Neutrophil Extracellular Trap in Human Diseases

Uncovering the role of cytoskeleton proteins in the formation of neutrophil extracellular traps

Neutrophils are a type of lymphocyte involved in innate immune defense. In response to specific stimuli, these phagocytic cells undergo a unique form of cell death, NETosis, during which they release neutrophil extracellular traps (NETs) composed of modified chromatin structures decorated with cytoplasmic and granular proteins. Multiple proteins and pathways have been implicated in the formation of NETs. The cytoskeleton, an interconnected network of filamentous polymers and regulatory proteins, plays a crucial role in resisting deformation, transporting intracellular cargo, and changing shape during movement of eukaryotic cells. It may also have evolved to defend eukaryotic organisms against infection. Recent research focuses on understanding the mechanisms underlying NETs formation and how cytoskeletal networks contribute to this process, by identifying enzymes that trigger NETosis or interact with NETs and influence cellular behavior through cytoskeletal dynamics. An enhanced understanding of the complex relationship between the cytoskeleton and NET formation will provide a framework for future research and the development of targeted therapeutic strategies, and supports the notion that the long-lived cytoskeleton structures may have a lasting impact on this area of research.

Worsening Thrombotic Complication of Atherosclerotic Plaques Due to Neutrophils Extracellular Traps: A Systematic Review

Neutrophil extracellular traps (NETs) recently emerged as a newly recognized contributor to venous and arterial thrombosis. These strands of DNA, extruded by activated or dying neutrophils, decorated with various protein mediators, become solid-state reactors that can localize at the critical interface of blood with the intimal surface of diseased arteries alongside propagating and amplifying the regional injury. NETs thus furnish a previously unsuspected link between inflammation, innate immunity, thrombosis, oxidative stress, and cardiovascular diseases. In response to disease-relevant stimuli, neutrophils undergo a specialized series of reactions that culminate in NET formation. DNA derived from either nuclei or mitochondria can contribute to NET formation. The DNA liberated from neutrophils forms a reticular mesh that resembles morphologically a net, rendering the acronym NETs particularly appropriate. The DNA backbone of NETs not only presents intrinsic neutrophil proteins (e.g., MPO (myeloperoxidase) and various proteinases) but can congregate other proteins found in blood (e.g., tissue factor procoagulant). This systematic review discusses the current hypothesis of neutrophil biology, focusing on the triggers and mechanisms of NET formation. Furthermore, the contribution of NETs to atherosclerosis and thrombosis is extensively addressed. Again, the use of NET markers in clinical trials was considered. Ultimately, given the vast body of the published literature, we aim to integrate the experimental evidence with the growing body of clinical information relating to NET critically.

Eating the Enemy: Mycoplasma Strategies to Evade Neutrophil Extracellular Traps (NETs) Promoting Bacterial Nucleotides Uptake and Inflammatory Damage

Neutrophils are effector cells involved in the innate immune response against infection; they kill infectious agents in the intracellular compartment (phagocytosis) or in the extracellular milieu (degranulation). Moreover, neutrophils release neutrophil extracellular traps (NETs), complex structures composed of a scaffold of decondensed DNA associated with histones and antimicrobial compounds; NETs entrap infectious agents, preventing their spread and promoting their clearance. NET formation is triggered by microbial compounds, but many microorganisms have evolved several strategies for NET evasion. In addition, the dysregulated production of NETs is associated with chronic inflammatory diseases. Mycoplasmas are reduced genome bacteria, able to induce chronic infections with recurrent inflammatory symptoms. Mycoplasmas' parasitic lifestyle relies on metabolite uptake from the host. Mycoplasmas induce NET release, but their surface or secreted nucleases digest the NETs' DNA scaffold, allowing them to escape from entrapment and providing essential nucleotide precursors, thus promoting the infection. The presence of Mycoplasma species has been associated with chronic inflammatory disorders, such as systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, Crohn's disease, and cancer. The persistence of mycoplasma infection and prolonged NET release may contribute to the onset of chronic inflammatory diseases and needs further investigation and insights.

A systematic review on neutrophil extracellular traps and its prognostication role in COVID-19 patients

Neutrophil extracellular traps (NETs) are extracellular webs composed of neutrophil granular and nuclear elements. Because of the potentially dangerous amplification circuit between inflammation and tissue damage, NETs are becoming one of the investigated components in the current Coronavirus Disease 2019 (COVID-19) pandemic. The purpose of this systematic review is to summarize studies on the role of NETs in determining the prognosis of COVID-19 patients. The study used six databases: PubMed, Science Direct, EBSCOHost, Europe PMC, ProQuest, and Scopus. This literature search was implemented until October 31, 2021. The search terms were determined specifically for each databases, generally included the Neutrophil Extracellular Traps, COVID-19, and prognosis. The Newcastle Ottawa Scale (NOS) was then used to assess the risk of bias. Ten studies with a total of 810 participants were chosen based on the attainment of the prerequisite. Two were of high quality, seven were of moderate quality, and the rest were of low quality. The majority of studies compared COVID-19 to healthy control. Thrombosis was observed in three studies, while four studies recorded the need for mechanical ventilation. In COVID-19 patients, the early NETs concentration or the evolving NETs degradations can predict patient mortality. Based on their interactions with inflammatory and organ dysfunction markers, it is concluded that NETs play a significant role in navigating the severity of COVID-19 patients and thus impacting their prognosis.

Swine spermatozoa trigger aggregated neutrophil extracellular traps leading to adverse effects on sperm function

In pigs, the number of PMN in uterus lumen increases within few hours after natural or artificial AI resulting in early PMN-derived innate immune reactions. Sperm-NETs formation was recently reported to occur in various mammalian species. Aim of this study was to investigate direct interactions of boar spermatozoa with swine PMN, the release of sperm-mediated NETs, and to assess NET-derived effects on sperm functionality. Sperm-triggered NETs were visualized by SEM- and immunofluorescence analyses. Sperm-mediated NETosis was confirmed by presence of extruded DNA with global histones and NE. Largest sizes of sperm-mediated aggNETs were detected after 5 h thereby resulting in effective massive sperm entrapment. The number of aggNETs increased from 3 h onwards. Kinetic studies of swine sperm-mediated NETosis showed to be a time-dependent cellular process. In addition, number of NETs-entrapped spermatozoa increased at 3 h of exposure whilst few free spermatozoa were detected after 3 h. Anchored NETs also increased from 3 h onwards. The cytotoxicity of NETs was confirmed by diminution of the total motility and the progressive motility. Spermatozoa membrane integrity and function loss exposed to NETs was confirmed from 3 h. Experiments revealed NETs-derived damaging effects on swine spermatozoa in membrane integrity, motility and functionality. We hypothesize that swine sperm-triggered aggNETs might play a critical role in reduced fertility potential in swine reproductive technique. Thus, aggNETs formation needs to be considered in future studies about uterine environment as well as advance of sperm in the porcine female reproductive tract.

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.

Characteristics of neutrophil extracellular traps in patients with periodontitis and gingivitis

We sought to compare the characteristics and clinical significance of neutrophil extracellular traps in gingival samples from patients with periodontitis and those with gingivitis. The clinical indexes of gingival samples from patients with periodontitis and gingivitis were measured; the expression of TNF-alpha and IL-8 was measured by real-time fluorescent quantitative PCR; and the expression of TLR-8 and MMP-9 was measured by western blotting assays. Chemotaxis, phagocytosis and phagocytic activity of neutrophils were measured. Compared with the healthy group, the expression of TNF-α and IL-8 in the periodontitis group and the gingivitis group increased significantly (p < 0.05), and TNF-α in the gingivitis group was significantly lower than that in the healthy group (p < 0.05). The expression of IL-8 in the periodontitis group was significantly higher than that in the periodontitis group (p < 0.05). Furthermore, the expression of TLR-8 and MMP-9 in the periodontitis group was different from that in the gingivitis group and the healthy group, and the expression of TLR-8 and MMP-9 in the gingivitis group was significantly different from that in the healthy group (p < 0.05). In addition, the neutrophil mobility index in healthy people was 3.02 ± 0.53, that in the periodontitis group was 2.21 ± 0.13, and that in the gingivitis group was 2.31 ± 0.12. In conclusion, the chemotaxis of neutrophils in gingival samples of patients with periodontitis and gingivitis was decreased, the phagocytotic ability and activity of neutrophils were reduced, and the release of the extracellular trap-releasing inducible factors TNF-alpha and IL-8 also declined.

The Role of DNA in the Extracellular Environment: A Focus on NETs, RETs and Biofilms

The capacity to actively release genetic material into the extracellular environment has been reported for bacteria, archaea, fungi, and in general, for microbial communities, but it is also described in the context of multicellular organisms, animals and plants. This material is often present in matrices that locate outside the cells. Extracellular matrices have important roles in defense response and disease in microbes, animal and plants cells, appearing as barrier against pathogen invasion or for their recognition. Specifically, neutrophils extracellular traps (NETs) in animals and root extracellular traps (RETs) in plants, are recognized to be important players in immunity. A growing amount of evidence revealed that the extracellular DNA, in these contexts, plays an active role in the defense action. Moreover, the protective role of extracellular DNA against antimicrobials and mechanical stress also appears to be confirmed in bacterial biofilms. In parallel, recent efforts highlighted different roles of self (homologous) and non-self (heterologous) extracellular DNA, paving the way to discussions on its role as a "Damage-associated molecular pattern" (DAMP). We here provide an evolutionary overview on extracellular DNA in extracellular matrices like RETs, NETs, and microbial biofilms, discussing on its roles and inferring on possible novel functionalities.

Differences and similarities in the phenomenon of NETs formation in oral inflammation and in oral squamous cell carcinoma

Taking into account the previously reported relationship between inflammation and carcinogenesis, and the scant amount of data concerning the role of neutrophil extracellular traps (NETs) in carcinogenesis, we decided to study the process of extracellular trap formation in patients with inflammation as well as in patients with cancer occurring in the same location. For preliminary isolation of neutrophils (PMNs), we used Polymorphprep™, then sorted with Microbeads. The cells were recorded in the incubation chamber with a BD Pathway 855 microscope system. Flow cytometric data (MPO+ neutrophils) were acquired on FACSCalibur flow cytometer. Amounts of cfDNA were determined by Abcam's Circulating DNA Quantification Kit. Neutrophils of patients with inflammation and of subjects with stage I/II oral squamous cell carcinoma (OSCC) produce increased amounts of NETs, while stage III/IV OSCC were comparable with the control group. In all of the studied groups of cells stimulation with LPS and rhIL-17 produced more NETs in relation to unstimulated cells. Neutrophil supernatant of inflammation patients and stage I/II cancer patients demonstrated the increased level of cfDNA, which decreased at stage III/IV. Patients with oral inflammations showed an increased rate of MPO+ neutrophils, which was lower than in stage I/II cancer patients and not significantly different than in Stage III/IV cancer patients and the control group. The direction of changes in NETs formation seems to be a new common element shared by inflammation and early stage cancer. Changes in the formation of NETs observed in patients with advanced cancer, other than an early phase or inflammation, indicate an alternative range of NETs involvement depending on different phases of this disease.

Platelet leukocyte aggregates and markers of platelet aggregation, immune activation and disease progression in HIV infected treatment naive asymptomatic individuals

Platelet aggregates play a crucial role in the immune defence mechanism against viruses. Increased levels of lipopolysaccharide have been reported in human immunodeficiency virus (HIV) infected individuals. Platelets are capable of interacting with bacterial LPS and subsequently forming platelet leukocyte aggregates (PLAs). This study aimed at determining the levels of circulating PLAs in treatment naïve HIV infected individuals and correlating them, with markers of immune activation, disease progression and platelet aggregation. Thirty-two HIV negative and 35 HIV positive individuals were recruited from a clinic in the Western Cape. Platelet monocyte and platelet neutrophil aggregates were measured using flow cytometry at baseline and were correlated with markers of platelet activation (CD62P); aggregation (CD36); monocyte and neutrophil activation (CD69); monocyte tissue factor expression (CD142); immune activation (CD38 on T+ cells); D-dimers (a marker of active coagulation); CD4 count and viral load. Platelet monocyte aggregates were also measured post stimulation with lipopolysaccharide. PMA levels were higher in HIV 25.26 (16.16-32.28) versus control 14.12 (8.36-18.83), p = 0.0001. PMAs correlated with %CD38/8 expression (r = 0.54624, p = 0.0155); CD4 count (r = -0.6964, p = 0.0039) viral load (r = 0.633, p < 0.009) and monocyte %CD69 expression (r = 0.757, p = 0.030). In addition the %PMAs correlated with platelet %CD36 (r = 0.606, p = 0.017). The HIV group showed increased levels of %CD62P 5.44 (2.72-11.87) versus control 1.15 (0.19-3.59), p < 0.0001; %CD36 22.53 (10.59-55.15) versus 11.01 (3.69-26.98), p = 0.0312 and tissue factor (CD142) MFI 4.84 (4.01-8.17) versus 1.74 (1.07-9.3), p = 0.0240. We describe increased levels of circulating PMAs which directly correlates with markers of immune activation, disease progression and platelet aggregation in HIV treatment naïve individuals.

Pleiotropic effects of 4-hydroxynonenal on oxidative burst and phagocytosis in neutrophils

Metabolic control of cellular function is significant in the context of inflammation-induced metabolic dysregulation in immune cells. Generation of reactive oxygen species (ROS) such as hydrogen peroxide and superoxide are one of the critical events that modulate the immune response in neutrophils. When activated, neutrophil NADPH oxidases consume large quantities of oxygen to rapidly generate ROS, a process that is referred to as the oxidative burst. These ROS are required for the efficient removal of phagocytized cellular debris and pathogens. In chronic inflammatory diseases, neutrophils are exposed to increased levels of oxidants and pro-inflammatory cytokines that can further prime oxidative burst responses and generate lipid oxidation products such as 4-hydroxynonenal (4-HNE). In this study we hypothesized that since 4-HNE can target glycolysis then this could modify the oxidative burst. To address this the oxidative burst was determined in freshly isolated healthy subject neutrophils using 13-phorbol myristate acetate (PMA) and the extracellular flux analyzer. Neutrophils pretreated with 4-HNE exhibited a significant decrease in the oxidative burst response and phagocytosis. Mass spectrometric analysis of alkyne-HNE treated neutrophils followed by click chemistry detected modification of a number of cytoskeletal, metabolic, redox and signaling proteins that are critical for the NADPH oxidase mediated oxidative burst. These modifications were confirmed using a candidate immunoblot approach for critical proteins of the active NADPH oxidase enzyme complex (Nox2 gp91phox subunit and Rac1 of the NADPH oxidase) and glyceraldehyde phosphate dehydrogenase, a critical enzyme in the metabolic regulation of oxidative burst. Taken together, these data suggest that 4-HNE-induces a pleiotropic mechanism to inhibit neutrophil function. These mechanisms may contribute to the immune dysregulation associated with chronic pathological conditions where 4-HNE is generated.

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Phagocytosis and glycolysis are inhibited in neutrophils by 4-hydroxynonenal.

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Click chemistry with alkyne-HNE identifies over 100 potential protein targets.

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Rac1, NOX2 and GAPDH are modified by 4-HNE.

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The 4-HNE-dependent inhibition of neutrophil function is mediated by a pleiotropic mechanism.

The effect of clindamycin and amoxicillin on neutrophil extracellular trap (NET) release

Neutrophil extracellular traps (NETs) are threads of nuclear DNA complexed with antimicrobial proteins released by neutrophils to extracellular matrix to bind, immobilise, and kill different pathogens. NET formation is triggered by different physiological and non-physiological stimulants. It is also suggested that antibiotics could be non-physiological compounds that influence NET release.

The aim of the study was to investigate the effect of clindamycin and amoxicillin on NET release and the phagocyte function of neutrophils.

Neutrophils isolated from healthy donors by density centrifugation method were incubated with amoxicillin or clindamycin for two hours, and then NET release was stimulated with phorbol 12-myristate 13-acetate (PMA). After three hours of incubation with PMA NETs were quantified as amount of extracellular DNA by fluorometry and visualised by immunofluorescent microscopy. The percent of phagocyting cells was measured by flow cytometry.

We showed that amoxicillin induces NET formation (increase of extracellular DNA fluorescence, p = 0.03), while clindamycin had no influence on NET release (p > 0.05), as confirmed by quantitative measurement and fluorescent microscopy. Regarding phagocyte function, both antibiotics increased bacterial uptake (43.3% and 61.6% median increase for amoxicillin and clindamycin, respectively).

We concluded that the ability of antibiotics to modulate NET release depends on the antibiotic used and is not associated with their ability to influence phagocytosis.

Ruscogenin suppresses mouse neutrophil activation: Involvement of protein kinase A pathway

Ruscogenin, a natural steroidal sapogenin, presents in both food and medicinal plants. It has been found to exert significant anti-inflammatory activities. Considering that activation of neutrophil is a key feature of inflammatory diseases, this study was performed to investigate the inhibitory effect of ruscogenin and its underlying mechanisms responsible for neutrophil activation. Ruscogenin displayed potent antioxidative effects against Formyl-Met-Leu-Phe (FMLP)-induced extra- and intracellular superoxide generation in mouse bone marrow neutrophils, with IC50 values of 1.07±0.32 μM and 1.77±0.46 μM, respectively. Phorbol myristate acetate (PMA)-elicited extra- and intracellular superoxide generation were also suppressed by ruscogenin, with IC50 values of 1.56±0.46 μM and 1.29±0.49 μM, respectively. However, ruscogenin showed weak inhibition in NaF-induced response. Inhibition of superoxide generation was mediated neither by a superoxide-scavenging ability nor by a cytotoxic effect. Furthermore, ruscogenin inhibited the membrane translocation of p47phox and p67phox. It reduced FMLP-induced phosphorylation of cytosolic phospholipase A2 (cPLA2) and p21-activated kinase (PAK). The cellular cyclic adenosine monophosphate (cAMP) levels and protein kinase A (PKA) expression were increased by ruscogenin. Moreover, ruscogenin inhibited phosphorylation of protein kinase B (Akt), p38 mitogen-activated protein kinase (p38MAPK), extracellular signal-regulated kinase 1 and 2 (ERK1/2), and c-Jun N-terminal kinase (JNK). In addition, the inhibitory effects of ruscogenin on superoxide production and the phosphorylation of Akt, p38MAPK, and ERK1/2 were reversed by PKA inhibitor (H89), suggesting a PKA-dependent mechanism. In summary, our data suggest that ruscogenin inhibits activation of neutrophil through cPLA2, PAK, Akt, MAPKs, cAMP, and PKA signaling pathways. Increased PKA activity is associated with suppression of the phosphorylation of Akt, p38MAPK, and ERK1/2 pathways.

Salmonella-Based Therapy Targeting Indoleamine 2,3-Dioxygenase Coupled with Enzymatic Depletion of Tumor Hyaluronan Induces Complete Regression of Aggressive Pancreatic Tumors

Bacterial-based therapies are emerging as effective cancer treatments and hold promise for refractory neoplasms, such as pancreatic ductal adenocarcinoma (PDAC), which has not shown significant improvement in therapy for more than 25 years. Using a novel combination of shIDO-ST, a Salmonella-based therapy targeting the immunosuppressive molecule indoleamine 2,3-dioxygenase (IDO), with an enzyme, PEGPH20, which depletes extracellular matrix hyaluronan, we observed extended survival with frequent total regression of autochthonous and orthotopic PDAC tumors. This observation was associated with migration and accumulation of activated polymorphonuclear neutrophils (PMN) from spleens into tumors, which was not seen using a scrambled control (shScr-ST). Purified splenic PMNs from PEGPH20/shIDO-ST-treated mice exhibited significant IDO knockdown and were able to kill tumor targets ex vivo through mechanisms involving FasL and serine proteases. In addition, CD8(+) T cells were observed to contribute to late control of pancreatic tumors. Collectively, our data demonstrate that entry of shIDO-ST and PMNs into otherwise impermeable desmoplastic tumors is facilitated by PEGPH20-mediated HA removal, further highlighting an important component of effective treatment for PDAC.

[Revision arthroplasty : Histopathological diagnostics in periprosthetic joint infections]

BACKGROUND

Histopathological differences in synovia and synovial-like interface membrane (SLIM) patterns can be used to differentiate periprosthetic particle-induced reactions, bacterial infections (bacterial synovitis and osteomyelitis), mechanical-induced tissue alterations, adverse reactions to implant material, and arthrofibrosis (SLIM consensus classification).

AIM

Because of differences in treatment the diagnosis of a bacterial implant infection is very important. Histopathological tests and scoring systems are important diagnostic tools in identifying deep implant infections in patients with unclear clinical history as well as radiographic and laboratory studies.

RESULTS

Modern enzyme PCR-based methods, histochemical- and immune-histopathological techniques (CD3,CD15, CD68) are useful in identifying specific and nonspecific infections, as well as differentiating postsurgical changes from recurrent infections in patients with a spacer. In all histopathological scoring systems for bacterial infection, quantifying the number of neutrophil granulocytes in a defined number of high power fields is crucial.

DISCUSSION

Neutrophil granulocytes can be detected through histochemical methods and more specifically by immune-histopathological techniques and by various quantification systems (histopathological scores) leading to the diagnosis of bacterial peri-implant infection. One important function of histopathology, apart from diagnosing infection, is to rule out other mechanisms of implant failure, such as tumor infiltrations, particle-induced reactions, and adverse reactions to implant materials.

Neutrophils in asthma--a review

Asthma is a chronic inflammatory disease, with an array of cells involved in the pathogenesis of the disease. The role of neutrophils in the development of bronchial asthma is found to be complex, as they may trigger activation of immunocompetent cells and are a potent source of free oxygen radicals and enzymes participating in airway remodeling. The review highlights the role of neutrophils in bronchial asthma.

Posttranslational protein modifications by reactive nitrogen and chlorine species and strategies for their prevention and elimination

Proteins are subject to various posttranslational modifications, some of them being undesired from the point of view of metabolic efficiency. Prevention of such modifications is expected to provide new means of therapy of diseases and decelerate the process of aging. In this review, modifications of proteins by reactive nitrogen species and reactive halogen species, is briefly presented and means of prevention of these modifications and their sequelae are discussed, including the denitrase activity and inhibitors of myeloperoxidase.

Extracellular traps in lipid-rich lesions of carotid atherosclerotic plaques: implications for lipoprotein retention and lesion progression

PURPOSE

To investigate the presence and location of extracellular traps (ETs) in atherosclerotic plaques and to determine whether they are spatially associated with inflammatory cells and the lipid core.

MATERIALS AND METHODS

Human carotid atherosclerotic plaques were collected from seven patients after surgical endarterectomy. Sequential tissue sections were stained with hematoxylin-eosin or subjected to immunohistochemistry to detect ETs, neutrophils and macrophages or apolipoprotein B (ApoB). To demonstrate the specificity of the antibody used to detect ETs, the adjacent tissue section was pretreated with deoxyribonuclease-1 (DNase-1) before immunostaining for ETs.

RESULTS

All seven carotid plaques demonstrated advanced atherosclerotic lesions. Extensive ET and ApoB immunostaining was detected predominantly within the acellular lipid core. Along the edges of the lipid core, confocal microscopy revealed areas suggestive of active release of ETs from MPO-positive cells. Pretreatment of tissue sections with DNase-1 abolished ET signal in the extracellular matrix, but not the signal within the cells along the margins of the core.

CONCLUSIONS

The localization of ETs to the lipid core suggests a possible binding site for lipoproteins, which may further promote lesion progression and inflammation.

Allelic heterogeneity in NCF2 associated with systemic lupus erythematosus (SLE) susceptibility across four ethnic populations

Recent reports have associated NCF2, encoding a core component of the multi-protein NADPH oxidase (NADPHO), with systemic lupus erythematosus (SLE) susceptibility in individuals of European ancestry. To identify ethnicity-specific and -robust variants within NCF2, we assessed 145 SNPs in and around the NCF2 gene in 5325 cases and 21 866 controls of European-American (EA), African-American (AA), Hispanic (HS) and Korean (KR) ancestry. Subsequent imputation, conditional, haplotype and bioinformatic analyses identified seven potentially functional SLE-predisposing variants. Association with non-synonymous rs17849502, previously reported in EA, was detected in EA, HS and AA (P(EA) = 1.01 × 10(-54), PHS = 3.68 × 10(-10), P(AA) = 0.03); synonymous rs17849501 was similarly significant. These SNPs were monomorphic in KR. Novel associations were detected with coding variants at rs35937854 in AA (PAA = 1.49 × 10(-9)), and rs13306575 in HS and KR (P(HS) = 7.04 × 10(-7), P(KR) = 3.30 × 10(-3)). In KR, a 3-SNP haplotype was significantly associated (P = 4.20 × 10(-7)), implying that SLE predisposing variants were tagged. Significant SNP-SNP interaction (P = 0.02) was detected between rs13306575 and rs17849502 in HS, and a dramatically increased risk (OR = 6.55) with a risk allele at each locus. Molecular modeling predicts that these non-synonymous mutations could disrupt NADPHO complex assembly. The risk allele of rs17849501, located in a conserved transcriptional regulatory region, increased reporter gene activity, suggesting in vivo enhancer function. Our results not only establish allelic heterogeneity within NCF2 associated with SLE, but also emphasize the utility of multi-ethnic cohorts to identify predisposing variants explaining additional phenotypic variance ('missing heritability') of complex diseases like SLE.

Neutrophil extracellular traps in bacterial infections: strategies for escaping from killing

Neutrophils are among the first responders to virulent factors. They kill microbes by phagocytosis, oxidative burst, and as neutrophil extracellular traps (NETs). NETs production leads to unique cell death depending on, inter alia, reactive oxygen species (ROS). Recently a number of studies highlight the mechanism of bacterial escape from extracellular traps; the process that may influence the outcome of bacterial infections.

A new hydroxychavicol dimer from the roots of Piper betle

A new hydroxychavicol dimer, 2-(g'-hydroxychavicol)-hydroxychavicol (1), was isolated from the roots of Piper betle Linn. along with five known compounds, hydroxychavicol (2), aristololactam A II (3), aristololactam B II (4), piperolactam A (5) and cepharadione A (6). The structures of these isolated compounds were elucidated by spectroscopic methods. Compounds 1 and 2 exhibited inhibitory effects on the generation of superoxide anion and the release of elastase by human neutrophils.

Potent inhibition of human neutrophil activations by bractelactone, a novel chalcone from Fissistigma bracteolatum

Fissistigma bracteolatum is widely used in traditional medicine to treat inflammatory diseases. However, its active components and mechanisms of action remain unclear. In this study, (3Z)-6,7-dihydroxy-4-methoxy-3-(phenylmethylidene)-5-(3-phenylpropanoyl)-1-benzofuran-2(3H) (bractelactone), a novel chalcone from F. bracteolatum, showed potent inhibitory effects against superoxide anion (O₂·⁻) production, elastase release, and CD11b expression in formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP)-induced human neutrophils. However, bractelactone showed only weak inhibition of phorbol myristate acetate-caused O₂·⁻ production. The peak cytosolic calcium concentration ([Ca²⁺](i)) was unaltered by bractelactone in FMLP-induced neutrophils, but the decay time of [Ca²⁺](i) was significantly shortened. In a calcium-free solution, changes in [Ca²⁺](i) caused by the addition of extracellular Ca²⁺ were inhibited by bractelactone in FMLP-activated cells. In addition, bractelactone did not alter the phosphorylation of p38 MAPK, ERK, JNK, or AKT or the concentration of cAMP. These results suggest that bractelactone selectively inhibits store-operated calcium entry (SOCE). In agreement with this concept, bractelactone suppressed sustained [Ca²⁺](i) changes in thapsigargin-activated neutrophils. Furthermore, bractelactone did not alter FMLP-induced formation of inositol 1,4,5-triphosphate. Taken together, our results demonstrate that the anti-inflammatory effects of bractelactone, an active ingredient of F. bracteolatum, in human neutrophils are through the selective inhibition of SOCE.