Thrombosis and Haemostasis

Patients receiving dual antiplatelet treatment with aspirin and clopidogrel are commonly treated with proton pump inhibitors (PPIs). Attenuating effects on platelet response to clopidogrel have been reported solely for the PPI omeprazole. PPIs differ in their metabolisation properties as well as their potential for drug-drug interactions. The aim of this study was to investigate the impact of different PPIs (pantoprazole, omeprazole, esomeprazole) on platelet response to clopidogrel in patients with previous coronary stent placement under chronic clopidogrel treatment. In a cross-sectional observational study, consecutive patients under clopidogrel maintenance treatment (n=1,000) scheduled for a control coronary angiography were enrolled. Adenosine diphosphate (ADP)-induced platelet aggregation (in AU*min) was measured with multiple electrode platelet aggregometry (MEA). From the entire study population, 268 (26.8%) patients were under PPI treatment at the time point of platelet function testing (pantoprazole, n=162; omeprazole, n=64; esomeprazole, n=42). Platelet aggregation (median [interquar-tile range]) was significantly higher in patients with omeprazole treatment (295.5 [193.5–571.2] AU*min) compared to patients without PPI treatment (220.0 [143.8–388.8] AU*min; p=0.001). Platelet aggregation was similar in patients with pantoprazole (226.0 [150.0–401.5] AU*min) or esomeprazole (209.0 [134.8–384.8] AU*min) treatment compared to patients without PPI treatment (p=0.69 and p=0.88, respectively). Attenuating effects of concomitant PPI treatment on platelet response to clopidogrel were restricted to the use of omeprazole. No attenuating effects on platelet response to clopidogrel were observed for pantoprazole or esomeprazole. Specifically designed and randomized clinical studies are needed to define the impact of concomitant PPI treatment on adverse events after percutaneous coronary intervention.

3-phosphoinositide-dependent protein kinase 1 (PDK1), a member of the protein A,G and C (AGC) family of proteins, is a Ser/Thr protein kinase that can phosphorylate and activate other protein kinases from the AGC family, including Akt at Thr308, all of which play important roles in mediating cellular responses. The functional role of PDK1 or the importance of phosphorylation of Akt on Thr308 for its activity has not been investigated in human platelets. In this study, we tested two pharmacological inhibitors of PDK1, BX795 and BX912, to assess the role of Thr308 phosphorylation on Akt. PAR4-induced phosphorylation of Akt on Thr308 was inhibited by BX795 without affecting phosphorylation of Akt on Ser473. The lack of Thr308 phosphorylation on Akt also led to the inhibition of PAR4-induced phosphorylation of two downstream substrates of Akt, viz. GSK3β and PRAS40. In vitro kinase activity of Akt was completely abolished if Thr308 on Akt was not phosphorylated. BX795 caused inhibition of 2-MeSADP-induced or collagen-induced aggregation, ATP secretion and thromboxane generation. Primary aggregation induced by 2-MeSADP was also inhibited in the presence of BX795. PDK1 inhibition also resulted in reduced clot retraction indicating its role in outside-in signalling. These results demonstrate that PDK1 selectively phosphorylates Thr308 on Akt thereby regulating its activity and plays a positive regulatory role in platelet physiological responses.

Acurhagin, a high-molecular mass hemorrhagic metalloproteinase, was purified from the crude venom of Agkistrodon acutus using anionexchange and hydrophobic interaction chromatography. Acurhagin is a monomer with a molecular mass of 51.4 kDa under non-reducing conditions on SDS-PAGE and 48,133 Da by mass spectrometry. Partial amino acid sequence of its metalloproteinase domain is homologous to other high-molecular mass metalloproteinases from snake venoms. It preferentially cleaved Aα. chain of fibrinogen, followed by Bβ chain, while γ chains was minimally affected. Monitored by RP-HPLC, it extensively degraded fibrinogen into various peptide fragments. In aqueous solution, acurhagin autoproteolyzed to a 30 kDa fragment at 37° C. The N-terminal sequence of the 30 kDa fragment of acurhagin showed a high homology to those proteins consisting of disintegrinlike and cysteine-rich domains. Caseinolytic assay showed that the proteinase activity of acurhagin was slightly enhanced by Ca2+ and Mg2+, but completely inhibited by Zn2+. When treated with metal chelators, acurhagin was completely inactivated. Furthermore, acurhagin exerts an inhibitory effect on ADP-induced platelet aggregation of plateletrich plasma in an incubation-time dependent manner. It also impairs collagen- and ristocetin-induced platelet aggregation by cleaving collagen and vWF, respectively.

Objective Activation of thromboxane A2 synthase (TXAS)/thromboxane A2 (TXA2)/thromboxane prostanoid (TP) receptor leads to arterial constriction, platelet aggregation and vascular injury. We attempted to characterize the microvascular dysfunction in ischaemia/reperfusion injury using genetically modified TXAS−/−, TP−/− and TXAS−/−TP−/− mice.

Approach and Results The cardiac micro-circulation and electrocardiograms were evaluated from B6, TXAS−/−, TP−/− and TXAS−/−TP−/− mice in response to intravenous saline, endothelin-1, U46619 (a TXA2 agonist) and myocardial ischaemia/reperfusion injury. Cardiac function was investigated with myocardial permeability, the troponin I concentration and the infarct size. Myocardial TXAS, TP, endothelial nitric oxide (NO) synthase (eNOS), nicotinamide adenine dinucleotide phosphate oxidase 4 (NOx4), 4-hydroxynonenal, interleukin (IL)-1β, cell apoptosis, coronary effluent thromboxane B2 (TXB2) and superoxide anions (O2 −) and NO concentrations were measured. Mice mesenteric reactivity in response to various drugs was assessed by wire myography. In vivo fluorescent platelet adhesiveness to the mesenteric arterial endothelium after FeCl3 stimulation was examined. In B6 mice, ischaemia/reperfusion significantly increased levels of ST-segment elevation, myocardial TXAS, TP, NOx4, IL-1β, apoptosis, coronary endothelin-1, TXB2, O2 − release and the infarct size, with concomitant decreases in eNOS, NO concentrations and cardiac micro-circulation. These effects were remarkably depressed in TXAS−/−, TP−/− and TXAS−/−TP−/− mice. Aspirin treatment or depletion of the TXAS, TP or TXAS/TP gene significantly attenuated the exaggerated vascular reactivity by vasoconstrictors and vasodilators and efficiently reduced platelet adhesion to the mesenteric endothelium under FeCl3 stimulation.

Conclusion Inhibiting TXAS/TXA2/TP signalling confers microvascular protection against oxidative injury in both cardiac and mesenteric arteries.

Background The CAVA trial did not show the anticipated risk reduction for postthrombotic syndrome (PTS) after thrombus removal via additional ultrasound-accelerated catheter-directed thrombolysis (UACDT) in patients with acute iliofemoral deep vein thrombosis (IFDVT). Difficulties in achieving an effective degree of recanalization through thrombolysis may have influenced outcomes. We therefore assessed whether successful UACDT (restored patency ≥ 90%) did reduce the development of PTS.

Methods This CAVA trial post hoc analysis compared the proportion of PTS at 1-year follow-up between patients with successful UACDT and patients that received standard treatment only. In addition, clinical impact as well as determinants of successful thrombolysis were explored.

Results UACDT was initiated in 77 (50.7%) patients and considered successful in 41 (53.2%, interrater agreement κ = 0.7, 95% confidence interval 0.47–0.83). PTS developed in 15/41 (36.6%) patients in the successful UACDT group versus 33/75 (44.0%) controls (p = 0.44). In this comparison, successful UACDT was associated with lower Venous Clinical Severity Score (3.50 ± 2.57 vs. 4.82 ± 2.74, p = 0.02) and higher EuroQOL-5D (EQ-5D) scores (40.2 ± 36.4 vs. 23.4 ± 34.4, p = 0.01). Compared with unsuccessful UACDT, successful UACDT was associated with a shorter symptom duration at inclusion (p = 0.05), and higher rates of performed adjunctive procedures (p < 0.001) and stent placement (p < 0.001).

Conclusion Successful UACDT was not associated with a reduced proportion of PTS 1 year after acute IFDVT compared with patients receiving standard treatment alone. There was, however, a significant reduction in symptom severity and improvement of generic quality of life according to the EQ-5D. Better patient selection and optimization of treatment protocols are needed to assess the full potential of UACDT for the prevention of PTS.

Trial Registration Number ClinicalTrials.gov number, NCT00970619.

The global assay of Overall Haemostasis Potential we previously described has been refined. The coagulation cascade in plateletpoor plasma is triggered by adding a minimal dose of recombinant tissue factor together with purified phospholipids and calcium; fibrinolysis is initiated by adding recombinant tissue type-plasminogen activator in a concentration similar to what can be obtained during thrombolysis. Numerical differentials of optical densities reflecting rates of fibrin formation and degradation are calculated by a new software, and the Coagulation Profile (Cp) and the Fibrinolysis Profile (Fp) are determined. The combined effect of these counteractive systems is expressed as a ratio of Cp to Fp, called the Overall Haemostasis Index. Commercially available coagulant-deficient patient plasma samples and plasma with various amounts of added PAI-1 are examined; changes of fibrin turbidity demonstrate that this assay can determine Cp and Fp in a physiologically relevant way. Increased Cp and decreased Fp in prothrombotic patients, as well as expected effects of heparin or a thrombin inhibitor on Cp and Fp, suggest that our method can detect hypercoagulability and assist in monitoring antithrombotic treatment. Ongoing studies will show whether this simple assay can be of value in clinical routine.

Many studies showed that the occurrence of cardiovascular and cerebrovascular events exhibits a seasonal and monthly variation. Evidences of a seasonal and monthly variation in the incidence of venous thromboembolism (VTE) are more conflicting. We conducted a systematic review and a meta-analysis of the literature to assess the presence of an infradian rhythm of this disease. MEDLINE and EMBASE databases were searched up to January 2010. Monthly and seasonal variation in the incidence of VTE were analysed. We included studies analysing seasonal or monthly aggregation in the incidence of deep-vein thrombosis (DVT) and/or pulmonary embolism (PE) with an objective diagnosis of VTE. Two authors independently reviewed and extracted data. Seventeen studies for a total of about 35,000 patients were included. Twelve studies analysed the seasonal variation and 10 studies the monthly variation of VTE. Our results showed a significantly increased incidence of VTE in winter (chi-square 146.04, p <0.001), with a relative risk (RR) of VTE of 1.143 (99% CI [1.141, 1.144]), and a significantly increased incidence of VTE in January (chi-square 232.57, p <0.001) with an RR of VTE of 1.194 (99% CI 1.186, 1.203). Subgroup analyses including only idiopathic venous thromboembolic events confirmed the results of principal analyses. In conclusion, our data support the presence of an infradian pattern in the incidence of venous thromboembolic events, with a significantly higher risk in Winter and in January. Future studies are needed to better clarify the mechanisms behind this pattern.

Haemophilia A is an X-linked, recessive, inherited bleeding disorder which affects 1 in 5000 males born worldwide. It is caused by mutations in the FactorVIII (F8) gene on chromosome Xq28. We describe for the first time two mutation specific, single cell protocols for pre-implantation genetic diagnosis (PGD) of haemophilia A that enable the selection of both male and female unaffected embryos. This approach offers an alternative to sexing, frequently used for X-linked disorders, that results in the discarding of all male embryos including the 50% that would have been normal. Two families witha history of severe haemophilia A requested carrier diagnosis and subsequently proceeded to PGD. The mutation in family1 isa single nucleotide substitution c. 5953C>T, R1966X in exon 18 and in family 2, c. 5122C>T, R1689C in exon 14 of the F8 gene. Amplification efficiency was compared between distilled water and SDS/proteinase K cell lysis (98.0%, 96/98 and 80%, 112/140 respectively) using 238 single lymphocytes. Blastomeres from spare IVF cleavage-stage embryos donated for research showed amplification efficiencies of 83.3% (45/54) for the R1966X and 92.9% (13/14) for the R1689C mutations. The rate of allele dropout (ADO) on heterozygous lymphocytes was 1.1% (1/93) for R1966X and 5.94% (6/101) for R1689C mutations. A single PGD treatment cycle for family1 resulted in two embryos for transfer but these failed to implant. However, with family 2, two embryos were transferred to the uterus on day 4 resulting in a successful singleton pregnancy and subsequent live birth of a normal non-carrier female.