Does soluble intercellular adhesion molecule-1 (ICAM-1) affect neutrophil activation and adhesion following ischaemia-reperfusion? (33/22844)

OBJECTIVES: To examine the effect of reperfusion plasma and sICAM-1 on neutrophil integrin expression and neutrophil adhesion to determine if sICAM-1 has a potential role in the regulation of neutrophil adhesion. MATERIALS: Twenty-seven patients, 17 men and 10 women undergoing femorodistal surgery. Blood was taken preoperatively and from the femoral vein following the release of the cross-clamp. Neutrophils were obtained from five volunteers and incubated with phosphate buffered saline (PBS), preoperative plasma or reperfusion plasma with and without sICAM-1. Neutrophil expression of CD11b and adhesion were measured. MAIN RESULTS: Neutrophil CD11b expression did not change following incubation in the three media. Neutrophil adhesion increased significantly following exposure to reperfusion plasma compared to PBS or preoperative plasma (45.5 adhesion vs. 12.75%, p < 0.01 Mann-Whitney U-test). Soluble ICAM-1 decreased CD11b expression and adhesion in neutrophils exposed to reperfusion plasma only (CD11b expression fell from 15.9 to 3.4 mcf, p < 0.01 Mann-Whitney U-test and adhesion fell to 11.6% cells adhered, p < 0.01). CONCLUSION: An increase in CD11b expression is not required for an increase in neutrophil adhesion. The change in neutrophil adhesion produced by reperfusion plasma can be blocked by sICAM-1. Soluble ICAM-1 may have a physiological role in the regulation of neutrophil adhesion.  (+info)

Adhesive and mammalian transglutaminase substrate properties of Candida albicans Hwp1. (34/22844)

The pathogenesis of candidiasis involves invasion of host tissues by filamentous forms of the opportunistic yeast Candida albicans. Morphology-specific gene products may confer proinvasive properties. A hypha-specific surface protein, Hwp1, with similarities to mammalian small proline-rich proteins was shown to serve as a substrate for mammalian transglutaminases. Candida albicans strains lacking Hwp1 were unable to form stable attachments to human buccal epithelial cells and had a reduced capacity to cause systemic candidiasis in mice. This represents a paradigm for microbial adhesion that implicates essential host enzymes.  (+info)

Tumor necrosis factor-alpha contributes to ischemia- and reperfusion-induced endothelial activation in isolated hearts. (35/22844)

-During myocardial reperfusion, polymorphonuclear neutrophil (PMN) adhesion involving the intercellular adhesion molecule-1 (ICAM-1) may lead to aggravation and prolongation of reperfusion injury. We studied the role of early tumor necrosis factor-alpha (TNF-alpha) cleavage and nuclear factor-kappaB (NF-kappaB) activation on ICAM-1 expression and venular adhesion of PMN in isolated hearts after ischemia (15 minutes) and reperfusion (30 to 480 minutes). NF-kappaB activation (electromobility shift assay) was found after 30 minutes of reperfusion and up to 240 minutes. ICAM-1 mRNA, assessed by Northern blot, increased during the same interval. Functional effect of newly synthesized adhesion molecules was found by quantification (in situ fluorescence microscopy) of PMN, given as bolus after ischemia, which became adherent to small coronary venules (10 to 50 microm in diameter). After 480 minutes of reperfusion, ICAM-1-dependent PMN adhesion increased 2.5-fold compared with PMN adhesion obtained during acute reperfusion. To study the influence of NF-kappaB on PMN adhesion, we inhibited NF-kappaB activation by transfection of NF-kappaB decoy oligonucleotides into isolated hearts using HJV-liposomes. Decoy NF-kappaB but not control oligonucleotides blocked ICAM-1 upregulation and inhibited the subacute increase in PMN adhesion. Similar effects were obtained using BB 1101 (10 microg), an inhibitor of TNF-alpha cleavage enzyme. These data suggest that ischemia and reperfusion in isolated hearts cause liberation of TNF-alpha, activation of NF-kappaB, and upregulation of ICAM-1, an adhesion molecule involved in inflammatory response after ischemia and reperfusion.  (+info)

Homocysteine enhances neutrophil-endothelial interactions in both cultured human cells and rats In vivo. (36/22844)

Despite intense investigation, mechanisms linking the development of occlusive vascular disease with elevated levels of homocysteine (HCY) are still unclear. The vascular endothelium plays a key role in regulating thrombogenesis and thrombolysis. We hypothesized that vascular lesions in individuals with elevated plasma HCY may be related to a dysfunction of the endothelium triggered by HCY. We investigated the effect of HCY on human neutrophil adhesion to and migration through endothelial monolayers. We also examined the effect of HCY on leukocyte adhesion and migration in mesenteric venules of anesthetized rats. We found that pathophysiological concentrations of HCY in vitro induce increased adhesion between neutrophils and endothelial cells. This contact results in neutrophil migration across the endothelial layer, with concurrent damage and detachment of endothelial cells. In vivo, HCY infused in anesthetized rats caused parallel effects, increasing leukocyte adhesion to and extravasation from mesenteric venules. Our results suggest that extracellular H2O2, generated by adherent neutrophils and/or endothelial cells, is involved in the in vitro endothelial cell damage. The possibility exists that leukocyte-mediated changes in endothelial integrity and function may lead to the vascular disease seen in individuals with elevated plasma HCY.  (+info)

Effect of leukocytes on corneal cellular proliferation and wound healing. (37/22844)

PURPOSE: To establish whether fucoidin, by blocking the adhesion of leukocytes on the limbal vascular endothelium, prevents extravasation of the cells from the blood stream into the limbal stroma and the wounded area after corneal injury. Successful leukocyte blocking enabled investigation of the influence of leukocytes on corneal cellular proliferation after corneal wounding. METHODS: Thirty-two New Zealand White rabbits were used. Photorefractive keratectomy (PRK) and a standardized alkali corneal wound were used as models in two sets of experiments. In half of the injured rabbits fucoidin was used to prevent leukocytes from leaving the local vessels. The efficiency of the blocking technique was evaluated by counting the number of leukocytes in the limbal and wounded corneal areas. Proliferating cell nuclear antigen (PCNA) was used as a marker for proliferative activity. RESULTS: The infiltration of leukocytes into the limbus and the cornea after PRK and alkali injuries can be blocked by fucoidin. The healing rate of corneal epithelium after alkali burn was retarded in the absence of leukocytes. PCNA expression was enhanced in the presence of leukocytes. Fucoidin per se had no influence on corneal cell proliferation and wound healing. CONCLUSIONS: Polymorphonuclear leukocytes (PMNs) can be prevented from entering the cornea in vivo by fucoidin after PRK and after alkali burn. The corneal epithelial healing rate is delayed in the absence of PMNs in vivo, and PCNA expression increases in the presence of leukocytes.  (+info)

In vivo significance of ICAM-1--dependent leukocyte adhesion in early corneal angiogenesis. (38/22844)

PURPOSE: Numerous investigations have stressed the significance of leukocytes in early angiogenesis. Leukocytes invade the cornea, and the location of their extravasation corresponds to the site of vessel ingrowth. The interactions between leukocytes and vascular endothelium are mediated by various proteins, including adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1). In this study, the role of ICAM-1 during early corneal angiogenesis was evaluated in vivo. METHODS: Corneal neovascularization was induced in New Zealand White rabbits by use of intrastromal pellets containing 750 ng vascular endothelial growth factor (VEGF). The fluorescent dye rhodamine 6G was used to stain leukocytes in vivo. Leukocyte adhesion and vessel growth were quantified in vivo by high-resolution fluorescence angiography. To inhibit ICAM-1 interactions a microemulsion containing anti-ICAM-1 antibody was applied topically. RESULTS: Limbal vessels showed increased leukocyte adhesion 24 hours after pellet implantation: The number of rolling and sticking leukocytes was significantly increased compared with the number in control animals (P < 0.01). Treatment with anti-ICAM-1 antibody resulted in reduced leukocyte sticking and increased leukocyte rolling. The area covered by new blood vessels was significantly diminished in eyes treated with anti-ICAM-1 (P < 0.05). CONCLUSIONS: The results support the hypothesis that ICAM-1-mediated leukocyte adhesion is a key event in early angiogenesis. This model may serve for investigation of the significance of adhesion molecules by in vivo observation and quantification.  (+info)

Repopulation of different layers of host human Bruch's membrane by retinal pigment epithelial cell grafts. (39/22844)

PURPOSE: To determine the morphology of human retinal pigment epithelium (RPE) after reattachment to different ultrastructural layers of human Bruch's membrane (BM). METHODS: Bruch's membrane explants were prepared from eyes of 23 human donors (age range, 11-89 years). The basal lamina of the RPE, inner collagenous layer, and elastin layer were removed sequentially by mechanical and enzymatic techniques. First-passage cells of human RPE (15,000 cells/6 mm explant) from three donors (ages, 52, 64, and 80 years) were plated onto different layers of human BM, and the explants were examined by scanning and transmission electron microscopy up to 21 days later. RESULTS: RPE flattened and extended footplates 6 hours after plating onto basal lamina. Cells remained round 6 and 24 hours after plating onto the inner collagenous, elastin, or outer collagenous layer. The RPE cells became confluent 14 days after plating onto basal lamina but did not become confluent up to 21 days after plating onto the inner collagenous or elastin layer. Sparse round cells were observed 21 days after plating onto deeper layers, suggesting extensive loss of RPE. CONCLUSIONS: The morphology and subsequent behavior of the RPE reattached to BM depends on the anatomic layer of BM available for cell reattachment. The results suggest that the ability of transplanted RPE to repopulate BM in age-related macular degeneration and other disorders may depend on the layer of BM available to serve as a substrate for cell reattachment.  (+info)

Treatment of mouse oocytes with PI-PLC releases 70-kDa (pI 5) and 35- to 45-kDa (pI 5.5) protein clusters from the egg surface and inhibits sperm-oolemma binding and fusion. (40/22844)

The effect of phosphatidyinositol-specific phospholipase C (PI-PLC) on mouse sperm-egg interaction was investigated in this study to determine if glycosyl-phosphatidylinositol (GPI)-anchored proteins are involved in mammalian fertilization. When both sperm and zona-intact oocytes were pretreated with a highly purified preparation of PI-PLC and coincubated, there was no significant effect on sperm-zona pellucida binding; however, fertilization was reduced from 59.6% (control group) to 2.8% (treatment group). A similar reduction in fertilization rates was found when zona-intact oocytes were treated with PI-PLC and washed prior to incubation with untreated sperm. The effect of PI-PLC on sperm binding and fusion with zona-free oocytes was then investigated. Treatment of sperm with PI-PLC had no significant effect on sperm-egg binding or fusion. However, treatment of eggs with PI-PLC significantly reduced sperm-egg binding and fusion from 6.2 bound and 2.1 fused sperm per egg in the control group to 2.1 bound and 0.02 fused sperm per egg in the treatment group. This decrease in sperm-egg binding and fusion depended on the dose of PI-PLC employed, with a maximal inhibitory effect on binding and fusion at 5 and 1 U/ml, respectively. PI-PLC-treated oocytes could be artificially activated by calcium ionophore, demonstrating that the oocytes were functionally viable following treatment. Furthermore, treatment of oocytes with PI-PLC did not reduce the immunoreactivity of the non-GPI-anchored egg surface integrin, alpha6beta1. Taken together, these observations support the hypothesis that PI-PLC affects fertilization by specifically releasing GPI-anchored proteins from the oolemma. In order to identify the oolemmal GPI-anchored proteins involved in fertilization, egg surface proteins were labeled with sulfo-NHS biotin, treated with PI-PLC, and analyzed by two-dimensional gel electrophoresis followed by avidin blotting. A prominent high-molecular-weight protein cluster (approximately 70 kDa, pI 5) and a lower molecular weight (approximately 35-45 kDa, pI 5.5) protein cluster were released from the oolemmal surface as a result of PI-PLC treatment. It is likely that these GPI-anchored egg surface proteins are required for sperm-egg binding and fusion.  (+info)