Protective effects of ulinastatin on pulmonary damage in rats following scald injury

Organ protection is desirable in severe burn/scald injuries, and damage mechanisms and thus effective therapies following scald injury have not been fully elucidated. Our aim was to examine the beneficial effects of ulinastatin on pulmonary damage associated with scald injury. Lewis rats were subjected to 30% total body surface area (TBSA) scald injury and were randomly divided into a burn control (S group) and an ulinastatin-treated group (U group). Lung malondialdehyde (MDA) and superoxide dismutase (SOD) levels were determined, and the lungs were examined histologically with immunohistochemistry (IHC) as well for the major histocompatibility complex (MHC) class I chain-related antigen A (MICA) and Bcl-2 at 24, 48 and 72 h after the injury. The expression of spleen human leucocyte antigen-DR (HLA-DR) was detected by immunohistochemistry analysis. Selectins and adhesion molecules in lungs and serum were also detected. The lung injury degree was represented as wet/dry (W/D) values and alveolar thickness. Ulinastatin decreased MDA levels and ameliorated the down-regulation of SOD activity. MICA was up-regulated after the scald, and this up-regulation was greatly diminished by ulinastatin. Bcl-2 was up-regulated after the scald, especially in the U group. The spleen HLA-DR expression demonstrated the immunoregulatory effects of ulinastatin, which effectively protected the pulmonary tissues from scald-induced injury. Our results demonstrated that pulmonary damage was associated with autoimmunity and oxidant attack after severe scald. Ulinastatin exhibits significant protective effects on these effects.

Selectin Inhibition Modulates NF-κ B and AP-1 Signaling After Liver Ischemia/Reperfusion

The infiltration of neutrophils after ischemia and reperfusion (I/R) is facilitated by the expression of adhesion molecules on the surface of both leukocytes and endothelial cells. Adhesion molecules of the selectin family are of particular importance at the onset of neutrophil mediated injury, as demonstrated by the occurrence of many cellular interactions with the final extravasation of inflammatory leukocytes at the site of I/R damage. Previous studies demonstrated a prevention of neutrophil extravasation and protection of ischemic damage when a small anti-selectin molecule was used. In this study, we tested a new small anti-selectin compound (OC-229) in a murine model of partial hepatic I/R. The aim of this study was to determine the effect of OC-229 on liver function and histology after I/R and to evaluate its role in the modulation of the inflammatory molecular signaling pathways of NF-kappa B and AP-1 under the same experimental condition. Mice subjected to 90 min of partial (70-80%) hepatic ischemia and 3 h of reperfusion were divided into three groups (n = 9/group): sham, ischemic control, and treated group, which received 25 mg/kg of the anti-selectin small molecule OC-229. These groups were studied when the treatment was given at the time of reperfusion (no pretreatment was given). The parameters measured at 3 h of reperfusion included liver function tests (ALT and AST), liver histology, and liver tissue electrophoretic mobility shift assay (EMSA) for NF-kappa B and AP-1. It was demonstrated that the multiselectin inhibitor OC-229 offered significant protection for the ischemic liver when given at 25 mg/kg at the time of reperfusion. ALT and AST serum levels significantly decreased when the ischemic control and the group receiving OC-229 were compared (p = .01). Treated animals demonstrated better histological findings as well. The EMSA showed dissociation of NF-kappa B and AP-1 activity in the liver nuclear extracts after selectin inhibition treatment. A reduction in the activity of AP-1 and an increment in NF-kappa B activation was seen. In this work, we obtained evidence that the small-molecule selectin inhibitor OC-229 offered functional and histological protection of the ischemic liver when given at 25 mg/kg at the time for reperfusion. There was dissociation in the activation signals of NF-kappa B and AP-1. Increase in NF-kappa B and reduction of the activation of AP-1 were noted at 3 h of reperfusion.

Non-anticoagulant heparins and inhibition of cancer

Low-molecular-weight heparins (LMWH) appear to prolong survival of patients with cancer. Such a beneficial effect is thought to be associated with interruption of molecular mechanisms involving the heparan sulfate (HS) chains of cell surface and extracellular matrix proteoglycans (HSPGs), growth factors and their receptors, heparanase, and selectins. The beneficial effects of heparin species could also be associated with their ability to release tissue factor pathway inhibitor from endothelium. The utility of heparin and LMWH as anticancer drugs is limited due to their anticoagulant properties. Non-anticoagulant heparins can be obtained either by removing chains containing the antithrombin-binding sequence, or by inactivating critical functional groups or units of this sequence. The non-anticoagulant heparins most extensively studied are regioselectively desulfated heparins and 'glycol-split' heparins. Some modified heparins of both types are potent inhibitors of heparanase. A number of them also attenuate metastasis in experimental models. With cancer cells overexpressing selectins, heparin-mediated inhibition of tumor cells-platelets aggregation and tumor cell interaction with the vascular endothelium appears to be the prevalent mechanism of attenuation of early stages of metastasis. The structural requirements for inhibition of growth factors, heparanase, and selectins by heparin derivatives are somewhat different for the different activities. An N-acetylated, glycol-split heparin provides an example of application of a non-anticoagulant heparin that inhibits cancer in animal models without unwanted side effects. Delivery of this compound to mice bearing established myeloma tumors dramatically blocked tumor growth and progression.

Therapeutic potential of selectin antagonists in psoriasis

Psoriasis is a systemic chronic inflammatory disorder. One of the major characteristics is an excess of infiltration of inflammatory cells, mainly lymphocytes, into the skin. Because the adhesion family of selectins is suggested to play a relevant role in this process, selectins have emerged as an interesting target for drug discovery and development in psoriasis. Different strategies targeting selectins have been described. This review discusses these approaches and summarises the current development of selectin antagonists for the treatment of psoriasis. An expert opinion will give the authors' personal opinion about selectin antagonism in psoriasis and which approach might be preferable.

5-HT acts on nociceptive primary afferents through an indirect mechanism to induce hyperalgesia in the subcutaneous tissue

We have recently demonstrated that s.c.-injected 5-hydroxytryptamine (5-HT) induces nociception by an indirect action on the primary afferent nociceptor in addition to its previously described direct action. Although the mechanisms mediating hyperalgesia can be quite separate and distinct from those mediating nociception, the aim of this study was to test the hypothesis that 5-HT induces mechanical hyperalgesia by mechanisms similar to those mediating nociception. s.c. injection of 5-HT induced a dose-dependent mechanical hyperalgesia measured by the mechanical paw withdrawal nociceptive threshold test in the rat. 5-HT-induced hyperalgesia was significantly reduced by local blockade of the 5-HT(3) receptor by tropisetron, by the nonspecific selectin inhibitor fucoidan, by the cyclooxygenase inhibitor indomethacin, by guanethidine depletion of norepinephrine in the sympathetic terminals, and by local blockade of the beta(1)- or beta(2)-adrenergic receptor by atenolol or ICI 118,551, respectively. Taken together, these findings indicate that like nociception, hyperalgesia induced by the injection of 5-HT in the s.c. tissue is also mediated by an indirect action of 5-HT on the primary afferent nociceptor. This indirect hyperalgesic action of 5-HT is mediated by a combination of mechanisms involved in inflammation such as neutrophil migration and the local release of prostaglandin and norepinephrine. However, in contrast to nociception, hyperalgesia induced by 5-HT in the s.c. tissue is mediated by a norepinephrine-dependent mechanism that involves the activation of peripheral beta(2) adrenoceptors.

The pharmacokinetics of subcutaneously injected bimosiamose disodium in healthy male volunteers

Bimosiamose is a novel synthetic pan-selectin antagonist developed for the treatment of acute and chronic inflammatory disorders. Therefore the pharmacokinetics of Bimosiamose disodium were studied in healthy male volunteers after single and multiple subcutaneous injections. A randomized, double-blind, placebo-controlled dose escalation trial was carried out. The subjects received subcutaneous injections of placebo or 100, 200 or 300 mg Bimosiamose disodium into the abdomen. Plasma and urine concentrations of Bimosiamose were determined. The maximum plasma concentration was 2.17+/-0.70 microg/ml and the AUC(0-infinity) 11.1+/-2.9 h microg/ml after the highest dose on day 1 (mean+/-SD). For the apparent clearance CL/f 28.7+/-7.3 l/h and the terminal half life t(1/2) 3.7+/-0.6 h were calculated. The mean residence time MRT(infinity) of 5.5 to 6.3 h for s.c. injection exceeded that after i.v. infusion due to an extended absorption time. For multiple dosing, constant pre-dose concentrations of about 20 ng/ml may be reached after two subsequent doses of 200 or 300 mg Bimosiamose disodium once daily. Almost 15% of the administered drug was excreted unchanged in urine. Moreover, Bimosiamose was well tolerated.

Targeting leukocyte trafficking to inflamed skin - still an attractive therapeutic approach?

Research into leukocyte trafficking and its therapeutic exploitation appears to be a multistep process, just like the trafficking cascade itself. The initial euphoria evoked by an early understanding of the trafficking steps was followed by considerable disappointment following the clinical failure of the first selectin antagonist Cylexin (CY-1503), a sialyl Lewis(X) mimetic. The research area recovered and identified additional attractive pharmacological targets such as chemokine receptors and integrins. However, after lack of efficacy in anti-chemokine trials and the fatalities associated with anti VLA-4 therapy (Tysabri), the question arose again whether targeting leukocyte trafficking is really promising or whether such a complex, multistep process with many redundant and/or functionally overlapping molecules is simply too challenging to deal with. In this article, we delineate some pros and cons of this approach followed by a brief update on where we stand in the field and where we might move in the future.

Mechanisms of heparin induced anti-cancer activity in experimental cancer models

BACKGROUND

Retrospective analyses of clinical trials and prospective clinical studies have suggested that heparins may have an effect on cancer survival. This putative anti-cancer activity of heparins is supported by data from studies in animal tumour models.

OBJECTIVE

To clarify the various potential mechanisms of heparin anti-cancer activity we evaluated the data from pre-clinical studies in which heparins have been tested as anti-cancer therapy.

METHODS

Pre-clinical studies, published between 1960 and 2005 were assessed. Data were collected on the type and dose of heparin used, duration of exposure to heparin, interval between heparin administration and cancer cell inoculation, and the animal tumour model used. In addition, a distinction was made in the analysis between heparin effects on the primary tumour or on established metastases and effects on the metastatic potential of infused cells.

RESULTS

Heparins seemed to affect the formation of metastasis rather than the growth of primary tumours. Chemically modified heparins with no or limited anticoagulant activity also showed anti-metastatic properties. Possible mechanisms to explain the effects on the process of metastases include inhibition of blood coagulation, inhibition of cancer cell-platelet and -endothelial interactions by selectin inhibition and inhibition of cell invasion and angiogenesis.

CONCLUSION

The anti-cancer activity of heparins depends more on inhibition of metastasis formation than on the effects on primary tumour growth. These effects are probably related to both coagulation and non-coagulation dependent factors. For a definitive proof of the anti-cancer activity of heparins in the clinic, prospective randomized trials especially in patients with early metastatic disease or in the adjuvant setting are urgently needed.

Protective role of selectin ligand inhibition in a large animal model of kidney ischemia-reperfusion injury

Experiments in rodents have demonstrated an important role for selectins in kidney ischemia-reperfusion injury (IRI). However, the relevance of this in larger mammals, as well as the impact on long-term structure and function is unknown. We tested the hypothesis that small molecule selectin ligand inhibition attenuates IRI, cellular inflammation, and long-term effects on renal interstitial fibrosis. We used a porcine model of kidney IRI and used Texas Biotechnology Corporation (TBC)-1269, a selectin ligand inhibitor. Renal function, tissue inflammation, and tubulointerstitial fibrosis development were evaluated up to 16 weeks. Both warm and cold ischemia models were studied for relevance to native and transplant kidney injury. Pigs treated with TBC-1269 during 45 min of warm ischemia (WI) showed significantly increased glomerular filtration rate compared to control animals. In pigs with severe IRI (WI for 60 min), TBC-1269 treatment during IRI significantly increased renal recovery. Cellular inflammation was strongly reduced, particularly influx of CD4 cells. Quantitative measurement of fibrosis by picrosirius red staining showed strong reduction in TBC-1269-treated groups. TBC-1269 also reduced cold IRI, inflammation, and fibrosis in kidneys preserved for 24 h at 4 degrees C and autotransplanted. The selectin ligand inhibitor TBC-1269 provides a novel and effective approach to attenuate IRI in both warm and cold ischemia in large mammals, in both short and long terms. Selectin ligand inhibition is an attractive strategy for evaluation in human kidney IRI.

Selectins--potential pharmacological targets?

Recent advances in our (patho)physiological understanding have underpinned the frequent involvement of the protein family of selectins in the progression of serious illnesses, including cancer and cancer metastasis, and immunological diseases, such as asthma, allergy and autoimmune reactions. Moreover, selectins seem to have a role in post-ischemic damage and during transplant failures (e.g. in graft-versus-host disease). Although the interplay between selectins and their counter-receptors and ligands is not always primarily involved in the development of these pathological conditions, selectins have been investigated as potential therapeutic targets for therapeutic intervention. This review focuses on the latest trends and developments in anti-selectin antibodies, anti-selectin receptor antibodies, recombinant selectin counter-receptors, low molecular weight selectin antagonists (glycomimetics), induction of selectin tolerance and selectin-targeted imaging agents.

Therapeutic targeting of molecules involved in leukocyte-endothelial cell interactions

Inflammation is traditionally viewed as a physiological reaction to tissue injury. Leukocytes contribute to the inflammatory response by the secretion of cytotoxic and pro-inflammatory compounds, by phagocytotic activity and by targeted attack of foreign antigens. Leukocyte accumulation in tissues is important for the initial response to injury. However, the overzealous accumulation of leukocytes in tissues also contributes to a wide variety of diseases, such as atherosclerosis, chronic inflammatory bowel disease, rheumatoid arthritis, multiple sclerosis, vasculitis, systemic inflammatory response syndrome, juvenile diabetes and psoriasis. Many therapeutic interventions target immune cells after they have already migrated to the site of inflammation. This review addresses different therapeutic strategies, used to reduce or prevent leukocyte-endothelial cell interactions and communication, in order to limit the progression of inflammatory diseases.

Structure–Function Relation of Efomycines, a Family of Small-Molecule Inhibitors of Selectin Functions

Selectin-mediated leukocyte adhesion to endothelia, the crucial first step initiating the pathogenic cascade of inflammation, is an attractive target for specific therapies. The small-molecule macrolide, efomycine M, inhibits selectin-mediated leukocyte adhesion in vitro and in vivo, and effectively alleviates inflammatory disorders in vivo. To define the molecular basis of the therapeutically relevant antiadhesive properties of efomycines, several new species of this family were purified and/or synthesized. Efomycines E and G were isolated from Steptomyces BS1261. Efomycine O was synthesized by Lewis acid-catalyzed acetalization and efomycine M was generated by base-catalyzed deglycosylation. Efomycine S resulted from ester cleavage of the macrolide ring system, and efomycine T represents the peracetylated form of efomycine M. When the functional activity of efomycines on adhesion of leukocytes to vascular endothelium was studied, some remarkable differences between the compounds became apparent, inasmuch as efomycines E, G, M, and O significantly inhibited adhesion of both human and porcine leukocytes to the vascular endothelium, whereas efomycines S and T did not show any biological activity. A novel docking engine (ProPose), generating an improved, fully configurable protein-ligand interaction model, demonstrated that biological activities of efomycines can be predicted in silico, thus highlighting the utility of such combinatorial approaches.

Blocking of leukocyte accumulation in the cerebrospinal fluid augments bacteremia and increases lethality in experimental pneumococcal meningitis

The role of leukocyte accumulation in the cerebrospinal fluid (CSF) in the evolution of the pathophysiological changes that occur in bacterial meningitis is unclear. Here, we investigate how leukocyte recruitment to the CSF, modulated by the leukocyte blocker fucoidin, affects the extent of brain damage and outcome in pneumococcal meningitis in rats treated with ceftriaxone from 28 h after infection. Rats treated with fucoidin from time of infection had an excess risk of a fatal outcome compared to rats not receiving fucoidin (25/63 versus 5/34, p=0.012), whereas the risk of cortical damage in surviving animals was comparable (16/44 versus 9/29, p=0.8). Pre-treatment with fucoidin attenuated CSF pleocytosis 24 h after infection (median 400 versus 800x10(6) cells/l, p=0.01) without affecting CSF bacterial counts (2.3x10(5) versus 3.6x10(5) CFU/ml, p=0.54). A significant increase in blood bacterial counts was found among rats pre-treated with fucoidin (median 9.6x10(2) versus 5.2x10(2) CFU/ml, p=0.03). Furthermore, blood bacterial count was found to be an important predictor of fatal outcome as shown by multivariate logistical regression analysis (OR 4.43, 95% CI [1.16-17.0] p=0.03). In summary, blocking leukocyte entry to the central nervous system in experimental pneumococcal meningitis compromises the survival prognosis but does not affect the risk of brain damage or level of infection in this compartment. Conversely, poorer prognosis was associated with an increase in bacterial load in blood, suggesting that leukocyte blockage affects the host's ability to control systemic infection.

Antagonism of selectin function attenuates microvascular platelet deposition and platelet-mediated myocardial injury after transient ischemia

OBJECTIVES

The goal of this study was to assess whether selectin blockade reduces myocardial platelet deposition and platelet-mediated injury after transient ischemia.

BACKGROUND

Selectins participate in platelet adhesion to reperfused endothelium.

METHODS

Thiopental-anesthetized, open-chest pigs were subjected to mechanical injury of the left anterior descending coronary artery followed by a 48-min occlusion and 2 (n = 20) or 4 (n = 16) h of reperfusion. Fifteen minutes before occlusion, animals were blindly allocated to receive a continuous intravenous infusion of the selectin blocker fucoidan (30 microg/kg/min, plus a 1-mg/kg bolus in the latter group) or saline. In isolated rat hearts infused with thrombin-activated platelets, the effects of fucoidan (30 microg/ml) administered during reperfusion after 40 min of global ischemia were also analyzed.

RESULTS

Fucoidan did not prevent the development of cyclic reductions in coronary flow, but reduced the content of (99m)Tc-labeled platelets in reperfused myocardium after 2 h of reperfusion (23.4 +/- 3.3 vs. 42.1 +/- 8.3 x 10(6) platelets/g in treated and untreated animals, p = 0.03) and attenuated the impairment in the coronary flow reserve and reduced infarct size after 4 h (53 +/- 2% vs. 73 +/- 5% of the ischemic region, respectively, p = 0.003). Treated animals showed a trend toward less neutrophil infiltration early after reperfusion, but not after 4 h. In isolated hearts, fucoidan improved functional recovery and reduced coronary resistance and lactate dehydrogenase release, lacking any beneficial effects if given in the absence of platelets.

CONCLUSIONS

The results suggest that selectin-dependent adhesion is a prominent mechanism of platelet deposition in reperfused cardiac microvessels and highlight its potential as a therapeutic target in patients with acute myocardial infarction.

Sulfated Hyaluronic Acid, a Potential Selectin Inhibitor, Ameliorates Experimentally Induced Crescentic Glomerulonephritis

BACKGROUND/AIMS

Sulfated polysaccharides are known to interfere with the binding of selectins and their ligands. Recently, we demonstrated that sulfated hyaluronic acid (SHA), a synthetic sulfated polysaccharide, showed preventive and therapeutic effects on experimental mesangial proliferative glomerulonephritis. Here we evaluated the protective potential of SHA on crescentic glomerulonephritis, using nephrotoxic serum (NTS) nephritis in Wistar-Kyoto (WKY) rats.

METHODS

Crescentic glomerulonephritis was induced by injection of NTS in WKY rats. Rats subsequently received intraperitoneal administration of SHA (0.5 or 1.5 mg/kg/day) or non-sulfated hyaluronic acid (HA) (1.5 mg/kg/day) for 14 days. The urinary protein excretion was measured, and expression of selectins, intraglomerular leukocytes and crescent formation were examined by immunohistochemistry. In addition, we examined the urinary protein excretion of SHA (1.5 mg/kg/day) administered from day 7 after the induction of crescentic glomerulonephritis.

RESULTS

The expression of P-selectin was increased in the glomerulus of crescentic glomerulonephritis. SHA reduced proteinuria, macrophage infiltration, and crescent formation in a dose-dependent manner. Furthermore, administration of SHA (1.5 mg/kg/day) from day 7 also reduced the urinary protein excretion on day 14 compared with that in saline and HA group.

CONCLUSION

Our results suggest that SHA inhibits intraglomerular infiltration of macrophages, and prevents progression of experimental crescentic glomerulonephritis. Sulfated polysaccharides might be beneficial for the treatment of crescentic glomerulonephritis.

Analysis of leukocyte rolling and migration--using inhibitors in the undisturbed microcirculation of the rat mesentery--on inflammatory stimulation

AIM

Our aim was to develop a method of migration analysis using the undisturbed microcirculation of rat mesentery, and using the new method, analyze leukocyte migration in casein-induced inflammation.

METHOD

Sprague Dawley (SD) rats were injected with tumor necrosis factor (TNF) alpha, interleukin (IL)-1alpha, or casein intraperitoneally. Following this, the rats were sacrificed and the mesentery tissue removed was fixed and stained with Giemsa. The leukocytes were counted as a rolling index in the venules and as a migration index in the perivascular area.

RESULTS

There was no relation between the diameter of venules and leukocyte migration. The time change curves of leukocyte activity in casein inflammation show about a 1 h difference between rolling and migration. From inhibitor experiments of casein-induced migration at 2 h, it has been suggested that selectin-related rolling is necessary. Platelet-activating factor (PAF) also appears partially involved.

CONCLUSION

The improved undisturbed microcirculation method is helpful not only for rolling analysis but also in analysis of leukocyte migration. Casein inflammation analyzed using this method revealed that rolling is necessary and also suggested that partial involvement of PAF is necessary for pathogenesis of leukocyte extravasations.

Selectins and integrins but not platelet-endothelial cell adhesion molecule-1 regulate opioid inhibition of inflammatory pain

1. Control of inflammatory pain can result from activation of opioid receptors on peripheral sensory nerves by opioid peptides secreted from leukocytes in response to stress (e.g. experimental swim stress or surgery). The extravasation of immunocytes to injured tissues involves rolling, adhesion and transmigration through the vessel wall, orchestrated by various adhesion molecules. 2. Here we evaluate the relative contribution of selectins, integrins alpha(4) and beta(2), and platelet-endothelial cell adhesion molecule-1 (PECAM-1) to the opioid-mediated inhibition of inflammatory pain. 3. We use flow cytometry, double immunofluorescence and nociceptive (paw pressure) testing in rats with unilateral hind paw inflammation induced by complete Freund's adjuvant. 4. In inflamed tissue, 43-58% of hematopoietic cells (CD45(+)) expressed opioid peptides. L-selectin and beta(2) were coexpressed by 7 and 98% of opioid-containing leukocytes, respectively. Alpha(4) integrin was expressed in low levels by the majority of leukocytes. Opioid-containing cells, vascular P- and E-selectin and PECAM-1 were simultaneously upregulated. 5. Swim stress produced potent opioid-mediated antinociception in inflamed tissue, unaffected by blockade of PECAM-1. However, blockade of L- and P-selectins by fucoidin, or of alpha(4) and beta(2) by monoclonal antibodies completely abolished peripheral stress-induced antinociception. This coincided with a 40% decrease in the migration of opioid-containing leukocytes to inflamed tissue. 6. These findings establish selectins and integrins alpha(4) and beta(2), but not PECAM-1, as important molecules involved in stress-induced opioid-mediated antinociception in inflammation. They point to a cautious use of anti-inflammatory treatments applying anti-selectin, anti-alpha(4) and anti-beta(2) strategies because they may impair intrinsic pain inhibition.

Development of cell adhesion molecule antagonists as therapeutics for asthma and COPD

Airway inflammation is a hallmark of respiratory diseases such as asthma and chronic obstructive pulmonary disease. Cell adhesion molecules play critical roles in the recruitment and migration of cells to sites of inflammation. Not surprisingly, these receptors have garnered the attention of the pharmaceutical industry as targets for the development of drugs to treat inflammatory and autoimmune diseases. Although several potential cell adhesion targets exist, development of compounds for pulmonary indications has centered around the selectins and the integrin VLA-4. In vitro and in vivo studies have implicated these receptors in the recruitment of inflammatory cells to the lung as well as to key cellular activation pathways. Several first generation compounds are currently in clinical development for asthma. Positive data from a phase II clinical trial using an inhaled formulation of a selectin antagonist has recently been reported. Initial results from clinical trials using first generation VLA-4 antagonists have been less promising but additional trials with more fully optimized compounds are underway. Results from these trials will provide insight into what the future holds for this exciting new class of drugs to treat pulmonary diseases.

Recent progress in the design of selectin inhibitors

The selectins are a family of cell-adhesion proteins that mediate the early stages of leukocyte recruitment from the blood stream to sites of tissue damage through recognition of the carbohydrate epitope sialyl Lewis(x) (sLe(x)). Current development of small molecule based inhibitors of this process and their clinical potential to address numerous acute and chronic diseases are explored.

Molecular mechanisms of leukocyte recruitment in postischemic liver microcirculation

Evidence shows that leukocyte recruitment into inflamed liver sinusoids does not require selectins, with one notable exception: ischemia-reperfusion (I/R). We used intravital microscopy to directly visualize the liver microcirculation during I/R and localized endotoxemia (liver superfused with lipopolysaccharide). General anti-selectin therapy (fucoidan) or anti-adhesion therapy with an antithrombin inhibitor (hirudin) was also used. Many neutrophils rolled and adhered in postsinusoidal vessels and sequestered in the sinusoids during I/R and local endotoxin superfusion. Although fucoidan blocked rolling in both forms of inflammation, leukocyte recruitment into sinusoids was only blocked in I/R. Adhesion was also inhibited in postischemic sinusoids with a second anti-adhesive agent (hirudin). Because liver I/R inevitably induces ischemia upstream in the intestine, anti-selectin therapy may prevent intestinal injury, which could prevent downstream liver inflammation. To test this hypothesis, we completely removed the intestine and rerouted blood flow from the superior mesenteric artery to the superior mesenteric vein. I/R was induced in the liver microcirculation, and many leukocytes rolled and adhered in postsinusoidal venules and adhered in sinusoids. Although fucoidan significantly reduced the rolling in postsinusoidal vessels, adhesion persisted in the sinusoids. Our data suggest that anti-adhesion therapy is effective in liver I/R in the sinusoids and postsinusoidal venules, perhaps in part due to its beneficial effect on the intestine.

Small molecule selectin ligand inhibition improves outcome in ischemic acute renal failure

BACKGROUND

The pathophysiologic and potential therapeutic role of selectins in renal ischemia-reperfusion injury (IRI) is not fully understood, due in part to redundancy in the roles of individual selectins. We hypothesized that blockade of ligands for all three selectins using a novel small molecule (TBC-1269) would improve the course of renal IRI by overcoming redundancy issues. This was investigated in a rat model of renal IRI.

METHODS

Rats were treated with TBC-1269 either during or post-IRI. The effects of TBC-1269 were investigated in two models of renal IRI: moderate IRI (30 minutes bilateral renal artery clamping) and severe IRI (45 minutes clamping). The combination of anti-E- and anti-P-selectin antibodies also was investigated in rats subjected to moderate IRI. Renal function, histological injury and mortality were assessed.

RESULTS

Rats treated with TBC-1269 during moderate IRI showed significantly reduced serum creatinine (SCr) and tubular necrosis post-ischemia compared to control animals. By contrast, delayed treatment (post-IRI) did not show a reduction in SCr. In rats with severe IRI, TBC-1269 treatment during IRI significantly reduced mortality at 48 hours post-ischemia. Rats with moderate IRI and treated with the combination of anti-E- and anti-P-selectin antibodies showed significantly reduced SCr compared to control rats at 24 hours post-ischemia.

CONCLUSIONS

Small molecule selectin ligand inhibition provides a novel and effective approach to attenuate ischemic acute renal failure. Timing of treatment is crucial to success.

Carbohydrates and derivatives as potential drug candidates with emphasis on the selectin and linear-B area

Enzymatic carbohydrate synthesis using glycosyltransferases is highly regio- and stereospecific and does not require extensive protecting group designs. Naturally occurring carbohydrates have been prepared by this biomimetic pathway successfully. As more and more transferases are isolated and get cloned and overexpressed, non-natural substrates were probed with these biocatalysts. Key-polar groups and non-essential residues of the substrates have been determined. Consequently, this technique was employed to generate natural and non-natural carbohydrate libraries for pharmaceutical purposes. The synthesis of sialyl-Lewis(a)- and sialyl-Lewis(x) libraries and non-natural Linear-B derivatives applying glycosyltransferases is presented in this article. The respective transferases investigated are alpha(1-3)galactosyltransferase, beta(1-3)galactosyltransferase, beta(1-4)galactosyltransferase, alpha(2-3)sialyltransferase, alpha(1- 3)fucosyltransferase III and alpha(1-3)fucosyltransferase VI. With respect to the natural acceptors, the aglycon part and the N-acetyl group of the glucosamide have been varied. All enzymes tolerate an unexpected wide range of non-natural acceptors, which is not yet exploited in its full scale. In addition, fucosyltransferase III and VI can be employed to convert also non-natural donors with non-natural acceptors at the same time. Thus sialyl- Lewis(a)- and sialyl-Lewis(x)-libraries which differ in three positions compared to the natural tetrasaccharides are generated very efficiently. Also a library of linear-B trisaccharides, a reactive xenoantigen, has been prepared enzymatically. The aglycon part and the natural N-acetyl group of the glucosamine which is part of the acceptor substrate have been altered widely. This convenient methodology is compared with the evolving solid-phase carbohydrate synthesis using conventional chemistry. The potential use of transferases in solid-phase carbohydrate chemistry is discussed together with the possibility to use these biocatalysts to synthesize carbohydrate mimetics. The presented findings may also be useful to design potential glycosyltransferase inhibitors.

Pharmacodynamic characterization of the interaction between abciximab or tirofiban with unfractionated or a low molecular weight heparin in healthy subjects

AIMS

The objective of our study was to define the interaction between either unfractionated heparin (UFH) or a low molecular weight heparin, reviparin (REV), and the pharmacodynamic profile of the GPIIb/IIIa-antagonists abciximab (ABC) or tirofiban (T).

METHODS

Two studies each containing 18 healthy subjects were performed, and all were pretreated with aspirin (ASA) for 3 days. Volunteers then received UFH (5000 IU bolus/infusion 7 IU kg(-1) h(-1) for 7 h, n = 6), REV (4200-anti-Xa-IU s.c., n = 6) or placebo (n = 6). One hour later, ABC (study I) or T (study II) were given by i.v. infusion for 6 h. The pharmacodynamic effects measured were bleeding time (BT), fibrinogen-binding at the GPIIb/IIIa-receptor (FIB), expression of the platelet secretion marker CD62, and ADP (20 microM)- and collagen (5 microg ml(-1))-induced platelet aggregation.

RESULTS

After treatment with both GPIIb/IIIa-antagonists, prolongation of BT occurred to a similar magnitude (approximately 25-30 min) and was not affected by UFH or REV-comedication. ABC or T with ASA alone resulted in nearly the same magnitude of reduction in FIB and platelet aggregation. After coadministration with UFH, FIB was significantly higher (thus less inhibited) than after after T + ASA alone (19 +/- 16% vs 55 +/- 36%) or ABC + ASA alone (8 +/- 9% vs 32 +/- 11%). This attenuation of FIB was not seen with REV. Inhibition of ADP-and collagen-induced aggregation tended to be attenuated by treatment with UFH (e.g. ADP-induced aggregation at 0.25 h after ABC + ASA alone =13 +/- 4%; after coadministration with UFH = 40 +/- 26%). No such changes were noted with REV. Minor reductions in CD62-expression were seen in subjects given ABC or T alone, but expression was not affected by UFH or REV.

CONCLUSIONS

Co-medication with UFH attenuated platelet inhibition during treatment with GPIIb/IIIa-antagonists, but these effects were not seen with the low molecular weight heparin reviparin. The results show that administration of reviparin together with abciximab or tirofiban did not adversely affect the pharmacodynamic profile of these GPIIb/IIIa-antagonists.

Effects of a new synthetic selectin blocker in an acute rat thrombotic glomerulonephritis

In an attempt to explore a novel therapeutic approach, a new synthetic sulfatide derivative (SKK60037) was evaluated in an acute rat model of P-selectin and leukocyte-dependent thrombotic glomerulonephritis (TG). In vitro, SKK60037 inhibits the function of P- and L-selectin more effectively than sialyl Lewis X (sLe(x)), a well-established selectin blocker. TG was induced by the intravenous administration of nephrotoxic globulin (NTG) to rats pretreated with a subclinical dose of lipopolysaccharide. In this model, platelet accumulation was remarkable within 10 minutes after induction of disease, followed by the infiltration of leukocytes, mainly neutrophils and macrophages. Thrombus formation and fibrinogen deposition in the glomeruli were observed within 1 hour, and they proceeded until 6 hours. P-selectin was highly expressed in glomeruli, whereas E-selectin and L-selectin ligands were not detected. We tested the effects of SKK60037 in this model in comparison with sLe(x) and antirat P-selectin monoclonal antibody (ARP2-4). SKK60037 blocked platelet accumulation in glomerular capillaries at 10 minutes after NTG injection. At 6 hours, leukocyte infiltration and thrombosis were significantly suppressed. Protective effects of SKK60037 were similar to those of ARP2-4, whereas sLe(x) showed minimum effect. The superior effects and more favorable characteristics of SKK60037 to sLe(x) suggest the potential of SKK60037 for clinical application.

Protein C anticoagulant pathway and its role in controlling microvascular thrombosis and inflammation

OBJECTIVE

To review the physiologic and biochemical mechanisms that suggest that protein C and activated protein C (APC) have unique properties that make them good candidates for the treatment of microvascular thrombosis, disseminated intravascular coagulation, and sepsis.

DATA SOURCES

A summary of published medical literature from MEDLINE search files and published reviews on protein C physiology, biochemical properties, and activity in experimental and human sepsis.

DATA SUMMARY

Protein C is critical to the regulation of microvascular coagulation, as seen most clearly in humans born with congenital deficiency of protein C, who develop neonatal purpura fulminans. Protein C supplementation reverses the lesion formation. In primate models of sepsis, APC blocks disseminated intravascular coagulation initiated by Escherichia coli infusion, and inhibition of APC function exacerbates both the coagulant and inflammatory responses of the animals to sublethal levels of E. coli. In vitro experiments have shown that APC can inhibit neutrophil binding to selectins: Endothelial cell protein C receptor, a protein C/APC binding receptor, can bind to proteinase 3 bound to Mac-1 on leukocytes, potentially blocking tight leukocyte adhesion; and APC can inhibit tumor necrosis factor-alpha secretion by monocytes and other cell lines by interfering with nuclear factor-kappaB nuclear translocation. By blocking nuclear factor-kappaB nuclear translocation, cytokine- and endotoxin-mediated adhesion molecule up-regulation is decreased. These properties of APC are consistent with a large number of animal studies demonstrating that APC can diminish complications of crush injury and leukocyte damage to lung and other tissues in response to sepsis and decrease the inflammatory response. The animal studies are consistent with the phase 2 studies reported on APC use in the treatment of human sepsis.

CONCLUSIONS

The protein C pathway is uniquely poised to interfere with the microvascular coagulation and inflammation that follows challenge with endotoxin. By limiting leukocyte activation, cytokine elaboration, and microvascular coagulation, APC has been shown to prevent organ damage in experimental models of sepsis. These results are consistent with the initial phase 2 reports of APC therapy in human sepsis suggesting a clinical benefit and demonstrating anti-inflammatory activity with several reports of apparent protein C effectiveness in severe sepsis, especially meningococcemia.

Analysis of increased leukocyte ratio induced by tumor necrosis factor-alpha using several inhibitors in the undisturbed microcirculation of the rat mesentery

Increased leukocyte ratio induced by intraperitoneal injection of TNF-alpha was analyzed in undisturbed rat mesentery venules, a long-term experimental model. TNF-alpha induced a biphasic increase in PMNL ratio in the mesentery venules; in particular, there was a large increase in PMNL ratio 3 h after injection of TNF-alpha. Anti-P and anti-L-selectin compounds, fucoidin and dextran sulfate, inhibited the PMNL ratio by about 40%. Dexamethasone completely inhibited the increased ratio. These results suggest that all selectins may be involved in the increased ratio, i.e. rolling and adhesion reaction.

Development of potent non-carbohydrate imidazole-based small molecule selectin inhibitors with antiinflammatory activity

A novel series of non-carbohydrate imidazole-based selectin inhibitors has been discovered via high-throughput screening using a P-selectin ELISA-based assay system. The initial lead 1 had an IC(50) of 17 microM in the P-selectin ELISA; this potency was significantly improved via an extensive SAR exploration. One of the current lead compounds (29) has an IC(50) of 300 nM in a P-selectin ELISA; it also has good activity in P- and E-selectin cell adhesion assays and shows efficacy in vivo. These compounds represent a novel series of sLe(X) mimetics with antiinflammatory activity. Their unique profile supports our interest in their further evaluation as drug candidates for the treatment of inflammation. Herein we describe the syntheses, optimization, and SAR of this series of novel potent selectin antagonists.

Studies on selectin blocker. 9. SARs of non-sugar selectin blocker against E-, P-, L-selectin bindings

As a part of study of selectin blockers, we have already reported that a non-sugar selectin antagonist (3) was successfully discovered using a computational screening (Hiramatsu, Y.; Tsukida, T.; Nakai, Y.; Inoue, Y.; Kondo, H. J. Med. Chem. 2000, 43, 1476). To investigate the SARs of compound 3 against E-, P-, and L-selectins, we synthesized the derivatives of compound 3 and evaluated their inhibitory activities toward selectin bindings. The structural diversity of compound 3 contained the following: (1) a modification of the spacer unit (4--7), (2) a modification of the tail unit (8--11), (3) a modification of the head unit (12--18). As a result, it was found that a non-sugar based selectin blocker (3) could be a potential lead compound for E-, P-, and L-selectin blockers and some of the derivatives showed broad and/or selective inhibitory activities toward the E-, P-, and L-selectins. In addition, it was found that the experimental evidence well supported that the computational screening using 3D-pharmacophore model could be useful methodology to find out a new lead for the several type of selectin blockers, which included a broad and/or a selective inhibitor.

Inhibition of selectin function and leukocyte rolling protects against dextran sodium sulfate-induced murine colitis

BACKGROUND

The selectin family of adhesion molecules (P-, E- and L-selectin) plays an important role in inflammatory reactions by mediating interactions between leukocytes and activated endothelial cells. However, a recent study using gene-targeted mice has suggested that adhesion molecules (P- and E-selectin and ICAM-1) may not be relevant targets in intestinal inflammation. The objective of the present study was to re-evaluate the potential role of selectins in experimental colitis in wild-type mice using the polysaccharide fucoidan, which inhibits the function of P- and L-selectin.

METHODS

For this purpose, Balb/c mice were exposed to 5% dextran sodium sulfate (DSS) in the drinking water for 5 days with and without daily administration of fucoidan (25 mg/kg, i.v.). In separate experiments, the effect of fucoidan on leukocyte-endothelium interactions was examined by use of intravital microscopy.

RESULTS

It was found that pretreatment with fucoidan (25 mg/kg/day) reduced mucosal damage and crypt destruction in the colon of DSS-treated mice. Moreover, this fucoidan treatment markedly reduced the colonic MPO activity in mice exposed to DSS. In vivo microscopy revealed that the dose of fucoidan used in the present study abolished TNF-alpha-induced venular leukocyte rolling and extravascular recruitment.

CONCLUSIONS

These results suggest that selectins mediate leukocyte infiltration and tissue damage in experimental colitis. Moreover, our data support the concept that functional interference with adhesion molecules of the selectin family may have a beneficial effect in the treatment of inflammatory bowel disease.

Discontinuation of fucose therapy in LADII causes rapid loss of selectin ligands and rise of leukocyte counts

Leukocyte adhesion deficiency type II (LADII) is a rare inherited disorder of fucose metabolism. Patients with LADII lack fucosylated glycoconjugates, including the carbohydrate ligands of the selectins, leading to an immunodeficiency caused by the lack of selectin-mediated leukocyte-endothelial interactions. A simple and effective therapy has recently been described for LADII, based on the administration of oral fucose. Parallel to this treatment the lack of E- and P-selectin ligands on neutrophils was corrected, and high peripheral neutrophil counts were reduced to normal levels. This study reports that discontinuation of this therapy leads to the complete loss of E-selectin ligands within 3 days and of P-selectin ligands within 7 days. Peripheral neutrophil counts increased parallel to the decrease of selectin ligands. Selectin ligands reappeared promptly after resumption of the fucose therapy, demonstrating a causal relationship between fucose treatment and selectin ligand expression and peripheral neutrophil counts.

The effects of inhibiting leukocyte migration with fucoidin in a rat peritonitis model

OBJECTIVES

To study the effects of fucoidin on leukocyte rolling and emigration and bacterial colonization in a peritonitis sepsis model in rats.

DESIGN AND INTERVENTIONS

A controlled study in 64 male Wistar rats, anesthetized and rendered septic by cecal ligation and puncture (CLP). Immediately after CLP 32 animals received a continuous infusion of fucoidin and 32 a continuous infusion of Ringer's lactate.

MEASUREMENTS AND MAIN RESULTS

Systemic leukocyte counts were determined every 2 h after CLP. Surviving animals were anesthetized 24 h after CLP, and intravital measurements of leukocyte rolling in venules in the cremaster muscle were performed. The animals were then killed and their organs harvested for histological and microbiological examinations. The 24-h survival was comparable in the two groups. Fucoidin-treated animals had higher leukocyte counts in the systemic circulation and lower counts in the lungs, liver, abdominal cavity, and brain than control animals. The number of bacterial colony forming units in the abdominal cavity, lungs, liver, brain and blood did not differ in the two groups. Fucoidin treatment changed the type of bacteria predominantly found in the examined organs from Escherichia coli to Pseudomonas aeruginosa.

CONCLUSIONS

In an intra-abdominal model of sepsis we found that treatment with fucoidin induces leukocytosis inhibits leukocyte rolling and reduces leukocyte emigration in the abdominal cavity, lungs, and liver. Reduction in the number of emigrating leukocytes was not associated with an increase in bacterial counts found in the examined organs.

Inhibition of leukocyte entry into the brain by the selectin blocker fucoidin decreases interleukin-1 (IL-1) levels but increases IL-8 levels in cerebrospinal fluid during experimental pneumococcal meningitis in rabbits

The polysaccharide fucoidin is a selectin blocker that inhibits leukocyte recruitment into the cerebrospinal fluid (CSF) during experimental pneumococcal meningitis. In the present study, the effect of fucoidin treatment on the release of the proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha), interleukin-1 (IL-1), and IL-8 into the CSF was investigated. Rabbits (n = 7) were treated intravenously with 10 mg of fucoidin/kg of body weight every second hour starting 4 h after intracisternal inoculation of approximately 10(6) CFU of Streptococcus pneumoniae type 3 (untreated control group, n = 7). CSF samples were obtained every second hour during a 16-h study period. Treatment with fucoidin caused a consistent and significant decrease in CSF IL-1 levels (in picograms per milliliter) between 12 and 16 h (0 versus 170, 0 versus 526, and 60 versus 1,467, respectively; P < 0.02). A less consistent decrease in CSF TNF-alpha levels was observed in the fucoidin-treated group, but with no significant difference between the two groups (P > 0.05). In contrast, there was no attenuation in CSF IL-8 levels. Indeed, there was a significant increase in CSF IL-8 levels (in picograms per milliliter) in the fucoidin-treated group at 10 and 12 h (921 versus 574 and 1,397 versus 569, respectively; P < 0.09). In conclusion, our results suggest that blood-derived leukocytes mainly are responsible for the release of IL-1 and to some degree TNF-alpha into the CSF during pneumococcal meningitis, whereas IL-8 may be produced by local cells within the brain.

Neutrophil mediated remote organ injury after lower torso ischemia and reperfusion is selectin and complement dependent

BACKGROUND

Lower torso ischemia and reperfusion leads to remote organ leukosequestration and injury. We now examine the intermediary role of selectins and complement in mediating lung and liver injury after hindlimb ischemia.

METHODS

Mice underwent a 2-hour bilateral tourniquet hind-limb ischemia followed by 3 hours of reperfusion.

RESULTS

Neutrophil depletion significantly decreased lung vascular permeability index (PI), measured by the extravasation of 125I-albumin, and liver injury as assessed by serum alanine aminotransferse levels. Lung PI and serum alanine aminotransferse levels were also reduced in mice treated with recombinant soluble P-selectin glycoprotein ligand-immunoglobulin fusion protein. Complement inhibition with soluble complement receptor type 1 decreased lung PI and serum alanine aminotransferse levels. C5-deficient mice exhibited a similar decrease in lung PI and liver injury. Lung and liver injury were restored in C5-deficient mice reconstituted with wild-type serum.

CONCLUSION

Remote organ injury after lower torso reperfusion is selectin and complement dependent.

Selectins in the HIT syndrome: pathophysiologic role and therapeutic modulation

The pathophysiology of heparin-induced thrombocytopenia (HIT) is now known to be a complex process which involves platelets, vascular endothelium, and leukocytes. The activation products from these sites also contribute to the activation of coagulation and to the fibrinolytic deficit. While many of the markers of hemostatic activation processes have been found to be at increased levels during acute phases of the HIT syndromes, the circulating levels of soluble P-, E-, and L- selectins have not been reported. Since the pathophysiology of HIT involves the activation of platelets, endothelium, and leukocytes, it is expected that activation products related to these hemostatic systems, including soluble selectins, will also be increased in circulating blood. These alterations may provide an index of the pathophysiologic process. With the availability of highly sensitive ELISAs for soluble P-, E-, and L-selectins, it is now possible to measure these adhesion molecules in biological fluids. This study reports on the circulating levels of P-, E-, and L-selectins in HIT patients and their modulation after therapeutic intervention. With the availability of recombinant hirudin, it is now possible to provide alternate anticoagulants to HIT patients. However, the immunoactivation of platelets and other cells may require additional adjunct therapeutic approaches.

Synthesis of sialyl Lewis x mimetics as selectin inhibitors by enzymatic aldol condensation reactions

Several D-mannosyl phosphate/phosphonate derivatives have been enzymatically prepared as sialyl Lewis x tetrasaccharide mimics, which showed strong-to-moderate inhibition against E-, P-, and L-selectins. The synthesis of these mimics is very straightforward; mannosyl aldehyde derivatives are condensed with dihydroxyacetone phosphate (DHAP) in the presence of a DHAP-dependent aldolase to provide mannosyl phosphates.

Selectin blockade reduces neutrophil interaction with platelets at the site of deep arterial injury by angioplasty in pigs

The adhesion of neutrophils to damaged arterial surfaces is increased in the presence of platelets by a mechanism implicating platelet P-selectin. Such interactions may enhance thrombus formation and the vascular response to injury. In this study, we investigated the effects of a selectin blocker (CY-1503), an analogue of sialyl Lewisx, on platelet and neutrophil interactions after arterial injury produced by angioplasty in pigs.51Cr-platelet deposition and 111In-neutrophil adhesion were quantified on intact, mildly and deeply injured carotid arterial segments, produced by balloon dilation, in control (saline, n=8) and treated (CY-1503, 15 mg/kg IV, n=7) pigs. The hematological parameters, the aggregation of whole blood in response to adenosine diphosphate, and the activating clotting time, as well as the heart rate and mean arterial blood pressure, were similar among groups and were not influenced significantly by CY-1503. The level of platelet and neutrophil adhesion increased significantly with the severity of arterial injury but was not influenced by CY-1503 on intact and mildly injured arterial segments. However, at the site of deep arterial injury, CY-1503 treatment was associated with a 58% reduction (P<0.01) in neutrophil adhesion, from 446.7+/-72.6x10(3) neutrophils/cm2 in the control group to 186.8+/-38.7x10(3) neutrophils/cm2 in the CY-1503-treated group, whereas platelet deposition remained unchanged (43.4+/-15.6x10(6) platelets/cm2 versus 50.1+/-12.2x10(6) platelets/cm2 in the control group). In in vitro adhesion experiments, using isolated platelet and neutrophil suspensions, we found that CY-1503 interfered with the adhesion of neutrophils to damaged arterial surfaces only in the presence of platelets. In contact with thrombogenic arterial surfaces, adherent and activated platelets supports neutrophil adhesion at the site of deep injury by an adhesive interaction involving neutrophil sialyl Lewisx. The inhibitory effect of CY-1503 on neutrophil interaction with adherent platelets may be clinically relevant in patients undergoing percutaneous transluminal coronary angioplasty where platelet and neutrophil interactions may enhance the acute and chronic arterial response to injury.

Fucoidin reduces coronary microvascular leukocyte accumulation early in reperfusion

BACKGROUND

Leukocytes rapidly accumulate in the heart early in reperfusion after ischemia, contributing to reperfusion injury. The purpose of this study was to determine whether treatment with the selectin blocker fucoidin (FCN) would attenuate early leukocyte retention in coronary venules and capillaries during low flow reperfusion.

METHODS

Isolated rat hearts subjected to 30 minutes of 37 degrees C, no-flow ischemia were initially reperfused with blood containing labeled leukocytes, followed by reperfusion with a Krebs red cell solution. The deposition of leukocytes in coronary capillaries and venules was observed using intravital microscopy. Three groups were studied: nonischemic control hearts, untreated postischemic hearts reperfused at low flow, and postischemic hearts reperfused at low flow, where both the hearts and the blood reperfusate were pretreated with FCN (0.36 mg/mL blood).

RESULTS

In the ischemia-reperfusion group, we observed a rapid and significant increase in leukocyte accumulation in both capillaries and venules. Treatment with FCN significantly reduced the leukocyte accumulation in both capillaries and venules (p<0.05). In addition, FCN significantly reduced the persistence of leukostasis in both capillaries and venules, indicating that FCN affected a transient adhesion process.

CONCLUSIONS

These results suggest that the selectin family of leukocyte-endothelial cell adhesion proteins mediates the initial retention of leukocytes in both coronary capillaries and venules during reperfusion. Selectin blockade may be effective in reducing the contribution of leukocytes to early reperfusion injury.

Effect of Sulfo Lewis C on smoke inhalation injury in an ovine model

OBJECTIVE

To evaluate the effect of Sulfo Lewis C (SO3-3âGal1-3GlcNAc-O(CH2)8-COOMe), a putative ligand of selectins, on smoke inhalation injury.

DESIGN

Prospective animal study with concurrent controls.

SETTING

An animal laboratory.

SUBJECTS

Twelve 1-yr-old female sheep, weighing 24 to 33 kg.

INTERVENTIONS

Twelve sheep received nine exposure units of smoke generated by thermolysis of pine woodchips (80 g). Group 1 (n = 6) was untreated. Group 2 (n = 6) was treated with an intravenous infusion of Sulfo Lewis C after smoke exposure. Animals were killed 48 hrs after injury.

MEASUREMENTS AND MAIN RESULTS

Cardiopulmonary variables and blood gases were measured serially. Granulocyte free-radical production was measured before smoke exposure and at 4 and 48 hrs after injury. Ventilation/perfusion distribution (VA/Q) was analyzed using the multiple inert gas elimination technique. Granulocyte free-radical production was increased after smoke exposure in both groups. Oxygenation was significantly improved by the administration of Sulfo Lewis C. VA/Q analysis demonstrated significantly less blood flow to low VA/Q lung segments in treated animals.

CONCLUSIONS

Selectin blockade attenuated lung injury after smoke exposure. These data support the hypothesis that neutrophils play a pivotal role in smoke inhalation injury.

Synthesis of sialyl Lewis X pentasaccharide analogue for high-throughput screening of selectin blockers

We have developed an effective synthesis of sLe(x) pentasaccharide glycolipid analogue 2. As a part of application of sLe(x) pentasaccharide glycolipid 2 synthesized here, we have investigated the construction of a high-through-put screening system for discovery of selectin blockers. As a result, it was found that compound 2 was a useful ligand for in vitro ELISA assay and could be an important material for high-throughput screening of selectin blockers.

In vitro and in vivo selectin-blocking activities of sulfated lipids and sulfated sialyl compounds

There is accumulating evidence that sulfated lipids, sulfated oligosaccharides and other sulfated compounds are reactive with selectins in a manner that interferes with selectin interactions with their natural ligands. In the report we describe the ability of sulfated lipids (sulfatides and gangliosides) and multimeric forms of sulfated sialic acid to block binding of P- and E-selectin-Ig to neutrophils. The in vivo ability of these compounds to block lung injury in rats following i.v. infusion of purified cobra venom factor (CVF), which induces injury that is L- and P-selectin dependent, was also determined as well as effects on recruitment of neutrophils, as measured by lung myeloperoxidase. There was a significant correlation between the ability of sulfated lipids and sialyl compounds to interfere in vitro with P-selectin-Ig binding to neutrophils and to protect against P-selectin-dependent acute lung injury induced by CVF. The biological effects of these sulfated compounds were also associated with diminished accumulation of neutrophils. The protective effects of these compounds may be linked to their ability to interfere with P-selectin binding to counter-receptors on neutrophils.

Studies on selection blockers. 5. Design, synthesis, and biological profile of sialyl Lewis x mimetics based on modified serine-glutamic acid dipeptides

We have rationally designed a sLe(x) mimetic based on molecular modeling, synthesized type II and type II' beta-turn dipeptides (3a,b), and evaluated their biological profiles both in vitro and in vivo. Against E-selectin-sLe(x) binding, the type II beta-turn dipeptide L-Ser-D-Glu 3a (IC50, 13 microM) and the type II' beta-turn dipeptide D-Ser-L-Glu 3b (IC50, 5.5 microM) were 20-100-fold more potent blockers than sLe(x) (1; IC50, 600 microM) and a 3'-sulfated Le(x) analog (2; IC50, 280 microM). On the other hand, other stereoisomers, such as L-Ser-L-Glu 3c and D-Ser-D-Glu 3d, were very weak blockers, with IC50 > 1000 microM for both 3c,d. Against the P- and L-selectins, despite much different stereochemistry of compounds 3a-d, the dipeptides 3a-d were all more potent blockers than either sLe(x) or compound 2. Interestingly, compound 3b provided significant in vivo efficacy against an immunoglobulin E-mediated skin reaction in a mouse model. These findings indicate that sLe(x) mimetics with type II and type II' beta-turn dipeptides could be useful in the design of an active selectin blocker in vitro and/or in vivo.

Small-molecule selectin inhibitor protects against liver inflammatory response after ischemia and reperfusion

BACKGROUND

The selectin family of adhesion molecules plays a key role in the neutrophil-mediated injury observed after ischemia and reperfusion. In our study, we investigated the effects of TBC-1269, a novel small-molecule, nonoligosaccharide inhibitor of P-, E-, and L-selectin binding, in the liver inflammatory response after 90 minutes of warm ischemia.

STUDY DESIGN

Total liver ischemia was produced in Sprague-Dawley rats for 90 minutes using an extracorporeal portosystemic shunt. The animals were divided into five groups including: the sham (group 1), ischemic control (group 2) receiving only the vehicle, and the treated groups receiving TBC-1269 at a dose of 25 mg/kg at different times of administration: 15 minutes before reperfusion (group 3), at reperfusion (group 4), and 15 minutes after reperfusion (group 5). The following indices were analyzed: 7-day survival, liver injury tests, liver tissue myeloperoxidase as an index of neutrophil infiltration, and liver histology.

RESULTS

TBC-1269 treated groups experienced a significant increase in survival compared with controls. Best overall survival, 70%, was observed when TBC-1269 (Texas Biotechnology Corporation, Houston, TX) was administered 15 minutes before reperfusion (p < 0.05). This group also showed a marked decrease (p < 0.05) in liver enzyme levels at 6 hours after reperfusion. Neutrophil migration was also significantly ameliorated (81%), as reflected by decreased myeloperoxidase levels. We observed improved histologic damage scores in the treated group compared with controls (p < 0.05).

CONCLUSIONS

A small-molecule selectin inhibitor (TBC-1269) had a protective effect in livers subjected to 90 minutes of warm hepatic ischemia and 6 hours of reperfusion by decreasing neutrophil infiltration, migration and subsequent tissue damage. The best protective effect was achieved when the compound was administered 15 minutes before reperfusion. These findings offer a new therapeutic alternative for protection against ischemia and reperfusion injury.

Carbohydrate selectin inhibitor CY-1503 reduces neutrophil migration and reperfusion injury in canine pulmonary allografts

BACKGROUND

Neutrophil adhesion is initiated by the interaction of rapidly expressed endothelial selectins with oligosaccharide structures (sialyl Lewis(x) on polymorphonuclear neutrophils (PMN). The carbohydrate sialyl Lewis X analogue CY-1503 blocks selectin receptors, thereby inhibiting PMN rolling and subsequent firm adhesion and migration.

METHODS

We evaluated the inhibitory effect of CY-1503 on PMN migration and reperfusion injury in canine left lung allografts. Donor lungs were flushed with modified Euro-Collins solution (1500 ml, 4 degrees C) and preserved for 21 hours at 1 degree C. Left lung allotransplantation was subsequently performed in 14 mongrel dogs. Immediately after transplantation and allograft reperfusion, the recipient contralateral right pulmonary artery and bronchus were ligated to permit assessment of isolated allograft function during a 6-hour postreperfusion period (FIO2 = 1.0). Allograft gas exchange (q 15 minutes) and hemodynamics (q 60 minutes) were assessed. After sacrifice, allograft bronchoalveolar lavage fluid (BALF) PMN count and allograft tissue myeloperoxidase (MPO) activity were measured. Two groups were studied: In group I (n = 7) CY-1503 was added to the donor lung flush (20 mg/L) and given to the recipient (35 mg/kg intravenous bolus) before reperfusion, followed by a continuous infusion (5.25 mg/kg/h intravenously) during the 6-hour assessment period. Group II animals (n = 7) received no CY-1503.

RESULTS

Gas exchange in group I was superior throughout the assessment period (p < 0.01 at 6 hours after reperfusion). BALF PMN count in group I was reduced to 0.57 +/- 0.3 x 10(6) PMN/ml compared with 3.9 +/- 1.3 x 10(6) PMN/ml in group II (p < 0.05). Group I allograft MPO activity was 0.21 +/- 0.06 compared with 0.40 +/- 0.02 delta OD/mg/ min in controls (p < 0.02). Two animals in each group died early after reperfusion as a result of graft failure and were excluded from analysis.

CONCLUSIONS

Our observations indicate that selectin inhibition effectively reduces PMN adhesion, migration, and subsequent reperfusion injury in preserved canine lung allografts.

Retinoic acid inhibits the regulated expression of vascular cell adhesion molecule-1 by cultured dermal microvascular endothelial cells

The regulated expression of cell adhesion molecules (CAM) on endothelial cells is central to the pathogenesis of various inflammatory processes. Retinoic acid and synthetic derivatives have been demonstrated to exert antiinflammatory effects in cutaneous diseases. To determine modes of retinoid action in the modulation of inflammatory responses, we explored effects of all-trans-retinoic acid (t-RA) on the TNFalpha-induced expression of vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and E-selectin in cultured human dermal microvascular endothelial cells. Pretreatment with t-RA specifically prevented TNFalpha-induced VCAM-1 expression, but not ICAM-1 and E-selectin induction. t-RA significantly reduced VCAM-1-dependent T cell binding to TNFalpha-treated human dermal microvascular endothelial cells as well. This differential modulation of TNFalpha-induced CAM expression by t-RA was reflected at steady state mRNA levels and in nuclear run-on studies. In transcriptional activation studies, the TNFalpha-mediated activation of the human VCAM-1 promoter was inhibited after t-RA treatment, while the ICAM-1 promoter activation was unaffected, indicating that the selective inhibition of CAM expression is regulated in part at the level of gene transcription. Furthermore, the transcriptional inhibition by t-RA appears to be mediated by its effects upon the activation of NF-kappaB-dependent complex formation. Analysis of protein-DNA binding assays revealed marked inhibition of specific NF-kappaB-dependent binding to the tandem NF-KB sites of the VCAM-1 promoter, but not to the functional NF-kappaB motif of the ICAM-1 promoter. The specific inhibition of cytokine-mediated VCAM-1 gene expression in vitro may provide a potential basis by which retinoids exert their biological effects at sites of inflammation in vivo.

Blockade of selectin-mediated leukocyte adhesion improves postischemic function in lamb hearts

BACKGROUND

Leukocyte-endothelial interactions appear to have a important role in ischemia/reperfusion injury and are mediated by specific leukocyte and endothelial adhesion molecules. The selectins are adhesion molecules found on leukocytes (L-selectin) and endothelium (P and E selectin) that bind to oligosaccharide ligands containing fucose and sialic acid to mediate leukocyte rolling on the endothelium. Fucoidin is a nontoxic sulfated fucose oligosaccharide derived from seaweed that blocks the selectins.

METHODS

We tested the effects of fucoidin in an isolated blood-perfused neonatal (age range, 3 to 7 days; mean age, 4.3 days) lamb heart model undergoing 2 hours of cold cardioplegic ischemia. In group F (n = 8) fucoidin (30 mg/L) was added at initial reperfusion. Group C (n = 9) received only cardioplegia with no reperfusion intervention. Isovolumic maximum developed pressure and the maximum positive and negative first derivatives of pressure were measured using a catheter-tip transducer in an intraventricular balloon before ischemia and at 30 minutes of reperfusion. Coronary blood flow, myocardial oxygen consumption, and white blood cell counts in the circulating blood were also measured.

RESULTS

Percent recoveries of baseline maximum developed pressure and maximum positive and negative first derivatives of pressure in group F (86% +/- 5%, 81% +/- 10%, and 74% +/- 8%, respectively; mean +/- standard deviation) were higher than in group C (77% +/- 5%, 70% +/- 9%, and 65% +/- 6%; p < 0.05). Group F postischemic coronary blood flow was greater (190% +/- 35%) than in group C (102% +/- 10%; p < 0.05). Recovery of myocardial oxygen consumption in group F (86% +/- 14%) was greater than group C (72% +/- 11%; p < 0.05). Postischemic white blood cell count in group F (88% +/- 4%) was greater than in group C (81% +/- 5%; p < 0.05).

CONCLUSIONS

Selectin blockade with fucoidin resulted in better recovery of left ventricular function, coronary blood flow, and myocardial oxygen consumption after cold ischemia, despite a higher circulating white blood cell count. These data support the hypothesis that endothelial-leukocyte interactions play an important role in ischemia/reperfusion and suggest that selectin blockade may be a useful therapeutic strategy.

Studies on selectin blockers. 2. Novel selectin blocker as potential therapeutics for inflammatory disorders

As a part of our studies of selectin blockers, we prepared 1-(2-tetradecylhexadecyl)-3'-O-sulfo Le(X) 1 and 1-(2-tetradecylhexadecyl) sLe(X) 2 and examined their inhibitory activities against natural ligand (sLe(X)) binding to E-, P-, and L-selectins. Compounds 1 and 2 were 2 times more potent than the sLe(X) tetrasaccharide toward E-selectin binding and up to 4 times more potent than sLe(X) toward P- and L-selectin binding. Interestingly, compound 1 provided dose-dependent protective effects against an immunoglobulin E-mediated skin reaction in mouse ears. This protective effect was associated with diminished tissue accumulation of neutrophils in the ear (as assessed by myeloperoxidase). These findings indicate that the modification of sLe(X) or 3'-O-sulfo Le(X) with a "branched anchor", a 2-tetradecylhexadecyl group, is useful in the design of a more potent selectin blocker, which has broad inhibitory activities toward all selectins.

Purine metabolism and immunosuppressive effects of mycophenolate mofetil (MMF)

Mycophenolate mofetil (MMF) is a novel immunosuppressive drug that shows promise in preventing the rejection of organ allografts and in the treatment of ongoing rejection. Orally administered MMF is hydrolyzed by esterases in the intestine and blood to release mycophenolic acid (MPA), a potent, selective, noncompetitive inhibitor of the type 2 isoform of inosine monophosphate dehydroxygenase (IMPDH) expressed in activated human T and B lymphocytes. By inhibiting IMPDH, MPA depletes the pool of dGTP required for DNA synthesis. MPA has a more potent cytostatic effect on lymphocytes than on other cell types, and this is the principal mechanism by which immunosuppressive activity is exerted. MPA also depletes pools of GTP in human lymphocytes and monocytes, thereby inhibiting the synthesis of fucose- and mannose-containing saccharide components of membrane glycoproteins. These are recognized by the family of adhesion molecules termed selectins. By this mechanism, MPA could decrease the recruitment of lymphocytes and monocytes into sites of graft rejection. In addition to preventing allograft rejection, MMF suppresses graft-versus-host reactions in lethal and nonlethal murine models. MMF inhibits primary antibody responses more efficiently than secondary responses. MPA inhibits the proliferation of human B lymphocytes transformed by Epstein-Barr virus and is not mutagenic. Clinically attainable concentrations of MPA suppress the proliferation of human arterial smooth muscle cells. These two properties of MPA may decrease the risk of lymphoma development and proliferative arteriopathy in long-term recipients of MMF.