Thrombin activatable fibrinolysis inhibitor (TAFI) at the interface between coagulation and fibrinolysis

Diabetes mellitus and aortic stenosis head to head: toward personalized medicine in patients with both pathologies

Diabetes mellitus (DM) and calcific aortic stenosis (CAS) are common morbidities in the elderly, which are both chronic, progressive and often concomitant diseases. Several studies revealed that DM increases the risk of developing severe CAS, yet clear information about the relationship between both these diseases and the influence of DM on the progression of CAS is currently lacking. To evaluate the effect of DM on aortic valves and on the process of calcification, and to achieve better patient management in daily clinical practice, we analysed calcified and noncalcified valve tissue from patients with severe CAS, with or without DM. A proteomic strategy using isobaric tags was adopted and the plasma concentrations of nine proteins were studied using 3 orthogonal methods and in a separate cell model. The differentially expressed proteins identified are implicated in biological processes like endopeptidase activity, lipid metabolism, coagulation, and fibrinolysis. The results obtained provide evidence that DM provokes changes in the proteome of aortic valves, affecting valve calcification. This finding may help enhance our understanding of the pathogenesis of CAS and how DM affects the evolution of this condition, an important step in identifying targets to personalize the treatment of these patients.

Fibrinolysis in Platelet Thrombi

The extent and duration of occlusive thrombus formation following an arterial atherothrombotic plaque disruption may be determined by the effectiveness of endogenous fibrinolysis. The determinants of endogenous fibrinolysis are the subject of much research, and it is now broadly accepted that clot composition as well as the environment in which the thrombus was formed play a significant role. Thrombi with a high platelet content demonstrate significant resistance to fibrinolysis, and this may be attributable to an augmented ability for thrombin generation and the release of fibrinolysis inhibitors, resulting in a fibrin-dense, stable thrombus. Additional platelet activators may augment thrombin generation further, and in the case of coronary stenosis, high shear has been shown to strengthen the attachment of the thrombus to the vessel wall. Neutrophil extracellular traps contribute to fibrinolysis resistance. Additionally, platelet-mediated clot retraction, release of Factor XIII and resultant crosslinking with fibrinolysis inhibitors impart structural stability to the thrombus against dislodgment by flow. Further work is needed in this rapidly evolving field, and efforts to mimic the pathophysiological environment in vitro are essential to further elucidate the mechanism of fibrinolysis resistance and in providing models to assess the effects of pharmacotherapy.

Trauma-induced coagulopathy

Uncontrolled haemorrhage is a major preventable cause of death in patients with traumatic injury. Trauma-induced coagulopathy (TIC) describes abnormal coagulation processes that are attributable to trauma. In the early hours of TIC development, hypocoagulability is typically present, resulting in bleeding, whereas later TIC is characterized by a hypercoagulable state associated with venous thromboembolism and multiple organ failure. Several pathophysiological mechanisms underlie TIC; tissue injury and shock synergistically provoke endothelial, immune system, platelet and clotting activation, which are accentuated by the 'lethal triad' (coagulopathy, hypothermia and acidosis). Traumatic brain injury also has a distinct role in TIC. Haemostatic abnormalities include fibrinogen depletion, inadequate thrombin generation, impaired platelet function and dysregulated fibrinolysis. Laboratory diagnosis is based on coagulation abnormalities detected by conventional or viscoelastic haemostatic assays; however, it does not always match the clinical condition. Management priorities are stopping blood loss and reversing shock by restoring circulating blood volume, to prevent or reduce the risk of worsening TIC. Various blood products can be used in resuscitation; however, there is no international agreement on the optimal composition of transfusion components. Tranexamic acid is used in pre-hospital settings selectively in the USA and more widely in Europe and other locations. Survivors of TIC experience high rates of morbidity, which affects short-term and long-term quality of life and functional outcome.

Healing of colonic anastomosis in rats under obstructive ileus conditions

BACKGROUND

The anastomosis leak in colon resections is a crucial post-operative complication with significant morbidity and mortality.  Methods: Forty (40) Wistar rats were allocated in two groups. In SHAM group only anastomosis was performed. In ILEUS group anastomosis was performed following one day of ileus. Animals in both groups were subdivided in two groups according to the day they were sacrificed, 4th or 8th post-operative day. A number of variables between the groups were estimated.

RESULTS

Body weight loss was higher following obstructive ileus on both days. Adhesion score in 4th and 8th post-operative day was higher in ILEUS1, ILEUS2 groups compared to SHAM1, SHAM2 groups respectively (p<0.001 for both). Neovascularization decreased following obstructive ileus compared to control on the 4th day (ILEUS1 vs. SHAM1, p=0.038). Bursting pressure was lower in ILEUS2 group than SHAM2 group (p<0.001). The number of fibroblasts decreased following obstructive ileus compared to control on the 4th and 8th day (ILEUS1 vs. SHAM1, p=0.001, ILEUS2 vs SHAM2, p=0.016). Hydroxyproline concentration was decreased in ILEUS2 group compared to SHAM2 group (p<0.001).

CONCLUSIONS

The balance of collagenolysis and collagenogenesis plays a decisive role in the healing of anastomoses following bowel obstruction. Under those circumstances, anastomosis' bursting pressure is reduced owning to decreased neovascularization, reduced fibroblast presence and lower hydroxyproline concertation. In our study, local inflammation, neocollagen concentration and collagenase activity were not associated with this adverse effect. However, further research should delineate the mechanisms of healing of colonic anastomoses and identify those factors that can improve our outcomes.

Is there thrombin-activatable fibrinolysis inhibitor in saliva?

The purpose of this study was to identify thrombin-activatable fibrinolysis inhibitor (TAFI) in saliva and to investigate the correlation between TAFI levels in saliva and plasma. Subjects included were healthy adults without diseases or medication that could affect coagulation. Samples of stimulated saliva and blood samples were obtained from 33 subjects. Levels of TAFI in saliva and plasma were analysed. The association between levels of TAFI in saliva and plasma was calculated using linear regression. Low levels of TAFIa/TAFIai were found in most saliva samples but only one sample had levels that were above the lower limit of detection of the assay used. TAFI (proenzyme) was not found in saliva, so no correlations could be calculated. In this study there was no indication that there is TAFI present in secreted saliva. Either TAFIa/TAFIai in saliva were much lower than in plasma and under the detection limit of the assay used, or there was no TAFIa/TAFIai in the saliva tested.

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

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

Higher Thrombin-Antithrombin III Complex Levels May Indicate Severe Acute Pancreatitis

AIM

Coagulation disorders may develop in association with severe acute pancreatitis (AP). Plasma thrombin-antithrombin III complex (TAT) levels are one of the principal markers of coagulation disorder. The purpose of this study was to evaluate TAT and other hemostatic parameters in patients with AP and to examine whether or not these parameters indicate the severity of AP.

METHOD

Forty-six patients with AP (14 severe, 32 non-severe) and a 30-member healthy control group were recruited. The severity of AP was determined using the revised Atlanta classification. ELISA was used to measure patients' plasma TAT levels.

RESULTS

The TAT levels of AP patients at presentation were higher than those of the control group (p = 0.005). The plasma TAT levels of patients with severe AP were also significantly higher than those of patients with non-severe AP (p = 0.05) and of the control group (p < 0.001). The general accuracy, sensitivity and specificity of TAT levels in predicting the severity of AP were 77.4, 77.8, and 77.3% respectively.

CONCLUSION

The coagulation cascade was activated in the AP patients in our study, and this was shown to become more pronounced as severity of the disease increased. Plasma TAT levels at the time of presentation in patients with AP can be used as a marker for predicting the severity of the disease.

Hemostasis in Hypothyroidism and Autoimmune Thyroid Disorders

CONTEXT

There are contradictory results on the effect of hypothyroidism on the changes in hemostasis. Inadequate population-based studies limited their clinical implications, mainly on the risk of venous thromboembolism (VTE). This paper reviews the studies on laboratory and population-based findings regarding hemostatic changes and risk of VTE in hypothyroidism and autoimmune thyroid disorders.

EVIDENCE ACQUISITION

A comprehensive literature search was conducted employing MEDLINE database. The following words were used for the search: Hypothyroidism; thyroiditis, autoimmune; blood coagulation factors; blood coagulation tests; hemostasis, blood coagulation disorders; thyroid hormones; myxedema; venous thromboembolism; fibrinolysis, receptors thyroid hormone. The papers that were related to hypothyroidism and autoimmune thyroid disorder and hemostasis are used in this review.

RESULTS

Overt hypothyroidism is more associated with a hypocoagulable state. Decreased platelet count, aggregation and agglutination, von Willebrand factor antigen and activity, several coagulation factors such as factor VIII, IX, XI, VII, and plasminogen activator-1 are detected in overt hypothyrodism. Increased fibrinogen has been detected in subclinical hypothyroidism and autoimmune thyroid disease rendering a tendency towards a hypercoagulability state. Increased factor VII and its activity, and plasminogen activator inhibitor-1 are among several findings contributing to a prothrombotic state in subclinical hypothyroidism.

CONCLUSIONS

Overt hypothyroidism is associated with a hypocoagulable state and subclinical hypothyroidism and autoimmune thyroid disorders may induce a prothrombotic state. However, there are contradictory findings for the abovementioned thyroid disorders. Prospective studies on the risk of VTE in various levels of hypofunctioning of the thyroid and autoimmune thyroid disorders are warranted.

Antiplatelet and antithrombotic activity of a fibrin(ogen)olytic protease from Bacillus cereus strain FF01

Fibrin(ogen)olytic enzymes offer great promise for the treatment of thrombosis associated disorders. The present study describes the characterization of an extracellular fibrin(ogen)olytic serine protease (named Bacethrombase) purified from the Bacillus cereus strain FF01. The molecular mass of the Bacethrombase was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis and matrix assisted laser desorption/ionization-time-of-flight-mass spectroscopy analyses at 39.5 kDa and 38,450.51 Da, respectively. The peptide mass fingerprinting and analyses of the composition of the amino acids revealed the similarity of the Bacethrombase to the bacterial serine proteases. The secondary structure of the Bacethrombase was composed of 14% helix, 6.6% beta-sheet, and 79.4% random coil. Bacethrombase was found to contain 48% sialic acid and it preferentially degraded the Aα-chain of fibrinogen, as well as fibrin. The anticoagulant potency of the Bacethrombase was comparable with that of warfarin and heparin, and was corroborated by its fibrinogenolytic activity rather than the inhibition of thrombin, prothrombin or FXa. Bacethrombase demonstrated antiplatelet activity, and dose-dependently inhibited the ADP-induced platelet aggregation. Bacethrombase (10 mg/kg) did not show toxicity after i.v. administration in Wistar rats; however, it revealed an in vivo anticoagulant effect and significantly inhibited the carrageenan-induced in vivo thrombus formation in rats.

Factor XI deficiency and orthognathic surgery: a case report on anesthesia management

Factor XI deficiency (Hemophilia C) is a very rare autosomal recessive bleeding disorder. Patients with factor XI deficiency do not typically show any spontaneous bleeding or specific symptoms. Sometimes those who have this disorder are identified during special situations such as trauma or surgery. Orthognathic surgery is particularly associated with a high bleeding risk. Therefore, great care must be taken when treating patients with bleeding disorders such as factor XI deficiency. There are a few reports that address the management of patients with bleeding disorders during orthognathic surgery. The current report describes a patient with factor XI deficiency who underwent Le Fort I osteotomy together with bilateral sagittal split osteotomy. The patient's condition was assessed using both rotation thromboelastometry (ROTEM™) and noninvasive measurements of total hemoglobin (SpHb) using Masimo Radical 7 (Masimo Co. CA, USA).

Impaired fibrinolysis in angiographically documented coronary artery disease

Impaired fibrinolysis may predispose to coronary artery disease (CAD). Hypofibrinolysis due to high levels of plasminogen activator inhibitor-1 (PAI-1) has been reported in CAD. A novel regulator of fibrinolytic activity, thrombin activatable fibrinolysis inhibitor (TAFI), has attracted attention in recent years. It acts by blocking the formation of a ternary complex of plasminogen, fibrin, and tissue plasminogen activator (t-PA). Previously ambiguous results regarding TAFI levels have been reported in CAD. We measured plasma levels of PAI-1 and TAFI antigen in 123 patients with age ranging from 40 to 65 years who had been submitted to coronary angiography and assessed the association of these markers with the extent of stenosis in three groups: angiographically normal artery (NAn), mild to moderate atheromatosis (MA), and severe atheromatosis (SA). Plasma levels of PAI-1 were increased in patients with severe atheromatosis compared to mild/moderate atheromatosis or to normal patients (66.60, 40.50, and 34.90 ng/mL, resp.; P < 0.001). For TAFI no difference was found between different groups. When patients were grouped in only two groups based on clinical cut-off point for intervention (stenosis less than or above 70%) we found increased plasma levels for PAI-1 (37.55 and 66.60 ng/mL, resp.; P < 0.001) and decreased plasma levels for TAFI (5.20 and 4.53 μg/mL, resp.; P = 0.04) in patients with stenosis above 70%. No difference was found in PAI-1 or TAFI levels comparing the number of affected vessels. Conclusion. As evidenced by a raised level of PAI-1 antigen, one can suggest an impaired fibrinolysis in stable CAD, although no correlation with the number of affected vessels was found. Curiously, a decreased plasma level of total TAFI levels was observed in patients with stenosis above 70%. Further studies measuring functional TAFI are required in order to elucidate its association with the extent of degree of atheromatosis.

Does decreased fibrinolysis have a role to play in the development of non-neoplastic portal vein thrombosis in patients with hepatic cirrhosis?

Hepatic cirrhosis is characterized by complex abnormalities of the fibrinolytic system. Little is known about the possible association between these alterations and thrombosis. The aim of this study was to evaluate the fibrinolytic profile in cirrhotic individuals with and without portal vein thrombosis (PVT). We measured thrombin activatable fibrinolysis inhibitor (TAFI), total amount of activated TAFI (TAFIa/ai), plasminogen activator inhibitor (PAI-1), plasminogen and fibrinogen plasma levels in 66 cirrhotic patients (33 with and 33 without PVT) and in 66 healthy volunteers. TAFI plasma levels (median [range]) were significantly lower in cirrhotic individuals (5.6 μg/ml [1.7-11.7]) than in controls (10.1 μg/ml [6.6-14.2], p < 0.0001), while TAFIa/ai levels were significantly higher in cases (18.3 ng/ml [0.3-35.4]) than in controls (15.9 ng/ml [7.4-41], p = 0.02). Cirrhotic patients with PVT had higher TAFI (6.6 μg/ml [2.9-10.1]), TAFIa/ai (19.2 ng/ml [11.6-35.4]) and PAI-1 (33.1 ng/ml [27.6-56.3]) plasma levels than those without PVT (3.9 μg/ml [1.7-11.7], p = 0.001; 15.6 ng/ml [10.3-33.9], p = 0.037; 15.9 ng/ml [2.5-29.1], p = 0.004. The fibrinolytic profile in cirrhotic individuals with PVT is characterized by higher levels of TAFI, TAFIa/ai and PAI-1 than in those without PVT. These alterations identify a hypofibrinolytic condition that may increase the risk of developing a thrombotic event.

Thrombin-activatable fibrinolysis inhibitor (TAFI) levels and its polymorphism rs3742264 are associated with dyslipidemia in a cohort of Brazilian subjects

BACKGROUND

Dyslipidemia, a metabolic alteration that affects lipoprotein levels, is considered a major risk factor for atherosclerosis and its complications. Dyslipidemia also affects the hemostatic system, especially impairing fibrinolysis, and increased levels of thrombin-activatable fibrinolysis inhibitor (TAFI) have been associated with cardiovascular events.

OBJECTIVES AND METHODS

This study evaluated the association of acquired risk factors (hypertension, body mass index - BMI, smoking, sedentary lifestyle, use or not of oral contraceptives and hormone replacement therapy, and post-menopause status), the polymorphisms Thr325Ile (rs1926447), Ala147Thr (rs3742264) and +1542C/G (rs940) in the TAFI gene, and TAFI plasma levels in 109 dyslipidemic and 105 normolipemic individuals. Biochemical analyses and TAFI levels were evaluated by colorimetric/turbidimetric assays and ELISA, respectively. Genotypic and allelic frequencies were determined by polymerase chain reaction (PCR).

RESULTS

Hypertension, increased BMI, and menopause were more common in dyslipidemic individuals, who had higher TAFI levels. The alleles 325Ile, Ala147, and C showed association with lower TAFI levels. The rs3742264 polymorphism was associated with dyslipidemia in males.

CONCLUSIONS

The results suggest that TAFI levels are independently associated to dyslipidemia and that the polymorphism rs3742264 may be related to cardiovascular risk in male subjects.

Coagulation and fibrynolitic parameters in women and the effects of hormone therapy; comparison of transdermal and oral administration

It is established that hormone therapy (HT) is related with significant increased prothrombotic risk factor. The aim of our study was to assess the effects of oral hormone therapy (o-HT) and transdermal hormone therapy (t-HT) on hemostasis parameters: fibrinogen (Fg) concentration, the maximum velocity of polymerization of clot formation, fibrin half-time lysis, plasma level of thrombin inhibitor of fibrinolysis (TAFI) and activity of generated thrombin and plasmin amidolytic activity. We observed that values of initial velocity of polymerization in o-HT group were increased (94.64 mOD/min vs. 131.50 mOD/min, p < 0.001) compared to control group. Fibrin lysis half-time increased in both groups with HT (controls - 18.26 min vs. 32.43 min (o-HT); 23.34 min transdermal hormone therapy (t-HT) p < 0.001) compared to controls. The activity of thrombin was statistically higher in plasma of women after o-HT (72.6 ± 8.5 mOD/min) than in patients with t-HT (53.7 ± 10.1 mOD/min) and controls (51.2 ± 10 mOD/min. Plasmin activity was the highest in controls (84.5 ± 10.2 mOD/min). The highest level of TAFI we observed in patients after oral hormones (80.38 ± 8.23%); women on transdermal HT had 61.58 ± 9.81% and the lowest concentration of TAFI we noted in controls 44.70 ± 10.16). The results of our study show that HT may partly explain the increase in venous thrombosis (VTE) and cardiovascular events reported after the use of it, especially the oral form of treatment.

Changes in ADMA and TAFI levels after stenting in coronary artery disease patients

The aim of this study was to examine the contribution of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase (NOS) and a novel marker of vascular endothelial dysfunction, and thrombin-activatable fibrinolysis inhibitor (TAFI), a risk factor for venous thrombosis, to the predisposition of coronary restenosis following stent implantation in coronary artery disease (CAD) patients. Thirty-seven patients with CAD were recruited from the Kobry El Obba Military Hospital, Cairo, Egypt. The patients were hospitalized for coronary angiography and coronary stenting (CS). Overnight fasting blood samples were collected from patients prior to CS and four months later for the determination of plasma ADMA and TAFI levels. The patients underwent follow-up coronary angiography to reveal in-stent restenosis. The results showed that plasma ADMA levels in CAD patients were significantly higher than those reported for healthy subjects. ADMA levels were significantly increased by 30% in CAD patients four months following CS. CAD patients who developed in-stent restenosis had a 35% increase in ADMA levels following CS. TAFI levels were not significantly changed after CS in CAD patients or in any of the subgroups. In conclusion, ADMA, but not TAFI, is linked to the predisposition of in-stent restenosis following CS.

Natural and engineered plasmin inhibitors: applications and design strategies

The serine protease plasmin is ubiquitously expressed throughout the human body in the form of the zymogen plasminogen. Conversion to active plasmin occurs through enzymatic cleavage by plasminogen activators. The plasminogen activator/plasmin system has a well-established function in the removal of intravascular fibrin deposition through fibrinolysis and the inhibition of plasmin activity; this has found widespread clinical use in reducing perioperative bleeding. Increasing evidence also suggests diverse, although currently less defined, roles for plasmin in a number of physiological and pathological processes relating to extracellular matrix degradation, cell migration and tissue remodelling. In particular, dysregulation of plasmin has been linked to cancer invasion/metastasis and various chronic inflammatory conditions; this has prompted efforts to develop inhibitors of this protease. Although a number of plasmin inhibitors exist, they commonly suffer from poor potency and/or specificity of inhibition that either results in reduced efficacy or prevents clinical use. Consequently, there is a need for further development of high-affinity plasmin inhibitors that maintain selectivity over other serine proteases. This review summarises clearly defined and potential applications for plasmin inhibition. The properties of naturally occurring and engineered plasmin inhibitors are discussed in the context of current knowledge regarding plasmin structure, specificity and function. This includes design strategies to obtain the potency and specificity of inhibition in addition to controlled temporal and spatial distribution tailored for the intended use.

The prothrombotic tendency in metabolic syndrome: focus on the potential mechanisms involved in impaired haemostasis and fibrinolytic balance

The metabolic syndrome is a clinical disorder characterized by impairment of glucose metabolism, increased arterial blood pressure, and abdominal obesity. The presence of these clinical features exposes patients to a high risk of atherothrombotic cardiovascular events. The pathogenesis of atherothrombosis in the metabolic syndrome is multifactorial, requiring a close relationship among the main components of the metabolic syndrome, including insulin resistance, alterations of glycaemic and lipid pattern, haemodynamic impairment, and early appearance of endothelial dysfunction. Furthermore, haemostatic alterations involving coagulation balance, fibrinolysis, and platelet function play a relevant role both in the progression of the arterial wall damage and in acute vascular events. The mechanisms linking abdominal obesity with prothrombotic changes in the metabolic syndrome have been identified and partially elucidated on the basis of alterations of each haemostatic variable and defined through the evidence of peculiar dysfunctions in the endocrine activity of adipose tissue responsible of vascular impairment, prothrombotic tendency, and low-grade chronic inflammation. This paper will focus on the direct role of adipose tissue on prothrombotic tendency in patients affected by metabolic syndrome, with adipocytes being able to produce and/or release cytokines and adipokines which deeply influence haemostatic/fibrinolytic balance, platelet function, and proinflammatory state.

Ocular Behçet disease: current therapeutic approaches

PURPOSE OF REVIEW

To alert physician to timely recognition and current treatment of recurrent hypopyon iridocyclitis or panuveitis in ocular Behçet disease (OBD).

RECENT FINDINGS

Interferon-α, rituximab, intravitreal triamcinolone, and biological response modifiers by tumor necrosis factor inhibitors such as infliximab and adalimumab are being used increasingly for the treatment of severe sight-threatening ocular inflammation including retinal vasculitis and cystoid macular edema (CME).

SUMMARY

Biological agents offer tremendous potential in the treatment of OBD. Given that OBD predominantly afflicts the younger adults in their most productive years, dermatologist, rheumatologist, internist, or general practitioners supervising patients with oculo-articulo-oromucocutaneous syndromes should be aware of systemic Behçet disease. Early recognition of ocular involvement is important and such patients should strongly be instructed to visit immediately an ophthalmologist, as uveitis management differs from extraocular involvements with high ocular morbidity from sight-threatening complications due to relapsing inflammatory attacks in the posterior segment of the eye. A single infliximab infusion should be considered for the control of acute panuveitis, whereas repeated long-term infliximab infusions were proved to be more effective in reducing the number of episodes in refractory uveoretinitis with faster regression and complete remission of CME.

Anticoagulant effect of polyphenols-rich extracts from black chokeberry and grape seeds

Blood coagulation consists of a series of zymogens that can be converted by limited proteolysis to active enzymes leading to the generation of thrombin. Fresh plasma and human thrombin was incubated with extracts from berries of Aronia melanocarpa or seeds of Vitis vinifera (0.5; 5; 50 μg/ml). The in vitro experiments showed that both extracts prolonged clotting time and decreased the maximal velocity of fibrin polymerization in human plasma. Moreover thrombin incubation with both extracts results in the inhibition of amidolytic activity of this enzyme. It gives hopes for development of diet supplements, which may be preventing thrombosis in pathological states.

Coagulation and inflammation. Molecular insights and diagnostic implications

Overwhelming evidence has linked inflammatory disorders to a hypercoagulable state. In fact, thromboembolic complications are among the leading causes of disability and death in many acute and chronic inflammatory diseases. Despite this clinical knowledge, coagulation and immunity were long regarded as separate entities. Recent studies have unveiled molecular underpinnings of the intimate interconnection between both systems. The studies have clearly shown that distinct pro-inflammatory stimuli also activate the clotting cascade and that coagulation in turn modulates inflammatory signaling pathways. In this review, we use evidence from sepsis and inflammatory bowel diseases as a paradigm for acute and chronic inflammatory states in general and rise hypotheses how a systematic molecular understanding of the "inflammation-coagulation" crosstalk may result in novel diagnostic and therapeutic strategies that target the inflammation-induced hypercoagulable state.

High incidence of tumors in diabetic thrombin activatable fibrinolysis inhibitor and apolipoprotein E double-deficient mice

BACKGROUND

Activation of the complement system has been implicated in tumor growth. The antifibrinolytic protein, activated thrombin-activatable fibrinolysis inhibitor (TAFIa), can modulate the activation of the complement system by inactivating the anaphylatoxins C3a and C5a. The apolipoprotein-E (ApoE) genotype has been associated with carcinogenesis.

OBJECTIVE

The aim of this study was to evaluate whether TAFIa can affect the development of cancer in the ApoE-deficient mouse model.

METHODS

TAFI and ApoE double-knockout mice were generated. A group of mice was treated with the diabetogenic and carcinogenic compound streptozotocin (stz). Mice treated with saline, single knockout mice and wild-type (wt) mice served as controls.

RESULTS

Six months after treatment with stz, mice were sacrificed. Hepatic tumors were found in male double-knockout mice treated with stz but none was found in control animals that were not treated with stz or in single knockout of ApoE or wt animals. There was no significant difference in coagulation system activation between the groups of mice. The plasma concentrations of C5a, factor D and transforming growth factor-β1 were increased in TAFI/ApoE double-deficient mice treated with stz compared with the mice of the same genotype treated with saline.

CONCLUSION

Apo-E deficiency alone was not associated with tumors but the lack of TAFI appears to make the mice permissive for tumor formation in ApoE mice.

Insights into the molecular inactivation mechanism of human activated thrombin-activatable fibrinolysis inhibitor

SUMMARY BACKGROUND

Thrombin-activatable fibrinolysis inhibitor (TAFI) is a validated target for thrombotic diseases. TAFI is converted in vivo to activated TAFI (TAFIa) by removal of its pro-domain. Whereas TAFI is stable and persists in the circulation, possibly in complex with plasminogen, TAFIa is unstable and poorly soluble, with a half-life of minutes.

OBJECTIVES

In order to study the molecular determinants of this instability, we studied the influence of protein inhibitors on human TAFIa.

RESULTS

We found that protein inhibitors significantly reduced the instability and insolubility of TAFIa. In addition, we solved the 2.5-A resolution crystal structure of human TAFIa in complex with a potent protein inhibitor, tick-derived carboxypeptidase inhibitor, which gives rise to a stable and soluble TAFIa species. The structure revealed a significant reduction in the flexibility of dynamic segments when compared with the structures of bovine and human TAFI. We also identified two latent hotspots, loop Lbeta2beta3 and segment alpha5-Lalpha5beta7-beta7, where conformational destabilization may begin. These hotspots are also present in TAFI, but the pro-domain may provide sufficient stabilization and solubility to guarantee protein persistence in vivo. When the pro-domain is removed, the free TAFIa moiety becomes unstable, its activity is suppressed, and the molecule becomes insoluble.

CONCLUSIONS

The present study corroborates the function of protein inhibitors in stabilizing human TAFIa and it provides a rigid and high-resolution mold for the design of small molecule inhibitors of this enzyme, thus paving the way for novel therapy for thrombotic disorders.

Thrombin-Activatable Fibrinolysis Inhibitor (TAFI) Antigen and Activity Assay in Patients With Primary Hypothyroidism

Hypothyroidism causes a tendency for cardiovascular diseases. It was recently shown that thrombin-activatable fibrinolysis inhibitor (TAFI) attenuates fibrinolysis and also fibrin-plasminogen interaction by the removal of lysine and arginine residues from fibrin monomers. The aim of this study was to determine the effects of overt hypothyroidism on the levels of TAFI antigen (TAFI Ag) and TAFI activity (TAFIa). Thirty-one overt primary hypothyroid patients and age- and gender-matched 25 healthy controls were enrolled in the study. Patients were treated with L-thyroxine after the collection of blood samples. Thyroid functions were reevaluated following the achievement of euthyroid status. Thrombin-activatable fibrinolysis inhibitor Ag, tissue plasminogen activator (t-PA), and plasminogen activator inhibitor 1 (PAI-1) levels were measured with the enzyme-linked immunosorbent assay (ELISA). Thrombin-activatable fibrinolysis inhibitor activity was assessed with the chromogenic assay. Thrombin-activatable fibrinolysis inhibitor Ag (1.63% ± 0.42% vs 1.32% ± 0.36%, P < .01) and TAFIa (14.2 ± 4.12 vs 11.6 ± 3.49 μg/mL, P < .05) levels were elevated in hypothyroid patient compared to controls. Plasminogen activator inhibitor 1 and t-PA levels were not significantly different between both groups. In hypothyroid patients, TAFI Ag levels were correlated with free T4 (r = -.373, P < .05) and thyroid-stimulating hormone (TSH) levels (r = .748, P < .001). Regression analysis showed that TSH levels were predictors of TAFI Ag levels (P < .001, β =.671, 95% confidence interval [CI]: 0.008-0.017). Following L-thyroxine treatment, TAFI Ag (1.63% ± 0.42%, 1.34% ± 0.33%, P < .05) and TAFIa (14.2 ± 4.12 μg/mL, 12.0 ± 2.77 μg/mL, P < .05) levels were significantly decreased, but t-PA and PAI-1 levels remained unchanged. This results point out that the fibrinolytic activity was decreased in hypothyroid patients, and therefore the achievement of euthyroid status is important in ameliorating the increased risk of cardiovascular disease.

Review article: Coagulation cascade and therapeutics update: relevance to nephrology. Part 1: Overview of coagulation, thrombophilias and history of anticoagulants

Coagulation involves the regulated sequence of proteolytic activation of a series of zymogens to achieve appropriate and timely haemostasis in an injured vessel, in an environment that overwhelmingly favours an anticoagulant state. In the non-pathological state, the inciting event involves exposure of circulating factor VII/VIIa to extravascularly expressed tissue factor, which brings into motion the series of steps which results in amplification of the initial stimulus, culminating in the conversion of fibrinogen to fibrin and clot formation. The precisely synchronized cascade of events is counter-balanced by a system of anticoagulant mechanisms, which serve to ensure that the haemostatic effect is regulated and does not extend inappropriately. Conversely, in pathological states, these events can escape normal control mechanisms, due to either inherited or acquired defects, which lead to thrombosis. Current anticoagulant therapy, although based on medications that have been in existence for upwards of 80 years, is moving towards targeted therapy for specific coagulation factors and events in the coagulation cascade, based on the current knowledge of the main triggers and key events within the series of reactions that culminates in haemostasis. It remains to be seen whether these newer medications will become first-line therapies for thrombosis in the coming decade. This review aims to elucidate the main events within the coagulation cascade as it is currently understood to operate in vivo, with a brief discussion focusing on hypercoagulable states, and also a short review of the history of anticoagulants as they relate to this model.

Extracellular proteases as targets for drug development

Proteases constitute one of the primary targets in drug discovery. In the present review, we focus on extracellular proteases (ECPs) because of their differential expression in many pathophysiological processes, including cancer, cardiovascular conditions, and inflammatory, pulmonary, and periodontal diseases. Many new ECP inhibitors are currently under clinical investigation and a significant increase in new therapies based on protease inhibition can be expected in the coming years. In addition to directly blocking the activity of a targeted protease, one can take advantage of differential expression in disease states to selectively deliver therapeutic or imaging agents. Recent studies in targeted drug development for the metalloproteases (matrix metalloproteinases, adamalysins, pappalysins, neprilysin, angiotensin-converting enzyme, metallocarboxypeptidases, and glutamate carboxypeptidase II), serine proteases (elastase, coagulation factors, tissue/urokinase plasminogen activator system, kallikreins, tryptase, dipeptidyl peptidase IV) and cysteine proteases (cathepsin B) are discussed herein.

Structure of activated thrombin-activatable fibrinolysis inhibitor, a molecular link between coagulation and fibrinolysis

Thrombin-activatable fibrinolysis inhibitor (TAFI) is a metallocarboxypeptidase (MCP) that links blood coagulation and fibrinolysis. TAFI hampers fibrin-clot lysis and is a pharmacological target for the treatment of thrombotic conditions. TAFI is transformed through removal of its prodomain by thrombin-thrombomodulin into TAFIa, which is intrinsically unstable and has a short half-life in vivo. Here we show that purified bovine TAFI activated in the presence of a proteinaceous inhibitor renders a stable enzyme-inhibitor complex. Its crystal structure reveals that TAFIa conforms to the alpha/beta-hydrolase fold of MCPs and displays two unique flexible loops on the molecular surface, accounting for structural instability and susceptibility to proteolysis. In addition, point mutations reported to enhance protein stability in vivo are mainly located in the first loop and in another surface region, which is a potential heparin-binding site. The protein inhibitor contacts both the TAFIa active site and an exosite, thus contributing to high inhibitory efficiency.

Thrombin-activatable fibrinolysis inhibitor polymorphisms and recurrent pregnancy loss

OBJECTIVE

To investigate the possible association between selected thrombin-activatable fibrinolysis inhibitor (TAFI) single nucleotide polymorphisms (SNPs) and recurrent pregnancy loss (RPL).

DESIGN

Case-control study.

SETTING

University hospital.

PATIENT(S)

One hundred fifty-eight women (86 cases and 72 controls).

INTERVENTION(S)

Determination of TAFI SNPs -438A/G, +505A/G, +1040T/C, +1542C/G, and +1583A/T by polymerase chain reaction (PCR) reactions and sequencing analysis performed on peripheral blood samples.

MAIN OUTCOME MEASURE(S)

Analysis of the genotype and allele frequencies of TAFI SNPs -438A/G, +505A/G, +1040T/C, +1542C/G, and +1583A/T in women with and without RPL.

RESULT(S)

Genotype and allele frequencies of TAFI +505 and +1583 SNPs were significantly different in women with RPL compared with control women. The frequencies of the +505A/A and +505G/G genotypes were 1.2% and 61.6% in women with RPL and 13.9% and 43.1% in control women, respectively. The frequencies of the +1583A/A and +1583T/T genotypes were 1.2% and 61.6% in women with RPL and 13.9% and 45.8% in control women, respectively. The genotype and allele frequencies at TAFI position -438, +1040, and +1542 were not significantly different between RPL and control women.

CONCLUSION(S)

The SNPs leading to increased TAFI levels are associated with a reduced risk of RPL. It is possible that TAFI is involved in RPL.

Cardiovascular disease and heritability of the prothrombotic state

Atherothrombotic disease remains a major cause of mortality worldwide, and family clustering suggests an important contribution of genetic factors to disease pathogenesis. Thrombus formation represents the final step in atherothrombosis, a process influenced by genetic and environmental factors. A major difficulty of investigating the genetic regulation of thrombotic conditions is the complexity of the phenotype and the relatively modest effects of individual genetic variations. We address in this review genetic aspects involved in regulating thrombosis potential and their impact on the development of atherothrombotic disease. The effects of common genetic polymorphisms in clotting factors are discussed and examples of complex gene-gene and gene-environment interactions are highlighted. Understanding the effects of genetic factors on predisposition to thrombotic disease and unravelling the complex gene-environment interactions will help to better understand the pathophysiology of this complex condition, which will enable the development of new preventative and treatment strategies.

Impact of neutrophil apoptosis on haemostatic activation in chronic liver disease patients

Recent studies suggest the impact of apoptosis on the mechanisms leading to hypercoagulability. We aimed to clarify the potential role of neutrophil apoptosis in neutropenia and hypercoagulable state encountered in chronic liver disease patients. This study was conducted on 15 normal controls and 45 patients with chronic liver disease classified according to modified Child Pugh classification into, Child A, B and C groups (15 cases each). Haemostatic parameters studied include, prothrombin time, partial thromboplastin time, tissue factor, protein C antigen, protein S antigen, and markers of haemostatic activation [prothrombin fragment 1+2 (F1+2), thrombus precursor protein (TpP) and D-dimer]. Flowcytometric study was done for quantitative assay of neutrophil apoptotic subpopulations to detect the percentage of early and late apoptotic, and necrotic neutrophils using Annexin V-FITC/propidium iodide dye. Semiquantitative assay of apoptotic neutrophils showing DNA fragmentation was performed on neutrophil culture using terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick end labelling test. In addition to enzyme-linked immunosorbent assay for soluble Fas (APO-1/CD95) in culture supernatant. The results revealed a rise in the neutrophil apoptotic and necrotic markers with progression of the disease, and they were inversely correlated with the absolute neutrophil count. The apoptotic neutrophil cells showed a significant positive correlation with several haemostatic parameters (tissue factor, prothrombin fragment 1+2, thrombus precursor protein and D-dimer). Regression analysis proved that apoptotic parameters are independent determinants of prothrombotic markers, which further incriminate the apoptotic mechanisms in the hypercoagulable state encountered in this clinical setting.

Ultrastructure of activated mouse platelets: a qualitative scanning electron microscopy study

Platelets form an integral part of the coagulation process, and their ultrastructure can provide valuable information regarding diseases associated with hemostasis. During coagulation, platelets aggregate; this aggregation can be achieved in vitro, by adding thrombin to platelet-rich plasma. Previous research showed that human thrombin could be used successfully to activate mouse platelets. When conservative changes are included, the amino acid similarity between human and mouse thrombin is approximately 75%. In this qualitative study, we compare the ultrastructure of mouse platelet aggregates activated by human thrombin as well as two concentrations of mouse thrombin, using the scanning electron microscope. Results show that both human and mouse thrombin activate platelets to form aggregates with typical pseudopodia formation. Magnification up to 250,000x showed membrane morphology with the open canalicular system pores visible in both the mouse- and human-activated platelets. It is therefore concluded that mouse platelets can be successfully aggregated using either mouse or human thrombin.

Crystal structures of TAFI elucidate the inactivation mechanism of activated TAFI: a novel mechanism for enzyme autoregulation

Thrombin-activatable fibrinolysis inhibitor (TAFI) is a pro-metallocarboxypeptidase that can be proteolytically activated (TAFIa). TAFIa is unique among carboxypeptidases in that it spontaneously inactivates with a short half-life, a property that is crucial for its role in controlling blood clot lysis. We studied the intrinsic instability of TAFIa by solving crystal structures of TAFI, a TAFI inhibitor (GEMSA) complex and a quadruple TAFI mutant (70-fold more stable active enzyme). The crystal structures show that TAFIa stability is directly related to the dynamics of a 55-residue segment (residues 296-350) that includes residues of the active site wall. Dynamics of this flap are markedly reduced by the inhibitor GEMSA, a known stabilizer of TAFIa, and stabilizing mutations. Our data provide the structural basis for a model of TAFI auto-regulation: in zymogen TAFI the dynamic flap is stabilized by interactions with the activation peptide. Release of the activation peptide increases dynamic flap mobility and in time this leads to conformational changes that disrupt the catalytic site and expose a cryptic thrombin-cleavage site present at Arg302. This represents a novel mechanism of enzyme control that enables TAFI to regulate its activity in plasma in the absence of specific inhibitors.

Biomarkers of altered coagulation and fibrinolysis as measures of disease activity in active inflammatory bowel disease: a gender-stratified, cohort analysis

BACKGROUND

Growing evidence recognizes inflammatory bowel disease (IBD) as a chronic inflammatory condition characterized by a hypercoagulable state and prothrombotic conditions. The aims of our study were to evaluate the abnormalities in coagulation and fibrinolysis status in patients with IBD, and to analyze parameters of altered coagulation and fibrinolysis status which can correlated with and predict inflammatory parameters of disease activity.

METHODS

A cohort of 271 consecutive IBD patients was compared with healthy controls for coagulation and fibrinolysis status. Associations between altered coagulation and fibrinolysis status stratified by gender and inflammatory parameters were analyzed.

RESULTS

The mean levels of platelet, platelet distribution width, prothrombin time, fibrinogen, activated partial thromboplastin time were significantly higher in IBD patients than in healthy controls (all P<0.05). Mean platelet volume was lower in male patients with IBD than in healthy controls (P<0.01). Furthermore, multiple linear regression indicated that fibrinogen was an independent predictor of ESR (beta=1.316, P=<0.001) and CRP (beta=1.233, P=0.015) in male patients with active ulcerative colitis. Platelet (beta=0.436, P=0.037) and prothrombin time (beta=0.810, P=<0.001) were predictors of Crohn's Disease Activity Index in female patients with Crohn's disease.

CONCLUSIONS

To our knowledge, this study provides characteristics on altered coagulation and fibrinolysis status in active IBD patients using the largest number of cases assembled in one study to date. Our data suggest that in IBD patients, abnormalities in coagulation and fibrinolysis status were associated with disease activity. Fibrinogen, platelet and prothrombin time were predictors of inflammation.

TAFI deficiency in liver cirrhosis: Relation with plasma fibrinolysis and survival

INTRODUCTION

TAFI (thrombin-activatable fibrinolysis inhibitor) is a potent anti-fibrinolytic and anti-inflammatory factor of liver origin. It is markedly reduced in liver cirrhosis but its effect on fibrinolysis remains controversial and no data are available on its prognostic value. We evaluated the relationship of TAFI level with plasma fibrinolysis and survival in cirrhotic patients.

PATIENTS AND METHODS

Sixty-five patients with liver cirrhosis were studied. TAFI antigen, plasma fibrinolysis and other laboratory variables were assayed at study entry and their association with mortality was assessed during a 3-year follow-up.

RESULTS

TAFI level and fibrinolysis time were markedly reduced in liver cirrhosis as compared to healthy subjects (p<0.0001) and TAFI deficiency was strongly correlated with fibrinolysis time (p=0.0002). TAFI level at entry, but not fibrinolysis time, was significantly lower in non-survivors (n=25) than in survivors (n=40, p=0.0001). By Cox regression analysis, after adjustment for possible confounding factors, TAFI, but not fibrinolysis time, was identified as an independent predictor of mortality. TAFI assay, moreover, showed a clinically relevant accuracy in assessing patients' survival (ROC curve analysis, p<0.0001) achieving a sensitivity of 92%, a specificity of 55%, and a negative predictive value of 91.7%.

CONCLUSIONS

Our data indicate that TAFI deficiency in liver cirrhosis is associated with enhanced plasma fibrinolysis. Moreover, they suggest that TAFI, but not fibrinolysis time, is a strong predictor of survival and thus TAFI assay might prove useful to select candidates for liver transplantation.

Plasma thrombin activatable fibrinolysis inhibitor and tissue factor pathway inhibitor changes following sepsis

Sepsis-induced systemic inflammation results in coagulation abnormalities that may be different in gram-positive and gram-negative infections. We used ciprofloxacin to induce a predominantly gram-positive Enterococcus faecalis polymicrobial sepsis in rats. Ciprofloxacin-untreated rats exhibited a predominantly gram-negative polymicrobial sepsis. Rats were subjected to 30% body surface area burn (B), cecal ligation puncture (CLP) with a 22-gauge needle, and B + CLP. Ciprofloxacin-treated B + CLP rats showed a significant decrease in plasma thrombin activatable fibrinolysis inhibitor (TAFI) levels compared with sham rats. However, plasma tissue factor pathway inhibitor (TFPI) levels decreased significantly in B, CLP, and B + CLP groups compared with sham rats. The ciprofloxacin-untreated group showed a significant decrease in plasma TAFI levels in CLP and B + CLP and plasma TFPI levels decreased in all 3 groups compared with sham rats. Histological changes in the liver and kidney included vascular congestion and parenchyma bleed following B + CLP in ciprofloxacin-untreated rats. These results suggest that plasma TAFI and TFPI levels differ depending on the type of bacteria involved in the septic process.

The role of tissue factor in patients undergoing open repair of ruptured and nonruptured abdominal aortic aneurysms

BACKGROUND

Ruptured abdominal aortic aneurysm (AAA) is associated with the development of a procoagulant and hypofibrinolytic state. Tissue factor (TF) and its naturally occurring inhibitor, tissue factor pathway inhibitor (TFPI), play a central role in the initiation and progression of such a hypercoagulable state, but their role in patients undergoing open AAA repair has not previously been examined.

METHODS

A prospective study was conducted of 17 patients undergoing elective AAA repair and 10 patients undergoing emergency AAA repair. Blood was taken before induction, and 5 minutes, 24 hours, and 48 hours after aortic cross-clamp release and assayed for plasma TF, TFPI, tissue plasminogen activator (t-PA), plasminogen activator inhibitor (PAI), and thrombin-activatable fibrinolysis inhibitor (TAFI) activities.

RESULTS

TF activity was significantly higher at all time points in patients with ruptured AAA compared with nonruptured AAA. The median (interquartile range, IRQ) TF activity (AU/mL) was 9.9 vs 3.2 (IRQ, 5.9 to 12.6 vs 2.0 to 7.6; P = .005) at preinduction; 10.7 vs 1.5 (IRQ, 9.2 to 18.3 vs 0.1 to 6.6; P = .003) at 5 minutes after clamp release; 9.5 vs 3.3 (IRQ, 7.0 to 13.5 vs 1.0 to 7.9; P = .013) at 24 hours, and 9.6 vs 3.9 (IRQ, 7.6 to 12.6 vs 2.4 to 8.7; P = .006) at 48 hours. TFPI levels were not significantly different between ruptured AAA and nonruptured AAA before or during operation but became significantly elevated at 24 and 48 hours in patients who had undergone repair of ruptured AAA. Ruptured AAA repair was associated with a hypofibrinolytic state compared with nonruptured AAA.

CONCLUSIONS

The present study has demonstrated for the first time, to our knowledge, that ruptured AAA is associated with significantly higher perioperative levels of circulating TF compared with nonruptured AAA. Furthermore, in the immediate perioperative period, the high levels of TF are not associated with a corresponding rise in TFPI levels, indicating an unopposed prothrombotic state. Direct inhibition of TF by administration of anti-TF antibodies or recombinant TFPI remains to be evaluated in subjects presenting with hemorrhage due to ruptured AAA, but if given early enough, it may attenuate the early deleterious effects of unopposed TF expression and ultimately contribute to improved outcomes.

Simvastatin ameliorates radiation enteropathy development after localized, fractionated irradiation by a protein C-independent mechanism

PURPOSE

Microvascular injury plays a key role in normal tissue radiation responses. Statins, in addition to their lipid-lowering effects, have vasculoprotective properties that may counteract some effects of radiation on normal tissues. We examined whether administration of simvastatin ameliorates intestinal radiation injury, and whether the effect depends on protein C activation.

METHODS AND MATERIALS

Rats received localized, fractionated small bowel irradiation. The animals were fed either regular chow or chow containing simvastatin from 2 weeks before irradiation until termination of the experiment. Groups of rats were euthanized at 2 weeks and 26 weeks for assessment of early and delayed radiation injury by quantitative histology, morphometry, and quantitative immunohistochemistry. Dependency on protein C activation was examined in thrombomodulin (TM) mutant mice with deficient ability to activate protein C.

RESULTS

Simvastatin administration was associated with lower radiation injury scores (p < 0.0001), improved mucosal preservation (p = 0.0009), and reduced thickening of the intestinal wall and subserosa (p = 0.008 and p = 0.004), neutrophil infiltration (p = 0.04), and accumulation of collagen I (p = 0.0003). The effect of simvastatin was consistently more pronounced for delayed than for early injury. Surprisingly, simvastatin reduced intestinal radiation injury in TM mutant mice, indicating that the enteroprotective effect of simvastatin after localized irradiation is unrelated to protein C activation.

CONCLUSIONS

Simvastatin ameliorates the intestinal radiation response. The radioprotective effect of simvastatin after localized small bowel irradiation does not appear to be related to protein C activation. Statins should undergo clinical testing as a strategy to minimize side effects of radiation on the intestine and other normal tissues.

Fibrinolysis, inflammation, and regulation of the plasminogen activating system

The maintenance of a given physiological process demands a coordinated and spatially regulated pattern of gene regulation. This applies to genes encoding components of enzyme cascades, including those of the plasminogen activating system. This family of proteases is vital to fibrinolysis and dysregulation of the expression pattern of one or more of these proteins in response to inflammatory events can impact on hemostasis. Gene regulation occurs on many levels, and it is apparent that the genes encoding the plasminogen activator (fibrinolytic) proteins are subject to both direct transcriptional control and significant post-transcriptional mechanisms. It is now clear that perturbation of these genes at either of these levels can dramatically alter expression levels and have a direct impact on the host's response to a variety of physiological and pharmacological challenges. Inflammatory processes are well known to impact on the fibrinolytic system and to promote thrombosis, cancer and diabetes. This review discusses how inflammatory and other signals affect the transcriptional and post-transcriptional expression patterns of this system, and how this modulates fibrinolysis in vivo.

Fibrinolysis and the risk of venous and arterial thrombosis

PURPOSE OF REVIEW

The fibrinolytic system is often regarded as just an innocent bystander in the pathogenesis of venous and arterial thrombosis, while (hyper)coagulation as a risk factor has been studied extensively. In this review, we evaluated studies that investigated the association between fibrinolysis and thrombosis.

RECENT FINDINGS

There is some evidence for an association between impaired overall fibrinolytic activity and increased risk of venous or arterial thrombosis. Plasminogen levels were found not to be related to thrombosis. Plasma levels of tissue-type plasminogen activator were related to arterial thrombosis in a number of studies but not to venous thrombosis. Thrombin activatable fibrinolysis inhibitor levels appeared to be associated with venous thrombosis. Studies on the association between thrombin activatable fibrinolysis inhibitor or plasminogen activator inhibitor-1 and arterial thrombosis had conflicting results.

SUMMARY

Current evidence on an association between fibrinolysis and thrombosis is inconclusive. Although overall assays point to an association, not all individual factors have an association with thrombosis. Most importantly, plasminogen deficiency is not related to thrombosis, which suggests that the fibrinolytic system as a whole is unimportant in the occurrence of thrombosis. Certain components of the fibrinolytic system, however, appear to be involved in processes unrelated to fibrin degradation but related to other processes important in the development of thrombosis.

Perioperative use of modified thrombelastography in factor XI deficiency: a helpful method to assess drug effects

Factor XI deficiency is a rare, hereditary bleeding disorder associated with a trauma-related bleeding tendency, caused by insufficient generation of the thrombin activatable fibrinolysis inhibitor (TAFI) evoking increased fibrinolysis. We present the case of a five year old girl with homozygote, severe factor XI deficiency presenting for surgery on two occasions. Modified thrombelastography (ROTEM) was used to assess effects of factor XI deficiency on coagulation, endogenous fibrinolysis, and potential effects of tranexamic acid, aprotinin and recombinant, activated Factor VII in an in vitro model of hyperfibrinolysis. According to our data and in consideration of the mechanisms of factor XI deficiency we decided on prophylactic use of tranexamic acid.

Plasma activity of thrombin activatable fibrinolysis inhibitor in Crimean-Congo hemorrhagic fever

OBJECTIVES

Crimean-Congo hemorrhagic fever (CCHF) is a potentially fatal viral infection. The exact mechanism for hemorrhage remains unknown. Thrombin activatable fibrinolysis inhibitor (TAFI) is a plasma procarboxypeptidase B-like proenzyme and synthesized in the liver, down-regulating fibrinolysis. In this study, we measured the TAFI activity in plasma of patients with CCHF to examine the relationship between hemorrhage and the pathogenesis of CCHF.

METHODS

Twenty-one patients and similar number of controls were included in the study. The diagnosis of CCHF was confirmed through detection of IgM by ELISA and/or PCR. TAFI activity was measured in plasma samples.

RESULTS

TAFI activity in CCHF patient group was mean 7.2+/-2.3 microg/ml (range: 0.95-10.31 microg/ml) and in the control group was mean 11.7+/-4.1 microg/ml (range: 3.07-23.9 microg/ml). There was a significant decrease of TAFI activity in CCHF patients when compared to controls. A positive correlation between CRP, PT, INR, serum albumin and TAFI activity levels were found. We suggest that the decrease of TAFI activity may be due to liver dysfunction during viral active disease state.

CONCLUSIONS

Low TAFI activity may be an attributable factor, leading to imbalance in fibrinolysis, resulting in bleeding complications in CCHF.

Hypertension pulmonaire postembolique

INTRODUCTION

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare disease characterized by the persistence of thromboemboli obstructing the pulmonary arteries as an organized tissue. The consequence is an increase in pulmonary vascular resistance resulting in pulmonary hypertension (PH) and progressive right heart failure.

BACKGROUND

It is difficult to recognize the postembolic nature of PH because there is no known history of thromboembolic disease in more than 50% of cases. Diagnosis is based on the presence of mismatched segmental defects in the ventilation-perfusion scanning. When CTEPH is suspected, pulmonary angiography and high-resolution CT scan are required to establish the diagnosis and to assess the operability. Pulmonary angiography is always performed in conjunction with a diagnostic right heart catheterization, which is required to confirm the diagnosis of PH and to determine the degree of hemodynamic impairement. If there is a good correlation between the pulmonary vascular resistance and the anatomical obstruction, pulmonary endarterectomy (PEA) must be proposed. Otherwise, vasodilator and antiproliferative treatments and lung transplantation represent interesting alternatives.

VIEWPOINT AND CONCLUSION

PEA remains the treatment of choice for eligible patients. Nevertheless, there is a need to conduct randomized trials to assess the efficacy of novel medical therapies in some situations: (1) in inoperable CTEPH due to distal lesions, (2) before PEA (therapeutic bridge) in patients who are considered "high risk" due to extremely poor hemodynamics, (3) in patients with persistent pulmonary hypertension after surgery.

Thrombin activatable fibrinolysis inhibitor (TAFI): A role in pre-eclampsia?

Pre-eclampsia (P-Ec) is a complex multisystem disorder of unknown aetiology reported to occur in about 6% to 8% of all pregnancies throughout the world. This disease is associated with fibrin deposition and occlusive lesions in placental vessels. Pro-thrombin activatable fibrinolysis inhibitor (pro-TAFI) is a relatively recently described glycoprotein that can be converted into its active form (TAFIa) by thrombin, thrombin-thrombomodulin and plasmin. TAFIa potentially inhibits fibrinolysis by removing C-terminal lysine and arginine residues from fibrin. These residues are required for adsorption of tissue-type plasminogen activator (t-PA) and plasminogen to fibrin. Therefore, TAFIa decreases plasmin formation and protects the fibrin clot against lysis. An increased of pro-TAFI/TAFIa levels has been reported in some clinical conditions associated with thrombotic tendency, as type II diabetes mellitus, deep vein thrombosis and symptomatic artery disease. Few studies have investigated pro-TAFI/TAFIa in normal or complicated pregnancy but contrasting results were reported. Understanding the role of pro-TAFI/TAFIa in the pathogenesis of P-Ec can hold great promise for improving P-Ec management. In this context, a large-scale study evaluating plasma TAFI antigen and activity, its synthesis and metabolism in pre-eclamptic women is required. Recently new selective TAFIa inhibitors have been developed. The design of a new therapy to treat and/or prevent P-Ec, based on successful use of TAFIa inhibitors, may have significant clinical ramifications.

Comparative Ultrastructural Analyses of Mouse, Rabbit, and Human Platelets and Fibrin Networks

Platelets and fibrin play an important role in the coagulation process, where they are involved in the maintenance of hemostasis. Fibrin dysfunction is associated with the development of vascular complications, while proneness to the formation of tight and rigid fibrin networks is independently associated with thrombotic disease. Here we investigate the ultrastructure of human, rabbit, and mouse platelets and fibrin networks, using the scanning electron microscope. Human and rabbit fibrin and platelets, with regards to morphology as well as size of major and minor fibers compare well with each other. However, mouse fibers are much thinner and form a flimsy branching network. Platelet aggregate morphology of all three species compare well with each other. We conclude that rabbit platelet and fibrin networks could be used successfully when studying the effect of pharmaceutical products in preclinical trials, when looking at the effects of these products on morphology and ultrastructure.