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PubMed2003

Nitrite reduction to nitric oxide by deoxyhemoglobin vasodilates the human circulation.

Nitrite anions comprise the largest vascular storage pool of nitric oxide (NO), provided that physiological mechanisms exist to reduce nitrite to NO. We evaluated the vasodilator properties and mechanisms for bioactivation of nitrite in the human forearm. Nitrite infusions of 36 and 0.36 micromol/min into the forearm brachial artery resulted in supra- and near-physiologic intravascular nitrite concentrations, respectively, and increased forearm blood flow before and during exercise, with or without NO synthase inhibition. Nitrite infusions were associated with rapid formation of erythrocyte iron-nitrosylated hemoglobin and, to a lesser extent, S-nitroso-hemoglobin. NO-modified hemoglobin formation was inversely proportional to oxyhemoglobin saturation. Vasodilation of rat aortic rings and formation of both NO gas and NO-modified hemoglobin resulted from the nitrite reductase activity of deoxyhemoglobin and deoxygenated erythrocytes. This finding links tissue hypoxia, hemoglobin allostery and nitrite bioactivation. These results suggest that nitrite represents a major bioavailable pool of NO, and describe a new physiological function for hemoglobin as a nitrite reductase, potentially contributing to hypoxic vasodilation.

Adult↗
PubMed2001

Chemoprotection by phenolic antioxidants. Inhibition of tumor necrosis factor alpha induction in macrophages.

Phenolic antioxidants exhibit anti-inflammatory activity in protection against chemical toxicity and cancer. To investigate the molecular mechanism of anti-inflammation, we analyzed the regulation of tumor necrosis factor alpha (TNF-alpha) expression in macrophages, a key step in inflammation, by the antioxidants. Whereas lipopolysaccharide (LPS), an inflammatory inducer, stimulates rapid synthesis of TNF-alpha protein, phenolic antioxidants, exemplified by tert-butyl hydroquinone and 1,4-dihydroquinone, block LPS-induced production of TNF-alpha protein in a time- and dose-dependent manner. Inhibition of TNF-alpha induction correlates with the capacity of the antioxidants to undergo oxidation-reduction cycling, implicating oxidative signaling in the inhibition. The antioxidants blocked LPS-induced increase of the steady-state mRNA of TNF-alpha but did not affect the half-life of the mRNA. Electrophoretic mobility shift assay reveals a total inhibition of LPS-induced formation of nuclear factor kappaB.DNA binding complexes by phenolic antioxidants. Finally, 1,4-dihydroquinone blocks the induction of TNF-alpha target genes interleukin 1beta and interleukin 6 at both mRNA and protein levels. Our findings demonstrate that phenolic antioxidants potently inhibit signal-induced TNF-alpha transcription and suggest a mechanism of anti-inflammation by the antioxidants through control of cytokine induction during inflammation.

Animals↗
PubMed2002

Photosynthetic carbon reduction and carbon oxidation cycles are the main electron sinks for photosystem II activity during a mild drought.

Stomatal closure can explain the inhibition of net CO2 uptake by a leaf subjected to a mild drought: the photosynthetic apparatus appears resistant to lack of water. Changes in both the water content of leaves maintained in a constant environment and the ambient CO2 molar fraction during measurements on well-hydrated leaves lead to similar effects on net CO2 uptake and whole chain electron transport as estimated by leaf chlorophyll fluorescence measurements. In particular, it is shown that photosystem II (PSII) functioning and its regulation are not qualitatively changed during desiccation and that the variations in PSII photochemistry can simply be understood by changes in substrate availability in this condition. Moreover, an analysis of the literature shows that when inhibition of net CO2 uptake by C3 leaves under drought (Phaseolus vulgaris L., Helianthus annus L. and Solanum tuberosum L.) was lower than 80 %, elevated CO2 completely restored the photosynthetic capacity. The CO2 molar fraction in the chloroplasts declines as stomata close in drying leaves. As a consequence, in C3 plants, ribulose-1,5-bisphosphate oxygenation increases and becomes the main sink for photosynthetic electrons. Depending on the prevailing photon flux density, the O2 uptake through photorespiratory activity can entirely replace carbon dioxide as an electron acceptor, or not. The rate of the Mehler reaction remains low and unchanged during desiccation. However, drought could also involve CO2-sensitive modification of the photosynthetic metabolism depending on plant growth conditions and possibly also on plant species.

Carbon↗
PubMed2006

Microbial community change of sulfate reduction and sulfur oxidation bacteria in the activated sludge cultivated with acetate and peptone.

The growth of sulfate reducing bacteria (SRB) and filamentous sulfur bacteria was monitored on a laboratory scale in activated sludge reactors using acetate and peptone as the artificial wastewater. When the artificial wastewater contained acetate and peptone, filamentous bacteria increased in the sludge and the SVI values increased. There was a good correlation between sulfate reducing activity and sulfur oxidation activity in the produced sludge. The microbial community change of filamentous sulfur bacteria and sulfate reducing bacteria was analyzed using the fluorescent in situ hybridization (FISH) method. The tendency for the growth of filamentous sulfur bacteria Thiothrix eikelboomii following the growth of SRB was observed. The percentage of SRB385- hybridized cells and DNMA657-hybridized cells found in the total cell area increased from 2-3% to 7-10% when the filamentous bulking occurred.

Acetates↗
PubMed2004

Effects of fluvastatin in type 2 diabetic patients with hyperlipidemia: reduction in cholesterol oxidation products and VCAM-1.

The purpose of this study was to investigate the lipid-lowering and anti-oxidative effects of fluvastatin, a 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor, in type 2 diabetic patients. Six patients (3 men and 3 women, mean age = 56.2) took 20 mg of fluvastatin once daily (at night) for 12 weeks. Several markers of oxidative stress were then measured in these patients including plasma cholesterol oxidation products, i.e. oxysterols, and the levels of circulating adhesion molecules. Plasma total cholesterol levels were reduced by 12.3% in these individuals after 4 weeks of treatment, with levels remaining below 220 mg/dl for the entire treatment period. LDL levels were significantly reduced at 4 (18.1%) and 12 weeks (16.1%), and triglyceride levels were significantly reduced after 8 (22.5%) and 12 (37.7%) weeks of treatment. HDL-C levels increased from 50.7 +/- 15.4 prior to treatment to 63.8 +/- 24.3 mg/dl after 12 weeks of treatment, though this increase was not statistically significant. Lipid hydroperoxide, thiobarbituric acid-reactive substance (TBARS), and oxysterol levels were also reduced, suggesting that fluvastatin also had anti-oxidative effects. Finally, VCAM-1 levels were similarly reduced by fluvastatin treatment. We conclude that fluvastatin safely improves the plasma lipid profile in type 2 diabetic patients with hyperlipidemia. We speculate that this drug might be doubly effective in reducing atherosclerosis and cardiac events in these patients as a result of its demonstrated anti-oxidative effects and its ability to reduce VCAM-1 levels.

Antioxidants↗
PubMed1985

Reductive alkylation with oxidized nucleotides. Use in affinity labeling or affinity chromatography.

A study has been made of the products of a reaction of oxidized ribonucleotides with a primary amine. As a model reaction, periodate-oxidized adenosine was combined with glycine in the presence of NaCNBH3. The purified major product of this reaction, adenine 9,2'-(4'-carboxymethyl-6'-hydroxymethylmorpholine), was characterized by 13C and 1H NMR spectroscopy, ultraviolet spectroscopy, and thin layer chromatography. When used to generate affinity columns, oxidized adenosine or oxidized ATP formed stable products with immobilized diaminohexane when treated with NaCNBH3. Failure to treat with NaCNBH3 yielded an unstable affinity matrix. These results are used in the interpretation of differing results when oxidized nucleotides have been used as affinity labels for different proteins.

Adenosine↗
PubMed1994

Transient thiyl radicals in yeast copper(I) thionein.

In an EPR study employing yeast copper(I) thionein, GSH and Cu-GSH it was shown that thiyl radicals could be successfully generated from the thiolate sulfur via oxidation by photochemically formed superoxide at 77 K. The g-value was 2.036. Essentially no EPR detectable copper(II) was monitored under the experimental conditions, indicating that the oxidation reduction process is restricted to the thiolate sulfur. The Cu(I)-thiolate chromophores remained fully intact as deduced from chiroptical and luminescence measurements. Thus, copper thionein is supposed to be actively involved in the scavenging of oxygen free radicals by a reversible thiolate oxidation reduction cycle. The coordinated Cu(I) seems to serve as a prominent candidate to stabilize the transiently formed thiyl radical.

Carrier Proteins↗
PubMed2002

Practical synthesis of optically active styrene oxides via reductive transformation of 2-chloroacetophenones with chiral rhodium catalysts.

[reaction: see text] A practical method for the synthesis of optically active styrene oxides has been developed via formation of optically active 2-chloro-1-phenylethanols generated by reductive transformation of ring-substituted 2-chloroacetophenones. The optically active alcohols with up to 98% ee are obtainable from the asymmetric reduction of acetophenones with an S/C = 1000-5000 with a formic acid triethylamine mixture containing a well-defined chiral Rh complex, CpRhCl[(R,R)-Tsdpen].

Journal Article↗
PubMed2006

Histochemical and enzymehistochemical alterations during experimental cardiomyopathy.

Investigation of ethiology, pathogenesis, morphogenesis, pathokinesis, treatment and prevention of cardiomyopathy is one of the most important problems of cardiology. Last years many scientific forums have been devoted to cardiomyopathy problems and still many issues remain disputable and needs further investigation and definition. In particular, investigation of metabolic processes in cardiac muscle seems of great importance. Obtained data will promote elaboration of adequate means toward the correction of cardiac decompensation during cardiomyopathy. The main goal of present study was the investigation of oxidation-reduction and electron transport associated protein activity in myocardium during experimental cardiomyopathy. Experiments were carried out on 30 male rats (180 - 200 g weight). Based on histological, histochemical, enzymehistological investigations conclusion has been made that during experimental autoimmune cardiomyopathy activity of oxidation-reduction and electron transport enzymes is sharply decreased along with the decrease of ascorbic acid and tiny granule glycogen amount (with altered topographic distribution) determining energy deficiency and weakening of cardiac muscle contractile function. It is possible to consider that the present study will open the way for future research and prompt us to select optimal therapeutic agents.

Animals↗
PubMed1999

Nitric oxide-induced reduction of lung cell and whole lung thioredoxin expression is regulated by NF-kappaB.

We examined whether nitric oxide (NO)-induced inhibition of thioredoxin (Thx) expression is regulated by a mechanism mediated by a transcription factor, i.e., nuclear factor-kappaB (NF-kappaB), in cultured porcine pulmonary artery endothelial cells (PAEC) and in mouse lungs. Western blot analysis revealed that IkappaB-alpha content was reduced by 20 and 60% in PAEC exposed to 8.5 ppm NO for 2 and 24 h, respectively. NO exposure also caused significant reductions of cytosol fraction p65 and p52 content in PAEC. The nuclear fraction p65 and p52 contents were significantly reduced only in PAEC exposed to NO for 24 h. Exposure to NO resulted in a 50% reduction of p52 mRNA but not of the IkappaB-alpha subunit. DNA binding activity of the oligonucleotide encoding the NF-kappaB sequence in the Thx gene was significantly reduced in PAEC exposed to NO for 24 h. Exposure of mice to 10 ppm NO for 24 h resulted in a significant reduction of lung Thx and IkappaB-alpha mRNA and protein expression and in the oligonucleotide encoding Thx and NF-kappaB/DNA binding. These results 1) demonstrate that the effects of NO exposure on Thx expression in PAEC are comparable to those observed in intact lung and 2) suggest that reduced expression of the NF-kappaB subunit, leading to reduced NF-kappaB/DNA binding, is associated with the loss of Thx expression in PAEC and in intact mouse lungs.

Animals↗
PubMed1996

Oxidative and reductive metabolism of 9-cis-retinoic acid in the rat. Identification of 13,14-dihydro-9-cis-retinoic acid and its taurine conjugate.

9-cis-Retinoic acid (9-cis-RA), a hormone that binds and activates all known retinoid receptor subtypes, is structurally similar to all-trans-retinoic acid and may share common metabolic fates. Both oral and intravenous doses of 9-cis-RA to rats led to hydroxylation and ketone formation at carbon-4. 9-Cis-RA also isomerized in vivo to 13-cis-retinoic acid, 9-cis, 13-cis-retinoic acid, and all-trans-retinoic acid. After administration of [11-3H]9-cis-RA, the proportion of plasma radioactivity that was volatile increased over time, which suggested that beta-oxidative chain-shortening of 9-cis-RA might occur. An equimolar mixture of [1-13C2H3]9-cis-RA and 9-cis-RA was administered to rats for stable-isotope-labeled metabolite production. A chromatographic peak that had a lambdamax = 290 nm vs. 348 nm for the parent compound, had a retention time similar to the parent, and yielded a 1:1 positive-ion isotope cluster at m/z 303/307 in its mass spectrum. NMR analysis revealed 9-cis and 13,14-dihydro configurations, indicating that 9-cis-RA can be metabolized in rat by reduction to 13,14-dihydro-9-cis-RA. An earlier-eluting HPLC peak that exhibited a lambdamax at 290 nm, and a negative-ion-MS isotope cluster at m/z 408/412 was observed during separations of rat liver extracts. LC/MS/MS analysis revealed product ions for this peak diagnostic for carboxylic acid taurine conjugates. In rats, reduction of 9-cis-RA to 13,14-dihydro-9-cis-RA may represent an initial step leading to beta-oxidation, although available data demonstrate it is conjugated with taurine to form a novel metabolite.

Animals↗
PubMed1990

Oxidation versus Reductive Detoxification of SO(2) by Chloroplasts.

Intact chloroplasts isolated from spinach (Spinacia oleracea L. cv Yates) both oxidized and reduced added sulfite in the light. Oxidation was fast only when endogenous superoxide dismutase was inhibited by cyanide. It was largely suppressed by scavengers of oxygen radicals. After addition of O-acetylserine, chloroplasts reduced sulfite to cysteine and exhibited sulfite-dependent oxygen evolution. Cysteine synthesis from sulfite was faster than from sulfate. The results are discussed in relation to species-specific differences in the phytotoxicity of SO(2).

Journal Article↗
PubMed1978

Characterization of the iron-sulfur protein of the mitochondrial outer membrane partially purified from beef kidney cortex.

The iron-sulfur protein present in the mitochondrial outer membrane has been partially purified from beef kidney cortex mitochondria by means of selective solubilization followed by DEAE-cellulose chromatography. The EPR spectrum of the iron-sulfur protein with g-values at 2.01, 1.94 and 1.89 was well resolved up to 200 K which is unusual for an iron-sulfur protein. Analyses confirmed a center with two iron and two labile sulfur atoms in the protein. By measuring the effect of oxidation-reduction potential on the EPR signal amplitude, midpoint potentials at pH 7.2 were determined both for the purified iron-sulfur protein, +75 (+/- 5) mV, and in prepared mitochondrial outer membrane, +62 (+/- 6) mV. At pH 8.2 slightly lower values were indicated, +62 and 52 mV, respectively. The oxidation-reduction equilibrium involved a one electron transfer. A functional relationship to the rotenone-insensitive NADH-cytochrome c oxidoreductase in the mitochondrial outer membrane is suggested. Both this activity and the iron-sulfur center were sensitive to acidities slightly below pH 7 in contrast to the iron-sulfur centers of the inner membrane.

Animals↗
PubMed1986

Biochemical alterations elicited in rat liver microsomes by oxidation and reduction products of chloroform metabolism.

The feasibility of an oxygen-independent mechanism of chloroform bioactivation was indicated by the covalent binding to lipid and protein occurring in anaerobic incubations of CHCl3 and microsomes in the presence of NADPH. Under these conditions, the loss of cytochrome P-450 and the inhibition of related monoxygenases were also observed. The chloroform anoxic biotransformation was negligible in uninduced microsomes and seemed to be catalyzed mainly by phenobarbital-inducible P-450 isozymes. Biotransformation could also be supported by NADH as the source of reducing equivalents. Anaerobic metabolism of chloroform led to decreased levels of the main PB-induced P-450 isozymes even at low CHCl3 concentration and did not affect benzo[a]pyrene hydroxylase activity. These effects were not decreased by thiolic compounds. The oxidation products of chloroform caused a general impairment of the monoxygenase system, probably related to the formation of protein aggregates with very high molecular weight. In the presence of physiological concentrations of GSH, the targets of aerobically-produced metabolites were lipids and, to a smaller extent, P-450. At low CHCl3 concentrations and/or in the presence of GSH the most changes to microsomal structures seemed to be produced by the reductively-formed intermediates.

Animals↗