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

Analogues of the pan-selectin antagonist rivipansel (GMI-1070)

The selectin family consisting of E-, P- and L-selectin plays dominant roles in atherosclerosis, ischemia-reperfusion injury, inflammatory diseases, and metastatic spreading of some cancers. An early goal in selectin-targeted drug discovery campaigns was to identify ligands binding to all three selectins, so-called pan-selectin antagonists. The physiological epitope, tetrasaccharide sialyl Lewisx (sLex, 1) binds to all selectins, albeit with very different affinities. Whereas P- and L-selectin require additional interactions contributed by sulfate groups for high binding affinity, E-selectin can functionally bind sLex-modified glycolipids and glycoproteins. Rivipansel (3) marked the first pan-selectin antagonist, which simultaneously interacted with both the sLex and the sulfate binding site. The aim of this contribution was to improve the pan-selectin affinity of rivipansel (3) by leveraging a new class of sLex mimetics in combination with an optimized linker length to the sulfate bearing group. As a result, the pan-selectin antagonist 11b exhibits an approximatively 5-fold improved affinity for E-, as well as P-selectin.

THE IMMUNOPATHOGENESIS OF POLYMICROBIAL SEPSIS

ABSTRACT

This report deals with the advances made in the areas of complement and its role in sepsis, both in mice and in humans. The study relates to work over the past 25 years (late 1990s to October 2022). During this period, there has been very rapid progress in understanding the activation pathways of complement and the activation products of complement, especially the anaphylatoxin C5a and its receptors, C5aR1 and C5aR2. Much has also been learned about these pathways of activation that trigger activation of the innate immune system and the array of strong proinflammatory cytokines that can cause cell and organ dysfunction, as well as complement products that cause immunosuppression. The work in septic humans and mice, along with patients who develop lung dysfunction caused by COVID-19, has taught us that there are many strategies for treatment of humans who are septic or develop COVID-19-related lung dysfunction. To date, treatments in humans with these disorders suggest that we are in the midst of a new and exciting area related to the complement system.

Thermogels containing sulfated hyaluronan as novel topical therapeutics for treatment of ocular surface inflammation

The development of long lasting therapeutic agents is critically important for efficient treatment of chronic diseases. We herein report a rational strategy to develop a therapeutic thermogel featured with prolonged anti-inflammatory and corneal-protective effects. Specifically, a hyaluronic acid with different sulfation degrees and an amine-terminated poly(N-isopropylacrylamide) are conjugated to achieve the thermogels. In vitro studies reveal that the thermogels are highly biocompatible to statens seruminstitut rabbit cornea cells and their anti-inflammatory properties are strongly dependent on the sulfation degree. In a rabbit model of ocular inflammation, single-dose topical administration of a thermogel formulation could repair defects in corneal epithelium (∼99% thickness restored), prevent corneal cell apoptosis (∼68.3% cells recovered), and suppress ocular surface inflammation (∼4-fold decrease) for a follow-up period of 7 days. This high treatment efficacy of the thermogel can be attributed to its potent inhibition in selectin-mediated leukocyte infiltration as well as effective corneal protection. These findings show a great promise for topical treatment of ocular inflammation and advancement of ophthalmic formulations using the bioactive thermogel as a therapeutic component that is not rapidly cleared from the eye and thus considerably reduces administration times.

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Sulfated hyaluronan thermogels served as intrinsic therapeutic agents.

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Thermogels exert inhibitory effects on selectin-mediated leukocyte infiltration.

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Sulfation degree is a key to achieve superior therapeutic thermogels.

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Highly sulfated agent reveals potent anti-inflammatory/corneal-protective effects.

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Single dose reduces corneal inflammation by 4-folds at 7 days post-instillation.

Sialic Acid-Modified Nanoparticles-New Approaches in the Glioma Management-Perspective Review

The cell surface is covered by a dense and complex network of glycans attached to the membrane proteins and lipids. In gliomas, the aberrant sialylation, as the final stage of glycosylation, is an important regulatory mechanism of malignant cell behavior and correlates with worse prognosis. Better understanding of the role of sialylation in cellular and molecular processes opens a new way in the development of therapeutic tools for human brain tumors. According to the recent clinical observation, the cellular heterogeneity, activity of brain cancer stem cells (BCSCs), immune evasion, and function of the blood–brain barrier (BBB) are attractive targets for new therapeutic strategies. In this review, we summarize the importance of sialic acid-modified nanoparticles in brain tumor progression.

Preparation of sulfatide mimicking oleic acid sulfated chitosan as a potential inhibitor for metastasis

Sulfatide is associated with numerous health problems, affecting different parts of the human body, including the metastasis; however, the underlying mechanisms are yet to be fully elucidated. Sulfatide has been used to potential inhibitor for tumor cell metastasis. In the present study we synthesized oleic acid sulfated chitosan (OlcShCs). It shows structural similarity to sulfatide because of its functional groups (sulfate and fatty acyl chains). Chitosan has smart properties such as biocompatibility, biodegradability and non-toxicity. We have prepared oleic acid sulfated chitosan (OlcShCs) by chitosan modification to mimic sulfatide. Its structure was characterized by FT-IR, H-NMR, and thermogravimetric analysis. After characterization studies its antimicrobial, antifungal and cytotoxic properties were investigated. Oleic acid sulfated chitosan (OlcShCs) was tested for its anti-cancer potential against human cancer cell lines (HeLa (ATCC® CCL-2™)) for 24 h, 48 h and 72 h using the MTT assays. This new material which is soluble at physiological conditions, is a potential candidate for further metastasis inhibition investigations.

Deciphering Isomers with a Multiple Reaction Monitoring Method for the Complete Detectable O-Glycan Repertoire of the Candidate Therapeutic, Lubricin

Glycosylation is a fundamental post-translational modification, occurring on half of all proteins. Despite its significance, our understanding is limited, in part due to the inherent difficulty in studying these branched, multi-isomer structures. Accessible, detailed, and quantifiable methods for studying glycans, particularly O-glycans, are needed. Here we take a multiple reaction monitoring (MRM) approach to differentiate and relatively quantify all detectable glycans, including isomers, on the heavily O-glycosylated protein lubricin. Lubricin (proteoglycan 4) is essential for lubrication of the joint and eye. Given the therapeutic potential of lubricin, it is essential to understand its O-glycan repertoire in biological and recombinantly produced samples. O-Glycans were released by reductive β-elimination and defined, showing a range of 26 neutral, sulfated, sialylated, and both sulfated and sialylated core 1 (Galβ1-3GalNAcα1-) and core 2 (Galβ1-3(GlcNAcβ1-6)GalNAcα1-) structures. Isomer-specific MRM transitions allowed effective differentiation of neutral glycan isomers as well as sulfated isomeric structures, where the sulfate was retained on the fragment ions. This strategy was not as effective with labile sialylated structures; instead, it was observed that the optimal collision energy for the m/z 290.1 sialic acid B-fragment differed consistently between sialic acid isomers, allowing differentiation between isomers when fragmentation spectra were insufficient. This approach was also effective for purchased Neu5Acα2-3Galβ1-4Glc and Neu5Acα2-6Galβ1-4Glc and for Neu5Acα2-3Galβ1-4GlcNAc and Neu5Acα2-6Galβ1-4GlcNAc linkage isomers with the Neu5Acα2-6 consistently requiring more energy for optimal generation of the m/z 290.1 fragment. Overall, this method provides an effective and easily accessible approach for the quantification and annotation of complex released O-glycan samples.

Erythrocyte membrane sulfatide plays a crucial role in the adhesion of sickle erythrocytes to endothelium

Enhanced adhesion of sickle erythrocytes to the vascular endothelium and subendothelial matrix is fundamental to the development of vascular occlusion in sickle cell disease. Erythrocyte membrane sulfatide is implicated in the pathogenesis of vasoocclusive crises in sickle cell disease (SCD) patients. Because previous evidence linking sulfatide to cell adhesion has largely been circumstantial due to a lack of reagents that specifically target sulfatide, we used two sulfatide-specific strategies to address the role of erythrocyte membrane sulfatide in sickle cell adhesion to the vascular endothelium: a single-chain fragment variable chain (scFv) antibody against sulfatide as well as cerebroside sulfotransferase-deficient mice incapable of synthesising sulfatide. The sickle erythrocytes from mice and humans adhered at a greater extent and at higher shear stresses to activated endothelium than normal erythrocytes, and approximately 60% of the adhesion was prevented by the anti-sulfatide scFv. Similarly, the extent of adhesion of sulfatide-deficient erythrocytes was lower than normal erythrocytes. These findings suggest an important role for membrane sulfatide in sickle cell disease pathophysiology.

Sulfatides inhibit adhesion, migration, and invasion of murine melanoma B16F10 cell line in vitro

Endogenous sulfatide, such as 3-sulfated galactosylceramide (3-sulfatide) has been reported to be involved in neuronal development and regulation of tumor cell metastasis. Recently, a new 6-sulfated glucosylceramide (6-sulfatide) has been isolated from the ascidian, Ciona intestinalis. To determine the antitumor function of the new sulfatide, we examined the effects of synthetic 6-sulfatide and 3-sulfatide on the metastatic features of a murine melanoma cell line, B16F10. Both sulfatides significantly inhibited the adhesion of melanoma cells onto fibronectin-coated tissue plates and, the motility and invasion of the cells, with 6-sulfatide showing stronger inhibitory activities. In addition, both sulfatides inhibited α(5)-, and β(1)- but not α(v)- or β(3)-integrin expression. Furthermore, these sulfatides inhibited the activation of focal adhesion kinase, Akt, and extracellular signal-regulated kinase signaling pathways, which are thought to be important for cell migration and invasion. Therefore, these sulfatides may serve as promising drug candidates for the treatment of cancer metastasis.

From carbohydrate leads to glycomimetic drugs

Carbohydrates are the most abundant natural products. Besides their role in metabolism and as structural building blocks, they are fundamental constituents of every cell surface, where they are involved in vital cellular recognition processes. Carbohydrates are a relatively untapped source of new drugs and therefore offer exciting new therapeutic opportunities. Advances in the functional understanding of carbohydrate-protein interactions have enabled the development of a new class of small-molecule drugs, known as glycomimetics. These compounds mimic the bioactive function of carbohydrates and address the drawbacks of carbohydrate leads, namely their low activity and insufficient drug-like properties. Here, we examine examples of approved carbohydrate-derived drugs, discuss the potential of carbohydrate-binding proteins as new drug targets (focusing on the lectin families) and consider ways to overcome the challenges of developing this unique class of novel therapeutics.

Sulfated glycosphingolipid as mediator of phagocytosis: SM4s enhances apoptotic cell clearance and modulates macrophage activity

Sulfoglycolipids are present on the surface of a variety of cells. The sulfatide SM4s is increased in lung, renal, and colon cancer and is associated with an adverse prognosis, possibly due to a low immunoreactivity of the tumor. As macrophages significantly contribute to the inflammatory infiltrate in malignancies, we postulated that SM4s may modulate macrophage function. We have investigated the effect of SM4s on the uptake of apoptotic tumor cells, macrophage cytokine profile, and receptor expression. Using flow cytometry and microscopic analyses, we found that coating apoptotic murine carcinoma cells from the colon and kidney with SM4s promoted their phagocytosis by murine macrophages up to 3-fold ex vivo and in vivo. This increased capacity was specifically inhibited by preincubation of macrophages with oxidized or acetylated low density lipoprotein and maleylated albumin, indicating involvement of scavenger receptors in this interaction. The uptake of SM4s-coated apoptotic cells significantly enhanced macrophage production of TGF-beta1, expression of P-selectin, and secretion of IL-6. These data suggest that SM4s within tumors may promote apoptotic cell removal and alter the phenotype of tumor-associated macrophages.

Colominic acid inhibits the proliferation of cultured bovine aortic endothelial cells and injures their monolayers: Cell density-dependent effects prevented by sulfation

Colominic acid (CA), produced by Escherichia coli K1, is a polymer of sialic acid linked through alpha (2-->8) glycosidic linkages. Although there are several studies on the biological activities of chemically sulfated CA, the activity of CA has been incompletely understood. In the present study, we investigated the effects of CA, prepared as an alpha2,8-linked homopolymer of N-acetylneuraminic acid, on the proliferation and monolayer maintenance of bovine aortic endothelial cells in culture. The results indicate that CA potently inhibits the proliferation of sparse endothelial cells without nonspecific cell damage. The inhibitory effect of CA was markedly stronger than those of sodium spirulan and calcium spirulan, known polysaccharides that inhibit endothelial cell proliferation. On the other hand, in dense endothelial cells, CA induced nonspecific cell damage and markedly injured the monolayer. These results indicate that CA has two distinct effects on vascular endothelial cells: one is the inhibition of proliferation when the cell density is low, and the other is the nonspecific cytotoxicity when the cell density is high. Interestingly, these cell density-dependent effects of CA could be prevented by sulfation of the CA chains. Therefore, it is concluded that CA not only inhibits the proliferation of sparse endothelial cells without nonspecific cell damage but also injures dense cells in a monolayer by nonspecific cytotoxicity, which can be prevented by sulfation of the polysaccharide.

Chemokines bind to sulfatides as revealed by surface plasmon resonance

Chemokines bind to sulfated cell surface glycosaminoglycans and thereby modulate signaling mediated by G-protein-coupled seven-transmembrane domain chemokine receptors. Similar to glycosaminoglycans, sulfated oligosaccharides are also exposed on the cell surface by sulfatides, a class of glycosphingolipids. We have now identified sulfated glycosphingolipids (sulfatides) as novel binding partners for chemokines. Using surface plasmon resonance (SPR), the binding of proinflammatory and homeostatic chemokines to glycosphingolipids, in particular sulfatides, was investigated. Chemokines were immobilized while glycosphingolipids or additional phospholipids incorporated into liposomes were applied as soluble analytes. A specific affinity of the chemokines MCP-1/CCL2, IL-8/CXCL8, SDF-1alpha/CXCL12, MIP-1alpha/CCL3 and MIP-1beta/CCL4 to the sulfatides SM4s, SM3, SM2a and SB2, SB1a was detected. No significant interactions with the chemokines were observed for gangliosides, neutral glycosphingolipids or phospholipids. Chemokine receptors have been associated with the detergent-insoluble fraction supposed to contain 'rafts', i.e., glycosphingolipid enriched microdomains of the cell surface. Accordingly, the data suggest that early chemokine receptor signaling may take place in the vicinity of sulfated glycosphingolipids on the cell surface, whereby these sulfatides could modulate the chemokine receptor-mediated cell activation signal.

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.

Inhibition of Cultured Bovine Aortic Smooth Muscle Cell Proliferation by Colominic Acid

Colominic acid (CA) is an alpha2,8-linked polymer of sialic acid, originally isolated from capsular Escherichia coli K1. Since inhibition of arterial smooth muscle cell hyperplasia is one of the effective strategies to prevent atherosclerosis, we investigated the effect of CA, purified as an alpha2,8-linked homopolymer of N-acetylneuraminic acid, on the proliferation of bovine aortic smooth muscle cells in culture. The results demonstrate that CA inhibits the proliferation of the cells without nonspecific cell damage. Sulfation did not modify the inhibitory effect of CA. Specifically, the inhibitory effect of sulfated CA was almost equal to that of CA in vascular smooth muscle cell proliferation. On the other hand, it was suggested that the inhibition of the proliferation by CA is in a degree similar to that by heparin but weaker than that by sodium/calcium-spirulans, known sulfated polysaccharides as the potent inhibitor of vascular smooth muscle cells. The present data suggest that CA with or without sulfate groups can be an origin of beneficial agents that prevents atherosclerosis through a moderate inhibition of arterial smooth muscle cell proliferation.

Sulfatides activate platelets through P-selectin and enhance platelet and platelet-leukocyte aggregation

OBJECTIVE

Sulfatides are sulfated glycosphingolipids present on the surface of a variety of cells; however, their exact physiological function is not known. Recently, we have shown that the inhibition of sulfatide-P-selectin interactions leads to disaggregation of platelet aggregates.

METHODS AND RESULTS

In this study, we show that sulfatides activated platelets as they increased activation of GPIIb/IIIa (PAC-1 epitope) and expression of P-selectin on the platelet surface. Furthermore, sulfatides aggregated washed platelets in a dose-dependent manner and enhanced platelet aggregation in platelet-rich plasma. Previous activation of platelets was necessary for this effect. Monoclonal anti-P-selectin antibodies inhibited not only sulfatide-induced PAC-1 binding to platelets but also sulfatide-induced platelet aggregation, suggesting that sulfatides activate platelet GPIIb/IIIa via signaling through P-selectin. The proaggegatory effect of sulfatides was also observed in an ex vivo thrombosis model using whole blood and pulsatile flow at 37 degrees C. In this model, sulfatides significantly enhanced platelet aggregation and the formation of platelet-leukocyte aggregates.

CONCLUSIONS

We show that sulfatide-P-selectin interactions lead to subsequent platelet activation and P-selectin expression, forming a positive feedback loop that can potentiate formation of stable platelet aggregates. In addition, sulfatides enhance the aggregation of platelet-leukocyte aggregates. These mechanisms may play a significant role in hemostasis and thrombosis.

P-selectin in arterial thrombosis

P-selectin is a transmembrane protein present in the alpha granules of platelets and the Weibel-Palade bodies of endothelial cells. Following activation, it is rapidly translocated to the cell surface. P-selectin expression in platelets has been shown to be elevated in disorders associated with arterial thrombosis such as coronary artery disease, acute myocardial infarction, stroke, and peripheral artery disease. P-selectin mediates rolling of platelets and leukocytes on activated endothelial cells as well as interactions of platelets with leukocytes. Platelet P-selectin interacts with P-selectin glycoprotein ligand-1 (PSGL-1) on leukocytes to form platelet-leukocyte aggregates. Furthermore, this interaction of P-selectin with PSGL-1 induces the upregulation of tissue factor, several cytokines in leukocytes and the production of procoagulant microparticles, thereby contributing to a prothrombotic state. P-selectin is also involved in platelet-platelet interactions, i. e. platelet aggregation which is a major factor in arterial thrombosis. P-selectin interacts with platelet sulfatides, thereby stabilizing initial platelet aggregates formed by GPIIb/IIIa-fibrinogen bridges. Inhibtion of the P-selectin-sulfatide interaction leads to a reversal of platelet aggregation. Thus, P-selectin plays a significant role in platelet aggregation and platelet- leukocyte interactions, both important mechanisms in the development of arterial thrombosis.

Therapeutic effect of sulphated hyaluronic acid, a potential selectin-blocking agent, on experimental progressive mesangial proliferative glomerulonephritis

The initial event in the process of leukocyte infiltration is characterized by leukocyte rolling on the surface of the endothelium, which is mediated by selectins. P- and L-selectin bind to the sulphated sugar chains of their natural ligands, including sulphated glycolipids such as sulphatide. Recently, it has been demonstrated that sulphated glycolipids and sulphated oligosaccharides interfere with selectin binding pathways. This study synthesized sulphated hyaluronic acid (SHA), which is a potential selectin-blocking agent, and examined its therapeutic effect on the experimental progressive mesangial proliferative glomerulonephritis induced by anti-Thy-1 monoclonal antibody (1-22-3 MAb) after unilateral nephrectomy. The selectin-inhibitory effect of SHA in vitro was confirmed. SHA inhibited the binding of P- and L-selectin to sulphatide, which is a glycolipid ligand for P- and L-selectin, at a concentration of 1.5 micro g/ml and 100 micro g/ml. Immunohistochemical examination showed that P-selectin was up-regulated in the glomeruli in the 1-22-3 MAb nephritis model, while the ligands for L-selectin were not detected in the glomerular tufts. A single administration of SHA ameliorated proteinuria and glomerular leukocyte infiltration in 24 h after the injection of anti-Thy-1 MAb. Anti-P-selectin MAb, but not anti-L-selectin MAb, inhibited proteinuria and glomerular leukocyte infiltration. To examine further the therapeutic effect of SHA on chronic glomerulonephritis, SHA was administered daily from day 3 to day 14 in this model. Proteinuria and glomerular leukocyte infiltration were significantly diminished in SHA-treated rats on day 14. These results suggest that SHA ameliorated rat progressive mesangial proliferative glomerulonephritis by inhibiting P-selectin-dependent leukocyte infiltration in glomeruli. Sulphated oligosaccharides may be beneficial for the therapy of mesangial proliferative glomerulonephritis.

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.

Synergistic effects of L- and P-selectin in facilitating tumor metastasis can involve non-mucin ligands and implicate leukocytes as enhancers of metastasis

P-selectin facilitates human carcinoma metastasis in immunodeficient mice by mediating early interactions of platelets with bloodborne tumor cells via their cell surface mucins, and this process can be blocked by heparin [Borsig, L., Wong, R., Feramisco, J., Nadeau, D. R., Varki, N. M. & Varki, A. (2001) Proc. Natl. Acad. Sci. USA 98, 3352-3357]. Here we show similar findings with a murine adenocarcinoma in syngeneic immunocompetent mice but involving a different P-selectin ligand, possibly a sulfated glycolipid. Thus, metastatic spread can be facilitated by tumor cell selectin ligands other than mucins. Surprisingly, L-selectin expressed on endogenous leukocytes also facilitates metastasis in both the syngeneic and xenogeneic (T and B lymphocyte deficient) systems. PL-selectin double deficient mice show that the two selectins work synergistically. Although heparin can block both P- and L-selectin in vitro, the in vivo effect of a single heparin dose given before tumor cells seems to be completely accounted for by blockade of P-selectin function. Thus, L-selectin on neutrophils, monocytes, and/or NK cells has a role in facilitating metastasis, acting beyond the early time points wherein P-selectin mediates interactions of platelet with tumor cells.

Sulphatides trigger polymorphonuclear granulocyte spreading on collagen-coated surfaces and inhibit subsequent activation of 5-lipoxygenase

Sulphatides are sulphate esters of galactocerebrosides that are present on the surfaces of many cell types and act as specific ligands to selectins. The present study was undertaken to investigate the effect of sulphatides on polymorphonuclear granulocyte (PMN) attachment, spreading and 5-lipoxygenase (5-LO) metabolism. Sulphatides, but not non-sulphated galactocerebrosides, dose-dependently enhanced attachment to collagen, as measured by the myeloperoxidase assay. Studies with blocking antibodies indicated that the increased attachment was mediated by CD11b/CD18 (Mac-1) beta 2 integrin. Scanning electron microscopy indicated that sulphatides also greatly enhanced the degree of cell spreading. In PMNs treated in suspension, sulphatides had no effect on the ionophore A23187-stimulated release of arachidonic acid and the synthesis of 5-LO metabolites. In contrast, in PMNs attached to collagen, the enzymic conversion of arachidonic acid by 5-LO was inhibited by sulphatides. Inhibition of 5-LO metabolism by sulphatides was observed even in the presence of exogenous substrate, suggesting that sulphatides directly inhibited 5-LO action. Consistent with this, sulphatides interfered with ionophore-induced translocation of the 5-LO to the nuclear envelope. Substances competing with sulphatide binding to cells, like dextran sulphate, or a strong inhibitor of cell spreading, like the actin-polymerizing agent jasplakinolide, prevented the effects of sulphatides on PMN attachment and spreading and leukotriene synthesis. We conclude that shape changes occurring in response to sulphatides specifically impair PMN leukotriene synthesis by inhibiting translocation of 5-LO.

The aglycone of sulfogalactolipids can alter the sulfate ester substitution position required for hsc70 recognition

3'-Sulfogalactolipids(SGLs), sulfogalactosyl ceramide (SGC), and sulfogalactoglycerolipid (SGG) bind to the N-terminal ATPase-containing domain of members of the heat shock protein 70 family. We have probed this binding specificity using a series of synthetic positional sulfated or phosphorylated glycolipid analogues, containing either a long-chain bisalkyl hydrocarbon-2-(tetradecyl)hexadecane (B30) or C(18) ceramide (SGC(18)) backbone. By TLC overlay and receptor ELISA, recombinant hsc70 bound ceramide-based glycoconjugates having 3'- or 4'-sulfogalactose glycone moieties and the 4'-sulfogalactose positional isomer conjugated to B30. Hsc70 binding was significantly decreased to the 3'-sulfogalactose conjugated to the long-chain branched alkane. 3'-Sulfoglucose conjugated to B30 was not bound, nor were similarly conjugated di-, tri-, and tetra-sulfated or phosphorylated galactolipids. These results highlight the importance of the position, rather than the number of sulfate esters within the galactose ring. This binding selectivity was shared by the sea urchin hsp70-related sperm receptor. A 3'-SGC-based soluble inhibitor, in which the acyl chain was replaced with an adamantyl group, inhibited binding of hsc70 to both 3'- and 4'-SGC species with an IC(50) of 50 and 75 microM, respectively, indicating a shared sulfogalactose binding site. These studies demonstrate the highly specific nature of hsc70/SGL binding and show, for the first time, that the lipid aglycone can alter the substitution position requirement for glycolipid recognition.

Protective effect of anti-P-selectin monoclonal antibody in lipopolysaccharide-induced lung hemorrhage

Excessive leukocyte accumulation is involved in the pathogenesis of the sepsis-induced acute lung injury. Selectins are essential to the interaction between leukocytes and endothelial cells. In this report, we investigated the role of selectins in the severe lung injury induced by lipopolysaccharide (LPS). Significant lung hemorrhage was observed 24 h after the intravenous administration of LPS (1 mg/kg). First, we evaluated the effect of sialyl Lewis X-oligosaccharide (SLeX-OS), a derivative of sialyl Lewis X which is one of the ligands for E-, P- and L-selectins. The treatment with SLeX-OS (26.5 mg/kg iv bolus + 19.8 mg/kg iv infusion) resulted in a decrease of lung hemorrhage by 49.5% (P<0.05 versus the control group). Second, we tested the effect of anti-P-selectin monoclonal antibody (MAb), PB 1.3, to investigate the role of P-selectin. The bolus administration of PB1.3 at a dose of 5 mg/kg attenuated the lung hemorrhage by 74.6% (P<0.05 versus the control group). In addition, we also detected an increase of soluble P-selectin in plasma 24 h after the injection of LPS. These results suggest that P-selectin has a substantial role in the pathogenesis of the lung injury induced by LPS.

Neutrophil and endothelial cell interactions in sepsis. The role of adhesion molecules

Although adhesion molecules present on circulating neutrophils and endothelial cells are essential for normal host defense, generalized activation of these molecules has been implicated in the inflammatory tissue injury occurring during sepsis and septic shock. A review of both preclinical and clinical studies suggests, however, that although these molecules mediate tissue injury related to a variety of microbial and host inflammatory mediators, their predominant role during sepsis with infection is a protective one.