APAC treatment limits collar-induced carotid atherosclerotic plaque development in apoE-/- mice

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Dutch Heart Foundation

Introduction and aim: Mimics of mast cell-derived heparin proteoglycans (HEP-PG) can be tailored to molecules carrying both antiplatelet and anticoagulant properties. These dual antiplatelet and anticoagulant (APAC) constructs can also shield adhesion molecules such as P-selectin and VCAM-1 expressed by endothelial cells upon atherosclerosis development. We hypothesize that via this way, APAC prevents macrophage accumulation and lesion development. In this study, we therefore determined the efficacy of APAC in inhibiting atherosclerosis.

Methods

Male western-type diet fed apoE-/- mice were equipped with perivascular carotid artery collars to induce atherosclerosis. In this collar model, mRNA expression of adhesion molecules such as ICAM-1, VCAM-1, P-Selectin but also of Platelet Factor 4 (PF4) are significantly upregulated upon lesion development (all P<0.05 at 2 weeks after collar placement compared with control arteries). From lesion initiation, mice were treated with 0.2 mg/kg APAC or vehicle control (i.v, 3x per week, n=12-14 per group) for 2.5 weeks. At 5 weeks after collar placement, mice were sacrificed.

Results

APAC treatment did not affect body weight or plasma total cholesterol levels of the mice during the experiment. Interestingly, carotid artery plaque size was reduced by over 50% upon APAC treatment (APAC: 50±10*10E3 versus controls: 102±13*10E3 square µm; P<0.01). This observation was aligned with reduced plaque macrophage area (APAC: 20±5*10E3 versus controls: 33±5*10E3 square µm) and collagen content (APAC: 13±4*10E3 versus controls: 28±6*10E3 square µm; P<0.05).

Conclusion

We here show that APAC effectively inhibits atherosclerotic lesion development when administered during lesion initiation and may have potential as therapeutic agent to prevent atherosclerosis.

Levels of the cancer biomarker CA 19-9 are associated with thrombin generation in plasma from treatment-naïve pancreatic cancer patients

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is associated with a hypercoagulable state and high mortality. Increases in the plasma levels of tumor marker carbohydrate antigen (CA) 19-9 are used in diagnosis and follow-up but have also been reported to precede venous thromboembolism (VTE).

AIMS

We examined the association between CA 19-9 and thrombin generation (TG) in plasma from PDAC patients, as well as their association with coagulation biomarkers prior to pancreatic surgery. In addition, we determined the effect of commercial sources of CA 19-9 on TG.

METHODS

We collected plasma from 58 treatment-naïve PDAC patients without any signs of VTE. We measured levels of CA 19-9, FVIII, fibrinogen, D-dimer, antithrombin and extracellular vesicle (EV) tissue factor (TF) activity and TG using a Calibrated Automated Thrombogram (CAT). The effect of different commercial sources of CA 19-9 on TG in Standard Human Plasma (SHP) was also studied.

RESULTS

Patient plasma samples were divided into 4 preoperative groups based on the level of CA 19-9: none < 2, low = 3-200, high = 201-1000, and very high > 1000 U/mL. CA 19-9 levels were associated with several of the TG parameters, including endogenous thrombin potential, peak, and time to peak. CA 19-9 did not associate with any of the coagulation biomarkers. Spiking of SHP with CA 19-9 increased TG but this was decreased by an anti-TF antibody.

CONCLUSIONS

CA 19-9 was associated with TG in patients prior to any pancreatic cancer treatments or signs of VTE. Some commercial sources of CA 19-9 enhanced TG in SHP seemingly due to contaminating TF.

Abnormal coagulation and enhanced fibrinolysis due to lysinuric protein intolerance associates with bleeds and renal impairment

INTRODUCTION

Lysinuric protein intolerance (LPI), a rare autosomal recessive transport disorder of cationic amino acids lysine, arginine and ornithine, affects intestines, lungs, liver and kidneys. LPI patients may display potentially life-threatening bleeding events, which are poorly understood.

AIMS

To characterize alterations in haemostatic and fibrinolytic variables associated with LPI.

METHODS

We enrolled 15 adult patients (8 female) and assessed the clinical ISTH/SSC-BAT bleeding score (BS). A variety of metabolic and coagulation assays, including fibrin generation test derivatives, clotting time (CT) and clot lysis time (CLT), thromboelastometry (ROTEM), and PFA-100 and Calibrated Automated Thrombogram (CAT), were used.

RESULTS

All patients had mild-to-moderate renal insufficiency, and moderate bleeding tendency (BS 4) without spontaneous bleeds. Mild anaemia and thrombocytopenia occurred. Traditional clotting times were normal, but in contrast, CT in fibrin generation test, and especially ROTEM FIBTEM was abnormal. The patients showed impaired primary haemostasis in PFA, irrespective of normal von Willebrand factor activity, but together with lowered fibrinogen and FXIII. Thrombin generation (TG) was reduced in vitro, according to CAT-derived endogenous thrombin potential, but in vivo TG was enhanced in the form of circulating prothrombin fragment 1 and 2 values. Very high D-dimer and plasmin-α2-antiplasmin (PAP) complex levels coincided with shortened CLT in vitro.

CONCLUSIONS

Defective primary haemostasis, coagulopathy, fibrin abnormality (FIBTEM, CT and CLT), low TG in vitro and clearly augmented fibrinolysis (PAP and D-dimer) in vivo were all detected in LPI. Altered fibrin generation and hyperfibrinolysis were associated with the metabolic and renal defect, suggesting a pathogenetic link in LPI.

Comprehensive re-evaluation of historical von Willebrand disease diagnosis in association with whole blood platelet aggregation and function

INTRODUCTION

Diagnosis of von Willebrand disease (VWD) is challenging, particularly for type 1. The current diagnostic guidelines emphasize simultaneous bleeding symptoms and von Willebrand factor (VWF) levels of <30-40 IU/dL. Historical diagnoses require updated evaluation. We assessed the accuracy of past VWD diagnoses in our comprehensive care center with the standardized bleeding score (BS) and central laboratory analysis, focusing on VWF-dependent platelet functions in whole blood.

METHODS

Our study comprised 83 adults with prior VWD who were diagnosed a median of 20 years ago. We assessed BS, VWF antigen and activity (minimum of 3 measurements), FVIII, PFA-100^® , and platelet aggregation via Multiplate^® . Genetic testing was targeted to types 3, 2N, 2B, and equivocal cases.

RESULTS

All 13/13 (100%) type 3 and 29/32 (90%) type 2, but only 10/38 (26%) of type 1 (overall 52/83 (63%)) patients met the current criteria for VWD. All confirmed cases had abnormal BS, impaired PFA-100^® , and decreased or absent ristocetin-induced platelet aggregation (RIPA), except subtype 2B. VWF, FVIII, RIPA, and PFA correlated with BS including all study subjects. Ten of the 38 patients with previous type 1 had low VWF (35-50 IU/dL) and variable VWF-dependent platelet function. Altogether, 21/83 patients (25%) had repeatedly normal VWF:RCo (>50 IU/dL).

CONCLUSION

von Willebrand disease is associated with impaired VWF-dependent whole blood platelet functions that match traditional VWF measurements. We detected normal VWF in 25% of historically diagnosed patients, mainly type 1 patients, implying that there is a need to systematically re-evaluate historical VWD diagnoses.

Effect of Val34Leu Polymorphism on the Activation of the Coagulation Factor XIII-A

Coagulation factor XIII (FXIII) is a protransglutaminase involved in the last step of the coagulation cascade by stabilising the fibrin clot. Recently, a common variation (FXIII Val34Leu) has been associated with a decreased risk of myocardial infarction and deep venous thrombosis. Val34Leu is critically located near the thrombin activation site of FXIII-A. In this study we investigated its effects on the activation of FXIII. Both recombinant and platelet-derived FXIII Val34Leu variants were shown to be more susceptible to thrombin cleavage than the wild type FXIII. The rate of enzymatic activation of FXIII Val34Leu was found increased, however, the specific activity of fully activated wild type FXIII and the Val34Leu mutant did not differ. During the course of thrombin-induced activation of FXIII fibrin γ-chain dimerisation and α-chain polymerisation developed more rapidly with the Val34Leu mutant. The increased rate of fibrin stabilisation brought about by the Val34Leu FXIII seems to be paradoxically associated with a protective effect against pathological thrombosis.

Abbreviations: AP, activation peptide of factor XIII; FXIII, blood coagulation factor XIII; FXIII-A, factor XIII subunit A; FXIII-A’, proteolytically activated subunit A; FXIII-B, factor XIII subunit B; SDS PAGE, sodium dodecyl sulfate polyacrylamide gel electrophoresis

Natural history and clinical characteristics of inhibitors in previously treated haemophilia A patients: a case series

BACKGROUND

Development of inhibitors is the most serious complication in haemophilia A treatment. The assessment of risk for inhibitor formation in new or modified factor concentrates is traditionally performed in previously treated patients (PTPs). However, evidence on risk factors for and natural history of inhibitors has been generated mostly in previously untreated patients (PUPs). The purpose of this study was to examine cases of de novo inhibitors in PTPs reported in the scientific literature and to the EUropean HAemophilia Safety Surveillance (EUHASS) programme, and explore determinants and course of inhibitor development.

METHODS

We used a case series study design and developed a case report form to collect patient level data; including detection, inhibitor course, treatment, factor VIII products used and events that may trigger inhibitor development (surgery, vaccination, immune disorders, malignancy, product switch).

RESULTS

We identified 19 publications that reported 38 inhibitor cases and 45 cases from 31 EUHASS centres. Individual patient data were collected for 55/83 (66%) inhibitor cases out of 12 330 patients. The median (range) peak inhibitor titre was 4.4 (0.5-135.0), the proportion of transient inhibitors was 33% and only two cases of 12 undergoing immune tolerance induction failed this treatment. In the two months before inhibitor development, surgery was reported in nine (22%) cases, and high intensity treatment periods reported in seven (17%) cases.

CONCLUSIONS

By studying the largest cohort of inhibitor development in PTPs assembled to date, we showed that inhibitor development in PTPs, is on average, a milder event than in PUPs.

Inhibitor development in previously untreated patients with severe haemophilia A: a nationwide multicentre study in Finland

INTRODUCTION

Currently the most serious treatment complication of haemophilia is the inhibitor development (ID), i.e. neutralizing antibody development.

AIM

This nationwide multicentre study in Finland evaluated the incidence and risk factors of ID in previously untreated patients (PUPs) with severe haemophilia A (FVIII:C < 0.01 IU mL(-1) ).

METHODS

We enrolled all PUPs (N = 62) born between June 1994 and May 2013 with at least 75 exposure days (EDs) to screen ID during follow-up extending to September 2013.

RESULTS

Thirteen ID (21% of 62) occurred; 10 (16% of 62) with high titre. Fifty-one patients (82%) were on primary prophylaxis (regular prophylaxis before the age of 2 and before the first joint bleed) from the median age of 11.4 months, 90% via a central venous access device. The initial product was rFVIII in 63% and pd-FVIII in 37%, moreover in 24% pd-FVIII was switched to rFVIII concentrate during the 75 EDs. Non-transient inhibitors developed in 9/51 (17.6%; 13.7% high titre) children with primary and in 4/11 (36.4%; 27.3% high titre) patients with secondary prophylaxis (P = 0.24). Overall, 74% had a high-risk genotype similarly distributed among the prophylaxis groups. The history of a major bleed enhanced ID (aHR, 4.0; 95% CI, 1.2-13.7), whereas FVIII treatment intensity or source and early implantation of ports did not increase ID risk.

CONCLUSION

The cumulative incidence of ID was low notwithstanding prevalent high-risk mutations. Despite patient-related risk factors, our management involving early intensive primary prophylaxis via ports helps to prevent bleeds and lower the incidence of inhibitors.

Interplay between Coagulation and Inflammation in Open and Endovascular Abdominal Aortic Aneurysm Repair — Impact of Intra-Aneurysmal Thrombus

Aims:

Our aim was to compare hemostatic and inflammatory mechanisms in abdominal aortic aneurysm (AAA) patients after open surgery (OPEN) and endovascular AAA repair (ENDO).

Subjects and Methods:

From the 32 consecutive AAA patients recruited, 17 represented ENDO and 15 OPEN. The intra-aneurysmal thrombus was removed during OPEN, but stayed intact after ENDO. The pre-operative volume of the intra-aneurysmal thrombus was calculated from computed tomography images. Markers of coagulation and inflammation were studied pre-operatively, at one, two, three, four and seven days and at three months postoperatively.

Results:

Preoperative upregulation of F 1 + 2, TAT and D-dimer was evident in both groups. The volume of intra-aneurysmal thrombus correlated with CRP (β=0.62, p=0.001), IL-6 (β=0.60, p=0.001) and PAI-1 ag (β=0.51, p=0.007). Surgery further enhanced inflammation, coagulation and fibrinolysis. IL-6 increased in both groups, but the increases of CRP and PIIINP were higher in the OPEN group. Postoperative CRP correlated with the intra-aneurysmal thrombus volume in the ENDO group. At three months D-dimer (p<0.05) was higher than pre-operatively in the ENDO, in contrast to the OPEN group.

Conclusion:

Preoperatively both prothrombotic and fibrinolytic mechanisms are activated in patients with AAA. Intraluminal thrombus induces prothrombotic and inflammatory interactions, which persist after endovascular aortic aneurysm repair.

Safety surveillance in haemophilia and allied disorders

The introduction of clotting factor concentrates has transformed the lives of persons with inherited bleeding disorders. With the use of prophylactic treatment, it is now possible to prevent bleeding in these individuals. The early concentrates were contaminated with the HIV and hepatitis C viruses (HCV) and resulted in major morbidity and mortality in the recipients. Current products are much safer, especially in terms of infectious agents, but other adverse events such as alloantibodies (inhibitors), allergic reactions and thrombotic risks remain of concern. Approximately 30% of previously untreated patients with severe haemophilia A develop inhibitors, making this the most important issue in haemophilia care today. Recently, it was suggested that one of the most commonly used concentrates was associated with a higher inhibitor risk, but this was not supported by the evidence from all studies. Good safety surveillance systems are essential for all diseases and products but are particularly so in the group of individuals with inherited bleeding disorders treated with clotting factor concentrates who have suffered disproportionately from the adverse effects of their treatment. National and multinational systems are now in place to allow reporting of adverse events in patients with inherited bleeding disorders. All clinicians treating individuals with inherited bleeding disorders should prospectively report adverse events to treatment even if they are believed to be common and well recognized.

Managing haemophilia for life: 4th Haemophilia Global Summit

The 4th Haemophilia Global Summit was held in Potsdam, Germany, in September 2013 and brought together an international faculty of haemophilia experts and delegates from multidisciplinary backgrounds. The programme was designed by an independent Scientific Steering Committee of haemophilia experts and explored global perspectives in haemophilia care, discussing practical approaches to the optimal management of haemophilia now and in the future. The topics outlined in this supplement were selected by the Scientific Steering Committee for their relevance and potential to influence haemophilia care globally. In this supplement from the meeting, Jan Astermark reviews current understanding of risk factors for the development of inhibitory antibodies and discusses whether this risk can be modulated and minimized. Factors key to the improvement of joint health in people with haemophilia are explored, with Carlo Martinoli and Víctor Jiménez-Yuste discussing the utility of ultrasound for the early detection of haemophilic arthropathy. Other aspects of care necessary for the prevention and management of joint disease in people with haemophilia are outlined by Thomas Hilberg and Sébastian Lobet, who highlight the therapeutic benefits of physiotherapy and sports therapy. Riitta Lassila and Carlo-Federico Perno describe current knowledge surrounding the risk of transmission of infectious agents via clotting factor concentrates. Finally, different types of extended half-life technology are evaluated by Mike Laffan, with a focus on the practicalities and challenges associated with these products.

Phenotypic and genotypic characterization of 10 Finnish patients with von Willebrand disease type 3: discovery of two main mutations

Severe von Willebrand's disease (VWD) type 3 is a rare autosomal-recessively inherited bleeding disorder, showing considerable genotypic heterogeneity. We investigated the phenotype in correlation with the genotype in Finnish type 3 VWD patients. Ten patients previously diagnosed with VWD type 3 treated at the Coagulation Disorder Unit in Helsinki University Hospital were re-evaluated for bleeding tendency and treatment. Phenotypic characterization included coagulation and platelet function testing confirming the diagnosis. The genotype was assessed by initial screening for the common c.2435delC mutation and subsequently if needed, by analysing all 51 coding exons of the von Willebrand factor gene. Our result confirmed the diagnosis of type 3 VWD for all 10 patients. We discovered two common mutations: nine of the 20 alleles (45%) were found to carry the c.2435delC frameshift mutation, previously described to be frequent in countries surrounding the Baltic Sea. The nonsense mutation c.4975C>T (p.R1659X) was found on 8/20 (40%) of the alleles. In addition, three novel mutations, a potential splice site mutation (c.874+2T>C) and two frameshift mutations (c.1668delC and c.2072delCCinsG) were found. Seven patients were homozygous and three compound heterozygous for the reported mutations. This study indicates that mainly two mutations (c.2435delC and p.R1659X) cause the majority of type 3 VWD in Finland. This result sets future standards for the genetic testing among the Finnish type 3 VWD population.

von Willebrand's disease: a report from a meeting in the Åland islands

von Willebrand's disease (VWD) is probably the most common bleeding disorder, with some studies indicating that up to 1% of the population may have the condition. Over recent years interest in VWD has fallen compared to that of haemophilia, partly the result of focus on blood-borne diseases such as HIV and hepatitis. Now the time has come to revisit VWD, and in view of this some 60 international physicians with clinical and scientific interest in VWD met over 4 days in 2010 in the Åland islands to discuss state-of-the-art issues in the disease. The Åland islands are where Erik von Willebrand had first observed a bleeding disorder in a number of members of a family from Föglö, and 2010 was also the 140th anniversary of his birth. This report summarizes the main papers presented at the symposium; topics ranged from genetics and biochemistry through to classification of VWD, pharmacokinetics and laboratory assays used in the diagnosis of the disease, inhibitors, treatment guidelines in different age groups including the elderly who often have comorbid conditions that present challenges, and prophylaxis. Other topics included managing surgeries in patients with VWD and the role of FVIII in VWF replacement, a controversial subject.

Role and Management of Coagulation Disorders in Peripheral Arterial Disease

Peripheral arterial disease (PAD) has often underlying risk factors, of which diabetes and cigarette smoking are the most common. Enhanced platelet activation and interaction with vessel wall associate with atherothrombotic disease, but also increased fibrinogen levels, thrombin generation and fibrin turnover are typical for PAD. The pathogenic role of fibrinogen, thrombin formation and fibrin degradation is suggested not only in acute thrombotic complications, but also in the stable form of PAD, where these markers associate with the functional severity (ankle-brachial blood pressure index). The coagulation-specific etiologies of PAD should be suspected if the atherothrombotic disease has severe manifestations, especially while the traditional risk factors are absent, or if the patient has also a history of venous thromboembolism. Malignant disease may be present in form of peripheral arterial thrombosis as well. Thrombophilia may expose patients to idiopathic thrombosis – both spontaneously and after vascular interventions. The management of these patients includes often combination therapies with antiplatelet agents and anticoagulants. Obviously, the strict policy to avoid risk factors and to treat them well in avoidance of progression of arterial disease is highly important. In the absence of published follow-up data the evidence to support the management strategies is weak and individual tailoring of efficacious and safe antithrombotic drug therapy remains our challenge. These patients benefit from continuous medical attention by the experts in the field of angiology. Management of PAD is an excellent example of the multidisciplinary approach where the hematologist meets the vascular surgeon or interventional radiologist to secure the best available patient care.

Management of post-partum haemorrhage

Management of post-partum haemorrhage (PPH) involves the treatment of uterine atony, evacuation of retained placenta or placental fragments, surgery due to uterine or birth canal trauma, balloon tamponade, effective volume replacement and transfusion therapy, and occasionally, selective arterial embolization. This article aims at introducing pregnancy- and haemorrhage-induced changes in coagulation and fibrinolysis and their relevant compensatory mechanisms, volume replacement therapy, optimal transfusion of blood products, and coagulation factor concentrates, and briefly cell salvage, management of uterine atony, surgical interventions, and selective arterial embolization. Special attention, respective management, and follow-up are required in women with bleeding disorders, such as von Willebrand disease, carriers of haemophilia A or B, and rare coagulation factor deficiencies. We also provide a proposal for practical instructions in the treatment of PPH.

Current challenges of pharmacovigilance in bleeding disorders: converting the burden to benefit

SUMMARY

Safety surveillance studies have proven essential in research and development of new biological therapies for bleeding disorders as well as other diseases. Although product safety regarding HIV, hepatitis, and other blood-borne infections is currently excellent, potential new infectious agents require continued vigilant monitoring. Inhibitor development is the most common serious side effect of haemophilia replacement therapy. Several aetiological factors associated with inhibitors have been identified, but their true impact is still largely unknown. Moreover, whether plasma-derived and recombinant factor products differ in their immunogenic profiles is an unresolved issue. Coagulation factor products under development and those currently on the market require uniform, long-term surveillance. The European Haemophilia Safety Surveillance (EUHASS) project was recently established to meet these goals. The pharmaceutical industry and clinicians face common challenges complying with these requirements. In rare diseases like haemophilia, obtaining adequate patient numbers poses a challenge. Another challenge is a lack of methods for assessing disease severity, a surprising deficiency in the era of modern medical and laboratory technology. National and international registries can be used to gather required safety surveillance information. Simultaneously, clinicians benefit from well-organized registry data in their daily practice and harmonize the quality of comprehensive haemophilia care by homogeneous follow-up platforms. Experience with such registries comes, for example, from Europe (PEDNET), the USA (CDC/UDC), the UK (UKHCDO), and Sweden (Malmö). It is important to commit to future pharmacovigilance efforts, aiming at high-quality safety surveillance programmes at both the pharmaceutical research community and clinical levels.

Peripheral arterial disease--natural outcome

Three hundred and twelve patients with peripheral arterial disease were followed up for 8 3/4 years or more (maximum 11 3/4 years) to assess the natural history of the disease and factors determining its outcome. Of the 312 patients, 188 (69%) died during the follow-up, 68% of the deaths having cardiovascular causes. The 10-year relative cumulative survival rate was 0.61 for males and 0.48 for females. The role of smoking as a risk factor could not be analysed without bias. In addition to known risk factors diabetes mellitus, cerebrovascular disease and coronary heart disease, the degree of peripheral arterial disease itself also proved to be a risk factor among men. The expected life lost for men with intermittent claudication was 20%, but 44.3% for men with advanced lower limb ischaemia (p less than 0.01). This difference could not be explained by the well-known association of advanced ischaemia and diabetes mellitus. The present results therefore suggest that the state of advanced ischaemia indicates larger involvement of the whole of the arterial tree and predicts fatal cardiovascular events among these patients.

Migration at early age from a high to a lower coronary heart disease risk country lowers the risk of subclinical atherosclerosis in middle-aged men

BACKGROUND

Study of migrants offers a natural model to assess environmental risk of coronary heart disease (CHD) in countries differing in CHD occurrence. In Sweden, CHD risk has been markedly lower than in Finland from where a large migration occurred in the 1970s.

OBJECTIVES

To study the structural and functional markers of subclinical atherosclerosis in twin pairs discordant for migration with the main focus on age at migration, length of residence and integration into Swedish society after migration from a high to a lower CHD risk country.

METHODS

Carotid intima-media thickness (IMT) and brachial artery endothelial function (EF) were assessed with high-resolution ultrasound and a set of cardiovascular, socio-economic and psychosocial risk factors were estimated in 76 middle-aged male twin pairs discordant for migration from Finland to Sweden.

RESULTS

Men who had migrated in adolescence had lower IMT values compared with their co-twins living in Finland (0.665 +/- 0.114 vs. 0.802 +/- 0.167 mm, P = 0.009). Also men who integrated well to Swedish society had lower (0.720 +/- 0.154 vs. 0.799 +/- 0.207 mm, P = 0.013) IMT values than their twin brothers living in Finland. Associations between IMT and migration age and between IMT and integration remained significant in multivariate analyses of several CHD risk factors. The intrapair difference in IMT was significantly associated with immigration age and integration (ANOVA, P = 0.0082), the difference being greatest among pairs where the brother living in Sweden had migrated at early age and integrated well to Swedish society. EF was better in men who had migrated to Sweden before the age of 21 years, but not later, compared with their co-twins in Finland (6.4 +/- 4.6% vs. 3.8 +/- 3.6%, P = 0.025).

CONCLUSIONS

Migration at an early age and good integration are beneficial to vascular health associated with moving from a high to a lower CHD risk country, suggesting that an environment-sensitive period influences atherogenesis before adulthood.

Successful liver-kidney transplantation in two children with aHUS caused by a mutation in complement factor H

A 12-month-old boy and his 16-year-old aunt became acutely ill 6 months apart and were diagnosed to have atypical hemolytic uremic syndrome (aHUS). Genetic analysis revealed heterozygous R1215Q mutation in complement factor H (CFH) in both patients. The same mutation was found in five healthy adult relatives indicating incomplete penetrance of the disease. The patients developed terminal renal failure and experienced reversible neurological symptoms in spite of plasma exchange (PE) therapy. In both cases, liver-kidney transplantation was successfully performed 6 months after the onset of the disease. To minimize complement activation and prevent thrombotic microangiopathy or overt thrombotic events due to the malfunctioning CFH, extensive PE with fresh frozen plasma was performed pre- and perioperatively and anticoagulation was started a few hours after the operation. No circulatory complications appeared and all four grafts started to function immediately. Also, no recurrence or other major clinical setbacks have appeared during the postoperative follow-up (15 and 9 months) and the grafts show excellent function. While more experience is needed, it seems that liver-kidney transplantation combined with pre- and perioperative PE is a rational option in the management of patients with aHUS caused by CFH mutation.

Protease-activated receptor-induced Akt activation--regulation and possible function

BACKGROUND

Thrombin induces the activation of the platelet serine/threonine kinase Akt. Akt activation is dependent on its phosphorylation at Thr308 and Ser473. The mechanism by which thrombin induces Akt phosphorylation is controversial, as is the role of Akt in platelet function.

OBJECTIVES

To investigate how protease-activated receptors (PARs) stimulate Akt and the role that Akt plays in human platelet function.

METHODS

Platelets were stimulated through PAR1 or PAR4. Specific inhibitors were used to evaluate, by Western blotting, signaling pathways regulating Akt phosphorylation, and the role of activated Akt was evaluated by aggregometry and flow cytometry.

RESULTS

Phospholipase C (PLC) controls Akt phosphorylation elicited by PARs. Stimulation of PAR1 or PAR4 resulted in rapid Akt phosphorylation, independently of secreted ADP and phosphatidylinositol-3-kinase (PI3K) activation. Akt phosphorylation approximately 60 s after PAR1 stimulation became entirely dependent on the purinergic receptor P2Y(12) and the activation of PI3K. In contrast, PAR4 partially sustained Akt phosphorylation independently of P2Y(12) and PI3K for up to 300 s. Pharmacologic inhibition of Akt reduced P-selectin expression and fibrinogen binding in platelets stimulated through PAR1, and delayed platelet aggregation in response to submaximal PAR1 or PAR4 stimulation, although aggregation at 300 s was unaffected.

CONCLUSIONS

Platelet PAR stimulation causes rapid Akt phosphorylation downstream of PLC, whereas with continuous stimulation, ADP and PI3K are required for maintaining Akt phosphorylation. Activated Akt regulates platelet function by modulating secretion and alpha(IIb)beta(3) activation.

Should prophylaxis be used in adolescent and adult patients with severe haemophilia? An European survey of practice and outcome data

A survey of 21 haemophilia doctors, throughout Europe, who care for a total of approximately 5000 patients with bleeding disorders addressing practice and opinions regarding prophylaxis in patients aged 16-24 years and adults aged over 50 years, is presented. The outcome of adolescent patients who reduced or stopped prophylaxis was recorded. Eighteen of 19 respondents would consider modification of established prophylaxis in the adolescent age group, principal considerations being avoidance of risks of further concentrate exposure, predicted poor compliance and treatment costs. The preferred age for modification was 16-20 years, but there was very little consensus on the particular prophylactic regime recommended. Approximately, half of a cohort of 218 patients with severe haemophilia successfully reduced or stopped prophylaxis when they reached adolescence. Only 26 of 92 (28%) of the patient cohort who stopped prophylaxis, required reintroduction of a prophylactic regime and 12 of 59 (20%) of those who reduced the intensity of prophylaxis had to reintroduce a more intensive regime. A majority of respondents would consider starting prophylaxis in those over 50 years. There was no consensus as to indications for this practice or the nature of the prophylaxis protocol. We conclude that there is an absence of consensus on the management of patients with severe haemophilia, as they pass through adolescence and young adulthood, and reach the age of 50. Aggregate outcome data suggest a significant proportion of patients in the 18-22 years age range may be able to reduce or stop prophylaxis. A substantial number of older patients are on prophylaxis.

Thrombin generation during reperfusion after coronary artery bypass surgery associates with postoperative myocardial damage

BACKGROUND

Cardiopulmonary bypass and coronary artery bypass grafting (CABG) result in significant thrombin generation and activation of fibrinolysis. Thrombin contributes to myocardial ischemia-reperfusion injury in animal studies, but the role of thrombin in myocardial damage after CABG is unknown.

OBJECTIVES

We measured thrombin generation and fibrin turnover during reperfusion after CABG to evaluate their associations with postoperative hemodynamic changes and myocardial damage.

METHODS

One hundred patients undergoing primary, elective, on-pump CABG were prospectively enrolled. Plasma prothrombin fragment F(1+2) and D-dimer were measured preoperatively and at seven time points thereafter. Mass of the Mb fraction of creatine kinase (Ck-Mbm) and troponin T (TnT) were measured on the first postoperative day.

RESULTS

Reperfusion induced an escalation of thrombin generation and fibrin turnover despite full heparinization. F(1+2) during early reperfusion associated with postoperative pulmonary vascular resistance index. F(1+2) at 6 h after protamine administration correlated with Ck-Mbm (r = 0.40, P < 0.001) and TnT (r = 0.44, P < 0.001) at 18 h postoperatively. Patients with evidence of myocardial damage (highest quintiles of plasma Ck-Mbm and TnT) had significantly higher F(1+2) during reperfusion than others (P < 0.002). Logistic regression models identified F(1+2) during reperfusion to independently associate with postoperative myocardial damage (odds ratios 2.5-4.4, 95% confidence intervals 1.04-15.7).

CONCLUSIONS

Reperfusion caused a burst in thrombin generation and fibrin turnover despite generous heparinization. Thrombin generation during reperfusion after CABG associated with pulmonary vascular resistance and postoperative myocardial damage.

Recommendations for postmarketing surveillance studies in haemophilia and other bleeding disorders

Prospective surveillance studies to monitor drug safety in the postapproval period are rarely employed systematically, although they are of greatest value for caregivers, drug users and regulatory authorities. Safety issues have affected not only conventional pharmaceuticals, but also especially coagulation factors in haemophilia treatment. The reputation of postmarketing surveillance (PMS) studies has been questionable, mainly due to their misuse to solicit prescriptions. Other weaknesses include inappropriate design, lack of standardized observation, limited follow-up periods, absence of rigour in identifying potential adverse drug effects, and infrequent publication. Although well-designed clinical trials represent the gold standard for generating sound clinical evidence, a number of aspects would make PMS studies valuable, if properly conducted. One of their main advantages is broader inclusion, and absence of an 'experimental' design. Lack of proper guidelines, and standardization may constitute a reason for the generally low quality of PMS studies. This paper proposes guidelines for haemophilia-specific PMS studies, in order to improve the acceptance of a basically valuable tool. In the absence of consistent regulatory guidance it will be especially important that the design and supervision of PMS studies involves physicians from the beginning. This will not only make such studies more scientifically relevant, but also help to implement them into daily clinical practice. Specifically in haemophilia, PMS studies may provide valuable data on clinical outcomes, or Quality of Life, which is of great importance when considering adequate standards of care in haemophilia patients.

Obesity is associated with impaired platelet-inhibitory effect of acetylsalicylic acid in nondiabetic subjects

OBJECTIVE

Platelet aggregation responses to acetylsalicylic acid (ASA) show considerable interindividual variation, the causes of which are largely unknown. We determined whether variation in insulin action is associated with that of ASA on platelets.

SUBJECTS

In all, 10 nonobese (age 50+/-3 y, BMI 25+/-1 kg/m(2)) and 11 obese (age 52+/-2 y, BMI 32+/-1 kg/m(2)) subjects.

MEASUREMENTS

Insulin sensitivity of glucose uptake was determined by the euglycemic insulin clamp technique. Platelet aggregation responses to four doses of arachidonic acid (AA) and adenosine diphosphate (ADP) were assessed in platelet-rich plasma before and 1 h after ingestion of 50 mg ASA using Born's turbidometric aggregometer.

RESULTS

Whole-body insulin sensitivity (M-value 0-180 min) was 36% lower in the obese (4.5+/-0.6) than the nonobese (7.1+/-0.6 mg/kg min, P<0.01) group. Before ASA, all doses of AA induced complete aggregation. After ASA ingestion, ASA inhibited maximal aggregation more in the nonobese than the obese group at AA concentrations of 0.75, 1 and 1.5 mmol/l (P=0.016 for ANOVA). ADP-induced aggregation at high doses (2 and 3 micromol/l) was also less inhibited in the obese group. In vivo insulin sensitivity (r=-0.68, P<0.001 for 1 mmol/l AA) and BMI (r=0.58, P<0.01 for 1 mmol/l AA) were closely correlated with residual aggregation after ASA administration.

CONCLUSION

These data demonstrate that obese insulin-resistant subjects have a blunted response to platelet-inhibitory effect of ASA. If this blunted effect is of a single dose of ASA preserved in continuous use, it could contribute to the increased risk of atherothrombosis in insulin-resistant individuals.

Adhesion molecule expression in symptomatic and asymptomatic carotid stenosis

BACKGROUND

Prior studies have suggested a central role for cellular adhesion molecules (CAMs) in the pathophysiology and symptoms of atherosclerotic carotid plaques (CPs).

OBJECTIVE

This study examined the role of CAMs in symptom generation in patients with advanced carotid artery disease.

METHODS

Ninety-two consecutive patients underwent carotid endarterectomy, six for both sides (54 symptomatic and 41 asymptomatic CPs). Intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), P-selectin, and E-selectin were immunostained in fresh-frozen CP specimens and examined semiquantitatively in the endothelium and intima-media. Plasma concentrations of soluble ICAM-1 and sVCAM-1 were analyzed by ELISA.

RESULTS

Endothelial expression of ICAM-1, VCAM-1, P-selectin, and E-selectin did not differ between symptomatic and asymptomatic CPs, but endothelial ICAM-1 was associated with serum sensitized C-reactive protein levels (p = 0.026). However, there was less ICAM-1 expression in the intima-media of the symptomatic CPs (p = 0.022), and there was a similar, but nonsignificant tendency for VCAM-1. Soluble ICAM-1 and soluble VCAM-1 were not associated with the symptom status.

CONCLUSIONS

In contrast to earlier studies, it was found that symptomatic carotid disease is not associated with increased expression of adhesion molecules in the endothelium of advanced carotid plaques or in circulation. Rather, there was less expression of adhesion molecules in the intima-media of symptomatic carotid plaques.

Abciximab inhibits procoagulant activity but not the release reaction upon collagen- or clot-adherent platelets

In addition to inhibiting platelet (plt) aggregation abciximab, a glycoprotein (GP) IIb/IIIa antagonist, reduces coagulation in blood or platelet-rich plasma. We assessed the effects of abciximab (10 micro g mL(-1)) on adhesion-dependent procoagulant activity (PCA) of plt upon: (i) collagen to model initial adhesion; or (ii) plasma clot or fibrin to model a preformed thrombus with retained thrombin activity. In a two-stage assay gel-filtered plt (GFP) first adhered on collagen, plasma clot, or fibrin, and plt activation was traced with platelet factor 4 (PF 4) release. Second, PCA was measured on adherent plt (i) by soluble prothrombin fragments (F1 + 2); and (ii) chromogenically by adding defibrinated plasma and thromboplastin. Abciximab inhibited aggregation upon collagen-adherent plt both in the absence and presence of plasma. In contrast, without plasma abciximab enhanced plt deposition to fibrin surfaces depending on thrombin generation and fibrin polymerization. However, abciximab reduced PCA and generation of F1 + 2 on adherent plt surface-independently by 35%, whereas PF 4 release persisted. Also, a GP Ib inhibitor, mAb SZ2, attenuated PCA by 40% alone, and by 65% together with abciximab, leaving 35% of PCA unaltered. Abciximab decreased generation of new thrombin on both collagen- and clot-adherent plt. However, abciximab did not inhibit alpha-granule release, suggesting distinct pathways for PCA and release reaction. Deposition of isolated plt on clots in the presence of abciximab was dependent on thrombin and polymerizing plt-derived fibrin(ogen). Due to local consumption of natural anticoagulants adjacent to a preformed thrombus the antithrombotic effect of abciximab benefits from additional inhibition of thrombin.

Epinephrine--via activation of p38-MAPK--abolishes the effect of aspirin on platelet deposition to collagen

The mechanism by which epinephrine enhances experimental thrombosis in the presence of aspirin is poorly understood. In this study, we set to explore, in aspirinised platelet-rich plasma (PRP), the effect of epinephrine (100 nmol/l) on platelet deposition to immobilised collagen and the subsequent involvement of several intracellular pathways. Under these experimental conditions, which allow platelet aggregation on top of the collagen-adherent platelets, epinephrine increased platelet deposition by 55-86%. This enhancement could be specifically prohibited by the alpha(2A)-adrenoceptor antagonist, atipamezole, the p38 mitogen-activated protein kinase (p38MAPK) inhibitor SB203580, and the cytosolic phospholipase A(2) (cPLA(2)) inhibitor, mepacrine. The effect of epinephrine coincided with increased phosphorylation of p38MAPK and cPLA(2) and with arachidonic acid (AA) release from platelet membrane. We conclude that epinephrine enhanced platelet deposition on collagen in aspirinised PRP via a mechanism dependent on both free AA in platelet cytosol (released by cPLA(2)) and p38MAPK.

Activation of coagulation and fibrinolysis during reconstructive microsurgery in patients with cancer

Cancer patients are subjected to increased systemic risk of thrombotic events and may therefore be at higher risk of even local thrombosis compromising the outcome of reconstructive microsurgery. Coagulation and fibrinolysis activities were studied serially during and after reconstructive microsurgery in seven patients with oropharyngeal cancer or sarcoma in the extremities. A preoperative hypercoagulable state was found in four patients (elevated fibrinogen, TAT, F1+2, or D-dimer); two of these patients also had a local thrombotic event. In all patients, the plasma markers generally varied perioperatively: fibrinogen decreased, whereas TAT and subsequently D-dimer increased at the end of the operation. However, tPA and PAI-1 remained unaltered, except in the patients with thrombosis in whom PAI-1 activity increased progressively during the operation. F1+2 was also clearly elevated in these two patients at the time of thrombosis. Preoperative assessment of hypercoagulability for this group of patients could be helpful in targeting meticulous antithrombotic protection.

Activation of coagulation and fibrinolysis in microsurgical reconstructions in the lower extremities

Coagulation and fibrinolysis activities in relation to trauma, surgery and thrombosed microanastomoses were studied during free-flap surgery in eight patients with lower-extremity defects due to recent trauma or chronic ulcers. One patient had an intraoperative thrombosis, and three more patients required reoperations on the same day due to postoperative thromboses; one of these also required a second reoperation due to flap failure. The baseline level of fibrinogen was slightly elevated in all patients except one, and was significantly higher in the patients who underwent reoperation. At the end of the primary surgery, distinct thrombin generation (TAT and F1+2) was seen in three patients with excessive bleeding, and all three later underwent reoperations. One of these patients generated excessive thrombin on the eighth postoperative day, upon removal of a necrotic flap. Thrombin generation (F1+2) was also seen at baseline in the patient with the intraoperative thrombosis, and persisted on the first postoperative day. D-dimer at baseline was higher in patients with recent trauma, and in two of these, both of whom underwent reoperations on the same day, D-dimer remained high perioperatively. Resistance to fibrinolysis with increased PAI-1 levels was seen in these two patients at the time of reoperation. In all, TAT and F1+2 were associated with the threat of flap failure. A preoperative hypercoagulable state and excessive bleeding during the operation were predictors of reoperation. The markers for coagulation and fibrinolysis could be used preoperatively to target antithrombotic control, and postoperatively to detect the threat of flap failure. Meticulous haemostasis during surgery might help to diminish the need for reoperations.

Intraoperative flow predicts the development of stenosis in infrainguinal vein grafts

OBJECTIVE

There are data to suggest that the development of myointimal hyperplasia is affected by long-term alterations in blood flow. However, the clinical relevance of these findings has not been demonstrated.

METHODS

In this retrospective clinical study, intraoperative volume flow measurement with transit time flowmeter was performed in 257 infrainguinal vein grafts carried out in 241 patients. The patients were enrolled in an intensive duplex scanning-based surveillance program. The relationship between the intraoperative graft flow and subsequent occlusion or development of stenosis was evaluated and controlled for other pertinent risk factors.

RESULTS

The median follow-up time was 13.6 months. A graft stenosis was found in 58 grafts. The mean graft flow for event-free grafts was 98 mL/min, which was significantly higher compared with 78 mL/min for stenosed or 69 mL/min for occluded grafts. The patients were divided into four groups according to quartiles of the sample distribution of graft flow measurements. The respective 2-year primary and assisted primary patency rates in the lowest to the highest graft flow groups were 39%, 49%, 47%, and 72% (P =.003) and 55%, 67%, 71%, and 84% (P =.01). Analogous significant differences were observed for maximal flow capacity measurements. Female sex (P =.009) and low graft flow in maximal flow capacity measurements (P =.003) were independent predictors of stenosis development in the multiple regression model.

CONCLUSION

Intraoperative graft volume flow is a predictor of bypass occlusion after infrainguinal bypass. In addition, this study verifies an association between the development of clinically evident graft stenoses and low graft flow.

Variability in platelet responses to collagen--comparison between whole blood perfusions, traditional platelet function tests and PFA-100

The purpose of this study was to determine if the results obtained in platelet function tests and whole blood perfusions are associated with those in platelet function analyser (PFA)-100. We used collagen type I monomers and fibrils to analyse the distinct roles of glycoprotein (GP) Ia/IIa and other collagen receptors in flowing blood under a high shear rate (1600/s) and in aggregation studies. Also, anticoagulation [citrate vs. D-phenylalanyl-1-prolyl-1 arginine chloromethyl ketone (PPACK)] was varied to enhance the functions of GP Ia/IIa, since it has been shown that the cation-poor environment of citrated blood impairs GP Ia/IIa-dependent platelet recruitment. Large interindividual variability (45-fold) was detected in deposition of platelets in whole blood perfusions over collagen monomers, whereas this variation was only fourfold in fibrils. In PFA, this variation was reduced to 2.5-fold. However, platelet deposition on monomers is associated with epinephrine-enhanced PFA (r=-.49, P<.03), whereas platelet deposition on fibrils is correlated with adenosine diphosphate (ADP)-enhanced PFA (r=-.47, P<.05), suggesting a distinct synergism between epinephrine and monomers (GP Ia/IIa) as well as ADP with fibrils (other collagen receptors). Donors with 807 C/C polymorphism of GP Ia (n=14) had longer lag phase in aggregation experiments compared with C/T (n=7) both by monomers and fibrils (P<.04), but these polymorphisms with their mild impact on GP Ia/IIa activity did not markedly differ in other tests. In conclusion, the results obtained in perfusion studies and PFA experiments correlated, but PFA fails to reveal the large-scale variability related to collagen-induced platelet responses.

Immunologic and hematologic properties of antibodies to prothrombin and plasminogen in a mouse model

Antibodies to prothrombin have been associated with venous and arterial thrombosis, and they cross-react with a structurally closely related protein plasminogen. We immunised 16 mice with human prothrombin and 15 mice with human plasminogen. Mice immunised with prothrombin developed cross-reactive antibodies to plasminogen (12/16), beta2-glycoprotein I (4/16), tissue-type plasminogen activator (6/16) and cardiolipin (11/16). Mice immunised with plasminogen developed cross-reactive antibodies to prothrombin (8/15), tissue-type plasminogen activator (2/12) and cardiolipin (5/12). Functional effects of antibodies were examined. Immunisation with prothrombin induced lupus anticoagulant activity in 9/14 mice. In mice immunised with plasminogen, radial fibrinolysis was inhibited in 8/10 and plasminogen activation in the chromogenic assay was inhibited in 9/11. No cross-functionality was observed. In conclusion, antibodies to prothrombin and plasminogen cross-react in vivo. Antibodies to prothrombin and plasminogen have different functional profiles, immunisation with prothrombin leads to prolonged blood clotting time, and immunisation with plasminogen induces antibodies interfering with fibrinolysis.

Procoagulant activity on platelets adhered to collagen or plasma clot

In a new 2-stage assay of platelet procoagulant activity (PCA), we first subjected gel-filtered platelets to adhesion on collagen (as a model of primary hemostasis) or plasma clots (as a model of preformed thrombus) for 30 minutes, and then the adherent platelets were supplemented with pooled, reptilase-treated, diluted plasma. Defibrinated plasma provided coagulation factors for assembly on platelet membranes without uncontrolled binding of thrombin to fibrin(ogen). Platelet adhesion to both surfaces showed modest individual variation, which increased at platelet densities that allowed aggregation. However, adhesion-induced PCA varied individually and surface-independently >3-fold, suggesting a uniform platelet procoagulant mechanism. Permanently adhered platelets showed markedly enhanced PCA when compared with the platelet pool in suspension, even after strong activation. The rate of thrombin generation induced by clot-adherent platelets was markedly faster than on collagen-adherent platelets during the initial phase of coagulation, whereas collagen-induced PCA proceeded slowly, strongly promoted by tissue thromboplastin. Therefore at 10 minutes, after adjustment for adhered platelets, collagen supported soluble thrombin formation as much as 5 times that of the thrombin-retaining clots. Activation of platelets by their firm adhesion was accompanied by formation of microparticles, representing about one third of the total soluble PCA. Collagen-adhered platelets provide soluble thrombin and microparticles, whereas the preformed clot serves to localize and accelerate hemostasis at the injury site, with the contribution of retained thrombin and microparticles.