Thrombin-Activatable Fibrinolysis Inhibitor (TAFI) Deficient Mice Are Susceptible to Intracerebral Thrombosis and Ischemic Stroke

Background: Thrombus formation is a key step in the pathophysiology of acute ischemic stroke and results from the activation of the coagulation cascade. Thrombin plays a central role in this coagulation system and contributes to thrombus stability via activation of thrombin-activatable fibrinolysis inhibitor (TAFIa). TAFIa counteracts endogenous fibrinolysis at different stages and elevated TAFI levels are a risk factor for thrombotic events including ischemic stroke. Although substantial in vitro data on the influence of TAFI on the coagulation-fibrinolysis-system exist, investigations on the consequences of TAFI inhibition in animal models of cerebral ischemia are still lacking. In the present study we analyzed stroke development and post stroke functional outcome in TAFI(-/-) mice. Methodology/Principal Findings: TAFI(-/-) mice and wild-type controls were subjected to 60 min transient middle cerebral artery occlusion (tMCAO) using the intraluminal filament method. After 24 hours, functional outcome scores were assessed and infarct volumes were measured from 2,3,5- Triphenyltetrazoliumchloride (TTC)-stained brain slices. Hematoxylin and eosin (H&E) staining was used to estimate the extent of neuronal cell damage. Thrombus formation within the infarcted brain areas was analyzed by immunoblot. Infarct volumes and functional outcomes did not significantly differ between TAFI(-/-) mice and controls (p>0.05). Histology revealed extensive ischemic neuronal damage regularly including the cortex and the basal ganglia in both groups. TAFI deficiency also had no influence on intracerebral fibrin(ogen) formation after tMCAO. Conclusion: Our study shows that TAFI does not play a major role for thrombus formation and neuronal degeneration after ischemic brain challeng

SELDI-TOF mass spectrometry of High-Density Lipoprotein

<p>Abstract</p> <p>Background</p> <p>High-Density Lipoprotein (HDL), one of the main plasma lipoproteins, serves as a docking station for proteins involved in inflammation, coagulation, and lipid metabolism.</p> <p>Methods</p> <p>To elucidate the protein composition of HDL, we employed SELDI-TOF mass spectrometry as a potential high-throughput proteomic candidate for protein profiling of HDL. HDL derived from normolipemic individuals was captured on PS20 protein-chips using covalently bound antibodies against apo A-I or A-II.</p> <p>Results</p> <p>After optimisation, on-chip capture of HDL particles directly from plasma or from pre-purified HDL resulted in comparable fingerprints confirming specific capture of HDL. Depending on the capture antibody some differences in the fingerprint were observed. The most detailed fingerprint was observed up to 50 kDa; approximately 95 peaks were detected in the 3–50 kDa molecular mass range. Between 50 and 160 kDa, 27 more peaks were detected.</p> <p>Conclusion</p> <p>Based on these results, SELDI-TOF MS may be a suitable high-throughput candidate for HDL protein profiling and marker search. This approach may be used to <it>i) </it>investigate the underlying mechanisms that lead to increased atherothrombotic risk and <it>ii) </it>to investigate the atherothrombotic state of an individual.</p

Vascular Endothelial Growth Factor in the Circulation in Cancer Patients May Not Be a Relevant Biomarker

Levels of circulating vascular endothelial growth factor (VEGF) have widely been used as biomarker for angiogenic activity in cancer. For this purpose, non-standardized measurements in plasma and serum were used, without correction for artificial VEGF release by platelets activated ex vivo. We hypothesize that "true" circulating (c)VEGF levels in most cancer patients are low and unrelated to cancer load or tumour angiogenesis. We determined VEGF levels in PECT, a medium that contains platelet activation inhibitors, in citrate plasma, and in isolated platelets in 16 healthy subjects, 18 patients with metastatic non-renal cancer (non-RCC) and 12 patients with renal cell carcinoma (RCC). In non-RCC patients, circulating plasma VEGF levels were low and similar to VEGF levels in controls if platelet activation was minimized during the harvest procedure by PECT medium. In citrate plasma, VEGF levels were elevated in non-RCC patients, but this could be explained by a combination of increased platelet activation during blood harvesting, and by a two-fold increase in VEGF content of individual platelets (controls: 3.4 IU/10(6), non-RCC: 6.2 IU/10(6) platelets, p = 0.001). In contrast, cVEGF levels in RCC patients were elevated (PECT plasma: 64 pg/ml vs. 21 pg/ml, RCC vs. non-RCC, p<0.0001), and not related to platelet VEGF concentration. Our findings suggest that "true" freely cVEGF levels are not elevated in the majority of cancer patients. Previously reported elevated plasma VEGF levels in cancer appear to be due to artificial release from activated platelets, which in cancer have an increased VEGF content, during the blood harvest procedure. Only in patients with RCC, which is characterized by excessive VEGF production due to a specific genetic defect, were cVEGF levels elevated. This observation may be related to limited and selective success of anti-VEGF agents, such as bevacizumab and sorafenib, as monotherapy in RCC compared to other forms of cance

Markers of inflammation and coagulation indicate a prothrombotic state in HIV-infected patients with long-term use of antiretroviral therapy with or without abacavir

Background: Abacavir (ABC) treatment has been associated with an increased incidence of myocardial infarction. The pathophysiological mechanism is unknown. In this study markers of inflammation and coagulation in HIV-infected patients using antiretroviral therapy with or without ABC were examined to pinpoint a pathogenic mechanism. Given the important role of high sensitivity C-reactive protein (hsCRP) levels in predicting cardiovascular risk, patient groups were also analyzed according to hsCRP levels.Method

Thrombin-Activatable Fibrinolysis Inhibitor Binds To Streptococcus Pyogenes By Interacting With Collagen-Like Proteins A And B

Regulation of proteolysis is a critical element of the host immune system and plays an important role in the induction of pro- and anti-inflammatory reactions in response to infection. Some bacterial species take advantage of these processes and recruit host proteinases to their surface in order to counteract the host attack. Here we show that Thrombin-activatable Fibrinolysis Inhibitor (TAFI), a zinc-dependent procarboxypeptidase, binds to the surface of group A streptococci of an M41 serotype. The interaction is mediated by the streptococcal collagen-like surface proteins A and B (Sc1A and Sc1B), and the streptococcal-associated TAFI is then processed at the bacterial surface via plasmin and thrombin-thrombomodulin. These findings suggest an important role for TAFI in the modulation of host responses by streptococci

Thrombin-Activatable Fibrinolysis Inhibitor Binds To Streptococcus Pyogenes By Interacting With Collagen-Like Proteins A And B

Regulation of proteolysis is a critical element of the host immune system and plays an important role in the induction of pro- and anti-inflammatory reactions in response to infection. Some bacterial species take advantage of these processes and recruit host proteinases to their surface in order to counteract the host attack. Here we show that Thrombin-activatable Fibrinolysis Inhibitor (TAFI), a zinc-dependent procarboxypeptidase, binds to the surface of group A streptococci of an M41 serotype. The interaction is mediated by the streptococcal collagen-like surface proteins A and B (Sc1A and Sc1B), and the streptococcal-associated TAFI is then processed at the bacterial surface via plasmin and thrombin-thrombomodulin. These findings suggest an important role for TAFI in the modulation of host responses by streptococci

Basic science research opportunities in thrombosis and hemostasis : Communication from the SSC of the ISTH

ACKNOWLEDGMENTS We thank Drs. Hari Hara Sudhan Lakshmanan and Sven Olson for illustrative assistance and design.Peer reviewedPublisher PD