From the cellular to tissue alterations induced by two rare earth elements in the mussel species Mytilus galloprovincialis: Comparison between exposure and recovery periods

Adverse effects and underlying mechanism of rare earth elements

BACKGROUND

Rare earth elements (REEs) have found broad application in a range of industries, including electronics, automotive, agriculture, and healthcare. However, their widespread utilization and release into the environment pose potential risks of human exposure. Despite extensive research on REEs toxicity, the relationship between exposure and subsequent health concerns remains ambiguous. Given that the biological effects of REEs can vary based on their design and application, assessing their toxicity can be highly challenging.

OBJECTIVE

This review is to offer a thorough comprehension of REEs' application and toxicity, guiding future research and policy-making to safeguard public health and environmental integrity.

METHODS

A systematic search across PubMed, Web of Science, Cochrane Library, and Embase was conducted using the terms: ("rare earth" OR "lanthanoid") AND ("health hazard" OR "toxic" OR "adverse health effect"). From 5,924 initial records, 89 studies were selected through deduplication and two-stage screening to assess systemic toxicity of REEs. An additional 100 articles on REEs mechanisms and applications were incorporated via citation tracking. All selections followed PRISMA guidelines with dual-author verification to ensure rigor.

CONCLUSION

The review emphasizes REEs' applications in various domains and documents potential environmental pathways. Furthermore, it elaborates on current processes to assess REEs-related toxicity across different model organisms and cell lines, estimating health threats posed by REEs exposure. Finally, based on the findings of both in vivo and in vitro experiments, the potential toxic mechanisms of REEs are detailed. To guide future research and policy development to safeguard public health and environmental integrity.

Investigating the effects of anthropogenic yttrium contamination: Biochemical alterations in the gills and digestive gland of exposed mussels (Mytilus galloprovincialis)

The rapid growth of electronic waste, including fluorescent lamp waste (FLW), has led to an increase in elements like yttrium (Y) and other rare earth elements (REE) in aquatic environments due to improper waste management. However, there are no guidelines for permissible concentrations of these elements in the environment. This study examines the biochemical impacts of varying Y concentrations (50, 100, and 200 µg L-1), mimicking a FLW discharge, on the gills and digestive gland of Mytilus galloprovincialis exposed for 14 days. Energy reserves, antioxidant and biotransformation enzymes, lipid peroxidation (LPO), and neurotoxicity were measured. Results showed a limited antioxidant capacity in the gills at the highest Y concentration. Additionally, increased LPO levels in both organs suggest oxidative stress-induced damage. The study underscores the need for regulations to address Y contamination and safeguard aquatic ecosystems, proposing a reference value for permissible concentrations based on the observed effects.

Effects of the Interaction of Salinity and Rare Earth Elements on the Health of Mytilus galloprovincialis: The Case of Praseodymium and Europium

The growing use of products containing rare earth elements (REEs) may lead to higher environmental emissions of these elements, which can potentially enter aquatic systems. Praseodymium (Pr) and europium (Eu) are widely used REEs with various applications. However, their ecotoxicological impacts remain largely unexplored, with poorly understood risks to wildlife. Moreover, organisms also face environmental stressors like salinity fluctuations, and the nature of the interaction between salinity variations and contaminants is not yet clear. Therefore, this study aimed to evaluate the influence of salinity shifts on the impacts of Pr and Eu on adult mussels and the sperm of the species Mytilus galloprovincialis after 28 days and 30 min of exposure, respectively. To do so, biochemical and histopathological alterations were evaluated in adults, while biochemical and physiological changes were analysed in sperm. Additionally, the Integrated Biological Index (IBR) was calculated to understand the overall impact of each treatment. The results showed that adult mussels were most affected when exposed to the combination of high salinity and each element, which altered the behaviour of defence mechanisms causing redox imbalance and cellular damage. On the other hand, sperm demonstrated sensitivity to specific REE-salinity combinations, particularly Pr at lower salinity and Eu at higher salinity. These specific treatments elicited changes in sperm motility and velocity: Pr 20 led to a higher production of O2- and a decrease in velocity, while Eu 40 resulted in reduced motility and an increase in irregular movement. At both lower and higher salinity levels, exposure to Eu caused similar sensitivities in adults and sperm, reflected by comparable IBR scores. In contrast, Pr exposure induced greater alterations in sperm than in adult mussels at lower salinity, whereas the reverse was observed at higher salinity. These findings suggest that reproductive success and population dynamics could be modulated by interactions between salinity levels and REE pollution, highlighting the need for further investigation into how REEs and environmental factors interact. This study offers valuable insights to inform policymakers about the potential risks of REE contamination, emphasising the importance of implementing environmental regulations and developing strategies to mitigate the impact of these pollutants.

Salinity influence on Mytilus galloprovincialis exposed to antineoplastic agents: a transcriptomic, biochemical, and histopathological approach

Nowadays, aquatic species face a variety of environmental risks associated with pharmaceutical consumption. More specifically, the increased number of cancer patients has been accompanied by an increased consumption of antineoplastic drugs, such as ifosfamide (IF) and cyclophosphamide (CP). These drugs have been found in aquatic ecosystems, raising concerns about their impact, especially on estuarine species, as marine waters are the final recipients of continental effluents. Simultaneously, predicted climatic changes, such as salinity shifts, may threaten organisms. Considering this, the present research aims to investigate the combined effects of IF and CP, and salinity shifts. For this, a transcriptomic, biochemical, and histopathological assessment was made using the bivalve species Mytilus galloprovincialis exposed for 28 days to IF and CP (500 ng/L), individually, at different salinity levels (20, 30, and 40). IF and CP up-regulated metabolism-related gene cyp3a1, with CP also affecting abcc gene, showing minimal salinity impact and highlighting the importance of these metabolic routes in mussels. Salinity shifts affected the transcription of genes related to apoptosis and cell cycle growth, such as p53, as well as the aerobic metabolism, the antioxidant and biotransformation mechanisms. These findings indicate mussels' high metabolic adaptability to osmotic stress. Under CP exposure and low salinity, mussels exhibited increased cellular damage and histopathological effects in digestive gland tubules, revealing detrimental effects towards M. galloprovincialis, and suggesting that a metabolic slowdown and activation of antioxidant mechanisms helped prevent oxidative damage at the control and high salinities. Overall, results reinforce the need for antineoplastics ecotoxicological risk assessment, especially under foreseen climate change scenarios.

Complex interactions of rare earth elements in aquatic systems: Comparing observed and predicted cellular responses on Mytilus galloprovincialis

Recent societal and technological developments have led to new sources of contamination, particularly from electronic waste (e-waste). The rapid increase in e-waste, combined with inadequate disposal and recycling practices has resulted in rising levels of hazardous substances in aquatic systems, including rare-earth elements (REEs). However, the effects of REEs on aquatic organisms remain poorly understood. This lack of understanding is concerning since REEs can simultaneously appear in aquatic systems. Thus, this study aimed to evaluate the impacts of Yttrium (Y), Lanthanum (La), and Gadolinium (Gd), individually and as mixtures on the mussel species Mytilus galloprovincialis. Biomarkers related to metabolism, energy reserves, defence enzymes, redox balance, cellular damage, and neurotoxicity were analyzed. The results obtained showed that Y alone caused minimal stress, while Gd, La, and their mixtures induced from moderate to severe stress, increasing metabolic activity, and enzyme responses. This study highlights the ecological impacts of REEs mixtures on aquatic organisms. The complex interactions and additive effects, especially with Gd, underline the need for further research on contaminant mixtures.

Evaluating the impact of gadolinium contamination on the marine bivalve Donax trunculus: Implications for environmental health

Gadolinium (Gd), commonly used in contrast agents for medical imaging, has been detected in hospital wastewater and aquatic environments, raising environmental concerns. This study examined the accumulation and cellular impacts of Gd in the clam species Donax trunculus, commonly used as bioindicator of contamination. Gadolinium accumulation in clams increased with exposure and over time. Biological responses varied with Gd levels: low concentrations (10 and 50 µg/L) led to low metabolic activity and glycogen content, but high antioxidant activities and lipid peroxidation levels (LPO); high concentrations (250 and 500 µg/L) resulted in increased metabolic activity, while antioxidant enzyme activity was inhibited and LPO levels were the lowest. Metabolic activity decreased after two weeks, suggesting limited long-term metabolic resilience. The study underscores D. trunculus as an effective early warning species for Gd pollution and highlights the ecological risks of rising Gd levels, emphasizing the need for environmental monitoring and regulation.

Rare earth elements and warming: Implications for adult mussel health and sperm quality

The present study aimed to investigate the effects of europium (Eu) exposure (10 μg/L), warming (a 4 °C increase), and their combination on Mytilus galloprovincialis. Biochemical and histopathological changes in adult mussels were evaluated after a 28-day exposure period. Additionally, biochemical and physiological alterations in sperm were measured following a 30-min exposure period. The overall responses to each treatment were assessed using the Integrated Biological Response index version 2 (IBRv2). In adult mussels, warming elevated metabolism and activated glutathione S-transferases (GSTs), leading to redox imbalance and cellular damage. Europium exposure alone slightly enhanced metabolism and GSTs activity, resulting in cellular damage and histopathological injuries in digestive tubules. The combined exposure to Eu and warming was the most detrimental treatment for adults, as indicated by the highest IBRv2 value. This treatment slightly increased metabolism and uniquely elevated the activity of antioxidant enzymes, as well as GSTs and carboxylesterases. Despite these responses, they were inadequate to prevent redox imbalance, cellular damage, and histopathological injuries in digestive tubules and gills. Regarding sperm, warming reduced reactive oxygen species (ROS) production but raised lipid peroxidation levels. Sperm exposed to this treatment also increased their oxygen consumption and exhibited reduced velocity. The IBRv2 indicated that Eu was the most harmful treatment for sperm, significantly increasing ROS production and notably decreasing sperm velocity. When combined with warming, Eu elevated superoxide anion (O2-) production, lowered sperm velocity, and increased oxygen consumption. This study underscores the importance of investigating the effects of rare earth elements and their interaction with climate change-related factors.

Praseodymium and warming interactions in mussels: Comparison between observed and predicted results

Being a crucial element for technological development, praseodymium (Pr) has been increasingly used, leading to a rise in its concentration in aquatic systems. However, its potential threats to organisms remain poorly understood. Besides contamination, organisms are also threatened by climate change-related factors, including warming. It is important to evaluate how climate change-related factors may influence the effects of contaminants. To address this, histopathological and biochemical analyses were performed in adult mussels of Mytilus galloprovincialis, following a 28-day exposure to Pr (10 μg/L) and warming (4 °C increase) separately, and in combination. Additionally, biochemical and physiological alterations were analysed in the sperm of mussels after 30-min exposure to the same treatments. Furthermore, it was used the Independent Action model to predict the interaction between Pr and warming. The results showed, in the case of adults exposed to Pr, an increase in superoxide dismutase (SOD) and glutathione S-transferases (GSTs) activities. However, it was insufficient, leading to histopathological injuries, redox imbalance, and cellular damage. In the case of sperm, Pr induced an increase of mitochondrial activity and respiration rate, in response to the increase in systemic metabolic rate and oxygen demand. Warming increased the metabolism, and induced redox imbalance and cellular damage in adults. In sperm, a rise in temperature induced lipid peroxidation and a decrease in velocity. Warming induced some alterations in how adult mussels responded to Pr, activating catalase instead of SOD, and in addition to GSTs, also activated carboxylesterases. However, it was not enough to avoid redox imbalance and cellular damage. In the case of sperm, the combination induced a decrease in H2O2 production, and higher oxygen demand, which prevented the decrease in motility and velocity. This study highlights the limitations of using models and emphasizes the importance of studying the impacts of emerging contaminants, such as rare earth elements, and their combination with climate change-related factors. Under environmental conditions, chronic exposure to the combined effect of different stressors might generate impacts at higher biological levels. This may affect organisms' respiratory and filtration capacity, nutrient absorption, defence capacity against infections or diseases, and sperm viability, ultimately resulting in reduced growth and reproduction, with consequences at the population level.

The role of warming in modulating neodymium effects on adults and sperm of Mytilus galloprovincialis

The use of rare earth elements (REEs) has been increasing and one of the most used is neodymium (Nd). Being an emergent contaminant, its negative impacts are poorly understood. Aquatic organisms are also threatened by climate change-related factors, as is the case of warming, which can change the effects of REEs. Thus, the impacts of Nd, warming, and the combination of both stressors were studied in adult mussels and sperm of the species Mytilus galloprovincialis, after an exposure period of 28 days (adults) and 30 min (sperm). The effects were evaluated through the analysis of biochemical and histopathological alterations in adults and biochemical and physiological responses given by sperm. The results showed that mussels only activated their biotransformation capacity when exposed to the stressors acting alone, which was insufficient to avoid lipid peroxidation. Furthermore, warming (alone and combined with Nd) also produces damage to proteins. The digestive gland was the most sensitive organ to Nd, presenting several histopathological alterations. In the case of sperm, all stressors induced lipid peroxidation, a higher oxygen demand, and a decrease in velocity, even if the sperm viability was maintained. It seems that warming influenced the effects of Nd to some extent. The present findings contribute significantly to the field of REEs environmental toxicology by offering valuable insights into the impacts of Nd on various biological levels of mussels. Additionally, within the context of climate change, this study sheds light on how temperature influences the effects of Nd. The obtained results indicate that both stressors can potentially compromise the overall health of mussel populations, thereby affecting other species reliant on them for food and habitat. Moreover, this study highlights impaired sperm health, which could adversely affect their reproductive capacity and ultimately lead to population decline.