Neurotoxicity induced by zinc oxide nanoparticles: age-related differences and interaction

Cu2−xSe nanoparticles (Cu2−xSe NPs) mediated neurotoxicityviaoxidative stress damage in PC-12 cells and BALB/c mice

Cu_2−xSe nanoparticles (Cu_2−xSe NPs) are widely used for optical diagnostic imaging and photothermal therapy due to their strong near-infrared (NIR) optical absorption. With the continuous expansion of applications using Cu_2−xSe NPs, their biosafety has received increasing attention in recent years. Cu_2−xSe NPs can enter the brain by crossing the blood–brain barrier, but the neurotoxicity of NPs remains unclear. The present investigation provides direct evidence that the toxicity of Cu_2−xSe NPs can be specifically exploited to kill rat pheochromocytoma PC-12 cells (a cell line used as an in vitro model for brain neuron research) in dose- and time-dependent manners. These cytotoxicity events were accompanied by mitochondrial damage, adenosine triphosphate (ATP) depletion, production of oxidizing species (including reactive oxygen species (ROS), malondialdehyde (MDA) and hydrogen peroxide (H₂O₂)), as well as reductions in antioxidant defense systems (glutathione (GSH) and superoxide dismutase (SOD)). Moreover, our in vivo study also confirmed that Cu_2−xSe NPs markedly induced neurotoxicity and oxidative stress damage in the striatum and hippocampal tissues of BALB/c mice. These findings suggest that Cu_2−xSe NPs induce neurotoxicity in PC-12 cells and BALB/c mice via oxidative stress damage, which provides useful information for understanding the neurotoxicity of Cu_2−xSe NPs.

Cu_2−xSe nanoparticles (Cu_2−xSe NPs) are widely used for optical diagnostic imaging and photothermal therapy due to their strong near-infrared (NIR) optical absorption.

Elemental zinc to zinc nanoparticles: is ZnO NPs crucial for life? Synthesis, toxicological, and environmental concerns

The semi-conducting material zinc is one of the essential trace elements for humans, is a co-factor of more than 300 enzymes, and plays an important role in maintaining vital cellular functions. Deficiency of zinc may lead to cancer initiation; however, a high concentration also has toxic effects that might be life threatening. The toxicity can be addressed by the disequilibrium of zinc-mediated proteins and oxidative stress that produce nascent oxygen, hydroxyl radicals, and other reactive oxygen species. Zinc-based nanoparticles (NPs) are among the most important and multifunctional compounds. Zinc oxide (ZnO) NPs exhibit attractive antimicrobial and photocatalytic properties due to the smaller particle size and increased particle surface reactivity. Further, these are more biocompatible compared to other metallic NPs, easily synthesizable, and have high selectivity, enhanced cytotoxicity, and are a promising anticancer agent. However, some of the pertinent concerns regarding nano-zinc still needs to be clarified. Current research also demonstrates their usage in wastewater treatment, textile, medicine, etc. This review covers the importance of zinc for living systems and its NPs, with more emphasis on ZnO NPs. A comprehensive overview of ZnO NPs, their synthesis, characterization techniques, crystal structure, properties, and brief industrial applications are presented.

Neuroinflammation is induced by tongue-instilled ZnO nanoparticles via the Ca2+-dependent NF-κB and MAPK pathways

Background

The extensive biological applications of zinc oxide nanoparticles (ZnO NPs) in stomatology have created serious concerns about their biotoxicity. In our previous study, ZnO NPs were confirmed to transfer to the central nervous system (CNS) via the taste nerve pathway and cause neurodegeneration after 30 days of tongue instillation. However, the potential adverse effects on the brain caused by tongue-instilled ZnO NPs are not fully known.

Methods

In this study, the biodistribution of Zn, cerebral histopathology and inflammatory responses were analysed after 30 days of ZnO NPs tongue instillation. Moreover, the molecular mechanisms underlying neuroinflammation in vivo were further elucidated by treating BV2 and PC12 cells with ZnO NPs in vitro.

Results

This analysis indicated that ZnO NPs can transfer into the CNS, activate glial cells and cause neuroinflammation after tongue instillation. Furthermore, exposure to ZnO NPs led to a reduction in cell viability and induction of inflammatory response and calcium influx in BV2 and PC12 cells. The mechanism underlying how ZnO NPs induce neuroinflammation via the Ca²⁺-dependent NF-κB, ERK and p38 activation pathways was verified at the cytological level.

Conclusion

This study provided a new way how NPs, such as ZnO NPs, induce neuroinflammation via the taste nerve translocation pathway, a new mechanism for ZnO NPs-induced neuroinflammation and a new direction for nanomaterial toxicity analysis.

Electronic supplementary material

The online version of this article (10.1186/s12989-018-0274-0) contains supplementary material, which is available to authorized users.

Zinc oxide nanoparticles in predicted environmentally relevant concentrations leading to behavioral impairments in male swiss mice

Although the potential neurotoxic effects from the exposure to zinc oxide nanoparticles (ZnO NPs) on humans and on experimental models have been reported in previous studies, the effects from the exposure to environmentally relevant concentrations of them remain unclear. Thus, the aim of the present study is to investigate the effects from the exposure to environmentally relevant concentrations of ZnO NPs on the behavior of male Swiss mice. The animals were daily exposed to environmentally relevant concentrations of ZnO NPs (5.625×10^-5mgkg^-1) at toxic level (300mgkg^-1) through intraperitoneal injection for five days; a control group was set for comparison purposes. Positive control groups (clonazepam and fluoxetine) and a baseline group were included in the experimental design to help analyzing the behavioral tests (open field, elevated plus maze and forced swim tests). Although we did not observe any behavioral change in the animals subjected to the elevated plus maze and forced swim tests, our data evidence the anxiogenic behavior of animals exposed to the two herein tested ZnO NPs concentrations in the open field test. The animals stayed in the central part of the apparatus and presented lower locomotion ratio in the central quadrants/total of locomotion during this test. It indicates that the anxiogenic behavior was induced by ZnO NP exposure, because it leads to Zn accumulation in the brain. Thus, the current study is the first to demonstrate that the predicted environmentally relevant ZnO NPs concentration induces behavioral changes in mammalian experimental models. Our results corroborate previous studies that have indicated the biological risks related to the water surface contamination by metal-based nanomaterials.

Zinc Oxide Nanoparticles Exhibit Both Cyclooxygenase- and Lipoxygenase-Mediated Apoptosis in Human Bone Marrow-Derived Mesenchymal Stem Cells

Nanoparticles (NPs) have been recognized as both useful tools and potentially toxic materials in various industrial and medicinal fields. Previously, we found that zinc oxide (ZnO) NPs that are neurotoxic to human dopaminergic neuroblastoma SH-SY5Y cells are mediated by lipoxygenase (LOX), not cyclooxygenase-2 (COX-2). Here, we examined whether human bone marrow-derived mesenchymal stem cells (MSCs), which are different from neuroblastoma cells, might exhibit COX-2- and/or LOX-dependent cytotoxicity of ZnO NPs. Additionally, changes in annexin V expression, caspase-3/7 activity, and mitochondrial membrane potential (MMP) induced by ZnO NPs and ZnO were compared at 12 hr and 24 hr after exposure using flow cytometry. Cytotoxicity was measured based on lactate dehydrogenase activity and confirmed by trypan blue staining. Rescue studies were executed using zinc or iron chelators. ZnO NPs and ZnO showed similar dose-dependent and significant cytotoxic effects at concentrations ≥ 15 μg/mL, in accordance with annexin V expression, caspase-3/7 activity, and MMP results. Human MSCs exhibited both COX-2 and LOX-mediated cytotoxicity after exposure to ZnO NPs, which was different from human neuroblastoma cells. Zinc and iron chelators significantly attenuated ZnO NPs-induced toxicity. Conclusively, these results suggest that ZnO NPs exhibit both COX-2- and LOX-mediated apoptosis by the participation of mitochondrial dysfunction in human MSC cultures.

Central neurotoxicity induced by the instillation of ZnO and TiO2 nanoparticles through the taste nerve pathway

AIM

To explore whether nanoparticles (NPs) can be transported into the CNS via the taste nerve pathway.

MATERIALS & METHODS

ZnO and TiO₂ NPs were tongue-instilled to male Wistar rats. Toxicity was assessed by Zn/Ti biodistribution, histopathological examination, oxidative stress assay, quantitative reverse-transcriptase PCR analysis, learning and memory capabilities.

RESULTS

ZnO NPs and TiO₂ NPs significantly deposited in the nerves and brain, respectively. The histopathological examination indicated a slight injury in the cerebral cortex and hippocampus. Ultrastructural changes and an imbalanced oxidative stress were observed. The Morris water maze results showed that the learning and memory of rats were impaired.

CONCLUSION

NPs can enter the CNS via the taste nerve translocation pathway and induce a certain adverse effect.

Zinc oxide nanoparticle energy band gap reduction triggers the oxidative stress resulting into autophagy-mediated apoptotic cell death

The physico-chemical properties of nanoparticle (NP), such as particle size, surface defects, crystallinity and accessible surface, affect NP photocatalytic activity that in turn defines the NP cytotoxic propensity. Since zinc oxide nanoparticle (ZnONP) energy band gap falls in a range of a semiconductor, the particle possesses photocatalytic activity. Hence, the study correlates energy band gap with cytotoxic propensity of ZnONP. To this end, ZnONPs with varying energy band gap are fabricated by varying calcination temperature. Cytotoxic propensity of the fabricated ZnONPs against HT1080 cell indicates that the particle with least energy band gap shows highest cytotoxicity. The data also indicate that the cytotoxicity is triggered primarily through reactive oxygen species (ROS)-mediated pathway. Additionally, the comet assay and γH2AX activity assay reveal that decreasing energy band gap of the particle increases DNA damaging propensity. Furthermore, cell cycle analysis indicates that the cell treatment with decreasing energy band gap ZnONP results in significant increase in cell population fraction in subG₁ phase. Whereas, acridine orange binding assay and increased expression level of LC3II indicate that the cell tries to recover the stress by scavenging damaged cellular biomolecules and ROS using autophagosomes. Nevertheless, cell with the non-recoverable damages led into apoptotic cell death, as confirmed by Annexin V apoptosis assay, DNA fragmentation assay and 4,6-Diamidino-2-phenylindole dihydrochloride (DAPI) staining.

Effect of orally administered zinc oxide nanoparticles on albino rat thymus and spleen

This study aimed to evaluate the toxicological effects of oral intake of Zinc oxide nanoparticles (ZnO NPs) on the structure of thymus and spleen. Twenty-four young male Wistar albino rats were assigned into two groups: group I (control) and group II (ZnO NPs treated group).The thymus and spleen were analyzed biochemically, histopathologically and immunohistochemically. After ZnO NPs intake, hematologically, the total leucocytic count was significantly increased while the RBCs and platelets counts and Hb % were significantly decreased. Biochemically, a significant decrease in serum total antioxidant capacity and anti-inflammatory cytokines including interleukin 4 and 10 (IL-4 and IL-10) levels was noted. While a significant increase in splenic and thymic malondialdehyde (MDA) and DNA shearing, as well as the studied proinflammatory cytokines; IL-1β, tumor necrotic factor (TNF-α) and interferon (INF-γ) levels was detected. Notably, we noted upregulation of the immunomodulatory [CD3, CD11b, heme oxygenase (HO-1)] and the inflammatory [toll-like receptor 4 and 6 (TLR4 and TLR6)] genes. Histopathologically, degenerative changes were detected in thymus and spleen of ZnO NPs treated group. While the immunohistochemical analysis of the ZnO NPs treated group revealed a decrease in the number of cells expressed positive reactions of anti-PCNA and an increase in the number of cells expressed positive reaction of anti-p53 in the thymus and spleen. In conclusion, ZnO NPs induced obvious immunotoxicity in the thymus and spleen, where oxidative/inflammatory pathway may be the potential mechanism underlying this immunotoxicity. © 2017 IUBMB Life, 69(7):528-539, 2017.

Neurotoxic effect of active ingredients in sunscreen products, a contemporary review

Sunscreen application is the main strategy used to prevent the maladies inflicted by ultraviolet (UV) radiation. Despite the continuously increasing frequency of sunscreen use worldwide, the prevalence of certain sun exposure-related pathologies, mainly malignant melanoma, is also on the rise. In the past century, a variety of protective agents against UV exposure have been developed. Physical filters scatter and reflect UV rays and chemical filters absorb those rays. Alongside the evidence for increasing levels of these agents in the environment, which leads to indirect exposure of wildlife and humans, recent studies suggest a toxicological nature for some of these agents. Reviews on the role of these agents in developmental and endocrine impairments (both pathology and related mechanisms) are based on both animal and human studies, yet information regarding the potential neurotoxicity of these agents is scant. In this review, data regarding the neurotoxicity of several organic filters: octyl methoxycinnamate, benzophenone-3 and −4, 4-methylbenzylidene camphor, 3-benzylidene camphor and octocrylene, and two allowed inorganic filters: zinc oxide and titanium dioxide, is presented and discussed. Taken together, this review advocates revisiting the current safety and regulation of specific sunscreens and investing in alternative UV protection technologies.

Nanoparticles as potential clinical therapeutic agents in Alzheimer's disease: focus on selenium nanoparticles

INTRODUCTION

In etiology of Alzheimer's disease (AD), involvement of amyloid β (Aβ) plaque accumulation and oxidative stress in the brain have important roles. Several nanoparticles such as titanium dioxide, silica dioxide, silver and zinc oxide have been experimentally using for treatment of neurological disease. In the last decade, there has been a great interest on combination of antioxidant bioactive compounds such as selenium (Se) and flavonoids with the oxidant nanoparticles in AD. We evaluated the most current data available on the physiological effects of oxidant and antioxidant nanoparticles. Areas covered: Oxidative nanoparticles decreased the activities of reactive oxygen species (ROS) scavenging enzymes such as glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase in the brain of rats and mice. However, Se-rich nanoparticles in small size (5-15 nm) depleted Aβ formation through decreasing ROS production. Reports on low levels of Se in blood and tissue samples and the low activities of GSH-Px, catalase and SOD enzymes in AD patients and animal models support the proposed crucial role of oxidative stress in the pathogenesis of AD. Expert commentary: In conclusion, present literature suggests that Se-rich nanoparticles appeared to be a potential therapeutic compound for the treatment of AD.

Is Neurotoxicity of Metallic Nanoparticles the Cascades of Oxidative Stress?

With the rapid development of nanotechnology, metallic (metal or metal oxide) nanoparticles (NPs) are widely used in many fields such as cosmetics, the food and building industries, and bio-medical instruments. Widespread applications of metallic NP-based products increase the health risk associated with human exposures. Studies revealed that the brain, a critical organ that consumes substantial amounts of oxygen, is a primary target of metallic NPs once they are absorbed into the body. Oxidative stress (OS), apoptosis, and the inflammatory response are believed to be the main mechanisms underlying the neurotoxicity of metallic NPs. Other studies have disclosed that antioxidant pretreatment or co-treatment can reverse the neurotoxicity of metallic NPs by decreasing the level of reactive oxygen species, up-regulating the activities of antioxidant enzymes, decreasing the proportion of apoptotic cells, and suppressing the inflammatory response. These findings suggest that the neurotoxicity of metallic NPs might involve a cascade of events following NP-induced OS. However, additional research is needed to determine whether NP-induced OS plays a central role in the neurotoxicity of metallic NPs, to develop a comprehensive understanding of the correlations among neurotoxic mechanisms and to improve the bio-safety of metallic NP-based products.

Chocolate, Air Pollution and Children's Neuroprotection: What Cognition Tools should be at Hand to Evaluate Interventions?

Millions of children across the world are exposed to multiple sources of indoor and outdoor air pollutants, including high concentrations of fine particulate matter (PM_2.5) and ozone (O₃). The established link between exposure to PM_2.5, brain structural, volumetric and metabolic changes, severe cognitive deficits (1.5-2 SD from average IQ) in APOE 4 heterozygous females with >75 − < 94% BMI percentiles, and the presence of Alzheimer's disease (AD) hallmarks in urban children and young adults necessitates exploration of ways to protect these individuals from the deleterious neural effects of pollution exposure. Emerging research suggests that cocoa interventions may be a viable option for neuroprotection, with evidence suggesting that early cocoa interventions could limit the risk of cognitive and developmental concerns including: endothelial dysfunction, cerebral hypoperfusion, neuroinflammation, and metabolic detrimental brain effects. Currently, however, it is not clear how early we should implement consumption of cocoa to optimize its neuroprotective effects. Moreover, we have yet to identify suitable instruments for evaluating cognitive responses to these interventions in clinically healthy children, teens, and young adults. An approach to guide the selection of cognitive tools should take into account neuropsychological markers of cognitive declines in patients with Alzheimer's neuropathology, the distinct patterns of memory impairment between early and late onset AD, and the key literature associating white matter integrity and poor memory binding performance in cases of asymptomatic familial AD. We highlight potential systemic and neural benefits of cocoa consumption. We also highlight Working Memory Capacity (WMC) and attention control tasks as opened avenues for exploration in the air pollution scenario. Exposures to air pollutants during brain development have serious brain consequences in the short and long term and reliable cognition tools should be at hand to evaluate interventions.