Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.6.99.5 (NADH dehydrogenase)
 2,135 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the accompanying paper (Davies, K. J. A., and Doroshow, J. A. (1986) J. Biol. Chem. 261, 3060-3067), we have demonstrated that anthracycline antibiotics are reduced to the semiquinone form at Complex I of the mitochondrial electron transport chain. In the experiments presented in this study we examined the effects of doxorubicin (Adriamycin), daunorubicin, and related quinonoid anticancer agents on superoxide, hydrogen peroxide, and hydroxyl radical production by preparations of beef heart submitochondrial particles. Superoxide anion formation was stimulated from (mean +/- S.E.) 1.6 +/- 0.2 to 69.6 +/- 2.7 or 32.1 +/- 1.5 nmol X min-1 X mg-1 by the addition of 90 microM doxorubicin or daunorubicin, respectively. However, the anthracycline 5-iminodaunorubicin, in which an imine group has been substituted in the C ring quinone moiety, did not increase superoxide production over control levels. In the presence of rotenone, initial rates of oxygen consumption and superoxide formation were identical under comparable experimental conditions. Furthermore, H2O2 production increased from undetectable control levels to 2.2 +/- 0.3 nmol X min-1 X mg-1 after treatment of submitochondrial particles with doxorubicin (200 microM). The hydroxyl radical, or a related chemical oxidant, was also detected after the addition of an anthracycline to this system by both ESR spectroscopy using the spin trap 5,5-dimethylpyrroline-N-oxide and by gas chromatographic quantitation of CH4 produced from dimethyl sulfoxide. Hydroxyl radical production, which was iron-dependent in this system, occurred in a nonlinear fashion with an initial lag phase due to a requirement for H2O2 accumulation. We also found that two quinonoid anti-cancer agents which produce less cardiotoxicity than the anthracyclines, mitomycin C, and mitoxantrone, stimulated significantly less or no hydroxyl radical production by submitochondrial particles. These experiments suggest that injury to cardiac mitochondria which is produced by anthracycline antibiotics may result from the generation of the hydroxyl radical during anthracycline metabolism by NADH dehydrogenase.
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PMID:Redox cycling of anthracyclines by cardiac mitochondria. II. Formation of superoxide anion, hydrogen peroxide, and hydroxyl radical. 300 79

In the present study we have used beef heart submitochondrial preparations (BH-SMP) to demonstrate that a component of mitochondrial Complex I, probably the NADH dehydrogenase flavin, is the mitochondrial site of anthracycline reduction. During forward electron transport, the anthracyclines doxorubicin (Adriamycin) and daunorubicin acted as one-electron acceptors for BH-SMP (i.e. were reduced to semiquinone radical species) only when NADH was used as substrate; succinate and ascorbate were without effect. Inhibitor experiments (rotenone, amytal, piericidin A) indicated that the anthracycline reduction site lies on the substrate side of ubiquinone. Doxorubicin and daunorubicin semiquinone radicals were readily detected by ESR spectroscopy. Doxorubicin and daunorubicin semiquinone radicals (g congruent to 2.004, signal width congruent to 4.5 G) reacted avidly with molecular oxygen, presumably to produce O2-, to complete the redox cycle. The identification of Complex I as the site of anthracycline reduction was confirmed by studies of ATP-energized reverse electron transport using succinate or ascorbate as substrates, in the presence of antimycin A or KCN respiratory blocks. Doxorubicin and daunorubicin inhibited the reduction of NAD+ to NADH during reverse electron transport. Furthermore, during reverse electron transport in the absence of added NAD+, doxorubicin and daunorubicin addition caused oxygen consumption due to reduction of molecular oxygen (to O2-) by the anthracycline semiquinone radicals. With succinate as electron source both thenoyltrifluoroacetone (an inhibitor of Complex II) and rotenone blocked oxygen consumption, but with ascorbate as electron source only rotenone was an effective inhibitor. NADH oxidation by doxorubicin during BH-SMP forward electron transport had a KM of 99 microM and a Vmax of 30 nmol X min-1 X mg-1 (at pH 7.4 and 23 degrees C); values for daunorubicin were 71 microM and 37 nmol X min-1 X mg-1. Oxygen consumption at pH 7.2 and 37 degrees C exhibited KM values of 65 microM for doxorubicin and 47 microM for daunorubicin, and Vmax values of 116 nmol X min-1 X mg-1 for doxorubicin and 114 nmol X min-1 X mg-1 for daunorubicin. In marked contrast with these results, 5-iminodaunodrubicin (a new anthracycline with diminished cardiotoxic potential) exhibited little or no tendency to undergo reduction, or to redox cycle with BH-SMP. Redox cycling of anthracyclines by mitochondrial NADH dehydrogenase is shown, in the accompanying paper (Doroshow, J. H., and Davies, K. J. A. (1986) J. Biol. Chem. 261, 3068-3074), to generate O2-, H2O2, and OH which may underlie the cardiotoxicity of these antitumor agents.
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PMID:Redox cycling of anthracyclines by cardiac mitochondria. I. Anthracycline radical formation by NADH dehydrogenase. 345 45

Iron-sulfur clusters present in rat liver submitochondrial particles were characterized by ESR at temperatures between 30 and 5.5 K combined with potentiometric titrations. The spectral and thermodynamic characteristics of the iron-sulfur clusters were generally similar to those previously reported for pigeon or bovine heart submitochondrial particles. Clusters N-1a, N-1b, N-2, N-3 and N-4 of NADH dehydrogenase had midpoint oxidation-reduction potentials at pH 7.5 of -425, -265, -85, -240 and -260 mV, respectively. Clusters S-1 and S-3 of succinate dehydrogenase had midpoint potentials of 0 and +65 mV, respectively. The iron-sulfur cluster of electron-transferring flavo-protein-ubiquinone oxidoreductase exhibited the gz signal at g = 2.08 and had a midpoint potential of +30 mV. This signal was relatively prominent in rat liver compared to pigeon or bovine heart. Submitochondrial particles from rats chronically treated with ethanol (36% of total calories, 40 days) showed decreases of 20-30+% in amplitudes of signals due to clusters N-2, N-3 and N-4 compared to those from pair-fed control rats. Signals from clusters N-1b, S-1, S-3 and electron-transferring flavoprotein-ubiquinone oxidoreductase were unaffected. Microwave power-saturation behavior was similar for both submitochondrial particle preparations, suggesting that the lower signal amplitudes reflected a lower content of these particular clusters. NADH dehydrogenase activity was significantly decreased (46%), whilst succinate dehydrogenase activity was elevated (25%), following chronic ethanol consumption. The results indicate that chronic ethanol treatment leads to an alteration of the structure and function of the NADH dehydrogenase segment of the electron transfer chain. This alteration is one of the factors contributing to the lower respiration rates observed following chronic ethanol administration.
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PMID:Characterization of iron-sulfur clusters in rat liver submitochondrial particles by electron paramagnetic resonance spectroscopy. Alterations produced by chronic ethanol consumption. 624 7

The molecular basis of the adriamycin (AQ)-dependent development of cardiotoxicity is still far from being clear. In contrast to our incomplete understanding of the organ-specific mechanism mitochondria are unequivocally accepted as the locus where the molecular disorder is triggered. A growing number of reports intimate the establishment of unbalanced oxygen activation through heart mitochondria in the presence of anthraquinones. In fact, in contrast to liver mitochondria, isolated heart mitochondria have been unequivocally shown to shuttle single electrons to AQ, giving rise to O2.- formation by autoxidizing AQ. semiquinones. Earlier we have demonstrated the involvement of the exogenous NADH dehydrogenase in this deleterious electron deviation from the respiratory chain. This enzyme that is associated with complex I of the respiratory chain catalyzes the oxidation of cytosolic NADH. AQ activation through isolated heart mitochondria was reported to require the external addition of NADH, suggesting a flux of reducing equivalents from NADH to AQ in the cytosol. Unlike heart mitochondria, intact liver mitochondria, which are lacking this NADH-related pathway of reducing equivalents from the cytosol to the respiratory chain, cannot be made to activate AQ to semiquinones by NADH or any other substrate of respiration. It appears, therefore, that the exogenous NADH dehydrogenase of heart mitochondria exerts a key function in the myocardial toxicogenesis of anthraquinones via oxygen activation through semireduced AQ. Assessing the toxicological significance of the exogenous NADH dehydrogenase in AQ-related heart injury requires analysis of reaction products and their impact on vital bioenergetic functions, such as energy gain from the oxidation of respiratory substrates. We have applied ESR technique to analyze the identity and possible interactions of radical species emerging from NADH-respiring heart mitochondria in the presence of AQ. The following metabolic steps occur causing depression of energy metabolism in the cardiac tissue. After one-electron transfer to the parent hydrophilic anthraquinone molecule destabilization of the radical formed causes cleavage of the sugar residue. Accumulation of the lipophilic aglycone metabolite in the inner mitochondrial membrane diverts electrons from the regular pathway to electron acceptors out of sequence such as H2O2. HO. radicals are formed and affect the functional integrity of energy-linked respiration. The key and possibly initiating role of the exogenous NADH dehydrogenase of cardiac mitochondria in this reaction pathway provides a rationale to explain the selective cardiotoxic potency of the cytostatic anthraquinone glycosides.
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PMID:Analyses of the molecular mechanism of adriamycin-induced cardiotoxicity. 929 55