Impaired clot lysis in the presence of human neutrophil elastase

Phenotypes of Disseminated Intravascular Coagulation

Two phenotypes of disseminated intravascular coagulation (DIC) are systematically reviewed. DIC is classified into thrombotic and fibrinolytic phenotypes characterized by thrombosis and hemorrhage, respectively. Major pathology of DIC with thrombotic phenotype is the activation of coagulation, insufficient anticoagulation with endothelial injury, and plasminogen activator inhibitor-1-mediated inhibition of fibrinolysis, leading to microvascular fibrin thrombosis and organ dysfunction. DIC with fibrinolytic phenotype is defined as massive thrombin generation commonly observed in any type of DIC, combined with systemic pathologic hyperfibrinogenolysis caused by underlying disorder that results in severe bleeding due to excessive plasmin formation. Three major pathomechanisms of systemic hyperfibrinogenolysis have been considered: (1) acceleration of tissue-type plasminogen activator (t-PA) release from hypoxic endothelial cells and t-PA-rich storage pools, (2) enhancement of the conversion of plasminogen to plasmin due to specific proteins and receptors that are expressed on cancer cells and endothelial cells, and (3) alternative pathways of fibrinolysis. DIC with fibrinolytic phenotype can be diagnosed by DIC diagnosis followed by the recognition of systemic pathologic hyperfibrin(ogen)olysis. Low fibrinogen levels, high fibrinogen and fibrin degradation products (FDPs), and the FDP/D-dimer ratio are important for the diagnosis of systemic pathologic hyperfibrin(ogen)olysis. Currently, evidence-based treatment strategies for DIC with fibrinolytic phenotypes are lacking. Tranexamic acid appears to be one of the few methods to be effective in the treatment of systemic pathologic hyperfibrin(ogen)olysis. International cooperation for the elucidation of pathomechanisms, establishment of diagnostic criteria, and treatment strategies for DIC with fibrinolytic phenotype are urgent issues in the field of thrombosis and hemostasis.

Recent advances in disseminated intravascular coagulation: endothelial cells and fibrinolysis in sepsis-induced DIC

Endothelial cells are highly active, sensing and responding to signals from extracellular environments. They act as gatekeepers, mediating the recruitment and extravasation of proinflammatory leukocytes to the sites of tissue damage or infection. Endothelial cells participate in fibrinolysis by secreting tissue-type plasminogen activator, which converts plasminogen to active enzyme plasmin through constitutive and regulated pathways. Fibrinolysis systems and inflammation are tightly linked, as both responses are major host defense systems against both healing processes of tissue repair as well as pathogenic microorganisms. Endothelial cell dysfunction is one of the early signs of systemic inflammation, and it is a trigger of multiple organ failure in sepsis. The marked increase in plasminogen activator inhibitor-1 level causes fibrinolytic shutdown in endotoxemia or sepsis and is one of the most important predictors of multiple organ dysfunction during sepsis-induced disseminated intravascular coagulation (DIC). Leukocytes exhibit the first-line response to microorganisms. Leukocyte-derived elastase degrades cross-linked fibrin to yield molecular species distinct from those generated by plasmin. The alternative systems for fibrinolysis that interact with the plasminogen activator-plasmin systems may play crucial roles in the lysis of fibrin clots in sepsis-induced DIC.

The activation of neutrophil elastase-mediated fibrinolysis is not sufficient to overcome the fibrinolytic shutdown of disseminated intravascular coagulation associated with systemic inflammation

INTRODUCTION

We conducted a prospective study to test the hypothesis that the activation of neutrophil elastase-mediated fibrinolysis is insufficient to overcome the fibrinolytic shutdown of disseminated intravascular coagulation (DIC) in patients associated with systemic inflammation.

MATERIALS AND METHODS

We investigated 45 consecutive patients with systemic inflammatory response syndrome (SIRS) and sepsis, classified as 11 DIC and 34 non-DIC. Fibrin degradation products by neutrophil elastase (Elastase-XDP) and by plasmin (FDP), cross-linked fibrin degradation products (D-dimer), soluble fibrin, antithrombin, protein C, plasminogen activator inhibitor-1 (PAI-1), and urinary trypsin inhibitor (UTI) were measured within 24 h after the patients met either the SIRS or sepsis criteria (day 0), as well as on days 2 and 4.

RESULTS

In DIC patients, higher levels of soluble fibrin, PAI-1, and FDP and markedly lower levels of antithrombin and protein C were observed in comparison to those in non-DIC patients. DIC patients showed a significantly higher level of peak Elastase-XDP than non-DIC patients (25.7+/-5.9 vs. 16.3+/-2.6 microg/mL, respectively; p=0.0333). However, we could not find any substantial difference in the levels of Elastase-XDP, UTI, and D-dimer on each day during the study period between the two groups. Good correlations were observed between the levels of D-dimer and Elastase-XDP in both patients with and without DIC (r(s)=0.699 and r(s)=0.817, respectively), but the coefficients of determination in both groups showed low values and the slopes of the regression lines were less than 1.0. A multivariate logistic regression analysis showed the elevated peak Elastase-XDP levels to inversely correlate with death. On the other hand, the DIC patients showed a higher number of organ dysfunctions and a poorer prognosis than did the non-DIC patients.

CONCLUSIONS

The activation of the neutrophil elastase-mediated fibrinolytic pathway may be insufficient to overcome the fibrinolytic shutdown by PAI-1 and may in part explain the poor prognosis of DIC patients associated with systemic inflammation.

Deep vein thrombosis resolution is modulated by monocyte CXCR2-mediated activity in a mouse model

OBJECTIVE

To determine the role of CXCR2, the receptor for cysteine-X-cysteine (CXC) chemokines, and its primary effector cell, the neutrophil (PMN), on deep venous thrombosis (DVT) resolution.

METHODS AND RESULTS

DVT in BALB/c, anti-CXCR2 antibody-treated, and BALB/c CXCR2(-/-) mice were created by infrarenal inferior vena cava (IVC) ligation and the thrombus harvested at various time points over 21 days. The CXCR2(-/-) mice had significantly larger thrombi at early time points (days 2 to 8), and significantly decreased intrathrombus PMNs, monocytes, and neovascularization as compared with controls. Thrombus KC/CXCL1 was significantly higher at 2 days in CXCR2-/- thrombi as measured by enzyme-linked immunosorbent assay. Fibrin content was significantly higher, with less uPA gene expression at 4 days in CXCR2-/- thrombi. Late fibrotic maturation of the thrombus was delayed in the CXCR2-/- mice, with significantly decreased 8 day MMP-2 activity, whereas MMP-9 activity was elevated as compared with controls. Similar impairment in DVT resolution was found at 8 days with anti-CXCR2 inhibition. However, systemic neutropenia, unlike CXCR2 deletion, did not increase the thrombus size as compared with controls.

CONCLUSIONS

Normal DVT resolution involves CXCR2-mediated neovascularization, collagen turnover, and fibrinolysis, and it is probably primarily monocyte-dependent.

D-dimers are degraded by human neutrophil elastase

To see if D-dimers were degraded by human neutrophil elastase (HNE), cross-linked fibrin was obtained by adding thrombin to purified fibrinogen in the presence of calcium ions and factor XIII, and the fibrin clot subsequently degraded by plasmin. Thereafter, the supernatant containing fibrin degradation products was removed and incubated with HNE. D-dimer levels were measured by two rapid semiquantitative tests, a latex agglutination test and the Nycocard immunofiltration test, and a quantitative ELISA-method. With increasing incubation time, D-dimer levels as measured by the latex and Nycocard tests rapidly decreased and subsequently became undetectable, while the ELISA D-dimer values remained essentially unchanged. By using SDS-electrophoresis and immunoblotting, the degradation of plasmic derivatives of cross-linked fibrin by fiNE was visualised. We conclude that in a purified system, D-dimers formed during plasmin mediated lysis of cross linked fibrin are further degraded by HNE. Such HNE degradation reduces the D-dimer concentration as measured by rapid semiquantitive tests, and may be partly responsible for discrepant results when using different D-dimer assays.