Ganglioside or sialic acid attenuates ethanol-induced decrements in locomotion, nose-poke exploration, and anxiety, but not body temperature

Ganglioside GM1 and the Central Nervous System

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

Behavioral effects of ethanol in the Red Swamp Crayfish (Procambarus clarkii)

Alcohol abuse remains one of the primary preventable sources of mortality in the United States. Model species can be used to evaluate behavioral and other biological changes associated with alcohol and to identify novel treatments. This report describes methods for evaluating the behavioral effects of ethanol (EtOH) in crayfish. Crayfish (Procambarus clarkii) were immersed in ethanol concentrations ranging from 0.1 to 1.0 molar, for 10-30 min. Studies evaluated hemolymph alcohol concentration, locomotion in an open field and anxiety-like behavior using a Light/Dark transfer approach. EtOH immersion produced dose-dependent increases in hemolymph EtOH (up to 249 mg/dL) and reductions in open field locomotion that depended on EtOH concentration or exposure duration. Untreated crayfish exhibit avoidance of the open parts of the locomotor arena and a preference for a covered portion. Acute EtOH immersion decreased time spent in the covered portion of the Light/Dark arena, consistent with a decrease in anxiety-like behavior. Daily EtOH immersion for 5 days did not alter locomotor responses, however, activity was increased 3 days after the repeated EtOH regimen. Overall, this study shows that this inexpensive, easily maintained species can be used for behavioral pharmacological experiments designed to assess the acute and repeated effects of EtOH.

Sex-Specific ADHD-like Behaviour, Altered Metabolic Functions, and Altered EEG Activity in Sialyltransferase ST3GAL5-Deficient Mice

A deficiency in GM3-derived gangliosides, resulting from a lack of lactosylceramide-alpha-2,3-sialyltransferase (ST3GAL5), leads to severe neuropathology, including epilepsy and metabolic abnormalities. Disruption of ganglioside production by this enzyme may also have a role in the development of neuropsychiatric disorders. ST3Gal5 knock-out (St3gal5^−/−) mice lack a-, b-, and c-series gangliosides, but exhibit no overt neuropathology, possibly owing to the production of compensatory 0-series glycosphingolipids. Here, we sought to investigate the possibility that St3gal5^−/− mice might exhibit attention-deficit/hyperactivity disorder (ADHD)-like behaviours. In addition, we evaluated potential metabolic and electroencephalogram (EEG) abnormalities. St3gal5^−/− mice were subjected to behavioural testing, glucose tolerance tests, and the levels of expression of brain and peripheral A and B isoforms of the insulin receptor (IR) were measured. We found that St3gal5^−/− mice exhibit locomotor hyperactivity, impulsivity, neophobia, and anxiety-like behavior. The genotype also altered blood glucose levels and glucose tolerance. A sex bias was consistently found in relation to body mass and peripheral IR expression. Analysis of the EEG revealed an increase in amplitude in St3gal5^−/− mice. Together, St3gal5^−/− mice exhibit ADHD-like behaviours, altered metabolic and EEG measures providing a useful platform for better understanding of the contribution of brain gangliosides to ADHD and associated comorbidities.

Gangliosides in the Brain: Physiology, Pathophysiology and Therapeutic Applications

Gangliosides are glycosphingolipids highly abundant in the nervous system, and carry most of the sialic acid residues in the brain. Gangliosides are enriched in cell membrane microdomains ("lipid rafts") and play important roles in the modulation of membrane proteins and ion channels, in cell signaling and in the communication among cells. The importance of gangliosides in the brain is highlighted by the fact that loss of function mutations in ganglioside biosynthetic enzymes result in severe neurodegenerative disorders, often characterized by very early or childhood onset. In addition, changes in the ganglioside profile (i.e., in the relative abundance of specific gangliosides) were reported in healthy aging and in common neurological conditions, including Huntington's disease (HD), Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), stroke, multiple sclerosis and epilepsy. At least in HD, PD and in some forms of epilepsy, experimental evidence strongly suggests a potential role of gangliosides in disease pathogenesis and potential treatment. In this review, we will summarize ganglioside functions that are crucial to maintain brain health, we will review changes in ganglioside levels that occur in major neurological conditions and we will discuss their contribution to cellular dysfunctions and disease pathogenesis. Finally, we will review evidence of the beneficial roles exerted by gangliosides, GM1 in particular, in disease models and in clinical trials.

Harnessing the power of yeast to elucidate the role of sphingolipids in metabolic and signaling processes pertinent to psychiatric disorders

The development of therapies for neuropsychiatric disorders is hampered by the lack of understanding of the mechanisms underlying their pathologies. While aberrant sphingolipid metabolism is associated with psychiatric illness, the role of sphingolipids in these disorders is not understood. The genetically tractable yeast model can be exploited in order to elucidate the cellular consequences of sphingolipid perturbation. Hypotheses generated from studies in yeast and tested in mammalian cells may contribute to our understanding of the role of sphingolipids in psychiatric disorders and to the development of new treatments. Here, we compare sphingolipid metabolism in yeast and mammalian cells, discuss studies implicating sphingolipids in psychiatric disorders and propose approaches that utilize yeast in order to elucidate sphingolipid function and identify drugs that target sphingolipid synthesis.

Sphingolipids in psychiatric disorders and pain syndromes

Despite the high prevalence and devastating impact of psychiatric disorders, little is known about their etiopathology. In this review, we provide an overview on the participation of sphingolipids and enzymes responsible for their metabolism in mechanisms underlying psychiatric disorders. We focus on the pathway from sphingomyelin to proapoptotic ceramide and the subsequent metabolism of ceramide to sphingosine, which is in turn phosphorylated to yield anti-apoptotic sphingosine-1-phosphate (S1P).The sphingomyelinase/ceramide system has been linked to effects of reactive oxygen species and proinflammatory cytokines in the central nervous system as well as to synaptic transmission. Compared to ubiquitously expressed acid sphingomyelinase, acid and neutral ceramidase and neutral sphingomyelinase are highly active in brain regions. Depressed patients show elevated plasma ceramide levels and increased activities of acid sphingomyelinase which is functionally inhibited by many anti-depressive drugs. Exposure to alcohol is associated with an activation of acid and neutral sphingomyelinase observed in cell culture, mouse models and in alcohol-dependent patients and with increased concentrations of ceramide in various organs.Levels of sphingomyelin and ceramide are altered in erythrocytes and post-mortem brain tissues of schizophrenic patients in addition to changes in expression patterns for serine palmitoyltransferase and acid ceramidase leading to impaired myelination. After induction of anxiety-like behavior in animal models, higher serum levels of S1P were reported to lead to neurodegeneration. Correspondingly, S1P infusion appeared to increase anxiety-like behavior. Significantly upregulated levels of the endogenous ceramide catabolite N,N-dimethylsphingosine were observed in rat models of allodynia. Conversely, rats injected intrathecally with N,N-dimethylsphingosine developed mechanical allodynia. Moreover, S1P has been implicated in spinal nociceptive processing.The increasing interest in lipidomics and improved analytical methods led to growing insight into the connection between psychiatric and neurological disorders and sphingolipid metabolism and may once provide new targets and strategies for therapeutic intervention.

Chronic ethanol consumption down-regulates CMP-NeuAc:GM3 α2,8-sialyltransferase (ST8Sia-1) gene in the rat brain

Alcoholics have an increase in sialic acid-deficient glycoconjugates such as carbohydrate-deficient transferrin, sialic acid-deficient gangliosides and free sialic acids. The elevated presence of these asialoconjugates could be a consequence of alcohol-mediated impaired sialylation rate or due to increased desialylation rate. Chronic ethanol-induced brain abnormalities and behavioral changes could be mediated through these asialogangliosides. We have therefore determined the level of brain CMP-NeuAc:GM(3) alpha2,8-sialyltransferase (ST8Sia-1) and Gal-beta1,3GalNAc alpha2,3-sialyltransferase (ST3Gal-11) messenger RNA (mRNA) and correlated with the activity of these key enzymes in male Wistar rats as a function of increasing dietary concentration of ethanol after 8 weeks of feeding. The relative level of brain synaptosomal ST8Sia-1 and ST3Gal-11 mRNA were determined by real-time quantitative polymerase chain reaction (RT-PCR). We compared the observed ST8Sia-1 gene expression with its enzymatic activity in the synaptosomal membrane fraction isolated from the rat brain in the ethanol and pair-fed control groups. The results showed that the relative level of brain ST8Sia-1 mRNA expression was down-regulated by 13% (p<0.05) in 10.6%, by 40% (p<0.01) in 20.8% and by 57% (p<0.01) in the 36% ethanol-calorie groups, compared to the control (0% ethanol-calorie) group. In addition, ethanol at 36% dietary calories caused a significant 61% (p<0.01) decrease in the brain synaptosomal ST8Sia-1 activity compared to the control group. However, ethanol (10.6, 20.8 or 36% level) did not significantly affect the relative level of brain ST3Gal-11 mRNA as compared to the control (0% ethanol-calorie) group. Thus, our findings imply that chronic ethanol exposure preferentially down-regulates brain ST8Sia-1 mRNA accompanied by a concomitant decrease in its activity in a dose-dependent manner. Therefore, the selective loss of 2,8-sialic acid residues from gangliosides might contribute towards the appearance of asialogangliosides and related brain-abnormalities associated with ethanol abuse.

Chronic ethanol feeding controls the activities of various sialidases by regulating their relative synthetic rates in the rat liver

We have determined the concentration effects of feeding for 8 weeks 10.8%, 21.6%, and 36% dietary ethanol calories on the activities and relative synthetic rates (RSRs) of various subcellular sialidases of rat liver. The hepatic RSRs of each species of sialidase was determined based on the ratio of 1-hour incorporation of [35S]-methionine into immunoprecipitable sialidase as percent of the incorporation into total protein in each subcellular fraction. Ganglioside sialidase activities in the hepatic subcellular fractions were also determined. Ethanol feeding at 36% dietary calories caused an increase in the ganglioside sialidase activity of the plasma membrane sialidase (PMS) by 232% (P < .01) and that of cytosolic sialidase (CS) by 184% (P < .05), but decreased the lysosomal membrane sialidase (LMS) by 54% (P < .01) when compared with the control animals. The specificity of each antisialidase antibody was verified by immunoblots. The RSR of PMS was increased by 40% (P < .01), 67% (P < .01), and 220% (P < .01) in the 10.8%, 21.6%, and 36% ethanol groups, respectively. Similarly, the RSR of CS was increased by 17% (P < .01), 19% (P < .01), and 63% (P < .01), respectively, in these ethanol groups. In contrast, the RSR of LMS was inhibited by 36% (P < .01), 34% (P < .01), and 69% (P < .01), respectively, in these ethanol groups. Intralysosomal sialidase failed to hydrolyze gangliosides. Thus, PMS and CS, but not LMS or intralysosomal sialidase, may play important roles in ethanol-modulated desialylation of gangliosides and consequent liver injury and behavioral alterations.

Monosialoganglioside attenuates the excitatory and behavioural sensitization effects of ethanol

The effects of long-term monosialoganglioside GM1 treatment on the acute excitatory effects of ethanol and behavioural sensitization to this effect were studied, using locomotion frequency of mice observed in an open field as an experimental parameter. GM1 (30 mg/kg, once a day, for 21 days) did not modify mouse behaviour but decreased both the acute excitatory (1.8 g/kg) and the behavioural sensitization effects of ethanol (1.8 g/kg, once a day for 21 days, 30 min after GM1 injections). GM1 administered acutely 30 min or 24 h before ethanol did not modify the ethanol-induced increase in locomotion frequency. These results agree with previous reports in which ganglioside treatment modified both dopaminergic plasticity and other behavioural and biochemical effects of ethanol.

Effect of an NMDA receptor antagonist and a ganglioside GM1 derivative upon ethanol-induced modification of parameters of oxidative stress in several brain regions

Dietary administration of ethanol to rats for 2 weeks was able to depress levels of glutathione (GSH) and Cu/Zn superoxide dismutase (SOD) in several brain regions. This was indicative of the generation of excess levels of reactive oxygen in treated animals. The potentially protective effect of both an NMDA receptor blocker (MK-801) and an internally esterified derivative of ganglioside GM1 (AGF2) upon ethanol-induced changes in these indices of oxidative stress, was studied. Both of these agents are reported to have neuroprotective properties, but neither was able to prevent ethanol-induced reduction of GSH and SOD levels in any brain area studied. In fact, both agents depressed SOD and GSH levels in midbrain independently of ethanol. MK-801 had a pronounced pro-oxidant potential, and when administered in combination with ethanol. GSH and SOD were reduced in midbrain and striatum to levels below those obtained with either agent alone. The pro-oxidant properties of ethanol may thus act independently of its actions upon the NMDA receptor. The protective properties of NMDA receptor inhibitors or gangliosides cannot be attributed to any antioxidant effect.

Effect of manganese on the development of glial cells cultured from prenatally alcohol exposed rats

Maternal alcohol abuse is known to produce retardation in brain maturation and brain functions. Using cultured glial cells as a model system to study these effects of alcohol we found an alcohol antagonizing property for manganese (Mn). Mn was added to the alcohol diet (MnCl2 25 mg/l of 20% v/v ethanol) of pregnant rats. Glial cells were cultured during 4 weeks from cortical brain cells of pups born to these mothers. Several biochemical parameters were examined: protein levels, enzymatic markers of glial cell maturation (enolase and glutamine synthetase), superoxide dismutase a scavenger of free radicals produced during alcohol degradation. The results were compared to appropriate controls. A beneficent effect of Mn was observed for the pups weight which was no more significantly different from the control values. Protein levels, enolase and glutamine synthetase activities were increased mainly during the proliferative period when Mn was added to the alcohol diet compared to the only alcohol treated animals. This Mn effect was not found for superoxide dismutase in cultured glial cells but exists in the total brain of the 2 week-old offspring. In the total 2 and 4 week-old brain the alcohol induced decrease of enolase and glutamine synthetase was also antagonized by the Mn supplementation. Our data suggest that Mn may act as a factor overcoming at least partially some aspects of alcohol induced retardation of nerve cell development.

Role of gangliosides in behavioral and biochemical actions of alcohol: cell membrane structure and function

Alcohol exerts its pharmacological effects in adult brain by altering the physicochemical properties of cellular plasma membranes. Although alcohol does induce changes in membrane lipid composition, studies to relate these alterations to the development of behavioral tolerance to alcohol and the withdrawal effects have been unsuccessful. Actions of alcohol on developing brain are even more complex. Some of the reported effects include inhibition of embryogenesis, cell migration, and differentiation, including synaptogenesis. Gangliosides have neuroprotective action against a variety of neural insults (e.g., mechanical injury, drug toxicity, or hypoxic insult). This review addresses the role and significance of gangliosides in the CNS pathophysiology of alcohol exposure, as well as the effect of changes in endogenous gangliosides on membrane structure and function. We also describe the role of exogenous gangliosides in prevention of alcohol (acute and/or chronic)-induced CNS (prenatal and postnatal) neurotoxicity through their action on cellular plasma membranes. We propose that ganglioside's neuroprotective effects against alcohol neurotoxicity involve protection and restoration of plasma membrane structure (proteins and lipids) and thereby its function (ionic homeostasis, neurotransmitter receptor-mediated signal transduction). Thus gangliosides may have potential therapeutic use in treatment of alcohol-related problems.

Lowering of blood ethanol by activated carbon products in rats and dogs

Earlier studies on the effects of activated carbon (charcoal) on blood alcohol levels (BAL) in animals have been conflicting. The present study was designed to study the effects of a commercially available product (Charcoaid) and a new patented product (Alcosorb), in capsules and in suspension on the BAL of rats and dogs. We compared peak BAL and the regression of BAL with time during ethanol clearance in rats given 1.5 g/kg of carbon products in sorbitol intragastrically, followed 5 min later by 3.5 g/kg ethanol intragastrically. Peak BAL were significantly higher after Charcoaid 1 h after intubation, compared to Alcosorb and sorbitol (vehicle for the charcoal suspension). A study in which ethanol was given intraperitoneally instead of intragastrically showed no differences in ethanol BAL produced by the intragastric carbon treatments. In a crossover study using Beagle dogs, 780 mg capsules of carbon products ("low dose") given 5 min before ethanol had no significant effect on BAL. A "high" dose of 20 g of charcoal products suspended in water, followed by ethanol intragastrically, was also ineffective in lowering blood ethanol. However, carbon products suspended in a water/ethanol vehicle (20% w/v) did significantly lower peak BAL. We conclude that carbon products significantly lower BAL in rats and dogs, and that in rats, Alcosorb and sorbitol produce a greater BAL lowering effect than Charcoaid for a brief time after administration. The mechanisms of the BAL lowering effect by sorbitol and charcoal products are probably different.

Placental transfer of (3H)-GM1 and its distribution to maternal and fetal tissues of the rat

The demonstration that ganglioside GM1 pretreatment reduced the ethanol induced neurobehavioral effects in adult pups exposed to ethanol in utero, prompted study to examine whether GM1 crosses the placenta and penetrates fetal tissues. The present results indicate that 3H-galactose labeled GM1 not only passes the placenta but also served as a substrate for the synthesis of polysialogangliosides, and remained in various tissues up to 48 h after maternal (3H)-GM1 administration.