Cerium oxide nanoparticles induce cytotoxicity in human hepatoma SMMC-7721 cells via oxidative stress and the activation of MAPK signaling pathways. Toxicol In Vitro. 2013;27:1082-1088. [PMID: 23416263 DOI: 10.1016/j.tiv.2013.02.005]

Various physicochemical and surface properties controlling the bioactivity of cerium oxide nanoparticles

Amidst numerous emerging nanoparticles, cerium oxide nanoparticles (CNPs) possess fascinating pharmacological potential as they can be used as a therapeutic for various oxidative stress-associated chronic diseases such as cancer, inflammation and neurodegeneration due to unique redox cycling between Ce³⁺ and Ce⁴⁺ oxidation states on their surface. Lattice defects generated by the formation of Ce³⁺ ions and compensation by oxygen vacancies on CNPs surface has led to switching between CeO₂ and CeO_2-x during redox reactions making CNPs a lucrative catalytic nanoparticle capable of mimicking key natural antioxidant enzymes such as superoxide dismutase and catalase. Eventually, most of the reactive oxygen species and nitrogen species in biological system are scavenged by CNPs via an auto-regenerative mechanism in which a minimum dose can exhibit catalytic activity for a longer duration. Due to the controversial outcomes on CNPs toxicity, considerable attention has recently been drawn towards establishing relationships between the physicochemical properties of CNPs obtained by different synthesis methods and biological effects ranging from toxicity to therapeutics. Unlike non-redox active nanoparticles, variations in physicochemical properties and the surface properties of CNPs obtained from different synthesis methods can significantly affect their biological activity (inactive, antioxidant, or pro-oxidant). Moreover, these properties can influence the biological identity, cellular interactions, cellular uptake, biodistribution, and therapeutic efficiency. This review aims to highlight the critical role of various physicochemical and the surface properties of CNPs controlling their biological activity based on 165 cited references.

Synergistic Effect of Metal Oxide Nanoparticles on Cell Viability and Activation of MAP Kinases and NFκB

In recent years, there has been an increase in the production of several types of nanoparticles (Nps) for different purposes. Several studies have been performed to analyse the toxicity induced by some of these individual Nps, but data are scarce on the potential hazards or beneficial effects induced by a range of nanomaterials in the same environment. The purpose of the study described here was to evaluate the toxicological effects induced by in vitro exposure of human cells to ZnO Nps in combination with different concentrations of other metal oxide Nps (Al₂O₃, CeO₂, TiO₂ and Y₂O₃). The results indicate that the presence of these Nps has synergistic or antagonistic effects on the cell death induced by ZnO Nps, with a quite marked beneficial effect observed when high concentrations of Nps were tested. Moreover, analysis by Western blot of the main components of the intracellular activation routes (MAPKs and NFκB) again showed that the presence of other Nps can affect cell activation. In conclusion, the presence of several Nps in the same environment modifies the functional activity of one individual Np. Further studies are required in order to elucidate the effects induced by combinations of nanomaterials.

Toxicogenomics: A New Paradigm for Nanotoxicity Evaluation

The wider applications of nanoparticles (NPs) has evoked a world-wide concern due to their possible risk of toxicity in humans and other organisms. Aggregation and accumulation of NPs into cell leads to their interaction with biological macromolecules including proteins, nucleic acids and cellular organelles, which eventually induce toxicological effects. Application of toxicogenomics to investigate molecular pathway-based toxicological consequences has opened new vistas in nanotoxicology research. Indeed, genomic approaches appeared as a new paradigm in terms of providing information at molecular levels and have been proven to be as a powerful tool for identification and quantification of global shifts in gene expression. Toxicological responses of NPs have been discussed in this chapter with the aim to provide a clear understanding of the molecular mechanism of NPs induced toxicity both in in vivo and in vitro test models.

Functional Recovery of Contused Spinal Cord in Rat with the Injection of Optimal-Dosed Cerium Oxide Nanoparticles

Spinal cord injury (SCI) produces excess reactive oxygen species (ROS) that can exacerbate secondary injury and lead to permanent functional impairment. Hypothesizing that cerium oxide nanoparticles (CONPs) as an effective ROS scavenger may offset this damaging effect, it is first demonstrated in vitro that CONPs suppressed inducible nitric oxide synthase (iNOS) generation and enhanced cell viability of hydrogen peroxide (H2O2)-insulted cortical neurons. Next, CONPs are administered at various does (50-4000 µg mL-1) to a contused spinal cord rat model and monitored the disease progression for up to eight weeks. At one day postinjury, the number of iNOS+ cells decreases in the treated groups compared with the control. At one week, the cavity size and inflammatory cells are substantially reduced, and the expression of proinflammatory and apoptotic molecules is downregulated with a concurrent upregulation of anti-inflammatory cytokine. By eight weeks, the treated groups show significantly improved locomotor functions compared with the control. This study shows for the first time that injection of optimal-dosed CONPs alone into contusion-injured spinal cord of rats can reduce ROS level, attenuate inflammation and apoptosis, and consequently help locomotor functional recovery, adding a promising and complementary strategy to the other treatments of acute SCI.

Recent developments in nanomedicine for melanoma treatment

Melanoma is a most aggressive skin cancer with limited therapeutic options and its incidence is increasing rapidly in recent years. The discovery and application of new targeted therapy agents have shown significant benefits. However, adverse side-effects and resistance to chemotherapy remain formidable challenges in the clinical treatment of malignant melanoma. Nanotherapeutics offers an important prospect of overcoming these drawbacks. The anti-tumoral applications of nanomedicine are varied, including those in chemotherapy, RNA interference, photothermal therapy, and photodynamic therapy. Furthermore, nanomedicine allows delivery of the effector structures into the tumor site via passive or active targeting, thereby allowing increased therapeutic specificity and reduced side effects. In this review, we summarize the latest developments in the application of nanocarrier-mediated targeted drug delivery to melanoma and nanomedicine-related clinical trials in melanoma treatment. We also discuss existing problems and opportunities for future developments, providing direction and new thoughts for further studies.

Iron oxide nanoparticles induced cytotoxicity, oxidative stress and DNA damage in lymphocytes

Over the past few decades nanotechnology and material science has progressed extremely rapidly. Iron oxide nanoparticles (IONPs) owing to their unique magnetic properties have a great potential for their biomedical and bioengineering applications. However, there is an inevitable need to address the issue of safety and health effects of these nanoparticles. Hence, the present study was aimed to assess the cytotoxic effects of IONPs on rats' lymphocytes. Using different assays, we studied diverse parameters including mitochondrial membrane potential, intracellular accumulation of reactive oxygen species (ROS), lactate dehydrogenase activity, antioxidant enzymes activity and DNA damage measurements. Intracellular metal uptake and ultrastructure analysis were also carried out through inductively coupled plasma atomic emission spectroscopy, transmission electron microscopy respectively. The results show that the IONP-induced oxidative stress was concentration-dependent in nature, with significant (P < 0.05) increase in ROS levels, lipid peroxidation level as well as depletion of antioxidant enzymes and glutathione. Moreover, we observed morphological changes in the cell after intracellular uptake and localization of nanoparticles in cells. From the findings of the study, it may be concluded that IONPs induce ROS-mediated cytotoxicity in lymphocytes. Copyright © 2017 John Wiley & Sons, Ltd.

Furanodienone induces G0/G1 arrest and causes apoptosis via the ROS/MAPKs-mediated caspase-dependent pathway in human colorectal cancer cells: a study in vitro and in vivo

Furanodienone, a major bioactive constituents of sesquiterpene derived from Rhizoma Curcumae, has been proven to possess the potent anticancer efficacy on human breast cancer cells. Here, we investigated the cytotoxicity of furanodienone on human colorectal carcinoma cell lines in vitro and in vivo, as well as its underlying molecular mechanisms in the induction of apoptosis. In this study, we found that furanodienone significantly inhibited proliferation of RKO and HT-29 cells, induced mitochondrial dysfunction characterized by collapse of mitochondrial transmembrane potential and reduction of ATP level, and promoted the production of reactive oxygen species (ROS) that functions upstream of caspase-dependent apoptosis. The antioxidant N-acetyl cysteine, a ROS scavenger, abolished this apoptosis induced by furanodienone. In addition, furanodienone elevated the expression of p-p38, p-JNK, but decreased p-ERK, as a result of the produced ROS. The specific inhibitors U0126, SP600125 and SB202190 attenuated the expression of MAPKs, and regulated the expression of cleaved caspase-8, -9 and -3. Furthermore, the potential inhibitory effect of furanodienone on CRC cells was also corroborated in mouse xenograft model. In conclusion, the results demonstrated that furanodienone-triggered ROS plays a pivotal role in apoptosis as an upstream molecule-modulating activity of caspases in mitochondrial pathway via stimulating MAPKs signaling pathway. Our finding may provide a novel candidate for development of antitumor drugs targeting on colorectal cancer.

Cerium oxide nanoparticles could ameliorate behavioral and neurochemical impairments in 6-hydroxydopamine induced Parkinson's disease in rats

BACKGROUND

Cerium oxide nanoparticles (CeO₂NPs) showed promising effects in neurodegenerative diseases including some animal models of Parkinsonism. However, the implication of CeO₂NPs in 6-hydroxydopamine (6-OHDA) induced Parkinsonism remains to be investigated.

AIM

This study was designed to assess whether CeO₂NPs treatment could alleviate neurobehavioral and neurobiochemical deficits in 6-OHDA induced neurotoxicity in rats.

MATERIAL AND METHODS

50 rats received left intrastriatal (IS) injection of either saline (control, n = 10) or 6-OHDA (n = 40). At the third week post-lesion, motor dysfunction was verified using neurobehavioral tests. Then diseased rats received intraperitoneal injection of 0.1, 0.5 or 1 mg/kg of CeO₂NPs or vehicle (10 rats each) for 3 weeks. Rats were subjected to behavioral assessments and then sacrificed for biochemical analyses of the striatum. Striatal dopamine levels, oxidative stress markers including total antioxidant capacity (TAC) and malondialdehyde (MDA), and caspase 3 activity as an apoptotic marker were assessed.

RESULTS

Different doses of CeO₂NPs variably improved motor dysfunctions induced by 6-OHDA injection in open field, Rota Rod and stepping tests. In addition, the neurobiochemical derangements were almost reversed by the 0.5 mg/kg dose of CeO₂NPs, while 0.1 mg/kg dose was not sufficient to alter biochemical measurements in the striatum. Administration of 1 mg/kg of CeO₂NPs partially ameliorated striatal dopamine and decreased apoptosis without significant effect on oxidative stress.

CONCLUSION

The present study showed a putative therapeutic role of CeO2NPs in the treatment of 6-OHDA-induced Parkinsonian rats, and suggested their antioxidant and antiapoptotic effects as possible mechanisms for elevated striatal dopamine level and improved motor performance.

Phytotoxicity of CeO2 nanoparticles on radish plant (Raphanus sativus)

Cerium oxide nanoparticles (CeO₂ NPs) have been considered as one type of emerging contaminants that pose great potential risks to the environment and human health. The effect of CeO₂ NPs on plant-edible parts and health evaluation remains is necessary and urgently to be developed. In this study, we cultivated radish in Sigma CeO₂ NP (<25 nm)-amended soils across a series of concentration treatments, i.e., 0 mg/kg as the control and 10, 50, and 100 mg/kg CeO₂ NPs. The results showed that CeO₂ NPs accelerated the fresh biomass accumulation of radish plant; especially in the treatment of 50 mg/kg CeO₂ NPs, root expansion was increased by 2.2 times as much as the control. In addition, the relative chlorophyll content enhanced by 12.5, 12.9, and 12.2% was compared to control on 40 cultivation days. CeO₂ NPs were mainly absorbed by the root and improved the activity of antioxidant enzyme system to scavenge the damage of free radicals in radish root and leaf. In addition, this study also indicated that the nanoparticles might enter the food chain through the soil into the edible part of the plant, which will be a potential threat to human health.

Alendronate-anchored PEGylation of ceria nanoparticles promotes human hepatoma cell proliferation via AKT/ERK signaling pathways

Previous work has suggested that ceria nanoparticles (CNPs) have regenerative antioxidant properties, which have motivated researchers to consider CNPs as therapeutic agents for treating a number of diseases, including cancer. Recent studies have shown CNPs to be toxic to cancer cells, to inhibit invasion and sensitize cancer cells to radiotherapy. In addition, several hydrophilic polymers have been used to coat the CNP surface in order to enhance its properties of extensive biocompatibility and systemic nontoxicity to normal cells and tissues. However, the results of previous studies were based on high CNP doses (10 μg/mL or more), and these doses may cause serious side effects in clinical applications. The impact of low CNP doses on tumor cells remains unknown. In this study, we report experiments indicating that CNPs‐AL‐ polyethylene glycol (PEG)600, a type of surface‐modified CNP that is more stable and less toxic than traditional CNPs could promote proliferation of hepatoma cells in a dose‐dependent manner. In addition, further research showed that a low dose (0.01 μg/mL) of CNPs‐AL‐PEG600 could reduce hepatoma cell apoptosis and activate AKT/ERK signaling pathways. These results may provide information that is important for using CNPs‐AL‐PEG600 as a therapeutic agent in clinical cancer treatments.

Cerium Oxide Nanoparticles Induce Oxidative Stress and Genotoxicity in Human Skin Melanoma Cells

Extensive applications of cerium oxide (CeO2) nanoparticles require a better understanding of their possible effects on human health. However, data demonstrating the effect of CeO2 nanoparticles on the human skin melanoma cell remain scanty. In the current study, we determined the mechanism through which CeO2 nanoparticles (APS <25 nm) induce toxicity in human skin melanoma cells (A375). The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] and neutral red uptake assays showed concentration and time-dependent cytotoxicity of CeO2 nanoparticles in A375 cells. CeO2 nanoparticles significantly induced the generation reactive oxygen species (ROS) and malondialdehyde, superoxide dismutase, and decreased glutathione levels in A375 cells. It was also observed that the CeO2 nanoparticles induced chromosomal condensation and caspase-3 activity. CeO2 nanoparticles exposed cells revealed the formation of DNA double-strand breakage as measured by percent tail DNA and olive tail moment through comet assay. The decline of cell viability, production of ROS, and DNA damage in A375 cells specifies that CeO2 nanoparticles have less capable to induce cyto and genotoxicity.

Amorphous silica nanoparticles trigger vascular endothelial cell injury through apoptosis and autophagy via reactive oxygen species-mediated MAPK/Bcl-2 and PI3K/Akt/mTOR signaling

Environmental exposure to silica nanoparticles (SiNPs) is inevitable due to their widespread application in industrial, commercial, and biomedical fields. In recent years, most investigators focus on the evaluation of cardiovascular effects of SiNPs in vivo and in vitro. Endothelial injury and dysfunction is now hypothesized to be a dominant mechanism in the development of cardiovascular diseases. This study aimed to explore interaction of SiNPs with endothelial cells, and extensively investigate the exact effects of reactive oxygen species (ROS) on the signaling molecules and cytotoxicity involved in SiNPs-induced endothelial injury. Significant induction of cytotoxicity as well as oxidative stress, apoptosis, and autophagy was observed in human umbilical vein endothelial cells following the SiNPs exposure (P<0.05). The oxidative stress was induced by ROS generation, leading to redox imbalance and lipid peroxidation. SiNPs induced mitochondrial dysfunction, characterized by membrane potential collapse, and elevated Bax and declined bcl-2 expression, ultimately leading to apoptosis, and also increased number of autophagosomes and autophagy marker proteins, such as LC3 and p62. Phosphorylated ERK, PI3K, Akt, and mTOR were significantly decreased, but phosphorylated JNK and p38 MAPK were increased in SiNPs-exposed endothelial cells. In contrast, all of these stimulation phenomena were effectively inhibited by N-acetylcysteine. The N-acetylcysteine supplement attenuated SiNPs-induced endothelial toxicity through inhibition of apoptosis and autophagy via MAPK/Bcl-2 and PI3K/Akt/mTOR signaling, as well as suppression of intracellular ROS property via activating antioxidant enzyme and Nrf2 signaling. In summary, the results demonstrated that SiNPs triggered autophagy and apoptosis via ROS-mediated MAPK/Bcl-2 and PI3K/Akt/mTOR signaling in endothelial cells, and subsequently disturbed the endothelial homeostasis and impaired endothelium. Our findings may provide experimental evidence and explanation for cardiovascular diseases triggered by SiNPs. Furthermore, results hint that the application of antioxidant may provide a novel way for safer use of nanomaterials.

Insight into Several Factors that Affect the Conversion between Antioxidant and Oxidant Activities of Nanoceria

Many conflicting results have been reported related to the antioxidant and oxidant activities of nanoceria. On the basis of this research, many factors might affect the antioxidant activity of nanoceria. However, all of the factors reported only affect the antioxidant activity of nanoceria to a limited extent or cause the antioxidant activity to be lost. We found that several factors can induce conversion between the protective effect and toxicity of nanoceria. At low concentrations of hydroxyl radicals (•OH) and nanomaterials, nanoceria exhibited antioxidant activity but could produce greater amounts of •OH at higher •OH or nanomaterial concentrations and subsequently exhibit oxidant activity. Moreover, the morphology and size of nanoceria can also affect this conversion. We found that high concentrations of •OH and nanoceria could introduce a high amount of Ce(3+) in the system, which might be the reason that nanoceria converted from exhibiting antioxidant to oxidant activity. Under this condition, nanoceria act as a catalyst similar to Fe(2+) to promote •OH production in a Fenton system and also as a catalyst promoter to boost Fe(2+) production of additional •OH during the redox reaction. These conclusions support a better understanding of conflicting reports on medicinal applications for nanoceria and promote their practical application.

Biosynthesis of Silver Nanoparticles Using Taxus yunnanensis Callus and Their Antibacterial Activity and Cytotoxicity in Human Cancer Cells

Plant constituents could act as chelating/reducing or capping agents for synthesis of silver nanoparticles (AgNPs). The green synthesis of AgNPs has been considered as an environmental friendly and cost-effective alternative to other fabrication methods. The present work described the biosynthesis of AgNPs using callus extracts from Taxus yunnanensis and evaluated their antibacterial activities in vitro and potential cytotoxicity in cancer cells. Callus extracts were able to reduce silver nitrate at 1 mM in 10 min. Transmission electron microscope (TEM) indicated the synthesized AgNPs were spherical with the size range from 6.4 to 27.2 nm. X-ray diffraction (XRD) confirmed the AgNPs were in the form of nanocrystals. Fourier transform infrared spectroscopy (FTIR) suggested phytochemicals in callus extracts were possible reducing and capping agents. The AgNPs exhibited effective inhibitory activity against all tested human pathogen bacteria and the inhibition against Gram-positive bacteria was stronger than that of Gram-negative bacteria. Furthermore, they exhibited stronger cytotoxic activity against human hepatoma SMMC-7721 cells and induced noticeable apoptosis in SMMC-7721 cells, but showed lower cytotoxic against normal human liver cells (HL-7702). Our results suggested that biosynthesized AgNPs could be an alternative measure in the field of antibacterial and anticancer therapeutics.

Lanthanides: Applications in Cancer Diagnosis and Therapy

Lanthanide complexes are of increasing importance in cancer diagnosis and therapy, owing to the versatile chemical and magnetic properties of the lanthanide-ion 4f electronic configuration. Following the first implementation of gadolinium(III)-based contrast agents in magnetic resonance imaging in the 1980s, lanthanide-based small molecules and nanomaterials have been investigated as cytotoxic agents and inhibitors, in photodynamic therapy, radiation therapy, drug/gene delivery, biosensing, and bioimaging. As the potential utility of lanthanides in these areas continues to increase, this timely review of current applications will be useful to medicinal chemists and other investigators interested in the latest developments and trends in this emerging field.

Analysis of the activation routes induced by different metal oxide nanoparticles on human lung epithelial cells

Nanoparticles (Nps) can induce toxicity in the lung by accidental or intentional exposure. The main objective of the study reported here was to characterize the effect that four metal oxide Nps (CeO₂, TiO₂, Al₂O₃ and ZnO) had at the cellular level on a human lung epithelial cell line. This goal was achieved by studying the capacity of the Nps to activate the main mitogen-activated protein kinases (MAPKs) and the nuclear factor NFκB. Only ZnO Nps were able to activate all of the MAPKs and the release of Zn²⁺ ions was the main cause of activation. ZnO and Al₂O₃ Nps activated the NFκB pathway and induced the release of inflammatory cytokines. CeO₂ and TiO₂ Nps were found to have safer profiles.

The graphical abstract was obtained using Servier Medical Art.

Lay abstract: When cells are exposed to a stimulus, they can activate different signaling pathways and these lead to different responses such as proliferation, differentiation, migration or inflammation. The objective of the work described here was to characterize the effects of several metal oxide nanoparticles at the cellular level by studying their capacity to activate the main mitogen-activated protein kinases (MAPKs) and the expression of the transcription factor NFκB on a human lung epithelial cell line. These signaling proteins play a relevant role in the vast majority of the cellular events that are triggered in eukaryotic cells after any stimulus.

Low doses of nanodiamonds and silica nanoparticles have beneficial hormetic effects in normal human skin fibroblasts in culture

Nanodiamonds (ND) and silica nanoparticles (SiO2-NP) have been much investigated for their toxicity at high doses, little is known about their biological activity at low concentrations. Here we report the biphasic dose response of ND and SiO2-NP in modulating normal human facial skin fibroblasts (FSF1) in culture. ND and SiO2-NP at low concentration (up to 0.5 μg/ml) had beneficial effects on FSF1 in terms of increasing their proliferation and metabolic activity. Exposure of FSF1 cells to low levels of NP enhanced their wound healing ability in vitro and slowed down aging during serial passaging as measured by maintenance of youthful morphology, reduction in the rate of loss of telomeres, and the over all proliferative characteristics. Furthermore, NP treatment induced the activation of Nrf2- and FOXO3A-mediated cellular stress responses, including an increased expression of heme oxygenease (HO-1), sirtuin (SIRT1), and DNA methyltransferase II (DNMT2). These results imply that ND and SiO2-NP at low doses are potential hormetins, which exert mild stress-induced beneficial hormetic effects through improved survival, longevity, maintenance, repair and function of human cells.

Inflammatory MAPK and NF-κB signaling pathways differentiated hepatitis potential of two agglomerated titanium dioxide particles

TiO2 nanoparticles (TiO2NPs) consumption and deposit in liver have possible implications for hepatitis risks. Specific signal dysregulation at early inflammatory responses needs to be characterized in TiO2NP-induced hepatopathy. MAPK and NF-κB signaling pathways are known to participate in inflammation and respond sensitively to chemical agents, making them preferable biomarkers for hepatitis. In the present study, dynamic activation of MAPK and NF-κB pathways were explored by immunoblotting and NF-κB luciferase reporter assay depending on characterization of TiO2NP agglomeration in human HepG2 cells. Inflammatory and cytotoxic potential of TiO2NPs were determined by qRT-PCR and WST-1 assay. AFM and TEM analyses uncovered ultrastructure damages underlying hepatotoxicity of TiO2NPs. Rod-like rutile agglomerated smaller and induced more pronounced cytotoxicity and immunogenicity than anatase. Correspondingly, though both rutile and anatase significantly activated p38, ERK1/2 and NF-κB pathways, rutile accelerated the maximum phosphorylation of ERK1/2 and elevated the potency of IκBα phosphorylation to its bell curve shape in comparison with a lower and sigmoid type of IκBα phosphorylation for anatase. Furthermore, cell elasticity indicated by Young's modulus and adhesion force increased accompanied with mitochondria damage, contributing to signal dysregulation and hepatotoxicity. The results suggested that differential activation of MAPK and NF-κB pathways could be early predictors for distinct hepatitis risks of two agglomerated TiO2NPs.

Radioprotective effects of ultra-small citrate-stabilized cerium oxide nanoparticles in vitro and in vivo

Different radioprotective action mechanisms of CeO₂ nanoparticles in vitro and in vivo are demonstrated and discussed.

Antibacterial activity of neem nanoemulsion and its toxicity assessment on human lymphocytes in vitro

Neem (Azadirachta indica) is recognized as a medicinal plant well known for its antibacterial, antimalarial, antiviral, and antifungal properties. Neem nanoemulsion (NE) (O/W) is formulated using neem oil, Tween 20, and water by high-energy ultrasonication. The formulated neem NE showed antibacterial activity against the bacterial pathogen Vibrio vulnificus by disrupting the integrity of the bacterial cell membrane. Despite the use of neem NE in various biomedical applications, the toxicity studies on human cells are still lacking. The neem NE showed a decrease in cellular viability in human lymphocytes after 24 hours of exposure. The neem NE at lower concentration (0.7-1 mg/mL) is found to be nontoxic while it is toxic at higher concentrations (1.2-2 mg/mL). The oxidative stress induced by the neem NE is evidenced by the depletion of catalase, SOD, and GSH levels in human lymphocytes. Neem NE showed a significant increase in DNA damage when compared to control in human lymphocytes (P<0.05). The NE is an effective antibacterial agent against the bacterial pathogen V. vulnificus, and it was found to be nontoxic at lower concentrations to human lymphocytes.

Effects of Nano-CeO₂ with Different Nanocrystal Morphologies on Cytotoxicity in HepG2 Cells

Cerium oxide nanoparticles (nano-CeO₂) have been reported to cause damage and apoptosis in human primary hepatocytes. Here, we compared the toxicity of three types of nano-CeO₂ with different nanocrystal morphologies (cube-, octahedron-, and rod-like crystals) in human hepatocellular carcinoma cells (HepG2). The cells were treated with the nano-CeO₂ at various concentrations (6.25, 12.5, 25, 50, 100 μg/mL). The crystal structure, size and morphology of nano-CeO₂ were investigated by X-ray diffractometry and transmission electron microscopy. The specific surface area was detected using the Brunauer, Emmet and Teller method. The cellular morphological and internal structure were observed by microscopy; apoptotic alterations were measured using flow cytometry; nuclear DNA, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) and glutathione (GSH) in HepG2 cells were measured using high content screening technology. The scavenging ability of hydroxyl free radicals and the redox properties of the nano-CeO₂ were measured by square-wave voltammetry and temperature-programmed-reduction methods. All three types of nano-CeO₂ entered the HepG2 cells, localized in the lysosome and cytoplasm, altered cellular shape, and caused cytotoxicity. The nano-CeO₂ with smaller specific surface areas induced more apoptosis, caused an increase in MMP, ROS and GSH, and lowered the cell’s ability to scavenge hydroxyl free radicals and antioxidants. In this work, our data demonstrated that compared with cube-like and octahedron-like nano-CeO₂, the rod-like nano-CeO₂ has lowest toxicity to HepG2 cells owing to its larger specific surface areas.

The Effect of Cerium Oxide Nanoparticle Valence State on Reactive Oxygen Species and Toxicity

Cerium oxide (CeO2) nanoparticles, which are used in a variety of products including solar cells, gas sensors, and catalysts, are expected to increase in industrial use. This will subsequently lead to additional occupational exposures, making toxicology screenings crucial. Previous toxicology studies have presented conflicting results as to the extent of CeO2 toxicity, which is hypothesized to be due to the ability of Ce to exist in both a +3 and +4 valence state. Thus, to study whether valence state and oxygen vacancy concentration are important in CeO2 toxicity, CeO2 nanoparticles were doped with gadolinium to adjust the cation (Ce, Gd) and anion (O) defect states. The hypothesis that doping would increase toxicity and decrease antioxidant abilities as a result of increased oxygen vacancies and inhibition of +3 to +4 transition was tested. Differences in toxicity and reactivity based on valence state were determined in RLE-6TN rat alveolar epithelial and NR8383 rat alveolar macrophage cells using enhanced dark field microscopy, electron paramagnetic resonance (EPR), and annexin V/propidium iodide cell viability stain. Results from EPR indicated that as doping increased, antioxidant potential decreased. Alternatively, doping had no effect on toxicity at 24 h. The present results imply that as doping increases, thus subsequently increasing the Ce(3+)/Ce(4+) ratio, antioxidant potential decreases, suggesting that differences in reactivity of CeO2 are due to the ability of Ce to transition between the two valence states and the presence of increased oxygen vacancies, rather than dependent on a specific valence state.

Mechanisms of Multi-walled Carbon Nanotubes-Induced Oxidative Stress and Genotoxicity in Mouse Fibroblast Cells

The extensive production and wide application of carbon nanotubes have made investigations of its toxic potentials necessary. In the present study, we explored the underlying mechanism through which multi-walled carbon nanotubes (MWCNTs) induce toxicity in mouse fibroblast cells (L929). 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and neutral red uptake viability assays were used to examine mechanisms of cytotoxicity. Dose and time-dependent cytotoxicity was observed in L929 cells. The MWCNTs significantly increased the generation of reactive oxygen species, lipid peroxidation, superoxide dismutase, and decreased glutathione. It was observed that the MWCNTs induced caspase 3 activity. The highest DNA strand breakage was detected by comet assay at 300 µg/mL of MWCNTs. Thus, the data indicate that MWCNTs induced cytotoxicity and apoptosis in L929 cells via oxidative stress.

Cerium oxide nanoparticles as promising ophthalmic therapeutics for the treatment of retinal diseases

Nanotechnology offers exciting new approaches for biology and medicine. In recent years, nanoparticles, particularly those of the rare metal cerium, are showing potential for a wide range of applications in medicine. Cerium oxide nanoparticles or nanoceria are antioxidants and possess catalytic activities that mimic those of super oxide dismutase and catalase, thereby protecting cells from oxidative stress. The retina is highly susceptible to oxidative stress because of its high oxygen consumption and high metabolic activity associated with exposure to light. Many retinal diseases progress through oxidative stress as a result of a chronic or acute rise in reactive oxygen species. Diseases of the retina are the leading causes of blindness throughout the world. Although some treatments may delay or slow the development of retinal diseases, there are no cures for most forms of blinding diseases. In this review is summarized evidence that cerium oxide nanoparticles can function as catalytic antioxidants in vivo in rodent models of age-related macular degeneration and inherited retinal degeneration and may represent a novel therapeutic strategy for the treatment of human eye diseases. This may shift current research and clinical practice towards the use of nanoceria, alone or in combination with other therapeutics.

Cerium dioxide nanoparticles protect against oxidative stress induced injury through modulation of TGF-β signalling

Cerium oxide nanoparticles attenuate oxidative stress induced alterations in TGF-β signalling pathway members.

Silica nanoparticles induce endoplasmic reticulum stress response, oxidative stress and activate the mitogen-activated protein kinase (MAPK) signaling pathway

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Silica nanoparticles (225 nm) induced ER stress and unfolded protein response.

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MAPK pathway and associated genes are induced.

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PP2Ac, TNFα, NFкB and interferon stimulated genes are up-regulated.

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p53 is down-regulated, indicating inhibition of apoptosis.

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The data suggest hepatotoxic, inflammatory and tumorigenic action of SiO₂-NPs.

Application of silica nanoparticles (SiO₂-NPs) may result in human exposure. Here we investigate unexplored modes of action by which SiO₂-NPs with average size of 225 nm act on human hepatoma cells (Huh7). We focused on the endoplasmic (ER) stress response and on mitogen-activated protein kinase (MAPK) signaling pathways. Both pathways were induced. ER stress and the associated three unfolded protein response (UPR) pathways were activated as demonstrated by significant inductions of BiP and XBP-1s and a moderate but significant induction of ATF-4 at 0.05 and 0.5 mg/ml. In addition to activation of NFкB interferon stimulated genes IP-10, IRF-9, and ISG-15 were up-regulated. As a consequence of ER stress, the pro-inflammatory cytokine TNFα and PP2Ac were induced following exposure to 0.05 mg/ml SiO₂-NPs. Additionally, this occurred at 0.005 mg/ml SiO₂-NPs for TNFα at 24 h. This in turn led to a strong transcriptional induction of MAP-kinases and its target genes cJun, cMyc and CREB. A strong transcriptional down-regulation of the proapoptotic gene p53 occurred at 0.05 and 0.5 mg/ml SiO₂-NP. Exposure of Huh7 cells to the anti-oxidant N-acetyl cysteine reduced transcriptional induction of ER stress markers demonstrating a link between the induction of oxidative stress and ER stress. Our study demonstrates that SiO₂-NPs lead to strong ER stress and UPR induction, oxidative stress, activation of MAPK signaling and down-regulation of p53. All of these activated pathways, which are analyzed here for the first time in detail, inhibit apoptosis and induce cell proliferation, which may contribute to a hepatotoxic, inflammatory and tumorigenic action of SiO₂-NPs.

DNA damage and oxidative stress induced by CeO2 nanoparticles in human dermal fibroblasts: Evidence of a clastogenic effect as a mechanism of genotoxicity

The broad range of applications of cerium oxide (CeO2) nanoparticles (nano-CeO2) has attracted industrial interest, resulting in greater exposures to humans and environmental systems in the coming years. Their health effects and potential biological impacts need to be determined for risk assessment. The aims of this study were to gain insights into the molecular mechanisms underlying the genotoxic effects of nano-CeO2 in relation with their physicochemical properties. Primary human dermal fibroblasts were exposed to environmentally relevant doses of nano-CeO2 (mean diameter, 7 nm; dose range, 6 × 10(-5)-6 × 10(-3) g/l corresponding to a concentration range of 0.22-22 µM) and DNA damages at the chromosome level were evaluated by genetic toxicology tests and compared to that induced in cells exposed to micro-CeO2 particles (mean diameter, 320 nm) under the same conditions. For this purpose, cytokinesis-blocked micronucleus assay in association with immunofluorescence staining of centromere protein A in micronuclei were used to distinguish between induction of structural or numerical chromosome changes (i.e. clastogenicity or aneuploidy). The results provide the first evidence of a genotoxic effect of nano-CeO2, (while not significant with micro-CeO2) by a clastogenic mechanism. The implication of oxidative mechanisms in this genotoxic effect was investigated by (i) assessing the impact of catalase, a hydrogen peroxide inhibitor, and (ii) by measuring lipid peroxidation and glutathione status and their reversal by application of N-acetylcysteine, a precusor of glutathione synthesis in cells. The data are consistent with the implication of free radical-related mechanisms in the nano-CeO2-induced clastogenic effect, that can be modulated by inhibition of cellular hydrogen peroxide release.

Synthesis and organic surface modification of luminescent, lanthanide-doped core/shell nanomaterials (LnF3@SiO2@NH2@organic acid) for potential bioapplications: spectroscopic, structural, and in vitro cytotoxicity evaluation

A facile coprecipitation reaction between Ce(3+), Gd(3+), Tb(3+), and F(-) ions, in the presence of glycerine as a capping agent, led to the formation of ultrafine, nanocrystalline CeF3:Tb(3+) 5%, Gd(3+) 5% (LnF3). The as-prepared fluoride nanoparticles were successfully coated with an amine modified silica shell. Subsequently, the obtained LnF3@SiO2@NH2 nanostructures were conjugated with 4-ethoxybenzoic acid in order to prove the possibility of organic modification and obtain a new functional nanomaterial. All of the nanophosphors synthesized exhibited intense green luminescence under UV light irradiation. Based on TEM (transmission electron microscopy) measurements, the diameters of the cores (≈12 nm) and core/shell particles (≈50 nm) were determined. To evaluate the cytotoxic activity of the nanomaterials obtained, their effect on human erythrocytes was investigated. LnF3 nanoparticles were bound to the erythrocyte membrane, without inducing any cytotoxic effects. After coating with silica, the nanoparticles revealed significant cytotoxicity. However, further functionalization of the nanomaterial with -NH2 groups as well as conjugation with 4-ethoxybenzoic acid entailed a decrease in cytotoxicity of the core/shell nanoparticles.

Cerium oxide nanoparticles protect against Aβ-induced mitochondrial fragmentation and neuronal cell death

Evidence indicates that nitrosative stress and mitochondrial dysfunction participate in the pathogenesis of Alzheimer's disease (AD). Amyloid beta (Aβ) and peroxynitrite induce mitochondrial fragmentation and neuronal cell death by abnormal activation of dynamin-related protein 1 (DRP1), a large GTPase that regulates mitochondrial fission. The exact mechanisms of mitochondrial fragmentation and DRP1 overactivation in AD remain unknown; however, DRP1 serine 616 (S616) phosphorylation is likely involved. Although it is clear that nitrosative stress caused by peroxynitrite has a role in AD, effective antioxidant therapies are lacking. Cerium oxide nanoparticles, or nanoceria, switch between their Ce(3+) and Ce(4+) states and are able to scavenge superoxide anions, hydrogen peroxide and peroxynitrite. Therefore, nanoceria might protect against neurodegeneration. Here we report that nanoceria are internalized by neurons and accumulate at the mitochondrial outer membrane and plasma membrane. Furthermore, nanoceria reduce levels of reactive nitrogen species and protein tyrosine nitration in neurons exposed to peroxynitrite. Importantly, nanoceria reduce endogenous peroxynitrite and Aβ-induced mitochondrial fragmentation, DRP1 S616 hyperphosphorylation and neuronal cell death.

Cerium oxide nanoparticles induced toxicity in human lung cells: role of ROS mediated DNA damage and apoptosis

Cerium oxide nanoparticles (CeO₂ NPs) have promising industrial and biomedical applications. In spite of their applications, the toxicity of these NPs in biological/physiological environment is a major concern. Present study aimed to understand the molecular mechanism underlying the toxicity of CeO₂ NPs on lung adenocarcinoma (A549) cells. After internalization, CeO₂ NPs caused significant cytotoxicity and morphological changes in A549 cells. Further, the cell death was found to be apoptotic as shown by loss in mitochondrial membrane potential and increase in annexin-V positive cells and confirmed by immunoblot analysis of BAX, BCl-2, Cyt C, AIF, caspase-3, and caspase-9. A significant increase in oxidative DNA damage was found which was confirmed by phosphorylation of p53 gene and presence of cleaved poly ADP ribose polymerase (PARP). This damage could be attributed to increased production of reactive oxygen species (ROS) with concomitant decrease in antioxidant “glutathione (GSH)” level. DNA damage and cell death were attenuated by the application of ROS and apoptosis inhibitors N-acetyl-L- cysteine (NAC) and Z-DEVD-fmk, respectively. Our study concludes that ROS mediated DNA damage and cell cycle arrest play a major role in CeO₂ NPs induced apoptotic cell death in A549 cells. Apart from beneficial applications, these NPs also impart potential harmful effects which should be properly evaluated prior to their use.

Toxicity study of cerium oxide nanoparticles in human neuroblastoma cells

The present study consisted of cytotoxic, genotoxic, and oxidative stress responses of human neuroblastoma cell line (IMR32) following exposure to different doses of cerium oxide nanoparticles (CeO2 NPs; nanoceria) and its microparticles (MPs) for 24 hours. Cytotoxicity was evaluated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide and lactate dehydrogenase assays whereas genotoxicity was assessed using the cytokinesis-block micronucleus and comet assays. A battery of assays including lipid peroxidation, reactive oxygen species (ROS), hydrogen peroxide, reduced glutathione, nitric oxide, glutathione reductase, glutathione peroxidase, superoxide dismutase, catalase, and glutathione S-transferase were performed to test the hypothesis that ROS was responsible for the toxicity of nanoceria. The results showed that nanosized CeO2 was more toxic than cerium oxide MPs. Hence, further study on safety evaluation of CeO2 NPs on other models is recommended.

Evaluation of deoxynivalenol-induced toxic effects on DF-1 cells in vitro: cell-cycle arrest, oxidative stress, and apoptosis

Deoxynivalenol (DON) is one of the most common mycotoxin contaminants of raw and processed cereal food. Lymphoid cells and fibroblasts are specified to be the most DON-sensitive cell types. In this study, we investigated the toxic effects of DON in chicken embryo fibroblast DF-1 cells. The results showed that DON significantly inhibited DF-1 cell viability in both a time- and concentration-dependent manner. DON could also inhibit the proliferation of DF-1 cells through G2/M phase arrest in the cell cycle progression. Moreover, oxidative stress induced by DON was indicated by increased levels of reactive oxygen species (ROS), malondialdehyde (MDA), and decreased levels of glutathione (GSH) and superoxide dismutase (SOD). In addition, DON could also cause mitochondrial damage by decreasing the mitochondrial membrane potential and induce apoptosis accompanied with the up-regulation of apoptosis-related genes including Caspase-3, Caspase-8, Caspase-9, and AIFM1. These results suggested that DON could cause cell cycle arrest, oxidative stress, and apoptosis in DF-1 cells.

Molecular interactions of nanomaterials and organisms: defining biomarkers for toxicity and high-throughput screening using traditional and next-generation sequencing approaches

The expression of molecular pathways in an organism provides a clue as to the potential impacts of exposure to nanomaterials.