs upon persistent neuroinflammation. This review focused on recent advances in understanding the mechanisms and effects of NETs release in neurological diseases, and we also discuss the role of molecules that regulate NETs release in anticipation of clinical applications in neurological diseases.

Hyponatremia unleashes neutrophil extracellular traps elevating life-threatening pulmonary embolism risk

Neutrophil extracellular traps (NETs), essential for controlling infections, can induce various pathologies when dysregulated. Known triggers for infection-independent NETs release exist, yet a comprehensive understanding of the conditions prompting such responses is lacking. In this study, we identify hyponatremia as an independent inducer of NETs release, a common clinical condition that disrupts sodium/calcium exchange within neutrophils. This disruption leads to an excess of intracellular calcium, subsequent elevation of reactive oxygen species (ROS), and the citrullination of histone H3, culminating in the activation of NETs-release pathways. Notably, under hyponatremic conditions, this mechanism is exacerbated during infectious states, leading to the deposition of NETs in the lungs and increasing the risk of life-threatening pulmonary embolism. Our findings underscore the critical role of sodium and calcium homeostasis in neutrophil functionality and provide insights into the pathogenesis of hyponatremia-associated diseases, highlighting potential therapeutic interventions targeting NETs dynamics.

Immunopathological markers and cell types linked to COVID-19 symptom manifestation

BACKGROUND

Numerous studies have investigated the molecular properties that contribute to the symptoms of COVID-19, such as the virus's genetic makeup, its replication mechanisms, and how it interacts with host cells. However, identifying the immunopathological properties, such as the immune system's response, cytokine levels, and the presence of specific biomarkers, that are associated with the severity of the infection remains crucial for developing effective treatments and preventions.

METHODS

We analyzed blood protein factor profiles from 420 individuals to identify features differentiating between test-negative healthy, asymptomatic, and symptomatic individuals using statistical comparison and the least absolute shrinkage and selection operator (i.e., LASSO) algorithm. Additionally, we examined single-cell RNA sequencing data from 141 individuals to identify specific cell types associated with the COVID-19 symptoms.

RESULTS

Healthy individuals who tested negative had distinct blood protein factor levels compared to asymptomatic individuals. We identified two key protein factors, Serpin A10 and Complement C9, that differentiate between asymptomatic and symptomatic patients. Symptomatic patients showed lower levels of CD4+ T naïve, CD4+ T effector & memory, and CD8+ T naïve cells, along with higher levels of CD14+ classical monocytes compared to asymptomatic patients. Additionally, CD16+ non-classical monocytes, major producers of C1QA/B/C, appeared to contribute to the observed Complement C9 levels.

CONCLUSIONS

These findings advance our understanding of the immunopathological mechanisms underlying COVID-19 and may inform the development of targeted therapies and preventative measures. Future research should focus on further elucidating these mechanisms and exploring their potential clinical applications in managing COVID-19 severity.

Circulating Proteins Associated with Anti-IL6 Receptor Therapeutic Resistance in the Sera of Patients with Severe COVID-19

Circulating proteomes provide a snapshot of the physiological state of a human organism responding to pathogenic challenges and drug interventions. The outcomes of patients with COVID-19 and acute respiratory distress syndrome triggered by the SARS-CoV2 virus remain uncertain. Tocilizumab is an anti-interleukin-6 treatment that exerts encouraging clinical activity by controlling the cytokine storm and improving respiratory distress in patients with COVID-19. We investigate the biological determinants of therapeutic outcomes after tocilizumab treatment. Overall, 28 patients hospitalized due to severe COVID-19 who were treated with tocilizumab intravenously were included in this study. Sera were collected before and after tocilizumab, and the patient's outcome was evaluated until day 30 post-tocilizumab infusion for favorable therapeutic response to tocilizumab and mortality. Hyperreaction monitoring measurements by liquid chromatography-mass spectrometry-based proteomic analysis with data-independent acquisition quantified 510 proteins and 7019 peptides in the serum of patients. Alterations in the serum proteome reflect COVID-19 outcomes in patients treated with tocilizumab. Our results suggested that circulating proteins associated with the most significant prognostic impact belonged to the complement system, platelet degranulation, acute-phase proteins, and the Fc-epsilon receptor signaling pathway. Among these, upregulation of the complement system by activation of the classical pathway was associated with poor response to tocilizumab, and upregulation of Fc-epsilon receptor signaling was associated with lower mortality.

Longitudinal transcriptional changes reveal genes from the natural killer cell-mediated cytotoxicity pathway as critical players underlying COVID-19 progression

Patients present a wide range of clinical severities in response severe acute respiratory syndrome coronavirus 2 infection, but the underlying molecular and cellular reasons why clinical outcomes vary so greatly within the population remains unknown. Here, we report that negative clinical outcomes in severely ill patients were associated with divergent RNA transcriptome profiles in peripheral immune cells compared with mild cases during the first weeks after disease onset. Protein-protein interaction analysis indicated that early-responding cytotoxic natural killer cells were associated with an effective clearance of the virus and a less severe outcome. This innate immune response was associated with the activation of select cytokine-cytokine receptor pathways and robust Th1/Th2 cell differentiation profiles. In contrast, severely ill patients exhibited a dysregulation between innate and adaptive responses affiliated with divergent Th1/Th2 profiles and negative outcomes. This knowledge forms the basis of clinical triage that may be used to preemptively detect high-risk patients before life-threatening outcomes ensue.

Fragmentomics of plasma mitochondrial and nuclear DNA inform prognosis in COVID-19 patients with critical symptoms

BACKGROUND

The mortality rate of COVID-19 patients with critical symptoms is reported to be 40.5%. Early identification of patients with poor progression in the critical cohort is essential to timely clinical intervention and reduction of mortality. Although older age, chronic diseases, have been recognized as risk factors for COVID-19 mortality, we still lack an accurate prediction method for every patient. This study aimed to delve into the cell-free DNA fragmentomics of critically ill patients, and develop new promising biomarkers for identifying the patients with high mortality risk.

METHODS

We utilized whole genome sequencing on the plasma cell-free DNA (cfDNA) from 33 COVID-19 patients with critical symptoms, whose outcomes were classified as survival (n = 16) and death (n = 17). Mitochondrial DNA (mtDNA) abundance and fragmentomic properties of cfDNA, including size profiles, ends motif and promoter coverages were interrogated and compared between survival and death groups.

RESULTS

Significantly decreased abundance (~ 76% reduction) and dramatically shorter fragment size of cell-free mtDNA were observed in deceased patients. Likewise, the deceased patients exhibited distinct end-motif patterns of cfDNA with an enhanced preference for "CC" started motifs, which are related to the activity of nuclease DNASE1L3. Several dysregulated genes involved in the COVID-19 progression-related pathways were further inferred from promoter coverages. These informative cfDNA features enabled a high PPV of 83.3% in predicting deceased patients in the critical cohort.

CONCLUSION

The dysregulated biological processes observed in COVID-19 patients with fatal outcomes may contribute to abnormal release and modifications of plasma cfDNA. Our findings provided the feasibility of plasma cfDNA as a promising biomarker in the prognosis prediction in critically ill COVID-19 patients in clinical practice.

Association of corticosteroid therapy with reduced acute kidney injury and lower NET markers in severe COVID-19: an observational study

BACKGROUND

Acute kidney injury (AKI) is common in critical cases of coronavirus disease 2019 (COVID-19) and associated with worse outcome. Dysregulated neutrophil extracellular trap (NET) formation is one of several suggested pathophysiological mechanisms involved in the development of COVID-19 associated AKI. The corticosteroid dexamethasone was implemented as a standard treatment for severe COVID-19 as of June 2020. A sub-analysis of a prospective observational single center study was performed to evaluate the effect of corticosteroid treatment on AKI development and NET markers in critical cases of COVID-19.

RESULTS

Two hundred and ten adult patients admitted to intensive care at a tertiary level hospital due to respiratory failure or shock secondary to SARS-CoV-2-infection between March 13th 2020 and January 14th 2021 were included in the study. Ninety-seven of those did not receive corticosteroids. One hundred and thirteen patients were treated with corticosteroids [dexamethasone (n = 98) or equivalent treatment (n = 15)], but the incidence of AKI was assessed only in patients that received corticosteroids before any registered renal dysfunction (n = 63). Corticosteroids were associated with a lower incidence of AKI (19% vs 55.8%, p < 0.001). Fewer patients demonstrated detectable concentrations of extracellular histones in plasma when treated with corticosteroids (8.7% vs 43.1%; p < 0.001). Extracellular histones and in particular non-proteolyzed histones were observed more frequently with increasing AKI severity (p < 0.001). MPO-DNA was found in lower concentrations in patients that received corticosteroids before established renal dysfunction (p = 0.03) and was found in higher concentrations in patients with AKI stage 3 (p = 0.03). Corticosteroids did not ameliorate established AKI during the first week of treatment.

CONCLUSION

Corticosteroid treatment in severe COVID-19 is associated with a lower incidence of AKI and reduced concentrations of NET markers in plasma.

Higher Platelet Count Mostly in the Normal Range Is Associated with the First Episode of Peritonitis Risk in Incident Peritoneal Dialysis Patients

INTRODUCTION

Platelets play parts in infection and immune processes. However, the association between platelet count and the risk of peritoneal dialysis (PD)-associated peritonitis is unclear.

METHODS

This was a retrospective, observational, single-center cohort study. A Cox regression analysis was used to evaluate the independent association of platelet count with the occurrence of first PD-associated peritonitis. Models were adjusted for gender, age, body mass index, cardiovascular disease, diabetes mellitus, white blood cell count, neutrophil-lymphocyte ratio, hemoglobin level, albumin level, potassium level, and anti-platelet medication usage.

RESULTS

A total of 2,374 patients were enrolled in this study (59% men; mean age 47.40 ± 12.12). The average platelet count was 229.30 ± 82.12 × 109/L. 467 (20%) patients suffered from PD-associated peritonitis at least once. In the multivariable model, the adjusted hazard ratios (HRs) for quartiles 2, 3 and 4 versus quartile 1 were 1.428 (95% CI 1.060-1.924, p = 0.019), 1.663 (95% CI 1.240-2.229, p < 0.001) and 1.843 (95% CI 1.363-2.492, p < 0.001) with baseline data. A nonlinear relationship between platelet count and first PD-associated peritonitis was observed. Further, the association between platelet and first PD-associated peritonitis was significant in the patients with hypokalemia (P for interaction = 0.040).

CONCLUSION

In PD patients, elevated platelet counts were significantly associated with an increased risk of the first onset of PD-associated peritonitis.

Crossing epigenetic frontiers: the intersection of novel histone modifications and diseases

Histone post-translational modifications (HPTMs), as one of the core mechanisms of epigenetic regulation, are garnering increasing attention due to their close association with the onset and progression of diseases and their potential as targeted therapeutic agents. Advances in high-throughput molecular tools and the abundance of bioinformatics data have led to the discovery of novel HPTMs which similarly affect gene expression, metabolism, and chromatin structure. Furthermore, a growing body of research has demonstrated that novel histone modifications also play crucial roles in the development and progression of various diseases, including various cancers, cardiovascular diseases, infectious diseases, psychiatric disorders, and reproductive system diseases. This review defines nine novel histone modifications: lactylation, citrullination, crotonylation, succinylation, SUMOylation, propionylation, butyrylation, 2-hydroxyisobutyrylation, and 2-hydroxybutyrylation. It comprehensively introduces the modification processes of these nine novel HPTMs, their roles in transcription, replication, DNA repair and recombination, metabolism, and chromatin structure, as well as their involvement in promoting the occurrence and development of various diseases and their clinical applications as therapeutic targets and potential biomarkers. Moreover, this review provides a detailed overview of novel HPTM inhibitors targeting various targets and their emerging strategies in the treatment of multiple diseases while offering insights into their future development prospects and challenges. Additionally, we briefly introduce novel epigenetic research techniques and their applications in the field of novel HPTM research.

Low-Density Neutrophils and Neutrophil Extracellular Traps (NETs) Are New Inflammatory Players in Heart Failure

BACKGROUND

Heart failure with reduced (HFrEF) or preserved ejection fraction (HFpEF) is characterized by low-grade chronic inflammation. Circulating neutrophils regroup 2 subtypes termed high- and low-density neutrophils (HDNs and LDNs). LDNs represent less than 2% of total neutrophil under physiological conditions, but their counts increase in multiple pathologies, releasing more inflammatory cytokines and neutrophil extracellular traps (NETs). The aims of this study were to assess the differential count and role of HDNs, LDNs, and NETs-related activities in patients with heart failure (HF).

METHODS

HDNs and LDNs were isolated from human blood by density gradient and purified by fluorescence-activated cell sorting (FACS) and their counts obtained by flow cytometry. Formation of NETs (NETosis) was quantified by confocal microscopy. Circulating inflammatory and NETosis biomarkers were measured by enzyme-linked immunosorbent assay (ELISA). Neutrophil adhesion onto human extracellular matrix (hECM) was assessed by optical microscopy.

RESULTS

A total of 140 individuals were enrolled, including 33 healthy volunteers (HVs), 41 HFrEF (19 stable patients and 22 presenting acute decompensated HF [ADHF]), and 66 patients with HFpEF (36 stable patients and 30 presenting HF decompensation). HDNs and LDNs counts were significantly increased up to 39% and 2740%, respectively, in patients with HF compared with HVs. In patients with HF, the correlations among LDNs counts and circulating inflammatory (CRP, IL-6 and -8), troponin T, N-terminal prohormone of brain natriuretic peptide (NT-proBNP), and NETosis components were significant. In vitro, LDNs expressed more citrullinated histone H3 (H3Cit) and NETs and were more proadhesive, with ADHFpEF patients presenting the highest proinflammatory profile.

CONCLUSIONS

Patients with HFpEF present higher levels of circulating LDNs- and NETs-related activities, which are the highest in the context of acute HF decompensation.

Recognition and control of neutrophil extracellular trap formation by MICL

Regulation of neutrophil activation is critical for disease control. Neutrophil extracellular traps (NETs), which are web-like structures composed of DNA and neutrophil-derived proteins, are formed following pro-inflammatory signals; however, if this process is uncontrolled, NETs contribute to disease pathogenesis, exacerbating inflammation and host tissue damage1,2. Here we show that myeloid inhibitory C-type lectin-like (MICL), an inhibitory C-type lectin receptor, directly recognizes DNA in NETs; this interaction is vital to regulate neutrophil activation. Loss or inhibition of MICL functionality leads to uncontrolled NET formation through the ROS-PAD4 pathway and the development of an auto-inflammatory feedback loop. We show that in the context of rheumatoid arthritis, such dysregulation leads to exacerbated pathology in both mouse models and in human patients, where autoantibodies to MICL inhibit key functions of this receptor. Of note, we also detect similarly inhibitory anti-MICL autoantibodies in patients with other diseases linked to aberrant NET formation, including lupus and severe COVID-19. By contrast, dysregulation of NET release is protective during systemic infection with the fungal pathogen Aspergillus fumigatus. Together, we show that the recognition of NETs by MICL represents a fundamental autoregulatory pathway that controls neutrophil activity and NET formation.

Autoantibodies in COVID-19 and Other Viral Diseases: Molecular, Cellular, and Clinical Perspectives

Autoantibodies are immune system-produced antibodies that wrongly target the body's cells and tissues for attack. The COVID-19 pandemic has made it possible to link autoantibodies to both the severity of pathogenic infection and the emergence of several autoimmune diseases after recovery from the infection. An overview of autoimmune disorders and the function of autoantibodies in COVID-19 and other infectious diseases are discussed in this review article. We also investigated the different categories of autoantibodies found in COVID-19 and other infectious diseases including the potential pathways by which they contribute to the severity of the illness. Additionally, it also highlights the probable connection between vaccine-induced autoantibodies and their adverse outcomes. The review also discusses the therapeutic perspectives of autoantibodies. This paper advances our knowledge about the intricate interaction between autoantibodies and COVID-19 by thoroughly assessing the most recent findings.

Neutrophil Extracellular Traps: An Emerging Therapeutic Target to Improve Infectious Disease Outcomes

Neutrophils possess a diverse repertoire of pathogen clearance mechanisms, one of which is the formation of neutrophil extracellular traps (NETs). NETs are complexes of histone proteins and DNA coated with proteolytic enzymes that are released extracellularly to entrap pathogens and aid in their clearance, in a process known as NETosis. Intravascular NETosis may drive a massive inflammatory response that has been shown to contribute to morbidity and mortality in many infectious diseases, including malaria, dengue fever, influenza, bacterial sepsis, and severe acute respiratory syndrome coronavirus 2 infection. In this review we seek to (1) summarize the current understanding of NETs, (2) discuss infectious diseases in which NET formation contributes to morbidity and mortality, and (3) explore potential adjunctive therapeutics that may be considered for future study in treating severe infections driven by NET pathophysiology. This includes drugs specifically targeting NET inhibition and US Food and Drug Administration-approved drugs that may be repurposed as NET inhibitors.

Emerging therapeutic strategies targeting extracellular histones for critical and inflammatory diseases: an updated narrative review

Extracellular histones are crucial damage-associated molecular patterns involved in the development and progression of multiple critical and inflammatory diseases, such as sepsis, pancreatitis, trauma, acute liver failure, acute respiratory distress syndrome, vasculitis and arthritis. During the past decade, the physiopathologic mechanisms of histone-mediated hyperinflammation, endothelial dysfunction, coagulation activation, neuroimmune injury and organ dysfunction in diseases have been systematically elucidated. Emerging preclinical evidence further shows that anti-histone strategies with either their neutralizers (heparin, heparinoids, nature plasma proteins, small anion molecules and nanomedicines, etc.) or extracorporeal blood purification techniques can significantly alleviate histone-induced deleterious effects, and thus improve the outcomes of histone-related critical and inflammatory animal models. However, a systemic evaluation of the efficacy and safety of these histone-targeting therapeutic strategies is currently lacking. In this review, we first update our latest understanding of the underlying molecular mechanisms of histone-induced hyperinflammation, endothelial dysfunction, coagulopathy, and organ dysfunction. Then, we summarize the latest advances in histone-targeting therapy strategies with heparin, anti-histone antibodies, histone-binding proteins or molecules, and histone-affinity hemoadsorption in pre-clinical studies. Finally, challenges and future perspectives for improving the clinical translation of histone-targeting therapeutic strategies are also discussed to promote better management of patients with histone-related diseases.

Clinical outcomes of coronavirus disease in patients with breast cancer treated with granulocyte colony-stimulating factor following chemotherapy: Triangulation of evidence using population-based cohort and Mendelian randomization analyses

Recombinant human granulocyte colony-stimulating factor (G-CSF) administration in patients with cancer and coronavirus disease (COVID-19) remains controversial. Concerns exist that it may worsen COVID-19 outcomes by triggering an inflammatory cytokine storm, despite its common use for managing chemotherapy-induced neutropenia (CIN) or febrile neutropenia post-chemotherapy. Here, we determined whether prophylactic or therapeutic G-CSF administration following chemotherapy exacerbates COVID-19 progression to severe/critical conditions in breast cancer patients with COVID-19. Between December 2022 and February 2023, all 503 enrolled breast cancer patients had concurrent COVID-19 and received G-CSF post-chemotherapy, with most being vaccinated pre-chemotherapy. We prospectively observed COVID-19-related adverse outcomes, conducted association analyses, and subsequently performed Mendelian randomization (MR) analyses to validate the causal effect of genetically predicted G-CSF or its associated granulocyte traits on COVID-19 adverse outcomes. Only 0.99% (5/503) of breast cancer patients experienced COVID-19-related hospitalization following prophylactic or therapeutic G-CSF administration after chemotherapy. No mortality or progression to severe/critical COVID-19 occurred after G-CSF administration. Notably, no significant associations were observed between the application, dosage, or response to G-CSF and COVID-19-related hospitalization (all p >.05). Similarly, the MR analyses showed no evidence of causality of genetically predicted G-CSF or related granulocyte traits on COVID-19-related hospitalization or COVID-19 severity (all p >.05). There is insufficient evidence to substantiate the notion that the prophylactic or therapeutic administration of G-CSF after chemotherapy for managing CIN in patients with breast cancer and COVID-19 would worsen COVID-19 outcomes, leading to severe or critical conditions, or even death, especially considering the context of COVID-19 vaccination.

Enhanced Treatment in Severe-Critical COVID-19 With Tocilizumab, Remdesivir, Dexamethasone: A Jordanian Cohort Study

BACKGROUND

Several medications have been proposed to manage COVID-19, with controversial data regarding their clinical benefits. We aimed to investigate the clinical efficacy of using remdesivir (RDV) with and without tocilizumab (TCZ) and standard therapy in treating severe COVID-19.

METHODS

This retrospective cohort study was conducted in a Jordanian tertiary hospital (September 26th, 2020 - August 28th, 2021) and included adult COVID-19 patients requiring oxygen support. Patients were categorized into three groups based on treatment: TCZ+RDV and standard therapy; RDV and standard therapy; and standard therapy alone, which included dexamethasone, vitamins, anticoagulants, and ceftriaxone.

RESULTS

Of 1,556 screened, 1,244 patients (mean age 62.33, 60.8% men) were included. Distribution was 106 in TCZ+RDV, 520 in RDV, and 618 in standard therapy. No significant differences were observed in age, gender, or BMI. Mortality was lowest in TCZ+RDV (32.1%), followed by RDV (40.6%) and standard therapy (47.1%) (p=0.005). Among ICU patients, TCZ+RDV showed significantly lower mortality (51.1%) compared to RDV (75%) and standard therapy (85.8%) (p<0.001). The ICU stays and invasive mandatory ventilation (IMV) durations were significantly shorter with TCZ+RDV (4.30 and 2.69 days, respectively) compared to RDV (7.61 and 4.52 days) and standard therapy (7.98 and 5.32 days) (p<0.001 for ICU stays, p=0.025 for IMV durations).

CONCLUSIONS

Combining TCZ, RDV, and dexamethasone shows promise in reducing mortality and ICU/IMV duration for severe COVID-19.

The Therapeutic Potential of Neutrophil Extracellular Traps and NLRP3 Inflammasomes in Mycoplasma pneumoniae Pneumonia

INTRODUCTION

Mycoplasma pneumoniae (MP) is the most common pathogen of community-acquired pneumonia in children. However, the role of neutrophil extracellular traps (NETs) in the pathogenesis of MP is unclear.

METHODS

Both the level of NETs were detected between the 60 MP pneumonia patients and 20 healthy controls, whose the clinical characteristics were compared. Additionally, NETs formation induced by community-acquired respiratory distress syndrome (CARDS) toxin was also analyzed through transcriptome sequencing.

RESULTS

The levels of cell-free DNA, Cit-H3, and MPO-DNA complexes were significantly increased in the patients with MP pneumonia. Importantly, both cell-free DNA and LDH were higher in hospitalized patients with severity than those without severity. In addition, CARDS toxin induced the NETs formation in vitro and in vivo. Transcriptomics GO and KEGG pathway analysis indicate that NOD like receptor signaling pathway and Toll-like receptor signaling pathway are significantly enriched. Finally, we found that DNase I significantly attenuated the higher levels of Cit-H3, and up-regulation of interleukin-1β (IL-1β) and interleukin-18 (IL-18) by down-regulating the expression of NLRP3 and Caspase1(p20) in the lung tissues.

DISCUSSION

These results indicate that inhibiting excessive activation of NLRP3 inflammasomes, and NETs formation may alleviate MP pneumonia.

The role of extracellular traps released by neutrophils, eosinophils, and macrophages in asthma

Extracellular traps (ETs) are a specialized form of innate immune defense in which leukocytes release ETs composed of chromatin and active proteins to eliminate pathogenic microorganisms. In addition to the anti-infection effect of ETs, researchers have also discovered their involvement in the pathogenesis of inflammatory disease, tumors, autoimmune disease, and allergic disease. Asthma is a chronic airway inflammatory disease involving multiple immune cells. The increased level of ETs in asthma patients suggests that ETs play an important role in the pathogenesis of asthma. Here we review the research work on the formation mechanism, roles, and therapeutic strategies of ETs released by neutrophils, eosinophils, and macrophages in asthma.