Reactive Oxygen Species O2 Research Articles

Insight of Oxidative Stress, Ultrastructural Transformations, and Elemental Variations in Rice Seedlings Exposed to Boron Toxicity: Unraveling the Role of Fe-SOD in Boron Tolerance

Rice (Oryza sativa L.) seedlings differing in boron tolerance were grown in hydroponics containing varying boron concentration. (as boric acid) for 8 days. Yoshida Nutrient Solution (Yoshida et al.1976) served as control, whereas 0.5 mM boron (moderately toxic) and 1.5 mM boron (highly toxic). Boron excess (B) caused marked reduction in length, biomass and relative water content of the seedlings, with more reductions in B-sensitive cv. Malaviya-36 as compared with B-tolerant cv. Brown Gora. B-sensitive seedlings showed higher B uptake in roots and shoots compared to the tolerant. Scanning electron microscopy (SEM) revealed ultrastructural damage to the guard cells with excess boron. Energy dispersive X-ray analysis (EDXA) of rice leaves showed decline in concentration of P, S, Ca and Mg in seedlings on B treatment. Increased production of reactive oxygen species O2˙−, H2O2, lipid peroxides, alteration in activity of antioxidative enzymes and increased membrane permeability was observed in B treated seedlings compared to controls. Real time PCR analysis of stress regulatory genes indicated differential expression of SOD isoforms in the two sets of cultivars with B treatment. Interestingly seedlings of B-tolerant cultivar were characterized by higher level of expression of Fe-SOD and its further increased expression on B treatment. Results suggest that B toxicity involves ultrastructural and elemental changes, increased generation of ROS and altered antioxidative enzyme activities in rice seedlings and increased expression Fe-SOD isoform appears to be associated with B tolerance.

Effects of humidity-cold combined stress at the seedling stage in direct-seeded indica rice

Low temperature (LT) and extreme humidity constantly threaten direct-seeded early indica rice production during the seedling stage. However, the physiological mechanism and damage induced by LT combined with high/low humidity are still unclear. A pot experiment was conducted to study seedling growth performance and physiological traits of two indica rice cultivars (i.e., the cold-sensitive cultivar Zhongjiazao17 and the cold-tolerant cultivar Xiangzaoxian6) under LT plus low humidity treatment (LL, 8°C; relative humidity, 25 %), LT plus high humidity treatment (LH, 8°C; relative humidity, 95 %) and a control treatment (CK, 25 °C; relative humidity, 75 %). The results showed that seedling height, rubisco concentration, and APX, PDH and α-KGDH activity significantly decreased under LL and LH compared to CK, and large decreases were found under LH, especially for the cold-sensitive cultivar Zhongjiazao17. However, LH significantly increased the reactive oxygen species O2− and the soluble protein, GSH and ABA concentrations. Moreover, the APX, PDH and α-KGDH activities, rubisco and chlorophyll concentrations, and GA3 induced by LH also significantly decreased after treatment. The differences in physiological traits of Zhongjiazao17 after LL and LH were significant. During three days of recovery, the physiological activity of the two cultivars under LL tended to recover to the level of CK, and the cold-tolerant cultivar showed reduced damage caused by humidity-cold combined stress. The results suggested that the double stress of low temperature plus high humidity rather than low temperature plus low humidity could decrease the growth performance by hampering photosynthetic and respiratory systems and altering the endogenous hormonal regulation of direct-seeded early indica rice, whereas it could significantly enhance the antioxidant protective system derived from the osmotic damage of leaves.

Ferroelectric spontaneous polarization steering charge carriers migration for promoting photocatalysis and molecular oxygen activation

Introducing a polarization electric field in photocatalyst system is regarded asa new concept for photocatalytic activity enhancement. In this work, we first unearth that the spontaneous polarization of ferroelectric BaTiO3 promotes the photocatalytic and molecular oxygen activation performance of the narrow-band-gap semiconductor BiOI. Ferroelectric tetragonal-phase BaTiO3 (T-BaTiO3) were prepared via calcination of nonferroelectric cubic-phase BaTiO3 (C-BaTiO3), and their polarization ability was verified via ultrasonication-assisted piezoelectric catalytic degradation. Then, the C-BaTiO3/BiOI and T-BaTiO3/BiOI heterostructures are fabricated by a soft-chemical method. To disclose the influence of ferroelectric spontaneous polarization on charge movement behavior, the photocatalytic and molecular oxygen activation properties are monitored by degradation of methyl orange (MO) and superoxide radical (O2−) evolution under visible light irradiation (λ>420nm), respectively. The results demonstrated that T-BaTiO3/BiOI far outperforms C-BaTiO3/BiOI and pristine BiOI. The ferroelectric spontaneous polarization of T-BaTiO3 can steer the migration of photogenerated charge carriers and induce efficient separation, accounting for the strengthened photodegradation and reactive oxygen species O2− production rate (11.02×10−7molL−1h−1). The study may furnish a new reference for developing efficient tactics to advance the photocatalytic and molecular oxygen activation ability for environmental chemistry and biochemistry applications.

Thione-Based Nickel(II) Complexes as Functional Antioxidant Mimics: Scavenging Activity of Reactive Oxygen Species O2 −· and X-Ray Crystal Structure of [Ni(Ttxyly)2]2 {Ttxylyl = Hydrotris(2-mercapto-1-xylyl-imidazolyl)borate}

Two new thione-based nickel complexes, viz., [Ni(Tmipr)2Cl2]⋅2H2O 1 and [Ni(Ttxyly)2] ⋅H2O⋅2CH3OH 2 {Tmipr = 1-(2-isopropylphenyl)-1H-imidazole-2(3H)-thione; Ttxylyl− = hydrotris[1-(2,6-dimethylphenyl)-1H-imidazole-2(3H)-thione]borate anion} have been synthesized. Their structures and properties were characterized by several physicochemical methods, namely elemental and thermal analysis, FT-IR and Raman and UV–Vis spectroscopes, as well as electrical molar conductivity measurements. Structural determination of complex 2 showed that the coordination geometry around nickel atom is distorted tetrahedral with four thione sulfur donors from two molecules of the ligand KTtxylyl. Steric interactions between the xylyl rings appear to be responsible for the formation of the mononuclear nickel(II) complex 2. Molecules of complex 2 are connected via S–H···O hydrogen bonds, involving hydrogen atoms of the coordinated thiones and lattice water molecules. The superoxide dismutase biomimetic catalytic activities of both complexes were tested and found to be promising candidates as functional mimic enzyme to serve for complete superoxide radical’s detoxification. The observed IC50 values of these complexes are 8.38 and 7.4 mM for complexes 1 and 2, respectively.

Flue Gas Desulfurization by Dielectric Barrier Discharge

There are many problems with flue gas desulfurization by traditional gas ionization discharge, including the large size of the plasma source, high energy consumption, and the need for a traditional desulfurization method. This paper introduces oxidization of SO2 to sulfuric acid (H2SO4) in a duct by reactive oxygen species (O2 +, O3) produced by strong ionization dielectric barrier discharge. The entire plasma reaction process is completed within the duct without the use of absorbents, catalysts, or large plasma source. The reactive oxygen species O2 + reacts with gaseous H2O in the flue gas to generate ·OH radicals, which can oxidize trace amounts of SO2 in large volumes of the flue gas to produce H2SO4. Sulfuric acid is also produced by O3 oxidation of SO2 to SO3, and SO3 reacting with gaseous H2O in the flue gas. Experimental results showed that with a gas temperature of 22 °C and reactive oxygen species injection rate of 0.84 mg/L, the SO2 removal rate was 81.4 %, and the SO4 2− concentration in the recovered liquid H2SO4 reached 53.8 g/L.

The {0 0 1} facets-dependent superior photocatalytic activities of BiOCl nanosheets under visible light irradiation

BiOCl nanosheets with tunable lamella thickness and dominantly exposed {001} facets were selectively synthesized via a facile hydrothermal method. By modifying the synthetic parameters, such as the amount of P123 and mannitol, the reaction time, types of surfactants, the size, thickness, morphologies, and percentage of {001} facets over BiOCl nanosheets were well controlled. The exposed {001} facets with high surface energy and high density of oxygen atoms are not only conducive to the adsorption of the rhodamine B (RhB) dye but also can accumulate the photo-generated electrons, which can be captured by O2 and converted into reactive oxygen species O2−. Therefore, the resultant ultrathin BiOCl nanosheets with exposed {001} facets exhibit superior catalytic activity for dye photosensitization degradation under visible light irradiation. Impressively, the ultrathin BiOCl nanosheets prepared with P123 and mannitol manifest superior catalytic activity and RhB was completely degraded within 20min. Our current work is expected to offer a new insight into photocatalytic theory for better understanding of visible light photocatalytic reactions and rational design of highly active photocatalysts.

TheNSAIDs Indomethacin and Diflunisal as Scavengers of Photogenerated Reactive Oxygen Species

Diflunisal (DFNS) and Indomethacin (IMTC) are two profusely employed NSAIDs that provide anti-inflammatory and analgesic effects in humans. The scavenging of reactive oxygen species (ROS) by both NSAIDs was systematically studied in pH 7 aqueous solution. The ROS O2 ((1)Δg), O2(•-) and H2O2, generated by visible light irradiation of Riboflavin (Rf) in the presence of DFNS and IMTC, are deactivated by the NSAIDs. The ROS scavenging action by both NSAIDs constitutes an interesting result and adds one more positive aspect to the beneficial actions attributed to these drugs. Nevertheless it should be taken into account that several NSAIDs, in particular IMTC, have been connected to the pathogenesis of gastric mucosal lesions, which in some cases includes ROS generating-ability. DFNS quenches ROS in a dominant physical fashion. It constitutes an excellent protective-antioxidant provided that is practically not destroyed/oxidized after the ROS scavenging action. IMTC, being also an efficient interceptor of ROS, belong to the so-called group of sacrificial-ROS quenchers: It is easily degraded by the oxidative species in the scavenging action. Although this property is negative in the context of prolonged ROS elimination, exhibits a promissory aspect for the degradation of pharmaceutical contaminants, such as NSAIDs, in waste waters.

NADPH Oxidase–Derived Superoxide Destabilizes Lipopolysaccharide-Induced Interleukin 8 mRNA Via p38, Extracellular Signal–Regulated Kinase Mitogen-Activated Protein Kinase, and the Destabilizing Factor Tristetraprolin

Expression of inflammatory cytokines is regulated by transcriptional and posttranscriptional mechanisms. We previously showed that NADPH oxidase-derived superoxide induces inflammatory mediators in response to tumor necrosis factor α (TNF-α) and lipopolysaccharide (LPS). In this study, we examined the role of endothelial NADPH oxidase in the regulation of mRNA stability of three inflammatory mediators: interleukin (IL) 8, IL-6, and intercellular adhesion molecule 1 (ICAM-1). Tumor necrosis factor α increased mRNA stability of ICAM-1, IL-8, and IL-6 by a p38 mitogen-activated protein kinase (MAPK)-dependent mechanism, but this did not involve NADPH oxidase. Surprisingly, whereas LPS treatment alone did not alter stability of these molecules, the antioxidant N-acetyl-L-cysteine; the flavine inhibitor diphenylene iodonium; short interfering RNA against Nox2, Nox4; and the p22(phox) subunit of NADPH oxidase all enhanced IL-8 mRNA stability in LPS-treated cells, indicating that LPS induced destabilization through NADPH oxidase. This occurred by a mechanism that involved extracellular signal-regulated kinase 1/2, p38 MAPK, and the mRNA-destabilizing factor tristetraprolin. On the other hand, N-acetyl-L-cysteine decreased mRNA stability of ICAM-1 and IL-6 in LPS-treated cells and IL-6 and ICAM-1 in TNF-α-treated cells. In conclusion, NADPH oxidase contributes to destabilization of IL-8 mRNA stability and propose a model for the complex underlying mechanism, which is dependent upon agonist (LPS vs. TNF-α) and target molecule (IL-8 vs. IL-6 and ICAM-1) and involves tristetraprolin, p38, and extracellular signal-regulated kinase 1/2 MAPK.

In Vitro Protective Effect of Hypericum androsaemum Extract Against Oxygen and Nitrogen Reactive Species

Hypericum androsaemum L. (Gutiferae) is a medicinal plant growing in Western Europe that has been used in traditional medicine in the prevention or treatment of liver diseases. Oxidative stress and nitrosative stress are common pathogenetic mechanisms contributing to initiation and progression of hepatic damage in several liver disorders. In the present study, an ethanol:water (4:6) extract from H. androsaemum branches and leaves were evaluated for its putative in vitro scavenging effects on 1,1-diphenyl-2-picrylhydrazil radical, on reactive oxygen species, namely HO•, O₂•-, ROO•, ¹O₂ and H₂O₂ and on reactive nitrogen species, namely •NO and ONOO⁻. The hypericum extract presented a remarkable capacity to scavenge all the tested reactive species, all the IC₅₀ values being found at the μg/ml level. IC₅₀ values for 1,1-diphenyl-2-picrylhydrazil, and for the reactive oxygen species O₂•-, H₂O₂, HO• and ¹O₂ were 11.3 ± 0.7, 32.7 ± 3.4, 944 ± 47, 595 ± 82, 28.3 ± 1.2 μg/ml respectively. The oxygen radical absorbance capacity value obtained for ROO• was 1.5 ± 0.1 μmol Trolox equivalents/mg extract. The IC₅₀ values for •NO and ONOO⁻ were 2.2 ± 0.2 and 1.2 ± 0.1 μg/ml respectively. The content of total phenolics was 281 ± 2 mg of gallic acid equivalents/g of lyophilized extract. The observed antioxidant activity provides scientific support for the reported therapeutic use of H. androsaemum, though further in vitro and in vivo studies are required to ascertain the risk/benefit score at therapeutic concentrations.

Noncovalent DNA Binding and the Mechanism of Oxidative DNA Damage by Fecapentaene-12

The fecapentaenes are a group of mutagenic, polyunsaturated lipids that are produced endogenously in the human gastrointestinal tract. Previous studies show that the fecapentaenes cause oxidative DNA damage, but the chemical mechanisms by which this occurs remain unclear. The data presented here indicate that fecapentaene-12 causes direct oxidative DNA damage via production of the reactive oxygen species O2*-, H2O2, and HO*. In addition, evidence is presented indicating that fecapentaene-12 associates noncovalently with duplex DNA. Fecapentaene-12 provides an interesting new example highlighting the potential for hydrophobic long chain hydrocarbons to associate noncovalently with duplex DNA.