Sphingolipids of a cestode Metroliasthes coturnix

A Comparative Metabolomics Approach Demonstrates That Octocrylene Accumulates in Stylophora pistillata Tissues as Derivatives and That Octocrylene Exposure Induces Mitochondrial Dysfunction and Cell Senescence

The objective of this work was to study the effect of octocrylene on Stylophora pistillata and to compare the metabolomic response of this coral species to that obtained with Pocillopora damicornis. When S. pistillata coral was exposed to octocrylene, it accumulated octocrylene derivatives similar to P. damicornis. Octocrylene-fatty acid conjugates were found, as well as octocrylene heterosides. Furthermore, the tissue concentrations of various acylcarnitines and three sphingoid bases increased significantly. This phenomenon was indicative of mitochondrial dysfunction and the induction of cellular senescence processes in exposed corals. Overall, the responses of the two corals to octocrylene pollution were consistent. The proven impact of octocrylene on a second coral species suggests that potential environmental octocrylene pollution could impact many reef-building species. Furthermore, this work demonstrates that octocrylene may be modified in vivo by many organisms and that levels of octocrylene contamination in the food chain have probably been underestimated until now.

Functions and applications of glycolipid-hydrolyzing microbial glycosidases

Glycolipids are important components of cell membranes in several organisms. The major glycolipids in mammals are glycosphingolipids (GSLs), which are composed of ceramides. In mammals, GSLs are degraded stepwise from the non-reducing end of the oligosaccharides via exo-type glycosidases. However, endoglycoceramidase (EGCase), an endo-type glycosidase found in actinomycetes, is a unique enzyme that directly acts on the glycosidic linkage between oligosaccharides and ceramides to generate intact oligosaccharides and ceramides. Three molecular species of EGCase, namely EGCase I, EGCase II, and endogalactosylceramidase, have been identified based on their substrate specificity. EGCrP1 and EGCrP2, which are homologs of EGCase in pathogenic fungi, were identified as the first fungal glucosylceramide- and sterylglucoside-hydrolyzing glycosidases, respectively. These enzymes are promising targets for antifungal drugs against pathogenic fungi. This review describes the functions and properties of these microbial glycolipid-degrading enzymes, the molecular basis of their differential substrate specificity, and their applications.

A Novel Endoglycoceramidase Hydrolyzes Oligogalactosylceramides to Produce Galactooligosaccharides and Ceramides

Enzymes capable of hydrolyzing the beta-glycosidic linkage between oligosaccharides and ceramides in various glycosphingolipids has been found in microorganisms and invertebrates and designated endoglycoceramidase (EC 3.2.1.123) or ceramide glycanase. Here we report the molecular cloning, characterization, and homology modeling of a novel endoglycoceramidase that hydrolyzes oligogalactosylceramides to produce galactooligosaccharides and ceramides. The novel enzyme was purified from a culture supernatant of Rhodococcus equi, and the gene encoding 488 deduced amino acids was cloned using peptide sequences of the purified enzyme. Eight residues essential for the catalytic reaction in microbial and animal endoglycoceramidases were all conserved in the deduced amino acid sequence of the novel enzyme. Homology modeling of the enzyme using endocellulase E1 as a template revealed that the enzyme displays a (beta/alpha)8 barrel structure in which Glu234 at the end of beta-strand 4 and Glu341 at the end of beta-strand 7 could function as an acid/base catalyst and a nucleophile, respectively. Site-directed mutagenesis of these glutamates resulted in a complete loss of the activity without a change in their CD spectra. The recombinant enzyme hydrolyzed the beta-galactosidic linkage between oligosaccharides and ceramides of 6-gala series glycosphingolipids that were completely resistant to hydrolysis by the enzymes reported so far. In contrast, the novel enzyme did not hydrolyze ganglio-, globo-, or lactoseries glycosphingolipids. The enzyme is therefore systematically named "oligogalactosyl-N-acylsphingosine 1,1'-beta-galactohydrolase" or tentatively designated "endogalactosylceramidase."

Chemical structures and immunolocalization of glycosphingolipids isolated from Diphyllobothrium hottai adult worms and plerocercoids

Glycosphingolipids (GSLs) were purified from adults and plerocercoids of the tapeworm Diphyllobothrium hottai, and their chemical structures were determined. Total lipid fractions prepared from chloroform/methanol extracts of whole tissues were fractionated successively on ion-exchange chromatography, silicic acid column chromatography, and preparative TLC. The purified GSLs were characterized by methylation analysis, TLC-immunostaining, liquid secondary ion MS, MALDI-TOF MS, and 1H-NMR. Ten GSLs were isolated from adult worms and four from plerocercoids, comprising mono-, di-, tri-, tetra-, and pentasaccharides. The GSL Gal beta 1-4(Fuc alpha 1-3)Glc beta 1-3Gal beta 1-Cer was found in adult worms but not in plerocercoids, whereas Ga lbeta 1-4 (Fuc alpha 1-3)Glc beta 1-3(Gal beta 1-6)Gal beta 1-Cer was found in both adult worms and plerocercoids. We previously found a similar series of GSLs in plerocercoids of the cestode Spirometra erinaceieuropaei, and termed them 'spirometosides'[Kawakami, Y. et al. (1996) Eur J. Biochem. 239, 905-911]. The core structure of spirometosides, Gal beta 1-4Glc beta 1-3 Gal beta 1-Cer, may have taxonomic significance, being characteristic of pseudophyllidean tapeworms. In the present study, GSL compositions were significantly different between adults and plerocercoids, and growth-dependent changes in composition were documented. We found a novel dihexosylceramide, Glc beta 1-3Gal beta 1-Cer, which is a possible precursor for spirometosides. Immunohistochemical examination showed that spirometoside GSLs are highly enriched in the inner surface of bothria, the major point of contact between the adult worm and the host's intestine. Our findings indicate that spirometosides are involved in host-parasite interaction.

A major Echinococcus multilocularis antigen is a mucin-type glycoprotein

The metacestode of Echinococcus multilocularis is surrounded by a carbohydrate-rich laminated layer, which plays a key role in the establishment of the infection in the mammalian host. A major component of the laminated layer is an antigen referred to as Em2(G11). This highly species-specific antigen has been used for serodiagnoses of alveolar echinococcosis and is suggested to contain carbohydrates as major constituents. The results of this work have shown that immunoaffinity-purified Em2(G11) subjected to size-exclusion chromatography eluted mainly in the void volume, indicating a high molecular weight structure of this antigen. Amino acid analysis revealed a large proportion of threonine and proline residues in Em2(G11). The carbohydrate moiety of the antigen was found to be composed of galactose, N-acetylgalactosamine, and N-acetylglucosamine with a ratio of 2.4:1.0:0.5 as determined by gas-chromatography/mass spectrometry. An isotope tag was introduced to the beta-eliminated glycans, and an integrated mass spectrometric O-glycan profiling and sequencing approach was employed to obtain detailed sequence and linkage information of the unseparated glycoform pool. Novel glycoforms containing mucin-type core Gal1-3GalNAc and branched core structures attached to both serine and threonine residues are described. The data presented reveal that the Em2(G11) antigen is a mucin-type glycosylated protein.

Structure and antigenicity of the major glycolipid from Taenia solium cysticerci

Lipids were extracted from cysticerci of the human tapeworm Taenia solium isolated from various infected pigs and analysed by two-dimensional thin-layer chromatography. These consisted of both alkali-labile and alkali-stable glycolipids, and phosphorylated non-glycosylated lipids. Because abundant and immunogenic glycolipids of parasites have been implicated in host-parasite interactions, the major lipid, an alkali-stable glycolipid, was purified by chromatography and its structure and antigenicity were determined. The structure of the major glycolipid of T. solium, GSL-I, was elucidated through a combination of chemical degradative methods, gas chromatography/mass spectrometry analyses of the degradative products, matrix-assisted-laser desorption/ionisation time of flight mass spectrometry and nuclear magnetic resonance spectroscopy. This analytical strategy led to the identification of a family of beta-galactosylceramides composed mainly of phytosphinganine (2-hydroxylated sphinganine) N-acylated by C16-C24 fatty acids, with the predominance of 2-hydroxylated homologues. Enzyme-linked immunosorbent assay showed no correlation between the antibody titres directed against GSL-I in the human sera and the infective status; in contrast, a very high specific immunoreactivity and a sensitivity above 50% were observed when GSL-I was tested with cerebrospinal fluids from well characterised infected humans. Thus, although these results do not support the use of GSL-I alone as an antigen for the detection of neurocysticercosis, its use as part of an antigen cocktail for the diagnosis of the disease in cerebrospinal fluids merits further investigations.

A monoclonal antibody against a glycolipid SEGLx from Spirometra erinaceieuropaei plerocercoid

A mouse monoclonal antibody AK97 (IgM) was established against a new type of glycosphingolipid, SEGLx, isolated from plerocercoids of tapeworm, Spirometra erinaceieuropaei. The chemical structure of SEGLx (Gal beta1-4(Fuc alpha1-3)(Glc beta1-3Gal beta1-ceramide) had been previously characterized. The specificity of AK97 was determined by thin-layer chromatography-immunostaining and enzyme-linked immunosorbent assay. AK97 was found to be directed to SEGLx and GalSEGLx (Gal beta1-4(Fuc alpha1-3)Glc beta1-3(Gal beta1-6)Gal beta1-ceramide) and also showed cross-reactivity with the stage specific embryonic antigen-1 (SSEA-1), the epitope being defined to be the non-reducing terminal trisaccharide sequence. On immunohistochemical examination, AK97 predominantly stained the tegument, the external surfaces of worms which have a brush border-like organization. Based on the immunohistochemical findings for the staining liability as to organic solvents and the results of Western blot analysis of the plerocercoid glycoproteins, it was proved that the antigens in the tapeworm were glycolipids. Considering that the tapeworm is in direct contact with its host's tissue through the tegument, the membrane surface of which is exposed to the external environment, it is suspected that SEGLx and GalSEGLx on the tegument play functionally important roles in the host parasite interaction.

Interaction of earthworm hemolysin with lipid membranes requires sphingolipids

Lytic activity in the coelomic fluid of earthworm (Eisenia fetida fetida) has been ascribed to eiseniapore, a hemolytic protein of 38 kDa. Since receptors for eiseniapore on target cell membranes are not known, we used lipid vesicles of various composition to determine whether specific lipids may serve as receptors. Lytic activity of eiseniapore was probed by the relief of fluorescence dequenching from the fluorophore 8-aminonaphthalene-1,3, 6-trisulfonic acid originally incorporated into the vesicle lumen as a complex with p-xylene-bis-pyridinium bromide. Hemolysin binds to and disturbs the lipid bilayer only when distinct sphingolipids consisting of a hydrophilic head group as phosphorylcholine or galactosyl as well as the ceramide backbone, e.g. sphingomyelin, are present. Cholesterol enhances eiseniapore lytic activity toward sphingomyelin-containing vesicles probably due to interaction with sphingomyelin. Leakage of vesicles was most efficient when the lipid composition resembled that of the outer leaflet of human erythrocytes. Presumably, an oligomeric protein pore formed by six monomers is responsible for leakage of sphingomyelin-containing vesicles. The secondary structure of eiseniapore did not change upon binding to lipid membranes. The lytic activity of eiseniapore was completely abolished after its denaturation or after preincubation with polyclonal antibodies. Our results suggest that the presence of specific sphingolipids is sufficient to mediate lytic activity of eiseniapore. This action contributes to our understanding of earthworm immune responses.

Structural analysis of neutral glycosphingolipids from Ascaris suum adults (Nematoda:Ascaridida)

The neutral glycosphingolipid fraction from adults of the pig parasitic nematode, Ascaris suum, was resolved into four components on thin-layer chromatography. The high-performance liquid chromatography-isolated components were structurally analysed by: methylation analysis; exoglycosidase cleavage; gas-liquid chromatography/mass spectrometry; liquid secondary-ion mass spectrometry; and, in particular, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Their chemical structures were determined as: Glc(beta 1-1)ceramide, Man(beta 1-4)Glc(beta 1-1)ceramide, GlcNAc(beta 1-3)Man(beta 1-4)Glc(beta 1-1)ceramide and Gal(alpha 1-3)GalNAc(beta 1-4)GlcNAc(beta 1-3)Man(beta 1-4)Glc(beta 1-1)ceramide; and were characterized as belonging to the arthro-series of protostomial glycosphingolipids. No glycosphingolipid component corresponding to ceramide tetrasaccharide was detected during these analyses. The ceramide composition of the parent glycosphingolipids was dominated by the 2-(R)-hydroxy C24:0 fatty acid, cerebronic acid, and C17 sphingoid-bases: 15-methylhexadecasphing-4-enine and 15-methylhexadecaphinganine in approximately equal proportions. The component ceramide monohexoside was characterized by an additional 15-methylhexadecaphytosphingosine.

Inhibition of human peripheral blood mononuclear cell proliferative response by glycosphingolipids from metacestodes of Echinococcus multilocularis

The effect on human peripheral blood mononuclear cells (PBMCs) of neutral glycosphingolipids extracted from metacestodes of the parasite Echinococcus multilocularis was investigated. Neutral glycosphingolipids inhibited [3H]thymidine uptake by human PBMCs upon stimulation by mitogens such as phytohemagglutinin A and pokeweed mitogen or by allogeneic Burkitt B cells. This effect was dose dependent and was related to a decrease in interleukin 2 (IL-2) synthesis, the expression of IL-2 receptors (CD25) being unmodified. Addition of exogenous recombinant IL-2 restored the cell proliferation. Partial inhibition of immunoglobulin G (IgG), IgA, and IgM synthesis was observed in the supernatant of cell culture in association with the inhibitory effect. Identification of active subfractions contained in the neutral glycosphingolipid fraction was also studied in relation to cell viability. The free ceramide fraction had an inhibitory effect, in part related to cell lysis, particularly at high concentration, while the monogalactosylceramides had a paradoxical effect: as an activator at low concentrations and as an inhibitor at high concentrations, with limited cell survival. The immunogenic neutral glycosphingolipids containing at least two carbohydrate residues, all having a structure based on Gal beta 1-->6Gal, were inhibitors of PBMC proliferation and showed good cell survival. These results suggest that parasite neutral glycosphingolipids may play an immunologically relevant role in alveolar hydatid disease.

A novel fucosyltetrahexosylceramide in plerocercoids of the parasite Spirometra erinacei

This glycosphingolipid was tentatively designated as GalSEGLx, in which the carbohydrate structure is characterized by an additional galactose molecule attached to the reducing-end galactose of SEGLx [Gal beta-4 (Fuc alpha-3) Glc beta-3 Gal beta Cer], which was previously determined by us [Kawakami, Y., Nakamura, K., Kojima, H., Suzuki, M., Inagaki, F., Suzuki, A., Sonoki, S., Uchida, A., Murata, Y. & Tamai, Y. (1993) J. Biochem. 114, 677-683], through a beta 1-6 linkage. The ceramide contained sphinganine and 4D-hydroxysphinganine in an about equimolar ratio, and a non-hydroxy fatty acid with carbon atoms ranging from 16 to 28, 26:0, 28:0 and 28:1 being major components. Based on the finding that a novel carbohydrate structure. Gal beta-4 Glc beta-3 Gal, was commonly found in glycosphingolipids from the parasite, S. erinacei, we here propose the terms, spirometo series, for this core structure series, and spirometosides, for glycosphingolipids having this carbohydrate structure.

Neutral glycolipids of Schistosoma mansoni as feasible antigens in the detection of schistosomiasis

The neutral glycolipid fraction from mouse-propagated, Schistosoma mansoni adult worms has been investigated as to its chromatographic and antigenic properties, and whether it fulfills the serodiagnostic antigen requirements of sensitivity and specificity in the detection of schistosomiasis. Serological analyses were performed by thin-layer chromatography immunostaining and ELISA. In the acute-phase form of mouse schistosomiasis, the kinetics of development of neutral glycolipid-specific antibody levels was correlated with the intensity of the initial infection and the response was dominated by IgG, as represented by the subclass IgG1. With the experimental animal helminthiases screened, glycolipid antigenicity fulfilled the fundamental traits for a serodiagnostic reagent. In the chronic-phase form of human schistosomiasis mansoni, neutral glycolipid-specific antibody levels were not correlated with the intensity of infection, as estimated from the faecal content of parasite eggs, whilst the isotypic response was dominated by IgM and IgG, the latter represented primarily by IgG1 and secondarily by IgG3. With other human helminthiases, glycolipid antigenicity was incomplete, in that, the specificity was only partially fulfilled. The reason for this incomplete specificity has been clarified, in part, by the detection of cryptic schistosomiasis infections in the cohorts of African patient sera examined.

The glycosylceramides of the nematode Caenorhabditis elegans contain an unusual, branched-chain sphingoid base

Caenorhabditis elegans was cultured in semi-defined medium containing yeast extract, soy peptone, glucose, hemoglobin, Tween 80, and sitosterol. Monoglycosylceramides were chromatographically purified from nematode extracts. Their structures were elucidated with mass spectrometry, nuclear magnetic resonance spectroscopy, and analysis of methanolysis products of the parent cerebrosides. The glycosylceramides were unusual in that the only long-chain sphingoid base detected was an iso-branched compound with a C-4 double bond (i.e., 15-methyl-2-aminohexadec-4-en-1,3-diol). Glucose was the only sugar moiety detected. The fatty acids consisted of a series of primarily straight-chain, saturated, 2-hydroxylated C20-C26 acids; some iso-branched analogs also occurred. The sphingomyelins of C. elegans were also hydrolyzed, and the same iso-branched C17 compound was the only sphingoid base detected. This is the first structural analysis of a nematode glycosphingolipid and the first report of an organism in which the long-chain sphingoid bases are entirely iso-branched.

Free ceramides of Echinococcus multilocularis metacestodes

Free ceramides were isolated and purified from the metacestodes of Echinococcus multilocularis. Two different fractions were obtained by preparative thin-layer chromatography. Their structure was determined by gas chromatography and electron impact mass spectrometry of trimethylsilylated derivatives. The ceramide with the higher thin-layer chromatographic migration rate contained exclusively erythro-sphinganine associated with saturated C16, C18 and very-long-chain fatty acids (up to C30) and unsaturated C24 fatty acid. The second ceramide contained 90.3% sphingosine and 9.7% sphinganine associated with saturated C16 and C24 and unsaturated C18 and C24 fatty acids. These findings were discussed with regard to the structure and metabolic pathway of neutral and acid glycosphingolipids found in the metacestodes.

Monohexosylceramides of larval and adult forms of the tapeworm, Spirometra erinacei

The occurrence of glycosphingolipids with unique carbohydrate structures in different species of cestode, Platyhelminth, which had been shown previously, prompted us to study the molecular species of the monohexosylceramides (cerebrosides) in the pseudophyllidean cestode, Spirometra erinacei. The purpose of the study was to obtain a basis for future investigations of the physiological role of glycolipids in parasitism. Cerebrosides were isolated from S. erinacei at two growth stages, i.e., from the larval form (plerocercoid) and from the adult tapeworms (intestinal form). The cerebrosides were separated into four subfractions by silica gel column chromatography, and their constituents were analyzed by gas-liquid chromatography, gas chromatography/mass spectrometry, and high-performance liquid chromatography/mass spectrometry. The hexoses of the cerebrosides consisted primarily of galactose in both growth stages, while only a small amount of glucose was detected. The ceramides were composed of sphinganine (d18:0) and phytosphingosine (t18:0) as sphingoid bases, and of nonhydroxy fatty acids ranging from C16 to C30 and hydroxy stearic acid (18h:0). The cerebrosides of adult tapeworms contained more 18h:0 than those of plerocercoids. The combination of hexoses and ceramides in the cerebroside molecules was slightly different in the two growth stages: the glucocerebrosides of plerocercoids contained only d18:0-nonhydroxy fatty acids in their ceramide moieties, whereas those of adult tapeworms contained varying ceramide moieties. Our data indicate that the molecular species of glycolipids present were essentially homeostatic throughout growth in spite of the entirely different environmental conditions, although there were slight differences in the hexose distribution in the two growth stages.

Litomosoides carinii: macrofilariae-derived glycolipids--chromatography, serology and potential in the evaluation of anthelminthic efficacy

A preliminary characterization of the glycolipids of Litomosoides carinii macrofilariae, resolved according to their chromatographic, chemical and serological properties, has been performed. Emphasis has been placed on the neutral fraction glycolipids. These are separable on thinlayer chromatography into two groups of fast and slow migrating band components, that differ in their migration, differential chemical staining and serological traits, respectively. Serological analyses have been accomplished by thin-layer chromatography immunostaining and ELISA. Only components of the slow migrating band group react with infection serum from Litomosoides carinii-infected Mastomys coucha. Cross-reactivity experiments with homologous and heterologous infection sera of various helminthiases indicate that, epitopes bound to the neutral glycolipid fraction show structural similarity within the Nematoda, but not to the Cestoda or Trematoda. The dynamic development of specific Ig-, IgG- and IgM-anti-neutral glycolipid fraction antibody levels were correlated with the different progression of L. carinii and Brugia malayi infections in the multimammate rat, Mastomys coucha. The reduction in the dynamics of IgG- and IgM-antibody levels on chemotherapeutic treatment with the filaricides flubendazole and CGP 20376 has been related to their macrofilaricide-activity.

Chromatographic and antigenic properties of Echinococcus granulosus hydatid cyst-derived glycolipids

The neutral and acidic fraction glycolipids of Echinococcus granulosus metacestode tissue compartments were isolated, defined by their chromatographic and antigenic properties, and assessed as to their efficacy as antigens in the serodiagnosis of human hepatic cystic and alveolar echinococcosis, and other helminthiases. Analyses were accomplished by thin-layer chromatography immunostaining and ELISA. The neutral glycolipid fraction's major carbohydrate epitope was the same as or very similar to that of Taenia crassiceps neutral glyco(sphingo)lipids, as represented by the 'neogala'-series core structure. The blood group-active, carbohydrate epitope P1 was expressed by a number of neutral fraction glycolipid component bands. The reverse-phase, thin-layer chromatography-isolated neutral fraction glycolipid component, designated Ag1, was efficient in the serological discrimination of cystic echinococcosis medium to high-titred sera. Ag1 did not specifically discriminate low-titred sera, i.e., other human helminthiases. The detected sialic acid residues of the acidic fraction glycolipids, on enzymatic cleavage, were identified as N-acylneuraminic acid and terminal. The acidic fraction glycolipids exhibited the paradox of only chemically minor components being antigenic towards cystic and alveolar echinococcosis infection sera. The combined acidic fraction glycolipid components Ra and Rx were capable of serological discrimination between cystic echinococcosis, alveolar echinococcosis and other helminthiases.

Sphingomyelin synthesis in Ascaridia galli

Adult Ascaridia galli incorporate label from [U-14C] serine into various intermediates of sphingomyelin synthesis (ketosphinganine, sphinganine, sphingosine, ceramide and sphingomyelin). From the results it is concluded that A. galli possesses the five enzymes involved in sphingomyelin synthesis, namely: serine palmitoyltransferase, 3-ketosphinganine reductase, flavoprotein sphinganine reductase, sphingosine acyltransferase and ceramide choline phosphotransferase.

Glycosphingolipids in cestodes. Chemical structures of ceramide monosaccharide, disaccharide, trisaccharide and tetrasaccharide from metacestodes of the fox tapeworm, Taenia crassiceps (Cestoda: Cyclophyllidea)

The presence of glycosphingolipids in the metacestodes of the fox tapeworm, Taenia crassiceps, has been established. The normal-phase TLC pattern of the neutral-fraction glycolipids revealed groups of bands corresponding to homologous components of increasing sugar chain length. The three simplest glycolipid components have been isolated and their chemical constitution determined as being of the neogala series: Gal beta 1Cer, Gal beta 6Gal beta 1Cer and Gal beta 6Gal beta 6Gal beta 1Cer. The ceramide tetrasaccharide fraction has been found to consist of a mixture of neogalatetraosylceramide, as an elongation of the neogala series, Gal beta 6Gal beta 6Gal beta 6Gal beta 1Cer and the component Gal alpha 4Gal beta 6Gal beta 6Gal beta 1Cer (both occurring in approximately equimolar proportions). The long-chain bases of the ceramide monogalactoside, digalactoside, trigalactoside and tetragalactosides contain, as well as small amounts of sphingosine, predominantly dihydrosphingosine/phytosphingosine in the approximate ratios 1.7:1, 1.4:1, 1:1 and 2.3:1, respectively. The major ceramide fatty acids have particularly long chains, with hexacosanoic and octacosanoic acids predominating. Upon reverse-phase TCL, the glycolipid components ceramide monogalactoside, digalactoside and trigalactoside were each separable into five component bands. Parent glycolipid components therefore show component band distributions comparable to one another in being governed by similar ceramide constitutions.