Exposure of adult zebrafish (Danio rerio) to SARS-CoV-2 at predicted environmentally relevant concentrations: Outspreading warns about ecotoxicological risks to freshwater fish.

While the multifaceted social, economic, and public health impacts associated with the COVID-19 pandemic are known, little is known about its effects on non-target aquatic ecosystems and organisms. Thus, we aimed to evaluate the potential ecotoxicity of SARS-CoV-2 lysate protein (SARS.CoV2/SP02.2020.HIAE.Br) in adult zebrafish (Danio rerio) at predicted environmentally relevant concentrations (0.742 and 2.226 pg/L), by 30 days. Although our data did not show locomotor alterations or anxiety-like or/and anxiolytic-like behavior, we noticed that exposure to SARS-CoV-2 negatively affected habituation memory and social aggregation of animals in response to a potential aquatic predator (Geophagus brasiliensis). An increased frequency of erythrocyte nuclear abnormalities was also observed in animals exposed to SARS-CoV-2. Furthermore, our data suggest that such changes were associated with a redox imbalance [↑ROS (reactive oxygen species), ↑H2O2 (hydrogen peroxide), ↓SOD (superoxide dismutase), and ↓CAT (catalase)], cholinesterasic effect [↑AChE (acetylcholinesterase) activity], as well as the induction of an inflammatory immune response [↑NO (nitric oxide), ↑IFN-γ (interferon-gamma), and ↓IL-10 (interleukin-10)]. For some biomarkers, we noticed that the response of the animals to the treatments was not concentration-dependent. However, principal component analysis (PCA) and the "Integrated Biomarker Response" index (IBRv2) indicated a more prominent ecotoxicity of SARS-CoV-2 at 2.226 pg/L. Therefore, our study advances knowledge about the ecotoxicological potential of SARS-CoV-2 and reinforces the presumption that the COVID-19 pandemic has negative implications beyond its economic, social, and public health impacts.

Shedding light on the toxicity of SARS-CoV-2-derived peptide in non-target COVID-19 organisms: A study involving inbred and outbred mice.

Despite advances in research on the vaccine and therapeutic strategies of COVID-19, little attention has been paid to the possible (eco)toxicological impacts of the dispersion of SARS-CoV-2 particles in natural environments. Thus, in this study, we aimed to evaluate the behavioral and biochemical consequences of the short exposure of outbred and inbred mice (male Swiss and C57Bl/6 J mice, respectively) to PSPD-2002 (peptide fragments of the Spike protein of SARS-CoV-2) synthesized in the laboratory. Our data demonstrated that after 24 h of intraperitoneal administration of PSPD-2002 (at 580 µg/kg) the animals did not present alterations in their locomotor, anxiolytic-like, or anxiety-like behavior (in the open field test), nor antidepressant-like or depressive behavior in the forced swimming test. However, the C57Bl/6 J mice exposed to PSPD-2002 showed memory deficit in the novel object recognition task, which was associated with higher production of thiobarbituric acid reactive substances, as well as the increased suppression of acetylcholinesterase brain activity, compared to Swiss mice also exposed to peptide fragments. In Swiss mice the reduction in the activity of superoxide dismutase and catalase in the brain was not associated with increased oxidative stress biomarkers (hydrogen peroxide), suggesting that other antioxidant mechanisms may have been activated by exposure to PSPD-2002 to maintain the animals' brain redox homeostasis. Finally, the results of all biomarkers evaluated were applied into the "Integrated Biomarker Response Index" (IBRv2) and the principal component analysis (PCA), and greater sensitivity of C57Bl/6 J mice to PSPD-2002 was revealed. Therefore, our study provides pioneering evidence of mammalian exposure-induced toxicity (non-target SARS-CoV-2 infection) to PSPD-2002, as well as "sheds light" on the influence of genetic profile on susceptibility/resistance to the effects of viral peptide fragments.

Can spike fragments of SARS-CoV-2 induce genomic instability and DNA damage in the guppy, Poecilia reticulate? An unexpected effect of the COVID-19 pandemic.

The identification of SARS-CoV-2 particles in wastewater and freshwater ecosystems has raised concerns about its possible impacts on non-target aquatic organisms. In this particular, our knowledge of such impacts is still limited, and little attention has been given to this issue. Hence, in our study, we aimed to evaluate the possible induction of mutagenic (via micronucleus test) and genotoxic (via single cell gel electrophoresis assay, comet assay) effects in Poecilia reticulata adults exposed to fragments of the Spike protein of the new coronavirus at the level of 40 µg/L, denominated PSPD-2002. As a result, after 10 days of exposure, we have found that animals exposed to the peptides demonstrated an increase in the frequency of erythrocytic nuclear alteration (ENA) and all parameters assessed in the comet assay (length tail, %DNA in tail and Olive tail moment), suggesting that PSPD-2002 peptides were able to cause genomic instability and erythrocyte DNA damage. Besides, these effects were significantly correlated with the increase in lipid peroxidation processes [inferred by the high levels of malondialdehyde (MDA)] reported in the brain and liver of P. reticulata and with the reduction of the superoxide dismutase (SOD) and catalase (CAT) activity. Thus, our study constitutes a new insight and promising investigation into the toxicity associated with the dispersal of SARS-CoV-2 peptide fragments in freshwater environments.

Toxicity of polystyrene nanoplastics and zinc oxide to mice.

The toxicity of zinc oxide (ZnO NPs) and polystyrene nanoplastics (PS NaPs) has been tested in different animal models; however, knowledge about their impact on mice remains incipient. The aim of the current study is to evaluate the effects of these nanomaterials on Swiss mice after their individual exposure to a binary combination of them. The goal was to investigate whether short exposure (three days) to an environmentally relevant dose (14.6 ng/kg, i.p.) of these pollutants would have neurotoxic, biochemical and genotoxic effects on the modelss. Data in the current study have shown that the individual exposure of these animals has led to cognitive impairment based on the object recognition test, although the exposure experiment did not cause locomotor and anxiogenic or anxiolitic-like behavioral changes in them. This outcome was associated with increased nitric oxide levels, thiobarbituric acid reactive species, reduction in acetylcholinesterase activity and with the accumulation of nanomaterials in their brains. Results recorded for the assessed parameters did not differ between the control group and the groups exposed to the binary combination of pollutants. However, both the individual and the combined exposures caused erythrocyte DNA damages associated with hypercholesterolemic and hypertriglyceridemic conditions due to the presence of nanomaterials. Based on the results, the toxicological potential of ZnO NPs and PS NaPs in the models was confirmed and it encouraged further in-depth investigations about factors explaining the lack of additive or synergistic effect caused by the combined exposure to the assessed pollutants.

Effects of polystyrene nanoplastics on Ctenopharyngodon idella (grass carp) after individual and combined exposure with zinc oxide nanoparticles.

The toxicity of polystyrene nanoparticles (PS NPs) and ZnO nanoparticles (ZnO NPs), in combination is poorly known. Thus, the aim of the current study was to evaluate the effects of PS NPs (760 µg/L) on Ctenopharyngodon idella exposed to it, both in separate and in combination with ZnO NPs (760 µg/L), based on behavioral, biochemical and genotoxic biomarkers. Current data have indicated that PS NPs, for a short exposure period (3 days), both in separate and in combination with nanoparticles, have affected animals' response to the mirror test. On the other hand, all treatments have equally induced C. idella inactivity towards alarm substances and DNA damage. There was increased oxidative stress, mainly in groups exposed to PS NPs (in combination, or not, with nanoparticles); although increased, the evaluated antioxidant levels did not appear to be enough to inhibit the effects of treatment-induced production of free radicals. Together, these results are likely co-responsible for the observed changes. The current study did not observe antagonistic, synergistic or additive effect on animals exposed to the combination between PS NPs and ZnO NPs; however, this outcome should not discourage the performance of similar studies focused on assessing the (eco)toxicity of pollutant mixtures comprising nanomaterials.

Trophic transfer of carbon nanofibers among eisenia fetida, danio rerio and oreochromis niloticus and their toxicity at upper trophic level.

Although the toxicity of carbon-based nanomaterials has already been demonstrated in several studies, their transfer in the food chain and impact on the upper trophic level remain unexplored. Thus, based on the experimental food chain "Eisenia fetida → Danio rerio → Oreochromis niloticus", the current study tested the hypothesis that carbon nanofibers (CNFs) accumulated in animals are transferred to the upper trophic level and cause mutagenic and cytotoxic changes. E. fetida individuals were exposed to CNFs and offered to D. rerio, which were later used to feed O. niloticus. The quantification of total organic carbon provided evidence of CNFs accumulation at all evaluated trophic levels. Such accumulation was associated with higher frequency of erythrocyte nuclear abnormalities such as constricted erythrocyte nuclei, vacuole, blebbed, kidney-shaped and micronucleated erythrocytes in Nile tilapia exposed to CNFs via food chain. The cytotoxic effect was inferred based on the smaller size of the erythrocyte nuclei and on the lower "nuclear/cytoplasmic" area ratio in tilapia exposed to CNFs via food chain. Our study provided pioneering evidence about CNFs accumulation at trophic levels of the experimental chain, as well as about the mutagenic and cytotoxic effect of these materials on O. niloticus.