Effects of a root-colonized dark septate endophyte on the glutathione metabolism in maize plants under cadmium stress

A high Cd-tolerant dark septate endophyte (DSE), Exophiala pisciphila, was inoculated into maize (Zea mays L.) roots under Cd stress. The Cd content, enzymes activity and thiol compound content relevant to glutathione (GSH) metabolism in maize leaves were analyzed. The Cd content in maize shoots increased with increasing Cd stress, but the DSE significantly reduced the Cd content at the 40?mg/kg Cd treatment. Cd stress increased the enzyme activity of glutathione reductase (GR), glutathione S-transferase (GST) and glutathione peroxidase (GSH-Px) as well as the thiol compound contents of sulfur, thiols (-SH) and oxidized glutathione (GSSG). The content of reduced GSH and the GSH/GSSG ratio reached a peak at the 5?mg/kg Cd treatment but then decreased with increasing Cd stress. Furthermore, the DSE significantly enhanced the GR and GSH-Px activity and increased the contents of -SH and GSH under low Cd stress (5 and 10?mg/kg), but decreased the γ-glutamylcysteine synthetase and GST activity under high Cd stress (20 and 40?mg/kg). Highly positive correlations between the Cd content with enzymes activity and enzymes activity with thiol compound content were observed. Results indicated that DSE played a role in activating GSH metabolism in maize leaves under Cd stress.     

Influence of some metal concentrations on the activity of antioxidant enzymes and concentrations of vitamin E and SH-groups in the digestive gland and gills of the freshwater bivalve Unio tumidus from the Serbian part of Sava River

We examined whether the freshwater bivalve Unio tumidus from the Sava River can serve as a bioindicator organism for long-term biomonitoring of river ecosystems for the presence of metal pollutants. To this end, we assessed in the digestive glands and gills of mussels, changes in activity of antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR), the phase II biotransformation enzyme glutathione-S-transferase (GST)), and changes in the concentrations of the non-enzymatic components of the antioxidant system (vitamin E and sulfhydryl groups (-SH), after exposure to metals in the environment. Mussels were collected at four sites where the concentrations of dissolved metals (Cu, Cd, Zn, Fe, Mn, Hg, Ni, As, Pb) were quantified. Cu, Ni and As exerted concentration-dependent inhibitory effects on CAT and GST activities. Increasing concentrations of Cd promoted increases in GSH-Px activity and -SH concentration. In response to increased Zn concentration GR activity increased whereas Fe promoted decreased enzymatic activity. Negative correlations between the concentrations of Cu and Cd and vitamin E, and a positive correlation between Mn and vitamin E concentrations were detected. The described correlations between components of the antioxidant system and metal levels in the environment reveal a high physiological sensitivity of freshwater mussels to pollution, supporting their use in biomonitoring of metal contamination in river ecosystems.     

The use of biomarkers of oxidative stress in zebra mussel <Emphasis Type="Italic">Dreissena polymorpha</Emphasis> (Pallas, 1771) for chronic anthropogenic pollution assessment of the Rybinsk Reservoir

Biomarkers of oxidative stress such as catalase (CAT), glutathione S-transferase (GST), glutathione reductase (GR) activity, and malondialdehyde and reduced glutathione content, as well as heavy metal concentrations (HM: Pb, V, Cr, Mn, Co, Ni, Cu, Zn, and Cd), were studied in Dreissena polymorpha tissues. Mussels were collected on three sites located on the Rybinskoe Reservoir different in levels of anthropogenic pressure: the most polluted sites were 1 and 2 and site 3 was relatively clean. Mussels from sites 1 and 2 had higher concentrations of HM (Pb, V, Cr, Mn, Ni, Cu, and Mn) and their response to the pollutant action was manifested in increased processes of lipid peroxidation (LPO), the activation of CAT, and elevated level of GHS.     

The glutathione-related detoxication responses to juvenile and ecdysone hormones in Galleria mellonella

The effect of 20-hydroxyecdysone (20E) and juvenile hormone (JH) on the glutathione pathway of the greater wax moth Galleria mellonella (Lepidoptera: Pyralidae) was determined by investigating glutathione peroxidase (GSH-Px), glutathione S-transferases (GST), and glutathione reductase (GR) activities as well as reduced and oxidized glutathione (GSH and GSSG) content with respect to developmental stage. The continuous decreases of GSH-Px and GST activities dependent on the growth period of G. mellonella occurred in JH and 20E groups over and under their controls, respectively. While the GR activities of G. mellonella showed increases in young pupa (YP) for both control and in old larvae (OL) for the 20E groups after the minimum at these periods, they also increased after old pupa (OP) for the JH group with a maximum in OL period. Although GR activity levels in the JH group were significantly higher compared with controls and 20E groups up to OP period, the activity levels for the control and 20E groups were higher than those of the JH group at adult (AD) and old pupa (OP) periods, respectively. In spite of increases in the GR activity of 20E and control groups of G. mellonella, decreased GSH and increased GSSG levels were observed at aging period. GSH levels in the JH group reached a maximum at prepupa (PP) and then decreased with non-significant changes from OL to AD period. According to the results, GSH and GSSG levels, as well as GSH/GSSG ratios, were below and over control levels in 20E and JH groups, respectively, during all of the investigated developmental stages. On the contrary, the LPO levels were higher than the control for 20E and lower for the JH groups during the developmental period. These results show that while ecdysone hormone has a negative effect on the glutathione-related detoxication capacity of G. mellonella, the juvenile hormone has a positive effect on this process.     

Chloramine T induced oxidative stress and the response of antioxidant system in <Emphasis Type="Italic">Phanerochaete chrysosporium</Emphasis>

In this study, the effect of chloramine T (Chl-T) on the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR) and glutathione S-transferase (GST); the levels of reduced (GSH) and oxidised glutathione (GSSG) and their ratios; and also membrane lipid peroxidation (LPO) levels in Phanerochaete chrysosporium were investigated in a dose- (0.25–1 mmol/L) and time-dependent (1.5–9 h) manner. The highest SOD activity was observed in 0.5 mmol/L Chl-T at 6th hour as 1.48-fold of its control. The observed highest level in CAT activities was 4.6-fold of control in 0.5 and 0.75 mmol/L at the 6th hour. The GSH levels that were over the control showed decreasing tendency from the beginning of incubation, except 0.25 mmol/L. In contrast with GSH level variations, GSSG levels reached 10.0-fold of its control by showing increasing tendency with the increases in concentration and time. While the GSH/GSSG ratios were over the control at 0.25 mmol/L during all incubation, they fell under the control values at the earlier hours of incubation with the increasing concentrations of Chl-T. Glutathione-related enzymes GSH-Px, GR and GST were also induced with Chl-T treatment, and the highest activities were 3.29-, 7.5- and 6.56-fold of their controls, respectively. On the other hand, the increases in LPO levels with increasing concentration and time up to 5.27-fold of its control showed that the inductions observed in antioxidant system could not prevent the Chl-T-based oxidative stress.     

Parameters related to oxygen free radicals in erythrocytes,plasma and epidermis of the hairless rat

The following parameters related to oxygen free radicals (OFR) were determined in erythrocytes and the epidermis of hairless rats: catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), reduced (GSH) and oxidized (GSSG) glutathione, glutathione S-transferase (GST), superoxide dismutase (SOD) and thiobarbituric acid reactive substances (TBARS). GSH, GSSG and TBARS were also analyzed in plasma. In erythrocytes, the Pearson correlation coefficients (r) were significant (p < 0.001) between glutathione and other parameters as follows: GSH correlated negatively with GSSG (r = -0.665) and TBARS (r = -0.669); GSSG correlated positively with SOD (r = 0.709) and TBARS (r = 0.752). Plasma GSSG correlated negatively with erythrocytic thermostable GST activity (r = -0.608; p=0.001) and with erythrocytic total GST activity (r = -0.677; p < 0.001). In epidermis (p < 0.001 in all cases), GSH content correlated with GSSG (r = 0.682) and with GPx (r = 0.663); GSSG correlated with GPx (r = 0.731) and with GR (r = 0.794). By multiple linear regression analysis some predictor variables (R(2)) were found: in erythrocytes, thermostable GST was predicted by total GST activity and GSSG, GSSG content was predicted by GSH and by the GSH/GSSG ratio and GPx activity was predicted by GST, CAT and SOD activities; in epidermis, GSSG was predicted by GR and SOD activities and GR was predicted by GSSG, TBARS and GPx. It is concluded that the hairless rat is a good model for studying OFR-related parameters simultaneously in blood and skin, and that it may provide valuable information about other animals under oxidative stress.     

Interactive effects of zinc and nickel on the glutathione system state in <Emphasis Type="Italic">Mimulus guttatus</Emphasis> plants

To determine whether the enhanced stress tolerance of ZnSO₄ with NiSO₄-treated Mimulus guttatus Fischer ex DC. plants was associated with the glutathione (GR-GSH) system, we investigated the changes in glutathione redox state (reduced (GSH), oxidized (GSSG) forms, total reduced (GSHt) glutathione, and GSH/GSSG ratio) and in the enzymatic activities of glutathione reductase (GR) and peroxidatic glutathione S-transferases (GST). The 6-week-old plants were grown in water culture during 4 weeks on a modified Rorison’s medium with ZnSO₄ (50, 100, and 200 μM) and NiSO₄ (20 and 80 μM) in a condition of separate or simultaneous supply of the components. Dry biomass accumulations of roots and shoots were not influenced by the examined treatments. The positive correlations between the total external concentrations of ZnSO₄ and NiSO₄ and the total Zn and Ni contents in roots and leaves were found. It was determined that the MDA content was higher in the ZnSO₄-treated plants than in the NiSO₄-treated ones. The supplementation of the ZnSO₄-treated plants with varied concentrations of NiSO₄ decreased the Zn-induced increase in the MDA levels. The inverse proportionality between the MDA and pigment levels in leaves was found. The Zn-Ni interactions were shown to induce the decreases in the GR activity, the total peroxidatic GST activity, and the GSH/GSSG ratio in roots. However, in leaves, the GR activity and the GSH/GSSG ratio were significantly increased and the total peroxidatic GST activity was decreased. The supplementation of the ZnSO₄-treated plants with varied concentrations of NiSO₄ restored the Zn-induced reduction in the GSHt levels in roots and decreased the Zn-induced increase in the GSSG levels in leaves, which resulted in more reduced state of the intracellular environment. It was likely to cause a decrease of the MDA level. Thus, our studies on the Zn?Ni interactions identified the antagonizing role of Ni in Zn toxicity by the GR-GSH system.     

Trace metal content in the seagrass Cymodocea nodosa: Differential accumulation in plant organs

Differences in the accumulation of seven metallic elements, including micronutrients (Cu, Fe, Mn, Ni and Zn) and non-essential elements (Cd and Pb) among plant organs (leaves, roots and rhizomes) were examined in the seagrass Cymodocea nodosa. Samples were taken from two coastal bays (Catalonia, Western Mediterranean), with a total of nine sampling sites encompassing different levels of metal availability. Metal content was generally higher in uptake organs (leaves and roots) than in rhizomes. However, accumulation in leaves and roots varied between elements. While Cd, Mn and Zn preferentially accumulate in leaves, Fe and Pb accumulate in roots and Cu and Ni in both. There were common spatial (between sites) trends in Cd, Mn, Cu and Zn accumulation in the three organs. However, these spatial trends varied according to the organ considered in the case of Fe, Pb, and Ni. Therefore, assessment of within-plant variability is strongly recommended prior to the use of C. nodosa for biomonitoring purposes, at least for Fe, Pb, and Ni.     

Exogenous Selenium Pretreatment Protects Rapeseed Seedlings from Cadmium-Induced Oxidative Stress by Upregulating Antioxidant Defense and Methylglyoxal Detoxification Systems

The protective effect of selenium (Se) on antioxidant defense and methylglyoxal (MG) detoxification systems was investigated in leaves of rapeseed (Brassica napus cv. BINA sharisha 3) seedlings under cadmium (Cd)-induced oxidative stress. Two sets of 11-day-old seedlings were pretreated with both 50 and 100???M Se (Na₂SeO₄, sodium selenate) for 24?h. Two concentrations of CdCl₂ (0.5 and 1.0?mM) were imposed separately or on the Se-pretreated seedlings, which were grown for another 48?h. Cadmium stress at any levels resulted in the substantial increase in malondialdehyde and H₂O₂ levels. The ascorbate (AsA) content of the seedlings decreased significantly upon exposure to Cd stress. The amount of reduced glutathione (GSH) increased only at 0.5?mM CdCl₂, while glutathione disulfide (GSSG) increased at any level of Cd, with concomitant decrease in GSH/GSSG ratio. The activities of ascorbate peroxidase (APX) and glutathione S-transferase (GST) increased significantly with increased concentration of Cd (both at 0.5 and 1.0?mM CdCl₂), while the activities of glutathione reductase (GR) and glutathione peroxidase (GPX) increased only at moderate stress (0.5?mM CdCl₂) and then decreased at 1.0?mM severe stress (1.0?mM CdCl₂). Monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), catalase (CAT), glyoxalase I (Gly I), and glyoxalase II (Gly II) activities decreased upon exposure to any levels of Cd. Selenium pretreatment had little effect on the nonenzymatic and enzymatic components of seedlings grown under normal conditions; i.e., they slightly increased the GSH content and the activities of APX, GR, GST, and GPX. On the other hand, Se pretreatment of seedlings under Cd-induced stress showed a synergistic effect; it increased the AsA and GSH contents, the GSH/GSSG ratio, and the activities of APX, MDHAR, DHAR, GR, GPX, CAT, Gly I, and Gly II which ultimately reduced the MDA and H₂O₂ levels. However, in most cases, pretreatment with 50???M Se showed better results compared to pretreatment with 100???M Se. The results indicate that the exogenous application of Se at low concentrations increases the tolerance of plants to Cd-induced oxidative damage by enhancing their antioxidant defense and MG detoxification systems.     

Modulation of cadmium-induced oxidative stress in Ceratophyllum demersum by zinc involves ascorbate-glutathione cycle and glutathione metabolism.

To understand the interaction between Zn, an essential micronutrient and Cd, a non-essential element, Cd-10 microM and Zn supplemented (10, 50, 100, and 200 microM) Cd 10 microM treated Ceratophyllum demersum L. (Coontail), a free floating freshwater macrophyte was chosen for the study. Cadmium at 10 microM concentration decreased thiol content, enhanced oxidation of ascorbate (AsA) and glutathione (GSH) to dehydroascorbate (DHA) and glutathione disulfide (GSSG), respectively, a clear indication of oxidative stress. Zinc supplementation to Cd (10 microM) treated plants effectively restored thiols, inhibited oxidation of AsA and GSH maintaining the redox molecules in reduced form. Cd-10 microM slightly induced ascorbate peroxidase (APX, E.C. 1.11.1.11) but inhibited monodehydroascorbate reductase (MDHAR, E.C. 1.6.5.4), dehydroascorbate reductase (DHAR, E.C. 1.8.5.1) and glutathione reductase (GR, E.C. 1.6.4.2), enzymes of ascorbate-glutathione cycle (AGC). Zn supplementation restored and enhanced the functional activity of all the AGC enzymes (APX, MDHAR, DHAR and GR). Gamma-glutamylcysteine synthetase (gamma-GCS, E.C. 6.3.2.2) was not affected by Cd as well as Zn, but Zn supplements increased glutathione-S-transferase (GST, E.C. 2.5.1.18) activity to a greater extent than Cd and simultaneously restored glutathione peroxidase (GSH-PX, E.C. 1.11.1.9) activity impaired by Cd toxicity. Zn-alone treatments did not change above investigated parameters. These results clearly indicate the protective role of Zn in modulating the redox status of the plant system through the antioxidant pathway AGC and GSH metabolic enzymes for combating Cd induced oxidative stress.     

Nitric oxide modulates antioxidant defense and the methylglyoxal detoxification system and reduces salinity-induced damage of wheat seedlings

The present study investigates the possible regulatory role of exogenous nitric oxide (NO) in antioxidant defense and methylglyoxal (MG) detoxification systems of wheat seedlings exposed to salt stress (150 and 300 mM NaCl, 4 days). Seedlings were pre-treated for 24 h with 1 mM sodium nitroprusside, a NO donor, and then subjected to salt stress. The ascorbate (AsA) content decreased significantly with increased salt stress. The amount of reduced glutathione (GSH) and glutathione disulfide (GSSG) and the GSH/GSSG ratio increased with an increase in the level of salt stress. The glutathione S-transferase (GST) activity increased significantly with severe salt stress (300 mM). The ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), catalase (CAT) and glutathione peroxidase (GPX) activities did not show significant changes in response to salt stress. The glutathione reductase (GR), glyoxalase I (Gly I), and glyoxalase II (Gly II) activities decreased upon the imposition of salt stress, especially at 300 mM NaCl, with a concomitant increase in the H₂O₂ and lipid peroxidation levels. Exogenous NO pre-treatment of the seedlings had little influence on the non-enzymatic and enzymatic components compared to the seedlings of the untreated control. Further investigation revealed that NO pre-treatment had a synergistic effect; that is, the pre-treatment increased the AsA and GSH content and the GSH/GSSG ratio, as well as the activities of MDHAR, DHAR, GR, GST, GPX, Gly I, and Gly II in most of the seedlings subjected to salt stress. These results suggest that the exogenous application of NO rendered the plants more tolerant to salinity-induced oxidative damage by enhancing their antioxidant defense and MG detoxification systems.     

Comparative in vitro effects of some metal ions on bovine kidney cortex glutathione reductase

Heavy metal pollution can arise from many sources and damage many organisms. Exposure to the metal ions can leads to a reduction in cellular antioxidant enzyme activities and lowers cellular defense against oxidative stress. In this study we have tested effects of the some metal ions on the purified bovine kidney cortex glutathione reductase (GR). Cadmium (Cd2+), nickel (Ni2+), and zinc (Zn2+) showed inhibitory effect on the enzyme. The obtained IC?? values of Cd2+, Ni2+, and Zn2+ are 0.027, 0.8, and 1 mM, respectively. Kinetic characterization of the inhibition is also investigated. Cd2+ inhibition is noncompetitive with respect to both oxidized glutathione (GSSG) (Ki(GSSG) 0.060 ± 0.005 mM) and NADPH (Ki(NADPH) 0.025 ± 0.002 mM). Ni2+ inhibition is noncompetitive with respect to GSSG (Ki(GSSG) 0.329 ± 0.016 mM) and uncompetitive with respect to NADPH (Ki(NADPH) 0.712 ± 0.047 mM). The effect of Zn2+ on GR activity is consistent with noncompetitive inhibition pattern when the varied substrate is the GSSG (Ki(GSSG) 0.091 ± 0.005 mM) and the NADPH (Ki(NADPH) 0.226 ± 0.01 mM), respectively. GR inhibition studies may be useful for understanding the mechanisms for oxidative damage associated with heavy metal toxicity.     

Accumulation and oxidative stress biomarkers in Japanese flounder larvae and juveniles under chronic cadmium exposure

This study investigated how Cd exposure affected oxidative biomarkers in Japanese flounder, Paralichthys olivaceus, at early life stages (ELS). Fish were exposed to waterborne Cd (0–48 µg L^− 1) from embryonic to juvenile stages for 80 days. Growth, Cd accumulation, activities of superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), glutathione S-transferase (GST, EC 2.5.1.18), and levels of glutathione (GSH) and lipid peroxidation (LPO) were investigated at three developmental stages. Flounder growth decreased and Cd accumulation increased with increasing Cd concentration. In metamorphosing larvae, CAT and SOD activities were inhibited and GSH level was elevated, while LPO was enhanced by increasing Cd concentrations. CAT and GST activities of settling larvae were inhibited but GSH level was elevated at high Cd concentrations. In juveniles, SOD activity and LPO level were increased but GST activity was inhibited as Cd concentration increased. Antioxidants in flounder at ELS were able to develop ductile responses to defend against oxidative stress, but LPO fatally occurred due to Cd exposure. These biochemical parameters could be used as effective oxidative biomarkers for evaluating Cd contamination and toxicity in marine environments: CAT, SOD, GSH, and LPO for metamorphosing stage; CAT, GSH, and GST for settling stage; and SOD, GST, and LPO for juvenile stage.     

Effects of fluoride on hepatic antioxidant system and transcription of Cu/Zn SOD gene in young pigs

Thirty-two barrows (Duroc x Landrace x Yorkshire) were randomly divided into four groups, each of which included eight pigs. The groups received the same basal diet supplemented with 0, 100, 250 and 400mg/kg fluoride, respectively. The malondialdehyde (MDA) and glutathione (GSH) levels, antioxidant enzymes activities and zinc/copper superoxide dismutase (Cu/Zn SOD) mRNA content in the liver were determined to evaluate the fluoride hepatic intoxication. Results showed the increased lipid peroxides (LPO) level and the reduced GSH content, along with a concomitant decrease in the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px). Moreover, the level of hepatic Cu/Zn SOD mRNA was also significantly reduced. We suggest the mechanism of fluoride injuring the liver as follows: fluoride causes a decrease in Cu/Zn SOD mRNA and the reduced activities of antioxidant enzymes, leads to the declined ability of scavenging free radicals with excessive production of LPO, which seriously damages the hepatic structure and function.     

Glutathione redox system,GSH-Px activity and lipid peroxidation (LPO) levels in tadpoles of R.r.ridibunda and B.viridis

Total glutathione (t-GSH), reduced glutathione (GSH), glutathione disulphide (GSSG) levels, t-GSH/GSSG ratio, glutathione peroxidase (GSH-Px) activity and lipid peroxidation (LPO) levels were investigated during the development period of a predominantly aquatic amphibian R.r.ridibunda and a predominantly terrestrial amphibian B. viridis. While t-GSH and GSH showed a similar trend, GSSG concentration increased significantly (p<0.05) during the larval stages in R.r.ridibunda larvae. In contrast to R.r.ridibunda larvae, there was no significant (p>0.05) change between 1 and 5 weeks in the t-GSH and GSH concentrations of B. viridis. t-GSH and GSH concentrations of B. viridis larvae became sharply elevated after the fifth week, GSSG levels increased 3.25-fold during the metamorphosis. The t-GSH/GSSG ratio fluctuated and the lowest t-GSH/GSSG ratios were observed at the third week for both species. GSH-Px activities for both species increased significantly (p<0.05) during the growing period. The highest GSH-Px activities in R.r.ridibunda and B.viridis were observed at the eighth week and they were 3.45 +/- 0.17 and 4.1 +/- 0.21 IU mg(-1), respectively. The membrane LPO levels in the R.r.ridibunda and B. viridis tadpoles significantly (p<0.001) decreased from 206 +/- 10.3 to 146 +/- 7.3 and from 198 +/- 9.9 to 23 +/- 1.15 nmol MDA g(-1) w.w., respectively.     

Comparison of the toxicity of heavy metals to cabbage growth

Summary Cabbage plants were grown for 55 days with a nutrient solution containing 1 and 10 ppm of V, Cr(III), Cr(VI), Mn, Fe, Co, Ni, Cu, Zn, Cd, Hg(I), orHg(II). A comparison of the plant growth and chemical analysis revealed that Cr(VI), Cu, Cd, and Hg(II) in the solution are most toxic to the plant growth (hence detrimental to the cabbage-head formation) and Mn, Fe, and Zn are less toxic than other heavy metals, and that Mn, Zn, Co, Ni, and Cd and translocated into all the plant organs while V, Cr(III), Cr(VI), Fe, Cu, Hg(I), and Hg(II) are accumulated in the roots.     

微波消解ICP-AES法测定糙苏不同部位中的微量元素

利用微波消解电感耦合等离子发射光谱(ICP-AES)法测定野生中药糙苏根、茎、叶、花和籽中钠、钾、钙、铁、锌、镁、锰、铜、镍、钼、铅和镉的含量,并进行了分析比较。糙苏不同用药部位的微量元素含量存在差异,其中钠、钾、钙、铁、镁在根、茎、叶、花和籽中的含量均较高,锌、锰、铜、镍、钼的含量较少,铅和镉只在根和茎中痕量存在,结果表明糙苏中含有大量人体必需的微量元素,可为进一步探讨糙苏中元素含量与其药效的相关性提供科学的理论依据。     

Changes in the glutathione level induced by transplasma membrane electron transport in maize (Zea mays L.)

Summary We investigated changes of thiols (GSH, GSSG, and cysteine) induced by transplasma membrane electron transport after addition of artificial electron acceptors and the influence of the thiol level on redox activity. GSH, GSSG, and cysteine content of maize (Zea mays L. cv. Golden Bantam) roots and coleoptile segments was determined by high performance liquid chromatography with a fluorescence detector. GSSG increased after treatment with 0.8 mM diamide, an SH-group oxidizer. GSH level of roots increased after treatment with diamide, while GSH levels of coleoptiles decreased. Incubation of roots with the GSH biosynthesis inhibitor buthionine-D,L-sulfoximine for 6 days lowered the glutathione level up to 80%. However, the GSH/GSSG ratio of maize roots remained constant after treatment with both effectors. The GSH/GSSG ratio and the glutathione level were changed by addition of artificial electron acceptors like hexacyanoferrate (III) or hexabromoiridate (IV), which do not permeate the plasma membrane. Hexacyanoferrate (III) reduction was inhibited up to 25% after the cellular glutathione level was lowered by treatment with diamide or buthionine-D,L-sulfoximine. Proton secretion induced by reduction of the electron acceptors was not affected by both modulators. The change in glutathione level is different for roots and coleoptiles. Our data are discussed with regard to the role of GSH in electron donation for a plasma membrane bound electron transport system.Abbreviations Buthionine-D,L-sulfoximine s-n-butyl-homocysteine sulfoximine - cys cysteine - diamide 1,1-azobis (N,N-dimethyl-formamide) - DTE dithioerythritol - EDTA ethylenediaminetetraacetic acid - GSH reduced glutathione - GSSG oxidizied glutathione, glutathione disulfide - HBI IV hexabromoiridate (IV) (K₂[IrBr₆]) - HCF III hexacyanoferrate (III) (K₃[Fe(CN)₆] - NEM N-ethylmaleimide - PM plasma membrane - Tris Tris(hydroxymethyl)aminomethane     

Differential response of wheat roots to Cu, Ni and Cd treatment: oxidative stress and defense reactions

Wheat seedlings cv. Zyta were treated with Cu, Ni and Cd at the concentrations causing approximately 50 % root growth inhibition, i.e. 12.5, 50 and 60 μM, respectively. Tissue metal accumulation, membrane permeability, lipid peroxidation, protein oxidation, concentration of thiol compounds as well as protease, glutathione S-transferase (GST) and peroxidase (POD) activities were studied in roots after 7 days of metal exposure. The metals showed different concentrations in root tissues with Cu and Cd being accumulated to the smallest and to the greatest extent, respectively. Membrane permeability was significantly enhanced by Cu and Ni but not by Cd treatment. All metals induced similar increase in protein oxidation, while significant enhancement of lipid peroxidation was observed only in the case of Cu treatment. The detected thiol compounds: cysteine (Cys), homocysteine (Hcy), γ-glutamylcysteine (γ-GluCys) and glutathione (GSH) were differently influenced by the metal treatment. Ni appeared to be the most effective inductor of GSH accumulation while both Cu and Ni similarly increased Cys content in the roots. Accumulation of γ-GluCys was found in response to Cu and Cd applications. Concentration of Hcy was enhanced by Cd treatment but exposure to Ni decreased its content below the level of detection. The activity of GST was considerably elevated by Cd and Ni treatments, while POD activity was increased only in response to Cu application. Our study showed that wheat roots differently responded to treatment with metals used at the concentrations having similar impact on growth.     

Exercise training with ageing protects against ethanol induced myocardial glutathione homeostasis

Glutathione plays a central role in the maintenance of cellular antioxidant defense. The alterations in the glutathione and associated recyclic enzymes caused by both exercise training and ethanol are well documented; however, their interactive effects with age are not well understood. Therefore, the influence of ageing and the interactive effects of exercise training and ethanol on the myocardial glutathione system in 3 months and 18 months old rats were examined. The results showed a significant (p<0.01) reduction in GSH content, Se and non-Se GSH-Px, GR and GST activities in the myocardium of rat with age. A significant increase (p<0.05) in the activities of these enzymes was observed in both age groups of rats in response to exercise training. This exercise-induced elevation of Se and non-Se GSH-Px and GR activities was more pronounced in the 18 months old rats when compared to 3 months old rats. Ethanol consumption significantly (p<0.05) reduced the GSH content, Se and non-Se GSH-Px and GR activities in both age groups of rats. In contrast, ethanol consumption significantly (p<0.05) increased the activity of GST. The combined action of exercise plus ethanol significantly (p<0.05) elevated the GSH content, Se and non-Se GSH-Px, GR and GST activities when compared to the ethanol treated rats in both age groups, indicating the suppression of ethanol-induced oxidative stress by exercise training. In conclusion, there was a compensatory myocardial response lessening ethanol-induced oxidative stress by exercise training, which seemed to result from the higher activity of glutathione recycling and utilizing enzymes, which may be critical for preventing chronic oxidative damage to the myocardium during ageing and even due to ethanol consumption.