Decrease In H2O2 Levels Research Articles

Exploring the impact of rice husk biochar on oxidative mechanisms and salt stress tolerance in lettuce plants

Salt stress, which impairs plant growth and induces oxidative stress, presents a major challenge in agriculture. In response, biochar has emerged as a promising soil amendment, capable of enhancing plants’ stress tolerance mechanisms. This study investigated the impact of rice husk biochar (RBC), derived from rice husks, on enhancing salt stress tolerance in lettuce plants grown under greenhouse conditions. Molecular and chemical characterization of the biochar samples was performed using Scanning Electron Microscopy (SEM) and Raman spectroscopy. Salinity reduced the fresh and dry weights of the plants from 25.0 g plant−1 and 1.83 g plant−1 to 20.4 g plant−1 and 1.42 g plant−1, respectively. The application of RBC recovered the growth decline caused by salinity, increasing the fresh and dry weights of the plants to 28.1 g plant−1 and 1.83 g plant−1, respectively. While the concentrations of sodium and chloride in plants decreased with RBC application, potassium and silicon concentrations significantly increased. As a result of salt stress, hydrogen peroxide levels (H2O2) increased in plant tissues, and a decrease in H2O2 levels was observed with an increase in superoxide dismutase, catalase, and ascorbate peroxidase activities. Consequently, RBC proved to be effective in enhancing salt tolerance in lettuce plants. In conclusion, while RBC demonstrates significant potential for enhancing salt tolerance, its successful application depends on several factors such as biochar dosage, application method, soil type, and plant species, underscoring the need for further research to elucidate the mechanisms at play and optimize its use for sustainable soil management in saline conditions.

Progesterone and brassinosteroids synergistically enhance progesterone removal and antioxidant capacity of Solanum nigrum L.

Progesterone (PROG) has been detected at various concentrations in the environment and has adverse effects on humans and wildlife. This work evaluated the impact of PROG in Solanum nigrum L. plants, its removal capacity, and how 2,4-epibrassinolide (24-EBL) affects this process. Three treatments were used: (1) control, (2) irrigation with 0.8 µM PROG, and (3) treatment with 0.8 µM PROG after a pre-treatment with a foliar application of 1 µM 2,4-EBL (PROG/24EBL). After 20 days of treatment, no PROG was detected in the nutrient solution or plant tissues, indicating that the PROG was removed and metabolized. Lipid peroxidation significantly decreased in response to PROG in shoots and roots, and this effect was even more significant for both organs of the PROG/24EBL plants. Additionally, both treatments in both organs showed a decrease in H2O2 levels, and both steroid hormones increased the plants’ antioxidant system at both the biochemical and gene expression levels. In conclusion, S. nigrum can swiftly remove PROG without affecting its growth, and the use of 24-EBL synergistically decreases oxidative damage by increasing the activity of the antioxidant system and enhancing plant PROG removal ability.

Essential oils combat Botrytis cinerea in apples: unveiling sugar, vitamin, and antioxidant dynamics

AbstractThis study investigated the effects of individual and combination applications of EOCs against Botrytis Cinerea in apple fruits, with a focus on sugar, vitamin, and antioxidant enzyme dynamics. In protective and curative treatments, sucrose content varied between 18.9 and 87.9 g.L-1, with the “CT” group exhibiting significantly higher sucrose levels (87.9 g.L-1). Glucose content ranged from 6.2 g.L-1 (“CT” and “C + F”) to 35.5 g.L-1 (“T + C + E + F”). Fructose content varied significantly, with the “F + T + C + E” treatment showing the highest (11.4 g.L-1) and the “CT” group the lowest (2.5 g.L-1). Rhamnose content in the curative treatment reached 14.9 g.L-1 (“F + T”) and in the protective treatment, the “C + E + F” group had the highest (3.3 g.L-1). Galactose content ranged from 0.1 to 13.0 g.L-1. Xylose content in curative treatment ranged from 12.1 to 13.6 g.L-1, with the combination “F + T” displaying the highest. In preventive treatment, arabinose content ranged from 0.7 to 3.0 g.L-1, with the “T + C + F” group having the highest. In terms of vitamins, the combination “T + F” showed the highest B1 (25.4 mg.100 g-1) and B2 (24.6 mg.100 g-1) content. Vitamin A, B1, and B2 increased in the “F + T” group, and vitamin C increased in the “F + T + C” group (33.4 mg.100 g-1). The quantification of oxidative stress markers and antioxidant enzymes revealed significant reductions in H2O2, MDA, and proline levels in EOC applications. In preventive treatment, the combination “T + C + E + F” exhibited the most effective improvement in SOD activity (556.5 EU mg-1 ), CAT activity increased significantly in the “T + C + F” group (189.3 EU mg-1), and APX activity saw the highest increase in the “T + C + E + F” group (185.6 EU mg-1). Contrastingly, curative treatments showed higher H2O2, MDA, and proline levels. The most significant decrease in H2O2 level occurred in the “T + C + E + F” group (36.7 nmol.g-1), and a significant decrease in MDA level was noted in the same group. Notable changes were observed in the activities of antioxidant enzymes, with the “F + T + C + E” group displaying the highest SOD activity (440.7 EU mg-1), and the “F + T” group showing the highest GST activity (542.0 EU mg-1). This research provided comprehensive insights into the biochemical responses of apple fruits to EOC treatments, offering potential strategies for effective fungal management in agriculture.

Redox differences between rat neonatal and adult cardiomyocytes under hypoxia

It is generally accepted that oxidative stress plays a key role in the development of ischemia-reperfusion injury in ischemic heart disease. However, the mechanisms how reactive oxygen species trigger cellular damage are not fully understood. Our study investigates redox state and highly reactive substances within neonatal and adult cardiomyocytes under hypoxia conditions. We have found that hypoxia induced an increase in H2O2 production in adult cardiomyocytes, while neonatal cardiomyocytes experienced a decrease in H2O2 levels. This finding correlates with our observation of the difference between the electron transport chain (ETC) properties and mitochondria amount in adult and neonatal cells. We demonstrated that in adult cardiomyocytes hypoxia caused the significant increase in the ETC loading with electrons compared to normoxia. On the contrary, in neonatal cardiomyocytes ETC loading with electrons was similar under both normoxic and hypoxic conditions that could be due to ETC non-functional state and the absence of the electrons transfer to O2 under normoxia. In addition to the variations in H2O2 production, we also noted consistent pH dynamics under hypoxic conditions. Notably, the pH levels exhibited a similar decrease in both cell types, thus, acidosis is a more universal cellular response to hypoxia. We also demonstrated that the amount of mitochondria and the levels of cardiac isoforms of troponin I, troponin T, myoglobin and GAPDH were significantly higher in adult cardiomyocytes compared to neonatal ones. Remarkably, we found out that under hypoxia, the levels of cardiac isoforms of troponin T, myoglobin, and GAPDH were elevated in adult cardiomyocytes, while their level in neonatal cells remained unchanged. Obtained data contribute to the understanding of the mechanisms of neonatal cardiomyocytes’ resistance to hypoxia and the ability to maintain the metabolic homeostasis in contrast to adult ones.

Transgenic tobacco plants overexpressing a cold-adaptive nitroreductase gene exhibited enhanced 2,4-dinitrotoluene detoxification rate at low temperature

Plants encounter many environmental factors such as low and high temperatures during phytoremediation processes. In this study, our aim was to produce the transgenic tobacco plants by using a newly characterized bacterial nitroreductase, Ntr, which was active at a broad range temperature in order to detoxify 2,4-dinitrotoluene (2,4-DNT) at lower temperature. The presence of Ntr and its heterologous expression was verified in T1 transgenic plants and their growing ability were determined under toxic amount of 2,4-DNT (35 µM). Fresh weight and dry weight of transgenic plants were significantly higher than wild type (WT) under toxic 2,4-DNT at 22 °C, indicating higher growth capacity of the transgenics. Transgenic plants also showed a higher tolerance than WT when exposed to 2,4-DNT at 15 °C. Moreover, transformation rate of 2,4-DNT was gradually decreased through decreasing temperatures in WT media, however, it was increased through decreasing temperatures in transgenic plant TR3-25 media and it had the highest transformation rate (54%) of 2,4-DNT at 4 °C. Correlatively, 2,4-DNT treatment at 4 °C led to a significant decrease in H2O2 level in transgenic plants. Thus, transgenic plants overexpressing nitroreductase might have an important advantage for phytoremediation of toxic nitroaromatic compounds in field applications at low temperatures.

Melatonin application confers enhanced salt tolerance by regulating Na+ and Cl− accumulation in rice

The mitigating effects of melatonin (MT) treatment on salt-stressed seed germination capacity and of MT pretreatment (including the whole period of seed germination and seedling cultivation) on the salt tolerance of two rice (Oryza sativa L. ssp. japonica) cultivars, Liaojing 4 (LJ4, salt tolerant) and Nipponbare (Nipp, salt sensitive), and the related physiological and molecular events were investigated in this study. The results showed that when additional MT solutions (10–500 μM) were added, the NaCl-decreased seed germination potential (GP), germination index (GI) and vigor index (VI) of LJ4 and Nipp were clearly restored. When MT pretreatment occurred during the period of seed germination and seedling cultivation prior to NaCl stress, relative electrolytic leakage in roots and leaves clearly decreased and thus restored the root vigor and growth of both plants. This could be fulfilled by multiple physiological mechanisms. For example, improving seed germination ability (GP, GI and VI), strengthening root vigor, reducing Na+ and Cl− contents in roots and leaves (especially for Cl− in roots and Na+ in leaves), and enhancing the activities of antioxidant enzymes (such as catalase and superoxide dismutase) in roots and leaves resulted in a decrease in H2O2 level. Moreover, the reduced contents of Na+ and Cl− in the roots and leaves of both salt-stressed rice plants under MT pretreatment displayed clear relations with the enhanced transcription of OsSOS1 in roots and of OsCLC1 and OsCLC2 in roots and leaves. These results could indicate that soaking with MT during seed germination and/or root application of MT at the seedling stage are very simple operations that require small doses and can effectively solve the problems of low germination rate and poor seedling establishment in saline soils. Therefore, these results provide a theoretical basis and technical support for the chemical regulation of salt tolerance and cultivation practices of rice and other crops in saline areas.

Sensitivity of two green microalgae to copper stress: Growth, oxidative and antioxidants analyses

Depending on species, heavy metals, including copper (Cu), differentially affect algal growth and metabolism. Here, we aim to evaluate the differential responses of two green microalgae, Chlorella sorokiniana and Scenedesmus acuminatus, exposed to sub-lethal doses of Cu (25 and 50µM, respectively) for 7 days. The changes in growth, oxidative damage markers, and antioxidants were analysed. We found that S. acuminatus could acclimatise during long-term exposure to Cu stress. S. acuminatus accumulated lower Cu content and showed a slight decrease in H2O2 levels when compared to C. sorokiniana. Cu stress induced membrane damage in the two microalgae species, however, this increase was slightly lower in S. acuminatus. To mitigate Cu stress impact, C. sorkiniana markedly increased proline, polyphenols, flavonoids, tocopherols, glutathione levels, as well as the activities of GST, APX, GR and SOD enzymes, which could explain less-stress sensitivity. On the other hand, S. acuminatus exhibited significant increases in proline, polyphenol, and tocopherol contents. Activity levels of POX, APX, GR and SOD enzymes, were also increased. These results suggest that the two microalgae differentially induced the antioxidant defence system to neutralise the oxidative damage induced by Cu stress. This study also provided new data for Cu tolerance and Cu removal abilities of two microalgal species, which commonly exist in surface water bodies, where low Cu uptake and efficient antioxidant defence system protected S. acuminatus against oxidative stress induced by Cu stress. This makes it feasible for treatment of Cu contaminated waters.

332 - Ethanol Withdrawal Induces Oxidative Damage and Hypertension: Role of AT1 Receptor Activation

Ethanol withdrawal (EW) is defined as the abrupt termination of excessive long-term ethanol consumption. EW causes oxidative damage and hypertension. We used a model of EW involving abrupt cessation of ethanol consumption (3-9% ethanol v/v for 21 days) for 48 hours. During the 48h period of EW, male Wistar rats were treated with losartan (LST - 10 mg/kg/daily, gavage) to investigate the role of angiotensin II on the systemic and tissue oxidative stress induced by EW. Oxidative markers (superoxide anion - O2–; thiobarbituric acid reactive substances – TBARS; hydrogen peroxide - H2O2), nitrate/nitrite (NOx), and antioxidant activity (superoxide dismutase – SOD; glutathione - GSH) were evaluated in plasma and aorta. Systolic blood pressure (SBP) was measured by plethysmography. Two-way ANOVA followed by Bonferroni test was used to analyze the results. Ethics Committee protocol (#11.1.1432.53.5). EW induced an imbalance in the production of reactive oxygen species (ROS) in the aortic tissue, represented by an increase in O2– generation and TBARS levels, and a decrease in H2O2 levels. Qualitative analysis in situ using the dyes DHE and DCFH-DA corroborated these findings. LST prevented these responses. In plasma, EW increased TBARS production and treatment with LST prevented this response. EW induced progression in oxidative damage and decreased the levels of NOx in plasma and aorta, and treatment with LST prevented these responses. No difference was found in plasma or aortic SOD activity. In plasma, but not aorta, EW increased GSH levels and LST did not prevent this response. Finally, we observed that LST prevented EW-induced increase in SBP. These findings show that angiotensin II plays a role on EW-induced oxidative damage and hypertension.

Natural Variation of Cold Deacclimation Correlates with Variation of Cold-Acclimation of the Plastid Antioxidant System in Arabidopsis thaliana Accessions.

Temperature variations impact on the balance between photosynthetic electron transport and electron-consuming assimilation reactions and transiently increase generation of reactive oxygen species (ROS). Previous studies demonstrated that the expression of C-repeat binding factors (CBFs), which activate cold acclimation reactions, respond to chloroplast ROS signals and that cold deacclimation is partly halted for days after the transfer of acclimated plants to optimal growth conditions in four Arabidopsis accessions from cold-continental habitats. We hypothesized that these accessions differ from others in the regulation of the plastid antioxidant system (PAS). In the present study, we compared the expression intensity of the 12 most prominent PAS genes for peroxidases, superoxide dismutase and low molecular weight antioxidant regenerating enzymes in 10 Arabidopsis accessions with regulation of CBF and COR (cold regulated genes) transcript levels and cold-regulated metabolite levels prior to cold, after 2 week long cold acclimation and during the first 3 days of deacclimation. In the accessions with prolonged activation of cold responses, by trend, weaker induction of various cold-inducible PAS genes and stronger decreases in the expression of negatively cold-regulated PAS genes were observed. Low PAS gene expression delayed the post-cold decrease in H2O2 levels after transfer of the plants from cold to optimal growth conditions. We conclude that weaker expression of various PAS genes in the cold is an adapted strategy of the Arabidopsis accessions N14, N13, Ms-0, and Kas-1 to avoid full inactivation of cold-responses in the first days after the end of the cold period.

Reduction of histopathological images through a decrease in H2O2 levels in diabetic rats with polysaccharide peptides

Atherosclerosis occurs as a result of the oxidation of low-density lipoprotein (LDL) deposits, which later form plaques. Hyperglycemia, which occurs in patients with type 2 diabetes mellitus, is a risk factor for this kind of vascular damage. Oxidative stress from hydrogen peroxide (H2O2) is increased in patients with hyperglycemia and therefore an antioxidant agent is required to prevent the destruction of the walls of blood vessels. This study aimed to show that Ganoderma lucidum polysaccharide peptide (PsP) can decrease the formation of H2O2. The study was an experimental in vivo post-test with control group design. Thirty-five Wistar rats (Rattus norwegicus) were divided into five groups (a normal diet group, a hypercholesterol diet group, and hypercholesterol groups that received doses of 50 mg/kg, 150 mg/kg, and 300 mg/kg body weight PsP). The parameters determined in this study were the level of H2O2, the lipid profile, insulin resistance, and the amounts of perivascular adipocyte tissue (PVAT), foam cells, and plaques. Each treatment group showed significant results for the administration of PsP using the one-way analysis of variance test (p < 0.050) for the reduction of H2O2 (p = 0.003), the lipid profile (cholesterol total and triglyceride; p = 0.010, p = 0.001), insulin resistance (p = 0.003), the amount of PVAT (p <0.001), and plaques (p <0.001). The decrease in foam cells was insignificant (p = 0.149), although an obvious pattern of reduction as a result of PsP treatment was observed. PsP from G. lucidum is a potent antioxidant and may prevent the pathophysiology of atherosclerosis in patients with type 2 diabetes mellitus. The optimum dose in patients with type 2 diabetes mellitus is 300 mg/kg body weight. Further studies are required to determine the antioxidant effects of G. lucidum PsP and its benefits in the management of type 2 diabetes mellitus.

Over-expression of catalase in myeloid cells confers acute protection following myocardial infarction.

Cardiovascular disease is the leading cause of death in the United States and new treatment options are greatly needed. Oxidative stress is increased following myocardial infarction and levels of antioxidants decrease, causing imbalance that leads to dysfunction. Therapy involving catalase, the endogenous scavenger of hydrogen peroxide (H2O2), has been met with mixed results. When over-expressed in cardiomyocytes from birth, catalase improves function following injury. When expressed in the same cells in an inducible manner, catalase showed a time-dependent response with no acute benefit, but a chronic benefit due to altered remodeling. In myeloid cells, catalase over-expression reduced angiogenesis during hindlimb ischemia and prevented monocyte migration. In the present study, due to the large inflammatory response following infarction, we examined myeloid-specific catalase over-expression on post-infarct healing. We found a significant increase in catalase levels following infarction that led to a decrease in H2O2 levels, leading to improved acute function. This increase in function could be attributed to reduced infarct size and improved angiogenesis. Despite these initial improvements, there was no improvement in chronic function, likely due to increased fibrosis. These data combined with what has been previously shown underscore the need for temporal, cell-specific catalase delivery as a potential therapeutic option.

Hydrogen peroxide scavenging mechanisms are components of Medicago truncatula partial resistance to Aphanomyces euteiches

The biochemical processes underlying the expression of resistance in the roots of Medicago truncatula against Aphanomyces euteiches infection was investigated, with emphasis on oxidative stress. The levels of H2O2, superoxide dismutase, peroxidase, ascorbate peroxidase, catalase, soluble phenolics and lignin were measured in the roots of two lines, A17 partially resistant and F83005.5 susceptible to A. euteiches at three infection stages; penetration of the epidermis (1 dpi), colonization of the cortex (3 dpi) and invasion of the root stele (6 dpi). A rapid and large decrease of the H2O2 levels in A17 roots occurred. However, in F83005.5 roots, the decrease in H2O2 levels was delayed until 3 dpi. In A17 roots, the activities of ascorbate peroxidase, peroxidase and catalase were induced as early as 1 dpi, whereas a general decrease in the activity of the four antioxidant enzymes was observed in F83005.5 roots. The levels of soluble phenolics and lignin were increased in A17 roots at 3 and 6 dpi, respectively. The H2O2 levels were negatively correlated to ascorbate peroxidase, catalase and lignin production at 1, 3 and 6 dpi, respectively in A17 roots. Physiological concentrations of H2O2 found in M. truncatula infected roots had no detrimental effect on the in vitro growth of this oomycete. Our data suggest that H2O2 does not have a direct antimicrobial effect on M. truncatula resistance to A. euteiches, but is involved in cell wall strengthening around the root stele, preventing pathogen invasion of the vascular tissues.

COMPARISON BETWEEN NORMAL COFFEE AND DECAFFEINATED COFFEE EFFECTS ON LYMPHOCYTES AND MACROPHAGES: ROLE OF THE ANTIOXIDANT ACTIVITY OF CAFFEINE

ABSTRACT Coffee (Coffea arabica L.) presents antioxidant effects. Due to negative effects of caffeine (Ca), more people consume decaffeinated coffee. Reactive oxygen species are involved in immune cell physiology controlling proliferation, death and cellular metabolism. The aim of this study was to evaluate the influence of Ca in the effect of normal and decaffeinated coffee on normal mice lymphocytes and macrophages. It were assayed MTT, nitroblue tetrazolium reduction, proliferation assays and superoxide and catalase-like activities were determined. The decaffeinated coffee induced a decrease in lymphocytes proliferation in all concentrations assayed; this effect was related to an increase of superoxide anion and with the absence of Ca, which by itself increased lymphocytes proliferation through a decrease in H2O2 level by CAT activity “per se.” On macrophages, both extracts induced cell activation not related to the presence of Ca. In conclusion, caffeinated coffee could be better than decaffeinated coffee in the maintenance of the oxidative balance in lymphocytes cells. PRACTICAL APPLICATIONS Coffee has become one of the most widely consumed psychoactive beverages. A major compound in coffee is caffeine (Ca). Because of the negative effects of Ca, more people consume decaffeinated coffee. Decaffeinated coffee would be able to exert negative properties on redox equilibrium in cells. The Ca in coffee could protect cells from death. It is proposed that it may be more beneficial to drink normal coffee than decaffeinated coffee as antioxidant to maintain redox equilibrium in cells. This work assists in the knowledge of the properties of coffee in order to select beverages with less negative effects for human health.

Bone Marrow Mesenchymal Stromal Cells Regulate the Metabolism of H2O2 In Human Leukemic Cells.

AbstractAbstract 1058Redox metabolism plays an important role in self-renewal and differentiation of hematopoietic cells and it has been recently established by the Guy Sauvageau's group (Institute for Research in Immunology and Cancer, MontreÌal, QC) that glutathione peroxydase 3 (GPx-3) promotes competitiveness of Hoxa9-Meis1 induced leukemic stem cells in which Gpx3 overexpression is concomitant of a decrease in H2O2 level and inactivation of p38 MAPK (Herault O et al, ASH annual meeting, 2010 - submitted). Leukemic cells located in the bone marrow (BM) are interacting with a microenvironment which plays a crucial role in the development and progression of leukemia. Mesenchymal stromal cells (MSCs) constitute a population of multipotential cells giving rise to the different hematopoietic microenvironmental cells (adipocytes, osteoblasts, chondrocytes, and vascular-smooth muscle-like hematopoietic supportive stromal cells). The aim of our study was to evaluate the effects of MSC-contact on the GPx-3/H2O2/p38 MAPK axis in human leukemic cells and to assess the cell cycle changes associated with the modification of H2O2 metabolism.BM MSCs were obtained from informed and consenting patients undergoing orthopedic surgery, following a procedure approved by the local ethical committee. Nucleated cells harvested from the iliac crest were seeded (5.104 cells per cm2) in α-MEM supplemented with 10% fetal calf serum (FCS), 20 mmol/l L-glutamine, and 100 units/mL penicillin G. Cells were incubated at 37°C in 95% humidified air and 5% CO2. When fully confluent, the layer of adherent cells was trypsinized (0.25% trypsin-EDTA), and the cells were resuspended in culture medium and seeded at 103 cells per cm2 (passage 1 - P1). BM MSCs were used at P2 in all experiments. The three-lineage mesenchymal differentiation of the BM MSCs used was systematically checked by culturing cells in adipogenic, chondrogenic, and osteogenic induction media as previously described (Delorme et al, Blood 2008, 111:2631). The human KG1a leukemic cell line (FAB M0/M1 CD34+ leukemic cells) was cultured in RPMI 1640 with 20 mmoL/L L-glutamine supplemented with 10% FCS, 100 units/mL penicillin G, and 100 mg/mL streptomycin. KG1a cells were seeded at 1.5 105 cells/cm2 and cocultured with MSCs for 72 h. We have defined two distinct localizations of leukemic cells relative to MSC layer: those in supernatant (non-adherent cells) and cells adhering on the surface of MSCs. The expression of antioxydative enzymes, H2O2 level, p38 MAPK activation (T180/Y182), cell cycle, proliferation and immunophenotype of these two cell fractions were evaluated at day 0 and day 3. The expression of SOD1, SOD2, SOD3, CAT, TXN, TXN2, GLRX, GLRX2, GLRX3, GLRX5, PRDX, PRDX2, PDRX3, PRDX4, PRDX5, PRDX6, GPX1, GPX2, GPX3, GPX4, GPX5, GPX6, GPX7 and GSR antioxydative genes and CDKN1A (p21CIP1) gene was quantified by qRT-PCR (Universal ProbeLibrary, Roche). SDS-PAGE and western-blot experiments were realized to quantify GPx-3 expression and p38 MAPK activation. Flow cytometry studies were performed: (a) to quantify H2O2 level by dichlorodihydrofluorescein diacetate (DCF-DA) staining; (b) to analyze the cell cycle by staining with 7-aminoactinomycin D (7AAD), Alexa Fluor®488-conjugated anti-human Ki67 and Alexa Fluor®488-conjugated anti-phospho-histone H3 (ser10) antibodies; (c) to track the cell divisions with carboxyfluorescein diacetate N-succinimidyl ester (CFSE).Supernatant of MSCs did not modify the GPx-3/H2O2/p38 MAPK axis in KG1a cells. Conversely, when compared with cells in the supernatant of MSCs, adhering KG1a cells were characterized by the exclusive overexpression of GPX3 antioxydative gene, the induction of GPx-3 production, a major decrease in H2O2 concentration and the inactivation of p38 MAPK. These effects were concomitant of cell cycle inhibition: increase in G0 phase, decrease in S and M phase, overexpression of CDKN1A and reduced mitotic activity (CFSE).Altogether these findings suggest that the bone marrow microenvironment plays a key role in the regulation of the oxidative metabolism of leukemic cells by promoting the inhibition of the H2O2/p38 MAPK axis via the induction of GPx-3. Modulation of the GPx-3/H2O2/p38 MAPK pathway by targeting of microenvironmental interactions in leukemia may have clinical relevance and it will be important to verify if these results can be extended in vivo to other models of human leukemias. Disclosures:No relevant conflicts of interest to declare.

Temporal Effects of Catalase Overexpression on Healing After Myocardial Infarction

Reactive oxygen species, such as hydrogen peroxide (H(2)O(2)), contribute to progression of dysfunction after myocardial infarction (MI). However, chronic overexpression studies do not agree with acute protein delivery studies. The purpose of the present study was to assess the temporal role of cardiomyocyte-derived H(2)O(2) scavenging on cardiac function after infarction using an inducible system. We developed a tamoxifen-inducible, cardiomyocyte-specific, catalase-overexpressing mouse. Catalase overexpression was induced either 5 days before or after MI. Mice exhibited a 3-fold increase in cardiac catalase activity that was associated with a significant decrease in H(2)O(2) levels at both 7 and 21 days. However, cardiac function improved only at the later time point. Proinflammatory and fibrotic genes were acutely upregulated after MI, but catalase overexpression abolished the increase despite no acute change in function. This led to reduced overall scar formation, with lower levels of Collagen 1A and increased contractile Collagen 3A expression at 21 days. In contrast to prior studies, there were no acute functional improvements with physiological catalase overexpression before MI. Scavenging of H(2)O(2), however, reduced proinflammatory cytokines and altered cardiac collagen isoforms, associated with an improvement in cardiac function after 21 days. Our results suggest that sustained H(2)O(2) levels rather than acute levels immediately after MI may be critical in directing remodeling and cardiac function at later time points.

Mechanism of Tolerance to Drought in Sugarcane Plant Enhanced by Foliage Dressing of Abscisic Acid under Water Stress

Drought is a major limiting factor for sugarcane growth.Abscisic acid (ABA) regulates much important plant physiological and biochemical processes,and induces tolerance to different stresses including drought.Understanding the mechanism of tolerance to drought in sugarcane plant with foliage dressing of ABA under water stress would facilitate breeding and field management for improving drought resistance.Thus,an experiment was set up to investigate the interrelationship between drought induced ABA biosynthesis and antioxidative defense system,and to confer the farther role of foliar application of ABA in imparting drought tolerance to the sugarcane plant.The treatments were: T1 (drought),T2 (drought + foliar application of 15 μmol L–1 ABA) and C (control,normal irrigation) using a drought tolerant cultivar ROC22.The results showed that drought treatment (T1) enhanced the ABA concentration in leaf that was significantly higher in combined treatment (T2),suggesting the ABA biosynthesis was triggered in leaf by the ABA application.Both T1 and T2 resulted in an increase in proline,H2O2 and MDA contents while the exogenous ABA alleviated the increase in MDA content.ABA application decreased the degradation of chlorophyll,and counteracted,at least in part,the decrease in maximal PSII efficiency (Fv/Fm) and quantum efficiency of PSII (ΦPSII).Overproduction of H2O2 in T1 was followed by increasing activities of CAT,GPX,GR,and APX,which was further improved by the ABA treatment (T2).A decrease in H2O2 level with increasing stress in T2 showed that ABA highly induced antioxidative defense system which was found to be vanished progressively in T1.The results clearly suggest that the tolerant cultivar showed an enhanced protective system against drought conditions,and the foliar application of ABA further improved its tolerance by triggering the over expression of antioxidative defense system.

Role and interrelationship of PTPases and H2O2 in light/dark-regulated stomatal movement in Vicia faba

Role and interrelationship of protein tyrosine phosphatases (PTPases) and H2O2 in light/dark-regulated stomatal movement in Vicia faba were investigated by epidermal strip bioassay, laser-scanning confocal microscopy and assays of PTPase activity. Our results indicate that phenylarsine oxide (PAO), a specific inhibitor of PTPases, ascorbic acid (ASA), an important reducing substrate for H2O2 removal, and catalase (CAT), one of the H2O2 scavenging enzymes, did not cause any change of stomatal aperture in light, but remarkably prevented dark-induced stomatal closure. Exogenous H2O2 had no obvious effect on stomatal aperture in the dark, but significantly induced stomatal closure in light. Both PTPase activity in epidermal strips and endogenous H2O2 level in guard cells in the dark were higher than those in light. The results showed that both PTPases and H2O2 mediate light/dark-regulated stomatal movement, that dark-induced stomatal closure requires the activation of PTPases and the enhancement of H2O2 levels in guard cells, and stomatal opening caused by light is associated with the inactivation of PTPases and the reduction of H2O2 levels in guard cells. Additionally, like ASA and CAT, PAO abolished dark-, exogenous H2O2-induced stomatal closure and dichlorofluorescein fluorescence in guard cells, indicating that activation of PTPases can enhance H2O2 levels probably via suppressing the decrease of H2O2 levels in guard cells. On the other hand, similar to PAO, ASA and CAT evidently prevented dark-, exogenous H2O2-induced stomatal closure and obviously inactivated PTPases in the dark. However, exogenous H2O2 significantly activated PTPases in light. The results show that H2O2 can induce activation of PTPases. Taken together, the present results provide evidence that both H2O2 and PTPases are involved in light/dark-regulated stomatal movement, and the interaction between H2O2 and PTPases plays a pivotal role in light/dark signal transduction process in guard cells.

Essential requirement of reduced glutathione (GSH) for the anti-oxidant effect of the flavonoid quercetin

We have analyzed the anti- or pro-oxidant effects of the flavonoid quercetin (QU) by evaluating, in U937 cell line, hydrogen peroxide (H2O2), superoxide anion reduced glutathione (GSH) content, mitochondrial membrane potential, DNA content, phosphatidylserine exposure on the outer face of the plasma membrane and cell viability. Polychromatic flow cytometry was used to evaluate in the same cells several functional parameters. For short periods of treatment QU exerted an anti-oxidant effect (decrease in H2O2 levels), whereas for long periods it showed a pro-oxidant activity (increase in ). In these conditions, GSH content was reduced, and this correlated with a lack of anti-oxidant activity of QU, which in turn could be correlated with proapoptotic activity of this molecule. Thus, QU can exert different effects (anti-/prooxidant) depending on exposure times and oxidative balance, and in particular on stores of GSH.

The Overexpression Catalase Reduces NO‐Mediated Inhibition of Endothelial NO Synthase

Previously, we have demonstrated that increased superoxide generation plays a role in the nitric oxide (NO)-mediated inhibition of endothelial NO synthase (eNOS) in endothelial cells (ECs) and that the overexpression of SOD1 could reduce the inhibitory effect of NO. However, SOD1 overexpression did not completely abolish the inhibition of eNOS by NO, indicating the presence of other inhibitory mechanisms. Because superoxide can be dismutated into hydrogen peroxide (H2O2), in this study we determined whether exposure of ECs to NO resulted in increased generation of H2O2 and the potential role of H2O2 in eNOS inhibition. Our results indicated that H2O2 levels were increased in response to NO. Using adenoviral-mediated infection, we demonstrated that catalase overexpression both increased basal eNOS activity in the absence of NO and provided a significant protective effect on eNOS activity in the presence of NO. This protective effect was associated with a significant decrease in H2O2 levels in the presence of NO. In conclusion, our results indicate that increased levels of H2O2 may be involved in the inhibition of eNOS by NO and that the scavenging of H2O2 may be useful to prevent eNOS inhibition during treatments that involve inhaled NO or NO donors.

Historic trend of the levels of atmospheric H2O2 during 1960's – 1980's in Los Angeles

The historic trend of the levels of gaseous H2O2 during 1960's–1980's in Los Angeles was assessed from field date and numerical simulations. The results indicate that during 1960's–1970's concentrations of H2O2, as well as O3, were likely to have been higher than those during 1980's, For the period 1969–1987, predicted summer peak concentrations of H2O2 and O3 in the ground level atmosphere were in a range of 6–10 ppb and 200–350ppb, respectively. Also H2O2 and 03 concentrations decreased by about 35% and 42% respectively from the levels of 1975 to 1987. Model simulations indicated that the reduction of NMHC and CO emissions from industrial and automotive sources have resulted in the decrease in H2O2 levels during the late 1970's–1980's, whereas the reduction of NMHC, CO and NOx emissions have resulted in lower O3 levels. The role of H2O2 as an oxidant for SO2 and as a possible toxin on trees in Los Angeles and surrounding mountains during the past decades are discussed. From the historic data of atmospheric levels of sulfate in Los Angeles, we suggest that the decrease in the levels of H2O2 and O3 may have contributed to the decrease in sulfite levels during the 1980's.