Plant defenses against oxidative stress

Many reactive oxygen species such as ozone, singlet oxygen, hydroxyl radical, and organic oxyradicals have been implicated in damage to plant organs and biopolymers such as chloroplasts, cell membranes, proteins, and DNA. The principal defenses against these reactive molecules and free radicals in plants include detoxifying enzymes (catalase, superoxide dismutase, etc.) and also lower molecular weight secondary products with antioxidant activity. These latter compounds include a great variety of phenolic compounds, carotenoids, nitrogenous, and sulfur-containing materials. Some of the more important mechanisms of action of the secondary compounds will be discussed, with emphasis on the use of structural and kinetic data to identify the most effective antioxidants against peroxy radical-induced damage, which is perhaps the most important of the oxidative stresses present in the usual environment of plants. © 1995 Wiley-Liss, Inc.     

Bacterial defenses against oxidative stress

Bacteria treated with low doses of oxidants such as hydrogen peroxide adapt to subsequent high doses of these oxidants by inducing the expression of numerous genes. The study of these genes and the roles they play in defending bacteria against oxidative damage has given general insights into what oxidants are hazardous to cells, what cell constituents are damaged by oxidants, and how cells sense and respond to oxidative stress.     

Insulin neuroprotection against oxidative stress in cortical neurons--involvement of uric acid and glutathione antioxidant defenses

In this study we investigated the effect of insulin on neuronal viability and antioxidant defense mechanisms upon ascorbate/Fe2+-induced oxidative stress, using cultured cortical neurons. Insulin (0.1 and 10 microM) prevented the decrease in neuronal viability mediated by oxidative stress, decreasing both necrotic and apoptotic cell death. Moreover, insulin inhibited ascorbate/Fe2+-mediated lipid and protein oxidation, thus decreasing neuronal oxidative stress. Increased 4-hydroxynonenal (4-HNE) adducts on GLUT3 glucose transporters upon exposure to ascorbate/Fe2+ were also prevented by insulin, suggesting that this peptide can interfere with glucose metabolism. We further analyzed the influence of insulin on antioxidant defense mechanisms in the cortical neurons. Oxidative stress-induced decreases in intracellular uric acid and GSH/GSSG levels were largely prevented upon treatment with insulin. Inhibition of phosphatidylinositol-3-kinase (PI-3K) or mitogen-induced extracellular kinase (MEK) reversed the effect of insulin on uric acid and GSH/GSSG, suggesting the activation of insulin-mediated signaling pathways. Moreover, insulin stimulated glutathione reductase (GRed) and inhibited glutathione peroxidase (GPx) activities under oxidative stress conditions, further supporting that insulin neuroprotection was related to the modulation of the glutathione redox cycle. Thus, insulin may be useful in preventing oxidative stress-mediated injury that occurs in several neurodegenerative disorders.     

Dapsone induces oxidative stress and impairs antioxidant defenses in rat liver

Dapsone (DDS) is currently used in the treatment of leprosy, malaria and in infections with Pneumocystis jirovecii and Toxoplasma gondii in AIDS patients. Adverse effects of DDS involve methemoglobinemia and hemolysis and, to a lower extent, liver damage, though the mechanism is poorly characterized. We evaluated the effect of DDS administration to male and female rats (30 mg/kg body wt, twice a day, for 4 days) on liver oxidative stress through assessment of biliary output and liver content of reduced (GSH) and oxidized (GSSG) glutathione, lipid peroxidation, and expression/activities of the main antioxidant enzymes glutathione peroxidase, superoxide dismutase, catalase and glutathione S-transferase. The influence of DDS treatment on expression/activity of the main DDS phase-II-metabolizing system, UDP-glucuronosyltransferase (UGT), was additionally evaluated. The involvement of dapsone hydroxylamine (DDS-NHOH) generation in these processes was estimated by comparing the data in male and female rats since N-hydroxylation of DDS mainly occurs in males. Our studies revealed an increase in the GSSG/GSH biliary output ratio, a sensitive indicator of oxidative stress, and in lipid peroxidation, in male but not in female rats treated with DDS. The activity of all antioxidant enzymes was significantly impaired by DDS treatment also in male rats, whereas UGT activity was not affected in any sex. Taken together, the evidence indicates that DDS induces oxidative stress in rat liver and that N-hydroxylation of DDS was the likely mediator. Impairment in the activity of enzymatic antioxidant systems, also associated with DDS-NHOH formation, constituted a key aggravating factor.     

Oxidative stress and antioxidant defenses in pregnant women

Abstract

Objectives

Oxidative stress (OS) is defined as an imbalance in the production of reactive oxygen species and the capacity of antioxidant defenses. The objective of this work was to investigate OS and antioxidant capacity in pregnant women.

Methods

Parameters of the oxidative status and antioxidant capacity in serum and whole blood were evaluated in thirty-nine women with normal pregnancy.

Results

The assessment of antioxidants indicated an increase in superoxide dismutase and catalase activities (P < 0.05 and P < 0.01) and a decrease in ascorbic acid levels and the total content of sulfhydryl (P < 0.05 and P < 0.001). Additionally, when the pro-oxidant system was investigated we found an increase (P < 0.01) in malondialdehyde and no significant change (P > 0.05) in protein carbonylation.

Discussion

This study demonstrates that there is a change in the pro-oxidant and antioxidant defenses associated with body and circulation changes that are inherent to the pregnancy process.     

Pro-oxidant and antioxidant potential of catecholestrogens against ferrylmyoglobin-induced oxidative stress

Ferryl heme proteins may play a major role in vivo under certain pathological conditions. Catecholestrogens, the estradiol-derived metabolites, can act either as antioxidants or pro-oxidants in iron-dependent systems. The aim of the present work was (1) to determine the effects of ferrylmyoglobin on hepatocyte cytotoxicity, and (2) to assess the pro/antioxidant potential of a series of estrogens (phenolic, catecholic and stilbene-derived) against ferrylmyoglobin induced lipid peroxidation in rat hepatocytes. Cells were exposed to metmyoglobin plus hydrogen peroxide to form ferrylmyoglobin in the presence of the transition metal chelator diethylentriaminepentaacetic acid. Results showed that ferrylmyoglobin induced an initial oxidative stress, mainly reflected in an early lipid peroxidation and further decrease in GSH and ATP. However, cells gradually adapted to this situation, by recovering the endogenous ATP and GSH levels at longer incubation times. Phenolic and stilbene-derived estrogens inhibited ferrylmyoglobin-induced lipid peroxidation to different degrees: diethylstilbestrol>estradiol>resveratrol. Catecholestrogens at concentrations higher than 1 microM also inhibited lipid peroxidation with similar efficacy. The ability of estrogens to reduce ferrylmyoglobin to metmyoglobin may account for their antioxidant activity. In contrast, physiological concentrations (100 pM-100 nM) of the catecholestrogens exerted pro-oxidant activities, 4-hydroxyestradiol being more potent than 2-hydroxyestradiol. The implications of these interactions should be considered in situations where local myoglobin or hemoglobin microbleeding takes place.     

Oxidative stress and antioxidant defenses in ethanol-induced cell injury

Although in the past several mechanisms and factors have been proposed to be responsible for alcoholic liver disease (ALD), at present the involvement of oxygen free radicals and consequently of oxidative stress has acquired remarkable credit. In numerous experimental studies it has been shown the occurrence of alcohol-induced generation of oxygen- and ethanol-derived free radicals through different pathways and from different sources. Mitochondria appear to be both an important source of reactive oxygen species (ROS) and also a primary target of ethanol-induced damage. The consistent induction of the mitochondrial antioxidant enzyme manganese superoxide dismutase (Mn-SOD) observed in experimental animals after acute and chronic ethanol administration has all the characteristics of a "stress response" to an oxidative insult.     

Aluminum-induced oxidative stress and changes in antioxidant defenses in the roots of rice varieties differing in Al tolerance

The effects of aluminum (Al) on root elongation, lipid peroxidation, hydrogen peroxide (H₂O₂) accumulation, antioxidant levels, antioxidant enzymatic activity, and lignin content in the roots of the Al-tolerant rice variety azucena and the Al-sensitive variety IR64 were investigated. Treatment with Al induced a greater decrease in root elongation and a greater increase in H₂O₂ and lipid peroxidation as determined by the total thiobarbituric acid-reactive substance (TBARS) level in IR64 than in azucena. Azucena had significantly higher levels of superoxide dismutase, ascorbate peroxidase, glutathione reductase, and glutathione peroxidase GSH POD activity compared with IR64. The concentrations of reduced glutathione (GSH) and ascorbic acid, and the GSH/GSSG ratio (reduced vs. oxidized glutathione) were also higher in azucena than in IR64 in the presence of Al. The addition of 1 mg/L GSH improved root elongation in both varieties and decreased H₂O₂ production under Al stress. By contrast, treatment with buthionine sulfoximine, a specific inhibitor of GSH synthesis, decreased root elongation in azucena and stimulated H₂O₂ production in both varieties. Moreover, Al treatment significantly increased the cytoplasmic activity of peroxidase (POD) as well as the levels of POD bound ionically and covalently to cell walls in the Al-sensitive variety. The lignin content was also increased. Treatment with exogenous H₂O₂ also increased the lignin content and decreased root elongation in IR64. These results suggest that Al induces lignification in the roots of Al-sensitive rice varieties, probably through an increase in H₂O₂ accumulation.     

Effect of monothiol along with antioxidant against mercury-induced oxidative stress in rat

Efficacy of thiol chelators viz. N-acetyl cysteine and D-penicillamine (NAC and DPA) along with nutritional supplements viz. zinc acetate, sodium selenite and magnesium sulphate (Zn, Se and Mg) in the treatment of mercury intoxication was investigated in rats. This is of particular interest since high bonding affinity between mercuric ion and the thiol group exits. The mutual antagonism of mercury and selenium is one of the strongest examples of the interaction in the trace element field. Adult rats of Sprague-Dawley strain were administered a bolus dose of dimethyl mercury (10 mg/kg) orally. A significant rise in the aspartate aminotransferase, alanine aminotransferase, serum alkaline phosphatase, lactate dehydrogenase, gamma glutamyltranspeptidase, bilirubin and creatinine were observed. Single mercury exposure also resulted in a significant increase in lipid peroxides with a concomitant decrease in reduced glutathione level in liver, kidney and brain. A decrease in the enzymatic activities of acetyl cholinesterase in different regions of the brain was observed. These parameters were restored considerably with chelating agents along with nutritional supplementation, but NAC+Se and DPA+Mg offered significant protection in comparison with other combinations.     

Positive control of a regulon for defenses against oxidative stress and some heat-shock proteins in Salmonella typhimurium

S. typhimurium become resistant to killing by hydrogen peroxide and other oxidants when pretreated with nonlethal levels of hydrogen peroxide. During adaptation to hydrogen peroxide, 30 proteins are induced. Nine are constitutively overexpressed in dominant hydrogen peroxide-resistant oxyR mutants. Mutant oxyR1 is resistant to a variety of oxidizing agents and overexpresses at least five enzyme activities involved in defenses against oxidative damage. Deletions of oxyR are recessive and uninducible by hydrogen peroxide for the nine proteins overexpressed in oxyR1, demonstrating that oxyR is a positive regulatory element. The oxyR1 mutant is also more resistant than the wild-type parent to killing by heat, and it constitutively overexpresses three heat-shock proteins. The oxyR regulatory network is a previously uncharacterized global regulatory system in enteric bacteria.     

Re-aeration-induced oxidative stress and antioxidative defenses in hypoxically pretreated lupine roots

The level of free radicals and activities of antioxidative enzymes were examined in roots of lupine seedlings (Lupinus luteus L.) that were deprived of oxygen by subjecting them to root hypoxia for 48 and 72 h and then re-aerated for up to 24 h. Using electron paramagnetic resonance (EPR), we found that the exposure of previously hypoxically grown roots to air caused the increase in free radicals level, irrespective of duration of hypoxic pretreatment. Immediately after re-aeration the level of free radicals was two times higher than in aerated control. The EPR signal with the g-values at the maximum absorption of 2.0057 and 2.0040 implied that the paramagnetic radicals are derived from a quinone. Directly after re-aeration of hypoxically pretreated roots, the activity of superoxide dismutase (SOD, EC 1.15.1.1) increased to its highest value, followed by a decline below the initial level, whereas activities of catalase (CAT, EC 1.11.1.6) and peroxidase (POX, EC 1.11.1.7) were diminished or only slightly influenced during re-aeration. The electrophoretic patterns of the soluble extracts show 4 isozymes of SOD, 4 isozymes of POX and 1 isozyme of CAT. The level of H2O2 was enhanced or lowered by re-aeration, depending on the previous duration of hypoxia. At the onset of re-aeration products of lipid peroxidation were present at a three-fourth of the levels found in aerobic control. Their levels increased after prolonged exposure to air but remained lower than those in aerobic control even after 24 h of re-aeration. Re-admission of oxygen resulted in about 20% rise in oxygen uptake by root axes segments immediately after transfer of roots from hypoxia and the high uptake rates were observed over whole re-aeration period. Oxygen consumption by root tips was significantly reduced just after transfer from hypoxic conditions as compared to aerated control but after 24 h of re-aeration even approached the control level. The results are discussed in relation to the ability of lupine roots to cope with oxidative stress caused by re-aeration following hypoxic pretreatment.     

Tetrahydropteridines possess antioxidant roles to guard against glucose-induced oxidative stress in Dictyostelium discoideum

Glucose effects on the vegetative growth of Dictyostelium discoideum Ax2 were studied by examining oxidative stress and tetrahydropteridine synthesis in cells cultured with different concentrations (0.5X, 7.7 g L^-1; 1X, 15.4 g L^-1; 2X, 30.8 g L^-1) of glucose. The growth rate was optimal in 1X cells (cells grown in 1X glucose) but was impaired drastically in 2X cells, below the level of 0.5X cells. There were glucose-dependent increases in reactive oxygen species (ROS) levels and mitochondrial dysfunction in parallel with the mRNA copy numbers of the enzymes catalyzing tetrahydropteridine synthesis and regeneration. On the other hand, both the specific activities of the enzymes and tetrahydropteridine levels in 2X cells were lower than those in 1X cells, but were higher than those in 0.5X cells. Given the antioxidant function of tetrahydropteridines and both the beneficial and harmful effects of ROS, the results suggest glucose-induced oxidative stress in Dictyostelium, a process that might originate from aerobic glycolysis, as well as a protective role of tetrahydropteridines against this stress. [BMB Reports 2013; 46(2): 86-91]     

Molecular basis of defence against oxidative stress in Entamoeba histolytica and Giardia lamblia

Gastrointestinal protozoa, viz. Entamoeba histolytica and Giardia, are able to survive in a microaerobic environment. The role of parasitic factors, particularly cysteine, cysteine-rich proteins, superoxide dismutase, and certain alternative mechanisms, has been described in the defence against oxidative stress. The role of the host-derived factors, particularly the phagocytosis of bacteria or host erythrocytes (intact or their enzymatic/non enzymatic components), in the detoxification of reactive oxygen metabolites in E. histolytica may provide novel approaches for the chemotherapy of invasive amoebiasis.     

Effects of temperature on modulation of oxidative stress and antioxidant defenses in testes of tropical tasar silkworm Antheraea mylitta

High temperatures are known to cause physiological stress in organisms. This is often associated with enhanced generation of reactive oxygen species (ROS) leading to oxidative damage. The commercially important tropical tasar silkworm Antheraea mylitta has to endure high summer temperature before egg production on the onset of monsoon. In this study the status of pro-oxidants and antioxidants was studied in the testes of male pupae of tasar silkworm A. mylitta under thermal stress condition. Further, to find out the impact of temperature on physiological activity, oxygen consumption rate was measured. The result indicated higher level of thiobarbituric acid reactive substances (TBARS, as an index of lipid peroxidation) and total hydroperoxides in the male pupae exposed to high temperature (40±1 °C). Similarly, it was found that increased levels of antioxidants such as superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), ascorbic acid (ASA) and low molecular thiols (L-SH) in testes are more prominent in high temperature rather than in moderate temperature (35±1 ^oC) suggesting the activation of physiological mechanism to scavenge the ROS produced during stress. Further more, the order of higher level of oxygen consumption rate was observed as high temperature (40±1°C) > moderate temperature (35±1°C) > control groups (28±1°C). Oxygen consumption rate was positively correlated with oxidative stress and antioxidant defence indices. We infer from these findings that the testes of A. mylitta pupae modulate testicular antioxidant responses to thermal stress.     

Characteristics of oxidative stress and antioxidant defenses by a mixed culture of acidophilic bacteria in response to Co2+ exposure

Extremophiles - During bioleaching of Cobalt from waste lithium-ion batteries, the biooxidation activity of acidophilic bacteria is inhibited by a high concentration of Co ion in the liquid phase....     

Oxidative stress and reduced antioxidant defenses in peripheral cells from familial Alzheimer's patients

We have measured the levels of typical end products of the processes of lipid peroxidation, protein oxidation, and total antioxidant capacity (TAC) in skin fibroblasts and lymphoblasts taken from patients with familial Alzheimer's disease (FAD), sporadic Alzheimer's disease (AD), and age-matched healthy controls. Compared to controls, the fibroblasts and lymphoblasts carrying amyloid precursor protein (APP) and presenilin-1 (PS-1) gene mutations showed a clear increase in lipoperoxidation products, malondialdehyde (MDA), and 4-hydroxynonenal (4-HNE). In contrast, the antioxidant defenses of cells from FAD patients were lower than those from normal subjects. Lipoperoxidation and antioxidant capacity in lymphoblasts from patients affected by sporadic AD were virtually indistinguishable from the basal values of normal controls. An oxidative attack on protein gave rise to greater protein carbonyl content in FAD patients than in age-matched controls. Furthermore, ADP ribosylation levels of poly(ADP-ribose) polymerase (PARP) nuclear substrates were significantly raised, whereas the PARP content did not differ significantly between fibroblasts carrying gene mutations and control cells. These results indicate that peripheral cells carrying APP and PS-1 gene mutations show altered levels of oxidative markers even though they are not directly involved in the neurodegenerative process of AD. These results support the hypothesis that oxidative damage to lipid, protein, and DNA is an important early event in the pathogenesis of AD.     

Americanin B protects cultured human keratinocytes against oxidative stress by exerting antioxidant effects

We evaluated the cytoprotective effects of americanin B, a lignan compound, against hydrogen peroxide (H₂O₂)-induced cell damage. Americanin B decreased the level of DPPH radicals, superoxide anions, hydroxyl radicals, and intracellular reactive oxygen species. Americanin B also attenuated DNA damage induced by H₂O₂ treatment, as shown by the inhibition of formation of comet tails, indicative of DNA strand breakage, and prevented the oxidation of protein and peroxidation of lipid, as determined by protein carbonyls and 8-isoprostane. Furthermore, americanin B protected against H₂O₂-induced apoptotic cell death, as determined by a reduction in the numbers of apoptotic bodies stained with Hoechst 33342. These findings suggest that americanin B protects cells against oxidative damage by exerting antioxidant effects and inhibiting apoptosis.     

Copper-induced oxidative stress and antioxidant defence in Arabidopsis thaliana

Content of reactive oxygen species (ROS): O2*-, H2O2 and OH* as well as activities of antioxidant enzymes: superoxide dismutase (SOD), guaiacol peroxidase (POX) and catalase (CAT) were studied in leaves of Arabidopsis thaliana ecotype Columbia, treated with Cu excess (0, 5, 25, 30, 50, 75, 100, 150 and 300 microM). After 7 days of Cu action ROS content and the activity of SOD and POX increased, while CAT activity decreased in comparison with control. Activities of SOD, POX and CAT were correlated both with Cu concentration (0-75 microM) in the growth medium and with OH* content in leaves. Close correlation was also found between OH* content and Cu concentration. Oxidative stress in A. thaliana under Cu treatment expressed in elevated content of O2*-, H2O2 and OH* in leaves. To overcome it very active the dismutase- and peroxidase-related (and not catalase-related, as in other plants) ROS scavenging system operated in A. thaliana. Visual symptoms of phytotoxicity: chlorosis, necrosis and violet colouring of leaves as well as a reduction of shoot biomass occurred in plants.