Tissue factor pathway inhibitor and thrombin activatable fibrinolytic inhibitor plasma levels following burn and septic injuries in rats

Elucidating the molecular mechanisms of fibrinolytic shutdown after severe injury: The role of thrombin-activatable fibrinolysis inhibitor

BACKGROUND

The mechanisms underlying trauma-induced coagulopathy remain elusive. Hyperfibrinolysis has been linked to increased plasminogen activation and antiprotease consumption; however, the mechanistic players in its counterpart, fibrinolysis shutdown, remain unclear. We hypothesize that thrombin-activatable fibrinolysis inhibitor (TAFI) plays a major role in fibrinolytic shutdown after injury.

METHODS

As part of this observational cohort study, whole blood was collected from trauma activation patients at a single, level 1 trauma center. Citrated rapid thrombelastography and the following enzyme-linked immunosorbent assays were conducted: thrombin, antithrombin, thrombin-antithrombin complex, TAFI, plasminogen, antiplasmin, plasmin-antiplasmin (PAP), tissue plasminogen activator, plasminogen activator inhibitor 1, and tissue plasminogen activator-plasminogen activator inhibitor 1 complex. Univariate and cluster analysis were performed.

RESULTS

Overall, 56 patients (median age, 33.5 years; 70% male) were included. The majority (57%) presented after blunt mechanism and with severe injury (median New Injury Severity Score, 27). Two clusters of patients were identified: Group 1 (normal fibrinolysis, n = 21) and Group 2 (fibrinolysis shutdown, n = 35). Group 2 had significantly lower fibrinolysis with a median LY30 of 1.1% (interquartile range [IQR], 0.1-1.9%) versus 2.1% (IQR, 0.5-2.8%) in Group 1; while the median LY30 was within physiologic range, 45% of patients in Group 2 were in shutdown (vs. 24% in Group 1, p = 0.09). Compared with Group 1, Group 2 had significantly higher PAP (median, 4.7 [IQR, 1.7-9.3] vs. 1.4 [1.0-2.1] μg/mL in Group 1; p = 0.002) and higher TAFI (median, 152.5% [IQR, 110.3-190.7%] vs. 121.9% [IQR, 93.2-155.6%]; p = 0.04). There was a strong correlation between PAP and TAFI ( R2 = 0.5, p = 0.0002).

CONCLUSION

The presented data characterize fibrinolytic shutdown, indicating an initial plasmin burst followed by diminished fibrinolysis, which is distinct from hypofibrinolysis (inadequate plasmin burst and fibrinolysis). After an initial thrombin and plasmin burst (increased PAP), fibrinolysis is inhibited, mediated in part by increased TAFI.

Circulating Syndecan-1 and Tissue Factor Pathway Inhibitor, Biomarkers of Endothelial Dysfunction, Predict Mortality in Burn Patients

OBJECTIVE

The aim of this study is to evaluate the association between burn injury and admission plasma levels of Syndecan-1 (SDC-1) and Tissue Factor Pathway Inhibitor (TFPI), and their ability to predict 30-day mortality.

BACKGROUND

SDC-1 and TFPI are expressed by vascular endothelium and shed into the plasma as biomarkers of endothelial damage. Admission plasma biomarker levels have been associated with morbidity and mortality in trauma patients, but this has not been well characterized in burn patients.Methods: This cohort study enrolled burn patients admitted to a regional burn center between 2013 and 2017. Blood samples were collected within 4 h of admission and plasma SDC-1 and TFPI were quantified by ELISA. Demographics and injury characteristics were collected prospectively. The primary outcome was 30-day in-hospital mortality.

RESULTS

Of 158 patients, 74 met inclusion criteria. Most patients were male with median age of 41.5 years and burn TBSA of 20.5%. The overall mortality rate was 20.3%. Admission SDC-1 and TFPI were significantly higher among deceased patients. Plasma SDC-1 >34 ng/mL was associated with a 32-times higher likelihood of mortality [OR: 32.65 (95% CI, 2.67-399.78); P = 0.006] and a strong predictor of mortality (area under the ROC [AUROC] 0.92). TFPI was associated with a nine-times higher likelihood of mortality [OR: 9.59 (95% CI, 1.02-89.75); P = 0.002] and a fair predictor of mortality (AUROC 0.68).

CONCLUSIONS

SDC-1 and TFPI are associated with a higher risk of 30-day mortality. We propose the measurement of SDC-1 on admission to identify burn patients at high risk of mortality. However, further investigation with a larger sample size is warranted.

Burn-Induced Coagulopathies: a Comprehensive Review

Burn-induced coagulopathy is not well understood, and consensus on diagnosis, prevention, and treatments are lacking. In this review, literature on burn-induced (and associated) coagulopathy is presented along with the current understanding of the effects of burn injury on the interactions among coagulation, fibrinolysis, and inflammation in the acute resuscitative phase and reconstructive phase of care. The role of conventional tests of coagulopathy and functional assays like thromboelastography or thromboelastometry will also be discussed. Finally, reported methods for the prevention and treatment of complications related to burn-induced coagulopathy will be reviewed.

Post-Traumatic Sepsis Is Associated with Increased C5a and Decreased TAFI Levels

Background: Sepsis frequently occurs after major trauma and is closely associated with dysregulations in the inflammatory/complement and coagulation system. Thrombin-activatable fibrinolysis inhibitor (TAFI) plays a dual role as an anti-fibrinolytic and anti-inflammatory factor by downregulating complement anaphylatoxin C5a. The purpose of this study was to investigate the association between TAFI and C5a levels and the development of post-traumatic sepsis. Furthermore, the predictive potential of both TAFI and C5a to indicate sepsis occurrence in polytraumatized patients was assessed. Methods: Upon admission to the emergency department (ED) and daily for the subsequent ten days, circulating levels of TAFI and C5a were determined in 48 severely injured trauma patients (injury severity score (ISS) ≥ 16). Frequency matching according to the ISS in septic vs. non-septic patients was performed. Trauma and physiologic characteristics, as well as outcomes, were assessed. Statistical correlation analyses and cut-off values for predicting sepsis were calculated. Results: Fourteen patients developed sepsis, while 34 patients did not show any signs of sepsis (no sepsis). Overall injury severity, as well as demographic parameters, were comparable between both groups (ISS: 25.78 ± 2.36 no sepsis vs. 23.46 ± 2.79 sepsis). Septic patients had significantly increased C5a levels (21.62 ± 3.14 vs. 13.40 ± 1.29 ng/mL; p < 0.05) and reduced TAFI levels upon admission to the ED (40,951 ± 5637 vs. 61,865 ± 4370 ng/mL; p < 0.05) compared to the no sepsis group. Negative correlations between TAFI and C5a (p = 0.0104) and TAFI and lactate (p = 0.0423) and positive correlations between C5a and lactate (p = 0.0173), as well as C5a and the respiratory rate (p = 0.0266), were found. In addition, correlation analyses of both TAFI and C5a with the sequential (sepsis-related) organ failure assessment (SOFA) score have confirmed their potential as early sepsis biomarkers. Cut-off values for predicting sepsis were 54,857 ng/mL for TAFI with an area under the curve (AUC) of 0.7550 (p = 0.032) and 17 ng/mL for C5a with an AUC of 0.7286 (p = 0.034). Conclusion: The development of sepsis is associated with early decreased TAFI and increased C5a levels after major trauma. Both elevated C5a and decreased TAFI may serve as promising predictive factors for the development of sepsis after polytrauma.

Plasma Levels of Unactivated Thrombin Activatable Fibrinolysis Inhibitor (TAFI) Are Down-Regulated in Young Adult Women: Analysis of a Normal Japanese Population

Thrombin-activatable fibrinolysis inhibitor (TAFI) is an anaphylatoxin-inactivating enzyme generated by proteolytic cleavage of its zymogen, and is the same enzyme as that first designated by our group as procarboxypeptidase R (proCPR). TAFI in plasma is presumed to influence vascular disease in its role as a fibrinolysis inhibitor. The activity of TAFI is strongly influenced by genetic polymorphism, especially at amino acids Thr/Ala-147 and Thr/Ile-325. In this study, we analyzed 202 healthy controls who were not on any medication, had no unusual medical history and whose blood data were normal. In a previous report, we established an enzyme-linked immunosorbent assay (ELISA) specific for non-activated TAFI (proCPR), and investigated levels of unactivated TAFI as an estimate of anti-fibrinolytic capacity. In this study, we determined normal Japanese TAFI levels for each age, sex, and genetic polymorphism of Thr/Ala-147 and Thr/Ile-325, and also showed that the TAFI level in young adult women is lower than in aged women.

Scanning electron microscopy investigation of fibrin networks after thermal injury

Injury due to burning is known to impact on coagulation and haemostasis by disturbing the coagulation cascade and is also associated with impaired fibrinolysis. Also, venous thrombosis, pulmonary embolism and hypercoagulability are common during thermal injury. Using a Wistar albino rat model, we investigated in this study whether burn injury affects the ultrastructure of the fibrin networks. A typical fibrin network will contain mostly major, thick fibres with minor, thin fibres distributed amongst them. We found that the clot architecture changes after burn injury, showing more prominent minor, thin fibres in a netted appearance. Also, the clot showed areas of matted fibrin. We suggest that the thrombotic events associated with burn injury are due to the thickened and netlike areas formed when thrombin activates the coagulation cascade. This is due to impaired fibrinolysis activities, causing the resulting fibrin clots not to be successfully disseminated. Small fragments of these netted, clumped areas may therefore break loose and lead to thrombotic events after burn injuries. The current study therefore provided morphological evidence for thrombotic events associated with burn injury.

Absence of thrombin-activatable fibrinolysis inhibitor protects against sepsis-induced liver injury in mice

Thrombin-activatable fibrinolysis inhibitor (TAFI), also known as carboxypeptidase R, has been implicated as an important negative regulator of the fibrinolytic system. In addition, TAFI is able to inactivate inflammatory peptides such as complement factors C3a and C5a. To determine the role of TAFI in the hemostatic and innate immune response to abdominal sepsis, TAFI gene-deficient (TAFI-/-) and normal wild-type mice received an i.p. injection with Escherichia coli. Liver TAFI mRNA and TAFI protein concentrations increased during sepsis. In contrast to the presumptive role of TAFI as a natural inhibitor of fibrinolysis, TAFI-/- mice did not show any difference in E. coli-induced activation of coagulation or fibrinolysis, as measured by plasma levels of thrombin-anti-thrombin complexes and D-dimer and the extent of fibrin depositions in lung and liver tissues. However, TAFI-/- mice were protected from liver necrosis as indicated by histopathology and clinical chemistry. Furthermore, TAFI-/- mice displayed an altered immune response to sepsis, as indicated by an increased neutrophil recruitment to the peritoneal cavity and a transiently increased bacterial outgrowth together with higher plasma TNF-alpha and IL-6 levels. These data argue against an important part for TAFI in the regulation of the procoagulant-fibrinolytic balance in sepsis and reveals a thus far unknown role of TAFI in the occurrence of hepatic necrosis.