Bioaccumulation and oxidative stress parameters in silver catfish (Rhamdia quelen) exposed to different thorium concentrations

Chronic toxicity and liver histopathology of mosquito fish (Gambusia holbrooki) exposed to natural and modified nanoclays

Nanoclays are found in the air, water, and soil, and modified nanoclays are being developed and used in several consumer products. For example, modified nanoclays are used to remove pollutants from wastewater. Ironically, however, nanoclays are now considered emerging contaminants. Indeed, release of modified nanoclays in aquatic systems, even as remediating agents, could adversely affect associated wildlife. However, aquatic organisms have interacted with natural nanoclays for millennia, and it is unclear if modified nanoclays induce stronger effects than the nanoclays that occur naturally. The concentrations over which nanoclays occur and illicit negative effects are not well studied. This study investigated the dose response of a natural nanoclay (Na+montmorillonite) relative to two modified nanoclays (Cloisite®30B and Novaclay™) on survival, body condition, and liver pathomorphology of Gambusia holbrooki after 14 days of exposure. Although none of the nanoclays affected survival and body condition of G. holbrooki over 14 days, each nanoclay induced histopathological changes in liver tissues at very low concentrations (LOAEL: 0.01 mgL-1). The effects of nanoclays on hepatic cell circulatory (blood cell aggregation with increased number of Kupffer cells and hemosiderin deposits), regressive (hepatocyte vacuolization), and degenerative (cell death) changes of mosquito fish varied among nanoclay types. Novaclay™ at low concentrations caused circulatory changes on hepatic tissues of G. holbrooki, whereas both natural nanoclays and Cloisite®30B showed little effect on circulatory endpoints. In contrast, all of the nanoclays induced regressive and degenerative changes on liver tissues of mosquito fish across all concentrations tested. This study clearly reveals that natural and modified nanoclays have important health implications for fish and other aquatic organisms. Consequently, the widespread use of modified nanoclays in several applications and increased release of natural nanoclays through erosion or other processes needs to be evaluated in more detail especially in the context of their safety for aquatic systems.

Expression of genes related to antioxidation, immunity, and heat stress in Gambusia affinis exposed to the heavy metals Cu and Zn

Water pollution is an increasingly serious problem. Here, Cu and Zn ions were used as stress factors, and G. affinis served as a test organism. Fluorescence quantitative PCR was used to detect changes in the expression of antioxidant genes (SOD, GST, CAT), heat stress genes (Hsp70, Hsp90, Hspd1, Hsc70), and immune system-related genes (IL-1β, IL-8) in G. affinis exposed to Cu and Zn ions over time. To explore the toxic effects of Cu and Zn on G. affinis. The results showed that the 48 h LC₅₀ concentrations of the heavy metals Cu and Zn to G. affinis were 0.17 mg/L and 44.67 mg/L, respectively. Within 48 h, with prolonged Cu exposure, the relative expression levels of the Hsp70, Hsp90, Hspd1, Hsc70, SOD, GST, and CAT genes in the gill tissue first showed a significant increase and then gradually decreased. Gene expression peaked between 9 and 36 h. The relative expression levels of SOD and GST genes in liver tissue showed a gradual decline. Within 48 h, with prolonged Zn exposure, the expression levels of SOD, CAT, and GST genes in G. affinis first increased and then fell before finally rising. The expression levels of IL-1β and IL-8 mRNA showed varying degrees of upward trends, and the expression of IL-8 was the highest for all gill tissue. To sum up, Cu and Zn have strong toxic effects on G. affinis, which makes it possible to use G. affinis as indicator organisms for aquatic environmental pollution.

Bioaccumulation of 35 metal(loid)s in organs of a freshwater mussel (Hyriopsis cumingii) and environmental implications in Poyang Lake, China

Benthic bioaccumulation of hazardous materials has been a great challenge to the health of lake ecosystems. As representative benthic macroinvertebrates, freshwater mussels and their accumulation characteristics have been regarded as effective indicators for assessing potential risks induced by sedimentary metal(loid)s in lakes. Here we profile organ-specific accumulation of 35 metal(loid)s in a freshwater mussel (Hyriopsis cumingii) and their correlations to metal speciation in sediments of Poyang Lake, the largest lake of China. Significant organ-specific characteristics of metal accumulation were found in gills, though higher thallium (Tl) and selenium (Se) were found in the hepatopancreas, and greater arsenic (As) mostly accumulated in gonads. Pearson correlation analysis revealed that the bioaccumulation of silver (Ag), cobalt (Co), and rare earth elements (ΣREE) in gills and As in gonads were closely associated with those in bioavailable fraction of sediments. Based on the biochemical analysis in the major organs, gills exhibited the highest enzymatic activity compared with hepatopancreas and gonads. Sedimentary metals, particularly for available Ag, Co, and ΣREE, play key roles in causing lipid peroxidation in gills and significantly promote the activities of superoxide dismutase (SOD)/glutathione reductase (GR), while many metals (e.g., cadmium, manganese, Se) inhibit the glutathione (GSH) content in gonads and hepatopancreas. Our study indicates a high physiological sensitivity of mussels to these target metals, which highlights the significance of organ-specific accumulation of metal(loid)s in understanding the potential ecological risks of sedimentary metal(loid)s in lake ecosystems.

Thorium inhibits human respiratory chain complex IV (cytochrome c oxidase)

Thorium is a radioactive heavy metal and an emerging environmental pollutant. Ecological and human health risks from thorium exposure are growing with the excavation of rare earth metals and implementation of thorium-based nuclear reactors. Thorium poisoning is associated with carcinogenesis, liver impairments, and congenital anomalies. To date, the biomolecular targets that underlie thorium-induced toxicity remain unknown. Here, we used in vitro enzymatic activity assays to comprehensively evaluate the effects of thorium on the mitochondrial respiration process. Thorium was found to inhibit respiratory chain complex IV (cytochrome c oxidase) at sub-micromolar concentrations (IC₅₀ ~ 0.4 μM, 90 μg/L). This is lower than the thorium level limit (246 μg/L) in drinking water specified by the World Health Organization. The inhibitory effects were further verified in mitochondria from human bone and liver cells (thorium mainly deposits in these organs). The inhibition of cytochrome c oxidase can readily rationalize well-documented cellular toxicities of thorium, such as alteration of mitochondrial membrane potential and production of reactive oxygen species. Therefore, cytochrome c oxidase is potentially a key molecular target underlying thorium-induced toxicological effect.

Role of calcium ion channels and cytoskeletal proteins in Thorium-232 induced toxicity in normal human liver cells (WRL 68) and its validation in swiss mice

Hepatic disorders reported in humans exposed to Thorium-232 (Th-232) rationalizes the present study investigating the toxicological response of normal human liver cells (WRL 68) and its validation in Swiss mice. Cell count analysis of WRL 68 cells-treated with Th-nitrate (1-200 μM) estimated IC50 of ∼24 μM (at 24 h) and 35 μM (at 48 h). Analysis of cell viability (trypan blue assay) showed the IC50 of ∼172 μM. Phase contrast bright-field microscopy revealed Th-induced morphological changes and cell-released microvesicle-like structures in extracellular space. Th-estimation by ICP-MS (Inductively-coupled plasma mass-spectrometry) showed uptake of Th by cells as a function of concentration and incubation time. Employing DTPA as a chelating agent in cell harvesting solution, cell-internalized/strongly-bound Th was estimated to be ∼42% of total incubated Th. Th-uptake studies in the presence of ion-channel specific inhibitors (e.g. nifedipine, thapsigargin) revealed the role of plasma membrane calcium channels and cytoplasmic calcium in modulating the Th-uptake. Transmission electron microscopy of Th-treated cells showed cell-derived extracellular vesicles, alterations in the shape and size of nucleus and mitochondria as well as cytoplasmic inclusions. The order of Th accumulation in various sub-cellular protein fractions was found to be as cytoskeleton (43%) > cytoplasmic (15%) > chromatin (7%) > nuclear (5%) & membrane (5%). Immunofluorescence analysis of WRL 68 cells showed that Th significantly altered the expression of cytoskeleton proteins (F-actin and keratin), which was further validated in liver tissues of Swiss mice administered with Th-232. Findings herein highlight the role of calcium channels and cytoskeleton in Th-induced toxicity. Keywords: Thorium toxicity; Liver cells; Calcium channels; Sub-cellular targets, Cytoskeleton; Swiss Mice.

Thorium and fetal neural tube defects: an epidemiological evidence from large case-control study

Background

Thorium is ubiquitous in the environment and its relationship with birth defects is still under discussion. This study aimed to investigate the associations of maternal exposure to thorium with risk of neural tube defects (NTDs) by using a case–control study, as well as the relationship between thorium exposure and the indoor air pollution from coal combustion.

Methods

This study was conducted in 11 local healthcare hospitals during 2003–2007 in Shanxi and Hebei provinces, China. A total of 774 mothers were included as participants who delivering 263 fetuses with NTDs including 123 with anencephaly, 115 with spina bifida, 18 with encephalocele, and 7 other NTD subtypes (cases), and 511 health fetuses without NTDs (controls). Their hair samples were collected as close as to the occipital posterior scalp, of which those grew from 3 months before to 3 months after conception was cut to measure the thorium concentration by inductively coupled plasma-mass spectrometry.

Results

We found a higher hair thorium concentration in the total NTD cases with 0.901 (0.588–1.382) ng/g hair [median (inter-quartile range)] than that in the controls with a value of 0.621 (0.334–1.058) ng/g hair. Similar results were found for the three concerned NTD subtypes. Maternal hair thorium concentration above its median of the controls was associated with an increased risk of the total NTDs with an adjusted odds ratio of 1.80 [95% confidence interval (CI), 1.23–2.63)] by adjusting for all confounders. There was obvious dose-response relationship between maternal hair thorium concentration and the risk of total NTDs, as well as their two subtypes (i.e. anencephaly and spina bifida). Maternal hair thorium concentration was positive associated with their exposure level to indoor air pollution from coal combustion during cooking.

Conclusions

Overall, our findings revealed that maternal periconceptional thorium exposure was associated with the risk of NTDs in North China. Reducing the coal usage in the household cooking activities may decrease maternal thorium exposure level.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s41021-021-00227-w.

Chronic nitrate exposure cause alteration of blood physiological parameters, redox status and apoptosis of juvenile turbot (Scophthalmus maximus)

Nitrate (NO₃^-) is one of the common inorganic nitrogen compound pollutants in natural ecosystems, which may have serious risks for aquatic organisms. However, its toxicological mechanism remains unclear. In the current study, juvenile turbot (Scophthalmus maximus) were exposed to different concentrations of NO₃^- (CK- 3.57 ± 0.16, LN - 60.80 ± 1.21, MN - 203.13 ± 10.97 and HN - 414.16 ± 15.22 mg/L NO₃-N) for 60 d. The blood biochemical assays results revealed that elevated NO₃^- exposure significantly increased the concentrations of plasma NO₃^-, NO₂^-, MetHb, K⁺, cortisol, glucose, triglyceride, lactate, while significantly decreased the concentrations of plasma Hb, Na⁺ and Cl^-, which meant that NO₃^- caused hypoxic stress and further affected the osmoregulation and metabolism in fish. Besides, exposure to MN and HN induced a significant decrease in the level of antioxidants, including SOD (Point: 60th day, MN, HN v.s. CK: 258.36, 203.73 v.s. 326.95 U/mL), CAT (1.97, 1.17 v.s. 2.37 U/mL), GSH (25.38, 20.74 v.s. 37.00 μmol/L), and GPx (85.32, 71.46 v.s. 129.36 U/mL), and a significant increase of MDA (7.54, 9.73 v.s. 5.27 nmol/L), suggesting that NO₃^- exposure leading to a disruption of the redox status in fish. Also, further research revealed that NO₃^- exposure altered the mRNA levels of p53 (HN: up to 4.28 folds) and p53-regulated downstream genes such as Bcl-2 (inferior to 0.44 folds), caspase-3 (up to 2.90 folds) and caspase-7 (up to 3.49 folds), indicating that NO₃^- exposure induced abnormal apoptosis in the fish gills. Moreover, IBRv2 analysis showed that the toxicity of NO₃^- exposure to turbot was dose-dependent, and the toxicity peaked on the 15th day. In short, NO₃^- is an environmental toxicological factor that cannot be ignored, because its toxic effects are long-term and could cause irreversible damage to fish. These results would be beneficial to improve our understanding of the toxicity mechanism of NO₃^- to fish, which provides baseline evidence for the risk assessment of environmental NO₃^- in aquatic ecosystems.

Thorium Exposure Drives Fatty Acid and Metal Transfer from Biofilms to the Grazer Lymnaea sp

Aquatic ecotoxicological risks associated with tetravalent metallic elements such as thorium (Th) are still poorly understood. Periphytic biofilm represents an important food source in aquatic environments; thus, such risks could severely affect nutrient and energy cycling in these ecosystems. The present study investigated the potential for Th to change the fatty acid composition of biofilm communities. Bioaccumulation of Th and fatty acids were measured after 4 wk to 2 exposure conditions: a control (C0) and Th exposure (C10). Some major fatty acids such as C16:1n-7 and docosahexaenoic acid C22:6n-3 differed significantly between control and C10 conditions. To determine if Th can be trophically transferred and to investigate the impacts of nutritional quality changes on primary consumers, common pond snails (Lymnaea sp.) were fed for 4 wk with control and Th-exposed biofilm. Thorium appeared to be trophically transferable to the grazers, although we cannot exclude that part of the Th accumulated by the snails may have been taken from the water through release from the biofilms. The composition of major fatty acids observed in the grazers was also significantly affected, notably by a decrease of total polyunsaturated fatty acids. These results indicate that very low Th concentrations can decrease the nutritional quality of organisms at the base of the food chain. Environ Toxicol Chem 2021;40:2220-2228. © 2021 SETAC.

Effects of thorium on bacterial, microalgal and micromeiofaunal community structures in a periphytic biofilm

Few ecotoxicity studies are available on thorium (Th) which hinders the ability to evaluate its ecotoxicological risk. Its release in the environment is often associated with the extraction of rare earth elements and uranium, as well as the field applications of phosphate fertilizers. This study investigates the effects of Th on microbial communities of periphytic biofilms. Ceramic plates were left to colonize for one month in the laboratory with a biofilm sampled from Cap Rouge river (QC, Canada). Plates were randomly placed in channels containing culture media representing three different conditions: a control condition (C0; background Th concentrations of 0.004 ± 0.002 nM), a low Th concentration condition (C1; 0.18 ± 0.09 nM Th) and a moderately high Th condition (C10; 8.7 ± 3.4 nM) for up to 4 weeks. The presence of Th modified the diatom community by changing its taxonomic structure, reducing diversity and increasing cell density. The taxonomic structure of the bacterial community, followed by 16S metabarcoding analysis, was affected with a significant decrease in Pseudanabaena and Shingopyxis genera in the two Th exposed conditions. No direct toxic effect of Th was observed on counted micromeiofauna but the changes in diatom and bacterial communities could explain the higher number of individual diatoms and micromeiofauna observed in Th-exposed conditions. This work shows that low concentrations of Th can modify biofilm structure, which, in turn, could disturb its ecologically key functions.

"Turn-on" fluorescent sensor for Th4+ in aqueous media based on a combination of PET-AIE effect

Previously reported fluorescent sensors for Th⁴⁺ experienced emission quenching or generated false positive signal upon aggregate formation in aqueous media. Herein, a simple and novel thorium sensor (CDB-BA) based on cyanodistyrene structure was designed and synthesized, which integrated the highly emitting characteristic of AIE effect and off-on response of PET modulation for the first time to construct the "turn-on" fluorescent probe for Th⁴⁺. Besides excellent selectivity, CDB-BA exhibited remarkable fluorescent enhancement which was linearly related to the concentration of Th⁴⁺ in the range of 0.25-8 μM. The detection limit was attained 0.074 μM, which was lower than that of most previously reported sensors. The mechanism of tris-chelate complex of CDB-BA with Th⁴⁺ was confirmed by mass spectra, IR spectra and DFT calculation. The excellent Th⁴⁺ sensing ability of CDB-BA was successfully applied to detecting Th⁴⁺ on TLC plates, in real water samples and living-cell imaging. This work suggested that the combination of AIE and PET photophysical mechanism could offer the merits of minimized background and enhanced signal fidelity to develop novel "turn-on" fluorescent probe in complicated aqueous environment and biological research.

Evaluation of softwood and hardwood sawmill wastes impact on the common carp "Cyprinus carpio" and its aquatic environment: An oxidative stress study

The aquatic pollution due to sawmill wood wastes constitutes a major threat to hydro-chemical and fauna characteristics of the aquatic ecosystems. When this kind of organics wastes enter aquatic environment it can be taken up by aquatic organisms through respiration and/or through their diet. This could concurrently result in oxidative stress and later having adverse effect on physiological and biochemical function. The importance of fish in the society cannot be over emphasized, hence there is the need to know the influence of sawmill wood wastes on the water quality and fish. Therefore, this work aims to study the impact of five species of wood wastes on a type of fish named common carp (Cyprinus carpio) known as the most widely cultured fish species in the world and on its aquatic environment. The monitoring of water parameters showed deterioration in water quality. The activities of superoxide dismutase (SOD), Catalase (CAT), glutathione peroxidase (GPx) and lipid peroxidation (MDA) were investigated to evaluate the degree of oxidative stress. According to t-student, there was a significant difference compared to control (P < 0.05) in the level of SOD, CAT, GPx and MDA activities in fish exposed to 5 g·l^-1 of each sawdust except for GPx, a non-significant difference (p > 0.05) was noted in the case of Beech and Dibetou. When the dispersed amount was about 0.375 g·l^-1 we noted a significant difference in the level of SOD and GPx, except for GPx a non-significant difference was detected in the case of Cedar. The level of CAT was significantly difference just in the case of Cedar and Dibetou and that of MDA was significantly difference just in the case of Beech and Mahogany. We conclude therefore that sawmill wood waste not only impact the water quality adversely but also alters the levels of different enzymes activities in Cyprinus Carpio fish by the inhibition of SOD, CAT and GPx activities and by the production of MDA, which reflects response to oxidative stress. This study provides a rational use of these enzymes as suitable biomarkers with different degrees of specificity and as important tool for environmental monitoring.

The effects of ethoxyquin and Angelica sinensis extracts on lipid oxidation in fish feeds and growth, digestive and absorptive capacities and antioxidant status in juvenile red carp (Cyprinus carpio var. xingguonensis): a comparative study

Firstly, a linoleic and linolenic acid emulsion and fish feeds were incubated with graded levels of ethoxyquin (EQ) and petroleum ether extract, ethyl acetate extract (EAE), ethanol extract and aqueous extract of Angelica sinensis. The results showed that EQ and extracts of Angelica sinensis (EAs) inhibited lipid oxidation in material above. Of all of the examined EAs, EAE showed the strongest protective effects against the lipid oxidation. Moreover, EAE at high concentrations showed a stronger inhibitory effect on lipid oxidation than that of EQ. Next, 7 experimental diets that respectively supplemented 0.0, 0.2, 0.8 and 3.2 g kg^-1 of EQ and EAE were fed to 280 juvenile red carp (Cyprinus carpio var. xingguonensis) with seven treatment groups for 30 days. The results indicated that dietary EAE improved growth performance in carp. Moreover, dietary EAE increased the activities of trypsin, lipase, alpha-amylase, alkaline phosphatase, glutamate-oxaloacetate transaminase and glutamate-pyruvate transaminase (GPT) and decreased plasma ammonia content in carp. Meanwhile, dietary EAE reduced the levels of malondialdehyde and raised the activities of anti-superoxide anion, anti-hydroxyl radical, superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase and the content of reduced glutathione in the hepatopancreas and intestine of carp. However, with the exception of GPT, dietary EQ got the opposite results to dietary EAE in carp. These results revealed that dietary EAE improved the digestive, absorptive and antioxidant capacities in fish. However, dietary EQ inhibited the digestive, absorptive and antioxidant capacities in fish. So, EAE could be used as a natural antioxidant for replacing EQ in fish feeds.

A Neuro-Comparative Study between Single/Successive Thorium Dose Intoxication and Alginate Treatment

The adult male albino rats were grouped into five groups (control group and four variably treated groups with thorium (Th) in single or successive with or without alginate treatment). The IP administration of thorium nitrate (13.6 mg/kg b.wt.) induced a regional distribution and accumulation ordered as cerebellum > cerebral cortex > brain stem > hippocampus > hypothalamus > striatum. Also, it induces a significant increase in Na⁺, Ca²⁺, and Fe³⁺ ion content and malondialdehyde (MDA) level while K⁺ ions and glutathione (GSH) level were significantly decreased. On the other hand, the daily oral administration of 5% alginate showed a significant decreasing in the accumulation of thorium in the different brain areas and mitigated its hazardous effects. By the alginate treatment, Na⁺, Ca²⁺, Fe³⁺, and level of MDA were declined while K⁺ ions and GSH level showed a significant increase. The improvement of the investigated parameters was attributed to the specific chelating, regeneration, and antioxidant properties of the alginate. So, alginate administration could ameliorate the hazardous effects of thorium nitrate.

Changes in intermediate metabolism and oxidative balance parameters in sexually matured three-barbeled catfishes exposed to herbicides from rice crops (Roundup®, Primoleo® and Facet®)

This study analyzed the effect of different concentrations of herbicides (Facet®, Primoleo®, and Roundup®) on metabolism and oxidative balance (superoxide dismutase and catalase activity, lipid peroxidation) in the gills, liver, kidneys, and tail muscle of adult catfish. All herbicides caused protein depletion in gills, increased glycogen and triacylglycerol consumption in the liver, and changes in muscle glycogen. Roundup® and Primoleo® stimulated lipid deposition in the liver, while Roundup® and Facet® stimulated lipid consumption in gills. In kidneys, protein content increased after Roundup® and Primoleo® exposure, glycogen increased after Facet®, and lipids increased after Roundup®. Primoleo® had the strongest effect on muscle, with changes in all metabolites. Regarding oxidative stress, the liver and kidneys were the organs most affected by exposure to herbicides, and catalase was the main enzyme involved in the detoxification of these herbicides. A hierarchy of toxicity was established for the tested chemicals: Facet® > Primoleo® > Roundup®.

Triphenyltin hydroxide induces changes in the oxidative stress parameters of fish

Among all organotin compounds , triphenyltin hydroxide (TPhTH) is widely used as fungicide and moluscicide in Brazil. However, the effects of TPhTH on the biochemical parameters of non-target organisms, such as fish, are little known. The aim of the present study is to assess the possible toxic effects of different concentrations of waterborne TPhTH on silver catfish belonging to species Rhamdia quelen. The fish were exposed to two different concentrations of TPhTH (1.08 and 1.70 µg/L as Sn) for 15 days and then compared to the control group (triplicate, n = 3). The antioxidant profile (catalase (CAT) and the glutathione S-transferase (GST)) and the oxidative stress parameters (TBARS-thiobarbituric acid-reactive substances and protein carbonyl (PC)) were set after the exposure to TPhTH. The TBARS level and the PC content increased in several organs of the Rhamdia quelen (brain, liver, muscle and gills) under the two concentrations of TPhTH in comparison to the control group. The CAT activity in the liver and gills has enhanced in all tested TPhTH concentrations. The GST activity increased in the brain, liver and muscle tissues under all the TPhTH concentrations. The significant changes in the biomarkers indicated that the investigated pesticide could have harmful effect on fish, in the field. However, these biomarkers were measured after the fish received doses lower than the recommended for use in agriculture.

Uranium (238U)-induced ROS and cell cycle perturbations, antioxidant responses and erythrocyte nuclear abnormalities in the freshwater iridescent shark fish Pangasius sutchi

The strategic plan of this study is to analyze any possible radiological impact on aquatic organisms from forthcoming uranium mining facilities around the Nagarjuna Sagar Dam in the future. The predominantly consumed and dominant fish species Pangasius sutchi, which is available year-round at Nagarjuna Sagar Dam, was selected for the study. To comprehend the outcome and to understand the mode of action of ²³⁸U, the fish species Pangasius sutchi was exposed to ¼ and ½ of the LC₅₀ doses of waterborne ²³⁸U in a static system in duplicate for 21 days. Blood and organs, including the gills, liver, brain and muscles, were collected at different time periods-0h, 24h, 48h, 72h, 96h, 7, days 14days and 21 days-using ICP-MS to determine the toxic effects of uranium and the accumulation of ²³⁸U concentrations. The bioaccumulation of ²³⁸U in P. sutchi tissues was dependent on exposure time and concentration. The accumulation of uranium was, in order of magnitude, measured as gills>liver>brain>tissue, with the highest accumulation in the gills. It was observed that exposure to ²³⁸U significantly reduced antioxidant enzymes such as superoxide dismutase, catalase, and lipid peroxidase. The analysis of DNA fragmentation by comet assay and cell viability by flow cytometry was performed at different time intervals. DNA histograms by flow cytometry analysis revealed an increase in the G2/M phase and the S phase. The long-term ²³⁸U exposure studies in fish showed increasing micronucleus frequencies in erythrocytes with greater exposure time. The higher the concentration of ²³⁸U is, the greater is the effect observed, suggesting a close relationship between accumulation and toxicity. A possible ROS-mediated ²³⁸U toxicity mechanism and antioxidant responses have been proposed.

Influence of Speciation of Thorium on Toxic Effects to Green Algae Chlorella pyrenoidosa

Thorium (Th) is a natural radioactive element present in the environment and has the potential to be used as a nuclear fuel. Relatively little is known about the influence and toxicity of Th in the environment. In the present study, the toxicity of Th to the green algae Chlorella pyrenoidosa (C. pyrenoidosa) was evaluated by algal growth inhibition, biochemical assays and morphologic observations. In the cultural medium (OECD TG 201), Th(NO₃)₄ was transformed to amorphous precipitation of Th(OH)₄ due to hydrolysis. Th was toxic to C. pyrenoidosa, with a 96 h half maximum effective concentration (EC₅₀) of 10.4 μM. Scanning electron microscopy shows that Th-containing aggregates were attached onto the surface of the algal cells, and transmission electron microscopy indicates the internalization of nano-sized Th precipitates and ultrastructural alterations of the algal cells. The heteroagglomeration between Th(OH)₄ precipitation and alga cells and enhanced oxidative stress might play important roles in the toxicity of Th. To our knowledge, this is the first report of the toxicity of Th to algae with its chemical species in the exposure medium. This finding provides useful information on understanding the fate and toxicity of Th in the aquatic environment.

Thorium impact on tobacco root transcriptome

Thorium is natural actinide metal with potential use in nuclear energetics. Contamination by thorium, originated from mining activities or spills, represents environmental risk due to its radioactivity and chemical toxicity. A promising approach for cleaning of contaminated areas is phytoremediation, which need to be based, however, on detail understanding of the thorium effects on plants. In this study we investigated transcriptomic response of tobacco roots exposed to 200μM thorium for one week. Thorium application resulted in up-regulation of 152 and down-regulation of 100 genes (p-value <0.01, fold change ≥2). The stimulated genes were involved in components of jasmonic acid and salicylic acid signaling pathways and various abiotic (e.g. oxidative stress) and biotic stress (e.g. pathogens, wounding) responsive genes. Further, up-regulation of phosphate starvation genes and down-regulation of genes involved in phytic acid biosynthesis indicated that thorium disturbed phosphate uptake or signaling. Also expression of iron responsive genes was influenced. Negative regulation of several aquaporins indicated disturbance of water homeostasis. Genes potentially involved in thorium transport could be zinc-induced facilitator ZIF2, plant cadmium resistance PCR2, and ABC transporter ABCG40. This study provides the first insight at the processes in plants exposed to thorium.

Toxicity of cerium and thorium on Daphnia magna

Cerium (Ce) and thorium (Th) are always thought to be chemically similar and have comparable toxic properties on living organisms. In the present study, the acute and chronic toxicity of these two elements to freshwater crustacean Daphnia magna were investigated in the modified reconstituted water (6mg/L KCl, 123mg/L MgSO₄·7H₂O, and 294mg/L CaCl₂·2H₂O in Milli-Q water, pH 7.8). It seemed that Ce and Th had comparable acute toxicity on Daphnia: 24/48h EC₅₀ for Th and Ce were 7.3/4.7μM and 16.4/10.7μM, respectively. However, Ce was present as soluble ions while all of Th was present as particulate ThO₂ in the exposure medium. Considering their different chemical forms and bioavailability, the toxic mechanisms of Ce³⁺ and ThO₂ on Daphnia would be totally different. To our knowledge, this is the first time to investigate the aquatic toxicity of thorium and cerium based on their actual chemical speciation in the exposure medium. The results also suggest that more attention should be paid on the detrimental effect of Th in the form of particulate ThO₂.

The essential oil from Lippia alba induces biochemical stress in the silver catfish (Rhamdia quelen) after transportation

This study investigated the effects of the essential oil (EO) from Lippia alba on biochemical parameters related to oxidative stress in the brain and liver of silver catfish (Rhamdia quelen) after six hours of transport. Fish were transported in plastic bags and divided into three treatments groups: control, 30 µL L- 1 EO from L.alba and 40 µL L-1 EO from L.alba. Prior to transport, the fish were treated with the EO from L. alba (200 µL L -1 for three minutes), except for the control group. Fish transported in bags containing the EO did not have any alterations in acetylcholinesterase, ecto -nucleoside triphosphate diphosphohydrolase and 5'nucleotidase activity in the brain or superoxide dismutase activity in the liver. The hepatic catalase (CAT), glutathione-S-transferase (GST), glutathione peroxidase (GPx), nonprotein thiol and ascorbic acid levels were significantly lower compared to the control group. However, the hepatic thiobarbituric acid- reactive substances, protein oxidation levels and the lipid peroxidation/catalase+glutathione peroxidase (LPO/CAT+GPx) ratio were significantly higher in fish transported with both concentrations of the EO, indicating oxidative stress in the liver. In conclusion, considering the hepatic oxidative stress parameters analyzed in the present experiment, the transport of previously sedated silver catfish in water containing 30 or 40 µL L-1 of EO from L. alba is less effective than the use of lower concentrations.

Effects of subchronic manganese chloride exposure on tambaqui (Colossoma macropomum) tissues: oxidative stress and antioxidant defenses

This study aimed to evaluate oxidative stress parameters in juvenile tambaqui (Colossoma macropomum) exposed to 3.88 mg l(-1) Mn(2+) for 96 hours. Biomarkers of oxidative stress, such as thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), catalase (CAT), and glutathione-S-transferase (GST) activities, as well as content of reduced glutathione (GSH), were analyzed in gill, liver, brain, and kidney. The presence of Mn(2+) in the water corresponded to increased levels of Mn(2+) accumulation according to the following sequence: gill > kidney > brain > liver. There was a significant increase in TBARS levels (40 %) and SOD activity (80 %) in addition to a significant decrease in GSH content (41 %) in gills of fish exposed to waterborne Mn(2+). In hepatic tissue of the exposed animals, TBARS levels decreased significantly (35 %), whereas SOD (82 %) and GST activities (51 %) as well as GSH content (43 %) increased significantly. In brain of exposed juvenile fish, only significant decreases in SOD (32 %) and CAT activities (65 %) were observed. Moreover, the kidney of exposed fish showed a significant increase in TBARS levels (53 %) and a significant decrease in SOD activity (41 %) compared with the control. Thus, the changes in biomarkers of oxidative stress were different in the tissues, showing a specific toxicity of this metal to each organ.

Oxidative stress parameters and anti-apoptotic response to hydroxyl radicals in fish erythrocytes: protective effects of glutamine, alanine, citrulline and proline

The present study explored the protective effects of glutamine (Gln), alanine (Ala), citrulline (Cit) and proline (Pro) on hydroxyl radical (·OH)-induced apoptosis in isolated carp erythrocytes. Hydroxyl radicals were generated by ferrous ion (Fe(2+))-mediated decomposition of hydrogen peroxide (H(2)O(2)) (Fenton reaction). In order to select an optimal ·OH concentration to induce apoptosis, cultures were treated with different concentrations of FeSO(4)/H(2)O(2) (0 μM/0 μM-50 μM/25 μM). The results showed that exposure to FeSO(4)/H(2)O(2) (0 μM/0 μM-40 μM/20 μM) increased apoptosis in a dose-dependent manner. Moreover, apoptosis was at its highest level at 40 μM FeSO(4)/20 μM H(2)O(2). We then examined the cytoprotective effects of Gln, Ala, Cit, Pro or the combination of Ala, Cit and Pro under conditions of apoptosis. Carp erythrocytes were treated with the substances listed above in the presence of 40 μM FeSO(4)/20 μM H(2)O(2) for 9 h. The controls were grown in Gln, Ala, Cit, Pro-free culture medium. The results showed that Gln, Ala, Cit, Pro and the combination of Ala, Cit and Pro effectively protected against annexin binding, decrease of forward scatter and DNA fragmentation in carp erythrocytes induced by ·OH. Furthermore, Gln, Ala, Cit, Pro and the combination of Ala, Cit and Pro effectively blocked ·OH-stimulated erythrocyte hemolysis, reduced the increase of superoxide anion and H(2)O(2) concentrations, inhibited the formation of malondialdehyde, protein carbonyls and met-hemoglobin, and prevented the decrease of superoxide dismutase, catalase and glutathione peroxidase activities and glutathione content in carp erythrocytes induced by ·OH. In addition, the results suggest that the combination of Ala, Cit and Pro produces a greater anti-apoptotic and anti-oxidative effect than their individual effects at the same concentrations. Taken together, the results showed that ·OH induces apoptosis and oxidative damage in carp erythrocytes. In addition to inhibiting apoptosis, Gln, Ala, Cit, Pro and the combination of Ala, Cit and Pro protected carp erythrocytes against oxidative damage induced by ·OH, which may be a major factor in the protection of erythrocytes from apoptosis.

Deltamethrin-induced oxidative stress and biochemical changes in tissues and blood of catfish (Clarias gariepinus): antioxidant defense and role of alpha-tocopherol

Background

The pyrethroid class of insecticides, including deltamethrin, is being used as substitutes for organochlorines and organophosphates in pest-control programs because of their low environmental persistence and toxicity. This study was aimed to investigate the impact of commonly used pesticides (deltamethrin) on the blood and tissue oxidative stress level in catfish (Clarias gariepinus); in addition to the protective effect of α-tocopherol on deltamethrin induced oxidative stress.

Catfish were divided into three groups, 1^st control group include 20 fish divided into two tanks each one contain 10 fish, 2^nd deltamethrin group, where Fish exposed to deltamethrin in a concentration (0.75 μg/l) and 3^rd Vitamin E group, Fish exposed to deltamethrin and vitamin E at a dose of 12 μg/l for successive 4 days.

Serum, liver, kidney and Gills were collected for biochemical assays. Tissue oxidative stress biomarkers malondialdhyde (MDA) and catalase activity in liver, kidney and gills tissues, serum liver enzymes (ALT and AST), serum albumin, total protein, urea and creatinine were analysed.

Results

Our results showed that 48 h. exposure to 0.75 μg/l deltamethrin significantly (p < 0.05) increased lipid peroxidation (MDA) in the liver, kidney and gills while catalase activity was significantly decreased in the same tissues. This accompanied by significant increase in serum ALT, AST activity, urea and creatinine and a marked decrease in serum albumin and total proteins.

Conclusions

It could be concluded that deltamethrin is highly toxic to catfish even in very low concentration (0.75 μg/l). Moreover the effect of deltamethrin was pronounced in the liver of catfish in comparison with kidneys and gills. Moreover fish antioxidants and oxidative stress could be used as biomarkers for aquatic pollution, thus helping in the diagnosis of pollution. Adminstration of 12 μg/l α-tocopherol restored the quantified tissue and serum parameters, so supplementation of α-tocopherol consider an effective way to counter the toxicity of deltamethrin in the catfish.

Evaluation of oxidative stress biomarkers in Zosterisessor ophiocephalus from the Venice Lagoon, Italy

Several studies carried out in the last years have demonstrated the presence of a wide range of contaminants in some areas of the Venice Lagoon. Many of these contaminants are able to drive free radical reactions, which lead to oxidative stress and can potentially affect fish health. In the present study, oxidative stress biomarkers were examined in three different sites (Porto Marghera, Val di Brenta and Caroman) of the Venice Lagoon and their levels monitored in Zosterisessor ophiocephalus, one of the most common fish species present in the lagoon. Schmorl's staining revealed the presence of melanomacrophage centres in spleen and head kidney, and the highest number of melanomacrophage centres was observed in the animals sampled at the Porto Marghera (Porto Marghera vs Val di brenta and Caroman: p<0.01). The cellular localization of HNE and NT, investigated through an immunohistochemical approach, showed that immunopositivity was mainly localized in melanomacrophage centres of spleen and kidney. It is relevant that the animals of the detoxified control group did not exhibit any immunoreactivity. By Western blot, the antibodies against HNE and NT recognized in the liver polypeptides damaged by oxidative stress with molecular weights under 66kDa. Comparing the relative densities, animals from the Val di Brenta site exhibited the lowest levels of HNE adducts (p<0.05), whereas animals from the Porto Marghera site exhibited the highest levels of NT adducts (p<0.05). MDA levels, measured spectrophotometrically by TBARS assay did not exhibit any statistical difference among sites.

Comparative estimation of 232Th and stable Ce (III) toxicity and detoxification pathways in freshwater alga Chlorella vulgaris

The impacts of radiological and chemical toxicity from naturally occurring radionuclides are discussed in the context of protecting freshwater ecosystems from radiation exposure. The present study aimed to determine the toxicity of (232)Th and it stable chemical analogue Ce to the green alga Chlorella vulgaris Beijerinck (thermophilic strain). Parameters of the regression equation for the concentration-effect relationship and concomitant Effective concentration (50%), EC(50), showed that (232)Th was more toxic to chlorella after a 24-h exposure than Ce. However, the No-observable-effect concentration (NOEC) and Lowest-observable-effect concentration (LOEC) for (232)Th were approximately equal to those for Ce. NOEC, LOEC and EC(50) for (232)Th were 1.6 μM, 2.2 μM and 15.4 respectively. Those for Ce were 1.8, 2.1 and 35.7 μM respectively. Consideration of the results obtained suggests differences in the main detoxification pathways of (232)Th and Ce (III). It was found that 0.02 mM caffeine (used as DNA metabolism disturbance reagent) has no effect on Ce toxic action, but 0.02 mM BSO (as a selective inhibitor of γ-ECS, a glutathione biosynthetic pathway enzyme) enhanced it. In contrast, 0.02 mM caffeine significantly increased the toxic action of (232)Th, but 0.02 mM BSO has no effect on it. The peculiarities mentioned were suggested to be caused by differences in the physicochemical properties of the elements. The combined potential detrimental effect of (232)Th acting both as a radiation source (α-, β- and γ-emitter) and a chemically toxic element is discussed.

Cytotoxicity of chromium ions may be connected with induction of oxidative stress

Chromium ions are frequently found in aquatic ecosystems and are known to be inducers of oxidative stress in fish solid tissues. The present study was designed to determine whether fish blood samples can be used to allow nonlethal diagnostic testing for chromium intoxication. First, we confirmed that 96 h exposures to water containing 10.0 mg L(-1) chromium ions, either Cr3+ or Cr6+, induced oxidative stress in brain of goldfish (Carassius auratus). Multiple blood parameters were then evaluated. Cr6+ exposure triggered a 579% increase in the number of erythrocytes containing micronuclei, a frequently used marker of cellular toxicity. Leucocyte numbers were also perturbed by exposure to either Cr3+ or Cr6+ indicating that chromium ions could impair the immune system as well. The content of protein carbonyl groups, a marker of oxidative damage to proteins, was enhanced in fish plasma by exposure to either chromium ion and activities of catalase and lactate dehydrogenase also were affected. The data demonstrate that chromium ions induced oxidative stress in goldfish blood and were cytotoxic for erythrocytes. This indicates that analysis of plasma can be used as a good early nonlethal diagnostic marker of fish intoxication by transition metal ions.