Sacha Zeerleder

Circulating Nucleosomes and Neutrophil Activation as Risk Factors for Deep Vein Thrombosis

Objective—The formation of neutrophil extracellular traps and the exposure of nucleosomes on these neutrophil extracellular traps contribute to coagulation activation and the propagation of deep vein thrombosis (DVT) in animal models. However, no data are available on the role of neutrophil extracellular traps or nucleosomes in patients with thrombosis. Methods and Results—We conducted a case–control study, in which levels of circulating nucleosomes and neutrophil elastase–&agr;1-antitrypsin complexes were assessed in plasma from 150 patients with objectified symptomatic DVT (cases) and compared with 195 patients with a clinical suspicion of DVT but in whom DVT was excluded (controls). We explored the association between both nucleosomes and elastase–&agr;1-antitrypsin complexes, and the presence of DVT by calculating the odds ratio with corresponding 95% CIs. Elevated levels of both circulating nucleosomes and elastase–&agr;1-antitrypsin complexes were associated with a 3-fold risk of DVT, and the associations remained similar after adjustment for potential confounders (malignancy, smoking, recent immobilization, recent hospitalization). The risk increased with higher nucleosome and elastase–&agr;1-antitrypsin complex levels, suggesting a dose-dependent relationship among circulating nucleosomes, activated neutrophils, and DVT. Conclusion—Our study suggests an association among circulating nucleosomes, activated neutrophils, and presence of DVT in humans, which might have implications for treatment and prevention.

C1-inhibitor in patients with severe sepsis and septic shock: beneficial effect on renal dysfunction.

ObjectiveTo investigate the efficacy and the safety of the parenteral administration of C1-inhibitor to patients with severe sepsis or septic shock. DesignDouble blind, randomized, and placebo-controlled trial. SettingSurgical and medical intensive care units of a tertiary care university hospital. PatientsForty consecutive patients (20 C1-inhibitor/20 placebo) who entered the intensive care unit with severe sepsis or septic shock. InterventionC1-inhibitor intravenously in a 1-hr infusion, starting with 6000 IU, followed by 3000 IU, 2000 IU, and 1000 IU at 12-hr intervals, compared with placebo. Measurements and Main ResultsC1-inhibitor administration significantly increased plasma C1-inhibitor antigen and activity levels during days 1–4 (p < .007). Patients in the C1-inhibitor group had significantly lower serum creatinine concentrations on day 3 (p = .048) and 4 (p = .01) than placebo patients. Multiple organ dysfunction assessed by logistic organ dysfunction and sepsis-related organ failure assessment scores was less pronounced in patients treated with C1-inhibitor. Mortality rate was similar in both groups. There were no C1-inhhibitor-related side effects. ConclusionsC1-inhibitor administration attenuated renal impairment in patients with severe sepsis or septic shock.

International Society on Thrombosis and Haemostasis score for overt disseminated intravascular coagulation predicts organ dysfunction and fatality in sepsis patients.

We evaluated the score for disseminated intravascular coagulation (DIC) recently published by the International Society for Thrombosis and Haemostasis (ISTH) in a well-defined series of sepsis patients. Thirty-two patients suffering from severe sepsis and eight patients with septic shock were evaluated following the ISTH DIC score. Fibrin monomer and D-dimer were chosen as fibrin-related markers (FRM), respectively. DIC scores for nonsurvivors (n = 13) as well as for septic shock patients were higher (P < 0.04) compared with survivors and patients with severe sepsis, respectively. Using fibrin monomer and D-dimer, 30 and 25% of patients suffered from overt DIC. Overt DIC was associated with significantly elevated thrombin–antithrombin complexes and plasminogen activator inhibitor type-1 levels as well as with significantly lower factor VII clotting activity. Patients with overt DIC had a significantly higher risk of death and of developing septic shock. Since more than 95% of the sepsis patients had elevated FRM, the DIC score was strongly dependent on prolongation of the prothrombin time and platelet counts. The ISTH DIC score is useful to identify patients with coagulation activation, predicting fatality and disease severity. It mainly depends on the prolongation of the prothrombin time and platelet counts.

C1-inhibitor: more than a serine protease inhibitor.

C1-inhibitor (C1-inh) is a crucial regulator of the activation of plasmatic cascade systems involved in inflammation contributing to the homeostasis in the generation of proinflammatory mediators. The importance of C1-inh is illustrated by patients with hereditary angioedema where decreased levels of C1-inh lead to an uncontrolled generation of vasoactive peptides resulting in potential life-threatening subcutaneous edema. Recent publications, however, suggest that the anti-inflammatory properties of C1-inh do not strictly depend on its capacity to regulate the complement and contact phase system. This review summarizes the biochemical characteristics of C1-inh and its role in the regulation of plasmatic cascade systems as well as the role of the nonserpin domain.

Administration of C1 Inhibitor Reduces Neutrophil Activation in Patients with Sepsis

ABSTRACT Forty patients with severe sepsis or septic shock recently received C1 inhibitor. In the present study we studied the effect of C1 inhibitor therapy on circulating elastase-α1-antitrypsin complex (EA) and lactoferrin (LF) levels in these patients to gain further insight about agonists involved in the activation of neutrophils in human sepsis. Elevated levels of EA and LF were found in 65 and 85% of the septic patients, respectively. Patients with elevated EA levels had higher organ dysfunction scores, higher levels of cytokines, and higher levels of complement activation products than patients with normal EA levels. C1 inhibitor therapy reduced EA as well as complement activation and IL-8 release in the patients with elevated EA on admission. We conclude that neutrophil activation in human sepsis correlates with the severity of organ dysfunction and involves complement and interleukin-8 as agonists. The effect of C1 inhibitor therapy on neutrophils may provide an explanation for the beneficial, although mild, effects of this treatment on organ dysfunction in sepsis.

Factor VII-Activating Protease Is Activated in Multiple Trauma Patients and Generates Anaphylatoxin C5a

Severe tissue injury results in early activation of serine protease systems including the coagulation and complement cascade. In this context, little is known about factor VII-activating protease (FSAP), which is activated by substances released from damaged cells such as histones and nucleosomes. Therefore, we have measured FSAP activation in trauma patients and have identified novel FSAP substrates in human plasma. Mass spectrometry-based methods were used to identify FSAP binding proteins in plasma. Anaphylatoxin generation was measured by ELISA, Western blotting, protein sequencing, and chemotaxis assays. Plasma samples from trauma patients were analyzed for FSAP Ag and activity, nucleosomes, C5a, and C3a. Among others, we found complement components C3 and C5 in FSAP coimmunoprecipitates. C3 and C5 were cleaved by FSAP in a dose- and time-dependent manner generating functional C3a and C5a anaphylatoxins. Activation of endogenous FSAP in plasma led to increased C5a generation, but this was not the case in plasma of a homozygous carrier of Marburg I single nucleotide polymorphism with lower FSAP activity. In multiple trauma patients there was a large increase in circulating FSAP activity and nucleosomes immediately after the injury. A high correlation between FSAP activity and C5a was found. These data suggest that activation of FSAP by tissue injury triggers anaphylatoxin generation and thereby modulates the posttraumatic inflammatory response in vivo. A strong link between C5a, nucleosomes, and FSAP activity indicates that this new principle might be important in the regulation of inflammation.

Activation of factor VII-activating protease in human inflammation: a sensor for cell death

IntroductionCell death is a central event in the pathogenesis of sepsis and is reflected by circulating nucleosomes. Circulating nucleosomes were suggested to play an important role in inflammation and were demonstrated to correlate with severity and outcome in sepsis patients. We recently showed that plasma can release nucleosomes from late apoptotic cells. Factor VII-activating protease (FSAP) was identified to be the plasma serine protease responsible for nucleosome release. The aim of this study was to investigate FSAP activation in patients suffering from various inflammatory diseases of increasing severity.MethodsWe developed ELISAs to measure FSAP-C1-inhibitor and FSAP-α2-antiplasmin complexes in plasma. FSAP-inhibitor complexes were measured in the plasma of 20 adult patients undergoing transhiatal esophagectomy, 32 adult patients suffering from severe sepsis and 8 from septic shock and 38 children suffering from meningococcal sepsis.ResultsWe demonstrate plasma FSAP to be activated upon contact with apoptotic and necrotic cells by an assay detecting complexes between FSAP and its target serpins α2-antiplasmin and C1-inhibitor, respectively. By means of that assay we demonstrate FSAP activation in post-surgery patients, patients suffering from severe sepsis, septic shock and meningococcal sepsis. Levels of FSAP-inhibitor complexes correlate with nucleosome levels and correlate with severity and mortality in these patients.ConclusionsThese results suggest FSAP activation to be a sensor for cell death in the circulation and that FSAP activation in sepsis might be involved in nucleosome release, thereby contributing to lethality.

Nucleosome-releasing factor: a new role for factor VII-activating protease (FSAP)

Plasma proteins such as early comple ment components and IgM are involved in the removal of late apoptotic or secondary necrotic (sn) cells. We have recently described how a plasma protease that could be inhibited by the protease inhibitor aprotinin was essential to remove nucleosomes from sn cells. An obvious candidate, plasmin, did indeed have nucleo some‐releasing factor (NRF) activity. However, recalci fied plasma (r‐plasma) retained its NRF activity after plasminogen depletion, which suggests the existence of another protease responsible for NRF activity in plasma. In this study we have used size‐exclusion and anion‐exchange chromatography to purify the protease responsible for NRF activity in plasma. SDS‐PAGE analysis of chromatography fractions containing NRF activity revealed a protein band corresponding with NRF activity. Sequence analysis showed this band to be factor VII‐activating protease (FSAP). We developed monoclonal antibodies to FSAP and were able to com pletely inhibit NRF activity in plasma with monoclonal antibodies to FSAP. Using affinity chromatography we were able to purify single‐chain (sc) FSAP from r‐ plasma. Purified scFSAP efficiently removes nucleo‐ somes from sn cells. We report that factor VII‐activat‐ ing protease may function in cellular homeostasis by catalyzing the release of nucleosomes from secondary necrotic cells.— Zeerleder, S., Zwart, B., te Velthuis, H., Stephan, F., Manoe, R., Rensink, I., Aarden, L. A. Nucleosome‐releasing factor: a new role for factor VII‐activating protease (FSAP). FASEB J. 22, 4077–4084 (2008)

Circulating nucleosomes and severity of illness in children suffering from meningococcal sepsis treated with protein C

Objective:Cell death leading to circulating nucleosomes and histones is a critical step in the pathogenesis of sepsis and contributes to lethality. Activated protein C was demonstrated to attenuate the harmful effects of histones. The objective of this retrospective study was to evaluate whether nucleosomes correlate with the severity of the inflammatory response and mortality in children suffering from severe meningococcal sepsis. Furthermore, we wanted to study the effects of infusion of protein C on nucleosome levels in children with septic purpura. Design:Retrospective analysis of nucleosome levels in children suffering from meningococcal sepsis treated with either placebo or protein C. Setting:Pediatric intensive care unit of a tertiary care university center. Patients:In a randomized, placebo-controlled study, either protein C or placebo was administered to 38 children suffering from meningococcal sepsis. Nucleosome levels have been measured retrospectively in these 38 children suffering from meningococcal sepsis. Measurements and Main Results:Twenty-eight children were treated with protein C and 10 received placebo. Nucleosome levels were significantly higher in nonsurvivors (n = 9) at any time point measured as compared to survivors (n = 29). Nucleosome levels significantly correlated with organ dysfunction scores, cytokines, and parameters for coagulation. Patients treated with protein C had significantly higher activated protein C levels than children receiving placebo. We could not find a clear effect of activated protein C on nucleosome levels in these patients. Conclusion:Circulating nucleosomes correlated with the severity of the inflammatory response and were associated with mortality in children suffering from meningococcal sepsis. We show that protein C administration does not decrease nucleosome levels in these patients.

Transfusion-related acute lung injury in cardiac surgery patients is characterized by pulmonary inflammation and coagulopathy: a prospective nested case-control study.

Objective: Transfusion-related acute lung injury is the leading cause of transfusion-related morbidity and mortality. Clinical data on the pathogenesis of transfusion-related acute lung injury are sparse. The objective of the present study was to determine inflammation and coagulation pathways involved in the onset of transfusion-related acute lung injury. Design: Nested case-control study. Setting: Operating theatre and intensive care department of a tertiary referral hospital. Patients: Elective cardiac surgery patients requiring postsurgery intensive care admission. Interventions: None. Measurements: Cardiac surgery patients (n = 668) were prospectively screened for the onset of transfusion-related acute lung injury. Transfusion-related acute lung injury cases (n = 16) were randomly assigned to transfused and nontransfused cardiac surgery controls in a 1:2 ratio. Blood samples were taken pre- and postoperatively and at onset of transfusion-related acute lung injury. In addition, at onset of transfusion-related acute lung injury, bronchoalveolar lavage fluid was obtained. In plasma and bronchoalveolar lavage fluid, levels of interleukin-6, interleukin-8, elastase-&agr;(1)-antitrypsin complexes, thrombin–antithrombin complexes, plasminogen activator activity, and plasminogen activator inhibitor-1 were determined by means of enzyme-linked immunosorbent assay. Main Results: In all patients, cardiac surgery was associated with systemic inflammation, evidenced by an increase in plasma levels of interleukin-6, interleukin-8, and elastase-&agr;(1)-antitrypsin complexes compared with presurgery levels (p < .001). Prior to onset of transfusion-related acute lung injury, systemic interleukin-8 and interleukin-6 levels were higher compared with nontransfused controls (p < .01). In transfusion-related acute lung injury cases, bronchoalveolar lavage fluid levels of interleukin-8, interleukin-6, and elastase-&agr;(1)-antitrypsin complexes were elevated compared with control groups (p < .05). Both plasma and bronchoalveolar lavage fluid levels of thrombin–antithrombin complexes were enhanced in transfusion-related acute lung injury cases compared with control groups (p < .01). Bronchoalveolar lavage fluid levels of plasminogen activator activity were decreased due to an increase in plasminogen activator inhibitor-1 levels in transfusion-related acute lung injury cases compared with control groups (p < .01), indicating suppressed fibrinolysis. Conclusions: Prior to onset of transfusion-related acute lung injury, there is systemic inflammation and neutrophil sequestration. Transfusion-related acute lung injury is characterized by both systemic and pulmonary inflammation and activation of neutrophils, as well as enhanced coagulation and suppressed fibrinolysis.