Protective effect of monoclonal antibodies against LFA-1 and ICAM-1 on myocardial reperfusion injury following global ischemia in rat hearts

LFA-1 and MAC-1 mediate pulmonary recruitment of neutrophils and tissue damage in abdominal sepsis

Neutrophil-mediated lung damage is an insidious feature in septic patients, although the adhesive mechanisms behind pulmonary recruitment of neutrophils in polymicrobial sepsis remain elusive. The aim of the present study was to define the role of lymphocyte function antigen-1 (LFA-1) and membrane-activated complex 1 (Mac-1) in septic lung injury. Pulmonary edema, bronchoalveolar infiltration of neutrophils, levels of myeloperoxidase, and CXC chemokines were determined after cecal ligation and puncture (CLP). Mice were treated with monoclonal antibodies directed against LFA-1 and Mac-1 before CLP induction. Cecal ligation and puncture induced clear-cut pulmonary damage characterized by edema formation, neutrophil infiltration, and increased levels of CXC chemokines in the lung. Notably, immunoneutralization of LFA-1 or Mac-1 decreased CLP-induced neutrophil recruitment in the bronchoalveolar space by more than 64%. Moreover, functional inhibition of LFA-1 and Mac-1 abolished CLP-induced lung damage and edema. However, formation of CXC chemokines in the lung was intact in mice pretreated with the anti-LFA-1 and anti-Mac-1 antibodies. Our data demonstrate that both LFA-1 and Mac-1 regulate pulmonary infiltration of neutrophils and lung edema associated with abdominal sepsis. Thus, these novel findings suggest that LFA-1 or Mac-1 may serve as targets to protect against lung injury in polymicrobial sepsis.

Toll-like receptor 4 mediates the early inflammatory response after cold ischemia/reperfusion

BACKGROUND

Ischemia/reperfusion (I/R) injury leads to graft dysfunction and may contribute to alloimmune responses posttransplantation. The molecular mechanisms of cold I/R injury are only partially characterized but may involve toll-like receptor (TLR)-4 activation by endogenous ligands. We tested the hypothesis that TLR4 mediates the early inflammatory response in the setting of cold I/R in a murine cardiac transplant model.

METHODS

Syngeneic heart transplants were performed in mutant mice deficient in TLR4 signaling (C3H/HeJ) and wild-type mice (C3H/HeOuJ). Transplants were also performed between the strains (mutant hearts into wild-type recipients and the converse). Donor hearts were subjected to 2 hr of cold ischemia. The grafts were retrieved at 3 and 24 hr after reperfusion. Serum samples were collected for cytokine analysis. Reverse-transcription polymerase chain reaction and histologic analysis were used to assess intra-graft inflammation.

RESULTS

After transplant, serum tumor necrosis factor (TNF), interleukin (IL)-6, JE/monocyte chemotractant protein (MCP)-1, IL-1beta, and troponin I levels, as well as intragraft TNF, IL-1beta, IL-6, early growth response (EGR)-1, intercellular adhesion molecule (ICAM)-1, and inducible nitric oxide synthase (iNOS) mRNA levels, were significantly lower in the mutant-->mutant group compared to the wild-type-->wild-type group (P< or =0.05). Intermediate levels of serum IL-6, JE/MCP-1, as well as intragraft TNF, IL-1beta, IL-6, and ICAM-1 mRNA were observed after transplants in the mutant-->wild-type and wild-type-->mutant groups. Immunohistochemistry revealed less myocardial nuclear factor-kappaB nuclear translocation at and less neutrophil infiltration in the mutant-->mutant group compared to the wild-type-->wild-type group.

CONCLUSIONS

These findings demonstrate that TLR4 signaling is central to both the systemic and intragraft inflammatory responses that occur after cold I/R in the setting of organ transplantation and that TLR4 signaling on both donor and recipient cells contributes to this response.

Blockage of intercellular adhesion molecule-1 (ICAM-1) in the prevention of reperfusion lesion in the skeletal musculature of EPM-1 Wistar rats

Purpose: Ischemia-reperfusion lesions are a form of acute inflammation in which leukocytes are considered to play a pivotal role. This study was made with the objective of determining whether the blockage of intracellular adhesion molecule-1, involved in the diapedesis of leukocytes, is efficacious in minimizing this lesions in the skeletal musculature of the posterior limbs of rats. Methods: The juxta-infrarenal aorta of three groups of six adult rats was clipped for six hours. After this, one group was sacrificed (control group) and the others underwent 24 hours of reperfusion, one with 0.9% physiological saline (reperfusion group) and the other with anti-ICAM-1 monoclonal antibodies (ICAM-1 group). A myeloperoxidase assay was utilized for estimating the infiltrate of neutrophils. Biopsies were obtained to make thin sections of hematoxylin-eosin and NADH. Blood samples were collected for making assays of biochemical parameters (creatinine; potassium; DHL; leukogram; venous pH; CK). Results: The myeloperoxidase levels were raised in the reperfusion (p < 0.001) and ICAM-1 (p < 0.019) groups in relation to the control group. The oxidative activity of the muscle fibers was significantly raised in the groups that underwent reperfusion. The other parameters did not present significant differences. Conclusions: The reperfusion lesion was bigger than the ischemic lesion. There was an increase in oxidative activity and inflammatory infiltrate with the reperfusion, without significant muscle necrosis being seen under the optical microscope. The blockage of ICAM-1 diminished the inflammatory infiltrate but not the rise in oxidative activity observed with the reperfusion.

Amelioration of ischemia-reperfusion injury with cyclic peptide blockade of ICAM-1

Neutrophils are pivotal in the pathogenesis of ischemia-reperfusion (I/R) injury leading to muscle damage. Firm adhesion of neutrophils to the endothelium is initiated by an interaction between intercellular adhesion molecular-1 (ICAM-1) on the endothelium and beta(2)-integrins on neutrophils. Inhibition of ICAM-1-dependent binding using monoclonal antibodies has been shown to be efficacious in ameliorating I/R injury by preventing the influx of neutrophils into the ischemic tissue. We recently described a cyclic peptide that is a potent and selective inhibitor of ICAM-1 (IP25) in vitro. In this study, we tested the hypothesis that IP25-mediated blockade of ICAM-1 would inhibit neutrophil influx during reperfusion of ischemic tissue and consequently attenuate muscle injury in a tourniquet hindlimb murine model of I/R injury. Varying amounts of peptide drug were injected at the beginning of the reperfusion period. The neutrophil influx and size of infarction at the end of 2 h of reperfusion were compared with those in untreated control mice and contralateral nonischemic limbs. Mice receiving IP25 immediately before reperfusion showed a 56% reduction in neutrophil infiltration in the ischemic muscle, accompanied by a 40% reduction in the infarct size. No effect on I/R injury was seen if IP25 administration was delayed for 60 min after reperfusion. We conclude that IP25 effectively inhibits ICAM-1-mediated adhesion of neutrophils to the endothelium in mice leading to a protective effect and suggests that synthetic peptide antagonists have a potential role as therapeutic tools.

Fundamental and distinct roles of P-selectin and LFA-1 in ischemia/reperfusion-induced leukocyte-endothelium interactions in the mouse colon

OBJECTIVE

To study the adhesive mechanisms underlying ischemia/reperfusion (I/R)-induced leukocyte-endothelium interactions in the colon.

SUMMARY BACKGROUND DATA

Leukocyte recruitment is a key feature in I/R-induced tissue injury, but the mechanisms regulating leukocyte rolling and adhesion in the colon are not known. The authors recently developed a new model to study the molecular mechanisms of I/R-provoked leukocyte-endothelium interactions in the colon microcirculation using inverted intravital fluorescence microscopy.

METHODS

The superior mesenteric artery was occluded for 30 minutes and leukocyte responses were analyzed after 120 minutes of reperfusion in colonic venules in mice. The adhesive mechanisms underlying I/R-induced leukocyte rolling and adhesion were investigated using monoclonal antibodies against L-, E- and P-selectin, and CD11a gene-targeted mice were used to examine the role of lymphocyte function antigen-1 (LFA-1, CD11a/CD18).

RESULTS

Reperfusion provoked a clear-cut increase in leukocyte rolling and adhesion in colonic venules compared to negative controls. Both P- and E-selectin mRNA were expressed in the colon after this I/R insult. Pretreatment with an anti-P-selectin antibody reduced leukocyte rolling and adhesion by 88% and 85%, respectively, whereas antibodies against L- and E-selectin had no effect. Moreover, I/R-induced leukocyte adhesion in LFA-1-deficient mice was reduced by more than 95%.

CONCLUSIONS

This study provides evidence that leukocyte rolling is exclusively and nonredundantly mediated by P-selectin and that firm adhesion is supported by LFA-1 in I/R-induced leukocyte recruitment in the colon. Taken together, both P-selectin and LFA-1 may be important targets to control pathologic inflammation in I/R-induced tissue injury in the colon.

Intercellular adhesion molecule-1 in the heart

Intercellular adhesion molecule-1 (ICAM-1) belongs to the superfamily of immunoglobulin-like adhesion molecules. Up-regulation of ICAM-1 occurs in many different pathophysiological processes. Also, cardiomyocytes can express ICAM-1-for example, in acute myocardial infarction. Moreover, inhibition of ICAM-1 expression in the heart dramatically reduces infarct size. Hence, inhibitors of ICAM-1 may provide a novel therapeutic option for acute myocardial infarction.

Therapeutic potential of monoclonal antibodies in myocardial reperfusion injury

While reperfusion therapy in myocardial infarction is associated with better short- and long-term outcomes, it paradoxically results in reperfusion injury mediated by interactions between leukocytes, endothelial cells, platelets, and the myocardium. Several surface receptors, adhesion molecules, and ligands have been shown to be important in the pathogenesis of myocardial reperfusion injury, and therapeutic strategies employing the use of monoclonal antibodies have been attempted against many of them. These have included monoclonal antibodies against activated complement 5 (C5a) to inhibit leukotaxis, monoclonal antibodies against P-selectin, P-selectin glycoprotein ligand (PSGL)-1, L-selectin and E-selectin to inhibit leukocyte rolling, and monoclonal antibodies against the Mac-1 (CD11b/CD18) receptor and intercellular adhesion molecule (ICAM)-1 to block firm adhesion of leukocytes to endothelial cells. In addition, although initially developed as an antiplatelet agent, the glycoprotein IIb/IIIa receptor antagonist abciximab shows significant ability to diminish or prevent reperfusion injury, presumably through its ability to block the Mac-1 receptor on leukocytes. Finally, monoclonal antibodies have also been tested against several cytokines and adhesion molecules implicated in so-called subacute endothelial activation, including interleukin-8 and vascular cell adhesion molecule (VCAM)-1. Studies in animals evaluating the use of monoclonal antibodies in reperfusion injury against various potential targets have largely been successful; however, studies in humans have been disappointing, underscoring the pitfalls of using animal models for the study of complex diseases. Based upon current knowledge, it is becoming clear that a successful strategy against reperfusion injury will require targeting several pathways at once, rather than attempting to block one final common pathway. In addition, inhibition of subacute endothelial activation through inhibition of transcription factors, namely nuclear factor (NF)-kappa B, may be a prerequisite to significantly reducing the extent of myocardial damage in this condition. The future of monoclonal antibodies in the overall strategy remains unclear. Newer small molecule inhibitors are also under development, and the eventual role of gene therapy remains to be elucidated.

PR-39 and PR-11 peptides inhibit ischemia-reperfusion injury by blocking proteasome-mediated I kappa B alpha degradation

PR-39 inhibits proteasome-mediated I kappa B alpha degradation and might protect against ischemia-reperfusion injury. We studied PR-39, its truncated form PR-11, and a mutant PR-11AAA, which lacks the ability to prevent I kappa B alpha degradation, in a rat heart ischemia-reperfusion model. After 30 min of ischemia and 24 h of reperfusion, cardiac function, infarct size, neutrophil infiltration, and myeloperoxidase activity were measured. Intramyocardial injection of 10 nmol/kg PR-39 or PR-11 at the time of reperfusion reduced infarct size by 65% and 57%, respectively, which improved blood pressure, left ventricular systolic pressure, and relaxation and contractility (+/-dP/dt) compared with vehicle controls 24 h later. Neutrophil infiltration, myeloperoxidase activity, and the expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule 1 were reduced. Thus PR-39 and PR-11 effectively inhibit myocardial ischemia-reperfusion injury in the rat in vivo. This effect is mediated by inhibition of I kappa B alpha degradation and subsequent inhibition of nuclear factor-kappa B-dependent adhesion molecules. The active sequence is located in the first 11 amino acids, suggesting a potential for oligopeptide therapy as an adjunct to revascularization.

alpha(4)-integrin mediates neutrophil-induced free radical injury to cardiac myocytes

Previous work has demonstrated that circulating neutrophils (polymorphonuclear leukocytes [PMNs]) adhere to cardiac myocytes via beta(2)-integrins and cause cellular injury via the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase enzyme system. Since PMNs induced to leave the vasculature (emigrated PMNs) express the alpha(4)-integrin, we asked whether (a) these PMNs also induce myocyte injury via NADPH oxidase; (b) beta(2)-integrins (CD18) still signal oxidant production, or if this process is now coupled to the alpha(4)-integrin; and (c) dysfunction is superoxide dependent within the myocyte or at the myocyte-PMN interface. Emigrated PMNs exposed to cardiac myocytes quickly induced significant changes in myocyte function. Myocyte shortening was decreased by 30-50% and rates of contraction and relaxation were reduced by 30% within the first 10 min. Both alpha(4)-integrin antibody (Ab)-treated PMNs and NADPH oxidase-deficient PMNs were unable to reduce myocyte shortening. An increased level of oxidative stress was detected in myocytes within 5 min of PMN adhesion. Addition of an anti-alpha(4)-integrin Ab, but not an anti-CD18 Ab, prevented oxidant production, suggesting that in emigrated PMNs the NADPH oxidase system is uncoupled from CD18 and can be activated via the alpha(4)-integrin. Addition of exogenous superoxide dismutase (SOD) inhibited all parameters of dysfunction measured, whereas overexpression of intracellular SOD within the myocytes did not inhibit the oxidative stress or the myocyte dysfunction caused by the emigrated PMNs. These findings demonstrate that profound molecular changes occur within PMNs as they emigrate, such that CD18 and associated intracellular signaling pathways leading to oxidant production are uncoupled and newly expressed alpha(4)-integrin functions as the ligand that signals oxidant production. The results also provide pathological relevance as the emigrated PMNs have the capacity to injure cardiac myocytes through the alpha(4)-integrin-coupled NADPH oxidase pathway that can be inhibited by extracellular, but not intracellular SOD.

Acute rejection and cardiac graft vasculopathy in the absence of donor-derived ICAM-1 or P-selectin

BACKGROUND

ICAM-1 and P-selectin are molecules that facilitate adhesion of circulating leukocytes to vessel walls. We have investigated the role of donor-derived ICAM-1 and P-selectin in acute and chronic cardiac allograft rejection.

METHODS

C57BL/6J (H-2(b)) mice were used as donors for heterotopic heart transplantation into CBA/Ca (H-2(k)) recipients. The donors were wild-type or homozygous for gene mutations of ICAM-1 or P-selectin. We measured acute rejection in non-immunosuppressed recipients by daily palpation and sacrificed mice at Days 2, 4, and 6 for immunohistochemical analysis. For chronic rejection, recipients received monoclonal antibody against CD4+ T cells. We removed hearts at Days 60 to 62 for histologic assessment of vasculopathy using quantitative morphometry to measure intimal thickening.

RESULTS

Time (days) to rejection was 7.1 +/- 0.57 for wild-type (n = 10), 7.0 +/- 0.71 for ICAM-1 -/- (not significantly different, n = 7) and 6.1 +/- 0.33 (p = 0.001) for P-selectin -/- donors. ICAM-1 deficiency was associated with delayed infiltrate at Day 4 compared with wild-type. In the model of chronic rejection, elastin-positive vessels showed a mean occlusion of 34% +/- 3% in transplanted wild-type hearts; vessels were divided into those showing 0% to 20%, 20% to 50%, and 50% to 100% occlusion. We observed no difference in the number of affected vessels or the amount of vascular thickening in donors lacking ICAM-1 or P-selectin compared with wild-type controls.

CONCLUSIONS

The absence of ICAM-1 or P-selectin in donor tissues neither lengthens the time of allograft survival nor inhibits the vascular lesions associated with chronic rejection. Indeed, the absence of P-selectin may exacerbate alloimmune injury.

Effects of humanized monoclonal antibody to rhesus CD11a in rhesus monkey cardiac allograft recipients

INTRODUCTION

Leukocyte function-associated antigen-1 (LFA-1, CD11a) monoclonal antibody (mAb) affects many leukocyte functions without cell depletion. We hypothesized that the use of a humanized, anti-rhesus modified LFA-1 mAb (H2C12) in rhesus monkeys would cause: (1) prolonged heart allograft survival, (2) inhibition of primary but not secondary antibody responses, and (3) minimal drug toxicity.

METHODS AND RESULTS

Control (n=5) and H2C12-treated (n=7) (8-20 mg/kg i.v. on day -1 followed by 10 mg/kg/day) adult male rhesus recipients were inoculated with GP120 protein antigen on day -28 and -1 and grafted with heterotopic abdominal hearts (day 0). Donor-recipient pairs were equally MLR mismatched (4329.8+/-1124.1 CPM controls vs. 7289.0+/-1926.5 treated, P=NS). Mean heart allograft survival as evaluated by daily abdominal palpation was significantly prolonged in high dose recipients (23.0+/-2.6, n=4) vesus controls (8.2+/-1.3, n=5, P<0.02, Mann-Whitney U test). H2C12 treatment did not produce signs of cytokine release or toxicity, was nondepleting, but down-modulated PBL CD11a expression to 43.4+/-3.6% (n=4) of control levels (n=5) at day 7 as demonstrated by flow cytometry. It had no effect on postoperative Con A or MLR and did not prevent mAb clearance due to the rhesus-antihuman antibody response. The addition of mycophenolate mofitil prevented rhesus-antihuman antibody response with therapeutic H2C12 levels seen for >35 days.

CONCLUSIONS

The use of this mAb to block CD11a had the benefit of being a well tolerated, highly targeted therapy. These are the first results showing that monotherapy with anti-leukocyte function-associated antigen-1 mAb prolonged survival of MLR mismatched allogenic cardiac grafts in primates.

ICAM-1 affects reperfusion injury and graft function after cardiac transplantation

BACKGROUND

The effects of increased expression of intercellular adhesion molecule (ICAM-1), an important mediator of neutrophil-mediated reperfusion injury (RI), were assessed in donor cardiac allografts in a heterotopic rat transplantation model.

METHODS

At -24 h, PVG donors were untreated (n = 35) or treated (n = 37) with lipopolysaccharide (LPS, 5 mg/kg ip). Hearts were procured at 0 h, stored at 4 degrees C for 45 min, and grafted heterotopically into ACI recipients pretreated with vehicle or anti-ICAM-1 (1A29) mAb. Intracardiac balloons (n = 8 per group) were used to measure allograft left ventricular function (dP/dt) prior to harvest and following reperfusion. RI was assessed at 6, 12, and 24 h by myeloperoxidase (MPO) levels, percentage wet weight (%w/w), and percentage contraction band necrosis (%CBN).

RESULTS

At 12 h, LPS-pretreated grafts showed increased ICAM-1 expression by Northern blot (n = 3) and immunohistochemistry (n = 3) and significantly increased MPO (0.33 +/- 0.2 U/mg vs 0.05 +/- 0.04 U/mg at 12 h), %w/w (81.7 +/- 1.8% vs 79.2 +/- 0.7% at 12 h), and %CBN (15.2 +/- 1. 9% vs 11.4 +/- 2.0% at 24 h). LPS pretreatment had no effect on graft function at early time points (baseline to 2 h) but led to depressed dP/dt at later time points with trends toward significance at 12 h (2101 +/- 1653 mmHg/s vs 173 +/- 201 mmHg/s, P = 0.06, ANOVA). Recipient 1A29 treatment (n = 6 per group) reversed the effects of LPS pretreatment in all three RI parameters and significantly improved functional recovery.

CONCLUSIONS

Alteration of cardiac graft phenotype to that likely seen in clinical organ donors leads to increased delayed-onset myocardial RI following transplantation in this model. The blockade of this increased RI following 1A29 mAb treatment supports a central role for ICAM-1 in this process.

Antisense oligodeoxynucleotides prevent acute cardiac allograft rejection via a novel, nontoxic, highly efficient transfection method

BACKGROUND

We hypothesized that ex vivo donor allograft transfection with antisense oligodeoxynucleotide (AS ODN) would inhibit the expression of intercellular adhesion molecule (ICAM)-1, an important mediator of T-cell adhesion and costimulation, and therefore suppress acute cardiac rejection.

METHODS

Hearts were transfected ex vivo with AS, reverse AS ODN, or saline by applying 3 atm pressure for 45 min at 4 degrees C. Grafts were then transplanted into allogenic recipients +/- treatment with leukocyte function-associated antigen (LFA)-1 monoclonal antibody (mAb) (1.5 mg/kg intravenously), cyclosporine (2.5 mg/ kg/day p.o.), or rapamycin (0.025 mg/kg/day intraperitoneally). Reperfusion injury was assessed in grafts harvested at early time points using the myeloperoxidase, %wet weight, and %contraction band necrosis assays; transfection efficiency was assessed using fluorescent microscopy; and efficacy of ICAM-1 blockade was assessed using immunohistochemistry. Other grafts were followed until rejection with donor/third-party skin grafting, adoptive transfer, and interleukin 2 infusion studies in selected recipients.

RESULTS

Transfection was highly efficient (fluorescein isothiocyanate-ODN in 48+/-5% of total myocardial nuclei), nontoxic, and reduced the ICAM-1-positive area to 53+/-14% versus having no effect on MHC class I expression (n=4). The incidence of survival >60 days after AS ODN + LFA-1 monoclonal antibody was 75%, significantly higher than other regimens.

CONCLUSION

AS ODN hyperbaric transfection proved highly efficient, effective at ICAM-1 blockade, and induced cardiac allograft tolerance when combined with LFA-1 monoclonal antibody. This highly targeted alteration of allograft immunogenicity may have an important role in future immunosuppressive strategies.

Thrombolysis with tissue plasminogen activator alters adhesion molecule expression in the ischemic rat brain

BACKGROUND AND PURPOSE

We tested the hypothesis that treatment of embolic stroke with recombinant human tissue plasminogen activator (rhtPA) alters cerebral expression of adhesion molecules.

METHODS

Male Wistar rats were subjected to middle cerebral artery occlusion by a single fibrin-rich clot. P-selectin, E-selectin, and intercellular adhesion molecule-1 (ICAM-1) immunoreactivity was measured at 6 or 24 hours after embolic stroke in control rats and in rats treated with rhtPA at 1 or 4 hours after stroke. To examine the therapeutic efficacy of combined rhtPA and anti-ICAM-1 antibody treatment at 4 hours after embolization, ischemic lesion volumes were measured in rats treated with rhtPA alone, rats treated with rhtPA and anti-ICAM-1 antibody, and nontreated rats.

RESULTS

Administration of rhtPA at 1 hour after embolization resulted in a significant reduction of adhesion molecule vascular immunoreactivity after embolization in the ipsilateral hemisphere compared with corresponding control rats. However, when rhtPA was administered to rats at 4 hours after embolization, significant increases of adhesion molecule immunoreactivity in the ipsilateral hemisphere were detected. A significant increase of ICAM-1 immunoreactivity was also detected in the contralateral hemisphere at 24 hours after ischemia. A significant reduction in lesion volume was found in rats treated with the combination of rhtPA and anti-ICAM-1 antibody compared with rats treated only with rhtPA.

CONCLUSIONS

The present study suggests that the time of initiation of thrombolytic therapy alters vascular immunoreactivity of inflammatory adhesion molecules in the ischemic brain and that therapeutic benefit can be obtained by combining rhtPA and anti-ICAM-1 antibody treatment 4 hours after stroke.

Ex vivo gene therapy prevents chronic graft vascular disease in cardiac allografts

OBJECTIVE

We hypothesized that ex vivo hyperbaric transfection of antisense oligodeoxynucleotides for blockade of intercellular adhesion molecule-1, an important mediator of cell adhesion and T-cell co-stimulation, would reduce chronic graft vascular disease in cardiac allografts.

METHODS

PVG hearts underwent ex vivo transfection with antisense, reverse antisense intercellular adhesion molecule-1 oligodeoxynucleotide (80 micromol/L), or saline solution at 3 atm pressure for 45 minutes at 4 degrees C and were transplanted heterotopically into ACI recipients with or without treatment with intercellular adhesion molecule-1 (1A29) or leukocyte function associated antigen-1 (WT.1) monoclonal antibodies. Transfection efficiency was confirmed with fluorescein isothiocyanate-labeled oligodeoxynucleotides and fluorescent microscopy. Efficacy of intracellular adhesion molecule-1 blockade was assessed with the use of immunohistochemistry. Graft reperfusion injury was evaluated at 6 to 24 hours by neutrophil infiltration (myeloperoxidase [MPO]), cardiac edema (%wt/wt), and histologic injury (percent contraction band necrosis). Grafts from recipients treated with cyclosporine A (5 mg/kg per day, days 0 to 9) were scored for chronic graft vascular disease on postoperative day 90 ranging from 0 (no involvement) to 4 (>50% vascular occlusion).

RESULTS

Transfection was highly efficient (fluorescein isothiocyanate-labeled oligodeoxynucleotides in 48%+/-5% of total myocardial nuclei) and effective at blocking intracellular adhesion molecule-1 expression (positive area in allografts taken on postoperative day 3 was reduced from 100%+/-0% to 52%+/-14%, n=4). Blockade with antisense oligodeoxynucleotides versus monoclonal antibodies was less effective at preventing reperfusion injury while more effective at reducing chronic graft vascular disease (score 0.98+/-0.48, p < 0.05). Reverse antisense oligodeoxynucleotides and vector control (antisense oligodeoxynucleotide infusion without pressure) groups failed to demonstrate this beneficial effect.

CONCLUSION

Hyperbaric transfection of antisense oligodeoxynucleotides proved highly efficient, effective at blockade of intracellular adhesion molecule-1, and demonstrated a sequence-specific reduction in chronic graft vascular disease. This highly targeted alteration of donor organ immunogenicity may have an important future role in clinical immunosuppressive strategies.

PAF and CD18 mediate neutrophil infiltration in upper gastrointestinal tract during intra-abdominal sepsis

Neutrophil infiltration is a critical event in the development of multiple organ failure during sepsis. We hypothesized that platelet-activating factor (PAF) release contributes to neutrophil infiltration in the gastrointestinal tract during sepsis. In the first experiments we administered exogenous PAF (1.56, 6.25, 25, and 100 ng . kg-1 . min-1 for 30 min) to urethan-anesthetized Sprague-Dawley rats. PAF was administered alone or in combination with either the PAF antagonist WEB-2086 (250 microg . kg-1 . min-1), a monoclonal antibody (MAb) to CD18, or a MAb to intercellular adhesion molecule 1 (ICAM-1). In separate groups of rats, cecal ligation and incision (CLI) was performed to create intra-abdominal sepsis, which we hypothesized would stimulate the release of endogenous PAF. CLI was performed in rats given either saline, WEB-2086, anti-CD18, or anti-ICAM-1 MAb. After these experiments, tissue myeloperoxidase (MPO) levels were determined as a marker of neutrophil infiltration. Both exogenous PAF and CLI induced significant increases in MPO activity in the stomach and duodenum. These increases were significantly attenuated by WEB-2086, anti-CD18 MAb, and anti-ICAM-1 MAb in both PAF- and CLI-treated rats. These results suggest that both the inflammatory mediator PAF and the CD18 integrins play a major role in neutrophil infiltration in the upper gastrointestinal tract during sepsis.

Cardiac graft intercellular adhesion molecule-1 (ICAM-1) and interleukin-1 expression mediate primary isograft failure and induction of ICAM-1 in organs remote from the site of transplantation

During the first few hours after heart transplantation, the occurrence of graft failure is unpredictable and devastating. An explosive cascade of inflammatory events within the reperfused graft vasculature is likely to be mediated, at least in part, by the local expression of the leukocyte adhesion receptor intercellular adhesion molecule-1 (ICAM-1, CD54). Furthermore, although proinflammatory cytokines such as interleukin-1 (IL-1) are known to autoinduce their own (and ICAM-1) expression in vitro, there are no data to identify their functional in vivo cross talk in the setting of isograft transplantation. To determine the role of ICAM-1 in primary graft failure, we used an isogeneic vascularized model of heterotopic cardiac transplantation. ICAM-1 mRNA and protein increased in grafts during the early posttransplant period and were predominantly localized in the endothelium. The functional significance of this was established using donor hearts obtained from either ICAM-1-deficient (ICAM-1 -/-) or control (ICAM-1 +/+) mice. ICAM-1 +/+ grafts exhibited increased neutrophil infiltration, reduced left ventricular compliance, and poorer survival than did ICAM-1 -/- grafts. Increased ICAM-1 expression was not limited to ICAM-1 +/+ grafts but also occurred in unmanipulated recipient organs located remote from the site of surgery (but only after transplantation of ICAM-1 +/+, not ICAM-1 -/-, cardiac grafts). This expression of ICAM-1 in remote organs appeared to be triggered by IL-1alpha released from the graft, because (1) in situ hybridization revealed increased IL-1 mRNA within cells of the reperfused graft, including myocytes and endothelial cells; (2) ICAM-1 expression in remote organs coincided with a significant increase in serum levels of IL-1alpha after transplantation of ICAM-1 +/+ grafts; both remote organ ICAM-1 expression and IL-1alpha levels were blunted by implantation of ICAM-1 -/- grafts; and (3) remote organ ICAM-1 expression and neutrophil infiltration and IL-1 levels could be blocked by the administration of an IL-1 receptor antagonist. These data demonstrate an apparent positive-feedback loop in which local ICAM-1 and IL-1 expression leads to a mutual amplification of each other's expression within the reperfused graft, promulgating inflammatory events that are likely to be an important cause of primary cardiac graft failure. Because IL-1 receptor blockade reduces the IL-1-mediated autoinduction of IL-1, reduces the expression of ICAM-1 in both the graft and remote organs, and improves graft survival, it may provide a new and effective strategy to prevent the occurrence of primary cardiac graft failure.

Effects of increased ICAM-1 on reperfusion injury and chronic graft vascular disease

BACKGROUND

The purpose of this study was to assess the impact of increased donor cardiac intercellular adhesion molecule (ICAM-1) expression on both reperfusion injury and chronic graft vascular disease after transplantation.

METHODS

Hearts were harvested from donor rats before and after pretreatment with lipopolysaccharide at -24 hours, underwent 45 minutes of cold ischemia, and were transplanted into ACI recipients with or without anti-ICAM-1 monoclonal antibody treatment. Grafts were procured early for analysis of ICAM-1 expression and reperfusion injury or the recipients were treated with cyclosporin A (to allow long-term graft acceptance) for postoperative days 0 through 9 with procurement on postoperative day 90 to histologically score for chronic graft vascular disease.

RESULTS

Lipopolysaccharide-pretreated PVG heart grafts showed increased ICAM-1 expression by Northern blot and immunohistochemical analysis leading to increased reperfusion injury as assessed by neutrophil infiltration (myeloperoxidase), cardiac edema (percentage wet weight), and histologic injury (percentage area of contraction band necrosis), which was reversed by recipient treatment with anti-ICAM-1 monoclonal antibody. After administration of cyclosporin A, 5 mg/kg for 10 days, lipopolysaccharide-treated grafts had significantly worse chronic graft vascular disease scores (2.56 +/- 0.57 versus 1.84 +/- 0.75; p < 0.05 by Mann-Whitney U test).

CONCLUSIONS

The induction donor inflammatory state before harvest leading to increased cardiac ICAM-1 expression promotes reperfusion injury and chronic graft vascular disease after transplantation in this rodent heterotopic heart model.

Anti-CD18 antibodies improve cardiac function following cardiopulmonary bypass in dogs

PURPOSE

Cardiopulmonary bypass is associated with activation of neutrophils, which may adhere to vascular endothelium causing lung, heart, and brain injury. We tested whether blocking neutrophil adherence would improve organ function following cardiopulmonary bypass in dogs.

MATERIALS AND METHODS

All dogs received a standard anesthetic, and then one group (n = 6) received 2 hours of cardiopulmonary bypass followed by 4 hours of observation. A second group (n = 6) received a monoclonal antibody (6 mg/kg) to CD18, a neutrophil adherence factor, immediately before cardiopulmonary bypass. A third group (n = 6) did not receive cardiopulmonary bypass or antibody.

RESULTS

Using flow cytometry we found that the antibody bound essentially all neutrophil CD18 sites. All three groups had similar gas exchange and hemodynamics. Lung and heart histology results were similar between groups. By echocardiography, five animals receiving cardiopulmonary bypass alone showed regional wall abnormalities, whereas only one receiving antibody showed wall motion abnormality (P < .05). Following cardiopulmonary bypass, intracellular myocardial pH was higher (P < .05) in the antibody-treated group compared with the group that had cardiopulmonary bypass alone (7.23 +/- 0.05 v 7.07 +/- 0.07 respectively).

CONCLUSION

Monoclonal antibodies to CD18 can prevent the deterioration in cardiac function routinely observed following cardiopulmonary bypass.

Neutrophil-independent myocardial dysfunction during an early stage of global ischemia and reperfusion of isolated hearts

The effect of global ischemia and reperfusion on the expression of cytokine genes and cell adhesion molecules by myocardial tissues and neutrophils was studied by using the Langendorff model. Although cardiac function deteriorated after reperfusion of ischemic hearts, there was no evidence of inflammation and myocardial degeneration, which is in contrast to previous findings that neutrophil-mediated inflammation is a critical step in post-ischemic reperfusion injury in regional ischemia. Flow cytometry analysis demonstrated that the global ischemia and reperfusion did not affect the expression of adhesion molecules on neutrophils. We also examined the expression of various cytokines which are involved in inflammatory responses. Only interleukin 1 alpha was induced after the reperfusion of the ischemic hearts. These results suggest that neutrophils barely contribute to the myocardial dysfunction and IL-1 alpha may play a role in post-ischemic myocardial dysfunction during the early stage of reperfusion.