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H2O2 Accumulation (h2o2 + accumulation)
Selected AbstractsAccumulation of hydrogen peroxide is an early and crucial step for paclitaxel-induced cancer cell death both in vitro and in vivo,INTERNATIONAL JOURNAL OF CANCER, Issue 1 2006Jérôme Alexandre Abstract Intracellular events following paclitaxel binding to microtubules that lead to cell death remain poorly understood. Because reactive oxygen species (ROS) are involved in the cytotoxicity of anticancer agents acting through independent molecular targets, we explored the role of ROS in paclitaxel cytotoxicity. Within 15 min after in vitro exposure of A549 human lung cancer cells to paclitaxel, a concentration-dependent intracellular increase in O°2, and H2O2 levels was detected by spectrofluorometry. Addition of N -acetylcysteine (NAC) or glutathione, two H2O2 scavenger, induced a 4-fold increase in paclitaxel IC50. Delaying NAC co-incubation by 4 hr, resulted in a 3-fold reduction in cell protection. The glutathione synthesis inhibitor, buthionine sulfoximine significantly increased paclitaxel cytotoxicity and H2O2 accumulation, but did not modify O°2, levels. Co-incubation with diphenylene iodonium suggested that paclitaxel induced-O°2, production was in part associated with increased activity of cytoplasmic NADPH oxidase. Concomitant treatment with inhibitors of caspases 3 and 8 increased cell survival but did not prevent the early accumulation of H2O2. To evaluate the role of ROS in paclitaxel antitumoral activity, mice were injected with LLC1 lung cancer cells and treated with paclitaxel i.p. and/or NAC. The antitumoral activity of paclitaxel in mice was abolished by NAC. In conclusion, the accumulation of H2O2 is an early and crucial step for paclitaxel-induced cancer cell death before the commitment of the cells into apoptosis. These results suggest that ROS participate in vitro and in vivo to paclitaxel cytotoxicity. © 2006 Wiley-Liss, Inc. [source] Cadmium Enhances Generation of Hydrogen Peroxide and Amplifies Activities of Catalase, Peroxidases and Superoxide Dismutase in MaizeJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 1 2008P. Kumar Abstract Maize (Zea mays L. cv. 777) plants grown in hydroponic culture were treated with 50 ,m CdSO4. Growth and metabolic parameters indicative of oxidative stress and antioxidant responses were studied in leaves of plants treated with Cd. Apart from increasing lipid peroxidation and H2O2 accumulation, supply of Cd suppressed growth, fresh and dry mass of plants and decreased the concentrations of chloroplastic pigments. The activities of catalase (CAT; EC 1.11.1.6), peroxidase (POD; EC 1.11.1.7), ascorbate peroxidase (APX; EC 1.11.1.11) and superoxide dismutase (SOD; EC 1.15.1.1) were increased in plants supplied 50 ,m Cd. Localization of activities of isoforms of these enzymes (POD, APX and SOD) on native gels also revealed increase in the intensities of pre-existing bands. Stimulated activities of CAT, POD, APX and SOD in maize plants supplied excess Cd do not appear to have relieved plants from excessive generation of reactive oxygen species (ROS). It is, therefore, concluded that supply of 50 ,m Cd induces oxidative stress by increasing production of ROS despite increased antioxidant protection in maize plants. [source] Carbon Metabolism Alterations in Sunflower Plants Infected with the Sunflower Chlorotic Mottle VirusJOURNAL OF PHYTOPATHOLOGY, Issue 5 2003M. C. Arias Abstract Sunflower chlorotic mottle virus (SuCMoV) causes chlorotic mottling symptoms and important growth reductions and yield losses in sunflower (Helianthus annuus L., cv. Contiflor 7). This paper describes the effects of SuCMoV on some aspects of carbon metabolism of sunflower plants. After symptoms became evident, CO2 fixation rates decreased, nevertheless, soluble sugars and starch increased in infected leaves. High H2O2 accumulation, lipid peroxidation and chlorophyll degradation were, like the other changes, observed only after symptom expression. Increased soluble carbohydrate accumulation was not related to changes in , -amylase (EC 3.2.1.1) activity, nor in the activities of enzymes associated with sugar import and hydrolysis such as invertase (EC 3.2.1.26) and sucrose synthase (EC 2.4.1.13), suggesting it did not derive from starch hydrolysis nor increased sugar import. Rather, it may derive from recycling of cell components associated with the development of oxidative damage. The physiological alterations caused by this virus share many common features with the development of senescence. [source] Excess nickel,induced changes in antioxidative processes in maize leavesJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 6 2007Praveen Kumar Abstract Maize (Zea mays L. cv. 777) plants grown in hydroponic culture were treated with 100 µM NiSO4 (moderate nickel (Ni) excess). In addition to growth parameters, metabolic parameters representative of antioxidant responses in leaves were assessed 24 h and 3, 7, and 14 d after initiating the Ni treatment. Extent of oxidative damage was measured as accumulation of malondialdehyde and hydrogen peroxide in leaves 7 and 14 d after treatment initiation. Apart from increasing membrane-lipid peroxidation and H2O2 accumulation, excess supply of Ni suppressed plant growth and dry mass of shoots but increased dry mass of roots and decreased the concentrations of chloroplastic pigments. Excess supply of Ni, though inhibited the catalase (EC 1.11.1.6) activity, increased peroxidase (EC 1.11.1.7), ascorbate peroxidase (EC 1.11.1.11), and superoxide dismutase (EC 1.15.1.1) activities. Localization of isoforms of these enzymes (peroxidase, ascorbate peroxidase, and superoxide dismutase) on native gels also revealed increases in the intensities of pre-existing bands. Enhanced activities of peroxidase, ascorbate peroxidase, and superoxide dismutase, however, did not appear to be sufficient to ameliorate the effects of excessively generated reactive oxygen species due to excess supply of Ni. [source] Oxidative behaviour of fresh-cut ,Fuji' apples treated with stabilising substancesJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 10 2008Dr Christian Larrigaudière Abstract BACKGROUND:Although changes in the quality of fresh-cut products treated with chemical stabilisers have been extensively described in the literature, very little is known about the physiology of these products. This work aims to describe the physiological aspect and particularly the effects of chemical preservatives on the oxidative behaviour of fresh-cut apples. RESULTS:Immediately after treatment, the samples treated with the anti-browning agents (ascorbic acid + cysteine) exhibited a sharp increase in H2O2 levels (a five-fold increase when compared to the other samples) and peroxidative damage, especially at the beginning of the storage period (two-fold increase after 1 day). In line with this result, peroxidase (POX) activity decreased by 50% during the first day of storage, but no significant changes in superoxide dismutase (SOD) and catalase (CAT) activities were found between the different samples. H2O2 accumulation was not attributed to the action of cysteine but to a specific action of ascorbic acid, which mainly acted as a pro-oxidant under these conditions. CONCLUSION:The results presented in this work showed that ascorbic acid cause important oxidative damage in fresh-cut Fuji apples. Alternatives are required to prevent detrimental loss of quality resulting from this oxidative action. Copyright © 2008 Society of Chemical Industry [source] Non-host resistance of barley is associated with a hydrogen peroxide burst at sites of attempted penetration by wheat powdery mildew fungusMOLECULAR PLANT PATHOLOGY, Issue 4 2001Ralph Hückelhoven Summary In barley, non-host resistance against the wheat powdery mildew fungus (Blumeria graminis f.sp. tritici, Bgt) is associated with the formation of cell wall appositions and a hypersensitive reaction in which epidermal cells die rapidly in response to fungal attack. In the interaction of barley with the pathogenic barley powdery mildew fungus (Blumeria graminis f.sp. hordei, Bgh), these defence reactions are also associated with accumulation of H2O2. To elucidate the mechanism of non-host resistance, the accumulation of H2O2 in response to Bgt was studied in situ by histochemical staining with diaminobenzidine. H2O2 accumulation was found in cell wall appositions under appressoria from Bgt and in cells undergoing a hypersensitive reaction. A mutation (mlo5) at the barley Mlo locus, that confers broad spectrum resistance to Bgh, did not influence the barley defence phenotype to Bgt. Significantly, Bgt triggered cell death on mlo5 -barley while Bgh did not. [source] Role of hydrogen peroxide during the interaction between the hemibiotrophic fungal pathogen Septoria tritici and wheatNEW PHYTOLOGIST, Issue 3 2007Nandini P. Shetty Summary ,,Hydrogen peroxide (H2O2) is reported to inhibit biotrophic but benefit necrotrophic pathogens. Infection by necrotrophs can result in a massive accumulation of H2O2 in hosts. Little is known of how pathogens with both growth types are affected (hemibiotrophs). The hemibiotroph, Septoria tritici, infecting wheat (Triticum aestivum) is inhibited by H2O2 during the biotrophic phase, but a large H2O2 accumulation occurs in the host during reproduction. ,,Here, we infiltrated catalase, H2O2 or water into wheat during the biotrophic or the necrotrophic phase of S. tritici and studied the effect of infection on host physiology to get an understanding of the survival strategy of the pathogen. ,,H2O2 removal by catalase at both early and late stages made plants more susceptible, whereas H2O2 made them more resistant. H2O2 is harmful to S. tritici throughout its life cycle, but it can be tolerated. ,,The late accumulation of H2O2 is unlikely to result from down-regulation of photosynthesis, but probably originates from damage to the peroxisomes during the general tissue collapse, which is accompanied by release of soluble sugars in a susceptible cultivar. [source] Multivesicular compartments proliferate in susceptible and resistant MLA12 -barley leaves in response to infection by the biotrophic powdery mildew fungusNEW PHYTOLOGIST, Issue 3 2006Qianli An Summary ,,There is growing evidence that multivesicular bodies and cell wall-associated paramural bodies participate in the enhanced vesicle trafficking induced by pathogen attack. ,,Here, we performed transmission electron microscopy in combination with cytochemical localization of H2O2 to investigate multivesicular compartments during establishment of compatible interaction in susceptible barley (Hordeum vulgare) and during hypersensitive response in resistant MLA12 -barley infected by the barley powdery mildew fungus (Blumeria graminis f. sp. hordei). ,,Multivesicular bodies, intravacuolar vesicle aggregates and paramural bodies proliferated in the penetrated epidermal cell during development of the fungal haustorium. These vesicular structures also proliferated at the periphery of intact cells, which were adjacent to the hypersensitive dying cells and deposited cell wall appositions associated with H2O2 accumulation. All plasmodesmata between intact cells and hypersensitive cells were constricted or blocked by cell wall appositions. ,,These results suggest that multivesicular compartments participate in secretion of building blocks for cell wall appositions not only to arrest fungal penetration but also to contain hypersensitive cell death through blocking plasmodesmata. They may also participate in internalization of damaged membranes, deleterious materials, nutrients, elicitors and elicitor receptors. [source] Time-course of lipoxygenase, antioxidant enzyme activities and H2O2 accumulation during the early stages of Rhizobium,legume symbiosisNEW PHYTOLOGIST, Issue 1 2001Pablo Bueno Summary ,,The involvement of lipoxygenase and antioxidant enzyme activities as well as hydrogen peroxide (H2O2) accumulation are reported during early infection steps in alfalfa (Medicago sativa) roots inoculated either with a wild type Sinorhizobium meliloti or with a mutant defective in Nod-factor synthesis (Nod C,). ,,Compatibility between M. sativa and Rhizobium correlates, at least in part, with an increase in the activities of these enzymes, particularly catalase and lipoxygenase, during the preinfection period (up to 12 h). The mutant strain, defective in Nod-factor biosynthesis, showed a decrease in all enzyme activities assayed, and an increase in H2O2 accumulation. ,,Enhancement of scavenging activities for several reactive oxygen species correlated with compatibility of the S. meliloti,alfalfa symbiosis, whereas the Nod C, strain triggered a defence response. Nod factors were essential to suppress this response. ,,Increase in lipoxygenase and lipid hydroperoxide decomposing activities, observed during the first hours after inoculation with a compatible strain, could be related to tissue differentiation and/or the production of signal molecules involved in autoregulation of nodulation by the plant. [source] Catalase inhibition alters suberization and wound healing in potato (Solanum tuberosum) tubersPHYSIOLOGIA PLANTARUM, Issue 3 2007Mohammed Bajji In response to wounding, potato (Solanum tuberosum L.) tubers generate hydrogen peroxide (H2O2) in association with suberization, a critical phase of the wound-healing process. In the present study, the effect of aminotriazole (AT), a catalase (CAT, EC 1.11.1.6) inhibitor, on cut tubers was investigated using fresh weight (FW) loss and pathogen attack symptoms as indicators of wound-healing efficiency. Seven days after treatment, AT-treated tuber halves lost more FW and developed infection signs compared with the controls. Thiourea, another CAT inhibitor, as well as exogenous H2O2 treatments induced the same effects as AT suggesting that the alteration of the wound healing may be caused by CAT inhibition and the resulting accumulation of H2O2. Using transgenic tubers, FW losses 1 week after wounding were either higher (CAT repression) or lower (CAT overexpression) than those of the wild-type. When tuber halves were allowed to wound heal for different periods before treatment, AT had no effect on the progress of their wound healing if wound-healed for at least 3 days. This implies that AT may affect early wound-healing-related events, especially those occurring before or during suberization. A time-course analysis of the effects of AT treatment on wounded tuber tissues revealed that AT prevented the deposition of the polyphenolic domain of suberin in association with CAT inhibition and H2O2 accumulation. These data are important in identifying factors that may be required to regulate suberization and contribute to a better understanding of this critical process to hasten its rate and limit wound-related losses in stored potato tubers. [source] Compatible and Incompetent Paxillus involutus Isolates for Ectomycorrhiza Formation in vitro with Poplar (Populus×canescens) Differ in H2O2 ProductionPLANT BIOLOGY, Issue 1 2004A. Gafur Abstract: Isolates of Paxillus involutus (Batsch) Fr. collected from different hosts and environmental conditions were screened for their ability to form ectomycorrhizal symbiosis with hybrid poplar P.×canescens (= Populus tremula L. ×P. alba) in vitro. The ability to form ectomycorrhiza varied between the fungal isolates and was not correlated with the growth rate of the fungi on agar-based medium. The isolate MAJ, which was capable of mycorrhiza synthesis under axenic conditions, and the incompetent isolate NAU were characterized morphologically and anatomically. MAJ formed a typical hyphal mantle and a Hartig net, whereas NAU was not able to penetrate the host cell walls and caused thickenings of the outer cell walls of the host. MAJ, but not NAU, displayed strong H2O2 accumulation in the outer hyphal mantle. Increases in H2O2 in the outer epidermal walls and adjacent hyphae of the incompetent isolate were moderate. No increases of H2O2 in response to the mycobionts were found inside roots. Suggested functions of H2O2 production in the outer hyphal mantle of the compatible interaction are: growth regulation of the host's roots, defence against other invading microbes, or increasing plant-innate immunity. The system established here for P.×canescens compatible and incompetent fungal associations will be useful to take advantage of genomic information now available for poplar to study tree-fungal interactions at the molecular and physiological level. [source] Phosphate Induces Rapid H2O2 Generation in Soybean Suspension CellsPLANT BIOLOGY, Issue 2 2000T. Shigaki Abstract: Involvement of reactive oxygen species has been implicated in plant defence against pathogens. We report here a novel pathway of H2O2 generation induced by the addition of phosphate in soybean (Glycine max L.) cell suspension cultures. This H2O2 generation was initiated shortly after the addition of phosphate, and lasted only approximately one hour, as opposed to several hours observed during an attack by an avirulent strain of the bacterial pathogen Pseudomonas syringae pv. glycinea (Psg). In addition, when cell cultures were treated with both phosphate and the avirulent pathogen, two distinct oxidative burst events were observed. In contrast to DPI-sensitive Psg -induced H2O2 generation, phosphate-induced H2O2 generation was insensitive to this NADPH oxidase inhibitor. This suggests that an NADPH oxidase-independent pathway may be involved in the phosphate-induced H2O2 accumulation, which could be involved in sensing of phosphate availability in the environment. [source] Effects of exogenous GABA on gene expression of Caragana intermedia roots under NaCl stress: regulatory roles for H2O2 and ethylene productionPLANT CELL & ENVIRONMENT, Issue 2 2010SHENG-QING SHI ABSTRACT , -aminobutyric acid (GABA) is a four-carbon non-protein amino acid presented in a wide range of organisms. In this study, a suppression subtractive hybridization (SSH) library was constructed using roots of a legume shrub, Caragana intermedia, with the combined treatment of 300 mm NaCl and 300 mm NaCl + 10 mm GABA. We obtained 224 GABA-regulated unique expressed sequence tags (ESTs) including signal transduction, transcriptional regulation, hormone biosynthesis, reactive oxygen species (ROS) and polyamine metabolism, etc. The key H2O2 -generated genes, NADPH oxidase (CaGR60), peroxidase (CaGR61) and amine oxidase (CaGR62), were regulated at the mRNA level by 10 mm GABA, which clearly inhibited H2O2 accumulation brought about by NaCl stress in roots and leaves with the observation of 3,3,-diaminobenzidine (DAB) staining. Similarly, 10 mm GABA also regulated the expression of 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACO) genes (CaGR30 and CaGR31) and ethylene production in NaCl-treated roots. Surprisingly, these H2O2 -generated genes were enhanced at the mRNA level by a lower concentration of GABA, at 0.25 mm, but not other alternative nitrogen sources, and endogenous GABA accumulated largely just by the application of GABA at either concentration. Our results further proved that GABA, as a signal molecule, participates in regulating the expression of genes in plants under salt stress. [source] | |||||||||||||