Induction Of E-selectin Research Articles

Late and persistent up-regulation of intercellular adhesion molecule-1 (ICAM-1) expression by ionizing radiation in human endothelial cells in vitro

. Adhesion molecules play a key role in cellular traffic through vascular endothelium, in particular during the inflammatory response when leukocytes migrate from blood into tissues. Since inflammation is one of the major consequences of radiation injury, we investigated the effect of ionizing radiation on cellsurface expression of the intercellular adhesion molecule-1 (ICAM-1), the vascular cell adhesion molecule-1 (VCAM-1) and E-selectin in cultured human umbilical vein endothelial cells (HUVEC). Flow cytometry performed on irradiated HUVEC revealed both a time- (from 2 to 10 days) and dose- (from 2 to 10 Gy) dependent up-regulation of basal expression of ICAM-1, and no induction of VCAM-1 or E-selectin. The radiationinduced increase in ICAM-1 expression on HUVEC was correlated with augmented adhesion of neutrophils on irradiated endothelial cells. Interleukin-6 (Il-6) or other soluble factors released by irradiation were not involved in the enhanced ICAM-1 expression by irradiation. Northern blot analysis showed an overexpression of ICAM-1 mRNA from 1 to 6 days after a 10 Gy exposure. Our data suggest that ICAM-1 participates in the radiation-induced inflammatory reaction of the endothelium.

Monocytes induce E-selectin gene expression in endothelial cells: role of CD11/CD18 and extracellular matrix proteins.

E-selectin is an endothelium-specific inducible adhesion molecule which binds several inflammatory cell types, including neutrophils, monocytes, natural killer cells and a subset of memory T cells. E-selectin is important in the initial rolling interaction of these cells on inflamed endothelium. The transient kinetics of E-selectin induction in vitro contrast with in vivo observations of prolonged expression of this adhesion molecule in chronic inflammation. This raises the possibility that signals generated within inflammatory tissues are more complex than the agonists used to activate endothelial cells in vitro. We investigated whether adhesive interactions with extravasating monocytes are able to provide activating signals that can induce E-selectin expression on endothelium, and prolong the response to cytokine stimulation. We report that co-culture with monocytes led to transcriptional activation of the E-selectin gene in endothelial cells, and marked enhancement of the response to substimulatory concentrations of interleukin-1. In addition, the presence of monocytes resulted in prolonged up-regulation of E-selectin. Induction of E-selectin by monocytes was inhibited when cell contact between monocytes and endothelium was prevented (80 +/- 8% inhibition, p < 0.001, n = 4). Monoclonal antibody (mAb) against tumor necrosis factor (TNF) was able to abolish 57.2 +/- 9.7% of the response (p < 0.01, n = 4). The ability of adherent monocytes to induce sustained E-selectin expression in endothelial cells could not be reproduced either by supernatants harvested from monocytes cultured for 18 h, or by maximal concentrations of TNF. The induction of E-selectin in monocyte/endothelium co-cultures was inhibited by mAb to CD11b, but not by those directed against VLA-4 or L-selectin. Extracellular matrix molecules may also play a role in adhesion-dependent cellular activation, as inclusion of soluble collagen type I led to significant reduction in E-selectin expression in monocyte/endothelium co-cultures. We conclude that adhesive interactions between monocytes and endothelial cells provide a source of signals which influence the activation state of the endothelium, and consequently, the continued influx of inflammatory cells.

Angiotensin II Increases Monocyte Binding to Endothelial Cells

Angiotensin II (AII) is recognized as being an important factor in the pathogenesis of hypertension and atherosclerosis. Monocyte binding to affected endothelial cells is one of the earliest features of atherosclerosis. However, the effect of AII on monocyte binding has not been fully studied. Treatment of human aortic endothelial cells (HAEC) and rabbit aortic endothelial cells (RAEC) for 18 hours with AII induced the adhesion of monocytes but not neutrophils to these cells. This induction was reduced by inhibitors of AII receptors (Type I and Type II). Angiotensin II-induced monocyte binding was not associated with induction of E-selectin, vascular cell adhesion molecule-1 (VCAM-1), or intercellular adhesion molecule-1 (ICAM-1). These results suggest that AII can accelerate the rate of atherosclerosis by increasing monocyte binding to the endothelium.

Tumor Angiogenesis Is Accompanied by a Decreased Inflammatory Response of Tumor-Associated Endothelium

We previously showed that endothelial cells (EC) from the vasculature of human solid tumors have a decreased expression of intercellular adhesion molecule-1 (ICAM-1) and ICAM-2 as compared with normal tissue EC. This effect is explained by EC exposure to angiogenic factors. It is known that upregulation of endothelial adhesion molecules (EAM) is a sign of EC activation in inflammatory responses. We therefore tested the effect of angiogenic factors on upregulation of EAM on tumor EC and human umbilical vein EC (HUVEC) by proinflammatory cytokines. Incubation of tumor-derived EC in tumor necrosis factor alpha (TNF alpha) did result in expression levels of only 20% of the level of similarly treated normal tissue-derived EC. Pretreatment of HUVEC with 10 ng/ml basic fibroblast growth factor (bFGF) for 3 days, before TNF alpha- or interleukin-1 alpha (IL-1 alpha) stimulation, resulted in ICAM-1 levels of only 30% to 60% of cells without pretreatment. Also, the induction of vascular EC adhesion molecule-1 (VCAM-1) and E-selectin by TNF alpha was significantly inhibited by prior exposure to bFGF. Vascular endothelial growth factor had similar but less prominent effects. The effect of transforming growth factor-beta and IL-8 was studied as well. The functional relevance of the finding of a decreased EC inflammatory response was confirmed by adhesion assays. Our results show that tumor angiogenesis induces EC anergy. This may serve as a tumor-protecting mechanism by impairing the development of an efficient leukocyte infiltrate in tumors.

Hypoxia enhances stimulus-dependent induction of E-selectin on aortic endothelial cells.

In many diseases, tissue hypoxia occurs in conjunction with other inflammatory processes. Since previous studies have demonstrated a role for leukocytes in ischemia/reperfusion injury, we hypothesized that endothelial hypoxia may "superinduce" expression of an important leukocyte adhesion molecule, E-selectin (ELAM-1, CD62E). Bovine aortic endothelial monolayers were exposed to hypoxia in the presence or absence of tumor-necrosis factor alpha (TNF-alpha) or lipopolysaccharide (LPS). Cell surface E-selectin was quantitated by whole cell ELISA or by immunoprecipitation using polyclonal anti-E-selectin sera. Endothelial mRNA levels were assessed using ribonuclease protection assays. Hypoxia alone did not induce endothelial E-selectin expression. However, enhanced induction of E-selectin was observed with the combination of hypoxia and TNF-alpha (270% increase over normoxia and TNF-alpha) or hypoxia and LPS (190% increase over normoxia and LPS). These studies revealed that a mechanism for such enhancement may be hypoxia-elicited decrements in endothelial intracellular levels of cAMP (<50% compared with normoxia). Addition of forskolin and isobutyl-methyl-xanthine during hypoxia resulted in reversal of cAMP decreases and a loss of enhanced E-selectin surface expression with the combination of TNF-alpha and hypoxia. We conclude that endothelial hypoxia may provide a novel signal for superinduction of E-selectin during states of inflammation.

Activated T cells induce expression of E-selectin in vitro and in an antigen-dependent manner in vivo.

E-selectin is an endothelial adhesion molecule for polymorphonuclear cells, monocytes and skin-homing T cells. We have analyzed whether murine T cells are able to induce expression of E-selectin in vitro and in vivo. Using models of inflammation in which T cells play either a significant or only a minor role, we compared induction of E-selectin between normal mice and mice lacking functional T cells (athymic nude mice). In irritant contact dermatitis, a model without a major role for T cells, E-selectin was transiently expressed within the first 24 h in both normal and nude mice. In experimental leishmaniasis (where specific T cells play an important role), a high expression of E-selectin was maintained for 48 h in normal mice, whereas in nude mice expression was only transient. However, reconstitution of nude mice with 10(8) T cells from draining lymph nodes (LN) of Leishmania-infected normal mice could restore sustained expression of E-selectin. Transfer of T lymphocytes from normal LN or from LN of mice sensitized to the contact allergen trinitrochlorobenzene (TNCB) did not have this effect. T cells from TNCB-sensitized mice, however, did induce sustained expression of E-selectin in nude mice when TNCB was applied locally; here, reconstitution with Leishmania-specific T cells had no effect. In vitro, T cells from infected or TNCB-sensitized normal mice increased expression of E-selectin on microvascular endothelial cells after 4 h of co-culture. T cells from untreated mice were less effective. Induction was dependent on direct cell-cell contact, but not on the action of interleukin-1 alpha, interleukin-1 beta, tumor necrosis factor-alpha or interferon-gamma. We conclude that sensitized T cells induce sustained expression of E-selectin in vivo in an antigen-dependent manner. This novel way of regulation could be relevant for cell-mediated immunity and chronic disease. The mechanisms are unknown, but, as in vitro, might require direct cell-cell contact.

Activation and homologous desensitization of human endothelial cells by CD40 ligand, tumor necrosis factor, and interleukin 1.

We have reported previously that activation of human umbilical vein endothelial cells (HUVECs) through CD40, using a recombinant soluble form of trimerized CD40 ligand, leads to induction of E-selectin, vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1). Here, we compare the effects of CD40 ligand with those of tumor necrosis factor (TNF) and interleukin 1 (IL-1). All three ligands induce transient increases in E-selectin (peak 4 h) and VCAM-1 (peak 8-24 h), as well as sustained increases in ICAM-1 (plateau 24 h). Quantitatively, TNF is more potent than IL-1, which is much more potent than CD40 ligand. The same hierarchy is observed for transcriptional activation of an E-selectin promoter reporter gene construct in transiently transfected HUVECs. TNF and CD40 ligand each induced activation of the transcription factors NF-kappa B, IRF-1, and ATF-2/c-Jun, measured by electrophoretic mobility shift assays, but this response appeared quantitatively similar. All three agents transiently (peak 30 min) activated Jun NH2-terminal kinase (JNK), which has been implicated in transcription of E-selectin through its actions on ATF-2/c-Jun. Activation of JNK again showed a hierarchy of potency (TNF > IL-1 >> CD40 ligand), although the time course of induction was similar for all three agents. After 44 h of pretreatment, TNF, IL-1, and CD40 ligand each display homologous desensitization for reinduction of surface expression of E-selectin. A similar pattern of homologous desensitization for reactivation of JNK was observed. We conclude that TNF, IL-1, and CD40 ligand all activate similar responses in ECs, and that homologous desensitization of JNK may explain the inability of individual cytokines to reinduce E-selectin expression.

DIRECT ACTIVATION OF PORCINE ENDOTHELIAL CELLS BY HUMAN NATURAL KILLER CELLS1

Endothelial cell (EC) activation is a consistent feature of discordant xenograft rejection. Treatment of xenograft recipients with complement inhibitors and xenoreactive natural antibody depletion leads to delayed xenograft rejection associated with a cellular infiltrate comprising up to 20% natural killer (NK) cells. To determine the importance of NK cells in xenograft rejection, we studied EC activation and cytotoxicity in co-cultures containing human NK cells and porcine EC. The addition of freshly isolated NK cells to porcine EC resulted in EC cell activation, characterized by the induction of mRNA and protein for the adhesion molecule E-selectin and the chemotactic cytokine interleukin (IL)-8. The induction of E-selectin and IL-8 occurred with three separate sources of NK cells: purified CD56+ve cells, the NK cell clone B22, and the Fc receptor-deficient NK cell line NK92. Transwell cultures demonstrated that direct NK-EC contact was required for the EC induction of E-selectin and IL-8. These effects could not be inhibited with human recombinant tumor necrosis factor-alpha receptor, and the transfer of supernatants or cell lysates from activated EC to secondary cultures did not result in EC activation. The addition of human IgG enhanced the level of E-selectin expression and cellular cytotoxicity, and resulted in tumor necrosis factor-alpha and interferon-gamma secretion. Thus, human NK cells can lyse or activate EC by direct cell contact and the addition of IgG enhances EC activation and NK cell cytokine secretion. These findings implicate NK cells in EC activation and cell-mediated xenograft rejection.

Involvement of tyrosine phosphorylation in endothelial adhesion molecule induction.

Induction of endothelial adhesion molecules by the cytokine tumor necrosis factor-alpha (TNF) can occur independently of protein kinase C and activation of a protein tyrosine kinase (PTK) has recently been implicated in the upregulation of vascular cell adhesion molecule 1 (VCAM-1) by interleukin-4 (IL-4) on endothelial cells. We demonstrate that the PTK inhibitors herbimycin A or genistein suppress induction of endothelial VCAM-1 and E-selectin, as well as subsequent monocytic cell adhesion to endothelial cells stimulated by TNF. Inhibition studies indicate that specific tyrosine phosphorylation following PTK activation is involved in the mobilization of the transcription factor, nuclear factor kappa B, and VCAM-1 mRNA expression. This may have implications for pathophysiological conditions that involve the upregulation of these molecules (e.g. inflammation and atherosclerosis).

Inhibitory Effect of Fish Oil N-3 Polyunsaturated Fatty Acids on the Expression of Endothelial Cell Adhesion Molecules

A rapid, cost-effective and sensitive method of Northern analysis using specific oligonucleotide probes combined with chemiluminescence was used to detect adhesion molecule transcripts with as little as 50 ng of total RNA from activated primary human umbilical vein endothelial cells (HUVEC). Activation of cultured HUVEC with the inflammatory cytokine interleukin 1β (IL-1β) resulted in distinct time- and dose-dependent patterns of expression of ICAM-1, E-Selectin and VCAM-1 transcripts. The levels of all three transcripts were maximal after 2.5 hours of stimulation with IL-1β. However, the upregulation of ICAM-1 mRNA levels in response to IL-1β was much more stable than the transient induction of E-selectin and VCAM-1 transcripts. In addition, we have found that eicosapentaenoic acid (EPA) and docosapentaenoic acid (DHA) ω3 fatty acids that have been reported to modulate the adhesive properties of cells involved in immune/inflammatory responses do not affect the expression of ICAM-1, VCAM-1 or E-selectin in resting HUVEC. However, EPA (65 μM) or DHA (65 μM) do attenuate the induction of each of these adhesion molecules in IL-1β-activated HUVEC.

Role of serum E-selectin (ELAM-1) and inflammatory parameters in patients with renal cell carcinoma

(BACKGROUND). E-selectin is an adhesion molecule expressed on IL-1 activated endothelial cells and it binds to carbohydrate ligands such as sialy Lewis A antigen (SLeA) or Lewis X antigen (SLeX) on cancer cells. This mechanism is supposed to play an important role during hematogenous metastasis. Some of renal cell carcinomas (RCC) are known to produce inflammatory cytokines such as IL-1 beta and IL-6 and clinical evidence shows that the prognosis of this type of tumor is generally poor. We investigated whether this adhesion molecule was involved in hematogenous metastasis. (METHOD). In the present study, soluble E-selectin level was measured in the sera of 89 patients with RCC prior to nephrectomy or IFN treatment using sanwich ELISA method. (RESULTS). The results indicated that high E-selectin concentration in the patients' sera was correlated with low incidence of metastasis and consequently correlated with good prognosis of RCC patients. Inflammatory serum parameters, such as serum C reactive protein (CRP), immunosuppressive acid protein (IAP) and erythrocyte sediment rate (ESR) were also assessed and these parameters were revealed to be negatively correlated with the serum level of E-selectin. In order to investigate this mechanism, we performed in vitro study on RCC cell/endothelial cell adhesion. IL-1 beta enhanced adhesion of 2 RCC cell lines and this adhesion was partially inhibited by adding exogenous E-selectin into the culture medium. Expression of SLeA and SLeX were demonstrated on the cell surface of 2 RCC cell lines by flowcytometric analysis. (CONCLUSION). The results suggested that E-selectin and SLeX/SLeA interaction was involved in the adhesion between RCC and endothelial cells and also inflammatory cytokine production by RCC cells was a risk factor for metastasis through E-selectin induction. Although expression of E-selectin on endothelial cells facilitates metastasis, excessive production of E-selectin into the serum was suggested to have inhibitory effect against metastasis.

Protein kinase c regulates cytokine-induced tissue factor transcription and procoagulant activity in human endothelial cells

Interleukin-lα (IL-lα) and tumor necrosis factor-α (TNF-α) induce tissue factor in endothelium, which results in activation of the coagulation cascade. Despite extensive investigation, in which various stimuli that induce tissue factor have been defined, the intracellular processes that control tissue factor expression are not well understood. It has been proposed that protein kinase C regulates tissue factor expression primarily because phorbol myristate acetate, the protein kinase C activator, induces tissue factor expression. In this study we examined whether IL-1α- or TNF-α-stimulated tissue factor production is regulated through a protein kinase C-dependent mechanism. Northern blot analysis showed that cytokine-induced tissue factor mRNA was significantly reduced in human umbilical vein endothelial cells treated with calphostin C, a specific protein kinase C inhibitor. Tissue factor functional activity was decreased in the presence of calphostin C as well. Calphostin C also inhibited phorbol myristate acetate-induced tissue factor expression. In contrast, calphostin C did not alter cytokine induction of E-selectin or prostacyclin release. Because calcium stimulates protein kinase C binding to the membrane and its resulting catalytic activity, human umbilical vein endothelial cells were exposed to IL-1α or TNF-α in the presence of calcium ionophore A23187. A23187 had little effect alone but significantly augmented cytokine stimulation of tissue factor mRNA. Okadaic acid, a phosphatase inhibitor, increased cytokine-induced tissue factor mRNA compared with cytokine alone, which suggests that a phosphorylation event is important in tissue factor expression. These results indicate that protein kinase C is involved in cytokine activation of endothelial cell tissue factor expression.

Protein tyrosine kinase inhibitors act downstream of IL-1 alpha and LPS stimulated MAP-kinase phosphorylation to inhibit expression of E-selectin on human umbilical vein endothelial cells.

HUVEC exposed to IL-1 alpha, TNF alpha or LPS showed a time dependent increase in E-selectin expression which was maximal at between 4-6h after stimulation. Stimulation of HUVEC with IL-1 alpha, TNF alpha or LPS for between 2 and 6h followed by removal or neutralisation of IL-1 alpha, TNF alpha or LPS and incubation in new media up to 6h resulted in identical levels of E-selectin expression at 6h, as cells which had been continuously stimulated for 6h with IL-1 alpha, TNF alpha or LPS. These studies demonstrated that HUVEC were committed to the induction of E-selectin following a 2 hr incubation with either IL-1 alpha, TNF alpha or LPS. The protein tyrosine kinase (PTK) inhibitors ST271, ST638 or genistein (0-100M) were ineffective in reducing cytokine or LPS stimulated E-selectin expression during a 2h cytokine or LPS stimulation of cells, in which inhibitors were either coincubated with cytokine/LPS or previously preincubated with the PTK inhibitors. However when PTK inhibitors were present during both agonist activation (2h) and subsequent expression of E-selectin after removal of agonist (4h) the PTK inhibitors resulted in a dose dependent reduction in both IL-1 alpha and LPS stimulated E-selectin expression (IC50 = 50M). Moreover when PTK inhibitors were only incubated with cells for the 4h after cytokine or LPS activation of cells, PTK inhibitors resulted in a more effective dose dependent reduction in IL-1 alpha or LPS stimulated E-selectin expression (IC50 = 10M). Determination of total and surface expressed E-selectin showed that the reduction in E-selectin expression represented a reduction in E-selectin protein and analysis of E-selectin mRNA by RT-PCR demonstrated that inhibition of E-selectin protein synthesis reflected reduced E-selectin mRNA. Other cytokine or LPS signalling pathways such as the activation of MAP-kinase (ERK-2) was unaffected by pre and coincubation with the PTK inhibitors. These studies suggest that HUVEC can become committed to the induction of E-selectin after removal of the stimulus and that protein tyrosine kinase inhibitors do not effect initial (5-30 min) cytokine or LPS signals which result in E-selectin expression but can inhibit the expression of cytokine/LPS induced E-selectin expression at a step distal to MAP-kinase activation.

Memory T lymphocytes' adherence to Interferon gamma-activated human dermal microvascular endothelial cells via E-selectin

The regulation of leukocytes-endothelial cells binding by biological response modifiers have an important role in determining the progression of acute and chronic inflammatory responses. In order to define the influence of E-selectin on the binding of T lymphocytes to human dermal microvascular endothelial cells (HDMEC), we examined the cell surface expression of E-selectin on HDMEC and the regulation of the binding of T lymphocytes to HDMEC by IFN-γ. We have demonstrated that stimulation of HDMEC with IL-1α or TNFα leads to transient E-selectin induction which disappears after 48 h, but stimulation of HDMEC with IFN-γ resulted in delayed E-selectin induction which was seen at 48 h of incubation and persisted until 72 h after stimulation. However, stimulation with IFN-γ failed to induce E-selectin expression on human umbilical vein endothelial cells. The delayed E-selectin expression on HDMEC by IFN-γ coincided with the increases in T lymphocyte binding to IFN-γ-activated HDMEC. The binding of memory T lymphocytes to IFN-γ-activated HDMEC was greater than that of naive T lymphocytes. Anti-E-selectin antibody partially inhibited memory T lymphocyte binding to HDMEC after 48 h of stimulation with IFN-γ. These data show that E-selectin expressions by IFN-γ on endothelial cells are regulated in a tissue-specific fashion and that E-selectin may be important in vivo in the preferential migration of memory T lymphocytes into inflammatory sites in the skin.

Inhibition of NF-κB by Pyrrolidine Dithiocarbamate Blocks Endothelial Cell Activation

Endothelial cell activation is achieved by the rapid, protein synthesis-independent induction of a characteristic set of genes. Because of the abundance of binding sites for the transcription factor NF-κB in the regulatory region of the aforementioned genes, we hypothesized that this factor might play a key role. Reactive oxygen intermediates act as second messengers in the activation of NF-κB. We have used the antioxidant pyrrolidine dithiocarbamate to analyze the effect of NF-κB inhibition on TNFα-induced EC activation in vitro. We show that pyrrolidine dithiocarbamate strongly reduces the TNFα-mediated induction of E-selectin, VCAM-1, ICAM-1, PAI-1, tissue factor, IL-8 and IκB-α. We present evidence identifying NF-κB as a central regulator of EC activation. Therefore, this factor may represent a prime target for therapeutic intervention in pathologic conditions associated with EC activation such as allo- and xenograft rejection, atherosclerosis, ischemic reperfusion injury and vasculitis.

Cloning and characterization of a new isoform of the interleukin 1 receptor antagonist.

By reverse transcriptase polymerase chain reaction on messenger RNA from human polymorphonuclear cells, we have isolated a sequence identical to the cDNA coding for intracellular interleukin 1 receptor antagonist (icIL-1ra), but containing an additional in-frame 63-bp sequence located three codons downstream of the translation start of icIL-1ra. This additional sequence is inserted between the first and second exon of the intracellular form, the latter of which is colinear with part of the first exon of the secreted form of IL-1ra. The additional sequence is coded by an extra exon located 2 kb downstream the first icIL-1ra-specific exon. The complementary DNA sequence of the alternatively spliced form of icIL-1ra shows that the predicted protein differs from classical icIL-1ra in the NH2 terminus by insertion of a leaderless sequence of 21 amino acids rich in glycine and glutamic acid residues. Transcripts coding for this new form of icIL-1ra were detected in activated fibroblasts, keratinocytes, and at low levels in myelomonocytic cells. The recombinant protein expressed in COS cells had an apparent molecular mass in sodium dodecyl sulfate polyacrylamide gel electrophoresis of 25 kD compared to 22 kD of classical icIL-1ra, and was mostly intracellular. The ability of this new form of icIL-1ra to inhibit IL-1 activity, in terms of induction of E-selectin and human immunodeficiency virus replication, was comparable to that of classical icIL-1ra. We propose to refer to this new form of icIL-1ra as icIL-1ra type II.

Hypothermia reversibly inhibits endothelial cell expression of E-selectin and tissue factor.

Hypothermia frequently accompanies cardiopulmonary bypass (CPB) and myocardial protection strategies during cardiac surgery. With CPB, the blood/artificial surface interface activates components of the humoral and cellular inflammatory cascades and may contribute to postoperative end organ dysfunction including the heart or multiple other organ systems. The endothelial cell (EC) monolayer normally mediates components of solute transport, vasomotor function, coagulation, cell differentiation/growth, and immune/inflammatory processes. E-selectin is a vascular adhesion molecule that mediates neutrophil adherence and that is inducible in ECs by inflammatory mediators such as cytokines. Tissue factor (TF) is similarly an inducible procoagulant factor in ECs that contributes to thrombosis. The induction, transcription, and expression of both molecules were studied in cultured human umbilical vein cells at normothermic (37 degrees), hypothermic (25 degrees), and rewarmed (37 degrees) conditions after stimulation with the cytokines tumor necrosis factor alpha and interleukin-1. Hypothermia reversibly inhibits the transcription and expression but not the induction of both E-selectin and TF.

Aspirin inhibits nuclear factor-kappa B mobilization and monocyte adhesion in stimulated human endothelial cells.

The induction of vascular cell adhesion molecule-1 (VCAM-1) and E-selectin by tumor necrosis factor-alpha (TNF) is mediated by mobilization of the transcription factor nuclear factor-kappa B (NF-kappa B). Since salicylates have been reported to inhibit NF-kappa B activation by preventing the degradation of its inhibitor I kappa B, we studied a potential inhibition of this pathway by acetylsalicylate (aspirin) in human umbilical vein endothelial cells (HUVECs). Gel-shift analyses demonstrated dose-dependent inhibition of TNF-induced NF-kappa B mobilization by aspirin at concentrations ranging from 1 to 10 mmol/L. Induction of VCAM-1 and E-selectin surface expression by TNF was dose-dependently reduced by aspirin over the same range, while induction of intercellular adhesion molecule-1 (ICAM-1) was hardly affected. Aspirin appeared to prevent VCAM-1 transcription, since it dose-dependently inhibited induction of VCAM-1 mRNA by TNF. As a functional consequence, adhesion of U937 monocytes to TNF-stimulated HUVECs was markedly reduced by aspirin due to suppression of VCAM-1 and E-selectin upregulation. These effects of aspirin were not related to the inhibition of cyclooxygenase activity, since indomethacin was ineffective. Our data suggest that aspirin inhibits NF-kappa B mobilization, induction of VCAM-1 and E-selectin, and subsequent monocyte adhesion in endothelial cells stimulated by TNF, thereby providing an additional mechanism for therapeutic effects of aspirin.

F125. Prolonged E-selectin induction by monocytes potentiates the adhesion of flowing neutrophils to endothelium

Endothelin (ET)-1 is causatively involved in ischemia-reperfusion induced acute inflammatory reactions and microcirculatory disturbances in many organs. We investigated the role of endothelin-1 in the microcirculatory consequences of ischemia-reperfusion of the bladder using intravital fluorescence videomicroscopy.Male Sprague-Dawley rats were used in the experiments. The animals were randomly assigned to a sham operated group or to 1 of 2 ischemia-reperfusion groups that underwent 60 minutes of ischemia followed by 30 minutes of bladder reperfusion. In 1 ischemia-reperfusion group the animals were pretreated with BQ 610, a specific ET-A receptor blocker. The bladder was placed on an especially designed stage for intravital fluorescence videomicroscopy measurements. Venular red blood cell velocity, functional capillary density, venular and arteriolar diameter, venular and arteriolar macromolecular leakage, and leukocyte-endothelial cell interactions in postcapillary venules were determined using a computer assisted analyzing system.Functional capillary density, red blood cell velocity, venular and arteriolar diameter were significantly decreased and macromolecular leakage was significantly enhanced after bladder ischemia-reperfusion. The number of rolling and adherent leukocytes was significantly increased in postcapillary venules. Pretreatment with BQ 610 was effective for attenuating the effects of ischemia-reperfusion induced inflammation but could not completely prevent microcirculatory failure.Ischemia-reperfusion induced cystitis leads to significant impairment of the microcirculation and ET-1 is suggested to have an important role in this process. Pretreatment with an ET-A receptor antagonist reduces ischemia-reperfusion related microvascular disturbances in the bladder.

Induction of E-Selectin by Endotoxin is Direct and not Mediated Through Intracellular or Extracellular Release of Secondary Cytokines

Using a fixed cell ELISA system E-selectin expression and adhesion of U937 cells were measured in both endotoxin (LPS: serotype 0111:B4) tregted and untreated cultures of human umbilical vein endothelial cells (HUVEC). Basal levels of E-selectin were unde-tectable whereas significant induction of both E-selectin and U937 cell adhesion were observed after exposure of HUVEC to LPS for 6h. The effect of LPS was serum dependent and unaffected by coincubation with neutralising antibodies to either IL-1α, IL-1β or TNFα either alone or in combination, even though each antibody was capable of neutralising the effect of exogenously added cytokine. In addition IgG fractions of neutralising anti-cytokine antibodies were purified, concentrated and microinjected into the cytosol of adherent HUVEC prior to treatment with 1 μg/ml LPS for 6 hrs. Immunofluorescence staining showed that cells microinjected with antibodies to IL-1α, IL-1β and TNFα either alone or in combination were positive for LPS-stimulated E-selectin, d...