Chilling, oxidative stress and antioxidant responses in shoot cultures of rice

Chilling of shoot cultures from Oryza sativa L. cv. Taipei 309, to 4 °C leads to conditions of oxidative stress. Tissue H₂O₂ was observed to increase more than fourfold by 8 d of chilling, and levels of reduced glutathione, which normally rise in growing shoot cultures at 25 °C, were considerably repressed in chilled cultures. Whilst the activity of ascorbate peroxidase in chilled shoots remained similar to the activities in control cultures at 25 °C, the most notable effects of chilling to 4 °C were the very significant loss of catalase and glutathione reductase activity. Although prior exposure of shoot cultures to abscisic acid (ABA) at 25 °C increased levels of catalase activity, such increased levels were not sustained when the pre-treated cultures were placed at 4 °C. Moreover such pre-treatment with ABA did not increase the subsequent ability of shoot cultures to grow at 4 °C.Abbreviations GSH reduced glutathione - GSSG oxidised glutathione - ABA cis-abscisic acid This work is supported by a grant from the Biotechnology and Biological Sciences Research Council.     

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.     

Ultraviolet-B-induced oxidative stress and antioxidant defense system responses in ascorbate-deficient vtc1 mutants of Arabidopsis thaliana

Ultraviolet-B (UV-B) radiation has a negative impact on plant cells, and results in the generation of reactive oxygen species (ROS). In order to increase our understanding of the effects of UV-B on antioxidant processes, we investigated the response of an ascorbate-deficient Arabidopsis thaliana mutant vtc1 to short-term increased UV-B exposure. After UV-B supplementation, vtc1 mutants exhibited oxidative damage. Evidence for damage included an increase in H(2)O(2) content and the production of thiobarbituric acid reactive substances (TBARS); a decrease in chlorophyll content and chlorophyll fluorescence parameters were also reported. The vtc1 mutants had higher total glutathione than the wild type (WT) during the first day of UV-B treatment. We found reduced ratio of glutathione/total glutathione and increased ratio of dehydroascorbate/total ascorbate in the vtc1 mutants, compared to the WT plants. In addition, the enzymes responsible for ROS scavenging, including superoxide dismutase, catalase, and ascorbate peroxidase, had insufficient activity in the vtc1 mutants, compared to the WT plants. The same reduced activity in the vtc1 mutants was reported for the enzymes responsible for the regeneration of ascorbate and glutathione (including monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase). These results suggest that the ascorbate-deficient mutant vtc1 is more sensitive to supplementary UV-B treatment than WT plants and ascorbate can be considered an important antioxidant for UV-B radiation.     

Combined effect of salicylic acid and salinity on some antioxidant activities,oxidative stress and metabolite accumulation in <Emphasis Type="Italic">Phaseolus vulgaris</Emphasis>

It has been shown that salicylic acid (SA) acts as an endogenous signal molecule responsible for inducing abiotic stress tolerance in plants. The effect of SA and sodium chloride (NaCl) on growth, metabolite accumulation, oxidative stress and enzymatic and non-enzymatic antioxidant responses on common bean plants (Phaseolus vulgaris, cv. F-15) was studied. Results revealed that either SA or NaCl decrease, shoot, root and total plant dry weights. SA treatments decreased the contents of proline, and reduced forms of ascorbate and glutathione, however, the content of soluble sugars (TSS), thiobarbituric acid-reactive substances (TBARs) and oxidized ascorbate remained unaffected. On the other hand, salinity significantly reduced the levels of endogenous SA but increased the content of proline, soluble sugars, TBARs, ascorbate and glutathione, as well as all increasing the levels of antioxidant enzyme activities assayed, except CAT. The application of SA improved the response of common bean plants to salinity by increasing plant dry weight and decreasing the content of organic solutes (proline and TSS) and damage to the membrane (TBARs). Moreover, SA application under saline conditions decreased the levels of antioxidant enzyme activities POX, APX and MDHAR which could indicate successful acclimatization of these plants to saline conditions.     

Oxidative stress and antioxidant defense responses by goldfish tissues to acute change of temperature from 3 to 23 °C

The effects of a rapid transfer from a low (3 °C) to a warm (23 °C) temperature on oxidative stress markers and antioxidant defenses were studied in the brain, liver and kidney of the goldfish, Carassius auratus. Cold-acclimated fish were acutely moved to 23 °C and sampled after 1, 6, 12, 24, 48 or 120 h of warm temperature exposure. Lipid peroxide levels increased quickly during the first few hours at 23 °C, but thiobarbituric acid-reactive substances changed little. Protein carbonyl content was reduced by 20–40% in the liver over the entire experimental course, but increased transiently in the kidney. The content of high-molecular mass thiols decreased by two-thirds in the brain and was affected slightly in other organs. By contrast, total low-molecular mass thiols (e.g. glutathione and others) increased transiently. Activities of the primary antioxidant enzymes—superoxide dismutase and catalase—were generally unaffected in goldfish organs, whereas glutathione-dependent enzymes were elevated in the brain and kidney after 24–48 h at 23 °C. Glutathione peroxidase increased by 1.5–2.3-fold and glutathione-S-transferase by 1.7-fold. Hence, a short-term exposure to warm temperature disturbed several oxidative stress markers, but only slightly affected the activities of antioxidant enzymes. However, comparison of the current data for cold-acclimated winter fish with the same parameters in summer fish suggests that longer exposure to high ambient temperature requires the enhancement of activities of glutathione-dependent enzymes for maintaining the steady-state levels lipid peroxidation and protein oxidation in goldfish tissues.     

Nasturtium officinale reduces oxidative stress and enhances antioxidant capacity in hypercholesterolaemic rats

Nasturtium officinale R. Br. (Brassicaceae) has been used as a home remedy by the people of south eastern (SE) region of Iran as a medicinal plant. This therapeutical application has been attributed to Nasturtium officinale (N. officinale) antioxidant capacity which is mostly tested by means of cell-free assays: 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP). In addition, the antioxidant effect of N. officinale extract has been investigated in hypercholesterolaemic rats in vivo. The results revealed that the extract has notable scavenging activity against DPPH radicals as well as potent reducing power in FRAP assay. Intragastric administration of N. officinale (500 mg/kg body weight per day) to groups of hypercholesterolaemic rats for 30 days lowered their blood total cholesterol (TC), triglyceride (TG), and low density lipoprotein cholesterol (LDL-C) levels by 37, 44 and 48%, respectively. However, the blood high density lipoprotein cholesterol (HDL-C) levels in the same treated rats increased by 16%. To evaluate the mechanism(s) of action, we studied the antioxidative potential of N. officinale extract in terms of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione reductase (GR) activities and also the level of reduced glutathione (GSH) in the liver tissues. In addition, hepatic tissue malondialdehyde level (MDA, an index of lipid peroxidation) was also determined. Under hypercholesterolaemic condition, hepatic MDA was increased. Moreover, our data indicated GSH depletion along with significant reduction in the activities of CAT and SOD in rats fed high-fat diet rats. On the other hand, significant elevation in the activities of GPx and GR were seen in the same group of rats. Treatment of hypercholesterolaemic rats with N. officinale extract significantly increased the GSH level along with enhanced CAT and SOD activities in liver tissues. Furthermore, N. officinale extract significantly decreased hepatic MDA as well as GPx and GR activities in plant-treated rats. Based on our data, it can be concluded that N. officinale has a high hypolipidaemic activity and this may be attributed to its antioxidative potential.     

Oxidative stress and antioxidant status in patients with autoimmune liver diseases

Abstract

Objective

To estimate oxidative stress and antioxidant components during different stages of autoimmune liver diseases and assess their possible implication on disease progression.

Methods

We determined several markers of oxidative injury (isoprostane, aldehydes, protein carbonyls, 3-nitrotyrosine, and myeloperoxidase) and antioxidant components (glutathione, glutathione peroxidase, glutathione reductase, superoxide dismutase, and catalase) in whole blood, serum, and urine in 49 patients with autoimmune cholestatic liver diseases (AC) and 36 patients with autoimmune hepatitis (AIH) and healthy subjects matched for sex and age.

Results

Both AC and AIH patients had increased levels of all lipid and protein oxidative injury products and significantly decreased whole blood glutathione levels compared to controls. AIH patients had significantly higher levels of aldehydes and glutathione peroxidase activity and significantly lower protein carbonyl levels compared to AC patients. Protein carbonyl and isoprostane levels increased and glutathione levels decreased gradually with progression from mild fibrosis to severe fibrosis and cirrhosis in both AC and AIH patients. In addition, both cirrhotic AC and AIH patients had significantly higher protein carbonyls compared to non-cirrhotics.

Discussion

We provide novel findings in support of a major contribution of oxidant/antioxidant imbalance in the progression of liver injury in AC and AIH.     

Genetic pathways controlling carpel development inArabidopsis thaliana

Carpel development inArabidopsis is known to be controlled by the organ identity geneAGAMOUS. However, even in the absence of AGAMOUS function, many carpel properties can arise suggesting that other genes are also involved. Two new carpel genes,CRABS CLAW andSPATULA, have been recognised by their specific disruptions to carpel development in mutant plants. These disruptions suggest thatCRABS CLAW normally plays a role in promoting the growth of specific regions of the carpel wall, whereasSPATULA apparently has a primary function in promoting development of the transmitting tract. When the function of these genes is also compromised along with that ofAGAMOUS in multiply mutant plants, carpelloid properties vanish. ThusAGAMOUS, CRABS CLAW andSPATULA act together in specifying carpel development, although none can do this alone. BecauseSPATULA mutants are epistatic to mutants of another carpel development gene,ETTIN, the latter may normally act by suppressing the action ofSPATULA in specific regions of the developing gynoecium. There is indirect evidence thatETTIN, and another morphogenetic gene,PINOID, act through regulating auxin-induced growth in specific regions of the developing flower, but it is not yet known how this could result in the suppression of SPATULA function. The extended abstract of a paper presented at the 13th International Symposium in Conjugation with Award of the International Prize for Biology “Frontier of Plant Biology”     

Effects of short-term heat stress on oxidative damage and responses of antioxidant system in Lilium longiflorum

This paper aims to determine the changes in reactive oxygen species (ROS) and the responses of the lily (Lilium longiflorum L.) antioxidant system to short-term high temperatures. Plants were exposed to three levels of heat stress (37°C, 42°C, 47°C) for 10 h when hydrogen peroxide (H₂O₂) and superoxide (O₂⁻) production rate along with membrane injury indexes, and changes in antioxidants were measured. Compared with the control (20°C), electrolyte leakage and MDA concentration varied slightly after 10 h at 37°C and 42°C, while increased significantly at 47°C. During 10 h at 37°C and 42°C, antioxidant enzyme activities, such as SOD, POD, CAT, APX and GR, were stimulated and antioxidants (AsA and GSH concentrations) maintained high levels, which resulted in low levels of O₂⁻ and H₂O₂ concentration. However, after 10 h at 47°C, SOD, APX, GR activities and GSH concentration were similar to the controls, while POD, CAT activities and AsA concentration decreased significantly as compared with the control, concomitant with significant increase in O₂⁻ and H₂O₂ concentrations. In addition, such heat-induced effects on antioxidant enzymes were also confirmed by SOD and POD isoform, as Cu/ZnSOD maintained high stability under heat stress and the intensity of POD isoforms reduced with the duration of heat stress, especially at 47°C. It is concluded that in lily plants, the oxidative damage induced by heat stress was related to the changes in antioxidant enzyme activities and antioxidants.     

Effects of vanadate on male rat reproductive tract histology, oxidative stress markers and androgenic enzyme activities

Vanadium has been recognized as industrial hazards that adversely affect male reproductive systems of humans and animals. However, less information is available concerning the underlying mechanism in the pathogenesis of male reproductive dysfunction. The present study investigated the possible involvement of oxidative stress to induce oxidative deterioration of testicular functions in adult rats. The results of in vitro and in vivo studies demonstrate that vanadium treatment resulted in a significant dose- and time-dependent increase in the testicular lipid peroxidation, marked inhibition in the level of superoxide dismutase and catalase activities, decreased sperm counts, and substantially inhibited the activities of Delta(5)3beta- and 17beta-hydroxysteroid dehydrogenase as well as serum testosterone level. Histopathological examination revealed inhibition of spermatogenesis and the preferential loss of maturing and elongated spermatids along with increased percent of abnormal sperm. Taken together, the results suggest that an increase in free radical formation relative to loss of antioxidant defense system during vanadium exposure may render testis more susceptible to oxidative damage leading to their functional inactivation. Thus the toxic effects of vanadium are cumulative and that vanadium produced damages in testes are dose- and time-dependent.     

Anthraquinones production,hydrogen peroxide level and antioxidant vitamins in Morinda elliptica cell suspension cultures from intermediary and production medium strategies

The effects of medium strategies [maintenance (M), intermediary (G), and production (P) medium] on cell growth, anthraquinone (AQ) production, hydrogen peroxide (H₂O₂) level, lipid peroxidation, and antioxidant vitamins in Morinda elliptica cell suspension cultures were investigated. These were compared with third-stage leaf and 1-month-old callus culture. With P medium strategy, cell growth at 49 g l^–1, intracellular AQ content at 42 mg g^–1 DW, and H₂O₂ level at 9 mol g^–1 FW medium were the highest as compared to the others. However, the extent of lipid peroxidation at 40.4 nmol g^–1 FW and total carotenoids at 13.3 mg g^–1 FW for cultures in P medium were comparable to that in the leaf, which had registered sevenfold lower AQ and 2.2-fold lower H₂O₂ levels. Vitamin C content at 30–120 g g^–1 FW in all culture systems was almost half the leaf content. On the other hand, vitamin E content was around 400–500 g g^–1 FW in 7-day-old cultures from all medium strategies and reduced to 50–150 g g^–1 FW on day 14 and 21; as compared to 60 g g^–1 FW in callus and 200 g g^–1 FW in the leaf. This study suggests that medium strategies and cell growth phase in cell culture could influence the competition between primary and secondary metabolism, oxidative stresses and antioxidative measures. When compared with the leaf metabolism, these activities are dynamic depending on the types and availability of antioxidants.Abbreviations AQ Anthraquinone - DW Dry cell weight - FW Fresh cell weight - G Intermediary medium - M Maintenance medium - MDA Malondialdehyde - P Production medium - ROS Reactive oxygen species - TBA Thiobarbituric acid - t_d Doubling time     

Accumulation, subcellular localization and ecophysiological responses to copper stress in two Daucus carota L. populations

Copper accumulation, subcellular localization and ecophysiological responses to excess copper were investigated using pot culture experiments with two Daucus carota L. populations, from a copper mine and an uncontaminated field site, respectively. Significant differences of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) concentrations and antioxidant enzyme [superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX)] activities of leaves under Cu treatment were observed between the two populations. At high Cu concentrations (400 and 800 mg kg⁻¹), a significant increase in contents of MDA and H₂O₂ but a significant decrease in activities of SOD, CAT and APX were observed in uncontaminated population. Contrarily, the population from copper mine maintained a lower level of MDA and H₂O₂ but higher activities of SOD, CAT and APX. Copper accumulation in roots and shoots increased significantly with the increase of copper concentrations in soils in the two populations. No significant difference of the total Cu in roots and shoots was found between the two populations at same copper treatment. There were also no striking differences of cell wall-bound Cu and protoplasts Cu of leaves between the two populations. The difference was that Cu concentration in vacuoles of leaves was 1.5-fold higher in contaminated site (CS) population than in uncontaminated site population. Hence, more efficient vacuolar sequestration for Cu and maintaining high activities of SOD, CAT and APX in the CS population played an important role in maintaining high Cu tolerance.     

Chitosan enhances leaf membrane stability and antioxidant enzyme activities in apple seedlings under drought stress

Chitosan is a cationic marine polysaccharide with unique bioactive properties that make it an effective scavenger of reactive oxygen species. Chitosan application has been suggested as an aid for reducing oxidative injury caused by drought stress in crop plants. In order to confirm the antioxidant effects of exogenous chitosan, cell membrane stability and antioxidant enzyme activities were analyzed in leaves of apple seedlings placed under a period of drought stress. Pretreatment of apple seedling leaves with chitosan solution (20, 50, 100, 150 and 200 mg l⁻¹) prior to drought stress significantly decreased electrolyte leakage and the production of malondialdehyde in the leaves, while increasing antioxidant enzyme activities (superoxide dismutase, catalase), following imposition of drought stress conditions. An optimum response was obtained at a chitosan concentration of 100 mg l⁻¹. When apple seedlings were pretreated with 100 mg l⁻¹ of chitosan, cell membrane stability and antioxidant enzyme activities were enhanced for 21 days of drought treatment. Following restoration of moisture and a repeated drought stress, similar results were obtained on day 35. It is proposed that chitosan may act as an exogenous antioxidant that enhances resistance to oxidative stress during drought.     

pARMS,multiple marker-containing plasmids for easy RFLP analysis inArabidopsis thaliana

A simplified way is presented for the analysis of 13 RFLP markers, each of them detecting solely a pair of polymorphic bands afterEcoR I digestion of genomic DNA fromArabidopsis thaliana ecotypes Landsbergerecta and Columbia. Five plasmids (pARMS) containing multiple marker inserts were constructed that score 13 loci, almost evenly distributed on the five chromosomes (Fabri and Schäffner, 1994). Since their polymorphic signals do not interfere with each other, pARMS2,?6, and?7 can be combined to score eight RFLP marker in a single Southern experiment. Two additional plasmids—pARMS5 and?8— allow the joint analysis of another five markers. If pARMS are used for rough mapping of a mutation, which will be the major application, this procedure reduces processing and handling to just five plasmids and also results in more uniform signal intensities due to a more even labeling.     

Experimental and genetic analysis of root development inArabidopsis thaliana

The cellular organisation of theArabidopsis thaliana root is remarkably regular. A fate map of the primary root and root meristem that predicts the developmental destinies of cells within the embryonic root primordium has been constructed. Nevertheless, laser ablation experiments demonstrate that root meristem cells develop according to position and not according to lineage. Mutational analysis has identified genes required for cell specification in the radial as well as in the apical-basal dimension. The corresponding gene functions appear to be necessary during embryogenesis for the formation of a correctly patterned primary root. H Lambers Section editor     

Induced resistance in cells exposed to repeated low doses of H2O2 involves enhanced activity of antioxidant enzymes

We have derived cells from the Chinese hamster V79 cell line by conditioning them with repeated low doses of hydrogen peroxide (H(2)O(2)). This mimics the physiological condition where cells are repeatedly exposed to low levels of oxidants. In an attempt to characterize such cells, we have exposed both conditioned cells (V79(C)) and the parental V79 cells (V79(P)) to different types of cytotoxic agents and compared their sensitivity to cell killing. The V79(C) cells were found to be stably resistant to killing by agents that produced toxicity through oxidative stress, e.g. H(2)O(2) and cisplatin. It was also found that the lipid peroxidation produced by these agents were considerably lower in the V79(C) cells. Thus, the difference in sensitivity could be due to lesser extent of damage to these cells. V79(C) cells had greater antioxidant defense through higher GSH content and greater activity of enzymes such as Cu-Zn superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), which provided protection from damage. Enzyme activities were also assayed at different times after treatment with various cytotoxic agents; there was a relatively large increase in SOD activity which perhaps plays a key role in determining the resistance of the V79(C) cells to killing.     

Involvement of oxidative stress and role of antioxidative defense system in growing rice seedlings exposed to toxic concentrations of aluminum

When seedlings of rice (Oryza sativa L.) cultivar Pant-12 were raised in sand cultures containing 80 and 160 μM Al³⁺ in the medium for 5–20 days, a regular increase in Al³⁺ uptake with a concomitant decrease in the length of roots as well as shoots was observed. Al³⁺ treatment of 160 μM resulted in increased generation of superoxide anion (O₂ ⁻) and hydrogen peroxide (H₂O₂), elevated amount of malondialdehyde, soluble protein and oxidized glutathione and decline in the concentrations of thiols (-SH) and ascorbic acid. Among antioxidative enzymes, activities of superoxide dismutase (SOD EC 1.15.1.1), guaiacol peroxidase (Guaiacol POX EC 1.11.1.7), ascorbate peroxidase (APX EC 1.11.1.11), monodehydroascorbate reductase (MDHAR EC 1.6.5.4), dehydroascorbate reductase (EC 1.8.5.1) and glutathione reductase (EC 1.6.4.2) increased significantly, whereas the activities of catalase (EC EC 1.11.1.6) and chloroplastic APX declined in 160 μM Al³⁺ stressed seedlings as compared to control seedlings. The results suggest that Al³⁺ toxicity is associated with induction of oxidative stress in rice plants and among antioxidative enzymes SOD, Guaiacol POX and cytosolic APX appear to serve as important components of an antioxidative defense mechanism under Al³⁺ toxicity. PAGE analysis confirmed the increased activity as well as appearance of new isoenzymes of APX in Al³⁺ stressed seedlings. Immunoblot analysis revealed that changes in the activities of APX are due to changes in the amounts of enzyme protein. Similar findings were obtained when the experiments were repeated using another popular rice cv. Malviya-36.     

Physiological and antioxidant enzyme responses to acute and chronic exposure of Laeonereis acuta (Polychaeta, Nereididae) to copper

Chronic (14 days) and acute (48 h) copper effects on the antioxidant defense system and some physiological variables of Laeonereis acuta (Polychaeta, Nereididae) were evaluated. In both assays, two nominal copper concentrations (chronic: C₁=31.25 and C₂=62.50 μg/l; acute: A₁=250 and A₂=500 μg/l) and one control group (C_c and A_c=0 μg/l) were tested. End points analyzed were antioxidant enzyme activity (catalase, CAT; superoxide dismutase, SOD; and glutathione S-transferase, GST), oxygen consumption, metahemoglobin concentration, and lipid peroxidation (LPO). In the chronic assay, CAT activity was significantly higher in worms exposed to both concentrations of copper tested (C₁=3.36±0.07 U CAT/mg protein; C₂=4.06 0.32 U CAT/mg protein) than in control worms (C_c=2.16±0.39 U CAT/mg protein). SOD activity was also increased in the two copper-exposed groups (C₁=16.85±4.22 U SOD/mg protein; C₂=38.19±4.31 U SOD/mg protein) than in control group (C_c=3.54±0.46 U SOD/mg protein). However, GST activity was increased only in worms exposed to the higher copper concentration (C₂=0.022±9.10⁻⁴ U GST/mg protein) when compared to the other groups tested (C_c=0.012±3.10⁻³ U GST/mg protein; C₁=0.016±9.10⁻⁴ U GST/mg protein). None of the physiological variables analyzed (oxygen consumption, metahemoglobin concentration, and lipid peroxidation) was affected by chronic copper exposure. In the acute assay, only GST activity was induced in worms exposed to copper. This induction was observed only in the A₁ group (0.027±2.10⁻³ U GST/mg protein) when compared to A_c (0.017±2.10⁻³ U GST/mg protein) or A₂ (0.016±7.10⁻⁴ U GST/mg protein) groups. On the other hand, lipid peroxidation was higher in A₂ (481.9±49.2 nmol CHP/g ww) than in control worms (A_c=337.9±25.0 nmol CHP/g ww). Oxygen consumption was higher in worms acutely exposed to the lower copper concentration tested (A₁=0.27±0.04 mg O₂/g ww/h) than in the higher concentration (A₂=0.14±0.01 mg O₂/g ww/h). Changes in the swimming behavior of copper-exposed animals in both assays and edemas in the body wall of worms acutely exposed to copper were also observed. Results suggest that copper exposure favors reactive oxygen species generation and that enzymatic defense system is induced under chronic exposure, preventing oxygen consumption changes and lipid peroxidation and metahemoglobin formation. However, in acutely exposed worms, in spite of a transient peak of GST activity, no induction of antioxidant enzymes occurs, leading to morphological and physiological changes.     

No evidence for oxidative stress as a mechanism of action of hyperhomocysteinemia in humans

Oxidative stress has been suggested as one of the physiopathologic conditions underlying the association of total plasma homocysteine (p-tHcy) with cardiovascular disease (CVD), but this hypothesis has not been validated in human epidemiological studies. We measured plasma and erythrocyte antioxidant enzymes glutathione peroxidase (GPx) and superoxide dismutase (SOD), along with serum lipid-soluble antioxidants alpha-tocopherol, beta-carotene, lycopene and retinol, in a sample of 123 healthy elderly subjects (54 men, 69 women). Plasma malondialdehyde (p-MDA) was determined as a marker of lipid peroxidation, and p-tHcy was quantified by HPLC. No significant differences were found for p-MDA, GPx or SOD activities or serum antioxidant concentrations, in subjects with elevated p-tHcy (≥15 μmol/l) as compared to those with lower plasma homocysteine. Hyperhomocysteinemia did not lead to increased risk of having the highest p-MDA values, in either sex. We found no evidence that p-tHcy was associated with lipid peroxidation in this elderly human sample. Our results do not support the view that hyperhomocysteinemia would induce an adaptive response of antioxidant systems, either. More epidemiologic and clinical research is needed to clarify whether homocysteine promotes atherosclerosis by means of an oxidative stress mechanism.