我国对神经节苷脂中GM1研究的新进展

大量的药理实验研究表明，单唾液酸四己糖神经节苷脂(GM1)对脑缺血、脑损伤、脑缺血再灌注损伤具有明显的保护作用，其作用机制可能是阻抑氧自由基产生过多的损害，减少脑出血的发生；减轻脑缺血对Na-K-ATPase的抑制作用，增强HSP70和TGF-β的表达；降低谷氨酸含量和明显减少细胞凋亡等。实验还证实，GM1对新生儿缺血缺氧性脑病、急性低压低氧脑损害、急性脊髓损伤、周围神经再生和修复都具有保护作用。临床主要用于急性缺血性脑卒中、原发性脑干损伤、急性脊髓损伤、外周神经损伤的治疗和研究。     

Glycosphingolipid composition of MDA-MB-231 and MCF-7 human breast cancer cell lines

Much evidence has shown that glycosphingolipids are involved in cellular recognition, regulation of cell growth, and metastasis. In the present study, the major glycosphingolipids of two widely studied human breast cancer cell lines were examined. The MCF-7 cell line has functional estrogen and EGF receptors, is dependent on estrogen and EGF for growth, and is uninvasive, while MDA-MB-231 cells are a model for more aggressive, hormone-independent breast cancer. There was twice as much neutral glycolipid in MCF-7 cells as in MDA-MB-231 cells. The major neutral glycolipids in MDA-MB-231 cells were identified as CTH and globoside. MCF-7 cells also contained as the major neutral glycolipids CTH as well as globoside and two other glycolipids which were tentatively identified as galactosylgloboside and fucosylgalactosylgloboside by exoglycosidase treatments. Conversely, the ganglioside content was four fold higher in MDA-MB-231 cells compared to MCF-7 cells. The abundant gangliosides in both cell lines were GM3, GM2, GM1, and GD1a. A minor monosialoganglioside was detected in MDA-MB-231 cells. The striking 18 fold greater amount of GM3 in MDA-MB-231 cells may have important implications because GM3 has been suggested to be involved in regulation of growth factor functions. In agreement, insertion of ganglioside GM3 into the plasma membrane of MCF-7 cells blocked the growth stimulatory effect of EGF.     

Alterations in ganglioside expression during the differentiation of human mast cells

Gangliosides are physiological components of the outer cell membrane. In the present study, the role of ganglioside expression during differentiation of human mast cells was evaluated. After 11 days of culture in medium known to induce mast cell differentiation, 70% of peripheral blood mononuclear cells (PBMC) showed positive staining for the high affinity IgE receptor and tryptase on immunocytochemistry and an associated 20-fold increase of ganglioside GM3 expression. Furthermore, exogenous addition of GM3 during cultivation of PBMC in medium containing low levels of growth factors induced an increase of mast cell specific tryptase. The association of ganglioside expression with mast cell differentiation was confirmed by experiments with the human mast cell line HMC-1. FcepsilonRI-positive cultured cells enriched with immunobeads exhibited a 3-fold higher expression of GM3, compared to FcepsilonRI negative HMC-1 cells. Furthermore, measurable amounts of the gangliosides GM2, GM1 and GD1a were found only in the FcepsilonRI positive cells. A corresponding transient increase of mRNA for GalNAcT, the key enzyme in the production of these latter gangliosides, could be detected preceding the expression of these gangliosides and the FcepsilonRI by RT-PCR. Taken together, these data point to a functional role of gangliosides in the differentiation of human mast cells.     

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.     

Gangliosides inhibit the development from monocytes to dendritic cells

Dendritic cell (DC) development and function is critical in the initiation phase of any antigen-specific immune response against tumours. Impaired function of DC is one explanation as to how tumours escape immunosurveillance. In the presence of various soluble tumour-related factors DC precursors lose their ability to differentiate into mature DC and to activate T cells. Gangliosides are glycosphingolipids shed by tumours of neuroectodermal origin such as melanoma and neuroblastoma. In this investigation we address the question of whether gangliosides suppress the development and function of monocyte-derived DC in vitro. In the presence of gangliosides, the monocytic DC precursors showed increased adherence, cell spreading and a reduced number of dendrites. The expression of MHC class II molecules, co-stimulatory molecules and the GM-CSF receptor (CD116) on the ganglioside-treated DC was significantly reduced. Furthermore, the function of ganglioside-treated DC was impaired as observed in endocytosis, chemotactic and T cell proliferation assays. In contrast to monocytic DC precursors, mature DC were unaffected even when higher doses of gangliosides were added to the culture. With regard to their carbohydrate structure, five different gangliosides (GM2, GM3, GD2, GD3, GT1b), which are typically shed by melanoma and neuroblastoma, were tested for their ability to suppress DC development and function. Suppression was induced by GM2, but not by the other gangliosides. These data suggest that certain gangliosides impair DC precursors, implying a possible mechanism for tumour escape.     

C6 cells express a sodium-calcium exchanger/GM1 complex in the nuclear envelope but have no exchanger in the plasma membrane: comparison to astrocytes

Previous work demonstrated the presence of an isoform of Na(+)/Ca(2+) exchanger in the nuclear envelope of neurons and NG108-15 cells that is tightly associated with GM1 ganglioside and potentiated by the latter. This contrasted with the Na(+)/Ca(2+) exchanger(s) in the plasma membrane, which were suggested to associate more loosely with GM1. To study these aspects of Na(+)/Ca(2+) exchanger expression in nonneuronal neural cells, we have examined nuclear and plasma membrane exchanger patterns in astrocytes and C6 cells, a glia-derived line. We find both cell types contain the tightly associated exchanger/GM1 complex in the nuclear envelope but, surprisingly, only astrocytes possess Na(+)/Ca(2+) exchanger activity in the plasma membrane. This is the first reported example of a cell (C6) with Na(+)/Ca(2+) exchangers in the nuclear envelope but not in the plasma membrane. RT-PCR established the presence of the NCX1 subtype in C6 cells and both NCX1 and NCX2 in astrocytes. Comparison was made with NG108-15 cells, which have Na(+)/Ca(2+) exchangers in both nuclear and plasma membranes, and Jurkat cells, which have no Na(+)/Ca(2+) exchanger in either membrane. Culturing of C6 cells in the presence dibutyryl-cAMP caused upregulation of a high molecular weight isoform of the exchanger together with GM1 in the nuclear envelope, resulting in significant elevation of Na(+)/Ca(2+) exchanger activity in the latter. Application of exogenous GM1 to nuclei from non-treated cells also potentiated exchanger activity, although to a lesser degree. The Na(+)/Ca(2+) exchanger/GM1 complex occurs in the inner membrane of the nuclear envelope, suggesting a functional role in transferring Ca(2+) between nucleoplasm and the envelope lumen.     

Anti-ganglioside antibodies and clinical outcome of patients with Guillain-Barré Syndrome in northeast Brazil

OBJECTIVES: The goal of this study was to investigate the frequency of GM1 antibodies and to assess whether exposure to Campylobacter jejuni was associated with a distinct clinical variant of Guillain-Barré Syndrome (GBS) or disease outcome in Rio Grande do Norte, Brazil. MATERIAL AND METHODS: Forty-one patients with a presumed diagnosis of GBS were enrolled and prospectively studied between June 1994 and November 1999. RESULTS: Anti-GM1 was present in 51.2% (n = 21) of patients. The presence of anti-GM1 was significantly associated with acute axonal motor neuropathy when compared to acute inflammatory demyelinating polyneuropathy (P = 0.01). Patients with anti-GM1 antibodies presented distal muscle involvement and fewer sensory deficits. Age, time to nadir and ventilatory assistance were not associated with anti-GM1 antibodies. Eight out of 21 patients (32%) presented with anti-C. jejuni antibodies. Clinical features were similar for patients with GBS with positive and negative C. jejuni antibodies. Anti-GM1 antibodies were associated with C. jejuni infection (P = 0.0005). Presence of anti-GM1 and C. jejuni antibodies did not indicate a worse prognosis. CONCLUSION: Patients with GBS and anti-GM1 antibodies had more distal muscle weakness, fewer sensory deficits, more axonal degeneration and C. jejuni infection, but these findings were not associated with a worse prognosis.     

NGF和GM1联合应用对去细胞异种神经支架移植后神经再生和修复的影响

为了探讨神经生长因子(NGF)和单唾液酸四己糖神经节苷脂(GM1)联合应用对去细胞异种神经支架移植后神经再生及功能恢复的影响,本研究将SD大鼠随机分为生理盐水对照组、NGF治疗组、GM1治疗组、NGF+GM1联合治疗组,选取兔胫神经进行化学萃取,形成去细胞异种神经支架桥接大鼠10mm坐骨神经缺损,移植前分别用等渗盐水(NS)、NGF液、GM1液或NGF+GM1液浸泡去细胞异种神经支架,术后各组大鼠术侧小腿肌内分别注射NS液、NGF液、GM1液或NGF+GM1液。术后4、8周行大体观察并用神经电生理、肌湿重、免疫组织化学等方法测定神经纤维再生及功能恢复情况。结果显示:在同一时间点,NGF+GM1联合治疗组坐骨神经运动传导速度恢复率、小腿腓肠肌复合动作电位波幅恢复率、小腿三头肌湿重恢复率均优于单独用药组(P<0.05);免疫组织化学结果显示NGF+GM1联合治疗组有大量再生有髓神经纤维顺畅地通过远端吻合口。本研究结果提示联合应用NGF和GM1可明显促进去细胞异种神经支架移植后的神经纤维再生与功能恢复。     

Glioma growth inhibition by neurostatin and O-But GD1b

In spite of their low incidence, central nervous system tumors have elevated morbidity and mortality, being responsible for 2.3% of total cancer deaths. The ganglioside O-acetylated GD1b (O-Ac GD1b; neurostatin), present in the mammalian brain, and the semi-synthetic O-butyrylated GD1b (O-But GD1b) are potent glioma proliferation inhibitors, appearing as possible candidates for the treatment of nervous system tumors. Tumoral cell division inhibitory activity in culture correlated with growth inhibition of glioma xenotransplants in Foxn1^nu nude mice and intracranial glioma allotransplants. Both O-Ac GD1b and O-But GD1b inhibited in vivo cell proliferation, induced cell cycle arrest, and potentiated immune cell response to the tumor. Furthermore, the increased stability of the butyrylated compound (O-But GD1b) enhanced its activity with respect to the acetylated ganglioside (neurostatin). These results are the first report of the antitumoral activity of neurostatin and a neurostatin-like compound in vivo and indicate that semi-synthetic O-acetylated and O-butyrylated gangliosides are potent antitumoral compounds that should be considered in strategies for brain tumor treatment.     

Long-Term Supplementation with Beta Serum Concentrate (BSC), a Complex of Milk Lipids,during Post-Natal Brain Development Improves Memory in Rats

We have previously reported that the supplementation of ganglioside-enriched complex-milk-lipids improves cognitive function and that a phospholipid-enriched complex-milk-lipid prevents age-related cognitive decline in rats. This current study evaluated the effects of post-natal supplementation of ganglioside- and phospholipid-enriched complex-milk-lipids beta serum concentrate (BSC) on cognitive function in young rats. The diet of male rats was supplemented with either gels formulated BSC (n = 16) or blank gels (n = 16) from post-natal day 10 to day 70. Memory and anxiety-like behaviors were evaluated using the Morris water maze, dark–light boxes, and elevated plus maze tests. Neuroplasticity and white matter were measured using immunohistochemical staining. The overall performance in seven-day acquisition trials was similar between the groups. Compared with the control group, BSC supplementation reduced the latency to the platform during day one of the acquisition tests. Supplementation improved memory by showing reduced latency and improved path efficiency to the platform quadrant, and smaller initial heading error from the platform zone. Supplemented rats showed an increase in striatal dopamine terminals and hippocampal glutamate receptors. Thus BSC supplementation during post-natal brain development improved learning and memory, independent from anxiety. The moderately enhanced neuroplasticity in dopamine and glutamate may be biological changes underlying the improved cognitive function.