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1.
The hydrogen peroxide (H2O2) stress response in Enterococcus faecalis ATCC19433 was investigated. A 2·4 mmol l−1 H2O2 pretreatment conferred protection against a lethal concentration (45 mmol l−1) of this agent. The relatively high concentrations of H2O2 used for adaptation and challenge treatments in Ent. faecalis emphasised the strong resistance towards oxidative stress in this species. Various stresses (NaCl, heat, ethanol, acidity and alkalinity) induced weak or strong H2O2 cross-protection. This paper describes the involvement of protein synthesis in the active response to lethal dose of H2O2, in addition to the impressive enhancement of synthesis of five H2O2 stress proteins. Combined results suggest that these proteins might play an important role in the H2O2 tolerance response.  相似文献   

2.
Abstract: H2O2 and free radical-mediated oxidative stresses have been implicated in mediating amyloid β(1–40) [Aβ(1–40)] neurotoxicity to cultured neurons. In this study, we confirm that addition of the H2O2-scavenging enzyme catalase protects neurons in culture against Aβ-mediated toxicity; however, it does so by a mechanism that does not involve its ability to scavenge H2O2. Aβ-mediated elevation in intracellular H2O2 production is suppressed by addition of a potent H2O2 scavenger without any significant neuroprotection. Three intracellular biochemical markers of H2O2-mediated oxidative stress were unchanged by Aβ treatment: (a) glyceraldehyde-3-phosphate dehydrogenase activity, (b) hexose monophosphate shunt activity, and (c) glucose oxidation via the tricarboxylic acid cycle. Ionspray mass spectra of Aβ in the incubation medium indicated that Aβ itself is an unlikely source of reactive oxygen species. In this study we demonstrate that intracellular ATP concentration is compromised during the first 24-h exposure of neurons to Aβ. Our results challenge a pivotal role for H2O2 generation in mediating Aβ toxicity, and we suggest that impairment of energy homeostasis may be a more significant early factor in the neurodegenerative process.  相似文献   

3.
4.
The present study aims at clarifying the impact of oxidative stress on type B trichothecene production. The responses to hydrogen peroxide (H2O2) of an array of Fusarium graminearum and Fusarium culmorum strains were compared, both species carrying either the chemotype deoxynivalenol (DON) or nivalenol (NIV). In both cases, levels of in vitro toxin production are greatly influenced by the oxidative parameters of the medium. A 0.5 mM H2O2 stress induces a two- to 50-fold enhancement of DON and acetyldeoxynivalenol production, whereas the same treatment results in a 2.4- to sevenfold decrease in NIV and fusarenone X accumulation. Different effects of oxidative stress on toxin production are the result of a variation in Fusarium 's antioxidant defence responses according to the chemotype of the isolate. Compared with DON strains, NIV isolates have a higher H2O2-destroying capacity, which partially results from a significant enhancement of catalase activity induced by peroxide stress. A 0.5 mM H2O2 treatment leads to a 1.3- to 1.7-fold increase in the catalase activity of NIV isolates. Our data, which show the higher adaptation to oxidative stress developed by NIV isolates, are consistent with the higher virulence of these Fusarium strains on maize compared with DON isolates.  相似文献   

5.
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.  相似文献   

6.
7.
Aims:  To investigate the effects of salicylates in Saccharomyces cerevisiae exposed to oxidative stress induced by hydrogen peroxide (H2O2).
Methods and Results:  Saccharomyces cerevisiae was cultured through to the postlogarithmic phase of growth. Stress was induced by the addition of 1·5 mmol l−1 H2O2 for 1 h, while N-acetyl-l-cysteine (NAC) and glutathione (GSSG) were used as control agents that affect the redox balance. Sodium salicylate, at 0·01–10 mmol l−1or acetylsalicylic acid, at 0·02–2·5 mmol l−1 was administered at various times before hydrogen peroxide stress. Both agents conferred resistance to a subsequent hydrogen peroxide stress, similarly to the induction of the adaptive response observed upon pretreatment with NAC and GSSG. Sodium salicylate was more potent as a short-term, but not as a long-term pretreatment agent, compared to acetylsalicylic acid.
Conclusions:  Pharmacological pretreatment with salicylates resulted in dose related increases in cell survival, indicating the induction of the protective response in yeast.
Significance and Impact of the study:  The possible role of salicylates in the modulation of the hydrogen peroxide stress response in eukaryotic cells address questions on the effects of these commonly used therapeutic agents in a number of disorders exhibiting an oxidative stress component.  相似文献   

8.
Abstract: The bcl-2 protooncogene product possesses antiapoptotic properties in neuronal and nonneuronal cells. Recent data suggest that Bcl-2's potency as a survival factor hinges on its ability to suppress oxidative stress, but neither the subcellular site(s) nor the mechanism of its action is known. In this report electron paramagnetic resonance (EPR) spectroscopy analyses were used to investigate the local effects of Bcl-2 on membrane lipid peroxidation. Using hydrogen peroxide (H2O2) and amyloid β-peptide (Aβ) as lipoperoxidation initiators, we determined the loss of EPR-detectable paramagnetism of nitroxyl stearate (NS) spin labels 5-NS and 12-NS. In intact cell preparations and postnuclear membrane fractions, Aβ and H2O2 induced significant loss of 5-NS and 12-NS signal amplitude in control PC12 cells, but not PC12 cells expressing Bcl-2. Cells were subjected to differential subcellular fractionation, yielding preparations of plasma membrane and mitochondria. In preparations derived from Bcl-2-expressing cells, both fractions contained Bcl-2 protein. 5-NS and 12-NS signals were significantly decreased following Aβ and H2O2 exposure in control PC12 mitochondrial membranes, and Bcl-2 largely prevented these effects. Plasma membrane preparations containing Bcl-2 were also resistant to radical-induced loss of spin label. Collectively, our data suggest that Bcl-2 is localized to mitochondrial and plasma membranes where it can act locally to suppress oxidative damage induced by Aβ and H2O2, further highlighting the important role of lipid peroxidation in apoptosis.  相似文献   

9.
Aims:  To investigate the infection biology of Colletotrichum sublineolum (isolate CP2126) and defence responses in leaves of resistant (SC146), intermediately resistant (SC326) and susceptible (BTx623) sorghum genotypes.
Methods and Results:  Infection biology and defence responses were studied quantitatively by light microscopy, H2O2 accumulation by DAB staining and HRGP accumulation by immunological methods. Inhibition of conidial germination and appressorium formation may represent prepenetration defence responses on the leaf surface. Inducible defence responses in the resistant genotypes included decreases in formation of appressoria as well as accumulation of H2O2, HRGPs and phytoalexins. Concomitant with these inducible responses, fungal growth was stopped during or just after penetration in genotypes SC146 and SC326. High levels of H2O2 accumulating at late infection stages (5 days after inoculation) in the susceptible genotype BTx623 correlated with necrosis and tissue degeneration.
Conclusions:  The early accumulation of H2O2 and HRGPs indicates roles in defence whereas the late accumulation in genotype BTx623 correlated with successful pathogenesis.
Significance and Impact of the Study:  The fact that there is a significant correlation between induced accumulation of H2O2, papilla formation and cell wall cross-linking, as evidenced by HRGP accumulation, and cessation of pathogen growth in resistant genotypes may help exploit host resistance in sorghum.  相似文献   

10.
The effects of salt stress on antioxidative activities were investigated in a coastal halophyte, Cakile maritima . Two Tunisian accessions, Jerba and Tabarka, were compared. Plants were subjected to 100, 200, or 400 m M NaCl for 20 days. Parameters of oxidative stress [malondialdehyde (MDA), electrolyte leakage (EL), and hydrogen peroxide (H2O2) concentration], activities of several enzymes [superoxide dismutase (SOD), catalase (CAT), peroxydase (POD), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR)], and antioxidant molecules (ascorbate, ASC, and glutathione, GSH) were determined. Growth of Jerba plants was improved at 100 m M NaCl as compared to that of control. Tabarka growth was inhibited by salt at all NaCl concentrations. The relative salt tolerance of Jerba was associated with high antioxidant enzyme activities and glutathione content, together with low MDA content, EL, and H2O2 concentration. Lower antioxidant activities and higher MDA content, EL, and H2O2 concentration were found in Tabarka. As a whole, these data suggest that the capacity to limit oxidative damage is important for salt tolerance of C. maritima .  相似文献   

11.
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Abstract: Mitochondrial complexes I, II, and III were studied in isolated brain mitochondrial preparations with the goal of determining their relative abilities to reduce O2 to hydrogen peroxide (H2O2) or to reduce the alternative electron acceptors nitroblue tetrazolium (NBT) and diphenyliodonium (DPI). Complex I and II stimulation caused H2O2 formation and reduced NBT and DPI as indicated by dichlorodihydrofluorescein oxidation, nitroformazan precipitation, and DPI-mediated enzyme inactivation. The O2 consumption rate was more rapid under complex II (succinate) stimulation than under complex I (NADH) stimulation. In contrast, H2O2 generation and NBT and DPI reduction kinetics were favored by NADH addition but were virtually unobservable during succinate-linked respiration. NADH oxidation was strongly suppressed by rotenone, but NADH-coupled H2O2 flux was accelerated by rotenone. α-Phenyl- N-tert -butyl nitrone (PBN), a compound documented to inhibit oxidative stress in models of stroke, sepsis, and parkinsonism, partially inhibited complex I-stimulated H2O2 flux and NBT reduction and also protected complex I from DPI-mediated inactivation while trapping the phenyl radical product of DPI reduction. The results suggest that complex I may be the principal source of brain mitochondrial H2O2 synthesis, possessing an "electron leak" site upstream from the rotenone binding site (i.e., on the NADH side of the enzyme). The inhibition of H2O2 production by PBN suggests a novel explanation for the broad-spectrum antioxidant and antiinflammatory activity of this nitrone spin trap.  相似文献   

13.
14.
Aims:  Vanadium chloroperoxidase and its directed evolution mutant P395D/L241V/T343A were investigated for their antibacterial and antiviral potential at slightly alkaline pH and at a H2O2 concentration that is low compared to current nonenzymatic formulations.
Methods and Results:  Two bacteria (the Gram-negative Pseudomonas aeruginosa and the Gram-positive Staphylococcus aureus ) and two viruses (the enveloped Herpes Simplex Virus and the nonenveloped Coxsackievirus B4) were incubated with the P395D/L241V/T343A mutant, 10 mmol l−1 H2O2 and 100 mmol l−1 Br at pH 8. Strong microbial reduction was observed and bactericidal and virucidal activities of the mutant were three to six orders of magnitude higher than for the wild-type enzyme.
Conclusions:  The P395D/L241V/T343A mutant of vanadium chloroperoxidase has a broad antimicrobial activity at alkaline conditions.
Significance and Impact of the Study:  For many disinfection formulations, antimicrobial activity at slightly alkaline pH values is required. To date, only the wild-type vanadium chloroperoxidase has been studied for its antibacterial activity, and only at acidic to neutral pH values. Its antiviral activity (e.g. useful for the cleaning of medical equipment) was not studied before. The observed activity for the alkalophilic P395D/L241V/T343A mutant is an important step forward in the application of this robust enzyme as a component in disinfection formulations.  相似文献   

15.
Abstract: In a model recently developed to study the parameters altering vulnerability to oxidative stress, it was shown via image analysis that H2O2-exposed PC12 cells exhibited increased levels of intracellular Ca2+ (baseline), decreases in K+-stimulated Ca2+ levels (peak), and decreased poststimulation Ca2+ clearance (recovery). The present experiments were performed to determine if the response patterns in these parameters to oxidative stress would be altered after modification of membrane lipid composition induced by incubating the PC12 cells with 660 µ M cholesterol (CHL) in the presence or absence of 500 µ M sphingomyelin (SPH) before low (5 µ M ) or high (300 µ M ) H2O2 exposure. Neither CHL nor SPH had synergistic effects with high concentrations of H2O2 on baseline. However, CHL in the presence or absence of SPH reversed the effect of low concentrations of H2O2 on baseline. SPH decreased significantly the cell's ability to clear excess Ca2+ in the presence or absence of H2O2 and increased significantly the level of conjugated dienes (CDs). It is surprising that in the cells pretreated with CHL, the CD levels were not significantly different from controls. However, in the presence of SPH, the effects of CHL on CDs were altered. These results suggest that the ratios of membrane lipids could be of critical importance in determining the vulnerability to oxidative stress and Ca2+ translocation in membranes. This may be of critical importance in aging where there is increased membrane SPH and significant loss of calcium homeostasis.  相似文献   

16.
Abstract. In experiments where mung beans ( Vigna radiata L.) and peas ( Pisum sativum L.) have been pre-exposed to ethylene and afterwards treated with ozone, it has been shown that such ethylenepretreated plants may become more resistant to ozone. Further experiments with hydrogen peroxide (H2O2) and the herbicide paraquat suggest that this increased resistance against ozone depends on the stimulation of ascorbate peroxidase activity which provides cells with increased resistance against the formation of H2O2 which is also formed when plants are fumigated with ozone. These results explain why increased production of ethylene can be observed in plants exposed with ozone or other oxidative stress and clearly demonstrate that in plants, as well as animals, peroxidases protect cells against harmful concentrations of hydroperoxides.  相似文献   

17.
Elevated levels of salicylic acid (SA) are required for the induction of systemic acquired resistance (SAR) in plants. Recently, a salicylic acid-binding protein (SABP) isolated from tobacco was shown to have catalase activity. Based on this finding elevated levels of hydrogen peroxide (H2O2) were postulated to act as a second messenger of SA in the SAR signal transduction pathway. A series of experiments have been carried out to clarify the role of H2O2 in SAR-signaling. No increase of H2O2 was found during the onset of SAR. Induction of the SAR gene, PR-1, by H2O2 and H2O2-inducing chemicals is strongly suppressed in transgenic tobacco plants that express the bacterial salicylate hydroxylase gene, indicating that H2O2 induction of SAR genes is dependent on SA accumulation. Following treatment of plants with increasing concentrations of H2O2, a dose-dependent accumulation of total SA species was found, suggesting that H2O2 may induce PR-1 gene expression through SA accumulation. While the results do not support a role for H2O2 in SAR signaling, it is suggested that SA inhibition of catalase activity may be important in tissues undergoing a hypersensitive response.  相似文献   

18.
The role of hydrogen peroxide (H2O2) and various antioxidants in the regulation of expression of the three Cat and Gst1 genes of maize ( Zea mays L.) has been investigated. Low concentrations of H2O2 appeared to inhibit Cat1 , Cat3 , and Gst1 gene expression, while higher doses strongly induced these genes. Time course experiments indicated that high concentrations of H2O2 induced Cat1 , Cat2 , and Gst1 gene expression to higher levels, and in less time, than lower H2O2 concentrations. Induction of Cat3 was superimposed on the circadian regulation of the gene. These results demonstrate a direct signaling action of H2O2 in the regulation of antioxidant gene responses in maize.The effects of the antioxidant compounds N-acetylcysteine, pyrrolidine dithiocarbamate, hydroquinone, and the electrophile antioxidant responsive element (ARE)-inducer β -naphthoflavone were quite different and specific for each gene/compound/concentration combination examined. The response of each gene to each antioxidant compound tested was unique, suggesting that the ability of these compounds to affect expression of the maize Cat and Gst1 genes may not be the result of a common (antioxidant) mode of action. A putative regulatory ARE motif involved in the regulation of antioxidant and oxidative stress gene responses in mammalian systems is present in the promoter of all three maize catalase genes and we tested its ability to interact with nuclear extracts prepared from 10 days post-imbibition senescing scutella. Protein-DNA interactions in the ARE motif and the U2 snRNA homologous regions of the Cat1 promoter were observed, suggesting that ARE may play a role in the high induction of Cat1 in a tissue which, due to senescence, is under oxidative stress.  相似文献   

19.
Mycobacterial catalases have been suggested as acting as virulence factors by protecting intracellular mycobacteria from reactive oxidative metabolites produced by host phagocytes. Mycobacterium intracellulare , like many other mycobacteria, produces two proteins with catalase activity: a heat-stable catalase (KatE) and an inducible, heat-labile catalase peroxidase (KatG). The M. intracellulare katG gene was cloned, and a plasmid derivative with a 4 bp insertion in the katG coding sequence was constructed and used for site-directed mutagenesis of M. intracellulare 1403 (ATCC 35761). The resulting katG mutant was highly resistant to isoniazid (INH), showed an increased sensitivity to H2O2 and had lost peroxidase and heat-sensitive catalase activity but retained heat-stable catalase activity. The plasmid carrying the katG frameshift allele was also used for mutagenesis of the mouse virulent M. intracellulare isolate D673. After intravenous injection into BALB/c mice, D673 and the isogenic katG mutant showed the same growth kinetics in the spleen, liver and lungs of the infected mice. Our results demonstrate that the KatG catalase peroxidase mediates resistance to H2O2 and susceptibility to INH but is not an essential virulence factor for the survival and growth of M. intracellulare in the mouse.  相似文献   

20.
Aims:  Development of the resazurin microplate method (RMM) as a novel test system for the evaluation of the antimicrobial activity of antiseptics and disinfectants. The validated RMM was subsequently applied for the evaluation of hydrogen peroxide (H2O2) and stabilized H2O2 combination products.
Methods and Results:  The European Committee for Standardization prescribes the plate count challenge test (PCCT) for antiseptic and disinfectant efficacy testing. This protocol was adapted to a microplate-based assay, using resazurin as viability indicator. The RMM was as accurate as the PCCT, had an identical detection limit and showed high intermediate precision. Using the validated RMM, it was shown that H2O2 combined with silver possessed a higher bactericidal and fungicidal activity compared to native H2O2 with and without glycerol.
Conclusions:  Validation showed that the RMM may replace the PCCT. When applying the RMM, H2O2 combined with silver was clearly a more potent disinfectant compared to H2O2 in killing bacteria and fungi.
Significance and Impact of the Study:  The RMM is easier to use for antimicrobial efficacy testing of antiseptics and disinfectants. As the RMM is in accordance with the norms of the European Committee for Standardization, it may become a more cost-effective alternative to the more laborious PCCT reference method. H2O2 with silver may replace native H2O2 to increase overall disinfection efficiency.  相似文献   

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