Chronic excessive erythrocytosis induces endothelial activation and damage in mouse brain

Excessive erythrocytosis results in severely increased blood viscosity, which may have significant detrimental effects on endothelial cells and, ultimately, function of the vascular endothelium. Because blood-brain barrier stability is crucial for normal physiological function, we used our previously characterized erythropoietin-overexpressing transgenic (tg6) mouse line (which has a hematocrit of 0.8-0.9) to investigate the effect of excessive erythrocytosis on vessel number, structure, and integrity in vivo. These mice have abnormally high levels of nitric oxide (NO), a potent proinflammatory molecule, suggesting altered vascular permeability and function. In this study, we observed that brain vessel density of tg6 mice was significantly reduced (16%) and vessel diameter was significantly increased (15%) compared with wild-type mice. Although no significant increases in vascular permeability under normoxic or acute hypoxic conditions (8% O2 for 4 h) were detected, electron-microscopic analysis revealed altered morphological characteristics of the tg6 endothelium. Tg6 brain vascular endothelial cells appeared to be activated, with increased luminal protrusions reminiscent of ongoing inflammatory processes. Consistent with this observation, we detected increased levels of intercellular adhesion molecule-1 and von Willebrand factor, markers of endothelial activation and damage, in brain tissue. We propose that chronic excessive erythrocytosis and sustained high hematocrit cause endothelial damage, which may, ultimately, increase susceptibility to vascular disease.

Autonomic function and prothrombotic activity in women after an acute coronary event

BACKGROUND: The link between decreased heart rate variability (HRV) and atherosclerosis progression is elusive. We hypothesized that reduced HRV relates to increased levels of prothrombotic factors previously shown to predict coronary risk. METHODS: We studied 257 women (aged 56 +/- 7 years) between 3 and 6 months after an acute coronary event and obtained very low frequency (VLF), low frequency (LF), and high frequency (HF) power, and LF/HF ratio from 24-hour ambulatory ECG recordings. Plasma levels of activated clotting factor VII (FVIIa), fibrinogen, von Willebrand factor antigen (VWF:Ag), and plasminogen activator inhibitor-1 (PAI-1) activity were determined, and their levels were aggregated into a standardized composite index of prothrombotic activity. RESULTS: In bivariate analyses, all HRV indices were inversely correlated with the prothrombotic index explaining between 6% and 14% of the variance (p < 0.001). After controlling for sociodemographic factors, index event, menopausal status, cardiac medication, lifestyle factors, self-rated health, metabolic variables, and heart rate, VLF power, LF power, and HF power explained 2%, 5%, and 3%, respectively, of the variance in the prothrombotic index (p < 0.012). There were also independent relationships between VLF power and PAI-1 activity, between LF power and fibrinogen, VWF:Ag, and PAI-1 activity, between HF power and FVIIa and fibrinogen, and between the LF/HF power ratio and PAI-1 activity, explaining between 2% and 3% of the respective variances (p < 0.05). CONCLUSIONS: Decreased HRV was associated with prothrombotic changes partially independent of covariates. Alteration in autonomic function might contribute to prothrombotic activity in women with coronary artery disease (CAD).

Predictors of inflammation in response to anthracycline-based chemotherapy for breast cancer

Although chemotherapy for breast cancer can increase inflammation, few studies have examined predictors of this phenomenon. This study examined potential contributions of demographics, disease characteristics, and treatment regimens to markers of inflammation in response to chemotherapy for breast cancer. Thirty-five women with stage I-III-A breast cancer (mean age 50 years) were studied prior to cycle 1 and prior to cycle 4 of anthracycline-based chemotherapy. Circulating levels of inflammatory markers with high relevance to breast cancer were examined, including C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-alpha), Interleukin-1 receptor antagonist (IL1-RA), vascular endothelial growth factor (VEGF), soluble intercellular adhesion molecule-1 (sICAM-1), Interleukin- (IL-6), soluble P-selectin (sP-selectin), and von Willebrand factor (vWf). Chemotherapy was associated with elevations in VEGF (p < or = 0.01), sICAM-1 (p < or = 0.01), sP-selectin (p < or = 0.02) and vWf (p < or = 0.05). Multiple regression analysis controlling for age and body mass index (BMI) showed that higher post-chemotherapy levels of inflammation were consistently related to higher pre-chemotherapy levels of inflammation (ps < or =0.05) as well as to certain disease characteristics. Post-chemotherapy IL-6 levels were higher in patients who had larger tumors (p < or = 0.05) while post-chemotherapy VEGF levels were higher in patients who had smaller tumors (p < or = 0.05). Post-chemotherapy sP-selectin levels were highest in women who had received epirubicin, cytoxan, 5-fluorouracil chemotherapy (p < or = 0.01). These findings indicate that chemotherapy treatment can be associated with elevations in certain markers of inflammation, particularly markers of endothelial and platelet activation. Inflammation in response to chemotherapy is most significantly related to inflammation that existed prior to chemotherapy but also potentially to treatment regimen and to certain disease characteristics.

Hereditary thrombotic thrombocytopenic purpura and the hereditary TTP registry

Hereditary thrombotic thrombocytopenic purpura, Upshaw-Schulman syndrome, ADAMTS13 Hereditary thrombotic thrombocytopenic purpura (TTP), also known as Upshaw-Schulman syndrome, is a rare recessively inherited disease. Underlying is a severe constitutional deficiency of the von Willebrand factor-cleaving protease, ADAMTS13, due to compound heterozygous or homozygous mutations in the ADAMTS13 gene. The clinical picture is variable and more and more patients with an adult-onset are diagnosed. In the majority of countries the only available treatment is plasma, which when administered regularly can efficiently prevent acute disease bouts. The decision to initiate regular prophylaxis is often not easy, as evidence based guidelines and long term outcome data are lacking. Through the hereditary TTP registry (www.ttpregistry.net, ClinicalTrials.gov identifier: NCT01257269), which was initiated in 2006 and is open to all patients diagnosed with Upshaw-Schulman syndrome and their family members, we aim to gain further information and insights into this rare disease, which eventually will help to improve clinical management of affected patients.

Acquired thrombotic thrombocytopenic purpura. Development of an autoimmune response

The von Willebrand factor (VWF)-cleaving metalloprotease, ADAMTS13 (adisintegrin and metalloprotease with thrombospondin type 1 motifs-13) is the only known target of the dysregulated immune response in acquired TTP. Autoantibodies to ADAMTS13 either neutralize its activity or accelerate its clearance, thereby causing a severe deficiency of ADAMTS13 in plasma. As a consequence, size regulation of VWF is impaired and the persistence of ultra-large VWF (ULVWF) multimers facilitates microvascular platelet aggregation causing microangiopathic haemolytic anaemia and ischaemic organ damage. Autoimmune TTP although a rare disease with an annual incidence of 1.72 cases has a mortality rate of 20% even with adequate therapy. We describe the mechanisms involved in ADAMTS13 autoimmunity with a focus on the role of B- and T-cells in the pathogenesis of this disorder. We discuss the potential translation of recent experimental findings into future therapeutic concepts for the treatment of acquired TTP.

Procoagulant reactivity to laboratory acute mental stress in Africans and Caucasians, and its relation to depressive symptoms: the SABPA study.

The risk of cardiovascular disease is dramatically increasing in Africans (black). The prothrombotic stress response contributes to atherothrombotic disease and is modulated by depressive symptoms. We examined coagulation reactivity to acute mental stress and its relation to psychological well-being in Africans relative to Caucasians (white). A total of 102 African and 165 Caucasian school teachers underwent the Stroop Color-Word Conflict test. Circulating levels of von Willebrand factor (VWF) antigen, fibrinogen, and D-dimer were measured before and after the Stroop. Cardiovascular reactivity measures were also obtained. All participants completed the Patient Health Questionnaire-9 and the General Health Questionnaire-28 for the assessment of depressive symptoms and total psychological distress, respectively. After controlling for covariates, resting levels of VWF, fibrinogen, and D-dimer were higher in Africans than in Caucasians (all p-values ≤0.006). Depressive symptoms and psychological distress were not significantly associated with resting coagulation measures. Stress reactivity in VWF (p<0.001) and fibrinogen (p=0.016), but not in D-dimer (p=0.27), were decreased in Africans relative to Caucasians with Africans showing greater reactivity of total peripheral resistance (p=0.017). Depressive symptoms, but not general psychological distress, were associated with greater VWF increase (p=0.029) and greater fibrinogen decrease (p=0.030) in Africans relative to Caucasians. In conclusion, Africans showed greater hypercoagulability at rest but diminished procoagulant reactivity to acute mental stress when compared with Caucasians. Ethnic differences in the vascular adrenergic stress response might partially explain this finding. Depressive symptoms were associated with exaggerated VWF reactivity in Africans relative to Caucasians. The clinical implications of these findings for Africans need further study.

Evaluation of 9 biomarkers for predicting 10-year cardiovascular risk in patients undergoing coronary angiography: findings from the LUdwigshafen RIsk and Cardiovascular Health (LURIC) study.

BACKGROUND Conventional factors do not fully explain the distribution of cardiovascular outcomes. Biomarkers are known to participate in well-established pathways associated with cardiovascular disease, and may therefore provide further information over and above conventional risk factors. This study sought to determine whether individual and/or combined assessment of 9 biomarkers improved discrimination, calibration and reclassification of cardiovascular mortality. METHODS 3267 patients (2283 men), aged 18-95 years, at intermediate-to-high-risk of cardiovascular disease were followed in this prospective cohort study. Conventional risk factors and biomarkers were included based on forward and backward Cox proportional stepwise selection models. RESULTS During 10-years of follow-up, 546 fatal cardiovascular events occurred. Four biomarkers (interleukin-6, neutrophils, von Willebrand factor, and 25-hydroxyvitamin D) were retained during stepwise selection procedures for subsequent analyses. Simultaneous inclusion of these biomarkers significantly improved discrimination as measured by the C-index (0.78, P = 0.0001), and integrated discrimination improvement (0.0219, P<0.0001). Collectively, these biomarkers improved net reclassification for cardiovascular death by 10.6% (P<0.0001) when added to the conventional risk model. CONCLUSIONS In terms of adverse cardiovascular prognosis, a biomarker panel consisting of interleukin-6, neutrophils, von Willebrand factor, and 25-hydroxyvitamin D offered significant incremental value beyond that conveyed by simple conventional risk factors.

Le purpura thrombotique thrombocytopénique - un diagtnostic méconnu

Le purpura thrombotique thrombocytopénique (PTT) est un diagnostic caractérisé par une hémolyse micro-angiopathique, se traduisant par la présence d’une thrombocytopénie et d’une schizocytose au frottis sanguin. Une déficience de l’enzyme ADAMTS13, enzyme protéolytique du facteur de von Willebrand (vWF), a été caractérisée comme cause pathogénique. L’importance de l’examen visuel du frottis sanguin dans le cadre d’une suspicion clinique ou hématologique d’un PTT est soulignée car il semble que le PTT soit sous-diagnostiqué, surtout parmi les enfants et jeunes adultes. Des superpositions avec le syndrome hémolytique et urémique associé aux diarrhées (SHU D+) et le syndrome hémolytique et urémique atypique (SHUa) sont discutées. Une revue actuelle des démarches diagnostiques, des options thérapeutiques et des facteurs pronostiques du PTT et des SHU est finalement proposée.

ADAMTS13 gene variants and function in women with preeclampsia: a population- based nested case- control study from the HUNT Study.

INTRODUCTION Known genetic variants with reference to preeclampsia only explain a proportion of the heritable contribution to the development of this condition. The association between preeclampsia and the risk of cardiovascular disease later in life has encouraged the study of genetic variants important in thrombosis and vascular inflammation also in relation to preeclampsia. The von Willebrand factor-cleaving protease, ADAMTS13, plays an important role in micro vascular thrombosis, and partial deficiencies of this enzyme have been observed in association with cardiovascular disease and preeclampsia. However, it remains unknown whether decreased ADAMTS13 levels represent a cause or an effect of the event in placental and cardiovascular disease. METHODS We studied the distribution of three functional genetic variants of ADAMTS13, c.1852C>G (rs28647808), c.4143_4144dupA (rs387906343), and c.3178C>T (rs142572218) in women with preeclampsia and their controls in a nested case-control study from the second Nord-Trøndelag Health Study (HUNT2). We also studied the association between ADAMTS13 activity and preeclampsia, in serum samples procured unrelated in time of the preeclamptic pregnancy. RESULTS No differences were observed in genotype, allele or haplotype frequencies of the different ADAMTS13 variants when comparing cases and controls, and no association to preeclampsia was found with lower levels of ADAMTS13 activity. CONCLUSION Our findings indicate that ADAMTS13 variants and ADAMTS13 activity do not contribute to an increased risk of preeclampsia in the general population.

Blood group O and black race are independent risk factors for thrombotic thrombocytopenic purpura associated with severe ADAMTS13 deficiency

It has been postulated that blood group O subjects may be partially protected against thrombotic thrombocytopenic purpura (TTP) because they have lower plasma levels of von Willebrand factor.

Humoral immune response to ADAMTS13 in acquired thrombotic thrombocytopenic purpura

The apparently spontaneous development of autoantibodies to ADAMTS13 in previously healthy individuals is a major cause of thrombotic thrombocytopenic purpura (TTP). Epitope mapping studies have shown that in most patients antibodies directed towards the spacer domain of ADAMTS13 are present. A single antigenic surface comprising Arg(660) , Tyr(661) and Tyr(665) that contributes to the productive binding of ADAMTS13 to unfolded von Willebrand factor is targeted by anti-spacer domain antibodies. Antibodies directed to the carboxyl-terminal CUB1-2 and TSP2-8 domains have also been observed in the plasma of patients with acquired TTP. As yet it has not been established whether this class of antibodies modulates ADAMTS13 activity. Inspection of the primary sequence of human monoclonal anti-ADAMTS13 antibodies suggests that the variable heavy chain germline gene segment VH1-69 is frequently incorporated. We suggest a model in which 'shape complementarity' between the spacer domain and residues encoded by the VH1-69 gene segment explain the preferential use of this variable heavy chain gene segment. Finally, a model is presented for the development of anti-ADAMTS13 antibodies in previously healthy individuals that incorporates the recent identification of HLA DRB1*11 as a risk factor for acquired TTP.

[Proteins influencing the blood coagulation]

This review describes some natural proteins, which can be employed, either as factor concentrates derived from human plasma or as recombinant drug, to modulate the coagulation system. I will address some biochemical characteristics and the physiological role of von Willebrand factor, the coagulation factors of the extrinsic and intrinsic pathways, and the physiological anticoagulant protein C. In addition, I will detail the pharmacological compounds, which are available for influencing or substituting the coagulation proteins: desmopressin (DDAVP), single coagulation factor concentrates, prothrombin complex concentrates, and protein C concentrate. In particular, I will address some treatment topics of general medical interest, such as the treatment of massive bleeding, the correction of the coagulopathy induced by vitamin K-antagonists in patients with cerebral haemorrhage, and of the coagulopathy of meningococcemia. Finally, I will describe some properties and practical clinical applications of the recombinant anticoagulans lepirudin and bivalirudin, which are derived from hirudin, the natural anticoagulant of the medical leech.

Cancer therapy modulates VEGF signaling and viability in adult rat cardiac microvascular endothelial cells and cardiomyocytes

This work was motivated by the incomplete characterization of the role of vascular endothelial growth factor-A (VEGF-A) in the stressed heart in consideration of upcoming cancer treatment options challenging the natural VEGF balance in the myocardium. We tested, if the cytotoxic cancer therapy doxorubicin (Doxo) or the anti-angiogenic therapy sunitinib alters viability and VEGF signaling in primary cardiac microvascular endothelial cells (CMEC) and adult rat ventricular myocytes (ARVM). ARVM were isolated and cultured in serum-free medium. CMEC were isolated from the left ventricle and used in the second passage. Viability was measured by LDH-release and by MTT-assay, cellular respiration by high-resolution oxymetry. VEGF-A release was measured using a rat specific VEGF-A ELISA-kit. CMEC were characterized by marker proteins including CD31, von Willebrand factor, smooth muscle actin and desmin. Both Doxo and sunitinib led to a dose-dependent reduction of cell viability. Sunitinib treatment caused a significant reduction of complex I and II-dependent respiration in cardiomyocytes and the loss of mitochondrial membrane potential in CMEC. Endothelial cells up-regulated VEGF-A release after peroxide or Doxo treatment. Doxo induced HIF-1α stabilization and upregulation at clinically relevant concentrations of the cancer therapy. VEGF-A release was abrogated by the inhibition of the Erk1/2 or the MAPKp38 pathway. ARVM did not answer to Doxo-induced stress conditions by the release of VEGF-A as observed in CMEC. VEGF receptor 2 amounts were reduced by Doxo and by sunitinib in a dose-dependent manner in both CMEC and ARVM. In conclusion, these data suggest that cancer therapy with anthracyclines modulates VEGF-A release and its cellular receptors in CMEC and ARVM, and therefore alters paracrine signaling in the myocardium.

Indications for a protective function of beta2-glycoprotein I in thrombotic thrombocytopenic purpura

It has been shown that β(2) -glycoprotein I (β(2) GPI) interacts with von Willebrand factor (VWF) in a glycoprotein (GP)Ib binding state. Given the presence of active VWF multimers in thrombotic thrombocytopenic purpura (TTP), we speculated that β(2) GPI might play a role in TTP. We found that β(2) GPI plasma levels were significantly lower in acute and remission TTP patients than in normal controls, showing a direct correlation with ADAMTS 13 levels and an inverse correlation with the extent of VWF activation. In vitro flow experiments demonstrated that β(2) GPI can block platelet adhesion to endothelial cell-derived VWF strings. We confirmed the direct binding of β(2) GPI to VWF by surface plasmon resonance, and determined that domain I of β(2) GPI is the binding site of VWF A1 domain. Adhesion of β(2) GPI to erythrocytes and platelets was increased in the presence of active VWF, indicating that β(2) GPI may be cleared from the circulation during TTP episodes together with blood cells. Our findings suggest that β(2) GPI may protect from the effects of hyper-functional VWF by inhibiting its interaction with platelets.

Virtual histology assessment of cardiac allograft vasculopathy following introduction of everolimus--results of a multicenter trial

In this 12-month multicenter Scandinavian study, 78 maintenance heart transplant (HTx) recipients randomized to everolimus with reduced calcineurin inhibitor (CNI) exposure or continued standard CNI-therapy underwent matched virtual histology (VH) examination to evaluate morphological progression of cardiac allograft vasculopathy (CAV). Parallel measurement of a range of inflammatory markers was also performed. A similar rate of quantitative CAV progression was observed in the everolimus (n = 30) and standard CNI group (n = 48) (plaque index 1.9 ± 3.8% and 1.6 ± 3.9%, respectively; p = 0.65). However, VH analysis revealed a significant increase in calcified (2.4 ± 4.0 vs. 0.3 ± 3.1%; p = 0.02) and necrotic component (6.5 ± 8.5 vs. 1.1 ± 8.6%; p = 0.01) among everolimus patients compared to controls. The increase in necrotic and calcified components was most prominent in everolimus patients with time since HTx >5.1 years and was accompanied by a significant increase in levels of von Willebrand (vWF) factor (p = 0.04) and vascular cell adhesion molecule (VCAM) (p = 0.03). Conversion to everolimus and reduced CNI is associated with a significant increase in calcified and necrotic intimal components and is more prominent in patients with a longer time since HTx. A significant increase in vWF and VCAM accompanied these qualitative changes and the prognostic implication of these findings requires further investigation.