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:1.1.1.1 (alcohol dehydrogenase)
9,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rat liver microsomes and, to a lesser extent, nuclei were previously shown to produce reactive oxygen species at elevated rates after chronic ethanol treatment. The ability of intact rat liver mitochondria to interact with iron and either NADH or NADPH, and the effects of ethanol treatment, on production of reactive oxygen intermediates was determined. In the presence of ferric-ATP, NADH or NADPH catalyzed mitochondrial lipid peroxidation. Rates were elevated two- to threefold with mitochondria from ethanol-fed rats with both reductants. Mitochondrial lipid peroxidation was insensitive to superoxide dismutase, catalase, or hydroxyl radical scavengers but was sensitive to GSH and anti-oxidants such as trolox. Mitochondrial generation of hydroxyl radical-like species (assayed by oxidation of chemical scavengers) was increased after chronic ethanol treatment, as was H2O2 production. Modifiers of mitochondrial metabolism such as rotenone, cyanide, or an uncoupling agent, had no effect on mitochondrial production of reactive oxygen intermediates. The membrane-impermeable thiol reagent, p-chloromercuribenzoate, was complete inhibitory with both mitochondrial preparations. The activity of the rotenone-insensitive NADH-cytochrome c reductase, an enzyme of the outer mitochondrial membrane, was increased 40 to 60% by the ethanol treatment. These results suggest that NADH acting via the outer membrane NADH reductase can catalyze an iron-dependent production of oxygen radicals by rat liver mitochondria. The outer mitochondrial membrane fraction, prepared by digitonin fractionation, displayed increased rotenone-insensitive NADH-cytochrome c reductase activity after ethanol treatment and was more reactive in catalyzing scission of pBR322 DNA from the supercoiled form to the open circular forms. Rates of oxygen radical production by mitochondria and the extent of increase produced by chronic ethanol treatment are similar to those previously found with microsomes when NADH is the cofactor. Oxidation of ethanol by alcohol dehydrogenase generates NADH, and NADH-dependent production of reactive oxygen species by various organelles is increased after chronic ethanol treatment. These acute metabolic interactions coupled to induction by chronic ethanol treatment may play an important role in the development of a state of oxidative stress in the liver by ethanol.
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PMID:Increased production of reactive oxygen species by rat liver mitochondria after chronic ethanol treatment. 813 51

Three decades of research in ethanol metabolism have established that alcohol is hepatotoxic not only because of secondary malnutrition, but also through metabolic disturbances associated with the oxidation of ethanol. Some of these alterations are due to redox changes produced by the NADH generated via the liver ADH pathway, which in turn affects the metabolism of lipids, carbohydrates, proteins, and purines. Exaggeration of the redox change by the relative hypoxia, which prevails physiologically in the perivenular zone, contributes to the exacerbation of the ethanol-induced lesions in zone III. Gastric ADH also explains first-pass metabolism by ethanol; its activity is low in alcoholics and in females and is decreased by some H2 blockers. In addition to ADH, ethanol can be oxidized by liver microsomes: studies over the last 20 years have culminated in the molecular elucidation of the ethanol-inducible cytochrome P450 (P4502E1) which contributes not only to ethanol metabolism and tolerance, but also to the selective hepatic perivenular toxicity of various xenobiotics. Their activation by P4502E1 now provides an understanding for the increased susceptibility of the heavy drinker to the toxicity of industrial solvents, anesthetic agents, commonly prescribed drugs, over-the-counter analgesics, chemical carcinogens, and even nutritional factors such as vitamin A. Ethanol causes not only vitamin A depletion, but it also enhances its hepatotoxicity. Furthermore, induction of the microsomal pathway contributes to increased acetaldehyde generation, with formation of protein adducts, resulting in antibody production, enzyme inactivation, decreased DNA repair; it is also associated with a striking impairment of the capacity of the liver to utilize oxygen. Moreover, acetaldehyde promotes GSH depletion, free-radical-mediated toxicity, and lipid peroxidation. In addition, acetaldehyde affects hepatic collagen synthesis; both in vivo (in our baboon model of alcoholic cirrhosis) and in vitro (in cultured myofibroblasts and lipocytes); ethanol and its metabolite acetaldehyde were found to increase collagen accumulation and mRNA levels for collagen. This new understanding may eventually improve therapy with drugs and nutrients. Encouraging results have been obtained with some "super" nutrients. On the one hand, SAMe, the active form of methionine, was found to attenuate the ethanol-induced depletion in SAMe and GSH and associated mitochondrial lesions. On the other hand, phosphatidylcholine, purified from polyunsaturated lecithin, was discovered to oppose the ethanol-induced fibrosis by decreasing the activation of lipocytes to transitional cells, and possibly also by stimulating collagenase activity, an effect for which dilinoleoylphosphatidylcholine, its major phospholipid species, was found to be responsible.
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PMID:Biochemical factors in alcoholic liver disease. 833 2

Toluene and its metabolites have been studied with respect to their reactive oxygen species-enhancing potential in isolated systems and in vivo. The induction of reactive oxygen species (ROS) production was assayed using the probe 2',7'-dichlorodihydrofluorescin diacetate (DCFH-DA). Intraperitoneal injection of toluene, benzyl alcohol or benzaldehyde caused a significant elevation in the rate of ROS formation within hepatic mitochondrial fractions (P2). In the brain, only toluene induced ROS formation, while benzyl alcohol and benzaldehyde did not have any effect. Glutathione (GSH) levels were depressed in liver and brain regions from toluene-treated rats. However, no such depression was evident in brains treated with toluene metabolites. P2 fractions from phenobarbital-pretreated rats exhibited a heightened ROS response when challenged with toluene, in vitro. Pretreatment of rats in vivo with 4-methylpyrazole, an alcohol dehydrogenase inhibitor, or sodium cyanamide, an aldehyde dehydrogenase inhibitor, prior to exposure to toluene, caused a significant decrease and increase, respectively, in toluene-stimulated rates of ROS generation in the CNS and liver. Electron spin resonance spectroscopy, employing the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO), was conducted. Incubation of the spin trap with P2 fractions and toluene or benzaldehyde elicited a spectrum corresponding to the hydroxyl radical. Incubation of benzaldehyde with aldehyde dehydrogenase produced a strong signal that was blocked completely by superoxide dismutase and inhibited partially by catalase, suggesting the presence of superoxide radicals and the involvement of the iron-catalyzed Haber-Weiss reaction leading to the production of hydroxyl radicals. Thus, ROS generation during toluene catabolism may occur at two steps: cytochrome P450 oxidation and aldehyde dehydrogenase oxidation. In addition, GSH may play an important role in protection against the induction of ROS generation in the CNS and liver following exposure to toluene.
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PMID:Free radical induction in the brain and liver by products of toluene catabolism. 839 73

It is well known that acetaldehyde is capable of covalent binding to liver proteins. However, in experiments using liver microsomes prepared from chronically ethanol-fed rats we have observed that the addition of EDTA-iron complex to the microsomes increases by about 4-5 fold both the spin trapping of hydroxyethyl radicals and the covalent binding of 14C-ethanol to proteins, while it only doubles acetaldehyde formation. Conversely, the presence of GSH strongly decreases the trapping of hydroxyethyl radicals and completely inhibits the covalent binding, without affecting acetaldehyde production. Furthermore, the spin trapping agent 4-pyridyl-N-oxide-t-butyl nitrone (4-POBN), previously employed for the detection of hydroxyethyl radicals, decreases by about 70% the covalent binding of 14C-ethanol to microsomal proteins. 4-POBN does not affect acetaldehyde production by liver microsomes, nor does it interfere with the covalent binding of acetaldehyde produced by ADH-mediated oxidation of ethanol. The results obtained indicate that hydroxyethyl radicals generated during ethanol oxidation by cytochrome P-450 play an important role in the alkylation of microsomal proteins consequent to ethanol metabolism.
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PMID:Evidence for the covalent binding of hydroxyethyl radicals to rat liver microsomal proteins. 839 27

The pancreatotoxin cyanohydroxybutene (CHB) causes a significant and prolonged elevation in glutathione (GSH) in liver and pancreas (Wallig and Jeffery, 1990). Here we report that urinary thiols also increase. This suggests that CHB may react with GSH, either directly or following phase I oxidation, to form an adduct, which is further metabolized to the corresponding mercapturic acid for urinary excretion. Metabolism of CHB by hepatic mixed function oxidase and cytosolic alcohol dehydrogenase enzymes was evaluated by monitoring microsomal NADPH consumption and alcohol dehydrogenase-dependent NADH generation, respectively. There was no apparent increase in the rate of microsomal NADPH consumption or alcohol dehydrogenase-dependent NADH generation in the presence of CHB. To evaluate in vitro formation of a glutathione-S-transferase (GST) catalyzed adduct, [3H-glycyl]-GSH and [14C-cyano]-CHB were incubated at 37 degrees C for 1 h, with or without GST. Dinitrophenol derivatization and high performance liquid chromatographic (HPLC) analysis (Farris & Reed, 1987) revealed no double-labeled peaks, suggesting that no stable conjugate was formed. However a tritiated product, not present in control samples, and with an identical retention time to cysteinyl-glycine (cys-gly) was formed. In addition, the product has a fast atom bombardment mass-spectrum consistent with cys-gly. These results suggest that while CHB may not undergo phase I oxidation, in the presence of CHB, GSH may break down to form cys-gly. A mechanism for CHB-dependent breakdown of GSH to cys-gly is proposed, and the pharmacological implications of this finding are discussed.
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PMID:In vitro metabolism of cyanohydroxybutene: formation of a glutathione-S-transferase catalyzed product. 848 79

2-Chloroacetaldehyde (CAA) formed during the metabolism of the anti-cancer drug ifosfamide (IP) has been implicated in ifosfamide-related neurotoxicity during chemotherapy but the neurotoxic mechanisms are unknown. We have found that IP (900 mg kg-1, p.o.) caused lethargy and mild hind limb paralysis after 6 h. Neurotoxicity and IP-induced mortality was markedly enhanced in mice pretreated with either phenobarbital or dexamethasone to induce cytochrome P4503A. Cerebral glutathione (GSH) levels were also markedly depleted in these pretreated mice. 2-Chloroethanol (92 mg kg-1, i.p.) (CE) also caused a 50% reduction in cerebral GSH 6 h after administration to mice. At this time maximum lethargy and unresponsiveness to touch was apparent in CE-treated mice. Severe hind limb paralysis developed and death ensued 12-18 h later. Prior depletion of cerebral GSH with 2-cyclohexene-1-one greatly accelerated the onset of CE-induced neurotoxicity suggesting that cerebral GSH status is an important determinant of CE-induced neurotoxicity. Furthermore, pretreatment with N-acetylcysteine delayed both CE-induced neurotoxicity and cerebral GSH depletion. Induction of cerebral but not hepatic CYP2E1 by ethanol before CE challenge also potentiated CE-induced cerebral GSH depletion and neurotoxicity. Hepatic GSH depletion was unaffected suggesting that CE-induced paralysis is dependent on a cerebral but not a hepatic CYP2E1 catalysed oxidation of CE to CAA. Ethanol was neuroprotective even if given 60 min after CE and prevented further cerebral GSH depletion. 4-Methylpyrazole, a CYP2E1 and alcohol dehydrogenase inhibitor, prevented both CE-induced hepatic and cerebral GSH depletion and paralysis. This suggests that the neurotoxicity associated with IP chemotherapy involves activation of chloroethanol by cerebral CYP2E1 to chloroacetaldehyde which mediates cerebral GSH depletion. Neurotoxicity may be prevented by restoring cerebral GSH status and/or by preventing activation of CE by CYP2E1 with ethanol.
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PMID:2-Chloroacetaldehyde-induced cerebral glutathione depletion and neurotoxicity. 876 99

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

The effects of verapamil, a calcium channel blocker, on allyl alcohol (AA) hepatotoxicity were studied in vivo. AA administration induced an increase of serum alanine aminotransferase (ALT) concentration and liver necrosis by means of glutathione (GSH) depletion. Pretreatment with verapamil reduced the increase of ALT in plasma and the morphological signs of necrosis induced by AA administration. Verapamil did not affect GSH levels by itself but prevented the decrease of the tripeptide by AA. In vitro, but not in vivo, verapamil inhibited the activity of alcohol dehydrogenase (ADH), the key enzyme in the conversion of AA into the toxic metabolite acrolein. These data indicate that verapamil protects against AA toxicity, probably by preventing the production of acrolein, its reactive metabolite.
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PMID:Effect of verapamil on allyl alcohol hepatotoxicity. 890 40

The effects of acute ethanol and acetaldehyde treatment on cell proliferation, cell adhesion capacity, neutral red incorporation into lysosomes, glutathione content, protein sulfhydryl compounds, lipid peroxidation, inner mitochondrial membrane integrity (MTT test), lactate dehydrogenase activity (LDH) and ultrastructural alterations were investigated in a human fetal hepatic cell line (WRL-68 cells). WRL-68 cells were used, due to the fact that, although this cell line expresses some hepatic characteristics, it does not express alcohol dehydrogenase or cytochrome P450 activity, so it could be a good model to study the effect of the toxic agents per se. Cells were exposed during 120 min with 200 mM ethanol or 10 mM acetaldehyde. Under these conditions, cells presented 100% viability and no morphological alteration was observed by light microscopy. Acetaldehyde-treated cells reduced their proliferative capacity drastically while the ethanol-treated ones presented no difference with control cells. Cell adhesion to substrate, measured as time required to adhere to the substrate and time required to detach from the substrate, was diminished in acetaldehyde WRL-68-treated cells. Cytotoxicity measures as neutral red and MTT test showed that acetaldehyde-treated cells presented more damage than ethanol-treated ones. Cellular respiratory capacity was compromised by acetaldehyde treatment due to 40% less oxygen consumption than control cells. Lipid peroxidation values, measured as malondialdehyde production, were higher in ethanol-treated WRL-68 cells (127%) than in acetaldehyde-treated ones (60%) to control cell values. Lactate dehydrogenase activity (LDH) in extracellular media of ethanol-treated cells presented the highest values. GSH content was reduced 95% and thiol protein content was diminished severely in acetaldehyde-treated cells. Transmission electron microscopy showed more ultrastructural alterations in cells treated with acetaldehyde. The results indicate that acetaldehyde, like ethanol, produced damage at cellular level, although more damage could be observed in acetaldehyde WRL-68-treated cells.
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PMID:Comparative study of the damage produced by acute ethanol and acetaldehyde treatment in a human fetal hepatic cell line. 918


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