Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.6.5.3 (complex I)
8,901 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We examine the evidence for free radical involvement and oxidative stress in the pathological process underlying Parkinson's disease, from postmortem brain tissue. The concept of free radical involvement is supported by enhanced basal lipid peroxidation in substantia nigra in patients with Parkinson's disease, demonstrated by increased levels of malondialdehyde and lipid hydroperoxides. The activity of many of the protective mechanisms against oxidative stress does not seem to be significantly altered in the nigra in Parkinson's disease. Thus, activities of catalase and glutathione peroxidase are more or less unchanged, as are concentrations of vitamin C and vitamin E. The activity of mitochondrial superoxide dismutase and the levels of the antioxidant ion zinc are, however, increased, which may reflect oxidative stress in substantia nigra. Levels of reduced glutathione are decreased in nigra in Parkinson's disease; this decrease does not occur in other brain areas or in other neurodegenerative illnesses affecting this brain region (i.e., multiple system atrophy, progressive supranuclear palsy). Altered glutathione metabolism may prevent inactivation of hydrogen peroxide and enhance formation of toxic hydroxyl radicals. In brain material from patients with incidental Lewy body disease (presymptomatic Parkinson's disease), there is no evidence for alterations in iron metabolism and no significant change in mitochondrial complex I function. The levels of reduced glutathione in substantia nigra, however, are reduced to the same extent as in advanced Parkinson's disease. These data suggest that changes in glutathione function are an early component of the pathological process of Parkinson's disease.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Oxidative stress as a cause of nigral cell death in Parkinson's disease and incidental Lewy body disease. The Royal Kings and Queens Parkinson's Disease Research Group. 151 Mar 85

In order to decide whether vitamin E action on ubiquinone-dependent enzymatic systems of mitochondria and on ubiquinone metabolism consisting in its antioxidative function, the effects of alpha-tocopherol and the most effective synthetic antioxidant, chlorohydrate 2-ethyl-6-methyl-3-hydroxypyridine, were compared. It was shown that the contents of vitamin E and ubiquinone as well as the activities of succinate- and NADH-ubiquinone reductase, succinate- and NADH-dehydrogenases in liver mitochondria are increased and the levels of ATP, adenine nucleotides and phosphate potential in the livers of vitamin E-deficient rats are elevated 3 hours after alpha-tocopherol injection (5 micrograms per 1 g of body weight). The synthetic antioxidant injected under identical conditions at a dose of 50 micrograms per 1 g of body weight did not change the ubiquinone content or the enzymatic activities, but considerably enhanced the ATP level. The same antioxidant when injected at a dose of 105 micrograms per 1 g of body weight did not significantly affect the parameters under study but decreased the activity of succinate-ubiquinone reductase. Thus, the role of vitamin E in oxidative phosphorylation may not only consist in its antioxidant action and is largely due to the regulation of metabolism and functioning of ubiquinone.
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PMID:[Comparative study of the effects of alpha-tocopherol and a synthetic antioxidant on respiration and oxidative phosphorylation in rat liver mitochondria]. 688 35

The interaction between ubiquinones and vitamin E was studied in the inner membranes of rat liver mitochondria, liposomes and human erythrocyte plasma membranes. Free radicals were produced by addition of exogenous oxidants, and their reaction with chromanols and ubiquinone was followed by ESR and HPLC. Membranes were made deficient in ubiquinone but sufficient in alpha-tocopherol and were reconstituted with added ubiquinone. With these membrane preparations it was shown that (i) in the inner mitochondrial membranes there is a requirements for ubiquinone in the enzymatic recycling of vitamin E; (ii) succinate-ubiquinone reductase incorporated in liposomes cannot protect vitamin E in the absence of ubiquinone and (iii) in human erythrocyte plasma membranes protection against the loss of vitamin E can be provided by NADH-cytochrome-b5-dependent enzymatic recycling. We conclude that ubiquinonols (ubisemiquinones) reduce vitamin E through electron transport.
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PMID:Interactions between ubiquinones and vitamins in membranes and cells. 775 45

The effects of vitamin E and its analogs--alpha-tocopheryl acetate with a shortened up to six carbon atoms side chain carrying a saturated and an unsaturated bonds at the chain terminus, alpha-tocopherol and alpha-tocopheryl quinone devoid of the side chain--on the rate of malonic dialdehyde formation, the diene conjugate and total lipid content in the liver as well as the activity of the respiratory chain enzymes--succinate--and NADH-dehydrogenase, succinate- and NADH-ubiquinone reductase, as well as the vitamin E and ubiquinone content in the liver mitochondria of vitamin E-deficient rats in vivo have been investigated. It has been found that alpha-tocopheryl acetate with a shortened (up to C6) side chain carrying a saturated bond at the chain terminus is the most effective analog of tocopherol. Further reduction of the tocopherol side chain or tocopherol conversion into quinone causes a decrease in their tocopherol activity.
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PMID:[Participation of tocopherol and its analogs in lipid peroxidation processes and electron transport in rat liver mitochondria in vivo]. 826 10

Levodopa, at concentrations of 0.25 x 10(-4) M or larger, is toxic for the human neuroblastoma cell NB69. Toxicity is associated with high levels of quinones, increased activity of complex II-III, and lack of changes of complex I of the mitochondrial respiratory chain. Deprenyl, which does not alter the production of quinones, has a partial protective effect. Tocopherol, 23 or 115 x 10(-6) M, lacks significant preventive effect on levodopa toxicity, but ascorbic acid, 10(-3) M, prevents levodopa toxicity and quinone formation. Deprenyl, 10(-4) M, provides additional protection in cultures treated with levodopa and ascorbic acid. Our results indicate that ascorbic acid and deprenyl prevent levodopa neurotoxicity by unrelated mechanisms. Both compounds should be considered as complementary drugs to test for slowing the progression of Parkinson's disease.
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PMID:Ascorbic acid protects against levodopa-induced neurotoxicity on a catecholamine-rich human neuroblastoma cell line. 834 Dec 91

Parkinson's disease, known also as striatal dopamine deficiency syndrome, is a degenerative disorder of the central nervous system characterized by akinesia, muscular rigidity, tremor at rest, and postural abnormalities. In early stages of parkinsonism, there appears to be a compensatory increase in the number of dopamine receptors to accommodate the initial loss of dopamine neurons. As the disease progresses, the number of dopamine receptors decreases, apparently due to the concomitant degeneration of dopamine target sites on striatal neurons. The loss of dopaminergic neurons in Parkinson's disease results in enhanced metabolism of dopamine, augmenting the formation of H2O2, thus leading to generation of highly neurotoxic hydroxyl radicals (OH.). The generation of free radicals can also be produced by 6-hydroxydopamine or MPTP which destroys striatal dopaminergic neurons causing parkinsonism in experimental animals as well as human beings. Studies of the substantia nigra after death in Parkinson's disease have suggested the presence of oxidative stress and depletion of reduced glutathione; a high level of total iron with reduced level of ferritin; and deficiency of mitochondrial complex I. New approaches designed to attenuate the effects of oxidative stress and to provide neuroprotection of striatal dopaminergic neurons in Parkinson's disease include blocking dopamine transporter by mazindol, blocking NMDA receptors by dizocilpine maleate, enhancing the survival of neurons by giving brain-derived neurotrophic factors, providing antioxidants such as vitamin E, or inhibiting monoamine oxidase B (MAO-B) by selegiline. Among all of these experimental therapeutic refinements, the use of selegiline has been most successful in that it has been shown that selegiline may have a neurotrophic factor-like action rescuing striatal neurons and prolonging the survival of patients with Parkinson's disease.
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PMID:Oxidative stress and antioxidant therapy in Parkinson's disease. 883 Mar 46

The effect of administration of ethionine on rat liver mitochondrial functions and the protective effect of vitamin E on ethionine induced damage was studied. Ethionine treatment decreased the rate of respiration, respiratory control ratio and P/O ratio. There was a significant decrease in the activities of NADH dehydrogenase, succinate cytochrome C reductase and cytochrome oxidase. A significant decrease was seen on membrane potential and on the levels of ATP. Among the mitochondrial phospholipids only cardiolipin decreased significantly. The lipid peroxide level increased significantly in ethionine treated rats. Administration of vitamin E prior to ethionine treatment relieved the effects (induced by ethionine) on all the parameters studied. This study shows that vitamin E protects against ethionine toxicity.
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PMID:Protective effect of vitamin E against ethionine toxicity. 911 39

Two Hep G2 subclones overexpressing CYP2E1 were established with the use of transfection and limited dilution screening techniques. The Hep G2-CI2E1-43 and -47 (E47) cells (transduced Hep G2 subclones that overexpress CYP2E1) grew at a slower rate than parental Hep G2 cells or control subclones that do not express CYP2E1, but remained fully viable. When GSH synthesis was inhibited by treatment with buthionine sulfoximine, GSH levels rapidly declined in E47 cells but not control cells, which is most likely a reflection of CYP2E1-catalyzed formation of reactive oxygen species. Under these conditions of GSH depletion, cytotoxicity and apoptosis were found only with the E47 cells. Low levels of lipid peroxidation were found in the E47 cells, which became more pronounced after GSH depletion. The antioxidants vitamin E, vitamin C, or trolox prevented the lipid peroxidation as well as the cytotoxicity and apoptosis, as did transfection with plasmid containing antisense CYP2E1 or overexpression of Bcl-2. Levels of ATP were lower in E47 cells because of damage to mitochondrial complex I. When GSH was depleted, oxygen uptake was markedly decreased with all substrates in the E47 extracts. Vitamin E completely prevented the decrease in oxygen uptake. Under conditions of CYP2E1 overexpression, two modes of CYP2E1-dependent toxicity can be observed in Hep G2 cells: a slower growth rate when cellular GSH levels are maintained and a loss of cellular viability when cellular GSH levels are depleted. Elevated lipid peroxidation plays an important role in the CYP2E1-dependent toxicity and apoptosis. This direct toxicity of overexpressed CYP2E1 may reflect the ability of this enzyme to generate reactive oxygen species even in the absence of added metabolic substrate.
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PMID:Cytotoxicity and apoptosis produced by cytochrome P450 2E1 in Hep G2 cells. 954 53

We have used a model of dietary deficiency that leads to a chronic oxidative stress to evaluate responses that are adaptations invoked to boost cellular defense systems. Long-Evans hooded rats were fed with a diet lacking vitamin E (E) and selenium (Se) for 7 wk from weaning leading to animals deficient in both nutrients (-E -Se). In the absence of an electron donor, liver plasma membranes from these rats were more sensitive to lipid peroxidation, although they contained 40% greater amounts of ubiquinone than the plasma membranes from rats consuming diets with sufficient vitamin E and Se (+E +Se). The incubation of plasma membranes with NAD(P)H resulted in protection against peroxidation, and this effect was more pronounced in -E -Se membranes. Deficiency was accompanied by a twofold increase in redox activities associated with trans plasma membrane electron transport such as ubiquinone reductase and ascorbate free radical reductase. Staining with a polyclonal antibody against pig liver cytochrome b5 reductase, which acts as one ubiquinone reductase in the plasma membrane, showed an increased expression of the enzyme in membranes from -E -Se rats. Little DT-diaphorase activity was measured in +E +Se plasma membranes, but this activity was dramatically increased in -E -Se plasma membranes. No such increase was found in liver cytosols, which contained elevated activity of calcium-independent phospholipase A2. Thus, ubiquinone-dependent antioxidant protection in +E +Se plasma membranes is based primarily on NADH-cytochrome b5 reductase, whereas additional protection needed in -E -Se plasma membranes is supported by the increase of ubiquinone levels, increased expression of the cytochrome b5 reductase, and translocation of soluble DT-diaphorase to the plasma membrane. Our results indicate that, in the absence of vitamin E and Se, enhancement of ubiquinone-dependent reductase systems can fulfill the membrane antioxidant protection.
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PMID:Vitamin E and selenium deficiency induces expression of the ubiquinone-dependent antioxidant system at the plasma membrane. 983 56

The mechanisms that lead to mitochondrial damage under oxidative stress conditions were examined in synaptosomes treated with ascorbate/iron. A loss of membrane integrity, evaluated by electron microscopy and by LDH leakage, was observed in peroxidized synaptosomes and it was prevented by pre-incubation with vitamin E (150 microM) and idebenone (50 microM). ATP levels decreased, in synaptosomes exposed to ascorbate/iron, as compared to controls. NADH-ubiquinone oxidoreductase (Cx I) and cytochrome c oxidase (Cx IV) activities were unchanged after ascorbate/iron treatment, whereas succinate-ubiquinone oxidoreductase (Cx II), ubiquinol cytochrome c reductase (Cx III) and ATP-synthase (Cx V) activities were reduced by 55%, 40%, and 55%, respectively. The decrease of complex II and ATP-synthase activities was prevented by reduced glutathione (GSH), whereas the other antioxidants tested (vitamin E and idebenone) were ineffective. However, vitamin E, idebenone and GSH prevented the reduction of complex III activity observed in synaptosomes treated with ascorbate/iron. GSH protective effect suggests that the oxidation of protein SH-groups is involved in the inhibition of complexes II, III and V activity, whereas vitamin E and idebenone protection suggests that membrane lipid peroxidation is also involved in the reduction of complex III activity. These results may indicate that the inhibition of the mitochondrial respiratory chain enzymatic complexes, that are differentially affected by oxidative stress, can be recovered by specific antioxidants.
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PMID:Mitochondrial function is differentially affected upon oxidative stress. 989 Jun 35


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