Fatty acid composition of rat liver mitochondrial phospholipids during ethanol inhalation.

Male Sprague-Dawley rats were exposed to increasing concentrations (15-22 mg/l) of ethanol vapor over a 4-day period. Phospholipids were analyzed in liver mitochondria isolated from ethanol-treated and pair-weighted control animals. After a 2-day inhalation period, the proportion of monoenoic acids in total phospholipids increased, whereas that of arachidonic acid decreased. These changes were more striking in phosphatidylcholine (PC) than in phosphatidylethanolamine (PE). The decrease in 20:4 may be related to increased lipid peroxidation. After a 4-day inhalation period, quite different changes in phospholipid fatty acids were found. They consisted in a trend towards a more unsaturated system, the proportion of 20:4 being increased in PC and that of 22:6 in PE. This increase in polyunsaturated acids might be related to a direct ethanol effect on lipid structure and/or metabolism that would be linked to the high blood alcohol level present at this stage of ethanol intoxication.

Hepatic lipid peroxidation and mitochondrial susceptibility to peroxidative attacks during ethanol inhalation and withdrawal.

Male Sprague-Dawley rats were exposed to increasing concentrations (15-22 mg/l) of ethanol vapor over a 4-day period. The hepatic lipid peroxide level as well as the sensitivity of mitochondria and microsomes to peroxidative attacks were studied during the early stage of alcohol intoxication, at the end of the inhalation period and, finally, during withdrawal. The level of hepatic lipid peroxide started to increase significantly after the first day of ethanol inhalation, whereas the in vitro mitochondrial sensitivity to peroxidation induced by ADP X Fe3+ in the presence of an O(2)-generating system was still unaltered after a 2-day inhalation period. Both the hepatic peroxide level and the mitochondrial sensitivity to peroxidation were significantly enhanced at the end of the 4-day inhalation period. Such an enhancement was still apparent 24 h after withdrawal, a time at which no more ethanol was present in the blood. Lipid peroxidation returned to normal values only 48 h after withdrawal. Microsomes were less affected than mitochondria by the ethanol treatment. It is suggested that the alterations of lipid peroxidation are related to the presence and/or the metabolism of ethanol at an early stage of inhalation, whereas changes in the membrane structure would be responsible for the maintenance of enhanced lipid peroxidation 24 h after ethanol withdrawal.

Implication of free radical mechanisms in ethanol-induced cellular injury.

Numerous experimental data reviewed in the present article indicate that free radical mechanisms contribute to ethanol-induced liver injury. Increased generation of oxygen- and ethanol-derived free radicals has been observed at the microsomal level, especially through the intervention of the ethanol-inducible cytochrome P450 isoform (CYP2E1). Furthermore, an ethanol-linked enhancement in free radical generation can occur through the cytosolic xanthine and/or aldehyde oxidases, as well as through the mitochondrial respiratory chain. Ethanol administration also elicits hepatic disturbances in the availability of non-safely-sequestered iron derivatives and in the antioxidant defense. The resulting oxidative stress leads, in some experimental conditions, to enhanced lipid peroxidation and can also affect other important cellular components, such as proteins or DNA. The reported production of a chemoattractant for human neutrophils may be of special importance in the pathogenesis of alcoholic hepatitis. Free radical mechanisms also appear to be implicated in the toxicity of ethanol on various extrahepatic tissues. Most of the experimental data available concern the gastric mucosa, the central nervous system, the heart, and the testes. Clinical studies have not yet demonstrated the role of free radical mechanisms in the pathogenesis of ethanol-induced cellular injury in alcoholics. However, many data support the involvement of such mechanisms and suggest that dietary and/or pharmacological agents able to prevent an ethanol-induced oxidative stress may reduce the incidence of ethanol toxicity in humans.

Effects of chronic ethanol administration on free radical defence in rat myocardium.

Cellular protection against free radical reactions was measured in myocardium from ethanol-fed rats using ethanol administration in drinking water as a model of moderate alcohol intoxication. The activities of Cu,Zn-superoxide dismutase (SOD) and glutathione-S-transferase were higher in ethanol-fed rats than in controls, whereas Mn-SOD, catalase and glutathione peroxidase activities were not altered by ethanol treatment. Myocardial zinc was higher and selenium concentration lower in ethanol-fed rats than in controls. Ethanol consumption, which failed to modify the myocardial vitamin E level, did not result in increased lipid peroxidation, but decreased cytosolic and membraneous protein thiols.

Changes in some pro- and antioxidants in rat cerebellum after chronic alcohol intake.

Some pro- and antioxidants were measured in the cerebellum from ethanol-fed rats using ethanol administration in drinking water as a model of moderate alcohol intoxication. After 4 weeks of ethanol intake, a 30% increase in the nonheme iron content in the cerebellum occurred in ethanol-fed rats as compared to control animals. The low-molecular-weight-chelated iron (LMWC-Fe) content as well as the percentage of total nonheme iron represented by LMWC-Fe were increased in the cerebellar cytosol after chronic ethanol administration. Cerebellar copper and selenium concentrations were lower and zinc concentration higher in ethanol-fed rats than in controls. Ethanol consumption decreased the cerebellar vitamin E level. Glutathione S-transferase [EC 2. 5. 1. 18] activity was higher, whereas glutathione peroxidase [glutathione: H2O2 oxidoreductase, EC 1. 11. 1. 9] activity was not altered by ethanol treatment. No significant changes in cerebellar lipid peroxidation, carbonyl protein content, or glutamine synthetase [L-glutamate:ammonia ligase (ADP-forming) EC 6. 3. 1. 2] activity were observed. These results suggest that adaptative increases in some elements of the antioxidant defense may counteract the increase in LMWC-Fe, a pro-oxidant factor, and prevent the occurrence of overt cellular lipid and protein damage. However, after 8 weeks of ethanol intake, the activity of glutamine synthetase, an enzyme specially sensitive to inactivation by oxygen radicals, was decreased, suggesting that this prevention was not totally achieved.

Effects of acute ethanol administration on the uptake of 59Fe-labeled transferrin by rat liver and cerebellum.

The uptake of iron by the liver and cerebellum was measured in rats using [59Fe]transferrin. An acute ethanol load (50 mmol/kg body wt., i.p.) elicited a significant increase in the hepatic and cerebellar non-heme iron concentration. The uptake of 59Fe by the liver and the cerebellum was significantly greater in the ethanol-treated rats than in control animals. The administration of allopurinol prior to the ethanol load prevented the changes in liver and cerebellar non-heme iron content. Moreover pretreatment with allopurinol reduced the ethanol-induced enhancement of 59Fe uptake by the liver and completely prevented the changes in 59Fe uptake by the cerebellum. These effects of allopurinol lead us to suggest that oxygen-derived free radicals are involved in the ethanol-induced disturbances of iron uptake both at the hepatic and cerebellar level.

Effect of acute ethanol administration on the subcellular distribution of iron in rat liver and cerebellum.

An acute ethanol load (50 mmol/kg, i.p.) produced altogether a decrease in the non-heme iron content of the serum and an increase in the iron content in liver and cerebellum. Subcellular fractionation studies indicated that the non-heme iron accumulated by the liver, 4 hr after the ethanol load, was recovered in light mitochondria, microsomes and cytosol, and that iron accumulated by the cerebellum was localized in heavy mitochondria, light mitochondria, microsomes and cytosol. The low molecular weight chelatable (LMWC) iron content as well as the percentage of total non-heme iron represented by LMWC-iron were increased in the cytosol of liver and cerebellum after the ethanol load. These results suggest that an acute ethanol load induces (i) a shift in the distribution between circulating and tissular non-heme iron; (ii) an increase in the cytosolic LMWC-iron which, by favouring the biosynthesis of reactive free radicals, may contribute to lipid peroxidation in liver and cerebellum.

Acute ethanol effects on rat liver tryptophan oxygenase and tyrosine aminotransferase.

In starved rats, ethanol administered acutely enhances tryptophan oxygenase (TO) and tyrosine aminotransferase (TAT) activities. Ethanol also inhibits the early phase of the cortisol-mediated TO and TAT induction. Ethanol administered at the same time as tryptophan does not modify the tryptophan-mediated TO and TAT induction. In cortisol-pretreated rats, ethanol enhances the subsequent TO and TAT induction whereas no additive effects are observed when ethanol is injected together with tryptophan. These results suggest that ethanol mimics the effects of tryptophan on TO and TAT activities. In fed animals, ethanol alone does not result in increased TO and TAT activities, but inhibits their cortisol induction. It increases TO activities when given together with a tryptophan dose which, when given alone, does not enhance these activities. It is suggested that the observed inhibitory effects of ethanol on cortisol-mediated TO and TAT induction in starved and fed animals are related to a defective cortisol transport in the liver cells.

[Alcohol and free radicals: from basic research to clinical prospects]. / Alcool et radicaux libres: de la recherche fondamentale aux espoirs cliniques.

An oxidative stress occurs in the liver of rats following various conditions of ethanol administration. The ethanol-inducible cytochrome P450 2E1 plays a key role in its generation, favoured itself by an increase in the "redox-active " fraction of intracellular non-heme iron. Administration of ethanol elicits the generation of the 1-hydroxyethyl radical, which has been identified in vivo. Its reactivity contributes to alcohol-induced immunological disturbances. Liver inflammatory and fibrotic disorders can be reproduced in rats by long-term ethanol administration associated with a high fat diet. The severity of these disorders is correlated to the intensity of the oxidative stress. Some conditions of ethanol administration to rats also elicit an oxidative stress in the myocardium and central nervous system. Through its inhibitory effect on glutamine synthetase activity and resulting excitotoxicity it may contribute to neuronal death and possibly to dependence on alcohol. Disorders related to an oxidative stress were also reported in the serum and erythrocytes as well as in liver biopsies from alcoholic individuals. Their detection may be useful to follow the evolution of alcoholic liver diseases. Supplementation with antioxidants such as vitamin E may be considered in the prevention of severe cellular disorders in individuals consuming large amounts of alcoholic beverages. An increase in free radical production is likely playing a role in the induction of severe cellular damage linked to repeated withdrawals occurring as a result of heavy and sporadic ethanol intake.

[Alcohol, iron and oxidative stress]. / Alcool, fer et stress oxydatif.

An oxidative stress has been reported to occur at the hepatic level after ethanol administration. We recently reported that such a stress is also apparent at the cerebellar level during acute ethanol intoxication in rats. Since low molecular weight iron chelates (LMW-Fe) are involved in the biosynthesis of aggressive prooxidant species we presently studied the influence of acute and chronic ethanol administration on hepatic and cerebellar total non-heme iron and LMW-Fe. The results show that an acute ethanol load (50 mmoles/kg b. wt.) administered (i.p.) to male Sprague-Dawley rats elicits altogether a decrease in the non-heme iron content of the serum and a highly significant increase in the hepatic and cerebellar non-heme iron concentration. The LMW-Fe content as well as the percentage of total non-heme iron represented by LMW-Fe are increased at the same time in the cytosolic fraction isolated from hepatic and cerebellar homogenates of the acutely ethanol-treated rats. The ethanol-induced disturbances in the non-heme iron content of liver and cerebellum can be prevented by the administration of allopurinol, which is known to reduce the severity of the oxidative stress observed in these tissues after an acute ethanol load. To study the effects of chronic ethanol administration, rats were given during 4 weeks a 10% (v/v) solution of ethanol in water as sole drinking fluid. The average daily ethanol consumption was 7-9 g. In such alcohol-fed rats the non-heme iron content was decreased by 31% in the serum whereas it was increased by 18% in the liver and by 30% in the cerebellum.(ABSTRACT TRUNCATED AT 250 WORDS)

[Alcohol and free radicals: from basic research to clinical prospects]. / Alcool et radicaux libres: de la recherche fondamentale aux espoirs cliniques.

An oxidative stress occurs in the liver of rats following various conditions of ethanol administration. The ethanol-inducible cytochrome P450 2E1 plays a key role in its generation, favoured itself by an increase in the "redox-active" fraction of intracellular non-heme iron. Administration of ethanol elicits the generation of the 1-hydroxyethyl radical, which has been identified in vivo. Its reactivity contributes to alcohol-induced immunological disturbances. Liver inflammatory and fibrotic disorders can be reproduced in rats by long-term ethanol administration associated with a high fat diet. The severity of these disorders is correlated to the intensity of the oxidative stress. Some conditions of ethanol administration to rats also elicit an oxidative stress in the myocardium and central nervous system. Through its inhibitory effect on glutamine synthetase activity and resulting excitotoxicity it may contribute to neuronal death and possibly to dependence on alcohol. Disorders related to an oxidative stress were also reported in the serum and erythrocytes as well as in liver biopsies from alcoholic individuals. Their detection may be useful to follow the evolution of alcoholic liver diseases. Supplementation with antioxidants such as vitamin E may be considered in the prevention of severe cellular disorders in individuals consuming large amounts of alcoholic beverages. An increase in free radical production is likely playing a role in the induction of severe cellular damage linked to repeated withdrawals occurring as a result of heavy and sporadic ethanol intake.

Ethanol-induced lipid peroxidation and oxidative stress in extrahepatic tissues.

An ethanol-induced oxidative stress is not restricted to the liver, where ethanol is actively oxidized, but can affect various extrahepatic tissues as shown by experimental data obtained in the rat during acute or chronic ethanol intoxication. Most of these data concern the central nervous system, the heart and the testes. An acute ethanol load has been reported to enhance lipid peroxidation in the cerebellum. This is accompanied by an increase in the cytosolic concentration of low-molecular-weight iron derivatives which may contribute to the generation of aggressive free radicals. The ethanol-induced decrease in the main antioxidant systems (superoxide dismutase, alpha-tocopherol, ascorbate and selenium) is a likely contributor to the cerebellar oxidative stress. Most of these disturbances can be prevented by allopurinol administration. Some experimental data support also the occurrence of pro- and anti-oxidant disturbances in the cerebellum and in other regions of the central nervous system after chronic ethanol administration. Chronic ethanol administration enhances lipid peroxidation in the heart. The increased conversion of xanthine dehydrogenase into xanthine oxidase as well as the activation of peroxisomal acyl CoA-oxidase linked to ethanol administration could contribute to the oxidative stress. Chronic ethanol administration elicits in the testes an enhancement in mitochondrial lipid peroxidation and a decrease in the glutathione level, which appear to be correlated to the gross testicular atrophy observed. Vitamin A supplementation attenuates the changes in lipid peroxidation, glutathione and testicular morphology. Whether the reported disturbances are involved in the pathogenesis of the tissue disorders observed in alcoholic patients remains unanswered.(ABSTRACT TRUNCATED AT 250 WORDS)