Plasma Thrombin-activatable Fibrinolysis Inhibitor Levels Research Articles

Relationship between plasma levels of thrombin activatable fibrinolysis inhibitor, plasminogen activator inhibitor-1 and tissue-type plasminogen activator and deep venous thrombosis in patients with systemic lupus erythematosus

Objective: To investigate the plasma levels of thrombin activatable fibrinolysis inhibitor (TAFI), plasminogen activator inhibitor-1 (PAI-1) and tissue-type plasminogen activator (t-PA) in patients with systemic lupus erythematosus (SLE), and their relationship with deep venous thrombosis of the lower limbs. Methods: A case-control study was conducted to retrospectively select 32 SLE patients with deep venous thrombosis of the lower extremities (thrombus group) admitted to Liaocheng People's Hospital in Shandong Province from June 2018 to June 2021, including 4 males and 28 females, with a mean age of (49.7±5.5) years. Meanwhile, 64 SLE patients without deep venous thrombosis of the lower extremities (control group) were also selected, including 11 males and 53 females, with a mean age of (50.8±5.5) years. The plasma levels of TAFI, PAI-1 and t-PA of the two groups were compared. A logistic regression model was used to analyze the correlation of TAFI, PAI-1 and t-PA with SLE in patients. Results: The plasma levels of TAFI, PAI-1 and t-PA were (32.77±5.17) mg/L, (29.43±5.51) μg/L and (6.58±1.40) μg/L in the thrombotic group, while the plasma levels of TAFI, PAI-1 and t-PA in the control group were (23.56±4.40) mg/L, (19.00±4.40) μg/L and (9.40±2.23) μg/L. The levels of TAFI and PAI-1 in the thrombotic group were higher than those in the control group, while the level of t-PA was lower than that in the control group (all P<0.05). The results of logistic regression model showed that higher TAFI levels (OR=1.75, 95%CI: 1.05-2.90, P=0.043), higher PAI-1 levels (OR=1.85, 95%CI: 1.04-3.29, P=0.046), and lower t-PA levels (OR=0.72, 95%CI: 0.52-0.99, P=0.048) were related factors for the occurrence of deep venous thrombosis of the lower limbs in SLE patients. Conclusion: The plasma levels of TAFI and PAI-1 in SLE patients with deep venous thrombosis of the lower extremities increase, while the t-PA level decreases, which are related factors for the occurrence of deep venous thrombosis of the lower extremities in SLE patients.

Quality of glycemic control in type 2 diabetes mellitus (T2DM) and its association with markers of coagulation and inhibitors of fibrinolysis: A case–control study in the Upper West Region, Ghana

AbstractBackground and AimsType 2 diabetes mellitus (T2DM) individuals are at a higher risk of developing diabetes complications, with approximately 80% complication‐related mortality. The increased morbidity and mortality among T2DM patients are partly due to dysregulated hemostasis. This study determined the quality of glycemic control in T2DM and its association with markers of coagulation and inhibitors of fibrinolysis.MethodsThis case–control study recruited 90 participants involving: 30 T2DM patients with good glycemic control, 30 with poor glycemic control, and 30 nondiabetic subjects as controls at a Municipal Hospital in Ghana. Fasting blood glucose, glycated hemoglobin, activated partial thromboplastin time (APTT), prothrombin time (PT), calculated international normalized ratio (INR), and full blood count (FBC) were determined for each respondent. Plasma levels of plasminogen activator inhibitor‐1 (PAI‐1) and thrombin activatable fibrinolysis inhibitor (TAFI) were determined using the solid‐phase sandwich enzyme‐linked immunosorbent assay method. Data were analyzed using R language software.ResultsPlasma PAI‐1 antigen levels were significantly higher in the participants with poor glycemic control as compared to participants with good glycemic control (p &lt; 0.0001). There was no significant difference in plasma TAFI levels between the participants with poor glycemic control as compared to participants with good glycemic control (p = 0.900). T2DM patients had significantly shorter APTT, PT, and INR than controls (p &lt; 0.05). At a cut‐off of ≥161.70 pg/μL, PAI was independently associated with increasing odds (adjusted odds ratio = 13.71, 95% confidence interval: 3.67–51.26, p &lt; 0.0001) of poor glycemic control and showed the best diagnostic accuracy for poor glycemic control (area under the curve = 0.85, p &lt; 0.0001).ConclusionPAI‐1 levels were significantly increased in T2DM with poor glycemic control and emerged as the best predictor for poor glycemic control. Good glycemic management to control the plasma levels of PAI‐1 is required to prevent hypercoagulability and thrombotic disorders.

Changes in fibrinolytic activity and coagulation factors after epicardial left atrial appendage closure in patients with atrial fibrillation.

The left atrial appendage (LAA) is known to be the primary source of thrombus formation in atrial fibrillation (AF). We investigate whether epicardial LAA occlusion (LAAO) from the cardiovascular system has an effect on coagulation and prothrombotic status in AF. Twenty-two patients with nonvalvular AF, who were not currently receiving oral anticoagulation (OAC) therapy, participated in a single-center prospective study. We measured fibrinogen and plasminogen levels along with plasma fibrin clot permeability, clot lysis time (CLT) and endogenous thrombin potential (ETP) before the LAAO procedure, at discharge and 1 month afterward. One month after the LAAO procedure, plasma fibrin clot permeability improved by 39.3% as measured by clots prepared from peripheral blood (P=0.019) and also after adjustment for fibrinogen (P=0.027). Higher plasma fibrin clot permeability was associated with improved clot susceptibility to lysis (r=-0.67, P=0.013). CLT was reduced by 10.3% (P=0.0020), plasminogen activator inhibitor-1 antigen levels were reduced by 52% (P=0.023) and plasminogen activity was increased by 8.9% (P=0.0077). A trend toward decreased thrombin generation, reflected by a decreased ETP and peak thrombin generated was also observed 1 month after LAAO procedure (P=0.072 and P=0.087, respectively). No differences were observed in tissue-type plasminogen activator and thrombin-activatable fibrinolysis inhibitor plasma levels (both P>0.05). Obtained results seem to confirm that LAA plays a key role in thrombogenesis. Elimination of LAA from the circulatory system may improve fibrin clot permeability and susceptibility to fibrinolysis in peripheral blood.

Serum thrombin-activatable fibrinolysis inhibitor levels and its relation with pathogenesis and bleeding and prognosis in patients with Crimean Congo hemorrhagic fever.

Crimean-Congo hemorrhagic fever (CCHF) is a viral hemorrhagic fever, which is common in Turkey and globally. The pathogenesis of coagulation disorders, which is seen in viral hemorrhagic fevers remains to be elucidated. Thrombin-activatable fibrinolysis inhibitor (TAFI) has a key role in this process In this study, we aimed to evaluate whether TAFI levels contributed to bleeding and whether it is related to prognosis in CCHF patients.Eighty-four patients older than 15 years of age, who were admitted to our hospital who had positive immunoglobulin M (enzyme-linked immunosorbent assay [ELISA]) and/or polymerase chain reaction test results for CCHF between 2009 and 2010, were included in the study. The control group included 30 healthy adults. The plasma TAFI levels were compared between patients and controls, and also between patients with bleeding and no bleeding, and between patients with mild-moderate and severe disease. The mean TAFI levels were lower in patients (mean: 87.82 ng/ml, median: 61.69 ng/ml (interquartile range [IQR] 30.49-537.95) than controls (mean: 313.5 ng/ml with a median: 338.5 ng/ml (IQR 182-418). However, median TAFI levels were significantly higher in patients with bleeding compared to those without bleeding (78.99 and 50.28 ng/ml, respectively; p = 0.032). Median IQR TAFI levels were similar between patients with mild-moderate and severe disease (64.72 (41.37-113.85), and, 58.66 (42.44-118.93) ng/ml, respectively; p = 0.09) and survivors and nonsurvivors (86.14 ± 77.98 and 103.48 ± 69.92, respectively; p = 0.3). Although TAFI levels were lower in the patients with CCHF compared to healthy controls, it does not seem to be a major player in the prognosis.

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.

Association of Thrombin-Activatable Fibrinolysis Inhibitor with Acute Pulmonary Embolism.

Thrombin-activatable fibrinolysis inhibitor (TAFI) inhibits fibrinolysis and high levels may have an association with thrombosis. The aim of the current study was to investigate the association of TAFI antigen levels with pulmonary thromboembolism (PTE). A case-control study was conducted with 29 patients with PTE and 17 age- and gender-matched control individuals. Plasma levels of TAFI were measured at the time of diagnosis, then at 3 and 6 months after the event. Initial TAFI levels (%) were higher in patients with PTE than in the control group (190,0 [65,0-250,0] vs 133,0 [83,0-153,0]; p = 0.003). TAFI levels significantly decreased at the third and sixth months after initial diagnosis (p < 0.05). The percentage reductions in TAFI levels were 12 and 36.8% at 3 and 6 months, respectively. The Odss ratio (OR) of TAFI level for PTE was found to be 1.024 (95% CI: 1.007-1.040; p = 0.005). There was no significant correlation of initial TAFI levels with age, gender, smoking status, history of thrombosis, pulmonary artery pressure, and D-dimer levels (p > 0.05). In the sixth month of treatment, patients with residual thrombosis were seen to have similar baseline levels and reductions of TAFI as patients without residual thrombosis (p > 0.05). The result of this study suggests that high TAFI levels may have a role in the occurrence of PTE without impact on treatment outcome.

S62798, a potent TAFIa inhibitor, accelerates endogenous fibrinolysis in a murine model of pulmonary thromboembolism

Enhancement of fibrinolysis constitutes a promising approach to treat thrombotic diseases. Venous thrombosis and thromboembolism risks are associated with increased plasma levels of TAFI (Thrombin Activatable Fibrinolysis Inhibitor) as well as its active form TAFIa. A new TAFIa inhibitor, namely S62798 has been identified. Its ability to enhance fibrinolysis was investigated both in vitro and in vivo in a mouse model of pulmonary thromboembolism, as well as its effect on bleeding.S62798 is a highly selective human, mouse and rat TAFIa inhibitor (IC50 = 11; 270; 178 nmol/L, respectively). It accelerates lysis of a human clot in vitro, evaluated by thromboelastometry (EC50 = 27 nmol/L). In a rat tail bleeding model, no effect of S62798 treatment was observed up to 20 mg/kg. Enhancement of endogenous fibrinolysis by S62798 was investigated in a mouse model of Tissue Factor-induced pulmonary thromboembolism. Intravenous administration of S62798 decreased pulmonary fibrin clots with a minimal effective dose of 0.03 mg/kg. Finally, effect of S62798 in combination with heparin was evaluated. When treatment of heparin was done in a curative setting, no effect was observed whereas a significantly decreased pulmonary fibrin deposition was observed in response to S62798 alone or in combination with heparin.This study demonstrates that S62798 is a potent TAFIa inhibitor with minimal risk of bleeding. In vivo, curative S62798 intravenous treatment, alone or associated with heparin, accelerated clot lysis by potentiating endogenous fibrinolysis and thus decreased pulmonary fibrin clots. S62798 is expected to be a therapeutic option for pulmonary embolism patients on top of anticoagulants.

Inside the Thrombus: Association of Hemostatic Parameters With Outcomes in Large Vessel Stroke Patients.

Background: Actual clinical management of ischemic stroke (IS) is based on restoring cerebral blood flow using tissue plasminogen activator (tPA) and/or endovascular treatment (EVT). Mechanical thrombectomy has permitted the analysis of thrombus structural and cellular classic components. Nevertheless, histological assessment of hemostatic parameters such as thrombin-activatable fibrinolysis inhibitor (TAFI) and matrix metalloproteinase 10 (MMP-10) remains unknown, although their presence could determine thrombus stability and its response to thrombolytic treatment, improving patient's outcome.Methods: We collected thrombi (n = 45) from large vessel occlusion (LVO) stroke patients (n = 53) and performed a histological analysis of different hemostatic parameters [TAFI, MMP-10, von Willebrand factor (VWF), and fibrin] and cellular components (erythrocytes, leukocytes, macrophages, lymphocytes, and platelets). Additionally, we evaluated the association of these parameters with plasma levels of MMP-10, TAFI and VWF activity and recorded clinical variables.Results: In this study, we report for the first time the presence of MMP-10 and TAFI in all thrombi collected from LVO patients. Both proteins were localized in regions of inflammatory cells, surrounded by erythrocyte and platelet-rich areas, and their content was significantly associated (r = 0.41, p < 0.01). Thrombus TAFI was lower in patients who died during the first 3 months after stroke onset [odds ratio (OR) (95%CI); 0.59 (0.36–0.98), p = 0.043]. Likewise, we observed that thrombus MMP-10 was inversely correlated with the amount of VWF (r = −0.30, p < 0.05). Besides, VWF was associated with the presence of leukocytes (r = 0.37, p < 0.05), platelets (r = 0.32, p < 0.05), and 3 months mortality [OR (95%CI); 4.5 (1.2–17.1), p = 0.029]. Finally, plasma levels of TAFI correlated with circulating and thrombus platelets, while plasma MMP-10 was associated with cardiovascular risk factors and functional dependence at 3 months.Conclusions: The present study suggests that the composition and distribution of thrombus hemostatic components might have clinical impact by influencing the response to pharmacological and mechanical therapies as well as guiding the development of new therapeutic strategies.

S62798, a TAFIa inhibitor, accelerates endogenous thrombolysis in a murine model of pulmonary thromboembolism

Abstract Pulmonary embolism (PE) is the third leading cause of cardiovascular death in western countries. The enhancement of fibrinolysis constitutes a promising approach to treat thrombotic diseases. In patients, venous thrombosis and thromboembolism risks are associated with increased plasma levels of TAFI (Thrombin Activatable Fibrinolysis Inhibitor) antigen as well as the active form TAFIa. S62798 is a competitive, selective and potent human TAFIa inhibitor (IC50±SD=11.2±0.4nM). It is however less potent on mouse TAFIa (IC50±SD=270±39nM). Here, we tested the ability of S62798 to enhance endogenous fibrinolysis in a mouse model of pulmonary thromboembolism. Human Tissue Factor (TF) was injected in C57Bl6 male mice. Ten minutes later, mice (n=4 to 14 per group) were treated (IV) with S62798 (from 0.01 to 100mg/kg) or vehicle (0.9% NaCl). Ten or twenty minutes (min) later, mice were anesthetized and lungs were collected, homogenized and pulmonary fibrin was quantified by ELISA. Results are expressed as ratio of geometric mean of pulmonary fibrin (μg/mL): tested treatment/ vehicle [95% confidence interval (CI)]. Ten minutes after S62798 treatment, pulmonary fibrin deposition was dose-dependently decreased with a Minimal Effective Dose of 0.04mg/kg [90% prediction interval 0.037 - 0.051] and an ED50 of 0.03mg/kg [95% CI: 0.01; 0.06]. Mice were then treated with 0.1mg/kg S62798 or vehicle (10 min after TF induction) and fibrin deposition in lungs was quantified 10 and 20 minutes post S62798 treatment. The level of pulmonary fibrin deposition was significantly decreased (p&amp;lt;0.0001) compared to vehicle group (ratio 0.31 [0.21; 0.45] at 10 min; 0.35 [0.24; 0.51] at 20 min). Finally, the effect of S62798 (1mg/kg) in combination with heparin was evaluated (n=10/group). When administered 10 min before TF injection, heparin (2000IU/kg) significantly (p&amp;lt;0.0001) decreased pulmonary fibrin level (20 min post TF: ratio 0.03 [0.01; 0.05]). When treatment was done in a curative setting (10 min post TF), heparin alone had no effect (p=0.85) on fibrin deposition (ratio 0.96 [0.65; 1.43]) whereas a similar significant (p&amp;lt;0.0001) decreased pulmonary fibrin deposition was observed in response to S62798 alone or associated with heparin (ratio 0.27 [0.18; 0.40] (S62798 alone) and 0.29 [0.20; 0.43] (S62798+heparin)). In this model, curative S62798 treatment, alone or associated to heparin, accelerated clot degradation by potentiating endogenous fibrinolysis and thus decreased pulmonary fibrin deposition. Due to its capacity to enhance endogenous fibrinolysis, S62798, which has completed phase I studies, is expected to be a therapeutic option for intermediate high risk PE patients on top of anticoagulants. With early recanalization, S62798 should rapidly reduce pulmonary artery pressure and resistance, with concomitant improvement in right ventricular function, preserving cardiac function, and reducing acute PE-related morbidity and mortality in these patients. Funding Acknowledgement Type of funding source: None

A new pedigree with thrombomodulin‐associated coagulopathy in which delayed fibrinolysis is partially attenuated by co‐inherited TAFI deficiency

BackgroundThrombomodulin‐associated coagulopathy (TM‐AC) is a rare bleeding disorder in which a single reported p.Cys537* variant in the thrombomodulin gene THBD causes high plasma thrombomodulin (TM) levels. High TM levels attenuate thrombin generation and delay fibrinolysis. ObjectivesTo report the characteristics of pedigree with a novel THBD variant causing TM‐AC, and co‐inherited deficiency of thrombin‐activatable fibrinolysis inhibitor (TAFI). Patients/methodsIdentification of pathogenic variants in hemostasis genes by next‐generation sequencing and case recall for deep phenotyping. ResultsPedigree members with a previously reported THBD variant predicting p.Pro496Argfs*10 and chain truncation in TM transmembrane domain had abnormal bleeding and greatly increased plasma TM levels. Affected cases had attenuated thrombin generation and delayed fibrinolysis similar to previous reported TM_AC cases with THBD p.Cys537*. Coincidentally, some pedigree members also harbored a stop‐gain variant in CPB2 encoding TAFI. This reduced plasma TAFI levels but was asymptomatic. Pedigree members with TM‐AC caused by the p.Pro496Argfs*10 THBD variant and also TAFI deficiency had a partially attenuated delay in fibrinolysis, but no change in the defective thrombin generation. ConclusionsThese data extend the reported genetic repertoire of TM‐AC and establish a common molecular pathogenesis arising from high plasma levels of TM extra‐cellular domain. The data further confirm that the delay in fibrinolysis associated with TM‐AC is directly linked to increased TAFI activation. The combination of the rare variants in the pedigree members provides a unique genetic model to develop understanding of the thrombin‐TM system and its regulation of TAFI.

Recent Advances in the Understanding of Thrombosis.

Recent Advances in the Understanding of Thrombosis.

Thrombin‐activatable fibrinolysis inhibitor in human abdominal aortic aneurysm disease

Background Intra-luminal thrombosis is a key factor in growth of abdominal aortic aneurysms (AAAs). Patients with AAA form dense clots that are resistant to fibrinolysis. Thrombin-activatable fibrinolysis inhibitor (TAFI) has been shown to influence AAA development in murine models. Objective The aim of this study is to characterize the role of TAFI in human AAA. Methods Plasma levels of TAFI, TAFI activation peptide (TAFI-AP), activated/inactivated TAFI (TAFIa/ai) and plasmin-α2-antiplasmin complex were measured by ELISAs in patients with AAA (n=202) and controls (n=188). Results TAFIa/ai and TAFI-AP levels were higher in patients than controls (median [IQR], 20.3 [14.6-32.8]ngmL-1 vs. 14.2 [11.2-19.3]ngmL-1 and 355.0 [232.4-528.1]ngmL-1 vs. 248.6 [197.1-328.1]ngmL-1 ). TAFIa/ai was positively correlated with TAFI-AP (r=0.164). Intact TAFI levels were not different between patients and controls (13.4 [11.2-16.1]μgmL-1 vs. 12.8 [10.6-15.4]μgmL-1 ). Plasmin-α2-antiplasmin was higher in AAA patients than controls (690.0 [489.1-924.3]ngmL-1 vs. 480.7 [392.6-555.3]ngmL-1 ). Conclusions The increase in TAFIa/ai and TAFI-AP suggests an increased TAFI activation in patients with AAA. Prospective studies are required to further elucidate the role of TAFI and fibrinolysis in AAA pathogenesis.

Dose-Response Relationship Between Thrombin-Activatable Fibrinolysis Inhibitor (TAFI) and Stroke: A Chinese Case-Control Study.

BackgroundBecause TAFI (thrombin-activatable fibrinolysis inhibitor) antigen varies widely among different populations, we performed this case-control study to explore the relationship between TAFI levels and stroke in a Chinese population.Material/MethodsOur population-based case-control study included 217 stroke patients and 218 healthy controls. The plasma TAFI level was measured by immune turbidimetry. Univariate and multivariate logistic regression analyses were used to analyze the association between different TAFI levels and stroke and its subtypes. Restricted cubic spline (RCS) combined with logistic regression analysis were used to explore the dose-response relationship between TAFI levels and stroke.ResultsThe plasma TAFI levels of cases were much higher than in the control group (p=0.038) and this difference persisted even after adjustment (OR=2.2). In the elderly (aged over 60) and female subgroups, TAFI levels in stroke patients were higher than those in controls, and the results were also noted in ischemic stroke. The dose-response curve showed that, as a whole, with the increase of TAFI levels, the relative risk of stroke first increased and then decreased (p=0.0127). Similarly, in general, with the increase of TAFI levels, the curve showed that the relative risk of ischemic stroke first increased and then decreased (p=0.0110).ConclusionsThere was a definite correlation between TAFI levels and stroke in this Chinese population, and with the increase of TAFI levels, the relative risk of stroke or ischemic stroke first increased and then decreased.

Activated TAFI Promotes the Development of Chronic Thromboembolic Pulmonary Hypertension: A Possible Novel Therapeutic Target.

Pulmonary hypertension is a fatal disease; however, its pathogenesis still remains to be elucidated. Thrombin-activatable fibrinolysis inhibitor (TAFI) is synthesized by the liver and inhibits fibrinolysis. Plasma TAFI levels are significantly increased in chronic thromboembolic pulmonary hypertension (CTEPH) patients. To determine the role of activated TAFI (TAFIa) in the development of CTEPH. Immunostaining showed that TAFI and its binding partner thrombomodulin (TM) were highly expressed in the pulmonary arteries (PAs) and thrombus in patients with CTEPH. Moreover, plasma levels of TAFIa were increased 10-fold in CTEPH patients compared with controls. In mice, chronic hypoxia caused a 25-fold increase in plasma levels of TAFIa with increased plasma levels of thrombin and TM, which led to thrombus formation in PA, vascular remodeling, and pulmonary hypertension. Consistently, plasma clot lysis time was positively correlated with plasma TAFIa levels in mice. Additionally, overexpression of TAFIa caused organized thrombus with multiple obstruction of PA flow and reduced survival rate under hypoxia in mice. Bone marrow transplantation showed that circulating plasma TAFI from the liver, not in the bone marrow, was activated locally in PA endothelial cells through interactions with thrombin and TM. Mechanistic experiments demonstrated that TAFIa increased PA endothelial permeability, smooth muscle cell proliferation, and monocyte/macrophage activation. Importantly, TAFIa inhibitor and peroxisome proliferator-activated receptor-α agonists significantly reduced TAFIa and ameliorated animal models of pulmonary hypertension in mice and rats. These results indicate that TAFIa could be a novel biomarker and realistic therapeutic target of CTEPH.

Abstract 13874: Thrombin Activatable Fibrinolysis Inhibitor Promotes Development of Chronic Thromboembolic Pulmonary Hypertension -A Possible Novel Therapeutic Target

Background: The pathogenesis of chronic thromboembolic pulmonary hypertension (CTEPH) still remains elusive. Methods and Results: CTEPH patients had higher plasma levels of and prevalence of SNPs of thrombin activatable fibrinolysis inhibitor (TAFI). Plasma levels of activated TAFI (aTAFI) were significantly increased in CTEPH patients (n=32) compared with controls (n=13) (8.7-fold, P&lt;0.01). Immunostaining showed that TAFI and its linker protein thrombomodulin (TM) were strongly expressed in the distal pulmonary arteries (PA) in CTEPH patients. TAFI-deficient mice (TAFI –/– ) exposed to hypoxia showed significantly reduced right ventricular systolic pressure (RVSP), RV hypertrophy and PA remodeling compared with controls (all P&lt;0.05, n=10 each). In contrast, TAFI-overexpressing mice (TAFI-Tg) exposed to hypoxia showed significantly augmented RVSP, RV hypertrophy and PA remodeling compared with controls (all P&lt;0.01, n=19 each). Importantly, systemic TAFI-Tg mice (n=19) showed a significantly reduced survival under hypoxia compared with controls (n=22) (63% vs. 95%, P&lt;0.01). Bone marrow transplantation demonstrated that the increased plasma levels of aTAFI, but not those in the bone marrow, promoted hypoxia-induced PA thrombus formation and PH (all P&lt;0.01, n=10 each). Interestingly, liver-specific TAFI overexpression exacerbated hypoxia-induced PH compared with controls (all P&lt;0.01, n=12 each). Plasma levels of TAFI were increased by hypoxia and were correlated with clot lysis time and the severity of PH. Morphological analysis using 3 dimensional-CT showed multiple obstruction of PAs in TAFI-Tg mice after hypoxic exposure (P&lt;0.01, n=10 each). Mechanistic experiments demonstrated that treatment with human TAFI (300 nM) increased permeability of PA endothelial cells and proliferation of PA smooth muscle cells compared with vehicle controls (n=10 each, both P&lt;0.01). Finally, a PPARα agonist, WY14643, significantly reduced plasma levels of TAFI, ameliorated hypoxia-induced PH and significantly improved mortality (-70%) in TAFI-Tg mice compared with controls (P&lt;0.01, n=12 each). Conclusions: TAFI promotes PA thrombus formation and the development of PH and could be a novel biomarker and therapeutic target for the disorder.

Thrombin-Activatable Fibrinolysis Inhibitor in Chronic Thromboembolic Pulmonary Hypertension.

The pathogenesis of chronic thromboembolic pulmonary hypertension (CTEPH) remains to be elucidated. Thrombin-activatable fibrinolysis inhibitor (TAFI) inhibits fibrinolysis. It remains to be elucidated whether TAFI is directly involved in the pathogenesis of CTEPH. We examined potential involvement of TAFI in the pathogenesis of CTEPH in humans. We enrolled 68 consecutive patients undergoing right heart catheterization in our hospital, including those with CTEPH (n=27), those with pulmonary arterial hypertension (n=22), and controls (non-pulmonary hypertension, n=19). Whole blood clot lysis assay showed that the extent of clot remaining after 4 hours was significantly higher in CTEPH compared with pulmonary arterial hypertension or controls (41.9 versus 26.5 and 24.6%, both P<0.01). Moreover, plasma levels of TAFI were significantly higher in CTEPH than in pulmonary arterial hypertension or controls (19.4±4.2 versus 16.1±4.5 or 16.3±3.3 μg/mL, both P<0.05), which remained unchanged even after hemodynamic improvement by percutaneous transluminal pulmonary angioplasty. Furthermore, the extent of clot remaining after 4 hours was significantly improved with CPI-2KR (an inhibitor of activated TAFI) or prostaglandin E1 (an inhibitor of activation of platelets). Importantly, plasma levels of TAFI were significantly correlated with the extent of clot remaining after 4 hours. In addition, the extent of clot remaining after 4 hours was improved with an activated TAFI inhibitor. These results indicate that plasma levels of TAFI are elevated in patients with CTEPH and are correlated with resistance to clot lysis in those patients.

Plasma Thrombin-activatable Fibrinolysis Inhibitor Levels Correlate with the Disease Activity of Ulcerative Colitis.

Objective Patients with ulcerative colitis (UC) are at an increased risk for thromboembolic events, particularly in patients with extensive and active disease. To date, a few studies have been published on the role of thrombin-activatable fibrinolysis inhibitor (TAFI) in UC. However, there are no reports in the literature investigating the effect of UC treatment on plasma TAFI levels. Methods The plasma TAFI antigen levels were quantitatively determined using ELISA kits for 20 UC patients at activation and remission, along with 17 healthy controls. The association between the TAFI levels and inflammatory markers was assessed to determine UC activation. To predict and determine the activation of UC, the Truelove-Witts index and the endoscopic activation index (EAI) were used for each subject. Results The plasma TAFI levels were higher in UC patients at activation of the disease compared with the remission state and in healthy controls. Spearman's correlation analyses revealed that the WBC (r: 0.586, p<0.001), hsCRP (r: 0.593, p<0.001) and EAI (r: 0.721, p<0.001) were significantly correlated with the TAFI levels. The overall accuracy of TAFI in determining UC activation was 82.5% with a sensitivity, specificity, NPV and PPV of 80%, 85%, 81% and 84.2%, respectively (cut-off value: 156.2% and AUC: 0.879). Conclusion The present study demonstrates that the TAFI levels are elevated in the active state of UC. The assessment of TAFI levels in patients with UC in conjunction with other markers of inflammation may provide additional information for estimating UC activation and severity.

Elevated thrombin activatable fibrinolysis inhibitor levels in women with polycystic ovary syndrome

Objective: The aim of the present study was to evaluate plasma concentrations of thrombin activatable fibrinolysis inhibitor (TAFI) in relation with hormonal, metabolic, and hemostatic profile in patients with and without polycystic ovary syndrome (PCOS).Study design: A total of 38 women with PCOS and 37 age and body mass index (BMI) matched controls were eligible for the study. Hirsutism scores, hormonal, metabolic, and hemostatic profile as well as TAFI levels were evaluated in each subject.Results: Women with PCOS exhibited higher plasma concentrations of TAFI levels than controls (107.42 ± 34.77% versus 91.86 ± 23.88%, p = 0.027). TAFI levels were significantly correlated positively with BMI, fasting insulin levels, modified Ferriman Gallwey scores and Homeostasis Model Assessment (HOMA) index, systolic blood pressure, and waist and hip circumferences, whereas negatively correlated with activated partial thromboplastin time (p < 0.05). However, after adjustment for all possible confounding factors, none of the parameters was significantly deterministic on TAFI levels.Conclusion: The data of the present study suggested that plasma TAFI levels were higher in women with PCOS as compared with healthy age and BMI-matched controls, indicating impaired fibrinolysis. This hypofibrinolytic state may be responsible for the increased cardiovascular disease risk in women with PCOS.

PP.39.23

Objective: We showed previously that acute aldosterone (ALDO) infusion resulted in impairment of the fibrinolytic process and activation of coagulation cascade, consequently leading to augmentation of stasis-induced venous thrombosis in rats. This prothrombotic effect of ALDO was only partially mediated by the mineralocorticoid receptor (MR). Bearing in mind that ALDO potentiates the angiotensin II (Ang II) effects, in the present study we investigated the role of Ang II in the mechanism of ALDO prothrombotic action. Design and method: Male Wistar rats (300–350 g, n = 8–12) were used in this study. Aldosterone (ALDO, 30 μg/kg/h) or 0,4% ethanol (VEH; 2 ml/kg/h) was infused into the femoral vein 5 minutes before the induction of venous thrombosis and was continued for 1 h. Valsartan (VAL, 10 mg/kg), AT1 antagonist, was injected as a bolus into femoral vein 5 minutes before ALDO infusion. Venous thrombosis was performed by the vena cava ligation. The formed thrombus was removed and weighted after 24 h. Plasminogen activator inhibitor (PAI-I), tissue plasminogen activator (t-PA), thrombin activatable fibrinolysis inhibitor (TAFI) plasma levels were measured by ELISA. Results: We observed that one-hour infusion of ALDO resulted in a significant increase in venous thrombus weight (p < 0.01) and markedly elevated incidence of venous thrombosis, paralleled by significant increase in PAI-1 (p < 0.001) and TAFI (p < 0.001) as well as decrease in t-PA (p < 0.001) plasma levels in comparison to VEH. VAL administered together with ALDO reduced thrombus formation (p < 0.05) and diminished the incidences of thrombosis. We also observed that pretreatment with VAL reversed slightly the ALDO-induced decrease in t-PA level and reduced significantly TAFI (p < 0.05) and PAI-1 plasma levels (p < 0.05, vs ALDO). Conclusions: This study provides evidence that prothrombotic effect of ALDO is also mediated by the angiotensin II AT1 receptor. The mechanism of ALDO-induced AT1 activation involved impairment of the fibrinolytic process. The present study supplies our knowledge about the multiple mechanism of ALDO prothrombotic action, which is mediated via MR and AT1 receptors.

Thrombin-activatable fibrinolysis inhibitor Thr325Ile polymorphism and plasma level in breast cancer: A pilot study

This study aimed to investigate thrombin-activatable fibrinolysis inhibitor (TAFI) Thr325Ile polymorphism and TAFI antigen (Ag) levels in breast cancer (BC) in the Egyptian population to clarify their role in relation to BC. A group of 300 females was recruited in this study; of these 150 unrelated patients with different stages of BC and 150 age-matched healthy controls. Plasma TAFI Ag was measured by ELISA and TAFI Thr325Ile (rs1926447) polymorphism was genotyped using TaqMan single nucleotide polymorphism (SNP) genotyping assay. The results showed the genotypes of the minor allele; Thr/Ile (CT) and Ile/Ile (TT) were significantly more frequent in patients compared to control group (50.0% and 22.0% vs. 42.0% and 13.3%, respectively) and were also associated with BC susceptibility [OR=1.9 and 2.6; 95% CI: (1.1–3.3) and (1.3–5.5), respectively P=0.01]. Ile325 allele carriers were more frequent in cases than in controls (47.0% vs. 34.0%) [OR=1.7, (95% CI=1.2–2.4), P=0.001]. However, TAFI Thr325Ile polymorphism was not associated with BC stage or other clincopathological characteristics. TAFI Ag levels were correlated with advanced stages of BC, poor prognosis and risk of recurrence (P=0.02, P=0.04 and P <0.001, respectively) and Thr325Ile SNP was significantly correlated with TAFI antigen levels with the C/C genotype corresponding to the highest and the T/T genotype to the lowest TAFI antigen levels (P<0.001) in the study groups. In conclusion, this study showed for the first time that TAFI Thr325Ile polymorphism could have a contribution to BC susceptibility in our population. Furthermore, high TAFI plasma levels may serve as a predictor of poor prognosis in patients with BC.