Antioxidant Enzymatic Responses Research Articles

Analysis of Biochemical Responses in Vigna Mungo Varieties Subjected to Drought Stress and Possible Amelioration

A complex response (in terms of physiological, biochemical and molecular level) is shown by plants exposed to drought and depending on that, plants show differential adaptation and tolerance mechanisms. Drought stress effects on plants are generally evident in terms of reduced growth, loss of membrane stability and integrity, reduction in essential pigments like chlorophyll etc. The pulse crops black gram (Vigna mungo L.) is an important protein source that is grown in all over India. In addition, it also plays an important role in sustaining soil fertility by fixing atmospheric nitrogen. However, productivity is adversely affected by various biotic and abiotic stresses necessitating screening of newer varieties for better adaptation to local conditions. In the present study, three varieties of Vigna mungo, viz., IPU 94-1, PU 40 and PU 19, widely grown in the northern India were evaluated for their response to short term drought stress at early growth stage. Drought stress had detrimental effect in several biochemical parameters like chlorophyll content, lipid peroxidation, oxidative stress, generation of H2O2. Modulations of several metabolic components like phenolics, proline and antioxidant enzymatic responses of superoxide dismutase, peroxidase and catalase were observed in drought and recovery to combat the stress.

Evaluation of antioxidant enzymes in response to predator odor stress in prefrontal cortex and amygdala

Conditions of stress can originate from diverse stimuli including physical, chemical, antigenic and psychological. The latter is processed in part via the hypothalamic-pituitary-adrenal (HPA) axis, with input from and communication between the amygdala (AM) and prefrontal cortex (PFC). The HPA axis generates an increase in circulating glucocorticoids, augmenting metabolism and, consequently, oxygen consumption, increasing the production of free radicals and reactive oxygen species (ROS). Exposure to predator odor as a model of non-invasive acute stress was used to evaluate the hypothesis that psychogenic stress can modify enzymatic antioxidant responses. The activities of various enzymes, catalase (CAT), cytosolic and mitochondrial superoxide dismutase (Cu, Zn-SOD and Mn-SOD, respectively) and glutathione S-transferase (GST), were determined in AM and PFC. Acute psychogenic stress inhibited CAT activity in the AM and PFC, and increased Mn-SOD activity in the PFC. These results demonstrate that different responses can be elicited by the same stressor in two separate brain regions involved in processing emotional stimuli, and that changes in specific antioxidant enzymatic responses can be seen with exposure to acute psychogenic stress.

Response to oxidative stress induced by cadmium and copper in tobacco plants (Nicotiana tabacum) engineered with the trehalose-6-phosphate synthase gene (AtTPS1)

The response of tobacco plants genetically engineered with the AtTPS1 gene to stress induced by excess Cu and Cd was evaluated in hydroponic solution (100 and 400 μM Cu and 50 and 200 μM Cd) after a 48 h exposure. Two transgenic lines, transformed with the AtTPS1 (trehalose-6-phosphate synthase) gene from Arabidopsis, with different levels of trehalose-6-phosphate synthase expression (B5H, higher and B1F, lower), and a wild type (WT) were investigated. Protein content, antioxidative enzymes (CAT, POD, SOD, and APX), glucose, fructose, lipid peroxidation, hydrogen peroxide and Cd and Cu contents were determined in leaves. The two transgenic lines were differently influenced by Cd and Cu exposure as they induced a different antioxidant enzymatic defense response. B1F and B5H plants showed a better acclimation to Cd and excess Cu compared to WT. Furthermore B1F was more tolerant than B5H to Cd and excess Cu. B1F accumulated less Cd and Cu in leaves, probably due to a more efficient exclusion mechanism. Catalase was shown to be the most important enzyme in the antioxidative system of these plants.

Benthic community structure and biomarker responses of the clam Scrobicularia plana in a shallow tidal creek affected by fish farm effluents (Rio San Pedro, SW Spain)

The effects of solid organic wastes from a marine fish farm on sediments were tested using benthic community as ecological indicators and biomarkers in native clam (Scrobicularia plana) as biochemical indicators. The benthic fauna and clam samples were collected in the intertidal sediment in October 2010 from five sites of the Rio San Pedro (RSP) creek, following a gradient of contamination from the aquaculture effluent to the control site. Numbers of species, abundance, richness and Shannon diversity were the biodiversity indicators measured in benthic fauna. Morphological and reproduction status of clams were assessed using the condition factor and gonado-somatic index, respectively. Phase I and Phase II detoxification enzymatic activities (ethoxyresorufin O-deethylase (EROD), glutathione S-transferase (GST)), antioxidant enzymatic activities (glutathione peroxidase (GPX), glutathione reductase (GR)) and oxidative stress parameters (Lipid Peroxidation (LPO) and DNA strand breaks) were measured in clams' digestive gland tissues. In parallel, temperature and salinity in the adjacent water, redox potential, pH and organic matter in sediment, and dissolved oxygen in the interstitial water were measured. The results suggested that RSP showed a spatial gradient characterised by hypoxia/anoxia, reduced potential, acidic conditions and high organic enrichment in sediments at the most contaminated sites. Significant (p<0.05) decrease of biodiversity indicators were observed in the areas impacted by the aquaculture discharges. Biomarkers did not show a clear pattern and of all biochemical responses tested, GPX, DNA damage and LPO were the most sensitive ones and showed significant (p<0.05) increase in the polluted sites. Benthic biodiversity indicators were significantly (p<0.05) positively correlated with pH, redox potential and dissolved oxygen and negatively correlated with organic matter. On the contrary, antioxidant enzymatic responses (GPX) and oxidative stress parameters were significantly (p<0.05) negatively correlated with those physico-chemical parameters. It has been demonstrated that effluents from fish aquaculture activities in Río San Pedro creek may produce an alteration of physico-chemical characteristics of seabed and induce oxidative stress and DNA damage in soft-sediment species which may lead to changes of the benthic population structure and health status of the exposed organisms.

Effect of waterborne zinc exposure on metal accumulation, enzymatic activities and histology of Synechogobius hasta

The present study was conducted to determine the metal accumulation, antioxidant enzymatic response, hepatic intermediary metabolism and histological changes in Synechogobius hasta exposed to 0.35 (control), 9.7 and 19.2 mg/L Zn, respectively, on the 0, 4th, 8th and 12th day. Waterborne Zn exposure significantly reduced hepatosomatic index, hepatic lipid contents and fatty liver occurrence rate, increased Zn, Fe and Mn contents and reduced the contents of Cu and Ca in liver, and increased muscle Zn content. Waterborne Zn exposure also significantly influenced enzymatic activities involved in antioxidant responses (superoxide dismutase, catalase, glutathione-S-transferase, malondialdehyde) in liver and spleen, and changed hepatic intermediary enzymatic activities (succinate dehydrogenase, malic dehydrogenase, lactate dehydrogenase, lipoprotein lipase, hepatic lipase), impaired the histological structure of the gill and spleen, and reduced vacuolated hepatocytes. Thus, our study demonstrated for the first time that waterborne Zn exposure could reduce fatty liver syndrome in S. hasta.

Amphotericin B induces trehalose synthesis and simultaneously activates an antioxidant enzymatic response in Candida albicans

Background Enzymes involved in trehalose metabolism have been proposed as potential targets for new antifungals. To analyse this proposal, the susceptibility to Amphotericin B (AmB) of the C. albicans trehalose-deficient mutant tps1Δ/tps1Δ, was examined. Methods Determination of endogenous trehalose and antioxidant enzymatic activities as well as RT-PCR analysis in cells subjected to AmB treatments was performed. Results Exponential tps1Δ null cultures showed high degree of cell killing upon exposure to increasing AmB doses respect to CAI.4 parental strain. Reintroduction of the TPS1 gene restored the percentage of cell viability. AmB induced significant synthesis of endogenous trehalose in parental cells, due to the transitory accumulation of TPS1 mRNA or to the moderate activation of trehalose synthase (Tps1p) with the simultaneous deactivation of neutral trehalase (Ntc1p). Since tps1Δ/tps1Δ mutant cells are highly susceptible to acute oxidative stress, the putative antioxidant response to AmB was also measured. A conspicuous activation of catalase and glutathione reductase (GR), but not of superoxide dismutase (SOD), was observed when the two cell types were exposed to high concentrations of AmB (5 μg/ml). However, no significant differences were detected between parental and tps1Δ null strains as regards the level of activities. Conclusions The protective intracellular accumulation of trehalose together with the induction of antioxidant enzymatic defences are worthy mechanisms involved in the resistance of C. albicans to the fungicidal action of AmB. General significance The potential usefulness of trehalose synthesis proteins as an interesting antifungal target is reinforced. More importantly, AmB elicits a complex defensive response in C. albicans.

Eicosanoids mediate hemolymph oxidative and antioxidative response in larvae of Galleria mellonella L.

Antioxidant enzymes play a major role in the defense against pro-oxidative effects of xenobiotics and pro-oxidant plant allelochemicals in insects. We posed the hypothesis that eicosanoids also mediate antioxidant enzymatic defense reactions to pro-oxidant challenge. To test this idea, we reared first-instar larvae of Galleria mellonella (L.) with the lypoxygenase inhibitor, esculetin (0.001%), the phospholipase A 2 inhibitor, dexamethasone (0.001%) and the dual inhibitor of cyclooxygenase and lipoxygenase, phenidone (0.1%) to seventh-instars. Newly ecdysed seventh-instars were then fed on artificial diet containing 0.05% xanthotoxin (XA) for 2 days. Treating seventh-instar larvae of G. mellonella with XA induced lipid peroxidation and protein carbonylation as evident from the increased content of malondialdehyde (MDA) and protein carbonyls respectively, and antioxidative enzymatic response in a dose-dependent manner. High dietary XA concentrations (0.005 and 0.1%) were associated with increasing MDA and carbonyl content (by 3-fold) and antioxidant enzyme activities, superoxide dismutase (SOD) (by 3-fold) and catalase (CAT) (by 4-fold), and glutathione-dependent enzymes, glutathione S-transferase (GST) (by 15-fold) and glutathione peroxidase (GPx) (by 7-fold). Relative to control, eicosanoid biosynthesis inhibitors (EBIs) esculetin, dexamethasone and phenidone also resulted in impaired MDA content and antioxidant enzyme activities. However, carbonyl content did not differ between control- and EBIs-feeding larvae. Finally, MDA and carbonyl content, and antioxidant enzymes SOD, GST and GPx activities exhibited an incremental increase while CAT activity was decreased in the experimental larvae that had been reared on media amended with esculetin, dexamethasone and phenidone and then challenged with our standard XA challenge dose. Two of the markers indicated that significantly higher levels of oxidative stress were produced in the hemolymph tissue of larvae fed diets supplemented with EBIs and then challenged with XA. This oxidative stress was associated with elicited antioxidative responses by increasing SOD, GST and GPx and decreasing CAT activities in hemolymph. We infer from these findings that eicosanoids mediate insect antioxidant enzymatic responses to dietary pro-oxidants.

Hepatitis C virus‐core and non structural proteins lead to different effects on cellular antioxidant defenses

Chronic hepatitis C virus (HCV) infection leads to increased oxidative stress in the liver. Hepatic antioxidant enzymes provide an important line of defense against oxidative injury. To understand the antioxidant responses of hepatocytes to different HCV proteins, we compared changes in antioxidative enzymes in HCV-core and HCV-nonstructural protein expressing hepatocyte cell lines. We found that expression of HCV-core protein in hepatocyte cell lines leads to increased oxidative stress as determined by increased in the oxidant-sensitive probe 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate (CM-DCFH(2)) fluorescence, decreased reduced glutathione (GSH), and increased oxidation of thioredoxin (Trx). Although the expression of HCV-nonstructural (HCV-NS) proteins led to increased oxidative stress as well, the antioxidant enzymatic responses were different. Over-expression of HCV-NS proteins increased antioxidant enzymes (MnSOD and catalase), heme oxygenase-1 (HO-1), and GSH, indicating different mechanism(s) of prooxidative activity than HCV-core protein. Our findings show that different HCV proteins induce different antioxidant defense responses in hepatocytes. These findings may facilitate understanding the interaction of different HCV proteins with infected liver cells and help identify possible factors contributing to hepatocyte damage during HCV infection.

Influence of repeated acid rain treatment on antioxidative enzyme activities and on lipid peroxidation in cucumber leaves

The effect of repeated treatment with simulated acid rain (AR) on antioxidative enzyme activities, lipid peroxidation and chlorophyll concentration in cucumber plants ( Cucumis sativus L.) was investigated. Measurements were carried out one, five and seven days after triple spraying. Ascorbate peroxidase (APx) and glutathione transferase (GST) activities increased considerably after the exposure to AR stress indicating a direct correlation with pH of the used solution. Both enzyme activities were enhanced to the end of the experiment, which could contribute to the scavenging of reactive oxygen species (ROS) and detoxification of potentially toxic products originating from AR stress. Contrary to APx and GST activities, increases in catalase (CAT) and glutathione peroxidase (GSH-Px) activities were observed shortly after AR stress only. Changes in chlorophyll concentration were strongly dependent on pH of the applied AR. It was also found that lipid peroxidation measured as 2-thiobarbituric acid reactive substances (TBARS) concentrations was increasing in cucumber plants to the fifth day after AR treatment. Leaf bleaching and increased TBARS concentration suggested premature senescence of the AR-treated plants. Our results indicated that antioxidant enzymatic response to AR stress was quite sufficient in leaf tissue exposed to AR pH 4.4 but was not effective at pH below 3.0. A hypothesis can be put forward that elevated activities of APx and GST are of importance in plant defence against AR stress. Moreover, GSH-Px and GST activities seemed to be sufficient to keep TBARS concentration at the control level in the final phase of the experiment.

Age-dependent ultrastructural alterations and biochemical response of rat skeletal muscle after hypoxic or hyperoxic treatments

This work deals with the antioxidant enzymatic response and the ultrastructural aspects of the skeletal muscle of young and aged rats kept under hypoxic or hyperoxic normobaric conditions. It is in fact well known that the supply of oxygen at concentrations higher or lower than those occurring under normal conditions can promote oxidative processes that can cause tissue damage. The enzymes investigated were both those directly involved in reactive oxygen species (ROS) scavenging (superoxide dismutase, catalase and selenium-dependent glutathione peroxidase), and those challenged with the detoxication of cytotoxic compounds produced by the action of ROS on biological molecules (glutathione transferase, glyoxalase I, glutathione reductase), in order to obtain a comparative view of the defence strategies used with respect to aging. Our results support the hypothesis that one of the major contributors to the aging process is the oxidative damage produced at least in part by an impairment of the antioxidant enzymatic system. This makes the aged organism particularly susceptible to oxidative stress injury and to the related degenerative diseases, especially in those tissues with high demand for oxidative metabolism.

Cd-induced Oxidative Burst in Tobacco BY2 Cells: Time Course, Subcellular Location and Antioxidant Response

The relation between Cd and oxidative stress in BY2 cell cultures of tobacco was studied. In response to 5 mM Cd, a rapid generation of H2O2 has been detected in tobacco cell cultures by the oxidative quenching of the fluorescent reporter dye pyranine. This oxidative burst reached the maximum production of H2O2 after 10 min of treatment with Cd. This response could be considered as short term hypersensitive response previous to the oxidative stress caused by the metal at the cell plasma membrane. The observed antioxidant enzymatic response to the oxidative burst was preceded by an increased peroxidation of lipids with a significant increase in the activities of superoxide dismutase and ascorbate peroxidase. The results presented in this study point out to the plasma membrane as the primary target for the short term production of activated oxygen species in response to Cd in BY2 tobacco cells followed by a coordinated activation of the antioxidant enzymatic system.