Alcohol ingestion, liver glutathione and lipoperoxidation: metabolic interrelations and pathological implications

Inhibitory effect of the flavonoid silymarin on the erythrocyte hemolysis induced by phenylhydrazine

The flavonoid silymarin, which is used as a therapeutical agent in the treatment of liver diseases, can inhibit the hemolysis and lipid peroxidation induced by phenylhydrazine on erythrocytes obtained from rats treated with the flavonoid. This effect is ascribed to the antioxidant properties as a free radical scavenger exhibited by the flavonoid. Silymarin failed to inhibit the glutathione depletion induced by phenylhydrazine on erythrocytes. It is proposed that the flavonoid acts at the membrane level of the cell avoiding the lipid peroxidative and fluidizing effect of phenylhydrazine.

Effects of combinations of maternal agents on the fetal cerebrum in rat--ethanol or caffeine with X-irradiation in utero

Fetal cerebral development influenced by maternal ethanol or caffeine either singly or in combination with X-irradiation was investigated in rat. Female Wistar rats were given 20% ethanol, 0.04% caffeine and water during the premating period and pregnancy, and 0.03% vitamin E only during pregnancy. Pregnant rats were X-irradiated with 100R or sham-irradiated on gestational day 13. Ethanol-treatment alone much reduced the fetal body and cerebral weights, and X-irradiation alone resulted in great reductions in weight and DNA concentration in the fetal cerebrum. The reduction in body weight with ethanol exceeded that with X-irradiation, therefore, the addition of X-irradiation had no effect on that of ethanol. The reduction in cerebral weight on X-irradiation exceeded that with ethanol, thus the addition of ethanol had only a slight effect on that with X-irradiation. The decrease in body and cerebral weights and the increase in lipid peroxide (LP) formation on caffeine-treatment and the decrease in cerebral weight and the increase in LP on vitamin E-treatment were inhibited by X-irradiation as compared to the combined effects of the other drink treatments. The increase in placental weight and the decrease in cerebral weight on ethanol-treatment and the decrease in placental, body and cerebral weights on caffeine-treatment, which findings were covered by the addition of X-irradiation, became much clearer on single drink treatment. Independently of X-irradiation, ethanol-treatment resulted in increased fetal mortality and LP, and decreased body weight. These results suggest that the combined effects of maternal agents on live fetuses should be investigated as to whether they act independently of or dependently with each other and how the effects appear either singly or mixed.

Hepatic catalase and superoxide dismutases after acute ethanol administration in rats

The administration of an acute ethanol load (2.3 g/kg, IP) to rats is followed by a decrease of the hepatic activity of cytosolic catalase, a decrease which precedes a reduction in the cytosolic Cu, Zn-superoxide dismutase (SOD) activity. Desferrioxamine, an iron chelator and scavenger of superoxide radicals, administered prior to ethanol, prevents the changes in the cytosolic catalase activity, changes which are unaffected by the administration of allopurinol, an inhibitor of xanthine oxidase. These data favour the hypothesis that acute ethanol results in an overproduction of oxygen free radicals which affects primarily the cytosolic catalase activity and increases hereby susceptibility of Cu, Zn-SOD to these radicals. They suggest also that xanthine oxidase does not play a major role in oxygen radical production in the liver cytosol during acute alcohol intoxication.

Chemically induced antioxidant-sensitive respiration. Relation to glutathione content and lipid peroxidation in the perfused rat liver

The interrelations between the hepatic chemically induced antioxidant-sensitive respiration and the contents of malondialdehyde (MDA) and of reduced glutathione (GSH), were studied in the isolated hemoglobin-free perfused rat liver. Antioxidant-sensitive respiration was induced by the infusion of agents such as ethanol, iron, xanthine or t-butyl hydroperoxide, or by phenylhydrazine pretreatment in vivo. The development of this respiratory component occurred concomitantly with high levels of MDA in the perfused livers, while those of GSH were diminished.

Hepatic antioxidant-sensitive respiration. Effect of ethanol, iron and mitochondrial uncoupling

The addition of the antioxidants (+)-cyanidanol-3, butylated hydroxyanisole and ascorbate to the perfused rat liver resulted in a decrease in the rate of oxygen consumption. This basal antioxidant-sensitive respiration of 110-130nmol X min-1 X (g of liver)-1 represents 5-7% of total respiration. Increased antioxidant-sensitive respiratory rates are found after the infusion of increasing concentrations of ethanol (1.8-72.2mM) or iron (35.5-248.5 microM). This respiratory component exhibits a dependence on ethanol or iron concentration, with maximal rates of 200-255 and 330nmol X min-1 X (g of liver)-1 respectively. After the addition of 100 microM-2,4-dinitriphenol, an antioxidant-sensitive respiratory component of 230nmol X min-1 X (g of liver)-1 is found, which is not observed at lower concentrations of the uncoupler (5-50 microM). The lack of effect of the antioxidants used on mitochondrial respiration [the preceding paper, Videla, Villena, Donoso, Giulivi & Boveris (1984) Biochem. J. 223, 879-883] and on the glycolytic rate of the perfused liver suggests that the basal and chemically induced antioxidant-sensitive respiration observed are related to oxygen required for one-electron transfer reactions associated with the generation of active species of oxygen and lipid peroxidation in the liver cell.

Effect of nitroheterocyclic drugs on lipid peroxidation and glutathione content in rat liver extracts

Incubation of rat liver cell-free extracts with an NADPH-generating system and with nifurtimox or benznidazole (two nitroheterocyclic drugs used in the treatment of Chagas' disease) produced oxidation of reduced glutathione (GSH) and increased lipid peroxidation, as shown by the generation of thiobarbituric-acid-reacting intermediates. Nifurtimox and benznidazole inhibited GSSG-reductase, but not GSH-peroxidase, the former inhibition contributing to GSH depletion. In every case, nifurtimox was more effective than benznidazole. Addition of GSH or free-radical scavengers (catalase, superoxide dismutase, mannitol, sodium benzoate or L-histidine) prevented the effect of nifurtimox on lipid peroxidation reactions. These results support the assumption [M. Dubin, S. N. J. Moreno, E. E. Martino, R. Docampo and A. O. M. Dubin, Biochem. Pharmac. 32, 483 (1983)] that, in the rat liver, GSH exerts a protective action against oxygen radicals generated by the nitroheterocyclic drugs.

Liver injuries induced by cyclochlorotine isolated from Penicillium islandicum

Sequential morphological changes in murine liver induced by cyclochlorotine (CC), a secondary metabolite of Penicillium islandicum were investigated by transmission electron microscopy and scanning electron microscopy. Within 15 min after the administration of CC there was a marked dilatation of Disse's space around the portal triads, and the exudates then poured out into the space which was formed by the invagination of the hepatocyte plasma membrane. Shortly after the invagination was completed, the connection between Disse's space and the invaginated space was pinched off, so that this space became a membrane-bound vacuole. After dehydration, the vacuoles became granular. The liver injuries induced by CC were influenced by various pretreatments. The results indicate that drug-metabolizing systems mediated by cytochrome p-450 in the hepatocytes may play an important role in the hepatotoxicity of CC.

Formaldehyde and hepatotoxicity: a review

Exposure to formaldehyde appears to be associated with hepatoxicity in many species, including humans, following injection, ingestion, or inhalation. Macroscopic, microscopic, and biochemical manifestations in the liver include alterations in weight, centrilobular vacuolization, focal cellular necrosis, and increased alkaline phosphatase concentrations. Time-related changes in the pattern of the effects are suggested as one goes from acute exposure by inhalation at greater concentrations to repeated exposure at lesser concentrations. Although the hepatic changes are generally not extensive and can be reversible following acute exposure, the potential exists for them to progressively become more serious with repeated exposures. There are several possible mechanisms for the toxicity. Depending on the route of exposure could include direct effects on hepatocytes and/or indirect effects through the circulatory and immune systems. The catabolism of formaldehyde includes conversion to CO2 by reactions involving glutathione. Many hepatotoxic chemicals require glutathione for detoxification. Formaldehyde may then have the potential to cause additive toxicity with such chemicals in some circumstances.

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.

Hepatic and biliary levels of glutathione and lipid peroxides following iron overload in the rat: effect of simultaneous ethanol administration

The administration of 125 mg of iron/kg (iron-dextran-Imferon) to fed rats was followed by an increase in the non-hem iron content in plasma and liver over a period of 22 hr, reaching a peak value after 6 hr. Plasma and hepatic iron levels were not modified by ethanol ingestion (5 g/kg). Iron and ethanol treatments enhanced liver lipid peroxidation (malondialdehyde (MDA) formation) by 70 and 35%, respectively, at 6 hr. Since the hepatic MDA formation increased by 92% after the joint iron-ethanol treatment, an additive effect in lipid peroxidation was suggested to occur in this condition. Both iron and ethanol treatments increased biliary levels and release of MDA, in the absence of changes in bile flow. These parameters were further enhanced by the joint iron-ethanol exposure, in that hepatic MDA levels and biliary MDA release were significantly correlated (r = 0.86; p less than 0.05). Plasma MDA levels also increased after iron, ethanol, and iron-ethanol treatments, but they did not reflect the changes in MDA levels in liver. Iron exposure resulted in 26 to 33% decreases in hepatic GSH content at the 6-hr treatment, associated with the peak effect on lipid peroxidation. In this situation, glutathione disulfide (GSSG) levels in liver were not changed, but its biliary release increased by 76%. Hepatic reduced glutathione (GSH) levels were recovered by 18 hr and increased by 23% after 22 hr of iron ingestion. Acute ethanol intake diminished liver GSH content by 30% and enhanced that of GSSG by 73%, thus eliciting a net decrease of 20% in total GSH equivalents (GSH + 2GSSG). Biliary release of total GSH was reduced in this condition. The combined administration of iron and ethanol further influenced the decrease in hepatic GSH and the increase in GSSG levels elicited by the separate treatments, but no alterations in the biliary content and release of total GSH were observed in this situation. These data indicate that iron exposure accentuates the changes in lipid peroxidation and in the glutathione status of the liver cell induced by acute ethanol intoxication.