TY - JOUR A1 - Reinhard, Matthias A1 - Halbrügge, Maria A1 - Scheer, Ulrich A1 - Wiegand, Christiane A1 - Jockusch, Brigitte M. A1 - Walter, Ulrich T1 - The 46/50 kDa phosphoprotein VASP purified from human platelets is a novel protein associated with actin filaments and focal contacts N2 - Vasoactive agents which elevate either cGMP or cAMP inhibit platelet activation by pathways sharing at least one component, the 46/50 kDa vasodilator-stimulated phosphoprotein (V ASP). V ASP is stoichiometrically phosphorylated by both cGMP-dependent and cAMPdependent protein kinases in intact human platelets, and its phosphorylation correlates very well with platelet inhibition caused by cGMP- and cAMP-elevating agents. Here we report that in human platelets spread on glass, V ASP is associated predominantly with the distal parts of radial micro filament bundles and with microfilaments outlining the periphery, whereas less V ASP is associated with a central microfilamentous ring. V ASP is also detectable in a variety of different cell types including fibroblasts and epithelial cells. In fibroblasts, V ASP is concentrated at focal contact areas, along microfilament bundles (stress fibres) in a punctate pattern, in the periphery of protruding lamellae, and is phosphorylated by cGMP- and cAMP-dependent protein kinases in response to appropriate stimuli. Evidence for the direct binding of V ASP to F -actin is also presented. The data demonstrate that V ASP is a novel phosphoprotein associated with actin filaments and focal contact areas, i.e. transmembrane junctions between microfilaments and the extracellular matrix. KW - cAMP / cGMP / cytoskeleton / phosphorylation / protein kinase Y1 - 1992 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-34246 ER - TY - JOUR A1 - Kraft, Peter A1 - Benz, Peter Michael A1 - Austinat, Madeleine A1 - Brede, Marc Elmar A1 - Schuh, Kai A1 - Walter, Ulrich A1 - Stoll, Guido A1 - Kleinschnitz, Christoph T1 - Deficiency of Vasodilator-Stimulated Phosphoprotein (VASP) Increases Blood-Brain-Barrier Damage and Edema Formation after Ischemic Stroke in Mice N2 - Background: Stroke-induced brain edema formation is a frequent cause of secondary infarct growth and deterioration of neurological function. The molecular mechanisms underlying edema formation after stroke are largely unknown. Vasodilator-stimulated phosphoprotein (VASP) is an important regulator of actin dynamics and stabilizes endothelial barriers through interaction with cell-cell contacts and focal adhesion sites. Hypoxia has been shown to foster vascular leakage by downregulation of VASP in vitro but the significance of VASP for regulating vascular permeability in the hypoxic brain in vivo awaits clarification. Methodology/Principal Findings: Focal cerebral ischemia was induced in Vasp2/2 mice and wild-type (WT) littermates by transient middle cerebral artery occlusion (tMCAO). Evan’s Blue tracer was applied to visualize the extent of blood-brainbarrier (BBB) damage. Brain edema formation and infarct volumes were calculated from 2,3,5-triphenyltetrazolium chloride (TTC)-stained brain slices. Both mouse groups were carefully controlled for anatomical and physiological parameters relevant for edema formation and stroke outcome. BBB damage (p,0.05) and edema volumes (1.7 mm360.5 mm3 versus 0.8 mm360.4 mm3; p,0.0001) were significantly enhanced in Vasp2/2 mice compared to controls on day 1 after tMCAO. This was accompanied by a significant increase in infarct size (56.1 mm3617.3 mm3 versus 39.3 mm3610.7 mm3, respectively; p,0.01) and a non significant trend (p.0.05) towards worse neurological outcomes. Conclusion: Our study identifies VASP as critical regulator of BBB maintenance during acute ischemic stroke. Therapeutic modulation of VASP or VASP-dependent signalling pathways could become a novel strategy to combat excessive edema formation in ischemic brain damage. KW - Vasodilatator-stimuliertes Phosphoprotein KW - Vasodilator-Stimulated Phosphoprotein Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-68522 ER - TY - JOUR A1 - Grube, Maike Miriam A1 - Koennecke, Hans-Christian A1 - Walter, Georg A1 - Meisel, Andreas A1 - Sobesky, Jan A1 - Nolte, Christian Hans A1 - Wellwood, Ian A1 - Heuschmann, Peter Ulrich T1 - Influence of Acute Complications on Outcome 3 Months after Ischemic Stroke JF - PLOS ONE N2 - Background: Early medical complications are potentially modifiable factors influencing in-hospital outcome. We investigated the influence of acute complications on mortality and poor outcome 3 months after ischemic stroke. Methods: Data were obtained from patients admitted to one of 13 stroke units of the Berlin Stroke Registry (BSR) who participated in a 3-months-follow up between June 2010 and September 2012. We examined the influence of the cumulative number of early in-hospital complications on mortality and poor outcome (death, disability or institutionalization) 3 months after stroke using multivariable logistic regression analyses and calculated attributable fractions to determine the impact of early complications on mortality and poor outcome. Results: A total of 2349 ischemic stroke patients alive at discharge from acute care were included in the analysis. Older age, stroke severity, pre-stroke dependency and early complications were independent predictors of mortality 3 months after stroke. Poor outcome was independently associated with older age, stroke severity, pre-stroke dependency, previous stroke and early complications. More than 60% of deaths and poor outcomes were attributed to age, pre-stroke dependency and stroke severity and in-hospital complications contributed to 12.3% of deaths and 9.1% of poor outcomes 3 months after stroke. Conclusion: The majority of deaths and poor outcomes after stroke were attributed to non-modifiable factors. However, early in-hospital complications significantly affect outcome in patients who survived the acute phase after stroke, underlining the need to improve prevention and treatment of complications in hospital. KW - hospital medical complications KW - quality-of-care KW - term mortality KW - Barthel-Index KW - rankin scale KW - risk-factors KW - trial KW - reliability KW - dependency KW - predictors Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-128362 SN - 1932-6203 VL - 8 IS - 9 ER - TY - JOUR A1 - Navdaev, Alexey A1 - Subramanian, Hariharan A1 - Petunin, Alexey A1 - Clemetson, Kenneth J. A1 - Gambaryan, Stepan A1 - Walter, Ulrich T1 - Echicetin Coated Polystyrene Beads: A Novel Tool to Investigate GPIb-Specific Platelet Activation and Aggregation JF - PLoS ONE N2 - von Willebrand factor/ristocetin (vWF/R) induces GPIb-dependent platelet agglutination and activation of αIIbβ3 integrin, which also binds vWF. These conditions make it difficult to investigate GPIb-specific signaling pathways in washed platelets. Here, we investigated the specific mechanisms of GPIb signaling using echicetin-coated polystyrene beads, which specifically activate GPIb. We compared platelet activation induced by echicetin beads to vWF/R. Human platelets were stimulated with polystyrene beads coated with increasing amounts of echicetin and platelet activation by echicetin beads was then investigated to reveal GPIb specific signaling. Echicetin beads induced αIIbβ3-dependent aggregation of washed platelets, while under the same conditions vWF/R treatment led only to αIIbβ3-independent platelet agglutination. The average distance between the echicetin molecules on the polystyrene beads must be less than 7 nm for full platelet activation, while the total amount of echicetin used for activation is not critical. Echicetin beads induced strong phosphorylation of several proteins including p38, ERK and PKB. Synergistic signaling via P2Y12 and thromboxane receptor through secreted ADP and TxA2, respectively, were important for echicetin bead triggered platelet activation. Activation of PKG by the NO/sGC/cGMP pathway inhibited echicetin bead-induced platelet aggregation. Echicetin-coated beads are powerful and reliable tools to study signaling in human platelets activated solely via GPIb and GPIb-triggered pathways. KW - tyrosine KW - ERK signaling cascade KW - integrins KW - phosphorylation KW - polystyrene KW - platelet activation KW - platelet aggregation KW - platelets Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-119815 SN - 1932-6203 VL - 9 IS - 4 ER - TY - THES A1 - Hofmann, Ulrich Dietmar Walter T1 - Einfluss von Tumor Nekrose Faktor-Alpha (TNF- Alpha) auf die myokardiale Energetik T1 - TNF-Alpha impairs economy of contraction in rat myocardium N2 - Es konnte erstmals gezeigt werden, dass Tumor Nekrose Faktor-α (TNF- α) (TNF-α) in pathophysiologisch relevanten Konzentrationen neben seiner bekannten negativ inotropen Wirkung einen deutlichen Effekt auf die myokardiale Energetik im Myokard der Ratte besitzt. Dieser wurde anhand des Sauerstoffverbrauchs an rechtsventrikulären Muskelstreifenpräparaten quantifiziert. Der erhöhte Energieumsatz bei gleichzeitig reduzierter myokardialer Arbeit, d.h. der gesteigerte spezifische Sauerstoffverbrauch, basiert auf einer verschlechterten Ökonomie des Kontraktionsprozesses. Diese schnelle Wirkung auf die myokardiale Energetik ist durch einen Sphingolipid Signaltransduktionsweg vermittelt. Dagegen spielt wohl für den mechanischen Effekt von TNF-α sowohl NO, als auch Sphingosin eine Rolle. N2 - Objective: Several experimental studies have demonstrated that tumor necrosis factor-α (TNF-α) impairs myocardial contractility. It was the aim of the present study to test the hypothesis that TNF-α influences myocardial energy metabolism as well. Methods: Oxygen consumption (MVO2) of isometrically contracting trabeculae isolated from right ventricular rat myocardium was analyzed using a clark-type oxygen probe. The slope of the force-time integral-MVO2 regression line indicates economy of contraction. Results: TNF-α impaired myocardial economy without altering baseline MVO2. Incubation with TNF-α in the presence of the NO-synthase inhibitor L-NAME further impaired myocardial economy. Pre-incubation with the ceramidase inhibitor NOE abrogated the TNF-α effect on myocardial economy. The negative inotropic effect of TNF-α was observed in NOE, but not in L-NAME pre-incubated muscle fibers. Moreover, exogenous sphingosine mimicked the TNF-α effect on mechanics and energetics. Conclusion: TNF-α impairs the economy of chemo-mechanical energy transduction primarily through a sphingosine-mediated pathway. KW - Myokardiale Energetik KW - Tumor Nekrose Faktor-Alpha KW - Zytokine KW - Sauerstoffverbrauch KW - myocardial energetics KW - tumor necrosis factor-Alpha KW - cytokines KW - oxygen consumption Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-23663 ER - TY - JOUR A1 - Gambaryan, Stepan A1 - Subramanian, Hariharan A1 - Kehrer, Linda A1 - Mindukshev, Igor A1 - Sudnitsyna, Julia A1 - Reiss, Cora A1 - Rukoyatkina, Natalia A1 - Friebe, Andreas A1 - Sharina, Iraida A1 - Martin, Emil A1 - Walter, Ulrich T1 - Erythrocytes do not activate purified and platelet soluble guanylate cyclases even in conditions favourable for NO synthesis JF - Cell Communication and Signaling N2 - Background Direct interaction between Red blood cells (RBCs) and platelets is known for a long time. The bleeding time is prolonged in anemic patients independent of their platelet count and could be corrected by transfusion of RBCs, which indicates that RBCs play an important role in hemostasis and platelet activation. However, in the last few years, opposing mechanisms of platelet inhibition by RBCs derived nitric oxide (NO) were proposed. The aim of our study was to identify whether RBCs could produce NO and activate soluble guanylate cyclase (sGC) in platelets. Methods To test whether RBCs could activate sGC under different conditions (whole blood, under hypoxia, or even loaded with NO), we used our well-established and highly sensitive models of NO-dependent sGC activation in platelets and activation of purified sGC. The activation of sGC was monitored by detecting the phosphorylation of Vasodilator Stimulated Phosphoprotein (VASPS239) by flow cytometry and Western blot. ANOVA followed by Bonferroni’s test and Student’s t-test were used as appropriate. Results We show that in the whole blood, RBCs prevent NO-mediated inhibition of ADP and TRAP6-induced platelet activation. Likewise, coincubation of RBCs with platelets results in strong inhibition of NO-induced sGC activation. Under hypoxic conditions, incubation of RBCs with NO donor leads to Hb-NO formation which inhibits sGC activation in platelets. Similarly, RBCs inhibit activation of purified sGC, even under conditions optimal for RBC-mediated generation of NO from nitrite. Conclusions All our experiments demonstrate that RBCs act as strong NO scavengers and prevent NO-mediated inhibition of activated platelets. In all tested conditions, RBCs were not able to activate platelet or purified sGC. KW - hemoglobin KW - erythrocytes KW - nitric oxide KW - soluble guanylate cyclase KW - platelets Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-161223 VL - 14 IS - 16 ER -