Neutrophil extracellular traps: is immunity the second function of chromatin?

Mechanisms of toxicity mediated by neutrophil and eosinophil granule proteins

Neutrophils and eosinophils are granulocytes which are characterized by the presence of granules in the cytoplasm. Granules provide a safe storage site for granule proteins that play important roles in the immune function of granulocytes. Upon granulocytes activation, diverse proteins are released from the granules into the extracellular space and contribute to the fight against infections. In this article, we describe granule proteins of both neutrophils and eosinophils able to kill pathogens and review their anticipated mechanism of antimicrobial toxicity. It should be noted that an excess of granules protein release can lead to tissue damage of the host resulting in chronic inflammation and organ dysfunction.

Tetrachlorobenzoquinone exhibits immunotoxicity by inducing neutrophil extracellular traps through a mechanism involving ROS-JNK-NOX2 positive feedback loop

Tetrachlorobenzoquinone (TCBQ) is a common metabolite of persistent organic pollutants pentachlorophenol (PCP) and hexachlorobenzene (HCB). Current reports on the toxicity of TCBQmainly focused on its reproductive toxicity, neurotoxicity, carcinogenicity and cardiovascular toxicity. However, the possible immunotoxicity of TCBQ remains unclear. The release of neutrophil extracellular traps (NETs) is a recently discovered immune response mechanism, however, excess NETs play a pathogenic role in various immune diseases. In an attempt to address concerns regarding the immunotoxicity of TCBQ, we adopted primary mouse neutrophils as the research object, explored the influence of TCBQ on the formation of NETs. The results showed that TCBQ could induce NETs rapidly in a reactive oxygen species (ROS)-dependent manner. Moreover, TCBQ promoted the phosphorylation of c-Jun N-terminal kinase (JNK) mitogen activated protein kinase (MAPK), but not p38 or extracellular signal related kinase (ERK) in neutrophils. Mechanistically, JNK activation enhanced the expression of NADPH oxidase enzyme 2 (NOX2), which further accelerated the generation of ROS and thus amplified the formation of NETs. The pharmacologic blockage of JNK or NOX2 effectively ameliorated TCBQ-induced ROS and NETs, implying that ROS-JNK-NOX2 positive feedback loop was involved in TCBQ-induced NETs. In conclusion, we speculated that targeting NETs formation would be a promising therapeutic strategy in modulating the immunotoxicity of TCBQ.

Neutrophils phagocytosing fungal hyphae in urinary sediment

The Phagocytosis of fungal structures by neutrophils is a well-documented function of these immune cells. However, neutrophil phagocytosis of hyphal structures in the urine sediment is not usually observed during routine sample evaluation. This is a case of hyphal phagocytosis by neutrophils in the urine of a kidney allograft recipient patient.

Neutrophils Return to Bloodstream Through the Brain Blood Vessel After Crosstalk With Microglia During LPS-Induced Neuroinflammation

The circulatory neutrophil and brain tissue-resident microglia are two important immune cells involved in neuroinflammation. Since neutrophils that infiltrate through the brain vascular vessel may affect the immune function of microglia in the brain, close investigation of the interaction between these cells is important in understanding neuroinflammatory phenomena and immunological aftermaths that follow. This study aimed to observe how morphology and function of both neutrophils and microglia are converted in the inflamed brain. To directly investigate cellular responses of neutrophils and microglia, LysM^GFP/+ and CX₃CR1^GFP/+ mice were used for the observation of neutrophils and microglia, respectively. In addition, low-dose lipopolysaccharide (LPS) was utilized to induce acute inflammation in the central nervous system (CNS) of mice. Real-time observation on mice brain undergoing neuroinflammation via two-photon intravital microscopy revealed various changes in neutrophils and microglia; namely, neutrophil infiltration and movement within the brain tissue increased, while microglia displayed morphological changes suggesting an activated state. Furthermore, neutrophils seemed to not only actively interact with microglial processes but also exhibit reverse transendothelial migration (rTEM) back to the bloodstream. Thus, it may be postulated that, through crosstalk with neutrophils, macrophages are primed to initiate a neuroinflammatory immune response; also, during pathogenic events in the brain, neutrophils that engage in rTEM may deliver proinflammatory signals to peripheral organs outside the brain. Taken together, these results both show that neuroinflammation results in significant alterations in neutrophils and microglia and lay the pavement for further studies on the molecular mechanisms behind such changes.

Neutrophil and Neutrophil-to-Lymphocyte Ratio as Clinically Predictive Risk Markers for Recurrent Pregnancy Loss

We aimed at exploring the value of neutrophil and neutrophil-to-lymphocyte ratio (NLR) as predictive risk markers for recurrent pregnancy loss (RPL) by conducting a retrospective case-control study and a systematic review and meta-analysis. This retrospective case-control study was conducted in an academic hospital from January 2012 to June 2018 and 133 cases of women with RPL and 140 control women. In parallel, we conducted a systematic review and meta-analysis on the value of NLR and neutrophil in RPL risk assessment. Neutrophil and NLR were higher in the women with RPL than those in the controls (median [interquartile range]: 4.32 [3.31-6.18] vs. 3.76 [2.78-4.81], p = 0.001; 2.17 [1.47-3.16] vs. 1.74 [1.40-2.34], p = 0.001). After the cut-off value of the neutrophil and NLR was determined to be 6.3 × 10⁹/L and 3.16, the prevalence of RPL became significantly increased in the high-neutrophil and the high-NLR group compared to the low-neutrophil and the low-NLR group (76.3% vs. 44.2%, p < 0.001; 66.6% vs. 44.5%, p < 0.001). Univariate logistic regression analysis indicated that high-neutrophil and high-NLR were risk factors for RPL, with ORs of 4.06 (95% CI: 1.84-8.95) and 2.49 (95% CI: 1.31-4.71), respectively. Multivariate logistic regression analysis indicated that high-neutrophil was a risk factor for RPL, with OR of 4.91 (95% CI: 1.66-14.50). Meta-analysis of 5 case-control studies (including the present study) indicated that increased neutrophil and NLR may be risk factors for RPL, with SMDs of 0.63 (95% CI: 0.45-0.80) and 0.61 (95% CI: 0.39-0.83). Based on current findings and the meta-analysis, this study indicated that neutrophil and NLR might be valuable for predicting RPL; more studies with large sample are needed to verify this conclusion. The mechanism of the association between neutrophil and RPL needs to be explored in further studies.

Targeting neutrophil extracellular traps in severe acute pancreatitis treatment

Severe acute pancreatitis (SAP) is a critical abdominal disease associated with high death rates. A systemic inflammatory response promotes disease progression, resulting in multiple organ dysfunction. The functions of neutrophils in the pathology of SAP have been presumed traditionally to be activation of chemokine and cytokine cascades accompanying the inflammatory process. Recently, since their discovery, a new type of antimicrobial mechanism, neutrophil extracellular traps (NETs), and their role in SAP, has attracted widespread attention from the scientific community. Significantly different from phagocytosis and degranulation, NETs kill extracellular microorganisms by releasing DNA fibers decorated with granular proteins. In addition to their strong antimicrobial functions, NETs participate in the pathophysiological process of many noninfectious diseases. In SAP, NETs injure normal tissues under inflammatory stress, which is associated with the activation of inflammatory cells, to cause an inflammatory cascade, and SAP products also trigger NET formation. Thus, due to the interaction between NET generation and SAP, a treatment targeting NETs might become a key point in SAP therapy. In this review, we summarize the mechanism of NETs in protecting the host from pathogen invasion, the stimulus that triggers NET formation, organ injury associated with SAP involving NETs, methods to interrupt the harmful effects of NETs, and different therapeutic strategies to preserve the organ function of patients with SAP by targeting NETs.

Quantification of Citrullinated Histone H3 Bound DNA for Detection of Neutrophil Extracellular Traps

Formation of neutrophil extracellular traps (NETs) has been associated with multiple pathologies including cancer. While the visualization of NETs by microscopy is a routine technique, their quantification presents a number of challenges. Commonly, as citrullination of histone H3 is required for NET formation, the presence of this modified histone along with DNA is considered to be a hallmark of NETs. Here, we describe and validate a novel assay for the quantification of NETs based on the detection of citrullinated histone H3 bound to DNA (CitH3DNA binding assay). Using this assay, we investigated the effect of phorbol 12-myristate 13-acetate (PMA) on NET formation by neutrophils isolated from the bone marrow of control and myeloma-bearing mice. We found that PMA induced citrullination of histone H3, an increase in the level of CitH3DNA, and NET formation in neutrophils from both tumor-free and myeloma-bearing mice. The levels of CitH3DNA in the NET fractions, as measured by our assay, directly correlated with the citrullination of histone H3 in neutrophils, as detected by Western blotting, and were significantly higher in PMA-stimulated compared to unstimulated neutrophils. Neutrophils from tumor-bearing mice produced more NETs than those from tumor-free counterparts following stimulation with PMA. The increase in NET production correlated with significantly higher histone H3 citrullination levels and increased measurements of CitH3DNA. Thus, our data indicate that bone marrow neutrophils from myeloma-bearing hosts are prone to NET formation.

Eimeria ninakohlyakimovae casts NOX-independent NETosis and induces enhanced IL-12, TNF-α, IL-6, CCL2 and iNOS gene transcription in caprine PMN

Eimeria ninakohlyakimovae represents a highly pathogenic coccidian parasite causing severe haemorrhagic typhlocolitis in goat kids worldwide. NETosis was recently described as an efficient defense mechanism of polymorphonuclear neutrophils (PMN) acting against different parasites in vitro and in vivo. In vitro interactions of caprine PMN with parasitic stages of E. ninakohlyakimovae (i. e. oocysts and sporozoites) as well as soluble oocyst antigens (SOA) were analyzed at different ratios, concentrations and time spans. Extracellular DNA staining was used to illustrate classical molecules induced during caprine NETosis [i. e. histones (H3) and neutrophil elastase (NE)] via antibody-based immunofluorescence analyses. Functional inhibitor treatments with DPI and DNase I were applied to unveil role of NADPH oxidase (NOX) and characterize DNA-backbone composition of E. ninakohlyakimovae-triggered caprine NETosis. Scanning electron microscopy (SEM)- and immunofluorescence-analyses demonstrated that caprine PMN underwent NETosis upon contact with sporozoites and oocysts of E. ninakohlyakimovae, ensnaring filaments which firmly entrapped parasites. Detailed co-localization studies of E. ninakohlyakimovae-induced caprine NETosis revealed presence of PMN-derived DNA being adorned with nuclear H3 and NE corroborating molecular characteristics of NETosis. E. ninakohlyakoimovae-induced caprine NETosis was found to be NOX-independent since DPI inhibition led to a slight decrease of NETosis. Exposure of caprine PMN to vital E. ninakohlyakimovae sporozoites as well as SOA resulted in up-regulation of IL-12, TNF-α, IL-6, CCL2 and iNOS gene transcription in stimulated PMN. Since vital E. ninakohlyakimovae-sporozoites induced caprine NETosis, this effective entrapment mechanism might reduce initial sporozoite epithelial host cell invasion during goat coccidiosis ultimately resulting in less macromeront formation and reduced merozoites I production.

Changes in serum citrullinated fibrinogen concentration associated with the phase of bacteremia patients

BACKGROUND

Citrullinated fibrinogen (C-Fbg) has been detected in rheumatoid arthritis; however, few studies have reported the role of C-Fbg in other inflammatory diseases. This study aimed to clarify the changes in serum C-Fbg associated with the bacteremia phase.

METHODS

We measured serum C-Fbg concentration in bacteremia patients. C-Fbg levels at each phase of bacteremia, classified by white blood cell (WBC) count and neutrophil left shift change, were compared with those of healthy control (HC). The correlation between C-Fbg concentration and certain inflammatory markers, or citrullinated histone H3 concentration was assessed. Multiple linear regression (MLR) analysis was used to examine the association of log C-Fbg with certain inflammatory markers.

RESULT

Serum C-Fbg levels were significantly higher in bacteremia patients than in HC (p < 0.001) and positively correlated with WBC and neutrophil count. Further, C-Fbg levels were significantly higher in phases III and IV of bacteremia than in HC (p < 0.001). MLR analysis indicated that log C-Fbg had a stronger relationship with log neutrophil counts than other certain inflammatory markers (p < 0.01).

CONCLUSION

Serum C-Fbg levels increased in bacteremia patients, and this was consistent with an influx of neutrophils into the blood stream in accordance with the bacteremia phase.

Pathogenesis of Human Immunodeficiency Virus-Mycobacterium tuberculosis Co-Infection

Given that infection with Mycobacterium tuberculosis (Mtb) is the leading cause of death amongst individuals living with HIV, understanding the complex mechanisms by which Mtb exacerbates HIV infection may lead to improved treatment options or adjuvant therapies. While it is well-understood how HIV compromises the immune system and leaves the host vulnerable to opportunistic infections such as Mtb, less is known about the interplay of disease once active Mtb is established. This review explores how glutathione (GSH) depletion, T cell exhaustion, granuloma formation, and TNF-α upregulation, as a result of Mtb infection, leads to an increase in HIV disease severity. This review also examines the difficulties of treating coinfected patients and suggests further research on the clinical use of GSH supplementation.

Inorganic arsenic administration suppresses human neutrophil function in vitro

Arsenic, a major environmental toxicant and pollutant, is a global public health concern. Among its many adverse effects, arsenic is immunotoxic, but its effects on human neutrophil functions are not yet well-defined. In this study, we aimed to evaluate the in vitro effects of acute low-dose NaAsO₂ exposure on human polymorphonuclear neutrophils (PMNs) for 12 h on the following innate defense mechanisms: formation of neutrophil extracellular traps (NETs), production of reactive oxygen species (ROS), and phagocytosis. Phorbol myristate acetate (PMA) was added to induce NETs formation, which was quantified by measuring cell-free extracellular DNA (cf-DNA), myeloperoxidase-conjugated (MPO)-DNA and neutrophil elastase-conjugated (NE)-DNA, and confirmed by immunofluorescence labeling and imaging. Extracellular bactericidal activity by NETs was evaluated by co-culturing Escherichia coli and PMNs in the presence of a phagocytic inhibitor. Levels of NETs in the culture medium after PMA stimulation was significantly lower in PMNs pre-exposed to arsenic than those not exposed to arsenic. Immunofluorescence staining and extracellular bactericidal activity by NETs revealed similar results. Phagocytosis and ROS production by PMNs were also significantly reduced by arsenic pre-exposure. Together, our findings provide new insights in arsenic immunotoxicity and suggest how it increases susceptibility to infectious diseases in humans.

Human CD8+ T Cells Release Extracellular Traps Co-Localized With Cytotoxic Vesicles That Are Associated With Lesion Progression and Severity in Human Leishmaniasis

Cell death plays a fundamental role in mounting protective and pathogenic immunity. Etosis is a cell death mechanism defined by the release of extracellular traps (ETs), which can foster inflammation and exert microbicidal activity. While etosis is often associated with innate cells, recent studies showed that B cells and CD4+ T cells can release ETs. Here we investigate whether CD8+ T cells can also release ETs, which might be related to cytotoxicity and tissue pathology. To these ends, we first employed an in vitro system stimulating human CD8+ T cells isolated from healthy volunteers with anti-CD3/anti-CD28. Using time-frame video, confocal and electron microscopy, we demonstrate that human CD8+ T cells release ETs upon stimulation (herein LETs – lymphocyte extracellular traps), which display unique morphology and functional characteristics. CD8+ T cell-derived LETs form long strands that co-localize with CD107a, a marker of vesicles containing cytotoxic granules. In addition, these structures connect the LET-releasing cell to other neighboring cells, often resulting in cell death. After demonstrating the release of LETs by human CD8+ T cells in vitro, we went on to study the occurrence of CD8-derived LETs in a human disease setting. Thus, we evaluated the occurrence of CD8-derived LETs in lesions from patients with human tegumentary leishmaniasis, where CD8+ T cells play a key role in mediating pathology. In addition, we evaluated the association of these structures with the intensity of the inflammatory infiltrate in early and late cutaneous, as well as in mucosal leishmaniasis lesions. We demonstrated that progression and severity of debilitating and mutilating forms of human tegumentary leishmaniasis are associated with the frequency of CD8+ T cells in etosis, as well as the occurrence of CD8-derived LETs carrying CD107a+ vesicles in the lesions. We propose that CD8+ T cell derived LETs may serve as a tool for delivering cytotoxic vesicles to distant target cells, providing insights into mechanisms of CD8+ T cell mediated pathology.

Danger signals in liver injury and restoration of homeostasis

Damage-associated molecular patterns are signalling molecules involved in inflammatory responses and restoration of homeostasis. Chronic release of these molecules can also promote inflammation in the context of liver disease. Herein, we provide a comprehensive summary of the role of damage-associated molecular patterns as danger signals in liver injury. We consider the role of reactive oxygen species and reactive nitrogen species as inducers of damage-associated molecular patterns, as well as how specific damage-associated molecular patterns participate in the pathogenesis of chronic liver diseases such as alcohol-related liver disease, non-alcoholic steatohepatitis, liver fibrosis and liver cancer. In addition, we discuss the role of damage-associated molecular patterns in ischaemia reperfusion injury and liver transplantation and highlight current studies in which blockade of specific damage-associated molecular patterns has proven beneficial in humans and mice.

Hookworms Evade Host Immunity by Secreting a Deoxyribonuclease to Degrade Neutrophil Extracellular Traps

Hookworms cause a major neglected tropical disease, occurring after larvae penetrate the host skin. Neutrophils are phagocytes that kill large pathogens by releasing neutrophil extracellular traps (NETs), but whether they target hookworms during skin infection is unknown. Using a murine hookworm, Nippostrongylus brasiliensis, we observed neutrophils being rapidly recruited and deploying NETs around skin-penetrating larvae. Neutrophils depletion or NET inhibition altered larvae behavior and enhanced the number of adult worms following murine infection. Nevertheless, larvae were able to mitigate the effect of NETs by secreting a deoxyribonuclease (Nb-DNase II) to degrade the DNA backbone. Critically, neutrophils were able to kill larvae in vitro, which was enhanced by neutralizing Nb-DNase II. Homologs of Nb-DNase II are present in other nematodes, including the human hookworm, Necator americanus, which also evaded NETs in vitro. These findings highlight the importance of neutrophils in hookworm infection and a potential conserved mechanism of immune evasion.

Cannabidiol Modifies the Formation of NETs in Neutrophils of Psoriatic Patients

Psoriasis is associated with increased production of reactive oxygen species which leads to oxidative stress. As antioxidants can provide protection, the aim of this study was to evaluate the effects of cannabidiol (CBD) on neutrophil extracellular trap (NET) formation in psoriatic and healthy neutrophils. Important markers of NETosis were measured in healthy and psoriatic neutrophils after incubation with CBD, lipopolysaccharide (LPS), and LPS + CBD). The percentage of neutrophils undergoing NETosis and the level of NETosis markers (cfDNA, MPO, elastase) were higher in the neutrophils and blood plasma of psoriatic patients, compared to controls. After LPS treatment, all of the markers of NETosis, except elastase, and p47 and citrullinated histones, were increased in samples from healthy subjects and psoriasis patients. CBD reduced the concentrations of NETosis markers. This led to a reduction in NETosis, which was more pronounced in psoriatic neutrophils and neutrophils treated with LPS in both psoriatic and healthy participants. These results suggest that psoriatic patients neutrophils are at a higher risk of NETosis both in vitro and in vivo. CBD reduces NETosis, mainly in psoriatic neutrophils, possibly due to its antioxidant properties. The anti-NET properties of CBD suggest the positive effect of CBD in the treatment of autoimmune diseases.

The Emerging Role of Neutrophil Extracellular Traps (NETs) in Tumor Progression and Metastasis

Neutrophil Extracellular Traps (NETs) are net-like structures composed of DNA-histone complexes and proteins released by activated neutrophils. In addition to their key role in the neutrophil innate immune response, NETs are also involved in autoimmune diseases, like systemic lupus erythematosus, rheumatoid arthritis, psoriasis, and in other non-infectious pathological processes, as coagulation disorders, thrombosis, diabetes, atherosclerosis, vasculitis, and cancer. Recently, a large body of evidence indicates that NETs are involved in cancer progression and metastatic dissemination, both in animal models and cancer patients. Interestingly, a close correlation between cancer cell recruitment of neutrophils in the tumor microenvironment (Tumor Associated Neutrophils. TANs) and NET formation has been also observed either in primary tumors and metastatic sites. Moreover, NETs can also catch circulating cancer cells and promote metastasis. Furthermore, it has been reported that wake dormant cancer cells, causing tumor relapse and metastasis. This review will primarily focus on the pro-tumorigenic activity of NETs in tumors highlighting their ability to serve as a potential target for cancer therapy.

Blockade of CXCR2 suppresses proinflammatory activities of neutrophils in ulcerative colitis

Ulcerative colitis (UC) is one chronically remittent and progressive inflammatory disorder. Chemokine receptor CXCR2 is reported to be involved in the pathogenesis of several inflammatory diseases. However, how CXCR2 modulate mucosal inflammation in UC is still obscure. In this study, CXCR2 expression was determined in inflamed mucosa and peripheral blood cells from patients with UC by qRT-PCR. Neutrophils isolated from peripheral blood were pretreated with CXCR2 inhibitor (SB225002), and proinflammatory mediators were examined by qRT-PCR, ELISA and IF. The migratory capacity of neutrophils after SB225002 treatment was examined by using Transwell plate. Furthermore, SB225002 was administrated daily in DSS-induced colitis mice. We found that CXCR2 expression was significantly increased in colonic mucosal tissues and peripheral blood cells from patients with active UC. Besides, CXCR2 was highly expressed in neutrophils, and was positively correlated with disease activity. Inhibition of CXCR2 in neutrophils decreased the production of proinflammatory mediators, such as reactive oxygen species (ROS), MPO, S100a8, S100a9, TNF-α, IL-1β, IL-8 and IL-6, and the migratory capacity of neutrophils was markedly impaired after SB225002 treatment. Moreover, blockade of CXCR2 with SB225002 could markedly ameliorate DSS-induced colitis in mice. In summary, CXCR2 plays a critical role in the pathogenesis of UC through modulating immune responses of neutrophils. Blockade of CXCR2 may serve as a new therapeutic approach for treatment of UC.

Autoantibody-dependent amplification of inflammation in SLE

Anti-double stranded DNA antibodies (anti-dsDNA) are a hallmark of SLE but their role in disease pathogenesis is not fully resolved. Anti-dsDNA in serum are highly heterogeneous therefore in this study, we aimed to dissect the functional specificities of anti-dsDNA using a panel of human monoclonal antibodies (humAbs) generated from patients with active lupus nephritis. A total of 46 ANA reactive humAbs were isolated and divided into four broad classes based on their reactivity to histones, DNA and Crithidia. Functional analysis indicated that one subclass of antibodies bound strongly to decondensed DNA areas in neutrophil extracellular traps (NETs) and protected NETs from nuclease digestion, similar to the sera from active SLE patients. In addition, these anti-dsDNA antibodies could stimulate type I interferon responses in mononuclear phagocytic cells, or NF-kB activity in endothelial cells, by uptake of NETs-anti-NETs immune complexes and subsequently trigging inflammatory responses in an Fc-gamma receptor (Fcg-R)-dependant manner. Together our data suggest that only a subset of anti-dsDNA antibodies is capable to amplify inflammatory responses by deposit in the nephritic kidney in vivo, protecting NETs digestion as well as uptake of NETs immune complexes into Fcg-R-expressing cells in vitro.

The relevance of pathophysiological alterations in redox signaling of 4-hydroxynonenal for pharmacological therapies of major stress-associated diseases

Modern analytical methods combined with the modern concepts of redox signaling revealed 4-hydroxy-2-nonenal (4-HNE) as particular growth regulating factor involved in redox signaling under physiological and pathophysiological circumstances. In this review current knowledge of the relevance of 4-HNE as "the second messenger of reactive oxygen species" (ROS) in redox signaling of representative major stress-associated diseases is briefly summarized. The findings presented allow for 4-HNE to be considered not only as second messenger of ROS, but also as one of fundamental factors of the stress- and age-associated diseases. While standard, even modern concepts of molecular medicine and respective therapies in majority of these diseases target mostly the disease-specific symptoms. 4-HNE, especially its protein adducts, might appear to be the bioactive markers that would allow better monitoring of specific pathophysiological processes reflecting their complexity. Eventually that could help development of advanced integrative medicine approach for patients and the diseases they suffer from on the personalized basis implementing biomedical remedies that would optimize beneficial effects of ROS and 4-HNE to prevent the onset and progression of the illness, perhaps even providing the real cure.

A Higher Abundance of O-Linked Glycans Confers a Selective Advantage to High Fertile Buffalo Spermatozoa for Immune-Evasion From Neutrophils

The glycans on the plasma membrane of cells manifest as the glycocalyx, which serves as an information-rich frontier that is directly in contact with its immediate milieu. The glycoconjugates (GCs) that adorn most of the mammalian cells are also abundant in gametes, especially the spermatozoa where they perform unique reproduction-specific functions e.g., inter-cellular recognition and communication. This study aimed to implicate the sperm glycosylation pattern as one of the factors responsible for low conception rates observed in buffalo bulls. We hypothesized that a differential abundance of glycans exists on the spermatozoa from bulls of contrasting fertilizing abilities endowing them with differential immune evasion abilities. Therefore, we investigated the role of glycan abundance in the phagocytosis and NETosis rates exhibited by female neutrophils (PMNs) upon exposure to such spermatozoa. Our results indicated that the spermatozoa from high fertile (HF) bulls possessed a higher abundance of O-linked glycans e.g., galactosyl (β-1,3)N-acetylgalactosamine and N-linked glycans like [GlcNAc]1-3, N-acetylglucosamine than the low fertile (LF) bull spermatozoa. This differential glycomic endowment appeared to affect the spermiophagy and NETosis rates exhibited by the female neutrophil cells (PMNs). The mean percentage of phagocytizing PMNs was significantly different (P < 0.0001) for HF and LF bulls, 28.44 and 59.59%, respectively. Furthermore, any introduced perturbations in the inherent sperm glycan arrangements promoted phagocytosis by PMNs. For example, after in vitro capacitation the mean phagocytosis rate (MPR) rate in spermatozoa from HF bulls significantly increased to 66.49% (P < 0.01). Likewise, the MPR increased to 70.63% (p < 0.01) after O-glycosidase & α2-3,6,8,9 Neuraminidase A treatment of spermatozoa from HF bulls. Moreover, the percentage of PMNs forming neutrophil extracellular traps (NETs) was significantly higher, 41.47% when exposed to spermatozoa from LF bulls vis-à-vis the spermatozoa from HF bulls, 15.46% (P < 0.0001). This is a pioneer report specifically demonstrating the role of O-linked glycans in the immune responses mounted against spermatozoa. Nevertheless, further studies are warranted to provide the measures to diagnose the sub-fertile phenotype thus preventing the losses incurred by incorrect selection of morphologically normal sperm in the AI/IVF reproduction techniques.

Mammalian histones facilitate antimicrobial synergy by disrupting the bacterial proton gradient and chromosome organization

First proposed as antimicrobial agents, histones were later recognized for their role in condensing chromosomes. Histone antimicrobial activity has been reported in innate immune responses. However, how histones kill bacteria has remained elusive. The co-localization of histones with antimicrobial peptides (AMPs) in immune cells suggests that histones may be part of a larger antimicrobial mechanism in vivo. Here we report that histone H2A enters E. coli and S. aureus through membrane pores formed by the AMPs LL-37 and magainin-2. H2A enhances AMP-induced pores, depolarizes the bacterial membrane potential, and impairs membrane recovery. Inside the cytoplasm, H2A reorganizes bacterial chromosomal DNA and inhibits global transcription. Whereas bacteria recover from the pore-forming effects of LL-37, the concomitant effects of H2A and LL-37 are irrecoverable. Their combination constitutes a positive feedback loop that exponentially amplifies their antimicrobial activities, causing antimicrobial synergy. More generally, treatment with H2A and the pore-forming antibiotic polymyxin B completely eradicates bacterial growth.

A review of advances in the understanding of lupus nephritis pathogenesis as a basis for emerging therapies

Lupus nephritis is an important cause of both acute kidney injury and chronic kidney disease that can result in end-stage renal disease. Its pathogenic mechanisms are characterized by aberrant activation of both innate and adaptive immune responses, dysregulation of inflammatory signaling pathways, and increased cytokine production. Treatment of lupus nephritis remains a challenging issue in the management of systemic lupus erythematosus since the clinical presentation, response to treatment, and prognosis all vary considerably between patients and are influenced by ethnicity, gender, the degree of chronic kidney damage, pharmacogenomics, and non-immunological modulating factors. Elucidation of the various immunopathogenic pathways in lupus nephritis has resulted in the development of novel therapies, including biologics that target specific antigens on B lymphocytes to achieve B cell depletion, agents that modulate B cell proliferation and development, drugs that block co-stimulatory pathways, drugs that target T lymphocytes primarily, and therapies that target complement activation, signaling pathways, pro-inflammatory cytokines, and neutrophil extracellular traps. This review will discuss recent advances in the understanding of disease pathogenesis in lupus nephritis in the context of potential emerging therapies.

Citrullination of extracellular histone H3.1 reduces antibacterial activity and exacerbates its proteolytic degradation

BACKGROUND

Cystic fibrosis (CF), involves excessive airway accumulation of neutrophils, often in parallel with severe infection caused by Pseudomonas aeruginosa. Free histones are known to possess bactericidal properties, but the degree of antibacterial activity exerted on specific lung-based pathogens is largely unknown. Neutrophils have a high content of peptidyl deiminase 4 (PADI4), which citrullinate cationic peptidyl-arginines. In histone H3.1, several positions in the NH₂-terminal tail are subject to citrullination.

METHODS

Full-length and segmented histone subunit H3.1 was investigated for bactericidal activity towards P. aeruginosa (strain PAO1). PADI4-induced citrullination of histone H3.1 was assessed for antibacterial activity towards P. aeruginosa. Next, the effect of neutrophil elastase (NE)-mediated proteolysis of histone H3.1 was investigated. Finally, PADI4, H3.1, and citrullinated H3.1 were examined in healthy control and CF patient lung tissues.

RESULTS

Full-length histone H3.1 and sections of the histone H3.1 tail, displayed bactericidal activity towards P. aeruginosa. These antibacterial effects were reduced following citrullination by PADI4 or proteolysis by NE. Interestingly, citrullination of histone H3.1 exacerbated NE-mediated degradation. In CF lung tissue, citrullinated histone H3.1 and PADI4 immunoreactivity was abundant. Degraded histone H3.1 was detected in the sputum of CF patients but was absent in the sputum of healthy controls.

CONCLUSIONS

Citrullination impairs the antibacterial activity of histone H3.1 and exacerbates its proteolytic degradation by NE. Citrullination is likely to play an important role during resolution of acute inflammation. However, in chronic inflammation akin to CF, citrullination may dampen host defense and promote pathogen survival, as exemplified by P. aeruginosa.

Platelet adherence to cancer cells promotes escape from innate immune surveillance in cancer metastasis

The impacts of post‑operative abdominal infectious complications increase hematogenous distant metastasis and result in poor long‑term survival after curative resection. Even if curative resection can be performed, the presence of circulating tumor cells is affected. The liver, the most common site of metastases, is an important organ in innate immune surveillance. However, the molecular mechanisms of distant hematogenous metastasis are not yet fully known. Platelets are crucial components in the tumor microenvironment that function to promote tumor progression and metastasis. The purpose of this study was to identify the effect of platelets on escape from innate immune surveillance in post‑operative abdominal infectious complications. Platelet adherence was assessed by co‑culturing human pancreatic cancer cells including transforming growth factor (TGF‑β)‑treated BxPC‑3. CD44 isoform, transcription factors and epithelial‑mesenchymal transition markers were examined using western blotting. We also assessed whether cancer cells surrounded by activated platelets could escape from innate immune surveillance, using infectious and non‑infectious mouse models injected intraperitoneally with LPS. Platelets were found to preferentially adhere to mesenchymal cells rather than epithelial cells. BxPC‑3 epithelial cells showed upregulation of CD44‑variant and epithelial splicing regulatory protein 1 (ESRP‑1) expression. However, Panc‑1 mesenchymal cells and TGF‑β‑treated BxPC‑3 cells showed upregulation of CD44‑standard and zinc finger E‑box‑binding homeobox 1 (ZEB‑1) expression and a reduction in ESRP‑1. In the non‑infectious model, cancer cells were not found in the liver. In the infectious model, although epithelial cells without platelet adhesion were in an apoptotic state, mesenchymal cells showed many viable cancer cells surrounded by activated platelets. Cancer cells were suggested to have phenotypic plasticity through the switching of CD44 isoforms. Mesenchymal cells, which express CD44‑standard, could escape from immune surveillance by becoming surrounded by adhered activated platelets. Therefore, it may be necessary to administer antiplatelet agents to prevent distant hematogenous metastasis when post‑operative abdominal infectious complications occur.

Molecular interaction between methicillin-resistant Staphylococcus aureus (MRSA) and chicken breast reveals enhancement of pathogenesis and toxicity for food-borne outbreak

To study pathogenesis and toxicity of Staphylococcus aureus in foods, FORC_062 was isolated from a human blood sample and complete genome sequence has a type II SCCmec gene cluster and a type II toxin-antitoxin system, indicating an MRSA strain. Its mobile gene elements has many pathogenic genes involved in host infection, biofilm formation, and various enterotoxin and hemolysin genes. Clinical MRSA is often found in animal foods and ingestion of MRSA-contaminated foods causes human infection. Therefore, it is very important to understand the role of contaminated foods. To elucidate the interaction between clinical MRSA FORC_062 and raw chicken breast, transcriptome analysis was conducted, showing that gene expressions of amino acid biosynthesis and metabolism were specifically down-regulated, suggesting that the strain may import and utilize amino acids from the chicken breast, but not able to synthesize them. However, toxin gene expressions were up-regulated, suggesting that human infection of S. aureus via contaminated food may be more fatal. In addition, the contaminated foods enhance multiple-antibiotic resistance activities and virulence factors in this clinical MRSA. Consequently, MRSA-contaminated food may play a role as a nutritional reservoir as well as in enhancing factor for pathogenesis and toxicity of clinical MRSA for severe food-borne outbreaks.

Neutrophil Modulation in Alpha-1 Antitrypsin Deficiency

Neutrophils have been implicated in the pathogenesis of alpha-1 antitrypsin deficiency (AATD) since the first descriptions of the disease. Neutrophil proteinases can cause all lung manifestations of AATD, from small airways destruction, to emphysema, to chronic bronchitis and airflow obstruction. Initially, it was proposed that neutrophil functions were normal in AATD, responding in an initially physiological manner to a high burden of pulmonary inflammation. More recent studies have shed new light on this, describing changes in neutrophil responses (a modulation of usual cellular functions) in the presence of inflammation or infection which might enhance tissue damage while impeding bacterial clearance, providing some evidence to support there being an AATD neutrophil phenotype. Many facets of neutrophil function in AATD can be explained by the loss of alpha-1 antitrypsin (AAT) in diverse biological processes. If this were the only reason for altered neutrophil functions, one would predict similar disease presentation across affected people. However, this is not the case. Despite similar (low) levels of AAT, lung disease is extremely variable in AATD, with some patients suffering a significant burden of lung disease and some much less, irrespective of smoking habits and, in some cases, despite augmentation therapy. This review will explore how complex neutrophil responses are and how they are altered with age, inflammation and AATD. Further, it will discuss the need to understand more completely which aspects of AATD-associated disease are driven by neutrophils and how patients more susceptible to neutrophil dysfunction could be identified to potentially stratify treatment approaches.

Neutrophil Extracellular Traps Generation Relates with Early Stage and Vascular Complications in Systemic Sclerosis

Systemic sclerosis (SSc) is a systemic disease characterized by a great clinical and immunological heterogeneity whose pathophysiology is still being unraveled. Recently, innate immunity has been proposed to participate to the pathogenesis of SSc. In this study, we investigated the release of neutrophil extracellular traps (NETs) according to patient phenotype. Polymorphonuclear neutrophils (PMN) from 34 SSc patients and 26 healthy controls were stimulated by serum from SSc or healthy subject. NETs were visualized using epifluorescence microscope after DNA, myeloperoxidase, and Histone H3 tagging. Area of NETs were quantified using an original macro running in ImageJ^® software. PMN from SSc patients were significantly more prone to releasing NETs than control PMN after autologous stimulation. PMN from patients with severe vascular complications (pulmonary arterial hypertension, digital ulcers) produced more NETs than PMN from other SSc patients and their aberrant NET production appeared to be sustained over time. In patients with pulmonary interstitial disease or extensive cutaneous fibrosis, NET production was high at an early stage of the disease before progressively decreasing. Both serum factors and PMN activation status were involved in the enhanced production of NETs in SSc. Consequently, neutrophils and especially NETosis represent new physiopathological and therapeutic fields in SSc.

Extracellular AMP Suppresses Endotoxemia-Induced Inflammation by Alleviating Neutrophil Activation

Intracellular adenosine monophosphate (AMP) is indispensable for cellular metabolic processes, and it is interconverted to ADP and/or ATP or activates AMP-activated protein kinase (AMPK). However, the specific biological function of extracellular AMP has not been identified. We evaluated the effect of extracellular AMP using in vivo and in vitro models of endotoxemia. We found that AMP inhibited inflammation and neutrophil activation in lipopolysaccharide (LPS)-induced endotoxemic mice. The effects of extracellular AMP were abolished by an adenosine 1 receptor (A1R) antagonist but were not influenced by inhibiting the conversion of AMP to adenosine (ADO), indicating that AMP inhibited inflammation by directly activating A1R. In addition, in vitro experiments using LPS-stimulated mouse neutrophils showed that AMP inhibited LPS-induced reactive oxygen species (ROS) production, degranulation, and cytokine production, while the effects were reversed by an A1R antagonist. Further research showed that AMP regulated LPS-stimulated neutrophil functions by inhibiting the p38 MAPK pathway. These findings were also confirmed in primary neutrophils derived from healthy human blood. Moreover, we collected serum samples from septic patients. We found that AMP levels were increased compared with those of healthy volunteers and that AMP levels were negatively correlated with disease severity. Together, these data provide evidence that extracellular AMP acts on A1R to suppress endotoxemia-induced inflammation by inhibiting neutrophil overactivation and that the p38 MAPK signaling pathway is involved.

DEHP induces neutrophil extracellular traps formation and apoptosis in carp isolated from carp blood via promotion of ROS burst and autophagy

Di (2-ethylhexyl) phthalate (DEHP), a widely spreading environmental endocrine disruptor, has been confirmed to adversely affect the development of animals and humans. The formation of neutrophil extracellular traps (NETs) termed NETosis, is a recently identified antimicrobial mechanism for neutrophils. Though previous researches have investigated inescapable role of the immunotoxicity in DEHP-exposed model, relatively little is known about the effect of DEHP on NETs. In this study, carp peripheral blood neutrophils were treated with 40 and 200 μmol/L DEHP to investigate the underlying mechanisms of DEHP-induced NETs formation. Through the morphological observation of NETs and quantitative analysis of extracellular DNA, we found that DEHP exposure induced NETs formation. Moreover, our results proved that DEHP could increase reactive oxygen species (ROS) levels, decrease the expression of the anti-autophagy factor (mTOR) and the anti-apoptosis gene Bcl-2, and increase the expression of pro-autophagy genes (Dynein, Beclin-1 and LC3B) and the pro-apoptosis factors (BAX, Fas, FasL, Caspase3, Caspase8, and Caspase9), thus promoting autophagy and apoptosis. These results indicate that DEHP-induced ROS burst stimulates NETs formation mediated by autophagy and increases apoptosis in carp neutrophils.

Neutrophil Extracellular Traps (NETs) Promote Pro-Metastatic Phenotype in Human Breast Cancer Cells through Epithelial-Mesenchymal Transition

Neutrophil extracellular traps (NETs) have been associated with several steps of tumor progression, including primary growth and metastasis. One of the key features for the acquisition of the metastatic ability is the epithelial-mesenchymal transition (EMT), a complex cellular program. In this study, we evaluated the ability of isolated NETs in modulating the pro-metastatic phenotype of human breast cancer cells. Tumor cells were treated with isolated NETs and then samples were generated for cell migration, quantitative RT-PCR, western blotting, immunofluorescence, and flow cytometry assays. RNA-seq data from The Cancer Genome Atlas (TCGA) database were assessed. NETs changed the typical epithelial morphology of MCF7 cells into a mesenchymal phenotype, a process that was accompanied by enhanced migratory properties. Additional EMT traits were observed: increased expression of N-cadherin and fibronectin, while the E-cadherin expression was repressed. Notably, NETs positively regulated the gene expression of several factors linked to the pro-inflammatory and pro-metastatic properties. Analyses of TCGA data showed that samples from breast cancer patients exhibit a significant correlation between pro-tumoral and neutrophil signature gene expression, including several EMT and pro-metastatic factors. Therefore, NETs drive pro-metastatic phenotype in human breast cancer cells through the activation of the EMT program.

Imaging flow cytometry methods for quantitative analysis of label-free crystalline silica particle interactions with immune cells

Exposure to respirable fractions of crystalline silica quartz dust particles is associated with silicosis, cancer and the development of autoimmune conditions. Early cellular interactions are not well understood, partly due to a lack of suitable technological methods. Improved techniques are needed to better quantify and study high-level respirable crystalline silica exposure in human populations. Techniques that can be applied to complex biological matrices are pivotal to understanding particle-cell interactions and the impact of particles within real, biologically complex environments. In this study, we investigated whether imaging flow cytometry could be used to assess the interactions between cells and crystalline silica when present within complex biological matrices. Using the respirable-size fine quartz crystalline silica dust Min-u-sil® 5, we first validated previous reports that, whilst associating with cells, crystalline silica particles can be detected solely through their differential light scattering profile using conventional flow cytometry. This same property reliably identified crystalline silica in association with primary monocytic cells in vitro using an imaging flow cytometry assay, where darkfield intensity measurements were able to detect crystalline silica concentrations as low as 2.5 μg/mL. Finally, we ultilised fresh whole blood as an exemplary complex biological matrix to test the technique. Even after the increased sample processing required to analyse cells within whole blood, imaging flow cytometry was capable of detecting and assessing silica-association to cells. As expected, in fresh whole blood exposed to crystalline silica, neutrophils and cells of the monocyte/macrophage lineage phagocytosed the particles. In addition to the use of this technique in in vitro exposure models, this method has the potential to be applied directly to ex vivo diagnostic studies and research models, where the identification of crystalline silica association with cells in complex biological matrices such as bronchial lavage fluids, alongside additional functional and phenotypic cellular readouts, is required.

Macrolets: Outsized Extracellular Vesicles Released from Lipopolysaccharide-Stimulated Macrophages that Trap and Kill Escherichia coli

Macrophages release a variety of extracellular vesicles (EVs). Here we describe a previously unreported class of EVs that are released from macrophages in response to Escherichia coli endotoxin, lipopolysaccharide (LPS), that we have named "macrolets" since they are extruded as large "droplets" released from macrophages. Morphologically, macrolets are anuclear, bounded by a single lipid membrane and structurally dependent on an actin cytoskeleton. Macrolets are enriched in tetraspanins and separable on this basis from their parent macrophages. Macrolets are distinguished from classic exosomes by their larger size (10–30 μm), discoid shape, and the presence of organelles. Macrolets are rich in both interleukin 6 (IL-6) and interleukin 6 receptor (IL-6R),and are capable of trapping and killing E. coli in association with production of reactive oxygen species. Our observations offer insights into the mechanisms by which macrophage activities may be amplified in sites of infection, inflammation, and healing.

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Macrolets, outsized extracellular vesicles, release from LPS-stimulated macrophages

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Macrolets are rich in tetraspanin proteins such as CD81, CD63, and CD9

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Macrolets capture and internalize E. coli bacteria within acidic compartments

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Macrolets kill E. coli by a mechanism associated with production of ROS and superoxide

Novel formyl peptide receptor (FPR) agonists with pyridinone and pyrimidindione scaffolds that are potentially useful for the treatment of rheumatoid arthritis

The resolution of inflammation is an active response involving the interaction of pro-resolving mediators with specific receptors, such as N-formyl peptide receptor 2 (FPR2). FPRs represent potentially important therapeutic targets for the treatment of some pathologies, including asthma and rheumatoid arthritis. Previously, we identified selective or mixed FPR agonists with a pyridazin-3(2H)-one scaffold, all containing a 4-bromophenylacetamide fragment at N-2. The most effective compounds in this series were EC3, a potent mixed FPR1/FPR2/FPR3 agonist, and EC10, which had a preference for FPR1. We report here a new series of pyridinone and pyrimidindione derivatives containing the 4-(bromophenyl)acetamide substituent that was essential for activity in the pyridazinone series. All new compounds were evaluated for FPR agonist activity in HL60 cells transfected with FPR1 or FPR2 and in human neutrophils. While most of the pyridinone derivatives had reasonable FPR agonist activity in the submicromolar/micromolar range, the pyrimidindione derivatives were less active. Compound 2a (N-(4-bromophenyl)-2-[3-cyano-5-(3-methoxyphenyl)-6-methyl-2-oxopyridin-1(2H)-yl]acetamide) was the most active pyridinone derivative and had a 10-fold preference for FPR2 (EC₅₀ = 120 nM) versus FPR1 (EC₅₀ = 1.6 μM). To assess their therapeutic activity, compounds 2a, EC3, and EC10 were evaluated in vivo using a rat model of rheumatoid arthritis. All three compounds increased the pain threshold and reduced pain hypersensitivity in the treated rats versus control rats, although 2a and EC10 were much more effective than EC3. Thus, these FPR agonists represent potential leads to develop for the treatment of inflammatory diseases such as rheumatoid arthritis.

Modern Conceptions about the Mechanisms of Interaction Between Biofilm and Cellular Immunity Factors

Features of the cellular immune response in the presence of a microbial biofilm are well described in the literature. Based on numerous studies, it became possible to establish a number of patterns: mature biofilms are better protected from immune factors, the effectiveness of antibiofilm strategies depends on species of the microorganisms, forming the biofilm, and, accordingly, on the composition of the biopolymer matrix. For example, rhamnolipids and alginate of Pseudomonas aeruginosa exert a significant negative effect on the function of immunocompetent cells. The bacteria of biofilms became able to turn to their advantage many of the protective reactions developed by the immune system and fixed evolutionarily, applying them for the growth and development of the microbial consortium.

Chromatin extracellular trap release in rainbow trout, Oncorhynchus mykiss (Walbaum, 1792)

Neutrophils release nuclear chromatin decorated with antimicrobial proteins into the extracellular milieu as an innate immune defence mechanism to counter invading microbes. These chromatin structures, called extracellular traps (ETs) and released by a process called NETosis, have been detected in mammals, certain invertebrates and some fish species, including fathead minnow, zebrafish, common carp, turbot, sole and barramundi. However, there have been no previous studies of ETs in the Salmonidae. ETs are released in response to chemical and biological stimuli, but observations from different fish species are inconsistent, particularly regarding the potency of various inducers and inhibitors. Thus, this present study aimed to describe ET release in a salmonid (rainbow trout, Oncorhynchus mykiss (Walbaum, 1792)) and uncover the inducers and inhibitors that can control this response. Highly enriched suspensions of polymorphonuclear cells (PMNs; mainly neutrophils) were prepared from head kidney tissues by a triple-layer Percoll gradient technique. ET structures were visualised in PMN-enriched suspensions through staining of the chromatin with nucleic acid-specific dyes and immunocytochemical probing of characteristic proteins expected to decorate the structure. ET release was quantified after incubation with inducers and inhibitors known to affect this response in other organisms. Structures resembling ETs stained positively with SYTOX Green (a stain specific for nucleic acid) while immunocytochemistry was used to detect neutrophil elastase, myeloperoxidase and H2A histone in the structures, which are diagnostic proteinaceous markers of ETs. Consistent with other studies on mammals and some fish species, calcium ionophore and flagellin were potent inducers of ETs, while cytochalasin D inhibited NETosis. Phorbol 12-myristate 13-acetate (PMA), used commonly to induce ETs, exerted only weak stimulatory activity, while heat-killed bacteria and lipopolysaccharide did not induce ET release. Unexpectedly, the ET-inhibitor diphenyleneiodonium chloride acted as an inducer of ET release, an observation not reported elsewhere. Taken together, these data confirm for the first time that ETs are released by salmonid PMNs and compounds useful for manipulating NETosis were identified, thus providing a platform for further studies to explore the role of this mechanism in fish immunity. This new knowledge provides a foundation for translation to farm settings, since manipulation of the innate immune response offers a potential alternative to the use of antibiotics to mitigate against microbial infections, particularly for pathogens where protection by vaccination has yet to be realised.

Does postoperative inflammation or sepsis generate neutrophil extracellular traps that influence colorectal cancer progression? A systematic review

BACKGROUND

Colorectal cancer is the third most common cancer worldwide. Almost half of those that have a potentially curative resection go on to develop metastatic disease. A recognized risk for recurrence is perioperative systemic inflammation and sepsis. Neutrophil extracellular traps have been implicated as promotors of tumor progression. We aimed to examine the evidence in the literature for an association between neutrophil extracellular traps and postoperative metastasis in colorectal cancer.

MATERIALS AND METHODS

Studies published between 2000 and December 2018 that examined the role of neutrophil extracellular traps in sepsis and inflammation in colorectal cancer and in relation to tumor-related outcomes were identified through a database search of Cochrane, CINAHL, and MEDLINE. Quality and bias assessment was carried out by 2 reviewers.

RESULTS

Of 8,940 screened and of the 30 studies included, 21 were observational, 5 were in vivo experimental, 1 was in vitro, and 3 used a combination of these approaches.

CONCLUSION

There is clear evidence from the literature that presence of a preoperative systemic inflammatory response predicts cancer recurrence following potentially curative resection, but the evidence for association of sepsis and progression is lacking. There is robust experimental evidence in murine models showing that neutrophil extracellular traps are present in sepsis and are associated with cancer progression. Some human observational studies corroborate the prognostic significance of neutrophil extracellular traps in progression of colorectal cancer. Further human studies are needed to translate the experimental evidence and to definitively associate sepsis and neutrophil extracellular traps with poor colorectal cancer-specific outcomes.

Autophagy-driven NETosis is a double-edged sword - Review

Autophagy is a cellular mechanism responsible for delivering protein aggregates or damaged organelles to lysosomes for degradation. It is also simultaneously a precise regulatory process, which is crucial for dealing with hunger, oxidative stress, and pathogen defense. Neutrophil Extracellular Traps (NETs), which form a part of a newly described bactericidal process, are reticular structures composed of a DNA backbone and multiple functional proteins, formed via a process known as NETosis. NETs exert their anti-infection activity by capturing pathogenic microorganisms, inhibiting their spread and inactivating virulence factors. However, NETs may also activate an immune response in non-infectious diseases, leading to tissue damage. Although the mechanism underlying this phenomenon is unclear, a large number of studies have suggested that autophagy may be involved. Autophagy-mediated NETs not only induce inflammation and tissue damage, but can also lead to cell senescence, malignant transformation, and cell death. Autophagy-dependent NETs also play a beneficial role in the hostwith respect to pathogen clearance and immune defense. Through careful review of the literature, we have found that the distinct roles of autophagy in NETosis may be dependent on the extent of autophagy and the specific manner in which it was induced. This article summarizes numerous recent studies, and reviews the role of autophagy-driven NETosis in various diseases, in the hope that this will lead to the development of more effective treatments.

Modern Conceptions about the Mechanisms of Interaction Between Biofilm and Cellular Immunity Factors

Features of the cellular immune response in the presence of a microbial biofilm are well described in the literature. Based on numerous studies, it became possible to establish a number of patterns: mature biofilms are better protected from immune factors, the effectiveness of antibiofilm strategies depends on species of the microorganisms, forming the biofilm, and, accordingly, on the composition of the biopolymer matrix. For example, rhamnolipids and alginate of Pseudomonas aeruginosa exert a significant negative effect on the function of immunocompetent cells. The bacteria of biofilms became able to turn to their advantage many of the protective reactions developed by the immune system and fixed evolutionarily, applying them for the growth and development of the microbial consortium.

Pf Bacteriophage and Their Impact on Pseudomonas Virulence, Mammalian Immunity, and Chronic Infections

Pf bacteriophage are temperate phages that infect the bacterium Pseudomonas aeruginosa, a major cause of chronic lung infections in cystic fibrosis (CF) and other settings. Pf and other temperate phages have evolved complex, mutualistic relationships with their bacterial hosts that impact both bacterial phenotypes and chronic infection. We and others have reported that Pf phages are a virulence factor that promote the pathogenesis of P. aeruginosa infections in animal models and are associated with worse skin and lung infections in humans. Here we review the biology of Pf phage and what is known about its contributions to pathogenesis and clinical disease. First, we review the structure, genetics, and epidemiology of Pf phage. Next, we address the diverse and surprising ways that Pf phages contribute to P. aeruginosa phenotypes including effects on biofilm formation, antibiotic resistance, and motility. Then, we cover data indicating that Pf phages suppress mammalian immunity at sites of bacterial infection. Finally, we discuss recent literature implicating Pf in chronic P. aeruginosa infections in CF and other settings. Together, these reports suggest that Pf bacteriophage have direct effects on P. aeruginosa infections and that temperate phages are an exciting frontier in microbiology, immunology, and human health.

Extracellular Traps: An Ancient Weapon of Multiple Kingdoms

The discovery, in 2004, of extracellular traps released by neutrophils has extended our understanding of the mode of action of various innate immune cells. This fascinating discovery demonstrated the extracellular trapping and killing of various pathogens by neutrophils. During the last decade, evidence has accumulated showing that extracellular traps play a crucial role in the defence mechanisms of various cell types present in vertebrates, invertebrates, and plants. The aim of this review is to summarise the relevant literature on the evolutionary history of extracellular traps used as a weapon in various kingdoms of life.

The action of Echis carinatus and Naja naja venoms on human neutrophils; an emphasis on NETosis

BACKGROUND

Neutrophils are the first line defense cells of the innate immunity. As a final defense, they discharge their de-condensed chromatin/DNA fibers, the NETs (Neutrophil Extracellular Traps), by a process called NETosis. Two types of NETosis have been currently described: the suicidal/delayed/classical-type, which is ROS dependent that results in the ejection of nuclear DNA, and the vital/rapid/early-type, which may or may not require ROS but, eject nuclear/mitochondrial DNA or both. Thus, Echis carinatus and Naja naja venoms are comparatively studied for their NET inducing property.

METHODS

Formation of NETs, cell viability, ROS, and Ca²⁺ levels are estimated. An in vivo toxicity study and possible cellular signaling have been addressed using immunoblots and pharmacological inhibitors.

RESULTS

E. carinatus and N. naja venoms respectively induce suicidal and vital NETosis. E. carinatus venom induces NETosis by activating NOX and PAD-4 enzymes in a ROS dependent manner via PKC/ERK/JNK signaling axis, while N. naja venom does it by activating PAD-4 enzyme, but independent of ROS requirement and as well as PKC/ERK/JNK activation.

CONCLUSION

For the first time our study demonstrates the distinct action of E. carinatus and N. naja venoms on the process of NETosis. NETosis being a newly explored area in snake venom pharmacodynamics, it is important to study its impact on the various pathophysiological properties induced by snake venoms.

SIGNIFICANCE

Understanding the varied actions of snake venoms on neutrophils/blood cells and the role of DNase are likely to provide insights for better management of snakebite pathophysiology.

In Vivo Imaging of Neutrophil Extracellular Traps (NETs): Visualization Methods and Outcomes

Neutrophils comprise the first line of innate immune defense during a host-pathogen interaction. They attack microorganisms directly through three different methods, of which, phagocytosis and degranulation have been known and well-studied for decades. The formation of neutrophil extracellular traps (NETs) is the third and unique method, which was unveiled in 2004. Since then, many studies on NETs have been carried out. However, only few have successfully demonstrated the activity of NETs in vivo. Results of the in vivo studies on NETs have strengthened our understanding of their role in different situations. This review highlights the main in vivo studies, which have contributed in extending our understanding of the role of NETs during infections and diseases, thus indicating their advantages and limitations.

Inhibition of Hyperuricemia and Gouty Arthritis in BALB/c Mice Using Copper Oxide Nanoparticles

Nanoparticles are known for their unique properties and are being utilized in various disciplines of sciences. Their nanosize enables them to higher exposure and higher availability when given orally. Gout is an inflammatory disease caused by deposition of monosodium urate (MSU) crystal deposition into the joints. The objective of this study was to evaluate the effects of copper oxide nanoparticles on hyperuricemia and gouty arthritis in mice. In this research, synthesized copper oxide nanoparticles of size ranging from 30 to 50 nm were administered orally to mice having gouty arthritis and hyperuricemia. Various biochemical markers were conducted to determine the effects of copper oxide nanoparticles. It was observed that the mice treated with CuO NPs at various concentrations showed a significant (0.001) decrease in the serum uric acid levels in comparison with the negative control. Furthermore, creatinine levels were also normal in comparison with the control mice. Measurement of synovial joints also revealed that mice administered with CuO NPs had reduced inflammation of synovial joints in comparison with the negative control. From this research, it was concluded that copper oxide nanoparticles have potential in the treatment of hyperuricemia and gouty arthritis by decreasing serum uric acid and inflammation in synovial joints.

Dolphin-derived NETosis results in rapid Toxoplasma gondii tachyzoite ensnarement and different phenotypes of NETs

Toxoplasma gondii is a cosmopolitan zoonotic parasite and nowadays considered as an emerging neozoan pathogen in the marine environment. Cetacean innate immune reactions against T. gondii stages have not yet been investigated. Thus, T. gondii tachyzoites were utilized to trigger neutrophil extracellular traps (NETs) in bottlenose dolphin (Tursiops truncatus) polymorphonuclear neutrophils (PMN). Scanning electron microscopy unveiled T. gondii tachyzoites as potent and rapid inducers of cetacean-derived NETosis. Co-localization of extracellular chromatin with global histones, granulocytic myeloperoxidase and neutrophil elastase confirmed classical characteristics of NETosis. Interestingly, different phenotypes of NETs were induced by tachyzoites resulting in spread, diffuse and aggregated NET formation and moreover, 'anchored' and 'cell free' NETosis was also detected. Current data indicate that cetacean-derived NETosis might represent an early, ancient and well-conserved host innate defense mechanism that not only acts against T. gondii but might also occur in response to other closely related emerging apicomplexan parasites affecting marine cetaceans.

The incidence and etiology of sperm DNA fragmentation in the ejaculates of males with spinal cord injuries

STUDY DESIGN

Retrospective descriptive study.

OBJECTIVES

To determine the incidence and probable etiology of sperm DNA fragmentation (SDF) in a sample of males with spinal cord injury (SCI).

SETTING

Hospital in Toledo, Spain; University-based Genetics laboratory in Madrid, Spain.

METHODS

Semen collected by vibro-stimulation from 27 males with various levels of spinal cord injury. Classical semen parameters, SDF, leukocytospermia and pro-oxidant capacity were assessed and compared with a cohort of normozoospermic fertile donors (n = 10).

RESULTS

Males with SCI presented with lower semen quality compared with normozoospermic donors with respect to progressive motility (p = 0.0002), SDF (p < 0.00005), pro-oxidant capacity (p = 0.0191) and leukocytospermia (p < 0.00005). Although there was no significant correlation between semen quality and time since the lesion occurred, the period of abstinence appeared to be positively correlated with SDF (r = 0.486; p = 0.041). When the semen parameters of males with SCI were categorized based on those with cervical and thoracic lesions, sperm concentration was higher for those with cervical damage (p = 0.0257). Males with complete lesions (AIS A) had ejaculates that were lower in progressive motility (p = 0.0040) than those with incomplete injuries (AIS B-D).

CONCLUSIONS

Ejaculates of males with SCI have excessively elevated SDF when compared with normozoospermic donors, which is likely to be associated with coincident high levels of leucocytospermia and pro-oxidant capacity. We propose that these phenomena are caused by the accumulation and degeneration of spermatozoa in the cauda epididymidis.

Platelets and extracellular traps in infections

Platelets have a well-recognized role in hemostasis and thrombosis, and they are important amplifiers of inflammation and innate immune responses. The formation of DNA extracellular traps (ETs) is a complex cellular mechanism, which occurs in response to microbial infections and sterile inflammation, and results in the release of DNA complexed with histones and various granular proteins. ETs were first discovered in neutrophils (NETs); however, it is now accepted that other leukocytes, including eosinophils (EETs) and monocytes/macrophages (MoETs/METs), can also generate them. Moreover, several types of ETs have been described.Increasing evidence has demonstrated that platelets modulate the formation of ETs. This review summarizes recent findings about the physiopathological role of platelets in the formation of ETs during infection and future perspectives in the field.

Anaplastic Thyroid Cancer Cells Induce the Release of Mitochondrial Extracellular DNA Traps by Viable Neutrophils

Neutrophils are key effector cells that orchestrate inflammatory responses in the tumor microenvironment. Although neutrophil extracellular DNA traps (NETs) entrap and kill pathogens, they also contribute to chronic inflammation and cancer progression. Thyroid cancer (TC) is the most frequently occurring cancer of the endocrine system, accounting for 70% of deaths due to endocrine tumors. Although anaplastic TC (ATC) is rare among TCs, it is highly lethal. We demonstrated in a recent study that tumor-infiltrating neutrophil density correlated with TC size. Moreover, TC-derived soluble mediators modulate the human neutrophil phenotype. Our study aimed to investigate the involvement of NETs in human TC. Highly purified neutrophils from healthy donors were primed in vitro with a papillary TC or ATC cell line conditioned medium (CM) or with a normal thyroid CM as control. NET release was quantified using a High-Content Imaging System. Neutrophil viability was assessed by flow cytometry. Fluorescence microscopy, flow cytometry, and PCR were performed to determine the mitochondrial origin of ATC-induced NETs. ATC CM-primed neutrophils were cocultured with ATC cells to determine the effects exerted by NETs on cell proliferation. ATC CM induce NET release, whereas papillary TC or normal thyroid CM did not. ATC CM-induced NET production occurred in a reactive oxygen species-dependent and cell death-independent manner and was associated with mitochondrial reactive oxygen species production; the NETs contained mitochondrial DNA. ATC CM-primed neutrophils promoted ATC cell proliferation in a NET-dependent manner.

Evaluation of neutrophil extracellular traps as the circulating marker for patients with acute coronary syndrome and acute ischemic stroke

Introduction

Neutrophil extracellular traps (NETs) are known to be induced by various factors. In this study, we tried to identify circulating levels of NETs in patients with acute coronary syndrome (ACS) and acute ischemic stroke (AIS) and to confirm its suitability as a new circulating marker in their detection.

Methods

We prospectively enrolled 95 patients with a diagnosis of ACS (N = 37) or AIS (N = 58) in Dong‐A University Hospital, Busan, Korea. The control group was selected from healthy adults (N = 25) who visited the hospital for health screening. Circulating levels of NETs were evaluated by measuring plasma concentrations of double‐stranded DNA (dsDNA) and DNA‐histone complex.

Results

The concentrations of dsDNA were statistically higher in patients with ACS or AIS than those in the control group (both P < .001). In the univariable and multivariable analyses, statistically significant risk factors were troponin I (TnI) level and dsDNA concentration in the ACS group (P = .046 and P = .015, respectively) and only dsDNA concentration in the AIS group (P = .002). In the receiver operating characteristic curve analyses, the area under the curve values for TnI level and dsDNA concentration in the ACS group were 0.878 and 0.968, respectively, and the value for dsDNA concentration in the AIS group was 0.859.

Conclusions

In this study, it was confirmed that the circulating level of NETs was increased in patients with ACS and AIS at initial presentation. Findings in this study show that NETs could be used as a new circulating marker for the initial diagnosis of ACS or AIS.

Contribution of neutrophils in the pathogenesis of rheumatoid arthritis

Neutrophils are major innate immune effector cells for host defense and have been a topic of active research for their participation in the pathogenesis of autoimmune inflammatory diseases including rheumatoid arthritis (RA) due to recently discovered neutrophil extracellular trap (NET) formation. NET formation and other mechanisms leading to the release of neutrophil nuclear and cytoplasmic contents are implicated as a source of citrullinated antigens in RA. Further investigations are required to delineate what factors diverge neutrophils from host defense to autoimmune response in RA.