Spencer Shaw

Depressed hepatic glutathione and increased diene conjugates in alcoholic liver disease. Evidence of lipid peroxidation.

The role of lipid peroxidation in the pathogenesis of alcoholic liver disease has been a subject of controversy. In order to study this question we measured hepatic glutathione and diene conjugates in liver biopsies from 16 alcoholics with different stages of liver injury and 8 nonalcoholics with liver disease. Patients with alcoholic liver disease were found to have decreased hepatic glutathione compared to patients with liver disease unrelated to alcohol (22.1±2.5 vs 33.5±4.6 nmol/mg protein,P<0.05). The decrease in glutathione was accompanied by an increase in diene conjugates in hepatic lipids (3.37±0.14 vs 2.26±0.21 OD at 232 nm/mg lipid,P<0.001). The changes were present in all stages of alcoholic liver damage including fatty liver but unrelated to nutritional status in these patients. They support the concept that lipid peroxidation may be an important mechanism in the pathogenesis of alcoholic liver disease.

Lipid peroxidation as a mechanism of alcoholic liver injury: role of iron mobilization and microsomal induction.

Lipid peroxidation has been invoked as a mechanism of alcoholic liver injury but its role has been controversial and the mechanism by which it occurs is unclear. Catalytic iron is known to play an important role in cellular injury and is produced during mobilization of ferritin iron. In vivo administration of a large acute dose of ethanol (5 g/kg) which produces hepatic lipid peroxidation in chow-fed rats resulted in mobilization of non-heme iron. The generation of NADH from alcohol metabolism via ADH or superoxide from acetaldehyde-xanthine oxidase mobilized iron from horse spleen ferritin in vitro. Chronic feeding of alcohol as 36% of energy for 6 weeks does not itself produce peroxidation in the rat but potentiates acute effects of ethanol. It produced microsomal induction which enhanced iron-stimulated lipid peroxidation and increased hepatic non-heme iron. Carbon monoxide increased rather than decreased accumulation of microsomal peroxidation products in vitro suggesting that cytochrome P-450 reductase mediates peroxidation but cytochrome P-450 may metabolize products. Incubation at lowered oxygen tensions equivalent to those observed in the perivenular zone (pO2 = 24 mmHg) enhanced in vitro iron mobilization but decreased peroxidation. Lipid peroxidation and its stimulation by iron mobilization and microsomal induction may be an important contributory mechanism of alcohol-induced liver injury.

Effect of ethanol-generated free radicals on gastric intrinsic factor and glutathione

The oxidation of acetaldehyde (generated from the metabolism of ethanol) by oxidases such as xanthine oxidase generates free radicals which can mobilize ferritin iron, alter hepatic glutathione and produce lipid peroxidation. The stomach, a site of ethanol metabolism and rich in xanthine oxidase, was studied with respect to the effects of ethanol on intrinsic factor (IF) binding of vitamin B-12 as well as gastric glutathione (GSH). Incubations of gastric homogenates with acetaldehyde-xanthine oxidase inhibited the B-12 binding ability by IF. A large acute dose of ethanol in vivo (5 g/kg, conc. greater than 40% w/v) decreased gastric IF binding of B-12 and depressed gastric GSH; these effects were markedly attenuated by the feeding of sodium tungstate which inhibited xanthine oxidase. Changes in B-12 binding paralleled changes in gastric GSH. Scatchard plots of IF binding of B-12 for homogenates suggested decreased number of binding sites rather than altered affinity. In conclusion, the gastric metabolism of ethanol generates free radicals which alter IF binding of B-12, depress gastric GSH and may play a role in alcohol-induced gastric injury.

Increased hepatic oxygenation following ethanol administration in the baboon.

Summary The effects of ethanol on hepatic oxygenation were measured by hepatic vein catheterization in the baboon. Chronic alcohol administration resulted in slightly lower oxygen tension in the hepatic vein, but not ischemia, when measured after an overnight fast when alcohol was no longer present in the blood. Intravenous alcohol administration resulted in an increase in hepatic vein oxygen tension regardless of prior exposure to alcohol or the presence of liver disease. The increased oxygen tension after alcohol was associated with a marked increase in hepatic blood flow. These data in conjunction with the observation of progressive liver injury in the alcohol-fed animals support the concept that alcoholic liver injury can develop despite unimpaired hepatic oxygenation.

Serum Ferritin Iron, a New Test, Measures Human Body Iron Stores Unconfounded by Inflammation

Serum ferritin protein is an acute phase reactant. We hypothesized that serum ferritin protein generated in response to an inflammatory process would have much less iron (Fe) in it than would “normal” ferritin protein, and therefore measuring serum ferritin iron would assess human body iron status unconfounded by inflammation.

Depression, suicide, and aggression in alcoholics and their relationship to plasma amino acids

In an earlier study we found an association in alcoholic patients between depression and low ratios of tryptophan over amino acids sharing with it the same transport carrier into the brain. A decreased tryptophan ratio has been shown to be correlated with lower brain tryptophan and serotonin. Because it has been postulated that altered serotonin metabolism may be a highly significant contributing factor not only to depression but also to aggressive and suicidal behavior, we decided to assess the existence of possible associations between amino acid abnormalities and these behaviors in a population of alcoholics. We observed a significant association between histories of aggression and depression. In addition, depressed patients with a history of aggression were found to have the lowest tryptophan ratio values. These values differed significantly from those found in depressed patients with no aggression history and from those observed in patients with no history of aggression and depression. Two of the three suicide attempters in the study fell also in the group of patients with an aggression history. Our data suggest the existence of a subgroup of alcoholics with marked amino acid abnormalities at risk for manifestations of depression, suicide, and aggression.

Lipid peroxidation, iron mobilization and radical generation induced by alcohol☆

Increasing evidence points to a major role for free radicals in the pathogenesis of alcohol-induced liver injury. In vitro, free radicals may be generated during ethanol metabolism by the further metabolism of acetaldehyde by molybdenum-dependent oxidases such as xanthine oxidase. Ferritin iron mobilized by such free radicals may serve as catalytic iron. Increased stores of ferritin iron and induction of microsomal P-450 reductase activity are mechanisms by which chronic alcohol feeding may potentiate the acute effects of alcohol.

Ethanol-induced iron mobilization: Role of acetaldehyde-aldehyde oxidase generated superoxide

Superoxide radicals, a species known to mobilize ferritin iron, and their interaction with catalytic iron have been implicated in the pathogenesis of alcohol-induced liver injury. The mechanism(s) by which ethanol metabolism generates free radicals and mobilizes catalytic iron, however, is not fully defined. In this investigation the role of hepatic aldehyde oxidase in the mobilization of catalytic iron from ferritin was studied in vitro. Iron mobilization due to the metabolism of ethanol to acetaldehyde by alcohol dehydrogenase was increased 100% by the addition of aldehyde oxidase. Iron release was favored by low pH and low oxygen concentration. Mobilization of iron due to acetaldehyde metabolism by aldehyde oxidase was completely inhibited by superoxide dismutase but not by catalase suggesting that superoxide radicals mediate mobilization. Acetaldehyde-aldehyde oxidase mediated reduction of ferritin iron was facilitated by incubation with menadione, an electron acceptor for aldehyde oxidase. Mobilization of ferritin iron due to the metabolism of acetaldehyde by aldehyde oxidase may be a fundamental mechanism of alcohol-induced liver injury.

DNA cleavage during ethanol metabolism: Role of superoxide radicals and catalytic iron

The generation of superoxide and related free radicals and the mobilization of catalytic iron due to ethanol metabolism have been suggested as mechanisms of alcohol-induced liver injury as well as of the increased risk of cancer observed in alcoholics. Cleavage of double stranded DNA is produced by both free radicals as well as by catalytic iron. The effects of ethanol metabolism on DNA cleavage were therefore studied in vitro as well as in vivo in isolated hepatocytes. Intactness of double stranded DNA was studied by measuring ethidium bromide fluorescence after DNA electrophoresis. In vitro, the metabolism of acetaldehyde by aldehyde oxidase caused cleavage of Lambda phage DNA. Cleavage was inhibited by both superoxide dismutase and desferrioxamine indicating the role of superoxide radicals and catalytic iron respectively. Studies with HIND III digests of the Lambda phage indicate a lack of specificity in the breaks with respect to nucleotide sequences. Addition of EDTA greatly enhanced cleavage. In vivo, ethanol metabolism caused minimal breakage in hepatocyte DNA and addition of acetaldehyde (100 microM) markedly enhanced cleavage; all cleavage was inhibited by desferrioxamine. The metabolism of ethanol to acetaldehyde and the further metabolism of acetaldehyde by aldehyde oxidase generates free radicals and mobilizes iron; these may contribute to alcohol-induced injury and carcinogenesis.

Ethanol impairs tryptophan transport into the brain and depresses serotonin

Abstract Alcoholics were found to have decreased plasma levels of tryptophan, the serotonin precursor, and a decreased ratio of tryptophan over amino acids competing for transport into the brain. Studies conducted in the plasma of rats and baboons with carefully controlled alcohol and dietary intake showed a decreased in the ratio of tryptophan over competing amino acids resulting mostly from increases in valine in the rat and in valine, leucine and isoleucine in the baboon. In the rat concomitant decreases in brain tryptophan and serotonin were noted. Central serotonin dificiency may contribute to the depressive states frequently seen in alcoholics.