Showing papers on "Catalase published in 2011"

Boronate Oxidation as a Bioorthogonal Reaction Approach for Studying the Chemistry of Hydrogen Peroxide in Living Systems

Abstract: Reactive oxygen species (ROS), such as hydrogen peroxide, are important products of oxygen metabolism that, when misregulated, can accumulate and cause oxidative stress inside cells. Accordingly, organisms have evolved molecular systems, including antioxidant metalloenzymes (such as superoxide dismutase and catalase) and an array of thiol-based redox couples, to neutralize this threat to the cell when it occurs. On the other hand, emerging evidence shows that the controlled generation of ROS, particularly H2O2, is necessary to maintain cellular fitness. The identification of NADPH oxidase enzymes, which generate specific ROS and reside in virtually all cell types throughout the body, is a prime example. Indeed, a growing body of work shows that H2O2 and other ROS have essential functions in healthy physiological signaling pathways.The signal–stress dichotomy of H2O2 serves as a source of motivation for disentangling its beneficial from its detrimental effects on living systems. Molecular imaging of this o...

Environmentally Persistent Free Radicals (EPFRs). 1. Generation of Reactive Oxygen Species in Aqueous Solutions

Abstract: Reactive oxygen species (ROS) generated by environmentally persistent free radicals (EPFRs) of 2-monochlorophenol, associated with CuO/silica particles, were detected using the chemical spin trap, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), in conjunction with electron paramagnetic resonance (EPR) spectroscopy. Yields of hydroxyl radical (•OH), superoxide anion radical (O2•–), and hydrogen peroxide (H2O2) generated by EPFR–particle systems were reported. Failure to trap superoxide radicals in aqueous solvent, formed from reaction of EPFRs with molecular oxygen, results from fast transformation of the superoxide to hydrogen peroxide. However, formation of superoxide as an intermediate product in hydroxyl radical formation in aprotic solutions of dimethyl sulfoxide (DMSO) and acetonitrile (AcN) was observed. Experiments with superoxide dismutase (SOD) and catalase (CAT) confirmed formation of superoxide and hydrogen peroxide, respectively, in the presence of EPFRs. The large number of hydroxyl radicals formed ...

Production and Detection of Reactive Oxygen Species (ROS) in Cancers

Abstract: Reactive oxygen species include a number of molecules that damage DNA and RNA and oxidize proteins and lipids (lipid peroxydation). These reactive molecules contain an oxygen and include H(2;)O(2;) (hydrogen peroxide), NO (nitric oxide), O(2;)(-) (oxide anion), peroxynitrite (ONOO(-)), hydrochlorous acid (HOCl), and hydroxyl radical (OH(-)). Oxidative species are produced not only under pathological situations (cancers, ischemic/reperfusion, neurologic and cardiovascular pathologies, infectious diseases, inflammatory diseases, autoimmune diseases , etc…) but also during physiological (non-pathological) situations such as cellular metabolism. Indeed, ROS play important roles in many cellular signaling pathways (proliferation, cell activation, migration etc..). ROS can be detrimental (it is then referred to as "oxidative and nitrosative stress") when produced in high amounts in the intracellular compartments and cells generally respond to ROS by upregulating antioxidants such as superoxide dismutase (SOD) and catalase (CAT), glutathione peroxidase (GPx) and glutathione (GSH) that protects them by converting dangerous free radicals to harmless molecules (i.e. water). Vitamins C and E have also been described as ROS scavengers (antioxidants). Free radicals are beneficial in low amounts. Macrophage and neutrophils-mediated immune responses involve the production and release of NO, which inhibits viruses, pathogens and tumor proliferation. NO also reacts with other ROS and thus, also has a role as a detoxifier (ROS scavenger). Finally NO acts on vessels to regulate blood flow which is important for the adaptation of muscle to prolonged exercise. Several publications have also demonstrated that ROS are involved in insulin sensitivity. Numerous methods to evaluate ROS production are available. In this article we propose several simple, fast, and affordable assays; these assays have been validated by many publications and are routinely used to detect ROS or its effects in mammalian cells. While some of these assays detect multiple ROS, others detect only a single ROS.

Plants as Biofactories: Physiological Role of Reactive Oxygen Species on the Accumulation of Phenolic Antioxidants in Carrot Tissue under Wounding and Hyperoxia Stress

Abstract: Plants subjected to postharvest abiotic stresses synthesize secondary metabolites with health-promoting properties. Here, we report the potential use of carrots (Daucus carota) as biofactories of caffeoylquinic acids when subjected to wounding and hyperoxia stresses. Wounding stress induced an increase of ∼287% in total phenolic content (PC) in carrots stored for 48 h at 20 °C. This increase was higher (∼349%) in the wounded tissue treated with hyperoxia stress. To further understand the physiological role of reactive oxygen species (ROS) as a signaling molecule for the stress-induced accumulation of phenolics in carrots, the respiration rate as well as the enzymatic activities of NADPH oxidase, superoxide dismutase, ascorbate peroxidase, and catalase were evaluated. Likewise, shredded carrots were treated with diphenyleneiodonium chloride solution to block NADPH oxidase ROS productions, and the phenylalanine ammonia lyase activity and total PC were evaluated. Results demonstrated that ROS play a key role as a signaling molecule for the stress-induced accumulation of PC in carrots.

Hydrogen peroxide fuels aging, inflammation, cancer metabolism and metastasis: the seed and soil also needs "fertilizer".

Abstract: In 1889, Dr. Stephen Paget proposed the "seed and soil" hypothesis, which states that cancer cells (the seeds) need the proper microenvironment (the soil) for them to grow, spread and metastasize systemically. In this hypothesis, Dr. Paget rightfully recognized that the tumor microenvironment has an important role to play in cancer progression and metastasis. In this regard, a series of recent studies have elegantly shown that the production of hydrogen peroxide, by both cancer cells and cancer-associated fibroblasts, may provide the necessary "fertilizer," by driving accelerated aging, DNA damage, inflammation and cancer metabolism, in the tumor microenvironment. By secreting hydrogen peroxide, cancer cells and fibroblasts are mimicking the behavior of immune cells (macrophages/neutrophils), driving local and systemic inflammation, via the innate immune response (NFκB). Thus, we should consider using various therapeutic strategies (such as catalase and/or other anti-oxidants) to neutralize the production of cancer-associated hydrogen peroxide, thereby preventing tumor-stroma co-evolution and metastasis. The implications of these findings for overcoming chemo-resistance in cancer cells are also discussed in the context of hydrogen peroxide production and cancer metabolism.

Peroxisome-Generated Hydrogen Peroxide as Important Mediator of Lipotoxicity in Insulin-Producing Cells

Abstract: OBJECTIVE Type 2 diabetes is a complex disease that is accompanied by elevated levels of nonesterified fatty acids (NEFAs), which contribute to β-cell dysfunction and β-cell loss, referred to as lipotoxicity. Experimental evidence suggests that oxidative stress is involved in lipotoxicity. In this study, we analyzed the molecular mechanisms of reactive oxygen species-mediated lipotoxicity in insulin-producing RINm5F cells and INS-1E cells as well as in primary rat islet cells. RESEARCH DESIGN AND METHODS The toxicity of saturated NEFAs with different chain lengths upon insulin-producing cells was determined by MTT and propidium iodide (PI) viability assays. Catalase or superoxide dismutase overexpressing cells were used to analyze the nature and the cellular compartment of reactive oxygen species formation. With the new H2O2-sensitive fluorescent protein HyPer H2O2 formation induced by exposure to palmitic acid was determined. RESULTS Only long-chain (>C14) saturated NEFAs were toxic to insulin-producing cells. Overexpression of catalase in the peroxisomes and in the cytosol, but not in the mitochondria, significantly reduced H2O2 formation and protected the cells against palmitic acid-induced toxicity. With the HyPer protein, H2O2 generation was directly detectable in the peroxisomes of RINm5F and INS-1E insulin-producing cells as well as in primary rat islet cells. CONCLUSIONS The results demonstrate that H2O2 formation in the peroxisomes rather than in the mitochondria are responsible for NEFA-induced toxicity. Therefore, we propose a new concept of fatty acid-induced β-cell lipotoxicity mediated via reactive oxygen species formation through peroxisomal β- oxidation.

Proline Accumulation Is Inhibitory to Arabidopsis Seedlings during Heat Stress

Abstract: The effect of proline (Pro) accumulation on heat sensitivity was investigated using transgenic Arabidopsis (Arabidopsis thaliana) plants ectopically expressing the Δ(1)-pyrroline-5-carboxylate synthetase 1 gene (AtP5CS1) under the control of a heat shock protein 17.6II gene promoter. During heat stress, the heat-inducible expression of the AtP5CS1 transgene was capable of enhancing Pro biosynthesis. Twelve-day-old seedlings were first treated with heat at 37°C for 24 h to induce Pro and then were stressed at 50°C for 4 h. After recovery at 22°C for 96 h, the growth of Pro-overproducing plants was significantly more inhibited than that of control plants that do not accumulate Pro, manifested by lower survival rate, higher ion leakage, higher reactive oxygen species (ROS) and malondialdehyde levels, and increased activity of the Pro/P5C cycle. The activities of antioxidant enzymes superoxide dismutase, guaiacol peroxidase, and catalase, but not those of glutathione reductase and ascorbate peroxidase, increased in all lines after heat treatment, but the increase was more significant in Pro-overproducing seedlings. Staining with MitoSox-Red, reported for being able to specifically detect superoxide formed in mitochondria, showed that Pro accumulation during heat stress resulted in elevated levels of ROS in mitochondria. Interestingly, exogenous abscisic acid (ABA) and ethylene were found to partially rescue the heat-sensitive phenotype of Pro-overproducing seedlings. Measurement of ethylene and ABA levels further confirmed that these two hormones are negatively affected in Pro-overproducing seedlings during heat stress. Our results indicated that Pro accumulation under heat stress decreases the thermotolerance, probably by increased ROS production via the Pro/P5C cycle and inhibition of ABA and ethylene biosynthesis.

Role of Mitochondrial Electron Transport Chain Complexes in Capsaicin Mediated Oxidative Stress Leading to Apoptosis in Pancreatic Cancer Cells

Abstract: We evaluated the mechanism of capsaicin-mediated ROS generation in pancreatic cancer cells The generation of ROS was about 4–6 fold more as compared to control and as early as 1 h after capsaicin treatment in BxPC-3 and AsPC-1 cells but not in normal HPDE-6 cells The generation of ROS was inhibited by catalase and EUK-134 To delineate the mechanism of ROS generation, enzymatic activities of mitochondrial complex-I and complex-III were determined in the pure mitochondria Our results shows that capsaicin inhibits about 25–9% and 5–20% of complex-I activity and 8–75% of complex-III activity in BxPC-3 and AsPC-1 cells respectively, which was attenuable by SOD, catalase and EUK-134 On the other hand, capsaicin treatment failed to inhibit complex-I or complex-III activities in normal HPDE-6 cells The ATP levels were drastically suppressed by capsaicin treatment in both BxPC-3 and AsPC-1 cells and attenuated by catalase or EUK-134 Oxidation of mitochondria-specific cardiolipin was substantially higher in capsaicin treated cells BxPC-3 derived ρ0 cells, which lack mitochondrial DNA, were completely resistant to capsaicin mediated ROS generation and apoptosis Our results reveal that the release of cytochrome c and cleavage of both caspase-9 and caspase-3 due to disruption of mitochondrial membrane potential were significantly blocked by catalase and EUK-134 in BxPC-3 cells Our results further demonstrate that capsaicin treatment not only inhibit the enzymatic activity and expression of SOD, catalase and glutathione peroxidase but also reduce glutathione level Over-expression of catalase by transient transfection protected the cells from capsaicin-mediated ROS generation and apoptosis Furthermore, tumors from mice orally fed with 25 mg/kg capsaicin show decreased SOD activity and an increase in GSSG/GSH levels as compared to controls Taken together, our results suggest the involvement of mitochondrial complex-I and III in capsaicin-mediated ROS generation and decrease in antioxidant levels resulting in severe mitochondrial damage leading to apoptosis in pancreatic cancer cells

Extranuclear protection of chromosomal DNA from oxidative stress

Abstract: Eukaryotic organisms evolved under aerobic conditions subjecting nuclear DNA to damage provoked by reactive oxygen species (ROS). Although ROS are thought to be a major cause of DNA damage, little is known about the molecular mechanisms protecting nuclear DNA from oxidative stress. Here we show that protection of nuclear DNA in plants requires a coordinated function of ROS-scavenging pathways residing in the cytosol and peroxisomes, demonstrating that nuclear ROS scavengers such as peroxiredoxin and glutathione are insufficient to safeguard DNA integrity. Both catalase (CAT2) and cytosolic ascorbate peroxidase (APX1) play a key role in protecting the plant genome against photorespiratory-dependent H2O2-induced DNA damage. In apx1/cat2 double-mutant plants, a DNA damage response is activated, suppressing growth via a WEE1 kinase-dependent cell-cycle checkpoint. This response is correlated with enhanced tolerance to oxidative stress, DNA stress-causing agents, and inhibited programmed cell death.

Manganese-excess induces oxidative stress, lowers the pool of antioxidants and elevates activities of key antioxidative enzymes in rice seedlings

Abstract: Manganese (Mn) is an essential element for plant growth but in excess, specially in acidic soils, it can become phytotoxic. In order to investigate whether oxidative stress is associated with the expression of Mn toxicity during early seedling establishment of rice plants, we examined the changes in the level of reactive oxygen species (ROS), oxidative stress induced an alteration in the level of non-enzymic antioxidants and activities of antioxidative enzymes in rice seedlings grown in sand cultures containing 3 and 6 mM MnCl2. Mn treatment inhibited growth of rice seedlings, the metal increasingly accumulated in roots and shoots and caused damage to membranes. Mn treated plants showed increased generation of superoxide anion (O2 .−), elevated levels of H2O2 and thiobarbituric acid reactive substances (TBARS) and decline in protein thiol. The level of nonprotein thiol, however, increased due to Mn treatment. A decline in contents of reduced ascorbate (AsA) and glutathione (GSH) as well as decline in ratios of their reduced to oxidize forms was observed in Mn-treated seedlings. The activities of antioxidative enzymes superoxide dismutase (SOD) and its isoforms Mn SOD, Cu/Zn SOD, Fe SOD as well as guaiacol peroxidase (GPX) increased in the seedlings due to Mn treatment however, catalase (CAT) activity increased in 10 days old seedlings but it declined by 20 days under Mn treatment. The enzymes of Halliwell-Asada cycle, ascorbate peroxidase (APX) monodehydoascorbate reductase (MDHAR), dehyroascorbate reductase (DHAR) and glutathione reductase (GR) increased significantly in Mn treated seedlings over controls. Results suggest that in rice seedlings excess Mn induces oxidative stress, imbalances the levels of antioxidants and the antioxidative enzymes SOD, GPX, APX and GR appear to play an important role in scavenging ROS and withstanding oxidative stress induced by Mn.

TGF-β regulates Nox4, MnSOD and catalase expression, and IL-6 release in airway smooth muscle cells

Abstract: Reactive oxygen species (ROS) are generated as a result of normal cellular metabolism, mainly through the mitochondria and peroxisomes, but their release is enhanced by the activation of oxidant enzymes such as NADPH oxidases or downregulation of endogenous antioxidant enzymes such as manganese-superoxide dismutase (MnSOD) and catalase. Transforming growth factor-β (TGF-β), found to be overexpressed in airway smooth muscle (ASM) from asthmatic and chronic obstructive pulmonary disease patients, may be a pivotal regulator of abnormal ASM cell (ASMC) function in these diseases. An important effect of TGF-β on ASMC inflammatory responses is the induction of IL-6 release. TGF-β also triggers intracellular ROS release in ASMCs by upregulation of NADPH oxidase 4 (Nox4). However, the effect of TGF-β on the expression of key antioxidant enzymes and subsequently on oxidant/antioxidant balance is unknown. Moreover, the role of redox-dependent pathways in the mediation of the proinflammatory effects of TGF-β in ASMCs is unclear. In this study, we show that TGF-β induced the expression of Nox4 while at the same time inhibiting the expression of MnSOD and catalase. This change in oxidant/antioxidant enzymes was accompanied by elevated ROS levels and IL-6 release. Further studies revealed a role for Smad3 and phosphatidyl-inositol kinase-mediated pathways in the induction of oxidant/antioxidant imbalance and IL-6 release. The changes in oxidant/antioxidant enzymes and IL-6 release were reversed by the antioxidants N-acetyl-cysteine (NAC) and ebselen through inhibition of Smad3 phosphorylation, indicating redox-dependent activation of Smad3 by TGF-β. Moreover, these findings suggest a potential role for NAC in preventing TGF-β-mediated pro-oxidant and proinflammatory responses in ASMCs. Knockdown of Nox4 using small interfering RNA partially prevented the inhibition of MnSOD but had no effect on catalase and IL-6 expression. These findings provide novel insights into redox regulation of ASM function by TGF-β.

Exogenous salicylic acid alleviates effects of long term drought stress and delays leaf rolling by inducing antioxidant system

Abstract: Salicylic acid (SA) is one of the important signal molecules modulating plant responses to environmental stress. In this study, the effects of exogenous SA on leaf rolling, one of drought avoidance mechanisms, and antioxidant system were investigated in Ctenanthe setosa during long term drought stress. The plants were subjected to 38-day drought period and they were treated with or without SA (10−6 M) on the 25th, 27th and 29th days of the period. Leaf samples were harvested on the 30th, 34th and 38th days. Some antioxidant enzyme activities (superoxide dismutase, catalase, ascorbate peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase, glutathione reductase), reactive oxygen species (hydrogen peroxide and superoxide) and lipid peroxidation were determined during the drought period. Treatment with SA prevented water loss and delayed leaf rolling in comparison with control leaves. Exogenous SA induced all antioxidant enzyme activities more than control leaves during the drought. Ascorbate and glutathione, α-tocopherol, carotenoid and endogenous SA level were induced by the SA treatment. Levels of reactive oxygen species were higher in SA treated plants than control ones on the 34th day. Their levels on the 38th day, however, fastly decreased in SA treated plants. SA treatment prevented lipid peroxidation while the peroxidation increased in control plants. The results showed that exogenous SA can alleviate the damaging effect of long term drought stress by decreasing water loss and inducing the antioxidant system in the plant having leaf rolling, alternative protection mechanism to drought.

Heat-stress induced inhibition in growth and chlorosis in mungbean (Phaseolus aureus Roxb.) is partly mitigated by ascorbic acid application and is related to reduction in oxidative stress

Abstract: The rising temperatures (>35°C) are proving detrimental to summer-sown mungbean genotypes that experience inhibition of vegetative and reproductive growth. In the present study, the mungbean plants growing hydroponically at varying temperatures of 30/20°C (control), 35/25, 40/30, and 45/35°C (as day/night 12 h/12 h) with (50 μM) or without ascorbic acid (ASC) were investigated for effects on growth, membrane damage, chlorophyll loss, leaf water status, components of oxidative stress, and antioxidants. The ASC-treated plants showed significant improvement in germination and seedling growth especially at 40/30 and 45/35°C. The damage to membranes, loss of water, decrease in cellular respiration, and chlorophyll were significantly prevented by ASC treatment to plants growing at these temperatures. The oxidative stress measured as malondialdehyde and hydrogen peroxide content was observed to be significantly lower at high temperatures with ASC application. The activities of superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase increased at 40/30°C but decreased at 45/35°C in the absence of ASC while with its application, the activities of these enzymes were appreciably resorted. Among all the antioxidants, the endogenous ASC content decreased to the greatest extent at 45/35°C grown plants indicating its vital role in affecting the response of mungbean to heat stress. Exogenously applied ASC raised its endogenous content along with that of glutathione and proline at 45/35°C. The findings indicated that heat stress-induced inhibition in growth and chlorosis was associated with decrease in leaf water status and elevation of oxidative stress, which could partly be prevented by exogenous application of ASC. Its role in imparting protection against heat stress is discussed.

Plant responses to water stress: Role of reactive oxygen species

Abstract: Terrestrial plants most often encounter drought stress because of erratic rainfall which has become compounded due to present climatic changes.Responses of plants to water stress may be assigned as either injurious change or tolerance index. One of the primary and cardinal changes in response to drought stress is the generation of reactive oxygen species (ROS), which is being considered as the cause of cellular damage. However, recently a signaling role of such ROS in triggering the ROS scavenging system that may confer protection or tolerance against stress is emerging. Such scavenging system consists of antioxidant enzymes like SOD, catalase and peroxidases, and antioxidant compounds like ascorbate, reduced glutathione; a balance between ROS generation and scavenging ultimately determines the oxidative load. As revealed in case of defence against pathogen, signaling via ROS is initiated by NADPH oxidase-catalyzed superoxide generation in the apoplastic space (cell wall) followed by conversion to hydrogen peroxide by the activity of cell wall-localized SOD. Wall peroxidase may also play role in ROS generation for signaling. Hydrogen peroxide may use Ca2+ and MAPK pathway as downstream signaling cascade. Plant hormones associated with stress responses like ABA and ethylene play their role possibly via a cross talk with ROS towards stress tolerance, thus projecting a dual role of ROS under drought stress.

Age‐related changes in skeletal muscle reactive oxygen species generation and adaptive responses to reactive oxygen species

Abstract: Skeletal muscle generates superoxide and nitric oxide at rest and this generation is increased by contractile activity. In young and adult animals and man, an increase in activities of these species and the secondary products derived from them (reactive oxygen species, ROS) stimulate redox-sensitive signalling pathways to modify the cellular content of cytoprotective regulatory proteins such as the superoxide dismutases, catalase and heat shock proteins that prevent oxidative damage to tissues. The mechanisms underlying these adaptive responses to contraction include activation of redox-sensitive transcription factors such as nuclear factor B (NFB), activator protein-1 (AP1) and heat shock factor 1 (HSF1). During ageing all tissues, including skeletal muscle, demonstrate an accumulation of oxidative damage that may contribute to loss of tissue homeostasis. The causes of this increased oxidative damage are uncertain, but substantial data now indicate that the ability of skeletal muscle from aged organisms to respond to an increase in ROS generation by increased expression of cytoprotective proteins through activation of redox-sensitive transcription factors is severely attenuated. This age-related lack of physiological adaptations to the ROS induced by contractile activity appears to contribute to a loss of ROS homeostasis and increased oxidative damage in skeletal muscle.

Crosstalk between reactive oxygen species and hormonal signalling pathways regulates grain dormancy in barley.

Abstract: Seed dormancy, defined as the inability to germinate under favourable conditions, is controlled by abscisic acid (ABA) and gibberellins (GAs). Phytohormone signalling interacts with reactive oxygen species (ROS) signalling regarding diverse aspects of plant physiology and is assumed to be important in dormancy alleviation. Using dormant barley grains that do not germinate at 30 °C in darkness, we analysed ROS content and ROS-processing systems, ABA content and metabolism, GA-responsive genes and genes involved in GA metabolism in response to hydrogen peroxide (H₂O₂) treatment. During after-ripening, the ROS content in the embryo was not affected, while the antioxidant glutathione (GSH) was gradually converted to glutathione disulphide (GSSG). ABA treatment up-regulated catalase activity through transcriptional activation of HvCAT2. Exogenous H₂O₂ partially alleviated dormancy although it was associated with a small increase in embryonic ABA content related to a slight induction of HvNCED transcripts. H₂O₂ treatment did not affect ABA sensitivity but up-regulated the expression of HvExpA11 (GA-induced gene), inhibited the expression of HvGA2ox3 involved in GA catabolism and enhanced the expression of HvGA20ox1 implicated in GA synthesis. In barley, H₂O₂ could be implicated in dormancy alleviation through activation of GA signalling and synthesis rather than repression of ABA signalling.

Proline induces heat tolerance in chickpea (Cicer arietinum L.) plants by protecting vital enzymes of carbon and antioxidative metabolism

Abstract: Chickpea is a heat sensitive crop hence its potential yield is considerably reduced under high temperatures exceeding 35 °C. In the present study, we evaluated the efficacy of proline in countering the damage caused by heat stress to growth and to enzymes of carbon and antioxidative metabolism in chickpea. The chickpea seeds were raised without (control) and with proline (10 μM) at temperatures of 30/25 °C, 35/30 °C, 40/35 °C and 45/40 °C as day/ night (12 h/12 h) in a growth chamber. The shoot and root length at 40/35 °C decreased by 46 and 37 %, respectively over control while at 45/40 °C, a decrease of 63 and 47 %, respectively over control was observed. In the plants growing in the presence of 10 μM proline at 40/35 °C and 45/40 °C, the shoot length showed improvement of 32 and 53 %, respectively over untreated plants, while the root growth was improved by 22 and 26 %, respectively. The stress injury (as membrane damage) increased with elevation of temperatures while cellular respiration, chlorophyll content and relative leaf water content reduced as the temperature increased to 45/40 °C. The endogenous proline was elevated to 46 μmol g−1 dw at 40/35 °C but declined to 19 μmol g−1 dw in plants growing at 45/40 °C that was associated with considerable inhibition of growth at this temperature. The oxidative damage measured as malondialdehyde and hydrogen peroxide content increased manifolds in heat stressed plants coupled with inhibition in the activities of enzymatic (superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase) and levels of non-enzymatic (ascorbic acid, glutathione, proline) antioxidants. The enzymes associated with carbon fixation (RUBISCO), sucrose synthesis (sucrose phosphate synthase) and sucrose hydrolysis (invertase) were strongly inhibited at 45/40 °C. The plants growing in the presence of proline accumulated proline up to 63 μmol g−1 dw and showed less injury to membranes, had improved content of chlorophyll and water, especially at 45/40 °C. Additionally, the oxidative injury was significantly reduced coupled with elevated levels of enzymatic and non-enzymatic antioxidants. A significant improvement was also noticed in the activities of enzymes of carbon metabolism in proline-treated plants. We report here that proline imparts partial heat tolerance to chickpea’s growth by reducing the cellular injury and protection of some vital enzymes related to carbon and oxidative metabolism and exogenous application of proline appears to have a countering effect against elevated high temperatures on chickpea.

Valproic acid increases formation of reactive oxygen species and induces apoptosis in postimplantation embryos: a role for oxidative stress in valproic acid-induced neural tube defects.

Abstract: Exposure to the anticonvulsant valproic acid (VPA) during the first trimester of pregnancy is associated with an increased risk of congenital malformations including heart defects, craniofacial abnormalities, skeletal and limb defects, and, most frequently, neural tube defects (NTDs). The mechanisms by which VPA induces teratogenic effects are not fully understood, although previous studies support a role for oxidative stress. To investigate the effects of VPA on early development, a whole-embryo culture model was used to evaluate the protective effects of antioxidants, measure intracellular reactive oxygen species (ROS) levels, and assess markers of oxidative damage and apoptosis. Furthermore, in vivo teratological evaluations of antioxidant protection were also completed. VPA (0.60 mM in embryo culture, 400 mg/kg in vivo) induced significant decreases in embryonic growth and increases in NTDs. Of the antioxidants tested, catalase provided partial protection against VPA-mediated reductions in morphological and developmental growth parameters in both whole-embryo culture and in vivo systems. VPA exposure resulted in an increase in ROS staining in the head region, as assessed by whole-mount staining with 5-(and-6)-chloromethyl-2′,7′-dichlorodihydrofluorescein diacetate. Markers of embryonic oxidative damage including 8-hydroxyguanosine, 4-hydroxynonenal adducts, and 3-nitrotyrosine were not affected by VPA treatment. Increased ROS levels were correlated with increased staining for apoptotic markers, as assessed by Western blotting and immunohistochemistry. Addition of catalase to the medium attenuated VPA-induced increases in ROS formation and apoptosis. These studies identify regions of the embryo susceptible to ROS and apoptosis induced by VPA, thus establishing a possible molecular pathway by which VPA exerts teratogenicity.

Acetylation of MnSOD directs enzymatic activity responding to cellular nutrient status or oxidative stress

Abstract: A fundamental observation in biology is that mitochondrial function, as measured by increased reactive oxygen species (ROS), changes significantly with age, suggesting a potential mechanistic link between the cellular processes governing longevity and mitochondrial metabolism homeostasis. In addition, it is well established that altered ROS levels are observed in multiple age-related illnesses including carcinogenesis, neurodegenerative, fatty liver, insulin resistance, and cardiac disease, to name just a few. Manganese superoxide dismutase (MnSOD) is the primary mitochondrial ROS scavenging enzyme that converts superoxide to hydrogen peroxide, which is subsequently converted to water by catalase and other peroxidases. It has recently been shown that MnSOD enzymatic activity is regulated by the reversible acetylation of specific, evolutionarily conserved lysine(s) in the protein. These results, suggest for the first time, that the mitochondria contain bidirectional post-translational signaling networks, similar to that observed in the cytoplasm and nucleus, and that changes in lysine acetylation alter MnSOD enzymatic activity. In addition, these new results demonstrate that the mitochondrial anti-aging or fidelity / sensing protein, SIRT3, responds to changes in mitochondrial nutrient and/or redox status to alter the enzymatic activity of specific downstream targets, including MnSOD that adjusts and/or maintains ROS levels as well as metabolic homeostatic poise.

Protein accumulation in leaves and roots associated with improved drought tolerance in creeping bentgrass expressing an ipt gene for cytokinin synthesis

Abstract: Cytokinins (CKs) may be involved in the regulation of plant adaptation to drought stress. The objectives of the study were to identify proteomic changes in leaves and roots in relation to improved drought tolerance in transgenic creeping bentgrass (Agrostis stolonifera) containing a senescence-activated promoter (SAG12) and the isopentyl transferase (ipt) transgene that increases endogenous CK content. Leaves of SAG12-ipt bentgrass exhibited less severe senescence under water stress, as demonstrated by maintaining lower electrolyte leakage and lipid peroxidation, and higher photochemical efficiency (Fv/Fm), compared with the null transformant (NT) plants. SAG12-ipt plants had higher root/shoot ratios and lower lipid peroxidation in leaves under water stress than the NT plants. The suppression of drought-induced leaf senescence and root dieback in the transgenic plants was associated with the maintenance of greater antioxidant enzyme activities (superoxide dismutase, peroxidase, and catalase). The SAG12-ipt and NT plants exhibited differential protein expression patterns under well-watered and drought conditions in both leaves and roots. Under equivalent leaf water deficit (47% relative water content), SAG12-ipt plants maintained higher abundance of proteins involved in (i) energy production within both photosynthesis and respiration [ribulose 1,5-bisphosphate carboxylase (RuBisCO) and glyceraldehyde phosphate dehydrogenase (GAPDH)]; (ii) amino acid synthesis (methionine and glutamine); (iii) protein synthesis and destination [chloroplastic elongation factor (EF-Tu) and protein disulphide isomerases (PDIs)]; and (iv) antioxidant defence system (catalase and peroxidase) than the NT plants. These results suggest that increased endogenous CKs under drought stress may directly or indirectly regulate protein abundance and enzymatic activities involved in the above-mentioned metabolic processes, thereby enhancing plant drought tolerance.

A permeable cuticle is associated with the release of reactive oxygen species and induction of innate immunity.

Abstract: Wounded leaves of Arabidopsis thaliana show transient immunity to Botrytis cinerea, the causal agent of grey mould. Using a fluorescent probe, histological staining and a luminol assay, we now show that reactive oxygen species (ROS), including H2O2 and O2−, are produced within minutes after wounding. ROS are formed in the absence of the enzymes Atrboh D and F and can be prevented by diphenylene iodonium (DPI) or catalase. H2O2 was shown to protect plants upon exogenous application. ROS accumulation and resistance to B. cinerea were abolished when wounded leaves were incubated under dry conditions, an effect that was found to depend on abscisic acid (ABA). Accordingly, ABA biosynthesis mutants (aba2 and aba3) were still fully resistant under dry conditions even without wounding. Under dry conditions, wounded plants contained higher ABA levels and displayed enhanced expression of ABA-dependent and ABA-reporter genes. Mutants impaired in cutin synthesis such as bdg and lacs2.3 are already known to display a high level of resistance to B. cinerea and were found to produce ROS even when leaves were not wounded. An increased permeability of the cuticle and enhanced ROS production were detected in aba2 and aba3 mutants as described for bdg and lacs2.3. Moreover, leaf surfaces treated with cutinase produced ROS and became more protected to B. cinerea. Thus, increased permeability of the cuticle is strongly linked with ROS formation and resistance to B. cinerea. The amount of oxalic acid, an inhibitor of ROS secreted by B. cinerea could be reduced using plants over expressing a fungal oxalate decarboxylase of Trametes versicolor. Infection of such plants resulted in a faster ROS accumulation and resistance to B. cinerea than that observed in untransformed controls, demonstrating the importance of fungal suppression of ROS formation by oxalic acid. Thus, changes in the diffusive properties of the cuticle are linked with the induction ROS and attending innate defenses.