Neuronal cytotoxicity and genotoxicity induced by zinc oxide nanoparticles
Introduction
Zinc oxide nanoparticles (ZnO NPs) are one of the most abundantly used nanomaterials in consumer products and biomedical applications due to their specific properties, e.g. transparency, high isoelectric point, biocompatibility, and photocatalytic efficiency. They are widely employed in a variety of devices including cosmetics, toothpaste, sunscreens, fillings in medical materials, textiles, wall paints, and other building materials, and they can be also utilized in environmental remediation for elimination or degradation of pollutants in water or air (Qiang, 2001). Furthermore, ZnO NPs have promising applications in the medicine field since they have been proposed as a possible treatment for cancer and/or autoimmune diseases after being found to be selectively toxic towards potential disease-causing cells (Hanley et al., 2008, Premanathan et al., 2011, Akhtar et al., 2012), and they are being considered to be used in fabrication of nerve guidance channels for treatment of nerve injury (Seil and Webster, 2008). As a result of all these uses, human exposure to these NPs is highly frequent. They can enter the organism through different pathways (respiratory tract, digestive system and parenteral routes) and have shown a systemic distribution in in vivo studies (Vandebriel and De Jong, 2012), so they can potentially reach any organ or tissue and involve a risk for human health. Toxicity of ZnO NPs has been extensively studied and they have been shown to affect many different cell types and animal systems (Chiang et al., 2012, De Berardis et al., 2010, Osman et al., 2010, Sharma et al., 2012a, Sharma et al., 2012b, Wahab et al., 2011). Commonly, the toxicity of NPs is associated with their small size and high specific surface area and therefore, nanoforms are theoretically expected to be more toxic than their bulk counterparts (Xiong et al., 2011).
In recent years, there have been an increasing number of works reporting that different NPs can reach the brain and cause neurological injuries, being associated even with neurodegenerative diseases (Block et al., 2004, Hu and Gao, 2010, Peters et al., 2006). This translocation can happen both directly, through axonal transport from olfactory epithelium, or indirectly by passing to the bloodstream and crossing the blood brain barrier (Oberdörster et al., 2004). Similarly to other metal oxide NPs, it has been recently found that ZnO NPs reach the brain of experimental animals after oral (Lee et al., 2012) and inhalatory (Kao et al., 2012a) administration. Still, there is a significant lack of toxicological data for ZnO NPs on nervous system, especially for human neuronal cells and tissues.
In vitro data have shown that ZnO NPs induce cytotoxicity in mouse neuroblastoma Neuro-2A cells and neural stem cells (Deng et al., 2009, Jeng and Swanson, 2006), in rat RSC96 Schwann cells and primary neuronal cells (Chiang et al., 2012, Yin et al., 2012), and in human glioma cells (Ostrovsky et al., 2009). Besides, they were found to enhance the excitability of rat neurons by altering the ion channels (Zhao et al., 2009) and to decrease the adhesion of rat astroglial cells (Seil and Webster, 2008), although in this last case the cells were exposed to composite materials with ZnO NPs.
The only in vivo study describing neurological effects after ZnO NP exposure reported attenuation in spatial learning and memory ability by alteration of synaptic plasticity in rats after intraperitoneal administration (Han et al., 2011). Besides, morphological and histochemical changes in brains of rats fed with bulk ZnO were also described (Kozik et al., 1980).
Given the wide and frequent use of ZnO NPs in many fields closely related to human beings, their promising beneficial applications in medicine, and the scarce knowledge on their potential neurotoxic effects, the main objective of this work was to investigate the cytotoxic and genotoxic effects of ZnO NPs on human SHSY5Y neuronal cells and to explore the underlying mechanisms involved in these effects.
Section snippets
Chemicals
ZnO NPs (CAS No. 1314-13-2), mytomycin C (MMC) (CAS No. 50-07-7), bleomycin (BLM) (CAS No. 9041-93-4), camptothecin (Campt) (CAS No. 7689-03-4), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) (CAS No. 298-93-1), 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethyl-imidacarbocyanine iodide (JC-1) (CAS No. 3520-43-2), neutral red dye (CAS No. 553-24-2), and propidium iodide (PI) were purchased from Sigma-Aldrich Co. (Madrid, Spain). MMC, BLM, and Campt were dissolved in sterile
Nanoparticle characterization
Table 1 summarizes the description and characterization data of the ZnO NPs employed in this study. The average hydrodynamic size, size distribution and zeta potential of ZnO NPs in water and in complete cell culture medium suspensions were assessed by Dynamic Light Scattering (DLS). Slightly higher values of the mean hydrodynamic diameter and the zeta potential (negative) were observed in culture medium supplemented with FBS (distributions shown in Fig. 1(a) and (b), respectively) than in
Discussion
The increasing use of the ZnO NPs in a number of worldwide industries and, specially, their potential benefits in the medicine field have brought attentions to their potential toxicity and health risks. It is well established that, under specific conditions, ZnO NPs may result toxic to a variety of mammalian and human cells (De Berardis et al., 2010, Kim et al., 2010, Osman et al., 2010, Sharma et al., 2009, Sharma et al., 2012b, Wahab et al., 2011) and to animals after intratracheal
Conclusions
Despite the fact that no cellular uptake was found, ZnO NPs induced considerable cytotoxicity, including viability decrease, apoptosis and cell cycle alterations, and different kinds of genetic damage, including oxidative DNA damage, on human neuronal cells in a dose- and time-dependent manner. Free Zn2 + ions released from the ZnO NPs were not responsible for the viability decrease, but their role on other types of cell damage cannot be ruled out. The results obtained in this work contribute to
Acknowledgments
This work was funded by the European Commission (ERA NET — New INDIGO Program, NanoLINEN — 045-036-073, PIM2010ENI-00632) and by Xunta de Galicia (EM 2012/079). G. Kiliç was supported by a fellowship from the University of A Coruña.
References (58)
- et al.
Toxicity determined in vitro by morphological alterations and neutral red absorption
Toxicol Lett
(1985) - et al.
Genotoxic damage in pathology anatomy laboratory workers exposed to formaldehyde
Toxicology
(2008) - et al.
Exposure to ZnO nanoparticles induces oxidative stress and cytotoxicity in human colon carcinoma cells
Toxicol Appl Pharmacol
(2010) - et al.
Association of zinc ion release and oxidative stress induced by intratracheal instillation of ZnO nanoparticles to rat lung
Chem Biol Interact
(2012) - et al.
Oxidative stress responses in different organs of carp (Cyprinus carpio) with exposure to ZnO nanoparticles
Ecotoxicol Environ Saf
(2012) - et al.
Effects of various physicochemical characteristics on the toxicities of ZnO and TiO nanoparticles toward human lung epithelial cells
Sci Total Environ
(2011) - et al.
Potential neurotoxicity of nanoparticles
Int J Pharm
(2010) - et al.
Serum heat inactivation affects protein corona composition and nanoparticle uptake
Biomaterials
(2010) - et al.
Toxicity of nano zinc oxide to mitochondria
Toxicol Res
(2012) Rapid colorimetric assay for cellular growth and survival, application to proliferation and cytotoxicity assays
J Immunol Methods
(1983)
Measurement of micronuclei by flow cytometry
Methods Cell Biol
Comparative in vitro toxicity of seven zinc-salts towards neuronal PC12 cells
Toxicol in Vitro
Selective toxicity of ZnO nanoparticles toward Gram positive bacteria and cancer cells by apoptosis through lipid peroxidation
Nanomedicine: NBM
DNA damaging potential of zinc oxide nanoparticles in human epidermal cells
Toxicol Lett
Induction of oxidative stress, DNA damage and apoptosis in mouse liver after sub-acute oral exposure to zinc oxide nanoparticles
Mutat Res
A simple technique for quantitation of low levels of DNA damage in individual cells
Exp Cell Res
Effects of nano-scale TiO2, ZnO and their bulk counterparts on zebrafish: acute toxicity, oxidative stress and oxidative damage
Sci Total Environ
Influences of nanoparticle zinc oxide on acutely isolated rat hippocampal CA3 pyramidal neurons
Neurotoxicology
Zinc oxide nanoparticles selectively induce apoptosis in human cancer cells through reactive oxygen species
Int J Nanomedicine
In vitro micronucleus scoring by flow cytometry: differential staining of micronuclei versus apoptotic and necrotic chromatin enhances assay reliability
Environ Mol Mutagen
Nanometer size diesel exhaust particles are selectively toxic to dopaminergic neurons: the role of microglia, phagocytosis, and NADPH oxidase
FASEB J
Nanoscale ZnO induces cytotoxicity and DNA damage in human cell lines and rat primary neuronal cells
J Nanosci Nanotechnol
A mechanism for zinc toxicity in neuroblastoma cells
Metab Brain Dis
Nanosized zinc oxide particles induce neural stem cell apoptosis
Nanotechnology
Comparative toxicity of nanoparticulate ZnO, bulk ZnO, and ZnCl2 to a freshwater microalga (Pseudokirchneriella subcapitata): the importance of particle solubility
Environ Sci Technol
Nano-zinc oxide damages spatial cognition capability via over-enhanced long-term potentiation in hippocampus of Wistar rats
Int J Nanomedicine
Preferential killing of cancer cells and activated human T cells using ZnO nanoparticles
Nanotechnology
Toxicity of metal oxide nanoparticles in mammalian cells
J Environ Sci Health A
Demonstration of an olfactory bulb–brain translocation pathway for ZnO nanoparticles in rodent cells in vitro and in vivo
J Mol Neurosci
Cited by (178)
Nose-to-brain translocation and nervous system injury in response to indium tin oxide nanoparticles of long-term low-dose exposures
2023, Science of the Total EnvironmentRecent advances in nanoantibiotics against multidrug-resistant bacteria
2023, Nanoscale AdvancesEnvironmental, health and safety assessment of nanoparticle application in drilling mud – Review
2023, Geoenergy Science and EngineeringZinc oxide nanoparticles in meat packaging: A systematic review of recent literature
2023, Food Packaging and Shelf Life
- 1
These authors contributed equally to this work.