Assessment of genotoxic, mutagenic, and recombinogenic potential of water resources in the Paranaíba River basin of Brazil: A case study

Genotoxicity of surface waters in Brazil

Brazil has abundant surface water resources, huge aquatic biodiversity and is home to 213 million people. Genotoxicity assays are sensitive tools to detect the effects of contaminants in surface waters and wastewaters, as well as to determine potential risks of contaminated waters to aquatic organisms and human health. This work aimed to survey the articles published in 2000-2021 that evaluated the genotoxicity of surface waters within Brazilian territory to unveil the profile and trends of this topic over time. In our searches, we considered articles focused on assessing aquatic biota, articles that conducted experiments with caged organisms or standardized tests in the aquatic sites, as well as articles that transported water or sediment samples from aquatic sites to the laboratory, where exposures were performed with organisms or standardized tests. We retrieved geographical information on the aquatic sites evaluated, the genotoxicity assays used, the percentage of genotoxicity detected, and, when possible, the causative agent of aquatic pollution. A total of 248 articles were identified. There was a trend of increase in the number of publications and annual diversity of hydrographic regions evaluated over time. Most articles focused on rivers from large metropolises. A very low number of articles were conducted on coastal and marine ecosystems. Water genotoxicity was detected in most articles, regardless of methodological approach, even in little-studied hydrographic regions. The micronucleus test and the alkaline comet assay were widely applied with blood samples, mainly derived from fish. Allium and Salmonella tests were the most frequently used standard protocols. Despite most articles did not confirm polluting sources and genotoxic agents, the detection of genotoxicity provides useful information for the management of water pollution. We discuss key points to be assessed to reach a more complete picture of the genotoxicity of surface waters in Brazil.

Using native fish in eco-genotoxic assessment of heavy metal contamination pollution arising from nearby large Brazilian rivers

Worldwide water quality has declined progressively due to continuous pollution of aquatic resources by agrochemicals in particular heavy metals. Fish genotoxicity biomarkers are vital to identify and complement chemical parameters for determining environmental risk of adverse effects. Therefore, it was of interest to examine the eco-genotoxicity attributed to water pollution over different stream sections of Brazilian rivers by using Cichlasoma paranaense (Teleostei: Cichlidae), a neotropical freshwater cichlid fish, as a biological model. Chemical analysis of water and sediments collected from different Brazilian rivers sites demonstrated contamination by metals. Cichlasoma paranaense were collected at a reference location (a permanent water preservation area), maintained in the lab under standard conditions (controlled temperature, lighting, daily feeding, and constant aeration) and exposed to environmental samples of water and sediments. Subsequently, micronucleus (MN) and nuclear abnormalities (NA) frequencies were assessed in erythrocytes obtained from the caudal and gill regions. The highest concentrations of Cu were found in samples from river sites with forest fragmentation attributed to intensive agriculture practices. Similarly, exposure of fish to samples from agricultural areas induced significantly higher number of genotoxic effects. There was no marked difference between the tissues (tail and gill) regarding the observed frequencies of MN and NA. Thus C. paranaense fish served as a reliable model for detecting genotoxic effects, especially when water samples were collected near the discharge of agrochemicals. Evidence indicates that this method be considered for other global river sites which are also exposed to agrochemicals discharges containing Cu.

Human Hazard Assessment Using Drosophila Wing Spot Test as an Alternative In Vivo Model for Genotoxicity Testing-A Review

Genomic instability, one of cancer's hallmarks, is induced by genotoxins from endogenous and exogenous sources, including reactive oxygen species (ROS), diet, and environmental pollutants. A sensitive in vivo genotoxicity test is required for the identification of human hazards to reduce the potential health risk. The somatic mutation and recombination test (SMART) or wing spot test is a genotoxicity assay involving Drosophila melanogaster (fruit fly) as a classical, alternative human model. This review describes the principle of the SMART assay in conjunction with its advantages and disadvantages and discusses applications of the assay covering all segments of health-related industries, including food, dietary supplements, drug industries, pesticides, and herbicides, as well as nanoparticles. Chemopreventive strategies are outlined as a global health trend for the anti-genotoxicity of interesting herbal extract compounds determined by SMART assay. The successful application of Drosophila for high-throughput screening of mutagens is also discussed as a future perspective.

Micronuclei in Fish Erythrocytes as Genotoxic Biomarkers of Water Pollution: An Overview

Freshwater and marine water bodies receive chemical contaminants from industrial, agricultural, urban, and domestic wastes. Eco-genotoxicity assays are useful tools to assess the cumulative genotoxicity of these pollutants. Fish are suitable indicators for biomonitoring of mutagenic and carcinogenic pollution.In this review, we present a complete overview of the studies performed so far using the micronucleus test in peripheral erythrocytes of fish exposed to polluted water. We have listed all the species of fish used and the geographical distribution of the investigations. We have analyzed and discussed all technical aspects of using this test in fish, as well as the advantages and disadvantages of the different experimental protocols. We have reported the results of all studies. This assay has become, for years, one of the simplest, fastest, and most cost-effective for assessing genotoxic risk in aquatic environments. However, there are still several factors influencing the variability of the results. Therefore, we have given indications and suggestions to achieve a standardization of experimental procedures and ensure uniformity of future investigations.

Water pollution affects fish community structure and alters evolutionary trajectories of invasive guppies (Poecilia reticulata)

Anthropogenic habitat alterations have the potential to affect both, ecological dynamics of communities and populations, as well as evolutionary processes within populations. Invasive species may benefit from anthropogenic disturbance, such as water pollution, to which they sometimes seem more resistant than native ones. They also allow investigating evolutionary divergence among populations occurring along pollution gradients. We assessed fish communities at 55 sampling sites in the degraded and heavily overstocked Mutara Rangelands of north-eastern Rwanda (upper Nile drainage), which receive pollution from domestic wastewater and cattle dung. Diverse fish communities became apparent that included invasive guppies (Poecilia reticulata, Poeciliidae), and canonical correspondence analyses found significant differentiation of community structures along several environmental parameters (condensed into principal components), including pollution-effects. As predicted, generalized linear models found guppies to have a higher likelihood of occurrence at polluted sites. Local abundances of guppies, however, decreased at polluted sites. Since guppies are color-polymorphic, and color patterns have a heritable basis, they allow inferences regarding both pollution-induced suppression of male ornamentation (e.g., through xenestrogens) and evolutionary population divergence. We thus quantified different ornament types (numbers and percent body surface cover). ANCOVAs uncovered several weak (based on effect strengths), but statistically significant pollution-effects and interactions with other environmental parameters. The direction of several interaction effects was similar for blue/black and red/orange ornaments, while white/iridescent ornaments responded dissimilarly. As responses differed between ornament types, they likely reflect evolutionary divergence due to site-specific alterations of selective regimes rather than developmental inhibition of male secondary sexual characters. We propose that pollution affects local fitness landscapes resulting, e.g., from predation and mate competition (as a function of local abundances), altogether driving evolutionary divergence of sexually selected traits. This study highlights how human activities not only impact ecological dynamics, but-mediated by altered Eco-Evo dynamics-might change the evolutionary trajectories of populations.

Comparative metal accumulation and toxicogenetic damage induction in three neotropical fish species with distinct foraging habits and feeding preferences

Environmental pollutants affect fish species differently because their routes of exposure make them more critical to a specific group regarding foraging habits or food preferences. However, the association between local problems and environmental conditions makes a particular species more suitable for use in monitoring programs. Thus, this study compared muscle accumulation of metals (Al, Ba, Cr, Cu, Fe, Mn, Ti and Zn) and toxicogenetic damage to three neotropical species from the Itapemirim River Basin (Brazil) with distinct foraging habits and feeding preferences: Geophagus brasiliensis (benthopelagic - omnivorous); Harttia sp. (benthic - detritivorous); and Leporinus copellandii (pelagic - omnivorous). There was seasonal influence on muscle metal concentrations: Ba and Mn concentrations in G. brasiliensis, Cr in Harttia sp. and Zn, Al and Fe in L. copellandii increased during the rainy season. G. brasiliensis was the most sensitive species, since it had a statistically higher prevalence of erythrocytic nuclear abnormalities, which was influenced by seasonality. This result might be an effect of its benthopelagic habits, which favors contact with a larger group of contaminants due to its interaction with both water column and sediment. The present study showed the differential sensitivity of fish species and that the combination of chemical analysis of pollutants with evaluation of toxicogenetic responses helps to choose the best species for field studies.

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.

Toxic effects of ornamental stone processing waste effluents on Geophagus brasiliensis (Teleostei: Cichlidae)

The ornamental stone industry generates considerable amounts of waste (OSPW), which may eventually reach natural environments and impact the local ecosystem. The aim of this study was to compare the toxic effects of two OSPW effluents in Geophagus brasiliensis: i) leachate effluent from a lagoon in an OSPW landfill (LE) and ii) decanted effluent from an ornamental stone processing industry (DE). G. brasiliensis were submitted to acute contamination with both OSPW effluents. After contamination, the gills were extracted for evaluation of histopathological alterations and ion concentration, while the liver underwent catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD) and glutathione s-transferase (GST) enzyme activity analysis. An induced biomarker response (IBRv2) index was determined to correlate the multi-biomarker response in G. brasiliensis. Fish gills exposed to DE showed increased concentration of Ca²⁺, Mg²⁺, Na⁺, and K⁺ when compared to those treated with LE. Histopathological lesions were observed in gills of animals exposed to both effluents. Micronucleus and comet assay were significantly greater in fish exposed to DE, when compared to those contaminated with LE. The evaluation of the enzymatic activity of CAT, GPx and SOD indicate greater oxidative stress in DE and LE-exposed fish, while GST activity was not altered. DE showed an IBRv2 value almost two-times higher in relation to LE, indicating that this waste may present higher toxic potential. The results demonstrate that both contaminants led to substantial toxic effects in G. brasiliensis, although the decanted waste induced the most remarkable responses in G. brasiliensis.

Genotoxicity assessment of polluted urban streams using a native fish Astyanax altiparanae

Water quality has declined globally due to increased contamination of aquatic ecosystems. The use of fish genotoxicity biomarkers may improve and complement parameters for environmental risk assessment. The aim of this study was to assess the genotoxicity of samples collected from streams of the Jordão River, a tributary of the Paranaíba River, Brazil with different levels of metal contamination, utilizing a native fish species to determine the sensitivity and viability of implementing a useful, reliable technique for routine biomonitoring programs. Chemical analysis of water and sediments collected from different sites indicated that a gradient of contamination existed as evidenced by different concentrations of metals detected. After chronic exposure to contaminated samples, micronucleus (MN) frequencies in fish erythrocytes were measured and correlation with environmental parameters determined. Sites where the water concentrations of the metals aluminum (Al), iron (Fe), manganese (Mn), zinc (Zn) and copper (Cu) were high indicating a greater genotoxic potential of these elements. At the samples collected from the urban zone, a gradual increase was found for chromium (Cr), cadmium (Cd) and nickel (Ni) indicative of adverse impacts of discharge of urban effluents. Data demonstrated that Astyanax altiparanae, used in the test, exhibited a reliable sensitivity for detection of genotoxic consequences attributed to exposure to water samples collected near the discharge of industrial and domestic waste.

Mutagenic, recombinogenic and carcinogenic potential of thiamethoxam insecticide and formulated product in somatic cells of Drosophila melanogaster

Thiamethoxam (TMX) belongs to a class of neuro-active insecticides referred as neonicotinoids, while actara^® (AC) is one of the most popular TMX-based products in Brazil. The aim of this study was to evaluate the mutagenic, recombinogenic and carcinogenic potential of TMX and AC insecticides. The mutagenic and recombinogenic effect of TMX and AC were evaluated in vivo by the Somatic Mutation and Recombination Test (SMART) while carcinogenic effects were evaluated through the Test for Detection of Epithelial Tumor Clones (wts test), both in somatic cells of Drosophila melanogaster. In the SMART, third instar larvae from standard (ST) and high bioactivation (HB) crosses were treated with different concentrations of TMX and AC (2.4; 4.8; 9.7 × 10^-4 mM and 1.9 × 10^-3 mM). The results revealed mutagenic effects at the highest concentrations tested in the HB cross. In the test for the detection of epithelial tumor, third instar larvae resulting from the cross between wts/TM3, Sb¹ virgin females and mwh/mwh males were treated with the same concentrations of TMX and AC used in the SMART. No carcinogenic effect was observed at any of the concentrations tested. In this work, the inhibition of the mechanism of repair by homologous recombination was observed in flies exposed to 9.7 × 10^-4 and 1.9 × 10^-3 mM of AC. In conclusion, TMX and AC demonstrated to be a promutagen in the highest concentrations tested.

Biochemical approaches to assess oxidative stress induced by exposure to natural and synthetic dyes in early life stages in zebrafish

Zebrafish early life stages were found to be sensitive to several synthetic dyes widely used in industries. However, as environmental concentrations of such contaminants are often at sublethal levels, more sensitive methods are required to determine early-warning adverse consequences. The aim of this study was to utilize a multibiomarker approach to examine underlying oxidative stress mechanisms triggered by sublethal concentrations of synthetic azo dye Basic Red 51 (BR51), the natural dye erythrostominone (ERY), and its light-degraded product using zebrafish embryos. Biochemical biomarkers included parameters of detoxification and markers of antioxidant system, as well as oxidative damage. Results showed pro-oxidant mechanisms attributed to BR51 and ERY as evidenced by increased glutathione S-transferase (GST) activity, a phase II detoxification enzyme related to reactive oxygen species detoxification. BR51 also elevated total glutathione (GSH+GSSG) levels and catalase activity. However, both dyes induced oxidative damage as evidenced by elevated lipid peroxidation content. In contrast, when the natural dye was photodegraded, no marked effects were observed for all biomarkers assessed. Data indicate that such dyes are pro-oxidants at sublethal concentrations, predominantly involving GSH and/or related enzymes pathway.