Copper-induced oxidative stress in the chlorophycean microalga Chlorella vulgaris: response of the antioxidant system

A concentration dependent increase in lipid peroxidation, carotenoid content and activity of superoxide dismutase was observed in the green microalga Chlorella vulgaris following copper exposure. In contrast, activities of catalase, ascorbate peroxidase and glutathione reductase, and the cellular GSH, ascorbate and K+ pool depicted a reverse trend. However, a significant rise in intracellular proline content was also evident in copper supplemented cultures. Though this study depicted the malfunction of the major antioxidant system of C. vulgaris under copper stress the test organism was found to survive and grow even at 3.0 microg mL(-1) of Cu treatment (32% growth). Further study is needed to establish the role of proline in metal toxicity regulation.     

Cadmium induced lipid peroxidation in rat testes and protection by selenium

The main goal of this study was to investigate the role of cadmium in the promotion of lipid peroxidation in the homogenates of rat testes and the effect of selenium on lipid peroxidation in testes of rats after cadmium injection. Treatment of rats with cadmium resulted in a time- and dose-related accumulation of the metal ions in testes. The concentrations of cadmium, copper, zinc, selenium and iron in the tissues were determined by an atomic absorption spectrophotometer and lipid peroxidation in testes was measured by a spectrophotometer. Cadmium produced enhanced lipid peroxidation in testes. These cadmium-induced changes were accompanied by a significant increase of iron and copper, and a decrease of zinc in testes. Concurrent treatment with selenium and cadmium reduced the cadmium-induced alterations in lipid peroxidation and essential metal levels. Data suggest that lipid peroxidation was associated with cadmium toxicity in testes and that the addition of selenium was found to be effective in attenuation of this effect.     

Relationship between copper- and zinc-induced oxidative stress and proline accumulation in<Emphasis Type="Italic"> Scenedesmus</Emphasis> sp.

A 4-h exposure of Scenedesmus sp. to Cu or Zn enhanced intracellular levels of both test metals and proline. The level of intracellular proline increased markedly up to 10 µM Cu, but higher concentrations were inhibitory. However, intracellular proline consistently increased with increasing concentration of Zn in the medium. Cu and Zn induced oxidative stress in the test alga by increasing lipid peroxidation and membrane permeability, and by reducing SH content. Pretreatment of the test alga with 1 mM proline for 30 min completely alleviated Cu-induced lipid peroxidation, minimized K⁺ efflux and also reduced depletion of the SH pool. But proline pretreatment could only slightly reduce Zn-induced oxidative stress. Interestingly, proline pretreatment increased the level of Cu (25–54%) and Zn (19–49%) inside the cells. It did not affect the activities of superoxide dismutase, ascorbate peroxidase or catalase, but improved glutathione reductase activity under Cu and Zn stress. A comparison of the effects of proline pretreatment on lipid peroxidation by Cu, Zn, methyl viologen and ultraviolet-B radiation suggests that proline protects cells from metal-induced oxidative stress by scavenging reactive oxygen species rather than by chelating metal ions. Pretreatment of cells with a known antioxidant (ascorbate) and a hydroxyl radical scavenger (sodium benzoate) considerably reduced metal-induced lipid peroxidation and proline accumulation. However, sodium benzoate had a very mild effect on Zn-induced lipid peroxidation and proline accumulation. The present study demonstrates that proline possibly acts by detoxifying reactive oxygen species, mainly hydroxyl radicals, rather than by improving the antioxidant defense system under metal stress.Abbreviations APOX Ascorbate peroxidase - CAT Catalase - GR Glutathione reductase - MDA Malondialdehyde - MV Methyl viologen - ROS Reactive oxygen species - SH Sulphydryl - SOD Superoxide dismutase - UV-B Ultraviolet-B radiation     

Changes in Proline Content Accompanying the Uptake of Zinc and Copper by Lemna minor

Lemna minor L. grown in Hoagland solution containing zinc (10ppm) or copper (5 ppm) for 4 d accumulated high levels of thesemetals. Zinc and Cu accumulation in the test plants was accompaniedby a specific pattern of change in proline content. The lattershowed a steep rise during early stages (peak at 12-24 h) followedby a gradual decline until 96 h of treatment. In a dose-responsestudy, lower metal concentrations induced a sharp rise in prolinelevel with a maximum value at 5 ppm, which declined when theconcentration was further enhanced. There was a correspondencebetween the level of proline and total free amino acids in metaltreated plants. The possibility of proline involvement in tolerancemechanisms to heavy metals has been discussed.Copyright 1993,1999 Academic Press Heavy metals, zinc, copper, proline, total free amino acids, Lemna minor     

Enterobacter asburiae KE17 association regulates physiological changes and mitigates the toxic effects of heavy metals in soybean

This study aimed to elucidate the role played by Enterobacter asburiae KE17 in the growth and metabolism of soybeans during copper (100 μm Cu) and zinc (100 μm Zn) toxicity. When compared to controls, plants grown under Cu and Zn stress exhibited significantly lower growth rates, but inoculation with E. asburiae KE17 increased growth rates of stressed plants. The concentrations of plant hormones (abscisic acid and salicylic acid) and rates of lipid peroxidation were higher in plants under heavy metal stress, while total chlorophyll, carotenoid content and total polyphenol concentration were lower. While the bacterial treatment reduced the abscisic acid and salicylic acid content and lipid peroxidation rate of Cu‐stressed plants, it also increased the concentration of photosynthetic pigments and total polyphenol. Moreover, the heavy metals induced increased accumulation of free amino acids such as aspartic acid, threonine, serine, glycine, alanine, leucine, isoleucine, tyrosine, proline and gamma‐aminobutyric acid, while E. asburiae KE17 significantly reduced concentrations of free amino acids in metal‐affected plants. Co‐treatment with E. asburiae KE17 regulated nutrient uptake by enhancing nitrogen content and inhibiting Cu and Zn accumulation in soybean plants. The results of this study suggest that E. asburiae KE17 mitigates the effects of Cu and Zn stress by reprogramming plant metabolic processes.     

Proline improves copper tolerance in chickpea (Cicer arietinum)

The present study suggests the involvement of proline in copper tolerance of four genotypes of Cicer arietinum (chickpea). Based on the data of tolerance index and lipid peroxidation, the order for copper tolerance was as follows: RSG 888?>?CSG 144?>?CSG 104?>?RSG 44 in the selected genotypes. The basis of differential copper tolerance in chickpea genotypes was characterized by analyzing, antioxidant enzymes (superoxide dismutase, ascorbated peroxidase and catalase), phytochelatins, copper uptake, and proline accumulation. Chickpea genotypes showed stimulated superoxide dismutase activity at all tested concentrations of copper, but H₂O₂ decomposing enzymes especially; ascorbate peroxidase did not increase with 25 and 50 μM copper treatments. Catalase activity, however, increased at lower copper concentrations but failed to stimulate at 50 μM copper. Such divergence in responses of these enzymes minimizes their importance in protecting chickpea against copper stress. The sensitive genotypes showed greater enhancement of phytochelatins than that of tolerant genotypes. Hence, the possibility of phytochelatins in improving copper tolerance in the test plant is also excluded. Interestingly, the order of proline accumulation in the chickpea genotypes (RSG 888?>?CSG 144?>?CSG 104?>?RSG 44) was exactly similar to the order of copper tolerance. Based on hyperaccumulation of proline in tolerant genotype (RSG 44) and the reduction and improvement of lipid peroxidation and tolerance index, respectively, by proline pretreatment, we conclude that hyperaccumulation of proline improves the copper tolerance in chickpea.     

The impacts of heavy metals on oxidative stress and growth of spring barley

Oxidative stress is accepted to play a significant role in stress symptoms, caused by different stressors in a variety of organisms. In this study seedlings of spring barley (Hordeum vulgare L.) were exposed to a wide range of copper, zinc, chromium, nickel, lead and cadmium concentrations in order to determine the relationships between heavy metals-induced oxidative stress and plant growth inhibition. All investigated heavy metals induced an essential increase in lipid peroxidation and a reduction of dry biomass along with an increase in metal concentration in the nutrient solution. A very close and statistically significant exponential relationship between lipid peroxidation and growth inhibition was detected in this study. According to the results of analysis of variance (ANOVA), the intensity of nonspecific oxidative stress is identified as the main factor of barley growth inhibition, explaining 75% of total variance. Almost 10% of growth inhibition is attributed to the specific impact of heavy metals. The most pronounced increase of malondialdehyde content and growth inhibition was observed in Cu and Cd treatments, whereas the lowest changes in observed indicators were detected after exposure to Zn and Pb.     

Comparisons of nine heavy metals in salt gland and liver of greater scaup (Aythya marila), black duck (Anas rubripes) and mallard (A. platyrhynchos)

Levels of nine heavy metals were measured in the livers and salt glands of greater scaup (Aythya marila), black duck (Anas rubripes) and mallard (A. platyrhynchos) from Raritan Bay, New Jersey to determine if the functioning avian salt gland concentrates heavy metals. Heavy metals examined were cadmium, cobalt, chromium, copper, lead, mercury, manganese, nickel and zinc. Heavy metal levels varied significantly by species and tissue for chromium, copper, lead, and manganese, and by tissue for cobalt, mercury, nickel and zinc. In comparing tissues cobalt was higher in the salt glands than in livers of all three species; chromium and nickel were higher in the salt gland than liver for mallard and black duck; and lead, manganese and zinc were higher in the liver than the salt gland in greater scaup. Generally metal levels were higher in the salt gland for mallard and black duck, and in the liver for greater scaup.     

Heavy metals in eelgrass (Zostera marina L.) during growth and decomposition

The distributions of cadmium, chromium, lead, and zinc in eelgrass were studied in samples collected from the field, and the loss/accumulation of the metals during decomposition of eelgrass leaves was studied in laboratory experiments.Concentrations of heavy metals in the below grounds parts were greater in the roots than in the different age groups of the rhizomes. In the rhizomes, the highest concentrations of lead were recorded in the oldest parts, whereas highest chromium and zinc concentrations were found in the youngest parts. The concentration of cadmium did not vary. In the above ground parts, the concentrations of cadmium, lead, and zinc increased with age of the leaves, and concentrations in the leaves were greater than in the stem fraction. The concentrations of chromium decreased with age of the leaves.In the laboratory study of decomposition of leaf material, the concentrations of chromium, lead and zinc increased significantly and a net absorption from the surrounding water was recorded. Cadmium concentrations were relatively constant and a loss of cadmium was proportional to the release of soluble organic compounds indicating an association of cadmium with the soluble phase.The investigation demonstrated the utility of compositional analyses and decomposition experiments in assessing the significance of eelgrass in the heavy metal cycling in coastal areas. Furthermore, significant differences in the fate of heavy metals associated with eelgrass detritus are discussed.     

Blockade of heavy metals accumulation in Chlorella vulgaris cells by 24-epibrassinolide

This study was conducted on the influence of 24-epibrassinolide (24-epiBL) mixed with varying concentrations of heavy metals (copper, lead, cadmium, zinc) upon the growth and accumulation of these heavy metals in the cell of the alga Chlorella vulgaris Beijerinck (Chlorophyceae). Heavy metals at the concentration of 10^–3 M, alone or mixed with 24-epiBL, showed a lethal effect on C. vulgaris. At metal concentrations of 10^–6–10^–4 M, a combination with 24-epiBL appeared to have a stronger stimulatory effect on a number of cells than a single metal (a stronger inhibitory effect). 24-EpiBL at the concentration of 10^–8 M in combination with heavy metals (in the range 10^–6–10^–4 M) blocked metal accumulation in algal cells. 24-EpiBL has an anti-stress effect on C. vulgaris contaminated by heavy metals. The inhibitory effect on metal accumulation of 24-epiBL mixed with different heavy metals was arranged in the following order: zinc > cadmium > lead > copper. This process is correlated with the stimulation of growth of C. vulgaris. The stimulatory effect of 24-epiBL mixed with heavy metals leading to an increased pH in the medium (5.28–6.20) was significantly higher than the impact due to the increased acidity in the medium due to metals alone (pH 3.10–5.85). Lower pH increased the toxicity of heavy metals in C. vulgaris cells.     

Heavy metals, lipid peroxidation, and ciguatera toxicity in the liver of the caribbean barracuda (Sphyraena barracuda)

Human consumption of over 400 species of tropical fish containing polyether toxins (e.g. ciguatoxins, maitotoxins) causes ciguatera fish poisoning. The Caribbean barracuda (Sphyraena barracuda) is one of the most potent ciguatoxic fish. The objective of this study was to determine whether toxicity of 14 barracuda livers was correlated with lipid peroxidation. A significant correlation (p = 0.015, Pearson’s correlation) between lipid peroxidation and toxicity of barracuda liver was found. Because iron and copper are well-known catalysts of hydroxyl radical production and lipid peroxidation in biological systems, the correlation between the concentrations of these metals in barracuda liver and lipid peroxidation and toxicity was also investigated. Cadmium was significantly correlated (p = 0.014) with the toxicity of barracuda livers. This study provides the first data concerning the concentration of iron, copper, and cadmium in the liver of the Caribbean barracuda. Of the three metals studied in barracuda liver, iron was the most abundant, followed by copper and cadmium. Lipid peroxidation was highly variable and detected in five (36%) of the liver samples. Lipid peroxidation was not statistically significantly correlated (p > 0.05) with concentrations of iron, copper, and cadmium in barracuda liver. Collectively, these findings provide additional evidence that lipid peroxidation can be a mechanistic component of ciguatera toxicity in the Caribbean barracuda.     

Aquatic Risk Assessment of Metals in Sediment from South Florida Canals

A major watershed restoration effort is underway in south Florida, yet there are significant gaps in scientific information on exposure and risks of contaminants to its natural resources. We conducted a two-tier aquatic screening-level ecological risk assessment for metals that were monitored in sediment at 32 sampling sites in south Florida freshwater canals from 1990–2002. For tier 1, the chemicals (or metals) of potential ecological concern (COPECs) were identified as arsenic, cadmium, chromium, copper, lead, nickel and zinc based on their exceedences of Florida sediment quality guidelines at 10 sites. For tier 2, we used a probabilistic risk assessment method to compare distributions of predicted pore water exposure concentrations of seven metal COPECs with distributions of species response data from laboratory toxicity tests to quantify the likelihood of risk. The overlap of pore water concentrations (90th centile for exposure) for metal COPECs and the effects distributions for arthropods (10th centile of LC50s) and all species (10th centile of chronic NOECs) were used as a measure of potential acute and chronic risks, respectively. Arsenic (25%) in the Holey Land tracts, in Broward County north of Everglades National Park (ENP), and chromium (25%) in the C-111 freshwater system, at the east boundary of ENP, were the most frequently detected COPECs in sediment. Antimony (6%), zinc (6%) and lead (5%) were the least frequently detected COPECs in sediment. The 90th centile concentrations for bulk sediment were highest for zinc (at S-178) and lead (at S-176) in the C-111system. The 90th centile concentration for pore water exposure was highest for arsenic in the Holey Land tracts and lowest for cadmium and chromium. The estimated acute 10th centile concentration for effects was lowest for copper and arthropods. The probabilities of pore water exposures of copper exceeding the estimated acute 10th centile concentration from the species sensitivity distributions (SSD) of acute toxicity data (for arthropods) were 57 and 100% for copper at S-177 and S-178 in the C-111 system, respectively. The probability of pore water exposures of copper exceeding the estimated NOEC 10th centile concentration from the SSD of chronic toxicity data (for all species) was 93 and 100% for copper at S-177 and S-178, respectively. Uncertainties in exposure and effects analysis and risk characterization are identified and discussed. The study presents a straightforward approach to estimate exposure and potential risks of metals detected in sediment from south Florida canals.     

Effect of transition metals on stress, lipid peroxidation and antioxidant enzyme activities in tobacco cell cultures

to-baccoBright Yellow 2 (BY-2) suspension culture to understand the mechanisms of metal resistance in plant cells.We have analysed superoxide dismutase, catalase, and ascorbate peroxidase enzyme activities and superoxidedismutase-isoforms by isoelectric focusing gels in tobacco cells grown at two different toxic concentrations ofeach of the transition metals: copper, iron, manganese and zinc. Exposure of tobacco cells to these metals causedchanges in total superoxide dismutase activity in a different manner, depending on the metal assayed: after cop-perand manganese treatments, total superoxide dismutase activity was enhanced, while it was reduced after ironand zinc exposure. Superoxide dismutase-isoforms were affected by the metal used, and a Fe-SOD band with thesame isoelectric point as a Cu, Zn-SOD from non-treated cells, was induced after iron and zinc treatments. Cu,Zn-SODs were present in all metal-treatments whereas Mn-SOD was not detected in any case. Concerning otherantioxidant enzymes tested, such as catalase and ascorbate peroxidase, the latter showed a remarkable increase inactivity in response to copper treatments and catalase activity was enhanced after iron and with the lowest man-ganeseconcentration. Lipid peroxidation was increased after each metal treatment, as an indication of the oxi-dativedamage caused by metal concentration assayed in tobacco cells. These results suggest that an activation ofsome antioxidant enzymes in response to oxidative stress induced by transition metals is not enough to confertolerance to metal accumulation.     

Biomonitoring of heavy metals by epiphytic lichen species in Black Sea region of Turkey

The heavy metal accumulation in epiphytic lichens along the Sarp-Samsun Highway in Black Sea Region of Turkey was analyzed by using energy dispersive X-ray fluorescence (EDXRF) and flame atomic absorption spectroscopy (FAAS) methods. The analysis showed that the lichen samples contained elevated concentrations of the following metals: titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, tin, barium, and lead. A strong positive correlation was observed between the lead concentration of the lichens and the traffic density.     

Effects of copper aspirinate and aspirin on tissue copper,zinc, and iron concentrations following chronic oral treatment in the adjuvant arthritic rat

Concentrations of copper, zinc, and iron were analyzed and compared in a number of tissues of adjuvant arthritic rats following 22 d of chronic treatment (per os) with either vehicle, aspirin or copper aspirinate, at doses of 100 mg/kg, 200 mg/kg, or 400 mg/kg. Such chronic treatment resulted in a negative balance in copper, zinc, and iron in many tissues. Among the tissues examined, liver and kidney exhibited the greatest changes in metal concentrations; brain and skeletal muscle exhibited the least. Arthritis-induced changes in the concentrations of all three metals in the liver were reversed upon treatment with aspirin. Treatment with copper aspirinate, on the other hand, resulted in an extremely high accumulation of copper in the liver. Arthritis-induced changes in copper, zinc, and iron concentrations in the pancreas and copper concentration in the plasma were generally not reversed upon treatment with either aspirin or copper aspirinate. Among the three metals examined, the degree of change observed as a result of drug treatments was greatest for iron and least for zinc. Finally, it appeared that the effects of aspirin and copper aspirinate on tissue metal concentrations were independent of the antiarthritic effects of these compounds.     

Heavy Metals Induce Lipid Peroxidation and Affect Antioxidants in Wheat Leaves

The possible role of Zn and Cr as catalytic inducers of free radicals in wheat leaves was investigated. Treatment of excess heavy metals decreased the chlorophyll and carotenoid content in wheat leaves with the increase in time of excision. A sharp increase in proline accumulation was marked with the increase in metal concentration. Total peroxide content and lipid peroxidation measured as malondialdehyde content showed uniform increase under metal treatment in excised leaves. At almost all concentrations, catalase, guaiacol peroxidase and superoxide dismutase activities decreased with a minor increase in the earlier days of excision. Though glutathione content decreased ascorbate content showed significant increase in wheat leaves under heavy metal treatment. This revised version was published online in July 2006 with corrections to the Cover Date.     

Stress Ameliorative Effects of Indole Acetic Acid on <i>Hordeum vulgare</i> L. Seedlings Subjected to Zinc Toxicity

The heavy metals present in the environment accumulate in the plants and affect their productivity and yield. By entering the food chain, metals cause several serious health problems in human beings as well as in other organisms. Indole acetic acid (IAA) is known to act as a signaling molecule between symbiotic association of metal accumulating plants and plant growth promoting rhizobacteria (PGPR). Present study demonstrated a protective role of IAA against surplus Zinc (Zn)-induced toxicity to Hordeum vulgare seedlings. Elevated Zn concentrations suppressed the plant growth, caused a reduction in leaf relative water contents (RWC) and elevated free proline and non-protein thiols (NPT) accumulation. Zinc treatment also led to enhanced lipid peroxidation (MDA contents) as well as the activity of ascorbate peroxidase (APX), showing the involvement of antioxidative defense mechanism to reduce Zn induced toxicity. IAA oxidase activity was also observed to increase due to Zn treatment. IAA pretreatment of H. vulgare caryopsis could partly revert the Zn-induced toxicity in seedlings.     

Heavy metal contamination of sediments in the Upper Connecting Channels of the Great Lakes

In 1985, sampling at 250 stations throughout the St. Marys, St. Clair, and Detroit rivers and Lake St. Clair — the connecting channels of the upper Great Lakes — revealed widespread metal contamination of the sediments. Concentrations of cadmium, chromium, copper, lead, mercury, nickel, and zinc each exceeded U.S. Environmental Protection Agency sediment pollution guidelines at one or more stations throughout the study area. Sediments were polluted more frequently by copper, nickel, zinc, and lead than by cadmium, chromium, or mercury. Sediments with the highest concentrations of metals were found (in descending order) in the Detroit River, the St. Marys River, the St. Clair River, and Lake St. Clair. Although metal contamination of sediments was most common and sediment concentrations of metals were generally highest near industrial areas, substantial contamination of sediments by metals was present in sediment deposition areas up to 60 km from any known source of pollution.Contribution 735 of the National Fisheries Research Center-Great Lakes, U.S. Fish and Wildlife Service, 1451 Green Road, Ann Arbor, MI 48105.     

Induction of oxidative stress and antioxidative mechanisms in Phaseolus vulgaris after Cd application.

Oxidative stress has been shown to be of great importance in the toxicity of several metals (copper, zinc, ...). In this study, the relationship of cadmium phytotoxicity and antioxidative reactions in bean (Phaseolus vulgaris L.) plants was investigated. Eleven-day-old seedlings were exposed to an environmentally realistic concentration of cadmium (2 microM CdSO(4)). Several biochemical and physiological parameters were influenced even by these low concentrations. At the biochemical level, the antioxidative defence mechanism was significantly activated after 24 h of cadmium exposure. Some enzymes able of quenching reactive oxygen species (syringaldazine peroxidase, EC 1.11.1.7; guaiacol peroxidase, EC 1.11.1.7) as well as enzymes important in the reduction of NAD(P)(+) (isocitrate dehydrogenase, EC 1.1.1.42; malic enzyme, EC 1.1.1.40) were significantly elevated by cadmium exposure. Furthermore, the ascorbate-glutathione cycle appeared to be a very important mechanism against cadmium-induced oxidative stress. In leaves, significant increases of ascorbate peroxidase (EC 1.11.1.11) and glutathione reductase (EC 1.6.4.2) and significant changes in the ascorbate and glutathione pool were observed. Morphological and other biochemical parameters (lipid peroxidation) were significantly enhanced 48 h after the start of the cadmium exposure. At the end of the experiment (72 h after the start of the metal treatment), even visual effects, such as chlorosis, were observed. The present data indicate that cadmium, like other metals, induces cellular redox disequilibrium suggesting that an environmentally realistic concentration of cadmium can cause oxidative stress.     

Heavy metals in relation to the biology of the mummichog, Fundulus heteroclitus

Heavy metal levels of cadmium, copper, mercury, manganese, and zinc were examined in the mummichog, Fundulus heteroditus from industrialized and non-industrialized environments. With one exception, the environment with the highest trace metal in its waters, had the fishes with the highest metal concentration. Except for mercury, the concentration factor varied inversely with the metal concentrations of the fish and water, suggesting a possible regulatory mechanism for metals in the tissues of mummichogs from environments with high metal concentrations. There was an inverse relationship between standard length and concentrations of zinc, manganese, copper and cadmium in whole male and female fishes. The viscera contained significantly greater concentrations of these metals than somatic muscle tissue. There were also significant differences between males and females with respect to whole-body zinc and copper concentrations, but no sex differences for manganese and cadmium.