ABSTRACT
Questions about which reactive oxygen species (ROS) or reactive nitrogen species (RNS) can escape from the mitochondria and activate signals must be addressed. In this study, two parameters, the calculated dipole moment (debye, D) and permeability coefficient (Pm) (cm s-1), are listed for hydrogen peroxide (H2O2), hydroxyl radical (â¢OH), superoxide (O2â¢-), hydroperoxyl radical (HO2â¢), nitric oxide (â¢NO), nitrogen dioxide (â¢NO2), peroxynitrite (ONOO-), and peroxynitrous acid (ONOOH) in comparison to those for water (H2O). O2â¢- is generated from the mitochondrial electron transport chain (ETC), and several other ROS and RNS can be generated subsequently. The candidates which pass through the mitochondrial membrane include ROS with a small number of dipoles, i.e., H2O2, HO2â¢, ONOOH, â¢OH, and â¢NO. The results show that the dipole moment of â¢NO2 is 0.35 D, indicating permeability; however, â¢NO2 can be eliminated quickly. The dipole moments of â¢OH (1.67 D) and ONOOH (1.77 D) indicate that they might be permeable. This study also suggests that the mitochondria play a central role in protecting against further oxidative stress in cells. The amounts, the long half-life, the diffusion distance, the Pm, the one-electron reduction potential, the pKa, and the rate constants for the reaction with ascorbate and glutathione are listed for various ROS/RNS, â¢OH, singlet oxygen (1O2), H2O2, O2â¢-, HO2â¢, â¢NO, â¢NO2, ONOO-, and ONOOH, and compared with those for H2O and oxygen (O2). Molecules with negative electrical charges cannot directly diffuse through the phospholipid bilayer of the mitochondrial membranes. Short-lived molecules, such as â¢OH, would be difficult to contribute to intracellular signaling. Finally, HO2⢠and ONOOH were selected as candidates for the ROS/RNS that pass through the mitochondrial membrane.
Subject(s)
Hydrogen Peroxide , Nitrogen Dioxide , Reactive Oxygen Species , Hydrogen Peroxide/pharmacology , Cytosol , Oxidative Stress , Nitric Oxide , Peroxynitrous Acid , Oxygen , MitochondriaABSTRACT
Here we studied cerium oxide nanoparticles (nanoceria) as an agent for the future treatment of oxidative damage by validating and evaluating its scavenging activity towards reactive oxygen species (ROS) in vitro. Nanoceria has been shown to mimic the activities of superoxide dismutase and catalase, degrading superoxide (O2â¢-) and hydrogen peroxide (H2O2). We examined the antioxidative activity of nanoceria, focusing on its ability to quench singlet oxygen (1O2) in an aqueous solution. Electron paramagnetic resonance (EPR) was used to determine the rates of second-order reactions between nanoceria and three ROS (1O2, O2â¢-, and H2O2) in aqueous solution, and its antioxidative abilities were demonstrated. Nanoceria shows a wide range of ultraviolet-light absorption bands and thus 1O2 was produced directly in a nanoceria suspension using high-frequency ultrasound. The quenching or scavenging abilities of nanoceria for 1O2 and hypoxanthine-xanthine oxidase reaction-derived O2â¢- were examined by EPR spin-trapping methods, and the consumption of H2O2 was estimated by the EPR oximetry method. Our results indicated that nanoceria interact not only with two previously reported ROS but also with 1O2. Nanoceria were shown to degrade O2â¢- and H2O2, and their ability to quench 1O2 may be one mechanism by which they protect against oxidative damage such as inflammation.
ABSTRACT
High efficacy and minimal toxicity radioprotectors are desirable options for the hazards posed by nuclear medical and energy technologies and the dangers presented by nuclear weapons in an unstable global situation. Although cysteamine is an effective radioprotector, it has considerable toxicity. In this study, the protective effects of the less toxic organosulfur compounds 2-aminoethylthiosulfate (AETS), thiotaurine (TTAU), and hypotaurine (HTAU) against X-ray damage in mice were compared with that of cysteamine. Intraperitoneal injection of either AETS or cysteamine (2.2â mmol/kg body weight) 30â min before X-ray irradiation (7.0â Gy) provided 100% survival for 30 days, limited the decrease in erythrocytes and neutrophils over 9 days, and reduced damage to bone marrow and spleen over 9 days. Neither TTAU nor HTAU provided any protection. In mice, 30â min after AETS administration, non-protein thiol content increased in the spleen, indicating cysteamine generation by AETS hydrolysis, the active protective species of AETS. All examined compounds scavenged â¢OH under diffusion control in aqueous solution, which is inconsistent with the difference in the protective effects among the compounds. The results indicate that AETS protects animals from ionizing radiation by several mechanisms, including scavenging â¢OH as cysteamine.
ABSTRACT
This commentary describes a highly cited paper by Eli Finkelstein, Gerald M. Rosen, and Elmer J. Raukman that appeared in Archives of Biochemistry and Biophysics published in 1980. They reviewed many reports being regularly appearing in the literature describing spin trapping and hydroxyl radicals from various sources and contributed to the development and progress that has been made in oxidative stress research.
Subject(s)
Hydroxyl Radical , Superoxides , Cyclic N-Oxides , Electron Spin Resonance Spectroscopy , Free Radicals , Spin Labels , Spin TrappingABSTRACT
This commentary describes a highly cited paper by Eli Finkelstein, Gerald M. Rosen, and Elmer J. Raukman that appeared in Archives of Biochemistry and Biophysics published in 1980. They reviewed many reports being regularly appearing in the literature describing spin trapping and hydroxyl radicals from various sources and contributed to the development and progress that has been made in oxidative stress research.
ABSTRACT
The effects of reaction environments on the radical-scavenging mechanisms of ascorbic acid (AscH2) were investigated using 2,2-diphenyl-1-picrylhydrazyl radical (DPPHâ¢) as a reactivity model of reactive oxygen species. Water-insoluble DPPH⢠was solubilized by ß-cyclodextrin (ß-CD) in water. The DPPHâ¢-scavenging rate of AscH2 in methanol (MeOH) was much slower than that in phosphate buffer (0.05 M, pH 7.0). An organic soluble 5,6-isopropylidene-l-ascorbic acid (iAscH2) scavenged DPPH⢠much slower in acetonitrile (MeCN) than in MeOH. In MeOH, Mg(ClO4)2 significantly decelerated the DPPHâ¢-scavenging reaction by AscH2 and iAscH2, while no effect of Mg(ClO4)2 was observed in MeCN. On the other hand, Mg(ClO4)2 significantly accelerated the reaction between AscH2 and ß-CD-solubilized DPPH⢠(DPPHâ¢/ß-CD) in phosphate buffer (0.05 M, pH 6.5), although the addition of 0.05 M Mg(ClO4)2 to the AscH2-DPPHâ¢/ß-CD system in phosphate buffer (0.05 M, pH 7.0) resulted in the change in pH of the phosphate buffer to be 6.5. Thus, the DPPHâ¢-scavenging reaction by iAscH2 in MeCN may proceed via a one-step hydrogen-atom transfer, while an electron-transfer pathway is involved in the reaction between AscH2 and DPPHâ¢/ß-CD in phosphate buffer solution. These results demonstrate that the DPPHâ¢-scavenging mechanism of AscH2 are affected by the reaction environments.
ABSTRACT
A large kinetic isotope effect (KIE, kH/kD) of 12.8 was observed for the hydrogen-transfer reaction from ascorbic acid to 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIOË) in a phosphate buffer solution (0.05 M, pH/pD 7.0) at 298 K. The isotopic difference in the activation energies (6.8 kJ mol-1) determined from the temperature dependence of the KIE suggests that quantum mechanical tunneling may partly play a role in the reaction, although the isotopic ratio of the Arrhenius prefactor (AH/AD = 0.86) is within the semiclassical limits.
ABSTRACT
More detailed investigations on the in vivo redox status are needed to elucidate the mechanisms contributing to damage caused by ionizing radiation. In the present study, the in vivo redox status of mice was examined using in vivo electron spin resonance (ESR) imaging after an intraperitoneal injection of 1-acetoxy-3-carbamoyl-2,2,5,5-tetramethylpyrrolidine (ACP) as a probe. ACP is easily hydrolyzed to its hydroxylamine form in the mouse body, and the interconversion between hydroxylamine and the corresponding nitroxyl radical reflects the biological redox status. Liver damage, based on changes in liver weight and plasma aspartate aminotransferase levels, was detected in mice 4 days after X-ray irradiation at 7.5 Gy. ESR imaging showed that the signal intensity of the nitroxyl radical was high at the liver area in both damaged and healthy mice after administration of ACP. Whereas the signal decayed at the liver area for healthy mouse, the decay was negligible in damaged mice. Unlike healthy mouse, signal in the chest for damaged mouse increased with time. The distribution of the sum of hydroxylamine and the nitroxyl radical was similar in damaged and healthy mice. X-ray irradiation slightly lowered the reduction activity of the liver microsomal fraction for the nitroxyl radical. Thiobarbituric acid reactive substances in the liver were higher in damaged mice than in healthy mice; however, no significant differences were noted in reduced glutathione. The present results indicate that the redox status of mice exposed to X-ray irradiation is more oxidative than that in healthy mice.
Subject(s)
Hydroxylamines , Nitrogen Oxides , Animals , Electron Spin Resonance Spectroscopy , Hydroxylamine , Mice , Oxidation-Reduction , Spin Labels , X-RaysABSTRACT
The reactivity of nitroxyl free radicals, 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPOL) and 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-N-oxyl (CmP), with reactive oxygen species (ROS) were compared as typical 6-membered and 5-membered ring nitroxyl compounds, respectively. The reactivity of the hydroxylamine forms of both these nitroxyl radicals (TEMPOL-H and CmP-H) was also assessed. Two free radical species of ROS, hydroxyl radical (â¢OH) and superoxide (O2 â¢-), were subjected to a competing reaction. â¢OH was generated by UV irradiation from an aqueous H2O2 solution (H2O2-UV system), and O2 â¢- was generated by a reaction between hypoxanthine and xanthine oxidase (HX-XO system). â¢OH and O2 â¢- generated by the H2O2-UV and HX-XO systems, respectively, were measured by electron paramagnetic resonance (EPR) spin-trapping, and the amount of spin adducts generated by each system was adjusted to be equal. The time courses of the one-electron oxidation of TEMPOL, CmP, TEMPOL-H, and CmP-H in each ROS generation system were compared. A greater amount of TEMPOL was oxidized in the HX-XO system compared with the H2O2-UV system, whereas the reverse was observed for CmP. Although the hydroxylamine forms of the tested nitroxyl radicals were oxidized evenly in the H2O2-UV and HX-XO systems, the amount of oxidized CmP-H was approximately 3 times greater compared with TEMPOL-H.
ABSTRACT
The quantitative evaluation of changes in the redox state induced by low linear energy transfer (LET) radiations such as the plateau region of heavy-ion beams via formation of reactive oxygen species is of considerable importance to eliminate the adverse effects of radiation therapy on normal tissues adjacent to a tumour. In this study, a 2,2-diphenyl-1-picrylhydrazyl radical (DPPHË) was used as a redox probe to estimate the redox states of protic and aprotic solutions irradiated by low LET carbon-ion (C-ion) beams. The dose dependence of the decrease in the absorption band due to DPPHË (which was solubilised by ß-cyclodextrin (ß-CD) in water) after irradiation with low LET C-ion beams (13 keV µm-1) was similar to that after X-irradiation. Similar results were obtained when H2O was replaced with methanol or acetonitrile although the slope values of the plots of the absorbance changes vs. radiation doses were twice larger as compared to the case in ß-CD-containing H2O. Moreover, DPPHË was more susceptible to the C-ion beam than to X-rays in isopropyl myristate (IPM), which is one of the saturated fatty acid esters.
ABSTRACT
Mitochondria are a major source of intracellular energy and reactive oxygen species in cells, but are also increasingly being recognized as a controller of cell death. Here, we review evidence of signal transduction control by mitochondrial superoxide generation via the nuclear factor-κB (NF-κB) and GATA signaling pathways. We have also reviewed the effects of ROS on the activation of MMP and HIF. There is significant evidence to support the hypothesis that mitochondrial superoxide can initiate signaling pathways following transport into the cytosol. In this study, we provide evidence of TATA signal transductions by mitochondrial superoxide. Oxidative phosphorylation via the electron transfer chain, glycolysis, and generation of superoxide from mitochondria could be important factors in regulating signal transduction, cellular homeostasis, and cell death.
Subject(s)
Mitochondria/metabolism , Reactive Oxygen Species/metabolism , Signal Transduction/physiology , Animals , Humans , NF-kappa B/physiologyABSTRACT
The effect of the aluminium ion (Al(3+)) on the scavenging reaction of a 2,2-diphenyl-1-picrylhydrazyl radical (DPPHË), as a reactivity model of reactive oxygen species, with hydroquinone (QH2) and its methylated derivatives (MenQH2, n = 1-4) was investigated using stopped-flow and electrochemical techniques in a hydroalcoholic medium. The second-order rate constants (k) for the DPPHË-scavenging reaction of the hydroquinones increased with the increasing number of methyl substituents. Upon addition of Al(3+), the k values significantly increased depending on the concentration of Al(3+). Such an accelerating effect of Al(3+) on the DPPHË-scavenging rates of the hydroquinones results from the remarkable positive shift of the one-electron reduction potential (Ered) of DPPHË in the presence of Al(3+). These results demonstrate that Al(3+), a strong Lewis acid, can act as a radical-scavenging promoter by stabilising the one-electron reduced species of the radical, although Al(3+) is reported not only to act as a pro-oxidant but also to strongly interact with biomolecules, showing toxicities.
Subject(s)
Aluminum/chemistry , Free Radical Scavengers/chemistry , Hydroquinones/chemical synthesis , Hydroquinones/chemistry , Ions/chemistry , Kinetics , Methylation , Molecular StructureABSTRACT
Two hallmarks of Alzheimer's disease (AD) observed in the brains of patients with the disease include oxidative injury and deposition of protein aggregates comprised of amyloid-ß (Aß) variants. To inhibit these toxic processes, we synthesized antioxidant-conjugated peptides comprised of Trolox and various C-terminal motifs of Aß variants, TxAßx-n (x=34, 36, 38, 40; n=40, 42, 43). Most of these compounds were found to exhibit anti-aggregation activities. Among them, TxAß36-42 significantly inhibited Aß1-42 aggregation, showed potent antioxidant activity, and protected SH-SY5Y cells from Aß1-42-induced cytotoxicity. Thus, this method represents a promising strategy for developing multifunctional AD therapeutic agents.
Subject(s)
Alzheimer Disease/drug therapy , Amyloid beta-Peptides/metabolism , Amyloid beta-Peptides/pharmacology , Antioxidants/pharmacology , Chromans/pharmacology , Peptide Fragments/metabolism , Peptide Fragments/pharmacology , Protein Aggregates/drug effects , Alzheimer Disease/metabolism , Amyloid beta-Peptides/chemistry , Antioxidants/chemistry , Chromans/chemistry , Drug Design , Humans , Peptide Fragments/chemistry , Reactive Oxygen Species/metabolismABSTRACT
Prof. Dr. Helmut Sies is a pioneer of "Oxidative Stress", and has published over 18 papers with the name of "Oxidative Stress" in the title. He has been Editor-in-Chief of the journal "Archives of Biochemistry and Biophysics" for many years, and is a former Editor-in-Chief of the journal "Free Radical Research". He has clarified our understanding of the causes of chronic developing diseases, and has studied antioxidant factors. In this article, importance of "Oxidative Stress" and our mitochondrial oxidative stress studies; roles of mitochondrial ROS, effects of vitamin E and its homologues in oxidative stress-related diseases, effects of antioxidants in vivo and in vitro, and a mitochondrial superoxide theory for oxidative stress diseases and aging are introduced, and some of our interactions with Helmut are described, congratulating and appreciating his great path.
Subject(s)
Oxidative Stress , Aging , Antioxidants , Humans , Mitochondria/metabolism , Reactive Oxygen Species/metabolism , Superoxides/metabolism , Vitamin E/physiologyABSTRACT
A 2,2-diphenyl-1-picrylhydrazyl radical (DPPHË) was successfully solubilised in water by ß-cyclodextrin (ß-CD). DPPHË/ß-CD thus obtained was demonstrated to be a powerful tool to evaluate the antioxidative activity of water-soluble antioxidants, such as ascorbate and Trolox, in aqueous buffer solutions.
Subject(s)
Biphenyl Compounds/chemistry , Free Radical Scavengers/chemistry , Free Radicals/chemistry , Picrates/chemistry , beta-Cyclodextrins/chemistry , Ascorbic Acid/chemistry , Chromans/chemistry , Solubility , Water/chemistryABSTRACT
Fridovich identified CuZnSOD in 1969 and manganese superoxide dismutase (MnSOD) in 1973, and proposed "the Superoxide Theory," which postulates that superoxide (O2 (â¢-)) is the origin of most reactive oxygen species (ROS) and that it undergoes a chain reaction in a cell, playing a central role in the ROS producing system. Increased oxidative stress on an organism causes damage to cells, the smallest constituent unit of an organism, which can lead to the onset of a variety of chronic diseases, such as Alzheimer's, Parkinson's, amyotrophic lateral sclerosis and other neurological diseases caused by abnormalities in biological defenses or increased intracellular reactive oxygen levels. Oxidative stress also plays a role in aging. Antioxidant systems, including non-enzyme low-molecular-weight antioxidants (such as, vitamins A, C and E, polyphenols, glutathione, and coenzyme Q10) and antioxidant enzymes, fight against oxidants in cells. Superoxide is considered to be a major factor in oxidant toxicity, and mitochondrial MnSOD enzymes constitute an essential defense against superoxide. Mitochondria are the major source of superoxide. The reaction of superoxide generated from mitochondria with nitric oxide is faster than SOD catalyzed reaction, and produces peroxynitrite. Thus, based on research conducted after Fridovich's seminal studies, we now propose a modified superoxide theory; i.e., superoxide is the origin of reactive oxygen and nitrogen species (RONS) and, as such, causes various redox related diseases and aging.
ABSTRACT
The scavenging activity of rat plasma against hyperthermia-induced reactive oxygen species was tested. The glutathione-dependent reduction of a nitroxyl radical, 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl, which was restricted by adding superoxide dismutase or by deoxygenating the reaction mixture, was applied to an index of superoxide (O2 (â¢-)) generation. A reaction mixture containing 0.1 mM 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl and 1 mM glutathione was prepared using 100 mM phosphate buffer containing 0.05 mM diethylenetriaminepentaacetic acid. The reaction mixture was kept in a screw-top vial and incubated in a water bath at 37 or 44°C. The time course of the electron paramagnetic resonance signal of 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl in the reaction mixture was measured by an X-band EPR spectrometer (JEOL, Tokyo, Japan). When the same experiment was performed using rat plasma instead of 100 mM PB, the glutathione-dependent reduction of 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl, i.e., generation of O2 (â¢-), was not obtained. Only the first-order decay reduction of 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl, which indicates direct reduction of 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl, was obtained in rat plasma. Adding 0.5% albumin to the phosphate buffer reaction mixture could almost completely inhibit O2 (â¢-) generation at 37°C. However, addition of 0.5% albumin could not inhibit O2 (â¢-) generation at 44°C, i.e., hyperthermic temperature. Ascorbic acid also showed inhibition of O2 (â¢-) generation by 0.01 mM at 37°C, but 0.02 mM or more could inhibit O2 (â¢-) generation at 44°C. A higher concentration of ascorbic acid showed first-order reduction, i.e., direct one-electron reduction, of 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl. Hyperthermia-induced O2 (â¢-) generation in rat plasma can be mostly inhibited by albumin and ascorbic acid in the plasma.
ABSTRACT
Chronic kidney disease (CKD) is a major epidemiologic problem and a risk factor for cardiovascular events and cerebrovascular accidents. Because CKD shows irreversible progression, early diagnosis is desirable. Renal function can be evaluated by measuring creatinine-based estimated glomerular filtration rate (eGFR). This method, however, has low sensitivity during early phases of CKD. Cystatin C (CysC) may be a more sensitive predictor. Using a metabolomic method, we previously identified metabolites in CKD and hemodialysis patients. To develop a new index of renal hypofunction, plasma samples were collected from volunteers with and without CKD and metabolite concentrations were assayed by quantitative liquid chromatography/mass spectrometry. These results were used to construct a multivariate regression equation for an inverse of CysC-based eGFR, with eGFR and CKD stage calculated from concentrations of blood metabolites. This equation was able to predict CKD stages with 81.3% accuracy (range, 73.9-87.0% during 20 repeats). This procedure may become a novel method of identifying patients with early-stage CKD.
Subject(s)
Cystatin C/blood , Glomerular Filtration Rate , Metabolomics/methods , Renal Insufficiency, Chronic/blood , Renal Insufficiency, Chronic/diagnosis , Adult , Aged , Aged, 80 and over , Chromatography, Liquid/methods , Cystatin C/metabolism , Early Diagnosis , Female , Humans , Kidney/metabolism , Kidney/physiopathology , Linear Models , Male , Mass Spectrometry/methods , Middle Aged , Multivariate Analysis , Renal Insufficiency, Chronic/physiopathologyABSTRACT
Electron-transfer disproportionation of a 2,2-diphenyl-1-picrylhydrazyl radical (DPPHË) occurred in the presence of Sc(3+) acting as a strong Lewis acid in deaerated acetonitrile. In contrast, in the case of weaker Lewis acids than Sc(3+), such as Mg(2+) and Li(+), external protons from acetic acid were required for the disproportionation of DPPHË to occur.
Subject(s)
Biphenyl Compounds/chemistry , Mesylates/chemistry , Picrates/chemistry , Reactive Oxygen Species/chemistry , Scandium/chemistry , Acetic Acid/chemistry , Acetonitriles/chemistry , Catalysis , Lewis Acids/chemistry , Magnesium Compounds/chemistry , Perchlorates/chemistryABSTRACT
To identify blood markers for early stages of chronic kidney disease (CKD), blood samples were collected from rats with adenine-induced CKD over 28 days. Plasma samples were subjected to metabolomic profiling by liquid chromatography-mass spectrometry, followed by multivariate analyses. In addition to already-identified uremic toxins, we found that plasma concentrations of N6-succinyl adenosine, lysophosphatidylethanolamine 20:4, and glycocholic acid were altered, and that these changes during early CKD were more sensitive markers than creatinine concentration, a universal indicator of renal dysfunction. Moreover, the increase in plasma indoxyl sulfate concentration occurred earlier than increases in phenyl sulfate and p-cresol sulfate. These novel metabolites may serve as biomarkers in identifying early stage CKD.