Oxidative stress in fish exposed to model xenobiotics. Oxidatively modified forms of Cu,Zn-superoxide dismutase as potential biomarkers

Biomarker responses in Danio rerio following an acute exposure (96 h) to e-waste leachate

Electronic waste (e-waste) has been identified as an emerging pollutant and is the fastest growing waste stream at the present time. Significant technological development and modernization within the last decade has led to the rapid accumulation of outdated, broken and unwanted electrical and electronic equipment (EEE). Electronic products mainly consist of a range of metal containing components that, when disposed of improperly, could result in metal constituents leached into the environment and posing a health risk to humans and animals alike. Metal exposure can induce oxidative stress in organisms, which could lead to synergistic, antagonistic and additive effects. The metals found highest in abundance in the simulated e-waste leachate, were nickel (Ni), barium (Ba), zinc (Zn), lithium (Li), iron (Fe), aluminium (Al) and copper (Cu). An acute exposure study was conducted over a 96 h period to determine the potential toxicity of e-waste on the test organism Danio rerio. Biomarker analysis results to assess the biochemical and physiological effects induced by e-waste leachate, showed a statistically significant effect induced on acetylcholinesterase activity, superoxide dismutase, catalase activity, reduced glutathione content, glutathione s-transferase, malondialdehyde and glucose energy available. The Integrated Biomarker Response (IBRv2) analysis revealed a greater biomarker response induced as the exposure concentration of e-waste leachate increased.

Effects of black sand on Oreochromis niloticus: insights into the biogeochemical impacts through an experimental study

Trace elements such as titanium, zirconium, thorium, and uranium, are found in black sand (BS) after weathering and corrosion. Precious metals are not the only valuable elements in black sand, rare earth elements are also found. The aquatic life in lakes and reservoirs is negatively affected by lithophilic elements such as lithium, uranium, and tin. Accordingly, intensive experiments were conducted on Nile tilapia (Oreochromis niloticus) after exposure to isolated black sand. Blood biomarkers, antioxidant balance, morpho-nuclear erythrocyte’s alterations, and histopathological signs have been investigated after fish exposure for 15 days to a 6.4 g BS/kg diet, 9.6 g BS/kg diet, and 2.4 g BS/kg diet. The blood profile, including platelets and white blood cells, was pronouncedly decreased as a result. Functions of the liver and kidneys were impaired. An increase in serum-antioxidant enzymes such as catalase activities and superoxide dismutase was recorded. Also, exposure to black sand induced cellular and nuclear abnormalities in the erythrocytes. In conclusion, the black sand isolated from the Red sea beach influenced Oreochromis niloticus’s hematology, biochemistry, and antioxidant parameters. Poikilocytosis and RBC nuclear abnormalities were also associated with exposure to black sand. The resulting erosion of rocks and rocks’ access to water forces us to consider the seriousness of climatic change on the aquatic ecosystem.

Characterising the Physiological Responses of Chinook Salmon (Oncorhynchus tshawytscha) Subjected to Heat and Oxygen Stress

In New Zealand, during the hottest periods of the year, some salmon farms in the Marlborough Sounds reach water temperatures above the optimal range for Chinook salmon. High levels of mortality are recorded during these periods, emphasising the importance of understanding thermal stress in this species. In this study, the responses of Chinook salmon (Oncorhynchus tshawytscha) to chronic, long-term changes in temperature and dissolved oxygen were investigated. This is a unique investigation due to the duration of the stress events the fish were exposed to. Health and haematological parameters were analysed alongside gene expression results to determine the effects of thermal stress on Chinook salmon. Six copies of heat shock protein 90 (HSP90) were discovered and characterised: HSP90AA1.1a, HSP90AA1.2a, HSP90AA1.1b, HSP90AA1.2b, HSP90AB1a and HSP90AB1b, as well as two copies of SOD1, named SOD1a and SOD1b. The amino acid sequences contained features similar to those found in other vertebrate HSP90 and SOD1 sequences, and the phylogenetic tree and synteny analysis provided conclusive evidence of their relationship to other vertebrate HSP90 and SOD1 genes. Primers were designed for qPCR to enable the expression of all copies of HSP90 and SOD1 to be analysed. The expression studies showed that HSP90 and SOD1 were downregulated in the liver and spleen in response to longer term exposure to high temperatures and lower dissolved oxygen. HSP90 was also downregulated in the gill; however, the results for SOD1 expression in the gill were not conclusive. This study provides important insights into the physiological and genetic responses of Chinook salmon to temperature and oxygen stress, which are critical for developing sustainable fish aquaculture in an era of changing global climates.

Effects of major and trace elements from the El Kahfa ring complex on fish: Geological, physicochemical, and biological approaches

The alkaline rocks are known for enriching rare lithophilic elements, including lithium, uranium, and tin, which negatively impact aquatic life. This study offers an intensive investigation of the influence of alkaline rocks on Nile Tilapia (Oreochromis niloticus). The variation in blood profile, the induction of antioxidant enzymes, morphological erythrocyte, and histological structure have been conducted for the fish after 15 days of exposure to alkaline rocks powder with a dose of 100 μg/L. As a result, there was a pronounced decrease in blood profiles, such as platelets and white blood cell counts. There was a failure in the liver and kidney functions. Moreover, it shows an increase in superoxide dismutase (SOD) and catalase (CAT) activities as antioxidant biomarkers. Also, exposure to alkaline rocks induced DNA mutation and erythrocyte distortion. We concluded that the bulk alkaline rocks induced changes in the hemato-biochemical and antioxidant parameters of Nile tilapia. Additionally, exposure to bulk alkaline rock compounds also caused poikilocytosis and nuclear abnormalities of RBCs. This draws our attention to the seriousness of climatic changes, the erosion of rocks, and their access to water.

Ecotoxicity in Hyriopsis bialatus of copper and zinc biocides used in metal-based antifouling paints

Biofouling is a costly burden for the shipping industry. Metal-based antifouling paints are widely used to protect submerged surfaces, but the release of metals from coatings and the recoating of hulls can leach large amounts of copper and zinc into aquatic environments, posing a risk for aquatic ecosystems and biodiversity. With this study, we studied the time-course metal accumulation and oxidative stress in the digestive gland and the gills of Hyriopsis bialatus, an Asian freshwater mussel, exposed to sublethal concentrations of cuprous chloride (50 and 5 µg/L) and zinc sulfate (1000 and 100 µg/L). Time-dependent accumulation was observed after exposure to copper, but zinc uptake was negligible. Integrated biomarker response (IBRv2) and statistical analysis of individual biomarker levels showed a greater biomarker response in the digestive gland and the gills after exposure to the higher concentration of CuCl and ZnSO₄. Both compounds elicited a biochemical response, especially in the digestive gland. Glutathione peroxidase activity was increased after exposure to both metals at both concentrations, suggesting a powerful defense against lipid peroxidation. The biological impact of zinc was less than that of copper, suggesting mitigated ecological pressure.

Investigating the effects of copper sulfate and copper oxide nanoparticles in Nile tilapia (Oreochromis niloticus) using multiple biomarkers: the prophylactic role of Spirulina

Copper has toxic effects in fish, whereas the cyanobacterium Spirulina reportedly has protective effects against metal toxicity in various animal species. The current study, therefore, aimed to investigate the prophylactic role of Spirulina platensis against the effects of copper sulfate (CuSO4) and copper oxide nanoparticles (CuO-NPs) in Nile tilapia (Oreochromis niloticus). Biochemical, antioxidant, erthyron profile and histopathological endpoints were assessed after for 15 days of exposure in five separate treatment groups: (1) fish pre-fed the normal diet (control), (2) fish pre-fed the normal diet and exposed to 15 mg/L of CuSO4, (3) fish pre-fed the normal diet augmented with 0.25% Spirulina and exposed to 15 mg/L of CuSO4, (4) fish pre-fed the normal diet and exposed to 15 mg/L of CuO-NPs, and (5) fish pre-fed the normal diet augmented with 0.25% Spirulina and exposed to 15 mg/L CuO-NPs. Exposure to CuSO4 or CuO-NPs significantly increased superoxide dismutase and catalase activities in fish, as well as serum total protein, glucose, aspartate aminotransferase, alanine aminotransferase, creatinine, and uric acid concentrations. In contrast, most hematological indices in fish significantly decreased after CuSO4 or CuO-NPs exposure. Moreover, CuSO4 and CuO-NPs caused a significant increase in the percentage of poikilocytosis and nuclear abnormalities of red blood cells, as well as histopathological changes in the brain, liver, intestine, and kidneys. Importantly, Spirulina supplementation mitigated against physiological disruption caused by CuSO4 or CuO-NPs.

Dietary Inclusion of Black Soldier Fly (Hermetia Illucens) Larvae Meal and Paste Improved Gut Health but Had Minor Effects on Skin Mucus Proteome and Immune Response in Atlantic Salmon (Salmo Salar)

The present study investigated effects of dietary inclusion of black soldier fly larvae (BSFL) (Hermetia illucens) meal and paste on gut health, plasma biochemical parameters, immune response and skin mucus proteome in pre-smolt Atlantic salmon (Salmo salar). The seven-week experiment consisted of seven experimental diets: a control diet based on fishmeal and plant protein (Control-1); three BSFL meal diets, substituting 6.25% (6.25IM), 12.5% (12.5IM) and 25% (25IM) of protein; two BSFL paste diets, substituting 3.7% (3.7IP) and 6.7% (6.7IP) of protein and an extra control diet with 0.88% of formic acid (Control-2). The 6.25IM diet reduced enterocyte steatosis in pyloric caeca, improved distal intestine histology, and reduced IgM in distal intestine. The fish fed 12.5IM diet reduced enterocyte steatosis in pyloric caeca, improved distal intestine histology, had a higher plasma lysozyme content compared to 6.25IM, and tend to increase phagocytic activity in head-kidney macrophages-like cells. On the other hand, 25IM diet improved distal intestine histology, but showed mild-moderate enterocyte steatosis in pyloric caeca, increased IFNγ and reduced IgM in distal intestine. In the case of BSFL paste diets, 3.7IP diet caused mild inflammatory changes in distal intestine, although it reduced enterocyte steatosis in pyloric caeca. The 6.7IP diet reduced enterocyte steatosis in pyloric caeca and improved distal intestine histology. Increasing level of BSFL meal in the diet linearly decreased plasma C-reactive protein, whereas increasing level of BSFL paste linearly increased plasma antioxidant capacity. Dietary inclusion of BSFL meal and paste had minor effects on the expression profile of proteins in skin mucus and no effects on immune markers in splenocytes. BSFL meal showed no negative effect on liver and muscle health as indicated by plasma alanine aminotranseferase, asparate aminotransferase and creatine kinase. The present study showed that replacing conventional protein sources with low to moderate levels of BSFL meal (6.25% and 12.5%) or paste (3.7% and 6.7%) reduced enterocyte steatosis in pyloric caeca, while replacing up to 25% with BSFL meal or 6.7% with paste improved distal intestine histology. Further, dietary inclusion of BSFL meal and paste had minor effects on skin mucus proteome and immune response in Atlantic salmon.

Comparative analyses of oxidative stress response and metallothionein induction in white sturgeon and rainbow trout during acute waterborne copper exposure

Early life-stages of the endangered white sturgeon (Acipenser transmontanus) have been shown to be among the most sensitive fishes to aqueous copper (Cu) exposure. In a recent analogous study, we examined the role of whole-body Cu accumulation and Na homeostasis in species-specific differences between the sensitivity of white sturgeon and a common laboratory fish model, rainbow trout, to Cu. However, the potential roles of important mechanisms such as Cu-induced oxidative stress and/or metallothionein (MT) induction as potential drivers of sensitivity of white sturgeon to Cu have not been investigated to date. Here, rainbow trout and white sturgeon from three different early life-stages were exposed to waterborne Cu for 96 h, following which major antioxidant parameters, lipid peroxidation and MT gene expression were evaluated. Results indicated that during larval and swim-up life-stages, Cu induced oxidative damage in white sturgeon was greater than in rainbow trout. Moreover, baseline glutathione (GSH) was significantly greater in rainbow trout than white sturgeon. Observations also suggested that trout exceedingly relied on GSH to combat Cu-induced oxidative stress as they grew older. In contrast, sturgeon recruited an increasing level of MT to neutralize Cu-induced oxidative stress and/or Cu loading. In our recent study, we demonstrated that Na homeostasis is more susceptible to Cu in white sturgeon than in rainbow trout. Collectively, these findings indicate that the greater degree of oxidative damage in early life-stages, in addition to the higher magnitude of the disruption of Na homeostasis, contributes to the higher sensitivity of white sturgeon to Cu exposure.

The Impact on Antioxidant Enzyme Activity and Related Gene Expression Following Adult Zebrafish (Danio rerio) Exposure to Dimethyl Phthalate

Simple Summary

Dimethyl phthalate (DMP) is a widespread environmental contaminant and its toxicological effects on fish have not been adequately examined. Our present study clearly showed that a high concentration induced oxidative damage in zebrafish, which proved the molecular regulation due to the negative effects of DMP, along with the physical damage in zebrafish. We also found that antioxidant enzymes might be used as appropriate biochemical markers for the toxic identification of DMP.

Abstract

Dimethyl phthalate (DMP) is a widespread environmental contaminant that poses potential toxicity risks for animals and humans. However, the toxicological effects of DMP on fish have not been adequately examined. In this study, the acute toxicity, oxidative damage, antioxidant enzyme activities, and relative gene expression patterns were investigated in the liver of adult zebrafish (Danio rerio) exposed to DMP. We found that the lethal concentration (LC₅₀) of DMP for zebrafish after 96 h of exposure was 45.8 mg/L. The zebrafish that were exposed to low, medium and high concentrations of DMP (0.5, 4.6, and 22.9 mg/L, respectively) for 96 h had an increased malondialdehyde (MDA) content and a lower antioxidant capacity compared with the control solvent group. The total superoxide dismutase (SOD) activity was significantly higher than 0 h after initial exposure for 24 h at low concentrations, and then decreased at high concentrations after exposure for 96 h. The catalase (CAT) and glutathione S-transferase (GST) activities were significantly reduced after 96 h of exposure to high concentrations of DMP, with the up- or down-regulation of the related transcriptional expression. These findings indicated that DMP could cause physiological effects in zebrafish by disturbing the expression levels of antioxidant enzymes. These results might contribute to the identification of biomarkers to monitor phthalate pollution.

Assessment of hematological, hepato-renal, antioxidant, and hormonal responses of Clarias gariepinus exposed to sub-lethal concentrations of oxyfluorfen

Little is known about the effects of oxyfluorfen, a diphenyl ether herbicide, exposure on the African catfish (Clarias gariepinus) health. Consequently, the existing investigation was designed to highlight the impacts of oxyfluorfen exposure on C. gariepinus hematological indices, liver and kidney functions, reproductive hormones, and oxidative status. Furthermore, a consequent 10-day depuration period was adopted to evaluate the recovery of the disturbed indicators to normal values. In the first experiment, the 96-h lethal concentration 50 (LC₅₀) of oxyfluorfen for C. gariepinus was determined using probit analysis. Next, in a second experiment, 180 healthy fish (average initial body weight: 164.23 ± 0.24) were randomly assigned to 4 experimental groups exposed to 0, 1/10, 1/8, or 1/5 96-h LC₅₀ of oxyfluorfen. The hematological profile, hepatic enzymes, kidney damage byproducts, reproductive hormones, oxidative stress, and lipid peroxidation indicators together with acetylcholinesterase (AChE) content were assessed. A histopathological examination of the hepatic, renal, brain, and testicular tissues was accomplished. Moreover, the expression of the oxidative stress-related gene was carried out. The results showed that 96-h LC₅₀ of oxyfluorfen for C. gariepinus was 11.698 mg/L. Exposure to sublethal levels of oxyfluorfen induced macrocytic hypochromic anemia, leukopenia, lymphopenia, monocytopenia, and eosinopenia. Also, a concentration-dependent increase in alanine transaminase, alkaline phosphatase, aspartate transaminase, urea, creatinine, catalase, and malondialdehyde was detected following oxyfluorfen exposure together with upregulation of catalase gene. But, significant concentration-dependent reductions in AChE, glutathione transferase, reduced to oxidized glutathione ratio, estradiol, and testosterone activities were recorded. These biochemical alterations were accompanied by pathological perturbations in hepatic, renal, brain, and testicular tissues. Following 10 days of recovery, only the hematological impairments were abolished. Conclusively, the herbicides oxyfluorfen could induce multiple negative impacts on C. gariepinus with oxidative stress as a probable underlying mechanism. Additionally, a recovery period of 10 days was not enough to restore these impairments.

Sweet Pepper (Capsicum annuum L.) Fruits Contain an Atypical Peroxisomal Catalase That is Modulated by Reactive Oxygen and Nitrogen Species

During the ripening of sweet pepper (Capsicum annuum L.) fruits, in a genetically controlled scenario, enormous metabolic changes occur that affect the physiology of most cell compartments. Peroxisomal catalase gene expression decreases after pepper fruit ripening, while the enzyme is also susceptible to undergo post-translational modifications (nitration, S-nitrosation, and oxidation) promoted by reactive oxygen and nitrogen species (ROS/RNS). Unlike most plant catalases, the pepper fruit enzyme acts as a homodimer, with an atypical native molecular mass of 125 to 135 kDa and an isoelectric point of 7.4, which is higher than that of most plant catalases. These data suggest that ROS/RNS could be essential to modulate the role of catalase in maintaining basic cellular peroxisomal functions during pepper fruit ripening when nitro-oxidative stress occurs. Using catalase from bovine liver as a model and biotin-switch labeling, in-gel trypsin digestion, and nanoliquid chromatography coupled with mass spectrometry, it was found that Cys377 from the bovine enzyme could potentially undergo S-nitrosation. To our knowledge, this is the first report of a cysteine residue from catalase that can be post-translationally modified by S-nitrosation, which makes it especially important to find the target points where the enzyme can be modulated under either physiological or adverse conditions.

Oxidative stress induction by the invasive sponge Paraleucilla magna growing on Peyssonnelia squamaria algae

The introduction of invasive species can lead to significant adverse effects on the colonized areas. The aim of the present research was to determine if the invasive behavior of Paraleucilla magna could induce the activation of the antioxidant defences in the native red algae, Peyssonnelia squamaria. Individuals of isolated P. squamaria and individuals epiphytized by P. magna, both growing on rocky bottoms, were collected. The activity of the antioxidant enzymes - catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase - and the levels of the malondialdehyde were significantly higher in the algae of the epiphytic group compared to the control group, while the detoxifying enzyme glutathione S-transferase did not show significant differences. The levels of reduced glutathione and total polyphenols were higher in the algae affected by the sponge. In conclusion, the arrival of the species P. magna induces an adaptative antioxidant response in P. squamaria determined by the use of biomarkers.

Modulation of mitochondrial functions by xenobiotic-induced microRNA: From environmental sentinel organisms to mammals

Mitochondria play a crucial role in energetic metabolism, signaling pathways, and overall cell viability. They are in the first line in facing cellular energy requirements in stress conditions, such as in response to xenobiotic exposure. Recently, a novel regulatory key role of microRNAs (miRNAs) in important signaling pathways in mitochondria has been proposed. Consequently, alteration in miRNAs expression by xenobiotics could outcome into mitochondrial dysfunction, reactive oxygen species overexpression, and liberation of apoptosis or necrosis activating proteins. The aim of this review is to show the highlights about mitochondria-associated miRNAs in cellular processes exposed to xenobiotic stress in different cell types involved in detoxification processes or sensitive to environmental hazards in marine sentinel organisms and mammals.

Biomarker responses of Cu-induced toxicity in European seabass Dicentrarchus labrax: Assessing oxidative stress and histopathological alterations

A comprehensive approach to chemical accumulation and biological effects of short-term Cu exposure in juveniles of European seabass (Dicentrarchus labrax) has been achieved. Fish were exposed to 0.01-10mgL^-1 nominal Cu concentrations for 24-96h. Metal concentrations in water and gills, liver, muscle and brain tissues were studied along with oxidative stress biomarkers (superoxide dismutase, catalase, glutathione peroxidase, lipid peroxidation). Induction of oxidative damage was observed in all the organs with differential antioxidant responses; gills appearing as the most sensitive from low environmentally water Cu concentrations as 0.01mgL^-1. Histopathological alterations were also observed in liver and gills, even without a significant Cu accumulation. The results show that the combination of oxidative stress parameters, particularly lipid peroxidation and glutathione peroxidase activities, and histopathological alterations provide a good model fish and reliable early biomarkers for monitoring Cu pollution in seawater and might call for the protection agencies to revise the Cu environmental standards.

Oxidative stress and related biomarkers in cupric and cuprous chloride-treated rainbow trout

We examined the time-course stress responses in the liver of rainbow trout exposed to cuprous chloride (CuCl) and cupric chloride (CuCl₂). The treatment groups received a single intraperitoneal injection of CuCl or CuCl₂ (both at a dose of 0.01 and 0.05 mg/kg); the control group received only the physiologic solution vehicle. Liver tissue samples were analyzed for total copper, superoxide dismutase, catalase, glutathione peroxidases, glutathione reductase, glutathione S-transferase, glyoxalases, and lactate dehydrogenase at 3, 6, and 9 days post-injection. Total glutathione, metallothionein, and malondialdehyde levels were also measured. The time course of metal accumulation differed between the groups; no dose-response relationship for metal load was found. Both copper species elicited significant changes in oxidative stress markers and in metal trapping. Copper underwent adaptive shifts in glutathione and metallothionein concentrations. The defense strategy primarily versus CuCl₂ first involved glutathione, with a peak in metallothionein levels at day 6 for CuCl₂ (at both doses) and for CuCl (0.05 mg/kg). Early stimulation of lipid peroxidation was noted after treatment with the higher copper dose and at day 9 after treatment with the lower dose of both CuCl and CuCl₂. Antioxidant enzyme activity was impaired due to a more or a less severe oxidative stress condition in relation to the copper species and exposure time. Copper dynamics, in terms of metal accumulation and homeostatic regulation, is noticeably complex. The present findings may advance our understanding of the effects of both copper species on the antioxidant response of rainbow trout.

Combined effects of cadmium and salinity on juvenile Takifugu obscurus: cadmium moderates salinity tolerance; salinity decreases the toxicity of cadmium

Obscure puffer Takifugu obscurus, a species of anadromous fish, experiences several salinity changes in its lifetime. Cadmium (Cd) is a toxic heavy metal that can potentially induce oxidative stress in fish. The present study aimed to detect the combined effects of Cd (0, 5, 10, 20 and 50 mg L(-1)) and salinity (0, 15 and 30 ppt) on juvenile T. obscurus. Results showed the juveniles could survive well under different salinities; however, with Cd exposure, the survival rates significantly decreased at 0 and 30 ppt. At 15 ppt, tolerance to Cd increased. Cd exposure clearly induced oxidative stress, and the responses among different tissues were qualitatively similar. Salinity acted as a protective factor which could reduce the reactive oxygen species and malondialdehyde levels. In addition, salinity could enhance the antioxidant defense system, including superoxide dismutase, catalase and glutathione. Na(+)/K(+)-ATPase activity significantly decreased under Cd exposure in gill, kidney and intestine. These findings indicated that Cd could moderate the adaptability of juvenile T. obscurus to high salinity and low salinity played a protective role upon Cd exposure. Thus, the role of salinity should be considered when evaluating the effect of heavy metals on anadromous and estuarine fishes.

Contaminant-induced oxidative stress in fish: a mechanistic approach

The presence of reactive oxygen species (ROS) in living organisms was described more than 60 years ago and virtually immediately it was suggested that ROS were involved in various pathological processes and aging. The state when ROS generation exceeds elimination leading to an increased steady-state ROS level has been called "oxidative stress." Although ROS association with many pathological states in animals is well established, the question of ROS responsibility for the development of these states is still open. Fish represent the largest group of vertebrates and they inhabit a broad range of ecosystems where they are subjected to many different aquatic contaminants. In many cases, the deleterious effects of contaminants have been connected to induction of oxidative stress. Therefore, deciphering of molecular mechanisms leading to such contaminant effects and organisms' response may let prevent or minimize deleterious impacts of oxidative stress. This review describes general aspects of ROS homeostasis, in particular highlighting its basic aspects, modification of cellular constituents, operation of defense systems and ROS-based signaling with an emphasis on fish systems. A brief introduction to oxidative stress theory is accompanied by the description of a recently developed classification system for oxidative stress based on its intensity and time course. Specific information on contaminant-induced oxidative stress in fish is covered in sections devoted to such pollutants as metal ions (particularly iron, copper, chromium, mercury, arsenic, nickel, etc.), pesticides (insecticides, herbicides, and fungicides) and oil with accompanying pollutants. In the last section, certain problems and perspectives in studies of oxidative stress in fish are described.

Metallothionein, oxidative stress and trace metals in gills and liver of demersal and pelagic fish species from Kuwaits' marine area

Two fish species yellowfin seabream (Acanthopagrus latus) and tonguesole (Cynoglossus arel) were collected from two locations in Kuwait's territorial waters in non-reproductive periods and used as bio-indicator organism for the assessment of metals in the marine environment. Species variation in fish was observed; seabream contained high metal content and metallothionein in liver and gill tissues compared to tonguesole, especially from Kuwait Bay area. Oxidative injury was registered in the gills of both species, but in tonguesole liver was also involved. Consequently, antioxidant enzyme catalase was elevated in tonguesole enabling bottom dwelling fish to combat oxidative assault. The study provided information about the current status of metals in marine sediment and levels of metals accumulated in representative species along with oxidative damage in exposed tissues and the range of biomarker protein metallothionein and enzymes of antioxidant defence mechanism enhancing our understanding about the biological response to the existing marine environment in Kuwait.

Chronic stress of rainbow trout Oncorhynchus mykiss at high altitude: a field study

The stress response of Oncorhynchus mykiss in high-altitude farms in central Mexico was investigated over two seasons: the cool (9·1-13·7° C) dry winter season, and the warmer (14·7-15·9° C), wetter summer season. Fish were subjected to an acute stress test followed by sampling of six physiological variables: blood cortisol, glucose, lactate, total antioxidant capacity, haemoglobin concentration and per cent packed cell volume (VPC %). Multivariate analyses revealed that lactate and total antioxidant capacity were significantly higher in the summer, when water temperatures were warmer and moderate hypoxia (4·9-5·3 mg l(-1) ) prevailed. In contrast, plasma cortisol was significantly higher in the winter (mean ± s.e.: 76·7 ± 4·0 ng ml(-1) ) when temperatures were cooler and dissolved oxygen levels higher (6·05-7·9 mg l(-1) ), than in the summer (22·7 ± 3·8 ng ml(-1) ). Haemoglobin concentrations (mg dl(-1) ) were not significantly different between seasons, but VPC % was significantly higher in the summer (50%) than in the winter (35%). These results suggest that in summer, effects of high altitude on farmed fish are exacerbated by stresses of high temperatures and hypoxia, resulting in higher blood lactate, increased total antioxidant capacity and elevated VPC % levels.

Oxidative stress and metabolic responses to copper in freshwater- and seawater-acclimated killifish, Fundulus heteroclitus

In freshwater (FW), many of the main mechanisms of copper (Cu) toxicity have been characterized; however, toxicity mechanisms in seawater (SW) are less well understood. We investigated the effects of salinity on Cu-induced oxidative stress and metabolic responses in adult killifish, Fundulus heteroclitus. We exposed FW and SW-acclimated killifish to either low Cu (LC, 50 μg/L) or high Cu (HC, 200 μg/L) for 96 h and compared them to controls (CTRL) under the same salinities without added Cu. Cu exerted minimal influence on tissue ion levels in either FW or SW. Salinity generally protected against Cu bioaccumulation in the gills and liver, but not in the carcass. Hematocrit (Hct) and hemoglobin (Hb) levels were increased by LC and HC in both FW and SW, and blood lactate was reduced in FW-killifish exposed to LC and HC. Rates of oxygen consumption were similar across treatments. Salinity reduced Cu load in gill, liver and intestine at LC but only in the gills at HC. In general, Cu increased gill, liver, and intestine catalase (CAT) activity, while superoxide dismutase (SOD) either decreased or remained unchanged depending on tissue-type. These changes did not directly correlate with levels of protein carbonyls, used as an index of oxidative stress. Cu-induced changes in carbohydrate metabolic enzymes were low across tissues and the effect of salinity was variable. Thus, while salinity clearly protects against Cu bioaccumulation in some tissues, it is unclear whether salinity protects against Cu-induced oxidative stress and metabolic responses.

Oxidative damage induced by copper and beta-cypermethrin in gill of the freshwater crayfish Procambarus clarkii

Copper (Cu) and pyrethroid are common contaminants found in the aquatic environment, and their potential toxicological effects on aquatic organisms have received extensive attention. However, the impact on crayfish species of exposure to the two chemicals are still largely unknown. The current study assessed the sublethal toxicities induced by Cu and commercial formulation of beta-cypermethrin in the freshwater crayfish Procambarus clarkii. The static test method of acute toxicity test was used. Five biomarkers of oxidative effects, i.e. reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA) and protein carbonyls, and pathologic changes were determined. The results demonstrated that there was a significant increase in the contents of ROS, MDA and protein carbonyls accompanied by markedly decreased SOD and CAT activities in a concentration-dependent manner. The linear relationship between protein carbonyls induction and MDA formation was observed evidently in crayfish gills at 96h. Higher contents of ROS enhanced the risk of lipid peroxidation and protein carbonylation, thus impacting vital physiological functions of gills. The results indicated that protein oxidation may be one of the main mechanisms of pollution-induced toxicity to crayfish gills. Protein carbonyl levels could be considered as a potential biomarker of exposure to environmental contaminants.

Reactive oxygen species and cytotoxicity in rainbow trout hepatocytes: effects of medium and incubation time

This study evaluated the effects of exposure medium and culture age on intracellular reactive oxygen species (ROS) development and cytotoxicity in fish hepatocytes following exposure to copper (Cu). ROS was quantified using the fluorescent probes DHR 123 and CM-H2DCFDA following exposure to Cu in Leibovitz' medium (L-15) or Tris-buffered saline (TBS). Similarly, culture age effects were investigated using 1-, 2- and 4-day-old cultured hepatocytes by exposing them to Cu in TBS. The exposure in L-15 resulted in significantly higher ROS compared to TBS using CM-H2DCFDA, but not DHR 123. The age of the primary cultures significantly affected the development of ROS for both probes. None of the exposures caused cytotoxicity in the hepatocytes. The results showed that both factors may affect responses to stressors, and suggested that the use of a simple medium such as TBS may be preferable for some applications. It is also preferable to use 1-day-old primary hepatocyte cultures.

Modulated expression and enzymatic activity of the monogonont rotifer Brachionus koreanus Cu/Zn- and Mn-superoxide dismutase (SOD) in response to environmental biocides

Superoxide dismutases (SODs) are important antioxidant enzymes whose expression levels are often used as biomarkers for oxidative stress. To investigate the biomarker potential of the monogonont rotifer Brachionus koreanus SOD genes, the full-length Cu/Zn-SOD (Bk-Cu/Zn-SOD) and Mn-SOD (Bk-Mn-SOD) genes were cloned from genomic DNA and characterized. All amino acid residues involved in the formation of tertiary structure and metal binding in Bk-Cu/Zn-SOD and Bk-Mn-SOD were highly conserved across species. Phylogenetic analysis revealed that Bk-Mn-SOD, in particular, was closely clustered with mitochondrial Mn-SOD. Transcript analysis after exposure to six different biocides (alachlor, chlorpyrifos, dimethoate, endosulfan, lindane, and molinate) revealed that the transcriptional level of Bk-Cu/Zn-SOD was significantly increased in a dose-dependent manner. In contrast, the level of Bk-Mn-SOD transcript was significantly increased compared with control cells in response to chlorpyrifos, endosulfan, and molinate at their no observed effect concentrations (NOECs). However, exposure to alachlor, chlorpyrifos, and molinate significantly reduced the enzymatic activity of total SOD protein, while a decreased pattern was observed in all biocide treatments. Taken together, these results indicate that exposure to waterborne environmental biocides induces the transcription of Bk-Cu/Zn-SOD and Bk-Mn-SOD, but inhibits the enzymatic activity of Bk-SODs. These results contribute to our understanding of the modes of action of oxidative stress-mediating biocides on rotifer.

Biochemical and histological changes in the liver and gills of Nile tilapia Oreochromis niloticus exposed to Red 195 dye

The present study investigates the biochemical and morphological responses induced in the liver and gills of Nile tilapia Oreochromis niloticus by exposure to various Red 195 dye concentrations (0.05, 0.1 and 0.2 mg L⁻¹) for various durations (7, 14 and 21 days).

Metal accumulation and oxidative stress biomarkers in liver of freshwater fish Carassius auratus following in vivo exposure to waterborne zinc under different pH values

In this study, laboratory experiments were conducted to investigate the combined effect of zinc and pH on metal accumulation and oxidative stress biomarkers in Carassius auratus. Fish were exposed to 0.1 and 1.0mg Zn/L at three pH values (5.0, 7.25, 9.0) for 3, 12, and 30 d. After each exposure, the contents of three trace elements (Zn, Fe and Cu) were determined in liver. Generally, longer exposure to zinc (12d and 30 d) increased hepatic Zn and Cu deposition, but decreased Fe content. Increasing accumulation of Zn in the tissue was also observed with increasing zinc concentration in the exposure medium. Moreover, hepatic antioxidant enzyme activities including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), together with the level of glutathione (GSH) were measured to evaluate the oxidative stress status. The decreases in the four measured biochemical parameters after 3d exposure might reflect the failure of the antioxidant defense system in neutralizing the ROS generated during the metabolic process, while the recovery of the antioxidants at days 12 and 30 suggested a possible shift toward a detoxification mechanism. With regard to the influence of pH on zinc toxicity, the general observation was that the living environment became more stressful when the water conditions changed from an acidic state toward a near-neutral or alkaline state.

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.

Malathion-induced changes in the haematological profile, the immune response, and the oxidative/antioxidant status of Cyprinus carpio carpio: protective role of propolis

The present study investigated the potential ameliorative effects of propolis against malathion toxicity in the blood and various tissues of carp. The fish were exposed to sublethal concentrations of malathion (0.5 and 1 mg/L) for 10 days, and propolis (10 mg/kg of fish weight) was simultaneously administered. Blood and tissue (liver, kidney, and gill) samples were collected at the end of the experiment and analysed to determine the haematological profile (red blood cell count, haemoglobin concentration, haematocrit level, and erythrocyte indices: mean corpuscular volume, mean corpuscular haemoglobin, and mean corpuscular haemoglobin concentration), immune response (white blood cell count, oxidative radical production, nitroblue tetrazolium (NBT) activity, total plasma protein and total immunoglobulin levels, and the phagocytic activity), and oxidant/antioxidant status (malondialdehyde and reduced glutathione levels and superoxide dismutase, catalase, and glutathione peroxidase activities) of the fish. The findings of this study demonstrate that malathion has a negative effect on the haematological parameters, immune response, and antioxidant enzyme activities of the fish. However, the administration of propolis ameliorated the malathion-induced toxic effects.

Integration of sediment contamination with multi-biomarker responses in a novel potential bioindicator (Sepia officinalis) for risk assessment in impacted estuaries

For the purpose of biomonitoring, species that combine ecological and commercial importance may provide a link between ecological and human health risk. The common cuttlefish, Sepia officinalis, holds both characteristics in south-western Europe, albeit remaining unsurveyed in ecotoxicological studies. Cuttlefish collected from an impacted estuary in SW Portugal and a reference location off the coast were analysed for a battery of biomarker responses in the digestive gland and gills. The contrast to reference animals revealed that biomarker responses, especially those related to oxidative stress, were consistent with sediment contamination by PAHs, even in a situation that combines complex toxicant mixtures, moderate levels of contamination and high ecotoxicological diversity. However, environmental parameters related to the differences between shore and estuarine habitats should not be overruled. Also, digestive gland metallothionein retained significant specificity to metals even though previous studies in the area with clams and fish failed to trigger a conclusive response. The highest net differences in biomarker responses were detected in the gills, likely indicating higher sensitivity to environmental stressors. Still, the digestive gland responses were overall the most consistent with sediment contamination and effectively differentiated between estuarine industrial- and rural-impacted sites. The results indicate that S. officinalis may be a candidate to meet the European Union's requirements for efficient biomonitoring programmes, with the additional importance of being cosmopolitan, abundant, commercially valuable and combining the molluscan biology that has been granting bivalves their high value for biomonitoring with foraging behaviour, thus better able to reflect anthropogenic stressors impacting a wider area than sedentary organisms. Nevertheless, further investigations in unpolluted sites are needed to better evaluate the background levels of biomarker responses in the species.

Toxic effects of malathion in carp, Cyprinus carpio carpio: protective role of lycopene

The present study was carried out in order to investigate the potential protective effects of lycopene against malathion-induced toxicity in carp. The fish were exposed to sublethal concentrations of malathion (0.5 and 1mgL(-1)) for 14 days, and lycopene (10mgkg(-1) of fish weight) was simultaneously administered. Samples of the blood and tissue (liver, kidneys, and gills) were collected at the end of the experimental period and their haematological profiles [red blood cell (RBC) counts, haemoglobin (Hb) concentrations, haematocrit (Ht) levels, and erythrocyte indices, including the mean corpuscular volume (MCV), the mean corpuscular haemoglobin (MCH) and the mean corpuscular haemoglobin concentration (MCHC)], immune responses [white blood cell (WBC) counts, oxidative radical production (nitroblue tetrazolium (NBT) activity), total plasma protein (TP) and total immunoglobulin (TI) levels and phagocytic activities (PA)] and oxidant/antioxidant statuses [malondialdehyde (MDA) levels, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) activities, and reduced glutathione (GSH) concentrations] were analysed. The findings of the present study demonstrated that the exposure of carp to malathion resulted in alterations in the haematological profiles and immune responses, and lead to increased reactive oxygen species formation, resulting in oxidative damage and inhibition of the antioxidant capacities. However, the administration of lycopene prevented malathion-induced toxic effects.

Combined use of native and caged mussels to assess biological effects of pollution through the integrative biomarker approach

Native and caged mussels were used in combination for the monitoring of pollution biological effects through an integrative biomarker approach. Mussels (Mytilus galloprovincialis) were deployed in cages in two well-known model localities with different pollution levels in the Basque coast. After 3 weeks caged and native mussels were collected from each site and a suite of effect and exposure biomarkers (from molecular/cellular to organism level) was applied and chemical contaminants (metals, PAHs, PCBs, phthalates and nonylphenol ethoxylates) were analytically determined. Integrative biomarker indices and pollutant indices of tissues were calculated. Several biomarkers used herein responded similarly in native and caged mussels, whereas others exhibited significant differences. Overall, biomarkers in-a-suite depicted site-specific profiles useful for the diagnostic of mussel health status and therefore for ecosystem health assessment in marine pollution biomonitoring. On the other hand, biomarkers and bioaccumulation exhibited different response times, which was especially evident when comparing biomarker and pollutant indices of tissues. The suite of biomarkers was more sensitive after caging (short-term response), whereas tissue pollutant concentrations were more sensitive in native mussels (long-term response). Thus, the combination of native and caged mussels is highly recommended to monitor biological effects of pollution in mussels through the integrative biomarker approach, especially in chronically polluted sites.

Effect of sublethal concentrations of waterborne copper on lipid peroxidation and enzymatic antioxidant response in Gambusia holbrooki

The aim of the current research was to assess the possible influence of copper sulphate contamination on the antioxidant enzymatic defenses and lipid peroxidation (LPO) in the mosquitofish (Gambusia holbrooki). Quadruplicated lots of this fish were exposed to three increasing sub-lethal concentrations of Cu (0.10; 0.17 and 0.25mgCu/L) and a control without Cu for 20 days. Previous to laboratory acclimation, 8 fish were taken to define the initial population. At the end of the trials, 12 fish/sex/treatment were sampled for the determination of levels of copper in gills, metallothioneins (MTs) content, total lipids, fatty acids profiles and antioxidant enzymatic activity, as well as lipid peroxidation. Most of the antioxidant enzymatic defenses assayed were not activated and lipid peroxidation decreased significantly in fish exposed to any concentration of copper applied. This leads us to presume the existence of a protective mechanism against peroxidation other than the enzymatic antioxidant defense, which could be related to the observed increase of copper content in the gills.

Biochemical responses in seabream (Sparus aurata) caged in-field or exposed to benzo(a)pyrene and paraquat. Characterization of glutathione S-transferases

Gilthead seabream (Sparus aurata) specimens were caged in-field at the Téboulba harbour or exposed to benzo(a)pyrene [B(a)P] or to paraquat [PQ] plus B(a)P, and several biochemical biomarker responses were investigated. Antioxidant enzymes, such as glutathione peroxidase, catalase and glutathione reductase, significantly increased in the in-field and B(a)P+PQ exposures, but were only moderately affected by B(a)P alone. Glucose-6-phosphate and 6-phosphogluconate dehydrogenases significantly diminished after in-field exposure. Different responses with biotransformation enzymes were observed: the P4501A-associated EROD activity was highly induced in response to B(a)P and B(a)P+PQ exposures, while total activity of the glutathione S-transferase (GST) was similar to control. However, after purification of the GST proteins by affinity chromatograpy and analysis by two-dimensional electrophoresis, nineteen highly reproducible isoforms were resolved. In addition, some of reproducible isoforms showed different and specific expression patterns in response to contaminants. Thus, proteomic analysis of the purified GST subunits is a reliable tool for ecotoxicological research, useful in polluted marine ecosystem as an effective biomarker of contamination.

Antioxidant defenses and biochemical changes in the neotropical fish pacu, Piaractus mesopotamicus: responses to single and combined copper and hypercarbia exposure

This study investigated the potentially detrimental effects of copper and elevated aquatic CO(2) (hypercarbia), alone or in combination, on pacu, Piaractus mesopotamicus. Fish were exposed for 48 h to control (no copper addition in normocarbia), to 400 μg Cu(2+)L(-1), to hypercarbic (1% CO(2); PCO(2) = 6.9 mm Hg) water and to 400 μg Cu(2+)L(-1) + hypercarbia. In liver the single factors caused an increase in lipid hydroperoxide concentration that was not observed when the factors were combined. Copper exposure elicited increased hepatic superoxide dismutase activity, irrespective of aquatic CO(2) level. On the other hand, the effects of copper on hepatic glutathione peroxidase activity were dependent on water CO(2) levels. The two stressors combined did not affect hepatic catalase activity. Hypercarbic water caused a decline in plasma glucose concentration, but this was not observed when hypercarbia was combined with copper exposure. Copper caused a decrease in branchial Na(+)/K(+)-ATPase activity that was independent of water CO(2) level. Copper caused an increase in branchial metallothionein concentration that was independent of water CO(2) level. Thus, branchial metallothionein and Na(+)/K(+)-ATPase were effective biomarkers of copper exposure that were not affected by water CO(2) level.

Increased oxidative stress is associated with the development of organophosphate-induced delayed neuropathy

Organophosphate-induced delayed neuropathy (OPIDN) is a progressive neuropathic disorder that manifests in days to weeks following exposure to an acute dose of organophosphates. The precise mechanism involved in the development of OPIDN is not clear as it develops after many days of the cessation of cholinergic crisis. The present study has been designed to understand the role of oxidative stress in the development of OPIDN, wherein neuropathy was developed by the administration of acute dose of monocrotophos (MCP) or dichlorvos (2,2-dichlorovinyl dimethyl phosphate (DDVP)) to rats. Significant motor deficits in terms of reduced spontaneous locomotor activity and performance on narrow beam test were observed after 14 days of exposure to MCP or DDVP, which persisted even on day 28, suggesting the development of OPIDN. Rats with OPIDN also exhibited an increase in malondialdehyde levels along with a decrease in thiol content in cerebral cortex, cerebellum and brain stem. Concomitantly, the activities of antioxidant enzymes, superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase were reduced in the three brain regions. The biochemical and functional changes were associated with histological alterations in the brain regions studied. The results clearly indicate that the development of OPIDN is mediated in part through an increased oxidative stress and suggest that the strategies aimed at restoration of antioxidant capacity may be beneficial for the individuals with OPIDN-like symptoms.

Oxidative stress parameters and antioxidant response to sublethal waterborne zinc in a euryhaline teleost Fundulus heteroclitus: protective effects of salinity

Zinc is an essential trace metal, but many aspects of its toxicity remain unclear. In this study, we investigated zinc effects on oxidative stress parameters and antioxidant profile in four tissues (gill, liver, kidney, and white muscle) of Fundulus heteroclitus. Possible interactive effects of salinity were also studied. Killifish were exposed to sublethal level (500 μgL(-1)) of waterborne zinc for 96 h in 0% (fresh water), 10% (3.5 ppt), 30% (10.5 ppt) and 100% sea water (35 ppt). Salinity per se had no effect on any parameter in the control groups. Zinc exposure clearly induced oxidative stress, and responses were qualitatively similar amongst different tissues. Salinity acted as a strong protective factor, with the highest levels of reactive oxygen species (ROS) and greatest damage (protein carbonyls, lipid peroxidation as indicated by thiobarbituric acid reactive substances (TBARS) in 0 ppt, the least in 100% sea water (35 ppt), and gradations in between in many of the observed responses. Increases in total oxidative scavenging capacity (TOSC) occurred at higher salinities, correlated with increases in the activities of superoxide dismutase (SOD) and glutathione-S-tranferase (GST), as well as in tissue glutathione (GSH) concentrations. However, TOSC was depleted in zinc-exposed fish at 0 ppt, accompanied by decreases in SOD, GST, GSH, and also catalase (CAT) activity. Our results confirm that sublethal waterborne zinc is an oxidative stressor in fish, and highlight the important protective role of higher salinities in ameliorating the oxidative stress associated with zinc toxicity in this model estuarine teleost.

Responses of AChE and GST activities to insecticide coexposure in Carassius auratus

Organophosphates and carbamates are widely used pesticides and play an important role in global agriculture. The misuse of these compounds has caused environmental problems and has had a negative impact on wildlife. In this study, the in vivo effects of commercial chlorpyrifos and isoprocarb on acetylcholinesterase (AChE) and glutathione S-transferase (GST) activities in goldfish (Carassius auratus) were investigated. Muscle and brain AChE activity was significantly inhibited by chlorpyrifos and isoprocarb (alone and in combination) after 2, 5, 10, and 15 days of exposure, and obvious concentration-response and time-response relationships were obtained. Gill GST activity was significantly inhibited by chlorpyrifos and isoprocarb (single compounds and in combination), however, concentration dependence and time dependence were not apparent. The joint effect of chlorpyrifos/isoprocarb was additive with regard to AChE activity inhibition and was antagonistic with regard to GST activity inhibition.

Effects of diazinon on antioxidant defense system and lipid peroxidation in the liver of Cyprinus carpio (L.)

Diazinon is a widely used organophosphorus pesticide in agriculture and environmental health, hence its adverse effects on nontarget animals, especially on fish is to be determined. The present study therefore aimed at detecting the biochemical changes caused by diazinon. To accomplish this aim, we studied the effects of sublethal concentrations (0.0036, 0.018, and 0.036 ppb) of diazinon on acetylcholine esterase activity, antioxidant enzyme activities, and lipid peroxidation in the liver of Cyprinus carpio on days 5, 15, and 30 after the exposure. The results revealed that the antioxidant enzyme activities such as superoxide dismutase, glutathione peroxidase, and catalase were induced by diazinon exposure. In addition, the highest catalytic activity of glutathione S-transferase (GST) was obtained with 1-chloro-2, 4-dinitrobenzene (CDNB). GST activity toward 1,2-dichloro-4-nitrobenzene (DCNB) was also observed in the liver, yet it was relatively low as opposed to the other substrates tested. On the other hand, hepatic malondialdehyde level did not show any significant alteration except after the exposure on day 15. The exposure of low concentrations of diazinon to C. carpio can induce oxidative stress in liver; yet restoring susceptibility and adapting to oxidative stress are likely to occur when low level of oxidative stress is administered. Furthermore, no significant change was observed in hepatic lipid peroxidation after diazinon treatment indicating that liver tissue resisted to oxidative stress by enhancing their antioxidant mechanisms. The level of lipid peroxidation was assumed to be associated with the concentrations of diazinon and experimentation periods. The induction of glutathione S-transferase and antioxidant enzyme activities were also assumed to have resulted from the defense against the toxicity of diazinon.

Chronic toxicity of pesticides to the mRNA expression levels of metallothioneins and cytochrome P450 1A genes in rainbow trout

The hazardous effects of pesticides on various metabolic pathways are a great problem for environmental health and should be well determined. In the present study, the authors treated rainbow trout with 0.6 μg/L deltamethrin for 28 days and 1.6 mg/L 2,2-dichlorovinyl dimethyl phosphate for 21 days. After this time period, the authors observed alterations in mRNA expression levels of MT-A, MT-B and CYP-1A. Chronic exposure to low levels of pesticides may have a more significant effect on fish populations than acute poisoning. While both pesticides caused a significant increase on mRNA levels of MT-A and CYP-1A, MT-B mRNA levels were increased significantly only upon deltamethin administration. The significant increase in mRNA levels of the corresponding genes may be considered as a defence mechanism in addition to the antioxidants against oxidative stress, as well as a detoxification mechanism against adverse effects of pesticides.

Impact of deltamethrin exposure on mRNA expression levels of metallothionein A, B and cytochrome P450 1A in rainbow trout muscles

Metallothioneins (MT) are widely utilized to identify specific responses to heavy metal pollution. In addition, there is evidence demonstrating that in vertebrates MT synthesis is stimulated by different endogenous and exogenous agents in particular compounds leading to production of ROS. Also, cytochrome P450 1A can enhance the generation of ROS. On this basis, MT and CYP 1A induction can be considered as biomarkers of oxidative stress. In the current study, we examined the influences of pesticide administration on the expression of MT-A, MT-B and CYP 1A. For this purpose, we produced muscle metallothionein-A, metallothionein-B and cytochrome P450 1A cDNAs and used quantitative RT-PCR to assay mRNAs in rainbow trout exposed to acute and long-term deltamethrin administration. We observed that deltamethrin exposure significantly (p<0.05) increased the expression levels of Cyp1A, MT-A and MT-B in a time dependent manner. Results of our study contributes to the identification of inducers of such biomarkers in addition to well known agents.

Environmentally induced oxidative stress in aquatic animals

Reactive oxygen species (ROS) are an unenviable part of aerobic life. Their steady-state concentration is a balance between production and elimination providing certain steady-state ROS level. The dynamic equilibrium can be disturbed leading to enhanced ROS level and damage to cellular constituents which is called "oxidative stress". This review describes the general processes responsible for ROS generation in aquatic animals and critically analyses used markers for identification of oxidative stress. Changes in temperature, oxygen levels and salinity can cause the stress in natural and artificial conditions via induction of disbalance between ROS production and elimination. Human borne pollutants can also enhance ROS level in hydrobionts. The role of transition metal ions, such as copper, chromium, mercury and arsenic, and pesticides, namely insecticides, herbicides, and fungicides along with oil products in induction of oxidative stress is highlighted. Last years the research in biology of free radicals was refocused from only descriptive works to molecular mechanisms with particular interest to ones enhancing tolerance. The function of some transcription regulators (Keap1-Nrf2 and HIF-1α) in coordination of organisms' response to oxidative stress is discussed. The future directions in the field are related with more accurate description of oxidative stress, the identification of its general characteristics and mechanisms responsible for adaptation to the stress have been also discussed. The last part marks some perspectives in the study of oxidative stress in hydrobionts, which, in addition to classic use, became more and more popular to address general biological questions such as development, aging and pathologies.

Teratogenicity and embryotoxicity in aquatic organisms after pesticide exposure and the role of oxidative stress

Many pesticides have been documented to induce embryotoxicity and teratogenicity in non-target aquatic biota such a fish, amphibians and invertebrates. Our review of the existing literature shows that a broad range of pesticides, representing several different chemical classes, induce variable toxic effects in aquatic species. The effects observed include diverse morphological malformations as well as physiological and behavioral effects. When development malformations occur, the myoskeletal system is among the most highly sensitive of targets. Myoskeletal effects that have been documented to result from pesticides were also known to interfere with the development of organ systems including the eyes or the heart and are also known to often cause lethal or sublethal edema in exposed organisms. The Physiological, behavioral, and population endpoints affected by pesticides include low or delayed hatching, growth suppression, as well as embryonal or larval mortality. The risks associated with pesticide exposure increase particularly during the spring. This is the period of time in which major pepticide applications take place, and this period unfortunately also coincides with many sensitive reproductive events such as spawning, egg laying, and early development of many aquatic organisms. Only few experimental studies with pesticides have directly linked developmental toxicity with key oxidative stress endpoints, such as lipid peroxidation, oxidative DNA damage, or modulation of antioxidant mechanisms. On the other hand, it has been documented in many reports that pesticide-related oxidative damage occurs in exposed adult fish, amphibians, and invertebrates. Moreover, the contribution of oxidative stress to the toxicity of pesticides has been emphasized in several recent review papers that have treated this topic. In conclusion, the available experimental data, augmented by several indirect lines of evidence, provide support to the concept that oxidative stress is a highly important mechanism in pesticide-induce reproductive or developmental toxicity. Other stressors may also act by oxidative mechanisms. This notwithstanding, there is much yet to learn about the details of this phenomenon and further research is needed to more fully elucidate the effects that pesticides have and the environmental risks they pose in the early development of aquatic organisms.

Effects of chronic dietary exposure to a low-dose of Malathion, Aroclor-1254 and 3-methylcholanthrene on three biomarkers in male mice

The aim of this research was to examine the applicability of some chronic toxicological tests in the determination of exposure to xenobiotics present in concentrations below No Observed Adverse Effect Level (NOAEL) and below the detection limit of analytical instruments. In the present experiment tested chemicals (Malathion, Aroclor-1254 and 3-methylcholanthrene (3-MC)) were mixed with wheat grains and given to male mice as feed over a period of 12 months. 7-ethoxyresorufin-O-deethylase (EROD) activity with the 3-MC and Aroclor-1254 treatments reached the peak at 9th month of exposure (26.7 and 42.4 pmol⁻¹ mg(prot)-⁻¹, respectively), while malathion did not have significant influence. Glutathione (GSH) level depletion was highest after three months of exposure. Unexpectedly, acetylcholinesterase (AChE) activity increased after treatment with malathion, an organophosphorous insecticide. In conclusion, low-level concentrations chronically administered exert certain effects on the levels of selected enzymes, e.g. biomarkers.

Multimarker approach analysis in common carp Cyprinus carpio sampled from three freshwater sites

The aim of this study is to assess the response of a multimarker approach in common carp Cyprinus carpio sampled from three Tunisian dam lakes selected according to different environmental and ecological characteristics. Glutathione-S-transferase (GST) activity was analyzed in carp liver and used as a phase II detoxification enzyme, hepatic metallothionein content (MTs) was used as a metallic stress indicator, and cholinesterase activities were analyzed in muscle and brain and used as neurotoxicity biomarker. Micronucleus frequency test (MN) as a genotoxicity marker. GST and MT levels showed an increase in fish from the Bir Mcherga site and a decrease in Sidi Saâd site with respect to fish from Nebhana site. Results showed a strong inhibition of cholinesterase activities in fish from Bir Mcherga and Sidi Saâd sites compared to Nebhana site. Relatively high level of MN is reported specially in fish blood from the Bir Mcherga site.

Effects of acute dieldrin exposure on neurotransmitters and global gene transcription in largemouth bass (Micropterus salmoides) hypothalamus

Exposure to dieldrin induces neurotoxic effects in the vertebrate CNS and disrupts reproductive processes in teleost fish. Reproductive impairment observed in fish by dieldrin is likely the result of multiple effects along the hypothalamic-pituitary-gonadal axis, but the molecular signaling cascades are not well characterized. To better elucidate the mode of action of dieldrin in the hypothalamus, this study measured neurotransmitter levels and examined the transcriptomic response in female largemouth bass (LMB) to an acute treatment of dieldrin. Male and female LMB were injected with either vehicle or 10 mg dieldrin/kg and sacrificed after 7 days. There were no significant changes in dopamine or DOPAC concentrations in the neuroendocrine brain of males and females after treatment but GABA levels in females were moderately increased 20-30% in the hypothalamus and cerebellum. In the female hypothalamus, there were 227 transcripts (p<0.001) identified as being differentially regulated by dieldrin. Functional enrichment analysis revealed transcription, DNA repair, ubiquitin-proteasome pathway, and cell communication, as biological processes over-represented in the microarray analysis. Pathway analysis identified DNA damage, inflammation, regeneration, and Alzheimer's disease as major cell processes and diseases affected by dieldrin. Using multiple bioinformatics approaches, this study demonstrates that the teleostean hypothalamus is a target for dieldrin-induced neurotoxicity and provides mechanistic evidence that dieldrin activates similar cell pathways and biological processes that are also associated with the etiology of human neurological disorders.

Effect assessment of the herbicide paraquat on a green alga using differential gene expression and biochemical biomarkers

Effects of the herbicide paraquat were assessed on the green freshwater alga Chlamydomonas reinhardtii using different endpoints of toxicity. Cell concentration and growth rate were monitored, whereas flow cytometry was applied to determine changes in chlorophyll content, viability and presence of reactive oxygen species. Furthermore, a transcriptomics approach using microarray hybridizations was applied to elucidate the mechanisms of toxicity. The results reveal that paraquat concentrations above 0.25 microM induce toxic effects in C. reinhardtii, reflected in a significantly reduced growth rate and cell concentration with a corresponding median effective concentration (EC50) value of 0.26 microM. With increasing paraquat concentrations, an increase in cell volume was registered with a particle counter as well as in the forward scattering signal of flow cytometric measurements, which is a measure of cell size. Flow cytometry, moreover, showed an increase in reactive oxygen species with increasing exposure concentration, corroborating the general knowledge that this herbicide exerts its toxicity through the generation of oxidative stress. At the same time, several genes involved in oxidative stress defense mechanisms, such as L-ascorbate peroxidase, glutaredoxin, and a possible glutathione-S-transferase were differentially expressed, demonstrating the value of microarrays for elucidating possible mechanisms of toxicity. The fact that several genes were differentially expressed at paraquat concentrations that caused no adverse effects on higher levels of biological organization indicates that a transcriptomics approach allows for the detection of early effects, even before they become manifest at higher levels.