Effect of Ebselen on polymorphonuclear leukocyte adhesion to and migration through cytokine-activated vascular endothelium.

Ebselen (PZ51, 2-Phenyl-1, 2-Benzoisoselenazol-3-(2H)-one) is a selinyl organic compound with anti-inflammatory properties. Some of its pharmacological effects are thought to result from its peroxidase activity. Here we examined the effects of Ebselen on polymorphonuclear leukocyte (PMNL) adhesion to umbilical vein endothelium and transendothelial migration in a modified Boyden chamber in which both PMNL-dependent and endothelial-dependent (IL-1, TNF alpha) PMNL adhesion and migration can be measured. Ebselen was found to dose dependently inhibit the adhesion of PMNL to IL-1 activated endothelium and to inhibit transendothelial PMNL migration induced by IL-1 alpha, and TNF alpha with an IC50 value of 28 microM. Transendothelial migration induced by the PMNL chemotactic agents C5adesArg and N-formyl-norleu-leu-phe was also inhibited at slightly higher concentrations. The effect of Ebselen was not on endothelial cell activation but on PMNL activation for adhesion and migration. This effect on PMNL was irreversible for the duration of the assay period (75 min). The results suggest that the anti-inflammatory activity of Ebselen may, in part, be due to direct inhibition of PMNL adhesion to vascular endothelium and transendothelial migration in response to a variety of inflammatory mediators.     

Chemoattractant-induced firm adhesion of leukocytes to vascular endothelium in vivo is critically dependent on initial leukocyte rolling.

Leukocyte rolling and firm adhesion at the venular endothelium are two discrete events in the cellular inflammatory response mediated via selectin and integrin adhesion molecules, respectively. The dependency of chemoattractant-induced firm leukocyte adhesion on the preceding rolling interaction was investigated in rat mesenteric microvessels through use of intravital microscopy. Leukocyte rolling was dose-dependently inhibited by systemic treatment with the sulphated polysaccharide fucoidin. The firm leukocyte adhesion following stimulation with the chemotactic peptide fMLP was similarly inhibited when fMLP challenge was performed subsequent to inhibition of leukocyte rolling by fucoidin. Thus, based on paired observations in single venules before and after fucoidin treatment, reduced rolling leukocyte flux prior to fMLP challenge was paralleled over a wide range by a proportional decrease in fMLP-induced leukocyte adhesion. The results demonstrate quantitatively a close relationship between the extent of leukocyte rolling and the magnitude of the subsequent firm adhesion response, and, that an initial rolling interaction is a precondition for firm adhesion to occur at physiological blood flow rates in vivo.     

Effect of platelet-activating factor on leukocyte adhesion to microvascular endothelium

The hamster cheek pouch microcirculation was used to investigate the effects of platelet-activating factor (PAF) on leukocyte adhesion to microvascular walls by means of intravital microscopy. PAF was applied topically at concentrations ranging from 10^–11 to 10^–5 M. An inverse relationship between PAF concentration and number of adhering white cells per 100-m length was found in venules ranging in diameter from 10 to 60 m (grouped into 10-m intervals). Importantly, the PAF-induced adhesion of leukocytes lasted for the 3-h experimental period. We postulate that induction of leukocyte adhesion to venular endothelium is an important role of PAF in inflammatory processes.     

Chemoattractant-induced firm adhesion of leukocytes to vascular endothelium in vivo is critically dependent on initial leukocyte rolling

Leukocyte rolling and firm adhesion at the venular endothelium are two discrete events in the cellular inflammatory response mediated via selectin and integrin adhesion molecules, respectively. The dependency of chemoattractant-induced firm leukocyte adhesion on the preceding rolling interaction was investigated in rat mesenteric microvessels through use of intravital microscopy. Leukocyte rolling was dose-dependently inhibited by systemic treatment with the sulphated polysaccharide fucoidin. The firm leukocyte adhesion following stimulation with the chemotactic peptide fMLP was similarly inhibited when fMLP challenge was performed subsequent to inhibition of leukocyte rolling by fucoidin. Thus, based on paired observations in single venules before and after fucoidin treatment, reduced rolling leukocyte flux prior to fMLP challenge was paralleled over a wide range by a proportional decrease in fMLP-induced leukocyte adhesion. The results demonstrate quantitatively a close relationship between the extent of leukocyte rolling and the magnitude of the subsequent firm adhesion response, and, that an initial rolling interaction is a precondition for firm adhesion to occur at physiological blood flow rates in vivo.     

Endothelial leukocyte adhesion molecule-1-dependent adhesion of colon carcinoma cells to vascular endothelium is inhibited by an antibody to Lewis fucosylated type I carbohydrate chain.

Endothelial leukocyte adhesion molecule-1 (ELAM-1) has been determined to be the mediator of adhesion of colon carcinoma cells to interleukin-1 (IL-1)-activated endothelial cells. To identify ELAM-1 ligand in colon carcinoma cells, we have screened a series of 11 monoclonal antibodies directed to these cells and found that only one MBr8 was able to inhibit the IL-1-induced increment in adhesion of HT29 and of SW948 colon carcinoma lines to endothelial cells. In contrast, MBr8 did not bind to polymorphonuclear cells, monocytes, and lymphocytes and did not inhibit polymorphonuclear adhesion to IL-1-activated endothelial cells. As expected, an ELAM-1 monoclonal antibody strongly inhibited IL-1 induced increment of adhesion of HT29, SW948, and polymorphonuclear cells. As negative control, MG63 osteosarcoma cells were used. These cells adhere more efficiently to IL-1 activated endothelial cells but MBr8 and ELAM-1 monoclonal antibodies did not affect their adhesion. The effect of MBr8 was also tested in an experimental system in vivo. As described previously, radiolabeled HT29 cell retention in the lung of nude mice was increased in animals given IL-1. MBr8 administration to nude mice or pretreatment of tumor cells with it inhibited this effect. These data suggest that cell adhesion to ELAM-1 might be mediated by different, cell type specific, sugar ligands.     

Neutrophil-mediated damage to human vascular endothelium. Role of cytokine activation.

Cytokine activation of cultured human vascular endothelial cells renders them hyperadhesive for blood leukocytes. Co-incubation of freshly isolated, unstimulated human blood neutrophils with confluent cytokine-activated human endothelial monolayers for 90 minutes results in extensive endothelial detachment and destruction of monolayer integrity. In contrast, unactivated endothelial monolayers remain intact. Using this in vitro model, we have explored the neutrophil-effector mechanisms involved in this injury. Coincubation in the presence of a serine protease inhibitor (phenylmethylsulfonyl fluoride) or specific elastase inhibitors (Ala-Ala-Pro-Val-chloromethyl ketone or alpha-1-protease inhibitor) markedly diminished injury. In contrast, scavengers or inhibitors of oxygen-derived free radicals (superoxide dismutase, catalase, mannitol, or sodium azide) were not protective. Purified human neutrophil elastase mimicked the effect of the neutrophils suggesting a key role for elastase in the neutrophil-mediated injury in this model. Interfering with direct neutrophil-endothelial cell contact by interposing a microporous barrier insert prevented endothelial cell detachment. Furthermore, this neutrophil-mediated detachment could be inhibited with interleukin-8, an action correlated with a decrease in neutrophil adhesion to activated endothelial monolayers. By defining the role of endothelial activation in neutrophil-mediated injury, this in vitro model may provide useful insights into potential therapeutic interventions designed to prevent disruption of the endothelial barrier function.     

TLR4激动对内皮细胞粘附功能的影响及阿托伐他汀的干预研究

目的：观察Toll样受体4（TLR4）激动对脐静脉内皮细胞（HUVECs）氧化低密度脂蛋白受体LOX-1的调节和对单核细胞与HUVECs粘附率的影响，以及LOX-1在内皮细胞粘附功能中的作用，并观察阿托伐他汀的干预作用方法：RT-PCR方法检测TLR4、LOX-1 mRNA表达水平，流式细胞术检测TLR4、LOX-1蛋白表达水平，细胞计数法计算单核细胞与HUVECs粘附率。结果：脂多糖(1 mg/L) 孵育24 h上调HUVECs TLR4、LOX-1 mRNA和蛋白的表达，增加单核细胞与HUVECs粘附率,抗LOX-1抗体部分抑制LPS介导的单核细胞与HUVECs粘附率的增加，阿托伐他汀（10 μmol/L）抑制脂多糖介导的上述效应。结论：TLR4激动上调LOX-1表达及增加内皮细胞粘附功能，LOX-1在LPS介导的单核内皮细胞粘附功能中起部分作用，阿托伐他汀可能通过抑制TLR4表达及TLR4 介导的LOX-1表达而发挥其内皮细胞保护作用。     

Interleukin-2 directly increases albumin permeability of bovine and human vascular endothelium in vitro.

The direct effects of interleukin-2 (IL-2) on albumin permeability of cultured bovine pulmonary artery endothelial cell (BPAEC) and human arterial endothelial cell (HAEC) monolayers were studied. BPAEC were exposed to IL-2 (500 to 25,000 U/ml) for 4 h. The steady-state transfer rate of [125I]albumin across the BPAEC monolayer was 3.3 +/- 0.4%/h (n = 10) in control BPAEC (diluent alone), was significantly increased in BPAEC exposed to 500 U/ml of IL-2 (72 +/- 3% above control values, n = 6, P less than 0.02), and further increased in BPAEC exposed to 5,000 U/ml (60 +/- 2% increase above 500 U/ml values, n = 5, P less than 0.02). No further increase was noted after exposure to 25,000 U/ml of IL-2. Additionally, no further increase in [125I]albumin transfer rates was noted in BPAEC exposed to 5,000 U/ml of IL-2 for 24 versus 4 h. Similar changes were found using HAEC. Preincubation of HAEC with an anti-IL-2 low-affinity receptor antibody (anti-IL-2R alpha) inhibited the IL-2-induced permeability increase. Expression of IL-2R alpha receptors in HAEC incubated with 5,000 U/ml of IL-2 for 4 h was also found. Thus, IL-2 appears to have a direct effect on cultural arterial endothelial monolayers not requiring the presence of other cell types or serum proteins. IL-2-induced increases in endothelial macromolecular permeability may play an important role in the pathogenesis of the IL-2-induced vascular leak syndrome seen in vivo.     

Reduction in cellular and vascular rejection by blocking leukocyte adhesion molecule receptors.

Whether antibody blockage of leukocyte receptors for intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 would prevent cardiac graft rejection was studied in a rabbit heterotopic transplant model. Monoclonal antibody 60.3, anti-CD18 (intercellular adhesion molecule-1 receptor, Group 1, n = 10) and monoclonal antibody HP1/2, anti-VLA-alpha 4 (vascular cell adhesion molecule-1 receptor, Group 2, n = 10) were administered to transplanted unimmunosuppressed animals. At 7 days, donor heart histology was compared to transplanted untreated controls (Group 3, n = 11). Peripheral white blood cell counts on postoperative day 2 were significantly higher in both treatment groups than controls. Significant increases in circulating neutrophils occurred in Group 1 (P < or = 0.05); lymphocytes predominated in Group 2 (P < or = 0.05). A significant reduction in cellular rejection was seen in Group 1 (P < or = 0.05) but not Group 2 hearts. Group 1 hearts demonstrated localization of lymphocytes to perivenular collections, whereas Group 2 hearts evidenced diffuse interstitial infiltration. Both treatment groups demonstrated a reduction in transplant arteritis compared to controls. Results suggest that monoclonal antibody 60.3 (anti-CD18) may hold promise as a therapeutic agent for both cellular and vascular rejection. Monoclonal antibody HP1/2 (anti-VLA-alpha 4) may reduce vascular rejection disproportionate to cellular rejection.     

Tumor cell-endothelial interactions. Increased adhesion of human melanoma cells to activated vascular endothelium.

The authors examined the adhesion of seven human melanoma cell lines to cultured human umbilical vein endothelial cells (HEC) that were activated by cytokines or bacterial endotoxin. The adhesion of Hs 294T and MEL-24 cells was markedly increased (approximately 2 to 12-fold) after pretreatment of HEC monolayers for 6 hours with tumor necrosis factor, interleukin-1, or endotoxin. Smaller increases were noted with the cell lines RPMI 7951, HT 144, Malme-3M, MEL-2, and no significant increase was observed with MEL-5. Cytokine and endotoxin effects on melanoma-HEC adhesion were concentration- and time-dependent, with onset by 2 hours, peak at 6-8 hours and maintenance through 48 hours. Cytokine induction of increased HEC adhesiveness for melanoma cells was blocked by actinomycin-D or cycloheximide, suggesting the requirement for RNA and protein synthesis. Interaction of melanoma cells with subendothelial matrix did not appear to play a primary role because: 1) phase contrast and electron microscopy revealed direct contact between tumor cells and endothelial cells in standardized monolayer adhesion assays; 2) increased adhesion (rosette formation) of tumor cells to activated HEC was also observed after nonenzymatic resuspension of HEC, and 3) the matrix peptide GRGDSP partially blocked (approximately 45%) Hs 294T cell adhesion to subendothelial matrix, but had little or no effect on adhesion to activated HEC monolayers. Taken together, these data suggest that inducible HEC surface changes may mediate the adhesion of certain melanoma cells, thereby exerting an active influence over the metastatic process.     

Warner-Lambert/Parke-Davis award lecture. Cytokine-mediated activation of vascular endothelium. Physiology and pathology.

The concept of endothelial cell activation has been extremely useful in understanding endothelial cell function. The morphologic definition of activation from the 1960s has been replaced by a cell biologic definition in the 1980s, but recent studies have suggested that these phenomena are two aspects of the same processes. Moreover, the initial distinction of endothelial cell activation, a beneficial reaction, from injury and dysfunction, a harmful sequence, has become more complex as clinical studies have revealed that activation can produce dysfunction, with or without injury. Most importantly, as our in vivo studies indicate, the concept of activation is a testable hypothesis, as modern immunochemical and molecular biologic techniques have been employed to bridge the gap between in vitro culture experiments and patient-based clinical research.     

The effect of prostacyclin on the adhesion of leucocytes to injured vascular endothelium

The effect of local application of various solutions on leucocyte adherence to the wall of small blood vessels in the microcirculation of the rat mesentery was examined. Leucocyte adhesion was produced by local application of zymosan-activated complement. Solutions of EDTA, lignocaine and prostacyclin when applied locally cause the release of a high proportion of leucocytes previously firmly adherent to the endothelium of venules and small veins without producing any significant change in the rate of blood flow through the affected vessels. Acetylcholine injected intravenously increases the rate of blood flow through the mesenteric microcirculation several fold but has no apparent effect on pre-existing leucocyte sticking. The findings suggest that in normal small blood vessels production of prostacyclin by vascular endothelium may inhibit adhesion of leucocytes to the vascular wall. When endothelium is injured local production of prostacyclin may be inhibited sufficiently to permit adhesion of leucocytes to the injured endothelium and so induce the earliest stage in the emigration of leucocytes into the area of injury. Lignocaine may possibly inhibit leucocyte sticking by increasing local production of prostacyclin, but the mode of action of EDTA and many other aspects of the mechanism responsible for leucocyte sticking remain obscure.     

Intercellular adhesion molecule-1 in human corneal endothelium. Modulation and function.

The endothelium lining the posterior corneal surface performs physiologic pump functions essential to corneal clarity and integrity. A hallmark of keratitis, anterior ocular inflammation, and corneal allograft rejection is leukocyte adherence to the corneal endothelium (CE) forming keratitic precipitates. To elucidate mechanisms governing cornea-leukocyte interactions, cultured human CE cells and intact corneas were examined for expression of intercellular adhesion molecule-1 (ICAM-1), which binds the lymphocyte function-associated antigen-1 (LFA-1) on all leukocytes and enhances delayed-type hypersensitivity mediated by class II major histocompatibility complex antigens. Immunohistochemistry on culture CE cells using monoclonal anti-ICAM-1 antibody yield positive staining that increased after exposure to interleukin-1-beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), and interferon-gamma (gamma-IFN). Standard leukocyte adherence assays demonstrated ICAM-1-mediated CE-neutrophil binding, which was specifically blocked by antibody to ICAM-1 or antibodies to LFA-1 on neutrophils. In whole human corneas, gamma-IFN increased CE and stromal keratocyte ICAM-1 immunoreactivity and enhanced CE-neutrophil adherence. As in CE cell cultures, antibody to ICAM-1 effectively blocked neutrophil binding to the CE cells of whole corneas. These results are the first to demonstrate ICAM-1 in ocular tissue. They indicate that CE cells express functional ICAM-1, which may be modulated by inflammatory cytokines, ICAM-1 provides mechanisms for keratitic precipitate formation, regulation of corneal leukocyte trafficking and the generation of immune responses that may be crucial to allograft rejection.     

Role of the LFA-1 adhesion glycoprotein in neutrophil adhesion to endothelium and plastic surfaces.

Neutrophil adherence to endothelium is known to be mediated, at least in part, by adhesion molecules such as LFA-1. Deficiency of these adhesion molecules leads to recurrent infection and early death from infection. As screening for defects of these adhesion glycoproteins is often performed by the ability of neutrophils to adhere to plastic plates, in this study a comparison of neutrophil adherence by the CD18/CD11a (LFA-1) mechanism to endothelium and plastic surfaces was examined. Baseline neutrophil adherence was two-fold higher to plastic than to endothelium (17% +/- 9 for plastic, 8% +/- 5 for endothelium). Baseline adherence to endothelium was partially inhibitable by anti-LFA-1 antibodies, whereas no inhibition of adherence occurred on plastic. Neutrophil stimulants increased adherence to both surfaces, although only on endothelium was this increase attributable to the LFA-1 mechanism. IL-1 increased adherence to endothelium, but had no effect on plastic. We conclude that adherence of neutrophils to plastic surfaces probably represents overall activation status through undefined mechanisms, is not by LFA-1 receptor ligand interactions, and is therefore a non-physiological phenomenon. Endothelial receptors are pivotal in neutrophil adherence. It would be more appropriate to screen leucocytes for leucocyte adhesion deficiency by assaying for specific receptor occupancy with monoclonal antibodies, rather than an assay such as adhesion to plastic where the adhesion ligand is non specific.     

Shear stress effects on bacterial adhesion, leukocyte adhesion, and leukocyte oxidative capacity on a polyetherurethane.

Infection of implanted cardiovascular biomaterials still occurs despite inherent host defense mechanisms. Using a rotating disk system, we investigated Staphylococcus epidermidis and polymorphonuclear leukocyte (PMN) adhesion to a polyetherurethane urea (PEUU-A') under shear stress (0-17.5 dynes/cm2) for time periods up to 6 h. In addition, the superoxide (SO) release capacity of PMNs after transient exposure to PEUU-A' under shear stress was determined. Bacterial adhesion in phosphate-buffered saline (PBS) showed a linear shear dependence, decreasing with increasing shear stress. Overall adhesion in PBS decreased with time. However, bacterial adhesion in 25% human serum was similar for all time points up to 360 min. Adhesion was observed at all shear levels, displaying no shear dependence. In contrast, PMN adhesion demonstrated a strong shear dependence similarly for times up to 240 min, decreasing sharply with increasing shear stress. Although PMNs preexposed to shear stress showed a slightly diminished SO release response compared to fresh cells for all stimuli, it was not statistically significant regardless of the stimulus. We conclude that circulating leukocytes are unable to adhere in regions of high shear which may contain adherent bacteria. In addition, exposure to PEUU-A' and shear stress (in the range 0-18 dynes/cm2) is insufficient to cause a depression in the oxidative response of PMNs.     

Benoxaprofen inhibits the adhesion of human monocytes to cultured vascular endothelium

Pretreatment of human monocytes with benoxaprofen for at least 2 h produced a dose-dependent abrogation of their adhesion to monolayers of cultured porcine endothelium with 0.05 g/ml and 50.0 g/ml of the drug inducing a mean 33% and 83% inhibition of adhesion respectively. When the endothelium was treated with the drug there was no modification of monocyte adhesion. In contrast, pretreatment of endothelium with 5.0 and 50.0 g/ml benoxaprofen for at least 6 h, resulted in a mean 35% and 31% inhibition of polymorphonuclear cell (PMN) adhesion in 6/11 experiments. This inhibitory effect was not seen when drug-treated PMNs were added to endothelium. An impairment of monocyte chemotactic migration was only apparent with high concentrations of the drug (50 g/ml). These results suggest that an important anti-inflammatory property of benoxaprofen is the inhibition of monocyte adhesion to vascular endothelium.     

Reciprocal expression of CD34 and cell adhesion molecule ELAM-1 on vascular endothelium in acute cutaneous graft-versus-host disease

The expression of CD34 and endothelial leucocyte adhesion molecule-1 (ELAM-1) on endothelial cells was studied in skin biopsies from normal human donors and recipients of allogeneic bone marrow. Both molecules were demonstrable on a variable number of cells in normals with no significant change after marrow transplantation in patients with no clinical evidence of skin disease. In patients with graft-versus-host disease (GvHD), however, there was a striking decrease in CD34-positive cells with a corresponding increase in ELAM-1 positivity. These changes were similar to those occurring in cultured endothelial cells after the addition of certain cytokines. They were seen only in the presence of a lymphocytic infiltrate and were not observed in the early stages of GvHD before lymphocytic infiltration was discernible. The reciprocal expression of these molecules may thus be important in the adhesion of lymphocytes to endothelium and their entry into the skin in GvHD and may be modulated by local cytokine release.