Assessing the pollution and ecotoxicological status of the Iguaçu River, southern Brazil: A review.

The degradation of water resources available for human consumption is increasing with the continuous release of chemicals into aquatic environments and their inefficient removal in wastewater treatment. Several watersheds in Brazil, such as the Iguaçu River, are affected by multiple sources of pollution and lack information about their pollution status. The Iguaçu River basin (IRB) has great socioeconomic and environmental relevance to both the supply of water resources and its considerable hydroelectric potential, as well as for the high rate of endemism of its ichthyofauna. Also, the IRB is home to large conservation units, such as the Iguaçu National Park, recognized by UNESCO as a natural World Heritage Site. Thus, this article discusses the chemical pollution in the IRB approaching: (i) the main sources of pollution; (ii) the occurrence of inorganic and organic micropollutants; (iii) the available ecotoxicological data; and (iv) the socioeconomic impacts in three regions of the upper, middle, and lower IRB. Different studies have reported relevant levels of emerging contaminants, persistent organic pollutants, toxic metals, and polycyclic aromatic hydrocarbons detected in the water and sediment samples, especially in the upper IRB region, associated with domestic and industrial effluents. Additionally, significant concentrations of pesticides and toxic metals were also detected in the lower IRB, revealing that agricultural practices are also relevant sources of chemicals for this watershed. More recently, studies indicated an association between fish pathologies and the detection of micropollutants in the water and sediments in the IRB. The identification of the main sources of pollutants, associated with the distribution of hazardous chemicals in the IRB, and their potential effects on the biota, as described in this review, represent an important strategy to support water management by public authorities for reducing risks to the local endemic biodiversity and exposed human populations. Integr Environ Assess Manag 2024;00:1-26. © 2023 SETAC.

Complex mixtures of pesticides and metabolites modulate the malignant phenotype of murine melanoma B16-F1 cells.

Pesticides use increased worldwide with a record in Brazil. Although several works addressed the effects of pesticides on living organisms, only a few considered their mixture, and even fewer tried to unravel their role in tumoral progression. Due to the relevance of cancer, in the present study, the effects of the mixture of pesticides widely used in Brazil (Glyphosate, 2,4-dichlorophenoxyacetic acid, Mancozeb, Atrazine, Acephate, and Paraquat) and their main metabolites (Aminomethylphosphonic Acid, 2,4-diclorophenol, Ethylenethiourea, Desethylatrazine, Methamidophos, and Paraquat) were investigated on the malignancy phenotype of murine melanoma B16-F1 cells after acute (24 h) and chronic (15 days) exposures. The tested concentrations were based on the Acceptable Daily Intake (ADI) value established by Brazilian legislation. The set of results showed that these chemicals modulate important parameters of tumor progression, affecting the expression of genes related to tumor aggressiveness (Mmp14 and Cd44) and multidrug resistance (Abcb1, Abcc1, and Abcc4), as well as tissue inhibitors of metalloproteinases (Timp1, Timp2, and Timp3). These findings revealed an absence of cytotoxicity but showed modulation of migration, invasion, and colonization capacity of B16-F1 cells. Together, the results point to some negative ways that exposure to pesticides can affect the progression of melanoma and raise a concern related to the increasing trend in pesticide use in Brazil, as the country is one of the major world food suppliers.

Physicochemical and bioinformatic characterization of Oreochromis niloticus vitellogenin as an endocrine disruption biomarker.

Aquatic biota is increasingly being exposed to chemical pollutants due to human activities and the relationship between the level of environmental pollution and fish reproduction is a continuously ongoing issue. The vitellogenin (Vtg) protein synthesis can be induced in the liver of juvenile and male fish after stimulation of the estrogen receptor and therefore, Vtg has been used as a biomarker of xenoestrogen exposure in several fish species. The current study reported the first physicochemical characterization of Vtg from Oreochromis niloticus. Adult male fish were exposed to 17α-ethinylestradiol for Vtg induction. Purified vitellogenin from plasma showed low stability at 25 and 4 °C in saline conditions, and good stability in acidic (low pH) or in heated conditions. The 3D modeling provided useful information on the structure of O. niloticus Vtg showing conserved structural features. According to bioinformatics and experimental results, there are important structural differences between the two chemical forms of Vtg (VtgAb and VtgC) in a phylogenetic context. The present results add information about the development of ecotoxicological immunoassays to study the endocrine disruption in O. niloticus improving the Vtg performance as a biomarker of reproduction in fish.

Exposure to pollutants present in Iguaçu River Southern Brazil affect the health of Oreochromis niloticus (Linnaeus, 1758): Assessment histological, genotoxic and biochemical.

Urban sewage is a source of major contamination in aquatic systems and contributes to environmental and human health disturbances. This study investigates the effects of sewage-polluted waters from Iguaçu River on the health of juvenile Oreochromis niloticus. Two hundred four specimens were exposed to riverine water in four groups: no diluted, 25 and 50 % diluted water and a control group without tested water for 72 days. Biological samples were obtained for histopathological, neurotoxicity, antioxidant defenses, genotoxicity, metallothionines expression and polycyclic aromatic hydrocarbons (PAHs) metabolites. The results showed histopathological alterations in liver and gills, genotoxic alteration in erythrocytes, reduction of acetylcholinesterase activity in brain and muscle, activation of antioxidant defenses in the liver, recruitment of metals by metallothionein and the detection of PAHs metabolites in bile. These results demonstrate that juveniles of O. niloticus are susceptible to Iguaçu River exposure water and they can be used as indicator of water quality.

Behavioral and neurochemical effects in mice after one-generation exposure to low doses of manganese: Focus on offspring development.

The risk of exposure to toxic metals is a known concern to human populations. The overexposure to Mn can lead to a pathological condition, with symptoms similar to Parkinson's disease. Although toxicity of Mn has been reported, studies in neonates are scarce but necessary, as Mn can cross biological barriers. The present study evaluated if chronic perinatal exposure to Mn at low doses lead to neurotoxic effects in mice, after direct and indirect exposure. Couples of mice were exposed to Mn (0.013, 0.13, and 1.3 mg kg-1.day-1) for 60 days prior to mating, as well as during gestation and lactation. The offspring was distributed into two groups: animals that were not exposed after weaning - parental exposure only (PE); and animals subject to additional 60-day exposure through gavages after weaning - parental and direct exposure (PDE). Neurological effects were evaluated by Mn quantification, behavior tests and biochemical markers in the brain. PDE animals had alterations in short/long-term memory and increased anxiety-like behavior. Exposure to Mn triggered a decrease of glutathione-s-transferase and increase of cholinesterase activity in different regions of the brain. These findings highlight the risk of exposure to low doses of Mn over a generation and at early stages of development.

Micropollutants impair the survival of Oreochromis niloticus and threat local species from Iguaçu River, Southern of Brazil.

The wastewater contamination of urban rivers is a concern for biodiversity and a consequence from poor urban conservation policies. In the current study, the impact of urban and industrial activities was investigated in Iguaçu river (Southern Brazil) using juvenile Oreochromis niloticus, after trophic and chronic exposure (25, 50 and 100 %), over 81 days. After exposure liver, gills, gonads, brain, muscle, and blood were sampled for chemical, biochemical, histopathological, genotoxic and molecular analyses. Water levels of persistent organic pollutants such as polychlorinated biphenyls, organochlorine pesticides, polycyclic aromatics hydrocarbon (PAHs) and metals were investigated. The redox unbalance, histopathological and increase in vitellogenin expression in fish revealed both the bioavailability of micropollutants and their harmful effects. According to the results, the level of Iguaçu river pollution negatively impacts the health of O. niloticus revealing and highlighting the risk of this pollution exposure to biota and human populations.

Cytotoxicity of bismuth nanoparticles in the murine macrophage cell line RAW 264.7.

A promising use of bismuth nanoparticles (BiNPs) for different biomedical applications leads to a search for the elucidation of their toxicity mechanisms, since toxicity studies are still at early stage. In the current study, cytotoxic effects of BiNPs produced by laser ablation in solution (LASiS) was investigated in the murine macrophage line RAW 264.7. The cells were exposed to 0.01-50 µg ml-1 of BiNPs for 24 and 48 h and then cytotoxicity assays were performed. Decrease of MTT conversion to formazan and of cell attachment were observed with no effects on cell proliferation. No loss of membrane integrity or significant changes of ROS and RNS levels were observed in exposed cells. Foremost, increased phagocytic activity and DNA repair foci occurred for cells exposed to BiNPs. These effects are important findings that must be considered in the case of biomedical application of BiNPs, since inappropriate macrophages activation and inactivation may lead to immunotoxicity. Bismuth nanoparticles (BiNPs) produced by laser ablation in solution and stabilized with BSA decrease enzyme-dependent MTT conversion to formazan and increase phagocytic activity and DNA repair foci in murine macrophage line RAW 264.7 when exposed to 50 µg ml-1. These effects are findings that should be considered in the case of biomedical application of BiNPs, since inappropriate macrophages activation and inactivation may lead to immunotoxicity.

Evaluation of Mn exposure in the male reproductive system and its relationship with reproductive dysfunction in mice.

Manganese (Mn) is essential for animal development and homeostasis. However, anthropogenic activities increase the concentration of Mn in the environment and lead to increased risk of exposure to high doses of the metal. Thus, this study aimed to evaluate the effect of high doses of Mn on the male reproductive system of swiss mice. The 22-day old mice were randomly sorted into four groups and exposed to 0 (control), 15, 30 and 60 mg of MnCl2/kg/day, via daily gavages for 45 days. After the exposure, the mice were euthanized and sperm, hormonal and oxidative stress endpoints were evaluated in the testis, seminal vesicle and hypothalamus. Exposure to Mn promoted weight reduction of androgen-dependent organs, as well as alteration of the levels of fecal androgenic metabolites. Sperm parameters were drastically affected in all treated groups and the antioxidants tested (catalase and glutathione-disulfide reductase activities, and non-protein thiols content) decreased in the testis. However, only a few endpoints were altered in the seminal vesicle. For the hypothalamus, there was a reduction in acetylcholinesterase activity, suggesting a neurotoxic potential of Mn. In conclusion, Mn may affect the hypothalamic-gonadal axis by impairing the development of androgen-dependent organs, testicular redox status and Leydig cell maturation.

Co-exposure to silver nanoparticles and cadmium induce metabolic adaptation in HepG2 cells.

Although multiple studies have reported the toxicological effects and underlying mechanisms of toxicity of silver nanoparticles (AgNP) in a variety of organisms, the interactions of AgNP with environmental contaminants such as cadmium are poorly understood. We used biochemical assays and mass spectrometry-based proteomics to assess the cellular and molecular effects induced by a co-exposure of HepG2 cells to AgNP and cadmium. Cell viability and energy homeostasis were slightly affected after a 4-h exposure to AgNP, cadmium, or a combination of the two; these endpoints were substantially altered after a 24-h co-exposure to AgNP and cadmium, while exposure to one of the two contaminants led only to minor changes. Proteomics analysis followed the same trend: while a 4-h exposure induced minor protein deregulation, a 24-h exposure to a combination of AgNP and cadmium deregulated 43% of the proteome. The toxicity induced by a combined exposure to AgNP and cadmium involved (1) inactivation of Nrf2, resulting in downregulation of antioxidant defense and proteasome-related proteins, (2) metabolic adaptation and ADP/ATP imbalance, and (3) increased protein synthesis possibly to reestablish homeostasis. The adaptation strategy was not sufficient to restore ADP/ATP homeostasis and to avoid cell death.

Brain effects of manganese exposure in mice pups during prenatal and breastfeeding periods.

Manganese (Mn) is a trace element essential for brain development and functioning of the central nervous system. However, there is a lack of information concerning the neurotoxicity of Mn under realistic doses in early stages of development, though excess of Mn results in a progressive disorder of the nervous system called manganism. In the current study, adult mice were exposed to three doses of Mn for 60 days through daily gavages, while mice pups were exposed to the same Mn doses during developmental period (gestational and breast-feeding). From the latter group of mice, a group was exposed for more 60 days to the same Mn doses. Chemical analysis revealed a dose-dependent bioaccumulation of Mn in mice's brain. Biochemical parameters revealed that (1) Mn affects non-protein thiol levels, glutathione S-tranferase and acetylcholinesterase activities, as well as the levels of oxidized lipids and proteins in mice brain, though lipids and proteins alterations were found only after exposure to high and unrealistic doses; (2) Realistic doses of Mn affects the activity of brain AChE and finally; (3) Pups' brain were affected by Mn even whether only the parental females had been previously exposed. The current study shows evidences of chemical stress in mice exposed to Mn during the early period of development and an efficient mechanism of Mn elimination under higher doses. These findings open new lines of investigation regarding manganese toxicity in vertebrates mainly in the early stages of development.

Mixtures of benzo(a)pyrene, dichlorodiphenyltrichloroethane and tributyltin are more toxic to neotropical fish Rhamdia quelen than isolated exposures.

The effects of benzo(a)pyrene (BaP), dichlorodiphenyltrichloroethane (DDT) and tributyltin (TBT) association were investigated through a multi-biomarker approach. Ten Rhamdia quelen fish per group were exposed through intraperitoneal injections either to BaP (0.3; 3 or 30 mg kg(-1)), DDT or TBT (0.03; 0.3 or 3 mg kg(-1)) or BaP/DDT, BaP/TBT, DDT/TBT or BaP/DDT/TBT on their lowest doses. The experiments were divided in acute (one dose, 5-day) and sub-chronic (3 doses, 15-day). Control groups received an equal volume of PBS or canola oil (1 ml kg(-1)). The three tested contaminants altered AChE activity in brain and muscle in similar ways; the mixtures antagonized the increase evoked by the contaminants alone. BaP and TBT increased GSH content and mixtures reduced it. GPx activity was increased by DDT and TBT in the 15-day experiment and reduced by the mixtures. BaP increased GST activity in sub-chronic experiment while TBT reduced it in the acute experiment. BaP/TBT increased GST activity compared to all groups; the other mixtures reduced it compared to BaP or DDT in the 5-day experiment. BaP, DDT and TBT increased δ-ALAd activity mainly in acute exposure; the mixtures also increased δ-ALAd compared to DDT or TBT in 5 and 15-day. BaP, TBT and BaP/DDT decreased LPO in the acute experiment. In the sub-chronic experiment DDT/TBT increased LPO when compared to TBT. None of the contaminants alone altered PCO, but all mixtures increased it compared to one or another contaminant. Contaminants isolated had a more acute effect in ALT plasma level; their lowest dose, which had no effect alone, in combination has led to an increase of this enzyme, especially after 15 days. DDT increased AST in the acute and sub-chronic experiments, while TBT did the same in the latter. DDT/TBT decreased AST opposing the effect of the contaminants alone in the 5-day experiment. Hepatic lesions index could be explained by a more acute effect of the contaminants alone or combined and by activation of cell defenses after the sub-chronic exposure. TBT increased melanomacrophages counting in the 5-day experiment and the mixtures increased it in the 5 and 15-day experiments. Overall, the majority of the biomarkers pointed to a more toxic effect when these contaminants were combined, leading to unexpected toxicities compared to individual exposure scenarios. These findings are relevant considering environmental exposure conditions, since organisms are often exposed to different combinations of contaminants.

Oxidative Damage in the Aging Heart: an Experimental Rat Model.

INTRODUCTION: Several theories have been proposed to explain the cause of 'aging'; however, the factors that affect this complex process are still poorly understood. Of these theories, the accumulation of oxidative damage over time is among the most accepted. Particularly, the heart is one of the most affected organs by oxidative stress. The current study, therefore, aimed to investigate oxidative stress markers in myocardial tissue of rats at different ages. METHODS: Seventy-two rats were distributed into 6 groups of 12 animals each and maintained for 3, 6, 9, 12, 18 and 24 months. After euthanasia, the heart was removed and the levels of non-protein thiols, lipid peroxidation, and protein carbonylation, as well as superoxide dismutase and catalase activities were determined. RESULTS: Superoxide dismutase, catalase activity and lipid peroxidation were reduced in the older groups of animals, when compared with the younger group. However, protein carbonylation showed an increase in the 12-month group followed by a decrease in the older groups. In addition, the levels of non-protein thiols were increased in the 12-month group and not detected in the older groups. CONCLUSION: Our data showed that oxidative stress is not associated with aging in the heart. However, an increase in non-protein thiols may be an important factor that compensates for the decrease of superoxide dismutase and catalase activity in the oldest rats, to maintain appropriate antioxidant defenses against oxidative insults.

Mercury distribution in target organs and biochemical responses after subchronic and trophic exposure to neotropical fish Hoplias malabaricus.

In the present study, we investigated the mercury distribution, mercury bioaccumulation, and oxidative parameters in the Neotropical fish Hoplias malabaricus after trophic exposure. Forty-three individuals were distributed into three groups (two exposed and one control) and trophically exposed to fourteen doses of methylmercury each 5 days, totalizing the doses of 1.05 µg g⁻¹ (M1.05) and 10.5 µg g⁻¹ (M10.5 group). Autometallography technique revealed the presence of mercury in the intestinal epithelia, hepatocytes, and renal tubule cells. Mercury distribution was dose-dependent in the three organs: intestine, liver, and kidney. Reduced glutathione concentration, glutathione peroxidase, catalase, and glutathione S-transferase significantly decreased in the liver of M1.05, but glutathione reductase increased and lipid peroxidation levels were not altered. In the M10.5, most biomarkers were not altered; only catalase activity decreased. Hepatic and muscle mercury bioaccumulation was dose-dependent, but was not influenced by fish sex. The mercury localization and bioaccumulation corroborates some histopathological findings in this fish species (previously verified by Mela et al. in Ecotoxicol Environ Saf 68:426-435, 2007). However, the results of redox biomarkers did not explain histopathological findings previously reported in M10.5. Thus, fish accommodation to the stressor may reestablish antioxidant status at the highest dose, but not avoid cell injury.

Mercury and DDT exposure risk to fish-eating human populations in Amazon.

In order to investigate the potential risk of mercury and DDTs exposure to fish-eating human populations in Samuel Reservoir, not affected directly by gold-mining activities, the axial muscle of Cichla monoculus was analyzed. Twenty-nine and thirty adults individuals were collected respectively on February (rainy season) and August (dry season) 2007. The specimens were sacrificed by spinal section before sex identification, body weight and total length determination. For total mercury, DDT and DDE quantifications and cholinesterase activity samples of the axial muscle were frozen at -20°C, and for histopathological studies gill and liver were fixed in ALFAC solution for 16 h. A value of 48.2% and 33% of the individuals, respectively from rainy and dry seasons, presented mercury concentrations higher than the maximum established for safe human consumption (0.5 µg g⁻¹) by World Health Organization. A positive correlation between body weight and Hg concentration was observed only in individuals from the rainy season, but no correlation was observed to DDT and DDE from both seasons. Differently from that observed to mercury, DDT levels presented a significant difference between both studied seasons, but no correlation was observed for both mercury and DDTs and sex. The levels of DDTs in muscle of C. monoculus are under the maximum established by FAO-Alimentarius CODEX and Swedish Food Regulation for human consumption. The histopathological and neurotoxic findings showed that the wild population of fish is affected by chronic exposure to mercury, meaning risk also to fish-eating populations. Finally, the results showed that C. monoculus is an important vehicle for human exposure to mercury and DDTs in Samuel Reservoir and that it is necessary a continuous biomonitoring of the levels of both pollutants in order to manage the risk of exposure to human populations.