Mechanisms Of Metal Toxicity Research Articles

Establishment a cell line of splenic fibroblasts from golden pompano and its application in heavy metal toxicology and pathogen infection

A cell line derived from golden pompano Trachinotus ovatus splenic fibroblasts (TOSF) was established, its application in toxicology and virus susceptibility was demonstrated in this study. The TOSF cells grew fastest with the L-15 medium containing 10% fetal bovine serum concentration at 28 °C. The chromosomal number of normal TOSF cells was 2N = 48. TOSF cells showed high sensitivity to grouper iridovirus (SGIV) and nervous necrosis virus (NNV). Cadmium and copper had toxic effects on TOSF cells, which could cause an oxidative stress response in TOSF cells and activate the antioxidant system to regulate the reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GSH) level in the cells. Cadmium and copper had an impact on the replication of SGIV and NNV in the TOSF cells, and copper could limit the proliferation of Aeromonas hydrophila in TOSF cells. Generally, the TOSF cell line can apply for heavy metal toxicity mechanisms study and environment monitoring, as well as the pathogen infection mechanism research.

Mediation analysis for TNF-α as a mediator between multiple metal exposure and kidney function

The association between metal mixtures and kidney function has been reported. However, reports on the mechanism of metal toxicity were limited. Oxidative stress was reported as a possible cause. This study aimed to determine the association between of kidney function and metals, such as arsenic (As), cadmium (Cd), cobalt (Co), copper (Cu), lead (Pb), selenium (Se), and zinc (Zn), and to explore the possible mediating role of tumor necrosis factor alpha (TNF-α) between metal toxicity and kidney function. In this study, we recruited 421 adults from a health examination. The concentration of blood metals was analyzed using inductively coupled plasma mass spectrometry. We used linear regression models to assess the association between metals and TNF-α. Then, mediation analysis was applied to investigate the relationship between metal exposure, TNF-α, and kidney function. In univariate linear regression, blood As, Cd, Co, Cu, Pb, and Zn levels significantly increased TNF-α and decreased kidney function. Higher blood As and Pb levels significantly increased TNF-α in multivariable linear regressions after adjusting for covariates. We found that blood levels of As (coefficients = −0.021, p = 0.011), Pb (coefficients = −0.060, p < 0.001), and Zn (coefficients = −0.230, p < 0.001) showed a significant negative association with eGFR in the multiple-metal model. Furthermore, mediation analysis showed that TNF-α mediated 41.7 %, 38.8 %, and 20.8 % of blood Cd, As and Pb, respectively. Among the essential elements, TNF-α mediated 24.5 %, 21.5 % and 19.9 % in the effects of blood Co, Cu, and Zn on kidney function, respectively. TNF-α, acting as a mediator, accounted for 20.1 % of the contribution between the WQS score of metal mixtures and the eGFR (p < 0.001). This study suggested that TNF-α may be a persuasive pathway mediating the association between metals and kidney function. Inflammation and kidney injury could be the underlying mechanisms of metal exposure. However, there is still a need to clarify the biochemical mechanism in follow-up studies.

Construction of metal interpretable scoring system and identification of tungsten as a novel risk factor in COPD

Numerous studies have highlighted the correlation between metal intake and deteriorated pulmonary function, emphasizing its pivotal role in the progression of Chronic Obstructive Pulmonary Disease (COPD). However, the efficacy of traditional models is often compromised due to overfitting and high bias in datasets with low-level exposure, rendering them ineffective in delineating the contemporary risk trends associated with pulmonary diseases. To address these limitations, we embarked on developing advanced, interpretable models, crucial for elucidating the intricate mechanisms of metal toxicity and enriching the domain knowledge embedded in toxicity models. In this endeavor, we scrutinized extensive, long-term metal exposure datasets from NHANES to explore the interplay between metal and pulmonary functionality. Employing a variety of machine-learning approaches, we opted for the “Mixer of Experts” model for its proficiency in identifying a myriad of toxicological trends and sensitivities. We conceptualized and illustrated the TSAP (Toxicity Score at Population-level), a metal interpretable scoring system offering performance nearly equivalent to the amalgamation of standard interpretable methods addressing the “black box” conundrum. This streamlined, bifurcated procedural analysis proved instrumental in discerning established risk factors, thereby uncovering Tungsten as a novel contributor to COPD risk. SynopsisTSAP achieved satisfied performance with transparent interpretability, suggesting tungsten intake need further action for COPD prevention.

MitomiR-1736-3p regulates copper-induced mitochondrial pathway apoptosis by inhibiting AATF in chicken hepatocytes

Copper (Cu) is a toxic heavy metal pollutant. The hepatic toxicity of Cu has attracted widespread attention from researchers. However, its underlying mechanism remains elusive. Mitochondrial microRNAs (mitomiRs) are considered important factors in regulating mitochondrial and cellular functions, and their roles have been implicated in the mechanisms of metal toxicity. Therefore, this research revealed the changes in the mitomiRs expression profile of chicken liver after Cu exposure. It was ultimately determined that mitomiR-1736-3p can be involved in Cu-induced chicken liver damage by targeting AATF. In particular, our investigations have uncovered that exposure to Cu can trigger heightened levels of apoptosis in the hepatic tissue of chickens and primary chicken embryo hepatocytes (CEHs). It is noteworthy that we found upregulation of miR-1736-3p expression can exacerbate Cu-induced cell apoptosis, while inhibition of miR-1736-3p can effectively reduce apoptosis occurrence. Subsequently, we found that Cu-induced cell apoptosis could be restored by overexpressing AATF, while silencing AATF exacerbated the level of apoptosis. Fascinatingly, this change in apoptotic level is directly influenced by AATF on Bax and Bak1, rather than on p53 and Bcl-2. Overall, these findings suggest that the mitomiR-1736-3p/AATF axis mediates the mitochondrial pathway of cell apoptosis potentially involved in Cu-induced chicken liver toxicity.

Metabolic Regulation of Copper Toxicity during Marine Mussel Embryogenesis.

The development of new tools for assessing the health of cultured shellfish larvae is crucial for aquaculture industries to develop and refine hatchery methodologies. We established a large-volume ecotoxicology/health stressor trial, exposing mussel (Perna canaliculus) embryos to copper in the presence of ethylenediaminetetraacetic acid (EDTA). GC/MS-based metabolomics was applied to identify potential biomarkers for monitoring embryonic/larval health and to characterise mechanisms of metal toxicity. Cellular viability, developmental abnormalities, larval behaviour, mortality, and a targeted analysis of proteins involved in the regulation of reactive oxygen species were simultaneously evaluated to provide a complementary framework for interpretative purposes and authenticate the metabolomics data. Trace metal analysis and speciation modelling verified EDTA as an effective copper chelator. Toxicity thresholds for P. canaliculus were low, with 10% developmental abnormalities in D-stage larvae being recorded upon exposure to 1.10 μg·L-1 bioavailable copper for 66 h. Sublethal levels of bioavailable copper (0.04 and 1.10 μg·L-1) caused coordinated fluctuations in metabolite profiles, which were dependent on development stage, treatment level, and exposure duration. Larvae appeared to successfully employ various mechanisms involving the biosynthesis of antioxidants and a restructuring of energy-related metabolism to alleviate the toxic effects of copper on cells and developing tissues. These results suggest that regulation of trace metal-induced toxicity is tightly linked with metabolism during the early ontogenic development of marine mussels. Lethal-level bioavailable copper (50.3 μg·L-1) caused severe metabolic dysregulation after 3 h of exposure, which worsened with time, substantially delayed embryonic development, induced critical oxidative damage, initiated the apoptotic pathway, and resulted in cell/organism death shortly after 18 h of exposure. Metabolite profiling is a useful approach to (1) assess the health status of marine invertebrate embryos and larvae, (2) detect early warning biomarkers for trace metal contamination, and (3) identify novel regulatory mechanisms of copper-induced toxicity.

Microglial Activation in Metal Neurotoxicity: Impact in Neurodegenerative Diseases.

Neurodegenerative processes encompass a large variety of diseases with different pathological patterns and clinical features, such as Alzheimer's and Parkinson's diseases. Exposure to metals has been hypothesized to increase oxidative stress in brain cells leading to cell death and neurodegeneration. Neurotoxicity of metals has been demonstrated by several in vitro and in vivo experimental studies, and most probably, each metal has its specific pathway to trigger cell death. As a result, exposure to essential metals, such as manganese, iron, copper, zinc, and cobalt, and nonessential metals, including lead, aluminum, and cadmium, perturbs metal homeostasis at the cellular and organism levels leading to neurodegeneration. In this contribution, a comprehensive review of the molecular mechanisms by which metals affect microglia physiology and signaling properties is presented. Furthermore, studies that validate the disruption of microglia activation pathways as an essential mechanism of metal toxicity that can contribute to neurodegenerative disease are also presented and discussed.

The Epitranscriptomic Mechanism of Metal Toxicity and Carcinogenesis.

Metals are common toxic environmental pollutants. Acute or chronic exposure to metal pollutants causes severe adverse health effects in animals and humans, such as developmental retardation, abnormal metabolism, and disorders of cardiovascular, neurologic, respiratory, reproductive, and urologic systems. Moreover, several metals (arsenic, cadmium, chromium, and nickel) are classified as potent Group I carcinogens and cause various types of cancer in humans. Although the toxicity and carcinogenicity of metal pollutants are well recognized, the underlying mechanisms have not been clearly defined. The epitranscriptome includes all kinds of chemical modifications of all forms of RNA molecules inside a cell. Recent progresses in demonstrating the reversible pattern of RNA modifications and their roles in physiology and pathogenesis represent a breakthrough in the field of RNA biology and function study. The epitranscriptomic study is now an exciting emerging field in toxicology research. While few studies have been conducted so far to determine the epitranscriptomic effects of metal pollutants, they offer novel insights for understanding the mechanisms of metal toxicity and carcinogenesis. The goal of this review is to discuss recent studies on the epitranscriptomic effects of metals and propose some thoughts for future studies in the field.

Evaluation of the developmental effects of a glyphosate-based herbicide complexed with copper, zinc, and manganese metals in zebrafish.

The use of glyphosate-based herbicides (GBH) has increased dramatically, being currently the most used herbicides worldwide. Glyphosate acts as a chelating agent, capable of chelate metals. The synergistic effects of metals and agrochemicals may pose an environmental problem as they have been shown to induce neurological abnormalities and behavioural changes in aquatic species. However, as their ecotoxicity effects are poorly understood, evaluating the impacts of GBH complexed with metals is an ecological priority. The main objective of the study was to evaluate the potentially toxic effects caused by exposure to a GBH (1 μg a.i. mL−1), alone or complexed with metals (Copper, Manganese, and Zinc (100 μg L−1)), at environmentally relevant concentrations, during the early period of zebrafish (Danio rerio) embryo development (96 h post-fertilization), a promising model for in vivo developmental studies. To clarify the mechanisms of toxicity involved, lethal and sublethal development endpoints were assessed. At the end of the exposure, biochemical and cell death parameters were evaluated and, 24 h later, different behavioural responses were assessed. The results showed that metals induced higher levels of toxicity. Copper caused high mortality, low hatching, malformations, and changes in biochemical parameters, such as decreased Catalase (CAT) activity, increased Glutathione Peroxidase (GPx), Glutathione S-Transferase (GST), reduced Glutathione (GSH) and decreased Acetylcholinesterase (AChE) activity, also inducing apoptosis and changes in larval behaviour. Manganese increased the activity of SODs enzymes. Zinc increased mortality, reactive oxygen species (ROS) levels, superoxide dismutase activity (SODs) and caused a decrease in AChE activity. Embryos/larvae exposed to the combination of GBH/Metal also showed teratogenic effects during their development but in smaller proportions than the metal alone. Although more studies are needed, the results suggest that GBH may interfere with the mechanisms of metal toxicity at the biochemical, physiological, and behavioural levels of zebrafish.

Metabolic status of the coral Mussismilia harttii in field conditions and the effects of copper exposure in vitro

It is widely known that metals can alter enzyme functioning, however, little is known about the mechanisms of metal toxicity in energy metabolism enzymes of corals. Thus, the present study had two objectives: firstly, we evaluated the activity of eight metabolic enzymes of the coral Mussismilia harttii to clarify metabolic functioning under field conditions. After that, we investigated the in vitro effect of copper (Cu) exposure in the activity of an enzyme representative of each metabolism stage. We evaluated enzymes involved in glycolysis (hexokinase, HK; phosphofructokinase, PFK; pyruvate kinase, PK and lactate dehydrogenase, LDH), Krebs cycle (citrate synthase, CS and isocitrate dehydrogenase, IDH), electron transport chain (electron transport system activity, ETS) and pentose phosphate pathway (glucose-6-phosphate dehydrogenase, G6PDH). The in vitro tests were performed through contamination of the reaction medium using Cu concentrations of 0, 1.4, 3.7 and 14.2 μg L−1. The results showed that M. harttii has elevated activity of HK, PK and CS in field conditions compared to the activity of other energy metabolism enzymes evaluated. Moreover, lower activities of LDH and ETS in exposed samples were observed. In conclusion, in field conditions this species has elevated aerobic metabolism and glucose may be an important energetic fuel. Also, exposure to Cu in vitro caused inhibition of LDH and ETS by direct binding.

Toward a comprehensive study for multielemental quantitative LA-ICP MS bioimaging in soft tissues

Quantitative localization of metals in biological tissue sections is critical to obtain insight into metal toxicity mechanisms or their beneficial characteristics. This study presents the development of a quantitative LA-ICP MS bioimaging methodology based on the polymer film strategy and internal standardization. To maximize the number of elements mapped, an aqueous soluble polymer (dextran) was selected. Among the elements studied, the great majority (eight out eleven), i.e., Co, Ni, Cu, Zn, Se, Mo, Cd and Pt, exhibited linear regression after LA-ICP MS analysis of metal-spiked polymer standards. Methodology performances were carefully assessed as a function of the three internal standards (In, Rh and Ir) considered, the analytical operational conditions (ICP power, addition of O2 to ICP, and laser fluency) and the thickness of the biological tissue section. The results indicated that three groups (Co, Mo; Ni, Cu, Pt; and Zn, Se, Cd) of elements could be distinguished from their analytical response as a function of analytical conditions and the internal standard. These different element behaviors appeared to be mainly First Ionization Potential dependent (FIP). For elements with lower FIP (Co, Ni, Cu, Mo and Pt), differential responses due to carbon load in the ICP MS plasma could be efficiently corrected as a function of analytical conditions. Matrix effects were more pronounced for higher FIP elements (i.e., Zn, Cd and Se), and analysis of <10-μm thin sections without the addition of O2 to ICP MS plasma is recommended. LODs are in the range of 0.1–0.5 μg g−1 for Co, Mo, Cu, Ni, Pt and Cd as well as 0.9 and 1 μg g−1 for Zn and Se, respectively. The methodology was validated by means of a homemade metal-spiked kidney homogenate analyzed by LA-ICP MS imaging, and Co, Ni, Cu, Mo, and Pt provided the closest concentrations (5–29% bias) to the target values determined by ICP MS after mineralization. The methodology was applied to two types of clinical human samples undergoing different sample preparation protocols that did not affect internal standard homogeneity in the polymer film. This methodology is the first reported for the quantitative bioimaging of eight elements simultaneously.

Cadmium sulfate induces apoptosis in planarians.

With rapid socio-economic development, heavy metal pollution in water has become common and affects both environment and human health. Cadmium (Cd) has been recognized as one of the heavy metals which cause acute or chronic toxic effects if ingested. Although its toxicity is undisputed, the underlying molecular mechanisms in vivo are not fully understood. Planarians, a model organism famous for their regenerative prowess, have long been utilized to study the effects of chemical exposure. In this study, we observed apoptosis with TUNEL assay in planarians induced by cadmium sulfate (CdSO4) in a dose-dependent manner. The apoptosis-related genes were detected with quantitative RT-PCR. Significant changes in c-Myc, P53, and BcL-2 were indicated, which may play a partial role in the regulation of the process of apoptosis in the planarians. H&E staining showed that Cd had obvious biological toxicity in the planarians. Here, new insights on metal toxicity mechanisms are provided, contributing to understand how CdSO4 induces the pathological and physiological processes of apoptosis in the living bodies. Meanwhile, planarians are proved to be a freshwater pollution indicator and toxicological research model.

Abstract A42: The search for new targets for mitigation of metal toxicity based on molecular pathways of action: A case study using cadmium and iron

Abstract Cadmium is a nonessential heavy metal, ubiquitous in nature with a long half-life in human beings. It is widely used in various industrial applications such as toy and jewelry making and is one of the key constituents of tobacco and cigarette smoke. Cadmium, both at occupational and environmental levels, has been implicated in the causation of cancerous and noncancerous health outcomes. In comparison, iron is an essential metal and is a constituent of hemoglobin and many vital enzymes and proteins and plays a pivotal role in human health. However, increased consumption of iron from fortified diets and iron supplements presents opportunities for exposure to supraphysiologic iron concentrations and toxicity. Additionally, hereditary iron disorders (thalassemia, hereditary hemochromatosis), other disease conditions such as cancer and kidney diseases, and certain environmental exposures (e.g., steel-welding fumes, asbestos, and air pollution) could also lead to iron toxicity with disturbed homeostasis mechanisms affecting intracellular and systemic regulation of iron. Chelation therapy has traditionally been used to mitigate the toxicity of metals. This talk will present the results of systematic reviews and analyses for both cadmium and iron toxicity and highlight the diverse molecular pathways by which these metals can elicit toxic effects. Using the examples of cadmium and iron, I will discuss some recent advances in our understanding of the molecular mechanisms of metal toxicity and how this information can be used to identify novel targets for toxicity mitigation. (The views expressed in this abstract are those of the author and do not necessarily reflect the views or policies of EPA.) Citation Format: Anuradha Mudipalli. The search for new targets for mitigation of metal toxicity based on molecular pathways of action: A case study using cadmium and iron [abstract]. In: Proceedings of the AACR Special Conference on Environmental Carcinogenesis: Potential Pathway to Cancer Prevention; 2019 Jun 22-24; Charlotte, NC. Philadelphia (PA): AACR; Can Prev Res 2020;13(7 Suppl): Abstract nr A42.

Review of Copper and Copper Nanoparticle Toxicity in Fish.

This review summarizes the present knowledge on the toxicity of copper and copper nanoparticles (CuNPs) to various fish species. In previous decades, the excessive usage of metal and metallic nanoparticles has increased significantly, increasing the probability of the accumulation and discharge of metals in various trophic levels of the environment. Due to these concerns, it is important to understand the toxicity mechanisms of metals and metallic nanoparticles before they lead to unhealthy effects on human health. In this review paper, we specifically focus on the effect of metal copper and CuNPs on different fish organs under different physiochemical parameters of various water bodies. Nowadays, different forms of copper have distinctive and specific usages, e.g., copper sulfate is a well-established pesticide which is used to control the growth of algae in lakes and ponds. Deactivating the fungi enzymes prevents fungal spores from germinating. This process of deactivation is achieved via the free cupric ions, which are established as the most toxic forms of copper. Complexes of copper with other ligands may or may not be bioavailable for use in aquatic organisms. On the other hand, CuNPs have shown cost-effectiveness and numerous promising uses, but the toxicity and availability of copper in a nanoparticle form is largely unknown, Additionally, physiochemical factors such as the hardness of the water, alkalinity, presence of inorganic and organic ligands, levels of pH, and temperature in various different water bodies affect the toxicity caused by copper and CuNPs. However, comprehensive knowledge and data regarding the pattern of toxicity for copper metal ions and CuNPs in marine organisms is still limited. In this review, we carry out a critical analysis of the availability of the toxicological profiles of copper metal ions and CuNPs for different fishes in order to understand the toxicity mechanisms of copper and CuNPs. We believe that this review will provide valuable information on the toxicological profile of copper, which will further help in devising safe guidelines for the usage of copper and CuNPs in a sustainable manner.

A multivariate analysis of comparative effects of heavy metals on cellular biomarkers of phytoremediation using Brassica oleracea

The biochemical/physiological variations in plant responses to heavy metals stress govern plant’s ability to phytoremediate/tolerate metals. So, the comparative effects of different types of heavy metals on various plant responses can better elucidate the mechanisms of metal toxicity and detoxification. This study compared the physiological modifications, photosynthetic performance and detoxification potential of Brassica oleracea under different levels of chromium (Cr), nickel (Ni) and selenium (Se). All the heavy metals induced a severe phytotoxicity to B. oleracea in terms of chlorophyll contents, Ni being the most toxic (76% decrease). Brassica oleracea showed high lipid oxidation: 87% and 273%, respectively in leaves and roots. Furthermore, all the metals increased the activities of catalase and peroxidase, while decreased superoxide dismutase and ascorbate peroxidase. Interestingly, heavy metals decreased hydrogen peroxide contents perhaps due to their possible transformation to another form of reactive oxygen species such as hydroxyl radical. Among the three metals, Ni was more phytotoxic than Cr and Se. Moreover, the phytoremediation/tolerance potential of B. oleracea to Ni, Cr and Se stress varied with the type of metal, their applied levels, response variables and plant organ type (root/shoot). The multivariate analysis separated different plant response variables and heavy metal treatments into different groups based on their correlations.

Quantifying correlations of metal ionic characters with ecological soil screening levels (Eco-SSLs) of metals using QICAR models

Soil pollution by heavy metals is a major challenge for soil ecosystems; therefore, many countries have published thresholds or standards for protecting soil organisms based on toxicity testing. However, there have been few studies on the mechanism of metal toxicity on organisms in soils, especially relationships between metal's ionic properties and its toxicity. Herein, we selected environmental soil screening levels (Eco-SSLs), which are internationally recognized ecotoxicity values recommended by the United States Environmental Protection Agency (USEPA), and investigated relationships between Eco-SSLs and metal ionic characteristics. The results showed that several ionic characteristics were significantly correlated with Eco-SSL using a classification of metal ions according to hard and soft acids and bases. Electrochemical potential, atomic ionization potential, the first hydrolysis constant, the maximum complex stability constant, a polarization force parameter and covalent radius showed significant correlations with Eco-SSLs for borderline plus hard ions, while the soft index exhibited significant fitting for borderline plus soft ions, suggesting that ionic bonding and covalent bonding played important roles in metal toxicity on borderline plus hard ions and soft ions, respectively. Then, we chose characteristics that had the strongest correlations with Eco-SSLs, and developed quantitative ion character–activity relationship (QICAR) for soil organisms. The QICARs predicted Eco-SSLs for metals that were reasonably consistent with those recommended by USEPA, with differences between them generally <0.5 orders of magnitude. Overall, QICAR provide a basis for ecological risk assessment and could be useful to interpret relationships between metal's ionic properties and its toxicity.

First studies on the interactions of the C-terminal cystatin C fragment 85–94 with Cu(II) ions

The hypothesis connecting dyshomeostasis of selected metal ions in the brain with increased probability of the development of severe neurodegenerative diseases is gaining increasing attention. The mechanisms of metal toxicity can be studied using different methodologies. One of the approaches is based on peptides as mimetics of the metal binding sites in proteins. In our studies, we have focused on human cystatin C (hCC) as one of the proteins involved in neurodegeneration. Physiologically, it is an important inhibitor of cysteine proteases and modulator of many physiological and pathological states. Native hCC is present at particularly high concentrations in cerebrospinal fluid (CSF) and was shown to possess both neurodegenerative and neuroprotective propensities. We have studied the copper(II) binding to its C-terminal fragment containing two histidine residues as potential site(s) for metal coordination. Our data indicate that the hCC fragment is fully capable of effective metal binding. Moreover, two potential metal binding sites can be proposed for the studied ligand. At the physiological range of pH formation of two types of complexes was observed: with imidazole and one/two amide donors in the coordination sphere of the metal ion and the final species characterized by the 4N-type of coordination.

Copper potentiates azole antifungal activity in a way that does not involve complex formation.

To survive, fungal pathogens must acquire nutrient metals that are restricted by the host while also tolerating mechanisms of metal toxicity that are induced by the host. Given this dual vulnerability, we hypothesized that a pathogen's access to and control of essential yet potentially dangerous metal ions would affect fungal tolerance to antifungal drug stress. Here, we show that Candida albicans becomes sensitized to both Cu limitation and Cu elevation during exposure in liquid culture to the antifungal drug fluconazole, a widely prescribed antifungal agent. Spectroscopic data confirm that while fluconazole forms a complex with Cu(ii) in water, interactions of fluconazole with neither Cu(ii) nor Cu(i) are observed in the cell culture media used for the cellular assays. This result is further supported by growth assays in deletion strains that lack Cu import machinery. Overall, we establish that increases in Cu levels by as little as 40 nM over basal levels in the growth medium reduce tolerance of C. albicans to fluconazole in a way that does not require formation of a Cu-fluconazole complex. Rather, our data point to a more complex relationship between drug stress and Cu availability that gives rise to metal-mediated outcomes of drug treatment.

Responses of Raphidocelis subcapitata exposed to Cd and Pb: Mechanisms of toxicity assessed by multiple endpoints

Microalgae have been widely used in ecotoxicological studies in order to evaluate the impacts of heavy metals in aquatic ecosystems. However, there are few studies that analyze the effects of metals in an integrative way on photosynthetic apparatus of freshwater microalgae in the generation of reactive oxygen species (ROS) and biochemical composition. Therefore, this study aimed to assess cadmium (Cd) and lead (Pb) toxicity using synchronously physiological and biochemical endpoints, specially detecting lipidic classes for the very first time during Cd and Pb-exposure to Raphidocelis subcapitata. Here we show that analyzing the algae growth, the IC50–72 h for Cd was 0.04 µM and for Pb was 0.78 µM. In general, the Cd affected the biochemical parameters more, leading to an increase in total lipid content (7.2-fold), total carbohydrates (3.5-fold) and ROS production (3.7-fold). The higher production of lipids and carbohydrates during Cd-exposure probably acted as a defense mechanism, helping to reduce the extent of damage caused by the metal in the photosynthetic apparatus. For Pb, the physiological parameters were more sensitive, which resulted in changes of chlorophyll a synthesis and a reduction of both efficiency of oxygen-evolving complex and quantum yields. Besides that, we observed changes in the lipid class composition during Cd and Pb-exposure, suggesting these analyses as great biomarkers to assess metal toxicity mechanisms in ecological risk assessments. Thereby, here we demonstrate the importance of using multiple endpoints in ecotoxicological studies in order to obtain a better understanding of the mechanisms of metal toxicity to R. subcapitata.

Growth, antioxidant capacity, intestinal morphology, and metabolomic responses of juvenile Oriental river prawn (Macrobrachium nipponense) to chronic lead exposure

Understanding the mechanisms of metal toxicity to organisms farmed for food may suggest mitigation strategies. We determined the 24-, 48-, 72-, and 96-h median lethal concentrations of lead in juvenile oriental river prawn (Macrobrachium nipponense). The prawns were then exposed to sub-lethal concentrations (13.13 and 26.26 μg/L) of lead for 60 days and growth, antioxidant enzyme activity, intestinal morphology, and metabolite profiles were assessed. Prawns exposed to 26.26 μg/L but not to 13.13 μg/L lead exhibited lower weight gain than controls. The lead burden in muscle was 0.067 and 0.25 μg/g of dry weight exposed to 13.13 and 26.26 μg/L, respectively. Levels of glutamic oxaloacetic transaminase and glutamic-pyruvic transaminase were not altered following exposure. Exposure increased malondialdehyde activity in the hepatopancreas and decreased superoxide dismutase and glutathione peroxidase activities. Catalase activity first increased and then decreased as lead concentrations increased. Some intestinal epithelial cells disassociated from the basement membrane in prawns exposed to 13.13 μg/L lead. Intestinal epithelial cells in prawns exposed to 26.26 μg/L lead separated completely from the basement membrane. Gas chromatography-mass spectrometry metabolomics assays showed the 13.13-μg/L exposure did not elicit significant metabolic alterations. Exposure to 26.26 μg/L lead differentially up-regulated 58 metabolites and down-regulated 21 metabolites. The metabolites identified were involved in galactose, purine, glutathione, and carbon metabolism, biosynthesis of amino acids and steroids, and neuroactive ligand-receptor interaction. These data indicate that chronic lead exposure can adversely affect growth, increase accumulation in muscle, impair intestinal morphology, and induce oxidant stress or neurotoxicity-related effects in M. nipponense.

Life and death of Trypanosoma cruzi in presence of metals.

Trypanosoma cruzi has many molecules that need metallic elements to work, allowing cell invasion and the establishment of infection, causing Chagas disease. Nonetheless, knowledge regarding how the parasites address metals and maintain homeostasis is lacking. To study this relationship, zinc, cadmium and mercury were chosen. Epimastigote, trypomastigote and intracellular forms of T. cruzi were incubated with these metals for different times and at different concentrations. In general, epimastigotes were the most sensitive and trypomastigotes the most resistant to metals. ZnCl2 induced low toxic effects to all parasite forms. Although the parasites were very sensitive to the toxic effects of CdCl2 and HgCl2, pretreatment with ZnCl2 decreased the death rate. The trypomastigotes pretreated with CdCl2 were unable to infect the host cells, and the treated intracellular forms were damaged after 2h of incubation, when the toxic effects were poorly reverted. New insights on metal toxicity mechanisms are provided, helping to understand how metallic ions influence the parasite's biochemical and physiological processes.