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In vivo characterization of neutrophil extracellular traps in various organs of a murine sepsis model.

ABSTRACT: Neutrophil extracellular traps (NETs) represent extracellular microbial trapping and killing. Recently, it has been implicated in thrombogenesis, autoimmune disease, and cancer progression. The aim of this study was to characterize NETs in various organs of a murine sepsis model in vivo and to investigate their associations with platelets, leukocytes, or vascular endothelium. NETs were classified as two distinct forms; cell-free NETs that were released away from neutrophils and anchored NETs that were anchored to neutrophils. Circulating cell-free NETs were characterized as fragmented or cotton-like structures, while anchored NETs were characterized as linear, reticular, membranous, or spot-like structures. In septic mice, both anchored and cell-free NETs were significantly increased in postcapillary venules of the cecum and hepatic sinusoids with increased leukocyte-endothelial interactions. NETs were also observed in both alveolar space and pulmonary capillaries of the lung. The interactions of NETs with platelet aggregates, leukocyte-platelet aggregates or vascular endothelium of arterioles and venules were observed in the microcirculation of septic mice. Microvessel occlusions which may be caused by platelet aggregates or leukocyte-platelet aggregates and heterogeneously decreased blood flow were also observed in septic mice. NETs appeared to be associated with the formation of platelet aggregates or leukocyte-platelet aggregates. These observational findings may suggest the adverse effect of intravascular NETs on the host during a sepsis.

SUBMITTER: Tanaka K

PROVIDER: S-EPMC4221155 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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In vivo characterization of neutrophil extracellular traps in various organs of a murine sepsis model.

Tanaka Koji K Koike Yuhki Y Shimura Tadanobu T Okigami Masato M Ide Shozo S Toiyama Yuji Y Okugawa Yoshinaga Y Inoue Yasuhiro Y Araki Toshimitsu T Uchida Keiichi K Mohri Yasuhiko Y Mizoguchi Akira A Kusunoki Masato M

PloS one 20141105 11

Neutrophil extracellular traps (NETs) represent extracellular microbial trapping and killing. Recently, it has been implicated in thrombogenesis, autoimmune disease, and cancer progression. The aim of this study was to characterize NETs in various organs of a murine sepsis model in vivo and to investigate their associations with platelets, leukocytes, or vascular endothelium. NETs were classified as two distinct forms; cell-free NETs that were released away from neutrophils and anchored NETs tha ...[more]

PMID: 25372699

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Project description:Organ dysfunction is a major concern in sepsis pathophysiology and contributes to its high mortality rate. Neutrophil extracellular traps (NETs) have been implicated in endothelial damage and take part in the pathogenesis of organ dysfunction in several conditions. NETs also have an important role in counteracting invading microorganisms during infection. The aim of this study was to evaluate systemic NETs formation, their participation in host bacterial clearance and their contribution to organ dysfunction in sepsis. C57Bl/6 mice were subjected to endotoxic shock or a polymicrobial sepsis model induced by cecal ligation and puncture (CLP). The involvement of cf-DNA/NETs in the physiopathology of sepsis was evaluated through NETs degradation by rhDNase. This treatment was also associated with a broad-spectrum antibiotic treatment (ertapenem) in mice after CLP. CLP or endotoxin administration induced a significant increase in the serum concentrations of NETs. The increase in CLP-induced NETs was sustained over a period of 3 to 24 h after surgery in mice and was not inhibited by the antibiotic treatment. Systemic rhDNase treatment reduced serum NETs and increased the bacterial load in non-antibiotic-treated septic mice. rhDNase plus antibiotics attenuated sepsis-induced organ damage and improved the survival rate. The correlation between the presence of NETs in peripheral blood and organ dysfunction was evaluated in 31 septic patients. Higher cf-DNA concentrations were detected in septic patients in comparison with healthy controls, and levels were correlated with sepsis severity and organ dysfunction. In conclusion, cf-DNA/NETs are formed during sepsis and are associated with sepsis severity. In the experimental setting, the degradation of NETs by rhDNase attenuates organ damage only when combined with antibiotics, confirming that NETs take part in sepsis pathogenesis. Altogether, our results suggest that NETs are important for host bacterial control and are relevant actors in the pathogenesis of sepsis.

Project description:Sepsis consists of life-threatening organ dysfunction resulting from a dysregulated response to infection. Recent studies have found that excessive neutrophil extracellular traps (NETs) contribute to the pathogenesis of sepsis, thereby increasing morbidity and mortality. Lysophosphatidic acid (LPA) is a small glycerophospholipid molecule that exerts multiple functions by binding to its receptors. Although LPA has been functionally identified to induce NETs, whether and how LPA receptors, especially lysophosphatidic acid receptor 3 (LPA3), play a role in the development of sepsis has never been explored. A comprehensive understanding of the impact of LPA3 on sepsis is essential for the development of medical therapy. After intraperitoneal injection of lipopolysaccharide (LPS), Lpar3 -/-mice showed a substantially higher mortality, more severe injury, and more fibrinogen content in the lungs than wild-type (WT) mice. The values of blood coagulation markers, plasma prothrombin time (PT) and fibrinogen (FIB), indicated that the Lpar3 -/- mice underwent a severe coagulation process, which resulted in increased thrombosis. The levels of NETs in Lpar3 -/- mice were higher than those in WT mice after LPS injection. The mortality rate and degree of lung damage in Lpar3 -/- mice with sepsis were significantly reduced after the destruction of NETs by DNaseI treatment. Furthermore, in vitro experiments with co-cultured monocytes and neutrophils demonstrated that monocytes from Lpar3 -/- mice promoted the formation of NETs, suggesting that LPA3 acting on monocytes inhibits the formation of NETs and plays a protective role in sepsis. Mechanistically, we found that the amount of CD14, an LPS co-receptor, expressed by monocytes in Lpar3 -/-mice was significantly elevated after LPS administration, and the MyD88-p65-NFκB signaling axis, downstream of toll-like receptor 4 signaling, in monocytes was overactivated. Finally, after an injection of the LPA3 agonist (2S)-1-oleoyl-2-methylglycero-3-phosphothionate (OMPT), the survival rate of mice with sepsis was improved, organ damage was reduced, and the production of NETs was decreased. This suggested the possible translational value and application prospects of (2S)-OMPT in the treatment of sepsis. Our study confirms an important protective role of LPA3 in curbing the development of sepsis by suppressing NETs production and thrombosis and provides new ideas for sepsis treatment strategies.

Project description:Introduction: Autoreactivity to histones is a pervasive feature of several human autoimmune disorders including systemic lupus erythematosus (SLE). Specific post-translational modifications (PTMs) of histones within neutrophil extracellular traps (NETs) may potentially drive the process by which tolerance to these chromatin-associated proteins is broken. We hypothesized that NETs and their unique histone PTMs might be capable of inducing autoantibodies that target histones. Methods: We developed a novel and efficient method for the in vitro production, visualization, and broad profiling of histone-PTMs of human and murine NETs. We also immunized Balb/c mice with murine NETs and profiled their sera on autoantigen and histone peptide microarrays for evidence of autoantibody production to their immunogen. Results: We confirmed specificity toward acetyl-modified histone H2B as well as to other histone PTMs in sera from patients with SLE known to have autoreactivity against histones. We observed enrichment for distinctive histone marks of transcriptionally silent DNA during NETosis triggered by diverse stimuli. However, NETs derived from human and murine sources did not harbor many of the PTMs toward which autoreactivity was observed in patients with SLE or in MRL/lpr mice. Further, while murine NETs were weak autoantigens in vivo, there was only partial overlap in the IgG and IgM autoantibody profiles induced by vaccination of mice with NETs and those seen in patients with SLE. Conclusions: Isolated in vivo exposure to NETs is insufficient to break tolerance and may involve additional factors that have yet to be identified. Serum samples from 20 systemic lupus erythematosis patients were run on the Human Epigenome Microarray Platform V1.0 (HEMP; a single-color platform), in order to profile their autoantibodies against a library of post-translationally modified histone peptides. These 20 samples were randomly selected from a larger cohort previously profiled (data not shown) on the Utz Lab Whole Protein Autoantigen Array V2.0 (a single-color platform), where 14 were histone-reactive and 6 were histone-nonreactive. Control sera from 9 healthy adults and a positive control comprising a mixture of autoimmune sera with defined reactivities, were also run on HEMP V1.0. Together, these samples comprise the data appearing in Figures 1 and S1 (IgG and IgM isotype reactivity profiles, respectively), identifying IgG reactivity to 9 peptides that significantly distinguish histone-reactive from -nonreactive sera among 96 peptides profiled. For data appearing in Figure 5, serum samples from a total of 6 Balb/c mice, consisting of two treatment groups, NETs (Neutrophil Extracellular Traps) and NETs + CRAMP (cathelicidin-related antimicrobial peptide) were collected monthly over a 3-month period, along with a zero time point. These samples were compared with a positive control consisting of serum collected from a MLR/lpr mice exhibiting lupus-like symptoms, and a negative control with no serum. The 0, 1 and 2 month time points were profiled on the Utz Lab Whole Protein Autoantigen Array V2.0 and are shown in Figure 5A-B, while the 1 and 3 month time points were profiled on HEMP V1.0 arrays and shown in Figure 5E. All samples were run once with no replicates.

Dataset Information

In vivo characterization of neutrophil extracellular traps in various organs of a murine sepsis model.

Publications

In vivo characterization of neutrophil extracellular traps in various organs of a murine sepsis model.

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