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Circulation Research. 1997;81:922-931

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(Circulation Research. 1997;81:922-931.)
© 1997 American Heart Association, Inc.

Articles

Molecular Mechanisms of Anoxia/Reoxygenation-Induced Neutrophil Adherence to Cultured Endothelial Cells

Hiroshi Ichikawa, Sonia Flores, Peter R. Kvietys, Robert E. Wolf, Toshikazu Yoshikawa, D. Neil Granger, , Tak Yee Aw

From the Departments of Physiology and Medicine (H.I., S.F., D.N.G., T.Y.A.) and the Center of Excellence in Arthritis and Rheumatism (R.E.W.), LSU Medical Center, Shreveport, La; the A.C. Burton Vascular Research Laboratory (P.R.K.), Victoria Hospital Research Institute, London, Ontario, Canada; and the First Department of Internal Medicine (T.Y.), Kyoto (Japan) Prefectural University of Medicine.

Correspondence to Dr Tak Yee Aw, Department of Physiology, LSU Medical Center, 1501 Kings Highway, Shreveport, LA 71130-3932. E-mail taw{at}lsumc.edu


*    Abstract
up arrowTop
 *Abstract
down arrowIntroduction
 down arrowMaterials and Methods
 down arrowResults
 down arrowDiscussion
 down arrowReferences
 
Abstract The objectives of this study were to (1) determine the time course of neutrophil adhesion to monolayers of human umbilical vein endothelial cells (HUVECs) that were exposed to 60 minutes of anoxia followed by 30 to 600 minutes of reoxygenation and (2) define the mechanisms responsible for both the early (minutes) and late (hours) hyperadhesivity of postanoxic HUVECs to human neutrophils. The results clearly demonstrate that anoxia/reoxygenation (A/R) leads to a biphasic increase in neutrophil adhesion to HUVECs, with peak responses occurring at 30 minutes (phase 1) and 240 minutes (phase 2) after reoxygenation. Oxypurinol and catalase inhibited phase-1 adhesion, suggesting a role for xanthine oxidase and H2O2. In comparison, platelet activating factor (PAF) contributed to both phases of neutrophil adhesion. Anti–intercellular adhesion molecule-1 (ICAM-1) and anti–P-selectin antibodies (monoclonal antibodies [mAbs]) attenuated phase-1 neutrophil adhesion, consistent with roles for constitutively expressed ICAM-1 and enhanced surface expression of preformed P-selectin. Phase-2 neutrophil adhesion was attenuated by an anti–E-selectin mAb, indicating a dominant role of this adhesion molecule in the late phase response. Pretreatment with actinomycin D and cycloheximide or with competing ds-oligonucleotides containing the nuclear factor-{kappa}B or activator protein-1 cognate DNA sequences significantly attenuated phase-2 response, suggesting a role for de novo macromolecule synthesis. Surface expression of ICAM-1, P-selectin, and E-selectin on HUVECs correlated with the phase-1 and -2 neutrophil adhesion responses. Collectively, these findings indicate that A/R elicits a two-phase neutrophil–endothelial cell adhesion response that involves transcription-independent and transcription-dependent surface expression of different endothelial cell adhesion molecules.


Key Words: nuclear transcription factor • endothelial cell adhesion molecule • leukocyte–endothelial cell adhesion • selectin • intercellular adhesion molecule-1


*    Introduction
up arrowTop
 up arrowAbstract
 *Introduction
down arrowMaterials and Methods
 down arrowResults
 down arrowDiscussion
 down arrowReferences
 
It is well recognized that the microvasculature is highly sensitive to I/R and that hyperadhesiveness of leukocytes to endothelial cells contributes to I/R-induced tissue injury.1 In an effort to define the mechanisms responsible for reperfusion-induced vascular injury, a number of in vitro models have been developed to simulate the responses of endothelial cells to I/R. Because of its simplicity, many investigators have used monolayers of cultured endothelial cells exposed to A/R as a model system to mimic I/R-induced vascular changes in vivo.2–4 These in vitro approaches yield responses that mimic changes in the microvasculature that often accompany I/R in vivo, ie, leukocyte–endothelial cell adhesion,5–8 increased endothelial monolayer permeability,9,10 and increased oxidant stress.11,12

Although the various in vitro models of I/R-induced NECA have largely yielded consistent results, there are some significant discrepancies between studies that appear to relate to differences in the magnitude and duration of the hypoxic insult as well as the times at which neutrophil adhesion was monitored after reoxygenation. For instance, different peak responses of leukocyte–endothelial cell adhesion have been reported, depending on the duration of anoxia and/or reoxygenation. We previously reported significant increases in neutrophil adherence to endothelial cells at 30 minutes of reoxygenation following 30 minutes of anoxia,1,2 which is consistent with an early and rapid inflammatory response to A/R. Other investigators have found that exposure of endothelial cell monolayers to hypoxia (PO2, 30 mm Hg) for 5 hours followed by reoxygenation for up to 24 hours exhibited not only a transient peak of neutrophil adhesion at 20 to 30 minutes but also a second adhesion response at 4 hours after reoxygenation.3 Discrepant findings also exist regarding the contribution of different adhesion molecules to A/R-induced NECA. For example, although E-selectin antibodies do not attenuate A/R-induced NECA at early periods (30 minutes), some investigators have demonstrated an inhibitory effect of these antibodies when neutrophil adhesion is examined at longer periods after reoxygenation.3 Collectively, these different findings, which are based on data obtained at various times after reoxygenation, suggest that A/R elicits time-dependent multiphase leukocyte–endothelial cell interactions that are likely to be mediated by different mechanisms.

At present, relatively little is known about the intracellular mediators and molecular determinants of the early and late phases of the NECA that is elicited by A/R. Current evidence based on studies with antioxidants implicates a role for oxidants such as H2O2 in A/R-mediated leukocyte hyperadhesiveness to endothelial cells.8,13 Several studies have used H2O2 as a standard oxidizing agent to evaluate neutrophil–endothelial cell interactions, endothelial monolayer permeability, expression of adhesion molecules, and activation of nuclear transcription factors14,15 in response to cellular oxidative stress. These studies suggest that H2O2 mimics many of the inflammatory and vascular responses elicited by I/R.5,8,13

The objectives of the present study were to determine the time course of the NECA responses elicited over several hours after reoxygenation of anoxic endothelial cell monolayers and to define the mechanisms responsible for both the early (minutes) and later (hours) NECA responses induced by A/R. Another objective was to determine whether the two-phase NECA response caused by A/R can be mimicked by physiologically relevant concentrations of H2O2.


*    Materials and Methods
up arrowTop
 up arrowAbstract
 up arrowIntroduction
 *Materials and Methods
down arrowResults
 down arrowDiscussion
 down arrowReferences
 
Materials
The following chemicals were obtained from Sigma Chemical Co: thymidine, Histopaque 1077, SOD, catalase, oxypurinol, and 3-aminobenzamide. Endothelial cell growth medium was purchased from Clonetics. Endothelial cell growth factor and Dil-Ac-LDL were from Biomedical Technologies, Inc. Fetal calf serum was obtained from Hyclone Laboratories Inc. Mouse anti-human factor VIII was from Calbiochem. The mAbs used in the present study were TS1/18 (murine IgG1{kappa} anti-human CD18),16 RR1/1 (murine IgG1 anti-human ICAM-1),17–19 PB1.3 (murine IgG1 anti-human P-selectin),20,21 and CL3 [murine IgG1 F(ab')2 anti-human E-selectin].22 RR1/1 was a gift from Dr Robert Rothlein at Boeringer-Ingelheim (Ridgefield, Colo). TS1/18, PB1.3, and CL3 were provided by Dr Donald Anderson from Pharmacia-UpJohn Laboratories (Kalamazoo, Mich). The proteasome inhibitor, MG132, was a gift from Dr Steve Brand from ProScript, Inc (Cambridge, Mass). The antioxidants, PDTC and H15, were gifts from Dr Russell Medford from Emory University (Atlanta, Ga). The PAF receptor antagonist, WEB 2086, was obtained from Boehringer-Ingelheim (Ingelheim, FRG). The sICAM-1 ELISA kit was purchased from Cayman Chemical Co.

Subjects
The procedures used to obtain human neutrophils and human umbilical cords were approved by the Institutional Review Board for Human Research at the Louisiana State University Medical Center. Each subject donating blood provided written consent and was compensated for participating in the study. Freshly discarded human umbilical cords were obtained from the delivery suite of Louisiana State University Medical Center.

Cell Culture and Treatment Protocols
HUVECs were harvested from umbilical cords by collagenase treatment as previously described.2 The cells were grown in endothelial cell growth medium supplemented with 10% heat-inactivated fetal calf serum, thymidine (2.4 mg/L), glutamine (230 mg/L), heparin sodium (10 IU/mL), antibiotics (100 IU/mL penicillin, 100 mg/mL streptomycin, and 0.125 mg amphotericin B), and endothelial cell growth factor (10 ng/mL). The cell cultures were incubated at 37°C in a humidified atmosphere with 5% CO2 and expanded by brief trypsinization with 0.25% trypsin in phosphate-buffered saline containing 0.02% EDTA. Primary passage HUVECs were seeded onto 11-mm 48-well tissue culture plates coated with gelatin (0.1%) and fibronectin (25 µg/mL). Culture medium was replaced every second day. Passage-1 cultures were used for the studies. Cells were identified as endothelial cells by their cobblestone appearance at confluence and positive labeling with acetylated LDL labeled with Dil-Ac-LDL or mouse anti-human factor VIII.

Neutrophils
Human neutrophilic PMNs were isolated from venous blood of healthy adults using standard dextran sedimentation and gradient separation on Histopaque 1077.2,4 This procedure yields a PMN population that is 95% to 98% viable (by trypan blue exclusion) and 98% pure (by acetic acid–crystal violet staining).

A/R Protocol
The in vitro model of A/R used in the present study is similar to that previously reported.2 Briefly, confluent HUVEC monolayers were exposed to anoxia by incubating in a Plexiglas chamber that was continuously purged (1 L/min) with an anoxic gas mixture (93% N2/5% CO2/2% H2). To ensure an oxygen-free environment, the gas mixture was passed through a catalytic deoxygenizer (Fisher Chemical) before entry into the chamber. Chamber PO2 was monitored during the entire experiment using an oxygen electrode (model OM-1, Microelectrodes). Temperature in the chamber was maintained at 37°C by a heating pad. After a 60-minute period of anoxia, reoxygenation was initiated by exposing the endothelial cells to room air for periods ranging between 15 and 600 minutes. Control endothelial cells were exposed to normoxia (21% O2/5% CO2/74% N2) for the duration of the experiment (normoxic controls).

Adhesion Assays
Isolated neutrophils were suspended in PBS (2x107 cells/mL) and radiolabeled with 30 µCi Na51CrO4/mL neutrophil suspension at 37°C for 1 hour. The cells were washed twice with 4°C PBS, spun at 250g for 8 minutes to remove unincorporated radioactivity, and resuspended in plasma-free HBSS. Labeled neutrophils were added to HUVEC monolayers at a neutrophil-to-HUVEC ratio of 10:1. After coincubation (30 minutes), the percentage of added neutrophils that adhered to the HUVEC monolayers was quantified.2

To assess whether superoxide, H2O2, xanthine oxidase, or PAF plays a role in the A/R-induced hyperadhesivity, we treated monolayers with SOD (1000 U/mL), catalase (1000 U/mL), oxypurinol (xanthine oxidase inhibitor, 100 µmol/L), or a PAF receptor antagonist (WEB 2086, 10 µmol/L).18 SOD, catalase, or oxypurinol was added to HUVECs before exposure to A/R, whereas the PAF receptor antagonist was added to the A/R-conditioned HUVECs 30 minutes before the adhesion assay. The role of adhesion molecules was tested using the respective mAbs for CD18 (TS1/18), P-selectin (PB1.3), ICAM-1 (RR1/1), and E-selectin (CL3). All mAbs were added to the A/R-conditioned HUVECs 30 minutes before the adhesion assay. To determine whether transcription and/or translation is involved in the A/R-dependent increase in PMN adherence, HUVECs were exposed to either ActD (2 µg/mL) or CHX (1 µg/mL) before A/R. The contribution of the nuclear transcription factors, AP-1 and NF{kappa}B to neutrophil adherence in A/R-conditioned endothelial cells was assessed using monolayers treated with 3-aminobenzamide (AP-1 inhibitor, 1 mmol/L)23,24 or MG132 (proteasome inhibitor, 40 µmol/L).25 Both inhibitors were added to HUVEC monolayers before A/R. To further define the role of NF{kappa}B and AP-1 in A/R-induced PMN adherence, HUVEC monolayers were exposed to double-stranded phosphorothioate oligonucleotides as decoys for the respective transcription factors. The oligonucleotides were purified by denaturing polyacrylamide gel electrophoresis26 according to the manufacturer's protocol (Eppendorf). The sequence of the sense strand of the {kappa}B oligonucleotide ({kappa}B-PT) was 5'-AGGGACTTTCCGCTGGG GACTTTCC-3',27 and that of the AP-1 oligonucleotide was 5'-CGCTTGATGAGTCAGCCGGAA-3'28; these sequences were annealed to their respective antisense complementary strands. Parallel experiments were performed using the nonprotein binding {kappa}B-PT sequence, 5'-AAAAGTCCCTTGCT GAAAGTCCCTT-3', or the nonprotein binding AP-1–PT sequence, 5'-CGCTTGACAGACTGGCCGGAA-3', annealed to their respective complements. HUVEC monolayers were pretreated with 20 µmol/L ds-oligonucleotides for 3 hours before anoxia. To determine whether activation of NF{kappa}B was mediated by oxidants, we used the antioxidant PDTC and its analogue, H15. Both antioxidants were added to HUVEC monolayers 60 minutes before anoxia.

In a separate series of experiments, HUVEC monolayers were treated with different concentrations of H2O2 (50, 100, 500, and 1000 µmol/L) under normoxic conditions for 15 to 600 minutes. 51Cr-labeled neutrophils were added to the endothelial cell monolayers after oxidant exposure, and neutrophil adherence was determined 30 minutes later.

sICAM-1 Assay
To determine the levels of sICAM-1, media from A/R-conditioned HUVEC monolayers at phase 1 and phase 2 were obtained, and the adhesion molecule was quantified using a commercially available ELISA kit as previously described.29,30

ELISA of ECAM Expression
HUVECs were plated on 48-well tissue culture dishes. Primary antibodies for either ICAM-1, P-selectin, or E-selectin in HBSS/PBS with 5% FBS were added to each well and incubated for 30 minutes at 37°C. The cells were washed and incubated with the secondary antibody, horseradish peroxide–conjugated goat anti-mouse IgG (IgG1+IgG2a+IgG2b+IgG3, Southern Biotechnology Associates, Inc) diluted 1:500 in HBSS/PBS with 5% FBS for 30 minutes. The wells were then washed, and the binding of antibody was detected by the addition of 100 µL of 0.1 mg/mL 3,3',5,5'-tetramethylbenzidine (Sigma Chemical Co) with 0.003% H2O2. The reaction was stopped by the addition of 25 µL of 8N sulfuric acid. The samples were transferred to 96-well plates, and color development was read on a spectrometer (Titertek Multiskan MCC/340, ICN) at an optical density of 450 nm after subtracting the background values in cells stained only with the second-step antibody. All data points were performed at least in duplicate.

Preparation of Nuclear Extracts
HUVECs were plated on P-100 tissue culture dishes. Confluent HUVECs were exposed to anoxia for 60 minutes and then reoxygenated for 240 minutes. Nuclear extracts were prepared by a modification of the method of Dignam et al.31 Briefly, after washing with PBS, cells were centrifuged, and the cell pellet was suspended in 500 µL of hypotonic buffer (10 mmol/L HEPES, pH 7.9, 1.5 mmol/L MgCl2, 10 mmol/L KCl, and 0.5 mmol/L DTT). After recentrifugation, the cells were resuspended in 1 mL of hypotonic buffer containing 0.1% IGEPAL (Sigma Chemical Co) by gentle homogenization to disrupt the cell membrane. After standing for 5 minutes at 4°C, the homogenate was centrifuged, and the nuclear pellet was resuspended in 100 µL of low salt buffer (20 mmol/L HEPES, pH 7.9, 0.2 mmol/L EDTA, 25% [vol/vol] glycerol, 1.5 mmol/L MgCl2, 20 mmol/L KCl, and 0.5 mmol/L DTT). Thereafter, 100 µL of hypertonic buffer (10 mmol/L HEPES, pH 7.9, 0.1 mmol/L EDTA, 50 mmol/L KCl, 300 mmol/L NaCl, 10% [vol/vol] glycerol, and 0.5 mmol/L DTT) was added in a dropwise manner. This suspension was incubated for 30 minutes at 4°C, followed by centrifugation at 17 000g for 5 minutes. The resulting supernatant (nuclear extract) was stored at -70°C. Protein concentrations were determined by the Bradford32 method. To minimize proteolysis, all buffers contained 0.2 mmol/L phenylmethylsulfonyl fluoride.

EMSAs
A [32P]-radiolabeled ds-DNA probe for NF{kappa}B and AP-1 was generated from [{gamma}-32P]ATP and ds-oligonucleotides in a kinase reaction. The {kappa}B and AP-1 ds-oligonucleotides used for the EMSAs were the same as those used as inhibitors in the adhesion molecule expression assay. The oligonucleotides (3.5 pmol) were 5' end–labeled with T4 polynucleotide kinase and [{gamma}-32P]ATP (10 µCi), according to manufacturer's specifications (Promega) at 37°C for 30 minutes, in a buffer containing 70 mmol/L Tris-HCl (pH 7.6), 10 mmol/L MgCl2, and 5 mmol/L DTT. The reaction was stopped by the addition of EDTA to 50 mmol/L, and the volume was adjusted to 100 µL with TE buffer (10 mmol/L Tris-HCl, pH 8.0, and 1 mmol/L EDTA). A typical binding reaction consisted of 10 µg of HUVEC nuclear proteins, 1x105 cpm of the synthetic 32P-labeled oligonucleotides, 4% glycerol, 1 mmol/L MgCl2, 0.5 mmol/L EDTA, 0.5 mmol/L DTT, 50 mmol/L NaCl, 10 mmol/L Tris-HCl (pH 7.5), and 0.5 mg/mL poly(dI-dC) with or without 50-fold molar excess of unlabeled competitor in a total volume of 20 µL. After incubation at room temperature for 30 minutes, the complexes were resolved on a 4% nondenaturing polyacrylamide (monomer-to-bis ratio of 40:1) gels at 35 mA for 3 hours at room temperature in 0.5x Tris–boric acid EDTA buffer.33 The gels were dried and autoradiographed. Band densities were determined by computer-assisted image analysis of autoradiograms using an NIH Image 1.57 software program. Intensity of each band was corrected for the respective background. For supershift assays, antibodies against p50 or p65 (Santa Crutz Biotechnology) were included in the binding reactions.

Statistical Analysis
All values are expressed as mean±SE. Data were analyzed using a one-way ANOVA with Bonferroni corrections for multiple comparisons.


*    Results
up arrowTop
 up arrowAbstract
 up arrowIntroduction
 up arrowMaterials and Methods
 *Results
down arrowDiscussion
 down arrowReferences
 
Fig 1Down illustrates the time course of A/R-induced neutrophil adherence to HUVEC monolayers. The data show that 60 minutes of anoxia followed by reoxygenation resulted in enhanced adhesivity of neutrophils to HUVECs, with peak adhesion responses at 30 minutes (phase 1) and 240 minutes (phase 2), indicating that A/R elicits early- and late-phase inflammatory responses. The A/R-induced hyperadhesivity of neutrophils to HUVECs in phase 1 is similar to results previously published from our laboratory.2 Light microscopy of HUVEC monolayers with or without neutrophils shows that significant adhesion of neutrophils to endothelial cells occurred at 30 and 240 minutes of reoxygenation after anoxia but not at the corresponding times after normoxia (data not shown). Moreover, exposure of HUVEC monolayers to 60 minutes of anoxia followed by 30 minutes and 240 minutes of reoxygenation with or without neutrophils did not disrupt the monolayers, and neutrophils were not binding to the matrix. The postanoxic HUVEC monolayers were similar in appearance to the those exposed to normoxia for the same experimental period. Furthermore, we observed no transmigration of adherent neutrophils through the endothelial cell monolayers under all experimental conditions. Taken together, these results suggest that the phase-1 and phase-2 neutrophil adhesions to endothelial cells induced by A/R are specific.



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  		Figure 1. Time-course of neutrophil adherence to HUVECs after A/R. HUVEC monolayers were exposed to 60 minutes of anoxia (or normoxia) and then reoxygenated. 51Cr-labeled neutrophils were added to HUVEC monolayers on reoxygenation, and neutrophil adherence was determined 30 minutes later. Each value represents mean±SE of four to six experiments performed in triplicate.

Fig 2Down shows the effect of catalase, SOD, oxypurinol, and a PAF receptor antagonist (WEB 2086) on A/R-induced NECA during phase 1 and phase 2. The increased adherence to A/R-conditioned HUVECs was significantly diminished by catalase and oxypurinol at phase 1, but not phase 2. However, the PAF receptor antagonist significantly inhibited A/R-induced leukocyte adherence at both phases. SOD was without effects at both phases.



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  		Figure 2. Effect of catalase (CAT), SOD, oxypurinol (OXY), and PAF receptor antagonist (WEB 2086) on A/R-induced neutrophil adhesion to HUVECs. Responses are shown for neutrophil adhesion at 30 minutes (phase 1) and 240 minutes (phase 2) after reoxygenation. Each value represents mean±SE of four to six experiments performed in triplicate. *P<.05 compared with normoxic controls; #P<.05 and ##P<.01 compared with untreated controls (A/R only).

Fig 3Down summarizes the effects of mAbs directed against ECAMs on neutrophil adherence to endothelial monolayers subjected to A/R at phase 1 and phase 2. The increase in neutrophil adherence to HUVECs was significantly reduced, in both phases, by anti–P-selectin (PB 1.3). Anti–ICAM-1 (RR1/1) also significantly reduced neutrophil adherence to A/R-conditioned HUVECs in phase 1. Interestingly, the standard saturating anti–ICAM-1 dose of 20 µg/mL, which effectively blocks the phase-1 adhesion response, had no effect on neutrophil adhesion at phase 2. The anti–E-selectin–specific antibody (CL3) significantly inhibited leukocyte adhesion to HUVECs in phase 2, but had no effect in phase 1. When anti–P-selectin and –E-selectin were used in combination, the increased NECA was further attenuated compared with either mAb alone (data not shown). The CD18-specific mAb largely abolished the leukocyte adhesion to HUVECs exposed to A/R in both phases (data not shown).



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  		Figure 3. Effect of mAbs to P-selectin (PB1.3, 20 µg/mL), ICAM-1 (RR1/1, 20 µg/mL), and E-selectin (CL3, 20 µg/mL) on neutrophil adherence to HUVECs in phase 1 and phase 2 of reoxygenation. Responses are shown for neutrophil adhesion at 30 minutes (phase 1) and 240 minutes (phase 2) after reoxygenation. Each value represents mean±SE of four to six experiments performed in triplicate. *P<.05 compared with normoxic controls; #P<.05 and ##P<.01 compared with untreated controls (results without antibody).

To determine whether the inability of the standard saturating dose of anti–ICAM-1 (20 µg/mL) to attenuate leukocyte–endothelial cell adhesion in phase 2 was due to a higher membranous ICAM-1 concentration, we exposed the monolayers to progressively increasing concentrations of the ICAM-1 mAb. The results in Fig 4Down show that the enhanced neutrophil adherence to A/R-conditioned HUVECs in phase 2 was dose-dependently decreased by the anti–ICAM-1 antibody. A significant reduction in the phase-2 adhesion response was noted at twice the standard saturating mAb dose (40 µg/mL). In addition, we quantified sICAM-1 levels in the incubation medium of A/R-conditioned HUVECs in phase 1 and 2 (Fig 5Down). The results show that sICAM-1 levels in the incubation medium of A/R-conditioned HUVEC monolayers were significantly higher in phase 2 compared with control levels. sICAM-1 levels were unchanged in phase 1.



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  		Figure 4. Effect of increasing concentration of a mAb to ICAM-1 (RR1/1) on neutrophil adherence to HUVECs at 240 minutes of reoxygenation (phase 2). Each value represents mean±SE of four to six experiments performed in triplicate. *P<.05 and **P<.01 compared with nontreated controls (A/R only).



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  		Figure 5. Change in sICAM-1 levels in incubation medium of HUVECs exposed to A/R. Responses are shown for sICAM-1 at 30 minutes (phase 1) and 240 minutes (phase 2) after reoxygenation. Each value represents mean±SE of nine experiments performed in duplicate. *P<.05 compared with normoxic controls.

The possibility that H2O2 may elicit a biphasic NECA response similar to A/R was examined in HUVEC monolayers exposed to different concentrations of the oxidant. In these experiments, neutrophil adhesion was monitored at 30 minutes (phase 1) and 240 minutes (phase 2) after H2O2 exposure. The results show that H2O2 dose-dependently increased leukocyte adhesion at phase 1 and 2, with lower concentrations exerting a more profound effect on phase-2 adhesion (Fig 6Down). The peroxide-induced neutrophil adhesion to endothelial cells was completely abolished in phase 1 and significantly attenuated in phase 2 by a PAF receptor antagonist (Fig 7Down), indicating that PAF production by endothelial cells contributes to both phases of the oxidant-mediated adhesion response. The anti–P-selectin mAb significantly reduced the hyperadhesiveness of peroxide-treated HUVECs to neutrophils in the early phase. However, in the late phase, the anti–P-selectin mAb did not inhibit the increase of adhesion levels induced by H2O2 (data not shown).



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  		Figure 6. Effect of increasing concentration of H2O2 on neutrophil adherence to naive HUVECs. HUVEC monolayers were exposed to H2O2 (0.1 to 1 mmol/L) for 30 minutes (phase 1) or 240 minutes (phase 2) under normoxic conditions. Each value represents mean±SE of four to six experiments performed in triplicate. *P<.05, **P<.01, and #P<.05 compared with nontreated controls.



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  		Figure 7. Effect of catalase (CAT) and a PAF receptor antagonist (WEB 2086) on H2O2 (1 mmol/L)–induced neutrophil adherence to normoxic HUVECs at 30 minutes (phase 1) and 240 minutes (phase 2). Each value represents mean±SE of four to six experiments performed in triplicate. *P<.05 compared with normoxic controls; #P<.05 and ##P<.01 compared with untreated controls (H2O2 only).

The finding of an enhanced inflammatory response 4 hours after reoxygenation, coupled to the evidence implicating E-selectin (which is not constitutively expressed on HUVEC), suggests that A/R elicits a transcription-dependent upregulation of ECAMs. Previous studies have invoked a role for NF{kappa}B and/or AP-1 in cytokine- and H2O2-mediated inflammatory reactions.14,15,24,25 To assess the contribution of these nuclear transcription factors to the A/R-induced enhancement of neutrophil adhesion, HUVEC monolayers were treated with inhibitors of macromolecule synthesis (CHX, 1 µg/mL, or ActD, 2 µg/mL), a proteasome inhibitor (MG132, 40 µmol/L), or an inhibitor of AP-1 (3-aminobenzamide, 1 mmol/L). In other experiments, HUVECs were treated with ds-phosphorothioate oligonucleotides (20 µmol/L each) as decoys for {kappa}B and AP-1. The results in Table 1Down show that inhibition of protein synthesis significantly attenuated the A/R-induced neutrophil adherence in phase 2, but not in phase 1. Moreover, blockade of NF{kappa}B and AP-1 activation significantly decreased the adhesion response in phase 2. Interestingly, the inhibitory effects of these agents on neutrophil adhesion to HUVECs in phase 2 were not complete. When anti–ICAM-1 antibody (60 µg/mL) was added to cells treated with ActD, MG132, aminobenzamide, or ds-phosphorothioate oligonucleotides, a further attenuation of the increased NECA response in phase 2 to baseline values was observed. Finally, the increased neutrophil adhesion response induced by A/R in phase 2 was also attenuated by the antioxidants, PDTC and H15 (100 µmol/L each).


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  		Table 1. Effect of Inhibitors of Macromolecule Synthesis, NF{kappa}B, and AP-1 on A/R-Induced NECA

To document that the phase-2 transcription-dependent adhesion response is associated with NF{kappa}B activation, we performed EMSAs on nuclear extracts prepared from A/R-conditioned HUVECs after 240 minutes of reoxygenation. The results are shown in Fig 8Down. Two specific nucleoprotein adducts were evident on the gel shift (designated as upper and lower bands, Fig 8ADown). Supershift analyses (see Fig 9Down) on these retarded products suggest that the faster migrating band represents the p50 homodimer and that the slower migrating band is mostly likely the p50-p65 heterodimer. Quantification of the nucleoprotein adducts is shown in Fig 8BDown. The results show that reoxygenation for 240 minutes increased the amount of the slower migrating adduct (Fig 8ADown and 8BDown). Pretreatment with the {kappa}B decoy almost completely abolished binding of the slower moving adduct to the radiolabeled oligonucleotide (Fig 8ADown, lane 5, and Fig 8BDown), suggesting that the inhibition by this decoy is specific. Nonbinding decoys had no effect on NF{kappa}B binding (data not shown). The proteasome inhibitor, on the other hand, resulted in a significant decrease in the faster migrating adduct but an enhancement of binding of the slower migrating adduct (Fig 8Down, lane 4, and Fig 8BDown). This observation suggests that MG132 may inhibit NF{kappa}B activation without affecting nuclear translocation, a suggestion that is consistent with recent findings by Cobb et al,34 who showed that the proteasome inhibitor, nor-LEU, inhibits NF{kappa}B activation and blocks interleukin 1ß–induced vascular cell adhesion molecule-1 and ICAM-1 gene expression in HUVECs without preventing nuclear translocation of NF{kappa}B. When antibodies to p50 or p65 were added to the binding reaction before addition of the labeled oligonucleotide, we observed a supershift and a decrease in the intensity of the faster or slower migrating adducts, respectively (Fig 9Down, lanes 2 and 3). In these studies, we found that the binding of the p65 antibody was considerably weaker than binding of the p50 antibody. In order to visualize the supershifted products, the gel was overloaded and overexposed, which also revealed the presence of some minor adducts. These, however, were nonspecific, since we were unable to eliminate them when molar excess of unlabeled oligonucleotide was used as a nonspecific competitor (data not shown).



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  		Figure 8. EMSAs on nuclear extracts from A/R-conditioned endothelial cells after 240 minutes reoxygenation pretreated with or without ds-oligonucleotide (20 µmol/L) or the proteasome inhibitor (MG132, 40 µmol/L). The NF{kappa}B-specific adducts are indicated by bold arrows and designated as upper and lower bands. Panel A shows a representative gel shift pattern from one of six experiments. Lanes 1 to 5 are nuclear extracts of cells from normoxia (lane 1), A/R (lane 2), A/R with addition of 50x unlabeled competitor in binding reaction (lane 3), A/R treated with proteasome inhibitor (lane 4), and A/R treated with ds-oligonucleotide (lane 5). Each lane was loaded with 4.5 µg nucleoprotein. Panel B shows the quantification of the NF{kappa}B adducts using computer-assisted image analyses of the autoradiogram in panel A. The intensity of each adduct was corrected for the respective background of the autoradiogram, and the result is expressed as units of NF{kappa}B activity relative to normoxia (NF{kappa}B activity equals 1).



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  		Figure 9. Electrophoretic mobility supershift assay on nuclear extracts from A/R-conditioned endothelial cells after 240 minutes of reoxygenation. The figure shows a representative supershift autoradiogram. The NF{kappa}B-specific adducts are indicated by bold arrows and designated as upper and lower bands. Lanes 1 to 3 are nuclear extracts of cells from A/R (lane 1), A/R with addition of p50 antibody in binding reaction (lane 2), and A/R with addition of p65 antibody in binding reaction (lane 3). Each lane was loaded with 15 µg nucleoprotein.

Fig 10aDown shows the time course of surface expression of P-selectin in HUVECs exposed to A/R. The data show that 60 minutes of anoxia followed by 30 minutes to 10 hours of reoxygenation resulted in increased expression of P-selectin, with peak responses at 30 minutes and between 4 and 6 hours after reoxygenation. This biphasic response is similar to the NECA response induced by A/R (see Fig 1Up). Fig 10bDown shows the kinetics of E-selectin expression in HUVECs induced by A/R. E-Selectin was not expressed in phase 1 but increased significantly in phase 2, with peak expression at 4 hours. Thereafter, E-selectin expression gradually decreased and returned to baseline values by 10 hours after reoxygenation, paralleling the kinetics of the phase-2 adhesion response induced by A/R. Fig 10cDown shows the time course of the surface expression of ICAM-1 in HUVECs exposed to A/R. Unlike P-selectin or E-selectin, surface expression of ICAM-1 was high in phase 1 (constitutive expression), increased in phase 2, and remained elevated for 10 hours despite decreased neutrophil adhesion (see Fig 1Up).



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  		Figure 10. Time course of ECAMs (P-selectin [a], E-selectin [b], and ICAM-1 [c]) on HUVECs exposed to A/R. HUVEC monolayers were exposed to 60 minutes of anoxia and then reoxygenated. Each value represents mean±SE of four to six experiments performed in duplicate. OD450 indicates optical density at 450 nm. *P<.05 and **P<.01 compared with normoxic controls.

To evaluate whether the A/R-induced induction of ECAM (P-selectin, ICAM-1, and E-selectin) expression in phase 2 is transcription dependent, we measured the surface expression of the different ECAMs in HUVECs treated with CHX (1 µg/mL) or ActD (2 µg/mL). The contributions of different transcription factors were examined using inhibitors of NF{kappa}B (MG132, 40 µmol/L) and AP-1 (3-aminobenzamide, 1 mmol/L), as well as their respective binding ds-oligonucleotides (20 µmol/L). The antioxidants PDTC and H15 were also examined. The results are summarized in Table 2Down. Upregulation of E-selectin induced by A/R was essentially abolished by CHX or ActD. Moreover, treatment with the proteasome inhibitor (MG132), AP-1 inhibitor (3-aminobenzamide), or antioxidants was effective in reducing the E-selectin expression induced by A/R. Interestingly, inhibition of protein synthesis and transcription resulted in only a 10% to 20% reduction in the A/R-induced expression of P-selectin or ICAM-1.


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  		Table 2. Effect of Inhibitors of macromolecule Synthesis, NF{kappa}B, and AP-1 on A/R-Induced Surface Expression of ECAMs


*    Discussion
up arrowTop
 up arrowAbstract
 up arrowIntroduction
 up arrowMaterials and Methods
 up arrowResults
 *Discussion
down arrowReferences
 
It has long been recognized that the microvasculature is exquisitely sensitive to the deleterious effects of ischemia and reperfusion.1 In recent years, a variety of bioactive compounds and effector cells have been invoked as mediators of reperfusion injury, including reactive oxygen metabolites, PAF, nitric oxide, platelets, mast cells, and granulocytes.10,35–39 In addition, a number of in vitro models have been developed to simulate the in vivo responses of vascular endothelial cells to I/R and to help define the mechanisms responsible for I/R-induced vascular injury. Previous studies using these in vitro models have successfully simulated some of the major microvascular responses that are elicited in vivo by I/R, ie, enhanced expression of ECAMs, neutrophil adhesion, and an increased endothelial monolayer permeability. The results of the present study extend these previous reports by demonstrating that exposure of HUVEC monolayers to A/R leads to a biphasic pattern of NECA, with peak responses observed at 30 minutes (phase 1) and 240 minutes (phase 2) after reoxygenation. Although the magnitude of the neutrophil adhesion responses in the two phases is similar, it appears that the contribution of ECAMs and chemical mediators to the adhesion response differs between the two phases.

The results of the present study implicate a role for xanthine oxidase, H2O2, and PAF in the early (minutes) neutrophil adhesion response (phase 1) elicited by A/R. These findings are consistent with earlier observations reported from our laboratory.2 A role for PAF in this response is supported by the inhibitory action of the receptor antagonist WEB 2086. We found that although PAF and leukotriene B4 are each capable of enhancing the neutrophil adhesion response to HUVECs at a concentration of 0.1 µmol/L, the PAF receptor antagonist (WEB 2086, 10 µmol/L) abolished the PAF-induced adhesion but did not affect the leukotriene B4–induced adhesion response (data not shown). These observations suggest that endothelial cells produce PAF or PAF-like substances during A/R and that WEB 2086 is a specific antagonist to PAF receptors. The observation that catalase is as effective as the PAF antagonist in blunting the phase-1 adhesion response suggests that endothelial cell–derived H2O2 elicits the production of PAF.40 Yoshida et al2 have reported that both WEB 2086 and catalase can ameliorate neutrophil adhesion to naive monolayers exposed to media obtained from A/R-conditioned endothelial cells. Hence, our findings, together with published observations, are consistent with the hypothesis that A/R enhances the production and liberation of H2O2 (in part due to xanthine oxidase) and PAF during the early stages of reoxygenation (phase 1).

In contrast to the early (phase 1) adhesion response to A/R, the enhanced neutrophil–endothelial cell interactions observed 4 hours after reoxygenation (phase 2) do not appear to involve either xanthine oxidase or H2O2. Nonetheless, PAF remains as a contributor to the adhesion response in phase 2 despite the absence of peroxide generation. These findings may be explained by different sources of H2O2 generation in phase 1 versus phase 2. One possibility is that the major source(s) of H2O2 in phase 1 is cell membrane–bound xanthine oxidase on endothelial cells41 and/or neutrophilic NADPH oxidase, whereas an intracellular source (eg, mitochondria) of H2O2 production by endothelial cells is responsible for phase 2. In such a scenario, exogenous catalase would have access to detoxify the H2O2 accumulating immediately outside endothelial cells in phase 1, but the enzyme would not have access to the intracellular H2O2 generated in phase 2. Since PAF appears to be formed in both phases of A/R-induced adhesion, this would suggest either that PAF formation in phase 2 is independent of H2O2 generation or that extracellular and intracellular sources of H2O2 generation are equally effective in promoting the formation of PAF in HUVECs.

An interesting and potentially important observation of the present study is the difference in the relative contribution of various ECAMs to the enhanced neutrophil adhesion elicited in phase 1 and phase 2 of A/R. In both phases, it appears that activation of ß2 integrins on neutrophils (presumably by PAF) contributes to the enhanced adhesion. In the present study, the CD18-specific mAb largely abolished leukocyte adhesion to HUVECs exposed to A/R in both phases. However, the relative contributions of ECAMs appear to differ between the two phases. In phase 1, P-selectin and ICAM-1, but not E-selectin, contribute to the neutrophil adhesion response. Our data also showed that P-selectin surface expression kinetics are biphasic, similar to the kinetics of the neutrophil adhesion response. E-Selectin was not expressed in phase 1 but increased significantly in phase 2, also paralleling the kinetics of the adhesion response. Surface expression of ICAM-1 was high in phase 1, increased in phase 2, and remained elevated for 10 hours despite decreased neutrophil adhesion. The pattern of participation of adhesion molecules in phase 1 could be explained by constitutively expressed ICAM-1,42 by a rapid mobilization of the preformed pool of P-selectin in endothelial cells,43–45 and by the upregulation of ß2 integrins by PAF or PAF-like substances that are liberated by endothelial cells.46,47 In phase 2, however, E-selectin makes a contribution, in addition to P-selectin and ICAM-1, to the A/R-induced neutrophil adhesion. The phase-2 E-selectin–dependent response pattern appears to be consistent with a transcription-dependent upregulation of E-selectin and possibly ICAM-1 and P-selectin.24,48,49 Several lines of evidence support the involvement of transcription-dependent upregulation of ECAMs.1 Our data show that reagents that interfere with the activation of either NF{kappa}B or AP-1 also inhibited phase-2 neutrophil adhesion and the increased surface expression of ECAMs, especially E-selectin.2 Treatment of HUVECs with inhibitors of transcription and translation prevented A/R-induced phase-2 expression of ECAMs and neutrophil adhesion to HUVEC monolayers.3 Results obtained with EMSAs on nuclear extracts from A/R-conditioned cells after 240 minutes of reoxygenation show that A/R causes specific upregulation and activation of NF{kappa}B.

Previous reports have implicated a role for NF{kappa}B and AP-1 in the transcriptional regulation of different ECAMs after exposure of HUVECs to cytokines or oxidants.24,48,49 The AP-1 inhibitor 3-aminobenzamide has been shown to be effective in attenuating H2O2-induced ICAM-1 upregulation,23 whereas MG132, an inhibitor of NF{kappa}B activation, has been shown to reduce the increased E-selectin expression elicited by different cytokines.25 In the present study, we have demonstrated that both MG132 and 3-aminobenzamide significantly attenuate the A/R-induced neutrophil adhesion and E-selectin expression in phase 2. Furthermore, we have shown that ds-phosphorothioate oligonucleotides, which have multiple copies of the DNA binding site for NF{kappa}B or AP-1, prevent the binding of these nuclear transcription factors to endogenous {kappa}B or AP-1 enhancer-promotor elements, thereby specifically inhibiting NF{kappa}B–or AP-1–dependent transcription. Concomitantly, these binding oligonucleotides also significantly inhibited the A/R-induced phase-2 E-selectin expression and neutrophil adhesion. Furthermore, the present data with EMSA have confirmed the suggestion that A/R results in NF{kappa}B activation and induction. Taken together, these observations provide the first evidence that implicates both nuclear transcription factors in the transcription-dependent upregulation of adhesion molecules and enhanced neutrophil-endothelial adhesion elicited by A/R.

A notable finding in the present study is that the saturating dose of ICAM-1 antibody that effectively blocked neutrophil adhesion to HUVECs in phase 1 was incapable of inhibiting the elevated adhesion response in phase 2. However, we noted that when a higher concentration of the same antibody was used, the phase-2 adhesion response was attenuated. The latter observation suggests that the pool of ICAM-1 that is available for reaction with the antibody was much higher in phase 2. Indeed, this possibility is supported by our finding that the sICAM-1 level on the surface of the HUVEC monolayers was elevated during phase 2, but not during phase 1. This observation suggests that the HUVEC monolayers shed membranous ICAM-1 into the extracellular fluid in the late phase of reoxygenation. The significance of this is, at present, unclear.

Exposure of endothelial cell monolayers to H2O2 is frequently used as a model system to investigate endothelial cell responses to acute oxidant stress, such as A/R. The results of the present study support previous reports that H2O2 promotes leukocyte adhesion to endothelial cells.13 However, a novel observation in the present study is that exposure of HUVECs to H2O2 concentrations as low as 100 µmol/L elicits a response that is similar to the phase-2 response induced by A/R. Studies with the PAF antagonist also support the view that H2O2 is a reasonable model for A/R, since WEB 2086, which was effective in attenuating A/R-induced neutrophil adhesion in phases 1 and 2, was also equally effective in decreasing phase-1 and -2 adhesion responses in the peroxide model. Hence, these findings indicate that extracellular H2O2 effectively mimics the neutrophil adhesion responses that are elicited by A/R.


*    Selected Abbreviations and Acronyms
 
ActD = actinomycin D
AP-1 = activator protein 1
A/R = anoxia/reoxygenation
CHX = cycloheximide
Dil-Ac-LDL = 1,11-dioctadecyl-13,3,31,31,3-tetramethylindocarbocyanine perchlorate
DTT = dithiothreitol
ECAM = endothelial cell adhesion molecule
EMSA = electrophoretic mobility gel-shift assay
HUVEC = human umbilical vein endothelial cell
ICAM-1 = intercellular adhesion molecule-1
I/R = ischemia/reperfusion
mAb = monoclonal antibody
NECA = neutrophil–endothelial cell adhesion
NF{kappa}B = nuclear factor kappa-B
PAF = platelet-activating factor
PDTC = pyrrolidine dithiocarbamate
PMN = polymorphonuclear leukocyte
sICAM-1 = soluble ICAM-1
SOD = superoxide dismutase


*    Acknowledgments
 
This study was supported by grants from the National Institutes of Health (P01 DK-43785, HL-48855, and DK-44510). We thank Loren P. Walsh for his assistance with the EMSA and supershift analyses.

Received March 13, 1997; accepted August 28, 1997.


*    References
up arrowTop
 up arrowAbstract
 up arrowIntroduction
 up arrowMaterials and Methods
 up arrowResults
 up arrowDiscussion
 *References
 

  1. Granger DN, Kvietys PR. Leukocyte-endothelial cell adhesion induced by ischemia and reperfusion. Can J Physiol Pharmacol. 1993;71:67–75.[Medline] [Order article via Infotrieve]
  2. Yoshida N, Granger DN, Anderson DC, Rothlein R, Lane C, Kvietys PR. Anoxia/reoxygenation-induced neutrophil adherence to cultured endothelial cells. Am J Physiol. 1992;262:H1891–H1898.[Abstract/Free Full Text]
  3. Paully O, Morliere L, Gris J, Bonne C, Modat G. Hypoxia/reoxygenation stimulates endothelium to promote neutrophil adhesion. Free Radic Biol Med. 1992;13:21–30.[Medline] [Order article via Infotrieve]
  4. Inauen W, Granger DN, Meininger CJ, Schelling ME, Granger HJ, Kvietys PR. An in vitro model of ischemia-reperfusion-induced microvascular injury. Am J Physiol. 1990;259:G134–G139.[Abstract/Free Full Text]
  5. Granger DN, Benoit JN, Suzuki M, Grisham MB. Leukocyte adherence to venular endothelium during ischemia-reperfusion. Am J Physiol. 1989;257:G683–G688.[Abstract/Free Full Text]
  6. Kubes P, Suzuki M, Granger DN. Modulation of PAF-induced leukocyte adherence and increased microvascular permeability. Am J Physiol. 1990;259:G859–G864.[Abstract/Free Full Text]
  7. Suzuki M, Inauen W, Kvietys PR, Granger HJ, Granger DN. Superoxide mediates reperfusion-induced leukocyte-endothelial cell interactions. Am J Physiol. 1989;257:H1740–H1745.[Abstract/Free Full Text]
  8. Suzuki M, Asako H, Kubes P, Jennings S, Grisham M, Granger DN. Neutrophil-derived oxidants promote leukocyte adherence in postcapillary venules. Microvasc Res. 1991;42:125–138.[Medline] [Order article via Infotrieve]
  9. Inauen W, Payne DK, Kvietys PR, Granger DN. Hypoxia/reoxygenation increased the permeability of endothelial cell monolayers: role of oxygen radicals. Free Radic Biol Med. 1990;9:219–223.[Medline] [Order article via Infotrieve]
  10. Granger DN, Hollwarth ME, Parks DA. Ischemia-reperfusion injury: role of oxygen-derived free radicals. Acta Physiol Scand Suppl. 1986;548:47–53.
  11. Grisham MB, Hernandez LA, Granger DN. Xanthine oxidase and neutrophil infiltration in intestinal ischemia. Am J Physiol. 1986;251:G567–G573.[Abstract/Free Full Text]
  12. Zimmerman BJ, Grisham MB, Granger DN. Role of oxidants in ischemia/reperfusion-induced granulocyte infiltration. Am J Physiol. 1990;258:G185–G190.[Abstract/Free Full Text]
  13. Lewis MS, Whatley RE, Cain P, McIntyre PM, Prescott SM, Zimmerman GA. Hydrogen peroxide stimulates the synthesis of platelet-activating factor by endothelium and induces endothelial cell-dependent neutrophil adhesion. J Clin Invest. 1988;82:2045–2055.
  14. Nose K, Shibanuma K, Kikuchi K, Kagayama H, Sakiyama S, Kuroki T. Transcriptional activation of early-response genes by hydrogen peroxide in a mouse osteoblastic cell line. Eur J Biochem. 1991;201:99–106.[Medline] [Order article via Infotrieve]
  15. Schreck R, Rieber P, Baeurle PA. Reactive oxygen intermediates as apparently widely used messengers in the activation of NF{kappa}B transcription factor and HIV-1. EMBO J. 1991;10:2247–2258.[Medline] [Order article via Infotrieve]
  16. Sanchez-Madrid F, Krensky AM, Ware CF, Robbins E, Strominger JL, Burakoff SJ, Springer TA. Three distinct antigens associated with human T-lymphocyte-mediated cytolysis: LFA-1, LFA-2, and LFA-3. Proc Natl Acad Sci U S A.. 1982;79:7489–7493.[Abstract/Free Full Text]
  17. Ma X, Lefer DJ, Lefer AM, Rothlein R. Coronary endothelial and cardiac protective effects of a monoclonal anti-body to intercellular adhesion molecule-1 in myocardial ischemia and reperfusion. Circulation. 1992;86:937–946.[Abstract/Free Full Text]
  18. Kurose I, Kubes P, Wolf RE, Anderson DC, Paulson J, Miyasaka M, Granger DN. Inhibition of nitric oxide production: mechanisms of vascular albumin leakage. Circ Res. 1993;73:164–171.[Abstract]
  19. Tamatani T, Kotani M, Mitasaka M. Characterization of the rat leukocyte integrin, CD11/CD18, by the use of LFA-1 subunit specific monoclonal antibodies. Eur J Immunol. 1991;21:627–633.[Medline] [Order article via Infotrieve]
  20. Weyrich AS, Ma X-L, Lefer AM. Protective effects of a P-selectin specific monoclonal antibody in myocardial ischemia and reperfusion. Circulation. 1992;86(suppl I):I-80. Abstract.
  21. Mulligan MS, Polley MJ, Bayer RJ, Nunn MF, Paulson JC, Ward PA. Neutrophil-dependent acute lung injury: requirement for P-selectin (GMP-140). J Clin Invest. 1992;91:577–587.
  22. Mulligan MS, Verani J, Dame MK, Lane CL, Smith CW, Anderson DC, Ward PA. Role of ELAM-1 in neutrophil-mediated lung injury in rats. J Clin Invest. 1991;88:1396–1406.
  23. Meyer T, Lengyel H, Fanick W, Hilz H. 3-Aminobenzamide inhibits cytotoxicity and adhesion of phorbol-ester-stimulated granulocytes to fibroblast monolayer cultures. Eur J Biochem. 1991;197:127–133.[Medline] [Order article via Infotrieve]
  24. Lo SK, Janakidevi K, Lai L, Malik AB. Hydrogen peroxide-induced increase in endothelial adhesiveness is dependent on ICAM-1 activation. Am J Physiol. 1993;264:L406–L412.[Abstract/Free Full Text]
  25. Read MA, Neish AS, Luscinskas FW, Palombella VJ, Maniatis T, Collins T. The proteasome pathway is required for cytokine-induced endothelial-leukocyte adhesion molecular expession. Immunity. 1995;2:493–506.[Medline] [Order article via Infotrieve]
  26. Sambrook J, Fritsch EF, Maniatis T. Molecular Cloning: A Laboratory Manual. 2nd ed. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory; 1989.
  27. Bielinska A, Shivdasani RA, Zhang L, Nabel GJ. Regulation of gene expression with double-stranded phosphorothioate oligonucleotides. Science. 1990;250:997–1000.[Abstract/Free Full Text]
  28. Velcich A, Ziff EB. Functional analysis of an isolated fos promoter element with AP-1 site homology reveals cell type-specific transcriptional properties. Mol Cell Biol. 1990;10:6273–6282.[Abstract/Free Full Text]
  29. Seth R, Raymond FD, Makgoba MW. Circulating ICAM-1 isoforms: diagnostic prospects for inflammatory and immune disorders. Lancet. 1991;338:83–84.[Medline] [Order article via Infotrieve]
  30. Rothlein R, Mainolfi EA, Czajkowski M, Marlin SD. A form of circulating ICAM-1 in human serum. J Immunol.. 1991;147:3788–3793.[Abstract]
  31. Dignam J, Lebovitz R, Roeder R. Accurate transcription initiation by RNA polymerase II in a soluble extract from isolated mammalian nuclei. Nucleic Acids Res. 1983;11:1476–1489.
  32. Bradford MM. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal Biochem. 1976;72:248–254.[Medline] [Order article via Infotrieve]
  33. Chodosh L; Ausbel FM, Brent R, Kingston RE, Moore DD, Smith JA, Seidman JG, Struhl K, eds. DNA-Protein Interactions in Current Protocols in Molecular Biology. New York, NY: John Wiley & Sons; 1988:12.2.1–12.2.10.
  34. Cobb RR, Felts KA, Parry GCN, Mackman N. Proteasome inhibitors block VCAM-1 and ICAM-1 gene expression in endothelial cells without affecting nuclear translocation of nuclear factor {kappa}B. Eur J Immunol. 1996;26:839–845.[Medline] [Order article via Infotrieve]
  35. Granger DN, Rutili G, McCord JM. Superoxide radicals in feline intestinal ischemia. Gastroenterology. 1981;81:22–29.[Medline] [Order article via Infotrieve]
  36. Granger DN. Role of xanthine oxidase and granulocytes in ischemia-reperfusion injury. Am J Physiol. 1986;90:80–84.
  37. Kubes P, Suzuki M, Granger DN. Platelet activating factor-induced microvascular dysfunction: role of adherent leukocytes. Am J Physiol. 1990;258:G158–G163.[Abstract/Free Full Text]
  38. Zimmerman BJ, Guillory DJ, Gaginella T, Grisham MB, Granger DN. Role of leukotriene B4 in granulocyte infiltration into the postischemic feline intestine. Gastroenterology. 1990;99:1358–1363.[Medline] [Order article via Infotrieve]
  39. Kubes P, Suzuki M, Granger DN. Nitric oxide: an endogenous modulator of leukocyte adhesion. Proc Natl Acad Sci U S A.. 1991;88:4651–4655.[Abstract/Free Full Text]
  40. Lefer AM. Significance of lipid mediators in shock states. Circ Shock. 1989;27:3–12.[Medline] [Order article via Infotrieve]
  41. Ratych RE, Chuknyiska RS, Bulkley GB. The primary localization of free radical generation after anoxia: reoxygenation in isolated endothelial cells. Surgery. 1987;102:122–131.[Medline] [Order article via Infotrieve]
  42. de Fourgerolles AR, Stacker SA, Schwarting R, Springer TA. Characterization of ICAM-2 and evidence for a third counter-recepter for LFA-1. J Exp Med. 1991;174:253–267.[Abstract/Free Full Text]
  43. Patel KD, Zimmerman GA, Prescott SM, McEver RP, McIntyre TM. Oxygen radicals induce human endothelial cells to express GMP-140 and bind neutrophils. J Cell Biol. 1991;112:749–759.[Abstract/Free Full Text]
  44. Bonfanti R, Furie C, Wagner DD. PADGEM (GMP140) is a component of Weibel-Palade bodies of human endothelial cells. Blood. 1989;73:1109–1112.[Abstract/Free Full Text]
  45. Hattori R, Hamilton KK, Fugate RD, McEver RP, Sims PJ. Stimulated secretion of endothelial von Willebrand factor is accompanied by rapid redistribution to the cell surface of the intracellular granules membrane protein GMP-140. J Biol Chem. 1989;246:7768–7771.
  46. Smith CW, Marlin SD, Rothlein R, Toman C, Anderson DC. Cooperative interactions of LFA-1 and Mac-1 with intercellular adhesion molecule-1 in facilitating adherence and transendothelial migration of human neutrophils in vitro. J Clin Invest. 1989;83:2008–2017.
  47. Zimmerman GA, McIntyre TM, Prescott SM. Thrombin stimulates the adherence of neutrophils to human endothelial cells in vitro. J Clin Invest. 1985;76:2235–2246.
  48. Collins T. Endothelial nuclear factor-{kappa}B and the initiation of the atherosclerotic lesion. Lab Invest. 1993;68:499–508.[Medline] [Order article via Infotrieve]
  49. Bradley JR, Johnson D, Pober JS. Endothelial activation by hydrogen peroxide: selective increases of intercellular adhesion molecule-1 and major histocompatibility complex class I. Am J Pathol. 1993;142:1598–1609.[Abstract]



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