Effects of intratracheal pretreatment with yttrium chloride (YCl3) on inflammatory responses of the rat lung following intratracheal instillation of YCl3

Yttrium chloride-induced cytotoxicity and DNA damage response via ROS generation and inhibition of Nrf2/PPARγ pathways in H9c2 cardiomyocytes

Increasing exploration of rare-earth elements (REEs) has resulted in a high REEs' exposure risk. Owing to their persistence and accumulation of REEs in the environment, their adverse effects have caused widespread concern. However, limited toxicological data are available for the adverse effects of yttrium (Y) and its underlying mechanisms of action. In the present study, H9c2 cardiomyocytes were used in vitro model to investigate the cardiotoxicity of yttrium chloride (YCl₃). Results show that YCl₃ treatment resulted in reactive oxygen species (ROS) overproduction, decrease in ∆Ψm, and DNA damage. Mechanistically, we detected expression levels of protein in response to cellular DNA damage and antioxidative defense. Results indicated that the phosphorylation of histone H2AX remarkably increased in a dose-dependent manner. At a high YCl₃-exposure concentration (120 μM), specific DNA damage sensors ATM/ATR-Chk1/Chk2 were significantly decreased. The protein levels of key antioxidant genes Nrf2/PPARγ/HO-1 were also remarkably inhabited. Additionally, the antioxidant N-acetyl-L-cysteine (NAC) pretreatment promoted the activation of antioxidative defense Nrf2/PPARγ signaling pathways, and prevented the production of cellular ROS, thus protecting the DNA from cleavage. Altogether, our findings suggest that YCl₃ can induce DNA damage through causing intracellular ROS overproduction and inhibition of antioxidative defense, leading to cytotoxicity in H9c2 cardiomyocytes.

Effects of Rare Earth Elements on Blood Pressure and Their Exposure Biomarkers: Evidence from Animal Experiments

Solid fuel combustion is an important source of the release of rare earth elements (REEs) into the ambient environment, resulting in potential adverse effects on human cardiovascular health. Our study aimed to identify reliable exposure biomarkers of REE intake and their potential role in blood pressure change. A total of 24 rats were administered with 14 REE chlorides at four doses (six rats per group). Fur samples were collected both before and after administration. Blood samples were collected after 12 weeks of REE intake. The REE concentrations in rat fur and blood samples were measured by inductively coupled plasma mass spectrometry. For each week, blood pressure, as well as heart rate and pulse pressure, were measured. The linear mixed-effect model was used to analyze the relationship between REE administration dose and blood pressure change. We found that the REE concentration in fur, but not blood, samples exhibited significant dose–response relationships with administration dose. It suggested that hair samples are a more efficient matrix for indicating the exposure level of a population to REEs than blood samples. However, there was no dose–response relationships between the administration dose and blood pressure change of rats, or with heart rate and pulse pressure for the 14 REEs. We also did not find a dose–response relationship between REE administration levels and plasma concentration of 8-hydroxy-2’-deoxyguanosine, as an important DNA oxidative stress damage biomarker. In conclusion, hair samples are more suitable as a sample type to reliably assess exposure to REEs than blood samples, and REEs did not have a direct adverse effect on blood pressure in our rat model.

Evaluation of general stress, detoxification pathways, and genotoxicity in rainbow trout exposed to rare earth elements dysprosium and lutetium

Rare earth elements (REEs) have been recently identified as emergent contaminants because of their numerous and increasing applications in technology. The impact of REEs on downstream ecosystems, notably aquatic organisms, is of particular concern, but has to date been largely overlooked. The purpose of this study was thus to evaluate the toxicity of lanthanide metals, lutetium (Lu) and dysprosium (Dy) in rainbow trout after 96 h of exposure. The lethal concentration (LC50) was determined and the expression of 14 genes involved in different pathways such as oxidative stress, xenobiotic detoxification, mitochondrial respiration, DNA repair, protein folding and turnover, inflammation, calcium binding and ammonia metabolism were quantified in surviving fish. In parallel, lipid peroxidation (LPO), DNA damage (DSB), metallothionein level (MT) and cyclooxygenase activity (COX) were examined. The acute 96 h-LC₅₀ data revealed that Lu was more toxic than Dy (1.9 and 11.0 mg/L, respectively) and was able to affect all investigated pathways by changing the expression of the studied genes, to the exception of superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST). It also induced a decrease in DNA repair at concentrations 29 times below the LC₅₀. This suggests that Lu could trigger a general stress to disrupt the cell homeostasis leading to genotoxicity without promoting oxidative stress. However, Dy induced modulation in the expression of genes involved in the protection against oxidative stress, detoxification, mitochondrial respiration, immunomodulation, protein turnover and an increase in the DNA strand breaks at concentrations 170 times lower than LC₅₀. Changes in mRNA level transcripts could represent an early signal to prevent against toxicity of Dy, which exhibited inflammatory and genotoxic effects. This study thus provides useful knowledge enhancing our understanding of survival strategies developed by rainbow trout to cope with the presence of lanthanides in the environment.

Review of Potentially Toxic Rare Earth Elements, Thallium and Tellurium in Plant-based Foods

In the last decades, there is an increasing inclusion of various trace metals and metalloids such as thallium, tellurium and rare earth elements (REEs; lanthanides, scandium, and yttrium) in the composition and production of alloys, in agricultural and medicinal applications, as well as in the manufacturing of hi-tech products. All these activities have led to an accumulation of the aforementioned elements both in soil and water bodies and consequently in the food chain, through discharges from mining and mineral processing, liquid industrial waste or disposal of urban and industrial products. It has been demonstrated that chronic exposure to some of these elements, even at low doses, might lead to a wide range of adverse health effects, even from the early stages of life, such as neurotoxicity, neurodevelopmental toxicity and hepatic alterations. Particularly in children, there have been studies suggesting that some of these elements might negatively affect the children's spatial learning and memory ability indirectly. Such effects are triggered by processes like the production of reactive oxygen species (ROS), lipid peroxidation and modulation of antioxidant activities. Nevertheless, the limited data from toxicological studies and their so-far naturally low occurrence levels in the environment acted as a deterrent in measuring their concentrations during routine analyses of metals in foodstuff. Thus, it is important to collect information on their occurrence data both in adults and in children's daily diet. This review sumrises the current knowledge on the concentration of these elements, in plant-based food products to identify whether a potential health risk occurs. As side projects, this Fellowship provided hands-on training on the evaluation of new biocides application and participation in the given advice to the Danish Food and Veterinary Administration, Danish Environmental Protection Agency, the Danish Medical Agency and the European Chemicals Agency.

Response of the freshwater mussel, Dreissena polymorpha to sub-lethal concentrations of samarium and yttrium after chronic exposure

Samarium (Sm) and yttrium (Y) are commonly used rare earth elements (REEs) but there is a scarcity of information concerning their biological effects in non-target aquatic organisms. The purpose of this study was to determine the bioavailability of those REEs and their toxicity on Dreissena polymorpha after exposure to increasing concentration of Sm and Y for 28 days at 15 °C. At the end of the exposure period, the gene expression of superoxide dismutase (SOD), catalase (CAT), metallothionein (MT), glutathione-S-transferase (GST), cytochrome c oxidase 1 (CO1) and cyclin D (Cyc D) were analysed. In addition, we examined lipid peroxidation (LPO), DNA strand breaks (DSB), GST and prostaglandin cyclooxygenase (COX) activities. Results showed a concentration dependent increase in the level of the REEs accumulated in the soft tissue of mussels. Both REEs decreased CAT but did not significantly modulated SOD and MT expressions. Furthermore, Sm³⁺ up-regulated GST, CO1 and Cyc D, while Y³⁺ increased and decreased GST and CO1 transcripts levels, respectively. Biomarker activities showed no oxidative damage as evidenced by LPO, while COX activity was decreased and DNA strand breaks levels were changed suggesting that Sm and Y exhibit anti-inflammatory and genotoxic effects. Factorial analysis revealed that the major impacted biomarkers by Sm were LPO, CAT, CO1 and COX, while GST gene expression, COX, Cyc D and CAT as the major biomarkers affected by Y. We conclude that these REEs display different mode of action but further investigations are required in order to define the exact mechanism involved in their toxicity.

Study on Biological Effects of La(3+) on Rat Liver Mitochondria by Microcalorimetric and Spectroscopic Methods

The effects of lanthanum on heat production of mitochondria isolated from Wistar rat liver were investigated with microcalorimetry; simultaneously, the effects on mitochondrial swelling and membrane potential (Δψ) were determined by spectroscopic methods. La(3+) showed only inhibitory action on mitochondrial energy turnover with IC50 being 55.8 μmol L(-1). In the spectroscopic experiments, La(3+), like Ca(2+), induced rat liver mitochondrial swelling and decreased membrane potential (Δψ), which was inhibited by the specific permeability transition inhibitor, cyclosporine A (CsA). The induction ability of La(3+) was stronger than that of Ca(2+). These results demonstrated that La(3+) had some biotoxicity effect on mitochondria; the effects of La(3+) and Ca(2+) on rat liver mitochondrial membrane permeability transition (MPT) are different, and La represents toxic action rather than Ca analogy.

Health effects and toxicity mechanisms of rare earth elements-Knowledge gaps and research prospects

In the recent decades, rare earth elements (REE) have undergone a steady spread in several industrial and medical applications, and in agriculture. Relatively scarce information has been acquired to date on REE-associated biological effects, from studies of bioaccumulation and of bioassays on animal, plant and models; a few case reports have focused on human health effects following occupational REE exposures, in the present lack of epidemiological studies of occupationally exposed groups. The literature is mostly confined to reports on few REE, namely cerium and lanthanum, whereas substantial information gaps persist on the health effects of other REE. An established action mechanism in REE-associated health effects relates to modulating oxidative stress, analogous to the recognized redox mechanisms observed for other transition elements. Adverse outcomes of REE exposures include a number of endpoints, such as growth inhibition, cytogenetic effects, and organ-specific toxicity. An apparent controversy regarding REE-associated health effects relates to opposed data pointing to either favorable or adverse effects of REE exposures. Several studies have demonstrated that REE, like a number of other xenobiotics, follow hormetic concentration-related trends, implying stimulatory or protective effects at low levels, then adverse effects at higher concentrations. Another major role for REE-associated effects should be focused on pH-dependent REE speciation and hence toxicity. Few reports have demonstrated that environmental acidification enhances REE toxicity; these data may assume particular relevance in REE-polluted acidic soils and in REE mining areas characterized by concomitant REE and acid pollution. The likely environmental threats arising from REE exposures deserve a new line of research efforts.

Molecular mechanism of oxidative damage of lung in mice following exposure to lanthanum chloride

Exposure to lanthanoids (Ln) elicits an adverse response such as oxidative injury of lung in animals and human. The molecular targets of Ln remain unclear. In the present study, the function and signal pathway of nuclear factor erythroid 2 related factor 2 (Nrf2) in LaCl3 -induced oxidative stress in mouse lung were investigated. Mice were exposed to 2, 5, and 10 mg/kg body weight by nasal administration for 6 consecutive months. With increased doses, La was markedly accumulated and promoted the reactive oxygen species (ROS) production in the lung, which in turn resulted in peroxidation of lipids, proteins and DNA, and severe pulmonary damages. Furthermore, LaCl3 exposure could significantly increase levels of Nrf2, heme oxygenase 1 (HO-1) and glutamate-cysteine ligase catalytic subunit (GCLC) expressions in the LaCl3 -exposed lung. These findings imply that the induction of Nrf2 expression is an adaptive intracellular response to LaCl3 -induced oxidative stress in mouse lung, and that Nrf2 may regulate the LaCl3 -induced pulmonary damages.

Pulmonary toxicity in mice following exposure to cerium chloride

The widespread application of lanthanoids (Lns) in manufacturing industries has raised occupational and environmental health concerns about the possible increased health risks to humans exposed to Lns in their working and living environments. Numerous studies have shown that exposures to Ln cause pulmonary injury in animals, but very little is known about the molecular mechanisms of the pulmonary inflammation caused by cerium chloride (CeCl3) exposure. In this study, we evaluated the oxidative stress and molecular mechanism underlying with the pulmonary inflammation associated with chronic lung toxicity in mice treated with nasally instilled CeCl3 for 90 consecutive days. Our findings suggest that significant cerium accumulated in the lung, leading the obvious increase of the lung indices, significant increases in inflammatory cells and levels of lactate dehydrogenase, alkaline phosphate, and total protein, overproduction of reactive oxygen species and peroxidation of lipids, reduced antioxidant capacity, and pulmonary inflammation. CeCl3 exposure also activated nuclear factor κB, increased the expression of tumor necrosis factor α, cyclooxygenase-2, heme oxygenase 1, interleukin 2, interleukin 4, interleukin 6, interleukin 8, interleukin 10, interleukin 18, interleukin 1β, and CYP1A1. However, CeCl3 reduced the expression of nuclear factor κB (NF-κB)-inhibiting factor and heat shock protein 70. These findings suggest that the pulmonary inflammation caused by CeCl3 in mice is closely associated with oxidative stress and inflammatory cytokine expression.

Yttrium decreases the intracellular Zn2+ concentration in rat thymocytes by attenuating a temperature-sensitive Zn2+ influx

Yttrium is used in the production of various electronic devices because the alloy it contains enhances or modifies the properties of other elements. In order to study the cytotoxic action of yttrium, the effect of yttrium chloride (YCl(3)) on the intracellular Zn(2+) level was examined in rat thymocytes using a flow cytometer with FluoZin-3-AM and propidium iodide. The application of YCl(3) significantly decreased the intensity of the FluoZin-3 fluorescence, suggesting a decrease in the intracellular Zn(2+) level or quenching of the FluoZin-3 fluorescence by Y(3+). However, since Y(3+) did not attenuate the FluoZin-3 fluorescence under cell-free conditions, the latter suggestion was ruled out. Rat thymocytes possess a temperature-sensitive membrane pathway that carries Zn(2+) into the cells. The application of YCl(3) attenuated the FluoZin-3 fluorescence augmented by externally applied ZnCl(2) in a concentration-dependent manner. This suggested that Y(3+) inhibited the Zn(2+) influx, resulting in the decrease in the intracellular Zn(2+) level. Yttrium may induce dyshomeostasis of intracellular Zn(2+), leading to some cytotoxic actions.

Liver injury and its molecular mechanisms in mice caused by exposure to cerium chloride

Cerium has been demonstrated to damage liver of mice, but very little is known about the molecular mechanisms underlying the mouse liver apoptosis. In order to understand the liver injury induced by intragastric administration of cerium chloride (CeCl3) for 60 consecutive days, the hepatocyte ultrasrtucture, various oxidative stress parameters, and the stress-related gene expression levels were investigated for the mouse liver. The results demonstrated that CeCl3 had an obvious accumulation in the mouse liver, leading to a classical laddering cleavage of DNA and hepatocyte apoptosis. CeCl3 significantly promoted the accumulation of reactive oxygen species and inhibited the stress-related gene expression of superoxide dismutase, catalase, glutathione peroxidase, metallothionein, heat-shock protein 70, glutathione-S-transferase, P53, and transferring, and it effectively activated the cytochrome p450 1A. It implied that CeCl3 resulted in apoptosis and alteration of expression levels of the genes related with metal detoxification/metabolism regulation and radical scavenging action in mice.

The impairment of liver DNA conformation and liver apoptosis of mice caused by CeCl3

Cerium (Ce) was shown to cause various toxic effects both in rats and mice; however, the molecular mechanism by which Ce exert theirs toxicity is still understood. In this report, the impairment of liver DNA conformation and liver apoptosis of mice caused by CeCl(3) was studied in vivo using inductively coupled plasma-mass spectrometry, various spectral methods, gel electrophoresis, and transmission electron micrograph. We found that the coefficients of liver to body weight of the mice treated with CeCl(3) were significantly increased. Ce(3+) could be significantly accumulated in the liver, and it insert itself into DNA base pairs and/or bind to DNA nucleotide, and alter the conformation of DNA. Furthermore, the evaluation by gel electrophoresis and transmission electron micrograph showed that higher dose of Ce(3+) could cause DNA cleavage and hepatocyte apoptosis in mice. Therefore, our study aroused the attention of Ce application and exposure effects especially on human liver for long-term and low-dose treatment.

Oxidative stress in the liver of mice caused by intraperitoneal injection with lanthanoides

In order to study the mechanisms underlying the effects of lanthanoid (Ln) on the liver, ICR mice were injected with LaCl₃, CeCl₃, and NdCl₃ at a dose of 20 mg/kg BW into the abdominal cavity daily for 14 days. We then examined oxidative stress-mediated responses in the liver. The increase of lipid peroxide in the liver produced by Ln suggested an oxidative attack that was activated by a reduction of antioxidative defense mechanisms as measured by analyzing the activities of superoxide dismutase, catalase, and ascorbate peroxidase, as well as antioxidant levels such as glutathione and ascorbic acid, which were greatest in Ce(3+) treatment, medium in Nd(3+), and least in La(3+). Our results also implied that the oxidative stress in the liver caused by Ln likely is Ce(3+) > Nd(3+) >La(3+), but the mechanisms need to be further studied in future.

A Window of Opportunity: Designing Carbon Nanomaterials for Environmental Safety and Health

Carbon nanomaterials are among the best known and most promising products of the nanotechnology movement. Some early studies suggest that fullerenes and nanotubes may pose significant health risks, and this has given rise to an emerging literature on carbon nanotoxicology. This young field has now begun to yield insight into toxicity mechanisms and the specific material features involved in those mechanisms. This paper explores the potential to alter those material features through post-processing or reformulation with the goal of reducing or eliminating carbon nanomaterial health risks. The paper emphasizes the important roles of metal content and bioavailability, carbon surface chemistry, and nanomaterial aggregation state. The nanotechnology movement has been given a unique "window of opportunity" to systematically investigate the toxicity of nanotechnology products and to develop ways to manage health risks before large scale manufacturing becomes widespread.