von Willebrand factor in CHD and stroke: Relationships and therapeutic implications

Regulation der primären Hämostase durch von-Willebrand-Faktor und ADAMTS13

Von Willebrand factor (VWF) is an adhesive, multi-functional huge multimerized protein with multiple domains harboring binding sites for collagen, platelet glycoprotein receptors and coagulation factor VIII (FVIII). The functional domains enable VWF to bind to the injured vessel wall, to recruit platelets to the site of injury by adhesion and aggregation and to bind and protect FVIII, an important cofactor of the coagulation cascade. VWF function in primary haemostasis is located in particular in the arterial and micro-circulation. This environment is exposed to high shear forces with hydrodynamic shear rates ranging over several orders of magnitude from 10–1 to 105 s-1 and requires particular mechanisms to enable platelet adhesion and aggregation under these variable conditions. The respective VWF function is strictly correlating with its multimer size. Lack or reduction of large VWF multimers is seen in patients with von Willebrand disease (VWD) type 2A which correlates with reduction of both VWF:platelet GPIb-binding and VWF:collagen binding and a bleeding phenotype. To prevent unlimited platelet adhesion and aggregation which is the cause of the microangiopathic disorder thrombotic thrombocytopenic purpura (TTP), VWF function is regulated by its specific protease ADAMTS13. Whereas a particular susceptibility of VWF to ADAMTS13 proteolysis is the cause of a frequent VWD type 2A phenotype, lack or dysfunction of ADAMTS13, either acquired by ADAMTS13 antibodies or by inherited ADAMTS13 deficiency (Upshaw-Schulman Syndrome), causes TTP. Therefore VWD and TTP represent the opposite manifestations of VWF related disorders, tightly linked to each other.

Circulating Biomarkers in Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy Patients

BACKGROUND

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited cerebral microangiopathy presenting with variable features, including migraine, psychiatric disorders, stroke, and cognitive decline and variable disability. On neuroimaging, CADASIL is characterized by leukoencephalopathy, multiple lacunar infarcts, and microbleeds. Previous studies suggest a possible role of endothelial impairment in the pathogenesis of the disease.

METHODS

We assessed plasma levels of von Willebrand factor (vWF) and thrombomodulin (TM) and the blood levels of endothelial progenitor cells (EPCs) and circulating progenitor cells (CPCs) in 49 CADASIL patients and 49 age-matched controls and their association with clinical/functional and neuroimaging features.

RESULTS

In multivariate analysis, CADASIL patients had significantly higher vWF and lower EPC levels. TM levels were similar in the 2 groups. CADASIL patients with a more severe clinical phenotype (history of stroke or dementia) presented lower CPC levels in comparison with patients with a milder phenotype. On correlation analysis, lower CPC levels were associated with worse performances on neuropsychological, motor and functional tests, and with higher lesion load on brain magnetic resonance imaging (degree of leukoencephalopathy and number of lacunar infarcts).

CONCLUSIONS

This is the first CADASIL series in which multiple circulating biomarkers have been studied. Our findings support previous studies on the presence and the possible modulating effect of endothelial impairment in the disease. Furthermore, our research data suggest that blood CPCs may be markers of disease severity.

Effect of continuous positive airway pressure on day/night rhythm of prothrombotic markers in obstructive sleep apnea

OBJECTIVE

Obstructive sleep apnea (OSA) has been associated with an increased risk of atherothrombotic events. A prothrombotic state might partially explain this link. This study investigated OSA patients' day/night rhythm of several prothrombotic markers and their potential changes with therapeutic continuous positive airway pressure (CPAP).

METHODS

The study included 51 OSA patients [apnea hypopnea index (AHI) ⩾10] and 24 non-OSA controls (AHI<10). Of the 51 OSA patients, 25 were randomized to CPAP and 26 to placebo-CPAP. Twelve blood samples were collected over a 24h period to measure prothrombotic markers. For the apneic patients these samples were collected before treatment and after 3weeks of treatment with either CPAP or placebo-CPAP. Day/night variation in prothrombotic markers was examined using a cosinor analysis.

RESULTS

Compared with controls, OSA patients showed lower mesor (mean) and amplitude (difference between maximum and minimum activity) of D-dimer. In unadjusted (but not in adjusted) analysis, patients showed higher mesor of plasminogen activator inhibitor-1 (p<0.05 in all cases). No significant group differences were seen in mesor and amplitude for either soluble tissue factor or von Willebrand factor, or the acrophase (time of the peak) and periodic pattern for any prothrombotic markers. There were no significant differences in changes of periodic pattern and in day/night rhythm parameters of prothrombotic markers pre- to post-treatment between the CPAP and placebo condition.

CONCLUSIONS

There may be altered day/night rhythm of some prothrombotic markers in OSA patients compared with controls. CPAP treatment for 3weeks did not affect day/night rhythm of prothrombotic markers in OSA patients differently from placebo-CPAP.

Thrombosis in VonWillebrand disease

OBJECTIVE

To date, only a few case studies have reported occurrence of thrombosis in patients with VonWillebrand disease (VWD). No studies have looked at its incidence in this patient population. The aim of this study was to test our hypothesis that decreased VonWillebrand factor (VWF) levels confer a protective effect on arterial and venous thrombosis.

METHODS

This is a retrospective cohort study including patients (n=350) with the ICD-9 code of VWD who were identified from our hospital database over a period of 25 years, out of which 198 patients were included in the final sample. A parallel control sample without VWD matched for age, sex, hypertension, hyperlipidemia, atrial fibrillation and diabetes mellitus was also obtained from the hospital database. The primary outcomes were incidence of diagnosis of symptomatic arterial and venous thrombosis. The results were computed using multivariate conditional logistic regression analysis and proportions were compared using McNemer's Chi - square test.

RESULTS

Out of 198 patients (mean age 44.2 ± 17.5, women 72%) with VWD, 170 (86%) were VWD type 1, 21 (10%) were type 2 and 7 (3%) were type 3. VWD was found to be an independent protective predictor from arterial thrombosis (OR 0.28, 95% CI 0.14-0.54, p<0.0001), more so in CAD (OR 0.28, 95% CI 0.12-0.64, p=0.002) than in CVD (OR 0.28, 95% CI 0.10-0.77, p=0.01). However this was not the case in venous thrombosis (p=0.42).

CONCLUSION

In a population of relatively younger individuals with VWD, our study suggests a reduced incidence of arterial thrombosis but not of venous thrombosis. This brings up the possibility that there could be other pathways or factors involved in arterial and venous thrombosis. To our knowledge, this is the first large observational study that has provided insight into the thrombotic disease in this group of patients.

Deficiency in core circadian protein Bmal1 is associated with a prothrombotic and vascular phenotype

Aging is associated with both the disturbances of circadian rhythms and a prothrombotic phenotype. It remains poorly understood how the circadian system regulates thrombosis, a critical outcome of aging-related cardiovascular disease. Using multiple in vivo models, we now show that mice with genetic ablation of the core clock gene Bmal1, which display pre-mature aging, have a dramatic prothrombotic phenotype. This phenotype is mechanistically linked to changes in the regulation of key risk factors for cardiovascular disease. These include circulating vWF, fibrinogen, and PAI-1, all of which are significantly elevated in Bmal1(-/-) mice. We also show that major circadian transcriptional regulators CLOCK and Bmal1 directly regulate the activity of vWF promoter and that lack of Bmal1 results in upregulation of vWF both at mRNA and protein level. Here we report a direct regulation of vWF expression in endothelial cells by biological clock gene Bmal1. This study establishes a mechanistic connection between Bmal1 and cardiovascular phenotype.

Age-related short-term effect of ramipril on N-terminal pro-brain natriuretic peptide and markers of hemostasis in patients after acute myocardial infarction

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors after acute myocardial infarction (MI) prevent heart failure and recurrent ischemic events. Our aim was to evaluate the effect of ramipril on N-terminal pro-brain natriuretic peptide (NT-proBNP) and on markers of hemostasis, including plasminogen-activator-inhibitor-1 (PAI-1), von Willebrand factor (vWF), factor VIII (FVIII) and fibrinogen, in patients after acute MI, with emphasis on those over 55 years of age.

METHODS

In this prospective, single-center, observational study 38 patients were treated with ramipril after the first Q-wave MI. Markers of hemostasis and NT-proBNP were estimated before and two weeks after ramipril treatment.

RESULTS

Significant differences were observed in PAI-1 and NT-proBNP levels in patients over 55 years. In this age group the mean PAI-1 level decreased significantly after ramipril therapy (3.6 +/- 1.25 U/ml vs. 2.65 +/- 1.4 U/ml, P = 0.011) and was significantly lower than in younger (<55 years) patients (2.65 +/- 1.4 U/ml vs. 4.39 +/- 1.7 U/ml, P = 0.002). In addition, in the older patients the mean baseline NT-proBNP level was significantly higher than in the younger age group (258.35 +/- 347.6 pmol/l vs. 17.1 +/- 22 pmol/l, P = 0.028) and was also higher after ramipril therapy (240.5 +/- 254.3 pmol/l vs. 67.3 +/- 75.2 pmol/l, P = 0.034). In the younger patients, mean NT-proBNP after short-term ramipril therapy increased significantly in comparison with baseline (67.3 +/- 75.2 pmol/l vs. 17.15 +/- 22.0 pmol/l, P = 0.046).

CONCLUSION

In acute Q-wave MI, increased PAI-1 levels, but not increased NT-proBNP, respond rapidly to early ACE inhibition by ramipril in patients over 55 years of age but not in younger patients.