UMLS:C1260386 - FACTA Search

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Query: UMLS:C1260386 (GSH)
38,102 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The main pathway for the hepatic oxidation of ethanol to acetaldehyde proceeds via ADH and is associated with the reduction of NAD to NADH; the latter produces a striking redox change with various associated metabolic disorders. NADH also inhibits xanthine dehydrogenase activity, resulting in a shift of purine oxidation to xanthine oxidase, thereby promoting the generation of oxygen-free radical species. NADH also supports microsomal oxidations, including that of ethanol, in part via transhydrogenation to NADPH. In addition to the classic alcohol dehydrogenase pathway, ethanol can also be reduced by an accessory but inducible microsomal ethanoloxidizing system. This induction is associated with proliferation of the endoplasmic reticulum, both in experimental animals and in humans, and is accompanied by increased oxidation of NADPH with resulting H2O2 generation. There is also a concomitant 4- to 10-fold induction of cytochrome P4502E1 (2E1) both in rats and in humans, with hepatic perivenular preponderance. This 2E1 induction contributes to the well-known lipid peroxidation associated with alcoholic liver injury, as demonstrated by increased rates of superoxide radical production and lipid peroxidation correlating with the amount of 2E1 in liver microsomal preparations and the inhibition of lipid peroxidation in liver microsomes by antibodies against 2E1 in control and ethanol-fed rats. Indeed, 2E1 is rather "leaky" and its operation results in a significant release of free radicals. In addition, induction of this microsomal system results in enhanced acetaldehyde production, which in turn impairs defense systems against oxidative stress. For instance, it decreases GSH by various mechanisms, including binding to cysteine or by provoking its leakage out of the mitochondria and of the cell. Hepatic GSH depletion after chronic alcohol consumption was shown both in experimental animals and in humans. Alcohol-induced increased GSH turnover was demonstrated indirectly by a rise in alpha-amino-n-butyric acid in rats and baboons and in volunteers given alcohol. The ultimate precursor of cysteine (one of the three amino acids of GSH) is methionine. Methionine, however, must be first activated to S-adenosylmethionine by an enzyme which is depressed by alcoholic liver disease. This block can be bypassed by SAMe administration which restores hepatic SAMe levels and attenuates parameters of ethanol-induced liver injury significantly such as the increase in circulating transaminases, mitochondrial lesions, and leakage of mitochondrial enzymes (e.g., glutamic dehydrogenase) into the bloodstream. SAMe also contributes to the methylation of phosphatidylethanolamine to phosphatidylcholine. The methyltransferase involved is strikingly depressed by alcohol consumption, but this can be corrected, and hepatic phosphatidylcholine levels restored, by the administration of a mixture of polyunsaturated phospholipids (polyenylphosphatidylcholine). In addition, PPC provided total protection against alcohol-induced septal fibrosis and cirrhosis in the baboon and it abolished an associated twofold rise in hepatic F2-isoprostanes, a product of lipid peroxidation. A similar effect was observed in rats given CCl4. Thus, PPC prevented CCl4- and alcohol-induced lipid peroxidation in rats and baboons, respectively, while it attenuated the associated liver injury. Similar studies are ongoing in humans.
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PMID:Role of oxidative stress and antioxidant therapy in alcoholic and nonalcoholic liver diseases. 889 26

3-Butene-1,2-diol (BDD) is a metabolite of the carcinogenic petrochemical 1,3-butadiene. BDD is produced by cytochrome P450-mediated oxidation of 1,3-butadiene to butadiene monoxide, followed by enzymatic hydrolysis by epoxide hydrolase. The metabolic disposition of BDD is unknown. The current work characterizes BDD oxidation by purified horse liver alcohol dehydrogenase (ADH) and by cytosolic ADH from mouse, rat, and human liver. BDD is oxidized by purified horse liver ADH in a stereoselective manner, with (S)-BDD oxidized at approximately 7 times the rate of (R)-BDD. Attempts to detect and identify metabolites of BDD using purified horse liver ADH demonstrated formation of a single stable metabolite, 1-hydroxy-2-butanone (HBO). A second possible metabolite, 1-hydroxy-3-butene-2-one (HBONE), was tentatively identified by GC/MS, but HBONE formation could not be clearly attributed to BDD oxidation, possibly due to its rapid decomposition in the incubation mixture. Formation of HBO by ADH was dependent upon reaction time, protein concentration, substrate concentration, and the presence of NAD. Inclusion of GSH or 4-methylpyrazole in the incubation mixture resulted in inhibition of HBO formation. Based on these results and other lines of evidence, a mechanism is proposed for HBO formation involving generation of several potentially reactive intermediates which could contribute to toxicity of 1,3-butadiene in exposed individuals. Comparison of kinetics of BDD oxidation in rat, mouse, and human liver cytosol did not reveal significant differences in catalytic efficiency (Vmax/K(m)) between species. These results may contribute to a better understanding of 1,3-butadiene metabolism and toxicity.
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PMID:Oxidation of 3-butene-1,2-diol by alcohol dehydrogenase. 890 67

Chinese hamster ovary cells were stably transfected with rat liver S-adenosylmethionine synthetase cDNA. As a result, S-adenosylmethionine synthetase activity increased 2.3-fold, an effect that was accompanied by increased S-adenosylmethionine, a depletion of ATP and NAD levels, elevation of the S-adenosylmethionine/S-adenosylhomocysteine ratio (the methylation ratio), increased DNA methylation and polyamine levels (spermidine and spermine), and normal GSH levels. By contrast, the transfected cells showed normal growth curves and morphology. Exposure to an oxidative stress by the addition of H2O2 resulted in a greater consumption of ATP and NAD in the transfected cells than in the wild-type cells. In turn, cell killing by H2O2 was greater in the transfected cells than in the wild-type cells. This killing of Chinese hamster ovary cells by H2O2 involved the activation of poly(ADP-ribose) polymerase with the resultant loss of NAD and ATP. 3-Aminobenzamide, an inhibitor of poly(ADP-ribose) polymerse, but not the antioxidant N,N'-diphenylphenylenediamine, prevented the killing of Chinese hamster ovary cells by H2O2 and maintained the contents of NAD and ATP. The results of this study indicate that a moderate activation of the synthesis of S-adenosylmethionine leads to ATP and NAD depletion and to a greater sensitivity to cell killing by oxidative stress.
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PMID:Increased sensitivity to oxidative injury in chinese hamster ovary cells stably transfected with rat liver S-adenosylmethionine synthetase cDNA. 892 Sep 79

The effect of chloroquine (CHQ) administration on antioxidant enzymes in rat liver and kidney was studied. Male Sprague-Dawley rats were administered 20 mg/kg CHQ once a week for 4 weeks (chronic treatment) or a single dose at 10 or 20 mg/kg (acute treatment). Antioxidant enzyme activities were determined in cytosolic fractions of liver and kidney, whereas reduced glutathione (GSH) and malondialdehyde (MDA) were determined in tissue samples. Results indicate minimal effects of acute CHQ treatment, whereas chronic treatment with CHQ differentially affected antioxidant enzymes in the two organs. Superoxide dismutase activity was increased nearly twofold, while activities of selenium glutathione peroxidase (GPX), catalase, and NAD (P) H: quinone oxidoreductase were decreased in livers of CHQ-treated rats compared to controls. No significant effects of CHQ on glutathione reductase, GSH, and MDA levels were seen in the liver. Fewer effects of CHQ were observed in the kidney where a decrease in GPX activity and an increase in MDA levels was seen. Lowering of antioxidant enzymes activities in the liver by CHQ could render the organ more susceptible to subsequent oxidative stress; while increased MDA production after CHQ treatment in the kidney indicate that the organ is being subjected to oxidative stress. This could have implications for prolonged chloroquine intake.
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PMID:Effects of chloroquine treatment on antioxidant enzymes in rat liver and kidney. 895 57

Metabolism of rhein (4,5-dihydroxyanthraquinone-2-carboxylic acid) in primary cultures of rat hepatocytes caused production of oxygen-derived free radicals by redox cycling; this was shown as an increased rate of superoxide-dismutasesensitive NAD(P)H oxidation and NAD(P)H-cytochrome c reduction. Furthermore, rhein caused a depletion of intracellular reduced glutathione and an immediate, almost 10-fold increase in intracellular free Ca2+. Exposure to rhein also induced the following: a decrease in the mitochondrial membrane potential, as analyzed by uptake of rhodamine 123 (Rh 123); initiation of lipid peroxidation, measured as accumulation of malondialdehyde and 4-hydroxyalkenals; and cell death (LD50 = 20 microM). Pretreatment of cell cultures with dithiothreitol (DTT), nifedipin or N',N'-diphenyl-p-phenylenediamine (DPPD) increased the intracellular free Ca2+ concentration 5-fold but inhibited rhein-induced cytotoxicity. Moreover, addition of these protecting substances maintained the level of ATP and glutathione (GSH) and prevented accumulation of lipid peroxidation products. Depletion of intracellular glutathione by pretreatment with buthionine sulfoximine (BSO), or inhibition of glutathione reductase with 1,3-bis-2-chloroethyl-1-nitrosourea (BCNU) decreased cell viability (LD50 = 2.5 microM). On the other hand, increasing GSH by pretreatment with L-2-oxothiazolidine-4-carboxylic acid (OTC) did not provide complete protection. In summary, rhein undergoes redox cycling that gives rise to oxygen metabolites that affect the mitochondrial membranes (recorded as a decreased membrane potential) and after the plasma membrane (i.e. induced the formation of surface blebs). Mitochondrial malfunction also causes changes in Ca2+ homeostasis and depletion of ATP, which eventually lead to cell death.
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PMID:The hepatotoxicity of rhein involves impairment of mitochondrial functions. 905 Nov 22

Phenolphthalein, a widely used laxative, is the active ingredient in more than a dozen commercial nonprescription formulations. Fast-flow EPR studies of the reaction of phenolphthalein with horseradish peroxidase (HRP) and hydrogen peroxide permit the direct detection of two free radicals. One has EPR parameters characteristic of phenoxyl radicals. The other has a broad unresolved spectrum, possibly arising from free radical polymeric products of the initial phenoxyl radical. EPR spin-trapping studies of incubations of phenolphthalein with lactoperoxidase, reduced glutathione (GSH), and hydrogen peroxide with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) demonstrate stimulated production of DMPO/.SG compared with an identical incubation lacking phenolphthalein. In the absence of DMPO, measurements with a Clark-type oxygen electrode show that molecular oxygen is consumed by a sequence of reactions initiated by the glutathione thiyl radical. Enhanced production of DMPO superoxide radical adduct is also found in a system of phenolphthalein, NADH, and lactoperoxidase. In this system the phenolphthalein phenoxyl radical abstracts hydrogen from NADH to generate NAD., which is not spin trapped by DMPO, but reacts with molecular oxygen to produce the superoxide radical detected by EPR. In the absence of DMPO, the oxygen consumption is measured using the Clark-type electrode. Production of ascorbate radical anion is also enhanced in a system of phenolphthalein, ascorbic acid, hydrogen peroxide, and lactoperoxidase. Ascorbate inhibits oxygen consumption when phenolphthalein is metabolized in the presence of either glutathione or NADH by reducing radical intermediates to their parent molecules and forming the relatively stable ascorbate anion radical. The detection of enhanced free radical production in these three systems, a consequence of futile metabolism (or redox cycling), suggests that phenolphthalein may be a significant source of oxidative stress in physiological systems. Parallel EPR and oxygen consumption studies with phenolphthalein glucuronide give analogous results, but with lesser enhancement of free radical production.
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PMID:In vitro free radical metabolism of phenolphthalein by peroxidases. 910 47

1. The effects of intracellular redox couples were investigated on the activation by voltage, Ca2+ and NS 1619 of maxi-K channels in enzymatically isolated smooth muscle cells from large pulmonary arteries of rabbits. 2. In inside-out membrane patches, maxi-K channels were characterized by a single-channel conductance of 266 pS in symmetrical 140 mM KCl solutions. The relationship between the open-state probability (Po) and the membrane potential could be fitted to the Boltzmann equation. The activating action of intracellular Ca2+ was reversible, concentration dependent, and was manifested as the reduction in the voltage necessary to half-activate the channel (V1/2) with no change in the slope factor. NS 1619 also predisposed the maxi-K channel to open at more hyperpolarized membrane potentials. 3. The oxidizing agent 5,5'-dithio-bis(2-nitrobenzoic acid) (DTNB, 1 mM) activated maxi-K channels by inducing a negative shift of the activity-voltage curve, while the reducing agent 2-hydroxy-1-ethanethiol (beta-mercaptoethanol) (BME, 1 mM) had no effect. DTNB increased the efficacy of Ca2+ in activating maxi-K channels. The action of DTNB was not reversible upon wash-out, but could be counteracted by BME. 4. Maxi-K channel activity was unaffected by other oxidizing agents, such as NAD (2 mM) and glutathione disulphide (GSSG, 5 mM), or by their reduced forms (NADH and GSH). Mg-ATP (0.1 and 1 mM) increased the channel activity in a dose-dependent manner, while guanine nucleotides (100 microM GTP gamma S, 500 microM GDP and 200 microM GDP beta S) had no effect. 5. Our data suggest that a change in the intracellular redox state, which would be expected during acute hypoxia, does not alter the activity of maxi-K channels of large pulmonary artery smooth muscle cells. The sulfhydryl-specific redox reagents (DTNB and BME) must act through another regulatory mechanism.
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PMID:Contrasting effects of intracellular redox couples on the regulation of maxi-K channels in isolated myocytes from rabbit pulmonary artery. 916 77

Two different NAD/coenzyme-dependent formaldehyde dehydrogenases exist, the well-known NAD/GSH-dependent (EC 1.2.1.1) and the more recently discovered NAD/Factor-dependent enzyme. The GSH-dependent one has been found in eukaryotes and Gram-negative bacteria, the Factor-dependent one in two different Gram-positive bacteria. Previous work also showed that Factor and GSH are not interchangeable in the enzymatic reactions. Here it is revealed that the Factor is identical to mycothiol (MySH), 1-O-(2'-[N-acetyl-L-cysteinyl]-amido-2'-deoxy-alpha-D-glucopyranosyl)-D- myo-inositol, a thiol compound which has recently been detected in Actinomycetes. Thus, MySH is GSH's companion as it is the coenzyme for the enzyme which henceforth can be indicated as NAD/MySH-dependent formaldehyde dehydrogenase.
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PMID:Mycothiol, 1-O-(2'-[N-acetyl-L-cysteinyl]amido-2'-deoxy-alpha-D-glucopyranosyl)-D- myo-inositol, is the factor of NAD/factor-dependent formaldehyde dehydrogenase. 920 49

We have previously shown that intact plants and cultured plant cells can metabolize and detoxify formaldehyde through the action of a glutathione-dependent formaldehyde dehydrogenase (FDH), followed by C-1 metabolism of the initial metabolite (formic acid). The cloning and heterologous expression of a cDNA for the glutathione-dependent formaldehyde dehydrogenase from Zea mays L. is now described. The functional expression of the maize cDNA in Escherichia coli proved that the cloned enzyme catalyses the NAD(+)- and glutathione (GSH)-dependent oxidation of formaldehyde. The deduced amino acid sequence of 41 kDa was on average 65% identical with class III alcohol dehydrogenase from animals and less than 60% identical with conventional plant alcohol dehydrogenases (ADH) utilizing ethanol. Genomic analysis suggested the existence of a single gene for this cDNA. Phylogenetic analysis supports the convergent evolution of ethanol-consuming ADHs in animals and plants from formaldehyde-detoxifying ancestors. The high structural conservation of present-day glutathione-dependent FDH in microorganisms, plants and animals is consistent with a universal importance of these detoxifying enzymes.
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PMID:Maize glutathione-dependent formaldehyde dehydrogenase cDNA: a novel plant gene of detoxification. 929 Jun 37

The effects of primaquine treatment on antioxidant enzyme activities were investigated in rat liver and kidney. Male Sprague-Dawley rats were treated with 0.21 mg/kg daily for two weeks (chronic treatment) or a single dose at 0.21 or 0.63 mg/kg. Antioxidant enzyme activities were determined in liver and kidney cytosolic fractions whereas glutathione (GSH) and malondialdehyde (MDA) levels were determined in tissue samples. Results for the liver showed increases in cytosolic superoxide dismutase (SOD) and glutathione peroxidase (GPX) enzymatic activities after chronic primaquine treatment. Levels of MDA, a marker for lipid peroxidation, were also increased by more than 50% indicating enhanced oxidative damage in the liver. In the single dose study, 0.63 mg/kg primaquine caused a more than 100% increase in liver SOD and a 36% increase in NAD (P) H: quinone oxidoreductase (NQOR) activities. Results for the kidney, however, showed fewer primaquine-induced changes in antioxidant enzyme activities when compared to the liver in both the chronic and single dose studies. Overall, our results indicate that primaquine treatment causes an oxidative stress in the two rat organs. These results are consistent with the known pro-oxidant effects of primaquine in vivo, and supplement current knowledge on the effects of antimalarial drugs on various enzyme systems.
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PMID:Primaquine alters antioxidant enzyme profiles in rat liver and kidney. 935 Apr 21

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