Release Of Tissue Plasminogen Activator Research Articles

SHock-INduced Endotheliopathy (SHINE): A mechanistic justification for viscoelastography-guided resuscitation of traumatic and non-traumatic shock.

Irrespective of the reason for hypoperfusion, hypocoagulable and/or hyperfibrinolytic hemostatic aberrancies afflict up to one-quarter of critically ill patients in shock. Intensivists and traumatologists have embraced the concept of SHock-INduced Endotheliopathy (SHINE) as a foundational derangement in progressive shock wherein sympatho-adrenal activation may cause systemic endothelial injury. The pro-thrombotic endothelium lends to micro-thrombosis, enacting a cycle of worsening perfusion and increasing catecholamines, endothelial injury, de-endothelialization, and multiple organ failure. The hypocoagulable/hyperfibrinolytic hemostatic phenotype is thought to be driven by endothelial release of anti-thrombogenic mediators to the bloodstream and perivascular sympathetic nerve release of tissue plasminogen activator directly into the microvasculature. In the shock state, this hemostatic phenotype may be a counterbalancing, yet maladaptive, attempt to restore blood flow against a systemically pro-thrombotic endothelium and increased blood viscosity. We therefore review endothelial physiology with emphasis on glycocalyx function, unique biomarkers, and coagulofibrinolytic mediators, setting the stage for understanding the pathophysiology and hemostatic phenotypes of SHINE in various etiologies of shock. We propose that the hyperfibrinolytic phenotype is exemplified in progressive shock whether related to trauma-induced coagulopathy, sepsis-induced coagulopathy, or post-cardiac arrest syndrome-associated coagulopathy. Regardless of the initial insult, SHINE appears to be a catecholamine-driven entity which early in the disease course may manifest as hyper- or hypocoagulopathic and hyper- or hypofibrinolytic hemostatic imbalance. Moreover, these hemostatic derangements may rapidly evolve along the thrombohemorrhagic spectrum depending on the etiology, timing, and methods of resuscitation. Given the intricate hemochemical makeup and changes during these shock states, macroscopic whole blood tests of coagulative kinetics and clot strength serve as clinically useful and simple means for hemostasis phenotyping. We suggest that viscoelastic hemostatic assays such as thromboelastography (TEG) and rotational thromboelastometry (ROTEM) are currently the most applicable clinical tools for assaying global hemostatic function-including fibrinolysis-to enable dynamic resuscitation with blood products and hemostatic adjuncts for those patients with thrombotic and/or hemorrhagic complications in shock states.

Point-of-care diagnosis and monitoring of fibrinolysis resistance in the critically ill: results from a feasibility study

BackgroundFibrinolysisis is essential for vascular blood flow maintenance and is triggered by endothelial and platelet release of tissue plasminogen activator (t-PA). In certain critical conditions, e.g. sepsis, acute respiratory failure (ARF) and trauma, the fibrinolytic response is reduced and may lead to widespread thrombosis and multi-organ failure. The mechanisms underpinning fibrinolysis resistance include reduced t-PA expression and/or release, reduced t-PA and/or plasmin effect due to elevated inhibitor levels, increased consumption and/or clearance. This study in critically ill patients with fibrinolysis resistance aimed to evaluate the ability of t-PA and plasminogen supplementation to restore fibrinolysis with assessment using point-of-care ClotPro viscoelastic testing (VET).MethodsIn prospective, observational studies, whole-blood ClotPro VET evaluation was carried out in 105 critically ill patients. In 32 of 58 patients identified as fibrinolysis-resistant (clot lysis time > 300 s on the TPA-test: tissue factor activated coagulation with t-PA accelerated fibrinolysis), consecutive experimental whole-blood VET was carried out with repeat TPA-tests spiked with additional t-PA and/or plasminogen and the effect on lysis time determined. In an interventional study in a patient with ARF and fibrinolysis resistance, the impact of a 24 h intravenous low-dose alteplase infusion on coagulation and fibrinolysis was prospectively monitored using standard ClotPro VET.ResultsDistinct response groups emerged in the ex vivo experimental VET, with increased fibrinolysis observed following supplementation with (i) t-PA only or (ii) plasminogen and t-PA. A baseline TPA-test lysis time of > 1000 s was associated with the latter group. In the interventional study, a gradual reduction (25%) in serial TPA-test lysis times was observed during the 24 h low-dose alteplase infusion.ConclusionsClotPro viscoelastic testing, the associated TPA-test and the novel experimental assays may be utilised to (i) investigate the potential mechanisms of fibrinolysis resistance, (ii) guide corrective treatment and (iii) monitor in real-time the treatment effect. Such a precision medicine and personalised treatment approach to the management of fibrinolysis resistance has the potential to increase treatment benefit, while minimising adverse events in critically ill patients.Trial registration: VETtiPAT-ARF, a clinical trial evaluating ClotPro-guided t-PA (alteplase) administration in fibrinolysis-resistant patients with ARF, is ongoing (ClinicalTrials.gov NCT05540834; retrospectively registered September 15th 2022).

Conventional and Pro-Inflammatory Pathways of Fibrinolytic Activation in Non-Traumatic Hyperfibrinolysis.

Hyperfibrinolysis (HF) frequently occurs after severe systemic hypoperfusion during major trauma and out-of-hospital cardiac arrest (OHCA). In trauma-induced HF, hypoperfusion, the activation of protein C (APC), and the release of tissue plasminogen activator (t-PA) have been identified as the driving elements of premature clot breakdown. The APC pathway also plays a role in inflammatory responses such as neutrophil extracellular trap formation (NETosis), which might contribute to lysis through cleavage of fibrin by neutrophil elastases. We investigated whether the APC and the plasminogen pathway were general drivers of HF, even in the absence of a traumatic incident. Additionally, we were interested in inflammatory activation such as the presence of NETs as potential contributing factors to HF. A total of 41 patients with OHCA were assigned to a HF and a non-HF group based on maximum lysis (ML) in thromboelastometry. Thrombin-antithrombin (TAT)-complex, soluble thrombomodulin (sTM), APC-PC inhibitor complex, t-PA, PAI-1, t-PA-PAI-1 complex, plasmin-antiplasmin (PAP), d-dimers, neutrophil elastase, histonylated DNA (hDNA) fragments, and interleukin-6 were assessed via immunoassays in the HF group vs. non-HF. APC-PC inhibitor complex is significantly higher in HF patients. Antigen levels of t-PA and PAI-1 do not differ between groups. However, t-PA activity is significantly higher and t-PA-PAI-1 complex significantly lower in the HF group. Consistent with these results, PAP and d-dimers are significantly elevated in HF. HDNA fragments and neutrophil elastase are not elevated in HF patients, but show a high level of correlation, suggesting NETosis occurs in OHCA as part of inflammatory activation and cellular decay. Just as in trauma, hypoperfusion, the activation of protein C, and the initiation of the plasminogen pathway of fibrinolysis manifest themselves in the HF of cardiac arrest. Despite features of NETosis being detectable in OHCA patients, early pro-inflammatory responses do not appear be associated with HF in cardiac arrest.

Laser thrombolysis and in vitro release kinetics of tPA encapsulated in chitosan polysulfate-coated nanoliposome

A major challenge in managing coronary artery disease is to find an effective thrombolytic therapy with minimal side effects. Laser thrombolysis is a practical procedure to remove the thrombus from inside blocked arteries, although it can cause embolism and re-occlusion of the vessel. The present study aimed to design a liposome drug delivery system for the controlled release of tissue plasminogen activator (tPA) and delivery of drug system into the thrombus by Nd:YAG laser at a wavelength of 532 nm for the treatment of arterial occlusive diseases. In this study, tPA encapsulated into the chitosan polysulfate-coated liposome (Lip/PSCS-tPA) was fabricated by a thin-film hydration technique. The particle size of Lip/tPA and Lip/PSCS-tPA was 88 and 100 nm, respectively. The release rate of tPA from Lip/PSCS-tPA was measured to be 35 % and 66 % after 24 h and 72 h, respectively. Thrombolysis through the delivery of Lip/PSCS-tPA into the thrombus during the laser irradiation was higher compared to irradiated thrombus without the nanoliposomes. The expression of IL-10 and TNF-α genes was studied by RT-PCR. The level of TNF-α for Lip/PSCS-tPA was lower than that of tPA, which can lead to improved cardiac function. Also, in this study, the thrombus dissolution process was studied using a rat model. After 4 h, the thrombus area in the femoral vein was significantly lower for groups treated with Lip/PSCS-tPA (5 %) compared to the groups treated with tPA alone (45 %). Thus, according to our results, the combination of Lip/PSCS-tPA and laser thrombolysis can be introduced as an appropriate technique for accelerating thrombolysis.

Arterial stiffness, endothelial dysfunction and impaired fibrinolysis are pathogenic mechanisms contributing to cardiovascular risk in ANCA-associated vasculitis

Cardiovascular disease is a complication of systemic inflammatory diseases including anti-neutrophil cytoplasm antibody-associated vasculitis (AAV). The mechanisms of cardiovascular morbidity in AAV are poorly understood, and risk-reduction strategies are lacking. Therefore, in a series of double-blind, randomized case-control forearm plethysmography and crossover systemic interventional studies, we examined arterial stiffness and endothelial function in patients with AAV in long-term disease remission and in matched healthy volunteers (32 each group). The primary outcome for the case-control study was the difference in endothelium-dependent vasodilation between health and AAV, and for the crossover study was the difference in pulse wave velocity (PWV) between treatment with placebo and selective endothelin-A receptor antagonism. Parallel invitro studies of circulating monocytes and platelets explored mechanisms. Compared to healthy volunteers, patients with AAV had 30% reduced endothelium-dependent vasodilation and 50% reduced acute release of endothelial active tissue plasminogen activator (tPA), both significant in the case-control study. Patients with AAV had significantly increased arterial stiffness (PWV: 7.3 versus 6.4 m/s). Plasma endothelin-1 was two-fold higher in AAV and independently predicted PWV and tPA release. Compared to placebo, both selective endothelin-A and dual endothelin-A/B receptor blockade reduced PWV and increased tPA release in AAV in the crossover study. Mechanistically, patients with AAV had increased platelet activation, more platelet-monocyte aggregates, and altered monocyte endothelin receptor function, reflecting reduced endothelin-1 clearance. Patients with AAV in long-term remission have elevated cardiovascular risk and endothelin-1 contributes to this. Thus, our data support a role for endothelin-blockers to reduce cardiovascular risk by reducing arterial stiffness and increasing circulating tPA activity.

Coagulation and Fibrinolytic Disorder

Traumatic brain injury(TBI)is associated with coagulation and fibrinolytic disorder. It is characterized by consumptive coagulopathy and secondary hyperfibrinolysis associated with hypercoagulability and by hyperfibrinolysis due to the release of tissue plasminogen activator from the injured brain. Thrombin antithrombin III complex, a coagulation parameter, is abnormally high immediately after TBI and declines 6 hours after TBI. Fibrinogen, a coagulation factor, is rapidly consumed and degraded within 3 hours of TBI. D-dimer, a fibrinolytic parameter, is abnormally high on arrival at the hospital and reaches its maximum value 3 hours after TBI; during this time, bleeding tendency increases. Plasminogen activator inhibitor-1, a parameter of fibrinolysis shutdown, peaks at 6 hours after TBI. D-dimer is also known to be a prognostic factor. Patients with a high D-dimer level despite a good level of consciousness on admission are more likely to be "talk and deteriorate." Administration of tranexamic acid, an anti-fibrinolytic agent, early in the acute phase of TBI may reduce mortality. Fresh frozen plasma transfusion should be performed within 3 hours of TBI with monitoring of fibrinogen levels, and the administration dose should be set with a target fibrinogen level of ≧ 150 mg/dL. However, excessive administration should also be avoided. Thus, in the acute phase of TBI, coagulation and fibrinolytic activity changes dynamically and may adversely affect the complicated injury; therefore, monitoring coagulation and fibrinolytic parameters while conducting treatment is recommended.

Assessment the role of tranexamic acid in prevention of postpartum hemorrhage

BackgroundPostpartum hemorrhage (PPH) is one of the leading causes of maternal mortality and morbidity worldwide. It is believed that hemostatic imbalance secondary to release of tissue plasminogen activator (tPA) and subsequent hyperfibrinolysis plays a major role in PPH pathogenesis. Antifibrinolytic drugs such as tranexamic acid (TXA) are widely used in hemorrhagic conditions associated with hyperfibrinolysis. TXA reduced maternal death due to PPH and its use as a part of PPH treatment is recommended, and in recent years, a number of trials have investigated the efficacy of prophylactic use of TXA in reducing the incidence and the severity of PPH.The study is aiming to assess the efficacy of tranexamic acid in reducing blood loss throughout and after the lower segment cesarean section and reducing the risk of postpartum hemorrhage.ResultsThe amount of blood loss was significantly lower in the study group than the control group (416.12±89.95 and 688.68±134.77 respectively). Also the 24-h postoperative hemoglobin was significantly higher in the study group (11.66±0.79 mg/dl) compared to the control group (10.53±1.07mg/dl), and the 24-h postoperative hematocrit value was significantly higher in the study group (34.99±2.40) compared to control (31.62±3.22).ConclusionProphylactic administration of tranexamic acid reduces intraoperative and postoperative bleeding in cesarean section and the incidence of postpartum hemorrhage.

Cytokine-Storm-Induced Coagulopathy In Critical COVID-19 and Septic Shock Patients: Head-to-Head Comparison

Background: A cytokine-storm-induced coagulopathy has been described in both critical COVID-19 and septic shock. Improving the understanding of the critical COVID-19 pathophysiology could help in finding new therapeutic targets already explored in the treatment of septic shock. Methods: This prospective observational was conducted between February 1, 2019, and June 1, 2020. Consecutive adult patients admitted to ICU for critical COVID-19 with acute respiratory distress syndrome (ARDS) (n=22), septic shock (n=48) and matched control patients (n=48) were enrolled. A between-group comparison of lung histopathology, clinical characteristics and outcomes and key plasmatic soluble biomarkers of inflammation and coagulopathy was performed. Findings: The histopathological findings showed microthrombi with NETosis in both COVID-19- and septic shock-related ARDS. In the prospective cohort, the critical COVID-19 patients exhibited a prolonged ICU length-of-stay, less organ failure, no sepsis-induced coagulopathy, a higher level of soluble tissue factor (106±57 versus 60±28pg/mL for septic shock, pInterpretation: Critical COVID-19 exhibits a prolonged disease course but less organ failure compared to septic shock. At ICU admission, COVID-19 is characterized by a lymphocytic immune response and distinct coagulopathy with less platelet or coagulation factor consumption, and fibrinolysis alterations. Clinical Trial Registration Details: NCT04107402.Funding Information: Fondation Saint-Luc (Brussels, Belgium) and QUALIblood s.a.Declaration of Interests: The Division of Cardiology at Cliniques universitaires Saint-Luc, Belgium, has received unrestricted research grants from AstraZeneca (Belgium). J.D. is the CEO and founder of QUALIblood s.a., a Belgian Contract Research Organization. The remaining authors declare no competing interests.Ethics Approval Statement: The ethics committee approved the study protocol, and all patients signed their informed consent (B403201938590, NCT04107402). Protocol amendment was done to include COVID-19 patients in the ongoing study.

Tranexamic acid is associated with reduced complement activation in trauma patients with hemorrhagic shock and hyperfibrinolysis on thromboelastography.

: Trauma with hemorrhagic shock causes massive tissue plasminogen activator release, plasmin generation, and hyperfibrinolysis. Tranexamic acid (TXA) has recently been used to treat bleeding in trauma by preventing plasmin generation to limit fibrinolysis. Trauma patients also have increased complement activation that correlates with mortality and organ failure, but the source of activation is not clear, and plasmin has recently been shown to efficiently cleave C3 and C5 to their activated fragments. We hypothesized that trauma patients in hemorrhagic shock with hyperfibrinolysis on thromboelastography (TEG) LY30 would have increased complement activation at early time points, as measured by soluble C5b-9 complex, and TXA would prevent this. Plasma samples were obtained from an unrelated, previously performed IRB-approved prospective randomized study of trauma patients. Three groups were studied with n = 5 patients in each group: patients without hyperfibrinolysis (TEG LY30 < 3%) (who therefore did not get TXA), patients with hyperfibrinolysis (TEG LY30 > 3%) who did not get TXA, and patients with hyperfibrinolysis who were then treated with TXA. We found that patients who did not receive TXA, regardless of fibrinolytic phenotype, had elevated soluble C5b-9 levels at 6 h relative to emergency department levels. In contrast, all five patients with initial TEG LY30 more than 3% and were then treated with TXA had reduced soluble C5b-9 levels at 6 h relative to emergency department levels. There were no differences in PF1 + 2, Bb, or C4d levels between groups, suggesting that coagulation and complement activation pathways may not be primarily responsible for the observed differences.

Pathophysiological Response to Trauma-Induced Coagulopathy: A Comprehensive Review.

Hypercoagulability can occur after severe tissue injury, that is likely related to tissue factor exposure and impaired endothelial release of tissue plasminogen activator (tPA). In contrast, when shock and hypoperfusion occur, activation of the protein C pathway and endothelial tPA release induce a shift from a procoagulant to a hypocoagulable and hyperfibrinolytic state with a high risk of bleeding. Both thrombotic and bleeding phenotypes are associated with increased mortality and are influenced by the extent and severity of tissue injury and degree of hemorrhagic shock. Response to trauma is a complex, dynamic process in which risk can shift from bleeding to thrombosis depending on the injury pattern, hemostatic treatment, individual responses, genetic predisposition, and comorbidities. Based on this body of knowledge, we will review and consider future directions for the management of severely injured trauma patients.

Acute vascular effects of vascular endothelial growth factor inhibition in the forearm arterial circulation.

Objective:Although vascular endothelial growth factor inhibition (VEGFi) represents a major therapeutic advance in oncology, it is associated with hypertension and adverse vascular thrombotic events. Our objective was to determine whether VEGFi caused direct vascular dysfunction through increased endothelin-1 (ET-1) activity or impaired endothelial vasomotor or fibrinolytic function.Methods:Using forearm venous occlusion plethysmography, we measured forearm blood flow during intra-arterial infusions of bevacizumab (36–144 μg/dl forearm volume per minute) administered for 15–60 min in healthy volunteers (n = 6–8). On two separate occasions in 10 healthy volunteers, we further measured forearm blood flow and tissue plasminogen activator (t-PA) release during intra-arterial bradykinin infusion (100 and 1000 pmol/min) in the presence and absence of bevacizumab (144 μg/dl forearm volume per minute), and the presence and absence of endothelin A receptor antagonism with BQ-123 (10 nmol/min). Plasma t-PA and plasminogen activator inhibitor-1 (PAI-1) concentrations were measured at baseline and with each dose of bradykinin.Results:Baseline blood flow and plasma ET-1, t-PA and PAI-1 concentrations were unaffected by bevacizumab. Bradykinin caused dose-dependent vasodilatation (P < 0.0001) and t-PA release (P < 0.01) but had no effect on plasma PAI-1 concentrations. Neither bevacizumab nor BQ-123 affected bradykinin-induced vasodilatation and t-PA release.Conclusion:Acute exposure to bevacizumab does not directly cause endothelial vasomotor or fibrinolytic dysfunction in healthy young volunteers.

Sulfenamide and Sulfonamide Derivatives of Metformin \u2013 A New Option to Improve Endothelial Function and Plasma Haemostasis

Type 2 diabetes mellitus (T2DM) is a multi-factorial disease which can cause multiple organ dysfunction, including that of the vascular endothelium. The aim of the present study was to evaluate the effects of metformin, and its sulfenamide and sulfonamide derivatives (compounds 1–8) on the selected markers of endothelial function and blood coagulation. The integrity of endothelial cells(ECs) was examined using the real-time cell electric impedance system. Tissue Factor(TF) production, the release of von Willebrand Factor (vWF) and tissue plasminogen activator(t-PA) from ECs were determined using immunoenzymatic assays, while the process of platelet thrombus formation using the Total Thrombus-Formation Analysis System. Sulfenamide with n-butyl alkyl chain(3) does not interfere with ECs integrity, and viability (nCI(24h) = 1.03 ± 0.03 vs. 1.06 ± 0.11 for control), but possesses anticoagulation properties manifested by prolonged platelet-dependent thrombus formation (Occlusion Time 370.3 ± 77.0 s vs. 286.7 ± 65.5 s for control) in semi-physiological conditions. Both p- and o-nitro-benzenesulfonamides (compounds7,8) exhibit anti-coagulant properties demonstrated by decreased vWF release and prolonged parameters of platelet thrombus formation and total blood thrombogenicity. In conclusion, chemical modification of metformin scaffold into sulfenamides or sulfonamides might be regarded as a good starting point for the design and synthesis of novel biguanide-based compounds with anticoagulant properties and valuable features regarding endothelial function.

An activated-platelet-sensitive nanocarrier enables targeted delivery of tissue plasminogen activator for effective thrombolytic therapy

It remains a major challenge to develop a selective and effective fibrinolytic system for thrombolysis with minimal undesirable side effects. Herein, we report a multifunctional liposomal system (164.6 ± 5.3 nm in diameter) which can address this challenge through targeted delivery and controlled release of tissue plasminogen activator (tPA) at the thrombus site. The tPA-loaded liposomes were PEGylated to improve their stability, and surface coated with a conformationally-constrained, cyclic arginine–glycine–aspartic acid (cRGD) to enable highly selective binding to activated platelets. The in vitro drug release profiles at 37 °C showed that over 90% of tPA was released through liposomal membrane destabilization involving membrane fusion upon incubation with activated platelets within 1 h, whereas passive release of the encapsulated tPA in pH 7.4 PBS buffer was 10% after 6 h. The release of tPA could be readily manipulated by changing the concentration of activated platelets. The presence of activated platelets enabled the tPA-loaded, cRGD-coated, PEGylated liposomes to induce efficient fibrin clot lysis in a fibrin-agar plate model and the encapsulated tPA retained 97.4 ± 1.7% of fibrinolytic activity as compared with that of native tPA. Furthermore, almost complete blood clot lysis was achieved in 75 min, showing considerably higher and quicker thrombolytic activity compared to the tPA-loaded liposomes without cRGD labelling. These results suggest that the nano-sized, activated-platelet-sensitive, multifunctional liposomes could facilitate selective delivery and effective release of tPA at the site of thrombus, thus achieving efficient clot dissolution whilst minimising undesirable side effects.

Graft Neutrophil Sequestration and Concomitant Tissue Plasminogen Activator Release During Reperfusion in Clinical Kidney Transplantation

BackgroundInflammation, coagulation, and fibrinolysis are tightly linked together. Reperfusion after transient ischemia activates both neutrophils, coagulation, and fibrinolysis. Experimental data suggest that tissue plasminogen activator (tPA) regulates renal neutrophil influx in kidney ischemia and reperfusion injury. MethodsIn 30 patients undergoing kidney transplantation, we measured renal neutrophil sequestration and tPA release from blood samples drawn from the supplying artery and renal vein early after reperfusion. tPA antigen levels were measured using a commercial enzyme-linked immunosorbent assay kit. For each parameter, transrenal difference (Δ) was calculated by subtracting the value of the arterial sample (ingoing blood) from the value of the venous sample (outgoing blood). ResultsPositive transrenal gradients of tPA antigen occurred at 1 minute [Δ = 14 (3–46) ng/mL, P < .01] and 5 minutes [Δ = 5 (-3 to 27) ng/mL, P < .01] after reperfusion. At 5 minutes after reperfusion, a negative transrenal gradient of neutrophils was observed [Δ = -0.17 (-1.45 to 0.24) x 10E9 cells/L, P < .001]. At 1 minute after reperfusion, neutrophil sequestration into the kidney (ie, negative transrenal neutrophil count) correlated significantly with tPA release from the kidney (ie, positive transrenal tPA concentration), (R = -0.513 and P = .006). ConclusionsThe findings suggest a proinflammatory role for tPA in ischemia and reperfusion injury in human kidney transplantation.

Heparin promotes recanalization of venous thrombotic occlusions.

Thrombosis is a consequence of disbalance between the procoagulant and fibrinolytic activity of blood and is frequently associated with chronic sequelae, which are the consequence of chronic occlusion of affected veins. Treatment of venous thrombosis should not be oriented in the prevention of thrombus progression and associated thromboembolic events, but also in stimulation of thrombolysis and recanalization of occluded veins, which are one of the most important preventive mechanisms of late sequelae, including post-thrombotic syndrome. The treatment of acute venous thrombosis (superficial and deep) is based on drugs with anticoagulant activity, like antagonists of vitamin K, heparins, and new oral anticoagulants. One of the most frequently used anticoagulant drugs is heparin, particularly the low molecular weight heparin (LMWH). It was shown that besides strong anticoagulant activity heparin has pro-fibrinolytic effects, which promote thrombolysis and recanalization of occluded veins. LMWH markedly increases tissue factor pathway inhibitor levels and a release of tissue plasminogen activator from vascular endothelium. Heparins are also capable of increasing the nitrogen oxide level, which is responsible for circulatory homeostasis.

Anxiety-Related Bleeding and Thrombosis.

Anxiety, a normal response to stressful situations, is characterized by increased levels of factor VIII, fibrinogen, and von Willebrand factor, and by enhanced platelet aggregability. One would expect acute anxiety to be a prothrombotic state, but since acute mental stress induces tissue plasminogen activator (tPA) release from endothelial and chromaffin cells, fibrinolysis counteracts procoagulant stimuli. It could be said that procoagulant changes accompanying the fight-or-flight response reduce the risk of bleeding in case of potential injuries, while activation of fibrinolysis counteracts activation of hemostasis to prevent intravascular thrombus formation before injuries occur. Acutely anxious patients are prone to bleeding or thrombosis when the balance between hypercoagulation and hyperfibrinolysis is disturbed. Acute anxiety not only increases the risk of bleeding in hemophilia or von Willebrand disease, but many reports have shown that anxiolytic interventions such as hypnosis are effective in controlling bleeding in hemostatic disorders. The pathogenesis of cardiovascular and thrombotic diseases in highly anxious patients is multifactorial. An important element is α-adrenergic vasoconstriction, which increases viscosity due to leakage of intravascular fluid into the interstitium, and also causes hypertension, favoring plaque rupture. Paradoxical as it may seem, over secretion of tPA may increase cardiovascular risk. This is because tPA degrades the extracellular matrix, causing vascular stiffness that increases cardiac workload, and thus oxygen requirements. Anxious patients with conditions associated with increased plasminogen activator inhibitor-1 levels, such as depression or postprandial hyperinsulinemia, are at high risk of thrombosis. Postprandial hyperinsulinemia may result from consumption of high-carbohydrate foods, considered anxiolytic, combined with a sedentary life, which is common among anxious individuals. Preliminary evidence suggests that high anxiety combined with either depression or a lifestyle that results in hyperinsulinemia has an important role in the pathogenesis of thrombotic events currently classified as unprovoked.

Tranexamic Acid for the Management of Obstetric Hemorrhage.

Obstetric hemorrhage remains the most common cause of maternal mortality worldwide. It is believed that increased fibrinolytic activity, secondary to release and activation of endothelial tissue plasminogen activator, is involved in its pathogenesis. Tranexamic acid (TXA), an antifibrinolytic agent, has been shown to be beneficial in trauma patients if used within 3 hours of injury. A recent large randomized controlled trial showed that TXA given to hemorrhaging women within 3 hours after delivery was associated with decreased risk of death resulting from bleeding with no increase in thromboembolic complications. Limited evidence suggests that prophylactic TXA reduces blood loss at the time of delivery and decreases transfusion rates in the obstetric population. Tranexamic acid appears to be a safe and effective option in the treatment of obstetric hemorrhage. In addition, the limited available evidence supports the need for a well-designed adequately powered clinical trial to test its benefit as a prophylactic agent.

A Blue Leg: An Interventional Approach to a Limb-Threatening Deep Vein Thrombosis

A Blue Leg: An Interventional Approach to a Limb-Threatening Deep Vein Thrombosis

Cytokine and estrogen stimulation of endothelial cells augments activation of the prekallikrein-high molecular weight kininogen complex: Implications for hereditary angioedema

When the prekallikrein-high molecular weight kininogen complex is bound to endothelial cells, prekallikrein is stoichiometrically converted to kallikrein because of release of heat shock protein-90 (Hsp90). Although bradykinin formation is typically initiated by factor XII autoactivation, it is also possible to activate factor XII either by kallikrein, thus formed, or by plasmin. Because attacks of hereditary angioedema can be related to infection and/or exposure to estrogen, we questioned whether estrogen or cytokine stimulation of endothelial cells could augment release of Hsp90 and prekallikrein activation. We also tested release of profibrinolytic enzymes, urokinase, and tissue plasminogen activator (TPA) as a source for plasmin formation. Cells were stimulated with agonists, and secretion of Hsp90, urokinase, and TPA was measured in the culture supernatants by ELISA. Activation of the prekallikrein-HK complex was measured by using pro-phe-arg-p-nitroanilide reflecting kallikrein formation. Hsp90 release was stimulated with optimal doses of estradiol, IL-1, and TNF-α (10ng/mL) from 15minutes to 120minutes. TPA release was not augmented by any of the agonists tested but urokinase was released by IL-1, TNF-α, and thrombin (positive control), but not estrogen. Augmented activation of the prekallikrein-HK complex to generate kallikrein was seen with each agonist that releases Hsp90. Addition of 0.1% factor XII relative to prekallikrein-HK leads to rapid formation of kallikrein; factor XII alone does not autoactivate. IL-1, TNF-α, and estrogen stimulate release of Hsp90 and augment activation of the prekallikrein-HK complex to generate kallikrein and bradykinin. IL-1 and TNF-α stimulate release of urokinase, which can convert plasminogen to plasmin and represents a possible source for plasmin generation in all types of hereditary angioedema, but particularly hereditary angioedema with normal C1 inhibitor with a factor XII mutation. Both kallikrein and plasmin activate factor XII; kallikrein is 20 times more potent on a molar basis.

Current Pathological and Laboratory Considerations in the Diagnosis of Disseminated Intravascular Coagulation.

Systemically sustained thrombin generation in vivo is the hallmark of disseminated intravascular coagulation (DIC). Typically, this is in response to a progressing disease state that is associated with significant cellular injury. The etiology could be infectious or noninfectious, with the main pathophysiological mechanisms involving cross-activation among coagulation, innate immunity, and inflammatory responses. This leads to consumption of both pro- and anticoagulant factors as well as endothelial dysfunction and disrupted homeostasis at the blood vessel wall interface. In addition to the release of tissue plasminogen activator (tPA) and soluble thrombomodulin (sTM) following cellular activation and damage, respectively, there is the release of damage-associated molecular patterns (DAMPs) such as extracellular histones and cell-free DNA. Extracellular histones are increasingly recognized as significantly pathogenic in critical illnesses through direct cell toxicity, the promotion of thrombin generation, and the induction of neutrophil extracellular trap (NET) formation. Clinically, high circulating levels of histones and histone–DNA complexes are associated with multiorgan failure, DIC, and adverse patient outcomes. Their measurements as well as that of other DAMPs and molecular markers of thrombin generation are not yet applicable in the routine diagnostic laboratory. To provide a practical diagnostic tool for acute DIC, a composite scoring system using rapidly available coagulation tests is recommended by the International Society on Thrombosis and Haemostasis. Its usefulness and limitations are discussed alongside the advances and unanswered questions in DIC pathogenesis.