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PubMed1995

Monitoring of ubiquinol-10, ubiquinone-10, carotenoids, and tocopherols in neonatal plasma microsamples using high-performance liquid chromatography with coulometric electrochemical detection.

A method for measuring the lipophilic antioxidants alpha-tocopherol, gamma-tocopherol, ubiquinol-10, ubiquinone-10, beta-cryptoxanthin, and beta-carotene in 5 or 10 microliters neonatal plasma is presented. First lipid extraction together with the internal standards gamma-tocotrienol, ubiquinone-7, ubiquinol-9, ubiquinone-9, and ethyl beta-apo-8'-carotenoate was carried out. Then the components were separated on a RPC2/C18 column. Coulometric electrochemical detection was performed using the reduction-oxidation mode (-0.60 V; -0.15 V; +0.60 V). Detection limits for all components were between 21 and 60 fmol, corresponding to 0.004 and 0.012 mumol/liter plasma; the within-day precision (coefficient of variation) was between 3 and 14% for all measured substances. Reference values are given for healthy newborn children from the second to the sixth day of life. Using the presented HPLC technique it is possible to monitor the concentrations of lipophilic antioxidants in plasma of sick immature newborn children in order to study effects of oxidative stress.

Antioxidants↗
PubMed2002

Redox regulation of pro-inflammatory cytokines and IkappaB-alpha/NF-kappaB nuclear translocation and activation.

Reduction-oxidation (redox) state constitutes such a potential signaling mechanism for the regulation of an inflammatory signal associated with oxidative stress. Exposure of alveolar epithelial cells to ascending DeltapO(2) regimen+/-reactive oxygen species (ROS)-generating systems induced a dose-dependent release of interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha. Similarly, the Escherichia coli-derived lipopolysaccharide-endotoxin (LPS) up-regulated cytokine biosynthesis in a dose- and time-dependent manner. Irreversible inhibition of gamma-glutamylcysteine synthetase, the rate-limiting enzyme in the biosynthesis of glutathione (GSH), by L-buthionine-(S,R)-sulfoximine (BSO), induced the accumulation of ROS and augmented DeltapO(2) and LPS-mediated release of cytokines. Analysis of the molecular mechanism implicated revealed an inhibitory-kappaB (IkappaB-alpha)/nuclear factor-kappaB (NF-kappaB)-independent pathway in mediating redox-dependent regulation of inflammatory cytokines. BSO stabilized cytosolic IkappaB-alpha and down-regulated its phosphorylation, thereby blockading NF-kappaB activation, yet it augmented cytokine secretion. Glutathione depletion is associated with the augmentation of oxidative stress-mediated inflammatory state in a ROS-dependent mechanism and the IkappaB-alpha/NF-kappaB pathway is redox-sensitive but differentially involved in regulating redox-dependent regulation of cytokines.

Active Transport, Cell Nucleus↗
PubMed2002

Oxygen homeostasis, thiol equilibrium and redox regulation of signalling transcription factors in the alveolar epithelium.

There is growing evidence linking the pathophysiology of lung disease to an imbalance state of reduction-oxidation (redox) equilibrium. The therapeutic potential of glutathione, an ubiquitous sulfhydryl thiol, and its immunopharmacological properties in the airway epithelium bears clinical consequences for the paediatric treatment of respiratory distress (RD). Dynamic variation in alveolar pO(2) and its effect on redox state may impose a direct role in modulating the pattern of gene expression in lung tissues and, accordingly, could be pivotal in determining cellular fate under these conditions. Hypoxia-inducible factor-1alpha (HIF-1alpha) and nuclear factor-kappaB (NF-kappaB) are redox-sensitive transcription factors of particular importance because their differential activation by reducing and oxidizing signals, respectively, regulate the expression/suppression of O(2)-responsive genes. The regulation of these transcription factors, therefore, which is redox sensitive, is consistent with their roles in coordinating adaptive homeostatic responses to oxidative stress. Functionally, the relationship between O(2), glutathione biosynthesis and transcription factor activity bears typical implications for the pattern of cellular survivorship and alveolarization on exposure to O(2)-linked stresses. In this review, I discuss (1) the HIF-1alpha/NF-kappaB responsiveness to dynamic changes in pO(2) characteristic of the transition period from placental to pulmonary-based respiration, (2) the capacity of the alveolar epithelium to engage in glutathione biosynthesis and redox shuttling, effectively forming a feedback mechanism governing gene expression, (3) the restitution of antioxidant/prooxidant equilibrium following oxidative challenge and its dependency on the adaptive coordination of responses between redox-associated signalling pathways controlling apoptosis and genetic regulatory factors and (4) a likely association between oxidative stress and the evolution of an inflammatory signal through the pleiotropic O(2)-sensitive cytokines.

Homeostasis↗
PubMed2001

Cellular thiols and reactive oxygen species in drug-induced apoptosis.

In higher eukaryotes, reactive oxygen species (ROS) are generated during respiration in mitochondria in the course of reduction of molecular oxygen as well as by distinct enzyme systems. ROS have been implicated in the regulation of diverse cellular functions including defense against pathogens, intracellular signaling, transcriptional activation, proliferation, and apoptosis. The reduction-oxidation (redox) state of the cell is primarily a consequence of the precise balance between the levels of ROS and endogenous thiol buffers present in the cell, such as glutathione and thioredoxin, which protect cells from oxidative damage. Dramatic elevation of ROS, exceeding compensatory changes in the level of the endogenous thiol buffers, may result in the sustained activation of signaling pathways and expression of genes that induce apoptosis in affected cells. Many cytotoxic drugs function selectively to kill cancer cells by the abrogation of proliferative signals, leading to cell death, and numerous reports have demonstrated that ROS are generated following treatment with these drugs. In this review, we will summarize recent contributions to our understanding of the importance of cytotoxic drug-induced modulation of cellular redox status for signaling and transcription leading to activation of apoptotic effector mechanisms.

Animals↗
PubMed2002

Change of redox status and modulation by thiol replenishment in retinal photooxidative damage.

PURPOSE: Cellular or tissue reduction-oxidation (redox) is crucial in various diseases. The present study was conducted to analyze how tissue redox status is affected by photooxidative stress and whether the exogenous thiol antioxidant N-acetylcysteine (NAC) affects photooxidative stress-induced retinal damage. METHODS: Mice were intraperitoneally injected with either NAC (250 mg/kg) or phosphate-buffered saline (PBS) and exposed to white fluorescent light (8000 lux) for 2 hours. Levels of thioredoxin (TRX), glutaredoxin (GRX), and glutathione (GSH), endogenous regulators of redox; 4-hydroxy-2-nonenal (HNE)-modified protein, a marker of lipid peroxidation; and nuclear factor (NF)-kappaB, a redox-sensitive transcription factor in retinal samples, was measured by immunohistochemistry and Western blot or enzymatic recycling assay. Light-induced retinal damage estimated by electroretinography and quantitative immunohistochemistry for 8-hydroxy-2-deoxyguanosine (8OHdG index), a marker of oxidative stress-induced DNA damage, was compared in NAC- and PBS-treated mice. RESULTS: Upregulation of TRX and HNE-modified protein, decrease of GSH, and nuclear translocation of NF-kappaB were noted after light exposure in PBS-treated mice. These changes were suppressed in NAC-treated mice compared with PBS-treated mice. GRX was not upregulated after light exposure in any mice. The a- and b-wave amplitudes were significantly higher, and the 8OHdG index was significantly lower after light exposure in NAC-treated mice than in PBS-treated mice. CONCLUSIONS: Retinal redox status is altered by intense light and is normalized partially by the effect of NAC on TRX and GSH tissue levels. Manipulation of the tissue redox state by exogenous thiol replenishment may be a useful strategy to prevent retinal photooxidative damage.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1985

Reduction of oxidized cytochrome c by ascorbate ion.

The kinetics and mechanism of the reduction of oxidized cytochrome c by ascorbate has been investigated in potassium nitrate, potassium 4-morpholineethanesulfonate (KMes), potassium sulfate and potassium ascorbate media. The results are consistent with simple second order electron transfer from ascorbate dianion to cytochrome c and do not support electron transfer from an ascorbate dianion bound to the protein of the cytochrome as recently proposed by Myer and Kumar. A rate constant of 8 X 10(5) M-1 X s-1 (25 degrees C, ionic strength, 0.1) was found for the electron-transfer step. This rate constant is essentially independent of the specific ions used in controlling ionic strength.

Alkanesulfonates↗
PubMed1997

Hormonal regulation of oxidative and reductive activities of 11 beta-hydroxysteroid dehydrogenase in rat Leydig cells.

We have proposed that the 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) of Leydig cells protects against glucocorticoid-induced inhibition of testosterone (T) production. However, Leydig cells express type I 11 beta-HSD, which has been shown to be reductive in liver parenchymal cells. Because reduction would have the opposite effect of activating glucocorticoid, the present study was designed to determine: 1) whether Leydig cell 11 beta-HSD is primarily oxidative or reductive; and 2) whether oxidative and reductive activities are separately modified by known regulators of Leydig cell steroidogenic function. Leydig cells and liver parenchymal cells were purified from mature male Sprague-Dawley rats (250 g BW), and 11 beta-HSD oxidative and reductive activities were measured using radiolabeled substrates and TLC of triplicate media samples from 1-h incubations immediately after cell isolation. Enzyme activities also were examined in purified Leydig cells at the end of 3 days of culture in vitro in the presence of LH (10 ng/ml), dexamethasone (DEX, 100 nM), T (50 nM), or epidermal growth factor (EGF, 50 ng/ml). In confirmation of previous reports, the reductive activity of 11 beta-HSD was predominant over oxidation in liver parenchymal cells. In contrast, 11 beta-HSD oxidative activity prevailed over reduction in Leydig cells by a ratio of 2:1. The activities of 11 beta-HSD also were analyzed in Leydig cells that were purified 7 days after endogenous glucocorticoid levels were suppressed by adrenalectomy (ADX). Oxidative activity declined in Leydig cells after ADX (22.53 +/- 1.12 pmol/h.10(6) cells, mean +/- SEM vs. 31.47 +/- 1.48 pmol/.10(6) cells in sham-operated controls, P < 0.05), whereas there was no change in reductive activity. This indicated that physiologically active corticosterone is involved in maintaining the predominance of 11 beta-HSD oxidation. When enzyme activities were analyzed in Leydig cells after 3 days of hormonal treatment in vitro, oxidation and reduction were observed to change in opposing directions. Culture of Leydig cells from sham-operated control rats with either LH, T, or EGF resulted in declines in oxidative activity from 33.35 +/- 0.77 to 28.24 +/- 1.93, 27.30 +/- 0.96, and 24.13 +/- 1.02 pmol/ h.10(6) cells (x +/- SE), respectively. However, EGF stimulated 11 beta-HSD reductive activity in cultured Leydig cells from both control (from 18.97 +/- 1.10 to 27.16 +/- 0.71 pmol/h.10(6) cells and ADX rats (from 16.51 +/- 0.75 to 23.56 +/- 0.84 pmol/h.10(6) cells). Among the hormonal treatments, only DEX increased oxidative activity and simultaneously decreased reductive activity in Leydig cells from ADX rats. This increase accentuated the predominance of oxidative activity in Leydig cells, with a ratio of oxidative to reductive activity of 4:1 after DEX treatment, compared with 2:1 in controls that were untreated. We conclude that 11 beta-HSD activity in Leydig cells is primarily oxidative. Moreover, oxidation and reduction are regulated separately by hormones.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1978

Diffusion-potential-induced oxidation and reduction of cytochromes in chromatophores from Rhodopseudomonas sphaeroides.

A membrane potential jump was induced by the addition of valinomycin in the presence of a KCl concentration gradient across the membrane of Rhodopseudomonas sphaeroides chromatophores. As well as a carotenoid band shift, which is known to be an indicator of membrane potential, absorbance changes due to the oxidation-reduction reactions of cytochromes accompanied the jump. Under aerobic conditions with no reductant added, a part of cytochrome c2 was reduced by an inside-positive potential jump of about 100 mV in the time range of tens of seconds. This can be explained by the location of the cytochrome on the inner side of the chromatophore membrane and electrophoretic flow of electrons across the membrane. On the other hand, in the presence of 1 mM ascorbate, a similar jump of membrane potential induced a rapid oxidation of cytochrome c2 and a subsequent reduction. A rapid reduction of b-type cytochrome was also observed. Antimycin A inhibited the c2 oxidation, but did not inhibit the b reduction. The oxidation of cytochrome c2 may be explained by a diffusion-potential-induced electron flow to cytochrome b and a simultaneous electron donation by cytochrome b and cytochrome c2 to a common electron acceptor, possibly a quinone.

Anaerobiosis↗
PubMed1997

Oxidatively Induced Reductive Eliminations. A Mechanistic Study of the Oxidation Chemistry of CnRhMe(3) (Cn = 1,4,7-Trimethyl-1,4,7-triazacyclononane).

The trimethylrhodium(III) complex CnRhMe(3) (1, Cn = 1,4,7-trimethyl-1,4,7-triazacyclononane) undergoes a nearly reversible one-electron oxidation at E degrees = -0.15 V vs Cp(2)Fe/Cp(2)Fe(+) (cyclic voltammetry, 1.0 V/s) in acetonitrile/0.1 M Bu(4)NPF(6). Preparative electrolysis as well as homogeneous oxidations with substituted ferricinium salts gives a mixture of CnRhMe(2)(NCMe)(+) (2) and CnRhMe(NCMe)(2)(2+) (3), the 2:3 ratio being independent of the nature of the oxidant. In addition, the reactions yielded ethane, mostly by intramolecular elimination. An investigation of the kinetics of the reaction of 1(*)(+) by derivative cyclic voltammetry revealed a unimolecular reaction (DeltaH() = 57.0 +/- 0.9 kJ/mol, DeltaS() = -35.4 +/- 3.0 J/(K.mol), k(20 degrees C) = 5.9 s(-)(1)) with negligible solvent effects (MeCN vs CH(2)Cl(2)). It is proposed that 1(*)(+) eliminates ethane to generate the formally 15-electron CnRhMe(*)(+) in the rate-determining step. The final Rh-containing products are likely formed from this species and 1(*)(+).

Journal Article↗
PubMed1975

The effect of functional differences in the alpha and beta chains on the cooperativity of the osidation reduction reaction of hemoglobin.

Partially oxidized solutions of hemoglobin have been reacted with azide to determine the extent of oxidation, of the alpha and beta chains according to the method of McQuarrie and Gibson (J. Biol. Chem. (1971) 246, 517-522) In 2, 2'2'' nitriloethanol buffer the fraction of oxidized material represented by the beta chains decreases with decreasing extent of total oxidation, of the alpha chains. Upon addition of insitol hexaphosphate, the degree of perferntial oxidation in terms of a two-state model similar to the description of oxygenation by Edelstein (nature(1971) 230, 224-227) but with the incorporation of chain heterogeneity. The results indicate that the pH-dependent cooperativity of the oxidation-reduction reaction can be described in terms of a bell curbe of n versus log l, the allosteric somewhat lower and shifted slightly to the left, due in part to an affnity of beta chains for electrons approximately twince that of alpha chains. Because the curve is shifted to the left, oxidation-reduction equilibria at l values corresponding to pH 6 to lie on the right side of the bell curve where cooperativity the preferntial affity of beta chains for electrons rises to about 4 times that of alpha chains. As a consequence, the coreesponding bell curve is lowered with the Hill coeficient falling to unity or below in the range of l encountered. Thus the principal cause of decreased cooperativity is chain heterogeneity and not stabilization in the t state as suggested by Perutz; under these conditions the molecules of methemoglobin in the t state are only a fractional part of the population.

Binding Sites↗
PubMed2006

pH dependence of proton translocation in the oxidative and reductive phases of the catalytic cycle of cytochrome c oxidase. The role of H2O produced at the oxygen-reduction site.

A study is presented on the pH dependence of proton translocation in the oxidative and reductive phases of the catalytic cycle of purified cytochrome c oxidase (COX) from beef heart reconstituted in phospholipid vesicles (COV). Protons were shown to be released from COV both in the oxidative and reductive phases. In the oxidation by O2 of the fully reduced oxidase, the H+/COX ratio for proton release from COV (R --> O transition) decreased from approximately 2.4 at pH 6.5 to approximately 1.8 at pH 8.5. In the direct reduction of the fully oxidized enzyme (O --> R transition), the H+/COX ratio for proton release from COV increased from approximately 0.3 at pH 6.5 to approximately 1.6 at pH 8.5. Anaerobic oxidation by ferricyanide of the fully reduced oxidase, reconstituted in COV or in the soluble case, resulted in H+ release which exhibited, in both cases, an H+/COX ratio of 1.7-1.9 in the pH range 6.5-8.5. This H+ release associated with ferricyanide oxidation of the oxidase, in the absence of oxygen, originates evidently from deprotonation of acidic groups in the enzyme cooperatively linked to the redox state of the metal centers (redox Bohr protons). The additional H+ release (O2 versus ferricyanide oxidation) approaching 1 H+/COX at pH < or = 6.5 is associated with the reduction of O2 by the reduced metal centers. At pH > or = 8.5, this additional proton release takes place in the reductive phase of the catalytic cycle of the oxidase. The H+/COX ratio for proton release from COV in the overall catalytic cycle, oxidation by O2 of the fully reduced oxidase directly followed by re-reduction (R --> O --> R transition), exhibited a bell-shaped pH dependence approaching 4 at pH 7.2. A mechanism for the involvement in the proton pump of the oxidase of H+/e- cooperative coupling at the metal centers (redox Bohr effects) and protonmotive steps of reduction of O2 to H2O is presented.

Anaerobiosis↗
PubMed2005

Oxidation and reduction control of the inactivation gating of Torpedo ClC-0 chloride channels.

Oxidation and reduction (redox) are known to modulate the function of a variety of ion channels. Here, we report a redox regulation of the function of ClC-0, a chloride (Cl(-)) channel from the Torpedo electric organ. The study was motivated by the occasional observation of oocytes with hyperpolarization-activated Cl(-) current when these oocytes expressed ClC-0. We find that these atypical recording traces can be turned into typical ClC-0 current by incubating the oocyte in millimolar concentrations of reducing agents, suggesting that the channel function is regulated by oxidation and reduction. The redox control apparently results from an effect of oxidation on the slow (inactivation) gating: oxidation renders it more difficult for the channel to recover from the inactivated states. Introducing the point mutation C212S in ClC-0 suppresses the inactivation state, and this inactivation-suppressed mutant is no longer sensitive to the inhibition by oxidizing reagents. However, C212 is probably not the target for the redox reaction because the regulation of the inactivation gating by oxidation is still present in a pore mutant (K165C/K165 heterodimer) in which the C212S mutation is present. Taking advantage of the K165C/K165 heterodimer, we further explore the oxidation effect in ClC-0 by methane thiosulfonate (MTS) modifications. We found that trimethylethylammonium MTS modification of the introduced cysteine can induce current in the K165C/K165 heterodimer, an effect attributed to the recovery of the channel from the inactivation state. The current induction by MTS reagents is subjected to redox controls, and thus the extent of this current induction can serve as an indicator to report the oxidation state of the channel. These results together suggest that the inactivation gating of ClC-0 is affected by redox regulation. The finding also provides a convenient method to "cure" those atypical recording traces of ClC-0 expressed in Xenopus oocytes.

Animals↗
PubMed2005

Fundamental roles of reactive oxygen species and protective mechanisms in the female reproductive system.

Controlled oxidation, such as disulfide bond formation in sperm nuclei and during ovulation, plays a fundamental role in mammalian reproduction. Excess oxidation, however, causes oxidative stress, resulting in the dysfunction of the reproductive process. Antioxidation reactions that reduce the levels of reactive oxygen species are of prime importance in reproductive systems in maintaining the quality of gametes and support reproduction. While anti-oxidative enzymes, such as superoxide dismutase and peroxidase, play a central role in eliminating oxidative stress, reduction-oxidation (redox) systems, comprised of mainly glutathione and thioredoxin, function to reduce the levels of oxidized molecules. Aldo-keto reductase, using NADPH as an electron donor, detoxifies carbonyl compounds resulting from the oxidation of lipids and proteins. Thus, many antioxidative and redox enzyme genes are expressed and aggressively protect gametes and embryos in reproductive systems.

Alcohol Oxidoreductases↗
PubMed1999

Stereoselective S-oxidation and reduction of flosequinan in rat.

1. The stereoselective S-oxidation and reduction pathways of flosequinan [(+/-)-7-fluoro-1-methyl-3-methylsulphinyl-4-quinolone] in rat were investigated in vitro. 2. Cytosol from both the liver and kidney catalysed the reduction of R(+)-flosequinan (R-FSO) and S(-)-flosequinan (S-FSO) to flosequinan sulphide (FS, 7-fluoro-1-methyl-3-methylthio-4-quinolone). Flosequinan sulphone (FSO2, 7-fluoro-1-methyl-3-methylsulphonyl-4-quinolone) was not reduced to R-FSO or S-FSO. 3. Liver microsomes catalysed four different S-oxidation pathways in the presence of NADPH, namely oxidation of FS to R-FSO and S-FSO and from R-FSO and S-FSO to FSO2. The formation of R-FSO and S-FSO from FS each exhibited a biphasic kinetic pattern, indicating that at least two distinct enzymes were involved. The pathway from FS to R-FSO appeared mainly catalysed by flavin-containing monooxygenases (FMO). 4. S-oxidation of FS to R-FSO was more rapid than that of FS to S-FSO. S-oxidation of FS to either R-FSO or S-FSO in liver microsomes was more rapid than that of either R-FSO or S-FSO to FSO2. 5. Microsomes from both the kidney and lung catalysed the stereoselective S-oxidation of FS to R-FSO, and FMO was likely to have participated in these reactions.

Animals↗
PubMed2006

Base pair motions control the rates and distance dependencies of reductive and oxidative DNA charge transfer.

In 1999, Wan et al. [Proc. Natl. Acad. Sci. USA 96, 6014-6019] published a pioneering paper that established the entanglement between DNA base pair motions and the transfer time of the charge carrier. The DNA assemblies contained an ethidium covalently bound via a flexible alkyl chain to the 5' hydroxyl group of the DNA backbone. Although covalently attached, the loose way in which the ethidium was linked to DNA allowed for large degrees of conformational freedom and thus raised some concern with respect to conformational inhomogeneity. In this letter, we report studies on a different set of ethidium DNA conjugates. In contrast to the "Caltech systems," these conjugates contain ethidium tightly incorporated (as a base pair surrogate) into the DNA base stack, opposite to an abasic site analog. Despite the tight binding, we found that charge transfer from the photoexcited ethidium base pair surrogate across two or more base pairs is several orders of magnitude slower than in case of the DNA systems bearing the tethered ethidium. To further broaden the scope of this account, we compared (oxidative) electron hole transfer and (reductive) electron transfer using the same ethidium chromophore as a charge donor in combination with two different charge acceptors. We found that both electron and hole transfer are characterized by similar rates and distance dependencies. The results demonstrate the importance of nuclear motions and conformational flexibility and underline the presence of a base gating mechanism, which appears to be generic to electronic transfer processes through pi-stacked nucleic acids.

Base Pairing↗