Biology of gangliosides: neuritogenic and neuronotrophic properties

Brain gangliosides and memory formation

It is generally accepted that the process of molecular facilitation of neuronal circuits by means of stabilization of synaptic contacts represents the structural basis for memory formation. At the distinct zone of synaptic contact the following basic events occur: alterations of the electrical field strength at the outer surface of synaptic membranes, conformational changes of membrane-bound functional proteins (ion channels, ion pumps, receptors) and activation of second messenger cascade. Finally a trophic feed-back between synaptic terminals and their cell bodies through retro- and anterograde neuronal transport exists, which guarantees a stabilization of the newly formed synaptic connection. As a controlled Ca(2+)-exchange between the extracellular space (mM Ca(2+)-concentration) and the synaptoplasm (microM Ca2+) is essential for all these events, the present research concentrates on Ca(2+)-mediated primary messenger systems at the outer leaflet of synaptic membranes and on Ca(2+)-mediated modulatory mechanisms. These enable an always efficient electroresponsiveness although the environmental temperature might have changed. In this regard gangliosides being amphiphilic sialic acid containing glycosphingolipids, which are highly accumulated in complex composition in synaptic membranes play an important role. According to specific physico-chemical properties, they are assumed to fulfill the task of neuromodulators in connection with calcium, and thus contribute to the transmission and storage of information. The outcome of a series of experiments derived from neurology, ecophysiology, behavioral sciences, electron microscopy, biochemistry and physical chemistry give strong circumstantial evidence for this concept.

GM1 ganglioside and darkly staining neurons in brains of rats subjected to neonatal hypoxia-ischemia

Rat pups, seven days old, with right carotid artery ligations were exposed to an atmosphere of oxygen 8% remainder nitrogen for 2 hr. The animals that survived for three weeks after the hypoxic-ischemic episode had clusters of darkly stained (hematoxylin-eosin) neurons in the cortex and reduced uptake of dopamine (frontal cortex) and choline (frontal cortex, hippocampus and striatum) in preparations of synaptosomes. Treatment with GM1 ganglioside partially corrected the loss of uptake activity and increased the number of darkly stained neurons.

Gangliosides. Their role in clinical neurology

Gangliosides are normal constituent of mammalian vertebrate cell membranes and are particularly abundant in the central and peripheral nervous systems. The biological effects of exogenously administered gangliosides have been extensively investigated in vitro and in experimental animal models where they have neuronotrophic and neuritogenic properties. Despite these findings there is still little evidence that treatment with parenteral gangliosides in humans can be effective in peripheral neuropathies or other neuromuscular diseases. The initial preliminary reports on the positive effects of GM1 in cerebrovascular diseases and spinal cord injury need to be confirmed in larger controlled trials. At the same time the occasional development of an acute motor neuropathy clinically presenting as the Guillain-Barré syndrome and associated with high titres of anti-ganglioside antibodies highlights the risks of their widespread use before more consistent data on their efficacy become available.

GM1 ganglioside partially rescues cultured dopaminergic neurons from MPP(+)-induced damage: dependence on initial damage and time of treatment

GM1 ganglioside is believed to be important in promoting the recovery of neurons from injury. The present study assesses the ability of GM1 to repair or prevent the damage of dopamine neurons caused by the neurotoxin 1-methyl-4-phenylpyridinium (MPP+). Treatment of mesencephalic cell cultures with 2.5 microM MPP+ resulted in the loss of 30% of tyrosine hydroxylase (TH) immunoreactive neurons. In contrast, cultures administered 100 microM GM1 ganglioside for 3 days after toxin treatment contained nearly control numbers of TH+ neurons (97%). This reparative effect of GM1 was reflected in parallel increases in TH enzyme activity, dopamine and dopac levels. Cultures sustaining greater insult from higher doses of MPP+ (5.0-10.0 microM) did not benefit from ganglioside treatment, suggesting that rescue by GM1 depended on the degree of initial damage to cells. Moreover, the timing of ganglioside treatment was critical; pretreatment with GM1 alone did not prevent or attenuate the damage caused by subsequent incubation in 2.5 microM MPP+.

Glycosphingolipids during skeletal muscle cell differentiation: comparison of normal and fusion-defective myoblasts

The regulation of glycosphingolipid (GSL) synthesis in culture by fusion-competent (E63) myoblasts and fusion-defective (fu-1) cells was examined. Upon reaching confluency E63 cells fused to form multinucleated myotubes and demonstrated many characteristics of developing skeletal muscle including induction of creatine kinase activity and a shift in creatine kinase isozymes to the MM isoform. The fu-1 cells displayed none of these characteristics, despite the fact that both cells were cloned from the same parental myoblast line (rat L8). There was a transient increase in the synthesis of total neutral GSLs by E63 cells at the time of membrane fusion. In contrast, neutral GSL synthesis by fu-1 cells gradually decreased with time in culture. The major GSLs synthesized by both cell types were lactosylceramide and ganglioside GM3, with more complex structures being observed with prolonged time in culture. Several glycosyltransferase activities were assayed at varying times in culture. Generally, the changes in activities fell into three groups. One group was maximally activated at the end of the culture period (GalT-3, GalNAcT-1 and GalT-6). Another group was maximally activated during the time of active membrane fusion (GlcT and SAT-1). A third group was maximally activated at the time of cell contact and the beginning of membrane fusion (GlcNAcT-1 and GalT-2). In terms of the times of maximal activation there were few differences between E63 and fu-1 cells, with one notable exception. The activity of GalT-2 (lactosylceramide synthase) in E63 cells increased dramatically upon contact and the beginning of membrane fusion, whereas there were no changes in GalT-2 activity in fu-1 cells during time in culture. These results support our hypothesis that membrane glycosphingolipids play an important role in the differentiation of skeletal muscle cells.

Oxidative stress: free radical production in neural degeneration

It is not yet established whether oxidative stress is a major cause of cell death or simply a consequence of an unknown pathogenetic factor. Concerning chronic diseases, as Parkinson's and Alzheimer's disease are assumed to be, it is possible that a gradual impairment of cellular defense mechanisms leads to cell damage because of toxic substances being increasingly formed during normal cellular metabolism. This point of view brings into consideration the possibility that, besides exogenous factors, the pathogenetic process of neurodegeration is triggered by endogenous mechanisms, either by an endogenous toxin or by inherited metabolic disorders, which become progressively more evident with aging. In the following review, we focus on the oxidative stress theory of neurodegeneration, on excitotoxin-induced cell damage and on impairment of mitochondrial function as three major noxae being the most likely causes of cell death either independently or in connection with each other. First, having discussed clinical, pathophysiological, pathological and biochemical features of movement and cognitive disorders, we discuss the common features of these biochemical theories of neurodegeneration separately. Second, we attempt to evaluate possible biochemical links between them and third, we discuss experimental findings that confirm or rule out the involvement of any of these theories in neurodegeneration. Finally, we report some therapeutic strategies evolved from each of these theories.

Gangliosides--a new therapeutic agent against stroke and Alzheimer's disease

Gangliosides are glycosphingolipids localized to the outer leaflet of the plasma membrane of vertebrate cells. The highest ganglioside concentration of any organ is found in the mammalian brain, where the gangliosides are enriched in the neuronal membrane, particularly in the synapses. There are four major brain gangliosides with the same neutral tetrasaccharide core to which one to three sialic acids are linked--the simplest being the GM1-ganglioside. These gangliosides have been shown to have neuritogenic and neuronotrophic activity and to facilitate repair of neuronal tissue after mechanical, biochemical or toxic injuries. Mixtures of native bovine brain gangliosides were adopted for pharmacological use in the treatment of peripheral nerve damage, and GM1-ganglioside has been applied for the treatment of CNS injuries and diseases. Beneficial effects of GM1 have been documented in the treatment of stroke and spinal cord injuries, particularly when the treatment has been initiated within a few hours of the acute event. Continuous intraventricular infusion of GM1 has recently been shown to have a significant beneficial effect in Alzheimer disease of early onset (AD Type I).

In vitro evaluation of nanoparticle formulations containing gangliosides

Due to their poor bioavailability after oral administration, the use of gangliosides in medicine is limited to the parenteral route of administration. In the present study, the association with poly(alkylcyanoacrylate) nanospheres and nanocapsules of monosialoganglioside GM1 and other chemically modified gangliosides was investigated with the aim of developing a colloidal drug delivery system suitable for use by the oral route. Our results show that gangliosides can be successfully associated with a biodegradable cyanoacrylic carrier either in the form of nanospheres or as nanocapsules, avoiding any degradation of the ganglioside molecule during the polymerization process. However, the drug-loading was found to be more efficient for nanocapsules. The amount of GM1 incorporated into nanospheres appeared to be dependent on the alkyl chain length of the cyanoacrylic polymer; this amount was however too low for pharmaceutical purposes. In contrast, nanocapsules allowed the attainment of very high drug encapsulation levels, especially with lipophilic derivatives of GM1, where an increase of lipophilicity has been obtained by chemical esterification of the sialic acid residue. Drug release experiments performed in the absence of enzymes indicated that nanocapsules were stable in acid medium, in which no drug release was observed, while their behaviour in basic medium was found to be affected by the composition of the oily phase and the oil/polymer ratio.

[Brain gangliosides and memory formation]

It is generally accepted that the process of molecular facilitation (= Bahnung) of neuronal circuits by means of stabilization of synaptic contacts represents the structural basis for memory formation. On the basis of physiological, electron microscopic, biochemical, and physicochemical data, a concept is presented speaking in favor of the idea that interactions between brain gangliosides (= amphiphilic sialic acid-containing glycosphingolipids with peculiar physicochemical properties), calcium, and functional membraneous proteins (ion channels, ion pumps, receptors, kinases) play a crucial modulatory role in the transmission and storage of information.

Cocaine exposure during pregnancy affects rat neonate and maternal brain glycosphingolipids

Behavioral dysfunctions in offspring exposed in utero to cocaine have been observed, along with alterations in dopamine systems, but few studies of the underlying biochemistry have been conducted. Because of their documented roles in neuronal maturation, glycosphingolipids were analyzed in whole brains of offspring exposed gestationally to cocaine. Rat offspring exposed to cocaine in utero exhibited markedly elevated levels of both total gangliosides (p < 0.001) and neutral glycosphingolipids (p < 0.01) at postnatal day 1. However, by postnatal day 11 levels of gangliosides and neutral glycosphingolipids returned to control values. These effects were not restricted to chronic cocaine exposure early in life, in that ganglioside content of whole maternal brains was also elevated (p < 0.001), though less than that observed with the neonate brains. Qualitatively, no differences in ganglioside nor neutral glycolipid structure distribution were observed between cocaine-exposed and normal animals following separation by HPTLC and HPLC. These elevations are in contrast to those following alcohol exposure, where decreases in brain gangliosides have been observed. Neurochemical consequences of prenatal exposure to cocaine may be far-reaching and may not be restricted to the dopamine system.

GM1 ganglioside reduces glutamate toxicity to cortical cells. Lowered LDH release and preserved membrane integrity

As an in vitro model of CNS excitatory amino acid (EAA) injury, rat cortical neuronal cultures were challenged with glutamate (0.5 or 10 mM) and the levels of released lactate dehydrogenase (LDH) were monitored at 1 h, 1, 2, and 7 d. LDH release is correlated with levels of plasma membrane damage. GM1 has been shown to be continuously distributed on the outer surface of CNS cellular membranes. By staining for the distribution of endogenous GM1 ganglioside using cholera toxin/antitoxin immunohistochemistry, we were able to assess morphologically cellular plasma membrane integrity after damage. We used these two measures (LDH and GM1 localization) to study the neuroprotective effects of exogenous GM1 ganglioside to further elucidate its mechanism. Cortical cultures derived from 15-d rat fetuses were subjected to the glutamate challenge for 30 min. Parallel cultures were either pre- or post-treated with 80 microM of GM1. Exposure to 10 mM glutamate caused a highly significant increase in LDH release at 1-48 h. Pretreatment with GM1 reduced the release, whereas posttreatment reduced the LDH release even more. Plasma membrane changes observed by the GM1 immunohistochemistry reflected the LDH release data. All cultures treated with GM1 evidenced substantial structural integrity (continuous staining of GM1 along perikarya and processes) as compared to untreated cultures. These data support our hypothesis that GM1 treatment (pre- and post-) reduces plasma membrane damage.

Acyl structure regulates galactosylceramide's interfacial interactions

Galactosylceramides (GalCer) with homogeneous acyl chains containing zero, one, or two cis double bonds have been synthesized and characterized at an argon-aqueous buffer interface using a Langmuir film balance. Both surface pressure and surface potential were measured as a function of molecular area at 24 degrees C. N-Lignoceroylgalactosylsphingosine (N-24:0-GalSph), N-stearoylgalactosylsphingosine (N-18:0-GalSph), and N-palmitoylgalactosylsphingosine (N-16:0-GalSph) form condensed films that are similar to that of bovine brain GalCer, which contains long saturated and mono-unsaturated acyl chains, almost half being hydroxylated. In contrast, a bovine brain GalCer subfraction (NFA-GalCer) that is devoid of the hydroxylated acyl chains displays an apparent two-dimensional phase transition near 9.0 mN/m at 54 A2/molecule. To determine the role of acyl unsaturation in regulating NFA-GalCer's surface behavior, GalCer derivatives containing different mono-unsaturated acyl residues were investigated. N-Nervonoyl-galactosylsphingosine (N-24:1 delta 15-GalSph) and N-docosenoylgalactosylsphingosine (N-22:1 delta 13-GalSph) show liquid-expanded to -condensed phase transitions in their force-area isotherms at 10 and 35 mN/m, respectively. Introduction of acyl chains that are short and saturated [e.g., N-decanoylgalactosylsphingosine (N-10:0-GalSph)] or that are long but contain two cis double bonds [e.g., N-linoleoylgalactosylsphingosine (N-18:2 delta 9,12-GalSph)] causes GalCer to display only liquid-expanded behavior at 24 degrees C. The surface potentials (delta V) of the condensed GalCer derivatives with long saturated acyl residues were quite similar and were over 100 mV higher than that of bovine brain GalCer.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of GM1 ganglioside on cardiac function following experimental hypoxia-reoxygenation

Rat hearts made hypoxic for 20 min by perfusion with 95% N2/5% CO2 and reoxygenated for 20 min in a Langerdorff apparatus showed a dose-dependent reduction of lactate dehydrogenase release when incubated with ganglioside GM1 (0.1-10 microM). The decline of contractile force during hypoxia was also reduced dose dependently in the presence of GM1. Similar effects were observed in hearts obtained from animals treated i.p. with 40 mg/kg GM1 for 14 days. The levels of Na+,K(+)-ATPase in ventricular tissue were also reduced after hypoxia-reoxygenation and the reduction was prevented in hearts from GM1-treated animals. GM1 (1-30 microM) reduced the functional response to field stimulation of adrenergic nerve terminals in isolated atria. Rat atria made hypoxic in glucose-free media maintained normal stores of tissue noradrenaline in the presence of 1 microM GM1. In the rabbit, GM1 (40 mg/kg i.p. for 4 days) reduced the alterations of the ST segment of the ECG during acute occlusion of the left descending and circumflex coronaries artery. In conclusion, ganglioside GM1 reduces some effects of hypoxia-reoxygenation in the heart, through still unknown mechanisms.

Age-related changes in the ceramide composition of the major gangliosides present in rat brain subcellular fractions enriched in plasma membranes of neuronal and myelin origin

Age-related changes of the ceramide composition of gangliosides were studied in the synaptosomal and myelin fractions from rat brain, carrying plasma membranes of neuronal and glial origin, respectively. The five major gangliosides (GM1, GD1a, GD1b, GT1b, and GQ1b) present in these fractions were separated and quantitated by normal-phase HPLC. Each ganglioside was then fractionated by reverse-phase HPLC into the molecular species carrying a single long-chain base (LCB). The largely preponderant LCBs in the synaptosomal and myelin fractions were the C18:1 and C20:1. The content of C20:1 LCB, generally low at 1 month, increased with age in all analyzed gangliosides and in all subcellular fractions and was greater in the "b series" than in the "a series" gangliosides. Remarkably, GM1 was the only ganglioside where the proportion of LCB 20:1 was higher in the synaptosomal fraction than in the myelin fraction. The fatty acid composition of the C18:1 or C20:1 LCB species of the different gangliosides in the synaptosomal and myelin fractions did not undergo appreciable changes with age. Stearic acid was largely predominant in all the gangliosides of the synaptosomal fraction, more in the C18:1 than in the C20:1 LCB species (80-90% vs. 60-70%). The gangliosides of the myelin fraction were characterized by a lower content of 18:0 and a much higher content of 16:0 and 18:1 fatty acids than those of the synaptosomal fraction. Thus, the ceramide composition is different in the gangliosides of neuronal and myelin origin and appears to be subjected to an age-related control.

Past and current clinical studies with GM-1 ganglioside in acute spinal cord injury

Two recent prospective, randomized, placebo-controlled, double-blinded clinical drug studies in acute spinal cord injury have reported enhancement of neurologic recovery of motor function. The drugs investigated in these studies were methylprednisolone and GM-1 ganglioside. Before these studies, the treatment of patients with spinal cord injuries had been restricted to prevention of further injury to the spinal cord, limiting secondary damage following the initial injury, increasing the patient's ability to function through intensive rehabilitation, and facilitating any spontaneous recovery of neurologic function. Methylprednisolone is a steroid administered at very high levels, and GM-1 is a complex acidic glycolipid found at high levels in cell membranes in the mammalian central nervous system with known neuroprotective and neurofunctional restoration potential. This article summarizes the previously reported Maryland GM-1 clinical trial and presents the clinical and statistical design of a larger clinical trial being conducted with the purpose of verifying a beneficial GM-1 drug effect when administered with methylprednisolone in acute spinal cord injury.

Alterations and recovery of rat brain gangliosides and glycosidases following long-term exposure to alcohol and rehabilitation during development

The present study examines effects of continuous exposure to alcohol during gestation, lactation and postweaning periods and rehabilitation on gangliosides and their catabolizing enzymes in whole brain (WB), cerebrum (C), cerebellum (CB) and brain stem (BS) of 63-day-old rats. Continuous exposure to alcohol was found to cause significant deficits in the body and brain weights. On the other hand, the concentration of total ganglioside in whole brain, cerebrum, cerebellum and brain stem showed an increase following exposure to alcohol. In agreement with the increased ganglioside concentration the activities of sialidase, beta-galactosidase, beta-glucosidase and beta-hexosaminidase, which are likely to be involved in the catabolism of gangliosides, showed reductions due to alcohol. Alcohol was also found to alter the proportions of individual gangliosides and the changes were found to be region-specific. However; the alcohol-induced alterations were reversed, at least to some extent, upon abstinence from alcohol. Body weights of control (CT), alcoholic (AC) and rehabilitated (AR) rats were 164 +/- 2, 107 +/- 7 and 139 +/- 3 (mean +/- S.E.M.), respectively. Decrease in tissue weight was significant in whole brain, cerebrum and brain stem but not in cerebellum. In AR rats significant deficits in tissue weights persisted in cerebrum and almost a complete recovery was observed in brain stem. On the other hand, the increase in the concentration of gangliosides in WB, C, CB and BS of AC rats amounted to 23, 19, 19 and 53% of controls, respectively. The corresponding values for the AR rats were 12, 14, 3 and 5%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Localization of the GM1 ganglioside in the vestibular system using cholera toxin

Cholera toxin is an ubiquitous activator of intracellular adenylate cyclase and is divided in two major components: A and B. The B-component consists of several subunits that specifically bind to the external cell membrane. The receptor for the toxin, the GM1 ganglioside, is concentrated in nervous tissues. The B subunit of the cholera toxin, conjugated to different molecules (i.e., choleragenoid) is therefore a sensitive anatomical tracer and has been used to detect the presence of GM1 in mammalian tissues. Using choleragenoid, unlabeled and labeled with FITC, we have determined the distribution of the GM1 ganglioside in the vestibular system of the chinchilla. Vestibular tissues were fixed in 4% paraformaldehyde in phosphate buffer, decalcified in 10% EDTA and prepared as either whole-mount, surface-preparations, or for radial cryosections. Positive control tissue consisted of binding to normal brain tissues. Negative controls consisted of several treatments: masking of the GM1 receptors with unlabeled choleragenoid, tissue extraction of GM1 using ethanol, and preabsorbing the choleragenoid with bovine GM1. In addition, to exclude staining of glycoproteins that may have a carbohydrate structure similar to GM1, tissues were digested with trypsin prior to choleragenoid exposure. In the vestibular system, a strongly positive reaction was observed in: the sensory stereocilia and supporting cells of the maculae and cristae, epithelial cells of the planum semilunatum, and polygonal cells of the semicircular canal. Positive but less strong reactivity was observed in the sensory cell body of maculae and cristae, nerve fibers, epithelial cells of utricle and ampulla walls and flattened epithelial cells of the semicircular canals. No reactivity was present in the supporting connective tissue cells and fibrils, blood vessels, gelatinous cupula of the cristae ampullaris and statoconial membranes. Brain tissue showed strong choleragenoid reactivity. The negative controls showed no or greatly reduced reactivity to choleragenoid. Trypsin digestion did not decrease reactivity to choleragenoid.

A novel glycosignaling system: GQ1b-dependent neuritogenesis of human neuroblastoma cell line, GOTO, is closely associated with GQ1b-dependent ecto-type protein phosphorylation

Previously, we reported that ganglioside GQ1b specifically promoted neuritogenesis of human neuroblastoma cells (GOTO), and also that is specifically stimulated the phosphorylation of several cell surface proteins on the same cells. To disclose the relationship between the two events, we examined them using a novel protein kinase inhibitor, K-252b, which is a derivative of K-252a and cannot pass through cell membrane. K-252b inhibited the GQ1b-dependent neuritogenesis as well as the GQ1b-stimulated phosphorylation. This suggests the direct coupling between the two cell events and the occurrence of a new biosignal transduction system.

Gangliosides as modulators of cell function

Gangliosides, sialic acid-containing glycosphingolipids, are found in the outer leaflet of the plasma membrane of all vertebrate tissues and species. This report presents a brief introduction to the gangliosides and reviews the chemistry and topography of their biosynthesis. It also presents an overview of the present evidence supporting a physiological significance for the gangliosides in a variety of experimental systems. This includes consideration of their potential roles in development and cell adhesion. In addition, experimental examples in which gangliosides appear to influence signal transduction processes through their interactions with plasma membrane proteins are discussed.

Exogenous gangliosides modulate calcium fluxes in cultured neuronal cells

Previous work from this and other laboratories has shown that the neuritogenic effect due to exogenous gangliosides on primary neurons in culture is accompanied by several morphological and biochemical modifications. The present results indicate that the treatment of these neurons with gangliosides, under the experimental conditions which are known to produce a sprouting effect, inhibited the influx of 45Ca2+ and increased the release of 45Ca2+ from the cells. No significant differences were noted using concentrations of gangliosides (10(-8)-10(-5) M) either below or above the critical micellar concentrations. No apparent specificity was observed among various species of individual sialocompounds (GM1, GD1a). Moreover the presence or absence of fetal calf serum in the culture medium influenced the levels of 45Ca2+ fluxes. This study confirms the hypothesis that gangliosides may be considered as Ca2+ flux modulators in neuronal cells.

Gangliosides and regeneration of the goldfish optic nerve in vivo and in vitro

One to forty days after optic nerve transection, goldfish received an i.p. injection of [3H]proline (proteins), 3HNAcGluc (gangliosides) or [3H]thymidine (DNA). After 1 or 2 days of incorporation, both optic systems were analyzed by biochemical and autoradiographical procedures. In the regenerating retina an enhanced retinal mitotic activity, protein synthesis (up to 2-fold) and ganglioside synthesis (up to 1.5-fold) was found. Simultaneously, a transiently enhanced accumulation (up to 4.5-fold) of axonally transported protein- and ganglioside-bound radioactivity in the regenerating optic nerve stump occurred. These regeneration-related proliferative and metabolic changes were found to be maximal at 6-8 days post lesion, but still measurable after 40 days. Concerning the endogenous ganglioside metabolism, in the regenerating retina no obvious change in ganglioside synthesis and composition could be observed, while in the regenerating optic nerve there was an enhanced accumulation of the ganglioside GP1c. Daily i.p. application of a ganglioside mixture from bovine brain (GMix) or of the monosialoganglioside GM1, did not alter significantly the degree and time course of the above regeneration induced metabolic changes or the regain of visual acuity. Sprouting activity of goldfish retinal explants was found to strongly depend upon a conditioning lesion of the optic nerve, reaching a maximum 8 days after nerve transection. This result strictly coincided with the profile of metabolic changes observed in vivo. Again, daily i.p. or i.o. injection of exogenous gangliosides did not influence the lesion induced increase of retinal sprouting activity. However, in normal, not regenerating animals, a local i.o. injection of GMix or GM1 led to a significant enhancement of the "basal" sprouting activity, normally occurring after lesion of the retina after injection of 0.9% NaCl. This ganglioside related stimulation was maximal at low concentrations (3 micrograms/eye) and did not occur at high concentrations (> 30 micrograms/eye). Injection of the phospholipid phosphatidylcholine or phosphatidylserine had no or a slightly inhibitory effect, when compared to NaCl controls. These data suggest an involvement of gangliosides in the complex process of induction of axonal sprouting.

Nuclear sialyl cholesterol causes changes in the structure of chromatin and its transcription level followed by the promotion of neuritogenesis

Exogenously added sialyl cholesterol (SC) induced neuritogenesis and accumulated in the nuclear fraction of a mouse neuroblastoma cell line, Neuro2a, as reported elsewhere. To clarify the significance of nuclear SC, we examined the structure of chromatin and its transcriptional level. The chromatin of SC-treated cells exhibits greater circular dichroism amplitude (260-310 nm) than that of nontreated cells. The transcriptional level of chromatin from SC-treated cells was significantly higher than that of nontreated cells. The chromatin structural change has a good correlation to the transcriptional enhancement. On the addition of SC to the chromatin of nontreated cells, the circular dichroism spectra increased in amplitude and the transcriptional level also increased in a concentration-dependent manner. alpha-Amanitin-treated cells did not show SC-dependent neuritogenesis. These results strongly suggest that nuclear SC affects gene expression, which results in promotion of the neuritogenesis of cells.

Lasting effects of postnatal hypoxia and saline injection on the striatal dopamine transport and their modification by gangliosides

Hypobaric hypoxia (10 h daily, pO2 10 kPa) and saline administration (2.5 microliters/g body wt) from the 2nd till the 11th day of life both induced a long-lasting increase of the low-affinity dopamine (DA) uptake capacity in S1-fractions of the rat striatum. Additionally, the potassium-stimulated DA release was enhanced in adult control rats postnatally injected with saline. The administration of a mixture of bovine brain gangliosides (30 micrograms/g body wt) was found to prevent these effects. However, the kinetic constants of the DA uptake of hypoxic rats treated with gangliosides were reduced in comparison to untreated controls. Thus, the effects of gangliosides appear to differ between hypoxic and control conditions. The modification of the dopaminergic activity during brain development is discussed as a possible mechanism of the preventive effects of gangliosides against long-term cerebral dysfunctions following hypoxia or stress.

Cell surface distribution of endogenous and effects of exogenous gangliosides on neuronal survival, cell shape and growth in vitro

In vitro immunostaining of neurons from spinal cord or brain of embryonic chicken by means of monoclonal anti-ganglioside antibodies (Q211, D21b) revealed a fluorescence-labeling of c-polysialogangliosides and GD1b evenly distributed over the entire neuronal surface including filopodia at the growth cones. On electronmicroscopical level the gold-stained ganglioside-antigens were found more or less densely packed in small adjacent areas suggesting a concentration in local "domains". Survival in serum-free or serum-containing medium of embryonic spinal cord motoneurons, which normally died if not cultivated in muscle conditioned medium or in contact to myotubes, was remarkably improved in the presence of a ganglioside mixture (10 microM) from bovine brain. If embryonic neurons from optic lobes were cultivated at low Ca(2+)-concentration (< 20 microM) they developed flat, broad cell bodies with many filopodia and only a few flat-shaped short processes. A very weak cytoskeleton-staining by means of rhodamine-linked phalloidine indicated that polymerization of actin was impaired in these neurons. At the same low Ca(2+)-concentration of < 20 microM but in the presence of ganglioside GM1 (up to 100 microM) most of the neurons developed a "normal" cell shape with rounded perikarya and thin neurites with "normal" shaped growth cones. In this case rhodamine-linked phalloidine revealed a much more intense staining mainly concentrated within the growing tips. The morphology and growth of the ganglioside-treated neurons resembled that of neurons cultivated at a higher Ca(2+)-concentration of at least 600 microM.

Immunohistochemical study of A2B5-positive ganglioside in postmortem human brain tissue of Alzheimer disease, amyotrophic lateral sclerosis, progressive supranuclear palsy and control cases

Localization of gangliosides positively stained by the monoclonal antibody A2B5 was investigated in postmortem brain tissue of Alzheimer disease, amyotrophic lateral sclerosis (ALS), progressive supranuclear palsy (PSP) and control cases. In control cases, A2B5-staining was granular, appearing in selective neuronal populations. In the neocortex, the A2B5-positive neurons were distributed mainly in deep cortical layers. In the cerebellum, A2B5-positive structures were detected in processes extending from the Purkinje cell layer into the molecular layer. In Alzheimer cases, many neurofibrillary tangles, neuropil threads and dystrophic neurites were strongly A2B5-positive. In addition, aggregations of A2B5-positive granules were detected in some neurons lacking neurofibrillary tangles. Alterations of A2B5-positive gangliosides were also detected in ALS and PSP cases. In ALS cases, A2B5-positive granules were aggregated in Betz cells of the precentral gyrus. In PSP cases, globose-type neurofibrillary tangles were also strongly A2B5-positive. The results indicate that A2B5-positive gangliosides are widely but selectively distributed in human brain and may be involved in several neuropathological processes.

Biochemical correlates of epilepsy in the E1 mouse: analysis of glial fibrillary acidic protein and gangliosides

The E1 (epileptic) mouse is considered a model for complex partial seizures in humans. Seizures in E1 mice begin around 7-8 weeks of age and persist throughout life. To determine if astrocytic gliosis was present in adult seizing E1 mice, the distribution of glial fibrillary acidic protein (GFAP) was studied in the hippocampus using an antibody to GFAP. The mean number of GFAP-positive cells per square millimeter of hippocampus was approximately 15- to 40-fold higher in adult E1 mice than in nonseizing control C57BL/6J (B6) mice or in young nonseizing E1 mice. Relative GFAP concentration (expressed per milligram of total tissue protein) in hippocampus and cerebellum was estimated by densitometric scanning of peroxidase-stained western blots. GFAP concentration was 2.7-fold greater in hippocampus of adult seizing E1 mice than in the control B6 mice. No differences in GFAP content were detected between the strains in the cerebellum. Because gangliosides can serve as cell surface markers for changes in neuronal cytoarchitecture, they were analyzed to determine if the gliotic response in E1 mice was associated with changes in neural composition. Although the total ganglioside concentration of hippocampus, cerebral cortex, and cerebellum was similar in adult E1 and control B6 mice, a synaptic membrane enriched ganglioside, GD1a, was elevated in the adult E1 cerebral cortex and hippocampus. The findings indicate that E1 mice express a type of gliosis that is not accompanied by obvious neuronal loss.

GM1 ganglioside enhances cholinergic parameters in the brain of senescent rats

GM1 ganglioside and nerve growth factor both promote the recovery of injured central cholinergic neurons in young animals. Brain cholinergic activity declines with aging and nerve growth factor has been shown to correct cholinergic deficits in senescent animals. We have administered GM1, to young (three months old) or senescent (22-24 months old) rats and evaluated acetylcholine and choline content, choline acetyltransferase and acetylcholinesterase activity as well as choline uptake in striatum, hippocampus and frontal cortex. For some studies, nerve growth factor was administered alone or together with GM1. Our results indicate that cholinergic neurochemical parameters are decreased in some brain areas of senescent animals and that both GM1 and nerve growth factor can enhance their recovery.

Sphingosylphosphorylcholine is a remarkably potent mitogen for a variety of cell lines

The effect of spingosylphosphorylcholine on cellular proliferation was investigated in a variety of cell types. Spingosylphosphorylcholine at low concentrations greatly stimulated DNA synthesis and cell division in quiescent Swiss 3T3 fibroblasts. The increased DNA synthesis was also accompanied by pronounced morphological alterations. Spingosylphosphorylcholine was remarkably more potent than other known growth factors and also acted synergistically with insulin, epidermal growth factor, fibroblast growth factor, and the tumor promoter, 12-O-tetradecanoylphorbol-13-acetate, to induce cellular proliferation. Sphingosylphosphorylcholine was less effective in stimulating DNA synthesis in rapidly growing normal and transformed cells. Spingosylphosphorylcholine appears to be a new type of potent, wide-spectrum growth promoting agent.

Stimulation of mono- and diacylglycerol lipase activities by gangliosides in chicken neuronal cultures

Chicken neurons in culture display measurable activities of mono- and diacylglycerol lipases. Treatment of chicken neuronal cultures with gangliosides (10(-8)M to 10(-5)M) resulted in a time and dose dependent increase in monoacylglycerol lipase activity. The diacylglycerol lipase showed significant increase in specific activity before that of monoacylglycerol lipase. The increase was observed only up to 24 hours and no differences between diacylglycerol lipase activity of control and ganglioside treated cells were observed after 48 hours. The data indicate that the treatment of neurons with exogenous gangliosides affect the diglyceride metabolism in stimulating not only the enzymes catalyzing their production but also those involved in their catabolism.

Exogenous gangliosides GD1b and GD1b-lactone, stably associated to rat brain P2 subcellular fraction, modulate differently the process of protein phosphorylation

GD1b and GD1b-lactone (GD1b-L) gangliosides bind to the same extent to a P2 crude membrane preparation from rat brain. After 30 min of incubation with 10(-4), 10(-5) and 10(-6) M solutions of ganglioside, 1,800, 450, and 100 pmol of ganglioside/mg of protein, respectively, were found to be stably associated to the P2 fraction. This association modifies the phosphorylation process of the P2 membrane proteins in a dose-dependent manner, the maximal effect being reached at a ganglioside association of 1.85 nmol/mg of protein and in large part at 450 pmol/mg of protein. The effects of GD1b and GD1b-L on the phosphorylation of five proteins, showing apparent molecular masses of 17, 20, 36, 41, and 44 kDa, were different after 0.5 min of phosphorylation reaction as well as after 15 min. After 0.5 min of reaction, in the presence of stably associated GD1b, the phosphorylation of the 36-, 41-, and 44-kDa proteins was increased with reference to the control, whereas the phosphorylation of the 17- and 20-kDa proteins was decreased. GD1b-L exerted qualitatively similar effects only on the 44-, 41-, and 36-kDa proteins and to a strongly reduced degree. After 15 min of reaction, only the phosphorylation of the 36-kDa protein was stimulated by GD1b; GD1b-L exerted a similar effect, but to a low degree.

Correlation of gangliotetraose gangliosides with neurite forming potential of neuroblastoma cells

Gangliosides of 11 different neuroblastoma cell lines, grown to confluence, were extracted and quantified with respect to: (a) total lipid-bound sialic acid, (b) total gangliotetraose family, and (c) GM1 content. The cultured cells were induced to grow neurites in 3 ways: (a) serum reduction, (b) exogenous ganglioside, and (c) retinoic acid. Neurite outgrowth was quantified in terms of % of cells bearing neurites and average number of neurites per cell. No correlation was observed between neurite outgrowth and total ganglioside concentration, but a reasonably good correlation was observed with respect to neuritogenesis and gangliotetraose content. When exogenous ganglioside was the stimulant the best correlation was with GM1, whereas retinoic acid-stimulated outgrowth was approximately proportional to GD1a content. The 'neurite minus' N1A-103 line, which had the lowest level of GM1, GD1a, and total gangliotetraose gangliosides, showed little if any response to any of the stimuli.

Recovery of motor function after spinal-cord injury--a randomized, placebo-controlled trial with GM-1 ganglioside

BACKGROUND

Spinal-cord injury is devastating; until recently, there was no medical treatment to improve recovery of the initial neurologic deficit. Studies in animals have shown that monosialotetrahexosylganglioside (GM-1) ganglioside enhances the functional recovery of damaged neurons.

METHODS

A prospective, randomized, placebo-controlled, double-blind trial of GM-1 ganglioside was conducted in patients with spinal-cord injuries. Of 37 patients entered into the study, 34 (23 with cervical injuries and 11 with thoracic injuries) completed the test-drug protocol (100 mg of GM-1 sodium salt or placebo intravenously per day for 18 to 32 doses, with the first dose taken within 72 hours of the injury) and a one-year follow-up period. Neurologic recovery was assessed with the Frankel scale (comprising five categories) and the American Spinal Injury Association (ASIA) motor score (a scale of scores from 0 to 100, derived from strength tests of 20 specific muscles, each scored from 0 to 5).

RESULTS

There was a significant difference between groups in the distribution of improvement of Frankel grades from base line to the one-year follow-up (improvement of 0, 1, 2, and 3 grades in 13, 4, 1, and 0 patients, respectively, in the placebo group and 8, 1, 6, and 1 patients, respectively, in the GM-1 group; P = 0.034 by the Cochran-Mantel-Haenszel chi-square test). The GM-1-treated patients also had a significantly greater mean improvement in ASIA motor score from base line to the one-year follow-up than the placebo-treated patients (36.9 vs. 21.6 points; P = 0.047 by analysis of covariance with the base-line ASIA motor score as the covariate). An analysis of individual muscle recoveries revealed that the increased recovery in the GM-1 group was attributable to initially paralyzed muscles that regained useful motor strength rather than to strengthening of paretic muscles.

CONCLUSIONS

This small study provides evidence that GM-1 enhances the recovery of neurologic function after one year. A larger study must be conducted, however, before GM-1 is considered efficacious and safe in treating spinal-cord injury.

Effect of monomethylethanolamine, dimethylethanolamine, gangliosides, isoproterenol, and 2-hydroxyethylhydrazine on the conversion of ethanolamine to methylated products by cultured chick brain neurons

The sequential methylation of ethanolamine and its phosphorylated derivatives has been studied with chick neurons in culture in the presence of several pharmacological agents. Incubation with [3H]ethanolamine in the presence of monomethylethanolamine and dimethylethanolamine indicated that in these neurons the preferential conversion to choline-containing compounds is via the methylation of phosphorylethanolamine. The possibility that there are two separate enzymes, i.e., one responsible for the methylation of water-soluble ethanolamine-containing compounds and another for the ethanolamine phospholipids, was examined with agents believed to influence these conversions. Incubation of neurons in the presence of a mixture of exogenous gangliosides at 10(-8) M and 10(-5) M concentrations showed that these neuritogenic compounds stimulate the methylation of phosphatidylethanolamine and decrease that of phosphorylethanolamine. The inhibitor of phosphatidylethanolamine methyltransferase (EC 2.1.1.17), 2-hydroxyethylhydrazine, decreased the conversion of phosphatidylethanolamine to phosphatidylcholine and increased that of phosphorylethanolamine to phosphorylcholine. The possible effects of adrenergic stimulation were studied by the incubation of neurons with isoproterenol at 10(-6) M and 10(-5) M concentrations. There was a reduction of phosphorylethanolamine methylation and a stimulation of that of phosphatidylethanolamine, and these effects were counteracted by the presence of 5 x 10(-5) M propranolol.

Differences in induction of c-fos transcription by cholera toxin-derived cyclic AMP and Ca2+ signals in astrocytes and 3T3 fibroblasts

The B subunit of cholera toxin, a protein which binds specifically to membrane ganglioside GM1, is known to affect cell growth and differentiation. To investigate the mechanism of these cellular responses at the nuclear level, we used the induction of c-fos in astrocytes and 3T3 fibroblasts as a model. Northern blot analysis showed that treatment with B subunit provokes a rapid and transient expression of c-fos mRNA, independent of a measurable increase in cyclic AMP. The B subunit signal, which is mediated by Ca2+, was compared to cholera toxin and other agents which increase intracellular cyclic AMP levels. In transient transfection assays of astrocytes and fibroblasts, functional analysis of c-fos promoter deletions was used to identify the elements involved in transcriptional activation by B subunit. In astrocytes, the DNA region including the serum response element and the cyclic AMP response element (CRE) are equally required, whereas 3T3 cells require only the CRE for maximal induction. A synergistic effect of signal transduction was mediated by calcium and cyclic AMP on the CRE, being positive in 3T3 cells and negative in astrocytes. Diverse regulatory elements may be thus involved in responses of different cell types to the same extracellular signal. Furthermore, a single regulatory element (CRE) can integrate both calcium and cyclic AMP signals in the control of gene expression.

High-performance capillary electrophoresis of gangliosides

Gangliosides are sialic acid-containing glycosphingolipids. In aqueous media, these glycolipids have been shown to exist as stable micelles. Ganglioside micelles could be analyzed by high-performance zonal capillary electrophoresis in uncoated fused-silica capillaries within 10 min. The mass sensitivity determined by monitoring the absorption of ultraviolet light at 195 nm was in the order of 10(-11) mol. Increasing the pH of the running buffer from 3.0 to 7.4 or the voltage from 10 to 30 kV increased the relative mobilities of gangliosides. By contrast, increasing the ionic strength of the buffer decreased the migration and broadened the elution peak widths of gangliosides. Ganglioside* micelles including GM1, GD1b, and GT1b were resolved into separate peaks by capillary electrophoresis at physiological pH shortly after mixing. Upon prolonged incubation, the ganglioside peaks merged to form a single species. The fusion process was temperature-dependent. At 50 degrees C, formation of mixed micelles between polysialogangliosides GD1b and GT1b was complete within 30 min. In contrast, no fusion of the ganglioside peaks was observed at 0 degrees C even after 75 h. Formation of mixed micelles between GD1b and other polysialogangliosides including GD1a, GT1b, and GQ1b at 37 degrees C required 1.5, 3.0, and 2.0 h, respectively. Formation of mixed micelles between monosialoganglioside GM1 and polysialogangliosides were 6- to 36-fold slower. No fusion was observed between monosialogangliosides GM1 and GM2 after 2 days of incubation. These findings indicate that polysialogangliosides may have higher propensities than monosialoganglioside to form mixed micelles.

Gangliosides inhibit glucosylceramide synthase: a possible role in ganglioside therapy

Gangliosides stimulate the hydrolysis of glucosylceramide (GlcCer), their precursor, and therefore may lower the level of cellular GlcCer and exert a feedback control effect to slow the formation of gangliosides. Tests were made to see if a similar effect on GlcCer levels can be exerted by the action of gangliosides on GlcCer synthesis. Using a new assay procedure, we showed that gangliosides do inhibit the synthase in brain membranes quite effectively, the most active being those lipids with more sugar and sialic acid moieties. Mice injected with a mixture of brain gangliosides for 5 days were found to have a lower level of ceramide:UDP-Glc glucosyltransferase activity in brain, liver, and kidney. The inhibition seems to be exerted by competition for the active site and binding to effector site(s) on the enzyme. It is possible that the reported therapeutic actions of gangliosides on the nervous system are, in part, the result of lowered levels of GlcCer. Malignant tumors shed gangliosides into the extracellular fluid, which are believed to block the generation of antibodies by the host's immunodefense system; this effect also may be due, in part, to reduction in the GlcCer level of immunogenic cells. A new finding is that a ceramide containing phytosphingosine is a markedly better substrate for GlcCer synthase than one containing the more common base.

Putative neurotrophic factors and functional recovery from peripheral nerve damage in the rat

1. In rats, recovery of sensory-motor function following a crush lesion of the sciatic or tibial nerve was monitored by measuring foot reflex withdrawal from a local noxious stimulation of the foot sole. 2. Putative neurotrophic compounds were tested on this functional recovery model: melanocortins (peptides derived from ACTH (corticotropin) and alpha-MSH (melanotropin], gangliosides and nimodipine were effective whereas isaxonine and TRH (thyrotropin releasing hormone) were not. 3. Structure-activity studies with melanocortins revealed a similar effectiveness of alpha-MSH, [N-Leu4, D-Phe7]-alpha-MSH, desacetyl-alpha-MSH and the ACTH analogue ORG 2766, questioning the validity of the previously suggested notion that the melanotrophic properties of these peptides are responsible for their neurotrophic effect. 4. As recovery of function after peripheral nerve damage follows a similar time course in hypophysectomized (five days post operation) and sham-operated rats, effective melanocortin therapy does not mimic an endogenous peptide signal in the repair process from pituitary origin. 5. Subcutaneous treatment with ORG 2766 (7.5 micrograms kg-1 48 h-1) facilitates recovery of function following peripheral nerve damage in young (6-7 weeks old), mature (5 month old) and old (20 month old) rats. 6. In view of the diversity in structure of the effective neurotrophic factors and the complexity of nerve repair, the present data support the notion that peripheral nerve repair may be facilitated by different humoral factors likely to be active on different aspects of the recovery process.

Gangliosides: the relevance of current research to neurosurgery

Gangliosides are complex glycolipids found on the outer surface of most cell membranes: they are particularly concentrated in tissues of the nervous system. Gangliosides form part of the immunological identity of mammalian cells and are involved in a variety of cell-surface phenomena such as cell-substrate binding and receptor functions. In tumorous tissue, the ganglioside composition is altered, sometimes in direct proportion to the degree of malignancy. The literature on the glycosphingolipid composition and immunology of intracranial tumors is reviewed. Some gangliosides induce neuritogenesis and exhibit a trophic effect on nerve cells grown in vitro. In vivo, a particular ganglioside, GM1, reduces cerebral edema and accelerates recovery from injury (traumatic and ischemic) to the peripheral and central nervous systems of laboratory animals. Preliminary clinical studies have shown that treatment with gangliosides may have corresponding effects on lesions of the human peripheral nervous system. Gangliosides have not been tested in human subjects with brain injury.

Stereotaxic injection of GD1a ganglioside induces limited recovery of striatal dopaminergic system in MPTP-treated aging mice

The systemic administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to young (2 months old) and aging (12 months old) C57BL/6 mice (4 x 20 mg/kg i.p. given 12 hr apart) reduced tyrosine hydroxylase (TH)-immunoreactive (IR) fibers in the striatum and reduced dopamine (DA) concentration to 35% of controls in young and 22% of controls in aging mouse brain 5 weeks after administration. Stereotaxic injection of GD1a ganglioside (3 x 100 micrograms, 5 days apart) into the striatum of MPTP-treated young mice restored striatal DA concentration to 52% of the control concentration 5 weeks after MPTP injection. Similar injections of GD1a ganglioside restored striatal DA concentration of MPTP-treated aging mice to only 31% of the control concentration. Immunocytochemical analysis showed significant recovery of TH-IR fibers in the striatum of MPTP-depleted young mice treated with GD1a ganglioside, while TH-IR fibers in the striatum of MPTP-depleted aging mice treated with GD1a ganglioside showed less recovery. We conclude that treatment of MPTP-depleted aging mice with GD1a ganglioside results in more limited recovery in the nigrostriatal DA system than in young mice.

Neurite outgrowth in dorsal root neuronal hybrid clones modulated by ganglioside GM1 and disintegrins

Subclones of F11 neuronal hybrid cells (neuroblastoma x dorsal root ganglion neurons) have segregated differing and/or overlapping neuritogenic mechanisms on three substrata--plasma fibronectin (pFN) with its multiple receptor activities, cholera toxin B subunit (CTB) for binding to ganglioside GM1, and platelet factor-4 (PF4) for binding to heparan sulfate proteoglycans. In this study, specific cell surface receptor activities for the three substrata were tested for their modulation during neuritogenesis by several experimental paradigms, using F11 subclones representative of three differentiation classes (neuritogenic on pFN only, on CTB only, or on all three substrata). When cycloheximide was included in the medium to inhibit protein synthesis during the active period, neurite formation increased significantly for all subclones on all three substrata, virtually eliminating substratum selectivity for differentiation mediated by cell surface integrin, ganglioside GM1, or heparan sulfate proteoglycans. Therefore, one or more labile proteins (referred to as disintegrins) must modulate functions of matrix receptors (e.g., integrins) mediating neurite formation. To verify whether cycloheximide-induced neuritogenesis was also regulated by integrin interaction with cell surface GM1, two approaches were used. When (Arg-Gly-Asp-Ser)-containing peptide A was added to the medium, it completely inhibited cycloheximide-induced neuritogenesis on all three substrata of all subclones, indicating stringent requirement for cell surface integrin function in these mechanisms. In contrast, when CTB or a monoclonal anti-GM1 antibody was also added to the medium, cycloheximide-induced neuritogenesis was amplified further on pFN and sensitivity to peptide A inhibition was abolished. Therefore, in some contexts ganglioside GM1 must complex with integrin receptors at the cell surface to modulate their function. These results also indicate that (a) cycloheximide treatment leads to loss of substratum selectivity in neuritogenesis, (b) this negative regulation of neurite outgrowth is affected by integrin receptor association with labile regulatory proteins (disintegrins) as well as with GM1, and (c) complexing of GM1 by multivalent GM1-binding proteins shifts neuritogenesis from an RGDS-dependent integrin mechanism to an RGDS-independent receptor mechanism.