Efficient Reactive Oxygen Species Scavenging Research Articles

Stress Signaling Responses in Plants.

Stress Signaling Responses in Plants.

Controlling the surface chemistry of cerium oxide nanoparticles for biological applications.

The catalytic activity of cerium oxide nanoparticles (CNPs) depends on the surface Ce3+/Ce4+ oxidation state. CNPs with a higher Ce3+ to Ce4+ ratio, oxygen vacancies and higher superoxide dismutase (SOD) mimetic activity are more effective against diseases associated with oxidative stress or inflammation. CNPs with a lower Ce3+/Ce4+ ratio show higher catalase mimetic activity and possess anticancer/antibacterial activity. However, different synthesis methods of CNPs and capping agents/surface coatings result in various Ce3+/Ce4+ oxidation states, thus limiting the use of particular CNPs for specific biological applications. In this study, we have shown that by selecting an appropriate doping method we can control the surface Ce3+/Ce4+ oxidation state to tune the catalytic activity and biological response. Importantly, superior SOD mimetic activity and efficient reactive oxygen species scavenging capability of one-step synthesized CNPs are linked to a uniform distribution of dopants in the CNP lattice and changes in the surface Ce3+/Ce4+ oxidation state.

Environmentally induced changes in antioxidant phenolic compounds levels in wild plants

Different adverse environmental conditions cause oxidative stress in plants by generation of reactive oxygen species (ROS). Accordingly, a general response to abiotic stress is the activation of enzymatic and non-enzymatic antioxidant systems. Many phenolic compounds, especially flavonoids, are known antioxidants and efficient ROS scavengers in vitro, but their exact role in plant stress responses in nature is still under debate. The aim of our work is to investigate this role by correlating the degree of environmental stress with phenolic and flavonoid levels in stress-tolerant plants. Total phenolic and antioxidant flavonoid contents were determined in 19 wild species. Meteorological data and plant and soil samples were collected in three successive seasons from four Mediterranean ecosystems: salt marsh, dune, semiarid and gypsum habitats. Changes in phenolic and flavonoid levels were correlated with the environmental conditions of the plants and were found to depend on both the taxonomy and ecology of the investigated species. Despite species-specific differences, principal component analyses of the results established a positive correlation between plant phenolics and several environmental parameters, such as altitude, and those related to water stress: temperature, evapotranspiration, and soil water deficit. The correlation with salt stress was, however, very weak. The joint analysis of all the species showed the lowest phenolic and flavonoid levels in the halophytes from the salt marsh. This finding supports previous data indicating that the halophytes analysed here do not undergo oxidative stress in their natural habitat and therefore do not need to activate antioxidant systems as a defence against salinity.

The activity of propolis in the scavenging of vitamin B2-photogenerated ROS

Objectives: The study was focused on the activity of propolis from Amaicha del Valle, Argentina (ProAV) as a promoter and scavenger of Riboflavin (Rf) – photogenerated reactive oxygen species (ROS).Methods: Through a kinetic and mechanistic study, employing stationary and time-resolved photochemical and electrochemical techniques, the protecting activity of ProAV was investigated.Results: In the absence of light and Rf, ProAV exerted a relatively efficient inhibitory effect on 1,1-diphenyl-2-picrylhydrazyl radicals and acts as a protector of artificially promoted linoleic acid oxidation. Under aerobic visible-light-irradiation conditions, in the presence of Rf as the only light-absorber species, a complex picture of competitive processes takes place, starting with the quenching of singlet and triplet electronically excited states of Rf by ProAV. The species O2(1 g), O2•−, H2O2, and OH• are generated and interact with ProAV.Discussion: ProAV behaves as an efficient ROS scavenger. It is scarcely photo-oxidized by interaction with the mentioned ROS. Quantitative results indicate that ProAV is even more resistant to photo-oxidation than the recognized antioxidant trolox. Two dihydroxychalcones, mostly present in the ProAV composition, are responsible for the protecting activity of the propolis.

Cross-generic studies with rice indicate that ion homeostasis and antioxidant defense is associated with superior salinity tolerance in Cynodon dactylon (L.) Pers.

A study was undertaken to evaluate the salt-tolerant attributes of Cynodon dactylon by comparing it with three varieties of the model glycophyte crop rice (Oryza sativa L.). For cross generic studies, all plants were uprooted and transferred to 0.1× Hoagland solution supplemented with 0, 10, 100, 200 and 500 mM NaCl. All plants were exposed to NaCl shock for 24 and 72 h. One of the most important attribute that conferred salinity tolerance in Cynodon was the presence of sodium ion exclusion mechanism in leaves. At high NaCl concentrations (200 and 500 mM NaCl), Na+ exclusion from the leaves was observed after 3 days. This helped to maintain a high K+/Na+ ratio inside the leaf tissues. The activity of different antioxidative enzymes such as superoxide dismutase, ascorbate peroxidase, catalase, peroxidase, and glutathione reductase were also evaluated, and it was observed that the synchronised activity of these enzymes was responsible for the detoxification of reactive oxygen species (ROS) generated under salinity stress in Cynodon. The relatively stable and controlled level of H2O2 and membrane lipid peroxidation in Cynodon with the increase in NaCl concentration and time of treatment could be due to efficient antioxidant machinery. Additionally, the controlled and least affected relative water content in leaves and roots of Cynodon in comparison to the rice varieties can be linked to the enhanced accumulation of proline and sugars, which helped to maintain the osmotic balance. On the other hand, all the three rice varieties lacked Na+ exclusion mechanism and efficient ROS scavenging system at par with Cynodon, as evidenced by higher oxidative stress markers such as lipid peroxidation, and H2O2 and lower activity of antioxidant enzymes. Besides there was little inter-varietal differences among the rice varieties in terms of NaCl tolerance.

Heterologous expression of EsSPDS1 in tobacco plants improves drought tolerance with efficient reactive oxygen species scavenging systems

It has previously been indicated that polyamines (PAs) are involved in the response to adverse environmental stresses in various plant species. Increased cellular PA levels or exogenous PA application can reduce the accumulation of reactive oxygen species (ROS) imposed by multiple abiotic stresses via increasing antioxidant enzyme activities. In this study, a novel spermidine synthase gene, designated as EsSPDS1, was cloned and characterized from the halophytic plant Eutrema salsugineum. Analyses of tissue-specific expression profiles revealed that EsSPDS1 was expressed in almost all tested organs including leaves, stems, flowers, roots and siliques. The expression of EsSPDS1 was obviously induced by polyethylene glycol (PEG) and high salinity treatments. Furthermore, the EsSPDS1 transcripts rapidly accumulated upon exposure to abscisic acid (ABA) treatments, implying that this gene was involved in ABA-mediated abiotic stress response. Transgenic tobacco plants harboring EsSPDS1 exhibited enhanced drought tolerance relative to wild-type (WT) plants. These transgenic plants had lower levels of malondialdehyde (MDA), less ion leakage (IL) and reactive oxygen species (ROS). However, relative water content (RWC) and activities of antioxidant enzymes including SOD and CAT of the transgenic plants was remarkably higher than those of WT plants under drought stress conditions. Collectively, our data suggested that the activation of EsSPDS1 expression in tobacco plants conferred drought tolerance, which might be attributed to enhance the ability to scavenge ROS levels.

Gamma radiation protects fruit quality in tomato by inhibiting the production of reactive oxygen species (ROS) and ethylene

Experiments were conducted to examine the individual and combined effect of two different electromagnetic energies, i.e., gamma ray viz 0.1, 0.5 and 1 kGy and static magnetic field (50 mT for 1 h) and their combination (0.5 kGy + 50 mT) on the shelf life of tomato and evaluates the biochemical attributes that influence the fruit ripening and fruit quality. Magnetic field application either alone or in combination with gamma irradiation was not effective in delaying the ripening process. Gamma ray exposed fruits at 0.5 and 1 kGy showed an extended shelf life due to delayed fruit ripening and reduced lycopene synthesis and ethylene production. Efficient ROS scavenging ability and consequent reduction in oxidative damage in the irradiated treatment may cause favorable biochemical changes to facilitate delayed ripening of the tomato fruits.

Radical scavenging activity of steviol glycosides, steviol glucuronide, hydroxytyrosol, metformin, aspirin and leaf extract of Stevia rebaudiana

Introduction: Reactive oxygen species (ROS), generated in many bioorganic redox processes, are the most dangerous by-products in the aerobic environment. The aim of this study was to compare the in vitro antioxidant activity of some chemical compounds and leaf extract of Stevia rebaudiana as natural antioxidant. Methods: The radical scavenging activity of ascorbic acid, quercetine, stevioside (ST), rebaudioside A (Reb A), steviol glucuronide (SVglu), glucose, sucrose, hydroxytyrosol, metformin and aspirin were measured and expressed as the inhibitory concentration in mM giving 50% reduction of radicals (IC50). Results: Ascorbic acid, quercetine, ST, Reb A, SVglu, glucose, sucrose, hydroxytyrosol, metformin and aspirin were active OH scavengers. Superoxide radicals were efficiently scavenged by ascorbic acid, SVglu, quercetine, hydroxytyrosol, ST, Reb A and aspirin. Quercetine, hydroxytyrosol, ascorbic acid and aspirin were active in limiting the amount of thiobarbituric acid (TBA) reactive material. Only ascorbic acid, quercetine and hydroxytyrosol showed DPPH and NO scavenging activity. Leaf extract of S. rebaudiana had an excellent ROS scavenging activity. Treatment of leaf extracts with PVPP and active charcoal removed a part of their scavenging activity. Results showed that sugars were not efficient ROS scavengers. Conclusion: Radical scavenging activity of steviol derivatives, aspirin, metformin and hydroxytyrosol might explain most of beneficial pharmacological effects on ROS related diseases, such as hypertension, type 2 diabetes, atherosclerosis, inflammation and certain forms of cancers. The results obtained in this study indicate that leaf extract of S. rebaudiana has a great potential to use as a natural antioxidant agent.

Abstract C59: Use of dietary antioxidant supplement during cancer therapy- pros and cons.

Abstract Black and green teas are rich in antioxidants and its flavonoids like thearubigins, epicatechins and catechins are known to have higher antioxidant efficacy than vitamin C. Despite significant research investigating the use of tea as dietary antioxidant supplement during conventional chemotherapy, no conclusion has been drawn regarding its mechanism of action and safety. In the present study chemopreventive effects of black tea extract (BTE) were evaluated on normal lymphocytes and compared with cancerous K562 cells. Chemotherapeutic drugs (Adriamycin and Daunomycin) act by generating oxidative stress and inducing apoptosis. The level of reactive oxygen species (ROS), apoptosis and gene expression in untreated and BTE treated cells were followed by different biochemical assays, flow cytometry and reverse transcription PCR. Results evidence that efficient scavenging of intracellular ROS by BTE resulting in reduced apoptotic cell population in normal lymphocytes. Gene expression of p53, bax, bcl2 and nrf2 show variation in untreated and BTE treated cells. Activity of endogenous antioxidant enzymes like SOD, GST and catalase is modified on tea treatment. Similar observations were recorded to a lower extent in K562 cells, suggesting BTE conferred protection to cancerous cells also. It can be summarized here that tea as a dietary supplement during chemotherapy shows interference in chemotherapeutic efficacy of the drugs in vitro. More in vitro, in vivo and clinical trials would shed light on the mechanism of action of the dietary antioxidant supplement during chemotherapy and its application. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C59. Citation Format: Debjani Ghosh, Subrata Dey, Chabita Saha. Use of dietary antioxidant supplement during cancer therapy- pros and cons. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C59.

Structurally-Tuned Nitrogen-Doped Cerium Oxide Exhibits Exceptional Regenerative Free Radical Scavenging Activity in Polymer Electrolytes

The regenerative free radical scavenging activity of cerium oxide (CeO2) nanoparticles was improved by tuning its microstructure via nitrogen doping (N-doping). Commercially available CeO2 (60 m2/g) and high-surface-area CeO2 (synthesized in-house; 220 m2/g) were doped with nitrogen by annealing in a nitrogen rich atmosphere. The evolution of CeO2 microstructure in Nitrogen doped (N-doped) commercial CeO2 (20 m2/g) and N-doped high-surface-area CeO2 (90 m2/g) was studied. XPS and Raman measurements revealed that N-doping of CeO2 enhanced Ce3+ surface concentration and concomitantly increased surface non-stoichiometry (surface oxygen vacancy concentration). XRD analysis of the doped samples confirmed that the nitrogen atom replaced the oxygen atom in the CeO2 lattice, yielding a lower electron density region around the N-doped sites. The high-surface-area CeO2 and its N-doped version had significantly larger lattice parameters than that of commercial CeO2 and its doped version. XAS studies revealed that the N-doped high-surface-area CeO2 had more Ce3+ active clusters than its counterparts, and effectively retained its active Ce3+ active clusters upon exposure to reactive oxygen species (ROS). To confirm, the regenerative ROS (hydroxyl radical) scavenging ability of N-doped CeO2 nanoparticles within the polymer electrolyte membrane (PEM) of an operating polymer electrolyte fuel cell (PEFC) was evaluated using in-situ fluorescence spectroscopy. The N-doped high-surface-area CeO2 showed at least 100 hours of efficient and quantitative ROS scavenging under harsh conditions - a 15-fold improvement over previous reports. This study unequivocally demonstrates that N-doping increases both the number of Ce3+ active clusters in the lattice and the Ce-O bond distance; these structural attributes enhance regenerative ROS scavenging activity of CeO2.

Reactive Oxygen Species, Oxidative Damage, and Antioxidative Defense Mechanism in Plants under Stressful Conditions

Reactive oxygen species (ROS) are produced as a normal product of plant cellular metabolism. Various environmental stresses lead to excessive production of ROS causing progressive oxidative damage and ultimately cell death. Despite their destructive activity, they are well-described second messengers in a variety of cellular processes, including conferment of tolerance to various environmental stresses. Whether ROS would serve as signaling molecules or could cause oxidative damage to the tissues depends on the delicate equilibrium between ROS production, and their scavenging. Efficient scavenging of ROS produced during various environmental stresses requires the action of several nonenzymatic as well as enzymatic antioxidants present in the tissues. In this paper, we describe the generation, sites of production and role of ROS as messenger molecules as well as inducers of oxidative damage. Further, the antioxidative defense mechanisms operating in the cells for scavenging of ROS overproduced under various stressful conditions of the environment have been discussed in detail.

Modulation of reactive oxygen species in skeletal muscle by myostatin is mediated through NF‐κB

SummaryAbnormal levels of reactive oxygen species (ROS) and inflammatory cytokines have been observed in the skeletal muscle during muscle wasting including sarcopenia. However, the mechanisms that signal ROS production and prolonged maintenance of ROS levels during muscle wasting are not fully understood. Here, we show that myostatin (Mstn) is a pro‐oxidant and signals the generation of ROS in muscle cells. Myostatin, a transforming growth factor‐β (TGF‐β) family member, has been shown to play an important role in skeletal muscle wasting by increasing protein degradation. Our results here show that Mstn induces oxidative stress by producing ROS in skeletal muscle cells through tumor necrosis factor‐α (TNF‐α) signaling via NF‐κB and NADPH oxidase. Aged Mstn null (Mstn−/−) muscles, which display reduced sarcopenia, also show an increased basal antioxidant enzyme (AOE) levels and lower NF‐κB levels indicating efficient scavenging of excess ROS. Additionally, our results indicate that both TNF‐α and hydrogen peroxide (H2O2) are potent inducers of Mstn and require NF‐κB signaling for Mstn induction. These results demonstrate that Mstn and TNF‐α are components of a feed forward loop in which Mstn triggers the generation of second messenger ROS, mediated by TNF‐α and NADPH oxidase, and the elevated TNF‐α in turn stimulates Mstn expression. Higher levels of Mstn in turn induce muscle wasting by activating proteasomal‐mediated catabolism of intracellular proteins. Thus, we propose that inhibition of ROS induced by Mstn could lead to reduced muscle wasting during sarcopenia.

Aloe vera or Resveratrol Supplementation in Larval Diet Delays Adult Aging in the Fruit Fly, Drosophila melanogaster

Longevity extension in Drosophila melanogaster by feeding diet supplemented with chemicals throughout adulthood can cause harmful side effects. We tested the effect of larval diet supplementation with five different concentrations of resveratrol and one concentration of Aloe vera extract on the adult longevity of short-lived D melanogaster populations. Resveratrol and A vera extract supplementation of larval diet extended adult longevity in both the male and female flies without reducing fecundity but by efficient reactive oxygen species scavenging through increased antioxidant enzymes activity and better neuroprotection as indicated by increased locomotor activity in adult males.

NO way to treat a cold

Gupta, K. J., Hinch, D. K., Mur, L. A. (2011). NO way to treat a cold. New Phytologist, 189, (2), 360-363. IMPF: 06.64

GSH Attenuates Organ Injury and Improves Function after Transplantation of Fatty Livers

Ischemia-reperfusion injury (IRI) is increased after transplantation of steatotic livers. Since those livers are increasingly used for transplantation, protective strategies must be developed. Reactive oxygen species (ROS) play a key role in hepatic IRI. In lean organs, glutathione (GSH) is an efficient scavenger of ROS, diminishing IRI. The aim of this study was to evaluate whether GSH also protects steatotic allografts from IRI following transplantation. Fatty or lean livers were explanted from 10-week-old obese or lean Zucker rats and preserved (obese 4 h, lean 24 h) in hypothermic University of Wisconsin solution. Arterialized liver transplantation was then performed in lean syngeneic Zucker rats. Recipients of fatty livers were treated with GSH (200 µmol/h/kg) or saline during reperfusion (2 h, n = 5). Parameters of hepatocellular damage and bile flow were measured. Transplantation of steatotic livers enhanced early reperfusion injury compared to lean organs as measured by increased aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase plasma levels. Bile flow was also reduced in steatotic grafts. Intravenous administration of GSH effectively decreased liver damage in fatty allografts and resulted in improved bile flow. Intravenous application of GSH effectively reduces early IRI in steatotic allografts and improves recovery of these marginal donor organs following transplantation.

Transcriptional response of Burkholderia cenocepacia J2315 sessile cells to treatments with high doses of hydrogen peroxide and sodium hypochlorite

BackgroundBurkholderia cepacia complex bacteria are opportunistic pathogens, which can cause severe respiratory tract infections in patients with cystic fibrosis (CF). As treatment of infected CF patients is problematic, multiple preventive measures are taken to reduce the infection risk. Besides a stringent segregation policy to prevent patient-to-patient transmission, clinicians also advise patients to clean and disinfect their respiratory equipment on a regular basis. However, problems regarding the efficacy of several disinfection procedures for the removal and/or killing of B. cepacia complex bacteria have been reported. In order to unravel the molecular mechanisms involved in the resistance of biofilm-grown Burkholderia cenocepacia cells against high concentrations of reactive oxygen species (ROS), the present study focussed on the transcriptional response in sessile B. cenocepacia J2315 cells following exposure to high levels of H2O2 or NaOCl.ResultsThe exposure to H2O2 and NaOCl resulted in an upregulation of the transcription of 315 (4.4%) and 386 (5.4%) genes, respectively. Transcription of 185 (2.6%) and 331 (4.6%) genes was decreased in response to the respective treatments. Many of the upregulated genes in the NaOCl- and H2O2-treated biofilms are involved in oxidative stress as well as general stress response, emphasizing the importance of the efficient neutralization and scavenging of ROS. In addition, multiple upregulated genes encode proteins that are necessary to repair ROS-induced cellular damage. Unexpectedly, a prolonged treatment with H2O2 also resulted in an increased transcription of multiple phage-related genes. A closer inspection of hybridisation signals obtained with probes targeting intergenic regions led to the identification of a putative 6S RNA.ConclusionOur results reveal that the transcription of a large fraction of B. cenocepacia J2315 genes is altered upon exposure of sessile cells to ROS. These observations have highlighted that B. cenocepacia may alter several pathways in response to exposure to ROS and they have led to the identification of many genes not previously implicated in the stress response of this pathogen.

Antiapoptotic effects of dietary antioxidants towards N‐nitrosopiperidine and N‐nitrosodibutylamine‐induced apoptosis in HL‐60 and HepG2 cells

The aim of this work was to determine the effect of vitamin C, diallyl disulfide (DADS) and dipropyl disulfide (DPDS) towards N-nitrosopiperidine (NPIP) and N-nitrosodibutylamine (NDBA)-induced apoptosis in human leukemia (HL-60) and hepatoma (HepG2) cell lines using the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay. None of the vitamin C (5-50 microm), DADS and DPDS (1-5 microm) concentrations selected induced a significant percentage of apoptosis. In simultaneous treatments, vitamin C, DADS and DPDS reduced the apoptosis induced by NPIP and NDBA in HL-60 and HepG2 cells (around 70% of reduction). We also investigated its scavenging activities towards reactive oxygen species (ROS) produced by NPIP and NDBA using 2',7'-dichlorodihydrofluorescein diacetate in both cell lines. ROS production induced by both N-nitrosamine was reduced to control levels by vitamin C (5-50 microm) in a dose-dependent manner. However, DADS (5 microm) increased ROS levels induced by NPIP and NDBA in HL-60 (40 and 20% increase, respectively) and HepG2 cells (18% increase), whereas DPDS was more efficient scavenger of ROS at the lowest concentration (1 microm) in both HL-60 (52 and 25% reduction, respectively) and HepG2 cells (24% reduction). The data demonstrated that the scavenging ability of vitamin C and DPDS could contribute to inhibition of the NPIP- and NDBA-induced apoptosis. However, more than one mechanism, such as inhibition of phase I and/or induction of phase II enzymes, could be implicated in the protective effect of dietary antioxidants towards NPIP- and NDBA-induced apoptosis in HL-60 and HepG2 cells.

Tea (Camellia sinensis) clones with shorter periods of winter dormancy exhibit lower accumulation of reactive oxygen species

Tea (Camellia sinensis (L.) O. Kuntze) is a perennial crop grown throughout the world. During winter, tea undergoes a dormancy period when growth of apical buds almost ceases, severely reducing the commercial yield of tea. Low temperatures prevail during the period of winter dormancy, which alone or in combination with high solar irradiance have the potential to induce oxidative stress in plants. We studied six tea clones under field conditions to test whether a relationship exists between oxidative stress and winter dormancy. Data on the behavior of the enzymatic antioxidative system was collected for all clones during different phases of winter dormancy. There was a strong positive correlation among clones between accumulation of reactive oxygen species (ROS) and the length of the dormancy period. Clones having shorter dormancy periods exhibited higher induction of antioxidative enzymes. Results suggest that efficient scavenging of ROS is a desirable feature in tea because it leads to lower accumulations of ROS during winter months and is associated with reduced winter dormancy.

Organic Solutes Protect Drought-Tolerant Populus × euramericana Against Reactive Oxygen Species

The mechanisms by which drought-induced oxidative stress is tolerated in poplar were appreciated by the ability of leaf extracts to scavenge reactive oxygen species (ROS) generated in vitro by a xanthine oxidase-hypoxanthine system. Their effects were detected by the protection towards the denaturation of malate dehydrogenase (MDH) of crude and dialysed extracts of a drought-sensitive (Populus × euramericana, Luisa Avanzo) and a drought-tolerant (P × euramericana, Dorskamp) poplar exposed to control and osmotic stress (-0.336 MPa). At the beginning of the incubation period in presence of ROS, MDH from crude extract of control Dorskamp was protected against the denaturation; boiled crude extracts of control Dorskamp also protected MDH from the dialysed extract of control Luisa Avanzo. In control Dorskamp, cysteine, proline, polyamines and ascorbate added in vitro were efficient ROS scavengers. Compared with the control condition, the rate of MDH denaturation in presence of ROS decreased in a dialysed extract of stressed Luisa Avanzo but increased in that of stressed Dorskamp. Under stress conditions, proline in vitro enhanced the rate of MDH denaturation by ROS in Luisa Avanzo, but competed as ascorbate with ROS in Dorskamp. In Dorskamp, the 12h-exposure to osmotic stress resulted in a decrease in catalase and gutathione reductase activities, in an enhancement of superoxide dismutase, ascorbate peroxidase and contents of some putative leaf antioxidants (putrescine and glutathione), but did not affect the contents of spermine, spermidine and ascorbate. The consequences of extract/solute effects are discussed for each clone as regards the drought response.