神经节苷脂的生物学活性

神经节苷脂(ganglioside, GS)是一类含唾液酸的糖鞘脂,广泛存在于脊椎动物各组织细胞膜上,尤其在胎儿和新生儿的脑中高浓度存在,因此被认为与神经细胞的分化、神经树突的伸长、突触的形成有重要关系,较早的研究就已发现外源性施加神经节苷脂可以促进神经系统的再生和突触的形成.随着合成技术和分子生物学技术的进步,发现神经节苷脂不仅与神经系统的发育、老年痴呆、帕金森症等神经退行性疾患有密切关系,而且与肿瘤的发病过程也有一定的联系,由此受到广泛关注.本文结合本实验室的研究工作,对近年国际上对神经节苷脂在生物学活性方面的研究进展,从突触可塑性、神经退行性疾病、肿瘤三方面予以综述.     

内源性神经节苷脂GM1与神经系统发育的关系

神经节苷脂GM1是膜表面一类重要的鞘糖脂，与神经系统发育密切相关。神经节苷脂GM1对神经细胞胞内钙离子浓度的调节具有重要作用。核膜神经节苷脂GM1与神经细胞轴突生长密切相关。     

急性重复性缺氧小鼠脑神经节苷脂含量的研究

以昆明鼠为实验对象,用CS-9000薄层扫描仪测定急性重复性缺氧小鼠脑组织中神经节苷脂GM1、GD1a、GD1b和GT的各个组分相对百分比及唾液酸的含量.结果发现:与未经缺氧处理的空白对照组(A)比较,缺氧一次的实验对照组(B)及急性重复缺氧4次后饲养2d(天)实验对照组(D)等3组小鼠比急性重复缺氧4次实验组(C)小鼠脑组织中的唾液酸含量显著下降,神经节苷脂GM1与GD1b相对百分比明显降低;神经节苷脂GT相对组分百分比明显上升,神经节苷脂GD1a,还没发现有统计学差异.结果提示脑组织中神经节苷脂可能参与急性重复缺氧小鼠的耐缺氧能力的形成,而且是一个短时间内不能恢复的过程.     

猪脑神经节苷脂的测定及其分析

神经节苷脂是神经酰胺寡糖苷类物质.在脊椎动物的中抠神经系统中含量十分丰富.猪脑神经节苷脂经分离、纯化后的成分和含量的分析显示,猪脑神经节苷脂的含量占猪脑组织重量的0.0894%(W/W),是猪脑总脂含量的0.39%(W/W).主要成分是GM1,GD3,GD1a,GD1b和GT1b,其中GM1和GD1a明显高于人脑.     

神经节苷脂GM1对帕金森模型小鼠黑质细胞凋亡及Bcl-2和Bax表达的影响

目的观察神经节苷脂GM1对帕金森模型小鼠黑质细胞凋亡及Bcl-2和Bax表达的影响,探讨其预防帕金森病的机制。方法成年C57-BL雄性小鼠分为正常对照组、模型组和神经节苷脂GMI治疗组。应用TUNEL法和免疫荧光组织化学染色技术观察各组小鼠黑质神经元凋亡及Bcl-2和Bax表达情况。结果TUNEL、Bcl-2和Bax阳性神经元主要位于黑质致密部。模型组黑质神经元凋亡数明显多于正常对照组,神经节苷脂GM1组黑质神经元凋亡数明显少于模型组。在模型组Bcl-2阳性神经元和Bax阳性神经元的数量均较正常对照组明显增多;在神经节苷脂GM1组Bcl-2阳性神经元的数量较模型组明显增多,但Bax阳性神经元的数量较模型组明显减少。结论神经节苷脂GM1可能通过增强黑质神经元内Bcl-2基因表达及抑制Bax基因表达的途径抑制黑质神经元的凋亡。     

高效薄层层析-病毒覆盖结合法比较细胞表面神经节苷脂与不同动物源性新城疫病毒结合特性

【目的】神经节苷脂是新城疫病毒入侵宿主细胞的受体,但不同动物源性的新城疫病毒利用受体的特性是否存在差异尚不明确。以鹅源新城疫病毒NA-1株和鸡源新城疫病毒F48E9株为研究对象,比较两株病毒受体结合特性的差异。【方法】提取鸡胚和鹅胚成纤维细胞新城疫病毒受体成分——神经节苷脂,用高效薄层层析法比较两种细胞所含神经节苷脂的类型和含量;通过高效薄层层析-病毒覆盖结合法比较两种病毒与不同细胞神经节苷脂的结合特性,最后通过病毒红细胞吸附抑制试验进一步验证神经节苷脂与病毒之间的相互作用关系。【结果】鸡胚和鹅胚成纤维细胞所含的神经节苷脂成分存在明显差异;高效薄层层析-病毒覆盖结合实验结果显示NA-1和F48E9与神经节苷脂的结合模式不同,NA-1主要与神经节苷脂GD1a结合,即包含双SAα2,3Gal末端的神经节苷脂,而F48E9可与更多类型的神经节苷脂结合,从单唾液酸到三唾液酸形式的神经节苷脂如GM1、GD1a、GD1b、GT1b等。【结论】鹅源新城疫病毒NA-1株和鸡源新城疫病毒F48E9株在入侵靶细胞时优先选择利用的受体不同。     

缺氧小鼠脑中神经节苷脂和单胺类神经递质水平

脑缺氧和缺氧后的再灌注常导致一系列复杂的生理生化改变．通过小鼠重复缺氧后,观察其脑组织中的神经节苷脂和单胺类递质水平变化情况,发现重复缺氧时,随着缺氧次数的增加,a．神经节苷脂水平（以唾液酸含量表示）非常明显地持续下降(P<0.01),其中GM1与GD1b相对组分百分比值下降尤为突出(GM1:P<0.05,GD1b:P<0.01); b.单胺类神经递质中NE和DOPA水平下降,DA和HIAA水平升高(P<0.01)．结果提示脑组织经重复缺氧后,中枢神经组织细胞膜受到一定程度的损伤,其结果可能影响到单胺类神经递质的合成、释放、重摄取和贮存的全过程;据此推测脑组织缺氧时神经节苷脂与单胺类神经递质水平改变时存在着相互联系．     

神经鞘脂病的酶学诊断方法——用培养的人皮肤成纤维细胞检测

 神经鞘脂病是一类神经鞘脂分解代谢障碍的遗传性疾病,酶学检测是确诊的一种主要手段。在通常采用的标本中,培养的人皮肤成纤维细胞是最理想的酶源。本文改良七种用人工底物检测酶活性的方法,通过控制细胞传代和细胞生长时相的措施,用自己培养的34个正常人的皮肤成纤维细胞建立对GM_1-神经节苷脂累积症,GM_2-神经节苷脂累积症,异染质型脑白质营养不良症,krabbe氏病,Gaucher氏病,Niemann-Pick氏病和Fabry氏病等七种相对常见的神经鞘脂病的酶学诊断正常值。并就标本供体的年龄,培养细胞的传代与细胞所处的生长时相对酶活性的影响进行探讨。     

糖鞘脂分析技术及相关疾病研究进展

糖鞘脂是一类广泛分布在动物细胞膜表面的糖脂类物质,它在调控细胞识别、黏附、增殖以及凋亡等方面均有重要的生物学作用.本综述主要讨论了在现代分析技术范畴中,糖鞘脂的鉴定及其糖链结构的分离与解析方面的研究进展和糖鞘脂在癌症等疾病发生发展中所起的生物学功能,以及糖鞘脂作为疾病治疗靶标的可能性.随着现代仪器技术,尤其是质谱技术和色谱-质谱联用技术的发展,糖鞘脂的分离与检测也进入了高速发展的时代.目前,使用质谱技术在肝癌、结直肠癌、乳腺癌等恶性肿瘤的组织样本中均发现了不同种类糖鞘脂不同程度的异常表达.其中,岩藻糖基化的糖鞘脂上调表达在众多癌症糖鞘脂检测中尤为突出,故岩藻糖基化的糖鞘脂可能会成为一类癌症的早期诊断标志物.近年来,随着对糖鞘脂理解的不断深入,糖鞘脂在诸多疾病,如癌症血管生成过程中的功能研究成为了热点之一.例如,从肿瘤细胞表面脱落的大多数糖鞘脂在肿瘤微环境中主要起到了促进血管生成的作用,而与此相反的是,另一种结构简单的神经节苷脂GM3却起到了抑制血管生成的作用.本综述汇集了对上述现象在分子水平上的不同解读以及利用此现象对癌症靶向治疗的研究与探索,并对基于抑制糖鞘脂合成的靶向治疗的发展前景进行了分析展望.     

棉铃虫幼虫中肠细胞脂筏的制备及鉴定

脂筏是细胞膜上富含胆固醇、鞘脂类和糖基磷脂酰肌醇锚着蛋白的去垢剂不溶性微结构域,被认为是多种细胞膜孔毒素在细胞表面形成寡聚体的平台。为研究脂筏与Bt毒素在细胞膜上形成寡聚体膜孔的关系,本文对棉铃虫Helicoverpa armigera幼虫中肠脂筏的制备与鉴定方法进行了研究。根据脂筏在低温（4℃）下不溶于去垢剂的特性,采用Triton X-100处理棉铃虫幼虫中肠刷状缘膜囊泡,溶解非脂质筏成分,以OptiPrep为介质进行密度梯度离心,分离去垢剂不溶组分,成功地得到了棉铃虫幼虫中肠上皮细胞的脂筏。再以脂筏的特有化学成分神经节苷脂GM1作为脂筏的标志分子,利用霍乱毒素β亚基能与GM1特异性结合的特性,以辣根过氧化物酶标记的霍乱毒素β亚基用点印迹法化学发光检测神经节苷脂的分布,从而对脂筏进行定性鉴定。结果表明我们建立的脂筏制备方法简便、易行,比传统的蔗糖梯度离心法大大缩短了制备所需时间。     

Gangliosides play important roles in the nervous system by regulating ion concentrations

Gangliosides are important components of the neuronal cell membrane and play a vital role in the development of neurons and the brain. They participate in neurotransmission and are considered as the structural basis of learning and memory. Gangliosides participate in several and important physiological processes, such as cell differentiation, cell signaling, neuroprotection, nerve regeneration and apoptosis. The stability of ion concentration in excitable cells is particularly important in the maintenance of a steady state of cells and in the regulation of physiological functions. Ion concentration has been found to be related to the ganglioside’s regulation in many neurological diseases, and several studies have found that they can stabilize intracellular ion concentration by regulating ion channels, which highlights their important regulatory role in neuronal excitability and synaptic transmission. Gangliosides can influence some forms of ion transport, by directly binding to ion transporters or through indirect binding and activation of transport proteins via appropriate signaling pathways. Therefore, the important and special role of gangliosides in the homeostasis of ion concentration is becoming a hot topic in the field and a theoretical basis in promoting help gangliosides use as key drugs for the treatment of nervous system diseases.

     

Role of ganglioside metabolism in the pathogenesis of Alzheimer's disease--a review

Gangliosides are expressed in the outer leaflet of the plasma membrane of the cells of all vertebrates and are particularly abundant in the nervous system. Ganglioside metabolism is closely associated with the pathology of Alzheimer's disease (AD). AD, the most common form of dementia, is a progressive degenerative disease of the brain characterized clinically by progressive loss of memory and cognitive function and eventually death. Neuropathologically, AD is characterized by amyloid deposits or "senile plaques," which consist mainly of aggregated variants of amyloid beta-protein (Abeta). Abeta undergoes a conformational transition from random coil to ordered structure rich in beta-sheets, especially after addition of lipid vesicles containing GM1 ganglioside. In AD brain, a complex of GM1 and Abeta, termed "GAbeta," has been found to accumulate. In recent years, Abeta and GM1 have been identified in microdomains or lipid rafts. The functional roles of these microdomains in cellular processes are now beginning to unfold. Several articles also have documented the involvement of these microdomains in the pathogenesis of certain neurodegenerative diseases, such as AD. A pivotal neuroprotective role of gangliosides has been reported in in vivo and in vitro models of neuronal injury, Parkinsonism, and related diseases. Here we describe the possible involvement of gangliosides in the development of AD and the therapeutic potentials of gangliosides in this disorder.     

Ganglioside molecular species containing C18- and C20-sphingosine in mammalian nervous tissues and neuronal cell cultures

Gangliosides exist as a very complex mixture of species differing in both the hydrophilic and hydrophobic moieties. They are particularly abundant in the central nervous system (CNS), where they have been associated with development and maturation of the brain, neuritogenesis, synaptic transmission, memory formation and synaptic aging. Today, many data suggest that some of the effects exerted by gangliosides are due to interactions with proteins that participate in the transduction of signals through the membrane in membrane microdomains. A specific characteristic of CNS gangliosides is the structure of their long-chain base (LCB). In fact, considering all the mammalian cell sphingolipids, gangliosides, sulphatides, neutral glycosphingolipids, sphingomyelin and ceramides, it would seem that while the LCB with 18 carbons is the main component of all sphingolipids, only CNS gangliosides contain significant amounts of LCB with 20 carbons. C18-Sphingosine is always present in cell gangliosides; the individual ganglioside species containing C18-sphingosine increase during cell differentiation then remain constant during cell aging. Gangliosides containing C20-sphingosine are absent, or present only in traces, in undifferentiated cells but with the onset of cell differentiation they appear, their content slowly but continuously increasing throughout the life span. In this review we discuss the chemistry, physico-chemistry and metabolism of ganglioside species differing in LCB length and introduce the hypothesis that the varying ratio between C18- and C20-gangliosides during CNS development and aging can be instrumental in modulating membrane domain organisation and cell properties.     

Functional Roles of Gangliosides in Neurodevelopment: An Overview of Recent Advances

Gangliosides are sialic acid-containing glycosphingolipids that are most abundant in the nervous system. They are localized primarily in the outer leaflets of plasma membranes and participated in cell–cell recognition, adhesion, and signal transduction and are integral components of cell surface microdomains or lipid rafts along with proteins, sphingomyelin and cholesterol. Ganglioside-rich lipid rafts play an important role in signaling events affecting neural development and the pathogenesis of certain diseases. Disruption of gangloside synthase genes in mice induces developmental defects and neural degeneration. Targeting ganglioside metabolism may represent a novel therapeutic strategy for intervention in certain diseases. In this review, we focus on recent advances on metabolic and functional studies of gangliosides in normal brain development and in certain neurological disorders.     

Brain gangliosides: functional ligands for myelin stability and the control of nerve regeneration

Gangliosides, sialylated glycosphingolipids which are the predominant glycans on vertebrate nerve cell surfaces, are emerging as components of membrane rafts, where they can mediate important physiological functions. Myelin associated glycoprotein (MAG), a minor constituent of myelin, is a sialic acid binding lectin with two established physiological functions: it is involved in myelin-axon stability and cytoarchitecture, and controls nerve regeneration. MAG is found selectively on the myelin membranes directly apposed to the axon surface, where it has been proposed to mediate myelin-axon interactions. Although the nerve cell surface ligands for MAG remain to be established, evidence supports a functional role for sialylated glycoconjugates. Here we review recent studies that reflect on the role of gangliosides, sialylated glycosphingolipids, as functional MAG ligands. MAG binds to gangliosides with the terminal sequence 'NeuAc alpha 3Gal beta 3GalNAc' which is found on the major nerve gangliosides GD1a and GT1b. Gangliosides lacking that terminus (e.g., GM1 or GD1b), or having any biochemical modification of the terminal NeuAc residue fail to support MAG binding. Genetically engineered mice lacking the GalNAc transferase required for biosynthesis of the 'NeuAc alpha 3Gal beta 3GalNAc' terminus have grossly impaired myelination and progressive neurodegeneration. Notably the MAG level in these animals is dysregulated. Furthermore, removal of NeuAc residues from nerve cells reverses MAG-mediated inhibition of neuritogenesis, and neurons from mice lacking the 'NeuAc alpha 3 Gal beta 3GalNAc' terminus have an attenuated response to MAG. Cross-linking nerve cell surface gangliosides can mimic MAG-mediated inhibition of nerve regeneration. Taken together these observations implicate gangliosides as functional MAG ligands.     

Localization and functional role of gangliosides from nerve tissue of vertebrates

Gangliosides in the animal organism are typical components of plasma membranes of nerve cells in which the concentration of polysialogangliosides is especially high. The high concentration of tri- and tetrasialoganyliosides and ganglioside GD1b is peculiar to primary cultures of nerve cells, whereas these gangliosides are practically not present in the culture of the transformed nerve cells which have lost their ability to sinaptogenesis, they are not found in cultures of oligodendro- and astroglia as well. The addition of exogenic gangliosides to nerve cells cultures stimulates the formation of processes in these cells and promotes their survivability. The neuritogenic and neuronotrophic effect of gangliosides, their participation in the processes of neurons' regeneration are shown in the in vivo experiments. Gangliosides are carriers of antigenic determinants typical of the cellular surface of neurons (or other cells) as well as of cells of different malignant tumours; typical carcinoembryonal antigenes are revealed among them. Such functions of gangliosides as participation in the processes of intercellular interaction, adhesion, pneuritogenic effect, possible participation to memorize one or another habit are, probably, interrelated and mutually conditioned. Recently the data, being in controversy with the notion that gangliosides are components of receptors of hormones and mediators, are obtained. Evidently, it ought to speak about the modulation of cell response by them on the action of these effectors.     

The diverse roles of mononuclear phagocytes in prion disease pathogenesis

Transmissible spongiform encephalopathies (TSEs), or prion diseases, are neurological diseases that can be transmitted through a number of different routes. A wide range of mammalian species are affected by the disease. After peripheral exposure, some TSE agents accumulate in lymphoid tissues at an early stage of disease prior to spreading to the nerves and the brain. Much research has focused on identifying the cells and molecules involved in the transmission of TSE agents from the site of exposure to the brain and several crucial cell types have been associated with this process. The identification of the key cells that influence the different stages of disease transmission might identify targets for therapeutic intervention. This review highlights the involvement of mononuclear phagocytes in TSE disease. Current data suggest these cells may exhibit a diverse range of roles in TSE disease from the transport or destruction of TSE agents in lymphoid tissues, to mediators or protectors of neuropathology in the brain.     

The diverse roles of mononuclear phagocytes in prion disease pathogenesis

Transmissible spongiform encephalopathies (TSEs), or prion diseases, are neurological diseases that can be transmitted through a number of different routes. A wide range of mammalian species are affected by the disease. After peripheral exposure, some TSE agents accumulate in lymphoid tissues at an early stage of disease prior to spreading to the nerves and the brain. Much research has focused on identifying the cells and molecules involved in the transmission of TSE agents from the site of exposure to the brain and several crucial cell types have been associated with this process. The identification of the key cells that influence the different stages of disease transmission might identify targets for therapeutic intervention. This review highlights the involvement of mononuclear phagocytes in TSE disease. Current data suggest these cells may exhibit a diverse range of roles in TSE disease from the transport or destruction of TSE agents in lymphoid tissues, to mediators or protectors of neuropathology in the brain.     

Gangliosides as apoptotic signals in ER stress response

Renewed attention has been given lately to gangliosides and to their function as intracellular messengers of the adaptive responses to stress. Gangliosides are vital components of cell membranes; therefore, deleterious consequences can result from changes in their chemical composition and concentration, that is, membrane dynamics and structure can be altered as can the behavior of other membrane proteins. The importance of gangliosides in human health is evident in neurodegenerative diseases associated with defects in their degradation. As key modulators of intracellular calcium flux, gangliosides are involved in cellular processes downstream of calcium signaling. In this review, we focus on the effect of ganglioside accumulation on the endoplasmic reticulum calcium homeostasis and on the integrity of the mitochondrial membranes. We discuss how these events elicit an apoptotic program that ultimately leads to cell death. Owing to interorganelle crosstalk, these events are not necessarily self-contained, and gangliosides may serve as the common factor.     

Gangliosides suppress the proliferation of autoreactive cells in experimental allergic encephalomyelitis: ganglioside effects on IL-2 activity

Gangliosides have been shown to suppress human and murine lymphocyte proliferative responses in vitro. We tested the suppressive effects of gangliosides on the proliferation of autoreactive lymphoid cells obtained from Lewis rats with experimental allergic encephalomyelitis (EAE). Exogenous rat brain gangliosides inhibited both antigen- and mitogen-induced proliferation by as much as 79 and 93%, respectively. Gangliosides similarly inhibited the antigen-induced proliferation of a myelin basic protein (MBP)-reactive T-cell line which is able to passively induce EAE. Suppression was greatest when gangliosides were added at the initiation of culture, and was not abrogated by supraoptimal antigen concentration. Interleukin 2 (IL-2) activity in culture supernatants was not diminished by the addition of gangliosides. Gangliosides did not inhibit the IL-2-induced proliferation of a murine IL-2-dependent cell line, CTLL-20, unless the IL-2 was first preincubated with gangliosides before the addition of CTLL-20. Preincubation of CTLL-20 with gangliosides resulted in no inhibition of the subsequent responses to IL-2. Exogenous gangliosides did not decrease the binding of a monoclonal antibody directed against the rat cell surface IL-2 receptor. Addition of exogenous IL-2 to ganglioside-suppressed cultures had no effect or only partially restored the proliferative responses. Therefore, gangliosides were shown to inhibit the proliferation of autoreactive lymphoid cells without affecting IL-2 production or IL-2 receptor expression.