P-selectin in haemostasis

During the past decade, interrelationships between inflammation and thrombosis have been the subject of extensive works, and it is now commonly recognized that inflammation (notably leucocyte recruitment) directly affects thrombosis, and that thrombosis also constitutes a pro-inflammatory event. This tight link is partly attributable to P-selectin, which is functional not only when expressed on the surface of activated platelets and endothelial cells, but also when shed, generating its soluble form, termed sP-selectin. In this review, we will provide an overview of the relative roles of the different compartments of P-selectin (platelet, endothelial cell, plasma) in haemostasis and vascular pathologies, and the potential therapeutic benefits achievable in targeting this molecule.     

Regulation of P-selectin binding to the neutrophil P-selectin counter-receptor P-selectin glycoprotein ligand-1 by neutrophil elastase and cathepsin G

In the inflammatory response, leukocyte rolling before adhesion and transmigration through the blood vessel wall is mediated by specific cell surface adhesion receptors. Neutrophil rolling involves the interaction of P-selectin expressed on activated endothelium and its counter-receptor on neutrophils, P-selectin glycoprotein ligand-1 (PSGL-1). Here, it is reported that P-selectin binding to neutrophils is lost under conditions that cause the release of proteinases from neutrophil primary granules. Treatment of neutrophils with the purified neutrophil granule proteinases, cathepsin G and elastase, rapidly abolished their capacity to bind P-selectin. This inactivation corresponded to loss of the N-terminal domain of PSGL-1, as assessed by Western blot analysis. A loss of intact PSGL-1 protein from the surfaces of neutrophils after the induction of degranulation was also detected by Western blot analysis. Cathepsin G initially cleaved near the PSGL-1 N-terminus, whereas neutrophil elastase predominantly cleaved at a more C-terminal site within the protein mucin core. Consistent with this, cathepsin G cleaved a synthetic peptide based on the PSGL-1 N-terminus between Tyr-7/Leu-8. Under conditions producing neutrophil degranulation in incubations containing mixtures of platelets and neutrophils, the loss of PSGL-1, but not P-selectin, from platelet-neutrophil lysates was detected. Cathepsin G- or neutrophil elastase-mediated PSGL-1 proteolysis may constitute a potential autocrine mechanism for down-regulation of neutrophil adhesion to P-selectin.     

P-selectin glycoprotein ligand-1 supports rolling on E- and P-selectin in vivo

Selectin-dependent rolling is the earliest observable event in the recruitment of leukocytes to inflamed tissues. Several glycoproteins decorated with sialic acid, fucose, and/or sulfate have been shown to bind the selectins. The best-characterized selectin ligand is P-selectin glycoprotein-1 (PSGL-1) that supports P-selectin- dependent rolling in vitro and in vivo. In vitro studies have suggested that PSGL-1 may also be a ligand for E- and L-selectins. To study the in vivo function of PSGL-1, without the influence of other leukocyte proteins, the authors observed the interaction of PSGL-1-coated microspheres in mouse venules stimulated to express P- and/or E-selectin. Microspheres coated with functional recombinant PSGL-1 rolled in surgically stimulated and tumor necrosis factor alpha (TNFalpha)-stimulated mouse venules. P-selectin deficiency or inhibition abolished microsphere rolling in surgically and TNFalpha-stimulated venules, whereas E-selectin deficiency or inhibition increased microsphere rolling velocity in TNFalpha-stimulated venules. The results suggest that P-selectin-PSGL-1 interaction alone is sufficient to mediate rolling in vivo and that E-selectin-PSGL-1 interaction supports slow rolling.     

P-选择素与肿瘤转移

肿瘤转移是复杂多步骤的肿瘤细胞与宿主相互作用的连续过程 ,包括肿瘤细胞侵袭周围组织、从原发灶脱离进入循环系统、逃避免疫监视以及在远隔器官形成与原发瘤同样类型的转移灶。近年来许多学者发现细胞粘附分子在肿瘤转移中起重要作用。选择素 (ｓｅｌｅｃｔｉｎ)是细胞粘附分子中的一个家族 ,包括Ｌ 选择素、Ｐ 选择素和Ｅ 选择素。研究证明 ,Ｐ 选择素能介导肿瘤细胞与血小板及血管内皮细胞间的粘附 ,促进肿瘤细胞的血道转移和扩散[1] 。本文就Ｐ 选择素及其在肿瘤转移中的有关研究作一综述。一、Ｐ 选择素的分子生物学特点Ｐ 选择素亦称…     

P-selectin in arterial thrombosis

P-selectin is a transmembrane protein present in the alpha granules of platelets and the Weibel-Palade bodies of endothelial cells. Following activation, it is rapidly translocated to the cell surface. P-selectin expression in platelets has been shown to be elevated in disorders associated with arterial thrombosis such as coronary artery disease, acute myocardial infarction, stroke, and peripheral artery disease. P-selectin mediates rolling of platelets and leukocytes on activated endothelial cells as well as interactions of platelets with leukocytes. Platelet P-selectin interacts with P-selectin glycoprotein ligand-1 (PSGL-1) on leukocytes to form platelet-leukocyte aggregates. Furthermore, this interaction of P-selectin with PSGL-1 induces the upregulation of tissue factor, several cytokines in leukocytes and the production of procoagulant microparticles, thereby contributing to a prothrombotic state. P-selectin is also involved in platelet-platelet interactions, i. e. platelet aggregation which is a major factor in arterial thrombosis. P-selectin interacts with platelet sulfatides, thereby stabilizing initial platelet aggregates formed by GPIIb/IIIa-fibrinogen bridges. Inhibtion of the P-selectin-sulfatide interaction leads to a reversal of platelet aggregation. Thus, P-selectin plays a significant role in platelet aggregation and platelet- leukocyte interactions, both important mechanisms in the development of arterial thrombosis.     

N-terminal residues in murine P-selectin glycoprotein ligand-1 required for binding to murine P-selectin

P-selectin binds to the N-terminal region of human P-selectin glycoprotein ligand-1 (PSGL-1). For optimal binding, this region requires sulfation on 3 tyrosines and specific core-2 O-glycosylation on a threonine. P-selectin is also thought to bind to the N terminus of murine PSGL-1, although it has a very different amino acid sequence than human PSGL-1. Murine PSGL-1 has potential sites for sulfation at Tyr13 and Tyr15 and for O-glycosylation at Thr14 and Thr17. We expressed murine PSGL-1 or constructs with substitutions of these residues in transfected Chinese hamster ovary cells that coexpressed the glycosyltransferases required for binding to P-selectin. The cells were assayed for binding to fluid-phase P-selectin and for tethering and rolling on P-selectin under flow. In both assays, substitution of Tyr13 or Thr17 markedly diminished, but did not eliminate, binding to P-selectin. In contrast, substitution of Tyr15 or Thr14 did not affect binding. Substitution of all 4 residues eliminated binding. Treatment of cells with chlorate, an inhibitor of sulfation, markedly reduced binding of wild-type PSGL-1 to P-selectin but did not further decrease binding of PSGL-1 with substitutions of both tyrosines. These data suggest that sulfation of Tyr13 and O-glycosylation of Thr17 are necessary for murine PSGL-1 to bind optimally to P-selectin. Because it uses only one tyrosine, murine PSGL-1 may rely more on other peptide components and O-glycosylation to bind to P-selectin than does human PSGL-1.     

P选择素与炎症性肠病

炎症性肠病(IBD)包括溃疡性结肠炎(UC)和克罗恩病(CD),目前认为血小板功能异常在其发病机制及发展过程中起着重要作用.P选择素是细胞黏附分子中选择素家族成员,介导血小板活化及炎症反应等.研究表明P选择素在炎症性肠病的病理过程中起重要作用.     

血小板膜及血清P选择素在急性冠脉综合征中的临床意义

目的 探讨血小板膜P选择素的表达率及血清P选择素的浓度在急性冠脉综合征(acute coronarysyndrome,ACS)中的临床意义.方法 采用间接免疫荧光流式细胞术和双抗夹心酶联免疫测定法分别检测30例ACS患者、20例稳定型心绞痛(stable angina,SA)患者和25例正常对照者(经冠状动脉造影检查提示冠状动脉正常)血小板膜P选择素表达率和血清P选择素浓度,并进行统计分析.结果 ACS组血小板膜P选择素表达率显著高于SA组[(17.19±8.05)%vs.(13.09±6.25)%,P<0.05],并显著高于对照组[(17.19±8.05)%vs.(10.83±5.76)%,P<0.05],SA组和对照组之间比较,差异无统计学意义(P>0.05).ACS组血清P-选择素的浓度显著高于SA组[(43.98±14.71)ng/ml vs.(36.14±13.42)ng/ml,P<0.05],并显著高于对照组[(43.98±14.71)ng/ml vs.(33.34±11.05)ng/ml,P<0.05],SA组和对照组比较,差异无统计学意义(P>0.05).冠状动脉性心脏病(冠心病)患者血小板膜P选择素表达率与血清P-选择素浓度呈正相关(r=0.295,P=0.017).结论 检测血清P选择素浓度对预测ACS发生、发展有重要的参考价值.     

P-选择素与缺血性脑血管病

P-选择素又称CD62,通过介导内皮细胞和血小板的活化以及动脉粥样硬化的形成和发展等过程,促进缺血性脑血管病的发生.多项研究证实,P-选择素在缺血性脑血管病危险因素,如高血压、糖尿病、高胆固醇血症、心脏病、吸烟、酗酒、高纤维蛋白原血症等的发生和发展中起重要作用.P-选择素能否作为独立危险因素预测缺血性脑血管病的发生,尚待进一步研究证实.     

Association between P-selectin gene polymorphisms and soluble P-selectin levels and their relation to coronary artery disease

P-selectin is a cellular adhesion molecule that mediates the interaction of activated endothelial cells or platelets with leukocytes. Increased levels of soluble P-selectin have been reported in various cardiovascular disorders. We measured serum soluble P-selectin levels as well as 3 polymorphisms of the P-selectin gene (C-2123G, A-1969G, and Thr715Pro) in a large cohort of patients with documented coronary artery disease (n=869) and a healthy control group (n=334). The 3 P-selectin polymorphisms were strongly associated with P-selectin levels and altogether explained 7.3% and 18.6% of the P-selectin variability in patients and controls, respectively. Genotype distributions did not significantly differ between patients and controls. P-selectin levels were increased in patients younger than 55 years of age compared with controls (135.2 vs 114.3 ng/mL, P<0.01). On the contrary, patients older than 65 years of age had significantly lower P-selectin levels than did controls (121.5 vs 134.7 ng/mL, P<0.02). In intermediate age groups, P-selectin levels did not significantly differ between the 2 groups. In conclusion, this study revealed a strong association between P-selectin gene polymorphisms and serum P-selectin levels and a complex age-dependent relation between soluble P-selectin levels and coronary artery disease, which suggests that this molecule might have different roles in the atherothrombotic process.     

P选择素在糖尿病肾病中的意义

60例2型糖尿病患者和30名正常对照者的研究显示,P选择素及其mRNA水平,T2DM患者高于正常人,糖尿病伴肾病患者高于无肾病患者。     

Platelet P-selectin facilitates atherosclerotic lesion development

P-selectin is an adhesion molecule expressed on activated platelets and endothelium. It is known to play an important role in atherosclerosis. P-selectin also circulates in plasma in a soluble form (sP-selectin), which induces procoagulant microparticle formation. We investigated the role of platelet versus endothelial P-selectin in generating sP-selectin and in the formation of atherosclerotic lesions in the apolipoprotein E (apoE)-deficient mouse model. For this we transplanted apoE(-/-)P-selectin(-/-) and apoE(-/-)P-selectin(+/+) lethally irradiated mice with bone marrow of either genotype. Seven months after transplantation, we determined from the chimeric animals that the majority of circulating sP-selectin was of endothelial origin. Thus, in atherosclerosis, the procoagulant sP-selectin reflects endothelial rather than platelet activation. We found that endothelial P-selectin was crucial for the promotion of atherosclerotic lesion growth because in its absence only relatively small lesions developed. However, platelet P-selectin also contributed to the lesion development because lesions in wild-type recipients receiving transplants with wild-type platelets were 30% larger than those receiving P-selectin-deficient platelets (P <.008) and were more frequently calcified (80% versus 44%). In comparison with P-selectin wild-type animals, absence of either endothelial or platelet P-selectin inhibited migration of smooth muscle cells into the lesion. Thus, in addition to endothelium, platelets and their P-selectin also actively promote advanced atherosclerotic lesion development.     

P—选择素在心血管疾病中的应用价值

近年来 ,血栓形成在心血管疾病中 ,尤其是急性心肌梗死 ( AMI)和不稳定型心绞痛 ( UAP)的发病中所起的重要作用逐渐被人们所重视 ,对血液中反映凝血功能的分子标志物的研究正方兴未艾 ,作为反映血小板活化状态的分子标志物 P-选择素对心血管疾病的诊断、预后及疗效判断均能提供有益的帮助 ,且对指导抗凝及预防心血管栓塞事件的发生有重要意义。1　概述选择素家族是粘附分子中的一员 ,其基因位于 1号染色体 ,有 P-选择素、L-选择素与 E-选择素 ,皆为单链跨膜糖蛋白。它们分子结构的共同特点是氨基端有一个凝集素 ( lectin)样的结合区 ,一…     

P选择素在静脉血栓栓塞症发病机制中的作用及与炎症的关系

静脉血栓栓塞症(venous thromboembolism,VTE)主要包括深静脉血栓形成(deep venous thrombosis,DVT)和肺血栓栓塞症(pulmonary thromboembolism,PTE),是同一疾病病程中两个不同阶段的不同临床表现.欧洲的研究资料表明,症状性VTE发生人数每年超过150万,VTE相关死亡人数每年约54.35万.我国VTE的诊断也呈逐年上升趋势.已有多项研究表明P选择素作为炎症因子,在VTE发病机制中起了重要作用,而炎症本身又与VTE有着密切的联系.我们即以VTE发病机制出发,总结P选择素在VTE中的作用及与炎症的关系.     

Core2 beta-1,6-N-acetylglucosaminyltransferase enzyme activity is critical for P-selectin glycoprotein ligand-1 binding to P-selectin

P-selectin glycoprotein ligand-1 (PSGL-1) is a high-affinity counterreceptor for P-selectin on myeloid cells and activated T-cells. In addition, PSGL-1 can serve, both in vitro and in vivo, as an E- selectin ligand. Appropriate glycosylation of PSGL-1 is crucial for binding to P-selectin. Functional PSGL-1 is known to bear sialyl lewis X (SLex) or a closely related oligosaccharide. In this study, we show that Chinese hamster ovary (CHO) cells expressing PSGL-1 and fucosyltransferase show a dramatic increase in binding to P-selectin when transfected with "core2" transferase, the enzyme that initiates branching of O-linked glycans. Moreover, only PSGL-1 from core2 transfectant CHO cells can be affinity-captured with P-selectin, suggesting that branched O-linked glycans are required for high- affinity binding to P-selectin. Analysis of PSGL-1-derived O-linked oligosaccharides produced in core2 transfected cells shows the presence of more elaborated glycans. Interestingly, transfection of core2 in these cells does not alter binding to E-selectin.     

Microparticle-associated P-selectin reflects platelet activation in preeclampsia

Platelet activation in preeclampsia is reflected by elevated levels of platelets exposing P-selectin. In plasma, a non-cell bound (soluble) form of P-selectin is present. Elevated levels of this soluble form have been reported in preeclampsia. Plasma P-selectin may consist of two fractions: microparticle (MP)--associated P-selectin and non-MP--associated P-selectin. In the present cross-sectional study, we investigated to which extent plasma P-selectin is MP--associated and whether such MP are elevated in preeclamptic patients. Preeclamptic patients (n?=?10) were matched with normotensive pregnant women (n?=?10) and non-pregnant controls (n?=?10). Plasma P-selectin was measured by ELISA. MP were isolated, double labelled with anti-CD61 (GPIIIa) and anti-CD62P (P-selectin) and subsequently analyzed with flowcytometry. Plasma P-selectin concentration was elevated in preeclamptic patients compared to non-pregnant controls (p?=?0.007), but not compared to normotensive pregnant women (p?=?0.210). Plasma P-selectin is partially MP--associated (3–5%). In pregnancy, the fraction of P-selectin exposing platelet-derived MP (PMP) (10.9%) was increased compared to non-pregnant controls (8%). This fraction further increased in preeclamptic patients (15.4%), and significantly differed from normotensive pregnant women (p?=?0.02). A minor fraction of plasma P-selectin is associated with PMP. The fraction of PMP exposing P-selectin is increased in preeclamptic patients and to a lesser extent in normotensive pregnancy. Because MP associated P-selectin exclusively originates from platelets, this fraction indicates platelet activation. Platelet activation is prominent in preeclampsia and this study proves that at least a part of the plasma P-selectin originates from platelets.     

Soluble P-selectin is influenced by cancer chemotherapy

'Aspirin resistance' is a poorly defined term to describe the inability of aspirin to protect individuals from thrombotic complications and there are conflicting reports on incidence rates and clinical relevance of this phenomenon. Using collagen (1 w g/ml)-induced platelet aggregation and thromboxane formation (measured as thromboxane B 2 ) in citrated platelet-rich plasma, this study demonstrates that aspirin resistance can be classified into three distinct types. In aspirin responders, both, collagen-induced platelet aggregation and thromboxane formation was completely (>95%) inhibited by oral aspirin treatment (100 mg/day). In type I resistance (pharmacokinetic type), oral treatment with aspirin was ineffective but addition of aspirin (100 w M) in vitro resulted in a complete inhibition of collagen-induced platelet aggregation and thromboxane formation. In type II resistance (pharmacodynamic type), neither oral treatment with aspirin nor addition of aspirin in vitro inhibited collagen-induced platelet aggregation and thromboxane formation. In type III resistance (pseudo-resistance), platelet aggregation was induced by a low concentration of collagen (1 w g/ml) despite of a complete inhibition of thromboxane formation by oral aspirin treatment. This typology of aspirin resistance should help to clarify the mechanisms, the actual rate, and the possible clinical consequences of this phenomenon.     

P-selectin mediates spontaneous leukocyte rolling in vivo

Rolling represents the initial step leading to leukocyte extravasation from blood vessels during an inflammatory reaction. In vitro studies indicate that P-selectin could be one of the ligands on endothelium involved in the rolling phenomenon, although the molecular determinants responsible for this transient attachment in vivo are still undefined. Our objectives were to develop a blocking monoclonal antibody against canine P-selectin and to use it to investigate the role of P-selectin in leukocyte rolling in vivo using the technique of intravital microscopy. P-selectin was immunoaffinity purified from canine platelets and used for the production of monoclonal antibodies. One of the hybridomas generated, MD6, was shown by enzyme-linked immunosorbent assay and by flow cytometry to bind preferentially to stimulated platelets and to completely prevent binding of stimulated platelets to neutrophils. Visualization of canine mesenteric venules by intravital microscopy showed that administration of MD6 resulted in a marked inhibition in the number of rolling leukocytes (18.96 +/- 9.92 v 156.40 +/- 19.50 leukocytes/min, P < .05; 88.3% +/- 6.0% inhibition). Control antibody MD3 (which recognizes a nonfunctional epitope of canine P- selectin) had no effect on the number of rolling leukocytes or on their rolling velocity. These results show for the first time that P-selectin plays an essential role in leukocyte rolling in vivo, and therefore may be a key participant of the inflammatory response.     

Microparticle-associated P-selectin reflects platelet activation in preeclampsia

Platelet activation in preeclampsia is reflected by elevated levels of platelets exposing P-selectin. In plasma, a non-cell bound (soluble) form of P-selectin is present. Elevated levels of this soluble form have been reported in preeclampsia. Plasma P-selectin may consist of two fractions: microparticle (MP)--associated P-selectin and non-MP--associated P-selectin. In the present cross-sectional study, we investigated to which extent plasma P-selectin is MP--associated and whether such MP are elevated in preeclamptic patients. Preeclamptic patients (n=10) were matched with normotensive pregnant women (n=10) and non-pregnant controls (n=10). Plasma P-selectin was measured by ELISA. MP were isolated, double labelled with anti-CD61 (GPIIIa) and anti-CD62P (P-selectin) and subsequently analyzed with flowcytometry. Plasma P-selectin concentration was elevated in preeclamptic patients compared to non-pregnant controls (p=0.007), but not compared to normotensive pregnant women (p=0.210). Plasma P-selectin is partially MP--associated (3-5%). In pregnancy, the fraction of P-selectin exposing platelet-derived MP (PMP) (10.9%) was increased compared to non-pregnant controls (8%). This fraction further increased in preeclamptic patients (15.4%), and significantly differed from normotensive pregnant women (p=0.02). A minor fraction of plasma P-selectin is associated with PMP. The fraction of PMP exposing P-selectin is increased in preeclamptic patients and to a lesser extent in normotensive pregnancy. Because MP associated P-selectin exclusively originates from platelets, this fraction indicates platelet activation. Platelet activation is prominent in preeclampsia and this study proves that at least a part of the plasma P-selectin originates from platelets.