Leukocyte-endothelial Cell Adhesion Research Articles

Cerebral microvessel responses to focal ischemia.

Cerebral microvessels have a unique ultrastructure form, which allows for the close relationship of the endothelium and blood elements to the neurons they serve, via intervening astrocytes. To focal ischemia, the cerebral microvasculature rapidly displays multiple dynamic responses. Immediate events include breakdown of the primary endothelial cell permeability barrier, with transudation of plasma, expression of endothelial cell-leukocyte adhesion receptors, loss of endothelial cell and astrocyte integrin receptors, loss of their matrix ligands, expression of members of several matrix-degrading protease families, and the appearance of receptors associated with angiogenesis and neovascularization. These events occur pari passu with neuron injury. Alterations in the microvessel matrix after the onset of ischemia also suggest links to changes in nonvascular cell viability. Microvascular obstruction within the ischemic territory occurs after occlusion and reperfusion of the feeding arteries ("focal no-reflow" phenomenon). This can result from extrinsic compression and intravascular events, including leukocyte(-platelet) adhesion, platelet-fibrin interactions, and activation of coagulation. All of these events occur in microvessels heterogeneously distributed within the ischemic core. The panorama of acute microvessel responses to focal cerebral ischemia provide opportunities to understand interrelationships between neurons and their microvascular supply and changes that underlie a number of central nervous system neurodegenerative disorders.

Endothelial cell glycocalyx modulates immobilization of leukocytes at the endothelial surface.

A thick endothelial glycocalyx provides the endothelial surface with a nonadherent shield. Oxidized LDL (Ox-LDL) degrades the endothelial glycocalyx. We hypothesized that glycocalyx degradation stimulates leukocyte-endothelial cell adhesion, whereas intravascular supplementation with sulfated polysaccharides reconstitutes the endothelial glycocalyx and attenuates Ox-LDL-induced leukocyte-endothelial cell adhesion. Degradation of the endothelial glycocalyx by local microinjection of heparitinase (10 to 50 U/mL) into mouse cremaster venules dose-dependently increased the number of adherent leukocytes. Systemic administration of Ox-LDL (0.4 mg/100 g body weight) induced 10.1+/-0.9 adherent leukocytes/100 microm at 60 minutes. In the venules perfused with 500-kDa dextran sulfate (1 mg/mL), the number of adherent leukocytes at 60 minutes after Ox-LDL bolus application was not influenced (9.2+/-1.0 leukocytes/100 microm). However, the venules locally perfused with heparan sulfate (10 mg/mL) or heparin (1 mg/mL) displayed a significantly lower number of adherent leukocytes induced by Ox-LDL: 5.1+/-0.7 and 5.4+/-0.9 leukocytes/100 microm, respectively (P<0.05). Fluorescently labeled heparan sulfate and heparin, but not dextran sulfate, attached to the venule luminal surface after Ox-LDL administration. Endothelial glycocalyx degradation stimulates leukocyte immobilization at the endothelial surface. Circulating heparan sulfate and heparin attach to the venule wall and attenuate Ox-LDL-induced leukocyte immobilization.

Molecular determinants of the prothrombogenic and inflammatory phenotype assumed by the postischemic cerebral microcirculation.

Circulating blood cells have been implicated in the pathogenesis of cerebral ischemia/reperfusion (I/R) injury and stroke. The objective of this study was to define the magnitude and molecular determinants of the platelet- and leukocyte-endothelial cell adhesive interactions induced by I/R in the mouse brain. Bilateral common carotid artery occlusion was induced for 1 hour in C57BL/6 mice, followed by either 40 minutes or 4 hours of reperfusion. Fluorescent platelets were administered intravenously, and the frontal brain surface was observed with intravital fluorescence microscopy. Leukocyte-endothelial cell adhesion was monitored with the use of rhodamine-6G. Ischemia followed by 40 minutes of reperfusion resulted in the rolling (125.1+/-23.6/mm2) and firm adhesion (109.5+/-25.8/mm2) of leukocytes but not platelets in venules. However, with 4 hours of reperfusion, rolling (138.8+/-24.6/mm2) and firm adhesion (153.7+/-22.3/mm2) of platelets were detected, and this was accompanied by a more intense recruitment of rolling (374.5+/-54.6/mm2) and adherent (445.2+/-57.1/mm2) leukocytes. In mice deficient in either P-selectin (P-selectin-/-) or intercellular adhesion molecule-1 (ICAM-1) (ICAM-1-/-), the I/R-induced platelet-endothelial cell (by 80% and 60%, respectively) and leukocyte-endothelial cell (by 84% and 78%, respectively) interactions were significantly blunted compared with those of wild-type mice. These findings indicate that I/R promotes the adhesion of both platelets and leukocytes in cerebral venules, with the accumulation of adherent leukocytes preceding the recruitment of platelets. Both P-selectin and ICAM-1 contribute to the inflammatory and prothrombogenic state induced by cerebral I/R.

Role of interferon-gamma in hypercholesterolemia-induced leukocyte-endothelial cell adhesion.

A T-cell-mediated inflammatory response occurs in the microcirculation during acute hypercholesterolemia. The objective of this study was to define the contribution of T-lymphocyte-derived interferon-gamma (IFN-gamma) to the leukocyte-endothelial cell adhesion induced by hypercholesterolemia. Intravital videomicroscopy was used to quantify the adhesion and emigration of leukocytes and oxidant stress (dihydrorhodamine [DHR] oxidation) in cremasteric venules. Wild-type (WT), IFN-gamma-/-, and severe combined immunodeficiency (SCID) mice were placed on either a normal (ND) or high-cholesterol (HC) diet for 2 weeks. WT-HC mice exhibited exaggerated adhesion and emigration of leukocytes and enhanced DHR oxidation compared with WT-ND. The exaggerated adhesion responses and increased DHR oxidation were not seen in IFN-gamma-/--HC mice. SCID-HC mice also exhibited attenuated inflammatory responses compared with WT-HC. Reconstitution of either SCID-HC or IFN-gamma-/--HC mice with WT-HC splenocytes restored the inflammatory responses, whereas reconstitution of SCID-HC with IFN-gamma-/--HC splenocytes did not. The HC-induced oxidant stress was restored in IFN-gamma-/--HC mice reconstituted with WT-HC splenocytes. These findings implicate IFN-gamma as a cause of the inflammatory phenotype that is assumed by the microvasculature of hypercholesterolemic mice and suggest that T lymphocytes are a major source of this proinflammatory cytokine.

Design and Synthesis of Sialyl Lewisx Mimics as E‐ and P‐Selectin Inhibitors

AbstractFor Abstract see ChemInform Abstract in Full Text.

Design and synthesis of sialyl Lewis(x) mimics as E- and P-selectin inhibitors.

The selectins are a family of cell-adhesion proteins that mediate the rolling of leukocytes on activated endothelial cells through the recognition of the carbohydrate epitope sialyl Lewis(x) (sLe(x)). Control of the leukocyte-endothelial cell adhesion process may prove useful in cases where excess recruitment of leukocytes can contribute to acute diseases such as stroke and reperfusion injury and chronic diseases such as psoriasis and rheumatoid arthritis. The development of molecules that block the interactions between sLe(x) and the selectins has become an active area of research. In this review, we will highlight the various approaches taken toward the development of sLe(x) mimetics as antagonists of E- and P-selectin, including the use of structural information about the selectins and their interactions with sLe(x) that have been revealed through the use of NMR, protein crystallography and molecular modeling.

Low venular shear rates promote leukocyte-dependent recruitment of adherent platelets

The influence of reductions in venular shear rate on platelet-endothelial (P/E) cell adhesion has not been previously addressed. The objectives of this study were to define the effects of reductions in venular shear rate on P/E cell adhesion and to determine the interdependence of P/E cell adhesion and leukocyte-endothelial (L/E) cell adhesion at low shear rates. Intravital videomicroscopy was used to quantify P/E and L/E cell adhesion in rat mesenteric venules exposed to shear rates ranging between 118 +/- 9 and 835 +/- 44 s(-1). Shear rate was altered in postcapillary venules by rapid, graded blood withdrawal, without retransfusion of shed blood. Reducing shear rate from >600 s(-1) to <200 s(-1) resulted in an eightfold increase in L/E cell adhesion, whereas P/E cell adhesion increased 18-fold. A blocking antibody directed against P-selectin blunted both the P/E and L/E cell adhesion elicited by low shear rates. Immunoneutralization of CD11/CD18 on leukocytes or rendering animals neutropenic also blocked the shear rate-dependent recruitment of both platelets and leukocytes. These findings indicate that 1) low shear rates promote P/E and L/E cell adhesion in mesenteric venules, and 2) adherent neutrophils (mediated by CD11/CD18) create a platform onto which platelets can bind to the venular wall at low shear rates.

Expression of leukocyte–endothelial cell adhesion molecules on monocyte adhesion to human endothelial cells on plasma treated PET and PTFE in vitro

We used a coculture model to evaluate the inflammatory potential of ammonia gas plasma modified PET and PTFE by flow cytometry and immunohistochemistry. In these studies, human endothelial cells from umbilical cord (HUVEC) and promonocytic U937 cells were used. HUVECs grown on polystyrene tissue culture coverslips and HUVECs stimulated with tumour necrosis factor (TNF- α) were used as controls. U937 adhesion to endothelium on each surface was evaluated at day 1 and day 7. To further investigate the role of leukocyte–endothelial cell adhesion molecules (CAMs) in cell-to-cell interaction on material surfaces, the expression of the leukocyte–endothelial CAMs: ICAM-1, VCAM-1, PECAM-1, and E-selectin on HUVECs were evaluated after U937 cell adhesion. The results demonstrated that plasma treated PET (T-PET) and treated PTFE (T-PTFE) did not increase U937 cell adhesion compared to the negative control. Maximal adhesion of U937 cells to HUVEC was observed on TNF- α stimulated endothelium with significant differences between day 1 and day 7, which is consistent with our prior observation that T-PET and T-PTFE did not cause HUVECs to increase the expression of adhesion molecules. After U937 cell adhesion, the expression of ICAM-1 and VCAM-1 of HUVECs were not different on T-PET and T-PTFE compared with the negative control. However, the expression of E-selectin was reduced on day 1, but not on day 7. The effects of plasma treated PET and PTFE on HUVEC adhesion and proliferation were also studied. On day 1 there were slight increases in the growth of HUVECs on both of T-PET and T-PTFE but this was not statistically significant. On day 7, the cell number increased significantly on the surfaces compared to the negative control. The results demonstrate that the plasma treatment of PET and PTFE with ammonia improves the adhesion and growth of endothelial cells and these surfaces do not exhibit a direct inflammatory effect in terms of monocyte adhesion and expression of leukocyte–endothelial CAMs. The monocyte adhesion to endothelial cells on surfaces can be used as a tool for the evaluation of material surface modification and further to study the mechanisms of cell-to-cell interactions in response to surfaces.

Leukocyte–endothelial cell adhesion molecule 1 (LECAM-1) polymorphism is associated with diabetic nephropathy in type 2 diabetes mellitus

Background/aims: Glomerular infiltration with monocytes/macrophages has been implicated in the pathogenesis of diabetic nephropathy. In this study, we evaluated the relationship between the genetic polymorphism in leukocyte–endothelial adhesion molecule-1 (LECAM-1) and diabetic nephropathy in patients with type 2 diabetes mellitus. Methods: We determined the frequency of the LECAM-1 P213S genotype in 102 diabetic patients with diabetic nephropathy, 90 diabetic patients with no evidence of diabetic nephropathy, and 200 healthy control individuals. Results: The frequency of the LECAM-1 213PP genotype and P allele in patients with diabetic nephropathy was significantly higher than that in patients without nephropathy (genotype 68% vs. 53%, χ 2=6.78, P=.034; allele 83% vs. 72%, χ 2=6.26, P=.012). The LECAM-1 P213 genotype was associated with a 1.86-fold increased risk for nephropathy independently of other risk factors. Conclusion: The data suggest that the LECAM-1 213PP genotype is a genetic risk factor for the development of nephropathy in type 2 diabetes mellitus.

Role of glycocalyx in leukocyte-endothelial cell adhesion.

The binding of fluorescently labeled microspheres (FLMs, 0.1-microm diameter) coated with antibody (1a29) to ICAM-1 was studied in postcapillary venules during topical application of the chemoattractant N-formylmethionyl-leucyl-phenylalanine (fMLP). FLM adhesion to endothelial cells (ECs) increased dramatically from 50 to 150 spheres per 100-microm length of venule after superfusion of the mesentery with fMLP and equaled or exceeded levels of leukocyte (WBC) adhesion. Removal of the EC glycocalyx by micropipette infusion of the venule with heparinase increased FLM-EC adhesion to levels attained with fMLP. Subsequent application of fMLP did not increase FLM adhesion further, suggesting that the FLMs saturated all ICAM-1 binding sites. Perfusion with heparinase after suffusion with fMLP significantly increased FLM-EC adhesion above levels attained with fMLP. However, WBC adhesion fell because of possible removal of selectins necessary to maintain WBC rolling at the wall. It is concluded that the glycocalyx serves as a barrier to adhesion and that its shedding during natural activation of ECs may be an essential part of the inflammatory response.

HSP70 as Endogenous Stimulus of the Toll/Interleukin-1 Receptor Signal Pathway

Human heat-shock protein (HSP)70 activates innate immune cells and hence requires no additional adjuvants to render bound peptides immunogenic. Here we tested the assumption that endogenous HSP70 activates the Toll/IL-1 receptor signal pathway similar to HSP60 and pathogen-derived molecular patterns. We show that HSP70 induces interleukin-12 (IL-12) and endothelial cell-leukocyte adhesion molecule-1 (ELAM-1) promoters in macrophages and that this is controlled by MyD88 and TRAF6. Furthermore, HSP70 causes MyD88 relocalization and MyD88-deficient dendritic cells do not respond to HSP70 with proinflammatory cytokine production. Using the system of genetic complementation with Toll-like receptors (TLR) we found that TLR2 and TLR4 confer responsiveness to HSP70 in 293T fibroblasts. The expanding list of endogenous ligands able to activate the ancient Toll/IL-1 receptor signal pathway is in line with the "danger hypothesis" proposing that the innate immune system senses danger signals even if they originate from self.

Leukocyte endothelial cell interactions in pig to human organ xenograft rejection

In cases where antibody- and complement-mediated hyperacute rejection (HAR) of vascularized organ xenografts has been prevented, acute vascular rejection (AVR) and acute T cell-mediated rejection (ACR) cause graft destruction. Infiltration of leukocytes (innate and graft-primed T cells) into the graft execute the latter two rejection modalities. The leukocyte extravasation process, which is a prerequisite for graft infiltration, is governed by adhesion molecules, including the selectin, integrin and immunoglobulin protein families, and the chemokine protein family. The compatibility between porcine endothelial cell and human leukocyte adhesion molecules was investigated in dynamic adhesion and static transendothelial migration assays. The effect of human anti-pig antibodies on human leukocyte adhesion to, and transendothelial migration across, porcine endothelium was assessed under dynamic and static conditions, respectively. In contrast to previously published results, no difference in the ability of neutrophils to adhere to pig and human endothelium was observed. Furthermore, no evident quantitative or qualitative differences in the capacity of human and porcine endothelium to support transendothelial migration of human leukocytes (T, B and natural killer (NK) cells, monocytes, and neutrophils) could be detected. The presence of human anti-pig antibodies (Abs) modulated the migration of leukocytes across porcine endothelium, as well as neutrophil adhesion to porcine endothelium under conditions of flow. Antibodies specific for pig endothelial adhesion molecules can potentially be used as species (graft)-specific immunosuppressive reagents in order to prevent cellular organ xenograft rejection.

Leukocyte adhesion factor Mac-1 and migration inhibitory factor-related protein (MRP) on granulocyte plays the essential role for causing vasculitis in kawasaki disease and the gamma globulin therapy inhibit leukocyte-endothelial cell adhesion

Leukocyte adhesion factor Mac-1 and migration inhibitory factor-related protein (MRP) on granulocyte plays the essential role for causing vasculitis in kawasaki disease and the gamma globulin therapy inhibit leukocyte-endothelial cell adhesion

Transplantation 03

Prostaglandin E1 (PgE1) may have a role in ameliorating hepatic ischaemia–reperfusion injury (IRI). Metabolism occurs after intravenous administration of PgE1 and limits its efficacy. This study has investigated the cytoprotective effect of PgE1 administered intraportally. Since leucocyte–endothelial cell adhesion has been strongly implicated in IRI, we also studied intracellular adhesion molcule-1 (ICAM-1) and vascular adhesion molecule-1 (VCAM-1) expression to assess if PgE1 acted through this pathway. Under general anaesthesia hepatic ischaemia was induced in 20 canine livers by 60 min of in situ inflow occlusion with continuous intraportal infusion of PgE1 0.02 µg kg−1 per min lactated Ringers solution (n = 10) or equal volumes of lactated Ringers solution (controls, n = 10). The infusion started 15 min before ischaemia and continued during the ischaemic phase and 30 min after reperfusion. Hepatic venous blood and liver biopsies were taken at baseline, 60-min ischaemia and 30-min reperfusion. The blood samples were assessed for liver enzymes, TNF-α, IL-1β, serum ICAM-1 (sICAM-1) and VCAM-1 (sVCAM-1), while the liver biopsies were assessed histologically for IRI and immunohistochemically for ICAM-1 and VCAM-1 expression. PgE1 treatment significantly reduced the rise in AST, ALT, TNF-α, sICAM-1 and sVCAM-1 following ischaemia and reperfusion (P < 0.05). It reduced hepatocyte necrosis and sinusoidal congestion. However, it did not reduce IL-1β. These changes were associated with significant down-regulation of ICAM-1 and VCAM-1 (P < 0.05). Intraportal PgE1 infusion ameliorates IRI, inhibits ICAM-1 and VCAM-1 expression and TNF-α secretion. One of the mechanisms of cytoprotection may be through ICAM-1 and VCAM-1 inhibition.

Platelets modulate ischemia/reperfusion-induced leukocyte recruitment in the mesenteric circulation.

P-selectin-dependent leukocyte-endothelial cell adhesion has been implicated in the pathogenesis of ischemia/reperfusion (I/R) injury in several vascular beds, including the gut. Because platelet-endothelial (P/E) cell adhesion also occurs in postischemic venules, the possibility exists that the expression of P-selectin on the surface of platelets that are adherent to venular endothelial cells may mediate the leukocyte recruitment elicited by I/R. P-selectin expression [dual radiolabeled monoclonal antibody (MAb) technique] and neutrophil accumulation [myeloperoxidase (MPO) activity] were measured in the postischemic small intestine of untreated rats and rats treated with either antiplatelet serum (APS) or MAbs directed against either P-selectin, GPIIb/IIIa, or fibrinogen. The increases in P-selectin expression and tissue MPO normally elicited by I/R were significantly attenuated in the different treatment groups, suggesting that I/R-induced neutrophil recruitment is a platelet-dependent, P-selectin-mediated process. Intravital microscopy was then employed to examine this process relative to leukocyte-endothelial cell adhesion in postischemic rat mesenteric venules. The recruitment of adherent and emigrated leukocytes after I/R was attenuated by pretreatment with a MAb against, either P-selectin, GPIIb/IIIa, or fibrinogen, as well as an Arg-Gly-Asp peptide. Whereas thrombocytopenia greatly blunted leukocyte emigration, it did not alter the leukocyte adherence response to I/R. These findings suggest that platelet-associated P-selectin contributes to the accumulation of leukocytes in postischemic tissue via a mechanism that alters transendothelial leukocyte migration.

Biologic effects of bacterial superantigens in a xenogeneic transplantation model for psoriasis.

Both clinical as well as experimental data support the concept of psoriasis being a T-cell-mediated immune disease possibly triggered by bacterial superantigens. Further analysis of its pathogenesis was facilitated by the generation of a xenogeneic transplantation model in which skin from psoriatic patients is grafted onto SCID mice lacking functional B and T cells. Applying this model it was demonstrated that psoriasis can be triggered by bacterial superantigens; this process depends on the presence of immunocytes. Mutated variants of the respective superantigens exhibiting no measurable affinity to HLA class II molecules can function as competitive inhibitors in vivo.

Synergism between Leukocyte Adherence and Shear Determines Venular Permeability in the Presence of Nitric Oxide

The effects of nitric oxide (NO) on vascular permeability tend to be controversial. While many studies indicate that NO plays a protective role in several models of inflammation by reducing leukocyte–endothelial cell adhesion, in vitro studies have shown that endothelial permeability to macromolecules increases with increasing shear forces via a NO-dependent mechanism. Most investigations of the role of shear on endothelial permeability have been performed either in vitro or in cannulated vessels, but whether NO and leukocyte adherence (WBC-adh) mediate shear-induced control of albumin leakage in autoperfused venules has yet to be determined. By measuring permeability under regular conditions of blood flow and WBC-adh, we recently found that venular albumin permeability of the rat mesentery correlates strongly with basal levels of both shear rate and WBC-adh. Using the same model in the present study, we were able to further elucidate some of the mechanisms and mediators of venular permeability. In one set of experiments, a role for NO in shear-mediated permeability was confirmed. In additional experiments, a permeability-enhancing collaboration between shear and WBC-adh was revealed: shear-induced permeability was found to be dependent on the presence of adherent leukocytes, and similarly, leukocyte-mediated permeability was found to be dependent on shear. This synergism was present both under basal conditions and following the inflammatory stimulus of ischemia–reperfusion.

Matrix metalloproteinases regulate neutrophil-endothelial cell adhesion through generation of endothelin-1[1-32

We recently reported that matrix metalloproteinase 2 (MMP-2, gelatinase A) cleaves big endothelin 1 (ET-1), yielding the vasoactive peptide ET-1[1-32]. We tested whether ET-1[1-32] could affect the adhesion of human neutrophils to coronary artery endothelial cells (HCAEC). ET-1[1-32] rapidly down-regulated the expression of L-selectin and up-regulated expression of CD11b/CD18 on the neutrophil surface, with EC50 values of 1-3 nM. These actions of ET-1[1-32] were mediated via ETA receptors and did not require conversion of ET-1[1-32] into ET-1 by neutrophil proteases, as revealed by liquid chromatography and mass spectroscopy. Moreover, ET-1[1-32] evoked release of neutrophil gelatinase B, which cleaved big ET-1 to yield ET-1[1-32], thus revealing a positive feedback loop for ET-1[1-32] generation. Up-regulation of CD11b/CD18 expression and gelatinase release was tightly associated with activation of extracellular signal-regulated kinase (Erk). Stimulation of Erk activity was due to activation of Ras, Raf-1, and MEK (MAPK kinase). ET-1[1-32] also produced slight increases in the expression of ICAM-1 and E-selectin on HCAEC, and markedly enhanced beta2 integrin-dependent adhesion of neutrophils to activated HCAEC. These results are the first indication that gelatinolytic MMPs via cleavage of big ET-1 to yield ET-1[1-32] activate neutrophils and promote leukocyte-endothelial cell adhesion and, consequently, neutrophil trafficking into inflamed tissues.

Adenovirus-mediated overexpression of dominant-negative mutant of c-Jun prevents intercellular adhesion molecule-1 induction by LDL: a critical role for activator protein-1 in endothelial activation.

Low density lipoprotein (LDL) induces intercellular adhesion molecule-1 (ICAM-1) gene expression and leads to endothelial cell (EC) leukocyte adhesion. However, the transcriptional mechanism for LDL-induced EC perturbation remains to be fully explained. Activator protein-1 (AP-1) is induced after the exposure of ECs to LDL. In the present study, a regulated adenovirus expressing a dominant-negative mutant of c-Jun (TAM-67) was used to examine the role of AP-1 in the LDL-induced ICAM-1 activation. Overexpression of TAM-67 specifically inhibited AP-1 activation and prevented the LDL-activated surface expression of ICAM-1 protein in human umbilical vein ECs and human coronary artery ECs. Northern analyses and promoter transactivation assays indicated that this effect of TAM-67 was likely mediated through a suppression of the transcriptional regulation of the ICAM-1 gene. Functionally, TAM-67 attenuated leukocyte adherence to ECs in response to LDL. Furthermore, electrophoresis mobility shift assays and site-directed mutagenesis suggested that an AP-1-like motif in the promoter region of the human ICAM-1 gene was a critical cis element for LDL induction. These results, for the first time, provide evidence suggesting that AP-1 is a major regulatory mechanism leading to endothelial activation.

The effect of prostaglandin E1 versus ischemia-reperfusion injury of musculocutaneous flaps.

The purpose of this study was twofold. To evaluate whether prostaglandin El can increase the survival of the flap, and to determine its function against ischemia-reperfusion injury in musculocutaneous flaps. Thirty-five Sprague-Dawley rats weighing 250 to 350 g were analyzed. The transverse rectus abdominis musculocutaneous flap was used in all rats. The rats were divided into three groups: group 1 (N = 15), the control group with 4-hour ischemic injury and intraflap injection of normal saline followed by reperfusion; group 2 (N = 15), prostaglandin E1 intraflap injection of 1 microg immediately after ischemic injury and reperfusion 4 hours later; and group 3 (N = 5), the sham-operated group. Analysis consisted of flap skin survival area measurements, immunohistochemical study using anti-intercellular adhesion molecule (anti-ICAM-1) monoclonal antibody, and histological evaluation including endothelium-sticking leukocytes at 24 hours and 5 days after reperfusion. The group treated with prostaglandin E1 showed immunohistochemical findings with decreased expression of ICAM-1 on the surface of the endothelium, and histology showed significant (p < 0.01) reduction of leukocyte adhesion at 24 hours and 5 days after reperfusion. These two factors were considered to play a role against ischemia-reperfusion injury, and led to improved survival of the flap. These results suggest that prostaglandin E1 may increase flap survival and may have a protective mechanism against ischemia-reperfusion injury by decreasing leukocyte-endothelial cell adhesion through decreased expression of ICAM-1.