Neutrophil extracellular traps (NETs) exacerbate severity of infant sepsis

Abstract

Background Neutrophil extracellular traps (NETs) are innate defense mechanisms that are also implicated in the pathogenesis of organ dysfunction. However, the role of NETs in pediatric sepsis is unknown. Methods Infant (2 weeks old) and adult (6 weeks old) mice were submitted to sepsis by intraperitoneal (i.p.) injection of bacteria suspension or lipopolysaccharide (LPS). Neutrophil infiltration, bacteremia, organ injury, and concentrations of cytokine, NETs, and DNase in the plasma were measured. Production of reactive oxygen and nitrogen species and release of NETs by neutrophils were also evaluated. To investigate the functional role of NETs, mice undergoing sepsis were treated with antibiotic plus rhDNase and the survival, organ injury, and levels of inflammatory markers and NETs were determined. Blood samples from pediatric and adult sepsis patients were collected and the concentrations of NETs measured. Results Infant C57BL/6 mice subjected to sepsis or LPS-induced endotoxemia produced significantly higher levels of NETs than the adult mice. Moreover, compared to that of the adult mice, this outcome was accompanied by increased organ injury and production of inflammatory cytokines. The increased NETs were associated with elevated expression of Padi4 and histone H3 citrullination in the neutrophils. Furthermore, treatment of infant septic mice with rhDNase or a PAD-4 inhibitor markedly attenuated sepsis. Importantly, pediatric septic patients had high levels of NETs, and the severity of pediatric sepsis was positively correlated with the level of NETs. Conclusion This study reveals a hitherto unrecognized mechanism of pediatric sepsis susceptibility and suggests that NETs represents a potential target to improve clinical outcomes of sepsis. Electronic supplementary material The online version of this article (10.1186/s13054-019-2407-8) contains supplementary material, which is available to authorized users.

X-Linked Immunodeficient Mice With No Functional Bruton's Tyrosine Kinase Are Protected From Sepsis-Induced Multiple Organ Failure

“…Excessive activation of neutrophils is known to decrease survival and enhance susceptibility to subsequent bacterial infections ( 41 ). One mechanism that may contribute to the pathology of sepsis is the release of neutrophil extracellular traps as they contain the beneficial antimicrobial nuclear proteins but also damaging citrullinated histones, elastase, myeloperoxidase and MMP-3 ( 42 , 43 ). The release of neutrophil extracellular traps results in ineffective phagocytosis ( 44 ).…”

SARS-CoV-2–triggered neutrophil extracellular traps mediate COVID-19 pathology

“…The release of NETs has been associated with tissue damage in several immune-mediated diseases, including chronic obstructive pulmonary disease, rheumatoid arthritis, and sepsis (Dicker et al, 2018;Khandpur et al, 2013;Colón et al, 2019). NETs cause tissue damage by extracellular exposure of DNA, granular proteins such as MPO, and histone, inducing apoptosis and fibrosis processes (Thammavongsa et al, 2013;Yadav et al, 2019).…”

“…The DNA bound to MPO was quantified using the Quant-iT PicoGreen kit (Invitrogen; cat. P11496), as described (Colón et al, 2019;Czaikoski et al, 2016).…”

“…Regarding sepsis, our group and others have described that during experimental and clinical sepsis, NETs are found in high concentrations in the blood and are positively correlated with biomarkers of vital organ injuries and sepsis severity. Furthermore, disruption or inhibition of NET release by pharmacological treatment with recombinant human DNase (rhDNase) or PAD-4 inhibitors, respectively, markedly reduced organ damage, especially in the lungs, and increased the survival rate of severe septic mice ( Colón et al, 2019 ; Czaikoski et al, 2016 ; Kambas et al, 2012 ; Martinod et al, 2015 ; Altrichter et al, 2010 ; Clark et al, 2007 ). The well-known similarities between sepsis and key events involved in the COVID-19 pathophysiology, such as cytokine overproduction ( Mehta et al, 2020 ), microthrombosis ( Magro et al, 2020 ; Dolhnikoff et al, 2020 ), and acute respiratory distress syndrome ( Lai et al, 2020 ), led us to hypothesize that NETs are triggered during SARS-CoV-2 infection and might contribute to tissue injury in COVID-19 patients.…”

Neutrophil extracellular trap stabilization leads to improved outcomes in murine models of sepsis

“…For example, cfDNA triggers the contact-pathway 13 and fixes complement 14 , MPO induces oxidative tissue damage 15 , NE cleaves tissue factor pathway inhibitor (TFPI) promoting thrombosis 16 , while histones cause platelet activation 17 and are directly toxic to endothelial cells 18 . In septic patients, plasma levels of NDPs correlate with end-organ damage and mortality 19,20 . It has been suggested that preventing NET release (NETosis) might be beneficial 21 , but we believe that this strategy may be ineffective as septic patients likely have a large amount of NETs released by the time they become clinically ill.…”