Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.9.3.1 (cytochrome oxidase)
 8,822 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The surface of rat visceral yolk sacs (VYS) of intact, viable rat conceptuses were continuously monitored with a microfiberoptic sensor optimized for detection of the reduced pyridine nucleotides, NADH and NADPH. Model chemical toxins, cyanide and alloxan, were used and evaluated on the basis of their differential ability to modulate NAD(H)- and NADP(H)-dependent cellular pathways, respectively. Exposure with 2 mM sodium cyanide for 5 min caused a reversible fluorescence increase of 325 arbitrary fluorescence units (AFU) and 225 AFU on Gestational Days (GD) 10 and 11, respectively. Exposure with 40 mM alloxan for 5 min resulted in a fluorescence decrease of 170 and 120 AFU on GD 10 and 11, respectively. Glutathione (GSH) levels in the VYS, as determined by HPLC, showed a marked decrease from 27.3 +/- 2.1 to 2.9 +/- 0.4 pmol/mg protein, within the 5-min alloxan exposure period on GD 10. No decrease in GSH levels was noted for the same exposure duration on GD 11. A 2-hr pretreatment with 25 microM BCNU [(1,3 bis(2-chloroethyl)-1-nitrosourea], to inhibit glutathione disulfide reductase (GSSG-Rd), resulted in an elimination of the fluorescence decrease, but still led to a significant drop in GSH levels as seen on both days of gestation. These results are consistent with overall changes in intracellular pyridine nucleotide concentrations, where the relative amounts of NADPH increase significantly and disproportionately from GD 10 to 11. The net oxidation of NADPH, through GSSG-Rd activity, appears to be responsible for the alloxan-induced decrease in surface fluorescence. Conversely, the cyanide-induced fluorescence increases appear to be the result of NAD+ reduction, mediated through the inhibition of the terminal cytochrome oxidase in the electron transport chain.
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PMID:Real time microfiberoptic redox fluorometry: modulation of the pyridine nucleotide status of the organogenesis-stage rat visceral yolk sac with cyanide and alloxan. 854 33

Morphological and biochemical changes in mitochondrial have been reported early in the course of cocaine-induced hepatotoxicity. This study was designed to examine the effects of repeated cocaine exposure in vivo on mitochondrial respiration, activities of respiratory chain enzymes, and lipid peroxide measures in liver. Male Sprague-Dawley rats were exposed to cocaine (5 i.p. injections of 25 mg/kg; 3-day period). Blood and liver samples were taken, and hepatic mitochondria were isolated by differential centrifugation. The cocaine-treated rats developed oxidative stress in hepatic mitochondria as evidenced by a significant increase in malonaldialdehyde (MDA; 52%; p < 0.0001) and a decreased glutathione (GSH; 22%; p < 0.0003). Blood aspartate aminotransferase (AST) and glutathione s-transferase (GST) levels in cocaine groups were significantly elevated (2.6 and 3.2 fold, respectively; p < 0.0001 for both). Cocaine caused a decrease in state-3 respiration and respiratory control ratio (RCR) ratio when exposed to site I and II substrates; these changes were parallelled by a decrease in complex I (22%; p < 0.003), succinate cytochrome c reductase (27%; p < 0.004), and complex IV (24%; p < 0.003). In conclusion, functional abnormalities of hepatic mitochondria accompany lipid peroxidation caused by cocaine, supporting the hypothesis that the mitochondria is one of the major intracellular targets of cocaine hepatotoxicity.
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PMID:Impairment of mitochondrial respiration and electron transport chain enzymes during cocaine-induced hepatic injury. 907 24

Ceramide is a sphingolipid that is generated in the signaling of inflammatory cytokines such as tumor necrosis factor (TNF), which exerts many functional roles depending on the cell type where it is produced. Since TNF cytotoxicity is mediated by overproduction of reactive oxygen species from mitochondria, we have examined the role of ceramide in generation of oxidative stress in isolated rat liver mitochondria. The present studies demonstrate that addition of N-acetylsphingosine (C2-ceramide) to mitochondria led to an increase of fluorescence of dihydrorhodamine 123 or dichlorofluorescein-stained mitochondria, indicating formation of hydrogen peroxide. Such effect was significant at 0.25 microM and maximal at 1-5 microM C2, decreasing at greater concentrations. This inductive effect of ceramide was mimicked by N-hexanoylsphingosine at the same concentration range, whereas the immediate precursor of C2, C2-dihydroceramide increased hydrogen peroxide at 1-5 microM. Sphingosine generated hydrogen peroxide at concentrations >/=10 microM, whereas diacylglycerol failed to increase hydrogen peroxide. The increase in hydrogen peroxide induced by C2 was not triggered by mitochondrial permeability transition as C2 did not induce mitochondrial swelling. Blocking electron transport chain at complex I and II prevented the increase in hydrogen peroxide induced by C2; however, interruption of electron flow at complex III by antimycin A potentiated the inductive effect of C2. Depletion of matrix GSH prior to exposure to ceramide resulted in a potentiated increase (2-fold) of hydrogen peroxide generation, leading to lipid peroxidation and loss of activity of respiratory chain complex IV compared with GSH-repleted mitochondria. Mitochondria isolated from TNF-treated cells showed an increase (2-3-fold) in the amount of ceramide compared with mitochondria from untreated cells. These results suggest that mitochondria are a target of ceramide produced in the signaling of TNF whose effect on mitochondrial electron transport chain leads to overproduction of hydrogen peroxide and consequently this phenomena may account for the generation of reactive oxygen species during TNF cytotoxicity.
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PMID:Direct effect of ceramide on the mitochondrial electron transport chain leads to generation of reactive oxygen species. Role of mitochondrial glutathione. 911 Oct 45

Mitochondria generate reactive oxygen species (ROS) as byproducts of molecular oxygen consumption in the electron transport chain. Most cellular oxygen is consumed in the cytochrome-c oxidase complex of the respiratory chain, which does not generate reactive species. The ubiquinone pool of complex III of respiration is the major site within the respiratory chain that generates superoxide anion as a result of a single electron transfer to molecular oxygen. Superoxide anion and hydrogen peroxide, derived from the former by superoxide dismutase, are precursor of hydroxyl radical through the participation of transition metals. Glutathione (GSH) in mitochondria is the only defense available to metabolize hydrogen peroxide. A small fraction of the total cellular GSH pool is sequestered in mitochondria by the action of a carrier that transports GSH from the cytosol to the mitochondrial matrix. Mitochondria are not only one of the main cellular sources of ROS, they also are a key target of ROS. Mitochondria are subcellular targets of cytokines, especially tumor necrosis factor (TNF); depletion of GSH in this organelle renders the cell more susceptible to oxidative stress originating in mitochondria. Ceramide generated during TNF signaling leads to increased production of ROS in mitochondria. Chronic ethanol-fed hepatocytes are selectively depleted of GSH in mitochondria due to a defective operation of the carrier responsible for transport of GSH from the cytosol into the mitochondrial matrix. Under these conditions, limitation of the mitochondrial GSH pool represents a critical contributory factor that sensitizes alcoholic hepatocytes to the prooxidant effects of cytokines and prooxidants generated by oxidative metabolism of ethanol. S-adenosyl-L-methionine prevents development of the ethanol-induced defect. The mitochondrial GSH carrier has been functionally expressed in Xenopus laevis oocytes microinjected with mRNA from rat liver. This critical carrier displays functional characteristics distinct from other plasma membrane GSH carriers, such as its ATP dependency, inhibitor specificity, and the size class of mRNA that encode the corresponding carrier, suggesting that the mitochondrial carrier of GSH is a gene product distinct from the plasma membrane transporters.
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PMID:GSH transport in mitochondria: defense against TNF-induced oxidative stress and alcohol-induced defect. 925 4

The present study investigates the influence of energy related metabolic stress on amyloid precursor protein (APP) non-amyloidogenic secretory processing in COS cells. The effect of glucose deprivation on soluble APP (sAPP) secretion has been evaluated: incubation of COS cells with 50 mM 2-deoxy-D-glucose (2-DG) in glucose free medium was able to reduce sAPP secretion (-26%). Sodium azide (NaN3), an inhibitor of cytochrome c oxidase (complex IV of the mitochondrial electron transfer chain) decreased sAPP release in a concentration dependent way (maximum -75%). Treatment of COS cells with the antioxidant glutathione (GSH) fully antagonized the inhibitory effect of azide (1 mM) and elicited sAPP release over basal level. These results suggest that the inhibition of energy metabolism can influence APP processing leading to a decreased secretion of non-amyloidogenic fragments of APP.
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PMID:Effect of energy shortage and oxidative stress on amyloid precursor protein metabolism in COS cells. 929 Nov 53

We investigated the effect of glutathione (GSH) depletion on mitochondrial function and generation of reactive oxygen intermediates (ROI) in PC12 cells in vitro. Direct depletion of cellular GSH using ethacrynic acid (EA, 500 mM) resulted in a concentration-dependent generation of ROI and cell death within 24 h. Treatment with 500 microM L-buthionine sulfoximine (BSO), which inhibits GSH synthesis, reduced cellular GSH but did not lead to generation of ROI. Furthermore, cells remained viable up to 72 h. Analysis of subcellular fractions revealed complete loss of cytosolic and mitochondrial GSH within 4 h of EA treatment. In contrast, BSO-treated cells still maintained 100% GSH in the mitochondrial fraction for 4 h and 6% for 48 h. Mitochondrial complex II/IIi and IV activities were not significantly decreased up to 48 h of BSO treatment while EA treatment resulted in a complete loss of complex II/III activity and a 70% reduction of complex IV activity within 4 h. These findings suggest that mitochondrial GSH is critical for the maintenance of mitochondrial function and cellular viability.
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PMID:Differential effects of L-buthionine sulfoximine and ethacrynic acid on glutathione levels and mitochondrial function in PC12 cells. 1031 99

Bilirubin is a well-known neurotoxin and presents a particular problem in newborn infants. This is partly due to the high incidence of unconjugated hyperbilirubinemia in that age group, but may also be due to increased vulnerability to bilirubin toxicity. The brain may be able to protect itself against bilirubin toxicity through a process of oxidation. The responsible enzyme is localized on the inner mitochondrial membrane and appears to be more active in glia than in neurons and to increase in activity with postnatal maturation. Here we have investigated the possibility that the responsible enzyme might be a cytochrome oxidase, malate dehydrogenase, or monoamine oxidase, all enzymes located on the inner mitochondrial membrane. Mitochondria were obtained from rat brains through homogenization and differential centrifugation in sucrose medium. The ability of mitochondrial membranes to oxidize bilirubin was measured by following the change in optical density at 440 nm of a bilirubin solution to which a membrane suspension had been added. The activity was not changed by in vitro inhibitors of malate dehydrogenase or monoamine oxidase, but was moderately inhibited by ketoconazole and clotrimazole, both known inhibitors of hepatic cytochrome P450 oxidases. Activity was inhibited by depletion of cytochrome c in the mitochondria and reconstituted by reintroducing cytochrome c into the reaction mixture. The reaction was not modified by the addition of a free radical quencher, but was inhibited by removal of oxygen from the reaction mixture. The activity was significantly inhibited by cyanide. Activity was retained in a 100,000-g pellet and was not influenced by the addition of NAD, NADP, NADH, NADPH, GSH, or GSSH to this pellet. We conclude that the bilirubin-oxidizing activity in brain mitochondrial membranes is cytochrome c dependent, but does not appear to be unequivocally identifiable as a cytochrome P450 oxidase.
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PMID:Oxidation of bilirubin in the brain-further characterization of a potentially protective mechanism. 1056 68

Biological systems that produce or are exposed to nitric oxide (NO radical) exhibit changes in the rate of oxygen free radical production. Considering that mitochondria are the main intracellular source of oxygen radicals, and based on the recently documented production of NO(radical) by intact mitochondria, we investigated whether NO(radical), produced by the mitochondrial nitric-oxide synthase, could affect the generation of oxygen radicals. Toward this end, changes in H(2)O(2) production by rat liver mitochondria were monitored at different rates of endogenous NO(radical) production. The observed changes in H(2)O(2) production indicated that NO(radical) affected the rate of oxygen radical production by modulating the rate of O(2) consumption at the cytochrome oxidase level. This mechanism was supported by these three experimental proofs: 1) the reciprocal correlation between H(2)O(2) production and respiratory rates under different conditions of NO(radical) production; 2) the pattern of oxidized/reduced carriers in the presence of NO(radical), which pointed to cytochrome oxidase as the crossover point; and 3) the reversibility of these effects, evidenced in the presence of oxymyoglobin, which excluded a significant role for other NO(radical)-derived species such as peroxynitrite. Other sources of H(2)O(2) investigated, such as the aerobic formation of nitrosoglutathione and the GSH-mediated decay of nitrosoglutathione, were found quantitatively negligible compared with the total rate of H(2)O(2) production.
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PMID:The modulation of oxygen radical production by nitric oxide in mitochondria. 1110 47

Glutathione deficiency is commonly associated with mitochondrial complex I dysfunction and loss of viability in neurones, but not in glia. In order to address the possible mechanism responsible for this cellular difference, the regulation of mitochondrial complex I expression by glutathione depletion was investigated in glial cells. Incubation of rat-cultured astrocytes and C6 glioma cells with the specific gamma-glutamylcysteine synthetase inhibitor L-buthionine-(S:,R:)-sulfoximine (L-BSO; 0.1-1 mM) decreased the total specific content of glutathione in a dose- and time-dependent fashion. Northern blot analyses revealed that glutathione deficiency caused by L-BSO (0.1 mM) was associated with a twofold enhancement in complex I regulatory subunit ND6 (mitochondrially encoded) mRNA expression after 24-72 h. This effect was accompanied by a twofold increase in complex-I activity at 72 h in L-BSO-treated cells, as compared with control cells, but complex II-III, complex IV and citrate synthase activities were unaltered. It is suggested that the oxidative stress caused by glutathione depletion in glial cells would up-regulate complex-I activity by enhancing the expression of the mitochondrially encoded regulatory subunit. These results could offer further insight into the different degree of cellular susceptibility observed in glial vs. neuronal cells against oxidative stress.
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PMID:Depletion of glutathione up-regulates mitochondrial complex I expression in glial cells. 1123 44

Rats fed a vitamin E-depleted diet for 48 weeks had undetectable levels of vitamin E in the gastrocnemius muscle and liver, leading to elevated malondialdehyde levels in both tissues and an elevated GSH level in muscle. Skeletal-muscle mitochondria showed decreased mitochondrial respiratory chain (MRC) activities, whereas liver MRC activities were increased. Exposure of normal rat liver submitochondrial particles (SMPs) to an in vitro NADPH-dependent lipid peroxidation system resulted in a dose-dependent increase in lipid peroxidation and inhibition of complex I and complex IV activities. Complex I exhibited greater sensitivity to lipid peroxidation than complex IV. At low and high NADPH concentrations, the rate of lipid peroxidation and the level of enzyme inhibition were essentially the same in liver SMPs from both vitamin E-deficient and control rats, suggesting that under these conditions, the loss of vitamin E did not exacerbate the effects of either lipid peroxidation or enzyme inhibition. These results indicate that normal vitamin E levels in liver mitochondria are not required for protection against lipid peroxidation and are consistent with the normal liver mitochondrial function in vitamin E-deficient animals. This suggests other antioxidants, such as ubiquinol and GSH, may be more important in protecting liver mitochondria and MRC from lipid peroxidation.
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PMID:Sensitivity of respiratory chain activities to lipid peroxidation: effect of vitamin E deficiency. 1146 62


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