Biomedical subjects

O Spertini

Publications and source records attributed to O Spertini.

At least 19 recordsLinked to original sources

PubMed2001

Endothelial cell activation by myeloblasts: molecular mechanisms of leukostasis and leukemic cell dissemination.

Leukostasis and tissue infiltration by leukemic cells are poorly understood life-threatening complications of acute leukemia. This study has tested the hypothesis that adhesion receptors and cytokines secreted by blast cells play central roles in these reactions. Immunophenotypic studies showed that acute myeloid leukemia (AML) cells (n = 78) of the M0 to M5 subtypes of the French-American-British Cooperative Group expressed various amounts of adhesion receptors, including CD11a, b, c/CD18, CD49d, e, f/CD29, CD54, sCD15, and L-selectin. The presence of functional adhesion receptors was evaluated using a nonstatic adhesion assay. The number of blast cells attached to unactivated endothelium increased by 7 to 31 times after a 6-hour exposure of endothelium to tumor necrosis factor (TNF)-alpha. Inhibition studies showed that multiple adhesion receptors--including L-selectin, E-selectin, VCAM-1, and CD11/CD18--were involved in blast cell adhesion to TNF-alpha-activated endothelium. Leukemic cells were then cocultured at 37 degrees C on unactivated endothelial cell monolayers for time periods up to 24 hours. A time-dependent increase in the number of blasts attached to the endothelium and a concomitant induction of ICAM-1, VCAM-1, and E-selectin were observed. Additional experiments revealed that endothelial cell activation by leukemic myeloblasts was caused by cytokine secretion by blast cells, in particular TNF-alpha and IL-1 beta, and direct contacts between adhesion receptors expressed by blast cells and endothelial cells. Thus, leukemic cells have the ability to generate conditions that promote their own adhesion to vascular endothelium, a property that may have important implications for the pathophysiology of leukostasis and tissue infiltration by leukemic blast cells. (Blood. 2001;97:2121-2129)

Antigens, CD↗

PubMed2000

Inhibition of selectin-mediated cell adhesion and prevention of acute inflammation by nonanticoagulant sulfated saccharides. Studies with carboxyl-reduced and sulfated heparin and with trestatin a sulfate.

Selectins play a major role in the inflammatory reaction by initiating neutrophil attachment to activated vascular endothelium. Some heparin preparations can interact with L- and P-selectin; however, the determinants required for inhibiting selectin-mediated cell adhesion have not yet been characterized. We now report that carboxyl-reduced and sulfated heparin (prepared by chemical modifications of porcine intestinal mucosal heparin leading to the replacement of carboxylates by O-sulfate groups) and trestatin A sulfate (obtained by sulfation of trestatin A, a non-uronic pseudo-nonasaccharide extracted from Streptomyces dimorphogenes) exhibit strong anti-P-selectin and anti-L-selectin activity while lacking antithrombin-mediated anticoagulant activity. In vitro experiments revealed that both compounds inhibited P-selectin- and L-selectin-mediated cell adhesion under laminar flow conditions. Moreover, carboxyl-reduced and sulfated heparin and trestatin A sulfate were also active in vivo, as assessed by experiments showing 1) that microinfusion of trestatin A sulfate reduced by 96% leukocyte rolling along rat mesenteric postcapillary venules and 2) that both compounds inhibited (by 58-81%) neutrophil migration into thioglycollate-inflamed peritoneum of BALB/c mice. These results indicate that nonanticoagulant sulfated saccharides targeted at P-selectin and L-selectin may have therapeutic potential in inflammatory disorders.

Antibodies↗

PubMed2000

Modification of P-selectin glycoprotein ligand-1 with a natural killer cell-restricted sulfated lactosamine creates an alternate ligand for L-selectin.

Natural killer (NK) cells are components of the innate immune system that can recognize and kill virally infected cells, tumor cells, and allogeneic cells without prior sensitization. NK cells also elaborate cytokines (e.g., interferon-gamma and tumor necrosis factor-alpha) and chemokines (e.g., macrophage inflammatory protein-1alpha) that promote the acquisition of antigen-specific immunity. NK cell differentiation is accompanied by the cell surface expression of a mucin-like glycoprotein bearing an NK cell-restricted keratan sulfate-related lactosamine carbohydrate, the PEN5 epitope. Here, we report that PEN5 is a post-translational modification of P-selectin glycoprotein ligand-1 (PSGL-1). The PEN5 epitope creates on PSGL-1 a unique binding site for L-selectin, which is independent of PSGL-1 tyrosine sulfation. On the surface of NK cells, the expression of PEN5 is coordinated with the disappearance of L-selectin and the up-regulation of Killer cell Ig-like Receptors (KIR). These results indicate that NK cell differentiation is accompanied by the acquisition of a unique carbohydrate, PEN5, that can serve as part of a combination code to deliver KIR(+) NK cells to specific tissues.

Amino Sugars↗

PubMed1999

Elastase and metalloproteinase activities regulate soluble complement receptor 1 release.

Complement receptor 1 (CR1) is cleaved from the surface of polymorphonuclear cells (PMN) in the membrane-proximal region to yield a soluble fragment (sCR1) that contains the functional domains. The enzymes involved in this cleavage are produced by the PMN itself, since in vitro stimulation of purified PMN is followed by sCR1 release. Purified human neutrophil elastase (HNE) cleaved CR1 from erythrocytes and urinary vesicles originating from podocytes and enhanced tenfold the cleavage of CR1 from activated PMN. The largest fragment released from PMN by HNE was identical in size to CR1 shed spontaneously. The CR1 fragments cleaved from erythrocytes were functional. The shedding of sCR1 by activated PMN was inhibited by phenylmethylsulfonyl fluoride (80 +/- 10%), alpha1-antiprotease (50 +/- 5%) and elafin (60 +/- 5%). Furthermore the cleavage was blocked by the metalloprotease inhibitor 1,10-phenanthroline (70 +/- 6 %) as well as by a monoclonal antibody against human neutrophil collagenase MMP8 (40 +/- 10%). Maximal inhibition of sCR1 shedding was obtained by a combination of 1,10-phenanthroline with elafin (86 +/- 6%). These inhibitors had no effect on L-selectin shedding, indicating that the cleavage of CR1 was specific. In conclusion, elastase or elastase-like activity may be responsible for the shedding of functional sCR1 in vivo, and this activity is controlled by the local release of PMN metalloproteases and alpha1antiprotease.

Complement C3b↗

PubMed1999

Soluble complement receptor 1 is increased in patients with leukemia and after administration of granulocyte colony-stimulating factor.

Complement receptor type 1 is expressed by erythrocytes and most leukocytes. A soluble form is shed from the leukocytes and found in plasma (sCR1). sCR1 is a powerful inhibitor of complement. We report an increased sCR1 in the plasma of leukemia patients, up to levels producing measurable complement inhibition. Half of the 180 patients with acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), and chronic lymphocytic leukemia (CLL) had sCR1 levels above the normal range. The highest levels were observed in T-ALL (17 patients). The complement function of a T-ALL serum was improved by blocking sCR1 with a specific mAb (3D9). Measurements in 16 peripheral stein cell donors before and after granulocyte colony-stimulating factor (G-CSF) administration showed an increase in sCR1 (before, 43.8+/-15.4; at day 5, 118.3+/-44.7 ng/mL; P < 0.0001). This increase paralleled the increase in total leukocyte counts and was concomitant with de novo leukocyte mRNA CR1 expression in all three individuals tested. Whether pharmacological intervention may be used to up-regulate sCR1 so as to inhibit complement in vivo should be further investigated.

Animals↗

PubMed1998

Relationship between cleaved L-selectin levels and the outcome of acute myeloid leukemia.

High plasma levels of the shed form of L-selectin (sL-selectin) are frequently detectable in acute myeloid leukemia (AML). sL-selectin can inhibit blast cell adhesion to vascular endothelium and may thereby influence the phenotype of AML. In this study, we have investigated the relationship between sL-selectin levels and clinical presentation or disease outcome in 100 patients with AML. Fifty-eight patients were found to have sL-selectin levels >/=3.12 microgram/mL (>/=3 SD above the mean of healthy controls: "increased"). Patients with extramedullary disease such as lymphadenopathies, splenomegaly, hepatomegaly, and/or muco-cutaneous infiltration had significantly increased sL-selectin levels (P < .001). sL-selectin levels were significantly heterogeneous in the French-American-British subtypes (P = .0003). Patients with "normal" sL-selectin levels had higher probability of achieving complete remission (CR) than with "increased" levels: 81% versus 64%, respectively (P = .06). When adjusting for clinically relevant covariates predictive for CR (sex, age, Auer rods), "normal" sL-selectin levels were significantly associated with CR (odds ratio, 3.08; 95% confidence interval [CI], 1.10 to 8.58; P = .03). Moreover, patients with "increased" sL-selectin levels (>/=3.12 microgram/mL) had shorter event-free survival (EFS) (median 7.3 v 12 months, P = .008) and overall survival (median 1 v 2.05 years, P = .03) than patients with sL-selectin <3.12 microgram/mL. Multivariate statistical analysis (adjusted for age and presence of Auer rods) indicated that sL-selectin was an independent prognostic factor for EFS (hazard ratio [HR], 1.96; 95% CI, 1.21 to 3.17, P = .006) and overall survival (HR, 1.80; 95% CI, 1.09 to 2.98; P = .02). Thus, plasma sL-selectin may be a useful prognostic marker in the evaluation of AML at diagnosis.

Acute Disease↗

PubMed1998

Pulse treatment of human vascular endothelial cells with high doses of tumor necrosis factor and interferon-gamma results in simultaneous synergistic and reversible effects on proliferation and morphology.

Regional administration of high doses of tumor necrosis factor (TNF), interferon gamma (IFNgamma) and melphalan to patients with advanced cancers of the limbs, results in rapid and specific tumor necrosis, while the normal adjacent tissues remain unaffected. The tumor vasculature is selectively destroyed by this treatment, and neovascular endothelial cells appear to be an early and specific target of TNF and IFNgamma. To further understand some of the cellular events underlying these in vivo effects, we have investigated the response of human macro- and microvascular endothelial cells in vitro, after exposure to high doses of TNF and IFNgamma (up to 40 x 10(3) U/ml each). TNF and IFNgamma synergistically inhibited endothelial-cell proliferation by up to 80% after 72 hr of treatment. Achievement of synergy required the simultaneous presence of both cytokines. A cytokine pulse as short as 30 min was sufficient to induce maximal growth inhibition measured after 48 hr. Both cytokines also induced progressive and dose-dependent elongation of the endothelial-cell morphology. The effects on endothelial-cell proliferation and morphology were reversible upon removal of the cytokines. Moreover, replating of treated cells onto a fresh substrate immediately resulted in re-acquisition of their normal shape. In contrast to the effect on cell proliferation, there was little or no effect on the rate of endothelial-cell apoptosis. The presented data extend reports on the effects of TNF and IFNgamma on human endothelial cells in vitro, and suggest that the in vivo disruption of the tumor vasculature caused by high doses of TNF and IFNgamma is not due to a direct cytotoxic effect on endothelial cells but occurs through an indirect mechanism.

Apoptosis↗

PubMed1998

The Fcgamma receptor-mediated respiratory burst of rolling neutrophils to cytokine-activated, immune complex-bearing endothelial cells depends on L-selectin but not on E-selectin.

Intracellular H2O2 generation, as a measure of the respiratory burst, was determined after stimulation of neutrophils by immune complex (IC)-bearing human umbilical vein endothelial cells. Under static conditions, neutrophils basically responded to the immune deposits on resting endothelial cells. The rotating shear forces of approximately 0.7 dynes/cm2, corresponding to the physiological flow in postcapillary venules, completely abolished this basal H2O2 generation. After activation of the IC-bearing endothelial layers with interleukin-1 (IL-1) or tumor necrosis factor (TNF), or both, for 4 hours, rolling adhesion of the neutrophils was induced, accompanied by considerable H2O2 production. The neutrophil respiratory burst was prominently inhibited by anti-FcgammaRIII MoAb 3G8 (72.4%), and partially by MoAb 2E1 against FcgammaRII (38.5%). Both MoAbs together inhibited the Fc-mediated H2O2 generation by 93. 4%. The respiratory burst and rolling adhesion were markedly blocked by MoAb LAM1-3 against L-selectin (91.3%), whereas the nonfunctional anti-L-selectin MoAb LAM1-14 was ineffective. F(ab)2' fragments of MoAb 7A9 against E-selectin inhibited neutrophil rolling by 98.6%, but not the respiratory burst. Moreover, rolling adhesion of neutrophils and the related oxidative burst were CD11b/CD18- independent. In summary, L-selectin has a unique auxiliary function in triggering the FcgammaR-mediated respiratory burst of rolling neutrophils to IC-bearing endothelial cells, thereby substituting CD11b/CD18 under conditions of flow.

Antigen-Antibody Complex↗

PubMed1997

Monocyte adhesion to activated aortic endothelium: role of L-selectin and heparan sulfate proteoglycans.

This study examines the role of L-selectin in monocyte adhesion to arterial endothelium, a key pathogenic event of atherosclerosis. Using a nonstatic (rotation) adhesion assay, we observed that monocyte binding to bovine aortic endothelium at 4 degrees C increased four to nine times upon endothelium activation with tumor necrosis factor (TNF)-alpha. mAb-blocking experiments demonstrated that L-selectin mediates a major part (64 +/- 18%) of monocyte attachment. Videomicroscopy experiments performed under flow indicated that monocytes abruptly halted on 8-h TNF-alpha-activated aortic endothelium, approximately 80% of monocyte attachment being mediated by L-selectin. Flow cytometric studies with a L-selectin/IgM heavy chain chimeric protein showed calcium-dependent L-selectin binding to cytokine-activated and, unexpectedly, unactivated aortic cells. Soluble L-selectin binding was completely inhibited by anti-L-selectin mAb or by aortic cell exposure to trypsin. Experiments with cycloheximide, chlorate, or neuraminidase showed that protein synthesis and sulfate groups, but not sialic acid residues, were essential for L-selectin counterreceptor function. Moreover, heparin lyases partially inhibited soluble L-selectin binding to cytokine-activated aortic cells, whereas a stronger inhibition was seen with unstimulated endothelial cells, suggesting that cytokine activation could induce the expression of additional ligand(s) for L-selectin, distinct from heparan sulfate proteoglycans. Under flow, endothelial cell treatment with heparinase inhibited by approximately 80% monocyte attachment to TNF-alpha-activated aortic endothelium, indicating a major role for heparan sulfate proteoglycans in monocyte-endothelial interactions. Thus, L-selectin mediates monocyte attachment to activated aortic endothelium, and heparan sulfate proteoglycans serve as arterial ligands for monocyte L-selectin.

Animals↗

PubMed1997

Plasminogen activators play an essential role in extracellular-matrix invasion by lymphoblastic T cells.

Involvement of extravascular sites, in particular infiltration of the central nervous system, is a frequent complication of T-lymphoblastic leukemia and contributes to leukemia-associated morbidity. In this report, we studied the contribution of plasminogen activators to the invasive properties of 7 human T-cell lines in a model of transmigration through an extracellular matrix. The T-cell lines were found to express either urokinase (u-PA) and high levels of u-PA receptor or tissue-type plasminogen activator (t-PA) and low levels of u-PA receptor. The rate of transmigration was consistently higher for u-PA-expressing cells than for t-PA-expressing cells. PA-inhibitor type 1 (PAI-1) was detected in the conditioned medium of one cell line and PAI-2 was detected in cell extracts from 6 lines. The transmigration of 6 out of 7 cell lines was inhibited by trasylol, an inhibitor of plasmin, by an excess of exogenous PAI-1 or PAI-2, and by antibodies to the particular PA type expressed by the cells. Partial inhibition of transmigration by the amino-terminal fragment of u-PA implies that the u-PA receptor contributes to transmigration. Thus, the transmigration of T-leukemia cells through a barrier of extracellular matrix requires PA-dependent proteolysis, which can be provided either by u-PA or t-PA. Specific inhibition of the PA system could provide a means to inhibit tissue invasion by T lymphoblastic cells.

Antigens, CD↗

PubMed1996

[Regulation of leukocyte migration by adhesion molecules].

The ability of leukocytes to leave the blood-stream and migrate into tissues is a critical feature of the immune system, essential in eliminating infectious pathogens and allowing leukocyte accumulation at sites of injury, infection or inflammation. Lymphocytes continuously recirculate between tissues, lymphoid organs and blood, whereas neutrophils or monocytes lack this capacity. Migration of various leukocyte subpopulations into tissues is regulated by specific combinations of adhesion receptors and chemoattractants which direct them into tissues. Selectins initiate leukocyte attachment along vascular endothelium by mediating leukocyte rolling along inflamed endothelium, whereas CD11/CD18 (alpha L, M, X/beta 2) integrins have a more important role in subsequent steps of leukocyte migration into tissues. alpha 4/beta 1 or alpha 4/beta 7 integrins play a role in mediating lymphocyte rolling and firm adhesion to vascular wall. Leukocyte migration is an important mechanism in the pathogenesis of inflammatory diseases, the regulation of hematopoiesis and hemostasis. This reaction is also involved in the pathogenesis of atherosclerosis, reperfusion injuries and malignant cell metastasis. Leukocyte migration inhibitors may have therapeutic potential against inflammation and associated diseases.

Cell Movement↗

PubMed1996

P-selectin glycoprotein ligand 1 is a ligand for L-selectin on neutrophils, monocytes, and CD34+ hematopoietic progenitor cells.

Selectins play a critical role in initiating leukocyte binding to vascular endothelium. In addition, in vitro experiments have shown that neutrophils use L-selectin to roll on adherent neutrophils, suggesting that they express a nonvascular L-selectin ligand. Using a L-selectin/IgM heavy chain (mu) chimeric protein as an immunocytological probe, we show here that L-selectin can bind to neutrophils, monocytes, CD34+ hematopoietic progenitors, and HL-60 and KG-1 myeloid cells. The interaction between L-selectin and leukocytes was protease sensitive and calcium dependent, and abolished by cell treatment with neuraminidase, chlorate, or O-sialoglycoprotein endopeptidase. These results revealed common features between leukocyte L-selectin ligand and the mucin-like P-selectin glycoprotein ligand 1 (PSGL-1), which mediates neutrophil rolling on P- and E-selectin. The possibility that PSGL-1 could be a ligand for L-selectin was further supported by the ability of P-selectin/mu chimera to inhibit L-selectin/mu binding to leukocytes and by the complete inhibition of both selectin interactions with myeloid cells treated with mocarhagin, a cobra venom metalloproteinase that cleaves the amino terminus of PSGL-1 at Tyr-51. Finally, the abrogation of L- and P-selectin binding to myeloid cells treated with a polyclonal antibody, raised against a peptide corresponding to the amino acid residues 42-56 of PSGL-1, indicated that L- and P-selectin interact with a domain located at the amino-terminal end of PSGL-1. The ability of the anti-PSGL-1 mAb PL-1 to inhibit L- and P-selectin binding to KG-1 cells further supported that possibility. Thus, apart from being involved in neutrophil rolling on P- and E-selectin, PSGL-1 also plays a critical role in mediating neutrophil attachment to adherent neutrophils. Interaction between L-selectin and PSGL-1 may be of major importance for increasing leukocyte recruitment at inflammatory sites.

Antigens, CD34↗

PubMed1995

Cleaved L-selectin concentrations in meningeal leukaemia.

Involvement of the central nervous system has important therapeutic implications in acute leukaemia. Because the identification of blast cells in cerebrospinal fluid (CSF) is often difficult, there is a need for sensitive markers of leukaemic infiltration. Since the shed form of L-selectin (sL-selectin) is frequently increased in acute leukaemia (sL-selectin+ leukaemia), we examined whether assay of sL-selectin in CSF could improve our ability to detect such meningeal involvement. CSF sL-selectin was significantly (p < 0.001) higher in 15 patients with sL-selectin+ meningeal leukaemia (median 60 ng/mL, range 34-150) than in 20 patients with acute leukaemia without meningeal involvement (12 ng/mL, 1-39) or 88 control patients (14 ng/mL, 0-37). Serial measurements of sL-selectin in patients with sL-selectin+ leukaemic meningitis showed increased CSF concentrations of the cleaved receptor in 4 patients with therapy-resistant meningeal leukaemia and sustained normal concentrations in 9 patients in remission. Our results suggest that CSF sL-selectin may be a useful marker in the detection of meningeal involvement by blast cells in patients with sL-selectin+ leukaemia.

Adult↗

PubMed1994

High levels of the shed form of L-selectin are present in patients with acute leukemia and inhibit blast cell adhesion to activated endothelium.

L-selectin is expressed by most leukocytes and mediates the initial step of adhesion to vascular endothelium. A feature of this adhesion receptor is to be shed from the cell surface. We report here the presence of high levels of the shed form of L-selectin (sL-selectin) in plasma from patients with acute leukemia. We also show that sL-selectin purified from acute leukemia plasma exhibits functional activity. The mean (+/- 1 SD) plasma level of sL-selectin among 100 healthy individuals was 2.1 +/- 0.7 micrograms/mL. This value was increased (> 2 SD above the mean) in 63% of 58 patients with acute lymphoblastic leukemia (ALL) and 59% of 93 patients with acute myelogenous leukemia ([AML] P < .001). Repeated measurements in 24 patients showed normal-range levels in 16 of 16 patients in complete remission and high levels in eight of eight patients with therapy-resistant acute leukemia or leukemia relapse. Furthermore, elevated sL-selectin levels were detected in cerebrospinal fluid of three patients with ALL suffering from a relapse limited to the central nervous system. Epitope mapping with monoclonal antibodies demonstrated that L-selectin shedding from leukemic blasts was accompanied by conformational changes of its epidermal growth factor-like domain. A functional role for sL-selectin purified from leukemic plasma was supported by its ability to completely inhibit L-selectin-dependent adhesion of blast cells to tumor necrosis factor-alpha (TNF-alpha)-activated endothelium in vitro. These results suggest that sL-selectin may have an important role in the regulation of leukemic cell adhesion to endothelium. In addition, monitoring of the sL-selectin level may be useful for evaluating leukemia activity, in particular for the detection of leukemia relapse.

Antigens, CD↗

PubMed1992

ELISA for quantitation of L-selectin shed from leukocytes in vivo.

L-selectin is a cell surface receptor on granulocytes, lymphocytes and monocytes that is responsible for the initial attachment of leukocytes to endothelium. The extracellular domain of L-selectin is proteolytically shed from leukocytes following cellular activation in vitro. The shed form of L-selectin (SL-selectin) is functionally active and at high concentrations can inhibit leukocyte attachment to endothelium. Therefore, an ELISA was developed to quantitate the levels of SL-selectin in biological fluids, biopsy specimens and during recombinant protein production. This simple, quantitative sandwich ELISA uses two monoclonal antibodies directed against the extracellular domain of SL-selectin. The assay has a detection range of 5-1300 ng/ml, is precise and sensitive. The ability of this assay to detect SL-selectin in serum, plasma, and culture supernatant fluid was demonstrated and it was used to quantitate circulating SL-selectin in normal and patient sera. Patients with sepsis and HIV infection showed markedly elevated SL-selectin levels in serum. Thus, the ELISA should prove useful both for laboratory purposes as well as in the diagnostic evaluation of patients with inflammatory diseases.

Animals↗

PubMed1992

Neutrophils, monocytes, and lymphocytes bind to cytokine-activated kidney glomerular endothelial cells through L-selectin (LAM-1) in vitro.

The role of L-selectin (LAM-1) as a regulator of leukocyte adhesion to kidney microvascular glomerular endothelial cells was assessed in vitro by using L-selectin-directed mAb and an L-selectin cDNA-transfected cell line. The initial attachment of neutrophils, monocytes, and lymphocytes to TNF-activated bovine glomerular endothelial cells was significantly inhibited by the anti-LAM1-3 mAb. Under static conditions, anti-LAM1-3 mAb inhibited neutrophil adhesion by 15 +/- 5%, whereas the anti-LAM1-10 mAb, directed against a functionally silent epitope of L-selectin, was without effect. The binding of a CD18 mAb inhibited adhesion by 47 +/- 6%. In contrast, when the assays were carried out under nonstatic conditions or at 4 degrees C, the anti-LAM1-3 mAb generated significantly greater inhibition (approximately 60%). CD18-dependent adhesion was minimal (approximately 10%) under these conditions. TNF-activated glomerular endothelial cells also supported adhesion of a mouse pre-B cell line transfected with L-selectin cDNA, but not wild-type cells. This process was also inhibited by the anti-LAM1-3 mAb. Leukocyte adhesion to unstimulated endothelial cells was independent of L-selectin, but, after TNF stimulation, L-selectin-mediated adhesion was observed at 4 h, with maximal induction persisting for 24 to 48 h. Leukocyte adhesion was not observed if glomerular endothelial cells were exposed to TNF in the presence of RNA or protein synthesis inhibitors. Leukocyte attachment to TNF-activated glomerular endothelial cells was also partially inhibited by treatment of the cells with mannose-6-phosphate or phosphomannan monoester, a soluble complex carbohydrate, or by prior treatment of glomerular endothelial cells with neuraminidase, suggesting that the glomerular endothelial cell ligand shares functional characteristics with those expressed by lymph node and large vessel endothelial cells. These data suggest that TNF activation induced the biosynthesis and surface expression of a ligand(s) for L-selectin on glomerular endothelial cells, which supports neutrophil, monocyte, and lymphocyte attachment under nonstatic conditions.

Antigens, CD↗

PubMed1992

Monocyte attachment to activated human vascular endothelium in vitro is mediated by leukocyte adhesion molecule-1 (L-selectin) under nonstatic conditions.

The receptors that mediate monocyte adhesion to cytokine-stimulated endothelial monolayers were assessed using a nonstatic (rotating) cell-attachment assay. In this system, leukocyte adhesion molecule-1 (LAM-1) (L-selectin) mediated a major portion (87 +/- 15% at 37 degrees C) of monocyte attachment to activated endothelium. mAb blocking of endothelial leukocyte adhesion molecule-1 (41% inhibition), CD18 (36%), and vascular cell adhesion molecule-1 (25%) function had lesser effects on attachment. These results suggest that LAM-1 may serve an important role in monocyte attachment to endothelium at sites of inflammation.

Antibodies, Monoclonal↗

PubMed1992

Reaction of acetaldehyde with human platelets.

Platelet function defects observed in chronic alcoholics are not wholly explained by the inhibitory action of ethanol on platelet aggregation; they are not completely reproduced either in vivo by short-term ethanol perfusion into volunteers or in vitro by the addition of ethanol to platelet-rich plasma. As acetaldehyde (AcH) binds to many proteins and impairs cellular activities, we investigated the effect of this early degradation product of ethanol on platelets. AcH formed adducts with human platelets at neutral pH at 37 degrees C which were stable to extensive washing, trichloracetic acid hydrolysis and heating at 100 degrees C, and were not reduced by sodium borohydride. The amount of platelet adducts formed was a function of the incubation time and of the concentration of AcH in the reaction medium. At low AcH concentrations (less than 0.2 mM), platelet bound AcH was directly proportional to the concentration of AcH in the reaction medium. At higher concentrations (greater than or equal to 0.2 mM), AcH uptake by platelets tended to reach a plateau. The amount of adducts was also proportional to the number of exposures of platelets to pulses of 20 microM AcH. AcH adducts formation severely impaired platelet aggregation and shape change induced by ADP, collagen and thrombin. A positive correlation was established between platelet-bound AcH and inhibition of aggregation. SDS-PAGE analysis of AcH adducts at neutral pH demonstrated the binding of [14C]acetaldehyde to many platelet proteins. AcH adduct formation with membrane glycoproteins, cytoskeleton and enzymes might interfere with several steps of platelet activation and impair platelet aggregation.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaldehyde↗