Cell-Type-Dependent Dissolution of CuO Nanoparticles and Efflux of Cu Ions following Cellular Internalization

Copper oxide nanoparticles induce pulmonary inflammation via triggering cellular cuproptosis

Copper oxide nanoparticles (CuO NPs) are increasingly used in various industrial fields, and the toxicity of CuO NPs raises concerns. However, the CuO NPs-induced pulmonary inflammation and the underlying mechanism have not been fully illustrated. Cellular cuproptosis provides a new perspective to elucidate the toxicity of CuO NPs. Here, we exposed C57BL/6 mice and murine alveolar macrophage cells (MH-S) to CuO NPs, respectively. A suspension of 2 mg/mL CuO NPs was directly once administered by intratracheal instillation, and mice were sacrificed on day 7. The histopathology results showed that CuO NPs induced pulmonary inflammation in C57BL/6 mice. CuO NPs increased Cu2 + levels by 203.0 % in mouse lung tissues. Also, CuO NPs increased the cuproptosis-related indicators of ferredoxin (FDX1), dihydrolipoamide succinyltransferase (DLST), dihydrolipoamide acetyltransferase (DLAT) and Cu transporter 1 (CTR1) in both mouse lung tissues and MH-S cells. Transcript sequencing and non-targeted metabolomics indicated that CuO NPs induced cellular cuproptosis and inflammatory responses both in vivo and in vitro. Interleukin-17a (IL-17A) was remarkably increased in the process of CuO NPs-induced cellular cuproptosis. Additionally, interference of FDX1 reduced cellular cuproptosis and decreased the release of IL-17A. In summary, CuO NPs increased the accumulation of intracellular Cu2+ and the expressions of cuproptosis-related proteins, induced FDX1-mediated cuproptosis, and led to pulmonary inflammation in mice. This study highlights the respiratory toxicity of CuO NPs and reveals a unique cuproptosis-driven mechanism underlying the CuO NPs-induced pulmonary inflammation.

Potential Therapeutic Effect of ZnO/CuO Nanocomposite as an Acaricidal, Immunostimulant, and Antioxidant in Rabbits

The present study aimed to identify a safe and novel approach using zinc oxide/copper oxide nanocomposites (AZ) to enhance growth parameters, immunity, and fight Sarcoptic mange in vitro and in vivo in rabbits. In vitro: the acaricidal activity of AZ was assessed at concentrations of AZ-25: 2.5% w/w AZ/molasses, AZ-125: 12.5% w/w AZ/molasses, and controls (normal saline, molasses, and Ivermectin) every hour for seven hours under a stereoscopic microscope. In vivo: involved 40 rabbits (10 replicates/group). G1 served as the control negative group (normal un-infected rabbits), G2 served as the control negative group (infected rabbits), the animals in the G3 group were given a combination of AZ (40 mg/kg body weight (BW)) and molasses (5 mg/mL), and G4 served as the control to the vehicle; receiving molasses 8 mL/kg BW twice weekly for 6 weeks. Blood, serum, and tissue samples were collected at the middle and the end of the trial. AZ was made using the sonication sol-gel method. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were performed to confirm the crystal structure, purity, particle size, and oxidation states. AZ showed immunostimulant, acaricidal, and antioxidant effects with normal tissue histological structure and low tissue residual levels. Additionally, there were improvements in blood interferon-gamma, immunoglobulin (Ig) M, IgG, phagocytic activity, phagocytic index, globulin, and total protein in the AZ group. The XRD patterns of AZ were coordinated by XRD reference codes Crystallography Open Database (COD): 9016326 for Tenorite (CuO) and by XRD reference COD: 9004179 for Zincite (ZnO). The CuO and ZnO crystal sizes were 21.87 Å and 24.89 Å, respectively. The XPS spectra indicated the presence of Cu as Cu (II) and Zn as ZnO.OH and ZnO. In conclusion, AZ exhibited antioxidant, acaricidal, and immunostimulant effects, with mild residues in the brain, liver, and kidney tissues, while maintaining a normal histological structure of tissues.

An effective method for distinguishing extracellular and intracellular nanoparticles through chemical extractions

Nanoparticles (NPs) can adsorb onto cell surfaces (i.e., extracellular NPs) and be internalized by cells (i.e., intracellular NPs), leading to their accumulation and potential toxicity. Therefore, distinguishing adsorbed and internalized NPs is crucial in studying their accumulation and toxicity. In this study, various washing agents (EDTA, sodium citrate, cysteine, and H+) were compared to differentiate internalized NPs from total accumulation in the protozoan Tetrahymena thermophila, by evaluating efficacies of extracting adsorbed NPs from cell surfaces. Key factors influencing the extraction procedures, including the type and concentration of washing agent, contact time, washing cycles, and effects of agents on the organism, were systematically optimized. Consequently, we identified an effective washing agent (i.e., a mixture of 3 mM EDTA, 10 mM sodium citrate, and 10 mM cysteine in Dryl's medium at pH 7) that efficiently extracted adsorbed metal NPs (Fe2O3-NPs, TiO2-NPs, SiO2-NPs, Ag-NPs, and Au-NPs modified by -COOH and -NH2) without causing growth inhibition or cell lysis. Further, a washing procedure was proposed, involving the extraction of samples with the mixture twice for 5 min each. Our study represents the first systematic optimization of a washing protocol for extracting adsorbed NPs across diverse NP types. The developed methodology demonstrates broad applicability, minimal impact on cellular function, and enhanced extraction efficiency compared to existing methods. It will facilitate further investigation into the underlying mechanisms of NP bioaccumulation (including uptake and efflux) and associated toxicity in protozoa, providing critical insights for environmental safety assessments and advancing nanotoxicology research.

Cu(II)-Dependent Spine Development Injury in Zebrafish (Danio rerio) with Organ Heterogeneous Cu Imbalance

Growing evidence suggests that the imbalance of Cu leads to multiorgan diseases or other adverse effects, but the underlying mechanisms remain largely unknown. Herein, we used zebrafish to uncover the mystery of organ heterogeneous responses to Cu stress and Cu(II)-dependent spine developmental injury in the early organogenesis stage. We first demonstrated that Cu(I) was distributed in the entire body, but high contents of Cu(II) were accumulated in the yolk sac and eye in normal zebrafish larvae. Cu exposure from birth to 144 hpf caused no obvious damage to Cu-metabolizing organs (liver and intestine), despite the elevated Cu(I) and Cu(II) levels. However, the spine was more sensitive to the Cu exposure. In the spine region, the Cu(I) level remained stable, whereas the level of Cu(II) significantly increased, which was highly associated with spine development injury. A significant negative correlation between Cu(II) and the spine-related parameters was identified. Moreover, cuproptosis caused spine development deformation during the early embryogenesis stage. Spine-related pathways such as somitegenesis significantly changed in the early embryogenesis period, and 5 spine-related pathways were significantly altered in the larval stage at 96 hpf. Our study suggested that Cu stress induced organ heterogeneous Cu imbalance and Cu(II)-dependent spine development injury in zebrafish.

A novel route of intercellular copper transport and detoxification in oyster hemocytes

Bivalve hemocytes are oyster immune cells composed of several cellular subtypes with different functions. Hemocytes accumulate high concentrations of copper (Cu) and exert critical roles in metal sequestration and detoxification in oysters, however the specific biochemical mechanisms that govern this have yet to be fully uncovered. Herein, we demonstrate that Cu(I) is predominately sequestered in lysosomes via the Cu transporter ATP7A in hemocytes to reduce the toxic effects of intracellular Cu(I). We also found that Cu(I) is translocated along tunneling nanotubes (TNTs) relocating from high Cu(I) cells to low Cu(I) cells, effectively reducing the burden caused by overloaded Cu(I), and that ATP7A facilitates the efflux of intracellular Cu(I) in both TNTs and hemocyte subtypes. We identify that elevated glutathione (GSH) contents and heat-shock protein (Hsp) levels, as well as the activation of the cell cycle were critical in maintaining the cellular homeostasis and function of hemocytes exposed to Cu. Cu exposure also increased the expression of membrane proteins (MYOF, RalA, RalBP1, and cadherins) and lipid transporter activity which can induce TNT formation, and activated the lysosomal signaling pathway, promoting intercellular lysosomal trafficking dependent on increased hydrolase activity and ATP-dependent activity. This study explores the intracellular and intercellular transport and detoxification of Cu in oyster hemocytes, which may help in understanding the potential toxicity and fate of metals in marine animals.

Copper redox state in cells and aquatic organisms: Implication for toxicity

Copper (Cu) redox state has been an important issue in biology and toxicology research, but many research gaps remain to be explored due to the limitations in the detecting techniques. Herein, the regulation of Cu homeostasis, including absorption, translocation, utilization, storage, and elimination behavior is discussed. Cuproptosis, a newly identified type of cell death caused by excessive Cu accumulation, which results in the aggregation of DLAT protein or the loss of Fe-S cluster and finally proteotoxic stress, is reviewed. Several longstanding mysteries of diseases such as Wilson disease and toxic effects, may be attributed to cuproptosis. Furthermore, we review the advanced detection methods and application of Cu(I) and Cu(II), especially the in-situ imaging techniques such as XANES, and chemosensors. Most of the existing studies using these detection techniques focus on the bioaccumulation and toxicity of Cu(I) and Cu(II) in cells and aquatic organisms. Finally, it will be important to identify the roles of Cu(I) and Cu(II) in the growth, development, and diseases of organisms, as well as the relationship between bioaccumulation and toxicity of Cu(I) and Cu(II) in cellular and aquatic toxicology.

Tracking the Cellular Degradation of Silver Nanoparticles: Development of a Generic Kinetic Model

Understanding the degradation of nanoparticles (NPs) after crossing the cell plasma membrane is crucial in drug delivery designs and cytotoxicity assessment. However, the key factors controlling the degradable kinetics remain unclear due to the absence of a quantification model. In this study, subcellular imaging of silver nanoparticles (AgNPs) was used to determine the intracellular transfer of AgNPs, and single particle ICP-MS was utilized to track the degradation process. A cellular kinetic model was subsequently developed to describe the uptake, transfer, and degradation behaviors of AgNPs. Our model demonstrated that the intracellular degradation efficiency of AgNPs was much higher than that determined by mimicking testing, and the degradation of NPs was highly influenced by cellular factors. Specifically, deficiencies in Ca or Zn primarily decreased the kinetic dissolution of NPs, while a Ca deficiency also resulted in the retardation of NP transfer. The biological significance of these kinetic parameters was strongly revealed. Our model indicated that the majority of internalized AgNPs dissolved, with the resulting ions being rapidly depurated. The release of Ag ions was largely dependent on the microvesicle-mediated route. By changing the coating and size of AgNPs, the model results suggested that size influenced the transfer of NPs into the degradation process, whereas coating affected the degradation kinetics. Overall, our developed model provides a valuable tool for understanding and predicting the impacts of the physicochemical properties of NPs and the ambient environment on nanotoxicity and therapeutic efficacy.

Molecular mechanism of dissolvable metal nanoparticles-enhanced CO2 fixation by algae: Metal-chlorophyll synthesis

Algae-driven photosynthetic CO2 fixation is a promising strategy to mitigate global climate changes and energy crises. Yet, the presence of metal nanoparticles (NPs), particularly dissolvable NPs, in aquatic ecosystems introduces new complexities due to their tendency to release metal ions that may perturb metabolic processes related to algal CO2 fixation. This study selected six representative metal NPs (Fe3O4, ZnO, CuO, NiO, MgO, and Ag) to investigate their impacts on CO2 fixation by algae (Chlorella vulgaris). We discovered an intriguing phenomenon that bivalent metal ions released from the metal NPs, especially from ZnO NPs, substituted Mg2+ within the porphyrin ring. This interaction led to 81.8% and 76.1% increases in Zinc-chlorophyll and Magnesium-chlorophyll contents within algal cells at 0.01 mM ZnO NPs, respectively. Integrating metabolomics and transcriptomics analyses revealed that ZnO NPs mainly promoted the photosynthesis-antenna protein pathway, porphyrin and chlorophyll metabolism, and carbon fixation pathway, thereby mitigating the adverse effects of Zn2+ substitution in light harvesting and energy transfer for CO2 fixation. Ultimately, the genes encoding Rubisco large subunit (rbcL) responsible for CO2 fixation were upregulated to 2.60-fold, resulting in a 76.3% increase in carbon fixation capacity. Similar upregulations of rbcL expression (1.13-fold) and carbon fixation capacity (76.1%) were observed in algal cells even at 0.001 mM ZnO NPs, accompanied by valuable lipid accumulation. This study offers novel insights into the molecular mechanism underlying NPs on CO2 fixation by algae and potentially introduces strategies for global carbon sequestration.

Interactions between CuO NPs and PS: The release of copper ions and oxidative damage

Copper oxide nanoparticles (CuO NPs) can adversely affect lung health possibly by inducing oxidative damage through the release of copper ions. However, the migration and transformation processes of CuO NPs in lung lining fluid is still unclear, and there are still conflicting reports of redox reactions involving copper ions. To address this, we examined the release of copper ions from CuO NPs in simulated lung fluid supplemented with pulmonary surfactant (PS), and further analyzed the mechanisms of PS-CuO NPs interactions and the health hazards. The results showed that the phospholipid of PS was adsorbed on the particle surface, which not only induced aggregation of the particles but also provided a reaction environment for the interaction of PS with CuO NPs. PS was able to promote the release of ions from CuO NPs, of which the protein was a key component. Lipid peroxidation, protein destabilization, and disruption of the interfacial chemistry also occurred in the PS-CuO NPs interactions, during which copper ions were present only as divalent cations. Meanwhile, the contribution of the particle surface cannot be neglected in the oxidative damage to the lung caused by CuO NPs. Through reacting with biomolecules, CuO NPs accomplished ion release and induced oxidative damage associated with PS. This research was the first to reveal the mechanism of CuO NPs releasing copper ions and inducing lipid oxidative damage in the presence of PS, which provides a new idea of transition metal-induced health risk in human body.

Phthalate acid esters contribute to the cytotoxicity of mask leachate: Cell-based assay for toxicity assessment

After the COVID-19 outbreak, masks have become an essential part of people lives. Although several studies have been conducted to determine the release of hazardous substances from masks, how their co-presence poses a potential exposure risk to human health remains unexplored. In this study, we quantitatively compared the leaching of substances from six different common types of masks, including phthalate acid esters (PAEs), metals, and microplastics (MPs), and comprehensively evaluated the potential cytotoxicity of different leachates. MPs smaller than 3 µm were quantified by Py-GC-MS, and reusable masks showed greater releasing potentials up to 1504 µg/g. We also detected the prevalence of PAEs in masks, with the highest release reaching 42 μg/g, with dibutyl phthalate (DBP), diisobutyl phthalate (DiBP) and bis (2-ethylhexyl) phthalate (DEHP) being the predominant types. Moreover, the antimicrobial cloth masks released 173.0 µg of Cu or 4.5 µg of Ag, representing 2.7% and 0.04% of the original masks, respectively. Our cell-based assay results demonstrated for the first time that mask leachate induced nuclear condensation with DNA damage, and simultaneously triggered high levels of glutathione and reactive oxidative stress production, which exacerbated mitochondrial fragmentation, eventually leading to cell death. Combined with substance identification and correlation analysis, PAEs were found to be the contributors to cytotoxicity. Masks containing Cu or Ag led to acidification of lysosomes and alkalinization of cells. These results strongly suggested that the levels of PAEs in the production of regulatory masks should be strictly controlled.

Exocytosis of Nanoparticles: A Comprehensive Review

Both biomedical applications and safety assessments of manufactured nanomaterials require a thorough understanding of the interaction between nanomaterials and cells, including how nanomaterials enter cells, transport within cells, and leave cells. However, compared to the extensively studied uptake and trafficking of nanoparticles (NPs) in cells, less attention has been paid to the exocytosis of NPs. Yet exocytosis is an indispensable process of regulating the content of NPs in cells, which in turn influences, even decides, the toxicity of NPs to cells. A comprehensive understanding of the mechanisms and influencing factors of the exocytosis of NPs is not only essential for the safety assessment of NPs but also helpful for guiding the design of safe and highly effective NP-based materials for various purposes. Herein, we review the current status and progress of studies on the exocytosis of NPs. Firstly, we introduce experimental procedures and considerations. Then, exocytosis mechanisms/pathways are summarized with a detailed introduction of the main pathways (lysosomal and endoplasmic reticulum/Golgi pathway) and the role of microtubules; the patterns of exocytosis kinetics are presented and discussed. Subsequently, the influencing factors (initial content and location of intracellular NPs, physiochemical properties of NPs, cell type, and extracellular conditions) are fully discussed. Although there are inconsistent results, some rules are obtained, like smaller and charged NPs are more easily excreted. Finally, the challenges and future directions in the field have been discussed.