Zinc oxide nanoparticles induce lipoxygenase-mediated apoptosis and necrosis in human neuroblastoma SH-SY5Y cells

Antioxidant and anti‑inflammatory effects of esculin and esculetin (Review)

Fraxinus chinensis Roxb is a deciduous tree, which is distributed worldwide and has important medicinal value. In Asia, the bark of Fraxinus chinensis Roxb is a commonly used traditional Chinese medicine called Qinpi. Esculetin is a coumarin compound derived from the bark of Fraxinus chinensis Roxb and its glycoside form is called esculin. The aim of the present study was to systematically review relevant literature on the antioxidant and anti-inflammatory effects of esculetin and esculin. Esculetin and esculin can promote the expression of various endogenous antioxidant proteins, such as superoxide dismutase, glutathione peroxidase and glutathione reductase. This is associated with the activation of the nuclear factor erythroid-derived factor 2-related factor 2 signaling pathway. The anti-inflammatory effects of esculetin and esculin are associated with the inhibition of the nuclear factor κ-B and mitogen-activated protein kinase inflammatory signaling pathways. In various inflammatory models, esculetin and esculin can reduce the expression levels of various proinflammatory factors such as tumor necrosis factor-α, interleukin (IL)-1β and IL-6, thereby inhibiting the development of inflammation. In summary, esculetin and esculin may be promising candidates for the treatment of numerous diseases associated with inflammation and oxidative stress, such as ulcerative colitis, acute lung and kidney injury, lung cancer, acute kidney injury.

Zinc Oxide Nanoparticles and Cancer Chemotherapy: Helpful Tools for Enhancing Chemo-sensitivity and Reducing Side Effects?

Cancer chemotherapy is still a serious challenge. Chemo-resistance and destructive side effects of chemotherapy drugs are the most critical limitations of chemotherapy. Chemo-resistance is the leading cause of chemotherapy failure. Chemo-resistance, which refers to the resistance of cancer cells to the anticancer effects of chemotherapy drugs, is caused by various reasons. Among the most important of these reasons is the increase in the efflux of chemotherapy drugs due to the rise in the expression and activity of ABC transporters, the weakening of apoptosis, and the strengthening of stemness. In the last decade, a significant number of studies focused on the application of nanotechnology in cancer treatment. Considering the anti-cancer properties of zinc, zinc oxide nanoparticles have received much attention in recent years. Some studies have indicated that zinc oxide nanoparticles can target the critical mechanisms of cancer chemo-resistance and enhance the effectiveness of chemotherapy drugs. These studies have shown that zinc oxide nanoparticles can reduce the activity of ABC transporters, increase DNA damage and apoptosis, and attenuate stemness in cancer cells, leading to enhanced chemo-sensitivity. Some other studies have also shown that zinc oxide nanoparticles in low doses can be helpful in minimizing the harmful side effects of chemotherapy drugs. In this article, after a brief overview of the mechanisms of chemo-resistance and anticancer effects of zinc, we will review all these studies in detail.

Size, Surface Properties, and Ion Release of Zinc Oxide Nanoparticles: Effects on Cytotoxicity, Dopaminergic Gene Expression, and Acetylcholinesterase Inhibition in Neuronal PC-12 Cells

The extensive applications of zinc oxide nanoparticles (ZnO NPs) have resulted in a substantial risk of human exposure. However, the knowledge of the toxicity of these NPs in the nervous system is still limited. A comparative analysis of ZnO NPs of various sizes and NPs of the same size, with and without surface coating, and the potential role of released zinc ions is yet to be thoroughly explored. As a result, we have studied the cellular toxicity of two different-sized ZnO NPs, ZnO-22 (22 nm) and ZnO-43 (43 nm), and NPs with similar size but with polyvinylpyrrolidone coating (ZnO-P, 45 nm). The findings from our study suggested a time-, size-, and surface coating-dependent cytotoxicity in PC-12 cells at a concentration ≥ 10 μg/ml. ZnO NP treatment significantly elevated reactive oxygen and reactive nitrogen species, thereby increasing oxidative stress. The exposure of ZnO-22 and ZnO-43 significantly upregulated the expression of monoamine oxidase-A and downregulated the α-synuclein gene expression associated with the dopaminergic system. The interaction of NPs enzymes in the nervous system is also hazardous. Therefore, the inhibition activity of acetylcholinesterase enzyme was also studied for its interaction with these NPs, and the results indicated a dose-dependent inhibition of enzyme activity. Particle size, coating, and cellular interactions modulate ZnO NP's cytotoxicity; smaller sizes enhance cellular uptake and reactivity, while coating reduces cytotoxicity by limiting direct cell contact and potentially mitigating oxidative stress. Furthermore, the study of released zinc ions from the NPs suggested no significant contribution to the observed cytotoxicity compared to the NPs.

Assessment of Protective Effects of DTPA, NAC, and Taurine on Possible Cytotoxicity Induced by Individual and Combined Zinc Oxide and Copper Oxide Nanoparticles in SH-SY5Y Cells

The present study investigated the cytotoxic effects of ZnO, CuO, and mixed combinations of them on SH-SY5Y cells. For this purpose, the cells were exposed to various concentrations of these NPs alone for 24-96 h and as a mixture for 24 h. Variations in cell viability were noted. MTT results showed that ZnO and/or CuO NPs decreased cell survival by about 59% at 200 (ZnO, at 24 h) and 800 µg/ml (ZnO and/or CuO, at 72 and 96 h). When the NR assay was used, slight decreases were noted with ZnO NPs at 72 and 96 h. With CuO NPs alone and NPs in a mixture, only the highest concentrations caused 40 and 70% decreases in cell survival, respectively. Especially with NR assays, DTPA, NAC, or taurine provided marked protection. ROS levels were increased with the highest concentration of CuO NPs and with all concentrations of the mixture. The highest concentration of ZnO NPs and the lowest concentration of CuO NPs caused slight decreases in mitochondrial membrane potential levels. Additionally, increases were noted in caspase 3/7 levels with ZnO and CuO NPs alone or with a mixture of them. Intracellular calcium levels were decreased in this system. These findings demonstrated that ZnO and CuO NPs, either separately or in combination, had a modest cytotoxic effect on SH-SY5Y cells. Protection obtained with DTPA, NAC, or taurine against the cytotoxicity of these NPs and the ROS-inducing effect of CuO NPs and the NPs' mixture suggests that oxidative stress might be involved in the cytotoxicity mechanisms of these NPs.

Nanoparticles and neurodegeneration: Insights on multiple pathways of programmed cell death regulated by nanoparticles

Currently, nanoparticles (NPs) are extensively applied in the diagnosis and treatment of neurodegenerative diseases (NDs). With the rapid development and increasing exposure to the public, the potential neurotoxicity associated with NDs caused by NPs has attracted the researchers' attentions but their biosafety assessments are still far behind relevant application studies. Based on recent research, this review aims to conduct a comprehensive and systematic analysis of neurotoxicity induced by NPs. The 191 studies selected according to inclusion and exclusion criteria were imported into the software, and the co-citations and keywords of the included literatures were analyzed to find the breakthrough point of previous studies. According to the available studies, the routes of NPs entering into the normal and injured brain were various, and then to be distributed and accumulated in living bodies. When analyzing the adverse effects induced by NPs, we focused on multiple programmed cell deaths (PCDs), especially ferroptosis triggered by NPs and their tight connection and crosstalk that have been found playing critical roles in the pathogenesis of NDs and their underlying toxic mechanisms. The activation of multiple PCD pathways by NPs provides a scientific basis for the occurrence and development of NDs. Furthermore, the adoption of new methodologies for evaluating the biosafety of NPs would benefit the next generation risk assessment (NGRA) of NPs and their toxic interventions. This would help ensure their safe application and sustainable development in the field of medical neurobiology.

A systematic review for the development of Alzheimer's disease in in vitro models: a focus on different inducing agents

Alzheimer's disease (AD) is the most common progressive neurodegenerative disease and is associated with dementia. Presently, various chemical and environmental agents are used to induce in-vitro models of Alzheimer disease to investigate the efficacy of different therapeutic drugs. We screened literature from databases such as PubMed, ScienceDirect, and Google scholar, emphasizing the diverse targeting mechanisms of neuro degeneration explored in in-vitro models. The results revealed studies in which different types of chemicals and environmental agents were used for in-vitro development of Alzheimer-targeting mechanisms of neurodegeneration. Studies using chemically induced in-vitro AD models included in this systematic review will contribute to a deeper understanding of AD. However, none of these models can reproduce all the characteristics of disease progression seen in the majority of Alzheimer's disease subtypes. Additional modifications would be required to replicate the complex conditions of human AD in an exact manner. In-vitro models of Alzheimer's disease developed using chemicals and environmental agents are instrumental in providing insights into the disease's pathophysiology; therefore, chemical-induced in-vitro AD models will continue to play vital role in future AD research. This systematic screening revealed the pivotal role of chemical-induced in-vitro AD models in advancing our understanding of AD pathophysiology and is therefore important to understand the potential of these chemicals in AD pathogenesis.

Surface Area of Graphene Governs Its Neurotoxicity

Due to their unique physicochemical properties, graphene and its derivatives are widely exploited for biomedical applications. It has been shown that graphene may exert different degrees of toxicity in in vivo or in vitro models when administered via different routes and penetrated through physiological barriers, subsequently being distributed within tissues or located within cells. In this study, in vitro neurotoxicity of graphene with different surface areas (150 and 750 m²/g) was examined on dopaminergic neuron model cells. SH-SY5Y cells were treated with graphene possessing two different surface areas (150 and 750 m²/g) in different concentrations between 400 and 3.125 μg/mL, and the cytotoxic and genotoxic effects were investigated. Both sizes of graphene have shown increased cell viability in decreasing concentrations. Cell damage increased with higher surface area. Lactate dehydrogenase (LDH) results have concluded that the viability loss of the cells is not through membrane damage. Neither of the two graphene types showed damage through lipid peroxidation (MDA) oxidative stress pathway. Glutathione (GSH) values increased within the first 24 and 48 h for both types of graphene. This increase suggests that graphene has an antioxidant effect on the SH-SY5Y model neurons. Comet analysis shows that graphene does not show genotoxicity on either surface area. Although there are many studies on graphene and its derivatives on their use with different cells in the literature, there are conflicting results in these studies, and most of the literature is focused on graphene oxide. Among these studies, no study examining the effect of graphene surface areas on the cell was found. Our study contributes to the literature in terms of examining the cytotoxic and genotoxic behavior of graphene with different surface areas.

ZnO Nanorods Create a Hypoxic State with Induction of HIF-1 and EPAS1, Autophagy, and Mitophagy in Cancer and Non-Cancer Cells

Nanomaterials are gaining increasing attention as innovative materials in medicine. Among nanomaterials, zinc oxide (ZnO) nanostructures are particularly appealing because of their opto-electrical, antimicrobial, and photochemical properties. Although ZnO is recognized as a safe material and the Zn ion (Zn²⁺) concentration is strictly regulated at a cellular and systemic level, different studies have demonstrated cellular toxicity of ZnO nanoparticles (ZnO-NPs) and ZnO nanorods (ZnO-NRs). Recently, ZnO-NP toxicity has been shown to depend on the intracellular accumulation of ROS, activation of autophagy and mitophagy, as well as stabilization and accumulation of hypoxia-inducible factor-1α (HIF-1α) protein. However, if the same pathway is also activated by ZnO-NRs and how non-cancer cells respond to ZnO-NR treatment, are still unknown. To answer to these questions, we treated epithelial HaCaT and breast cancer MCF-7 cells with different ZnO-NR concentrations. Our results showed that ZnO-NR treatments increased cell death through ROS accumulation, HIF-1α and endothelial PAS domain protein 1 (EPAS1) activation, and induction of autophagy and mitophagy in both cell lines. These results, while on one side, confirmed that ZnO-NRs can be used to reduce cancer growth, on the other side, raised some concerns on the activation of a hypoxic response in normal cells that, in the long run, could induce cellular transformation.

Spectroscopic signature of ZnO NP-induced cell death modalities assessed by non-negative PCA

Selective cytotoxicity of ZnO nanoparticles among different cell types and cancer and non-cancerous cells has been demonstrated earlier. In the view of anticancer potential of ZnO nanoparticles and their presence in numerous industrial products, it is of great importance to carefully evaluate their effects and mechanisms of action in both cancerous and healthy cells. In this paper, the effects of ZnO nanoparticles on cancerous HeLa and non-cancerous MRC-5 cells are investigated by studying the changes in the vibrational properties of the cells using Raman spectroscopy. Both types of cells were incubated with ZnO nanoparticles of average size 40 nm in the doses from the range 10-40 µg/ml for the period of 48 h, after which Raman spectra were collected. Raman modes' intensity ratios I₁₆₅₉/I₁₄₄₄, I₂₈₅₅/I₂₉₃₃ and I₁₃₃₇/I₁₃₀₅ were determined as spectral markers of the cytotoxic effect of ZnO in both cell types. Non-negative principal component analysis was used instead of standard one for analysis and detection of spectral features characteristic for nanoparticle-treated cells. The first several non-negative loading vectors obtained in this analysis coincided remarkably well with the Raman spectra of particular biomolecules, showing increase of lipid and decrease of nucleic acids and protein content. Our study pointed out that Raman spectral markers of lipid unsaturation, especially I₁₂₇₀/I₁₃₀₀, are relevant for tracing the cytotoxic effect of ZnO nanoparticles on both cancerous and non-cancerous cells. The change of these spectral markers is correlated to the dose of applied nanoparticles and to the degree of cellular damage. Furthermore, great similarity of spectral features of increasing lipids to spectral features of phosphatidylserine, one of the main apoptotic markers, was recognized in treated cells. Finally, the results strongly indicated that the degree of lipid saturation, presented in the cells, plays an important role in the interaction of cells with nanoparticles.

Trichotorquatus salinus sp. nov. (Oculatellaceae, Cyanobacteria) from a Saltern of Gomso, Republic of Korea

Six strains of subaerial cyanobacteria were isolated from a Gomso saltern in the Republic of Korea, all of which were studied using morphological and molecular traits. Trichotorquatus salinus sp. nov. was studied using a light microscope (LM), transmission electron microscope (TEM), 16S rRNA, 16S–23S ITS region, and ecological data. T. salinus is a thin and simple filament with a false branch and a firm collar sheath. The phylogenetic analyses of 16S rRNA revealed that Trichotorquatus formed a monophyletic lineage and the strains of T. salinus formed a distinct clade among the species in the genus Trichotorquatus. In the statistical analysis, the inter-species genetic distance of the five species of Trichotorquatus, including T. salinus, is shown to be greater than the distance of the previously reported species of Trichotorquatus. Additionally, 16S–23S ITS gene sequences between T. salinus and four species of Trichotorquatus showed dissimilarities of 55.3–59.4%. In the secondary structure of 16S–23S ITS region (type 2 operon), D1–D1′, Box-B, and V3 helix of T. salinus were different from the other taxa in the genus Trichotorquatus. These results demonstrate that T. salinus sp. nov. has unique morphological, ecological, and molecular traits. Therefore, we propose that T. salinus sp. nov. is a novel species belonging to the genus Trichotorquatus.

Three New Plectolyngbya Species (Leptolyngbyaceae, Cyanobacteria) Isolated from Rocks and Saltern of the Republic of Korea

Thin filamentous cyanobacteria isolated from three collection sites in the Republic of Korea were suggested as three new species belonging to the genus Plectolyngbya, mainly according to their molecular characteristics. The species of Plectolyngbya, including the type species of P. hodgsonii, were cryptic species that were difficult to distinguish morphologically from each other, and had appeared in ecologically diverse habitats. P. terrestris and P. koreana were subaerophytes collected from certain black spots and soils between stone walls in Seoul, Republic of Korea. In addition, hypersaline species collected from a saltern, P. salina, shared the same halophytic feature as the P. hodgsonii from the littoral zone of a coastal lake in the Antarctic. The 16S rRNA gene phylogeny supported the monophyly of Plectolyngbya with solid support, 99% Maximum Likelihood, 98% Neighbor-Joining bootstrap support values, and 1.0 Bayesian posterior probability. The ITS sequences of P. terrestris, P. koreana, and P. salina were unique in length and nucleotide composition, with different secondary structures of D1–D1ʹ and Box-B helices, compared with those of P. hodgsonii. These results demonstrate that the proposed new Plectolyngbya species were unique in their molecular traits. Therefore, we suggest them as new species belonging to the genus Plectolyngbya with the names P. terrestris sp. nov., P. koreana sp. nov., and P. salina sp. nov.

Esculetin and Fucoidan Attenuate Autophagy and Apoptosis Induced by Zinc Oxide Nanoparticles through Modulating Reactive Astrocyte and Proinflammatory Cytokines in the Rat Brain

We examined the protective effects of esculetin and fucoidan against the neurotoxicity of ZnO NPs in rats. Ninety rats were divided into nine groups and pre-treated with esculetin or fucoidan 1 h before ZnO NP administration on a daily basis for 2 weeks. Serum and brain homogenates were examined by enzyme-linked immunosorbent assay (ELISA), and neurons, microglia, and astrocytes in the hippocampal region were examined with immunohistochemical analysis. The serum levels of interleukin-1-beta (IL-1β), 3-nitrotyrosine (3-NT), superoxide dismutase (SOD), and 8-hydroxy-2′-deoxyguanosine (8-OHdG) were altered in the ZnO NP treatment groups. Brain IL-1β and TNF-α levels were elevated after ZnO NP administration, and these effects were inhibited by esculetin and fucoidan. SOD, 8-OHdG, and acetylcholinesterase (AChE) levels in the brain were decreased after ZnO NP administration. The brain levels of beclin-1 and caspase-3 were elevated after ZnO NP treatment, and these effects were significantly ameliorated by esculetin and fucoidan. The number of reactive astrocytes measured by counting glial fibrillary acidic protein (GFAP)-positive cells, but not microglia, increased following ZnO NP treatment, and esculetin and fucoidan ameliorated the changes. Esculetin and fucoidan may be beneficial for preventing ZnO NP-mediated autophagy and apoptosis by the modulation of reactive astrocyte and proinflammatory cytokines in the rat brain.

Histological and biochemical apoptosis changes of female rats' ovary by Zinc oxide nanoparticles and potential protective effects of l-arginine: An experimental study

Background

This research aims to investigate the adverse effects of ZnO NP on ovarian tissue and the follicular and menstrual cycle and the protective effects of l-arginine on the aforementioned tissues.

Material and methods

30 rats were divided into five groups. The first group was the control group. The second and fourth groups received 100 mg/kg and 200 mg/kg ZnO NP, respectively. The third and fifth groups received the same doses of ZnO NP as the second and fourth groups, respectively. However, the third and fifth groups received an additional dose of 1.3 gr/kg of LA amino acid. ZnO NP and LA are given intraperitoneal for 21 days. Blood samples from each rat and a part of the ovarium were collected to test for gene expression and histological analysis.

Results

Compared to levels of housekeeping gene β-actine, levels of apoptosis effectors such as Bax, Bcl, Caspase 3, and Caspase 9 were significantly increased in all groups. In groups that received doses of LA (three and five), atretic follicle size was smaller compared to groups that did not receive LA (two and four). In addition, in the third group, the secondary and primordial follicle's generated oocytes were smaller compared with groups two, four, and five. Compared with the control group, all groups experienced morphological degeneration of follicles and tissue.

Conclusion

ZnO NP has inevitable, morphological, and physiological effects on the ovary and can detrimentally impact the tissue. LA can aid in the regeneration of the tissue and block damage induced by stress and toxicity.

•

Zinc oxide nanoparticles are widely used in various everyday products, such as food packaging, additives, cosmetics, and bioimaging.

•

Using Zinc oxide nanoparticles in daily life may cause infertility by reducing the number of follicles in the ovary.

•

L-Arginine may be a beneficial daily supplement to prevent damage to the ovaries induced by Zinc oxide nanoparticles.

Anticancer properties of novel zinc oxide quantum dot nanoparticles against breast cancer stem-like cells

Cancer stem cells (CSCs) play an essential role in cancer development, metastasis, relapse, and resistance to treatment. In this article, the effects of three synthesized ZnO nanofluids on proliferation, apoptosis, and stemness markers of breast cancer stem-like cells are reported. The antiproliferative and apoptotic properties of ZnO nanoparticles were evaluated on breast cancer stem-like cell-enriched mammospheres by MTS assay and flowcytometry, respectively. The expression of stemness markers, including WNT1, NOTCH1, β-catenin, CXCR4, SOX2, and ALDH3A1 was assessed by real-time PCR. Western blotting was used to analyze the phosphorylation of Janus kinase 2 (JAK2) and Signal Transducer and Activator of Transcription 3 (STAT3). Markers of stemness were significantly decreased by ZnO nanofluids, especially sample (c) with code ZnO-148 with a different order of addition of polyethylene glycol solution at the end of formulation, which considerably decreased all the markers compared to the controls. All the studied ZnO nanofluids considerably reduced viability and induced apoptosis of spheroidal and parental cells, with ZnO-148 presenting the most effective activity. Using CD95L as a death ligand and ZB4 as an extrinsic apoptotic pathway blocker, it was revealed that none of the nanoparticles induced apoptosis through the extrinsic pathway. Results also showed a marked inhibition of the JAK/STAT pathway by ZnO nanoparticles; confirmed by downregulation of Mcl-1 and Bcl-XL expression. The present data demonstrated that ZnO nanofluids could combat breast CSCs via decreasing stemness markers, stimulating apoptosis, and suppressing JAK/STAT activity.

Esculetin: A review of its pharmacology and pharmacokinetics

Esculetin is a natural dihydroxy coumarin; it is mainly extracted from twig skin and the trunk bark of the Chinese herbal medicine Fraxinus rhynchophylla Hance. Emerging evidence suggests that esculetin has a wide range of pharmacological activities. Based on its fundamental properties, including antioxidant, antiinflammatory, antiapoptotic, anticancer, antidiabetic, neuroprotective, and cardiovascular protective activities, as well as antibacterial activity, among others, esculetin is expected to be a therapeutic drug for specific disease indications, such as cancer, diabetes, atherosclerosis, Alzheimer's disease (AD), Parkinson's disease (PD), nonalcoholic fatty liver disease (NAFLD), and other diseases. The oral bioavailability of esculetin was shown by studies to be low. The extensive glucuronidation was described to be the main metabolic pathway of esculetin and C-7 phenolic hydroxyl to be its major metabolic site. With the development of scientific research technology, the pharmacological effects of esculetin are identified and its potential for the treatment of diseases is demonstrated. The underlining mechanisms of action and biological activities as well as the pharmacokinetic data of the analyzed compound reported so far are highlighted in this review with the aim of becoming a proven, and applicable insight and reference for further studies on the utilization of esculetin.

Fabrication of nano-decorated ZnO-fibrillar chitosan exhibiting a superior performance as a promising replacement for conventional ZnO

In this research, bioactive nano-hybrids based on the nano-fibrillar chitosan-ZnO (NF-CS-ZnO) were synthesized to diminish the toxicity of ZnO-NPs. The successful formation of nano-hybrids was confirmed by FT-IR, UV-Vis, and FE-SEM analyses, showing a uniform spherical ZnO-NPs with an average diameter of 20-30 nm, homogeneously dispersed on NF-CS. The obtained results demonstrated a remarkable antibacterial activity of NF-CS-ZnO-0.6 nano-hybrid against E. coli and S. aureus and, interestingly, no cytotoxic on normal cells (even at a high concentration of 100 μg/mL). Furthermore, NF-CS hybridization efficiently decreased the up-regulation in Cas3, Cas9, and Il6 of inspected fishes compared to the ZnO-NPs. Histopathological examination revealed hepatocyte necrosis in the fish exposed to ZnO-NPs and hyperemia exposed to NF-CS-ZnO-0.6 nano-hybrid. Finally, NF-CS efficiently improved the bio-safety and bactericidal activity of ZnO-NPs; therefore, NF-CS-ZnO nano-hybrid is prominently recommended as a talented low-toxicity antibacterial agent replacement of conventional ZnO-NPs for use in different applications.

Diethylene glycol and its metabolites induce cell death in SH-SY5Y neuronal cells in vitro

Diethylene glycol (DEG) intoxication results in metabolic acidosis, renal and hepatic dysfunction, and late-stage neurotoxicity. Though the renal and hepatic toxicity of DEG and its metabolites 2-hydroxyethoxyacetic acid (2-HEAA) and diglycolic acid (DGA) have been well characterized, the resultant neurotoxicity has not. SH-SY5Y neuroblastoma cells were incubated with all 3 compounds at increasing concentrations for 24, 48, or 120 h. At all 3 time points, 50 mmol/L DGA and 100 mmol/L DEG showed significant Annexin V and propidium iodide (PI) staining with additional concentrations showing similar staining patterns at 24 h (100 mmol/L DGA) and 48 h (50 mmol/L DEG, 100 mmol/L DGA). Only the 200 mmol/L 2-HEAA concentration induced SH-SY5Y cell death. Interestingly at 24 and 48 h, 100 mmol/L DEG induced significant increases in apoptotic cell death markers, which progressed to necrosis at 120 h. Similar to DEG, 50 mmol/L DGA induced significant increases in SH-SY5Y cell apoptosis and necrosis markers at both 24 and 48 h. As expected, high DGA concentrations (100 mmol/L) at 120 h induced significant SH-SY5Y cell necrosis with no apoptosis detected. However, at 120 h lower DGA concentrations (20 mmol/L) significantly increased oligonucleosome formation alone and in combination with 2-HEAA or DEG. Taken together, these results indicate that DGA and DEG at threshold concentrations induce neurotoxicity in SH-SY5Y cells.

Zinc oxide nanoparticles (ZnO NPs) combined with cisplatin and gemcitabine inhibits tumor activity of NSCLC cells

Non-small cell lung cancer (NSCLC) is one of the most common malignancies worldwide. The use of a combination of chemotherapy drugs and zinc oxide nanoparticles (ZnO-NPs), which have proven to induce tumor-selective cell death, reduce the drug resistance and reduce the side effects in vitro. In the present study, we developed ZnO-NPs loaded with both cisplatin (Cp) and gemcitabine (Gem) (ZnO-NPs(Cp/Gem)), then the morphologies and the size distribution of ZnO-NPs(Cp/Gem) particles were observed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). Also, MTT, western blot and Annexin V-PI were used to assess the anti-tumor role of ZnO-NPs(Cp/Gem) in A549 cells. The viability for A549 cells showed a significant decrease in the ZnO NPs(Cp/Gem) group, respectively relative to Cp, Gem, the combination of Cp and Gem (Cp+Gem), and ZnO-NPs loaded with Cp (ZnO-NPs(Cp)) or Gem (ZnO-NPs(Gem)). Furthermore, ZnO-NPs(Cp/Gem) remarkably enhanced the apoptosis-promoting effect of Cp and Gem in A549 cells. The xenograft model showed that Zno-NPS (Cp/Gem) significantly enhanced the inhibition of Cp and Gem on tumor formation. The above results suggested that therapy of NSCLC with ZnO-NPs(Cp/Gem) could enhance the cytotoxic action of chemotherapeutic agents synergistically, indicating a promising potential for ZnO-NPs in antitumor applications.

The Influences of Aqueous Dispersion Media on the Cytotoxic Effect of Zinc Oxide Nanoparticles

Zinc oxide nanoparticles (ZnO-NPs) are widely utilized in many applications due to distinct physical and chemical characteristics. There are growing concerns that abundant use of ZnO-NPs can cause harm to humans and the environment. There is a substantial problem with reproducibility in nanotoxicology research due to the inherent properties of nanoparticles. Dispersion media are used for the preparation of nanoparticles. However, the physical and biological behaviors of ZnO-NPs in aqueous dispersion media are poorly understood. In this study, we investigated the effect of ZnO-NPs on the viability of SH-SY5Y cells. Our results showed that ZnO-NPs diluted from water-dispersed stock solution caused significant cell death at a much lower dose compared to their counterpart diluted from the phosphate-buffered saline (PBS)-dispersed stock solution. Electron microscopic data indicated that ZnO-NPs from the PBS-dispersed stock solution form much larger agglomerates compared to the one from the water-dispersed stock solution. From these data, we can conclude that the types of media used for particle dispersion impact the change in the physical property and cytotoxicity of ZnO-NPs.

Zinc oxide nanoparticles modulate the gene expression of ZnT1 and ZIP8 to manipulate zinc homeostasis and stress-induced cytotoxicity in human neuroblastoma SH-SY5Y cells

Zinc ions (Zn²⁺) are important messenger molecules involved in various physiological functions. To maintain the homeostasis of cytosolic Zn²⁺ concentration ([Zn²⁺]_c), Zrt/Irt-related proteins (ZIPs) and Zn²⁺ transporters (ZnTs) are the two families of proteins responsible for decreasing and increasing the [Zn²⁺]_c, respectively, by fluxing Zn²⁺ across the membranes of the cell and intracellular compartments in opposite directions. Most studies focus on the cytotoxicity incurred by a high concentration of [Zn²⁺]_c and less investigate the [Zn²⁺]_c at physiological levels. Zinc oxide-nanoparticle (ZnO-NP) is blood brain barrier-permeable and elevates the [Zn²⁺]_c to different levels according to the concentrations of ZnO-NP applied. In this study, we mildly elevated the [Zn²⁺]_c by ZnO-NP at concentrations below 1 μg/ml, which had little cytotoxicity, in cultured human neuroblastoma SH-SY5Y cells and characterized the importance of Zn²⁺ transporters in 6-hydroxy dopamine (6-OHDA)-induced cell death. The results show that ZnO-NP at low concentrations elevated the [Zn²⁺]_c transiently in 6 hr, then declined gradually to a basal level in 24 hr. Knocking down the expression levels of ZnT₁ (located mostly at the plasma membrane) and ZIP₈ (present in endosomes and lysosomes) increased and decreased the ZnO-NP-induced elevation of [Zn²⁺]_c, respectively. ZnO-NP treatment reduced the basal levels of reactive oxygen species and Bax/Bcl-2 mRNA ratios; in addition, ZnO-NP decreased the 6-OHDA-induced ROS production, p53 expression, and cell death. These results show that ZnO-NP-induced mild elevation in [Zn²⁺]_c activates beneficial effects in reducing the 6-OHDA-induced cytotoxic effects. Therefore, brain-delivery of ZnO-NP can be regarded as a potential therapy for neurodegenerative diseases.

Nanotechnology-based Drug Delivery, Metabolism and Toxicity

BACKGROUND

Nanoparticles (NPs) are being used extensively owing to their increased surface area, targeted delivery and enhanced retention. NPs have the potential to be used in many disease conditions. Despite widespread use, their toxicity and clinical safety still remain a major concern.

OBJECTIVE

The purpose of this study was to explore the metabolism and toxicological effects of nanotherapeutics.

METHODS

Comprehensive, time-bound literature search was done covering the period from 2010 till date. The primary focus was on the metabolism of NP including their adsorption, degradation, clearance, and bio-persistence. This review also focuses on updated investigations on NPs with respect to their toxic effects on various in vitro and in vivo experimental models.

RESULTS

Nanotechnology is a thriving field of biomedical research and an efficient drug delivery system. Further their applications are under investigation for diagnosis of disease and as medical devices.

CONCLUSION

The toxicity of NPs is a major concern in the application of NPs as therapeutics. Studies addressing metabolism, side-effects and safety of NPs are desirable to gain maximum benefits of nanotherapeutics.

Effects of Zinc Oxide Nanoparticles in HUVEC: Cyto- and Genotoxicity and Functional Impairment After Long-Term and Repetitive Exposure in vitro

Purpose

The present study focuses on threshold levels for cytotoxicity after long-term and repetitive exposure for HUVEC as a model for the specific microvascular endothelial system. Furthermore, possible genotoxic effects and functional impairment caused by ZnO NPs in HUVEC are elucidated.

Methods

Thresholds for cytotoxic effects are determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Annexin V assay. To demonstrate DNA damage, single-cell microgel electrophoresis (comet) assay is performed after exposure to sub-cytotoxic concentrations of ZnO NPs. The proliferation assay, dot blot assay and capillary tube formation assay are also carried out to analyze functional impairment.

Results

NPs showed to be spherical in shape with an average size of 45–55 nm. Long-term exposure as well as repetitive exposure with ZnO NPs exceeding 25 µg/mL lead to decreased viability in HUVEC. In addition, DNA damage was indicated by the comet assay after long-term and repetitive exposure. Twenty-four hours after long-term exposure, the proliferation assay does not show any difference between negative control and exposed cells. Forty-eight hours after exposure, HUVEC show an inverse concentration-related ability to proliferate. The dot blot assay provides evidence that ZnO NPs lead to a decreased release of VEGF, while capillary tube formation assay shows restriction in the ability of HUVEC to build tubes and meshes as a first step in angiogenesis.

Conclusion

Sub-cytotoxic concentrations of ZnO NPs lead to DNA damage and functional impairment in HUVEC. Based on these data, ZnO NPs may affect neo-angiogenesis. Further investigation based on tissue cultures is required to elucidate the impact of ZnO NPs on human cell systems.

Investigation of cell death mechanism and activity of esculetin-loaded PLGA nanoparticles on insulinoma cells in vitro

AIM

The purpose of this study was to prepare targeted cancer therapy formulation against insulinoma INS-1 cells and to study its effect on cell death with related mechanisms in vitro.

METHODS

Polylactide-co-glycolide (PLGA) nano-micelles were used for preparation of esculetin nano-formulation (nano-esculetin). The cells were treated with nano-esculetin and free esculetin. Apoptotic and necrotic cell death percentages, cell proliferation, ATP and GTP reductions and insulin levels were investigated on insulinoma INS-1 cells for both free and nano-esculetin formulations.

RESULTS

About 50 mg of PLGA was able to carry 20 mg esculetin in 20 ml of formulation. The obtained optimized formulation was 150 nm, with 92% encapsulation efficiency and a slow-release behaviour was observed during release studies. Nano-esculetin bearing 25, 50 and 100 μg esculetin and free esculetin in equivalent doses successfully decreased cell viability. The prevailing cell death mechanism was necrosis. Along with cell proliferation, intracellular insulin and the ratio of ATP and GTP were decreased even with 12.5, 25 and 50 μg esculetin bearing nano-formulation and its equivalent free esculetin.

CONCLUSIONS

The results revealed that esculetin is able to show its anti-tumor afficacy after loading to PLGA nano-micelles and nano-encapsulation intensifies its cytotoxic activity in vitro. Current study shows that esculetin and its nano formulations are promising agents in treatment of insulinoma.

Redox interactions and genotoxicity of metal-based nanoparticles: A comprehensive review

Nanotechnology is a growing science that may provide several new applications for medicine, food preservation, diagnostic technologies, and sanitation. Despite its beneficial applications, there are several questions related to the safety of nanomaterials for human use. The development of nanotechnology is associated with some concerns because of the increased risk of carcinogenesis following exposure to nanomaterials. The increased levels of reactive oxygen species (ROS) that are due to exposure to nanoparticles (NPs) are primarily responsible for the genotoxicity of metal NPs. Not all, but most metal NPs are able to directly produce free radicals through the release of metal ions and through interactions with water molecules. Furthermore, the increased production of free radicals and the cell death caused by metal NPs can stimulate reduction/oxidation (redox) reactions, leading to the continuous endogenous production of ROS in a positive feedback loop. The overexpression of inflammatory mediators, such as NF-kB and STATs, the mitochondrial malfunction and the increased intracellular calcium levels mediate the chronic oxidative stress that occurs after exposure to metal NPs. In this paper, we review the genotoxicity of different types of metal NPs and the redox mechanisms that amplify the toxicity of these NPs.

Zinc Oxide Nanoparticles Induce Autophagy and Apoptosis via Oxidative Injury and Pro-Inflammatory Cytokines in Primary Astrocyte Cultures

The present study examined the potential toxic concentrations of zinc oxide nanoparticles (ZnO NPs) and associated autophagy and apoptosis-related injuries in primary neocortical astrocyte cultures. Concentrations of ZnO NPs ≥3 μg/mL induced significant toxicity in the astrocytes. At 24 h after exposure to the ZnO NPs, transmission electron microscopy revealed swelling of the endoplasmic reticulum (ER) and increased numbers of autophagolysosomes in the cultured astrocytes, and increased levels of LC3 (microtubule-associated protein 1 light chain 3)-mediated autophagy were identified by flow cytometry. Apoptosis induced by ZnO NP exposure was confirmed by the elevation of caspase-3/7 activity and 4′,6′-diamidino-2-phenylindole (DAPI) staining. Significant (p < 0.05) changes in the levels of glutathione peroxidase, superoxide dismutase, tumor necrosis factor (TNF-α), and interleukin-6 were observed by enzyme-linked immunoassay (ELISA) assay following the exposure of astrocyte cultures to ZnO NPs. Phosphatidylinositol 3-kinase (PI3K)/mitogen-activated protein kinase (MAPK) dual activation was induced by ZnO NPs in a dose-dependent manner. Additionally, the Akt (protein kinase B) inhibitor BML257 and the mTOR (mammalian target of rapamycin) inhibitor rapamycin contributed to the survival of astrocytes. Inhibitors of cyclooxygenase-2 and lipoxygenase attenuated ZnO NP-induced toxicity. Calcium-modulating compounds, antioxidants, and zinc/iron chelators also decreased ZnO NP-induced toxicity. Together, these results suggest that ZnO NP-induced autophagy and apoptosis may be associated with oxidative stress and the inflammatory process in primary astrocyte cultures.

Apoptosis and oxidative stress as relevant mechanisms of antitumor activity and genotoxicity of ZnO-NPs alone and in combination with N-acetyl cysteine in tumor-bearing mice

Background: Several in vitro studies have revealed that zinc oxide nanoparticles (ZnO-NPs) were able to target cancerous cells selectively with minimal damage to healthy cells.

Purpose: In the current study, we aimed to evaluate the antitumor activity of ZnO-NPs in Ehrlich solid carcinoma (ESC) bearing mice by measuring their effect on the expression levels of P53, Bax and Bcl2 genes as indicators of apoptotic induction in tumor tissues. Also, we assessed the potential ameliorative or potentiation effect of 100 mg/kg N-acetyl cysteine (NAC) in combination with ZnO-NPs.

Materials and methods: ESC bearing mice were gavaged with three different doses of ZnO-NPs (50, 300 and 500 mg/kg body weight) alone or in combination with NAC for seven consecutive days. In addition to measuring the tumor size, pathological changes, zinc content, oxidative stress biomarkers and DNA damage in ESC, normal muscle, liver and kidney tissues were assessed.

Results: Data revealed a significant reduction in tumor size with a significant increase in p53 and Bax and decrease in Bcl2 expression levels in the tissues of ZnO-NPs treated ESC bearing mice. Moreover, a significant elevation of MDA accompanied with a significant reduction of CAT and GST. Also, a marked increase in all comet assay parameters was detected in ZnO-NPs treated groups. On the other hand, the combined treatment with ZnO-NPs and NAC significantly reduced reactive oxygen species production and DNA damage in liver and kidney tissues in all ZnO-NPs treated groups.

Conclusion: ZnO-NPs exhibited a promising anticancer efficacy in ESC, this could serve as a foundation for developing new cancer therapeutics. Meanwhile, the combined treatment with ZnO-NPs and NAC could act as a protective method for the healthy normal tissue against ZnO-NPs toxicity, without affecting its antitumor activity.

Nanoparticles and neurotoxicity: Dual response of glutamatergic receptors

Although the use of nanoparticles for neuro-diagnostic and neurotherapeutic purposes provides superior benefits than the conventional approaches, it may be potentially toxic in central nervous system. In this respect, nanotechnological research focuses on nanoneurotoxicity-nanoneurosafety concepts. Despite these efforts, nanoparticles (NPs) may cause neurotoxicity, neuroinflammation, and neurodegeneration by penetrating the brain-olfactory route and blood-brain barrier (BBB). Indeed, due to their unique structures nanomaterials can easily cross biological barriers, thus avoid drug delivery problems. Despite the advancement of nanotechnology for designing therapeutic agents, toxicity of these nanomaterials is still a concern. Activation of neurons by astrocytic glutamate is a result of NPs-mediated astrocyte-neuron crosstalk. Increased extracellular glutamate levels due to enhanced synthesis and reduced reuptake may induce neuronal damage by abnormal activation of extrasynaptic N-methyl d-aspartate receptor (NMDAR) subunits. NMDAR is the key factor that mediates the disturbances in intracellular calcium homeostasis, mitochondrial dysfunction and generation of reactive oxygen species in NPs exposed neurons. While some NPs cause neuronal death by inducing NMDARs, others may be neurotoxic through the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors or protect the neurons via blocking NMDARs. However, mechanisms of dual effects of NPs, neurotoxicity or neuroprotection are not precisely known. Some NPs present neuroprotective effect either by selectively inhibiting extrasynaptic subunit of NMDARs or by attenuating oxidative stress. NPs-related proinflammatory activation of microglia contributes to the dysfunction and cytotoxicity in neurons. Therefore, investigation of the interaction of NPs with the neuronal signaling molecules and neuronal receptors is necessary for the better understanding of the neurotoxicity or neurosafety of nanomaterials.

Necrotic, apoptotic and autophagic cell fates triggered by nanoparticles

Nanomaterials have gained a rapid increase in use in a variety of applications that pertain to many aspects of human life. The majority of these innovations are centered on medical applications and a range of industrial and environmental uses ranging from electronics to environmental remediation. Despite the advantages of NPs, the knowledge of their toxicological behavior and their interactions with the cellular machinery that determines cell fate is extremely limited. This review is an attempt to summarize and increase our understanding of the mechanistic basis of nanomaterial interactions with the cellular machinery that governs cell fate and activity. We review the mechanisms of NP-induced necrosis, apoptosis and autophagy and potential implications of these pathways in nanomaterial-induced outcomes. Abbreviations: Ag, silver; CdTe, cadmium telluride; CNTs, carbon nanotubes; EC, endothelial cell; GFP, green fluorescent protein; GO, graphene oxide; GSH, glutathione; HUVECs, human umbilical vein endothelial cells; NP, nanoparticle; PEI, polyethylenimine; PVP, polyvinylpyrrolidone; QD, quantum dot; ROS, reactive oxygen species; SiO2, silicon dioxide; SPIONs, superparamagnetic iron oxide nanoparticles; SWCNT, single-walled carbon nanotubes; TiO2, titanium dioxide; USPION, ultra-small super paramagnetic iron oxide; ZnO, zinc oxide.

Tau folding and cytotoxicity of neuroblastoma cells in the presence of manganese oxide nanoparticles: Biophysical, molecular dynamics, cellular, and molecular studies

Manganese oxide nanoparticles (Mn₂O₃ NPs) have been widely used in the medical and biological applications. However, few studies have been undertaken to investigate the cytotoxicity of Mn₂O₃ NPs against nervous system. Herein, we studied the toxicity of Mn₂O₃ NPs against tau protein and neuroblastoma cells (SH-SY5Y) in vitro. Circular dichroism (CD) spectroscopy, fluorescence spectroscopy, molecular docking, and molecular dynamic studies were used to explore the conformational changes of protein. The cell-based experiments, such as viability, activation of caspases-3/9, apoptosis, and gene (Bax and Bcl-2) expression assays were performed in vitro. Spectroscopic methods and molecular dynamic studies revealed that Mn₂O₃ NPs can fold the structure of tau toward a more packed structure. The Mn₂O₃ NPs also decreased the cell viability in a dose-dependent manner. Indeed, caspase-3 and caspase-9 activation, Bax/Bcl-2 ratio elevation and apoptosis induction were observed after exposure of SH-SY5Y to Mn₂O₃ NPs. In conclusion, tau folding and cytotoxicity against SH-SY5Y cells may be involved in adverse effects induced by Mn₂O₃ NPs.

Nanoparticles induce apoptosis via mediating diverse cellular pathways

With a special size and structure, nanoparticles (NPs) have excellent application prospects in various fields and are widely used in the biomedicine, cosmetics and chemical industries nowadays. However, there have been some reports on the biosafety of this new type of material, pointing out its cytotoxicity in inducing apoptosis. With different physicochemical properties in size, shape, surface charge, and ligand, NPs exhibit different biocompatibilities when interacting with different cells. Therefore, a comprehensive and deep study into the proapoptotic mechanism of NPs is necessary. In the present review, we summarize the NP-triggered apoptotic signal pathways in detail and highlight some important functional molecules involved. We hope our findings and perspectives provide a new direction for the sound development of nanotechnology in the future.

Zinc Metabolism and Metallothioneins

Among the trace elements, zinc is one of the most used elements in biological systems. Zinc is found in the structure of more than 2700 enzymes, including hydrolases, transferases, oxyreductases, ligases, isomerases, and lyases. Not surprisingly, it is present in almost all body cells. Preserving the stability and integrity of biological membranes and ion channels, zinc is also an intracellular regulator and provides structural support to proteins during molecular interactions. It acts as a structural element in nucleic acids or other gene-regulating proteins. Metallothioneins, the low molecular weight protein family rich in cysteine groups, are involved significantly in numerous physiological and pathological processes including particularly oxidative stress. A critical role of metallothioneins (MT) is to bind zinc with high affinity and to serve as an intracellular zinc reservoir. By releasing free intracellular zinc when needed, MTs mediate the unique physiological roles of zinc. MT expression is induced by zinc elevation, and thus, zinc homeostasis is maintained. That MT mediates the effects of zinc, besides having strong radical scavenging effects, points to the critical part it plays in oxidative stress. The present review aims to give information on metallothioneins, which have critical importance in the metabolism and molecular pathways of zinc.

Toxicological characterization of ZnO nanoparticles in malignant and non-malignant cells

The increasing usage of zinc oxide nanoparticles (ZnO-NPs) in industrial applications as well as in consumer products raises concern regarding their potential adverse effects to a greater extend. Numerous studies have demonstrated toxic properties of NPs, however there is still a lack of knowledge concerning the underlying mechanisms. This study was designed to systematically investigate cytotoxicity, apoptosis, cell cycle alterations, and genotoxicity induced by ZnO-NP. Moreover, it was an aim of the investigations to specify the diverse effects of nanoparticle exposure in malignant in comparison with non-malignant cells. Therefore, human head and neck squamous cell carcinoma-derived FaDu cells were incubated with 4-20 µg/ml of ZnO-NPs for 1-48 hr and tested for cell viability, cell cycle alterations, apoptosis and caspase-3 gene expression as a sensitive marker of molecular apoptotic processes with regard to time- and dose-dependent effects. Human mesenchymal bone marrow stem cells were used as non-malignant representatives to examine oxidative stress-related genotoxicity. Results showed a significant reduction in cell viability as well as dose- and time-dependent increase of apoptotic cells following nanoparticle treatment. Likewise, caspase-3 gene expression enhanced already before first apoptotic cells were detectable. It could be observed that doses that were cytotoxic in tumor cells did not reduce viability in stem cells. However, the same concentrations already induced significant DNA damage. The findings of the study suggest to keep a more critical eye on the use of nanoparticles as anti-cancer agents. Yet, additional in vivo studies are needed to assess safety concerns for consumers and patients. Environ. Mol. Mutagen. 59:247-259, 2018. © 2017 Wiley Periodicals, Inc.

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.

Silver nanoparticles induce SH-SY5Y cell apoptosis via endoplasmic reticulum- and mitochondrial pathways that lengthen endoplasmic reticulum-mitochondria contact sites and alter inositol-3-phosphate receptor function

Silver nanoparticles (AgNPs) have many medical and commercial applications, but their effects on human health are poorly understood. The aim of this study was to assess the effect of AgNPs on the human neuroblastoma cell line SH-SY5Y and to explore their potential mechanisms of action. We found that AgNPs decreased SH-SY5Y cell viability in a dose- and time-dependent manner. Exposure to AgNPs activated endoplasmic reticulum (ER) stress, as reflected by upregulated expression of glucose-regulated protein 78 (GRP78), phosphorylated PKR-like endoplasmic reticulum kinase (p-PERK), phosphorylated eukaryotic translation initiation factor 2α (p-eIF2α), C/EBP homology protein (CHOP), spliced X-box binding protein-1 (XBP1), and phosphorylated inositol-requiring enzyme (p-IRE), all of which are involved in the cellular unfolded protein response. Prolonged exposure of cells to AgNPs damaged calcium (Ca²⁺) homeostasis, increased the length of contact sites between the ER and mitochondria, altered IP₃R function by the increased levels of phosphatase and tensin homolog deleted on chromosome ten (PTEN) in the ER and enhanced mitochondrial Ca²⁺ uptake. Finally, Ca²⁺ overload and disrupted homeostasis in the mitochondria triggered apoptotic cell death. Our results suggest that caution should be exercised in the use of AgNPs in humans.

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.

RNA-binding protein RBM3 prevents NO-induced apoptosis in human neuroblastoma cells by modulating p38 signaling and miR-143

Nitric oxide (NO)-induced apoptosis in neurons is an important cause of neurodegenerative disease in humans. The cold-inducible protein RBM3 mediates the protective effects of cooling on apoptosis induced by various insults. However, whether RBM3 protects neural cells from NO-induced apoptosis is unclear. This study aimed to investigate the neuroprotective effect of RBM3 on NO-induced apoptosis in human SH-SY5Y neuroblastoma cells. Firstly, we demonstrated that mild hypothermia (32 °C) induces RBM3 expression and confers a potent neuroprotective effect on NO-induced apoptosis, which was substantially diminished when RBM3 was silenced by siRNA. Moreover, overexpression of RBM3 exhibited a strong protective effect against NO-induced apoptosis. Signaling pathway screening demonstrated that only p38 inhibition by RBM3 provided neuroprotective effect, although RBM3 overexpression could affect the activation of p38, JNK, ERK, and AKT signaling in response to NO stimuli. Notably, RBM3 overexpression also blocked the activation of p38 signaling induced by transforming growth factor-β1. Furthermore, both RBM3 overexpression and mild hypothermia abolished the induction of miR-143 by NO, which was shown to mediate the cytotoxicity of NO in a p38-dependent way. These findings suggest that RBM3 protects neuroblastoma cells from NO-induced apoptosis by suppressing p38 signaling, which mediates apoptosis through miR-143 induction.

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.

Involvement of Programmed Cell Death in Neurotoxicity of Metallic Nanoparticles: Recent Advances and Future Perspectives

The widespread application of metallic nanoparticles (NPs) or NP-based products has increased the risk of exposure to NPs in humans. The brain is an important organ that is more susceptible to exogenous stimuli. Moreover, any impairment to the brain is irreversible. Recently, several in vivo studies have found that metallic NPs can be absorbed into the animal body and then translocated into the brain, mainly through the blood-brain barrier and olfactory pathway after systemic administration. Furthermore, metallic NPs can cross the placental barrier to accumulate in the fetal brain, causing developmental neurotoxicity on exposure during pregnancy. Therefore, metallic NPs become a big threat to the brain. However, the mechanisms underlying the neurotoxicity of metallic NPs remain unclear. Programmed cell death (PCD), which is different from necrosis, is defined as active cell death and is regulated by certain genes. PCD can be mainly classified into apoptosis, autophagy, necroptosis, and pyroptosis. It is involved in brain development, neurodegenerative disorders, psychiatric disorders, and brain injury. Given the pivotal role of PCD in neurological functions, we reviewed relevant articles and tried to summarize the recent advances and future perspectives of PCD involvement in the neurotoxicity of metallic NPs, with the purpose of comprehensively understanding the neurotoxic mechanisms of NPs.

An Experimental and Computational Approach to the Development of ZnO Nanoparticles that are Safe by Design

Zinc oxide nanoparticles have found wide application due to their unique optoelectronic and photocatalytic characteristics. However, their safety aspects remain of critical concern, prompting the use of physicochemical modifications of pristine ZnO to reduce any potential toxicity. However, the relationships between these modifications and their effects on biology are complex and still relatively unexplored. To address this knowledge gap, a library of 45 types of ZnO nanoparticles with varying particle size, aspect ratio, doping type, doping concentration, and surface coating is synthesized, and their biological effects measured. Three biological assays measuring cell damage or stress are used to study the responses of human umbilical vein endothelial cells (HUVECs) or human hepatocellular liver carcinoma cells (HepG2) to the nanoparticles. These experimental data are used to develop quantitative and predictive computational models linking nanoparticle properties to cell viability, membrane integrity, and oxidative stress. It is found that the concentration of nanoparticles the cells are exposed to, the type of surface coating, the nature and extent of doping, and the aspect ratio of the particles make significant contributions to the cell toxicity of the nanoparticles tested. Our study shows that it is feasible to generate models that could be used to design or optimize nanoparticles with commercially useful properties that are also safe to humans and the environment.

Nano-ZnO leads to tubulin macrotube assembly and actin bundling, triggering cytoskeletal catastrophe and cell necrosis

Zinc is a crucial element in biology that plays chief catalytic, structural and protein regulatory roles. Excess cytoplasmic zinc is toxic to cells so there are cell-entry and intracellular buffering mechanisms that control intracellular zinc availability. Tubulin and actin are two zinc-scavenging proteins that are essential components of the cellular cytoskeleton implicated in cell division, migration and cellular architecture maintenance. Here we demonstrate how exposure to different ZnO nanostructures, namely ZnO commercial nanoparticles and custom-made ZnO nanowires, produce acute cytotoxic effects in human keratinocytes (HaCat) and epithelial cells (HeLa) triggering a dose-dependent cell retraction and collapse. We show how engulfed ZnO nanoparticles dissolve intracellularly, triggering actin filament bundling and structural changes in microtubules, transforming these highly dynamic 25 nm diameter polymers into rigid macrotubes of tubulin, severely affecting cell proliferation and survival. Our results demonstrate that nano-ZnO causes acute cytoskeletal collapse that triggers necrosis, followed by a late reactive oxygen species (ROS)-dependent apoptotic process.