Metal and metalloid content, bioavailability and sorption processes in glitter and raw glitter materials and associations with human and ecological risk concerns

BACKGROUND

Microplastics comprise a significant group of emerging environmental contaminants with the capacity to adsorb several contaminants. These, in turn, undergo bioaccumulation and biomagnification processes throughout aquatic trophic chains.

METHODS

Glitter, a microplastic powder composed of a combination of polymers, and raw glitter materials were investigated herein concerning metal and metalloid content, bioavailability, and sorption processes by inductively coupled plasma mass spectrometry (ICP-MS).

RESULTS

Metal and metalloid concentrations were higher in glitter than in raw glitter materials, but all were below the limits established by the Brazilian National Health Surveillance Agency. Elements present in glitter originate mainly from pigments and, thus, depend on glitter color. The bioavailability of the determined elements concerning human skin was assessed. Low desorbed concentrations in solution indicate that glitter does not represent a health risk through dermal contact concerning metal and metalloid contamination. However, several elements were shown to undergo significant desorption and adsorption processes.

CONCLUSION

The findings reported herein indicate seemingly low human health risks from dermal glitter contact but reinforce glitter risks as aquatic environment metal and metalloid transport vectors.

Before the Dam: A Fish-Mercury Contamination Baseline Survey at the Xingu River, Amazon Basin Before the Belo Monte Dam

In the last decades, mega-diverse rivers worldwide (e.g., the Amazon and their tributaries) have experienced several human-driven transformations, although impact assessments oftentimes lack baseline data or reference values to better estimate observed disturbances. Herein, we assessed THg and δ¹⁵N in fish muscle tissue to determine biomagnification processes, also including seasonal assessments, concerning Hg in fish from the Belo Monte reservoir, located on the Xingu River, prior to its impoundment. A total of 312 samples from 19 fish species belonging to distinct feeding guilds were sampled. None presented THg concentrations above the threshold levels of 0.5 μg g^-1 established by the World Health Organization. However, biomagnification was observed (R = 0.8; p < 0.001), also confirmed by a trophic magnification factor of 1.76 for the entire food web. The THg content in the water was less than 0.001 mg L^-1 and only Hemiodus unimaculatus presented seasonal variations for THg. Therefore, at the time of this study, the Xingu River presented low Hg contamination levels in both water and target fish.

Cytosolic and Metallothionein-Bound Hepatic Metals and Detoxification in a Sentinel Teleost, Dules auriga, from Southern Rio de Janeiro, Brazil

Dules auriga, a native Brazilian teleost, was applied as a sentinel species regarding metal contamination at Ilha Grande Bay, previously considered a reference site in Southeastern Brazil. Cytosolic (S50) and metallothionein-bound (HTS50) hepatic iron (Fe), zinc (Zn), copper (Cu), manganese (Mn), cadmium (Cd), and silver (Ag) were determined by inductively coupled plasma optical emission spectrometry (ICP-OES), while metallothionein (MT) concentrations were determined by polarography. Ag concentrations in both cytosolic fractions were below the limit of detection. All other HTS50 metal contents were significantly lower than S50 contents. No significant associations were found for MT. Fe and Mn S50 were positively and moderately correlated to total length, as well as HTS50 Mn, while total weight was correlated to both Mn fractions, suggesting that environmental Mn and Fe concentrations may influence fish growth. A moderate correlation between the condition factor and the S50 Cu fraction was observed, also indicating that Cu may affect fish growth. Inter-element correlations were observed, including between Cd, a toxic element, and Mn and Zn, both essential elements. Calculated molar ratios indicate that both Mn and Zn are in molar excesses compared with Cd, corroborating literature assessments regarding protective Mn and Zn effects against Cd. Lack of MT correlations suggests that metal concentrations may not be high enough to reach an MT induction threshold and that MT variability is probably linked to environmental metal concentrations. Therefore, the increased environmental contaminant levels observed in the study area indicate the need for biomonitoring efforts aiming at the application of efficient mitigation measures.

Ecological Risks of Metal and Metalloid Contamination in the Rio Doce Estuary

The rupture of a mining dam in southeastern Brazil in 2015 was the country's greatest environmental tragedy. In order to evaluate the ecological risks of the mine tailings on the Rio Doce estuary, this study assessed trace metal contamination and sediment quality indices up to 2.9 y after the dam rupture. Surface sediments were collected from 17 stations on the Rio Doce estuary and Cd, Pb, Cr, Zn, Cu, and As concentrations were determined by inductively coupled plasma atomic emission spectroscopy (ICP-OES). Four ecological risk indices (modified contamination degree [mCd], pollution load index [PLI], risk index [RI], and sediment quality guideline quotient [SQG-Q]) suggest a high risk by metal contamination with possible adverse biological effects, with moderate seasonal variability. Based on a precautionary approach, our results support fisheries closures and the need for public health monitoring in the affected areas, and support other studies that suggest chronic metal contamination of the Rio Doce estuary. Integr Environ Assess Manag 2020;16:655-660. © 2020 SETAC.

Metallothionein determination can be applied to learn about aquatic metal pollution and oxidative stress detoxification mechanisms through Problem-based Learning

A simple, repeatable and inexpensive laboratory practice applied to teach and discuss aquatic metal pollution and oxidative stress detoxification mechanisms through biomarker analyses, as well as important ecotoxicology concepts, is presented herein. It has been implemented in a university in Brazil to both undergraduate and Master's and PhD students, indicating usefulness to all these levels. Students learned to detect metallothionein and reduced glutathione concentrations in biological samples and investigate several variables of interest in biomonitoring assessments. In addition, statistical correlations were used to indicate the potential dual role played by MT in aquatic organisms, allowing for biological inferences regarding both aquatic metal pollution and oxidative stress detoxification mechanisms and maturing of ecotoxicological and biomonitoring concepts discussed and presented both theoretically and integrated to the laboratory findings.

Metal-Associated Biomarker Responses in Crabs from a Marine Protected Area in Southeastern Brazil

The environmental quality of a Ramsar wetland site located at the Cananéia-Iguape-Peruíbe Protected Area (CIP-PA), in São Paulo, Brazil, was assessed by geochemical analyses and biomarker assessments (GPx, GST, GSH, GST, MT, LPO, DNA damage) performed in swimming crab Callinectes danae Smith, 1869 organs (posterior and anterior gills and hepatopancreas) to estimate sediment contaminant bioavailability. The results indicated that two sampling stations, PT and PM, exhibited the worst environmental conditions, as sediments collected at both points contained metal contamination, while crabs exhibited significant responses for GPx, GST, and LPO (mostly during winter). Sediment contamination tended to be associated to fine sediments (both seasons) and organic matter (winter). During the summer survey, Pb concentrations in sediments of station PT exceeded the Brazilian Sediment Quality Guidelines (SQGs) and the Canadian Interim Marine Sediment Quality Guidelines. Metal concentrations in sediments sampled in winter were higher compared with summer, with Co, Ni, and Pb exceeding SQGs levels at PT, whereas Co, Ni, Hg, Zn, and Pb exceeded SQGs at PM. Biomarker induction during summer appeared to be caused by natural variables (water salinity and temperature, and molting cycle), whereas oxidative stress and tissue damage during winter appeared to be more clearly linked to metal contamination. Anterior gills presented the clearest signs of seasonal variability, being more responsive to sediment contamination. The results suggest that metals originated from the upper Ribeira de Iguape River are transported toward the estuarine system, causing effects on C. danae individuals. Additionally, seasonality is a strong factor concerning CIP-PA toxicity, since the rainfall regime significantly modifies the freshwater flow and, consequently, estuarine water salinity, suspended particle and metal inputs, as well as the location of depositional areas. Thus, efforts to mitigate CIP-PA contamination should be based on the control of upstream pollution sources.

Role of Sonic hedgehog signaling in cell cycle, oxidative stress, and autophagy of temozolomide resistant glioblastoma

The first-line chemotherapy treatment for Glioblastoma (GBM) - the most aggressive and frequent brain tumor - is temozolomide (TMZ). The Sonic hedgehog (SHH) pathway is involved with GBM tumorigenesis and TMZ chemoresistance. The role of SHH pathway inhibition in the potentiation of TMZ's effects using T98G, U251, and GBM11 cell lines is investigated herein. The combination of GANT-61 and TMZ over 72 hr suggested a synergistic effect. All TMZ-resistant cell lines displayed a significant decrease in cell viability, increased DNA fragmentation and loss of membrane integrity. For T98G cells, G₂ /M arrest was observed, while U251 cells presented a significant increase in reactive oxygen species production and catalase activity. All the cell lines presented acidic vesicles formation correlated to Beclin-1 overexpression. The combined treatment also enhanced GLI1 expression, indicating the presence of select resistant cells. The selective inhibition of the SHH pathway potentiated the cytotoxic effect of TMZ, thus becoming a promising in vitro strategy for GBM treatment.

Hepatic Metal and Metallothionein Levels in a Potential Sentinel Teleost, Dulesauriga, from a Southeastern Brazilian Estuary

The identification of estuarine sentinel species is of paramount importance. The potential of the species Dules auriga sampled from Guanabara Bay, Brazil regarding metal contamination was assessed. Hepatic metallothionein (MT) and Fe, Zn, Cu, Mn, Cd and Ag concentrations were determined in cytosolic fractions (S50 and HT S50) by polarography and ICP-OES, respectively. HT S50 Fe, Mn and Zn were lower than in the S50 fraction, indicating MT-detoxification. MT was correlated to HT S50 Zn, indicating Zn homeostasis. Zn was negatively correlated to weight (TW) and length (TL), suggesting environmental Zn influence. A moderate negative correlation between HT S50 Cu and the condition factor (CF) was observed, indicating that increasing environmental Cu concentrations may decrease D. auriga CF. Several inter-elemental correlations were observed. No MT, TW and TL correlations were found. Thus, MT variability is probably linked to environmental metal concentrations. D. auriga fulfills most sentinel requisites, and MT may be an adequate metal contamination biomarker in this species.

Inihibition of mullet (M. liza) brain acetylcholinesterase activity by in vitro polycyclic aromatic hydrocarbon exposure

Polycyclic aromatic hydrocarbons (PAH) have been reported as acetylcholinesterase (AChE) inibitors, although in vitro studies on PAH effects on AChE activity are scarce and have only been performed using electric eel brain extracts. Thus, this study investigated PAH effects on brain AChE activity in a tropical fish species in Southeastern Brazil, mullet (Mugil liza). Mullet specimens were obtained from Guanabara Bay (N = 20), Rio de Janeiro, Brazil. Brain AChE was extracted and exposed to an environmentally relevant concentration of Pyrene, Chrysene, Phenanthrene, and Naphthalene, and PAH metabolites, 2-Naphthol and 1-OH-Pyrene. AChE activity inhibition was observed, although no difference was observed between high- and low- molecular weight PAH. 2-Naphthol was a less potent AChE inhibitor than Naphthalene, albeit non-significantly. Further studies are required, since only one PAH concentration was used herein. Mullet brain extracts seem to be adequate to assess possible neurotoxic PAH effects on fish AChE.

Biliary and hepatic metallothionein, metals and trace elements in environmentally exposed neotropical cichlids Geophagus brasiliensis

One of the metal detoxifying mechanisms that occurs in fish is metallothionein (MT) induction and metal binding. Hepatic MT induction has been well described, but biliary MT metal detoxification has only recently been described in fish. In this scenario, metal-metal interactions have been increasingly evaluated to further understand the behavior of these contaminants regarding homeostasis and biological functions, as well as their toxic effects. Studies, however, have been mainly conducted concerning the elemental pair Se-Hg, and scarce reports are available concerning other metal pairs. Therefore, this study aimed to evaluate biliary and hepatic MT metal detoxification mechanisms in a territorial neotropical cichlid, Geophagus brasiliensis. Fish were sampled from the anthropogenically impacted estuarine Rodrigo de Freitas Lagoon, located in Southern Rio de Janeiro, and trace elements and MT were determined by inductively coupled plasma mass spectrometry (ICP-MS) and UV-Vis spectrophotometry, respectively, in fish liver and bile. MT in bile were significantly lower than in liver. Significant differences between bile and liver were observed for many trace elements, and, although most were higher in liver, Cd and Ni were significantly higher in bile, indicating efficient excretion from the body via the biliary route. A significant correlation was observed between MT and Fe in bile, and between MT in liver and Cu and Zn in bile. Molar ratio calculations demonstrated protective elements effects against Al, As, Cd, Hg, Pb and V in both bile and liver, as well as some novel interrelationships, indicating the importance of these investigations regarding the elucidation of element detoxifying mechanisms. Furthermore, investigation of other elemental associations may aid in decision-making processes regarding environmental contamination scenarios linked to public health.

Glutathione peroxidase and glutathione S-transferase in blood and liver from a hypoxia-tolerant fish under oxygen deprivation

Liver enzyme activities can be employed as biomarkers, but liver can only be obtained with death of the specimen. On the other hand, blood withdrawal is a non-lethal procedure. Accordingly, the hypothesis of this study is to verify if glutathione peroxidase (GPX) and glutathione S-transferase (GST) activities in blood parallel those in the liver of the hypoxia-tolerant fish, Piaractus mesopotamicus (pacu), submitted to hypoxia conditions. GPX was assayed with H₂O₂ in cytosols from both liver and erythrocytes and exhibited no significant variation, either in erythrocytes or in liver, when comparing pacus under normoxia with those under hypoxia (42 h). GST activity with chloro-dinitrobenzene (CDNB), an artificial substrate suitable for almost all GST isoenzymes, was compared to activity with 4-hydroxy-nonenal (4-HNE), a physiological endogenous substrate. GST activity with CDNB did not change in liver or in erythrocyte cytosols in pacus under hypoxia compared to those under normoxia. On the other hand, a significant decrease in erythrocyte activity with 4-HNE was observed after 42 h of hypoxia in both erythrocytes and liver, which may be a response to increased lipid oxidation in erythrocytes. Erythrocyte GST activity was 3-fold higher with 4-HNE than with CDNB, indicating that 4-HNE is a more appropriate substrate to determine GST activity in pacu erythrocytes.

Investigating heavy metal bioaccumulation by macrofauna species from different feeding guilds from sandy beaches in Rio de Janeiro, Brazil

The relationship between metal accumulation and feeding behavior of macrofauna species is a key concept to understand the bioavailability of different metals in the marine environment. We examined and compared the concentrations of eight heavy metals (Cr, Zn, Pb, Ni, Cu, Cd, Co and V) in different feeding guilds of macrofauna species, from a data set including 68 sandy beaches along the Rio de Janeiro coast. For this purpose, macrofauna species were classified in five feeding guild categories: carnivorous, herbivorous, detritivorous, suspensivorous and filter feeders. The coast of Rio de Janeiro was divided into seven regions according to environmental characteristics and historical human activities. For each region, generalized linear models were adjusted to test for differences between feeding guild abundances. Redundancy Analysis was performed to explore the relationship among the feeding guilds composition and the environmental variables. We found high variability in abundance and composition among feeding guilds, linked with environmental heterogeneity. In general, carnivorous species showed a higher heavy metal concentrations compared to other trophic guilds evaluated. However, bioaccumulation across the feeding guild was not the rule and patterns varied across regions. Our hypothesis is that variations are probably related to the different magnitudes of metal contamination along the coast as also in to the trophic structure found in each beach. This data highlighted the crucial role of the relationship between variability of environmental drivers and bioaccumulation in macrofauna species in sandy beaches ecosystem.

Metal loads and biomarker suite responses in a tropical carnivorous fish indicative of anthropogenic impacts in a Southeastern Brazilian lagoon

Tropical coastal lagoons are highly productive environments exhibiting high biodiversity. However, the use of these ecosystems by local communities is of concern, since this generally leads to environmental degradation. The Imboassica coastal lagoon, located in Macaé city, in Northern Rio de Janeiro, is an important ecosystem in the state, however, already displaying signs of anthropogenic impacts. Carnivorous fish Hoplias malabaricus specimens were sampled from this impacted site, as well as from a reference area. Fish from Imboassica Lagoon presented lower condition factor, lower cholinesterase activity, and higher percentage of erythrocyte micronuclei when compared to fish from the reference site. Metals in fish from Imboassica Lagoon were always higher than Encantada Lagoon, with some seasonal differences, where some metals were higher in the rainy season compared to the dry season in muscle tissue, with the exception of Cu, Fe, Sr, and Zn; and in the liver, except for Ba, Cd, Cr, Ni, and Sr. Cr and Mn in the edible muscle portion of the fish were higher than the limits established by Brazilian and International legislations as permissible for human consumption, thus leading to concerns regarding public health risks for the local population that use fish as their main protein source.

Variation in mercury concentration in juvenile Magellanic penguins during their migration path along the Southwest Atlantic Ocean

The vulnerability of seabirds related to their migratory dynamics is frequently linked to environmental problems along the migration path. In this context, Magellanic penguins (Sphenicus magellanicus) seem to be vulnerable to an extensive range of environmental disturbances during their northward migration along the Atlantic waters of South America, which include by catch, marine debris ingestion, overfishing and environmental contamination. In this study, we investigate mercury accumulation in muscle and hepatic tissues of juveniles penguins collected along the Brazilian coast during three migratory seasonal years (2006, 2008 and 2012) and three areas along a latitudinal gradient. We found significant differences in Hg levels across the years, with higher hepatic Hg levels found in tissues of penguins sampled in 2008. The higher Hg levels in samples of penguins from 2008 might be attributed to variations in body condition or Hg uptake, associated with the trophic imbalance linked to an extreme El Niño event during that year. Significant differences in Hg accumulation across the latitudinal areas were also observed. The penguins sampled at the farthest area from the breeding ground presented the higher levels of Hg and also the poorest body condition. Body condition and other traits may influence the levels of chemical pollutants and decrease the migratory success rate in the juvenile age phase, compromising population dynamics.

The importance of an efficient extraction protocol for the use of fish muscle cholinesterases as biomarkers

Esterase activity found in muscle extracts is useful to evaluate harmful effects of anticholinesterase pollutants. Yet, most procedures applied in the extraction of fish muscle esterases in order to investigate their activity as a biomarker of environmental exposure comprise the homogenization of muscle tissue in low-salt solutions, followed by centrifugation to separate the supernatant as the enzyme source. However, acetylcholinesterase (AChE), the main target in these monitoring efforts, is a membrane-bound protein and is only present in muscle extracts if homogenization is carried out using chaotropic high-salt solutions. In this context, four extraction procedures using muscle tissue from six fish species were evaluated in order to establish a reproducible and reliable AChE assay for the determination of this biomarker. Results indicate that over 80% of AChE activity might be lacking in low-salt supernatants, and that the highest activities are obtained after extraction with solutions containing either 1molL^-1 NaCl or 1molL^-1 NaCl plus 3% Triton X-100, preserving almost 100% esterase activity over acetylthiocholine as substrate after centrifugation. Thus, many studies in the literature suffer from theoretical flaws and report erroneous AChE activity, since typical muscle AChE activity, the end-point biomarker for anticholinesterase pollutants, may have not been consistently assayed.

Correction to: Cryptosporidium Spp. Contamination in Perna perna Mussels Destined for Human Consumption in Southeastern Rio de Janeiro, Brazil

The original version of this article unfortunately contained a mistake.

Cryptosporidium spp. Contamination in Perna perna Mussels Destined for Human Consumption in Southeastern Rio de Janeiro, Brazil

Cryptosporidium spp. has been recognized as an important pathogen. As bivalve mollusks are noted as potential sources of several pathogens due to their consumption as foodstuffs, the aim of this study was to investigate the occurrence of Cryptosporidium spp. oocysts in Perna perna mussels and in seawater samples from a mussel farm in Southeastern Brazil, where mussels are grown directly in the sea, attached to ropes. Oocysts were observed by microscopy and confirmed by an enzyme-linked immunosorbent assay. Oocysts were present in mussel gills and GI tracts, as well as in the seawater. Of the 100 females, 10% and 11% showed contaminated GI tracts and gills, respectively, while this rate was lower in males, at 5% and 8.9%. Oocysts were present in higher amounts in the GI tract compared to gills and water. Contamination of the study area is apparent, leading to public health risks. More in-depth studies are needed, including molecular investigations, to identify Cryptosporidium species in mussels, as well as the implementation of monitoring actions in animals destined for human consumption.

Heavy metal contamination in sandy beach macrofauna communities from the Rio de Janeiro coast, Southeastern Brazil

We evaluated concentrations of eight heavy metals Cr, Zn, Pb, Ni, Cu, Cd, Co and V, in tissues of representative macrofauna species from 68 sandy beaches from the coast of Rio de Janeiro state. The links between contamination levels and community descriptors such as diversity, evenness, density and biomass, were also investigated. Metal concentrations from macrofaunal tissues were compared to maximum permissible limits for human ingestion stipulated by the Brazilian regulatory agency (ANVISA). Generalized linear models (GLM's) were used to investigate the variability in macrofauna density, richness, eveness and biomass in the seven different regions. A non-metric multidimensional scaling analysis (n-MDS) was used to investigate the spatial pattern of heavy metal concentrations along the seven regions of Rio de Janeiro coast. Variation partitioning was applied to evaluate the variance in the community assemblage explained by the environmental variables and the heavy metal concentrations. Our data suggested high spatial variation in the concentration of heavy metals in macrofauna species from the beaches of Rio de Janeiro. This result highlighted a diffuse source of contamination along the coast. Most of the metals concentrations were under the limits established by ANVISA. The variability in community descriptors was related to morphodynamic variables, but not with metal contamination values, indicating the lack of direct relationships at the community level. Concentration levels of eight heavy metals in macrofauna species from 68 sandy beaches on Rio de Janeiro coast (Brazil) were spatially correlated with anthropogenic activities such as industrialization and urbanization.

Mercury, selenium and stable isotopes in four small cetaceans from the Southeastern Brazilian coast: Influence of feeding strategy

Dolphins are good bioindicators of the contamination status of marine ecosystems, since their dietary and habitat plasticity in both coastal and offshore ecotypes provide information on the trace elements levels originated from natural and anthropogenic sources. In this context, this study aimed to investigate provides mercury (Hg), selenium (Se) levels, trophic ecology and feeding environments of four small cetaceans (Tursiops truncatus, Steno bredanensis, Sotalia guianensis and Pontoporia blainvillei) inhabiting the central-northern coast of Rio de Janeiro State, southeastern Brazil. For the latter, δ¹⁵N and δ¹³C stable isotopes were used as indicators in this regard. Stable isotope values indicate that the four studied species have distinctive foraging habitats, coastal and least coastal, and occupy different trophic positions. The significant relationship found between muscle Hg and δ¹⁵N suggests that individual foraging preference remains relatively constant for the studied dolphin species over extended periods. The individual prey size and species are probably responsible for the differences found in Hg and Se concentrations in muscle tissue among all dolphin species. The vulnerable small coastal cetacean, P. blainvillei, which feeds on small teleost fish and squid, presented the lowest muscular Hg concentrations (less than 3.5 μg g^-1 dry wt.). Meanwhile, S. bredanensis is more likely to uptake large amounts of trace elements among the four dolphin species, due to its feeding habits mainly being large offshore fish that accumulate high amounts of trace elements in organs and tissues. Differences found between Hg concentrations in fetus-mother pairs were much higher in S. guianensis than in P. blainvillei, suggesting that maternal contribution of Hg via placenta was more significant for the former.

Differential metallothionein, reduced glutathione and metal levels in Perna perna mussels in two environmentally impacted tropical bays in southeastern Brazil

Mussel farming is an important economic activity in Brazil, and these organisms are consumed by the majority of the population in most coastal zones in the country. However, despite the increasing pollution of aquatic ecosystems in Brazil, little is known about the biochemical activity in mussels in response to metal exposure. In this context, the aim of the present study was to investigate metal and metalloid exposure effects in Perna perna mussels, by determining metal levels, the induction of metallothionein (MT) synthesis, and oxidative stress, in the form of reduced glutathione (GSH) in 3 contaminated areas from the Guanabara Bay in comparison to a reference site, Ilha Grande Bay, both in summer and winter. Metal and metalloid concentrations were also compared to Brazilian and international guidelines, to verify potential health risks to human consumers. Mussels from all sampling sites were shown to be improper for human consumption due to metal contamination, including Ilha Grande Bay, which has previously been considered a reference site. Several statistically significant correlations and seasonal differences were observed between MT, GSH and metals and metalloids in both analyzed tissues. A Discriminant Canonical Analysis indicated that the digestive gland is a better bioindicator for environmental contamination by metals and metalloids in this species and offers further proof that MT variations observed are due to metal exposure and not oxidative stress, since GSH influence for both muscle tissue and the digestive glands was non-significant in this analysis. These results show that P. perna mussels are an adequate sentinel species for metal contamination with significant effects on oxidative stress and metal exposure biomarkers. To the best of our knowledge, this is the first study to report metals, metalloids, MT and GSH levels in the muscle tissue of this species.

Mercury species, selenium, metallothioneins and glutathione in two dolphins from the southeastern Brazilian coast: Mercury detoxification and physiological differences in diving capacity

In the present study, the concentration of trace elements, total mercury (Hg) and selenium (Se) and mercury forms (MeHg, Hginorg and HgSe) in the vulnerable coastal dolphins Pontoporia blainvillei and Sotalia guianensis were appraised and compared, using metallothioneins (MT) and glutathione (GSH) as biomarkers for trace element exposure. The trace element concentrations varied between muscle and liver tissues, with liver of all dolphin specimens showing higher Hg and Se concentrations than those found in muscle. Hg, MeHg and Hginorg molar concentrations showed a clear increase with Se molar concentrations in the liver of both dolphins, and Se concentrations were higher than those of Hg on a molar basis. Se plays a relevant role in the detoxification of MeHg in the hepatic tissue of both dolphins, forming Hg-Se amorphous crystals in liver. In contrast, MT were involved in the detoxification process of Hginorg in liver. GSH levels in P. blainvillei and S. guianensis muscle tissue suggest that these dolphins have different diving capacities. Muscle Hg concentrations were associated to this tripeptide, which protects dolphin cells against Hg stress.

Acute selenium selenite exposure effects on oxidative stress biomarkers and essential metals and trace-elements in the model organism zebrafish (Danio rerio)

Selenium (Se) is an essential trace-element that becomes toxic when present at high concentrations. Little is known regarding Se effects on parameters such as oxidative stress biomarkers. The aim of the present study was to investigate the effects of acute selenium exposure on oxidative stress biomarkers in a model organism, zebrafish (Danio rerio). Fish were exposed to selenium selenite at 1mgL(-1). Reduced glutathione (GSH), and metallothionein (MT) concentrations were determined in liver, kidney and brain, with MT also being determined in bile. Essential metals and trace-elements were also determined by inductively coupled mass spectrometry (ICP-MS) in order to verify possible metal homeostasis alterations. GSH concentrations in liver, kidney and brain increased significantly (1.05±0.03μmolg(-1) ww, 1.42±0.03μmolg(-1) ww and 1.64±0.03μmolg(-1) ww, respectively) in the Se-exposed group when compared to the controls (0.88±0.05μmolg(-1) ww, 0.80±0.04μmolg(-1) ww and 0.89±0.03μmolg(-1) ww for liver, kidney and brain, respectively). MT levels in Se-exposed liver (0.52±0.03μmolg(-1) ww) decreased significantly in comparison to the control group (0.64±0.02μmolg(-1) ww), while levels in bile increased, albeit non-significantly. This is in accordance with previous studies that indicate efficient biliary MT action, leading to a rapid metabolism and elimination of contaminants from the body. Levels in the brain increased significantly after Se-exposure (0.57±0.01μmolg(-1) ww) when compared to the control group (0.35±0.03μmolg(-1) ww) since this organ does not present a detoxification route as quick as the liver-gallbladder route. Several metal and trace-elements were altered with Se-exposure, indicating that excess of selenium results in metal dyshomeostasis. This is the first report on metal dyshomeostasis due to Se-exposure, which may be the first step in the mechanism of action of selenium toxicity, as is postulated to occur in certain major human pathophysiologies.

Trace-elements, methylmercury and metallothionein levels in Magellanic penguin (Spheniscus magellanicus) found stranded on the Southern Brazilian coast

Magellanic penguins have been reported as good biomonitors for several types of pollutants, including trace-elements. In this context, selenium (Se), total mercury, methylmercury, inorganic mercury (Hg(inorg)), cadmium (Cd) and lead (Pb), as well as metallothionein (MT) levels, were evaluated in the feathers, liver and kidney of juvenile Magellanic penguins found stranded along the coast of Southern Brazil. The highest concentrations of all trace-elements and methylmercury were found in internal organs. Concentrations of Cd and Se in feathers were extremely low in comparison with their concentrations in soft tissues. The results showed that both Se and MT are involved in the detoxification of trace-elements (Cd, Pb and Hg(inorg)) since statistically significant relationships were found in liver. Conversely, hepatic Se was shown to be the only detoxifying agent for methylmercury.

Bile and liver metallothionein behavior in copper-exposed fish

The present study analyzed metallothionein (MT) excretion from liver to bile in Nile Tilapia (Oreochromis niloticus) exposed to sub-lethal copper concentrations (2mgL(-1)) in a laboratory setting. MTs in liver and bile were quantified by spectrophotometry after thermal incubation and MT metal-binding profiles were characterized by size exclusion high performance liquid chromatography coupled to ICP-MS (SEC-HPLC-ICP-MS). Results show that liver MT is present in approximately 250-fold higher concentrations than bile MT in non-exposed fish. Differences between the MT profiles from the control and exposed group were observed for both matrices, indicating differential metal-binding behavior when comparing liver and bile MT. This is novel data regarding intra-organ MT comparisons, since differences between organs are usually present only with regard to quantification, not metal-binding behavior. Bile MT showed statistically significant differences between the control and exposed group, while the same did not occur with liver MT. This indicates that MTs synthesized in the liver accumulate more slowly than MTs excreted from liver to bile, since the same fish presented significantly higher MT levels in liver when compared to bile. We postulate that bile, although excreted in the intestine and partially reabsorbed by the same returning to the liver, may also release MT-bound metals more rapidly and efficiently, which may indicate an efficient detoxification route. Thus, we propose that the analysis of bile MTs to observe recent metal exposure may be more adequate than the analysis of liver MTs, since organism responses to metals are more quickly observed in bile, although further studies are necessary.

Polybrominated diphenyl ethers (PBDES) and polychlorinated biphenyls (PCBS) in mussels and two fish species from the estuary of the Guanabara Bay, Southeastern Brazil

The present investigation aimed to analyze PBDE and PCB contamination in mussels (Perna perna) and two commercially important fish species, croaker (Micropogonias furnieri) and mullet (Mugil liza), in the Guanabara Bay, the most important Brazilian estuary, by gas chromatography coupled to mass spectrometry, in order to further knowledge regarding these compounds in the southern hemisphere. This is also the first report of PBDE in this mussel species in the Guanabara Bay. Fish were captured in September (dry season, winter) and March (wet season, summer) 2007 and September 2008. Mussels were collected in August (dry season, winter) 2006, in February (wet season, summer) 2007, and in August 2007 (winter). The results show that all samples showed higher PCB contamination when compared to other ecosystems around the world. On the other hand, PBDEs presented lower concentrations in 41 % of the samples. Croakers presented the highest PCB and PBDE levels, with mullet showing intermediary values and mussels, the lowest.

Enzymatic GST levels and overall health of mullets from contaminated Brazilian Lagoons

Glutathione S-transferase (GST) assays in non-mammalian organisms are usually conducted inappropriately, since no previous standardization of the optimal concentrations of proteins and substrates and adequate pH is conducted. Standardization is a key task to adjust enzyme assays at their kinetically correct maximal initial velocities, if one wants these velocities to indicate the amount of enzyme in a sample. In this paper GST assays were standardized in liver cytosol to compare seasonal GST levels in liver of mullet from two contaminated lagoons in the Rio de Janeiro to those from a reference bay. GST potential as a biomarker of sublethal intoxication in this species was also evaluated. Mullet liver GST levels assayed with substrates that corresponded to three different GST isoenzymes varied throughout the year. The differences indicated that mullets are suffering from sublethal intoxication from contaminants in these lagoons. Seasonal variations of activity were relevant, since these could indicate differences in xenobiotic input into the areas. An analysis of overall mullet health condition using a morphological index (the Fulton Condition Factor) and macroscopic abnormalities corroborated the differences in GST levels, with fish from one of the sites in worse overall health condition showing lower and significantly different FCF when compared to the reference site. Therefore, GST standardized activity levels are useful biomarkers of environmental contamination for mullet.

Alterations in morphometric and organosomatic indices and histopathological analyses indicative of environmental contamination in Mullet, Mugil liza, from Southeastern Brazil

Mullet (Mugil liza) were sampled in five different areas along the Guanabara Bay, southeastern Brazil, classified as non-contaminated, moderately contaminated and contaminated. Morphometric (Fulton condition factor, relative condition factor and weight to length scaling coefficient) and organosomatic (hepatosomatic index) indices of environmental stress were analysed. Fish from the differentially contaminated areas show statistically different Fulton and relative condition factors and hepatosomatic indices, but not the weight to length scaling coefficient. The Kn and the FCF followed the same trend, with fish from São Gonçalo (1.07 ± 0.04 and 0.89 ± 0.03), Itaipu (0.84 ± 0.01 and 0.86 ± 0.01) and the Rodrigo de Freitas Lagoon (1.03 ± 0.01 and 0.87 ± 0.20) showing higher FCFs than fish from Magé (0.96 ± 0.01 and 0.81 ± 0.01). Fish from Itaipu showed significantly higher HSI values than the other sampling sites (1.68 ± 0.07), with fish from Olaria and Ipiranga showing the lowest (1.56 ± 0.12 and 1.60 ± 0.07, respectively).

First-time report of metalloproteinases in fish bile and their potential as bioindicators regarding environmental contamination

Gallbladder bile from 2 fish species, mullet (Mugil liza) and tilapias (Tilapia rendalli), contain substantial matrix metalloproteinases (MMPs). Extensive purification studies were conducted in order to obtain workable samples for SDS-PAGE and zymography analysis. Proteinase activities were assayed by gelatin substrate zymography. Several protein bands were observed, corresponding to molecular weights of 200, 136, 43, 36, 34, 29, 23 and 14 kDa in mullet bile and 179, 97, 79, 61, 54, 45, 36, 33 and 21 kDa in tilapia bile. Specific inhibitor studies were conducted, in which MMPS were inhibited by EDTA and 1,10 phenanthroline, but not by serine and cysteine protease inhibitors, such as phenylmethylsulfonyl fluoride (PMSF) and transepoxysuccinyl-l-leucylamido-l-guanidino butane (E-64), confirming the proteinase identities as MMPs. Differences in proteinase expression were observed in fish from a contaminated and reference site. Some studies regarding MMPs in different fish tissues exist, however this is the first study conducted in fish bile, and their involvement in detoxification processes and organism protection against the effects of aquatic contaminants may be a possibility.