Acute exposure to ZnO nanoparticles induces autophagic immune cell death

FeSA‐Ir/Metallene Nanozymes Induce Sequential Ferroptosis‐Pyroptosis for Multi‐Immunogenic Responses Against Lung Metastasis

For cancer metastasis inhibition, the combining of nanozymes with immune checkpoint blockade (ICB) therapy remains the major challenge in controllable reactive oxygen species (ROS) generation for creating effective immunogenicity. Herein, new nanozymes with light-controlled ROS production in terms of quantity and variety are developed by conjugating supramolecular-wrapped Fe single atom on iridium metallene with lattice-strained nanoislands (FeSA-Ir@PF NSs). The Fenton-like catalysis of FeSA-Ir@PF NSs effectively produced •OH radicals in dark, which induced ferroptosis and apoptosis of cancer cells. While under second near-infrared (NIR-II) light irradiation, FeSA-Ir@PF NSs showed ultrahigh photothermal conversion efficiency (𝜂, 75.29%), cooperative robust •OH generation, photocatalytic O2 and 1O2 generation, and caused significant pyroptosis of cancer cells. The controllable ROS generation, sequential cancer cells ferroptosis and pyroptosis, led 99.1% primary tumor inhibition and multi-immunogenic responses in vivo. Most importantly, the inhibition of cancer lung metastasis is completely achieved by FeSA-Ir@PF NSs with immune checkpoint inhibitors, as demonstrated in different mice lung metastasis models, including circulating tumor cells (CTCs) model. This work provided new inspiration for developing nanozymes for cancer treatments and metastasis inhibition.

Nanomaterials-induced programmed cell death: Focus on mitochondria

Nanomaterials are widely utilized in several domains, such as everyday life, societal manufacturing, and biomedical applications, which expand the potential for nanomaterials to penetrate biological barriers and interact with cells. Multiple studies have concentrated on the particular or improper utilization of nanomaterials, resulting in cellular death. The primary mode of cell death caused by nanotoxicity is programmable cell death, which includes apoptosis, ferroptosis, necroptosis, and pyroptosis. Based on our prior publications and latest research, mitochondria have a vital function in facilitating programmed cell death caused by nanomaterials, as well as initiating or transmitting death signal pathways associated with it. Therefore, this review takes mitochondria as the focal point to investigate the internal molecular mechanism of nanomaterial-induced programmed cell death, with the aim of identifying potential targets for prevention and treatment in related studies.

Environmental Chemical-Induced Reactive Oxygen Species Generation and Immunotoxicity: A Comprehensive Review

Significance: Reactive oxygen species (ROS), the reactive oxygen-carrying chemicals moieties, act as pleiotropic signal transducers to maintain various biological processes/functions, including immune response. Increased ROS production leads to oxidative stress, which is implicated in xenobiotic-induced adverse effects. Understanding the immunoregulatory mechanisms and immunotoxicity is of interest to developing therapeutics against xenobiotic insults. Recent Advances: While developmental studies have established the essential roles of ROS in the establishment and proper functioning of the immune system, toxicological studies have demonstrated high ROS generation as one of the potential mechanisms of immunotoxicity induced by environmental chemicals, including heavy metals, pesticides, aromatic hydrocarbons (benzene and derivatives), plastics, and nanoparticles. Mitochondrial electron transport and various signaling components, including NADH oxidase, toll-like receptors (TLRs), NF-κB, JNK, NRF2, p53, and STAT3, are involved in xenobiotic-induced ROS generation and immunotoxicity. Critical Issues: With many studies demonstrating the role of ROS and oxidative stress in xenobiotic-induced immunotoxicity, rigorous and orthogonal approaches are needed to achieve in-depth and precise understanding. The association of xenobiotic-induced immunotoxicity with disease susceptibility and progression needs more data acquisition. Furthermore, the general methodology needs to be possibly replaced with high-throughput precise techniques. Future Directions: The progression of xenobiotic-induced immunotoxicity into disease manifestation is not well documented. Immunotoxicological studies about the combination of xenobiotics, age-related sensitivity, and their involvement in human disease incidence and pathogenesis are warranted. Antioxid. Redox Signal. 40, 691-714.

Engineered Nanomaterials for Immunomodulation: A Review

The immune system usually provides a defense against invading pathogenic microorganisms and any other particulate contaminants. Nonetheless, it has been recently reported that nanomaterials can evade the immune system and modulate immunological responses due to their unique physicochemical characteristics. Consequently, nanomaterial-based activation of immune components, i.e., neutrophils, macrophages, and other effector cells, may induce inflammation and alter the immune response. Here, it is essential to distinguish the acute and chronic modulations triggered by nanomaterials to determine the possible risks to human health. Nanomaterials size, shape, composition, surface charge, and deformability are factors controlling their uptake by immune cells and the resulting immune responses. The exterior corona of molecules adsorbed over nanomaterials surfaces also influences their immunological effects. Here, we review current nanoengineering trends for targeted immunomodulation with an emphasis on the design, safety, and potential toxicity of nanomaterials. First, we describe the characteristics of engineered nanomaterials that trigger immune responses. Then, the biocompatibility and immunotoxicity of nanoengineered particles are debated, because these factors influence applications. Finally, future nanomaterial developments in terms of surface modifications, synergistic approaches, and biomimetics are discussed.

Compensatory response of Hong Kong oysters to co-occurring stressors: Zinc oxide nanoparticles and low salinity exposure

Zinc Oxide nanoparticles (ZnO NPs), due to their ubiquitous use in industrial and consumer applications, present potential risks to marine ecosystems and biota, especially oysters. The physiological and immunological health of marine species is highly dependent on salinity levels. However, the combined impact of lowered salinity and exposure to ZnO NPs, particularly on key marine species like oysters, is an area that requires more research. Our study aimed to examine these concurrent stressors' impacts on phenotypic markers, gill and hepatopancreas physiological indices, and hemocyte immune parameters of Crassostrea hongkongensis. We subjected six oyster cohorts to varied ZnO NPs concentrations and salinity levels over 21 days. Our findings reveal that individual exposure to ZnO NPs or diminished salinity disrupts oyster physiology, impacting metabolism, antioxidant capacity, immune response, and energy distribution through distinct mechanisms. Remarkably, low salinity constituted a more significant threat than isolated ZnO NPs. However, when confronted with combined stressors, oysters exhibited a compensatory response, attenuating individual stressors' detrimental effects. This adaptation was characterised by reduced apoptosis rates, increased calcium ion concentration in mature hemocytes, and a restoration of conditioned indices, hepatopancreas alkaline phosphatase, and gill catalase activity to baseline levels. Principal Component Analysis and Integrated Biomarker Responses validated this compensatory phenomenon. Partial Least Squares Pathway Model analysis underscored these stressors' profound implications on oyster health, primarily driven by stressor exposure rather than mere zinc concentrations, despite acknowledging zinc's immunosuppressive impact on oyster immunity. Our research emphasises the importance of assessing multiple stressors' cumulative effects on aquatic species' ecological resilience, accentuating the need for comprehensive analyses incorporating functional specificity among diverse organs and immune components, including gill, hepatopancreas, and the critical hemocytes.

Food-grade titanium dioxide and zinc oxide nanoparticles induce toxicity and cardiac damage after oral exposure in rats

BACKGROUND

Metallic nanoparticles (NPs) are widely used as food additives for human consumption. NPs reach the bloodstream given their small size, getting in contact with all body organs and cells. NPs have adverse effects on the respiratory and intestinal tract; however, few studies have focused on the toxic consequences of orally ingested metallic NPs on the cardiovascular system. Here, the effects of two food-grade additives on the cardiovascular system were analyzed.

METHODS

Titanium dioxide labeled as E171 and zinc oxide (ZnO) NPs were orally administered to Wistar rats using an esophageal cannula at 10 mg/kg bw every other day for 90 days. We evaluated cardiac cell morphology and death, expression of apoptotic and autophagic proteins in cardiac mitochondria, mitochondrial dysfunction, and concentration of metals on cardiac tissue.

RESULTS

Heart histology showed important morphological changes such as presence of cellular infiltrates, collagen deposition and mitochondrial alterations in hearts from rats exposed to E171 and ZnO NPs. Intracellular Cyt-C levels dropped, while TUNEL positive cells increased. No significant changes in the expression of inflammatory cytokines were detected. Both NPs altered mitochondrial function indicating cardiac dysfunction, which was associated with an elevated concentration of calcium. ZnO NPs induced expression of caspases 3 and 9 and two autophagic proteins, LC3B and beclin-1, and had the strongest effect compared to E171.

CONCLUSIONS

E171 and ZnO NPs induce adverse cardiovascular effects in rats after 90 days of exposure, thus food intake containing these additives, should be taken into consideration, since they translocate into the bloodstream and cause cardiovascular damage.

Autophagy and Biomaterials: A Brief Overview of the Impact of Autophagy in Biomaterial Applications

Macroautophagy (hereafter autophagy), a tightly regulated physiological process that obliterates dysfunctional and damaged organelles and proteins, has a crucial role when biomaterials are applied for various purposes, including diagnosis, treatment, tissue engineering, and targeted drug delivery. The unparalleled physiochemical properties of nanomaterials make them a key component of medical strategies in different areas, such as osteogenesis, angiogenesis, neurodegenerative disease treatment, and cancer therapy. The application of implants and their modulatory effects on autophagy have been known in recent years. However, more studies are necessary to clarify the interactions and all the involved mechanisms. The advantages and disadvantages of nanomaterial-mediated autophagy need serious attention in both the biological and bioengineering fields. In this mini-review, the role of autophagy after biomaterial exploitation and the possible related mechanisms are explored.

Recent insights into autophagy and metals/nanoparticles exposure

Some anthropogenic pollutants, such as heavy metals and nanoparticles (NPs), are widely distributed and a major threat to environmental safety and public health. In particular, lead (Pb), cadmium (Cd), chromium (Cr), arsenic (As), and mercury (Hg) have systemic toxicity even at extremely low concentrations, so they are listed as priority metals in relation to their significant public health burden. Aluminum (Al) is also toxic to multiple organs and is linked to Alzheimer's disease. As the utilization of many metal nanoparticles (MNPs) gradually gain traction in industrial and medical applications, they are increasingly being investigated to address potential toxicity by impairing certain biological barriers. The dominant toxic mechanism of these metals and MNPs is the induction of oxidative stress, which subsequently triggers lipid peroxidation, protein modification, and DNA damage. Notably, a growing body of research has revealed the linkage between dysregulated autophagy and some diseases, including neurodegenerative diseases and cancers. Among them, some metals or metal mixtures can act as environmental stimuli and disturb basal autophagic activity, which has an underlying adverse health effect. Some studies also revealed that specific autophagy inhibitors or activators could modify the abnormal autophagic flux attributed to continuous exposure to metals. In this review, we have gathered recent data about the contribution of the autophagy/mitophagy mediated toxic effects and focused on the involvement of some key regulatory factors of autophagic signaling during exposure to selected metals, metal mixtures, as well as MNPs in the real world. Besides this, we summarized the potential significance of interactions between autophagy and excessive reactive oxygen species (ROS)-mediated oxidative damage in the regulation of cell survival response to metals/NPs. A critical view is given on the application of autophagy activators/inhibitors to modulate the systematic toxicity of various metals/MNPs.

Zinc Oxide Nanoparticles Blunt Potassium-Bromate-Induced Renal Toxicity by Reinforcing the Redox System

Potassium bromate (PB) is a general food additive, a significant by-product during water disinfection, and a carcinogen (Class II B). The compound emits toxicity depending on the extent of its exposure and dose through consumable items. The current study targeted disclosing the ameliorative efficacy of zinc oxide nanoparticles (ZnO NPs) prepared by green technology in PB-exposed Swiss albino rats. The rats were separated into six treatment groups: control without any treatment (Group I), PB alone (Group II), ZnO alone (Group III), ZnO NP alone (Group IV), PB + ZnO (Group V), and PB + ZnO NPs (Group VI). The blood and kidney samples were retrieved from the animals after following the treatment plan and kept at -20 °C until further analysis. Contrary to the control (Group I), PB-treated rats (Group II) exhibited a prominent trend in alteration in the established kidney function markers and disturbed redox status. Further, the analysis of the tissue and nuclear DNA also reinforced the biochemical results of the same treatment group. Hitherto, Groups III and IV also showed moderate toxic insults. However, Group VI showed a significant improvement from the PB-induced toxic insults compared to Group II. Hence, the present study revealed the significant therapeutic potential of the NPs against PB-induced nephrotoxicity in vivo, pleading for their usage in medicines having nephrotoxicity as a side effect or in enhancing the safety of the industrial use of PB.

Immunotoxicity of metal and metal oxide nanoparticles: from toxic mechanisms to metabolism and outcomes

The influence of metal and metal oxide nanomaterials on various fields since their discovery has been remarkable. They have unique properties, and therefore, have been employed in specific applications, including biomedicine. However, their potential health risks cannot be ignored. Several studies have shown that exposure to metal and metal oxide nanoparticles can lead to immunotoxicity. Different types of metals and metal oxide nanoparticles may have a negative impact on the immune system through various mechanisms, such as inflammation, oxidative stress, autophagy, and apoptosis. As an essential factor in determining the function and fate of immune cells, immunometabolism may also be an essential target for these nanoparticles to exert immunotoxic effects in vivo. In addition, the biodegradation and metabolic outcomes of metal and metal oxide nanoparticles are also important considerations in assessing their immunotoxic effects. Herein, we focus on the cellular mechanism of the immunotoxic effects and toxic effects of different types of metal and metal oxide nanoparticles, as well as the metabolism and outcomes of these nanoparticles in vivo. Also, we discuss the relationship between the possible regulatory effect of nanoparticles on immunometabolism and their immunotoxic effects. Finally, we present perspectives on the future research and development direction of metal and metal oxide nanomaterials to promote scientific research on the health risks of nanomaterials and reduce their adverse effects on human health.

Assessing regulated cell death modalities as an efficient tool for in vitro nanotoxicity screening: a review

Nanomedicine is a fast-growing field of nanotechnology. One of the major obstacles for a wider use of nanomaterials for medical application is the lack of standardized toxicity screening protocols for assessing the safety of newly synthesized nanomaterials. In this review, we focus on less frequently studied nanomaterials-induced regulated cell death (RCD) modalities, including eryptosis, necroptosis, pyroptosis, and ferroptosis, as a tool for in vitro nanomaterials safety evaluation. We summarize the latest insights into the mechanisms that mediate these RCDs in response to nanomaterials exposure. Comprehensive data from reviewed studies suggest that ROS (reactive oxygen species) overproduction and ROS-mediated pathways play a central role in nanomaterials-induced RCDs activation. On the other hand, studies also suggest that individual properties of nanomaterials, including size, shape, or surface charge, could determine specific toxicity pathways with consequent RCD induction as well. We anticipate that the evaluation of RCDs can become one of the mechanism-based screening methods in nanotoxicology. In addition to the toxicity assessment, evaluation of necroptosis-, pyroptosis-, and ferroptosis-promoting capacity of nanomaterials could simultaneously provide useful information for specific medical applications as could be their anti-tumor potential. Moreover, a detailed understanding of molecular mechanisms driving nanomaterials-mediated induction of immunogenic RCDs will substantially aid novel anti-tumor nanodrugs development.

Comparative toxicological evaluations of novel forms nano-pesticides in liver and lung of albino rats

Copper oxide Nanoparticles (CuONPs) are used in different agricultural applications. Large amounts of CuONPs cause organ dysfunction in animals. Our study aim to compare between the toxic effects of CuONanSphere (CuONSp) and CuONanoFlower (CuONF) as new nano-pesticides, determine a less toxic form when used in agricultural applications. To characterize CuONSp and CuONF, we used X-ray diffraction (XRD), Field emission scanning electron microscopy (SEM), and High resolution transmission electron microscopy (HRTEM) and Zeta-sizer device.18 adult male albino rats were divided into three groups (n = 6), (I) control group, (II) and (III) groups were given orally 50 mg/kg/day of CuONSp and CuONF 30 days respectively. CuONSp induced oxidant-antioxidant abnormalities, including an increase in malondialdhyde (MDA) and a decrease in glutathione (GSH) in comparison to CuONF-treated one. CuONSp induced an increase in liver enzymes activities compared to CuONF. Tumour necrosis factor-alfa (TNF-α) detected an increased in liver and lung compared to CuONF. However, histological examinations revealed changes in CuONSp group than CuONF group. Changes in immune-expressions of TNF-α, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kβ) and tumour suppressor gene (p53) were also more identified in CuONSp group than CuONF group. Ultrastructural studies of liver and lung tissues marked alternations were observed in CuONSp group than CuONF group. In conclusion, CuONSp induced biological alternation in liver and lung more than CuONF. So, CuONF is less toxic compared to CuONSp when used as nano-pesticide in agricultural applications.

Bioactive inorganic nanomaterials for cancer theranostics

Bioactive materials are a special class of biomaterials that can react in vivo to induce a biological response or regulate biological functions, thus achieving a better curative effect than traditional inert biomaterials. For cancer theranostics, compared with organic or polymer nanomaterials, inorganic nanomaterials possess unique physical and chemical properties, have stronger mechanical stability on the basis of maintaining certain bioactivity, and are easy to be compounded with various carriers (polymer carriers, biological carriers, etc.), so as to achieve specific antitumor efficacy. After entering the nanoscale, due to the nano-size effect, high specific surface area and special nanostructures, inorganic nanomaterials exhibit unique biological effects, which significantly influence the interaction with biological organisms. Therefore, the research and applications of bioactive inorganic nanomaterials in cancer theranostics have attracted wide attention. In this review, we mainly summarize the recent progress of bioactive inorganic nanomaterials in cancer theranostics, and also introduce the definition, synthesis and modification strategies of bioactive inorganic nanomaterials. Thereafter, the applications of bioactive inorganic nanomaterials in tumor imaging and antitumor therapy, including tumor microenvironment (TME) regulation, catalytic therapy, gas therapy, regulatory cell death and immunotherapy, are discussed. Finally, the biosafety and challenges of bioactive inorganic nanomaterials are also mentioned, and their future development opportunities are prospected. This review highlights the bioapplication of bioactive inorganic nanomaterials.

Plant and Microbial Approaches as Green Methods for the Synthesis of Nanomaterials: Synthesis, Applications, and Future Perspectives

The unique biological and physicochemical characteristics of biogenic (green-synthesized) nanomaterials (NMs) have attracted significant interest in different fields, with applications in the agrochemical, food, medication delivery, cosmetics, cellular imaging, and biomedical industries. To synthesize biogenic nanomaterials, green synthesis techniques use microorganisms, plant extracts, or proteins as bio-capping and bio-reducing agents and their role as bio-nanofactories for material synthesis at the nanoscale size. Green chemistry is environmentally benign, biocompatible, nontoxic, and economically effective. By taking into account the findings from recent investigations, we shed light on the most recent developments in the green synthesis of nanomaterials using different types of microbes and plants. Additionally, we cover different applications of green-synthesized nanomaterials in the food and textile industries, water treatment, and biomedical applications. Furthermore, we discuss the future perspectives of the green synthesis of nanomaterials to advance their production and applications.

Zinc oxide nanoparticles trigger autophagy-mediated cell death through activating lysosomal TRPML1 in normal kidney cells

Zinc oxide nanoparticles (ZnO NPs) have been widely used in various materials including sunscreens, cosmetics, over-the-counter topical skin products, and pigments. As traces of the used ZnO NPs have been found in the kidney, it is crucial to uncover their potential risks. The aim of this study is to elucidate detrimental effects of ZnO NPs and the molecular mechanism behind their renal toxicity. Cytotoxic effects were measured by MTT assay after HK2 cells were exposed to ZnO NPs for 24 h and IC₅₀ value was determined. ROS and intracellular Zn²⁺ levels were detected by flow cytometry, and localization of Zn²⁺ and lysosome was determined by confocal microscopy. Occurrence of autophagy and detection of autophagic flux were determined by Western blot and confocal microscopy, respectively. We performed unpaired student t test for two groups, and one-way ANOVA with Tukey's post hoc for over three groups. ZnO NPs induced cell death in human renal proximal tubule epithelial cells, HK2. Cytosolic Zn²⁺ caused autophagy-mediated cell death rather than apoptosis. Cytosolic Zn²⁺ processed in lysosome was released by TRPML1, and inhibition of TRPML1 significantly decreased autophagic flux and cell death. The findings of this study suggest that ZnO NPs strongly induce autophagy-mediated cell death in human kidney cells. Controlling TRPML1 can be potentially used to prevent the kidney from ZnO NPs-induced toxicity.

Recent advances of nanotechnology in COVID 19: A critical review and future perspective

The global anxiety and economic crisis causes the deadly pandemic coronavirus disease of 2019 (COVID 19) affect millions of people right now. Subsequently, this life threatened viral disease is caused due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, morbidity and mortality of infected patients are due to cytokines storm syndrome associated with lung injury and multiorgan failure caused by COVID 19. Thereafter, several methodological advances have been approved by WHO and US-FDA for the detection, diagnosis and control of this wide spreadable communicable disease but still facing multi-challenges to control. Herein, we majorly emphasize the current trends and future perspectives of nano-medicinal based approaches for the delivery of anti-COVID 19 therapeutic moieties. Interestingly, Nanoparticles (NPs) loaded with drug molecules or vaccines resemble morphological features of SARS-CoV-2 in their size (60–140 nm) and shape (circular or spherical) that particularly mimics the virus facilitating strong interaction between them. Indeed, the delivery of anti-COVID 19 cargos via a nanoparticle such as Lipidic nanoparticles, Polymeric nanoparticles, Metallic nanoparticles, and Multi-functionalized nanoparticles to overcome the drawbacks of conventional approaches, specifying the site-specific targeting with reduced drug loading and toxicities, exhibit their immense potential. Additionally, nano-technological based drug delivery with their peculiar characteristics of having low immunogenicity, tunable drug release, multidrug delivery, higher selectivity and specificity, higher efficacy and tolerability switch on the novel pathway for the prevention and treatment of COVID 19.

Meta-analysis of in-vitro cytotoxicity evaluation studies of zinc oxide nanoparticles: Paving way for safer innovations

Nano-based products have shown their daunting presence in several sectors. Among them, Zinc Oxide (ZnO) nanoparticles wangled the reputation of providing "next-generation solutions" and are being utilized in plethora of products. Their widespread application has led to increased exposure of these particles, raising concerns regarding toxicological repercussions to the human health and environment. The diversity, complexity, and heterogeneity in the available literature, along with correlation of befitting attributes, makes it challenging to develop one systematic framework to predict this toxicity. The present study aims at developing predictive modelling framework to tap the prospective features responsible for causing cytotoxicity in-vitro on exposure to ZnO nanoparticles. Rigorous approach was used to mine the information from complete body of evidence published to date. The attributes, features and experimental conditions were systematically extracted to unmask the effect of varied features. 1240 data points from 76 publications were obtained, containing 14 qualitative and quantitative attributes, including physiochemical properties of nanoparticles, cell culture and experimental parameters to perform meta-analysis. For the first time, the efforts were made to investigate the degree of significance of attributes accountable for causing cytotoxicity on exposure to ZnO nanoparticles. We show that in-vitro cytotoxicity is closely related with dose concentration of nanoparticles, followed by exposure time, disease state of the cell line and size of these nanoparticles among other attributes.

Perturbation of autophagy: An intrinsic toxicity mechanism of nanoparticles

Nanoparticles (NPs) have been widely used for various purposes due to their unique physicochemical properties. Such widespread applications greatly increase the possibility of human exposure to NPs in various ways. Once entering the human body, NPs may interfere with cellular homeostasis and thus affect the physiological system. As a result, it is necessary to evaluate the potential disturbance of NPs to multiple cell functions, including autophagy. Autophagy is an important cell function to maintain cellular homeostasis, and minimizing the disturbance caused by NP exposures to autophagy is critical to nanosafety. Herein, we summarized the recent research progress in nanotoxicity with particular focuses on the perturbation of NPs to cell autophagy. The basic processes of autophagy and complex relationships between autophagy and major human diseases were further discussed to emphasize the importance of keeping autophagy under control. Moreover, the most recent advances on perturbation of different types of NPs to autophagy were also reviewed. Last but not least, we also discussed major research challenges and potential coping strategies and proposed a safe-by-design strategy towards safer applications of NPs.

Copper oxide nanoparticles trigger macrophage cell death with misfolding of Cu/Zn superoxide dismutase 1 (SOD1)

Background

Copper oxide (CuO) nanoparticles (NPs) are known to trigger cytotoxicity in a variety of cell models, but the mechanism of cell death remains unknown. Here we addressed the mechanism of cytotoxicity in macrophages exposed to CuO NPs versus copper chloride (CuCl₂).

Methods

The mouse macrophage cell line RAW264.7 was used as an in vitro model. Particle uptake and the cellular dose of Cu were investigated by transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry (ICP-MS), respectively. The deposition of Cu in lysosomes isolated from macrophages was also determined by ICP-MS. Cell viability (metabolic activity) was assessed using the Alamar Blue assay, and oxidative stress was monitored by a variety of methods including a luminescence-based assay for cellular glutathione (GSH), and flow cytometry-based detection of mitochondrial superoxide and mitochondrial membrane potential. Protein aggregation was determined by confocal microscopy using an aggresome-specific dye and protein misfolding was determined by circular dichroism (CD) spectroscopy. Lastly, proteasome activity was investigated using a fluorometric assay.

Results

We observed rapid cellular uptake of CuO NPs in macrophages with deposition in lysosomes. CuO NP-elicited cell death was characterized by mitochondrial swelling with signs of oxidative stress including the production of mitochondrial superoxide and cellular depletion of GSH. We also observed a dose-dependent accumulation of polyubiquitinated proteins and loss of proteasomal function in CuO NP-exposed cells, and we could demonstrate misfolding and mitochondrial translocation of superoxide dismutase 1 (SOD1), a Cu/Zn-dependent enzyme that plays a pivotal role in the defense against oxidative stress. The chelation of copper ions using tetrathiomolybdate (TTM) prevented cell death whereas inhibition of the cellular SOD1 chaperone aggravated toxicity. Moreover, CuO NP-triggered cell death was insensitive to the pan-caspase inhibitor, zVAD-fmk, and to wortmannin, an inhibitor of autophagy, implying that this was a non-apoptotic cell death. ZnO NPs, on the other hand, triggered autophagic cell death.

Conclusions

CuO NPs undergo dissolution in lysosomes leading to copper-dependent macrophage cell death characterized by protein misfolding and proteasomal insufficiency. Specifically, we present novel evidence for Cu-induced SOD1 misfolding which accords with the pronounced oxidative stress observed in CuO NP-exposed macrophages. These results are relevant for our understanding of the consequences of inadvertent human exposure to CuO NPs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-022-00467-w.

Immunotoxicity of nanomaterials in health and disease: Current challenges and emerging approaches for identifying immune modifiers in susceptible populations

Nanosafety assessment has experienced an intense era of research during the past decades driven by a vivid interest of regulators, industry, and society. Toxicological assays based on in vitro cellular models have undergone an evolution from experimentation using nanoparticulate systems on singular epithelial cell models to employing advanced complex models more realistically mimicking the respective body barriers for analyzing their capacity to alter the immune state of exposed individuals. During this phase, a number of lessons were learned. We have thus arrived at a state where the next chapters have to be opened, pursuing the following objectives: (1) to elucidate underlying mechanisms, (2) to address effects on vulnerable groups, (3) to test material mixtures, and (4) to use realistic doses on (5) sophisticated models. Moreover, data reproducibility has become a significant demand. In this context, we studied the emerging concept of adverse outcome pathways (AOPs) from the perspective of immune activation and modulation resulting in pro-inflammatory versus tolerogenic responses. When considering the interaction of nanomaterials with biological systems, protein corona formation represents the relevant molecular initiating event (e.g., by potential alterations of nanomaterial-adsorbed proteins). Using this as an example, we illustrate how integrated experimental-computational workflows combining in vitro assays with in silico models aid in data enrichment and upon comprehensive ontology-annotated (meta)data upload to online repositories assure FAIRness (Findability, Accessibility, Interoperability, Reusability). Such digital twinning may, in future, assist in early-stage decision-making during therapeutic development, and hence, promote safe-by-design innovation in nanomedicine. Moreover, it may, in combination with in silico-based exposure-relevant dose-finding, serve for risk monitoring in particularly loaded areas, for example, workplaces, taking into account pre-existing health conditions. This article is categorized under: Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

Mechanisms of immune response to inorganic nanoparticles and their degradation products

Careful assessment of the biological fate and immune response of inorganic nanoparticles is crucial for use of such carriers in drug delivery and other biomedical applications. Many studies have elucidated the cellular and molecular mechanisms of the interaction of inorganic nanoparticles with the components of the immune system. The biodegradation and dissolution of inorganic nanoparticles can influence their ensuing immune response. While the immunological properties of inorganic nanoparticles as a function of their physicochemical properties have been investigated in detail, little attention has been paid to the immune adverse effects towards the degradation products of these nanoparticles. To fill this gap, we herein summarize the cellular mechanisms of immune response to inorganic nanoparticles and their degradation products with specific focus on immune cells. We also accentuate the importance of designing new methods and instruments for the in situ characterization of inorganic nanoparticles in order to assess their safety as a result of degradation. This review further sheds light on factors that need to be considered in the design of safe and effective inorganic nanoparticles for use in delivery of bioactive and imaging agents.

Nano-sized zinc addition enhanced mammary zinc translocation without altering health status of dairy cows

This study aimed to evaluate role of nano-sized zinc (Zn) on lactation performance, health status, and mammary permeability of lactating dairy cows. Thirty multiparous dairy cows with similar days in milk (158 ± 43.2) and body weight (694 ± 60.5 kg) were chosen based on parity and milk production and were randomly assigned to 3 treatment groups: basal diet (control, 69.6 mg/kg of Zn adequate in Zn requirement), basal diet additional Zn-methionine (Zn-Met, providing 40 mg/kg of Zn), and basal diet additional nano-sized Zn oxide (nZnO, providing 40 mg/kg of Zn). The study lasted for 10 wk, with the first 2 wk as adaptation. Feed intake, milk yield and the related variables, and plasma variables were determined every other week. Blood hematological profiles were determined in the 8th week of the study. We found that feed intake, milk yield, and milk composition were similar across the 3 groups. The nZnO- and Zn-Met-fed cows had greater milk Zn concentrations in the milk (3.89 mg/L (Zn-Met) and 3.93 mg/L (nZnO)) and plasma (1.25 mg/L (Zn-Met) and 1.29 mg/L (nZnO)) than the control cows (3.79 mg/L in milk and 1.21 mg/L in plasma). The nZnO-fed cows had higher Zn concentrations in plasma but not in milk compared to Zn-Met-fed cows. The Zn appearance in milk was greater in nZnO-fed (area under curve during the first 4 h post-feeding for milk Zn: 16.1 mg/L) and Zn-Met-fed cows (15.7 mg/L) than in control cows (15.0 mg/L). During the first 4 h post-feeding, milk to blood Zn ratio was greater in nZnO-fed animals but lower in Zn-Met-fed cows compared with control cows. Oxidative stress-related variables in plasma, blood hematological profiles, and mammary permeability related variables were not different across treatments. In summary, lactation performance, Zn concentrations in milk and plasma, hematological profiles, mammary permeability were similar in cows fed nZnO and Zn-Met. We therefore suggested that nZnO feeding can improve Zn bioavailability without impairing lactation performance, health status, and mammary gland permeability in dairy cows.

The cytotoxicity of zinc oxide nanoparticles to 3D brain organoids results from excessive intracellular zinc ions and defective autophagy

Although the neurotoxicity of ZnO nanoparticles (NPs) has been evaluated in animal and nerve cell culture models, these models cannot accurately mimic human brains. Three-dimensional (3D) brain organoids based on human-induced pluripotent stem cells have been developed to study the human brains, but this model has rarely been used to evaluate NP neurotoxicity. We used 3D brain organoids that express cortical layer proteins to investigate the mechanisms of ZnO NP-induced neurotoxicity. Cytotoxicity caused by high levels of ZnO NPs (64 μg/mL) correlated with high intracellular Zn ion levels but not superoxide levels. Exposure to a non-cytotoxic concentration of ZnO NPs (16 μg/mL) increased the autophagy-marker proteins LC3B-II/I but decreased p62 accumulation, whereas a cytotoxic concentration of ZnO NPs (64 μg/mL) decreased LC3B-II/I proteins but did not affect p62 accumulation. Fluorescence micro-optical sectioning tomography revealed that 64 μg/mL ZnO NPs led to decreases in LC3B proteins that were more obvious at the outer layers of the organoids, which were directly exposed to the ZnO NPs. In addition to reducing LC3B proteins in the outer layers, ZnO NPs increased the number of micronuclei in the outer layers but not the inner layers (where LC3B proteins were still expressed). Adding the autophagy flux inhibitor bafilomycin A1 to ZnO NPs increased cytotoxicity and intracellular Zn ion levels, but adding the autophagy inducer rapamycin only slightly decreased cellular Zn ion levels. We conclude that high concentrations of ZnO NPs are cytotoxic to 3D brain organoids via defective autophagy and intracellular accumulation of Zn ions.

Endoplasmic reticulum stress-related calcium imbalance plays an important role on Zinc oxide nanoparticles-induced failure of neural tube closure during embryogenesis

Zinc oxide nanoparticles (ZnO NPs) have been increasingly and widely utilized in various fields, such as agriculture, food and cosmetics. However, various levels of adverse impacts of ZnO NPs on the ecological environment and public health have been associated with each stage of their production, use and disposal. ZnO NPs can be ingested by pregnant women and transferred to developing embryos/foetus through the placental barrier, however, the potential toxicity of ZnO NPs to embryonic and foetal development is largely unclear. In this study, we discovered that ZnO NPs exposure caused growth proportional failure of neural tube closure in mouse and chicken embryos and a simultaneous increase in apoptosis in the developing neural tubes of chicken embryos, which was verified in an in vitro experiment using the SH-SY5Y cell line. Furthermore, removal of free Zn²⁺ ions with EDTA or inhibition of Zn²⁺ ion absorption by CaCl₂ partially alleviated the neurotoxicity induced by ZnO NPs, implying that ZnO NPs-induced developmental neurotoxicity is probably due to both ZnO NPs and the Zn²⁺ ions released from ZnO NPs. In addition, we found that ZnO NPs exposure caused endoplasmic reticulum stress-mediated apoptosis driven mainly by an increase in intracellular calcium (Ca²⁺) concentrations, rather than by the activation of three membrane protein receptors (ATF6, IRE-1 and PERK). Thus, Ca²⁺ imbalance-mediated apoptosis in the context of ZnO NPs exposure may lead to cellular dysfunctions in developing neural precursors, such as, abnormalities involved in neural tube closure, ultimately leading to neural tube defects (NTDs) during embryogenesis. In sum, our results revealed that ZnO NPs exposure greatly increases the risk of failure of neural tube closure through endoplasmic reticulum stress-mediated neural cell death in the developing embryos, which may further lead to the NTD in fetal stage, including failure of neural tube closure.

Micro- and Nanosized Substances Cause Different Autophagy-Related Responses

With rapid industrialization, humans produce an increasing number of products. The composition of these products is usually decomposed. However, some substances are not easily broken down and gradually become environmental pollutants. In addition, these substances may cause bioaccumulation, since the substances can be fragmented into micro- and nanoparticles. These particles or their interactions with other toxic matter circulate in humans via the food chain or air. Whether these micro- and nanoparticles interfere with extracellular vesicles (EVs) due to their similar sizes is unclear. Micro- and nanoparticles (MSs and NSs) induce several cell responses and are engulfed by cells depending on their size, for example, particulate matter with a diameter ≤2.5 μm (PM2.5). Autophagy is a mechanism by which pathogens are destroyed in cells. Some artificial materials are not easily decomposed in organisms. How do these cells or tissues respond? In addition, autophagy operates through two pathways (increasing cell death or cell survival) in tumorigenesis. Many MSs and NSs have been found that induce autophagy in various cells and tissues. As a result, this review focuses on how these particles interfere with cells and tissues. Here, we review MSs, NSs, and PM2.5, which result in different autophagy-related responses in various tissues or cells.

Ecotoxicity to Freshwater Organisms and Cytotoxicity of Nanomaterials: Are We Generating Sufficient Data for Their Risk Assessment?

The aim of the present study was to investigate the eco-cytotoxicity of several forms of nanomaterials (NM), such as nano-CuO, nano-TiO₂, nano-SiO₂ and nano-ZnO, on different aquatic species (Raphidocelis subcapitata, Daphnia magna and Lemna minor) following standard protocols and on human cell lines (Caco-2, SV-80, HepG2 and HaCaT). Predicted no-effect concentrations (PNEC) or hazard concentrations for 5% of the species (HC₅) were also estimated based on the compilation of data available in the literature. Most of the NM agglomerated strongly in the selected culture media. For the ecotoxicity assays, nano-CuO and nano-ZnO even in particle agglomeration state were the most toxic NM to the freshwater organisms compared to nano-TiO₂ and nano-SiO₂. Nano-ZnO was the most toxic NM to R. subcapitata and D. magna, while nano-CuO was found to be very toxic to L. minor. Nano-CuO was very toxic to Caco-2 and HepG2 cells, particularly at the highest tested concentrations, while the other NM showed no toxicity to the different cell lines. The HC₅ and PNEC values are still highly protective, due to data limitations. However, the present study provides consistent evidence of the potential risks of both nano-CuO and nano-ZnO against aquatic organisms and also their effects on public health.

Recent Advances in Zinc Oxide Nanostructures with Antimicrobial Activities

This article reviews the recent developments in the synthesis, antibacterial activity, and visible-light photocatalytic bacterial inactivation of nano-zinc oxide. Polycrystalline wurtzite ZnO nanostructures with a hexagonal lattice having different shapes can be synthesized by means of vapor-, liquid-, and solid-phase processing techniques. Among these, ZnO hierarchical nanostructures prepared from the liquid phase route are commonly used for antimicrobial activity. In particular, plant extract-mediated biosynthesis is a single step process for preparing nano-ZnO without using surfactants and toxic chemicals. The phytochemical molecules of natural plant extracts are attractive agents for reducing and stabilizing zinc ions of zinc salt precursors to form green ZnO nanostructures. The peel extracts of certain citrus fruits like grapefruits, lemons and oranges, acting as excellent chelating agents for zinc ions. Furthermore, phytochemicals of the plant extracts capped on ZnO nanomaterials are very effective for killing various bacterial strains, leading to low minimum inhibitory concentration (MIC) values. Bioactive phytocompounds from green ZnO also inhibit hemolysis of Staphylococcus aureus infected red blood cells and inflammatory activity of mammalian immune system. In general, three mechanisms have been adopted to explain bactericidal activity of ZnO nanomaterials, including direct contact killing, reactive oxygen species (ROS) production, and released zinc ion inactivation. These toxic effects lead to the destruction of bacterial membrane, denaturation of enzyme, inhibition of cellular respiration and deoxyribonucleic acid replication, causing leakage of the cytoplasmic content and eventual cell death. Meanwhile, antimicrobial activity of doped and modified ZnO nanomaterials under visible light can be attributed to photogeneration of ROS on their surfaces. Thus particular attention is paid to the design and synthesis of visible light-activated ZnO photocatalysts with antibacterial properties.

The investigation of the parameters affecting the ZnO nanoparticle cytotoxicity behaviour: a tutorial review

In the last 30 years the research about zinc oxide nanoparticles (ZnO NPs) and their related toxicity has shown a boom. ZnO NPs show cytotoxicity for both prokaryotic and eukaryotic cells and many studies demonstrated their selective toxicity towards cancer cells. However, with the increasing number of publications, it is observed an increase in the discrepancies obtained between the various results. Soon the scientific community understood that the ZnO NC toxicity behaviour is affected by many factors, related not only to the ZnO NPs themselves, but also to the experimental conditions used. Many recent reviews discussed these parameters by reporting experimental evidence and tried to assess the general statements about the ZnO NP cytotoxicity. This information is extremely useful for the evaluation of which type of ZnO NPs is more or less suitable for a specific study or application. However, despite that, a deep comprehension of the ZnO NP behaviour in relation to the different experimental conditions is still lacking. Actually, a full understanding of the reasons behind the NP behaviour is essential to better assess their biological activity and in particular their therapeutic application, avoiding undesired effects both in the experimental and clinical contexts. This tutorial review aims to be an experimental and practical guide for scientists that faced with the use of ZnO NPs for biomedical applications and, in particular, for their therapeutic purposes. The driving idea is to not simply summarize the results reported in the literature, but to provide instruments for a deep comprehension of the mechanisms affecting the ZnO NP cytotoxicity and behavior. This review also aims to point out the critical experimental parameters to be considered when working with these NPs, as well as the main related risks and limitations that scientists have to face.

Nanomaterial-mediated autophagy: coexisting hazard and health benefits in biomedicine

BACKGROUND

Widespread biomedical applications of nanomaterials (NMs) bring about increased human exposure risk due to their unique physicochemical properties. Autophagy, which is of great importance for regulating the physiological or pathological activities of the body, has been reported to play a key role in NM-driven biological effects both in vivo and in vitro. The coexisting hazard and health benefits of NM-mediated autophagy in biomedicine are nonnegligible and require our particular concerns.

MAIN BODY

We collected research on the toxic effects related to NM-mediated autophagy both in vivo and in vitro. Generally, NMs can be delivered into animal models through different administration routes, or internalized by cells through different uptake pathways, exerting varying degrees of damage in tissues, organs, cells, and organelles, eventually being deposited in or excreted from the body. In addition, other biological effects of NMs, such as oxidative stress, inflammation, necroptosis, pyroptosis, and ferroptosis, have been associated with autophagy and cooperate to regulate body activities. We therefore highlight that NM-mediated autophagy serves as a double-edged sword, which could be utilized in the treatment of certain diseases related to autophagy dysfunction, such as cancer, neurodegenerative disease, and cardiovascular disease. Challenges and suggestions for further investigations of NM-mediated autophagy are proposed with the purpose to improve their biosafety evaluation and facilitate their wide application. Databases such as PubMed and Web of Science were utilized to search for relevant literature, which included all published, Epub ahead of print, in-process, and non-indexed citations.

CONCLUSION

In this review, we focus on the dual effect of NM-mediated autophagy in the biomedical field. It has become a trend to use the benefits of NM-mediated autophagy to treat clinical diseases such as cancer and neurodegenerative diseases. Understanding the regulatory mechanism of NM-mediated autophagy in biomedicine is also helpful for reducing the toxic effects of NMs as much as possible.

TRPM2 channel-mediated cell death: An important mechanism linking oxidative stress-inducing pathological factors to associated pathological conditions

Oxidative stress resulting from the accumulation of high levels of reactive oxygen species is a salient feature of, and a well-recognised pathological factor for, diverse pathologies. One common mechanism for oxidative stress damage is via the disruption of intracellular ion homeostasis to induce cell death. TRPM2 is a non-selective Ca2+-permeable cation channel with a wide distribution throughout the body and is highly sensitive to activation by oxidative stress. Recent studies have collected abundant evidence to show its important role in mediating cell death induced by miscellaneous oxidative stress-inducing pathological factors, both endogenous and exogenous, including ischemia/reperfusion and the neurotoxicants amyloid-β peptides and MPTP/MPP+ that cause neuronal demise in the brain, myocardial ischemia/reperfusion, proinflammatory mediators that disrupt endothelial function, diabetogenic agent streptozotocin and diabetes risk factor free fatty acids that induce loss of pancreatic β-cells, bile acids that damage pancreatic acinar cells, renal ischemia/reperfusion and albuminuria that are detrimental to kidney cells, acetaminophen that triggers hepatocyte death, and nanoparticles that injure pericytes. Studies have also shed light on the signalling mechanisms by which these pathological factors activate the TRPM2 channel to alter intracellular ion homeostasis leading to aberrant initiation of various cell death pathways. TRPM2-mediated cell death thus emerges as an important mechanism in the pathogenesis of conditions including ischemic stroke, neurodegenerative diseases, cardiovascular diseases, diabetes, pancreatitis, chronic kidney disease, liver damage and neurovascular injury. These findings raise the exciting perspective of targeting the TRPM2 channel as a novel therapeutic strategy to treat such oxidative stress-associated diseases.

Zinc oxide nanoparticles effectively regulate autophagic cell death by activating autophagosome formation and interfering with their maturation

BACKGROUND

With the development of zinc oxide nanoparticles (ZnO NPs) in the field of nanotechnology, their toxicological effects are attracting increasing attention, and the mechanisms for ZnO NPs neurotoxicity remain obscure. In an attempt to address concerns regarding neurotoxicity of ZnO NPs, we explored the relationship between free zinc ions, reactive oxygen species (ROS) and neurotoxic mechanisms in ZnO NPs-exposed PC12 cells.

RESULT

This study demonstrated the requirement of free zinc ions shed by ZnO NPs to over generation of intracellular ROS. Next, we identified autophagic cell death was the major mode of cell death induced by ZnO NPs, and autophagosome accumulation resulted from not only induction of autophagy, but also blockade of autophagy flux. We concluded that autophagic cell death, resulting from zinc ions-ROS-c-Jun N-terminal kinase (JNK)-autophagy positive feedback loop and blockade of autophagosomal-lysosomal fusion, played a major role in the neurotoxicity of ZnO NPs.

CONCLUSION

Our study contributes to a better understanding of the neurotoxicity of ZnO NPs and might be useful for designing and developing new biosafety nanoparticles in the future.

Molecular Mechanisms, Characterization Methods, and Utilities of Nanoparticle Biotransformation in Nanosafety Assessments

It is a big challenge to reveal the intrinsic cause of a nanotoxic effect due to diverse branches of signaling pathways induced by engineered nanomaterials (ENMs). Biotransformation of toxic ENMs involving biochemical reactions between nanoparticles (NPs) and biological systems has recently attracted substantial attention as it is regarded as the upstream signal in nanotoxicology pathways, the molecular initiating event (MIE). Considering that different exposure routes of ENMs may lead to different interfaces for the arising of biotransformation, this work summarizes the nano-bio interfaces and dose calculation in inhalation, dermal, ingestion, and injection exposures to humans. Then, five types of biotransformation are shown, including aggregation and agglomeration, corona formation, decomposition, recrystallization, and redox reactions. Besides, the characterization methods for investigation of biotransformation as well as the safe design of ENMs to improve the sustainable development of nanotechnology are also discussed. Finally, future perspectives on the implications of biotransformation in clinical translation of nanomedicine and commercialization of nanoproducts are provided.

Interactions of Zinc Oxide Nanostructures with Mammalian Cells: Cytotoxicity and Photocatalytic Toxicity

This article presents a state-of-the-art review and analysis of literature studies on the morphological structure, fabrication, cytotoxicity, and photocatalytic toxicity of zinc oxide nanostructures (nZnO) of mammalian cells. nZnO with different morphologies, e.g., quantum dots, nanoparticles, nanorods, and nanotetrapods are toxic to a wide variety of mammalian cell lines due to in vitro cell-material interactions. Several mechanisms responsible for in vitro cytotoxicity have been proposed. These include the penetration of nZnO into the cytoplasm, generating reactive oxygen species (ROS) that degrade mitochondrial function, induce endoplasmic reticulum stress, and damage deoxyribonucleic acid (DNA), lipid, and protein molecules. Otherwise, nZnO dissolve extracellularly into zinc ions and the subsequent diffusion of ions into the cytoplasm can create ROS. Furthermore, internalization of nZnO and localization in acidic lysosomes result in their dissolution into zinc ions, producing ROS too in cytoplasm. These ROS-mediated responses induce caspase-dependent apoptosis via the activation of B-cell lymphoma 2 (Bcl2), Bcl2-associated X protein (Bax), CCAAT/enhancer-binding protein homologous protein (chop), and phosphoprotein p53 gene expressions. In vivo studies on a mouse model reveal the adverse impacts of nZnO on internal organs through different administration routes. The administration of ZnO nanoparticles into mice via intraperitoneal instillation and intravenous injection facilitates their accumulation in target organs, such as the liver, spleen, and lung. ZnO is a semiconductor with a large bandgap showing photocatalytic behavior under ultraviolet (UV) light irradiation. As such, photogenerated electron-hole pairs react with adsorbed oxygen and water molecules to produce ROS. So, the ROS-mediated selective killing for human tumor cells is beneficial for cancer treatment in photodynamic therapy. The photoinduced effects of noble metal doped nZnO for creating ROS under UV and visible light for killing cancer cells are also addressed.

MTH1 is involved in the toxic and carcinogenic long-term effects induced by zinc oxide and cobalt nanoparticles

The nanoparticles (NPs) exposure-related oxidative stress is considered among the main causes of the toxic effects induced by these materials. However, the importance of this mechanism has been mostly explored at short term. Previous experience with cells chronically exposed to ZnO and Co NPs hinted to the existence of an adaptative mechanism contributing to the development of oncogenic features. MTH1 is a well-described enzyme expressed exclusively in cancer cells and required to avoid the detrimental consequences of its high prooxidant microenvironment. In the present work, a significantly marked overexpression was found when MTH1 levels were monitored in long-term ZnO and Co NP-exposed cells, a fact that correlates with acquired 2.5-fold and 3.75-fold resistance to the ZnO and Co NPs treatment, respectively. The forced stable inhibition of Mth1 expression by shRNA, followed by 6 additional weeks of exposure, significantly reduced this acquired resistance and sensitized cells to the oxidizing agents H₂O₂ and KBrO₃. When the oncogenic phenotype of Mth1 knock-down cells was evaluated, we found a decrease in several oncogenic markers, including proliferation, anchorage-independent cell growth, and migration and invasion potential. Thus, MTH1 elicits here as a relevant player in the NPs-induced toxicity and carcinogenicity. This study is the first to give a mechanistic explanation for long-term NPs exposure-derived effects. We propose MTH1 as a candidate biomarker to unravel NPs potential genotoxic and carcinogenic effects, as its expression is expected to be elevated only under exposure conditions able to induce DNA damage and the acquisition of an oncogenic phenotype.

Zinc oxide nanoparticles exposure-induced oxidative stress restricts cranial neural crest development during chicken embryogenesis

Zinc oxide Nanoparticles (ZnO NPs) are widely used as emerging materials in agricultural and food-related fields, which exists potential safety hazards to public health and environment while bringing an added level of convenience to our original life. It has been proved that ZnO NPs could be taken up by pregnant women and passed through human placental barrier. However, the toxic potential for embryo development remains largely unanswered. In this study, we discovered that ZnO NPs caused the cytotoxicity in vitro. Inhibition of free Zn²⁺ ions in solution by EDTA or inhibition of Zn²⁺ ions absorption by CaCl₂ could partially eliminate ZnO NPs-mediated cell toxicity, though not redeem completely. This indicated that both nanoparticles and the release of Zn²⁺ ions were involved in ZnO NPs-mediated cytotoxicity. In addition, we also found that both nanoparticles and Zn²⁺ ion release triggered reactive oxygen species (ROS) production, which further induced cell toxicity, inflammation and apoptosis, which are mediated by NF-κB signaling cascades and the mitochondria dysfunction, respectively. Eventually, these events lead to the suppressed production and migration of cranial neural crest cells (CNCCs), which subsequently prompts the craniofacial defects in chicken embryos. The application of the antioxidant N-Acetyl-L-cysteine (NAC) rescued the ZnO NPs-induced cell toxicity and malformation of the CNCCs, which further verified our hypothesis. Our results revealed the relevant mechanism of ZnO NPs exposure-inhibited the development of CNCCs, which absolutely contribute to assess the risk of nanoparticles application.

When Would Immunologists Consider a Nanomaterial to be Safe? Recommendations for Planning Studies on Nanosafety

The immune system is professional in recognizing and responding to non-self, including nanomaterials. Immune responses by professional and nonprofessional immune cells are thus nearly inevitable upon exposure of cells and organisms to such materials. The state of research into taking the immune system into account in nanosafety studies is reviewed and three aspects in which further improvements are desirable are identified: 1) Due to technical limitations, more stringent testing for endotoxin contamination should be made. 2) Since under overdose conditions immunity shows unphysiological responses, all doses used should be justified by being equivalent to tissue-delivered doses. 3) When markers of acute inflammation or cell stress are observed, functional assays are necessary to distinguish between homeostatic fluctuation and genuine defensive or tolerogenic responses. Since immune activation can also indicate that the immune system considers a stimulus to be harmless and induces tolerance, activation markers by themselves do not necessarily imply a danger to the body. Guidelines such as these are necessary to approach the point where specific nanomaterials are classified as safe based on reliable testing strategies.

Toxicity of alumina nanoparticles in the immune system of mice

Aim: Alumina nanoparticles (AlNPs) exert toxic effects in several organs. This study aimed to investigate the toxicity of AlNPs to the immune system. Materials & methods: AlNPs distribution was assessed using CRi in vivo fluorescence imaging. Inductively coupled plasma atomic emission spectrometry was used to detect the content of aluminum in the spleen. Cytokines expression was detected in the immune organs and blood of mice. Results & conclusion: AlNPs can accumulate in mice spleen. Superoxide dismutase and glutathione levels decreased, whereas the level of malondialdehyde increased with decreasing particle size. AlNPs exposure caused cytokine level changes in the spleen, thymus and serum, besides causing damage to immune organs and dysfunction of immune cells, leading to abnormal immune-related cytokine expression.

High-throughput transcriptomics: An insight on the pathways affected in HepG2 cells exposed to nickel oxide nanoparticles

Nickel oxide nanoparticles (NiO-NPs) have been used in several consumer goods, reported to demonstrate the hepatotoxic effects in vitro and in vivo test models. Nonetheless the molecular mechanism of hepatotoxicity is still missing. Hence, a toxicogenomic approach integrating microscopic techniques and high-throughput RNA sequencing (RNA-Seq) was applied to reveal hepatotoxicity in human hepatocellular carcinoma cells (HepG2). NiO-NPs induced a concentration dependent (5-100 μg/ml) cytotoxicity, with a No observed effect level (NOEL) of 5 μg/ml. Hypoxia-inducible transcription factor-1α (HIF-1α) and miR-210 microRNA were upregulated at 25 and 100 μg/ml, while significant alteration on transcriptome at mRNA and pathway level was observed at non-toxic level of NiO-NPs treatment. The treated cells also showed activation of glycolysis, glutathione, lysosomes and autophagy pathways by a pathway-driven analysis. Flow cytometric analysis affirmed the elevation in nitric oxide (NO), Ca⁺⁺ influx, esterase, and disruption of mitochondrial membrane potential (ΔΨm). Cell cycle dysregulation was affirmed by the appearance of 30.5% subG1 apoptotic peak in NiO-NPs (100 μg/ml) treated cells. The molecular responses were consistent with the microscopic observation that NiO-NPs induced subcellular alterations in HepG2 cells. We conclude that hypoxia stress played a pivotal role in NiO-NPs induced hepatoxicity in HepG2 cells. Concentration dependent effects on transcriptomics specify a powerful tool to evaluate the molecular mechanisms of nanoparticle induced cytotoxicity. Overall our study unequivocally affirmed the transcriptomic alterations in human cells, consequently the prevalent usage of NiO-NPs should be given subtle consideration owing to its effects on biological processes.

The Current Understanding of Autophagy in Nanomaterial Toxicity and Its Implementation in Safety Assessment-Related Alternative Testing Strategies

Nanotechnology has rapidly promoted the development of a new generation of industrial and commercial products; however, it has also raised some concerns about human health and safety. To evaluate the toxicity of the great diversity of nanomaterials (NMs) in the traditional manner, a tremendous number of safety assessments and a very large number of animals would be required. For this reason, it is necessary to consider the use of alternative testing strategies or methods that reduce, refine, or replace (3Rs) the use of animals for assessing the toxicity of NMs. Autophagy is considered an early indicator of NM interactions with cells and has been recently recognized as an important form of cell death in nanoparticle-induced toxicity. Impairment of autophagy is related to the accelerated pathogenesis of diseases. By using mechanism-based high-throughput screening in vitro, we can predict the NMs that may lead to the generation of disease outcomes in vivo. Thus, a tiered testing strategy is suggested that includes a set of standardized assays in relevant human cell lines followed by critical validation studies carried out in animals or whole organism models such as C. elegans (Caenorhabditis elegans), zebrafish (Danio rerio), and Drosophila (Drosophila melanogaster)for improved screening of NM safety. A thorough understanding of the mechanisms by which NMs perturb biological systems, including autophagy induction, is critical for a more comprehensive elucidation of nanotoxicity. A more profound understanding of toxicity mechanisms will also facilitate the development of prevention and intervention policies against adverse outcomes induced by NMs. The development of a tiered testing strategy for NM hazard assessment not only promotes a more widespread adoption of non-rodent or 3R principles but also makes nanotoxicology testing more ethical, relevant, and cost- and time-efficient.

"Iron free" zinc oxide nanoparticles with ion-leaking properties disrupt intracellular ROS and iron homeostasis to induce ferroptosis

Exposure to nanomaterials (NMs) is an emerging threat to human health, and the understanding of their intracellular behavior and related toxic effects is urgently needed. Ferroptosis is a newly discovered, iron-mediated cell death that is distinctive from apoptosis or other cell-death pathways. No evidence currently exists for the effect of “iron free” engineered NMs on ferroptosis. We showed by several approaches that (1) zinc oxide nanoparticles (ZnO NPs)-induced cell death involves ferroptosis; (2) ZnO NPs-triggered ferroptosis is associated with elevation of reactive oxygen species (ROS) and lipid peroxidation, along with depletion of glutathione (GSH) and downregulation of glutathione peroxidase 4 (GPx4); (3) ZnO NPs disrupt intracellular iron homeostasis by orchestrating iron uptake, storage and export; (4) p53 largely participates in ZnO NPs-induced ferroptosis; and (5) ZnO particle remnants and dissolved zinc ion both contribute to ferroptosis. In conclusion, our data provide a new mechanistic rationale for ferroptosis as a novel cell-death phenotype induced by engineered NMs.

Early-life long-term exposure to ZnO nanoparticles suppresses innate immunity regulated by SKN-1/Nrf and the p38 MAPK signaling pathway in Caenorhabditis elegans

The widespread use of zinc oxide nanoparticles (ZnO-NPs) has led to their release into the environment, and they thus represent a potential risk for both humans and ecosystems. However, the negative impact of ZnO-NPs on the immune system, especially in relation to host defense against pathogenic infection and its underlying regulatory mechanisms, remains largely unexplored. This study investigated the effects of early-life long-term ZnO-NPs exposure (from L1 larvae to adults) on innate immunity and its underlying mechanisms using a host-pathogen Caenorhabditis elegans model, and this was compared with the effect of ionic Zn. The results showed that the ZnO-NPs taken up by C. elegans primarily accumulated in the intestine and that early-life long-term ZnO-NPs exposure at environmentally relevant concentrations (50 and 500 μg/L) decreased the survival of wild-type C. elegans when faced with pathogenic Pseudomonas aeruginosa PA14 infection. Early-life long-term ZnO-NPs (500 μg/L) exposure significantly increased (by about 3-fold) the accumulation of live P. aeruginosa PA14 colonies in the intestine of C. elegans. In addition, ZnO-NPs (500 μg/L) inhibited the intestinal nuclear translocation of SKN-1 and also downregulated gcs-1 gene expression, which is an SKN-1 target gene. Further evidence revealed that early-life long-term exposure to ZnO-NPs (500 μg/L) did not increase susceptibility to mutation among the genes (pmk-1, sek-1, and nsy-1) encoding the p38 mitogen-activated protein kinase (MAPK) cascade in response to P. aeruginosa PA14 infection, though ZnO-NPs significantly decreased the mRNA levels of pmk-1, sek-1, and nsy-1. This study provides regulatory insight based on evidence that ZnO-NPs suppress the innate immunity of C. elegans and highlights the potential health risks of certain environmental nanomaterials, including ZnO-NPs, in terms of their immunotoxicity at environmentally relevant concentrations.

Pomegranate Juice Diminishes The Mitochondria-Dependent Cell Death And NF-kB Signaling Pathway Induced By Copper Oxide Nanoparticles On Liver And Kidneys Of Rats

BACKGROUND

Pomegranate (Punica granatum L) has been used since ancient times in the traditional medicine of several cultures, particularly in the Middle East. It is an essential commercial crop full of bioactive compounds with several medical applications. Pomegranate is very popular for its biological effects exerted by phenolic compounds via free radical scavenging abilities. It has revealed high antioxidant and anti-inflammatory activities and is beneficial for the amelioration of liver and kidney diseases.

PURPOSE

To elucidate the potential efficacy of pomegranate juice (PJ) against copper oxide nanoparticles (CuO-NPs)-induced apoptosis, inflammation, and oxidative stress damage.

STUDY DESIGN

37 nm sized CuO-NPs were prepared by precipitation method and characterized by using X-ray diffractometer (XRD), Zetasizer nano-and high-resolution transmission electron microscope (HR-TEM). 30 Wistar rats were partitioned into 6 equal groups as follows: Group 1 (negative control), groups 2 & 3 (PJ control groups), group 4 (CuO-NPs group), groups 5 & 6 (CuO-NPs + PJ groups). Methods: Hepato-renal protective effect of PJ was evaluated by measuring levels of serum marker enzymes (ALT, AST,blood urea nitrogen and creatinine). Cu NPs bioaccumulation in liver and kidneys was determined by using atomic absorption spectrophotometer. The oxidative stress markers, Rt-PCR analysis, histopathological and immunohistochemical studies were carried out in the liver and kidneys to support the above parameters.

RESULTS

Rats injected with CuO-NPs showed higher levels of the above serum marker enzymes, alteration of oxidant-antioxidant balance together with severe pathological alterations in liver and kidney tissues and overexpression of both caspase-3 and nuclear factor kappa B protein (NF-ĸB) associated with upregulation of Bax gene and downregulation of Bcl2 gene in these organs. PJ ameliorated all of the above toxicological parameters.

CONCLUSION

PJ was proved to be a potential hepato-renal protective agent against liver and kidney damage induced by CuO-NPs via its antioxidant, anti-inflammatory, and anti-apoptotic effects.

Rebalancing Immune Homeostasis to Treat Autoimmune Diseases

During homeostasis, interactions between tolerogenic dendritic cells (DCs), self-reactive T cells, and T regulatory cells (Tregs) contribute to maintaining mammalian immune tolerance. In response to infection, immunogenic DCs promote the generation of proinflammatory effector T cell subsets. When complex homeostatic mechanisms maintaining the balance between regulatory and effector functions become impaired, autoimmune diseases can develop. We discuss some of the newest advances on the mechanisms of physiopathologic homeostasis that can be employed to develop strategies to restore a dysregulated immune equilibrium. Some of these designs are based on selectively activating regulators of immunity and inflammation instead of broadly suppressing these processes. Promising approaches include the use of nanoparticles (NPs) to restore Treg control over self-reactive cells, aiming to achieve long-term disease remission, and potentially to prevent autoimmunity in susceptible individuals.

Application of ZnO-Based Nanocomposites for Vaccines and Cancer Immunotherapy

Engineering and application of nanomaterials have recently helped advance various biomedical fields. Zinc oxide (ZnO)-based nanocomposites have become one of the most promising candidates for biomedical applications due to their biocompatibility, unique physicochemical properties, and cost-effective mass production. In addition, recent advances in nano-engineering technologies enable the generation of ZnO nanocomposites with unique three-dimensional structures and surface characteristics that are optimally designed for in vivo applications. Here, we review recent advances in the application of diverse ZnO nanocomposites, with an especial focus on their development as vaccine adjuvant and cancer immunotherapeutics, as well as their intrinsic properties interacting with the immune system and potential toxic effect in vivo. Finally, we summarize promising proof-of-concept applications as prophylactic and therapeutic vaccines against infections and cancers. Understanding the nano-bio interfaces between ZnO-based nanocomposites and the immune system, together with bio-effective design of the nanomaterial using nano-architectonic technology, may open new avenues in expanding the biomedical application of ZnO nanocomposites as a novel vaccine platform.

Role of Autophagy in Zinc Oxide Nanoparticles-Induced Apoptosis of Mouse LEYDIG Cells

Zinc oxide nanoparticles (ZnO NPs) have shown adverse health impact on the human male reproductive system, with evidence of inducing apoptosis. However, whether or not ZnO NPs could promote autophagy, and the possible role of autophagy in the progress of apoptosis, remain unclear. In the current study, in vitro and in vivo toxicological responses of ZnO NPs were explored by using a mouse model and mouse Leydig cell line. It was found that intragastrical exposure of ZnO NPs to mice for 28 days at the concentrations of 100, 200, and 400 mg/kg/day disrupted the seminiferous epithelium of the testis and decreased the sperm density in the epididymis. Furthermore, serum testosterone levels were markedly reduced. The induction of apoptosis and autophagy in the testis tissues was disclosed by up-regulating the protein levels of cleaved Caspase-8, cleaved Caspase-3, Bax, LC3-II, Atg 5, and Beclin 1, accompanied by down-regulation of Bcl 2. In vitro tests showed that ZnO NPs could induce apoptosis and autophagy with the generation of oxidative stress. Specific inhibition of autophagy pathway significantly decreased the cell viability and up-regulated the apoptosis level in mouse Leydig TM3 cells. In summary, ZnO NPs can induce apoptosis and autophagy via oxidative stress, and autophagy might play a protective role in ZnO NPs-induced apoptosis of mouse Leydig cells.