Hydrogen peroxide-induced apoptosis: oxidative or reductive stress?
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Amino Acid Chloromethyl Ketones↗
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Kinetics of oxidation of chlorobenzenes and phenyl-ureas by Fe(II)/H2O2 and Fe(III)/H2O2. Evidence of reduction and oxidation reactions of intermediates by Fe(II) or Fe(III).
The rates of degradation of 1,2,4-trichlorobenzene (TCB), 2,5-dichloronitrobenzene (DCNB), diuron and isoproturon by Fe(II)/H2O2 and Fe(III)/H2O2 have been investigated in dilute aqueous solution ([Organic compound]0 approximately 1 microM, at 25.0 +/- 0.2 degrees C and pH < or = 3). Using the relative rate method with atrazine as the reference compound, and the Fe(II)/H2O2 (with an excess of Fe(II)) and Fe(III)/H2O2 systems as sources of OH radicals, the rate constants for the reaction of OH* with TCB and DCNB were determined as (6.0 +/- 0.3)10(9) and (1.1 +/- 0.2)10(9) M(-1) s(-1). Relative rates of degradation of diuron and isoproturon by Fe(II)/H2O2 were about two times smaller in the absence of dissolved oxygen than in the presence of oxygen. These data indicate that radical intermediates are reduced back to the parent compound by Fe(II) in the absence of oxygen. Oxidation experiments with Fe(III)/H2O2 showed that the rate of decomposition of atrazine markedly increased in the presence of TCB and this increase has been attributed to a regeneration of Fe(II) by oxidation reactions of intermediates (radical species and dihydroxybenzenes) by Fe(III).
Chlorobenzenes↗
Chemical reduction of oxidized human lymphocytes inhibits interleukin 2 production but not induction of interleukin 2 responsiveness.
Treatment with neuraminidase (NA) plus galactose oxidase (GalOxase) does not cause stimulation of human thymocytes. However, stimulation can be achieved by addition of exogenous interleukin 2 (IL-2). The IL-2-induced stimulation was inhibited with anti-Tac antibody, indicating that NA/GalOxase-oxidized cells can serve as inducers of functional IL-2 receptors on IL-2-responding T cells. The induction of IL-2 receptors by the oxidized cells was not inhibited by subsequent reduction with borohydride, since the cells could still be stimulated with IL-2. The presence of IL-2 receptors was also confirmed by flow cytometry using indirect immunofluorescence. Peripheral blood lymphocytes can be stimulated by NA/GalOxase treatment, and the conditioned medium from this treatment can support the growth of an IL-2-dependent line. This stimulation can be inhibited with borohydride and restored with IL-2. The conditioned medium derived from the borohydride-reduced cells cannot support the growth of the IL-2-dependent line, indicating that borohydride inhibits the oxidation-induced IL-2 production. The results suggest that NA/GalOxase-oxidized sites can be modified chemically without losing the potential to induce IL-2 receptors.
Cell Line↗
Dechlorination by combined electrochemical reduction and oxidation.
Chlorophenols are typical priority pollutants listed by USEPA (U.S. Environmental Protection Agency). The removal of chlorophenol could be carried out by a combination of electrochemical reduction and oxidation method. Results showed that it was feasible to degrade contaminants containing chlorine atoms by electrochemical reduction to form phenol, which was further degraded on the anode by electrochemical oxidation. Chlorophenol removal rate was more than 90% by the combined electrochemical reduction and oxidation at current of 6 mA and pH 6. The hydrogen atom is a powerful reducing agent that reductively dechlorinates chlorophenols. The instantaneous current efficiency was calculated and the results indicated that cathodic reduction was the main contributor to the degradation of chlorophenol.
Chlorine↗
Haem propionates control oxidative and reductive activities of horseradish peroxidase by maintaining the correct orientation of the haem.
The role of haem propionates in oxidative and reductive reactions catalysed by horseradish peroxidase (HRP) was studied after successful reconstitution of ferric protoporphyrin IX dimethyl ester (PPDME) into the apoperoxidase. The reconstituted enzyme oxidizes neither guaiacol (aromatic electron donor) nor iodide or thiocyanate (inorganic donor). Although the reconstituted enzyme binds guaiacol with a similar Kd (13 mM) to that of the native enzyme (10 mM), the Kd for SCN- binding (5 mM) is decreased 20-fold compared with that of the native enzyme (100 mM). This indicates that haem propionates hinder the entry or binding of inorganic anion to the active site of the native HRP. However, the reconstituted enzyme is catalytically inactive as it does not form spectroscopically detectable compound II with H2O2. CD measurements indicate a significant loss of haem CD spectrum of the reconstituted enzyme at 409 nm, suggesting a loss of asymmetry of the haem-protein interaction. Thus the inability of the reconstituted enzyme to form catalytic intermediates results from the change in orientation of the haem due to loss of interactions via the haem propionates. HRP also catalyses reductive reactions such as reduction of iodine (I+) in the presence of EDTA and H2O2. The reconstituted enzyme cannot catalyse I+ reduction because of the loss of I+ binding to the haem propionate. Since I+ reduction requires formation of the catalytically active enzyme-I+-EDTA ternary complex, the loss of reductive activity is primarily due to the loss of active enzyme formation. Haem propionates thus play a vital role in the oxidative and reductive reactions of HRP by favouring the formation of catalytic intermediates with H2O2 by maintaining the correct orientation of the haem with respect to the surrounding residues.
Apoenzymes↗
Mitochondrial enzyme-catalyzed oxidation and reduction reactions of stilbene estrogen.
We have demonstrated for the first time that mitoplasts (i.e. mitochondria without outer membrane) were able to convert stilbene estrogen (diethylstilbestrol, DES) to reactive metabolites, which covalently bind to mitochondrial (mt)DNA. Depending on the cofactor used, mitochondrial enzymes catalyzed the oxidation and/or reduction of DES. DES was oxidized to DES quinone by peroxide-supported mitochondrial enzyme. A Lineweaver-Burk plot of rate of formation of DES quinone at various substrate concentrations yielded a Km of 33 microM and Vmax of 39 nmol/mg protein/min. The oxidation of DES to DES quinone by mitochondria was drastically decreased by known inhibitors of cytochrome P450. DES quinone was reduced to DES by mitoplasts in the presence of NADH. The Km and Vmax for the DES quinone reduction in the absence of mitoplasts and NADH were 3.2 microM and 5.6 nmol respectively. The reduction of DES quinone to DES by mitoplasts was significantly inhibited by inhibitors of cytochrome b5 reductase and diaphorase. DES quinone was also reduced to DES by pure diaphorase, a mitochondrial reducing enzyme, in the presence of NADH. The Km and Vmax for the DES quinone reduction by diaphorase were 9.0 microM and 4.3 nmol respectively. Under reaction conditions similar to oxidation of DES to DES quinone by mitoplasts, it was observed that mitochondrial metabolic products of DES were able to covalently bind to mtDNA. These data provide direct evidence of mitochondrial enzyme-catalyzed oxidation and reduction reactions of DES. In the cell, activation of DES in the mitochondria (the organelle in which mtDNA synthesis, mtDNA repair and transcription systems are localized) is of utmost importance, because an analogous in vivo mitochondrial metabolism of DES through covalent modifications in mitochondrial genome may produce instability in the mitochondrial genome of the cells. These modifications may in turn play a role in the development of DES-induced hepatocarcinogenicity.
Animals↗
[Persistence for ancient and recent reactions. Penetration of oxidative and reductive reactions in the field of clinical chemistry].
In clinical practice, the importance of analyses for biological materials has increased remarkably. The circumstances of the determination methods, i.e. using oxidative or reductive reactions as their bases, are reviewed. Then, I present the methods we developed. The objective substances include metal containing proteins, such as ceruloplasmin, diamine oxidase, and hemoglobin, and organic carbonic acids, such as xanthurenic acid, uric acid, and lactic acid. Since these substances are hardly related to some conditions of diseases, they are usually measured on routine clinical analysis either oxidatively or reductively, and are afford interest in the reactivity, reacting processes, etc., emphatically.
Amine Oxidase (Copper-Containing)↗
Reactions of cytochromes a and a3. I. Studies of oxidation and reduction of the pigments in a purified preparation.
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Cytochromes↗
Rates of pi-electron oxidation and reduction of free base and Zn(II) porphyrins, chlorins, and isobacteriochlorins.
The rates of pi-electron oxidation and reduction of two homologous series of free base and Zn(II) porphyrins, chlorins, and isobacteriochlorins were studied by chronocoulometry at a platinum disk electrode. The macrocycles were octaethylporphyrin, tetraphenylporphyrin, and the chlorins and isobacteriochlorins derived therefrom. The rates were found to vary to within a factor of 3, and some consistent trends are noted. However, the most important conclusion of this work is that pi-electron redox processes for these macrocycles occur at essentially the same rate, despite the previously noted large differences in pi-electron redox potentials.
Bacteria↗
Electrochemical studies of arsenite oxidase: an unusual example of a highly cooperative two-electron molybdenum center.
Arsenite oxidase from Alcaligenes faecalis, an unusual molybdoenzyme that does not exhibit a Mo(V) EPR signal during oxidative-reductive titrations, has been investigated by protein film voltammetry. A film of the enzyme on a pyrolytic graphite edge electrode produces a sharp two-electron signal associated with reversible reduction of the oxidized Mo(VI) molybdenum center to Mo(IV). That reduction or oxidation of the active site occurs without accumulation of Mo(V) is consistent with the failure to observe a Mo(V) EPR signal for the enzyme under a variety of conditions and is indicative of an obligate two-electron center. The reduction potential for the molybdenum center, 292 mV (vs SHE) at pH 5.9 and 0 degrees C, exhibits a linear pH dependence for pH 5-10, consistent with a two-electron reduction strongly coupled to the uptake of two protons without a pK in this range. This suggests that the oxidized enzyme is best characterized as having an L(2)MoO(2) rather than L(2)MoO(OH) center in the oxidized state and that arsenite oxidase uses a "spectator oxo" effect to facilitate the oxo transfer reaction. The onset of the catalytic wave observed in the presence of substrate correlates well with the Mo(VI/IV) potential, consistent with catalytic electron transport that is limited only by turnover at the active site. The one-electron peaks for the iron-sulfur centers are difficult to observe by protein film voltammetry, but spectrophotometric titrations have been carried out to measure their reduction potentials: at pH 6.0 and 20 degrees C, that of the [3Fe-4S] center is approximately 260 mV and that of the Rieske center is approximately 130 mV.
Alcaligenes faecalis↗
Exercise training improves baroreflex sensitivity associated with oxidative stress reduction in ovariectomized rats.
The protection from coronary events that young women have is sharply reduced at menopause. Oxidative stress and baroreflex sensitivity impairment of the circulation have been demonstrated to increase cardiovascular risk. On the other hand, exercise training has been indicated as a nonpharmacological treatment for many diseases. The aim of the present study was to test the hypothesis that exercise training can improve baroreflex sensitivity associated with reduction in oxidative stress in ovariectomized rats, an experimental model of menopause. Exercise training was performed on a treadmill for 8 weeks. Arterial pressure and baroreflex sensitivity, which were evaluated by tachycardic and bradycardic responses to changes in arterial pressure, were monitored. Oxidative stress was evaluated by chemiluminescence and superoxide dismutase and catalase antioxidant enzyme activities. Exercise training reduced resting mean arterial pressure (112+/-2 vs 122+/-3 mm Hg in the sedentary group) and heart rate (325+/-4 vs 356+/-12 bpm in the sedentary group) and also improved baroreflex sensitivity (tachycardic response, 63% and bradycardic response, 58%). Myocardium (25%) and gastrocnemius muscle (48%) chemiluminescence were reduced, and myocardial superoxide dismutase (44%) and gastrocnemius catalase (97%) activities were enhanced in trained rats in comparison with sedentary rats. Myocardium chemiluminescence was positively correlated with systolic arterial pressure (r=0.6) and inversely correlated with baroreflex sensitivity (tachycardic response, r=-0.8 and bradycardic response, r=-0.7). These results indicate that exercise training in ovariectomized rats improves resting hemodynamic status and reflex control of the circulation, probably associated with oxidative stress reduction, suggesting a homeostatic role for exercise training in reducing cardiovascular risk in postmenopausal women.
Animals↗
Nitro-functionalized oligothiophenes as a novel type of electroactive molecular material: spectroscopic, electrochemical, and computational study.
A novel series of terthiophenes bearing electron-donor and electron-acceptor groups at the end alpha-positions has been prepared. The analysis of the UV-vis, infrared, and Raman spectra, performed with the aid of density functional theory calculations, shows that the asymmetrically substituted nitro compounds PhT(3)NO(2) and BrT(3)NO(2) behave as push-pull systems and present an intense photoinduced charge transfer in the visible spectrum. The symmetrically substituted dinitro compound NO(2)T(3)NO(2) displays a highly delocalized structure with a low single-double bond length alternation and also displays a low-energy absorption band in the visible region. The novel nitroterthiophenes possess attractive electrochemical properties since they generate stable species both upon oxidation and reduction. Oxidation mainly involves changes in the oligothiophene backbone and leads to the formation of stable cations even for NO(2)T(3)NO(2). Reduction is mainly nitro-centered but also affects the conjugated structure. Radical anions and dianions are formed for PhT(3)NO(2) and BrT(3)NO(2). Dianions, not radical anions, and trianions are obtained for NO(2)T(3)NO(2). Nitro-functionalized terthiophenes are shown to be very promising as electroactive molecular materials since they behave as push-pull systems, present a very intense photoinduced charge transfer in the visible region, and could act as both n- and p-channel conductors in organic electronic transistors.
Journal Article↗
Accelerated CuZn-SOD-mediated oxidation and reduction in the presence of hydrogen peroxide.
Copper, zinc-superoxide dismutase (CuZn-SOD) is a cytosolic, antioxidant enzyme that scavenges potentially damaging superoxide radical (()O(2)(-)). Under the proper conditions, CuZn-SOD also catalyzes the oxidation and reduction of certain small molecules. Here, we demonstrate that increased exposure to hydrogen peroxide (H(2)O(2)), a by-product of the ()O(2)(-) scavenging reaction, dramatically increases the ability of CuZn-SOD to oxidize melatonin and reduce S-nitrosoglutathione (GSNO). After a 15min in vitro incubation with CuZn-SOD and 1mM H(2)O(2), 76% of the melatonin was oxidized, compared to 52% with 0.25mM H(2)O(2), and just 9% without H(2)O(2). Pre-incubation with 1mM H(2)O(2) resulted in a 100% increase in the rate of GSNO breakdown by CuZn-SOD in the presence of glutathione (GSH) compared to untreated CuZn-SOD. Collectively, these data suggest that even small increases in intracellular H(2)O(2) levels may result in the oxidation and/or reduction of small molecules critical for proper cellular function.
Binding Sites↗
Oxidative damage and reduction of redox factor-1 expression after transient spinal cord ischemia in rabbits.
OBJECTIVE: The mechanism of spinal cord injury has been thought to be related to the vulnerability of spinal motor neuron cells against ischemia. However, the mechanisms of such vulnerability are not fully understood. We previously reported that spinal motor neurons may be lost by programmed cell death and thus now investigate a possible mechanism of neuronal death with immunohistochemical analysis for 8-hydroxy-2'-deoxyguanosine (8-OHdG) and redox factor-1 (Ref-1). METHODS: We used a rabbit spinal cord ischemia model with a balloon catheter. The spinal cord was removed at 8 hours, 1, 2, or 7 days after 15 minutes of transient ischemia, and histologic changes were studied with hematoxylin-eosin staining. Western blot analysis for Ref-1, temporal profiles of 8-OHdG and Ref-1 immunoreactivity, and double-label fluorescence immunocytochemical studies were performed. RESULTS: Most motor neurons were preserved until 2 days but were selectively lost at 7 days of reperfusion. Western blot analysis of a sample from sham control spinal cord showed a characteristic 37-kDa band that was reduced after ischemia. Immunohistochemistry showed the nuclear expression of Ref-1 in motor neurons of control spinal cords, and immunoreactivity was decreased 1 day after ischemia. On the other hand, no nuclear expression was seen of 8-OHdG in motor neurons of control spinal cords, and immunoreactivity was increased 1 day after ischemia. Double-label fluorescence immunocytochemical study revealed that both 8-OHdG and Ref-1 were positive at 8 hours of reperfusion in the same motor neurons, which eventually die. CONCLUSION: These results suggest that Ref-1 decreased in motor neurons after transient spinal cord ischemia and that this reduction preceded oxidative DNA damage. The reduction of Ref-1 protein at the moderately late stage of reperfusion may be one of the factors responsible for the delay in neuronal death after spinal cord ischemia.
8-Hydroxy-2'-Deoxyguanosine↗
Structure-property relationships in push-pull amino/cyanovinyl end-capped oligothiophenes: quantum chemical and experimental studies.
A series of push-pull chromophores built around thiophene-based pi-conjugating spacers and bearing various types of amino donors and cyanovinyl acceptors have been analyzed by means of UV-vis-NIR, IR, and Raman spectroscopic measurements in the solid state as well as in solution. The intramolecular charge transfer (ICT) of these pi-conjugated systems has also been tested by analyzing the ability of the solute molecules to undergo shifts in their fluorescence emission maxima with increasing solvent polarity. These push-pull oligomers also display an attractive electrochemical behavior since they generate stable species both upon oxidation and reduction. Oxidation mainly involves changes in the electron-rich aminooligothienyl half-part of the molecule and leads to the formation of stable cations. On the other hand, reduction to radical anions and dianions is mainly cyanovinyl-centered but also affects the pi-conjugated electron relay. Density functional theory (DFT) calculations have been carried out to help the assignment of the most relevant electronic and vibrational features and to derive useful information about the molecular structure of these NLO-phores.
Journal Article↗
Developmental changes in glucocorticoid receptor and 11beta-hydroxysteroid dehydrogenase oxidative and reductive activities in rat Leydig cells.
Glucocorticoids directly regulate testosterone production in Leydig cells through a glucocorticoid receptor (GR)-mediated repression of the genes that encode testosterone biosynthetic enzymes. The extent of this action is determined by the numbers of GR within the Leydig cell, the intracellular concentration of glucocorticoid, and 11beta-hydroxysteroid dehydrogenase (11betaHSD) activities that interconvert corticosterone (in the rat) and its biologically inert derivative, 11-dehydrocorticosterone. As glucocorticoid levels remain stable during pubertal development, GR numbers and 11betaHSD activities are the primary determinants of glucocorticoid action. Therefore, in the present study, levels of GR and 11betaHSD messenger RNA (mRNA) and protein were measured in rat Leydig cells at three stages of pubertal differentiation: mesenchymal-like progenitors (PLC) on day 21, immature Leydig cells (ILC) that secrete 5alpha-reduced androgens on day 35, and adult Leydig cells (ALC) that are fully capable of testosterone biosynthesis on day 90. Numbers of GR, measured by [3H]dexamethasone binding, in purified cells were 6.34 +/- 0.27 (x 10(3) sites/cell; mean +/- SE) for PLC, 30.45 +/- 0.74 for ILC, and 32.54 +/- 0.84 for ALC. Although GR binding was lower in PLC, steady state levels for GR mRNA were equivalent at all three stages (P > 0.05). Oxidative and reductive activities of 11betaHSD were measured by assaying the conversion of radiolabeled substrates in incubations of intact Leydig cells. Both oxidative and reductive activities were barely detectable in PLC, intermediate in ILC, and highest in ALC. The ratio of the two activities favored reduction in PLC and ILC and oxidation in ALC (oxidation/reduction, 0.33 +/- 0.33 for PLC, 0.43 +/- 0.05 for ILC, and 2.12 +/- 0.9 for ALC, with a ratio of 1 indicating equivalent rates for both activities). The mRNA and protein levels of type I 11betaHSD in Leydig cells changed in parallel with 11betaHSD reductive activity, which increased gradually during the transition from PLC to ALC, compared with the sharp rise that was seen in oxidative activity. We conclude that Leydig cells at all developmental stages have GR and that their ability to respond to glucocorticoid diminishes as net 11betaHSD activity switches from reduction to oxidation. This provides a mechanism for the Leydig cell to regulate its intracellular concentration of corticosterone, thereby varying its response to this steroid during pubertal development.
11-beta-Hydroxysteroid Dehydrogenases↗
[Effects of alpha-tocopherol on oxidation and reduction systems of blood and tissues].
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Blood↗
Substituent effects on the oxidation and reduction potentials of phenylthiyl radicals in acetonitrile.
Oxidation (E(1/2)(ox)) and reduction potentials (E(1/2)(red)) of a series of para-substituted phenylthiyl radicals XC(6)H(4)S* generated from the pertinent disulfides or thiophenols have been measured by means of photomodulated voltammetry in acetonitrile. The values of E(1/2)(ox) are of particular interest as they give access to the hitherto unknown thermochemistry of short-lived phenylsulfenium cations in solution. Both E(1/2)(OX) and E(1/2)(red) decrease as the electron-donating power of the substituent raises, resulting in linear correlations with the Hammett substituent coefficient sigma(+) with slopes rho(+) of 4.7 and 6.4, respectively. The finding of a larger substituent effect on than is a consequence of a corresponding development in the electron affinities and ionization potentials of XC(6)H(4)S* as revealed by quantum-chemical calculations. Solvation energies extracted for XC(6)H(4)S(+) and XC(6)H(4)S(-) from thermochemical cycles show the expected substituent dependency; i.e., the absolute values of the solvation energies decrease as the charge becomes more delocalized in the ions. Acetonitrile is better in solvating XC(6)H(4)S(+) than XC(6)H(4)S(-) for most substituents, even if there is a substantial delocalization of the charge in the series of phenylsulfenium cations. The substituent effect on is smaller in aqueous solution than acetonitrile, which is attributed to the ability of water to stabilize in particular localized anions through hydrogen bonding.
Journal Article↗