Nanomaterials and Annelid Immunity: A Comparative Survey to Reveal the Common Stress and Defense Responses of Two Sentinel Species to Nanomaterials in the Environment

A broad-taxa approach as an important concept in ecotoxicological studies and pollution monitoring

Aquatic invertebrates play a pivotal role in (eco)toxicological assessments because they offer ethical, cost-effective and repeatable testing options. Additionally, their significance in the food chain and their ability to represent diverse aquatic ecosystems make them valuable subjects for (eco)toxicological studies. To ensure consistency and comparability across studies, international (eco)toxicology guidelines have been used to establish standardised methods and protocols for data collection, analysis and interpretation. However, the current standardised protocols primarily focus on a limited number of aquatic invertebrate species, mainly from Arthropoda, Mollusca and Annelida. These protocols are suitable for basic toxicity screening, effectively assessing the immediate and severe effects of toxic substances on organisms. For more comprehensive and ecologically relevant assessments, particularly those addressing long-term effects and ecosystem-wide impacts, we recommended the use of a broader diversity of species, since the present choice of taxa exacerbates the limited scope of basic ecotoxicological studies. This review provides a comprehensive overview of (eco)toxicological studies, focusing on major aquatic invertebrate taxa and how they are used to assess the impact of chemicals in diverse aquatic environments. The present work supports the use of a broad-taxa approach in basic environmental assessments, as it better represents the natural populations inhabiting various ecosystems. Advances in omics and other biochemical and computational techniques make the broad-taxa approach more feasible, enabling mechanistic studies on non-model organisms. By combining these approaches with in vitro techniques together with the broad-taxa approach, researchers can gain insights into less-explored impacts of pollution, such as changes in population diversity, the development of tolerance and transgenerational inheritance of pollution responses, the impact on organism phenotypic plasticity, biological invasion outcomes, social behaviour changes, metabolome changes, regeneration phenomena, disease susceptibility and tissue pathologies. This review also emphasises the need for harmonised data-reporting standards and minimum annotation checklists to ensure that research results are findable, accessible, interoperable and reusable (FAIR), maximising the use and reusability of data. The ultimate goal is to encourage integrated and holistic problem-focused collaboration between diverse scientific disciplines, international standardisation organisations and decision-making bodies, with a focus on transdisciplinary knowledge co-production for the One-Health approach.

Crucial physicochemical factors mediating mitochondrial toxicity of nanoparticles at noncytotoxic concentration

Nanomaterials have been extensively applied in multiple industries, among which silver nanoparticles (AgNPs), silicon dioxide nanoparticles (SiNPs), and gold nanoparticles (AuNPs) have become representative of widely consumed NPs. Limited knowledge is available regarding the subcellular responses of NPs with different physicochemical properties, i.e. material type and size, under the noncytotoxic concentrations. Macrophages are important sensitive cells exposed to NPs, and mitochondria are sensitive organelles that respond at the subcellular level. Herein, we found that sublethal concentrations of AgNPs and SiNPs, not AuNPs, decreased the mitochondrial membrane potential (MMP) and tubular mitochondria, and further resulted in an increase of ROS level and a decrease of ATP generation. AgNPs and SiNPs can also disturb mitochondrial dynamics manifested as increasing Mfn2 expression and decreasing Drp1 expression. Further assessments for mitochondrial function showed that AgNPs and SiNPs exposure led to a decrease in the gene expressions related to complex I (Ndufa8 and Ndufs2), complex III (Uqcrc2 and Uqcrfs1), complex IV (Cox6b1), and activity of complex I, suggesting their potential roles in impairing cellular respiration. In terms of the effects of NPs with different sizes, stronger toxicity was observed in smaller-sized nanoparticles. Among the above mitochondrial changes, we identified that ROS, ATP, MMP, tubular mitochondria, and expression of Drp1 were relatively sensitive indicators in subcellular response to NPs. With the above sensitive indicators, the comparison of heterogeneity between material type and size of the NPs showed that material type occupied a main influence on subcellular mitochondrial effects. Our finding provided important data on the potential subcellular risks of NPs, and indicated the vital role of material type for a better understanding of the nanomaterial biological safety.

Toxicity of carbon nanofibers in earthworms (Lumbricus terrestris) naturally infected with Monocystis sp

Although the ecotoxicity of carbon-based nanomaterials (CBNs) is known, the potential effect of carbon nanofibers (CNFs) on edaphic organisms has been insufficiently explored. Thus, we aimed at the ecotoxicity of CNFs (at 10 and 100 mg/kg) in Lumbricus terrestris earthworms naturally infected with Monocystis sp. After 28 days of exposure, treatments did not affect the survival rate. However, we observed a significant loss of body biomass, and Monocystis sp. infection in seminal vesicles was potentiated by exposure to CNFs. Earthworms exposed to CNFs showed a redox imbalance in the seminal vesicle, muscle, and intestine and an alteration in nitric oxide production in these organs. In muscles, we also noticed a significant reduction in AChE activity in earthworms exposed to CNFs. The histopathological analyses revealed the treatments' significant effect on the structures of the different evaluated tissues. Although we did not notice a concentration-response for several of the biomarkers, when taken together and after the application of Integrated Biomarker Response (IBR) and principal component analysis (PCA), we noticed that the response of earthworms to CNFs at 100 mg/kg showed a more significant deviation from the unexposed group. This was mainly determined by inhibiting antioxidant activity in the seminal vesicle, biochemical biomarkers assessed in muscle and intestine, and histomorphometric muscle biomarkers from earthworms exposed to CNFs at 100 mg/kg. Thus, we demonstrate that CNFs increase the parasite load of Monocystis sp. of adult L. terrestris earthworms and induce biochemical and histopathological changes, especially at 100 mg/kg. Our results point to the additional impact these nanomaterials can have on the health of earthworms, signaling the need for greater attention to their disposal and ecotoxicological effects on soil organisms.

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.

Hirudo verbana as a freshwater invertebrate model to assess the effects of polypropylene micro and nanoplastics dispersion in freshwater

Plastics are a heterogeneous class of synthetic compounds that, due to their unique characteristics find numerous applications both in industrial and civil fields. However, despite the great advantages that these materials brought in everyday life, the plastic wastes resulting from their massive use represent one of the main environmental problems at the global level. Once released, plastics persist for a long time and are subjected both to biotic and abiotic processes leading to the formation of small particles, known as micro and to nanoplastics, that interact with organisms, accumulating inside tissues and risking to enter in the trophic chain. Among the different types of plastic, polypropylene (PP) is one of the diffused, widely exploited in food and textile industries for disposable packaging and to produce surgical masks. Owing to the huge distribution and the resultant abundant presence of PP waste products, it results necessary investigate the possible toxicity on living organisms. For these reasons, here we analyzed the effects of PP micro and nanoplastics dispersed in freshwater, using the medicinal leech Hirudo verbana as invertebrate model. To better follow the plastics fate, fluorescent particles, labeled with a fluorophore, have been used. Animals were examined at various timings after plastics exposure and results were analyzed by means of microscopy, immunofluorescent and molecular biology analyses. After assessing the entrance of PP fragments into leech tissues, the activation of the innate immune response was evaluated. The results show that the presence of micro and nanoplastics induces an initial physical protection that consists in the secretion of mucus, followed by an increase of blood vessels and the recruitment of immune cells, in particular macrophages. Moreover, macrophages were directly involved in both phagocytic and encapsulation processes, as demonstrated by acid phosphatase (ACP) histoenzymatic and Thioflavin-T assays, expressing specific pro-inflammatory factors, such as HvRNASET2 and HmAIF-1, as demonstrated by immunolocalization and qPCR experiments. Finally, the expression levels of genes related to oxidative stress-induced enzymes have been investigated, in order to evaluate the possible increase in reactive oxygen species (ROS), due to the entry into the leech tissues of PP micro and nanoplastics. This work allows deepening the current knowledge of the possible harmful effects on human health deriving from micro and nanoplastics dispersion, leading new insight about freshwater ecosystems that often represent the first environments interested in plastic pollution.

Effect of silver nanoparticles on gene transcription of land snail Helix aspersa

Silver nanoparticles (Ag-NPs) are extremely useful in a diverse range of consumer goods. However, their impact on the environment is still under research, especially regarding the mechanisms involved in their effect. Aiming to provide some insight, the present work analyzes the transcriptional activity of six genes (Hsp83, Hsp17.2, Hsp19.8, SOD Cu-Zn, Mn-SOD, and BPI) in the terrestrial snail Helix aspersa in the presence of different concentrations of Ag-NPs. The animals were exposed for seven days to Lactuca sativa soaked for one hour in different concentrations of Ag-NPs (20, 50, 100 mg/L). The results revealed that the highest concentration tested of Ag-NPs (100 mg/L) led to a statistically significant induction of the Hsp83 and BPI expression in the digestive gland compared to the control group. However, a trend to upregulation with no statistical significance was observed for all the genes in the digestive gland and the foot, while in the hemolymph, the trend was to downregulation. Ag-NPs affected the stress response and immunity under the tested conditions, although the impact was weak. It is necessary to explore longer exposure times to confirm that the effect can be maintained and impact on health. Our results highlight the usefulness of the terrestrial snail Helix aspersa as a bioindicator organism for silver nanoparticle pollution biomonitoring and, in particular, the use of molecular biomarkers of pollutant effect as candidates to be included in a multi-biomarker strategy.

Toxicological Effects of Inorganic Nanoparticle Mixtures in Freshwater Mussels

The toxicological effects of nanoparticles mixtures in aquatic organisms are poorly understood. The purpose of this study was to examine the tissue metal loadings and sublethal effects of silver (nAg), cerium oxide (nCeO), copper oxide (nCuO) and zinc oxide (nZnO) nanoparticles individually at 50 µg/L and in two mixtures to freshwater mussels Dreissena bugensis. The mixtures consisted of 12.5 µg/L of each nanoparticle (Mix50) and 50 µg/L of each nanoparticles (Mix200). After a 96-h exposure period, mussels were analyzed for morphological changes, air time survival, bioaccumulation, inflammation (cyclooxygenase or COX activity), lipid peroxidation (LPO), DNA strand breaks, labile Zn, acetylcholinesterase (AChE) and protein–ubiquitin levels. The data revealed that mussels accumulated the nanoparticles with nCeO and nAg were the least and most bioavailable, respectively. Increased tissue metal loadings were observed for nCeO and nCuO in mixtures, while no mixture effects were observed for nAg and nZnO. The weight loss during air emersion was lower in mussels exposed to nCuO alone but not by the mixture. On the one hand, labile Zn levels was increased with nZnO but returned to control values with the Mix50 and Mix200, suggesting antagonism. On the other hand, DNA strand breaks were reduced for both mixtures compared to controls or to the nanoparticles individually, suggesting potentiation of effects. The same was found for protein–ubiquitin levels, which were decreased by nCeO and nCuO alone but not when in mixtures, which increased their levels. In conclusion, the data revealed that the behavior and effects of nanoparticles were influenced by other nanoparticles where antagonist and potentiation interactions were identified.