Ceria nanoparticles: biomedical applications and toxicity. / 二氧化铈纳米颗粒：生物医学应用和毒性.

Ceria nanoparticles (CeO2 NPs) have become popular materials in biomedical and industrial fields due to their potential applications in anti-oxidation, cancer therapy, photocatalytic degradation of pollutants, sensors, etc. Many methods, including gas phase, solid phase, liquid phase, and the newly proposed green synthesis method, have been reported for the synthesis of CeO2 NPs. Due to the wide application of CeO2 NPs, concerns about their adverse impacts on human health have been raised. This review covers recent studies on the biomedical applications of CeO2 NPs, including their use in the treatment of various diseases (e.|g., Alzheimer's disease, ischemic stroke, retinal damage, chronic inflammation, and cancer). CeO2 NP toxicity is discussed in terms of the different systems of the human body (e.|g., cytotoxicity, genotoxicity, respiratory toxicity, neurotoxicity, and hepatotoxicity). This comprehensive review covers both fundamental discoveries and exploratory progress in CeO2 NP research that may lead to practical developments in the future.

The cerium oxide nanoparticles toxicity induced physiological, histological and biochemical alterations in freshwater mussels, Unio crassus.

INTRODUCTION: Releasing of cerium oxide nanoparticles (nano-CeO2) to the nature has increased due to the widespread use in many fields ranging from cosmetics to the food industry. Therefore, nano-CeO2 has been included in the Organization for Economic Co-operation and Development's (OECD) priority list for engineering nanomaterials. In this study, the effects of nano-CeO2 on the freshwater mussels were investigated to reveal the impact on the freshwater systems on model organism. METHODS: First, the chemical and structural properties of nano-CeO2 were characterized in details. Second, the freshwater mussels were exposed to environmentally relevant concentrations of nano-CeO2 as 10 mg, 25 mg and 50 mg/L during 48-h and 7-d. Third, after the exposure periods, hemolymph and tissue samples were taken to analyse the Total Hemocyte Counts (THCs) histology and oxidative stress parameters (total antioxidant status, glutathione, glutathione-S-transferase, and advanced oxidative protein products). RESULTS: Significant decrease of the THCs was observed in the nano-CeO2 exposed mussels compared to the control group (P < 0.05). The histological results showed a positive association between nano-CeO2 exposure concentration in the water and level of tissue damage and histopathological alterations were detected in the gill and the digestive gland tissues. Oxidative stress parameters were slightly affected after exposure to nano-CeO2 (P > 0.05). In conclusion, this study showed that acute exposure of freshwater mussels to nano-CeO2 did not pose significant biological risk. However, it has been proven that mussels are able to accumulate nano-CeO2 significantly in their bodies. CONCLUSION: This suggests that nano-CeO2 may be a potential risk to other organisms in the ecosystem through trophic transfer in the food-web based on their habitat and niche in the ecosystem.

Genotoxic hazard assessment of cerium oxide and magnesium oxide nanoparticles in Drosophila.

The use of metal oxide nanoparticles (NPs) is steadily spreading, leading to increased environmental exposures to many organisms, including humans. To improve our knowledge of this potential hazard, we have evaluated the genotoxic risk of cerium oxide (CeO2NPs) and magnesium oxide (MgONPs) nanoparticle exposures using Drosophila as an in vivo assay model. In this study, two well-known assays, such as the wing somatic mutation and recombination test (wing-spot assay) and the single-cell gel electrophoresis test (comet assay) were used. As a novelty, and for the first time, changes in the expression levels of a wide panel of DNA repair genes were also evaluated. Our results indicate that none of the concentrations of CeO2NPs increased the total spot frequency in the wing-spot assay, while induction was observed at the highest dose of MgONPs. Regarding the comet assay, both tested NPs were unable to induce single DNA strand breaks or oxidative damage in DNA bases. Nevertheless, exposure to CeO2NPs induced significant increases in the expression levels of the Mlh1 and Brca2 genes, which are involved in the double-strand break repair pathway, together with a decrease in the expression levels of the MCPH1 and Rad51D genes. Regarding the effects of MgONPs exposure, the expression levels of the Ercc1, Brca2, Rad1, mu2, and stg genes were significantly increased, while Mlh1 and MCPH1 genes were decreased. Our results show the usefulness of our approach in detecting mild genotoxic effects by evaluating changes in the expression of a panel of genes involved in DNA repair pathways.

In Vitro Hepatotoxic and Neurotoxic Effects of Titanium and Cerium Dioxide Nanoparticles, Arsenic and Mercury Co-Exposure.

Considering the increasing emergence of new contaminants, such as nanomaterials, mixing with legacy contaminants, including metal(loid)s, it becomes imperative to understand the toxic profile resulting from these interactions. This work aimed at assessing and comparing the individual and combined hepatotoxic and neurotoxic potential of titanium dioxide nanoparticles (TiO2NPs 0.75-75 mg/L), cerium oxide nanoparticles (CeO2NPs 0.075-10 µg/L), arsenic (As 0.01-2.5 mg/L), and mercury (Hg 0.5-100 mg/L) on human hepatoma (HepG2) and neuroblastoma (SH-SY5Y) cells. Viability was assessed through WST-1 (24 h) and clonogenic (7 days) assays and it was affected in a dose-, time- and cell-dependent manner. Higher concentrations caused greater toxicity, while prolonged exposure caused inhibition of cell proliferation, even at low concentrations, for both cell lines. Cell cycle progression, explored by flow cytometry 24 h post-exposure, revealed that TiO2NPs, As and Hg but not CeO2NPs, changed the profiles of SH-SY5Y and HepG2 cells in a dose-dependent manner, and that the cell cycle was, overall, more affected by exposure to mixtures. Exposure to binary mixtures revealed either potentiation or antagonistic effects depending on the composition, cell type and time of exposure. These findings prove that joint toxicity of contaminants cannot be disregarded and must be further explored.

Controlled decoration of nanoceria on the surface of MoS2nanoflowers to improve the biodegradability and biocompatibility inDrosophila melanogastermodel.

In recent years, nanozymes based on two-dimensional (2D) nanomaterials have been receiving great interest for cancer photothermal therapy. 2D materials decorated with nanoparticles (NPs) on their surface are advantageous over conventional NPs and 2D material based systems because of their ability to synergistically improve the unique properties of both NPs and 2D materials. In this work, we report a nanozyme based on flower-like MoS2nanoflakes (NFs) by decorating their flower petals with NCeO2using polyethylenimine (PEI) as a linker molecule. A detailed investigation on toxicity, biocompatibility and degradation behavior of fabricated nanozymes in wild-typeDrosophila melanogastermodel revealed that there were no significant effects on the larval size, morphology, larval length, breadth and no time delay in changing larvae to the third instar stage at 7-10 d for MoS2NFs before and after NCeO2decoration. The muscle contraction and locomotion behavior of third instar larvae exhibited high distance coverage for NCeO2decorated MoS2NFs when compared to bare MoS2NFs and control groups. Notably, the MoS2and NCeO2-PEI-MoS2NFs treated groups at 100µg ml-1covered a distance of 38.2 mm (19.4% increase when compared with control) and 49.88 mm (no change when compared with control), respectively. High-resolution transmission electron microscopy investigations on the new born fly gut showed that the NCeO2decoration improved the degradation rate of MoS2NFs. Hence, nanozymes reported here have huge potential in various fields ranging from biosensing, cancer therapy and theranostics to tissue engineering and the treatment of Alzheimer's disease and retinal therapy.

Protein interaction, monocyte toxicity and immunogenic properties of cerium oxide crystals with 5% or 14% gadolinium, cobalt oxide and iron oxide nanoparticles - an interdisciplinary approach.

Metal oxide nanoparticles are widely used in both consumer products and medical applications, but the knowledge regarding exposure-related health effects is limited. However, it is challenging to investigate nanoparticle interaction processes with biological systems. The overall aim of this project was to improve the possibility to predict exposure-related health effects of metal oxide nanoparticles through interdisciplinary collaboration by combining workflows from the pharmaceutical industry, nanomaterial sciences, and occupational medicine. Specific aims were to investigate nanoparticle-protein interactions and possible adverse immune reactions. Four different metal oxide nanoparticles; CeOx nanocrystals with 5% or 14% Gd, Co3O4, and Fe2O3, were characterized by dynamic light scattering and high-resolution transmission electron microscopy. Nanoparticle-binding proteins were identified and screened for HLA-binding peptides in silico. Monocyte interaction with nanoparticle-protein complexes was assessed in vitro. Herein, for the first time, immunogenic properties of nanoparticle-binding proteins have been characterized. The present study indicates that especially Co3O4-protein complexes can induce both 'danger signals', verified by the production of inflammatory cytokines and simultaneously bind autologous proteins, which can be presented as immunogenic epitopes by MHC class II. The clinical relevance of these findings should be further evaluated to investigate the role of metal oxide nanoparticles in the development of autoimmune disease. The general workflow identified experimental difficulties, such as nanoparticle aggregate formation and a lack of protein-free buffers suitable for particle characterization, protein analyses, as well as for cell studies. This confirms the importance of future interdisciplinary collaborations.

Size-Dependent Cytotoxicity and Reactive Oxygen Species of Cerium Oxide Nanoparticles in Human Retinal Pigment Epithelia Cells.

PURPOSE: The use of cerium oxide nanoparticles (CeO2 NPs), a lanthanide element oxide and bivalent compound, has been growing continuously in industry and biomedicine. Due to their wide application, the potential human health problems of CeO2 NPs have attracted attention, but studies on the toxicity of this compound to human eyes are lacking. This study investigated the cytotoxicity and reactive oxygen species (ROS) of CeO2 NPs in human retinal pigment epithelial cells (ARPE-19 cells). METHODS: Using the transmission electron microscope (TEM), the size distribution and shape of CeO2 NPs were characterized. To explore the effect of CeO2 NP size on ophthalmic toxicity in vitro, three sizes (15, 30 and 45 nm) of CeO2 NPs were investigated using ATP content measurement, LDH release measurement and cell proliferation assay in ARPE-19 cells. ROS values and mitochondrial membrane potential depolarization were evaluated by H2DCF-DA staining and JC-1 staining. Morphology changes were detected using a phase-contrast microscope. RESULTS: The cytotoxicity of 15 nm CeO2 NPs was found to be the highest and hence was further explored. Treatment with 15 nm CeO2 NPs caused the morphology of ARPE-19 cells to change in a dose- and time-dependent manner. Moreover, the treatment induced excessive ROS generation and mitochondrial membrane potential depolarization. In addition, cytotoxicity was attenuated by the application of a ROS scavenger N-acetyl-L- cysteine (NAC). CONCLUSION: CeO2 NPs induced cytotoxicity in ARPE-19 cells and excessive production of ROS and decreasing mitochondrial membrane potential. The Overproduction of ROS partially contributes to CeO2 NP-induced cytotoxicity.

Macrophage autophagy protects mice from cerium oxide nanoparticle-induced lung fibrosis.

BACKGROUND: Cerium (Ce) is a rare earth element, rapidly oxidizing to form CeO2, and currently used in numerous commercial applications, especially as nanoparticles (NP). The potential health effects of Ce remain uncertain, but literature indicates the development of rare earth pneumoconiosis accompanied with granuloma formation, interstitial fibrosis and inflammation. The exact underlying mechanisms are not yet completely understood, and we propose that autophagy could be an interesting target to study, particularly in macrophages. Therefore, the objective of our study was to investigate the role of macrophagic autophagy after pulmonary exposure to CeO2 NP in mice. Mice lacking the early autophagy gene Atg5 in their myeloid lineage and their wildtype counterparts were exposed to CeO2 NP by single oropharyngeal administration and sacrificed up to 1 month after. At that time, lung remodeling was thoroughly characterized (inflammatory cells infiltration, expression of fibrotic markers such as αSMA, TGFß1, total and type I and III collagen deposition), as well as macrophage infiltration (quantification and M1/M2 phenotype). RESULTS: Such pulmonary exposure to CeO2 NP induces a progressive and dose-dependent lung fibrosis in the bronchiolar and alveolar walls, together with the activation of autophagy. Blockage of macrophagic autophagy protects from alveolar but not bronchiolar fibrosis, via the modulation of macrophage polarization towards M2 phenotype. CONCLUSION: In conclusion, our findings bring novel insight on the role of macrophagic autophagy in lung fibrogenesis, and add to the current awareness of pulmonary macrophages as important players in the disease.

Exacerbation of Coagulation and Cardiac Injury in Rats with Cisplatin-Induced Nephrotoxicity Following Intratracheal Instillation of Cerium Oxide Nanoparticles.

BACKGROUND/AIMS: Exposure to particulate air pollution is associated with increased cardiovascular morbidity and mortality. These effects are particularly aggravated in patients with pre-existing kidney diseases. Cerium oxide nanoparticles (CNPs), used as diesel fuel additives, are emitted in vehicle exhaust and affect humans when inhaled. However, thrombotic and cardiac injury resulting from pulmonary exposure to CNPs in experimental acute kidney injury (AKI) is not fully understood. The objective of the present study was to evaluate the thrombotic and cardiac injury effects of CNPs in a rat model of AKI. METHODS: AKI was induced in rats by a single intraperitoneal injection of cisplatin (CDDP, 6 mg/kg). Six days after injection, rats were intratracheally (i.t.) instilled with either CNPs (1 mg/kg) or saline (control), and various cardiovascular variables and markers of inflammation, oxidative stress and DNA injury were assessed by enzyme linked immunosorbent assay, colorimetric assay, single-cell gel electrophoresis assay and immunohistochemistry, the following day. RESULTS: Compared with individual CDDP or CNPs treatments, the combined CDDP + CNPs treatment elevated significantly the coagulation function, relative heart weight, and troponin I, lactate dehydrogenase, interleukin-6 (IL-6), tumor necrosis factor α (TNFα), and total nitric oxide levels in the plasma. In heart homogenates, the combination of CDDP and CNPs induced a significant increase in IL-6, TNFα, catalase, and glutathione. Furthermore, significantly more DNA damage was observed in this group than in the CDDP or CNPs groups. Immunohistochemical analysis of the heart revealed that expression of nuclear factor erythroid-derived 2-like 2 (Nrf2) and glutathione peroxidase by cardiac myocytes and endothelial cells was increased in the CDDP + CNPs group more than in either CDDP or CNPs group. CONCLUSION: I.t. administration of CNPs in rats with AKI exacerbated systemic inflammation, oxidative stress, and coagulation events. It also aggravated cardiac inflammation, DNA damage, and Nrf2 expression.

In Vivo Regenerable Cerium Oxide Nanozyme-Loaded pH/H2O2-Responsive Nanovesicle for Tumor-Targeted Photothermal and Photodynamic Therapies.

Photodynamic therapy (PDT) and photothermal therapies (PTTs) are both promising strategies for effective tumor therapy. However, the absence of O2 at tumor sites hinders the sustained response of photosensitizers. Here, we develop a recycled cerium oxide (CeO2) catalase nanozyme-loaded hyaluronic acid nanovesicle to address the hypoxic tumor microenvironments and targeted delivery of the photosensitizers [indocyanine green (ICG)] to tumors. A polysaccharide complex effectively modifies the surface of a polyethylenimine phenylboronic acid nanostructure to achieve the CeO2 nanozyme-loading nanovesicles that exhibit both tumor-targeted enhancement and an improved hypoxic microenvironment. Also, the hydrogen peroxide responsiveness and acid-sensitive cleavage of phenylboronic acid specifically disintegrate the ICG/nanozyme coloaded nanovesicles in the tumor microenvironment. The in vitro synergistic tests and tumor suppression rate tests indicated that the cerium oxide nanozyme significantly improves the outcomes of PDT via cerium-element valence state recycling and hypoxia improvement, thus enhancing the tumor suppression efficiency. This pH/H2O2-responsive nanozyme/ICG codelivery system provides a good carrier model for improving the tumor microenvironment and increasing the efficiency of tumor-targeted PTT and PDT therapies.

Multi-biomarker approach to assess the acute effects of cerium dioxide nanoparticles in gills, liver and kidney of Oncorhynchus mykiss.

Cerium oxide nanoparticles (CeO2-NP) have already been detected in the aquatic compartment, however, the evaluation of potential ecotoxicological effects on biota are scarce. The present study aimed to assess the toxic effects of CeO2-NP in Oncorhynchus mykiss in different organs/tissues (gills, liver and kidney) after acute exposure (96 h) to three concentrations: 0.25, 2.5 and 25 mg/L. Oxidative stress response (catalase - CAT; glutathione S-transferases - GSTs), lipid peroxidation (thiobarbituric acid reactive substances - TBARS), Na+/K+-ATPase activity, genotoxicity (genetic damage index - GDI) and histopathology (organ's pathological indices) were evaluated. CAT activity was increased in gills and decreased in liver of fish exposed to the highest CeO2-NPs concentration tested. However, GSTs and Na+/K+-ATPase activities and TBARS levels were not significantly altered in analysed organs. CeO2-NP caused marked changes in the gills (aneurysms, blood capillary congestion, lamellar hypertrophy and hyperplasia, secondary lamella fusion and epithelial lifting), in liver (pyknotic nucleus, hyperemia, enlargement of sinusoids and leucocyte infiltration) and kidney (shrinkage of the glomeruli, enlargement of the Bowman space, tubular degeneration and nuclear hypertrophy). Moreover, a semi-quantitative histopathological scoring system (pathological index) confirmed significant alterations in the three organs of all exposed fish. Furthermore, a significant increase of GDI indices observed in gills and liver, for all tested concentrations, indicated a dose-dependent effect. The present study suggests that the release of CeO2-NP into the aquatic environment promotes biochemical, genotoxic and histopathological damages in fish. However, the mechanisms underlying the occurrence of such effects require further investigation.

In vitro and in vivo assessment of the genotoxic effects of ceric ammonium nitrate and 1,3-propane sultone.

A variety of methods have been developed for accurate and systematic evaluation of chemical genotoxicity. Ceric ammonium nitrate (CAN) and 1,3-propane sultone (1,3-PS) have been extensively applied in industrial fields. Although 1,3-PS, but not CAN, has been reported as a potent carcinogen, systematic assessment of the genotoxic properties of these chemicals has not been conducted. The purpose of this study was to establish a decision tree for evaluating genotoxicity based on the good laboratory practices (GLP) system using 1,3-PS and CAN as test chemicals. In vitro studies were performed including the bacterial reverse mutation assay, chromosomal aberration assay, and micronucleus assay. We conducted in vivo studies using a combined micronucleus and alkaline comet (MN-CMT) assay and the Pig-a gene mutation assay, which is a promising method for detecting gene mutations in vivo. CAN showed negative responses in all in vitro genotoxicity assays and the in vivo combined MN-CMT assay. Meanwhile, 1,3-PS had positive results in all in vitro and in vivo genotoxicity assays. In this study, we confirmed the genotoxicity of 1,3-PS and CAN using both in vitro and in vivo assays. We propose a decision tree for evaluating chemical-induced genotoxicity.

Treatment of Human Lens Epithelium with High Levels of Nanoceria Leads to Reactive Oxygen Species Mediated Apoptosis.

Nanoceria (cerium oxide nanoparticles) have been shown to protect human lens epithelial cells (HLECs) from oxidative stress when used at low concentrations. However, there is a lack of understanding about the mechanism of the cytotoxic and genotoxic effects of nanoceria when used at higher concentrations. Here, we investigated the impact of 24-hour exposure to nanoceria in HLECs. Nanoceria's effects on basal reactive oxygen species (ROS), mitochondrial morphology, membrane potential, ATP, genotoxicity, caspase activation and apoptotic hallmarks were investigated. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) studies on isolated mitochondria revealed significant uptake and localization of nanoceria in the mitochondria. At high nanoceria concentrations (400 µg mL-1), intracellular levels of ROS were increased and the HLECs exhibited classical hallmarks of apoptosis. These findings concur with the cells maintaining normal ATP levels necessary to execute the apoptotic process. These results highlight the need for nanoceria dose-effect studies on a range of cells and tissues to identify therapeutic concentrations in vitro or in vivo.

Maternal exposure to CeO2NPs during early pregnancy impairs pregnancy by inducing placental abnormalities.

Cerium dioxide nanoparticles (CeO2NPs) has been widely used in many fields, and also recommended as a promising carrier for cancer targeted drugs in human medicine for its excellent properties. However, its biological safety to human health remains controversial. In this study, we propose a mouse model exposed to CeO2NPs during early pregnancy, to clarify the effect of maternal CeO2NPs exposure and related molecular mechanism. Pregnant mice are injected intravenously with CeO2NPs by once a day on D5, D6, and D7. The effects of CeO2NPs exposure on pregnancy outcomes are observed on D8, D9, D10 and D12. The results show that CeO2NPs exposure during early pregnancy would lead to poor pregnancy outcomes. Further study find that low-quality decidualization, including the imbalance of trophoblast invasion regulators secreted by decidual cells and abnormal recruitment and differentiation of uNK cells, leads to subsequent biological negative "ripple effects", including placental dysfunction, fetal loss or growth restriction. This study broadens the understanding of the biological safety of CeO2NPs, and provide clues for the prevention of its negative biological effects. Improving the function of uNK cells can be used as one of the therapeutic targets to prevent negative effects of CeO2NPs on pregnancy.

Bioavailability and cytotoxicity of Cerium- (IV), Copper- (II), and Zinc oxide nanoparticles to human intestinal and liver cells through food.

Anthropogenic nanoparticles (NPs) are emitted to the environment and may be present in vegetables for human consumption. However, the toxicity of NPs exposure through food lack systematical investigations. In order to propose a systematical study, lettuce grown in a Cerium- (IV), Copper- (II) and Zinc oxide NP contaminated environment were digested. This digestate was used to culture human intestine cells (i.e. epithelial colorectal adenocarcinoma cells, Caco-2). The basolateral juice produced by the intestinal cells was then used to culture normal human liver (HL-7702) cells. Bioavailability and biotoxicity of the NPs in the vitro models were assessed. NPs were found to be taken up from the environment by vegetables, and may thus be transferred to humans through oral exposure. Bioavailability and the effect of their concentration in the digestate medium differed in regards to NP materials. The levels of NPs found in the digestate were detrimental to intestine cells, while the liver cells exposed to lower concentrations of NP in the bodily fluid showed no statically significant change in cell necrosis. A closer assessment of the detrimental effect of the studied NPs to Caco-2 cells revealed that the damage was mainly related to the solubility of the NPs. This may partly be due to that the more soluble NP material (ZnO > CuO > CeO2) render higher metal ion release and thus higher bioavailability. This appeared to cause more cell death, and even lead to local intestinal inflammation. Although no liver cells died, there was an increase of ROS level, causing ROS-related DNA damage prior to cell necrosis. The findings in this study enhances our understanding of the relative detrimental effect of different types of NPs, and the mechanisms causing their biotoxicity in human cells through food.

Diminished amyloid-ß uptake by mouse microglia upon treatment with quantum dots, silver or cerium oxide nanoparticles: Nanoparticles and amyloid-ß uptake by microglia.

Alzheimer's disease (AD) is a chronic neurodegenerative disease leading to progressive dementia in elderly people. The disease is characterized, among others, by formation of amyloid-ß (Aß) polypeptide plaques in the brain. Although etiology of the disease is not fully understood, recent research suggest that nanomaterials may affect AD development. Here, we described the consequences of exposure of mouse BV-2 microglia to silver nanoparticles (AgNPs, 50 µg/mL), cerium oxide nanoparticles (CeO2NPs, 100 µg/mL), and cadmium telluride quantum dots (CdTeQDs, 3 or 10 µg/mL) in the context of its ability to clear Aß plaques. The brain microglial cells play an important role in removing Aß plaques from the brain. Cell viability and cycle progression were assessed by trypan blue test and propidium iodide binding, respectively. The uptake of Aß and NPs was measured by flow cytometry. Secretion of proinflammatory cytokines was measured with the use of cytometric bead array. Aß (0.1 µM) did not affect viability, whereas NPs decreased microglia growth by arresting the cells in G1 phase (CdTeQDs) or in S phase (AgNPs and CeO2NPs) of cell cycle. The uptake of Aß was significantly reduced in the presence of AgNPs and CeO2NPs. In addition, the least toxic CeO2NPs induced the release of proinflammatory cytokine, tumor necrosis factor α. In summary, each of the NPs tested affected either the microglia phagocytic activity (AgNPs and CeO2NPs) and/or its viability (AgNPs and CdTeQDs) that may favor the occurrence of AD and accelerate its development.

Subchronic toxicity of cerium nitrate by 90-day oral exposure in wistar rats.

This study evaluated the subchronic toxicity of cerium nitrate and determined the no observed adverse effect level (NOAEL) in Wistar rats. In accordance with the Organization for Economic Co-operation and Development guidelines, cerium nitrate was orally administered to Wistar rats by gavage at 0, 0.2, 75, 150, and 300 mg/kg bw/day for 90 days, followed by 28 days of recovery period in the 300 mg/kg bw/day and the control groups. The following parameters were evaluated: mortality, abnormalities, body weight, food consumption, hematology, serum biochemistry, urinanalysis, gross necropsy and histopathology. At the end of the treatment, several significant changes were observed in the 300 mg/kg bw/day groups: relatively decreased mean body weight of males, increased LYMPH%, RET% and decreased NEUT%, RBC of the females, increased ALT, AST and decreased ALB, T-Bil, CHO, CK, LDH of males. Significantly decreased T-Bil, CHO, CK and LDH were also observed in males of the 150 mg/kg bw/day group. Pathological examination revealed that the incidences of foreign body granulomatous lesions in lungs were higher in the 150 and 300 mg/kg bw/day groups as compared with the control group. These findings were attributed to unexpected gavage exposure because the granuloma exhibited a bronchiole-derived distribution. Taken together, the NOAEL of cerium nitrate in Wistar rats is set to be 75 mg/kg bw/day in the present study.

Aortic Oxidative Stress, Inflammation and DNA Damage Following Pulmonary Exposure to Cerium Oxide Nanoparticles in a Rat Model of Vascular Injury.

Pulmonary exposure to cerium oxide nanoparticles (CeO2 NPs) can occur either at the workplace, or due to their release in the environment. Inhaled CeO2 NPs are known to cross the alveolar-capillary barrier and reach various parts of the body, including the vasculature. The anticancer drug cisplatin (CP) causes vascular damage. However, the effects CeO2 NPs on vascular homeostasis in a rat model of CP-induced vascular injury remain unclear. Here, we assessed the impact and underlying mechanism of pulmonary exposure to CeO2 NPs on aorta in rats given a single intraperitoneal injection of cisplatin (CP, 6 mg/kg) to induce vascular damage. Six days later, the rats were intratracheally instilled with either CeO2 NPs (1 mg/kg) or saline (control), and various variables were studied 24 h thereafter in the aortic tissue. The concentration of reduced glutathione and the activity of catalase were significantly increased in the CP + CeO2 NPs group compared with both the CP + saline and the CeO2 NPs groups. The activity of superoxide dismutase was significantly decreased in the CP + CeO2 NPs group compared with both the CP + saline and CeO2 NPs groups. The expression of nuclear factor erythroid-derived 2-like 2 (Nrf2) by the nuclei of smooth muscles and endocardial cells assessed by immunohistochemistry was significantly augmented in CeO2 NPs versus saline, in CP + saline versus saline, and in CP + CeO2 NPs versus CeO2 NPs. Moreover, the concentrations of total nitric oxide, lipid peroxidation and 8-hydroxy-2-deoxyguanosine were significantly elevated in the CP + CeO2 NPs group compared with both the CP + saline and the CeO2 NPs groups. Similarly, compared with both the CP + saline and CeO2 NPs groups, the combination of CP and CeO2 NPs significantly elevated the concentrations of interleukin-6 and tumour necrosis factor-α. Additionally, aortic DNA damage assessed by Comet assay was significantly increased in CeO2 NPs compared with saline, and in CP + saline versus saline, and all these effects were significantly aggravated by the combination of CP and CeO2 NPs. We conclude that pulmonary exposure to CeO2 NPs aggravates vascular toxicity in animal model of vascular injury through mechanisms involving oxidative stress, Nrf2 expression, inflammation and DNA damage.

Impact of Pulmonary Exposure to Cerium Oxide Nanoparticles on Experimental Acute Kidney Injury.

BACKGROUND/AIMS: Cerium oxide nanoparticles (CeO2 NPs) are released from diesel engines that use cerium compounds as a catalytic agent to decrease the diesel exhaust particles, leading to human exposure by inhalation to CeO2 NPs. We have recently demonstrated that pulmonary exposure to CeO2 NPs induces lung inflammation, thrombosis, and oxidative stress in various organs including kidneys. It is well known that particulate air pollution effects are greater in patients with renal diseases. The aim of this study is to investigate the effects of pulmonary exposure to CeO2 NPs in a rat model of acute kidney injury (AKI). METHODS: AKI was induced in rats by a single intraperitoneal injection of cisplatin (CP, 6 mg/kg). Six days later, the rats were intratracheally (i.t.) instilled with either CeO2 NPs (1 mg/kg) or saline (control), and various renal and pulmonary endpoints were assessed 24 h afterward using histological, colorimetric assay, enzyme-linked immunosorbent assay and Comet assay techniques. RESULTS: CP alone decreased body weight, and increased water intake, urine volume and relative kidney weight. CP also increased the plasma concentrations urea and creatinine, and decreased creatinine clearance. In the kidneys, CP significantly increased renal injury molecule-1, interleukin-6 (IL-6), tumor necrosis factor α (TNFα) and glutathione concentrations, and caused renal tubular necrosis, and DNA injury assessed by Comet assay. All these actions were significantly aggravated in rats given both CP and CeO2 NPs. Histopathological changes in lungs of CeO2 NPs-treated rats included marked interstitial cell infiltration and congestion. These were aggravated by the combination of CP + CeO2 NPs. Moreover, this combination exacerbated the increase in the concentrations of TNFα and IL-6, and the decrease in the activity of pulmonary catalase and total nitric oxide concentration, and lung DNA damage. CONCLUSION: We conclude that the presence of CeO2 NPs in the lung exacerbated the renal and lung effects of CP-induced AKI.

Effects of cerium oxide nanoparticles on bacterial growth and behaviors: induction of biofilm formation and stress response.

In this paper, the effects of cerium oxide nanoparticles (CeO2 NPs) on the group bacterial behaviors were elaborated. After 36-h cultivation, the biofilm biomass was enhanced by the sub-lethal concentrations of 0.5 and 2 mg/L CeO2 NP exposure. Meanwhile, the promoted production of total amino acids in microbes further resulted in the increased surface hydrophobicity and percentage aggregation. To resist the CeO2 NPs stress, the biofilm exhibited a double-layer microstructure, with the protein (PRO) and living cells occupying the bottom, the polysaccharide (PS), and dead cells dominating the top. The bacterial diversity was highly suppressed and Citrobacter and Pseudomonas from the phylum of γ-Proteobacteria strongly dominated the biofilm, indicating the selective and enriched effects of CeO2 NPs on resistant bacteria. The stimulated inherent resistance of biofilm was reflected by the reduced adenosine triphosphate (ATP) content after 4 h exposure. The increased levels of reactive oxygen species (ROS) in the treatments of 8 h CeO2 NP exposure led to the upregulated quorum sensing signals of acylated homoserine lactone (AHL) and autoinducer 2 (AI-2), beneficial to mitigating the environmental disturbance of CeO2 NPs. These results provide evidences for the accelerating effects of CeO2 NPs on biofilm formation through oxidative stress, which expand the understanding of the ecological effects of CeO2 NPs.