Sphingolipid composition of human platelets

Neutrophil Extracellular Traps Induced by Shiga Toxin and Lipopolysaccharide-Treated Platelets Exacerbate Endothelial Cell Damage

Hemolytic uremic syndrome (HUS) is the most common cause of acute renal failure in the pediatric population. The etiology of HUS is linked to Gram-negative, Shiga toxin (Stx)-producing enterohemorrhagic bacterial infections. While the effect of Stx is focused on endothelial damage of renal glomerulus, cytokines induced by Stx or bacterial lipopolysaccharide (LPS) and polymorphonuclear cells (PMNs) are involved in the development of the disease. PMN release neutrophil extracellular traps (NETs) to eliminate pathogens, although NETs favor platelets (Plts) adhesion/thrombus formation and can cause tissue damage within blood vessels. Since thrombus formation and occlusion of vessels are characteristic of HUS, PMN–Plts interaction in the context of Stx may promote netosis and contribute to the endothelial damage observed in HUS. The aim of this study was to determine the relevance of netosis induced by Stx in the context of LPS-sensitized Plts on endothelial damage. We observed that Stx2 induced a marked enhancement of netosis promoted by Plts after LPS stimulation. Several factors seemed to promote this phenomenon. Stx2 itself increased the expression of its receptor on Plts, increasing toxin binding. Stx2 also increased LPS binding to Plts. Moreover, Stx2 amplified LPS induced P-selectin expression on Plts and mixed PMN–Plts aggregates formation, which led to activation of PMN enhancing dramatically NETs formation. Finally, experiments revealed that endothelial cell damage mediated by PMN in the context of Plts treated with LPS and Stx2 was decreased when NETs were disrupted or when mixed aggregate formation was impeded using an anti-P-selectin antibody. Using a murine model of HUS, systemic endothelial damage/dysfunction was decreased when NETs were disrupted, or when Plts were depleted, indicating that the promotion of netosis by Plts in the context of LPS and Stx2 plays a fundamental role in endothelial toxicity. These results provide insights for the first time into the pivotal role of Plts as enhancers of endothelial damage through NETs promotion in the context of Stx and LPS. Consequently, therapies designed to reduce either the formation of PMN–Plts aggregates or NETs formation could lessen the consequences of endothelial damage in HUS.

Function of Platelet Glycosphingolipid Microdomains/Lipid Rafts

Lipid rafts are dynamic assemblies of glycosphingolipids, sphingomyelin, cholesterol, and specific proteins which are stabilized into platforms involved in the regulation of vital cellular processes. The rafts at the cell surface play important functions in signal transduction. Recent reports have demonstrated that lipid rafts are spatially and compositionally heterogeneous in the single-cell membrane. In this review, we summarize our recent data on living platelets using two specific probes of raft components: lysenin as a probe of sphingomyelin-rich rafts and BCθ as a probe of cholesterol-rich rafts. Sphingomyelin-rich rafts that are spatially and functionally distinct from the cholesterol-rich rafts were found at spreading platelets. Fibrin is translocated to sphingomyelin-rich rafts and platelet sphingomyelin-rich rafts act as platforms where extracellular fibrin and intracellular actomyosin join to promote clot retraction. On the other hand, the collagen receptor glycoprotein VI is known to be translocated to cholesterol-rich rafts during platelet adhesion to collagen. Furthermore, the functional roles of platelet glycosphingolipids and platelet raft-binding proteins including G protein-coupled receptors, stomatin, prohibitin, flotillin, and HflK/C-domain protein family, tetraspanin family, and calcium channels are discussed.

Protection against Shiga Toxins

Shiga toxins consist of an A-moiety and five B-moieties able to bind the neutral glycosphingolipid globotriaosylceramide (Gb3) on the cell surface. To intoxicate cells efficiently, the toxin A-moiety has to be cleaved by furin and transported retrogradely to the Golgi apparatus and to the endoplasmic reticulum. The enzymatically active part of the A-moiety is then translocated to the cytosol, where it inhibits protein synthesis and in some cell types induces apoptosis. Protection of cells can be provided either by inhibiting binding of the toxin to cells or by interfering with any of the subsequent steps required for its toxic effect. In this article we provide a brief overview of the interaction of Shiga toxins with cells, describe some compounds and conditions found to protect cells against Shiga toxins, and discuss whether they might also provide protection in animals and humans.

Reflections on my career in analytical chemistry and biochemistry

My career has been focused in two major areas, analytical chemistry and biochemistry of complex lipids and glycoconjugates. Included here are the pioneering work on the gas chromatography of long-chain sphingolipid bases, carbohydrates, steroids and urinary organic acids. Mass spectrometry was utilized extensively in structural studies of sphingolipids, fatty acids, carbohydrates, steroids, urinary organic acids, polyisoprenoid alcohols, and juvenile hormone. Computer systems were developed for the acquisition and analysis of mass spectra, and were used for development of automated metabolic profiling of complex mixtures of metabolites. Fabry's disease was discovered to be a glycosphingolipidosis. Enzymes of lysosomal metabolism of glycosphingolipids were purified, characterized, and used in one of the first demonstrations of the feasibility of enzyme replacement therapy in a lysosomal storage disorder (Fabry's disease). Extracellular sialidases were studied to evaluate the hypothesis that they might be involved in the regulation of membrane growth factor receptors. The enzyme for hematoside synthesis was purified and characterized.

Involvement of GD3 in platelet activation. A novel association with Fcgamma receptor

Gangliosides are sialic acid-containing glycosphingolipids present in the outer leaflet of the plasma membrane of many cell types where they modulate adhesive processes. The main population of glycolipids in resting platelets is represented by ganglioside M3 (GM3). It has been demonstrated that following platelet activation ganglioside D3 (GD3) is rapidly formed from the GM3 pool. The present study was designed to evaluate the link between platelet activation and GD3 expression and to verify whether this ganglioside might play a role in modulating signal transduction events. Our results suggest that following platelet activation, GD3 is rapidly expressed on the platelet surface and internalised to the cytoskeleton where it transiently associates first with the Src family tyrosine kinase Lyn then with the Fc receptor gamma chain. This sequence of events ultimately leads to an enhanced CD32 (the Fc receptor isoform present in platelets) expression on the platelet membrane. These data drive us to speculate that GD3 might act as second messenger in the activatory cascade, which leads to CD32 expression and triggers platelet adhesion and spreading to the subendothelial matrix.

Expression of the Gb3/CD77 synthase gene in megakaryoblastic leukemia cells: implication in the sensitivity to verotoxins

Expression levels of Gb3/CD77 synthase together with Gb3/CD77 antigen were analyzed using human hematopoietic tumor cell lines and normal cells. Among about 40 kinds of cells, Burkitt lymphoma cells showed the highest gene expression concomitant with the expression levels of Gb3/CD77. Unexpectedly, megakaryoblastic leukemia lines also expressed fairly high levels of mRNA of Gb3/CD77 synthase and its product. A megakaryoblastic leukemia line, MEG-01 was sensitive to verotoxins from Escherichia coli O157 and apoptosis was induced via the caspase pathway. We also demonstrated that the cell surface Gb3/CD77 expression was reduced on differentiated MEG-01 although the mRNA level of the alpha1,4Gal-T gene increased. In this case, the localization of Gb3/CD77 was changed from the cell surface to the cytoplasm as stained with a granular pattern, co-localizing with platelet GPIIb-IIIa, indicating that some of them were platelet precursors. Small particles outside of cells also showed similar staining patterns. These results agreed with the previous report that platelets produced in mature megakaryoblasts abundantly contained Gb3/CD77 antigen. Here, we propose the possibility that verotoxins bind immature megakaryoblasts and induce their apoptosis, leading to the arrest of platelet generation in the bone marrow. This may be one of the causes of thrombocytopenia in patients with hemolytic uremic syndrome.

Sphingolipid metabolism during human platelet activation

Thrombin activation of human platelets causes release of sphingosine-1-phosphate from platelets and an increase in sphingosine levels. Sphingosine-1-phosphate is also known to potentiate platelet aggregation. Thus, these sphingolipids may serve as second messengers during platelet activation making it possible that another sphingolipid, ceramide, might play a role in platelet function. Platelets are known to contain sphingomyelinase activity and hydrolysis of sphingomyelin by this enzyme yields phosphocholine and ceramide. Since ceramide is thought to exert its effects through regulation of protein kinases and phosphatases, both of which are involved in platelet function, it is possible that ceramide produced during platelet activation could be involved in regulating signal transduction events. To investigate this possibility, potential changes in levels of ceramide and sphingomyelin in resting and thrombin-activated platelets have been evaluated. Thin-layer chromatographic analysis of the total mass or of radiolabeled (14C-palmitate or 14C-serine) pools of ceramide and sphingomyelin did not reveal any significant changes in the concentrations of either of these molecules during platelet activation. In addition, activation of platelets labeled with [14C-choline]-sphingomyelin did not lead to production of 14C-phosphocholine, suggesting that platelet activation did not cause sphingomyelinase to hydrolyze the [14C-choline]-sphingomyelin. Taken together, our results suggest that ceramide does not serve as a second messenger during platelet aggregation.

Shiga toxin binds human platelets via globotriaosylceramide (Pk antigen) and a novel platelet glycosphingolipid

Hemolytic-uremic syndrome is a clinical syndrome characterized by acute renal failure, microangiopathic hemolytic anemia, and thrombocytopenia that often follows infection by Shiga toxin- or verotoxin-producing strains of Escherichia coli. Because thrombocytopenia and platelet activation are hallmark features of hemolytic-uremic syndrome, we examined the ability of Shiga toxin to bind platelets by flow cytometry and high-performance thin-layer chromatography (HPTLC) of isolated platelet glycosphingolipids. By HPTLC, Shiga toxin was shown to bind globotriaosylceramide (Gb3) and a minor platelet glycolipid with an Rf of 0.03, band 0.03. In a survey of 20 human tissues, band 0.03 was identified only in platelets. In individuals, band 0.03 was expressed by 20% of donors and was specifically associated with increased platelet Gb3 expression. Based on glycosidase digestion and epitope mapping, band 0.03 was hypothesized to represent a novel glycosphingolipid, IV3-beta-Galalpha1-4galactosylglobotetraosylceramide. Based on incidence, structure, and association with increased Gb3 expression, band 0.03 may represent the antithetical Luke blood group antigen. By flow cytometry, Shiga toxin bound human platelets, although the amount of Shiga toxin bound varied in donors. Differences in Shiga toxin binding to platelet membranes did not reflect differences in platelet Gb3 expression. In contrast, there was a loose association between Shiga toxin binding and decreasing forward scatter, suggesting that Shiga toxin and verotoxins bind more efficiently to smaller, older platelets. In summary, Shiga and Shiga-like toxins may bind platelets via specific glycosphingolipid receptors. Such binding may contribute to the thrombocytopenia, platelet activation, and microthrombus formation observed in hemolytic-uremic syndrome.

A novel carbohydrate-glycosphingolipid interaction between a beta-(1-3)-glucan immunomodulator, PGG-glucan, and lactosylceramide of human leukocytes

The immunomodulator Betafectin(R) PGG-glucan is a homopolymer of glucose derived from yeast cell walls which has been demonstrated to enhance leukocyte anti-infective activity in vitro and in vivo, without the induction of proinflammatory cytokines. We report here the purification of a PGG-glucan-binding element from human leukocytes and its identification as lactosylceramide, a major glycosphingolipid of neutrophils, which includes the CDw17 epitope. The binding of radiolabeled PGG-glucan to purified lactosylceramide was saturable, specific, and time- and temperature-dependent. Lactosylceramides from human leukocytes were fractionated by high performance liquid chromatography in order to analyze the effect of ceramide structure on binding. A variety of fatty acid chain lengths with varying degrees of unsaturation were found to support binding to radiolabeled PGG-glucan. However, DL-lactosylceramides containing dihydrosphingosine did not bind. Radiolabeled PGG-glucan bound several other neutral glycosphingolipids with a terminal galactose, including galactosylceramide, globotriaosylceramide, and gangliotetraosylceramide. The binding of radiolabeled PGG-glucan to lactosylceramide was not inhibited by glycogen, dextran, mannan, pustulan, laminarin, or a low molecular weight beta-(1-3)-glucan, but was inhibited by high molecular weight beta-(1-3)-glucans and by a monoclonal antibody to lactosylceramide. Although this glycosphingolipid has been shown in numerous reports to bind various microorganisms, this represents the first report of lactosylceramide binding to a macromolecular carbohydrate.

Rapid internalization of exogenous ganglioside GM3 and its metabolism to ceramide in human myelogenous leukemia HL-60 cells compared with control ganglioside GM1

Incorporation and metabolism of exogenous GM3 in human myelogenous leukemia HL-60 cells were analyzed using 3H-labeled GM3 ([3H]GM3). [3H]GM3 was rapidly internalized into the cells (trypsin-resistant fraction) 8 times more than the control, 3H-labeled GM1 ([3H]GM1). In addition, not only incorporation but also metabolism of [3H]GM3 was more rapid than [3H]GM1 in HL-60 cells. Moreover, one of the metabolites was found to co-migrate with ceramide in thin-layer chromatography analysis and ceramide formation from exogenous GM3 is more rapid than that from exogenous GM1. These results suggested that there would be some preferential mechanism to produce ceramide from differentiation-inducible GM3 in HL-60 cells rather than from non-inducing GM1.

Clinical significance of anti-GM3 antibodies in recurrent pregnancy loss with elevated level of antiphospholipid antibodies

PROBLEM

The ganglioside-GM3 neutralizes the reactivity of antiphospholipid antibodies (APLs) to phospholipids in vitro. The question of whether anti-GM3 antibodies might exert influence in APLs-positive recurrent pregnancy loss patients who are undergoing prednisolone and aspirin (PSL/ASA) treatment was investigated.

METHOD

The anti-GM3 antibody assay of sera was accomplished by ELISA. Sera of 56 patients with recurrent pregnancy loss, including 30 APLs-positive cases given PSL/ASA treatment, were examined.

RESULTS

Patients positive for IgG or IgM type anti-GM3 antibodies constituted 13/30 (43%) of the APLs-positive group as compared with only 2/26 (8%) of those who were negative (P < 0.01). In pregnant women with APLs-positive treated with PSL/ASA, live births occurred in only 6/13 (46%) patients with detectable anti-GM3 antibodies, while in 16/17 (94%) who tested negative for anti-GM3 antibodies (P < 0.01).

CONCLUSIONS

This observation suggests the possibility that presence of anti-GM3 antibodies may be an indicator for determining the prognosis in recurrent pregnancy loss with elevated level of APLs.

Antiplatelet effects of a new de-N-acetyl-lyso-glycosphingolipid

Gal beta 1-->3GalN beta 1-->4Gal(3<--2 alpha Neu)beta 1-->4Glc beta-->1Sph (WILD20), a new glycosphingolipid, a breakdown product of the monosialoganglioside GM1 obtained through alkaline hydrolysis, shows dose-dependent platelet anti-aggregating properties in vitro and in vivo. This effect is agonist- and species-independent. The family of lysosphingolipids, to which the compound belongs, is present in platelets particularly after thrombin treatment. WILD20 antiplatelet effect is due to the interference with ADP or thrombin-induced aggregation, probably via phospholipase A2 (PLA2) blockade; the substance is also effective when arachidonic acid is used as an agonist. Serotonin blood levels are also reduced. The substance, orally active at dosages of 0.1-0.01 mg/kg as antiplatelets agent, prolonged bleeding time without interfering with the coagulative or fibrinolytic processes.

Palmitic acid-labeled lipids selectively incorporated into platelet cytoskeleton during aggregation

Previous experiments showed that during the early stages (20-30 seconds) of aggregation induced by adenosine diphosphate (ADP, 2 microM) or thrombin (0.1 U/mL) of rabbit or human platelets prelabeled with [3H]palmitic acid, labeled lipid became associated with the cytoskeleton isolated after lysis with 1% Triton X-100, 5 mM EGTA [ethylene glycol-bis-(beta-aminoethyl ether)]-N,N,N',N'-tetra-acetic acid. The association appeared to be related to the number of sites of contact and was independent of the release of granule contents. We have now investigated the nature of the labeled lipids by thin-layer and column chromatography and found differences between the distribution of the label in intact platelets (both stimulated and unstimulated) and the isolated cytoskeletons. In both species, and with either ADP or thrombin as aggregating agent, 70-85% of the label in both intact platelets and in the cytoskeletons was in phospholipids. The distribution of label among the phospholipids in the cytoskeletons was similar to that in intact platelets except that the percentage of label in phosphatidylcholine was significantly higher in the cytoskeletons of human platelets than in the intact platelets, and the percentage of label in phosphatidylserine/phosphatidylinositol was significantly lower in the cytoskeletons of rabbit platelets and thrombin-aggregated human platelets than in intact platelets. The cytoskeletons contained a lower percentage of label in triacylglycerol, diacylglycerol, and cholesterol ester than the intact platelets. Contrary to a report in the literature, we found no evidence for the incorporation of diacylglycerol and palmitic acid into the cytoskeleton.(ABSTRACT TRUNCATED AT 250 WORDS)

Neutral glycosphingolipids isolated from porcine corneas

Six neutral glycosphingolipids were isolated from porcine corneas using silicic acid column chromatography and preparative thin-layer chromatography. Five of these glycolipids were partially identified by gas-liquid chromatography. Two were glucosylceramides, two were lactosylceramides and one was tetrahexosylceramide containing galactose, glucose and N-acetylgalactosamine in the molar ratio of 2:1:1. Glucosylceramides were found to be the predominating component, with lactosyl- and tetrahexosylceramides being the minor constituents. Sphingosine was the major long-chain base in all fractions. The fatty acids of the corneal neutral glycosphingolipids were variable in chain length. This represents the first investigation of neutral glycosphingolipids in corneas of any species.

Damaging effects of Clostridium perfringens delta toxin on blood platelets and their relevance to ganglioside GM2

The lytic effect of Clostridium perfringens delta toxin was investigated on goat, human, rabbit, and guinea pig platelets. In contrast to erythrocytes from the latter three species, which are insensitive to the toxin, the platelets were equally lysed by the same amount of toxin. These results suggest the presence of GM2 or GM2-like ganglioside(s) as a specific recognition site of the toxin on platelet plasmic membrane as previously established for sensitive erythrocytes. Plasmic membrane damage of human platelets was evidenced by the release of entrapped alpha-[14C]aminoisobutyric acid used as a cytoplasmic marker. The specific binding of hemolytically active 125I-delta toxin by human and rabbit platelets was practically identical, dose dependent, and inhibitable by GM2. Labeled toxin was also bound by various subcellular organelles separated from rabbit platelets except the 5-hydroxytryptamine (5-HT)-containing dense bodies, suggesting the absence or inaccessibility of GM2 on the surface of the latter organelles. This result correlates with the low amounts of 5-[3H]HT liberated after platelet challenge with delta toxin whereas this mediator was massively liberated upon lysis by the sulfhydryl-activated toxin alveolysin. The levels of M and P forms of phenol sulfotransferase (PST), involved in 5-HT catabolism, were determined in human platelet lysates after challenge with delta toxin, alveolysin, and other disruptive treatments. The low PST-M activities detected after lysis by delta toxin suggest that this isoenzyme is very likely associated to dense bodies in contrast to PST-P which is cytoplasmic. Platelet lysis by the toxin allows easy separation of these organelles.

Antibodies against glycosphingolipids in sera of patients with idiopathic thrombocytopenic purpura

Evidence is presented for the existence of antibodies against platelet glycosphingolipids in sera of patients with chronic idiopathic thrombocytopenic purpura and antiplatelet antibodies. Increased binding of IgG/IgM to neutral glycosphingolipids or gangliosides extracted from donor platelets was measured by an ELISA in 17 sera of 30 patients. Thirteen sera, five with anticardiolipin antibodies, demonstrated an increased binding to sulphatides confirmed by immuno HPTLC. Four sera showed reactivity with the platelet minor gangliosides established by immuno-HPTLC.

A murine monoclonal IgM antibody specific for blood group P antigen (globoside)

A murine monoclonal IgM erythrocyte antibody appeared to have anti-P (anti-globoside) specificity. The antibody was a relatively weak cold agglutinin, but a strong haemolysin and its reactivity with red cells was markedly enhanced by enzyme treatment. This antibody was used to study the cell and tissue distribution of globoside. Globoside was not only detectable on red cells and erythroblasts, but also on endothelial cells and on subsets of platelets, megakaryocytes and fibroblasts. It was not detectable on granulocytes, monocytes and most peripheral blood lymphocytes. Neither was it present on erythroblast precursors (CFU-E, BFU-E), pro-erythroblasts or on the cells of the pro-erythroblastic cell lines K562 and HEL. However, K562 cells expressed globoside when induced to mature into erythroblasts by sodium butyrate. Cells of patients with various leukaemias were also tested. A significant number of positively reacting cells was frequently (six out of 18) seen in cases with a CML blast crisis (CML-BC) and rarely in AML (four out of 37 cases). In CML-BC the P-positive cells were probably erythroblasts and/or megakaryoblasts. Thus, globoside appeared to be an interesting marker in CML-BC of the erythroblastic or mixed erythroblastic-megakaryoblastic type.

Antiglycolipid antibodies in normal and pathologic human sera and synovial fluids

Antiglycolipid antibodies were measured in normal and pathologic sera and synovial fluids by means of a modified microplate method of complement-mediated immune lysis of fluorescent dye-trapped liposomes. All sera of normal subjects had antibodies against globopentaosylceramide (IV3 GalNAcGbOse4Cer), ganglioside GM1, gangliotriaosylceramide, gangliotetraosylceramide, and galactosylneolactotetraosylceramide antigens. Most sera of normal subjects had antibodies against lactotriaosylceramide, N-glycolylneuraminosyl-neolactotetraosylceramide (NeuGcnLcOse4Cer), GM3 ganglioside with N-glycolylneuraminic acid (NeuGcGM3) and GD1a antigens. Differences of titers against IV3GalNAcGbOse4Cer, neolactotetraosylceramide, NeuGcGM3 and NeuGcnLcOse4Cer antigens were observed between sera of normal subjects and pathologic sera from cases of leukemias, lymphomas, several autoimmune diseases and liver diseases.

Glycosphingolipids of the globo-series are associated with the monocytic lineage of human myeloid cells

Neutral glycosphingolipids (neutral GSLs) of the human myeloid leukemia cell lines ML-2, ML-3, HL-60 and THP-1-0 were metabolically labeled with [3H]galactose and [3H]glucosamine, and analyzed by high-performance liquid chromatography. They were compared with unlabeled neutral GSLs from purified human granulocytes and monocytes. Neutral GSLs were identified by retention times and the structures were further confirmed by degradation with specific exoglycosidases. Two neutral GSLs of the globoseries, globotetraosylceramide and globotriaosylceramide were found in monocytes and the monoblastic leukemia line THP-1-0. The leukemia-derived cell-lines, ML-3 and HL-60, representing successively earlier stages of myeloid differentiation, contained respectively less neutral GSLs of the globoseries and an increasing proportion of (neo)lacto neutral GSLs. Granulocytes and the cell line ML-2 contained almost exclusively neutral GSLs of the (neo)lacto series.

A new family of fucose-containing gangliosides isolated from human senile cataracts

Gangliosides were isolated from human cataracts by solvent extraction, silicic acid chromatography, thin-layer chromatography and gas-liquid chromatography. A total of 11 resorcinol-positive bands were revealed by thin-layer chromatography. Bands 1, 5 and 7 were partially identified as hematoside. GM1 ganglioside and disialoganglioside by gas-liquid chromatography as the O-trimethylsilylated methylglycosides. In addition to galactose and glucose, fucose was found to be present in seven ganglioside fractions (bands 3, 4, 6 and 8-11). All these fucolipids contained N-acetylglucosamine in addition to sialic acid. Fucogangliosides G-3, G-4 and G-6 contained a 2:1 molar ratio of galactose to glucose, while G-8 had a galactose/glucose molar ratio of 1:1. Long-chain fatty acids constituted 60-77% of the total normal fatty acids in N-acetylgalactosamine-containing gangliosides, whereas the fucogangliosides contained primarily palmitate, although significant amounts of long-chain acids were also detected. The major long-chain base of the fucoganglioside was sphinganine (dihydrosphinogosine). The role of fucose-containing gangliosides in maintaining adhesions between lens membranes in cataracts is discussed with reference to glycosphingolipids in other tissues.

Isolation and partial characterization of fucose- and N-acetylglucosamine-containing neutral glycosphingolipids from human senile cataracts

Five neutral glycosphingolipids were isolated from human cataracts using silicic acid column chromatography and preparative thin-layer chromatography. Three of these glycolipids were partially identified by gas-liquid chromatography as glucosylceramide, lactosylceramide, and trihexosylceramide. Two glucosamine-containing glycosphingolipids (one of which contained fucose) were also detected. One of these two lipids contained galactose, glucose, N-acetylglucosamine in the molar ratio of 2:1:1, while the other contained fucose, galactose, glucose, and N-acetylglucosamine with the molar ratio of 1:2:1:1. Dihydrosphingosine (sphinganine) was the major long-chain base detected in all these fractions. The fatty acids of these neutral glycosphingolipids were variable in chain length, although the majority of them were greater than 20 carbons. This represents the first time whereby a family of neutral glycosphingolipids has been detected in human cataracts. This is also the first demonstration of the existence of a neutral fucolipid in the lenses of any species.

Isolation and structural characterization of human lymphocyte neutral glycosphingolipids

The neutral glycosphingolipids of human peripheral blood lymphocytes and of the lymphoid cells from a patient with B cell chronic lymphocytic leukemia were chemically analyzed. Four neutral glycosphingolipids were chemically analyzed. Four neutral glycosphingolipids were isolated from each of these two sources and studied by gas chromatography, methylation analysis, and electron impact--desorption mass spectrometry. The results of these studies indicate that the compounds have the following structures: Glc1 leads to 1Cer Gal1 leads to 4Glc1 leads to 1Cer Gal1 leads to 4Gal1 leads to 4Glc1 leads to 1Cer GalNAc1 leads to 3Gal1 leads to 4Gal1 leads to 4Glc1 leads to 1Cer These compounds, belonging to the globo series, were the only neutral glycosphingolipids found in the lymphoid cells. The ceramide (Cer) moiety of all these compounds contained 4-sphingenine with C16:0, C24:0, and C24:1 as the major fatty acid species. There were no structural differences in the neutral glycosphingolipids of peripheral blood lymphocytes compared to those of chronic lymphocytic leukemia cells. Peripheral blood lymphocytes contained more di- than monohexosylceramide whereas the reverse was true of the chronic lymphocytic leukemia cells. The proportion of tri- and tetrahexosylceramide was less than 10% for both types of cells. The results of our analyses did not support the existence of any differences in the major neutral glycosphingolipids among T, B, and chronic lymphocytic leukemia cells.

Isolation and partial characterization of the neutral glycosphingolipids and gangliosides of the human heart

The glycosphingolipids (GSL) of the human heart muscle have been isolated from total lipids by column and thin layer chromatography and their sugars and fatty acids analyzed by gas liquid chromatography. Hearts from traffic victims were obtained at autopsy between 12 and 16 hr after death and dissected into parts (left and right ventricular walls, intraventricular septum and papillary muscle). The neutral GSL content for those parts of the hearts of two males aged 22 and one female aged 14 ranged from about 90 to 160 nmoles/g wet weight. Trihexosyl ceramide and globoside were the most abundant neutral GSL. Total ganglioside content was about 50 nmoles/g wet weight, and the most abundant gangliosides were partially characterized as GM3 and GM1; other mono-, di- and trisialogangliosides were also present. Differences in the content and composition of neutral GSL and gangliosides between the heart and other human tissues are discussed. It is concluded that the patterns of these two GSL fractions of the heart are more complex than those of the extraneural human tissues.

Structures and fatty acid compositions of neutral glycosphingolipids of human plasma

Major neutral glycosphingolipids were isolated from human plasma and their structures and fatty acid compositions studied. The four neutral glycosphingolipids of plasma were characterized as Glc beta(1 leads to 1)ceramide, Gal beta(1 leads to 1)- ceramide, Gal beta(1 leads to 4) Glc beta (1 leads to 1)ceramide, Gal alpha(1 leads to 4) Gal beta(1 leads to 4) Glc beta(1 leads to 1)ceramide and GalNAc beta(1 leads to 3) Gal (1 leads to 4) Gal (1 leads to 4) Glc beta(1 leads to 1)-ceramide. The glycosphingolipids contained mostly short chain fatty acids of which most prominent was C16. Erythrocyte glucosylceramide and lactosylceramide exhibited similar fatty acid compositions as their plasma counterparts. Triglycosylceramide and globoside of erythrocytes contained almost exclusively long-chain fatty acids. In lactosylceramide obtained from "p" erythrocytes, an accumulation of long-chain fatty acids was found; this accumulation was not observed, however, in lactosylceramide isolated from "p" plasma. It was concluded that plasma and erythrocyte glycosphingolipids are synthesized at separate sites where short- and long-chain fatty acids, respectively, are available. Plasma and erythrocyte glucosylceramide, and probably a fraction of lactosylceramide, exchange between plasma and erythrocyte pools. The latter conclusion is discussed in the light of the relative roles of carbohydrate and lipid moieties of the glycosphingolipids in maintaining their association with erythrocyte membranes.

A simple and novel method for tritium labeling of gangliosides and other sphingolipids

A very simple method for introducing tritium specifically into the ceramide portion of gangliosides, neutral glycosphingolipids and sphingomyelin has been developed using potassium boro [3H]hydride and palladium as catalyst. In this way six different gangliosides, five different neutral glycosphingolipids and sphinomyelin with high specific radioactivity were prepared for the first time. This simple procedure which does not require sophisticated apparatuses is suitable for large scale preparation of tritium-labeled sphingolipids as well as for nanogram quantities of individual sphingolipids so as to serve for analytical purposes. During the course of the labeling procedure no degradation of even the most labile trisialosyl-gangliotetraosylceramide has been observed. The yield of tritiated compounds is almost quantitative. The specific radioactivity depends on the unsaturation of the ceramide moiety and the specific activity of the boro[3H]hydride employed.

Lipid composition of sputum from patients with asthma and patients with cystic fibrosis

Lipids from the sputum of patients with asthma and with cystic fibrosis were isolated and characterized. In both cases, lipids constituted approximately 30% of the dry material. Phosphatidlycholine was the most abundant lipid, Significant amounts of phosphatidylethanolamine and phosphatidylglycerol were present. Hexosyl ceramides, sphingomyelin, phosphatidylinositol, lysophosphatidylcholine, and lysophosphatidylethanolamine were present as minor lipid components. Apperciable quantities of neutral lipids were present, of which triglycerides and cholesterol were the main constituents. Phosphatidylcholine, sphingomyelin, and phosphatidylgycerol were highly saturated. Large amounts of phosphatidylcholine containing mostly palmitic acid, particularly in the asthmatic sputum, suggest htat this highly saturated. Large amounts of phosphatidylcholine containing mostly palmitic acid, particularly in the asthmatic sputum, suggests that this highly saturated phospholipid is synthesized in the upper airways for reasons other than its beneficial surface-active properties in the alveoli.

Isolation and characterization of poly(glycosyl)ceramides (megaloglycolipids) with A, H and I blood-group activities

Very complex glycosphingolipids with A, H and I blood-group activities were isolated from human erythrocyte membranes. The membranes were obtained from erythrocytes of blood group A, A2 and O respectively. A general formula for the antigens is: (Fuc)3-4(Gal)n(LlcNAc)n-2(Glc)1(Sphingosine)1(where Fus is fucose, Gal is galactose, GlcNAc is N-acetylglucosamine and Glc is glucose) with values of n ranging from 10-27. A-active preparations contain additionally 2-3 residues of N-acetylgalactosamine. In view of the unusual complexity of these compounds they were designated poly(glycosyl)ceramides (formerly megaloglycolipids). Individual poly(glycosyl)ceramide fractions were isolated from A erythrocytes and were found to differ by about 8 glycosyl residues per molecule forming a series of compounds with 22, 30, 38, 51 and 59 glycosyl residues per mole. Structural studies indicate that the main sequence of poly(glycosyl)ceramides consists of the residues of galactopyranose and 2-deoxy-2-acetamidoglucopyranose substituted at 3 and 4 position respectively. These residues are probably alternating. N-Acdtylglucosamine substituted at 3 position was not found in poly(glycosyl)ceramides. Brances of poly(glycosyl)ceramides originate from 3 and 6 position of galactopyranosyl residues. The number of branches is proportional to the degree of molecular complexity. In poly(glycosyl)ceramides isolated from A and A2 erythrocytes the branches are terminated with the following structures GalNAc alpha 1 leads to 3 [Fuc alpha 1 leads to 2] Gal; Fuc alpha 1 leads to 2 Gal and Gal (presumably Gal beta 1 leads to 4 GlcNAc). In poly(glycosyl)ceramides from A cells the total number of A and H-active structures per average molecule of 30-35 glycosyl residues amounts to 2.1 and 1.2 respectively while the number of terminal galactose structures is 1.8. For poly(glycosyl)ceramides from A2 erythrocytes the corresponding figures are 0.75, 3.5, and 2.1 respectively. Poly(glycosyl)ceramides from O cells comprise about 3.8 H-active structures and 1.8 terminal galactopyranosyl residues. In poly(glycosyl)ceramides with high "n" values the number of terminal galactose structures is increased. These fractions display high blood-group I activity. However, the removal of terminal galactose with beta-galactosidase affects I-activity only slightly.

Branched long-chain bases from the bivalve Corbicula sandai

Long-chain bases were liberated from a crude mixture of sphingolipids from whole tissue of the fresh-water bivalve C. sandai, and conversion of the bases into N-acetyl-0-trimethylsily derivatives was accomplished. The derivatized bases were analyzed by combined gas-liquid chromatography and mass spectrometry. A portion of the sphingolipids was subjected to catalytic hydrogenation from whch saturated long-chain bases (sphinganines) were obtained. The saturated bases were oxidized with lead tetra-acetate and the aldehydes produced were analyzed by gas-liquid chromatography. The aldehydes were further oxidized to acids with silver oxide, the resulting fatty acids methylated and also analyzed by gas-liquid chromatography. By these analyses, altogether five long-chain bases were identified, consisting of hexadeca-4-sphingenine (15%), heptadeca-4-sphingenine (2%), iso-octadeca-4-sphingenine (13%), octadeca-4-sphingenine (39%) and anteiso-noadeca-4-sphingenine (31%). So far no branches have been found in shellfish spingolipid long-chain bases.

Foamy histiocytosis of the spleen in patients with chronic thrombocytopenia

In 17 of the 64 spleens removed from patients with chronic thrombocytopenia lipid-laden histiocytotes were demonstrated. No correlation was found between these pathological findings and the age of the patients at diagnosis or splenectomy, the duration before splenectomy of therapy with glucocorticoids, the period with thrombocytopenia or the platelet count. 7 of the patients, who relapsed after splenectomy had lipid-laden histiocytes in their spleens i.e. 58% of the patients with relapse, compared with 10 patients with foamy histiocytosis and without relapse i.e. 19% of the patients without relapse. At follow up, 3 of the 17 patients with splenic histiocytosis still had thrombocytopenia, compared with 1 of the 47 patients without foamy cells. Foamy histiocytosis of the spleen from a patient with chronic thrombocytopenia may indicate a dubious prognosis.

Ceramides of human normal and cataractous lens

Ceramides were quantitatively isolated from human normal and cataractous lens by solvent extraction, silicic acid chromatography, thin-layer chromatography, and gas-liquid chromatography. Only two species of ceramides with normal fatty acids were detected. In the mature cataracts, there was an increase in palmitate and nervonate at the expense of the other fatty acids. Due to the increase of 24 : 1, the ratio of 24 : 1/24 : 0 increased significantly from normals to cataracts. Sphinganine was the major long-chain base, but 4-sphingenine was also present. The total amount of ceramides in the immature and mature cataracts was 1.8 and 3.0 times higher than the normals of the same age group. Such an increase does not seem to be the result of an age-dependent process.