Ethanol can modify the effects of certain free radical-generating systems on astrocytes

The central nervous system is vulnerable to oxidative stress, especially when a toxicant can modify the physiological balance between anti- and pro-oxidant mechanisms. Among brain cells, astrocytes seem less vulnerable than neurons, but their impairment can dramatically affect neurons because of their protective role toward neurons. Ethanol is able to stimulate the formation of reactive oxygen species and modify the activity of most of the antioxidant agents. However, ethanol can react with the OH* radical to form the alpha-hydroxyethyl radical, which is considered to be less toxic. Ethanol also can stimulate H2O2 degradation through catalase activation. This study, therefore, sought to determine whether ethanol affected the sensitivity of astrocytes exposed to various free radical-generating systems. The cellular impact of such exposure was assessed by assays exploring cytotoxicity (i.e., NR (neutral red) and MMT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetiazolium bromide) reduction assays) and genotoxicity (comet assay) induced by these treatments. DNA alterations were evaluated by single-cell gel electrophoresis (comet assay), considered a precocious biomarker of intracellular alterations. After concomitant exposure to H2O2 and ethanol, the viability of astrocytes decreased significantly whereas the mean percentage of DNA in the tail increased,reflecting DNA damage (H2O2 was either directly added to the culture medium or endogenously produced from menadione). Ethanol also reduced the loss of viability and DNA alterations after exposure to OH* radicals produced by a Fenton system. The exposure to a xanthine/xanthine oxidase system had the same effect.     

Hypothalamic-Pituitary-Thyroid Axis in Chronic Alcoholism. II. Deiodinase Activities and Thyroid Hormone Concentrations in Brain and Peripheral Tissues of Rats Chronically Exposed to Ethanol

Thyroxine (T₄), triiodothyronine (T₃) concentrations, and the activities of the three deiodinase isoenzymes were measured in different brain regions and peripheral tissues of rats. According to an animal model of alcohol addiction, “behaviorally” dependent rats having lost control over their intake of ethanol were compared with alcohol-naive controls and ethanol-experienced, but “controlled” consumers. The two kinds of alcohol-experienced rats were investigated either 24 hr or 3 months after ethanol withdrawal. The results of these four groups were compared with those of an ethanol-naive control group. During withdrawal, the activities of type II 5′-deiodinase (which catalyzes deiodination of T₄, and T₃ in the CNS) in both the “behaviorally dependent” rats and the “controlled drinkers” were significantly lower than in the alcohol-naive controls in the frontal cortex, parieto-occipital cortex, hippocampus, and striatum, but not in the cerebellum or pituitary. Probably as a result, the tissue concentrations of T₄ were higher in areas of the CNS in the groups exposed to alcohol. However, the T₃ concentrations were normal. No relevant differences were seen between the activities of type III 5-deiodinase (which catalyzes the further deiodination of T₃) observed in these groups. Atter 3 months of abstinence, the type II 5′-deiodinase activities had almost returned to nomal in both “controlled drinkers” and “behaviorally dependent” animals, whereas type III 5-deiodinase activity was inhibited, possibly to maintain physiological concentrations of T₃ during abstinence. Indeed, the tissue levels of T₃ were normal in the areas of the CNS, and the T₄ levels were still elevated. However, the liver concentrations of T₃ and T₄ were significantly lower in the “behaviorally dependent” animals than in the “controlled” drinkers after 3 months of abstinence, whereas no differences were found between the T₄ and T₃ concentrations in the areas of the CNS investigated in the two groups exposed to ethanol. These results suggest that chronic administration of ethanol affects intracellular thyroid hormone metabolism in both rat CNS and liver in a highly complex manner. No direct evidence of ethanolinduced enhancement of tissue uptake or concentrations was obtained. However, taking into account the numerous similarities between the clinical picture of hyperthyroidism and the symptomatology of alcoholism, it may be hypothesized that ethanol may directly influence any step in the as yet unknown biochemical cascade of thyroid hormone function.     

β‐Endorphin Mediates Behavioral Despair and the Effect of Ethanol on the Tail Suspension Test in Mice

Background: The opioid peptide β‐endorphin (β‐E) is synthesized and released in response to stressful stimuli as well as acute alcohol administration. The release of β‐E following exposure to an inescapable aversive situation may mediate behaviors that contribute to allostasis of the stress response. The present study examines the effects of β‐E on immobility in assays involving inescapable stress, both under basal conditions and after acute administration of EtOH. Methods: Female and male transgenic mice with varying capacities to translate β‐E were subjected to either the forced swim (FST, Experiment 1) or the tail suspension test (TST, Experiment 2). In Experiment 3, mice were divided into three groups based on hormonal status (male, female‐estrous, and female‐nonestrous) and injected with either 1 g/kg EtOH or equivolume saline 14 minutes prior to behavioral assessment on the TST. Results: Experiments 1 and 2 demonstrated a direct relationship between β‐E levels and immobility. There were also sex differences in behavior in these tests, with males displaying more immobility than females. A main effect of genotype in Experiment 3 replicated findings in Experiments 1 and 2. There was also an effect of EtOH (increasing immobility) and a significant interaction reflecting a particularly robust effect of the drug in mice with low β‐E. In addition, there were interactions between β‐E, EtOH effects, and hormonal status. Conclusions: These findings support the contention that β‐E moderates behavioral responses to stressful stimuli and suggest a role for this peptide in coping behavior. Furthermore, the effects of EtOH on the response to stress may be mediated by β‐E. Sex differences in this influence may contribute to sex differences in disease susceptibility and expression.     

Differential Effects of Ethanol on Serum GABAergic 3α,5α/3α,5β Neuroactive Steroids in Mice,Rats, Cynomolgus Monkeys,and Humans

Background: Acute ethanol administration increases plasma and brain levels of progesterone and deoxycorticosterone‐derived neuroactive steroids (3α,5α)‐3‐hydroxypregnan‐20‐one (3α,5α‐THP) and (3α,5α)‐3,21‐dihydroxypregnan‐20‐one (3α,5α‐THDOC) in rats. However, little is known about ethanol effects on GABAergic neuroactive steroids in mice, nonhuman primates, or humans. We investigated the effects of ethanol on plasma levels of 3α,5α‐ and 3α,5β‐reduced GABAergic neuroactive steroids derived from progesterone, deoxycorticosterone, dehydroepiandrosterone, and testosterone using gas chromatography‐mass spectrometry. Methods: Serum levels of GABAergic neuroactive steroids and pregnenolone were measured in male rats, C57BL/6J and DBA/2J mice, cynomolgus monkeys, and humans following ethanol administration. Rats and mice were injected with ethanol (0.8 to 2.0 g/kg), cynomolgus monkeys received ethanol (1.5 g/kg) intragastrically, and healthy men consumed a beverage containing 0.8 g/kg ethanol. Steroids were measured after 60 minutes in all species and also after 120 minutes in monkeys and humans. Results: Ethanol administration to rats increased levels of 3α,5α‐THP, 3α,5α‐THDOC, and pregnenolone at the doses of 1.5 g/kg (+228, +134, and +860%, respectively, p < 0.001) and 2.0 g/kg (+399, +174, and +1125%, respectively, p < 0.001), but not at the dose of 0.8 g/kg. Ethanol did not alter levels of the other neuroactive steroids. In contrast, C57BL/6J mice exhibited a 27% decrease in serum 3α,5α‐THP levels (p < 0.01), while DBA/2J mice showed no significant effect of ethanol, although both mouse strains exhibited substantial increases in precursor steroids. Ethanol did not alter any of the neuroactive steroids in cynomolgus monkeys at doses comparable to those studied in rats. Finally, no effect of ethanol (0.8 g/kg) was observed in men. Conclusions: These studies show clear species differences among rats, mice, and cynomolgus monkeys in the effects of ethanol administration on circulating neuroactive steroids. Rats are unique in their pronounced elevation of GABAergic neuroactive steroids, while this effect was not observed in mice or cynomolgus monkeys at comparable ethanol doses.