A GPVI-platelet-neutrophil-NET axis drives systemic sclerosis.

Systemic sclerosis (SSc) is characterized by progressive fibrosis of skin, lung, and other organs and retains among the highest rates of mortality among autoimmune diseases. We identified activation of circulating neutrophils from patients with diffuse SSc, together with concordant transcriptomic evidence of neutrophil activation in blood, skin, and lungs, and in mice with experimental SSc of skin and lung induced by hypochlorous acid or bleomycin. Neutrophil depletion abrogated experimental SSc, while adoptive transfer of SSc neutrophils induced skin and lung fibrosis in healthy mice, identifying neutrophils as both necessary and sufficient for disease.

Sex-specific NLRP3 activation in neutrophils promotes neutrophil recruitment and NETosis in the murine model of diffuse alveolar hemorrhage.

Objectives: Diffuse alveolar hemorrhage (DAH) is a life-threatening complication of systemic lupus erythematosus and small vessel vasculitis. We previously showed that neutrophil extracellular traps (NETs) were associated with the pathogenesis of pristane-induced DAH and demonstrated that neutrophil NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome assembly participated in NET generation under sterile stimulation. We investigated whether NLRP3 inflammasome assembly in neutrophils may drive pulmonary NETosis in a mouse model of pristane-induced DAH.

Neutrophil NLRP3 promotes cardiac injury following acute myocardial infarction through IL-1β production, VWF release and NET deposition in the myocardium.

NLRP3 inflammasome has been implicated in neutrophil polarization and extrusion of neutrophil extracellular traps (NETs) in vitro and facilitates secretion of Il1-beta (IL-1β). Permanent ligation of the left anterior descending artery was used to induce MI in WT and NLRP3 mice as well as in NLRP3 recipient mice transfused with either WT or NLRP3 neutrophils. NLRP3 deficiency reduced infarct size to roughly a third of WT heart injury and preserved left ventricular (LV) function at 12 h after MI as assessed by echocardiography and triphenyltetrazolium chloride staining of live tissue.

Neutrophil peptidylarginine deiminase 4 plays a systemic role in obesity-induced chronic inflammation in mice.

Background: Obesity is an increasing problem in our current society and is expected to keep rising in incidence. With its multiorigin, complex pathophysiology, it is difficult to treat and easy to acquire unnoticeably. During obesity, it has been established that the body is in a constant state of low-grade inflammation, thereby causing changes in immune cell physiology.

NLRP3 is essential for neutrophil polarization and chemotaxis in response to leukotriene B4 gradient.

Neutrophil recruitment to sites of infection and inflammation is an essential process in the early innate immune response. Upon activation, a subset of neutrophils rapidly assembles the multiprotein complex known as the NLRP3 inflammasome. The NLRP3 inflammasome forms at the microtubule organizing center, which promotes the formation of interleukin (IL)-1β and IL-18, essential cytokines in the immune response.

Inhibition of protein arginine deiminase 4 prevents inflammation-mediated heart failure in arthritis.

Rheumatoid arthritis is a prototypic inflammatory condition with affected patients being at greater risk of incident heart failure (HF). Targeting innate immune cell function in the pathogenesis of HF bears the potential to guide the development of future therapies. A collagen-induced arthritis (CIA) model in DBA/1 J mice was used to generate arthritis.

Alleviation of arthritis through prevention of neutrophil extracellular traps by an orally available inhibitor of protein arginine deiminase 4.

Protein arginine deiminases (PAD) 4 is an enzyme that catalyzes citrullination of protein and its role in autoimmune diseases has been established through clinical genetics and gene knock out studies in mice. Further, studies with PAD4 - deficient mice have shown that PAD4 deficiency does not lead to increased infection or immune suppression, which makes PAD4 an attractive therapeutic target for auto-immune and inflammatory diseases. PAD4 has critical enzymatic role of promoting chromatin decondensation and neutrophil extracellular traps (NETs) formation that is associated with a number of immune-mediated pathological conditions.

NLRP3 inflammasome activation in neutrophils directs early inflammatory response in murine peritonitis.

NLR family pyrin domain containing 3 (NLRP3) inflammasome mediates caspase-1-dependent processing of inflammatory cytokines such as IL-1β, an essential endothelial activator, and contributes to the pathology of inflammatory diseases. To evaluate the role of NLRP3 in neutrophils in endothelial activation, which is still elusive, we used the thioglycollate-induced peritonitis model characterized by an early neutrophil influx, on Nlrp3 and Nlrp3 mice. Nlrp3 mice recruited fewer neutrophils than Nlrp3 into the peritoneum and showed lower IL-1β in peritoneal lavage fluid.

Anti-inflammatory protective effect of ADAMTS-13 in murine arthritis models.

Background: Patients with rheumatoid arthritis (RA) have frequent thrombotic events with endothelial dysfunction. Von Willebrand factor (VWF) has been shown to bind neutrophil extracellular traps (NETs) and NETs are part of RA etiology.

Objectives: This study aims to elucidate whether this prothrombotic status exacerbates inflammation in arthritis.

Thromboinflammation: From Atherosclerosis to COVID-19.

The activating interplay of thrombosis and inflammation (thromboinflammation) has been established as a major underlying pathway, driving not only cardiovascular disease but also autoimmune disease and most recently, COVID-19. Throughout the years, innate immune cells have emerged as important modulators of this process. As the most abundant white blood cell in humans, neutrophils are well-positioned to propel thromboinflammation.

Neutrophil phenotypes and functions in cancer: A consensus statement.

Neutrophils are the first responders to infection and inflammation and are thus a critical component of innate immune defense. Understanding the behavior of neutrophils as they act within various inflammatory contexts has provided insights into their role in sterile and infectious diseases; however, the field of neutrophils in cancer is comparatively young. Here, we summarize key concepts and current knowledge gaps related to the diverse roles of neutrophils throughout cancer progression.

The Prominent Role of Hematopoietic Peptidyl Arginine Deiminase 4 in Arthritis: Collagen- and Granulocyte Colony-Stimulating Factor-Induced Arthritis Model in C57BL/6 Mice.

Objective: Genome-wide association studies have connected PADI4, encoding peptidylarginine deiminase 4 (PAD4), with rheumatoid arthritis (RA). PAD4 promotes neutrophil extracellular trap (NET) formation. This study was undertaken to investigate the origin of PAD4 and the importance of NET formation in a C57BL/6 mouse model of arthritis.

Inflammasome activation in neutrophils of patients with severe COVID-19.

Infection by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) engages the inflammasome in monocytes and macrophages and leads to the cytokine storm in COVID-19. Neutrophils, the most abundant leukocytes, release neutrophil extracellular traps (NETs), which have been implicated in the pathogenesis of COVID-19. Our recent study shows that activation of the NLRP3 inflammasome is important for NET release in sterile inflammation.

NLRP3 Inflammasome Assembly in Neutrophils Is Supported by PAD4 and Promotes NETosis Under Sterile Conditions.

Neutrophil extracellular trap formation (NETosis) and the NLR family pyrin domain containing 3 (NLRP3) inflammasome assembly are associated with a similar spectrum of human disorders. While NETosis is known to be regulated by peptidylarginine deiminase 4 (PAD4), the role of the NLRP3 inflammasome in NETosis was not addressed. Here, we establish that under sterile conditions the cannonical NLRP3 inflammasome participates in NETosis.

Neutrophil stimulation with citrullinated histone H4 slows down calcium influx and reduces NET formation compared with native histone H4.

Peptidylarginine deiminase 4 (PAD4) catalyzes posttranslational modification of many target proteins through converting protein arginine or mono-methylarginine to citrulline. Neutrophil extracellular trap (NET) formation is the most dramatic manifestation of PAD4-mediated hypercitrullination reaction in neutrophils, which is characterized by the release of nuclear chromatin to form a chromatin network in the extracellular space. Histones H4, one of the major protein components of chromatin, is released into the extracellular space during sepsis, trauma, and ischemia-reperfusion injury and can also be released during the process of NET formation, along with its citrullinated form.

The role of platelets in thrombus fibrosis and vessel wall remodeling after venous thrombosis.

Purpose: Platelets are known to play an important role in venous thrombogenesis, but their role in thrombus maturation, resolution, and postthrombotic vein wall remodeling is unclear. The purpose of this study was to determine the role that circulating platelets play in the later phases of venous thrombosis.

Methods: We used a murine inferior vena cava (IVC) stenosis model.

Cellular Mechanisms of NETosis.

Neutrophils are critical to innate immunity, including host defense against bacterial and fungal infections. They achieve their host defense role by phagocytosing pathogens, secreting their granules full of cytotoxic enzymes, or expelling neutrophil extracellular traps (NETs) during the process of NETosis. NETs are weblike DNA structures decorated with histones and antimicrobial proteins released by activated neutrophils.

NETosis proceeds by cytoskeleton and endomembrane disassembly and PAD4-mediated chromatin decondensation and nuclear envelope rupture.

Neutrophil extracellular traps (NETs) are web-like DNA structures decorated with histones and cytotoxic proteins that are released by activated neutrophils to trap and neutralize pathogens during the innate immune response, but also form in and exacerbate sterile inflammation. Peptidylarginine deiminase 4 (PAD4) citrullinates histones and is required for NET formation (NETosis) in mouse neutrophils. While the in vivo impact of NETs is accumulating, the cellular events driving NETosis and the role of PAD4 in these events are unclear.

Recombinant human ADAMTS13 treatment and anti-NET strategies enhance skin allograft survival in mice.

Enhancing skin allograft longevity lessens the need for new allografts before optimal intervention is available. Reduced activity of ADAMTS13 (an enzyme that cleaves the pro-thrombotic and proinflammatory von Willebrand factor) and presence of neutrophil extracellular traps (NETs) have been implicated in liver and lung allograft failures. The effect of ADAMTS13 treatment and the impact of NETs on skin allografts, however, remain unexplored.

Extracellular DNA NET-Works With Dire Consequences for Health.

Neutrophils play a central role in innate immune defense. Advances in neutrophil biology have brought to light the capacity of neutrophils to release their decondensed chromatin and form large extracellular DNA networks called neutrophil extracellular traps (NETs). NETs are produced in response to many infectious and noninfectious stimuli and, together with fibrin, block the invasion of pathogens.

Resolvin D4 attenuates the severity of pathological thrombosis in mice.

Deep vein thrombosis (DVT) is a common cardiovascular disease with a major effect on quality of life, and safe and effective therapeutic measures to efficiently reduce existent thrombus burden are scarce. Using a comprehensive targeted liquid chromatography-tandem mass spectrometry-based metabololipidomics approach, we established temporal clusters of endogenously biosynthesized specialized proresolving mediators (SPMs) and proinflammatory and prothrombotic lipid mediators during DVT progression in mice. Administration of resolvin D4 (RvD4), an SPM that was enriched at the natural onset of thrombus resolution, significantly reduced thrombus burden, with significantly less neutrophil infiltration and more proresolving monocytes in the thrombus, as well as an increased number of cells in an early apoptosis state.

Plasma Peptidylarginine Deiminase IV Promotes VWF-Platelet String Formation and Accelerates Thrombosis After Vessel Injury.

Rationale: PAD4 (peptidylarginine deiminase type IV), an enzyme essential for neutrophil extracellular trap formation (NETosis), is released together with neutrophil extracellular traps into the extracellular milieu. It citrullinates histones and holds the potential to citrullinate other protein targets. While NETosis is implicated in thrombosis, the impact of the released PAD4 is unknown.