Thrombin-activatable Fibrinolysis Inhibitor Research Articles

A randomized controlled trial of indobufen versus aspirin in the prevention of bridging restenosis after coronary artery bypass grafting

Objective: To compare the efficacy and safety between indobufen and aspirin in the prevention of restenosis of bridge vessels at 1 year after off-pump coronary artery bypass grafting. Methods: This study was a prospective cohort study. We selected 152 patients who received coronary artery bypass grafting in Beijing Anzhen Hospital from December 2016 to December 2018. Patients were divided into the indobufen group and the aspirin group. Patients in the aspirin group were treated with aspirin and clopidogrel, and patients in the indobufen group were treated with indobufen and clopidogrel. During the 1-year follow-up, the rate of restenosis of saphenous vein bridge and internal mammary artery bridge, the rate of adverse cardiac events and adverse reactions were compared between the two groups. The levels of fibrinogen (FIB), D-dimer (D-D), thrombomodulin (TM) and thrombin-activatable fibrinolysis inhibitor (TAFI) were compared before and after antiplatelet therapy. Results: There were 76 cases in the indobufen group, including 57 males (75.0%), aged (60.3±6.6) years. There were 76 cases in the aspirin group, including 62 males (81.6%), aged (59.7±7.2) years. Baseline data were comparable between the two groups (P>0.05). During the follow-up, 3 cases were lost to follow up. Follow-up was completed in 74 patients in the indobufen group and 75 in the aspirin group. A total of 268 bridging vessels were grafted in the indobufen group and 272 in the aspirin group. One year after surgery, the patency rates of great saphenous vein bridge and internal mammary artery bridge were 94.5% (189/200) and 97.1% (66/68) in the indobuphen group, and 91.3% (189/207) and 96.9% (63/65) in the aspirin group, respectively. There was no significant difference in patency rate of great saphenous vein bridge and internal mammary artery bridge between the two groups (χ²=0.282, 0.345, P>0.05). The total incidence of adverse cardiac events was 5.4% (4/74) in the indobufen group and 6.7% (5/75) in the aspirin group (χ²=0.126, P>0.05). The overall incidence of gastrointestinal adverse reactions was significantly lower in the indobufen group than in the aspirin group (4.1% (3/74) vs. 13.3% (10/75), χ²=4.547, P<0.05). The levels of FIB, D-D, TM and TAFI in the two groups were lower than those before surgery (P<0.05), and there was no statistical significance between the two groups at baseline and post-operation (P>0.05). Conclusion: The efficacy of indobufen combined with clopidogrel in the prevention of 1-year restenosis after coronary artery bypass graft is similar to that of aspirin combined with clopidogrel, but the incidence of adverse reactions is lower, and the safety is higher in patients treated with indobufen combined with clopidogrel compared to aspirin combined with clopidogrel strategy.

CM-352 Efficacy in a Mouse Model of Anticoagulant-Associated Intracranial Hemorrhage.

Background Intracranial hemorrhage (ICH) is one of the major devastating complications of anticoagulation. Matrix metalloproteinase (MMP) inhibition has been proposed as a novel pharmacological approach for ICH treatment. Objectives We evaluated the effects of CM-352 (MMP-fibrinolysis inhibitor) in an experimental ICH model associated with oral anticoagulants as compared with clinically used prothrombin complex concentrate (PCC). Methods ICH was induced by collagenase injection into the striatum of wild type (C57BL/6J) anticoagulated mice (warfarin or rivaroxaban) and Mmp10 −/− mice. Hematoma volume and neurological deficits were measured 24 hours later by diaminobenzidine staining and different behavioral tests. Circulating plasminogen activator inhibitor-1 (PAI-1) activity and interleukin-6 (IL-6) were measured in plasma samples and local inflammation was assessed by neutrophil infiltration. Finally, fibrinolytic effects of MMP-10 and rivaroxaban were evaluated by thromboelastometry and thrombin-activatable fibrinolysis inhibitor (TAFI) activation assays. Results Only PCC reduced hemorrhage volume and improved functional outcome in warfarin-ICH, but both PCC and CM-352 treatments diminished hemorrhage volume (46%, p < 0.01 and 64%, p < 0.001, respectively) and ameliorated functional outcome in rivaroxaban-ICH. We further demonstrated that CM-352, but not PCC, decreased neutrophil infiltration in the hemorrhage area at 24 hours. The effect of CM-352 could be related to MMP-10 inhibition since Mmp10 −/− mice showed lower hemorrhage volume, better neurological score, reduced IL-6 levels and neutrophil infiltration, and increased PAI-1 after experimental ICH. Finally, we found that CM-352 reduced MMP-10 and rivaroxaban-related fibrinolytic effects in thromboelastometry and TAFI activation. Conclusion CM-352 treatment, by diminishing MMPs and rivaroxaban-associated fibrinolytic effects, might be a novel antihemorrhagic strategy for rivaroxaban-associated ICH.

VhH anti‐thrombomodulin clone 1 inhibits TAFI activation and enhances fibrinolysis in human whole blood under flow

BackgroundThrombomodulin on endothelial cells can form a complex with thrombin. This complex has both anticoagulant properties, by activating protein C, and clot‐protective properties, by activating thrombin‐activatable fibrinolysis inhibitor (TAFI). Activated TAFI (TAFIa) inhibits plasmin‐mediated fibrinolysis. ObjectivesTAFIa inhibition is considered a potential antithrombotic strategy. So far, this goal has been pursued by developing compounds that directly inhibit TAFIa. In contrast, we here describe variable domain of heavy‐chain‐only antibody (VhH) clone 1 that inhibits TAFI activation by targeting human thrombomodulin. MethodsTwo llamas (Lama Glama) were immunized, and phage display was used to select VhH anti‐thrombomodulin (TM) clone 1. Affinity was determined with surface plasmon resonance and binding to native TM was confirmed with flow cytometry. Clone 1 was functionally assessed by competition, clot lysis, and thrombin generation assays. Last, the effect of clone 1 on tPA‐mediated fibrinolysis in human whole blood was investigated in a microfluidic fibrinolysis model. ResultsVhH anti‐TM clone 1 bound recombinant TM with a binding affinity of 1.7 ± 0.4 nM and showed binding to native TM. Clone 1 competed with thrombin for binding to TM and attenuated TAFI activation in clot lysis assays and protein C activation in thrombin generation experiments. In a microfluidic fibrinolysis model, inhibition of TM with clone 1 fully prevented TAFI activation. DiscussionWe have developed VhH anti‐TM clone 1, which inhibits TAFI activation and enhances tPA‐mediated fibrinolysis under flow. Different from agents that directly target TAFIa, our strategy should preserve direct TAFI activation via thrombin.

The role of thrombin in haemostasis.

Thrombin is a multifunctional serine protease generated in injured cells. The generation of thrombin in coagulation plays a central role in the functioning of haemostasis. The last enzyme in the coagulation cascade is thrombin, with the function of cleaving fibrinogen to fibrin, which forms the fibrin clot of a haemostatic plug. Although thrombin primarily converts fibrinogen to fibrin, it also has many other positive regulatory effects on coagulation. Thrombin has procoagulant, inflammatory, cellular proliferation and anticoagulant effects. In coagulation system, thrombin has two very distinct roles. Firstly, it acts as a procoagulant when it converts fibrinogen into an insoluble fibrin clot, activates factor (F) XIII, activates thrombin activatable fibrinolysis inhibitor (TAFI) and activates FV, FVIII and FXI. Thrombin also enhances platelet adhesion by inactivating a disintegrin and metalloprotease with thrombospondin type1 motif (ADAMTS13). However, when thrombin activates protein C, it acts as an anticoagulant. A natural anticoagulant pathway that supplies regulation of the blood coagulation system contains protein C, which is the key component. This is accomplished by the specific proteolytic inactivation of FV and FVIII. In this review, the multiple roles of thrombin in the haemostatic response to injury are studied in addition to the cofactors that determine thrombin activity and how thrombin activity is thought to be coordinated.

Intensive low-density lipoprotein cholesterol lowering improves fibrin clot properties: Association with lipoproteins and C-reactive protein

ObjectiveDense fibrin networks resistant to lysis characterize coronary artery disease (CAD) patients. We investigated whether a statin-induced decrease of low-density lipoprotein cholesterol (LDL-C) could improve fibrin clot phenotype in CAD patients. MethodsWe recruited 130 consecutive patients with advanced CAD (baseline LDL-C of 4.4 [IQR, 3.8–4.8] mmol/L), who on statins did not achieve the LDL-C goal based on the 2016 ESC/EAS guidelines. On standard statin treatment and after 6–12 months of high-dose statin treatment (atorvastatin 80 mg/day or rosuvastatin 40 mg/day), plasma fibrin clot permeability (Ks), clot lysis time (CLT), thrombin generation, coagulation and fibrinolytic factors were determined. ResultsAfter a median high-dose statin therapy of 7 months there was 25% reduction in LDL-C associated with increased Ks and shorter CLT, together with lower thrombin activatable fibrinolysis inhibitor, factor VIII, D-dimer, and C-reactive protein (CRP); thrombin generation was unaltered. The patients who achieved the therapeutic goal (n = 49, 37.7%) had 29.2% increase in Ks and 16.3% shorter CLT compared with the standard therapy, while there were no similar changes in the remaining patients. After adjustment for potential confounders, including CRP, an increase in Ks (by 1 × 10−9 cm2) and decrease in CLT (by 10 min) were independently predicted by on-treatment LDL-C goal (odds ratio [OR] 6.23, 95% confidence interval [CI] 1.97–20.33 and OR 3.11, 95% CI 1.05–8.99, respectively). ConclusionsFor the first time we showed that a decrease of LDL-C ≤ 1.8 mmol/L, or a reduction of at least 50% if the baseline LDL-C is between 1.8 and 3.5 mmol/L, is associated with favorable alterations to fibrin clot phenotype, with a stronger impact of lipoprotein reduction than CRP lowering, which might suggest that other potent cholesterol-lowering drugs can exert similar antithrombotic actions.

Assessment of risk factors for deep vein thrombosis associated with natural anticoagulants and fibrinolytic regulatory proteins.

Deep vein thrombosis (DVT) is a critical condition and a potential cause of mortality and morbidity in Africa and worldwide with a high recurrence rate. The study was designed to assess the roles of natural anticoagulants and fibrinolytic regulatory factors in the development of DVT in Sudanese patients. A case-control study was conducted in Omdurman Teaching Hospital, Khartoum State over a period of 1 year. The study enrolled 200 patients diagnosed with DVT and 200 age-matched and gender-matched controls. Demographic data and data on acquired risk factors were collected using a semi-structured questionnaire. Protein C (PC), protein S (PS), antithrombin III (AT-III), thrombin-activable fibrinolysis inhibitor (TAFI), and plasminogen activator inhibitor-1 (PAI-1) were measured in patients and controls. Among the patients with DVT, 5.5% had PC deficiency, 8.5% had PS deficiency, and 3% had AT-III deficiency. Elevated TAFI and PAI-1 levels were demonstrated in 1.5 and 0.5% of patients, respectively. Risk factors for DVT (overweight, surgical history, and family history of DVT) were remarkably higher in patients than in controls. Among the female participants, pregnancy and usage of oral contraceptive pills were the highest associated risk factors for DVT. The findings concluded that the early assessment of risk factors, including the measurements of natural inhibitors, can predict the occurrence of DVT before it is actually detected in patients.

A Case-Control Study of the Dose-Response Relationship Between Thrombin Activatable Fibrinolysis Inhibitor and Acute Myocardial Infarction.

BackgroundAcute myocardial infarction (AMI) is considered an acute coronary syndrome (ACS), which is caused by the death of myocardial cells after prolonged ischemia, and there is a high risk of sudden death during AMI. Therefore, the purpose of this study is to explore the relationship between thrombin activatable fibrinolysis inhibitor (TAFI) and AMI and provide evidence for their association and potentially the prevention of AMI.MethodsThere were 228 subjects included in this retrospective study, which included 78 AMI patients and 150 controls. The immune turbidimetry was used to measure TAFI concentration in the serum. Mann–Whitney U test was used to compare serum TAFI levels. The logistic regression analysis was used to construct a model of influencing factors of AMI. The dose-response relationship between serum TAFI level and AMI was explored by using the restricted cubic spline (RCS) functions combined with logistic regression analysis.ResultsThe serum TAFI levels of the AMI group were higher than the control group’s (P = 0.003). The risk of AMI in the high-TAFI level group was 2.24 times higher than the low-TAFI level group (P = 0.007) and it was 2.74 times higher after adjustment of other risk factors (P = 0.025). According to the dose-response curve, the risk of AMI increased significantly with an increase of serum TAFI concentration (P = 0.0387).ConclusionAcute myocardial infarction patients had higher serum TAFI levels, and TAFI was an independent risk factor for AMI patients. Serum TAFI levels demonstrated a dose- dependent response to the risk of AMI. Our study provides evidence that TAFI could be used for risk stratification of AMI patients.

An evaluation of circulating activated TAFI in septic DIC: a case series and review of the literature

BackgroundAdministration of recombinant human soluble thrombomodulin (rTM) is often used in Japan to treat septic disseminated intravascular coagulation (DIC). Thrombin-activatable fibrinolysis inhibitor (TAFI) is a fibrinolysis inhibitor activated by the thrombin-thrombomodulin complex, however, it is unknown whether circulating activated TAFI is increased after rTM administration in patients with DIC. Furthermore, the relationship between TAFI activation and the prognosis of septic DIC is not defined yet.Case presentationWe report a series of 8 patient’s TAFI activation with septic DIC treated by rTM. We sought to investigate the effect of rTM on TAFI activation and the association of plasma activated TAFI (TAFIa/ai) levels with the prognosis of septic DIC.Using plasma samples from clinical studies conducted from May 2016–March 2017 on eight patients with septic DIC at Kagoshima University Hospital, we measured plasma levels of total TAFI, TAFIa/ai, thrombin-antithrombin complex (TAT), prothrombin fragment 1 + 2 (F1 + 2), soluble fibrin (SF), antithrombin (AT), protein C (PC), protein S (PS), and plasminogen activator inhibitor-1 (PAI-1) before and after intravenous rTM administration. Then, we evaluated the relationship of these marker levels to prognosis. The thrombin-rTM complex activated TAFI in vitro in plasma from a healthy volunteer. However, TAFIa/ai levels did not significantly increase over baseline in the septic DIC patients after intravenous rTM administration. Baseline TAFIa/ai levels in non-survivors were significantly higher than those in survivors.ConclusionsPlasma TAFIa/ai did not increase with rTM administration. Elevated baseline TAFIa/ai concentration may be a negative prognostic indicator in septic DIC. Larger studies are needed to confirm the in vivo effect of rTM on TAFI activation.

Safety, Pharmacokinetics and Pharmacodynamics of DS-1040, in Combination with Thrombectomy, in Japanese Patients with Acute Ischemic Stroke.

Background and ObjectivesDS-1040 is a novel inhibitor of the activated form of thrombin-activatable fibrinolysis inhibitor that may have therapeutic potential in thromboembolic diseases, such as acute ischemic stroke (AIS) or pulmonary embolism. We undertook a Phase I clinical trial to investigate the safety, pharmacokinetics, and pharmacodynamics of DS-1040 in Japanese patients who were eligible for thrombectomy following AIS.MethodsThe trial enrolled patients with AIS due to large vessel occlusion, who were planned for thrombectomy within 8 h of symptom onset. Subjects were randomized to receive a single intravenous infusion of placebo or DS-1040 (0.6, 1.2, 2.4 or 4.8 mg) in a sequential-cohort design. The primary endpoints were the incidence of intracranial hemorrhage (ICH) and major extracranial bleeding within 36 and 96 h, respectively, of treatment initiation. Treatment-emergent adverse events (TEAEs) and pharmacokinetic/pharmacodynamic parameters were also assessed.ResultsNine patients received placebo and 32 patients received DS-1040. There were no cases of symptomatic ICH or major extracranial bleeding with either placebo or DS-1040 after 36 and 96 h. One patient, who received DS-1040 0.6 mg, experienced a subarachnoid hemorrhage that was considered to be drug-related. Three patients died (2 placebo, 1 DS-1040), but no deaths were adjudicated as study drug-related. In vivo exposure to DS-1040 increased in proportion to dosage, but no clear dose-response relationship was seen for D-dimer levels and thrombin-activatable fibrinolysis inhibitor activity.ConclusionsSingle doses of DS-1040 0.6–4.8 mg were well tolerated in Japanese patients with AIS undergoing thrombectomy.Clinical trial registration numberNCT03198715; JapicCTI-163164.Supplementary InformationThe online version contains supplementary material available at 10.1007/s40261-021-01112-8.

Pre-administration of a carboxypeptidase inhibitor enhances tPA-induced thrombolysis in mouse microthrombi: Evidence from intravital imaging analysis

IntroductionThrombolysis using recombinant tissue-type plasminogen activator (rt-PA) is the pharmacological treatment of choice in acute thrombotic events. However, a narrow therapeutic window and bleeding complications limit its use. We describe the role of carboxypeptidase inhibitor from potato tuber (PTCI), an inhibitor of activated thrombin-activatable fibrinolysis inhibitor (TAFIa), on Glu-plasminogen accumulation and microthrombus dynamics in vivo and demonstrate its influence on rt-PA-mediated thrombolysis. Materials and methodsIn conjunction with real-time intravital two-photon excitation fluorescence microscopy, we produced and imaged laser-induced microthrombi in the mesenteric venules of Green Fluorescent Protein (GFP)-expressing mice. We examined microthrombus dynamics and thrombolysis patterns in vivo by measuring the changes in the fluorescence intensity of labeled Glu-plasminogen following administration of epsilon aminocaproic acid (EACA), PTCI, and rt-PA. ResultsPTCI enhanced Glu-plasminogen accumulation at the core of the thrombus by inhibiting TAFIa, while EACA inhibited this process. Exogenous rt-PA effectively triggered Glu-plasminogen activation within the thrombus and promoted thrombolysis. Administration of PTCI and rt-PA together showed no significant benefit on thrombolysis compared to rt-PA administration alone. However, early-phase systemic administration of PTCI before thrombolytic therapy by rt-PA expedited clot lysis as evidenced by significantly faster time to reach peak Glu-plasminogen fluorescence intensity and shorter time to achieve near-complete clot lysis (P = 0.014 and P = 0.003, respectively). ConclusionsPTCI potentiates rt-PA-mediated thrombolysis when administered early in acute thrombotic events. Further studies are warranted to explore the potential of TAFI inhibitors as adjunct agents in thrombolysis or thromboprophylaxis.

Fibrinolytic Changes in Women with Preeclampsia.

ObjectivesPreeclampsia (PE) is a serious complication of pregnancy. The fibrinolytic system play crucial roles regarding placentation and evolution of PE.AimTo study comprehensively components of the fibrinolytic system and fibrin lysability in women with PE.Design and Methods117 women with PE and matched controls were included. Tissue type plasminogen activator (t-PA), plasminogen, PAI-1, plasmin inhibitor (PI), D-dimer, the fibrinolytic potential of dextran sulphate euglobulin fraction (DEF), PAI-2, polymere PAI-2, fibrin clot lysability, thrombin activatable fibrinolysis inhibitor (TAFI) and fibrinogen were assessed.ResultsWomen with PE had significantly increased concentrations of t-PA and PAI-1, whereas the plasma concentration of PAI-2 was significantly lower compared to controls, p < 0.0001. Polymere PAI-2 was detected in both groups. DEF, TAFI and fibrinogen were not different between the groups. D-dimer was significantly increased and plasminogen/PI together with fibrin clot lysability time decreased in the PE-group, p = 0.0004 p = 0.04, p = 0.03, p < 0.0001 respectively.ConclusionThis study demonstrates that PE is associated with an affected t-PA/PAI-1 system, decreased PAI-2 and increased fibrin lysability. Furthermore, PAI-2 has the potential to polymerize during pregnancy.

Mechanisms for the allodynia caused by complementanaphylatoxin C5a in mice

The thrombin-thrombomodulin (TM) complex generates activated forms of protein C(APC) and thrombin-activatable fibrinolysis inhibitor (TAFIa), known ascarboxypeptidase B (CPB), and degrades high mobility group box 1 (HMGB1), apronociceptive molecule. We have shown that soluble TM (TMα) preventschemotherapy-induced peripheral neuropathy (CIPN) in rodents, and that APC andTAFIa/CPB, as well as HMGB1 degradation, contribute to the anti-CIPN effect ofTMα. Given our recent evidence for the involvement of complement C5a, degradableby TAFIa/CPB, in CIPN, we analyzed the mechanisms for peripheral C5a-mediatedpain in mice. Intraplantar (i.pl.) injection of C5a at 30-300 ng induceddose-dependent mechanical allodynia, as assessed by von Frey test, an effectabolished by i.p. administration of DF2593A, a mouse C5a receptor (C5aR)antagonist, TAFIa/CPB, TMα or an anti-HMGB1-neutralizing antibody. Systemic(i.p.), but not local (i.pl.), administration of liposomal clodronate, amacrophage depletor, partially reduced the C5a-induced allodynia. Inmacrophage-like RAW 264.7 cells, C5a caused HMGB1 release in the presence, butnot absence, of a sub-effective concentration of lipopolysaccharide. Together,C5a-induced allodynia is considered to involve C5aR-dependent HMGB1 release frommonocyte-derived macrophages and non-macrophage cells.

In Vitro study of Thrombolytic activity from the different parts of Carica papaya plant on COVID-19 patients.

Background: Carica papaya plant has been used for medicinal purpose throughout the world because it have anti-inflammatory, anti-oxidant, antiviral, anti-cancer and wound healing like properties.&#x0D; Objective: The main object of this research was to evaluate the thrombolytic activity of Carica papaya plant in normal healthy individuals and COVID-19 patients to determine either parts of the plant (roots, seeds and leaves) exhibit more activity in normal persons or in COVID-19 patients.&#x0D; Material and method: For this study, total 20 blood samples were taken, 10 for normal individuals and 10 for positive COVID-19 patients. We used two different solvents i.e. autoclaved distilled water and concentrated methanol to prepare the 10% root, seed and leaf extracts of Carica papaya plant. For the thrombolytic activity of these plant extracts, samples were arranged as a triplicate for the accuracy of results percentage. &#x0D; Results: Our results evaluated that in normal individuals, distilled water root extract and methanolic seed extract exhibits maximum thrombolytic activity. The mean value with distilled water (root extract) and methanol (seed extract) is 36.9% and 32.9% respectively. While in covid-19 patients, distilled water leaf extract and methanolic leaf extract reveal maximum thrombolytic activity. In patients, the mean value with distilled water and methanol (leaf extract) is 21.8% and 23% respectively.&#x0D; Conclusion: In our study, we have observed that normal persons showed highly significant results as compared to COVID-19 patients. Because in COVID-19 disease, plasminogen activator inhibitor 1 (PAI-1), thrombin activatable fibrinolysis inhibitor and tissue plasminogen activator (tPA) factors elevate which results in hypo-fibrinolysis.

Extended Coagulation Profiling in Isolated Traumatic Brain Injury: A CENTER-TBI Analysis

BackgroundTrauma-induced coagulopathy in traumatic brain injury (TBI) remains associated with high rates of complications, unfavorable outcomes, and mortality. The underlying mechanisms are largely unknown. Embedded in the prospective multinational Collaborative European Neurotrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) study, coagulation profiles beyond standard conventional coagulation assays were assessed in patients with isolated TBI within the very early hours of injury.MethodsResults from blood samples (citrate/EDTA) obtained on hospital admission were matched with clinical and routine laboratory data of patients with TBI captured in the CENTER-TBI central database. To minimize confounding factors, patients with strictly isolated TBI (iTBI) (n = 88) were selected and stratified for coagulopathy by routine international normalized ratio (INR): (1) INR < 1.2 and (2) INR ≥ 1.2. An INR > 1.2 has been well adopted over time as a threshold to define trauma-related coagulopathy in general trauma populations. The following parameters were evaluated: quick’s value, activated partial thromboplastin time, fibrinogen, thrombin time, antithrombin, coagulation factor activity of factors V, VIII, IX, and XIII, protein C and S, plasminogen, D-dimer, fibrinolysis-regulating parameters (thrombin activatable fibrinolysis inhibitor, plasminogen activator inhibitor 1, antiplasmin), thrombin generation, and fibrin monomers.ResultsPatients with iTBI with INR ≥ 1.2 (n = 16) had a high incidence of progressive intracranial hemorrhage associated with increased mortality and unfavorable outcome compared with patients with INR < 1.2 (n = 72). Activity of coagulation factors V, VIII, IX, and XIII dropped on average by 15–20% between the groups whereas protein C and S levels dropped by 20%. With an elevated INR, thrombin generation decreased, as reflected by lower peak height and endogenous thrombin potential (ETP), whereas the amount of fibrin monomers increased. Plasminogen activity significantly decreased from 89% in patients with INR < 1.2 to 76% in patients with INR ≥ 1.2. Moreover, D-dimer levels significantly increased from a mean of 943 mg/L in patients with INR < 1.2 to 1,301 mg/L in patients with INR ≥ 1.2.ConclusionsThis more in-depth analysis beyond routine conventional coagulation assays suggests a counterbalanced regulation of coagulation and fibrinolysis in patients with iTBI with hemostatic abnormalities. We observed distinct patterns involving key pathways of the highly complex and dynamic coagulation system that offer windows of opportunity for further research. Whether the changes observed on factor levels may be relevant and explain the worse outcome or the more severe brain injuries by themselves remains speculative.

Assessment of fibrinolytic markers in patients with deep vein thrombosis

The association of the fibrinolytic markers with deep vein thrombosis (DVT) is still a matter of debate. The present study aimed to investigate the association between fibrinolytic markers and DVT. This observational study recruited 52 adult cases with lower limb DVT and 52 healthy adult volunteers as controls. The quantitative determination of plasminogen activator inhibitor-1 (PAI-1), plasminogen, thrombin activable fibrinolysis inhibitor (TAFI), tissue plasminogen activator (tPA) and α2-antiplasmin (α2-AP) was performed by ELISA. TAFI, plasminogen and t-PA were significantly higher in cases than controls and PAI-1 was significantly lower in cases than controls. In addition, TAFI, plasminogen and t-PA levels were significantly increased in unprovoked and idiopathic DVT cases than controls. The present study suggests that the fibrinolytic markers tested in patients with a remote history of DVT are different than in individuals with no history of DVT and, with further study, may prove useful as screening assays for DVT risk.

Altered fibrin clot structure and dysregulated fibrinolysis contribute to thrombosis risk in severe COVID-19

AbstractThe high incidence of thrombotic events suggests a possible role of the contact system pathway in COVID-19 pathology. In this study, we determined the altered levels of factor XII (FXII) and its activation products in critically ill patients with COVID-19 in comparison with patients with severe acute respiratory distress syndrome related to the influenza virus (acute respiratory distress syndrome [ARDS]-influenza). Compatible with those data, we found rapid consumption of FXII in COVID-19 but not in ARDS-influenza plasma. Interestingly, the lag phase in fibrin formation, triggered by the FXII activator kaolin, was not prolonged in COVID-19, as opposed to that in ARDS-influenza. Confocal and electron microscopy showed that increased FXII activation rate, in conjunction with elevated fibrinogen levels, triggered formation of fibrinolysis-resistant, compact clots with thin fibers and small pores in COVID-19. Accordingly, clot lysis was markedly impaired in COVID-19 as opposed to that in ARDS-influenza. Dysregulated fibrinolytic system, as evidenced by elevated levels of thrombin-activatable fibrinolysis inhibitor, tissue-plasminogen activator, and plasminogen activator inhibitor-1 in COVID-19 potentiated this effect. Analysis of lung tissue sections revealed widespread extra- and intravascular compact fibrin deposits in patients with COVID-19. A compact fibrin network structure and dysregulated fibrinolysis may collectively contribute to a high incidence of thrombotic events in COVID-19.

Fibrinogen and Antifibrinolytic Proteins: Interactions and Future Therapeutics

Thrombus formation remains a major cause of morbidity and mortality worldwide. Current antiplatelet and anticoagulant therapies have been effective at reducing vascular events, but at the expense of increased bleeding risk. Targeting proteins that interact with fibrinogen and which are involved in hypofibrinolysis represents a more specific approach for the development of effective and safe therapeutic agents. The antifibrinolytic proteins alpha-2 antiplasmin (α2AP), thrombin activatable fibrinolysis inhibitor (TAFI), complement C3 and plasminogen activator inhibitor-2 (PAI-2), can be incorporated into the fibrin clot by FXIIIa and affect fibrinolysis by different mechanisms. Therefore, these antifibrinolytic proteins are attractive targets for the development of novel therapeutics, both for the modulation of thrombosis risk, but also for potentially improving clot instability in bleeding disorders. This review summarises the main properties of fibrinogen-bound antifibrinolytic proteins, their effect on clot lysis and association with thrombotic or bleeding conditions. The role of these proteins in therapeutic strategies targeting the fibrinolytic system for thrombotic diseases or bleeding disorders is also discussed.

The G505A Nonsynonymous Single-Nucleotide Polymorphism (SNP) in TAFI, the Gene Encoding Thrombin-Activatable Fibrinolysis Inhibitor (TAFI) Is Pleiotropically Associated with TAFI Antigen Levels and Coronary Heart Disease (CHD) in Mexican Americans of South Texas

Studies have reported that the G505A nonsynonymous (ns)-SNP encoding the Ala147Thr amino acid substitution in TAFI, is associated with a reduction in risk of venous thrombosis and myocardial infarction. Interestingly, homozygosity for the A-allele (AA) of G505A is associated with increased TAFI antigen (TAFI:Ag) levels in plasma. In our study of the genetic determinants of cardiovascular disease (CVD) in Mexican Americans of South Texas, we performed an exome-wide scan in relation to plasma TAFI antigen levels in 784 individuals. While accounting for age, sex, and their interactions as confounders in linear mixed model, we found a heritability of 59% for TAFI:Ag levels (p=1.4E-19), and that ns-SNP G505A was the only variant showing exome-wide significance (p=3.5E-14; Figure A). Figure B shows the quantile-quantile distribution of the p-values from all the exome-wide tests. Clearly, the p-value distribution reveals that there is no systematic bias that may act to skew the p-values, and that the lone exception¾in agreement between observed and expected quantiles¾is due to this TAFI SNP, which strongly suggests a truly significant effect. Consistent with previous reports, the regression coefficient for G505A as a predictor of TAFI:Ag levels showed them to be increasing from the homozygous for the major G-allele (GG), to the heterozygous individuals (GA), to the individuals homozygous for the minor A-allele (AA) (Figure B). We also investigated if G505A is associated with our CHD variable. Using a statistical genetic model for the liability to disease conditional on a threshold, which is equivalent to a probit mixed model, we found that the G505A ns-SNP in TAFI, encoding TAFI Ala147Thr, is significantly associated with a reduction in the risk of CHD (p=0.002). As observed in existing literature, potential limitations of this study include the ELISA assay used for the quantification of TAFI levels. Some ELISA assays measure proTAFI, TAFIa, and TAFIi. However, recent evidence suggests that there may be cross reactivity between TAFIa and TAFIi. This can result in measuring ongoing TAFI activation peptides and elevated levels of TAFIa which ultimately goes on to make resistant fibrin. This is likely the marker that results in the increased risk of venous thromboembolism. To mitigate this confounding factor, an ELISA assay specific to measuring TAFI antigen is needed. In conclusion, we found that TAFI G505A is pleiotropically associated with TAFI:Ag levels and risk of CHD. [Display omitted] DisclosuresDeFronzo: AstraZeneca: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novo Nordisk: Membership on an entity's Board of Directors or advisory committees; Boehringer-Ingelheim: Membership on an entity's Board of Directors or advisory committees, Research Funding; Intarcia: Membership on an entity's Board of Directors or advisory committees; Merck: Research Funding.

Prothrombotic and Inflammatory Markers in Elderly Patients with Non-Alcoholic Hepatic Liver Disease before and after Weight Loss: A Pilot Study.

Background: Non-alcoholic fatty liver disease (NAFLD) is a pathological condition, ranging from fatty liver to chronic steatohepatitis (NASH), liver cirrhosis, and eventually to hepatocellular carcinoma. Recent findings suggest that patients with NAFLD have an increased risk of cardiovascular events and thromboembolism, which is independent of metabolic diseases that are frequently associated with NAFLD, such as diabetes, hyperlipidemia, and obesity. Methods: We evaluated 30 NAFLD patients, before and after weight loss. Plasma levels of C-reactive protein (CRP), fibrinogen, plasminogen activator inhibitor-1 (PAI-1), von Willebrand factor (VWF), homocysteine, coagulation protein S, Thrombin activable fibrinolysis inhibitor (TAFI), and factor VII (FVII) were assessed to evaluate whether they should be responsible of the prothrombotic state of NAFLD after weight loss. Results: At baseline, patients affected by NAFLD had a significantly higher levels of CRP, fibrinogen, PAI-1, VWF antigen, and FVII levels. After weight reduction, we observed a significant drop of inflammatory and prothrombotic markers, as well as glucometabolic, lipid profile. Conclusion: These findings provide evidence for a link between NAFLD/NASH and thromboembolism. The association seems to be linked with primitive thrombotic state and hypercoagulation due to increased levels of coagulation factors and reduced levels of PAI-1. This hypercoagulation state might explain increased levels of thrombosis and splanchnic thrombosis observed in NASH correlated cirrhosis.

Assessment of plasminogen activator inhibitor-1(PAI1) and thrombin activitable fibrinolysis inhibitor (TAFI) in Egyptian children with hemophilia A

Patients with hemophilia A display varied bleeding phenotypes not correlated with degree of deficiency of factor VIII level. We investigated Plasminogen Activator Inhibitor 1(PAI1) level and Thrombin Activatable Fibrinolysis Inhibitor (TAFI) also known as Carboxypeptidase B2 (CPB2) level in Patients with hemophilia A and their possible correlation with bleeding tendency. Twenty-six patients attending in hematology unit of pediatric department were included in this study. In addition, fourteen apparently healthy subjects matched ages and genders were included as control group. The International Society of Thrombosis Bleeding Assessment Tool (ISTH/BAT) was used to assess bleeding score in patients. Plasma levels of Plasminogen Activator Fibrinolysis Inhibitor (PAI1) and Thrombin Activatable Fibrinolysis Inhibitor (TAFI) zymogen were measured by enzyme-linked immunosorbent assay (ELIZA). As compared to controls, hemophilic patients had significantly high bleeding score, low PAI 1 level and high TAFI level. There was no significant correlation between bleeding score by ISTH/BAT and patient severity. PAI 1 and TAFI level have no significant correlation with patient severity. PAI 1 level was statistically significant different between intense and non-intense hemorrhagic groups, while TAFI level has no significant correlation with bleeding phenotype. PAI 1 and TAFI levels had significantly correlation between patients and controls. PAI-1 level had statistically significant correlation with bleeding phenotype, while TAFI level failed to show any correlation between intense and non-intense hemorrhagic groups. So, PAI-1 levels may have predictive value of bleeding tendency in hemophiliacs.