Life-time exposure to waterborne copper II: Patterns of tissue accumulation and gene expression of the metal-transport proteins ctr1 and atp7b in the killifish Poecilia vivipara

Organic contamination and multi-biomarker assessment in watersheds of the southern Brazil: an integrated approach using fish from the Astyanax genus

We aimed to examine the responses of pollution biomarkers in feral fish from Astyanax genus collected at three hydrographic regions in southern Brazil and the capacity of these tools to differentiate between various levels of contamination. To achieve this, levels of organochlorine pesticides (liver), as well as the biomarkers AChE (muscle and brain), TBARS (liver), and EROD (liver) were assessed. Collections were conducted in four municipalities (Alegrete, Caraá, Lavras, and Santa Vitória) during 1 year, encompassing winter and summer. Fish from Alegrete were the most contaminated overall, but animals sampled in Caraá, and Lavras also displayed elevated levels of current-use pesticides. Elevated levels of endosulfans, DDTs, HCHs, and current-use pesticides were accompanied by elevated levels of TBARS in the liver. Conversely, fish from Santa Vitória exhibited the highest levels of PAHs, accompanied by elevated levels of EROD in the liver and reduced levels of AChE in muscle and brain. TBARS proved to be a reliable biomarker for assessing impacts arising from pesticide accumulation, while EROD and AChE served as valuable indicators of impacts resulting from PAHs accumulation. Ultimately, the results obtained in this study demonstrate the reliable use of the proposed biomarkers for tracking biological impacts stemming from aquatic pollution using feral Astyanax as biomonitoring species.

The Role of Glutathione and Sulfhydryl Groups in Cadmium Uptake by Cultures of the Rainbow Trout RTG-2 Cell Line

The aim of this study is to investigate the role of cellular sulfhydryl and glutathione (GSH) status in cellular cadmium (Cd) accumulation using cultures of the rainbow trout cell line RTG-2. In a first set of experiments, the time course of Cd accumulation in RTG-2 cells exposed to a non-cytotoxic CdCl2 concentration (25 μM) was determined, as were the associated changes in the cellular sulfhydryl status. The cellular levels of total GSH, oxidized glutathione (GSSG), and cysteine were determined with fluorometric high-performance liquid chromatography (HPLC), and the intracellular Cd concentrations were determined with inductively coupled plasma mass spectrometry (ICP-MS). The Cd uptake during the first 24 h of exposure was linear before it approached a plateau at 48 h. The metal accumulation did not cause an alteration in cellular GSH, GSSG, or cysteine levels. In a second set of experiments, we examined whether the cellular sulfhydryl status modulates Cd accumulation. To this end, the following approaches were used: (a) untreated RTG-2 cells as controls, and (b) RTG-2 cells that were either depleted of GSH through pre-exposure to 1 mM L-buthionine-SR-sulfoximine (BSO), an inhibitor of glutathione synthesis, or the cellular sulfhydryl groups were blocked through treatment with 2.5 μM N-ethylmaleimide (NEM). Compared to the control cells, the cells depleted of intracellular GSH showed a 25% reduction in Cd accumulation. Likewise, the Cd accumulation was reduced by 25% in the RTG-2 cells with blocked sulfhydryl groups. However, the 25% decrease in cellular Cd accumulation in the sulfhydryl-manipulated cells was statistically not significantly different from the Cd accumulation in the control cells. The findings of this study suggest that the intracellular sulfhydryl and GSH status, in contrast to their importance for Cd toxicodynamics, is of limited importance for the toxicokinetics of Cd in fish cells.

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.

Avian blood and feathers as biological tools to track impacts from trace-metals: Bioaccumulation data from the biggest environmental disaster in Brazilian history

The Mariana's dam collapse was the worst environmental disaster in Brazilian history and one of the biggest worldwide. This perverse disaster resulted in the release of a contaminated mud tsunami that greatly impacted both aquatic and terrestrial biota. The aim of this study was to track environmental impacts resulting from Mariana's disaster using trace-element accumulation in avian blood and feathers as monitoring tool. For this, animals were collected at Doce River mouth (Regência), origin of the contaminated mud, and at southern (Aracruz) and northern (São Mateus) coastal areas. There were two sampling events (2018-2019), one during the winter period (first collection) and another during the summer period (second collection). Trace-element assessed were As, Cd, Cr, Cu, Fe, Pb, Hg, Mn and Zn. Findings show that inorganic contamination in birds followed a strong spatial and temporal behavior. In terms of time patterns, blood and feather contamination levels were markedly elevated in samples from the first collection event in comparison to the second. In terms of space, bioaccumulation was greater in Doce River mouth (Regência) and southern area (Aracruz). Additionally, levels found for Pb, Hg, As and Cd in birds from the first expedition were above proposed threshold levels, indicating possible health impacts. Finally, it is concluded that avian from areas impacted by Mariana's disaster still presents elevated levels of inorganic contamination even after 5 years following the event. Additionally, local climatic factors might pose as major drivers for bioaccumulation patterns in these animals, resulting in marked spatial and temporal fluctuations.

Response of biomarkers to metals, hydrocarbons and organochlorine pesticides contamination in crabs (Callinectes ornatus and C. bocourti) from two tropical estuaries (São José and São Marcos bays) of the Maranhão State (northeastern Brazil)

Response of biomarkers to chemical contamination was evaluated in crabs of the Callinectes genus (Callinectes ornatus and C. bocourti) from two tropical estuaries (São José and São Marcos bays) of the Maranhão State (northeastern Brazil). Biomarkers evaluated included hepatopancreatic metallothionein-like proteins (MTLP) and lipid peroxidation (LPO), as well as muscle acetylcholinesterase (AChE). Tissue concentrations of metals (pereiopod muscle and hepatopancreas), hydrocarbons (hepatopancreas) and organochlorine pesticides (hepatopancreas) were also evaluated. Crab samples were collected in three sites of each estuary (São Marcos Bay and São José Bay). Sampling was performed in August/2012 (dry season), January/2013 (rainy season), August/2013 (dry season), and January/2014 (rainy season). Concentrations of chemical contaminants and responses of biomarkers showed significant spatial (São Marcos Bay and São José Bay) and/or seasonal (dry and rainy seasons) and annual (2012-2014) variability. However, a general higher Zn concentration was observed in hepatopancreas of crabs from São José Bay. In turn, a general higher Cd concentration paralleled by oxidative damage (LPO) was observed in hepatopancreas of crabs from São Marcos Bay. As expected, these findings support the idea that this bay is more intensively or chronically impacted by industrial activities while the São José Bay is likely more affected by domestic activities. Interestingly, LPO level in crab hepatopancreas showed to be the most reliable and adequate biomarker to distinguish the two bays.

Metal Accumulation and Ion Regulation in the Fish Hyphessobrycon luetkenii Living in a Site Chronically Contaminated by Copper: Insights from Translocation Experiments

Fish living in the João Dias creek (southern Brazil) have to deal with trace-metal contamination in the long-term basis, as this aquatic environment has been historically impacted by copper mining activities. In order to survive in this harsh environment, the local biota had to develop adaptations related to pollution tolerance. The aim of this study was to test if biochemical mechanisms related to osmoregulation were among these adaptations, using translocation experiments. Water ionic and trace-metal compositions were measured in a nonmetal impacted site (NMIS) and in a metal impacted site (MIS) of this creek. Also, whole-body metal accumulation, ion concentration and branchial enzyme activity (Na,K-ATPase and carbonic anhydrase) were evaluated in Hyphessobrycon luetkenii. In both NMIS and MIS, fish were collected and immediately stored, kept caged or translocated from sites. The result shows that waterborne Cu was 3.4-fold higher at the MIS. Accordingly, animals that had contact with this site showed elevated whole-body Cu levels. Moreover, both translocated groups showed elevated Na,K-ATPase activity. Additionally, fish translocated from the NMIS to the MIS showed lower carbonic anhydrase activity. These findings indicate that H. luetkenii chronically or acutely exposed to naturally elevated waterborne Cu showed a rapid Cu bioaccumulation but was unable to readily excrete it. Moreover, classic Cu osmoregulatory toxicity related to Na,K-ATPase inhibition was not observed. Conversely, impacts in ammonia excretion related to carbonic anhydrase inhibition may have occurred.

Combined exposure to environmentally relevant copper and 2,2'-dithiobis-pyridine induces significant reproductive toxicity in male guppy (Poecilia reticulata)

Metal pyrithiones (MePTs), the most widely used biocides in antifouling paints (AFs) coated on the hulls, are usually used in combination with Cu-containing substances. In the aquatic environment, 2,2'-dithiobis-pyridine ((PS)₂), the main degradation product of MePTs, and Cu usually coexist. However, their combined impacts on aquatic organisms are unclear. This study exposed male guppy (Poecilia reticulata) to an environmentally realistic concentration of Cu (10 μg/L) alone or Cu (10 μg/L) combined with 20, 200, and 2000 ng/L (PS)₂ to explore their combined reproductive toxicity. The results showed that co-exposure to Cu and (PS)₂ increased Cu accumulation in the fish body in a dose-dependent manner and induced obvious spermatozoon apoptosis and necrosis, which was mediated by the peroxidation and caspase activation. Compared to Cu alone, co-exposure to Cu and 200, 2000 ng/L (PS)₂ significantly decreased the testosterone level and collapsed spermatogenesis, and depressed male's sexual interest and mating behavior were observed in three co-exposure groups. Moreover, co-exposure to Cu and (PS)₂ increased the disturbance on cyp19a and cyp19b transcription and suppressed the "display" reproductive behavior. Eventually, co-exposure to Cu and (PS)₂ caused male reproductive failure. Therefore, the concurrence of Cu and (PS)₂ induced significant reproductive toxicity in male guppies and would threaten the sustainability of fish populations. Considering the extensive usage of MePTs products in the AFs, their ecological risk warrants more evaluation.

Temperature Effects During a Sublethal Chronic Metal Mixture Exposure on Common Carp (Cyprinus carpio)

The aquatic environment is the final sink of various pollutants including metals, which can pose a threat for aquatic organisms. Waterborne metal mixture toxicity might be influenced by environmental parameters such as the temperature. In the present study, common carp were exposed for 27 days to a ternary metal mixture of Cu, Zn, and Cd at two different temperatures, 10 and 20°C. The exposure concentrations represent 10% of the 96 h-LC₅₀ (concentration lethal for the 50% of the population in 96 h) for each metal (nominal metal concentrations of Cu: 0.08 μM; Cd: 0.02 μM and Zn: 3 μM). Metal bioaccumulation and toxicity as well as changes in the gene expression of enzymes responsible for ionoregulation and induction of defensive responses were investigated. Furthermore the hepatosomatic index and condition factor were measured as crude indication of overall health and energy reserves. The obtained results showed a rapid Cu and Cd increase in the gills at both temperatures. Cadmium accumulation was higher at 20°C compared to 10°C, whereas Cu and Zn accumulation was not, suggesting that at 20°C, fish had more efficient depuration processes for Cu and Zn. Electrolyte (Ca, Mg, Na, and K) levels were analyzed in different tissues (gills, liver, brain, muscle) and in the remaining carcasses. However, no major electrolyte losses were observed. The toxic effect of the trace metal ion mixture on major ion uptake mechanisms may have been compensated by ion uptake from the food. Finally, the metal exposure triggered the upregulation of the metallothionein gene in the gills as defensive response for the organism. These results, show the ability of common carp to cope with these metal levels, at least under the condition used in this experiment.

Antagonistic bioaccumulation of waterborne Cu(II) and Cd(II) in common carp (Cyprinus carpio) and effects on ion-homeostasis and defensive mechanisms

In the aquatic environment, metals are present as mixtures, therefore studies on mixture toxicity are crucial to thoroughly understand their toxic effects on aquatic organisms. Common carp (Cyprinus carpio) were used to assess the effects of short-term Cu(II) and Cd(II) mixtures, using a fixed concentration of one of the metals, representing 25 % of its individual 96h-LC₅₀ (concentration lethal for 50 % of the population) combined with a variable concentration of the other metal corresponding to 10, 25 or 50 % of its 96h-LC₅₀, and vice versa. Our results showed a fast Cu and Cd bioaccumulation, with the percentage of increase in the order gill > liver > carcass. An inhibitory effect of Cu on Cd uptake was observed; higher Cu concentrations at fixed Cd levels resulted in a decreased accumulation of Cd. The presence of the two metal ions resulted in losses of total Na, K and Ca. Fish tried to compensate for the Na loss through the induction of the genes coding for Na⁺/K⁺-ATPase and H⁺-ATPase. Additionally, a counterintuitive induction of the gene encoding the high affinity copper transporter (CTR1) occurred, while a downregulation was expected to prevent further metal ion uptake. An induction of defensive mechanisms, both metal ion binding protein and anti-oxidant defences, was observed. Despite the metal accumulation and electrolyte loss, the low mortality suggest that common carp is able to cope with these metal levels, at least during a one-week exposure.

Combining elevated temperature with waterborne copper: Impacts on the energy metabolism of the killifish Poecilia vivipara

We have previously demonstrated in a companion work that acclimation to 28 °C potentiated waterborne copper (Cu) toxic effects in Poecilia vivipara through oxidative stress-related processes. In the present study, we hypothesized that these results were related to kinetic metabolic adjustments in enzymes from aerobic and anaerobic pathways. To test this, P. vivipara was acclimated to two temperatures (22 °C or 28 °C) for three weeks and then exposed to Cu (control, 9 or 20 μg/L) for 96 h. The activity of enzymes from glycolysis (pyruvate kinase [PK] and lactate dehydrogenase [LDH]), Krebs cycle (citrate synthase [CS]) and the electron transport chain system (ETS) were assessed in gills, liver and muscle. Interactive effects were only seen for hepatic LDH activity, as both metal exposure and heat stress, combined or not, inhibited this enzyme, showing a suppression in anaerobic pathways. Conversely, a Cu main effect was present in the liver, expressed as an elevation in ETS activity, showing an enhancement in hepatic aerobic metabolism likely related with the very energy-demanding process of metal detoxification. Moreover, this study shows that P. vivipara has a remarkable ability to compensate heat stress in terms of energy metabolism, as we could not observe acclimation temperature effects for most of the cases. Nonetheless, a tissue-dependent effect of elevated temperature was observed, as we could observe an inhibition in muscular CS activity. Finally, it is concluded that kinetic adjustments in terms of the energy metabolism are not related with the temperature-dependent elevation of Cu toxicity in P. vivipara as we previously hypothesized.

Using native and invasive livebearing fishes (Poeciliidae, Teleostei) for the integrated biological assessment of pollution in urban streams

Invasive species are increasingly replacing native species, especially in anthropogenically transformed or polluted habitats. This opens the possibility to use invasive species as indicator taxa for the biological assessment of pollution. Integrated biological assessment, however, additionally relies on the application of multiple approaches to quantify physiological or cytogenetic responses to pollution within the same focal species. This is challenging when species are restricted to either polluted or unpolluted sites. Here, we make use of a small group of neotropical livebearing fishes (family Poeciliidae) for the integrated biological assessment of water quality. Comparing urban and suburban stream sections that receive varying degrees of pollution from industrial and domestic waste waters in and around the Brazilian city of Uberlândia, we demonstrate that two members of this family may indeed serve as indicators of water pollution levels. The native species Phalloceros caudimaculatus appears to be replaced by invasive guppies (Poecilia reticulata) at heavily polluted sites. Nevertheless, we demonstrate that both species could be used for the assessment of bioaccumulation of heavy metals (Pb, Cu, and Cr). Ambient (sediment) concentrations predicted concentrations in somatic tissue across species (R²-values between 0.74 and 0.96). Moreover, we used cytogenetic methods to provide an estimate of genotoxic effects of water pollution and found pollution levels (multiple variables, condensed into principal components) to predict the occurrence of nuclear abnormalities (e.g., frequencies of micro-nucleated cells) across species (R² between 0.69 and 0.83). The occurrence of poeciliid fishes in urban and polluted environments renders this family a prime group of focal organisms for biological water quality monitoring and assessment. Both species could be used interchangeably to assess genotoxic effects of water pollution, which may facilitate future comparative analyses over extensive geographic scales, as members of the family Poeciliidae have become invasive in tropical and subtropical regions worldwide.

Life-time exposure to waterborne copper IV: Sperm quality parameters are negatively affected in the killifish Poecilia vivipara

In previous studies, we have shown that copper (Cu) is significantly accumulated in various tissues of killifish Poecilia vivipara following chronic exposure. Also, we showed that chronic metal exposure disrupted energy production and growth in this species. In the present study, we aimed to evaluate if chronic exposure to this metal could also affect reproductive parameters of P. vivipara males (sperm quality). In order to test that, newborn (<24 h-old) fish were exposed to two concentrations of waterborne Cu (5 and 9 μg/L) for 345 days. After exposure, fish were euthanized and the testes were collected for sperm analysis. We could observe that exposed animals had reduced sperm motility and period of motility. Also, the sperm of exposed fish had reduced plasma membrane integrity, mitochondrial functionality and DNA integrity when compared to sperm of control animals. It is suggested that the well-known association of Cu with elevated oxidative damage, endocrine disruption and energetic disturbance are involved with the observed outcomes. The results obtained in the present study show that chronic exposure to environmentally relevant concentrations of waterborne Cu caused reductions in all parameters used to evaluate sperm quality. Therefore, it is concluded that life-time exposure to this metal may disrupt fish reproduction and negatively affect the maintenance of its populations.

Transcriptional effects in the estuarine guppy Poecilia vivipara exposed to sanitary sewage in laboratory and in situ

The urban growth has increased sanitary sewage discharges in coastal ecosystems, negatively affecting the aquatic biota. Mangroves, one of the most human-affected coastal biomes, are areas for reproduction and nursing of several species. In order to evaluate the effects of sanitary sewage effluents in mangrove species, this study assessed the hepatic transcriptional responses of guppy fish Poecilia vivipara exposed to sanitary sewage 33% (v:v), using suppressive subtraction hybridization (SSH), high throughput sequencing of RNA (Ion-proton) and quantification of transcript levels by qPCR of some identified genes in fish kept in a sewage-contaminated environment. Genes identified are related predominantly to xenobiotic biotransformation, immune system and sexual differentiation. The qPCR results confirmed the induction of cytochrome P450 1A (CYP1A), glutathione S transferase A-like (GST A-like) methyltransferase (MET) and UDP glycosyltransferase 1A (UDPGT1A), and repression of complement component C3 (C3), doublesex and mab-3 related transcription factor 1 (DMRT1), and transferrin (TF) in the laboratory experiment. In the field exposure, the transcript levels of CYP1A, DMRT1, MET, GST A-like and UDPGT1A were higher in fishes exposed at the contaminated sites compared to the reference site. Chemical analysis in fish from the laboratory and in situ experiments, and surface sediment from the sewage-contaminated sites revealed relevant levels of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyl (PCBs) and linear alkylbenzenes (LABs). These data reinforce the use of P. vivipara as a sentinel for monitoring environmental contamination in coastal regions.

Functional characterization of copper transporters zCtr1, zAtox1, zAtp7a and zAtp7b in zebrafish liver cell line ZFL

Copper (Cu) is an essential element for all organisms, serving as an enzyme cofactor to maintain cellular activity and vitality. However, Cu homeostasis must be maintained at the physiological and cellular levels as Cu ions can be highly toxic. In mammals, ATP7A is expressed in most tissues, but relatively lower expression is found in the liver, and is responsible for the intestinal uptake of Cu, while ATP7B is highly expressed in the liver, kidneys and placenta, and is responsible for removal of Cu in the liver. CTR1 and ATOX1 are responsible for cellular Cu uptake and intracellular Cu transport, respectively. Here, using a zebrafish liver cell line (ZFL), we studied the cellular functions of four zebrafish Cu transporters. In zebrafish, zAtp7a is expressed mainly in the liver and zAtp7b is expressed mainly in the intestines, different from that of humans which have a high ATP7b level in the liver and high ATP7a level in the intestines. We here found that zctr1 or zatox1 overexpression increased Cu accumulation in ZFL cells. Moreover, zctr1 overexpression made ZFL cells more sensitive to Cu and Zn exposure, and overexpression of zatox1 or zatp7b increased Cu uptake and Cu tolerance in ZFL cells. Overexpression of zatp7a made ZFL cells more sensitive to Zn. Taken together, our findings suggest that zatp7b is responsible for Cu export despite its expression level being much lower than zatp7a in ZFL cells.

Life-time exposure to waterborne copper III: Effects on the energy metabolism of the killifish Poecilia vivipara

Copper ions (Cu) are essential to life maintenance, nonetheless, elevated concentrations can be hazardous. Acute and sub-chronic toxic effects of this metal are well known and are usually related to enzymatic inhibition, elevated ROS production and dysfunction of energy metabolism. Despite that, chronic studies are extremely rare. Therefore, the aim of this study was to assess the effects of chronic exposure to 5, 9 and 20 μg/L Cu (28 ad 345 days) on the energy metabolism and survival of the killifish Poecilia vivipara. To accomplish that, we evaluated the activity of enzymes related to aerobic (pyruvate kinase (PK); citrate synthase (CS)) and anaerobic metabolism (lactate dehydrogenase (LDH)) in whole-body (28 days) or in gills, liver and muscle (345 days) of exposed fish. Additionally, whole-body oxygen consumption was evaluated in fish exposed for 28 days and hepatic and muscular expression of genes involved in mitochondrial metabolism (cox I, II and III and atp5a1) was assessed in animals exposed for 345 days. Finally, final survival was evaluated. Following 28 days, Cu did not affect survival neither enzyme activities. However, increased whole-body oxygen consumption was observed in comparison to control condition. After 345 days, 76.8%, 63.9%, 60.9% and 0% survival were observed for control, 5, 9 and 20 μg/L groups, respectively. Animals exposed to 5 and 9 μg/L had a significant reduction in branchial and muscular LDH activity and in hepatic PK activity. Also, exposure to 9 μg/L significantly increased hepatic CS activity. For gene expression, Cu down-regulated muscular cox II (9 μg/L) and III (5 and 9 μg/L), and up-regulated hepatic atp5a1 (9 μg/L). Findings reported in the present study indicate that chronic exposure to Cu induces tissue-specific responses in key aspects of the energetic metabolism. In gills and muscle, Cu leads to reduced energy production through inhibition of anaerobic pathways and mitochondrial respiratory chain. This effect is paralleled by an increased ATP consumption in the liver, characterized by the augmented CS activity and atp5a1 expression. Finally, reduced PK activity indicate that oxidative stress may be involved with the observed outcomes.