Ethanol and brain protein synthesis

Protective influence of zinc against the deleterious effects of ethanol in postimplantation rat embryos in vivo

Zinc is a cofactor for alcohol dehydrogenase, the ethanol metabolizing enzyme. Ethanol-induced zinc deficiency could decrease ethanol metabolism, resulting in an increase in circulating and tissue ethanol levels. This may cause retardation in embryonic growth and development. The influence of zinc supplementation on ethanol-induced embryopathy was studied by the simultaneous administration of ethanol and zinc to pregnant SD rats from gestational day 6 through 12. Ethanol was given in the form of a liquid diet and zinc was administered intraperitoneally. The ethanol group received the liquid ethanol diet, the ethanol+zinc group received the ethanol diet and zinc and the pair-fed control group was given an isocaloric control diet. Embryos were explanted from all groups on day 12 of gestation. Embryos of animals treated with ethanol alone exhibited a significantly higher rate of resorption and retarded embryonic growth and development compared to the pair-fed control group. The embryonic protein content, crown-rump length, the number of somites and embryonic morphological score were significantly reduced in the ethanol-treated group. In addition, serum zinc concentration also was lower. Compared to embryos from ethanol-treated animals, embryos from ethanol+zinc treated animals showed a significantly higher number of somites; cardiac development was more advanced and embryonic protein content was higher. These observations suggest that zinc supplementation of ethanol-treated pregnant rats may have some protective influence against the embryopathic effects of ethanol.

Subacute ethanol consumption reverses p-xylene-induced decreases in axonal transport

Human exposure to organic solvents is often complicated by ethanol ingestion and the literature is replete with demonstrations of metabolic interactions between ethanol and organic solvents at a pharmacokinetic level. Because of the possible modulation of xylene toxicity by ethanol consumption, the present group of studies characterizes the effect of ethanol on the p-xylene-induced decrease in axonal transport in the rat optic system previously reported by our laboratory. Long-Evans, hooded, male rats were divided randomly into two groups: those receiving 10% ethanol in their drinking water and those receiving water only. These two groups were further subdivided into two groups which were either exposed by inhalation to 1600 ppm p-xylene for 6 h/day, 5 days/week for 8 exposure-days or were treated identically except that they were exposed to air while in the inhalation chambers. The ethanol-drinking rats were given ethanol 6 days prior to and on the days of the inhalation exposure. Immediately after removal from the inhalation chambers on the last exposure day, the animals were injected intraocularly with [35S]methionine and [3H]fucose to measure the synthesis and rapid axonal transport of proteins and glycoproteins, respectively, in the retinal ganglion cells. The animals were sacrificed 20 h later, and the amount of radioactivity in different areas of the retinal ganglion cells was determined by liquid scintillation counting. As in previous experiments, the xylene exposure group showed a significant reduction in axonal transport of proteins and glycoproteins, whereas the ethanol exposure alone produced no significant reductions in the transport of either proteins or glycoproteins. In the animals receiving both ethanol and xylene, however, the ethanol treatment prevented the decreased transport characteristic of the xylene only animals, i.e. in all areas of the optic projections the level of transport were similar to the level present in the control groups. These data suggest that the xylene-induced reduction in rapid axonal transport was reversed (or prevented) by subacute ethanol consumption.

Effect of prenatal exposure to ethanol on the ultrastructure of layer V of mature rat somatosensory cortex

Recent data have shown that the structure and function of layer V pyramidal neurons, e.g. corticospinal neurons, is altered by prenatal exposure to ethanol. We examined the effect of ethanol on the ultrastructure of layer V in somatosensory cortex. Timed pregnant rats were fed a diet containing 6.7% (v/v) ethanol (E) or pair-fed a nutritionally matched control diet (C). Thirty-day-old offspring of these mothers were prepared by standard electron microscopic techniques. The somata of pyramidal and local circuit neurons and the neuropil were analysed. Prenatal exposure to ethanol induced alterations in the somata of both populations of neurons. The parallel stacking of cisternae characteristic of C-treated rats was disorganized in E-treated rats. Moreover, the Golgi complex and lysosomes occupied a larger fraction of the somata of E-treated rats. The number and frequency of symmetric axosomatic synapses, but not asymmetric axosomatic synapses, formed by both types of neurons were significantly greater in E-treated rats. Gestational exposure to ethanol produced a variety of changes in the neuropil. Dendrites, particularly dendritic shafts, occupied less space in E-treated rats. In contrast, axons accounted for significantly more of the neuropil in E-treated rats than in controls. This increase in axonal space was due to a significantly greater coverage by non-myelinated axons and a significantly smaller coverage by myelinated axons in E-treated rats than in C-treated rats. Although the overall frequency of synapses was similar in both treatment groups, there were significantly more asymmetric synapses in E-treated rats, and most of these were axospinous synapses. These differences may contribute to documented physiological changes such as the lower rate of glucose utilization in layer V of somatosensory cortex of E-treated rats and they may underlie the mental retardation which is characteristic of children with foetal alcohol syndrome.

Preparation of a cell-free extract from rat brain which can initiate protein synthesis in vitro

A cell-free protein synthesis system, derived from brains of 3 mo-old male Fischer-344 rats, has been characterized. The optimum conditions for amino acid incorporation in the system were 5 mM magnesium ion and 200 mM potassium ion. Incorporation depended on the addition of ATP, GTP, and an energy-generating system, and was sensitive to addition of the drugs aurintricarboxylic acid and sodium fluoride, inhibitors of initiation of protein synthesis. Both 40S and 80S initiation complexes were labeled in vitro, using [35S]methionine. Such labeling was sensitive to the protein synthesis inhibitors, aurintricarboxylic acid and sodium fluoride. The system, which can initiate protein synthesis, should be of use for examining mechanisms which underlie alterations in rat brain protein synthesis induced by various treatments.

Ethanol and brain protein synthesis in the rat in vivo

The effect of ethanol consumption (27% of calories) for 21 days, concomitant with a low-protein (6% calories) or a normal protein diet (17.5% calories), on tyrosine kinetics and protein synthesis in the brain, was investigated. Ethanol consumption did not affect tyrosine concentrations in the plasma, cerebellum, forebrain or olfactory bulb but increased significantly the rate of synthesis of total mixed protein in the forebrain and cerebellum. This effect was observed in rats fed on both dietary protein regimes.

Effects of ethanol, given during pregnancy, on the offspring dopaminergic system

The fetal alcohol syndrome is characterized by a number of abnormalities consisting of a pre- and post-natal growth deficiency, microcephaly, areas of abnormal nerve cell migration in the brain, mental and psychomotor retardation in children of alcoholic women. These findings may be referred as a teratogenic effect of ethanol on the central nervous system. In order to investigate the above ethanol-neurotoxic effect the striatal dopaminergic transmission was studied. The dopaminergic turnover was measured by 3,4-dihyroxyphenilacetic acid content and 3H-Spiperone binding has been carried out to determine dopaminergic receptor alterations induced by chronic ethanol consumption during pregnancy. Our work demonstrates long-lasting modifications of dopaminergic neuronal function after exposure of the experimental animal to ethanol during fetal life. In particular, a decreased receptor function has been observed in rats exposed to ethanol only during the perinatal period. In the same group of rats, diminished receptor activity leads to an enhancement in DOPAC content still detectable after a long period from cessation of ethanol treatment. Neurochemical data are reinforced by behavioral observations. In fact, a significant decrease of spontaneous locomotor activity in the rats chronically treated with ethanol during fetal life was observed. In addition, the altered response of locomotor activity after drug administration may be ascribed to the modified dopaminergic function. With this experimental approach we assume that the action of ethanol on the central nervous system may be a marker of its teratogenic effect.

Effect of daily oral intake of manganese on free polysomal protein synthesis of rat brain

The effect of manganese on free polysomal protein synthesis of immature rat brain (3 weeks old) has been determined after 1, 2, 3, and 4 weeks of daily intake of 55 micrograms manganese/ml of drinking water. The protein synthesis was inhibited up to 35% during the first 3 weeks and returned toward the control level during the fourth week of treatment. Cross-incubation experiments with polysomes and pH 5 enzyme fractions indicated that the inhibition of protein synthesis is due to alteration of the pH 5 enzyme fraction. Furthermore, cerebral t-RNA content was reduced by 20% during the first 3 weeks and also returned to the control level after 4 weeks. The data suggest that the previously reported retardation in learning and memory of manganese treated immature rats may partly be due to alteration of cerebral RNA and protein synthesis. It was also evident that an adaptation mechanism to the observed effect of manganese developes after three weeks of daily intake of 55 micrograms manganese/ml.

Effect of ethanol on nucleolar structure: a cytological indication of change in RNA/protein synthesis

The effects of chronic ethanol ingestion on an organelle known to be involved in protein synthesis were studied cytologically in nerve cells of the adult hamster. Twenty-six animals were administered standard laboratory chow and either tap water (controls) or a 15% ethanol solution (experimentals) for a period of 7 weeks. Brains were perfusion-fixed, sectioned transversely, and stained with buffered thionin for microscopic analysis. Reported here are changes in an RNA-rich intranucleolar body (INB) seen in facial motor neurons and cerebellar Purkinje cells of the golden hamster. After chronic ethanol ingestion, the size and frequency of the INB increased significantly in both cell populations. Theoretical considerations are discussed concerning the correlation between this apparent storing of nucleolar RNA/RNP and the biochemical evidence of other investigators for ethanol-induced alterations in RNA/protein synthesis and utilization in neurons.

Lipofuscin granules in Purkinje cells after long-term alcohol consumption in rats

The increased number of lipofuscin granules in Purkinje cells from chronic alcohol-fed rats was studied by morphometric methods. These granules were autofluorescent and had marked acid phosphatase activity. No significant changes were found in the mean nuclear and perikaryon volumes when alcohol-fed and control groups were compared. The number of lipofuscin granules per unit of surface area of cell cytoplasm (Na) and their volumetric density (Vv) were significantly greater in alcohol-fed groups than in controls. These values were also significantly different when the 6- and 12-month control groups were compared. Na and Vv values in alcohol-fed groups increased progressively. The increased number is probably related to disturbances in neuronal cell metabolism. The importance of age and malnutrition in the formation of these granules was also considered.

The neurotoxicity of ethanol

Alterations in nervous system functioning following acute and chronic ethanol exposure have been studied in a great number of experimental investigations. Results from many of these investigations can be difficult to interpret, particularly since a variety of techniques and exposure models are employed. This review emphasizes those studies which, in the opinion of the author, fit into a pattern where results from studying one function of the nervous system is in accordance with results from studying another. Thus, the fluidizing effect of ethanol on the neuronal membrane - an effect which ethanol shares with anaesthetics - leads to a change in protein function which in turn affects ion transport such as Na+ and Ca++ across the membrane due to changes in the ion channels. Cation influx is probably directly coupled to neurotransmitter release which is in agreement with the finding that ethanol exposure results in inhibition of Na+ and Ca++ current as well as acetylcholine release. The sensitization of the dopaminergic system after ethanol exposure may also be related to the changes in cation flux, and the changes in this system probably play a crucial rôle in the development of tolerance and withdrawal symptoms. Other aspects such as impairment of protein synthesis, altered GABA function of impairment of neuron excitability and conduction are more difficult to place in proper perspective. The rôle of acetaldehyde in acute as well as chronic ethanol intoxication also remains a controversy. These may, however, be secondary phenomena to primary changes in different part of the nervous system not necessarily important in the clinical situation. Behavioural and anatomical studies particularly from recent years have shown that experimental animals develop memory disturbances following chronic exposure even when kept on sufficient diet. These findings argue strongly for a direct toxic effect of ethanol, and are furthermore compatible with behavioural changes in chronic alcoholics, dominated by memory impairment. Since it has been argued that the cholinergic system plays a significant rôle for memory function, a possible explanation for some of the psychological and anatomical deficits caused by ethanol is thus the changes in the function of the cholinergic system particularly in the hippocampal regions.

Protein turnover in brain during the development of alcohol dependence

The chronic effect of ethanol on central nervous system protein turnover was investigated in selected regions of brain following intoxication and withdrawal in a strain of ethanol preferring mice. Mice were serially injected with [14C]glucose in order to achieve a constant specific radioactivity of brain glutamate. Protein turnover was calculated from the specific activities of extracted protein and free glutamate. Results from these studies show that ethanol causes a significant increase in protein turnover in all sections of brain. The brain protein turnover in animals following alcohol withdrawal also shows an increase which deviates significantly from controls in 2 of the 3 regions examined.

Cognitive impairment and other psychological scores derived from the content analysis of speech in detoxified male chronic alcoholics

Sober chronic alcoholic males, sober nonalcoholic males, and intoxicated nonalcoholic males were assessed along several psychological dimensions by means of the content analysis of speech. Average cognitive impairment scores were significantly greater among intoxicated nonalcoholics than sober chronic alcoholics and significantly greater in sober chronic alcoholics than in sober nonalcoholics. Sober chronic alcoholics, also, had a significantly higher score than sober nonalcoholics on depression, social alienation-personal disorganization (schizoid traits), separation, guilt, and diffuse anxiety, and hostility inward. The general mental health, including cognitive function, of sober chronic alcoholics is clearly impaired when compared to sober nonalcoholic individuals.

Maternal ethanol consumption and synaptic membrane glycoproteins in offspring

The present study was undertaken to assess the influences of chronic maternal ethanol consumption, prior to and during gestation, on the development of synaptic plasma membranes (SPMs) and on the synthesis of SPM glycoproteins in offspring. Comparisons were made between animals whose mothers were pair-fed a control or 6.6% (v/v) ethanol liquid diet in which protein accounted for either 18% (original) (C & E) or 21% (revised) (*C & *E) of the calories. In addition, groups of pups that were either cross-fostered (*C & *E) with chow-fed surrogate mothers or reverse cross-fostered (offspring of chow-fed mothers with *C & *E mothers) were examined. Ethanol and matched (same dietary group) control pups had comparable brain and body weights, brain protein content, and yield of SPM proteins during the 10-24 day age period examined. However, the yield of SPM proteins from ethanol and control offspring of and/or reared by the three groups of rat mothers that received the *E and *C liquid diets was greater than that of the offspring of rats that were fed the original diets. This suggests that the original diets were not nutritionally adequate for pregnant rats. Despite the fact that the content of SPM proteins was comparable in ethanol and matched control pups, the offspring of ethanol-treated rats had an abnormal distribution of [3H]- or [14C]-fucose-derived radioactivity among SPM glycoproteins. The SPM abnormalities were most severe in the non-cross-fostered offspring of E rats. No SPM glycoprotein abnormalities were found in the reverse cross-fostered group. The results of the present study demonstrate that chronic maternal ethanol consumption prior to parturition has a severe effect on the synthesis of SPM glycoproteins in developing offspring without affecting the content of SPMs per se. It also demonstrates the importance of optimizing the composition of liquid diets used to feed pregnant rats.

Ethanol-induced changes in properties of rat brian ribosomes

Altered in vivo and in vitro brain protein metabolism have been demonstrated in rodents following long-term ethanol ingestion. In the present study, ethanol effects were examined on properties of brain ribosomes of male Sprague-Dawley rats ingesting a specially formulated Lieber-DeCarli liquid diet. The development of physical dependence was demonstrated by the presence of withdrawal reactions within 24 hr of ethanol abstinence. Data showed significant inhibition of in vitro protein synthesis by ribosomes from the "ethanol" and "1-day-withdrawn" groups. Partial reversal of inhibition occurred by using a control brain pH 5 enzymes source instead of the matched source. The observed [14C]leucine-incorporating activity was temperature dependent, with the optimum temperature being 37 degrees C. The determination of the state of ribosomal aggregation showed an increased monosomes--disomes ratio in the "ethanol" group. The ratio was even more increased in the "1-day-withdrawn" group. Data suggest that reduced ribosomal binding to stable mRNA may be a contributing factor in the ethanol-induced effects on protein synthesis.

Ethanol induced changes of in vitro protein synthesis during the development and maturation of brain tissue

Decreased protein synthesis in a cell free system of brain has been reported for male adult rats following chronic ethanol ingestion. To assess the developmental and maturational changes occurring in the neonatal brain, the effects of pre- and postnatal maternal ingestion of ethanol were determined. For these studies young female rats were given a 10% w/v ethanol/water solution for varying periods after impregnation and seven days post pregnancy. Data showed that maternal ethanol ingestion produced a large deficit in the in vitro incorporation of (14C) leucine into the hot TCA extractable residue of ribosomes of neonatal brain. Maximum inhibition was obtained when ethanol was given postnatally. To determine the molecular sites of ethanol's action, ribosomes and pH 5 enzymes from the adult and neonatal brain were examined. Data showed that the highest activity was obtained with control neonatal brain enzymes and ribosomal fractions.

Mutagenic, cancerogenic and teratogenic effects of alcohol

Alcohol is mutagenic, cancerogenic and teratogenic in man. Ethanol is mutagenic via its first metabolite, acetaldehyde. This is substantiated by the findings that acetaldehyde induces chromosomal aberrations, sister-chromatid exchanges and cross-links between DNA strands. Methanol, a contaminant of many alcoholic beverages, is also mutagenic via its metabolite, formaldehyde. In addition, different indirect pathways may lead to mutations by alcohol. The cancerogenic activity of alcohol remains unverified by modern standard carcinogenicity tests. Ethanol and other alcohols, as well as aldehydes, inhibit RNA synthesis in cells and in cell-free transcriptional systems. A reduction of cellular RNA synthesis may play an important role in the mutagenic, carcinogenic and teratogenic activity of alcohol.

Comparative effects of chronic ethanol and acetaldehyde exposure on myocardial function in rats

This study was conducted to compare separately the chronic effects of high blood levels of ethanol and acetaldehyde on the metabolism of the heart. Levels of ethanol and acetaldehyde were altered by administration of either 4-methylpyrazole (4-MP), a potent alcohol dehydrogenase inhibitor, or pargyline (PAR), a monoamine oxidase inhibitor that markedly increases acetaldehyde levels in the blood following ethanol administration. Measurements were made in rats consuming ethanol for three to four weeks. Mitochondrial respiration, in vitro contractility of glycerinated heart muscle fibers, and myocardial protein synthesis were determined. As compared to animals receiving only ethanol, administration of either-4-methyl-pyrazole or pargyline plus ethanol resulted in more severe damage to mitochondrial respiration and myocardial protein synthesis. The data illustrate that both acetaldehyde and ethanol in high concentrations can cause severe damage to myocardial metabolism.

Effects of chronic ingestion and withdrawal of sodium barbitone on learning in rats

Rats were submitted to three different manipulations: chronic ingestion of sodium barbitone, which was added to the drinking water; chronic administration of barbitone and subsequent withdrawal of the drug; and drinking water only. Both groups of experimental animals showed deficient acquisition in both shuttle-box avoidance and passive-avoidance response when compared to the control animals. Nevertheless, no impairment was observed in passive avoidance when the period of withdrawal was 15 days. Neither was impairment observed when the animals were tested in a T-maze or in another appetitive task. These results cannot be explained by differences in weight or fluid consumption.

Effect of chronic administration and withdrawal of sodium barbitone on protein synthesis of rat brain

After chronic administration of sodium barbitone to rats, a marked increase incorporation of [14C]-Leucine into isolated nerve endings was observed. Withdrawal of the drug resulted in a decreased incorporation with respect to values obtained with chronic ingesting animals. On the other hand chronic administration of the barbiturate produced a decreased incorporation in mitochondrial and microsomal fractions. These results are discussed in relation to the development of tolerance and abstinence syndrome to this drug.

Studies on the effects of chronic ethanol ingestion on the properties of rat brain ribosomes

Previous observations have demonstrated decreased in vivo and in vitro protein synthesis by brain ribosomal systems following long-term ethanol ingestion. For further investigation of the properties of brain ribosomes, the 40S and 60S ribosomal subunits were successfully isolated from control and chronic 10% ethanol-drinking rats. For a successful dissociation of ribosomes into subunits NH4Cl, puromycin and a high-salt treatment at 10 degrees C were essential with a critical concentration of Mg2+ since ribosomes could not be resolved at less than 7 mM Mg2+. Analysis of the A260 profile of the subunits on the sucrose gradients showed no significant differences between the control and ethanol-ingesting groups. Studies on 3H-labeled ribosomes following in vivo RNA labeling showed correspondence of the radioactive profiles from the incorporation of [5(-3) H) orotic acid into RNA with the sucrose gradient absorbance profile of 60S and 40S ribosomal subunits. Furthermore, active reassociation of both subunits occurred at 37 degrees C as demonstrated by the increased [14 C]-phenylalanine incorporation in the presence of poly(U). Results further showed that the poly(U)-dependent [14C]phenylalanine incorporation was significantly reduced by the subunits from the ethanol-ingesting animals. These findings suggest that long-term ingestion of ethanol caused functional changes in the properties of brain ribosomes, specifically on the reassociation process of the two subunits.

Alterations in cell free brain protein synthesis following ethanol withdrawal in physically dependent rats

The effects of ethanol withdrawal were determined on cell free brain protein synthesis in physically dependent rats. Following the development of physical dependence, ethanol abstinence for 24 h resulted in decreased protein synthesis in cerebral tissue. The observed inhibition of [14C]leucine incorporation into protein was found to be reversible after 7 days of ethanol withdrawal. Although the ribosomes from control, ethanol-treated and ethanol-withdrawn animals were highly responsive to polyuridylic acid stimulation, the ribosomes from the control group consistently exhibited higher activity. The determination of protein content of the ribosomal fraction showed a significant increase following ethanol administration and was further enhanced by ethanol abstinence. The results suggest that ethanol-induced changes at the ribosomal level may result in defective association of mRNA causing depression of brain protein synthesis.

Alterations of macromolecule biosynthesis after chronic administration of opiates and ethanol

The literature concerning the effects of opiates, alcohol and barbiturates on RNA and protein metabolism is reviewed. Recent findings from this laboratory suggest that chronic morphine treatment increases the template activity of chromatin from oligodendroglial nuclei while chronic ethanol treatment decreases this activity. In addition, chronic morphine treatment stimulates protein synthesis in cell free systems and may increase the synthesis of discrete synaptic membrane proteins. Results from other laboratories suggest a general decrease in macromolecule biosynthesis with long term ethanol consumption. These results are discussed in terms of the possible roles of protein synthesis in the effects of chronic opiate and ethanol administration.

Effects of ethanol on brain metabolism

The influence of acute or chronic ethanol administration on the biochemical processes in brain and cerebral metabolic pathways has been discussed. Ethanol seems to affect cerebral carbohydrate metabolism mainly through increased glycogenolysis, although the possibility of decreased cerebral glucose utilization remains eminent. Ethanol affects the consumption of oxygen by the brain tissue presumably through alterations in the brain cell membranes. Inhibition of Na+-K+-ATP-ase observed during ethanol intoxication is suspected to result in alterations in the membranes of the nerve cells. Isotope studies in addition to total respiratory carbon dioxide production strongly suggest the inhibition of citric acid cycle function during ethanol metabolism. Although synthetic pathways for lipids do not seem to be affected by ethanol, lipid oxidation in the cerebral tissue is significantly inhibited. In addition to above mentioned alterations in the cerebral metabolic processes, ethanol also affects ionic transport processes, adenine nucleotides, and amino acid and protein metabolism. The metabolic consequences of such effects of ethanol have been discussed.