Increased surface glycoconjugates of synaptic membranes in mice during chronic ethanol treatment

Fetal alcohol effects: mechanisms and treatment

This article represents the proceedings of a symposium at the 2000 ISBRA Meeting in Yokohama, Japan. The chair was Edward P. Riley. The presentations were (1) Does alcohol withdrawal contribute to fetal alcohol effects? by Jennifer D. Thomas and Edward P. Riley; (2) Brain damage and neuroplasticity in an animal model of binge alcohol exposure during the "third trimester equivalent," by Charles R. Goodlett, Anna Y. Klintsova, and William T. Greenough; (3) Ganglioside GM1 reduces fetal alcohol effects, by Basalingappa L. Hungund; and (4) Fetal alcohol exposure alters the wiring of serotonin system at mid-gestation, by F. Zhou, Y. Sari, Charles Goodlett, T. Powrozek, and Ting-Kai Li.

Quantification of ethanol concentrations in the extracellular fluid of the rat brain: in vivo calibration of microdialysis probes

Traditional microdialysis techniques provide qualitative data, although quantitative data are often required for pharmacodynamic analyses. This study evaluated a potentially useful in vivo delivery technique to calibrate microdialysis probes for ethanol. We measured in vivo delivery extraction fractions within subjects across 2 days and found no change over time. We tested the effect of diffusion direction on extraction fraction and found that it was higher for ethanol diffusion out of the probe than for diffusion into the probe, both in vitro and in vivo. The in vivo extraction fraction ratio of diffusion(IN) versus diffusion(OUT) was 0.65+/-0.03. Finally, we predicted extracellular brain ethanol concentrations after 1 g/kg ethanol administration using in vivo delivery, "no net flux" dialysis, or in vivo delivery corrected for diffusion direction with the in vivo extraction fraction ratio. Both in vivo delivery and "no net flux" dialysis predicted brain concentrations that were approximately one-third lower than blood concentrations, whereas the corrected in vivo delivery predicted extracellular concentrations very similar to blood concentrations. We conclude that microdialysis calibration methods for ethanol require a measure of extraction fraction for diffusion into the probe. Further studies are needed to establish whether this effect is common to other alcohols.

Ethanol binding to a model carbohydrate, glycogen

The binding affinity of ethanol for carbohydrates is unknown. Glycoconjugates are postulated to be sensitive targets of ethanol action. The glycogen content of muscle, liver, and brain is sensitive to ethanol. To explore whether carbohydrates as a class have a specific affinity to bind ethanol, we measured the binding of ethanol and other small molecules to the carbohydrate glycogen. Ethanol binding was found to be weak. The polar alcohol, glycerol, bound to glycogen with a greater affinity than ethanol did. Other small polar molecules (methanol, sucrose, acetate, glycine, and dimethyl sulfoxide) also bound more strongly than ethanol did. Ethanol and glycerol binding were concentration independent. No evidence of saturable or specific sites for these alcohols was obtained. Water binding was determined and was in agreement with hydrodynamic measures. Water binding exceeded the binding of all solutes studied. The loosely structured water of hydration in glycogen apparently was able to accommodate polar solutes, but tended to exclude ethanol and, to a lesser extent, methanol. We conclude that carbohydrates as a class exhibit no strong affinity or specificity for ethanol.

Cortical cell plasma membrane alterations after in vitro alcohol exposure: prevention by GM1 ganglioside

Using choleratoxin/antitoxin immunohistochemistry, this study examined the effects of in vitro alcohol exposure on the morphology of cell plasma membranes in mixed fetal rat cortical cultures, and assessed the neuroprotective effects of exogenous monosialoganglioside (GM1). Gangliosides are involved in critical biological functions, including maintenance of membrane integrity. Plasma membranes are directly affected by alcohol exposure through multiple mechanisms. Results indicate that exposure to alcohol altered plasma membrane morphology as assessed by staining for the surface distribution of membrane GM1. Pretreatment with endogenous GM1 ameliorated the alcohol-induced alterations.

GM1 ganglioside reduces ethanol intoxication and the development of ethanol dependence

The monosialoganglioside, GM1, protects the nervous system against a variety of insults. In this study, we evaluated the protective properties of GM1 on ethanol intoxication and development of dependence. GM1 (20-40 mg/kg, IP) reduced the extent and duration of ataxia produced by ethanol (2 g/kg, IP, 15-95 min), and delayed the onset of loss and reduced the duration of the righting reflex (LORR) produced by ethanol (4.2 g/kg, IP). GM1 did not alter ethanol-induced hypothermia or the rate of ethanol clearance. Rather, GM1 increased the waking blood ethanol concentration. In animals fed a complete liquid diet containing 4.5% ethanol, concurrent administration of GM1 (40 mg/kg/day) blocked the tremors, hypolocomotion, and anxiety-like behavior associated with ethanol withdrawal. These findings demonstrate that GM1 reduces both ethanol's acute intoxication and the signs and symptoms of ethanol withdrawal by a mechanism not related to ethanol pharmacokinetics.

In utero ethanol exposure retards growth and alters morphology of cortical cultures: GM1 reverses effects

Ethanol, a developmental neurotoxin, alters plasma membranes' physicochemical properties affecting embryogenesis, cell migration, differentiation, and synaptogenesis. In a previous study using a model for fetal alcohol effects, GM1 ganglioside treatment was shown to reduce ethanol-induced accumulation of endogenous GM1 and fatty acid ethyl esters in rat fetuses. The present study was initiated to define further the in utero effects of ethanol and the capacity of GM1 treatment to ameliorate such effects. Wistar dams were exposed to ethanol (intragastrically) on gestation day (GD) 7 and GD8 and GD13 and GD14. GM1 ganglioside (10 mg/kg, im) was given 24 hr before ethanol administration. Cortical cultures were derived from GD15 and GD20 fetuses. GM1, which is highly localized on the cellular plasma membrane outer surface of CNS cells, was used as a marker molecule to assess cell integrity. Cholera toxin/antitoxin/fluorescence immunohistochemistry was used to localize GM1. Results indicate that the brief in utero exposure to ethanol affected cell growth and morphology. A marked retardation of cell development and arborization was observed as early as 24 hr after plating. Ethanol-exposed cells evidenced considerably altered GM1 localization. Such alterations likely reflect losses of membrane integrity. These in utero ethanol-induced pathologies are remarkably diminished in cultures derived from ethanol-exposed fetuses of dams treated with GM1.

Region distribution of the gangliosides in rat brain after chronic ethanol treatment

In this study the effects of chronic ethanol administration on the regional distribution of brain gangliosides were investigated. A total of 36 60-d-old male Wistar rats weighing approximately 200 g was divided into two groups of 18 animals each. The ethanol-consuming group was offered drinking fluid (25% sucrose-32% ethyl alcohol, w/w) ad libitum, and the control group was given a sucrose solution isocaloric with the ethanol-sucrose solution. After 6 mo of chronic ethanol treatment, cerebral cortex, N. caudatus, hypothalamus, thalamus, and hippocampus were analyzed with respect to their ganglioside pattern (GM2, GM1, GD1a, GD1b, GT1b, and GQ). The results showed that there were highly significant effects of ethanol on hypothalamus GD1b and GT1b, thalamus GM1 and GD1a, and hippocampus GM1, GD1b, and GT1b ganglioside distribution. It was found that ethanol differently affected the gangliosides in these brain regions.

Ganglioside GM1 reduces fetal alcohol effects in rat pups exposed to ethanol in utero

We have investigated the effect of in utero ethanol exposure and ganglioside GM1 pretreatment on the endogenous ganglioside profile of the rat fetal brain. Prenatal ethanol exposure on gestation day (GD) 7 and GD8 and/or GD13 and GD14 leads to a very significant increase in the ganglioside GM1 content in at least 50% of the pup brains when assayed on GD20. This treatment protocol also results in significant decrease in the content of polysialogangliosides GD1a, GT1b, and GQ1b. GM1 treatment of pregnant dams before ethanol administration prevented this alteration in pup brain ganglioside profile. Ganglioside GM1 pretreatment appears to block the cellular membrane changes associated with fetal alcohol effects and thereby minimizes alterations in brain maturation and associated behavioral dysfunction.

Exposure to galactose oxidase of GM1 ganglioside molecular species embedded into phospholipid vesicles

The exposure of GM1 molecular species present in the native ganglioside, carrying C18:1 or C20:1 long-chain bases (LCB), to Dactylium dendroides galactose oxidase was studied. When native GM1 (49.3% C18:1 and 50.7% C20:1 LCB, respectively), was inserted in dipalmitoylphosphatidylcholine vesicles and partially oxidized (10%), the proportion of C18:1 and C20:1 species in the oxidized GM1 was 59.6% and 40.4%, respectively, suggesting a preferential action of the enzyme on the shorter species. The Vmax of the enzyme was higher on C18:1 GM1 than on C20:1 GM1. The molecular species were affected without any preference after partial (10%) oxidation of GM1 incorporated in egg phosphatidylcholine vesicles or in micellar form. These data indicate that the exposure of the terminal galactose moiety of GM1 ganglioside to galactose oxidase is affected by the ganglioside ceramide composition as well as the phospholipid environment, that presumably determine the distribution (molecular dispersion, segregation) of the ganglioside within the membrane.

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.

Selective breeding for initial sensitivity to ethanol

Selective breeding for initial sensitivity to ethanol has been carried out by a number of investigators in order to investigate the mechanisms by which ethanol brings about a myriad of effects on the mammalian central nervous system. In addition the availability of these selectively bred animals provides clues to the causes of the genetic predisposition of humans to alcoholism. Eventually it is envisioned that the synteny between the mouse and human genomes will allow identification of specific genes responsible for acute effects of ethanol in both species as well as clues as to how alcoholism in humans can be better identified, prevented, and treated.

Surface exposure of synaptosomal gangliosides from long-sleep and short-sleep mice

A galactose oxidase/NaB[3H]4 technique was used to examine the relative surface exposure of gangliosides from whole brain synaptosomes of long-sleep (LS) and short-sleep (SS) mice. The surface exposure of the monosialoganglioside, GM1, did not differ between the two lines. Surface exposure of the polysialogangliosides GD1a, GD1b, and GT1b, however, was significantly greater in LS synaptosomes than in SS. Hydrolysis of the polysialogangliosides by neuraminidase to the end-product, GM1, at early time periods occurred more rapidly in LS than in SS synaptosomes. Upon exposure to either 250 mM or 50 mM ethanol, LS synaptosomal ganglioside surface exposure was decreased, but that of SS was increased. Pairwise comparisons of the individual ganglioside classes indicated that the decrease in LS synaptosomal ganglioside surface exposure was attributable to decreases in the polysialogangliosides, compared with controls. The ethanol-induced increase in SS synaptosomal ganglioside surface exposure, however, was mainly due to an increased surface exposure of only GD1a. These results suggest that intrinsic differences in the surface exposure of gangliosides and/or the magnitude and direction of ethanol-induced changes in ganglioside surface distribution may reflect biophysical or modulatory mechanisms by which this class of compounds modifies membrane sensitivity to ethanol. These results suggest that further studies should be performed to determine whether gangliosides are factors in genetically determined sensitivity to ethanol.

Alcohol intoxication and sialic acid in erythrocyte membrane and in serum transferrin

Microheterogeneity of serum transferrin as well as erythrocyte membrane sialic acid content were examined in alcoholic patients and healthy controls. Both the sialic acid content of erythrocyte membranes and of the circulating transferrin were significantly lower in alcoholic patients than in controls. A moderate daily ethanol intake (less than 80 g) allowed to observe a proportional relationship between alcohol intake and the carbohydrate deficient forms of transferrin, and also a correlation between alcohol intake and the membrane sialic acid content. This supports the hypothesis of ubiquitary alterations of glycosylations in connection to ethanol intoxication. Additional disturbances could explain the absence of correlations between membrane sialic acid, pattern of abnormal forms of serum transferrin, and alcohol intake in heavy alcoholic patients.

Carbohydrate-deficient transferrin (CDT) in serum in women with early alcohol addiction

Carbohydrate-deficient transferrin (CDT) in serum was determined by micro anion exchange chromatography and a transferrin radioimmune assay in 58 consecutive women treated for early alcohol dependence compared, with 62 healthy females with an alcohol consumption of 0-15 g of ethanol/day. The upper normal CDT level was 74 mg/l. CDT was elevated above this value in 83% of the alcoholic women with an intake of 60 g of ethanol/day or more for at least 7 days within the preceding two weeks. CDT values were significantly positively correlated with daily alcohol consumption but not with GT, ASAT, ALAT or MCV. During abstinence CDT level declined exponentially with a half-life of 14 +/- 3 days. The results indicated that CDT may be as sensitive and specific a marker in women with early alcohol addiction as in previously studied male alcoholics. The amount of alcohol consumed appeared to be more important than sex or liver function. Determination of CDT may thus offer a means for early objective diagnosis and adequate treatment also of women in early stages of alcoholism.

Carbohydrate-deficient transferrin in serum in patients with liver diseases

Carbohydrate-deficient transferrin (CDT) in serum was analyzed by isocratic microanion exchange chromatography at pH 5.65 followed by a transferrin radioimmunoassay in 102 patients with biopsy-verified liver diseases. CDT values were normal in all of the 87 nonalcohol-abusing patients irrespective of type or degree of liver disease. Thirteen of the 15 alcoholic patients (87%) with current abuse showed elevated CDT values while in abstaining alcoholics with remaining liver disease the values were normal. No correlations were found between CDT level and volume density of liver fibrosis or steatosis or values of a number of clinicochemical liver tests. The only significant correlation demonstrated was between CDT concentration and the level of present daily alcohol consumption in the alcoholic patients. These results indicate that CDT can be used as a marker of present but not previous alcohol abuse, even in patients with various liver diseases.

Gangliosides of long sleep and short sleep mouse cerebellum and hippocampus and cerebellar and whole brain synaptosomal plasma membranes

Gangliosides appear to be factors in CNS membrane responses to ethanol. Responses of membranes to ethanol might be influenced by the membrane concentration of gangliosides, the distribution of ganglioside molecular species, or the surface orientation of gangliosides at the plasma membrane surface. To determine the importance of these influences to the acute effect of ethanol, we have chosen to study them in long sleep (LS) and short sleep (SS) mice. This report presents our findings on the composition of gangliosides from LS and SS mouse cerebellum and hippocampus, the composition of gangliosides from synaptosomal plasma membranes (SPM) of LS and SS mice, and the molecular species of cerebellar gangliosides from the two lines. It has been found that GM1 is elevated in the cerebellum and in cerebellar SPM of LS mice compared to SS mice, but that there is no difference between the GM1 concentration in the whole hippocampus of the two lines. Further, there are no differences in the molecular species of the cerebellar gangliosides of LS and SS mice.

Micro anion exchange chromatography of carbohydrate-deficient transferrin in serum in relation to alcohol consumption (Swedish Patent 8400587-5)

A new simplified and rapid method for detection and quantitation of "carbohydrate-deficient transferrin" in serum is described. The method is based on isocratic anion exchange chromatography of isotransferrins in disposable microcolumns followed by a double antibody transferrin radioimmune assay. This technique, which separates all transferrin components isoelectric above pH 5.65, showed a very good reproducibility and accuracy with a coefficient of variation between 5 and 9%. 77 alcoholic patients could be clearly separated from 80 healthy "normal consumers" and 33 total abstainers with a specificity of 100% and a sensitivity of 91%. The values were significantly correlated to the amount of alcohol consumed during the latest month, and declined in abstaining alcoholics with a mean biological half-life of 17 days. Elevated levels occasionally appeared in healthy individuals after daily consumption of 60 g of ethanol during a 10-day period. In a sample of 187 patients with nonalcohol-related conditions only 2% false-positive values were found. This method is suggested as a potential tool for detecting and monitoring alcohol abuse.

Glycoprotein sialyl- and galactosyl transferase activities in erythrocyte membranes in alcoholic patients and healthy controls

In investigating possible mechanisms underlying carbohydrate deficiencies in serum transferrin and erythrocyte membranes in alcoholics, a total of 27 alcoholic patients and 27 healthy controls were examined for the activities of sialytransferase in serum and erythrocyte membranes and galactosyltransferase in erythrocyte membranes. The enzymes were assayed with endogenous and different exogenous glycoprotein acceptors and with [14C] CMP-sialic acid and [14C] UDP-galactose as substrates. No decrease in enzyme activities were found in alcoholic patients compared to controls, indicating that chronic ethanol abuse does not exert any direct inhibitory effect on these glycosyltransferases in isolated erythrocyte membranes or on sialytransferase in serum. Further studies of the effect of ethanol on the metabolism of complex carbohydrates are clearly necessary.

Carbohydrate composition of serum transferrin in alcoholic patients

Previous studies have shown that sialic acid-deficient isotransferrins appear in serum during chronic alcohol abuse. In this investigation whole serum transferrin from alcoholic patients and healthy controls was isolated by antitransferrin affinity chromatography and the total levels of sialic acid, galactose, N-acetylglucosamine, and mannose were analyzed. The results showed that the concentrations of sialic acid and galactose as well as N-acetylglucosamine were reduced in all of the alcoholics studied. These findings indicate that chronic ethanol misuse exerts a more complex effect on the glycans of transferrin than previously realized.