Maria Maisano

In the context of the global transition towards a more sustainable economy, the use of bioplastics (BPs) is rapidly increasing across several sectors, including industry, medicine and cosmetics. Among BPs, polylactic acid (PLA) is the “polymer of the 21st century”. Because of its wide use and slow degradation capacity, it can be found in various aquatic matrices, causing potential health concerns for biota. This work evaluated the influence of environmental concentrations (0.5 µg/mL) of PLA BPs on the reproductive health of the Mediterranean mussel Mytilus galloprovincialis, following a short-term exposure of 7 days. This resulted in an early spawning event from the gonads of both sexes, accompanied by an intense hemocyte recall, suggesting the onset of a pro-inflammatory condition. Alterations in the bioenergetic pathway affecting glycogen reserves as an adaptive strategy were revealed in both sexes by proton Nuclear Magnetic Resonance (¹H NMR)-based metabolomics, in addition to disorders in the redox balance. This latter was more evident in males, as confirmed by the increased activity of antioxidant (catalase) and detoxifying (glutathione S-transferase) enzymes, while no lipid peroxidation occurred. Overall, this study highlights the threat of PLA BPs on the reproductive system of non-target organisms, raising further questions on the reproductive fitness and survival of a species with high ecological and economic value.

Microplastics pose a growing threat to marine ecosystems as they can accumulate in aquatic organisms, interfering with essential physiological processes including reproduction. This study analyzed the effects of short-term exposure (48 h) to two concentrations (0.5 and 1 µg/mL) of 5 µm diameter polystyrene microplastic bead particles in female Mytilus galloprovincialis mussels, a bioindicator species of the Mediterranean Sea. Histological analyses revealed progressive oocyte degeneration and the development of hypertrophic PAS-positive mucous cells, indicative of a stress response, in a dose-dependent manner. Changes in hemocyte classes, which are major effectors of bivalve immunity, were evidenced by the May–Grünwald Giemsa reaction. Biochemical data showed that microplastics increased levels of stress proteins, such as HSP70 and p53, and altered the composition of ovarian glycoproteins. Metabolomic analysis based on ¹H NMR spectrometry revealed significant alterations in metabolites involved in energy (glucose, glycogen, and malonate) and amino acid (branched-chain amino acids arginine, glycine, glutamate, histidine, betaine, and choline) metabolism, suggesting impairment to bioenergetic and antioxidant pathways. Overall, these results suggest that even short-term exposure to polystyrene microplastic beads can alter the ovarian function and metabolism of female M. galloprovincialis, highlighting their vulnerability.

The toxicity of micro- and nanoplastics in aquatic life is well documented, yet limited information is available on their effects in humans; moreover, most in vitro nanotoxicology studies rely on cancer cells. This study examined the effects of pristine and aged polystyrene micro- and nanoparticles on human dental pulp stem cells. While both particle sizes were internalized by the cells, primarily through endocytosis, they did not affect cell viability. In contrast, leachates from particles, aged for one month in culture medium, significantly reduced viability, indicating that toxicity arises from degradation byproducts rather than the particles themselves. Atomic force microscopy confirmed surface changes in aged plastics. Both particle sizes disorganized the cytoskeleton, leading to reduced actomyosin cortex integrity. Gene expression analysis revealed that leachates and aged particles activated inflammatory pathways, markedly increasing IL-8 and TGF-β1 expression, while also decreasing SOD levels associated with oxidative stress. No notable effects were observed on genes related to stemness or senescence. These results suggest that, while pristine micro- and nanoplastics may be relatively inert, their degradation products pose greater toxicological risks to human health. The findings highlight the importance of considering leachate toxicity in plastic pollution studies and demonstrate the value of stem cell-based models for evaluating the cellular and molecular impacts of environmental contaminants on human health.

In many agroecosystems, agrochemicals are widely used to control crop pests, but often affect many non-target species of ecological and agronomic interest, such as earthworms. Earthworms are considered useful indicators of soil contamination. Exposure of these organisms to contaminants occurs mainly through the large amount of soil ingested, which passes through the digestive tract, which is closely associated with the coelom and its fluids. In this work, we used the coelomic fluids of earthworms exposed to copper sulfate and chlorpyrifos to standardize a set of non-destructive biomarkers useful for assessing the contamination in agroecosystems. Metallothionein concentrations, acetylcholinesterase inhibition, lysosomal membrane stability, micronucleus frequency, morphometric alterations, and granulocyte cytoskeleton polymerization were analyzed. The results showed that all the biomarkers used were detectable in the coelomic fluid. Furthermore, the data obtained showed highly significant variations for all biomarkers studied, thus demonstrating that the use of coelomic fluid for biomarker assessment in non-target species offers numerous advantages for field applications.

In recent years, micro- and nanoplastics (MNPs) have represented an emerging threat for the aquatic environment due to their persistence and widespread distribution. Indeed, their small size and increased surface area lead to a high biological reactivity, which can be crucial for the health status of biota. To date, several studies have investigated lethal and sublethal endpoints of MNPs, while one of the main challenges is to understand their mechanisms of toxicity in a comprehensive manner. With this aim, the field of aquatic ecotoxicology can now benefit from the -omics approaches. This review focuses on the recent advances related to the use of transcriptomics, proteomics, and metabolomics to deeply investigate the molecular and biochemical responses of aquatic organisms, both fishes and aquatic invertebrates, to pristine polystyrene (PS) MNPs. The literature reviewed revealed that transcriptomics and metabolomics are the most frequently used -omic approaches. Overall, the studies taken into consideration shed light on the events triggered by PS MNPs at molecular and cellular levels, identifying as mechanisms of toxicity the pathways involved in oxidative stress, energy metabolism, immune response, and the nervous system. Future studies should therefore focus on the use and integration of multi-omics approaches for a more comprehensive understanding of the mechanisms involved in MNPs toxicity.

This study combines a traditional chemical characterization with a simultaneous biological evaluation through histological, immunohistochemical, and enzymatic observations to assess the efficiency and sustainability of soil washing on Hg-contaminated sediment in terms of the bioavailability of the contaminant before and after the treatment, as well as the potential drawbacks of the treatment that are not revealed by a simple chemical characterization of treated sediments on its own. Different extracting agents, that is, ethylenedinitrilotetraacetic acid (EDTA), ethylenediaminedisuccinic acid (EDDS), sodium thiosulfate, potassium iodide (KI), and iodine (I₂), have been compared in this work to evaluate their efficiency in the removal of Hg from contaminated sediments. Speciation analysis was applied to assess the mobility of Hg from different fractions of aged sediments. Biological evaluation was carried out through the use of large mesocosms and Mytilus galloprovincialis as biological sentinels. Results from bench scale tests have shown Hg removal of up to 93% by means of the multi-step KI/I₂ washing process of the sediment. Results from histological, immunohistochemical, and enzymatic analysis have shown significant differences in the degree of alteration of biological tissues and their functional integrity between organisms in contact with contaminated and restored sediments. The reduction in 5-HT3R immunopositivity in the mesocosm with treated sediments suggests a tendency for mussels to recover a healthy condition. This result was also confirmed by the measurement of the enzymatic activity of AChE in mussel gills, which was significantly reduced in organisms from the mesocosm with polluted sediments compared with those from the one with restored sediments. The proposed approach could help stakeholders all over the world select, at an early stage, the most efficient cleaning action from a more holistic perspective, including not only pollutant concentration and economic reduction but also a direct assessment of the ultimate impact of the selected process on the biological system.

The gastrointestinal tract (GIT) promotes the digestion and absorption of feeds, in addition to the excretion of waste products of digestion. In fish, the GIT is divided into four regions, the headgut, foregut, midgut, and hindgut, to which glands and lymphoid tissues are associated to release digestive enzymes and molecules involved in the immune response and control of host-pathogens. The GIT is inhabited by different species of resident microorganisms, the microbiota, which have co-evolved with the host in a symbiotic relationship and are responsible for metabolic benefits and counteracting pathogen infection. There is a strict connection between a fish’s gut microbiota and its health status. This review focuses on the modulation of fish microbiota by feed additives based on prebiotics and probiotics as a feasible strategy to improve fish health status and gut efficiency, mitigate emerging diseases, and maximize rearing and growth performance. Furthermore, the use of histological assays as a valid tool for fish welfare assessment is also discussed, and insights on nutrient absorptive capacity and responsiveness to pathogens in fish by gut morphological endpoints are provided. Overall, the literature reviewed emphasizes the complex interactions between microorganisms and host fish, shedding light on the beneficial use of prebiotics and probiotics in the aquaculture sector, with the potential to provide directions for future research.