The impact of dissolved oxygen on sulfate radical-induced oxidation of organic micro-pollutants: A theoretical study.

PubMed

Zhang, Rui; Wang, Xiaoxiang; Zhou, Lei; Liu, Zhu; Crump, Doug

2018-05-15

Sulfate radical (SO 4 .- )-induced oxidation is an important technology in advanced oxidation processes (AOPs) for the removal of pollutants. To date, few studies have assessed the effects of dissolved oxygen (DO) on the SO 4 .- -induced oxidation of organic micro-pollutants. In the present work, a quantum chemical calculation was used to investigate the influence of the external oxygen molecule on the Gibbs free energy (G pollutant ) and HOMO-LUMO gap (ΔE) of 15 organic micro-pollutants representing four chemical categories. Several thermodynamic and statistical models were combined with the data from the quantum chemical calculation to illustrate the impact of DO on the oxidation of organic micro-pollutants by SO 4 .- . Results indicated that the external oxygen molecule increased G pollutant of all studied chemicals, which implies DO has the potential to decrease the energy barrier of the SO 4 .- -induced oxidation and shift the chemical equilibrium of the reaction towards the side of products. From the perspective of kinetics, DO can accelerate the oxidation by decreasing ΔE of organic micro-pollutants. In addition, changes of G pollutant and ΔE of the SO 4 .- -induced oxidation were both significantly different between open-chain and aromatic chemicals, and these differences were partially attributed to the difference of polarizability of these two types of chemicals. Furthermore, we revealed that all changes of G pollutant and ΔE induced by DO were dependent on the DO content. Our study emphasizes the significance of DO on the oxidation of organic micro-pollutants by SO 4 .- , and also provides a theoretical method to study the effect of components in wastewater on removal of organic pollutants in AOPs. Copyright © 2018 Elsevier Ltd. All rights reserved.

Oxidation mechanism of Penicillium digitatum spores through neutral oxygen radicals

NASA Astrophysics Data System (ADS)

Hashizume, Hiroshi; Ohta, Takayuki; Takeda, Keigo; Ishikawa, Kenji; Hori, Masaru; Ito, Masafumi

2014-01-01

To investigate the inactivation process of Penicillium digitatum spores through neutral oxygen species, the spores were treated with an atmospheric-pressure oxygen radical source and observed in-situ using a fluorescent confocal-laser microscope. The treated spores were stained with two fluorescent dyes, 1,1‧-dioctadecyl-3,3,Y,3‧-tetramethylindocarbocyanine perchlorate (DiI) and diphenyl-1-pyrenylphosphine (DPPP). The intracellular organelles as well as the cell membranes in the spores treated with the oxygen radical source were stained with DiI without a major morphological change of the membranes. DPPP staining revealed that the organelles were oxidized by the oxygen radical treatment. These results suggest that neutral oxygen species, especially atomic oxygen, induce a minor structural change or functional inhibition of cell membranes, which leads to the oxidation of the intracellular organelles through the penetration of reactive oxygen species into the cell.

Lipid-derived free radical production in superantigen-induced interstitial pneumonia

PubMed Central

Miyakawa, Hisako; Mason, Ronald P.; Jiang, JinJie; Kadiiska, Maria B.

2009-01-01

We studied the free radical generation involved in the development of interstitial pneumonia (IP) in an animal model of autoimmune disease. We observed an electron spin resonance (ESR) spectrum of α-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN) radical adducts detected in the lipid extract of lungs in autoimmune-prone mice after intratracheal instillation of staphylococcal enterotoxin B. The POBN adducts detected by ESR were paralleled by infiltration of macrophages and neutrophils in the bronchoalveolar lavage fluid. To further investigate the mechanism of free radical generation, mice were pretreated with the macrophage toxicant gadolinium chloride, which significantly suppressed the radical generation. Free radical generation was also decreased by pretreatment with the xanthine oxidase (XO) inhibitor allopurinol, the iron chelator Desferal, and the inducible nitric oxide synthase (iNOS) inhibitor 1400W. Histopathologically, these drugs significantly reduced both the cell infiltration to alveolar septal walls and the synthesis of pulmonary collagen fibers. Experiments with NADPH oxidase knockout mice showed that NADPH oxidase did not contribute to lipid radical generation. These results suggest that lipid-derived carbon-centered free radical production is important in the manifestation of IP and that a macrophage toxicant, an XO inhibitor, an iron chelator, and an iNOS inhibitor protect against both radical generation and the manifestation of IP. PMID:19376221

Phenylethylamine-induced generation of reactive oxygen species and ascorbate free radicals in tobacco suspension culture: mechanism for oxidative burst mediating Ca2+ influx.

PubMed

Kawano, T; Pinontoan, R; Uozumi, N; Morimitsu, Y; Miyake, C; Asada, K; Muto, S

2000-11-01

In the previous paper [Kawano et al. (2000a) Plant Cell Physiol. 41: 1251], we demonstrated that addition of phenylethylamine (PEA) and benzylamine can induce an immediate and transient burst of active oxygen species (AOS) in tobacco suspension culture. Detected AOS include H2O2, superoxide anion and hydroxyl radicals. Use of several inhibitors suggested the presence of monoamine oxidase-like H2O2-generating activity in the cellular soluble fraction. It was also suggested that peroxidase(s) or copper amine oxidase(s) are involved in the extracellular superoxide production as a consequence of H2O2 production. Since more than 85% of the PEA-dependent AOS generating activity was localized in the extracellular space (extracellular fluid + cell wall), extracellularly secreted enzymes, probably peroxidases, may largely contribute to the oxidative burst induced by PEA. The PEA-induced AOS generation was also observed in the horseradish peroxidase (HRP) reaction mixture, supporting the hypothesis that peroxidases catalyze the oxidation of PEA leading to AOS generation. In addition to AOS production, we observed that PEA induced an increase in monodehydroascorbate radicals (MDA) in the cell suspension culture and in HRP reaction mixture using electron spin resonance spectroscopy and the newly invented MDA reductase-coupled method. Here we report that MDA production is an indicator of peroxidase-mediated generation of PEA radical species in tobacco suspension culture.

Candidemia-induced pediatric sepsis and its association with free radicals, nitric oxide, and cytokine level in host.

PubMed

Kumar, Dharmendra; Kumar, Abhai; Singh, Smita; Tilak, Ragini

2015-04-01

Candida species has become the seventh most frequent causal microorganisms of nosocomial sepsis. Prematurity and low birth weights are strongly associated with the development of neonatal nosocomial bloodstream infections. Candida albicans has been the species most often associated with neonatal infections, but recently, there has been a changing pattern in the isolates recovered from neonates with invasive candidiasis, which poses resistance to the existing class of azoles such as fluconazole antifungals along with cross resistance to newer triazoles, which results in a therapeutic challenge in invasive fungal infections causing high incidence of mortality. Candida species was isolated from blood of neonates and children younger than 15 years admitted to hospital and susceptible for Candida-induced sepsis. Polymerase chain reaction-based identification and confirmation of individual Candida species were done using DNA sequencing. Antibiotic susceptibility assay and resistance pattern for fluconazole, voriconazole, and amphotericin were done for all the isolates. Furthermore, the change in free radical, cytokine release, and nitric oxide synthase expression and nitric oxide release from polymorphonuclear leukocytes isolated from control and pediatric sepsis cases were also performed. The present study probably for the first time reports the change in increasing incidence of nonalbicans Candida-induced sepsis in neonates and children admitted to the intensive care unit of hospital, and current antibiotics load posing resistance for antifungal treatment strategy and provide serious threats in future treatment. The increase in free radicals in polymorphonuclear leukocytes and increase in expression of nitric oxide synthase expression and nitric oxide release in Candida-infected pediatric sepsis cases underlie the role of host factor in dissemination and invasiveness of infection from exogenous sources and pathogenesis of systemic inflammation during sepsis. Copyright

Laser-induced oxidation of cholesterol observed during MALDI-TOF mass spectrometry.

PubMed

McAvey, Kevin M; Guan, Bing; Fortier, Chanel A; Tarr, Matthew A; Cole, Richard B

2011-04-01

Conditions for the detection of three odd-electron cholesterol oxidation peaks were determined and these peaks were shown to be artifacts of the matrix-assisted laser desorption time of flight (MALDI-TOF) process. Matrix choice, solvent, laser intensity and cholesterol concentration were systematically varied to characterize the conditions leading to the highest signals of the radical cation peaks, and it was found that initial cholesterol solution concentration and resultant density of solid cholesterol on the MALDI target were important parameters in determining signal intensities. It is proposed that hydroxyl radicals, generated as a result of laser irradiation of the employed 2,5-dihydroxybenzoic acid (DHB) matrix, initiate cholesterol oxidation on the MALDI target. An attempt to induce the odd-electron oxidation peaks by means of adding an oxidizing agent succeeded using an acetonitrile solution of DHB, cholesterol, and cumene hydroperoxide. Moreover, addition of free radical scavengers reduced the abundances of some oxidation products under certain conditions. These results are consistent with the mechanism of oxidation proposed herein involving laser-induced hydroxyl radical production followed by attack on neutral cholesterol. Hydroxyl radical production upon irradiation of dithranol matrix may also be responsible for generation of the same radical peaks observed from cholesterol in dithranol by an analogous mechanism. © American Society for Mass Spectrometry, 2011

Free-radical chemistry of sulfite.

PubMed Central

Neta, P; Huie, R E

1985-01-01

The free-radical chemistry of sulfite oxidation is reviewed. Chemical transformations of organic and biological molecules induced by sulfite oxidation are summarized. The kinetics of the free-radical oxidations of sulfite are discussed, as are the kinetics of the reactions of the sulfite-derived radicals SO3 and the peroxy derivative SO5 with organic compounds. PMID:3830699

Immuno-spin trapping of heme-induced protein radicals: Implications for heme oxygenase-1 induction and heme degradation

PubMed Central

Ganini, Douglas; Deterding, Leesa J.; Ehrenshaft, Marilyn; Chatterjee, Saurabh; Mason, Ronald P.

2013-01-01

Heme, in the presence of hydrogen peroxide, can act as a peroxidase. Intravascular hemolysis results in a massive release of heme into the plasma in several pathophysiological conditions such as hemolytic anemia, malaria, and sickle cell disease. Heme is known to induce heme oxygenase-1(HO-1) expression, and the extent of induction depends on the ratio of albumin to heme in plasma. HO-1 degrades heme and ultimately generates the antioxidant bilirubin. Heme also causes oxidative stress in cells, but whether it causes protein-radical formation has not yet been studied. In the literature, two purposes for the degradation of heme by HO-1 are discussed. One is the production of the antioxidant bilirubin and the other is the prevention of heme-dependent adverse effects. Here we have investigated heme-induced protein-radical formation, which might have pathophysiological consequences, and have used immunospin trapping to establish the formation of heme-induced protein radicals in two systems: human serum albumin (HSA)/H2O2 and human plasma/H2O2.We found that excess heme catalyzed the formation of HSA radicals in the presence of hydrogen peroxide. When heme and hydrogen peroxide were added to human plasma, heme was found to oxidize proteins, primarily and predominantly HSA; however, when HSA-depleted plasma was used, heme triggered the oxidation of several other proteins, including transferrin. Thus, HSA in plasma protected other proteins from heme/H2O2-induced oxidation. The antioxidants ascorbate and uric acid significantly attenuated protein-radical formation induced by heme/ H2O2; however, bilirubin did not confer significant protection. Based on these findings, we conclude that heme is degraded by HO-1 because it is a catalyst of protein-radical formation and not merely to produce the relatively inefficient antioxidant bilirubin. PMID:23624303

Oxidation of DNA bases, deoxyribonucleosides and homopolymers by peroxyl radicals.

PubMed Central

Simandan, T; Sun, J; Dix, T A

1998-01-01

DNA base oxidation is considered to be a key event associated with disease initiation and progression in humans. Peroxyl radicals (ROO. ) are important oxidants found in cells whose ability to react with the DNA bases has not been characterized extensively. In this paper, the products resulting from ROO. oxidation of the DNA bases are determined by gas chromatography/MS in comparison with authentic standards. ROO. radicals oxidize adenine and guanine to their 8-hydroxy derivatives, which are considered biomarkers of hydroxyl radical (HO.) oxidations in cells. ROO. radicals also oxidize adenine to its hydroxylamine, a previously unidentified product. ROO. radicals oxidize cytosine and thymine to the monohydroxy and dihydroxy derivatives that are formed by oxidative damage in cells. Identical ROO. oxidation profiles are observed for each base when exposed as deoxyribonucleosides, monohomopolymers and base-paired dihomopolymers. These results have significance for the development, utilization and interpretation of DNA base-derived biomarkers of oxidative damage associated with disease initiation and propagation, and support the idea that the mutagenic potential of N-oxidized bases, when generated in cellular DNA, will require careful evaluation. Adenine hydroxylamine is proposed as a specific molecular probe for the activity of ROO. in cellular systems. PMID:9761719

Mars Oxidant and Radical Detector

NASA Technical Reports Server (NTRS)

Yen, A. S.; Kim, S. S.

2003-01-01

The Mars Oxidant and Radical Detector is an instrument designed to characterize the reactive nature of the martian surface environment. Using Electron Paramagnetic Resonance (EPR) techniques, this instrument can detect, identify, and quantify radical species in soil samples, including those inferred to be present by the Viking experiments. This instrument is currently funded by the Mars Instrument Development Program and is compatible with the Mars Science Laboratory mission.

[Free radical oxidation in workers engaged into petrochemistry].

PubMed

Iapparov, R N; Kamilov, R F; Shakirov, D F; Sidorcheva, O V

2007-01-01

The article deals with results of studies covering free radical oxidation and peroxidation in RBC, serum, saliva and urine of petrochemistry workers. Individuals exposed to chemical pollutants in production of rubber, tyre and mechanical rubber goods appeared to have considerably increased free radical oxidation parameters in RBC, serum, saliva and urine.

Role of Oxygen Free Radicals, Nitric Oxide and Mitochondria in Mediating Cardiac Alterations During Liver Cirrhosis Induced by Thioacetamide.

PubMed

Amirtharaj, G Jayakumar; Natarajan, Sathish Kumar; Pulimood, Anna; Balasubramanian, K A; Venkatraman, Aparna; Ramachandran, Anup

2017-04-01

Thioacetamide (TAA) administration is widely used for induction of liver cirrhosis in rats, where reactive oxygen radicals (ROS) and nitric oxide (NO) participate in development of liver damage. Cardiac dysfunction is an important complication of liver cirrhosis, but the role of ROS or NO in cardiac abnormalities during liver cirrhosis is not well understood. This was investigated in animals after TAA-induced liver cirrhosis and temporal changes in oxidative stress, NO and mitochondrial function in the heart evaluated. TAA induced elevation in cardiac levels of nitrate before development of frank liver cirrhosis, without gross histological alterations. This was accompanied by an early induction of P38 MAP kinase, which is influenced by ROS and plays an important signaling role for induction of iNOS. Increased nitrotyrosine, protein oxidation and lipid peroxidation in the heart and cardiac mitochondria, suggestive of oxidative stress, also preceded frank liver cirrhosis. However, compromised cardiac mitochondrial function with a decrease in respiratory control ratio and increased mitochondrial swelling was seen later, when cirrhosis was evident. In conclusion, TAA induces elevations in ROS and NO in the heart in parallel to early liver damage. This leads to later development of functional deficits in cardiac mitochondria after development of liver cirrhosis.

Immunolocalization of hypochlorite-induced, catalase-bound free radical formation in mouse hepatocytes

PubMed Central

Bonini, Marcelo G.; Siraki, Arno G.; Atanassov, Boyko S.; Mason., Ronald P.

2007-01-01

The establishment of oxidants as mediators of signal transduction has renewed the interest of investigators in oxidant production and metabolism. In particular, H2O2 has been demonstrated to play pivotal roles in mediating cell differentiation, proliferation and death. Intracellular concentrations of H2O2 are modulated by its rate of production and its rate of decomposition by catalase and peroxidases. In inflammation and infection some of the H2O2 is converted to hypochlorous acid, a key mediator of the host immune response against pathogens. In vivo HOCl production is mediated by myeloperoxidase, which uses excess H2O2 to oxidize Cl−. Mashino and Fridovich (1988) observed that a high excess of HOCl over catalase inactivated the enzyme by mechanisms that remain unclear. The potential relevance of this as an alternative mechanism for catalase activity control and its potential impact on H2O2-mediated signaling and HOCl-production compelled us to explore in depth the HOCl-mediated catalase inactivation pathways. Here, we demonstrate that HOCl induces formation of catalase protein radicals and carbonyls, which are temporally correlated with catalase aggregation. Hypochlorite-induced catalase aggregation and free radical formation that paralleled the enzyme loss of function in vitro were also detected in mouse hepatocytes treated with the oxidant. Interestingly, the novel immunospin-trapping technique was applied to image radical production in the cells. Indeed, in HOCl-treated hepatocytes, catalase and protein-DMPO nitrone adducts were colocalized in the cells’ peroxisomes. In contrast, when hepatocytes from catalase-knockout mice were treated with hypochlorous acid, there was extensive production of free radicals in the plasma membrane. Because free radicals are short-lived species with fundamental roles in biology, the possibility of their detection and localization to cell compartments is expected to open new and stimulating research venues in the interface of

Action of 6-amino-3-pyridinols as novel antioxidants against free radicals and oxidative stress in solution, plasma, and cultured cells.

PubMed

Omata, Yo; Saito, Yoshiro; Yoshida, Yasukazu; Jeong, Byeong-Seon; Serwa, Remigiusz; Nam, Tae-gyu; Porter, Ned A; Niki, Etsuo

2010-05-15

Free radical-mediated lipid peroxidation has been implicated in the pathogenesis of various diseases. Lipid peroxidation products are cytotoxic and they modify proteins and DNA bases, leading eventually to degenerative disorders. Various synthetic antioxidants have been developed and assessed for their capacity to inhibit lipid peroxidation and oxidative stress induced by free radicals. In this study, the capacity of novel 6-amino-2,4,5-trimethyl-3-pyridinols for scavenging peroxyl radicals, inhibiting plasma lipid peroxidation in vitro, and preventing cytotoxicity induced by glutamate, 6-hydroxydopamine, 1-methyl-4-phenylpyridium (MPP(+) ), and hydroperoxyoctadecadienoic acid was assessed. It was found that they exerted higher reactivity toward peroxyl radicals and more potent activity for inhibiting the above oxidative stress than alpha-tocopherol, the most potent natural antioxidant, except against the cytotoxicity induced by MPP(+). These results suggest that the novel 6-amino-3-pyridinols may be potent antioxidants against oxidative stress. Copyright 2010 Elsevier Inc. All rights reserved.

Effects of Kombucha on oxidative stress induced nephrotoxicity in rats

PubMed Central

2009-01-01

Background Trichloroethylene (TCE) may induce oxidative stress which generates free radicals and alters antioxidants or oxygen-free radical scavenging enzymes. Methods Twenty male albino rats were divided into four groups: (1) the control group treated with vehicle, (2) Kombucha (KT)-treated group, (3) TCE-treated group and (4) KT/TCE-treated group. Kidney lipid peroxidation, glutathione content, nitric oxide (NO) and total blood free radical concentrations were evaluated. Serum urea, creatinine level, gamma-glutamyl transferase (GGT) and lactate dehydrogenase (LDH) activities were also measured. Results TCE administration increased the malondiahyde (MDA) and NO contents in kidney, urea and creatinine concentrations in serum, total free radical level in blood and GGT and LDH activities in serum, whereas it decreased the glutathione (GSH) level in kidney homogenate. KT administration significantly improved lipid peroxidation and oxidative stress induced by TCE. Conclusion The present study indicates that Kombucha may repair damage caused by environmental pollutants such as TCE and may be beneficial to patient suffering from renal impairment. PMID:19943946

Effects of Kombucha on oxidative stress induced nephrotoxicity in rats.

PubMed

Gharib, Ola Ali

2009-11-27

Trichloroethylene (TCE) may induce oxidative stress which generates free radicals and alters antioxidants or oxygen-free radical scavenging enzymes. Twenty male albino rats were divided into four groups: (1) the control group treated with vehicle, (2) Kombucha (KT)-treated group, (3) TCE-treated group and (4) KT/TCE-treated group. Kidney lipid peroxidation, glutathione content, nitric oxide (NO) and total blood free radical concentrations were evaluated. Serum urea, creatinine level, gamma-glutamyl transferase (GGT) and lactate dehydrogenase (LDH) activities were also measured. TCE administration increased the malondiahyde (MDA) and NO contents in kidney, urea and creatinine concentrations in serum, total free radical level in blood and GGT and LDH activities in serum, whereas it decreased the glutathione (GSH) level in kidney homogenate. KT administration significantly improved lipid peroxidation and oxidative stress induced by TCE. The present study indicates that Kombucha may repair damage caused by environmental pollutants such as TCE and may be beneficial to patient suffering from renal impairment.

Free Radical Oxidation in Rat Myocardium after Maximum Permissible Hepatic Resection.

PubMed

Ermolaev, P A; Khramykh, T P; Barskaya, L O

2016-03-01

Free radical oxidation in rat myocardial homogenate was studied by chemiluminescent assay during the early terms after maximum permissible liver resection. During this period, activation of free radical oxidation was biphasic. The critical terms characterized by dramatic intensification of free radical oxidation in the myocardium are the first hour and the first day after surgery. The period from 3 to 12 h after surgery, in which the indices of chemiluminescence decrease, can be tentatively termed as the period of "putative wellbeing". Normalization of the free radical oxidation processes in the myocardium occurred by day 7 after surgery.

IRON AND FREE RADICAL OXIDATIONS IN CELL MEMBRANES

PubMed Central

Schafer, Freya Q.; Yue Qian, Steven; Buettner, Garry R.

2013-01-01

Brain tissue being rich in polyunsaturated fatty acids, is very susceptible to lipid peroxidation. Iron is well known to be an important initiator of free radical oxidations. We propose that the principal route to iron-mediated lipid peroxidations is via iron-oxygen complexes rather than the reaction of iron with hydrogen peroxide, the Fenton reaction. To test this hypothesis, we enriched leukemia cells (K-562 and L1210 cells) with docosahexaenoic acid (DHA) as a model for brain tissue, increasing the amount of DHA from approximately 3 mole % to 32 mole %. These cells were then subjected to ferrous iron and dioxygen to initiate lipid peroxidation in the presence or absence of hydrogen peroxide. Lipid-derived radicals were detected using EPR spin trapping with α-(4-pyridyl-1-oxide)-N-t-butylnitrone (POBN). As expected, lipid-derived radical formation increases with increasing cellular lipid unsaturation. Experiments with Desferal demonstrate that iron is required for the formation of lipid radicals from these cells. Addition of iron to DHA-enriched L1210 cells resulted in significant amounts of radical formation; radical formation increased with increasing amount of iron. However, the exposure of cells to hydrogen peroxide before the addition of ferrous iron did not increase cellular radical formation, but actually decreased spin adduct formation. These data suggest that iron-oxygen complexes are the primary route to the initiation of biological free radical oxidations. This model proposes a mechanism to explain how catalytic iron in brain tissue can be so destructive. PMID:10872752

Diffusive confinement of free radical intermediates in the OH radical oxidation of semisolid aerosols

DOE PAGES

Wiegel, Aaron A.; Liu, Matthew J.; Hinsberg, William D.; ...

2017-02-07

Multiphase chemical reactions (gas + solid/liquid) involve a complex interplay between bulk and interface chemistry, diffusion, evaporation, and condensation. Reactions of atmospheric aerosols are an important example of this type of chemistry: the rich array of particle phase states and multiphase transformation pathways produce diverse but poorly understood interactions between chemistry and transport. Their chemistry is of intrinsic interest because of their role in controlling climate. Their characteristics also make them useful models for the study of principles of reactivity of condensed materials under confined conditions. Previously, we have reported a computational study of the oxidation chemistry of a liquidmore » aliphatic aerosol. In this study, we extend the calculations to investigate nearly the same reactions at a semisolid gas-aerosol interface. A reaction-diffusion model for heterogeneous oxidation of triacontane by hydroxyl radicals (OH) is described, and its predictions are compared to measurements of aerosol size and composition, which evolve continuously during oxidation. Our results are also explicitly compared to those obtained for the corresponding liquid system, squalane, to pinpoint salient elements controlling reactivity. The diffusive confinement of the free radical intermediates at the interface results in enhanced importance of a few specific chemical processes such as the involvement of aldehydes in fragmentation and evaporation, and a significant role of radical-radical reactions in product formation. The simulations show that under typical laboratory conditions semisolid aerosols have highly oxidized nanometer-scale interfaces that encapsulate an unreacted core and may confer distinct optical properties and enhanced hygroscopicity. This highly oxidized layer dynamically evolves with reaction, which we propose to result in plasticization. The validated model is used to predict chemistry under atmospheric conditions, where the OH

Effect of curcumin against oxidation of biomolecules by hydroxyl radicals.

PubMed

Borra, Sai Krishna; Mahendra, Jaideep; Gurumurthy, Prema; Jayamathi; Iqbal, Shabeer S; Mahendra, Little

2014-10-01

Among various reactive oxygen species, hydroxyl radicals have the strongest chemical activity, which can damage a wide range of essential biomolecules such as lipids, proteins, and DNA. The objective of this study was to investigate the beneficial effects of curcumin on prevention of oxidative damage of biomolecules by hydroxyl radicals generated in in vitro by a Fenton like reaction. We have incubated the serum, plasma and whole blood with H2O2/Cu2+/ Ascorbic acid system for 4 hours at 37 0C and observed the oxidation of biomolecules like albumin, lipids, proteins and DNA. Curcumin at the concentrations of 50,100 and 200 μmoles, prevented the formation of ischemia modified albumin, MDA, protein carbonyls, oxidized DNA and increased the total antioxidant levels and GSH significantly. These observations suggest the hydroxyl radical scavenging potentials of curcumin and protective actions to prevent the oxidation of biomolecules by hydroxyl radicals.

Oxidative stress induces protein and DNA radical formation in follicular dendritic cells (FDCs) of the germinal center and modulates its cell death patterns in late sepsis

PubMed Central

Chatterjee, Saurabh; Lardinois, Olivier; Bhattacharjee, Suchandra; Tucker, Jeff; Corbett, Jean; Deterding, Leesa; Ehrenshaft, Marilyn; Bonini, Marcelo; Mason, Ronald P.

2011-01-01

Profound depletion of follicular dendritic cells (FDCs) is a hallmark of sepsis-like syndrome, but the exact causes for the ensuing cell death are unknown. The cell death-driven depletion contributes to immunoparalysis and is responsible for most of the morbidity and mortality in sepsis. Here we have utilized immuno-spin trapping, a method for detection of free radical formation, to detect oxidative stress-induced protein and DNA radical adducts in FDCs isolated from the spleen of septic mice and human tonsil-derived HK cells, a subtype of germinal center FDCs, to study their role in FDC depletion. At 24 h post-LPS administration, protein radical formation and oxidation was significantly elevated in vivo and in HK cells as shown by ELISA and confocal microscopy. The xanthine oxidase inhibitor allopurinol and the iron chelator desferrioxamine significantly decreased the formation of protein radicals, suggesting the role of xanthine oxidase and Fenton-like chemistry in radical formation. Protein and DNA radical formation correlated mostly with apoptotic features at 24 h and necrotic morphology of all the cell types studied at 48 h with concomitant inhibition of caspase-3. The cytotoxity of FDCs resulted in decreased CD45R/CD138+ve plasma cell numbers, indicating a possible defect in B cell differentiation. In one such mechanism, radical formation initiated by xanthine oxidase formed protein and DNA radicals which may lead to cell death of germinal center FDCs. PMID:21215311

Putative free radical-scavenging activity of an extract of Cineraria maritima in preventing selenite-induced cataractogenesis in Wistar rat pups

PubMed Central

Anitha, Thirugnanasambandhar Sivasubramanian; Muralidharan, Arumugam Ramachandran; Annadurai, Thangaraj; Jesudasan, Christdas Arul Nelson; Thomas, Philip Aloysius

2013-01-01

Purpose To investigate the possible free radical-scavenging activity of an extract of Cineraria maritima on selenite-induced cataractous lenses in Wistar rat pups. Methods In the present study, Wistar rat pups were divided into three experimental groups. On P10, Group I (control) rat pups received an intraperitoneal injection of 0.89% saline. Rats in groups II (selenite-challenged, untreated) and III (selenite-challenged, C. maritima treated) received a subcutaneous injection of sodium selenite (19 μmol/kg bodyweight); Group III rat pups also received an intraperitoneal injection of the extract of C. maritima (350 mg/kg bodyweight) once daily P9–14. Both eyes of each pup were examined from P16 until P30. Cytochemical localization of nitroblue tetrazolium salts and generation of superoxide, hydroxyl, and nitric oxide levels were measured. The expression of the inducible nitric oxide synthase gene was evaluated with reverse transcription-PCR. Immunoblot analysis was also performed to confirm the differential expression of the inducible nitric oxide synthase protein. Results Subcutaneous injection of sodium selenite led to severe oxidative damage in the lenticular tissues, shown by increased formation of formazan crystals, elevated generation of superoxide, hydroxyl, and nitric oxide radicals, and elevated inducible nitric oxide synthase gene and protein expression that possibly contributed to the opacification of the lens and thus cataract formation. When rat pups were treated with intraperitoneal administration of the extract of C. maritima, the generation of free radicals as well as the messenger ribonucleic acid and protein expression of inducible nitric oxide synthase were maintained at near normal levels. Conclusions The data generated by this study suggest that an ethanolic extract of C. maritima possibly prevents cataractogenesis in a rat model by minimizing free radical generation. PMID:24357923

Effect of Curcumin Against Oxidation of Biomolecules by Hydroxyl Radicals

PubMed Central

Mahendra, Jaideep; Gurumurthy, Prema; Jayamathi; Iqbal, Shabeer S; Mahendra, Little

2014-01-01

Background: Among various reactive oxygen species, hydroxyl radicals have the strongest chemical activity, which can damage a wide range of essential biomolecules such as lipids, proteins, and DNA. Objective: The objective of this study was to investigate the beneficial effects of curcumin on prevention of oxidative damage of biomolecules by hydroxyl radicals generated in in vitro by a Fenton like reaction. Materials and Methods: We have incubated the serum, plasma and whole blood with H2O2/Cu2+/ Ascorbic acid system for 4 hours at 37 0C and observed the oxidation of biomolecules like albumin, lipids, proteins and DNA. Results: Curcumin at the concentrations of 50,100 and 200 μmoles, prevented the formation of ischemia modified albumin, MDA, protein carbonyls, oxidized DNA and increased the total antioxidant levels and GSH significantly. Conclusion: These observations suggest the hydroxyl radical scavenging potentials of curcumin and protective actions to prevent the oxidation of biomolecules by hydroxyl radicals. PMID:25478334

Evaluation of hydrogen radical treatment for indium surface oxide removal and analysis of re-oxidation behavior

NASA Astrophysics Data System (ADS)

Furuyama, Kohta; Yamanaka, Kazuyuki; Higurashi, Eiji; Suga, Tadatomo

2018-02-01

Indium is a commonly used metal for sealing, bonding, and soldering due to its good malleability and ductility even at cryogenic temperatures. The effects of hydrogen radical treatment on indium surface oxide removal were evaluated by the spreading ratio test of indium balls (diameter, 300 µm purity, 99.99%). It was found that hydrogen radical treatment longer than 20 s at temperatures higher than 170 °C results in successful surface oxide removal. X-ray photoelectron spectroscopy analysis was carried out to study the re-oxidation behavior after treatment, and it was found that hydrogen radical treatment slows down the re-oxidation of indium compared with surface oxide removal realized by physical bombardment with an argon fast atom beam.

Oxidative stress, free radicals and protein peroxides.

PubMed

Gebicki, Janusz M

2016-04-01

Primary free radicals generated under oxidative stress in cells and tissues produce a cascade of reactive secondary radicals, which attack biomolecules with efficiency determined by the reaction rate constants and target concentration. Proteins are prominent targets because they constitute the bulk of the organic content of cells and tissues and react readily with many of the secondary radicals. The reactions commonly lead to the formation of carbon-centered radicals, which generally convert in vivo to peroxyl radicals and finally to semistable hydroperoxides. All of these intermediates can initiate biological damage. This article outlines the advantages of the application of ionizing radiations to studies of radicals, with particular reference to the generation of desired radicals, studies of the kinetics of their reactions and correlating the results with events in biological systems. In one such application, formation of protein hydroperoxides in irradiated cells was inhibited by the intracellular ascorbate and glutathione. Copyright © 2015 Elsevier Inc. All rights reserved.

Inhibition of free radical-induced erythrocyte hemolysis by 2-O-substituted ascorbic acid derivatives.

PubMed

Takebayashi, Jun; Kaji, Hiroaki; Ichiyama, Kenji; Makino, Kazutaka; Gohda, Eiichi; Yamamoto, Itaru; Tai, Akihiro

2007-10-15

Inhibitory effects of 2-O-substituted ascorbic acid derivatives, ascorbic acid 2-glucoside (AA-2G), ascorbic acid 2-phosphate (AA-2P), and ascorbic acid 2-sulfate (AA-2S), on 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced oxidative hemolysis of sheep erythrocytes were studied and were compared with those of ascorbic acid (AA) and other antioxidants. The order of the inhibition efficiency was AA-2S> or =Trolox=uric acid> or =AA-2P> or =AA-2G=AA>glutathione. Although the reactivity of the AA derivatives against AAPH-derived peroxyl radical (ROO(*)) was much lower than that of AA, the derivatives exerted equal or more potent protective effects on AAPH-induced hemolysis and membrane protein oxidation. In addition, the AA derivatives were found to react per se with ROO(*), not via AA as an intermediate. These findings suggest that secondary reactions between the AA derivative radical and ROO(*) play a part in hemolysis inhibition. Delayed addition of the AA derivatives after AAPH-induced oxidation of erythrocytes had already proceeded showed weaker inhibition of hemolysis compared to that of AA. These results suggest that the AA derivatives per se act as biologically effective antioxidants under moderate oxidative stress and that AA-2G and AA-2P may be able to act under severe oxidative stress after enzymatic conversion to AA in vivo.

Oxidant-induced DNA damage of target cells.

PubMed Central

Schraufstätter, I; Hyslop, P A; Jackson, J H; Cochrane, C G

1988-01-01

In this study we examined the leukocytic oxidant species that induce oxidant damage of DNA in whole cells. H2O2 added extracellularly in micromolar concentrations (10-100 microM) induced DNA strand breaks in various target cells. The sensitivity of a specific target cell was inversely correlated to its catalase content and the rate of removal of H2O2 by the target cell. Oxidant species produced by xanthine oxidase/purine or phorbol myristate acetate-stimulated monocytes induced DNA breakage of target cells in proportion to the amount of H2O2 generated. These DNA strand breaks were prevented by extracellular catalase, but not by superoxide dismutase. Cytotoxic doses of HOCl, added to target cells, did not induce DNA strand breakage, and myeloperoxidase added extracellularly in the presence of an H2O2-generating system, prevented the formation of DNA strand breaks in proportion to its H2O2 degrading capacity. The studies also indicated that H2O2 formed hydroxyl radical (.OH) intracellularly, which appeared to be the most likely free radical responsible for DNA damage: .OH was detected in cells exposed to H2O2; the DNA base, deoxyguanosine, was hydroxylated in cells exposed to H2O2; and intracellular iron was essential for induction of DNA strand breaks. PMID:2843565

Thermochemical and kinetic analyses on oxidation of isobutenyl radical and 2-hydroperoxymethyl-2-propenyl radical.

PubMed

Zheng, X L; Sun, H Y; Law, C K

2005-10-13

In recognition of the importance of the isobutene oxidation reaction in the preignition chemistry associated with engine knock, the thermochemistry, chemical reaction pathways, and reaction kinetics of the isobutenyl radical oxidation at low to intermediate temperature range were computationally studied, focusing on both the first and the second O2 addition to the isobutenyl radical. The geometries of reactants, important intermediates, transition states, and products in the isobutenyl radical oxidation system were optimized at the B3LYP/6-311G(d,p) and MP2(full)/6-31G(d) levels, and the thermochemical properties were determined on the basis of ab initio, density functional theory, and statistical mechanics. Enthalpies of formation for several important intermediates were calculated using isodesmic reactions at the DFT and the CBS-QB3 levels. The kinetic analysis of the first O2 addition to the isobutenyl radical was performed using enthalpies at the CBS-QB3 and G3(MP2) levels. The reaction forms a chemically activated isobutenyl peroxy adduct which can be stabilized, dissociate back to reactants, cyclize to cyclic peroxide-alkyl radicals, and isomerize to the 2-hydroperoxymethyl-2-propenyl radical that further undergoes another O2 addition. The reaction channels for isomerization and cyclization and further dissociation on this second O2 addition were analyzed using enthalpies at the DFT level with energy corrections based on similar reaction channels for the first O2 addition. The high-pressure limit rate constants for each reaction channel were determined as functions of temperature by the canonical transition state theory for further kinetic model development.

Photolysis and oxidation of azidophenyl-substituted radicals: delocalization in heteroatom-based radicals.

PubMed

Serwinski, Paul R; Esat, Burak; Lahti, Paul M; Liao, Yi; Walton, Richard; Lan, Jiang

2004-08-06

2-(4-Azidophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (14), 2-(4-azidophenyl)benzimidazole-1-oxide-3-oxyl (16), 2-(4-azidophenyl)-1,2,6-triphenylverdazyl (19), 2-(3-azidophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (21), and (3-azidophenyl)-N-tert-butyl-N-aminoxyl (25) were photolyzed in frozen solution to give S = 3/2 state ESR spectra of the corresponding nitrenophenyl radicals with the following zero-field splitting parameters: |D/hc| = 0.277 cm(-1), |E/hc| < or = 0.002 cm(-1) (7 from 14); |D/hc| = 0.256 cm(-1), |E/hc| < or = 0.002 cm(-1) (8 from 16); |D/hc| = 0.288 cm(-1), |E/hc| < or = 0.002 cm(-1) (9 from 19); |D/hc| = 0.352 cm(-1), |E/hc| = 0.006 cm(-1) (10 from 21); |D/hc| = 0.336 cm(-1), |E/hc| = 0.004 cm(-1) (11 from 25). UB3LYP/6-31G computations and ESR spectroscopic analyses suggest that these are nitreno radicals, even para-linked systems with possible quinonoidal resonance forms. Neat samples of azidophenyl radicals 14 and 21 showed bulk paramagnetic behavior, consistent with the lack of close contacts in their crystal structures. Efforts to make photolabile coordination complexes of 14 and 21 with paramagnetic transition metal ions were unsuccessful: Cu(ClO4)2 x 6H2O instead oxidized them to the corresponding diamagnetic nitrosonium perchlorate salts. Copyright 2004 American Chemical Society

Acute Pre-/Post-Treatment with 8th Day SOD-Like Supreme (a Free Radical Scavenging Health Product) Protects against Oxidant-Induced Injury in Cultured Cardiomyocytes and Hepatocytes In Vitro as Well as in Mouse Myocardium and Liver In Vivo.

PubMed

Leong, Pou Kuan; Chen, Jihang; Chan, Wing Man; Leung, Hoi Yan; Chan, Lincoln; Ko, Kam Ming

2017-04-10

8th Day superoxide dismutase (SOD)-Like Supreme (SOD-Like Supreme, a free radical scavenging health product) is an antioxidant-enriched fermentation preparation with free radical scavenging properties. In the present study, the cellular/tissue protective actions of SOD-Like Supreme against menadione toxicity in cultured H9c2 cardiomyocytes and in AML12 hepatocytes as well as oxidant-induced injury in the mouse myocardium and liver were investigated. SOD-Like Supreme was found to possess potent free radical scavenging activity in vitro as assessed by an oxygen radical absorbance capacity assay. Incubation with SOD-Like Supreme (0.5-3% (v/v)) was shown to protect against menadione-induced toxicity in H9c2 and AML12 cells, as evidenced by increases in cell viability. The ability of SOD-Like Supreme to protect against menadione cytotoxicity was associated with an elevation in the cellular reduced glutathione (GSH)/oxidized glutathione (GSSG) ratio in menadione-challenged cells. Consistent with the cell-based studies, pre-/post-treatment with SOD-Like Supreme (0.69 and 2.06 mL/kg, three intermittent doses per day for two consecutive days) was found to protect against isoproterenol-induced myocardial injury and carbon tetrachloride hepatotoxicity in mice. The cardio/hepatoprotection afforded by SOD-Like Supreme was also paralleled by increases in myocardial/hepatic mitochondrial GSH/GSSG ratios in the SOD-Like Supreme-treated/oxidant-challenged mice. In conclusion, incubation/treatment with SOD-Like Supreme was found to protect against oxidant-induced injury in vitro and in vivo, presumably by virtue of its free radical scavenging activity.

Black soybean seed coat polyphenols prevent AAPH-induced oxidative DNA-damage in HepG2 cells

PubMed Central

Yoshioka, Yasukiyo; Li, Xiu; Zhang, Tianshun; Mitani, Takakazu; Yasuda, Michiko; Nanba, Fumio; Toda, Toshiya; Yamashita, Yoko; Ashida, Hitoshi

2017-01-01

Black soybean seed coat extract (BE), which contains abundant polyphenols such as procyanidins, cyanidin 3-glucoside, (+)-catechin, and (−)­epicatechin, has been reported on health beneficial functions such as antioxidant activity, anti-inflammatory, anti-obesity, and anti-diabetic activities. In this study, we investigated that prevention of BE and its polyphenols on 2,2'-azobis(2-methylpropionamide) dihydrochloride (AAPH)-induced oxidative DNA damage, and found that these polyphenols inhibited AAPH-induced formation of 8-hydroxy-2'-deoxyguanosine (8-OHdG) as a biomarker for oxidative DNA damage in HepG2 cells. Under the same conditions, these polyphenols also inhibited AAPH-induced accumulation of reactive oxygen species (ROS) in the cells. Inhibition of ROS accumulation was observed in both cytosol and nucleus. It was confirmed that these polyphenols inhibited formation of AAPH radical using oxygen radical absorbance capacity assay under the cell-free conditions. These results indicate that polyphenols in BE inhibit free radical-induced oxidative DNA damages by their potent antioxidant activity. Thus, BE is an effective food material for prevention of oxidative stress and oxidative DNA damages. PMID:28366989

Synergistic antibacterial effects of localized heat and oxidative stress caused by hydroxyl radicals mediated by graphene/iron oxide-based nanocomposites.

PubMed

Pan, Wen-Yu; Huang, Chieh-Cheng; Lin, Tzu-Tsen; Hu, Hsin-Yi; Lin, Wei-Chih; Li, Meng-Ju; Sung, Hsing-Wen

2016-02-01

This work develops a composite system of reduced graphene oxide (rGO)-iron oxide nanoparticles (rGO-IONP) that can synergistically induce physical and chemical damage to methicillin-resistant Staphylococcus aureus (MRSA) that are present in subcutaneous abscesses. rGO-IONP was synthesized by the chemical deposition of Fe(2+)/Fe(3+) ions on nanosheets of rGO in aqueous ammonia. The antibacterial efficacy of the as-prepared rGO-IONP was evaluated in a mouse model with MRSA-infected subcutaneous abscesses. Upon exposure to a near-infrared laser in vitro, rGO-IONP synergistically generated localized heat and large amounts of hydroxyl radicals, which inactivated MRSA. The in vivo results reveal that combined treatment with localized heat and oxidative stress that is caused by hydroxyl radicals accelerated the healing of wounds associated with MRSA-infected abscesses. The above results demonstrate that an rGO-IONP nanocomposite system that can effectively inactivate multiple-drug-resistant bacteria in subcutaneous infections was successfully developed. The emergence of methicillin-resistant S. aureus (MRSA) has posed a significant problem in the clinical setting. Thus, it is imperative to develop new treatment strategies against this. In this study, the authors described the use of reduced graphene oxide (rGO)-iron oxide nanoparticles (rGO-IONP) to induce heat and chemical damage to MRSA. This approach may provide a platform the design of other treatment modalities against multiple-drug-resistant bacteria. Copyright © 2015 Elsevier Inc. All rights reserved.

Pomegranate Juice Polyphenols Induce Macrophage Death via Apoptosis as Opposed to Necrosis Induced by Free Radical Generation: A Central Role for Oxidative Stress.

PubMed

Rom, Oren; Volkova, Nina; Nandi, Sukhendu; Jelinek, Raz; Aviram, Michael

2016-08-01

At high concentrations, polyphenols induce cell death, and the polyphenols-rich pomegranate juice (PJ), known for its antioxidative/antiatherogenic properties, can possibly affect cell death, including macrophage death involved in atherogenesis. In the present study, apoptotic/necrotic macrophage death was analyzed in J774A.1 macrophages and in peritoneal macrophages isolated from atherosclerotic apoE-/- mice treated with PJ. The effects of PJ were compared with those of the free radical generator 2, 2'-azobis (2-amidinopropane) dihydrochloride (AAPH). Both PJ and AAPH significantly increased J774A.1 macrophage death; however, flow cytometric and microscopic analyses using annexin V/propidium iodide revealed that PJ increased the early apoptosis of the macrophage dose dependently (up to 2.5-fold, P < 0.01), whereas AAPH caused dose-dependent increases in late apoptosis/necrosis (up to 12-fold, P < 0.001). Unlike PJ, AAPH-induced macrophage death was associated with increased intracellular oxidative stress (up to 7-fold, P < 0.001) and with lipid stress demonstrated by triglyceride accumulation (up to 3-fold, P < 0.01) and greater chromatic vesicle response to culture medium (up to 5-fold, P < 0.001). Accordingly, recombinant paraoxonase 1, which hydrolyzes oxidized lipids, attenuated macrophage death induced by AAPH, but not by PJ. Similar apoptotic and oxidative effects were found in macrophages from apoE-/- mice treated with PJ or AAPH. As macrophage apoptotic/necrotic death has considerable impact on atherosclerosis progression, these findings may provide novel mechanisms for the antiatherogenicity of PJ.

H2S protects against methionine-induced oxidative stress in brain endothelial cells.

PubMed

Tyagi, Neetu; Moshal, Karni S; Sen, Utpal; Vacek, Thomas P; Kumar, Munish; Hughes, William M; Kundu, Soumi; Tyagi, Suresh C

2009-01-01

Homocysteine (Hcy) causes cerebrovascular dysfunction by inducing oxidative stress. However, to date, there are no strategies to prevent Hcy-induced oxidative damage. Hcy is an H2S precursor formed from methionine (Met) metabolism. We aimed to investigate whether H2S ameliorated Met-induced oxidative stress in mouse brain endothelial cells (bEnd3). The bEnd3 cells were exposed to Met treatment in the presence or absence of NaHS (donor of H2S). Met-induced cell toxicity increased the levels of free radicals in a concentration-dependent manner. Met increased NADPH-oxidase-4 (NOX-4) expression and mitigated thioredxion-1(Trx-1) expression. Pretreatment of bEnd3 with NaHS (0.05 mM) attenuated the production of free radicals in the presence of Met and protected the cells from oxidative damage. Furthermore, NaHS enhanced inhibitory effects of apocynin, N-acetyl-l-cysteine (NAC), reduced glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), Nomega-nitro-l-arginine methyl ester (L-NAME) on ROS production and redox enzymes levels induced by Met. In conclusion, the administration of H2S protected the cells from oxidative stress induced by hyperhomocysteinemia (HHcy), which suggested that NaHS/H2S may have therapeutic potential against Met-induced oxidative stress.

Aerosol Fragmentation Driven by Coupling of Acid-Base and Free-Radical Chemistry in the Heterogeneous Oxidation of Aqueous Citric Acid by OH Radicals.

PubMed

Liu, Matthew J; Wiegel, Aaron A; Wilson, Kevin R; Houle, Frances A

2017-08-10

A key uncertainty in the heterogeneous oxidation of carboxylic acids by hydroxyl radicals (OH) in aqueous-phase aerosol is how the free-radical reaction pathways might be altered by acid-base chemistry. In particular, if acid-base reactions occur concurrently with acyloxy radical formation and unimolecular decomposition of alkoxy radicals, there is a possibility that differences in reaction pathways impact the partitioning of organic carbon between the gas and aqueous phases. To examine these questions, a kinetic model is developed for the OH-initiated oxidation of citric acid aerosol at high relative humidity. The reaction scheme, containing both free-radical and acid-base elementary reaction steps with physically validated rate coefficients, accurately predicts the experimentally observed molecular composition, particle size, and average elemental composition of the aerosol upon oxidation. The difference between the two reaction channels centers on the reactivity of carboxylic acid groups. Free-radical reactions mainly add functional groups to the carbon skeleton of neutral citric acid, because carboxylic acid moieties deactivate the unimolecular fragmentation of alkoxy radicals. In contrast, the conjugate carboxylate groups originating from acid-base equilibria activate both acyloxy radical formation and carbon-carbon bond scission of alkoxy radicals, leading to the formation of low molecular weight, highly oxidized products such as oxalic and mesoxalic acid. Subsequent hydration of carbonyl groups in the oxidized products increases the aerosol hygroscopicity and accelerates the substantial water uptake and volume growth that accompany oxidation. These results frame the oxidative lifecycle of atmospheric aerosol: it is governed by feedbacks between reactions that first increase the particle oxidation state, then eventually promote water uptake and acid-base chemistry. When coupled to free-radical reactions, acid-base channels lead to formation of low molecular

Aerosol Fragmentation Driven by Coupling of Acid–Base and Free-Radical Chemistry in the Heterogeneous Oxidation of Aqueous Citric Acid by OH Radicals

DOE PAGES

Liu, Matthew J.; Wiegel, Aaron A.; Wilson, Kevin R.; ...

2017-07-14

A key uncertainty in the heterogeneous oxidation of carboxylic acids by hydroxyl radicals (OH) in aqueous-phase aerosol is how the free-radical reaction pathways might be altered by acid-base chemistry. In particular, if acid-base reactions occur concurrently with acyloxy radical formation and unimolecular decomposition of alkoxy radicals, there is a possibility that differences in reaction pathways impact the partitioning of organic carbon between the gas and aqueous phases. To examine these questions, a kinetic model is developed for the OH-initiated oxidation of citric acid aerosol at high relative humidity. The reaction scheme, containing both free-radical and acid-base elementary reaction steps withmore » physically validated rate coefficients, accurately predicts the experimentally observed molecular composition, particle size, and average elemental composition of the aerosol upon oxidation. The difference between the two reaction channels centers on the reactivity of carboxylic acid groups. Free-radical reactions mainly add functional groups to the carbon skeleton of neutral citric acid, because carboxylic acid moieties deactivate the unimolecular fragmentation of alkoxy radicals. In contrast, the conjugate carboxylate groups originating from acid-base equilibria activate both acyloxy radical formation and carbon-carbon bond scission of alkoxy radicals, leading to the formation of low molecular weight, highly oxidized products such as oxalic and mesoxalic acid. Subsequent hydration of carbonyl groups in the oxidized products increases the aerosol hygroscopicity and accelerates the substantial water uptake and volume growth that accompany oxidation. These results frame the oxidative lifecycle of atmospheric aerosol: it is governed by feedbacks between reactions that first increase the particle oxidation state, then eventually promote water uptake and acid-base chemistry. When coupled to free-radical reactions, acid-base channels lead to formation of low

Aerosol Fragmentation Driven by Coupling of Acid–Base and Free-Radical Chemistry in the Heterogeneous Oxidation of Aqueous Citric Acid by OH Radicals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Matthew J.; Wiegel, Aaron A.; Wilson, Kevin R.

A key uncertainty in the heterogeneous oxidation of carboxylic acids by hydroxyl radicals (OH) in aqueous-phase aerosol is how the free-radical reaction pathways might be altered by acid-base chemistry. In particular, if acid-base reactions occur concurrently with acyloxy radical formation and unimolecular decomposition of alkoxy radicals, there is a possibility that differences in reaction pathways impact the partitioning of organic carbon between the gas and aqueous phases. To examine these questions, a kinetic model is developed for the OH-initiated oxidation of citric acid aerosol at high relative humidity. The reaction scheme, containing both free-radical and acid-base elementary reaction steps withmore » physically validated rate coefficients, accurately predicts the experimentally observed molecular composition, particle size, and average elemental composition of the aerosol upon oxidation. The difference between the two reaction channels centers on the reactivity of carboxylic acid groups. Free-radical reactions mainly add functional groups to the carbon skeleton of neutral citric acid, because carboxylic acid moieties deactivate the unimolecular fragmentation of alkoxy radicals. In contrast, the conjugate carboxylate groups originating from acid-base equilibria activate both acyloxy radical formation and carbon-carbon bond scission of alkoxy radicals, leading to the formation of low molecular weight, highly oxidized products such as oxalic and mesoxalic acid. Subsequent hydration of carbonyl groups in the oxidized products increases the aerosol hygroscopicity and accelerates the substantial water uptake and volume growth that accompany oxidation. These results frame the oxidative lifecycle of atmospheric aerosol: it is governed by feedbacks between reactions that first increase the particle oxidation state, then eventually promote water uptake and acid-base chemistry. When coupled to free-radical reactions, acid-base channels lead to formation of low

Atmospheric Oxidation Mechanism of Furfural Initiated by Hydroxyl Radicals.

PubMed

Zhao, Xiaocan; Wang, Liming

2017-05-04

Furfural is emitted into the atmosphere because of its potential applications as an intermediate to alkane fuels from biomass, industrial usages, and biomass burning. The kinetic and mechanistic information on the furfural chemistry is necessary to assess the fate of furfural in the atmosphere and its impact on the air quality. Here we studied the atmospheric oxidation mechanisms of furfural initiated by the OH radicals using quantum chemistry and kinetic calculations. The reaction of OH and furfural was initiated mainly by OH additions to C 2 and C 5 positions, forming R2 and R5 adducts, which could undergo rapid ring-breakage to form R2B and R5B, respectively. Our calculations showed that these intermediate radicals reacted rather slowly with O 2 under the atmospheric conditions because the additions of O 2 to these radicals are only slightly exothermic and highly reversible. Alternatively, these radicals would react directly with O 3 , NO 2 , HO 2 /RO 2 , etc. Namely, the atmospheric oxidation of furfural would unlikely result in ozone formation. Under typical atmospheric conditions, the main products in OH-initiated furfural oxidation include 2-oxo-3-pentene-1,5-dialdehyde, 5-hydroxy-2(5H)-furanone, 4-oxo-2- butenoic acid, and 2,5-furandione. These compounds will likely stay in the gas phase and are subject to further photo-oxidation.

In vitro genotoxicity of asbestos substitutes induced by coupled stimulation of dissolved high-valence ions and oxide radicals.

PubMed

Huo, Tingting; Dong, Faqin; Deng, Jianjun; Zhang, Qingbi; Ye, Wei; Zhang, Wei; Wang, Pingping; Sun, Dongping

2017-08-01

The wide use of asbestos and its substitutes has given rise to studies on their possible harmful effects on human health and environment. However, their toxic effects remain unclear. The present study was aimed to disclose the coupled effects of dissolved high-valence ions and oxide radicals using the in vitro cytotoxicity and genotoxicity of chrysotile (CA), nano-SiO 2 (NS), ceramic fiber (CF), glass fiber (GF), and rock wool (RW) on Chinese hamster lung cells V79. All samples induced cell mortality correlated well with the chemical SiO 2 content of asbestos substitutes and the amount of dissolved Si. Alkali or alkaline earth metal elements relieved mortality of V79 cells; Al 2 O 3 reinforced toxicity of materials. Asbestos substitutes generated lasting, increasing amount of acellular ·OH which formed at the fiber surface at sites with loose/unsaturated bonds, as well as by catalytic reaction through dissolved iron. Accumulated mechanical and radical stimulation induced the intracellular reactive oxygen species (ROS) elevation, morphology change, and deviating trans-membrane ion flux. The cellular ROS appeared as NS > GF > CF ≈ CA > RW, consistent with cell mortality rather than with acellular ·OH generation. Chromosomal and DNA lesions in V79 cells were not directly associated with the cellular ROS, while influenced by dissolved high-valence irons in the co-culture medium. In conclusion, ions from short-time dissolution of dust samples and the generation of extracellular ·OH presented combined effects in the elevation of intracellular ROS, which further synergistically induced cytotoxicity and genotoxicity.

On the complex •OH/•O--induced free radical chemistry of arylalkylamines with special emphasis on the contribution of the alkylamine side chain.

PubMed

Szabó, László; Mile, Viktória; Tóth, Tünde; Balogh, György T; Földes, Tamás; Takács, Erzsébet; Wojnárovits, László

2017-02-01

A full account of the • OH-induced free radical chemistry of an arylalkylamine is given taking all the possible reaction pathways quantitatively into consideration. Such knowledge is indispensable when the alkylamine side chain plays a crucial role in biological activity. The fundamental reactions are investigated on the model compound N-methyl-3-phenypropylamine (MPPA), and extended to its biologically active analog, to the antidepressant fluoxetine (FLX). Pulse radiolysis techniques were applied including redox titration and transient spectral analysis supplemented with DFT calculations. The contribution of the amine moiety to the free radical-induced oxidation mechanism appeared to be appreciable. • O - was used to observe hydrogen atom abstraction events at pH 14 giving rise to the strongly reducing α-aminoalkyl radicals (∼38% of the radical yield) and to benzyl (∼4%), β-aminoalkyl (∼24%), and aminyl radicals (∼31%) of MPPA. One-electron transfer was also observed yielding aminium radicals with low efficiency (∼3%). In the • OH-induced oxidation protonated α-aminoalkyl (∼49%), β-aminoalkyl (∼27%), benzyl radicals (∼4%), and aminium radicals (∼5%) are initially generated on the side chain of MPPA at pH 6, whereas hydroxycyclohexadienyl radicals (∼15%) were also produced. These initial events are followed by complex protonation-deprotonation reactions establishing acid-base equilibria; however, these processes are limited by the transient nature of the radicals and the kinetics of the ongoing reactions. The contribution of the radicals from the side chain alkylamine substituent of FLX totals up to ∼54% of the initially available oxidant yield.

Vernonia cinerea L. scavenges free radicals and regulates nitric oxide and proinflammatory cytokines profile in carrageenan induced paw edema model.

PubMed

Kumar, P Pratheesh; Kuttan, Girija

2009-01-01

In this study, we evaluated the anti-oxidant and anti-inflammatory activities of the medicinal plant, Vernonia cinerea L (Asteraceae) using in vitro as well as in vivo models. Methanolic extract of Vernonia cinerea was found to scavenge the hydroxyl radical generated by Fenton reaction (IC(50)130 microg/ml), Superoxide generated by photo reduction of riboflavin (IC(50)190 microg/ml) and inhibited lipid peroxidation significantly (IC(50)130.5 microg/ml). The drug also scavenged nitric oxide (IC(50)210 microg/ml). Intraperitoneal administration of Vernonia cinerea was found to inhibit the PMA induced Superoxide generation in mice peritoneal macrophages. The administration of Vernonia cinerea to mice significantly increased the levels of catalase, superoxide dismutase, glutathione, glutathione peroxidase and glutathione-S transferase in blood and liver, whereas lipid peroxidation activity was significantly decreased. It was also found that Vernonia cinerea extract significantly inhibited carrageenan induced inflammation, compared with control models. Down regulation of pro-inflammatory cytokine level and gene expression were also support the above result.

Spin trapping combined with quantitative mass spectrometry defines free radical redistribution within the oxidized hemoglobin:haptoglobin complex.

PubMed

Vallelian, Florence; Garcia-Rubio, Ines; Puglia, Michele; Kahraman, Abdullah; Deuel, Jeremy W; Engelsberger, Wolfgang R; Mason, Ronald P; Buehler, Paul W; Schaer, Dominik J

2015-08-01

Extracellular or free hemoglobin (Hb) accumulates during hemolysis, tissue damage, and inflammation. Heme-triggered oxidative reactions can lead to diverse structural modifications of lipids and proteins, which contribute to the propagation of tissue damage. One important target of Hb׳s peroxidase reactivity is its own globin structure. Amino acid oxidation and crosslinking events destabilize the protein and ultimately cause accumulation of proinflammatory and cytotoxic Hb degradation products. The Hb scavenger haptoglobin (Hp) attenuates oxidation-induced Hb degradation. In this study we show that in the presence of hydrogen peroxide (H2O2), Hb and the Hb:Hp complex share comparable peroxidative reactivity and free radical generation. While oxidation of both free Hb and Hb:Hp complex generates a common tyrosine-based free radical, the spin-trapping reaction with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) yields dissimilar paramagnetic products in Hb and Hb:Hp, suggesting that radicals are differently redistributed within the complex before reacting with the spin trap. With LC-MS(2) mass spectrometry we assigned multiple known and novel DMPO adduct sites. Quantification of these adducts suggested that the Hb:Hp complex formation causes extensive delocalization of accessible free radicals with drastic reduction of the major tryptophan and cysteine modifications in the β-globin chain of the Hb:Hp complex, including decreased βCys93 DMPO adduction. In contrast, the quantitative changes in DMPO adduct formation on Hb:Hp complex formation were less pronounced in the Hb α-globin chain. In contrast to earlier speculations, we found no evidence that free Hb radicals are delocalized to the Hp chain of the complex. The observation that Hb:Hp complex formation alters free radical distribution in Hb may help to better understand the structural basis for Hp as an antioxidant protein. Copyright © 2015 Elsevier Inc. All rights reserved.

Moringa oleifera Lam. seed extract prevents fat diet induced oxidative stress in mice and protects liver cell-nuclei from hydroxyl radical mediated damage.

PubMed

Das, Nilanjan; Ganguli, Debdutta; Dey, Sanjit

2015-12-01

High fat diet (HFD) prompts metabolic pattern inducing reactive oxygen species (ROS) production in mitochondria thereby triggering multitude of chronic disorders in human. Antioxidants from plant sources may be an imperative remedy against this disorder. However, it requires scientific validation. In this study, we explored if (i) Moringa oleifera seed extract (MoSE) can neutralize ROS generated in HFD fed mice; (ii) protect cell-nuclei damage developed by Fenton reaction in vitro. Swiss mice were fed with HFD to develop oxidative stress model (HFD group). Other groups were control, seed extract alone treated, and MoSE simultaneously (HS) treated. Treatment period was of 15 days. Antioxidant enzymes with tissue nitrite content (TNC) and lipid peroxidation (LPO) were estimated from liver homogenate. HS group showed significantly higher (P < 0.05) superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), reduced glutathione (GSH) activity, and ferric reducing antioxidant power (FRAP) compared to only HFD fed group. Further, TNC and LPO decreased significantly (P < 0.05) in HS group compared to HFD fed group. MoSE also protected hepatocytes nuclei from the hydroxyl radicals generated by Fenton reaction. MoSE was found to be polyphenol rich with potent reducing power, free radicals and hydroxyl radicals scavenging activity. Thus, MoSE exhibited robust antioxidant prospective to neutralize ROS developed in HFD fed mice and also protected the nuclei damage from hydroxyl radicals. Hence, it can be used as herbal medication against HFD induced ROS mediated disorders.

H2S Protects Against Methionine–Induced Oxidative Stress in Brain Endothelial Cells

PubMed Central

Tyagi, Neetu; Moshal, Karni S.; Sen, Utpal; Vacek, Thomas P.; Kumar, Munish; Hughes, William M.; Kundu, Soumi

2009-01-01

Abstract Homocysteine (Hcy) causes cerebrovascular dysfunction by inducing oxidative stress. However, to date, there are no strategies to prevent Hcy-induced oxidative damage. Hcy is an H2S precursor formed from methionine (Met) metabolism. We aimed to investigate whether H2S ameliorated Met-induced oxidative stress in mouse brain endothelial cells (bEnd3). The bEnd3 cells were exposed to Met treatment in the presence or absence of NaHS (donor of H2S). Met-induced cell toxicity increased the levels of free radicals in a concentration-dependent manner. Met increased NADPH-oxidase-4 (NOX-4) expression and mitigated thioredxion-1(Trx-1) expression. Pretreatment of bEnd3 with NaHS (0.05 mM) attenuated the production of free radicals in the presence of Met and protected the cells from oxidative damage. Furthermore, NaHS enhanced inhibitory effects of apocynin, N-acetyl-l-cysteine (NAC), reduced glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), Nω-nitro-l-arginine methyl ester (L-NAME) on ROS production and redox enzymes levels induced by Met. In conclusion, the administration of H2S protected the cells from oxidative stress induced by hyperhomocysteinemia (HHcy), which suggested that NaHS/H2S may have therapeutic potential against Met-induced oxidative stress. Antioxid. Redox Signal. 11, 25–33. PMID:18837652

Aliphatic peptidyl hydroperoxides as a source of secondary oxidation in hydroxyl radical protein footprinting

PubMed Central

Saladino, Jessica; Liu, Mian; Live, David; Sharp, Joshua S.

2009-01-01

Hydroxyl radical footprinting is a technique for studying protein structure and binding that entails oxidizing a protein system of interest with diffusing hydroxyl radicals, and then measuring the amount of oxidation of each amino acid. One important issue in hydroxyl radical footprinting is limiting amino acid oxidation by secondary oxidants to prevent uncontrolled oxidation which can cause amino acids to appear more solvent accessible than they really are. Previous work suggested that hydrogen peroxide was the major secondary oxidant of concern in hydroxyl radical footprinting experiments; however, even after elimination of all hydrogen peroxide, some secondary oxidation was still detected. Evidence is presented for the formation of peptidyl hydroperoxides as the most abundant product upon oxidation of aliphatic amino acids. Both reverse phase liquid chromatography and catalase treatment were shown to be ineffective at eliminating peptidyl hydroperoxides. The ability of these peptidyl hydroperoxides to directly oxidize methionine is demonstrated, suggesting the value of methionine amide as an in situ protectant. Hydroxyl radical footprinting protocols require the use of an organic sulfide or similar peroxide scavenger in addition to removal of hydrogen peroxide in order to successfully eradicate all secondary oxidizing species and prevent uncontrolled oxidation of sulfur-containing residues. PMID:19278868

Site-specific radical formation in DNA induced by Cu(II)-H2O2 oxidizing system, using ESR, Immuno-spin trapping, LC/MS and MS/MS

PubMed Central

Bhattacharjee, Suchandra; Deterding, Leesa J.; Chatterjee, Saurabh; Jiang, JinJie; Ehrenshaft, Marilyn; Lardinois, Olivier; Ramirez, Dario C.; Tomer, Kenneth B.; Mason, Ronald P.

2011-01-01

Oxidative stress-related damage to the DNA macromolecule produces a multitude of lesions that are implicated in mutagenesis, carcinogenesis, reproductive cell death and aging. Many of these lesions have been studied and characterized by various techniques. Of the techniques that are available, the comet assay, HPLC-EC, GC-MS, HPLC-MS and especially HPLC-MS/MS remain the most widely used and have provided invaluable information on these lesions. However, accurate measurement of DNA damage has been a matter of debate. In particular, there have been reports of artifactual oxidation leading to erroneously high damage estimates. Further, most of these techniques measure the end product of a sequence of events and thus provide only limited information on the initial radical mechanism. We report here a qualitative measurement of DNA damage induced by a Cu(II)-H2O2 oxidizing system using immuno spin-trapping (IST) with EPR, MS and MS/MS. The radical generated is trapped by DMPO immediately upon formation. The DMPO adduct formed is initially EPR active but subsequently is oxidized to the stable nitrone, which can then be detected by IST and further characterized by MS and MS/MS. PMID:21382477

Nitric oxide ameliorates the damaging effects of oxidative stress induced by iron deficiency in cyanobacterium Anabaena 7120.

PubMed

Kaushik, Manish Singh; Srivastava, Meenakshi; Srivastava, Alka; Singh, Anumeha; Mishra, Arun Kumar

2016-11-01

In cyanobacterium Anabaena 7120, iron deficiency leads to oxidative stress with unavoidable consequences. Nitric oxide reduces pigment damage and supported the growth of Anabaena 7120 in iron-deficient conditions. Elevation in nitric oxide accumulation and reduced superoxide radical production justified the role of nitric oxide in alleviating oxidative stress in iron deficiency. Increased activities of antioxidative enzymes and higher levels of ROS scavengers (ascorbate, glutathione and thiol) in iron deficiency were also observed in the presence of nitric oxide. Nitric oxide also supported the membrane integrity of Anabaena cells and reduces protein and DNA damage caused by oxidative stress induced by iron deficiency. Results suggested that nitric oxide alleviates the damaging effects of oxidative stress induced by iron deficiency in cyanobacterium Anabaena 7120.

Selective and Catalyst-free Oxidation of D-Glucose to D-Glucuronic acid induced by High-Frequency Ultrasound

NASA Astrophysics Data System (ADS)

Amaniampong, Prince N.; Karam, Ayman; Trinh, Quang Thang; Xu, Kai; Hirao, Hajime; Jérôme, François; Chatel, Gregory

2017-01-01

This systematic experimental investigation reveals that high-frequency ultrasound irradiation (550 kHz) induced oxidation of D-glucose to glucuronic acid in excellent yield without assistance of any (bio)catalyst. Oxidation is induced thanks to the in situ production of radical species in water. Experiments show that the dissolved gases play an important role in governing the nature of generated radical species and thus the selectivity for glucuronic acid. Importantly, this process yields glucuronic acid instead of glucuronate salt typically obtained via conventional (bio)catalyst routes, which is of huge interest in respect of downstream processing. Investigations using disaccharides revealed that radicals generated by high frequency ultrasound were also capable of promoting tandem hydrolysis/oxidation reactions.

Selective and Catalyst-free Oxidation of D-Glucose to D-Glucuronic acid induced by High-Frequency Ultrasound

PubMed Central

Amaniampong, Prince N.; Karam, Ayman; Trinh, Quang Thang; Xu, Kai; Hirao, Hajime; Jérôme, François; Chatel, Gregory

2017-01-01

This systematic experimental investigation reveals that high-frequency ultrasound irradiation (550 kHz) induced oxidation of D-glucose to glucuronic acid in excellent yield without assistance of any (bio)catalyst. Oxidation is induced thanks to the in situ production of radical species in water. Experiments show that the dissolved gases play an important role in governing the nature of generated radical species and thus the selectivity for glucuronic acid. Importantly, this process yields glucuronic acid instead of glucuronate salt typically obtained via conventional (bio)catalyst routes, which is of huge interest in respect of downstream processing. Investigations using disaccharides revealed that radicals generated by high frequency ultrasound were also capable of promoting tandem hydrolysis/oxidation reactions. PMID:28084448

Probing the Time Scale of FPOP (Fast Photochemical Oxidation of Proteins): Radical Reactions Extend Over Tens of Milliseconds

NASA Astrophysics Data System (ADS)

Vahidi, Siavash; Konermann, Lars

2016-07-01

Hydroxyl radical (ṡOH) labeling with mass spectrometry detection reports on protein conformations and interactions. Fast photochemical oxidation of proteins (FPOP) involves ṡOH production via H2O2 photolysis by UV laser pulses inside a flow tube. The experiments are conducted in the presence of a scavenger (usually glutamine) that shortens the ṡOH lifetime. The literature claims that FPOP takes place within 1 μs. This ultrafast time scale implies that FPOP should be immune to labeling-induced artifacts that may be encountered with other techniques. Surprisingly, the FPOP time scale has never been validated in direct kinetic measurements. Here we employ flash photolysis for probing oxidation processes under typical FPOP conditions. Bleaching of the reporter dye cyanine-5 (Cy5) served as readout of the time-dependent radical milieu. Surprisingly, Cy5 oxidation extends over tens of milliseconds. This time range is four orders of magnitude longer than expected from the FPOP literature. We demonstrate that the glutamine scavenger generates metastable secondary radicals in the FPOP solution, and that these radicals lengthen the time frame of Cy5 oxidation. Cy5 and similar dyes are widely used for monitoring the radical dose experienced by proteins in solution. The measured Cy5 kinetics thus strongly suggest that protein oxidation in FPOP extends over a much longer time window than previously thought (i.e., many milliseconds instead of one microsecond). The optical approach developed here should be suitable for assessing the performance of future FPOP-like techniques with improved temporal labeling characteristics.

Could a vegetarian diet reduce exercise-induced oxidative stress? A review of the literature.

PubMed

Trapp, Denise; Knez, Wade; Sinclair, Wade

2010-10-01

Oxidative stress is a natural physiological process that describes an imbalance between free radical production and the ability of the antioxidant defence system of the body to neutralize free radicals. Free radicals can be beneficial as they may promote wound healing and contribute to a healthy immune response. However, free radicals can have a detrimental impact when they interfere with the regulation of apoptosis and thus play a role in the promotion of some cancers and conditions such as cardiovascular disease. Antioxidants are molecules that reduce the damage associated with oxidative stress by counteracting free radicals. Regular exercise is a vital component of a healthy lifestyle, although it can increase oxidative stress. As a typical vegetarian diet comprises a wide range of antioxidant-rich foods, it is plausible that the consumption of these foods will result in an enhanced antioxidant system capable of reducing exercise-induced oxidative stress. In addition, a relationship between a vegetarian diet and lower risks of cardiovascular disease and some cancers has been established. This review explores the current available evidence linking exercise, vegetarians, antioxidants, and oxidative stress.

Time resolved study of hydroxyl radical oxidation of oleic acid at the air-water interface

NASA Astrophysics Data System (ADS)

Zhang, Xinxing; Barraza, Kevin M.; Upton, Kathleen T.; Beauchamp, J. L.

2017-09-01

The ubiquity of oleic acid (OA) renders it a poster child for laboratory investigations of environmental oxidation chemistry. In the current study, mechanistic details of the oxidation of OA by hydroxyl radicals at the air-water interface are investigated using field-induced droplet ionization mass spectrometry (FIDI-MS). Products from OH oxidation of both unsaturated and saturated carbon atoms are identified, and mechanisms for both types of oxidation processes are proposed. Uptake of oxygen in the interfacial layer increases linearly with time, consistent with Langmuir-Hinshelwood reaction kinetics. These results provide fundamental knowledge relating to OH initiated degradation of fatty acids in atmospheric aerosols.

Hypochlorite and superoxide radicals can act synergistically to induce fragmentation of hyaluronan and chondroitin sulphates

PubMed Central

2004-01-01

Activated phagocytes release the haem enzyme MPO (myeloperoxidase) and also generate superoxide radicals (O2•−), and hence H2O2, via an oxidative burst. Reaction of MPO with H2O2 in the presence of chloride ions generates HOCl (the physiological mixture of hypochlorous acid and its anion present at pH 7.4). Exposure of glycosaminoglycans to a MPO–H2O2–Cl− system or reagent HOCl generates long-lived chloramides [R-NCl-C(O)-R′] derived from the glycosamine N-acetyl functions. Decomposition of these species by transition metal ions gives polymer-derived amidyl (nitrogen-centred) radicals [R-N•-C(O)-R′], polymer-derived carbon-centred radicals and site-specific strand scission. In the present study, we have shown that exposure of glycosaminoglycan chloramides to O2•− also promotes chloramide decomposition and glycosaminoglycan fragmentation. These processes are inhibited by superoxide dismutase, metal ion chelators and the metal ion-binding protein BSA, consistent with chloramide decomposition and polymer fragmentation occurring via O2•−-dependent one-electron reduction, possibly catalysed by trace metal ions. Polymer fragmentation induced by O2•− [generated by the superoxide thermal source 1, di-(4-carboxybenzyl)hyponitrite] was demonstrated to be entirely chloramide dependent as no fragmentation occurred with the native polymers or when the chloramides were quenched by prior treatment with methionine. EPR spin-trapping experiments using 5,5-dimethyl1-pyrroline-N-oxide and 2-methyl-2-nitrosopropane have provided evidence for both O2•− and polymer-derived carbon-centred radicals as intermediates. The results obtained are consistent with a mechanism involving one-electron reduction of the chloramides to yield polymer-derived amidyl radicals, which subsequently undergo intramolecular hydrogen atom abstraction reactions to give carbon-centred radicals. The latter undergo fragmentation reactions in a site-specific manner. This synergistic

Watson-Crick Base Pair Radical Cation as a Model for Oxidative Damage in DNA.

PubMed

Feketeová, Linda; Chan, Bun; Khairallah, George N; Steinmetz, Vincent; Maitre, Philippe; Radom, Leo; O'Hair, Richard A J

2017-07-06

The deleterious cellular effects of ionizing radiation are well-known, but the mechanisms causing DNA damage are poorly understood. The accepted molecular events involve initial oxidation and deprotonation at guanine sites, triggering hydrogen atom abstraction reactions from the sugar moieties, causing DNA strand breaks. Probing the chemistry of the initially formed radical cation has been challenging. Here, we generate, spectroscopically characterize, and examine the reactivity of the Watson-Crick nucleobase pair radical cation in the gas phase. We observe rich chemistry, including proton transfer between the bases and propagation of the radical site in deoxyguanosine from the base to the sugar, thus rupturing the sugar. This first example of a gas-phase model system providing molecular-level details on the chemistry of an ionized DNA base pair paves the way toward a more complete understanding of molecular processes induced by radiation. It also highlights the role of radical propagation in chemistry, biology, and nanotechnology.

Mechanisms of free radical-induced damage to DNA.

PubMed

Dizdaroglu, Miral; Jaruga, Pawel

2012-04-01

Endogenous and exogenous sources cause free radical-induced DNA damage in living organisms by a variety of mechanisms. The highly reactive hydroxyl radical reacts with the heterocyclic DNA bases and the sugar moiety near or at diffusion-controlled rates. Hydrated electron and H atom also add to the heterocyclic bases. These reactions lead to adduct radicals, further reactions of which yield numerous products. These include DNA base and sugar products, single- and double-strand breaks, 8,5'-cyclopurine-2'-deoxynucleosides, tandem lesions, clustered sites and DNA-protein cross-links. Reaction conditions and the presence or absence of oxygen profoundly affect the types and yields of the products. There is mounting evidence for an important role of free radical-induced DNA damage in the etiology of numerous diseases including cancer. Further understanding of mechanisms of free radical-induced DNA damage, and cellular repair and biological consequences of DNA damage products will be of outmost importance for disease prevention and treatment.

Hydroxyl radical formation and oxidative DNA damage induced by areca quid in vivo.

PubMed

Chen, Chiu-Lan; Chi, Chin-Wen; Liu, Tsung-Yun

2002-02-01

Chewing areca quid (AQ) has been implicated as a major risk factor for the development of oral squamous-cell carcinoma (OSCC). Recent studies have suggested that AQ-generated reactive oxygen species (ROS) is one of the contributing factors for oral carcinogenesis. However, the AQ used in Taiwan is different from that used in other countries. This study is designed to test whether ROS are generated and the consequent effects in locally prepared AQ in vivo. We measured the hydroxyl radical formation, as represented by the presence of o- and m-tyrosine in saliva from volunteers who chewed AQ containing 20 mg phenylalanine. Their saliva contained significantly higher amounts (p < .05) of o- and m-tyrosine as compared to the controls. In addition, chewing AQ containing Piper betle inflorescence generated higher amounts of m-tyrosine, but not o-tyrosine, in saliva than did chewing AQ containing betel leaf. We further tested the oxidative DNA damaging effect of the reconstituted AQ, as evidenced by the elevation of 8-hydroxy-2'-deoxyguanosine (8-OH-dG) levels, in hamster buccal pouch. Following daily painting for 14 d, the 8-OH-dG level in hamster buccal pouch is significantly elevated (p < .05) in the AQ-treated group versus the controls. These findings demonstrate that ROS, such as hydroxyl radical, are formed in the human oral cavity during AQ chewing, and chewing such prepared AQ might cause oxidative DNA damage to the surrounding tissues.

Investigating free radical generation in HepG2 cells using immuno-spin trapping.

PubMed

Horinouchi, Yuya; Summers, Fiona A; Ehrenshaft, Marilyn; Kawazoe, Kazuyoshi; Tsuchiya, Koichiro; Tamaki, Toshiaki; Mason, Ronald P

2014-10-01

Oxidative stress can induce the generation of free radicals, which are believed to play an important role in both physiological and pathological processes and a number of diseases such as cancer. Therefore, it is important to identify chemicals which are capable of inducing oxidative stress. In this study, we evaluated the ability of four environmental chemicals, aniline, nitrosobenzene (NB), N,N-dimethylaniline (DMA) and N,N-dimethyl-4-nitrosoaniline (DMNA), to induce free radicals and cellular damage in the hepatoma cell line HepG2. Cytotoxicity was assessed using lactate dehydrogenase (LDH) assays and morphological changes were observed using phase contrast microscopy. Free radicals were detected by immuno-spin trapping (IST) in in-cell western experiments or in confocal microscopy experiments to determine the subcellular localization of free radical generation. DMNA induced free radical generation, LDH release and morphological changes in HepG2 cells whereas aniline, NB and DMA did not. Confocal microscopy showed that DMNA induced free radical generation mainly in the cytosol. Preincubation of HepG2 cells with N-acetylcysteine and 2,2'-dipyridyl significantly prevented free radical generation upon subsequent incubation with DMNA, whereas preincubation with apocynin and dimethyl sulfoxide did not. These results suggest that DMNA induces oxidative stress and that reactive oxygen species, metals and free radical generation play a critical role in DMNA-induced cytotoxicity. Copyright © 2014. Published by Elsevier Inc.

Is Nitrate radical a major oxidant of elemental mercury in the atmosphere?

NASA Astrophysics Data System (ADS)

Luria, M.; Obrist, D.; Peleg, M.; Matveev, V.; Tas, E.

2012-12-01

Nitrate radicals (NO3) play a major role in the nighttime atmospheric oxidation of VOC. The radicals are produced throughout the reaction between O3 and NO2 and are removed via a sequence of homogeneous and heterogeneous reactions. Nitrate radicals reach significant levels only at night and mostly under conditions of low humidity (Asaf et al, 2009, 2010 and references therein). Because of its very high photolysis rate, daytime levels are extremely low, and thus are insignificant in atmospheric oxidation processes. The reaction of Hg with NO3 has not been sufficiently investigated; a value of 4x10-15 cm3 molec-1 s-1 (Sommar et al 1997) is most commonly used. Its importance for the atmospheric mercury chemistry was discussed by Mao el al., (2008) who examined the potential oxidation of mercury by the most common atmospheric oxidants applying the best available rate coefficients. According to their report, the uncertainty in the oxidation capacity of O3 is very large (a factor of 20). If the lower limit is applied, as suggested by Calvert and Lindberg (2005), oxidation by O3 is nearly negligible and, NO3 radicals, at typical nighttime levels, are responsible for the bulk of the Hg oxidation. Obviously this is true in the absence of reactive halogen compounds (RHC, Peleg et al., 2008). The most common method of measuring nitrate radicals is the differential optical absorption system (DOAS) technique. In a recent study performed at an urban semi arid site (Jerusalem, Israel; Asaf et al., 2009, 2010) it was found that nitrate levels could reach levels of up to 800 ppt, significantly higher than ever reported in the past. They further demonstrated that under the conditions prevailed; nitrate radicals are at least as important as the hydroxyl radicals in the overall oxidation capacity of VOC in the atmosphere. Side by side measurements of Nitrate radicals using the DOAS technique and speciated mercury compounds (Total, Particulate and Reactive gaseous) were performed

A Derivative Method with Free Radical Oxidation to Predict Resveratrol Metabolites by Tandem Mass Spectrometry

PubMed Central

Liu, Wangta; Shiue, Yow-Ling; Lin, Yi-Reng; Lin, Hugo You-Hsien; Liang, Shih-Shin

2015-01-01

In this study, we demonstrated an oxidative method with free radical to generate 3,5,4′-trihydroxy-trans-stilbene (trans-resveratrol) metabolites and detect sequentially by an autosampler coupling with liquid chromatography electrospray ionization tandem mass spectrometer (LC-ESI–MS/MS). In this oxidative method, the free radical initiator, ammonium persulfate (APS), was placed in a sample bottle containing resveratrol to produce oxidative derivatives, and the reaction progress was tracked by autosampler sequencing. Resveratrol, a natural product with purported cancer preventative qualities, produces metabolites including dihydroresveratrol, 3,4′-dihydroxy-trans-stilbene, lunularin, resveratrol monosulfate, and dihydroresveratrol monosulfate by free radical oxidation. Using APS free radical, the concentrations of resveratrol derivatives differ as a function of time. Besides simple, convenient and time- and labor saving, the advantages of free radical oxidative method of its in situ generation of oxidative derivatives followed by LC-ESI–MS/MS can be utilized to evaluate different metabolites in various conditions. PMID:27594817

A Derivative Method with Free Radical Oxidation to Predict Resveratrol Metabolites by Tandem Mass Spectrometry.

PubMed

Liu, Wangta; Shiue, Yow-Ling; Lin, Yi-Reng; Lin, Hugo You-Hsien; Liang, Shih-Shin

2015-10-01

In this study, we demonstrated an oxidative method with free radical to generate 3,5,4'-trihydroxy- trans -stilbene ( trans -resveratrol) metabolites and detect sequentially by an autosampler coupling with liquid chromatography electrospray ionization tandem mass spectrometer (LC-ESI-MS/MS). In this oxidative method, the free radical initiator, ammonium persulfate (APS), was placed in a sample bottle containing resveratrol to produce oxidative derivatives, and the reaction progress was tracked by autosampler sequencing. Resveratrol, a natural product with purported cancer preventative qualities, produces metabolites including dihydroresveratrol, 3,4'-dihydroxy- trans -stilbene, lunularin, resveratrol monosulfate, and dihydroresveratrol monosulfate by free radical oxidation. Using APS free radical, the concentrations of resveratrol derivatives differ as a function of time. Besides simple, convenient and time- and labor saving, the advantages of free radical oxidative method of its in situ generation of oxidative derivatives followed by LC-ESI-MS/MS can be utilized to evaluate different metabolites in various conditions.

Generation of hydroxyl radicals and singlet oxygen during oxidation of rhododendrol and rhododendrol-catechol.

PubMed

Miyaji, Akimitsu; Gabe, Yu; Kohno, Masahiro; Baba, Toshihide

2017-03-01

The generation of hydroxyl radicals and singlet oxygen during the oxidation of 4-(4-hydroxyphenyl)-2-butanol (rhododendrol) and 4-(3,4-dihydroxyphenyl)-2-butanol (rhododendrol-catechol) with mushroom tyrosinase in a phosphate buffer (pH 7.4) was examined as the model for the reactive oxygen species generation via the two rhododendrol compounds in melanocytes. The reaction was performed in the presence of 5,5-dimethyl-1-pyrroline- N -oxide (DMPO) spin trap reagents for hydroxyl radical or 2,2,6,6-tetramethyl-4-piperidone (4-oxo-TEMP), an acceptor of singlet oxygen, and their electron spin resonances were measured. An increase in the electron spin resonances signal attributable to the adduct of DMPO reacting with the hydroxyl radical and that of 4-oxo-TEMP reacting with singlet oxygen was observed during the tyrosinase-catalyzed oxidation of rhododendrol and rhododendrol-catechol, indicating the generation of hydroxyl radical and singlet oxygen. Moreover, hydroxyl radical generation was also observed in the autoxidation of rhododendrol-catechol. We show that generation of intermediates during tyrosinase-catalyzed oxidation of rhododendrol enhances oxidative stress in melanocytes.

Effects of hydroxylated benzaldehyde derivatives on radiation-induced reactions involving various organic radicals

NASA Astrophysics Data System (ADS)

Ksendzova, G. A.; Samovich, S. N.; Sorokin, V. L.; Shadyro, O. I.

2018-05-01

In the present paper, the effects of hydroxylated benzaldehyde derivatives and gossypol - the known natural occurring compound - on formation of decomposition products resulting from radiolysis of ethanol and hexane in deaerated and oxygenated solutions were studied. The obtained data enabled the authors to make conclusions about the effects produced by the structure of the compounds under study on their reactivity towards oxygen- and carbon-centered radicals. It has been found that 2,3-dihydroxybenzaldehyde, 4,6-di-tert-butyl-2,3-dihydroxybenzaldehyde and 4,6-di-tert-butyl-3-(1,3-dioxane-2-yl)-1,2-dihydroxybenzene are not inferior in efficiency to butylated hydroxytoluene - the industrial antioxidant - as regards suppression of the radiation-induced oxidation processes occurring in hexane. The derivatives of hydroxylated benzaldehydes were shown to have a significant influence on radiation-induced reactions involving α-hydroxyalkyl radicals.

Purification and in vitro antioxidative effects of giant squid muscle peptides on free radical-mediated oxidative systems.

PubMed

Rajapakse, Niranjan; Mendis, Eresha; Byun, Hee-Guk; Kim, Se-Kwon

2005-09-01

Low molecular weight peptides obtained from ultrafiltration (UF) of giant squid (Dosidicus gigas) muscle protein were studied for their antioxidative effects in different in vitro oxidative systems. The most potent two peptides, Asn-Ala-Asp-Phe-Gly-Leu-Asn-Gly-Leu-Glu-Gly-Leu-Ala (1307 Da) and Asn-Gly-Leu-Glu-Gly-Leu-Lys (747 Da), exhibited their antioxidant potential to act as chain-breaking antioxidants by inhibiting radical-mediated peroxidation of linoleic acid, and their activities were closer to highly active synthetic antioxidant, butylated hydroxytoluene. Addition of these peptides could enhance the viability of cytotoxic embryonic lung fibroblasts significantly (P<.05) at a low concentration of 50 microg/ml, and it was presumed due to the suppression of radical-induced oxidation of membrane lipids. Electron spin trapping studies revealed that the peptides were potent scavengers of free radicals in the order of carbon-centered (IC(50) 396.04 and 304.67 microM), hydroxyl (IC(50) 497.32 and 428.54 microM) and superoxide radicals (IC(50) 669.34 and 573.83 microM). Even though the exact molecular mechanism for scavenging of free radicals was unclear, unusually high hydrophobic amino acid composition (more than 75%) of giant squid muscle peptides was presumed to be involved in the observed activities.

Detection and Quantification of Free Radicals in Peroxisomal Disorders: A Comparative Study with Oxidative Stress Parameters.

PubMed

Abd-Elmaksoud, Sohair Abd-El Mawgood; El-Bassyouni, Hala; Afifi, Hanan; Thomas, Manal Micheal; Ibrahim, Alshaymaa Ahmed; Shalaby, Aliaa; Hamid, Tamer Ahmed Abdel; Hamid, Nehal Abdel; El-Ghobary, Hany

2015-11-01

Free radicals have been thought to participate in pathogenesis of peroxisomal disorders. The aim of the work is to detect free oxide radicals in blood of patients with peroxisomal disorders and to study their relation with various oxidative stress parameters. Twenty patients with peroxisomal disorders and 14 age and sex matched healthy subjects were included in the study. Patients with peroxisomal disorders were subdivided according to diagnosis into peroxisomal biogenesis disorders and single enzyme deficiency. Oxidative stress was evaluated in both patients and control subjects by assessment of free radicals, malondialdehyde, nitric oxide metabolites and superoxide dismutase. There was increase in free radicals, malondialdehyde, nitric oxide metabolites in patients compared with control subjects. However, there was decrease in superoxide dismutase levels in patients compared with control subjects. We concluded that there is excess free radicals production accompanied with decrease in antioxidant defenses in patients with peroxisomal disorders. These results strongly support a role of free radicals in the pathophysiology of peroxisomal disorders and strengthen the importance of oxidative stress phenomenon in peroxisomal disorders pathogenesis.

Chemical determination of free radical-induced damage to DNA.

PubMed

Dizdaroglu, M

1991-01-01

Free radical-induced damage to DNA in vivo can result in deleterious biological consequences such as the initiation and promotion of cancer. Chemical characterization and quantitation of such DNA damage is essential for an understanding of its biological consequences and cellular repair. Methodologies incorporating the technique of gas chromatography/mass spectrometry (GC/MS) have been developed in recent years for measurement of free radical-induced DNA damage. The use of GC/MS with selected-ion monitoring (SIM) facilitates unequivocal identification and quantitation of a large number of products of all four DNA bases produced in DNA by reactions with hydroxyl radical, hydrated electron, and H atom. Hydroxyl radical-induced DNA-protein cross-links in mammalian chromatin, and products of the sugar moiety in DNA are also unequivocally identified and quantitated. The sensitivity and selectivity of the GC/MS-SIM technique enables the measurement of DNA base products even in isolated mammalian chromatin without the necessity of first isolating DNA, and despite the presence of histones. Recent results reviewed in this article demonstrate the usefulness of the GC/MS technique for chemical determination of free radical-induced DNA damage in DNA as well as in mammalian chromatin under a vast variety of conditions of free radical production.

Expression of a truncated human tau protein induces aqueous-phase free radicals in a rat model of tauopathy: implications for targeted antioxidative therapy.

PubMed

Cente, Martin; Filipcik, Peter; Mandakova, Stanislava; Zilka, Norbert; Krajciova, Gabriela; Novak, Michal

2009-01-01

Oxidative stress has been implicated in the pathogenesis of many neurodegenerative diseases including Alzheimer's disease (AD). We investigated the effect of a truncated form of the human tau protein in the neurons of transgenic rats. Using electron paramagnetic resonance we observed significantly increased accumulation of ascorbyl free radicals in brains of transgenic animals (up to 1.5-fold increase; P < 0.01). Examination of an in vitro model of cultured rat corticohippocampal neurons revealed that even relatively low level expression of human truncated tau protein (equal to 50% of endogenous tau) induced oxidative stress that resulted in increased depolarization of mitochondria (approximately 1.2-fold above control, P < 0.01) and increases in reactive oxygen species (approximately 1.3-fold above control, P < 0.001). We show that mitochondrial damage-associated oxidative stress is an early event in neurodegeneration. Furthermore, using two common antioxidants (vitamin C and E), we were able significantly eliminate tau-induced elevation of reactive oxygen species. Interestingly, vitamin C was found to be selective in the scavenging activity, suggesting that expression of truncated tau protein preferentially leads to increases in aqueous phase oxidants and free radicals such as hydrogen peroxide and hydroxyl and superoxide radicals. Our results suggest that antioxidant strategies designed to treat AD should focus on elimination of aqueous phase oxidants and free radicals.

Kinetic determinations of accurate relative oxidation potentials of amines with reactive radical cations.

PubMed

Gould, Ian R; Wosinska, Zofia M; Farid, Samir

2006-01-01

Accurate oxidation potentials for organic compounds are critical for the evaluation of thermodynamic and kinetic properties of their radical cations. Except when using a specialized apparatus, electrochemical oxidation of molecules with reactive radical cations is usually an irreversible process, providing peak potentials, E(p), rather than thermodynamically meaningful oxidation potentials, E(ox). In a previous study on amines with radical cations that underwent rapid decarboxylation, we estimated E(ox) by correcting the E(p) from cyclic voltammetry with rate constants for decarboxylation obtained using laser flash photolysis. Here we use redox equilibration experiments to determine accurate relative oxidation potentials for the same amines. We also describe an extension of these experiments to show how relative oxidation potentials can be obtained in the absence of equilibrium, from a complete kinetic analysis of the reversible redox kinetics. The results provide support for the previous cyclic voltammetry/laser flash photolysis method for determining oxidation potentials.

ELECTRON SPIN RESONANCE STUDIES ON PEROXIDE RADICALS IN IRRADIATED POLYPROPYLENE (in German)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fischer, H.; Hellwege, K.-H.; Neudoerfl, P.

1963-06-01

Peroxide radicals are formed by oxidation of carbon radicals in irradiated isotactic polypropylene. An interpretation of their ESR spectra is given. The recombination of the peroxide radicals follows a chain reaction mechanism, which is derived from the reversibility of formation of peroxide radicals, the time dependence of their concentration, and from the oxygen consumption of samples containing peroxide radicals. The reactions are discussed in view of the radiation induced oxidative degradation of polypropylene. (auth)

2,4,8-trihydroxybicyclo [3.2.1]octan-3-one scavenges free radicals and protects against xenobiotic-induced cytotoxicity.

PubMed

Srivastava, Anup; Jagan Mohan Rao, L; Shivanandappa, T

2012-03-01

Currently, there is a great deal of interest in the study of natural compounds with free-radical-scavenging activity because of their potential role in maintaining human health and preventing diseases. In this paper, we report the antioxidant and cytoprotective properties of 2,4,8-trihydroxybicyclo [3.2.1]octan-3-one (TBO) isolated from the aqueous extract of Decalepis hamiltonii roots. Our results show that TBO is a potent scavenger of superoxide (O(2)·-), hydroxyl (·OH), nitric oxide (·NO) and lipid peroxide (LOO·) - physiologically relevant free radicals with IC(50) values in nmolar (42-281) range. TBO also exhibited concentration-dependent secondary antioxidant activities such as reducing power, metal-chelating activity and inhibition of protein carbonylation. Further, TBO at nmolar concentration prevented CuSO(4)-induced human LDL oxidation. Apart from the in vitro free-radical-scavenging activity, TBO demonstrated cytoprotective activity in primary hepatocytes and Ehrlich ascites tumour (EAT) cells against oxidative-stress-inducing xenobiotics. The mechanism of cytoprotective action involved maintaining the intracellular glutathione (GSH), scavenging of reactive oxygen species (ROS) and inhibiting lipid peroxidation (LPO). Based on the results, it is suggested that TBO is a novel bioactive molecule with implications in both prevention and amelioration of diseases involving oxidative stress as well as in the general well-being.

Oxidation of spin-traps by chlorine dioxide (ClO2) radical in aqueous solutions: first ESR evidence of formation of new nitroxide radicals.

PubMed

Ozawa, T; Miura, Y; Ueda, J

1996-01-01

The reactivities of the chlorine dioxide (ClO2), which is a stable free radical towards some water-soluble spin-traps were investigated in aqueous solutions by an electron spin resonance (ESR) spectroscopy. The ClO2 radical was generated from the redox reaction of Ti3+ with potassium chlorate (KClO3) in aqueous solutions. When one of the spin-traps, 5,5-dimethyl-1-pyrroline N-oxide (DMPO), was included in the Ti3+-KClO3 reaction system, ESR spectrum due to the ClO2 radical completely disappeared and a new ESR spectrum [aN(1) = 0.72 mT, aH(2) = 0.41 mT], which is different from that of DMPO-ClO2 adduct, was observed. The ESR parameters of this new ESR signal was identical to those of 5,5-dimethylpyrrolidone-(2)-oxyl-(1) (DMPOX), suggesting the radical species giving the new ESR spectrum is assignable to DMPOX. The similar ESR spectrum consisting of a triplet [aN(1) = 0.69 mT] was observed when the derivative of DMPO, 3,3,5,5-tetramethyl-1-pyrroline N-oxide (M4PO) was included in the Ti3+-KClO3 reaction system. This radical species is attributed to the oxidation product of M4PO, 3,3,5,5-tetramethylpyrrolidone-(2)-oxyl-(1) (M4POX). When another nitrone spin-trap, alpha-(4-pyridyl-1-oxide)-N-t-butylnitrone (POBN) was used as a spin-trap, the ESR signal intensity due to the ClO2 radical decreased and a new ESR signal consisting of a triplet [aN(1) = 0.76 mT] was observed. The similar ESR spectrum was observed when N-t-butyl-alpha- nitrone (PBN) was used as a spin-trap. This ESR parameter [a(N)(1) = 0.85 mT] was identical to the oxidation product of PBN, PBNX. Thus, the new ESR signal observed from POBN may be assigned to the oxidation product of POBN, POBNX. These results suggest that the ClO2, radical does not form the stable spin adducts with nitrone spin-traps, but oxidizes these spin-traps to give the corresponding nitroxyl radicals. On the other hand, nitroso spin-traps, 5,5-dibromo-4-nitrosobenzenesulfonate (DBNBS), and 2-methyl-2-nitrosopropane (MNP) did not trap

Effect of antioxidant oxidation potential in the oxygen radical absorption capacity (ORAC) assay.

PubMed

Bisby, Roger H; Brooke, Rachel; Navaratnam, Suppiah

2008-06-01

The "oxygen radical absorption capacity" (ORAC) assay (Ou, B., Hampsch-Woodill, M., Prior, R.L. (2001). Development and validation of an improved oxygen radical absorbance capacity assay using fluorescein as the fluorescent probe. Journal of Agricultural and Food Chemistry 49, 4619-4626) is widely employed to determine antioxidant content of foods and uses fluorescein as a probe for oxidation by peroxyl radicals. Kinetic modeling of the ORAC assay suggests that the lag phase for loss of fluorescence results from equilibrium between antioxidant and fluorescein radicals and the value of the equilibrium constant determines the shape of the lag phase. For an efficient antioxidant this constitutes a "repair" reaction for fluoresceinyl radicals and produces a well defined lag phase. The lag phase becomes less marked with increasing oxidation potential of the antioxidant. Pulse radiolysis confirms that fluoresceinyl radicals are rapidly (k∼10(9)dm(3)mol(-1)s(-1)) reduced by Trolox C, a water soluble vitamin E analogue. ORAC assays of phenols with varying oxidation potentials suggest that it might be employed to obtain an estimate of the redox potential of antioxidants within food materials. Copyright © 2007 Elsevier Ltd. All rights reserved.

SULFATE RADICAL-BASED ADVANCED OXIDATION PROCESSES- ACS MEETING

EPA Science Inventory

This paper will present an overview of sulfate radical-based advanced oxidation technologies for the destruction of environmentally toxic chemicals in wastewater, industrial water, groundwater and sources of water supply. The paper will include fundamental aspects of the generati...

Free radicals and antioxidants in primary fibromyalgia: an oxidative stress disorder?

PubMed

Bagis, Selda; Tamer, Lulufer; Sahin, Gunsah; Bilgin, Ramazan; Guler, Hayal; Ercan, Bahadir; Erdogan, Canan

2005-04-01

The role of free radicals in fibromyalgia is controversial. In this study, 85 female patients with primary fibromyalgia and 80 age-, height-, and weight-matched healthy women were evaluated for oxidant/antioxidant balance. Malondialdehyde is a toxic metabolite of lipid peroxidation used as a marker of free radical damage. Superoxide dismutase is an intracellular antioxidant enzyme and shows antioxidant capacity. Pain was assessed by visual analog scale. Tender points were assessed by palpation. Age, smoking, body mass index (BMI), and duration of disease were also recorded. Malondialdehyde levels were significantly higher and superoxide dismutase levels significantly lower in fibromyalgic patients than controls. Age, BMI, smoking, and duration of disease did not affect these parameters. We found no correlation between pain and number of tender points. In conclusion, oxidant/antioxidant balances were changed in fibromyalgia. Increased free radical levels may be responsible for the development of fibromyalgia. These findings may support the hypothesis of fibromyalgia as an oxidative disorder.

Nitric oxide mitigates arsenic-induced oxidative stress and genotoxicity in Vicia faba L.

PubMed

Shukla, Pratiksha; Singh, A K

2015-09-01

The protective effects of nitric oxide (NO) against arsenic (As)-induced structural disturbances in Vicia faba have been investigated. As treatment (0.25, 0.50, and 1 mM) resulted in a declined growth of V. faba seedlings. Arsenic treatment stimulates the activity of SOD and CAT while the activities of APX and GST content were decreased. The oxidative stress markers such as superoxide radical, hydrogen peroxide and malondialdehyde (lipid peroxidation) contents were enhanced by As. Overall results revealed that significant accumulation of As suppressed growth, photosynthesis, antioxidant enzymes (SOD, CAT, APX, and GST activity), mitotic index, and induction of different chromosomal abnormalities, hence led to oxidative stress. The concentration of SNP (0.02 mM) was very effective in counteracting the adverse effect of As toxicity. These abnormalities use partially or fully reversed by a simultaneous application of As and NO donor and sodium nitroprusside and has an ameliorating effect against As-induced oxidative stress and genotoxicity in V. faba roots.

Sulfur Dioxide Accelerates the Heterogeneous Oxidation Rate of Organic Aerosol by Hydroxyl Radicals

DOE PAGES

Richards-Henderson, Nicole K.; Goldstein, Allen H.; Wilson, Kevin R.

2016-03-08

There remains considerable uncertainty in how anthropogenic gas phase emissions alter the oxidative aging of organic aerosols in the troposphere. Here we observe a 10-20 fold acceleration in the effective heterogeneous OH oxidation rate of organic aerosol in the presence of SO 2. This acceleration originates from the radical chain reactions propagated by alkoxy radicals, which are formed efficiently inside the particle by the reaction of peroxy radicals with SO 2. As the OH approaches atmospheric concentrations, the radical chain length increases, transforming the aerosol at rates predicted to be up to 10 times the OH-aerosol collision frequency. Model predictions,more » constrained by experiments over orders of magnitude changes in [OH] and [SO 2], suggest that in polluted regions the heterogeneous processing of organic aerosols by OH ([SO 2] ≥ 40 ppb) occur on similar time scales as analogous gas-phase oxidation reactions. These results provide evidence for a previously unidentified mechanism by which organic aerosol oxidation is enhanced by anthropogenic gas phase emissions. (Chemical Equation Presented).« less

Prevention of dopaminergic neurotoxicity by targeting nitric oxide and peroxynitrite: implications for the prevention of methamphetamine-induced neurotoxic damage.

PubMed

Imam, S Z; Islam, F; Itzhak, Y; Slikker, W; Ali, S F

2000-09-01

Methamphetamine (METH) is a neurotoxic psychostimulant that produces catecholaminergic brain damage by producing oxidative stress and free radical generation. The role of oxygen and nitrogen radicals is well documented as a cause of METH-induced neurotoxic damage. In this study, we have obtained evidence that METH-induced neurotoxicity is the resultant of interaction between oxygen and nitrogen radicals, and it is mediated by the production of peroxynitrite. We have also assessed the effects of inhibitors of neuronal nitric oxide synthase (nNOS) as well as scavenger of nitric oxide and a peroxynitrite decomposition catalyst. Significant protective effects were observed with the inhibitor of nNOS, 7-nitroindazole (7-NI), as well as by the selective peroxynitrite scavenger or decomposition catalyst, 5,10,15,20-tetrakis(2,4,6-trimethyl-3,5-sulfonatophenyl)porphyrinato iron III (FeTPPS). However, the use of a nitric oxide scavenger, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO), did not provide any significant protection against METH-induced hyperthermia or peroxynitrite generation and the resulting dopaminergic neurotoxicity. In particular, treatment with FeTPPS completely prevented METH-induced hyperthermia, peroxynitrite production, and METH-induced dopaminergic depletion. Together, these data demonstrate that METH-induced dopaminergic neurotoxicity is mediated by the generation of peroxynitrite, which can be selectively protected by nNOS inhibitors or peroxynitrite scavenger or decomposition catalysts.

Evidence for hydroxyl radical scavenging action of nitric oxide donors in the protection against 1-methyl-4-phenylpyridinium-induced neurotoxicity in rats.

PubMed

Banerjee, Rebecca; Saravanan, Karuppagounder S; Thomas, Bobby; Sindhu, Kizhake M; Mohanakumar, Kochupurackal P

2008-06-01

In the present study we provide evidence for hydroxyl radical (*OH) scavenging action of nitric oxide (NO*), and subsequent dopaminergic neuroprotection in a hemiparkinsonian rat model. Reactive oxygen species are strongly implicated in the nigrostriatal dopaminergic neurotoxicity caused by the parkinsonian neurotoxin, 1-methyl-4-phenylpyridinium (MPP+). Since the role of this free radical as a neurotoxicant or neuroprotectant is debatable, we investigated the effects of some of the NO* donors such as S-nitroso-N-acetylpenicillamine (SNAP), 3-morpholinosydnonimine hydrochloride (SIN-1), sodium nitroprusside (SNP) and nitroglycerin (NG) on in vitro *OH generation in a Fenton-like reaction involving ferrous citrate, as well as in MPP+-induced *OH production in the mitochondria. We also tested whether co-administration of NO* donor and MPP+ could protect against MPP+-induced dopaminergic neurotoxicity in rats. While NG, SNAP and SIN-1 attenuated MPP+-induced *OH generation in the mitochondria, and in a Fenton-like reaction, SNP caused up to 18-fold increase in *OH production in the latter reaction. Striatal dopaminergic depletion following intranigral infusion of MPP+ in rats was significantly attenuated by NG, SNAP and SIN-1, but not by SNP. Solutions of NG, SNAP and SIN-1, exposed to air for 48 h to remove NO*, when administered similarly failed to attenuate MPP+-induced neurotoxicity in vivo. Conversely, long-time air-exposed SNP solution when administered in rats intranigrally, caused a dose-dependent depletion of the striatal dopamine. These results confirm the involvement of *OH in the nigrostriatal degeneration caused by MPP+, indicate the *OH scavenging ability of NO*, and demonstrate protection by NO* donors against MPP+-induced dopaminergic neurotoxicity in rats.

Protective effect of Anoectochilus roxburghii polysaccharide against CCl4-induced oxidative liver damage in mice.

PubMed

Yang, Zhenguo; Zhang, Xiaohui; Yang, Lawei; Pan, Qunwen; Li, Juan; Wu, Yongfu; Chen, Meizhen; Cui, Shichao; Yu, Jie

2017-03-01

This study investigated the isolation and characterization of Anoectochilus roxburghii polysaccharides (ARP), and further evaluated whether ARP possessed hepatoprotective activities against CCl 4 -induced oxidative liver damage in mice. ARP is comprised of glucose and galactose in a 1.9:1 molar ratio, and the molecular weight is 19.5kDa. ARP displayed significant scavenging effects against hydroxyl radical, superoxide anion radical, DPPH radical and a strong reducing power. In vivo experiment demonstrated ARP (150mg/kg) administrated to mice for 7days prior to carbon tetrachloride treatment, attenuated the elevated expression levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), triglyceride (TG) in serum and inhibited the formation of hepatic malondialdehyde (MDA). ARP pretreatment also increased antioxidant enzyme activities such as glutathione (GSH), superoxide dismutase (SOD), and total antioxidant capacity (T-AOC) in the liver of CCl 4 -induced mice. Furthermore, hepatic histopathological changes induced by CCl 4 were significantly normalized by ARP pretreatment. These findings demonstrated that ARP possessed hepatoprotective effect against acute CCl 4 -induced liver damage by reducing lipid oxidation. Copyright © 2016 Elsevier B.V. All rights reserved.

Formation of 8-oxo-7,8-dihydroguanine-radicals in γ-irradiated DNA by multiple one-electron oxidations

PubMed Central

Shukla, Lata I.; Adhikary, Amitava; Pazdro, Robert; Becker, David; Sevilla, Michael D.

2004-01-01

Electron spin resonance (ESR) studies of radicals formed by radiation-induced multiple one-electron oxidations of guanine moieties in DNA are reported in this work. Annealing of gamma-irradiated DNA from 77 to 235 K results in the hydration of one electron oxidized guanine (G•+) to form the 8-hydroxy-7,8-dihydroguanin-7-yl-radical (•GOH) having one β-proton coupling of 17–28 G and an anisotropic nitrogen coupling, A‖, of ∼20 G, A⊥ = 0 with g‖ = 2.0026 and g⊥ = 2.0037. Further annealing to 258 K results in the formation of a sharp singlet at g = 2.0048 with line-width of 5.3 G that is identified as the 8-oxo-7,8-dihydroguanine one-electron-oxidized radical (8-oxo-G•+). This species is formed via two one-electron oxidations of •GOH. These two one-electron oxidation steps leading to the formation of 8-oxo-G•+ from •GOH in DNA, are in accordance with the expected ease of oxidation of •GOH and 8-oxo-G. The incorporation of oxygen from water in G•+ leading to •GOH and to 8-oxo-G•+ is verified by ESR studies employing 17O isotopically enriched water, which provide unambiguous evidence for the formation of both radicals. ESR analysis of irradiated-DNA in the presence of the electron scavenger, Tl3+, demonstrates that the cationic pathway leads to the formation of the 8-oxo-G•+. In irradiated DNA–Tl3+ samples, Tl3+ captures electrons. Tl2+ thus produced is a strong oxidant (2.2 V), which is metastable at 77 K and is observed to increase the formation of G•+ and subsequently of 8-oxo-G•+ upon annealing. We find that in the absence of the electron scavenger the yield of 8-oxo-G•+ is substantially reduced as a result of electron recombinations with G•+ and possible reaction with •GOH. PMID:15601999

Lycopene as A Carotenoid Provides Radioprotectant and Antioxidant Effects by Quenching Radiation-Induced Free Radical Singlet Oxygen: An Overview

PubMed Central

Pirayesh Islamian, Jalil; Mehrali, Habib

2015-01-01

Radio-protectors are agents that protect human cells and tissues from undesirable effects of ionizing radiation by mainly scavenging radiation-induced free radicals. Although chemical radio-protectors diminish these deleterious side effects they induce a number of unwanted effects on humans such as blood pressure modifications, vomiting, nausea, and both local and generalized cutaneous reactions. These disadvantages have led to emphasis on the use of some botanical radio-protectants as alternatives. This review has collected and organized studies on a plant-derived radio-protector, lycopene. Lycopene protects normal tissues and cells by scavenging free radicals. Therefore, treatment of cells with lycopene prior to exposure to an oxidative stress, oxidative molecules or ionizing radiation may be an effective approach in diminishing undesirable effects of radiation byproducts. Studies have designated lycopene to be an effective radio-protector with negligible side effects. PMID:25685729

Efficient depletion of ascorbate by amino acid and protein radicals under oxidative stress.

PubMed

Domazou, Anastasia S; Zelenay, Viviane; Koppenol, Willem H; Gebicki, Janusz M

2012-10-15

Ascorbate levels decrease in organisms subjected to oxidative stress, but the responsible reactions have not been identified. Our earlier studies have shown that protein C-centered radicals react rapidly with ascorbate. In aerobes, these radicals can react with oxygen to form peroxyl radicals. To estimate the relative probabilities of the reactions of ascorbate with protein C- and O-centered radicals, we measured by pulse radiolysis the rate constants of the reactions of C-centered radicals in Gly, Ala, and Pro with O₂ and of the resultant peroxyl radicals with ascorbate. Calculations based on the concentrations of ascorbate and oxygen in human tissues show that the relative probabilities of reactions of the C-centered amino acid radicals with O₂ and ascorbate vary between 1:2.6 for the pituitary gland and 1:0.02 for plasma, with intermediate ratios for other tissues. The high frequency of occurrence of Gly, Ala, and Pro in proteins and the similar reaction rate constants of their C-centered radicals with O₂ and their peroxo-radicals with ascorbate suggest that our results are also valid for proteins. Thus, the formation of protein C- or O-centered radicals in vivo can account for the loss of ascorbate in organisms under oxidative stress. Copyright © 2012 Elsevier Inc. All rights reserved.

Synthesis of a Novel Nitronyl Nitroxide Radical and Determination of its Protective Effects Against Infrasound-Induced Injury.

PubMed

Wang, Haibo; Wang, Jin; Yang, Qi; Zhang, Xinwei; Gao, Peng; Xu, Shenglong; Sun, XiaoLi; Wang, YuKun

2015-07-01

Infrasound causes functional disorders and structural injury to the central nervous system. However, few anti-infrasound drugs exist, and they are inefficient. Nitronyl nitroxide radicals have been reported to be good antioxidants that act as superoxide dismutase mimics and directly react with reactive oxygen species, such as ·OH, H2O2, and O 2 (∙) -. Our previous research showed that the nitronyl nitroxide radical L-NNNBP has good protective effects against β-amyloid deposition and memory deficits in an AD rat model of APP/PS1. The objective of the present study was to find a new group of anti-infrasound drugs and determine the underlying pharmacological actions of nitronyl nitroxide radicals against infrasound-induced neuronal impairment in vivo. We synthesized a new stable nitronyl nitroxide radical, NRbt, and characterized its crystal structure. The results of the anti-oxidative damage effects of NRbt and the positive control drug tempol showed that they could significantly increase the SOD activity, CAT activity and GSH level and decrease the MDA level in rat hippocampi compared with infrasound exposure without pretreatment. Moreover, the ability of NRbt to regulate the activity or level of these biochemical markers was better than that of tempol. Our results showed that both NRbt and tempol significantly protected against the learning and memory impairments induced by infrasound exposure in a Morris water maze, but there were no significant differences in the path length or escape latency between the rats in the tempol group and the three NRbt groups (P > 0.05). In addition, the infrasound-induced neuronal apoptosis in rat hippocampi was significantly suppressed by NRbt and tempol. The results demonstrated that compared with the infrasound exposure group, the expression of Bcl-2 was up-regulated and the expressions of Bax and caspase-3 were down-regulated in rats pretreated with NRbt (40 mg/kg) or tempol (40 mg/kg). These results showed that the newly

Role of enzymatic free radical scavengers in management of oxidative stress in autoimmune disorders.

PubMed

Srivastava, Shikha; Singh, Deependra; Patel, Satish; Singh, Manju R

2017-08-01

Autoimmune disorders are distinct with over production and accumulation of free radicals due to its undisclosed genesis. The cause of numerous disorders as cancer, arthritis, psoriasis, diabetes, alzheimer's, cardiovascular disease, Parkinson's, respiratory distress syndrome, colitis, crohn's, pulmonary fibrosis, obesity and ageing have been associated with immune dysfunction and oxidative stress. In an oxidative stress, reactive oxygen species generally provoke the series of oxidation at cellular level. The buildup of free radicals in turn triggers various inflammatory cells causing release of various inflammatory interleukins, cytokines, chemokines, and tumor necrosis factors which mediate signal transduction and transcription pathways as nuclear factor- kappa B (NF-κB), signal transducer and activator of transcription 3 (STAT3), hypoxia-inducible factor-1 (HIF-1α) and nuclear factor-erythroid 2-related factor (Nrf2). The imbalance could only be combat by supplementing natural defensive antioxidant enzymes such as superoxide dismutase and catalase. The efficiency of these enzymes is enhanced by use of colloidal carriers which include cellular carriers, vesicular and particulate systems like erythrocytes, leukocytes, platelets, liposomes, transferosomes, solid lipid nanoparticles, microspheres, emulsions. Thus this review provides a platform for understanding importance of antioxidant enzymes and its therapeutic applications in treatment of various autoimmune disorders. Copyright © 2017 Elsevier B.V. All rights reserved.

IRON-PEROXYMONOSULFATE: A NOVEL SULFATE RADICAL BASED ADVANCED OXIDATION TECHNOLOGY FOR DEGRADATION OF PCBS

EPA Science Inventory

This study investigates the degradation of recalcitrant polychlorinated biphenyl (PCBs) using sulfate radical-based advanced oxidation technologies. Sulfate radicals are generated through coupling of peroxymonosulfate (PMS) with iron (Fe(II), Fe(III)). Sulfate radicals have very ...

[The relationship between neuroendocrine dysfunction and free-radical oxidation in old age alcoholism].

PubMed

Vinogradov, D B; Mingazov, A Kh; Izarovskaya, I V; Babin, K A; Sinitsky, A I

2015-01-01

to study the relationship between dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis and free-radical oxidation in old age alcoholism. Authors examined 46 men and women, aged 60-80 years, with alcoholism. Contents of cortisol, lipid peroxidation products and the level of an oxidatively modified protein were measured. A decrease in blood cortisol content and correlations between its level and activity of free-radical oxidation were identified. The severity of neuroendocrine dysfunction in old patients was sex-related. It has been suggested that the impairment of HPA system activity may be a cause of oxidative stress and development of alcoholism.

Ceruloplasmin (ferroxidase) oxidizes hydroxylamine probes: deceptive implications for free radical detection

PubMed Central

Ganini, Douglas; Canistro, Donatella; Jang, JinJie; Stadler, Krisztian; Mason, Ronald P.; Kadiiska, Maria B.

2012-01-01

Ceruloplasmin (ferroxidase) is a copper-binding protein known to promote Fe2+ oxidation in plasma of mammals. Besides its classical ferroxidase activity, ceruloplasmin is known to catalyze the oxidation of various substrates, such as amines and catechols. Assays based on cyclic hydroxylamine oxidation are used to quantify and detect free radicals in biological samples ex vivo and in vitro. We show here that human ceruloplasmin promotes the oxidation of the cyclic hydroxylamine 1-hydroxy-3-carboxy-2,2,5,5-tetramethylpyrrolidine hydrochloride (CPH) and related probes in Chelex-treated phosphate buffer and rat serum. The reaction is suppressed by the metal chelators DTPA, EDTA and Desferal, while heparin and bathocuproine have no effect. Catalase or SOD additions do not interfere with the CPH-oxidation yield, demonstrating that free radicals are not involved in the CPH oxidation mediated by ceruloplasmin. Plasma samples immunodepleted of ceruloplasmin have lower levels of CPH oxidation, which confirms the role of ceruloplasmin (ferroxidase) as a biological oxidizing agent of cyclic hydroxylamines. In conclusion, we show that the ferroxidase activity of ceruloplasmin is a possible biological source of artifacts in the cyclic hydroxylamine-oxidation assay used for ROS detection and quantification. PMID:22824865

RELATIVE REACTIVITY OF CONTAMINANT CANDIDATE LIST PESTICIDES TO OH RADICAL OXIDATION

EPA Science Inventory

Advanced oxidation processes (AOPs) represent those technologies that bring about enhanced oxidative degradation of pollutants in aqueous solution by the generation of hydroxyl radical (•OH). US Environmental Protection Agency (EPA) published, in February 2005, the second Contam...

[Effect of calcium cations on acid-base properties and free radical oxidation of dopamine and pyrocatechol].

PubMed

Lebedev, A V; Ivanova, M V; Timoshin, A A; Ruuge, E K

2008-01-01

Ca2+-induced increase in the rate of pyrocatechol and dopamine oxidation by dioxygen and Ca2+-dependent acid-base properties of the catechols were studied by potentiometric titration, UV/Vis-spectrophotometry, EPR-spectroscopy, and by measurement of oxygen consumption. The effect of Ca2+ on the chain reactions of oxidation can be explained by additional deprotonation (decrease in pKai) of the catechols that accelerates one electron transport to dioxygen and formation of calcium semiquinonate, undergoing further oxidation. The described Ca2+-dependent redox-conversion of ortho-phenols proposes that an additional function of calcium in the cell can be its involvement in free radical oxidoreductive reactions at pH > pKai.

Towards a "free radical theory of graying": melanocyte apoptosis in the aging human hair follicle is an indicator of oxidative stress induced tissue damage.

PubMed

Arck, Petra Clara; Overall, Rupert; Spatz, Katharina; Liezman, Christiane; Handjiski, Bori; Klapp, Burghard F; Birch-Machin, Mark A; Peters, Eva Milena Johanne

2006-07-01

Oxidative stress is generated by a multitude of environmental and endogenous challenges such as radiation, inflammation, or psychoemotional stress. It also speeds the aging process. Graying is a prominent but little understood feature of aging. Intriguingly, the continuous melanin synthesis in the growing (anagen) hair follicle generates high oxidative stress. We therefore hypothesize that hair bulb melanocytes are especially susceptible to free radical-induced aging. To test this hypothesis, we subjected human scalp skin anagen hair follicles from graying individuals to macroscopic and immunohistomorphometric analysis and organ culture. We found evidence of melanocyte apoptosis and increased oxidative stress in the pigmentary unit of graying hair follicles. The "common" deletion, a marker mitochondrial DNA-deletion for accumulating oxidative stress damage, occurred most prominently in graying hair follicles. Cultured unpigmented hair follicles grew better than pigmented follicles of the same donors. Finally, cultured pigmented hair follicles exposed to exogenous oxidative stress (hydroquinone) showed increased melanocyte apoptosis in the hair bulb. We conclude that oxidative stress is high in hair follicle melanocytes and leads to their selective premature aging and apoptosis. The graying hair follicle, therefore, offers a unique model system to study oxidative stress and aging and to test antiaging therapeutics in their ability to slow down or even stop this process.

Photochemical Oxidation of Dissolved Elemental Mercury by Carbonate Radicals in Water

DOE PAGES

He, Feng; Zhao, Weirong; Liang, Liyuan; ...

2014-11-11

Photochemical oxidation of dissolved elemental mercury [Hg(0)] affects mercury chemical speciation and its transfer at the water-air interface in the aquatic environment. The mechanisms and factors that control Hg(0) photooxidation, however, are not completely understood, especially in natural freshwaters containing dissolved organic matter (DOM) and carbonate. Here, we evaluate Hg(0) photooxidation rates affected by various reactive ionic species [e.g., DOM, CO 3 2-, NO 3 -] and free radicals in a creek water and a phosphate buffer solution (pH=8) under simulated solar irradiation. We report a high Hg(0) photooxidation rate (k = 1.44 h -1) in the presence of bothmore » HCO 3 2- and NO 3 -, whereas HCO 3 2-, NO 3 -, or DOM alone increased the oxidation rate slightly (k = 0.1 0.17 h -1). Using scavengers and enhancers for singlet oxygen ( 1O 2) and hydroxyl (HO ∙ ) radicals, as well as electron paramagnetic resonance spectroscopy, we identify that carbonate radicals (CO 3 ∙-) primarily drive the Hg(0) photooxidation, whereas addition of DOM resulted in a 2-fold decrease in Hg(0) oxidation. This study identifies an unrecognized pathway of Hg(0) photooxidation by CO 3 ∙- radicals and the inhibitory effect of DOM, which could be important in assessing Hg transformation and fate in water containing carbonate such as hard water and seawater.« less

New insights into the aquatic photochemistry of fluoroquinolone antibiotics: Direct photodegradation, hydroxyl-radical oxidation, and antibacterial activity changes.

PubMed

Ge, Linke; Na, Guangshui; Zhang, Siyu; Li, Kai; Zhang, Peng; Ren, Honglei; Yao, Ziwei

2015-09-15

The ubiquity and photoreactivity of fluoroquinolone antibiotics (FQs) in surface waters urge new insights into their aqueous photochemical behavior. This study concerns the photochemistry of 6 FQs: ciprofloxacin, danofloxacin, levofloxacin, sarafloxacin, difloxacin and enrofloxacin. Methods were developed to calculate their solar direct photodegradation half-lives (td,E) and hydroxyl-radical oxidation half-lives (tOH,E) in sunlit surface waters. The td,E values range from 0.56 min to 28.8 min at 45° N latitude, whereas tOH,E ranges from 3.24h to 33.6h, suggesting that most FQs tend to undergo fast direct photolysis rather than hydroxyl-radical oxidation in surface waters. However, a case study for levofloxacin and sarafloxacin indicated that the hydroxyl-radical oxidation induced risky photochlorination and resulted in multi-degradation pathways, such as piperazinyl hydroxylation and clearage. Changes in the antibacterial activity of FQs caused by photodegradation in various waters were further examined using Escherichia coli, and it was found that the activity evolution depended on primary photodegradation pathways and products. Primary intermediates with intact FQ nuclei retained significant antibacterial activity. These results are important for assessing the fate and risk of FQs in surface waters. Copyright © 2015. Published by Elsevier B.V.

Methyl Radicals in Oxidative Coupling of Methane Directly Confirmed by Synchrotron VUV Photoionization Mass Spectroscopy

PubMed Central

Luo, Liangfeng; Tang, Xiaofeng; Wang, Wendong; Wang, Yu; Sun, Shaobo; Qi, Fei; Huang, Weixin

2013-01-01

Gas-phase methyl radicals have been long proposed as the key intermediate in catalytic oxidative coupling of methane, but the direct experimental evidence still lacks. Here, employing synchrotron VUV photoionization mass spectroscopy, we have directly observed the formation of gas-phase methyl radicals during oxidative coupling of methane catalyzed by Li/MgO catalysts. The concentration of gas-phase methyl radicals correlates well with the yield of ethylene and ethane products. These results lead to an enhanced fundamental understanding of oxidative coupling of methane that will facilitate the exploration of new catalysts with improved performance. PMID:23567985

Toward an understanding of mechanism of aging-induced oxidative stress in human mesenchymal stem cells.

PubMed

Benameur, Laila; Charif, Naceur; Li, Yueying; Stoltz, Jean-François; de Isla, Natalia

2015-01-01

Under physiological conditions, there is a production of limited range of free radicals. However, when the cellular antioxidant defence systems, overwhelm and fail to reverse back the free radicals to their normal basal levels, there is a creation of a condition of redox disequilibrium termed "oxidative stress", which is implicated in a very wide spectrum of genetic, metabolic, and cellular responses. The excess of free radicals can, cause unfavourable molecular alterations to biomolecules through oxidation of lipids, proteins, RNA and DNA, that can in turn lead to mutagenesis, carcinogenesis, and aging. Mesenchymal stem cells (MSCs) have been proven to be a promising source of cells for regenerative medicine, and to be useful in the treatment of pathologies in which tissue damage is linked to oxidative stress. Moreover, MSCs appeared to efficiently manage oxidative stress and to be more resistant to oxidative insult than normal somatic cells, making them an interesting and testable model for the role of oxidative stress in the aging process. In addition, aging is accompanied by a progressive decline in stem cell function, resulting in less effective tissue homeostasis and repair. Also, there is an obvious link between intracellular reactive oxygen species levels and cellular senescence. To date, few studies have investigated the promotion of aging by oxidative stress on human MSCs, and the mechanism by which oxidative stress induce stem cell aging is poorly understood. In this context, the aim of this review is to gain insight the current knowledge about the molecular mechanisms of aging-induced oxidative stress in human MSCs.

Pulsed Corona Discharge Induced Hydroxyl Radical Transfer Through the Gas-Liquid Interface.

PubMed

Ajo, Petri; Kornev, Iakov; Preis, Sergei

2017-11-23

The highly energetic electrons in non-thermal plasma generated by gas phase pulsed corona discharge (PCD) produce hydroxyl (OH) radicals via collision reactions with water molecules. Previous work has established that OH radicals are formed at the plasma-liquid interface, making it an important location for the oxidation of aqueous pollutants. Here, by contacting water as aerosol with PCD plasma, it is shown that OH radicals are produced on the gas side of the interface, and not in the liquid phase. It is also demonstrated that the gas-liquid interfacial boundary poses a barrier for the OH radicals, one they need to cross for reactive affinity with dissolved components, and that this process requires a gaseous atomic H scavenger. For gaseous oxidation, a scavenger, oxygen in common cases, is an advantage but not a requirement. OH radical efficiency in liquid phase reactions is strongly temperature dependent as radical termination reaction rates increase with temperature.

Ceruloplasmin (ferroxidase) oxidizes hydroxylamine probes: deceptive implications for free radical detection.

PubMed

Ganini, Douglas; Canistro, Donatella; Jiang, JinJie; Jang, JinJie; Stadler, Krisztian; Mason, Ronald P; Kadiiska, Maria B

2012-10-01

Ceruloplasmin (ferroxidase) is a copper-binding protein known to promote Fe(2+) oxidation in plasma of mammals. In addition to its classical ferroxidase activity, ceruloplasmin is known to catalyze the oxidation of various substrates, such as amines and catechols. Assays based on cyclic hydroxylamine oxidation are used to quantify and detect free radicals in biological samples ex vivo and in vitro. We show here that human ceruloplasmin promotes the oxidation of the cyclic hydroxylamine 1-hydroxy-3-carboxy-2,2,5,5-tetramethylpyrrolidine hydrochloride (CPH) and related probes in Chelex-treated phosphate buffer and rat serum. The reaction is suppressed by the metal chelators DTPA, EDTA, and desferal, whereas heparin and bathocuproine have no effect. Catalase or superoxide dismutase additions do not interfere with the CPH-oxidation yield, demonstrating that oxygen-derived free radicals are not involved in the CPH oxidation mediated by ceruloplasmin. Plasma samples immunodepleted of ceruloplasmin have lower levels of CPH oxidation, which confirms the role of ceruloplasmin (ferroxidase) as a biological oxidizing agent of cyclic hydroxylamines. In conclusion, we show that the ferroxidase activity of ceruloplasmin is a possible biological source of artifacts in the cyclic hydroxylamine-oxidation assay used for reactive oxygen species detection and quantification. Published by Elsevier Inc.

Free radicals generated during oxidation of green tea polyphenols: electron paramagnetic resonance spectroscopy combined with density functional theory calculations.

PubMed

Severino, Joyce Ferreira; Goodman, Bernard A; Kay, Christopher W M; Stolze, Klaus; Tunega, Daniel; Reichenauer, Thomas G; Pirker, Katharina F

2009-04-15

Electron paramagnetic resonance spectroscopy and density functional theory calculations have been used to investigate the redox properties of the green tea polyphenols (GTPs) (-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC), and (-)-epicatechin gallate (ECG). Aqueous extracts of green tea and these individual phenols were autoxidized at alkaline pH and oxidized by superoxide anion (O(2)(-)) radicals in dimethyl sulfoxide. Several new aspects of the free radical chemistry of GTPs were revealed. EGCG can be oxidized on both the B and the D ring. The B ring was the main oxidation site during autoxidation, but the D ring was the preferred site for O(2)(-) oxidation. Oxidation of the D ring was followed by structural degradation, leading to generation of a radical identical to that of oxidized gallic acid. Alkaline autoxidation of green tea extracts produced four radicals that were related to products of the oxidation of EGCG, EGC, ECG, and gallic acid, whereas the spectra from O(2)(-) oxidation could be explained solely by radicals generated from EGCG. Assignments of hyperfine coupling constants were made by DFT calculations, allowing the identities of the radicals observed to be confirmed.

Molecular detection of exercise-induced free radicals following ascorbate prophylaxis in type 1 diabetes mellitus: a randomised controlled trial.

PubMed

Davison, G W; Ashton, T; George, L; Young, I S; McEneny, J; Davies, B; Jackson, S K; Peters, J R; Bailey, D M

2008-11-01

Patients with type 1 diabetes mellitus are more susceptible than healthy individuals to exercise-induced oxidative stress and vascular endothelial dysfunction, which has important implications for the progression of disease. Thus, in the present study, we designed a randomised double-blind, placebo-controlled trial to test the original hypothesis that oral prophylaxis with vitamin C attenuates rest and exercise-induced free radical-mediated lipid peroxidation in type 1 diabetes mellitus. All data were collected from hospitalised diabetic patients. The electron paramagnetic resonance spectroscopic detection of spin-trapped alpha-phenyl-tert-butylnitrone (PBN) adducts was combined with the use of supporting markers of lipid peroxidation and non-enzymatic antioxidants to assess exercise-induced oxidative stress in male patients with type 1 diabetes (HbA(1c) 7.9 +/- 1%, n = 12) and healthy controls (HbA(1c) 4.6 +/- 0.5%, n = 14). Following participant randomisation using numbers in a sealed envelope, venous blood samples were obtained at rest, after a maximal exercise challenge and before and 2 h after oral ingestion of 1 g ascorbate or placebo. Participants and lead investigators were blinded to the administration of either placebo or ascorbate treatments. Primary outcome was the difference in changes in free radicals following ascorbate ingestion. Six diabetic patients and seven healthy control participants were randomised to each of the placebo and ascorbate groups. Diabetic patients (n = 12) exhibited an elevated concentration of PBN adducts (p < 0.05 vs healthy, n = 14), which were confirmed as secondary, lipid-derived oxygen-centred alkoxyl (RO.) radicals (a(nitrogen) = 1.37 mT and abeta(hydrogen) = 0.18 mT). Lipid hydroperoxides were also selectively elevated and associated with a depression of retinol and lycopene (p < 0.05 vs healthy). Vitamin C supplementation increased plasma vitamin C concentration to a similar degree in both groups (p < 0.05 vs pre

Oxidative generation of guanine radicals by carbonate radicals and their reactions with nitrogen dioxide to form site specific 5-guanidino-4-nitroimidazole lesions in oligodeoxynucleotides.

PubMed

Joffe, Avrum; Mock, Steven; Yun, Byeong Hwa; Kolbanovskiy, Alexander; Geacintov, Nicholas E; Shafirovich, Vladimir

2003-08-01

A simple photochemical approach is described for synthesizing site specific, stable 5-guanidino-4-nitroimidazole (NIm) adducts in single- and double-stranded oligodeoxynucleotides containing single and multiple guanine residues. The DNA sequences employed, 5'-d(ACC CG(1)C G(2)TC CG(3)C G(4)CC) and 5'-d(ACC CG(1)C G(2)TC C), were a portion of exon 5 of the p53 tumor suppressor gene, including the codons 157 (G(2)) and 158 (G(3)) mutation hot spots in the former sequence with four Gs and the codon 157 (G(2)) mutation hot spot in the latter sequence with two Gs. The nitration of oligodeoxynucleotides was initiated by the selective photodissociation of persulfate anions to sulfate radicals induced by UV laser pulses (308 nm). In aqueous solutions, of bicarbonate and nitrite anions, the sulfate radicals generate carbonate anion radicals and nitrogen dioxide radicals by one electron oxidation of the respective anions. The guanine residue in the oligodeoxynucleotide is oxidized by the carbonate anion radical to form the neutral guanine radical. While the nitrogen dioxide radicals do not react with any of the intact DNA bases, they readily combine with the guanine radicals at either the C8 or the C5 positions. The C8 addition generates the well-known 8-nitroguanine (8-nitro-G) lesions, whereas the C5 attack produces unstable adducts, which rapidly decompose to NIm lesions. The maximum yields of the nitro products (NIm + 8-nitro-G) were typically in the range of 20-40%, depending on the number of guanine residues in the sequence. The ratio of the NIm to 8-nitro-G lesions gradually decreases from 3.4 in the model compound, 2',3',5'-tri-O-acetylguanosine, to 2.1-2.6 in the single-stranded oligodeoxynucleotides and to 0.8-1.1 in the duplexes. The adduct of the 5'-d(ACC CG(1)C G(2)TC C) oligodeoxynucleotide containing the NIm lesion in codon 157 (G(2)) was isolated in HPLC-pure form. The integrity of this adduct was established by a detailed analysis of exonuclease digestion

Absence of an effect of vitamin E on protein and lipid radical formation during lipoperoxidation of LDL by lipoxygenase

PubMed Central

Ganini, Douglas; Mason, Ronald P.

2014-01-01

LDL oxidation is the primary event in atherosclerosis, where LDL lipoperoxidation leads to modifications in the apolipoprotein B-100 (apo B-100) and lipids. Intermediate species of lipoperoxidation are known to be able to generate amino acid-centered radicals. Thus, we hypothesized that lipoperoxidation intermediates induce protein-derived free radical formation during LDL oxidation. Using DMPO and immuno spin-trapping, we detected the formation of protein free radicals on LDL incubated with Cu2+ or the soybean lipoxidase (LPOx)/phospholipase A2 (PLA2). With low concentrations of DMPO (1 mM), Cu2+ dose-dependently induced oxidation of LDL and easily detected apo B-100 radicals. Protein radical formation in LDL incubated with Cu2+ showed maximum yields after 30 minutes. In contrast, the yields of apo B-100-radicals formed by LPOx/PLA2 followed a typical enzyme-catalyzed kinetics that was unaffected by DMPO concentrations of up to 50 mM. Furthermore, when we analyzed the effect of antioxidants on protein radical formation during LDL oxidation, we found that ascorbate, urate and Trolox dose-dependently reduced apo B-100-free radical formation in LDL exposed to Cu2+. In contrast, Trolox was the only antioxidant that even partially protected LDL from LPOx/PLA2. We also examined the kinetics of lipid radical formation and protein radical formation induced by Cu2+ or LPOx/PLA2 for LDL supplemented with α-tocopherol. In contrast to the potent antioxidant effect of α-tocopherol on the delay of LDL oxidation induced by Cu2+, when we used the oxidizing system LPOx/PLA2, no significant protection was detected. The lack of protection of α-tocopherol on the apo B-100 and lipid free radical formation by LPOx may explain the failure of vitamin E as a cardiovascular protective agent for humans. PMID:25091900

Quantifying protein interface footprinting by hydroxyl radical oxidation and molecular dynamics simulation: application to galectin-1.

PubMed

Charvátová, Olga; Foley, B Lachele; Bern, Marshall W; Sharp, Joshua S; Orlando, Ron; Woods, Robert J

2008-11-01

Biomolecular surface mapping methods offer an important alternative method for characterizing protein-protein and protein-ligand interactions in cases in which it is not possible to determine high-resolution three-dimensional (3D) structures of complexes. Hydroxyl radical footprinting offers a significant advance in footprint resolution compared with traditional chemical derivatization. Here we present results of footprinting performed with hydroxyl radicals generated on the nanosecond time scale by laser-induced photodissociation of hydrogen peroxide. We applied this emerging method to a carbohydrate-binding protein, galectin-1. Since galectin-1 occurs as a homodimer, footprinting was employed to characterize the interface of the monomeric subunits. Efficient analysis of the mass spectrometry data for the oxidized protein was achieved with the recently developed ByOnic (Palo Alto, CA) software that was altered to handle the large number of modifications arising from side-chain oxidation. Quantification of the level of oxidation has been achieved by employing spectral intensities for all of the observed oxidation states on a per-residue basis. The level of accuracy achievable from spectral intensities was determined by examination of mixtures of synthetic peptides related to those present after oxidation and tryptic digestion of galectin-1. A direct relationship between side-chain solvent accessibility and level of oxidation emerged, which enabled the prediction of the level of oxidation given the 3D structure of the protein. The precision of this relationship was enhanced through the use of average solvent accessibilities computed from 10 ns molecular dynamics simulations of the protein.

Chitooligosaccharides protect human embryonic hepatocytes against oxidative stress induced by hydrogen peroxide.

PubMed

Xu, Qingsong; Ma, Pan; Yu, Weiting; Tan, Chengyu; Liu, Hongtao; Xiong, Chuannan; Qiao, Ying; Du, Yuguang

2010-06-01

Chitooligosaccharides (COS) has many biological activities, such as antitumor activity and hepatoprotective effect. Herein, we investigated the protective effect of COS against hydrogen peroxide (H2O2)-induced oxidative stress on human embryonic hepatocytes (L02 cells) and its scavenging activity against the 1,1-diphenyl-2-picrylhydrazyl radical in vitro. The results showed that the lost cell viability induced by H2O2 was markedly restored after 24 h pre-incubation with COS (0.1-0.4 mg/ml). This rescue effect could be related to the antioxidant property of COS, in which we showed that the radical scavenging activity of COS reached 80% at concentration of 2 mg/ml. In addition, COS could prevent cell apoptosis induced by H2O2, as shown by the inhibition of the cleavage of poly (adenosine diphosphate-ribose) polymerase and increased expression of the anti-apoptotic protein Bcl-xL. Furthermore, we have utilized confocal laser microscopy to observe cellular uptake of COS, an important step for COS to exert its effects on target cells. Taken together, our findings suggested that COS could effectively protect L02 cells against oxidative stress, which might be useful in clinical setting during the treatment of oxidative stress-related liver damages.

RELATIVE REACTIVITY OF CONTAMINANT CANDIDATE LIST PESTICIDES TO OH RADICAL OXIDATION ABSTRACT

EPA Science Inventory

Advanced oxidation processes (AOPs) represent those technologies that bring about enhanced oxidative degradation of pollutants in aqueous solution by the generation of hydroxyl radical (•OH). US Environmental Protection Agency (EPA) published, in February 2005, the second Contami...

Betanodavirus induces oxidative stress-mediated cell death that prevented by anti-oxidants and zfcatalase in fish cells.

PubMed

Chang, Chih-Wei; Su, Yu-Chin; Her, Guor-Mour; Ken, Chuian-Fu; Hong, Jiann-Ruey

2011-01-01

The role of oxidative stress in the pathogenesis of RNA nervous necrosis virus infection is still unknown. Red-spotted grouper nervous necrosis virus (RGNNV) induced free radical species (ROS) production at 12-24 h post-infection (pi; early replication stage) in fish GF-1 cells, and then at middle replication stage (24-48 h pi), this ROS signal may upregulate some expressions of the anti-oxidant enzymes Cu/Zn SOD and catalase, and eventually expression of the transcription factor Nrf2. Furthermore, both antioxidants diphenyliodonium and N-acetylcysteine or overexpression of zebrafish catalase in GF-1 cells also reduced ROS production and protected cells for enhancing host survival rate due to RGNNV infection. Furthermore, localization of ROS production using esterase activity and Mitotracker staining assays found that the ROS generated can affect mitochondrial morphology changes and causes ΔΨ loss, both of which can be reversed by antioxidant treatment. Taken together, our data suggest that RGNNV induced oxidative stress response for playing dual role that can initiate the host oxidative stress defense system to upregulate expression of antioxidant enzymes and induces cell death via disrupting the mitochondrial morphology and inducing ΔΨ loss, which can be reversed by anti-oxidants and zfcatalase, which provide new insight into betanodavirus-induced ROS-mediated pathogenesis.

π to σ Radical Tautomerization in One-Electron Oxidized 1-Methylcytosine and its Analogs

PubMed Central

Adhikary, Amitava; Kumar, Anil; Bishop, Casandra T.; Wiegand, Tyler J.; Hindi, Ragda M.; Adhikary, Ananya; Sevilla, Michael D.

2015-01-01

In this work iminyl σ-radical formation in several one-electron oxidized cytosine analogs including 1-MeC, cidofovir, 2′-deoxycytidine (dCyd), and 2′-deoxycytidine 5′-monophosphate (5′-dCMP) were investigated in homogeneous aqueous (D2O or H2O) glassy solutions at low temperatures employing electron spin resonance (ESR) spectroscopy. Employing density functional theory (DFT) (DFT/B3LYP/6-31G* method), the calculated hyperfine coupling constant (HFCC) values of iminyl σ-radical agree quite well with the experimentally observed ones thus confirming its assignment. ESR and DFT studies show that the cytosine-iminyl σ-radical is a tautomer of the deprotonated cytosine π-cation radical (cytosine π-aminyl radical, C(N4-H)•). Employing 1-MeC samples at various pHs ranging ca. 8 to ca. 11, ESR studies show that the tautomeric equilibrium between C(N4-H)• and the iminyl σ-radical at low temperature is too slow to be established without added base. ESR and DFT studies agree that in the iminyl-σ radical, the unpaired spin is localized to the exocyclic nitrogen (N4) in an in-plane pure p-orbital. This gives rise to an anisotropic nitrogen hyperfine coupling (Azz = 40 G) from N4 and a near isotropic β-nitrogen coupling of 9.7 G from the cytosine ring nitrogen at N3. Iminyl σ-radical should exist in its N3-protonated form as the N3-protonated iminyl σ-radical is stabilized in solution by over 30 kcal/mol (ΔG= −32 kcal/mol) over its conjugate base, the N3-deprotonated form. This is the first observation of an isotropic β-hyperfine ring nitrogen coupling in an N-centered DNA-radical. Our theoretical calculations predict that the cytosine iminyl σ-radical can be formed in dsDNA by a radiation-induced ionization–deprotonation process that is only 10 kcal/mol above the lowest energy path. PMID:26237072

EPR spectral investigation of radiation-induced radicals of gallic acid.

PubMed

Tuner, Hasan

2017-11-01

In the present work, spectroscopic features of the radiation-induced radicals of gallic acid compounds were investigated using electron paramagnetic resonance (EPR) spectroscopy. While un-irradiated samples presented no EPR signal, irradiated samples exhibited an EPR spectrum consisting of an intense resonance line at the center and weak lines on both sides. Detailed microwave saturation investigations were carried out to determine the origin of the experimental EPR lines. It is concluded that the two side lines of the triplet satellite originate from forbidden "spin-flip" transitions. The spectroscopic and structural features of the radiation-induced radicals were determined using EPR spectrum fittings. The experimental EPR spectra of the two gallic acid compounds were consistent with the calculated EPR spectroscopic features of the proposed radicals. It is concluded that the most probable radicals are the cyclohexadienyl-type, [Formula: see text] radicals for both compounds.

Free radical reaction characteristics of coal low-temperature oxidation and its inhibition method.

PubMed

Li, Zenghua; Kong, Biao; Wei, Aizhu; Yang, Yongliang; Zhou, Yinbo; Zhang, Lanzhun

2016-12-01

Study on the mechanism of coal spontaneous combustion is significant for controlling fire disasters due to coal spontaneous combustion. The free radical reactions can explain the chemical process of coal at low-temperature oxidation. Electron spin resonance (ESR) spectroscopy was used to measure the change rules of the different sorts and different granularity of coal directly; ESR spectroscopy chart of free radicals following the changes of temperatures was compared by the coal samples applying air and blowing nitrogen, original coal samples, dry coal samples, and demineralized coal samples. The fragmentation process was the key factor of producing and initiating free radical reactions. Oxygen, moisture, and mineral accelerated the free radical reactions. Combination of the free radical reaction mechanism, the mechanical fragmentation leaded to the elevated CO concentration, fracturing of coal pillar was more prone to spontaneous combustion, and spontaneous combustion in goaf accounted for a large proportion of the fire in the mine were explained. The method of added diphenylamine can inhibit the self-oxidation of coal effectively, the action mechanism of diphenylamine was analyzed by free radical chain reaction, and this research can offer new method for the development of new flame retardant.

Gallic acid prevents nonsteroidal anti-inflammatory drug-induced gastropathy in rat by blocking oxidative stress and apoptosis.

PubMed

Pal, Chinmay; Bindu, Samik; Dey, Sumanta; Alam, Athar; Goyal, Manish; Iqbal, Mohd Shameel; Maity, Pallab; Adhikari, Susanta S; Bandyopadhyay, Uday

2010-07-15

Nonsteroidal anti-inflammatory drug (NSAID)-induced oxidative stress plays a critical role in gastric mucosal cell apoptosis and gastropathy. NSAIDs induce the generation of hydroxyl radical ((*)OH) through the release of free iron, which plays an important role in developing gastropathy. Thus, molecules having both iron-chelating and antiapoptotic properties will be beneficial in preventing NSAID-induced gastropathy. Gallic acid (GA), a polyphenolic natural product, has the capacity to chelate free iron. Here, we report that GA significantly prevents, as well as heals, NSAID-induced gastropathy. In vivo, GA blocks NSAID-mediated mitochondrial oxidative stress by preventing mitochondrial protein carbonyl formation, lipid peroxidation, and thiol depletion. In vitro, GA scavenges free radicals and blocks (*)OH-mediated oxidative damage. GA also attenuates gastric mucosal cell apoptosis in vivo as well as in vitro in cultured gastric mucosal cells as evident from the TUNEL assay. GA prevents NSAID-induced activation of caspase-9, a marker for the mitochondrial pathway of apoptosis, and restores NSAID-mediated collapse of the mitochondrial transmembrane potential and dehydrogenase activity. Thus, the inhibition of mitochondrial oxidative stress by GA is associated with the inhibition of NSAID-induced mitochondrial dysfunction and activation of apoptosis in gastric mucosal cells, which are responsible for gastric injury or gastropathy. Copyright 2010 Elsevier Inc. All rights reserved.

Can Carbamates Undergo Radical Oxidation in the Soil Environment? A Case Study on Carbaryl and Carbofuran.

PubMed

Ćwieląg-Piasecka, Irmina; Witwicki, Maciej; Jerzykiewicz, Maria; Jezierska, Julia

2017-12-19

Radical oxidation of carbamate insecticides, namely carbaryl and carbofuran, was investigated with spectroscopic (electron paramagnetic resonance [EPR] and UV-vis) and theoretical (density functional theory [DFT] and ab initio orbital-optimized spin-component scaled MP2 [OO-SCS-MP2]) methods. The two carbamates were subjected to reaction with • OH, persistent DPPH • and galvinoxyl radical, as well as indigenous radicals of humic acids. The influence of fulvic acids on carbamate oxidation was also tested. The results obtained with EPR and UV-vis spectroscopy indicate that carbamates can undergo direct reactions with various radical species, oxidizing themselves into radicals in the process. Hence, they are prone to participate in the prolongation step of the radical chain reactions occurring in the soil environment. Theoretical calculations revealed that from the thermodynamic point of view hydrogen atom transfer is the preferred mechanism in the reactions of the two carbamates with the radicals. The activity of carbofuran was determined experimentally (using pseudo-first-order kinetics) and theoretically to be noticeably higher in comparison with carbaryl and comparable with gallic acid. The findings of this study suggest that the radicals present in soil can play an important role in natural remediation mechanisms of carbamates.

π vs σ-Radical States of One-Electron Oxidized DNA/RNA Bases: A Density Functional Theory Study

PubMed Central

Kumar, Anil; Sevilla, Michael D.

2013-01-01

As a result of their inherent planarity, DNA base radicals generated by one electron oxidation/reduction or bond cleavage form π- or σ-radicals. While most DNA base systems form π-radicals there are a number of nucleobase analogs such as one-electron oxidized 6-azauraci1, 6-azacytosine, and 2-thiothymine or one-electron reduced 5-bromouracil that form more reactive σ-radicals. Elucidating the availability of these states within DNA, base radical electronic structure is important to the understanding of the reactivity of DNA base radicals in different environments. In this work, we address this question by the calculation of the relative energies of π- and σ-radical states in DNA/RNA bases and their analogs. We used density functional theory B3LYP/6-31++G** method to optimize the geometries of π- and σ-radicals in Cs symmetry (i.e., planar) in the gas phase and in solution using the polarized continuum model (PCM). The calculations predict that σ- and π-radical states in one electron oxidized bases of thymine, T(N3-H)•, and uracil, U(N3-H)• are very close in energy, i.e., the π-radical is only ca. 4 kcal/mol more stable than the σ-radical. For the one electron oxidized radicals of cytosine, C•+, C(N4-H)•, adenine, A•+, A(N6-H)•, and guanine, G•+, G(N2-H)•, G(N1-H)• the π-radicals are ca. 16 to 41 kcal/mol more stable than their corresponding σ-radicals. Inclusion of solvent (PCM) is found to stabilize the π- over σ-radical of each of the systems. U(N3-H)• with three discrete water molecules in the gas phase, is found to form a three-electron σ bond between N3 atom of uracil and O atom of a water molecule but on inclusion of full solvation and discrete hydration the π-radical remains most stable.. PMID:24000793

π- vs σ-radical states of one-electron-oxidized DNA/RNA bases: a density functional theory study.

PubMed

Kumar, Anil; Sevilla, Michael D

2013-10-03

As a result of their inherent planarity, DNA base radicals generated by one-electron oxidation/reduction or bond cleavage form π- or σ-radicals. While most DNA base systems form π-radicals, there are a number of nucleobase analogues such as one-electron-oxidized 6-azauraci1, 6-azacytosine, and 2-thiothymine or one-electron reduced 5-bromouracil that form more reactive σ-radicals. Elucidating the availability of these states within DNA, base radical electronic structure is important to the understanding of the reactivity of DNA base radicals in different environments. In this work, we address this question by the calculation of the relative energies of π- and σ-radical states in DNA/RNA bases and their analogues. We used density functional theory B3LYP/6-31++G** method to optimize the geometries of π- and σ-radicals in Cs symmetry (i.e., planar) in the gas phase and in solution using the polarized continuum model (PCM). The calculations predict that σ- and π-radical states in one-electron-oxidized bases of thymine, T(N3-H)(•), and uracil, U(N3-H)(•), are very close in energy; i.e., the π-radical is only ca. 4 kcal/mol more stable than the σ-radical. For the one-electron-oxidized radicals of cytosine, C(•+), C(N4-H)(•), adenine, A(•+), A(N6-H)(•), and guanine, G(•+), G(N2-H)(•), G(N1-H)(•), the π-radicals are ca. 16-41 kcal/mol more stable than their corresponding σ-radicals. Inclusion of solvent (PCM) is found to stabilize the π- over σ-radical of each of the systems. U(N3-H)(•) with three discrete water molecules in the gas phase is found to form a three-electron σ bond between the N3 atom of uracil and the O atom of a water molecule, but on inclusion of full solvation and discrete hydration, the π-radical remains most stable.

Chemical instability of graphene oxide following exposure to highly reactive radicals in advanced oxidation processes.

PubMed

Wang, Zhaohui; Sun, Linyan; Lou, Xiaoyi; Yang, Fei; Feng, Min; Liu, Jianshe

2017-12-01

The rapidly increasing and widespread use of graphene oxide (GO) as catalyst supports, requires further understanding of its chemical stability in advanced oxidation processes (AOPs). In this study, UV/H 2 O 2 and UV/persulfate (UV/PS) processes were selected to test the chemical instability of GO in terms of their performance in producing highly reactive hydroxyl radicals (OH) and sulfate radicals (SO 4 - ), respectively. The degradation intermediates were characterized using UV-visible absorption spectra (UV-vis), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Raman spectroscopy, and matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Experimental data indicate that UV/PS process was more effective in enhancing GO degradation than the UV/H 2 O 2 system. The overall oxygen-containing functionalities (e.g. CO, CO and OCO groups) dramatically declined. After radical attack, sheet-like GO was destructed into lots of flakes and some low-molecular-weight molecules were detected. The results suggest GO is most vulnerable against SO 4 - radical attack, which deserves special attention while GO acts as a catalyst support or even as a catalyst itself. Therefore, stability of GO and its derivatives should be carefully assessed before they are applied to SO 4 - -based AOPs. Copyright © 2017 Elsevier Inc. All rights reserved.

Oxidation of trichloroethylene by the hydroxyl radicals produced from oxygenation of reduced nontronite.

PubMed

Liu, Xixiang; Yuan, Songhu; Tong, Man; Liu, Deng

2017-04-15

Reduction by Fe(II)-bearing silicate minerals has been proposed as an important mechanism for the attenuation of chlorinated hydrocarbons (CHCs) in anoxic subsurfaces. The redox condition of subsurface often changes from anoxic to oxic due to natural processes and human activities, but little is known about the transformation of CHCs induced by Fe(II)-bearing silicate minerals under oxic conditions. This study reveals that trichloroethylene (TCE) can be efficiently oxidized during the oxygenation of reduced nontronite at pH 7.5, whereas the reduction was negligible under anoxic conditions. The maximum oxidation of TCE (initially 1 mg/L) attained 89.6% for 3 h oxygenation of 2 g/L nontronite with 50% reduction extent. TCE oxidation is attributed to the strongly oxidizing hydroxyl radicals (OH) produced by the oxygenation of Fe(II) in nontronite. Fe(II) on the edges is preferentially oxygenated for OH production, and the interior Fe(II) serves as an electron pool to regenerate the Fe(II) on the edges. Oxidation of TCE could be sustainable through chemically or biologically reducing the oxidized silicate minerals. Our findings present a new mechanism for the transformation of CHCs and other redox-active substances in the redox-fluctuation environments. Copyright © 2017 Elsevier Ltd. All rights reserved.

Oxidation Inhibits Iron-Induced Blood Coagulation

PubMed Central

Pretorius, Etheresia; Bester, Janette; Vermeulen, Natasha; Lipinski, Boguslaw

2013-01-01

Blood coagulation under physiological conditions is activated by thrombin, which converts soluble plasma fibrinogen (FBG) into an insoluble clot. The structure of the enzymatically-generated clot is very characteristic being composed of thick fibrin fibers susceptible to the fibrinolytic degradation. However, in chronic degenerative diseases, such as atherosclerosis, diabetes mellitus, cancer, and neurological disorders, fibrin clots are very different forming dense matted deposits (DMD) that are not effectively removed and thus create a condition known as thrombosis. We have recently shown that trivalent iron (ferric ions) generates hydroxyl radicals, which subsequently convert FBG into abnormal fibrin clots in the form of DMDs. A characteristic feature of DMDs is their remarkable and permanent resistance to the enzymatic degradation. Therefore, in order to prevent thrombotic incidences in the degenerative diseases it is essential to inhibit the iron-induced generation of hydroxyl radicals. This can be achieved by the pretreatment with a direct free radical scavenger (e.g. salicylate), and as shown in this paper by the treatment with oxidizing agents such as hydrogen peroxide, methylene blue, and sodium selenite. Although the actual mechanism of this phenomenon is not yet known, it is possible that hydroxyl radicals are neutralized by their conversion to the molecular oxygen and water, thus inhibiting the formation of dense matted fibrin deposits in human blood. PMID:23170793

Evaluation of free radical scavenging capacity and antioxidative damage effect of resveratrol-nanostructured lipid carriers

NASA Astrophysics Data System (ADS)

Jin, Ju; Shi, Fan; Li, Qiu-wen; Li, Pei-shan; Chen, Tong-sheng; Wang, Yi-fei; Wang, Zhi-ping

2016-03-01

Cellular damage induced by free-radicals like reactive oxygen species has been implicated in several diseases. 2, 2-azobis(2-amidino-propane) dihydrochloride(AAPH) generates two potent ROS capable of inducing lipid peroxidation: alkoxy radical(RO-) and peroxy radical(ROO-). These radicals are similar to those that are physiologically active and thus might initiate a cascade of intracellular toxic events leading to oxidation, lipid peroxidation, DNA damage and subsequent cell death. Hence naturally anti-oxidant play a vital role in combating these conditions. In this study, resveratrol loaded nanostructured lipid carriers (Res-NLC) was prepared by hot melting and then high pressure homogenization technique. The effects of Res-NLC on free radical scavenging capacity and antioxidative damage is investigated. The particle size and zeta potential of Res-NLC were 139.3 ± 1.7 nm and -11.21 ± 0.41 mV, respectively. By free radical scavenging assays, the IC50 value of Res-NLC were 19.25, 5.29 μg/mL with DPPH, ABTS assay respectively, and 0.161 mg ferrous sulfate/1 mg Res-NLC with FRAP assay; and by AAPH-induced oxidative injury cell model assay, Res-NLC showed the strong protective effect against the human liver tumor HepG2 cell oxidative stress damage. These results indicated that the antioxidant properties of Res-NLC hold great potential used as an alternative to more toxic synthetic antioxidants as an additive in food, cosmetic and pharmaceutical preparations for the oxidative diseases treatment.

Sulfur Radical-Induced Redox Modifications in Proteins: Analysis and Mechanistic Aspects.

PubMed

Schöneich, Christian

2017-03-10

The sulfur-containing amino acids cysteine (Cys) and methionine (Met) are prominent protein targets of redox modification during conditions of oxidative stress. Here, two-electron pathways have received widespread attention, in part due to their role in signaling processes. However, Cys and Met are equally prone to one-electron pathways, generating intermediary radicals and/or radial ions. These radicals/radical ions can generate various reaction products that are not commonly monitored in redox proteomic studies, but they may be relevant for the fate of proteins during oxidative stress. Recent Advances: Time-resolved kinetic studies and product analysis have expanded our mechanistic understanding of radical reaction pathways of sulfur-containing amino acids. These reactions are now studied in some detail for Met and Cys in proteins, and homocysteine (Hcy) chemically linked to proteins, and the role of protein radical reactions in physiological processes is evolving. Radical-derived products from Cys, Hcy, and Met can react with additional amino acids in proteins, leading to secondary protein modifications, which are potentially remote from initial points of radical attack. These products may contain intra- and intermolecular cross-links, which may lead to protein aggregation. Protein sequence and conformation will have a significant impact on the formation of such products, and a thorough understanding of reaction mechanisms and specifically how protein structure influences reaction pathways will be critical for identification and characterization of novel reaction products. Future studies must evaluate the biological significance of novel reaction products that are derived from radical reactions of sulfur-containing amino acids. Antioxid. Redox Signal. 26, 388-405.

Gas-Phase Ozonolysis of Cycloalkenes: Formation of Highly Oxidized RO2 Radicals and Their Reactions with NO, NO2, SO2, and Other RO2 Radicals.

PubMed

Berndt, Torsten; Richters, Stefanie; Kaethner, Ralf; Voigtländer, Jens; Stratmann, Frank; Sipilä, Mikko; Kulmala, Markku; Herrmann, Hartmut

2015-10-15

The gas-phase reaction of ozone with C5-C8 cycloalkenes has been investigated in a free-jet flow system at atmospheric pressure and a temperature of 297 ± 1 K. Highly oxidized RO2 radicals bearing at least 5 O atoms in the molecule and their subsequent reaction products were detected in most cases by means of nitrate-CI-APi-TOF mass spectrometry. Starting from a Criegee intermediate after splitting-off an OH-radical, the formation of these RO2 radicals can be explained via an autoxidation mechanism, meaning RO2 isomerization (ROO → QOOH) and subsequently O2 addition (QOOH + O2 → R'OO). Time-dependent RO2 radical measurements concerning the ozonolysis of cyclohexene indicate rate coefficients of the intramolecular H-shifts, ROO → QOOH, higher than 1 s(-1). The total molar yield of highly oxidized products (predominantly RO2 radicals) from C5-C8 cycloalkenes in air is 4.8-6.0% affected with a calibration uncertainty by a factor of about two. For the most abundant RO2 radical from cyclohexene ozonolysis, O,O-C6H7(OOH)2O2 ("O,O" stands for two O atoms arising from the ozone attack), the determination of the rate coefficients of the reaction with NO2, NO, and SO2 yielded (1.6 ± 0.5) × 10(-12), (3.4 ± 0.9) × 10(-11), and <10(-14) cm(3) molecule(-1) s(-1), respectively. The reaction of highly oxidized RO2 radicals with other peroxy radicals (R'O2) leads to detectable accretion products, RO2 + R'O2 → ROOR' + O2, which allows to acquire information on peroxy radicals not directly measurable with the nitrate ionization technique applied here. Additional experiments using acetate as the charger ion confirm conclusively the existence of highly oxidized RO2 radicals and closed-shell products. Other reaction products, detectable with this ionization technique, give a deeper insight in the reaction mechanism of cyclohexene ozonolysis.

Environmentally persistent free radicals amplify ultrafine particle mediated cellular oxidative stress and cytotoxicity

PubMed Central

Balakrishna, Shrilatha; Lomnicki, Slawo; McAvey, Kevin M; Cole, Richard B; Dellinger, Barry; Cormier, Stephania A

2009-01-01

Background Combustion generated particulate matter is deposited in the respiratory tract and pose a hazard to the lungs through their potential to cause oxidative stress and inflammation. We have previously shown that combustion of fuels and chlorinated hydrocarbons produce semiquinone-type radicals that are stabilized on particle surfaces (i.e. environmentally persistent free radicals; EPFRs). Because the composition and properties of actual combustion-generated particles are complex, heterogeneous in origin, and vary from day-to-day, we have chosen to use surrogate particle systems. In particular, we have chosen to use the radical of 2-monochlorophenol (MCP230) as the EPFR because we have previously shown that it forms a EPFR on Cu(II)O surfaces and catalyzes formation of PCDD/F. To understand the physicochemical properties responsible for the adverse pulmonary effects of combustion by-products, we have exposed human bronchial epithelial cells (BEAS-2B) to MCP230 or the CuO/silica substrate. Our general hypothesis was that the EPFR-containing particle would have greater toxicity than the substrate species. Results Exposure of BEAS-2B cells to our combustion generated particle systems significantly increased reactive oxygen species (ROS) generation and decreased cellular antioxidants resulting in cell death. Resveratrol treatment reversed the decline in cellular glutathione (GSH), glutathione peroxidase (GPx), and superoxide dismutase (SOD) levels for both types of combustion-generated particle systems. Conclusion The enhanced cytotoxicity upon exposure to MCP230 correlated with its ability to generate more cellular oxidative stress and concurrently reduce the antioxidant defenses of the epithelial cells (i.e. reduced GSH, SOD activity, and GPx). The EPFRs in MCP230 also seem to be of greater biological concern due to their ability to induce lipid peroxidation. These results are consistent with the oxidizing nature of the CuO/silica ultrafine particles and the

Oxidative capacity of the Mexico City atmosphere - Part 1: A radical source perspective

NASA Astrophysics Data System (ADS)

Volkamer, R.; Sheehy, P. M.; Molina, L. T.; Molina, M. J.

2007-04-01

A detailed analysis of OH, HO2 and RO2 radical sources is presented for the near field photochemical regime inside the Mexico City Metropolitan Area (MCMA). During spring of 2003 (MCMA-2003 field campaign) an extensive set of measurements was collected to quantify time resolved ROx (sum of OH, HO2, RO2) radical production rates from day- and nighttime radical sources. The Master Chemical Mechanism (MCMv3.1) was constrained by measurements of (1) concentration time-profiles of photosensitive radical precursors, i.e., nitrous acid (HONO), formaldehyde (HCHO), ozone (O3), glyoxal (CHOCHO), and other oxygenated volatile organic compounds (OVOCs); (2) respective photolysis-frequencies (J-values); (3) concentration time-profiles of alkanes, alkenes, and aromatic VOCs (103 compound are treated) and oxidants, i.e., OH- and NO3 radicals, O3; and (4) NO, NO2, meteorological and other parameters. The ROx production rate was calculated directly from these observations; MCM was used to estimate further ROx production from unconstrained sources, and express overall ROx production as OH-equivalents (i.e., taking into account the propagation efficiencies of RO2 and HO2 radicals into OH radicals). Daytime radical production is found to be about 10-25 times higher than at night; it does not track the abundance of sunlight. 12-h average daytime contributions of individual sources are: HCHO and O3 photolysis, each about 20%; O3/alkene reactions and HONO photolysis, each about 15%; unmeasured sources about 30%. While the direct contribution of O3/alkene reactions appears to be moderately small, source-apportionment of ambient HCHO and HONO identifies O3/alkene reactions as being largely responsible for jump-starting photochemistry about one hour after sunrise. The peak radical production is found to be higher than in any other urban influenced environment studied to date; further, differences exist in the timing of radical production. Our measurements and analysis comprise a database

Evaluation of Both Free Radical Scavenging Capacity and Antioxidative Damage Effect of Polydatin.

PubMed

Jin, Ju; Li, Yan; Zhang, Xiuli; Chen, Tongsheng; Wang, Yifei; Wang, Zhiping

Cellular damage such as oxidation and lipid peroxidation, and DNA damage induced by free-radicals like reactive oxygen species, has been implicated in several diseases. Radicals generated by 2,2-azobis (2-amidino-propane) dihydrochloride (AAPH) are similar to physiologically active ones. In this study we found that polydatin, a resveratrol natural precursor derived from many sources, has the capacity of free radical scavenging and antioxidative damage. Using free radical scavenging assays, the IC50 values of polydatin were 19.25 and 5.29 μg/ml with the DPPH and the ABTS assay, respectively, and 0.125 mg ferrous sulfate/1 mg polydatin with the FRAP assay. With the AAPH-induced oxidative injury cell model assay, polydatin showed a strong protective effect against the human liver tumor HepG2 cell oxidative stress damage. These results indicate that the antioxidant properties of polydatin have great potential for use as an alternative to more toxic synthetic antioxidants as an additive in food, cosmetics and pharmaceutical preparations for the treatment of oxidative diseases.

The effect of amylose content and level of oxidation on the structural changes of acetylated corn starch and generation of free radicals.

PubMed

Pietrzyk, Sławomir; Fortuna, Teresa; Łabanowska, Maria; Juszczak, Lesław; Gałkowska, Dorota; Bączkowicz, Małgorzata; Kurdziel, Magdalena

2018-02-01

This study was aimed at determining the effect of starch oxidation on its acetylation, structure of starch granules, and generation of free radicals. Corn and waxy corn starches were oxidised by NaClO applied in doses of 10, 20, and 30g Cl/kg of starch, and then acetylated using acetic acid anhydride. The carboxyl, carbonyl, acetyl groups were determined in modified starches. Structural properties of starch granules were evaluated based on molecular weight distribution, gelatinisation, crystallinity, specific surface, intrinsic viscosity. EPR measurements were carried out to establish starch susceptibility to UV irradiation induced generation of free radicals. It was found that the number of carbon centered radicals was dependent on the kind of starch and its chemical modification. Study results allowed concluding that the applied modifications contributed to significant changes in starch granules that were determined not only by the amylose content of starch but also by the degree of its oxidation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Betanodavirus Induces Oxidative Stress-Mediated Cell Death That Prevented by Anti-Oxidants and Zfcatalase in Fish Cells

PubMed Central

Chang, Chih-Wei; Su, Yu-Chin; Her, Guor-Mour; Ken, Chuian-Fu; Hong, Jiann-Ruey

2011-01-01

The role of oxidative stress in the pathogenesis of RNA nervous necrosis virus infection is still unknown. Red-spotted grouper nervous necrosis virus (RGNNV) induced free radical species (ROS) production at 12–24 h post-infection (pi; early replication stage) in fish GF-1 cells, and then at middle replication stage (24–48 h pi), this ROS signal may upregulate some expressions of the anti-oxidant enzymes Cu/Zn SOD and catalase, and eventually expression of the transcription factor Nrf2. Furthermore, both antioxidants diphenyliodonium and N-acetylcysteine or overexpression of zebrafish catalase in GF-1 cells also reduced ROS production and protected cells for enhancing host survival rate due to RGNNV infection. Furthermore, localization of ROS production using esterase activity and Mitotracker staining assays found that the ROS generated can affect mitochondrial morphology changes and causes ΔΨ loss, both of which can be reversed by antioxidant treatment. Taken together, our data suggest that RGNNV induced oxidative stress response for playing dual role that can initiate the host oxidative stress defense system to upregulate expression of antioxidant enzymes and induces cell death via disrupting the mitochondrial morphology and inducing ΔΨ loss, which can be reversed by anti-oxidants and zfcatalase, which provide new insight into betanodavirus-induced ROS-mediated pathogenesis. PMID:21991373

Isoprenoid Alcohols are Susceptible to Oxidation with Singlet Oxygen and Hydroxyl Radicals.

PubMed

Komaszylo Née Siedlecka, Joanna; Kania, Magdalena; Masnyk, Marek; Cmoch, Piotr; Lozinska, Iwona; Czarnocki, Zbigniew; Skorupinska-Tudek, Karolina; Danikiewicz, Witold; Swiezewska, Ewa

2016-02-01

Isoprenoids, as common constituents of all living cells, are exposed to oxidative agents--reactive oxygen species, for example, singlet oxygen or hydroxyl radicals. Despite this fact, products of oxidation of polyisoprenoids have never been characterized. In this study, chemical oxidation of isoprenoid alcohols (Prenol-2 and -10) was performed using singlet oxygen (generated in the presence of hydrogen peroxide/molybdate or upon photochemical reaction in the presence of porphyrin), oxygen (formed upon hydrogen peroxide dismutation) or hydroxyl radical (generated by the hydrogen peroxide/sonication, UV/titanium dioxide or UV/hydrogen peroxide) systems. The structure of the obtained products, hydroxy-, peroxy- and heterocyclic derivatives, was studied with the aid of mass spectrometry (MS) and nuclear magnetic resonance (NMR) methods. Furthermore, mass spectrometry with electrospray ionization appeared to be a useful analytical tool to detect the products of oxidation of isoprenoids (ESI-MS analysis), as well as to establish their structure on the basis of the fragmentation spectra of selected ions (ESI-MS/MS analysis). Taken together, susceptibility of polyisoprenoid alcohols to various oxidizing agents was shown for the first time.

Redox- and non-redox-metal-induced formation of free radicals and their role in human disease.

PubMed

Valko, Marian; Jomova, Klaudia; Rhodes, Christopher J; Kuča, Kamil; Musílek, Kamil

2016-01-01

Transition metal ions are key elements of various biological processes ranging from oxygen formation to hypoxia sensing, and therefore, their homeostasis is maintained within strict limits through tightly regulated mechanisms of uptake, storage and secretion. The breakdown of metal ion homeostasis can lead to an uncontrolled formation of reactive oxygen species, ROS (via the Fenton reaction, which produces hydroxyl radicals), and reactive nitrogen species, RNS, which may cause oxidative damage to biological macromolecules such as DNA, proteins and lipids. An imbalance between the formation of free radicals and their elimination by antioxidant defense systems is termed oxidative stress. Most vulnerable to free radical attack is the cell membrane which may undergo enhanced lipid peroxidation, finally producing mutagenic and carcinogenic malondialdehyde and 4-hydroxynonenal and other exocyclic DNA adducts. While redox-active iron (Fe) and copper (Cu) undergo redox-cycling reactions, for a second group of redox-inactive metals such as arsenic (As) and cadmium (Cd), the primary route for their toxicity is depletion of glutathione and bonding to sulfhydryl groups of proteins. While arsenic is known to bind directly to critical thiols, other mechanisms, involving formation of hydrogen peroxide under physiological conditions, have been proposed. Redox-inert zinc (Zn) is the most abundant metal in the brain and an essential component of numerous proteins involved in biological defense mechanisms against oxidative stress. The depletion of zinc may enhance DNA damage by impairing DNA repair mechanisms. Intoxication of an organism by arsenic and cadmium may lead to metabolic disturbances of redox-active copper and iron, with the occurrence of oxidative stress induced by the enhanced formation of ROS/RNS. Oxidative stress occurs when excessive formation of ROS overwhelms the antioxidant defense system, as is maintained by antioxidants such as ascorbic acid, alpha

Chondracanthus tenellus (Harvey) hommersand extract protects the human keratinocyte cell line by blocking free radicals and UVB radiation-induced cell damage.

PubMed

Piao, Mei Jing; Hyun, Yu Jae; Oh, Tae-Heon; Kang, Hee Kyoung; Yoo, Eun Sook; Koh, Young Sang; Lee, Nam Ho; Suh, In Soo; Hyun, Jin Won

2012-12-01

The aim of this study was to investigate the protective effects of the ethanol extract of the red algae Chondracanthus tenellus (Harvey) Hommersand (CTE) on cultured human keratinocyte cell line. The cellular protection conferred by CTE was evidenced by the ability of the extract to absorb ultraviolet B (UVB; 280-320 nm) and to scavenge the radical 1,1-diphenyl-2-picrylhydrazyl, as well as intracellular reactive oxygen species (ROS), induced by either hydrogen peroxide (H(2)O(2)) or UVB radiation. In addition, both superoxide anion generated by the xanthine/xanthine oxidase system and hydroxyl radical generated by the Fenton reaction (FeSO(4) + H(2)O(2)) were scavenged by CTE, as confirmed using electron spin resonance spectrometry. In the human keratinocyte cell line, CTE decreased the degree of injury resulting from UVB-induced oxidative stress to lipids, proteins, and DNA. CTE-treated cells also showed a reduction in UVB-induced apoptosis, as exemplified by fewer apoptotic bodies and less DNA fragmentation. Taken together, these results suggest that CTE confers protection on the human keratinocyte cell line against UVB-induced oxidative stress by absorbing UVB ray and scavenging ROS, thereby reducing injury to cellular constituents.

One-electron oxidation of electronically diverse manganese(III) and nickel(II) salen complexes: transition from localized to delocalized mixed-valence ligand radicals.

PubMed

Kurahashi, Takuya; Fujii, Hiroshi

2011-06-01

Ligand radicals from salen complexes are unique mixed-valence compounds in which a phenoxyl radical is electronically linked to a remote phenolate via a neighboring redox-active metal ion, providing an opportunity to study electron transfer from a phenolate to a phenoxyl radical mediated by a redox-active metal ion as a bridge. We herein synthesize one-electron-oxidized products from electronically diverse manganese(III) salen complexes in which the locus of oxidation is shown to be ligand-centered, not metal-centered, affording manganese(III)-phenoxyl radical species. The key point in the present study is an unambiguous assignment of intervalence charge transfer bands by using nonsymmetrical salen complexes, which enables us to obtain otherwise inaccessible insight into the mixed-valence property. A d(4) high-spin manganese(III) ion forms a Robin-Day class II mixed-valence system, in which electron transfer is occurring between the localized phenoxyl radical and the phenolate. This is in clear contrast to a d(8) low-spin nickel(II) ion with the same salen ligand, which induces a delocalized radical (Robin-Day class III) over the two phenolate rings, as previously reported by others. The present findings point to a fascinating possibility that electron transfer could be drastically modulated by exchanging the metal ion that bridges the two redox centers. © 2011 American Chemical Society

Metallothionein blocks oxidative DNA damage induced by acute inorganic arsenic exposure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qu, Wei, E-mail: qu@niehs.nih.gov; Waalkes, Michael P.

We studied how protein metallothionein (MT) impacts arsenic-induced oxidative DNA damage (ODD) using cells that poorly express MT (MT-I/II double knockout embryonic cells; called MT-null cells) and wild-type (WT) MT competent cells. Arsenic (as NaAsO{sub 2}) was less cytolethal over 24 h in WT cells (LC{sub 50} = 11.0 ± 1.3 μM; mean ± SEM) than in MT-null cells (LC{sub 50} = 5.6 ± 1.2 μM). ODD was measured by the immuno-spin trapping method. Arsenic (1 or 5 μM; 24 h) induced much less ODD in WT cells (121% and 141% of control, respectively) than in MT-null cells (202% andmore » 260%). In WT cells arsenic caused concentration-dependent increases in MT expression (transcript and protein), and in the metal-responsive transcription factor-1 (MTF-1), which is required to induce the MT gene. In contrast, basal MT levels were not detectable in MT-null cells and unaltered by arsenic exposure. Transfection of MT-I gene into the MT-null cells markedly reduced arsenic-induced ODD levels. The transport genes, Abcc1 and Abcc2 were increased by arsenic in WT cells but either showed no or very limited increases in MT-null cells. Arsenic caused increases in oxidant stress defense genes HO-1 and GSTα2 in both WT and MT-null cells, but to much higher levels in WT cells. WT cells appear more adept at activating metal transport systems and oxidant response genes, although the role of MT in these responses is unclear. Overall, MT protects against arsenic-induced ODD in MT competent cells by potential sequestration of scavenging oxidant radicals and/or arsenic. - Highlights: • Metallothionein blocks arsenic toxicity. • Metallothionein reduces arsenic-induced DNA damage. • Metallothionein may bind arsenic or radicals produced by arsenic.« less

Brand variation in oxidant production in mainstream cigarette smoke: Carbonyls and free radicals.

PubMed

Reilly, Samantha M; Goel, Reema; Trushin, Neil; Elias, Ryan J; Foulds, Jonathan; Muscat, Joshua; Liao, Jason; Richie, John P

2017-08-01

Oxidative stress/damage resulting from exposure to cigarette smoke plays a critical role in the development of tobacco-caused diseases. Carbonyls and free radicals are two major classes of oxidants in tobacco smoke. There is little information on the combined delivery of these oxidants across different cigarette brands; thus, we set out to measure and compare their levels in mainstream smoke from popular US cigarettes. Mainstream smoke from 28 different cigarette brands produced by smoking (FTC protocol) was analyzed for five important, abundant carbonyls, and levels were compared to previously determined free radical for the same brands. Overall, there were large variations (3- to 6-fold) in carbonyl levels across brands with total carbonyl levels ranging from 275 to 804 μg/cigarette, which persisted even after adjusting for ventilation. Individual carbonyl levels were highly correlated with each other (r 2 : 0.40-0.95, P < 0.003) except for formaldehyde. Both gas-phase (r 2 : 0.37, P = 0.006) and particulate-phase (r 2 : 0.27, P = 0.005) free radicals were correlated to total carbonyl content; however, this correlation disappeared after adjusting for ventilation. These data show that overall oxidant production varies widely by cigarette brand and the resulting difference in oxidant burden could potentially lead to differences in disease risk. Copyright © 2017 Elsevier Ltd. All rights reserved.

Hypochlorite-induced damage to DNA, RNA, and polynucleotides: formation of chloramines and nitrogen-centered radicals.

PubMed

Hawkins, Clare L; Davies, Michael J

2002-01-01

Stimulated monocytes and neutrophils generate hypochlorite (HOCl) via the release of the enzyme myeloperoxidase and hydrogen peroxide. HOCl is a key bactericidal agent, but can also damage host tissue. As there is a strong link between chronic inflammation and some cancers, we have investigated HOCl damage to DNA, RNA, and polynucleotides. Reaction of HOCl with these materials is shown to yield multiple semistable chloramines (RNHCl/RR'NCl), which are the major initial products, and account for 50-95% of the added HOCl. These chloramines decay by thermal and metal-ion catalyzed processes, to give nucleoside-derived, nitrogen-centered, radicals. The latter have been characterized by EPR spin trapping. The propensity for radical formation with polynucleotides is cytidine > adenosine = guanosine > uridine = thymidine. The rates of decay, and yield of radicals formed, are dependent on the nature of the nucleobase on which they are formed, with chloramines formed from ring heterocyclic amine groups being less stable than those formed on exocyclic amines (RNH2 groups). Evidence is presented for chlorine transfer from the former, kinetically favored, sites to the more thermodynamically favored exocyclic amines. EPR experiments have also provided evidence for the rapid addition of pyrimidine-derived nitrogen-centered radicals to other nucleobases to give dimers and the oxidation of DNA by radicals derived from preformed nucleoside chloramines. Direct reaction of HOCl with plasmid DNA gives rise to single- and double-strand breaks via chloramine-mediated reactions. Preformed nucleoside chloramines also induce plasmid cleavage, though this only occurs to a significant extent with unstable thymidine- and uridine-derived chloramines, where radical formation is rapid. Overall the data rationalize the preferential formation of chlorinated 2'-deoxycytidine and 2'-deoxyadenosine in DNA and suggest that DNA damage induced by HOCl, and preformed chloramines, occurs at sequence

Thiaflavan scavenges radicals and inhibits DNA oxidation: a story from the ferrocene modification.

PubMed

Lai, Hai-Wang; Liu, Zai-Qun

2014-06-23

4-Thiaflavan is a sulfur-substituted flavonoid with a benzoxathiin scaffold. The aim of this work is to compare abilities of sulfur and oxygen atom, hydroxyl groups, and ferrocene moiety at different positions of 4-thiaflavan to trap radicals and to inhibit DNA oxidation. It is found that abilities of thiaflavans to trap radicals and to inhibit DNA oxidation are increased in the presence of ferrocene moiety and are further improved by the electron-donating group attaching to thiaflavan skeleton. It can be concluded that the ferrocene moiety plays the major role for thiaflavans to be antioxidants even in the absence of phenolic hydroxyl groups. On the other hand, the antioxidant effectiveness of phenolic hydroxyl groups in thiaflavans can be improved by the electron-donating group. The influences of sulfur and oxygen atoms in thiaflavans on the antioxidant property of para-hydroxyl group exhibit different manners when the thiaflavans are used to trap radicals and to inhibit DNA oxidation. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

[The role of free radicals in the UV-induced skin damage. Photo-aging].

PubMed

Emri, Gabriella; Horkay, Irén; Remenyik, Eva

2006-04-23

The natural (intrinsic) ageing of the skin is enhanced by environmental factors (extrinsic ageing). One of the most important exogenous factors is the solar UV exposure, which results in photo-aging. Besides this, epidemiological and experimental data show a rapid increase in the incidence of human skin cancers, which is also in relation to the increased sunlight exposure of the skin. In the background of these processes there are cell biological effects, photochemical reactions, membrane receptor changes, lipid- and protein modifications, DNA-damage induced by UV. The qualities and quantities of them are wavelength dependent. The UVB photons are absorbed mostly by the DNA of the epidermal keratinocytes, therefore this spectrum is more relevant for photocarcinogenesis. The effect of UVA-irradiation is mainly manifested in the induction of free radicals, which have not only DNA-damaging, but also immunomodulating effect, which also can influence on tumour development. Furthermore, the free radicals cause dermal connective tissue damage as well via activating transcription factors, inducing matrix metalloproteinases, diminishing the procollagen I and fibrillin-1 synthesis. These processes are augmented by mitochondrial DNA mutations, protein oxidation, apoptosis induction. Therefore the enzymes neutralising free radicals and antioxidant molecules, respectively, have an important role in the defence mechanisms. In the therapy of photo-aging the local retinoids lived up to expectations, but the clinical effectiveness of antioxidant vitamins is lower than expected. The most important factor in the prevention of the photo-aging and photocarcinogenesis is the sun protection at present.

Lipid oxidation in bilayer liposomes induced by radicals from the surrounding water phases

NASA Astrophysics Data System (ADS)

Sprinz, H.; Brede, O.

1996-03-01

Some features of the radiation chemistry of organized assemblies were studied in aqueous dispersions of small unilamellar vesicles of egg yolk lecithin. The kinetics for the reaction of OH radicals with the bilayer was determined by pulse radiolysis. The conversion of OH radicals into N 3 radicals results in a remarkable reduction of the radiolysis of the hydrophylic part of the phospholipid and in an enhanced degradation of the most radiosensitive group of polyunsaturated fatty acid residues. The transverse proton relaxation of the choline head group is very sensitive to the radical attack on the bilayer.

Developments in laser-induced fluorescence spectroscopy for quantitative in situ measurements of free radicals in the troposphere

NASA Astrophysics Data System (ADS)

Heard, Dwayne

2015-04-01

Photo-oxidation in the troposphere is highly complex, being initiated by short lived free radical species, in the daytime dominated by the hydroxyl radical, OH. Chemical oxidation cycles, which also involve peroxy radicals (HO2 and RO2), remove natural or anthropogenic emissions (for example methane) and generate a range of secondary products, for example ozone, nitrogen dioxide, acidic and multifunctional organic species, and secondary organic aerosol, which impact on human health and climate. Owing to their short lifetime in the atmosphere, the abundance of radicals is determined solely by their rate of chemical production and loss, and not by transport. Field measurements of the concentrations of radicals and comparison with calculations using a numerical model therefore constitutes one of the very best ways to test whether the chemistry in each of these locations is understood and accurately represented in the model. Validation of the chemistry is important, as the predictions of climate and air quality models containing this chemistry are used to drive the formulation of policy and legislation. However, in situ measurements of radical species, owing to their very low abundance (often sub part per trillion) and short lifetimes (< 1 second for OH), remain extremely challenging. Laser-induced fluorescence spectroscopy (LIF) has enjoyed considerable success worldwide for the quantitative detection of radicals in a range of environments. The radicals are either excited directly by the laser (e.g. OH, IO) or are first chemically converted to OH prior to detection (e.g. HO2, RO2). Recent developments in the LIF technique for radical detection, which uses a supersonic expansion with detection at low pressure and multi kHz pulse repetition rate tunable laser systems, will be discussed, together with calibration methods to make signals absolute, and identification of potential interferences. LIF instruments have been operated on ground, ship and aircraft platforms at a

In vitro electron paramagnetic resonance characterization of free radicals: relevance to exercise-induced lipid peroxidation and implications of ascorbate prophylaxis.

PubMed

Davison, Gareth W; Ashton, Tony; Davies, Bruce; Bailey, Damian M

2008-04-01

This study tested the hypothesis that exercise-induced oxidative stress is caused by free radical-mediated damage to polyunsaturated fatty acids (PUFA) which can be prevented following ascorbate prophylaxis. Hyperfine coupling constants (HCC) of alpha-phenyl-tert-butylnitrone (PBN)-adducts were measured via room temperature electron paramagnetic resonance (EPR) spectroscopy in the venous blood of 12 subjects at rest and following maximal exercise during a randomized double-blind placebo-controlled trial and compared to those observed following room-air incubation (2 h at 37 degrees C) of L-alpha-phosphatidycholine, linoleic acid, alpha-linolenic acid and arachidonic acid. All adducts exhibited similar HCC [a(N) 13.6 Gauss (G) and a beta(H) 1.8 G] with the exception of L-alpha-phosphatidycholine [a(N1)=13.4 G, a beta(H1)=1.6 G (37%) and a(N2)=14.9 G, a beta(H2)=0.3 G (63%)] consistent with the trapping of lipid-derived alkoxyl and oleate radicals, respectively. Ascorbate pre-treatment ablated radical formation in both systems. These findings identify circulating PUFA as a potential source of secondary radicals that are capable of initiating oxidative stress in the exercising human.

Effect of Sophora subprosrate polysaccharide on oxidative stress induced by PCV2 infection in RAW264.7 cells.

PubMed

Su, Zi-Jie; Wei, Ying-Yi; Yin, Dan; Shuai, Xue-Hong; Zeng, Yun; Hu, Ting-Jun

2013-11-01

In this study, an oxidative stress model was first developed in a mouse macrophage cell line (RAW264.7 cells) by infecting the cells with porcine circovirus type 2 (PCV2). The regulatory effect of Sophora subprosrate polysaccharide (SSP) on PCV2-induced oxidative stress was investigated. The results showed that after infection with PCV2, reactive oxygen species (ROS) and nitric oxide (NO) production, myeloperoxidase (MPO) activity, and inducible nitric oxide synthase (iNOS) expression were significantly increased. Meanwhile, the ratio of reduced glutathione to oxidized glutathione (GSH/GSSG) and hydroxyl radical prevention capacity were greatly reduced. These data indicate successful creation of an oxidative stress model in RAW264.7 cells. A dramatic decrease in cell viability was observed in the cells exposed to oxidative stress compared to the control. When the cells were treated with SSP in concentrations of 100, 200 or 400 μg/mL post PCV2 infection, an increase in the GSH/GSSG ratio and hydroxyl radical prevention capacity was observed. We also observed decreased ROS and NO production, MPO activity, and iNOS expression in the infected cells. Our results demonstrated that PCV2 infection was able to induce oxidative stress in RAW264.7 cells and that SSP could reduce the negative effects resulting from the PCV2 infection. Copyright © 2013 Elsevier B.V. All rights reserved.

Evaluation of Cassia tora Linn. against Oxidative Stress-induced DNA and Cell Membrane Damage

PubMed Central

Kumar, R Sunil; Narasingappa, Ramesh Balenahalli; Joshi, Chandrashekar G; Girish, Talakatta K; Prasada Rao, Ummiti JS; Danagoudar, Ananda

2017-01-01

Objective: The present study aims to evaluate antioxidants and protective role of Cassia tora Linn. against oxidative stress-induced DNA and cell membrane damage. Materials and Methods: The total and profiles of flavonoids were identified and quantified through reversed-phase high-performance liquid chromatography. In vitro antioxidant activity was determined using standard antioxidant assays. The protective role of C. tora extracts against oxidative stress-induced DNA and cell membrane damage was examined by electrophoretic and scanning electron microscopic studies, respectively. Results: The total flavonoid content of CtEA was 106.8 ± 2.8 mg/g d.w.QE, CtME was 72.4 ± 1.12 mg/g d.w.QE, and CtWE was 30.4 ± 0.8 mg/g d.w.QE. The concentration of flavonoids present in CtEA in decreasing order: quercetin >kaempferol >epicatechin; in CtME: quercetin >rutin >kaempferol; whereas, in CtWE: quercetin >rutin >kaempferol. The CtEA inhibited free radical-induced red blood cell hemolysis and cell membrane morphology better than CtME as confirmed by a scanning electron micrograph. CtEA also showed better protection than CtME and CtWE against free radical-induced DNA damage as confirmed by electrophoresis. Conclusion: C. tora contains flavonoids and inhibits oxidative stress and can be used for many health benefits and pharmacotherapy. PMID:28584491

Mechanisms leading to oligomers and SOA through aqueous photooxidation: insights from OH radical oxidation of acetic acid and methylglyoxal

NASA Astrophysics Data System (ADS)

Tan, Y.; Lim, Y. B.; Altieri, K. E.; Seitzinger, S. P.; Turpin, B. J.

2012-01-01

Previous experiments have demonstrated that the aqueous OH radical oxidation of methylglyoxal produces low volatility products including pyruvate, oxalate and oligomers. These products are found predominantly in the particle phase in the atmosphere, suggesting that methylglyoxal is a precursor of secondary organic aerosol (SOA). Acetic acid plays a central role in the aqueous oxidation of methylglyoxal and it is a ubiquitous product of gas phase photochemistry, making it a potential "aqueous" SOA precursor in its own right. However, the fate of acetic acid upon aqueous-phase oxidation is not well understood. In this research, acetic acid (20 μM-10 mM) was oxidized by OH radicals, and pyruvic acid and methylglyoxal experimental samples were analyzed using new analytical methods, in order to better understand the formation of SOA from acetic acid and methylglyoxal. Glyoxylic, glycolic, and oxalic acids formed from acetic acid and OH radicals. In contrast to the aqueous OH radical oxidation of methylglyoxal, the aqueous OH radical oxidation of acetic acid did not produce succinic acid and oligomers. This suggests that the methylgloxal-derived oligomers do not form through the acid catalyzed esterification pathway proposed previously. Using results from these experiments, radical mechanisms responsible for oligomer formation from methylglyoxal oxidation in clouds and wet aerosols are proposed. The importance of acetic acid/acetate as an SOA precursor is also discussed. We hypothesize that this and similar chemistry is central to the daytime formation of oligomers in wet aerosols.

Lithium formate for EPR dosimetry: radiation-induced radical trapping at low temperatures.

PubMed

Krivokapić, André; Aalbergsjø, Siv G; De Cooman, Hendrik; Hole, Eli Olaug; Nelson, William H; Sagstuen, Einar

2014-05-01

Radiation-induced primary radicals in lithium formate. A material used in EPR dosimetry have been studied using electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR) and ENDOR-Induced EPR (EIE) techniques. In this study, single crystals were X irradiated at 6-8 K and radical formation at these and higher temperatures were investigated. Periodic density functional theory calculations were used to assist in assigning the radical structures. Mainly two radicals are present at 6 K, the well-known CO2(•-) radical and a protonated electron-gain product. Hyperfine coupling tensors for proton and lithium interactions were obtained for these two radicals and show that the latter radical exists in four conformations with various degrees of bending at the radical center. Pairs of CO2(•-) radicals were also observed and the tensor for the electron-electron dipolar coupling was determined for the strongest coupled pair, which exhibited the largest spectral intensity. Upon warming, both the radical pairs and the reduction product decay, the latter apparently by a transient species. Above 200 K the EPR spectrum was mainly due to the CO2(•-) (mono) radicals, which were previously characterized as the dominant species present at room temperature and which account for the dosimetric EPR signal.

Hydroxyl radical mediates cisplatin-induced apoptosis in human hair follicle dermal papilla cells and keratinocytes through Bcl-2-dependent mechanism.

PubMed

Luanpitpong, Sudjit; Nimmannit, Ubonthip; Chanvorachote, Pithi; Leonard, Stephen S; Pongrakhananon, Varisa; Wang, Liying; Rojanasakul, Yon

2011-08-01

Induction of massive apoptosis of hair follicle cells by chemotherapy has been implicated in the pathogenesis of chemotherapy-induced alopecia (CIA), but the underlying mechanisms of regulation are not well understood. The present study investigated the apoptotic effect of cisplatin in human hair follicle dermal papilla cells and HaCaT keratinocytes, and determined the identity and role of specific reactive oxygen species (ROS) involved in the process. Treatment of the cells with cisplatin induced ROS generation and a parallel increase in caspase activation and apoptotic cell death. Inhibition of ROS generation by antioxidants inhibited the apoptotic effect of cisplatin, indicating the role of ROS in the process. Studies using specific ROS scavengers further showed that hydroxyl radical, but not hydrogen peroxide or superoxide anion, is the primary oxidative species responsible for the apoptotic effect of cisplatin. Electron spin resonance studies confirmed the formation of hydroxyl radicals induced by cisplatin. The mechanism by which hydroxyl radical mediates the apoptotic effect of cisplatin was shown to involve down-regulation of the anti-apoptotic protein Bcl-2 through ubiquitin-proteasomal degradation. Bcl-2 was also shown to have a negative regulatory role on hydroxyl radical. Together, our results indicate an essential role of hydroxyl radical in cisplatin-induced cell death of hair follicle cells through Bcl-2 regulation. Since CIA is a major side effect of cisplatin and many other chemotherapeutic agents with no known effective treatments, the knowledge gained from this study could be useful in the design of preventive treatment strategies for CIA through localized therapy without compromising the chemotherapy efficacy.

Effects of ozone oxidative preconditioning on radiation-induced organ damage in rats

PubMed Central

Gultekin, Fatma Ayca; Bakkal, Bekir Hakan; Guven, Berrak; Tasdoven, Ilhan; Bektas, Sibel; Can, Murat; Comert, Mustafa

2013-01-01

Because radiation-induced cellular damage is attributed primarily to harmful effects of free radicals, molecules with direct free radical scavenging properties are particularly promising as radioprotectors. It has been demonstrated that controlled ozone administration may promote an adaptation to oxidative stress, preventing the damage induced by reactive oxygen species. Thus, we hypothesized that ozone would ameliorate oxidative damage caused by total body irradiation (TBI) with a single dose of 6 Gy in rat liver and ileum tissues. Rats were randomly divided into groups as follows: control group; saline-treated and irradiated (IR) groups; and ozone oxidative preconditioning (OOP) and IR groups. Animals were exposed to TBI after a 5-day intraperitoneal pretreatment with either saline or ozone (1 mg/kg/day). They were decapitated at either 6 h or 72 h after TBI. Plasma, liver and ileum samples were obtained. Serum AST, ALT and TNF-α levels were elevated in the IR groups compared with the control group and were decreased after treatment with OOP. TBI resulted in a significant increase in the levels of MDA in the liver and ileal tissues and a decrease of SOD activities. The results demonstrated that the levels of MDA liver and ileal tissues in irradiated rats that were pretreated with ozone were significantly decreased, while SOD activities were significantly increased. OOP reversed all histopathological alterations induced by irradiation. In conclusion, data obtained from this study indicated that ozone could increase the endogenous antioxidant defense mechanism in rats and there by protect the animals from radiation-induced organ toxicity. PMID:22915786

Propofol attenuates oxidant-induced acute lung injury in an isolated perfused rabbit-lung model.

PubMed

Yumoto, Masato; Nishida, Osamu; Nakamura, Fujio; Katsuya, Hirotada

2005-01-01

Reactive oxygen species have been strongly implicated in the pathogenesis of acute lung injury (ALI). Some animal studies suggest that free radical scavengers inhibit the onset of oxidant-induced ALI. Propofol (2,6-diisopropylphenol) is chemically similar to phenol-based free radical scavengers such as the endogenous antioxidant vitamin E. Both in vivo and in vitro studies have suggested that propofol has antioxidant potential. We hypothesized that propofol may attenuate ALI by acting as a free-radical scavenger. We investigated the effects of propofol on oxidant-induced ALI induced by purine and xanthine oxidase (XO), in isolated perfused rabbit lung, in two series of experiments. In series 1, we examined the relationship between the severity of ALI and the presence of hydrogen peroxide (H2O2). In series 2, we evaluated the effects of propofol on attenuating ALI and the dose dependence of these effects. The lungs were perfused for 90 min, and we evaluated the effects on the severity of ALI by monitoring the pulmonary capillary filtration coefficient (Kfc), pulmonary arterial pressure (Ppa), and the pulmonary capillary hydrostatic pressure (Ppc). In series 1, treatment with catalase (an H2O2 scavenger) prior to the addition of purine and XO resulted in complete prevention of ALI, suggesting that H2O2 may be involved closely in the pathogenesis of ALI. In series 2, pretreatment with propofol at concentrations in excess of 0.5 mM significantly inhibited the increases in the Kfc values, and that in excess of 0.75 mM significantly inhibited the increase in the Ppa values. Propofol attenuates oxidant-induced ALI in an isolated perfused rabbit lung model, probably due to its antioxidant action.

Mechanisms leading to oligomers and SOA through aqueous photooxidation: insights from OH radical oxidation of acetic acid

NASA Astrophysics Data System (ADS)

Tan, Y.; Lim, Y. B.; Altieri, K. E.; Seitzinger, S. P.; Turpin, B. J.

2011-06-01

Previous experiments have demonstrated that the aqueous OH radical oxidation of methylglyoxal produces low volatility products including oxalate and oligomers. These products are found predominantly in the particle phase in the atmosphere, suggesting that methylglyoxal is a precursor of secondary organic aerosol (SOA). Acetic acid is an important intermediate in aqueous methylglyoxal oxidation and a ubiquitous product of gas phase photochemistry, making it a potential "aqueous" SOA precursor in its own right. Altieri et al. (2008) proposed that acetic acid was the precursor of oligoesters observed in methylglyoxal oxidation. However, the fate of acetic acid upon aqueous-phase oxidation is not well understood. In this research, acetic acid at concentrations relevant to atmospheric waters (20 μM-10 mM) was oxidized by OH radical. Products were analyzed by ion chromatography (IC), electrospray ionization mass spectrometry (ESI-MS), and IC-ESI-MS. The formation of glyoxylic, glycolic, and oxalic acids were observed. In contrast to methylglyoxal oxidation, succinic acid and oligomers were not detected. Using results from these and methylglyoxal + OH radical experiments, radical mechanisms responsible for oligomer formation from methylglyoxal oxidation in clouds and wet aerosols are proposed. The importance of acetic acid/acetate as an SOA precursor is also discussed. We hypothesize that this and similar chemistry is central to the daytime formation of oligomers in wet aerosols.

Hypochlorite-induced damage to proteins: formation of nitrogen-centred radicals from lysine residues and their role in protein fragmentation.

PubMed Central

Hawkins, C L; Davies, M J

1998-01-01

Stimulated monocytes and neutrophils generate hypochlorite (HOCl) via the release of the enzyme myeloperoxidase and hydrogen peroxide. HOCl damages proteins by reaction with amino acid side-chains or backbone cleavage. Little information is available about the mechanisms and intermediates involved in these reactions. EPR spin trapping has been employed to identify radicals on proteins, peptides and amino acids after treatment with HOCl. Reaction with HOCl gives both high- and low-molecular-mass nitrogen-centred, protein-derived radicals; the yield of the latter increases with both higher HOCl:protein ratios and enzymic digestion. These radicals, which arise from lysine side-chain amino groups, react with ascorbate, glutathione and Trolox. Reaction of HOCl-treated proteins with excess methionine eliminates radical formation, which is consistent with lysine-derived chloramines (via homolysis of N-Cl bonds) being the radical source. Incubation of HOCl-treated proteins, after removal of excess oxidant, gives rise to both nitrogen-centred radicals, over a period of hours, and time-dependent fragmentation of the protein. Treatment with excess methionine or antioxidants (Trolox, ascorbate, glutathione) protects against fragmentation; urate and bilirubin do not. Chloramine formation and nitrogen-centred radicals are therefore key species in HOCl-induced protein fragmentation. PMID:9620862

The effect of alpha-tocopherol on the oxidation and free radical decay in irradiated UHMWPE.

PubMed

Oral, Ebru; Rowell, Shannon L; Muratoglu, Orhun K

2006-11-01

We developed a radiation cross-linked ultra-high molecular weight polyethylene (UHMWPE) stabilized with alpha-tocopherol (Vitamin E) as a bearing material in total joint replacements. The stabilizing effect of alpha-tocopherol on free radical reactions in UHMWPE is not well understood. We investigated the effect of alpha-tocopherol on the oxidation and transformation of residual free radicals during real-time aging of alpha-tocopherol-doped, irradiated UHMWPE (alphaTPE) and irradiated UHMWPE (control). Samples were aged at 22 degrees C (room temperature) in air, at 40 degrees C in air and at 40 degrees C in water for 7 months. During the first month, alphaTPE showed some oxidation at the surface, which stayed constant thereafter. Control exhibited substantial oxidation in the subsurface region, which increased with time. The alkyl/allyl free radicals transformed to oxygen centered ones in both materials; this transformation occurred faster in alpha-TPE. In summary, the real-time oxidation behavior of alpha-TPE was consistent with that observed using accelerated aging methods. This new UHMWPE is oxidation resistant and is expected to maintain its properties in the long term.

TREATMENT OF PAHS AND PCBS USING SULFATE RADICAL-BASED OXIDATION PROCESSES

EPA Science Inventory

Polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in aquatic systems pose serious threat to public health due to their toxicity and potential carcinogenicity [1]. Sulfate radical-based oxidation processes can be effectively used for degradation of these...

DESTRUCTION OF PAHS AND PCBS IN WATER USING SULFATE RADICAL-BASED CATALYTIC ADVANCED OXIDATION PROCESSES

EPA Science Inventory

A new class of advanced oxidation processes (AOPs) based on sulfate radicals is being tested for the degradation of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in aqueous solution. These AOPs are based on the generation of sulfate radicals through...

The 2013 Discovery Award from the Society for Free Radical Biology and Medicine: Selected Discoveries from the Butterfield Laboratory of Oxidative Stress and Its Sequelae in Brain in Cognitive Disorders Exemplified by Alzheimer Disease and Chemotherapy Induced Cognitive Impairment

PubMed Central

Butterfield, D. Allan

2014-01-01

This retrospective review on discoveries of the roles of oxidative stress in brain of subjects with Alzheimer disease (AD) and animal models thereof as well as brain from animal models of chemotherapy induced cognitive impairment (CICI) results from the author receiving the 2013 Discovery Award from the Society for Free Radical Biology and Medicine. The paper reviews our laboratory's discovery of: protein oxidation and lipid peroxidation in AD brain regions rich in amyloid β-peptide (Aβ) but not in Aβ-poor cerebellum; redox proteomics as a means to identify oxidatively modified brain proteins in AD and its earlier forms that are consistent with the pathology, biochemistry, and clinical presentation of these disorders; how Aβ in in vivo, ex vivo, and in vitro studies can lead to oxidative modification of key proteins that also are oxidatively modified in AD brain; the role of the single methionine residue of Aβ(1-42) in these processes; and some of the potential mechanisms in the pathogenesis and progression of AD. CICI affects a significant fraction of the 14 million American cancer survivors, and due to diminished cognitive function, reduced quality of life of the persons with CICI (called “chemobrain” by patients) often results. A proposed mechanism for CICI employed the prototypical ROS-generating and non-blood brain barrier (BBB)-penetrating chemotherapeutic agent doxorubicin (Dox, also called adriamycin, ADR). Because of the quinone moiety within the structure of Dox, this agent undergoes redox cycling to produce superoxide free radical peripherally. This, in turn, leads to oxidative modification of the key plasma protein, Apolipoprotein A1 (ApoA1). Oxidized ApoA1 leads to elevated peripheral TNFα, a pro-inflammatory cytokine that crosses the BBB to induce oxidative stress in brain parenchyma that affects negatively brain mitochondria. This subsequently leads to apoptotic cell death resulting in CICI. This review outlines aspects of CICI consistent

Nanoparticle-induced oxidation of corona proteins initiates an oxidative stress response in cells†

PubMed Central

Jayaram, Dhanya T.; Runa, Sabiha; Kemp, Melissa L.

2017-01-01

Titanium dioxide nanoparticles (TiO2 NPs), used as pigments and photocatalysts, are ubiquitous in our daily lives. Previous work has observed cellular oxidative stress in response to the UV-excitation of photocatalytic TiO2 NPs. In comparison, most human exposure to TiO2 NPs takes place in the dark, in the lung following inhalation or in the gut following consumption of TiO2 NP food pigment. Our spectroscopic characterization shows that both photocatalytic and food grade TiO2 NPs, in the dark, generate low levels of reactive oxygen species (ROS), specifically hydroxyl radicals and superoxides. These ROS oxidize serum proteins that form a corona of proteins on the NP surface. This protein layer is the interface between the NP and the cell. An oxidized protein corona triggers an oxidative stress response, detected with PCR and western blotting. Surface modification of TiO2 NPs to increase or decrease surface defects correlates with ROS generation and oxidative stress, suggesting that NP surface defects, likely oxygen vacancies, are the underlying cause of TiO2 NP-induced oxidative stress. PMID:28537609

Radiation-induced oxidative damage to the DNA-binding domain of the lactose repressor

PubMed Central

Gillard, Nathalie; Goffinont, Stephane; Buré, Corinne; Davidkova, Marie; Maurizot, Jean-Claude; Cadene, Martine; Spotheim-Maurizot, Melanie

2007-01-01

Understanding the cellular effects of radiation-induced oxidation requires the unravelling of key molecular events, particularly damage to proteins with important cellular functions. The Escherichia coli lactose operon is a classical model of gene regulation systems. Its functional mechanism involves the specific binding of a protein, the repressor, to a specific DNA sequence, the operator. We have shown previously that upon irradiation with γ-rays in solution, the repressor loses its ability to bind the operator. Water radiolysis generates hydroxyl radicals (OH· radicals) which attack the protein. Damage of the repressor DNA-binding domain, called the headpiece, is most likely to be responsible of this loss of function. Using CD, fluorescence spectroscopy and a combination of proteolytic cleavage with MS, we have examined the state of the irradiated headpiece. CD measurements revealed a dose-dependent conformational change involving metastable intermediate states. Fluorescence measurements showed a gradual degradation of tyrosine residues. MS was used to count the number of oxidations in different regions of the headpiece and to narrow down the parts of the sequence bearing oxidized residues. By calculating the relative probabilities of reaction of each amino acid with OH· radicals, we can predict the most probable oxidation targets. By comparing the experimental results with the predictions we conclude that Tyr7, Tyr12, Tyr17, Met42 and Tyr47 are the most likely hotspots of oxidation. The loss of repressor function is thus correlated with chemical modifications and conformational changes of the headpiece. PMID:17263689

Exercise-Induced Oxidative Stress Responses in the Pediatric Population

PubMed Central

Avloniti, Alexandra; Chatzinikolaou, Athanasios; Deli, Chariklia K.; Vlachopoulos, Dimitris; Gracia-Marco, Luis; Leontsini, Diamanda; Draganidis, Dimitrios; Jamurtas, Athanasios Z.; Mastorakos, George; Fatouros, Ioannis G.

2017-01-01

Adults demonstrate an upregulation of their pro- and anti-oxidant mechanisms in response to acute exercise while systematic exercise training enhances their antioxidant capacity, thereby leading to a reduced generation of free radicals both at rest and in response to exercise stress. However, less information exists regarding oxidative stress responses and the underlying mechanisms in the pediatric population. Evidence suggests that exercise-induced redox perturbations may be valuable in order to monitor exercise-induced inflammatory responses and as such training overload in children and adolescents as well as monitor optimal growth and development. The purpose of this review was to provide an update on oxidative stress responses to acute and chronic exercise in youth. It has been documented that acute exercise induces age-specific transient alterations in both oxidant and antioxidant markers in children and adolescents. However, these responses seem to be affected by factors such as training phase, training load, fitness level, mode of exercise etc. In relation to chronic adaptation, the role of training on oxidative stress adaptation has not been adequately investigated. The two studies performed so far indicate that children and adolescents exhibit positive adaptations of their antioxidant system, as adults do. More studies are needed in order to shed light on oxidative stress and antioxidant responses, following acute exercise and training adaptations in youth. Available evidence suggests that small amounts of oxidative stress may be necessary for growth whereas the transition to adolescence from childhood may promote maturation of pro- and anti-oxidant mechanisms. Available evidence also suggests that obesity may negatively affect basal and exercise-related antioxidant responses in the peripubertal period during pre- and early-puberty. PMID:28106721

Degradation of polyvinyl alcohol (PVA) by UV/chlorine oxidation: Radical roles, influencing factors, and degradation pathway.

PubMed

Ye, Bei; Li, Yue; Chen, Zhuo; Wu, Qian-Yuan; Wang, Wen-Long; Wang, Ting; Hu, Hong-Ying

2017-11-01

Polyvinyl alcohol (PVA) is widely used in industry but is difficult to degrade. In this study, the synergistic effect of UV irradiation and chlorination on degradation of PVA was investigated. UV irradiation or chlorination alone did not degrade PVA. By contrast, UV/chlorine oxidation showed good efficiency for PVA degradation via generation of active free radicals, such as OH and Cl. The relative importance of these two free radicals in the oxidation process was evaluated, and it was shown that OH contributed more to PVA degradation than Cl did. The degradation of PVA followed pseudo first order kinetics. The rate constant k increased linearly from 0 min -1 to 0.3 min -1 with increasing chlorine dosage in range of 0 mg/L to 20 mg/L. However, when the chlorine dosage was increased above 20 mg/L, scavenging effect of free radicals occurred, and the degradation efficiency of PVA did not increase much more. Acidic media increased the degradation efficiency of PVA by UV/chlorine oxidation more than basic or neutral media because of the higher ratio of [HOCl]/[OCl - ], higher free radical quantum yields, and the lower free radical quenching effect under acidic conditions. Results of Fourier Transform Infrared Spectroscopy showed that carbonyl groups in degradation products were formed during UV/chlorine oxidation, and a possible degradation pathway via alcohol to carbonyl was proposed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Radical-induced chemistry from VUV photolysis of interstellar ice analogues containing formaldehyde

NASA Astrophysics Data System (ADS)

Butscher, Teddy; Duvernay, Fabrice; Danger, Grégoire; Chiavassa, Thierry

2016-09-01

Surface processes and radical chemistry within interstellar ices are increasingly suspected to play an important role in the formation of complex organic molecules (COMs) observed in several astrophysical regions and cometary environments. We present new laboratory experiments on the low-temperature solid state formation of complex organic molecules - glycolaldehyde, ethylene glycol, and polyoxymethylene - through radical-induced reactivity from VUV photolysis of formaldehyde in water-free and water-dominated ices. Radical reactivity and endogenous formation of COMs were monitored in situ via infrared spectroscopy in the solid state and post photolysis with temperature programmed desorption (TPD) using a quadripole mass spectrometer. We show the ability of free radicals to be stored when formed at low temperature in water-dominated ices, and to react with other radicals or on double bonds of unsaturated molecules when the temperature increases. It experimentally confirms the role of thermal diffusion in radical reactivity. We propose a new pathway for formaldehyde polymerisation induced by HCO radicals that might explain some observations made by the Ptolemy instrument on board the Rosetta lander Philae. In addition, our results seem to indicate that H-atom additions on H2CO proceed preferentially through CH2OH intermediate radicals rather than the CH3O radical.

Formation and implications of alpha-synuclein radical in Maneb- and paraquat-induced models of Parkinson’s disease

PubMed Central

Kumar, Ashutosh; Leinisch, Fabian; Kadiiska, Maria B.; Corbett, Jean; Mason, Ronald P.

2015-01-01

Parkinson’s disease (PD) is a debilitating, progressive, neurodegenerative disorder characterized by progressive loss of dopaminergic neurons and motor deficits. Alpha-synuclein-containing aggregates represent a feature of a variety of neurodegenerative disorders, including PD; however, the mechanism that initiates and promotes intraneuronal alpha-synuclein aggregation remains unknown. We hypothesized protein radical formation as an initiating mechanism for alpha-synuclein aggregation. Therefore, we used the highly sensitive immuno-spin trapping technique to investigate protein radical formation as a possible mechanism of alpha-synuclein aggregation as well as to investigate the source of protein radical formation in the midbrains of Maneb and paraquat coexposed mice. Coexposure to Maneb and paraquat for 6 weeks resulted in active microgliosis, NADPH oxidase activation, and inducible nitric oxide synthase (iNOS) induction, which culminated in protein radical formation in the midbrains of mice. Results obtained with immuno-spin trapping and immunoprecipitation experiments confirmed formation of alpha-synuclein radicals in dopaminergic neurons of exposed mice. Free radical formation requires NADPH oxidase and iNOS, as indicated by decreased protein radical formation in knockout mice (P47phox−/− and iNOS−/−) and in mice treated with inhibitors such as FeTPPS (a peroxynitrite decomposition catalyst), 1400W (an iNOS inhibitor), or apocynin (a NADPH oxidase inhibitor). Concurrence of protein radical formation with dopaminergic neuronal death indicated a link between protein radicals and disease progression. Taken together, these results show for the first time the formation and detection of the alpha-synuclein radical and suggest that NADPH oxidase and iNOS play roles in peroxynitrite-mediated protein radical formation and subsequent neuronal death in the midbrains of Maneb and paraquat coexposed mice. PMID:25952542

Environmentally persistent free radicals induce airway hyperresponsiveness in neonatal rat lungs

PubMed Central

2011-01-01

Background Increased asthma risk/exacerbation in children and infants is associated with exposure to elevated levels of ultrafine particulate matter (PM). The presence of a newly realized class of pollutants, environmentally persistent free radicals (EPFRs), in PM from combustion sources suggests a potentially unrecognized risk factor for the development and/or exacerbation of asthma. Methods Neonatal rats (7-days of age) were exposed to EPFR-containing combustion generated ultrafine particles (CGUFP), non-EPFR containing CGUFP, or air for 20 minutes per day for one week. Pulmonary function was assessed in exposed rats and age matched controls. Lavage fluid was isolated and assayed for cellularity and cytokines and in vivo indicators of oxidative stress. Pulmonary histopathology and characterization of differential protein expression in lung homogenates was also performed. Results Neonates exposed to EPFR-containing CGUFP developed significant pulmonary inflammation, and airway hyperreactivity. This correlated with increased levels of oxidative stress in the lungs. Using differential two-dimensional electrophoresis, we identified 16 differentially expressed proteins between control and CGUFP exposed groups. In the rats exposed to EPFR-containing CGUFP; peroxiredoxin-6, cofilin1, and annexin A8 were upregulated. Conclusions Exposure of neonates to EPFR-containing CGUFP induced pulmonary oxidative stress and lung dysfunction. This correlated with alterations in the expression of various proteins associated with the response to oxidative stress and the regulation of glucocorticoid receptor translocation in T lymphocytes. PMID:21388553

Edaravone attenuates monocyte adhesion to endothelial cells induced by oxidized low-density lipoprotein.

PubMed

Li, Zhijuan; Cheng, Jianxin; Wang, Liping

2015-10-30

Oxidized low-density lipoprotein (oxLDL) plays a vital role in recruitment of monocytes to endothelial cells, which is important during early stages of atherosclerosis development. Edaravone, a potent and novel scavenger of free radicals inhibiting hydroxyl radicals, has been clinically used to reduce the neuronal damage following ischemic stroke. In the present study, Edaravone was revealed to markedly reduce oxLDL-induced monocyte adhesion to human umbilical vein endothelial cells (HUVECs). The inhibitory mechanism of Edaravone was associated with suppression of the chemokine MCP-1 and adhesion molecule VCAM-1 and ICAM-1 expression. In addition, luciferase reporter assay results revealed that administration of Edaravone attenuated the increase in NF-κB transcriptional activity induced by oxLDL. Notably, it's also shown that Edaravone treatment blocked oxLDL induced p65 nuclear translocation in HUVECs. Results indicate that Edaravone negatively regulates endothelial inflammation. Copyright © 2015. Published by Elsevier Inc.

Anchoring ceria nanoparticles on graphene oxide and their radical scavenge properties under gamma irradiation environment.

PubMed

Xia, Wei; Zhao, Jun; Wang, Tao; Song, Li; Gong, Hao; Guo, Hu; Gao, Bing; Fan, Xiaoli; He, Jianping

2017-06-28

Polymer networks such as those of epoxy resin, as common protection materials, possess radiolytic oxidation degradation effects under gamma irradiation environment, which have a great accelerating effect on the ageing rate and severely limit their potential applications for metal protection in the nuclear industry. To overcome this, we report a simple scheme of anchoring crystalline ceria nanoparticles onto graphene sheets (CG) and incorporate it into the epoxy resin, followed by thermal polymerization to obtain CeO 2 /graphene-epoxy nanocomposite coating (CGNS). We had proven that graphene might act as "interwalls" in the epoxy matrix, which will result in space location-obstruct effect as well as absorb the radicals induced by γ-ray irradiation. Moreover, owing to the interconversion of cerium ions between their +3 and +4 states coupled with the formation of oxygen vacancy defects, electron spin resonance (ESR) detection shows that CeO 2 /graphene (CG) could act as a preferable radical scavenger and achieve better performance in trapping radicals than single graphene based composite. Electrochemical data strongly demonstrate that CeO 2 /graphene is capable of maintaining the anti-corrosion properties under gamma irradiation environment. Therefore, the designed hybrid CeO 2 /graphene-epoxy composite can be considered as potential candidates for protective coatings in nuclear industry.

Antimutagenic and free radical scavenger effects of leaf extracts from Accacia salicina

PubMed Central

2011-01-01

Background Three extracts were prepared from the leaves of Accacia salicina; ethyl acetate (EA), chloroform (Chl) and petroleum ether (PE) extracts and was designed to examine antimutagenic, antioxidant potenty and oxidative DNA damage protecting activity. Methods Antioxidant activity of A. salicina extracts was determined by the ability of each extract to protect against plasmid DNA strand scission induced by hydroxyl radicals. An assay for the ability of these extracts to prevent mutations induced by various oxidants in Salmonella typhimurium TA102 and TA 104 strains was conducted. In addition, nonenzymatic methods were employed to evaluate anti-oxidative effects of tested extracts. Results These extracts from leaf parts of A. salicina showed no mutagenicity either with or without the metabolic enzyme preparation (S9). The highest protections against methylmethanesulfonate induced mutagenicity were observed with all extracts and especially chloroform extract. This extract exhibited the highest inhibitiory level of the Ames response induced by the indirect mutagen 2- aminoanthracene. All extracts exhibited the highest ability to protect plasmid DNA against hydroxyl radicals induced DNA damages. The ethyl acetate (EA) and chloroform (Chl) extracts showed with high TEAC values radical of 0.95 and 0.81 mM respectively, against the ABTS.+. Conclusion The present study revealed the antimutagenic and antioxidant potenty of plant extract from Accacia salicina leaves. PMID:22132863

Antimutagenic and free radical scavenger effects of leaf extracts from Accacia salicina.

PubMed

Boubaker, Jihed; Mansour, Hedi Ben; Ghedira, Kamel; Chekir-Ghedira, Leila

2011-12-01

Three extracts were prepared from the leaves of Accacia salicina; ethyl acetate (EA), chloroform (Chl) and petroleum ether (PE) extracts and was designed to examine antimutagenic, antioxidant potenty and oxidative DNA damage protecting activity. Antioxidant activity of A. salicina extracts was determined by the ability of each extract to protect against plasmid DNA strand scission induced by hydroxyl radicals. An assay for the ability of these extracts to prevent mutations induced by various oxidants in Salmonella typhimurium TA102 and TA 104 strains was conducted. In addition, nonenzymatic methods were employed to evaluate anti-oxidative effects of tested extracts. These extracts from leaf parts of A. salicina showed no mutagenicity either with or without the metabolic enzyme preparation (S9). The highest protections against methylmethanesulfonate induced mutagenicity were observed with all extracts and especially chloroform extract. This extract exhibited the highest inhibitiory level of the Ames response induced by the indirect mutagen 2- aminoanthracene. All extracts exhibited the highest ability to protect plasmid DNA against hydroxyl radicals induced DNA damages. The ethyl acetate (EA) and chloroform (Chl) extracts showed with high TEAC values radical of 0.95 and 0.81 mM respectively, against the ABTS(.+). The present study revealed the antimutagenic and antioxidant potenty of plant extract from Accacia salicina leaves. © 2011 Boubaker et al; licensee BioMed Central Ltd.

Large enhancement in the heterogeneous oxidation rate of organic aerosols by hydroxyl radicals in the presence of nitric oxide

DOE PAGES

Richards-Henderson, Nicole K.; Goldstein, Allen H.; Wilson, Kevin R.

2015-10-27

In this paper we report an unexpectedly large acceleration in the effective heterogeneous OH reaction rate in the presence of NO. This 10–50 fold acceleration originates from free radical chain reactions, propagated by alkoxy radicals that form inside the aerosol by the reaction of NO with peroxy radicals, which do not appear to produce chain terminating products (e.g., alkyl nitrates), unlike gas phase mechanisms. Lastly, a kinetic model, constrained by experiments, suggests that in polluted regions heterogeneous oxidation plays a much more prominent role in the daily chemical evolution of organic aerosol than previously believed.

Oxidative Degradation of Methyl Orange Solution by Fe-MKSF Catalyst: Identification of Radical Species

NASA Astrophysics Data System (ADS)

Abdullah, N. H.; Selamat, M. K. A.; Nasuha, N.; Hassan, H.; Zubir, N. A.

2018-06-01

Iron–immobilized montmorillonite KSF (Fe-MKSF) has been recognized as promising catalyst in degrading persistence organic contaminants. However, detailed mechanistic insight during the catalysis which involving the formation and identification of radical species were remained indeterminate due to complex reaction. Inspiring by this gap, iron-immobilized clay (Fe-MKSF) was synthesized and used as heterogeneous catalyst in the oxidative degradation of methyl orange (MO) solution. Identification of radical species were determined through the inclusion of different types of radical scavenging agent during the Fenton-like reaction at optimum condition. Interestingly, dominant radical species were found to be hydroperoxyl radicals (•OOH) which subsequently followed by hydroxyl radicals (•OH) during the catalysis. Based on the percentage of MO removal, it was suggested that approximately 88% of the •OOH radicals existed at the interface of catalyst while 39% presence in bulk solution. Meanwhile, the interface •OH radicals promoted 38% of MO removal, whilst 4% by the bulk •OH radicals. Hence, these findings have conveyed novel insight on detailed radicals’ identification as well as its’ interaction during the catalysis.

Hydrogen-Rich Water Ameliorates Total Body Irradiation-Induced Hematopoietic Stem Cell Injury by Reducing Hydroxyl Radical

PubMed Central

Xue, Xiaolei; Han, Xiaodan; Li, Yuan; Lu, Lu; Li, Deguan

2017-01-01

We examined whether consumption of hydrogen-rich water (HW) could ameliorate hematopoietic stem cell (HSC) injury in mice with total body irradiation (TBI). The results indicated that HW alleviated TBI-induced HSC injury with respect to cell number alteration and to the self-renewal and differentiation of HSCs. HW specifically decreased hydroxyl radical (∙OH) levels in the c-kit+ cells of 4 Gy irradiated mice. Proliferative bone marrow cells (BMCs) increased and apoptotic c-kit+ cells decreased in irradiated mice uptaken with HW. In addition, the mean fluorescence intensity (MFI) of γ-H2AX and percentage of 8-oxoguanine positive cells significantly decreased in HW-treated c-kit+ cells, indicating that HW can alleviate TBI-induced DNA damage and oxidative DNA damage in c-kit+ cells. Finally, the cell cycle (P21), cell apoptosis (BCL-XL and BAK), and oxidative stress (NRF2, HO-1, NQO1, SOD, and GPX1) proteins were significantly altered by HW in irradiated mouse c-kit+ cells. Collectively, the present results suggest that HW protects against TBI-induced HSC injury. PMID:28243358

Hydrogen-Rich Water Ameliorates Total Body Irradiation-Induced Hematopoietic Stem Cell Injury by Reducing Hydroxyl Radical.

PubMed

Zhang, Junling; Xue, Xiaolei; Han, Xiaodan; Li, Yuan; Lu, Lu; Li, Deguan; Fan, Saijun

2017-01-01

We examined whether consumption of hydrogen-rich water (HW) could ameliorate hematopoietic stem cell (HSC) injury in mice with total body irradiation (TBI). The results indicated that HW alleviated TBI-induced HSC injury with respect to cell number alteration and to the self-renewal and differentiation of HSCs. HW specifically decreased hydroxyl radical ( ∙ OH) levels in the c-kit + cells of 4 Gy irradiated mice. Proliferative bone marrow cells (BMCs) increased and apoptotic c-kit + cells decreased in irradiated mice uptaken with HW. In addition, the mean fluorescence intensity (MFI) of γ -H2AX and percentage of 8-oxoguanine positive cells significantly decreased in HW-treated c-kit + cells, indicating that HW can alleviate TBI-induced DNA damage and oxidative DNA damage in c-kit + cells. Finally, the cell cycle (P21), cell apoptosis (BCL-XL and BAK), and oxidative stress (NRF2, HO-1, NQO1, SOD, and GPX1) proteins were significantly altered by HW in irradiated mouse c-kit + cells. Collectively, the present results suggest that HW protects against TBI-induced HSC injury.

Damage of polyesters by the atmospheric free radical oxidant NO3 •: a product study involving model systems

PubMed Central

Goeschen, Catrin

2013-01-01

Summary Manufactured polymer materials are used in increasingly demanding applications, but their lifetime is strongly influenced by environmental conditions. In particular, weathering and ageing leads to dramatic changes in the properties of the polymers, which results in decreased service life and limited usage. Despite the heavy reliance of our society on polymers, the mechanism of their degradation upon exposure to environmental oxidants is barely understood. In this work, model systems of important structural motifs in commercial high-performing polyesters were used to study the reaction with the night-time free radical oxidant NO3 • in the absence and presence of other radical and non-radical oxidants. Identification of the products revealed ‘hot spots’ in polyesters that are particularly vulnerable to attack by NO3 • and insight into the mechanism of oxidative damage by this environmentally important radical. It is suggested that both intermediates as well as products of these reactions are potentially capable of promoting further degradation processes in polyesters under environmental conditions. PMID:24204400

Free radical generation induced by ultrasound in red wine and model wine: An EPR spin-trapping study.

PubMed

Zhang, Qing-An; Shen, Yuan; Fan, Xue-Hui; Martín, Juan Francisco García; Wang, Xi; Song, Yun

2015-11-01

Direct evidence for the formation of 1-hydroxylethyl radicals by ultrasound in red wine and air-saturated model wine is presented in this paper. Free radicals are thought to be the key intermediates in the ultrasound processing of wine, but their nature has not been established yet. Electron paramagnetic resonance (EPR) spin trapping with 5,5-dimethyl-l-pyrrolin N-oxide (DMPO) was used for the detection of hydroxyl free radicals and 1-hydroxylethyl free radicals. Spin adducts of hydroxyl free radicals were detected in DMPO aqueous solution after sonication while 1-hydroxylethyl free radical adducts were observed in ultrasound-processed red wine and model wine. The latter radical arose from ethanol oxidation via the hydroxyl radical generated by ultrasound in water, thus providing the first direct evidence of the formation of 1-hydroxylethyl free radical in red wine exposed to ultrasound. Finally, the effects of ultrasound frequency, ultrasound power, temperature and ultrasound exposure time were assessed on the intensity of 1-hydroxylethyl radical spin adducts in model wine. Copyright © 2015 Elsevier B.V. All rights reserved.

Preventive efficacy of hydroalcoholic extract of Cymbopogon citratus against radiation-induced DNA damage on V79 cells and free radical scavenging ability against radicals generated in vitro.

PubMed

Rao, B S S; Shanbhoge, R; Rao, B N; Adiga, S K; Upadhya, D; Aithal, B K; Kumar, M R S

2009-04-01

This study presents the findings of free radical scavenging and antigenotoxic effect of hydroalcoholic extract of Cymbopogon citratus (CCE). The CCE at a concentration of 60 microg/mL resulted in a significant scavenging ability of 2,2-diphenyl-2-picryl hydrazyl (DPPH; (85%), 2,2-azinobis (3-ethyl benzothiazoline-6-sulphonic acid) (ABTS; 77%), hydroxyl (70%), superoxide (76%), nitric oxide (78%) free radicals generated using in vitro and also a moderate anti-lipid peroxidative effect (57%). Further, the radiation-induced antigenotoxic potential of CCE was assessed in Chinese hamster lung fibroblast cells (V79) using micronucleus assay. The CCE resulted in a dose-dependent decrease in the yield of radiation-induced micronuclei, with a maximum effect at 125 microg/mL CCE for 1 h before 2 Gy of radiation. Similarly, there was a significant (P < 0.05-0.0001) decrease in percentage of micronuclei when V79 cells were treated with optimal dose of CCE (125 microg/mL) before exposure to different doses of gamma radiation, that is, 0.5-4 Gy, compared with radiation alone groups. The results of the micronucleus study indicated antigenotoxic effect demonstrating the radioprotective potential of CCE and, which may partly due to its and antioxidant capacity as it presented its ability to scavenge various free radicals in vitro and anti-lipid peroxidative potential.

Hepatoprotective Role of Wheatgrass on Alcohol and ΔPUFA-Induced Oxidative Stress in Rats.

PubMed

Durairaj, Varalakshmi; Shakya, Garima; Rajagopalan, Rukkumani

2015-06-01

Alcohol abuse is recognized as the most common cause for the development of various abnormalities including liver disease. Excessive free radicals are generated during the metabolism of ethanol. The ingestion of alcohol along with polyunsaturated fatty acid (PUFA) aggravates the production of free radicals and enhances the oxidative stress. Medicinal plants contain active phytocomponents, which are the principal healthcare resources. We aimed to analyze the effect of wheatgrass extract on alcohol and thermally oxidized PUFA (ΔPUFA) induced oxidative stress in male albino Wistar rats. The levels of marker enzymes gamma-glutamyl transferase (GGT), alkaline phosphatase (ALP), lipid peroxidative markers; thiobarbutric acid reactive substances (TBARS) and lipid hydroperoxides (LH), the levels of enzymatic (catalase [CAT], superoxide dismutase [SOD], glutathione peroxidase [GPx]) and nonenzymatic (reduced glutathione [GSH], vitamin E, vitamin C) antioxidants were analyzed in liver to evaluate the effects of wheatgrass. The levels of TBARS and LH were significantly (p ≤ .05) increased in alcohol + ΔPUFA group, which were found to be reduced on treatment with wheatgrass. The levels of both enzymatic and nonenzymatic antioxidants were significantly (p ≤ .05) decreased in alcohol + ΔPUFA group, which were found to be restored on treatment with wheatgrass. From the results obtained, we conclude that wheatgrass protects the liver against alcohol and ΔPUFA induced oxidative stress.

Tandem SN2' nucleophilic substitution/oxidative radical cyclization of aryl substituted allylic alcohols with 1,3-dicarbonyl compounds.

PubMed

Zhang, Zhen; Li, Cheng; Wang, Shao-Hua; Zhang, Fu-Min; Han, Xue; Tu, Yong-Qiang; Zhang, Xiao-Ming

2017-04-11

A novel and efficient tandem S N 2' nucleophilic substitution/oxidative radical cyclization reaction of aryl substituted allylic alcohols with 1,3-dicarbonyl compounds has been developed by using Mn(OAc) 3 as an oxidant, which enables the expeditious synthesis of polysubstituted dihydrofuran (DHF) derivatives in moderate to high yields. The use of weakly acidic hexafluoroisopropanol (HFIP) as the solvent rather than AcOH has successfully improved the yields and expanded the substrate scope of this type of radical cyclization reactions. Mechanistic studies confirmed the cascade reaction process involving a final radical cyclization.

Kinetic Study of Hydroxyl and Sulfate Radical-Mediated Oxidation of Pharmaceuticals in Wastewater Effluents.

PubMed

Lian, Lushi; Yao, Bo; Hou, Shaodong; Fang, Jingyun; Yan, Shuwen; Song, Weihua

2017-03-07

Advanced oxidation processes (AOPs), such as hydroxyl radical (HO • )- and sulfate radical (SO 4 •- )-mediated oxidation, are alternatives for the attenuation of pharmaceuticals and personal care products (PPCPs) in wastewater effluents. However, the kinetics of these reactions needs to be investigated. In this study, kinetic models for 15 PPCPs were built to predict the degradation of PPCPs in both HO • - and SO 4 •- -mediated oxidation. In the UV/H 2 O 2 process, a simplified kinetic model involving only steady state concentrations of HO • and its biomolecular reaction rate constants is suitable for predicting the removal of PPCPs, indicating the dominant role of HO • in the removal of PPCPs. In the UV/K 2 S 2 O 8 process, the calculated steady state concentrations of CO 3 •- and bromine radicals (Br • , Br 2 •- and BrCl •- ) were 600-fold and 1-2 orders of magnitude higher than the concentrations of SO 4 •- , respectively. The kinetic model, involving both SO 4 •- and CO 3 •- as reactive species, was more accurate for predicting the removal of the 9 PPCPs, except for salbutamol and nitroimidazoles. The steric and ionic effects of organic matter toward SO 4 •- could lead to overestimations of the removal efficiencies of the SO 4 •- -mediated oxidation of nitroimidazoles in wastewater effluents.

Photochemical sensitization by azathioprine and its metabolites. Part 3. A direct EPR and spin-trapping study of light-induced free radicals from 6-mercaptopurine and its oxidation products.

PubMed

Moore, D E; Sik, R H; Bilski, P; Chignell, C F; Reszka, K J

1994-12-01

Sunlight has been implicated in the high incidence of skin cancer found in patients receiving 6-mercaptopurine (PSH) in the form of its pro-drug azathioprine. In this study we have used EPR spectroscopy in conjunction with the spin-trapping technique to determine whether PSH and its metabolic or photochemical oxidation products generate highly reactive free radicals upon UV irradiation. When an aqueous anaerobic solution (pH 5 or 9) of PSH (pKa = 7.7) and either 2-methyl-2-nitrosopropane (MNP) or nitromethane (NM) were irradiated (lambda > 300 nm) with a Xe arc lamp, the corresponding purine-6-thiyl (PS.) radical adduct and the reduced form of the spin trap (MNP/H. or CH3NO2.-) were observed. However, no radical adducts were detected when PSH and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) were irradiated (lambda = 320 nm) in oxygen-free buffer. These findings suggest that PSH does not photoionize but that instead MNP and NM are reduced by direct electron transfer from excited state PSH, 1.3(PSH)*. In aerobic solution, oxygen can act as an electron acceptor and the O2.- and PS. radicals are formed and trapped by DMPO. 6-Mercaptopurine did photoionize when irradiated with a Nd:YAG laser at 355 nm as evidenced by the appearance of the DMPO/H.(eq- + H+) adduct, which decreased in intensity in the presence of N2O. 1.3(6-Mercaptopurine)* oxidized ascorbate, formate and reduced glutathione to the corresponding ascorbyl, CO2.- or glutathiyl radicals. The photochemical behavior of 6-thioxanthine and 6-thiouric acid was similar to PSH. However, the excited states of these metabolic oxidation products exhibited stronger reducing properties than 1.3(PSH)*.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromium (VI)-induced oxidative stress, apoptotic cell death and modulation of p53 tumor suppressor gene.

PubMed

Bagchi, D; Bagchi, M; Stohs, S J

2001-06-01

Chromium (VI) is a widely used industrial chemical, extensively used in paints, metal finishes, steel including stainless steel manufacturing, alloy cast irons, chrome, and wood treatment. On the contrary, chromium (III) salts such as chromium polynicotinate, chromium chloride and chromium picolinate, are used as micronutrients and nutritional supplements, and have been demonstrated to exhibit a significant number of health benefits in rodents and humans. However, the cause for the hexavalent chromium to induce cytotoxicity is not entirely understood. A series of in vitro and in vivo studies have demonstrated that chromium (VI) induces an oxidative stress through enhanced production of reactive oxygen species (ROS) leading to genomic DNA damage and oxidative deterioration of lipids and proteins. A cascade of cellular events occur following chromium (VI)-induced oxidative stress including enhanced production of superoxide anion and hydroxyl radicals, increased lipid peroxidation and genomic DNA fragmentation, modulation of intracellular oxidized states, activation of protein kinase C, apoptotic cell death and altered gene expression. In this paper, we have demonstrated concentration- and time-dependent effects of sodium dichromate (chromium (VI) or Cr (VI)) on enhanced production of superoxide anion and hydroxyl radicals, changes in intracellular oxidized states as determined by laser scanning confocal microscopy, DNA fragmentation and apoptotic cell death (by flow cytometry) in human peripheral blood mononuclear cells. These results were compared with the concentration-dependent effects of chromium (VI) on chronic myelogenous leukemic K562 cells and J774A.1 murine macrophage cells. Chromium (VI)-induced enhanced production of ROS, as well as oxidative tissue and DNA damage were observed in these cells. More pronounced effect was observed on chronic myelogenous leukemic K562 cells and J774A.1 murine macrophage cells. Furthermore, we have assessed the effect of a

Buffer Modulation of Menadione-Induced Oxidative Stress in Saccharomyces cerevisiae

PubMed Central

Lushchak, Oleh V.; Bayliak, Maria M.; Korobova, Olha V.; Levine, Rodney L.; Lushchak, Volodymyr I.

2012-01-01

The objective of this study was to compare in vivo the effects of bicarbonate and phosphate buffers on surviving and menadione-induced oxidative stress in yeast cells. The latter were treated with different concentrations of menadione in the presence of these two buffers. If at 25 mM concentration of buffers menadione only slightly reduced yeast surviving, at 50 mM concentration cell killing by menadione was much more pronounced in bicarbonate than in phosphate buffer. Although the content of protein carbonyl groups did not show development of oxidative stress under menadione-induced stress, inactivation of aconitase and decrease in glutathione level mirrored its induction. However, cellular glutathione and aconitase activity decrease did not correlate with yeast survival. In vitro, aconitase was more quickly inactivated in 50 mM carbonate, than in 50 mM phosphate buffer. The possible involvement of the carbonate radical in these processes is discussed. PMID:19843376

Buffer modulation of menadione-induced oxidative stress in Saccharomyces cerevisiae.

PubMed

Lushchak, Oleh V; Bayliak, Maria M; Korobova, Olha V; Levine, Rodney L; Lushchak, Volodymyr I

2009-01-01

The objective of this study was to compare, in vivo, the effects of bicarbonate and phosphate buffers on survival and menadione-induced oxidative stress in yeast cells. The latter were treated with different concentrations of menadione in the presence of these two buffers. At 25 mM concentration of buffers, menadione only slightly reduced yeast surviving; at 50 mM concentration, cell killing by menadione was much more pronounced in bicarbonate than in phosphate buffer. Although the content of protein carbonyl groups did not show development of oxidative stress under menadione-induced stress, inactivation of aconitase and decrease in glutathione level mirrored its induction. However, cellular glutathione and aconitase activity decrease did not correlate with yeast survival. In vitro, aconitase was more quickly inactivated in 50 mM carbonate, than in 50 mM phosphate buffer. The possible involvement of the carbonate radical in these processes is discussed.

Nitrate radicals and biogenic volatile organic compounds: oxidation, mechanisms, and organic aerosol

EPA Science Inventory

Oxidation of biogenic volatile organic compounds (BVOC) by the nitrate radical (NO3) represents one of the important interactions between anthropogenic emissions related to combustion and natural emissions from the biosphere. This interaction has been recognized for more than 3 d...

Metal-Diazo Radicals of α-Carbonyl Diazomethanes

PubMed Central

Li, Feifei; Xiao, Longqiang; Liu, Lijian

2016-01-01

Metal-diazo radicals of α-carbonyl diazomethanes are new members of the radical family and are precursors to metal-carbene radicals. Herein, using electron paramagnetic resonance spectroscopy with spin-trapping, we detect diazo radicals of α-carbonyl diazomethanes, induced by [RhICl(cod)]2, [CoII(por)] and PdCl2, at room temperature. The unique quintet signal of the Rh-diazo radical was observed in measurements of α-carbonyl diazomethane adducts of [RhICl(cod)]2 in the presence of 5,5-dimethyl-pyrroline-1-N-oxide (DMPO). DFT calculations indicated that 97.2% of spin density is localized on the diazo moiety. Co- and Pd-diazo radicals are EPR silent but were captured by DMPO to form spin adducts of DMPO-N∙ (triplet-of-sextets signal). The spin-trapping also provides a powerful tool for detection of metal-carbene radicals, as evidenced by the DMPO-trapped carbene radicals (DMPO-C∙, sextet signal) and 2-methyl-2-nitrosopropane-carbene adducts (MNP-C∙, doublet-of-triplets signal). The transformation of α-carbonyl diazomethanes to metal-carbene radicals was confirmed to be a two-step process via metal-diazo radicals. PMID:26960916

Metal-Diazo Radicals of α-Carbonyl Diazomethanes

NASA Astrophysics Data System (ADS)

Li, Feifei; Xiao, Longqiang; Liu, Lijian

2016-03-01

Metal-diazo radicals of α-carbonyl diazomethanes are new members of the radical family and are precursors to metal-carbene radicals. Herein, using electron paramagnetic resonance spectroscopy with spin-trapping, we detect diazo radicals of α-carbonyl diazomethanes, induced by [RhICl(cod)]2, [CoII(por)] and PdCl2, at room temperature. The unique quintet signal of the Rh-diazo radical was observed in measurements of α-carbonyl diazomethane adducts of [RhICl(cod)]2 in the presence of 5,5-dimethyl-pyrroline-1-N-oxide (DMPO). DFT calculations indicated that 97.2% of spin density is localized on the diazo moiety. Co- and Pd-diazo radicals are EPR silent but were captured by DMPO to form spin adducts of DMPO-N• (triplet-of-sextets signal). The spin-trapping also provides a powerful tool for detection of metal-carbene radicals, as evidenced by the DMPO-trapped carbene radicals (DMPO-C•, sextet signal) and 2-methyl-2-nitrosopropane-carbene adducts (MNP-C•, doublet-of-triplets signal). The transformation of α-carbonyl diazomethanes to metal-carbene radicals was confirmed to be a two-step process via metal-diazo radicals.

Metal-Diazo Radicals of α-Carbonyl Diazomethanes.

PubMed

Li, Feifei; Xiao, Longqiang; Liu, Lijian

2016-03-10

Metal-diazo radicals of α-carbonyl diazomethanes are new members of the radical family and are precursors to metal-carbene radicals. Herein, using electron paramagnetic resonance spectroscopy with spin-trapping, we detect diazo radicals of α-carbonyl diazomethanes, induced by [Rh(I)Cl(cod)]2, [Co(II)(por)] and PdCl2, at room temperature. The unique quintet signal of the Rh-diazo radical was observed in measurements of α-carbonyl diazomethane adducts of [Rh(I)Cl(cod)]2 in the presence of 5,5-dimethyl-pyrroline-1-N-oxide (DMPO). DFT calculations indicated that 97.2% of spin density is localized on the diazo moiety. Co- and Pd-diazo radicals are EPR silent but were captured by DMPO to form spin adducts of DMPO-N∙ (triplet-of-sextets signal). The spin-trapping also provides a powerful tool for detection of metal-carbene radicals, as evidenced by the DMPO-trapped carbene radicals (DMPO-C∙, sextet signal) and 2-methyl-2-nitrosopropane-carbene adducts (MNP-C∙, doublet-of-triplets signal). The transformation of α-carbonyl diazomethanes to metal-carbene radicals was confirmed to be a two-step process via metal-diazo radicals.

The enhancement of oxidative DNA damage by anti-diabetic metformin, buformin, and phenformin, via nitrogen-centered radicals.

PubMed

Ohnishi, Shiho; Mizutani, Hideki; Kawanishi, Shosuke

2016-08-01

Metformin (N,N-dimethylbiguanide), buformin (1-butylbiguanide), and phenformin (1-phenethylbiguanide) are anti-diabetic biguanide drugs, expected to having anti-cancer effect. The mechanism of anti-cancer effect by these drugs is not completely understood. In this study, we demonstrated that these drugs dramatically enhanced oxidative DNA damage under oxidative condition. Metformin, buformin, and phenformin enhanced generation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in isolated DNA reacted with hydrogen peroxide (H2O2) and Cu(II), although these drugs did not form 8-oxodG in the absence of H2O2 or Cu(II). An electron paramagnetic resonance (EPR) study, utilizing alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone and 3,3,5,5-tetramethyl-1-pyrroline-N-oxide as spin trapping agents, showed that nitrogen-centered radicals were generated from biguanides in the presence of Cu(II) and H2O2, and that these radicals were decreased by the addition of DNA. These results suggest that biguanides enhance Cu(II)/H2O2-mediated 8-oxodG generation via nitrogen-centered radical formation. The enhancing effect on oxidative DNA damage may play a role on anti-cancer activity.

Photo-protection by 3-bromo-4, 5-dihydroxybenzaldehyde against ultraviolet B-induced oxidative stress in human keratinocytes.

PubMed

Hyun, Yu Jae; Piao, Mei Jing; Zhang, Rui; Choi, Yung Hyun; Chae, Sungwook; Hyun, Jin Won

2012-09-01

Exposure of the skin to ultraviolet B (UVB) radiation leads to epidermal damage and the generation of reactive oxygen species (ROS) in skin cells, including keratinocytes. Therefore, the photo-protective effect of 3-bromo-4, 5-dihydroxybenzaldehyde (BDB) against UVB was assessed in human HaCaT keratinocytes exposed to UVB radiation in vitro. BDB restored cell viability, which decreased upon exposure to UVB radiation. BDB exhibited scavenging activity against 1, 1-diphenyl-2-picrylhydrazyl radicals, intracellular ROS induced by hydrogen peroxide (H(2)O(2)) or UVB radiation, the superoxide anion generated by the xanthine/xanthine oxidase system, and the hydroxyl radical generated by the Fenton reaction (FeSO(4)+H(2)O(2)). Moreover, BDB absorbed UVB and decreased injury resulting from UVB-induced oxidative stress to lipids, proteins and DNA. Finally, BDB reduced UVB-induced apoptosis, as exemplified by fewer apoptotic bodies and a reduction in DNA fragmentation. Taken together, these results suggest that BDB protects human keratinocytes against UVB-induced oxidative stress by scavenging ROS and absorbing UVB rays, thereby reducing injury to cellular components. Copyright © 2012 Elsevier Inc. All rights reserved.

A review: oxidative stress in fish induced by pesticides.

PubMed

Slaninova, Andrea; Smutna, Miriam; Modra, Helena; Svobodova, Zdenka

2009-01-01

The knowledge in oxidative stress in fish has a great importance for environmental and aquatic toxicology. Because oxidative stress is evoked by many chemicals including some pesticides, pro-oxidant factors' action in fish organism can be used to assess specific area pollution or world sea pollution. Hepatotoxic effect of DDT may be related with lipid peroxidation. Releasing of reactive oxygen species (ROS) after HCB exposure can be realized via two ways: via the uncoupling of the electron transport chain from monooxygenase activity and via metabolism of HCB major metabolite pentachlorophenol. Chlorothalonil disrupts mitochondrial metabolism due to the impairment of NADPH oxidase function. Activation of spleen macrophages and a decrease of catalase (CAT) activity have been observed after endosulfan exposure. Excessive release of superoxide radicals after etoxazole exposure can cause a decrease of CAT activity and increase phagocytic activity of splenocytes. Anticholinergic activity of organophosphates leads to the accumulation of ROS and resulting lipid peroxidation. Carbaryl induces changes in the content of glutathione and antioxidant enzymes activities. The antioxidant enzymes changes have been observed after actuation of pesticides deltamethrin and cypermethrin. Bipyridyl herbicides are able to form redox cycles and thereby cause oxidative stress. Low concentrations of simazine do not cause oxidative stress in carps during sub-chronic tests while sublethal concentrations of atrazin can induce oxidative stress in bluegill sunfish. Butachlor causes increased activity of superoxide dismutase -catalase system in the kidney. Rotenon can inhibit the electron transport in mitochondria and thereby increase ROS production. Dichloroaniline, the metabolite of diuron, has oxidative effects. Oxidative damage from fenpyroximate actuation is related to the disruption of mitochondrial redox respiratory chain. Low concentration of glyphosate can cause mild oxidative stress.

Free radicals: properties, sources, targets, and their implication in various diseases.

PubMed

Phaniendra, Alugoju; Jestadi, Dinesh Babu; Periyasamy, Latha

2015-01-01

Free radicals and other oxidants have gained importance in the field of biology due to their central role in various physiological conditions as well as their implication in a diverse range of diseases. The free radicals, both the reactive oxygen species (ROS) and reactive nitrogen species (RNS), are derived from both endogenous sources (mitochondria, peroxisomes, endoplasmic reticulum, phagocytic cells etc.) and exogenous sources (pollution, alcohol, tobacco smoke, heavy metals, transition metals, industrial solvents, pesticides, certain drugs like halothane, paracetamol, and radiation). Free radicals can adversely affect various important classes of biological molecules such as nucleic acids, lipids, and proteins, thereby altering the normal redox status leading to increased oxidative stress. The free radicals induced oxidative stress has been reported to be involved in several diseased conditions such as diabetes mellitus, neurodegenerative disorders (Parkinson's disease-PD, Alzheimer's disease-AD and Multiple sclerosis-MS), cardiovascular diseases (atherosclerosis and hypertension), respiratory diseases (asthma), cataract development, rheumatoid arthritis and in various cancers (colorectal, prostate, breast, lung, bladder cancers). This review deals with chemistry, formation and sources, and molecular targets of free radicals and it provides a brief overview on the pathogenesis of various diseased conditions caused by ROS/RNS.

PLA2 mediated arachidonate free radicals: PLA2 inhibition and neutralization of free radicals by anti-oxidants--a new role as anti-inflammatory molecule.

PubMed

Nanda, B L; Nataraju, A; Rajesh, R; Rangappa, K S; Shekar, M A; Vishwanath, B S

2007-01-01

PLA2 enzyme catalyses the hydrolysis of cellular phospholipids at the sn-2 position to liberate arachidonic acid and lysophospholipid to generate a family of pro-inflammatory eicosanoids and platelet activating factor. The generation of pro-inflammatory eicosanoids involves a series of free radical intermediates with simultaneous release of reactive oxygen species (superoxide and hydroxyl radicals). Reactive oxygen species formed during arachidonic acid metabolism generates lipid peroxides and the cytotoxic products such as 4-hydroxy nonenal and acrolein, which induces cellular damage. Thus PLA2 catalyzes the rate-limiting step in the production of pro-inflammatory eicosanoids and free radicals. These peroxides and reactive oxygen species in turn activates PLA2 enzyme and further attenuates the inflammatory process. Therefore scavenging these free radicals and inhibition of PLA2 enzyme simultaneously by a single molecule such as antioxidants is of great therapeutic relevance for the development of anti-inflammatory molecules. PLA2 enzymes have been classified into calcium dependent cPLA2 and sPLA2 and calcium independent iPLA2 forms. In several inflammatory diseases sPLA2 group IIA is the most abundant isoform identified. This isoform is therefore targeted for the development of anti-inflammatory molecules. Many secondary metabolites from plants and marine sponges exhibit both anti-inflammatory and antioxidant properties. Some of them include flavonoids, terpenes and alkaloids. But in terms of PLA2 inhibition and antioxidant activity, the structural aspects of flavonoids are well studied rather than terpenes and alkaloids. In this line, molecules having both anti-oxidant and PLA2 inhibitions are reviewed. A single molecule with dual activities may prove to be a powerful anti-inflammatory drug.

Reaction mechanisms of DNT with hydroxyl radicals for advanced oxidation processes-a DFT study.

PubMed

Zhou, Yang; Yang, Zhilin; Yang, Hong; Zhang, Chaoyang; Liu, Xiaoqiang

2017-04-01

In advanced oxidation processes (AOPs), the detailed degradation mechanisms of a typical explosive of 2,4-dinitrotoluene (DNT) can be investigated by the density function theory (DFT) method at the SMD/M062X/6-311+G(d) level. Several possible degradation routes for DNT were explored in the current study. The results show that, for oxidation of the methyl group, the dominant degradation mechanism of DNT by hydroxyl radicals (•OH) is a series of sequential H-abstraction reactions, and the intermediates obtained are in good agreement with experimental findings. The highest activation energy barrier is less than 20 kcal mol -1 . Other routes are dominated by an addition-elimination mechanism, which is also found in 2,4,6-trinitrotoluene, although the experiment did not find the corresponding products. In addition, we also eliminate several impossible mechanisms, such as dehydration, HNO 3 elimination, the simultaneous addition of two •OH radials, and so on. The information gained about these degradation pathways is helpful in elucidating the detailed reaction mechanism between nitroaromatic explosives and hydroxyl radicals for AOPs. Graphical Abstract The degradation mechanism of an important explosive, 2,6-dinitrotoluene (DNT), by the hydroxyl radical for advanced oxidation progresses.

Capturing the radical ion-pair intermediate in DNA guanine oxidation

PubMed Central

Jie, Jialong; Liu, Kunhui; Wu, Lidan; Zhao, Hongmei; Song, Di; Su, Hongmei

2017-01-01

Although the radical ion pair has been frequently invoked as a key intermediate in DNA oxidative damage reactions and photoinduced electron transfer processes, the unambiguous detection and characterization of this species remain formidable and unresolved due to its extremely unstable nature and low concentration. We use the strategy that, at cryogenic temperatures, the transient species could be sufficiently stabilized to be detectable spectroscopically. By coupling the two techniques (the cryogenic stabilization and the time-resolved laser flash photolysis spectroscopy) together, we are able to capture the ion-pair transient G+•⋯Cl− in the chlorine radical–initiated DNA guanine (G) oxidation reaction, and provide direct evidence to ascertain the intricate type of addition/charge separation mechanism underlying guanine oxidation. The unique spectral signature of the radical ion-pair G+•⋯Cl− is identified, revealing a markedly intense absorption feature peaking at 570 nm that is distinctive from G+• alone. Moreover, the ion-pair spectrum is found to be highly sensitive to the protonation equilibria within guanine-cytosine base pair (G:C), which splits into two resolved bands at 480 and 610 nm as the acidic proton transfers along the central hydrogen bond from G+• to C. We thus use this exquisite sensitivity to track the intrabase-pair proton transfer dynamics in the double-stranded DNA oligonucleotides, which is of critical importance for the description of the proton-coupled charge transfer mechanisms in DNA. PMID:28630924

Spirulina platensis prevents high glucose-induced oxidative stress mitochondrial damage mediated apoptosis in cardiomyoblasts.

PubMed

Jadaun, Pratiksha; Yadav, Dhananjay; Bisen, Prakash Singh

2018-04-01

The current study was undertaken to study the effect of Spirulina platensis (Spirulina) extract on enhanced oxidative stress during high glucose induced cell death in H9c2 cells. H9c2 cultured under high glucose (33 mM) conditions resulted in a noteworthy increase in oxidative stress (free radical species) accompanied by loss of mitochondrial membrane potential, release of cytochrome c, increase in caspase activity and pro-apoptotic protein (Bax). Spirulina extract (1 μg/mL), considerably inhibited increased ROS and RNS levels, reduction in cytochrome c release, raise in mitochondrial membrane potential, decreased the over expression of proapoptotic protein Bax and suppressed the Bax/Bcl2 ratio with induced apoptosis without affecting cell viability. Overall results suggest that Spirulina extract plays preventing role against enhanced oxidative stress during high glucose induced apoptosis in cardiomyoblasts as well as related dysfunction in H9c2 cells.

Hydrogen peroxide-induced reduction of delayed rectifier potassium current in hippocampal neurons involves oxidation of sulfhydryl groups.

PubMed

Hasan, Sonia M K; Redzic, Zoran B; Alshuaib, Waleed B

2013-07-03

This study examined the effect of H2O2 on the delayed rectifier potassium current (IKDR) in isolated hippocampal neurons. Whole-cell voltage-clamp experiments were performed on freshly dissociated hippocampal CA1 neurons of SD rats before and after treatment with H2O2. To reveal the mechanism behind H2O2-induced changes in IKDR, cells were treated with different oxidizing and reducing agents. External application of membrane permeable H2O2 reduced the amplitude and voltage-dependence of IKDR in a concentration dependent manner. Desferoxamine (DFO), an iron-chelator that prevents hydroxyl radical (OH) generation, prevented H2O2-induced reduction in IKDR. Application of the sulfhydryl-oxidizing agent 5,5 dithio-bis-nitrobenzoic acid (DTNB) mimicked the effect of H2O2. Sulfhydryl-reducing agents dithiothreitol (DTT) and glutathione (GSH) alone did not affect IKDR; however, DTT and GSH reversed and prevented the H2O2-induced inhibition of IKDR, respectively. Membrane impermeable agents GSH and DTNB showed effects only when added intracellularly identifying intracellular sulfhydryl groups as potential targets for hydroxyl-mediated oxidation. However, the inhibitory effects of DTNB and H2O2 at the positive test potentials were completely and partially abolished by DTT, respectively, suggesting an additional mechanism of action for H2O2, that is not shared by DTNB. In summary, this study provides evidence for the redox modulation of IKDR, identifies hydroxyl radical as an intermediate oxidant responsible for the H2O2-induced decrease in current amplitude and identifies intracellular sulfhydryl groups as an oxidative target. Copyright © 2013 Elsevier B.V. All rights reserved.

Hydroxyl Radical Modification of Collagen Type II Increases Its Arthritogenicity and Immunogenicity

PubMed Central

Shahab, Uzma; Ahmad, Saheem; Moinuddin; Dixit, Kiran; Habib, Safia; Alam, Khursheed; Ali, Asif

2012-01-01

Background The oxidation of proteins by endogenously generated free radicals causes structural modifications in the molecules that lead to generation of neo-antigenic epitopes that have implications in various autoimmune disorders, including rheumatoid arthritis (RA). Collagen induced arthritis (CIA) in rodents (rats and mice) is an accepted experimental model for RA. Methodology/Principal Findings Hydroxyl radicals were generated by the Fenton reaction. Collagen type II (CII) was modified by •OH radical (CII-OH) and analysed by ultraviolet-visible (UV-VIS), fluorescence and circular dichroism (CD) spectroscopy. The immunogenicity of native and modified CII was checked in female Lewis rats and specificity of the induced antibodies was ascertained by enzyme linked immunosorbent assay (ELISA). The extent of CIA was evaluated by visual inspection. We also estimated the oxidative and inflammatory markers in the sera of immunized rats. A slight change in the triple helical structure of CII as well as fragmentation was observed after hydroxyl radical modification. The modified CII was found to be highly arthritogenic and immunogenic as compared to the native form. The CII-OH immunized rats exhibited increased oxidative stress and inflammation as compared to the CII immunized rats in the control group. Conclusions/Significance Neo-antigenic epitopes were generated on •OH modified CII which rendered it highly immunogenic and arthritogenic as compared to the unmodified form. Since the rodent CIA model shares many features with human RA, these results illuminate the role of free radicals in human RA. PMID:22319617

Edaravone attenuates monocyte adhesion to endothelial cells induced by oxidized low-density lipoprotein

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Zhijuan, E-mail: zjlee038@163.com; Cheng, Jianxin; Wang, Liping

2015-10-30

Oxidized low-density lipoprotein (oxLDL) plays a vital role in recruitment of monocytes to endothelial cells, which is important during early stages of atherosclerosis development. Edaravone, a potent and novel scavenger of free radicals inhibiting hydroxyl radicals, has been clinically used to reduce the neuronal damage following ischemic stroke. In the present study, Edaravone was revealed to markedly reduce oxLDL-induced monocyte adhesion to human umbilical vein endothelial cells (HUVECs). The inhibitory mechanism of Edaravone was associated with suppression of the chemokine MCP-1 and adhesion molecule VCAM-1 and ICAM-1 expression. In addition, luciferase reporter assay results revealed that administration of Edaravone attenuatedmore » the increase in NF-κB transcriptional activity induced by oxLDL. Notably, it's also shown that Edaravone treatment blocked oxLDL induced p65 nuclear translocation in HUVECs. Results indicate that Edaravone negatively regulates endothelial inflammation. - Highlights: • Edaravone reduces oxLDL-induced monocyte adhesion to HUVECs. • Edaravone attenuates oxLDL-induced expression of MCP-1, VCAM-1, and ICAM-1. • Edaravone reduces NF-κB transcriptional activity and p65 nuclear translocation.« less

Copper oxide-based model of persistent free radical formation on combustion-derived particulate matter.

PubMed

Lomnicki, Slawo; Truong, Hieu; Vejerano, Eric; Dellinger, Barry

2008-07-01

We have found that environmentally persistent free radicals (PFRs) are formed by adsorption of substituted aromatic molecular precursors on the surface of cupric oxide-containing particles at temperatures between 100 and 400 degrees C. This temperature range corresponds to the conditions in the postflame, cool zone of combustion, and thermal processes. Depending upon the nature of the precursor and the adsorption temperature, both substituted phenoxyl and semiquinone radicals are formed. The PFRs are formed through a mechanism of initial physisorption, followed by chemisorption via elimination of water or hydrogen chloride, and electron transfer resulting in the simultaneous reduction of Cu(II) to Cu(I) and formation of the PFR. The PFRs are still observable by electron paramagnetic resonance (EPR) after exposure to air for more than a day. Their lifetimes under vacuum appear to be infinite. Other redox-active transition metals such as iron are expected to also mediate or catalyze the formation of PFRs. The properties of the observed radicals are consistent with radicals previously observed on airborne and combustion-generated particulate matter. We propose a catalytic biochemical cycle for both the particle-associated semiquinone and phenoxyl PFRs that result in the formation of hydroxyl radical and other reactive oxygen species (ROS). This suggests that combustion-generated, particle-associated PFRs may be responsible for the oxidative stress resulting in cardiopulmonary disease and probably cancer that has been attributed to exposure to airborne fine particles.

NADH induces the generation of superoxide radicals in leaf peroxisomes. [Pisum sativum L

DOE Office of Scientific and Technical Information (OSTI.GOV)

del Rio, L.A.; Sandalio, L.M.; Palma, J.M.

1989-03-01

In peroxisomes isolated from pea leaves (Pisum sativum L.) the production of superoxide free radicals (O{sub 2}{sup {minus}}) by xanthine and NADH was investigated. In peroxisomal membranes, 100 micromolar NADH induced the production of O{sub 2}{sup {minus}} radicals. In the soluble fractions of peroxisomes, no generation of O{sub 2}{sup {minus}} radicals was observed by incubation with either NADH or xanthine, although xanthine oxidase was found located predominantly in the matrix of peroxisomes. The failure of xanthine to induce superoxide generation was probably due to the inability to fully suppress the endogenous Mn-superoxide dismutase activity by inhibitors which were inactive againstmore » xanthine oxidase. The generation of superoxide radicals in leaf peroxisomes together with the recently described production of these oxygen radicals in glyoxysomes suggests that O{sub 2}{sup {minus}} generation could be a common metabolic property of peroxisomes and further supports the existence of active oxygen-related roles for peroxisomes in cellular metabolism.« less

Antioxidant capacity contributes to protection of ketone bodies against oxidative damage induced during hypoglycemic conditions.

PubMed

Haces, María L; Hernández-Fonseca, Karla; Medina-Campos, Omar N; Montiel, Teresa; Pedraza-Chaverri, José; Massieu, Lourdes

2008-05-01

Ketone bodies play a key role in mammalian energy metabolism during the suckling period. Normally ketone bodies' blood concentration during adulthood is very low, although it can rise during starvation, an exogenous infusion or a ketogenic diet. Whenever ketone bodies' levels increase, their oxidation in the brain rises. For this reason they have been used as protective molecules against refractory epilepsy and in experimental models of ischemia and excitotoxicity. The mechanisms underlying the protective effect of these compounds are not completely understood. Here, we studied a possible antioxidant capacity of ketone bodies and whether it contributes to the protection against oxidative damage induced during hypoglycemia. We report for the first time the scavenging capacity of the ketone bodies, acetoacetate (AcAc) and both the physiological and non-physiological isomers of beta-hydroxybutyrate (D- and L-BHB, respectively), for diverse reactive oxygen species (ROS). Hydroxyl radicals (.OH) were effectively scavenged by D- and L-BHB. In addition, the three ketone bodies were able to reduce cell death and ROS production induced by the glycolysis inhibitor, iodoacetate (IOA), while only D-BHB and AcAc prevented neuronal ATP decline. Finally, in an in vivo model of insulin-induced hypoglycemia, the administration of D- or L-BHB, but not of AcAc, was able to prevent the hypoglycemia-induced increase in lipid peroxidation in the rat hippocampus. Our data suggest that the antioxidant capacity contributes to protection of ketone bodies against oxidative damage in in vitro and in vivo models associated with free radical production and energy impairment.

Ambient Particulate Matter Induces Oxidative Dna Damage in Lung Epithelial Cells.

PubMed

Knaapen, A M; Schins, R P; Steinfartz, Y; Doris, H; Dunemann, L; Borm, P J

2000-01-01

Although epidemiological studies have established a correlation between PMIO levels and acute cardiovascular and respiratory complications, hardly any data is available on possible chronic effects such as cancer. The purpose of this study was to investigate the production of free radicals by ambient particulate matter (TSP) and to link these data to oxidative DNA damage in lung epithelial cells. In line with previous findings on PMIO, supercoiled plasmid DNA was depleted by JSP as well as JSP supernatant (p < .001), and this effect was reduced in the presence of mannitol (5 mM). Using electron spin resonance (ESR) and the spin trap dimethyl-1-pyrroline N-oxide (DMPO) we were able to show that hydroxy/radicals ('OH) are formed from both JSP and JSP supernatant. The DMPO-OH signal was completely abrogated when TSP was preincubated with deferoxamine (5 mM), showing the importance of iron and other soluble metals in this process. Atomic absorption spectroscopy (AAS) analysis of the TSP supernatant showed the presence of soluble Fe, V, and Ni (respectively 253.0, 14.7, and 76.0 µ/g insoluble TSP). To investigate the biological significance of OH formation by TSP, 8-hydroxydeoxyguanosine (8-oxodC) was measured in a rat type II cell line by immunocytochemistry. The formation of this hydroxyl-radical-specific DNA adduct was increased twofold (p < .01) after incubation with TSP supernatants, and this effect was inhibited by deferoxamine (p < .01). In summary, our results provide direct evidence that ambient particulate matter generates hydroxyI radicals in acellular systems. Furthermore, we showed that these particulates induce the hydroxyl-radical-specific DNA lesion 8-oxodC in lung target cells via an iron-mediated mechanism.

Oxidation of carbon monoxide, hydrogen peroxide and water at a boron doped diamond electrode: the competition for hydroxyl radicals.

PubMed

Kisacik, Izzet; Stefanova, Ana; Ernst, Siegfried; Baltruschat, Helmut

2013-04-07

Boron doped diamond (BDD) electrodes have an extremely high over-voltage for oxygen evolution from water, which favours its use in oxidation processes of other compounds at high potentials. We used a rotating ring disc (RRDE) assembly and differential electrochemical mass spectrometry (DEMS) in order to monitor the consumption or the production of species in the course of the electrode processes. By intercepting the intermediate of the electrochemical water oxidation with chemical reactions we demonstrate clearly, albeit indirectly, that in the water oxidation process at BDD above 2.5 V the first step is the formation of ˙OH radicals. The electro-oxidation of CO to CO2 at BDD electrodes proceeds only via a first attack by ˙OH radicals followed by a further electron transfer to the electrode. At potentials below the onset of oxygen evolution from water, H2O2 is oxidised by a direct electron transfer to the BDD electrode, while at higher potentials, two different reactions paths compete for the ˙OH radicals formed in the first electron transfer from water: one, where these ˙OH radicals react with each other followed by further electron transfers leading to O2 on the one hand and one, where ˙OH radicals react with other species like H2O2 or CO with subsequent electron transfers on the other hand.

Facile Rearrangement of 3-Oxoalkyl Radicals is Evident in Low-Temperature Gas-Phase Oxidation of Ketones

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scheer, Adam M.; Welz, Oliver; Sasaki, Darryl Y.

The pulsed photolytic chlorine-initiated oxidation of methyl-tert-butyl ketone (MTbuK), di-tert-butyl ketone (DTbuK), and a series of partially deuterated diethyl ketones (DEK) is studied in the gas phase at 8 Torr and 550–650 K. Products are monitored as a function of reaction time, mass, and photoionization energy using multiplexed photoionization mass spectrometry with tunable synchrotron ionizing radiation. The results establish that the primary 3-oxoalkyl radicals of those ketones, formed by abstraction of a hydrogen atom from the carbon atom in γ-position relative to the carbonyl oxygen, undergo a rapid rearrangement resulting in an effective 1,2-acyl group migration, similar to that inmore » a Dowd–Beckwith ring expansion. Without this rearrangement, peroxy radicals derived from MTbuK and DTbuK cannot undergo HO2 elimination to yield a closed-shell unsaturated hydrocarbon coproduct. However, not only are these coproducts observed, but they represent the dominant oxidation channels of these ketones under the conditions of this study. For MTbuK and DTbuK, the rearrangement yields a more stable tertiary radical, which provides the thermodynamic driving force for this reaction. Even in the absence of such a driving force in the oxidation of partially deuterated DEK, the 1,2-acyl group migration is observed. Quantum chemical (CBS-QB3) calculations show the barrier for gas-phase rearrangement to be on the order of 10 kcal mol–1. The MTbuK oxidation experiments also show several minor channels, including β-scission of the initial radicals and cyclic ether formation.« less

Formation of OH radicals in the gas phase ozonolysis of alkenes: the unexpected role of carbonyl oxides

NASA Astrophysics Data System (ADS)

Gutbrod, Roland; Schindler, Ralph N.; Kraka, Elfi; Cremer, Dieter

1996-04-01

According to CCSD(T)/TZ + 2P calculations, the decomposition of carbonyl oxide, H 2COO to HCO and OH radicals is unlikely in view of an activation enthalpy ΔΔHf0(298) of 31 kcal/mol. However, for dimethylcarbonyl oxide there is a low energy rearrangement mode ( ΔΔHf0(298): 14.4 kca/mol) which involves a H atom of ghe methyl group and which leads to a hydroperoxy methyl ethene intermediate, which in turn can decompose to OH and CH 2COCH 3 radicals ( ΔΔHf0(298): 23 kcal/mol). In the gas phase ozonolysis of alkyl substituted alkenes the formation of OH radicals is the most likely process. This has important consequences for the chemistry of the atmosphere.

Detecting free radicals in sunscreens exposed to UVA radiation using chemiluminescence.

PubMed

Millington, Keith R; Osmond, Megan J; McCall, Maxine J

2014-04-05

One of the current concerns with the application of nanoparticles in sunscreens, and in particular nano-TiO2 and ZnO, is their potential to photogenerate free radicals and reactive oxygen species (ROS) when they absorb ultraviolet wavelengths from sunlight. Free radicals and ROS are known to be associated with UV-induced skin damage and oxidative stress, from which sunscreens are expected to offer significant protection. Here we describe a simple method, based on chemiluminescence emission, for detecting free radicals generated in commercial sunscreens alone, and when applied to various substrates, following exposure to UVA (320-400nm) radiation. This photo-induced chemiluminescence (PICL) technique could be used to optimise sunscreen formulations so as to minimise free radical photogeneration during exposure to sunlight. Crown Copyright © 2014. Published by Elsevier B.V. All rights reserved.

Impact of induced levels of specific free radicals and malondialdehyde on chicken semen quality and fertility.

PubMed

Rui, Bruno R; Shibuya, Fábio Y; Kawaoku, Allison J T; Losano, João D A; Angrimani, Daniel S R; Dalmazzo, Andressa; Nichi, Marcilio; Pereira, Ricardo J G

2017-03-01

Over the past decades, scientists endeavored to comprehend oxidative stress in poultry spermatozoa and its relationship with fertilizing ability, lipid peroxidation (LPO), free-radical scavenging systems, and antioxidant therapy. Although considerable progress has been made, further improvement is needed in understanding how specific reactive oxygen species (ROS) and malondialdehyde (MDA, a toxic byproduct of LPO) disrupt organelles in avian spermatozoon. Hence, this study examined functional changes in chicken spermatozoa after incubation with different ROS, and their implications for the fertility. First, semen samples from 14 roosters were individually diluted and aliquoted into five equal parts: control, superoxide anion, hydrogen peroxide (H 2 O 2 ), hydroxyl radicals, and MDA. After incubation with these molecules, aliquots were analyzed for motility, plasma membrane and acrosome integrity, mitochondrial activity, and LPO and DNA damage. Hydrogen peroxide was more detrimental for sperm motility than hydroxyl radicals, whereas the superoxide anion and MDA exhibited no differences compared with controls. In turn, plasma membrane and acrosome integrity, mitochondrial activity, LPO and DNA integrity rates were only affected by hydroxyl radicals. Thereafter, semen aliquots were incubated under the same conditions and used for artificial insemination. In accordance to our in vitro observations, H 2 O 2 and hydroxyl radicals sharply reduced egg fertility, whereas superoxide anion and MDA only induced slight declines. Thus, chicken sperm function was severely impaired by H 2 O 2 and hydroxyl radicals, but their mechanisms of action seemingly comprise different pathways. Further analysis regarding susceptibility of spermatozoon organelles to specific radicals in other poultry will help us to understand the development of interspecific differences in scavenging systems and to outline more oriented antioxidant approaches. Copyright © 2016 Elsevier Inc. All rights

Suicidal inactivation of methemoglobin by generation of thiyl radical: insight into NAC mediated protection in RBC.

PubMed

Balaji, S N; Trivedi, V

2013-07-01

N-acetyl-L-cysteine (NAC) improves antioxidant potentials of RBCs to provide protection against oxidative stress induced hemolysis. The antioxidant mechanism of NAC to reduce oxidative stress in RBC, studied through inactivation of pro-oxidant MetHb. NAC causes irreversible inactivation of the MetHb in an H2O2 dependent manner, and the inactivation follows the pseudo- first- order kinetics. The kinetic constants are ki = 8.5μM, kinact = 0.706 min(-1) and t1/2 = 0.9 min. Spectroscopic studies indicate that MetHb accepts NAC as a substrate and oxidizes through a single electron transfer mechanism to the NACox. The single e- oxidation product of NAC has been identified as the 5, 5'- dimethyl-1- pyrroline N- oxide (DMPO) adduct of the sulfur centered radical (a(N) = 15.2 G and a(H)=16.78 G). Binding studies indicate that NACox interacts at the heme moiety and NAC oxidation through MetHb is essential for NAC binding. Heme-NAC adduct dissociated from MetHb and identified (m/z 1011.19) as 2:1 ratio of NAC/heme in the adduct. TEMPO and PBN treatment reduces NAC binding to MetHb and protects against inactivation confirms the role of thiyl radical in the inactivation process. Furthermore, scavenging thiyl radicals by TEMPO abolish the protective effect of NAC in hemolysis. Current work highlights antioxidant mechanism of NAC through NAC thiyl radical generation, and MetHb inactivation to exhibit protection in RBC against oxidative stress induced hemolysis.

Cyclooxygenase Reaction Mechanism of PGHS ------- Evidence for a Reversible Transition between a Pentadienyl Radical and a New Tyrosyl Radical by Nitric Oxide Trapping

PubMed Central

Lü, Jian-Ming; Rogge, Corina E.; Wu, Gang; Kulmacz, Richard J.; van der Donk, Wilfred A.; Tsai, Ah-lim

2011-01-01

Incubation of prostaglandin H synthase-1 (PGHS-1) under anaerobic conditions with peroxide and arachidonic acid leads to two major radical species: a pentadienyl radical and a radical with a narrow EPR spectrum. The proportions of the two radicals are sensitive to temperature, favoring the narrow radical species at 22 °C. The EPR characteristics of this latter radical are somewhat similar to the previously reported narrow-singlet tyrosine radical NS1a and are insensitive to deuterium labeling of AA. To probe the origin and structure of this radical, we combined EPR analysis with nitric oxide (NO) trapping of tyrosine and substrate derived radicals for both PGHS-1 and -2. Formation of 3-nitrotyrosine in the proteins was analyzed by immunoblotting, whereas NO adducts to AA and AA metabolites were analyzed by mass spectrometry and by chromatography of 14C-labeled products. The results indicate that both nitrated tyrosine residues and NO-AA adducts formed upon NO trapping. The NO-AA adduct was predominantly an oxime at C11 of AA with three conjugated double bonds, as indicated by absorption at 275 nm and by mass spectral analysis. This adduct amounted to 10% and 20% of the heme concentration of PGHS-1 and -2, respectively. For PGHS-1, the yield of NO-AA adduct matched the yield of the narrow radical signal obtained in parallel EPR experiments. High frequency EPR characterization of this narrow radical, reported in an accompanying paper, supports assignment to a new tyrosyl radical, NS1c, rather than an AA-based radical. To reconcile the results from EPR and NO-trapping studies, we propose that the NS1c is in equilibrium with an AA pentadienyl radical, and that the latter reacts preferentially with NO. PMID:21403766

[The significance of free radicals and antioxidants due to the load induced by sport activity].

PubMed

Holecek, V; Liska, J; Racek, J; Rokyta, R

2004-01-01

Sport performance is followed by a high production of free radicals. The main reasons are reperfusion after the previous imbalance between the increased need of the organism and the ability of blood supply by oxygen, increased production of ATP, decomposition of the cells particularly white blood cells, oxidation of the purin basis from DNA, stress, output of epinephrine release of free iron, increased temperature in the muscle and its inflammation, and the reception of free radicals from external environment. Peroxidation of lipids, proteins, DNA and other compounds follows the previous biochemical steps. Antioxidants are consumed by free radicals, antioxidative enzymes are released into blood plasma, intracellular calcium is increased, the production of nitric oxide rises, the levels of hydrogen peroxide and hypochlorous acid increase. These penetrate through the membranes and oxidatively damage the tissues. Training improves the ability of the organism to balance the increased load of free radicals. The damage can be lowered by the application of a mixture of antioxidants, the most important are vitamin C, A, E, glutathione, selenium, carnosine, eventually bioflavonoids and ginkgo biloba. The lack of antioxidants can significantly diminish the sport performance and therefore the supplementation with antioxidants is for top sportsmen but also for aged people advisable.

Quantification of Lightning-induced Nitrogen Oxides in CMAQ and the Assessment of its impact on Ground-level Air Quality

EPA Science Inventory

Lightning-induced nitrogen oxides (LNOX), in the presence of sunlight, volatile organic compounds and water, can be a relatively large but uncertain source for ozone (O3) and hydroxyl radical (OH) in the atmosphere. Using lightning flash data from the National Lightning Detection...

Anti-inflammatory and anti-oxidant properties of Sida rhombifolia stems and roots in adjuvant induced arthritic rats.

PubMed

Narendhirakannan, R T; Limmy, T P

2012-04-01

Free radical stress leads to tissue injury and progression of disease conditions such as arthritis, hemorrhagic shock, atherosclerosis, diabetes, hepatic injury, aging and ischemia, reperfusion injury of many tissues, gastritis, tumor promotion, neurodegenerative diseases and carcinogenesis. Safer anti-oxidants suitable for long term use are needed to prevent or stop the progression of free radical mediated disorders. Herbal medicine provides a foundation for various traditional medicine systems worldwide. The Sida species is one of the most important families of medicinal plants in India. Hence, the present study was aimed to investigate the possible anti-oxidant potential of Sida rhombifolia extracts for 30 days on adjuvant induced arthritis in experimental rats. The altered levels of hematological parameters were reverted to near normal levels, especially the elevated rate of erythrocyte sedimentation was significantly reduced by S. rhombifolia extracts in experimental rats. Oral administration of root and stem of S. rhombifolia extracts significantly increased the levels of thiobarbituric acid reactive substances and activities of catalase and glutathione peroxidase and decreased the levels of reduced glutathione and superoxide dismutase activity in arthritis induced rats. The free radical scavenging activity of the plant was further evidenced by histological and transmission electron microscopy observations made on the hind limb tissue.

Pueraria thunbergiana inhibits cisplatin-induced damage of HEI-OC1 auditory cells through scavenging free radicals.

PubMed

Yu, Hyeon-Hee; Jung, Su-Young; Shin, Mee-Kyung; Park, Raekil; So, Hong-Seob; You, Yong-Ouk

2010-06-01

The radix of Pueraria thunbergiana (P. thunbergiana) is traditionally prescribed to attenuate the clinical manifestation of inner ear dysfunction and various clinical situations including fevers, gastrointestinal disorders, skin problems, migraine headaches, lowering cholesterol, and treating chronic alcoholism in oriental medicine. In the present study, we examined the protective effect of ethanol extract of the radix of P. thunbergiana (RPT) on cisplatin-induced damage of HEI-OC1 auditory hair cells. When the cells were cultured in the medium containing 5-100 microg/mL of RPT, RPT showed protective effect against the cisplatin-induced HEI-OC1 cell damage. We also measured the effects of RPT on lipid peroxidation of cisplatin-treated cells as well as scavenging activities against superoxide radical, hydroxyl radical, hydrogen peroxide, and DPPH radical. RPT reduced cisplatin-induced lipid peroxidation in a dose-dependent manner. Furthermore, RPT showed strong scavenging activity against superoxide radical, hydroxyl radical, hydrogen peroxide, and DPPH radical. These results indicate that RPT protects cisplatin-induced HEI-OC1 cell damage through inhibition of lipid peroxidation and scavenging activities of free radials. (c) 2009 John Wiley & Sons, Ltd.

Aircraft-borne, laser-induced fluorescence instrument for the in situ detection of hydroxyl and hydroperoxyl radicals

NASA Technical Reports Server (NTRS)

Wennberg, P. O.; Cohen, R. C.; Hazen, N. L.; Lapson, L. B.; Allen, N. T.; Hanisco, T. F.; Oliver, J. F.; Lanham, N. W.; Demusz, J. N.; Anderson, J. G.

1994-01-01

The odd-hydrogen radicals OH and HO2 are central to most of the gas-phase chemical transformations that occur in the atmosphere. Of particular interest is the role that these species play in controlling the concentration of stratospheric ozone. This paper describes an instrument that measures both of these species at volume mixing ratios below one part in 10(exp 14) in the upper troposphere and lower stratosphere. The hydroxyl radical (OH) is measured by laser induced fluorescence at 309 nm. Tunable UV light is used to pump OH to the first electric state near 282 nm. the laser light is produced by a high-repetition rate pulsed dye-laser powered with all solid-state pump lasers. HO2 is measured as OH after gas-phase titration with nitric oxide. Measurements aboard a NASA ER-2 aircraft demonstrate the capability of this instrument to perform reliably with very high signal-to-noise ratios (greater than 30) achieved in short integration times (less than 20 sec).

Edaravone is a free radical scavenger that protects against laser-induced choroidal neovascularization in mice and common marmosets.

PubMed

Masuda, Tomomi; Shimazawa, Masamitsu; Takata, Shinsuke; Nakamura, Shinsuke; Tsuruma, Kazuhiro; Hara, Hideaki

2016-05-01

Choroidal neovascularization (CNV) is a main characteristic in exudative type of age-related macular degeneration (AMD). Our study aimed to evaluate the effects of edaravone, a free radical scavenger on laser-induced CNV. CNV was induced by laser photocoagulation to the subretinal choroidal area of mice and common marmosets. Edaravone was administered either intraperitoneally twice a day for 2 weeks or intravenously just once after laser photocoagulation. The effects of edaravone on laser-induced CNV were evaluated by fundus fluorescein angiography, CNV area measurements, and the expression of 4-hydroxy-2-nonenal (4-HNE) modified proteins, a marker of oxidative stress. Furthermore, the effects of edaravone on the production of H2O2-induced reactive oxygen species (ROS) and vascular endothelial growth factor (VEGF)-induced cell proliferation were evaluated using human retinal pigment epithelium cells (ARPE-19) and human retinal microvascular endothelial cells, respectively. CNV areas in the edaravone-treated group were significantly smaller in mice and common marmosets. The expression of 4-HNE modified proteins was upregulated 3 h after laser photocoagulation, and intravenously administered edaravone decreased it. In in vitro studies, edaravone inhibited H2O2-induced ROS production and VEGF-induced cell proliferation. These findings suggest that edaravone may protect against laser-induced CNV by inhibiting oxidative stress and endothelial cell proliferation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Oxidative stress is involved in Dasatinib-induced apoptosis in rat primary hepatocytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xue, Tao; Luo, Peihua; Zhu, Hong

2012-06-15

Dasatinib, a multitargeted inhibitor of BCR–ABL and SRC kinases, exhibits antitumor activity and extends the survival of patients with chronic myeloid leukemia (CML) and Philadelphia chromosome-positive acute lymphoblastic leukemia (ALL). However, some patients suffer from hepatotoxicity, which occurs through an unknown mechanism. In the present study, we found that Dasatinib could induce hepatotoxicity both in vitro and in vivo. Dasatinib reduced the cell viability of rat primary hepatocytes, induced the release of alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) in vitro, and triggered the ballooning degeneration of hepatocytes in Sprague–Dawley rats in vivo. Apoptotic markers (chromatin condensation, cleaved caspase-3 andmore » cleaved PARP) were detected to indicate that the injury induced by Dasatinib in hepatocytes in vitro was mediated by apoptosis. This result was further validated in vivo using terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assays. Here we found that Dasatinib dramatically increased the level of reactive oxygen species (ROS) in hepatocytes, reduced the intracellular glutathione (GSH) content, attenuated the activity of superoxide dismutase (SOD), generated malondialdehyde (MDA), a product of lipid peroxidation, decreased the mitochondrial membrane potential, and activated nuclear factor erythroid 2-related factor 2 (Nrf2) and mitogen-activated protein kinases (MAPK) related to oxidative stress and survival. These results confirm that oxidative stress plays a pivotal role in Dasatinib-mediated hepatotoxicity. N-acetylcysteine (NAC), a typical antioxidant, can scavenge free radicals, attenuate oxidative stress, and protect hepatocytes against Dasatinib-induced injury. Thus, relieving oxidative stress is a viable strategy for reducing Dasatinib-induced hepatotoxicity. -- Highlights: ►Dasatinib shows potential hepatotoxicity both in vitro and in vivo. ►Apoptosis plays a vital role in

α-Tocopherol/Gallic Acid Cooperation in the Protection of Galactolipids Against Ozone-Induced Oxidation.

PubMed

Rudolphi-Skórska, Elżbieta; Filek, Maria; Zembala, Maria

2016-04-01

The protective ability of α-tocopherol (TOH) and gallic acid (GA) acting simultaneously at the moment of oxidizer application was evaluated by determination of galactolipid layers' oxidation degree. Addition of GA resulted in a significant decrease of ozone-derived radicals shifting the threshold of lipid sensitivity by an amount approximately corresponding to the GA intake in bulk reaction with ozone. TOH presence in lipid layers results in a change of the role of GA which additionally may be involved in the reduction of tocopheroxyl radical formed during oxidation. This leads to a decrease in effectiveness of GA in diminishing the amount of ozone radicals. Such an effect was not observed for mixed layers containing galactolipid and pre-oxidized tocopherol where the ozone threshold level was associated with a stoichiometry of GA + O3 reaction. It was concluded that probably subsequent transformations of tocopheroxyl radical to less reactive forms prevent its reaction with GA the entire quantity of which is used for radicals scavenging. This result shows the role of time parameter in systems where substrates are engaged in various reactions taking place simultaneously. The inactivation of 1,1-diphenyl-2-picrylhydrazyl radical by studied antioxidants in homogeneous system confirmed observations made on the basis of lipid layer properties indicating their antagonistic action (at least at studied conditions). Formation of layers in post-oxidation situation did not depend whether tocopherol was oxidized during oxidation of lipid/tocopherol mixture or was introduced as pre-oxidized. This may be interpreted as indication that products of tocopherol oxidation may stabilize lipid layers.

Theoretical and modeling studies of the atmospheric chemistry of sulfur oxide and hydroxyl radical systems

NASA Astrophysics Data System (ADS)

El-Zanan, Hazem S.

Models are the tools that integrate our understanding of the atmospheric processes. Box models are utilized frequently and used to simulate the fates and transformation of atmospheric pollutants. The results from models are usually used to produce one integrated system and further help the policy makers to develop control strategies. We have investigated the atmospheric chemistry of the SOx and HOx systems. The results of 15 laboratory experiments that involved the studies of the HO-SO2, reaction have been analyzed. Mixtures of HONO, NO, NO2, H2O, SO2 and CO were photolyzed in synthetic air or in nitrogen containing approximately 50 ppm oxygen. Upon analyzing the data we have found that a very large amount of the observed SO2 oxidation (70.0 +/- 9.1%) can not be explained through the gas phase reaction of HO + SO2 reaction alone. The Regional Atmospheric Chemistry Mechanism, Version 2 (RACM2) was used to investigate additional chemical pathways for the oxidation of SO2. The results indicate that a mechanism(s) involving photochemical heterogeneous reactions could account for the observed additional sulfur dioxide oxidation not accounted for by gas phase oxidation alone. We have also investigated the distribution of the hydroxyl radical in different urban and rural areas. Photolysis of ozone and its reactions with nitrogen oxides and organic compounds, including both anthropogenic and biogenic volatile organic compounds (VOCs), control the mixing ratios of the hydroxyl radical (HO). Measurements of ozone, nitrogen oxides and volatile hydrocarbons from a deciduous forest in July 1999 and six sites located in the San Joaquin Valley obtained during the Central California Ozone Study (CCOS) measured in July 2000 and September 2000 were used to estimate the hydroxyl radical concentrations. Two methods were employed to determine the concentrations: (1) box model simulations and (2) steady state approximation of the species concentrations (Production-Loss Method). The

Visible light-induced OH radicals in Ga2O3: an EPR study.

PubMed

Tzitrinovich, Zeev; Lipovsky, Anat; Gedanken, Aharon; Lubart, Rachel

2013-08-21

Reactive oxygen species (ROS) were found to exist in water suspensions of several metal oxide nanoparticles (NPs), such as CuO, TiO2 and ZnO. Visible light irradiation enhanced the capability of TiO2 and ZnO NPs to generate ROS, thus increasing their antibacterial effects. Because of the possible toxic effects on the host tissue it is desired to find nano-metal oxides which do not produce ROS under room light, but only upon a strong external stimulus. Using the technique of electron-spin resonance (ESR) coupled with spin trapping, we examined the ability of Ga2O3 submicron-particle suspensions in water to produce reactive oxygen species with and without visible light irradiation. We found that in contrast to ZnO and TiO2 NPs, no ROS are produced by Ga2O3 under room light. Nevertheless blue light induced hydroxyl radical formation in Ga2O3. This finding might suggest that NPs of Ga2O3 could be used safely for infected skin sterilization.

Chlorine as a primary radical: evaluation of methods to understand its role in initiation of oxidative cycles

NASA Astrophysics Data System (ADS)

Young, C. J.; Washenfelder, R. A.; Edwards, P. M.; Parrish, D. D.; Gilman, J. B.; Kuster, W. C.; Mielke, L. H.; Osthoff, H. D.; Tsai, C.; Pikelnaya, O.; Stutz, J.; Veres, P. R.; Roberts, J. M.; Griffith, S.; Dusanter, S.; Stevens, P. S.; Flynn, J.; Grossberg, N.; Lefer, B.; Holloway, J. S.; Peischl, J.; Ryerson, T. B.; Atlas, E. L.; Blake, D. R.; Brown, S. S.

2014-04-01

The role of chlorine atoms (Cl) in atmospheric oxidation has been traditionally thought to be limited to the marine boundary layer, where they are produced through heterogeneous reactions involving sea salt. However, recent observation of photolytic Cl precursors (ClNO2 and Cl2) formed from anthropogenic pollution has expanded the potential importance of Cl to include coastal and continental urban areas. Measurements of ClNO2 in Los Angeles during CalNex (California Nexus - Research at the Nexus of Air Quality and Climate Change) showed it to be an important primary (first generation) radical source. Evolution of ratios of volatile organic compounds (VOCs) has been proposed as a method to quantify Cl oxidation, but we find no evidence from this approach for a significant role of Cl oxidation in Los Angeles. We use a box model with the Master Chemical Mechanism (MCM v3.2) chemistry scheme, constrained by observations in Los Angeles, to examine the Cl sensitivity of commonly used VOC ratios as a function of NOx and secondary radical production. Model results indicate VOC tracer ratios could not detect the influence of Cl unless the ratio of [OH] to [Cl] was less than 200 for at least a day. However, the model results also show that secondary (second generation) OH production resulting from Cl oxidation of VOCs is strongly influenced by NOx, and that this effect obscures the importance of Cl as a primary oxidant. Calculated concentrations of Cl showed a maximum in mid-morning due to a photolytic source from ClNO2 and loss primarily to reactions with VOCs. The [OH] to [Cl] ratio was below 200 for approximately 3 h in the morning, but Cl oxidation was not evident from the measured ratios of VOCs. Instead, model simulations show that secondary OH production causes VOC ratio evolution to follow that expected for OH oxidation, despite the significant input of primary Cl from ClNO2 photolysis in the morning. Even though OH is by far the dominant oxidant in Los Angeles, Cl

Regulation of exercise blood flow: Role of free radicals.

PubMed

Trinity, Joel D; Broxterman, Ryan M; Richardson, Russell S

2016-09-01

During exercise, oxygen and nutrient rich blood must be delivered to the active skeletal muscle, heart, skin, and brain through the complex and highly regulated integration of central and peripheral hemodynamic factors. Indeed, even minor alterations in blood flow to these organs have profound consequences on exercise capacity by modifying the development of fatigue. Therefore, the fine-tuning of blood flow is critical for optimal physical performance. At the level of the peripheral circulation, blood flow is regulated by a balance between the mechanisms responsible for vasodilation and vasoconstriction. Once thought of as toxic by-products of in vivo chemistry, free radicals are now recognized as important signaling molecules that exert potent vasoactive responses that are dependent upon the underlying balance between oxidation-reduction reactions or redox balance. Under normal healthy conditions with low levels of oxidative stress, free radicals promote vasodilation, which is attenuated with exogenous antioxidant administration. Conversely, with advancing age and disease where background oxidative stress is elevated, an exercise-induced increase in free radicals can further shift the redox balance to a pro-oxidant state, impairing vasodilation and attenuating blood flow. Under these conditions, exogenous antioxidants improve vasodilatory capacity and augment blood flow by restoring an "optimal" redox balance. Interestingly, while the active skeletal muscle, heart, skin, and brain all have unique functions during exercise, the mechanisms by which free radicals contribute to the regulation of blood flow is remarkably preserved across each of these varied target organs. Published by Elsevier Inc.

Regulation of Exercise Blood Flow: Role of Free Radicals

PubMed Central

Trinity, Joel D.; Broxterman, Ryan M.; Richardson, Russell S.

2016-01-01

During exercise, oxygen and nutrient rich blood must be delivered to the active skeletal muscle, heart, skin, and brain through the complex and highly regulated integration of central and peripheral hemodynamic factors. Indeed, even minor alterations in blood flow to these organs have profound consequences on exercise capacity by modifying the development of fatigue. Therefore, the fine-tuning of blood flow is critical for optimal physical performance. At the level of the peripheral circulation, blood flow is regulated by a balance between the mechanisms responsible for vasodilation and vasoconstriction. Once thought of as toxic by-products of in vivo chemistry, free radicals are now recognized as important signaling molecules that exert potent vasoactive responses that are dependent upon the underlying balance between oxidation-reduction reactions or redox balance. Under normal healthy conditions with low levels of oxidative stress, free radicals promote vasodilation, which is attenuated with exogenous antioxidant administration. Conversely, with advancing age and disease where background oxidative stress is elevated, an exercise-induced increase in free radicals can further shift the redox balance to a pro-oxidant state, impairing vasodilation and attenuating blood flow. Under these conditions, exogenous antioxidants improve vasodilatory capacity and augment blood flow by restoring an “optimal” redox balance. Interestingly, while the active skeletal muscle, heart, skin, and brain all have unique functions during exercise, the mechanisms by which free radicals contribute to the regulation of blood flow is remarkably preserved across each of these varied target organs. PMID:26876648

Halobenzoquinone-Induced Alteration of Gene Expression Associated with Oxidative Stress Signaling Pathways.

PubMed

Li, Jinhua; Moe, Birget; Liu, Yanming; Li, Xing-Fang

2018-06-05

Halobenzoquinones (HBQs) are emerging disinfection byproducts (DBPs) that effectively induce reactive oxygen species and oxidative damage in vitro. However, the impacts of HBQs on oxidative-stress-related gene expression have not been investigated. In this study, we examined alterations in the expression of 44 genes related to oxidative-stress-induced signaling pathways in human uroepithelial cells (SV-HUC-1) upon exposure to six HBQs. The results show the structure-dependent effects of HBQs on the studied gene expression. After 2 h of exposure, the expression levels of 9 to 28 genes were altered, while after 8 h of exposure, the expression levels of 29 to 31 genes were altered. Four genes ( HMOX1, NQO1, PTGS2, and TXNRD1) were significantly upregulated by all six HBQs at both exposure time points. Ingenuity pathway analysis revealed that the Nrf2 pathway was significantly responsive to HBQ exposure. Other canonical pathways responsive to HBQ exposure included GSH redox reductions, superoxide radical degradation, and xenobiotic metabolism signaling. This study has demonstrated that HBQs significantly alter the gene expression of oxidative-stress-related signaling pathways and contributes to the understanding of HBQ-DBP-associated toxicity.

The oxidative hypothesis of senescence.

PubMed

Gilca, M; Stoian, I; Atanasiu, V; Virgolici, B

2007-01-01

The oxidative hypothesis of senescence, since its origin in 1956, has garnered significant evidence and growing support among scientists for the notion that free radicals play an important role in ageing, either as "damaging" molecules or as signaling molecules. Age-increasing oxidative injuries induced by free radicals, higher susceptibility to oxidative stress in short-lived organisms, genetic manipulations that alter both oxidative resistance and longevity and the anti-ageing effect of caloric restriction and intermittent fasting are a few examples of accepted scientific facts that support the oxidative theory of senescence. Though not completely understood due to the complex "network" of redox regulatory systems, the implication of oxidative stress in the ageing process is now well documented. Moreover, it is compatible with other current ageing theories (e.g, those implicating the mitochondrial damage/mitochondrial-lysosomal axis, stress-induced premature senescence, biological "garbage" accumulation, etc). This review is intended to summarize and critically discuss the redox mechanisms involved during the ageing process: sources of oxidant agents in ageing (mitochondrial -electron transport chain, nitric oxide synthase reaction- and non-mitochondrial- Fenton reaction, microsomal cytochrome P450 enzymes, peroxisomal beta -oxidation and respiratory burst of phagocytic cells), antioxidant changes in ageing (enzymatic- superoxide dismutase, glutathione-reductase, glutathion peroxidase, catalase- and non-enzymatic glutathione, ascorbate, urate, bilirubine, melatonin, tocopherols, carotenoids, ubiquinol), alteration of oxidative damage repairing mechanisms and the role of free radicals as signaling molecules in ageing.

Modulation of oxidative damage by nitroxide free radicals.

PubMed

Dragutan, Ileana; Mehlhorn, Rolf J

2007-03-01

Piperidine nitroxides like 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) are persistent free radicals in non-acidic aqueous solutions and organic solvents that may have value as therapeutic agents in medicine. In biological environments, they undergo mostly reduction to stable hydroxylamines but can also undergo oxidation to reactive oxoammonium compounds. Reactions of the oxoammonium derivatives could have adverse consequences including chemical modification of vital macromolecules and deleterious effects on cell signaling. An examination of their reactivity in aqueous solution has shown that oxoammonium compounds can oxidize almost any organic as well as many inorganic molecules found in biological systems. Many of these reactions appear to be one-electron transfers that reduce the oxoammonium to the corresponding nitroxide species, in contrast to a prevalence of two-electron reductions of oxoammonium in organic solvents. Amino acids, alcohols, aldehydes, phospholipids, hydrogen peroxide, other nitroxides, hydroxylamines, phenols and certain transition metal ions and their complexes are among reductants of oxoammonium, causing conversion of this species to the paramagnetic nitroxide. On the other hand, thiols and oxoammonium yield products that cannot be detected by ESR even under conditions that would oxidize hydroxylamines to nitroxides. These products may include hindered secondary amines, sulfoxamides and sulfonamides. Thiol oxidation products other than disulfides cannot be restored to thiols by common enzymatic reduction pathways. Such products may also play a role in cell signaling events related to oxidative stress. Adverse consequences of the reactions of oxoammonium compounds may partially offset the putative beneficial effects of nitroxides in some therapeutic settings.

Kinetics of the heterogeneous photo oxidation of the pesticide bupirimate by OH-radicals and ozone under atmospheric conditions.

PubMed

Bouya, H; Errami, M; Chakir, A; Roth, E

2015-09-01

This article is concerned with the study of the photochemical degradation of bupirimate adsorbed on a quartz surface by atmospheric oxidants, namely ozone and OH radicals. OH oxidation experiments were conducted relative to two reference compounds, terbuthylazine and (4-chlorophenyl)(3,4-dimethoxyphenyl) methanone. Meanwhile, ozone oxidation experiments were performed in the absolute mode and were interpreted by both, the Surface Layer Reaction and the Gas Surface Reaction models of heterogeneous reactions. The obtained results show that the rate constants for the reactions between bupirimate and OH radicals and ozone are (cm(3)molecule(-1)s(-1)): (1.06 ± 0.87) × 10(-12) and (5.4 ± 0.3) × 10(-20), respectively. As a consequence, for the experimental conditions used in this study, the lifetime of bupirimate at quartz like surface/atmosphere interfaces is several months against ozone and a tenth of days against OH-radical. Copyright © 2015 Elsevier Ltd. All rights reserved.

Free Radical Chemistry Enabled by Visible Light-Induced Electron Transfer

PubMed Central

2016-01-01

Conspectus Harnessing visible light as the driving force for chemical transformations generally offers a more environmentally friendly alternative compared with classical synthetic methodology. The transition metal-based photocatalysts commonly employed in photoredox catalysis absorb efficiently in the visible spectrum, unlike most organic substrates, allowing for orthogonal excitation. The subsequent excited states are both more reducing and more oxidizing than the ground state catalyst and are competitive with some of the more powerful single-electron oxidants or reductants available to organic chemists yet are simply accessed via irradiation. The benefits of this strategy have proven particularly useful in radical chemistry, a field that traditionally employs rather toxic and hazardous reagents to generate the desired intermediates. In this Account, we discuss our efforts to leverage visible light photoredox catalysis in radical-based bond-forming and bond-cleaving events for which few, if any, environmentally benign alternatives exist. Mechanistic investigations have driven our contributions in this field, for both facilitating desired transformations and offering new, unexpected opportunities. In fact, our total synthesis of (+)-gliocladin C was only possible upon elucidating the propensity for various trialkylamine additives to elicit a dual behavior as both a reductive quencher and a H-atom donor. Importantly, while natural product synthesis was central to our initial motivations to explore these photochemical processes, we have since demonstrated applicability within other subfields of chemistry, and our evaluation of flow technologies demonstrates the potential to translate these results from the bench to pilot scale. Our forays into photoredox catalysis began with fundamental methodology, providing a tin-free reductive dehalogenation that exchanged the gamut of hazardous reagents previously employed for such a transformation for visible light

Free Radical Chemistry Enabled by Visible Light-Induced Electron Transfer.

PubMed

Staveness, Daryl; Bosque, Irene; Stephenson, Corey R J

2016-10-18

Harnessing visible light as the driving force for chemical transformations generally offers a more environmentally friendly alternative compared with classical synthetic methodology. The transition metal-based photocatalysts commonly employed in photoredox catalysis absorb efficiently in the visible spectrum, unlike most organic substrates, allowing for orthogonal excitation. The subsequent excited states are both more reducing and more oxidizing than the ground state catalyst and are competitive with some of the more powerful single-electron oxidants or reductants available to organic chemists yet are simply accessed via irradiation. The benefits of this strategy have proven particularly useful in radical chemistry, a field that traditionally employs rather toxic and hazardous reagents to generate the desired intermediates. In this Account, we discuss our efforts to leverage visible light photoredox catalysis in radical-based bond-forming and bond-cleaving events for which few, if any, environmentally benign alternatives exist. Mechanistic investigations have driven our contributions in this field, for both facilitating desired transformations and offering new, unexpected opportunities. In fact, our total synthesis of (+)-gliocladin C was only possible upon elucidating the propensity for various trialkylamine additives to elicit a dual behavior as both a reductive quencher and a H-atom donor. Importantly, while natural product synthesis was central to our initial motivations to explore these photochemical processes, we have since demonstrated applicability within other subfields of chemistry, and our evaluation of flow technologies demonstrates the potential to translate these results from the bench to pilot scale. Our forays into photoredox catalysis began with fundamental methodology, providing a tin-free reductive dehalogenation that exchanged the gamut of hazardous reagents previously employed for such a transformation for visible light-mediated, ambient

Chlorine atom-initiated low-temperature oxidation of prenol and isoprenol: The effect of C=C double bonds on the peroxy radical chemistry in alcohol oxidation

DOE PAGES

Welz, Oliver; Savee, John D.; Osborn, David L.; ...

2014-07-04

The chlorine atom-initiated oxidation of two unsaturated primary C5 alcohols, prenol (3-methyl-2-buten-1-ol, (CH 3) 2CCHCH 2OH) and isoprenol (3-methyl-3-buten-1-ol, CH 2C(CH 3)CH 2CH 2OH), is studied at 550 K and low pressure (8 Torr). The time- and isomer-resolved formation of products is probed with multiplexed photoionization mass spectrometry (MPIMS) using tunable vacuum ultraviolet ionizing synchrotron radiation. The peroxy radical chemistry of the unsaturated alcohols appears much less rich than that of saturated C4 and C5 alcohols. The main products observed are the corresponding unsaturated aldehydes – prenal (3-methyl-2-butenal) from prenol oxidation and isoprenal (3-methyl-3-butenal) from isoprenol oxidation. No significant productsmore » arising from QOOH chemistry are observed. These results can be qualitatively explained by the formation of resonance stabilized allylic radicals via H-abstraction in the Cl + prenol and Cl + isoprenol initiation reactions. The loss of resonance stabilization upon O 2 addition causes the energies of the intermediate wells, saddle points, and products to increase relative to the energy of the initial radicals and O 2. These energetic shifts make most product channels observed in the peroxy radical chemistry of saturated alcohols inaccessible for these unsaturated alcohols. The experimental findings are underpinned by quantum-chemical calculations for stationary points on the potential energy surfaces for the reactions of the initial radicals with O 2. Under our conditions, the dominant channels in prenol and isoprenol oxidation are the chain-terminating HO 2-forming channels arising from radicals, in which the unpaired electron and the –OH group are on the same carbon atom, with stable prenal and isoprenal co-products, respectively. These results suggest that the presence of C=C double bonds in alcohols will reduce low-temperature reactivity during autoignition.« less

Protection from radiation-induced pneumonitis using cerium oxide nanoparticles.

PubMed

Colon, Jimmie; Herrera, Luis; Smith, Joshua; Patil, Swanand; Komanski, Chris; Kupelian, Patrick; Seal, Sudipta; Jenkins, D Wayne; Baker, Cheryl H

2009-06-01

In an effort to combat the harmful effects of radiation exposure, we propose that rare-earth cerium oxide (CeO(2)) nanoparticles (free-radical scavengers) protect normal tissue from radiation-induced damage. Preliminary studies suggest that these nanoparticles may be a therapeutic regenerative nanomedicine that will scavenge reactive oxygen species, which are responsible for radiation-induced cell damage. The effectiveness of CeO(2) nanoparticles in radiation protection in murine models during high-dose radiation exposure is investigated, with the ultimate goal of offering a new approach to radiation protection, using nanotechnology. We show that CeO(2) nanoparticles are well tolerated by live animals, and they prevent the onset of radiation-induced pneumonitis when delivered to live animals exposed to high doses of radiation. In the end, these studies provide a tremendous potential for radioprotection and can lead to significant benefits for the preservation of human health and the quality of life for humans receiving radiation therapy.

Controlling the orientation of spin-correlated radical pairs by covalent linkage to nanoporous anodic aluminum oxide membranes.

PubMed

Chen, Hsiao-Fan; Gardner, Daniel M; Carmieli, Raanan; Wasielewski, Michael R

2013-10-07

Ordered multi-spin assemblies are required for developing solid-state molecule-based spintronics. A linear donor-chromophore-acceptor (D-C-A) molecule was covalently attached inside the 150 nm diam. nanopores of an anodic aluminum oxide (AAO) membrane. Photoexcitation of D-C-A in a 343 mT magnetic field results in sub-nanosecond, two-step electron transfer to yield the spin-correlated radical ion pair (SCRP) (1)(D(+)˙-C-A(-)˙), which then undergoes radical pair intersystem crossing (RP-ISC) to yield (3)(D(+)˙-C-A(-)˙). RP-ISC results in S-T0 mixing to selectively populate the coherent superposition states |S'> and |T'>. Microwave-induced transitions between these states and the unpopulated |T(+1)> and |T(-1)> states result in spin-polarized time-resolved EPR (TREPR) spectra. The dependence of the electron spin polarization (ESP) phase of the TREPR spectra on the orientation of the AAO membrane pores relative to the externally applied magnetic field is used to determine the overall orientation of the SCRPs within the pores at room temperature.

Autoxidation and toxicant-induced oxidation of lipid and DNA in monkey liver: reduction of molecular damage by melatonin.

PubMed

Cabrer, J; Burkhardt, S; Tan, D X; Manchester, L C; Karbownik, M; Reiter, R J

2001-11-01

Melatonin, the main secretory product of the pineal gland, is a free radical scavenger and antioxidant which protects against oxidative damage due to a variety of toxicants. However, there is little information regarding melatonin's antioxidative capacity in tissues of primates. In this study we examined the protective effects of melatonin in monkey liver homogenates against lipid damage that occurred as a result of autoxidation or that induced by exogenous addition of H202 and ferrous iron (Fe2+). Additionally, we tested melatonin's protective effect against oxidative damage to DNA induced by chromium(III) (CrIII) plus H202. The levels of malondialdehyde and 4-hydroxyalkenals were assayed as an index of lipid peroxidation, and the concentrations of 8-hydroxydeoxyguanosine (8-OHdG) as an endpoint of oxidative DNA damage. The increases in malondialdehyde+4-hydroxyalkenals concentrations as a consequence of autoxidation or after the addition of H202 plus Fe2+ to the homogenates were time-dependent. The accumulation of these damaged products due to either auto-oxidative processes or induced by H202 and Fe2+ were significantly reduced by melatonin in a concentration-dependent-manner. The levels of 8-OHdG were elevated in purified monkey liver DNA incubated with a combination of CrCl3 plus H2O2. This rise in oxidatively damaged DNA was prevented by 10 microM concentration of melatonin. Also, melatonin reduced the damage to DNA that was caused by auto-oxidative processes. These findings in monkey liver tissue document the ability of melatonin to protect against oxidative damage to both lipid and DNA in primate tissue, as observed previously in rodent tissue. The findings provide support for the use of melatonin as suitable agent to reduce damage inflicted by free radical species in primates.

Oxidation of glycosaminoglycans by free radicals and reactive oxidative species: A review of investigative methods.

PubMed

Parsons, B J

2015-05-01

Glycosaminoglycans, in particular hyaluronan (HA), and proteoglycans are components of the extracellular matrix (ECM). The ECM plays a key role in the regulation of cellular behaviour and alterations to it can modulate both the development of human diseases as well as controlling normal biochemical processes such as cell signalling and pro-inflammatory responses. For these reasons, in vitro fragmentation studies of glycosaminoglycans by free radicals and oxidative species are seen to be relevant to the understanding of in vivo studies of damage to the ECM. A wide range of investigative techniques have therefore been applied to gain insights into the relative fragmentation effects of several reactive oxidative species with the ultimate goal of determining mechanisms of fragmentation at the molecular level. These methods are reviewed here.

Importance of sulfate radical anion formation and chemistry in heterogeneous OH oxidation of sodium methyl sulfate, the smallest organosulfate

DOE PAGES

Kwong, Kai Chung; Chim, Man Mei; Davies, James F.; ...

2018-02-27

Organosulfates are important organosulfur compounds present in atmospheric particles. While the abundance, composition, and formation mechanisms of organosulfates have been extensively investigated, it remains unclear how they transform and evolve throughout their atmospheric lifetime. To acquire a fundamental understanding of how organosulfates chemically transform in the atmosphere, this study investigates the heterogeneous OH radical-initiated oxidation of sodium methyl sulfate (CH 3SO 4Na) droplets, the smallest organosulfate detected in atmospheric particles, using an aerosol flow tube reactor at a high relative humidity (RH) of 85%. Aerosol mass spectra measured by a soft atmospheric pressure ionization source (direct analysis in real time,more » DART) coupled with a high-resolution mass spectrometer showed that neither functionalization nor fragmentation products are detected. Instead, the ion signal intensity of the bisulfate ion (HSO 4 -) has been found to increase significantly after OH oxidation. We postulate that sodium methyl sulfate tends to fragment into a formaldehyde (CH 2O) and a sulfate radical anion (SO 4 .-) upon OH oxidation. The formaldehyde is likely partitioned back to the gas phase due to its high volatility. The sulfate radical anion, similar to OH radical, can abstract a hydrogen atom from neighboring sodium methyl sulfate to form the bisulfate ion, contributing to the secondary chemistry. Kinetic measurements show that the heterogeneous OH reaction rate constant, k, is (3.79 ± 0.19) × 10 -13cm 3molecule -1s -1 with an effective OH uptake coefficient, γ eff, of 0.17 ± 0.03. While about 40% of sodium methyl sulfate is being oxidized at the maximum OH exposure (1.27 × 10 12molecule cm -3s), only a 3% decrease in particle diameter is observed. This can be attributed to a small fraction of particle mass lost via the formation and volatilization of formaldehyde. Overall, we firstly demonstrate that the heterogeneous OH oxidation of an

Importance of sulfate radical anion formation and chemistry in heterogeneous OH oxidation of sodium methyl sulfate, the smallest organosulfate

NASA Astrophysics Data System (ADS)

Chung Kwong, Kai; Chim, Man Mei; Davies, James F.; Wilson, Kevin R.; Nin Chan, Man

2018-02-01

Organosulfates are important organosulfur compounds present in atmospheric particles. While the abundance, composition, and formation mechanisms of organosulfates have been extensively investigated, it remains unclear how they transform and evolve throughout their atmospheric lifetime. To acquire a fundamental understanding of how organosulfates chemically transform in the atmosphere, this work investigates the heterogeneous OH radical-initiated oxidation of sodium methyl sulfate (CH3SO4Na) droplets, the smallest organosulfate detected in atmospheric particles, using an aerosol flow tube reactor at a high relative humidity (RH) of 85 %. Aerosol mass spectra measured by a soft atmospheric pressure ionization source (direct analysis in real time, DART) coupled with a high-resolution mass spectrometer showed that neither functionalization nor fragmentation products are detected. Instead, the ion signal intensity of the bisulfate ion (HSO4-) has been found to increase significantly after OH oxidation. We postulate that sodium methyl sulfate tends to fragment into a formaldehyde (CH2O) and a sulfate radical anion (SO4 ṡ -) upon OH oxidation. The formaldehyde is likely partitioned back to the gas phase due to its high volatility. The sulfate radical anion, similar to OH radical, can abstract a hydrogen atom from neighboring sodium methyl sulfate to form the bisulfate ion, contributing to the secondary chemistry. Kinetic measurements show that the heterogeneous OH reaction rate constant, k, is (3.79 ± 0.19) × 10-13 cm3 molecule-1 s-1 with an effective OH uptake coefficient, γeff, of 0.17 ± 0.03. While about 40 % of sodium methyl sulfate is being oxidized at the maximum OH exposure (1.27 × 1012 molecule cm-3 s), only a 3 % decrease in particle diameter is observed. This can be attributed to a small fraction of particle mass lost via the formation and volatilization of formaldehyde. Overall, we firstly demonstrate that the heterogeneous OH oxidation of an

Importance of sulfate radical anion formation and chemistry in heterogeneous OH oxidation of sodium methyl sulfate, the smallest organosulfate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwong, Kai Chung; Chim, Man Mei; Davies, James F.

Organosulfates are important organosulfur compounds present in atmospheric particles. While the abundance, composition, and formation mechanisms of organosulfates have been extensively investigated, it remains unclear how they transform and evolve throughout their atmospheric lifetime. To acquire a fundamental understanding of how organosulfates chemically transform in the atmosphere, this study investigates the heterogeneous OH radical-initiated oxidation of sodium methyl sulfate (CH 3SO 4Na) droplets, the smallest organosulfate detected in atmospheric particles, using an aerosol flow tube reactor at a high relative humidity (RH) of 85%. Aerosol mass spectra measured by a soft atmospheric pressure ionization source (direct analysis in real time,more » DART) coupled with a high-resolution mass spectrometer showed that neither functionalization nor fragmentation products are detected. Instead, the ion signal intensity of the bisulfate ion (HSO 4 -) has been found to increase significantly after OH oxidation. We postulate that sodium methyl sulfate tends to fragment into a formaldehyde (CH 2O) and a sulfate radical anion (SO 4 .-) upon OH oxidation. The formaldehyde is likely partitioned back to the gas phase due to its high volatility. The sulfate radical anion, similar to OH radical, can abstract a hydrogen atom from neighboring sodium methyl sulfate to form the bisulfate ion, contributing to the secondary chemistry. Kinetic measurements show that the heterogeneous OH reaction rate constant, k, is (3.79 ± 0.19) × 10 -13cm 3molecule -1s -1 with an effective OH uptake coefficient, γ eff, of 0.17 ± 0.03. While about 40% of sodium methyl sulfate is being oxidized at the maximum OH exposure (1.27 × 10 12molecule cm -3s), only a 3% decrease in particle diameter is observed. This can be attributed to a small fraction of particle mass lost via the formation and volatilization of formaldehyde. Overall, we firstly demonstrate that the heterogeneous OH oxidation of an

Hexavalent chromium induces reactive oxygen species and impairs the antioxidant power of human erythrocytes and lymphocytes: Decreased metal reducing and free radical quenching ability of the cells.

PubMed

Husain, Nazim; Mahmood, Riaz

2017-08-01

The toxicity of hexavalent chromium [Cr(VI)] in biological systems is thought to be closely associated with the generation of free radicals and reactive oxygen species. These species are produced when Cr(VI) is reduced to its trivalent form in the cell. This process results in oxidative stress due to an imbalance between the detoxifying ability of the cell and the production of free radicals. We have studied the effect of potassium dichromate (K 2 Cr 2 O 7 ), a [Cr(VI)] compound, on the antioxidant power of human erythrocytes and lymphocytes under in vitro conditions. Incubation of erythrocytes and lymphocytes with different concentrations of K 2 Cr 2 O 7 resulted in a marked dose-dependent decrease in reduced glutathione and an increase in oxidized glutathione and reactive oxygen species levels. The antioxidant power of the cells was decreased, as determined by metal reducing and free radical quenching assays. These results show that [Cr(VI)] upregulates the generation of reactive oxygen species and, as a consequence, the cellular antioxidant defences are compromised. The resulting oxidative stress may contribute to Cr(VI)-induced cellular damage.

Free radicals impair the anti-oxidative stress activity of DJ-1 through the formation of SDS-resistant dimer.

PubMed

Yasuda, Tatsuki; Niki, Takeshi; Ariga, Hiroyoshi; Iguchi-Ariga, Sanae M M

2017-04-01

DJ-1 is a causative gene for familial Parkinson's disease (PD). Loss-of-function of DJ-1 protein is suggested to contribute to the onset of PD, but the causes of DJ-1 dysfunction remain insufficiently elucidated. In this study, we found that the SDS-resistant irreversible dimer of DJ-1 protein was formed in human dopaminergic neuroblastoma SH-SY5Y cells when the cells were exposed to massive superoxide inducers such as paraquat and diquat. The dimer was also formed in vitro by superoxide in PQ redox cycling system and hydroxyl radical produced in Fenton reaction. We, thus, found a novel phenomenon that free radicals directly affect DJ-1 to form SDS-resistant dimers. Moreover, the formation of the SDS-resistant dimer impaired anti-oxidative stress activity of DJ-1 both in cell viability assay and H 2 O 2 -elimination assay in vitro. Similar SDS-resistant dimers were steadily formed with several mutants of DJ-1 found in familial PD patients. These findings suggest that DJ-1 is impaired due to the formation of SDS-resistant dimer when the protein is directly attacked by free radicals yielded by external and internal stresses and that the DJ-1 impairment is one of the causes of sporadic PD.

Free radicals produced by the oxidation of gallic acid: An electron paramagnetic resonance study.

PubMed

Eslami, Angelique C; Pasanphan, Wanvimol; Wagner, Brett A; Buettner, Garry R

2010-08-05

Gallic acid (3,4,5-trihydroxybenzoic acid) is found in a wide variety of plants; it is extensively used in tanning, ink dyes, as well as in the manufacturing of paper. The gallate moiety is a key component of many functional phytochemicals. In this work electron paramagnetic spectroscopy (EPR) was used to detect the free radicals generated by the air-oxidation of gallic acid. We found that gallic acid produces two different radicals as a function of pH. In the pH range between 7-10, the spectrum of the gallate free radical is a doublet of triplets (aH = 1.00 G, aH = 0.23 G, aH = 0.28 G). This is consistent with three hydrogens providing hyperfine splitting. However, in a more alkaline environment, pH >10, the hyperfine splitting pattern transforms into a 1:2:1 pattern (aH (2) = 1.07 G). Using D2O as a solvent, we demonstrate that the third hydrogen (i.e. aH = 0.28 G) at lower pH is a slowly exchanging hydron, participating in hydrogen bonding with two oxygens in ortho position on the gallate ring. The pKa of this proton has been determined to be 10. This simple and novel approach permitted the understanding of the prototropic equilibrium of the semiquinone radicals generated by gallic acid, a ubiquitous compound, allowing new insights into its oxidation and subsequent reactions.

Degradation of cytokinins by maize cytokinin dehydrogenase is mediated by free radicals generated by enzymatic oxidation of natural benzoxazinones.

PubMed

Frébortová, Jitka; Novák, Ondrej; Frébort, Ivo; Jorda, Radek

2010-02-01

Hydroxamic acid 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-one (DIMBOA) was isolated from maize phloem sap as a compound enhancing the degradation of isopentenyl adenine by maize cytokinin dehydrogenase (CKX), after oxidative conversion by either laccase or peroxidase. Laccase and peroxidase catalyze oxidative cleavage of DIMBOA to 4-nitrosoresorcinol-1-monomethyl ether (coniferron), which serves as a weak electron acceptor of CKX. The oxidation of DIMBOA and coniferron generates transitional free radicals that are used by CKX as effective electron acceptors. The function of free radicals in the CKX-catalyzed reaction was also verified with a stable free radical of 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid. Application of exogenous cytokinin to maize seedlings resulted in an enhanced benzoxazinoid content in maize phloem sap. The results indicate a new function for DIMBOA in the metabolism of the cytokinin group of plant hormones.

Biochemistry of free radicals: from electrons to tissues.

PubMed

Boveris, A

1998-01-01

Free radicals are chemical species with an unpaired electron in the outer valence orbitals. The unpaired electron makes them paramagnetic (physics) and relatively reactive (chemistry). The free radicals that are normal metabolites in aerobic biological systems have varied reactivities, ranging from the high reactivity of hydroxyl radical (t1/2 = 10(-9) s) to the low reactivity of melanins (t1/2 = days). The univalent reduction of oxygen that takes place in mammalian organs produces superoxide radicals at a rate of about 2% of the total oxygen uptake. The primary production of superoxide radicals sustains a free radical chain reaction involving a series of reactive oxygen species (hydrogen peroxide, hydroxyl and peroxyl radical and singlet oxygen). Nitric oxide is almost unreactive as free radical except for its termination reaction with superoxide radical to yield the strong oxidant peroxynitrite. Nitric oxide also reacts with ubiquinol in a redox reaction, with cytochrome oxidase competitively with oxygen, and oxymyoglobin and oxyhemoglobin displacing oxygen. Septic shock and endotoxemia produce muscle dysfunction and oxidative stress due to increased steady state concentrations of reactive oxygen and nitrogen species.

Endogeous sulfur dioxide protects against oleic acid-induced acute lung injury in association with inhibition of oxidative stress in rats.

PubMed

Chen, Siyao; Zheng, Saijun; Liu, Zhiwei; Tang, Chaoshu; Zhao, Bin; Du, Junbao; Jin, Hongfang

2015-02-01

The role of endogenous sulfur dioxide (SO2), an efficient gasotransmitter maintaining homeostasis, in the development of acute lung injury (ALI) remains unidentified. We aimed to investigate the role of endogenous SO2 in the pathogenesis of ALI. An oleic acid (OA)-induced ALI rat model was established. Endogenous SO2 levels, lung injury, oxidative stress markers and apoptosis were examined. OA-induced ALI rats showed a markedly downregulated endogenous SO2/aspartate aminotransferase 1 (AAT1)/AAT2 pathway and severe lung injury. Chemical colorimetry assays demonstrated upregulated reactive oxygen species generation and downregulated antioxidant capacity in OA-induced ALI rats. However, SO2 increased endogenous SO2 levels, protected against oxidative stress and alleviated ALI. Moreover, compared with OA-treated cells, in human alveolar epithelial cells SO2 downregulated O2(-) and OH(-) generation. In contrast, L-aspartic acid-β-hydroxamate (HDX, Sigma-Aldrich Corporation), an inhibitor of endogenous SO2 generating enzyme, promoted free radical generation, upregulated poly (ADP-ribose) polymerase expression, activated caspase-3, as well as promoted cell apoptosis. Importantly, apoptosis could be inhibited by the free radical scavengers glutathione (GSH) and N-acetyl-L-cysteine (NAC). The results suggest that SO2/AAT1/AAT2 pathway might protect against the development of OA-induced ALI by inhibiting oxidative stress.

Iron as a catalyst of human low-density lipoprotein oxidation: Critical factors involved in its oxidant properties.

PubMed

Lapenna, Domenico; Ciofani, Giuliano; Obletter, Gabriele

2017-05-01

Iron-induced human LDL oxidation, which is relevant to atherosclerosis, has not yet been properly investigated. We addressed such issue using iron(II) and (III) basically in the presence of phosphates, which are present in vivo and influence iron oxidative properties, at pH 4.5 and 7.4, representative, respectively, of the lysosomal and plasma environment. In 10mM phosphate buffered saline (PBS), iron(II) induces substantial LDL oxidation at pH 4.5 at low micromolar concentrations, while at pH 7.4 has low oxidative effects; iron(III) promotes small LDL oxidation only at pH 4.5. In 10mM sodium acetate/NaCl buffer, pH 4.5, iron-induced LDL oxidation is far higher than in PBS, highlighting the relevance of phosphates in the inhibitory modulation of iron-induced LDL oxidation. LDL oxidation is related to iron binding to the protein and lipid moiety of LDL, and requires the presence of iron(II) bound to LDL together with iron(III). Chemical modification of LDL carboxyl groups, which could bind iron especially at pH 4.5, decreases significantly iron binding to LDL and iron-induced LDL oxidation. Hydroxyl radical scavengers are ineffective on iron-induced LDL oxidation, which is inhibited by metal chelation, scavengers of alkoxyl/peroxyl radicals, or removal of LDL lipid hydroperoxides (LOOH). Overall, substantial human LDL oxidation is induced LOOH-dependently by iron(II) at pH 4.5 even in the presence of phosphates, suggesting the occurrence of iron(II)-induced LDL oxidation in vivo within lysosomes, where pH is about 4.5, iron(II) and phosphates coexist, plasma with its antioxidants is absent, and glutathione peroxidase is poorly expressed resulting in LOOH accumulation. Copyright © 2017 Elsevier GmbH. All rights reserved.

Theoretical perspectives on the mechanism and kinetics of the OH radical-initiated gas-phase oxidation of PCB126 in the atmosphere.

PubMed

Dang, Juan; Shi, Xiangli; Zhang, Qingzhu; Wang, Wenxing

2015-06-01

Polychlorinated biphenyls (PCBs) primarily exist in the gas phase in air and may undergo atmospheric oxidation degradations, particularly the oxidation reaction initiated by OH radicals. In this work, the mechanism of the OH radical-initiated atmospheric oxidation of the most toxic PCB congener 3,3',4,4',5-pentachlorobiphenyl (PCB126) was investigated by using quantum chemistry methods. The rate constants of the crucial elementary reactions were estimated by the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. The oxidation products of the reaction of PCB126 with OH radicals include 3,3',4,4',5-pentachlorobiphenyl-ols, chlorophenols, 2,3,4,7,8-pentachlorodibenzofuran, 2,3,4,6,7-pentachlorodibenzofuran, dialdehydes, 3,3',4,4',5-pentachloro-5'-nitro-biphenyl, and 4,5-dichloro-2-nitrophenol. Particularly, the formation of polychlorinated dibenzofurans (PCDFs) from the atmospheric oxidation of PCBs is revealed for the first time. The overall rate constant of the OH addition reaction is 2.52×10(-13)cm(3)molecule(-1)s(-1) at 298K and 1atm. The atmospheric lifetime of PCB126 determined by OH radicals is about 47.08days which indicates that PCB126 can be transported long distances from local to global scales. Copyright © 2015 Elsevier B.V. All rights reserved.

Induced oxidative stress management in wounds through phenolic acids engineered fibrous protein: An in vitro assessment using polymorphonuclear (PMN) cells.

PubMed

Thiruselvi, T; Thirupathi Kumara Raja, S; Shanuja, S K; Iswarya, S; Gnanamani, A

2017-03-01

The present study explores the preparation, characterization and the role of phenolic acid tethered fibrous protein in the management of induced oxidative stress studied under in vitro conditions. In brief, the biomaterial is prepared by engineering the fibrous protein with dihydroxy and trihydroxy phenolic acid moieties and subjected to characterization to ensure the tethering. The resultant biomaterial studied for its efficacy as a free radical scavenger using polymorphonuclear (PMN) cells with induced oxidative stress and also as an agent for cell migration using fibroblasts cells. Results revealed that induced oxidative stress in PMN cells after exposure to UVB radiation managed well with the prepared biomaterial by reducing the levels of superoxide anion, oxygen and hydroxyl radicals. Further, the protein and the phenolic acid interaction supports the cell migration as evidenced from the scratch assay. In conclusion, though phenolic acids are well known for their antimicrobial and antioxidant potential, indenting these acids directly to the wounds is not sensible, but tethering to protein explored the scavenging activity as expected. The present study infers that phenolic acid engineered protein has a significant role in managing the imbalance in the redox state prevailing in wounds and supports the healing at appreciable level. Copyright © 2016 Elsevier B.V. All rights reserved.

Vitamin E, γ-tocotrienol, Protects Against Buthionine Sulfoximine-Induced Cell Death by Scavenging Free Radicals in SH-SY5Y Neuroblastoma Cells.

PubMed

Tan, Jen-Kit; Then, Sue-Mian; Mazlan, Musalmah; Jamal, Rahman; Ngah, Wan Zurinah Wan

2016-01-01

The induction of reactive oxygen species (ROS) to selectively kill cancer cells is an important feature of radiotherapy and various chemotherapies. Depletion of glutathione can induce apoptosis in cancer cells or sensitize them to anticancer treatments intended to modulate ROS levels. In contrast, antioxidants protect cancer cells from oxidative stress-induced cell death by scavenging ROS. The role of exogenous antioxidants in cancer cells under oxidative insults remains controversial and unclear. This study aimed to identify protective pathways modulated by γ-tocotrienol (γT3), an isomer of vitamin E, in human neuroblastoma SH-SY5Y cells under oxidative stress. Using buthionine sulfoximine (BSO) as an inhibitor of glutathione synthesis, we found that BSO treatment reduced the viability of SH-SY5Y cells. BSO induced cell death by increasing apoptosis, decreased the level of reduced glutathione (GSH), and increased ROS levels in SH-SY5Y cells. Addition of γT3 increased the viability of BSO-treated cells, suppressed apoptosis, and decreased the ROS level induced by BSO, while the GSH level was unaffected. These results suggest that decreasing GSH levels by BSO increased ROS levels, leading to apoptosis in SH-SY5Y cells. γT3 attenuated the BSO-induced cell death by scavenging free radicals.

Quantification of superoxide radical production in thylakoid membrane using cyclic hydroxylamines.

PubMed

Kozuleva, Marina; Klenina, Irina; Mysin, Ivan; Kirilyuk, Igor; Opanasenko, Vera; Proskuryakov, Ivan; Ivanov, Boris

2015-12-01

Applicability of two lipophilic cyclic hydroxylamines (CHAs), CM-H and TMT-H, and two hydrophilic CHAs, CAT1-H and DCP-H, for detection of superoxide anion radical (O2(∙-)) produced by the thylakoid photosynthetic electron transfer chain (PETC) of higher plants under illumination has been studied. ESR spectrometry was applied for detection of the nitroxide radical originating due to CHAs oxidation by O2(∙-). CHAs and corresponding nitroxide radicals were shown to be involved in side reactions with PETC which could cause miscalculation of O2(∙-) production rate. Lipophilic CM-H was oxidized by PETC components, reducing the oxidized donor of Photosystem I, P700(+), while at the same concentration another lipophilic CHA, TMT-H, did not reduce P700(+). The nitroxide radical was able to accept electrons from components of the photosynthetic chain. Electrostatic interaction of stable cation CAT1-H with the membrane surface was suggested. Water-soluble superoxide dismutase (SOD) was added in order to suppress the reaction of CHA with O2(∙-) outside the membrane. SOD almost completely inhibited light-induced accumulation of DCP(∙), nitroxide radical derivative of hydrophilic DCP-H, in contrast to TMT(∙) accumulation. Based on the results showing that change in the thylakoid lumen pH and volume had minor effect on TMT(∙) accumulation, the reaction of TMT-H with O2(∙-) in the lumen was excluded. Addition of TMT-H to thylakoid suspension in the presence of SOD resulted in the increase in light-induced O2 uptake rate, that argued in favor of TMT-H ability to detect O2(∙-) produced within the membrane core. Thus, hydrophilic DCP-H and lipophilic TMT-H were shown to be usable for detection of O2(∙-) produced outside and within thylakoid membranes. Copyright © 2015 Elsevier Inc. All rights reserved.

Theoretical insight into reaction mechanisms of 2,4-dinitroanisole with hydroxyl radicals for advanced oxidation processes.

PubMed

Zhou, Yang; Liu, Xiaoqiang; Jiang, Weidong; Shu, Yuanjie

2018-01-24

The detailed degradation mechanism of an insensitive explosive, 2,4-dinitroanisole (DNAN), in advanced oxidation processes (AOPs) was investigated computationally at the M06-2X/6-311 + G(d,p)/SMD level of theory. Results obtained show that the addition-elimination reaction is the dominant mechanism. The phenol products formed can continue to be oxidized to benzoquinone radicals that are often detected by experiments and may be the initial reactants of ring-opening reactions. The H-abstraction reaction is an unavoidable competing mechanism; the intermediate generated can also undergo the process of addition-elimination reaction. The nitro departure reaction involves not only hydroxyl radical (•OH), but also other active substances (such as •H). More importantly, we found that AOP technology can easily degrade DNAN, similar to TNT and DNT. Thus, this method is worth trying in experiments. The conclusions of this work provide theoretical support for such experimental research. Graphical abstract Possible pathways of degradation by •OH radicals in advanced oxidation processes (AOPs) of the typical insensitive explosive 2,4-dinitroanisole (DNAN) were investigated by density functional theory (DFT) methods. Based on the Gibbs free energy barriers and intermediates, the dominant reaction mechanism was determined. The conclusions will be helpful in utilizing AOP technology to remove DNAN pollution.

Radical-induced purine lesion formation is dependent on DNA helical topology.

PubMed

Terzidis, Michael A; Prisecaru, Andreea; Molphy, Zara; Barron, Niall; Randazzo, Antonio; Dumont, Elise; Krokidis, Marios G; Kellett, Andrew; Chatgilialoglu, Chryssostomos

2016-11-01

Herein we report the quantification of purine lesions arising from gamma-radiation sourced hydroxyl radicals (HO • ) on tertiary dsDNA helical forms of supercoiled (SC), open circular (OC), and linear (L) conformation, along with single-stranded folded and non-folded sequences of guanine-rich DNA in selected G-quadruplex structures. We identify that DNA helical topology and folding plays major, and unexpected, roles in the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) and 8-oxo-7,8-dihydro-2'-deoxyadenosine (8-oxo-dA), along with tandem-type purine lesions 5',8-cyclo-2'-deoxyguanosine (5',8-cdG) and 5',8-cyclo-2'-deoxyadenosine (5',8-cdA). SC, OC, and L dsDNA conformers together with folded and non-folded G-quadruplexes d[TGGGGT] 4 (TG4T), d[AGGG(TTAGGG) 3 ] (Tel22), and the mutated tel24 d[TTGGG(TTAGGG) 3 A] (mutTel24) were exposed to HO • radicals and purine lesions were then quantified via stable isotope dilution LC-MS/MS analysis. Purine oxidation in dsDNA follows L > OC ≫ SC indicating greater damage towards the extended B-DNA topology. Conversely, G-quadruplex sequences were significantly more resistant toward purine oxidation in their unfolded states as compared with G-tetrad folded topologies; this effect is confirmed upon comparative analysis of Tel22 (∼50% solution folded) and mutTel24 (∼90% solution folded). In an effort to identify the accessibly of hydroxyl radicals to quadruplex purine nucleobases, G-quadruplex solvent cavities were then modeled at 1.33 Å with evidence suggesting that folded G-tetrads may act as potential oxidant traps to protect against chromosomal DNA damage.

Nitroaryl-1,4-dihydropyridines as antioxidants against rat liver microsomes oxidation induced by iron/ascorbate, nitrofurantoin and naphthalene.

PubMed

Letelier, María Eugenia; Entrala, Paz; López-Alarcón, Camilo; González-Lira, Víctor; Molina-Berríos, Alfredo; Cortés-Troncoso, Juan; Jara-Sandoval, José; Santander, Paola; Núñez-Vergara, Luis

2007-12-01

1,4-Dihydropyridines (DHPs) used in the treatment of cardiovascular diseases, are calcium channel antagonists and also antioxidant agents. These drugs are metabolized through cytochrome P(450) oxidative system, majority localized in the hepatic endoplasmic reticulum. Several lipophilic drugs generate oxidative stress to be metabolized by this cellular system. Thus, DHP antioxidant properties may prevent the oxidative stress associated with hepatic biotransformation of drugs. In this work, we tested the antioxidant capacity of several synthetic nitro-phenyl-DHPs. These compounds (I-IV) inhibited the microsomal lipid peroxidation, UDPGT oxidative activation and microsomal thiols oxidation; all phenomena induced by Fe(3+)/ascorbate, a generator system of oxygen free radicals. As the same manner, these compounds inhibited the oxygen consumption induced by Cu(2+)/ascorbate in the absence of microsomes. Furthermore, compound III (2,6-dimethyl-4-(4-nitrophenyl)-1,4-dihydropyridin-3,5-ethyl-dicarboxylate) and compound V (N-ethyl-2,6-dimethyl-4-(4-nitrophenyl)-1,4-dihydropyridin-3,5-methyl-dicarboxylate) inhibited the microsomal lipid peroxidation induced by Nitrofurantoin and naphthalene in the presence of NADPH. Oxidative stress induced on endoplasmic reticulum may alter the biotransformation of drugs, so, modifying their plasmatic concentrations and therapeutic effects. When drugs which are activated by biotransformation are administered together with antioxidant drugs, such as DHPs, oxidative stress induced in situ may be prevented.

Studies on free radicals, antioxidants, and co-factors

PubMed Central

Rahman, Khalid

2007-01-01

The interplay between free radicals, antioxidants, and co-factors is important in maintaining health, aging and age-related diseases. Free radicals induce oxidative stress, which is balanced by the body’s endogenous antioxidant systems with an input from co-factors, and by the ingestion of exogenous antioxidants. If the generation of free radicals exceeds the protective effects of antioxidants, and some co-factors, this can cause oxidative damage which accumulates during the life cycle, and has been implicated in aging, and age dependent diseases such as cardiovascular disease, cancer, neurodegenerative disorders, and other chronic conditions. The life expectancy of the world population is increasing, and it is estimated that by 2025, 29% of the world population will be aged ≥60 years, and this will lead to an increase in the number of older people acquiring age-related chronic diseases. This will place greater financial burden on health services and high social cost for individuals and society. In order to acheive healthy aging the older people should be encouraged to acquire healthy life styles which should include diets rich in antioxidants. The aim of this review is to highlight the main themes from studies on free radicals, antioxidants and co-factors, and to propose an evidence-based strategy for healthy aging. PMID:18044138

Trivalent chromium induces oxidative stress in goldfish brain.

PubMed

Lushchak, Oleh V; Kubrak, Olha I; Torous, Ihor M; Nazarchuk, Tetyana Yu; Storey, Kenneth B; Lushchak, Volodymyr I

2009-03-01

Although information on the effects of Cr(6+) in biological systems is abundant, Cr(3+) has received less attention. Toxic effects of chromium compounds are partially associated with activation of redox processes. Recently we found that Cr(6+) induced oxidative stress in goldfish tissues and the glutathione system was shown to play a protective role. The present study aimed to investigate free radical processes in brain of goldfish exposed to CrCl(3). Trivalent chromium at a concentration of 50 mg L(-1) was lethal and therefore we chose to examine sublethal dosages of 1.0-10.0 mg L(-1) in aquarium water. The levels of lipid peroxides and protein carbonyls (measures of oxidative damage to lipids and proteins) in brain increased after 96 h exposure of goldfish to Cr(3+). However, exposure to 1.0-10.0 mg L(-1) Cr(3+) decreased total glutathione concentration in brain by approximately 50-60%. Oxidized glutathione levels also fell by approximately 40-60% except at the 10.0 mg L(-1) dosage where they decreased by 85%. Therefore, 10.0 mg L(-1) Cr(3+) significantly reduced the ratio [GSSG]/[totalGSH] to 35% of the control value. Chromium treatment did not affect the activity of superoxide dismutase, but reduced the activities of catalase by 55-62% and glutathione-S-transferase by 14-21%. The activities of glucose-6-phosphate dehydrogenase and glutathione reductase were unchanged under any experimental conditions used. Therefore, it can be concluded that although Cr(3+) exposure induced oxidative stress in goldfish brain, it failed to enhance the efficiency of the antioxidant system in the organ.

Evaluation of fatty acid oxidation by reactive oxygen species induced in liquids using atmospheric-pressure nonthermal plasma jets

NASA Astrophysics Data System (ADS)

Tani, Atsushi; Fukui, Satoshi; Ikawa, Satoshi; Kitano, Katsuhisa

2015-10-01

We investigated fatty acid oxidation by atmospheric-pressure nonthermal helium plasma using linoleic acid, an unsaturated fatty acid, together with evaluating active species induced in liquids. If the ambient gas contains oxygen, direct plasma such as plasma jets coming into contact with the liquid surface supplies various active species, such as singlet oxygen, ozone, and superoxide anion radicals, to the liquid. The direct plasma easily oxidizes linoleic acid, indicating that fatty acid oxidation will occur in the direct plasma. In contrast, afterglow flow, where the plasma is terminated in a glass tube and does not touch the surface of the liquid sample, supplies mainly superoxide anion radicals. The fact that there was no clear observation of linoleic acid oxidation using the afterglow reveals that it may not affect lipids, even in an atmosphere containing oxygen. The afterglow flow can potentially be used for the sterilization of aqueous solutions using the reduced pH method, in medical and dental applications, because it provides bactericidal activity in the aqueous solution despite containing a smaller amount of active species.

Diazinon, an organophosphate pesticide, induces oxidative stress and genotoxicity in cells deriving from large intestine.

PubMed

Boussabbeh, Manel; Ben Salem, Intidhar; Hamdi, Mohamed; Ben Fradj, Salsabil; Abid-Essefi, Salwa; Bacha, Hassen

2016-02-01

Diazinon (DZ) (O,O-diethyl-O-[2-isopropyl-6-methyl-4-pyrimidinyl]phosphorothioate) is an organophosphate pesticide which is extensively used to control household insects and fruit and vegetable crops. The exposure to this pesticide has been linked to the development of the serious problem in several experimental animals. The contamination of food by DZ may increase its danger to humans. The aim of this study was to investigate the toxic effect of DZ on intestine using an in vitro model (HCT116). Therefore, we evaluated the cell viability, elucidated the generation of free radicals, measured the mitochondrial membrane potential, and valued DNA fragmentation. Our results showed that DZ is cytotoxic to HCT116. It causes oxidative damage through the generation of free radicals and induces lipid peroxidation and DNA fragmentation. We also demonstrated that such effects can be responsible for DZ-induced apoptosis.

Dosimetry determines the initial OH radical concentration in fast photochemical oxidation of proteins (FPOP).

PubMed

Niu, Ben; Zhang, Hao; Giblin, Daryl; Rempel, Don L; Gross, Michael L

2015-05-01

Fast photochemical oxidation of proteins (FPOP) employs laser photolysis of hydrogen peroxide to give OH radicals that label amino acid side-chains of proteins on the microsecond time scale. A method for quantitation of hydroxyl radicals after laser photolysis is of importance to FPOP because it establishes a means to adjust the yield of •OH, offers the opportunity of tunable modifications, and provides a basis for kinetic measurements. The initial concentration of OH radicals has yet to be measured experimentally. We report here an approach using isotope dilution gas chromatography/mass spectrometry (GC/MS) to determine quantitatively the initial •OH concentration (we found ~0.95 mM from 15 mM H2O2) from laser photolysis and to investigate the quenching efficiencies for various •OH scavengers.

Well-Known Mediators of Selective Oxidation with Unknown Electronic Structure: Metal-Free Generation and EPR Study of Imide-N-oxyl Radicals.

PubMed

Krylov, Igor B; Kompanets, Mykhailo O; Novikova, Katerina V; Opeida, Iosip O; Kushch, Olga V; Shelimov, Boris N; Nikishin, Gennady I; Levitsky, Dmitri O; Terent'ev, Alexander O

2016-01-14

Nitroxyl radicals are widely used in chemistry, materials sciences, and biology. Imide-N-oxyl radicals are subclass of unique nitroxyl radicals that proved to be useful catalysts and mediators of selective oxidation and CH-functionalization. An efficient metal-free method was developed for the generation of imide-N-oxyl radicals from N-hydroxyimides at room temperature by the reaction with (diacetoxyiodo)benzene. The method allows for the production of high concentrations of free radicals and provides high resolution of their EPR spectra exhibiting the superhyperfine structure from benzene ring protons distant from the radical center. An analysis of the spectra shows that, regardless of the electronic effects of the substituents in the benzene ring, the superhyperfine coupling constant of an unpaired electron with the distant protons at positions 4 and 5 of the aromatic system is substantially greater than that with the protons at positions 3 and 6 that are closer to the N-oxyl radical center. This is indicative of an unusual character of the spin density distribution of the unpaired electron in substituted phthalimide-N-oxyl radicals. Understanding of the nature of the electron density distribution in imide-N-oxyl radicals may be useful for the development of commercial mediators of oxidation based on N-hydroxyimides.

Lipoxin A4 inhibits UV radiation-induced skin inflammation and oxidative stress in mice.

PubMed

Martinez, R M; Fattori, V; Saito, P; Melo, C B P; Borghi, S M; Pinto, I C; Bussmann, A J C; Baracat, M M; Georgetti, S R; Verri, W A; Casagrande, R

2018-04-27

Lipoxin A4 (LXA 4 ) is a metabolic product of arachidonic acid. Despite potent anti-inflammatory and pro-resolution activities, it remains to be determined if LXA 4 has effect on ultraviolet (UV) radiation-induced skin inflammation. To investigate the effects of systemic administration with LXA 4 on UV radiation-induced inflammation and oxidative damage in the skin of mice. Varied parameters of inflammation and oxidative stress in the skin of mice were evaluated after UV radiation (4.14 J/cm 2 ). Pretreatment with LXA 4 significantly inhibited UV radiation-induced skin edema and myeloperoxidase activity. LXA 4 efficacy was enhanced by increasing the time of pre-treatment to up to 72 h. LXA 4 reduced UV radiation-induced skin edema, neutrophil recruitment (myeloperoxidase activity and LysM-eGFP + cells), MMP-9 activity, deposition of collagen fibers, epidermal thickness, sunburn cell counts, and production of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6 and IL-33). Depending on the time point, LXA 4 increased the levels of anti-inflammatory cytokines (TGF-β and IL-10). LXA 4 significantly attenuated UV radiation-induced oxidative damage returning the oxidative status to baseline levels in parameters such as ferric reducing ability, scavenging of free radicals, GSH levels, catalase activity and superoxide anion production. LXA 4 also reduced UV radiation-induced gp91 phox [nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (NOX2) subunit] mRNA expression and enhanced nuclear factor erythroid 2-related factor 2 (Nrf2) and its downstream target enzyme nicotinamide adenine dinucleotide (phosphate) quinone oxidoreductase (Nqo1) mRNA expression. LXA 4 inhibited UV radiation-induced skin inflammation by diminishing pro-inflammatory cytokine production and oxidative stress as well as inducing anti-inflammatory cytokines and Nrf2. Copyright © 2018. Published by Elsevier B.V.

Protective effects of buckwheat honey on DNA damage induced by hydroxyl radicals.

PubMed

Zhou, Juan; Li, Peng; Cheng, Ni; Gao, Hui; Wang, Bini; Wei, Yahui; Cao, Wei

2012-08-01

To understand the antioxidant properties of buckwheat honeys, we investigated their antioxidant effects on hydroxyl radical-induced DNA breaks in the non-site-specific and site-specific systems, the physicochemical properties, antioxidant activities (1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl radical scavenging activity, chelating, and reducing power assays), total phenolic content and individual phenolic acids were also determined. Total phenolic content of buckwheat honeys ranged from 774 to 1694 mg PA/kg, and p-hydroxybenzoic and p-coumaric acids proved to be the main components in buckwheat honeys. All the buckwheat honey samples possess stronger capability to protect DNA in the non-site-specific systems than in the site-specific systems from being damaged by hydroxyl radicals. In the non-site-specific and site-specific system, buckwheat honeys samples prevented ()OH-induced DNA breaks by 21-78% and 5-31% over control value, respectively. Copyright © 2012 Elsevier Ltd. All rights reserved.

Photochemical Kinetics of a Phosphine Oxide Free Radical Initiator from Femtosecond UV-Pump/Mid-IR-Probe Spectroscopy.

PubMed

Straub, Steffen; Lindner, Jörg; Vöhringer, Peter

2017-07-06

Femtosecond UV-pump/mid-infrared-probe spectroscopy was used to explore in detail the primary photochemical events of the free radical initiator, (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, in liquid dichloromethane solution at room temperature. Following electronic excitation of its lowest excited singlet state, S 1 , the radical initiator undergoes an intersystem crossing to the triplet ground state, T 1 , with a time constant of 135 ps. A subsequent α-cleavage occurs from the triplet state with a time constant of 15 ps and yields a trimethylbenzoyl radical together with a diphenylphosphinoyl radical. Transient absorptions from the S 1 and T 1 states are observed that can be assigned to the P═O stretching mode and the symmetric in-plane deformation mode of the trimethylphenyl moiety of the radical initiator.

Protective and antioxidative effect of rubropunctatin against oxidative protein damage induced by metal catalyzed reaction.

PubMed

Dhale, Mohan A; Javagal, Manjunatha; Puttananjaiah, Mohan-Kumari H

2018-05-03

Monascus purpureus is known to produce several coloured secondary metabolites. In this study, M. purpureus CFR 410-11 mutant fermented with rice was dried and extracted in hexane for purification of pigment. The purity of the isolated pigment was confirmed by different chromatography techniques. The spectroscopic analysis revealed its structural identity as rubropunctatin. The antioxidant potencies of isolated rubropunctatin were evaluated. Rubropunctatin scavenged 16% 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical and inhibited 20% superoxide generation at 8 μg/ml concentration. The multiple antioxidant abilities of rubropunctatin were evidenced by its ferric reducing capacity also. The oxidative damage of BSA protein was induced by the metal catalyzed oxidation (MCO) by Fe 2+ /H 2 O 2 . The protective effects of rubropunctatin and M. purpureus (MTCC-410 and CFR 410-11) extracts were compared with glutathione and ascorbic acid. The M. purpureus extracts and rubropunctatin inhibited the formation of carbonyl content and protein oxidation assayed by SDS-PAGE. Rubropunctatin (42-169 μM) efficiently inhibited the protein oxidation compared to glutathione (48-195 μM) and ascorbic acid (85-340 μM) by scavenging the superoxide and hydroxyl radical generated in the system. Copyright © 2018 Elsevier B.V. All rights reserved.

Chlorophytum borivilianum as potential terminator of free radicals in various in vitro oxidation systems.

PubMed

Visavadiya, Nishant P; Soni, Badrish; Dalwadi, Nirav; Madamwar, Datta

2010-04-01

Chlorophytum borivilianum is a very popular herb in traditional Indian medicine and used as a potent "Rasayana" drug in "Ayurveda" as a rejuvenator. Currently, a large body of evidence supports the key role of free radicals in diverse pathological conditions such as aging and atherosclerosis. The present investigation essentially focuses on the comprehensive account of in vitro antioxidant activity exerted by C.borivilianum root extracts (i.e., aqueous and ethanolic), to clarify the pharmacological antagonism of chemicals/metals-mediated oxidation. Graded-dose (25 to 1000 microg/ml) of aqueous extract exhibited higher antioxidant potency as evidenced by powerful nitric oxide, superoxide, hydroxyl, DPPH and ABTS(*+) radicals scavenging activity along with reducing capacity (Fe(3+)/ferricyanide complex and FRAP assays), metal chelating ability, as well as markedly suppressed the lipid peroxidation in mitochondrial fractions as compared to ethanolic extract. Further, aqueous extract significantly decreased (P < 0.05) copper-mediated human serum and kinetics of LDL oxidation, as demonstrated by prolongation of lag phase time with decline of oxidation rate, conjugated dienes, lipid hydroperoxides and thiobarbituric acid reactive substances. In addition, the total polyphenol and flavonoid contents of aqueous extract were higher than that of ethanolic extract, which indicated a positive correlation between antioxidant activity and contents of total phenols. The IC(50) values of both extracts were also compared with appropriate antioxidant standards. Overall, aqueous extract of C.borivilianum root has significant powerful antioxidant activity and may favorably affect atherosclerosis risk status by reducing LDL oxidation susceptibility.

Roles of free radicals in NO oxidation by Fenton system and the enhancement on NO oxidation and H2O2 utilization efficiency.

PubMed

Zhao, Haiqian; Dong, Ming; Wang, Zhonghua; Wang, Huaiyuan; Qi, Hanbing

2018-06-20

Low H 2 O 2 utilization efficiency is the main problem when Fenton system was used to oxidize NO in flue gas. To understand the behavior of the free radicals during NO oxidation process in Fenton system is crucial to solving this problem. The oxidation capacity of ·OH and HO 2 · on NO in Fenton system was compared and the useless consumption path of ·OH and HO 2 · that caused the low utilization efficiency of H 2 O 2 were studied. A method to enhance the oxidation ability and H 2 O 2 utilization efficiency by adding reducing additives in Fenton system was proposed. The results showed that both of ·OH and HO 2 · were active substances that oxidize NO. However, the oxidation ability of ·OH radicals was stronger. The vast majority of ·OH and HO 2 · was consumed by rapid reaction ·OH+HO 2 ·→H 2 O+O 2 , which was the primary reason for the low utilization efficiency of H 2 O 2 in Fenton system. Hydroxylamine hydrochloride and ascorbic acid could accelerate the conversion of Fe 3+ to Fe 2+ , thereby increase the generation rate of ·OH and decrease the generation rate of HO 2 ·. As a result, the oxidation ability and H 2 O 2 utilization efficiency were enhanced.

Quercetin, a Flavonoid Antioxidant, Ameliorated Procarbazine-Induced Oxidative Damage to Murine Tissues

PubMed Central

Olayinka, Ebenezer Tunde; Ore, Ayokanmi; Adeyemo, Oluwatobi Adewumi; Ola, Olaniyi Solomon; Olotu, Olaoluwa Oluwaseun; Echebiri, Roseline Chinonye

2015-01-01

Procarbazine (PCZ) (indicated in Hodgkin’s disease), is an alkylating agent known to generate free radicals in vivo, while Quercetin (QCT) is a flavonoid antioxidant with proven free radical scavenging capacity. This study investigated the protective effects of QCT on PCZ-induced oxidative damage in the rat. Male Wistar rats (160–180 g) were randomized into five groups (n = 5/group): I (control), II PCZ-treated (2 mg/kg body weight (bw) for seven days); III pre-treated with QCT (20 mg/kg bw) for seven days, followed by PCZ for seven days; IV co-treated with PCZ and QCT for seven days and V administered QCT alone for seven days. PCZ caused a significant increase in plasma total bilirubin, urea, and creatinine when compared with control (P < 0.05). Similarly, plasma activities of alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and γ-glutamyl transferase (γ-GT) were significantly increased in the PCZ-treated group relative to control. Furthermore, PCZ caused a significant decrease in the activities of hepatic superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST) as well as levels of ascorbic acid (AA) and glutathione (GSH). This was followed by a significant increase in hepatic malondialdehyde (MDA) content. However, QCT pre-treatment and co-treatment ameliorated the PCZ-induced changes in plasma levels of urea, creatinine, and bilirubin as well as the activities of ALP, AST, ALT, and GGT. QCT also ameliorated hepatic AA and GSH levels and the activities of SOD, CAT, and GST. This all suggests that QCT protected against PCZ-induced oxidative damage in rats. PMID:26783707

Grapevine fruit extract protects against radiation-induced oxidative stress and apoptosis in human lymphocyte.

PubMed

Singha, Indrani; Das, Subir Kumar

2015-11-01

Ionizing radiation (IR) causes oxidative stress through overwhelming generation of reactive oxygen species (ROS) in the living cells leading the oxidative damage further to biomolecules. Grapevine (Vitis vinifera L.) posses several bioactive phytochemicals and is the richest source of antioxidants. In this study, we investigated V. vinifera for its phytochemical content, enzymes profile and, ROS- and oxidant-scavenging activities. We have also studied the fruit extract of four different grapevine viz., Thompson seedless, Flame seedless, Kishmish chorni and Red globe for their radioprotective actions in human lymphocytes. The activities of ascorbic acid oxidase and catalase significantly (P < 0.01) differed among extracts within the same cultivar, while that of peroxidase and polyphenol oxidase did not differ significantly. The superoxide radical-scavenging activity was higher in the seed as compared to the skin or pulp of the same cultivar. Pretreatment with grape extracts attenuated the oxidative stress induced by 4 Gy γ-radiation in human lymphocytes in vitro. Further, γ-radiation-induced increase in caspase 3/7 activity was significantly attenuated by grape extracts. These results suggest that grape extract serve as a potential source of natural antioxidants against the IR-induced oxidative stress and also inhibit apoptosis. Furthermore, the protective action of grape depends on the source of extract (seed, skin or pulp) and type of the cultivars.

Antioxidative effects of fermented sesame sauce against hydrogen peroxide-induced oxidative damage in LLC-PK1 porcine renal tubule cells

PubMed Central

Song, Jia-Le; Choi, Jung-Ho; Seo, Jae-Hoon; Kil, Jeung-Ha

2014-01-01

BACKGROUND/OBJECTIVES This study was performed to investigate the in vitro antioxidant and cytoprotective effects of fermented sesame sauce (FSeS) against hydrogen peroxide (H2O2)-induced oxidative damage in renal proximal tubule LLC-PK1 cells. MATERIALS/METHODS 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl radical (•OH), and H2O2 scavenging assay was used to evaluate the in vitro antioxidant activity of FSeS. To investigate the cytoprotective effect of FSeS against H2O2-induced oxidative damage in LLC-PK1 cells, the cellular levels of reactive oxygen species (ROS), lipid peroxidation, and endogenous antioxidant enzymes including catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-px) were measured. RESULTS The ability of FSeS to scavenge DPPH, •OH and H2O2 was greater than that of FSS and AHSS. FSeS also significantly inhibited H2O2-induced (500 µM) oxidative damage in the LLC-PK1 cells compared to FSS and AHSS (P < 0.05). Following treatment with 100 µg/mL of FSeS and FSS to prevent H2O2-induced oxidation, cell viability increased from 56.7% (control) to 83.7% and 75.6%, respectively. However, AHSS was not able to reduce H2O2-induced cell damage (viability of the AHSS-treated cells was 54.6%). FSeS more effectively suppressed H2O2-induced ROS generation and lipid peroxidation compared to FSS and AHSS (P < 0.05). Compared to the other sauces, FSeS also significantly increased cellular CAT, SOD, and GSH-px activities and mRNA expression (P < 0.05). CONCULUSIONS These results from the present study suggest that FSeS is an effective radical scavenger and protects against H2O2-induced oxidative damage in LLC-PK1 cells by reducing ROS levels, inhibiting lipid peroxidation, and stimulating antioxidant enzyme activity. PMID:24741396

Development of the radical-stable Coprinus cinereus peroxidase (CiP) by blocking the radical attack.

PubMed

Kim, Su Jin; Joo, Jeong Chan; Kim, Han Sang; Kwon, Inchan; Song, Bong Keun; Yoo, Young Je; Kim, Yong Hwan

2014-11-10

Despite the potential use of peroxidases as industrial biocatalysts, their practical application is often impeded due to suicide inactivation by radicals generated in oxidative reactions. Using a peroxidase from Coprinus cinereus (CiP) as a model enzyme, we revealed a dominant factor for peroxidase inactivation during phenol oxidation, and we engineered radical-stable mutants by site-directed mutagenesis of an amino acid residue susceptible to modification by phenoxyl radical. Mass spectrometry analysis of inactivated CiP identified an adduct between F230 and a phenoxyl radical, and subsequently, the F230 residue was mutated to amino acids that resisted radical coupling. Of the F230 mutants, the F230A mutant showed the highest stability against radical inactivation, retaining 80% of its initial activity, while the wild-type protein was almost completely inactivated. The F230A mutant also exhibited a 16-fold higher turnover of the phenol substrate compared with the wild-type enzyme. Furthermore, the F230A mutant was stable during the oxidation of other phenolic compounds, including m-cresol and 3-methoxyphenol. No structural changes were observed by UV-vis and CD spectra of CiP after radical coupling, implying that the F230-phenol radical adduct inactivated CiP by blocking substrate access to the active site. Our novel strategy can be used to improve the stability of other peroxidases inactivated by radicals. Copyright © 2014 Elsevier B.V. All rights reserved.

Levofloxacin oxidation by ozone and hydroxyl radicals: kinetic study, transformation products and toxicity.

PubMed

Hamdi El Najjar, Nasma; Touffet, Arnaud; Deborde, Marie; Journel, Romain; Leitner, Nathalie Karpel Vel

2013-10-01

This work was carried out to investigate the fate of the antibiotic levofloxacin upon oxidation with ozone and hydroxyl radicals. A kinetic study was conducted at 20 °C for each oxidant. Ozonation experiments were performed using a competitive kinetic method with carbamazepin as competitor. Significant levofloxacin removal was observed during ozonation and a rate constant value of 6.0×10(4) M(-1) s(-1) was obtained at pH 7.2. An H2O2/UV system was used for the formation of hydroxyl radicals HO. The rate constant of HO was determined in the presence of a high H2O2 concentration. The kinetic expressions yielded a [Formula: see text] value of 4.5×10(9) M(-1) s(-1) at pH 6.0 and 5.2×10(9) M(-1) s(-1) at pH 7.2. These results were used to develop a model to predict the efficacy of the ozonation process and pharmaceutical removal was estimated under different ozonation conditions (i.e. oxidant concentrations and contact times). The results showed that levofloxacin was completely degraded by molecular ozone during ozonation of water and that hydroxyl radicals had no effect in real waters conditions. Moreover, LC/MS/MS and toxicity assays using Lumistox test were performed to identify ozonation transformation products. Under these conditions, four transformation products were observed and their chemical structures were proposed. The results showed an increase in toxicity during ozonation, even after degradation of all of the observed transformation products. The formation of other transformation products not identified under our experimental conditions could be responsible for the observed toxicity. These products might be ozone-resistant and more toxic to Vibrio fisheri than levofloxacin. Copyright © 2013 Elsevier Ltd. All rights reserved.

Properties of Flavonoids Isolated from the Bark of Eysenhardtia polystachya and Their Effect on Oxidative Stress in Streptozotocin-Induced Diabetes Mellitus in Mice.

PubMed

Perez-Gutierrez, Rosa Martha; Garcia-Campoy, Abraham Heriberto; Muñiz-Ramirez, Alethia

Six new flavonoids 2',4'-dihydroxychalcone-6'-O- β -d-glucopyranoside ( 1 ), α ,3,2',4'-tetrahydroxy-4-methoxy-dihydrochalcone-3'-C- β -glucopyranosy-6'-O- β -d-glucopyranoside ( 2 ), 7-hydroxy-5,8'-dimethoxy-6' α -l-rhamnopyranosyl-8-(3-phenyl-trans-acryloyl)-1-benzopyran-2-one ( 3 ), 6'7-dihydroxy-5,8-dimethoxy-8(3-phenyl-trans-acryloyl)-1-benzopyran-2-one ( 4 ), 9-hydroxy-3,8-dimethoxy-4-prenylpterocarpan ( 5 ), and α ,4,4'-trihydroxydihydrochalcone-2'-O- β -d-glucopyranoside ( 6 ) were isolated from bark of Eysenhardtia polystachya. Antidiabetic activity of compounds 1 - 5 in terms of their cellular antioxidant and free radical scavenging and also in streptozotocin- (STZ-) induced diabetic mice was evaluated on liver transaminases, lipid peroxidation, total bilirubin, total protein, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (CSH-Px), and glutathione reductase (GSH). Results indicated that 1 - 5 scavenged 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl ( ∙ OH), nitric oxide radicals (NO ∙ ), superoxide anion radical (O 2 ∙- ), radical cation (ABTS ∙+ ), and hydrogen peroxide (H 2 O 2 ) radical, and protection against H 2 O 2 induced BSA damage was also observed. Furthermore, 1 - 5 showed ability to decrease the oxidative stress in H9c2 cell. Diabetic mice present high levels of lipid peroxide, total protein, SGPT, SGOT, ALP, and TB. However, treatment of STZ-induced diabetes in mice with 1 - 5 reduced levels of these enzymes leading to protector effect of liver. In addition, with treatment with 1 - 5 , increases in radical scavenging enzymes of CSH-Px, SOD, GSH, and CAT have also been observed in diabetic mice. The antioxidant properties of compounds 1 - 5 are a promising strategy for ameliorating therapeutic effects by avoiding disorders in the normal redox reactions in healthy cells which consequently could alleviate complications of diabetes.

The Load of Lightning-induced Nitrogen Oxides and Its Impact on the Ground-level Ozone during Summertime over the Mountain West States

EPA Science Inventory

Lightning-induced nitrogen oxides (LNOX), in the presence of sunlight, volatile organic compounds and water, can be a relatively large but uncertain source for ozone (O3) and hydroxyl radical (OH) in the atmosphere. Using lightning flash data from the National Lightning Detection...

OH-radical induced degradation of hydroxybenzoic- and hydroxycinnamic acids and formation of aromatic products—A gamma radiolysis study

NASA Astrophysics Data System (ADS)

Krimmel, Birgit; Swoboda, Friederike; Solar, Sonja; Reznicek, Gottfried

2010-12-01

The OH-radical induced degradation of hydroxybenzoic acids (HBA), hydroxycinnamic acids (HCiA) and methoxylated derivatives, as well as of chlorogenic acid and rosmarinic acid was studied by gamma radiolysis in aerated aqueous solutions. Primary aromatic products resulting from an OH-radical attachment to the ring (hydroxylation), to the position occupied by the methoxyl group (replacement -OCH 3 by -OH) as well as to the propenoic acid side chain of the cinnamic acids (benzaldehyde formations) were analysed by HPLC-UV and LC-ESI-MS. A comparison of the extent of these processes is given for 3,4-dihydroxybenzoic acid, vanillic acid, isovanillic acid, syringic acid, cinnamic acid, 4-hydroxycinnamic acid, caffeic acid, ferulic acid, isoferulic acid, chlorogenic acid, and rosmarinic acid. For all cinnamic acids and derivatives benzaldehydes were significant oxidation products. With the release of caffeic acid from chlorogenic acid the cleavage of a phenolic glycoside could be demonstrated. Reaction mechanisms are discussed.

High-altitude pulmonary hypertension is associated with a free radical-mediated reduction in pulmonary nitric oxide bioavailability

PubMed Central

Bailey, Damian M; Dehnert, Christoph; Luks, Andrew M; Menold, Elmar; Castell, Christian; Schendler, Guido; Faoro, Vitalie; Gutowski, Mariusz; Evans, Kevin A; Taudorf, Sarah; James, Philip E; McEneny, J; Young, Ian S; Swenson, Erik R; Mairbäurl, Heimo; Bärtsch, Peter; Berger, Marc M

2010-01-01

High altitude (HA)-induced pulmonary hypertension may be due to a free radical-mediated reduction in pulmonary nitric oxide (NO) bioavailability. We hypothesised that the increase in pulmonary artery systolic pressure (PASP) at HA would be associated with a net transpulmonary output of free radicals and corresponding loss of bioactive NO metabolites. Twenty-six mountaineers provided central venous and radial arterial samples at low altitude (LA) and following active ascent to 4559 m (HA). PASP was determined by Doppler echocardiography, pulmonary blood flow by inert gas re-breathing, and vasoactive exchange via the Fick principle. Acute mountain sickness (AMS) and high-altitude pulmonary oedema (HAPE) were diagnosed using clinical questionnaires and chest radiography. Electron paramagnetic resonance spectroscopy, ozone-based chemiluminescence and ELISA were employed for plasma detection of the ascorbate free radical (A·−), NO metabolites and 3-nitrotyrosine (3-NT). Fourteen subjects were diagnosed with AMS and three of four HAPE-susceptible subjects developed HAPE. Ascent decreased the arterio-central venous concentration difference (a-cvD) resulting in a net transpulmonary loss of ascorbate, α-tocopherol and bioactive NO metabolites (P < 0.05 vs. LA). This was accompanied by an increased a-cvD and net output of A·− and lipid hydroperoxides (P < 0.05 vs. sea level, SL) that correlated against the rise in PASP (r= 0.56–0.62, P < 0.05) and arterial 3-NT (r= 0.48–0.63, P < 0.05) that was more pronounced in HAPE. These findings suggest that increased PASP and vascular resistance observed at HA are associated with a free radical-mediated reduction in pulmonary NO bioavailability. PMID:20876202

Free-radical reactions induced by OH-radical attack on cytosine-related compounds: a study by a method combining ESR, spin trapping and HPLC.

PubMed Central

Hiraoka, W; Kuwabara, M; Sato, F; Matsuda, A; Ueda, T

1990-01-01

Free-radical reactions induced by OH-radical attack on cytosine-related compounds were investigated by a method combining ESR, spin trapping with 2-methyl-2-nitrosopropane and high-performance liquid chromatography (HPLC). Cytidine, 2'-deoxycytidine, cytidine 3'-monophosphate, cytidine 5'-monophosphate, 2'-deoxycytidine 5'-monophosphate and their derivatives, of which 5,6-protons at the base moiety were replaced by deuterons, and polycytidylic acid (poly(C] were employed as samples. OH radicals were generated by X-irradiating an N2O-saturated aqueous solution. Five spin adducts were separated by HPLC. Examination of them by ESR spectroscopy and UV photospectrometry showed that spin adducts assigned to C5 and C6 radicals due to OH addition to the 5,6 double-bond, a deaminated form of the spin adduct derived from a C5 radical due to the cyclization reaction between C5' of the sugar and C6 of the base, and a spin adduct assigned to the C4' radical due to H abstraction by OH radicals were produced. From these results the sites of OH-radical attack and the subsequent radical reactions in cytosine-related compounds were clarified. PMID:2157193

Isomer distribution of hydroxyoctadecadienoates (HODE) and hydroxyeicosatetraenoates (HETE) produced in the plasma oxidation mediated by peroxyl radical, peroxynitrite, hypochlorite, 15-lipoxygenase, and singlet oxygen.

PubMed

Umeno, Aya; Morita, Mayuko; Yoshida, Yasukazu; Naito, Yuji; Niki, Etsuo

2017-12-01

Free and ester forms of unsaturated fatty acids and cholesterol are oxidized in vivo by multiple oxidants to give diverse products. Some lipid oxidation is mediated by enzymes to selectively give specific products, while others proceed randomly to produce mixtures of many kinds of regioisomers and stereoisomers. The efficacy of antioxidants against lipid oxidation depends on the nature of the oxidants and therefore the identification of oxidant is important for understanding the roles and effects of lipid oxidation and antioxidants in vivo. In the present study, the isomer distribution of hydro(pero)xyoctadecadienoates (H(p)ODEs) and hydro(pero)xyeicosatetraenoates (H(p)ETEs), the most abundant lipid oxidation products found in human plasma, produced in the oxidation of plasma by peroxyl radicals, peroxynitrite, hypochlorite, 15-lipoxygenase, and singlet oxygen were examined. It was shown that 9- and 13-(E,E)-HODEs, 13(S)-(Z,E)-HODE, and 10- and 12-(Z,E)-HODEs were specific lipid oxidation products by free radical, 15-lipoxygenase, and singlet oxygen, respectively. The isomer distribution of HODEs produced by peroxynitrite was similar to that by peroxyl radical, suggesting that the peroxynitrite mediated lipid oxidation proceeds by free radical mechanisms. The production of HODEs and HETEs by hypochlorite was very small. HODEs may be a better biomarker than HETEs since linoleates are oxidized by simpler mechanisms than arachidonates and all the HODEs isomers can be quantified more easily. These products may be used as specific biomarkers for the identification of responsible oxidants and for the assessment of oxidant-specific lipid oxidation levels and effects of antioxidants in vivo. Copyright © 2017 Elsevier Inc. All rights reserved.

Ethanol exposure induces oxidative stress and impairs nitric oxide availability in the human placental villi: a possible mechanism of toxicity.

PubMed

Kay, H H; Grindle, K M; Magness, R R

2000-03-01

We undertook this investigation to explore the effects of ethanol exposure on nitric oxide synthase levels and nitric oxide release. Our hypothesis was that ethanol exposure modifies nitric oxide activity within the placenta as a result of oxidative stress. Four 10-g samples of term normal human placental villous tissue were perifused with nonrecirculating Dulbecco's modified Eagle's medium and 25-mmol/L N-[2-hydroxyethyl]piperazine-N'-[2-ethanesulfonic acid] with 0-, 50-, 100-, or 200-mmol/L ethanol. After 2 hours of exposure, tissue was removed, fixed, and frozen for analysis. Immunohistochemical analysis was performed for subtype I or neuronal nitric oxide synthase (nNOS), subtype II or inducible nitric oxide synthase (iNOS), and subtype III or endothelial nitric oxide synthase (eNOS) localization. Western blot analysis was performed for eNOS quantitation. Cyclic guanosine monophosphate and copper-zinc superoxide dismutase levels were measured by electroimmunoassay and kinetic assay, respectively. Nitric oxide release was analyzed by a Sievers nitric oxide analyzer. Immunohistochemical examination confirmed that only eNOS was localized to the syncytiotrophoblasts. After ethanol exposure, eNOS protein expression increased 2.5- to 3.0-fold over that of the control. Tissue cyclic guanosine monophosphate content and nitric oxide release into the effluent were decreased, whereas superoxide dismutase levels were increased at higher ethanol levels (P <.05). Ethanol exposure appears to induce oxidative stress, which may account for the decreased nitric oxide release, because nitric oxide may be shunted toward scavenging free radicals. Increased eNOS protein expression may be a response to the increased demand for nitric oxide. Decreased nitric oxide availability could adversely affect placental blood flow regulation, which could, in turn, account for the growth restriction seen in ethanol-exposed fetuses.

Kinetics and Near-Infrared Spectroscopy of Organic Peroxy Radicals

NASA Astrophysics Data System (ADS)

Smarte, M. D.; Okumura, M.

2016-12-01

Organic peroxy radicals are important intermediates in atmospheric chemistry with fates that control the rate of radical propagation in an oxidation mechanism. Laboratory methods for detecting peroxy radicals are essential to measuring precise rate constants that constrain these fates. In this work, we discuss the use of near-infrared cavity ringdown spectroscopy to detect organic peroxy radicals for the purpose of laboratory kinetics measurements. We focus on chlorine-substituted peroxy radicals generated in the oxidation of alkenes by chlorine, a minor tropospheric oxidant found in marine and coastal regions. Previous kinetics experiments on peroxy radicals have largely used UV absorption spectroscopy via the dissociative B-X transition. However, the spectra produced are featureless and exhibit substantial overlap; determining the concentration profile of an individual peroxy radical can be an arduous task. In our work, we probe the forbidden peroxy radical A-X transition in the near-infrared. While this approach requires overcoming small cross sections ( 10-21 cm2), the A state is bound and leads to structured absorption spectra that may be useful in constraining the kinetics of mixtures of organic peroxy radicals formed in the oxidation of complex hydrocarbons. Only a few kinetics studies utilizing the A-X transition exist in the literature and they are focused on small, unsubstituted species. This presentation explores the ability of the A-X transition to unravel the kinetics of more complex peroxy radicals in laboratory experiments using several example systems: (1) Determining rate constants for the self and cross reactions of β-chloroethylperoxy and HO2. (2) Detecting the second generation of peroxy radicals formed from alkoxy radical decomposition in the chlorine-initiated oxidation of 2-butene. (3) Observing different rates of reactivity with NO across the pool of peroxy radical isomers formed in the chlorine-initiated oxidation of isoprene.

Near-Infrared Free-Radical and Free-Radical-Promoted Cationic Photopolymerizations by In-Source Lighting Using Upconverting Glass.

PubMed

Kocaarslan, Azra; Tabanli, Sevcan; Eryurek, Gonul; Yagci, Yusuf

2017-11-13

A method is presented for the initiation of free-radical and free-radical-promoted cationic photopolymerizations by in-source lighting in the near-infrared (NIR) region using upconverting glass (UCG). This approach utilizes laser irradiation of UCG at 975 nm in the presence of fluorescein (FL) and pentamethyldiethylene triamine (PMDETA). FL excited by light emitted from the UCG undergoes electron-transfer reactions with PMDETA to form free radicals capable of initiating polymerization of methyl methacrylate. To execute the corresponding free-radical-promoted cationic polymerization of cyclohexene oxide, isobutyl vinyl ether, and N-vinyl carbazole, it was necessary to use FL, dimethyl aniline (DMA), and diphenyliodonium hexafluorophosphate as sensitizer, coinitiator, and oxidant, respectively. Iodonium ions promptly oxidize DMA radicals formed to the corresponding cations. Thus, cationic polymerization with efficiency comparable to the conventional irradiation source was achieved. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Conversion of 3-imidazoline-3-oxide nitroxyl radicals into nitronylnitroxyl radicals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grigor'ev, I.A.; Shchukin, G.I.; Khramtsov, V.V.

1986-04-20

Continuing the studies of the effect of the pH of the medium on the EPR spectra of nitroxyl radicals (NR) containing acid-base functional groups at a distance of 2-3 sigma-bonds from the radical center, they have examined the EPR spectra of NR, which contain OH groups in the 2-position of the heterocycle. It is assumed that deprotonation of the OH group is accompanied by changes in the hfc constant a/sub N//sup 1/ and the g-factor. At pH values greater than or equal to 12, however, the EPR spectra of aqueous solutions of radicals undergo irreversible changes from a triplet tomore » a more complex multiplet, similar to the spectra of nitronylnitroxyl radicals. The EPR spectra of these solutions remain unchanged over periods of several days. The spectra have a quintet structure, with further splitting into four or three components. When similar experiments are carried out in D/sub 2/O, the additional hfs disappear as a result of deuterium exchange in the CH/sub 2/ and CH/sub 3/ groups of the radicals. A simulation of the EPR spectra was carried out, assuming splitting into two N nuclei (a/sub N//sup 1/ and a/sub N//sup 3/), with three or two equivalent H. This resulted in complete agreement between the calculated and experimental spectra. In order to assign the nitrogen hfc constants, they synthesized radicals containing the N/sup 15/ isotope in the 3-position of the imidazole ring. Comparison of the results of simulations of the EPR spectra enabled unambiguous assignments of the hfc constants a/sub N//sup 1/ and a/sub N//sup 3/ to be made.« less

SULFATE RADICAL-BASED FERROUS-PEROXYMONOSULFATE OXIDATIVE SYSTEM FOR PCBs DEGRADATION IN AQUEOUS AND SEDIMENT SYSTEMS

EPA Science Inventory

Polychlorinated biphenyls (PCBs) in the environment pose long-term risk to public health because of their persistent and toxic nature. This study investigates the degradation of PCBs using sulfate radical-based advanced oxidation processes (SR-AOPs). These processes are based o...

Lignin peroxidase-catalyzed oxidation of nonphenolic trimeric lignin model compounds: fragmentation reactions in the intermediate radical cations.

PubMed

Baciocchi, Enrico; Fabbri, Claudia; Lanzalunga, Osvaldo

2003-11-14

The H(2)O(2)-promoted oxidations of the two nonphenolic beta-O-aryl lignin model trimers 1 and 2, catalyzed by lignin peroxidase (LiP) at pH = 3.5, have been studied. The results have been compared with those obtained in the oxidation of 1 and 2 with the genuine one-electron oxidant potassium 12-tungstocobalt(III)ate. These models present a different substitution pattern of the three aromatic rings, and by one-electron oxidation, they form radical cations with the positive charge, which is localized in the dialkoxylated ring as also evidenced by a pulse radiolysis study. Both the oxidations with the enzymatic and with the chemical systems lead to the formation of products deriving from the cleavage of C-C and C-H bonds in a beta position with respect to the radical cation with the charge residing in the dialkoxylated ring (3,4-dimethoxybenzaldehyde (5) and a trimeric ketone 6 in the oxidation of 1 and a dimeric aldehyde 8 and a trimeric ketone 9 in the oxidation of 2). These products are accompanied by a dimeric aldehyde 7 in the oxidation of 1 and 4-methoxybenzaldehyde (10) in the oxidation of 2. The unexpected formation of these two products has been explained by suggesting that 1.+ and 2.+ can also undergo an intramolecular electron transfer leading to the radical cations 1a.+ and 2a.+ with the charge residing in a monoalkoxylated ring. The fast cleavage of a C-C bond beta to this ring, leading to 7 from 1.+ and to 10 from 2.+, is the driving force of the endoergonic electron transfer. A kinetic steady-state investigation of the LiP-catalyzed oxidation of the trimer 2, the dimeric model 1-(3,4-dimethoxyphenyl)-2-phenoxy-1-ethanol (4), and 3,4-dimethoxybenzyl alcohol (3) has indicated that the turnover number (k(cat)) and the affinity for the enzyme decrease significantly by increasing the size of the model compound. In contrast, the three substrates exhibited a very similar reactivity toward a chemical oxidant [Co(III)W]. This suggests a size

The tetrahydrobiopterin radical with high- and low-spin heme in neuronal nitric oxide synthase -- a new indicator of the extent of NOS coupling

PubMed Central

Krzyaniak, Matthew D.; Cruce, Alex A.; Vennam, Preethi; Lockart, Molly; Berka, Vladimir; Tsai, Ah-Lim; Bowman, Michael K.

2016-01-01

Reaction intermediates trapped during the single-turnover reaction of the neuronal ferrous nitric oxide synthase oxygenase domain (Fe(II)nNOSOX) show four EPR spectra of free radicals. Fully-coupled nNOSOX with cofactor (tetrahydrobiopterin, BH4) and substrate (l-arginine) forms the typical BH4 cation radical with an EPR spectrum ~4.0 mT wide and hyperfine tensors similar to reports for a biopterin cation radical in inducible NOSOX (iNOSOX). With excess thiol, nNOSox lacking BH4 and l-arg is known to produce superoxide. In contrast, we find that nNOSOX with BH4 but no l-arg forms two radicals with rather different, fast (~ 250 µs at 5 K) and slower (~ 500 µs at 20 K), electron spin relaxation rates and a combined ~7.0 mT wide EPR spectrum. Rapid freeze-quench CW- and pulsed-EPR measurements are used to identify these radicals and their origin. These two species are the same radical with identical nuclear hyperfine couplings, but with spin-spin couplings to high-spin (4.0 mT component) or low-spin (7.0 mT component) Fe(III) heme. Uncoupled reactions of nNOS leave the enzyme in states that can be chemically reduced to sustain unregulated production of NO and reactive oxygen species in ischemia-reperfusion injury. The broad EPR signal is a convenient indicator of uncoupled nNOS reactions producing low-spin Fe(III) heme. PMID:27989753

Anti-Oxidative Effects of Rooibos Tea (Aspalathus linearis) on Immobilization-Induced Oxidative Stress in Rat Brain

PubMed Central

Kim, Hyun-Pyo

2014-01-01

Exposure to chronic psychological stress may be related to increased reactive oxygen species (ROS) or free radicals, and thus, long-term exposure to high levels of oxidative stress may cause the accumulation of oxidative damage and eventually lead to many neurodegenerative diseases. Compared with other organs, the brain appears especially susceptible to excessive oxidative stress due to its high demand for oxygen. In the case of excessive ROS production, endogenous defense mechanisms against ROS may not be sufficient to suppress ROS-associated oxidative damage. Dietary antioxidants have been shown to protect neurons against a variety of experimental neurodegenerative conditions. In particular, Rooibos tea might be a good source of antioxidants due to its larger proportion of polyphenolic compounds. An optimal animal model for stress should show the features of a stress response and should be able to mimic natural stress progression. However, most animal models of stress, such as cold-restraint, electric foot shock, and burn shock, usually involve physical abuse in addition to the psychological aspects of stress. Animals subjected to chronic restraint or immobilization are widely believed to be a convenient and reliable model to mimic psychological stress. Therefore, in the present study, we propose that immobilization-induced oxidative stress was significantly attenuated by treatment with Rooibos tea. This conclusion is demonstrated by Rooibos tea’s ability to (i) reverse the increase in stress-related metabolites (5-HIAA and FFA), (ii) prevent lipid peroxidation (LPO), (iii) restore stress-induced protein degradation (PD), (iv) regulate glutathione metabolism (GSH and GSH/GSSG ratio), and (v) modulate changes in the activities of antioxidant enzymes (SOD and CAT). PMID:24466326

Oxidative capacity of the Mexico City atmosphere - Part 1: A radical source perspective

NASA Astrophysics Data System (ADS)

Volkamer, R.; Sheehy, P.; Molina, L. T.; Molina, M. J.

2010-07-01

A detailed analysis of OH, HO2 and RO2 radical sources is presented for the near field photochemical regime inside the Mexico City Metropolitan Area (MCMA). During spring of 2003 (MCMA-2003 field campaign) an extensive set of measurements was collected to quantify time-resolved ROx (sum of OH, HO2, RO2) radical production rates from day- and nighttime radical sources. The Master Chemical Mechanism (MCMv3.1) was constrained by measurements of (1) concentration time-profiles of photosensitive radical precursors, i.e., nitrous acid (HONO), formaldehyde (HCHO), ozone (O3), glyoxal (CHOCHO), and other oxygenated volatile organic compounds (OVOCs); (2) respective photolysis-frequencies (J-values); (3) concentration time-profiles of alkanes, alkenes, and aromatic VOCs (103 compound are treated) and oxidants, i.e., OH- and NO3 radicals, O3; and (4) NO, NO2, meteorological and other parameters. The ROx production rate was calculated directly from these observations; the MCM was used to estimate further ROx production from unconstrained sources, and express overall ROx production as OH-equivalents (i.e., taking into account the propagation efficiencies of RO2 and HO2 radicals into OH radicals). Daytime radical production is found to be about 10-25 times higher than at night; it does not track the abundance of sunlight. 12-h average daytime contributions of individual sources are: Oxygenated VOC other than HCHO about 33%; HCHO and O3 photolysis each about 20%; O3/alkene reactions and HONO photolysis each about 12%, other sources <3%. Nitryl chloride photolysis could potentially contribute ~15% additional radicals, while NO2* + water makes - if any - a very small contribution (~2%). The peak radical production of ~7.5 107 molec cm-3 s-1 is found already at 10:00 a.m., i.e., more than 2.5 h before solar noon. O3/alkene reactions are indirectly responsible for ~33% of these radicals. Our measurements and analysis comprise a database that enables testing of the representation of

Volatile organic compound conversion by ozone, hydroxyl radicals, and nitrate radicals in residential indoor air: Magnitudes and impacts of oxidant sources

NASA Astrophysics Data System (ADS)

Waring, Michael S.; Wells, J. Raymond

2015-04-01

Indoor chemistry may be initiated by reactions of ozone (O3), the hydroxyl radical (OH), or the nitrate radical (NO3) with volatile organic compounds (VOC). The principal indoor source of O3 is air exchange, while OH and NO3 formation are considered as primarily from O3 reactions with alkenes and nitrogen dioxide (NO2), respectively. Herein, we used time-averaged models for residences to predict O3, OH, and NO3 concentrations and their impacts on conversion of typical residential VOC profiles, within a Monte Carlo framework that varied inputs probabilistically. We accounted for established oxidant sources, as well as explored the importance of two newly realized indoor sources: (i) the photolysis of nitrous acid (HONO) indoors to generate OH and (ii) the reaction of stabilized Criegee intermediates (SCI) with NO2 to generate NO3. We found total VOC conversion to be dominated by reactions both with O3, which almost solely reacted with D-limonene, and also with OH, which reacted with D-limonene, other terpenes, alcohols, aldehydes, and aromatics. VOC oxidation rates increased with air exchange, outdoor O3, NO2 and D-limonene sources, and indoor photolysis rates; and they decreased with O3 deposition and nitric oxide (NO) sources. Photolysis was a strong OH formation mechanism for high NO, NO2, and HONO settings, but SCI/NO2 reactions weakly generated NO3 except for only a few cases.

Free Radical Scavenging Properties of Skin and Pulp Extracts of Different Grape Cultivars In Vitro and Attenuation of H2O2-Induced Oxidative Stress in Liver Tissue Ex Vivo.

PubMed

Singha, Indrani; Das, Subir Kumar

2015-07-01

Grapes are the richest source of antioxidants due to the presence of potent bioactive phytochemicals. In this study, the phytochemical contents, scavenging activities and protective role against H2O2-induced oxidative stress in liver tissue ex vivo of four grape (Vitis vinifera) cultivars extracts, namely Flame seedless (black), Kishmish chorni (black with reddish brown), Red globe (red) and Thompson seedless mutant (green), were evaluated. The total phenolics and flavonoids content in pulp or skin fractions of different grape cultivars were in the range of 47.6-310 mg gallic acid equivalent/g fresh weight (fw), and 46.6-733.3 µg catechin equivalent/g fw respectively. The scavenging activities in skin of different grape varieties against 2,2-diphenyl-1-picrylhydrazyl (44-58 %), hydrogen peroxide (15.3-18.6 %), and hydroxyl radicals (50-85 %), were higher than pulp of the corresponding cultivars. These scavenging activities of grape extracts were found to be significantly (p < 0.01) correlated with the levels of total phenols, flavonoids and ascorbic acid. Liver tissues from goat treated with H2O2 (500 μM) showed significantly decreased GSH content by 42.9 % and activities of catalase by 50 % and glutathione reductase by 66.6 %; while increased thiobarbituric acid reactive substances and nitric oxide level by 2.53- and 0.86-fold, respectively, and activity of glutathione S-transferase by 0.96-fold. Grape skin extracts showed the stronger protective activity against H2O2-induced oxidative stress in liver tissue ex vivo, than its pulp of any cultivar; and the Flame seedless (black) cultivar showed the highest potential. In conclusion, our study suggested that the higher antioxidant potential, phytochemical contents and significant scavenging capacities in pulp and skin of grape extracts showed the protective action of grape extracts against H2O2-induced oxidative stress in liver tissue ex vivo.

Electronic paramagnetic resonance (EPR) for the study of ascorbyl radical and lipid radicals in marine organisms.

PubMed

González, Paula Mariela; Aguiar, María Belén; Malanga, Gabriela; Puntarulo, Susana

2013-08-01

Electron paramagnetic resonance (EPR) spectroscopy detects the presence of radicals of biological interest, such as ascorbyl radical (A(•)) and lipid radicals. A(•) is easily detectable by EPR even in aqueous solution at room-temperature. Under oxidative conditions leading to changes in total ascorbate (AH(-)) content, the A(•)/AH(-) ratio could be used to estimate early oxidative stress in the hydrophilic milieu. This methodology was applied to a wide range of aquatic systems including algae, sea urchin, limpets, bivalves and fish, under physiological and oxidative stress conditions as well. The A(•)/AH(-) ratio reflected the state of one part of the oxidative defense system and provided an early and simple diagnosis of environmental stressing conditions. Oxidative damage to lipids was assessed by the EPR-sensitive adduct formation that correlates well with cell membrane damage with no interference from other biological compounds. Probe instability, tissue metabolism, and lack of spin specificity are drawback factors for employing EPR for in vivo determination of free radicals. However, the dependability of this technique, mostly by combining it with other biochemical strategies, enhances the value of these procedures as contributors to the knowledge of oxidative condition in aquatic organisms. Copyright © 2013 Elsevier Inc. All rights reserved.

Regulated production of free radicals by the mitochondrial electron transport chain: Cardiac ischemic preconditioning.

PubMed

Matsuzaki, Satoshi; Szweda, Pamela A; Szweda, Luke I; Humphries, Kenneth M

2009-11-30

Excessive production of free radicals by mitochondria is associated with, and likely contributes to, the progression of numerous pathological conditions. Nevertheless, the production of free radicals by the mitochondria may have important biological functions under normal or stressed conditions by activating or modulating redox-sensitive cellular signaling pathways. This raises the intriguing possibility that regulated mitochondrial free radical production occurs via mechanisms that are distinct from pathologies associated with oxidative damage. Indeed, the capacity of mitochondria to produce free radicals in a limited manner may play a role in ischemic preconditioning, the phenomenon whereby short bouts of ischemia protect from subsequent prolonged ischemia and reperfusion. Ischemic preconditioning can thus serve as an important model system for defining regulatory mechanisms that allow for transient, signal-inducing, production of free radicals by mitochondria. Defining how these mechanism(s) occur will provide insight into therapeutic approaches that minimize oxidative damage without altering normal cellular redox biology. The aim of this review is to present and discuss evidence for the regulated production of superoxide by the electron transport chain within the ischemic preconditioning paradigm of redox regulation.

Reactions of nitroxide radicals in aqueous solutions exposed to non-thermal plasma: limitations of spin trapping of the plasma induced species

NASA Astrophysics Data System (ADS)

Gorbanev, Yury; Stehling, Nicola; O'Connell, Deborah; Chechik, Victor

2016-10-01

Low temperature (‘cold’) atmospheric pressure plasmas have gained much attention in recent years due to their biomedical effects achieved through the interactions of plasma-induced species with the biological substrate. Monitoring of the radical species in an aqueous biological milieu is usually performed via electron paramagnetic resonance (EPR) spectroscopy using various nitrone spin traps, which form persistent radical adducts with the short-lived radicals. However, the stability of these nitroxide radical adducts in the plasma-specific environment is not well known. In this work, chemical transformations of nitroxide radicals in aqueous solutions using a model nitroxide 4-oxo-TEMPO were studied using EPR and LC-MS. The kinetics of the nitroxide decay when the solution was exposed to plasma were assessed, and the reactive pathways proposed. The use of different scavengers enabled identification of the types of reactive species which cause the decay, indicating the predominant nitroxide group reduction in oxygen-free plasmas. The 2H adduct of the PBN spin trap (PBN-D) was shown to decay similarly to the model molecule 4-oxo-TEMPO. The decay of the spin adducts in plasma-treated solutions must be considered to avoid rendering the spin trapping results unreliable. In particular, the selectivity of the decay indicated the limitations of the PTIO/PTI nitroxide system in the detection of nitric oxide.

Antihemolytic and antioxidant properties of pearl powder against 2,2'-azobis(2-amidinopropane) dihydrochloride-induced hemolysis and oxidative damage to erythrocyte membrane lipids and proteins.

PubMed

Yang, Hsin-Ling; Korivi, Mallikarjuna; Lin, Ming-Kuem; Chang, Hebron Chun-Wei; Wu, Chi-Rei; Lee, Meng-Shiou; Chen, William Tzu-Liang; Hseu, You-Cheng

2017-10-01

Pearl powder, a well-known traditional mineral medicine, is reported to be used for well-being and to treat several diseases from centuries in Taiwan and China. We investigated the in vitro antihemolytic and antioxidant properties of pearl powder that could protect erythrocytes against 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced oxidative damage to membrane proteins/lipids. Human erythrocytes were incubated with different concentrations of pearl powder (50-200 μg/mL) for 30 minutes and then exposed to AAPH for 2-6 hours. We found that AAPH alone time dependently increased the oxidative hemolysis of erythrocytes, while pearl powder pretreatment substantially inhibited the hemolysis in a concentration-/time-dependent manner. AAPH-induced oxidative damage to erythrocyte membrane lipids was evidenced by the elevated malondialdehyde (MDA) levels. However, pearl powder remarkably inhibited the malondialdehyde formation, and the 200 μg/mL concentration showed almost similar malondialdehyde values to the control. Furthermore, pearl powder suppressed the AAPH-induced high-molecular-weight protein formation and concomitantly increased the low-molecular-weight proteins in erythrocytes. Antioxidant potential that was measured as superoxide dismutase activity and glutathione content was significantly dropped by AAPH incubation, which suggests the vulnerability of erythrocytes to AAPH-induced oxidative stress. Noteworthy, erythrocytes pretreated with pearl powder showed restored superoxide dismutase activity and glutathione levels against AAPH-induced loss. Our findings conclude that pearl powder attenuate free radical-induced hemolysis and oxidative damage to erythrocyte membrane lipids/proteins. The potent antioxidant property of pearl powder may offer protection from free radical-related diseases. Copyright © 2016. Published by Elsevier B.V.

Free radicals hasten head and neck cancer risk: A study of total oxidant, total antioxidant, DNA damage, and histological grade

PubMed Central

Singh, AK; Pandey, P; Tewari, M; Pandey, HP; Gambhir, IS; Shukla, HS

2016-01-01

Background: Free radicals such as reactive oxygen species (ROS), which induce oxidative stress, are the main contributors to head and neck carcinogenesis (HNC). The present study was conducted with the aim to assess the oxidant/antioxidant status and DNA damage analysis in head and neck cancer/control patients. Materials and Methods: This prospective study was conducted on 60 patients with biopsy-proven HNC and 17 patients of head and neck disease (HND). The total antioxidant status (TAS), total oxidant status (TOS), and oxidative stress index (OSI) were determined by novel automatic colorimetric methods from tissue homogenate. DNA damage analysis was determined by single cell gel electrophoresis (SCGE). Results: The mean age of the study cohort was 46.65 ± 14.84 years for HNC patients, while it was 49.41 ± 13.00 years for HND patients. There were no significant differences found between the two groups with respect to demographic presentation except tobacco addiction. The association between oxidative stress parameters and DNA damage analysis with study group revealed the following. (A) DNA damage - tissue homogenate TOS and OSI were significantly higher in HNC subjects than in HND (16.06 ± 1.78 AU vs 7.86 ± 5.97 AU, P < 0.001; 53.00 ± 40.61 vs 19.67 ± 21.90, P < 0.01; 7.221 ± 5.80 vs 2.40 ± 2.54, P < 0.01, respectively), while TAS was significantly decreased. (B) Aggressive histological features were identified, more commonly with higher TOS and lower TAS [probability (P) = 0.002, relative risk (RR) = 11.838, 95% confidence interval CI = 2.514-55.730 and P = 0.043, RR = 0.271, 95% CI = 0.077-0.960, respectively]. Conclusion: The increase in free radicals may be the event that led to the reduction of antioxidant status in HNC, thus explaining the oxidative damage of DNA and the severity of disease. Increased OSI represents a general mechanism in its pathogenesis. PMID:27089108

STABLE FREE-RADICAL FORMS OF PLASMA PROTEINS OR SIMPLER RELATED STRUCTURES WHICH INDUCE BRAIN EXCITATORY EFFECTS

PubMed Central

Polis, B. David; Wyeth, John; Goldstein, Leonide; Graedon, Joe

1969-01-01

Stable free radicals have been prepared from purified plasma proteins, pituitary peptides, and simpler related structures like 5-OH tryptophan and melatonin by oxidation with the free-radical nitrosyl disulfonate in alkaline solution under controlled conditions. The presence of tyrosine or trytophan amino acid residues in the protein was found essential for free-radical formation. These red-colored, stable free radicals showed electron spin resonance spectra in aqueous solutions at room temperature and maintained this characteristic for weeks when stored at 5°C. Illumination, by visible light, of the free-radical proteins and peptides separated from excess nitrosyl disulfonate by salt fractionation or chromatography enhanced the free-radical concentration in the light. The increased signal decayed in the dark. Intravenous administration of the free-radical proteins or peptides into rabbits equipped with chronic cranial electrodes and sedated with a small dose of pentobarbital caused a sudden EEG arousal accompanied by behavioral changes indicative of brain excitation. Illumination of the free-radical compounds prior to administration enhanced the effects. Untreated control proteins or peptides had no effects. The observations are interpreted to suggest the involvement of free-radical structures in the transfer of energy in nervous tissue. PMID:4311379

Anthocyanins encapsulated by PLGA@PEG nanoparticles potentially improved its free radical scavenging capabilities via p38/JNK pathway against Aβ1-42-induced oxidative stress.

PubMed

Amin, Faiz Ul; Shah, Shahid Ali; Badshah, Haroon; Khan, Mehtab; Kim, Myeong Ok

2017-02-07

In order to increase the bioavailability of hydrophilic unstable drugs like anthocyanins, we employed a polymer-based nanoparticles approach due to its unique properties such as high stability, improved bioavailability and high water-soluble drug loading efficiency. Anthocyanins constitute a subfamily of flavonoids that possess anti-oxidative, anti-inflammatory and neuroprotective properties. However, anthocyanins are unstable because their phenolic hydroxyl groups are easily oxidized into quinones, causing a reduced biological activity. To overcome this drawback and improve the free radical scavenging capabilities of anthocyanins, in the current study we for the first time encapsulated the anthocyanins in biodegradable nanoparticle formulation based on poly (lactide-co-glycolide) (PLGA) and a stabilizer polyethylene glycol (PEG)-2000. The biological activity and neuroprotective effect of anthocyanin loaded nanoparticles (An-NPs) were investigated in SH-SY5Y cell lines. Morphological examination under transmission electron microscopy (TEM) showed the formation of smooth spherically shaped nanoparticles. The average particle size and zeta potential of An-NPs were in the range of 120-165 nm and -12 mV respectively, with a low polydispersity index (0.4) and displayed a biphasic release profile in vitro. Anthocyanins encapsulation in PLGA@PEG nanoparticles (NPs) did not destroy its inherent properties and exhibit more potent neuroprotective properties. An-NPs were nontoxic to SH-SY5Y cells and increased their cell viability against Aβ 1-42 by its free radical scavenging characteristics and abrogated ROS generation via the p38-MAPK/JNK pathways accompanied by induction of endogenous nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1). Comparative to native bulk anthocyanins, An-NPs effectively attenuated Alzheimer's markers like APP (amyloid precursor protein), BACE-1 (beta-site amyloid precursor protein cleaving enzyme 1

Piroxicam attenuates 3-nitropropionic acid-induced brain oxidative stress and behavioral alteration in mice.

PubMed

C, Jadiswami; H M, Megha; Dhadde, Shivsharan B; Durg, Sharanbasappa; Potadar, Pandharinath P; B S, Thippeswamy; V P, Veerapur

2014-12-01

3-Nitropropionic acid (3-NP) is a fungal toxin that produces Huntington's disease like symptoms in both animals and humans. Piroxicam, a non-selective cyclooxygenase (COX) inhibitor, used as anti-inflammatory agent and also known to decrease free oxygen radical production. In this study, the effect of piroxicam was evaluated against 3-NP-induced brain oxidative stress and behavioral alteration in mice. Adult male Swiss albino mice were injected with vehicle/piroxicam (10 and 20 mg/kg, i.p.) 30 min before 3-NP challenge (15 mg/kg, i.p.) regularly for 14 days. Body weights of the mice were measured on alternative days of the experiment. At the end of the treatment schedule, mice were evaluated for behavioral alterations (movement analysis, locomotor test, beam walking test and hanging wire test) and brain homogenates were used for the estimation of oxidative stress markers (lipid peroxidation, reduced glutathione and catalase). Administration of 3-NP significantly altered the behavioral activities and brain antioxidant status in mice. Piroxicam, at both the tested doses, caused a significant reversal of 3-NP-induced behavioral alterations and oxidative stress in mice. These findings suggest piroxicam protects the mice against 3-NP-induced brain oxidative stress and behavioral alteration. The antioxidant properties of piroxicam may be responsible for the observed beneficial actions.

Nitric oxide is a mediator of methamphetamine (METH)-induced neurotoxicity. In vitro evidence from primary cultures of mesencephalic cells.

PubMed

Sheng, P; Cerruti, C; Ali, S; Cadet, J L

1996-10-31

METH is a monoaminergic toxic that destroys dopamine terminals in vivo. Oxidative mechanisms associated with DA metabolism are thought to play an important role in its toxic effects. These ideas were supported by the demonstration that CuZn-superoxide dismutase (CuZnSOD) transgenic mice were protected against the toxic effects of the drug. In the present study, we sought to determine if nitric oxide (NO) production was also involved in METH-induced neurotoxicity using primary cultures obtained from fetal rat mesencephalon. METH caused dose- and time-dependent cell death in vitro. Blockade of nitric oxide (NO) formation with several nitric oxide (NO) synthase blockers attenuated METH-mediated toxicity. Moreover, inhibition of ADP-ribosylation with nicotinamide and benzamide also provided protection against the toxicity of the drug. These results, together with our previous results in transgenic mice, support a role for free radicals in METH-induced toxic effects.

Effects of various vitamins and coenzymes Q on reactions involving alpha-hydroxyl-containing radicals.

PubMed

Shadyro, Oleg I; Sosnovskaya, Anna A; Edimecheva, Irina P; Grintsevich, Ivan B; Lagutin, Petr Yu; Alekseev, Aleksei V; Kazem, Kamel

2005-07-01

Effects of vitamins B, C, E, K and P, as well as coenzymes Q, on formation of final products of radiation-induced free-radical transformations of ethanol, ethylene glycol, alpha-methylglycoside and glucose in aqueous solutions were studied. Based on the obtained results, it can be concluded that there are substances among vitamins and coenzymes that effectively interact with alpha-hydroxyl-containing radicals. In the presence of these substances, recombination reactions of alpha-hydroxyalkyl radicals and fragmentation of alpha-hydroxy-beta-substituted organic radicals are suppressed. It has been established that the observed effects are due to the ability of the vitamins and coenzymes under study to either oxidize alpha-hydroxyl-containing radicals yielding the respective carbonyl compounds or reduce them into the initial molecules.

Modulation of ionizing radiation induced oxidative imbalance by semi-fractionated extract of Piper betle

PubMed Central

Verma, Savita; Dutta, Ajaswrata; Sankhwar, Sanghmitra; Shukla, Sandeep Kumar

2010-01-01

The study was planned to evaluate modulatory effect of aqueous extract of Piper betle leaf (PBL) on ionizing radiation mediated oxidative stress leading to normal tissues damage during radiotherapy and other radiation exposures. The total polyphenols and flavonoids known as free radical scavenger (chelators) were measured in the extract. To ascertain antioxidant potential of PBL extract, we studied free radical scavenging, metal chelation, reducing power, lipid peroxidation inhibition and ferric reducing antioxidant properties (FRAP ) using in vitro assays. Mice were exposed to varied radiation doses administered with the same extract prior to irradiation to confirm its oxidative stress minimizing efficacy by evaluating ferric reducing ability of plasma, reduced glutathione, lipid peroxidation and micro-nuclei frequency. PBL extract was effective in scavenging DPPH (up to 92% at 100 µg/ml) and superoxide radicals (up to 95% at 80 µg/ml), chelated metal ions (up to 83% at 50 µg/ml) and inhibited lipid peroxidation (up to 45.65% at 500 µg/ml) in a dose dependant manner using in vitro model. Oral administration of PBL extract (225 mg/kg body weight) 1 hr before irradiation in mice significantly enhanced (p < 0.01) radiation abated antioxidant potential of plasma and GSH level in all the observed organs. The treatment with extract effectively lowered the radiation induced lipid peroxidation at 24 hrs in all the selected organs with maximum inhibition in thymus (p < 0.01). After 48 hrs, lipid peroxidation was maximally inhibited in the group treated with the extract. Frequency of radiation induced micronucleated cells declined significantly (34.78%, p < 0.01) at 24 hrs post-irradiation interval by PBL extract administration. The results suggest that PBL extract has high antioxidant potential and relatively non-toxic and thus could be assertively used to mitigate radiotherapy inflicted normal tissues damage and also injuries caused by moderate doses of radiation

Effect of flavoring chemicals on free radical formation in electronic cigarette aerosols.

PubMed

Bitzer, Zachary T; Goel, Reema; Reilly, Samantha M; Elias, Ryan J; Silakov, Alexey; Foulds, Jonathan; Muscat, Joshua; Richie, John P

2018-05-20

Flavoring chemicals, or flavorants, have been used in electronic cigarettes (e-cigarettes) since their inception; however, little is known about their toxicological effects. Free radicals present in e-cigarette aerosols have been shown to induce oxidative stress resulting in damage to proliferation, survival, and inflammation pathways in the cell. Aerosols generated from e-liquid solvents alone contain high levels of free radicals but few studies have looked at how these toxins are modulated by flavorants. We investigated the effects of different flavorants on free radical production in e-cigarette aerosols. Free radicals generated from 49 commercially available e-liquid flavors were captured and analyzed using electron paramagnetic resonance (EPR). The flavorant composition of each e-liquid was analyzed by gas chromatography mass spectroscopy (GCMS). Radical production was correlated with flavorant abundance. Ten compounds were identified and analyzed for their impact on free radical generation. Nearly half of the flavors modulated free radical generation. Flavorants with strong correlations included β-damascone, δ-tetradecalactone, γ-decalactone, citral, dipentene, ethyl maltol, ethyl vanillin, ethyl vanillin PG acetal, linalool, and piperonal. Dipentene, ethyl maltol, citral, linalool, and piperonal promoted radical formation in a concentration-dependent manner. Ethyl vanillin inhibited the radical formation in a concentration dependent manner. Free radical production was closely linked with the capacity to oxidize biologically-relevant lipids. Our results suggest that flavoring agents play an important role in either enhancing or inhibiting the production of free radicals in flavored e-cigarette aerosols. This information is important for developing regulatory strategies aimed at reducing potential harm from e-cigarettes. Copyright © 2018 Elsevier Inc. All rights reserved.

Molecular hydrogen protects against oxidative stress-induced SH-SY5Y neuroblastoma cell death through the process of mitohormesis.

PubMed

Murakami, Yayoi; Ito, Masafumi; Ohsawa, Ikuroh

2017-01-01

Inhalation of molecular hydrogen (H2) gas ameliorates oxidative stress-induced acute injuries in the brain. Consumption of water nearly saturated with H2 also prevents chronic neurodegenerative diseases including Parkinson's disease in animal and clinical studies. However, the molecular mechanisms underlying the remarkable effect of a small amount of H2 remain unclear. Here, we investigated the effect of H2 on mitochondria in cultured human neuroblastoma SH-SY5Y cells. H2 increased the mitochondrial membrane potential and the cellular ATP level, which were accompanied by a decrease in the reduced glutathione level and an increase in the superoxide level. Pretreatment with H2 suppressed H2O2-induced cell death, whereas post-treatment did not. Increases in the expression of anti-oxidative enzymes underlying the Nrf2 pathway in H2-treated cells indicated that mild stress caused by H2 induced increased resistance to exacerbated oxidative stress. We propose that H2 functions both as a radical scavenger and a mitohormetic effector against oxidative stress in cells.

Metal-free carbon materials-catalyzed sulfate radical-based advanced oxidation processes: A review on heterogeneous catalysts and applications.

PubMed

Zhao, Qingxia; Mao, Qiming; Zhou, Yaoyu; Wei, Jianhong; Liu, Xiaocheng; Yang, Junying; Luo, Lin; Zhang, Jiachao; Chen, Hong; Chen, Hongbo; Tang, Lin

2017-12-01

In recent years, advanced oxidation processes (AOPs), especially sulfate radical based AOPs have been widely used in various fields of wastewater treatment due to their capability and adaptability in decontamination. Recently, metal-free carbon materials catalysts in sulfate radical production has been more and more concerned because these materials have been demonstrated to be promising alternatives to conventional metal-based catalysts, but the review of metal-free catalysts is rare. The present review outlines the current state of knowledge on the generation of sulfate radical using metal-free catalysts including carbon nanotubes, graphene, mesoporous carbon, activated carbon, activated carbon fiber, nanodiamond. The mechanism such as the radical pathway and non-radical pathway, and factors influencing of the activation of sulfate radical was also be revealed. Knowledge gaps and research needs have been identified, which include the perspectives on challenges related to metal-free catalyst, heterogeneous metal-free catalyst/persulfate systems and their potential in practical environmental remediation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Free radical development in phacoemulsification cataract surgery.

PubMed

Takahashi, Hiroshi

2005-02-01

Phacoemulsification and aspiration (PEA) has become the most popular cataract surgery, due to the establishment of safe surgical techniques and development of associated instruments. However, corneal endothelial damage still represents a serious complication, as excessive damage can lead to irreversible bullous keratopathy. In addition to causes such as mechanical or heat injuries, free radical formation due to ultrasound has been posited as another cause of corneal endothelium damage in PEA. Ultrasound in aqueous solution induces cavitation, directly causing water molecule disintegration and resulting in the formation of hydroxylradicals, the most potent of the reactive oxygen species. Considering the oxidative insult to endothelial cells caused by free radicals, their presence in the anterior chamber may represent one of the most harmful factors during these procedures. Indeed, some researchers have recently started to evaluate PEA from the perspective of oxidative stress. Conversely, the major ingredient in ophthalmic viscosurgical devices (OVDs), which are indispensable for maintaining the anterior chamber in PEA surgery, is sodium hyaluronate, a known free radical scavenger. OVDs can thus be expected to provide some anti-free radical effect during PEA procedures. In addition, since commercially available OVDs display different properties regarding retention in the anterior chamber during PEA, the anti-free radical effect of OVDs is likely to depend on behavior during irrigation and aspiration. The present study followed standard PEA procedures in an eye model and measured hydroxylradicals in the anterior chamber using electron spin resonance. The kinetics of free radical intensity and effects of several OVDs during clinical PEA were also demonstrated. These studies may be of significance in re-evaluating OVDs as a chemical protectant for corneal endothelium, since the OVD has thus far only been regarded as a physical barrier. In addition, many reports about

Tyrosyl Radicals in Dehaloperoxidase

PubMed Central

Dumarieh, Rania; D'Antonio, Jennifer; Deliz-Liang, Alexandria; Smirnova, Tatyana; Svistunenko, Dimitri A.; Ghiladi, Reza A.

2013-01-01

Dehaloperoxidase (DHP) from Amphitrite ornata, having been shown to catalyze the hydrogen peroxide-dependent oxidation of trihalophenols to dihaloquinones, is the first oxygen binding globin that possesses a biologically relevant peroxidase activity. The catalytically competent species in DHP appears to be Compound ES, a reactive intermediate that contains both a ferryl heme and a tyrosyl radical. By simulating the EPR spectra of DHP activated by H2O2, Thompson et al. (Thompson, M. K., Franzen, S., Ghiladi, R. A., Reeder, B. J., and Svistunenko, D. A. (2010) J. Am. Chem. Soc. 132, 17501–17510) proposed that two different radicals, depending on the pH, are formed, one located on either Tyr-34 or Tyr-28 and the other on Tyr-38. To provide additional support for these simulation-based assignments and to deduce the role(s) that tyrosyl radicals play in DHP, stopped-flow UV-visible and rapid-freeze-quench EPR spectroscopic methods were employed to study radical formation in DHP when three tyrosine residues, Tyr-28, Tyr-34, and Tyr-38, were replaced either individually or in combination with phenylalanines. The results indicate that radicals form on all three tyrosines in DHP. Evidence for the formation of DHP Compound I in several tyrosine mutants was obtained. Variants that formed Compound I showed an increase in the catalytic rate for substrate oxidation but also an increase in heme bleaching, suggesting that the tyrosines are necessary for protecting the enzyme from oxidizing itself. This protective role of tyrosines is likely an evolutionary adaptation allowing DHP to avoid self-inflicted damage in the oxidative environment. PMID:24100039

Pharmacological Prevention and Reversion of Erectile Dysfunction After Radical Prostatectomy, by Modulation of Nitric Oxide/cGMP Pathways

DTIC Science & Technology

2010-03-01

cancer in men. Now, we have shown that much lower doses of sildenafil, combined or not with a nitric oxide donor, molsidomine, also correct the CVOD...ED) subsequent to radical prostatectomy for prostate cancer can be prevented and even reversed by long-term sustained treatment with PDE5...erectile dysfunction subsequent to radical prostatectomy for prostate cancer , based on the long term sustained administration of PDE5 inhibitors. Our

Observation of OH radicals produced by pulsed discharges on the surface of a liquid

NASA Astrophysics Data System (ADS)

Kanazawa, Seiji; Kawano, Hirokazu; Watanabe, Satoshi; Furuki, Takashi; Akamine, Shuichi; Ichiki, Ryuta; Ohkubo, Toshikazu; Kocik, Marek; Mizeraczyk, Jerzy

2011-06-01

The hydroxyl radical (OH) plays an important role in plasma chemistry at atmospheric pressure. OH radicals have a higher oxidation potential compared with other oxidative species such as free radical O, atomic oxygen, hydroperoxyl radical (HO2), hydrogen peroxide(H2O2) and ozone. In this study, surface discharges on liquids (water and its solutions) were investigated experimentally. A pulsed streamer discharge was generated on the liquid surface using a point-to-plane electrode geometry. The primary generation process of OH radicals is closely related to the streamer propagation, and the subsequent secondary process after the discharge has an influence on the chemical reaction. Taking into account the timescale of these processes, we investigated the behavior of OH radicals using two different diagnostic methods. Time evolution of the ground-state OH radicals above the liquid surface after the discharge was observed by a laser-induced fluorescence (LIF) technique. In order to observe the ground-state OH, an OH [A 2∑+(v' = 1) <-- X 2Π(v'' = 0)] system at 282 nm was used. As the secondary process, a portion of OH radicals diffused from gas phase to the liquid surface and dissolved in the liquid. These dissolved OH radicals were measured by a chemical probe method. Terephthalic acid was used as an OH radical trap and fluorescence of the resulting 2-hydroxyterephthalic acid was measured. This paper directly presents visualization of OH radicals over the liquid surface by means of LIF, and indirectly describes OH radicals dissolved in water by means of a chemical method.

Oxidative cyclization reactions: controlling the course of a radical cation-derived reaction with the use of a second nucleophile.

PubMed

Redden, Alison; Perkins, Robert J; Moeller, Kevin D

2013-12-02

Construction of new ring systems: Oxidative cyclizations (see picture; RVC=reticulated vitreous carbon) have been conducted that use two separate intramolecular nucleophiles to trap an enol ether-derived radical cation intermediate. The reactions provide a means for rapidly trapping the radical cation intermediate in a manner that avoids competitive decomposition reactions. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Alkyl radical generation by an intramolecular homolytic substitution reaction between iron (II) and trialkylsulfonium groups.

PubMed

Jungen, Stefan; Chen, Peter

2018-05-16

Intramolecular, homolytic substitution reactions between iron (II) species and various trialkylsulfonium groups were directly observed in the gas phase upon collision induced dissociation. In spite of the notoriously low reduction potential of trialkylsulfonium species and the mismatched oxidation potential of iron (II), the reactions proceed at moderate collision energies, forming an alkyl radical as well as a thioether coordinated to the iron. In contrast to classical homolytic substitutions, the attacking radical is a "metalloradical", namely iron (II) that is oxidized to iron (III) during the reaction. With this process we demonstrate that the conceptually analogous, putative radical generation step in Radical S-Adenosyl Methionine Enzymes is possible and plausible. Further, we show that this kind of reaction only occurs in constrained systems with a defined geometry. Combining experimental measurements with DFT studies and NBO analyses allowed us to gain insights into the reactivity and transition states of these systems. Based on our findings, we challenge the notion of a collinear transition state in the radical generation step of Radical SAM Enzymes and propose it to be bent instead. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Neuroprotective effects of curcumin and highly bioavailable curcumin on oxidative stress induced by sodium nitroprusside in rat striatal cell culture.

PubMed

Nazari, Qand Agha; Kume, Toshiaki; Izuo, Naotaka; Takada-Takatori, Yuki; Imaizumi, Atsushi; Hashimoto, Tadashi; Izumi, Yasuhiko; Akaike, Akinori

2013-01-01

Curcumin, a polyphenolic compound extracted from Curcuma longa, has several pharmacological activities such as anticancer, anti-inflammatory, and antioxidant effects. The purpose of this study was to investigate the protective effects of curcumin and THERACURMIN, a highly bioavailable curcumin, against sodium nitroprusside (SNP)-induced oxidative damage in primary striatal cell culture. THERACURMIN as well as curcumin significantly prevented SNP-induced cytotoxicity. To elucidate the cytoprotective effects of curcumin and THERACURMIN, we measured the intracellular glutathione level in striatal cells. Curcumin and THERACURMIN significantly elevated the glutathione level, which was decreased by treatment with SNP. Moreover, curcumin showed potent 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging ability. Finally, a ferrozine assay showed that curcumin (10-100 µg/mL) has potent Fe(2+)-chelating ability. These results suggest that curcumin and THERACURMIN exert potent protective effects against SNP-induced cytotoxicity by free radical-scavenging and iron-chelating activities.

Studying mechanism of radical reactions: From radiation to nitroxides as research tools

NASA Astrophysics Data System (ADS)

Maimon, Eric; Samuni, Uri; Goldstein, Sara

2018-02-01

Radicals are part of the chemistry of life, and ionizing radiation chemistry serves as an indispensable research tool for elucidation of the mechanism(s) underlying their reactions. The ever-increasing understanding of their involvement in diverse physiological and pathological processes has expanded the search for compounds that can diminish radical-induced damage. This review surveys the areas of research focusing on radical reactions and particularly with stable cyclic nitroxide radicals, which demonstrate unique antioxidative activities. Unlike common antioxidants that are progressively depleted under oxidative stress and yield secondary radicals, nitroxides are efficient radical scavengers yielding in most cases their respective oxoammonium cations, which are readily reduced back in the tissue to the nitroxide thus continuously being recycled. Nitroxides, which not only protect enzymes, cells, and laboratory animals from diverse kinds of biological injury, but also modify the catalytic activity of heme enzymes, could be utilized in chemical and biological systems serving as a research tool for elucidating mechanisms underlying complex chemical and biochemical processes.

Cranberry flavonoids prevent toxic rat liver mitochondrial damage in vivo and scavenge free radicals in vitro.

PubMed

Lapshina, Elena A; Zamaraeva, Maria; Cheshchevik, Vitali T; Olchowik-Grabarek, Ewa; Sekowski, Szymon; Zukowska, Izabela; Golovach, Nina G; Burd, Vasili N; Zavodnik, Ilya B

2015-06-01

The present study was undertaken for further elucidation of the mechanisms of flavonoid biological activity, focusing on the antioxidative and protective effects of cranberry flavonoids in free radical-generating systems and those on mitochondrial ultrastructure during carbon tetrachloride-induced rat intoxication. Treatment of rats with cranberry flavonoids (7 mg/kg) during chronic carbon tetrachloride-induced intoxication led to prevention of mitochondrial damage, including fragmentation, rupture and local loss of the outer mitochondrial membrane. In radical-generating systems, cranberry flavonoids effectively scavenged nitric oxide (IC50  = 4.4 ± 0.4 µg/ml), superoxide anion radicals (IC50  = 2.8 ± 0.3 µg/ml) and hydroxyl radicals (IC50  = 53 ± 4 µg/ml). The IC50 for reduction of 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH) was 2.2 ± 0.3 µg/ml. Flavonoids prevented to some extent lipid peroxidation in liposomal membranes and glutathione oxidation in erythrocytes treated with UV irradiation or organic hydroperoxides as well as decreased the rigidity of the outer leaflet of the liposomal membranes. The hepatoprotective potential of cranberry flavonoids could be due to specific prevention of rat liver mitochondrial damage. The mitochondria-addressed effects of flavonoids might be related both to radical-scavenging properties and modulation of various mitochondrial events. Copyright © 2015 John Wiley & Sons, Ltd.

The free-radical scavenger, edaravone, augments NO release from vascular cells and platelets after laser-induced, acute endothelial injury in vivo.

PubMed

Yamashita, T; Shoge, M; Oda, E; Yamamoto, Y; Giddings, J C; Kashiwagi, S; Suematsu, M; Yamamoto, J

2006-05-01

In vitro and in vivo experimental models have demonstrated that vascular endothelial function is significantly impaired as a result of oxidative stress, mediated by the generation of oxygen-derived free radicals in response to chronic or acute inflammation. In particular, super-oxide () at specific concentrations leads to the impairment of nitric oxide (NO) bioactivity, and it is known that NO plays a fundamental role in the maintenance of vascular homeostasis. The relationship between reactive oxygen species (ROS) and NO release in thrombosis-related endothelial damage in the peripheral microvasculature remains unclear, however. The purpose of the present study was to investigate the effect of the free-radical scavenger, edaravone, on NO synthesis and thrombotic potential in arterioles after exposure to laser irradiation. Highly sensitive electrochemical NO microsensors were positioned in femoral arterioles of mice, and the kinetics of NO release were recorded in response to standardized laser irradiation in vivo. In addition, images of NO release from damaged vascular cells were investigated in a similar rat model using the NO-sensitive dye 4,5-diaminofluorescein diacetate (DAF-2DA). Thrombogenesis was assessed in carotid arterioles by continuous video microscopy using image analysis software. Laser irradiation led to NO release from perturbed endothelial cells and from platelet-rich thrombi. Edaravone had no significant effect on NO release in non-laser treated, intact endothelium compared with placebo. In contrast, edaravone demonstrated a dose-dependent effect on NO release and thrombogenicity. At a concentration of 10.5 mg/kg per h, edaravone promoted a 5-fold increase in NO and a reduction in platelet-rich thrombus volume to 58% of the placebo values. Our data provide direct evidence to confirm that acute endothelial damage in peripheral microvessels initially induces NO release and that the free-radical scavenger, edaravone, augments NO synthesis leading to

SOMO–HOMO Level Inversion in Biologically Important Radicals

PubMed Central

2017-01-01

Conventionally, the singly occupied molecular orbital (SOMO) of a radical species is considered to be the highest occupied molecular orbital (HOMO), but this is not the case always. In this study, we considered a number of radicals from smallest diatomic anion radicals such as superoxide anion radical to one-electron oxidized DNA related base radicals that show the SOMO is energetically lower than one or more doubly occupied molecular orbitals (MOs) (SOMO–HOMO level inversion). The electronic configurations are calculated employing the B3LYP/6-31++G** method, with the inclusion of aqueous phase via the integral equation formalism of the polarized continuum model solvation model. From the extensive study of the electronic configurations of radicals produced by one-electron oxidation or reduction of natural-DNA bases, bromine-, sulfur-, selenium-, and aza-substituted DNA bases, as well as 20 diatomic molecules, we highlight the following important findings: (i) SOMO–HOMO level inversion is a common phenomenon in radical species. (ii) The more localized spin density in σ-orbital on a single atom (carbon, nitrogen, oxygen, sulfur, or selenium), the greater the gap between HOMO and SOMO. (iii) In species with SOMO–HOMO level inversion, one-electron oxidation takes place from HOMO not from the SOMO, which produces a molecule in its triplet ground state. Oxidation of aqueous superoxide anion producing triplet molecular oxygen is one example of many. (iv) These results are for conventional radicals and in contrast with those reported for distonic radical anions in which SOMO–HOMO gaps are smaller for more localized radicals and the orbital inversions vanish in water. Our findings yield new insights into the properties of free radical systems. PMID:29240424

Oxysterols from Free Radical Chain Oxidation of 7-Dehydrocholesterol: Product and Mechanistic Studies

PubMed Central

Xu, Libin; Korade, Zeljka; Porter, Ned A.

2010-01-01

Free radical chain oxidation of highly oxidizable 7-dehydrocholesterol (7-DHC) initiated by 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) was carried out at 37°C in benzene for 24 hours. Fifteen oxysterols derived from 7-DHC were isolated and characterized with 1D- and 2D-NMR spectroscopy and mass spectrometry. A mechanism that involves abstraction of hydrogen atoms at C-9 and/or C-14 is proposed to account for the formation of all of the oxysterols and the reaction progress profile. In either the H-9 or H-14 mechanism, a pentadienyl radical intermediate is formed after abstraction of H-9 or H-14 by a peroxyl radical. This step is followed by the well-precedented transformations observed in peroxidation reactions of polyunsaturated fatty acids such as oxygen addition, peroxyl radical 5-exo cyclization, and SHi carbon radical attack on the peroxide bond. The mechanism for peroxidation of 7-DHC also accounts for the formation of numerous oxysterol natural products isolated from fungal species, marine sponges, and cactaceous species. In a cell viability test, the oxysterol mixture from 7-DHC peroxidation was found to be cytotoxic to Neuro2a neuroblastoma cells in the micromolar concentration range. We propose that the high reactivity of 7-DHC and the oxysterols generated from its peroxidation may play important roles in the pathogenesis of Smith-Lemli-Opitz syndrome (SLOS), X-linked dominant chondrodysplasia punctata (CDPX2), and cerebrotendinous xanthomatosis (CTX), all of these being metabolic disorders having an elevated level of 7-DHC. PMID:20121089

Properties of Flavonoids Isolated from the Bark of Eysenhardtia polystachya and Their Effect on Oxidative Stress in Streptozotocin-Induced Diabetes Mellitus in Mice

PubMed Central

Garcia-Campoy, Abraham Heriberto; Muñiz-Ramirez, Alethia

2016-01-01

Six new flavonoids 2′,4′-dihydroxychalcone-6′-O-β-d-glucopyranoside (1), α,3,2′,4′-tetrahydroxy-4-methoxy-dihydrochalcone-3′-C-β-glucopyranosy-6′-O-β-d-glucopyranoside (2), 7-hydroxy-5,8′-dimethoxy-6′α-l-rhamnopyranosyl-8-(3-phenyl-trans-acryloyl)-1-benzopyran-2-one (3), 6′7-dihydroxy-5,8-dimethoxy-8(3-phenyl-trans-acryloyl)-1-benzopyran-2-one (4), 9-hydroxy-3,8-dimethoxy-4-prenylpterocarpan (5), and α,4,4′-trihydroxydihydrochalcone-2′-O-β-d-glucopyranoside (6) were isolated from bark of Eysenhardtia polystachya. Antidiabetic activity of compounds 1–5 in terms of their cellular antioxidant and free radical scavenging and also in streptozotocin- (STZ-) induced diabetic mice was evaluated on liver transaminases, lipid peroxidation, total bilirubin, total protein, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (CSH-Px), and glutathione reductase (GSH). Results indicated that 1–5 scavenged 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl (∙OH), nitric oxide radicals (NO∙), superoxide anion radical (O2 ∙−), radical cation (ABTS∙+), and hydrogen peroxide (H2O2) radical, and protection against H2O2 induced BSA damage was also observed. Furthermore, 1–5 showed ability to decrease the oxidative stress in H9c2 cell. Diabetic mice present high levels of lipid peroxide, total protein, SGPT, SGOT, ALP, and TB. However, treatment of STZ-induced diabetes in mice with 1–5 reduced levels of these enzymes leading to protector effect of liver. In addition, with treatment with 1–5, increases in radical scavenging enzymes of CSH-Px, SOD, GSH, and CAT have also been observed in diabetic mice. The antioxidant properties of compounds 1–5 are a promising strategy for ameliorating therapeutic effects by avoiding disorders in the normal redox reactions in healthy cells which consequently could alleviate complications of diabetes. PMID:27668038

Effect of copper oxide concentration on the formation and persistency of environmentally persistent free radicals (EPFRs) in particulates.

PubMed

Kiruri, Lucy W; Khachatryan, Lavrent; Dellinger, Barry; Lomnicki, Slawo

2014-02-18

Environmentally persistent free radicals (EPFRs) are formed by the chemisorption of substituted aromatics on metal oxide surfaces in both combustion sources and superfund sites. The current study reports the dependency of EPFR yields and their persistency on metal loading in particles (0.25, 0.5, 0.75, 1, 2, and 5% CuO/silica). The EPFRs were generated through exposure of particles to three adsorbate vapors at 230 °C: phenol, 2-monochlorophenol (2-MCP), and dichlorobenzene (DCBz). Adsorption resulted in the formation of surface-bound phenoxyl- and semiquinoine-type radicals with characteristic EPR spectra displaying a g value ranging from ∼ 2.0037 to 2.006. The highest EPFR yield was observed for CuO concentrations between 1 and 3% in relation to MCP and phenol adsorption. However, radical density, which is expressed as the number of radicals per copper atom, was highest at 0.75-1% CuO loading. For 1,2-dichlorobenzene adsorption, radical concentration increased linearly with decreasing copper content. At the same time, a qualitative change in the radicals formed was observed--from semiquinone to chlorophenoxyl radicals. The two longest lifetimes, 25 and 23 h, were observed for phenoxyl-type radicals on 0.5% CuO and chlorophenoxyl-type radicals on 0.75% CuO, respectively.

Effect of Copper Oxide Concentration on the Formation and Persistency of Environmentally Persistent Free Radicals (EPFRs) in Particulates

PubMed Central

2015-01-01

Environmentally persistent free radicals (EPFRs) are formed by the chemisorption of substituted aromatics on metal oxide surfaces in both combustion sources and superfund sites. The current study reports the dependency of EPFR yields and their persistency on metal loading in particles (0.25, 0.5, 0.75, 1, 2, and 5% CuO/silica). The EPFRs were generated through exposure of particles to three adsorbate vapors at 230 °C: phenol, 2-monochlorophenol (2-MCP), and dichlorobenzene (DCBz). Adsorption resulted in the formation of surface-bound phenoxyl- and semiquinoine-type radicals with characteristic EPR spectra displaying a g value ranging from ∼2.0037 to 2.006. The highest EPFR yield was observed for CuO concentrations between 1 and 3% in relation to MCP and phenol adsorption. However, radical density, which is expressed as the number of radicals per copper atom, was highest at 0.75–1% CuO loading. For 1,2-dichlorobenzene adsorption, radical concentration increased linearly with decreasing copper content. At the same time, a qualitative change in the radicals formed was observed—from semiquinone to chlorophenoxyl radicals. The two longest lifetimes, 25 and 23 h, were observed for phenoxyl-type radicals on 0.5% CuO and chlorophenoxyl-type radicals on 0.75% CuO, respectively. PMID:24437381

RELATIONSHIP BETWEEN INDUCED OXIDENT GENERATION AND ASTHMA SEVERITY

EPA Science Inventory

The role of oxygen radicals is implicated in many disease processes, including asthma. There is evidence that elevated oxidant status is associated with airway hyper responsiveness, however it is less clear whether increased levels of circulating reactive oxygen species are assoc...

Thyroid hormone-induced oxidative damage on lipids, glutathione and DNA in the mouse heart.

PubMed

Gredilla, R; Barja, G; López-Torres, M

2001-10-01

Oxygen radicals of mitochondrial origin are involved in oxidative damage. In order to analyze the possible relationship between metabolic rate, oxidative stress and oxidative damage, OF1 female mice were rendered hyper- and hypothyroid by chronic administration of 0.0012% L-thyroxine (T4) and 0.05% 6-n-propyl-2-thiouracil (PTU), respectively, in their drinking water for 5 weeks. Hyperthyroidism significantly increased the sensitivity to lipid peroxidation in the heart, although the endogenous levels of lipid peroxidation were not altered. Thyroid hormone-induced oxidative stress also resulted in higher levels of GSSG and GSSG/GSH ratio. Oxidative damage to mitochondrial DNA was greater than that to genomic DNA. Hyperthyroidism decreased oxidative damage to genomic DNA. Hypothyroidism did not modify oxidative damage in the lipid fraction but significantly decreased GSSG and GSSG/GSH ratio and oxidative damage to mitochondrial DNA. These results indicate that thyroid hormones modulate oxidative damage to lipids and DNA, and cellular redox potential in the mouse heart. A higher oxidative stress in the hyperthyroid group is presumably neutralized in the case of nuclear DNA by an increase in repair activity, thus protecting this key molecule. Treatment with PTU, a thyroid hormone inhibitor, reduced oxidative damage in the different cell compartments.

Radical Anions of Oxidized vs. Reduced Oxytocin: Influence of Disulfide Bridges on CID and Vacuum UV Photo-Fragmentation

NASA Astrophysics Data System (ADS)

MacAleese, Luke; Girod, Marion; Nahon, Laurent; Giuliani, Alexandre; Antoine, Rodolphe; Dugourd, Philippe

2018-06-01

The nonapeptide oxytocin (OT) is used as a model sulfur-containing peptide to study the damage induced by vacuum UV (VUV) radiations. In particular, the effect of the presence (or absence in reduced OT) of oxytocin's internal disulfide bridge is evaluated in terms of photo-fragmentation yield and nature of the photo-fragments. Intact, as well as reduced, OT is studied as dianions and radical anions. Radical anions are prepared and photo-fragmented in two-color experiments (UV + VUV) in a linear ion trap. VUV photo-fragmentation patterns are analyzed and compared, and radical-induced mechanisms are proposed. The effect of VUV is principally to ionize but secondary fragmentation is also observed. This secondary fragmentation seems to be considerably enabled by the initial position of the radical on the molecule. In particular, the possibility to form a radical on free cysteines seems to increase the susceptibility to VUV fragmentation. Interestingly, disulfide bridges, which are fundamental for protein structure, could also be responsible for an increased resistance to ionizing radiations. [Figure not available: see fulltext.

Effects of phenylpropanoid and iridoid glycosides on free radical-induced impairment of endothelium-dependent relaxation in rat aortic rings.

PubMed

Ismailoglu, U B; Saracoglu, I; Harput, U S; Sahin-Erdemli, I

2002-02-01

The protective effect of phenylpropanoid glycosides, forsythoside B and alyssonoside, and the iridoid glycoside lamiide, isolated from the aerial parts of Phlomis pungens var. pungens, against free radical-induced impairment of endothelium-dependent relaxation in isolated rat aorta was investigated. Aortic rings were exposed to free radicals by the electrolysis of the physiological bathing solution. Free radical-induced inhibition of the endothelium-dependent relaxation in response to acetylcholine was countered by incubation of the aortic rings before electrolysis with the aqueous extract (200 microg/ml), phenylpropanoid fraction (100 microg/ml) and iridoid fraction (150 microg/ml) of P. pungens var. pungens. Major components of the phenylpropanoid fraction forsythoside B and alyssonoside also prevented the inhibition of the acetylcholine response, at 10(-4) M concentration. However, the major component of iridoid fraction lamiide was found ineffective at the same concentration. The protective activity of phenylpropanoid glycosides against the free radical-induced impairment of endothelium-dependent relaxation may be related to their free radical scavenging property.

Retinal Diseases Associated with Oxidative Stress and the Effects of a Free Radical Scavenger (Edaravone)

PubMed Central

Hara, Hideaki

2017-01-01

Oxidative stress plays a pivotal role in developing and accelerating retinal diseases including age-related macular degeneration (AMD), glaucoma, diabetic retinopathy (DR), and retinal vein occlusion (RVO). An excess amount of reactive oxygen species (ROS) can lead to functional and morphological impairments in retinal pigment epithelium (RPE), endothelial cells, and retinal ganglion cells (RGCs). Here we demonstrate that edaravone, a free radical scavenger, decreased apoptotic cell death, oxidative damage to DNA and lipids, and angiogenesis through inhibiting JNK and p38 MAPK pathways in AMD, glaucoma, DR, and RVO animal models. These data suggest that the therapeutic strategy for targeting oxidative stress may be important for the treatment of these ocular diseases, and edaravone may be useful for treating retinal diseases associated with oxidative stress. PMID:28194256

Retinal Diseases Associated with Oxidative Stress and the Effects of a Free Radical Scavenger (Edaravone).

PubMed

Masuda, Tomomi; Shimazawa, Masamitsu; Hara, Hideaki

2017-01-01

Oxidative stress plays a pivotal role in developing and accelerating retinal diseases including age-related macular degeneration (AMD), glaucoma, diabetic retinopathy (DR), and retinal vein occlusion (RVO). An excess amount of reactive oxygen species (ROS) can lead to functional and morphological impairments in retinal pigment epithelium (RPE), endothelial cells, and retinal ganglion cells (RGCs). Here we demonstrate that edaravone, a free radical scavenger, decreased apoptotic cell death, oxidative damage to DNA and lipids, and angiogenesis through inhibiting JNK and p38 MAPK pathways in AMD, glaucoma, DR, and RVO animal models. These data suggest that the therapeutic strategy for targeting oxidative stress may be important for the treatment of these ocular diseases, and edaravone may be useful for treating retinal diseases associated with oxidative stress.

Free radical scavenging and anti-oxidative activities of an ethanol-soluble pigment extract prepared from fermented Zijuan Pu-erh tea.

PubMed

Fan, Jiang Ping; Fan, Chong; Dong, Wen Min; Gao, Bin; Yuan, Wei; Gong, Jia Shun

2013-09-01

An ethanol-soluble pigment extract was separated from fermented Zijuan Pu-erh tea. The compositions of the ethanol soluble pigment extract were analyzed by high-performance liquid chromatography-tandem mass spectroscopy (HPLC-MS/MS). The extract was prepared into a series of ethanol solutions and analyzed for free radical-scavenging activities (against two free radicals: 1,1-diphenyl-2-picrylhydrazyl (DPPH) and (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO)) and in vitro anti-oxidative properties. Electron spin resonance spectroscopy showed that the peaks of DPPH and TEMPO decreased with increasing extract concentration, suggesting that the extract had excellent free radical-scavenging activities. In vitro cell culture suggested that, at 50-200 mg/L, the extract had no measurable effect on the viability of vascular endothelial cells (ECV340) but produced significant protective effects for cells that underwent oxidative injuries due to hydrogen peroxide (H₂O₂) treatment. Compared with the H₂O₂ treatment alone cells group, 200 mg/L of the extract increased the activity of superoxide dismutase (SOD) in cells by 397.3%, and decreased the concentration of malondialdehyde (MDA) and the activity of lactate acid dehydrogenase (LDH) by 47.8% and 69.6%, respectively. These results suggest that the extract has excellent free radical scavenging and anti-oxidative properties. Copyright © 2013 Elsevier Ltd. All rights reserved.

Molecular basis of intramolecular electron transfer in proteins during radical-mediated oxidations: Computer simulation studies in model tyrosine-cysteine peptides in solution

PubMed Central

Petruk, Ariel A.; Bartesaghi, Silvina; Trujillo, Madia; Estrin, Darío A.; Murgida, Daniel; Kalyanaraman, Balaraman; Marti, Marcelo A.; Radi, Rafael

2012-01-01

Experimental studies in hemeproteins and model Tyr/Cys-containing peptides exposed to oxidizing and nitrating species suggest that intramolecular electron transfer (IET) between tyrosyl radicals (Tyr-O●) and Cys residues controls oxidative modification yields. The molecular basis of this IET process is not sufficiently understood with structural atomic detail. Herein, we analyzed using molecular dynamics and quantum mechanics-based computational calculations, mechanistic possibilities for the radical transfer reaction in Tyr/Cys-containing peptides in solution and correlated them with existing experimental data. Our results support that Tyr-O● to Cys radical transfer is mediated by an acid/base equilibrium that involves deprotonation of Cys to form the thiolate, followed by a likely rate-limiting transfer process to yield cysteinyl radical and a Tyr phenolate; proton uptake by Tyr completes the reaction. Both, the pKa values of the Tyr phenol and Cys thiol groups and the energetic and kinetics of the reversible IET are revealed as key physico-chemical factors. The proposed mechanism constitutes a case of sequential, acid/base equilibrium-dependent and solvent-mediated, proton-coupled electron transfer and explains the dependency of oxidative yields in Tyr/Cys peptides as a function of the number of alanine spacers. These findings contribute to explain oxidative modifications in proteins that contain sequence and/or spatially close Tyr-Cys residues. PMID:22640642

Doxorubicin-induced nitrosative stress is mitigated by vitamin C via the modulation of nitric oxide synthases.

PubMed

Akolkar, Gauri; Bagchi, Ashim K; Ayyappan, Prathapan; Jassal, Davinder S; Singal, Pawan K

2017-04-01

An increase in oxidative stress is suggested to be the main cause in Doxorubicin (Dox)-induced cardiotoxicity. However, there is now evidence that activation of inducible nitric oxide synthase (iNOS) and nitrosative stress are also involved. The role of vitamin C (Vit C) in the regulation of nitric oxide synthase (NOS) and reduction of nitrosative stress in Dox-induced cardiotoxicity is unknown. The present study investigated the effects of Vit C in the mitigation of Dox-induced changes in the levels of nitric oxide (NO), NOS activity, protein expression of NOS isoforms, and nitrosative stress as well as cytokines TNF-α and IL-10 in isolated cardiomyocytes. Cardiomyocytes isolated from adult Sprague-Dawley rats were segregated into four groups: 1 ) control, 2 ) Vit C (25 µM), 3 ) Dox (10 µM), and 4 ) Vit C + Dox. Dox caused a significant increase in the generation of superoxide radical (O 2 ·- ), peroxynitrite, and NO, and these effects of Dox were blunted by Vit C. Dox increased the expression of iNOS and altered protein expression as well as activation of endothelial NOS (eNOS). These changes were prevented by Vit C. Dox induced an increase in the ratio of monomeric/dimeric eNOS, promoting the production of O 2 ·- , which was prevented by Vit C by increasing the stability of the dimeric form of eNOS. Vit C protected against the Dox-induced increase in TNFα as well as a reduction in IL-10. These results suggest that Vit C provides cardioprotection by reducing oxidative/nitrosative stress and inflammation via a modulation of Dox-induced increase in the NO levels and NOS activity. Copyright © 2017 the American Physiological Society.

A novel antioxidant agent caffeic acid phenethyl ester prevents long-term mobile phone exposure-induced renal impairment in rat. Prognostic value of malondialdehyde, N-acetyl-beta-D-glucosaminidase and nitric oxide determination.

PubMed

Ozguner, Fehmi; Oktem, Faruk; Ayata, Ali; Koyu, Ahmet; Yilmaz, H Ramazan

2005-09-01

Caffeic acid phenethyl ester (CAPE), a flavonoid like compound, is one of the major components of honeybee propolis. It has been used in folk medicine for many years in Middle East countries. It was found to be a potent free radical scavenger and antioxidant recently. The aim of this study was to examine long-term applied 900 MHz emitting mobile phone-induced oxidative stress that promotes production of reactive oxygen species (ROS) and, was to investigate the role of CAPE on kidney tissue against the possible electromagnetic radiation (EMR)-induced renal impairment in rats. In particular, the ROS such as superoxide and nitric oxide (NO) may contribute to the pathophysiology of EMR-induced renal impairment. Malondialdehyde (MDA, an index of lipid peroxidation) levels, urinary N-acetyl-beta-D-glucosaminidase (NAG, a marker of renal tubular injury) and nitric oxide (NO, an oxidant product) levels were used as markers of oxidative stress-induced renal impairment and the success of CAPE treatment. The activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in renal tissue were determined to evaluate the changes of antioxidant status. The rats used in the study were randomly grouped (10 each) as follows: i) Control group (without stress and EMR), ii) Sham-operated rats stayed without exposure to EMR (exposure device off), iii) Rats exposed to 900 MHz EMR (EMR group), and iv) A 900 MHz EMR exposed + CAPE treated group (EMR + CAPE group). In the EMR exposed group, while tissue MDA, NO levels and urinary NAG levels increased (p < 0.0001), the activities of SOD, CAT, and GSH-Px in renal tissue were reduced (p < 0.001). CAPE treatment reversed these effects as well (p < 0.0001, p < 0.001 respectively). In conclusion, the increase in NO and MDA levels of renal tissue, and in urinary NAG with the decrease in renal SOD, CAT, GSH-Px activities demonstrate the role of oxidative mechanisms in 900 MHz mobile phone-induced renal tissue damage

A polyphenol-enriched cocoa extract reduces free radicals produced by mycotoxins.

PubMed

Corcuera, L A; Amézqueta, S; Arbillaga, L; Vettorazzi, A; Touriño, S; Torres, J L; López de Cerain, A

2012-03-01

Polyphenols are characterized by the presence of phenol units in the molecules. These compounds may show antioxidant ability by scavenging reactive oxygen species (ROS) of the free radical type. A polyphenol enriched cocoa extract (PECE) was obtained from cocoa seeds with 28% of procyanidins which were mainly epicatechin oligomers. PECE was very active as free radical scavenger against 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and tris(2,4,6-trichloro-3,5-dinitrophenyl)methyl (HNTTM) radicals; and the tris(2,3,5,6-tetrachloro-4-nitrophenyl)methyl (TNPTM) assay showed that the PECE might not be pro-oxidant. Thus it was considered a good candidate to be tested in in vitro models. It showed mild cytotoxic power on Hep G2 cells and induced ROS in a dose-dependent manner being weak oxidant only at high concentrations near the limit of solubility. The antioxidant properties were assayed in Hep G2 treated with the mycotoxins ochratoxin A (OTA) and/or aflatoxin B1 (AFB1). The PECE was not effective against AFB1 but it increased the cell viability and reduced significantly the amounts of ROS in cells treated with OTA or mixtures of AFB1+OTA. These results are coherent with the role of oxidative pathways in the mechanism of OTA and indicate that polyphenols extracted from cocoa may be good candidates as antioxidant agents. Copyright © 2011 Elsevier Ltd. All rights reserved.

INVESTIGATION OF THE RADICAL-MEDIATED PRODUCTION OF BENZENE OXIDE PROTEIN ADDUCTS IN VITRO AND IN VIVO

EPA Science Inventory

High background levels of benzene oxide (BO) adducts with hemoglobin and albumin (BO-Hb and BO-Alb) have been measured in unexposed humans and animals. To test the influence of radical-mediated pathways on production of these BO-protein adducts, we employed Fenton chemistry to...

Hydrogen protects auditory hair cells from cisplatin-induced free radicals.

PubMed

Kikkawa, Yayoi S; Nakagawa, Takayuki; Taniguchi, Mirei; Ito, Juichi

2014-09-05

Cisplatin is a widely used chemotherapeutic agent for the treatment of various malignancies. However, its maximum dose is often limited by severe ototoxicity. Cisplatin ototoxicity may require the production of reactive oxygen species (ROS) in the inner ear by activating enzymes specific to the cochlea. Molecular hydrogen was recently established as an antioxidant that selectively reduces ROS, and has been reported to protect the central nervous system, liver, kidney and cochlea from oxidative stress. The purpose of this study was to evaluate the potential of molecular hydrogen to protect cochleae against cisplatin. We cultured mouse cochlear explants in medium containing various concentrations of cisplatin and examined the effects of hydrogen gas dissolved directly into the media. Following 48-h incubation, the presence of intact auditory hair cells was assayed by phalloidin staining. Cisplatin caused hair cell loss in a dose-dependent manner, whereas the addition of hydrogen gas significantly increased the numbers of remaining auditory hair cells. Additionally, hydroxyphenyl fluorescein (HPF) staining of the spiral ganglion showed that formation of hydroxyl radicals was successfully reduced in hydrogen-treated cochleae. These data suggest that molecular hydrogen can protect auditory tissues against cisplatin toxicity, thus providing an additional strategy to protect against drug-induced inner ear damage. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Engineering a horseradish peroxidase C stable to radical attacks by mutating multiple radical coupling sites.

PubMed

Kim, Su Jin; Joo, Jeong Chan; Song, Bong Keun; Yoo, Young Je; Kim, Yong Hwan

2015-04-01

Peroxidases have great potential as industrial biocatalysts. In particular, the oxidative polymerization of phenolic compounds catalyzed by peroxidases has been extensively examined because of the advantage of this method over other conventional chemical methods. However, the industrial application of peroxidases is often limited because of their rapid inactivation by phenoxyl radicals during oxidative polymerization. In this work, we report a novel protein engineering approach to improve the radical stability of horseradish peroxidase isozyme C (HRPC). Phenylalanine residues that are vulnerable to modification by the phenoxyl radicals were identified using mass spectrometry analysis. UV-Vis and CD spectra showed that radical coupling did not change the secondary structure or the active site of HRPC. Four phenylalanine (Phe) residues (F68, F142, F143, and F179) were each mutated to alanine residues to generate single mutants to examine the role of these sites in radical coupling. Despite marginal improvement of radical stability, each single mutant still exhibited rapid radical inactivation. To further reduce inactivation by radical coupling, the four substitution mutations were combined in F68A/F142A/F143A/F179A. This mutant demonstrated dramatic enhancement of radical stability by retaining 41% of its initial activity compared to the wild-type, which was completely inactivated. Structure and sequence alignment revealed that radical-vulnerable Phe residues of HPRC are conserved in homologous peroxidases, which showed the same rapid inactivation tendency as HRPC. Based on our site-directed mutagenesis and biochemical characterization, we have shown that engineering radical-vulnerable residues to eliminate multiple radical coupling can be a good strategy to improve the stability of peroxidases against radical attack. © 2014 Wiley Periodicals, Inc.

Enhanced in vitro biological activity generated by surface characteristics of anodically oxidized titanium--the contribution of the oxidation effect.

PubMed

Wurihan; Yamada, A; Suzuki, D; Shibata, Y; Kamijo, R; Miyazaki, T

2015-05-20

Anodically oxidized titanium surfaces, prepared by spark discharge, have micro-submicron surface topography and nano-scale surface chemistry, such as hydrophilic functional groups or hydroxyl radicals in parallel. The complexity of the surface characteristics makes it difficult to draw a clear conclusion as to which surface characteristic, of anodically oxidized titanium, is critical in each biological event. This study examined the in vitro biological changes, induced by various surface characteristics of anodically oxidized titanium with, or without, release of hydroxyl radicals onto the surface. Anodically oxidized titanium enhanced the expression of genes associated with differentiating osteoblasts and increased the degree of matrix mineralization by these cells in vitro. The phenotypes of cells on the anodically oxidized titanium were the same with, or without, release of hydroxyl radicals. However, the nanomechanical properties of this in vitro mineralized tissue were significantly enhanced on surfaces, with release of hydroxyl radicals by oxidation effects. In addition, the mineralized tissue, produced in the presence of bone morphogenetic protein-2 on bare titanium, had significantly weaker nanomechanical properties, despite there being higher osteogenic gene expression levels. We show that enhanced osteogenic cell differentiation on modified titanium is not a sufficient indicator of enhanced in vitro mineralization. This is based on the inferior mechanical properties of mineralized tissues, without either being cultured on a titanium surface with release of hydroxyl radicals, or being supplemented with lysyl oxidase family members.

Experimental and theoretical understanding of the gas phase oxidation of atmospheric amides with OH radicals: kinetics, products, and mechanisms.

PubMed

Borduas, Nadine; da Silva, Gabriel; Murphy, Jennifer G; Abbatt, Jonathan P D

2015-05-14

Atmospheric amides have primary and secondary sources and are present in ambient air at low pptv levels. To better assess the fate of amides in the atmosphere, the room temperature (298 ± 3 K) rate coefficients of five different amides with OH radicals were determined in a 1 m(3) smog chamber using online proton-transfer-reaction mass spectrometry (PTR-MS). Formamide, the simplest amide, has a rate coefficient of (4.44 ± 0.46) × 10(-12) cm(3) molec(-1) s(-1) against OH, translating to an atmospheric lifetime of ∼1 day. N-methylformamide, N-methylacetamide and propanamide, alkyl versions of formamide, have rate coefficients of (10.1 ± 0.6) × 10(-12), (5.42 ± 0.19) × 10(-12), and (1.78 ± 0.43) × 10(-12) cm(3) molec(-1) s(-1), respectively. Acetamide was also investigated, but due to its slow oxidation kinetics, we report a range of (0.4-1.1) × 10(-12) cm(3) molec(-1) s(-1) for its rate coefficient with OH radicals. Oxidation products were monitored and quantified and their time traces were fitted using a simple kinetic box model. To further probe the mechanism, ab initio calculations are used to identify the initial radical products of the amide reactions with OH. Our results indicate that N-H abstractions are negligible in all cases, in contrast to what is predicted by structure-activity relationships. Instead, the reactions proceed via C-H abstraction from alkyl groups and from formyl C(O)-H bonds when available. The latter process leads to radicals that can readily react with O2 to form isocyanates, explaining the detection of toxic compounds such as isocyanic acid (HNCO) and methyl isocyanate (CH3NCO). These contaminants of significant interest are primary oxidation products in the photochemical oxidation of formamide and N-methylformamide, respectively.

Effect of Gum Arabic on Oxidative Stress and Inflammation in Adenine–Induced Chronic Renal Failure in Rats

PubMed Central

Ali, Badreldin H.; Al-Husseni, Isehaq; Beegam, Sumyia; Al-Shukaili, Ahmed; Nemmar, Abderrahim; Schierling, Simone; Queisser, Nina; Schupp, Nicole

2013-01-01

Inflammation and oxidative stress are known to be involved in the pathogenesis of chronic kidney disease in humans, and in chronic renal failure (CRF) in rats. The aim of this work was to study the role of inflammation and oxidative stress in adenine-induced CRF and the effect thereon of the purported nephroprotective agent gum arabic (GA). Rats were divided into four groups and treated for 4 weeks as follows: control, adenine in feed (0.75%, w/w), GA in drinking water (15%, w/v) and adenine+GA, as before. Urine, blood and kidneys were collected from the rats at the end of the treatment for analysis of conventional renal function tests (plasma creatinine and urea concentration). In addition, the concentrations of the pro-inflammatory cytokine TNF-α and the oxidative stress markers glutathione and superoxide dismutase, renal apoptosis, superoxide formation and DNA double strand break frequency, detected by immunohistochemistry for γ-H2AX, were measured. Adenine significantly increased the concentrations of urea and creatinine in plasma, significantly decreased the creatinine clearance and induced significant increases in the concentration of the measured inflammatory mediators. Further, it caused oxidative stress and DNA damage. Treatment with GA significantly ameliorated these actions. The mechanism of the reported salutary effect of GA in adenine-induced CRF is associated with mitigation of the adenine-induced inflammation and generation of free radicals. PMID:23383316

Alterations of hepatocyte function with free radical generators and reparation or prevention with coffee polyphenols.

PubMed

Saidi Merzouk, Amel; Hafida, Merzouk; Medjdoub, Amel; Loukidi, Bouchra; Cherrak, Sabri; Merzouk, Sid Ahmed; Elhabiri, Mourad

2017-03-01

Liver diseases are linked in the majority of cases to oxidative stress that antioxidants could neutralize with reducing liver injury. Chlorogenic acid, a coffee polyphenol, possesses antioxidant prosperities. The aim of this study was to evaluate in vitro preventive and corrective effects of cholorogenic acid in hepatocyte toxicity induced by free radicals. Hepatocytes were isolated from adult male Wistar rats. To determine corrective effects and reparation, cells were first exposed to two free radical generators (hydrogen peroxide/iron sulfate for hydroxyl radical formation, and phenazine methosulfate/nicotinamide adenine dinucleotide for superoxide anion formation) for 12H and thereafter treated by chlorogenic acid (1 and 10 μM final concentration) for another 12H. To show preventive effects, cells were pretreated by chlorogenic acid and thereafter exposed to free radical generators. Hepatocyte proliferation, glucose uptake, ATP contents, membrane fluidity and integrity, and intracellular redox status were investigated after 24H culture. The results showed that chlorogenic acid reversed the decrease in cell proliferation, glucose uptake and ATP levels, the increased LDH release and the reduced membrane fluidity and restored the oxidant/antioxidant status under oxidative stress. When pre-treated with chlorogenic acid, hepatocytes became very resistant to oxidative conditions and cellular homeostasis was maintained. In conclusion, chlorogenic acid displayed not only corrective but also preventive effects in hepatocytes exposed to oxidative stress and could be beneficial in patients with or at risk of liver diseases.

Prostaglandin H synthase-catalyzed oxidation of all-trans- and 13-cis-retinoic acid to carbon-centered and peroxyl radical intermediates.

PubMed

Freyaldenhoven, M A; Lloyd, R V; Samokyszyn, V M

1996-06-01

Due to the importance of all-trans-retinoic acid (RA) in the treatment of various dermatological conditions and the wide distribution of prostaglandin H synthase (PGHS) in tissues, we have further examined the mechanisms involved in the hydroperoxide-dependent cooxidation of RA and its isomer, 13-cis-retinoic acid ((13Z)-RA), by PGHS. Hydroperoxide-dependent, PGHS-catalyzed oxidation of RA and (13Z)-RA was shown to form free radical adducts, using electron spin resonance (ESR) spin trapping techniques and 5-phenyl-4-penten-1-yl hydroperoxide (PPHP) or 13-hydroperoxy-9-cis-11-trans-octadecadienoic acid (13-OOH-18:2) as hydroperoxide substrates. Utilization of the spin trap alpha-phenyl-N-tert-butylnitrone (PBN) resulted in the detection of (13Z)-RA-PBN and RA-PBN adducts whose spectra were characterized by hyperfine coupling constants of aH = 4.16/aN = 15.69 and aH = 3.01/aN =15.92, respectively. Identical experiments under anaerobic conditions were carried out using the spin trap 2-methyl-2-nitrosopropane (NtB) which yielded nitroxide adducts whose spectra were characterized by a triplet of doublets with values of aH = 3.49/aN = 15.84 for the (13Z)-RA adduct and aH = 3.49/aN = 15.88 for the RA adduct. These results are indicative of secondary carbon-centered radical formation. We also used (+)-benzo[a]pyrene 7(S),8(S)-dihydrodiol ((+)-BP-7,8-diol) as a peroxyl radical probe. The results demonstrated the formation of (+)-BP-7,8-diol-derived tetrols, with the trans-anti tetrol representing the major oxidation product in systems undergoing PPHP-dependent, PGHS-catalyzed oxidation of (13Z)-RA or RA. These results are consistent with the formation of peroxyl radicals in these systems. In all experiments, the (13Z)-RA isomer appeared to be a better substrate for the enzyme compared to the all-trans isomer. Collectively these results provide further evidence to support the previously proposed mechanism for retinoid oxidation by PGHS involving the intermediacy of C4 carbon

Lipid oxidation induced oxidative degradation of cereal beta-glucan.

PubMed

Wang, Yu-Jie; Mäkelä, Noora; Maina, Ndegwa Henry; Lampi, Anna-Maija; Sontag-Strohm, Tuula

2016-04-15

In food systems, lipid oxidation can cause oxidation of other molecules. This research for the first time investigated oxidative degradation of β-glucan induced by lipid oxidation using an oil-in-water emulsion system which simulated a multi-phased aqueous food system containing oil and β-glucan. Lipid oxidation was monitored using peroxide value and hexanal production while β-glucan degradation was evaluated by viscosity and molecular weight measurements. The study showed that while lipid oxidation proceeded, β-glucan degradation occurred. Emulsions containing β-glucan, oil and ferrous ion showed significant viscosity and molecular weight decrease after 1 week of oxidation at room temperature. Elevated temperature (40°C) enhanced the oxidation reactions causing higher viscosity drop. In addition, the presence of β-glucan appeared to retard the hexanal production in lipid oxidation. The study revealed that lipid oxidation may induce the degradation of β-glucan in aqueous food systems where β-glucan and lipids co-exist. Copyright © 2015 Elsevier Ltd. All rights reserved.

Evidences of extracellular abiotic degradation of hexadecane through free radical mechanism induced by the secreted phenazine compounds of P. aeruginosa NY3.

PubMed

Nie, Hongyun; Nie, Maiqian; Wang, Lei; Diwu, Zhenjun; Xiao, Ting; Qiao, Qi; Wang, Yan; Jiang, Xin

2018-03-02

The aim of this work was to investigate the effects of secreted extracellular phenazine compounds (PHCs) on the degradation efficiency of alkanes by P. aeruginosa NY3. Under aerobic conditions, the PHCs secreted by P. aeruginosa NY3 initiate the oxidation of alkanes outside cells, in coupling with some reducing agents, such as β-Nicotinamide adenine dinucleotide, reduced disodium salt (NADH) or reduced glutathione (GSH). This reaction might be via free radical reactions similar to Fenton Oxidation Reaction (FOR). P. aeruginosa NY3 secretes pyocyanin (Pyo), 1-hydroxyphenazine (HPE), phenazine-1-carboxylic acid (PCA), and phenazine-1-amide (PCN) simultaneously. The cell-free extracellular fluid containing these four PHCs degrades hexadecane effectively. The observation of Electron Spin Resonance (EPR) signals of superoxide anion radical (O 2 - ), hydroxyl radical (OH) and/or carbon free radicals (R) both in vivo and in vitro suggested the degradation of hexadecane could be via a free radical pathway. Secretion of PHCs has been found to be characteristic of Pseudomonas which is often involved in or related to the degradation of organic pollutants. Our work suggested that certain organic contaminants may be oxidized through ubiquitously extracellular abiotic degradation by the free radicals produced during bio-remediation and bio-treatment. Copyright © 2018. Published by Elsevier Ltd.

A Hybrid Nanomaterial for the Controlled Generation of Free Radicals and Oxidative Destruction of Hypoxic Cancer Cells.

PubMed

Shen, Song; Zhu, Chunlei; Huo, Da; Yang, Miaoxin; Xue, Jiajia; Xia, Younan

2017-07-17

Anticancer modalities based on oxygen free radicals, including photodynamic therapy and radiotherapy, have emerged as promising treatments in the clinic. However, the hypoxic environment in tumor tissue prevents the formation of oxygen free radicals. Here we introduce a novel strategy that employs oxygen-independent free radicals generated from a polymerization initiator for eradicating cancer cells. The initiator is mixed with a phase-change material and loaded into the cavities of gold nanocages. Upon irradiation by a near-infrared laser, the phase-change material is melted due to the photothermal effect of gold nanocages, leading to the release and decomposition of the loaded initiator to generate free radicals. The free radicals produced in this way are highly effective in inducing apoptosis in hypoxic cancer cells. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Redox-Sensitive Cerium Oxide Nanoparticles Protect Human Keratinocytes from Oxidative Stress Induced by Glutathione Depletion.

PubMed

Singh, Ragini; Karakoti, Ajay S; Self, William; Seal, Sudipta; Singh, Sanjay

2016-11-22

Cerium oxide nanoparticles (CeNPs) have gathered much attention in the biomedical field due to its unique antioxidant property. It can protect cells and tissues from oxidative stress induced damage due to its autoregenerative redox cycle. Our study explores the antioxidant and antigenotoxic behavior of PEGylated CeNPs toward oxidative insult produced by buthionine sulfoximine (BSO) in human keratinocytes (HaCaT cells). BSO inhibits the γ-glutamylcysteinesynthetase (γ-GCS) enzyme and thus acts as a glutathione (GSH) depleting agent to modulate the cellular redox potential. GSH is a natural ROS scavenger present in the mammalian cells, and its depletion causes generation of reactive oxygen species (ROS). In this study, we challenged HaCaT cells (keratinocytes) with BSO to alter the redox potential within the cell and monitored toxicity, ROS generation, and nuclear fragmentation. We also followed changes in expressions of related proteins and genes. We found that PEGylated CeNPs can protect HaCaT cells from BSO-induced oxidative damage. BSO-exposed cells, preincubated with PEGylated CeNPs, showed better cell survival and significant decrease in the intracellular levels of ROS. We also observed decrease in lactate dehydrogenase (LDH) release and nuclear fragmentation in CeNP-treated cells that were challenged with BSO as compared to treatment with BSO alone. Exposure of HaCaT cells with BSO leads to altered expression of antioxidant genes and proteins, i.e., thioredoxin reductase (TrxR) and peroxiredoxin 6 (Prx6) whereas, in our study, pretreatment of PEGylated CeNPs reduces the need for induction of genes that produce enzymes involved in the defense against oxidative stress. Since, growing evidence argued the involvement of ROS in mediating death of mammalian cells in several ailments, our finding reinforces the use of PEGylated CeNPs as a potent pharmacological agent under the lower cellular GSH/GSSG ratios for the treatment of diseases mediated by free radicals.

Cyanidin-3-glucoside attenuates angiotensin II-induced oxidative stress and inflammation in vascular endothelial cells.

PubMed

Sivasinprasasn, Sivanan; Pantan, Rungusa; Thummayot, Sarinthorn; Tocharus, Jiraporn; Suksamrarn, Apichart; Tocharus, Chainarong

2016-10-28

Angiotensin II (Ang II) causes oxidative stress and vascular inflammation, leading to vascular endothelial cell dysfunction, and is associated with the development of inflammatory cardiovascular diseases such as atherosclerosis. Therefore, interventions of oxidative stress and inflammation may contribute to the reduction of cardiovascular diseases. Cyanidin-3-glucoside (C3G) plays a role in the prevention of oxidative damage in several diseases. Here, we investigated the effect of C3G on Ang II-induced oxidative stress and vascular inflammation in human endothelial cells (EA.hy926). C3G dose-dependently suppressed the free radicals and inhibited the nuclear factor-kappa B (NF-κB) signaling pathway by protecting the degradation of inhibitor of kappa B-alpha (IκB-α), inhibiting the expression and translocation of NF-κB into the nucleus through the down-regulation of NF-κB p65 and reducing the expression of inducible nitric oxide synthase (iNOS). Pretreatment with C3G not only prohibited the NF-κB signaling pathway but also promoted the activity of the nuclear erythroid-related factor 2 (Nrf2) signaling pathway through the upregulation of endogenous antioxidant enzymes. Particularly, we observed that C3G significantly enhanced the production of superoxide dismutase (SOD) and induced the expression of heme oxygenase (HO-1). Our findings confirm that C3G can protect against vascular endothelial cell inflammation induced by AngII. C3G may represent a promising dietary supplement for the prevention of inflammation, thereby decreasing the risk for the development of atherosclerosis. Copyright © 2016. Published by Elsevier Ireland Ltd.

6-gingerol ameliorates gentamicin induced renal cortex oxidative stress and apoptosis in adult male albino rats.

PubMed

Hegazy, Ahmed M S; Mosaed, Mohammed M; Elshafey, Saad H; Bayomy, Naglaa A

2016-06-01

Ginger or Zingiber officinale which is used in traditional medicine has been found to possess antioxidant effect that can control the generation of free radicals. Free radicals are the causes of renal cell degeneration that leads to renal failure in case of gentamicin induced toxicity. This study was done to evaluate the possible protective effects of 6-gingerol as natural antioxidant on gentamicin-induced renal cortical oxidative stress and apoptosis in adult male albino rats. Forty adult male albino rats were used in this study and were randomly divided into four groups, control group; 6-gingerol treated group; gentamicin treated group and protected group (given simultaneous 6-gingerol and gentamicin). At the end of the study, blood samples were drawn for biochemical study. Kidney sections were processed for histological, and immunohistochemical examination for caspase-3 to detect apoptosis and anti heat shock protein 47 (HSP47) to detect oxidative damage. Gentamicin treated rats revealed a highly significant increase in renal function tests, tubular dilatation with marked vacuolar degeneration and desquamation of cells, interstitial hemorrhage and cellular infiltration. Immunohistochemically, gentamicin treated rats showed a strong positive immunoreaction for caspase-3 and anti heat shock protein 47 (HSP47). Protected rats showed more or less normal biochemical, histological, and immunohistochemical pictures. In conclusion, co-administration of 6-gingerol during gentamicin 'therapy' has a significant reno-protective effect in a rat model of gentamicin-induced renal damage. It is recommended that administration of ginger with gentamicin might be beneficial in men who receive gentamicin to treat infections. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ultraviolet radiation and nanoparticle induced intracellular free radicals generation measured in human keratinocytes by electron paramagnetic resonance spectroscopy.

PubMed

Rancan, F; Nazemi, B; Rautenberg, S; Ryll, M; Hadam, S; Gao, Q; Hackbarth, S; Haag, S F; Graf, C; Rühl, E; Blume-Peytavi, U; Lademann, J; Vogt, A; Meinke, M C

2014-05-01

Several nanoparticle-based formulations used in cosmetics and dermatology are exposed to sunlight once applied to the skin. Therefore, it is important to study possible synergistic effects of nanoparticles and ultraviolet radiation. Electron paramagnetic resonance spectroscopy (EPR) was used to detect intracellular free radicals induced by ultraviolet B (UVB) radiation and amorphous silica nanoparticle and to evaluate the influence of nanoparticle surface chemistry on particle cytotoxicity toward HaCaT cells. Uncoated titanium dioxide nanoparticles served as positive control. In addition, particle intracellular uptake, viability, and induction of interleukin-6 were measured. We found that photo-activated titanium dioxide particles induced a significant amount of intracellular free radicals. On the contrary, no intracellular free radicals were generated by the investigated silica nanoparticles in the dark as well as under UVB radiation. However, under UVB exposure, the non-functionalized silica nanoparticles altered the release of IL-6. At the same concentrations, the amino-functionalized silica nanoparticles had no influence on UVB-induced IL-6 release. EPR spectroscopy is a useful technique to measure nanoparticle-induced intracellular free radicals. Non-toxic concentrations of silica particles enhanced the toxicity of UVB radiation. This synergistic effect was not mediated by particle-generated free radicals and correlated with particle surface charge and intracellular distribution. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Antioxidant properties of xanthones from Calophyllum brasiliense: prevention of oxidative damage induced by FeSO₄.

PubMed

Blanco-Ayala, Tonali; Lugo-Huitrón, Rafael; Serrano-López, Elizabeth M; Reyes-Chilpa, Ricardo; Rangel-López, Edgar; Pineda, Benjamín; Medina-Campos, Omar Noel; Sánchez-Chapul, Laura; Pinzón, Enrique; Cristina, Trejo-Solis; Silva-Adaya, Daniela; Pedraza-Chaverrí, José; Ríos, Camilo; de la Cruz, Verónica Pérez; Torres-Ramos, Mónica

2013-10-11

Reactive oxygen species (ROS) are important mediators in a number of degenerative diseases. Oxidative stress refers to the imbalance between the production of ROS and the ability to scavenge these species through endogenous antioxidant systems. Since antioxidants can inhibit oxidative processes, it becomes relevant to describe natural compounds with antioxidant properties which may be designed as therapies to decrease oxidative damage and stimulate endogenous cytoprotective systems. The present study tested the protective effect of two xanthones isolated from the heartwood of Calophyllum brasilienses against FeSO₄-induced toxicity. Through combinatory chemistry assays, we evaluated the superoxide (O₂·⁻), hydroxyl radical (OH·), hydrogen peroxide (H₂O₂) and peroxynitrite (ONO⁻) scavenging capacity of jacareubin (xanthone III) and 2-(3,3-dimethylallyl)-1,3,5,6-tetrahydroxyxanthone (xanthone V). The effect of these xanthones on murine DNA and bovine serum albumin degradation induced by an OH· generator system was also evaluated. Additionally, we investigated the effect of these xanthones on ROS production, lipid peroxidation and glutathione reductase (GR) activity in FeSO₄-exposed brain, liver and lung rat homogenates. Xanthone V exhibited a better scavenging capacity for O₂·⁻, ONOO⁻ and OH· than xanthone III, although both xanthones were unable to trap H₂O₂. Additionally, xanthones III and V prevented the albumin and DNA degradation induced by the OH· generator system. Lipid peroxidation and ROS production evoked by FeSO₄ were decreased by both xanthones in all tissues tested. Xanthones III and V also prevented the GR activity depletion induced by pro-oxidant activity only in the brain. Altogether, the collected evidence suggests that xanthones can play a role as potential agents to attenuate the oxidative damage produced by different pro-oxidants.

2,4,6-Trichlorophenylhydrazine Schiff bases as DPPH radical and super oxide anion scavengers.

PubMed

Khan, Khalid Mohammed; Shah, Zarbad; Ahmad, Viqar Uddin; Khan, Momin; Taha, Muhammad; Rahim, Fazal; Ali, Sajjad; Ambreen, Nida; Perveen, Shahnaz; Choudhary, M Iqbal; Voelter, Wolfgang

2012-05-01

Syntheses of thirty 2,4,6-trichlorophenylhydrazine Schiff bases 1-30 were carried out and evaluated for their in vitro DPPH radical and super oxide anion scavenging activities. Compounds 1-30 have shown a varying degree of DPPH radical scavenging activity and their IC50 values range between 4.05-369.30 µM. The compounds 17, 28, 18, 14, 8, 15, 12, 2, 29, and 7 exhibited IC50 values ranging between 4.05±0.06-24.42±0.86 µM which are superior to standard n-propylgallate (IC50=30.12±0.27 µM). Selected compounds have shown a varying degree of superoxide anion radical scavenger activity and their IC50 values range between 91.23-406.90 µM. The compounds 28, 8, 17, 15, and 14, showed IC50 values between 91.23±1.2-105.31±2.29 µM which are superior to standard n-propylgallate (IC50=106.34±1.6 µM).

Sono-activated persulfate oxidation of diclofenac: Degradation, kinetics, pathway and contribution of the different radicals involved.

PubMed

Monteagudo, J M; El-Taliawy, H; Durán, A; Caro, G; Bester, K

2018-06-20

Degradation of a diclofenac aqueous solution was performed using persulfate anions activated by ultrasound. The objective of this study was to analyze different parameters affecting the diclofenac (DCF) removal reaction by the ultrasonic persulfate (US/PS) process and to evaluate the role played by various intermediate oxidative species such as hydroxyl- and sulfate radicals, superoxide radical anion or singlet oxygen in the removal process as well as to determine a possible reaction pathway. The effects of pH, initial persulfate anion concentration, ultrasonic amplitude and temperature on DCF degradation were examined. Sulfate and hydroxyl radicals were involved in the main reaction pathway of diclofenac. Diclofenac amide and three hydroxy-diclofenac isomers (3´-hydroxy diclofenac, 4´-hydroxy diclofenac and 5-hydroxy diclofenac) were identified as reaction intermediates. Copyright © 2018 Elsevier B.V. All rights reserved.

Kinetics and structure-activity relationship of dendritic bridged hindered phenol antioxidants to protect styrene against free radical induced peroxidation

NASA Astrophysics Data System (ADS)

Li, Cui-Qin; Guo, Su-Yue; Wang, Jun; Shi, Wei-Guang; Zhang, Zhi-Qiu; Wang, Peng-Xiang

2017-12-01

A series of dendritic poly(amido-amine) (PAMAM) bridged hindered phenols antioxidants were synthesized. The active antioxidant group (3-(3,5-di- tert-butyl-4-hydroxyphenyl)propionic acid) was attached to two generations of PAMAM dendrimers, and their structure was verified by nuclear magnetic resonance (NMR) and fourier transform infrared spectra (FT-IR). The antioxidant abilities of the dendritic phenols to inhibit the oxidation of styrene were evaluated and the relationships between the length of core, the generation of dendrimers and the antioxidant activities were established. The reaction kinetics of scavenging peroxyl radicals was followed by oxygen consumption. The inhibition time ( t inh) values showed the dendritic phenols had the ability of scavenging peroxyl radicals, and that the antioxidant ability increased with the increasing length of the core and the generation. The kinetic analysis demonstrated that dendritic phenols could slow the rate of styrene peroxidation induced by AIBN, as shown by the number of trapping ROO· ( n), and this role was in accordance with that of the t inh values.

Are free radicals involved in thiol-based redox signaling?

PubMed

Winterbourn, Christine C

2015-03-01

Cells respond to many stimuli by transmitting signals through redox-regulated pathways. It is generally accepted that in many instances signal transduction is via reversible oxidation of thiol proteins, although there is uncertainty about the specific redox transformations involved. The prevailing view is that thiol oxidation occurs by a two electron mechanism, most commonly involving hydrogen peroxide. Free radicals, on the other hand, are considered as damaging species and not generally regarded as important in cell signaling. This paper examines whether it is justified to dismiss radicals or whether they could have a signaling role. Although there is no direct evidence that radicals are involved in transmitting thiol-based redox signals, evidence is presented that they are generated in cells when these signaling pathways are activated. Radicals produce the same thiol oxidation products as two electron oxidants, although by a different mechanism, and at this point radical-mediated pathways should not be dismissed. There are unresolved issues about how radical mechanisms could achieve sufficient selectivity, but this could be possible through colocalization of radical-generating and signal-transducing proteins. Colocalization is also likely to be important for nonradical signaling mechanisms and identification of such associations should be a priority for advancing the field. Copyright © 2014 Elsevier Inc. All rights reserved.

Acetyl-L-carnitine prevents total body hydroxyl free radical and uric acid production induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in the rat.

PubMed

Loots, Du Toit; Mienie, Lodewyk J; Bergh, Jacobus J; Van der Schyf, Cornelis J

2004-07-23

Acetyl-L-carnitine (ALCAR) is intimately involved in the transport of long chain fatty acids across the inner mitochondrial membrane during oxidative phosphorylation. ALCAR also has been reported to attenuate the occurrence of parkinsonian symptoms associated with 1-methyl-1,2,3,6-tetrahydropyridine (MPTP) in vivo, and protects in vitro against the toxicity of the neurotoxic 1-methyl-4-phenylpyridinium (MPP+) metabolite of MPTP. The mechanism for these protective effects remains unclear. ALCAR may attenuate hydroxyl (HO*) free radical production in the MPTP/MPP+ neurotoxic pathway through several mechanisms. Most studies on MPTP/MPP+ toxicity and protection by ALCAR have focused on in vivo brain chemistry and in vitro neuronal culture studies. The present study investigates the attenuative effects of ALCAR on whole body oxidative stress markers in the urine of rats treated with MPTP. In a first study, ALCAR totally prevented the MPTP-induced formation of HO* measured by salicylate radical trapping. In a second study, the production of uric acid after MPTP administration-a measure of oxidative stress mediated through xanthine oxidase-was also prevented by ALCAR. Because ALCAR is unlikely to be a potent radical scavenger, these studies suggest that ALCAR protects against MPTP/MPP+-mediated oxidative stress through other mechanisms. We speculate that ALCAR may operate through interference with organic cation transporters such as OCTN2 and/or carnitine-acylcarnitine translocase (CACT), based partly on the above findings and on semi-empirical electronic similarity calculations on ALCAR, MPP+, and two other substrates for these transporters.

Radical-Mediated Enzymatic Polymerizations

PubMed Central

Zavada, Scott R.; Battsengel, Tsatsral; Scott, Timothy F.

2016-01-01

Polymerization reactions are commonly effected by exposing monomer formulations to some initiation stimulus such as elevated temperature, light, or a chemical reactant. Increasingly, these polymerization reactions are mediated by enzymes―catalytic proteins―owing to their reaction efficiency under mild conditions as well as their environmental friendliness. The utilization of enzymes, particularly oxidases and peroxidases, for generating radicals via reduction-oxidation mechanisms is especially common for initiating radical-mediated polymerization reactions, including vinyl chain-growth polymerization, atom transfer radical polymerization, thiol–ene step-growth polymerization, and polymerization via oxidative coupling. While enzyme-mediated polymerization is useful for the production of materials intended for subsequent use, it is especially well-suited for in situ polymerizations, where the polymer is formed in the place where it will be utilized. Such polymerizations are especially useful for biomedical adhesives and for sensing applications. PMID:26848652

Measurements of hydroxyl and hydroperoxy radicals during CalNex-LA: Model comparisons and radical budgets

NASA Astrophysics Data System (ADS)

Griffith, S. M.; Hansen, R. F.; Dusanter, S.; Michoud, V.; Gilman, J. B.; Kuster, W. C.; Veres, P. R.; Graus, M.; de Gouw, J. A.; Roberts, J.; Young, C.; Washenfelder, R.; Brown, S. S.; Thalman, R.; Waxman, E.; Volkamer, R.; Tsai, C.; Stutz, J.; Flynn, J. H.; Grossberg, N.; Lefer, B.; Alvarez, S. L.; Rappenglueck, B.; Mielke, L. H.; Osthoff, H. D.; Stevens, P. S.

2016-04-01

Measurements of hydroxyl (OH) and hydroperoxy (HO2*) radical concentrations were made at the Pasadena ground site during the CalNex-LA 2010 campaign using the laser-induced fluorescence-fluorescence assay by gas expansion technique. The measured concentrations of OH and HO2* exhibited a distinct weekend effect, with higher radical concentrations observed on the weekends corresponding to lower levels of nitrogen oxides (NOx). The radical measurements were compared to results from a zero-dimensional model using the Regional Atmospheric Chemical Mechanism-2 constrained by NOx and other measured trace gases. The chemical model overpredicted measured OH concentrations during the weekends by a factor of approximately 1.4 ± 0.3 (1σ), but the agreement was better during the weekdays (ratio of 1.0 ± 0.2). Model predicted HO2* concentrations underpredicted by a factor of 1.3 ± 0.2 on the weekends, while measured weekday concentrations were underpredicted by a factor of 3.0 ± 0.5. However, increasing the modeled OH reactivity to match the measured total OH reactivity improved the overall agreement for both OH and HO2* on all days. A radical budget analysis suggests that photolysis of carbonyls and formaldehyde together accounted for approximately 40% of radical initiation with photolysis of nitrous acid accounting for 30% at the measurement height and ozone photolysis contributing less than 20%. An analysis of the ozone production sensitivity reveals that during the week, ozone production was limited by volatile organic compounds throughout the day during the campaign but NOx limited during the afternoon on the weekends.

Palm kernel cake extract exerts hepatoprotective activity in heat-induced oxidative stress in chicken hepatocytes.

PubMed

Oskoueian, Ehsan; Abdullah, Norhani; Idrus, Zulkifli; Ebrahimi, Mahdi; Goh, Yong Meng; Shakeri, Majid; Oskoueian, Armin

2014-10-02

Palm kernel cake (PKC), the most abundant by-product of oil palm industry is believed to contain bioactive compounds with hepatoprotective potential. These compounds may serve as hepatoprotective agents which could help the poultry industry to alleviate adverse effects of heat stress on liver function in chickens. This study was performed to evaluate the hepatoprotective potential of PKC extract in heat-induced oxidative stress in chicken hepatocytes. The nature of the active metabolites and elucidation of the possible mechanism involved were also investigated. The PKC extract possessed free radical scavenging activity with values significantly (p < 0.05) lower than silymarin as the reference antioxidant. Heat-induced oxidative stress in chicken hepatocyte impaired the total protein, lipid peroxidation and antioxidant enzymes activity significantly (p < 0.05). Treatment of heat-induced hepatocytes with PKC extract (125 μg/ml) and silymarin as positive control increased these values significantly (p < 0.05). The real time PCR and western blot analyses revealed the significant (p < 0.05) up-regulation of oxidative stress biomarkers including TNF-like, IFN-γ and IL-1β genes; NF-κB, COX-2, iNOS and Hsp70 proteins expression upon heat stress in chicken hepatocytes. The PKC extract and silymarin were able to alleviate the expression of all of these biomarkers in heat-induced chicken hepatocytes. The gas chromatography-mass spectrometry analysis of PKC extract showed the presence of fatty acids, phenolic compounds, sugar derivatives and other organic compounds such as furfural which could be responsible for the observed hepatoprotective activity. Palm kernel cake extract could be a potential agent to protect hepatocytes function under heat induced oxidative stress.

Pulsed corona discharge: the role of ozone and hydroxyl radical in aqueous pollutants oxidation.

PubMed

Preis, S; Panorel, I C; Kornev, I; Hatakka, H; Kallas, J

2013-01-01

Ozone and hydroxyl radical are the most active oxidizing species in water treated with gas-phase pulsed corona discharge (PCD). The ratio of the species dependent on the gas phase composition and treated water contact surface was the objective for the experimental research undertaken for aqueous phenol (fast reaction) and oxalic acid (slow reaction) solutions. The experiments were carried out in the reactor, where aqueous solutions showered between electrodes were treated with 100-ns pulses of 20 kV voltage and 400 A current amplitude. The role of ozone increased with increasing oxygen concentration and the oxidation reaction rate. The PCD treatment showed energy efficiency surpassing that of conventional ozonation.

The first radical-based spintronic memristors: Towards resistive RAMs made of organic magnets

NASA Astrophysics Data System (ADS)

Goss, Karin; Krist, Florian; Seyfferle, Simon; Hoefel, Udo; Paretzki, Alexa; Dressel, Martin; Bogani, Lapo; Institut Fuer Anorganische Chemie, University of Stuttgart Collaboration; 1. Physikalisches Institut, University of Stuttgart Team

2014-03-01

Using molecules as building blocks for electronic devices offers ample possibilities for new device functionalities due to a chemical tunability much higher than that of standard inorganic materials, and at the same time offers a decrease in the size of the electronic component down to the single-molecule level. Purely organic molecules containing no metallic centers such as organic radicals can serve as an electronic component with magnetic properties due to the unpaired electron in the radical state. Here we present memristive logic units based on organic radicals of the nitronyl-nitroxide kind. Integrating these purely molecular units as a spin coated layer into crossbar arrays, electrically induced unipolar resistive switching is observed with a change in resistance of up to 100%. We introduce a model based on filamentary reorganization of molecules of different oxidation state revealing the importance of the molecular nature for the switching properties. The major role of the oxidation state of these paramagnetic molecules introduces a magnetic field dependence to the device functionality, which goes along with magnetoresistive charactistics observed for the material. These are the first steps towards a spintronic implementation of organic radicals in electronic devices.

HOx Radical Chemistry in an Indiana Forest Environment: Measurement and Model Comparison

NASA Astrophysics Data System (ADS)

Lew, M.; Bottorff, B.; Sigler, P. S. R.; Stevens, P. S.; Sklaveniti, S.; Leonardis, T.; Locoge, N.; Dusanter, S.; Kundu, S.; Deming, B.; Wood, E. C. D.; Gentner, D. R.

2015-12-01

Reactions of the hydroxyl (OH) and peroxy radicals (HO2 and RO2) play a central role in the chemistry of the atmosphere. In addition to controlling the lifetimes of many trace gases important to issues of global climate change, OH radical reactions initiate the oxidation of volatile organic compounds (VOCs) which can lead to the production of ozone and secondary organic aerosols in the atmosphere. Previous measurements of these radicals in forest environments characterized by high mixing ratios of isoprene and low mixing ratios of NOx have shown serious discrepancies with modeled concentrations. These results bring into question our understanding of the atmospheric chemistry of isoprene and other biogenic VOCs under low NOx conditions. In the summer of 2015, HOx radicals were measured using Laser-Induced Fluorescence Fluorescence Assay by Gas Expansion (LIF-FAGE) technique as part of the Indiana Radical, Reactivity and Ozone Production Intercomparison (IRRONIC). This campaign took place in a forested area at the Indiana Research and Teaching Preserve (IURTP) near the Bloomington campus characterized by high mixing ratios of isoprene and low mixing ratios of NOx. Supporting measurements of photolysis rates, volatile organic compounds, nitrogen oxides, and other species were used to constrain a zero-dimensional box model based on the Regional Atmospheric Chemistry Mechanism (RACM2) and the Master Chemical Mechanism (MCM).

Ellagic and ferulic acids alleviate gamma radiation and aluminium chloride-induced oxidative damage.

PubMed

Salem, Ahmed M; Mohammaden, Tarek F; Ali, Mohamed A M; Mohamed, Enas A; Hasan, Hesham F

2016-09-01

Ionizing radiation interacts with biological systems through the generation of free radicals, which induce oxidative stress. Aluminium (Al) can negatively impact human health by direct interaction with antioxidant enzymes. Ellagic acid (EA) and Ferulic acid (FA) are plant polyphenolic compounds, have gained attention due to their multiple biological activities. To date, no studies investigating the antioxidant effect of EA/FA in a model involving both γ radiation and aluminium chloride (AlCl3) have been reported. Herein, we investigated the protective effect of EA and FA against oxidative stress induced by γ radiation and AlCl3 in rats. Rats were divided into thirteen groups: a negative control group, 3 positive control groups (γ-irradiated, AlCl3-treated and γ-irradiated+AlCl3-treated) and 9 groups (3 γ-irradiated, 3 AlCl3-treated and 3 γ-irradiated+AlCl3-treated) treated with EA and/or FA. Liver function and lipid profile were assessed. Levels of lipid peroxidation, protein oxidation and endogenous antioxidants as well as the concentrations of copper, iron and zinc were estimated in liver tissue homogenate. Furthermore, liver tissue sections were histologically examined. Oral administration of EA and/or FA resulted in 1) amelioration of AlCl3 and/or γ-radiation-induced hepatic function impairment, dyslipidemia and hepatic histological alterations; 2) reduction in liver MDA and PCC levels; 3) elevation of liver CAT, GPx and SOD activity as well as GSH level; 4) elevation in liver Cu concentrations which was accompanied by a reduction in Fe and Zn concentrations. Oral administration of EA and/or FA may be useful for ameliorating γ radiation and/or AlCl3-induced oxidative damage. Copyright © 2016 Elsevier Inc. All rights reserved.

OH radical induced depolymerization of poly(methacrylic acid)

NASA Astrophysics Data System (ADS)

Ulanski, Piotr; Bothe, Eberhard; von Sonntag, Clemens

1999-05-01

Hydroxyl radicals (generated pulse radiolytically in dilute N 2O-saturated aqueous solutions) react with poly(methacrylic acid) producing two kinds of radicals. The primary radical is converted into a secondary one by H-abstraction ( k=3.5 × 10 2 s -1) as monitored by changes in the UV spectrum. Subsequently, the secondary radicals undergo chain scission ( k=1.8 s -1 at pH 7-9). This process has been followed both by spectrophotometry as well as by conductometry. In competition with the bimolecular decay of the radicals the ensuing end-chain radicals undergo efficient depolymerization resulting in the release of monomer. Since the lifetime of the radicals is much longer at high pH, where the polymer attains a rod-like conformation, depolymerization is most efficient in basic solution.

The benzylperoxyl radical as a source of hydroxyl and phenyl radicals.

PubMed

Sander, Wolfram; Roy, Saonli; Bravo-Rodriguez, Kenny; Grote, Dirk; Sanchez-Garcia, Elsa

2014-09-26

The benzyl radical (1) is a key intermediate in the combustion and tropospheric oxidation of toluene. Because of its relevance, the reaction of 1 with molecular oxygen was investigated by matrix-isolation IR and EPR spectroscopy as well as computational methods. The primary reaction product of 1 and O2 is the benzylperoxyl radical (2), which exists in several conformers that can easily interconvert even at cryogenic temperatures. Photolysis of radical 2 at 365 nm results in a formal [1,3]-H migration and subsequent cleavage of the O-O bond to produce a hydrogen-bonded complex between the hydroxyl radical and benzaldehyde (4). Prolonged photolysis produces the benzoyl radical (5) and water, which finally yield the phenyl radical (7), CO, and H2O. Thus, via a sequence of exothermic reactions 1 is transformed into radicals of even higher reactivity, such as OH and 7. Our results have implications for the development of models for the highly complicated process of combustion of aromatic compounds. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Copper toxicity, oxidative stress, and antioxidant nutrients.

PubMed

Gaetke, Lisa M; Chow, Ching Kuang

2003-07-15

Copper (Cu) is an integral part of many important enzymes involved in a number of vital biological processes. Although normally bound to proteins, Cu may be released and become free to catalyze the formation of highly reactive hydroxyl radicals. Data obtained from in vitro and cell culture studies are largely supportive of Cu's capacity to initiate oxidative damage and interfere with important cellular events. Oxidative damage has been linked to chronic Cu-overload and/or exposure to excess Cu caused by accidents, occupational hazards, and environmental contamination. Additionally, Cu-induced oxidative damage has been implicated in disorders associated with abnormal Cu metabolism and neurodegenerative changes. Interestingly, a deficiency in dietary Cu also increases cellular susceptibility to oxidative damage. A number of nutrients have been shown to interact with Cu and alter its cellular effects. Vitamin E is generally protective against Cu-induced oxidative damage. While most in vitro or cell culture studies show that ascorbic acid aggravates Cu-induced oxidative damage, results obtained from available animal studies suggest that the compound is protective. High intakes of ascorbic acid and zinc may provide protection against Cu toxicity by preventing excess Cu uptake. Zinc also removes Cu from its binding site, where it may cause free radical formation. Beta-carotene, alpha-lipoic acid and polyphenols have also been shown to attenuate Cu-induced oxidative damage. Further studies are needed to better understand the cellular effects of this essential, but potentially toxic, trace mineral and its functional interaction with other nutrients.