Sediment toxicity assessment using zebrafish (Danio rerio) as a model system: Historical review, research gaps and trends

Genotoxicity and cytotoxicity in male reproductive cells caused by sediment pollutants

In recent years, mounting evidence has highlighted a global decline in male semen quality, paralleling an increase in male infertility problems. Such developments in the male reproductive system are likely due to a range of environmental factors, which could negatively affect the outcomes of pregnancy, reproductive health, and the well-being of fetuses. Different environmental contaminants ultimately accumulate in riverbed sediments due to gravity, so these sediments are frequently considered hotspots for pollutants. Therefore, understanding the detrimental effects of river sediment pollution on human reproductive health is crucial. This study indicates male germ cells' high vulnerability to environmental contaminants. There is a strong positive correlation between the concentration of complex accumulated pollutants from human activities and the reproductive toxicity observed in human testicular embryonic cell lines NCCIT and NTERA-2. This toxicity is characterized by increased levels of reactive oxygen species, disruption of critical cellular functions, genotoxic impacts, and the induction of cell apoptosis. This research marks a significant step in providing in vitro evidence of the damaging effects of environmental pollutants on the human male germline.

Impact of antiparasitic used in livestock: effects of ivermectin spiked sediment in Prochilodus lineatus, an inland fishery species of South America

Ivermectin (IVM) is a widely used antiparasitic. Concerns have been raised about its environmental effects in the wetlands of Río de la Plata basin where cattle have been treated with IVM for years. This study investigated the sublethal effects of environmentally relevant IVM concentrations in sediments on the Neotropical fish Prochilodus lineatus. Juvenile P. lineatus were exposed to IVM-spiked sediments (2 and 20 µg/Kg) for 14 days, alongside a control sediment treatment without IVM. Biochemical and oxidative stress responses were assessed in brain, gills, and liver tissues, including lipid damage, glutathione levels, enzyme activities, and antioxidant competence. Muscle and brain acetylcholinesterase activity (AChE) and stable isotopes of 13C and 15N in muscle were also measured. The lowest IVM treatment resulted in an increase in brain lipid peroxidation, as measured by thiobarbituric acid reactive substances (TBARs), decreased levels of reduced glutathione (GSH) in gills and liver, increased catalase activity (CAT) in the liver, and decreased antioxidant capacity against peroxyl radicals (ACAP) in gills and liver. The highest IVM treatment significantly reduced GSH in the liver. Muscle (AChE) was decreased in both treatments. Multivariate analysis showed significant overall effects in the liver tissue, followed by gills and brain. These findings demonstrate the sublethal effects of IVM in P. lineatus, emphasizing the importance of considering sediment contamination and trophic habits in realistic exposure scenarios.

Metal-contaminated sediment toxicity in a highly impacted Neotropical river: Insights from zebrafish embryo toxicity assays

The Fundão dam collapse was one of the largest mining-related disasters globally. It resulted in the release of mining tailings containing heavy metals, which contaminated the Doce River in southeastern Brazil. This study assessed the effects of acute exposure of Danio rerio embryos to sediments contaminated by mine tailings six years after the Fundão dam collapse. The study sites included P2, P3, and P4 in the upper Doce River, as well as site P1 on the Piranga River, an uncontaminated river. Sediment samples were analyzed for 10 metals/metalloid by atomic absorption spectrometry. In the assays, embryos were exposed to sediment from P1-P4 sites, and uncontaminated quartz was used as control sediment. Various biomarkers were applied to assess biological responses, and the integrated biomarker response (IBR) index was calculated for each site. Sediment samples revealed elevated levels of As, Cr, Cu, Hg, and Ni beyond Brazilian legislation limits. At 96-h exposure, embryo mortality rates exceeded 20% in P1, P2, and P3, higher than the control and P4 (p < 0.0001). Hatching rates ranged from 60 to 80% in P1, P2, and P3, lower than the control and P4 (p < 0.001). Larvae exposed to P2 sediment (closest to the Fundão dam) exhibited skeletal, physiological, and sensory malformations. Neurotoxicity was indicated by increased acetylcholinesterase activity and reduced spontaneous movements in embryos exposed to Doce River sediment. Contamination also increased metallothionein and heat shock protein 70 levels, along with changes in cell proliferation and apoptosis. Principal component analysis showed a good correlation between metals/metalloid in the sediment and larval morphometric endpoints. The IBR index highlighted suitable biomarkers for monitoring metal contamination in fish embryos. Overall, our findings suggest that sediment toxicity following the Fundão dam failure may compromise the sustainability of fish communities in the Doce River.

To spread or not to spread? Assessing the suitability of sewage sludge and other biogenic wastes for agriculture reuse

Sewage sludge (biosolids) management represents a worldwide issue. Due to its valuable properties, approximately one half of the EU production is recovered in agriculture. Nevertheless, growing attention is given to potential negative effects deriving from the presence of harmful pollutants. It is recognized that a (even very detailed) chemical characterization is not able to predict ecotoxicity of a mixture. However, this can be directly measured by bioassays. Actually, the choice of the most suitable tests is still under debate. This paper presents a multilevel characterization protocol of sewage sludge and other organic residues, based on bioassays and chemical-physical-microbiological analyses. The detailed description of the experimental procedure includes all the involved steps: the criteria for selecting the organic matrices to be tested and compared; the sample pre-treatment required before the analyses execution; the chemical, physical and microbiological characterisation; the bioassays, grouped in three classes (baseline toxicity; specific mode of action; reactive mode of action); data processing. The novelty of this paper lies in the integrated use of advanced tools, and is based on three pillars:•the direct ecosafety assessment of the matrices to be reused.•the adoption of innovative bioassays and analytical procedures.•the original criteria for data normalization and processing.

Effects of sodium dodecylbenzene sulfonate (SDBS) on zebrafish (Danio rerio) gills and blood

Sodium dodecylbenzene sulfonate (SDBS) is an important surfactant used as a cleaning agent and industrial additive to remove unwanted chemicals which have been detected in the aquatic environment. The aim of this study was to examine the toxicological potential of SDBS on the gills of adult male zebrafish (Danio rerio) exposed to this chemical. For the 96 hr acute exposure, fish were divided into three groups: control, 0.25 mg/L, and 0.5 mg/L of SDBS. After the experiment, morphophysiological analyses (gill histopathology and histochemistry), oxidative stress (determination of gill activities of superoxide dismutase (SOD) and catalase (CAT)), and hematological analyses (leukocyte differentiation) were conducted. Data demonstrated that SDBS at both tested concentrations altered the histopathological index and initiated circulatory disturbances, as well as adverse, progressive, and immunological changes in the gills. In the 0.5 mg/L group, SOD activity decreased significantly, but CAT activity was not altered. Prominent blood changes observed in this group were neutrophilia and lymphocytosis. The number of mucous and chloride cells increased significantly in both groups. Taken together, our findings demonstrated that exposure of D. rerio to SDBS, even for 96 hr, produced adverse morphological and hematological effects associated with a reduction in SOD activity. Our findings indicate that exposure of aquatic species to the anionic surfactant SDBS may lead to adverse consequences associated with oxidative stress. Therefore, this study highlights the risks that this substance may pose to aquatic ecosystems and emphasizes the need for further investigations and strict regulations on its disposal.

Cold plasma turns mixed-dye-contaminated wastewater bio-safe

The excessive and uncontrollable discharge of diverse organic pollutants into the environment has emerged as a significant concern, presenting a substantial risk to human health. Among the advanced oxidation processes used for the purification of wastewater, cold plasma technology is superior in fast and effective decontamination but often fails facing mixed pollutants. To address these issues, here we develop the new conceptual approach, plasma process, and proprietary reactor that ensure, for the first time, that the efficiency of treatment (114.7%) of two mixed organic dyes, methylene blue (MB) and methyl orange (MO), is higher than when the two dyes are treated separately. We further reveal the underlying mechanisms for the energy-efficient complete degradation of the mixed dyes. The contribution of plasma-induced ROS and the distinct degradation characteristics and mechanism of pollutants in mixed treatment are discussed. The electron transfer pathway revealed for the first time suggest that the mixed pollutants reduce the overall redox potentials and facilitate electron transfer during the plasma treatment, promoting synergistic degradation effects. The integrated frameworks including both direct and indirect mechanisms provide new insights into the high-efficiency mixed-contaminant treatment. The degradation products for mixed degradation are revealed based on the identification of intermediate species. The plasma-treated water is proven safe for living creatures in waterways and sustainable fishery applications, using in vivo zebrafish model bio-toxicity assay. Overall, these findings offer a feasible approach and new insights into the mechanisms for the development of highly-effective, energy-efficient technologies for wastewater treatment and reuse in agriculture, industry, and potentially in urban water networks.

Plastic microfibers as a risk factor for the health of aquatic organisms: A bibliometric and systematic review of plastic pandemic

Plastic microfibers (PMFs) are emerging pollutants widely distributed in the environment. In the early 2020s, the need for personal protection due to the COVID-19 pandemic led to increased consumption of plastic materials (e.g., facemasks and gloves) and ultimately to increased plastic pollution, especially by PMFs. The PMFs present in the environment may be released in this form (primary particles) or in larger materials, that will release them as a result of environmental conditions. Although a considerable number of studies have been addressing the effects of microplastics, most of them studied round particles, with fewer studies focusing on PMFs. Thus, the current study aimed to summarize and critically discuss the available data concerning the ecotoxicological impact of PMFs on aquatic organisms. Aquatic organisms exposed to PMFs showed accumulation, mainly in the digestive tract, and several toxic effects, such as DNA damage, physiological alterations, digestive damage and even mortality, suggesting that PMFs can pose a risk for the health of aquatic organisms. The PMFs induced toxicity to aquatic invertebrate and vertebrate organisms depends on size, shape, chemical association and composition of fibers. Regarding other size range (nm) of plastic fibers, the literature review highlighted a knowledge gap in terms of the effects of plastic nanofibers on aquatic organisms. There is a knowledge gap in terms of the interaction and modes of action of PMFs associated with other pollutants. In addition, studies addressing effects at different trophic levels as well as the use of other biological models should be considered. Overall, research gaps and recommendations for future research and trends considering the environmental impact of the COVID-19 pandemic are presented.

NMR-based metabolomics applied to ecotoxicology with zebrafish (Danio rerio) as a prominent model for metabolic profiling and biomarker discovery: Overviewing the most recent approaches

Metabolomics is an innovative approach used in the medical, toxicological, and biological sciences. As an interdisciplinary topic, metabolomics and its relation with the environment and toxicological research are extensive. The use of substances, such as drugs and pesticides, contributes to the continuous releasing of xenobiotics into the environment, harming organisms and their habitats. In this context, fish are important bioindicators of the environmental condition and have often been used as model species. Among them, zebrafish (Danio rerio) presents itself as a versatile and straightforward option due to its unique attributes for research. Zebrafish proves to be a valuable model for toxicity assays and also for metabolomics profiling by analytical tools. Thus, NMR-based metabolomics associated with statistical analysis can reasonably assist researchers in critical factors related to discovering and validating biomarkers through accurate diagnosis. Therefore, this review aimed to report the studies that applied zebrafish as a model for (eco)toxicological assays and essentially utilized NMR-based metabolomics analysis to assess the biochemical profile and thus suggest the potential biological marker.

Liquiritin exhibits anti-acute lung injury activities through suppressing the JNK/Nur77/c-Jun pathway

BACKGROUND

Licorice (Glycyrrhiza uralensis Fisch.), a well-known traditional medicine, is traditionally used for the treatment of respiratory disorders, such as cough, sore throat, asthma and bronchitis. We aim to investigate the effects of liquiritin (LQ), the main bioactive compound in licorice against acute lung injury (ALI) and explore the potential mechanism.

METHODS

Lipopolysaccharide (LPS) was used to induce inflammation in RAW264.7 cells and zebrafish. Intratracheal instillation of 3 mg/kg of LPS was used for induction an ALI mice model. The concentrations of IL-6 and TNF-α were tested using the enzyme linked immunosorbent assay. Western blot analysis was used to detect the expression of JNK/Nur77/c-Jun related proteins. Protein levels in bronchoalveolar lavage fluid (BALF) was measured by BCA protein assay. The effect of JNK on Nur77 transcriptional activity was determined by luciferase reporter assay, while electrophoretic mobility shift assay was used to examine the c-Jun DNA binding activity.

RESULTS

LQ has significant anti-inflammatory effects in zebrafish and RAW264.7 cells. LQ inhibited the expression levels of p-JNK (Thr183/Tyr185), p-Nur77 (Ser351) and p-c-Jun (Ser63), while elevated the Nur77 expression level. Inhibition of JNK by a specific inhibitor or small interfering RNA enhanced the regulatory effect of LQ on Nur77/c-Jun, while JNK agonist abrogated LQ-mediated effects. Moreover, Nur77-luciferase reporter activity was suppressed after JNK overexpression. The effects of LQ on the expression level of c-Jun and the binding activity of c-Jun with DNA were attenuated after Nur77 siRNA treatment. LQ significantly ameliorated LPS-induced ALI with the reduction of lung water content and BALF protein content, the downregulation of TNF-α and IL-6 levels in lung BALF and the suppression of JNK/Nur77/c-Jun signaling, which can be reversed by a specific JNK agonist.

CONCLUSION

Our results indicated that LQ exerts significant protective effects against LPS-induced inflammation both in vivo and in vitro via suppressing the activation of JNK, and consequently inhibiting the Nur77/c-Jun signaling pathway. Our study suggests that LQ may be a potential therapeutic candidate for ALI and inflammatory disorders.

Ecological risk assessment and corrective actions for dioxin-polluted sediment in a chemical plant's brine water storage pond

Despite the known high toxicity of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs, or dioxins), there are few case studies of PCDD/Fs contamination in sediment and there remains much to learn regarding their ecological impact. In this study, we performed an environmental risk assessment of a brine water storage pond near a chemical plant with high PCDD/Fs pollution potential before and after corrective actions. We found PCDD/F accumulation in the pond's fish and crab from the brine water storage pond, and the PCDD/Fs concentrations in biota higher than Taiwan's food safety standard (3.5 pg-TEQ/g). Furthermore, we found a high degree of pollution using different indices, including contamination factor (CF), modified degree of contamination (mCd), and pollution index (PI), in the pond's sediment. Before corrective actions, we also found high risk in the PCDD/F contamination in the sediment using various biological risk indices, including potential ecological risk index (RI) and risk quotient (RQ). After the corrective actions, including institutional/engineering control and remediation, the CF, mCd, and PI had decreased by 20-41 % and RI and RQ by 41-56 %. In addition, despite the slight reduction of pollution and risk index values in the whole pond, significant reduction was observed in the sediment of highly polluted area A owing to the lower disturbing suction dredging. In conclusion, the corrective actions used in this study helped decrease the pollution and ecological risk associated with this site's PCDD/Fs polluted sediment to some extent, suggesting that contamination and risk could be reduced to acceptable levels if these corrective actions are continued.

Morphological and Functional Alterations Induced by Two Ecologically Relevant Concentrations of Lead on Danio rerio Gills

Lead (Pb), due to its high toxicity and bioaccumulation tendency, is one of the top three pollutants of concern for both humans and wildlife and occupies second place in the Priority List of Hazardous Substances. In freshwater fish, Pb is mainly absorbed through the gills, where the greatest accumulation occurs. Despite the crucial role of gills in several physiological functions such as gas exchange, water balance, and osmoregulation, no studies evaluated the effects of environmentally relevant concentrations of Pb on this organ, and existing literature only refers to high levels of exposure. Herein we investigated for the first time the molecular and morphological effects induced by two low and environmentally relevant concentrations of Pb (2.5 and 5 μg/L) on the gills of Danio rerio, a model species with a high translational value for human toxicity. It was demonstrated that Pb administration at even low doses induces osmoregulatory dysfunctions by affecting Na⁺/K⁺-ATPase and AQP3 expression. It was also shown that Pb upregulates MTs as a protective response to prevent cell damage. Modulation of SOD confirms that the production of reactive oxygen species is an important toxicity mechanism of Pb. Histological and morphometric analysis revealed conspicuous pathological changes, both dose- and time-dependent.

The zebrafish (Danio rerio) embryo-larval contact assay combined with biochemical biomarkers and swimming performance in sewage sludge and hydrochar hazard assessment

Hydrothermal carbonization is considered a powerful technology to convert sewage sludge (SS) into a valuable carbonaceous solid known as hydrochar (HC). Up to now criteria for landfill application of SS and HC are based only on physicochemical properties and levels of pollutant residues. Nevertheless, to ensure their safe environmental applications it is mandatory to develop biosensors which can provide relevant information on their toxic potential for natural ecosystems. Therefore, this study aimed to assess the suitability of a contact assay using zebrafish embryo/larvae combined with sub-lethal end-points to evaluate the hazard associated with SS and related HC exposure. A suite of biomarkers was also applied on larvae, related to detoxification and oxidative stress as the activity of Ethoxyresorufin-O-deethylase, glutathione-S-transferase, and catalase, the content of reactive oxygen species and the behavioral assay using the DanioVision™ chamber. Legacy priority pollutants were also measured either in SS and HC tested samples and in contact waters. The exposure to SS caused higher lethality compared to HC. No significant changes in the activity of oxidative stress markers was observed upon exposure to both matrices. The behavioral test showed a hypoactivity condition in larvae exposed to both SS and HC with the effects of SS stronger than HC. Chemical analysis revealed the presence of trace elements and halogenated compounds in either SS, HC. Heavy metals were also released in contact waters, while volatile hydrocarbons (C6-C10) and halogenated compounds resulted below LOD (<0.05 μ L^-1). Our study highlights the suitability of zebrafish embryotoxicity test, coupled with behavioral traits, as screening tool for assessing potential risks, associated with the landfill application of both SS and HC, for aquatic wildlife.

Detrimental impact of fine dust on zebrafish: Investigating a protective agent against ocular-damage using in vitro and in vivo models

Pollution caused by fine dust is becoming a global problem in the aquatic environment. Many studies have investigated the hazards that fine dust may pose to terrestrial organisms; however, information on the effects on aquatic environments remain limited. In this study, the physicochemical characteristics of the fine dust associated with the captured powder or liquid state were compared using scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). Raw fine dust (RFD), in the captured powder state, was suspended in water (SFD), and the elemental composition, morphology, and size distribution of both were analyzed. Zebrafish were used as a model to study the effects of SFD-exposure on aquatic organisms. A fatal malformation was observed in the integuments of zebrafish exposed to SFD, specifically in the exterior and interior eye tissues. Furthermore, the exposure of SFD to Tg (flk; EGFP) zebrafish remarkably increased ocular vessel diameter expansion along with blood flow velocity. Regarding vessel diameter expansion, EA.hy926 cells exposed to SFD were adversely affected, with a significant increase in cell migration and capillary-like structure formation, which are angiogenic markers. The SFD-induced angiogenesis in vitro and in vivo was dramatically restored to normal via α/β-adenosine isolated from the anti-angiogenic brown algae Ishige okamurae extract. Taken together, the current study presents solid evidence of the altered physicochemical characteristics of SFD compared to RFD, and the detrimental impact of SFD in an aquatic in vivo zebrafish model. In addition, the protective effect of α/β-adenosine, a marine natural product, on SFD-induced angiogenesis suggests that it can be used as an agent to reduce the adverse effects of SFD on aquatic animals.