Interference of the co-exposure of mercury with silica-coated iron oxide nanoparticles can modulate genotoxicity induced by their individual exposures--a paradox depicted in fish under in vitro conditions

Co-exposure of iron oxide nanoparticles with glyphosate herbicides in Poecilia reticulata: Fish liver damages is reversible during iron accumulation and elimination period

Iron oxide nanoparticles (IONPs) are advanced materials for water remediation technologies. It is therefore relevant to evaluate the cellular and tissue behavior of fishes in response to IONPs and their associations with agrochemicals such as glyphosate (GLY) and glyphosate-based herbicides (GBHs). Iron accumulation, tissue integrity and lipid distribution in the hepatocytes of Poecilia reticulata (guppy) were investigated in a control group and in groups exposed to soluble iron ions, namely IFe (0.3 mgFe/L), IONPs (0.3 mgFe/L), and IONPs, associated with GLY (0.65 mg/L), GBHs 0.65 mgGLY/L (IONPs + GBH1), and 1.30 mgGLY/L (IONPs + GBH2), for 7, 14, and 21 days, followed by an equal period of postexposure in clean reconstituted water. The results showed that the accumulation of iron was greater in the subjects in the IONP treatment group when compared to that in the Ife group. In addition, the subjects in the mixtures with GBHs had a greater accumulation of iron than those in the IONP + GLY treatment group. Tissue integrity assessments demonstrated an intense accumulation of lipids, formation of necrotic zones and leukocyte infiltrates in all the treated groups, with a greater quantity of lipids in the animals treated with IONP + GLY and IFe. During postexposure, the results indicated an elimination of iron in all treated groups, reaching the same level as the control group, throughout the 21 days postexposure. Thus, the damage caused to animal livers by IONP mixtures is reversible, providing promising results for the development of safe environmental remediation practices using nanoparticles.

Nanoparticles: Weighing the Pros and Cons from an Eco-genotoxicological Perspective

The exponential growth of nanotechnology and the industrial production have raised concerns over its impact on human and environmental health and safety (EHS). Although there has been substantial progress in the assessment of pristine nanoparticle toxicities, their EHS impacts require greater clarification. In this review, we discuss studies that have assessed nanoparticle eco-genotoxicity in different test systems and their fate in the environment as well as the considerable confounding factors that may complicate the results. We highlight key mechanisms of nanoparticle-mediated genotoxicity. Then we discuss the reliability of endpoint assays, such as the comet assay, the most favored assessment technique because of its versatility to measure low levels of DNA strand breakage, and the micronucleus assay, which is complementary to the former because of its greater ability to detect chromosomal DNA fragmentation. We also address the current recommendations on experimental design, including environmentally relevant concentrations and suitable exposure duration to avoid false-positive or -negative results. The genotoxicity of nanoparticles depends on their physicochemical features and the presence of co-pollutants. Thus, the effect of environmental processes (e.g., aggregation and agglomeration, adsorption, and transformation of nanoparticles) would account for when determining the actual genotoxicity relevant to environmental systems, and assay procedures must be standardized. Indeed, the engineered nanoparticles offer potential applications in different fields including biomedicine, environment, agriculture, and industry. Toxicological pathways and the potential risk factors related to genotoxic responses in biological organisms and environments need to be clarified before appropriate and sustainable applications of nanoparticles can be established.

Status Quo in Data Availability and Predictive Models of Nano-Mixture Toxicity

Co-exposure of nanomaterials and chemicals can cause mixture toxicity effects to living organisms. Predictive models might help to reduce the intensive laboratory experiments required for determining the toxicity of the mixtures. Previously, concentration addition (CA), independent action (IA), and quantitative structure–activity relationship (QSAR)-based models were successfully applied to mixtures of organic chemicals. However, there were few studies concerning predictive models for toxicity of nano-mixtures before June 2020. Previous reviews provided comprehensive knowledge of computational models and mechanisms for chemical mixture toxicity. There is a gap in the reviewing of datasets and predictive models, which might cause obstacles in the toxicity assessment of nano-mixtures by using in silico approach. In this review, we collected 183 studies of nano-mixture toxicity and curated data to investigate the current data and model availability and gap and to derive research challenges to facilitate further experimental studies for data gap filling and the development of predictive models.

Co-exposure of iron oxide nanoparticles and glyphosate-based herbicide induces DNA damage and mutagenic effects in the guppy (Poecilia reticulata)

Iron oxide nanoparticles (IONPs) have been tested to remediate aquatic environments polluted by chemicals, such as pesticides. However, their interactive effects on aquatic organisms remain unknown. This study aimed to investigate the genotoxicity and mutagenicity of co-exposure of IONPs (γ-Fe2O3 NPs) and glyphosate-based herbicide (GBH) in the fish Poecilia reticulata. Thus, fish were exposed to citrate-functionalized γ-Fe2O3 NPs (0.3 mg L-1; 5.44 nm) alone or co-exposed to γ-Fe2O3 NPs (0.3 mg L-1) and GBH (65 and 130 μg of glyphosate L-1) during 14 and 21 days. The genotoxicity (DNA damage) was analyzed by comet assay, while the mutagenicity evaluated by micronucleus test (MN test) and erythrocyte nuclear abnormalities (ENA) frequency. The co-exposure induced clastogenic (DNA damage) and aneugenic (nuclear alterations) effects on guppies in a time-dependent pattern. Fish co-exposed to NPs and GBH (130 μg glyphosate L-1) showed high DNA damage when compared to NPs alone and control group, indicating synergic effects after 21 days of exposure. However, mutagenic effects (ENA) were observed in the exposure groups after 14 and 21 days. Results showed the potential genotoxic and mutagenic effects of maghemite NPs and GBH co-exposure to freshwater fish. The transformation and interaction of iron oxide nanoparticles with other pollutants, as herbicides, in the aquatic systems are critical factors in the environmental risk assessment of metal-based NPs.

Will temperature rise change the biochemical alterations induced in Mytilus galloprovincialis by cerium oxide nanoparticles and mercury?

It is known that, for marine coastal ecosystems, pollution and global warming are among the most threatening factors. Among emerging pollutants, nanoparticles (NPs) deserve particular attention as their possible adverse effects are significantly influenced by environmental factors such as salinity, pH and temperature, as well as by their ability to interact with other contaminants. In this framework, the present study aimed to evaluate the potential interactions between CeO₂ NPs and the toxic classic metal mercury (Hg), under current and warming conditions. The marine bivalve Mytilus galloprovincialis was used as biological model and exposed to CeO₂ NPs and Hg, either alone or in combination, for 28 day at 17 °C and 22 °C. A suite of biomarkers related to energetic metabolism, oxidative stress/damage, redox balance, and neurotoxicity was applied in exposed and non-exposed (control) mussels. The Hg and Ce accumulation was also assessed. Results showed that the exposure to CeO₂ NPs alone did not induce toxic effects in M. galloprovincialis. On the contrary, Hg exposure determined a significant loss of energetic metabolism and a general impairment in biochemical performances. Hg accumulation in mussels was not modified by the presence of CeO₂ NPs, while the biochemical alterations induced by Hg alone were partially canceled upon co-exposure with CeO₂ NPs. The temperature increase induced loss of metabolic and biochemical functions and the effects of temperature prevailed on mussels exposed to pollutants acting alone or combined.

Environmental mixtures of nanomaterials and chemicals: The Trojan-horse phenomenon and its relevance for ecotoxicity

The usage of engineered nanomaterials (NM) offers many novel products and applications with advanced features, but at the same time raises concerns with regard to potential adverse biological effects. Upon release and emission, NM may interact with chemicals in the environment, potentially leading to a co-exposure of organisms and the occurrence of mixture effects. A prominent idea is that NM may act as carriers of chemicals, facilitating and enhancing the entry of substances into cells or organisms, subsequently leading to an increased toxicity. In the literature, the term 'Trojan-horse effect' describes this hypothesis. The relevance of this mechanism for organisms is, however, unclear as yet. Here, a review has been performed to provide a more systematic picture on existing evidence. It includes 151 experimental studies investigating the exposure of various NM and chemical mixtures in ecotoxicological in vitro and in vivo model systems. The papers retrieved comprised studies investigating (i) uptake, (ii) toxicity and (iii) investigations considering both, changes in substance uptake and toxicity upon joint exposure of a chemical with an NM. A closer inspection of the studies demonstrated that the existing evidence for interference of NM-chemical mixture exposure with uptake and toxicity points into different directions compared to the original Trojan-horse hypothesis. We could discriminate at least 7 different categories to capture the evidence ranging from no changes in uptake and toxicity to an increase in uptake and toxicity upon mixture exposure. Concluding recommendations for the consideration of relevant processes are given, including a proposal for a nomenclature to describe NM-chemical mixture interactions in consistent terms.

Genotoxicity of metal based engineered nanoparticles in aquatic organisms: A review

Engineered nanoparticles (ENPs) are an emerging class of environmental contaminants, but are generally found in very low concentrations and are therefore likely to exert sub-lethal effects on aquatic organisms. In this review, we: (i) highlight key mechanisms of metal-based ENP-induced genotoxicity, (ii) identify key nanoparticle and environmental factors which influence the observed genotoxic effects, and (iii) highlight the challenges involved in interpreting reported data and provide recommendations on how these challenges might be addressed. We review the application of eight different genotoxicity assays, where the Comet Assay is generally preferred due to its capacity to detect low levels of DNA damage. Most ENPs have been shown to cause genotoxic responses; e.g., DNA or/and chromosomal fragmentation, or DNA strand breakage, but at unrealistic high concentrations. The genotoxicity of the ENPs was dependent on the inherent physico-chemical properties (e.g. size, coating, surface chemistry, e.tc.), and the presence of co-pollutants. To enhance the value of published genotoxicity data, the role of environmental processes; e.g., dissolution, aggregation and agglomeration, and adsorption of ENPs when released in aquatic systems, should be included, and assay protocols must be standardized. Such data could be used to model ENP genotoxicity processes in open environmental systems.

Phagocytic cell responses to silica-coated dithiocarbamate-functionalized iron oxide nanoparticles and mercury co-exposures in Anguilla anguilla L

Immune system responses in fish are considered as suitable and sensitive biomarkers for monitoring aquatic pollution. However, a clear knowledge gap persists in the literture on the immunotoxic potential of engineered nanoparticles toward aquatic organisms such as fish. Employing major enzymatic- (glutathione reductase, GR; glutathione peroxidase, GPX; glutathione sulfo-transferase, GST; catalase, CAT) and thiol- (non-protein thiols, NP-SH; total glutathione, TGSH)-based defense biomarkers, this study assessed the response of phagocytes isolated from peritoneum (P-phagocytes), gill (G-phagocytes), head kidney (HK-phagocytes), and spleen (S-phagocytes) of European eel (Anguilla anguilla L.) to silica-coated magnetite particles (Fe3O4@SiO2/SiDTC, hereafter called IONP; size range: 82 ± 21 to 100 ± 30 nm; 2.5 mg L(-1)) alone and IONP and mercury (Hg; 50 μg L(-1)) concomitant exposures. Responses of previous biomarkers were studied in P-phagocytes, G-phagocytes, HK-phagocytes, and S-phagocytes collected during 0, 2, 4, 8, 16, 24, 48, and 72 h of exposures. Contingent to hour of exposure to IONP, Hg, and IONP + Hg GST, GPX, CAT, NP-SH, and TGSH exhibited their differential responses in all the phagocytic cells considered. In particular, under IONP exposure, the potential occurrence of the GSH-independent antioxidant defense was indicated by the observed herein inhibition in the enzymatic- and thiol-based defense in A. anguilla phagocytes. In contrast, the response of P-, G-, HK-, and S-phagocytes to the increasing Hg exposure period reflected an increased detoxification activity. Notably, the occurrence of an antagonism between IONP and Hg was depicted during late hours (72 h) under IONP + Hg concomitant exposure, where elevations in the defense biomarkers were depicted. Overall, the P-, G-, HK-, and S-phagocytic cells exhibited a differential induction in the studied enzymes and thiols to counteract impacts of IONP, Hg, and IONP + Hg concomitant exposures. Future studies on the fish immunotoxicity responses to IONP exposure in multi-pollution conditions can be benefited with the major outcomes of the present study.

Rescheduling the process of nanoparticle removal used for water mercury remediation can increase the risk to aquatic organism: evidence of innate immune functions modulation in European eel (Anguilla anguilla L.)

This study aimed to assess the mechanisms of innate immune function responses to silica-coated iron oxide nanoparticle functionalized with dithiocarbamate groups (IONP) exposure alone and its associated mercury (Hg) in European eel (Anguilla anguilla L.) phagocytes isolated from peritoneum (P-phagocytes), gill (G-phagocytes), head kidney (HK-phagocytes) and spleen (S-phagocytes). The study evaluated viability, phagocytosis, oxidative burst activity (OBA) and lipid peroxidation (LPO). Four groups were made: (1) 2 × 10(6) phagocytes + RPMI-1640 (control), (2) 2 × 10(6) phagocytes + IONP (2.5 mg L(-1)), (3) 2 × 10(6) phagocytes + Hg (50 μg L(-1)) and (4) 2 × 10(6) phagocytes + IONP + Hg. Samplings were performed at 0, 2, 4, 8, 16, 24, 48 and 72 h of exposure. A. anguilla P-, G-, HK- and S-phagocytes in vitro exposure to IONP alone revealed either increased (except HK-phagocytes at 16 h) or no change in viability, suggesting that the cells are metabolically active and resistant to IONP exposure alone. In terms of phagocytes overactivation and reactive oxygen species (ROS) production as an indirect mechanism of immunotoxicity, the phagocytes responded in the following manner: P- > S- > HK- = G-phagocytes for IONP exposure alone, S- > HK- > P- = G-phagocytes for Hg exposure alone and HK- > G- = S- > P-phagocytes for concomitant exposure. Overall, considering Hg as a surrogate for metals and its association with IONP, as well as the likelihood that it could pose a serious threat to aquatic organisms by modulating their immune defense mechanisms if accidentally discharged into the aquatic environment, current results suggest that the step of IONP-metal complex removal must not be underrated and should be processed without any more ado.

Mutagenic Effects of Iron Oxide Nanoparticles on Biological Cells

In recent years, there has been an increased interest in the design and use of iron oxide materials with nanoscale dimensions for magnetic, catalytic, biomedical, and electronic applications. The increased manufacture and use of iron oxide nanoparticles (IONPs) in consumer products as well as industrial processes is expected to lead to the unintentional release of IONPs into the environment. The impact of IONPs on the environment and on biological species is not well understood but remains a concern due to the increased chemical reactivity of nanoparticles relative to their bulk counterparts. This review article describes the impact of IONPs on cellular genetic components. The mutagenic impact of IONPs may damage an organism's ability to develop or reproduce. To date, there has been experimental evidence of IONPs having mutagenic interactions on human cell lines including lymphoblastoids, fibroblasts, microvascular endothelial cells, bone marrow cells, lung epithelial cells, alveolar type II like epithelial cells, bronchial fibroblasts, skin epithelial cells, hepatocytes, cerebral endothelial cells, fibrosarcoma cells, breast carcinoma cells, lung carcinoma cells, and cervix carcinoma cells. Other cell lines including the Chinese hamster ovary cells, mouse fibroblast cells, murine fibroblast cells, Mytilus galloprovincialis sperm cells, mice lung cells, murine alveolar macrophages, mice hepatic and renal tissue cells, and vero cells have also shown mutagenic effects upon exposure to IONPs. We further show the influence of IONPs on microorganisms in the presence and absence of dissolved organic carbon. The results shed light on the OPEN ACCESS Int. J. Mol. Sci. 2015, 16 23483 transformations IONPs undergo in the environment and the nature of the potential mutagenic impact on biological cells.