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S Ladisch

Publications and source records attributed to S Ladisch.

At least 37 records · Page 2Linked to original sources
PubMed1998

Nerve growth factor-induced neurite formation in PC12 cells is independent of endogenous cellular gangliosides.

The PC12 rat pheochromocytoma cell line is an established model for nerve growth factor (NGF)-induced neurite formation. It has been shown that when gangliosides are added to the culture medium of PC12 cells, NGF-induced neurite formation of PC12 cells is enhanced. To determine the role of endogenous cellular gangliosides themselves in NGF-elicited neurite formation, we depleted cellular gangliosides using the new specific glucosylceramide synthase inhibitor, d, l-threo-1-phenyl-2-hexadecanoylamino-3-pyrrolidino-1-propanol.HCl (PPPP). 0.5-2 microM PPPP rapidly inhibited ganglioside synthesis and depletedcellular gangliosides. Nonetheless, over a concentration range of 5-100 ng/ml NGF, in both low serum and serum-free medium, neurite formation was normal. Even pretreatment of PC12 cells for up to 6 days with 1 microM PPPP followed by cotreatment with PPPP and NGF for 10 days, still did not inhibit neurite formation. The conclusion that ganglioside depletion did not block neurite formation stimulated by NGF was supported by the lack of effect of PPPP, under these same conditions, on cellular acetylcholine esterase activity, a neuronal differentiation marker (73.8 +/- 12.1 versus 67.2 +/- 4.6 nmol/min/mg protein at 50 ng/ml NGF; control versus 1 microM PPPP). These findings, together with previous studies showing enhancement of NGF-induced neurite formation by exogenous gangliosides, underscore the vastly different effects that exogenous gangliosides and endogenous gangliosides may have upon cellular functions.

Acetylcholinesterase↗
PubMed1998

Langerhans cell histiocytosis.

The term histiocytosis identifies a group of disorders characterized by localized or generalized reactive or neoplastic proliferation of cells similar, if not identical, to cells of the mononuclear phagocyte and dendritic cell systems. In Langerhans cell histiocytosis (LCH), the proliferating cell is the Langerhans cell, and the morphologic and immunohistochemical criteria for the definitive diagnosis of LCH have been established. The clinically evident pathology of LCH is broadly divided into two categories: direct involvement with the disease (e.g., lytic lesions of the bone or organ involvement) and secondary consequences resulting from permanent damage by the primary disease, LCH (eg, diabetes insipidus, fractures, and tooth loss). Current knowledge suggests tailoring the therapy to the extent of disease. Single-system disease can be treated by excisional biopsy, low-dose radiotherapy, or mild chemotherapy. Multisystem disease should be treated with combination chemotherapy, and current experimental therapeutic approaches include randomized treatment protocols for multisystem disease. A pressing current controversy regarding LCH is that its etiology is unknown. Whether LCH is reactive or neoplastic is even debated, and several features provide seemingly contradictory evidence on this point (spontaneous resolution of disease on one hand and clonality of lesional LCH cells on the other), underscoring the need for further studies to elucidate the etiology and pathogenesis of LCH.

Antigen-Presenting Cells↗
PubMed1997

Detection of medulloblastoma and astrocytoma-associated ganglioside GD3 in cerebrospinal fluid.

Shedding of gangliosides by tumor cells may enhance tumor development. We recently showed that cells of the human brain tumor, medulloblastoma, shed gangliosides in vitro and have therefore examined ganglioside shedding by pediatric brain tumors into the cerebrospinal fluid (CSF). GD3, a major ganglioside in medulloblastoma and astrocytoma, was the target for detection in the CSF by immunostaining using the monoclonal antibody R24 and enhanced chemiluminescence detection. Mean CSF GD3 levels in patients with medulloblastomas (n = 9) and astrocytomas (n = 10) were significantly higher than those of controls (mean +/- SD 44.7 +/- 8.4 versus 18.2 +/- 1.9 pmol/ml, n = 20, P < 0.0002). Mass spectrometric analysis showed that tumor-derived ganglioside GD3 contained heterogeneous ceramide structures and, interestingly, the ceramide subspecies with shorter fatty acyl chains were selectively shed. The elevated CSF GD3 concentrations in patients with medulloblastoma and astrocytoma support the concept that ganglioside shedding, which may have significant biological consequences, is characteristic of human brain tumors.

Astrocytoma↗
PubMed1997

Shedding of gangliosides by human medulloblastoma cells.

Shedding of immunosuppressive gangliosides is an important characteristic of both experimental and human tumors. Using a medulloblastoma cell line, Daoy, with a very high ganglioside expression (141 +/- 13 nmol/10(8) cells) and a well-characterized ganglioside complement, we have now studied ganglioside shedding by human brain tumor cells. Shedding of gangliosides, quantified by metabolic radiolabeling, was significant (169 pmol/10(8) cells/h) and was generalized with respect to the major ganglioside carbohydrate structures (G(M2), G(M3), and G(D1a)). For each ganglioside, however, shedding was selective for ceramide structures containing shorter fatty acyl chains. Rapid and ceramide-selective shedding was confirmed in two additional human medulloblastoma cell lines, D341 Med and D283 Med (112 and 59 pmol/10(8) cells/h). Significant ganglioside shedding is therefore a common characteristic of human medulloblastoma cells and may influence the biological behavior of this tumor, in view of immunosuppressive and other biological properties of shed gangliosides.

Cell Division↗
PubMed1997

Inhibition of endogenous ganglioside synthesis does not block neurite formation by retinoic acid-treated neuroblastoma cells.

Gangliosides are believed to play a critical role in cellular differentiation. To test this concept, we determined the effect of inhibition of endogenous ganglioside synthesis upon neurite formation induced by retinoic acid in LAN-5 human neuroblastoma cells. Ganglioside synthesis and content of LAN-5 cells exposed for 6 days to 10 microM D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP) (an inhibitor of glucosylceramide synthase) were reduced by >90%. However, these ganglioside-depleted cells were not blocked from forming neurites when exposed to 10 microM retinoic acid. Even more extensive treatment of LAN-5 cells with 20 microM D-PDMP (6 day pretreatment followed by 6 days together with 10 microM retinoic acid) still did not block the retinoic acid-induced neurite formation. An element of neuroblastoma tumor cell differentiation, neurite formation, is therefore dependent neither on an intact cellular ganglioside complement nor on new ganglioside synthesis.

Down-Regulation↗
PubMed1997

Contemporary classification of histiocytic disorders. The WHO Committee On Histiocytic/Reticulum Cell Proliferations. Reclassification Working Group of the Histiocyte Society.

Pathologists and pediatric hematologist/ oncologists of the World Health Organization's Committee on Histiocytic/Reticulum Cell Proliferations and the Reclassification Working Group of the Histiocyte Society present a classification of the histiocytic disorders that primarily affect children. Nosology, based on the lineage of lesional cells and biological behavior, is related to the ontogeny of histiocytes (macrophages and dendritic cells of the immune system). Dendritic cell-related disorders of varied biological behavior are dominated by Langerhans cell histiocytosis, but separate secondary proliferations of dendritic cells must be differentiated. Juvenile xanthogranuloma represents a disorder of dermal dendrocytes, another dendritic cell of skin. The hemophagocytic syndromes are the most common of the macrophage-related disorders of varied biological behavior. Guidelines for distinguishing the exceedingly rare malignant diseases of histiocytes from large cell lymphomas through the use of a battery of special studies are provided.

Cell Lineage↗
PubMed1997

Human medulloblastoma gangliosides.

To establish a model system for the study of ganglioside metabolism of the human brain tumor, medulloblastoma, we have chemically characterized the gangliosides of the Daoy cell line. These cells contain a high concentration of gangliosides (143 +/- 13 nmol LBSA/10(8) cells). The major species have been structurally confirmed to be GM2 (65.9%), GM3 (13.0%), and GD1a (10.3%). Isolation of individual gangliosides homogeneous in both carbohydrate and ceramide moieties by reversed-phase HPLC and analysis by negative-ion fast atom bombardment collisionally activated dissociation tandem mass spectrometry have allowed us to unequivocally characterize ceramide structures. In the case of GM2, 10 major ceramide subspecies were identified: d18:1-hC16:0, d18:1-C16:0, d18:0-C16:0, d18:1-C18:0, d18:1-C20:0, d18:1-C22:0, d18:2-C24:1, d18:1-C23:1, d18:1-C24:1, and d18:1-C24:0. Taken together with previous studies, these findings in buman medulloblastoma cells support the view that high expression and marked heterogeneity of ceramide structure are general characteristics of tumor gangliosides, molecules which are shed by the tumor cells and which are biologically active in vivo.

Ceramides↗
PubMed1996

Abrogation of shedding of immunosuppressive neuroblastoma gangliosides.

Shedding of tumor cell gangliosides may contribute to tumor cell escape from host immune destruction. Thus, it would be of interest to block the shedding of these immunosuppressive molecules. To this end, we studied a ceramide analogue, D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP). D-PDMP is a potent inhibitor of glucosylceramide synthase and thereby the synthesis of cellular glycosphingolipids. Exposure of LAN-5 human neuroblastoma cells to 10 microM D-PDMP for 5 days almost completely abolished the shedding of gangliosides (from 240 to 8 pmol/10(8) cells/h), whereas cellular ganglioside synthesis was reduced by 90%. A shorter (3-day) treatment of LAN-5 cells with 10 microM D-PDMP was already effective in inhibiting shedding (by 86%) even while the cellular ganglioside content was still high. Specificity was evidenced by the only minimal effect of D-PDMP on the synthesis of sphingomyelin and phosphatidylcholine. Therefore, certain pharmacological agents, such as D-PDMP, may be useful in abrogating tumor ganglioside shedding and its consequent biological effects in vivo.

Cell Division↗
PubMed1996

Induction of programmed cell death and immunosuppression by exogenous sphingolipids are separate processes.

Gangliosides are highly immunosuppressive molecules but the mechanism(s) by which they act upon cells remains to be fully defined. Several metabolic products of exogenous gangliosides, including ceramide, have recently been suggested as second messengers in programmed cell death (PCD). Therefore, we have probed the role of gangliosides and ceramides in the induction of PCD and in the inhibition of in vitro lymphoproliferation. PCD was caused only by exogenous ceramides with short fatty acyl groups-d18:1-C2:0 (C2-ceramide, where d18:1 is sphingosine and C2:O is an acetyl group) and d18:1-C6:0 (C6-ceramide, where C6:O is a hexanoyl group). None of the gangliosides studied induced PCD, including naturally occurring GM3, synthetic d18:1-C18:0 GM3 (C18-Cer GM3, where C18:0 is a stearoyl group), or even d18:1-C2:0 GM3 (C2-Cer GM3), which itself contains a PCD-causing ceramide. However, these gangliosides were highly immunosuppressive, inhibiting antigen-induced lymphoproliferation at micromolar concentrations. We conclude that exogenous sphingolipids cause inhibition of lymphoproliferation and PCD by two separate and distinct mechanisms of action.

Apoptosis↗
PubMed1996

Gangliosides block antigen presentation by human monocytes.

Gangliosides, immunosuppressive molecules shed by tumor cells, are potent inhibitors of monocyte accessory cell function. However, the specific monocyte cellular defect caused by gangliosides is unknown. Here we sought to delineate whether this abnormality is in the induction of suppressor cells, in intracellular antigen processing, or in intercellular antigen presentation. Three sets of studies of the tetanus toxoid (TT)-induced lymphoproliferative response, which is dependent upon monocyte accessory function, address this issue: (1) Antigen (TT)-primed human monocytes incubated with 50-100 microM human brain gangliosides for 24-48 h, washed, and then combined with T-cells, were inhibited in triggering T-cell proliferation, showing that the effect was occurring after antigen processing was complete. (2) T-cell responses to immobilized anti-CD3 or to antigen-primed control monocytes in the presence of ganglioside-exposed monocytes were unaffected, showing that ganglioside-exposed monocytes did not act as suppressor cells. (3) Stimulation by TT peptide fragment 830-843, which does not require processing, was completely inhibited by exposure of monocytes to gangliosides. These findings identify ganglioside interference with monocyte accessory cell function at the level of antigen presentation. We conclude that tumor gangliosides may inhibit host anti-tumor cellular immune responses by preventing the effective cellular interactions of the antigen-primed monocyte with the responding T-lymphocyte.

Antigen Presentation↗
PubMed1996

Tumor gangliosides enhance alpha2 beta1 integrin-dependent platelet activation.

Gangliosides, sialic acid-containing glycosphingolipids, enhance platelet adhesion to collagen and consequent platelet activation. For example, gangliosides shed by neuroblastoma tumor cells (NBTG) added to a subthreshold (non-activating) concentration (1 microgram/ml) of collagen, cause platelet aggregation (59 +/- 10%) and ATP release (2.3 +/- 0.2 nmol) equivalent to that caused by 10 micrograms/ml collagen alone. Here we report further studies to characterize this effect. Platelet aggregation and ATP release were not induced by NBTG in combination with subthreshold concentrations of adenosine diphosphate, epinephrine, thrombin or arachidonic acid, suggesting that NBTG specifically influences collagen-mediated platelet activation. Maximal platelet aggregation and ATP release required extracellular magnesium and only a short (1 min) preincubation with NBTG, suggesting a collagen receptor-mediated mechanism of this ganglioside activity. Since gangliosides interact with several integrin receptors, we determined whether NBTG influences alpha 2 beta 1, a major integrin collagen receptor on platelets. Incubation of platelets with a monoclonal antibody directed against the alpha 2 chain (5E8) blocked the increase in platelet aggregation (9 +/- 3% vs. 80 +/- 2%) and ATP release ( < 0.2 vs 2.5 +/- 0.1 nmol) induced by NBTG and 1 microgram/ml collagen. Incubation with an antibody to the non-integrin collagen receptor, CD36, or with an isotype control antibody did not abrogate the effect of NBTG. Finally, NBTG and its major component, GD2, enhanced alpha 2 beta 1-mediated platelet adhesion to immobilized collagen in an antibody 5E8-inhibitable manner. These findings implicate the alpha 2 beta 1-collagen interaction as a target of the effect of tumor-derived gangliosides.

Cations, Divalent↗
PubMed1996

Intercellular transfer of shed tumor cell gangliosides.

Three distinct steps underlie immumosuppression by tumor gangliosides: (i) their shedding by the tumor cell, (ii) binding to target leukocytes in the tumor microenvironment, and (iii) action upon the target cell. While shedding is well documented, cell to cell transfer of shed gangliosides is not. To address this, we employed a dual chamber culture system. In this system, metabolically radiolabeled lymphoma cells shed gangliosides into the conditioned medium of the contralateral chamber, which contained normal fibroblasts as the target cell. The shed lymphoma cell gangliosides bound avidly to the target fibroblasts in a trypsin-resistant manner (1-2 x 10(6) and 7 x 10(6) molecules/fibroblast in 24 and 48 h). Significantly higher than binding rates of purified lymphoma gangliosides added exogenously, these binding rates in a system which models the in vivo microenvironment suggest that cell to cell ganglioside transfer is a highly efficient process.

Animals↗
PubMed1996

Structural characterization and in vivo immunosuppressive activity of neuroblastoma GD2.

Shedding of neuroblastoma gangliosides is positively correlated with tumour progression in patients with neuroblastoma. In assessing the biological activity of these ganglioside molecules, we recently found that total human neuroblastoma gangliosides inhibit cellular immune responses. Here, we have studied the major neuroblastoma ganglioside, GD2. GD2 was purified by high performance liquid chromatography and structurally characterized by mass spectrometry. Immunoregulatory effects of GD2 in vivo were then determined in an established murine model. GD2 significantly downregulated the local cellular immune response to an allogeneic cell challenge; the usual increase in mass of the lymph node draining the injection site was reduced by 88%, from 1.52 to 0.19 mg (control versus GD2-treated mice; p < 0.01). In parallel, lymphocyte recovery from each node was also reduced from 2.4 to 1.2 x 10(6) cells, and lymphocyte DNA synthesis was reduced to half of the control level. These results show that certain shed tumour gangliosides, such as GD2, function as intercellular signalling molecules, downregulate the cellular immune response, and may thereby enhance tumour formation and progression.

Animals↗
PubMed1995

Immunosuppressive activity of chemically synthesized gangliosides.

New chemical synthetic methods have permitted the synthesis of a spectrum of glycosphingolipid molecular species, some of which are not naturally occurring. Here we have studied a number of chemically synthesized gangliosides for immunosuppressive activity, using a human in vitro specific antigen (tetanus toxoid)-induced assay of the cellular immune response. Chemically synthesized GM3 and GM4 had the same high degree of immunosuppressive activity as did natural GM3 and GM4 gangliosides, verifying that inhibition is intrinsic to the ganglioside molecules and not caused by other molecules sometimes found in natural preparations (e.g., proteins). Studies of modified molecular species of GM3 and GM4, also prepared by chemical synthesis, have shown the influence of certain structural details upon the immunosuppressive activity of gangliosides: (i) the inverse relationship between fatty acyl chain length and immunosuppressive activity is extended to even shorter chain lengths, with the synthetic gangliosides d18:1-C2:0-GM3 and d18:1-C14:0-GM3 being more immunosuppressive than d18:1-C18:0-GM3 and d18:1-C24:0-GM3; (ii) hydroxylation of the fatty acyl group decreases immunosuppressive activity; (iii) substitution of an S-glycosidic bond for an O-glycosidic bond in the sialic acid ketosidic linkage in GM4 does not alter its activity; and (iv) modifications of the sialic acid group variably influence immunosuppressive activity, since KDN-GM3 and -GM4 ganglioside analogues, which contain a 3-deoxy-D-glycero-D-galacto-2-nonulopyranosonic acid in place of N-acetylneuraminic acid, retain activity, while other modifications such as 8-epi-GM3, and to a lesser extent 9-deoxy-GM3, reduce immunosuppressive activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain Chemistry↗
PubMed1995

Human tumor gangliosides inhibit murine immune responses in vivo.

Gangliosides which are shed by tumor cells clearly inhibit cellular immune responses in vitro. However, the immunosuppressive activity of these molecules have been more difficult to ascertain in vivo. Here we have adapted a murine model to determine the effects of tumor gangliosides in an in vivo microenvironment, the lymph node draining the site of stimulation by allogeneic cells. In this model, allogeneic splenocytes (BALB/c) are s.c. injected into C3H mice. The cellular immune response in the draining popliteal lymph nodes 4 days later is evidenced as an increase in lymph node mass (2-fold), lymphocyte number (6-fold), and lymphocyte DNA synthesis (6-fold). Purified human neuroblastoma gangliosides (10 nmol) coinjected with the stimulating allogeneic cells significantly suppressed this in vivo immune response. The increase in the lymph node mass was reduced by 65% (0.66 versus 1.89 mg), the increase in lymphocyte number (4.0 x 10(6) cells/node) was almost completely inhibited (1.1 x 10(6) cells/node), and in vitro [3H]thymidine uptake by the lymphocytes recovered in vivo was reduced by 80%. In contrast to the inhibition by tumor gangliosides, liposomes of cholesterol:lecithin were not inhibitory. Thus, tumor gangliosides, specifically, modulate cellular immune responses in vivo, which may contribute to the observed enhancement of tumor formation by these molecules.

Animals↗
PubMed1994

A chemically synthesized sialic acid-containing glycoconjugate, 2-(tetradecylhexadecyl)-O-(5-acetamido-3,5-dideoxy-D-glycero-alpha-D-ga lacto-2-nonulopyranosylonic acid)-(2-->3)-O-beta-D-galactopyrannosyl-(1-->4)-beta-D- glucopyrannoside, is a potent inhibitor of cellular immune responses.

Structural variations among gangliosides significantly influence their immunosuppressive activity. By total chemical synthesis, a sialic acid-containing glycoconjugate, 2-(tetradecylhexadecyl)-O-(5-acetamido-3,5-dideoxy-D-glycero-alpha -D-galacto-2-nonulopyranosylonic acid)-(2-->3)-O-beta-D-galactopyrannosyl-(1-->4)-beta-D- glucopyrannoside was synthesized. This glycoconjugate has the same carbohydrate structure as does GM3 ganglioside and a branched alkane in place of ceramide. It markedly inhibits the tetanus toxoid-induced human lymphoproliferative response in vitro (ID90 < 7 microM) and is five-fold more active than d18:1-C18:0 GM3 ganglioside, to which it is structurally related. This glycoconjugate is also a potent inhibitor of the murine alloimmune response in vivo: 10 nmol of the molecule injected subcutaneously together with an allogeneic cell challenge markedly inhibits the cellular immune response in the draining popliteal lymph node. In fact, the effect is quantitatively similar to that of systemically administered cyclosporin A, a well-studied immunosuppressive agent.

Animals↗