Diminished thrombus formation and alleviation of myocardial infarction and reperfusion injury through antibody- or small-molecule-mediated inhibition of selectin-dependent platelet functions.

BACKGROUND AND OBJECTIVES: P-selectin ctin has been implicated in important platelet functions. However, neither its role in thrombus formation and cardiovascular disorders nor its suitability as a therapeutic target structure is entirely clear. DESIGN AND METHODS: Platelet aggregation was assessed in complementary in vitro settings by measurements of static aggregation, standardized aggregometry and dynamic flow chamber assays. Degradation of aggregates was also analyzed under flow conditions using video microscopy. In vivo, platelet rolling in cutaneous venules was assessed by intravital microscopy in wild-type mice treated with selectin-blocking compounds as well as in P-selectin-deficient mice. FeCl3-induced arterial thrombosis was studied by intravital microscopy in untreated mice or mice treated with an inhibitor of selectin functions. Finally, inhibition of selectin functions was studied in an ischemia/reperfusion injury model in rats. RESULTS: Antibody- or small-molecule-mediated inhibition of P-selectin functions significantly diminished platelet aggregation (p<0.03) and platelet-neutrophil adhesion in vitro (p<0.01) as well as platelet aggregate sizes under flow (p<0.03). Established aggregates were degraded, either via detachment of single platelets following addition of efomycine M, or via detachment of multicellular clumps when P-selectin-directed Fab-fragments were used. In vivo, selectin inhibition resulted in a greater than 50% reduction of platelet rolling in cutaneous venules (p<0.01), producing rolling fractions similar to those observed in P-selectin-deficient mice (p<0.05). Moreover, inhibition of selectin functions significantly decreased the thrombus size in FeCl3-induced arterial thrombosis in mice (p<0.05). In an ischemia/reperfusion injury model in rats, small-molecule-mediated selectin inhibition significantly reduced myocardial infarct size from 18.9% to 9.42% (p<0.001) and reperfusion injury (p<0.001). INTERPRETATION AND CONCLUSIONS: Inhibition of P-selectin functions reduces platelet aggregation and can alleviate platelet-related disorders in disease-relevant preclinical settings.

A novel strategy for myocardial protection by combined antibody therapy inhibiting both P-selectin and intercellular adhesion molecule-1 via retrograde intracoronary route.

BACKGROUND: Antibody therapy to inhibit either P-selectin or intercellular adhesion molecule-1 (ICAM-1) has been reported to provide myocardial protection against leukocyte-mediated reperfusion injury. Because these molecules play different roles in the leukocyte-endothelial interaction, co-inhibition of both may achieve further enhanced cardioprotection. In addition, the therapeutic efficacy of such antibody therapy may be affected by the delivery route used. Retrograde intracoronary infusion will offer an effective, direct access to the postcapillary venules, where the target event (leukocyte-endothelial interaction) takes place. We investigated the feasibility and efficiency of the combined antibody therapy targeting both P-selection and ICAM-1 via the retrograde intracoronary route to attenuate myocardial ischemia-reperfusion injury. METHODS AND RESULTS: Lewis rats underwent 30-minute left coronary artery occlusion. Just before reperfusion, anti-P-selectin monoclonal antibody (150 microg/kg), anti-ICAM-1 monoclonal antibody (200 microg/kg), both antibodies together, or control antibody were retrogradely infused into the left cardiac vein. At 24 hours after reperfusion, administration of either anti-P-selectin or anti-ICAM-1 antibody significantly (P<0.05) improved left ventricular ejection fraction and attenuated infarct size (40.6+/-3.2% and 34.8+/-3.5%, respectively) compared with the control (56.8+/-3.4%). This was associated with reduced leukocyte accumulation and improved regional blood flow in the ischemic area. Noticeably, co-administration of both antibodies achieved a much greater reduction in infarct size (19.1+/-3.6%), associated with greater attenuation in leukocyte infiltration, compared with administration of either single antibody. CONCLUSIONS: Combined antibody therapy inhibiting both P-selectin and ICAM-1 via the retrograde intracoronary route could be a promising new strategy for myocardial protection against ischemia-reperfusion injury.

Preventive effect of sulphated colominic acid on P-selectin-dependent infiltration of macrophages in experimentally induced crescentic glomerulonephritis.

Leucocytes infiltrate into renal tissue and are involved in the pathogenesis of crescentic glomerulonephritis. The initial event in the process of leucocyte infiltration is characterized by selectin-mediated leucocyte rolling on endothelial surface. Role of selectins in pathogenesis of glomerulonephritis has still been controversial. Sulphated glycolipids and sulphated polysaccharides interfere with the binding of P- and L-selectin with carbohydrate ligands on endothelial cells or on leucocytes. Here we evaluated the role of selectins and the preventive effects of sulphated colominic acid (SCA), a synthetic sulphated polysaccharide, on experimental crescentic glomerulonephritis in Wistar-Kyoto (WKY) rats. Crescentic glomerulonephritis was induced by injection of nephrotoxic serum (NTS) in WKY rats. Rats subsequently received intraperitoneal injection of saline, neutralizing or non-neutralizing monoclonal antibody (mAb) to rat P-selectin and L-selectin, SCA (5 or 10mg/kg/day) or nonsulphated colominic acid (CA) (10mg/kg/day) for 2 weeks. Localization of P-, E-selectin, ligands for L-selectin and intraglomerular leucocytes was examined by immunohistochemistry. Gene expression of platelet-derived growth factor (PDGF) B chain in glomeruli was quantified using real-time RT-PCR. P-selectin was highly expressed on glomerular endothelial cells after injection of NTS, whereas E-selectin and L-selectin ligands were not detected. Anti-P-selectin mAb, but not anti-L-selectin mAb, significantly reduced glomerular infiltration of macrophages, crescent formation, and proteinuria. SCA also reduced proteinuria, macrophage infiltration, and crescent formation in a dose-dependent manner. Furthermore, SCA suppressed gene expression of PDGF B chain in glomeruli. Our results indicate that P-selectin partially mediates glomerular infiltration of macrophage in experimental crescentic glomerulonephritis. Moreover, SCA may inhibit intraglomerular infiltration of macrophages by interfering with P-selectin-dependent adhesion pathway, and progression of experimental crescentic glomerulonephritis.

Effects of Saiko-ka-ryukotsu-borei-to in patients with hyperlipidemia.

We measured and compared levels of platelet-derived microparticles (PMPs), monocyte-derived microparticles (MMPs), CD62P on activated platelets, soluble E-selectin (sE-selectin), and anti-oxidized low density lipoprotein (LDL) antibody in hyperlipidemia patients and control subjects. Binding of anti-GPIIb/IIIa and anti-GPIb monoclonal antibodies to platelets was not significantly different between hyperlipidemia patients and controls. However, expression of CD62P on platelets and levels of PMPs were higher for hyperlipidemia patients than in controls, although the difference between groups in CD62P expression was not significant (PMPs: 534 +/- 63 vs. 388 +/- 47, p < 0.05; CD62P: 9.1% +/- 1.45 vs. 7.3% +/- 1.15, N.S.). Although there were no differences in expression of CD36 and CD40 by monocytes between the two groups, levels of MMPs were higher in hyperlipidemia patients than in controls (MMPs: 147 +/- 21 vs. 59 +/- 8, respectively, p < 0.01). Levels of anti-oxidized LDL antibody and sE-selectin were also higher in hyperlipidemia patients. We studied the effects of Saiko-ka-ryukotsu-borei-to on levels of these factors in patients with elevated triglyceride levels. After Saiko-ka-ryukotsu-borei-to treatment, levels of CD62P, PMPs, sE-selectin, and anti-oxidized LDL antibody were reduced significantly. Levels of triglycerides, total cholesterol and MMPs also decreased, but the changes were not significant. These findings suggest that Saiko-ka-ryukotsu-borei-to prevents the development of vascular complications in hyperlipidemia patients.

Role of P-selectin and intercellular adhesion molecule-1 in TNB-induced colitis in rats.

It has been proposed that neutrophil-endothelial cell interactions mediated by adhesion molecules are involved in the pathogenesis of inflammatory bowel disease. The objective of the present study was to determine the effects of monoclonal antibodies (MAbs) directed against endothelial adhesion molecules, P-selectin and intercellular adhesion molecule-1 (ICAM-1), in rats with colitis induced by 2,4,6-trinitrobenzene sulfonic acid (TNB). Colonic inflammation was induced by administering an enema of TNB dissolved in 50% ethanol (120 mg/ml) to male Wistar rats (at a total volume of 0.25 ml per rat) after a 48-hour fast. Anti-P-selectin MAb or anti-ICAM-1 MAb was injected via the tail vein at a dose of 1 mg/kg after the induction of colitis. Rats in the control group received nonbinding mouse immunoglobulin G1. The plasma level of soluble P-selectin showed an increase within 48 h after the TNB enema. Colonic inflammation was assessed at 1 week after TNB administration. The colonic damage score and the wet weight of the colon were significantly decreased by treatment with either MAb. The increase of myeloperoxidase (MPO) activity, an index of neutrophil accumulation, and the increase of thiobarbituric acid-reactive substances (TBA-RS), an index of lipid peroxidation, in the colonic mucosa were inhibited by both MAbs. These results suggest that neutrophil-endothelial cell interactions via P-selectin and ICAM-1 play an important role in the development of TNB-induced colitis in rats.

Persantine attenuates hemorrhagic shock-induced P-selectin expression.

Ischemia/reperfusion (I/R), a phenomenon that is associated with conditions such as organ transplantation, trauma, vascular disease, and stroke, involves the recruitment of activated and adherent leukocytes that subsequently mediate tissue injury. Endothelial cell adhesion molecules such as P-selectin mediate I/R-induced leukocyte recruitment and allow the adherent leukocytes to damage the vascular wall and parenchymal cells. This study examines the influence of dypiridamole (persantine) on hemorrhagic shock (H/S)-induced P-selectin expression. H/S was induced in C57BL/6 mice by withdrawing blood to drop the mean arterial blood pressure to 30 to 35 mm Hg for 45 minutes. The mice were resuscitated by infusing the shed blood and Ringer's lactate (50% shed blood volume). In vivo P-selectin expression was determined using a dual monoclonal antibody technique in the heart, lung, liver, kidneys, stomach, small bowel, and colon of a control group, a hemorrhagic shock group, and a hemorrhagic shock group that was pretreated with Persantine (Boehringer, Ingelheim, Ingelheim, Germany). H/S significantly (P < 0.01) increased P-selectin expression in all regional vascular beds of untreated mice. Persantine treatment largely prevented the H/S-induced P-selectin expression in the same vascular beds. Persantine significantly attenuates the upregulation of P-selectin in the hemorrhagic shock model.

Selective requirements for leukocyte adhesion molecules in models of acute and chronic cutaneous inflammation: participation of E- and P- but not L-selectin.

Adhesion molecules borne by both endothelial cells and circulating leukocytes are in large measure responsible for guiding the process of extravasation. The selectin family has been primarily associated with the early stages of adhesion involving initial contact and rolling. A significant body of evidence has accumulated indicating a fundamental role for the endothelial members of this family, E- and P-selectin, in a variety of inflammatory states and models. Although originally identified as the lymph node-specific lymphocyte homing receptor, L-selectin has also been suggested to play an important role in leukocyte recruitment to sites of inflammation. We have recently demonstrated, using L-selectin-deficient mice, that defects in contact hypersensitivity (CHS) responses are in essence due to the inability of T cells to home to and be sensitized within peripheral lymph nodes, whereas nonspecific effector cells are fully capable of entry into sites of cutaneous inflammation (Catalina et al, J Exp Med 184:2341, 1996). In the present study, we perform an analysis of adhesion molecule usage in two models of skin inflammation and show in both L-selectin-deficient as well as wild-type mice that a combination of P- and E-selectin is crucial for the development of both acute (croton oil) and chronic (contact hypersensitivity) inflammation at sites of the skin, whereas L-selectin does not appear to play a significant role. Moreover, alpha4 integrins are shown to be integral to a CHS but not an acute irritant response, whereas CD44 does not significantly contribute to either. These results provide a systematic examination in one study of major adhesion molecules that are critical in acute and chronic skin inflammation. They reinforce the essential role of the collaboration of E- and P-selectin in both specific and nonspecific skin inflammatory responses and the importance of alpha4 in the specific response only. In addition, they substantiate only a limited role, if any, for L-selectin in these cutaneous effector mechanisms and demonstrate the essential equivalence in this analysis of L-selectin-deficient mice compared with normal mice treated with blocking antibodies.

Effect of short-term treatment with a monoclonal antibody to P-selectin on balloon catheter-induced: intimal hyperplasia, re-endothelialization, and attenuation of endothelial-dependent relaxation.

The effects of an anti-P-selectin monoclonal antibody (MAb, PB1.3; Cytel Corporation) on neoendothelialization; neoendothelial function, as evidenced by acetylcholine-induced relaxation (nitric oxide formation); and intimal hyperplasia following embolectomy catheter-induced injury to the rabbit thoracic aorta were investigated. Catheter injury was induced in two groups of New Zealand White rabbits. One group received no treatment, while the second group received short-term treatment with the MAb (i.p., immediately before and 12 h after induction of catheter injury). A third group underwent a sham operation and served as uninjured controls. Following sacrifice at 2 weeks after injury, aortic rings were assessed for degree of intimal hyperplasia, neoendothelial morphology (scanning electron microscopy), and acetylcholine-induced relaxation. Aortic tissue from catheter-injured animals that received treatment exhibited improved neoendothelial morphology, as compared with tissue from untreated but catheterized animals; however, no statistically significant attenuation of the hyperplastic response or improvement in the attenuated neoendothelial-dependent acetylcholine-induced relaxant response that is characteristic of neoendothelium that forms after catheter denudation was observed. These data suggest that short-term attenuation of P-selectin-mediated polymorphonuclear leukocyte (PMN)/endothelium, PMN/platelet interactions, and/or thrombin formation beneficially affects neoendothelialization of the vascular wall following balloon catheter-induced injury.

Sialyl Lewis(x) analog improves liver function by decreasing neutrophil migration after hemorrhagic shock.

BACKGROUND: Little is known about the changes in the hepatic microcirculation and the leukocyte-endothelial adhesion processes during the early reperfusion period after resuscitation in hemorrhagic shock. P-selectin and its natural ligand Sialyl Lewis(x) (SLe(x)) are involved in the early stages of reperfusion events leading to neutrophil migration. Therefore, the aim of this study was to investigate the effect of the administration of CY-1503 [corrected], a synthetic SLe(x) analog, in the liver inflammatory response and neutrophil migration after hemorrhagic shock. MATERIALS AND METHODS: Rats, each weighing 275 to 300 grams, were subjected to 60 minutes of pressure controlled hemorrhagic shock. After this period, animals were resuscitated according to the following protocol: shed blood was reinfused to equal 50% of the total volume bled, and the other 50% was replaced with 3x volume of Ringer's lactated solution. Animals were divided into sham and two study groups to receive vehicle (controls) and CY-1503 [corrected] (10 mg/kg intravenously) diluted in 1 mL of normal saline 45 minutes after initiating hemorrhagic shock. The following parameters were analyzed: 7-day survival, liver injury tests, liver tissue myeloperoxidase as an index of neutrophil infiltration, and liver histology. RESULTS: Survival was significantly increased from 48% in the controls to 90% in the CY-1503 [corrected] treated group. Animals treated with the SLe(x) analog showed significantly better mean arterial blood pressure after 15 minutes after resuscitation. Also, the treated group showed a marked decrease in liver enzymes levels at 5 minutes and 4 hours after reperfusion. Neutrophil migration was significantly ameliorated as reflected by decreased myeloperoxidase levels in the SLe(x) analog treated group. Furthermore, we observed improved histologic damage scores in the treated group when compared with controls. CONCLUSIONS: The SLe(x) analog, CY-1503 [corrected], had a protective effect in ischemic livers by decreasing neutrophil migration after hemorrhagic shock and resuscitation. This protective effect also resulted in improved survival and mean arterial blood pressure after resuscitation.

Anti-P-selectin antibody decreases inflammation and thrombus formation in venous thrombosis.

PURPOSE: Venous thrombosis and inflammation are interrelated. P-selectin contributes to activation of leukocyte-mediated inflammation. Therefore, we hypothesized that the neutralization of P-selectin would decrease vein wall inflammation and thrombosis. METHODS: Twelve baboons underwent infrarenal inferior vena caval balloon occlusion to induce thrombosis. Two groups of four baboons received neutralizing intravenous anti-P-selectin antibody (PSab) GA6 or CY1748 before occlusion and at days 2 and 4. Four baboons received saline control injections. One baboon per group was killed at days 2, 6, and 13, and at 2 months. Analysis included phlebography, ultrasound, gadolinium (Gd)-enhanced magnetic resonance venography (reflecting vein wall inflammation), and histologic, morphometric, and protein evaluation of the vein wall. Thrombus presence or absence was assessed. RESULTS: By day 2 in PSab baboons, vein wall Gd enhancement was decreased in the mid-inferior vena cava and the right iliac vein (p < 0.05; GA6 vs control baboons), normalizing by 2 months. The mid-inferior vena cava revealed fewer neutrophils and total leukocytes in PSab baboons; however, for GA6 in the right iliac vein these decreases were not present despite the absence of Gd enhancement; they were decreased with CY1748. PSab baboons demonstrated significantly less thrombus than control baboons (p < 0.01, GA6 and CY1748 vs control baboons). CONCLUSIONS: Anti-P-selectin antibody decreases vein wall inflammation and thrombus formation. Inhibition of P-selectin may be useful in venous thrombosis prophylaxis.

Role of P-selectin in total hepatic ischemia and reperfusion.

BACKGROUND: Ischemia and reperfusion of the liver are associated with changes in the interaction of leukocyte-endothelium cells. The role of an adhesion molecule, P-selectin, is studied in ischemia and reperfusion injury of the liver. STUDY DESIGN: Total hepatic ischemia was produced in the rat for 90 minutes, using a portosystemic shunt. To determine the role of P-selectin in ischemia and reperfusion, a murine IgG1 monoclonal antibody to P-selectin (1 mg/kg) was used at different times (30 minutes before and at reperfusion and five minutes and 24 hours after reperfusion). Rats survived for seven days, and tests showing hepatic injury, myeloperoxidase in hepatic tissue, and histologic studies were analyzed at four hours postreperfusion. RESULTS: Survival improved from 15 percent for the rats in the ischemia control group to 55 percent for those in the group receiving anti-P-selectin antibody given 30 minutes before reperfusion (p < 0.05). We observed an improved statistically significant difference in tests demonstrating hepatic injury, myeloperoxidase in hepatic tissue, and histologic studies in the treated and ischemia control groups. The other groups did not show consistent significant differences. CONCLUSIONS: P-selectin has a significant role in ischemia and reperfusion injury of the liver. Early modulation of the interaction between P-selectin and its ligand decreased neutrophil adhesion and migration and consequently diminished damage to the liver.