Olga I. Kubrak

Tissue specificity in nickel uptake and induction of oxidative stress in kidney and spleen of goldfish Carassius auratus, exposed to waterborne nickel

Toxic and carcinogenic effects of nickel compounds are suggested to result from nickel-mediated oxidative damage to macromolecules and/or inhibition of cellular antioxidant defenses. We investigated the effects of waterborne Ni(2+) (10, 25 and 50 mg/L) on the blood and blood-producing tissues (kidney and spleen) of goldfish to identify relationships between Ni accumulation and oxidative stress. Whereas the main hematological parameters (total hemoglobin and hematocrit) were unaffected, Ni(2+) exposure had substantial influence on goldfish immune system, causing lymphopenia. Ni accumulation increased renal iron content (by 49-78%) and resulted in elevated lipid peroxide (by 29%) and protein carbonyl content (by 274-278%), accompanied by suppression of the activities of superoxide dismutase (by 50-53%), glutathione peroxidase (15-45%), glutathione reductase (31-37%) and glucose-6-phosphate dehydrogenase (20-44%), indicating development of oxidative stress in kidney. In contrast to kidney, in spleen the activation of glutathione peroxidase (by 34-118%), glutathione-S-transferase (by 41-216%) and glutathione reductase (by 47%), as well as constant levels of low molecular mass thiols and metals together with enhanced activity of glucose-6-phosphate dehydrogenase (by 41-94%) speaks for a powerful antioxidant potential that counteracts Ni-induced ROS production. Further, as Ni accumulation in this organ was negligible, Ni-toxicity in spleen may be minimized by efficient exclusion of this otherwise toxic metal.

Nickel induces hyperglycemia and glycogenolysis and affects the antioxidant system in liver and white muscle of goldfish Carassius auratus L.

The toxicity of nickel to mammals is well studied, whereas information on nickel effects on fish is scant. Goldfish exposure to 10-50 mg L(-1) of waterborne Ni(2+) for 96 h showed reduced glycogen levels by 27-33% and 37-40% in liver and white muscle, respectively, accompanied by substantial increases in blood glucose levels (by 15-99%). However, indices of oxidative damage to proteins (carbonyl proteins) and lipids (lipid peroxides) were largely unaffected by nickel exposure. In liver, the activities of antioxidant enzymes, superoxide dismutase (SOD) and glutathione peroxidase (GPx), were not affected by Ni(2+) treatment, while catalase activity was elevated by 26%. In white muscle, however, substantial increases in SOD (by 38-147%) and GPx (by 2.5-5.5-fold) activities appeared to compensate for decreased catalase activity (by 59-69%) in order to resist Ni-induced oxidative perturbations. Both hepatic and muscular glutathione reductase activities were suppressed by 10-30% and 12-21%, respectively, after goldfish exposure to all Ni(2+) concentrations used. However, the activity of glucose-6-phosphate dehydrogenase was remarkably enhanced (by 1.6-5.4-fold) in white muscle of Ni-exposed fish, indicating a strong potential increase in NADPH production under Ni exposure. Thus, the exposure of goldfish to 10-50 mg L(-1) of Ni(2+) for 96 h induces glycogenolysis and hyperglycemia, showing some similarities with a hypoxia response, and leads to a substantial activation of defense systems against reactive oxygen species in liver and white muscle in tissue-specific and concentration-dependent manner.

Oxidative stress responses in blood and gills of Carassius auratus exposed to the mancozeb-containing carbamate fungicide Tattoo

Intensive use of pesticides, particularly dithiocarbamates, in agriculture often leads to contamination of freshwater ecosystems. To our knowledge, the mechanisms of toxicity to fish by the carbamate fungicide Tattoo that contains mancozeb [ethylenebis(dithiocarbamate)] have not been studied. The present study aimed to evaluate the effects of Tattoo on goldfish gills and blood, tissues that would have close early contact with the pollutant. Exposure of goldfish Carassius auratus to 3, 5 or 10mgL(-1) of Tattoo for 96h resulted in moderate lymphopenia (by 8 percent) with a concomitant increase in both stab (by 66-88 percent) and segmented (by 166 percent) neutrophils. An increase in the content of protein carbonyl groups in blood (by 137-184 percent) together with decreased levels of protein thiols (by 23 percent) and an enhancement of lipid peroxide concentrations (by 29 percent) in gills after exposure to 10mgL(-1) of Tattoo demonstrated the induction of mild oxidative stress in response to Tattoo exposure. At the same time, the activities of selected antioxidant enzymes were enhanced in gills: superoxide dismutase by 18-25 percent and catalase by 27 percent. A 34 percent increment in low molecular mass thiol concentrations (mainly represented by glutathione) also occurred in gills and could be related to increased activity (by 13-30 percent) of glucose-6-phosphate dehydrogenase. The results indicate that Tattoo exposure perturbs free radical processes, i.e. induces mild oxidative stress and enhances the activity of certain antioxidant and associated enzymes in goldfish gills. It is clear that goldfish respond to the presence of waterborne pesticide by adjusting antioxidant defenses through upregulation of activities of antioxidant and associated enzymes.

The mancozeb-containing carbamate fungicide tattoo induces mild oxidative stress in goldfish brain, liver, and kidney

Tattoo belongs to the group of carbamate fungicides and contains Mancozeb (ethylene(bis)dithiocarbamate) as its main constituent. The toxicity of Mancozeb to living organisms, particularly fish, is not resolved. This work investigated the effects of 96 h of exposure to 3, 5, or 10 mg L−1 of Tattoo (corresponding to 0.9, 1.5, or 3 mg L−1 of Mancozeb) on the levels of oxidative stress markers and the antioxidant enzyme system of brain, liver, and kidney of goldfish, Carassius auratus). In liver, Tattoo exposure resulted in increased activities of superoxide dismutase (SOD) by 70%–79%, catalase by 23%–52% and glutathione peroxidase (GPx) by 49%. The content of protein carbonyls (CP) in liver was also enhanced by 92%–125% indicating extensive damage to proteins. Similar increases in CP levels (by 98%–111%) accompanied by reduced glucose‐6‐phosphate dehydrogenase activity (by 13%–15%) was observed in kidney of fish exposed to Tattoo; however, SOD activity increased by 37% in this tissue after treatment with 10 mg L−1 Tattoo. In brain, a rise in lipid peroxide level (by 29%) took place after exposure to 10 mg L−1 Tattoo and was accompanied by elevation of high‐molecular mass thiols (by 14%). Tattoo exposure also resulted in a concentration‐dependent decrease in glutathione reductase activity (by 26%–37%) in brain. The data collectively show that exposure of goldfish to 3–10 mg L−1 of the carbamate fungicide Tattoo resulted in the development of mild oxidative stress and activation of antioxidant defense systems in goldfish tissues.

Goldfish exposure to cobalt enhances hemoglobin level and triggers tissue-specific elevation of antioxidant defenses in gills, heart and spleen

Cobalt ions can enhance the generation of reactive oxygen species (ROS), which may be the reason for cobalt toxicity. This study aimed to determine whether Co(2+) toxicity in goldfish is related to induced oxidative stress in gills, heart and spleen, and to assess responses of antioxidant systems. Exposure of goldfish to 50, 100 and 150 mg L(-1) of Co(2+) for 96 h elevated total hemoglobin in blood by 23, 44 and 78%, respectively. In gills, cobalt exposure enhanced lipid peroxide levels and activities of primary antioxidant enzymes; superoxide dismutase (SOD) rose by 125% and glutathione peroxidase (GPx) increased by 53-296%. Glutathione-S-transferase (GST) activity also increased by 117-157% and glucose-6-phosphate dehydrogenase (G6PDH) enhanced by 46-96%. Heart showed limited effects of fish exposure to 50 or 100 mg L(-1) of Co(2+), but the exposure to 150 mg L(-1) of Co(2+) elevated concentrations of lipid peroxides by 123% and activities of GPx by 98% and SOD by 208%. The most substantial effects of goldfish exposure to Co(2+) were observed in spleen: a decrease in total protein concentration by 44-60% and high molecular mass thiols by 59-82%, reduced activities of catalase by 24-58% and GR by 25-68%, whereas the level of low molecular mass thiols increased by 153-279% and activities of GPx, GST, G6PDH were enhanced by 114-120%, 192-769%, and 256-581%, respectively. The data show that fish exposure to 50-150 mg L(-1) of Co(2+) elevates blood hemoglobin level, mimicking effects of hypoxia, and causes the activation of defense systems against ROS.

Tissue-specific induction of oxidative stress in goldfish by 2,4-dichlorophenoxyacetic acid: mild in brain and moderate in liver and kidney.

This study investigated the effects of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) on free radical-related processes in tissues of goldfish given 96 h exposures to 1, 10 or 100 mg/L of 2,4-D as well as 96 h recovery from the 100 mg/L treatment. In liver, 2,4-D exposure increased levels of protein carbonyls and lipid peroxides by 36-53% and 24-43%, respectively, but both parameters reverted during recovery, whereas in brain glutathione status improved in response to 2,4-D. Lipid peroxide content in kidney was enhanced by 40-43% after exposure to 2,4-D with a decrease during recovery. Exposure to 2,4-D also reduced liver acetylcholinesterase activity by 31-41%. The treatment increased catalase activity in brain, but returned it to initial levels after recovery. In kidney, exposure to 100 mg/L of 2,4-D caused a 33% decrease of superoxide dismutase activity. Thus, goldfish exposure to 2,4-D induced moderate oxidative stress in liver and kidney and mild oxidative stress in brain.

Goldfish can recover after short-term exposure to 2,4-dichlorophenoxyacetate: Use of blood parameters as vital biomarkers

This study investigated the effects of 2,4-dichlorophenoxyacetic acid (2,4-D), a widely used herbicide, on the metabolism of goldfish, Carassius auratus, using only vital (non-lethal) approaches. After 96 h exposure to 1, 10 or 100 mg/L of 2,4-D selected hematological (total hemoglobin and hematocrit) and biochemical (glucose content, aspartate transaminase and acetylcholinesterase activities) parameters were unchanged in blood of exposed fish. At 100 mg/L of 2,4-D lymphocyte numbers decreased by 8%, whereas promyelocyte and metamyelocyte numbers increased by 7- and 2-fold, respectively. Exposure to 100 mg/L of 2,4-D also elevated carbonyl protein levels (by 2-fold), triglyceride content (by 43%) and alanine transaminase activity (by 46%) in goldfish plasma. All of these hematological and biochemical parameters reverted to control values after a 96 h recovery period. These data indicate that 2,4-D has toxicological effects on goldfish that can be monitored with multiple diagnostic tests using non-lethal blood testing.

Goldfish brain and heart are well protected from Ni2+-induced oxidative stress

After 96 h goldfish exposure to 10, 25 or 50 mg/L of Ni(2+) no Ni accumulation was found in the brain, but lipid peroxide concentration was by 44% elevated in the brain, whereas carbonyl protein content was by 45-45% decreased in the heart. High molecular mass thiol concentration was enhanced by 30% in the heart, while in the brain low molecular mass thiol concentration increased by 28-88%. Superoxide dismutase activity was by 27% and 35% increased in the brain and heart, respectively. Glutathione peroxidase activity was lowered to 38% and 62% of control values in both tissues, whereas catalase activity was increased in the heart by 15-45%, accompanied by 18-29% decreased glutathione reductase activity. The disturbances of free radical processes in the brain and heart might result from Ni-induced injuries to other organs with more prominent changes in the heart, because of close contact of this organ with blood, whereas the blood-brain barrier seems to protect the brain.

Transient effects of 2,4-dichlorophenoxyacetic acid (2,4-D) exposure on some metabolic and free radical processes in goldfish white muscle.

This study aims to assess effects of 96 h goldfish exposure to 1, 10 and 100 mg/L of the herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D), on metabolic indices and free radical process markers in white muscle of a commercial fish, the goldfish Carassius auratus L. Most oxidative stress markers and antioxidant enzymes were not affected at 2,4-D fish treatment. 2,4-D fish exposure induced the elevated levels of total (by 46% and 40%) and reduced (by 77% and 73%) glutathione in muscles of goldfish of 10 mg/L 2,4-D and recovery (after 100 mg/L of 2,4-D exposure) groups, respectively. However, in muscles of 100 mg/L 2,4-D exposed goldfish these parameters were depleted (by 47% and 64%). None of investigated parameters of protein and carbohydrate metabolisms changed in white muscles of 2,4-D exposed fish, with exception of lactate dehydrogenase activity, which was slightly (by 11-15%) elevated in muscles of goldfish exposed to 10-100 mg/L of 2,4-D, but also recovered. Thus, the short term exposure of goldfish to the selected concentrations of 2,4-D does not substantially affect their white muscle, suggesting the absence of any effect under the environmentally relevant concentrations.