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PubMed1995

Differential reactivity of anti-E-selectin monoclonal antibodies in human gingival tissue.

E-selectin is a cytokine-inducible endothelial glycoprotein which participates in the binding of leukocytes to vascular endothelium. Variable levels of expression of E-selectin have been reported in gingivitis and periodontitis, and two differing concepts of its significance have emerged: either gingival blood vessels express E-selectin constitutively, or are continuously activated by inflammatory mediators arising from the gingival environment. A range of monoclonal antibodies reacting with different epitopes of E-selectin are available commercially. The present study explored the possibility that the choice of antibody could affect estimation of the level of expression of E-selectin in vivo. Five monoclonal antibodies were used to investigate E-selectin expression in serial cryosections of human gingival tissue. While E-selectin-positive vascular endothelial cells were detected with all antibodies, the number of positively staining endothelial cells varied, with BBA1 > H4/18 = H18/7 = 4D10 > 1.2B6. The frequency of strong staining in tissue specimens was BBA1 > 4D10 > H4/18 = H18/7 > 1.2B6, while the frequency of weak staining showed the reverse trend. Additionally, with antibodies H18/7 and 1.2B6, 17 and 36% of the specimens were E-selectin negative. The occurrence of what appear to be false positives and false negatives confounds estimation of the level of E-selectin expression. Based on these findings, patterns of endothelial E-selectin expression in gingivitis and periodontitis should be re-evaluated.

Adult↗
PubMed1997

Infections in neonates delivered at term are associated with increased serum levels of ICAM-1 and E-selectin.

All newborn infants consecutively admitted to the Neonatal Intensive Care Unit (NICU) at the University Hospital of Trondheim during 1993 were eligible to participate in the study. In total, 241 neonates were included, for whom anamnestic, clinical and laboratory characteristics were recorded. Peripheral blood was retrieved at admittance, and serum levels of soluble intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-selectin were determined. Newborn infants were classified as infected or non-infected according to selected criteria, and 24 newborn infants fulfilled the criteria of having an infection, whereas 168 newborn infants were classified as non-infected. ICAM-1, VCAM-1 and E-selectin were detected in all neonatal samples. Serum concentrations of E-selectin varied by gestational age (GA), higher levels were found in non-infected term (GA > or = 37 weeks) neonates (n = 53) than in those (n = 115) delivered prematurely (GA < 37 weeks) without infection (p < 0.0001), whereas ICAM-1 and VCAM-1 concentrations did not differ between groups of non-infected term and preterm newborn infants. Similarly, newborn infants delivered at term (n = 16) demonstrated higher levels of E-selectin than premature infants (n = 8) in association with infection (p < 0.001). Both ICAM-1 and E-selectin were increased in term newborn infants with infection (n = 16) compared to the non-infected term group (n = 53) (both p < 0.01), whereas VCAM-1 concentrations did not differ between the two groups. In the premature groups of infected (n = 8) and non-infected (n = 115) neonates, no differences in ICAM-1, VCAM-1 and E-selectin concentrations were observed. The use of ICAM-1 concentration (cut-off level: 250 micrograms l-1) as a diagnostic test for infection in term neonates yielded a sensitivity of 80% and a specificity of 61%, whereas a sensitivity of 70% and a specificity of 79% were found when E-selectin concentration (cut-off level: 150 micrograms l-1) was used. Conclusively, increased shedding of soluble ICAM-1 and E-selectin is one component of infection-induced neonatal immune response after full-time pregnancies. Our data suggest that the ability of increased shedding of soluble ICAM-1 and E-selectin molecules is developed during the final weeks of pregnancy. Assessment of ICAM-1 and E-selectin concentrations may be used as diagnostic tools with a high sensitivity and a moderate specificity in term neonates suspected of infection.

Age Factors↗
PubMed2000

Role of E-selectin in bleomycin induced lung fibrosis in mice.

BACKGROUND: Bleomycin (BLM), a well known anti-cancer drug, often causes acute lung injury and fibrosis by mechanisms that are not well understood. It is suspected that some proteases and active oxygen species generated from inflammatory cells cause the lung injury and subsequent lung fibrosis. It was therefore hypothesised that inhibition of adhesion of inflammatory cells to the endothelium might prevent these developments. METHODS: BLM (100 mg/kg) was injected into the tail veins of ICR mice to evaluate the induction of E-selectin, an adhesion molecule known to induce neutrophil attachment on endothelial cells. E-selectin mRNA induction was detected by reverse transcriptase polymerase chain reaction (RT-PCR). The myeloperoxidase (MPO) activities in the lung tissues of BLM treated and control mice were compared to evaluate neutrophil infiltration. Pathological changes in the lungs of soluble E-selectin transgenic mice (TG) and their TG negative (non-TG) littermates after BLM treatment were also compared. Serum samples of TG mice and non-TG mice were tested for their ability to block the binding of sialyl Lewis(x) to recombinant E-selectin in vitro. RESULTS: E-selectin mRNA was maximally induced at six hours after BLM treatment in the ICR mice. The soluble form of E-selectin which can competitively inhibit the binding of sialylated antigens on inflammatory cells to E- and P-selectins on the endothelium was detected in the serum of TG mice. BLM induced lung fibrosis occurred in non-TG mice but not in TG mice. This result confirms the finding that the serum of TG mice inhibits the binding of sialyl Lewis(x) to E-selectin in vitro. CONCLUSION: E-selectin plays an essential role in BLM induced lung fibrosis through the induction of neutrophil and other inflammatory cell accumulation, and soluble E-selectin may be of use in the prophylactic treatment of lung fibrosis.

Animals↗
PubMed2004

Endothelial P-selectin as a target of heparin action in experimental melanoma lung metastasis.

Spontaneous and experimental metastasis can be effectively inhibited by the widely used anticoagulant heparin in different tumor models. At the cellular level, many of the antimetastatic effects of heparin in vivo are due to its action on P-selectin-mediated binding. Whereas previous attention has focused on P-selectin-dependent tumor-cell-platelet interactions in blood-borne metastasis, we sought to address the potential contribution of endothelial P-selectin expression to adhesive events between the microvasculature and melanoma cells in vivo. Transplantation of bone marrow from P-selectin-deficient into wild-type mice conveyed inhibition of ex-perimental melanoma metastasis. However, the extent to which bone marrow-conferred lack of platelet P-selectin expression attenuated melanoma lung metastasis was significantly less than that seen in P-selectin-deficient mice, suggesting that endothelial P-selectin expression may additionally contribute to formation of hematogenous metastases. This assumption was supported by our intravital microscopy studies, in which a significant proportion of melanoma cells were capable of directly interacting with postcapillary venules of the murine ear in a P-selectin-dependent manner. Heparin not only inhibits P-selectin-mediated melanoma cell rolling but also attenuates melanoma metastasis formation in vivo, further supporting the concept that endothelial P-selectin expression may represent an additional target of heparin action in experimental melanoma lung metastasis.

Animals↗
PubMed1999

Selectins and IL-6 during the clinical course of idiopathic thrombocytopenic purpura.

'Stress thrombocytes', i.e. large and presumably hyperfunctioning platelets, is a well-known characteristic of patients with idiopathic thrombocytopenic purpura (ITP). Therefore, despite what may be severe thrombocytopenia these patients generally do not suffer from severe life-threatening hemorrhage. The plasma level of soluble P-selectin (sP-selectin) is a valuable marker reflecting platelet activation. Available data suggest that interleukin-6 (IL-6) may contribute to the regulation of megakaryocytopoiesis and platelet activity. The purpose of this study is to investigate the status and kinetics of IL-6 and selectins, which are involved in the platelet function, production, and immunologic functions, during the clinical course of ITP, that may be helpful for understanding the biology of the disease. Twenty-two ITP patients were studied prospectively in the course of their disease. Sixteen, 8 and 6 patients were available after platelet recovery, relapse and splenectomy, respectively. Fifteen healthy persons served as a control group. Higher levels of both sP-selectin and IL-6 were observed in all clinical stages of disease compared to the control group. However, more prominent elevations were present during active stages of ITP, i.e. pretreatment (p < 0.001 vs. control group for both sP-selectin and IL-6) and relapse periods (p < 0.001 vs. control group for both sP-selectin and IL-6). Pretreatment soluble L-selectin and soluble E-selectin levels were not different from the controls. Both sP-selectin (r = -0.32, p = 0.019) and IL-6 (r = -0. 41, p = 0.002) levels inversely correlated with platelet count during disease course. There was a positive correlation between the sL-selectin level and leukocyte count (r = 0.60, p < 0.001). These results suggest that residual platelets are activated in ITP, which offers a relatively benign clinical course compared to other thrombocytopenias. High IL-6 concentration during thrombocytopenia may be involved in compensatory megakaryocytopoiesis and augmented 'residual platelet' functions in ITP.

Adult↗
PubMed1998

Soluble P-selectin is released from activated platelets in vivo during hemodialysis.

During hemodialysis, platelets are activated across a dialyzer. Soluble P-selectin (sP-selectin) is a form of P-selectin which is a glycoprotein relocated from secretory granules to the surfaces of platelets and endothelial cells after these cells have been physiologically activated. To investigate whether sP-selectin is useful as a marker of platelet activation during hemodialysis, we measured the plasma concentration of sP-selectin by enzyme-linked immunosorbent assay in 6 patients hemodialyzed in our institute using regenerated cellulose (RC) membranes and thereafter polysulfone membranes. Concomitantly, we also measured the plasma concentration of platelet factor 4 and beta-thromboglobulin which are released from alpha-granules of activated platelets. During hemodialysis with RC membranes, the beta-thromboglobulin level was significantly increased 15 min (p < 0.05) and the sP-selectin level 15 (p < 0.05) and 180 min (p < 0.05) after initiation of dialysis on the venous side as compared with the arterial side of the hemodialyzer. During hemodialysis with polysulfone membranes, no significant variation in plasma beta-thromboglobulin and sP-selectin levels was detected. The platelet factor 4 level increased more significantly across a dialyzer 180 min after initiation of dialysis with RC than with polysulfone membranes (p < 0.01). The changes in plasma platelet factor 4 and beta-thromboglobulin levels demonstrated that platelets are more activated during hemodialysis with RC than with polysulfone membranes. The changes in plasma sP-selectin levels during hemodialysis with RC confirm that the release of P-selectin purely from activated platelets was detected by enzyme-linked immunosorbent assay. sP-selectin may be a marker of platelet activation during hemodialysis.

Adult↗
PubMed2002

Deposition of platelet RANTES triggering monocyte recruitment requires P-selectin and is involved in neointima formation after arterial injury.

BACKGROUND: Chemokines expressed on atherosclerotic endothelium or deposited by activated platelets have been implicated in monocyte recruitment during atherogenesis and restenosis. Although the involvement of P-selectin in these processes is evident from studies in knockout mice, it has not been elucidated whether delivery of platelet chemokines requires P-selectin, thus serving as a P-selectin-dependent effector function. METHODS AND RESULTS: Using immunofluorescence and laminar flow assays, we found that the deposition of the platelet-derived chemokine RANTES and monocyte arrest subsequently triggered by RANTES immobilized on inflamed endothelium are more efficient after preperfusion than after static preincubation of platelets and appear to depend on interactions of platelet but not endothelial P-selectin. This was revealed by the effects of P-selectin antibodies and comparison of P-selectin-deficient and wild-type platelets. Immunohistochemistry detected a substantial luminal expression of RANTES on neointimal lesions in wire-injured carotid arteries of apolipoprotein E (apoE)-deficient mice but not of mice with a combined deficiency in apoE and P-selectin (or platelet P-selectin). As assessed by histomorphometry, treatment of apoE-deficient mice with the RANTES receptor antagonist Met-RANTES markedly reduced neointimal plaque area and macrophage infiltration. CONCLUSIONS: Our data suggest that RANTES deposition and subsequent monocyte arrest are promoted by platelet P-selectin and involved in wire-induced intimal hyperplasia, and that blocking RANTES receptors attenuates neointima formation and macrophage infiltration. This mechanism represents an important component explaining the protection against neointimal growth in P-selectin-deficient mice and may represent a novel approach to the treatment of restenosis or atherosclerosis by the administration of chemokine receptor antagonists.

Animals↗
PubMed1997

Adhesion molecule P-selectin and vascular cell adhesion molecule-1 in enhanced heart allograft arteriosclerosis in the rat.

BACKGROUND: The increase of P-selectin on endothelial cells (EC) overlying human atherosclerotic plaques in classic atherosclerosis was recently established. We have previously shown that vascular cell adhesion molecule-1 (VCAM-1) is extensively expressed on EC of occluded arteries during accelerated transplant arteriosclerosis. In the present study, with the use of rat heart allografts under different doses of cyclosporine A (CsA), we investigated whether the expression of P-selectin is increased during chronic rejection and possibly coexpressed with VCAM-1 on EC. METHODS AND RESULTS: Rat cardiac allografts from DA donors to WF recipients were used. Without immunosuppression, these allografts show an irreversible rejection 7 days after transplantation. In the acute rejection model, syngeneic and allogeneic grafts were harvested 5 days after transplantation. In the chronic rejection model, allograft recipients received triple-drug immunosuppression, including azathioprine, methylprednisolone, and CsA in different doses. The grafts were removed 3 months after transplantation. During acute rejection, a significant expression of P-selectin (P < .01) and VCAM-1 (P < .05) on microvascular endothelia, but not on arteries, was noticed. During intense chronic rejection (5 mg/kg CsA), arterial EC expressed P-selectin (P < .01) and VCAM-1 (P < .05) extensively. The expression of tumor necrosis factor-alpha, a cytokine inducing both P-selectin and VCAM-1 expression, was upregulated in vascular medial cells (P < .05), in intimal cells (P < .01), and in interstitial mononuclear cells (P < .05). Linear regression analysis revealed a significant correlation between arterial P-selectin (P < .01) and VCAM-1 (P < .01) expression and the intensity of intimal thickening. Also, a significant correlation and coexpression of P-selectin and VCAM-1 in epicardial arteries was demonstrated (P < .05). CONCLUSIONS: The early expression of P-selectin on microvascular EC during acute rejection may be the basis of cell adhesion and infiltration into the site of inflammation. During chronic rejection, the intensity of arterial intimal thickening was significantly correlated with the intensity of P-selectin expression on EC, in addition to that of previously reported VCAM-1 expression. Thus, P-selectin may have a crucial role in the pathogenesis of chronic rejection in the vascular wall, augmenting the immune-mediated injury against the allograft.

Acute Disease↗
PubMed1998

Increased levels of soluble P-selectin in hypercholesterolemic patients.

BACKGROUND: Hypercholesterolemia is considered a major risk factor for the development of atherosclerosis. Enhanced lipid peroxidation and persistent platelet activation can be observed in vivo in hypercholesterolemic patients and may have pathophysiological implications in the occurrence of cardiovascular events. P-selectin may play an important role in the pathogenesis of multicellular events, including atherosclerosis. We studied the impact of hypercholesterolemia and oxidative stress on plasma levels of P-selectin. METHODS AND RESULTS: Plasma levels of P-selectin were measured by means of an enzyme immunoassay in 20 hypercholesterolemic patients with no clinical evidence of cardiovascular disease and in 20 sex- and age-matched normocholesterolemic subjects. Hypercholesterolemic patients had higher levels of P-selectin compared with that of control subjects (98+/-61 versus 56+/-14 ng/mL; P=.001). They also displayed increased von Willebrand Factor (vWF) levels (176+/-22 versus 119+/-12%; P=.0001). A direct correlation was observed between P-selectin and LDL cholesterol levels (p=.453). Administration of vitamin E (600 mg/d for 2 weeks) to hypercholesterolemic patients significantly reduced plasma P-selectin (40%), and an inverse correlation was observed between vitamin E and P-selectin plasma levels (p=-.446). CONCLUSIONS: Hypercholesterolemia is associated with elevated plasmatic P-selectin. Altered oxidative processes leading to endothelial dysfunction and persistent platelet activation may contribute to increased soluble P-selectin levels. P-selectin may be proposed as a marker of endothelial dysfunction in hypercholesterolemic patients.

Cholesterol, LDL↗
PubMed2002

Induction of mucosal tolerance to E-selectin prevents ischemic and hemorrhagic stroke in spontaneously hypertensive genetically stroke-prone rats.

BACKGROUND AND PURPOSE: Inflammatory and immune mechanisms can precipitate cerebrovascular thrombosis and hemorrhage. Immunologic tolerance can be induced to a specific antigen by intranasal instillation of that antigen. Lymphocytes tolerized in this way provide local immunosuppression on restimulation with the same antigen. This study tests whether tolerization of lymphocytes to E-selectin can suppress local vessel activation and prevent stroke. METHODS: Spontaneously hypertensive genetically stroke-prone rats (n=113) were distributed among the following studies: comparison of ischemic infarcts/intraparenchymal hemorrhages after single or repetitive tolerization schedules with ovalbumin, E-selectin, or PBS; comparison of E-selectin tolerization- and PBS tolerization-induced suppression of delayed-type hypersensitivity in animals subsequently sensitized to E-selectin; and comparison of PBS-, ovalbumin-, and E-selectin-tolerized groups (after intravenous lipopolysaccharide to activate vessels) regarding transforming growth factor-beta1-positive splenocyte counts, plasma interferon-gamma levels, anti-human E-selectin antibodies, endothelial intercellular adhesion molecule-1, and anti-endothelial cell antibodies. RESULTS: Nasal instillation of E-selectin, which is specifically expressed on activated endothelium, potently inhibited the development of ischemic and hemorrhagic strokes in spontaneously hypertensive stroke-prone rats with untreated hypertension. Repeated schedules of tolerization were required to maintain the resistance to stroke. Suppression of delayed-type hypersensitivity to E-selectin and increased numbers of transforming growth factor-beta1-positive splenocytes showed that intranasal exposure to E-selectin induced immunologic tolerance. E-selectin tolerization also reduced endothelial activation and immune responses after intravenous lipopolysaccharide, as shown by marked suppression of intercellular adhesion molecule-1 expression, anti-endothelial cell antibodies on luminal endothelium, and plasma interferon-gamma levels compared with the control condition. CONCLUSIONS: The novel findings in this study support further investigation of immunologic tolerance as applied to the prevention of stroke.

Animals↗
PubMed2001

Selectins in normal pregnancy, pre-eclampsia and missed abortus.

Selectins, are known to be increased in the serum of patients with pre-eclampsia, indicating that these molecules are possible markers of endothelial cell injury. In this study, we investigated P, E and L selectin levels in normal pregnancy, pre-eclampsia, and missed abortus. Plasma P and L selectins levels were significantly higher in normal pregnancy and pre-eclampsia than healthy controls; but plasma concentrations of E selectins were not different between these groups. Plasma P selectin was significantly higher in pre-eclampsia than normal pregnancy. Plasma concentrations of all selectins were significantly higher in missed abortus than healthy control. L selectin levels were higher in pre-eclampsia and missed abortus than normal pregnancy. We found the levels of selectins were increased in pre-eclampsia and missed abortus. Although selectins were suspected to play a role in the pathogenesis of pre-eclampsia, in conjunction with previous studies, we thought that elevated selectin levels are a non-specific consequence of endothelial injury rather than being a cause.

Abortion, Missed↗
PubMed1995

L-selectin expression increases on peripheral blood polymorphonuclear leukocytes during active marrow release.

The cell adhesion molecule L-selectin is highly expressed on mature bone marrow polymorphonuclear leukocytes (PMN), and the release of these cells from the bone marrow could produce a population of circulating PMN expressing high levels of L-selectin. Because L-selectin initiates the interaction of PMN with activated endothelium, these cells could be important in the pathogenesis of multiorgan failure following sepsis and septic shock. The present study was designed to test the hypothesis that the release of PMN from the bone marrow increases the expression of L-selectin on circulating PMN. Peripheral blood and bone marrow samples were obtained immediately after sternotomy (BM1) and during (BM2) and just before closing the sternum (BM3) in five normothermic and five hypothermic cardiopulmonary bypass (CPB) procedures. L-selectin was measured using both immunocytochemistry and flow cytometry. The results showed that L-selectin expression on bone marrow PMN was greater than on peripheral blood PMN (p < 0.01) in all patients at baseline. Bone marrow release of PMN during normothermic CPB was associated with a rise in peripheral blood band cells (0.18 +/- 0.7 versus 0.56 x 10(9)/L) (p < 0.01) and an increase in the percentage of PMN expressing high levels of L-selectin (9 +/- 3.3 to 36 +/- 6.6%, p < 0.03) and the L-selectin mean fluorescence intensity (MFI) on PMN (p < 0.05). The expression of L-selectin on band cells was higher than on segmented PMN in the circulation (p < 0.01). Hypothermia (27 degrees C) prevented the release of band cells into the circulation and the increased expression of L-selectin on the PMN.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1997

Soluble E-selectin levels in sepsis and critical illness. Correlation with infection and hemodynamic dysfunction.

E-selectin, an early mediator of leukocyte-endothelial adhesion, is expressed on activated endothelium. Soluble E-selectin is present in the supernatant of cytokine-activated endothelial cells and elevated serum levels are found in a variety of inflammatory conditions. We documented elevated E-selectin serum levels in 119 critically ill medical ICU patients (log transformed mean E-selectin level, measured by ELISA, was 5.28 ng/ml) compared to normal volunteers (1 ng/ml). Forty-three patients with culture-positive sepsis had higher (p < 0.05) E-selectin levels (15.39 ng/ml) than 24 patients with culture-negative sepsis (4.87 ng/ml), 44 with noninfectious SIRS (2.33 ng/ml), and eight without SIRS (1.97 ng/ml). E-selectin levels related strongly to the degree of hemodynamic compromise (p < 0.0001). Further analysis demonstrated microbiological status and hemodynamic status to be independent variables related to E-selectin level. Day 1 E-selectin levels correlated positively with peak organ failure score over the course of ICU hospitalization (r = 0.30, p = 0.001) and were higher (p < 0.05) for nonsurvivor (10.61 ng/ml, n = 26) than survivors (4.35 ng/ml, n = 93). We conclude that soluble E-selectin levels are higher in serum of patients with microbiologically documented sepsis than in other critically ill medical ICU patients. Day 1 E-selectin levels correlate highly with hemodynamic compromise and modestly with subsequent organ dysfunction and survival.

APACHE↗
PubMed1993

Inflammatory roles of P-selectin.

Polymorphonuclear leukocytes (PMNs) bind rapidly and reversibly to endothelial cells induced to express P-selectin, a glycoprotein that mediates adhesive intercellular interactions. In addition, PMNs adherent to endothelium expressing P-selectin demonstrate an intracellular Ca2+ transient, functionally up-regulate beta-2-integrins (CD11/CD18 glycoproteins), become polarized in shape, and are primed for enhanced degranulation when subsequently stimulated with chemotactic factors. However, P-selectin induces none of these responses directly when used alone, when incorporated into model membranes, or when expressed by transfected cells. The absence of direct activation of the PMNs is not due to competing antiinflammatory effects of P-selectin; instead, purified P-selectin and P-selectin in membranes support agonist-stimulated PMN responses. Furthermore, tethering of PMNs to endothelial surfaces by P-selectin is required for priming to occur efficiently, as shown by experiments with blocking monoclonal antibodies. The priming event is directly mediated by the signaling molecule, platelet-activating factor (PAF), and is inhibited by blocking the PAF receptor on PMNs. Thus, P-selectin and PAF are components of an adhesion and activation cascade, but have distinct roles: P-selectin tethers and captures the PMN, whereas PAF mediates juxtacrine activation. In vivo, selectins may facilitate interaction of target cells with membrane-bound molecules that send intercellular signals, in addition to mediating rolling of leukocytes and other adhesive functions.

Antigens, CD↗
PubMed1999

Memory B lymphocytes from secondary lymphoid organs interact with E-selectin through a novel glycoprotein ligand.

Recirculation of B lymphocytes through the secondary lymphoid organs is key for recognition and response to foreign antigen. B lymphocytes within secondary lymphoid organs comprise a heterogeneous population of cells at distinct differentiation stages. To ascribe a particular adhesive behavior to discrete B-cell subsets within secondary lymphoid organs, we investigated their functional interaction with endothelial selectins under flow. We describe herein the characterization of a subset of human tonsillar B cells that interact with E-selectin but not P-selectin. E-selectin-interacting B cells had a phenotype of non-germinal center (CD10(-), CD38(-), CD44(+)), memory (IgD-) cells. Furthermore, FucT-VII was expressed selectively in CD44(+) E-selectin-adherent B lymphocytes. B-cell rolling on E-selectin required sialic acid but was independent of previously described selectin ligands. A novel glycoprotein ligand of 240 kDa carrying N-linked glycans was isolated from B-cell membranes by an E-selectin immunoadhesin. Binding of this protein was strictly Ca2+ dependent, was inhibited by a cell adhesion-blocking mAb against E-selectin, and required the presence of sialic acid but not N-linked carbohydrates. Our results enable us to assign to resident memory B lymphocytes a novel adhesion function, the rolling on E-selectin, that provides insights on the adhesion pathways involved in homing of memory B cells to tertiary sites.

Animals↗
PubMed2000

Soluble P-selectin in human plasma: effect of anticoagulant matrix and its levels in patients with cardiovascular disorders.

P-Selectin represents a cell surface glycoprotein that is constitutively present in the Weibel-Palade bodies of endothelial cells and in the alpha-granules of platelets. In inflammation and thrombogenic conditions, plasmatic P-selectin levels are markedly elevated, indicating the leakage of this marker from these sites. In this study, a quantitative sandwich enzyme-linked immunosorbent assay (ELISA) utilizing a monoclonal soluble P-selectin (sP-selectin) antibody was employed to assess this marker in blood samples collected in various anticoagulants such as heparin, hirudin, sodium citrate (3.2% and 3.8%), and ethylenediaminetetraacetic acid (EDTA). The soluble P-selectin levels ranged from 26 ng/mL to 44 ng/mL. Sodium citrate (3.8%) was used to collect platelet-poor plasma (PPP) from patients with heparin-induced thrombocytopenia (HIT), coronary angioplasty (CA), or coronary atherectomy (CAT). In comparison with the control group (approximately 30 ng/mL), all of these patient groups showed a marked elevation of sP-selectin levels (HIT = 96 ng/mL [n = 18], CA = 46 ng/mL [n = 6] and CAT = 60 ng/mL [n = 10]). In platelet-rich plasma (PRP) preparations using various anticoagulants, the sP-selectin levels were markedly higher, ranging from 87 ng/ mL to 117 ng/mL (n = 10). In patients recruited into a clinical trial (the argatroban [ARG] 911 Study), in which argatroban was used as an alternate anticoagulant in patients with HIT, a 25% to 35% decrease in sP-selectin levels was observed after 72 hours of argatroban treatment. In addition, the relative ratio between levels in PRP and PPP in these patients differed, suggesting that the anticoagulant matrix influences the sP-selectin levels. These data clearly suggest that the anticoagulant matrix and blood collection procedures may significantly influence the plasmatic P-selectin levels. Furthermore, in different clinical conditions, elevation of this marker may reflect endogenous platelet activation; however, optimal anticoagulant for blood collection is important for proper diagnostic validation.

Adult↗
PubMed2003

L-selectin stimulation enhances functional expression of surface CXCR4 in lymphocytes: implications for cellular activation during adhesion and migration.

L-selectin mediates leukocyte tethering and rolling, the first step in a sequential process of leukocyte adhesion and migration. Additionally, L-selectin has important signaling roles perhaps contributing to leukocyte activation and integrin-mediated adhesion. Because chemokines are critically involved in leukocyte activation, we questioned whether L-selectin signaling affects chemokine receptor expression and function. We observed that whereas only 5% to 15% of freshly isolated lymphocytes expressed CXCR4 on the cell surface, intracellular CXCR4 was detectable in all cells. Engagement of L-selectin by antibody cross-linking or the L-selectin ligands fucoidan or sulfatide mobilized intracellular CXCR4 to significantly increase surface CXCR4 expression but did not affect CCR5, CCR7, or beta2-integrin expression. L-selectin stimulation also inhibited stromal-derived factor 1 (SDF-1)-induced CXCR4 internalization. The combined effects of L-selectin on CXCR4 trafficking are likely important in markedly enhancing cell activation by SDF-1. Blockade of SDF-1-induced CXCR4 internalization resulted in enhanced actin polymerization on subsequent exposure to SDF-1. Physiologically more important, L-selectin stimulation increased SDF-1-induced lymphocyte adhesion and transendothelial migration, which were inhibited by anti-leukocyte function-associated antigen 1 antibodies, tyrosine kinase inhibitors, and pertussis toxin. To further corroborate the additive stimulating effects, L-selectin signaling and SDF-1 increased beta2-integrin activation. Taken together, L-selectin-mediated signals specifically enhance CXCR4 expression and function, suggesting a novel mechanism for the modulation of lymphocyte activation during cell adhesion and transmigration.

Actins↗
PubMed2003

P-selectin anchors newly released ultralarge von Willebrand factor multimers to the endothelial cell surface.

von Willebrand factor (VWF) released from endothelium is ultralarge (UL) and hyperreactive. If released directly into plasma, it can spontaneously aggregate platelets, resulting in systemic thrombosis. This disastrous consequence is prevented by the ADAMTS13 (ADisintegrin and Metalloprotease with ThromboSpondin motif) cleavage of ULVWF into smaller, less active forms. We previously showed that ULVWF, on release, forms extremely long stringlike structures. ADAMTS13 cleaves these strings under flow significantly faster than it does under static conditions. As ULVWF tethering to endothelium is important for its rapid proteolysis, we investigated 2 molecules for their potential to anchor the ULVWF strings: P-selectin and integrin alpha v beta 3. We demonstrated that P-selectin anchors ULVWF to endothelium by several means. First, Chinese hamster ovary (CHO) cells expressing P-selectin specifically adhered to immobilized ULVWF and ULVWF-coated beads to immobilized P-selectin. Second, an anti-VWF antibody coimmunoprecipitates P-selectin from the histamine-activated endothelial cells. Third, P-selectin antibody or soluble P-selectin, but not a alpha v beta 3 antibody, RGDS peptide, or heparin, blocked the formation of ULVWF strings. Fourth, P-selectin expression was in clusters predominantly along the ULVWF strings. Finally, the strength of the minimal ULVWF-P-selectin bond was measured to be 7.2 pN. We, therefore, conclude that P-selectin may anchor ULVWF strings to endothelial cells and facilitate their cleavage by ADAMTS13.

ADAM Proteins↗