bluuebunny/crossref_metadata_2025 huggingface dataset:
Use Of Fibrinogen and Fibrin D-Dimer in Prediction of Arterial Thrombotic Events
Authors: Rumley Ann , Lowe Gordon D.O.
Published: March 2018

Introduction

There is increasing clinical and laboratory interest in the measurement of both plasma fibrinogen and fibrin D-dimer to predict arterial thrombotic events, such as cardiovascular death, myocardial infarction (MI), stroke, leg ischemia, arterial surgery (e.g., angioplasty, bypass grafting), and postsurgical arterial occlusion. There are several possible reasons for such interest.

First, there is substantial evidence from prospective studies that the plasma fibrinogen level is a strong, consistent predictor of such cardiovascular events in people with or without clinically detectable arterial disease. Furthermore, fibrinogen adds to the predictive valve of major conventional risk predictors (e.g., smoking, blood pressure, serum cholesterol) in healthy people (Fig.1).1-7

Second, we and others have shown, in several prospective studies, that plasma fibrin D-dimer (measured quantitatively by enzyme-linked immunosorbent assays [ELISAs]) is also a strong, consistent predictor of such cardiovascular events in people with or without clinically detectable arterial disease.8-14 Again, fibrin D-dimer may add to the predictive value of major conventional risk predictors (e.g., smoking, blood pressure, serum cholesterol, plasma fibrinogen) in healthy people (Fig. 2).

Third, there are several interactive, plausible, potential biological mechanisms through which increasing plasma fibrinogen levels, which are due to multiple gene-environment interactions, may promote ischemic events. These include increased blood viscosity, atherogenesis, and platelet-fibrin thrombogenesis (Fig. 3). Increased plasma D-dimer levels are a marker of turnover of cross-linked fibrin, whether vascular or extravascular (Fig. 3).

Fourth, not only is there more evidence for fibrinogen and D-dimer as predictors of arterial thrombotic events than for other hemostatic or thrombotic variables, but these two assays are more stable and more practical to measure in clinical and epidemiological studies. These tests are also already available in many district hospitals for the diagnosis of disseminated intravascular coagulation (DIC) and, in the case of D-dimer, venous thromboembolism.15,16 As with other major cardiovascular risk factors (e.g., smoking, blood pressure, serum cholesterol), there is a need for standardization of both fibrinogen assays17-23 and D-dimer assays.24

Finally, clinical interest in plasma assays of fibrinogen also may increase in the event that ongoing clinical trials of plasma fibrinogen reduction (e.g., with certain fibrates or ancrod) show that such treatments are beneficial.25 Likewise, clinical interest in plasma assays of D-dimer may also increase if future studies show that oral anticoagulant prophylaxis is the most costeffective and risk-effective in people with elevated plasma D-dimer levels, who are normalized by full-dose warfarin.15,19,26-28 This review discusses each of these aspects of fibrinogen and fibrin D-dimer.
Antithrombotic Treatments in Acute Ischemic Stroke
Authors: del Zoppo Gregory
Published: March 2018

Introduction

Stroke may be defined as a syndrome of thrombohemorrhagic disorders affecting the central nervous system. In this setting, considerable efforts have been directed to improve clinical outcome with antithrombotic agents, including platelet inhibitors, anticoagulants, and plasminogen activators. The search for a role for antithrombotic agents in ischemic stroke rests on the observation that, overall, 75% to 80% of strokes involve thrombotic events. Recent experience with plasminogen activators (PAs) in acute ischemic stroke indicates that, in select patients, clinical improvement is associated with shorter interval from symptom onset to treatment, while clinically significant hemorrhagic transformation increases with delays in treatment. The time-dependence and the subpopulation characteristics of outcomes following PA exposure is entirely compatible with an evolution of brain injury and varies individually, but where microvascular integrity in the ischemic bed decreases with time. These relationships have not been developed or explored with other antithrombotic agents, including antiplatelet agents or anticoagulants. Thus, among antithrombotic agents, only certain PAs have been used in a strictly “acute” setting, that is within 6 to 8 hours of symptom onset. This presentation summarizes current experience with antithrombotic interventions in focal cerebral ischemia in the acute and early (>8) hours following symptom onset.
Plasma Levels of Free and Total TFPI, Relationship with Cardiovascular Risk Factors and Endothelial Cell Markers
Authors: Morange P. E. , Renucci J. F. , Charles M. A. , Aillaud M. F. , Giraud F. , Grimaux M. , Juhan-Vague I.
Published: March 2018

Free-TFPI (f-TFPI) presents high anticoagulant activity and its plasma level correlates with unfavorable outcomes in unstable angina. Total TFPI (t-TFPI) represents mainly the lipid-bound form which seems to have a poor anticoagulant activity. Until now, it is not known whether the variations of f-TFPI plasma levels are determined by environmental factors. The aim of our study was to evaluate the influence of cardiovascular risk factors on plasma levels of f-TFPI and relations with other endothelial derived molecules in a population of 626 patients (277 men and 349 women) attending a metabolic ward for primary prevention of coronary disease.

Free and total TFPI plasma levels were poorly correlated. f-TFPI levels increased with age in both sexes, t-TFPI in women only. Ageadjusted correlations of TFPI levels with conventional cardiovascular risk factors and endothelial cell markers showed different patterns for f-TFPI and t-TFPI. f-TFPI correlated with parameters associated with insulin resistance, particularly in females. f-TFPI was also positively associated in both genders with fibrinogen and endothelial cell markers: t-PA, thrombomodulin (TM) and von Willebrand factor (vWF). t-TFPI correlated strongly with LDL-C in both sexes. It also correlated negatively with parameters of the insulin resistance syndrome. t-TFPI also correlated with TM but not with other endothelial cell markers. The results of the multivariate step by step analysis showed that cardiovascular risk factors poorly explained the f-TFPI variability (7% and 4% in men and women, respectively), whereas they explained 16 and 20% of t-TFPI variability in men and women respectively (mostly related to LDL-C).

In conclusion, this study showed that free- and total-TFPI are regulated differently. f-TFPI strongly correlates with endothelial cell markers and t-TFPI is more related to conventional cardiovascular risk factors. The strong gender effect on f-TFPI levels remains to be explained.
Polymorphisms in the Prothrombin Gene and their Association with Plasma Prothrombin Levels
Authors: Bertina R. M. , van Hylckama Vlieg A. , Rosendaal F. R. , Vos H. L. , Ceelie H.
Published: March 2018

To find genetic causes of high plasma prothrombin levels, an established prothrombotic risk factor, we searched for sequence variations in the prothrombin gene. We selected subjects with the 20210-GG genotype (since the 20210-A allele is already known to be associated with high levels) and elevated prothrombin levels (≥ 130 U/dl) from the Leiden Thrombophilia Study (LETS). No mutations were found in the 1 kb promoter region of the prothrombin gene in seven individuals with an isolated high prothrombin level. Comparison of the allelic frequencies of four different polymorphisms in the prothrombin gene in healthy volunteers and in the control subjects among the selected LETS individuals indicated a higher frequency of the 19911-G allele in the latter group (allele frequency 52 vs. 78%, respectively). Homozygous carriers of the 19911-G allele had 8 U/dl higher plasma prothrombin levels than 19911-AA carriers. This difference in prothrombin levels did not affect the thrombotic risk in 20210-GG carriers. In heterozygous 20210-A carriers the odds ratio increased from 1.6 (95% CI: 0.6-4.3) in subjects with 19911-A to 4.7 (1.6-14.0) in subjects with 19911-G on the other prothrombin allele.
Analytical Considerations for Free Protein S Assays in Protein S Deficiency
Authors: Hillarp Andreas , Dahlbäck Björn , Persson Kristina
Published: March 2018

Protein S is an anticoagulant protein that circulates in plasma in complex with C4b-binding protein (C4BP) or in free form. Deficiency of protein S increases the risk of venous thrombosis. Measurement of free protein S, as compared to total levels, has been shown to be superior for prediction of protein S deficiency. We studied the effects of different handling protocols for an immuno- and a ligand (C4BP)-based assay for free protein S. When the assay was performed at 37° C, the levels of free protein S in plasma from protein S deficient patients were approximately twice those obtained at room temperature. The reason for this phenomenon was that plasmas from protein S deficient patients exhibited a time-, temperature-, and dilution-dependent increase in free protein S, which was more pronounced than corresponding dilution of the normal plasma that was used to create the standard curve. These findings demonstrate the importance of assay procedure and sample handling in assays for free protein S.
Prediction of Pulmonary Embolism Extent by Clinical Findings, D-dimer Level and Deep Vein Thrombosis Shown by Ultrasound
Authors: Galle Cécile , Papazyan Jean-Pierre , Miron Marie-José , Slosman Daniel , Bounameaux Henri , Perrier Arnaud
Published: March 2018

Pulmonary embolism (PE) may encompass a wide spectrum of severity. To determine whether clinical findings, D-dimer (DD) concentration, and deep vein thrombosis (DVT) shown by lower-limb venous compression ultrasonography (US) might predict the scintigraphic extent of PE, we studied 104 hemodynamically stable consecutive outpatients with acute PE diagnosed by a high-probability ventilation-perfusion lung scan. Scintigraphic extent of PE was classified into three categories: perfusion defects corresponding to <30%, 30–50%, or >50% of the total lung area. Median respiratory and heart rates were found to be significantly related to the extent of PE. Higher median alveolar-arterial oxygen difference values were observed as the proportion of lung perfusion defects increased (>50% vs. <30%, 6.3 vs. 3.6 kPa, P <.0001). Median plasma DD concentration was 7950 g/L in patients with >50% perfusion defects compared to 2731 g/L in those with <30% defects (P = .0001). DD levels above 4000 g/L were associated to more extensive perfusion defects (>50% vs. <30% defects, OR 30; 95% CI 5.8–155). Finally, a proximal DVT was more likely among patients with larger perfusion defects (>50% vs. <30% defects, OR 4.5; 95% CI 1.5–13.6). In conclusion, clinical signs such as tachypnea and tachycardia, alveolar-arterial oxygen difference, plasma DD concentration, and presence of DVT on US are predictors of a larger PE, as assessed by the extent of perfusion defects on high probability lung scans.
Anti-β2 Glycoprotein I Antibodies Cause Inflammation and Recruit Dendritic Cells in Platelet Clearance
Authors: Bondanza Attilio , Manfredi Angelo , Zimmermann Valérie , Iannacone Matteo , Tincani Angela , Balestrieri Genesio , Sabbadini Maria Grazia , Querini Patrizia Rovere
Published: March 2018

Scavenger phagocytes are mostly responsible for the in vivo clearance of activated or senescent platelets. In contrast to other particulate substrates, the phagocytosis of platelets does not incite pro-inflammatory responses in vivo. This study assessed the contribution of macrophages and dendritic cells (DCs) to the clearance of activated platelets. Furthermore, we verified whether antibodies against the β2 Glycoprotein I (β2GPI), which bind to activated platelets, influence the phenomenon. DCs did not per se internalise activated platelets. In contrast, macrophages efficiently phagocytosed platelets. In agreement with the uneventful nature of the clearance of platelets in vivo, phagocytosing macrophages did not release IL-1β, TNF-α or IL-10. β2GPI bound to activated platelets and was required for their recognition by anti-ββ2GPI antibodies. DCs internalised platelets opsonised by anti-ββ2GPI antibodies. The phagocytosis of opsonised platelets determined the release of TNF-α and IL-1β by DCs and macrophages. Phagocytosing macrophages, but not DCs, secreted the antiinflammatory cytokine IL-1β0. We conclude that anti-ββ2GPI antibodies cause inflammation during platelet clearance and shuttle platelet antigens to antigen presenting DCs.
Magnesium Inhibits Arterial Thrombi after Vascular Injury in Rat: In Vivo Impairment of Coagulation
Authors: Sironi Luigi , Tedeschi Luca , Calvio Anna Maria , Colli Susanna , Tremoli Elena , Mussoni Luciana
Published: March 2018

Magnesium deficiency is associated with a high frequency of cardiac arrhythmia, hypertension and sudden ischemic death. We investigated the in vivo effects of intravenous magnesium administration in a rat model of chemically induced (FeCl3) carotid thrombosis. The infusion of magnesium sulfate (MgSO4) before the topical application of FeCl3 prevented thrombus formation at concentrations of 0.3 M and 0.6 M, and delayed it even at 0.15 M. Similar results were obtained with MgCl2. The infusion of MgSO4 0.6 M seven minutes after FeCl3 application delayed but did not prevent thrombus formation. MgSO4 slightly reduced platelet aggregation ex vivo without affecting plasma clotting tests, but in vivo blood clotting time was markedly prolonged (tail transection method), thus indicating profoundly impaired coagulation. These data provide a rationale for the use of magnesium as an anti-thrombotic agent, but its pharmacological effect critically depends on the timing of administration.
Different Effects of Oral and Transdermal Hormone Replacement Therapies on Factor IX, APC Resistance, t-PA, PAI and C-reactive Protein
Authors: Upton Mark , Rumley Ann , McConnachie Alex , O’Reilly Denis , Watt Graham , Lowe Gordon
Published: March 2018

The effects of hormone replacement therapy (HRT) on thrombosis risk, thrombotic variables, and the inflammatory marker C-reactive protein (CRP) may vary by route of administration (oral versus transdermal). We studied the relationships of 14 thrombotic variables (previously related to cardiovascular risk) and CRP to menopausal status and to use of HRT subtypes in a cross-sectional study of 975 women aged 40-59 years. Our study confirmed previously-reported associations between thrombotic variables and menopausal status. Oral HRT use was associated with increased plasma levels of Factor IX, activated protein C (APC) resistance, and CRP; and with decreased levels of tissue plasminogen activator (t-PA) antigen and plasminogen activator inhibitor (PAI) activity. Factor VII levels were higher in women taking unopposed oral oestrogen HRT. The foregoing associations were not observed in users of transdermal HRT; hence they may be consequences of the “first-pass” effect of oral oestrogens on hepatic protein synthesis. We conclude that different effects of oral and transdermal HRT on thrombotic and inflammatory variables may be relevant to their relative thrombotic risk; and suggest that this hypothesis should be tested in prospective, randomised studies.
Impairment of the Plasmin Activation System in Primary Pulmonary Hypertension: Evidence for Gender Differences
Authors: Graf Senta , Huber-Beckmann Renate , Zorn Gerlinde , Lang Irene , Kneussl Meinhard , Binder Bernd , Huber Kurt , Christ Günter
Published: March 2018

Primary pulmonary hypertension (PPH) is a rare disorder, with marked in-situ thrombosis of small pulmonary vessels occurring primarily in adult women. We investigated whether differences in the plasmin- and thrombin activation system are associated with the predominate affection of females. Plasma levels of plasminogen activator inhibitor type 1 (PAI-1), tissue-type plasminogen activator (t-PA), fibrinogen, thrombin-antithrombin (TAT) complexes, and prothrombin fragments (F1.2) were measured at baseline and after standardized venous occlusion (VO) in patients with PPH (24 female, 9 male). At baseline, females showed significant higher TAT levels (p = 0.05), higher t-PA antigen levels (p = 0.01) and higher fibrinogen levels (p = 0.03) with positive correlation to mean pulmonary artery pressure (mPAP), as well as nonsignificant lower t-PA activity, higher PAI-1 antigen and activity and F1.2 levels. After VO, females showed a significantly blunted increase in t-PA antigen (p = 0.01) and t-PA activity (p = 0.001), correlating with mPAP, as well as increased PAI-1 activity (p = 0.05). We hypothesize, that the observed presence of gender differences in the plasmin- and thrombin activation system in PPH leading to an antifibrinolytic/prothrombotic state might, in part, explain the female predominant incidence of this disease.
Quantification of Lupus Anticoagulants in Clinical Samples Using Anti- β2GP1 and Anti-Prothrombin Monoclonal Antibodies
Authors: Querrec A. Le , Arnout J. , Arnoux D. , Borg J. Y. , Caron C. , Darnige L. , Delahousse B. , Reber G. , Sié P.
Published: March 2018

Quantification of lupus anticoagulant (LA) in clinical samples is hampered by the lack of a suitable standard of activity. We evaluated the use of mAbs displaying LA activity for this purpose. As most patient samples contain both β2Glycoprotein I (β2GP1) and prothrombin dependent LA, a combination of two mAbs, one of each specificity, was added to normal plasma in a concentration from 0 to 60 g/ml. Eight assay systems using different reagents and instruments were used. The calibration curves were linear for all but one, with marked differences between the responsiveness to each mAb. A panel of plasmas from 69 patients with persistent LA diagnosed using the SSCISTH criteria was tested. An antiphospholipid syndrome (APS) was present in 40, whereas 29 were asymptomatic. LA activities of individual plasmas varied between assays (p <10–4), but homogeneous subgroups were identified. In a majority of samples, LA activity displayed a prothrombin-dependent profile, with a variable contribution of β2GP1-dependent activity. The latter was associated to β2GP1 antibodies detected by solid-phase immunoassay. By using 3 dilute Russell viper venom time assays, higher LA titers were found in APS, compared to asymptomatic patients (p <0.05).
A Factor VIII Minigene Comprising the Truncated Intron I of Factor IX Highly Improves the In Vitro Production of Factor VIII
Authors: Plantier Jean-Luc , Rodriguez Marie-Hélène , Enjolras Nathalie , Attali Olivier , Négrier Claude
Published: March 2018

The biosynthesis of coagulation factor VIII (FVIII) is hampered by successive controls that limit its production. To improve this production, a truncated intron I sequence of factor IX (TFIXI1) was inserted in FVIII cDNA in place of FVIII introns 1, 12 and 13 and also as a combination between introns 1 and 12, and introns 1 and 13. The intron 12 and 13 locations were targeted because this region was previously shown to contain a transcriptional silencer. The expression of FVIII in CHO and HepG2 cells revealed important variations in the properties of the minigenes depending on the TFIXI1 insertion sites. In FVIII intron 13 location the TFIXI1 seemed to diminish the transcriptional silencer activity, whereas it was poorly spliced in intron 12 position. Among the five constructs, FVIII I1+13 leaded to a significant improvement in FVIII secretion (13 times) that was associated with a dramatic intracellular accumulation in cells. Therefore, the FVIII I1+13 minigene could represent a particular interest to produce recombinant FVIII in vitro as well as in the aim of gene therapy of haemophilia A.
Selection of Phages that Inhibit vWF Interaction with Collagen under both Static and Flow Conditions
Authors: Ulrichts H. , Depraetere H. , Harsfalvi J. , Deckmyn H.
Published: March 2018

Phages from a pentadecamer phage display library were selected for binding to vWF by affinity panning. Bound phages were selectively eluted with human collagen type I. After the third round of panning 95% of individual phage clones bound to vWF. The B8-phage inhibited the binding of collagen to vWF with an IC50 of 0.6 × 1010 phages/ml, and of vWF to collagen with an IC50 of 1.0 × 1010 phages/ml at 0.5 μg/ml vWF. Under flow conditions, 1.5 × 1011 B8-phage/ml nearly completely inhibited platelet deposition on a human collagen type I coated surface at a shear rate of 1200 s-1, while phages without an insert had no effect. The peptide corresponding to the one displayed on the B8-phage competed with the phage for binding to vWF with an IC50 of 30 μg/ml (16 μM). The peptide furthermore inhibited vWF-binding to collagen with a maximum of 40% at a concentration of 1.25 mg/ml (650 μM), higher concentrations of peptide could not improve this. We thus have selected phages that are potent vWF-binders and that can be used as tools to detect vWF, to inhibit vWF-collagen interaction and to further analyse the role of vWF-collagen binding.
Plasma PAI-1 Levels in Obese Children – Effect of Weight Loss and Influence of PAI-1 Promoter 4G/5G Genotype
Authors: Dalmau Jaime , Falcó Cristina , Berbel Octavio , Castelló Remedios , España Francisco , Aznar Justo , Estellés Amparo
Published: March 2018

An association between an increase in plasminogen activator inhibitor type 1 (PAI-1) and obesity, and also between elevated levels of PAI-1 and the presence of PAI-1 promoter 4G allele has been described in adults and can contribute to increased risk of cardiovascular disease. It has also been suggested that in adults a decrease in adiposity has beneficial effects on the haemostatic system. However, less information is available regarding adiposity and fibrinolysis in children. The aim of the present study is to evaluate the effect of weight loss and the influence of the PAI-1 promoter 4G/5G genotype on the fibrinolytic system and lipid parameters in obese children. The clinical groups included 102 obese children and 105 controls of similar age and sex distribution. A significant decrease in fibrinolytic activity due to a significant increase in PAI-1 antigen and activity levels was observed in the obese children in comparison with the control group. In obese children, no significant differences in PAI-1 levels between the PAI-1 4G/5G genotypes were obtained. A significant correlation was observed between PAI-1 antigenic and functional levels and body mass index (BMI), as well as between PAI-1 levels and both triglyceride and insulin levels. No correlation between PAI-1 levels and either cholesterol or glucose levels was observed.

After a three-month period of treatment to reduce weight, an increase in fibrinolytic activity due to a decrease in PAI-1 levels was observed in the obese children who had reduced their BMI in comparison with the group of obese children who did not show a decrease in their BMI. No significant differences between the two groups with respect to the variations in tissue type plasminogen activator and fibrinogen levels were obtained after three months of intervention to reduce weight. A significant correlation was observed between variations in BMI and variations in PAI-1 levels, and a significant inverse correlation was also observed between previous PAI-1 levels and variation in PAI-1 levels. Therefore, the largest decrease in PAI-1 levels was observed in the obese children with the highest previous PAI-1 levels.

In conclusion, a decrease in BMI in obese children shows a favourable effect on the fibrinolytic system due to a decrease in PAI-1 levels. However, no influence of 4G/5G genotype on PAI-1 levels was observed.
Human Endothelial Cell-derived Nuclear Proteins that Recognise Polymorphic DNA Elements in the von Willebrand Factor Gene Promoter Include YY1
Authors: Costa Magdaline , Grant Peter , Rice Gillian , Futers Simon , Medcalf Robert
Published: March 2018

Four common base-change polymorphisms have been found in the von Willebrand factor gene promoter: (-1793 C/G, -1234 T/C, -1185 G/A and -1051 A/G). All four polymorphisms are in strong linkage dis-equilibrium and recent reports have indicated these polymorphisms are associated with plasma vWF:Ag levels suggesting that one or more of these elements influence regulation of the vWF gene. We report that human endothelial cell-derived trans-acting factors display allelic preferences in binding activity to each polymorphic site. The common A allele variant of the –1051 polymorphism and the rarer A allele variant of the –1185 polymorphism provided specific binding of nuclear proteins. The G allele counterpart of these two variants did not produce any complex formation indicating that the nucleotide substitution at these positions alters the DNA binding ability of nuclear factors. The two alleles of the –1234 polymorphism produced two complexes with a similar migration pattern however stronger binding was found to the common T variant of this allele. Two specific complexes associated with the rarer G allele of the –1793 polymorphism, but only one associated with the C allele. Supershift experiments revealed that the trans-acting factor YY1 recognised the slower migrating complex formed on the –1234 T/C and the –1051 A polymorphic sites with a strong binding preference for the –1234 T allele variant. The identification of YY1 as a component of the factors that recognise these elements suggests that this ubiquitous nuclear protein may play a role in the regulation of the vWF promoter.
A Monoclonal Antibody to Platelet Type III Collagen-binding Protein (TIIICBP) Binds to Blood and Vascular Cells, and Inhibits Platelet Vessel-wall Interactions
Authors: Monnet Emmanuel , Depraetere Hilde , Legrand Chantal , Deckmyn Hans , Fauvel-Lafève Françoise
Published: March 2018

TIIICBP is a new platelet receptor involved in platelet-type III collagen and platelet-subendothelium interactions. This receptor is composed of a doublet of 72-68 kDa proteins. In this study, the major protein (68 kDa) was purified and used to produce monoclonal antibodies. One of these antibodies, 7F4, binds to platelets as confirmed by flow cytometry. 7F4 inhibited platelet contact, spreading and aggregation induced by type III collagen. Under flow conditions, 7F4 prevented platelet interactions with type III collagen, endothelial cell matrix and the KOGEOGPK type III collagen octapeptide: the specific sequence recognized by TIIICBP. On the other hand, 7F4 had no effect on platelet-type I collagen interactions. TIIICBP was also detected on lymphocytes, granulocytes and monocytes. TIIICBP was expressed on endothelial cells and fibroblasts but not on smooth-muscle cells. These results show that TIIICBP is expressed on several cell types and participates in cell adhesion to the subendothelium.
αIIbβ3 and Its Antagonism at the New Millennium
Authors: Cierniewski Czeslaw , Xiao Zihui , Haas Thomas , Byzova Tatiana , Plow Edward
Published: March 2018

Because of its major role in regulating platelet functions and its prominence on the cell surface, integrin αIIbβ3 has been the subject of intensive investigations. Such studies have provided substantial insights into its structure-function relationships and have led to the development of anti-thrombotic drugs that target the receptor. Nevertheless, recent findings have indicated that our understanding of the structure and function of αIIbβ3 remains inadequate. This article addresses two aspects of still evolving αIIbβ3 function: 1) the interface between αIIbβ3 and the blood coagulation system, resulting from interaction of prothrombin with the receptor; and 2) the molecular basis for recognition of the RGD and the fibrinogen γ-chain peptide ligands by αIIbβ3. As illustrated by these two examples, there is still much to be learned about αIIbβ3 if we are to fully appreciate its functions and its potential as a therapeutic target.
Physiopathology and Regulation of Factor XIII
Authors: Ichinose Akitada
Published: March 2018

Factor XIII is a plasma transglutaminase. Transglutaminases are at least 8 enzymes which cross-link a number of proteins. This type of reaction not only enhances the original functions of substrate proteins, but also adds new functions to them. Factor XIII in plasma is a tetramer (A2B2), and the A subunit contains the active site. Although transglutaminases are homologous, the nucleotide sequences in their 5’-flanking region differ significantly. Accordingly, transcription factors play a major role in the cell type-specific expression of each transglutaminase. A variety of missense and nonsense mutations, and deletions/insertions with or without out-of-frame shift/premature termination and splicing abnormalities have been identified in the genes for A and B subunits in factor XIII deficiency. In some cases, the mRNA level of the A or B subunit was severely reduced. Molecular and cellular bases have also been explored by expression experiments and by molecular modeling. In most cases, impaired folding and/or conformational change of the mutant A or B subunit leads to both intra- and extra-cellular instability, which is responsible for factor XIII deficiency.
Oral Contraceptives, Hormone Replacement Therapy and Thrombosis
Authors: Helmerhorst F. M. , Vandenbroucke J. P. , Rosendaal F. R.
Published: March 2018

Oral contraceptives and hormone replacement therapy are used by hundreds of millions of women worldwide. Since the early 1960s it is known that female hormones increase the risk of venous thrombosis, myocardial infarction and stroke. This risk is still present with current low-dose oral contraceptives and, even though in absolute terms the risk is small, oral contraceptives form the major cause of thrombotic disease in young women. The risk is higher during the first year of use (up to 1 per 1000 per year), with the use of desogestrel- or gestodene-containing oral contraceptives (“third generation progestogens”) and among women with a prothrombotic predispositon. Hormone replacement therapy increases the risk of venous thrombosis, while results of randomised trials so far do not substantiate the expectation of a beneficial effect on the risk of arterial cardiovascular disease. First results are emerging that specific subgroups of women, with prothrombotic or other abnormalities, may be at risk, especially during the first years of use of hormone substitution.
Getting at the Variable Expressivity of Von Willebrand Disease
Authors: Levy Gallia , Ginsburg David
Published: March 2018

Von Willebrand disease (VWD) is a heterogeneous bleeding disorder caused by abnormalities of von Willebrand factor (VWF). VWF levels vary widely in the general population, and this variation is likely to be a major factor accounting for the incomplete penetrance and variable expressivity of VWD. In addition, variation in VWF level may play an important role in determining the risk of venous thrombosis. A large component of the variation in VWF level in the general population has been shown to be attributable to genetic factors. This review will focus on the current understanding of the genetic causes for variation in VWF level, and will highlight future directions for getting at the variable expressivity of von Willebrand disease.
The Molecular Basis of Inherited Afibrinogenaemia
Authors: Neerman-Arbez Marguerite
Published: March 2018

This article reviews the substantial progress made in understanding the molecular basis of inherited afibrinogenaemia (or congenital afibrinogenaemia), an autosomal recessive disorder characterised by the complete absence of detectable fibrinogen. The identification in 1999 of the first genetic defect, recurrent homozygous deletions of approximately 11 kb of the fibrinogen alpha-chain (FGA) gene, revealed that the disease was caused by defective fibrinogen synthesis, and led to the subsequent analysis of the three fibrinogen genes in other affected individuals with the identification of numerous causative mutations. Combined analyses of more than thirty unrelated afibrinogenaemia families from various ethnic groups have shown that the majority of patients have truncating mutations in the FGA gene although intuitively all three fibrinogen genes might be equally implicated. These results will facilitate molecular diagnosis of the disorder, permit prenatal diagnosis for families who so desire, and pave the way for new therapeutic approaches such as gene therapy.
The Vascular Biology of the Glycoprotein Ib-IX-V Complex
Authors: Shen Yang , Dopheide Sacha , Gardiner Elizabeth , Andrews Robert , Berndt Michael
Published: March 2018

It has long been recognized that binding of von Willebrand factor (vWf) by the platelet membrane glycoprotein (GP) Ib-IX-V complex initiates the cascade of events leading to thrombosis and haemostasis. In the last several years, however, it has become apparent that the GP Ib-IX-V complex plays a much broader role in vascular biology, a recognition in part due to the identification of novel adhesive ligands for GP Ib-IX-V such as P-selectin and Mac-1. Binding of vWf by the GP Ib-IX-V complex is also important in formation of the developing thrombus. Platelets can utilize the GP Ib-IX-V complex and PSGL-1 to roll on activated endothelium via surface-expressed endothelial P-selectin. The GP Ib-IX-V complex can bind the I domain of Mac-1, a binding interaction potentially relevant to transmigration of macrophages through mural thrombus, a process required for vessel remodeling post angioplasty. This review will focus on recent advances in our understanding of the structure and function of this important platelet receptor, with particular emphasis on insights made within the last two years.
Cytoskeletal Proteins and Platelet Signaling
Authors: Fox Joan
Published: March 2018

The actin filament network fills the cytoplasm of unstimulated platelets and connects with a submembranous latticework of short cross-linked actin filaments, known as the membrane skeleton. One function of the cytoskeleton is to direct the contours of the membrane in the unstimulated platelet and the rapid changes in shape in the activated platelet. Activation-induced changes result from events such as phosphorylation or calpain-induced cleavage of cytoskeletal proteins. The specific reorganizations depend upon the combination of signals to which platelets are exposed. A second function of the cytoskeleton is to bind other cellular components; it binds signaling molecules, localizing them to specific cellular locations; it binds the plasma membrane regulating properties of the membrane, maintaining microdomains in the membrane, or regulating activities of membrane proteins. In this way, the cytoskeleton plays a critical role in regulation of spatial organizations and, thus, in the integration of cellular activities.
β3 Tyrosine Phosphorylation in αIIbβ3 (Platelet Membrane GP IIb-IIIa) Outside-in Integrin Signaling
Authors: Nannizzi-Alaimo Lisa , Prasad K. S. Srinivasa , Phillips David
Published: March 2018

The platelet integrin αIIbβ3 not only binds fibrinogen and von Willebrand factor to mediate platelet aggregation and adhesion, it also serves as a signaling receptor. Platelet agonists such as ADP, thrombin and collagen induce “inside-out” signaling which activates the receptor function of αIIbβ3 for soluble fibrinogen. Subsequent platelet aggregation leads to “outside-in” signaling, inducing platelet aggregate stabilization and triggering a variety of functions important to platelet physiology. This review focuses on the role of β3 tyrosine phosphorylation in αIIbβ3 outside-in signaling. Tyrosine phosphorylation of β3 in platelets is a dynamic process which is initiated upon platelet aggregation and also by adhesion of platelets to immobilized fibrinogen. Tyrosine phosphorylation occurs on the β3 integrin cytoplasmic tyrosine (ICY) domain, a conserved motif found in thesubunits of several integrins. β3 ICY domain tyrosine phosphorylation induces the recruitment of two proteins to the cytoplasmic domains of αIIbβ3: the cytoskeletal protein myosin, important to clot retraction; and the signaling adapter protein Shc, important to platelet stimulation. The critical role of β3 tyrosine phosphorylation to platelet function was established by the diYF mouse, a novel strain which expresses an αIIbβ3 in which the two β3 ICY domain tyrosines have been mutated to phenylalanine. These mice are selectively impaired in outside-in αIIbβ3 signaling, with defective aggregation and clot-retraction responses in vitro, and an in vivo bleeding defect which is characterized by a pronounced tendency to rebleed. Taken together, the data suggest that the β3 tyrosine phosphorylation signaling mechanism is important to αIIbβ3 function and might be applicable to a wide variety of integrin-mediated events.
Interendothelial Junctions and their Role in the Control of Angiogenesis, Vascular Permeability and Leukocyte Transmigration
Authors: Spagnuolo Raffaella , Bazzoni Gianfranco , Dejana Elisabetta
Published: March 2018

Endothelial cell-cell junctions play an important role in vascular hemostasis. The two junctional proteins VE-cadherin and JAM-1 are localized at adherens and tight junctions, respectively. VE-cadherin is only expressed by endothelial cells, suggesting that it can exert cell specific function. Absence of VE-cadherin or blocking of its adhesive activity prevents a normal organization of new vascular structures, suggesting that VE-cadherin may be a molecular target of antiangiogenic therapy. In addition, the ability of permeability-increasing agents and adherent leukocytes to modify VE-cadherin/catenin organization may be related to a role in the control of vascular permeability and leukocyte infiltration. JAM-1 is an integral membrane protein expressed in endothelial and epithelial cells. Its extracellular domain can dimerize and bind homophilically. The intracellular domain (and in particular a PDZ-binding motif) enables JAM-1 to interact with structural and signaling proteins. Study of the molecular interactions of JAM-1 may help explain mechanisms of JAM-mediated function, such as control of paracellular permeability and leukocyte transmigration.
Anti-GPIIb/IIIa Drugs: Current Strategies and Future Directions
Authors: Coller Barry
Published: March 2018

Three platelet glycoprotein (GP) IIb/IIIa receptor antagonists have been approved as adjunctive therapy to decrease the ischemic complications of percutaneous coronary interventions (PCI) and/or unstable angina. They include the chimeric murine/human monoclonal antibody 7E3 Fab fragment (abciximab), a cyclic heptapeptide based on the KGD amino acid sequence (eptifibatide), and a nonpeptide mimetic of the RGD sequence (tirofiban). The agents are very effective in providing both short-term and long-term benefit after PCI, and one agent has also demonstrated a progressive long-term mortality benefit. The long-term mortality benefit is highly cost-effective when compared to other medical interventions. The benefits in treating unstable angina without PCI are less dramatic and robust, with some agents providing no benefit. Severe thrombocytopenia is an infrequent, but potentially serious, complication of therapy with all of the agents. The risk of major bleeding is increased only minimally or not at all by the drugs. Currently, a number of new indications for GPIIb/IIIa antagonists are under study, including acute myocardial infarction (± thrombolytic therapy, ± PCI) and stroke. In addition to their impact on improving outcome, the results of clinical trials with these agents provide crucial insights into the contribution of GPIIb/IIIa-mediated platelet function in the pathophysiology of thrombotic vascular disease.
Immundefekte als Ursache von chronisch-entzündlichen Erkrankungen des Darmes
Authors: Gerner P. , Speckmann C. , Klemann C. , Tegtmeyer D. , Baumann U.
Published: March 2018

Chronisch-entzündliche Darmerkrankungen (CED), mit ihren beiden prominentesten Vertretern M. Crohn und Colitis ulcerosa, zeichnen sich durch eine multifaktorielle Ätiologie mit komplexer Regulation zwischen polygenetischer Grundlage und Umwelteinflüssen aus. In den letzten Jahren wurden zahlreiche, jedoch insgesamt seltene, monogenetische Erkrankungen identifiziert, die sich mit einem CED-Phänotyp manifestieren können. Das frühe Erkennen und Anpassen der Therapien dieser heterogenen, immunologischen Erkrankungen sind von hoher Relevanz für den weiteren Verlauf der Erkrankung. In diesem Review diskutieren wir charakteristische Befunde und Umstände, die an das Vorliegen einer monogenetischen Ursache für die intestinale Inflammation denken lassen: Hinweisend können ein früher Krankheitsbeginn, ein Versagen klassischer Therapien, elterliche Konsanguinität, eine auffallende Infektanfälligkeit oder CED-untypische Begleiterkrankungen, Pathologien oder Blutwerte sein. Wir beschreiben ausgewählte Erkrankungen anhand von Fallbeispielen und zeigen auf, wie diese Erkrankungen durch die Kombination von anamnestischen Angaben und klinischen, zellulären sowie genetischen Untersuchungen diagnostiziert werden können. Hierfür schlagen wir eine gestufte, diagnostische Strategie vor, um diesen außergewöhnlichen Erkrankungen als Differenzialdiagnose einer CED nachzugehen.
Störungen des Wasserhaushaltes bei Kindern und Jugendlichen
Authors: Bettendorf M.
Published: March 2018

Die Wasserhomöostase des Körpers wird wesentlich über die Osmolarität der Extrazellulärflüssigkeit geregelt. Die Stellglieder dieses Prozesses sind auf der einen Seite das Durstgefühl und auf der anderen Seite das Antidiuretische Hormon (ADH oder Arginin-Vasopressin, AVP), die durch sensitive Osmorezeptoren im Hypothalamus vermittelt die orale Flüssigkeitsaufnahme steigern und die renale Wasserrückresorption vermehren.

Der Diabetes insipidus ist gekennzeichnet durch den Mangel oder die verminderte Wirksamkeit des ADH (DI) und führt zu einer Verminderung der Harnkonzentrierung durch fehlende Wasserrückresorption in den distalen Tubuli und Sammelrohren der Niere und bedingt eine Polyurie mit hypertoner Dehydratation und bewirkt konsekutiv eine Polydipsie.

Eine inadäquat hohe Sekretion von ADH (SIADH) oder eine Überdosierung von Desmopressin bewirkt eine Oligurie mit Ausscheidung eines hypertonen Urins trotz hypotoner Extrazellulärflüssigkeit. Diese Konstellation entspricht einer hypotonen Hyperhydratation (Wasserintoxikation).

Primäre oder sekundäre Störungen des Durstgefühls können mit einer Polydipsie oder Adipsie einhergehen.

Im Vordergrund der Diagnostik stehen die Flüssigkeitsbilanzierung und der standardisierte Durstversuch, um die Störung zu objektivieren, eine zentrale von einer peripheren Störung des Wasserhaushaltes abzugrenzen und primäre von sekundären Formen zu unterscheiden, damit zugrunde liegende Pathologien und die Störung des Wasserhaushaltes adäquat behandelt werden können.
Combined use of 64-slice computed tomography angiography and gated myocardial perfusion SPECT for the detection of functionally relevant coronary artery stenoses
Authors: Jakobs T. , Hack N. , Nikolaou K. , Becker C. , von Ziegler F. , Knez A. , König A. , Klauss V. , Tiling R. , Hacker M.
Published: March 2018

Aim: In patients with stable angina pectoris both morphological and functional information about the coronary artery tree should be present before revascularization therapy is performed. High accuracy was shown for spiral computed tomography (MDCT) angiography acquired with a 64-slice CT scanner compared to invasive coronary angiography (ICA) in detecting „obstructive” coronary artery disease (CAD). Gated myocardial SPECT (MPI) is an established method for the noninvasive assessment of functional significance of coronary stenoses. Aim of the study was to evaluate the combination of 64-slice CT angiography plus MPI in comparison to ICA plus MPI in the detection of hemodynamically relevant coronary artery stenoses in a clinical setting. Patients, methods: 30 patients (63 ± 10.8 years, 23 men) with stable angina (21 with suspected, 9 with known CAD) were investigated. MPI, 64-slice CT angiography and ICA were performed, reversible and fixed perfusion defects were allocated to determining lesions separately for MDCT angiography and ICA. The combination of MDCT angiography plus MPI was compared to the results of ICA plus MPI. Results: Sensitivity, specificity, negative and positive predictive value for the combination of MDCT angiography plus MPI was 85%, 97%, 98% and 79%, respectively, on a vessel-based and 93%, 87%, 93% and 88%, respectively, on a patient-based level. 19 coronary arteries with stenoses ≥50% in both ICA and MDCT angiography showed no ischemia in MPI. Conclusion: The combination of 64-slice CT angiography and gated myocardial SPECT enabled a comprehensive non-invasive view of the anatomical and functional status of the coronary artery tree.
Management von Patienten mit heparininduzierter Thrombozytopenie
Authors: Madlener K. , Pötzsch B.
Published: March 2018

Patienten mit einer heparininduzierten Thrombozytopenie (HIT) tragen ein hohes Risiko zur Entwicklung von thromboembolischen Komplikationen. Deswegen sollte beim klinischen Verdacht einer HIT die Heparingabe beendet und gleichzeitig eine Behandlung mit alternativen Antikoagulanzien eingeleitet werden. Geeignete alternative Antikoagulanzien sind die direkten Thrombininhibitoren Hirudin, Bivalirudin und Argatroban sowie das Heparinoid Danaparoid. Darüber hinaus scheint auch das synthetische Pentasaccharid Fondaparinux geeignet zu sein. Die Entscheidung welches der alternativen Antikoagulanzien im konkreten Einzelfall eingesetzt wird, ist abhängig von der klinischen Konstellation, den pharmakokinetischen Eigenschaften und den vor Ort verfügbaren Monitoring-Möglichkeiten. Dieses Übersichtsreferat beschreibt verschiedene alternative Antikoagulationsstrategien und geht abschließend auf das langfristige Management von Patienten mit anamnestisch bekannter heparininduzierter Thrombozytopenie ein.
Sekundärprophylaxe der venösen Thromboembolie
Authors: Sternitzky R. , Hochauf S. , Schellong S. M.
Published: March 2018

Der Standard in der Erhaltungstherapie (Sekundärprophylaxe) der venösen Thromboembolie ist die Gabe von Vitamin- K-Antagonisten mit einer Ziel-INR von 2,0 bis 3,0. Die Rezidivrate sinkt hierunter auf ein Minimum von ca. 1% pro Jahr. Allerdings muss in Abhängigkeit vom Patientenprofil mit größeren Blutungen in einer Häufigkeit von 1 bis 3% gerechnet werden. Die Standarddauer der Erhaltungstherapie beträgt 3-6 Monate. Zu diesem Zeitpunkt endet sie in jedem Fall bei Patienten mit einem vorübergehenden Risikofaktor (Operation, Trauma). Die Verlängerung der Erhaltungstherapie kommt nur für Patienten mit erhöhtem Rezidivrisiko in Frage. Bereits nach der ersten Episode kann sie auf unbestimmte Dauer angesetzt werden bei Patienten mit aktiver Krebserkrankung oder schweren thrombophilen Defekten (Antiphospholipidsyndrom, schwerem familiären Antithrombin-, Protein-C- oder Protein-S-Mangel). Zunächst auf ein Jahr befristen wird man die Erhaltungstherapie bei einer ersten idiopathischen Episode von VTE oder mittelschweren (z. B. kombinierten) thrombophilen Defekten. Der einfache heterozygote Faktor-V-Leiden-Defekt oder die Prothrombin-20210-Variante fallen nicht darunter. Das Rezidiv einer idiopathischen Thrombose wiederum sollte Anlass für eine längerfristige oder dauerhafte Erhaltungstherapie sein. Jede Entscheidung über die Dauer muss eine – periodisch wiederholte – Abschätzung des individuellen Blutungsrisikos beinhalten und individuelle Präferenzen des Patienten berücksichtigen. Als alternative Medikation zur Erhaltungstherapie stehen zurzeit niedermolekulare Heparine zur Verfügung. Neue parenterale und oral zu verabreichende Wirkstoffe befinden sich in der klinischen Erprobung.