bluuebunny/crossref_metadata_2025_split huggingface dataset:
Platelet tetraspanin complexes and their association with lipid rafts
Authors: McMillan-Ward Eileen , Israels Sara 
Published: October 2007

SummaryTetraspanins are a superfamily of integral membrane proteins that facilitate the organization of membrane and intracellular signaling molecules into dynamic signaling microdomains, tetraspaninenriched microdomains (TEMs). Four tetraspanin family members have been identified in platelets: CD9, CD151 and TSSC6, which are constitutively associated with αIIb3, and CD63, which is present on granule membranes in resting platelets and associates with αIIbβ3-CD9 following platelet activation. CD63 and CD9 associate with a type II phosphatidylinositol 4-kinase, PI4K55, in both resting and activated platelets. Immunoelectron microscopic studies showed co-localization of CD63 and PI4K55 on internal membranes of resting platelets and on the filopodia of thrombin-activated platelets. Because TEMs in malignant cell lines appear to be distinct from prototypic lipid rafts, this study examined whether CD63-PI4K55 and CD9-PI4K55 complexes were resident in platelet-lipid rafts, or formed distinct microdomains. CD63, CD9 and PI4K55 were recovered from low-density membrane fractions (LDMFs) of sucrose gradients following platelet lysis in Brij 35, but unlike lipidraft proteins were not insoluble in Triton X-100, being absent from LDMFs of platelets lysed with Triton. In cubation of platelets with methyl-β-cyclodextrin, to deplete cholesterol and disrupt lipid rafts, shifted the complexes to higher density sucrose gradient fractions, but did not disrupt the tetraspanin-PI4K55 complexes. These results demonstrate that tetraspanin complexes in platelets form cholesterol-associated microdomains that are distinct from lipid rafts. It is probable thatTEMs and lipid rafts associate under certain conditions, resulting in the close proximity of distinct sets of signaling molecules, facilitating signal transduction.
Residual platelet reactivity is an independent predictor of myocardial injury in acute myocardial infarction patients on antiaggregant therapy
Authors: Paniccia Rita , Antonucci Emilia , Poli Serena , Gori Anna Maria , Valente Serafina , Giglioli Cristina , Lazzeri Chiara , Prisco Domenico , Abbate Rosanna , Gensini Gian Franco , Marcucci Rossella 
Published: October 2007

SummaryIn this study we sought to evaluate if platelet function measured after percutaneous coronary intervention (PCI) affects the severity of myocardial infarction (MI), measured by markers of cardiac necrosis. We measured platelet function by both a point-of-care assay (PFA-100) and platelet-rich plasma aggregation by two agonists (arachidonic acid –AA- and 2 and 10 μM ADP) in 367 patients with MI after PCI (200 patients on dual antiplatelet agents – group A- and 167 on dual antiplatelet agents plus GpIIb/ IIIa inhibitors – group B). One hundred twenty-one (32.9%) patients were found to have a residual platelet reactivity (RPR) by PFA (CT/EPI <203 sec): 74/200 (37%) in group A and 47/167 (28.1%) in group B (p=0.07). In 129 (35.1%) patients we found a RPR by AA-PA: 80/200 (40%) in group A and 49/167 (29.3%) in group B (p<0.05). Seventeen out of 367 (4.6%) were found to have a RPR by ADP2-PA [15/200 (7.5%) in group A and 2/167 (1.2%) in group B; p<0.005] and 88/367 (23.9%) by ADP10-PA [64/200 (32%) in group A and 24/167 (14.4%) in group B, p<0.0001]. CK-MB and cTnI mean peak values were significantly higher in the first tertile of CT/ADP and CT/EPI distribution with respect to the other tertiles and they were significantly higher in patients with RPR by CT/EPI in both groupA and group B patients. CK-MB and cTnI peak values were significantly higher in the third tertile of AA-PA,ADP 2 μM-PA and ADP 10 μM-PA distribution with respect to the other tertiles and were significantly higher in patients with RPR by AA-PA and by ADP 10-PA in both group A and group B patients. Multivariate analysis revealed platelet function as an independent predictor of CK-MB and cTnI peak values in both groups of patients independently of clinical, laboratory ad procedural parameters. In conclusion, we found that the severity of MI in patients with MI undergoing primary PCI is influenced by a persistent platelet activation on multiple antiplatelet therapy.
Factor VIIa and tissue factor procoagulant activity in diabetes mellitus after acute ischemic stroke: Impact of hyperglycemia
Authors: Vaidyula Vijender , Kanamalla Uday , De Angelis Michael , Gaughan John , Gentile Nina , Rao Koneti 
Published: October 2007

SummaryAlterations in blood coagulation may explain the poorer neurological outcome with diabetes mellitus and hyperglycemia after acute ischemic stroke. We studied the relationships between diabetes mellitus, hyperglycemia, whole blood tissue factor procoagulant activity (TF-PCA) and plasma Factor VIIa (FVIIa) in ten patients with type 2 diabetes mellitus and 11 non-diabetic patients at baseline and 6, 12, 24, and 48 hours (h) after presentation for acute stroke. In addition, we examined plasma prothrombin fragment 1+2 (F1.2) and thrombin-antithrombin complexes (TAT) as markers of thrombin generation. Stroke severity, assessed by National Institute of Health Stroke Scale (NIHSS), was similar at baseline (p=0.26) but worse in diabetic (8.20 ± 4.3) than nondiabetic patients (2.67 ± 2.1,p=0.023) at 48 h. At presentation, diabetic patients had higher FVIIa (p=0.004) and lower TF-PCA (p=0.027) than non-diabetic patients but both were higher than in normal control subjects. FVIIa levels remained higher in diabetic patients at 6, 12 and 24 h after stroke. In diabetic patients, FVIIa (r=0.40, p=0.02) and TF-PCA (r=0.50, p=0.02) correlated with blood glucose; and, FVIIa correlated with plasma F1.2 (r=0.34, p=0.002) and TAT levels (r=0.62, p<0.0001). In non-diabetic patients, TF-PCA, but not FVIIa, correlated with F1.2 (r=0.402, p=0.010) andTAT (r=0.39, p=0.011). Combining both groups, NIHSS scores were positively related to FVIIa levels (r=0.50,p=0.021) and inversely related toTF-PCA levels (r=-0.498, p=0.02). Acute ischemic stroke patients with diabetes and hyperglycemia have a more intense procoagulant state compared with nondiabetic patients. This is related to glucose levels and provides a potential mechanism for the observed worse prognosis in such patients after acute stroke.
Staphylococcal infections impair the mesothelial fibrinolytic system: The role of cell death and cytokine release
Authors: Brück Michaela , Grundmeier Matthias , Peters Georg , Sinha Bhanu , Haslinger-Löffler Bettina 
Published: October 2007

SummaryBacterial peritonitis is a serious complication of peritoneal dialysis patients and of patients after abdominal surgery. Especially episodes due to Staphylococcus aureus can harm the peritoneum severely, resulting in peritoneal fibrosis. Human peritoneal mesothelial cells play a critical role in maintaining the integrity of the peritoneum, as they release components of the fibrinolytic system and regulate the influx of immune cells by expressing chemokines and adhesion molecules. Using cultured human peritoneal mesothelial cells (HMCs) and blood mononuclear cells,we analyzed the effect of different staphylococcal strains on mesothelial fibrinolysis and on inflammatory reactions and show that only S. aureus strains with an invasive and hemolytic phenotype decrease the production of fibrinolytic system components, most likely via cell death induction. Furthermore, HMCs react to invading staphylococci by enhanced expression of chemokines and adhesion molecules. Mononuclear cells were activated by all staphylococcal strains tested, and their culture supernatants impaired mesothelial fibrinolysis. Simvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, efficiently enhanced the mesothelial fibrinolytic capacity under these inflammatory conditions, but did not protect HMCs against S. aureus-induced cell death. We conclude that only selected S. aureus strains decrease the release of fibrinolytic system components and provoke a mesothelial inflammatory response. These factors most likely contribute to peritoneal fibrosis and might account for the severe clinical presentation of S. aureus peritonitis.
Elevated factor VIII in hereditary haemorrhagic telangiectasia (HHT): Association with venous thromboembolism
Authors: Sulaiman Laila , Govani Fatima , Jackson James , Begbie Megan , Shovlin Claire 
Published: October 2007

SummaryHereditary haemorrhagic telangiectasia (HHT) causes chronic nasal and gastrointestinal haemorrhage. Prothrombotic agents are commonly used for severe haemorrhage. Thrombotic risks have not been defined. In order to identify prothrombotic variables in HHT patients, and assess their potential functional significance, a pilot ELISA-based study comparing plasma proteins in healthy individuals with HHT to age/sex-matched non-HHT controls was validated in a full study of 309 consecutive HHTaffected individuals. In the pilot study, factor VIII (FVIII) and von Willebrand factor antigen concentrations were elevated in the HHT group compared to non-HHT controls (p<0.0013, Mann- Whitney). Service laboratory measurements confirmed high FVIII:Ag in 125 HHT-affected individuals with no recent illhealth, intervention or venous thromboemboli. FVIII:Ag levels increased with age. Logistic regression also suggested an age-independent association with HHT-associated pulmonary arteriovenous malformations (AVMs). No association was demonstrated between FVIII:Ag and acute phase response, disseminated intravascular coagulation, ABO group, pulmonary artery pressure, or markers of HHT haemorrhage. Elevated FVIII:Ag were associated with shortened activated partial thromboplastin times (APTTs), andVTE:VTE affected 20/309 (6.5%) HHT-affected individuals, at median age 61(36–71) years. Four VTE occurred in factorV Leiden heterozygotes in the months following PAVM-associated brain abscess. The strongest association with VTE was with log-transformed FVIII:Ag measured 10–132 months from VTE (odds ratio 2.41, 95% confidence intervals 1.254, 4.612, p=0.008). Age made no additional contribution to VTE risk once adjusted for FVIII:Ag. In conclusion, HHT-related elevation of FVIII:Ag levels may influence thrombotic risk in HHT. Individualised risk-benefit considerations may be helpful in HHT management.
Microparticles from apoptotic monocytes induce transient platelet recruitment and tissue factor expression by cultured human vascular endothelial cells via a redox-sensitive mechanism
Authors: Essayagh Sanah , Xuereb Jean-Marie , Terrisse Anne-Dominique , Tellier-Cirioni Lise , Pipy Bernard , Sié Pierre 
Published: October 2007

SummaryCirculating microparticles derived from different types of blood cells have been reported to impair endothelial function and to induce pro-inflammatory and prothrombotic endothelial phenotypes. Although the number of monocyte-derived microparticles (M-MPs) is elevated in the blood of patients with various inflammatory conditions, their interaction with endothelial cells has been poorly investigated so far. In this study, we produced microparticles in vitro from apoptotic human monocytes and examined the effects of their interaction with cultured human umbilical vascular endothelial cells (HUVECs). We found that low concentrations of M-MPs induced the production of reactive oxygen species (ROS), mainly anion superoxide, by the endothelial cells. At sub-toxic concentrations, M-MPs induced a rapid expression of von Willebrand factor at the cell surface, which mediated the transient attachment of non-activated platelets to the endothelium in flow conditions. In parallel, M-MPs up-regulated the expression of functional tissue factor by the endothelial cells. ROS controlled these two major changes and the process involved the phosphorylation of p38 mitogen activated protein kinase. We conclude that M-MPs may contribute to thrombotic events by producing redox signalling in endothelial cells.
Role of murine integrin α2β1 in thrombus stabilization and embolization: Contribution of thromboxane A2
Authors: Pozgajova Miroslava , Cosemans Judith , Munnix Imke , Eckes Beate , Nieswandt Bernhard , Heemskerk Johan , Kuijpers Marijke 
Published: October 2007

SummaryPlatelets stably interact with collagen via glycoprotein (GP)VI and α2β1 integrin. With α2-null mice, we investigated the role of α2β1 in thrombus formation and stability in vivo and in vitro. Using a FeCl3-induced thrombosis model, in arteries from α2-null mice smaller thrombi were formed with more embolization compared to vessels from wild-type mice. Aspirin treatment of wild-type mice causes similar effects, while the thromboxane A2 analogue U46619 was borderline effective in suppressing the embolisation in α2-null mice. In vitro, perfusion of α2-null blood over collagen resulted in formation of thrombi that were smaller and looser in appearance, regardless of the presence or absence of coagulation. Aspirin treatment or blockage of thromboxane receptors provoked embolus formation in wildtype blood, while U46619 normalized thrombus formation in blood from α2-null mice. We conclude that integrin α2β1 plays a role in stabilizing murine thrombi, likely by enhancing GPVI activation and thromboxane A2 release. The increased embolization in α2-null mice may argue against the use of α2β1 integrin inhibitors for antithrombotic therapy.
Platelet interaction with progenitor cells: Potential implications for regenerative medicine
Authors: Stellos Konstantinos , Gawaz Meinrad 
Published: October 2007

SummaryCirculating endothelial progenitor cells have been shown to instigate new vessel formation via angiogenesis and neovascularisation and to induce ongoing vascular and tissue repair by domiciliation to sites of vascular or tissue damage. However, the mechanisms that recruit circulating endothelial progenitor cells towards vascular lesions and regulate repair mechanisms of ischemic peripheral organs are poorly described. Domiciliation of endothelial progenitor cells in peripheral tissue is a multi-step cascade including initial adhesion to subendothelial matrix or endothelium, transmigration and invasion of the target tissue. Platelets are the first circulating blood cells that interact with the injured vessel wall. They contain a number of growth factors, chemokines, cytokines and adhesive proteins that are released or surface-expressed upon platelet activation including adhesion. Recent studies suggest that platelet interaction with endothelial progenitor cells influences chemotaxis, adhesion, activation and differentiation of progenitor cells. Release of the chemokine SDF-1 from platelets enhances neovascularization through mobilization of progenitor cells. Adherent platelets recruit bone marrow-derived progenitor cells to arterial thrombi in vitroand in vivoand induce their subsequent differentiation towards an endothelial phenotype. Moreover, platelet accumulation in a co-culture system with CD34+ progenitor cells results in the differentiation of the latter to macrophages in vitro. Although further studies are needed to elucidate the mechanisms that platelets determine the fate of endothelial progenitor cells into vascular lesions, platelet interaction with progenitor cells seems to play a decisive role in vascular and tissue regeneration.
Fibrotic injury after experimental deep vein thrombosis is determined by the mechanism of thrombogenesis
Authors: Varma Manu , Moaveni Daria , Dewyer Nicholas , Moore Andrea , Lynch Erin , Longo Christopher , Deatrick Barry , Kunkel Steven , Upchurch Gilbert , Wakefield Thomas , Henke Peter 
Published: October 2007

SummaryVessel wall matrix changes occur after injury, although this has not been well studied in the venous system. This study tested the hypothesis that the thrombus dictates the vein wall response and vein wall damage is directly related to the duration of thrombus contact. To determine the injury response over time, rats underwent inferior vena cava (IVC) ligation to produce a stasis thrombus, with harvest at various time points to 28 days (d). Significant vein wall matrix changes occurred with biomechanical injury (stiffness) peaking at 7–14 d, with concurrent early reduction in total collagen, an increase in early matrix metalloproteinase (MMP)-9 and late MMP-2, and concomitant increase in tumor necrosis factor (TNF)α, monocyte chemoattractant( MCP)-1 and tumor growth factor (TGF)β (all P <0.05). To isolate the effect of the thrombus and its mechanism of genesis, rats underwent 7 d or limited stasis (24 hours), non-stasis thrombosis, or non-thrombotic IVC occlusion (Silicone plug). Vein wall stiffness was increased seven-fold, with a five-fold reduction in collagen, and 5.5- to seven-fold increase in TNFα, MCP-1, and TGFβ with 7 d stasis as compared with controls (all P <0.05). By Picosirus red staining analysis, collagenolysis was significantly greater with 7 d stasis injury (P = 0.01) but neither MMP-9 nor MMP-2 activity correlated with injury mechanism. In addition, vein wall cellular proliferation and uPA gene expression paralled the stasis thrombotic injury. Limited stasis, non-stasis thrombosis and non-thrombotic IVC occlusion showed a lesser inflammatory response. These data suggest both a static component and the thrombus directs vein wall injury via multiple mechanisms.
Matrix metalloproteinase (MMP) induction and inhibition at different doses of recombinant tissue plasminogen activator following experimental stroke
Authors: Burggraf Dorothe , Martens Helge , Dichgans Martin , Hamann Gerhard 
Published: October 2007

SummaryAlthough recombinant tissue plasminogen activator (rt-PA) is successfully used for thrombolysis in human stroke, it may increase the risk of haemorrhagic complications. It was shown that the matrix metalloproteinase (MMP) system is critically involved in basal lamina degradation after middle cerebral artery occlusion and reperfusion following rt-PA administration. We describe the effects of different doses of rt-PA (saline, 0.9, 9, or 18 mg rt-PA/kg body weight) on the MMPs, their specific inhibitors (TIMPs), and also their inducer protein EMMPRIN following experimental cerebral ischemia (3 hours [h], 24 h reperfusion, suture model) in rats. The amount of MMP-2 and -9 was measured by gelatine zymography, TIMP-1 and -2 by reverse gelatine zymography, and the content of EMMPRIN and the basal lamina component collagen type IV by Western blotting. The amount of both MMPs steadily rose with increasing doses of rt- PA (p<0.05). In contrast, their endogenous inhibitors TIMPs decreased (p<0.001). A balance between the proteases and their inhibitors was achieved at the low dose of 0.9 mg/kg rt-PA in the rats, which significantly coincided with the demonstrated protection of collagen type IV degradation at this dose. The inducer protein EMMPRIN increased in parallel to its substrate MMP-2. Exogenous rt-PA leads to an increase of the MMP-inducing system by EMMPRIN, and a rise of the degrading MMPs follows. However, at low to moderate doses of rt-PA the microvascular basal lamina was protected, probably due to inhibition of MMP-2 and MMP-9 by the upregulation of their inhibitors. This strongly supports use of the lowest effective dosage of rt-PA available.
PSGL-1 regulates platelet P-selectin-mediated endothelial activation and shedding of P-selectin from activated platelets
Authors: Dole Vandana , Bergmeier Wolfgang , Patten Ian , Hirahashi Junichi , Mayadas Tanya , Wagner Denisa 
Published: October 2007

SummaryWe have previously shown that activated platelets in circulation stimulate release of endothelial Weibel-Palade bodies thus increasing leukocyte rolling in venules. P-selectin on the activated platelets mediates adhesion to leukocytes via PSGL-1 and is rapidly shed into plasma. We were interested in studying the role of PSGL-1 in regulating expression and function of platelet P-selectin. We show here that PSGL-1 is critical for the activation of endothelial cells in venules of mice infused with activated platelets. The interaction of platelet P-selectin with PSGL-1 is also required for P-selectin shedding, as P-selectin was retained significantly longer on the surface of activated platelets infused into PSGL-1-/- compared to wild-type mice. The leukocyte integrin αMβ2 (Mac-1) was not required for P-selectin shedding. In addition to shedding, P-selectin can be downregulated from the platelet surface through internalization and this is the predominant mechanism in the absence of PSGL-1. We demonstrate that leukocyte- neutrophil elastase,known to cleave P-selectin in vitro, is not the major sheddase for P-selectin in vivo. In conclusion, interaction of platelet P-selectin with PSGL-1 is crucial for activation of the endothelium andWeibel-Palade body secretion. The interaction with PSGL-1 also results in rapid shedding of P-selectin thus downregulating the inflammatory potential of the platelet.
The angiotensin-converting enzyme insertion/deletion polymorphism and serum levels of angiotensin-converting enzyme in venous thromboembolism
Authors: Ay Cihan , Bencur Peter , Vormittag Rainer , Sailer Thomas , Jungbauer Christof , Vukovich Thomas , Mannhalter Christine , Pabinger Ingrid 
Published: October 2007

SummaryThe angiotensin-converting enzyme (ACE) has been suggested to affect blood coagulation and fibrinolysis. Results from literature on the role of the frequent insertion/deletion (I/D) polymorphism in the ACE gene in venous thromboembolism (VTE) are controversial. Only limited data on ACE serum levels in VTE exist. We determined the ACE I/D polymorphism by genotyping and ACE serum levels by an enzymatic assay in 100 high-risk patients with objectively confirmed recurrent VTE and at least one event of an unprovoked deep venous thrombosis or pulmonary embolism. One hundred twenty-five age- and sex-matched healthy individuals served as controls. ACE genotype frequencies were not significantly different between patients (DD: 26.0%,ID: 52.0%, II: 22.0%) and controls (DD: 29.6%, ID: 44.8%, II: 25.6%; p=0.56). Neither individuals with ACE DD genotype nor those with ACE ID genotype had a higher risk for VTE in comparison to those with ACE II genotype (odds ratio and [95% confidence interval]: 1.0 [0.5–2.1] and 1.4 [0.7–2.6], respectively). Serum ACE levels (U/l) did not differ between patients (median = 25.25, 25th –75th percentile: 20.20–33.70) and controls (24.20, 17.85–34.50, p=0.49). In the total population involved in the study the ACE DD genotype (n=63: 36.00 [26.40–43.00]) was associated with higher ACE levels than the ACE ID genotype (n=108: 24.10 [19.80–31.48], p<0.001) and the ACE II genotype (n=54: 19.35 [15.00–22.95], p<0.001). In conclusion, we found a significant association of the ACE I/D polymorphism with ACE serum levels. However, neither the serum levels nor the I/D genotype were associated with VTE.