Toxic Effects Of Cu Research Articles

Mechanisms by Which Increased pH Ameliorates Copper Excess in Citrus sinensis Roots: Insight from a Combined Analysis of Physiology, Transcriptome, and Metabolome.

Limited data are available on copper (Cu)-pH interaction-responsive genes and/or metabolites in plant roots. Citrus sinensis seedlings were treated with 300 μM (Cu toxicity) or 0.5 μM (control) CuCl2 at pH 3.0 or 4.8 for 17 weeks. Thereafter, gene expression and metabolite profiles were obtained using RNA-Seq and widely targeted metabolome, respectively. Additionally, several related physiological parameters were measured in roots. The results indicated that elevating the pH decreased the toxic effects of Cu on the abundances of secondary metabolites and primary metabolites in roots. This difference was related to the following several factors: (a) elevating the pH increased the capacity of Cu-toxic roots to maintain Cu homeostasis by reducing Cu uptake and Cu translocation to young leaves; (b) elevating the pH alleviated Cu toxicity-triggered oxidative damage by decreasing reactive oxygen species (ROS) formation and free fatty acid abundances and increasing the ability to detoxify ROS and maintain cell redox homeostasis in roots; and (c) increasing the pH prevented root senescence and cell wall (CW) metabolism impairments caused by Cu toxicity by lowering Cu levels in roots and root CWs, thus improving root growth. There were some differences and similarities in Cu-pH interaction-responsive genes and metabolites between leaves and roots.

CaAl-Layered Double Hydroxides-Modified Biochar Composites Mitigate the Toxic Effects of Cu and Pb in Soil on Pea Seedlings.

Compound contamination of soil with heavy metals copper (Cu) and lead (Pb) triggered by mining development has become a serious problem. To solve this problem, in this paper, corncob kernel, which is widely available and inexpensive, was used as the raw material of biochar and modified by loading CaAl-layered double hydroxides to synthesize biochar-loaded CaAl-layered double hydroxide composites (CaAl-LDH/BC). After soil remediation experiments, either BC or CaAl-LDH/BC can increase soil pH, and the available phosphorus content and available potassium content in soil. Compared with BC, CaAl-LDH/BC significantly reduced the available content of Cu and Pb in the active state (diethylenetriaminepentaacetic acid extractable state) in the soil, and the passivation rate of Cu and Pb by a 2% dosage of CaAl-LDH/BC reached 47.85% and 37.9%, respectively. CaAl-LDH/BC can significantly enhance the relative abundance of beneficial microorganisms such as Actinobacteriota, Gemmatimonadota, and Luteimonas in the soil, which can help to enhance the tolerance and reduce the enrichment ability of plants to heavy metals. In addition, it was demonstrated by pea seedling (Pisum sativum L.) growing experiments that CaAl-LDH/BC increased plant fresh weight, root length, plant height, catalase (CAT) activity, and protein content, which promoted the growth of the plant. Compared with BC, CaAl-LDH/BC significantly reduced the Cu and Pb contents in pea seedlings, in which the Cu and Pb contents in pea seedlings were reduced from 31.97 mg/kg and 74.40 mg/kg to 2.92 mg/kg and 6.67 mg/kg, respectively, after a 2% dosage of CaAl-LDH/BC, which was a reduction of 90.84% and 91.03%, respectively. In conclusion, compared with BC, CaAl-LDH/BC improved soil fertility and thus the plant growth environment, and also more effectively reduced the mobility of heavy metals Cu and Pb in the soil to reduce the enrichment of Cu and Pb by plants.

Multiple stressors unpredictably affect primary producers and decomposition in a model freshwater ecosystem

Freshwater ecosystems are affected by various stressors, such as contamination and exotic species, making them amongst the most imperilled biological systems on the planet. In Australia and elsewhere, copper is one of the most common metal contaminants in freshwater systems and the European carp (Cyprinus carpio L.) is one of the most pervasive and widespread invasive fish species. Copper (Cu) and carp can both directly affect primary production and decomposition, which are critical and interrelated nutrient cycling processes and ecosystem services. The aim of this study was to explore the direct and indirect effects of Cu and carp individually, and together on periphyton cover, chlorophyll a concentration, growth of the macrophyte Vallisneria spiralis L., and the decomposition of leaf litter and cotton strips in a controlled, factorial experiment in outdoor experimental ponds. In isolation, Cu reduced macrophyte growth and organic matter decomposition, while chlorophyll a concentrations and periphyton cover remained unchanged, possibly due to the Low-Cu concentrations in the overlying water. Carp addition alone had a direct negative effect on the biomass of aquatic plants outside protective cages, but also increased plant biomass inside the cages, periphyton cover and chlorophyll a concentrations. Leaf litter was more decomposed in the carp only ponds compared to controls, while there was no significant effect on cotton strip decomposition. Aquatic plants were absent in the Cu + carp ponds caused by the combined effects of Cu toxicity, carp disturbance and the increase in turbidity due to carp bioturbation. Increases in periphyton cover in Low-Cu + carp, while absence in the High-Cu + carp ponds, and differences in the decomposition of surface and buried cotton strips were not as predicted, which highlights the need for such studies to understand the complex interactions among stressors for environmental risk assessment.

Analyzing soil enzymes to assess soil quality parameters in long-term copper accumulation through a machine learning approach

Soil contamination by agrochemicals is a big concern for soil health and ecosystem functioning. This is especially true for non-degradable substances like heavy metals (HM) that, because of their long-term use, are reaching significant values today due to soil accumulation. Among agrochemicals, copper (Cu) has been important in fighting fungal diseases on perennial crops for centuries.Laboratory experiments can be useful to understand the highest potential toxic effect of Cu but need to reflect what happens with long-term application in a dynamic and living agroecosystem. This study uses multivariate data analysis and machine learning to investigate long-term Cu accumulation on soil quality parameters, especially soil extracellular enzymatic activities. We collected soil samples from 21 apple orchards in South Tyrol, Italy. The orchards had different concentrations of Cu. We took 315 samples in total and analyzed them for various soil properties. We also measured the concentrations of elements in apple leaves and the activities of soil extracellular enzymes. We depicted the effect of Cu on several enzymatic activities, shedding light on the effect of Cu on the soil microbial communities functionality. Our results show that Cu concentrations in the study area affect only phosphatase activity, showing effects above 60 mg kg−1 of available Cu. Protease activity was positively correlated with Cu, while soil organic matter and management mainly influenced the carbon (C) cycle enzymes. Phosphatase decrease could be of concern for the potential disruption of the Phosphorus (P) cycle in the soil and plays a role in plant nutrition, as seen by P concentration in apple trees' leaves.We demonstrated how machine learning can help interpret complex and multivariate environmental data and overcome some downsides of traditional statistical models.

Control of copper-induced physiological damage in okra (Abelmoschus esculentus L.) via Bacillus subtilis and farmyard manure: A step towards sustainable agriculture

Copper (Cu) stress is a serious problem in contaminated soils that causes significant reduction in okra growth and production. To determine the toxic effect of Cu on okra plant and identify an effective way to mitigate Cu toxicity on okra, seeds of okra were inoculated with Bacillus subtilis and sown with farmyard manure. There were 13 treatments (T0= Control, T1= 400 mg kg−1 of soil Cu, T2= 400 mg kg−1 of soil Cu+ B. subtilis, T3= 400 mg kg−1 of soil Cu+ FYM, T4= 400 mg kg−1 of soil Cu+ B. subtilis+ FYM, T5= 450 mg kg−1 of soil Cu, T6= 450 mg kg−1 of soil Cu+ B. subtilis, T7=450 mg kg−1 of soil Cu+ FYM, T8=450 mg kg−1 of soil Cu+ B. subtilis+ FYM, T9=500 mg kg−1 of soil Cu, T10=500 mg kg−1 of soil Cu+ B. subtilis, T11=500 mg kg−1 of soil Cu+ FYM, T12=500 mg kg−1 of soil Cu+ B. subtilis+ FYM) planned with the complete randomize design (CRD). Results of this research reveal that the okra production and soil physiological properties decreased with the addition of Cu in the soil, this is a new approach for sustainable crop production under Cu stress condition. 500 mg kg−1 of Cu in the soil have the more negative effect on plant growth but negative effect of Cu can be control with the addition of B. subtilis and FYM. Combine application of B. subtilis and FYM improve the soil properties and plant growth by improving the microbial activities, nutrients availability in the soil and production of growth hormones.

Bacteria-driven copper redox reaction coupled electron transfer from Cr(VI) to Cr(III): A new and alternate mechanism of Cr(VI) bioreduction

Cr(VI) released into the environment inevitably co-exists with other contaminants, such as heavy metal ions, thus altering the performance of bacteria for Cr(VI) reduction; however, the mechanism underlying Cr(VI)-reducing bacterial response to heavy metal ions remains elusive. Herein, we investigate the toxic effects of Cu(II) and Cr(VI) on Cr(VI)-reducing bacterium Pannonibacter phragmitetus D-6 (hereafter D-6), which changes the primary metabolic pattern of Cr(VI). At Cu(II) concentrations of 10–100 mg/L, the efficiency of Cr(VI) reduction increases significantly. The co-exposure of Cr(VI) and Cu(II) induces D-6 to preferentially respond to Cu(II) through electrostatic forces, which is then reduced to Cu(I) outside and inside the bacterial cells. The original pathways for Cr(VI) reduction are weakened via downregulating genes related to Cr(VI) transport and reduction. A new mechanism involving Cu(II)-mediated electron transfer from D-6 to Cr(VI) is elucidated. Specially, Cu(II) accumulates around the cells as an electron shuttle and promotes Cr(VI) reduction. Genes encoding cytochromes involved in electron transfer are significantly up-regulated, thus promoting Cu(II) reduction. The Cu(II)/Cu(I) redox cycle ensures the continuous bioremoval of Cr(VI) in a cycle test. This study reveals an overlooked mechanism for Cr(VI) reduction, which provides theoretical guidance for designing practical microbial process to remediate Cr(VI) contamination.

Responses of Bacillus sp. under Cu(II) stress in relation to extracellular polymeric substances and functional gene expression level.

The production and composition of extracellular polymeric substances (EPS), as well as the EPS-related functional resistance genes and metabolic levels of Bacillus sp. under Cu(II) stress, were investigated. EPS production increased by 2.73 ± 0.29 times compared to the control when the strain was treated with 30 mg L-1 Cu(II). Specifically, the polysaccharide (PS) content in EPS increased by 2.26 ± 0.28 g CDW-1 and the PN/PS (protein/polysaccharide) ratio value increased by 3.18 ± 0.33 times under 30 mg L-1 Cu(II) compared to the control. The increased EPS secretion and higher PN/PS ratio in EPS strengthened the cells' ability to resist the toxic effect of Cu(II). Differential expression of functional genes under Cu(II) stress was revealed by Gene Ontology pathway enrichment analysis and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. The enriched genes were most obviously upregulated in the UMP biosynthesis pathway, the pyrimidine metabolism pathway, and the TCS metabolism pathway. This indicates an enhancement of EPS regulation-related metabolic levels and their role as a defense mechanism for cells to adapt to Cu(II) stress. Additionally, seven copper resistance genes were upregulated while three were downregulated. The upregulated genes were related to the heavy metal resistance, while downregulated genes were related to cell differentiation, indicating that the strain had initiated an obvious resistance to Cu(II) despite its severe cell toxicity. These results provided a basis for promoting EPS-regulated associated functional genes and the application of gene-regulated bacteria in heavy metal-containing wastewater treatment.

Hydrogen Peroxide Mitigates Cu Stress in Wheat

Abiotic stress imposed by heavy metals (HMs) adversely influences plant growth. In crop plants, such stresses penalize grain yield and ultimately could have enduring connotations for sustainable food security. Although copper (Cu) is an essential micronutrient for crop life, excessive availability of copper impairs plant growth and/or reproductive performance. Anecdotal evidence suggests that hydrogen peroxide (H2O2) is produced in plants under either biotic or abiotic stresses to mitigate oxygen-derived cell toxicity, although the influence of H2O2 remains to be definitively quantified. Here, our aim was to investigate the effects of hydrogen peroxide (H2O2) on the growth, grain yield, and yield components, as well as copper uptake of stressed wheat grown in sandy soil. We found that applications rates of 150 or 300 mg Cu kg−1 soil significantly reduced net photosynthesis, leaf area, chlorophyll, and grain yield. Foliar application of H2O2 to plants grown under 150 and 300 mg Cu kg−1 soil had improved growth, physiological, and yield traits. For instance, foliar application of H2O2 Cu-stressed plants grown under 300 mg Cu kg−1 soil reduced detrimental effects of Cu toxicity by −12% in terms of grains per spike and −7% for 1000-grain weight in comparison to the control treatment. Foliar application of H2O2 on wheat grown under copper stress reduced accumulation of other heavy metals such as cadmium. We suggest that the potential for foliar application of H2O2 in mitigating heavy metal stress in crop plants has large global potential; however, further work is required to elucidate the environmental conditions and application rates required to attain optimal benefit.

Response of Coccomyxa cimbrica sp.nov. to Increasing Doses of Cu(II) as a Function of Time: Comparison between Exposure in a Microfluidic Device or with Standard Protocols.

In this study, we explore how the in vitro conditions chosen to cultivate and observe the long-term (up to 72 h) toxic effect of Cu(II) on the freshwater microalga Coccomyxa cimbrica sp.nov. can affect the dose response in time. We test three different cultivation protocols: (i) under static conditions in sealed glass cells, (ii) in a microfluidic device, where the sample is constantly circulated with a peristaltic pump, and (iii) under continuous agitation in plastic falcons on an orbital shaker. The advantage and novelty of this study resides in the fact that each condition can mimic different environmental conditions that alga cells can find in nature. The effect of increasing dose of Cu(II) as a function of time (24, 48, and 72 h) is monitored following chlorophyll a fluorescence intensity from single cells. Fluorescence lifetime imaging experiments are also explored to gain information on the changes induced by Cu(II) in the photosynthetic cycle of this microalga.

Effect of Copper Exposure on the Cholesterol Metabolism in Broiler Liver.

Copper (Cu) is a kind of widely used dietary supplement in poultry production, and a common environmental pollutant at the same time. Excess Cu exposure has been reported to accumulate in the liver and induce cytotoxicity, but the effect of Cu toxicity on hepatic cholesterol metabolism is still uncertain. Herein, we aimed to reveal the effect of excess Cu on the liver and primary hepatocytes of broilers at various concentrations. We found that 110mg/kg Cu supplement remarkably increased blood cholesterol levels by detecting serum TC, LDL-C, and HDL-C in the broilers, while there was no significant difference in 220 and 330mg/kg Cu supplements. In addition, high Cu exposure resulted in severe hepatic steatosis and hepatic cord derangement in the broilers. Oil red O staining of primary hepatocytes showed that Cu treatment caused intracellular neutral lipid accumulation. However, the hepatic TC content indicated a downward trend in both liver tissues and hepatocytes after Cu exposure. Furthermore, the expression of cholesterol metabolism-related indicators (SREBP2, HMGCR, LDLR, and CYP7A1) was notably decreased in the Cu-treated groups. While the expression of the key enzyme of cholesterol esterification (ACAT2) did not change significantly. Taken together, our findings preliminarily revealed excess Cu-induced hepatic cholesterol metabolism dysfunction, providing a deeper understanding of the molecular mechanisms of Cu-induced hepatotoxicity.

Zinc (Zn) mitigates copper (Cu) toxicity and retrieves yield and quality of lettuce irrigated with Cu and Zn-contaminated simulated wastewater.

Owing to a competitive interaction, zinc (Zn) contained in highly Cu-contained wastewater was hypothesized to mitigate Cu toxicity-induced negative effects on the growth and quality of lettuce. Thus, growth, metal accumulation and biochemical responses of lettuce irrigated with simulated wastewater (SW, control), Cu-contaminated SW (CuSW, 20mg Cu L-1), Zn-contaminated SW (ZnSW, 100mg Zn L-1) and both Cu- and Zn-contaminated SW (CuZnSW, 20mg Cu and 100mg Zn L-1) were evaluated. Results revealed that irrigation with CuSW negatively affected growth (dry matters, root length and plant height) and quality (low mineral concentrations) of lettuce, which were associated with higher Cu uptake. Irrigation with Zn + Cu-contaminated SW retrieved Cu toxicity and improved root and shoot dry matters and root length by 13.5%, 46% and 19%, respectively compared to that with alone Cu-contaminated SW. Moreover, CuZnSW improved lettuce leaf quality compared to CuSW and increased concentrations of Mg (30%), P (15%), Ca (41%), Mn (24%) and Fe (23%). Moreover, compared to CuSW, CuZnSW improved flavonoids (54%), total polyphenolic compounds (1.8-fold), polyphenolic acids (77%) and antiradical activities (16.6%). Most importantly, Zn addition boosted up lettuce Cu tolerance index by 18% under Cu-contaminated SW treatment. Pearson's correlation analysis among various growth and mineral parameters demonstrated that shoot Zn concentration was positively related to elemental concentrations, phytochemical contents and antioxidant activity under Cu-contaminated environment. Thus, it is concluded that Zn supplementation retrieves negative effects of Cu toxicity to lettuce grown with Cu-contaminated wastewater.

Involvement of abscisic acid in silicon-mediated enhancement of copper stress tolerance in Artemisia annua

Heavy metal (HM) toxicity is a well-known hazard which causes deleterious impact on the growth and development of plants. The impact of abscisic acid (ABA) in presence of silicon (Si) on plant development and quality traits has largely gone unexplored. The effects of ABA and Si on the growth, yield, and quality characteristics of Artemisia annua L. plants growing under copper (Cu) stress (20 and 40 mg kg−1) were investigated in a pot experiment. During this investigation, Cu stress caused severe damage to the plants but exogenous administration of Si and ABA ameliorated the harmful effects of Cu toxicity, and the plants displayed higher biomass and improved physio-biochemical attributes. Copper accumulated in the roots and shoots and its toxicity caused oxidative stress as demonstrated by the increased 2-thiobarbituric acid reactive substance (TBARS) content. It also resulted in the increased activity of antioxidant enzymes, however, the exogenous Si and ABA supplementation decreased the buildup of reactive oxygen species (ROS) and lipid peroxidation, alleviating the oxidative damage produced by HM stress. Copper toxicity had a considerable negative impact on glandular trichome density, ultrastructure as well as artemisinin production. However, combined Si and ABA enhanced the size and density of glandular trichomes, resulting in higher artemisinin production. Taken together, our results demonstrated that exogenous ABA and Si supplementation protect A. annua plants against Cu toxicity by improving photosynthetic characteristics, enhancing antioxidant enzyme activity, protecting leaf structure and integrity, avoiding excess Cu deposition in shoot and root tissues, and helping in enhanced artemisinin biosynthesis. Our results indicate that the combined application of Si and ABA improved the overall growth of plants and may thus be used as an effective approach for the improvement of growth and yield of A. annua in Cu-contaminated soils.

Exogenous application of citric acid alleviates copper-induced stress in Withania coagulans (Dunal)

The current study aimed to determine the mitigating effect of citric acid (CA) on various physiological and biochemical attributes in Withania coagulans, exposed to copper (Cu) stress. The viable seeds of Withania coagulans were planted in a controlled environment. After reaching the four-leaf stage, the plants were given simultaneous treatment with two concentrations of Cu [TCu1 and TCu2 (10mM, 15mM)] alone and/or with CA [TCa1 and TCa2 (05mM, 10mM)]. After harvesting, the physiological and biochemical characteristics of the plants were assessed. The findings demonstrated that using a higher dosage of Cu has significant toxic effects on plant growth and biomass. The agronomic attributes of the plant were significantly reduced by 24% (number of leaves), 22% (shoot length), 7% (root length), 8% (fresh weight), and 38% (dry weight) compared to the control. Higher concentration of Cu was also found toxic to photosynthetic pigments and significantly reduced by 27% (chl a), 6% (chl b), and 35% (carotenoids) compared to the control. However, the application of CA under Cu stress significantly improved the physiological attributes of Withania coagulans. The plant's agronomic traits significantly increased by 66% (number of leaves), 31% (shoot length), 87% (root length), 43% (fresh weight), and 78% (dry weight), whereas photosynthetic pigments by 25% (chl a), 58% (chl b), and 125% (carotenoids). Based on the results, it could be concluded that CA can play a role in mitigating the toxic effect of Cu in Withania coagulans

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.

New insights into the interaction between duodenal toxicity and microbiota disorder under copper exposure in chicken: Involving in endoplasmic reticulum stress and mitochondrial toxicity

Copper (Cu) has been widely used in industrial agricultural production, but excess use can lead to toxic effect on host physiology, which poses a threaten to public hygiene. However, the relationship between gut microbiota and Cu-induced intestinal toxicity is unclear. Here, we identified that intestinal flora disturbance was related to duodenal toxicity under Cu exposure. We found that excess Cu disturbed gut microbiota homeostasis, resulting in Cu accumulation and intestinal damage. In addition, Cu considerably increased intestinal permeability by reducing expression of tight junction proteins (Claudlin-1, Occludin, and ZO-1). Meanwhile, Cu could induce endoplasmic reticulum stress, mitophagy, and mitochondria-mediated apoptosis in the duodenum, with the evidence by the elevated levels of GRP78, GRP94, LC3Ⅱ/LC3Ⅰ and Caspase-3 protein expression. Correlation analysis showed that Melainabacteria was closely related to tight junction proteins and endoplasmic reticulum stress of duodenum, indicating that disturbance of intestinal flora may aggravate the toxic effect of Cu. Therefore, our results suggest that the destruction of intestinal flora induced by excessive Cu may further lead to intestinal barrier damage, ultimately leading to endoplasmic reticulum stress, mitophagy and apoptosis. This research provides a new insight into interpretation of the interrelationship between microbiota disorder and duodenal toxicity under Cu exposure.

Revealing degradation and enhancement mechanisms affecting copper (Cu) immobilization using microbial-induced carbonate precipitation (MICP)

Inappropriate handling of copper-rich water bodies could cause serious threats to surrounding environments and human health. Remedying Cu2+ using the environmental-friendly MICP technology starts drawing great attention from scientists and practitioners, but a rather low Cu immobilization efficiency has been reported in a significant body of research. The present work investigated how the degree of urea hydrolysis and pH surrounding conditions varied with the effect of culture medium, bacterial suspension dosage, and CaCl2 addition using the test tube experiments. The speciation of carbonate precipitation was further analysed by the numerical simulations to reveal the underlying mechanisms affecting the Cu immobilization efficiency. The results indicated that a low Cu immobilization efficiency is attained either using lower or higher degrees of urea hydrolysis. Although higher bacterial suspension dosages cause an improvement in the resistance of the ureolytic bacteria against the effect of Cu toxicity, pH surrounding is lifted up, promoting the formation of copper-ammonia complex and imposing risks of Cu2+ migration. A combination of yeast extract and CaCl2 addition can not only improve the degree of urea hydrolysis by competing for adsorption with Cu2+ but also accelerate the consumption of OH-, thereby securing the Cu immobilization efficiency. The findings shed light on the potential of applying the MICP technology to copper-rich water bodies immobilization.

Biomolecular modifications in the sacfry of Mogurnda adspersa in response to copper stress

Copper (Cu) is one of the most harmful contaminants in fresh-water systems. Fish larvae such as sacfry are particularly vulnerable to metals such as copper (Cu) due to a less-developed excretory organ system and permeable skin that can absorb metals directly from the water. However, the sublethal effects of metals on this life stage are not well understood. This study assessed the sublethal toxicity of Cu on purple-spotted gudgeon sacfry (PSG, Mogurnda adspersa). For this purpose, 96h Cu toxicity bioassays were performed and toxic effects of Cu on PSG were measured at different levels of biological organization, from the individual (loss of equilibrium, wet weight), to tissue (chemical changes in retinal tissue composition) and molecular responses (whole body amino acid (AA) profiles). The EC10 and EC50 (ECx: effect concentration that affected X% of test organisms) were found to be 12 (9 - 15) µg Cu L-1 and 22 (19 - 24) µg Cu L-1, respectively. Copper stress caused a decrease in total amino acid content and changed the AA profile of PSG compared to the controls. Proton-induced X-ray emission (PIXE) mapping techniques showed accumulation of Cu in the retinal tissues disturbing the distribution of other elements such as zinc, sulfur, phosphorus and potassium. Fourier-transform infrared (FTIR) microspectroscopy of control and Cu treated eye tissues revealed a change in protein secondary structure in retinal tissues in response to Cu accumulation, as well as decreased levels of the molecular retinal, consistent with the degradation of rhodopsin, a key protein in the visual sensory system. This is the first study to demonstrate the multi-level responses of PSG arising from exposure to environmentally realistic Cu concentrations and suggests that AA profiling can serve as a useful tool to assess the impacts of metals on fresh-water organisms.

Environmental co-exposure of high temperature and Cu induce hormonal disturbance of cortisol signaling and altered responses of cellular defense genes in zebrafish

Global warming is causing a continuous increase in environmental temperatures, which simultaneously activates toxic environmental stresses, such as heavy metal exposure, in aquatic ecosystems. The present study aimed at evaluating the effects of Cu toxicity along with increased temperature during zebrafish embryogenesis. Decreased survival rates were observed following combined exposure to high temperature and Cu. Heart rates of zebrafish embryos were significantly increased only during heat stress. An abnormal morphology with curved body shape was induced by exposure to a combination of Cu and heat stress. Furthermore, heat stress also triggered Cu-induced intracellular reactive oxygen species (ROS) production, with upregulation of superoxide dismutase (SOD) and glutathione s-transferase (GST) expression, and cell death with modified expression of p53 and B-cell lymphoma-2 (Bcl-2) in zebrafish embryos. Finally, increased cortisol levels and altered expression of cortisol-signaling genes were observed following exposure to Cu and high temperatures. These results highlight that realistic exposure to combined stressors induces developmental disturbances via stress-induced responses involving oxidative stress and cell death as well as transcriptional alterations leading to cortisol signaling in fish.

The Toxic Effects of Cu and CuO Nanoparticles on Euplotes aediculatus.

The single-celled eukaryote Euplotes aediculatus was chosen to test and compare the toxic effects of Cu and CuO nanoparticles (NPs). The antioxidant enzymatic activity, morphological changes, and functional groups on the membrane were determined using spectrophotometry, microscopy, and Fourier transform infrared spectroscopy after NPs treatment. The toxicity of the NPs to cells was dose-dependent, and the 24h-LC50 values of the CuNPs and CuONPs were 0.46µg/L and 1.24 × 103µg/L, respectively. These NPs increased the activities of superoxide dismutase, glutathione peroxidase, and catalase and destroyed the cell structure; moreover, the CuNPs were more toxic than the CuONPs. In addition to the higher enzymatic activity, CuNPs also caused nucleoli disappearance, chromatin condensation, and mitochondrial and pellicle damage. The oxidization of the functional groups of the membrane (PO2 - , C-O-C, and δ(COH) of carbohydrates) also confirmed the severe damage caused by CuNPs. Our study showed that oxidative stress and organelle destruction played important roles in the toxic effects of these NPs on this protozoan. Compared with other aquatic organisms, E. aediculatus can be considered a potential indicator at the preliminary stage of environmental pollution.

Effect of trace elements in the toxicity of copper to Chlamydomonas reinhardtii.

Copper sulfate (CuSO4) is widely used in the control of algal blooms. Cu can promote or inhibit algal growth, while also affecting trace element uptake, therefore, the response mechanisms of algae cells under Cu2+ interference should be studied. In this study, wild-type Chlamydomonas reinhardtii (C. reinhardtii) and wall-less mutant C. reinhardtii were selected as the research objects. Except for the cell wall, these two algae were physiologically the same. While manipulating the concentration of Cu, the accumulation of Cu, Fe, Zn, and Mn by the two algal cell types was studied. The cell wall hindered the accumulation of Cu by cells and alleviated the toxicity of Cu to C. reinhardtii. The addition of Cu increased the accumulation of Fe by both cell types. In an environment with excess Cu, the total amount of Zn and Mn accumulated by cells also increased. On the one hand, this may be due to the synergistic and antagonistic effects of trace elements in the adsorption and uptake process, and on the other hand, it may be due to the changes in metal speciation in the culture medium. In addition, the difference in the total accumulation of various trace elements between wild-type and wall-less-type C. reinhardtii may be due to the structure and function differences between cell wall and cell membrane. At the same time, by measuring the changes in the levels of glutathione (GSH) in algal cells, the relevant mechanisms underlying the algae's uptake of trace elements by algae were further explored.