Induction of Hepatic Metallothionein by Trivalent Cerium: Role of Interleukin 6

Toxicity of two heavy rare earth elements to freshwater mussels Dreissena polymorpha

Rare earth elements (REE) are essential components of many electronic devices that could end-up in solid waste disposal sites and inadvertently released in the environment. The purpose of this study was to examine the toxicity of two heavy REEs, erbium (Er) and lutetium (Lu), in freshwater mussels Dreissena polymorpha. Mussels were exposed to 14 days to increasing concentration (10, 50, 250, and 1250 µg/L) of either Er and Lu at 15 °C and analyzed for gene expression in catalase (CAT), superoxide dismutase (SOD), metallothionein (MT), cytochrome c oxidase (CO1), and cyclin D for cell cycle. In addition, lipid peroxidation (LPO), DNA damage (DNAd), and arachidonate cyclooxygenase were also determined. The data revealed that mussels accumulated Er and Lu similarly and both REEs induced changes in mitochondrial COI activity. Er increased cell division, MT, and LPO, while Lu increased DNAd and decreased cell division. Tissue levels of Er were related to changes in MT (r = 0.7), LPO (r = 0.42), CO1 (r = 0.69), and CycD (r = 0.31). Lu tissue levels were related to changes in CO1 (r = 0.73), CycD (r =  - 0.61), CAT (r = 0.31), DNAd (r = 0.43), and SOD (r = 0.34). Although the lethal threshold was similar between Er and Lu, the threshold response for LPO revealed that Er produced toxicity at concentrations 25 times lower than Lu suggesting that Er was more harmful than Lu in mussels. In conclusions, the data supports that the toxicity pattern differed between Er and Lu although they are accumulated in the same fashion.

Typical 2-Cys Peroxiredoxins as a Defense Mechanism against Metal-Induced Oxidative Stress in the Solitary Ascidian Ciona robusta

Typical 2-Cys peroxiredoxins (2-Cys Prdxs) are proteins with antioxidant properties belonging to the thioredoxin peroxidase family. With their peroxidase activity, they contribute to the homeostatic control of reactive oxygen species (ROS) and, therefore, participate in various physiological functions, such as cell proliferation, differentiation, and apoptosis. Although Prdxs have been shown to be potential biomarkers for monitoring aquatic environments, minimal scientific attention has been devoted to describing their molecular architecture and function in marine invertebrates. Our study aims to clarify the protective role against stress induced by exposure to metals (Cu, Zn, and Cd) of three Prdxs (Prdx2, Prdx3, and Prdx4) in the solitary ascidian Ciona robusta, an invertebrate chordate. Here, we report a detailed pre- and post-translational regulation of the three Prdx isoforms. Data on intestinal mRNA expression, provided by qRT-PCR analyses, show a generalized increase for Prdx2, -3, and -4, which is correlated to metal accumulation. Furthermore, the increase in tissue enzyme activity observed after Zn exposure is slower than that observed with Cu and Cd. The obtained results increase our knowledge of the evolution of anti-stress proteins in invertebrates and emphasize the importance of the synthesis of Prdxs as an efficient way to face adverse environmental conditions.

Insights on the toxicity of selected rare earth elements in rainbow trout hepatocytes

The increasing extraction of rare earth elements (REEs) for technology applications raised concerns for contamination and toxicity in the environment. The purpose of this study was to examine the toxicity of the following REEs in primary cultures of rainbow trout hepatocytes: yttrium (Y), samarium (Sm), gadolinium (Gd), terbium (Tb) and lutetium (Lu). Hepatocytes were exposed to increasing concentrations of the above elements for 24 h at 15 °C and they were analyzed for viability, metallothioneins (MT), glutathione-S-transferase (GST) and arachidonate cyclooxygenase (COX) as markers of oxidative stress and inflammation. The results revealed that the cytoxicity of REEs were as follows in decreasing order: Y > Sm > Lu > Tb > Gd in concordance with published rainbow trout mortality data. While effects on GST and COX activities were marginal, MT levels were more strongly increased with the 2 most toxic REEs (Y and Sm) and Gd, while MT levels were decreased in the least toxic ones (Tb, Lu). While cell viability followed published trout mortality data, it also followed the redox potential and the glutathione affinity constant (log k). The capacity to induce/decrease MT levels was associated with ionic radius, log k (glutathione) and electronegativity. A proposed mechanism of toxicity for REEs is presented based on the chemical properties of REEs, namely the glutathione binding constant and ionic radius, in light of the observed effects in trout hepatocytes.

Stress granules in Ciona robusta: First evidences of TIA-1-related nucleolysin and tristetraprolin gene expression under metal exposure

Stress granules are non-membranous cytoplasmic foci, composed of non-translating messenger ribonucleoproteins, translational initiation factors and other additional proteins. They represent a primary mechanism to rapidly modulate gene expression when cells are subjected to adverse environmental conditions. Very few works have been devoted to study the presence of the molecular components of stress granules in invertebrates. In this work, we characterized the transcript sequences for two important protein components of stress granules, TIA-1-related nucleolysin (TIAR) and tristetraprolin (TTP), in the solitary ascidian Ciona robusta, an invertebrate chordate, and carried out the first studies on their gene expression under stress conditions induced by metals (Cu, Zn and Cd). Data on mRNA expression levels, provided by qRT-PCR analyses, show a generalized decrease at the second day of metal-exposure for both tiar and ttp, suggesting that metal accumulation induces acute stress and the inhibition of the transcription for the two studied proteins. In-situ hybridization analyses demonstrate that TIAR and TTP antisense riboprobes recognize circulating granular amoebocytes in the hemolymph, in both blood lacunae and tunic. The results obtained in this work increase our knowledge on the evolution of anti-stress proteins in metazoans and emphasize the importance of the transcription of tiar and ttp, which represents an efficient physiological response allowing organisms to survive in the environment under stress conditions.

A Novel Synthetic Compound, Bismuth Zinc Citrate, Could Potentially Reduce Cisplatin-Induced Toxicity Without Compromising the Anticancer Effect Through Enhanced Expression of Antioxidant Protein

Cisplatin is a common anticancer drug, but it comes with significant nephrotoxicity. Further cisplatin-induced oxidative stress contributes to the pathogenesis of the nephrotoxicity. A new compound, BiZn, can potentially prevent this complication. We verified our postulation by in vitro and in vivo models. From our findings, BiZn did not affect cisplatin-induced cytotoxicity on neuroblastoma cells under both in vitro and in vivo settings. However, BiZn significantly reduced the blood urea nitrogen and creatinine levels in cisplatin-treated mice. Under the lethal dosage of cisplatin, co-treatment of BiZn significantly increased the survival rate. BiZn stimulated antioxidant proteins metallothionein (MT) and glutathione (GSH) generation from kidney cells and minimized cisplatin-induced apoptosis. Knocking down MT-IIA and inhibiting GSH abolished such protection. In conclusion, pretreatment of BiZn decreased cisplatin-induced renal toxicity without affecting its antitumor activity. BiZn-induced antioxidant proteins MT and GSH may contribute to the renal protection effect.

Molecular characterization and metal induced gene expression of the novel glutathione peroxidase 7 from the chordate invertebrate Ciona robusta

In the present study, we describe the identified and characterized the gene and the transcript of a novel glutathione peroxidase-7 (GPx7) from the solitary ascidian Ciona robusta, an invertebrate chordate widely distributed in temperate shallow seawater. The putative nucleotide and amino acid sequences were compared with those of GPx7 from other metazoans and phylogenetic analysis suggests the presence of a high evolutionary pressure in the contest of neutral evolution. The mRNA of CrGPx7 is located in hemocytes and ovarian follicular cells, as revealed by in situ hybridization. The time course of CrGPx7 mRNA levels in the presence of Cd, Cu and Zn, showed upregulation in the final stages of the experiments, suggesting a role of GPx7 in late protection from oxidative stress. Our in silico analyses of the crgpx7 promoter region revealed putative consensus sequences similar to mammalian metal-responsive elements (MRE) and xenobiotic-responsive elements (XRE), suggesting that the transcription of these genes directly depends on metals. Cell-free extract from C. robusta tissues show the presence of selenium-independent GPx activity that is inhibited by the presence of metals.

In vivo protective role against water contamination with cerium via chronic administration of omega 3

In the present study, adult, healthy male Wistar rats (120 ± 10 g) were pre-treated by intragastric administration of cerium chloride (CeCl₃) 10 mg/kg (BW) each day during 60 days. Control animal were treated with omega 3, a polyunsaturated fatty acid (ω-3), by an intragastric administration at 10 mg/kg of BW for 60 days. Our results showed that CeCl₃-induced alterations in all tested oxidative stress markers. In fact, CeCl₃-induced the increase the level of both the creatinine concentration and the expression of lactate dehydrogenase, alkaline phosphatase, and transaminase activities in serum. On the other hand, CeCl₃ significantly increased the levels of lipid peroxidation in the renal and hepatic tissues. The capacity of CeCl₃ to generate reactive oxygen species (ROS) could explain his ability to induce morphological alterations, such as centrilobular hemorrhage, hepatic necrosis, and vacuolization of the cytoplasm in hepatic tissues, and the atrophy of the glomerulus and dilatation of urinary space in renal tissues. However, omega 3, after gastric administration, reduced significantly the toxic effect caused by CeCl₃ according to his high ability to scavenge ROS. The present study indicates that omega 3 is a significant compound with protective activity against intoxication with heavy metal, the cerium, and thus may be useful for chemoprevention.

Determination of Rare Earth Elements in Human Sperm and Association with Semen Quality

The aim of the present study was to measure lanthanum (La), cerium (Ce), europium (Eu), and gadolinium (Gd) concentrations in human semen and correlate the results with sperm quality. The median semen content of La was 19.5 µg kg(-1) dry weight (dw) (range 2.27-269), of Ce was 41.9 µg kg(-1) dw (range 4.52 to 167), of Eu was 0.68 µg kg(-1) dw (range 0.06-1.95), of Gd was 3.19 µg kg(-1) dw (range 0.38-12.0), and of calcium (Ca) was 4063 mg kg(-1) dw (range 484-17,191). Concentrations of La, Ce, Eu, Gd, and Ca were significantly lower in nondrinkers' semen than in semen from drinkers. Significant differences were detected between La, Ce, Eu, Gd, and Ca concentrations in semen from nondrinkers and moderate drinkers. Concentrations of La, Ce, and Gd in semen of short-term smokers were significantly lower than those in extremely long-term smokers. Significant differences were also detected between La concentration in semen from a group of short-term smokers and that of a group of long-term smokers. Positive correlations were found between La, Ce, Eu, Gd, and Ca concentrations in semen. La, Ce, Gd, and Ca concentrations in semen were positively associated with progressive motility and percentage of normal spermatozoa. Positive correlations were found between Ca and sperm concentration. Concentrations of La, Ce, and Gd were negatively associated with sperm concentration, whilst Ca concentration was negatively associated with volume of ejaculate. At the examined level, La, Ce, Eu, and Gd did not affect sperm quality, whereas alcohol consumption and smoking might have increased the level of rare earth elements in semen.

The effects of acute waterborne exposure to sublethal concentrations of molybdenum on the stress response in rainbow trout, Oncorhynchus mykiss

To determine if molybdenum (Mo) is a chemical stressor, fingerling and juvenile rainbow trout (Oncorhynchus mykiss) were exposed to waterborne sodium molybdate (0, 2, 20, or 1,000 mg l^-1 of Mo) and components of the physiological (plasma cortisol, blood glucose, and hematocrit) and cellular (heat shock protein [hsp] 72, hsp73, and hsp90 in the liver, gills, heart, and erythrocytes and metallothionein [MT] in the liver and gills) stress responses were measured prior to initiation of exposure and at 8, 24, and 96 h. During the acute exposure, plasma cortisol, blood glucose, and hematocrit levels remained unchanged in all treatments. Heat shock protein 72 was not induced as a result of exposure and there were no detectable changes in total hsp70 (72 and 73), hsp90, and MT levels in any of the tissues relative to controls. Both fingerling and juvenile fish responded with similar lack of apparent sensitivity to Mo exposure. These experiments demonstrate that exposure to waterborne Mo of up to 1,000 mg l^-1 did not activate a physiological or cellular stress response in fish. Information from this study suggests that Mo water quality guidelines for the protection of aquatic life are highly protective of freshwater fish, namely rainbow trout.

Metallothionein-1 and nitric oxide expression are inversely correlated in a murine model of Chagas disease

Chagas disease, caused by Trypanosoma cruzi, represents an endemic among Latin America countries. The participation of free radicals, especially nitric oxide (NO), has been demonstrated in the pathophysiology of seropositive individuals with T. cruzi. In Chagas disease, increased NO contributes to the development of cardiomyopathy and megacolon. Metallothioneins (MTs) are efficient free radicals scavengers of NO in vitro and in vivo. Here, we developed a murine model of the chronic phase of Chagas disease using endemic T. cruzi RyCH1 in BALB/c mice, which were divided into four groups: infected non-treated (Inf), infected N-monomethyl-L-arginine treated (Inf L-NAME), non-infected L-NAME treated and non-infected vehicle-treated. We determined blood parasitaemia and NO levels, the extent of parasite nests in tissues and liver MT-I expression levels. It was observed that NO levels were increasing in Inf mice in a time-dependent manner. Inf L-NAME mice had fewer T. cruzi nests in cardiac and skeletal muscle with decreased blood NO levels at day 135 post infection. This affect was negatively correlated with an increase of MT-I expression (r = -0.8462, p < 0.0001). In conclusion, we determined that in Chagas disease, an unknown inhibitory mechanism reduces MT-I expression, allowing augmented NO levels.

The potential toxic effects of cerium on organism: cerium prolonged the developmental time and induced the expression of Hsp70 and apoptosis in Drosophila melanogaster

Due to the widespread application of cerium, a rare earth element, the risk of exposure to cerium has increased. Therefore, understanding the physiological effects of cerium is of great importance. Our previous work showed that cerium caused significant lifespan shortening accompanied by oxidative damage in Drosophila melanogaster, however, little is known about the detailed mechanism of cerium-induced cytotoxicity. Thus, we examined the developmental time during metamorphosis, and assessed the toxic effects of cerium by evaluating heat shock protein 70 (Hsp70), DNA damage markers and apoptosis in D. melanogaster. We found that cerium extended the developmental time of D. melanogaster and up-regulated the expression of Hsp70 when the concentration of cerium was increased (especially concentrations over 26.3 μg/g). Up-regulation of the cell cycle checkpoint p53 and cell signaling protein p38 were also observed when the concentration of cerium was over 104 μg/g. In addition, the activities of caspase-3 and caspase-9, markers of apoptosis, were significantly higher when the larvae were exposed to ceric sulfate. These results suggest that high concentrations of cerium may result in DNA damage and ultimately apoptosis in D. melanogaster, and strongly indicate that cerium should be applied with caution and the potential toxic effects in humans should also be taken into consideration.

Lanthanum(III) impacts on metallothionein MTT1 and MTT2 from Tetrahymena thermophila

Metallothionein MTT1 and MTT2 from Tetrahymena thermophila are sulfydryl-rich proteins that can bind to and are inducible by heavy metals such as mercury, cadmium, zinc, and copper. However, little is known about the induction and binding of T. thermophila metallothionein by trivalent metals. In this study, we found that 10-80 μM La(3+) can promote Tetrahymena cells proliferation, and fluorescence spectrum analysis showed that La(3+) can enter T. thermophila cells. Real-time quantitative polymerase chain reaction showed La(3+) induced the expression of MTT1 and MTT2. Furthermore, Fluorescence analysis indicated La(3+) bind to MTT1 and MTT2. These results implied that La(3+) could interact with MTT1 and MTT2 via aspartic or glutamic acid oxygen atoms.

In vitro cytotoxicity evaluation of biomedical nanoparticles and their extracts

The present study presents a new approach for evaluating in vitro cytotoxicity of nanoparticles. The approach is based on American National Standard ISO 10993-5. Hepatoma HepG2 and fibroblast NIH3T3 cell lines were incubated with nanoparticles, and their associated extracts were derived at 70 and 121 degrees C. Nanoparticles proposed as potential biomedical imaging probes were evaluated on the basis of the detection of metabolic activities and cell-morphology changes. In general, nanoparticles incubated directly with cells showed higher cytotoxicity than their associated extracts. CdSe and core-shell CdSe@ZnS quantum dots resulted in low cell viability for both cell lines. The cytotoxicity of the quantum dots was attributed to the Cd ion and the presence of the nanoparticle itself. A statistically significant (p < 0.05) decrease in cell viability was found in higher dosage concentrations. Rare earth nanoparticles and their extracts appear to affect NIH3T3 cells only, with cell viability as low as 71.4% +/- 4.8%. Magnetic nanoparticles have no observable effects on the cell viabilities for both cell lines. In summary, we found the following: (1) both direct incubation and extracts of nanoparticles are required for complete assessment of nanoparticle cytotoxicity, (2) the rare earth oxide nanoparticles are less cytotoxic than the Cd-based quantum dots, and (3) the extent of cytotoxicity is dependent upon the cell line.

Cerium caused life span shortening and oxidative stress resistance in Drosophila melanogaster

To investigate the effects of the rare earth element cerium (Ce) on the life span and biomarkers of oxidative stress in the fruit fly (Drosophila melanogaster). Fruit flies were fed on media with different dose of ceric sulfate (1, 4, 16, 64, 256, 1024mg/L, corresponding to cerium concentrations of 0.45, 1.65, 6.91, 26.3, 104, and 429microg/g culture medium). Mean life span, maximum life span, and fertility were calculated. There was a significant decrease in mean life span and maximum life span with increasing doses of cerium. At some concentrations, there was a decrease in reproductive output, especially concentrations >6.91microg/g. We also measured superoxide dismutase (SOD) activity, catalase (CAT) activity, and lipid peroxidation product levels (malondialdehyde (MDA) content). Cerium caused a significant increase in MDA content and decrease in SOD and CAT activities at concentrations >6.91microg/g. These results suggest that cerium may result in oxidative toxicity to D. melanogaster.

Dichotomous effects of lead acetate on the expression of metallothionein in the liver and kidney of mice

Metallothionein (MT) is a low-molecular-weight cysteine-rich protein which has a high affinity for metals and plays important roles in the protection against metal toxicity. As little information is available concerning the mechanism of MT induction by lead (Pb) compounds, we investigated the induction of MT by Pb acetate both at mRNA and protein levels in mice. Administration of Pb increased the levels of MT-I mRNA in the liver and kidney in six strains of mice. However, MT protein was detected only in the liver, and little or no increases in MT protein were detected in the kidney of any strains of mice. Speciation of metals in the liver cytosol showed that the major metal bound to MT was zinc but not Pb. The increases in plasma concentrations of interleukin-6 suggest that the production of interleukin-6 by Pb administration is involved in the induction of MT in the liver. Treatment of renal cells with Pb in vitro also resulted in the increase in MT mRNA but little increase in MT protein. These data suggest that Pb exerts a dual effect on MT expression; enhancement of MT gene transcription both in the liver and kidney and suppression of MT mRNA translation in the kidney.

Induction of metallothionein by manganese is completely dependent on interleukin-6 production

Metallothionein (MT) is a cysteine-rich protein that binds to and is inducible by heavy metals such as cadmium and zinc. However, the precise mechanism of MT induction by other metals remains unclear. In the present study, we investigated the mechanism of MT induction by manganese, focusing on the involvement of cytokine production. Administration of MnCl(2) to mice resulted in the induction of MT dose-dependently in the liver with little accumulation of manganese. Speciation analysis of metals in the liver cytosol showed that the major metal bound to the induced MT was zinc. Administration of MnCl(2) caused an increase in mRNA levels of interleukin-6 (IL-6) in the liver as well as an increase in serum levels of IL-6 but not those of other inflammatory cytokines. Subsequently, serum levels of serum amyloid A (SAA), an acute-phase protein induced by IL-6, increased with a peak at 24 h. However, no increase in serum alanine aminotransferase activity was observed, suggesting that manganese enhanced the production of IL-6 and SAA without causing liver injury. In response to IL-6, the expression of a zinc transporter, ZIP14, was enhanced in the liver, possibly contributing to the synthesis of hepatic zinc-MT. In IL-6-null mice, the induction of hepatic MT by treatment with MnCl(2) was completely suppressed to the control level. These results suggest that manganese is a unique metal that induces the synthesis of hepatic MT completely depending on the production of IL-6 without accompanying liver injury.