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 role of thiol redox systems in the peroxide stress response of <Emphasis Type="Italic">Escherichia coli</Emphasis>

The effect of mutations in the genes encoding glutathione, glutaredoxin, thioredoxin, and thioredoxin reductase on the response of growing Escherichia coli to oxidative stress was studied. The gshA mutants defective in glutathione synthesis had the lowest resistance to high doses of H₂O₂, whereas the trxB mutants defective in thioredoxin reductase synthesis had the highest resistance to this oxidant, exceeding that of the parent strain. Among the studied mutants, the trxB cells demonstrated the highest basic levels of catalase activity and intracellular glutathione; they were able to rapidly reach the normal GSH level after oxidative stress. At the same time, these bacteria showed high frequency of induced mutations. The expression of the katG and sulA genes suggests that, having different sensitivity to high oxidant concentrations, the studied mutants differ primarily in their ability to induce the antioxidant genes of the OxyR and SOS regulons.     

<Emphasis Type="Italic">Piriformospora indica</Emphasis> Alleviates Salinity by Boosting Redox Poise and Antioxidative Potential of Tomato

More than 20% of irrigated land has been influenced by salt stress, decreasing crop production. In this research, we investigated the effect of different levels of salinity (0, 50, 100 and 150 mM NaCl) and the efficiency of Piriformospora indica on growth, biochemical traits, antioxidative defense system in tomato (Solanum lycopersicum L.). NaCl stress reduced chlorophyll content, height and biomass of plants. Higher level of salinity (150 mM) declined the plant height by 22.65%, total dry weight by 56.44% and total chlorophyll by 44.34%, however, P. indica inoculation raised plant height by 43.47%, dry weight by 69.23% and total chlorophyll content by 48.09%. Salinity stress increased H₂O₂, malondialdehyde (MDA), superoxide anion and 1,1-diphenyl-2-picrylhydrazyl (DPPH) level in leaves and roots tomato seedlings. However, P. indica inoculation reduced H₂O₂, MDA and superoxide anion and enhanced DPPH compared to non-inoculated plants at all NaCl levels. The total phenol and flavonoids increased with NaCl treatment. On the other hand, the total phenolic and flavonoid increased more in P. indica inoculated plants compared to non-inoculated ones. Moreover, inoculation of P. indica implicated noteworthy improvement of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR), and glutathione reductase (GR) activity in tomato upon salinity. Notably, colonization with P. indica significantly improved the content of reduced ascorbic acid (AsA), glutathione (GSH) and redox ratio in the tomato plants under salinity resulting in reduced redox state. Our findings confirmed that salinity had negative effect on tomato seedling; however, P. indica inoculation increased tolerance to salinity by improving the content of phenolic compounds, non-enzymatic antioxidants, and increasing the activity of antioxidant enzymes.     

Antioxidant responses of different microalgal species to nonylphenol-induced oxidative stress

The antioxidant responses of four green microalgae, i.e., Chlorella vulgaris, Chlorella sp., Selenastrum capricornutum and Scenedesmus quadricauda, under control, low (0.1 mg L^?1) and high (1.0 mg L^?1) nonylphenol (NP) concentration were studied. The antioxidant responses of microalgae to NP depended on both NP concentrations and exposure time. The effects of NP on antioxidant responses were most obvious on the first day of exposure and the effects decreased with prolonged exposure time. At low NP concentration, there were no significant changes in activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), or in glutathione (GSH) content, in all four species, while high concentration of NP led to different changes in these parameters. In NP-tolerant species, i.e., C. vulgaris and Chlorella sp., activities of SOD, CAT and POD increased remarkably when exposed to high NP concentration, while the increase was less evident or insignificant in Se. capricornutum and Sc. quadricauda, the two NP-sensitive species. On the other hand, the malondialdehyde (MDA) content declined gradually with increase in NP concentrations, particularly in C. vulgaris and Chlorella sp. Similarly, NP exposure caused an inhibition of glutathione peroxidase (GPX) activity in all four species. However, the changes of glutathione reductase (GR) and glutathione S-transferase (GST) activity did not seem to correlate with the NP tolerance of microalgae. These results suggested that various antioxidant mechanisms were involved in microalgae when exposed to NP, and the NP-tolerant species displayed more evident and rapid changes in some antioxidant responses than the NP-sensitive ones.     

Responses of the antioxidative and biotransformation enzymes in the aquatic fungus <Emphasis Type="Italic">Mucor hiemalis</Emphasis> exposed to cyanotoxins

Objectives

To investigate antioxidative and biotransformation enzyme responses in Mucor hiemalis towards cyanotoxins considering its use in mycoremediation applications.

Results

Catalase (CAT), glutathione reductase (GR), and glutathione peroxidase (GPx) in M. hiemalis maintained their activities at all tested microcystin-LR (MC-LR) exposure concentrations. Cytosolic glutathione S-transferase (GST) activity decreased with exposure to 100 µg MC-LR l^?1 while microsomal GST remained constant. Cylindrospermopsin (CYN) at 100 µg l^?1 led to an increase in CAT activity and inhibition of GR, as well as to a concentration-dependent GPx inhibition. Microsomal GST was inhibited at all concentrations tested. β-N-methylamino-l-alanine (BMAA) inhibited GR activity in a concentration-dependent manner, however, CAT, GPx, and GST remained unaffected.

Conclusions

M. hiemalis showed enhanced oxidative stress tolerance and intact biotransformation enzyme activity towards MC-LR and BMAA in comparison to CYN, confirming its applicability in bioreactor technology in terms of viability and survival in their presence.

     

Effect of 24-Epibrassinolide on Antioxidative Defence System Against Lead-Induced Oxidative Stress in The Roots of <Emphasis Type="Italic">Brassica juncea</Emphasis> L. Seedlings

Lead (Pb) toxicity causes oxidative stress by increasing the production of reactive oxygen species. The aim of the present study was to investigate the role of 24-epibrassinolide (24-EBL) on the antioxidant defence system as a response to Pb stress in Brassica juncea L. Surface-sterilized seeds were exposed to Pb ion (0 and 2 mM) toxicity in Petri dishes and subsequently, the seeds were sprayed with either (i) deionized water or (ii) different concentrations (10^–12, 10^–10, and 10^–8 M) of 24-EBL on alternate days. After nine days, the roots of the B. juncea seedlings were harvested to analyze the heavy metal content, root length, hydrogen peroxide level, lipid peroxidation, total protein content and activities of the antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase, peroxidase, glutathione reductase and glutathione-S-transferase). According to our results, the Pb ions accumulated by the B. juncea roots led to oxidative stress by increasing the level of H₂O₂ and malondialdehyde, and thus, increased the activity of the antioxidative enzymes (except for catalase) and the growth and total protein content decreased. Whereas, the 24-EBL treatment to the roots of Pb stressed seedlings was able to alleviate the Pb-induced oxidative stress. Upon the application of 24-EBL, a reduction in Pb accumulation, H₂O₂ and malondialdehyde levels as well as an increased total protein content and activity of antioxidative enzymes detoxifying hydrogen peroxide (catalase, ascorbate peroxidase and peroxidase) were observed. As a result, the stress protective properties of 24-EBL depending on concentration in B. juncea roots were revealed in this study.     

Age-related changes in antioxidant and glutathione S-transferase enzyme activities in the Asian clam

Aging is accompanied by increased production of free oxygen radicals and impairment of normal cellular functions. The aim of this work was to provide preliminary data on age-related differences in the activities of antioxidant enzymes and phase II biotransformation enzyme glutathione S-transferase (GST) in a wild population of the Asian clam Corbicula fluminea. The antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR), and GST were assessed in visceral mass of four age classes (0+-, 1+-, 2+-, and 3+-year-old) of C. fluminea clams. Age-related changes were seen in antioxidant enzyme status: levels of total SOD (totSOD) (P < 0.05), MnSOD, and CuZnSOD (P < 0.05) activities increased progressively during aging from younger to older clams. Changes in CAT and GR activities with advancing age were found, the levels being the highest in age class II, then being lower in age classes III and IV (P < 0.05). Activities of GPX and GST were lower in the senescent individuals (2+- and 3+-year-old clams) compared with young individuals (0+- and 1+-year-old clams). Overall, the decline of glutathione-dependent enzyme activities, coupled with higher and lower activities of totSOD and CAT, respectively, as the individual grows older, may render the older animals more susceptible to oxidative stress. Data reported here are not intended to be exhaustive since they concern only age/size structure of the population at one locality, so more detailed studies on both the developmental stages and levels of antioxidant enzymes of this new alien species in Serbian rivers are required.     

Enhancement of phenol stress tolerance in transgenic <Emphasis Type="Italic">Arabidopsis</Emphasis> plants overexpressing glutathione S-transferase

Plant glutathione S-transferases (GSTs) are important for protecting plants against oxidative damage. We studied the function of a glutathione S-transferase family protein in Arabidopsis, AtGSTF2. Our results indicate the transgenic plants showed increased tolerance to oxidative stress caused by application of phenol. Under phenol stress, the lipid hydroperoxidation [the production of malondialdehyde (MDA)] of the leaves in overexpressing lines was suppressed compared with that of control plants. The antioxidative enzyme activities (SOD and POD) were higher in transgenic plants than in control. Furthermore, the residual phenol in medium was decreased more in transgenic plants than in control plants. These results indicate overexpressing GST protein reduce the damage of lipid hydroperoxidation and oxidative damage caused by phenol. Our findings also provide a suitable remediation strategy for sites contaminated by phenol.     

In planta characterization of a tau class glutathione S-transferase gene from <Emphasis Type="Italic">Juglans regia</Emphasis> (<Emphasis Type="Italic">JrGSTTau1</Emphasis>) involved in chilling tolerance

Key message

JrGSTTau1 is an important candidate gene for plant chilling tolerance regulation.

Abstract

A tau subfamily glutathione S-transferase (GST) gene from Juglans regia (JrGSTTau1, GeneBank No.: KT351091) was cloned and functionally characterized. JrGSTTau1 was induced by 16, 12, 10, 8, and 6 °C stresses. The transiently transformed J. regia showed much greater GST, glutathione peroxidase (GPX), superoxide dismutase (SOD), and peroxidase (POD) activities and lower H₂O₂, malondialdehyde (MDA), reactive oxygen species (ROS), and electrolyte leakage (EL) rate than prokII (empty vector control) and RNAi::JrGSTTau1 under cold stress, indicating that JrGSTTau1 may be involved in chilling tolerance. To further confirm the role of JrGSTTau1, JrGSTTau1 was heterologously expressed in tobacco, transgenic Line5, Line9, and Line12 were chosen for analysis. The germinations of WT, Line5, Line9, and Line12 were similar, but the fresh weight, primary root length, and total chlorophyll content (tcc) of the transgenic lines were significantly higher than those of WT under cold stress. When cultivated in soil, the GST and SOD activities of transgenic tobacco were significantly higher than those of WT; however, the MDA and H₂O₂ contents of WT were on average 1.47- and 1.96-fold higher than those of Line5, Line9, and Line12 under 16 °C. The DAB, Evans blue, and PI staining further confirmed these results. Furthermore, the abundances of NtGST, MnSOD, NtMAPK9, and CDPK15 were elevated in 35S::JrGSTTau1 tobacco compared with WT. These results suggested that JrGSTTau1 improves the plant chilling tolerance involved in protecting enzymes, ROS scavenging, and stress-related genes, indicating that JrGSTTau1 is a candidate gene for the potential application in molecular breeding to enhance plant abiotic stress tolerance.

     

Transgenic <Emphasis Type="Italic">Arabidopsis</Emphasis> Plants Expressing Grape Glutathione S-Transferase Gene (<Emphasis Type="Italic">VvGSTF13</Emphasis>) Show Enhanced Tolerance to Abiotic Stress

Although glutathione S-transferase (GST, EC 2.5.1.18) is thought to play important roles in abiotic stress, limited information is available regarding the function of its gene in grapes. In this study, a GST gene from grape, VvGSTF13, was cloned and functionally characterized. Transgenic Arabidopsis plants containing this gene were normal in terms of growth and maturity compared with control plants but had enhanced resistance to salt, drought, and methyl viologen stress. The increased tolerance of the transgenic plants correlated with changes in activities of antioxidative enzymes. Our results indicate that the gene from grape plays a positive role in improving tolerance to salinity, drought, and methyl viologen stresses in Arabidopsis.     

SkQ1 Controls <Emphasis Type="Italic">CASP3</Emphasis> Gene Expression and Caspase-3-Like Activity in the Brain of Rats under Oxidative Stress

Here, we studied the effect of the mitochondria-targeted antioxidant SkQ1 (plastoquinone cationic derivative) on the CASP3 gene expression and caspase-3 activity in rat cerebral cortex and brain mitochondria under normal conditions and in oxidative stress induced by hyperbaric oxygenation (HBO). Under physiological conditions, SkQ1 administration (50 nmol/kg, 5 days) did not affect the CASP3 gene expression and caspase-3-like activity in the cortical cells, as well as caspase-3-like activity in brain mitochondria, but caused a moderate decrease in the content of primary products of lipid peroxidation (LPO) and an increase in the reduced glutathione (GSH) level. HBO-induced oxidative stress (0.5 MPa, 90 min) was accompanied by significant upregulation of CASP3 mRNA and caspase-3-like activity in the cerebral cortex, activation of the mitochondrial enzyme with simultaneous decrease in the GSH content, increase in the glutathione reductase activity, and stimulation of LPO. Administration of SkQ1 before the HBO session maintained the basal levels of the CASP3 gene expression and enzyme activity in the cerebral cortex cells and led to the normalization of caspase-3-like activity and redox parameters in brain mitochondria. We hypothesize that SkQ1 protects brain cells from the HBO-induced oxidative stress due to its antioxidant activity and stimulation of antiapoptotic mechanisms.     

Effects of exogenous spermidine on antioxidant system of tomato seedlings exposed to high temperature stress

The effects of foliar spraying with spermidine (Spd) on antioxidant system in tomato (Lycopersicon esculentum Mill.) seedlings were investigated under high temperature stress. The high temperature stress significantly inhibited plant growth and reduced chlorophyll (Chl) content. Application of exogenous 1 mM Spd alleviated the inhibition of growth induced by the high temperature stress. Malondialdehyde (MDA), hydrogen peroxide (H₂O₂) content and superoxide anion (O₂) generation rate were significantly increased by the high temperature stress, but Spd significantly reduced the accumulation of reactive oxygen species (ROS) and MDA content under the stress. The high temperature stress significantly decreased glutathione (GSH) content and activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR), but increased contents of dehydroascorbic acid (DHA), ascorbic acid (AsA), and oxidized glutathione (GSSG) in tomato leaves. However, Spd significantly increased the activities of antioxidant enzymes, levels of antioxidants and endogenous polyamines in tomato leaves under the high temperature stress. In addition, to varying degrees, Spd regulated expression of MnSOD, POD, APX2, APX6, GR, MDHAR, DHAR1, and DHAR2 genes in tomato leaves exposed to the high temperature stress. These results suggest that Spd could change endogenous polyamine levels and alleviate the damage by oxidative stress enhancing the non-enzymatic and enzymatic antioxidant system and the related gene expression.     

<Emphasis Type="Italic">Arbutus andrachne</Emphasis> L. Reverses Sleep Deprivation-Induced Memory Impairments in Rats

Sleep deprivation (SD) is associated with cognitive deficits. It was found to affect the hippocampus region of the brain by impairing memory formation. This impairment is suggested to be caused by elevation in oxidative stress in the body, including the brain during SD. It was hypothesized that the methanolic extract of the fruits of Arbutus andrachne L. (Ericaceae) will prevent chronic SD-induced impairment of hippocampal memory via its antioxidative properties. The methanolic extract of the fruits of A. andrachne was evaluated for its beneficial properties to reverse SD-induced cognitive impairment in rats. Animals were sleep deprived for 8 weeks using a multiple platform model. The extract was administered i.p. at three doses (50, 200, and 500 mg/kg). Behavioral studies were conducted to test the spatial learning and memory using radial arm water maze (RAWM). In addition, the hippocampus was dissected to analyze the following oxidative stress markers: glutathione (GSH), oxidized glutathione (GSSG), GSH/GSSG, glutathione peroxidase (GPx), and catalase. Chronic SD impaired short- and long-term memories (P < 0.05). Treatment of animals with A. andrachne fruit extract at all doses prevented long-term memory impairment induced by SD while such treatment prevented short-term memory impairment only at 200 and 500 mg/kg dose levels. Moreover, A. andrachne fruit extract normalized the reduction in the hippocampus GSH/GSSG ratio and activity of GPx, and catalase (P < 0.05) induced by chronic sleep deprivation. Chronic sleep deprivation impaired both short- and long-term memory formation, while methanolic extract of A. andrachne fruits reversed this impairment, probably through normalizing oxidative stress in the hippocampus.     

Effects of exogenous <Emphasis Type="Italic">myo</Emphasis>-inositol on leaf water status and oxidative stress of <Emphasis Type="Italic">Capsicum annuum</Emphasis> under drought stress

Drought-stressed plants accumulate cyclitols such as myo-inositol, pinitol, quercitol in the cytosol. These solutes (compatible solutes) protect plants from stress effects. Synthetic myo-inositol was used in the investigation of drought stress tolerance in pepper plants. Hydrogen peroxide (H₂O₂), membrane damage, ascorbate peroxidase (AP), catalase (CAT), proline and calcium increased in plants under drought conditions. Water status, calcium level, glutathione reductase activities increased in myo-inositol treated Capsicum annuum L. (pepper) under drought stress. Exogenous myo-inositol significantly decreased H₂O₂, membrane damage and proline levels and AP (except for 5 µM) and CAT activity, compared with untreated plants. Myo-inositol can play a role as effective as proline in signal transduction and in regulating concentrations of reactive oxygen species within tolerable ranges and in maintaining cell turgor by binding water molecules. Myo-inositol may become a useful instrument to eliminate the negative effects of drought environments.     

Silicon enhances the tolerance of <Emphasis Type="Italic">Poa annua</Emphasis> to cadmium by inhibiting its absorption and oxidative stress

Silicon (Si) could enhance plant tolerance to heavy metals; however, the mechanism of Si-mediated alleviation of cadmium (Cd) toxicity in Poa annua was not clear. In this study, we found that 100 μM Cd significantly inhibited the growth of Poa annua seedlings. Furthermore, Cd enhanced the H₂O₂ and malondialdehyde content. The activities of superoxide dismutase and ascorbate peroxidase were enhanced, but the catalase and peroxidase activities were reduced by Cd treatment. Cd also altered the activity and expression of glucose-6-phosphate dehydrogenase (G6PDH) in Poa annua roots. Application of Na₃PO₄, an inhibitor of G6PDH, decreased the activity of G6PDH, the expression of G6PDH, and increased the Cd toxicity, suggesting that G6PDH is involved in the regulation of oxidative stress induced by Cd. Application of 1 mM Si alleviated the inhibition of Cd on the growth of Poa annua seedlings. Si application not only led to reduced oxidative injuries but also decreased the accumulation of Cd in Poa annua seedlings under Cd stress. Furthermore, Si decreased the activity of G6PDH and the expression of G6PDH under Cd stress, which demonstrated that Si attenuates the Cd toxicity in Poa annua probably through decreasing the expression of G6PDH under Cd stress. When G6PDH was inhibited, the alleviation impact of Si on Cd stress was abolished. Taken together, these results demonstrated that the Cd tolerance in Poa annua enhanced by Si is mainly due to the decrease of Cd uptake in roots and lowering the oxidative stress induced by Cd.     

Hydrogen sulfide is involved in the regulation of ascorbate and glutathione metabolism by jasmonic acid in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

This study investigated the role of hydrogen sulfide (H₂S) in the regulation of the ascorbate (AsA) and glutathione (GSH) metabolism by jasmonic acid (JA) in the leaves of Arabidopsis thaliana by using H₂S scavenger hypotaurine (HT) and H₂S synthetic mutant (SALK_041918, designated Atl-cdes). The results showed that JA significantly increased the H₂S content, the activities of L-cysteine desulfhydrase (L-CDes), D-cysteine desulfhydrase (D-CDes), ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), L-galactono-1,4-lactone dehydrogenase (GalLDH) and γ-glutamylcysteine synthetase (γ-ECS), the ratio of AsA to dehydroascorbate (DHA), and decreased the content of malondialdehyde (MDA) and H₂O₂ in the wild type of A. thaliana, compared to control. The above effects of JA except the increased activities of L-CDes and D-CDes were suppressed by addition of HT. However, JA and HT+JA had no significant effects on the ratio of reduced GSH to oxidized GSH (GSSG) in the wild type of A. thaliana. Application of HT to the control decreased H₂S content, AsA/DHA ratio, and activities of APX, GR, DHAR, MDHAR, γ-ECS, and GalLDH, but had no effects on MDA content, activities of L-CDes and D-CDes, and GSH/GSSG ratio. In the H₂S synthetic mutant, JA had no obvious effects on above mentioned parameters except the D-CDes activity compared with the control. Our results suggest that JA-induced H₂S, which is a signal that leads to the up-regulation of the AsA and GSH metabolism.