Earthworm coelomocytes as nanoscavenger of ZnO NPs

Interaction between nanomaterials and the innate immune system across evolution

Interaction of engineered nanomaterials (ENMs) with the immune system mainly occurs with cells and molecules of innate immunity, which are present in interface tissues of living organisms. Immuno-nanotoxicological studies aim at understanding if and when such interaction is inconsequential or may cause irreparable damage. Since innate immunity is the first line of immune reactivity towards exogenous agents and is highly conserved throughout evolution, this review focuses on the major effector cells of innate immunity, the phagocytes, and their major sensing receptors, Toll-like receptors (TLRs), for assessing the modes of successful versus pathological interaction between ENMs and host defences. By comparing the phagocyte- and TLR-dependent responses to ENMs in plants, molluscs, annelids, crustaceans, echinoderms and mammals, we aim to highlight common recognition and elimination mechanisms and the general sufficiency of innate immunity for maintaining tissue integrity and homeostasis.

Effects of silver sulfide nanoparticles on the earthworm Eisenia andrei

The massive production and use of silver nanoparticles (Ag NPs) have led to their increasing release into the environment. Even though the antimicrobial and cytotoxic effects of native nanoparticles have been well studied, the environmental impacts of transformation products such as silver sulfide nanoparticles (Ag₂S NPs) have not been elucidated. In the present study, we assessed the toxicity of Ag₂S NPs and silver nitrate (AgNO₃), as a source of Ag, to the earthworm Eisenia andrei using a nominal concentration of 5 mg Ag kg^-1 soil. We used the OECD guidelines to assess effects on weight loss and mortality for 14 days. After exposure, we also extracted the immune effector cells (coelomocytes) and conducted a battery of biomarker tests. To ensure the quality of the toxicological results, the structural changes of NPs during the experiment and the uptake of silver by the earthworms were monitored. During the experiment, mortality effects were not detected, but a weight loss was observed in the earthworms exposed to Ag₂S NPs. Altough Ag₂S NPs were engulfed by E. andrei cells, neither phenoloxidase activity nor lipid peroxidation differed from the untreated control group. Cells from earthworms treated with Ag₂S NPs exerted very broad value range of nitric oxide (NO) generation, suggesting an imbalance in the NO metabolism. Overall, this study suggests minimal risks associated with Ag₂S NPs exposure to earthworms. However, further studies are needed to assure no immunotoxicological or chronic effects on a wider range of terrestrial organisms.

Differences in kinetic metabolomics in Eisenia fetida under single and dual exposure of imidacloprid and dinotefuran at environmentally relevant concentrations

Metabolomic responses of earthworms to neonicotinoids are important for understanding their molecular-level toxicity and assessing their ecological risks, but little is known until now. We investigated impact of imidacloprid (IMI, 52.6 ng/g) and dinotefuran (DIN, 52.5 ng/g) on Eisenia fetida metabolomics under single- and dual-compound exposure scenarios for one to four weeks. Dissimilar metabolites and anti-stress strategies were found for different neonicotinoids and exposure scenarios. Specifically, IMI exposure first increased myo-inositol and UDP-glucuronate associated with transmembrane absorption and transformation to IMI-urea, and then increased glutathione and fourteen amino acids (TCA cycle precursors) to resist stress and replenish energy. In contrast, worms exposed to DIN first prepared TCA cycle intermediates from glucosamine-6-phosphate and amino acids, suppressed urea cycle and DIN transformation, and then alleviated oxidative stress by increasing carnosine, nicotinate-D-ribonucleotide and nicotinamide-β-riboside. Dual exposure increased four eicosanoids by 1.6-1.9-fold, possibly associated with membrane lipid peroxidation; the amino acids consumed to balance the energy metabolism exhibited a wave-like pattern. This study first systematically revealed the compound/time/exposure scenario- dependent effects of trace neonicotinoids on earthworm metabolomics and advanced the understanding of their action modes. Neonicotinoid transformation was closely related to worms' metabolic profiles, providing important insights in contaminant fate in soil ecosystems.

Cross-Species Comparisons of Nanoparticle Interactions with Innate Immune Systems: A Methodological Review

Many components of the innate immune system are evolutionarily conserved and shared across many living organisms, from plants and invertebrates to humans. Therefore, these shared features can allow the comparative study of potentially dangerous substances, such as engineered nanoparticles (NPs). However, differences of methodology and procedure between diverse species and models make comparison of innate immune responses to NPs between organisms difficult in many cases. To this aim, this review provides an overview of suitable methods and assays that can be used to measure NP immune interactions across species in a multidisciplinary approach. The first part of this review describes the main innate immune defense characteristics of the selected models that can be associated to NPs exposure. In the second part, the different modes of exposure to NPs across models (considering isolated cells or whole organisms) and the main endpoints measured are discussed. In this synergistic perspective, we provide an overview of the current state of important cross-disciplinary immunological models to study NP-immune interactions and identify future research needs. As such, this paper could be used as a methodological reference point for future nano-immunosafety studies.

In Vitro Interactions of TiO2 Nanoparticles with Earthworm Coelomocytes: Immunotoxicity Assessment

Titanium dioxide nanoparticles (TiO₂ NPs) are manufactured worldwide. Once they arrive in the soil environment, they can endanger living organisms. Hence, monitoring and assessing the effects of these nanoparticles is required. We focus on the Eisenia andrei earthworm immune cells exposed to sublethal concentrations of TiO₂ NPs (1, 10, and 100 µg/mL) for 2, 6, and 24 h. TiO₂ NPs at all concentrations did not affect cell viability. Further, TiO₂ NPs did not cause changes in reactive oxygen species (ROS) production, malondialdehyde (MDA) production, and phagocytic activity. Similarly, they did not elicit DNA damage. Overall, we did not detect any toxic effects of TiO₂ NPs at the cellular level. At the gene expression level, slight changes were detected. Metallothionein, fetidin/lysenin, lumbricin and MEK kinase I were upregulated in coelomocytes after exposure to 10 µg/mL TiO₂ NPs for 6 h. Antioxidant enzyme expression was similar in exposed and control cells. TiO₂ NPs were detected on coelomocyte membranes. However, our results do not show any strong effects of these nanoparticles on coelomocytes at both the cellular and molecular levels.

Differential histological, cellular and organism-wide response of earthworms exposed to multi-layer graphenes with different morphologies and hydrophobicity

The growing use of graphene-based nanomaterials (GBNs) for various applications increases the probability of their environmental releases and calls for a systematic assessment of their potential impacts on soil invertebrates that serve as an important link along terrestrial food chains. Here, we investigated the response of earthworms (Eisenia fetida) to three types of multi-layer graphenes (MLGs) (G1, G2 and G3 with 12-15 layers) with variable morphology (lateral sizes: 7.4 ± 0.3, 6.4 ± 0.1 and 2.8 ± 0.1 μm; thicknesses: 5.0 ± 0.1, 4.2 ± 0.1 and 4.0 ± 0.2 nm, respectively) and hydrophobicity ((O + N)/C ratios: 0.029, 0.044 and 0.075; contact angles: 122.8, 118.8 and 115.1°, respectively). Exposure to these materials was conducted for 28 days (except for 48-h avoidance test) separately in potting or farm soil at 0.2% and 1% by weight. Earthworms avoided both soils when amended with 1% of the smaller and more hydrophilic MLGs (G2 and G3), leading to a decreased trend in worm cocoon formation. The smallest and most hydrophilic MLG (G3), which was easier to assimilate, also significantly inhibited the viability (20.2-56.0%) and mitochondrial membrane potential (32.0-48.5%) of worm coelomocytes in both soils. In contrast, oxidative damage (indicated by lipid peroxides) was more pronounced upon exposure to more hydrophobic and larger graphenic materials (G1 and G2), which were attributed to facilitated adhesion to and disruption of worm membranes. These findings highlight the importance of MLG morphology and hydrophobicity in their potential toxicity and mode of action, as well as ecological risks associated with incidental and accidental releases.

Immunotoxicity of copper nanoparticle and copper sulfate in a common Indian earthworm

Copper oxide nanoparticles and copper sulfate are established contaminants of water and soil. Metaphire posthuma is a common variety of earthworm distributed in moist soil of Indian subcontinent. Comparative toxicity of copper nanoparticles and copper sulfate were investigated with reference to selected immune associated parameters of earthworm. Total count, phagocytic response, generation of cytotoxic molecules (superoxide anion, nitric oxide), activities of enzymes like phenoloxidase, superoxide dismutase, catalase, acid phosphatase, alkaline phosphatase and total protein of coelomocytes were estimated under the exposures of 100, 500, 1000mg of copper oxide nanoparticles and copper sulfate per kg of soil for 7 and 14 d. A significant decrease in the total coelomocyte count were recorded with maximum depletion as 15.45 ± 2.2 and 12.5 ± 2 × 10⁴ cells/ml under the treatment of 1000mg/kg of copper nanoparticles and copper sulfate for 14 d respectively. A significant decrease in generation of nitric oxide and activity of phenoloxidase were recorded upon exposure of both toxins for 7 and 14 d indicating possible decline in cytotoxic status of the organism. A maximum inhibition of superoxide dismutase activity was recorded as 0.083 ± 0.0039 and 0.055 ± 0.0057 unit/mg protein/minute against 1000mg/kg of copper nanoparticles and copper sulfate treatment for 14 d respectively. Activities of catalase and alkaline phosphatase were inhibited by all experimental concentrations of both toxins in the coelomocytes of earthworm. These toxins were recorded to be modifiers of the major immune associated parameters of M. posthuma. Unrestricted contamination of soil by sulfate and oxide nanoparticles of copper may lead to an undesirable shift in the innate immunological status of earthworm leading to a condition of immune compromisation and shrinkage in population density of this species in its natural habitat. This article is the first time report of immunological toxicity of nanoparticles and sulfate salt of copper in M.posthuma inhabiting the soil of India, an agriculture based country.

Silver (nano)materials cause genotoxicity in Enchytraeus crypticus, as determined by the comet assay

Enchytraeids have been used in standard ecotoxicity testing for approximately 20 yr. Since adopting the standard test for survival and reproduction, a number of additional tools have been developed, including transcriptomics and enzymatic biomarkers. So far, a genotoxicity tool and endpoint have not been used; hence, the goals of the present study included optimization of the in vivo alkaline comet assay in Enchytraeus crypticus. Further, the effect of silver nanomaterial (Ag NM300K, dispersed, 15 nm) was tested and compared with silver nitrate. Hydrogen peroxide was used as a positive control. The various steps were optimized. The fully detailed standard operating procedure is presented. Silver materials caused genotoxicity, this being differentiated for the nano and non-nano forms. Silver nitrate caused genotoxicity after 3 d of exposure in a dose-related manner, although after 7 d the effects were either reduced or repaired. Ag NM300K caused higher genotoxicity after 7 d for the lowest concentration, highlighting a potential nonmonotonic dose-response effect. Overall, the comet assay showed the power to discriminate effects between materials and also toxicity at low relevant doses. Environ Toxicol Chem 2018;37:184-191. © 2017 SETAC.

Oxidative stress and genotoxicity of an organic and an inorganic nanomaterial to Eisenia andrei: SDS/DDAB nano-vesicles and titanium silicon oxide

In the past few years the number of studies on the toxic effects of nanomaterials (NMs) in the environment increased significantly. Nonetheless, the data is still scarce, since there is a large number of NMs and new ones are being developed each day. Soils are extremely important for life, and are easily exposed to the released NMs, thus enhanced efforts are needed to study the impacts on soil biota. The objective of the present work was to determine if different concentrations of two NMs, one inorganic (TiSiO₄) and other organic (nano-vesicles of sodium sodecyl sulfate/ didodecyl dimethylammonium bromide - SDS/DDAB), are genotoxic to soil invertebrates. Additionally, it was intended to understand whether, in the event of occurring, genotoxicity was caused by the incapability of the cells to deal with the oxidative stress caused by these NMs. With that purpose, Eisenia andrei were exposed for 30 days to the artificial OECD soil contaminated with different concentrations of the NMs being tested. After the exposure, coelomocytes were extracted from earthworms and DNA damage was measured by the comet assay. The activity of antioxidant enzymes (e.g. glutathione peroxidase, glutathione reductase and glutathione-S-Transferase) and lipid peroxidation were also assessed. The results showed that both NMs were genotoxic, particularly TiSiO₄ for which significant DNA damages were recorded for concentrations above 444mg of TiSiO₄-NM/kg of soil_dw. Since no statistically significant differences were found in the tested antioxidant enzymes and in lipid peroxidation, the mechanism of genotoxicity of these NMs seemed to be unrelated with oxidative stress.

Optimization of ZnO-NPs to Investigate Their Safe Application by Assessing Their Effect on Soil Nematode Caenorhabditis elegans

Zinc oxide nanoparticles (ZnO-NPs) are increasingly receiving attention due to their widespread application in cosmetics, pigments and coatings. This has raised concerns in the public and scientific communities regarding their unexpected health effects. Toxicity effect of ZnO-NPs on the environment was assessed in the present study using Caenorhabditis elegans. Multiple toxicity end points including their mortality, behaviour, reproduction, in vitro distribution and expression of stress response mtl-1 and sod-1 genes were observed to evaluate safe application of ZnO-NPs. C. elegans were exposed to 10, 50, and 100 nm ZnO-NPs (0.1 to 2.0 g/l). Application of 10 nm ≥0.7g/l adversely affects the survivability of worms and was significantly not affected with exposure of 50 and 100 nm ≤1.0 g/l. However, reproduction was affected at much low concentration as compared to their survivability. LC50 was recorded 1.0 ± 0.06 (g/l) for 100 nm, 0.90 ± 0.60 for 50 nm and 0.620 ± 0.08 for 10 nm. Expression of mtl-1 and sod-1 was significantly increased with application of 10 nm ≥0.7g/l and significantly unaffected with exposure of 50 and 100 nm at the same concentration. ZnO-NPs (10 nm) had shown even distribution extended nearly the entire length of the body. The distribution pattern of ZnO-NPs indicates that the intestine is the major target tissues for NP toxicity. Study demonstrates that small-sized (10 nm) ZnO-NPs ≥0.7g/l is more toxic than larger-sized particles. This may be suggested on the basis of available data; application of 50 and 100 nm ≤1.0 g/l ZnO-NPs may be used to the environment as this shows no significant toxicity. However, further calibration is warranted to explore safe dose on soil compartments prior to their field application.