Limited value of testing for factor XIII and α2-antiplasmin deficiency in patients with a bleeding disorder of unknown cause.

INTRODUCTION: In patients with an increased bleeding tendency, extensive diagnostic blood testing is often performed. When results of tier 1 assays of primary haemostasis are normal, protocols recommend additional testing to rule out rare disorders including coagulation factor XIII (FXIII) and α2-antiplasmin (α2AP) deficiency. AIM: To evaluate the added diagnostic value of FXIII and α2AP levels in patients with a bleeding disorder of unknown cause (BDUC). METHODS: A retrospective monocentre cohort study between August 2011 and August 2023 was conducted. In all patients with bleeding tendencies and normal diagnostic tests for von Willebrand disease and platelet function, FXIII and α2AP were measured. RESULTS: We included 158 consecutive patients; mean ISTH-BAT scores were 8.2 (SD ± 3.7) in children, 6.2 (SD ± 2.1) in men and 10.6 (SD ± 3.3) in women. Median age was 37 (range 5-79) years, 88.6% of patients were female. Patients displayed median FXIII activity of 111% (IQR = 97-131) and median α2AP activity of 112% (IQR = 103-119). Three (1.9%) patients had FXIII levels < 50%, respectively 43%, 45% and 46%. Corresponding ISTH-BAT scores were 7, 12 and 14. No α2AP levels < 60% was observed. No significant association was found between FXIII levels and ISTH-BAT scores. CONCLUSION: In our cohort of BDUC patients, no clinical relevant FXIII deficiencies were detected; absolute values were well above the 30% cutoff considered adequate for normal haemostasis. No α2AP deficiencies were detected. These data suggest that in BDUC patients, measuring FXIII or AP activity is of limited value.

Development of a chemiluminescence assay for tissue plasminogen activator inhibitor complex and its applicability to gastric cancer.

BACKGROUND: Venous thromboembolism (VTE), is a noteworthy complication in individuals with gastric cancer, but the current diagnosis and treatment methods lack accuracy. In this study, we developed a t-PAIC chemiluminescence kit and employed chemiluminescence to detect the tissue plasminogen activator inhibitor complex (t-PAIC), thrombin-antithrombin III complex (TAT), plasmin-α2-plasmin inhibitor complex (PIC) and thrombomodulin (TM), combined with D-dimer and fibrin degradation products (FDP), to investigate their diagnostic potential for venous thrombosis in gastric cancer patients. The study assessed variations in six indicators among gastric cancer patients at different stages. RESULTS: The t-PAIC reagent showed LOD is 1.2 ng/mL and a linear factor R greater than 0.99. The reagents demonstrated accurate results, with all accuracy deviations being within 5%. The intra-batch and inter-batch CVs for the t-PAIC reagent were both within 8%. The correlation coefficient R between this method and Sysmex was 0.979. Gastric cancer patients exhibited elevated levels of TAT, PIC, TM, D-D, FDP compared to the healthy population, while no significant difference was observed in t-PAIC. In the staging of gastric cancer, patients in III-IV stages exhibit higher levels of the six markers compared to those in I-II stages. The ROC curve indicates an enhancement in sensitivity and specificity of the combined diagnosis of four or six indicators. CONCLUSION: Our chemiluminescence assay performs comparably to Sysmex's method and at a reduced cost. The use of multiple markers, including t-PAIC, TM, TAT, PIC, D-D, and FDP, is superior to the use of single markers for diagnosing VTE in patients with malignant tumors. Gastric cancer patients should be screened for the six markers to facilitate proactive prophylaxis, determine the most appropriate treatment timing, ameliorate their prognosis, decrease the occurrence of venous thrombosis and mortality, and extend their survival.

A novel method to quantify fibrin-fibrin and fibrin-α2-antiplasmin cross-links in thrombi formed from human trauma patient plasma.

BACKGROUND: The widespread use of the antifibrinolytic agent, tranexamic acid (TXA), interferes with the quantification of fibrinolysis by dynamic laboratory assays such as clot lysis, making it difficult to measure fibrinolysis in many trauma patients. At the final stage of coagulation, factor (F)XIIIa catalyzes the formation of fibrin-fibrin and fibrin-α2-antiplasmin (α2AP) cross-links, which increases clot mechanical strength and resistance to fibrinolysis. OBJECTIVES: Here, we developed a method to quantify fibrin-fibrin and fibrin-α2AP cross-links that avoids the challenges posed by TXA in determining fibrinolytic resistance in conventional assays. METHODS: Fibrinogen alpha (FGA) chain (FGA-FGA), fibrinogen gamma (FGG) chain (FGG-FGG), and FGA-α2AP cross-links were quantified using liquid chromatography-mass spectrometry (LC-MS) and parallel reaction monitoring in paired plasma samples from trauma patients prefibrinogen and postfibrinogen replacement. Differences in the abundance of cross-links in trauma patients receiving cryoprecipitate (cryo) or fibrinogen concentrate (Fg-C) were analyzed. RESULTS: The abundance of cross-links was significantly increased in trauma patients postcryo, but not Fg-C transfusion (P < .0001). The abundance of cross-links was positively correlated with the toughness of individual fibrin fibers, the peak thrombin concentration, and FXIII antigen (P < .05). CONCLUSION: We have developed a novel method that allows us to quantify fibrin cross-links in trauma patients who have received TXA, providing an indirect measure of fibrinolytic resistance. Using this novel approach, we have avoided the effect of TXA and shown that cryo increases fibrin-fibrin and fibrin-α2AP cross-linking when compared with Fg-C, highlighting the importance of FXIII in clot formation and stability in trauma patients.

α2-Antiplasmin is associated with macrophage activation and fibrin deposition in a macrophage activation syndrome mouse model.

Macrophage activation syndrome (MAS) is a life-threatening condition, characterized by cytopenia, multi-organ dysfunction, and coagulopathy associated with excessive activation of macrophages. In this study, we investigated the roles of alpha2-antiplasmin (α2AP) in the progression of MAS using fulminant MAS mouse model induced by toll-like receptor-9 agonist (CpG) and D-(+)-galactosamine hydrochloride (DG). α2AP deficiency attenuated macrophage accumulation, liver injury, and fibrin deposition in the MAS model mice. Interferon-γ (IFN-γ) is associated with macrophage activation, including migration, and plays a pivotal role in MAS progression. α2AP enhanced the IFN-γ-induced migration, and tissue factor production. Additionally, we showed that fibrin-induced macrophage activation and tumor necrosis factor-α production. Moreover, the blockade of α2AP by neutralizing antibodies attenuated macrophage accumulation, liver injury, and fibrin deposition in the MAS model mice. These data suggest that α2AP may regulate IFN-γ-induced responses and be associated with macrophage activation and fibrin deposition in the MAS progression.

Alpha2-antiplasmin deficiency affects depression and anxiety-like behavior and apoptosis induced by stress in mice.

OBJECTIVES: Depression is a psychiatric disorder that affects about 10% of the world's population and is accompanied by anxiety. Depression and anxiety are often caused by various stresses. However, the etiology of depression and anxiety remains unknown. It has been reported that alpha2-antiplasmin (α2AP) not only inhibits plasmin but also has various functions such as cytokine production and cell growth. This study aimed to determine the roles of α2AP on the stress-induced depression and anxiety. METHODS: We investigated the mild repeated restraint stress-induced depressive and anxiety-like behavior in the α2AP+/+ and α2AP-/- mice using the social interaction test (SIT), sucrose preference test (SPT), and elevated plus maze (EPM). RESULTS: The stresses such as the mild repeated restraint stress suppressed α2AP expression in the hippocampus of mice, and the treatment of fluoxetine (selective serotonin reuptake inhibitor [SSRI]) recovered the stress-caused α2AP suppression. We also showed that α2AP deficiency promoted the mild restraint stress-stimulated depression-like behavior such as social withdrawal and apathy and apoptosis in mice. In contrast, α2AP deficiency attenuated the mild restraint stress induced the anxiety-like behavior in mice. CONCLUSIONS: α2AP affects the pathogenesis of depression and anxiety induced by stress.

Pre-Operative Plasma Extracellular Vesicle Proteins are Associated with a High Risk of Long Term Secondary Major Cardiovascular Events in Patients Undergoing Carotid Endarterectomy.

OBJECTIVE: Patients undergoing carotid endarterectomy (CEA) maintain a substantial residual risk of major cardiovascular events (MACE). Improved risk stratification is warranted to select high risk patients qualifying for secondary add on therapy. Plasma extracellular vesicles (EVs) are involved in atherothrombotic processes and their content has been related to the presence and recurrence of cardiovascular events. The association between pre-operative levels of five cardiovascular disease related proteins in plasma EVs and the post-operative risk of MACE was assessed. METHODS: In 864 patients undergoing CEA from 2002 to 2016 included in the Athero-Express biobank, three plasma EV subfractions (low density lipoprotein [LDL], high density lipoprotein [HDL], and tiny extracellular vesicles [TEX]) were isolated from pre-operative blood samples. Using an electrochemiluminescence immunoassay, five proteins were quantified in each EV subfraction: cystatin C, serpin C1, serpin G1, serpin F2, and CD14. The association between EV protein levels and the three year post-operative risk of MACE (any stroke, myocardial infarction, or cardiovascular death) was evaluated using multivariable Cox proportional hazard regression analyses. RESULTS: During a median follow up of three years (interquartile range 2.2 - 3.0), 137 (16%) patients developed MACE. In the HDL-EV subfraction, increased levels of CD14, cystatin C, serpin F2, and serpin C1 were associated with an increased risk of MACE (adjusted hazard ratios per one standard deviation increase of 1.30, 95% confidence interval [CI] 1.15-1.48; 1.22, 95% CI 1.06-1.42; 1.36, 95% CI 1.16-1.61; and 1.29, 95% CI 1.10-1.51; respectively), independently of cardiovascular risk factors. No significant associations were found for serpin G1. CD14 improved the predictive value of the clinical model encompassing cardiovascular risk factors (net re-classification index = 0.16, 95% CI 0.08-0.21). CONCLUSION: EV derived pre-operative plasma levels of cystatin C, serpin C1, CD14, and serpin F2 were independently associated with an increased long term risk of MACE after CEA and are thus markers for residual cardiovascular risk. EV derived CD14 levels could improve the identification of high risk patients who may benefit from secondary preventive add on therapy in order to reduce future risk of MACE.

Tranexamic acid rapidly inhibits fibrinolysis, yet transiently enhances plasmin generation in vivo.

Tranexamic acid (TXA) is a lysine analogue that inhibits plasmin generation and has been used for decades as an antifibrinolytic agent to reduce bleeding. Recent reports have indicated that TXA can paradoxically promote plasmin generation. Blood was obtained from 41 cardiac surgical patients randomly assigned to TXA or placebo before start of surgery (preOP), at the end of surgery (EOS), then again on postoperative day 1 (POD-1) as well as POD-3. Plasma levels of tissue-type plasminogen activator (t-PA), urokinase (u-PA), the plasmin-antiplasmin (PAP) complex, as well as t-PA and u-PA-induced clot lysis assays were then determined. Clot lysis and PAP complex levels were also assessed in healthy volunteers before and at various time points after taking 1 g TXA orally. Surgery induced an increase in circulating t-PA, yet not u-PA at EOS. t-PA levels were unaffected by TXA; however, u-PA levels were significantly reduced in patients on POD-3. t-PA and u-PA-induced clot lysis were both inhibited in plasma from TXA-treated patients. In contrast, PAP complex formation, representing plasmin generation, was unexpectedly enhanced in the plasma of patients administered TXA at the EOS time point. In healthy volunteers, oral TXA effectively blocked fibrinolysis within 30 min and blockade was sustained for 8 h. However, TXA also increased PAP levels in volunteers 4 h after administration. Our findings demonstrate that TXA can actually augment PAP complex formation, consistent with an increase in plasmin generation in vivo despite the fact that it blocks fibrinolysis within 30 min. This may have unanticipated consequences in vivo.

Terminal Phase Components of the Clotting Cascade in Patients with End-Stage Renal Disease Undergoing Hemodiafiltration or Hemodialysis Treatment.

Hemostasis disorder in patients with end-stage renal disease (ESRD) is frequently associated with bleeding diathesis but it may also manifest in thrombotic complications. Analysis of individual coagulation and fibrinolytic factors may shed light on the background of this paradox situation. Here we explored components essential for fibrin formation/stabilization in ESRD patients being on maintenance hemodiafiltration (HDF) or hemodialysis (HD). Pre-dialysis fibrinogen, factor XIII (FXIII) antigen concentrations and FXIII activity were elevated, while α2-plasmin inhibitor (α2PI) activity decreased. The inflammatory status, as characterized by C-reactive protein (CRP) was a key determinant of fibrinogen concentration, but not of FXIII and α2PI levels. During a 4-h course of HDF or HD, fibrinogen concentration and FXIII levels gradually elevated. When compensated for the change in plasma water, i.e., normalized for plasma albumin concentration, only FXIII elevation remained significant. There was no difference between HDF and HD treatments. Individual HDF treatment did not influence α2PI activity, however after normalization it decreased significantly. HD treatment had a different effect, α2PI activities became elevated but the elevation disappeared after normalization. Elevated fibrinogen and FXIII levels in ESRD patients might contribute to the increased thrombosis risk, while decreased α2PI activity might be associated with elevated fibrinolytic potential.

Plasma fibrin clots of pulmonary embolism patients present increased amounts of factor XIII and alpha2-antiplasmin at 3 months' anticoagulation since the acute phase.

Fibrin cross-linking by coagulation factor (F)XIII leads to clot stabilization. Reduced plasma FXIII levels have been reported in acute pulmonary embolism (PE) patients. We investigated the impact of anticoagulant therapy on clot-bound amounts of FXIII and α2-antiplasmin and their associations with fibrin clot properties in patients with PE. Clots generated from plasma of 18 acute symptomatic patients on admission and after a 3-month treatment with rivaroxaban were assessed off anticoagulation using mass spectrometry. Plasma FXIII and α2-antiplasmin activity were determined at the 2 time points along with thrombin generation markers, plasma fibrin clot permeability (Ks), and clot lysis time (CLT). Following anticoagulant therapy, clot-bound FXIII increased from 2.97 (interquartile range, 1.98 - 4.08) to 4.66 (3.5 - 6.9) mg/g protein and α2-antiplasmin from 9.4 (7.2 - 10.6) to 11 (9.5 - 14) mg/g protein (both p < 0.0001). The two parameters showed positive correlation at baseline only (r = 0.63, p = 0.0056). Similarly to clot-bound amounts, plasma FXIII (+25.8%) and α2-antiplasmin activity (+12%) increased at 3 months. Plasma FXIII activity on admission, but not after 3 months since the index PE, was associated with amounts of clot-bound FXIII (r = 0.35, p = 0.043) and α2-antiplasmin (r = 0.47, p = 0.048). At baseline, clot-bound FXIII correlated with plasma F1+2 prothrombin fragments levels (r = 0.51, p = 0.03), while clot-bound α2-antiplasmin correlated with CLT (r = 0.43, p = 0.036). At 3 months associations of clot-bound FXIII and α2-antiplasmin were abolished. This study assessed for the first time changes in the fibrin clot composition following acute PE, suggesting an increase of clot-bound and plasma FXIII and α2-antiplasmin levels after 3 months.

α2-Antiplasmin as a potential regulator of the spatial memory process and age-related cognitive decline.

α2-Antiplasmin (α2AP), a principal physiological plasmin inhibitor, is mainly produced by the liver and kidneys, but it is also expressed in several parts of the brain, including the hippocampus and cerebral cortex. Our previous study demonstrated that α2AP knockout mice exhibit spatial memory impairment in comparison to wild-type mice, suggesting that α2AP is necessary for the fetal and/or neonatal development of the neural network for spatial memory. However, it is still unclear whether α2AP plays a role in the memory process. The present study demonstrated that adult hippocampal neurogenesis and remote spatial memory were enhanced by the injection of an anti-α2AP neutralizing antibody in WT mice, while the injection of α2AP reduced hippocampal neurogenesis and impaired remote spatial memory, suggesting that α2AP is a negative regulator in memory processing. The present study also found that the levels of α2AP in the brains of old mice were higher than those in young mice, and a negative correlation between the α2AP level and spatial working memory. In addition, aging-dependent brain oxidative stress and hippocampal inflammation were attenuated by α2AP deficiency. Thus, an age-related increase in α2AP might cause cognitive decline accompanied by brain oxidative stress and neuroinflammation. Taken together, our findings suggest that α2AP is a key regulator of the spatial memory process, and that it may represent a promising target to effectively regulate healthy brain aging.

Decrease in matrix metalloproteinase­3 activity in systemic sclerosis fibroblasts causes α2­antiplasmin and extracellular matrix deposition, and contributes to fibrosis development.

Systemic sclerosis (SSc) is a connective tissue disease of autoimmune origin characterized by fibrosis of the skin and visceral organs, and peripheral circulatory disturbance. α2­antiplasmin (α2AP) is the major circulating inhibitor of plasmin and is a key regulator of fibrinolysis. It has been demonstrated that the expression of α2AP is elevated in dermal fibroblasts obtained from patients with SSc patients. It has also been determined that α2AP is associated with the development and progression of fibrosis in SSc. The present study assessed the relationship between α2AP and matrix metalloproteinase­3 (MMP­3), an extracellular matrix (ECM)­degrading enzyme. Serum levels of α2AP and MMP­3 were measured in healthy controls and patients with SSc using ELISA. No significant differences were determined between these two groups. α2AP, MMP­3 and tissue inhibitor of metalloproteinase­1 (TIMP­1) expression was subsequently evaluated in normal and SSc fibroblasts via western blotting. The results revealed that α2AP expression increased in SSc dermal fibroblasts, while the ratio of MMP­3/TIMP­1 decreased. Additionally, incubation of recombinant α2AP with MMP­3 caused α2AP degradation. The mixture of recombinant α2AP with MMP­3 was subsequently added to normal fibroblasts prior to western blotting. The results revealed decreased α­smooth muscle actin (α­SMA; a marker of the myofibroblast phenotype) and type I collagen expression. The stimulation of SSc fibroblasts with MMP­3 decreased protein levels of α2AP, α­SMA and type I collagen, thus reversing the pro­fibrotic phenotype of SSc fibroblasts. SSc fibroblast transfection with microRNA­29a resulted in a decreased TIMP­1 expression, but also decreased the protein expression of α2AP. The results indicated that MMP­3 attenuated fibrosis progression by degrading α2AP and ECM, and might therefore contribute to a novel therapeutic approach for SSc treatment.

Interaction of glycated and acetylated human α2-antiplasmin with fibrin clots.

: In type 2 diabetes mellitus (T2DM), increased α2-antiplasmin incorporation in fibrin and impaired fibrinolysis have been reported. Acetylsalicylic acid (ASA), used in cardiovascular prevention, modulates fibrinolysis and exerts weaker therapeutic effect in this disease. We investigated how glycation and acetylation of α2-antiplasmin affects its interaction with fibrin. Using surface plasmon resonance, we analyzed fibrin binding by α2-antiplasmin incubated with no ß-D-glucose or ASA (control); incubated with ß-D-glucose (5, 10, 50 mmol/l); (3) incubated with 1.6 mmol/l acetylsalicylic acid (ASA) and (4) incubated with 1.6 mmol/l ASA and 50 mmol/l ß-D-glucose. Incubation with glucose decreased affinity of α2-antiplasmin for fibrin compared with control α2-antiplasmin in a glucose concentration-depending manner. α2-Antiplasmin incubation with ASA did not affect its affinity to fibrin. α2-Antiplasmin incubation with ASA and glucose resulted in 4.2-fold increased affinity to fibrin compared with α2-antiplasmin incubated with 50 mmol/l glucose (P < 0.001). In conclusion, α2-antiplasmin incubation with glucose at concentrations encountered in T2DM is associated with decreased binding affinity of α2-antiplasmin to fibrin. ASA alone does not affect the binding affinity of α2-antiplasmin to fibrin, but partly reverses the effect introduced by the incubation with 50 mmol/l glucose. This study suggests new mechanisms involved in regulating fibrinolysis efficiency in hyperglycemia.

Selection of mutant µplasmin for amyloid-ß cleavage in vivo.

One of the main culprits of Alzheimer's disease (AD) is the formation of toxic amyloid-ß (Aß) peptide polymers and the aggregation of Aß to form plaques in the brain. We have developed techniques to purify the catalytic domain of plasmin, micro-plasmin (µPlm), which can be used for an Aß-clearance based AD therapy. However, in serum, µPlm is irreversibly inhibited by its principal inhibitor α2-antiplasmin (α2-AP). In this study, we engineered and selected mutant forms of µPlm that are both catalytically active and insensitive to α2-AP inhibition. We identified surface residues of µPlm that might interact and bind α2-AP, and used an alanine-scanning mutagenesis method to select residues having higher activity but lower α2-AP inhibition. Then we employed saturation mutagenesis for further optimize both properties. Modeled complex structure of µPlm/α2-AP shows that F587 is a critical contact residue, which can be used as a starting position for further investigation.

Quantitative Volumetric Comparison of Direct Oral Anticoagulant and Vitamin K Antagonist Treatment for Pulmonary Thrombus Reduction During the Acute Phase in Symptomatic Patients.

BACKGROUND: Recent clinical trials' findings have revealed the therapeutic noninferiority of direct oral anticoagulant (DOAC) to standard therapy with vitamin K antagonist (VKA) in patients with pulmonary thromboembolism (PTE). However, few studies have quantitatively analyzed thrombus reduction in the pulmonary artery. METHODS: This observational study included 38 symptomatic PTE patients with stable hemodynamics. All patients received an intravenous heparin bolus followed by continual heparin injections immediately after the PTE diagnosis. The heparin was discontinued after edoxaban therapy began in the DOAC group (n = 22) or after the therapeutic range for the prothrombin time-international normalized ratio was achieved in the VKA group (n = 16). The thrombus volumes in the pulmonary arteries were quantitatively analyzed using contrast-enhanced computed tomography scans, and they were compared at baseline and at 2 weeks after admission. RESULTS: The pulmonary thrombus volumes declined in the VKA and DOAC groups from 7.9 to 4.2 cm3 (P = 0.048) and from 7.1 to 3.7 cm3 (P < 0.01), respectively, and the thrombus reduction rates did not differ significantly between the groups (-34% vs. -64%, respectively; P = 0.38). The fibrinogenolysis parameter changes during the14 days after admission were similar in both groups. Compared with the VKAgroup, the average hospital stay was 9days shorter in the DOAC group. There were no in-hospital deaths, and 1 case experienced major bleeding in the VKA group. CONCLUSIONS: In relation to pulmonary artery thrombus volume reduction, DOAC monotherapy for PTE may be comparable with standard therapy involving VKAs.

Alternatively activated macrophages are associated with the α2AP production that occurs with the development of dermal fibrosis : The role of alternatively activated macrophages on the development of fibrosis.

BACKGROUND: Fibrotic diseases are characterized by tissue overgrowth, hardening, and/or scarring because of the excessive production, deposition, and contraction of the extracellular matrix (ECM). However, the detailed mechanisms underlying these disorders remain unclear. It was recently reported that α2-antiplasmin (α2AP) is elevated in fibrotic tissue and that it is associated with the development of fibrosis. In the present study, we examined the mechanism underlying the production of α2AP on the development of fibrosis. METHODS: To clarify the mechanism underlying the production of α2AP on the development of fibrosis, we focused on high-mobility group box 1 (HMGB1), which is associated with the development of fibrosis. The mouse model of bleomycin-induced fibrosis was used to evaluate the production of α2AP on the development of fibrosis. RESULTS: We found that HMGB1 induced the production of α2AP through receptor for advanced glycation end products (RAGE) in fibroblasts. Next, we showed that macrophage reduction by a macrophage-depleting agent, clodronate, attenuated the progression of fibrosis and the production of α2AP and HMGB1 in the bleomycin-induced mice. We also showed that IL-4-stimulated alternatively activated macrophages induced the production of HMGB1, that IL-4-stimulated alternatively activated macrophage conditioned media (CM) induced pro-fibrotic changes and α2AP production, and that the inhibition of HMGB1 and RAGE attenuated these effects in fibroblasts. Furthermore, the blockade of IL-4 signaling by IL-4Rα neutralizing antibodies attenuated the progression of fibrosis and the production of α2AP and HMGB1 in the bleomycin-induced mice. CONCLUSION: These findings suggest that alternatively activated macrophage-derived HMGB1 induced the production of α2AP through RAGE and that these effects are associated with the development of fibrosis. Our findings may provide a clinical strategy for managing fibrotic disorders.

Combined effect of a direct oral anticoagulant edoxaban and an inhibitor of activated thrombin-activatable fibrinolysis inhibitor on clot lysis.

Fibrinolysis is regulated by the thrombin/thrombin-activatable fibrinolysis inhibitor (TAFI) system. Thus, anticoagulants and inhibitors of TAFI are expected to accelerate fibrinolysis. The combined effects of an anticoagulant and a TAFIa inhibitor on fibrinolysis remain unknown. The aim of this study was to evaluate the combined effect of edoxaban, an oral direct factor Xa (FXa) inhibitor, and a TAFIa inhibitor, potato tuber carboxypeptidase inhibitor (PCI) on tissue-type plasminogen activator (t-PA)-induced clot lysis in human plasma in vitro. Pooled human plasma (containing 180 ng/mL t-PA and 0.1 nM thrombomodulin) was mixed with edoxaban and/or PCI. Clot formation was induced by 2.5 pM tissue factor and 4 µM phospholipids and clot lysis time was examined. Plasma plasmin-α2 antiplasmin complex (PAP) concentration was measured as a marker of plasmin generation. Edoxaban or PCI alone significantly shortened the t-PA-induced clot lysis time and plasma PAP concentration. The combination of these compounds significantly accelerated the clot lysis compared with the inhibitors alone. Addition of PCI (0.3, 1, and 3 µg/mL) to 75 ng/mL edoxaban increased plasma PAP concentration compared with edoxaban alone; however, compared with PCI alone only the combination of 0.3 µg/mL PCI + 75 ng/mL edoxaban showed the significant increase in PAP concentration. Concomitant use of an oral direct FXa inhibitor, edoxaban, and a TAFIa inhibitor, PCI, significantly accelerate fibrinolysis via enhancement of plasmin generation. These results suggest that the combination of edoxaban and a TAFIa inhibitor might be beneficial for the treatment of thromboembolic diseases.

Increased plasma plasmin-α2-plasmin inhibitor complex levels correlate with postoperative rebleeding after endoscopic surgery for spontaneous intracerebral hemorrhage.

BACKGROUND: Postoperative rebleeding (PR) is one of the most severe complications of endoscopic surgery, often performed to remove spontaneous intracerebral hemorrhage (sICH). However, the risk factors for PR remain unclear. OBJECTIVE: This study retrospectively investigated whether increased preoperative plasma plasmin-α2-plasmin inhibitor complex (PIC) levels, indicating activation of fibrinolysis, are associated with PR. METHODS: A total of 101 patients underwent endoscopic surgery to evacuate sICH at our institution from January 2010 to June 2019, and 79 patients who underwent examinations of plasma PIC levels at admission with available radiographical data were included. Correlations between PR and increased plasma PIC levels were retrospectively evaluated. RESULTS: PR occurred in eight patients (10.1%), and high PIC levels (≥ 4 or 6 µg/ml) were significantly associated with PR. The sensitivities employing high PIC levels of ≥ 4 µg/ml and ≥ 6 µg/ml were both 0.63, and the specificities using the same PIC levels were 0.86 and 0.92, respectively. Multivariable analyses showed that high plasma PIC levels of ≥ 4 µg/ml (odds ratio (OR), 12.77; 95% confidence interval (CI), 1.65-98.77; p = 0.02) or ≥ 6 µg/ml (OR, 18.33; 95% CI, 2.32-144.82; p = 0.006) were independent predictors of PR. CONCLUSIONS: This study found that increased plasma PIC levels were associated with PR following the endoscopic evacuation of sICHs, indicating that increased plasma PIC levels could be potentially used to predict PR. Further studies are needed to establish new surgical strategies and adjuvant treatments to improve surgical outcomes in patients with sICH prone to PR.

Identification of glycated and acetylated lysine residues in human α2-antiplasmin.

BACKGROUND: The post-translational protein modification via lysine residues can significantly alter its function. α2-antiplasmin, a key inhibitor of fibrinolysis, contains 19 lysine residues. AIM: We sought to identify sites of glycation and acetylation in human α2-antiplasmin and test whether the competition might occur on the lysine residues of α2-antiplasmin. METHODS: We analyzed human α2-antiplasmin (1) untreated; (2) incubated with increasing concentrations of ß-d-glucose (0, 5, 10, 50 mM); (3) incubated with 1.6 mM acetylsalicylic acid (ASA) and (4) incubated with 1.6 mM ASA and 50 mM ß-d-glucose, using the ultraperformance liquid chromatography system coupled to mass spectrometer. RESULTS: Eleven glycation sites and 10 acetylation sites were found in α2-antiplasmin. Incubation with ß-d-glucose was associated with glycation of 4 (K-418, K-427, K-434, K-441) out of 6 lysine residues, known to be important for mediating the interaction with plasmin. Glycation and acetylation overlapped at 9 sites in samples incubated with ß-d-glucose or ASA. Incubation with concomitant ASA and ß-d-glucose was associated with the decreased acetylation at all sites overlapping with glycation sites. At K-182 and K-448, decreased acetylation was associated with increased glycation when compared with α2-antiplasmin incubated with 50 mM ß-d-glucose alone. Although K-24 located in the proximity of the α2-antiplasmin cleavage site, was found to be only acetylated, incubation with ASA and 50 mM ß-d-glucose was associated the absence of acetylation at that site. CONCLUSION: Human α2-antiplasmin is glycated and acetylated at several sites, with the possible competition between acetylation and glycation at K-182 and K-448. Our finding suggests possibly relevant alterations to α2-antiplasmin function at high glycemia and during aspirin use.

Defibrotide enhances fibrinolysis in human endotoxemia - a randomized, double blind, crossover trial in healthy volunteers.

Defibrotide is approved for the treatment of sinusoidal obstruction syndrome after allogeneic stem cell transplantation. The exact mode of action of defibrotide is unclear and human in vivo data are scarce. In this randomized, double blind, crossover trial we included 20 healthy volunteers. Four were randomized to receive placebo, while 16 received a 2 ng/kg bodyweight bolus of lipopolysaccharide (LPS). Infusion of 6.25 mg/kg defibrotide or placebo was started one hour before the injection of the LPS bolus. Plasma levels of prothrombin fragments F1 + 2, thrombin-antithrombin complexes, von Willebrand factor, E-selectin, tissue-type plasminogen activator (t-PA), plasminogen activator inhibitor-1 (PAI-1), plasmin-antiplasmin complexes (PAP), tumor necrosis factor-α, interleukin 6, and C-reactive protein were measured. Thromboelastometry was performed. Infusion of defibrotide did not reduce the LPS-induced activation of coagulation, the endothelium or the release of pro-inflammatory cytokines. However, defibrotide increased t-PA antigen levels by 31% (Quartiles: 2-49%, p = 0.026) and PAP concentrations by 13% (-4-41%, p = 0.039), while PAI-1 levels remained unaffected. Moreover, defibrotide reduced C-reactive protein levels by 13% (0-17%, p = 0.002). A transient increase in the clotting time in thromboelastometry and a decrease in F1 + 2 prothrombin fragments suggests modest anticoagulant properties. In conclusion, defibrotide infusion enhanced fibrinolysis and reduced C-reactive protein levels during experimental endotoxemia.

Fibrinolysis in patients with chemotherapy-induced thrombocytopenia and the effect of platelet transfusion.

Essentials Bleeding in chemotherapy induced thrombocytopenia (CIT) might be influenced by hyperfibrinolysis. t-PA-thromboelastography is a fast and reliable assay for hyperfibrinolysis in CIT patients. Clots of CIT patients are more susceptible to t-PA induced lysis compared to healthy individuals. Besides platelets, other factors are likely to influence clot lysis in CIT patients. BACKGROUND: Bleeding events in chemotherapy-induced thrombocytopenic (CIT) patients with similar platelet counts might be influenced by changes in clot lysis potential. OBJECTIVES: To investigate, in an observational study, thromboelastographic lysis parameters, alterations in clot strength and susceptibility to clot lysis in CIT patients. To identify factors associated with fibrinolytic profiles, and to evaluate the effects of platelet transfusions. METHODS: Independent determinants of tissue-type plasminogen activator (t-PA)-ROTEM lysis parameters were identified with multivariable linear regression. Clot formation, strength and lysis parameters were compared with the results of healthy individuals. Characteristics of CIT patients with and without hyperfibrinolytic profiles were compared. t-PA-ROTEM results before, 1 hour after and 24 hours after platelet transfusion were compared. RESULTS: A total of 72 consecutive CIT patients were included. t-PA-ROTEM lysis parameters correlated with changes in fibrinolytic proteins. Clot formation time was longer, maximum clot firmness was weaker and lysis times were shorter than in healthy individuals. CIT patients had low plasminogen activator inhibitor-1 and thrombin-activatable fibrinolysis inhibitor levels, and 40% showed hyperfibrinolytic profiles. Platelet transfusions resulted in less hyperfibrinolytic profiles in many, but not all CIT patients. Patients without hyperfibrinolytic profiles had higher fibrinogen, factor VIII and α2 -antiplasmin levels. CONCLUSIONS: t-PA-ROTEM can be used as a fast and reliable assay to detect hyperfibrinolytic profiles in CIT patients. CIT patients have weaker clots, which are more susceptible to clot lysis, than healthy individuals. Besides platelets, other factors are likely to influence clot susceptibility to fibrinolysis in CIT patients. The impact of a hyperfibrinolytic t-PA-ROTEM profile on bleeding remains to be investigated.