Reduction In Von Willebrand Factor Research Articles

S1563 ACE Inhibitor Use Is Associated With Angioectasias on Video Capsule Endoscopy (VCE) in Patients With Iron Deficiency Anemia

Introduction: Small bowel bleeding poses a clinical challenge in patients with vascular lesions. Bleeding recurrence after endoscopic therapy is high and medical therapies have limited efficacy. In those with left ventricular assist devices (LVADs), the use of angiotensin converting enzyme inhibitors (ACEi) has been associated with a reduced rate of gastrointestinal bleeding. Conversely, the antiplatelet effects of ACEi have been described thought due to their effects in decreasing platelet aggregation. Our aim was to determine whether ACEi or angiotensin receptor blocker (ARB) therapy had an impact on the rate of positive VCE small bowel findings in those with iron deficiency anemia (IDA). Methods: Data was collected from consecutive inpatient and outpatient VCE examinations performed between January 1, 2009 to March 1, 2018 at a single U.S. tertiary medical center performed for IDA. VCE studies were excluded in those with incomplete small bowel examinations (9) or technical failure (1). Patient demographics, laboratory values, medication use and endoscopic findings were recorded. VCE findings were based on the P0-P2 grading system. The primary outcome of interest was a positive (P2) VCE. Data were analyzed using Wilcoxon rank-sum test for continuous variables and Fischer’s exact test for dichotomous variables. Bivariate logistic regression was performed to identify independent factors predictive of positive VCE. Results: Eighty-two VCE were included in the final analysis. Median age was 67.6 (IQR: 57.1-75.5) years and 38 (46.3%) patients were male. Thirty-seven (45.1%) VCE examinations were positive with the most common finding of angiectasia in 21 (55.3%). Risk factors for positive VCE are listed in Table 1. In univariate analysis, ACEi therapy associated with both positive VCE (P=0.014) and the presence of angiectasia (P=0.021), whereas ARB therapy did not associate with positive VCE. ACEi findings remained significant in bivariate analysis after controlling for cardiac and pulmonary comorbidities. Conclusion: In this single center study the presence of ACEi use was associated with small bowel and/or stomach angiectasias on VCE in univariate analysis and when controlled for cardiac and pulmonary risk factors. Further studies are required to determine the mechanistic impact of ACEi on gastrointestinal bleeding risk such as the reduction in von Willebrand factor or factors that affect platelet aggregation. Table 1. - Univariate predictors of positive video capsule endoscopy in iron deficiency anemia Negative VCE (n = 45) Positive VCE (n =37) P-value Age, years, mean (SD) 63.6 (15.8) 68.6 (9.3) 0.303 Male sex, n (%) 21 (46.7) 17 (46) 1 White race, n (%) 22 (48.9) 20 (54.1) 0.223 Active smoking, n (%) 6 (14) 11 (29.7) 0.105 Outpatient location, n (%) 31 (68.9) 21 (56.8) 0.357 Chronic kidney disease, n (%) 10 (22.2) 13 (35.1) 0.224 Chronic liver disease, n (%) 3 (6.7) 4 (10.8) 0.696 Congestive heart failure, n (%) 10 (22.2) 13 (35.1) 0.224 Diabetes mellitus, n (%) 15 (33.3) 15 (40.5) 0.645 Cardiac valvular disease, n (%) 7 (15.6) 6 (16.2) 1 Coronary artery disease, n (%) 14 (31.1) 14 (37.8) 0.641 Cardiac arrhythmia, n (%) 10 (22.2) 18 (48.7) 0.019 Chronic lung disease, n (%) 10 (22.2) 13 (35.1) 0.224 Left ventricular assist device, n (%) 2 (4.4) 2 (5.4) 1 Blood transfusion in the preceding 4 weeks, n (%) 17 (37.8) 16 (43.2) 0.656 Aspirin, n (%) 20 (44.4) 14 (37.8) 0.654 Thienopyridine, n (%) 3 (6.7) 2 (5.4) 1 Coumadin, n (%) 1 (2.2) 5 (13.5) 0.086 SSRI/SNRI, n (%) 7 (15.6) 9 (24.3) 0.404 ACEi 7 (15.6) 15 (40.5) 0.014 ARB 9 (20) 7 (18.9) 1 Hemoglobin, g/dL1 9.9 (1.7) 9.2 (2.3) 0.216 Platelets, 109/L1 225.4 (67.5) 208.6 (84.9) 0.202 BUN, mg/dL1 21.9 (13.1) 26.7 (22) 0.869 Creatinine, mg/dL1 1.3 (0.5) 1.9 (1.5) 0.197 Ferritin, ng/mL,1 128 (259) 39.6 (28.7) 0.966 Percent saturation, %1 14.8 (15.1) 13.7 (15.4) 0.76

Effects of diagnostic ultrasound with cRGD-microbubbles on simultaneous detection and treatment of atherosclerotic plaque in ApoE-/- mice.

BackgroundAtherosclerotic vulnerable plaque is the leading cause of acute fatal cardiovascular events. Thus, early rapid identification and appropriate treatment of atherosclerotic plaque maybe can prevent fatal cardiovascular events. However, few non–invasive molecular imaging techniques are currently available for the simultaneous detection and targeted treatment of atherosclerotic plaques. We hypothesized that diagnostic ultrasound (DU) combined with cyclic Arg-Gly-Asp-modified microbubbles (MBR) could provide targeted imaging and dissolution of activated platelets to identify advanced atherosclerotic plaques and improve plaque instability.MethodsThree mouse models, apolipoprotein E-deficient mice on a hypercholesterolemic diet (HCD) or normal chow diet and wild-type mice on an HCD were used. The most appropriate ultrasonic mechanical index (MI) was determined based on the expression of GP IIb/IIIa in sham, DU alone and DUMBR-treated groups at MI values of 0.5, 1.5, and 1.9. The video intensity (VI) values, activated platelets and plaque instability were analyzed by ultrasound molecular imaging, scanning electron microscopy and histopathological methods.ResultsWe found that the VI values of ultrasound molecular imaging of MBR were positively correlated with plaque GP IIb/IIIa expression, vulnerability index and necrotic center / fiber cap ratio. 24 h after treatment at different MIs, compared with those of the other groups, both the VI values and GP IIb/IIIa expression were significantly reduced in MI 1.5 and MI 1.9 DUMBR-treated groups. The plaque vulnerability index and necrotic center / fiber cap ratio were significantly decreased in MI 1.5-treated group, which may be due to targeted dissolution of activated platelets, with a reduction in von Willebrand factor expression.ConclusionDUMBR targeting GP IIb/IIIa receptors could rapidly detect advanced atherosclerotic plaques and simultaneously give targeted therapy by dissolving activated and aggregated platelets. This technology may represent a novel approach for the simultaneous identification and treatment of atherosclerotic plaques.

Pro-inflammatory Vascular Stress in Spontaneously Hypertensive Rats Associated With High Physical Activity Cannot Be Attenuated by Aldosterone Blockade.

The effect of high physical activity, performed as voluntary running wheel exercise, on inflammation and vascular adaptation may differ between normotensive and spontaneously hypertensive rats (SHRs). We investigated the effects of running wheel activity on leukocyte mobilization, neutrophil migration into the vascular wall (aorta), and transcriptional adaptation of the vascular wall and compared and combined the effects of high physical activity with that of pharmacological treatment (aldosterone antagonist spironolactone). At the start of the 6th week of life, before hypertension became established in SHRs, rats were provided with a running wheel over a period of 10-months'. To investigate to what extent training-induced changes may underlie a possible regression, controls were also generated by removal of the running wheel for the last 4 months. Aldosterone blockade was achieved upon oral administration of Spironolactone in the corresponding treatment groups for the last 4 months. The number of circulating blood cells was quantified by FACS analysis of peripheral blood. mRNA expression of selected proteins was quantified by RT-PCR. Histology and confocal laser microscopy were used to monitor cell migration. Although voluntary running wheel exercise reduced the number of circulating neutrophils in normotensive rats, it rather increased it in SHRs. Furthermore, running wheel activity in SHRs but not normotensive rats increased the number of natural killer (NK)-cells. Except of the increased expression of plasminogen activator inhibitor (PAI)-1 and reduction of von Willebrand factor (vWF), running wheel activity exerted a different transcriptional response in the vascular tissue of normotensive and hypertensive rats, i.e., lack of reduction of the pro-inflammatory IL-6 in vessels from hypertensive rats. Spironolactone reduced the number of neutrophils; however, in co-presence with high physical activity this effect was blunted. In conclusion, although high physical activity has beneficial effects in normotensive rats, this does not predict similar beneficial effects in the concomitant presence of hypertension and care has to be taken on interactions between pharmacological approaches and high physical activity in hypertensives.

Von Willebrand Factor Levels in Polycythemia Vera Are Not Reduced and Can be Predicted By Erythrocyte Counts

Introduction . Polycythemia Vera (PV) is a myeloproliferative neoplasm (MPN) whose major features are peripheral erythrocytosis and increased thrombotic risk, affecting morbidity and mortality. Essential Thrombocythemia (ET), a MPN characterized by high platelet generation rate, has been shown to be associated with a reduction in von Willebrand factor (vWf) large multimers and activity which depends on platelet turnover (Lancellotti et al, JTH 2015;13:1226-37). The acquired vWf type 2A defect in ET is thought to influence bleeding rate. Data on vWf and on a possible acquired von Willebrand deficiency in PV are less clear. Previous studies included PV patients with marked thrombocytosis, with bleeding history or included treated and untreated patients, with heterogeneous results. Therefore, the phenotypic features of vWf in PV patients with well-controlled haematocrit, routinely accessing the outpatient clinics remain largely undefined. In addition, whether the acquired vWf defect is similar between PV and ET remains poorly defined.Methods . This is an observational, cross sectional study on consecutive PV patients diagnosed according to the 2008 WHO criteria, treated to keep the hematocrit <45% and on antithrombotic prophylaxis with low-dose aspirin, according to current recommendations. VWF:antigen (VWF:ag) and WVF:activity (VWF:act) were measured by chemiluminescence assays (Instrumentation Laboratory, Milan, Italy). Routine hematochemistry, genotype, clinical characteristics and medications were also recorded. To compare vWF-associated phenotype in PV and ET, we selected age- and sex-matched ET patients from a cohort of 69 patients previously-published from our group (Lancellotti et al., JTH 2015; 13:1226-37). PV and ET plasma samples were measured in the same laboratory with the same methods.Results . Forty-one consecutive PV patients gave their written consent (age 66±11 years, 32% females). Mean (±SD) haematologic values were: hematocrit 43.9±2.9%, leukocytes 9.5±4.6x103/µl, platelets 353±260x103/µl. vWf:ag levels averaged 120±24%, vWf:act 115±21%, the act/ag ratio was 0.96±0.06. VWf:ag and vWf:act were significantly correlated (rho=0.98, p<0.001). On univariate analysis, both vWf:ag and vWf:act significantly and positively correlated with male sex, blood groups (higher in non-0 vs. 0 blood groups), hydroxyurea treatment, JAK2V617F allelic burden, and inversely correlated with erythrocytes and platelets. Multivariable analysis confirmed erythrocyte count (inversely, p<0.001, Figure), blood group (p=0.01) and JAK2V617F allele burden (p=0.02) as significant predictors of vWf:ag (adj Rsqr for the entire model=0.54). Erythrocyte count (inversely, p<0.001) and blood group (p=0.02) independently predicted vWf:Act as well (adj Rsqr for the entire model=0.49).We then compared vWf:ag and vWf:act between these PV patients and 41 ET patients (age 64±11 years p=0.4 vs. PV patients, 38% females). As compared to ET patients, PV patients showed similar levels of vWf:ag (120±23 and 136±57% in PV and ET, respectively; p=0.4), but significantly (p<0.01) higher levels of vWf:act (114±20 and 86±47%, in PV and ET, respectively) and act/ag ratios (0.9±0.06 and 0.6±0.2, in PV and ET, respectively).Conclusions. PV patients treated according to current recommendations do not show evidence for acquired vWf defect. In PV patients vWf levels seem dependent on erythrocyte count (inversely), blood groups (as in the normal population) and JAK2V617F allelic burden, with features different from age- and sex-matched ET patients. Future studies are needed to investigate the pathophysiological mechanisms linking eytrhocytes and vWf levels in PV. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Cost effectiveness of caplacizumab in acquired thrombotic thrombocytopenic purpura

AbstractAcquired thrombotic thrombocytopenic purpura (TTP) is a life-threatening disease characterized by thrombotic microangiopathy leading to end-organ damage. The standard of care (SOC) treatment is therapeutic plasma exchange (TPE) alongside immunomodulation with steroids, with increasing use of rituximab ± other immunomodulatory agents. The addition of caplacizumab, a nanobody targeting von Willebrand factor, was shown to accelerate platelet count recovery and reduce TPE treatments and hospital length of stay in TTP patients treated in 2 major randomized clinical trials. The addition of caplacizumab to SOC also led to increased bleeding from transient reductions in von Willebrand factor and increased relapse rates. Using data from the 2 clinical trials of caplacizumab, we performed the first-ever cost-effectiveness analysis in TTP. Over a 5-year period, the projected incremental cost-effectiveness ratio (ICER) in our Markov model was $1 482 260, significantly above the accepted 2019 US willingness-to-pay threshold of $195 300. One-way sensitivity analyses showed the utility of the well state and the cost of caplacizumab to have the largest effects on ICER, with a reduction in caplacizumab cost demonstrating the single greatest impact on lowering the ICER. In a probabilistic sensitivity analysis, SOC was favored over caplacizumab in 100% of 10 000 iterations. Our data indicate that the addition of caplacizumab to SOC in treatment of acquired TTP is not cost effective because of the high cost of the medication and its failure to improve relapse rates. The potential impact of caplacizumab on health system cost using longer term follow-up data merits further study.

Effects of Psychosocial Interventions and Caregiving Stress on Cardiovascular Biomarkers in Family Dementia Caregivers: The UCSD Pleasant Events Program (PEP) Randomized Controlled Trial.

This study examined whether biological mechanisms linking dementia caregiving with an increased risk of coronary heart disease can be modified by psychosocial interventions and which caregivers might benefit the most from an intervention. Spousal dementia caregivers were randomized to 12-week treatment with either a behavioral activation intervention (ie, Pleasant Events Program [PEP]; n = 60), or an active control Information and Support (IS; n = 63) condition. Indicators of caregiving stress were assessed pretreatment and circulating cardiovascular biomarkers were measured pre- and posttreatment. There were no significant changes in biomarker levels from pre- to posttreatment both by treatment condition and across all caregivers. Regardless of the treatment condition, exploratory regression analysis revealed that caregivers were more likely to show significant decreases in C-reactive protein (CRP) and D-dimer when their spouse had severe functional impairment; in interleukin (IL)-6 and CRP when they had greater distress due to care recipient's problem behaviors; in tumor necrosis factor (TNF)-α when they had higher levels of negative affect; and in IL-6, CRP, TNF-α, and D-dimer when they had higher personal mastery. Within the PEP group, caregivers with higher negative affect and those with higher positive affect were more likely to show a reduction in von Willebrand factor and D-dimer, respectively. Within the IS group, caregivers whose spouse had severe functional impairment were more likely to show a decrease in IL-6. Unlike the average caregiver, caregivers high in burden/distress and resources might benefit from psychosocial interventions to improve cardiovascular risk, although these observations need confirmation.

Schisandrin Attenuates Lipopolysaccharide-Induced Lung Injury by Regulating TLR-4 and Akt/FoxO1 Signaling Pathways.

Objective: Acute lung injury is a severe clinic condition with limited therapeutic approaches. This study evaluated whether schisandrin (Sch), an ingredient of Schisandra chinensis, has preventive effects on endothelium and epithelium injury induced by lipopolysaccharide (LPS) and the underlying mechanisms.Methods: Male Wistar rats were continuously infused with LPS (5 mg/kg/h) via the left jugular vein for 90 min. In some rats, Sch (2.5 mg/kg/h) was administrated through the left jugular vein 30 min before LPS infusion. Leukocyte recruitment, levels of inflammatory cytokines, lung histology and edema, vascular and alveolar barrier disruption and related proteins were evaluated at indicated time point after LPS challenge.Results: LPS infusion for 90 min resulted in an increased leukocyte adhesion to pulmonary venules and overproduction of cytokine and chemokine in both serum and lung homogenate. At 8 h after termination of LPS infusion, obvious Evans blue extravasation and lung edema were observed, along with an increased apoptosis, a decreased expression of tight junction and adherent junction proteins, and a reduction in von Willebrand factor (vWF) and keratin, all of which were attenuated by Sch treatment. Meanwhile, the LPS-elicited activation of TLR-4/NF-κB/MAPK and FoxO1 signaling was inhibited by Sch.Conclusion: The present study revealed that pretreatment with Sch alleviated lung endothelium and epithelium injury after LPS stimulation, which is attributable to inhibition of cell injury and activation of cell regeneration via regulation of TLR-4/NF-κB/MAPK and Akt/FoxO1 signaling pathway.

Association between the severity of acquired von Willebrand syndrome and gastrointestinal bleeding after continuous-flow left ventricular assist device implantation.

Acquired von Willebrand syndrome, characterized by the reduction in von Willebrand factor (vWF) large multimers, has recently been considered as one of the causes of gastrointestinal bleeding (GIB). It remains unclear whether its haematological severity is linked with susceptibility to bleeding because the definition of the haematological severity of acquired von Willebrand syndrome has not been precisely determined. This study sought to establish a quantitative methodology to assess the haematological severity of acquired von Willebrand syndrome and to define the threshold for occurrence of GIB in patients implanted with left ventricular assist devices (LVADs). In total, 41 patients treated with continuous-flow LVAD implanted between 2011 and 2017 at Tohoku University Hospital were investigated. vWF large multimers were quantitatively evaluated using the 'vWF large multimer index' defined as the ratio of a large multimer proportion in total vWF derived from a patient to that from a normal control. Using this index, the amount of vWF large multimers was expressed as a percentage of its normal control value obtained with a simultaneous analysis of each time measurement. Twelve (29%) patients developed GIB events during follow-up periods (median 591 days) after an LVAD implantation. The vWF large multimer index in patients with GIB was significantly lower than that in those without GIB (25.0 ± 10.3% vs 37.5 ± 17.8%, P = 0.008). Most importantly, all patients experiencing GIB exhibited a vWF large multimer index below 40%. Patients with GIB exhibited a more severe loss of vWF large multimers. The vWF large multimer index may dictate the risk of GIB after an LVAD implantation. UMIN000018135.

Novel Insights into the Clinical Phenotype and Pathophysiology Underlying Low VWF Levels: The Low Von Willebrand Factor in Ireland Cohort (LoVIC) Study

▪Cohort studies have identified VWF gene mutations in ~65% of patients with type 1 Von Willebrand Disease (VWD). However, in patients with mild reductions in Von Willebrand Factor (VWF) levels, VWF mutations are less common and linkage studies suggest that the reduced plasma VWF levels are often independent of the VWFgene. Important clinical questions therefore remain unanswered regarding diagnosis and management of patients with Low VWF (levels 30-50 IU/dL). Evidence-based diagnostic criteria are needed for establishing the diagnosis of Low VWF, and the relationship between Low VWF levels and bleeding phenotype needs to be defined. Furthermore, the molecular mechanisms responsible for the reduced plasma VWF levels remain unclear. To address these questions, we established the Low VWF Ireland Cohort (LoVIC) study. In contrast to previous Type 1 VWD studies, this prospective longitudinal cohort study recruited only patients with Low VWF levels, (defined by bleeding history and lowest VWF levels 30-50 IU/dL on two occasions, three months apart) and recruited 140 adult Irish patients.Although Bleeding Assessment Tools (BATs) have been used in type 1 VWD, their utility has not been studied in patients with Low VWF. As determined using either the ISTH BAT or the Condensed MCMDM-1 VWD score, we observed significant bleeding histories in the majority of LoVIC patients. For example, among female patients (n=112), 77% had positive ISTH BAT scores (≥6) and 72% had positive MCMDM-1 scores (≥4). Importantly, bleeding tendency did not correlate with plasma VWF levels within the 30-50 IU/dL range. To further investigate this bleeding phenotype, hemostatic studies (including platelet aggregation and coagulation factor assays) were performed. Additional mild coagulation defects were identified in only 10 subjects. Furthermore, abnormal multimer patterns were identified in only 3 patients. To investigate the pathophysiology underlying Low VWF levels, plasma FVIII:C and VWF propeptide (VWF:pp) levels were defined. Interestingly, plasma FVIII:C/VWF:Ag ratios were significantly increased in LoVIC patients compared to normal controls (mean 1.3 versus 1.07; p<0.001). In contrast, increased plasma VWF:pp/VWF:Ag ratios > 3 were observed in only 6% of the total cohort. Taken together, these data demonstrate that the reduced plasma VWF levels in patients with Low VWF are predominantly attributable to decreased VWF synthesis and/or secretion rather than enhanced VWF clearance. To determine whether quantitative and/or qualitative abnormalities in platelet (plt)-VWF may influence bleeding phenotype in patients with Low VWF, we studied plt-VWF:Ag and VWF:CB in 50 consecutive LoVIC patients. In keeping with the hypothesis that reduced VWF synthesis plays a key role in the pathogenesis underlying Low VWF levels, plt-VWF:Ag and plt-VWF:CB levels were both significantly reduced in LoVIC patients compared to controls (mean plt-VWF:Ag 0.16 versus 0.21 IU/109/L, p<0.05; mean plt-VWF:CB 0.18 versus 0.34 IU/109/L, p<0.001).To further study the molecular mechanisms underlying Low VWF levels, plasma VWF:Ag and VWF:RCo responses following desmopressin (DDAVP) administration were examined. In 88% of patients, the post-DDAVP peak levels exceeded 100 IU/dL. Importantly, the response to DDAVP was also sustained with both VWF:Ag and VWF:RCo above 100 IU/dL after 4 hours in 72% subjects. These DDAVP responses demonstrate that Weibel Palade body stores of VWF are maintained in patients with Low VWF, and that the regulated pathway of VWF secretion is intact. Furthermore, the sustained plasma VWF response observed following DDAVP supports the hypothesis that enhanced VWF clearance does not play a major role in the pathogenesis of Low VWF levels.In conclusion, we demonstrate that Low VWF levels are associated with a significant bleeding phenotype. In addition, we further show that in the majority of patients with Low VWF levels, the bleeding phenotype cannot be explained by the presence of concomitant bleeding disorders. Finally, our novel data demonstrate that Low VWF levels are due in large part to reductions in VWF synthesis and/or constitutive secretion. Although enhanced VWF clearance may contribute to the pathophysiology in a minority of individuals with Low VWF, the absolute reduction in VWF plasma half-life is usually mild and not sufficient to significantly impact upon the duration of DDAVP-induced VWF response. DisclosuresLavin:Baxalta: Consultancy, Research Funding. O'Sullivan:Pzifer: Research Funding. O'Connell:Baxalta: Consultancy, Research Funding. James:Octapharma: Research Funding; Bayer: Research Funding; CSL Behring: Research Funding; Biogen: Consultancy; Basalt: Consultancy. Di Paola:CSL BEhring: Consultancy; Biogen: Consultancy. O'Donnell:Bayer: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Baxalta: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novo Nordisk: Research Funding, Speakers Bureau; Boehringer Ingelheim: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding; Octapharma: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Leo Pharma: Speakers Bureau; CSL Behring: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees.

TRIMETAZIDINE MB ROLE IN THE OPTIMISATION OF THE ACUTE CORONARY SYNDROME TREATMENT: EFFECTS ON ENDOTHELIAL DYSFUNCTION AND SYSTEMIC INFLAMMATION

Aim. To study the effects of trimetazidine MB therapy on the clinical manifestations and markers of endothelial dysfunction and systemic inflammation in patients with acute coronary syndrome (ACS). Material and methods. This open, comparative, randomised parallel-group study included 60 patients with a verified ACS diagnosis (34 men and 26 women, aged 40–84 years). All participants were randomised into two treatment groups: the main group receiving trimetazidine MB (PreductalMB) 35 mg twice a day, and the control group receiving standard therapy but not trimetazidine MB. The examination included electrocardiography (ECG), echocardiography, 24-hour ECG monitoring, and chest X-ray. Results. After 3 months of the treatment, the main group demonstrated a significant reduction in the incidence and duration of anginal attacks (–58% and –42%, respectively), as well as in the weekly nitrate intake (–66%). There was a nonsignificant (possibly, due a relatively small sample size) tendency towards a reduction in the severity of anginal attacks (–36%). The control group demonstrated a less prominent dynamics of clinical parameters: the incidence of anginal attacks decreased by 21%, the weekly nitrate intake by 20%, and the duration and severity of anginal attacks only by 6%. Conclusion. The combination of trimetazidine MB with the standard ACS therapy improves the treatment effectiveness, in terms of the anginal syndrome manifestations and endothelial function stabilisation, as suggested by a significant reduction in von Willebrand factor and endothelin levels, compared to the control group.

ADAMTS-13: double trouble for von Willebrand factor.

See also Yeh HC, Zhou Z, Choi H, Tekeoglu S, May W III, Wang C, Turner N, Scheiflinger F, Moake JL, Dong JF. Disulfide bond reduction of von Willebrand factor by ADAMTS-13. This issue, pp 2778–88.

Disulfide bond reduction of von Willebrand factor by ADAMTS-13.

von Willebrand factor (VWF) released from endothelial cells is rich in ultra-large (UL) multimers that are intrinsically active in binding platelets, whereas plasma-type VWF multimers require shear stress to be activated. This functional difference may be attributed to thiols exposed on the surface of plasma-type VWF multimers, but not on ULVWF multimers. Shear stress induces the exposed thiols to form disulfide bonds between laterally apposed plasma-type VWF multimers, leading to enhanced VWF binding to platelets. We tested a hypothesis that ADAMTS-13 has a disulfide bond reducing activity that regulates shear-induced thiol-disulfide exchange of VWF. Thiol blocking agents and active thiol bead capturing were used to identify and locate this activity, along with truncated ADAMTS-13 mutants. ADAMTS-13 contains a disulfide bond reducing activity that primarily targets disulfide bonds in plasma-type VWF multimers induced by high shear stress or formed with thiol beads, but not disulfide bonds in native multimeric structures. Cysteine thiols targeted by this activity are in the VWF C-domain and are known to participate in shear-induced thiol-disulfide exchange. ADAMTS-13 contains cysteine thiols that remain exposed after being subjected to hydrodynamic forces. Blocking these active thiols eliminates this reducing activity and moderately decreases ADAMTS-13 activity in cleaving ULVWF strings anchored to endothelial cells under flow conditions, but not under static conditions. This activity is located in this C-terminal region of ADAMTS-13. This novel disulfide-bond-reducing activity of ADAMTS-13 may prevent covalent lateral association and increased platelet adherence of plasma-type VWF multimers induced by high fluid shear stress.

The Diagnostic Dilemma: Dual Presentations of Clinical Mucosal Bleeding and Venous Thrombosis Associated with the Presence of Thrombophilia Markers and Mild Reduction in von Willebrand Factor

A prothrombotic and hemorrhagic state can separately manifest in one patient and can potentially cause several diagnostic problems. We report an intriguing case as an example of a potential hemostasis-based diagnostic dilemma. A 29-year-old female patient presented with a personal history of menorrhagia and other mucosal bleeding and renal ovarian thrombosis. Previous investigations had uncovered several diagnostic anomalies, including von Willebrand disease (VWD), factor V Leiden (FVL), antiphospholipid syndrome, and thrombocytopaenia. Previous therapy in this patient included heparin and warfarin for the thrombosis and desmopressin acetate (DDAVP) and antifibrinolytic therapy for surgical management. Subsequent laboratory testing with fresh samples consistently confirmed an equivocal (borderline normal/abnormal) level of von Willebrand factor (VWF) and FVL with activated protein C resistance (APCR). A patient sample, differentially labeled according to the tests being performed, was later distributed for blind testing to participants within several modules of the RCPA Quality Assurance Program (QAP). Most participants reported a low level of VWF consistent with possible mild Type 1 VWD, and most (but not all) reported a positive finding for APCR. All participants correctly reported the sample as heterozygous for the FVL mutation, negative for the Prothrombin gene mutation G20210A, and heterozygous for the methylenetetrahydrofolate reductase (MTHFR) mutation C677T. Interestingly, a significant number of laboratories performing Protein S testing using clot-based procedures also identified a false Protein S deficiency. In conclusion, this exercise showed how, either depending on the clinical review and specific laboratory investigation and tests performed, a pro-bleeding diagnosis (of either VWD or thrombocytopenia) or pro-thrombophilia risk (Antiphospholipid Syndrome or FVL/APCR or false Protein S deficiency) could potentially and differentially arise in the one patient.

Reduction of von Willebrand Factor by Endothelial Cells

The haemostatic activity of plasma von Willebrand factor (vWF) is a function of multimer size. Only the large vWF multimers are effective in promoting platelet adhesion to a site of vascular injury. We observed that the conditioned medium of cultured human umbilical vein, human microvascular and bovine aortic endothelial cells contained an activity which reduced the average multimer size of plasma or purified vWF. The average multimer size of vWF produced endogenously by human umbilical vein endothelial cells was similarly reduced following secretion. The reducing activity was ablated by pre-treatment with heat or the thiol blocking agents. iodoacetamide, N-ethylmaleimide or E-64, but not by a range of specific serine-, cysteine-, aspartic-, or metalloproteinase inhibitors. Reduction in vWF multimer size was associated with formation of new thiols in vWF and there was no evidence for additional proteolytic processing of vWF. The reducing activity was associated with a protein with an anionic pi that binds heparin and contains reactive thiol(s). These results suggested that the interchain disulfide bonds that link the vWF homodimers near the N-termini were being reduced by a vWF reductase secreted by endothelial cells. In support of this hypothesis, incubation of vWF with the protein reductants, protein disulfide isomerase and thioredoxin, resulted in formation of new thiols in vWF and reduction in the average multimer size of vWF. These findings may have consequences for control of vWF haemostatic activity.

Impaired Haemostasis by Intravenous Administration of a Gelatin-based Plasma Expander in Human Subjects

The aim of this study was to investigate the effects of a gelatin-based plasma expander on blood coagulation and haemostasis in human subjects. Six healthy men were studied in a randomised, controlled cross-over study to investigate the effects of a 60 min intravenous infusion of either 1 l gelatin-based plasma substitute (Gelofusine) or 0.9% NaCl (control). The infusion of gelatin resulted in a 1.7 fold increase in bleeding time at 60 min and a 1.4 fold increase at 120 min, while saline had no effect (p <0.05). Aggregation studies revealed a significant impairment of ristocetin-induced platelet aggregation (p <0.05), associated with a substantial decrease of vWF:ag (-32% vs. -5%, p <0.05) and ristocetin co-factor (-29% vs. +1%, p <0.05) and without in vitro impairment of the platelet glycoprotein 1b receptor. Gelatin caused a decrease in thrombin-antithrombin complexes (-45% vs. -4%, p <0.05) and F1+2 (-40% vs. +1%, p <0.05). The decrease in circulating levels of vWF:ag, vWF R:Co, thrombin-antithrombin complexes and F1+2 was more than could be expected by the calculated plasma-dilution generated by Gelofusine. Our results demonstrated that the administration of a gelatin-based plasma substitute results in a significant impairment of primary haemostasis and thrombin generation. The defect in primary haemostasis appears to be related to a gelatin-induced reduction in von Willebrand factor, whereas the decreased thrombin generation may be due to the dilution of coagulation factors induced by Gelofusine.

Von Willebrand factor and soluble E-selectin in hyperlipidaemia: relationship to lipids and vascular disease.

Our objective was to determine whether endothelial cell products von Willebrand factor and soluble E-selectin are related to serum lipids, lipoprotein (a), and vascular disease in patients with hyperlipidaemia. In order to achieve our aim, blood samples were obtained for four experiments from 1) 160 patients (49 with symptomatic vascular disease) with hypercholesterolaemia and an equal number of age and sex matched controls; 2) 31 patients who were studied serially before and after successful resolution of their hypercholesterolaemia; 3) 15 patients with hypertriglyceridaemia; and 4) 20 controls, half of whom consumed a lipid-rich breakfast. von Willebrand factor and soluble E-selectin were measured by enzyme linked immunosorbent assay (ELISA) using commercial reagents. In experiment (1) von Willebrand factor was increased in the patients with hypercholesterolaemia (P=0.0077) and was higher still in patients with vascular disease (P<0.0001). Soluble E-selectin was not influenced by hypercholesterolaemia or vascular disease. The correlation of von Willebrand factor with total and LDL cholesterol (both P<0.001) remained after both age and blood pressure were controlled. Experiment (2) showed that serial studies in patients over an average of 7 months a reduction in total cholesterol was associated with a reduction in von Willebrand factor (r=0.51, P=0.002). Experiment (3) demonstrated that von Willebrand factor was not increased in patients with hypertriglyceridaemia (median 8.9 mmol/L), and in experiment (4) a lipid-rich breakfast taken by fasted, healthy controls produced an increase in serum triglycerides (P<0.01) but did not influence von Willebrand factor over an 8 hour period. We conclude that von Willebrand factor, but not soluble E-selectin, is raised in hypercholesterolaemia and therefore may be a potential indicator of endothelial cell physiology in subjects with, or at risk of, atherosclerotic vascular disease.

Reduction in cholesterol is associated with reduction in Von Willebrand factor

Reduction in cholesterol is associated with reduction in Von Willebrand factor

Von Willebrand’s Disease

Studies of von Willebrand's disease typically show either a quantitative or a qualitative abnormality of the factor VIII/von Willebrand factor protein. In studies of five patients we found a combination of quantitative and qualitative defects. Quantitative abnormalities included decreased levels of procoagulant, antigen and von Willebrand factor activities in the plasma and in the column fractions of cryopercipitate from gel chromatography. Qualitative abnormalities included annormal migration or shape of the crossed antigen-antibody arcs, disproportionate reduction of von Willebrand factor in relation to antigen, altered gel elution patterns of procoagulant, and von Willebrand factor activities the negative carbohydrate stain of the VIII protein on polyacryl-amide-gel electrophoresis and, in two patients, a decreased sialic acid content of factor VIII protein. Our studies indicate that von Willebrand's disease comprises both quantitative and qualitative defects.