Gangliosides in human fetal brain

Biology of GD2 ganglioside: implications for cancer immunotherapy

Part of the broader glycosphingolipid family, gangliosides are composed of a ceramide bound to a sialic acid-containing glycan chain, and locate at the plasma membrane. Gangliosides are produced through sequential steps of glycosylation and sialylation. This diversity of composition is reflected in differences in expression patterns and functions of the various gangliosides. Ganglioside GD2 designates different subspecies following a basic structure containing three carbohydrate residues and two sialic acids. GD2 expression, usually restrained to limited tissues, is frequently altered in various neuroectoderm-derived cancers. While GD2 is of evident interest, its glycolipid nature has rendered research challenging. Physiological GD2 expression has been linked to developmental processes. Passing this stage, varying levels of GD2, physiologically expressed mainly in the central nervous system, affect composition and formation of membrane microdomains involved in surface receptor signaling. Overexpressed in cancer, GD2 has been shown to enhance cell survival and invasion. Furthermore, binding of antibodies leads to immune-independent cell death mechanisms. In addition, GD2 contributes to T-cell dysfunction, and functions as an immune checkpoint. Given the cancer-associated functions, GD2 has been a source of interest for immunotherapy. As a potential biomarker, methods are being developed to quantify GD2 from patients' samples. In addition, various therapeutic strategies are tested. Based on initial success with antibodies, derivates such as bispecific antibodies and immunocytokines have been developed, engaging patient immune system. Cytotoxic effectors or payloads may be redirected based on anti-GD2 antibodies. Finally, vaccines can be used to mount an immune response in patients. We review here the pertinent biological information on GD2 which may be of use for optimizing current immunotherapeutic strategies.

Ganglioside GM1 and the Central Nervous System

GM1 is one of the major glycosphingolipids (GSLs) on the cell surface in the central nervous system (CNS). Its expression level, distribution pattern, and lipid composition are dependent upon cell and tissue type, developmental stage, and disease state, which suggests a potentially broad spectrum of functions of GM1 in various neurological and neuropathological processes. The major focus of this review is the roles that GM1 plays in the development and activities of brains, such as cell differentiation, neuritogenesis, neuroregeneration, signal transducing, memory, and cognition, as well as the molecular basis and mechanisms for these functions. Overall, GM1 is protective for the CNS. Additionally, this review has also examined the relationships between GM1 and neurological disorders, such as Alzheimer's disease, Parkinson's disease, GM1 gangliosidosis, Huntington's disease, epilepsy and seizure, amyotrophic lateral sclerosis, depression, alcohol dependence, etc., and the functional roles and therapeutic applications of GM1 in these disorders. Finally, current obstacles that hinder more in-depth investigations and understanding of GM1 and the future directions in this field are discussed.

Comprehensive characterization of complex glycosphingolipids in human pancreatic cancer tissues

Pancreatic ductal adenocarcinoma (PDAC) is one of the most common causes of cancer-related deaths worldwide, accounting for 90% of primary pancreatic tumors with an average 5-year survival rate of less than 10%. PDAC exhibits aggressive biology, which, together with late detection, results in most PDAC patients presenting with unresectable, locally advanced, or metastatic disease. In-depth lipid profiling and screening of potential biomarkers currently appear to be a promising approach for early detection of PDAC or other cancers. Here, we isolated and characterized complex glycosphingolipids (GSL) from normal and tumor pancreatic tissues of patients with PDAC using a combination of TLC, chemical staining, carbohydrate-recognized ligand-binding assay, and LC/ESI-MS². The major neutral GSL identified were GSL with the terminal blood groups A, B, H, Le^a, Le^b, Le^x, Le^y, P1, and PX2 determinants together with globo- (Gb₃ and Gb₄) and neolacto-series GSL (nLc₄ and nLc₆). We also revealed that the neutral GSL profiles and their relative amounts differ between normal and tumor tissues. Additionally, the normal and tumor pancreatic tissues differ in type 1/2 core chains. Sulfatides and GM₃ gangliosides were the predominant acidic GSL along with the minor sialyl-nLc₄/nLc₆ and sialyl-Le^a/Le^x. The comprehensive analysis of GSL in human PDAC tissues extends the GSL coverage and provides an important platform for further studies of GSL alterations; therefore, it could contribute to the development of new biomarkers and therapeutic approaches.

Maternal Nutrition and Neurodevelopment: A Scoping Review

In this scoping review, we examined the association between maternal nutrition during pregnancy and neurodevelopment in offspring. We searched the Pubmed and ScienceDirect databases for articles published from 2000 to 2020 on inadequate intake of vitamins (B12, folate, vitamin D, vitamin A, vitamin E, vitamin K), micronutrients (cooper, iron, creatine, choline, zinc, iodine), macronutrients (fatty acids, proteins), high fat diets, ketogenic diets, hypercaloric diets, and maternal undernutrition. Some older relevant articles were included. The search produced a total of 3590 articles, and 84 studies were included in the qualitative synthesis. Data were extracted and analyzed using charts and the frequency of terms used. We concluded that inadequate nutrient intake during pregnancy was associated with brain defects (diminished cerebral volume, spina bifida, alteration of hypothalamic and hippocampal pathways), an increased risk of abnormal behavior, neuropsychiatric disorders (ASD, ADHD, schizophrenia, anxiety, depression), altered cognition, visual impairment, and motor deficits. Future studies should establish and quantify the benefits of maternal nutrition during pregnancy on neurodevelopment and recommend adequate supplementation.

Characterization of Glycosphingolipids in the Human Parathyroid and Thyroid Glands

As part of a systematic investigation of the glycosphingolipids in human tissues, acid and non-acid glycosphingolipids from human thyroid and parathyroid glands were isolated and characterized with mass spectrometry and binding of carbohydrate-recognizing ligands, with a focus on complex compounds. The glycosphingolipid patterns of the human parathyroid and thyroid glands were very similar. The major acid glycosphingolipids were sulfatide and the gangliosides GM3, GD3, GD1a, GD1b, GT1b and Neu5Ac-neolactotetraosylceramide, and the major non-acid glycosphingolipids were globotriaosylceramide and globoside. We also found neolactotetra- and neolactohexaosylceramide, the x₂ glycosphingolipid, and complex glycosphingolipids with terminal blood group O and A determinants in both tissues. A glycosphingolipid with blood group Le^b determinant was identified in the thyroid gland, and the parathyroid sample had a glycosphingolipid with terminal blood group B determinant. Immunohistochemistry demonstrated the expression of blood group A antigens in both the thyroid and parathyroid glands. A weak cytoplasmatic expression of the GD1a ganglioside was present in the thyroid, while the parathyroid gland had a strong GD1a expression on the cell surface. Thus, the glycosylation of human thyroid and parathyroid glands is more complex than previously appreciated. Our findings provide a platform for further studies of alterations of cell surface glycosphingolipids in thyroid and parathyroid cancers.

Characterization of glycosphingolipids from gastrointestinal stromal tumours

Gastrointestinal stromal tumours (GISTs) are the major nonepithelial neoplasms of the human gastrointestinal tract with a worldwide incidence between 11 and 15 per million cases annually. In this study the acid and non-acid glycosphingolipids of three GISTs were characterized using a combination of thin-layer chromatography, chemical staining, binding of carbohydrate recognizing ligands, and mass spectrometry. In the non-acid glycosphingolipid fractions of the tumors globotetraosylceramide, neolactotetraosylceramide, and glycosphingolipids with terminal blood group A, B, H, Le^x, Le^a, Le^y and Le^b determinants were found. The relative amounts of these non-acid compounds were different in the three tumour samples. The acid glycosphingolipid fractions had sulfatide, and the gangliosides GM3, GD3, GM1, Neu5Acα3neolactotetraosylceramide, GD1a, GT1b and GQ1b. In summary, we have characterized the glycosphingolipids of GISTs and found that the pattern differs in tumours from different individuals. This detailed characterization of glycosphingolipid composition of GISTs could contribute to recognition of new molecular targets for GIST treatment and sub-classification.

Comparison of the glycosphingolipids of human-induced pluripotent stem cells and human embryonic stem cells

High expectations are held for human-induced pluripotent stem cells (hiPSC) since they are established from autologous tissues thus overcoming the risk of allogeneic immune rejection when used in regenerative medicine. However, little is known regarding the cell-surface carbohydrate antigen profile of hiPSC compared with human embryonic stem cells (hESC). Here, glycosphingolipids were isolated from an adipocyte-derived hiPSC line, and hiPSC and hESC glycosphingolipids were compared by concurrent characterization by binding assays with carbohydrate-recognizing ligands and mass spectrometry. A high similarity between the nonacid glycosphingolipids of hiPSC and hESC was found. The nonacid glycosphingolipids P1 pentaosylceramide, x2 pentaosylceramide and H type 1 heptaosylceramide, not previously described in human pluripotent stem cells (hPSC), were characterized in both hiPSC and hESC. The composition of acid glycosphingolipids differed, with increased levels of GM3 ganglioside, and reduced levels of GD1a/GD1b in hiPSC when compared with hESC. In addition, the hESC glycosphingolipids sulf-globopentaosylceramide and sialyl-globotetraosylceramide were lacking in hiPSC. Neural stem cells differentiating from hiPSC had a reduced expression of sialyl-lactotetra, whereas expression of the GD1a ganglioside was significantly increased. Thus, while sialyl-lactotetra is a marker of undifferentiated hPSC, GD1a is a novel marker of neural differentiation.

Sialyl-lactotetra, a novel cell surface marker of undifferentiated human pluripotent stem cells

Cell surface glycoconjugates are used as markers for undifferentiated pluripotent stem cells. Here, antibody binding and mass spectrometry characterization of acid glycosphingolipids isolated from a large number (1 × 10⁹ cells) of human embryonic stem cell (hESC) lines allowed identification of several novel acid glycosphingolipids, like the gangliosides sialyl-lactotetraosylceramide and sialyl-globotetraosylceramide, and the sulfated glycosphingolipids sulfatide, sulf-lactosylceramide, and sulf-globopentaosylceramide. A high cell surface expression of sialyl-lactotetra on hESC and human induced pluripotent stem cells (hiPSC) was demonstrated by flow cytometry, immunohistochemistry, and electron microscopy, whereas sulfated glycosphingolipids were only found in intracellular compartments. Immunohistochemistry showed distinct cell surface anti-sialyl-lactotetra staining on all seven hESC lines and three hiPSC lines analyzed, whereas no staining of hESC-derived hepatocyte-like or cardiomyocyte-like cells was obtained. Upon differentiation of hiPSC into hepatocyte-like cells, the sialyl-lactotetra epitope was rapidly down-regulated and not detectable after 14 days. These findings identify sialyl-lactotetra as a promising marker of undifferentiated human pluripotent stem cells.

The role of gangliosides in brain development and the potential benefits of perinatal supplementation

The maternal diet provides critical nutrients that can influence fetal and infant brain development and function. This review highlights the potential benefits of maternal dietary ganglioside supplementation on fetal and infant brain development. English-language systematic reviews, preclinical studies, and clinical studies were obtained through searches on PubMed. Reports were selected if they included benefits and harms of maternal ganglioside supplementation during pregnancy or ganglioside-supplemented formula after pregnancy. The potential benefits of ganglioside supplementation were explored by investigating the following: (1) their role in neural development, (2) their therapeutic use in neural injury and disease, (3) their presence in human breast milk, and (4) their use as a dietary supplement during or after pregnancy. Preclinical studies indicate that ganglioside supplementation at high doses (1% of total dietary intake) can significantly increase cognitive development and body weight when given prenatally. However, lower ganglioside supplementation doses have no beneficial cognitive effects, even when given throughout pregnancy and lactation. In human clinical trials, infants given formula supplemented with gangliosides showed increased cognitive development and an increase in ganglioside content. Ganglioside supplementation may promote brain development and function in offspring when administered at the optimum dosage. We propose that prenatal maternal dietary supplementation with gangliosides throughout pregnancy may promote greater long-term effects on brain development and function. Before this concept can be encouraged in preconception clinics, future research and clinical trials are needed to confirm the ability of dietary gangliosides to improve cognitive development, but available results already encourage this area of research.

Biological functions of sphingomyelins

Sphingomyelin (SM) is a dominant sphingolipid in membranes of mammalian cells and this lipid class is specifically enriched in the plasma membrane, the endocytic recycling compartment, and the trans Golgi network. The distribution of SM and cholesterol among cellular compartments correlate. Sphingolipids have extensive hydrogen-bonding capabilities which together with their saturated nature facilitate the formation of sphingolipid and SM-enriched lateral domains in membranes. Cholesterol prefers to interact with SMs and this interaction has many important functional consequences. In this review, the synthesis, regulation, and intracellular distribution of SMs are discussed. The many direct roles played by membrane SM in various cellular functions and processes will also be discussed. These include involvement in the regulation of endocytosis and receptor-mediated ligand uptake, in ion channel and G-protein coupled receptor function, in protein sorting, and functioning as receptor molecules for various bacterial toxins, and for non-bacterial pore-forming toxins. SM is also an important constituent of the eye lens membrane, and is believed to participate in the regulation of various nuclear functions. SM is an independent risk factor in the development of cardiovascular disease, and new studies have shed light on possible mechanism behind its role in atherogenesis.

Ganglioside biochemistry

Gangliosides are sialic acid-containing glycosphingolipids. They occur especially on the cellular surfaces of neuronal cells, where they form a complex pattern, but are also found in many other cell types. The paper provides a general overview on their structures, occurrence, and metabolism. Key functional, biochemical, and pathobiochemical aspects are summarized.

Profiling and sequencing of gangliosides from human caudate nucleus by chip-nanoelectrospray mass spectrometry

Gangliosides (GGs), sialic acid-containing glycosphingolipids are involved in many brain functions at the cell and molecular level. Compositional and structural elucidation of GGs in mixtures extracted from human brain is essential for correlating their profile with the specialized function of each brain area in health and disease. As a part of our ongoing study on GG expression and structure in different healthy and diseased brain regions, in this work, a preliminary investigation of GGs in a specimen of human caudate nucleus (CN) was carried out using an advanced mass spectrometry (MS) technique. By chip-nanoelectrospray MS performed on a NanoMate robot coupled to a high capacity ion trap instrument, 81 GG components were detected in human CN in only 1.5 min of signal acquisition. Although the native GG mixture from CN was found dominated by mono-, di- and trisialylated GGs with a slight dominance of disialylated forms (GD), four tetrasialylated structures (GQ) and two pentasialylated (GP) species were also identified. Additionally, species with unusually long fatty acid chains, exceeding 30 carbon atoms in their ceramide (Cer) composition, and several glycoforms modified by fucosyl (Fuc), O-acetyl (O-Ac) and/or lactonization were discovered. By tandem MS (MS(2) ) using collision-induced dissociation, two atypical mono and disialylated species with long-chain fatty acids in their Cer could be confirmed and structurally characterized. These results may be a starting point for new GG-based approaches in the study of CN functions and ethiopathogenesis of CN-related neurodegenerative disorders.

Localization and imaging of gangliosides in mouse brain tissue sections by laserspray ionization inlet

A new ionization method for the analysis of fragile gangliosides without undesired fragmentation or salt adduction is presented. In laserspray ionization inlet (LSII), the matrix/analyte sample is ablated at atmospheric pressure, and ionization takes place in the ion transfer capillary of the mass spectrometer inlet by a process that is independent of a laser wavelength or voltage. The softness of LSII allows the identification of gangliosides up to GQ1 with negligible sialic acid loss. This is of importance to the field of MS imaging, as undesired fragmentation has made it difficult to accurately map the spatial distribution of fragile ganglioside lipids in tissue. Proof-of-principle structural characterization of endogenous gangliosides using MS(n) fragmentation of multiply charged negative ions on a LTQ Velos and subsequent imaging of the GD1 ganglioside is demonstrated. This is the first report of multiply charged negative ions using inlet ionization. We find that GD1 is detected at higher levels in the mouse cortex and hippocampus compared with the thalamus. In LSII with the laser aligned in transmission geometry relative to the inlet, images were obtained in approximately 60 min using an inexpensive nitrogen laser.

Neural precursor cell cultures from GM2 gangliosidosis animal models recapitulate the biochemical and molecular hallmarks of the brain pathology

In this work we showed that genotype-related patterns of hexosaminidase activity, isoenzyme composition, gene expression and ganglioside metabolism observed during embryonic and postnatal brain development are recapitulated during the progressive stages of neural precursor cell (NPC) differentiation to mature glia and neurons in vitro. Further, by comparing NPCs and their differentiated progeny established from Tay-Sachs (TS) and Sandhoff (SD) animal models with the wild-type counterparts, we studied the events linking the accumulation of undegraded substrates to hexosaminidase activity. We showed that similarly to what observed in brain tissues in TS NPCs and progeny, the stored GM2 was partially converted by sialidase to GA2, which can be then degraded in the lysosomes to its components. The latter can be used in a salvage pathway for the formation of GM3. Interestingly, results obtained from ganglioside feeding assays and from measurement of lysosomal sialidase activity suggest that a similar pathway might work also in the SD model.

Increase of ceramide monohexoside and dipalmitoyl glycerophospholipids in the brain of Zellweger syndrome

The lipid composition and molecular species of phospholipids were examined in the brain of a patient with Zellweger syndrome (ZS), and were compared with those of control infants. In the cerebral gray matter of the ZS patient, the amounts of ceramide monohexoside and cholesterol ester were larger than those of controls. By contrast, the amount of ceramide monohexoside in the white matter was smaller in the ZS patient than that in the age-matched control. Although the amount of phosphatidylcholine (PC) plus phosphatidylserine (PS) was the same, dipalmitoyl PC and PS were increased in both the gray and white matter of the ZS cerebrum. These alterations in the molecular species of brain lipids may play crucial roles in the pathogenesis of ZS.

Interaction of cholera toxin with three life-cycle stages of Schistosoma mansoni: adult worm, egg and cercaria

We have previously reported that there is an immunological cross-reactivity between Schistosoma mansoni and cholera toxin (CT). In this study, using an immunofluorescence technique with anti-CT antibody, we provide further evidence for this cross-reactivity by demonstrating an antigen, localized in the tegument of S. mansoni adult worms which is cross-reactive with a CT antigen. Anti-CT antibodies also reacted with structures in S. mansoni cercariae and eggs. Additionally, CT itself was found to bind strongly to the gut of the adult worm, gut cells of cercaria and the egg shell. The binding of CT to the parasite was blocked when parasite sections were incubated with CT which had been incubated with the ganglioside GM1. Lipid extraction and isolation of gangliosides demonstrated the presence of GM1 in adult worms. For further analysis of CT-binding structures, the possible interaction of CT with two major schistosome gut antigens, circulating cathodic antigen (CCA) and circulating anodic antigen (CAA), was studied. We found that CT blocked the binding of anti-CCA antibody to the gut of adult worms and that anti-CCA blocked the binding of CT to the worm gut. These findings indicate that CT binds to CCA present in the gut of the parasite and thus has, in addition to GM1, a second binding specificity.

Analysis of human hippocampus gangliosides by fully-automated chip-based nanoelectrospray tandem mass spectrometry

Modern microfluidic devices are currently introduced in electrospray (ESI) mass spectrometry (MS), tending to substitute the classical capillary-based ESI infusion. Automated systems using the combination of robotized sample handling and chip-based ESI are significantly increasing the analysis reproducibility, precision, throughput, and efficiency. In the last couple of years our group developed the chip-based ESI-MS approach for glycomics in biomedical research and applied it for oligosaccharide, glycopeptide and ganglioside investigation. Here we report upon the optimization and application of this modern technique for the analysis of differential ganglioside expression patterns in human fetal and adult hippocampus. By this methodology, ganglioside species exhibiting high degree of heterogeneity in the ceramide motifs and biologically-relevant modifications could be identified in human hippocampus. The ultra-high reproducibility of the experiments uniquely provided by the chip-ESI approach allowed for a reliable MS-based ganglioside comparative assay. Moreover, the particular feature of chip ESI-tandem MS to provide structural information at high sensitivity was useful for detailed characterization of hippocampus-associated species. The experimental data presented in this study indicate the benefits of microfluidic/MS for determination of the topospecific brain ganglioside composition and development-related changes in their expression, which might be of high value in clinical investigation and for studies related to ganglioside-based therapy of central nervous system diseases.

Structural characterization of the GM1 ganglioside by infrared multiphoton dissociation, electron capture dissociation, and electron detachment dissociation electrospray ionization FT-ICR MS/MS

Gangliosides play important biological roles and structural characterization of both the carbohydrate and the lipid moieties is important. The FT-ICR MS/MS techniques of electron capture dissociation (ECD), electron detachment dissociation (EDD), and infrared multiphoton dissociation (IRMPD) provide extensive fragmentation of the protonated and deprotonated GM1 ganglioside. ECD provides extensive structural information, including identification of both halves of the ceramide and cleavage of the acetyl moiety of the N-acetylated sugars. IRMPD provides similar glycan fragmentation but no cleavage of the acetyl moiety. Cleavage between the fatty acid and the long-chain base of the ceramide moiety is seen in negative-ion IRMPD but not in positive-ion IRMPD of GM1. Furthermore, this extent of fragmentation requires a range of laser powers, whereas all information is available from a single ECD experiment. However, stepwise fragmentation by IRMPD may be used to map the relative labilities for a series of cleavages. EDD provides the alternative of electron-induced fragmentation for negative ions with extensive fragmentation, but suffers from low efficiency as well as complication of data analysis by frequent loss of hydrogen atoms. We also show that analysis of MS/MS data for glycolipids is greatly simplified by classification of product ion masses to specific regions of the ganglioside based solely on mass defect graphical analysis.

Activation of Fas receptor is required for the increased formation of the disialoganglioside GD3 in cultured cerebellar granule cells committed to apoptotic death

Apoptosis was induced in cultured cerebellar granule cells by lowering extracellular K+ concentrations (usually from 25 to 10 mM). The apoptotic phenotype was preceded by an early and transient increase in the intracellular levels of the disialoganglioside, GD3, which behaves as a putative pro-apoptotic factor. We examined whether activation of Fas receptor mediates the increase in GD3 formation in granule cells committed to die. Degenerating granule cells showed increased expression of both Fas receptor and its ligand (Fas-L), at times that coincided with the increase in GD3 levels and the induction of GD3 synthase mRNA. Addition of neutralizing anti-Fas-L antibodies reduced the extent of 'low-K+'-induced apoptosis and abolished the increase in GD3 levels and GD3 synthase mRNA. Similar reductions were observed in cultures prepared from gld or lpr mice, which harbor loss-of-function mutations of Fas-L and Fas receptor, respectively. In addition, exogenous application of soluble Fas-L further enhanced both the increase in GD3 formation and cell death in cultured granule cells switched from 25 into 10 mM K+. We conclude that activation of Fas receptor is entirely responsible for the increase in GD3 levels and contributes to the development of apoptosis by trophic deprivation in cultured cerebellar granule cells.

Alterations of fatty acid metabolism and membrane fluidity in peroxisome-defective mutant ZP102 cells

We investigated lipid composition and FA metabolism in Chinese hamster ovary CHO-K1) cells and Pex5-mutated CHO-K1 (ZP102) cells to clarify the biochemical bases of peroxisome biogenesis disorders (PBD). ZP102 cells have defective peroxisomes and exhibit impairments of peroxisomal beta-oxidation of FA and plasmalogen biosynthesis. In addition, we identified FA metabolic alterations in the synthesis of several classes of lipids in ZP102 cells. The concentration of FFA in ZP102 cells was twice that in CHO-K1 cells, but methyl esters and TAG were decreased in ZP102 cells in comparison with control cells. Also, ceramide monohexoside (CMH) concentration with ZP102 cells was significantly increased compared with the control cells. The FA molecular species, particularly the saturated to unsaturated ratios, of individual lipids also differed between the two cell types. The rate of incorporation of [14C]-labeled saturated acids into sphingomyelin (SM) and CMH in ZP102 cells was higher than that in CHO-K1 cells. Lignoceric acid incorporated into cells was predominantly utilized for the synthesis of SM at 24 h after removal of [14C]lignoceric acid from the culture medium. ZP102 cells showed higher fluorescence anisotropy of 1,3,5-diphenylhexatriene, corresponding to lower membrane mobility than in CHO-K1 cells. In particular, alteration of lipid metabolism by a Pex5 mutation enhanced metabolism of saturated FA and sphingolipids. This may be related to the reduced membrane fluidity of ZP102 cells, which has been implicated in the dysfunction of membrane-linked processes in PBD.

Gangliosides as therapeutic targets for cancer

Gangliosides, sialic acid-containing glycosphingolipids, have engendered great interest for more than 20 years in the search for target molecules of relevance for tumour growth and formation of metastases and as potential targets for immunotherapy. These molecules show large quantitative and structural variability, which is related to cell type and developmental stage. Their potential role in the formation of tumour metastases was suggested from data supporting that they are involved in cell growth regulation and in cell-cell and cell-matrix adhesion. Moreover, gangliosides are expressed on the cell surface and thereby are accessible for antibodies or other ganglioside-binding molecules to induce cell death, inhibit cell growth and/or inhibit formation of tumour metastasis. All tumours exhibit aberrant ganglioside expression. This includes overexpression of normal ganglioside constituents, which appears to be common among various tumours, and expression of gangliosides not found in normal adult tissue but often found during fetal development. The ganglioside composition of melanoma cells has been found to correlate with their metastatic potential and also to be selectively expressed in cells of a tumour mass and invading tumour cells. Passive immunotherapy using murine or murine/human chimeric monoclonal antiganglioside antibodies in their native form or combined with various effector molecules has been investigated. However, the vaccination strategy using native or structurally modified tumour-associated gangliosides in combination with adjuvants is currently the dominant method in clinical trials. The outcomes reported so far vary between type of tumour and treatment strategies. However, we believe that targeting gangliosides is as promising as any other immune therapeutic strategy, and basic research as well as clinical trials utilising new aspects is encouraged.

Molecular cloning of Chinese hamster ceramide glucosyltransferase and its enhanced expression in peroxisome-defective mutant Z65 cells

To clarify the metabolic bases of characteristic increases in the concentrations of glucosylceramide (CMH) and GM3 in peroxisome-defective mutant Chinese hamster ovary (CHO) cells (Z65), we measured the ceramide glucosyltransferase (CGT) and beta-glucosidase activities in Z65 and CHO-K1 cells, and found that the former enzyme was responsible for the accumulation of CMH in Z65 cells. Inhibition of CGT by D,L-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) caused a marked reduction in a incorporation of [3-14C]serine to CMH in both CHO-K1 and Z65 cells, but resulted in the accumulation of ceramide in Z65 cells in a concentration higher than that in CHO-K1 cells. Then, we cloned the cDNA encoding CGT from CHO-K1 cells, which exhibited sequence homology with the human gene product (98.7%). Northern blot analysis of CGT revealed increased expression of it in Z65 cells compared with that in CHO-K1 cells, which probably caused the simultaneous increase in GM3. With an immunohistochemical procedure, GM3 was found to be more strongly expressed in the cell membrane of Z65 cells than in CHO-K1 cells.

An early increase in the disialoganglioside GD3 contributes to the development of neuronal apoptosis in culture

We induced apoptosis in primary cultures of cerebellar granule neurons by switching the growing medium into a medium containing lower concentrations of K(+) (5 or 10 mM instead of 25 mM) or, alternatively, by addition of staurosporine. The apoptotic phenotype was always preceded by an early increase in the intracellular levels of the disialoganglioside GD3, which peaked at 2-6 h and returned back to normal at 12 h. GD3 synthase, the enzyme that forms GD3 from the monosialoganglioside GM3, was also induced at early times after the induction of apoptosis in granule cells. Immunofluorescent staining showed that GD3 increased in neuronal cell bodies and neurites, but was never localized in cell nuclei. In cultures switched into a low K(+)-containing medium, exogenously applied GD3, but not the disialoganglioside GD1a, accelerated the development of neuronal apoptosis. In contrast, the antisense-induced knock-down of GD3 synthase was protective against granule cell death induced by lowering extracellular K(+) from 25 to 10 - but not 5 - mM. These results demonstrate that an early and transient increase in GD3 synthesis is one of the factors that contribute to the induction of neuronal apoptosis in culture.

Beta-amyloid-induced synthesis of the ganglioside GD3 is a requisite for cell cycle reactivation and apoptosis in neurons

We have shown that cortical neurons challenged with toxic concentrations of beta-amyloid peptide (betaAP) enter the S phase of the cell cycle before apoptotic death. Searching for a signaling molecule that lies at the border between cell proliferation and apoptotic death, we focused on the disialoganglioside GD3. Exposure of rat cultured cortical neurons to 25 microm betaAP(25-35) induced a substantial increase in the intracellular levels of GD3 after 4 hr, a time that precedes neuronal entry into S phase. GD3 levels decreased but still remained higher than in the control cultures after 16 hr of exposure to betaAP(25-35). Confocal microscopy analysis showed that the GD3 synthesized in response to betaAP colocalized with nuclear chromatin. The increase in GD3 was associated with a reduction of sphingomyelin (the main source of the ganglioside precursor ceramide) and with the induction of alpha-2,8-sialyltransferase (GD3 synthase), the enzyme that forms GD3 from the monosialoganglioside GM3. A causal relationship between GD3, cell-cycle activation, and apoptosis was demonstrated by treating the cultures with antisense oligonucleotides directed against GD3 synthase. This treatment, which reduced betaAP(25-35)-stimulated GD3 formation by approximately 50%, abolished the neuronal entry into the S phase and was protective against betaAP(25-35)-induced apoptosis.

The glioma-associated gangliosides 3'-isoLM1, GD3 and GM2 show selective area expression in human glioblastoma xenografts in nude rat brains

This work describes the in vivo expression and distribution of glioma-associated gangliosides (GD3, GM2, 3'-isoLM1) in a novel human brain tumour nude rat xenograft model. In this model, the tumours, which are established directly from human glioblastoma biopsies, show extensive infiltrative growth within the rat brain. This model therefore provides an opportunity to study ganglioside expression not only within the macroscopic tumour, but also in brain areas with tumour cell infiltration. The ganglioside expression was studied by confocal microscopy of immunostained brain sections using antiganglioside monoclonal antibodies. Xenografts from four human glioblastoma multiformes were established in rats and the brains removed after 3-4 months. Ganglioside GD3 was expressed in the tumour parenchyma while ganglioside 3'-isoLM1 was more abundantly expressed in the periphery of the tumour associated with areas of tumour cell invasion. GM2 expression was only seen in one tumour, where it was located within the main tumour mass. Double staining with a pan antihuman monoclonal antibody (3B4) and the antiganglioside monoclonal antibodies confirmed that the ganglioside expression was associated with tumour cells. This work supports the concept of different biological roles for individual gangliosides and indicates that antibodies or ligands directed against GD3 and 3'-isoLM1 might be complementary when applied in the treatment of human glioblastomas.

Enhanced expression of a-series gangliosides in fibroblasts of patients with peroxisome biogenesis disorders

Peroxisome biogenesis disorders (PBD) are classified into Zellweger syndrome (ZS), infantile Refsum disease (IRD) and neonatal adrenoleukodystrophy. Disturbances in the differentiation of neural cells such as migration arrest are characteristic of PBD. So far the pathogenesis of these disturbances is not clearly understood. We describe an altered metabolism of glycosphingolipids in PBD which has not yet been investigated. We observed an increased amount of a-series gangliosides, GM2, GM1 and GD1a, in the fibroblasts of patients with ZS and IRD. Gangliosides GM1 and GD1a were not present in detectable amounts in normal subjects. A key step in the synthesis of a-series gangliosides is a transfer of GalNAc to ganglioside GM3, so we determined the level of ganglioside GM3 by immunohistochemical methods. We found a granular structure, which was positive toward anti-ganglioside GM3 antibody in the cytoplasm of the patients' fibroblasts. In control cells, the cell membrane was slightly positive toward anti-GM3 antibody. These results may help to clarify the pathogenesis of PBD with respect to the functional roles of glycosphingolipids in cell differentiation, proliferation and apoptosis.

Neuroblastomas of infancy exhibit a characteristic ganglioside pattern

BACKGROUND

Gangliosides are membrane-bound glycolipid molecules particularly prominent in neural tissue. Changes in ganglioside expression during embryologic development result from a shift in biosynthesis from the fetal b pathway to the adult a pathway. Tumor gangliosides may play a role in the clinical behavior of certain subtypes of neuroblastoma. Because neuroblastoma, which presents in infancy, has a different biologic and clinical phenotype than that which presents in older children, the authors determined whether differences in ganglioside biosynthesis exist between these two neuroblastoma subgroups.

METHODS

Sixty-eight tumor specimens (25 diagnosed by screening and 43 diagnosed clinically) were obtained from the Quebec Neuroblastoma Screening Project. Gangliosides were isolated and purified by solvent partitioning, separated by high performance thin-layer chromatography, and quantitated by scanning densitometry. The sum of a and b pathway gangliosides were determined for each tumor.

RESULTS

Gangliosides of the b (fetal) pathway predominated in both screened and clinically diagnosed tumors of patients younger than 1 year of age. Twenty-three of 25 screened patients (92%) and 21 of 23 patients with clinically diagnosed tumors at younger than 1 year of age (91%) had tumor b pathway ganglioside content greater than 60%. In contrast, tumors of only 8 of 20 patients 1 year or older (40%) had b pathway ganglioside predominance. Predominance of b pathway tumor gangliosides correlated with improved outcome. Event free survival was significantly higher among patients with b pathway ganglioside tumor content greater than 60% versus those with b pathway ganglioside tumor content less than 60% (118.1 +/- 3.9 months vs. 69.2 +/- 8.6 months, P < 0.01).

CONCLUSIONS

Fetal patterns of ganglioside biosynthesis predominate in neuroblastoma tumors from patients younger than 1 year of age and adult patterns of ganglioside biosynthesis predominate in tumors from older children, supporting the view that neuroblastoma consists of distinct but overlapping disorders, and that gangliosides may play a biologic role in the clinical differences among these patients.

Anencephaly: structural characterization of gangliosides in defined brain regions

Gangliosides from histopathologically-defined human cerebrum-resembling remnant and cerebellum from 37 and 30 gestational week-old anencephaluses were identified using mass spectrometry and high performance thin layer chromatography combined with immunochemical analysis in comparison to respective normal newborn/fetal and adult brain regions. A novel strategy of nano-electrospray ionization quadrupole time-of-flight tandem MS has been developed for identification of ganglioside components in complex mixtures. By morphoanatomical and histological investigation the anencephalic cerebral remnant was found to be aberrant, while the anencephalic cerebellum was defined as normal. Total ganglioside concentrations in the anencephalic cerebral remnant and the cerebellum were 34% and 13% lower in relation to the age-matched controls. In the cerebral remnant, GD3, GM2 and GT1b were elevated, while GD1a was decreased in the anencephalic cerebral remnant, but enriched in anencephalic cerebellum. GQ1b was reduced in both anencephalic regions. Gg4Cer, GM1b and GD1alpha, members of the alpha-series biosynthetic pathway, and neolacto-series gangliosides were found to be present in anencephalic, as well as in normal, fetal and adult brain tissues, indicating the occurrence of these biosynthetic pathways in human brain. In both cerebral and cerebellar anencephalic tissues, GM1b, GD1alpha, nLM1 and nLD1 were expressed at a higher rate in relation to normal tissue. It can be demonstrated that the anencephalic cerebral remnant, as a primitive brain structure, represents a naturally-occurring model to study the ganglioside involvement in induction of aberrant brain development.

Nano-electrospray ionization time-of-flight mass spectrometry of gangliosides from human brain tissue

A general approach for the detection and structural elucidation of brain ganglioside species GM1, GD1 and GT1 by nano-electrospray ionization quadrupole time-of-flight (nanoESI-QTOF) mass spectrometry (MS), using combined data from MS and MS/MS analysis of isolated native ganglioside fractions in negative ion mode and their permethylated counterparts in the positive ion mode is presented. This approach was designed to detect and sequence gangliosides present in preparatively isolated ganglioside fractions from pathological brain samples available in only very limited amounts. In these fractions mixtures of homologue and isobaric structures are present, depending on the ceramide composition and the position of the sialic acid attachment site. The interpretation of data for the entire sequence, derived from A, B, C and Y ions by nanoESI-QTOFMS/MS in the negative ion mode of native fractions, can be compromised by ions arising from double and triple internal cleavages. To distinguish between isobaric carbohydrate structures in gangliosides, such as monosialogangliosides GM1a and GM1b, disialogangliosides GD1a, GD1b and GD1c or trisialogangliosides GT1b, GT1c and GT1d, the samples were analysed after permethylation in the positive ion nanoESI-QTOFMS/MS mode, providing set of data, which allows a clear distinction for assignment of outer and inner fragment ions according to their m/z values. The fragmentation patterns from native gangliosides obtained by low-energy collision induced dissociation (CID) by nanoESI-QTOF show common behaviour and follow inherent rules. The combined set of data from the negative and positive ion mode low-energy CID can serve for the detection of structural isomers in mixtures, and to trace new, not previously detected, components.

Accumulation of glycolipids in mutant Chinese hamster ovary cells (Z65) with defective peroxisomal assembly and comparison of the metabolic rate of glycosphingolipids between Z65 cells and wild-type CHO-K1 cells

The influence of peroxisomal dysfunction on glycosphingolipid metabolism was investigated using mutant Chinese hamster ovary (CHO) cells (Z65) with defective assembly of the peroxisomal membranes. In accordance with previous observations, the concentration of very long chain fatty acid (C24:0) was shown to be higher in Z65 cells than in control cells. We then compared the composition of glycolipids in Z65 cells with that in CHO-K1 cells, which are wild-type Chinese hamster ovary cells with intact peroxisomes, and found significantly increased concentrations of ceramide monohexoside (CMH) and ganglioside GM3 in Z65 cells. However, there were no differences in the concentrations of glycerophospholipids, triglycerides, free fatty acids and cholesterol between Z65 and CHO-K1 cells. Further, to investigate the metabolic rate of the major lipids, Z65 and CHO-K1 cells were pulse-labeled with [3-14C]serine. [3-14C]Serine was incorporated into phosphatidylserine, phosphatidylethanolamine and sphingomyelin more quickly in CHO-K1 than in Z65 cells. However, after 48 h, the radioactivity incorporated into those lipids, including CMH, was greater in Z65 cells than in CHO-K1 cells. Thus, the altered metabolism of glycosphingolipids, probably due to peroxisomal dysfunction, was thought to be responsible for the change in glycosphingolipid composition in Z65 cells.

A new procedure for determining ganglioside GD3 a potential glial cell activation marker in cerebrospinal fluid

Increased amounts of ganglioside GD3 [II3 (NeuAc)2-LacCer], associated with reactive gliosis, have been documented in a variety of neurodegenerative disorders. GD3 expression has also been reported in microglial cells, not only during development but also in reactive states, where the glial activation is considered to be part of the repair process. It is important to find markers in cerebrospinal fluid that will enable us to identify damage and register changes in pathological processes within the brain. A sensitive and practically applicable method for determination of GD3 ganglioside in cerebrospinal fluid has been developed. The procedure, which includes extraction, purification on silica gel and thin-layer enzyme-linked immunostaining, also allows determination of sulphatide, a marker of demyelinating processes, in the same portion of CSF. The method has been applied to CSF samples from 101 normal individuals aged 2-83 years. The GD3 concentration was found to be significantly correlated to age and reflecting the concentrations within the brain. GD3 ganglioside analysis by means of this method might be useful for studying glial changes during brain maturation as well as in brain disorders.

Neuronal differentiation of human neuroblastoma SH-SY5Y cells by gangliosides

Exogenous administration of gangliosides induced neuronal differentiation with prominent neuritogenesis in human neuroblastoma SH-SY5Y cells in vitro. Neuritogenesis was characterized by ruffling of the cell membrane, the development of lamellipodia and filopodia, and the subsequent elongation and branching of the neurites ultrastructurally. Both axons and neurites were identified. Increased numbers of cell organelles in the neurites and cell bodies were noted. Nonsynaptic contacts and gap junctions formed between neurites or between each neurite and cell body. These findings could be implicated in histopathologic changes from neuroblastoma to ganglioneuroblastoma.

Differential expression of gangliosides and galactolipids in fetal human oligodendrocytes and astrocytes in culture

The phenotypic expression of gangliosides and galactolipids was investigated using primary cultures of fetal human oligodendrocytes and astrocytes. These glial cells were isolated from fetal human brains of 12-18 weeks' gestation. Expression of gangliosides and galactolipids in oligodendrocytes and astrocytes was investigated by double labeling immunocytochemistry using rabbit antibodies specific for galactocerebroside (GalC, a cell type-specific marker for oligodendrocyte) and glial fibrillary acidic protein (GFAP, a cell type-specific marker for astrocyte) in combination with a panel of mouse monoclonal antibodies which react with specific gangliosides or galactolipids. A considerable number of GalC+ oligodendrocytes expressed intense immunoreactivities specific for GM3 (19%) and GM2 (45%) gangliosides. Approximately 11% of GalC+ oligodendrocytes expressed GM4 immunoreactivity, and smaller numbers of GalC+ oligodendrocytes expressed GD3 (4%), GD2 (1%), GT1b (5%) and A2B5 (3%) immunoreactivities. However, GalC+ oligodendrocytes did not express GM1, GD1a, GT1b or GQ1c. Major populations of GalC+ oligodendrocytes immunolabeled by rabbit anti-GalC antibody reacted with anti-GalC mAb (Ranscht mAb, 81%) or by anti-sulfatide mAb (O4 mAb, 91%). A considerable number of GFAP+ astrocytes expressed intense GM2 (26%) and GD2 (15%) immunoreactivities, while a smaller population expressed intense GM3 (3%), GD3 (6%) and GM4 (4%) immunoreactivities. Weak immunoreactions specific for GD1b, A2B5 and sulfatide were found in less than 1% each of GFAP+ astrocytes, while GFAP+ astrocytes did not express GM1, GD1a, GT1a, GT1b or GQ1b. These results indicate that GM3, GM2 and sulfatide are expressed in a major population of GalC+ oligodendrocytes, while GM3, GM2, GD3, GD2, and GM4 are expressed in a small but distinctive population of GFAP+ astrocytes. Our results suggest that GM4, GM1 and GD3, which are utilized as markers for adult human oligodendrocytes and myelin, are not the major ganglioside constituents in cultured fetal human oligodendrocytes.

Expression of neolactoglycolipids: sialosyl-, disialosyl-, O-acetyldisialosyl- and fucosyl- derivatives of neolactotetraosyl ceramide and neolactohexaosyl ceramide in the developing cerebral cortex and cerebellum

The following neolacto glycolipids were identified and their developmental expression was studied in the rat cerebral cortex and cerebellum: Fuc alpha 1-3IIInLcOse4Cer,Fuc alpha 1-3VnLcOse6Cer and (Fuc)2 alpha 1-3III,3VnLcOse6Cer, as well as acidic glycolipids, NeuAc alpha 2-3IVnLcOse4Cer [nLM1], (NeuAc)2 alpha 2-3IVnLcOse4Cer [nLD1], O-acetyl (NeuAc)2 alpha 2-3IVnLcOse4Cer [OAc-nLD1] and their higher neolactosaminyl homologues NeuAc alpha 2-3VlnLcOse6Cer [nHM1] and (NeuAc)2 alpha 2-3VlnLcOse6Cer [nHD1]. These glycolipids were expressed in the cerebral cortex only during embryonic stages and disappeared postnatally. This loss was ascribed to the down regulation of the synthesis of the key precursor LcOse3Cer which is synthesized by the enzyme lactosylceramide: N-acetylglucosaminyl transferase. On the other hand in the cerebellum, these glycolipids increased with postnatal development due to increasing availability of LcOse3Cer. In the cerebellum, only nLM1 and fucosyl-neolactoglycolipids declined after postnatal day 10-15, perhaps due to regulation by other glycosyltransferases. Also, in the cerebellum, nLD1 and nHD1 were shown to be specifically associated with Purkinje cells and their dendrites in the molecular layer and with their axon terminals in the deep cerebellar nuclei, similar to other neolactoglycolipids shown previously.

Ganglioside GM1 and GM3 in early human brain development: an immunocytochemical study

The distribution of GM1 and GM3 gangliosides in human brain development between gestational week (g.w.) 6 and 15 was demonstrated by an immunocytochemical approach using polyclonal anti-GM1 and anti-GM3 antibodies. The first appearance of GM1- and GM3-positive cells was recorded as early as in g.w.6. Both antibodies labeled the cells in the ventricular zone of the telencephalic wall, with radially oriented fibers toward the pial surface, which represent radial glia cells with glia fibers. The intensive GM3 immunoreactivity was also exhibited in proliferating cells in the ventricular zone between g.w.6 and 12. During the period from g.w. 12 to 15, characterized by a rapid multiplication of neurons and glia cells, an increased number of GM1- and GM3-positive cells was observed. Prominent GM1 ganglioside staining was observed at the surface of the cell bodies in the ventricular zone. Besides surface labeling in migrating cells, GM1 immunoreactivity was identified inside the soma in the regions of cortical plate and subplate. GM1 immunoreactivity was more pronounced on the membrane of neuronal cells migrating along radial glia fibers, especially at the contact site between neuronal and glial cells. The GM3 ganglioside was localized mostly inside the soma, showing a granular immunoreactivity pattern. Our observations confirm the presence of GM1 and GM3 gangliosides in neuronal and glial cells in early human brain development. The involvement, especially of GM1 ganglioside in glia-neuronal contacts during migration of neuroblasts to their final destination, as well as the presence of GM3 ganglioside in proliferative cells in the ventricular zone of the telencephalic wall was also recorded.

Gangliosides have a bimodal effect on DNA synthesis in U-1242 MG human glioma cells

GM1, GD1a, and GT1b inhibit both PDGF-stimulated and serum-stimulated DNA synthesis in Swiss 3T3 cells and the human glioma cell line U-1242 MG in a dose-dependent manner. The ganglioside inhibitory effect is counteracted in a dose-responsive fashion by serum such that ganglioside-induced inhibition is essentially abolished in 10% serum. Because of the potentially important role that gangliosides play in growth regulation of human gliomas, this phenomenon was studied in detail using U-1242 MG cells. Stimulation of DNA synthesis by low doses of serum in U-1242 MG cells is inhibited in a dose-responsive fashion by ganglioside GM1. However, serum itself counteracts the inhibitory effect of ganglioside in a dose responsive way. Kinetic analyses demonstrate that GM1 competes with some components of serum for sites on U-1242 MG cells (Kb of GM1 = 12.5 microM). On the other hand, GM1, GD1a, and GT1b stimulate DNA synthesis in quiescent U-1242 MG cells in both sparse and confluent conditions, indicating that ganglioside-stimulated DNA synthesis is dependent on the phase of cellular growth rather than cellular density. This growth stimulatory effect of gangliosides is more potent on quiescent, confluent cells than quiescent, sparse cells. These results demonstrate that exogenously added gangliosides can have opposite (bimodal) effects on progression of human glioma cells through the cell cycle depending upon the growth phase of the cells.

Ganglioside modulation of the PDGF receptor. A model for ganglioside functions

Gangliosides are a family of glycolipids that are present at the cell surface of all mammalian cells. Patterns of gangliosides are different in gliomas than normal brain, and exogenously added gangliosides affect the growth of cultured glioma cells. Gangliosides inhibit the activities of several kinases, including protein kinase C (PKC) and cAMP-kinase. U-1242 MG cells (derived from a human malignant glioma) have receptors for platelet-derived growth factor (PDGF) that become phosphorylated on tyrosine when exposed to PDGF. Exposure of these cells to PDGF also causes an increase in intracellular calcium concentration ([Ca2+]i) and induces a translocation of PKC to the membrane. Preincubation of U-1242 MG cells with several species of gangliosides inhibits the increase in ([Ca2+]i) and PKC translocation in response to PDGF, but GM3 is much less effective than other species tested. This is due to a lack of activation of the receptor tyrosine kinase as monitored by phosphorylation of the receptor on tyrosine residues, but is not due to an inhibition of binding of PDGF to its receptors. The lack of activation of the PDGF receptor tyrosine kinase is due to an inhibition of dimerization of the receptor monomers by gangliosides GM1, GM2, GD1a, GT1b, but not GM3. Therefore, gangliosides may be involved in coordinating the activities of multiple trophic factors simultaneously acting on a cell by regulating the dimerization of their respective receptor monomers.

Gangliosides as diagnostic markers of human astrocytomas and primitive neuroectodermal tumors

BACKGROUND

Limitations of classification schemes for brain tumors based solely on morphology have stimulated searches for molecular markers of nosologic and prognostic value. Gangliosides are logical candidates because there are high concentrations of them in the nervous system, there is evidence of their roles in regulation of growth and differentiation, and data from small series suggest correlations between ganglioside composition and glioma type.

METHODS

Ganglioside compositions were determined for 70 primary human brain tumors: 16 low grade astrocytomas (LG), 12 anaplastic astrocytomas (AA), 34 glioblastoma multiformes (GBM), and 8 primitive neuroectodermal tumors (PNET). This method involved identification and quantitation of specific gangliosides using chemical analysis and immunoanalysis.

RESULTS

Among all tumor types, histologic grade correlated with a progressive loss of 1b gangliosides (P < 0.0001). GQ1b was higher in LGs than in AAs (P < 0.001). Both GT1b and GD1b were higher in AAs than GBMs (P < 0.01 and 0.05, respectively) and lower in PNETs than in GBMs (P < 0.05). GM3 was higher in PNETs than in any astrocytoma group and higher in GBMs than in either AAs or LGs. There was a significant difference in the content of 3'-LM1 among all groups (P < 0.005), between AAs and GBMs (P < 0.05), and between low grade ordinary and juvenile pilocytic astrocyomas (P < 0.01). The lacto-series ganglioside 3'-isoLM1 was present in all groups except PNET.

CONCLUSIONS

These results indicate that patterns of gangliosides could be of considerable value in refining the classification and diagnosis of primary human brain tumors.

Developmental profile of ganglioside GD3 in the central nervous system: an immunocytochemical study in the rat

Light and electron microscopy observations were made of developing rat brain at gestation days (E) E13, E16, E19, and postnatal days (P) P1, P3, P5, P7 after immunocytochemical staining for ganglioside GD3 (II3 alpha(NeuAc alpha 2-8NeuAc)-LacCer, GD3) using mouse IgM anti-GD3 monoclonal antibody (DSG-1). Immunoreactivity was observed in neuroblasts (E13, E16) and immature neuronal cells (P1, P3, P5, P7), and also in glioblasts (E19). Electron microscopy revealed that at E13 peroxidase reaction product for GD3 (RP) was present on the plasma membrane and in the cytoplasm of neuroblasts, with accentuation in the former. At E16, RP was observed predominantly in the cytoplasm of neuroblasts. At E19, EP was seen mainly in the cytoplasm of glioblasts. At P1, P3, P5, and P7, immature neuronal cells in the cerebrum were immunoreactive. In the cerebellum, immature Purkinje cells and immature neuronal cells in the external and internal granular layers were also immunoreactive for GD3, the reaction product being located in the cytoplasm. The present findings suggest that changes in the localization of GD3 in neuroblasts were correlated with the alteration in their biological functions.

Patterns of reactivity with anti-glycolipid antibodies in human primary brain tumors

Antibodies against carbohydrates of three glycolipids were used to determine patterns of immunohistochemical reactivity of histologically identifiable cell subpopulations in 101 human primary brain tumors. For all tumor types fibrillary cells, polar cells, and gemistocytes (commonly seen in astrocytomas and ependymomas) stained more frequently for galactosylcerebroside with mAbO1 than small tumor cells and macrophages. Frequency of staining for sulfatide with mAbO4 was fibrillary > polar > small cells = macrophages. Gemistocytes stained more frequently with mAbO4 than polar cells in all tumors except low grade astrocytomas. These data indicate that tumors classified on histological grounds as astrocytic are often stained with antibodies that recognize oligodendrocytes and their progenitors. Thus, anti-glycolipid antibodies used in the study of developmental lineage may offer useful tools for classification of human brain tumors. Staining of fibrillary cells, polar cells, and gemistocytes for paragloboside directly with mAb F1H11 was much less common than with mAbO1, but this increased by pretreatment of the tissues with neuraminidase (F1H11 + N). Of particular note was the finding that small tumor cells frequently stained with F1H11 + N. Evidence that these were not macrophages was obtained using double immunostaining with F1H11 + N and anti-macrophage antibodies. In astrocytomas the frequency of small tumor cells immunostained with F1H11 + N was high grade > anaplastic > low grade, demonstrating a correlation of this tumor cell population with more aggressive astrocytomas. Thus, immunostaining with F1H11 + N may be of value in identifying small, anaplastic tumor cells, especially in small biopsies or tissue taken adjacent to the main tumor mass.

Immunohistochemical demonstration of ganglioside GD3 in the central nervous system

Immunohistochemical staining for GD3 in adult rat brain was carried out using mouse IgM anti-GD3 monoclonal antibody (DSG-1). Neuronal cells in the cerebral cortex, striatum, hippocampus and various nuclei of the thalamus were immunoreactive. In the cerebellum, Purkinje cells, granule cells and also basket cells were immunoreactive. However, astrocytes and oligodendrocytes in the cerebrum and cerebellum were not immunoreactive. The GD3 immunoreactivity was located in the cytoplasm. These findings are of considerable interest, being the first reported demonstration of GD3 in the adult rat brain. The implications and possible significance of the presence of GD3 are discussed.

Specificity of S fimbriae on recombinant Escherichia coli: preferential binding to gangliosides expressing NeuGc alpha (2-3)Gal and NeuAc alpha (2-8)NeuAc

The adhesins of Escherichia coli strains HB101(pANN801-13) and HB101(pAZZ50), which express S fimbriae encoded by a recombinant plasmid containing the sfaI and sfaII gene clusters, respectively, were characterized with regard to the detailed structural requirements of their binding to sialyloligosaccharides on (neo)glycoproteins and (neo)glycolipids. From binding and binding inhibition studies in solid-phase enzyme immunoassays with isolated S fimbriae, several major conclusions can be drawn. S fimbriae bind specifically to sialic acid on gangliosides. The most active structural variant of sialic acid on GM3 ganglioside is N-glycolylneuraminic acid (NeuGc). In contrast to previous reports, high binding activities were measured also for b-series gangliosides expressing NeuAc alpha (2-8)NeuAc. In agreement with earlier studies, the site of sialic acid substitution to subterminal sugars strongly influences the binding to sialyloligosaccharides, i.e., alpha-6-linked sialic acid is only poorly recognized by the adhesin compared with alpha-3-linked sialic acid. C-8 and C-9 hydroxyl groups form essential structural elements of sialic acid in the binding event.

Immunohistochemical localization of gangliosides in ENU-induced rat glioma

Biochemical studies have indicated that the structurally simple gangliosides, including GD3 and GM3, are major glycolipid components of glioma tissues. In order to clarify the localization of the gangliosides in ethylnitrosourea-induced rat glioma, an immunohistochemical study was performed using antibodies against GM1, GM3, and GD3. The results obtained in normal fetus, newborn, and adult rat brain, and also in human glioma, were compared. In fetal and newborn rat brain, GD3 was present mainly in the neuroepithelial cell surface of the matrix and subependymal layers of the ventricular wall, but GM3 and GM1 were not detected. In adult rat brain, GD3-positive cells were absent, or present in diminished number, and GM1 was found chiefly in the neuropil of the cerebral cortex. Most of the rat glioma cells were positive for GD3, but not for GM1. It was demonstrated that the ganglioside composition of glioma cells was similar to that of immature neuroectodermal cells in fetal and newborn rat brain. Furthermore, the number of GD3-positive oligodendroglioma cells increased with tumor growth. In anaplastic gliomas and gross oligodendrogliomas, most tumor cells expressed not only GD3 but also GM3. These results suggest that GD3 is a marker of proliferating neuroectodermal cells, and that activity of the key enzymes in ganglioside synthesis alters with tumor growth and anaplastic change.

Effects of exogenous GM1 ganglioside on LTP in rat hippocampal slices perfused with different concentrations of calcium

Combined actions of GM1 ganglioside molecules and Ca2+ ions on long-term potentiation (LTP) of the hippocampal CA1 synapses were examined in slice preparations. Application of exogenous GM1 ganglioside significantly enhanced LTP. Antigenic blocking of endogenous GM1 ganglioside by applying anti-GM1 antiserum appeared to attenuate LTP. Exogenous GM1 treatment not only antagonized LTP suppression caused by low Ca2+ (1.0 microM) in the perfusion medium, but also amplified LTP at high Ca2+ (5.0 microM) condition. Thus, GM1 may stabilize intracellular calcium levels to enhance synaptic potentiation.